JPH0455592B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a salt-resistant water absorbent article. More specifically, it is a fibrous or sheet-like water absorbing material that absorbs large amounts of aqueous liquids even when it comes into contact with aqueous liquids containing polyvalent metal ions, such as seawater or groundwater, and whose water absorption capacity does not decrease over time. It concerns sexual articles. (Prior Art) In recent years, water-absorbing acrylic fibers have been developed, and applications such as sealing materials have been proposed. These water-absorbing acrylic fibers include hydrolyzed acrylic synthetic fibers made of acrylonitrile (co)polymer (JP-A-57-82567, JP-A-55-98915).
No.) and acrylic water-absorbing fibers made of acrylonitrile-acrylic acid copolymer (Japanese Patent Application Laid-open No. 61-239034
No.) has been proposed. However, these water-absorbing fibers have poor salt resistance, so when they come into contact with aqueous liquids containing polyvalent metal ions, they do not exhibit sufficient absorption capacity or their absorption capacity decreases over time. There are drawbacks. Further, these conventional sheet-like articles using water-absorbing fibers also have poor salt resistance. (Problems to be Solved by the Invention) The present inventors have conducted intensive research to develop a fibrous or sheet-like water-absorbent article with salt resistance that can solve the above-mentioned problems, and as a result, the present invention has been developed. It was completed. Therefore, an object of the present invention is to provide water-absorbing fibers and water-absorbing fibers that exhibit sufficient absorption capacity even for aqueous liquids containing polyvalent metal ions such as seawater and groundwater, and that do not lose their absorption capacity over time. The goal is to provide sex sheets. (Means and effects for solving the problems) The present invention provides 0.5mg of sulfonic acid group or its salt.
An organic compound consisting of a (meth)acrylic acid ester copolymer containing 1 mg equivalent/g or more of hydrophilic groups per 100 parts by weight of a crosslinked polymer containing 1.0 mg equivalent/g or more of a dissociative group. The present invention relates to a water-absorbing article in which the crosslinked polymer is fixed on the surface of fibers or sheets by using 5 to 1000 parts by weight of a polymeric binder. Examples of the sulfonic acid group or its salt contained in the crosslinked polymer used in the present invention include sulfonic acid groups and metal salts of sulfonic acid groups such as sodium salts, potassium salts, calcium salts, magnesium salts, and zinc salts; Examples include ammonium salts of sulfonic acid groups and organic amine salts of sulfonic acid groups. Furthermore, the dissociative groups contained in the crosslinked polymer used in the present invention include anionic dissociative groups such as sulfonic acid groups, carboxylic acid groups and their metal salts, ammonium salts, and organic amine salts, as well as amines and quaternary Includes cationic dissociative groups such as ammonium salts. The crosslinked polymer used in the present invention must contain sulfonic acid groups or salts thereof in an amount of 0.5 mg equivalent/g or more and dissociable groups in an amount of 1.0 mg equivalent/g or more. If the amount of dissociable groups is less than 1.0 mg equivalent/g, the liquid absorbing ability of the resulting water absorbent article will be reduced. Furthermore, when the amount of sulfonic acid groups or their salts is less than 0.5 mg equivalent/g, the resulting water-absorbing article becomes susceptible to the effects of polyvalent metal salts and does not exhibit stable liquid-absorbing ability over a long period of time. The crosslinked polymer used in the present invention preferably has a water absorption capacity of 5 times or more of its own weight for deionized water. If the water absorption capacity is less than 5 times, the obtained water absorbent article may not be sufficiently effective even when used as a sealing material or the like. The crosslinked polymer used in the present invention can be prepared, for example, by a method of polymerizing a sulfonic acid group-containing unsaturated monomer (A) in the presence of a crosslinking agent (C) if necessary; A) and other polymerizable monomers (B)
A method of copolymerizing a polymerizable monomer (B) in the presence of a crosslinking agent (C) if necessary, and a polymer crosslinked product obtained by polymerizing a polymerizable monomer (B) in the presence of a crosslinking agent (C) if necessary. A method of sulfonating with a sulfonating agent such as sulfuric acid, sulfuric anhydride, 1,3-propanesultone, 1,4-butanesultone, etc. A method of sulfonating the linear polymer obtained by polymerizing the polymerizable monomer (B) with a crosslinking agent It can be produced by a method of reacting with (C) and simultaneously sulfonating with a sulfonating agent. Examples of the sulfonic acid group-containing unsaturated monomer (A) that can be used in producing the crosslinked polymer in the present invention include vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, 2-sulfoethyl (meth)acrylate, 3-sulfopropyl (meth)acrylate, 1-sulfopropan-2-yl (meth) Unsaturated sulfonic acids such as acrylate, 2-sulfopropyl (meth)acrylate, 1-sulfobutan-2-yl (meth)acrylate, 2-sulfobutyl (meth)acrylate, 3-sulfobutan-2-yl (meth)acrylate; Examples include alkali metal salts such as sodium and potassium, alkaline earth metal salts such as calcium and magnesium, other metal salts such as zinc, ammonium salts, and organic amine salts, and one or two types from these. The above can be used. Other polymerizable monomers (B) that can be used in the present invention include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, and citraconic acid; Carboxyl group-containing unsaturated monomers such as alkali metal salts, alkaline earth metal salts, ammonium salts or organic amine salts; (meth)acrylamide, (meth)acrylonitrile, vinyl acetate, N,N-dimethylaminoethyl (meth) ) Acrylate, 2-(methacryloyloxyethyl)
Water-soluble unsaturated monomers such as trimethylammonium chloride and vinylpyridine; hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polybutylene glycol mono (meth)acrylate, methoxypolyethylene glycol mono(meth)acrylate,
Methoxypolypropylene glycol mono(meth)
Acrylate, methoxypolybutylene glycol mono(meth)acrylate, ethoxypolyethylene glycol mono(meth)acrylate, ethoxypolypropylene glycol mono(meth)acrylate, ethoxypolybutylene glycol mono(meth)acrylate, methoxypolyethylene glycol/polypropylene glycol mono(meth)acrylate (meth)acrylic acid esters such as acrylate, phenoxypolyethylene glycol mono(meth)acrylate, benzyloxypolyethylene glycol mono(meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and Examples include hydrophobic unsaturated monomers such as styrene, vinyl chloride, and vinylidene chloride, and one or more of these can be used. Examples of the crosslinking agent (C) that can be used in the present invention include divinylbenzene, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and propylene glycol di(meth)acrylate. , polyethylene glycol (meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol di(meth)acrylate, N,N-methylenebisacrylamide, triallyl isocyanurate, trimethylolpropane diallyl ether Compounds having two or more ethylenically unsaturated groups in one molecule such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, diethanolamine, triethanolamine, polypropylene glycol, polyvinyl alcohol, Polyhydric alcohols such as pentaerythritol, sorbitol, sorbitan, glucose, mannitol, mannitan, sucrose, glucose; ethylene glycol diglycidyl ether, glycerin diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl Ether, neopentyl glycol diglycidyl ether, 1,6-
Examples include polyepoxy compounds such as hexanediol diglycidyl ether, trimethylolpropane diglycidyl ether, trimethylolpropane triglycidyl ether, and glycerin triglycidyl ether, and one or more of these can be used. When a polyhydric alcohol is used as a crosslinking agent, it is preferable to carry out post-polymerization heat treatment at a temperature of 150°C to 250°C, and when a polyepoxy compound is used, a temperature of 50°C to 250°C is preferable. Use of a crosslinking agent is preferable because the crosslinking density of the obtained crosslinked polymer can be freely controlled. The amount of crosslinking agent used is preferably 0.00001 to 0.00001 molar ratio to the monomer.
It is in the range of 0.3. The amount of crosslinking agent used is 0.3 in molar ratio
If the amount exceeds 100%, the crosslinking density of the resulting crosslinked polymer tends to become too high and the water absorption capacity tends to decrease. On the other hand, if the amount is less than 0.00001, the crosslinking density is too low and stickiness occurs after absorbing water, which may cause problems in handling. The polymerization method for obtaining the crosslinked polymer used in the present invention may be any conventionally known method, such as a method using a radical polymerization catalyst or a method of irradiating with radiation, electron beams, ultraviolet rays, etc. It will be done. Radical polymerization catalysts include hydrogen peroxide, peroxides such as benzoyl peroxide and kyumene hydroperoxide, azo compounds such as azobisisobutyronitrile, and radicals such as persulfates such as ammonium persulfate and potassium persulfate. Generating agents, these together with sodium bisulfite, L-
Redox initiators are used in combination with reducing agents such as ascorbic acid and ferrous salts. As the polymerization solvent, for example, water, methanol, ethanol, acetone, dimethylformamide, dimethyl sulfoxide, and mixtures thereof can be used. Although the temperature during polymerization varies depending on the type of catalyst used, a relatively low temperature is preferable because the molecular weight of the crosslinked polymer increases. However, in order to complete the polymerization, the temperature is preferably within the range of 20°C or higher and 100°C or lower. Although there is no particular restriction on the monomer concentration in the polymerization system, it is preferably in the range of 20 to 80% by weight, considering ease of control of the polymerization reaction, yield, and economy.
Various forms of polymerization can be adopted, including suspension polymerization, cast polymerization, and a method in which a gel-like water polymer is polymerized while being fragmented by the shearing force of a double-arm kneader (Japanese Patent Application Laid-open No. 34101/1983). is preferred. Examples of the organic polymer binder used in the present invention to fix the crosslinked polymer onto the fiber or sheet surface include polyurethane, polyester, polyamide, ethylene-vinyl acetate copolymer, and acrylic acid (co)polymer. , polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, polyacrylic acid ester, and the like. However, in order to increase the flexibility and absorption rate of the resulting water-absorbent article, it is necessary to use an organic polymer binder made of a (meth)acrylate copolymer containing 1 mg equivalent/g or more of hydrophilic groups. There is. Here, the (meth)acrylic acid ester copolymer is a copolymer derived from a monomer mixture containing (meth)acrylic acid ester as the main component, and the hydrophilic group is, for example, a sulfonic acid ester. and carboxylic acid groups and their metal salts, ammonium salts, and organic amine salts; cationic dissociative groups such as amines and quaternary ammonium salts; and nonionic groups such as hydroxyl groups and amide groups. can. The polymer crosslinker is fixed onto the fiber or sheet surface by using the binder.
Immobilization methods include, for example, applying a binder to the surface of fibers or sheets and then spraying the crosslinked polymer thereon, or applying a mixture of crosslinked polymer and binder to the surface of the fibers or sheet. Can be mentioned. The organic polymer binder is a crosslinked polymer 100
It is preferable to use 5 to 1000 parts by weight. If it is less than 5 parts by weight, the immobilization of the crosslinked polymer will be insufficient, and the crosslinked polymer will be likely to be missing from the resulting water absorbent article. Furthermore, if the amount exceeds 1000 parts by weight, it becomes difficult for the crosslinked polymer to fully exhibit its inherent liquid absorbing ability in a water absorbent article. When applying the polymer crosslinker and/or binder, a solvent may be used if necessary. Examples of solvents include water, methanol, ethanol, isopropyl alcohol, acetone,
dimethylformamide, dimethylacetamide,
Mention may be made of dimethyl sulfoxide, ethyl acetate, etc. and mixtures thereof. In addition, when fixing a crosslinked polymer with an organic polymer binder, the filler is fixed on the fiber or sheet surface together with the crosslinked polymer by mixing a filler with the crosslinked polymer and the binder. It's okay. Examples of the filler include inorganic substances such as silica, alumina, zeolite, and carbon black. Examples of the fibers for immobilizing the polymer crosslinker include synthetic fibers such as acrylic, nylon, and polyester; natural fibers such as cotton and wool; recycled fibers such as rayon; and inorganic fibers such as glass fiber. Further, as the sheet for immobilizing the polymer crosslinked material, for example, paper, woven fabric, and nonwoven fabric made of the above-mentioned fibers; polyester, polyvinyl chloride, polyethylene, polypropylene, polycarbonate,
Examples include plastic sheets such as cellophane and metal foils such as aluminum. (Effects of the Invention) The fibrous or sheet-like water-absorbing article of the present invention obtained as described above has excellent salt resistance, so it is not only resistant to sweat, blood, urine, groundwater, etc. It absorbs even aqueous liquids containing high concentrations of salts, such as seawater, at a high absorption rate and absorption rate, and has the property that its liquid absorption ability decreases over time. Therefore, the water-absorbing article of the present invention can be used as sealing materials and water-stopping materials for civil engineering and industrial use, water-stopping materials for optical and power cables, curing sheets for concrete, medical hygiene materials such as diapers and sanitary products, and agricultural and horticultural materials. Suitable for water retention materials, etc. Furthermore, since the water-absorbing article of the present invention has excellent hygroscopicity, it is suitable for use as a desiccant material, a dew-preventing material, and the like. (Examples) Hereinafter, the present invention will be explained in detail with reference to Examples, but the scope of the present invention is not limited only to these Examples. Reference example 1 21.6g of sodium salt of 2-sulfoethyl methacrylate in a 500ml cylindrical separable flask
(0.10 mol), methacrylic acid 21.5 g (0.25 mol), sodium methacrylate 70.2 g (0.65 mol), N,
N-methylenebisacrylamide 0.92g (0.006
mol) and 170 g of water were added and stirred to uniformly dissolve. After purging with nitrogen, heat to 40°C in a hot water bath, add 1.0 g of 10% ammonium persulfate aqueous solution and 0.5 g of 1% L-ascorbic acid aqueous solution,
Stirring was stopped to allow polymerization. After polymerization starts, heat is generated,
The temperature rose to 95°C after 30 minutes. After confirming that the temperature of the polymerization system had begun to drop, the water bath was raised to 90°C and heated for an additional hour. The obtained hydrogel of the crosslinked polymer was divided into small pieces, dried in a hot air dryer at 150° C. for 3 hours, and pulverized to obtain the crosslinked polymer (1). The physical properties of this crosslinked polymer (1) are shown in Table 1. Reference Example 2 157 g (0.07 mol) of ammonium 2-acrylamido-2-methylpropanesulfonate and 21.3 mol of acrylamide in a 500 ml cylindrical separable flask.
(0.30 mol), 0.31 g (0.002 mol) of N,N-methylenebisacrylamide, and 270 g of water were stirred and uniformly dissolved. Thereafter, polymerization, drying, and pulverization were performed in the same manner as in Reference Example 1 to obtain a crosslinked polymer (2). The physical properties of this crosslinked polymer (2) are shown in Table 1. Reference Example 3 220 ml of n-hexane was charged into a 500 ml four-necked flask equipped with a stirrer, a reflux condenser, a dropping funnel, and a nitrogen gas inlet tube, and 1.8 g of sorbitan monostearate was added and dissolved therein, followed by purging with nitrogen. In a dropping funnel, add 23.3 g (0.10 mol) of calcium salt of 3-sulfopropyl acrylate and 0.72 g of acrylic acid.
(0.01 mol), calcium acrylate 5.55g (0.05
mol), methacrylamide 4.25g (0.05mol), ethylene glycol diglycidyl ether 0.0174g
(0.0001 mol), 50 g of water and 0.05 potassium persulfate
After adding and dissolving the solution, nitrogen gas was blown into the aqueous solution to remove oxygen present in the aqueous solution. Next, the contents of the dropping funnel were added to the four-necked flask and dispersed, and the polymerization reaction was continued for 3 hours by maintaining the temperature of the polymerization system at 60 to 65°C in a hot water bath while introducing a slight amount of nitrogen gas. . Thereafter, n-hexane was distilled off under reduced pressure, and the remaining hydrogel of the crosslinked polymer was dried under reduced pressure at 90°C to obtain a crosslinked polymer (3). The physical properties of this crosslinked polymer (3) are shown in Table 1. Reference Example 4 In a 1000 ml cylindrical separable flask, 51 g (0.2 mol) of monoethanolamine salt of 2-sulfoethyl methacrylate, 4.3 g (0.05 mol) of methacrylic acid, 16.2 g (0.15 mol) of sodium methacrylate, and methoxypolyethylene glycol mono 216 g (0.4 mol) of methacrylate (containing an average of 10 ethylene oxide units per molecule), N,
N-methylenebisacrylamide 0.154g (0.001
mol) and 250 g of water were added and stirred to uniformly dissolve. Thereafter, polymerization, drying, and pulverization were performed in the same manner as in Reference Example 1 to obtain a crosslinked polymer (4). The physical properties of this polymer crosslinked product (4) are shown in Table 1. Reference example 5 18 g (0.25 mol) of acrylic acid and 70.5 mol of sodium acrylate in a 500 ml cylindrical separable flask
(0.75 mol), 0.92 g (0.006 mol) of N,N-methylenebisacrylamide, and 135 g of water were charged and stirred to uniformly dissolve them. Thereafter, polymerization, drying, and pulverization were performed in the same manner as in Reference Example 1 to obtain comparative polymer crosslinked product (1). The physical properties of this comparative crosslinked polymer (1) are shown in Table 1.

[Table] Examples 1 to 4 Average molecular weight of 60,000 obtained by polymerizing a monomer mixture consisting of 35% by weight of methyl methacrylate, 40% by weight of butyl acrylate, 15% by weight of acrylic acid, and 10% by weight of hydroxyethyl methacrylate.
After immersing a 3-denier acrylic fiber in a mixture of 20 g of polyacrylic acid ester, 40 g of each of the crosslinked polymers (1) to (4) obtained in Reference Examples 1 to 4, and 40 g of isopropyl alcohol, It was pulled up and immediately dried at 80°C for 10 minutes. The thus obtained fibrous absorbent article of the present invention
Each of (1) to (4) was immersed in synthetic seawater having the composition shown in Table 2, and the liquid absorption capacity after 1 hour and 30 days was measured using the following formula. In addition, water absorbent articles (1) to (4)
The amount of the polymer crosslinked material and polyacrylic acid ester (binder) attached per gram of acrylic fiber was also measured. The results are shown in Table 3. Absorption capacity (times) = Weight of water-absorbent article after immersion in synthetic seawater (g) / Weight of water-absorbent article before immersion in synthetic seawater (g) Comparative example 1 Comparative polymer crosslinked product obtained in Reference example 5 as a polymer crosslinked product A fibrous comparative water-absorbent article (1) was prepared in the same manner as in Examples 1 to 4 except that the body (1) was used.
The performance of this comparative water-absorbent article (1), such as liquid absorption capacity, was measured in the same manner as in Examples 1-4. The result is the third
Shown in the table.

【table】

[Table] Examples 5 to 8 Polyacrylic esters used in Examples 1 to 4
15g, polymer crosslinked product (1) obtained in Reference Examples 1 to 4
55g each of (4) and isopropyl alcohol
A mixed solution of 30g was applied to a 20μ thick polyester film using a bar coater. Then 80℃
The water-absorbent article of the present invention is dried in a sheet form for 10 minutes.
Obtained (5) to (8). The liquid absorption capacity of these water absorbent articles (5) to (8) was measured in the same manner as in Examples 1 to 4. Also,
Sheet-shaped water absorbent articles (5) to (8) Polymer crosslinked material and polyacrylic acid ester (binder) per 1 m ²
The amount of adhesion was also measured. Furthermore, by placing 800 cm ² of each of water absorbent articles (5) to (8) in a sealed container with an inner capacity of 2, and measuring the relative humidity inside the sealed container after 2 hours, the drying capacity of the water absorbent articles was determined. was evaluated. The results are shown in Table 4. In addition, the liquid absorption rate of the water absorbent article (5) was measured by the following method. As a result, after 1 minute of addition of synthetic seawater, 55μ
m, the liquid absorption rate was 190 μm after 30 minutes. Liquid absorption rate measurement method A water-absorbing article obtained by immobilizing a cross-linked polymer on a polyester film with an organic polymer binder is cut into a circle with a diameter of 80 mm, and the shape shown in Figure 1 is 40 mm deep and a base area of 50.2 mm. It was placed on the bottom of a cm ² cylindrical container 1, and the nonwoven fabric 4 was placed on top of it. Furthermore, 91.6
A lid 5 weighing 1.5 g was placed on top, a distance sensor 6 was placed on top of the lid 5, and 50 g of synthetic seawater was added to the container 1. One minute and 30 minutes after addition of the synthetic seawater, the distance that the water-absorbent article swelled by water absorption and pushed up the lid 5 was measured, and this was defined as the liquid absorption rate. Comparative Example 2 A sheet-shaped comparative water absorbent article (2) was produced in the same manner as Examples 5 to 8 except that the comparative crosslinked polymer (1) obtained in Reference Example 5 was used as the crosslinked polymer. . The performance of this comparative water-absorbent article (2), such as liquid absorption capacity, was measured in the same manner as in Examples 5-8. The results are shown in Table 4. Comparative Example 3 The polymer crosslinked product was the polymer crosslinked product (1) obtained in Reference Example 1, the organic polymer binder was ethylene-vinyl acetate copolymer (manufactured by Mitsui Polychemical Co., Ltd., EVAFLEX), and toluene was used as the solvent. A comparative water-absorbent article (3) in the form of a sheet was prepared in the same manner as in Examples 5 to 8 except for the use of the following materials. The liquid absorption capacity, amount of polymer crosslinked material and ethylene-vinyl acetate copolymer (binder) attached per 1 m ² , and liquid absorption rate of this comparative water-absorbent article (3) were measured in the same manner as in Examples 5 to 8. did. As a result, the liquid absorption rate was 6.5 times after 1 hour and 6.4 times after 30 days, the adhesion amount was 25.2 g/ ^m2 , and the liquid absorption rate was 6.5 times after 1 hour.
It was 14 μm and 30 minutes later it was 150 μm.

【table】 [Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a partially broken liquid absorption rate measuring device. 1... Container, 2... Polyester film, 3
...polymer crosslinked body + organic polymer binder, 4
...Non-woven fabric, 5...Lid, 6...Distance sensor.

Claims (1)

[Claims] 1 0.5mg equivalent/g of sulfonic acid group or its salt
An organic polymer made of a (meth)acrylic acid ester copolymer containing 1 mg equivalent/g or more of a hydrophilic group per 100 parts by weight of a crosslinked polymer containing 1.0 mg equivalent/g or more of a dissociative group. A water-absorbing article in which the polymer crosslinked product is fixed on the surface of fibers or sheets by using 5 to 1000 parts by weight of a binder.