JPH08296121A - Production of fibril comprising polyvinyl alcohol and starch - Google Patents

Abstract

PURPOSE: To obtain fibrils capable of highly absorbing an alkaline solution and capable of being dissolved in hot water and wasted by (dry)wet-spinning a sea phase-island phase-separable solution containing a vinyl alcohol polymer and starch and subsequently processing the spun fiber into the fibrils. CONSTITUTION: (A) A polyvinyl alcohol polymer and (B) starch are dissolved in a common solvent in a weight ratio of 95/5 to 50/50 to obtain the solution capable of being separated into the seas comprising the component A and the islands comprising the component B. The solution is (dry)wet-spun as a spinning raw solution, and the obtained fibers are processed into fibrils having diameters of approximately 10μm or less by a chemical swelling force and/or a mechanical stress. The fiber is little in foaming due to its dissolution on beating, and can easily be fibrillated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fibril composed of a polyvinyl alcohol-based polymer (hereinafter abbreviated as PVA) and starch, and more specifically, a fibril which can be used for a nonwoven fabric for medical use having a bacterial barrier. Of the manufacturing method of.

[0002]

2. Description of the Related Art In recent years, along with the development of electronics and information communication, batteries have been required to have higher performance, while silver-free batteries have been required from the viewpoint of pollution-free production and disposal. The separator used for separating the anode and cathode materials is required to have a high alkali absorbing property in order to improve the performance under a mercury-free condition, for example, a separator such as an alkali manganese battery. For this reason, it is necessary to reduce the pore size of vinylon having a good alkali resistance, which is used for a separator of an alkaline manganese battery, in order to improve short-circuiting, and fine denier has been promoted. Currently, 0.3 dr is commercially available. However, since vinylon alone has insufficient alkali absorbing ability, it is inevitable to mix with cellulose fibers having excellent absorbing ability and polynosic fibers which can be finely fibrillated by beating. However, polynosic fibers have pollution problems in the manufacturing process. Therefore, there is a demand for PVA fibers that can be finely fibrillated and have excellent alkali-absorbing properties, but at present, there are no PVA fibers that are superior to polynosic fibers.

[0003] In addition, medical hygiene workers are increasingly required to wear clothing to protect themselves from pathogens, viruses and body fluids of patients, and medical products using woven fabrics, knitted fabrics and non-woven fabrics such as surgical clothes, masks, hats and surgery. Although base sheets, bed covers, patient gowns, pillow covers, etc. have been researched and developed and are commercially available, a non-woven fabric made of fibrillated hydrophilic fibrils, which is expected to be dense, lightweight, and flexible, has been earnestly desired as a barrier material. In addition, these medical products are generally disposed of after use, but the waste is usually incinerated in Japan, and there is an environmental problem due to air pollution due to foul odors, nitrogen oxides, dioxins, etc. Inexpensive non-woven fabric products that can be dissolved in hot water or discarded or biodegraded are desired.

Many attempts have been made to utilize the phenomenon of phase separation of blend polymers in order to obtain hydrophilic ultrafine fibrils. For example, JP-A-5-17609, JP-A-48-56925, JP-A-49-6203 and the like disclose polyacrylonitrile-based polymers as sea components,
It has been shown that fibrillation is possible when a PVA graft-copolymerized with acrylonitrile or a sea-island fiber containing a polymethylmethacrylate polymer as an island component is beaten. However, it cannot be used for applications requiring alkali resistance and high alkali liquid absorption, or applications requiring hot water solubility.

Regarding fibers other than PVA fibers containing starch, for example, in Japanese Patent Publication No. Sho 55-116814, the dyeing effect of rayon fibers containing starch is uniform over the entire cross section of the fiber and is more effective than ordinary rayon. Is disclosed to be improved. Japanese Patent Publication 60-183
No. 53 discloses that water absorption is improved by graft-polymerizing acrylonitrile onto starch-containing cellulose fibers. In addition, Japanese Patent Publication No. 60-35480 discloses a method for producing paper in which starch fibers are mixed. None of them discloses a method for obtaining a hydrophilic ultrafine fibril which is the object of the present invention.

As a known example of PVA fiber containing starch, for example, Japanese Patent Publication No. 38-7517 has reported PVA fiber having a uniform cross section and a good dyeing effect.
In addition, Japanese Patent Publication No. 3-249208 and Japanese Patent Publication No. 4-10
No. 0913 discloses a method for producing biodegradable fibers and fibrils, and neither discloses a method for obtaining hydrophilic ultrafine fibrils which is the object of the present invention.

The fact that the blended fiber with starch is fibrillated is disclosed in Japanese Patent Publication No. Sho 35-8565, but since it is a stock solution containing an aqueous solution as a solvent, starch and P
The compatibility of VA is good, and it is difficult for PVA to be in the state of phase separation into sea and starch into islands at the stock solution stage. When this is used as a spinning stock solution, it is impossible to obtain ultrafine fibrils having a diameter of 3 μm or less.

[0008]

From the above, PVA having a large amount of the same hydroxyl groups as wood pulp as a sea component, less foaming due to elution during beating, easy fibrillation, high alkali absorbency, and heat Despite the strong desire for water soluble disposable PVA fibrils, they have not yet been obtained. In view of such a situation, the present inventors have earnestly made efforts and finally arrived at the present invention.

[0009]

That is, the present invention is based on P
The weight ratio of VA (A) and starch (B) is 95/5.
Dissolved in a common organic solvent at ~ 50/50 and A is a sea component,
A sea-island phase separation solution in which B is an island component is used, and this solution is subjected to dry-wet or wet-spinning in a coagulation bath as a spinning stock solution, and the obtained fiber is used alone or in combination with a chemical swelling force and a mechanical stress. A method for producing fibrils composed of PVA and starch, characterized in that the fibrils have a diameter of 10 μm or less.

In the fibril manufacturing method of the present invention, P
VA is the sea component. In order to achieve the object of the present invention, it is essential that PVA having a molecular chain that is easily oriented and crystallized, high-strength fibrils are easily obtained, and that PVA having a large amount of alkali resistance and hydrophilicity constitutes a sea component, that is, a continuous phase. Importantly. The PVA referred to here is not particularly limited as long as it has a vinyl alcohol unit of 70 mol% or more. There is no limitation as long as the degree of saponification is 80 mol% or more. The degree of polymerization of PVA is not particularly limited, but in order to obtain high strength fibrils, the degree of polymerization is preferably 500 or more, more preferably 1500 or more. Although starch is hydrophilic, it easily undergoes phase separation with PVA in an organic solvent and is easily fibrillated.

Further, in the present invention, as the starch serving as the island component, corn starch, potato starch, wheat starch, rice starch, tapioca starch and modified products thereof such as cationic starch, pregelatinized starch, oxidized starch, Examples thereof include etherified starch and acetylated starch.

The weight ratio of sea islands is 95/5 to 50/50. If the island component starch is less than 5%, it is difficult to fibrillate. If the PVA of the sea component is less than 50%, the starch partially forms the sea component, and the PVA cannot form a clear matrix phase, and it becomes difficult to obtain high strength fibrils. The weight ratio of PVA / starch is 90/1
0 to 52/48 is good, and more preferably 80/20 to 5
It is 5/45, more preferably 75/25 to 60/40.

Next, the method for producing the fibrils of the present invention will be described. It is important to dissolve the above PVA (A) and starch (B) in a common solvent. Examples of the common solvent include dimethyl sulfoxide (hereinafter abbreviated as DMSO), glycerin, ethylene glycol, diethylene glycol, dimethylformamide and the like. In the present invention, a solution having a sea-island structure in which PVA is phase-separated into sea and starch is phase-separated into islands at the spinning dope stage. Factors that determine sea-island components include compatibility between PVA and starch, composition ratio, stock solution concentration,
There are solvent types, temperatures, etc., and it is important to appropriately control these. The viscosity of the spinning dope is preferably 10 to 4000 poise, more preferably 20 to 200 poise.

The spinning dope thus obtained is spun into a coagulation bath through a nozzle. In the present invention, a wet or dry-wet spinning method is used, and either one can be appropriately selected according to the purpose and application, but in order to obtain staples for forming a nonwoven fabric, a multi-hole nozzle spinning method is used. Easy wet spinning is preferred. For example, when DMSO is used as a solvent, the coagulation bath contains alcohols such as methanol and ethanol, ketones such as acetone, methyl ethyl ketone, methyl isopropyl ketone and methyl isobutyl ketone, esters such as methyl acetate and ethyl acetate, toluene and xylene. It is possible to use aromatics such as and mixtures of these with DMSO.

The obtained spun raw yarn is dried and then, if necessary, subjected to dry heat drawing and dry heat treatment, but the total draw ratio is preferably 6
Dry heat stretching is performed so as to double or more. When it becomes 6 times or more,
Due to the difference in stretchability between PVA and starch, strains and cracks easily occur at the sea-island boundaries, and fibrillation becomes easy.

The fibers thus obtained are fibrillated by a chemical swelling force and a mechanical stress, either alone or in combination. The chemical swelling power means the ability to swell PVA which is a sea component or starch which is an island component, and water is used as a typical swelling agent, but when mechanical shearing force is applied in a swollen state, It is preferable because many fibrils can be obtained.

Fibrillation includes a method of cutting fibers into fibers and a method of forming a sheet-like material. The former is, for example, a method in which the fiber of the present invention is cut into 1 to 10 mm, immersed in water, dispersed, and subjected to mechanical stress with a beater, refiner, mixer or the like to be fibrillated. The latter is, for example, a wet-processed base paper obtained by crimping and cutting the fibers of the present invention into staples, and then dispersing the fibers of the present invention into a web formed by passing through a card or dispersing the fibers of the present invention into water as a stock material in water. 30 kg / c
A high-pressure water stream of m ² or more, preferably 60 kg / cm ² or more is applied and fibrillated by impact or shearing by the high-pressure water stream.

The fibril size referred to in the present invention means that the fibril of the present invention is embedded in paraffin, thin sections are prepared with a microtome, and a cross-sectional area is determined from a cross-sectional photograph magnified 200 to 800 times with a transmission optical microscope. The converted diameter of a circle the same as the area was calculated, and the average diameter of n = 10 was calculated. When the diameter exceeds 10 μm, the obtained fibrils are large and the original function of the fibrils is not fulfilled. The size of fibrils is preferably 0.03 to 10 μm, preferably 0.1 to 6 μm, more preferably 0.5 to 3 μm, and contains 1% or more fibrils. Further, since the fiber of the present invention is split only by a strong mechanical shearing force, a needle punch method can also be used as a method of fibrillation. However, as described above, the fiber of the present invention is further split into fibrils when subjected to mechanical shearing force in a wet strained state such as hydroentanglement, and thus the fiber of the needle punch method is used. If you need to be strict. That is, as the fibrillation condition, preferably puncture needle density 250 lines / cm ² or more, and more preferably puncture needle density 400 / cm ² or more.

Both the dry water junction method and the needle punching method are commonly known as carding methods such as roller card, semi-random card and random card, and web forming methods such as tandem web, cross web and criss cross web. You can use the existing one. Further, as for the base paper used in the wet water-flooding method, a base paper obtained by a generally known paper machine such as a cylinder, a short-net and a fourdrinier may be used, and as long as it can be led to a support for water stream treatment, The base paper may be in a dried state or before being dried.
With the fiber of the present invention, as the raw cotton mixed with the web or the raw paper mixed with the raw paper, rayon, solvent-spun cellulose fiber, polynosic, polyester, acrylic, nylon, polypropylene, vinylon, etc., which are generally known, are used. You can Regarding the lamination of webs, not only the lamination by the same kind of web containing at least a part of the fibers of the present invention, but the lamination of webs having different mixing ratios of the fibers of the present invention, or the lamination of webs not containing the fibers of the present invention But good. That is, if the fibers of the present invention are partially contained in a fibrillated state, they may not be uniformly present and may be unevenly distributed. In addition, the obtained dry-water-entangled nonwoven fabric, wet-water-entangled nonwoven fabric, needle punch dry-type nonwoven fabric, vinyl acetate-based, acrylic-based, polyethylene It is also possible to add a generally known resin binder such as a resin type, a vinyl chloride type, a urethane type, a polyester type, an epoxy type or a rubber type. In order to produce the fibril of the present invention, in addition to PVA and starch, an inorganic pigment, an organic pigment, a heat deterioration preventing agent, a pH adjusting agent, a cross-linking agent, an oil agent and the like are contained within a range not departing from the object of the present invention. Alternatively, these may be applied in each manufacturing process stage such as a stock solution stage, a solidification stage, an extraction stage, immediately before drying, immediately before stretching, after hot stretching, after heat treatment, etc. depending on the purpose.

[0020]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples. Example 1 PVA having a polymerization degree of 1750 and a saponification degree of 99.9 mol% and corn starch oxidized starch (hereinafter abbreviated as starch) were mixed with P
It was stirred and dissolved in DMSO at 100 ° C. for 10 hours under a nitrogen atmosphere so that the weight ratio of VA and starch was 60/40 and the total concentration was 20% by weight. This solution is not completely clear,
It was a little cloudy, and it was a sea-island phase separation solution with PVA as the sea component and starch as the island component, but there was no tendency for further phase separation even when left at 100 ° C for 24 hours without stirring, and it was stable and uniform. It was a dispersion. This solution is used as a spinning dope, and is passed through a nozzle with a hole diameter of 0.06 mmφ and 1000 holes, and DM
SO / methanol weight ratio 30/70 and temperature 10 ° C
Wet spinning in the solidifying bath of No. 3 and wet drawing of 3.5 times, DMSO in the thread is extracted with methanol, dried with hot air of 80 ° C., and dry drawn at 200 ° C. with a total draw ratio of 10 times. Was carried out to obtain a PVA / starch blend fiber. 2000 denier / 1000 filament yarn strength is 5.8g
Was / d.

Example 2 2 mm of the PVA / starch sea-island fiber obtained in Example 1
Cut into 5 pieces, and disperse 5 g of the same in 500 ml of water at 20 ° C.,
The mixture was stirred and beaten with a household mixer (National MX-X40) for 5 minutes, and the beaten liquid was collected by filtration to obtain hydrous fibrils. As a result of observing the fibrils with an optical microscope and a scanning electron microscope, 2 fibrils having a diameter of 3.0 μm or less were found.
There was 5%. The diameter of the fiber before beating was 15 μm. To 4 g (pure amount) of the obtained hydrous fibril fiber, 1.5 liters of water was added and allowed to disintegrate with a disintegrator, a viscous agent was added, and the mixture was sufficiently stirred to prepare a papermaking solution. Take 300 ml of this papermaking solution and add water to make 1 liter.
Papermaking was performed with a handmade paper machine. The obtained papermaking paper was thoroughly dehydrated with No3 filter paper and air-dried to obtain a handmade paper having a basis weight of 40 g / m ² . The amount of alkali absorption in the fiber of the obtained paper is 2.6 g.
/ G, which was a high alkali absorption property equivalent to the alkali absorption amount of 2.2 g / g of paper obtained by mixing beaten polynosic rayon fibers and vinylon fibers. The amount of alkali liquid absorbed in the fiber of the paper is 5 cm × 5 cm (weight after drying W _D
g) is immersed in 35% KOH aqueous solution at 20 ° C. for 30 minutes, and 3
The weight of the paper after centrifugal deliquoring at 000 rpm x 10 minutes is W
when a _c g, calculated as _{(W C -W D) / W} D (g / g).

Example 3 The PVA / starch fiber obtained in Example 1 was crimped and cut, and the obtained staple fiber was applied to a card machine to prepare a web having a basis weight of 40 g / m ² , and the web was washed with water. After wetting, a high-pressure water stream of 80 kg / cm ² was applied to split and entangle the fibers. As a result of observing the non-woven fabric with a scanning electron microscope, 18 fibrils with a diameter of 3 μm or less were found.
%Were present. The amount of alkali liquid absorption in the fiber of the obtained non-woven fabric was 2.6 g / g, indicating high alkali liquid absorption. The fibril count ratio was determined from the number of fibrils having a diameter of 1.0 μ or less existing per unit area by taking a photograph of a cross section of the fibrillated fiber with a scanning electron microscope.

COMPARATIVE EXAMPLE 1 The PVA / starch fiber obtained in Example 1 was cut into 2 mm, and paper was made as it was without beating. The amount of alkali liquid absorbed in the fiber of this paper was a low value of 1.5 g / g.

Comparative Example 2 A hydroentangled nonwoven fabric was produced in the same manner as in Example 3 except that a high-pressure water flow of 20 kg / cm ² was applied. As a result of observing this nonwoven fabric with a scanning electron microscope, there were almost no divided fibrils.

Example 4 PVA having an average degree of polymerization of 4000 and a degree of saponification of 99.9 mol%
And corn starch starch (hereinafter abbreviated as starch) in a weight ratio of 70/30 and a total concentration of 15 wt% 10
It was dissolved in 0 ° C DMSO with stirring in a nitrogen atmosphere for 10 hours, then the solution was discharged from a nozzle of 0.15 mmφ and 40 holes, and wet with a coagulating liquid of methanol / DMSO = 7/3 (weight ratio) and a temperature of 2 ° C. Spun 4 more obtained yarn
After wet stretching 4 times in a methanol bath at 0 ° C., the solvent was extracted with methanol, dried with hot air at 100 ° C., and dry-heat stretched at 220 ° C. with a total draw ratio of 12 times to obtain a PVA / starch blend fiber. It was The yarn strength of this fiber at 88 dr / 40 f was 15.3 g / d. The fibers were beaten in the same manner as in Example 2 to obtain ultrafine fibrils. As a result of observation with a scanning electron microscope, the number of fibrils with a diameter of 3 μm or less is 1
2% was present.

Example 5 PVA having an average degree of polymerization of 1700 and a degree of saponification of 98.5 mol%
And corn starch oxidised starch (hereinafter abbreviated as starch) at a weight ratio of 80/20 and a total concentration of 20% 10
It was dissolved in 0 ° C DMSO with stirring in a nitrogen atmosphere for 10 hours, and then the solution was discharged from a nozzle of 0.08 mmφ and 1000 holes, and wet with a coagulating solution of methanol / DMSO = 7/3 (weight ratio) and a temperature of 2 ° C. Spun The obtained raw yarn was further wet-drawn 4 times in a methanol bath at 40 ° C.,
After extracting the solvent with methanol and drying with hot air at 100 ℃, 22
Dry heat stretching at a total stretching ratio of 13.8 times at 0 ° C., and further 2
Heat treatment was performed at 30 ° C. for 30 seconds. 1806 dr / of this fiber
The yarn strength at 1000f was 4.83 g / d. The fibers were hydroentangled in the same manner as in Example 3 to obtain a dense and flexible nonwoven fabric. As a result of observation with a scanning electron microscope, fibrils having a diameter of 3 μm or less were 32%. When the nonwoven fabric was immersed in hot water at 82 ° C., it was completely dissolved.

Comparative Example 3 PVA having a polymerization degree of 1750, saponification of 99.9 mol% and corn starch oxidized starch in a weight ratio of 60/40%, and a polymer concentration of 20 wt% were stirred and dissolved in water at 90 ° C. for 8 hours. Using this solution as a stock solution, the hole diameter is 0.06 mmφ, 100
Wet spinning from a 0-hole nozzle into a saturated sodium sulfate bath at 45 ° C, then wet-stretching twice at 20 ° C in water, and 220 ° C.
Then, the film was subjected to dry heat drawing so that the total draw ratio was 18 times. When a cross section of this fiber was observed with an optical microscope, no clear sea-island structure was observed. Therefore, the beating was tried in the same manner as in Example 2, but division was observed, but the diameter was 3.0 without being ultrafine.
The number of fibrils of μm was less than 1%.

Example 6 The PVA / starch fiber obtained in Example 1 is crimped, 44
The staple fiber thus obtained was cut into mm, and the obtained staple fiber was applied to a semi-random card machine to obtain a 20 g / m ² semi-random web (A). Separately, rayon 1.3d ×
A 30 g / m ² semi-random web (B) was similarly obtained using 40 mm staples. These webs were laminated with a wrapper, the web (A) was laminated on the upper and lower layers, and the web (B) was laminated on the intermediate layer.
A high-pressure water stream of kg / cm ² is applied to split and entangle the fibers, and then dried at a dryer temperature of 110 ° C. to 70 g / m 2.
A dry water-flooded nonwoven fabric of ² was obtained. From the microscopic observation of the obtained nonwoven fabric, the fiber of the present invention has a diameter of 2 μm and an aspect ratio of 2
It was found to be well entangled with each web divided into more than 000 fibrils.

Comparative Example 5 A rayon 1.3d × 40 mm staple was applied to a semi-random card machine in the same manner as in Example 6, and 2 each.
Semi-random webs of 0 g / m ² and 30 g / m ² were obtained.
These webs were wrapped with a wrapper, 15 g / m ² webs were laminated on the upper and lower layers, and 30 g / m ² webs were laminated on the intermediate layer, placed on a wire mesh woven belt, and a high-pressure water stream of 80 kg / cm ² was applied, After entanglement of fibers, dryer temperature 110
Drying was carried out at 0 ° C. to obtain 70 g / m ² of a dry hydroentangled nonwoven fabric.
The obtained non-woven fabric had a low density and was inferior in the wipeability of the spectacle lens as compared with the non-woven fabric obtained in Example 6.

Example 7 The PVA / starch fiber obtained in Example 1 was crimped, 51
The staple fiber thus obtained is cut into mm, carded with a parallel card, and cross-wrapped with a cross-wrapper, and needle punched at a needle density of 500 needles / cm ² to divide and entangle the fibers, and 300 g / m ² To obtain a dry non-woven fabric. From the microscopic observation of the obtained nonwoven fabric,
It was found that the fiber was divided into fibrils having a diameter of 4 μm and an aspect ratio of 500 or more, and the fibrils were entangled with each other.
The diameter of the unbeaten fiber before needle punching is 15μ.
It was m.

Example 8 A slurry was prepared by mixing 40% of the PVA / starch fiber obtained in Example 1 cut into 15 mm and 60% of wood pulp. This was paper-made by a short-net paper making machine and dried at a dryer temperature of 110 ° C. to obtain a base paper of 30 g / m ² . Three pieces of this base paper are piled up, placed on a wire mesh woven belt, and a high-pressure water stream of 80 kg / cm ² is applied to divide and entangle the fibers, followed by drying at a dryer temperature of 110 ° C., and 85 g / m ² of A wet, water-woven nonwoven fabric was obtained. From the microscopic observation of the obtained nonwoven fabric, it was found that the fibers were divided into fibrils having a diameter of 1 μm and an aspect ratio of 2000 or more, and each was well entangled. The diameter of the unbeaten fiber before the high-pressure water stream treatment was 15 μm.

[0032]

The sheet obtained by using the fibril fiber of the present invention has a denseness, a shielding property, an alkali resistance, an opacity, a wiping property, a water absorption property, an oil absorption property, a moisture permeability, a heat retention property, a weather resistance property, High strength, high tear strength, abrasion resistance, anti-static property, drape property, dyeing property, safety, etc. are extremely excellent, so air filters, bag filters, liquid filters, vacuum cleaner filters, drain filters, bacteria shielding filters, etc. Sheets for various filters, battery separators, condenser paper, sheets for various electrical equipment such as floppy disk packaging materials, FRP surfacers, adhesive tape base cloth, oil absorbing materials,
Various industrial sheets such as paper-making felt, household / business / medical wipers, wipers for printing rolls, wipers for cleaning copiers, wipers for optical devices, surgical wipes / gowns, covers, caps, masks , Sheets, towels, gauze, patch base cloth, diapers, diaper liners, diaper covers, adhesive plaster base cloths, hand towels, wipes, tissues, etc. Sheet, artificial / synthetic leather base cloth, table top, wallpaper, shoji paper, blinds, calendar, wrapping, body warmer / desiccant bag, shopping bag, furoshiki, suit cover, pillow cover, etc. Various types of agricultural sheets such as liner curtains, flat covers, light-shielding / weedproof sheets, agricultural packaging materials, seedling pot underlayment paper, etc. Theft, smoke and dust mask, lab coat,
Various protective sheets for dustproof clothing, house wraps, drain materials, filtration materials, separation materials, overlays, roofing, tuft / carpet base cloth, condensation prevention sheets, wall covering materials, sound / vibration prevention sheets, wooden boards, curing sheets Sheets for civil engineering and construction, floor / trunk mats, ceiling molding materials, etc.
It can be used for various purposes such as seats for various vehicle interior materials such as headrests and lining cloths. Further, when the fiber of the present invention is dispersed and stirred with hard inorganic fine particles, it is fibrillated, and it is possible to obtain fibrils excellent in fine particle capturing property and reinforcing property, and also excellent in heat resistance and flame retardance, which is useful as a friction material.
In addition, when this fibril is mixed and dispersed in cement, it has excellent trapping properties for cement particles and also has a reinforcing property.
A high strength slate plate can be easily obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shunpei Naramura, 1621 Sakazu, Kurashiki, Okayama Prefecture, Kuraray Co., Ltd. (72) Inventor, Akio Omori, 1621, Satsuki, Kurashiki, Okayama

Claims (7)

[Claims] 1. A vinyl alcohol polymer (A) and starch (B) are dissolved in a common organic solvent at a weight ratio of A / B of 95/5 to 50/50, where A is a sea component and B is an island component. Of the sea-island phase separation solution, the solution is used as a spinning stock solution, and the solution is subjected to dry-wet or wet-spinning in a coagulation bath, and the obtained fibers are used individually or in combination of a chemical swelling force and a mechanical stress to obtain a diameter of 10 μm or less A method for producing a fibril comprising a vinyl alcohol-based polymer and starch. 2. The method for producing fibrils according to claim 1, wherein the spinning method is a wet spinning method. 3. A method for producing fibrils, wherein the fiber according to claim 1 is beaten in water. 4. A method for producing fibrils, which comprises applying a high-pressure water stream of 30 kg / cm ² or more to the web made of the fiber according to claim 1. 5. The fiber according to claim 1, wherein a high-pressure water stream of 30 kg / cm ² or more is applied to a web obtained by carding the raw cotton containing at least a part of the fiber according to claim 1. A method for producing a dry-type water-entangled nonwoven fabric, which comprises fibrillating. 6. A web obtained by carding the raw cotton containing at least a part of the fiber according to claim 1 is needle punched at a needle insertion density of 250 or more per cm ² to obtain a web. A method for producing a dry nonwoven fabric, which comprises fibrillating the described fiber. 7. A high-pressure water stream of 30 kg / cm ² or more is applied to the base paper obtained by paper-making the slurry containing the fiber according to claim 1 as at least a part of the main fiber, whereby A process for producing a wet hydroentangled nonwoven fabric, which comprises fibrillating the described fiber.