JPH0473208A - Production of moisture-absorbing and desorbing split fiber - Google Patents

Abstract

PURPOSE:To obtain the subject fiber having excellent moisture-absorbing and desorbing property by using a dope consisting of a mixed aqueous solution containing specific amounts of a polyvinyl alcohol resin and a polymer containing free carboxyl groups in the molecule and subjecting the dope to spinning, forming and splitting. CONSTITUTION:The objective fiber is produced by spinning a dope consisting of a mixed aqueous solution containing (A) a polyvinyl alcohol resin and (B) a polymer containing free carboxyl groups in the molecule at a weight ratio of 90:10 to 20:80, drawing the formed fiber, preferably neutralizing the free carboxyl groups in the component B and splitting the product.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing moisture absorbing and desorbing split fibers having excellent moisture absorbing and moisture releasing properties.

Conventional technology Split fibers, which have the property of absorbing and releasing moisture depending on the environmental humidity, can be applied to clothing, sanitary products, agricultural and horticultural materials, interior materials, dehydrating agents, sealing materials, etc. Be expected.

JP-A No. 63-219618 states that at least 3 m
eq, polycarboxylic acid (A) having 7 g of carboxyl groups and 5 to 75% of which is an alkali metal salt or amine salt, polyvinyl alcohol (B) with a degree of polymerization of 500 to 3000, and to (A) 0.1 to 5% by weight of polyhydric alcohol (C) is an essential component, and (A) and (B) are microscopically incompletely mixed just before the nozzle or at the nozzle part and spun by a dry method. A method of producing water absorbent fibers by heat treatment is shown.

JP-A-1-103643 discloses salts of carboxyl group-containing polymers (1), polyvinyl alcohol (■), polyhydric alcohols (m), and polyepoxy compounds (TV).
A film-like or fibrous water-absorbing composition obtained by molding and heat-treating a mixture consisting of four components is shown.

Although it is not for the purpose of absorbing and desorbing moisture,
Publication No. 0 discloses a water-soluble film made of a homogeneous mixture of water-soluble polyvinyl alcohol and polyacrylic acid, and claims that this water-soluble film is useful for packaging applications for dry detergents and similar water-soluble products. .

In addition, the present applicant has filed applications related to the present invention as Japanese Patent Application No. 1-328919 and Japanese Patent Application No. 2-80354.

Problems to be Solved by the Invention In the method described in JP-A No. 63-219618, (A) and (B) are not included in order to achieve smooth stretching and desired water absorption and elongation. A method of spinning a completely mixed spinning stock solution is adopted. However, such a special method is hardly desirable from an industrial standpoint. In addition, in the invention of this publication,
No consideration has been given to splitting the obtained filament.

The film-like or fibrous water-absorbing composition described in JP-A-1-103643 is based on a salt (I) of a carboxyl group-containing polymer, and a polyvinyl alcohol (II).
The polyvalent alcohol (III) ensures toughness, the polyvalent alcohol (III) ensures flexibility, and the polyvalent epoxy compound (rV) performs crosslinking to control the water absorption capacity. However, it is difficult for this film-like or fibrous water-absorbing composition to have all the properties of moisture absorption and desorption properties, mechanical strength, water resistance, and dimensional stability in a well-balanced manner, and its applications are limited. Sometimes. In addition, a trace amount of polyepoxy compound (rV) is added and crosslinking is attempted by heat treatment, so
Another problem is that it is difficult to stably produce products with a constant degree of crosslinking. Furthermore, in the invention of this publication, splitting the obtained film or fibers is not considered.

The purpose of the water-soluble film described in JP-A-57-125240 is to provide a water-soluble film suitable for uses such as detergent packaging, and therefore is not suitable as a moisture-absorbing and desorbing molded product.

Against this background, the present invention aims to obtain a moisture absorbing and desorbing stretched molded product that has industrial productivity and has excellent moisture absorbing and desorbing properties, mechanical strength, water resistance, and dimensional stability. It was designed to provide a method that allows for

Means for Solving the Problems The method for producing the moisture-absorbing and desorbing split fiber of the present invention is to use a polyvinyl alcohol resin (Al and a polymer containing free carboxyl groups in the molecule (Bl) in a weight ratio of 90:1.
A mixed aqueous solution containing a ratio of 0 to 20:80 is used as a stock solution for molding, and the following steps are performed: Step 1 of molding into a molded product, Step 2 of stretching the molded product, Step 4 of splitting the obtained stretched molded product. It is characterized in that it is carried out in the order of Step 1→Step 2→Step 4.

In this case, between the above steps 2 and 4 or claim 1
After step 4, the polymer (Bl
Step 3 is provided to neutralize the free carboxyl groups contained in the
- It is particularly desirable to perform step 4 or in the order of step 1 - step 2 - step 4 - step 3.

The present invention will be explained in detail below.

Step 1 (Molding step) The polyvinyl alcohol resin (A) may have various degrees of polymerization (for example, 300 or more) and degrees of saponification (for example, 70 to 1) as long as it has water solubility or water swelling property.
00 mol%) of polyvinyl alcohol is used. In this case, for the purpose of the present invention, a higher degree of polymerization is desirable;
Those having a degree of polymerization of 3,100 or more, particularly 3,500 or more, particularly 4,000 or more are preferred.

In addition to polyvinyl alcohol, monomers copolymerizable with vinyl acetate (α-olefin, ethylenically unsaturated carboxylic acid, salt, alkyl ester, anhydride, nitrile, amide, ethylenically unsaturated sulfonic acid, vinyl ether, other than vinyl acetate) "Copolymer modified" polyvinyl alcohol copolymerized with vinyl ester, vinyl chloride, etc.)
"Post-modified" polyvinyl alcohol, which is obtained by acylating or urethanizing polyvinyl alcohol or copolymerized modified polyvinyl alcohol, can also be used.

Examples of the polymer (B) containing a free carboxyl group in the molecule include ethylenically unsaturated monocarboxylic acids (acrylic acid, methacrylic acid, crotonic acid, etc.), ethylenically unsaturated dicarboxylic acids (maleic acid, fumaric acid, itaconic acid, etc.). acids, etc.)
or a polymer of at least one monomer selected from ethylenically unsaturated carboxylic acids such as anhydrides and partial alkyl esters thereof, or monomers copolymerizable with the above monomers (ethylenically unsaturated carboxylic esters,
Examples include copolymers with α-olefins, styrene monomers, vinyl esters, (meth)acrylonitrile, vinyl ethers, vinyl chloride, etc.).

It is preferable that all of the carboxyl groups in the molecule of the polymer (Bl) be free carboxyl groups from the viewpoint of compatibility with (A) and (B), but it is less than 5 mol%, especially 3 mol%. If it is less than %, there is no problem even if it is partially neutralized and in the salt form.Salt refers to water-soluble salts such as alkali metal salts, alkaline earth metal salts, amine salts, and ammonium salts. .

Among the above, particularly preferred are polyacrylic acid or copolymerization ratio of sodium acrylate of less than 5 mol% (
especially less than 3 mol %) of acrylic acid-sodium acrylate copolymers.

The blending ratio of the polyvinyl alcohol resin (A) and the polymer (B) containing free carboxyl groups in the molecule is as follows:
Weight ratio of 90:10 to 20:80, especially 80:20
~30: It is desirable to select from the range of 70.
Too much of the former (FA) and too little of the latter (B) will lead to insufficient moisture absorption and desorption properties, while too little of the former (A) and too much of the latter (B) will lead to a lack of mechanical strength and dimensional stability.

By using a mixed aqueous solution containing a polyvinyl alcohol resin (A) and a polymer containing free carboxyl groups in the molecule (B) in the above proportions as a stock solution for molding, sheet (including film) or linear shapes can be formed. A molded article is produced.

As a molding method, an extrusion method or a casting method is usually adopted. That is, a solvent, a plasticizer (polyhydric alcohol, etc.), a crosslinking agent (polyepoxy compound, dialdehyde,
methylolmelamine, etc.), gelling agents (boric acid, borax,
After compounding metal salts, etc.), fillers, colorants, stabilizers, functional drugs, etc., it is discharged into the air or into a coagulating liquid from a gun or nozzle, or it is cast onto a substrate and dried if necessary. do. Typically, the aqueous solution of (A+) and the aqueous solution of (B) are mixed, other additives are added as necessary, and the mixture is discharged from a goo or nozzle or cast onto a substrate, and then In step 2 of drying, the obtained molded product is subjected to stretching in the present invention.In this case, there is no problem even if water remains at a level corresponding to the natural moisture absorption rate.

When the molded product is in the form of a sheet, the stretching ratio is at least 2 times (particularly 3 times or more, and even 4 times) in area magnification in at least one axial direction (that is, -axial direction, biaxial direction, or even multiaxial direction). 2 times or more), and if the molded product is linear, 2 times or more in one axis direction.
Each is set to be at least twice as large (especially three times or more). When the stretching ratio is small, mechanical strength, water resistance, and dimensional stability are insufficient, and the intended purpose cannot be achieved.

The stretching temperature during the above stretching operation is 100 to 300.
℃, especially 140 to 250°C is suitable. Heat treatment can be performed before the stretching operation to an extent that does not impair the stretching operation, and heat setting can also be performed after the stretching operation.

The hot water dissolution rate of the stretched product is 30% by weight or less, and even 2% by weight.
It is preferable that the content is 0% by weight or less, and the content is preferably 10% by weight or less.

Step 4 (splitting step) Step 4 is a step of splitting the drawn product obtained above.

The fibers of the drawn product can be split by various methods, including a method using a friction machine, a method using a file, a method using a beater, and a method using compressed air.

Step 3 (Neutralization Step) Step 3 is a step of neutralizing free carboxyl groups contained in the polymer (B) in the stretched product obtained as described above.

Neutralization can be achieved by bringing the stretched product into contact with a neutralizing agent, which is an aqueous solution of sodium hydroxide, potassium hydroxide, sodium carbonate, ethanolamine, etc. at a concentration of about 001 to IN. The temperature conditions during neutralization are often from room temperature to about 80°C. During neutralization, it is preferable to keep the stretched product under tension. Heat treatment can also be performed after neutralization treatment.

By this neutralization operation, the carboxyl groups contained in the polymer + Bl in the stretched product are neutralized to a high degree of neutralization (particularly 30 mol % or more). Insufficient degree of neutralization has a disadvantageous effect on hygroscopicity.

Although this step 3 is not an essential step, it is a step that is definitely desired to be included in order to improve water absorption.

Crosslinking process In the present invention, the stretched molded product obtained above can be subjected to a crosslinking process. The crosslinking treatment is carried out by bringing the stretched product into contact with a crosslinking agent solution by dipping, spraying, etc. before or after the above neutralization step 3, at the same time as the neutralization step 3, or before or after the fiber splitting step 4, and further as necessary. This can be done by heat treatment depending on the conditions. Such a crosslinking treatment further improves the mechanical properties such as tensile strength of the target product, resulting in a more practical target product.

As the crosslinking agent, any known crosslinking agent for polyvinyl alcohol or polyacrylic acid can be used, such as polyvalent epoxy compounds, dialdehydes, polyvalent incyanates, methylolmelamine, methylolurea, metal Salts, metal chelates, etc. are used.

Moreover, crosslinking treatment is also possible by irradiating active energy rays such as electron beams and ultraviolet rays without using any particular crosslinking agent.

1 reaction jj Each of the above steps is Step 1 - Step 2 - Step 4, Step 1 - Step 2 → Process 3 - Step 4, or Step 1 - Step 2 - Step 4
- carried out in the order of step 3;

As mentioned earlier, step 3 is not an essential step, but it is preferable to provide step 3.6 When step 3 is provided, the order of steps 3 and 4 is arbitrary, but the thickness of the molded product When the material is relatively thick or thick, it is advantageous to perform step 3 after step 4.

A The moisture-absorbing and desorbing split fiber obtained by the method of the present invention can be used alone or in combination with other materials for textile products (yarns, cotton-like materials, woven fabrics, non-woven fabrics, knitted fabrics, etc.), sanitary products, agricultural and horticultural products. Materials, interior materials (wall materials, etc.), dehydration/dehumidification materials,
It can be suitably used for various purposes including water retention/moisturizing materials, civil engineering materials/air conditioning materials, heat exchanger elements, and transpiration plates.

Actions and Effects of the Invention The method of the present invention can be applied to polyvinyl alcohol resins (FA) and polymers containing free carboxyl groups in their molecules (
A molded product is formed from the composition consisting of B), then the molded product is stretched, and the stretched molded product is split into fibers, or before or after the splitting, the free material contained in the polymer FB+ is It neutralizes carboxyl groups.

According to the present invention, the stability of the stock solution for molding is good even when the polymer concentration in the stock solution for molding is considerably high, or even when a polyvinyl alcohol resin (A) with a high degree of polymerization is used. Moreover, it is possible to perform smooth molding.

Since the molded product (A) is made of a blend of CB and two types of polymers, and the polymer (B) is not a crystalline polymer, the stretched molded product after the stretching process has regions with high and low crystallinity. It is formed. Therefore, smooth splitting is possible in the splitting process, and thin split fibers can be easily obtained.

Since each step of drawing and splitting is provided, and preferably a neutralization step is further provided, the moisture absorbing and desorbing split fiber obtained by the method of the present invention has excellent moisture absorbing and desorbing properties (hygroscopicity and It has both water resistance and dimensional stability.

Examples Example 1 Polyvinyl alcohol with a degree of polymerization of 4000 and a degree of saponification of 999 mol% was used as an example of the polyvinyl alcohol resin (A), and this was dissolved in water to prepare a polyvinyl alcohol aqueous solution with a concentration of 5% by weight. did.

Further, as an example of the polymer (B), polyacrylic acid having a degree of polymerization of 5000 was used and dissolved in water to prepare an aqueous polyacrylic acid solution having a concentration of 5% by weight.

Polyvinyl alcohol aqueous solution with the above concentration of 5% by weight 70
parts by weight and 30 parts by weight of the above 5% by weight aqueous polyacrylic acid solution were mixed to form a homogeneous solution, which was cast onto a 120 μm thick polyester sheet as a base material and dried with hot air to form a 40 μm thick polyester sheet. A sheet-like molded product was obtained.

Next, this sheet-like molded product was stretched 10 times in the longitudinal direction at a stretching temperature of 180° C. using a tenter-type stretching machine, and heat-set at a temperature of 180° C. for 1 minute.

The obtained sheet-like stretched product was supplied to a friction machine, and a friction force was applied for 1 minute to split the fibers. The average thickness of the resulting split fibers was 21 μm.

Next, this split fiber material was neutralized by immersing it in a 0.2N aqueous sodium hydroxide solution under tension for 20 seconds at a temperature of 50°C, followed by washing with water, drying, and then immersing it at a temperature of 200°C.
Heat treatment was performed for 10 seconds.

As a result, the desired moisture-absorbing and desorbing split fibers were obtained. The degree of neutralization of carboxyl groups in the polymer (Bl) in this split fiber was about 90 mol%.

Example 2 Example 1 was repeated except that a homogeneous solution obtained by mixing 50 parts by weight of a polyvinyl alcohol aqueous solution with a concentration of 5% by weight and 50 parts by weight of a polyacrylic acid aqueous solution with a concentration of 5% by weight was used as the stock solution. Ta. The average thickness of the resulting split fibers was 15 μm. Further, the degree of neutralization of carboxyl groups in the polymer (Bl) in this split fiber was about 90 mol%.

Example 3 The split fiber obtained in Example 1 was further heated at a temperature of 50°C.
A crosslinking operation was carried out by introducing the sample into an aqueous methylolated melamine solution (Sumimar M-30W, manufactured by Sumitomo Chemical Co., Ltd.) having a concentration of 2% by weight, running it under tension, and then heat-treating it at 220°C.

Examples 4 to 6 As polyvinyl alcohol resin (A), degree of polymerization is 56
00 (Example 4), degree of polymerization 3500 (Example 5),
Example 1 was repeated except that polyvinyl alcohol with a degree of polymerization of 1800 (Example 6) was used to obtain split fibers.

Example 7 A polyvinyl alcohol resin (polyvinyl alcohol having a degree of polymerization of 4000 and a degree of saponification of 99.9 mol% as an example of Al was dissolved in water to prepare a polyvinyl alcohol aqueous solution having a concentration of 12% by weight).

Further, as an example of the polymer (B), polyacrylic acid having a degree of polymerization of 5000 was used, and this was dissolved in water to prepare an aqueous polyacrylic acid solution having a concentration of 12% by weight.

Polyvinyl alcohol aqueous solution 7 with the above concentration of 12% by weight
0 parts by weight and 30 parts by weight of the above polyacrylic acid aqueous solution having a concentration of 12% by weight are mixed to form a homogeneous solution, the solution is supplied to a container equipped with a piston and a nozzle, and is discharged from the nozzle in the form of a strand, The mixture was then introduced into acetone at a temperature of 20° C. to solidify, and then air-dried. The thickness of the obtained strand was 115 denier.

Next, the above strand was stretched six times in the length direction at a stretching temperature of 180°C using a roll-type stretching machine, and subsequently stretched twice in the length direction at a stretching temperature of 220°C.
Heat set for 1 minute.

The drawn strand was then neutralized by running it under tension in a 0.2N aqueous sodium hydroxide solution at a temperature of 50°C, washed with water, dried, and then heat-treated at a temperature of 220°C under tension.

The drawn strand after neutralization was supplied to a friction machine, and a friction force was applied for 1 minute to split the fibers. The average thickness of the resulting split fibers was 12 μm.

As a result, the desired moisture-absorbing and desorbing split fibers were obtained. The degree of neutralization of carboxyl groups in the polymer (B) in this split fiber was approximately 90 mol%.

Comparative Example 1 Using a 40 μm thick film of polyvinyl alcohol with a degree of polymerization of 400o and a degree of saponification of 99.9 mol%, Example 1
The average thickness of the resulting split fibers, which were drawn and split under the same conditions as above, was 32 μm.

Comparative Example 2 70 parts by weight of the polyvinyl alcohol aqueous solution of Example 1 with a concentration of 5% by weight and the polyacrylic acid of Example 1 were partially neutralized in advance with an aqueous sodium hydroxide solution to a degree of neutralization of 50 mol%,
Next, 30 parts by weight of an aqueous solution of acrylic acid-sodium acrylate copolymer whose concentration was adjusted to 5% by weight was mixed to form a homogeneous solution, which was then molded, stretched and heat-set under the same conditions as in Example 1. A stretched film was obtained.

<Characteristics evaluation> For the split fibers, films, or shredded products obtained in Examples 1 to 7 and Comparative Examples 1 to 2 (in the case of split fibers and shredded products, a 1560 d multifilament yarn was prepared and ), moisture absorption and desorption properties, water resistance (hot water insolubility rate), and dimensional stability were measured by the following methods.

Moisture absorption and desorption properties were measured using a tabletop constant temperature incubator manufactured by Nagano Scientific Machinery Co., Ltd.
The sample was brought to a high temperature condition of 0% RH, and the value after 24 hours was taken as the equilibrium moisture absorption rate, and the hygroscopicity was judged. In addition, the sample used for the measurement of hygroscopicity was brought to low humidity conditions of 40° C. and 40% RH, and the value after 24 hours was taken as the equilibrium moisture absorption rate to judge the moisture releasing property.

The rate of hot water insolubility is as follows: Accurately weigh 1.0±0.1g of the absolute dry weight of the sample a), keep it at 20℃ and 65% RH for more than 48 hours, and then add 500ml of water at a temperature of 98℃! 1 and stirred for 60 minutes at 50 rpm, taken out, and the weight (b) after absolute drying was measured and calculated using the following formula.

Hot water insolubility rate (%)・100b/a Regarding dimensional stability, after keeping the sample fiber (or film) at 20℃ and 65%RH for more than 48 hours,
Cut it into lengths of m (or size of 50 mm x 50 mm), then put it into a beaker containing 500 ml of water at a temperature of 20°C and stir it for 60 minutes at 50 rpIll, then take it out and remove the water attached to the surface. was removed using filter paper, and the length change (%) (or area change (%)) was determined.

The results are shown in Table 1.

From the results in Table 1, in the examples, even when the degree of polymerization of polyvinyl alcohol is high or the concentration of the stock solution for molding is high, a stock solution for molding with excellent stability can be obtained, and the resulting split It can be seen that the fiber has a well-balanced absorption/release property, water resistance, and dimensional stability.

Example 8 In Example 1, only the neutralization step was omitted.

In this case, the hot water insolubility rate and dimensional stability are the same as in Example 1, the hygroscopicity is about 50% of that in Example 1, and the moisture release property is 70% compared to Example 1. A reasonable amount of data was obtained. However, the split fiber obtained in Example 8 also has practical uses.

Example 9 In Example 2, only the neutralization step was omitted.

In this case, the hot water insolubility rate and dimensional stability are the same as in Example 2, the hygroscopicity is about 50% of that in Example 2, and the moisture release is 70% compared to Example 2. A reasonable amount of data was obtained. However, the split fiber obtained in Example 9 also has practical uses.

ｊ□ 1-Cor 1 2゜3゜Procedural amendment (voluntary) Indication of the case dated August 9, 1991 1990 Patent Application No. 183138 Name of the invention Case of a person amending the manufacturing method of moisture-absorbing and desorbing split fibers Relationship with Patent Applicant Address 9-6 Nozaki-cho, Kita-ku, Osaka-shi, Osaka Name (
410) Masaru Ohashi, Representative of Nippon Gosei Chemical Industry Co., Ltd.

Claims (1)

[Claims] 1. Molding a mixed aqueous solution containing a polyvinyl alcohol resin (A) and a polymer (B) containing free carboxyl groups in a weight ratio of 90:10 to 20:80. Step 1 of using it as a stock solution and forming it into a molded article; Step 2 of stretching the molded article; and Step 4 of splitting the obtained stretched molded article in the order of Step 1 → Step 2 → Step 4. A method for producing moisture-absorbing and desorbing split fibers. 2. Neutralizing free carboxyl groups contained in the polymer (B) in the obtained stretched product between steps 2 and 4 of claim 1 or after step 4 of claim 1. A process 3 is provided, and these processes are performed as follows: process 1 → process 2 → process 3 →
A method for producing moisture-absorbing and desorbing split fibers, which is performed in the order of Step 4, or Step 1→Step 2→Step 4→Step 3. 3. The production method according to claim 2, characterized in that free carboxyl groups contained in the polymer (B) in the stretched product are neutralized to a degree of neutralization of 30 mol% or more. 4. Polyvinyl alcohol resin (A) has a polymerization degree of 31
Claim 1: The resin is a polyvinyl alcohol-based resin having a molecular weight of 00 or more.
Manufacturing method described. 5. Polymers containing free carboxyl groups in the molecule (
2. The method according to claim 1, wherein B) is polyacrylic acid or an acrylic acid-sodium acrylate copolymer in which the copolymerization ratio of sodium acrylate is less than 5 mol%.