KR20120081113A - Particulate water absorbent and method for producing same - Google Patents

Abstract

In the particulate water absorbent containing polyacrylic acid (salt) -based water absorbent resin as a main component, it is possible to exhibit excellent water absorption performance, and furthermore has a good time-lapse-coloring prevention performance, and is a particulate water absorbent for absorbent body which is very suitable in practical use without odor. To give.
Polyacrylic acid (salt) -based water absorbent comprising a polymerization step of an aqueous monomer solution containing 10 to 200 ppm of methoxy phenols as a main component, a drying step of a hydrous gel crosslinked aggregate obtained by polymerization, and a surface crosslinking step A method for producing a particulate water absorbent containing a resin as a main component, comprising a step of adding a chelating agent and an inorganic reducing agent and satisfying the following (a) and / or (b), a polyacrylic acid (salt) -based water absorbent A method for producing a particulate water absorbent containing a resin as a main component. (a) A step of adding water-insoluble inorganic fine particles. (b) In the drying step and the surface crosslinking step, controlling the moisture content of the aggregate to 3 to 15% by weight.

Description

Particulate absorbent and its manufacturing method {PARTICULATE WATER ABSORBENT AND METHOD FOR PRODUCING SAME}

The present invention relates to a particulate water absorbing agent having a polyacrylic acid (salt) -based water absorbent resin as a main component and a method for producing the same. More specifically, the present invention relates to a particulate water absorbing agent for absorbents used in paper diapers, sanitary napkins, and the like, and to a method for producing the same, which is excellent in preventing yellowing, has no odor, and exhibits excellent absorbing ability. The present invention relates to a particulate water absorbent containing a acrylic acid (salt) -based water absorbent resin as a main component and a method for producing the same.

In recent years, absorbent resins having high absorbency have been developed, and are widely used as disposable absorbents such as paper diapers and sanitary napkins, and mainly used as agricultural horticultural repair agents, industrial water repellents, and the like. It is becoming. As such a water absorbent resin, many monomers and hydrophilic polymers have been proposed as raw materials, and among them, polyacrylic acid (salt) -based water absorbent resins using acrylic acid and / or salts thereof as monomers are most industrially available because of their high absorbency. It is used a lot.

Such polyacrylic acid (salt) -based water absorbent resin is neutralized before or after polymerization to form a polyacrylate. However, such neutralization and polymerization are disclosed in Patent Documents 1 to 4 and Non-Patent Document 1.

As the absorbent properties desired for the above absorbent resins, the absorption ratio under pressure (CRC), absorption ratio under pressure (AAP), absorption rate (FSR / Vortex), liquid pressure under pressure, liquid flow under pressure, Numerous characteristics (parameters) such as impact resistance, urinary resistance, fluidity, gel strength, color, and particle size are known, and in addition, various properties can be obtained even in the same physical properties (for example, absorption under pressure). In view of the numerous provisions (parameter measurements) have been proposed.

The absorbent resin (particulate absorbent) which has been developed in view of these many physical properties can be controlled even if the above-mentioned physical properties (e.g., "Unpressurized absorption ratio (CRC)", "Absorbing ratio under pressure (AAP)", etc.) are controlled. There has been a problem that it is difficult to say that sufficient performance is still exhibited in actual use of absorbers such as paper diapers.

In addition, since the main use of these absorbents is sanitary materials such as paper diapers and sanitary napkins, when the powdered absorbent is compounded in white pulp and sanitary materials, the initial color tone of the absorbent (alias) is not applied so as not to give foreign matters due to coloring. Initial color), and the water absorbent resin is required to be white at the time of shipment from the factory. In addition, although the said absorbent is generally white powder, it is known that the said absorbent will color over time (coloring from yellow to brown) when it is used for the hygiene material during the storage, transport, or even after shipment. Even when it is a color tone with time (alias; coloring with time), it is calculated | required to be white also when storing an absorbent article for a long time. In recent years, the coloring problem becomes more important because the use ratio (weight%) of the absorbent resin in the sanitary material tends to increase.

Therefore, various proposals regarding the improvement of the whiteness of a water absorbent resin, and the prevention of coloring are proposed by patent documents 5-31 etc. Specifically, as a method of controlling the polymerization inhibitor in the monomer, a technique of controlling methoxy phenol in acrylic acid to 10 to 160 ppm (Patent Document 5) and a technique of controlling hydroquinone in acrylic acid to 0.2 ppm or less (Patent Document 6) , Technology of treating monomer with activated carbon (Patent Document 7), technology using tocophenol as inhibitor (Patent Document 8), technology using N-oxyl compound, manganese compound, etc. as polymerization inhibitor (Patent Document 9) , The technique (patent document 10, 11) etc. which use a methoxy phenol and a specific polyvalent metal salt are known.

Moreover, as a coloring inhibitor of a water absorbing resin, the technique of adding reducing agents, such as hypophosphite (patent document 12), the technique of adding antioxidant (patent documents 13, 14), a metal chelating agent, and other reducing agents are added as needed. The technique (patent documents 15-19), the organic carbonic acid, and the technique (patent documents 20-23) which add another compound as needed are known.

Moreover, in order to prevent coloring, patent documents 24-26 are known as a technique focusing on a polymerization initiator. Moreover, as a coloring agent, the technique (patent documents 27 and 28) which pays attention to the quantity of iron in aluminum or a reducing agent is also proposed, The compound or sulfur type reducing agent which uses ammonium acrylate salt for a monomer, or contains a phosphorus atom The technique (patent document 29) which adds multiple times is also known. Moreover, the technique (patent document 30, 31) which controls the amount of oxygen in a drying process or a surface crosslinking process is also known.

However, even in the coloring prevention method of the said patent documents 5-31, the whiteness of the particulate water absorbing agent obtained by continuous polymerization shows a deviation. Because of the strong demand for whiteness of the particulate water absorbent, there is still room for improvement in whiteness. In addition, in the conventional anti-coloring technology that softens the polymerization and drying conditions of the water-absorbent resins which greatly increase the purity of raw materials such as acrylic acid, or uses a new anti-coloring agent, an increase in production cost, a decrease in productivity, and coloring There exists a possibility that the problem of the fall of safety and absorption characteristics by use of an inhibitor may arise.

In addition, in addition to the problem of coloring disclosed in Patent Documents 5 to 31, a problem of odor of the absorbent resin itself is known, and when the absorbent is used as a sanitary material such as a paper diaper or a sanitary napkin, it is used so as not to cause discomfort to the user. It is required that there is no odor even before. In recent years, unpleasant odors and odors, which are thought to be derived from substances to be newly used in conjunction with high performance of absorbents, may be problematic.

Therefore, various odor reduction methods, namely acrylic acid (patent document 32), acetic acid and propionic acid (patent document 33), volatile organic solvent (patent document 34), sulfur reducing agent (patent document 35), alcohol-based volatile substance (patent document) 36) has been proposed to reduce the odor. However, it is not sufficient in terms of excellent anti-yellowing and excellent absorbing ability, and particularly has a high physical property, particularly AAP (absorption under pressure) of 20 [g / g] or more, using a reducing agent, or When the SFC (saline flow inducibility) is 30 [× 10 ^-7 · cm 3 · s · g ^-1 ] or more, or the absorption rate is 60 [sec] or less, an unknown odor other than the odor derived from the reducing agent is unknown. I had a job.

Patent Document 1: US Patent No. 5210298 Patent Document 2: US Patent Application Publication No. 2008/242816 Patent Document 3: International Publication No. 2007/28747 Pamphlet Patent Document 4: US Patent Application Publication No. 2008/194863 Patent Document 5: International Publication No. 2003/051940 Pamphlet Patent Document 6: US Patent No. 6444744 Patent Document 7: International Publication No. 2004/052819 Pamphlet Patent Document 8: International Publication No. 2003/053482 Patent Document 9: International Publication No. 2008/096713 Patent Document 10: International Publication No. 2008/092843 Pamphlet Patent Document 11: International Publication No. 2008/092842 Pamphlet Patent Document 12: US Patent 6,635,49 Patent Document 13: International Publication No. 2009/060062 Patent Document 14: International Publication No. 2009/011717 Pamphlet Patent Document 15: US Patent Application Publication No. 2005/085604 Patent Document 16: International Publication No. 2003/059961 Pamphlet Patent Document 17: European Patent No. 1645596 Patent Document 18: Japanese Patent No. 3107873 Patent Document 19: International Publication No. 2009/005114 Pamphlet Patent Document 20: International Publication No. 2008/026772 Pamphlet Patent Document 21: Japanese Patent Application Laid-Open No. 2000-327926 Patent Document 22: Japanese Patent Application Laid-Open No. 2003-052742 Patent Document 23: Japanese Patent Application Laid-Open No. 2005-186016 Patent Document 24: Japanese Patent Application Laid-Open No. 4-331205 Patent Document 25: US Patent Application Publication No. 2006/089611 Patent Document 26: US Patent No. 7528291 Patent Document 27: International Publication No. 2007/072969 Pamphlet Patent Document 28: US Patent Application Publication No. 2006/074160 Patent Document 29: International Publication No. 2006/109882 Pamphlet Patent Document 30: US Patent Application Publication No. 2007/293632 Patent Document 31: International Publication No. 2006/008905 Pamphlet Patent Document 32: International Publication No. 2004/052949 Pamphlet Patent Document 33: International Publication No. 2003/095510 Pamphlet Patent Document 34: US Patent Application Publication No. 2009/036855 Patent Document 35: International Publication No. 2006/088115 Pamphlet Patent Document 36: US Patent Application Publication No. 2008/075937

[Non-Patent Document 1] Modern > Superabsorbent < RTI ID = 0.0 > Polymer < / RTI > 39-44, etc.

The problem to be solved by the present invention is a particulate water absorbing agent having a polyacrylic acid (salt) -based water absorbent resin as a main component and a method for producing the same. The present invention provides a particulate water absorbing agent for absorbent material which is very suitable for practical use and a method for producing the same. In addition, the problem to be solved by the present invention is to provide a particulate water absorbing agent for absorbent material which is also very suitable for practical use and excellent in urine resistance, and a method for producing the same.

(Particulate absorbent)

In order to solve the said subject, the particulate water absorbing agent of this invention is a particulate water absorbing agent which has a polyacrylic acid (salt) type water absorbing resin as a main component, contains a chelating agent and an inorganic reducing agent, and the content of the chelating agent is 0.001 to 0.5% by weight. , The following (1)? (3)

(1) Content of methoxy phenols is 5-60 ppm.

(2) Contains water insoluble inorganic fine particles.

(3) Water content is 3-15 weight%.

It satisfies any one or more requirements of.

(Manufacturing method of particulate absorbent)

Moreover, in order to solve the said subject, the manufacturing method of the particulate water absorbing agent of this invention is a polymerization process of the monomer aqueous solution which has acrylic acid (salt) as a main component, the drying process of the water-containing gel crosslinked polymer obtained by superposition | polymerization, and the surface As a manufacturing method of the particulate water absorbing agent which has a polyacrylic acid (salt) type water absorbing resin as a main component containing a crosslinking process,

Further comprising the addition step of 0.001 to 0.5% by weight of the chelating agent and the addition step of the inorganic reducing agent,

The monomer contains 10-200 ppm of methoxy phenols in terms of large acrylic acid,

(A) to (c) below

(a) adding a water-insoluble inorganic fine particle.

(b) controlling the water content of the polymer to 3 to 15% by weight in the drying step and in the surface crosslinking step.

(c) After the surface crosslinking step, adding an inorganic reducing agent.

It satisfies any one or more requirements of.

(A very suitable sub concept of the particulate water absorbent)

(Method for producing particulate water absorbent, part 1)

As a manufacturing method of the particulate water absorbing agent of this invention, the manufacturing method of the subconcept which makes the said (c) an essential part, 1 is a polymerization process of the aqueous monomer solution which has acrylic acid (salt) containing 10-200 ppm of methoxy phenols as a main component. And a method for producing a particulate water absorbing agent comprising a drying step of a hydrous gel crosslinked polymer obtained by polymerization, a surface crosslinking step, and an addition step of 0.001 to 0.5% by weight of a chelating agent, followed by a step of adding an inorganic reducing agent after the surface crosslinking step. It is characterized by performing. Such a manufacturing method and the specific example of the 1 are shown to Examples 1-1 to 1-16 and Tables 1 to 5 below.

(Method for producing particulate water absorbent, part 2)

As a method for producing the particulate water absorbent of the present invention, a method of producing a sub-concept of the above-mentioned (b), which is a polymerization process of a monomer aqueous solution containing acrylic acid (salt) as a main component, and a hydrogel-like crosslinked polymer obtained by polymerization As a method for producing a particulate water absorbing agent comprising a drying step and a surface crosslinking step, the method further includes an addition step of 0.001 to 0.5% by weight of a chelating agent and an addition step of an inorganic reducing agent, wherein the monomer is methoxy phenols in terms of large acrylic acid. ? 200 ppm, and further comprising the step of adding (a) water-insoluble inorganic fine particles. Such a manufacturing method and the specific example of the 2 are shown in Examples 2-1 to 2-14 and Tables 6 to 7 below.

(Method for producing particulate water absorbent, part 3)

As a method for producing the particulate water absorbent of the present invention, the production method of the subordinate concept in which (c) is an essential part thereof is a polymerization step of a monomer aqueous solution containing acrylic acid (salt) as a main component, and a hydrogel-like crosslinked polymer obtained by polymerization. A method for producing a particulate water absorbing agent, including a drying step and a surface crosslinking step, further includes an addition step of 0.001 to 0.5% by weight of a chelating agent and an addition step of an inorganic reducing agent, wherein the monomer is methoxy phenols in terms of large acrylic acid. 10 to 200 ppm, and after the drying step and / or the surface crosslinking step, controlling the moisture content of the polymer to 3 to 15% by weight, even more preferably, adding the inorganic reducing agent to the hydrous gel-like crosslinked polymer before drying. It features. Such a manufacturing method and the specific example of the 3 are shown in Examples 3-1 to 3-13 and Tables 8-9 which will be described later.

According to the particulate water absorbing agent according to the present invention, it is possible to provide a particulate water absorbing agent for an absorbent body which has excellent time-coloring preventing performance, has no odor and is excellent in urine resistance, and is very suitable in practical use.

1 is a side view showing a schematic configuration of an apparatus for measuring AAP (pressure absorption magnification under pressure) according to the present embodiment.
2 is a side view showing a schematic configuration of a measuring apparatus of SFC (saline flow inducibility) according to the present embodiment.
3 is an electron micrograph of representative granulated particles.

EMBODIMENT OF THE INVENTION Hereinafter, although this invention is demonstrated, the scope of the present invention is not restrained by these description, and it can change suitably in the range which does not impair the meaning of this invention other than the following illustration.

First, the abbreviation used below is defined.

In this specification, "CRC" (Centrifuge Retention_Capacity) is "centrifuge retention capacity" and means the value obtained by the measuring method described in the Example mentioned later. "CRC" is also called "absorption rate under no pressure" or only "absorption rate". In addition, "SFC" (Saline®Flow®Conductivity) is "saline flow inductive" and means the value obtained by the measuring method as described in the Example mentioned later. In addition, "AAP" (Absorbency-against-Pressure) is "absorption rate under pressure" with respect to 4.83 kPa or 2.0 kPa, and means the value obtained by the measuring method as described in the Example mentioned later. In addition, "FSR" (Free Swell_Rate) is a "absorption rate" and means the value obtained by the measuring method as described in the Example mentioned later. In addition, "D50" (Distribution) is a "weight average particle diameter", and means the value obtained by the measuring method as described in the Example mentioned later. In addition, "σξ" is "the logarithmic standard deviation of particle size distribution", and means the value obtained by the measuring method as described in the Example mentioned later. In addition, "FHA" (Fixed Height Height Absorption) is "fixed height absorption" and means the value obtained by the measuring method described in the Example mentioned later. "Vortex" is a "absorption rate" on it, and means the value obtained by the measuring method as described in the Example mentioned later.

In addition, in this specification, "saline solution" means "aqueous solution of sodium chloride", and "X? Y" which shows the range means "X or more and Y or less", and "ppm" means especially unless there is a tin. "Ppm" or "mass ppm", "? Acid (salt)" means "? Acid and / or its salt", and "(meth) acryl" means "acrylic and / or methacryl". do.

The particulate water absorbing agent according to the present invention contains a polyacrylic acid (salt) -based water absorbent resin as a main component, a chelating agent having a content of 0.001 to 0.5% by weight, and an inorganic reducing agent, and any one of the following (1) to (3): It is an absorption solidifying agent of an aqueous liquid satisfying more than two pieces.

(1) Content of 5-60 ppm of methoxy phenols,

(2) containing water-insoluble inorganic fine particles,

(3) Water content is 3-15 weight%.

It is essential that the particulate water absorbing agent of the present invention satisfies any one or more of the above (1) to (3), preferably an aqueous solidifying agent for satisfying any two or more, particularly preferably three at the same time. However, if the chelating agent and the inorganic reducing agent are not used in combination within the above range, the effect of preventing coloring or deterioration is low. In coloring and deterioration prevention, said (1) methoxy phenols and said (2) water-insoluble inorganic fine particle contribute to prevention of deterioration and also prevention of coloring. In addition, the moisture content (3) affects the coloring (for example, Comparative Example 3-8 of the present application), and also contributes to the absorption rate (for example, Example 1-16 of the present application), and furthermore, odor or dust problems. Solve. Especially, in order to solve the subject of this invention, it is preferable that content of said (1) methoxy phenols is 5-60 ppm, and when said (3) moisture content is 3-15 weight%, said (2) number It is preferable to contain insoluble inorganic fine particles. That is, in the method of using a chelating agent and an inorganic reducing agent together within the above ranges, any of the above (1) to (3) affects the prevention of coloration or prevention of deterioration, and in the present invention, at least one of them, preferably Two or more, particularly preferably three, are selected.

In addition, a "main component" means that content of a water absorbent resin is 50 weight% or more with respect to the whole water absorbent, and content of a water absorbent resin is the water content of all the water absorbents containing a chelating agent and an inorganic reducing agent as essential, Preferably it is 3? Since it is 15 weight%, it contains less than 97 weight% of water absorbing resin, and the minimum of water absorbing resin is 60 weight% or more, 70 weight% or more on it, especially 80 weight% or more, and 85 weight% or more on it. Moreover, when moisture content is less than 3 weight%, content of a water absorbing resin is 60 weight% or more and less than 99.999 weight%, More preferably, it is 70 weight% or more and less than 99.9 weight%, More preferably, it is 80 weight% or more and less than 99.7 weight%. Especially preferably, they are 90 weight% or more and less than 99.5 weight%.

The particulate water absorbing agent of the present invention refers to an absorption solidifying agent (alias; gelling agent) of an aqueous liquid containing a polyacrylic acid (salt) -based water absorbing resin as a main component. The aqueous liquid is not limited to water, but may include urine, blood, feces, waste liquid, moisture, steam, ice, a mixture of water with an organic solvent or an inorganic solvent, rain water, ground water, and the like, as long as they contain water. Although it does not restrict | limit especially, Preferably, the particulate water absorbing agent of this invention turns into absorption solidification agent of urine, especially human urine.

It is preferable that the particulate water absorbing agent which concerns on this invention is an absorption solidifying agent of the aqueous liquid containing the (alpha)-hydroxy carboxylic acid compound further, in order to prevent coloring or deterioration.

It is preferable that the particulate water absorbing agent which concerns on this invention is an absorption solidification agent of the aqueous liquid containing a polyvalent metal salt and / or a cationic polymer further in order to prevent deterioration and improve fluid permeability. Conventionally, when a polyvalent metal salt and / or a cationic polymer is used, the coloring problem of the obtained absorbent tends to occur, but there is no such problem in the present invention.

The particulate water absorbing agent according to the present invention can provide an excellent water absorbing performance, and also has an excellent anti-coloring performance, has no odor, and can provide a particulate water absorbing agent for an absorbent which is very suitable for practical use with excellent urine resistance. have.

[1] polyacrylic acid (salt) -based water absorbent resin, [2] chelating agent, [3] inorganic reducing agent, [4] methoxy phenol, [5] water-insoluble inorganic fine particles, [6] α-hydroxy carboxylic acid The compound, [7] polyvalent metal salt and / or cationic polymer, [8] granulation, [9] particulate absorbent, [10] particulate absorbent manufacturing method, and [11] absorber will be described in order.

[1] polyacrylic acid (salt) absorbent polymers

(1-1) monomer

The water absorbent resin used for the particulate water absorbent of the present invention optionally includes a graft component and has a structural unit derived from acrylic acid. Preferably, this water absorbing resin has the structural unit derived from acrylic acid as a main component. Although the manufacturing method of this water absorbing resin is not specifically limited, Preferably this water absorbing resin is obtained by superposing | polymerizing the monomer component which has acrylic acid and / or its salt as a main component.

In addition, the structural unit derived from the said monomer corresponds to the structure which the polymerizable double bond of each monomer opened by the polymerization reaction, for example. The structure in which a polymerizable double bond was opened is a structure in which the double bond (C = C) between carbons became a single bond (-C-C-), for example.

In this invention, the water absorbing resin used for a particulate water absorbing agent is a water swellable water insoluble polymer which introduce | transduced the crosslinked structure into the polymer.

In addition, "water swellability" means the absorption ratio under pressure (CRC) with respect to physiological saline is 2 [g / g] or more, Preferably it is 5-200 [g / g], More preferably, it is 20-100 [g / g], and "water insoluble" means that the water-soluble content in the water absorbent resin is essentially 50% by weight or less, preferably 0 to 25% by weight, more preferably 0 to 15% by weight, Even more preferably, it is 0 to 10 weight%, and it says substantially water-insoluble. These "water swellability (CRC)" and "water insoluble (water-soluble)" are calculated | required by the measuring method prescribed | regulated in the Example mentioned later.

In the present invention, the polyacrylic acid (salt) -based water absorbent resin is essentially 50 to 100 mol%, more preferably 50 to 100 mol% of the total mole% of acrylic acid and / or its salt in the total monomer (except the crosslinking agent) used for the polymerization. Preferably it is 70-100 mol%, More preferably, it is 90-100 mol%, Especially preferably, it is a thing of 100 mol% real. In addition, polyacrylic acid is not only limited to the polymer of acrylic acid, but is also a concept containing polyacrylic acid (salt) which is a hydrolyzate of polyacrylonitrile and polyacrylamide, but polyacrylic acid obtained by superposition | polymerization of acrylic acid mentioned later from a physical property point of view This is preferred.

Examples of the acrylate used in the present invention include alkali metal salts such as lithium salts, sodium salts and potassium salts; Ammonium salts; Monovalent salts of acrylic acid such as amine salts are usually used, and preferably alkali metal salts of acrylic acid are used, and more preferably sodium salts or potassium salts of acrylic acid. Moreover, you may use together polyvalent metal salts, such as a calcium salt and an aluminum salt, in the range which has water swellability.

The neutralization rate of the water absorbing resin obtained in this invention becomes like this. Preferably it is 10 mol% or more and less than 90 mol% with respect to an acidic radical, More preferably, it is 40 mol% or more and less than 80 mol% with respect to an acidic radical, More preferably, It is 50 mol% or more and less than 74 mol% with respect to an acidic radical. If the neutralization rate is less than 10 mol%, the absorption performance, in particular, the absorption magnification may be considerably lowered, and if the neutralization rate is 90 mol% or more, the absorbent having a high absorption performance, in particular, the absorption magnification under pressure, It may not be obtained and is not preferable. Moreover, it is especially preferable to make a neutralization rate less than 74 mol% from the viewpoint of water absorption performance below 72 mol% on it. That is, also in the method of this invention, when neutralization rate is high, there exists a tendency to color, and therefore, the upper limit of neutralization rate becomes the said range.

The said neutralization process may be performed about the monomer component before superposition | polymerization, and may be performed about the hydrous gel-like crosslinked polymer during superposition | polymerization or after superposition | polymerization. Moreover, you may use together neutralization of a monomer component, and neutralization of a hydrous gel-like crosslinked polymer. Preferably, neutralization is made with acrylic acid as the monomer component.

The moisture content (prescribed by the measuring method of this specification) of the water absorbing resin obtained in this invention is in the range mentioned later in the drying process, surface crosslinking process, etc. which are mentioned later, and the moisture content of the particulate water absorbing agent as a final product is 3-15 weight%. It is desirable to adjust. As a matter of course, when the particulate water absorbent according to the present invention does not satisfy the requirements of the above (1) and (2), the moisture content of the particulate water absorbent as the final product is always adjusted to 3 to 15% by weight. When the water content is higher than 15% by weight, the obtained absorbent tends to be colored, and when less than 3% by weight, problems of odor and dust may occur.

(1-2) Monomers other than acrylic acid (salt)

Although acrylic acid (salt) is used in said range as a monomer in this invention, you may use other monomers together. When using monomers other than acrylic acid (salt), the usage-amount of monomers other than acrylic acid (salt) is 0-50 mol% with respect to the total amount of acrylic acid (salt) and other monomers used as a main component, Preferably it is 0-30 mol. %, More preferably, it is 0-10 mol%. By using monomers other than acrylic acid (salt) in the said ratio, the water absorption characteristic of the finally obtained particulate absorbent can be improved further, and a particulate water absorbent can be obtained further at low cost.

As a monomer used together besides acrylic acid (salt), the monomer illustrated by the below-mentioned US patent or European patent is mentioned, for example. Specifically, a water-soluble or hydrophobic unsaturated monomer etc. are mentioned as a monomer used together. As a water-soluble or hydrophobic unsaturated monomer, methacrylic acid, (anhydride) maleic acid, fumaric acid, crotonic acid, itaconic acid, vinyl sulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, (meth) Acryloxyalkanesulfonic acid and its alkali metal salt, ammonium salt, N-vinyl-2-pyrrolidone, N-vinylacetamide, (meth) acrylamide, N-isopropyl (meth) acrylamide, N, N-dimethyl (meth ) Acrylamide, 2-hydroxyethyl (meth) acrylate, methoxy polyethylene glycol (meth) acrylate, polyethyleneglycol (meth) acrylate, isobutylene, lauryl (meth) acrylate, etc. are mentioned. The particulate water absorbing agent according to the present invention also includes a copolymerized component of the water-soluble or hydrophobic unsaturated monomer.

(1-3) Internal Crosslinking Agent

The crosslinking method used in the present invention is not particularly limited, and examples thereof include a method of adding a crosslinking agent during polymerization or after polymerization and then crosslinking, a radical crosslinking by a radical polymerization initiator, a radiation crosslinking by an electron beam, or the like. However, a method of carrying out polymerization by adding a predetermined amount of internal crosslinking agent to the monomer in advance and performing a crosslinking reaction simultaneously with or after polymerization is preferred.

As an internal crosslinking agent used by this invention, N, N'-methylenebisacrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, (polyoxy Ethylene) trimethylolpropane tri (meth) acrylate, (polyoxyethylene) glycerol tri (meth) acrylate, trimethylolpropanedi (meth) acrylate, polyethylene glycol di (β-acryloyloxypropionate), Trimethylolpropane tri (β-acryloyloxypropionate), poly (meth) aryloxyalkane, polyethylene glycol diglycidyl ether, ethylene glycol, propylene glycol, glycerin, butanediol, erythritol, xylitol, sorbitol, polyethylene glycol These etc. are mentioned, These 1 type, or 2 or more types are used. In addition, when using 1 or more types of internal crosslinking agents, it is preferable to use the compound which has two or more polymerizable unsaturated groups at the time of superposition | polymerization in consideration of the water absorption characteristic of the water absorbing resin obtained, etc.

The internal crosslinking agent is preferably 0.005 to 2 mol%, more preferably 0.01 to 1 mol%, still more preferably 0.05 to 0.2 mol% with respect to the monomer. When the usage-amount of the said internal crosslinking agent is less than 0.005 mol%, or more than 2 mol%, there exists a possibility that a desired absorption characteristic may not be obtained.

(1-4) polymerization concentration

In the polymerization step, when the monomer component is an aqueous solution, the concentration of the monomer component in the aqueous solution (hereinafter referred to as the monomer aqueous solution) is appropriately determined by the kind and the physical properties of the monomer, and is not particularly limited, but in terms of physical properties Preferably it is 10-70 weight%, More preferably, it is 15-65 weight%, More preferably, it is 30-55 weight%. Moreover, you may use together solvents other than water as needed, and the kind of solvent which can be used together is not specifically limited. The monomer concentration may be a slurry that exceeds the saturation concentration, but is preferably in the above range, still more preferably at most the saturation concentration.

(1-5) Other Ingredients

Moreover, in polymerization, water-soluble resin (for example, starch, cellulose, polyvinyl alcohol) or water absorbent resin (or its fine powder) is used with respect to the monomer which has acrylic acid (salt) as a main component, for example, 0-50. By weight%, Preferably 0-20 weight% may be added and the general physical properties of a water absorbing resin may be improved. In polymerization, various blowing agents (carbonates, azo compounds, bubbles, etc.), surfactants, chelating agents, chain transfer agents and the like are, for example, 0 to 5% by weight, preferably 0 to 1, based on the monomers. % May be added to improve the overall physical properties of the water absorbent resin. In addition, use of the said water-soluble resin or water absorbing resin gives a graft polymer (for example, starch graft polymer and PVA graft polymer), but these are also generically called polyacrylic acid (salt) type water absorbing resin in this invention.

(1-6) Polymerization Process

In the present invention, reverse phase suspension polymerization, aqueous solution polymerization, spraying, or droplet polymerization can be applied. However, in the polymerization of the monomer aqueous solution, the aqueous phase polymerization or reverse phase suspension polymerization can be carried out from the viewpoint of the performance and the ease of control of the polymerization. It is preferable to carry out. These polymerizations can be carried out even under an air atmosphere. Preferably, the polymerization is carried out in an inert gas atmosphere (for example, 1 vol% or less of oxygen) such as nitrogen or argon, and the dissolved oxygen of the monomer component is inert. It is preferably used for polymerization after being sufficiently substituted (eg, less than 1 [mg / L] oxygen) with gas. In the present invention, continuous belt polymerization is particularly suitable for aqueous solution polymerization, in which polymerization control has been difficult to obtain high productivity and high physical properties of water-absorbent resins, and as a particularly preferred aqueous solution polymerization (US Patent No. 4893999, US Patent No. 6241928 or US Patent). Patent Application Publication No. 2005/215734, etc.), and BATCH KNEADER polymerization (described in US Pat. No. 6,871,151, US Pat. No. 6,141,141, etc.).

Aqueous polymerization is a method of polymerizing an aqueous monomer solution without using a dispersing solvent. For example, U.S. Pat.Nos. 4,500,501,48,73299, 4,428,602, 4,736,32,49,518, 5124416, 5250640, 55264495, 5145906, 5330808, etc., US Patents 0,083,36, 00955086, 0922717, 1178059, etc. Described in European patents. The monomers, crosslinking agents, polymerization initiators, and other additives described in these US patents and European patents can also be applied in the present invention.

Reverse phase suspension polymerization is a polymerization method in which a monomer aqueous solution is suspended in a hydrophobic organic solvent. For example, U.S. Patent Nos. 4093776, 4,367,323, 4,626, 1,468,274, 52,735, etc. Described in the patent.

In addition, in the present invention, in order to achieve the improvement of absorption characteristics and time-lapse coloration, which are also subjects of the present invention, the total time from the time of adjusting the monomer components to the start of polymerization is preferable. And, the total time of these is preferably within 24 hours, more preferably within 12 hours, even more preferably within 3 hours, particularly preferably within 1 hour.

Industrially, since the neutralization and the adjustment of the monomer component are carried out in large quantities in tanks, the residence time, that is, the total time usually exceeds 24 hours, but the time after the adjustment of the monomer component and / or the neutralization of acrylic acid (described above) The longer the total time), the higher the residual monomer and the yellowing phenomenon (coloring with time) of the water absorbent resin. Accordingly, in order to shorten the residence time, preferably, batch neutralization or continuous polymerization is carried out by continuous neutralization and continuous monomer component adjustment, and more preferably continuous polymerization is performed.

In the aqueous solution polymerization method, the polymerization start temperature of the monomer aqueous solution is preferably at least 40 ° C, more preferably at least 50 ° C, at least 60 ° C, particularly at least 70 ° C. When the production method according to the present invention is applied to the hydrous gel obtained by such high temperature polymerization (high temperature start polymerization), the effect of the present invention can be exhibited to the maximum including particle size control. In addition, an upper limit is below the boiling point of aqueous solution, Preferably it is 105 degrees C or less.

Moreover, the high temperature superposition | polymerization (boiling polymerization) of the peak temperature of polymerization temperature is 95 degreeC or more, More preferably, it is 100 degreeC or more, More preferably, it is 105 degreeC or more. When the present invention is applied to the hydrogel obtained by such boiling polymerization, the effect of the present invention can be maximized, including particle size control. Moreover, an upper limit is enough below boiling point, Preferably it is 130 degrees C or less, More preferably, it is 120 degrees C or less.

In order to exhibit the effect of this invention further, a polymerization process is aqueous solution polymerization. In aqueous solution polymerization, acrylic acid may be neutralized in advance or neutralized after polymerization, but in order to improve the relative relationship between the opposite absorption ratio (CRC) and the soluble fraction, a granular step of hydrogel polymer is included during or after polymerization. The monomer contains acrylic acid as a main component and includes a neutralization step of the hydrous gel-like crosslinked polymer after polymerization.

In addition, when the reducing agent is mixed after the polymerization, the high-crosslinked polymer gel may have difficulty in mixing the neutralizing agent or the reducing agent due to the high gel strength. Therefore, from the ease of uniform mixing, the hydrogel-like crosslinked polymer after polymerization and before drying It is preferable to further crosslink. The crosslinking agent which reacts with a carboxyl group can be used for bridge | crosslinking like the surface crosslinking agent mentioned later, A polyglycidyl compound, a polyhydroxy compound, etc. can be used suitably, The usage-amount is preferably 0.001? 2 mol%, More preferably, it is 0.01-1 mol%, Especially preferably, it can determine suitably in 0.05-0.5 mol%.

Moreover, polymerization time is not specifically limited, either, What is necessary is just to determine suitably according to the kind of hydrophilic monomer, a polymerization initiator, reaction temperature, etc., Usually, it is 0.5 minutes-3 hours, Preferably it is 1 minute-1 hour.

Moreover, also from the point of control of the methoxy phenols (especially p-methoxy phenol) in the obtained absorbent (preferably 5-60 ppm in the absorbent), in the present invention, the polymerization step is preferably a methoxy phenol (especially p- Methoxy phenol) maximum monomer temperature of 0.001-1 mol% of the monomer aqueous solution of monomer concentration of 30-55 weight% containing 90-100 mol% of acrylic acid (salt) in the monomer containing 10-200 ppm of radical polymerization initiators Is 130 ° C. or less, and the polymerization step is preferably a step of performing aqueous solution polymerization or reverse phase suspension polymerization under conditions of 0.5 minutes to 3 hours, and the total mole% of acrylic acid and / or its salt in the above or the following range thereon, and monomers thereon. Concentration of components, amount of polymerization initiator used, peak temperature of polymerization temperature, polymerization time and the like.

When the monomer aqueous solution is polymerized, for example, persulfates such as potassium persulfate, ammonium persulfate and sodium persulfate, hydroperoxides such as t-butyl hydroperoxide and hydrogen peroxide, and 2,2'-azobis (2- Radical polymerization initiators, such as azo compounds, such as amidino propane) dihydrochloride, 2-hydroxy-1-phenyl-propane-1-one, and benzoin methyl ether, and L which promotes decomposition | disassembly of these radical polymerization initiators further -Redox-type initiator etc. which used reducing agents, such as ascorbic acid, are used. The usage-amount of a polymerization initiator is the range of 0.001-1 mol% or 0.001-0.5 mol% normally with respect to a monomer.

When superposing | polymerizing with the said redox-type initiator, it is preferable to use a persulfate, a peroxide, and the said reducing agent together, and as a reducing agent, (heavy) sulfite (salt), such as sodium sulfite and sodium hydrogen sulfite, L-ascor Reducing metals (salts), such as a poor acid (salt) and ferrous salt, amines, etc. are mentioned. As for the usage-amount of these reducing agents, 0.0001-0.02 mol% is preferable normally with respect to a monomer component.

Instead of using a polymerization initiator, a polymerization reaction may be carried out by irradiating the reaction system with active energy rays such as radiation, electron beams and ultraviolet rays. Moreover, you may use together an active energy ray, such as radiation, an electron beam, an ultraviolet-ray, and a polymerization initiator.

Moreover, it is preferable to add the methoxy phenols (especially p-methoxy phenol) mentioned later, and also to add a chelating agent to the aqueous monomer solution at the time of superposition | polymerization or superposition | polymerization in the point which can demonstrate the effect of this invention further.

In the present invention, reverse phase suspension polymerization, aqueous solution polymerization, spray polymerization or droplet polymerization can be applied. However, in order to further exhibit the effects of the present invention, the polymerization step is preferably aqueous solution polymerization. In aqueous solution polymerization, acrylic acid may be neutralized in advance or neutralized after polymerization, but in order to improve the relative relationship between the opposite absorption ratio (CRC) and the water-soluble component, the hydrogel polymer may be further broken down after polymerization (1-7). Process.

(1-7) Gel Granulation Process

Although the hydrogel-like crosslinked polymer obtained by polymerization may be dried as it is, it is preferable to refine the hydrogel-like crosslinked polymer during or after polymerization. Further, if necessary, fine granulation is carried out using a gel crusher or the like, and preferably 0.1 to 3 mm in weight average particle diameter (prescribed by body classification), and 0.5 to 2 mm thereon. After being granulated, it is dried. The shape of the polyacrylic acid (salt) -based water absorbent resin of the present invention can be in any form without particular limitation, for example, in granular form, powder form, flake form, or fibrous form.

Therefore, the granulation is carried out by various methods, but is extruded from a screw extruder having a porous structure of any shape after granulation during polymerization in the kneader polymerization or polymerization in belt polymerization or tank polymerization. The method of disintegration can be illustrated. In extrusion disintegration, color change can be further reduced by adding the chelating agent described later in the form of an aqueous solution.

In the present invention, an inorganic reducing agent is preferably added simultaneously with the granulation of the hydrous gel-like crosslinked polymer. In the gel granulation step, by mixing and kneading the hydrogel and the inorganic reducing agent, the effect of the present invention can be achieved at a higher level. In addition, when an inorganic reducing agent is added before the drying step, such as a gel granulation step or a polymerization step (during), the water content of the present invention is preferably 3 to 15% by weight in view of the problem of odor as described below. In addition, in the manufacturing method of the absorbent of this invention, it is preferable to control the water content of a polymer at 3-15 weight% after a drying process and a surface crosslinking process.

When the inorganic reducing agent (additionally, the chelating agent or α-hydroxy carboxylic acid compound) is added after the particulate form such as reverse phase suspension polymerization, the inorganic reducing agent is mixed only on the surface of the absorbent resin, but in view of the effect of the present invention It is preferable that the chelating agent and the α-hydroxy carboxylic acid compound are mixed with the inorganic reducing agent and, if necessary, not only the surface of the absorbent resin particles but also the inside thereof. Therefore, it is preferable to knead | mix the said polymeric reducing agent (especially block gel or sheet-like gel) after aqueous solution polymerization, and the said inorganic reducing agent etc. simultaneously.

Also, kneaders or screw-type extruders (alias, "meat choppers") are very suitable for fine-graining and mixing (especially kneading), and they may be used in plural in series, and other devices such as kneaders and meat choppers You may use together. One screw extruder may be sufficient and two or more screw extruders may be used.

(1-8) Drying Process

The drying step in the method for producing a particulate water absorbent of the present invention is a hydrous gel obtained by a polymerization step, preferably a hydrous gel, and even more preferably a hydrogel having a weight average particle diameter of 0.1 to 3 mm defined by body classification. It is a process of drying gel.

As a drying method, one of various methods, such as heat drying, hot air drying, vacuum drying, fluidized bed drying, infrared drying, microwave drying, drum dryer drying, azeotropic dehydration with a hydrophobic organic solvent, and high humidity drying using high temperature water vapor Or 2 or more types can be employ | adopted. As preferable embodiment, dew point 40-40 degreeC, More preferably, contact drying with the gas of 50-90 degreeC can be illustrated. When using hot air drying, the wind speed (speed of the wind passing vertically with respect to the drying object spreading horizontally) is preferably 0.01 to 10 [m / sec], more preferably 0.1 to 5 [m / sec]. Range.

Although the drying temperature used very suitably in this invention is not restrict | limited, For example, the range of 50-300 degreeC (it is preferable to carry out under reduced pressure in the case of 100 degrees C or less), Preferably it is 100-250 degreeC. More preferably, it is 130-220 degreeC, Especially preferably, it is the temperature range of 150-200 degreeC. Drying time is 10 to 120 minutes normally, More preferably, it is 20 to 90 minutes, More preferably, it is 30 to 60 minutes. If the drying time is less than 10 minutes, it is considered that the change occurring in the polymer chain inside the absorbent resin is small, whereby a sufficient improvement effect is not obtained, and thus the improvement effect of the overall physical properties may not be seen. Moreover, when drying time is 120 minutes or more, as a result of damaging an absorbent resin, a water-soluble content may increase and the improvement effect of general physical properties may not be found.

That is, in the present invention, in terms of the control of the methoxy phenol and the adjustment of the moisture content, preferably, the drying step is performed by drying the particulate hydrogel to have a water content of 20% by weight or less at a drying temperature of 100 to 250 ° C and a drying time of 10 to 120 minutes. It is preferable that it is a process of implementing, Moreover, it is a drying temperature, drying time, and water content of the said or the following range.

In the drying process of this invention, it is preferable to dry until the water content of the hydrogel-like crosslinked polymer obtained by the said superposition | polymerization becomes 20 weight% or less, It is more preferable to dry to 15 weight% or less, It is 10 weight% or less It is especially preferable to dry to. Here, as water content after drying, it is preferable in order of 2 weight% or more, 3 weight% or more, 4 weight% or more, 5 weight% or more, 6 weight% or more, 7 weight% or more, and the water content after drying is more than such a lower limit. By using it, the problem of odor by using a reducing agent can be suppressed. Water content in these ranges becomes like this. Preferably it is 2-20 weight%, More preferably, it is 3-15 weight%, More preferably, it is 5-15 weight%, Especially preferably, it is 7-15 weight%. Further, the drying step (1-8) and the surface crosslinking step (1-10) described later may be performed simultaneously. Further, a surface crosslinking agent may be added during the drying step, and further to the water content at the same time as the surface crosslinking or after the surface crosslinking. You may dry.

In the present invention, with respect to the water content of the final absorbent after the drying step, if the water content is high, the remaining monomers are likely to remain, and subsequent handling properties are poor, and even if the water content is high even when the chelating agent and the inorganic reducing agent are used together, the color is easy to be colored. Found. In addition, when the moisture content is low, productivity and physical properties (for example, absorption rate) decrease due to excessive drying, or when a reducing agent is used before drying, problems of odor may occur. In addition, Patent Document 17 (European Patent No. 1645596) and Patent Document 15 (US Patent Application Publication No. 2005/0856604) do not disclose the use of a specific amount of p-methoxy phenol or water-insoluble fine particles. In addition, the importance of the specific moisture content (3-15 wt%, 4-14 wt%, 6-12 wt%, 7-11 wt%) as an absorbent is not disclosed.

When an inorganic reducing agent is added before the drying step, the problem of the odor is found, and in the present invention, such a problem is solved by controlling the moisture content. This odor is a complex odor of a trace component such as a hydrous gel or a residual monomer after polymerization and a reducing agent, rather than a simple decomposition of a reducing agent, and is estimated to occur by lowering the water content of the water absorbent resin to a predetermined value or less. It was found that the water content in the surface crosslinking process described later is very important. Moreover, when the moisture content after drying is too high, it may be accompanied by the fall of productivity in grinding | pulverization and classification mentioned later, and it is unpreferable.

(1-9) Grinding and classification process

The water absorbent resin of the present invention obtained by drying may be subjected to a process such as pulverization and classification for controlling the particle size as necessary according to the purpose. These methods are described, for example, in International Publication No. 2004/69915.

Dry polymer is obtained by drying the hydrous gel-like crosslinked polymer after superposition | polymerization. A dry polymer may be used as a dry powder (preferably 80 weight% or more of solid content) as it is, and you may adjust a particle size after drying as needed. The water-absorbent resin after drying is preferably a specific particle size for improving the physical properties in the surface crosslinking described later. The particle size can be appropriately adjusted by polymerization, pulverization, classification, granulation, fine powder recovery, and the like.

As the weight average particle diameter (D50) of the water absorbent resin (denoted as the water absorbent resin powder in the examples herein) before the surface crosslinking, 200 to 550 µm, preferably 250 to 500 µm, more preferably 300 to 450 µm, particularly preferred. It is adjusted to 350-400 micrometers. Moreover, it is so good that there are few particles less than 150 micrometers. The weight ratio of the particle | grains whose particle size is less than 150 micrometers with respect to the weight of the whole dry polymer is 0-5 weight% normally, Preferably it is 0-3 weight%, Especially preferably, it is adjusted to 0-1 weight%. In addition, the smaller the particle size of 850 µm or more, the better. The weight ratio of the particle | grains of 850 micrometers or more with respect to the weight of the whole dry polymer is 0-5 weight% normally, Preferably it is 0-3 weight%, Especially preferably, it is adjusted to 0-1 weight%. The logarithmic standard deviation (σξ) of the particle size distribution is preferably 0.20 to 0.45, preferably 0.27 to 0.40, preferably 0.25 to 0.37. Such particle size is preferably also applied to the water absorbent resin after the surface crosslinking and the water absorbent of the final product. Therefore, a classification step and a pulverization step are preferably provided after the surface crosslinking step or after the addition of the chelating agent or the inorganic reducing agent.

(1-10) Surface Crosslinking Process

The particulate water absorbing agent obtained in the present invention can be made a very suitable absorbent for sanitary materials further through a conventionally known surface crosslinking treatment step. Surface crosslinking is to provide a part having a high crosslinking density in addition to the surface layer of the water absorbent resin (near the surface: usually around 10 μm on the surface of the water absorbent resin), and crosslinking reaction with radical crosslinking on the surface, surface polymerization, or a surface crosslinking agent. Or the like.

As the surface crosslinking agent which can be used in the present invention, various organic or inorganic crosslinking agents can be exemplified as the functional group of the polyacrylic acid-based water absorbent resin and an ionic or covalent surface crosslinking agent (preferably a covalent surface crosslinking agent). However, from the viewpoint of physical properties and handleability, a crosslinking agent capable of reacting with a carboxyl group can be preferably used. For example, polyhydric alcohol compounds, polyhydric epoxy compounds represented by polyhydric glycidyl compounds, polyhydric amine compounds or condensates with halo epoxy compounds, oxazoline compounds, mono, di, or polyoxazolidinone compounds, polyvalent metal salts 1 type, or 2 or more types, such as an alkylene carbonate compound, an oxetane compound, a cyclic urea compound, can be illustrated.

More specifically, the compounds exemplified in US Pat. No. 6,258,30,976,6254990 and the like can be given. For example, mono, di, tri, tetra or polyethylene glycol, monopropylene glycol, 1,3-propanediol, dipropylene glycol, 2,3,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerin , Polyglycerol, 2-butene-1,4-diol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol Polyhydric alcohol compounds; Epoxy compounds such as ethylene glycol diglycidyl ether and glycidol; Polyvalent amine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyethyleneimine and polyamide polyamine; Halo epoxy compounds such as epichlorohydrin, epibromhydrin and α-methyl epichlorohydrin; A condensate of the polyvalent amine compound and the halo epoxy compound; Oxazolidinones such as 2-oxazolidinones; Alkylene carbonate compounds such as ethylene carbonate; Oxetane compound; Although cyclic urea compounds, such as 2-imidazolidinone, etc. are mentioned, It is not specifically limited.

Among these surface crosslinking agents, in order to improve AAP and SFC, as the surface crosslinking agent, a dehydrating reactive crosslinking agent selected from a polyhydric alcohol compound, an oxazolidinone compound, and an alkylene carbonate compound is suitably used. In order to control to the water content of 3-15 weight% mentioned later, the polyhydric epoxy compound represented by the polyhydric glycidyl compound is used suitably as a surface crosslinking agent.

Although the usage-amount of a surface crosslinking agent is based also on the compound to be used, its combination, etc., the inside of 0.001 weight part-10 weight part is preferable with respect to 100 weight part of water absorbent resin powder, and the inside of the range which is 0.01 weight part-5 weight part is more preferable. In the present invention, water may be used in accordance with the surface crosslinking agent. At this time, the amount of water used is preferably 0.5 to 20 parts by weight, more preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the water absorbent resin powder. In the present invention, it is also possible to use a hydrophilic organic solvent in addition to water.

At this time, the quantity of the hydrophilic organic solvent used is 0-10 weight part with respect to 100 weight part of water absorbing resin powder, Preferably it is the range of 0-5 weight part. Moreover, in mixing of the crosslinking agent solution into the water absorbent resin powder, the range which does not prevent the effect of this invention, for example, 0-10 weight% or less, Preferably it is 0-5 weight%, More preferably, it is 0-1. It is weight% and you may coexist water insoluble inorganic fine particles and surfactant. Surfactants used and the amount thereof used are exemplified in US Pat.

As a mixer used for mixing the surface crosslinker solution, various mixers may be used. Preferably, a high speed stirring mixer, in particular a high speed stirring continuous mixer, is preferable, for example, a trade name Turbulizer ) (Made by Hosokawa Micron Co., Ltd. of Japan), a brand name reggae mixer (made by the German reggae company), etc. can be illustrated.

Surface treatment in the manufacturing method of the particulate water absorbing agent of this invention is a process of performing surface crosslinking reaction for increasing the crosslinking density of the surface of a water absorbent resin. In order to obtain the desired performance of the particulate water absorbent of the present invention, the water absorbent resin after mixing the surface crosslinking agent is preferably heat treated, and then cooled after necessity.

The heating temperature (heating temperature) of the said heat processing is 70-300 degreeC, for example, Preferably it is 120-250 degreeC, More preferably, it is 150-250 degreeC, The heating time becomes like this. It is in the range of 1 minute-2 hours. Heat processing can be performed using a normal dryer or a heating furnace. Here, when using high temperature surface crosslinking, such as 150-250 degreeC, or dehydrating reactive surface agents (of the carboxyl group of a water absorbent resin), such as a polyhydric alcohol, a water absorbing resin is further dried and water content after surface crosslinking is less than 3%, especially 1%. It tends to be less.

In particular, in the case of producing a particulate water absorbing agent having a water content of 3 to 15% by weight, the heating temperature (the fruit temperature and the material temperature) is preferably carried out at a temperature range of 80 to 250 ° C, more preferably of 80 to 160 ° C. It is a temperature range, More preferably, it is a temperature range of 80-120 degreeC, Most preferably, it is a temperature range of 80-100 degreeC. When the heating time is less than 80 ° C., the surface crosslinking of the water absorbent resin is not sufficient, and the absorption magnification and saline flow induction rate under pressure are low. In order to control to 3-15 weight% of water content, the polyhydric epoxy compound represented by the polyhydric glycidyl compound is used suitably as a surface crosslinking agent. Moreover, when it is higher than 250 degreeC, when a particulate water absorbing agent colors or produces unpleasant odor, it is not preferable. In addition, the water content of the water absorbent resin is not limited only to the heating temperature, but depends on the heating time, the pressure (decompression) of the reaction apparatus, the dew point, the production amount (the throughput per unit time), and the like. Since the material temperature of the resin is generally lower than the heating temperature, it is also preferable to obtain an absorbent having a predetermined water content by maintaining the material temperature below the boiling point of water and heating it.

These surface crosslinking treatment methods are various European patents such as European Patent No. 049240, No. 0605150, No. 0450923, No. 0812873, No. 0450924, No. 0668080, and Japanese Patent Laid-Open No. 7- 242709, various Japanese patents, such as US Pat. No. 7-224304, US Pat. No. 5409771, US 55597873, US 5385983, US 5610220, US 5633316, US 5674633, US 5546972 Various U.S. Patents, such as US Patent Application Publication No. 99/42494, US Patent Application Publication No. 99/43720, US Patent Application Publication No. 99/42496, etc., and the like, can also be applied to the present invention. have. In the surface crosslinking treatment step, after the crosslinking reaction, a water-soluble polyvalent metal salt such as an aqueous aluminum sulfate solution may be further added. These methods are also described in International Publication Nos. 2004/69915, 2004/69293, and the like, and are applicable to the present invention.

In the present invention, also in terms of controlling methoxy phenol, the surface crosslinking step is preferably 0.001 to 10 parts by weight of the surface crosslinking agent with respect to 100 parts by weight of the water absorbent resin powder after the drying step, followed by 1 minute at 70 to 300 ° C. It is performed by heat processing for 2 hours, and is the said or following surface crosslinking agent and its quantity, heating temperature, and time further.

In addition, the polyvalent metal and / or cationic polymer mentioned later may be added simultaneously with or after surface crosslinking. These polyvalent metals and / or cationic polymers can also function as ionic bond surface crosslinking agents, and can be further improved in liquid permeability by use in combination with the covalent surface crosslinking agents.

Here, when manufacturing the particulate water absorbing agent of 3-15 weight% of water content, the water content of the water absorbing resin after surface crosslinking is 3 weight% or more, 4 weight% or more, 5 weight% or more, 6 weight% or more, 7 weight% It is preferable in the above order, and by making the moisture content of surface crosslinking into such a range, the odor by using a reducing agent, especially the odor of the absorbent obtained when adding an inorganic reducing agent in the surface crosslinking process or before it, can be suppressed, As a result, the odor of the absorbent finally obtained can be further suppressed. This effect is remarkable when added to the inorganic reducing agent at the time of the surface crosslinking step or before the surface crosslinking step, particularly before the drying step after the drying step to the polymerization, and thus the water content is particularly controlled in the addition of such an inorganic reducing agent. As another means, the water content at the time of surface crosslinking is less than 3% by weight, for example, at a high temperature surface crosslinking at a fruit temperature and a material temperature of 150 to 250 ° C or a surface crosslinking with a dehydrating reactive surface crosslinking agent, an inorganic after surface crosslinking process. It is more preferable to add a reducing agent from the point of odor.

It is estimated that this odor is a complex odor of a trace component such as a water absorbent resin or a residual monomer thereof and a reducing agent rather than a simple decomposition of the reducing agent, and occurs by lowering a water content of the water absorbent resin to a predetermined value or less. It has been found that the moisture content in the drying process and the surface crosslinking process is very important. In addition, in order to obtain an absorbent having a higher absorption rate and a higher absorption rate under pressure, the water content of the water absorbent resin after surface crosslinking is preferably within the above range.

In addition, in the case of producing a particulate water absorbent having a water content of 3 to 15% by weight, it is preferable to perform surface crosslinking in a state where the water content of the water absorbent resin is maintained at 3 to 15% by weight, and the state maintained at 4 to 14% by weight. It is more preferable to carry out surface crosslinking at a temperature, it is even more preferable to carry out surface crosslinking in a state maintained at 5 to 13% by weight, and surface crosslinking at a state maintained at 6 to 12% by weight and 7 to 11% by weight. It is most preferable to carry out. If water content is more than the said range, it can avoid that the water absorption magnification of a water absorbing resin falls significantly. When water content is below the said range (15 weight%), coloring improves further, and the deterioration of the handleability of a water absorbing resin, and the fall of the fluidity | liquidity of powder can be suppressed.

After surface crosslinking, you may further dry as needed, and you may adjust water content and its physical property by adding water and other additives. The reducing agent, the chelating agent, and water-insoluble inorganic fine particles, which are preferably added in the present invention, may be preferably added after the surface crosslinking. In addition, the additive is preferably 0.001 to 20% by weight based on 100 parts by weight of the water absorbent resin. More preferably, 0.01 to 10 parts by weight, particularly preferably 0.1 to 5 parts by weight of an antibacterial agent, a deodorant, a polyvalent metal compound, or the like may be added.

(1-11) Other Process

In addition to the above, if necessary, an assembly step, a fine powder removal step, a water content adjustment step (for example, Example 1-16 of the present application), a fine separation cycle step, or the like may be provided. In addition, you may provide the addition process of a chelating agent and an inorganic reducing agent after (1-10) a surface crosslinking process. For the addition, various mixers used in the above (1-10) surface crosslinking step, granulation [8] and the like can be suitably used.

The particulate water absorbing agent of the present invention is a particulate water absorbing agent having a polyacrylic acid (salt) -based water absorbent resin as a main component, and includes a chelating agent and an inorganic reducing agent, and the content of the chelating agent is 0.001 to 0.5% by weight, and the following (1) ? (3)

(1) Content of methoxy phenols is 5-60 ppm.

(2) Contains water insoluble inorganic fine particles.

(3) Water content is 3-15 weight%.

It satisfies any one or more requirements of.

Hereinafter, the [2] chelating agent, [3] inorganic reducing agent, [4] methoxy phenols, and [5] water insoluble inorganic fine particles will be described.

[2] chelating agents

In order to solve the subject, the particulate water absorbent of the present invention essentially includes a chelating agent. As the chelating agent of the present invention, from the standpoint of the effect, a high molecular compound or a non-polymeric compound, a non-polymeric compound among them, is preferable, and specifically, it is selected from amino polyhydric carboxylic acid, organic polyvalent phosphoric acid, inorganic polyvalent phosphoric acid and amino polyvalent phosphoric acid. Preferred are those compounds. From the viewpoint of the effect, the molecular weight of the chelating agent is preferably 100 to 5000, more preferably 200 to 1000. When there is no chelating agent, it becomes an absorbent which is inferior in terms of coloring or deterioration.

Herein, a polyvalent molecule has a plurality of corresponding functional groups, and preferably has 2 to 30, 3 to 20, and 4 to 10 corresponding functional groups thereon. Moreover, it is preferable that these chelating agents are water-soluble chelating agents, specifically, water-soluble chelating agent which melt | dissolves in 1 g or more and 10 g or more in 100 g (25 degreeC) water.

Examples of the amino polyhydric carboxylic acid include imino diacetic acid, hydroxyethylimino diacetic acid, nitrile triacetic acid, nitrile 3 propionic acid, ethylenediamine tetraacetic acid, diethylenetriamine pentaacetic acid, triethylenetetramine hexaacetic acid, trans -1,2-diaminocyclohexane tetraacetic acid, N, N-bis (2-hydroxyethyl) glycine, diaminopropanol tetraacetic acid, ethylenediamine 2 propionic acid, hydroxyethylenediamine triacetic acid, glycol etherdiamine tetraacetic acid, Diaminopropane tetraacetic acid, N, N'-bis (2-hydroxybenzyl) ethylenediamine-N, N'-2 acetic acid, 1,6-hexamethylenediamine-N, N, N ', N'-4 acetic acid And salts thereof.

Examples of the organic polyvalent phosphoric acid include nitrilo acetate-di (methylenephosphinic acid), nitrilodiacetic acid- (methylenephosphinic acid), nitriloacetic acid-β-propionic acid-methylenephosphonic acid, nitrilotris (methylenephosphonic acid) and 1- Hydroxyethylidene diphosphonic acid etc. are mentioned, As said inorganic polyhydric phosphoric acid, a pyrophosphoric acid, a tripolyphosphoric acid, their salt, etc. are mentioned.

Moreover, as said amino polyvalent phosphoric acid, ethylenediamine-N, N'- di (methylene phosphinic acid), ethylenediamine tetra (methylene phosphinic acid), cyclohexanediamine tetra (methylene phosphonic acid), ethylenediamine-N, N'- Diacetic acid-N, N'-di (methylenephosphonic acid), ethylenediamine-N, N'-di (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), polymethylenediaminetetra (methylenephosphonic acid), di Ethylene triamine penta (methylene phosphonic acid), these salts, etc. are mentioned.

Moreover, ethylene diamine tetra (methylene phosphonic acid), its salt, etc. are mentioned as the most preferable amino polyvalent phosphoric acid in this invention. Preferable salts include valent monovalent salts, especially alkali metal salts such as sodium salts and potassium salts, ammonium salts and amine salts. Moreover, as a salt, sodium salt and potassium salt are especially preferable.

Moreover, among these, an amino carboxylic acid type metal chelating agent, an amino polyvalent phosphoric acid type metal chelating agent, and salts thereof are used suitably. In particular, diethylene triamine pentacetic acid, triethylene tetramin hexaacetic acid, trans-1,2-diaminocyclohexane tetraacetic acid, ethylene diamine tetra (methylenephosphinic acid), diethylenetriaminepenta (methylene phosphonic acid) and their Salts are more suitably used. Among these, ethylene diamine tetra (methylene phosphonic acid) or its salt is most preferable, and monovalent salt is preferable as a salt, Alkali metal salts, such as a sodium salt and potassium salt, ammonium salt, and an amine salt are mentioned. Moreover, sodium salt and potassium salt are especially preferable among these salts.

The content of the chelating agent in the particulate water absorbing agent of the present invention is 0.001 to 0.5% by weight, preferably 0.001 to 0.1% by weight, still more preferably 0.002 to 0.1% by weight, still more preferably 0.003 to 0.05% by weight, 0.005-0.05 weight% is especially preferable. When content of the said chelating agent is less than 0.001 weight%, since the time-coloring of a particulate water absorbing agent worsens and the time-color tone of the said particulate water absorbing agent deteriorates, it is unpreferable. Moreover, when content of the said chelating agent exceeds 0.5 weight%, such as the Example of the said patent document 29, it is discovered that the initial coloring of a particulate water absorbing agent becomes large, and since the initial color tone of the said particulate water absorbing agent may deteriorate, it is not preferable. . Moreover, since the color tone of the said particulate water absorbing agent may also worsen, it is not preferable.

In addition, time-coloring means coloring of the particulate water absorbing agent, such as when stored for a long time under high temperature and high humidity, and initial coloring means the color tone or degree of coloring of the particulate water absorbing agent at the time obtained by manufacture.

Such chelating agents include the above (1-6) polymerization step, (1-7) gel granulation step, (1-8) drying step, (1-9) grinding step and classification step, and (1-10) surface. It may be added to any one or more of the crosslinking step and the other step (1-11), and in the polymerization step (1-6), a chelating agent may be added during the monomer adjustment before the polymerization step, or a chelating agent may be added during the polymerization. good. Although the amount used in each of the production steps such as (1-6) to (1-11) is substantially the content in the obtained absorbent, the chelating agent in the absorbent is determined by water or physiological saline, in the same manner as the quantification of the remaining monomers and water-soluble components. The chelating agent can be extracted from the absorbent and appropriately quantified by liquid chromatography, ion chromatography, or the like.

Further, Patent Document 29 (International Publication No. 2006/109882 pamphlet) discloses a method for preventing coloration using an ammonium acrylate salt in a monomer or a method for preventing coloration in which a compound containing a phosphorus atom or a sulfur-based reducing agent is added a plurality of times. As well as the specific water content (3 to 15% by weight) of the present invention, the document 29 has a specific addition amount (0.001 to 0.5% by weight, preferably 0.001 to 0.1% by weight) of a compound containing a phosphorus atom or a sulfur-based reducing agent. In Example 5 of patent document 29, addition of 1.0 weight% of 1-hydroxyethylidene-1,1- diphosphonic acids is not carried out and 1-hydroxyethylidene-1,1- like in Example 4 similarly is not disclosed. The use of a total of 2.0 weight% diphosphonic acid is started. The use of such a chelating agent of more than 0.5% by weight was found to adversely affect the coloring of the obtained absorbent, as shown in Comparative Example 1-5, which will be described later, also in combination with the inorganic reducing agent, thereby completing the present invention.

[3] reducing agents

The particulate water absorbent according to the present invention essentially includes an inorganic reducing agent, and preferably includes a water-soluble inorganic compound having a reducing inorganic element or a water-soluble organic compound having a reducing inorganic element as the inorganic reducing agent. In addition, said "water-soluble" means melt | dissolving 1g or more, 5g or more, especially 10g or more with respect to 100g of 25 degreeC water. When there is no chelating agent, it becomes an absorbent which is inferior in terms of remaining monomer, coloring, or deterioration.

The inorganic reducing agent in this invention is used distinguishing from the reducing agent as a polymerization initiator used at the said superposition | polymerization process. That is, the inorganic reducing agent refers to a compound having a reducing property, and may have a reducing inorganic element, and specifically, a compound having a reducing sulfur atom or a reducing phosphorus atom may be mentioned, and preferably a reducing sulfur atom The water-soluble compound containing the compound or reducing phosphorus atom to contain is mentioned. Therefore, an inorganic compound or an organic compound, if it has a reducing sulfur atom or a reducing phosphorus atom, is regarded as the inorganic reducing agent of the present invention.

Although the said inorganic reducing agent may be acid type, Preferably it is salt type, As a salt, Monovalent or polyvalent metal salt is more preferable, Monovalent salt is still more preferable. Of these inorganic reducing agents, oxygen-reducing inorganic compounds exemplified below, that is, inorganic reducing agents in which sulfur and phosphorus are bonded to oxygen, and oxygen-containing reducing inorganic salts are particularly preferred. The inorganic reducing agent may be an inorganic reducing agent having a reducing inorganic atom, preferably a reducing sulfur atom or a phosphorus atom, in an organic compound such as an alkyl group or a hydroxyalkyl group.

In addition, as an inorganic reducing agent having a reducing sulfur atom or a reducing phosphorus atom used in the present invention, the oxidation number of the most stable sulfur atom is +6 (positive hexavalent), and the phosphorus atom is +5 (positive 5-valent). In general, however, each atom of the oxidized water below is reducible and has a + tetravalent sulfur compound (e.g., sulfite, hydrogen sulfite, pyrosulfite), and a trivalent sulfur compound (e.g., dithionate). + Bivalent sulfur compounds (eg sulfoxylates), + tetravalent phosphorus compounds (eg hypophosphates), + trivalent phosphorous compounds (eg phosphites, pyrophosphates), + monovalent phosphorus compounds ( Hypophosphite) is used. In these reducing inorganic compounds, a reducing sulfur atom or a reducing phosphorus atom may be substituted with an organic substance.

Although it does not specifically limit as an inorganic compound containing the sulfur atom which is an inorganic reducing agent, For example, sulfites, such as sodium sulfite, potassium sulfite, calcium sulfite, zinc sulfite, ammonium sulfite; Hydrogen sulfite salts such as sodium hydrogen sulfite, potassium hydrogen sulfite, calcium hydrogen sulfite and ammonium hydrogen sulfite; Pyrosulfite, such as sodium pyrosulfite, potassium pyrosulfite, and ammonium pyrosulfite; Dithionates such as sodium dithionate, potassium dithionate, ammonium dithionate, calcium dithionate, and zinc dithionate; Trithiate salts such as potassium trithiate and sodium trithiate; Tetrathiate, such as potassium tetrathionate and sodium tetrathionate; Thiosulfates, such as sodium thiosulfate, potassium thiosulfate, and ammonium thiosulfate; Nitrites such as sodium nitrate, potassium nitrate, calcium nitrate, and zinc nitrate. Examples of the inorganic compound containing a phosphorus atom include sodium hypophosphite and the like. Among these, sulfite, hydrogen sulfite, pyrosulfite, and dithionate are preferable, and sodium sulfite, sodium hydrogen sulfite, potassium pyrosulfite and sodium dithionate are more preferable.

The water-soluble organic compound containing a sulfur atom which is an inorganic reducing agent is not particularly limited, but for example, 2-hydroxy-2-sulfinate acetate formaldehyde sulfoxylate, formamidine sulfinic acid and thioglycolic acid tris ( 2-carboxyethyl) phosphine hydrochloride (TCEP), tributylphosphine (TBP), and the like, among them, 2-hydroxy-2-sulfinate acetate, 2-hydroxy-2-sulfonato acetate, And / or salts thereof are preferably illustrated. Preferable salts are alkali metals and alkaline earth metal salts, Li, Na and K are preferred, and sodium salts are particularly preferred. 2-hydroxy-2-sulfinate acetic acid (salt) may be used in combination with 2-hydroxy-2-sulfonato acetic acid (salt), or may be used in combination with the above-mentioned inorganic compound.

As a preferable inorganic reducing agent, 2-hydroxy-2-sulfinate acetate is an inorganic reducing agent of the present invention because it has a reducing sulfur atom as a sulfinate group, and is a BRUGGOLITE (R) FF7 commercially available from Brueggemann Chemical (Heilbron, Germany). and it can be obtained, 2-hydroxy-2-ethyl sulfinyl carbonate the disodium salt of 50? 60% by weight, sodium sulfite (Na ₂ SO ₃₎ of 30? 35 weight%, and 2-hydroxy-2-sulfo ethyl NATO It can obtain as BRUGGOLITE (R) FF6 containing 10-15 weight% of 2 sodium salts.

The inorganic reducing agent contained in the particulate water absorbing agent of the present invention is preferably 0.01 to 1.0% by weight, more preferably 0.05 to 1.0% by weight, particularly preferably 0.05 to 0.5% by weight. When content of the said inorganic reducing agent is 0.01 weight% or more, the time-dependent coloring of a particulate water absorbing agent can be suppressed. Moreover, when content of the said inorganic reducing agent is 1.0 weight% or less, the odor of a particulate water absorbing agent can be suppressed, In particular, the odor after a particulate water absorbing agent absorbs an aqueous liquid can be suppressed effectively.

In addition, the inorganic reducing agent described in (1-6) polymerization step, (1-7) gel granulation step, (1-8) drying step, (1-9) grinding step and classification step, (1-10) surface crosslinking It can be added to any one or more of the step, (1-11) other steps (addition step after surface crosslinking, etc.), and in the (1-6) polymerization step, it may be added at the start of the polymerization, but generally a reducing agent is consumed. It is preferable to add, preferably during the polymerization and after the polymerization step, and the amount of the reducing agent consumed in the manufacturing step, particularly the step or the drying step, may be added. If the amount of the inorganic reducing agent in the absorbent obtained is the addition of the inorganic reducing agent after the drying step, particularly after the surface crosslinking, the amount used in each manufacturing step is substantially the content in the obtained absorbent, but the chelating agent in the inorganic absorbent added before the drying step remains. The chelating agent can be extracted from the absorbent with water or physiological saline similarly to the quantification of the monomer and the water-soluble component, and can be appropriately quantified by liquid chromatography, ion chromatography, or the like. The amount used in each of the manufacturing steps such as (1-6) to (1-11) is substantially the absorbent obtained, but the chelating agent in the absorbent is absorbed from the absorbent by water or physiological saline in the same manner as the amount of the remaining monomers or water-soluble components. The chelating agent can be extracted and quantified appropriately by liquid chromatography or ion chromatography.

The inorganic reducing agent of the present invention is preferably added after the surface crosslinking treatment step from the viewpoint of odor. As in Patent Document 5, when the inorganic reducing agent is added to the surface crosslinking treatment step or before, without being controlled by the specific water content (3-15% by weight) of the present invention, the particulate water absorbing agent obtained may have a bad smell. In particular, the obtained particulate water absorbing agent is not preferable because it absorbs the aqueous liquid and generates odor. Such odor is not limited to the odor of a simple inorganic reducing agent, and is presumed to be a by-product of the surface crosslinking process, particularly a surface crosslinking process aimed at high SFC or high AAP.

That is, the manufacturing method of the water absorbent of this invention is the manufacturing method of the subordinate concept which makes the said (c) an essential part 3, The manufacturing method of the particulate water absorbing agent of this invention (3) is aqueous monomer solution which has acrylic acid (salt) as a main component. A method for producing a particulate water absorbent containing, as a main component, a polyacrylic acid (salt) -based water absorbent resin, including a polymerization step, a drying step of a hydrous gel crosslinked polymer obtained by polymerization, and a surface crosslinking step, wherein the chelating agent is 0.001 to 0.5% by weight. And an inorganic reducing agent addition step, wherein the monomer contains 10 to 200 ppm of methoxy phenols in terms of large acrylic acid, and after the drying step and in the surface crosslinking step, the water content of the polymer is 3 to 15% by weight. It is a manufacturing method of a particulate water absorbing agent (third manufacturing method) which controls to%, More preferably, the said inorganic reducing agent is added to the hydrous gel-like crosslinked polymer before drying.

[4] methoxy phenols

When the particulate water absorbing agent of the present invention does not satisfy the requirements of (2) and (3), it contains 5 to 60 ppm of methoxy phenols, but it satisfies any of the requirements of (2) and (3). Even in this case, it is preferable to include methoxy phenols, and more preferably 5 to 60 ppm of methoxy phenols.

Specific examples of the methoxy phenols include o, m and p-methoxy phenols, and methoxy phenols having one or two or more substituents such as methyl group, t-butyl group and hydroxyl group in addition thereto. Especially preferably, p-methoxy phenol is used in the present invention, in particular in the above (1-6) polymerization step.

It is preferable that p-methoxy phenol is contained in acrylic acid which is a monomer main component which comprises the polyacrylic acid (salt) type water absorbing resin of this invention. As for content of the methoxy phenols (especially p-methoxy phenol) in the particulate water absorbing agent of this invention, 5-50 ppm is more preferable, 6-50 ppm is still more preferable, 7-40 ppm is especially preferable, and 8-30 ppm is Most preferred. In the polymerization step (1-6), the content (10 to 200 ppm) of the methoxy phenols is further controlled within the range described in the section of (10-1) acrylic acid described later, and at the time of use such as urine resistance with polymerization control. Since gel stability becomes further higher, it is preferable.

When the content of the methoxy phenols is less than 5 ppm, that is, when p-methoxy phenol, which is a polymerization inhibitor, is removed by purification such as distillation, not only there is a risk that polymerization occurs before initiation of polymerization, but also acrylic acid (salt ) Is not preferable because the weather resistance of the particulate water absorbent of the present invention obtained as a main raw material deteriorates. Moreover, when content of the said methoxy phenols exceeds 60 ppm, since the problem of not being able to control superposition | polymerization reactions, such as a polymerization delay, arises, it is unpreferable, and since the particulate water absorbing agent of this invention colors, it is not preferable.

The methoxy phenols (5 to 60 ppm) in the particulate water absorbent of the present invention are polymerized (the above concentration, temperature, polymerization initiator, etc.) of a monomer aqueous solution containing acrylic acid (salt) containing 10 to 200 ppm of methoxy phenol as the main component. And the hydrogel-like crosslinked polymer obtained by polymerization can be adjusted by going through the step of drying (temperature, time, wind speed, solid content, etc.) under the above-mentioned preferred range conditions. It is well known that p-methoxy phenol is generally used in an amount of 200 ppm as a polymerization inhibitor of acrylic acid. In addition, acrylic acid (boiling point of 143 ° C.) is distilled and purified during polymerization of the water absorbent resin (for example, US Patent No. 6388000). It is also known to treat acrylate with activated charcoal (Patent Document 7). In such distillation purification, p-methoxy phenol is substantially removed from acrylic acid, and thus, p-methoxy phenol of the present invention can be used. none.

Patent Literature 17 (European Patent No. 1645596) discloses an absorbent resin composition containing an oxygen reducing inorganic salt, an aminocarboxylic acid chelating agent, and an organic antioxidant, and an alkyl hydroxy as an example of an organic antioxidant. Although anisole (1 weight% is used in Claim 7, Example 6 of patent document 17) is disclosed, alkyl hydroxy anisole does not exhibit sufficient effect compared with p-methoxy phenol.

In addition, in the coloring prevention technique by the reducing agent etc. which were described in the said patent document 12 and patent documents 15-19, a chelating agent and an inorganic reducing agent are used together, and methoxy phenol (especially p-methoxy phenol) is further controlled by specific content. It does not disclose the problem and effect as described in this application by making it use especially at the time of superposition | polymerization, and containing a trace amount uniformly inside a water absorbent resin.

Likewise, in Patent Document 15 and Example 5, when the inorganic reducing agent before drying is added, odor is generated due to the final moisture content after the surface crosslinking. Although patent document 5 starts superposition | polymerization of the water absorbing resin in 10-160 ppm of p-methoxyphenol, including patent documents 10 and 11 which discloses p-methoxyphenol, the use of the chelating agent and reducing agent of this application, and a preferable final water content It does not disclose about. In addition, these patent documents disclose the use of p-methoxy phenol during polymerization, but p-methoxy phenol is consumed even during polymerization and drying and does not disclose the control method of the present invention. The amount of p-methoxy phenol is not disclosed. In addition, Tables 5 and 2 on page 41 of Non-Patent Document 1 (The 'Modern' Superaborbent 'Polymer' Technology; 1998) describe residual p-methoxy phenol (MEHQ) in absorbent resins from eight manufacturing sites A to H. Although MEHQ discloses 16-151 ppm of water-absorbent resin, Non-Patent Literature 1 also does not disclose the use of a chelating agent and an inorganic reducing agent in a specific MEHQ (5-60 ppm) of the present invention.

[5] inorganic particles, water insoluble

When the particulate water absorbing agent of the present invention does not satisfy the requirements of the above (1) and (3), it contains water-insoluble inorganic fine particles, but the case of satisfying any one of the above (1) and (3). In addition, it is preferable to contain water-insoluble inorganic fine particles, especially white water-insoluble inorganic fine particles from a viewpoint of fluid permeability (SFC) improvement, fluidity | liquidity at the time of moisture absorption, etc. It is preferable to add white water-insoluble inorganic fine particles because the white color of the obtained water absorbent resin is further improved and the gel strength of the water absorbent resin is improved. Patent documents 15-17 do not disclose the use of a trace amount of p-methoxy phenol and white water-insoluble inorganic fine particles. Here, the whiteness of the water-insoluble inorganic fine particles is in the range of 70 or more, within ± 5 and within ± 10 in L, a, b, and preferably, within 80 or more, within ± 3, within ± 7, preferably, 90 As mentioned above, insoluble inorganic fine particles of less than or equal to ± 2 and less than or equal to 5 and white (preferably 5 or more in L and 7 or more) in water-absorbent resin before mixing are used. In particular, when the water content is 3 to 15% by weight, and the above range is used as the absorbent, the water-insoluble inorganic fine particles are preferably used in combination for solving the problems of the present invention.

The water-insoluble inorganic fine particles are fine particles having an average particle diameter of 0.001 to 200 µm, more preferably 0.005 to 50 µm, still more preferably 0.01 to 10 µm, as measured by the Coulter Counter method. Preferably, they are hydrophilic fine particles and include, for example, metal oxides such as silica (silicon dioxide) and titanium oxide, composite hydrous oxides containing zinc and silicon, or zinc and aluminum (for example, in WO 2005/010102). Examples), silicic acid (salt) such as natural zeolite or synthetic zeolite, kaolin, talc, clay, bentonite, calcium phosphate, barium phosphate, silicic acid or its salts, clay, diatomaceous earth, silica gel, zeolite, bentonite, hydroxy apatite, Hydrotalcite, belmyulite, pearlite, isolite, activated clay, silica sand, silica, strontium ore, fluorite, bauxite and the like. Among these, silicon dioxide and silicic acid (salt) are more preferable, and silicon dioxide and silicic acid (salt) are even more preferable.

Although the said silicon dioxide is not specifically limited, It is preferable that it is amorphous fumed silica manufactured by the dry method. Silicon dioxide and the like called quartz are not preferable because they may cause health problems.

The water-insoluble inorganic fine particles contained in the particulate water absorbent of the present invention are preferably in the range of 0.05 to 1.0% by weight, more preferably 0.05 to 0.8% by weight, still more preferably 0.05 to 0.7% by weight, particularly preferably 0.1? It is the range of 0.5 weight%. When content of a water insoluble inorganic fine particle is 0.05 weight% or more, the deterioration of the urine resistance of a particulate water absorbing agent can be suppressed. When content of a water-insoluble inorganic fine particle is 1.0 weight% or less, the fall of the absorption magnification under pressure of a particulate water absorbing agent can be suppressed.

The water absorbent resin of the above [1] contains the following [6] α-hydroxy carboxylic acid compound, [7] polyvalent metal salt and / or cationic polymer in addition to the [2] chelating agent? [5] water-insoluble inorganic fine particles; It is also preferable, and [8] may be granulated.

[6] α-hydroxy carboxylic acid compounds

The particulate water absorbing agent of the present invention, in addition to the above-mentioned reducing sulfur compound (for example, 2-hydroxy-2-sulfinate acetic acid), from the viewpoints of new anti-coloring and anti-deterioration (weather resistance, urine resistance), and the like, It is preferable to include a hydroxy carboxylic acid compound, and it is more preferable to include a non-reducing alpha -hydroxy carboxylic acid compound. Here, a non-reducing alpha-hydroxy carboxylic acid compound refers to the hydroxy carboxylic acid compound which does not have a reducing inorganic element (for example, reducing sulfur, a sulfinate group, etc.). In particular, when satisfying a high AAP or high SFC, or when containing a polyvalent metal salt and / or a polyamine polymer, it is preferable to include an α-hydroxy carboxylic acid compound from anti-pigmentation or anti-deterioration, and from the surface crosslinking process to It is preferable to mix after that.

The (alpha)-hydroxy carboxylic acid compound used by this invention is a carboxylic acid which has a hydroxyl group in a molecule | numerator, or its salt, and is a hydroxy carboxylic acid compound which has a hydroxyl group in the (alpha) position. As for the (alpha)-hydroxy carboxylic acid compound, non-polymer (alpha)-hydroxy carboxylic acids are preferable, and since it is easy to add and the effect of addition, the molecular weight becomes like this. Preferably it is 40-2000, More preferably, it is 60-1000, Especially Preferably it is the range of 100-500, and it is preferable that it is water-soluble. Examples of such α-hydroxy carboxylic acid compounds include glycolic acid, tartaric acid, lactic acid (salts), citric acid (salts), malic acid (salts), isocitric acid (salts), glycerin acids (salts), and polyα-hydroxy acrylic acids ( Salts); and the like. Especially, lactic acid (salt) and malic acid (salt) are preferable, and lactic acid (salt) is more preferable.

Although it does not specifically limit as a salt of (alpha)-hydroxy carboxylic acid, As a salt, monovalent or polyvalent salt is used, Preferably monovalent or trivalent salt, specifically sodium salt, potassium salt, calcium salt, magnesium salt , Aluminum salts are preferred, and sodium salts are more preferred. In addition, the acid group of (alpha)-hydroxy carboxylic acid may be substituted by 100% salt, and may be partially substituted.

From the viewpoint of cost performance, the content of the α-hydroxy carboxylic acid compound in the particulate water absorbing agent is preferably in the range of 0.05 to 1.0% by weight, more preferably 0.05 to 0.5% by weight, still more preferably 0.1 to 0.5% by weight. It is% of range. In addition, the particulate water absorbing agent of the present invention containing a specific range of methoxy phenol, a chelating agent and an inorganic reducing agent further includes an α-hydroxy carboxylic acid compound, thereby further enhancing the above-described effects of the present invention.

[7] polyvalent metal salts and / or cationic polymers

It is preferable that the particulate water absorbing agent of the present invention further contains a polyvalent metal salt and / or a cationic polymer from the viewpoints of improving the absorption rate (Vortex), improving the liquid permeability (SFC), fluidity at the time of moisture absorption, and the like.

As said polyvalent metal salt, it is an organic acid salt or an inorganic acid salt of a polyvalent metal, and polyvalent metal salts, such as aluminum, zirconium, iron, titanium, calcium, magnesium, and zinc, are preferable. The polyvalent metal salt may be either water-soluble or water-insoluble, but a water-soluble polyvalent metal salt is preferable, and a water-soluble polyvalent metal salt which dissolves at least 2% by weight and further 5% by weight in water at 25 ° C can be used. Specifically, for example, aluminum chloride, polyaluminum chloride, aluminum sulfate, aluminum nitrate, potassium bisulfate, sodium bisulfate, potassium alum, ammonium alum, sodium alum, sodium aluminate, calcium chloride, calcium nitrate, magnesium chloride And organic acid salts such as inorganic acid salts such as magnesium sulfate, magnesium nitrate, zinc chloride, zinc sulfate, zinc nitrate, zirconium chloride, zirconium sulfate, and zirconium nitrate, and polyvalent metal salts and acetates.

Moreover, it is preferable to use the salt which has these crystal water also from the point of solubility with absorbing liquids, such as urine. Particularly preferred are aluminum compounds, especially aluminum chloride, polyaluminum chloride, aluminum sulfate, aluminum nitrate, potassium bisulfate aluminum, sodium bisulfate aluminum, potassium alum, ammonium alum, sodium alum, sodium aluminate, and aluminum sulfate This is particularly preferable, and the powder of hydrous crystals such as aluminum sulfate 18 hydrate and aluminum sulfate 14-18 hydrate can be most suitably used. These may use only 1 type and may use 2 or more types together.

As said cationic polymer, it is a cationic polymer which has an amino group, Furthermore, it is a water-soluble cationic polymer, Preferably, it is a water-soluble polymer which melt | dissolves 2 weight% or more and 5 weight% or more in 25 degreeC water. For example, polyalkylenemin, such as polyethyleneimine, polyether polyamine, polyetheramine, polyvinylamine, polyalkylamine, polyarylamine, polydiarylamine, poly (N-alkylarylamine), monoarylamine- Diallylamine copolymer, N-alkylarylamine-monoarylamine copolymer, monoarylamine-dialkyldiarylammonium salt copolymer, diallylamine-dialkyldiarylammonium copolymer, polyethylene polyamine, polypropylene polyamine , Polyamidine and the like; These salts are mentioned preferably. Moreover, the modified cationic polymer described in international publication 2009/041727 is more preferable.

It is preferable that the weight average molecular weight of a cationic polymer is 5000 or more, It is more preferable that it is 10000 or more, It is further more preferable that it is 30000 or more. There exists a possibility that the effect anticipated that a weight average molecular weight is less than 5000 may not be acquired. In addition, the upper limit of the weight average molecular weight of the said cationic polymer is not specifically limited, It is preferable that it is 1 million or less, and it is more preferable that it is 500,000 or less. Since the viscosity becomes low because the weight average molecular weight of the said cationic high molecular compound is 1 million or less, and it is excellent in handleability and mixing property, it is preferable. In addition, a weight average molecular weight can be measured by well-known methods, such as GPC, a viscosity measurement, static light scattering.

Surface crosslinking by a polyvalent metal is disclosed in International Publication Nos. 2007/121037, 2008/09843, 2008/09842, US Pat. No. 7157141, US Pat. No. 6,567,366, US Pat. 2005/0288182, 2005/0070671, 2007/0106013, and 2006/0073969. In addition to the organic surface crosslinking agent, a polyamine polymer, in particular, a polyamine polymer having a weight average molecular weight of about 50 to 1 million may be used simultaneously or separately to improve the fluid permeability and the like.

The polyamine polymer to be used is, for example, U.S. Pat.No.7098284, WO 2006/082188, WO 2006/082189, WO 2006/082197, WO 2006/111402, WO 2006/111403. No. 2006/111404 and the like.

The usage-amount of the polyvalent metal salt and / or cationic polymer contained in the particulate water absorbent of this invention is 0-5 weight part with respect to 100 weight part of particulate water absorbers, Preferably it is 0.001-3 weight part, More preferably, it is 0.01-2. It is the range of weight part. When the content of the polyvalent metal salt and / or the cationic polymer is more than 5 parts by weight, the water absorption performance, in particular, the absorption magnification may be remarkably lowered, which is not preferable, and may cause coloring, which is not preferable.

[8] assembly

It is preferable that the particulate water absorbing agent of this invention is a granulated material. The amount of dust contained in a particulate water absorbing agent is reduced by being a granulated material.

In order to obtain the particulate water absorbent of the present invention, it is preferably granulated during or after polymerization. By assembling, it is further excellent in the absorption rate and the particle size, and becomes an excellent absorbent for practical use as a paper diaper.

Here, granulation means that a plurality of particulate water-absorbent resins are bonded to form one large particle, and as long as they are finally bound particles, a hydrogel may be used at the time of bonding, a dried product or a monomer may be used. The bonding particles may be point contact or surface contact, the interface between the particles may be present, and the interface may be completely extinguished depending on the bonding between the particles, but the particles are preferably granulated particles having an interface from the point of absorption rate.

The water absorbent resin before granulation used in the present invention may be only a fine powder (with a particle diameter of less than 150 µm) or a mixture of fine powder and particles having a larger particle diameter than the fine powder, but the particle diameter of the water absorbent resin before granulation is a weight average particle diameter. It is preferable that it is 500 micrometers or less, and it is more preferable that it is 400 micrometers or less since it improves performance, such as a absorption rate and a capillary absorption magnification. The granulation of the present invention refers to an absorbent resin particle which binds a plurality of absorbent resin particles and has an interface between the bonded particles or removes an interface between the particles, and usually increases the weight average particle diameter (for example, 1.01 to 10 times). ) And / or reduction of the fine powder (e.g., a pass through 150 µm, a reduction of 106 µm thereon).

Moreover, it is preferable that the ratio of the particle | grains whose particle diameter is less than 300 micrometers is 10 weight% or more with respect to the said water absorbent resin, It is more preferable that it is 30 weight% or more, More preferably, it is 50 weight% or more among the water absorbent resins before granulation. . The water absorbent resin having such a particle diameter can be obtained by reverse phase suspension polymerization (particularly two-stage polymerization), and can be preferably obtained by pulverizing the water absorbent resin obtained by aqueous solution polymerization or by sieving them to adjust the particle size. . In addition, the granulated water-absorbent resin powder having a particle size of 300 µm or less may be granulated, and the particle size may be adjusted, or the absorbent resin obtained by partially mixing the granulated material of fine powder may be used in the amorphous particles of the primary particles obtained by grinding. In the case where a granulated product of the water absorbent resin is partially mixed, the water absorbent resin composition of the present invention having excellent absorption characteristics such as absorption rate and maternal absorption ratio can be obtained. The amount of the fine powder to be mixed is preferably 5% by weight or more, more preferably 10% by weight or more, even more preferably 15% by weight or more.

As a granulation method, if a plurality of polymerized particles are combined to form a large particle, the method is not particularly limited, and the granulation in reverse phase suspension, that is, aggregation during reverse phase polymerization (European Patent No. 0695762, US Patent No. 4732968), or It can be carried out by two-stage polymerization (European Patent No. 0807646) or reverse phase assembly (US Patent No. 4732968) by addition of inert inorganic matter after polymerization. By assembling, an absorbent much more excellent in actual use in paper diapers is obtained. 3 shows an electron micrograph of representative granulated particles.

In addition, in order to obtain the particulate water absorbing agent of the present invention as a granulation method other than reverse phase suspension polymerization, a known technique for regenerating fine powder can be used as a method for producing finely divided granules.

For example, a method of mixing and drying fine powder of hot water and an absorbent resin (US Pat. No. 6,289,30), or a method of mixing and polymerizing fine powder of an absorbent resin with an aqueous monomer solution (US Pat. No. 5,526,495), fine powder of an absorbent resin. Water to the granules and granulated above a specific surface pressure (European Patent No. 844270), a method of sufficiently wetting the fine powder of the absorbent resin to form an amorphous gel, drying and pulverizing it (US Patent No. 4950692), A method of mixing the fine powder and the polymer gel (US Pat. No. 5,588,79) or the like can be used. Preferably, a method of mixing and drying the above-mentioned hot water and the fine powder of the water absorbent resin is used. In addition, the particle diameter is represented by the eye diameter of the sieve classified. Water may be used as a binder for granulation, and water may contain the chelating agent or the reducing inorganic substance.

Further, after the surface crosslinking treatment, an aqueous liquid is added, the granules are heated while maintaining a water content of 1 to 10% by weight, and granulated as necessary, and are adjusted to a specific particle size as a powder. The aqueous liquid to be added may be water alone or may contain a chelating agent or inorganic reducing agent of the present invention, or a plant component, an antibacterial agent, a water-soluble polymer, an inorganic salt, or the like. Their content is 0.001-50 weight%, More preferably, it is 0.001-30 weight%, Most preferably, it is 0.01-10 weight% of range. In the present invention, the granulation is preferably a method of spraying or dropping the aqueous liquid onto the absorbent resin, and more preferably spraying the aqueous liquid. The size of the droplets to be sprayed is preferably within the range of 0.1 to 300 µm and more preferably 0.1 to 200 µm in terms of the average particle diameter. As a granulation apparatus used at the time of granulation, what has big mixing power is preferable.

Specifically, a stirring granulation method, a rolling granulation method, a compression granulation method, a fluidized bed granulation method, etc. are illustrated, and can be preferably performed by either method. Especially, the stirring type granulation method is more preferable at the point of simplicity. In the case of carrying out these methods, the same technique as in the prior art can be applied to the apparatus, the operation conditions, and the like except that the water supply can be performed by water vapor. In addition, in the present invention, since water is supplied by supplying steam into the apparatus, the apparatus to be used is equipped with a nozzle or the like for injecting steam, and also has high airtightness and internal pressure so that the steam can be supplied smoothly. It is preferable that the device be capable of adjusting.

For example, when it carries out by agitation type granulation method, the stirring apparatus which can be used includes a continuous type and a batch type, and there exist a vertical type and a horizontal type, respectively. As a vertical type continuous stirring apparatus, a spiral pin mixer (made by Pacific Engineering, Ltd.), a flow jet mixer, and a chuchu type granulation system (made by Hunken Powerex) etc. are illustrated, As a horizontal type continuous stirring apparatus, an annular A layer mixer (manufactured by Dreiberke company), a two-axis mixer (manufactured by List), and the like are exemplified.

Examples of the vertical batch stirring device include Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) and a turbo hair mixer (manufactured by Moritz Co., Ltd.), and the like. (Made by Garrick & Co.) and Prosure Mixer (manufactured by Pacific Engineering).

Moreover, as said granulation apparatus, for example, a cylindrical mixer, a double wall conical mixer, a high speed stirring mixer, a V-shaped mixer, a ribbon mixer, a screw mixer, a double kneader, a grinding kneader, a rotary mixer, an airflow mixer, for example, , Turbulizers, batch reggae mixers and continuous reggae mixers are very suitable.

Moreover, when granulating after surface crosslinking, it is preferable to heat-process after mixing aqueous liquid and maintaining moisture content. In such a step, a chelating agent or an inorganic reducing agent may be added as an aqueous solution, and a chelating agent or an inorganic reducing agent may be added at the same time as granulation. In general, when water is added to the water absorbent resin, the adhesiveness is generated. However, when heated while maintaining the water content, the adhesiveness is lost in a short time and the fluidity of the powder is recovered. Therefore, the manufacturing process can be simplified and shortened.

In addition, in this invention, this heating process is called hardening process. From the viewpoint of the granulation rate and the strength of the granulation, the water content (prescribed as a loss of drying of 3 hours at 180 ° C.) during the heat treatment is preferably 1 to 10% by weight, more preferably 2 to 8% by weight, even more preferably It heats, maintaining 2.5-6 weight%. Fruits such as hot air are used for heating, and the heating temperature (fruit temperature or material temperature) is preferably in the range of 40 to 120 ° C, more preferably in the range of 50 to 100 ° C, and the heating time is The range of 1 minute-2 hours is preferable. Very suitable examples of the combination of the heating temperature and the heating time are 0.1 to 1.5 hours at 60 ° C and 0.1 to 1 hour at 100 ° C.

[9] absorbers, particulate

The particulate water absorbing agent of the present invention is a particulate water absorbing agent having a polyacrylic acid (salt) -based water absorbent resin as a main component, and includes a chelating agent and an inorganic reducing agent, and the content of the chelating agent is 0.001 to 0.5% by weight. It is characterized by satisfy | filling any one or more requirements of 1)-(3).

(1) Content of methoxy phenols is 5-60 ppm.

(2) Contains water insoluble inorganic fine particles.

(3) Water content is 3-15 weight%.

That is, the novel absorbent (first absorbent) of the present invention, which is also shown in the examples described later as an absorbent comprising (1), is a particulate absorbent mainly composed of a polyacrylic acid (salt) -based absorbent resin, and includes a chelating agent and an inorganic reducing agent. The content of the said chelating agent is 0.001-0.5 weight%, and the content of methoxy phenols (especially p-methoxy phenol) is 5-60 ppm. The novel absorbent of the present invention, which is also shown in the examples below, preferably has a pressureless absorption ratio (CRC) of 25 [g / g] or higher and a pressure absorption ratio (AAP 4.83 kPa) of 20 [g / g] or higher with a saline flow induced (SFC) is at least 30 [× · s and g 10- ⁷ and ㎤ ^-1]. Such an absorbent is preferably a high absorption rate with an absorption rate (FSR) of 0.2 [g / g / sec] or more, and satisfies the following particle size. In addition, such absorbents preferably further include an α-hydroxy carboxylic acid compound. It further includes polyvalent metal salts and / or cationic polymers. Since these absorbents have no initial or aging coloration and are white and have high liquid permeability (SFC) and high absorption magnification (AAP) under pressure, high liquid diffusion and low re-wet, even when used in diapers with high concentrations of pulp There is also no coloring problem derived from the absorbent and provides a good paper diaper.

In addition, the novel absorbent (second absorbent) of the present invention, which is also shown in the examples described later as an absorbent having the above (2), is a particulate water absorbent containing a polyacrylic acid (salt) -based absorbent resin as a main component, and includes a chelating agent and It contains an inorganic reducing agent, the content of the chelating agent is 0.001 to 0.5% by weight, and contains water-insoluble inorganic fine particles. Such absorbent may contain methoxy phenols (especially p-methoxy phenol), and may be 0-200 ppm, Preferably, it is 5? Like the said (1) and the novel absorbent (1st absorbent) of this invention. It is in the range of 60 ppm and weatherability and coloring are further improved. The novel water absorbent (second absorbent) of the present invention may have a moisture content of less than 3% by weight similarly to the first absorbent, but preferably satisfies (3) and is in the range of 3 to 15% by weight. The novel absorbent of the present invention, which is also shown in the examples described below, preferably has a non-pressurized absorption ratio (CRC) of 25 [g / g] or higher and a pressurized absorption ratio (AAP2.0 kPa) of 25 [g / g] or higher Absorption rate Vortex is 60 seconds or less.

Moreover, the novel absorbent (third absorbent) of this invention shown also in the Example mentioned later as an absorbent which makes the said (3) essential is a particulate water absorbent which has a polyacrylic acid (salt) type water absorbent resin as a main component, and has a chelating agent and Including an inorganic reducing agent, the content of the chelating agent is 0.001 to 0.5% by weight, and the water content is 3 to 15% by weight. Such absorbent may contain methoxy phenols (especially p-methoxy phenol), and may be 0-200 ppm, Preferably, it is 5? Like the said (1) and the novel absorbent (1st absorbent) of this invention. It is in the range of 60 ppm and weatherability and coloring are further improved. The novel absorbent (third absorbent) of the present invention preferably contains water-insoluble inorganic fine particles similarly to the above (1) and the novel absorbent (first absorbent) of the present invention, and further improves urine resistance. The novel absorbent of the present invention, which is also shown in the examples described below, preferably has a non-pressurized absorption ratio (CRC) of 25 [g / g] or more and a pressurized absorption ratio (AAP2.0 kPa) of 25 [g / g]. The remaining monomer is 500 ppm or less. Such absorbents also preferably further comprise an α-hydroxy carboxylic acid compound. It further includes polyvalent metal salts and / or cationic polymers.

These novel absorbents (particularly the first absorbents, and also the second and third absorbents) of the present invention are the? -Hydroxy carboxylic acids (salts) and / or "[[6] alpha -hydroxy carboxylic acid compounds" described above. 7] polyvalent metal salts and / or cationic polymers and the like shown in " polyvalent metal salts and / or cationic polymers " and the like. These are polyacrylic acids (salts) shown in " [1] polyacrylic acid (salt) absorbent resins " ) Is integrated with the water-absorbent resin.

In addition, the particulate water absorbing agent of the present invention is liquid permeable (SFC), absorbent under magnification (AAP), and more preferably absorbent rate, in order to be used suitably for high-density diapers of white color among the physical properties illustrated below. residual monomer also important, under pressure absorption magnification (AAP) is 20 [g / g] or more, saline flow induced (SFC) is 30 [× 10- ⁷ and ㎤ · s and g ^-1] or more, the absorption rate ( Vortex) preferably satisfies any of the requirements of 60 seconds or less and the residual monomers of 500 ppm or less.

More very suitable ranges of these physical properties are shown below.

Samurai reduction absorption magnification (CRC) is 25 [g / g] or more, under pressure absorption magnification (AAP4. 83㎪) is 20 [g / g] or more, saline flow induced (SFC) is 30 [× 10- ⁷ and Cm 3 · s · g ⁻¹ ] or more. In addition, the absorption ratio under pressure (CRC) is 25 [g / g] or more, the absorption ratio under pressure (AAP2.0 kPa) is 25 [g / g] or more, and the absorption rate (Vortex) is 60 seconds or less. The absorbents satisfy the following thereon.

(a) Fe

In addition, the particulate water absorbing agent of the present invention has a preferred Fe content (in terms of Fe ₂ O ₃ ) of 1 ppm or less, more preferably 0.1 ppm or less, particularly preferably 0.02 ppm or less from the viewpoint of preventing the coloring. The Fe amount can be controlled by appropriately purifying the amount of Fe in the raw material of the absorbent resin, in particular, the base used for neutralization, and removing, for example, Fe of NaOH and Na ₂ CO ₃ . The amount of Fe may be measured in a raw material or may be measured with a final absorbent.

Further, "Fe ₂ O ₃ in terms of value as" refers to a compound of iron, alone or containing the iron (Fe ₂ O ₃ and the ferrous salt, iron hydroxide, iron complex, etc.) in the Fe absolute amount of, Fe ₂ O ₃ (molecular weight 159.7) It is expressed as an iron compound represented by, and is a weight obtained by oxidizing all of the counters of Fe, and the amount of iron as Fe powder is 55.85 × 2 / 159.7, which can be calculated uniquely by a molecular weight (Fe in Fe ₂ O ₃ ).

That is, the base used for neutralization is preferably derived from the particulate water absorbing agent of the present invention. The particulate water absorbing agent of the present invention preferably contains 2 ppm or less of iron (Fe), more preferably 1.5 ppm or less, even more preferably 1 ppm or less, and particularly preferably 0.5 ppm or less. It is included, and the lower limit is preferably 0.001 ppm, even more preferably 0.01 ppm.

For example, when Fe is 10 (if available the Fe amount from the amount of Fe ₂ O ₃ is calculated as Fe ₂ O ₃ amount × 5.85 × 2 / 159.7) and neutralized with a ppm NaOH, CH ₂ = CHCOOH ( From the molecular weight 72) + NaOH (molecular weight 40, Fe is about 7 ppm) → CH ₂ = CHCOONa (94), the sodium polyacrylate obtained was 7 ppm x 40 / 88.55 = approximately 3 ppm at 75% mol of sodium acrylate (molecular weight 88.55). Fe amount becomes. Such a predetermined amount of iron promotes decomposition of the absorbent resin when discarded after use, but excessive iron is not preferable because it causes deterioration during use and coloring before use.

The amount of iron is mainly controlled by the base (especially caustic soda) to be used for neutralization, and in addition to the control of trace iron of raw materials (acrylic acid, crosslinking agent, water, etc.), and also of various absorbent resins such as polymerization apparatus and monomer piping. It can carry out by resin coat, glass coat, stainless steel control of an apparatus or piping. The amount of iron in the base and the absorbent resin can be quantified, for example, by the ICP emission spectrometry method described in JIS K1200-6, and reference can be made to International Publication No. 2008/090961 as a reference for the quantification method. .

(b) particle shape

The shape of the particles of the particulate water absorbing agent (absorbents 1 to 3) of the present invention is not limited to a specific shape, and is spherical, substantially spherical, indefinite crushed, rod-like, polyhedral, A sausage phase (for example, US Pat. No. 4,736,32), wrinkled particles (for example, US Pat. No. 5,574,464), and the like. They may be primary particles, granulated particles, or a mixture thereof. The particles may be foamed porous. Preferred particles include amorphous crushed primary particles or granulated materials. It is preferable to assemble fine powder alone to fine powder to reduce dust, to increase the ratio of the surface to particle diameter and to improve the absorption rate.

(c) particle size

The absorbent (absorbent 1 to absorbent 3) of the present invention is particulate in terms of absorbent properties, preferably having a weight average particle diameter (D50) in the range of 200 to 600 µm, and more preferably in the range of 200 to 550 µm. More preferably, it is the range of 250-500 micrometers. Moreover, the less particle | grains less than 150 micrometers of JIS standards are good, and the content is 0-5 weight% normally, Preferably it is 0-3 weight%, Especially preferably, it is 0-1 weight%. In addition, the fewer particles having a JIS standard of 850 µm or more are better, and the content thereof is usually 0 to 5% by weight, preferably 0 to 3% by weight, particularly preferably 0 to 1% by weight.

The volume fraction of the absorbent of the present invention (as defined in US Pat. No. 662879) is 0.30-0.90, preferably 0.50-0.80, more preferably 0.60-0.75. The particle size can be controlled by the above grinding or classification.

(d) other additives

Furthermore, in order to impart various functions in accordance with the intended function, the water-insoluble inorganic or organic powders such as surfactants, oxidizing agents and metal soaps, deodorants, antibacterial agents, pulp or thermoplastic fibers, etc., are added to the absorbents of the present invention. 3 weight%, Preferably you may add 0-1 weight%. Moreover, as surfactant, surfactant of international publication 2005/075070 is illustrated preferably.

(e) moisture content

The moisture content of the particulate water absorbent (the absorbent 1 to 3) of the present invention is, for example, 0.5 to 16% by weight, preferably 3 to 15% by weight (essentially in the absorbent 2), and 4 to 14 weight % Is more preferable, 5-13 weight% is still more preferable, Especially it is 6-12 weight%, 7-11 weight% on it. The moisture content is controlled by drying and surface crosslinking of the said predetermined moisture content as an example of the adjustment method, and further adding or drying water as needed. If the moisture content is 0.5% by weight or more, in particular 3% by weight or more, the absorption rate (Vortex / FSR) is further improved, and it is difficult to cause problems of odor, a decrease in absorption rate, a decrease in impact resistance, dust generation, and the like. If it is weight% or less, coloring may also be suppressed and the fall of the adhesiveness and water absorption of a particle | grain can be suppressed. If the water content of the absorbent is low, the absorption rate (Vortex / FSR) is lowered, and there is a problem of odor when the inorganic reducing agent is added (particularly in the surface crosslinking process or before). Therefore, it becomes like this. Preferably it is the said moisture content.

(f) Absorption Absorption Ratio (CRC)

CRC of the particulate water absorbing agent used in the present invention is preferably 5 [g / g] or more, More preferably, it is 15 [g / g] or more, More preferably, it is 25 [g / g] or more. Although the upper limit of CRC is not specifically limited, Preferably it is 70 [g / g] or less, More preferably, it is 50 [g / g] or less, More preferably, it is 40 [g / g] or less. When the CRC is less than 5 [g / g], when the particulate water absorbent is used in the absorber, the amount of absorption is too small and is not suitable for use of sanitary materials such as diapers. In addition, when the CRC is larger than 70 [g / g], the absorption ratio under pressure (AAP) and liquid permeability (SFC) may be lowered. When the particulate water absorbent is used in an absorber such as a paper diaper, In some cases, an absorbent having an excellent absorption rate may not be obtained. CRC can be controlled with the above internal crosslinking agent, surface crosslinking agent and the like.

(g) Absorption magnification under pressure (AAP)

The AAP of the particulate water absorbing agent used in the present invention (4.83 kPa above 2.0 kPa) is 20 [g / g] or more, preferably 22 [g / g] or more, and more preferably 23 [g / g] or more. More preferably, it is 24 [g / g] or more, Most preferably, it is 25 [g / g] or more. Although the upper limit of AAP is not specifically limited, Preferably it is 30 [g / g] or less. When AAP is 20 [g / g] or more, when a particulate water absorbent is used for an absorber, an absorbent with less return of liquid (commonly called Re-Wet) when a pressure is applied to the absorber can be obtained. . AAP can be controlled by said surface crosslinking, particle size, etc.

In addition, the load condition of AAP may select 4.83 kV or 2.0 kV suitably according to the type of particulate absorbent obtained, and if the said numerical range is shown, any of the load conditions may be sufficient, Preferably, it is a load of 4.83 kPa on 2.0 kPa. Satisfies the AAP.

(h) Saline flow inducible (SFC)

The SFC of the particulate water absorbing agent used in the present invention is preferably 30 [× 10 ⁻⁷ · cm · s · g ⁻¹ ] or more, more preferably 50 [× 10 ⁻⁷ · cm · s · g ⁻¹ ] Or more, More preferably, it is 70 [x10 <^-7> cm <3> * s * g <^-1> ] or more, Especially preferably, it is 80 [x10 <^-7> * cm <3> * s * g < ^-1 > or more]. If the SFC is 30 [× 10 ^-7 .cm 3 · s · g ^-1 ] or more, the liquid permeability can be further improved. You can get it. Although the upper limit of SFC is not specifically specified, Preferably it is 3000 [x10 <^-7> cm <3> * s * g < ^-1 > or less, More preferably, it is 2000 [x10 <^-7> * cm <3> s * g < ^-1 > or less], More preferably to be. If SFC is 3000 [x10 <^-7> * cm <3> * s * g < ^-1 > or less, when a particulate water absorbent is used for an absorber, liquid leakage from an absorber can be suppressed. SFC can be controlled by the above-mentioned surface crosslinking, particle size, control of CRC to the said range, the polyvalent metal salt, polyamine polymer, etc. which were shown by the said "[7] polyvalent metal salt and / or cationic polymer". In addition, in this specification, saline flow inducibility (SFC) may be described as liquid permeability or liquid permeability (SFC).

(i) Absorption rate 1 (FSR)

The particulate water absorbing agent according to the present invention preferably has an FSR of 0.1 [g / g / sec] or more, more preferably 0.15 [g / g / sec] or more, even more preferably 0.20 [g / g / sec] or more, most preferably 0.25 [g / g / sec] or more. Although the upper limit value of FSR is not specifically specified, excessive high absorption rate (Vortex or FSR) may impair liquid permeability (for example, SFC) and liquid diffusion property, so it is preferably 5.0 [g / g / sec. ] Or less, More preferably, it is 3.0 [g / g / sec] or less. If the FSR is 0.05 [g / g / sec] or more, for example, when a particulate water absorbing agent is used in the absorber, it is possible to further suppress that the liquid is not sufficiently absorbed and liquid leakage occurs. FSR can be controlled by the particle size, foam polymerization, or the like described above.

(j) Absorption rate 2 (Vortex)

Vortex of the particulate water absorbing agent which concerns on this invention becomes like this. Preferably it is 60 second or less, More preferably, it is 55 second or less, More preferably, it is 50 second or less, Most preferably, it is 40 second or less. Although the lower limit of Vortex is not specifically specified, Preferably it is 10 second or more. If Vortex is 60 seconds or less, for example, when a particulate water absorbing agent is used for the absorber, it is possible to further suppress that the liquid is not sufficiently absorbed and liquid leakage occurs. Vortex can be controlled by the above-mentioned particle size, foaming polymerization and the like.

(k) water soluble (Extr)

As for the particulate water absorbing agent which concerns on this invention, water solubility is essentially 50 weight% or less, Preferably it is 35 weight% or less, More preferably, it is 25 weight% or less, More preferably, it is 15 weight% or less. If the water-soluble content is 35% by weight or less, the gel strength is stronger, and the liquid permeability is further excellent. Moreover, when a particulate water absorbent is used for an absorber, an absorbent with less return of liquid (common name RE-Wet) when a pressure is applied to an absorber can be obtained. The water-soluble component can be controlled with the above internal crosslinking agent.

(l) remaining monomers

From the viewpoint of safety, the particulate water absorbing agent according to the present invention is controlled to 500 ppm or less, preferably 400 ppm or less, and more preferably 300 ppm or less. The remaining monomer can be reduced by the use of an inorganic reducing agent, in particular an inorganic reducing agent having a sulfur element, in addition to the polymerization and drying. Since the absorbent of the present invention has fewer residual monomers, even when the absorbent is used at a high concentration (increase in use) in the paper diaper, it is preferable because the residual monomer eluted in the paper diaper is small.

(m) Initial color tone (alias; initial coloration)

The particulate water absorbing agent according to the present invention can be suitably used exclusively for sanitary materials such as paper diapers, and is preferably white powder. The particulate water absorbent according to the present invention has a L value (Lightness) of at least 88, more preferably 89 or more, preferably 90 or more in the Hunter Lab colorimetric measurement by a spectroscopic colorimeter of the particulate water absorbent after the production of the particulate water absorbent. It is preferable. In addition, although the upper limit of L value is 100 normally, when it is 88 as a powder, the problem by a color tone does not arise in products, such as a sanitary material. The b value is 0 to 12, preferably 0 to 10, and 0 to 9 thereon, and the a value to -3 to 3, preferably -2 to 2, and -1 to 1 thereon.

In addition, although initial stage color tone is a color tone after particulate absorber manufacture, it becomes a color tone measured before factory shipment generally. In addition, it is a value measured within 1 year after manufacture, if it is storage in the atmosphere of 30 degrees C or less and relative humidity 50% RH.

(n) color over time (alias; color over time)

The particulate water absorbing agent according to the present invention can be suitably used exclusively for sanitary materials such as paper diapers. At that time, it is preferable to maintain a remarkable and clean white state even in a long-term storage state under high humidity or temperature conditions. The long-term storage state includes the examples described below as a long-term storage color stability promotion test, and the spectroscopic color difference of the absorbent after exposing the particulate water absorbent to the atmosphere at a temperature of 70 ± 1 ° C. and a relative humidity of 65 ± 1% RH for 7 days. We can investigate by measuring L value (Lightness) of Hunter Lab colorimeter by system. The particulate water absorbing agent according to the present invention has a L value (Lightness) of at least 80 or more, 81 or more, and thereon, in the Hunter Lab colorimetric measurement by the spectroscopic colorimeter of the absorbent after the long-term storage color stability promotion test. It is preferable to represent 82 or more, especially 83 or more. In addition, although the upper limit of L value is 100 normally, when L value after an accelerated test is 80 or more, it is a level which does not produce a real problem even in long-term storage state under high humidity or temperature conditions. The b value is 0 to 15, preferably 0 to 12, and 0 to 10 thereon, and the a value to -3 to 3, preferably -2 to 2, and -1 to 1 thereon.

[10] preparation of particulate absorbent

The manufacturing method of the particulate water absorbing agent of this invention is implemented by the method as described in said [1]-[8] as an example.

Specifically, the polyacrylic acid containing the polymerization process of the monomer aqueous solution which has acrylic acid (salt) containing 10-200 ppm of methoxy phenols as a main component, the drying process of the hydrous gel-like crosslinked polymer obtained by superposition | polymerization, and a surface crosslinking process ( A method for producing a salt) -based particulate water-absorbing agent further includes an addition step of 0.001 to 0.5 wt% of a chelating agent and an addition step of an inorganic reducing agent, wherein the monomer contains 10 to 200 ppm of methoxy phenols in terms of large acrylic acid, and It is a manufacturing method which satisfy | fills one or more of (a)-(c).

(a) Further comprising the step of adding water-insoluble inorganic fine particles.

(b) controlling the water content of the polymer to 3 to 15% by weight in the drying step and in the surface crosslinking step.

(c) After the surface crosslinking step, adding an inorganic reducing agent.

According to the above production method, it is possible to obtain a particulate water absorbent for absorbent body having excellent absorption performance and time-lapse coloring performance, surprisingly very low odor and excellent urine resistance, which is very suitable for practical use.

Moreover, it is preferable that the manufacturing method of the particulate water absorbing agent of this invention is a manufacturing method of the particulate water absorbing agent formed by adding the chelating agent mentioned in the said [1], [2], etc. to the monomer aqueous solution before superposition | polymerization or the polymerization degree.

Moreover, it is preferable that the manufacturing method of the particulate water absorbing agent of this invention is a manufacturing method of the particulate water absorbing agent formed by adding the inorganic reducing agent mentioned in the said [1], [3], etc. to the hydrous gel-like crosslinked polymer before drying.

It is preferable that the manufacturing method of the particulate water absorbing agent of this invention is a manufacturing method of the particulate water absorbing agent including the addition process of the (alpha)-hydroxy carboxylic acid (salt) mentioned further in the said [6] etc. further.

It is preferable that the manufacturing method of the particulate water absorbing agent of this invention is a manufacturing method of the particulate water absorbing agent including the addition process of the polyvalent metal salt and / or cationic polymer mentioned further by said [7] etc. further.

It is preferable that the manufacturing method of the particulate-form absorbent of this invention is a manufacturing method of the particulate-form absorbent further including the granulation process demonstrated by said [8].

In addition, the manufacturing method of the particulate water absorbing agent of this invention is implemented by the method as described in said [1]-[8] as an example. More specifically, the monomer aqueous solution of 30-55 weight% of monomer concentrations containing 90-100 mol% of acrylic acid (salt) in a monomer is based on 0.001-1 mol% of radical polymerization initiators, The maximum temperature is 130 degrees C or less. It is a step of performing aqueous solution polymerization or reverse phase suspension polymerization under the conditions of polymerization time of 0.5 minutes to 3 hours, and the neutralization step is composed of a base having a Fe content of 0 to 10 (× 55.85 × 2 / 159.7) ppm, The drying step is a step of drying the particulate hydrogel at a drying temperature of 100 to 250 ° C. to a water content of 20% by weight or less with a drying time of 10 to 120 minutes, and the surface crosslinking step is a surface with respect to 100 parts by weight of the water absorbent resin powder after the drying step. 0.001-10 weight part of crosslinking agents are mixed, and it carries out by heat processing at 70-300 degreeC for 1 minute-2 hours, The manufacturing method which makes methoxy phenol content of the particulate water absorbing agent obtained 5-60 ppm is mentioned. Control of the methoxy phenol content of the particulate water absorbing agent obtained can be performed by the method mentioned above or the method mentioned later.

Although the above-mentioned methoxy phenols in the manufacturing method of the particulate water absorbent of this invention may be added at any point in the manufacturing process of a particulate water absorbent, it is preferable that it is contained in the above-mentioned acrylic acid used as a main component of a monomer, and acrylic acid It is preferable to adjust content suitably in the refinement | purification process of the.

In the manufacturing method of the particulate water absorbing agent of this invention, it is preferable to use acrylic acid containing 10-200 ppm of methoxy phenols.

(10-1) acrylic acid

As a method for producing acrylic acid used in the present invention, the contact gas phase oxidation method of propylene and / or acrolein, ethylene cyanhydrin method, high pressure repe method, improved repe method, ketene method, acrylonitrile hydrolysis method, etc. It is known as, and the gas phase oxidation method of propylene and / or acrolein is the most employ | adopted among these. And in this invention, acrylic acid obtained by such a gas phase oxidation method is used suitably.

In the manufacturing method of the particulate water absorbing agent which concerns on this invention, the monomer containing 10-200 ppm of methoxy phenols is used suitably in large acrylic acid conversion value. Acrylic acid may be sufficient as the main component of this monomer, and acrylic acid and an acrylate may be sufficient as it. Specific examples of the methoxy phenols include o, m and p-methoxy phenols, and methoxy phenols having one or two or more substituents such as methyl group, t-butyl group and hydroxyl group in addition thereto. Especially preferably, p-methoxy phenol is used in the present invention.

The content of methoxy phenols is in terms of large acrylic acid, preferably 10 to 120 ppm, preferably 10 to 90 ppm, more preferably 20 to 90 ppm. When content of p-methoxy phenol is 200 ppm or less, coloring (yellowing / yellowing) of the obtained water absorbing resin can be suppressed. In addition, when the content of p-methoxy phenol is less than 10 ppm, that is, when p-methoxy phenol, which is a polymerization inhibitor, is removed by purification such as distillation, not only there is a risk of polymerization occurring before initiation of polymerization. As described above, the weather resistance of the water absorbent resin and the absorbent obtained by using acrylic acid (salt) as the main raw material is not preferable.

In addition, when methoxy phenols at the time of polymerization are based on acrylic acid (molecular weight 72), the acrylate obtained by neutralization as needed increases molecular weight (for example, molecular weight 88.5 in 75 mol% neutralized sodium salt), In addition, since the component mentioned in [2]-[7] mentioned above is added, content of methoxy phenols is comparatively reduced. In addition, in consideration of consumption at the time of polymerization, in the present invention, the methoxy phenols in the obtained polyacrylate are 5 to 60 ppm with respect to the content of 10 to 200 ppm of the methoxy phenols in the acrylate before the polymerization.

It is preferable that the manufacturing method of the particulate water absorbing agent of this invention is a manufacturing method of the particulate water absorbing agent which acrylic acid undergoes superposition | polymerization of the monomer aqueous solution containing 10-200 ppm of methoxy phenols (especially p-methoxy phenol). Furthermore, by passing through the polymerization process (concentration, initiator, temperature) and drying process (temperature, time, solid content, air volume, etc.), a predetermined amount of methoxy phenol is consumed, and the methoxy phenol of the above-mentioned range (especially p-methoxy It is possible to obtain a particulate water absorbing agent containing 5 to 60 ppm of oxy phenol), particularly uniformly contained in the polymer.

That is, in the manufacturing method of this invention, you may use the manufacturing method which makes 5 to 60 ppm of methoxy phenols of the water absorbing resin obtained by the said radical polymerization process and a drying process by using a monomer whose methoxy phenols content is 10-200 ppm.

In addition, the control method of the methoxy phenol in a water absorbing resin is not limited to the said example, The following method can be illustrated as another method, You may use these together.

Manufacturing method 2; A method in which a predetermined amount of methoxy phenols are added after polymerizing the water absorbent resin in the absence or less than 10 ppm of methoxy phenols and further drying.

Manufacturing method 3; A method in which a predetermined amount of methoxy phenols is removed by washing after polymerization to an absorbent resin with a monomer containing an excess of methoxy phenols before drying. Moreover, water or a water alcohol mixed liquid can be used for washing | cleaning.

In addition, the monomer used by this invention may use polymerization inhibitors other than p-methoxy phenol in a manufacturing process, and may use this polymerization inhibitor together with p-methoxy phenol.

As polymerization inhibitors other than p-methoxy phenol, phenothiazine, hydroquinone, copper salt, manganese acetate, methylene blue, etc. are effective, for example. However, unlike these methoxy phenols, these polymerization inhibitors inhibit polymerization, so the final amount is better, and when used in combination with p-methoxy phenol, the concentration in the monomer is preferably 0.01 to 10 ppm.

In addition, in order to solve the problem (coloring prevention) of the present invention, the smaller the amount of water in acrylic acid is better, usually 1000ppm or less, preferably 750ppm or less, more preferably 500ppm or less, even more preferably 300ppm or less, particularly preferably Is preferably in the order of 200 ppm or less, 100 ppm or less, 80 ppm or less, and 50 ppm or less. Less water is preferable, but about 1 ppm from the dehydration cost, and about 5 ppm on it are enough. In order to obtain such low moisture acrylic acid, distillation or crystallization may be repeated to purify the acrylic acid to adjust to a predetermined amount of water, or the acrylic acid may be brought into contact with an inorganic or organic dehydrating agent to obtain a predetermined amount of water. When the amount of water in the monomer exceeds 1000 ppm, the coloring of the obtained water absorbent resin (particularly over time coloring) tends to deteriorate.

The main components of the monomer are acrylic acid and / or acrylate, but the molecular weight is different in these acrylic acid and acrylate. Considering the difference of this molecular weight, in this invention, a large acrylic acid conversion value is defined. A large acrylic acid conversion value is content ratio (weight ratio) of the weight of the said trace component with respect to the weight of acrylic acid, when all the acrylates are converted into equimolar unneutralized acrylic acid. That is, for example, the sodium acrylate (molecular weight 94) after neutralization is converted into acrylic acid (molecular weight 72) by weight, and the content ratio of the above trace components such as p-methoxy phenol at the weight after acrylic acid conversion (converted 94 to 72). (Weight ratio) and the like are prescribed. In the particulate water absorbing agent after polymerization, when the partially neutralized or fully neutralized acrylate is a polymer, the large acrylic acid conversion value is calculated by converting all partially neutralized or fully neutralized polyacrylates into equimolar unneutralized polyacrylic acid. Can be. The said partial neutralization means that neutralization rate exceeds 0 mol% and is less than 100 mol%. The said complete neutralization means that neutralization rate is 100 mol%. The said unneutralization means that neutralization rate is 0 mol%.

In addition, the said component can be quantified by liquid chromatography or gas chromatography.

(10-2) neutralizer

In the present invention, neutralizing agents (bases) such as caustic soda and sodium carbonate used for neutralization of monomers and polymers are preferred as the iron content is smaller, and the content (as a Fe ₂ O ₃ equivalent) is usually a base. It is the range of 0-10.0 ppm with respect to solid content, Preferably it is contained in the range of 0.2-5.0 ppm, More preferably, it is 0.5-5.0 ppm. If the iron content is less than 0.01 ppm, not only there is a risk of polymerization occurring before the polymerization initiator is added, but there is a possibility that the polymerization may be reversed even if the initiator is added. As this iron, but even a Fe ion, and is preferably trivalent iron in terms of effectiveness, especially Fe ₂ O _3. In addition, the amount of Fe in the above range, it is possible to uniquely calculate the molecular weight ratio of iron and iron oxide (55.85 × 2 / 159.7 (Fe 2 O 3 in the Fe)) of.

In the present invention, regardless of the type of counter anion, the absolute amount of Fe is important. Here, the amount of Fe in terms of Fe ₂ O ₃ is the counter anion (for example, an oxide of Fe (II) or Fe (III), lactate, hydrochloride, hydroxides, etc.) relationship will of an oxide of Fe ₂ O ₃ of the Fe (ⅲ) without the, from the Fe (molecular weight 55.85) and the molecular weight (159.7) of Fe ₂ O _3, the preferred Fe amount in the present invention, a base (Fe conversion) is 0-7.0 ppm.

If the iron content is less than 0.01 ppm, not only there is a risk of polymerization occurring before the polymerization initiator is added, but there is a possibility that the polymerization may be reversed even if the initiator is added. As the iron used in the present invention, but even a Fe ion, preferably from the viewpoint of effect is a trivalent iron, in particular Fe ₂ O ₃ or iron hydroxide.

That is, in the present invention, the neutralization step is preferably made of a Fe content (in terms of Fe) of 0 to 7.0 ppm of a base (especially NaOH or sodium carbonate controlled in the Fe content), and more preferably of the Fe content. Range.

(10-3) Addition method of inorganic reducing agent

The addition method of the inorganic reducing agent in the manufacturing method of the particulate water absorbent of this invention is the said (1-6) polymerization process, (1-7) gel granulation process, (1-8) drying process, (1-9) It can be added to any one or more of the grinding step, the classification step, the (1-10) surface crosslinking step, and the (1-11) other step, and is not particularly limited, but may be added as a powder, a solution, an emulsion, or a suspension. It is preferable to add it as a solution, and it is more preferable to add it as aqueous solution.

When the inorganic reducing agent in the method for producing a particulate water absorbent of the present invention is added in powder form, the average particle diameter of the powder particles is preferably 0.001 to 850 µm, more preferably 0.01 to 600 µm, further preferably 0.05 to 300 µm. Even more preferred. In addition, an average particle diameter can be measured as a volume average particle diameter with a laser. One example of a laser is described in US Patent Application Publication No. 2004/0110006.

As a solvent used when the inorganic reducing agent in the manufacturing method of the particulate water absorbent of this invention is added to a solution, although it does not specifically limit, For example, Water; Alcohols such as ethanol, methanol, propylene glycol and glycerin; Polyethylene glycol etc. can be used suitably. Among them, it is preferable to use water or a mixed solution of water and alcohols, and most preferably added as an aqueous solution. In addition, the concentration of the inorganic reducing agent in such a solution is appropriately determined, and may be a dispersion or a supersaturated solution exceeding the saturation concentration, but is a solution in the following range, especially an aqueous solution, and the upper limit is a saturated concentration.

In addition, as a dispersion medium used when the said inorganic reducing agent is mixed in suspension, although it does not specifically limit, For example, Water; Alcohols such as ethanol, methanol, propylene glycol and glycerin; Polyethylene glycol etc. can be used suitably. Moreover, it is preferable that it is 1-100 weight%, and, as for the density | concentration of the said inorganic reducing agent in such a dispersion liquid, it is more preferable that it is 10-100 weight%. Moreover, you may add a water-soluble polymer, surfactant, etc. further as a dispersing agent.

In addition, in addition to a solution or a suspension, the said inorganic reducing agent may be mixed with an emulsifier and a water absorbent resin as an emulsion in water, for example. Although it does not specifically limit as a dispersion medium in such a case, For example, water etc. can be used suitably.

In addition, as an emulsifier, although it does not specifically limit, A nonionic surfactant, a cationic surfactant, etc. may be used. Moreover, it is preferable that it is 1-90 weight%, and, as for the density | concentration of the said inorganic reducing agent in such an emulsion, it is more preferable that it is 10-90 weight%.

Furthermore, in the manufacturing method of the particulate water absorbing agent which concerns on this invention, it is further more preferable that the said inorganic reducing agent is added as aqueous solution. Moreover, it is preferable that the density | concentration of the inorganic reducing agent in such aqueous solution is 0.01-90 weight%, It is more preferable that it is 0.5-60 weight%, It is still more preferable that it is 1-90 weight%, It is 10-60 weight% It is especially preferable, and it is most preferable that it is 10 to 90 weight%. The upper limit may be a dispersion liquid or a supersaturated solution within the above range, but the upper limit is a saturated concentration.

Although addition of the inorganic reducing agent in the manufacturing method of the particulate water absorbing agent of this invention may be performed at any time after the monomer solution before superposition | polymerization, the hydrous gel-like crosslinked body during superposition | polymerization, before a surface crosslinking process, and after a surface crosslinking process, During the polymerization, it is more preferable to add the hydrogel-like crosslinked polymer after polymerization (that is, the hydrogel-like crosslinked polymer before drying) or after the surface crosslinking step.

In the case where an inorganic reducing agent is added to the hydrogel-like crosslinked polymer after polymerization, it is preferable to add an inorganic reducing agent in the step of refining the hydrogel-like crosslinked polymer after polymerization or to add and mix an inorganic reducing agent to the hydrous gel-like crosslinked polymer after the granulated polymerization. Do. When the inorganic reducing agent is added at the time of surface crosslinking or before the surface crosslinking as in Patent Document 15, when the water content is not controlled at 3 to 15% by weight as in the present invention, the particulate water absorbing agent is colored and the odor becomes strong. .

In addition, after the surface crosslinking process, the time of performing the said addition process is not specifically limited, The addition of the said polyhydric metal salt and / or cationic polymer at any time before, simultaneously with, or after addition of the said polyvalent metal salt and / or cationic polymer is added. You may also In addition, you may add the said (alpha)-hydroxy carboxylic acid compound at any time after addition, simultaneous with addition, or after addition.

It is preferable that the inorganic reducing agent in the manufacturing method of the particulate water absorbent of this invention is mixed with the said polyacrylic acid (salt) type water absorbing resin after addition or simultaneously with addition. The specific mixing method to add or mix is not specifically limited, It can mix using a well-known crushing apparatus, the crushing apparatus, or the stirring apparatus.

As such a pulverization apparatus and a crushing apparatus, a kneader and the screw type extruder (alias: meat chopper) which have a porous structure of arbitrary shape can be illustrated. In addition, a plurality of such disintegrating apparatuses may be used in series, and other apparatuses, such as a kneader and a meat chopper, may be used together. One screw extruder may be sufficient and two or more screw extruders may be used. As such a stirring apparatus, for example, a cylindrical mixer, a screw mixer, a screw extruder, a turbulizer, a nuter mixer, a V mixer, a double kneader, a fluid mixer, an airflow mixer, a rotary disk mixer, a roll mixer, Electric mixers, ready-mixed mixers, paddle blenders, ribbon mixers, rotary blenders, jar stubbers, plaza mixers, mortar mixers and the like can be suitably used. Moreover, such a stirring apparatus may be equipped with the heating apparatus which heats the mixture containing the polyacrylic acid (salt) type water absorbing resin after surface crosslinking, the said inorganic reducing agent, and the said other additive as needed, You may be provided with the cooling apparatus which cools the said mixture heated by heating. Although the time to perform stirring by the said stirring apparatus is not specifically limited, Preferably it is 60 minutes or less, More preferably, it is 30 minutes or less.

(10-4) How to Add Chelating Agent

The chelating agent described above in the method for producing a particulate water absorbent of the present invention includes the above-mentioned (1-6) polymerization step? (1-10) surface crosslinking step and (1-11) other step; Although it may add at any time, it is preferable to add to the monomer aqueous solution before superposition | polymerization or during superposition | polymerization in the said (1-6) polymerization process. When added to the monomer aqueous solution before or during superposition | polymerization, since a chelating agent can be contained more uniformly in a particulate water absorbing agent, it is especially preferable at the point which can prevent coloring over time effectively.

In said (1-6) polymerization process, when adding a chelating agent to the monomer solution before superposition | polymerization, it is preferable to carry out line mixing in the monomer feed line to a polymerization reactor, or to stir-mix in a reactor. In addition, when it adds in the middle of superposition | polymerization, it is preferable to add, after a polymerization reaction starts until it reaches a peak temperature, or until the polymer is discharged | emitted from a polymerization reactor. The addition of the chelating agent to the aqueous monomer solution during the polymerization or during the polymerization is preferable in that the chelating agent can be added uniformly to the particulate water absorbing agent of the present invention, which can further bring about the effect of the present invention.

(10-5) Method of adding water-insoluble inorganic fine particles

The above water-insoluble inorganic fine particles in the method for producing a particulate water absorbent of the present invention include the above-mentioned (1-6) polymerization step? (1-10) surface crosslinking step and (1-11) other step. Although you may add at any time of an absorbent manufacturing process, it is preferable to add after a surface crosslinking process (1-10). That is, it is preferable to add water-insoluble inorganic fine particles simultaneously with the above-mentioned surface crosslinking agent, to crosslink a water absorbent resin surface, or to add water-insoluble inorganic fine particles after crosslinking water absorbent resin surface with the above-mentioned surface crosslinking agent. In particular, by adding the water-insoluble inorganic fine particles to the water-absorbing resin after the surface crosslinking by the surface crosslinking agent and surface-treating, desired absorption characteristics, particularly high liquid permeation characteristics are achieved. In addition, the water-insoluble inorganic fine particles are preferably added simultaneously with the above-described? -Hydroxy carboxylic acid compound or as a mixture previously mixed with the? -Hydroxy carboxylic acid compound.

(10-6) Method of adding α-hydroxy carboxylic acid compound

The above-mentioned -hydroxy carboxylic acid compound in the manufacturing method of the particulate water absorbing agent of this invention contains said (1-6) polymerization process, (1-10) surface crosslinking process, and (1-11) other process. Although it may add at any time in the manufacturing process of a particulate water absorbing agent, in consideration of the effect of color stability over time, it may be contained in a polymerizable monomer beforehand, and it is preferable to add in a post-stage process after completion of the above-mentioned polymerization reaction. . As a method to add in the post-stage process after completion | finish of a polymerization reaction, the method of adding to the hydrous gel-like polymer after superposition | polymerization, the method of adding to the dry matter after a drying process, the surface crosslinking process, or the method of adding after that is preferable.

Although the addition method of the (alpha)-hydroxy carboxylic acid compound in the manufacturing method of the particulate water absorbing agent of this invention is not specifically limited, It is preferable to add as a powder form, a solution, emulsion, or a suspension, and to add as a solution. More preferably, it is even more preferable to add it as an aqueous solution. In addition, the α-hydroxy carboxylic acid compound may be added simultaneously with the chelating agent, the polyvalent metal salt and / or the cationic polymer, and the water-insoluble inorganic fine particles described above, or may be added as a mixture previously mixed with each of these components. .

(10-7) Method of adding polyvalent metal salts and / or cationic polymers

The above-mentioned polyvalent metal salt and / or cationic polymer in the method for producing a particulate water absorbing agent of the present invention comprises the above (1-6) polymerization step (1-10) surface crosslinking step or (1-11) other step. It may contain, and may add at any time of the manufacturing process of a particulate water absorbing agent, but it is preferable to add at the time of surface treatment.

That is, in the above (1-10) surface crosslinking step, a method of crosslinking the water absorbent resin surface by adding a polyvalent metal salt and / or a cationic polymer simultaneously with the above-mentioned surface crosslinking agent, or crosslinking the water absorbent resin surface with the above-mentioned surface crosslinking agent Then, the method of adding a polyvalent metal salt and / or a cationic polymer as a 2nd surface crosslinking process is preferable. The polyvalent metal salt and / or cationic polymer further improves the physical properties of the absorbent obtained as a surface crosslinking agent which reacts with the functional groups of the polyacrylic acid-based absorbent resin, in particular ionic bonds (first or second). In particular, the desired water absorption characteristics, particularly high liquid permeation characteristics (SFC), are achieved by adding a polyvalent metal salt and / or a cationic polymer to the surface-absorbing resin after surface crosslinking by the surface crosslinking agent. Moreover, it is preferable to add a polyvalent metal salt and / or a cationic polymer simultaneously with the said (alpha)-hydroxy carboxylic acid compound, respectively, or as a mixture previously mixed with the (alpha)-hydroxy carboxylic acid compound. Conventionally, the use of polyvalent metal salts and / or cationic polymers has caused coloring of the water absorbent resin, but there is no problem in the present invention, and the physical property improvement by the polyvalent metal salts and / or cationic polymers is achieved.

(10-8) drying after addition

Moreover, you may dry the obtained mixture after the addition process of said (10-3)-(10-7). Here, drying is preferably carried out at a temperature range of at least 40 ° C. and less than 100 ° C. through at least 50% of the time involved in the drying step, more preferably through all the drying steps. By drying in such a temperature range, since an absorbent is not damaged by heat, it does not adversely affect the physical property of the obtained absorbent.

In addition, the drying temperature is specified by the fruit temperature, but when it cannot be specified by the fruit temperature such as microwave, it is specified by the material temperature. As a drying method, if a drying temperature is in the said range, it will not specifically limit, Hot air drying, airless drying, vacuum drying, infrared drying, microwave drying, etc. can be used suitably. The drying temperature is more preferably in the range of 40 ° C to 100 ° C, and even more preferably in the range of 50 ° C to 90 ° C. The drying may be dried at a constant temperature or may be dried by varying the temperature. However, it is preferable that the drying process is performed so that the actual and all drying steps are within the above-described temperature range and the water content to be described later.

The drying time depends on the surface area of the absorbent, the moisture content, and the type of the dryer, and is appropriately selected so as to achieve the desired moisture content. Drying time is 10 to 120 minutes normally, More preferably, it is 20 to 90 minutes, More preferably, it is 30 to 60 minutes. If drying time is less than 10 minutes, drying may not be enough and handling property may not be enough. In addition, when the drying time is 120 minutes or more, damage to the absorbent is caused by excessive drying (presumably a combination of the inorganic reducing agent and the absorbent resin), resulting in odor, and an increase in the amount of water to occur. The improvement effect of all the physical properties may not be seen, either. By this drying process, you may adjust so that the moisture content of the particulate water absorbing agent of this invention may be 5 weight% or less.

As water content after drying, 3-15 weight% is preferable, 4-14 weight% is more preferable, 5-13 weight% is still more preferable, Especially it is 6-12 weight%, It is 7-11 weight% on it. The above-mentioned method is illustrated as an example of a moisture content adjustment method.

Patent Document 17 (European Patent No. 1645596) discloses a water-absorbent resin composition having a color resistance that contains an absorbent resin, an oxygen-containing reducing inorganic salt, an amino carboxylic acid-based metal chelating agent, and an organic antioxidant. The use of an amount of p-methoxy phenol and water insoluble fine particles is not disclosed, nor is the importance of the moisture content of the obtained water absorbent resin composition. In the Example of patent document 17, in Example 1-7, 80weight% acrylic acid (92g + 119.1g) and 30weight% NaOH aqueous solution (102.2g + 132.2g) etc. were used for preparation example, and 214.4g of water absorbing resin obtained as a monomer. An oxygen-reducible inorganic salt, an amino carboxylic acid metal chelating agent, and an organic antioxidant are mixed without a solvent to obtain a water absorbent resin composition. Therefore, in patent document 17, the water content of the water absorbent resin is calculated | required by calculation by 17 weight% from the raw material (g) of water-absorbent resin, and the quantity (212.2g), Therefore, patent document 17 has a very suitable water content of 3-15 weight% of this application. 4-14 weight%, 5-13 weight%, 6-12 weight%, and 7-11 weight% are not disclosed on it. In addition, Patent Document 17 discloses an alkyl hydroxy anisole and the like (such as butyl) as an organic antioxidant (paragraph [Example 6]), but does not disclose a small amount of p-methoxy phenol.

(11) absorbers

The absorber which concerns on this invention contains the particulate water absorbing agent which concerns on this invention. By combining the particulate water absorbent of the present invention with a suitable material, for example, an absorbent body which is very suitable as an absorbent layer of hygiene material can be obtained. Hereinafter, the absorber of this invention is demonstrated. The absorbent of the present invention is white in color, having high liquid permeability, high absorption ratio under pressure, high absorption rate, and low residual monomer. Therefore, the absorbent of the present invention can be suitably used for high concentration absorbents, especially diapers.

In this invention, an absorber is a composition used for the sanitary material which absorbs blood, a bodily fluid, urine, etc., It is a molded composition which consists of a particulate water absorbing agent and another material. Here, as said sanitary material, a paper diaper, a sanitary napkin, an incontinence pad, a medical pad, etc. are mentioned, for example. Cellulose fiber is mentioned as another raw material used for an absorber.

As a specific example of such a cellulose fiber, For example, wood pulp fibers, such as a mechanical pulp from a wood, a chemical pulp, a semi-chemical pulp, a dissolution pulp; Artificial cellulose fibers, such as rayon and an acetate, can be illustrated. More preferred cellulose fibers are wood pulp fibers. Moreover, these cellulose fibers may contain some synthetic fibers, such as nylon and polyester.

When using the particulate water absorbing agent according to the present invention as part of the absorber, the content of the particulate water absorbing agent contained in the absorber is preferably 20% by weight or more, more preferably 30% by weight or more, even more preferably 50% by weight. It is the range above. When the weight of the particulate water absorbent of the present invention contained in the absorber is less than 20% by weight, there is a fear that a sufficient absorbing effect cannot be obtained.

In order to manufacture an absorbent body using the particulate water absorbing agent and cellulose fiber which concerns on this invention, the said absorbent is spread | dispersed in paper, mat, etc. which consist of cellulose fibers, for example, the method of sandwiching these papers, a mat, etc. as needed, a cellulose fiber And a well-known means for obtaining an absorber, such as a method of uniformly blending a water absorbent and the like, can be appropriately selected. As a more preferable method, the method of compressing after a dry mixing of a particulate water absorbing agent and a cellulose fiber is mentioned. By this method, it is possible to remarkably suppress the dropping of the particulate water absorbent from the cellulose fibers. It is preferable to perform compression under heating, and the temperature range is 50-200 degreeC, for example.

When the particulate water absorbing agent according to the present invention is used in an absorber, the absorbent is excellent in overall physical properties, so that a very good absorbent is obtained, in which the absorption of the liquid is quick and the amount of remaining liquid in the absorber surface layer is small.

Since the particulate water absorbing agent which concerns on this invention has the outstanding water absorption characteristic, it can be used as water absorption repair agent of various uses. Specifically, for example, absorption repair agents for absorbent articles such as paper diapers, sanitary napkins, incontinence pads, and medical pads; Agricultural horticultural repair agents such as water moss replacement, soil reforming improvers, repair agents, and pesticide sustainability agents; Building repair agents such as condensation inhibitors for interior walls and cement additives; It can be used as release control agent, coolant, disposable hot pack, sludge coagulant, food freshener, ion exchange column material, sludge or oil dehydrating agent, desiccant, humidity control material. Among them, the absorbent according to the present invention is particularly suitably used for hygiene materials for absorbing feces, urine or blood, such as paper diapers and sanitary napkins.

Absorbent according to the present invention, when used in sanitary materials such as paper diapers, sanitary napkins, incontinence pads, medical pads, (a) liquid permeable top sheet disposed adjacent to the wearer's body, (b) wearer's It is preferably used in a configuration comprising a back sheet impermeable to liquid, disposed away from the body, adjacent to the wearer's clothing, and (c) an absorber disposed between the top sheet and the back sheet. The absorber may be two or more layers or may be used together with a pulp layer or the like.

As mentioned above, the particulate water absorbing agent which concerns on this invention can also be changed as follows.

(1) A particulate water absorbent containing polyacrylic acid (salt) -based water absorbent resin as a main component, containing 5 to 60 ppm of methoxy phenols, a chelating agent, and an inorganic reducing agent, wherein the polyacrylic acid (salt) absorbent resin is a main component. Particulate water absorbing agent.

(2) A particulate water absorbent containing a polyacrylic acid (salt) -based water absorbent resin as a main component, and comprising a chelating agent, an inorganic reducing agent, and water-insoluble inorganic fine particles. Absorbent.

(3) Polyacrylic acid (salt) having a water-absorption rate of 3 to 15% by weight of a particulate water-absorbing agent having a surface-crosslinked polyacrylic acid (salt) -based water absorbent resin as a main component and containing an inorganic reducing agent, a chelating agent, and p-methoxy phenol. A particulate water absorbing agent having a) -based water absorbent resin as a main component.

In addition, the manufacturing method of the particulate water absorbing agent of this invention can be changed as follows.

(1) The polymerization step of the aqueous monomer solution containing 10 to 200 ppm of methoxy phenols as the main component, the drying step of the hydrous gel crosslinked polymer obtained by polymerization, the surface crosslinking step, and the addition step of the chelating agent As a manufacturing method of a particulate water absorbent containing,

A process for producing a particulate water absorbing agent, characterized in that an inorganic reducing agent is added after the surface crosslinking step.

(2) A method for producing a particulate water absorbing agent comprising a polymerization step of an aqueous monomer solution containing acrylic acid (salt) as a main component and a drying step of a hydrous gel crosslinked polymer obtained by polymerization.

A method of producing a particulate water absorbing agent comprising a surface crosslinking step, a step of adding a chelating agent, and an step of adding an inorganic reducing agent and water-insoluble inorganic fine particles.

(3) Polymerization step of monomer aqueous solution containing acrylic acid (salt) containing 10-200 ppm methoxy phenols, drying step of hydrous gel crosslinked polymer obtained by polymerization, surface crosslinking step, inorganic reducing agent and chelating agent As a manufacturing method of a particulate water absorbing agent whose main component is a polyacrylic acid (salt) -based water absorbent resin including an addition step,

A method for producing a particulate water absorbent comprising polyacrylic acid (salt) -based water absorbent resin as a main component, wherein the water content of the polymer is controlled to 3 to 15 wt% in the drying step and the surface crosslinking step.

This invention is not limited to each above-mentioned embodiment, Various changes are possible in the range shown to the claim, and also about embodiment obtained by combining suitably the technical means disclosed in each other in the technical scope of this invention also in the technical scope of this invention. Included.

(A very suitable sub concept of the particulate water absorbent)

(Method for producing particulate water absorbent, part 1)

As a manufacturing method of the particulate water absorbing agent of this invention, the manufacturing method of the subconcept which makes the said (c) an essential part, 1 is a polymerization process of the aqueous monomer solution which has acrylic acid (salt) containing 10-200 ppm of methoxy phenols as a main component. And a method for producing a particulate water absorbing agent comprising a drying step of a hydrous gel crosslinked polymer obtained by polymerization, a surface crosslinking step, and an addition step of 0.001 to 0.5% by weight of a chelating agent, followed by a step of adding an inorganic reducing agent after the surface crosslinking step. It is characterized by performing. Such a manufacturing method and the specific example of the 1 are shown in Examples 1-1 to 1-16 and Tables 1 to 5 described later.

(Method for producing particulate water absorbent, part 2)

As a method for producing a particulate water absorbent of the present invention, the production method of a subordinate concept in which (b) is essential, and 2 are a polymerization step of a monomer aqueous solution containing acrylic acid (salt) as a main component, and a hydrous gel crosslinked polymer obtained by polymerization. A method for producing a particulate water absorbing agent comprising a drying step and a surface crosslinking step, the method further includes an addition step of 0.001 to 0.5% by weight of a chelating agent and an addition step of an inorganic reducing agent, and the monomers convert methoxy phenols into large acrylic acid. 10 to 200 ppm, and further comprising the step of adding (a) water-insoluble inorganic fine particles. Such a manufacturing method and the specific example of the 2 are shown in Examples 2-1-2-14 and Tables 6-7 which mention later.

(Method for producing particulate water absorbent, part 3)

As a method for producing the particulate water absorbent of the present invention, the production method of the subordinate concept in which (c) is an essential part thereof is a polymerization step of a monomer aqueous solution containing acrylic acid (salt) as a main component, and a hydrous gel crosslinked polymer obtained by polymerization. A method for producing a particulate water absorbing agent comprising a drying step and a surface crosslinking step, the method further includes an addition step of 0.001 to 0.5% by weight of a chelating agent and an addition step of an inorganic reducing agent, and the monomers convert methoxy phenols into large acrylic acid. 10 to 200 ppm, and controlling the moisture content of the polymer to 3 to 15% by weight in the drying step and / or the surface crosslinking step, and more preferably, the inorganic reducing agent is added to the hydrous gel-like crosslinked polymer before drying. It is characterized by. Such a manufacturing method and the specific example of the 3 are shown in Examples 3-1 to 3-13 and Tables 8-9 which will be described later.

Example

Hereinafter, although an Example demonstrates this invention, this invention is limited to an Example and is not made to interpret. In addition, the general physical properties described in the claims and the examples of the present invention were obtained according to the following measurement methods. In addition, although the following measuring method is describing about a particulate water absorbing agent, it measures also by changing a particulate water absorbing agent into water absorbing resin also about water absorbing resin. In addition, the electrical equipment used in the Example was 200V or 100V, and was used on 60 Hz conditions. In addition, the particulate water absorbing agent was used under the conditions of 25 ° C ± 2 ° C and 50% RH relative humidity, unless otherwise specified. The reagents and instruments exemplified in the following measurement methods or examples may be appropriately replaced with equivalents.

In addition, although the particulate water absorbing agent of this invention contains an inorganic reducing agent as an essential part, hereafter, it may be called a particulate water absorbing precursor with respect to the water absorbing resin before addition of an inorganic reducing agent as surface-crosslinked water absorbing resin (Reference; Example 1-) 1 to 1-8, Comparative Examples 1-3, 1-4 and the like).

[Evaluation method of physical property]

[CRC]

After 0.2 g of the particulate water absorbent was uniformly placed in a nonwoven fabric bag (60 × 60 mm) and sealed, it was immersed in 500 g of a 0.9 wt% aqueous sodium chloride solution (alias; physiological saline) adjusted to 25 ± 3 ° C. After 60 minutes had elapsed, the bag was lifted up and dehydrated at 250 G for 3 minutes using a centrifuge, and then the weight W1 [g] of the bag was measured. The same operation was performed without putting a particulate water absorbing agent, and the weight W2 [g] at that time was calculated | required. CRC (absorption rate under no pressure) was calculated according to the following equation.

[1]

CRC [g / g] = (W1-W2) /0.2... One

[Solubles]

184.3 g of 0.90% by weight aqueous sodium chloride solution and 1.00 g of particulate water absorbent were placed in a plastic container with a capacity of 250 ml with a capacity. The mixture was stirred for 16 hours, and the aqueous solution in the particulate water absorbent was extracted. The extract was filtered using one piece of filter paper (ADVANTEC Dongyang Co., Ltd., name: JIS # P # 3801, No. 2, thickness 0.26 mm, retention particle diameter of 5 µm), and 50.0 g of the obtained filtrate was used as a measurement solution.

Subsequently, titration was carried out with 0.1 N aqueous NaOH solution until pH 10, and then titrated with 0.1 N aqueous HCl solution until pH 2.7. At this time, an appropriate amount ([NaOH] ml, [HCl] ml) was obtained. In addition, the same titration operation was performed only with respect to 184.3g of 0.90 weight% sodium chloride aqueous solution, and the empty titration amount ([bNaOH] ml, [bHCl] ml) was calculated | required.

In the case of the particulate water absorbent of the present invention, the water-soluble content in the particulate water absorbent can be calculated by the following number 2 based on the average molecular weight of the monomer and the appropriate amount obtained by the above operation. In addition, when the average molecular weight of the monomer is unknown, the average molecular weight of the monomer can be calculated using the neutralization rate determined by titration. This neutralization rate is computed by following formula 3.

[Number 2]

Water-soluble content [% by weight] = 0.1 x (monomer average molecular weight) x 184.3 x 100 x ([HCl]-[bHCl]) /1000/1.0/50.0

[Number 3]

Neutralization rate [mol%] = (1-([NaOH]-[bNaOH]) / ([HCl]-[bHCl])) × 100

[Residual Monomer]

The residual monomer (residual acrylic acid (salt)) contained in the particulate water absorbing agent of the present invention is filtered by performing the same operation except that the stirring time in the measuring method of [water content] is changed from 16 hours to 2 hours. It is calculated | required by analyzing liquid. Specifically, the remaining monomer in the particulate water absorbent can be obtained by analyzing the filtrate obtained by the above operation by high performance liquid chromatography. In addition, a residual monomer is represented by ppm (large particulate absorbent).

[AAP]

Absorption to pressure (AAP) represents an absorption ratio of 60 minutes at 4.83 kPa or 2.0 kPa for 0.90 wt% saline. In addition, AAP may also be called absorption under magnification at 4.83 kPa or 2.0 kPa.

Using the apparatus shown in FIG. 1, the stainless steel 400 mesh wire mesh 101 (38 micrometers in size) was fused to the bottom of the support cylinder 100 of 60-mm-diameter plastic, and room temperature (20-25 degreeC), humidity Under conditions of 50 RH%, 0.900 g of a particulate absorbent is evenly distributed on the net, and adjusted to uniformly apply a load of 4.83 kPa (0.7 psi) or 2.0 kPa (0.3 psi) to the particulate water absorber thereon. One set of this measuring device is provided with a piston 103 and a load 104 in this order which do not have a gap with the support cylinder and whose external diameter is slightly smaller than 60 mm, and which cannot prevent the movement of up and down. The weight Wa [g] of was measured.

A 0.90% by weight aqueous sodium chloride solution 108 (20) was placed inside a petri dish 105 having a diameter of 150 mm and a glass filter 106 having a diameter of 90 mm (a mutual chemical glass making company, a pore diameter: 100-120 µm). 25 ° C.) was added at the same level as the upper surface of the glass filter. Filter paper 107 (ADVANTEC Dongyang Co., Ltd., product name: JIS P # 3801, No. 2, thickness 0.26mm, holding particle diameter 5 micrometers) of 90 mm in diameter is put on it, and the surface is all wet, and excess The liquid was removed.

One set of measuring devices was placed on the wet filter paper and the liquid was absorbed under load. After 1 hour, one set of measuring devices was lifted and the weight Wb [g] was measured. And AAP [g / g] was computed from Wa and Wb according to the following formula.

[4]

AAP [g / g] = (Wb-Wa) / (weight of particulate absorbent (0.900 g))

[SFC]

SFC (saline flow inducibility) is a value which shows the liquid permeability at the time of swelling of water absorbent resin particle or an absorbent. The larger the value of the SFC, the higher the liquid permeability. The saline flow induction (SFC) test described in US Pat. No. 5849405 was carried out.

Using the apparatus shown in FIG. 2, 0.900 [g] of the particulate water absorbing agent uniformly placed in the container 40 was swollen for 60 minutes under pressure of 2.07 kPa (0.3 psi) in artificial urine, and then gel layer of gel 44 Hit the height. Next, under pressure of 2.07 Pa, a 0.69% by weight aqueous sodium chloride solution 33 was passed through the gel 44 swollen from the tank 31 at a constant hydrostatic pressure. This SFC test was performed at room temperature (20-25 degreeC). Using a computer and a balance, the amount of liquid passing through the gel layer at 20 second intervals as a function of time was recorded for 10 minutes.

The flow rate Fs (T) passing through the swollen gel 44 (mainly between particles) is obtained by dividing the increase weight [g] by the elapsed time [s] [unit; g / s]. The time at which a constant hydrostatic pressure and a stable flow rate are obtained is Ts, and only the data obtained between Ts and 10 minutes is used for the flow rate calculation, and the value of Fs (T = 0) is obtained by using the flow rate obtained between Ts and 10 minutes. That is, the first flow rate through the gel layer was calculated. Fs (T = 0) was calculated by extrapolating the result of at least two multiplications of Fs (T) vs. time to T = 0.

[Number 5]

SFC [10 ⁻⁷ · cm · s · g ⁻¹ ] = (Fs (t = 0) × L0) / (ρ × A × ΔP)

From here,

Fs (t = 0): flow rate [g / s]

L0: height of the gel layer [cm]

ρ: density of aqueous sodium chloride solution (1.003 [g / c㎥])

A: area (28.27 [cm 2]) above the gel layer in the cell 41

ΔP: Hydrostatic pressure (4920 [dyn / cm 2]) applied to the gel layer.

The SFC measuring apparatus shown in FIG. 2 will be described in detail.

The tank 31 has a glass tube 32 inserted therein, and the lower end of the glass tube 32 has a 0.69% by weight aqueous sodium chloride solution 33 at a height of 5 cm above the bottom of the swelling gel 44 in the cell 41. Placed to keep. A 0.69% by weight aqueous sodium chloride solution 33 in the tank 31 was supplied to the cell 41 through an L-shaped tube 34 with a cock 35. Under the cell 41, the container 48 which collects and collects the liquid which passed through is arrange | positioned, and the supplement collection container 48 was provided on the dish scale 49. As shown in FIG. The inner diameter of the cell 41 was 6 cm, and the stainless steel wire mesh 42 of 38 micrometers of eye size was provided in the bottom surface. The lower part of the piston 46 has a hole 47 sufficient for liquid to pass therethrough, and the bottom part is equipped with a glass filter 45 having good permeability so that a particulate absorbent or its swelling gel does not enter the hole 47. . The cell 41 is placed on the pedestal for placing the cell, and the surface of the pedestal in contact with the cell is placed on a stainless steel wire 43 that does not interfere with the permeation of the liquid.

In addition, artificial urine contained 994.25 [g] of pure water, 0.25 [g] of calcium chloride dihydrate, 2.0 [g] of potassium chloride, 0.50 [g] of magnesium chloride hexahydrate, 2.0 [g] of sodium sulfate, and 0.85 [of ammonium dihydrogen phosphate]. g] and 0.15 [g] which added ammonium hydrogen phosphate were used.

[Absorption rate 1 (FSR)]

FSR (absorption rate) is an index of the speed of absorbing the liquid of the absorbent. It is desirable that the absorption rate be a high value. By using an absorbent having a high absorption rate in the absorber, it becomes possible to obtain an absorbent having excellent absorption rate of the liquid. Absorption rate is measured by the following method.

1.000 ± 0.0005 [g] of the particulate water absorbent is accurately weighed to four digits after the decimal point (Wc [g]), and the top surface of the particulate water absorbent is horizontally placed in a 25 ml glass beaker (32 to 34 mm in diameter and 50 mm in height). Put in. If necessary, treatment such as beating the beaker carefully is carried out to level the particulate water absorbent. Next, 20 ml of 0.9 weight% sodium chloride aqueous solution adjusted to 23 +/- 2.0 degreeC was taken in 50 ml of glass beakers, and the weight of the said aqueous solution was measured to 4 decimal places (Wd [g]).

Next, the 0.9 weight% sodium chloride aqueous solution was poured quickly into the 25 ml beaker containing a particulate water absorbing agent, and time measurement was started from the instant when the sodium chloride aqueous solution and the particulate water absorbing agent contacted. The liquid level in the beaker which poured the said sodium chloride aqueous solution was visually observed at the angle of about 20 degrees, and time (Th [sec]) until the liquid level was transferred from aqueous solution to a particulate-form absorbent was measured. Next, the weight (We [g]) of the aqueous sodium chloride solution (beaker remaining amount) attached to the beaker after pouring the aqueous sodium chloride solution was measured to four decimal places. FSR (absorption rate) [g / g / sec] was calculated | required by the following formula. In addition, it measured three times about one sample, and made the average value into the representative value.

[Number 6]

FSR [g / g / sec] = (Wd-We) / (Th-We)

[Absorption rate 2 (Vortex)]

To 1.000 parts by weight of an aqueous 0.90% by weight aqueous sodium chloride solution (physiological saline) 0.02 part by weight of food additive No. 1 (CAS No. 3844-45-9) as a food additive was added and adjusted to a liquid temperature of 30 ° C. 50 ml of the physiological saline is taken in a beaker (e.g., a beaker in accordance with JISR-3503 sold by Mutai Chemical Glass Co., Ltd.) with a body diameter of 55 mm and a height of 70 mm. The length is 40 mm and the thickness is 8 mm. While stirring under a condition of 600 rpm with a cylindrical stirrer made of Cylindrical Teflon (for example, S-type sold by Mutai Chemical Glass Co., Ltd.), 2.0 g of the particulate water absorbing agent obtained in Examples or Comparative Examples described later was added. The absorption rate (seconds) is measured. The starting point and the end point are in accordance with the standards described in JIS K 7224 (1996), "Explanation of Absorption Rate Test Method for Superabsorbent Polymers," and the particulate water absorbent absorbs the physiological saline, and the physiological saline in the gelation is rotated. The time of rotation (covered by the V-shape in cross section) until the covering of the stirrer chip is measured and evaluated as the absorption rate (seconds).

[Weight average particle diameter (D50), logarithmic standard deviation of particle size distribution (σξ) and particles smaller than 150 μm]

The weight average particle diameter (D50) was measured according to the method described in the international publication 2004/069404 pamphlet. JIS standard bodies (JIS # Z8801-1 (2000)) having a predetermined amount of particulate water absorbing agent having an eye size of 850 µm, 710 µm, 600 µm, 500 µm, 425 µm, 300 µm, 212 µm, 150 µm, 106 µm, and 45 µm, Or sieve separation was carried out using sieves corresponding to these JIS standards, and the residual percentage R was plotted on the logarithmic probability paper. Thus, the particle size corresponding to R = 50% by weight was read as the weight average particle diameter (D50).

The logarithmic standard deviation (σξ) of the particle size distribution is represented by the following equation, and the smaller the value of σξ, the narrower the particle size distribution.

[Numeral 7]

σξ = 0.5 × ln (X2 / X1)

From here,

X1: particle size corresponding to R = 84.1 [wt%]

X2: It is a particle size corresponded to R <= 15.9 [weight%].

Particles [Weight%] of less than 150 [mu] m prescribed by the standard body classification are the weight of the particles passing through the JIS standard body (JIS # Z8801-1 (2000)) having an eye size of 150 [mu] m, and the ratio [weight to the total weight of the particulate water absorbent] %]to be. In this specification, it is also only called "particle [weight%] less than 150 micrometers, or" 150 micrometers pass | pass [%].

[Coloring Evaluation of Particulate Absorber (Hunter Lab Colorimeter / L Value)]

The color evaluation of the particulate water absorbing agent was performed using LabScan (registered trademark) XE manufactured by HunterLab. As the measurement setting conditions, reflection measurement is selected, and a powder / paste sample container having an inner diameter of 30 mm and a height of 12 mm is used. As a standard, a standard round white plate No. 2 for powder and paste is used, and a 30φ light-emitting pipe is used. It became. About 5 g of a particulate water absorbing agent was filled in the container for a sample provided. This filling was to fill the container for non-sample about about 60%. The L value (Lightness: brightness index) of the surface was measured by the said spectrophotometer on the conditions of room temperature (20-25 degreeC), and humidity 50RH%. This value is referred to as "brightness index before exposure", and the larger the value, the more white.

In addition, by the same measuring method of the same apparatus, the object colors a and b (chromaticity) of different scales can also be measured simultaneously. The smaller a / b indicates the closer to real white color with low coloration. Immediately after the particulate water absorbent is produced or under conditions of 30 ° C. or lower and a relative humidity of 50% RH or lower, the color evaluation result of the particulate water absorbent stored for a period of one year or less becomes an initial color tone.

Subsequently, the paste sample container was filled with about 5 g of a particulate water absorbent and adjusted to an atmosphere of 70 ± 1 ° C. and a relative humidity of 65 ± 1% (Small Environmental Tester, Spec SH-641). The paste sample container filled with the particulate water absorbent was exposed for 7 days. This exposure is a 7-day color promotion test. After exposure, the L value (Lightness) a / b value of the surface was measured with the said spectrophotometer. This measured value is used as coloring with time after an accelerated test.

[Odor test]

1 part by weight of the particulate water absorbent was placed in a 100 ml beaker, 20 parts by weight of 0.9% by weight aqueous sodium chloride solution was added, the beaker was sealed with a film, and left to stand at 37 ° C for 1 hour. Subsequently, a test was carried out for the organs of 10 adults. The evaluation method made into what was judged to be the odor which can be used for sanitary materials, such as a diaper, without an unpleasant odor, and was determined to be an odor which has unpleasant odor, and is unusable for sanitary materials, such as a diaper. In particular, the unpleasant odor was made into xx.

[Water content]

1.00 [g] of a particulate water absorbent was rewound in the aluminum cup of about 50 mm in diameter of the bottom surface, and the total weight W8 [g] of the particulate water absorbent and the aluminum cup was measured. Then, it left still for 3 hours and dried in oven of atmospheric temperature 180 degreeC. After 3 hours, the particulate water absorbing agent and the aluminum cup were taken out of the oven and cooled to room temperature in a desiccator. Then, the gross weight W9 [g] of the particulate water absorbing agent and aluminum cup after drying was calculated | required, and the water content was calculated | required according to following drinking water 8.

[Numeral 8]

Water content [% by weight] = (W8-W9) / (weight of the particulate water absorbent [g]) × 100

[Weather resistance promotion test] (gel degradation test 1)

3.0 g of the particulate water absorbent was placed in a quartz separable flask having an inner diameter of 7.0 cm and a height of 14.0 cm, and 57.0 g of deionized water was added thereto. Subsequently, the metal halide lamp (Ushio) was stirred while stirring 20 times swollen gel particles (60 g) in the separable flask with stirring blades having four flat blades 3.0 cm wide and 1.0 cm wide from the center of the shaft to the tip of the blade. Using an ultraviolet irradiating apparatus (copper, UV-152 / 1MNSC3-AA06) equipped with an electric agent, UVL-1500M2-N1), the ultraviolet ray was irradiated at room temperature for 1 minute at an irradiation intensity of 60 [mW / cm 2] and weather resistance. A hydrous gel-like absorbent that had undergone accelerated testing was obtained.

Subsequently, 184.3 g of 0.90% by weight aqueous sodium chloride solution and 2.00 g of a hydrous gel absorbent were placed in a plastic container with a capacity of 250 ml with a capacity. The mixture was stirred for 16 hours using a magnetic stiller to extract a soluble component of the hydrous gel absorbent. This extract was filtered using one piece of filter paper (ADVANTEC Dongyang Co., Ltd., JIS P 3801, No. 2, thickness 0.26 mm, retained particle diameter 5 μm), and 5.0 g of the obtained filtrate and an aqueous solution of 0.90% by weight sodium chloride 45.0 g mixed solution was used as the measurement solution.

Subsequently, titration was performed with 0.1 N aqueous NaOH solution until the pH was 10, and then titrated with 0.1 N aqueous HCl solution until the pH was 2.7. At this time, an appropriate amount ([NaOH] ml, [HCl] ml) was obtained. The same titration was carried out only for 184.3 g of 0.90% by weight aqueous sodium chloride solution to obtain a co-titration amount ([bNaOH] ml, [bHCl] ml).

In the case of the hydrogel absorbent of the present invention, based on the average molecular weight of the monomer and the appropriate amount obtained by the above operation, the soluble content of the hydrogel absorber can be calculated by the following number 9. In addition, when the average molecular weight of the monomer is unknown, the average molecular weight of the monomer can be calculated using the neutralization rate determined by titration. This neutralization rate is computed by following number 10.

[Number 9]

Water-soluble content [% by weight] = 0.1 x (average molecular weight of the monomer) x 184.3 x 100 x ([HCl]-[bHCl]) /1000/1.0/50.0

[Number 10]

Neutralization rate [mol%] = (1-([NaOH]-[bNaOH]) / ([HCl]-[bHCl])) × 100

Degradation rate is computed by following formula 11 from the soluble content of a particulate water absorbing agent, and the soluble content of a hydrous gel water absorbing agent.

[Jos 11]

Degradation rate [%] = (soluble component of water-containing gel absorbent)-(soluble component of particulate absorbent)

[Urine resistance test] (gel deterioration test 2)

1 part by weight of the particulate water absorbent was placed in a plastic container with a 250 ml lid (pack ace made by Teroka Co., Ltd.), 25 parts by weight of simulated artificial urine was added, and then sealed to deteriorate the particulate water absorbent at a predetermined temperature and time. Then, when the plastic container with a 250 ml lid was put to the side, and left to stand for 10 minutes, it evaluated whether the swollen gel flows. In addition, in this test, it carried out on the following two deterioration conditions.

(1) urine resistance test (L-ascorbic acid concentration normal) (gel deterioration test 2-1)

[Gel Deterioration Condition (1)]

Simulated artificial urine: Physiological saline at a concentration of 0.005% by weight L-ascorbic acid

Degradation temperature: 37 ℃

Degradation time: 24 hours

(2) urine resistance test (L-ascorbic acid 1000 times) (gel deterioration test 2-2)

[Gel deterioration condition (2)]

Simulated artificial urine: Physiological saline at a concentration of 5% by weight of L-ascorbic acid

Degradation temperature: 90 ℃

Degradation time: 1 hour

[Dust measurement]

The amount of dust from a particulate water absorbing agent was measured on condition of the following conditions using the "Heubach" Dustmeter # 2000 by Seishin Corporation.

Measuring conditions

Work environment: 18-22 ℃ ／ 45-55RH%

Sample: 100.00g

 Type: Type (I) (horizontal type)

Rotat .: 30 [R / min]

Airflow: 20.0 [L / min]

Time: 60min (30 min is performed twice because the setting upper limit is 30 minutes)

Collection filter: Filter paper (ADCANTEC® GC90)

By measuring the weight increase [mg] of the filter paper 10 minutes after the measurement, the amount of dust from a particulate water absorbing agent was calculated | required from following Formula.

[Joe 12]

Dust amount [mg / kg] = (weight increase of filter paper after measurement ten minutes) * 10

[P-methoxy phenol contained in particulate water absorbing agent]

P-methoxy phenol contained in the particulate water absorbing agent of the present invention was analyzed for the filtrate obtained by performing the same operation except that the stirring time in the evaluation method of the above [soluble content] was changed from 16 hours to 1 hour. Is obtained. Specifically, p-methoxy phenol in the particulate water absorbent can be obtained by analyzing the filtrate obtained by the above operation by high performance liquid chromatography. In addition, p-methoxy phenol is expressed in ppm (large particulate absorbent).

[Reducing agent (sodium hydrogen sulfite) contained in particulate water absorbing agent]

The measuring method of sodium hydrogen sulfite is illustrated as a reducing agent contained in the particulate water absorbing agent of this invention. 50 g of pure water and 0.5 g of a particulate water absorbing agent were added to a 200 ml beaker and left to stand for 1 hour. Next, after adding 50 g of methanol, 2.5 g of the solution which melt | dissolved 2 mmol of malachite green in the eluate mentioned later is added. The solution is stirred for about 30 minutes, filtered, and the filtrate is analyzed by high performance liquid chromatography to determine the amount of reducing agent contained in the particulate water absorbent. In addition, the eluate was adjusted in proportion to 400 ml of methanol, 6 ml of n-hexane, 0.0 M-2-N-morpholino-ethanesulfonic acid, and 100 ml of sodium sodium salt. In addition, the analytical curve can be prepared by analyzing the spike of the reducing agent in the particulate water absorbent containing no reducing agent.

[Chelating agent contained in particulate water absorbing agent]

The chelating agent contained in the particulate water absorbing agent of the present invention is obtained by analyzing the filtrate obtained by performing the same operation except that the stirring time in the evaluation method of the above [soluble content] is changed from 16 hours to 1 hour. . Specifically, the chelating agent in the particulate water absorbent can be obtained by analyzing the filtrate obtained by the above operation by high performance liquid chromatography. In addition, the amount of a chelating agent is expressed in ppm (large particulate absorbent). In addition, the analytical curve can be prepared by analyzing the spike of the chelating agent in the particulate water absorbent containing no chelating agent.

Example 1-1

A hydrous gel-like crosslinked polymer was produced according to the following procedure using the apparatus shown in FIG. 3 described in US Pat. No. 7265190.

First, 35.2 weight part of acrylic acid which adjusted the content of p-methoxy phenol to 70 ppm, 11.7 weight part of 48 weight% sodium hydroxide aqueous solution, 0.23 weight part of polyethylene glycol diacrylates (average number of ethylene oxide units: n = 9), chelate The monomer aqueous solution (1-1) which consists of a composition of 0.22 weight part of aqueous solutions of 1 weight% diethylene triamine 5 triacetate acetate (abbreviation: DTPA.3Na) aqueous solution, and 33.6 weight part of deionized water was produced.

Next, the said monomer aqueous solution (1-1) adjusted to 40 degreeC was supplied to the superposition | polymerization process continuously using the metering pump. Before introducing into the belt polymerizer, 17.7 parts by weight of a 48% by weight aqueous sodium hydroxide solution (0.7 ppm iron content (large NaOH solid content)) was continuously mixed by line mixing. At this time, the monomer temperature rose to 86 degreeC by the heat of neutralization.

Subsequently, 1.38 weight part of 4 weight% sodium persulfate aqueous solution was continuously mixed by line mixing, and the obtained continuous mixture (1-1) was supplied so that it might become about 7.5 mm in thickness on the flat belt which has frozen at both ends. It superposed | polymerized continuously for 3 minutes and obtained the hydrous gel-like crosslinked polymer (1-1).

Next, the hydrous gel-like crosslinked polymer (1-1) was subdivided into about 1.5 mm with a meat chopper having a hole diameter of 22 mm. This granular gel was spread on a moving porous plate of a continuous draft band drier and dried at 185 ° C. for 30 minutes to obtain a dry polymer (1-1). After pulverizing the obtained dry polymer (1-1) with a roll mill, the water absorbing resin powder (1-1) of 175-710 micrometers was obtained by sieving with the sieve separator which has a metal sieve of 710 micrometers and 175 micrometers of eye size. .

After mixing the surface crosslinking agent which consists of a liquid mixture of 0.3 weight part of 1, 4- butanediol, 0.6 weight part of propylene glycol, and 3.0 weight part of deionized water with respect to 100 weight part of obtained water absorbing resin powder (1-1), the mixture was 208 The surface crosslinkable water absorbent resin powder (1-1) was obtained by heat-processing 40 degreeC for 40 minutes.

After cooling the obtained surface crosslinkable water absorbent resin powder (1-1), 1.66 weight part of 30weight% sodium hydrogen sulfite aqueous solution is added and mixed with respect to 100 weight part of surface crosslinkable water absorbent resin powder (1-1), and a particulate water absorbent precursor ( 1-1) was obtained. Subsequently, the obtained particulate water absorbent precursor (1-1) was left to stand in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard body having an eye size of 710 μm, thereby obtaining a particulate water absorbent (1-1). The water content of the obtained particulate water absorbent (1-1) was 1.8% by weight. Table 1 shows the physical properties of the obtained particulate water absorbent (1-1).

[Example 1-2]

A particulate water absorbing agent (1-2) was obtained in the same manner as in Example 1-1 except that the addition amount of the 30 wt% aqueous sodium hydrogen sulfite solution described in Example 1-1 was changed from 1.66 parts by weight to 3.33 parts by weight. Table 1 shows the physical properties of the obtained particulate water absorbing agent (1-2).

[Example 1-3]

50 weight% of 100 wt% of absorbents obtained by carrying out similarly to Example 1-1 except having changed the addition amount of the 30 weight% sodium hydrogen sulfite aqueous solution of Example 1-1 from 1.66 weight part to 0.166 weight part 0.6 weight part of aqueous sodium lactate solutions were added and mixed to obtain a particulate water absorbent precursor (1-3). Subsequently, the obtained particulate water absorbent precursor (1-3) was left to stand in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard body having an eye size of 710 μm to obtain a particulate water absorbent (1-3). The moisture content of the obtained particulate water absorbent (1-3) was 2.0 weight%. The physical properties of the obtained particulate water absorbing agent (1-3) are shown in Table 1-1.

[Example 1-4]

Except having changed the addition amount of the 30 weight% sodium hydrogen sulfite aqueous solution in Example 1-3 from 0.166 weight part to 1.66 weight part, and also changing the addition amount of the 50 weight% sodium lactate aqueous solution from 0.6 weight part to 0.1 weight part. In the same manner as in Example 1-3, the particulate water absorbing agent (1-4) was obtained. The physical properties of the obtained particulate water absorbing agent (1-4) are shown in Table 1-1.

[Example 1-5]

A particulate water absorbing agent (1-5) was obtained in the same manner as in Example 1-3 except that the amount of the 30 wt% aqueous sodium hydrogen sulfite solution in Example 1-3 was changed from 0.166 parts by weight to 1.66 parts by weight. Table 1 shows the physical properties of the obtained particulate water absorbing agent (1-5).

Example 1-6

To 100 parts by weight of the surface-crosslinked water absorbent resin powder (1-1) in Example 1-1, 0.33 parts by weight of a 30% by weight sodium hydrogen sulfite aqueous solution was added and mixed, and further, an aqueous aluminum sulfate solution (8 weight in terms of aluminum oxide). %) A particulate water absorbent precursor (1-6) was obtained by uniformly mixing 1.22 parts by weight of a mixed solution consisting of 0.9 part by weight, 0.30 part by weight of a 60% by weight sodium lactate aqueous solution, and 0.02 part by weight of propylene glycol. Subsequently, the obtained particulate water absorbent precursor (1-6) was left to stand in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard body having an eye size of 710 μm, thereby obtaining a particulate water absorbent (1-6). Table 1 shows the physical properties of the obtained particulate water absorbing agent (1-6).

Example 1-7

The hydrogel-like crosslinked polymer was produced according to the following by using the apparatus shown in FIG. 3 described in US Patent No. 7265190.

First, 35.2 weight part of acrylic acid which adjusted the content of p-methoxy phenol to 70 ppm, 11.7 weight part of 48 weight% sodium hydroxide aqueous solution, polyethylene glycol diacrylate (average number of ethylene oxide units: n = 9) 0.23 weight part, 31 A monomer aqueous solution (1-7) consisting of 0.03 parts by weight of an aqueous solution of ethylene diamine tetra (methylenephosphonic acid) 5 sodium (abbreviated as EDTMPA.5Na) and 33.6 parts by weight of deionized water was prepared.

Subsequently, the said monomer aqueous solution (1-7) adjusted to 40 degreeC was supplied to the superposition | polymerization process continuously using the metering pump. Prior to introducing into the belt polymerizer, 17.7 parts by weight of an aqueous 48% by weight aqueous sodium hydroxide solution was continuously mixed by line mixing. At this time, the monomer temperature rose to 86 degreeC by the heat of neutralization. Subsequently, 1.38 weight part of 4 weight% sodium persulfate aqueous solution was continuously mixed by line mixing, and the obtained continuous mixture (1-7) was supplied so that it might become about 7.5 mm in thickness on the flat belt which has frozen at both ends. It superposed | polymerized continuously for 3 minutes and obtained the hydrous gel-like crosslinked polymer (1-7).

Subsequently, the hydrogel-like crosslinked polymer (1-7) was subdivided into about 1.5 mm with a meat chopper having a hole diameter of 22 mm. This granulated gel was spread on a moving porous plate of a continuous draft band drier and dried at 185 ° C. for 30 minutes to obtain a dry polymer (1-7). The resulting dry polymer (1-7) was pulverized with a roll mill and then sieved with a sieve separator having an eye size of 710 μm and a 175 μm metal sieve network, thereby absorbing resin powder having a particle diameter of 175 to 710 μm (1-7). Got.

To 100 parts by weight of the obtained water absorbent resin powder (1-7), after mixing the surface crosslinking agent consisting of a mixture of 0.3 parts by weight of 1,4-butanediol, 0.6 parts by weight of propylene glycol, and 3.0 parts by weight of deionized water, the mixture was mixed. The surface crosslinkable water absorbent resin powder (1-7) was obtained by heat-processing at 208 degreeC for 40 minutes.

After cooling the obtained surface crosslinkable water absorbent resin powder (1-7), 1.66 weight part of 30weight% sodium hydrogen sulfite aqueous solution, and 30weight% aluminum sulfate aqueous solution with respect to 100 weight part of surface crosslinkable water absorbent resin powder (1-7) ( A particulate water absorbent precursor (1-7) was obtained by uniformly adding and mixing 1.23 parts by weight of a mixed solution consisting of 0.9 parts by weight of 8% by weight), 0.30 parts by weight of a 60% by weight aqueous sodium lactate solution, and 0.03 parts by weight of propylene glycol. Subsequently, the obtained particulate water absorbent precursor (1-7) was left to stand in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard body having an eye size of 710 μm, thereby obtaining a particulate water absorbing agent (1-7). Table 1 shows the physical properties of the obtained particulate water absorbing agent (1-7).

Example 1-8

Commercially available acrylic acid (wako pure, reagent grade; containing 200 ppm of p-methoxy phenol) obtained by gas phase catalytic oxidation was supplied to the bottom of the high boiling point impurity separation tower having 50 stages of non-porous plates, and the reflux ratio was 1. As a result of distillation and further distillation, purified acrylic acid (1-8) consisting of 99% by weight or more of acrylic acid and a trace amount of impurities (mainly water) was obtained. The amount of p-methoxy phenol in purified acrylic acid (1-8) was ND (less than 1 ppm).

The adjusted acrylic acid (1-8) was obtained by adding 15 ppm of p-methoxy phenol to purified acrylic acid (1-8).

The hydrogel-like crosslinked polymer was produced according to the following by using the apparatus shown in FIG. 3 described in US Patent No. 7265190.

First, 35.2 weight part of said adjusted acrylic acid (1-8), 48 weight% sodium hydroxide aqueous solution (0.7 ppm of iron content (large NaOH solid content)) 11.7 weight part, polyethylene glycol diacrylate (average number of ethylene oxide units: n = 9) ) A monomer aqueous solution (1-8) consisting of 0.03 parts by weight of an aqueous solution of 0.23 parts by weight, 31% by weight of ethylene diamine tetra (methylenephosphonic acid) 5 sodium (abbreviated as EDTMPA.5Na), and 33.6 parts by weight of deionized water was prepared. .

Next, the said monomer aqueous solution (1-8) was adjusted to 40 degreeC, and it fed continuously with the metering pump. 17.7 weight part of 48 weight% sodium hydroxide aqueous solution was continuously mixed with the said monomer aqueous solution (1-8) by line mixing. At this time, the temperature of the monomer rose to 86 degreeC by the heat of neutralization. Subsequently, 1.38 weight part of 4 weight% sodium persulfate aqueous solution was continuously mixed by line mixing. The continuous mixture (1-8) obtained by this line mixing was supplied on a flat belt having frozen ends at both ends so as to have a thickness of about 7.5 mm, and polymerization was carried out continuously for 3 minutes to give a hydrogel-like crosslinked polymer (1-8). Got it.

Subsequently, the hydrogel-like crosslinked polymer (1-8) was subdivided into about 1.5 mm with a meat chopper having a hole diameter of 22 mm. This granulated gel was pulverized on a moving porous plate of a continuous draft band dryer and dried at 185 ° C. for 30 minutes to obtain a dry polymer (1-8). After pulverizing the obtained dry polymer (1-8) with a roll mill, the water-absorbent resin powder (1-8) of 175-710 micrometers was obtained by sieving with the sieve apparatus which has a metal mesh of 710 micrometers and 175 micrometers of eye size. .

After mixing the surface crosslinking agent which consists of a mixed liquid of 0.3 weight part of 1, 4- butanediol, 0.6 weight part of propylene glycol, and 3.0 weight part of deionized waters with respect to 100 weight part of obtained water absorbing resin powders (1-8), the mixture was mixed 208 The surface crosslinkable water absorbing resin powder (1-8) was obtained by heat-processing 40 degreeC for 40 minutes.

After cooling the obtained surface crosslinkable water absorbent resin powder (1-8), 1.66 weight part of 30 weight% sodium hydrogen sulfite aqueous solution and aluminum sulfate aqueous solution (aluminum oxide conversion) with respect to 100 weight part of surface crosslinkable water absorbent resin powder (1-8). 8% by weight), 1.44 parts by weight of a mixed liquid consisting of 0.9 parts by weight of 0.9 part by weight, 60% by weight aqueous sodium lactate solution and 0.04 part by weight of propylene glycol was added and mixed to obtain a particulate water absorbent precursor (1-8). Subsequently, the obtained particulate water absorbent precursor (1-8) was left to stand in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard body having an eye size of 710 μm to obtain a particulate water absorbent (1-8). Table 1 shows the physical properties of the obtained particulate water absorbing agent (1-8).

[Example 1-9]

The adjusted acrylic acid (1-9) was obtained by adding 200 ppm of p-methoxy phenols to the purified acrylic acid (1-8) of Example 1-8.

Except having used the adjusted acrylic acid (1-9) instead of the adjusted acrylic acid (1-8), surface crosslinking absorbent resin powder (1-9) was performed by performing surface crosslinking process from superposition | polymerization similarly to Example 1-8. Got it.

After cooling the obtained surface crosslinkable water absorbent resin powder (1-9), 1.66 weight part of 30weight% sodium hydrogen sulfite aqueous solution is added and mixed with respect to 100 weight part of surface crosslinkable water absorbent resin powder (1-9), and a particulate water absorbent precursor (1 -9) was obtained. Subsequently, the obtained particulate water absorbent precursor (1-9) was left to stand in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard body having an eye size of 710 μm to obtain a particulate water absorbent (1-9). The moisture content of the obtained particulate water absorbing agent (1-9) was 1.8 weight%. Table 1 shows the physical properties of the obtained particulate water absorbing agent (1-9).

[Comparative Example 1-1]

Comparative particulate water absorbing agent (1-1) in the same manner as in Example 1-1 except that the addition amount of the 30 wt% sodium hydrogen sulfite aqueous solution was changed from 1.66 parts by weight to 0.166 parts by weight without using a chelating agent. Got. Table 1 shows the physical properties of the obtained comparative particulate water absorbing agent (1-1).

Comparative Example 1-2

A comparative particulate water absorbing agent (1-2) was obtained in the same manner as the method described in Example 1-1 except that a 30 wt% aqueous sodium hydrogen sulfite solution was not used. Table 1 shows the physical properties of the obtained comparative particulate water absorbing agent (1-2).

Comparative Example 1-3

0.9 parts by weight of aqueous aluminum sulfate solution (8% by weight in terms of aluminum oxide), 0.30 parts by weight of 60% by weight aqueous sodium lactate solution, and propylene glycol 0.02 to 100 parts by weight of the comparative particulate water absorbing agent (1-2) obtained in Comparative Example 1-2. The comparative particulate water absorbent precursor (1-3) was obtained by uniformly mixing 1.22 parts by weight of the mixed solution consisting of parts by weight.

Subsequently, the obtained comparative particulate water absorbent precursor (1-3) was left to stand in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard body having an eye size of 710 μm, thereby obtaining a comparative particulate water absorbing agent (1-3). Table 1 shows the physical properties of the obtained comparative particulate absorbent (1-3).

[Comparative Example 1-4]

100 weight of the comparative surface crosslinkable absorbent resin powder (1-4) obtained in the same manner as in Example 1-1 except that the content of p-methoxy phenol in acrylic acid described in Example 1-1 was changed from 70 ppm to 270 ppm. 0.166 parts by weight of an aqueous 30% by weight sodium hydrogen sulfite aqueous solution was uniformly added and mixed to give a comparative particulate water absorbent precursor (1-4). Subsequently, the obtained comparative particulate water absorbent precursor (1-4) was left to stand in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard body having an eye size of 710 μm, thereby obtaining a comparative particulate water absorbing agent (1-4). Table 1 shows the physical properties of the obtained comparative particulate absorbent (1-4).

Comparative Example 1-5

With reference to patent document 29 and its Examples 4 and 5, the comparative example with many chelating agents is shown. That is, the addition amount of the 1 weight% diethylene triamine 5 sodium triacetate (abbreviation: DTPA.3Na) aqueous solution was changed from 0.22 part by weight to 25.8 parts by weight, and the amount of deionized water was changed from 33.6 parts by weight to 8.0 parts by weight, and further 30 A comparative particulate water absorbent comprising the same operation as in Example 1-1, except that the amount of the aqueous solution of the wt% aqueous sodium hydrogen sulfite solution was changed from 1.66 parts by weight to 3.33 parts by weight, containing 6000 ppm of a chelating agent and 1.0% by weight of the inorganic reducing agent ( 1-5). The water content of the obtained comparative particulate water absorbing agent (1-5) was 1.9% by weight. Table 1 shows the physical properties of the obtained comparative particulate water absorbing agent (1-5).

Example 1-10

A particulate water absorbing agent (1-10) was obtained in the same manner as in Example 1-7 except that the adjusted acrylic acid in Example 1-7 was changed to the adjusted acrylic acid (1-9) described in Example 1-9. . Table 1 shows the physical properties of the obtained particulate water absorbing agent (1-10).

[Example 1-11]

The particulate water absorbing agent (1-11) was obtained in the same manner as in Example 1-7 except that the adjusted acrylic acid described in Example 1-7 was changed to the adjusted acrylic acid (1-8) described in Example 1-8. Table 1 shows the physical properties of the obtained particulate water absorbing agent (1-11).

[Example 1-12]

A particulate water absorbing agent was prepared in the same manner as in Example 1-11 except that the amount of the aqueous solution of 31 wt% ethylene diamine tetra (methylenephosphonic acid) 5 sodium (abbreviated as EDTMPA.5Na) was changed from 0.03 part by weight to 0.07 part by weight. -12). Table 1 shows the physical properties of the obtained particulate water absorbing agent (1-12).

[Example 1-13]

Table 2 shows the deterioration rate obtained as a result of performing the weather resistance test on the particulate water absorbent (1-1) described in Example 1-1.

[Comparative Example 1-6]

The p-methoxy phenol obtained in Example 1-8 was substituted with p-methoxy to the purified acrylic acid (1-8) of ND instead of the acrylic acid which adjusted content of p-methoxy phenol of Example 1-1 to 70 ppm. Except having used the comparative adjustment acrylic acid (1-6) obtained by adding 1 ppm of phenols, it superposed | polymerized similarly to the method of Example 1-1, and obtained the comparative particulate water absorbing agent (1-6). The p-methoxy phenol of the obtained comparative particulate water absorbing agent (1-6) was ND (less than 1 ppm). Table 2 shows the results of the weather resistance test using the obtained comparative particulate water absorbing agent (1-6).

Example 1-14

Table 3 shows the results of measuring the residual p-methoxy phenol, the residual chelating agent, and the residual sodium hydrogen sulfite of the particulate water absorbing agents (1-1), (1-8), and (1-9).

[Comparative Example 1-7]

Table 3 shows the results of measuring the residual p-methoxy phenol, the residual chelating agent, and the residual sodium hydrogen sulfite of the comparative particulate water absorbing agents (1-4) and (1-5).

[Table 1]

[Table 2]

[Table 3]

[Comparative Example 1-8]

As described above, Patent Document 17 (European Patent No. 1645596) does not disclose a water insoluble inorganic fine particle, a specific amount of p-methoxy phenol, and a specific water content (3 to 15% by weight). In addition, Patent Document 17 discloses an alkyl hydroxy anisole (such as butyl) as an organic antioxidant (paragraph [Example 6]). Therefore, since the significance of this invention is shown, the comparative particulate-form absorber (1-8) was obtained according to Example 6 of patent document 17 and its corresponding Unexamined-Japanese-Patent No. 3940103.

Specifically, the ratio of 100 parts by weight of the water absorbent resin, 3 parts by weight of sodium nitrite, and 3 parts of hydroxy ethylene diamine trisodium acetate (particles having a particle diameter of 106 µm or less) is obtained in a polyethylene container having a capacity of 2 L. 89 weight%) 1.5 weight part and 1 weight part of butyl hydroxy anisoles disclosed by patent document 17 were put, and it mixed for 1 hour with the mixer provided with a stirring blade, and obtained the comparative particulate water absorbing agent (1-8).

19.0 g of 0.9 wt% aqueous sodium chloride solution (alias; physiological saline) was added to 1.0 g of the comparative particulate water absorbing agent (1-8), followed by swelling 20 times. Subsequently, the swelled comparative particulate water absorbing agent (1-8) was placed in a plastic container with a lid of 120 ml in capacity and left in an oven at 37 ° C. for 3 hours to obtain a swelling comparative particulate water absorbing agent (1-8). . The 20-fold swelling gel of the comparative particulate water absorbing agent (1-8) obtained in accordance with Patent Document 17 was colored yellow.

Subsequently, the color tone (initial color tone) of the 20-fold swelling gel of the comparative particulate water absorbing agent (1-8) was measured using LabScanXE manufactured by Hunter @ Lab. Table 4 shows the measurement results.

In addition, color tone measurement was performed by filling a test substance in the container made from the white propylene of diameter 5.0cm and height 1.2cm. In addition, the color tone of the above-mentioned white propylene container as a blank was L value: 54.73, a value: 0.16, and b value: -0.50.

Furthermore, about the powder of the comparative particulate water absorbing agent (1-8) based on patent document 17 (1 weight part of butyl hydroxy anisole), the coloring promotion test similarly to Example 1-1-1-12 and its Table 2 for 7 days. (70 DEG C, RH65%) was carried out, but the particulate water absorbing agent of the present invention was colored in orange color while the comparative particulate water absorbing agent (1-8) was kept substantially white. Similarly, color tone was measured. Table 5 shows the measurement results. In addition, the comparative particulate water absorbing agent (1-8) after the color promotion test for 7 days was odorous.

Example 1-15

The same procedure as in Comparative Example 1-8 was carried out on the particulate water absorbent (1-1) obtained in Example 1-1 to obtain a 20-fold swelling gel (1-15) of the particulate water absorbent (1-1). The obtained swelling particulate water absorbing agent (1-15) is a particulate water absorbing agent (1), in which yellow swelling gel of the comparative particulate water absorbing agent (1-8) according to Patent Document 17 (1 part by weight of butyl hydroxy anisole) discolors yellow. The 20-fold swelling gel (1-15) of 1-1)) remained a clear hydrous gel.

The color tone of the 20-fold swelling gel (1-15) of the particulate water absorbing agent (1-1) was also measured in the same manner as in Comparative Example 1-8. Table 4 shows the measurement results.

[Example 1-16]

It was 0.23 [g / g / sec] when the absorption rate (FSR) was measured about the particulate-form water absorbent (1-1) of 1.8 wt% of water content obtained in Example 1-1. In order to investigate the influence of the water content, 10% by weight of water was added to the particulate water absorbent (1-1), and further dried under reduced pressure at 80 ° C to obtain a particulate water absorbent (1-15) having a water content of 3.9% by weight.

The water absorption rate (FSR) of the particulate water absorbent (1-15) having a water content of 3.9% by weight is 0.27 [g / g / sec], and improves the water content, in particular, the water content is 3-15% by weight. It can be seen that is improved. Hereinafter, the manufacturing method of the water absorbing agent set to 3-15 weight% of water content is described in Example 3-1-Example 3-13.

[Table 4]

[Table 5]

(theorem)

The said Example 1-1-1-16 and Table 1-Table 5 are related with the manufacturing method 1 of the particulate water absorbing agent of this invention, The monomer which has acrylic acid (salt) containing 10-200 ppm of methoxy phenols as a main component A method of producing a particulate water absorbing agent comprising a polymerization step of an aqueous solution, a drying step of a hydrous gel crosslinked polymer obtained by polymerization, a surface crosslinking step, and an addition step of 0.001 to 0.5% by weight of a chelating agent, followed by an inorganic reducing agent after the surface crosslinking step. It is a manufacturing method of a particulate water absorbing agent, characterized by performing the addition process of the.

As in Examples 1-1 to 1-13, the absorbent according to the present invention has excellent temporal hue and initial hue, and after the surface crosslinking step, an inorganic reducing agent is added, and is less than 3% by weight. Even at a low water content and a low water content of less than 3% by weight at a high temperature surface crosslinking (150 to 250 ° C), the obtained absorbent had no unpleasant odor. Such odor is more complex odor in absorbent resin, inorganic reducing agent, and manufacturing process than simply odor of raw materials (especially inorganic reducing agent), and could not be expected to occur, but the present invention finds such a new problem. , Solved it above. In addition, in Comparative Examples 1-1 to 1-3 contained only one of the chelating agent and the inorganic reducing agent, the color tone was poor even when the amount of methoxy phenol was in the range of 5 to 60 ppm. In Comparative Example 1-4 (82 ppm in absorbents) and Comparative Example 1-6 (1 ppm in acrylic acid, ND in the obtained absorbents) whose methoxy phenol amount is out of the range of 5-60 ppm, time-lapse color tone is bad, or weather resistance (acceleration of Table 2) Bad after test). In addition, Patent Document 29, as well as the specific moisture content (3 to 15% by weight) of the present invention, as well as the specific addition amount (0.001 to 0.5% by weight, 0.001 to 0.1% by weight) of the compound containing a phosphorus atom or sulfur-based reducing agent In Example 5 of patent document 29, addition of 1.0 weight% of 1-hydroxy ethylidene-1,1- diphosphonic acids is not disclosed, and 1-hydroxy ethylidene-1,1-diphosphone is similarly applied in Example 4 Although the use of acid total 2.0% by weight is disclosed, as shown in Comparative Example 1-5, the use of such a chelating agent exceeding 0.5% by weight was found to adversely affect the coloring of the obtained absorbent, and it was found in a specific range. This was solved by controlling the moisture content of the furnace. In addition, as shown in Examples 1-16, the specific moisture content in the absorbent is also preferable from the improvement of the absorption rate.

That is, as shown in the said Example, the novel absorbent of this invention is a particulate water absorbent which has a polyacrylic acid (salt) type water absorbing resin as a main component, contains a chelating agent and an inorganic reducing agent, and content of the said chelating agent is 0.001-0.5 It is weight% and content of methoxy phenols is 5-60 ppm. The novel absorbent of the present invention shown in the above examples preferably has a pressureless absorption ratio (CRC) of 25 [g / g] or more and a pressure absorption ratio (AAP4.83 kPa) of 20 [g / g] or more and a saline flow induced (SFC) is at least 30 [× · s and g 10- ⁷ and ㎤ ^-1]. In addition, although not shown in a table | surface, such a water absorbing agent has a FSR of about 0.25 (+/- 0.02) [g / g / sec], and also has a residual monomer of 400 ppm or less and a weight average particle diameter (D50) of about 360? 380 micrometers. In addition, such absorbents preferably further comprise an α-hydroxy carboxylic acid compound. It further includes polyvalent metal salts and / or cationic polymers. These absorbents have no initial or time-based coloration and are white in liquid permeability (SFC) or high pressure absorption ratio (AAP), so they can be used for high-density paper diapers with low pulp. ), There is no coloring problem derived from the absorbent, and a good paper diaper is provided.

Example 2-1

A monomer aqueous solution having a monomer concentration of 38% by weight and a neutralization rate of 75% by weight was prepared, which was composed of sodium acrylate, acrylic acid and water neutralized with NaOH containing 0.7 ppm of iron in a kneader having two sigma-shaped braids. In addition, acrylic acid used the thing which adjusted content of p-methoxy phenol to 70 ppm. Polyethylene glycol diacrylate (average number of ethylene glycol units: 9) was dissolved in this monomer aqueous solution so as to be 0.045 mol% (large monomer).

Subsequently, nitrogen gas was blown into the monomer aqueous solution to reduce dissolved oxygen in the monomer aqueous solution, and the entire reaction vessel was nitrogen-substituted. Subsequently, after adjusting the temperature of the monomer aqueous solution to 22 degreeC, rotating two sigma-type braids, 0.12 [g / mol] (monomer) of sodium persulfate and 0.005 [g / mol] of L-ascorbic acid as a polymerization initiator. Mol] (high monomer).

Since polymerization started immediately and the aqueous monomer solution became cloudy, the rotation of the braid was stopped. After the polymerization temperature reached 50 ° C, the braid was rotated again, and the polymerization was continued while stirring in the kneader to obtain a hydrous gel-like crosslinked polymer (2-1) having a weight average particle diameter of about 2 mm after about 50 minutes.

The hydrous gel-like crosslinked polymer (2-1) obtained was dried in a hot air dryer at 170 ° C. for about 60 minutes. Subsequently, the dried product was pulverized with a roll mill grinder, and sifted (with the upper and lower sieves removed) by a sieve having an eye size of 850 µm and 150 µm to absorb water particles having a water content of 3% by weight and a weight average particle diameter of 370 µm (2-1). Got. As for the obtained water absorbing resin particle (2-1), the particle diameter of the particle | grain of 850 micrometers or more was substantially not contained, and the fine powder of less than 150 micrometers contained 2 weight%.

Surface crosslinking agent which consists of 0.025 weight part of ethylene glycol diglycidyl ether, 0.3 weight part of 1, 4- butanediol, 0.5 weight part of propylene glycol, and 3.0 weight part of deionized water with respect to 100 weight part of obtained water absorbing resin particles (2-1). After uniformly mixing, the mixture was heat-processed at 208 degreeC for 40 minutes, and surface crosslinking water absorbing resin powder (2-1) was obtained.

After cooling the obtained surface crosslinkable water absorbent resin powder (2-1), 1.66 parts by weight of a 30% by weight aqueous sodium hydrogen sulfite solution and 45% by weight diethylene triamine 5 with respect to 100 parts by weight of the surface crosslinkable water absorbent resin powder (2-1) 5 0.44 parts by weight of an aqueous sodium acetate solution was added and mixed to obtain a particulate water absorbent precursor (2-1). Subsequently, the obtained particulate water absorbent precursor (2-1) was left to stand in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard body having an eye size of 810 μm. Furthermore, a particulate water absorbent was added and mixed with 0.3 weight part of silica (brand name: Air quality 200CF-5, Japan Air Quality Co., Ltd.) as white water-insoluble inorganic fine particles with respect to 100 weight part of surface crosslinkable water absorbing resin powders (2-1). (2-1) was obtained. Table 6 shows the physical properties of the obtained particulate water absorbing agent (2-1). In addition, L, a, and b of silica were 93.6, -0.8, and -3.6, respectively, and were whiter than a water absorbing resin.

Example 2-2

A particulate water absorbing agent in the same manner as in Example 2-1 except that the amount of silica added to 100 parts by weight of the surface-crosslinked water absorbent resin powder (2-1) in Example 2-1 was changed from 0.3 parts by weight to 1.0 parts by weight. (2-2) was obtained. Table 6 shows the physical properties of the obtained particulate water absorbing agent (2-2).

Example 2-3

A particulate water absorbing agent in the same manner as in Example 2-1 except that the addition amount of silica to 100 parts by weight of the surface-crosslinked water absorbent resin powder (2-1) in Example 2-1 was changed from 0.3 parts by weight to 0.5 parts by weight. (2-3) was obtained. Table 6 shows the physical properties of the obtained particulate water absorbing agent (2-3).

[Example 2-4]

A particulate water absorbing agent in the same manner as in Example 2-1 except that the amount of silica added to 100 parts by weight of the surface-crosslinked water absorbent resin powder (2-1) in Example 2-1 was changed from 0.05 parts by weight to 0.05 parts by weight. (2-4) was obtained. Table 6 shows the physical properties of the obtained particulate water absorbing agent (2-4).

Example 2-5

Except having changed the addition amount of the 45 weight% diethylene triamine 5 sodium acetate aqueous solution with respect to 100 weight part of surface crosslinkable water absorbing resin powder (2-1) in Example 2-1, it changed from 0.44 weight part to 0.022 weight part. In the same manner as in Example 2-1, a particulate water absorbing agent (2-5) was obtained. Table 6 shows the physical properties of the obtained particulate water absorbing agent (2-5).

[Example 2-6]

Except having changed the addition amount of the 45 weight% diethylene triamine 5 sodium acetate aqueous solution with respect to 100 weight part of surface crosslinkable water absorbing resin powder (2-1) in Example 2-1, from 0.44 weight part to 2.2 weight part, In the same manner as in Example 2-1, a particulate water absorbing agent (2-6) was obtained. Table 6 shows the physical properties of the obtained particulate water absorbing agent (2-6).

[Example 2-7]

36.8 weight part of acrylic acid which adjusted content of p-methoxy phenol to 70 ppm, 12.2 weight part of 48 weight% sodium hydroxide aqueous solution, polyethylene glycol diacrylate (average number of ethylene oxide units: n = 9) 0.08 weight part, 1 weight% The monomer aqueous solution (2-2) which consists of 0.42 weight part of diethylene triamine 5 trisodium acetate (abbreviation: DTPA.3Na) aqueous solution, and 30.3 weight part of deionized water was produced.

Next, the said monomer aqueous solution (2-2) adjusted to 40 degreeC was supplied to the superposition | polymerization process continuously using the metering pump. Prior to introducing into the belt polymerizer, 18.5 parts by weight of 48% by weight aqueous sodium hydroxide solution were continuously mixed by line mixing. At this time, the monomer temperature rose to 86 degreeC by the heat of neutralization. Subsequently, 1.66 weight part of 4 weight% sodium persulfate aqueous solution was continuously mixed by line mixing, and the obtained continuous mixture (2-2) was supplied so that it might become about 7.5 mm in thickness on the flat belt which has frozen at both ends. The polymerization was carried out continuously for 3 minutes to obtain a hydrous gel crosslinked polymer (2-2).

Next, the hydrous gel-like crosslinked polymer (2-2) was subdivided into about 1.5 mm with a meat chopper having a hole diameter of 22 mm. This granular gel was spread on a moving porous plate of a continuous draft band dryer and dried at 185 ° C. for 30 minutes to obtain a dry polymer (2-2). The resulting dry polymer (2-2) was pulverized with a roll mill, and then sifted (with the top and bottom of the sieve removed) by a sieve having an eye size of 850 µm and 150 µm to absorb water particles having a water content of 3% by weight and a weight average particle diameter of 370 µm. (2-2) was obtained. The obtained water absorbent resin particles (2-2) were substantially free of particles having a particle diameter of 850 µm or more, and contained 2% by weight of fine powder of less than 150 µm.

After mixing the surface crosslinking agent which consists of a mixed liquid of 0.3 weight part of 1, 4- butanediol, 0.5 weight part of propylene glycol, and 3.0 weight part of deionized water with respect to 100 weight part of obtained water absorbing resin particles (2-2), the mixture was mixed 208 By surface-heat-processing 40 degreeC, surface crosslinkable water absorbing resin powder (2-2) was obtained.

After cooling the obtained surface crosslinkable water absorbent resin powder (2-2), 1.66 parts by weight of a 30% by weight aqueous sodium hydrogen sulfite solution and 45% by weight of diethylene triamine 5 with respect to 100 parts by weight of the surface crosslinkable water absorbent resin powder (2-2) 5 0.44 parts by weight of an aqueous sodium acetate solution was added and mixed to obtain a particulate water absorbent precursor (2-2). Subsequently, the obtained particulate water absorbent precursor (2-2) was left to stand in a hot air dryer at 60 ° C. for 30 minutes, and then passed through a JIS standard body having an eye size of 810 μm. Further, the particulate water absorbing agent (2-7) was added to and mixed with 0.3 part by weight of silica (trade name: Air Quality 200CF-5, manufactured by Nippon Air Corp.) based on 100 parts by weight of the surface-crosslinked water absorbent resin powder (2-2). Got it. Table 6 shows the physical properties of the obtained particulate water absorbing agent (2-7).

Example 2-8

Example 2--1 except that the amount of 30 wt% aqueous sodium hydrogen sulfite solution added to 100 parts by weight of the surface-crosslinked water absorbent resin powder (2-1) was changed from 1.66 parts by weight to 0.22 parts by weight. In the same manner as in 1, a particulate water absorbing agent (2-8) was obtained. Table 6 shows the physical properties of the obtained particulate water absorbing agent (2-8).

[Example 2-9]

Example 2--1 except that the addition amount of the 30 weight% sodium hydrogen sulfite aqueous solution with respect to 100 weight part of surface crosslinkable water absorbing resin powders (2-1) was changed from 1.66 weight part to 22 weight part. In the same manner as in 1, a particulate water absorbing agent (2-9) was obtained. Table 6 shows the physical properties of the obtained particulate water absorbing agent (2-9).

[Example 2-10]

A particulate water absorbing agent (2-10) was prepared in the same manner as in Example 2-1 except that 3 parts by weight of water was further added to 100 parts by weight of the surface-crosslinked water absorbent resin powder (2-1) in Example 2-1. Got. Table 6 shows the physical properties of the obtained particulate water absorbing agent (2-10).

Example 2-11

1.8 parts by weight of an aqueous 50% by weight aqueous aluminum sulfate solution, 0.55 parts by weight of an aqueous 60% sodium lactate solution, and 0.05 parts by weight of propylene glycol, based on 100 parts by weight of the surface-crosslinked water absorbent resin powder (2-1) in Example 2-1. A particulate water absorbing agent (2-11) was obtained in the same manner as in Example 2-1 except that the mixed solution was added. Table 6 shows the physical properties of the obtained particulate water absorbing agent (2-11).

Example 2-12

The addition amount of the polyethylene glycol diacrylate (average number of ethylene glycol units: 9) in Example 2-1 was made into 0.023 mol% from 0.035 mol% (large monomer), and the weight average of water absorbent resin particle (2-1) Classification was carried out so that the particle diameter was 350 µm, and further, except that the heat treatment conditions in the surface crosslinking process were changed from 208 ° C. to 40 minutes to 200 minutes in 35 minutes, in the same manner as in Example 2-1. To obtain a particulate water absorbing agent (2-12). Table 6 shows the physical properties of the obtained particulate water absorbing agent (2-12).

Comparative Example 2-1

A comparative particulate water absorbing agent (2-1) was obtained in the same manner as the method described in Example 2-1 except that 0.22 parts by weight of an aqueous 45% by weight diethylene triamine 5 sodium acetate solution was not added. Table 6 shows the physical properties of the obtained comparative particulate water absorbing agent (2-1).

Comparative Example 2-2

A comparative particulate water absorbent was prepared in the same manner as in Example 2-1 except that 1.66 parts by weight of a 30% by weight aqueous sodium hydrogen sulfite solution was not added and the amount of silica was changed from 0.3 parts by weight to 0.5 parts by weight. 2) was obtained. Table 6 shows the physical properties of the obtained comparative particulate water absorbing agent (2-2).

Comparative Example 2-3

A comparative particulate water absorbing agent (2-3) was obtained in the same manner as in Comparative Example 2-2 except that 0.5 part by weight of silica (brand name: Air Quality 200CF-5, manufactured by Nippon Air Japan Co., Ltd.) was not added. Table 6 shows the physical properties of the obtained comparative particulate water absorbing agent (2-3).

Example 2-13

In Example 2-1, a particulate water absorbing agent (2-13) was prepared in the same manner as in Example 2-1 except that 0.3 part by weight of silica (trade name: Air Quality 200CF-5, manufactured by Nippon Air Corp.) was not added. Got it. Table 6 shows the physical properties of the obtained particulate water absorbing agent (2-13).

The AAP (28 [g / g]) of Example 2-1 was improved to 31 [g / g] (Example 2-13), but on the contrary, Vortex (absorption rate) was 50 seconds (Example 2-1). The temperature was reduced to 64 seconds (Example 2-13), and further, the urinary resistance (the amount of deterioration component was 1000 times) became "flowable (Example 2-13)". It can be seen that water-insoluble inorganic fine particles, which are not disclosed in Patent Document 17 and the like, are important for urinary resistance and absorption rate (Vortex).

Example 2-14

In Example 2-1, a particulate water absorbing agent (2-14) was obtained in the same manner as in Example 2-1 except that p-methoxy phenol was not added to acrylic acid at the time of polymerization. Table 6 shows the physical properties of the obtained particulate water absorbing agent (2-14). In Example 2-1 (0 ppm in acrylic acid and 0 ppm in an absorbent), in Example 2-1 (70 ppm of p-methoxy phenol in acrylic acid), the degradation rate was 27.3%. When p-methoxy phenol did not satisfy this application, weather resistance fell. This result is also shown in Table 7. It turns out that trace amount of p-methoxy phenol which is not disclosed by patent document 17 etc. is important for weather resistance.

TABLE 6

[Table 7]

(theorem)

Examples 2-1 to 2-14 and Tables 6 to 7 relate to Method 2 of the preparation of the particulate water absorbing agent of the present invention, wherein the polymerization step of a monomer aqueous solution containing acrylic acid (salt) as a main component and the hydrous gel crosslinking obtained by polymerization As a method for producing a particulate water absorbent containing a polyacrylic acid (salt) -based water absorbent resin as a main component, including a drying step of a polymer and a surface crosslinking step, an addition step of 0.001 to 0.5% by weight of a chelating agent and an addition step of an inorganic reducing agent are added. It is a manufacturing method of the particulate water absorbing agent (2nd manufacturing method), Comprising: The monomer contains 10-200 ppm of methoxy phenols in conversion of large acrylic acid, and further includes the addition process of (a) water-insoluble inorganic fine particles.

As in Examples 2-1 to 2-12, the absorbent according to the present invention is excellent in anti-coloring resistance, urine resistance, and absorption rate. In Comparative Examples 2-1 to 2-3 added to only one of the chelating agent and the inorganic reducing agent, the color tone is bad. Comparative examples 2-1 and 2-3 added only to either of the water-insoluble inorganic fine particles and the chelating agent have poor urinary resistance. Moreover, the comparative example 2-3 which does not contain a water insoluble inorganic fine particle (silica) has a slow absorption rate. Regarding the water content, the amount of dust is 6 mg at 4.1% by weight of water in Example 2-10, the amount of dust is 21 mg at 2.0% by weight of water in Example 2-1, and the amount of dust is 40 mg at 1.7% in water content of Comparative Example 2-3. Compared with the water content of 3.0% by weight or more, the amount of dust is drastically reduced.

As mentioned above, the novel absorbent (second absorbent) of this invention shown in the said Example is a particulate water absorbent which has a polyacrylic acid (salt) type water absorbing resin as a main component, and contains a chelating agent and an inorganic reducing agent, and content of the said chelating agent It is 0.001-0.5 weight%, and contains water-insoluble inorganic fine particles. The novel absorbent of the present invention related to the above embodiment preferably has a pressureless absorption ratio (CRC) of 25 [g / g] or more and a pressure absorption ratio (AAP2.0 kPa) of 25 [g / g] or more Vortex (absorption rate) is 60 seconds or less. Such absorbents contain any amount of methoxy phenols (especially p-methoxy phenol), but are in the range of 5 to 60 ppm in the same manner as in (1) and the novel absorbent (first absorbent) of the present invention (about 10 ppm in the above embodiment). Before and after), and weather resistance and coloring are further improved. The novel water absorbent (second absorbent) of the present invention may have a moisture content of less than 3% by weight similarly to the first absorbent, but preferably satisfies (3) and is in the range of 3 to 15% by weight. Since these absorbents have no initial or aging coloration, white color, high absorption rate (Vortex), and high absorption magnification (AAP) under pressure, high liquid diffusion and low recovery amount (Re- There is no problem of coloring derived from the absorbent of wet), and a good paper diaper is provided.

[Production Example 3-1]

Commercial acrylic acid (wako pure, reagent grade; containing 200 ppm of p-methoxy phenol) obtained by gas phase catalytic oxidation was fed to the bottom of the high boiling point impurity separation column having 50 stages of non-porous plates, and the reflux ratio was distilled as 1, By further distilling, purified acrylic acid (3-1) consisting of 99% or more acrylic acid and a trace amount of impurities (mainly water) was obtained. The amount of p-methoxy phenol in purified acrylic acid (3-1) was ND (less than 1 ppm). ND means that the content rate with respect to purified acrylic acid (3-1) is less than 1 ppm.

The adjusted acrylic acid (3-1) was obtained by adding 70 ppm of p-methoxy phenol to purified acrylic acid (3-1).

Comparative Example 3-1

408.4 g of adjusted acrylic acid (3-1) obtained in Preparation Example 3-1 in a reactor formed by attaching a lid to a stainless steel double arm type kneader with a inner volume of 10 liters having two sigma wings 4321.9 g of aqueous 37% by weight aqueous sodium acrylate solution obtained by diluting the adjusted acrylic acid (3-1) obtained in Example 3-1 with neutral water and neutralizing with aqueous sodium hydroxide solution (iron content of 0.7 ppm (large NaOH solid content)), pure water 724.2 g And 4.74 g of polyethylene glycol diacrylate (molecular weight 523) were dissolved to obtain a reaction solution.

Next, this reaction liquid was degassed for 30 minutes in a nitrogen gas atmosphere. Subsequently, 29.5 g of 10 wt% sodium persulfate aqueous solution and 11.3 g of 0.1 wt% L-ascorbic acid aqueous solution were added to the reaction solution with stirring, and polymerization was started after approximately 25 seconds. Then, polymerization was carried out at 25 ° C. or higher and 95 ° C. or lower while pulverizing the resulting gel, and the hydrous gel-like crosslinked polymer (C1-a) was taken out 30 minutes after the polymerization was started. The obtained hydrogel-like crosslinked polymer was subdivided in diameter of about 5 mm or less. In addition, solid content (calculated from the drying loss in 180 degreeC and 3 hours) of hydrous gel-like crosslinked polymer (C1-a) was 37.5 weight%.

The hydrogel-like crosslinked polymer (C1-a) was spread over a 50 mesh wire mesh and subjected to hot air drying at 170 ° C. for 65 minutes, and the dried product was pulverized using a roll mill, and further classified and combined with a JIS standard having an eye size of 850 μm. As a result, amorphous fractured absorbent resin particles (C1-c) having a weight average particle diameter (D50) of 371 µm and a logarithmic standard deviation (σξ) of particle size distribution of 0.34 were obtained. The centrifuge holding capacity (CRC) of the water absorbent resin particles (C1-c) was 46 (g / g) and the aqueous content was 18% by weight.

It consists of 0.027 weight part of ethylene glycol diglycidyl ether, 0.3 weight part of 1, 4- butanediol, 0.5 weight part of 1, 2- propylene glycol, and 2.8 weight part of pure waters, 100 weight part of obtained water absorbing resin particles (C1-c). After the surface crosslinking agent was uniformly mixed, the mixture was heated at 180 ° C. for 60 minutes. Then, the obtained particle | grains were pulverized until it passed the JIS standard body of 850 micrometers of eye size, and the comparative particulate water absorbing agent (3-1) with which the surface was crosslinked was obtained. The analysis results of the comparative particulate water absorbent (3-1) are shown in Tables 8 and 9.

[Example 3-1]

By polymerizing in the same manner as in Comparative Example 3-1, a hydrous gel-like crosslinked polymer (1-a) was obtained. The aqueous hydrogel polymer (1-a) was added at a feed rate of 600 [g / min] while adding 0.375% by weight aqueous sodium hydrogen sulfite solution at a feed rate of 30 [g / min] (MEAT-CHOPPER TYPE: 12VR-400KSOX). Izuka Industrial Co., Ltd., the die pore diameter: 11 mm, the number of holes: 10, die thickness 8 mm), and re-grinding and uniformly mixing (500 ppm as a reducing agent) aqueous sodium hydrogen sulfite solution to the hydrous gel-like crosslinked polymer (1-a) The granular hydrous gel crosslinked polymer (1-b) was obtained.

This granular hydrogel-like crosslinked polymer (1-b) was spread on a 50 mesh wire mesh and subjected to hot air drying at 170 ° C. for 65 minutes, and the dried product was pulverized using a roll mill. By classifying and combining, an amorphous crushed water absorbent resin particle (1-c) having a weight average particle diameter (D50) of 371 µm and a logarithmic standard deviation (σξ) of particle size distribution of 0.34 was obtained. The centrifuge retention capacity (CRC) of the water absorbent resin particles (1-c) was 46 (g / g) and the aqueous content was 18% by weight.

After uniformly mixing the surface crosslinking agent which consists of 0.020 weight part of ethylene glycol diglycidyl ether, 1.5 weight part of 1, 2- propylene glycol, and 3.5 weight part of pure water parts to 100 weight part of obtained water absorbing resin particles (1-c), The mixture was uniformly spread over a stainless steel batt, the entire batt was sealed with a polyethylene bag, and heated at 100 ° C. for 40 minutes. Then, the obtained particle | grains were pulverized until it passed the JIS standard body of 850 micrometers of eye size, and the water absorbent resin particle (1-d) with which the surface was crosslinked was obtained.

1.0 weight part of 0.5 weight% ethylene diamine tetra (methylene phosphonic acid) 5 sodium (abbreviation: EDTMPA, 5Na) aqueous solution was added and mixed with 100 weight part of obtained water absorbing resin particles (1-d), and the particulate water absorbing agent (3-1) was obtained. . The analysis results of the particulate water absorbing agent (3-1) are shown in Tables 8 and 9.

[Example 3-2]

A particulate water absorbing agent (3-2) was obtained in the same manner as in Example 3-1 except that the feed rate of the 0.375% by weight sodium hydrogen sulfite aqueous solution was changed from 30 [g / min] to 12 [g / min]. Table 8 and Table 9 show the analysis results of the particulate water absorbing agent (3-2).

[Example 3-3]

An aqueous solution of 0.5 wt% ethylene diamine tetra (methylene phosphonic acid) 5 sodium (abbreviated as EDTMPA.5Na) was changed to an aqueous solution of 2.5 wt% ethylene diamine tetra (methylene phosphonic acid) 5 sodium (abbreviated as EDTMPA.5Na) and the amount added Absorbent resin particles (3-e) were obtained in the same manner as in Example 3-1, except that 2.0 parts by weight of the absorbent resin particles were used. A particulate water absorbing agent (3-3) was obtained by adding and mixing 0.3 parts by weight of silica gel (brand name: Air Quality 200, manufactured by Nippon Air Japan Co., Ltd.) with 100 parts by weight of the obtained absorbent polymer particles (3-e). Table 8 and Table 9 show the analysis results of the particulate water absorbing agent (3-3).

[Example 3-4]

An aqueous solution of 0.5 wt% ethylene diamine tetra (methylene phosphonic acid) 5 sodium (abbreviated as EDTMPA.5Na) was changed to an aqueous solution of 2.5 wt% ethylene diamine tetra (methylene phosphonic acid) 5 sodium (abbreviated as EDTMPA.5Na) and the amount added A particulate water absorbing agent (3-4) was obtained in the same manner as in Example 3-1 except that the amount of the water absorbent resin particles was 4.0 parts by weight. Table 8 and Table 9 show the analysis results of the particulate water absorbing agent (3-4).

Example 3-5

The concentration of 0.375% by weight aqueous sodium hydrogen sulfite solution was changed to 0.1% by weight, the feed rate was changed from 30 [g / min] to 22.5 [g / min], and 0.5% by weight ethylene diamine tetra (methylene phosphonic acid) 5 An aqueous sodium (abbreviation: EDTMPA, 5Na) solution was changed to 2.5 parts by weight of an ethylene diamine tetra (methylene phosphonic acid) 5 sodium (abbreviation: EDTMPA, 5Na) aqueous solution, and the addition amount thereof was 2.0 parts by weight based on 100 parts by weight of the absorbent resin particles. A particulate water absorbing agent (3-5) was obtained in the same manner as in Example 3-1 except for the above. The analysis results of the particulate water absorbing agent (3-5) are shown in Tables 8 and 9.

Example 3-6

The feed rate of 0.375% by weight aqueous sodium hydrogen sulfite solution was changed from 30 [g / min] to 60 [g / min], and 0.5% by weight of an aqueous solution of 0.5% by weight ethylene diamine tetra (methylene phosphonic acid) 5 sodium (abbreviated as EDTMPA.5Na) A particulate water absorbing agent (3-6) was obtained in the same manner as in Example 3-1 except that the addition amount was changed to 4.0 parts by weight with respect to 100 parts by weight of the absorbent resin particles. The analysis results of the particulate water absorbing agent (3-6) are shown in Tables 8 and 9.

Example 3-7

Except for changing the concentration of 0.375% by weight sodium hydrogen sulfite aqueous solution to 3.75% by weight and changing its feed rate from 60 [g / min] to 30 [g / min] in the same manner as in Example 3-6, particulate matter Absorbent (3-7) was obtained. The analysis results of the particulate water absorbing agent (3-7) are shown in Tables 8 and 9.

Example 3-8

A particulate water absorbing agent (3-8) was obtained in the same manner as in Example 3-7 except that the feed rate of the 3.75% by weight sodium hydrogen sulfite aqueous solution was changed from 30 [g / min] to 60 [g / min]. The analysis results of the particulate water absorbing agent (3-8) are shown in Tables 8 and 9.

Example 3-9

The adjusted acrylic acid (3-2) was obtained by changing the addition amount of p-methoxy phenol to the purified acrylic acid of manufacture example 3-1 from 70 ppm to 10 ppm.

Except having used adjustment acrylic acid (3-2), it carried out similarly to Example 3-1, and obtained water-absorbing resin particle (9-d) with which the surface was crosslinked.

To 100 parts by weight of the obtained water absorbent resin particles (9-d), 4.0 parts by weight of 0.5% by weight aqueous solution of ethylene diamine tetra (methylene phosphonic acid) 5 sodium (abbreviated as EDTMPA.5Na) was added and mixed to absorb the water absorbent resin particles (9-e). Got it.

A particulate water absorbing agent (3-9) was obtained by adding and mixing 0.3 parts by weight of silica gel (brand name: Air Quality 200, manufactured by Nippon Air Corp.) to 100 parts by weight of the obtained water absorbent resin particles (9-e). Table 8 and Table 9 show the analysis results of the particulate water absorbent (3-9). In addition, the degradation rate by the weather resistance promotion test of a particulate-form absorbent (3-9) was 12%.

Example 3-10

The adjusted acrylic acid (3-3) was obtained by changing the addition amount of p-methoxy phenol to the purified acrylic acid of manufacture example 3-1 from 70 ppm to 200 ppm.

Except having used the adjustment acrylic acid (3-3), it carried out similarly to Example 3-1, and obtained the water absorbing resin particle 10-d with which the surface was crosslinked.

2.0 parts by weight of an aqueous solution of 1% by weight of ethylene diamine tetra (methylene phosphonic acid) 5 sodium (abbreviated as: EDTMPA.5Na) in 100 parts by weight of the obtained absorbent resin particles (10-d) was added and mixed with the absorbent resin particles (10-e). Got it.

A particulate water absorbing agent (3-10) d was obtained by adding 0.3 parts by weight of a silica gel (trade name: Air Quality 200, manufactured by Nippon Air Japan Co., Ltd.) to 100 parts by weight of the obtained water absorbent resin particles (10-e). The analysis results of the particulate water absorbing agent (3-10) are shown in Tables 8 and 9.

Example 3-11

The concentration of 0.375% by weight aqueous sodium hydrogen sulfite solution was changed to 1% by weight, and the feed rate thereof was changed from 30 [g / min] to 45 [g / min], and 1% by weight ethylene diamine tetra (methylene phosphonic acid) 5 The addition amount of the aqueous solution of sodium (abbreviation: EDTMPA.5Na) is 5.0 parts by weight based on 100 parts by weight of the absorbent resin particles, and 2 parts by weight of an aqueous 15% by weight aqueous sodium lactate solution is added to 100 parts by weight of the absorbent resin particles. In the same manner as in Example 3-1, a particulate water absorbing agent (3-11) was obtained. The analysis results of the particulate water absorbing agent (3-11) are shown in Tables 8 and 9.

Example 3-12

The concentration of 0.375% by weight aqueous sodium hydrogen sulfite solution was changed to 1% by weight, and the feed rate thereof was changed from 30 [g / min] to 45 [g / min], and 1% by weight ethylene diamine tetra (methylene phosphonic acid) 5 The addition amount of the aqueous solution of sodium (abbreviation: EDTMPA.5Na) is 5.0 parts by weight based on 100 parts by weight of the absorbent resin particles, and 2 parts by weight of an aqueous solution of 25% by weight aluminum sulfate and 15% by weight of lactic acid based on 100 parts by weight of the absorbent resin particles. A particulate water absorbing agent (3-12) was obtained in the same manner as in Example 3-1 except that 2 parts by weight of an aqueous sodium solution was added. The analysis results of the particulate water absorbing agent (3-12) are shown in Tables 8 and 9.

Example 3-13

The particulate water absorbing agent (3-13) was obtained by adding and mixing 0.5 parts by weight of silica (brand name: Air Quality 200, manufactured by Nippon Air Japan) to 100 parts by weight of the water absorbent resin particles (3-11) described in Example 3-11. . The analysis results of the particulate water absorbing agent (3-13) are shown in Tables 8 and 9.

Comparative Example 3-2

By polymerizing in the same manner as in Comparative Example 3-1, a hydrous gel-like crosslinked polymer (C2-a) was obtained. The aqueous hydrogel polymer (C2-a) was added at a feed rate of 600 [g / min] while adding 0.1% aqueous sodium hydrogen sulfite solution at a feed rate of 18 [g / min]. MEAT-CHOPPER TYPE: 12VR-400KSOX Fine-grained hydrogel-like crosslinking by regrinding to a die pore diameter of 11 mm, number of holes of 10 and die thickness of 8 mm) and uniformly mixing an aqueous sodium hydrogen sulfite solution with the hydrous gel-like crosslinked polymer (C2-a). Polymer (C2-b) was obtained.

This granular hydrogel-like crosslinked polymer (C2-b) was spread over a 50 mesh wire mesh and subjected to hot air drying at 170 ° C. for 65 minutes, and the dried product was pulverized using a roll mill. By classifying and combining, an amorphous crushed water absorbent resin particle (1-c) having a weight average particle diameter (D50) of 371 µm and a logarithmic standard deviation (σξ) of particle size distribution of 0.34 was obtained. The centrifuge retention capacity (CRC) of the water absorbent resin particles (C2-c) was 46 (g / g) and the aqueous content was 18% by weight.

It consists of a liquid mixture of 0.027 weight part of ethylene glycol diglycidyl ether, 0.3 weight part of 1, 4- butanediol, 0.5 weight part of 1, 2- propylene glycol, and 2.8 weight part of pure waters to 100 weight part of obtained water absorbing resin particles (C2-c). After the surface crosslinking agent was uniformly mixed, the mixture was heated at 180 ° C. for 60 minutes. Then, the obtained particle | grains were pulverized until it passed the JIS standard body of 850 micrometers of eye size, and the comparative particulate water absorbing agent (3-2) with which the surface was crosslinked was obtained. The analysis results of the comparative particulate water absorbent (3-2) are shown in Tables 8 and 9.

Comparative Example 3-3

Comparative particulate water absorbing agent (3-3) by mixing 1.0 parts by weight of an aqueous solution of 0.05% by weight of ethylene diamine tetra (methylene phosphonic acid) 5 sodium (abbreviation: EDTMPA.5Na) in 100 parts by weight of the comparative water absorbent resin particles (3-1). ) Table 8 and Table 9 show the analysis results of the comparative particulate water absorbent (3-3).

Comparative Example 3-4

The same operation as in Example 3-1 was carried out except that the concentration of the 0.375% by weight aqueous sodium hydrogen sulfite solution was changed to 30% by weight, and the feed rate was changed from 60 [g / min] to 26.25 [g / min]. A granular comparative function gel crosslinked polymer (C4-b) was obtained.

The granular comparative function gel-like crosslinked polymer (C4-b) was spread on a 50 mesh wire mesh and subjected to hot air drying at 170 ° C. for 65 minutes, and the dried product was pulverized using a roll mill. By classifying and combining, the amorphous water-absorbing resin particle (C4-c) of 371 micrometers of weight average particle diameters (D50) and a logarithmic standard deviation ((sigma)) of particle size distribution of 0.34 was obtained. The centrifuge retention capacity (CRC) of the comparative water absorbent resin particles (C4-c) was 44 [g / g] and the water-soluble content was 16 weight%.

0.027 part by weight of ethylene glycol diglycidyl ether, 0.3 part by weight of 1,4-butanediol, 0.5 part by weight of 1,2-propylene glycol, and 2.8 parts by weight of pure water in 100 parts by weight of the obtained comparative absorbent resin particles (C4-c). After uniformly mixing the surface crosslinking agent which consists of, the mixture was heat-processed at 180 degreeC for 60 minutes. Then, the obtained particle | grains were pulverized until it passed the JIS standard body of 850 micrometers of eye size, and the comparative particulate water absorbing agent (3-4) with which the surface was crosslinked was obtained. Table 8 and Table 9 show the analysis results of the comparative particulate water absorbing agent (3-4).

[Comparative Example 3-5]

The concentration of the aqueous sodium hydrogen sulfite solution was changed from 0.375 wt% to 30 wt%, and the feed rate thereof was changed from 60 [g / min] to 45 [g / min], and 5 sodium ethylene diamine tetra (methylene phosphonic acid) Abbreviated-name: The comparative particulate-form absorber (3-5) was obtained like Example 3-1 except not adding EDTMPA * 5Na) aqueous solution.

Comparative Example 3-6

In Production Example 3-1, adjusted acrylic acid (3-6) was obtained by changing the amount of p-methoxy phenol added to purified acrylic acid from 70 ppm to 1 ppm. Except having used the adjusted acrylic acid (3-6), it carried out similarly to description of Example 3-1, and obtained the refined comparative hydrous gel-like crosslinked polymer (C6-b).

This granular comparative hydrous gel crosslinked polymer (C6-b) was spread over a 50 mesh wire mesh and subjected to hot air drying at 170 ° C. for 65 minutes, and the dried product was pulverized using a roll mill, and further, a JIS standard having an eye size of 850 μm. By classifying and combining with each other, the amorphous water-absorbing resin particles (C6-c) having a weight average particle diameter (D50) of 371 µm and a logarithmic standard deviation (σξ) of 0.34 in particle size distribution were obtained. The centrifuge holding capacity (CRC) of the comparative water absorbent resin particles (C6-c) was 50 [g / g] and the water-soluble content was 24 weight%.

0.027 part by weight of ethylene glycol diglycidyl ether, 0.3 part by weight of 1,4-butanediol, 0.5 part by weight of 1,2-propylene glycol, and 2.8 parts by weight of pure water in 100 parts by weight of the obtained comparative absorbent resin particles (C6-c). After uniformly mixing the surface crosslinking agent which consists of, the mixture was heat-processed at 180 degreeC for 60 minutes. Then, the obtained particle | grains were pulverized until it passed the JIS standard body of 850 micrometers of eye size, and the comparative water absorptive resin particle (C6-d) with which the surface was crosslinked was obtained.

0.4 weight part of 5 weight% ethylene diamine tetra (methylene phosphonic acid) 5 sodium (abbreviation: EDTMPA, 5Na) aqueous solution was added and mixed with 100 weight part of obtained comparative absorbent resin particles (C6-d), and the comparative absorbent resin particle (C6-e) )

A comparative particulate water absorbing agent (3-6) was obtained by mixing 0.3 parts by weight of silica gel (brand name: Air Quality 200, manufactured by Nippon Air J.K.) with 100 parts by weight of the obtained comparative absorbent resin particles (6-e).

The degradation rate by the weather resistance promotion test of the comparative particulate water absorbing agent (3-6) was 24%, and was a particulate water absorbing agent with bad weather resistance.

[Comparative Example 3-7]

In Production Example 3-1, adjusted acrylic acid (3-7) was obtained by changing the amount of p-methoxy phenol added to purified acrylic acid from 70 ppm to 270 ppm. A comparative particulate water absorbing agent (3-7) was obtained in the same manner as in Comparative Example 3-6 except that adjustment acrylic acid (3-7) was used.

[Comparative Example 3-8]

It shows below about the relationship between water content and coloring. That is, Example 3- except having changed the density | concentration of the 0.375 weight% sodium hydrogen sulfite aqueous solution into 0.1 weight%, and also changed the feed rate from 30 [g / min] to 22.5 [g / min]. The same procedure as in 1 was carried out to obtain water absorbent resin particles (C8-d) having a crosslinked surface.

1.0 weight part of 0.5 weight% ethylene diamine tetra (methylene phosphonic acid) 5 sodium (abbreviation: EDTMPA, 5Na) aqueous solution was added and mixed with 100 weight part of obtained absorbent resin particles (C8-d), and 13 weight part of deionized water was further added. By mixing, the comparative particulate water absorbing agent (3-8) having a water content of 17% by weight was obtained. The analysis results of the comparative particulate water absorbent (3-8) are shown in Tables 8 and 9. In addition, as shown in the table, the comparative particulate water absorbing agent (3-8) having a water content of 17% by weight was worse in coloration than the water absorbent of the water content of the present invention, and the particles were easily aggregated to form agglomerates, and the handleability was poor.

[Table 8]

TABLE 9

(theorem)

As mentioned above, Example 3-1-Example 3-13, Table 8, and Table 9 are related with the manufacturing method 3 of the particulate water absorbing agent of this invention, The polymerization process of the aqueous monomer solution which has acrylic acid (salt) as a main component, A method for producing a particulate water absorbent containing polyacrylic acid (salt) -based water absorbent resin as a main component, including a drying step of a hydrous gel crosslinked polymer obtained by polymerization and a surface crosslinking step, and a step of adding a chelating agent of 0.001 to 0.5% by weight and an inorganic Further comprising a step of adding a reducing agent, wherein the monomer contains 10 to 200 ppm of methoxy phenols in terms of large acrylic acid, and after the drying step and in the surface crosslinking step, controlling the water content of the polymer to 3 to 15% by weight. Even more preferably, the inorganic reducing agent is added to the hydrous gel-like crosslinked polymer before drying.

As in Examples 3-1 to 3-13, the particulate water absorbing agent according to the present invention has a water content of 3 to 15% by weight, including a chelating agent and an inorganic reducing agent. It was excellent and there was no unpleasant odor. The color tone over time was bad in Comparative Examples 3-1 to 3-3 which contained only one of the chelating agent and the inorganic reducing agent. In addition, Comparative Examples 3-4 and 3-5 in which the addition amount was many only by the reducing agent were particulate absorbents with very strong odor. Comparative example 3-6 (1 ppm in acrylic acid) whose methoxy phenol amount was out of the range of 10-200 ppm in acrylic acid or 5-60 ppm in an absorbent was a particulate water absorbing agent with high deterioration rate and bad weatherability. In addition, Comparative Example 3-7 (270 ppm in acrylic acid) had poor initial coloring, and also caused odor. Such odor is considered to be odor derived from by-products in surface crosslinking rather than odor of the reducing agent itself. In addition, in Comparative Example 3-8 (water content of 17% by weight), the coloration was worse than that of the water absorbent of the present invention and the urine resistance (degradation component 1000 times) was also inferior to the water content. In addition, the production method of the present invention solves the problems of deterioration, odor and coloration, and the residual monomer is 400 ppm or less, and low thereon at 300 ppm or less.

As described above, the novel absorbent (third absorbent) of the present invention, which is also shown in the above examples, is a particulate absorbent containing polyacrylic acid (salt) -based absorbent resin as a main component, and includes a chelating agent and an inorganic reducing agent. It is 0.001 to 0.5 weight%, and water content is 3 to 15 weight%. The novel absorbent of the present invention, which is also shown in the above embodiment, preferably has a pressureless absorption ratio (CRC) of 25 [g / g] or more and a pressure absorption ratio (AAP2.0 kPa) of 25 [g / g] or more The residual monomer is 500 ppm or less. Such absorbent may contain methoxy phenols (especially p-methoxy phenol), and may be 0-200 ppm, Preferably, it is 5? Like the said (1) and the novel absorbent (1st absorbent) of this invention. It becomes the range of 60 ppm (about 10 ppm back and forth in the said Example 3-1-3-8), and weather resistance and coloring improve further. The novel absorbent (third absorbent) of the present invention preferably contains water-insoluble inorganic fine particles similarly to the above (1) and the novel absorbent (first absorbent) of the present invention, and further improves urine resistance. Such absorbents also preferably further comprise an α-hydroxy carboxylic acid compound. It further includes polyvalent metal salts and / or cationic polymers.

These sorbents have no initial or aging coloration, white residual monomer, high absorption rate (Vortex), and high absorption magnification (AAP) under pressure, so they can be used for high density paper diapers with little pulp. There is no coloring problem derived from the absorbent of the re-wet, and a good paper diaper is provided.

The particulate water absorbing agent obtained by the production method according to the present invention is suitable for sanitary materials such as paper diapers, sanitary napkins, and incontinence pads.

31: tank 32: glass tube
33: 0.69 wt% saline 34: L-shaped tube with cock
35: cock 40: container
41: cell 42: stainless steel wire mesh
43: wire mesh made of stainless steel 44: swelling gel
45: glass filter 46: piston
47: hole in the piston 48: collection container
49: dish scale 100: plastic support cylinder
101: 400 mesh wire mesh made of stainless steel 102: swelling gel
103: piston 104: load (weight)
105: Petri dish 106: Glass filter
107: filter paper 108: 0.90% by weight saline

Claims (39)

As a particulate water absorbing agent whose main component is a polyacrylic acid (salt) -based water absorbent resin,
Including chelating agent and inorganic reducing agent,
Content of the said chelating agent is 0.001-0.5 weight%,
The particulate water absorbing agent which satisfies any one or more of the following (1) to (3).
(1) Content of methoxy phenols is 5-60 ppm.
(2) Contains water insoluble inorganic fine particles.
(3) Water content is 3-15 weight%. The method of claim 1,
The particulate water absorbing agent that satisfies any two or more of the above (1) to (3). The method according to claim 1 or 2,
The particulate water absorbing agent which satisfies all of the above (1) to (3). The method according to any one of claims 1 to 3,
The particulate water absorbing agent, wherein the content of the chelating agent is 0.001 to 0.1% by weight. The method according to any one of claims 1 to 4,
The particulate water absorbing agent whose content of methoxy phenols is 5-60 ppm. 6. The method according to any one of claims 1 to 5,
The particulate water absorbing agent, wherein the chelating agent is at least one compound selected from the group consisting of amino polyhydric carboxylic acid, organic polyvalent phosphoric acid, inorganic polyvalent phosphoric acid, and amino polyvalent phosphoric acid. The method according to any one of claims 1 to 6, wherein
A particulate water absorbing agent, wherein the content of the inorganic reducing agent is 0.01 to 1.0% by weight. The method according to any one of claims 1 to 7,
A particulate water absorbing agent, wherein the inorganic reducing agent is a water-soluble inorganic compound having a reducing inorganic element. The method according to any one of claims 1 to 7,
The particulate water absorbing agent, wherein the inorganic reducing agent is a water-soluble organic compound having a reducing inorganic element. 10. The method according to any one of claims 1 to 9,
The particulate water absorbing agent, wherein the inorganic reducing agent is at least one compound selected from the group consisting of sulfite, hydrogen sulfite, pyrosulfite, and dithionate. 11. The method according to any one of claims 1 to 10,
Contains water-insoluble inorganic fine particles,
The particulate water absorbing agent, wherein the content of the water-insoluble inorganic fine particles is 0.05 to 1.0% by weight. The method of claim 11,
The particulate water absorbing agent, wherein the water-insoluble inorganic fine particles are silica. The method according to any one of claims 1 to 12.
A particulate water absorbing agent, further comprising an α-hydroxy carboxylic acid compound. The method of claim 13,
The particulate water absorbing agent, wherein the α-hydroxy carboxylic acid compound is at least one or more compounds selected from the group consisting of lactic acid (salt) and malic acid (salt). 15. The method according to any one of claims 1 to 14,
The particulate water absorbent further comprising a polyvalent metal salt and / or a cationic polymer. The method according to any one of claims 1 to 15,
The particulate water absorbing agent having an iron content of 2 ppm or less. 17. The method according to any one of claims 1 to 16,
The particulate water absorbing agent, wherein the polyacrylic acid (salt) -based water absorbent resin is a granulated product. 18. The method according to any one of claims 1 to 17,
The particulate water absorbing agent which further satisfies any one of the following (4) to (7).
(4) Absorption magnification under pressure (AAP4.83 kPa) or absorption magnification under pressure (AAP2.0 kPa) is 20 [g / g] or more
(5) Saline flow inducibility (SFC) is 30 [× 10 ⁻⁷ · cm · s · g ⁻¹ ] or more
(6) Absorption rate (Vortex) is 60 seconds or less or Absorption rate (FSR) is 0.20 [g / g / sec] or more
(7) 500 ppm or less of residual monomer 18. The method according to any one of claims 1 to 17,
Absorption Absorption Ratio (CRC) under no pressure is 25 [g / g] or higher, Absorption Magnification Under Pressure (AAP4.83㎪) is 20 [g / g] or higher, and Saline Flow Induction (SFC) is 30 [× 10 ^-7 Particulate absorbent which is more than cm <3> * s * g < ^-1 >. 18. The method according to any one of claims 1 to 17,
A particulate water absorbent having a non-pressurized absorption magnification (CRC) of 25 [g / g] or more, a pressurized absorption magnification (AAP2.0 kPa) of 25 [g / g] or more, and a Vortex (absorption rate) of 60 seconds or less. Preparation of the particulate water absorbing agent containing polyacrylic acid (salt) -based water absorbent resin as a main component, including a polymerization step of an aqueous monomer solution containing acrylic acid (salt) as a main component, a drying step of a hydrous gel crosslinked polymer obtained by polymerization, and a surface crosslinking step. As a method,
Further comprising the addition step of 0.001 to 0.5% by weight of the chelating agent and the addition step of the inorganic reducing agent,
Methoxy phenols in the monomer aqueous solution contains 10 ~ 200ppm in terms of large acrylic acid,
The manufacturing method of the particulate water absorbing agent whose main component is polyacrylic acid (salt) type water absorbing resin characterized by satisfy | filling any 1 or more requirements of the following (a)-(c).
(a) Further comprising the step of adding water-insoluble inorganic fine particles.
(b) controlling the water content of the polymer to 3 to 15% by weight in the drying step and in the surface crosslinking step.
(c) After the surface crosslinking step, adding the inorganic reducing agent. 22. The method of claim 21,
The manufacturing method in any one of said (a)-(c) which satisfy | fills two or more requirements. The method of claim 21 or 22,
The manufacturing method which satisfy | fills said (a) and (b). The method of claim 21 or 22,
The manufacturing method which satisfy | fills all of said (a)-(c). 25. The method according to any one of claims 21 to 24,
It includes a polymerization step of an aqueous monomer solution containing acrylic acid (salt) containing 10 to 200 ppm by weight of methoxy phenols, a drying step of a hydrous gel crosslinked polymer obtained by polymerization, a surface crosslinking step, and a chelating agent addition step. As a method for producing a particulate water absorbent,
The manufacturing method of the said (c) addition process of an inorganic reducing agent is performed after a surface crosslinking process. 26. The method according to any one of claims 21 to 25,
The methoxy phenol contained in the said monomer aqueous solution is p-methoxy phenol, and is a manufacturing method which contains 10-120 ppm in conversion of large acrylic acid. 27. The method of any of claims 21 to 26,
The said chelating agent is added to the monomer aqueous solution before superposition | polymerization or during superposition | polymerization. The method according to any one of claims 21 to 27,
The said inorganic reducing agent is added to the hydrous gel-like crosslinked polymer before drying. 29. The method according to any one of claims 21 to 28,
The inorganic reducing agent is a water-soluble inorganic compound having a reducing inorganic element. The method according to any one of claims 21 to 29,
The inorganic reducing agent is a water-soluble organic compound having a reducing inorganic element. The method according to any one of claims 21 to 30,
The inorganic reducing agent is a compound having a reducing sulfur atom or a reducing phosphorus atom. 32. The method according to any one of claims 21 to 31,
The manufacturing method further including the addition process of the (alpha)-hydroxy carboxylic acid compound. 33. The method according to any one of claims 21 to 32,
Further comprising the step of adding a polyvalent metal salt and / or a cationic polymer. The method according to any one of claims 21 to 33,
A manufacturing method further comprising an assembly process. The method according to any one of claims 21 to 34, wherein
The said polymerization process is a process of performing aqueous solution polymerization. The method according to any one of claims 21 to 35,
The method of manufacturing further including the gel granulation process of performing granulation of a hydrous gel-like crosslinked polymer during or after superposition | polymerization. The method of claim 36,
And an inorganic reducing agent is added simultaneously with the granulation of the hydrogel-like crosslinked polymer. 38. A compound according to any of claims 21 to 37,
The surface crosslinking agent used in the surface crosslinking process is a polyvalent epoxy compound. 39. The method of any of claims 21-38,
In addition to the neutralization process,
The said polymerization process is the maximum temperature of 130 degrees C or less by the radical polymerization initiator 0.001-1 mol% in the monomer aqueous solution of 30-55 weight% of monomers containing 90-100 mol% of acrylic acid (salt) in a monomer, It is a process of performing aqueous solution polymerization or reverse phase suspension polymerization on the conditions of polymerization time 0.5 minute-3 hours,
The neutralization step is made of a Fe content of 0-7ppm base,
The drying step is a step of drying the hydrous gel crosslinked polymer obtained by polymerization in a particulate form at a drying temperature of 100 to 250 ° C. to a water content of 20% by weight or less at a drying time of 10 to 120 minutes,
The said surface crosslinking process is a process of mixing 0.001-10 weight part of surface crosslinking agents with respect to 100 weight part of absorbent resin powders after completion of a drying process, and heat-processing at 70-300 degreeC for 1 minute-2 hours,
The manufacturing method which makes methoxy phenol content of the particulate water absorbing agent obtained 5-60 ppm.

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