JPH02169766A - Production of water-swelling fiber having high liquid retention - Google Patents

Abstract

PURPOSE:To obtain the subject fiber useful for physiological goods having excellent liquid retention under load by treating specific acrylonitrile-based fiber with alkali in aqueous solution of highly concentrated alkali metal in specific condition. CONSTITUTION:Acrylonitrile-based fiber composed of acrylonitrile-based polymer containing >=80wt.% acrylonitrile and 0.2-0.7mmol/g carboxylic acid group and having >=5.0 dry strength and >=10% fiber shrinkage at 120 deg.C wet heat is treated with alkali of >=10mol/1000g, preferably 13mol/1000g aqueous solution of highly concentrated alkali metal at >=120 deg.C for >=10min, preferably 20-50 min to afford the aimed fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to water-swellable fibers having high liquid retention properties under load.

In recent years, highly water-swellable polymers have attracted attention for their special functions and are being applied to a wide range of fields of use. For example, such polymers can be used to make diapers, sanitary products, etc. by using their instantaneous large amount of water absorption ability, to make soil conditioners, instant sandbags, etc. by using their water retention ability, and by focusing on their affinity with human tissue. Attempts have been made to apply it to soft contact lenses, artificial organs, surgical suture materials, etc., and some of these applications have already entered the stage of practical use.

<Prior Art> Water-swellable polymers (hydrogel), which have a wide range of applicability, are often preferable to be in the form of fibers depending on their uses, and such fibrous hydrogels It is also known. However, although such existing natural or synthetic fibers have a certain degree of water swelling ability, their degree of water swelling is extremely low, or they are water soluble, and in any case, their water swelling capacity is several times their own weight. However, it was far from the scope of water-swellable fibers, which absorb and retain hundreds of times more water than conventional fibers, and are water-insoluble.

Japanese Patent Publication No. 52-42916 discloses a highly swellable fibrous structure obtained by introducing a specific crosslinked structure and a large amount of carboxyl groups in the form of salt into acrylic fibers. However, in such a fibrous structure, an extremely large amount of carboxyl groups in the form of salt is introduced, and the entire inner and outer layers of the #il fibers are hydrogelated, so they certainly have a high degree of water swelling performance. However, it was extremely brittle and had physical properties far from the concept of fibers. In other words, the reality is that water-swellable fibers with satisfactory performance still do not exist, and imparting high water-swellability and maintaining fiber physical properties are contradictory issues.

As a method to solve such problems, JP-A-60-19
In Japanese Patent No. 4175, a fiber made of an acrylonitrile polymer having latent or actual crimp is hydrophilically polarized in a specific high concentration alkaline aqueous solution or a low concentration alkali metal hydroxide aqueous solution coexisting with electrolyte salts. A method for producing water-swellable fibers has been proposed in which only the outer layer of the fibers is hydrogelated.

This method aims to maintain the fiber properties before treatment by appropriately adjusting the hydrophilic crosslinking treatment conditions, but sufficient fiber properties are not maintained and highly water-swellable fibers are obtained. The above method is still not sufficient.

<Problems to be Solved by the Invention> The present invention produces water-swellable fibers that maintain sufficient fiber properties even after hydrophilic crosslinking and have high water-swellability, particularly excellent liquid retention under load. This provides a method to do so.

Means for Solving the Problems> The present invention is based on an acrylonitrile polymer having a carboxylic acid group of Q, 2 to 0.7 m mat/f, and a dry strength of 50 f/d. 10 mot710 acrylonitrile fibers having the above properties and a fiber shrinkage rate of 10% or more under moist heat at 120°C.
120℃ in a high concentration alkali metal aqueous solution of 009 or higher
The above provides a method for producing water-swellable fibers having a high level of liquid retention, which is characterized by carrying out an alkali treatment for 10 minutes or more.

The acrylonitrile (hereinafter referred to as AN)-based polymer according to the present invention is a general term for polymers containing AN as a copolymerization component, and is an A1J homopolymer or AN and one or more other ethylene-based polymers. Copolymers with saturated compounds, or graft copolymers of AN and other polymers, such as starch, polyvinyl alcohol, AN polymers and other polymers, such as polyvinyl chloride, polyamide, polyolefin, Examples include polystyrene, polyvinyl alcohol, and cellulose 11:O mixed polymers.

The content of AN in such an AN-based polymer is 50
It is desirable that the AN content be higher than the weight ratio, and if a fiber made of a polymer with an AN content lower than this recommended range is used as a starting material, not only will the fiber after alkali treatment not have sufficient physical properties, but the alkali This is because the hydrolysis process is too busy to make it sufficiently hydrophilic. 9. There are no special constraints on the polymer composition, such as the type of the ethylenically unsaturated compound that is a copolymerization component of the AN polymer or the molecular weight of the polymer, and the required performance of the final product and monomer It can be arbitrarily selected depending on the copolymerizability and the like.

AN: It is a long-known fact that when a F-polymer is heat-treated in a highly concentrated alkali metal aqueous solution, NiDOIJLEM is hydrolyzed and becomes a carboxylic acid group, which has a high degree of water swelling. However, it was discovered that if an AN-based polymer is pre-contained with a carboxylic acid group and then heat-treated in the same alkaline aqueous solution under the same conditions, the water swelling property of the resulting fiber increases dramatically. Ta.

The content of carboxylic acid groups in the AM polymer according to the present invention is (
It is preferably in the range of 12 to 0.7 mmO2/l, and this carboxylic acid group may be present in the polymer in either the acid form or the salt form.

The content of this carboxylic acid group is Q, 2 mmol/r
If it is less than 1c (L7mmol
If /f/ is exceeded, the resulting fibers will have a high degree of water swelling but will lose the excellent physical properties of the AN-based fibers possessed by Kiku.

A method for incorporating a carboxylic acid group into an AN-based polymer is to copolymerize a vinyl monomer having a carboxylic acid group, such as acrylic acid or methacrylic acid, with AN. The AN-based fiber according to the present invention can be obtained by shaping the fiber into the following. The content of carboxylic acid groups in the fiber can be adjusted by adjusting the amount of vinyl monomers having carboxylic acid groups in the copolymerization reaction system, or by preparing an AN-based polymer having a large amount of carboxyl groups in advance so that it does not contain carboxyl groups. It can also be obtained by mixing with AN polymer.

The production of these AN-based polymers and the production of AN-based fibers using these polymers can be carried out by any method selected from known methods.

This invention 1c91. The AN-based fiber must have a fiber shrinkage rate of 104 J or more under moist heat at 120°C and a dry strength of S, Q t/a or more.

This is because if the shrinkage rate of the fiber under moist heat at 120° C. is less than 10, the fiber treated with alkali in a highly concentrated alkali metal aqueous solution will not have sufficient fiber physical properties, and it is preferably 15 or more. In order to increase the fiber shrinkage rate under humid heat at 120°C to a factor of 10 or higher, dyeing clarity,
This can be easily achieved by not performing the heat-and-moisture relaxation treatment that is performed to improve the balance of strength and elongation, or by lowering the pressure of the heat-and-moisture relaxation treatment.

In addition, the requirements for the AN-based fiber according to the present invention are 5.0P/
It is necessary to have a dry strength of d or more. In order to obtain water-swellable fibers that have a high level of liquid retention under load, it is necessary to perform alkali treatment at high temperatures in a highly concentrated alkali metal aqueous solution. It is an unavoidable phenomenon that fiber strength decreases after alkali treatment, and as a preventive measure, the treated fJ! It can also be said that it is an advantageous method to set the fiber strength to s, or 7'a or more in advance. As a method of increasing the strength of fibers, it is common to perform high-strength stretching.5. '
A dry strength of Ot/eL or higher is achieved. The AM-based woven fiber effect according to the present invention has the effect of preventing hydrophilization of the inner layer of the fiber by shrinking the fiber when performing alkali treatment at high temperature in a highly concentrated alkali metal aqueous solution. The aim is to provide sufficient physical properties to the fibers after alkali treatment by using high-strength type fibers in advance to overcome the decrease in fiber strength caused by this process. The shape of the fiber according to the present invention is not particularly restricted, and as long as it satisfies the requirements set forth in claim 1, it can be made of a single component, or a mixture of two components, three or more components. Either fibers or composite fibers can be employed as the starting fibers of the present invention. Furthermore, the cross-sectional shape and denier of the fibers can be arbitrarily selected.

Further, the present invention does not particularly require latent or actual crimp as required in Japanese Patent Application Laid-Open No. 60-194175.

Fibers can be subjected to subsequent hydrolysis treatment in any form, such as short fibers, long fibers, fiber tows, threads, knitted fabrics, and non-woven fabrics. In order to form AN fibers with liquid retention properties, it is necessary to perform alkali treatment at high temperatures in a highly concentrated alkali metal aqueous solution.

The high concentration alkali metal aqueous solution used in the present invention is 10
A concentration of at least 13 mol/10009 is required, more preferably at least 13 mol/10009. 1
This is because if it is less than 0 mol/1000f, it is not possible to obtain a high level of liquid retention under load, and if it is added to a lower concentration, the treated fibers will dissolve and water-swellable fibers with sufficient fiber properties cannot be obtained. be. The alkali metal hydroxide referred to herein includes hydroxides of alkali metals such as Na, hydroxides of alkaline earth metals such as Oa, or mixtures thereof. It is preferable to raise the alkali treatment temperature, and it is advantageous to carry out the treatment in a boiling state of a highly concentrated alkaline aqueous solution, and the actual temperature is 120° C. or higher. If this temperature is lower than 120℃, sufficient hydrophilic crosslinking treatment will not be performed, and not only will high liquid retention properties not be obtained, but the fibers will not shrink in the cage during alkali treatment, and the fibers after alkali treatment will be zelkova, miscellaneous. It becomes a fragile product with impaired physical properties. Furthermore, the alkali treatment time is set at 10 minutes or more, preferably between 20 and 50 minutes.

If it deviates from this recommended range, sufficient liquid retention under load cannot be obtained. In addition, the ratio of the fibers to be treated and the amount of treatment liquid used in alkaline treatment is selected appropriately based on the quality of the starting fibers, the final liquid retention performance, etc., but if contact with the aqueous solution is easy under these conditions, then Any ratio is possible, but approximately 10 times or more to less than 100 times is selected.

Furthermore, as a method for applying the MIK alkaline aqueous solution to AN-based fibers, short fibers cut into arbitrary fibers are suspended in an aqueous solution, and then cut using a shearing device such as a screw type stirring device, a mixer, or a kneader. Method of stirring or kneading using a kneading device etc., long FI1. A method in which continuous fibers such as fibers, fiber tows, threads, knitted fabrics, non-woven fabrics, etc. are run under tension or without tension in an alkaline aqueous solution, or short fibers, long fibers, etc. are filled in a mesh container and an alkali solution is run. A wide range of known heterogeneous treatment methods can be selected, such as a method of shaking in an aqueous solution.

The thus obtained water-swellable fibers are washed with water to remove the alkali metal hydroxide remaining in the fibers, and then, if necessary, the salt-type carboxyl groups are converted to alkali metal or ammonium salts by known methods. After processing,
It is then optionally subjected to a drying treatment to form a dry product.

The water-swellable fiber of the present invention, which has such high water-swellability and excellent physical properties, can be used alone or by blending or making with existing natural, semi-synthetic or synthetic fibers, etc.
As a new fiber material or textile product with outstanding moisture absorption, water absorption, and water retention properties, it is used for diapers, sanitary products, filter paper, etc.
Alternatively, it can be applied to dehydration materials from organic solvents that are immiscible with water, sealing materials, cation exchange am, etc. Furthermore, it can be applied to existing hydrogel powders, interstitial instant sandbags, artificial soil, drainage, heat/cold insulation materials, etc. be able to.

<Example> The present invention will be explained below using examples.

In addition, liquid retention and carboxyl group (
-000X)] was measured and calculated using the following method.

(1) Liquid retention (t/1-F) Sample fiber approximately CL1f was immersed in pure water and kept at 25℃ for 24 hours.
After a period of time, the fibers were wrapped in a nylon filter cloth (200 mesh) and the water between the fibers was removed using a centrifugal dehydrator (10G x 10 minutes, where G is gravitational acceleration). The weight of the sample thus prepared is measured (Lg). Next, the sample is dried in a vacuum dryer at 80°C until it reaches a constant weight, and the weight is measured (
W2g). From the above measurement results, it was calculated using the following formula. Therefore, the degree of ice-water swelling is #i! This value indicates how many times the weight of the fiber can absorb and retain water.

W Yi (2) Amount of carboxylic acid group (m mol/g)? 11
P was dissolved in 50-dimethylformamide and passed through an ion exchange resin to form a free acid, and then neutralized and titrated with α01N potassium hydroxide methanol solution for measurement.

Example 1 24 parts by weight of an AN-based polymer consisting of AM91 by weight and methyl acrylate by 6.4 parts by weight and having a carboxylic acid group content of 0.3 mmoL/l was mixed with dimethylacetamide (DMAC) 7 parts by weight.
It was dissolved in 6 parts by weight to obtain a spinning dope having a viscosity of 600 voids. This stock solution was discharged into a mixed coagulation solution of DMAc and water to form fibers, and then stretched 6 times with wet heat, 2 times with dry heat, and 12 times in total to achieve a dry strength of &2f/cl, an elongation of 12.0 inches, and
A fiber having a contraction rate of 15 when heated at 20° C. was obtained. 10 tons of this fiber was mixed with 16 mol/100 sodium hydroxide.
0LN) aqueous solution 190 was subjected to alkali treatment in a medium boiling state (130° C.) for a predetermined period of time to obtain water-swellable fibers shown in No. 1 Wheat.

Table 1 Table 2 Example 2 The same AN fiber as used in Example 1 was used in 10? Alkali metal hydroxide aqueous solution 19 with changed sodium hydroxide concentration
Alkali treatment was carried out for 20 minutes at boiling temperature at 0 f to obtain water-swellable fibers as shown in Table 2.

Example 6 AN-based fibers 102 similar to those used in Example 1 were treated with alkali for 20 minutes at various temperatures in an aqueous solution containing 16 mol/100,054 sodium hydroxide and 190 ml to form water-swellable fibers as shown in Table 3. I got it.

As is clear from the results of Examples 1 and 2.3 in Table 3, the water-swellable fibers according to the present invention have outstanding water retention properties, as well as strength and elongation of AM type fibers, which are usually used for clothing and interior applications. It is understood that it has a material properties that are inferior to those of woven fibers.

On the other hand, under alkaline treatment conditions outside the recommended range of the present invention, not only high water retention performance may be required, but also the fiber properties may be insufficient.

Example 4 A terpolymer of AN/methyl acrylate/methacrylic acid was polymerized using a redox polymerization catalyst of ammonium persulfate/acidic sodium sulfite in a water suspension continuous polymerization method, and 1 methacrylic acid was added. The amount was adjusted to prepare four types of polymers having different amounts of carboxylic acid groups. Obtained polymer 2
The fibers shown in Table 4 were obtained by dissolving 4 parts by weight and 76 parts by weight of DMA in the same manner as in Example 1. The obtained fiber io
t is immersed in a 40% sodium hydroxide aqueous solution at 190°C,
Alkali treatment was performed for 20 minutes in a boiling state while stirring.

The fibers treated with alkali were washed with water to remove excess salt and neutralized, and after drying, water-swellable fibers as shown in Table 4 were obtained.

Table 4 As is clear from this example, as the amount of carboxylic acid groups in the AN polymer forming the fiber increases, the liquid retention of the fiber after alkali treatment increases dramatically. However, fibers made of AN-based polymers having a carboxylic acid group of α8 mmoL/f exceeding the recommended range of the present invention had high water retention properties after hydrophilic crosslinking, but the fiber strength was too low to be of practical use.

Example 5 24 parts by weight of the AN polymer containing α5 m mOL/ of carboxylic acid groups used in Example 1 was dissolved in 76 parts by weight of dimethylformamide to obtain a spinning dope. This spinning stock solution was placed in a coagulation bath consisting of a mixture of DMAQ and water with a diameter of α10.
After shaping the fibers discharged from the nozzle (2), the stretching ratio was changed to obtain AN fibers having various dry strengths and submerged shrinkage rates. i 6 mol/1000 of these fibers 109
Fibers as shown in Table 5 were obtained by immersing the fibers in a +P sodium hydroxide aqueous solution of 190 ml and subjecting them to an alkali treatment in a boiling state for 20 minutes.

Table 5 Comparative Examples The AN-based fiber obtained in Example 1 was subjected to a relaxation treatment under moist heat of 2.35 kgG, so that the shrinkage rate under moist heat at 120° C. was reduced to 0. Add this fiber a1oy to 16% sodium hydroxide.
mol/10011111F, aqueous solution 190 was immersed in it and alkali treatment was performed in boiling state for 20 minutes. Although the liquid retention property showed a high value of 709/f-F, the fiber strength after alkali treatment was 1.39/f-F. 1, making it difficult to put it to practical use.

As shown in Example 5 and Comparative Example, increasing the temperature of the fiber before alkali treatment and maintaining the submerged shrinkage rate at a factor of 10 or higher makes the physical properties of the fiber after alkali treatment, especially the dry strength, practical. It turns out that it is necessary for

<Effects of the Invention> The water-swellable fibers of the present invention possess the excellent physical properties of conventional acrylonitrile fibers and also have high liquid retention properties under load, so they can be used in a wide range of industrial applications such as diapers and sanitary products. Therefore, the industrial significance of the present invention is extremely high.

Agent: Patent Attorney Toshio Yoshizawa

Claims (1)

[Claims] 80% by weight or more of acrylonitrile, 0 carboxylic acid groups
．． Consisting of an acrylonitrile polymer containing 2 to 0.7 mmol/g, with a dry strength of 5.0 g/d or more and 120°C
Acrylonitrile fibers with a fiber shrinkage rate of 10% or more under moist heat are treated with alkali in a highly concentrated alkali metal aqueous solution of 10 mol/1000 g or more at 120°C or more for 10 minutes or more. A method for producing a water-swellable fiber comprising: