JP2584495B2 - Method for producing super absorbent fiber sheet - Google Patents

Description

The present invention relates to a highly water-absorbent fiber sheet and a method for producing the same. More specifically, the present invention relates to a product requiring high water absorbency and water retention, for example, The present invention relates to a highly water-absorbent fiber sheet which can be used for an oil-water separator, a dew condensation preventing material, a sanitary product, a disposable diaper and the like, and a method for producing the same.

[Conventional technology]

Granular water-absorbent resin has water supply capacity several times to 1,000 times,
Disposable diapers, sanitary products, soil improvement materials for agricultural and horticultural use, sealing materials,
Applications are being developed in a wide range of fields, such as fresheners.

On the other hand, depending on the application, the form of a fiber product such as a yarn, a nonwoven fabric, a mat, or a knitted fabric is often preferred, and a water-absorbing resin having such a form is desired.

Examples of fiberization include, as disclosed in JP-A-49-7526, a specific crosslinked structure of acrylic fiber,
Methods for introducing a carboxyl group in the form of a salt derived from the remaining nitrile group have been widely studied.

On the other hand, as a method of directly fibrillating a polycarboxylic acid such as polyacrylic acid or a salt thereof (hereinafter abbreviated as polycarboxylic acid (salt)) without performing the chemical modification as described above, Japanese Patent Application Laid-Open No. JP-138622-A discloses that an aqueous solution of an alkali metal salt polymer of acrylic acid is spun from a spinning nozzle into a mixed bath of an organic solvent and water, shaped into a fibrous form, and then dried. JP-A-63-28912 proposes dry spinning a high-concentration aqueous solution containing a polycarboxylic acid and a polyhydric alcohol as substantial components, followed by heat treatment.

[Problems to be solved by the invention]

However, there are the following problems in making a sheet-like material such as a nonwoven fabric from a direct fiberization of these polycarboxylic acids (salts).

That is, since polycarboxylic acid (salt) has a strong hydrogen bond in nature and cannot be hot-drawn, even if it is directly fiberized by the above-described method, it has a drawback that it has no fiber strength and is hard and brittle upon drying. I have. Accordingly, it has been extremely difficult to defibrate and card the fibers to form a sheet such as a web or a nonwoven fabric.

[Means for solving the problem]

The present inventors have conducted intensive studies to overcome the above difficulties, and as a result, by subjecting a fiberized polycarboxylic acid (salt) to a surfactant treatment and a humidification treatment, a high water-absorbing ability was obtained. The present inventors have found the fact that a sheet-shaped material having a soft feeling can be produced, and have reached the present invention.

That is, the present invention is characterized in that after attaching an anionic and / or nonionic surfactant to a superabsorbent fiber comprising a polycarboxylic acid or a salt thereof, a humidifying treatment is performed, and the resultant is formed into a sheet. To provide a method for producing a highly water-absorbent fiber sheet comprising a polycarboxylic acid or a salt thereof containing 5 to 80% by weight of water.

In the present invention, examples of the polycarboxylic acid (salt) include acrylic acid (salt), methacrylic acid (salt), crotonic acid (salt), itaconic acid (salt), maleic acid (salt), fumaric acid (salt) and the like. Polymer or copolymer of ethylenically unsaturated carboxylic acid (salt); these ethylenically unsaturated carboxylic acid (salt), 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate , Ethylenically unsaturated carboxylic acid esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, vinyl esters such as vinyl acetate, vinyl propionate, vinyl stearate, styrene, styrene sulfonic acid, acrylamide, methacrylamide, Copolymers with ethylenically unsaturated monomers such as acrylonitrile; saponified vinyl acetate-methyl acrylate copolymer, saponified vinyl acetate-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer ken And a starch-acrylic acid graft polymer, a saccharide-acrylic acid graft polymer, and a saponified starch-acrylonitrile graft polymer. These may be linear polymers or suitably crosslinked. As the salt, an alkali metal salt, an ammonium salt, an amine salt or the like can be appropriately selected, and the degree of neutralization can be arbitrarily selected. Among these, polyacrylic acid (salt) is particularly preferable in terms of increasing the water absorption.

The method for producing these polycarboxylic acids (salts) is not particularly limited, and conventionally known methods such as solution polymerization, suspension polymerization, reversed-phase suspension polymerization, and precipitation polymerization can be appropriately selected.

The fiberization of the polycarboxylic acid (salt) is carried out by wet spinning or dry spinning a solution of the polymer, mainly an aqueous solution, if desired, with the addition of a crosslinking agent or a plasticizer.

In the present invention, the fiber thus obtained is formed into a desired shape after containing a specific amount of moisture. As a method for adding moisture to the fibers, a method of supplying the fibers in the form of steam or mist (fine droplets), that is, a humidification treatment is preferable.

When water is simply supplied in the form of liquid droplets or fluid, only the surface or non-uniform water content is generated, and stickiness and local swelling occur, making it difficult to process such as defibration and carding. On the other hand, when the humidification treatment is performed, uniform water content is possible from the inner layer to the outer layer of the fiber.

Examples of the humidifying method include a method of passing the spun fiber through a mist, and a method of leaving the fiber in a space conditioned at 50% RH or more, preferably 70% RH or more.
The temperature at the time of the treatment is usually from room temperature to about 40 ° C., but the temperature may be further increased as long as the performance of the product is not hindered.

In the humidification treatment, the water content of the fibers needs to be adjusted within a range of 5 to 80% by weight, preferably 10 to 50% by weight, based on the weight of the dry fibers. If the water content is too low, the fibers are stiff and brittle, and cannot be formed into a sheet by the dry method.On the other hand, if the water content is too high, the fiber strength decreases, and shape changes such as yarn breakage during molding may occur. Not preferred.

Therefore, the time of the humidification treatment may be appropriately set in a period until the fiber has a suitable moisture content. By appropriately measuring the weight of the fiber during the humidification treatment, the moisture content of the fiber can be known.

If the fibers after spinning are treated with a surfactant prior to such a humidification treatment, the workability when forming into a sheet after the humidification treatment is remarkably improved, which is preferable.

As the surfactant, an anionic and / or nonionic surfactant is preferable.

Specifically, examples of the anionic surfactant include sulfate salts (higher alcohol sulfate salts, higher alkyl ether sulfates, sulfated fatty acid esters, sulfated olefins, etc.), sulfonates (sodium alkylbenzene sulfonate, α- Olefinsulfonic acid, etc.), phosphate ester salts and the like, and nonionic surfactants include higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, fatty acid ethylene oxide adducts, sorbitan fatty acid esters and their ethylene oxide adducts, glycerin fatty acids Esters and polyglycene fatty acid esters.

These surfactants may be used alone or in combination of two or more. The treatment method is not particularly limited. For example, the superabsorbent fiber is immersed in a solution in which the surfactant is dissolved in methyl alcohol, ethyl alcohol, or the like, squeezed, and then dried. This treatment causes the surfactant to adhere to the surface of the fiber. The adhesion amount is usually 0.1% by weight or more, preferably 0.1 to 5% by weight per dry fiber weight.

If the amount of adhesion is less than 0.1% by weight, frictional electrification of the fiber is likely to occur during processing, and slippage is poor, so that rolls may fall and the web may hardly be formed.

On the other hand, if the amount is too large, the surface of the fiber itself becomes sticky due to the surfactant itself and moisture absorption, which is not preferable.

During this surfactant treatment, a part of the water to be impregnated in the subsequent humidification treatment can be contained.

As a method of forming the fiber subjected to the above treatment into a sheet shape, a method generally known as a method for producing a nonwoven fabric can be applied.For example, through a roller card machine, after defibration, an aligned web is formed. Alternatively, thereafter, a method of performing needle punching to increase the density of the web or make the web stiff may be used.

In this way, the fibers subjected to the treatment of the present invention are formed into products such as webs (cotton-like forms) and non-woven fabrics, as well as forms such as papermaking sheets and knitted fabrics by ordinary fiber processing methods. be able to.

The obtained sheet-like material has high water-absorbing performance, which is the original property of polycarboxylic acid (salt), and may be used as it is or mixed with other hydrophilic or hydrophobic fibers. Processes such as lamination, cutting, twisting, and joining using an adhesive can be used in a wide range of application fields. For example, disposable diapers, sanitary products, absorbent paper, water retention materials for agriculture and horticulture, soil improvement materials, freshening materials, sealing materials, oil / water separation materials,
Applicable to heat and cold insulation materials.

〔Example〕

Hereinafter, the present invention will be described in more detail by examples,
The present invention is not limited to these examples.

The water absorption and water content described in the examples were measured by the following methods. In the examples, “parts” and “%” are based on weight unless otherwise specified.

Water absorption (g / g) Approximately 1 g (W ₁ ) of a test piece was weighed, immersed in 100 ml of physiological saline for 30 minutes in a static state, and allowed to absorb water. The weight (W ₂ ) of the swollen fiber sheet obtained as above was measured and calculated by the following equation.

Moisture (%) Approximately 1 g (W ₁ ) of the test piece was weighed and left in a vacuum drier at 105 ° C. for 4 hours to determine a volatilization loss (W).

Example 1 20 parts of polyacrylic acid having a molecular weight of 250,000 and 27.8 parts of 30
% Caustic soda and 125 parts of water were placed in a kneader, uniformly dissolved, and heated and defoamed at 100 ° C. for 24 hours to obtain an aqueous solution of sodium polyacrylate having a neutralization degree of 75 mol%. Next, after cooling the aqueous solution, 0.5 parts of ethylene glycol diglycidyl ether was added and uniformly mixed by a roll mill to obtain a spinning solution.

The thus prepared spinning dope is extruded from a nozzle having a pore size of 0.08 mm and 20 holes into a coagulation bath of ethanol, passed through a heating furnace at 200 ° C for 15 seconds, and wound around a roller at a spinning speed of 12 m / min. Was.

This fiber was immersed in a 1% ethanol solution of polyoxyethylene lauryl ether (Emulgen 108; manufactured by Kao Corporation) to adhere to 100% of the dry fiber weight.
It dried with hot air at ° C. After that, it was humidified at 30 ° C./80% RH for 13 hours, cut into a length of about 5 cm, defibrated and carded with a roller card machine to obtain a web. This web had a bulky and flexible hand and a water content of 20%. The water absorption was 50 g / g.

Example 2 The same spinning dope as in Example 1 was placed in a dry air stream at 200 ° C. with a pore size
Dry spinning was performed by extruding from a nozzle having a bore of 20 mm.

This fiber was immersed in a 1% ethanol solution of polyoxyethylene oleyl ether (Emulgen 409P; manufactured by Kao Corporation) and attached to a dry fiber weight of 150%.
Hot air drying was performed at 00 ° C. Then, it was humidified at 30 ° C./80% RH for 18 hours, cut into a length of about 5 cm, defibrated and carded with a roller card machine to obtain a web. Needle punching is performed on this web with a needle punch machine,
A non-woven fabric was used.

The water content of this nonwoven fabric was 35%, and the water absorption was 52 g / g.

Example 3 500% aqueous solution of 20% sodium acrylate (neutralization degree: 75 mol%)
Methoxy polyethylene glycol # 400 acrylate (NK ester AM-90G; manufactured by Shin-Nakamura Chemical Co., Ltd.) 5.5
Parts and an initiator azobiscyanovaleric acid 0.348 parts were added,
Polymerization was performed at 65 ° C. for 2 hours in a nitrogen atmosphere. Next, after cooling this aqueous solution, 2 parts of ethylene glycol diglycidyl ether was added and uniformly mixed by a roll mill to obtain a spinning dope.

The spinning dope thus prepared was wet-spun in the same manner as in Example 1.

The fiber was immersed in a 1% ethanol solution of polyoxyethylene lauryl ether (Emulgen 108; manufactured by Kao Corporation), and allowed to adhere to a dry fiber weight of 120%.
It dried with hot air at ° C. Then, it was humidified at 30 ° C./80% RH for 2 hours, cut into a length of about 5 cm, defibrated and carded with a roller card machine to obtain a web. This web had a bulky and soft hand and a water content of 40%. The water absorption was 43 g / g.

Example 4 500% aqueous solution of 20% sodium acrylate (neutralization degree: 75 mol%)
16.38 parts of 2-hydroxyethyl methacrylate, 0.384 part of azobiscyanovaleric acid as an initiator and 1 part of ion-exchanged water
5.52 parts were added, and polymerization was carried out at 65 ° C. for 2 hours under a nitrogen atmosphere.
Next, after cooling this aqueous solution, 2 parts of ethylene glycol diglycidyl ether was added and uniformly mixed by a roll mill to obtain a spinning dope.

The spinning dope thus prepared was wet-spun in the same manner as in Example 1.

This fiber was immersed in a 1% ethanol solution of polyoxyethylene oleyl ether (Emulgen 409P; manufactured by Kao Corporation) and allowed to adhere to the dry fiber weight by 130%.
Hot air drying was performed at 00 ° C. Then, it was humidified at 30 ° C./80% RH for 30 hours, cut into a length of about 5 cm, defibrated and carded with a roller card machine to obtain a web. This web had a moisture content of 50%, and had a bulky and soft texture.
The water absorption was 40 g / g.

Example 5 Using a roller card machine, 50 parts of the sodium polyacrylate fiber (cut to 5 cm, water content 20%) and 50 parts of polyester fiber (3 denier / 51 mm) subjected to the surfactant treatment and the humidification treatment of Example 1 were used. Defibration and card hanging to make a composite web. This web had a bulky and flexible hand. The water absorption was 25 g / g.

Example 6 86.09 parts of vinyl acetate, 98.06 parts of maleic anhydride, and 0.61 part of benzoyl peroxide as an initiator were dissolved in 576 parts of benzene, and polymerized at 60 ° C. for 3 hours under a nitrogen atmosphere. Benzene
The solvent was distilled off under reduced pressure at 80 ° C.
Neutralized with 436 parts of an aqueous sodium hydroxide solution. Then
1.7 parts of ethylene glycol diglycidyl ether was added to this aqueous solution, and uniformly mixed by a roll mill to obtain a spinning dope.

The spinning dope thus prepared was wet-spun in the same manner as in Example 1.

This fiber was immersed in a 1% ethanol solution of polyoxyethylene lauryl ether (Emulgen 108; manufactured by Kao Corporation) to adhere to 100% of the dry fiber weight.
It dried with hot air at ° C. After that, it was humidified at 30 ° C./80% RH for 13 hours, cut into a length of about 5 cm, defibrated and carded with a roller card machine to obtain a web. This web had a bulky and flexible hand and a water content of 20%. The water absorption was 40 g / g.

Example 7 1204 parts of toluene and 205.9 parts of maleic anhydride were placed in a two-separable flask equipped with a gas bag and equipped with a stirrer, a gas inlet tube, a thermometer, and a cooling tube. Under stirring, the temperature was raised to 70 ° C. As a polymerization initiator, 3.43 parts of 2,2'-azobisisobutyronitrile was added, and then isobutylene gas was introduced into the solution from a gas cylinder through a separately prepared cylinder. While maintaining the reaction temperature at 70 ° C., 135 parts of isobutylene gas (molar ratio to maleic anhydride: 1.14) were continuously blown in over 3 hours. The mixture was aged at that temperature for 3 hours under stirring, and then cooled. The slurry reaction solution containing the polymer precipitate was taken out, filtered, and dried under reduced pressure at 70 ° C. for 24 hours.

A 30% aqueous solution of sodium hydroxide was added to 25.7 parts of the dried polymer to neutralize 75% of the maleic anhydride unit, and 69.43 parts of ion-exchanged water was added to obtain a 20% aqueous solution. Next, 0.5 parts of ethylene glycol glycidyl ether was added to this aqueous solution, and uniformly mixed by a roll mill to obtain a spinning stock solution.

The spinning dope thus prepared was wet-spun in the same manner as in Example 1.

This fiber was immersed in a 1% ethanol solution of polyoxyethylene lauryl ether (Emulgen 108; manufactured by Kao Corporation), and allowed to adhere to a dry fiber weight of 120%.
It dried with hot air at ° C. After that, it was humidified at 30 ° C./80% RH for 18 hours, cut into a length of about 5 cm, defibrated and carded by a roller card machine to obtain a web. This web had a moisture content of 35%, and had a bulky and soft texture. The water absorption was 36 g / g.

Comparative Example 1 When the sodium polyacrylate fiber (water content: 4%) before the surfactant treatment in Example 1 was defibrated and carded by a roller card machine as it was, it rolled off and did not become a web.

Comparative Example 2 When the sodium polyacrylate fiber (water content: 3%) obtained by dry spinning in Example 2 was defibrated and carded by a roller card machine as it was, it rolled off and did not become a web.

〔The invention's effect〕

According to the present invention, a polycarboxylic acid (salt) which has conventionally been difficult to be processed into a web or nonwoven fabric form
It has become possible to process the superabsorbent fiber made of into a sheet such as a web, a nonwoven fabric, a papermaking sheet, and a knitted fabric.

Further, the highly water-absorbent fiber sheet obtained by the present invention has a high water-supply capacity as high as a granular water-absorbent resin, has a soft feel, can be processed into various forms, Can be combined with other fiber materials according to the conditions.

The highly water-absorbent fiber sheet of the present invention can be applied not only to the field in which the conventional granular water-absorbent resin is used, but also to the field in which the form as a fiber product is suitable, and is extremely useful industrially. is there.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-28912 (JP, A) JP-A-56-118938 (JP, A) JP-A-57-121657 (JP, A)

Claims (2)

(57) [Claims] The present invention is characterized in that an anionic and / or nonionic surfactant is attached to a superabsorbent fiber comprising a polycarboxylic acid or a salt thereof, and then a humidifying treatment is applied to form a sheet. A method for producing a highly water-absorbent fiber sheet comprising a polycarboxylic acid or a salt thereof containing 5 to 80% by weight of water. 2. The method according to claim 1, wherein the polycarboxylic acid or a salt thereof is polyacrylic acid or a salt thereof.