JPH10102322A - Readily fibrillatable fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fiber able to be formed into a hydrophilic fibril having a high strength, excellent in fine particles capturing property and reinforcing property as well as alkali liquid-absorbing property, resistance to heat and melt, free from elution of fiber component in fibrillation and not causing pollution problem of foaming and beating solution in beating and extremely useful in separator paper of alkali battery, reinforcing fiber of cement slate panel, reinforcing fiber, etc., of abrasive material. SOLUTION: In an island phase separation fiber, the sea component of this fibrillated fiber comprises a highly oriented and highly crystallized polyvinyl alcohol-based polymer and the island component comprises a water-insoluble cellulose-based polymer excellent in alkali liquid-absorbing property, heat resistance and flame retardant and the size of island is 0.03-10μm and tensile strength is >=3g/d. When the fiber is wetted with water and mechanical stress is applied to the fiber, the fiber can readily be divided into a fibril having 0.05-8μm diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easily fibrillated fiber comprising a vinyl alcohol-based polymer (hereinafter abbreviated as PVA) and a cellulosic polymer, which can be easily fibrillated. The present invention relates to fibers and fibrils which can be easily formed into ultrafine fibrils by alone or in combination of stress, and which can be used for wet or dry nonwoven fabrics, separators for alkaline batteries, reinforcing fibers for friction materials, reinforcing fibers for cement products, and the like.

[0002]

2. Description of the Related Art Conventionally, nonwoven fabrics made of PVA-based fibers have been used as separators for alkaline manganese batteries because of their excellent alkali resistance. In recent years, with the development of electronics and information and communication, batteries have been required to have higher performance, while on the other hand, mercury-free has been demanded from the viewpoint of eliminating pollution during production and after disposal. Further, separators used in batteries are required to have better separating properties for higher performance under mercury-free conditions. For this reason, PV used for the separator of the alkaline manganese battery
The denaturation of the A-based fiber is progressing, and a 0.3 denier fiber is now commercially available. However, simply reducing the denaturation of the PVA-based fiber does not provide sufficient alkali liquid absorption (that is, absorption of a KOH aqueous solution), which is a very important property in a separator for an alkaline manganese battery. As a separator for solving these problems, a cellulose fiber having excellent alkali absorbing property and a polynosic fiber which can be finely fibrillated by beating is used as fine denier P.
What is mixed with VA fiber is used. However, polynosic fibers have a problem of pollution in the manufacturing process. In the case of polynosic fibers, the beating properties are not good, and the resulting fibrils also have a thick stem at the center of the fibers, and it is extremely difficult to obtain fibrils that are sufficiently finely divided up to the stem. Therefore, a PVA-based fiber which can be fibrillated into ultrafine fibers and has excellent alkali absorption property and alkali resistance has been desired.

Conventionally, asbestos has been frequently used as a reinforcing fiber for various friction materials used for automobile brakes and clutch plates in view of the ability to trap inorganic fine particles, heat resistance, infusibility and reinforcement. Recognition that asbestos has health problems has begun to severely limit its use. Recently, asbestos has been replaced by expensive aramid fiber fibrils. However, the use of aramid fibers is limited due to their high cost, and in practice, fibers having insufficient reinforcing properties such as pulp are used. For these reasons, a fiber which is excellent in fibrillation property for achieving particle trapping property, has both heat resistance, infusibility and reinforcement, and is inexpensive than aramid fiber has been desired.

Conventionally, asbestos has been used as a reinforcing fiber for cement products such as slate boards.
Its use is strictly restricted for the reasons described above. As an alternative to asbestos, PVA-based fibers are used because of their excellent alkali resistance against cement alkali. However, PVA-based fibers are too thick as compared with asbestos, and therefore have low slate green strength. To compensate for this, it is necessary to mix fibrils such as pulp. If fibrillable PVA-based fibers are present, the complexity of using conventional PVA-based fibers and pulp together will be eliminated.

[0005] Further, conventionally, many attempts have been made to utilize the phase separation phenomenon of blended polymers in order to obtain ultrafine synthetic fibers. For example, Japanese Patent Publication No. 49-10617
No., JP-B-51-17609, JP-A-48-5692.
No. 5, JP-A-49-6203 and the like, sea-island fibers having a polyacrylonitrile-based polymer as a sea component, and a graft copolymer of acrylonitrile and PVA with an acrylonitrile polymer or a polymethyl methacrylate-based polymer as an island component, It has been shown that fibrillation is possible by beating. However, these are techniques for improving so-called polyacrylonitrile fibers containing polyacrylonitrile as a sea component.Polyacrylonitrile fibers are poor in alkali resistance and high alkali absorption property, and are required for applications requiring excellent performance in these applications and heat resistance. It cannot be used for applications that require performance.

Japanese Patent Publication No. 47-31376 discloses a PVA-based easy fibril fiber comprising completely saponified PVA as a sea component and partially saponified PVA as an island component. However, in the case of this fiber, there is a problem that water-soluble partially saponified PVA is eluted when it is beaten and fibrillated in water, and foaming is large at the time of beating.

[0007]

As described above, PVA having a large amount of the same hydroxyl group as wood pulp is used as the sea component, the foaming due to elution of the fiber component during beating is small, easy fibrillation is possible, and high alkali absorbing property is obtained. PVA-based fibers which are excellent in heat resistance and infusibility and have higher strength have been strongly desired. However, to date no such fibers have been obtained.

[0008]

In view of such a situation,
The present inventors have worked diligently and have finally arrived at the present invention. That is, the present invention relates to a fiber comprising PVA (A) and a water-insoluble cellulosic polymer (B). In the fiber cross section, A constitutes a sea component, B constitutes an island component, and the average size of the island is 0%. It is an easily fibrillated sea-island structural fiber composed of a PVA-based polymer and a cellulose-based polymer, which has a diameter of 0.03 μm to 10 μm and a tensile strength of 3 g / d or more. In the fiber of the present invention, PVA is used as a sea component. The molecular chains are easily oriented and crystallized, high-strength fibrils are easily obtained, and alkali resistance, excellent in heat resistance, and PVA having a large amount of hydrophilic hydroxyl groups similar to wood pulp constitute a sea component, that is, a continuous phase. Is fundamentally important in achieving the object of the present invention.

The PVA is not particularly limited as long as it has a vinyl alcohol unit of 70 mol% or more. Also included are those in which monomers such as ethylene, itaconic acid, vinylamine, acrylamide, vinyl pivalate, maleic anhydride, and a sulfonic acid-containing vinyl compound are copolymerized with vinyl alcohol at a ratio of less than 30 mol%. When the vinyl alcohol is obtained by saponifying a vinyl ester, the degree of saponification is not limited as long as it is at least 80 mol%, but for orientational crystallization, the vinyl alcohol unit should be at least 95 mol%. It is preferably at least 98 mol%, more preferably at least 99 mol%, most preferably at least 99.8 mol%.
There is no particular limitation on the degree of polymerization of the PVA-based polymer.
The above is preferred, and more preferably 1500 or more. In order to improve the hot water resistance, PVA may be crosslinked by an intramolecular and / or intermolecular acetalization by an aldehyde compound represented by formaldehyde or a crosslinkable agent by a post-reaction after fiberization.

In the fiber of the present invention, a water-insoluble cellulosic polymer is used as an island component. Examples of the water-insoluble cellulose polymer include cellulose itself, cellulose acetate such as cellulose diacetate and cellulose triacetate, cellulose nitrate, and methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, and carboxymethyl cellulose, and water-insoluble low-substituted cellulose. Among them, cellulose is highly alkali-absorbent and low-water-swellable, hydrophilic, and resistant to heat and infusibility.
Cellulose acetate is preferred in that PVA has low compatibility, low water absorption, low heat resistance, and particularly easy fibrillation. Starch has a problem that it is amorphous and has a large dissolution property, and thus does not fall under the category of the water-insoluble cellulose-based polymer according to the present invention. In addition, cellulose acetate may be converted into cellulose by a post-reaction in a fibrous form.In particular, it is extremely easy to use cellulose acetate as a raw material of a water-insoluble cellulosic polymer, and to saponify cellulose acetate after forming a fiber into cellulose. It is the most preferable polymer in the present invention because it is fibrillated.
Once a cellulose polymer is dissolved and amorphized, it is difficult to obtain a high strength by orientational crystallization, and rather it has a unique property that it has a low degree of swelling in water but shows high liquid absorption to alkali. It is important that the cellulosic polymer is present as an island component, ie, a dispersed phase, in order to effectively utilize the heat resistance and the infusibility.

The weight ratio of sea / island, that is, PVA / cellulosic polymer is preferably 95/5 to 50/50. If the cellulosic polymer of the island component is less than 5%, it is difficult to fibrillate. If the PVA of the sea component is less than 50%,
Cellulosic polymer partially forms a sea component, PV
A cannot form a clear matrix phase, and it is difficult to obtain high-strength fibrils. The weight ratio of PVA / cellulose-based polymer is more preferably from 90/10 to 52/48, even more preferably from 80/20 to 55/45, and most preferably from 75/25 to 60/40.

The average size of the islands is 0.03 to 10 μm.
It is. The term "island size" as used in the present invention means that the fiber of the present invention is subjected to a water-resistant treatment, an ultra-thin section of the fiber section is formed, stained with osmium tetroxide, and then subjected to transmission electron microscopy at 20,000 to 6
The area of each island was determined from the cross-sectional photograph magnified 0000 times, the converted diameter of the same circle as the area was calculated, and defined as the arithmetic mean of the converted diameter of each island. If the average diameter is less than 0.03 μm, the size of the island is too small to make it difficult to fibrillate. If the size of the island exceeds 10 μm, the obtained fibril becomes large (that is, thick), and the inherent function of the fibril is obtained. In addition, the fiber is not easily processed, and a trouble is easily caused in the fiberizing process, which is problematic in terms of processability. The size of the island is preferably from 0.1 to 6 μm, and more preferably from 0.5 to 3 μm. Further, in the fiber of the present invention, it is preferable that the cross-sectional shape of the island is non-circular or irregular, because the contact area between the sea component and the island component is large, the portion that is easily divided is increased, and the fibril is easily formed.

The islands composed of the cellulosic polymer of the fiber of the present invention may have a three-phase structure of islands in which PVA is dispersed. In the three-phase structure fiber, the island phase itself is divided, which is effective for obtaining finer fibrils. The easily fibrillated fiber of the present invention needs to have a tensile strength (hereinafter, sometimes simply referred to as strength) of 3 g / d or more. When the strength is less than 3 g / d, the fiber cannot be used for applications requiring strength such as a battery separator, a reinforcing fiber of a friction material, a reinforcing fiber of a cement slate plate and the like. Also has the problem that it is difficult to fibrillate. The strength is preferably 4 g / d or more, more preferably 5 g / d or more,
More preferably, it is 7 g / d or more. The fiber strength referred to in the present invention is a value measured according to JIS L1015. Fiber having a strength of 3 g / d or more is produced by a method described later.

It is preferable that the fiber of the present invention has a beating property of 30 minutes or less. The beating property referred to in the present invention means that 4 g of a fiber sample left at 20 ° C. in an atmosphere of 65% relative humidity is cut into 2 mm,
Was added to a mixer (National MX-X40) manufactured by Matsushita Electric Industrial Co., Ltd., and beaten by stirring at 11,000 rpm. After stirring for a predetermined time, a water-dispersed beaten solution was sampled, and the drainage time was measured by the method described below. It refers to the stirring and beating time at which the drainage time becomes 60 seconds. The drainage time is as follows: the bottom of a 63 mm plastic measuring cylinder is cut out, and a 350 mesh wire mesh is attached to it.
This refers to the time required to filter 750 cc of a water-dispersed beating solution containing 0.5 g of fibrils.

If the beating property exceeds 30 minutes, it may not be able to be used for the intended application because it does not fibrillate or is insufficiently fibrillated when actually used. Of course, even fibers that are difficult to fibrillate can be fibrillated by a method such as lengthening the beating time or using more severe conditions for the beating treatment, but the fibrils obtained in this way are The fibrils are severely entangled with each other or the fibrils are cut short, which is not suitable for the intended use.

Next, a method for producing the fiber of the present invention will be described.
First, it is important to dissolve the PVA (A) and the water-insoluble cellulose-based polymer (B) in a common organic solvent.
As the common organic solvent, when the cellulosic polymer is cellulose acetate or cellulose nitrate, dimethyl sulfoxide (hereinafter abbreviated as DMSO), dimethylacetamide, a mixture of dimethylformamide and a metal salt such as zinc chloride or the like can be used. . When an organic solvent is used, PVA can be gel-spun, so that high-strength fibers can be obtained.

The weight ratio of A / B of both polymers is 95/5.
Dissolve in a common organic solvent so as to be ~ 50/50.
The spinning stock solution obtained by dissolution is not always a completely transparent homogeneous solution depending on the compatibility between PVA and the cellulosic polymer. In order to obtain a sea-island fiber in which the PVA of the present invention is a sea component and the cellulosic polymer is an island component having an average size of 0.03 to 10 μm, in the spinning solution stage, PVA is sea and the cellulosic polymer is island. It is preferably a solution having a sea-island structure with phase separation. However, the size of the islands at the stock solution stage does not need to be 0.03 to 10 μm at all, since the state of phase separation changes depending on the presence of a solvent and solidification conditions. Factors that determine the sea-island structure include the compatibility of the two polymers, the composition ratio, the polymer concentration, the type of organic solvent, the temperature of the stock solution, etc. These are appropriately controlled, and the processability such as spinnability and the ease of fibrillation are evaluated. It is important to balance performances such as strength, water resistance and the like. The viscosity of the spinning dope is 10 to 400 when using the wet spinning method.
50 to 200 when using the poise or dry-wet spinning method
0 poise is suitable and is considerably lower than the viscosity during melt spinning. In this regard, there is one factor that allows the shape of the island to be non-circular or irregular.

Water, which is a conventional spinning solvent for PVA, cannot be used because it cannot dissolve a water-insoluble cellulosic polymer. Conventionally, a method of adding a PVA aqueous solution to a viscose stock solution and spinning it into an aqueous solution containing sodium sulfate and sulfuric acid has been known to improve the strength and dyeability of viscose rayon. The fibers are regenerated cellulose as the sea component and PVA as the island component, which is different from the fiber of the present invention in terms of strength and fibrillation property. Also, in this method, the amount of PVA is increased so that PVA becomes the sea component. Even so, the fiber of the present invention is remarkably inferior in performance such as fibrillation property and strength. That is, it is important in the method for producing the fiber of the present invention to dissolve PVA and a cellulose-based polymer at a predetermined ratio in a common organic solvent to obtain a spinning solution having a sea-island structure such that PVA is a sea component and the cellulose-based polymer is an island component. It is one of the important points.

The spinning dope thus obtained is wet- or dry-wet spinning through a spinning nozzle into a solidification bath. Wet spinning, in which the solidification bath is brought into contact with the spinning nozzle, is suitable for spinning using a multi-hole nozzle because spinning can be performed without sticking even if the nozzle hole pitch is narrowed. Is suitable for high-speed spinning because of its large elongation in the air layer. In the present invention, the wet or dry-wet method can be appropriately selected depending on the purpose and application.

In the present invention, the solidification bath is not particularly limited. However, as in the case of alcohols such as methanol and ethanol, ketones such as acetone and methyl ethyl ketone, and mixed solutions of these with a stock solution, PVA contains fine crystals at a low temperature. It is preferable to produce a non-uniform coagulation and induce uniform gelation, and it is not preferable to easily induce non-uniform coagulation such as an aqueous sodium sulfate solution. Uniformly solidified gel Ishino is subjected to wet drawing, extraction washing, oil application, drying, dry heat drawing and, if necessary, dry heat treatment to form sea-island fibers in which the PVA molecules of the sea component are oriented and crystallized. .

The size of the island is determined by the sea-island phase separation structure in the above-mentioned spinning dope stage and the balance between the gelling behavior and the phase separation behavior in the solidification stage. The larger the island size in the stock solution stage and the lower the gelation rate and the higher phase separation rate in the solidification step, the larger the island size of the obtained fiber tends to be. Factors that determine the gelling behavior and the phase separation behavior in the solidification stage include the composition of the solidification bath, the temperature and residence time, the stock solution temperature immediately before the spinning nozzle discharge, and the shear rate. Therefore, by controlling the determinants of the island size in the undiluted solution and the solidification stage, the average island size is 0.03 to 10 μm.
m can be obtained.

Further, the performance can be improved by causing a chemical reaction to the fiber produced as described above. For example, by immersing the fiber of the present invention in which PVA is an ocean and cellulose acetate is an island in 1N caustic soda at 50 ° C. for 30 minutes,
By saponifying cellulose acetate, it is possible to obtain a fiber in which PVA is an ocean, highly alkali-absorbent, heat-resistant and hardly-fusible cellulose is an island. This fiber is the most preferred of the fibers of the present invention as described above. Further, in order to improve the hot water resistance of the fiber, the fiber is immersed in a mixed aqueous solution of an aldehyde represented by formaldehyde and an acid such as sulfuric acid to convert the amorphous part of PVA into an intramolecular and / or intermolecular acetal. You can do it.

The fiber of the present invention may be any other than PVA and cellulosic polymer within a range not departing from the object of the present invention.
It may contain an inorganic pigment, an organic pigment, a dye, a heat deterioration inhibitor, a pH adjuster, a cross-linking agent, an oil agent, and the like. These may be a stock solution stage, a solidification stage, an extraction stage, immediately before drying, and immediately before stretching depending on the purpose. , After thermal stretching, after heat treatment, after post-reaction, etc.

The fibers thus obtained are converted into fibrils by chemical swelling force and mechanical stress alone or more preferably in combination. The size (thickness) of the fibrils in the present invention is 0.05 to 8 μm in terms of reduced diameter. The size of the fibril in the present invention is a value obtained by enlarging the cross section of the fibril with a scanning or transmission electron microscope, measuring the cross-sectional area, and converting it into the diameter of a circle having the same area as the cross-sectional area. An arithmetic mean of 20 or more was defined as the size of the fibril aggregate. Fibril size 0.05
If it is less than μm, the fibrils are too thin, and the fibrils are entangled with each other to form fibril aggregates, cannot be uniformly dispersed, and cannot function as fibrils. On the other hand, when the size of the fibrils exceeds 8 μm, the fibrils are too thick, the specific surface area becomes small, and the function as a fibril such as capturing inorganic fine particles cannot be achieved.
The size of the fibrils is preferably from 0.2 to 5 μm, more preferably from 0.6 to 2.5 μm, from the viewpoints of fibril reinforcement, liquid absorption, fine particle trapping, and dispersibility. Although the size of the fibrils has some correlation with the size of the islands of the fiber of the present invention, the fibrils are not always completely divided into island components, and have a three-phase structure in which islands exist among the island components. In this case, the size of the fibrils and the size of the islands of the fibers before beating do not always coincide with each other because the possibility of further dividing the island component is high.

Although the entire surface of the fibril may be covered with PVA as the sea component, it is sometimes preferable that the cellulosic polymer as the island component is exposed on a part of the surface of the fibril. When the alkali-absorbing property was evaluated by changing the beating time of sea-island fibers of PVA and cellulose, before the beating, despite the fact that it contained alkali-absorbing cellulose, P
It is almost the same as the liquid absorbency of VA alone, but the alkali absorbency increases as the beating progresses, and the fibril size tends to further decrease when the beating progresses to a certain degree, but the alkali absorbency does not increase. I found a surprising fact that they tend to level off. Although the cause is not completely clear, before beating, the entire surface of the fiber is covered with PVA, which has a low swelling with respect to alkali, and there is alkali swelling cellulose inside the fiber. Also, since the PVA on the surface plays the role of a so-called tub tag, it shows only the alkali-absorbing property of the PVA-only fiber, whereas it is beaten and PVA
When the layer is divided between the cellulose layer and the cellulose layer, the cellulose layer comes out to the surface and the “tag” of the PVA is released, so that the cellulose exhibits the original alkali liquid absorption property, and further the beating proceeds, and the size of the fibrils increases. It is presumed that after the PVA becomes "tagged" and the "tag" of the PVA disappears, the alkali liquid absorbing property does not increase and the level is turned off. Therefore, in applications in which fibrillation is not only a matter of reducing the fiber diameter, but also an alkali-absorbing property such as a separator for an alkaline manganese battery, at least 10% of the fibril having a highly alkali-absorbing component exposed on the surface is used. It is preferable that these are present. More preferably, it is present in an amount of at least 20%.
It is even more preferred that the content be 0% or more.

In the present invention, the ratio of the fibrils having cellulose exposed on the surface is simply indicated by the increase ratio of the alkali absorption of the fibrils after beating to the alkali absorption of the fibers before beating. .

The fibril has an aspect ratio (length / diameter) of 50 or more. When the aspect ratio is less than 50, the reinforcing property and the fine particle capturing property are insufficient. Aspect ratio is 20
If it exceeds 00, the entanglement between fibrils becomes large and uniform dispersion becomes difficult. The aspect ratio is preferably 100 or more, and more preferably 200 or more, from the viewpoint of reinforcement and trapping. Here, the diameter means the diameter of a circle corresponding to the average cross-sectional area of the fibril.

Next, a method for producing the fibrils of the present invention will be described. Fibrils are produced by applying chemical swelling force and mechanical stress alone or more preferably both to the sea-island phase-separated structural fibers of the PVA (A) and the water-insoluble cellulosic polymer (B) of the present invention. The chemical swelling power in the present invention refers to the ability to swell PVA (A) as a sea component or cellulosic polymer (B) as an island component. To swell PVA (A), it is typically used. Is contact with water. The water-insoluble cellulosic polymer (B) of the island component has a low swelling property with respect to water, and PVA
A stress distortion occurs due to a difference in swelling force between the layer and the cellulosic polymer layer. If the distortion is large, the layer is divided only by the swelling force. PVA (A) and cellulosic polymer (B)
Is not necessarily strong, so the fibers of the present invention may be split when a strong mechanical shear is applied,
It is more preferable to apply a mechanical shearing force in a state of swelling strain because split fibrillation is more complete. Although the chemical swelling force has a great effect on the fibrillation property, the fiber of the present invention is characterized by the fact that the chemical swelling force can be obtained by water, an extremely inexpensive substance that does not require pollution treatment or recovery treatment. For fibrillation, swelling of the island phase is important, and there is a view that swelling of the sea phase does not contribute to easy fibrillation, but the results of the fiber of the present invention show that swelling of the sea phase is sufficiently effective. At present, it seems reasonable to think that increasing the internal strain due to the difference in swelling force between the sea and island phases is effective for easy fibrillation.

Next, the fibrillation method includes a method of fibrillating the fibers and then forming the fibrils in a sheet form, and a method of forming a sheet-like material in a fiber state and then fibrillating the fibers. First, the former uses 1 of the fiber of the present invention.
~ 30mm, cut short, immersed in water, dispersed, beater, refiner, mechanical stress is applied by a mixer, etc., fibrillated, the method of papermaking the resulting fibrils as paper stock, or fibrils in cement liquid And a method of dispersing and making a paper. Since it is composed of fine fibers by fibrillation, a thin and strong paper with high tenacity can be obtained. For separators of alkaline manganese batteries, porous paper is desirable to increase the inter-fiber absorption,
It is preferable to mix the fibril of the present invention with another material, for example, vinylon having a density of 0.3 to 1 denier, and to make paper so that the porosity can be secured. The separator thus obtained has a high alkali-absorbing liquid both in and between the fibers. Further, when the fibrils are mixed and stirred with inorganic fine particles or thermosetting plastic fine particles, the fine particles are captured by the fibrils, and the fine particles can be formed, whereby a friction material suitable for a brake shoe or a clutch plate can be obtained.

In the latter method, the fiber of the present invention is crimped and cut into staples and then dispersed on a web formed through a carding machine, or the fiber of the present invention cut into 1 to 30 mm as paper stock in water. Let the wet paper base paper,
A typical example is a method in which a high-pressure water stream of 30 kg / cm ² or more, preferably 60 kg / cm ² or more is applied, and the fiber of the present invention is fibrillated by impact or shear by the high-pressure water stream. Since this method fibrillates with a high-pressure water flow after web formation, there is an advantage that dispersion failure due to fibrils and high tension due to fibrils can be avoided,
A porous two-dimensional sheet can be obtained while being composed of ultrafine fibers, and is useful as a battery separator or as a wiper or filter.

Conventionally, in the case of a composite fiber composed of two incompatible polymers using a fiber material other than PVA, the composite fiber is divided by a high-pressure water flow. There was an inverse relationship between the reproducibility and the resolvability during high-pressure water flow treatment, and it was difficult to achieve both good process passability and good resolvability. That is, fibers that are easily split by the conventional high-pressure water flow treatment are easily split even in the spinning step, the drawing step, the crimping step, and the card step, and these steps tend to cause trouble. Conversely, in the case of a conjugate fiber having a small division property up to the web forming step and passing through without any trouble, it is difficult to divide even the high-pressure water flow treatment, and it is difficult to obtain a nonwoven fabric composed of the divided ultrafine fibers.

On the other hand, in the case of the fiber based on the PVA of the present invention, as described above, the fibrillation property is small in the dry state before the high-pressure water flow treatment, and therefore, the trouble due to the fibrillation in the dry step is small. Even
When it becomes wet by the high-pressure water flow, the internal strain increases at a stretch, and the fibril splitting is easily caused by the high-pressure water flow. Further, since the fiber of the present invention is divided only by strong mechanical shearing force, a needle punch method can be used as a fibrillation method. However, as described above, the fiber of the present invention is further divided into fibrillated when subjected to a mechanical shearing force in a state of wet distortion, such as in a water entanglement, so that the needle punch method is used. In that case, the conditions need to be strict. That is, as the fibrillation condition, the needle density is 250 needles / cm.
^It is preferably ² or more, more preferably 400 needles / density.
cm ² or more.

In the above-mentioned method for producing a dry web used in the hydroentanglement method or the needle punching method, examples of carding methods include a roller card, a semi-random card, a random card, and the like. , Tandem web, cross web, Chris cross web and the like. Further, as a method for producing a wet papermaking base paper used in the hydroentanglement method, a method using a generally known paper machine such as a circular net, a short net, and a long net can be used. If possible, the finished base paper may be dried or before drying.

For the raw cotton mixed with the web or the base paper together with the fiber of the present invention, generally known fibers such as rayon, solvent-spun cellulose fiber, polynosic, polyester, acrylic, nylon, polypropylene, vinylon and the like are used. be able to. Regarding the lamination of webs, not only lamination with the same kind of web containing at least a part of the fiber of the present invention, but also lamination between webs having different mixing ratios of the fiber of the present invention, and lamination with a web not containing the fiber of the present invention But it is good. That is, the fiber of the present invention may be partially contained in a fibrillated state,
They may not be present uniformly but may be unevenly distributed.

Further, the obtained nonwoven fabric is subjected to an emulsion binder applying method such as a saturating method, a spraying method, a printing method, a foaming method, or a powder method, or a powder method, etc., to obtain a vinyl acetate, acrylic, polyethylene, PVC, urethane, or the like. A generally known resin binder such as a polyester-based, epoxy-based, or rubber-based resin can also be added.

[0036]

The present invention will be described in more detail with reference to the following 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 cellulose acetate having a polymerization degree of 180 and an acetylation degree of 55% (hereinafter abbreviated as CA) were treated with dimethyl sulfoxide (DMSO).
) And stirred and dissolved at 80 ° C for 10 hours under a nitrogen stream to obtain a mixed solution in which the weight ratio of PVA / CA was 70/30, the total concentration of the polymer was 18% by weight, and the color was slightly brown. This solution is not completely clear, is slightly cloudy,
VA was the sea-island phase separation solution of the sea component and CA was the island-island phase separation solution. However, even if the solution was left at 80 ° C. for 24 hours without stirring, no further tendency for phase separation was observed, and the solution was a stable uniform dispersion. Was. This solution was used as a spinning dope, and the number of holes was 1,000 and the pore diameter was 0.0
Through a 6 mmφ spinneret, wet spinning is performed in a solidification bath at a weight ratio of DMSO / methanol of 25/75 and a temperature of 10 ° C., subjected to 3.5 times wet stretching, and DMSO in the yarn is extracted with methanol. And dried with hot air at 80 ° C.
Dry heat drawing was performed at a total draw ratio of 13 times to obtain PVA / CA sea-island fibers. Then, at 50 ° C in 1N caustic soda for 30
The cellulose is saponified to obtain cellulose by saponification, and formaldehyde 30 g / l, sulfuric acid 200 g / l and sodium sulfate 1
It was immersed in a 50 g / l bath at 70 ° C. for 30 minutes to form acetal. The cross section of this fiber was magnified with a transmission electron microscope, and the size of the island was determined to be 1.2 μm. Further, the shape of the island was hardly circular, and was irregular, such as a square having four or more squares, a star, and an amoeba. This 2000 denier /
The multifilament yarn consisting of 1000 filaments has a strength of 10.2 g / d and a fiber strength of 11.2 g / d, and has a high strength in spite of containing 30% by weight of CA as an island component. The temperature is as high as 120 ° C,
It is estimated that the PVA of the sea component is sufficiently oriented and crystallized. The beating property of this fiber was 18 minutes.

This PVA / cellulose sea-island fiber is 2 mm
Then, 5 g of the mixture was dispersed in 500 cc of water, beaten and beaten with a household juice mixer (National MX-X40) for 10 minutes, and the beaten solution was subjected to suction filtration to obtain hydrated fibrils. As a result of observing this fibril with an optical microscope and an electron microscope, the average thickness was 1.0 μm and the aspect ratio was 8
00, indicating that the cross-sectional shape was not circular but irregular. The diameter of the fiber before beating is about 15 μm
Met. 4 g (pure amount) of the obtained hydrous fibrils and 0.2 g of PVA-based binder fiber of 1 denier × 3 mm are added to 1.5 l of water, disintegrated sufficiently by a defibrillator, and a viscous agent is added thereto and sufficiently stirred, and papermaking is performed. A liquid was prepared. This papermaking liquid 300
Water was added to 1 ml to make 1 liter, and the paper was made with a Tappi handmade paper machine. The obtained papermaking paper was sufficiently dehydrated with No. 3 filter paper, dried with a roll drier at 110 ° C. for 85 seconds, and dried with a basis weight of 40.
g / m ² of handmade paper was obtained.

The obtained paper has an alkali absorption rate in fiber of 2.
2 g / g, which is clearly higher than the alkali absorption rate of 0.5 g / g of paper made with ordinary 1-denier vinylon fiber alone, and the alkali absorption of paper obtained by mixing beaten polynosic fiber and vinylon fiber. It exhibited high alkali liquid absorbency comparable to that of 2.2 g / g. The alkali absorption rate in the fiber of the paper was determined by immersing a 5 cm × 5 cm paper (weight after drying WDg) in a 35 wt% KOH aqueous solution at 20 ° C. for 30 minutes and 3,000 g.
When the weight of the paper after centrifugal dewatering at rpm × 10 minutes was WCg, it was determined as (WC-WD) / WD (g / g).

Reference Example 2 m of the PVA / cellulose sea-island fiber obtained in Example 1 was used.
m and paper-made as it was without beating treatment. The alkali absorption rate in the fiber of this paper was 1.0 g / g, which was an improvement over ordinary vinylon fibers, but a sufficient improvement effect was not seen. This is presumed to be due to the fact that although the inside contains alkali-swellable cellulose, the outermost surface is covered with low-alkali-swellable PVA, and the "hatch" is in the state.

Example 2 PVA having a degree of polymerization of 4000 and a saponification degree of 99.1 mol% and cellulose acetate having a degree of polymerization of 110 and an acetylation degree of 45% were dissolved in DMSO with stirring in the same manner as in Example 1 to obtain a mixture of PVA / CA. A slightly turbid homogeneous finely dispersed solution having a weight ratio of 63/37 and a total polymer concentration of 13% by weight was obtained. This solution was stable without any apparent change in the phase separation state even after one day of standing. This solution was used as a spinning solution, and the number of holes was 500, and the hole diameter was 0.08.
DMSO / methanol = 30
Wet spinning in a solidification bath at a temperature of 5 ° C. at / 70, wet drawing 3.5 times, extraction and drying, and drawing 12 times dry heat at 235 ° C. to obtain PVA / CA sea-island fiber Was. The size of the island of this blend fiber was 1.8 μm, and the shape of the island was not circular but irregular. 1000 denier / 500
Multifilament yarn strength of the filament is 8.5
g / d, the fiber strength was as high as 9.2 g / d, and the hot / cold temperature was as high as 118 ° C., and it was presumed that PVA of the sea component was sufficiently oriented and crystallized. The beating property of this fiber is 2
It was 0 minutes.

The PVA / CA sea-island fiber was crimped to a length of 38 m.
m, and the obtained staple fiber was applied to a parallel card machine to produce a web having a basis weight of 40 g / m ^2. The web was wet with water, and then 80 kg / cm.
^The fibers were split and entangled by applying a high-pressure water stream of No. ² . Microscopic observation of the obtained nonwoven fabric showed that the fibers were divided into fibrils having a thickness of 2 μm and an aspect ratio of 2000 or more. The diameter of the unbeaten fiber before the high-pressure water flow treatment was 15 μm.

Comparative Example 1 A hydroentangled nonwoven fabric was prepared in the same manner as in Example 2 except that a high-pressure water flow of 20 kg / cm ² was applied. When the nonwoven fabric was observed with a microscope, there were almost no split fibrils.

Example 3 The PVA / cellulose fiber obtained in Example 1 was crimped and cut, and the obtained staple fiber was set on a card machine.
After forming a web and wetting the web with water,
High-pressure water flows of kg / cm ² and 80 kg / cm ² were applied for 2 seconds each and dried to obtain a nonwoven fabric having a basis weight of 40 g / m ² . Microscopic observation of the obtained nonwoven fabric showed that the fiber was divided into fibrils having a thickness of 1.2 μm and an aspect ratio of 2,000 or more. Before splitting, the fibers were formed into a web-like sheet and fibrillated in the sheet state, whereby a non-woven fabric uniformly dispersed even with an aspect ratio of 2,000 or more could be obtained. When the inter-fiber alkali absorption rate and the intra-fiber alkali absorption rate of this nonwoven fabric were measured,
They were 6.2 g / g and 2.9 g / g, respectively. On the other hand, the wet papermaking of fibril fibers obtained in Example 1 had a high alkali absorption in fiber of 2.2 g / g, but a low alkali absorption in fiber of 2.5 g / g. This is presumably because the sheet was formed as an ultrafine fibril, and the sheet had a high tensile strength to reduce the gap between the fibers. In the wet-laid paper of unbeaten fibers obtained in the above Reference Example, the alkali absorption in fiber was as low as 1.0 g / g, but the alkali absorption in fiber was as high as 6.0 g / g. The nonwoven fabric obtained by hydroentanglement of the dry card web obtained in this example showed a high value of the inter-fiber and intra-fiber alkali liquid absorption.
In addition, the liquid absorption between fibers of a sheet such as paper or dry nonwoven fabric,
A 5 cm × 5 cm sample (weight WDg after drying) is 35
Assuming that the weight after dipping in a 30% by weight KOH aqueous solution at 20 ° C. for 30 minutes and dripping for 30 seconds is defined as WTg, the total liquid absorption (WT-WD) / WD was determined. The internal liquid absorption was determined, and the internal liquid absorption was subtracted from the total liquid absorption to determine the internal liquid absorption.

Comparative Example 2 The weight ratio of PVA / CA was 97/3, and the total polymer concentration was 16
Melting, spinning, and dry drawing were performed in the same manner as in Example 1 except that the content was changed to wt% to obtain a PVA / CA blend fiber. The fibers were dispersed in water, stirred and beaten with a juice mixer for 40 minutes in the same manner as in Example 2, and the obtained fibers were observed with a microscope. However, no tendency to split fibrillation was observed. The beating property of this fiber was 40 minutes or more.

Comparative Example 3 The PVA / CA weight ratio was 40/60, and the total polymer concentration was 2
It was dissolved in DMSO in the same manner as in Example 1 except that the content was changed to 5% by weight. An attempt was made to spin the obtained solution in the same manner as in Example 1. However, it was difficult to normally discharge the solution from the nozzle, and the obtained gel yarn was too weak to pass through the subsequent fiberization step. Was. This is probably because the sea component serving as the matrix in the solution stage is CA.

Example 4 The PVA / CA fiber obtained in Example 2 was crimped to 40 mm
The resulting staple fiber was set on a semi-random card machine to obtain a semi-random web (A) of 15 g / m ² . Separately, using a staple of rayon 1.3 denier x 40 mm, similarly, 30 g / m ²
(B) was obtained. Using these webs as wrappers, web (A) as upper and lower layers, web (B)
Is laminated on the intermediate layer, and placed on a wire mesh woven belt.
After applying a high-pressure water flow of 0 kg / cm ² to split and entangle the fibers, the fibers were dried at a dryer temperature of 110 ° C.
Thus, a dry-type non-woven fabric of m ² was obtained. Microscopic observation of the obtained nonwoven fabric revealed that the fiber of the present invention was divided into fibrils having a diameter of 2 μm and an aspect ratio of 2,000 or more, and each web was well entangled.

[0047] Using the staples of Comparative Example 4 Rayon 1.3 denier × 40 mm, similarly subjected to semi-random carding machine as in Example 4, to give the respective ^{15g / m 2, 30g / m} 2 of a semi-random web. These webs were laminated 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 middle layer, and placed on a wire mesh woven belt, and 80 kg / cm ²
After the fibers were split and entangled with each other by applying a high-pressure water stream, the fibers were dried at a dryer temperature of 110 ° C. to obtain a dry-type non-woven fabric of 60 g / m ² . The obtained nonwoven fabric had a lower density than the nonwoven fabric obtained in Example 4 and was inferior in the wiping properties of eyeglass lenses.

Example 5 The PVA / cellulose sea-island fiber obtained in Example 1 was crimped, cut into 51 mm, and the obtained staple fiber was carded with a parallel card. Needle punching at 450 fibers / cm ² to split and entangle the fiber, 400
g / m ² of a dry nonwoven fabric was obtained. Microscopic observation of the obtained nonwoven fabric showed that the fiber was divided into fibrils having a diameter of 4 μm and an aspect ratio of 500 or more, and each was entangled. The diameter of the unbeaten fiber before the needle punching treatment was 15 μm.

Example 6 The PVA / cellulose sea-island fibers obtained in Example 1
A slurry prepared by mixing 40% by weight of the material cut into mm and 60% by weight of wood pulp was prepared. This is made into a short paper machine and dried at a dryer temperature of 110 ° C.
g / m ² of base paper was obtained. Four sheets of the base paper are stacked, placed on a wire mesh woven belt, and subjected to a high-pressure water flow of 100 kg / cm ² to split and entangle the fibers. The fibers are dried at a dryer temperature of 110 ° C. and dried at a dryer temperature of 91 g / m ² . A wet-type nonwoven fabric was obtained. Microscopic observation of the obtained nonwoven fabric showed that the fiber was divided into fibrils having a diameter of 1 μm and an aspect ratio of 2,000 or more, and each was well entangled. The diameter of the unbeaten fibers before the high-pressure water flow treatment was 15 μm.

[0050]

The sheet obtained by using the fibril fiber of the present invention is dense, shieldable, alkali-resistant, opaque, wiping, water-absorbing, oil-absorbing, moisture-permeable, heat-insulating, weather-resistant, Extremely high strength, high tear strength, abrasion resistance, antistatic properties, drape properties, dyeing properties, safety, etc.Besides the above alkaline battery separator paper, air filters, bag filters, liquid filters, vacuum cleaners Filter for
Sheets for various filters such as draining filters and fungus shielding filters, sheets for various electrical equipment such as condenser paper and floppy disk packaging, FRP surfacers,
Various types of industrial sheets such as adhesive tape base cloth, oil absorbing material, papermaking felt, household / business / medical wipers, wipers for printing rolls, wipers for copier cleaning, wipers for optical equipment, etc. Sheets for various medical and sanitary materials such as gowns, cloths, caps, masks, sheets, towels, gauze, base cloths for diapers, diapers, diaper liners, diaper covers, plaster base cloths, towels, tissues, interlining, pats, Various clothing sheets such as jumper liners and disposable underwear, artificial / synthetic leather base cloth, table tops, wallpapers, shoji paper, blinds, calendars,
Wrapping, cairo / desiccant bags, shopping bags, furoshiki, suit covers, pillow covers, etc., sheets for various living materials, cold gauze, lining curtains, sticky, light-shielding / weed-proof sheets, pesticide packaging materials, seedling seedlings, etc. Various types of agricultural sheets, smoke and dust masks, experimental clothes, various protective sheets such as dustproof clothes, house wraps, drain materials, filtration materials, separation materials, overlays, roofing, tufted carpet base fabrics, condensation prevention sheets, Wall coverings, sound and vibration proof sheets, wood boards,
It can be used for various civil engineering and architectural sheets such as curing sheets, floor / trunk mats, ceiling molding materials, headrests, lining cloth and other various vehicle interior material sheets and the like.
In addition, the fibers of the present invention are dispersed and stirred with inorganic fine particles to form fibrils, and fibrils excellent in fine particle trapping and reinforcing properties and excellent in heat resistance and flame retardancy can be obtained, and are useful as friction materials. Further, when the fibrils are mixed and dispersed in the cement, the cement particles are excellent in trapping property of cement particles and also have a reinforcing property, so that a high strength slate plate can be easily obtained.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Satoru Kobayashi 1-2-1, Kaigandori, Okayama City Inside Kuraray Co., Ltd. (72) Inventor Shunpei Naramura 1-2-1, Kaigandori, Okayama City Kuraray Co., Ltd. Inside

Claims (8)

[Claims] 1. A fiber comprising a vinyl alcohol-based polymer (A) and a water-insoluble cellulose-based polymer (B), wherein A is a sea component, B is an island component, and the size of the island is An easily fibrillated sea-island structural fiber having an average particle size of 0.03 to 10 µm and a tensile strength of 3 g / d or more. 2. The easily fibrillated sea-island structural fiber according to claim 1, which has a beating property of 30 minutes or less. 3. A method for producing fibrils, comprising fibrillating the fibers according to claim 1 by beating them in water. 4. A method for producing fibrils, wherein a fibril is formed by applying a high-pressure water stream of 30 kg / cm ² or more to a web made of the fiber according to claim 1. 5. A web obtained by carding a raw cotton containing at least a part of the fiber according to claim 1, is exposed to a high-pressure water flow of 30 kg / cm ² or more, or 250 fibers / cm ² or more. A method for producing a dry nonwoven fabric, characterized in that the fibers are fibrillated by needle punching at a needle insertion density. 6. A base paper obtained by forming a slurry containing the fiber according to claim 1 as at least a part of a main fiber is subjected to a high-pressure water flow of 30 kg / cm ² or more to fibrillate the fiber. A method for producing a wet-type water-impregnated nonwoven fabric. 7. A fibril comprising a vinyl alcohol polymer (A) and a water-insoluble cellulose polymer (B), having an average thickness of 0.05 to 8 μm and an aspect ratio of 50 or more. 8. A weight ratio of vinyl alcohol polymer (A) to water-insoluble cellulose polymer (B) of A / B of 9
5/5 to 50/50 dissolved in a common organic solvent, A is a sea component and B is an island component sea-island phase separation solution, and this solution is used as a spinning solution and wet-spun or dry-wet spinning in a solidification bath. A method for producing an easily fibrillated sea-island structural fiber, comprising: