JPH0241451A - Highly water absorbing fiber sheetlike material and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject processable sheetlike material, having a high level of water absorbability and flexible feeling and useful as oil-water separation materials, etc., by using a highly water absorbing fiber consisting of a polycarboxylic acid containing moisture in a specific proportion or a salt thereof. CONSTITUTION:The objective sheetlike material obtained by applying an anionic and/or nonionic surfactant to a highly water absorbing fiber consisting of a polycarboxylic acid containing 5-80wt.% moisture or a salt thereof (preferably polyacrylic acid or salt thereof), humidifying the resultant fiber and molding the fiber into a sheetlike form.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a highly water-absorbent fiber sheet and a method for producing the same, and more specifically relates to products that require high water absorption or water retention, such as The present invention relates to a superabsorbent fiber sheet material that can be used for oil/water separation materials, dew condensation prevention materials, sanitary products, disposable diapers, etc., and a method for producing the same.

[Conventional technology] Granular water-absorbing resin has a water absorption capacity of several times to 1,000 times, and has been developed for use in a wide range of fields such as disposable diapers, sanitary products, soil improvement materials for agriculture and horticulture, sealing materials, and freshwater preservation materials. is in progress.

On the other hand, depending on the application, the form of fiber products such as threads, nonwoven fabrics, mats, and knitted fabrics is often preferable, and water-absorbing resins in such forms are highly desired.

An example of fiberization is a method of introducing a specific crosslinked structure into acrylic fibers and carboxyl groups in the form of salts derived from residual nitrile groups, as disclosed in Japanese Patent Application Laid-open No. 49-7526. Test II4 is widely accepted.

On the other hand, as a method for directly forming fibers from polycarboxylic acids such as polyacrylic acid or their salts (hereinafter abbreviated as polycarboxylic acids (salts)) without chemical modification as described above, there is a method disclosed in Japanese Patent Application Laid-Open No. 54 In Publication No. 138622, an aqueous solution of an alkali metal salt of acrylic acid is spun into a mixed bath of an organic solvent and water through a spinning nozzle, and after being shaped into a fiber,
Furthermore, Japanese Patent Application Laid-Open No. 63-28912 proposes dry spinning a highly concentrated aqueous solution containing polycarboxylic acid and polyhydric alcohol as essential components, followed by heat treatment.

[Problem to be solved by the invention]

However, there are the following problems in producing sheet-like products such as nonwoven fabrics from directly fiberized polycarboxylic acids (salts).

That is, polycarboxylic acids (salts) inherently have strong hydrogen bonds and cannot be hot-stretched, so even if they are made into fibers directly by the method described above, they have the disadvantage of lacking fiber strength and being stiff and brittle when dry. There is. Therefore, it has been extremely difficult to defibrate and card these fibers to make sheet-like products such as webs and nonwoven fabrics.

[Means to solve the problem]

As a result of intensive studies to overcome the above-mentioned difficulties, the inventors of the present invention have developed a highly water-absorbing ability by applying surfactant treatment and humidification treatment to polycarboxylic acid (salt) fibers. The present invention was achieved based on the discovery that it is possible to produce a sheet-like product with a flexible texture and a flexible texture.

That is, the present invention provides a highly water-absorbent fiber sheet material characterized by being made of a polycarboxylic acid (salt) containing 5 to 80% by weight of water.

In the present invention, polycarboxylic acids (salts) include acrylic acid (salts), methacrylic acid (salts), and crotonic acid (salts).
, polymers or copolymers of ethylenically unsaturated carboxylic acids (salts) such as itaconic acid (salts), maleic acid (salts), fumaric acid (salts); these ethylenically unsaturated carboxylic acids (salts)
and ethylenically unsaturated carboxylic acid esters such as 2-hydroquine ethyl acrylate, 2-hydroxyethyl methacrylate, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, methyl acrylate, methyl methacrylate, ethyl acrylate, and ethyl methacrylate, vinyl acetate, and propion. Copolymers with vinyl esters such as vinyl acid and vinyl stearate, ethylenically unsaturated monomers such as styrene, styrene sulfonic acid, acrylamide, methacrylamide, and acrylonitrile; saponified vinyl acetate-methyl acrylate copolymers; Saponified vinyl acetate-maleic anhydride copolymer, saponified isobutylene-maleic anhydride copolymer, starch-acrylic acid graft polymer, tJ!
Examples thereof include 14-acrylic acid graft polymer, saponified starch-acrylonitrile graft polymer, and the like. These may be linear polymers or suitably crosslinked. As the salt, alkali metal salts, ammonium salts, amine salts, etc. can be selected as appropriate, and the degree of neutralization can be selected arbitrarily. Among these, polyacrylic acid (salt) type is particularly preferred from the viewpoint of high water absorption.

The method for producing these polycarboxylic acids (salts) is not particularly limited, and conventionally known methods such as solution polymerization, suspension polymerization, reverse phase suspension polymerization, and precipitation polymerization can be appropriately selected.

When the above-mentioned polycarboxylic acid (salt) is made into fibers, a solution of the polymer (mainly water) is mixed with a cross-linking agent or a plasticizer, if desired, and wet-spinning or dry-spinning is carried out. be exposed.

In the present invention, the fibers thus obtained are made to contain a specific amount of water and then molded into a desired shape. As a method for adding moisture to the fibers, a method of supplying water vapor or mist (fine droplets), that is, a humidification process is preferable.

If water is simply supplied in the form of droplets or fluid, water will be contained only on the surface or unevenly, causing stickiness and local swelling, making processing such as defibration and carding difficult.

On the other hand, when the fiber is subjected to humidification treatment, it is possible to uniformly absorb water from the inner layer to the outer layer of the fiber.

The humidification treatment method includes a method of passing the spun fibers through a mist, and a method of passing the spun fibers through a mist.
Examples include a method of leaving the fibers in a space whose humidity is adjusted to %RH or higher. The temperature during the treatment is usually about room temperature to 40°C, but it may be carried out at a higher temperature as long as it does not impede the performance of the product.

In the above humidification treatment, the moisture content of the fibers needs to be adjusted to a range of 5 to 80% by weight, preferably 10 to 50% by weight, based on the weight of dry fibers. If the moisture content is too low, the fibers will be stiff and brittle, making it impossible to form them into a sheet using the dry method.On the other hand, if the moisture content is too high, the fiber strength will decrease,
This is undesirable because it causes shape changes such as thread breakage during molding.

Therefore, the time for the humidification treatment may be appropriately set to a period until the fiber reaches a suitable moisture content. The moisture content of the fibers can be determined by appropriately measuring the weight of the fibers during the humidification process.

It is preferable to treat the spun fibers with a surfactant prior to such humidification treatment, as this will significantly improve processability when forming the fibers into a sheet after the humidification treatment.

The surfactant is preferably an anionic and/or nonionic surfactant.

Specifically, anionic surfactants include sulfate ester salts (higher alcohol sulfate sulfates, higher alkyl ether sulfates, sulfated fatty acid esters, sulfated olefins, etc.), sulfonates (sodium alkylbenzene sulfonate, α -olefin sulfonates, etc.), phosphate ester salts, etc. Nonionic surfactants include higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, fatty acid ethylene oxide adducts, sorbitan fatty acid esters and their ethylene oxide adducts, glycerin Examples include fatty acid esters and polyglycerin fatty acid esters.

These surfactants may be used alone or in combination of two or more. Although the method of treatment is not particularly limited, for example, the superabsorbent fibers are immersed in a solution of the above-mentioned surfactant dissolved in methyl alcohol, ethyl alcohol, etc., squeezed, and then dried. This treatment causes the surfactant to adhere to the surface of the fibers. The adhesion amount is usually 0.1% by weight or more, preferably 0.1 to 5% by weight based on the weight of the dry fiber.
is within the range of

If the amount of adhesion is less than 0.1% by weight, frictional charging of the fibers is likely to occur during processing, and roll slippage may occur due to poor slippage, making it difficult to form a web.

On the other hand, if the amount of adhesion is too large, the fiber surface becomes sticky due to the surfactant itself and moisture absorption, which is not preferable.

During this surfactant treatment, it is also possible to contain a portion of the water to be impregnated in the subsequent humidification treatment.

As a method for forming the fibers subjected to the above treatment into a sheet shape, a method known as a method for producing nonwoven fabrics can be applied. For example, by passing the fibers through a roller card machine,
Methods include forming an aligned web after fibrillation, or subsequently applying knee punching to increase the density of the web and give it stiffness.

In this way, the fibers treated according to the present invention can be formed into products such as webs (cotton-like forms) and non-woven fabrics, as well as forms such as paper sheets and knitted fabrics using ordinary fiber processing methods. be able to.

The obtained sheet material has high water absorption performance, which is an inherent property of polycarboxylic acid (salt), and can be used as it is or mixed with other hydrophilic or hydrophobic fibers, and further subjected to surface treatment if desired. It can be used in a wide range of applications by processing it by laminating, cutting, twisting, bonding using adhesives, etc.

For example, disposable diapers, sanitary products, absorbent paper, water retention materials for agriculture and horticulture, soil improvement materials, freshwater preservation materials, sealing materials, oil/water separation materials, heat retention and
Can be applied to cold insulation materials, etc.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples.

Incidentally, the water absorption amount and moisture content described in the Examples were measured by the following method. Furthermore, in the examples, "parts" and "U%" are based on weight unless otherwise specified.

Weigh out approximately 1 g (IL) of the water absorption test piece and add it to 100 g of physiological saline.
ml for 30 minutes to absorb water, then filtered through an 80-mesh wire mesh, and the weight (W2) of the swollen fiber sheet obtained as a filter cake was measured and calculated from the next generation. did.

z Water absorption - W.

Weigh out approximately 1 g (L) of water jm test piece and place it in a vacuum dryer at 105
"C" for 4 hours, and the volatilization N!jt (oath) was determined.

Example 1 For 20 parts of polyacrylic acid with a molecular weight of 250,000, 27.8
1 part of 30% caustic soda and 125 parts of water were uniformly dissolved in a Nigu, and heated and defoamed at 100'C overnight to obtain an aqueous solution of sodium polyacrylate with a degree of neutralization of 75 mol%. Next, after cooling this aqueous solution, 0.5 part of ethylene glycol diglycidyl ether was added and mixed uniformly with a roll mill to obtain a spinning stock solution.

The spinning stock solution prepared in this manner was
Extruded into an ethanol coagulation bath through a nozzle of 200
After passing through a heating furnace at °C for 15 seconds, the spinning speed was 12 m.
It was wound onto a roller at a speed of /min.

This fiber was immersed in a 1% ethanol solution of polyoxyethylene lauryl ether (Emulken 108; manufactured by Kao ■), and after adhesion was 100% based on the weight of the dry fiber, 1
It was dried with hot air at 00'C.

Thereafter, it was humidified at 30°C/80% R1+ for 13 hours, cut into lengths of about 5 cm, defibrated and carded using a roller card machine, and made into a web. This web had a bulky and soft texture, and had a moisture content of 20%. Moreover, the water absorption amount was 50 g/g.

Example 2 Dry spinning was carried out by extruding the same spinning dope as in Example 1 through a nozzle with a hole diameter of 1fflI11 and a number of holes of 20 into a dry air stream at 200°C.

The fibers were immersed in a 1% ethanol solution of polyoxyethylene oleyl ether (Emulken 409P; manufactured by Kao ■) to adhere to the solution at 150% based on the weight of the dry fibers, and then dried with hot air at 100°C.

Thereafter, it was humidified at 30°C/80% R11 for 18 hours, cut into lengths of about 5 cm, defibrated and carded using a roller card machine, and made into a web. This web was needle punched using a needle punch machine to obtain a nonwoven fabric.

The water content of this nonwoven fabric was 35%, and the water absorption amount was 52 g/g.

Example 3 20% sodium acrylate aqueous solution (degree of neutralization 75 mol%) 5
00 parts, 5.5 parts of methoxypolyethylene glycol #400 acrylate (NK ester AMiOG; manufactured by Shin Nakamura Chemical Industry ■) and 0 parts of azobiscyanovaleric acid as an initiator.
．． 348 parts were added and polymerized at 65°C for 2 hours under a nitrogen atmosphere. Next, after cooling this aqueous solution, 2 parts of ethylene glycol diglycidyl ether was added and uniformly mixed using a roll mill to obtain a spinning stock solution.

The spinning dope thus prepared was wet-spun in the same manner as in Example 1.

This fiber was immersed in a 1% ethanol solution of polyoxyethylene lauryl ether (Emulken 108; manufactured by Kao ■), and after adhesion was 120% based on the weight of the dry fiber, 1
It was dried with hot air at 00''C.

Thereafter, it was humidified at 30°C/80% R11 for 22 hours, cut into lengths of about 5 cans, defibrated and carded using a roller card machine, and made into a web. This web has a bulky and flexible texture and has a moisture content of 40%.
Met. Moreover, the water absorption amount was 43 g/g.

Example 4 20% sodium acrylate aqueous solution (degree of neutralization 75 mol%) 5
00 parts of 2-hydroxyethyl methacrylate) 16.3
8 parts, 0.384 parts of azobiscyanovaleric acid as an initiator, and 15.52 parts of ion-exchanged water were added, and under a nitrogen atmosphere, 65
Polymerization was carried out at °C for 2 hours. Next, after cooling this aqueous solution,
Two parts of ethylene glycol diglycidyl ether were added and uniformly mixed using a roll mill to obtain a spinning dope.

The spinning dope thus prepared was wet-spun in the same manner as in Example 1.

The fibers were immersed in a 1% ethanol solution of polyoxyethylene oleyl ether (Emulgen 409P i manufactured by Kao ■) so that the fibers adhered at 130% based on the weight of the dry fibers, and then dried with hot air at 100°C.

After that, it was humidified for 30 hours at 30°C/80% R11, and this was 5CII! It was cut into lengths, defibrated and carded using a roller card machine, and made into a web. This web had a moisture content of 50% and had a bulky and soft texture.

Moreover, the water absorption amount was 40 g/g.

Example 5 Sodium polyacrylate fiber subjected to surfactant treatment and humidification treatment of Example 1 (cut into 5 cry pieces, water content 20%)
50 parts and polyester fiber (3 denier 151 mm) 5
Part 0 was defibrated and carded using a roller card machine to form a composite web. This web had a bulky and flexible texture. Moreover, the water absorption amount was 25 g/g.

Example 6 86.09 parts of vinyl acetate, 98.06 parts of maleic anhydride, and 0.61 parts of benzoyl peroxide as an initiator were dissolved in 576 parts of benzene and polymerized at 60''C for 3 hours under a nitrogen atmosphere. Benzene was distilled off under reduced pressure at 80°C, and 86.92 parts of the resulting dry polymer was neutralized with 436 parts of a 7% aqueous sodium hydroxide solution.Next, 1.7 parts of ethylene glycol diglycidyl ether was added to this aqueous solution. The mixture was added and mixed uniformly using a roll mill to obtain a spinning stock solution.

The spinning dope thus prepared was wet-spun in the same manner as in Example 1.

The fibers were immersed in a 1% ethanol solution of polyoxyethylene lauryl ether (Emulgen 108; manufactured by Kao ■), and 100% of the weight of the dry fibers was adhered to the fibers.
It was dried with hot air at 00°C.

Thereafter, it was humidified at 30°C/80% R1+ for 13 hours, cut into lengths of about 5 cm, defibrated and carded using a roller card machine, and made into a web. This web had a bulky and soft texture, and had a moisture content of 20%. Moreover, the water absorption amount was 40 g/g.

Example 7 1204 parts of toluene and 205.9 parts of maleic anhydride were put into a 22-separable flask equipped with a stirring device, a gas introduction pipe, a thermometer, and a cooling pipe, and a gas bag was attached to the end of the cooling pipe, and a nitrogen atmosphere was placed. The temperature was raised to 70'C under stirring. 3.43 parts of 2.2''-azobisisobutyronitrile was added as a polymerization initiator, and then isobutylene gas from a separately prepared cylinder was introduced into the solution through a gas introduction tube.The reaction temperature was raised to 70°C. 135 parts of isobutylene gas was added in 3 hours (molar ratio to maleic anhydride: 1.14)
was continuously blown. The mixture was further aged at that temperature for 3 hours with stirring, and then cooled. A slurry-like reaction solution containing polymer precipitate was taken out, filtered, and then dried under reduced pressure at 70°C for 24 hours.

A 30% aqueous sodium hydroxide solution was added to 25.7 parts of the above dry polymer, and 75% of the maleic anhydride unit was added.
Neutralize, add 69.43 parts of ion-exchanged water, and
It was made into a 0% aqueous solution. Next, 0.5 parts of ethylene glycol diglycidyl ether was added to this aqueous solution, and the mixture was uniformly mixed using a roll mill to obtain a spinning dope.

The spinning dope thus prepared was wet-spun in the same manner as in Example 1.

The fibers were immersed in a 1% ethanol solution of polyoxyethylene lauryl ether (Emulgen 108; manufactured by Kao (I(1)) to adhere to the fibers at 120% based on the weight of the dry fibers, and then dried with hot air at 100°C. .

Thereafter, it was humidified with 30"C/80% l?I for 18 hours, cut into lengths of about 5cm, defibrated and carded using a roller card machine, and made into a web. This web had a water content of 35%. %, and had a bulky and soft texture. Also, the water absorption amount was 36 g/g.

Comparative Example 1 When the sodium polyacrylate fiber (water content 4%) before surfactant treatment in Example 1 was defibrated and carded using a roller card machine, it fell off the roll and did not form a web.

Comparative Example 2 When the sodium polyacrylate fiber (water content 3%) obtained by dry spinning in Example 2 was defibrated and carded using a roller card machine, it fell off the roll and did not form a web.

〔Effect of the invention〕

According to the present invention, super absorbent fibers made of polycarboxylic acid (salts), which have conventionally been difficult to process into forms such as webs and non-woven fabrics, can be used to produce webs, non-woven fabrics, paper sheets, and knitted fabrics. It has become possible to process it into a sheet like this.

In addition, the super absorbent fiber sheet obtained by the present invention has a high water absorption capacity comparable to that of granular water absorbent resin, has a flexible texture, and can be processed into various shapes. It can be combined with other fiber materials if necessary.

The super absorbent fiber sheet of the present invention can be applied not only to fields where conventional granular water absorbent resins have been used, but also to fields where the form of textile products is suitable, and is extremely useful industrially. be.

Claims (4)

[Claims] 1. A superabsorbent fiber sheet comprising polycarboxylic acid or a salt thereof containing 5 to 80% by weight of moisture. 2. The superabsorbent fiber sheet according to claim 1, wherein the polycarboxylic acid or its salt is polyacrylic acid or its salt. 3. 2. The method according to claim 1, wherein an anionic and/or nonionic surfactant is attached to superabsorbent fibers made of polycarboxylic acid or a salt thereof, and then subjected to a humidification treatment and formed into a sheet shape. A method for producing a super absorbent fiber sheet. 4. 4. The method for producing a superabsorbent fiber sheet according to claim 3, wherein the polycarboxylic acid or its salt is polyacrylic acid or its salt.