JPH1143854A - Hydrolyzable non-woven fabric and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hydrolyzable non-woven fabric having a sufficient strength for works, e.g. cleaning, and composed of fibers dissociable in a flow of large quantity of water, and also provide a method for producing the same. SOLUTION: This hydrolyzable non-woven fabric is composed of (A) 55 to 20 wt.% of recycled cellulosic fibers, comprising (a) 70 to 30 wt.% of first recycled cellulosic fibers of smaller diameter and (b) 30 to 70 wt.% of second recycled cellulosic fibers of larger diameter, and (B) 45 to 80 wt.% of pulp fibers, wherein these fibers are entwining each other by a columnar flow of high-pressure water to form a fabric. Ratio of diameter of the first cellulosic fiber (D1, μm) to that of the second cellulosic fiber (D2, μm), i.e., D1/D2, is 1.2 to 2.0. This method for producing the hydrolyzable, non-woven fabric places the web on a bored, movable supporter, and treats the web with a columnar flow of high-pressure water at least from one side of the web in such a way to entwine the recycled cellulosic fibers and pulp fibers each other to form a fabric.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-disintegratable nonwoven fabric which has a strength which can withstand operations such as cleaning in a dry state and a wet state, and which can disintegrate fibers constituting the nonwoven fabric in a large amount of water flow. And its manufacturing method. More specifically, it can withstand practical use when dried or when wetted with water or a chemical solution for use as a wet tissue, cloth, or cleaning wiper, or when used as a top sheet for disposable diapers or sanitary napkins. The present invention relates to a water-disintegratable nonwoven fabric which maintains strength and can be easily defibrated in a large amount of water flow in a toilet or the like, and a method for producing the same.

[0002]

2. Description of the Related Art In general, wet products such as wet tissues, wipes, and wipers for cleaning, and many hygiene products such as disposable diapers and sanitary napkins are discarded as garbage after use. For example, considering the use of wet wipes, treatment with a wet wiper is superior to stool wiping compared to treatment with toilet paper,
It has excellent performance such as low skin irritation. However, it has a drawback that it cannot be flushed to a flush toilet after use, and disposal treatment tends to be unsanitary.

[0003] For this reason, generally used wipes are used only for very limited uses such as baby wipes and nursing wipes for nursing care. Not in. As a method of improving the wiping property and skin irritation of the toilet paper, a method of impregnating the toilet paper with a humectant or the like has been proposed, but has not yet reached a performance comparable to the case where a wet wiper is used.

[0004] Examples of the water-disintegrable non-woven fabric usable as a top sheet for wet tissues and sanitary articles include, for example, JP-A-47-9486, JP-A-1-168999, JP-A-2-149237, and JP-A-3-149. 277
No. 335, Japanese Patent Application Laid-Open No. 4-370300, Japanese Patent Application No. 8-142825, Japanese Patent Application No. 9-48870, and the like have been proposed.

In Japanese Patent Application Laid-Open No. 47-9486, polyvinyl alcohol and borax react by spraying a binder solution containing polyvinyl alcohol and borax onto a sheet and then heating and drying the sheet. It is described that this hydrolyzed paper is useful as an absorbent pad for napkins, diapers and the like. However, this water-disintegrated paper does not have a strength enough to withstand a mechanically-cleaning operation such as that used for wiping a butt or a cleaning sheet for a toilet or the like when impregnated with water.

JP-A-1-168999 proposes using a calcium salt of water-insoluble carboxymethylated pulp as a base paper. However, in the water-disintegrated paper proposed in the publication, the upper limit of the water content in the cleaning liquid is 60%, and it is necessary to add at least 30% of an organic solvent such as alcohol. The use in which the liquid can be used is limited, and it is particularly difficult to use it for uses such as wiping the ass. Also, by adding an organic solvent, it is necessary to add a large amount of fragrance to eliminate the smell of the organic solvent, and the strength may be reduced during cleaning work due to an increase in the percentage of water due to volatilization of the organic solvent. There is a disadvantage that. Furthermore, the adverse effect on the human body due to the high concentration of the organic solvent cannot be ignored.

[0007] Japanese Patent Application Laid-Open No. 2-149237 discloses that a hydrolyzed paper containing a specific water-soluble binder is impregnated with an aqueous solution containing a specific metal ion and an organic solvent.
We propose to obtain a water-disintegratable cleaning article that has sufficient strength to perform cleaning work in a state of being impregnated with a water-containing cleaning agent, and has a water-disintegrating performance that can be easily washed away in a toilet or the like. I have. However, this cleaning article needs to contain specific metal ions and an organic solvent in the impregnating liquid to be impregnated into the hydrolyzed paper, and its use is extremely limited because the impregnating liquid cannot be freely selected according to the purpose. It was done.

Further, a water-soluble binder having a carboxyl group is used as a specific water-soluble binder, and polysaccharide derivatives such as alkali metal salts such as carboxymethylcellulose, carboxyethylcellulose and carboxymethylated starch are used as such water-soluble binders. Molecules, natural products and the like are mentioned, but the blending of these binders has the disadvantage that the texture of the sheet becomes hard.

In Japanese Patent Application Laid-Open No. 3-277335, water-soluble carboxymethylcellulose calcium is used as a paper strength enhancer for base paper, and calcium ions are allowed to coexist in the cleaning solution, so that a sufficient cleaning solution can be obtained even in a cleaning solution having a high water content. A wiping material that exhibits strength and easily disperses in 100% water has been proposed. Calcium chloride or calcium acetate is used as a calcium ion source, but it is likely to cause rough hands when used as a wiping material, and is difficult to use for cleaning the skin such as wiping the ass. The upper limit of the water content during the impregnation is also about 85%. However, from the viewpoint of diversification of uses, a base material that can be used even if the water content in the impregnating liquid is even higher is desired.

Japanese Patent Application Laid-Open No. Hei 4-370300 has a multilayer structure having at least two layers, and one outermost layer has 10 layers.
~ 60% paper strength agent, the other outermost layer is 5% by weight
Hydrolysis papers containing the following paper-strengthening agents have been proposed. As the paper strength enhancer used in the outermost layer of the hydrolyzed paper, carboxymethylated pulp salt, water-soluble polyvinyl alcohol, water-soluble polyvinyl alcohol fiber, or a mixture thereof is used. This water-disintegrated paper is intended to reduce the deterioration of the releasability in the dryer part during papermaking due to the addition of a paper strength enhancer, and to improve the productivity. However, when there is much moisture in the chemical solution to be impregnated, it is difficult to have sufficient wet strength for use, and the texture is hard because a large amount of paper strength enhancer is compounded in the outermost layer on one side of the hydrolyzed paper. It will be something.

In view of these drawbacks of the hydrolyzed paper, the present inventors have proposed a water-disintegratable nonwoven fabric which is free of binder and has both sufficient strength and water-disintegrability for use, and a method for producing the same. That is, in Japanese Patent Application No. 8-142825, a high-pressure water column flow is applied to a wet paper-made web obtained by mixing 40 to 85% by weight of regenerated cellulose fiber having a specific fiber length and 60 to 15% of pulp fiber having a specific freeness. By applying the composition, fiber entanglement is imparted, and a water-disintegratable nonwoven fabric having both wet strength and water-disintegration is obtained. However, since the water-disintegratable nonwoven fabric has a high content of rayon fibers of 40 to 80% by weight, the cost is high. Therefore, a water-disintegratable nonwoven fabric which can be produced at lower cost is desired.

Japanese Patent Application No. 9-48870 discloses a regenerated cellulose fiber 55 to 55 having a specific fineness and L / D.
Wood pulp fiber 45 to 15% by weight and specific Runkel ratio
85% by weight, and wet-papermaking web is subjected to high pressure water column flow treatment under the condition of a specific additional specific energy to impart fiber entanglement to obtain a water-disintegratable nonwoven fabric having both wet strength and water-disintegrability. Propose that. Although the water-disintegratable nonwoven fabric according to this proposal has a certain level of performance, it is desired to achieve both wet strength and water-disintegration at a higher level when considering more applications.

[0013]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fiber which has a strength which can withstand operations such as cleaning in a dry state and a wet state, and which constitutes a nonwoven fabric in a large amount of water flow. And a method for producing the same.

[0014]

In view of this situation, the present inventors have developed a water-disintegratable nonwoven fabric which has strength enough to be used in a wet state and easily disintegrates into a fibrous form in a large amount of water. The inventor has studied diligently about the manufacturing method.

As a result, the present inventors mixed a first regenerated cellulose fiber having a relatively small fiber diameter, a second regenerated cellulose fiber having a relatively large fiber diameter, and a wood pulp fiber, and then mixed with a conventionally known wet process. A wood pulp fiber is formed by forming a web by a papermaking method, placing the web on a transportable perforated support made of a wire mesh or a plastic mesh, and subjecting at least one surface of the web to a high-pressure water column flow treatment. It has been found that both the strength that can withstand use even in the state of being mixed at a high rate and the water dissolvability in a large amount of water flow can be achieved, and the present invention has been completed.

A first aspect of the present invention is a regenerated cellulose fiber comprising a first regenerated cellulose fiber having a relatively small diameter of 70 to 30% by weight and a second regenerated cellulose fiber having a relatively large diameter of 30 to 70% by weight. A water-disintegratable nonwoven fabric comprising 55 to 20% by weight of a group and 45 to 80% by weight of wood pulp fibers, wherein each fiber is entangled and integrated by a high-pressure water column flow.

A second aspect of the present invention is that the fiber diameter ratio D2 / D1 of the fiber diameter D1 (μm) of the first regenerated cellulose fiber to the fiber diameter D2 (μm) of the second regenerated cellulose fiber is 1.2. It is a water-disintegrable nonwoven fabric characterized by being ~ 2.0.

A third aspect of the present invention is that the first regenerated cellulose fiber, the second regenerated cellulose fiber, and the wood pulp fiber are mixed, formed into a web by a conventionally known wet papermaking method, and the web can be transferred. Placed on a hole support, subjected to high-pressure water column flow treatment from at least one surface of the web,
This is a method for producing a water-disintegratable nonwoven fabric, wherein each regenerated cellulose fiber and wood pulp fiber are entangled and integrated.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to obtain a water-disintegratable nonwoven fabric of the present invention, first, a first regenerated cellulose fiber having a relatively small fiber diameter, a second regenerated cellulose fiber having a relatively large fiber diameter, and a wood pulp fiber are combined. prepare.

The two kinds of regenerated cellulose fibers used here are cellulose pulp, cotton linter, or other cellulose in the form of viscose, and then regenerated and spun in an acid. Is dissolved in a copper ammonia solution, and then regenerated and spun in an acid to obtain copper ammonia rayon, N-methylmorpholine-N
And regenerated cellulose fibers obtained by dissolving cellulose in a non-aqueous cellulose solvent such as oxide and spinning.

An important point in the present invention is to use a first regenerated cellulose fiber having a relatively small fiber diameter and a second regenerated cellulose fiber having a relatively large fiber diameter. That is, in general, a fiber having a small fiber diameter has a high flexibility due to a low rigidity of the fiber itself, and shows a strong inter-fiber entanglement when a confounding action by a high-pressure water column flow or the like acts. For this reason, when only the small diameter fiber is used, a high-strength sheet can be obtained,
Even in a large amount of water flow, the entanglement of fiber entanglement does not progress very much, and the sheet tends to be poor in water disintegration.

On the contrary, a fiber having a large fiber diameter is inferior in flexibility due to high rigidity of the fiber itself, and does not show too strong inter-fiber entanglement even when the entanglement action by a high-pressure water column flow or the like works.
For this reason, if only the large-diameter fiber is used, a high-strength sheet cannot be obtained, but the fiber entanglement in a large amount of water flow is rapidly disintegrated, and the sheet tends to be excellent in water dissolvability.

Therefore, when the regenerated cellulose fibers having a small diameter and the regenerated cellulose fibers having a large diameter are simultaneously used and the fibers are entangled by a high-pressure water column flow or the like, the entangled strength of the regenerated cellulose fibers having a small diameter can be obtained. The wet strength of the nonwoven fabric is maintained, and in a large amount of water flow, the large-diameter regenerated cellulose fibers disintegrate at an early stage and fall off from the nonwoven fabric. The small-diameter fibers that have been used can be easily disintegrated, and the water dissolvability of the obtained nonwoven fabric can be maintained.

In particular, in the present invention, when the ratio of the fiber diameters of the two types of regenerated cellulose fibers used satisfies the following expression (1), the above-mentioned characteristics are effectively exhibited. D2 / D1 = 1.2 to 2.0 (D2> D1) (1) where D1: fiber diameter of first regenerated cellulose fiber D2: fiber diameter of second regenerated cellulose fiber

In the above formula, if the fiber diameter ratio D2 / D1 is less than 1.2, the difference in properties between the two types of regenerated cellulose fibers used becomes small. It is difficult to simultaneously provide sufficient wet strength and water disintegration. Also, the fiber diameter ratio D2 / D1
Is larger than 2.0, it is not preferable because the regenerated cellulose fibers have a difference in the added specific energy required for obtaining an appropriate entanglement. In other words, with the additional specific energy at which the first regenerated cellulose fiber having a relatively small fiber diameter is appropriately entangled, the second regenerated cellulose fiber having a relatively large fiber diameter can hardly be entangled. Shows a tendency for wet strength to decrease,
On the contrary, if the added specific energy is such that the second regenerated cellulose fiber having a relatively large fiber diameter is appropriately entangled, the entanglement of the first regenerated cellulose fiber having a relatively small fiber diameter becomes too strong. The resulting water-disintegratable nonwoven fabric tends to have poor water-disintegrability, which is not preferred.

Of the regenerated cellulose fibers used in the present invention, the fiber diameter D1 of the relatively thin first regenerated cellulose fiber
Is preferably 9.5 to 15.5 μm. When the fiber diameter of the first regenerated cellulose fiber is less than 9.5 μm, it is difficult to disperse during wet paper making, and it is difficult to obtain a wet paper web with good formation. Further, it is difficult to stably produce regenerated cellulose fibers having a fiber diameter of less than 9.5 μm, and it is difficult to obtain them at low cost. Furthermore, the rigidity of the fiber itself tends to be too low, and the fiber entanglement due to the high-pressure water column flow treatment is too strong, and the water dissolvability tends to be poor, which is not preferable. Conversely, the fiber diameter of the first regenerated cellulose fiber is 1
If it exceeds 5.5 μm, the entanglement between the fibers becomes relatively weak, and it is not preferable because the required wet strength cannot be sufficiently imparted to the obtained water-disintegrable nonwoven fabric.

The fiber diameter D2 of the second regenerated cellulose fiber having a relatively large fiber diameter is selected from those satisfying the fiber diameter ratio D2 / D1 based on the fiber diameter D1 of the first regenerated cellulose fiber. What is necessary is just to select and determine suitably.

Although the fiber length of the two regenerated cellulose fibers used in the present invention is arbitrary, the first regenerated cellulose fiber is used mainly for maintaining the wet strength of the obtained water-disintegratable nonwoven fabric, and the second regenerated cellulose fiber is used for the purpose. Since the purpose of the obtained water-disintegratable nonwoven fabric is mainly to maintain the water-disintegrability, these properties must be appropriately selected according to the required degree. As a guide, there is a balance with the fiber diameter of the fiber to be used, but in general, the shorter the fiber length, the lower the strength and the tendency to improve water disintegration, and conversely, the longer the fiber length, the higher the strength and the better the water dissolution. Sex tends to decrease.

The wood pulp fiber used in the present invention is not particularly limited, and unbleached pulp fiber obtained by digesting softwood and hardwood wood by a kraft method, a sulfite method, a soda method, a polysulfite method, or the like. Bleached pulp fibers, or mechanical pulp such as ground pulp fibers or thermomechanical pulp fibers from the above-mentioned coniferous wood can be used alone or in combination as necessary.

These pulp fibers are JIS P 812.
It is desirable to use one having a Canadian standard freeness shown in No. 1 of 550 ml or more. Pulp fibers having a freeness of less than 550 ml are not preferred because they have a high density when formed into sheets and become hard sheets. Further, the bonding force between the wood pulp fibers is too strong, and the water-disintegrable property of the obtained water-disintegratable nonwoven fabric is inferior. In addition, the amount of waste materials during high-pressure water column flow treatment increases, which is not economical. The freeness is the highest value when wood pulp is used without being beaten, and generally the freeness of unbeaten wood pulp is 750 to 650 m.
It is about l.

In the present invention, a regenerated cellulose fiber group 55-70 composed of 70-30% by weight of first regenerated cellulose fiber having a relatively small fiber diameter and 30-70% by weight of second regenerated cellulose fiber having a relatively large fiber diameter. After mixing 20% by weight and 45 to 80% by weight of wood pulp fiber, wet papermaking is performed using a conventionally known paper machine such as a round paper machine, a short wire machine, an inclined wire paper machine, and a fourdrinier machine. The web is formed, and then the web is placed on a perforated support capable of being transported to perform high-pressure water column flow treatment.

In the present invention, the blending ratio of the regenerated cellulose fiber group and the wood pulp fiber is 55 to 20% by weight / 45 to 45% by weight.
80% by weight. The blending ratio of the regenerated cellulose fiber group is 2
When the content is less than 0% by weight, in the fiber entanglement by the high-pressure water column flow treatment, the entanglement between the wood pulp fibers becomes relatively too large, so that both the wet strength and the water disintegration of the obtained water-disintegratable nonwoven fabric decrease. Not preferred. Conversely, when the blending ratio of the regenerated cellulose fiber group exceeds 55% by weight, the ratio of the regenerated cellulose fiber, which is more expensive than wood pulp fiber, becomes larger, so that it becomes difficult to produce the water-disintegratable nonwoven fabric according to the present invention at low cost. Absent.

The mixing ratio of the first regenerated cellulose fiber and the second regenerated cellulose fiber constituting the regenerated cellulose fiber group is 70 to 30% by weight / 30 to 70% by weight. If emphasis is placed on the wet strength of the obtained water-disintegratable nonwoven fabric, the ratio of the first regenerated cellulose fiber having a relatively small fiber diameter may be increased.
What is necessary is just to raise the ratio of the 2nd regenerated cellulose fiber with a relatively large fiber diameter. However, regardless of which performance is emphasized, if the ratio exceeds 70% by weight, the other performance becomes inferior, and it becomes difficult to achieve both wet strength and water disintegration of the obtained water-disintegratable nonwoven fabric. Not preferred.

The total basis weight of the wet paper web obtained in the present invention measured by a method according to JIS P 8124 is in the range of 30 to 80 g / m ² . Basis weight 30g /
When it is less than m ² , when the obtained water-disintegratable nonwoven fabric is used for an application such as a wiper, the strength tends to be insufficient, and there is a high possibility that the nonwoven fabric will break during use and become unusable. On the other hand, when the basis weight exceeds 80 g / m ² , the obtained water-disintegratable nonwoven fabric has an increased rigidity and is difficult to use, and the water-disintegratable nonwoven fabric tends to have poor water-disintegrability when introduced into a water stream, which is not preferable.

The high pressure water column flow treatment in the present invention can be carried out by a conventionally known method. That is, the wet papermaking web is placed on a porous support such as a wire mesh,
From at least one side of the web, the pore size is 0.08 to
High-pressure water is sprayed at a water pressure of 15 to 150 kg / cm ² through a nozzle having a large number of pores of about 0.30 mm, and the fibers constituting the web are entangled with each other. The energy imparted to the wet papermaking web by the high-pressure water column flow treatment is represented by the additional specific energy of the following formula (2). In the present invention, 0.07 to 0.20 kWh / kg per high-pressure water column flow treatment It is. E = (A × (2 / ρ) ^1/2 × (g × P) ^3/2 ) / (M × 60 × S) (2) where E: additional specific energy (kWh / kg) ρ: water Density (kg / cm ³ ) g: gravity acceleration (m / s ² ) P: water pressure at the nozzle (Pa) S: web passing speed (m / min) M: web mass (g / m ² )

When the added specific energy per one high pressure water column flow treatment is less than 0.07 kWh / kg, the fibers constituting the wet papermaking web become insufficiently entangled with each other, and the obtained water-disintegratable nonwoven fabric has a low wet strength. At the same time, the fibers constituting the obtained water-disintegrable nonwoven fabric are difficult to arrange in the thickness direction of the sheet, and the texture becomes paper-like, which is not preferable. Conversely, the added energy is 0.20 kW
If it exceeds h / kg, the entanglement between fibers becomes too strong, and the water-disintegrable property of the resulting water-disintegratable nonwoven fabric is unfavorably low.

The high-pressure water column flow treatment may be performed online immediately after wet-papermaking to form a web, or may be performed online or offline after the wet-paper-made web is once dried.

The nonwoven fabric which has been subjected to the high-pressure water column flow treatment by the above-described method and in which the fibers are entangled is dried by a dryer such as an air through drier and then wound up.

The water-disintegratable nonwoven fabric thus obtained has a water-disintegrability of 60 to 300 seconds. The water-disintegration property is as follows: a water-disintegratable nonwoven fabric having a size of 5 cm square is put into 100 ml of pure water, shaken at a shaking speed of 300 cycles / minute, and the water-disintegratable nonwoven fabric is disintegrated in water. About 1cm ²
It was expressed as the time required for defibration until If the water disintegration is longer than 300 seconds, the disintegration of the nonwoven fabric in the water stream is slow, which is unfavorable because it tends to cause pipe clogging when flushed into a toilet or the like. Therefore, the shorter the water disintegration is, the more preferable it is. However, the value of the water disintegration achieved while maintaining the strength of the nonwoven fabric is naturally limited, and is about 60 seconds at the shortest.

The wet strength of the water-disintegratable nonwoven fabric varies depending on the application, but wet products such as wet tissues, baby wipes, and wipers for cleaning which are one of the main applications of the water-disintegrable nonwoven fabric according to the present invention. When it is used, the wet tensile strength measured according to JIS P 8135 is 200 gf / 25 m in the longitudinal wet tensile strength.
m or more, and preferably 50 gf / 25 mm or more in terms of wet tensile strength in the transverse direction, and more preferably 200 gf / 25 mm or more in terms of the geometric mean represented by the formula (3). Average of wet tensile strength = (XY) ^1/2 (3) where X: wet tensile strength (g) in the longitudinal direction of the water-disintegratable nonwoven fabric
f: 25 mm) Y: Wet tensile strength in the transverse direction of the water-disintegratable nonwoven fabric (gf / 25)
mm)

When a water-disintegratable nonwoven fabric is used as a wet product, it is easy to process into a wet product (suitability for processing: difficulty in occurrence of trouble due to paper cutting, etc.), and resistance to tearing when taking out from a container after processing (suitability for removal). ), It is required to be difficult to be broken during use (suitability for use). Processing suitability and take-out suitability are as follows.
If it is more than 00 gf / 25 mm, it can be used. The suitability for use is 50 g in the vertical and horizontal directions of the water-disintegratable nonwoven fabric.
There is almost no problem if the wet strength is f / 25 mm or more. Further, the value of the geometric average of the wet tensile strength is 200 g / 2.
If it is 5 mm or more, it can be used without any practical problem even in an application for wiping with a very strong force such as a part of a cleaning wiper, and it is more preferable. However, when the water-disintegratable nonwoven fabric is manufactured by the method according to the present invention, the value of the wet strength when the water-disintegrability is 300 seconds or less is about 1000 gf / 25 mm.
The degree is the upper limit.

In order to use the water-disintegrable nonwoven fabric of the present invention as a wet product such as a wet tissue, a wiping wipe, a wiper, etc., if necessary, water and a wetting agent such as propylene glycol, an alcohol or parabenzoic acid ester, etc. Various agents such as antibacterial, fungicide, fragrance, and components having a specific medicinal effect can be impregnated alone or in combination. Further, when the water-disintegratable nonwoven fabric according to the present invention is used as a surface material such as a sanitary material, it can be used as it is, but the nonwoven fabric may be subjected to a treatment for enhancing hydrophilicity and water repellency as desired.

As described above, the water-disintegratable nonwoven fabric according to the present invention has a strength that can withstand operations such as cleaning in a dry state and a wet state, and forms a nonwoven fabric in a large amount of water flow. The fiber can be disintegrated and can be used as a wet product such as a wet tissue, a cloth, a cleaning wiper, or a top sheet of a disposable diaper or a sanitary napkin.After use, it is easily disintegrated by a large amount of water flow in a toilet or the like. It can be.

[0044]

The present invention will be described in more detail with reference to the following examples, which, of course, are not intended to limit the present invention. In Examples and Comparative Examples, “%” means “% by weight” unless otherwise specified. The density of rayon fibers used in Examples and Comparative Examples is 1.53 g / cm ³ unless otherwise specified.

Example 1 First rayon fiber (L / D = 594) 50 having a fineness of 1.5 denier (fiber diameter D1 = 11.8 μm) and a fiber length of 7 mm
% And fineness of 3.0 denier (fiber diameter D2 = 16.7μ)
m), a second rayon fiber having a fiber length of 7 mm (L / D = 41
9) Inclined using 40% rayon fiber group consisting of 50% (constituent fiber diameter ratio D2 / D1 = 1.42) and 60% unbleached softwood bleached kraft pulp (Canada standard freeness: 720 ml) as raw materials A wet papermaking web was formed using a wire-type papermaking machine and then dried to obtain a rayon / pulp mixed paper having a basis weight of 50 g / m ² .

Next, the above rayon / pulp mixed paper was mixed with 50
Placed on a transfer support net formed of mesh wire mesh,
While transferring the rayon / pulp mixed paper at a speed of 50 m / min, a nozzle hole having a hole diameter of 0.15 mm was made 1.0 m
75k using a high pressure water column flow treatment device arranged at m intervals
A high-pressure water column flow was sprayed from the surface (the surface not in contact with the wire mesh) at a water pressure of g / cm ² , subjected to a high-pressure water column flow treatment, and then dried to obtain a water-disintegratable nonwoven fabric. The added specific energy given to the mixed paper by this high-pressure water column flow treatment is 0.11 kW.
h / kg.

The quality of the obtained water-disintegratable nonwoven fabric was evaluated by the following evaluation method. 1. Wet tensile strength (gf / 25 mm) With the width of the test piece set to 25 mm, the strength in the vertical and horizontal directions was measured according to JIS P 8135, and the following formula (4)
, The geometric average of the wet strength was determined. Average of wet tensile strength = (XY) ^1/2 (4) where X is the wet tensile strength (g) in the longitudinal direction of the water-disintegratable nonwoven fabric.
f: 25 mm) Y: Wet tensile strength in the transverse direction of the water-disintegratable nonwoven fabric (gf / 25)
mm)

2. Water-disintegrable (second) A water-disintegratable nonwoven fabric having a size of 5 cm × 5 cm square is prepared.
Put 100 ml of pure water into a 150 ml Erlenmeyer flask,
The water disintegratable nonwoven fabric is put into a flask and shaken at a speed of 3
Shake at 00 cycles / minute, stop shaking every 30 seconds, observe the disintegration state of the water-disintegratable nonwoven fabric, and repeat shaking. The largest piece of water-disintegratable non-woven fabric is about 1cm ²
The time required for deflocculation until the water disintegration rate was defined as the water disintegration value (second), and represented by the average value of n = 5. Water disintegration is 30
If it is 0 second or less, it can be said that the water dissolving property is excellent.

3. Texture (point) The texture was determined by a tactile test by 20 monitors.
In the test method, the water-disintegratable nonwoven fabric was gripped by hand, and expressed as a total score (a maximum of 100 points) of the results of a rating of 5 points per monitor based on the following evaluation criteria. If the total score is 75 points or more, it can be said that the texture is good. 5 points: Very good feel 4 points: Excellent feel 3 points: Normal feel 2 points: Somewhat poor feel 1 point: Poor feel 0 points: Very poor feel

Example 2 First rayon fiber (L / D = 735) 5 having a fineness of 2.0 denier (fiber diameter D1 = 13.6 μm) and a fiber length of 10 mm5
0% and fineness 5.0 denier (fiber diameter D2 = 21.5μ
m), a second rayon fiber having a fiber length of 10 mm (L / D = 4
60) Except that the raw materials were 40% rayon fiber group consisting of 50% (constituent fiber diameter ratio D2 / D1 = 1.58) and 60% unbeaten softwood bleached kraft pulp (Canadian standard freeness: 600 ml). A water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1.

Example 3 The mixing ratio of the first rayon fiber in the rayon fiber group was 6
A water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1 except that the blending ratio of 0% and the second rayon fiber was 40%.

Example 4 The mixing ratio of the first rayon fiber in the rayon fiber group was 4
A water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1 except that the blending ratio of 0% and the second rayon fiber was 60%.

Example 5 The second rayon fiber had a fineness of 1.8 denier (fiber diameter D2 =
13.0 μm), rayon fiber with a fiber length of 7 mm (L / D
= 538, constituent fiber diameter ratio D2 / D1 = 1.10), except that water-disintegratable nonwoven fabric was obtained in the same manner as in Example 1.
evaluated.

Example 6 The second rayon fiber had a fineness of 8.0 denier (fiber diameter D2 =
Rayon fiber (L / D) with a fiber length of 7 mm
= 257, constituent fiber diameter ratio D2 / D1 = 2.31) except that water-disintegratable nonwoven fabric was obtained in the same manner as in Example 1.
evaluated.

Example 7 The first rayon fiber had a fineness of 0.5 denier (fiber diameter D1 =
Rayon fiber having a fiber length of 7 mm (L / D = 6.8 μm)
1029), a rayon fiber (L / D = 735) having a denier of 2.0 denier (fiber diameter D2 = 13.6 μm) and a fiber length of 10 mm was used as the second rayon fiber, and the constituent fiber diameter ratio D2
A water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1 except that / D1 was set to 2.00.

Example 8 The first rayon fiber had a fineness of 2.8 denier (fiber diameter D1 =
16.1 μm), rayon fiber with a fiber length of 7 mm (L / D
= 435), and the constituent fiber diameter ratio D2 / D1 = 1.03
A water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1 except that the sample was set to 7.

Comparative Example 1 A water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1 except that the mixing ratio of the first and second rayon fibers constituting the rayon fiber group was changed to 10% / 90%.

Comparative Example 2 A water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1 except that the blending ratio of the first and second rayon fibers constituting the rayon fiber group was changed to 90% / 10%.

Comparative Example 3 The mixing ratio of the rayon fiber group to the wood pulp fiber was 10% /
A water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1 except that the content was 90%.

Comparative Example 4 The rayon fibers constituting the rayon fiber group were changed to a fineness of 1.5
Denier (fiber diameter D1 = 11.8 μm), fiber length 7 mm
A water-disintegrable nonwoven fabric was obtained and evaluated in the same manner as in Example 1 except that only the first rayon was used.

Comparative Example 5 The rayon fiber constituting the rayon fiber group was changed to a fineness of 3.0.
Denier (fiber diameter D2 = 16.7 μm), fiber length 7 mm
A water-disintegratable nonwoven fabric was obtained and evaluated in the same manner as in Example 1 except that only the second rayon was used.

Table 1 shows the quality of the water-disintegrable nonwoven fabrics according to the examples and comparative examples.

[Table 1]

As can be seen from Table 1, the water-disintegrable nonwoven fabric according to the present invention has an excellent balance between wet tensile strength and water-disintegrability, and has a good feel. On the other hand, of the two regenerated cellulose fibers constituting the regenerated cellulose fiber group,
If the blending ratio of the regenerated cellulose fiber is too low, the wet tensile strength will be inferior (Comparative Example 1). Conversely, if the blending ratio of the second regenerated cellulose fiber is too low, the water disintegration will be inferior ( Comparative Example 2). Further, when the blending ratio of the regenerated cellulose fiber group constituting the water-disintegratable nonwoven fabric is too small, the entanglement between the wood pulp fibers is relatively increased, so that both the wet strength and the water-disintegrability are inferior, and The texture was paper-like and significantly inferior (Comparative Example 3). Further, when the regenerated cellulose fiber group is composed of only the first regenerated fiber having a relatively small fiber diameter, the portion having strong fiber entanglement increases, resulting in poor water dissolvability (Comparative Example 4). When the cellulose fiber group was composed only of the second regenerated cellulose fiber having a relatively large fiber diameter, strong entanglement was not obtained, and the wet tensile strength was inferior (Comparative Example 5).

[0064]

As described above, according to the present invention, a first regenerated cellulose fiber having a relatively small fiber diameter and a second regenerated cellulose fiber having a relatively large fiber diameter are mixed together with wood pulp fiber, and Web forming by a known wet papermaking method,
By subjecting the web to a high-pressure water column flow treatment, the fibers constituting the web are entangled and integrated,
The present invention has the effect of providing a water-disintegratable nonwoven fabric capable of achieving both wet strength that can withstand use even when wood pulp fibers are blended at a high rate and water-disintegrability in a large amount of water, and a method for producing the same.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI D04H 1/42 D04H 1/42 G

Claims (3)

[Claims] A regenerated cellulose fiber group comprising 70 to 30% by weight of a first regenerated cellulose fiber having a relatively small fiber diameter and 30 to 70% by weight of a second regenerated cellulose fiber having a relatively large fiber diameter. % And wood pulp fiber 45-8
A water-disintegratable nonwoven fabric comprising 0% by weight, and wherein each fiber is entangled and integrated by a high-pressure water column flow. 2. The fiber diameter D1 of the first regenerated cellulose fiber
(Μm) and the fiber diameter D2 (μm) of the second regenerated cellulose fiber.
The water-disintegratable nonwoven fabric according to claim 1, wherein a fiber diameter ratio D2 / D1 with m) is 1.2 to 2.0. 3. A first regenerated cellulose fiber, a second regenerated cellulose fiber, and a wood pulp fiber are mixed, formed into a web by a conventionally known wet papermaking method, and the web is placed on a perforated support capable of being transported. 3. The method for producing a water-disintegratable nonwoven fabric according to claim 1, wherein the web is subjected to a high-pressure water column flow treatment from at least one surface thereof so that each regenerated cellulose fiber and wood pulp fiber are entangled and integrated. Method.