JP2016030862A - Fibrillated fiber and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fibrillated fiber that is fibrillated from a polyvinyl alcohol (PVA) single polymer fiber and a method for producing the same.SOLUTION: (1) There is provided a fibrillated fiber which is fibrillated from a PVA single polymer cross-linked fiber that is obtained by introducing cross-linking into a PVA single polymer fiber having a saponification degree of 98 mol% or more and dissolves in water at a temperature of 100°C or more. (2) A water dispersion of a PVA single polymer cross-linked fiber which is formed of a PVA single polymer having a saponification degree of 98 mol% or more, dissolves in water at a temperature of 100°C or more, and has a fineness of 0.1 to 4 denier and a fiber length of 0.2 to 3 mm is injected at 150 to 275 MPa to collide and merge the water dispersion each other. Thus the PVA single polymer cross-linked fiber is fibrillated.SELECTED DRAWING: Figure 2

Description

  The present invention fibrillates a PVA homopolymer crosslinked fiber having a water dissolution temperature of 100 ° C. or higher, obtained by spinning, hot drawing and crosslinking a polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) homopolymer. It is related with the fibrillated fiber obtained by this, and its manufacturing method.

In order to improve the shielding performance of the separator and to capture fine particles of the filter, it is effective to use a sheet formed from finely pulverized (fibrillated) fibers, but the PVA homopolymer fiber has a fineness of about 6 μm. However, finer fibrillated fibers have not been put into practical use.
In the past, attempts have been made to obtain fibrillated PVA fibers. In Patent Document 1, an independent phase mainly composed of polyacrylonitrile is uniformly finely dispersed in a continuous phase mainly composed of PVA, and PVA is mainly composed of the independent phase mainly composed of polyacrylonitrile. PVA-based easily fibrillated fibers forming a structure of three or more phases in which the third phase is uniformly dispersed are disclosed.
In Patent Document 2, a vinyl-alcohol-based polymer (A) and a water-insoluble cellulose-based polymer (B) are dissolved in a common organic solvent to prepare a sea-island layer separation solution in which the A component is a sea component and the B component is an island component. Then, the fibrillated fiber is obtained by spinning this solution as a spinning dope.

JP-A-8-81818 JP-A-10-102322

  In all of the above prior art documents, fibrillation is achieved using sea-island fibers made of PVA, polyacrylonitrile, cellulose and the like. That is, a fiber in which PVA and another kind of polymer are mixed is formed, and a fibrillated fiber is obtained therefrom. However, the PVA homopolymer fiber has a dense fiber structure after being stretched and fixed by heat, and even when beaten with a beater, a single descriptor, a double descriptor, or the like, it could not be fibrillated. For this reason, the fibrillated fiber of PVA has not been put into practical use.

  The present inventors set it as the technical subject which should be solved to obtain the fibrillated fiber which fibrillated the PVA homopolymer fiber.

In order to solve the above-mentioned problems, the present inventors have intensively studied about fibrillation of PVA homopolymer fibers, and it has been impossible to fibrillate using a wet atomizer using high-pressure injection. However, in order to fibrillate the PVA homopolymer fiber, the raw material particles (PVA fiber aqueous dispersion) pressed to an ultra-high pressure were found to be fibrillated. When attempting to atomize (fibrillate) by colliding each other, the water temperature of the aqueous dispersion rises, causing the problem that the PVA homopolymer fiber dissolves in water and fibrillated fibers cannot be obtained. .
As a result of further diligent investigations on this point, the present inventors, as a result of (1) preventing the dissolution of the PVA homopolymer fiber by using the PVA homopolymer crosslinked fiber in which crosslinking is introduced into the PVA homopolymer, and (2) PVA. The slurry in which the fibers are dispersed (aqueous dispersion) is sprayed at a high pressure, and the high pressure sprayed slurries are made to collide at one point to perform fibrillation treatment, so that the fibers can be atomized without causing the fibers to dissolve ( It has been found that fibrillation can be achieved, and the present invention has been completed.

The first configuration of the present invention is a fibrillation in which a PVA homopolymer fiber having a saponification degree of 98 mol% or more is introduced into the fiber and a PVA homopolymer crosslinked fiber having a water dissolution temperature of 100 ° C or more is fibrillated. Fiber.
In the present invention, the PVA homopolymer refers to a polymer obtained by saponifying a polymer obtained by polymerizing only vinyl acetate (polyvinyl acetate) to a saponification degree of 98 mol% or more.
Further, the PVA homopolymer crosslinked fiber is a fiber in which crosslinking is introduced into a fiber formed only from the above PVA homopolymer. Therefore, “PVA” includes an OH group of PVA after the fiber formation. The modified PVA is modified by introducing a cross-link.

  The introduction of cross-linking may be cross-linking introduction by formalization or cross-linking introduction by dialdehyde.

  The average fiber diameter of the fibrillated fibers is preferably in the range of 0.5 to 3 μm, and the variation coefficient of the average fiber diameter of the fibrillated fibers is preferably in the range of 20 to 50%.

  The fiber length of the fibrillated fiber is preferably in the range of 0.2 to 3 mm, and more preferably in the range of 0.2 to 2 mm.

  The second configuration of the present invention is formed from a PVA homopolymer having a saponification degree of 98 mol% or more, a dissolution temperature in water of 100 ° C. or more, a fineness of 0.1 to 4 denier, and a fiber length of 0.2 to PVA homopolymer fibers are fibrillated by injecting an aqueous dispersion of PVA homopolymer crosslinked fibers within a range of 3 mm at a high pressure of 150 to 275 MPa and causing the water dispersions to collide at one point. It is a manufacturing method of fibrillated fiber.

  The fiber concentration in the aqueous dispersion is preferably 0.1 to 3.2% by weight.

  It is preferable that the temperature of the aqueous dispersion is controlled so as not to exceed 40 ° C.

  The third configuration of the present invention is a wet nonwoven fabric in which the fibrillated fiber is blended.

  In the first configuration of the present invention, even a PVA homopolymer fiber that could not be fibrillated conventionally can be fibrillated. As a result, a product such as a wet nonwoven fabric can be obtained from a PVA homopolymer fibrillated fiber in which other polymers such as cellulose and acrylonitrile are not mixed, and the PVA fiber having alkali resistance, adhesion to rubber and cement can be obtained. It can be applied to applications that make use of its features.

  In the second configuration of the present invention, a PVA homopolymer crosslinked fiber having a dissolution temperature in water of 100 ° C. or more is used, and an aqueous dispersion of the fiber is injected at a high pressure, and the water dispersions injected at a high pressure collide at one point. By merging, fibrillation can be performed without dissolving the PVA fiber during the treatment.

  In the third configuration of the present invention, a functional paper (wet nonwoven fabric) having high density and high water retention can be obtained by such a fibrillated fiber.

It is explanatory drawing which shows an example of the fibrillation processing apparatus used in this invention. It is an electron micrograph (magnification: 1000 times) showing an example of fibrillated PVA fiber. It is an electron micrograph (magnification: 1000 times) which shows an example of the PVA fiber before a fibrillation process.

(PVA fiber)
In the present invention, the PVA fiber subjected to the fibrillation treatment is a PVA homopolymer (for example, viscosity average polymerization degree: 1200 to 3000, saponification degree: 98 mol% or more, preferably 99 mol% or more, more preferably 99.8 Mol% or more).
A spinning yarn is formed from a spinning solution obtained by dissolving a PVA homopolymer in a solvent (water, organic solvent) by a wet method (sodium salt coagulation bath spinning, alkali coagulation bath spinning), a dry method, or a wet-dry method. As a spinning method of PVA fiber, a fiber obtained by any one of spinning methods, such as salt cake coagulation bath spinning fiber, alkali coagulation bath spinning fiber, dry spinning fiber, and organic solvent fiber, can be used. The spun fiber is preferable because it is easily fibrillated.
A PVA homopolymer crosslinked fiber having a dissolution temperature in water of 100 ° C. or higher can be obtained by subjecting the spinning yarn to heat drawing (wet heat drawing, dry heat drawing) / fixing treatment and further crosslinking treatment.
Among these, in order to reduce the solubility of PVA homopolymer fibers during high-pressure water treatment, fibers are formed using PVA having a high saponification degree (99.9 mol%), and crosslinking is introduced into the fibers. It is preferable to make the fiber.

(Crosslinking treatment)
In the present invention, as a fiber to be subjected to fibrillation treatment, after spin-drawing heat setting (non-acetalization), further crosslinking treatment [formalization, PVA modification treatment by acetalization with dialdehyde (gliogizar, glutaraldehyde, etc.)] It is necessary to use the fiber which performed. By introducing cross-linking, elution of PVA during fibrillation treatment can be suppressed.

(Fineness)
The fineness of the single fiber in the PVA homopolymer fiber is not particularly limited. However, the smaller the single fineness of the starting raw material fiber is, the smaller the fineness after fibrillation is. For example, 0.1 to 4 denier (preferably, It is preferably selected from the range of 0.2 to 3 denier). Fibers smaller than the above-mentioned fineness are difficult to produce, and if the fineness is too large, the fineness of the fibers after fibrillation tends to be high, and a dense wet nonwoven fabric tends to be difficult to obtain.

(Fiber length)
A fiber bundle of PVA fibers is cut to a length of, for example, 0.2 to 3 mm (preferably 0.5 to 2 mm) by a cutter, and a raw fiber for performing a fibrillation treatment is adjusted. If the fiber length is too long, nozzle clogging for injecting the dispersion in the processing apparatus tends to occur, and if the fiber length is too short, the strength of the wet nonwoven fabric may be difficult to obtain.

(Adjustment of aqueous dispersion of PVA homopolymer crosslinked fiber)
PVA homopolymer fiber obtained by dispersing the above-mentioned PVA homopolymer crosslinked fiber cut to the fiber length in water at a concentration of 0.1 to 5% by weight, preferably 0.1 to 3.2% by weight. Adjust the water dispersion. If the fiber concentration is too low, the efficiency for processing a predetermined amount of fiber is deteriorated. If the fiber concentration is too high, the fluidity of the slurry is lowered and the orifice nozzle cannot be clogged.

(Fibrillation treatment)
The fibrillation treatment can be performed by causing the water dispersion to collide using a high-pressure jet flow. For example, an apparatus capable of performing such processing includes a starburst processing apparatus using high-pressure injection developed by Sugino Machine Co., Ltd.
Using this processing apparatus, the aqueous dispersion of the above-mentioned PVA homopolymer crosslinked fiber is injected at high pressure (for example, pressure of high pressure injection) from two orifice nozzles (nozzle diameter: 0.1 to 0.8 mm) arranged opposite to each other. : 150 to 275 MPa, jetting speed: 440 to 700 m / s), and the aqueous dispersions collide and join at one point, whereby fibrillation of the PVA homopolymer crosslinked fiber in the aqueous dispersion starts. Then, the collided and joined water dispersion is recovered, and the dispersed fluids are again collided and joined at one point from the orifice nozzle. Fibrilization is performed by repeating this operation about 20 to 100 times (preferably about 30 to 80 times, more preferably about 40 to 60 times). If the number of repetitions is too small, fibrillation becomes insufficient, and even if the number of repetitions is increased too much, further fibrillation does not proceed, but on the other hand, the productivity of the apparatus decreases.
It is to be noted that fibrillation is possible even when the water dispersion of the cross-linked fiber is collided with an impact hard body (ceramic or metal ball or flat body) from an orifice nozzle.

(Fibrilization processing equipment)
An example of the fibrillation apparatus used in the present invention is shown in FIG. In the fibrillation processing apparatus 14 shown in FIG. 1, an aqueous dispersion (dispersion) 30 is supplied from an inlet 22 through flow paths 24a and 24a, and the aqueous dispersion 30 is injected from the orifice nozzles 26a and 26a to the above-described jet. Inject with pressure. The injection direction of the high-pressure injection flow injected from the orifice nozzles 26a and 26a is, for example, a direction in which the inner wall surface intersects the liquid level of the water dispersion 30 stored in the chamber 28 having a smooth surface, and both high-pressure injections It is preferable to adjust the orientation of the orifice nozzles 26 a and 26 a so that the flow collides and merges on the liquid level of the water dispersion 30 stored in the chamber 28. The aqueous dispersion stored in the chamber 28 is an aqueous dispersion 30 containing a fibrillated product of PVA homopolymer cross-linked fibers generated by collision joining of high-pressure jets from the orifice nozzles 26a and 26a. Further, the discharge amount of the water dispersion (dispersion) 30 from the chamber 28 is adjusted to store the water dispersion (dispersion) 30 in the chamber 28 and to start the dispersion stored in the supply tank. While supplying to the burst processing apparatus 14, the dispersion liquid 30 in the chamber 28 and the dispersion liquid 30 in the processed tank are returned to the supply tank, and the dispersion liquid 30 is again sprayed from each of the orifice nozzles 26a and 26a as the dispersion liquid 30. Thus, the impact of the high-pressure jet collision is repeatedly applied to the PVA homopolymer crosslinked fiber in the aqueous dispersion. It is preferable to give the impact of such high-pressure jet collision to the PVA homopolymer crosslinked fiber, for example, about 20 to 100 times as described above.

The injection trajectory of the high-pressure injection flow injected from the nozzles 26 a and 26 a is a direction that intersects the liquid level of the solution 30 stored in the chamber 28. In order to inject a high-pressure injection flow from the nozzles 26a, 26a, the injection direction of the high-pressure injection flow from the nozzles 26a, 26a is the solution stored in the chamber 28 from the injection trajectory of the high-pressure injection flow and the collision confluence of the high-pressure injection flow. It is preferable to adjust so that the injection angles θ ₁ and θ _{2 in the} liquid surface direction formed by the perpendicular line 30 to the liquid surface become obtuse. By making the injection angles θ ₁ and θ _{2 the} same, the injection direction of the nozzles 26a and 26a can be easily adjusted.

  Due to the repeated collision of the high-pressure jet flow, the temperature of the dispersion liquid may increase to 60 to 70 ° C., and there is a risk of partial elution of the PVA fibers. Therefore, the dispersion liquid in the supply tank is cooled so that the supply tank is cooled with water, and the temperature of the dispersion liquid is controlled so as not to exceed 40 ° C, preferably 30 ° C. It is preferable because dissolution of the can be prevented.

  The fiber diameter of the fibrillated fiber can be changed by selecting the water pressure of the high-pressure jet at the time of jetting, the number of passes, and the fiber concentration. For example, the fiber concentration is 0.8 to 1.6%, and the water pressure is 200 to 275 MPa. A fibrillated fiber having a fiber diameter of 1.6 to 1.8 μm can be obtained by 30 passes, and a fibrillated fiber having a fiber diameter of 1.3 to 1.5 μm can be obtained by 50 passes.

(Fibrillation of PVA homopolymer crosslinked fiber)
In the present invention, fibrillation means that at least one single fiber contained in the treated fiber is separated in the direction parallel to the fiber axis to become a fine fiber.
The fibrillated fiber obtained by the present invention usually has an average fiber diameter of 0.5 to 3 μm and a fiber diameter variation coefficient of 20 to 50%, and a fibrillated polyvinyl alcohol fiber suitable for wet nonwoven fabric formation can be obtained. .

(Wet non-woven fabric formation)
In the case of forming a wet nonwoven fabric, for example, the fibrillated fiber as a main fiber, and if necessary, a normal polyvinyl alcohol-based main fiber, cellulose fibers such as pulp, etc. are added to the fibrillated fiber. Further, a wet non-woven fabric is formed by a papermaking method with the addition of a vinyl alcohol binder.
The PVA fiber used in the present invention is a fiber having a high-stretched dense fiber structure as a PVA fiber having a dissolution temperature in water of 100 ° C. or higher. In the conventional method, such PVA fibers (main fibers) are made by making a small amount of PVA binder fibers (dissolving temperature in water of 80 ° C. or less) and making a paper to form a wet nonwoven fabric. In the conventional method, the PVA fiber as the main fiber is bonded between the fibers by dissolution of the binder fiber to form a wet nonwoven fabric. However, in the case of the fibrillated PVA fiber according to the present invention, In addition to adhesion between fibers by dissolution, entanglement formed between the main fibers by fibrillation is added, so that a denser wet nonwoven fabric can be formed.

(Use of binder fiber)
As the binder used for forming the wet nonwoven fabric of the present invention, a polyvinyl alcohol-based binder is preferably used from the viewpoint of resistance to electrolytic solution and liquid absorption. Although there are fibrous, powdery, and solution-like forms, a fibrous binder is preferred when the separator is made by wet papermaking.
The dissolution temperature of the polyvinyl alcohol-based binder fiber in water is preferably 60 to 90 ° C, more preferably 70 to 90 ° C. Further, it is composed of a polyvinyl alcohol polymer having a viscosity average degree of polymerization of about 500 to 3000 and a saponification degree of 97 to 99 mol%, and unspun fibers after spinning or lightly stretched fibers are preferably used.

(Use)
The wet nonwoven fabric blended with the fibrillated polyvinyl alcohol fiber according to the present invention,
Dense, shielding, alkali resistance, opacity, wiping, water absorption, oil absorption, moisture permeability, heat retention, weather resistance, high strength, high tearing force, wear resistance, antistatic, drape, dyeing Sheets for various electrical equipment such as alkaline battery separator paper, air filters, bag filters, liquid filters, condenser paper, floppy disk registration materials, FRP, etc. Various industrial sheets such as surfacer, adhesive tape base, oil absorbent, paper felt, various wiper sheets such as household / business / medical wiper, wiper for printing roll, wiper for copier cleaning, wiper for optical device, operation Clothes / gowns, cover cloths, caps, masks, sheets, towels, gauze, dressing base cloth, diapers, diaper liners, diaper bagsー, Various plaster bases, towels, tissue and other medical and hygiene sheets, interlining, pads, jumper liners, disposable underwear and other clothing sheets, artificial and synthetic leather bases, table tops, wallpaper, shoji paper , Blinds, calendars, wrapping, warmers / desiccant bags, shopping bags, furoshiki, suit covers, pillow covers, etc., sheets for daily life, chills, lining curtains, bedding, shading / anti-weed sheets, pesticide packaging materials, Various agricultural sheets such as nursery pot underlay paper, smoke / dust masks, experimental clothes, various protective sheets such as dust proof clothes, house wrap, drain material, filter material, separation material, overlay, roofing, tufted carpet base fabric , Anti-condensation sheets, wall coverings, sound / vibration-proof sheets, wooden boards, curing sheets such as curing sheets, floor trunk mats, Well molding material, head rest, can be used in applications of various vehicles interior materials for sheets or the like of the lining cloth. Further, when the fiber of the present invention is dispersed and stirred with inorganic fine particles, the fibers are fibrillated, and fibrils excellent in fine particle capturing and reinforcing properties and excellent in heat and flame resistance can be obtained, and are useful as friction materials. Further, when this fibril is mixed and dispersed in cement, it has excellent cement particle scavenging properties and also has reinforcing properties, so that a high-strength slate plate can be easily obtained.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

(Measurement of dissolution temperature in water)
The fiber sample is immersed in water with a weight of 500 mg / dr suspended, the temperature at which the fiber sample breaks when the temperature is raised at a rate of 1 ° C./min, and the temperature is determined as the dissolution temperature in water. It was.

(Measurement of average fiber diameter)
Take 10 or more magnified photographs of the surface of the fiber mass after air-drying taken with an electron microscope (manufactured by Hitachi, Ltd .: S-340N) at a magnification of 1000 times. Randomly capture 15 or more fibers for each photograph. Select and measure their fiber diameter. The average value of all photographs was determined and used as the average fiber diameter.

(Examples 1-2)
PVA fiber having a fineness of 0.3 denier (average fiber diameter of 5 μm), fiber length of 1 mm, and a dissolution temperature in water of 100 ° C. or higher [spinning in which a PVA homopolymer having a saponification degree of 99.9 mol% and a viscosity average polymerization degree of 1750 is dissolved in water. The stock solution is solidified in a sodium sulfate coagulation bath and formed by hot drawing (wet heat drawing → dry heat drawing), heat setting, formalization (FA) (formalization degree: 27 mol%)] Using a starburst 70) manufactured by Sugino Machine, fibrillation treatment was performed under the conditions shown in Table 1. In Table 1, the number of passes of 50 means that the aqueous dispersion having the fiber concentration shown in Table 1 was jetted and collided 50 times from two orifice nozzles.
The temperature of the aqueous dispersion was controlled so as not to exceed 30 ° C. by cooling the supply tank by water cooling.

(Comparative Examples 1-5)
As shown in Table 1, fibers having a fineness of 0.3 denier, a fiber length of 1 mm or 5 mm, and a water dissolution temperature of 96 ° C. or 100 ° C. or higher were used. The fiber having a solubility in water of 100 ° C. or higher is the same formalized fiber as in Examples 1 and 2. The fiber having a water solubility of 96 ° C. used in Comparative Example 1 is an unacetalized product after hot drawing and fixing.
In Comparative Example 1 and Comparative Examples 4 to 5, the same high-pressure water flow as in Examples 1 and 2 was used. In Comparative Example 2,
Fibrilization was attempted using a refiner (Waldron type disc refiner: Toyo Seiki Seisakusho Co., Ltd.) and Comparative Example 3 using a beater (Tappy Standard Niagara Test Beater: Yasuda Seiki Seisakusho Co., Ltd.).

(Experimental result)
(1) In the case of PVA fiber having a dissolution temperature in water of 96 ° C. (Comparative Example 1), the fiber was dissolved during the starburst treatment.
(2) When a refiner (Comparative Example 2) or a beater (Comparative Example 3) was used as the processing apparatus, it was not fibrillated.
(3) Nozzle clogging occurred at a fiber length of 5 mm in both cases where the water pressure was 245 MPa and the fiber concentration was 0.8% by weight (Comparative Example 4) and 3.2% by weight (Comparative Example 5).
(4) In Examples 1 and 2, raw fiber having a fineness of 0.3 denier (fiber diameter: 5 μm) was fibrillated, and the average fiber diameter after fibrillation was 1.4 μm and 1.5 μm, respectively. there were.

(Fiber diameter distribution of fibrillated fibers after treatment)
Eleven samples were collected from the fibrillated fibers treated in Example 1, and the average value of the fiber diameter of each sample (14 to 23 data was collected for each sample, and the average value was calculated). Table 2 shows the results obtained for the maximum value, minimum value, and coefficient of variation. The sample was collected by tweezers using the solid content of the slurry.
The obtained result was an average value of fineness: 1.39 μm (minimum value: 0.56 μm, maximum value: 2.81 μm, coefficient of variation: 28.5%).
Considering that the fiber diameter before treatment is 5 μm, it is clear that the fiber is fibrillated.
In this example, it can be seen that the fibrillated fiber having high uniformity was obtained when the variation coefficient of the fibrillated fiber was 28.5%. And it was obtained as a fibrillated fiber formed from a homopolymer crosslinked fiber of polyvinyl alcohol, which was not achieved by the prior art.

  An electron microscope cross-sectional photograph of the fibrillated fiber (Example 1) is shown in FIG. 2, and an electron micrograph of the fiber before the fibrillation treatment is shown in FIG. When comparing FIG. 2 with FIG. 3, it can be seen that the fibers are split and bent due to fibrillation.

Even when a part of a dense paper composed of fibrillated cellulose having an air permeability of 10 cc / cm ² / sec was replaced with the fibrillated PVA fiber, a dense sample showing the same air permeability was obtained.

  According to the present invention, fibrillated fibers can be obtained from polyvinyl alcohol homopolymer crosslinked fibers formed from a polyvinyl alcohol homopolymer and having a dissolution temperature in water of 100 ° C. or higher. This fibrillated fiber has industrial applicability because it can be used for new wet nonwoven fabrics and the like.

  As described above, the preferred embodiments of the present invention have been described, but various additions, modifications, or deletions can be made without departing from the spirit of the present invention. Therefore, such a thing is also included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 14 Fibrilization processing apparatus 15 Piping 20 Main body part 22 Inlet 24a Flow path 26a Orifice nozzle 28 Chamber 30 Water dispersion body θ1, θ2 Injection angle

Claims (9)

  A fibrillated fiber in which cross-linking is introduced into a fiber of a polyvinyl alcohol homopolymer having a saponification degree of 98 mol% or more, and a polyvinyl alcohol homopolymer cross-linked fiber having a water dissolution temperature of 100 ° C or higher is fibrillated.   The fibrillated fiber according to claim 1, wherein the introduction of the crosslinking is introduction of crosslinking by formalization.   The fibrillated fiber according to claim 1, wherein the introduction of the crosslinking is introduction of crosslinking by dialdehyde.   The fibrillated fiber according to any one of claims 1 to 3, wherein an average fiber diameter of the fibrillated fiber is in a range of 0.5 to 3 µm.   The fibrillated fiber according to any one of claims 1 to 4, wherein a variation coefficient of an average fiber diameter of the fibrillated fiber is in a range of 20 to 50%.   Polyvinyl alcohol formed from a polyvinyl alcohol homopolymer having a saponification degree of 98 mol% or more, a dissolution temperature in water of 100 ° C. or more, a fineness of 0.1 to 4 denier, and a fiber length of 0.2 to 3 mm. Manufacture of fibrillated fibers for fibrillating polyvinyl alcohol homopolymer crosslinked fibers by injecting an aqueous dispersion of alcohol homopolymer crosslinked fibers at a high pressure of 150 to 275 MPa and causing the water dispersions to collide at one point. Method.   The method for producing fibrillated fibers according to claim 6, wherein the fiber concentration in the aqueous dispersion is 0.1 to 3.2% by weight.   The method for producing a fibrillated fiber according to claim 6 or 7, wherein the temperature of the aqueous dispersion is controlled so as not to exceed 40 ° C. The wet nonwoven fabric which mix | blended the fibrillated fiber as described in any one of Claims 1-5.

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