JPS6012443B2 - hygroscopic acrylic fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides water absorption and
This relates to an acrylic woven finish with excellent moisture absorption.

In recent years, substantially water-insoluble and water-swellable substances (hydrogel) obtained by imparting a crosslinked structure to water-soluble or hydrophilic polymers have been developed to have hydrophilic properties, water retention properties, instantaneous large water absorption properties, It has attracted attention because it has characteristic functions such as hygroscopicity and affinity for human tissue, and studies are becoming more active in using this substance for various uses.

Among these, the lack of performance such as hygroscopicity, water absorption, and flame retardancy, which is generally observed in synthetic polymer materials that are the raw materials for synthetic fiber products and various plastic molded products, can be overcome by mixing the above hydrogel into such synthetic polymer materials. Attempts to solve the problem by forming materials are one of the important technologies that are expected to yield results, and several research results regarding such composite technology have been reported recently.

For example, research reports from the Institute of Textile and Polymer Materials, Agency of Industrial Science and Technology,
No. 107, pp. 23-29 (1975), flame retardancy is achieved by mixing a hydrogel made of polyvinyl alcohol cross-linked by radiation irradiation into a plastic such as polyethylene or polypropylene, which is swollen with water, and then molded. A method for obtaining improved composite materials is described.

However, the results of such research indicate that by mixing hydrogel into a synthetic polymer material, strength, which is essential as a basic performance of the synthetic polymer material, can be improved.
It has been recognized that mechanical properties such as elastic modulus generally decrease, and this has been the biggest obstacle in completing the technology to mix hydrogels into synthetic polymer materials to form composites. However, the above reports also suggest that it is possible to minimize the decrease in mechanical properties by making the hydrogel into fine particles to deal with such problems. Finding a concrete and industrial means for making the particles into fine particles has extremely important significance in the production of such composite materials, and progress in its development has been strongly desired. Conventionally, methods for atomizing hydrogel include pulverizing dry hydrogel powder using a pulverizer such as a ball mill, or dispersing hydrogel in water to form a swollen state.
A method of micronizing the material using a deep cutting device such as a mixer and then drying it, or as described in the above report,
An aqueous solution of a hydrophilic polymer is dispersed in a water-insoluble solvent such as toluene as fine liquid vials using a cutting device such as a mixer.Then, a crosslinked structure is formed in the hydrophilic polymer by means such as radiation irradiation. A method has been proposed in which the material is formed, then heated in an oven, and washed and dried.

However, no matter which of the above known methods is adopted, the particle size of the obtained hydrogel is only a few 1 at the smallest particle size.
0r, which is usually only a few hundred particles, making it virtually impossible to form a hydrogel with the extremely fine particle size necessary to maintain the mechanical properties of the composite material at a practically satisfactory level. Met.

In particular, with regard to hydrogels with particle diameters of 10 mm or less, which are to be incorporated into fibrous materials with diameters of about 10 mm, even a basic idea regarding the manufacturing method has not yet been found. there were. In this), the present inventors mixed an aqueous solution of a hydrophilic polymer containing a reactive group with a water-miscible organic solvent to precipitate the hydrophilic polymer as fine particles. The mixed solvent is evaporated from a suspension consisting of fine hydrophilic polymer particles and an aqueous mixed solvent of the organic solvent while preventing an increase in moisture content, and the thus obtained dry powder product of the hydrophilic polymer is obtained. By drying the hydrophilic polymer to form a cross-linked structure, we can achieve a microhydrogelization effect that could not be achieved in the past, and we have created a microhydrogel that has a fine particle size of 10 mm or less in an absolutely dry state. The present invention was achieved by discovering the fact that acrylic fibers with excellent water and hygroscopic properties can be obtained by containing such microhydrogel.

That is, the main object of the present invention is to provide an acrylic fiber with excellent water absorption and hygroscopicity, which contains a novel microhydrogel having an extremely fine particle size of 10 pores or less. Other objects of the present invention will become apparent from the following description. The above-mentioned object of the present invention is to prepare an aqueous solution of a hydrophilic polymer containing a cross-linking reactive group with a water-miscible organic solvent to form a co-mixture with water and a water/organic solvent weight composition of the co-producer mixture. The hydrophilic polymer is precipitated as fine particles by mixing with a water-miscible organic solvent having a boiling point higher than that of water, or which does not form an azeotrope with water. The mixed solvent is evaporated from a suspension consisting of the aqueous mixed solvent of the combined fine particles and the organic solvent while preventing an increase in the moisture content, and the dry powder product of the hydrophilic polymer thus obtained is subjected to a dry heat treatment. This is achieved by forming a cross-sealed structure in the hydrophilic polymer and incorporating into the acrylic fibers a microhydrogel having a particle size of 10 mm or less when left dry.

The present invention will be explained in more detail below.

In the present invention, hydrophilic polymers containing crosslinking reactive groups include carboxyl groups, sulfonic acid groups, phosphoric acid groups, quaternary ammonium bases, ami/groups, imino groups, pyridinium bases, hydroxyl groups, ether groups, Contains one or more hydrophilic groups selected from ionizable hydrophilic groups such as chain or cyclic amide groups and nitrile groups, salts thereof, and nonionic hydrophilic groups, and the remainder undergoes intermolecular cross-linking reaction. Substantially water-soluble hydrophilic polymers containing functional groups capable of generating .

In addition, as such a functional group, a functional group that can form an Eikyakyo structure in the polymer by dry heat treatment can be appropriately selected. is suitable for carrying out the present invention.The content of hydrophilic groups and crosslinking reactive groups in the hydrophilic polymer according to the present invention, the molecular weight of the hydrophilic polymer, etc. are determined depending on the various uses of the hydrogel. The performance varies depending on the required performance, and it is impossible to limit it unambiguously.It can be determined as appropriate depending on the characteristics of the final product, such as the desired degree of water swelling. In order to obtain the combination, the hydrophilic monomer or the hydrophilic monomer and another monomer are copolymerized by conventionally known methods such as emulsion polymerization, solution polymerization, and aqueous polymerization, or Alternatively, it is possible to use a precursor polymeric substance that can be easily made into a hydrophilic polymer by treatment with a chemical such as an acid, an alkali, an oxidizing agent, or a reducing agent.

In the present invention, first, a hydrophilic polymer as described above is dissolved in water to prepare a hydrophilic polymer aqueous solution.

As a method for preparing an aqueous solution of a hydrophilic polymer, generally known dissolution methods can be employed to substantially dissolve the hydrophilic polymer in water. For example, acids,
A precursor polymer substance that can easily produce a hydrophilic polymer by the action of an alkali, an oxidizing agent, a reducing agent, etc. is suspended in water, and then a hydrophilic polymer is formed by the action of an acid, an alkali, etc. and dissolved. Naturally, a method of polymerizing the above-mentioned hydrophilic monomers in an aqueous system to form an aqueous hydrophilic polymer solution at the same time as the polymerization can also be adopted as a preferred embodiment of the present invention. Note that such hydrophilic polymers can be used without any particular restrictions as long as they are substantially soluble in water;
Even if opacity or the like is observed, there is no problem as long as it does not cause an increase in the particle size of the obtained hydrogel.

Further, the content of the hydrophilic polymer in the hydrophilic polymer aqueous solution can be appropriately selected depending on the particle size to be imparted to the hydrogel, but it is usually desirable to set it to 5% or less; A polymer content in the above range is not preferable because it becomes difficult to perform the operation of forming fine grains. The hydrophilic polymer aqueous solution prepared as described above is then mixed with a water-miscible organic solvent to precipitate the hydrophilic polymer as fine particles.

The first group of water-miscible organic solvents used in this step include low-boiling organic solvents that have a boiling point comparable to or lower than water and that can form a covalent mixture with water. Non-solvents for iron hydrophilic polymers selected from: On the other hand, when using a low-fine-point organic solvent that cannot form a co-marriage mixture with water, the organic solvent is mixed with water in the process of evaporating the aqueous mixed solvent of the organic solvent, as described below. As it evaporates preferentially, the water content in the mixed solvent increases, and as a result, the hydrophilic polymer fine particles suspended in the mixed solvent are redissolved, or particles are bonded or fused to each other. , it is not possible to produce the microhydrogel according to the present invention. Regarding water miscibility in such an organic solvent, it is desirable that the organic solvent has the ability to be miscible with water in an amount of 1% by weight or more. The miscibility may be less than 1% by weight as long as the gist of the present invention, which is to precipitate the hydrophilic polymer as fine particles by mixing, can be satisfied. Specific examples of such water-friendly organic solvents include iso-propyl alcohol, n-propyl alcohol, ter-butyl alcohol, acetonitrile, acrylonitrile, methyl ethyl ketone, dioxane, and triethylamine. When such an organic solvent is used as a water-miscible organic solvent, it is necessary to adjust the ratio at which the aqueous hydrophilic polymer solution is mixed into the water-miscible organic solvent.

That is, the upper limit of the weight ratio between the water content and the water-miscible organic solvent contained in the hydrophilic polymer aqueous solution is the lowest azeotrope (single component) in the two-component mixed solution consisting of water and the organic solvent. It is necessary to determine the mixing ratio so as not to exceed the weight composition ratio (amount of water/organic solvent) of the azeotrope having a lower boiling point.

By adopting such a mixing ratio, in the step of evaporating the aqueous mixed solvent of the organic solvent as described below, it is possible to proceed with the evaporation of the mixed solvent without increasing the moisture content in the mixed solvent. Therefore, it is possible to dry the hydrophilic polymer while maintaining it in a fine particle state.
On the other hand, when a hydrophilic polymer aqueous solution is mixed according to a mixing ratio such that the water content is higher than the lowest azeotrope composition, the organic solvent evaporates in preference to water, so that As the moisture content increases, bonding or fusing action occurs between the fine particles of the hydrophilic polymer suspended in the mixed solvent, and eventually the moisture content becomes high and the fine particles are redissolved, forming a lump-like structure. However, only an evaporated dry matter of 20% is produced, and the microhydrogel which is the object of the present invention cannot be formed. As the second group of water-miscible organic solvents according to the present invention, organic solvents that have a boiling point higher than that of water and are non-solvents for the hydrophilic polymer can be used.

Regarding the water miscibility of organic solvents in this),
It is desirable that the organic solvent has the ability to be miscible with water in an amount equal to or more than a weight percent of the organic solvent. As long as it is within the scope that satisfies the gist of the invention 1
The miscibility may be less than or equal to % by weight. Also"
Among the high boiling point organic solvents mentioned above, any solvent that can form a conjugate with water or a solvent that cannot form a conjugate with water can be used.

When using an organic solvent that can form a co-progeny mixture with water, the mixing ratio of the hydrophilic polymer aqueous solution and the organic solvent should be adjusted as shown in the above example of using a low-boiling point organic solvent. The decision can be made under the same restrictive conditions. On the other hand, when using a high boiling point organic solvent that cannot form an azeotrope, there are no particular restrictions on the mixing ratio of the L hydrophilic polymer aqueous solution and the organic solvent, and the particle size to be imparted to the hydrogel is determined. Such high boiling point organic solvents include butyl alcohol, methyl cellosolve, methyl cellosolve acetate, propionic acid, butyric acid, diacetone alcohol, piveridine, etc. It is also possible to use a mixture of two or more organic solvents selected from the first group and the second group of water-miscible organic solvents such as (a) and (b) to increase the moisture content of the aqueous solvent of the above solvent. If it is compatible with the process conditions of the present invention that allow evaporation and desolvation without evaporation, it can of course be adopted as a preferred embodiment of the present invention.

The aqueous suspension of the organic solvent containing the hydrophilic polymer fine particles obtained by mixing the hydrophilic polymer aqueous solution with the water-miscible organic solvent is then desolvated by evaporation to make the hydrophilic After producing a dry powder of the polymer, a drying treatment is performed to impart a crosslinked structure to the hydrophilic polymer, and if necessary, the hydrophilic polymer is ground by a grinding device such as a ball mill under dry conditions to form a microhydrogel. urge

There are no particular restrictions on the evaporative desolvation method used in the hydrogel, or the dry heat treatment method and treatment conditions to form a crosslinked structure, and there are no restrictions on the particle size, water swelling, etc. that should be imparted to the hydrogel. It can be selected as appropriate depending on the degree of boxiness, etc. By carrying out the above-described method of the present invention, an effect of turning the hydrogel into fine particles, which could not be achieved conventionally, has been achieved, and it has become possible to produce extremely fine microhydrogel having particles of 10 French or less.

In addition, the microhydrogel thus obtained has properties that could not be expected in conventional hydrogels, such as an amazing water absorption rate and moisture absorption rate, and thus has greatly expanded the range of its industrial applicability. Furthermore, when the microhydrogel produced by the method of the present invention is mixed into a synthetic polymer material such as acrylic woven material, the mechanical properties (tensile strength, elastic modulus, etc.) of the polymer material can be adjusted to a practical level. It is possible to maintain the final product at a level that is fully satisfactory, and to significantly improve the performance of the final product, such as hygroscopicity and water absorption.

The acrylonitrile (AN) polymer that forms the acrylic fiber containing the microhydrogel mentioned above is not limited in any way and may be any one that has been used in the production of conventionally known acrylic fibers. As is well known, it is desirable to use a copolymer of 80% by weight or more, more preferably 90% or more, of AN and the balance being other vinyl monomers in terms of fiber properties, dyeability, etc.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the gist of the present invention is not limited in any way by the description of these Examples.

It should be noted that all percentages and parts shown in the examples are based on weight unless otherwise specified. Example 1 17 parts of an acrylonitrile copolymer containing 90% acrylonitrile and 10% methyl acrylate (intrinsic viscosity in dimethylformamide solution: 1.5) was suspended in 83 parts of a 10% aqueous sodium hydroxide solution, and 90q.
An aqueous solution of a polymer containing sodium acrylate and acrylamide was prepared by boiling for 43 minutes at o.

6.7 parts of a 6.0% formaldehyde aqueous solution was added to 10 parts of the aqueous solution of the polymer, and the mixture was heated at 90°C for 3 hours to contain an N-methylolamide group as a reactive group. An aqueous solution of a hydrophilic polymer was obtained. Next, 3 parts of the aqueous solution was diluted in 10 parts of water to obtain a hydrophilic polymer aqueous solution according to the present invention, and then 1 part of the hydrophilic polymer aqueous solution was diluted with iso-propyl alcohol (boiling point: 32.3 °C, azeotropic point: 80.4oo, content of water in the confederate mixture: 12
．． 2%) was added to 10 parts of a clear aqueous solution to precipitate the hydrophilic polymer as fine particles, and the suspension thus obtained was boiled at 90:00 to form an aqueous mixture of iso-propyl alcohol. The solvent was evaporated. The resulting hydrophilic polymer dry powder product was then subjected to a dry heat treatment at 200° C. for 1 hour to form a crosslinked structure in the hydrophilic polymer and produce a microhydrogel having a particle size of 11 or less. . Four types of solvents listed in Table 1 below were prepared in place of the above iso-propyl alcohol as a water-miscible organic solvent, and 10 parts of the above hydrophilic polymer aqueous solution was mixed with 1 part of each of these solvents.
It was added to Nada Azusa in Ikari Kaku, and treated in the same manner as above to form a microhydrogel having a particle size of 5 or less.

On the other hand, as a comparative example, acetone and ethyl alcohol, which cannot substantially form a co-mixture with water, were used to prepare a microhydrogel in the same manner as above, but in both cases the hydrogels were hydrophilic. In the evaporation process of an aqueous mixed solvent in which a hydrophilic polymer is suspended, "these organic solvents evaporate before the water, and the moisture content in the aqueous mixed solvent increases beyond the permissible limit. The polymer was redissolved and then evaporated to dryness, and as a result, only a nodule-like precipitate was obtained, making it impossible to form a microhydrogel similar to that of the above example.

On the other hand, as another comparative example, iso-propyl alcohol,
Methyl ethyl ketone and tert-butyl alcohol were used, and the amount of the hydrophilic polymer aqueous solution mixed with 10 parts of these solvents was adjusted by 2 parts to adjust the water content in the aqueous mixed solvent to that of the solvent and water. The water content in the azeotrope of
These organic solvents evaporated preferentially to water, and only a lump-like product was obtained, making it impossible to obtain the microhydrogel according to the present invention.

This fact proves that the mixing ratio of the aqueous hydrophilic polymer solution and the organic solvent is of critical importance when using the organic solvent.

Table 1: 0.5 part of the microhydrogel thus obtained,
Dispersed in 99.5 parts of 50% Rodan soda aqueous solution.
In 10 parts of the obtained microhydrogel-dispersed rhodan salt aqueous solution, 10 parts of a copolymer containing 90% acrylonitrile and 10% methyl acrylate (intrinsic viscosity in dimethylformamide solution: 1.5) was dissolved. A spinning dope was prepared by using the same method, and the paper yarn dope was discharged through a yarn nozzle with a hole diameter of 0.09 and a number of holes of 100, and the paper yarn was heated to -3°C.
It was coagulated in a 10% Rodan soda aqueous solution whose temperature was adjusted to .

Claims (1)

[Claims] 1. A hygroscopic acrylic fiber containing the following microhydrogel. The above-mentioned microhydrogel is prepared by combining an aqueous solution of a hydrophilic polymer containing a crosslinking reactive group with a water-miscible organic solvent that forms an azeotrope with water and a water/organic solvent weight composition ratio of the azeotrope or less. Hydrophilic polymer fine particles obtained by precipitating the hydrophilic polymer as fine particles by mixing with a water-miscible organic solvent having a boiling point higher than that of water that is miscible with water or does not form an azeotrope with water. The aqueous mixed solvent is evaporated from a suspension consisting of an aqueous mixed solvent of the organic solvent while preventing an increase in moisture content, and the dry powder product of the hydrophilic polymer thus obtained is subjected to dry heat treatment. A crosslinked structure is formed in a hydrophilic polymer, and the particle size is 10 μm or less in an absolutely dry state.