JPH1060014A - Water-absorptive resin of high absorption rate and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water-absorptive resin that has a high water absorption rate under normal and higher pressure, can be easily dried and ground at low load, and is useful for hygienic materials by copolymerizing specific compounds in aqueous solution in the presence of a fluorine-based surfactant. SOLUTION: This water-absorptive resin of a high water absorption rate is obtained by copolymerizing (B) aqueous solution of (i) a water-soluble unsaturated monomer, preferably (meth)acrylic acid or (meth)acrylate, 1-(meth) acryloylmethane sulfonic acid or sulfonate, etc., and (ii) a crosslinkable monomer, preferably a compound having two or more ethylenic unsaturated groups in one molecule, for example, ethylene glycol di(meth)acrylate, in the presence of (A) a fluorine-based surfactant (e.g. fluoroalkyl 2-10C carboxylic acids) in a quantity of 0.0001-10 pts.wt. based on 100 pts.wt. of component B, while bubbling the reaction solution with an inert gas introduced into the solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high water absorption rate water absorbing resin and a method for producing the same. More specifically, the present invention relates to a water-absorbent resin which has a high absorption rate under no pressure and under pressure, is easy to dry, and has a small load during pulverization, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, water-absorbent resins have been developed which absorb water tens to hundreds of times as much as their own weight. Various water-absorbing resins have been used for applications requiring water absorption and water retention, such as in the field, industrial fields such as dew condensation prevention and cooling materials.

[0003] As such a water-absorbing resin, for example,
Hydrolyzate of starch-acrylonitrile graft polymer (JP-B-49-43395) and neutralized product of starch-acrylic acid graft polymer (JP-A-51-125468)
No.), saponified vinyl acetate-acrylate copolymer (JP-A-52-14689), hydrolyzate of acrylonitrile copolymer or acrylamide copolymer (JP-B-53-15959), or a mixture thereof. Cross-linked product, self-cross-linked sodium polyacrylate obtained by reverse phase suspension polymerization (JP-A-53-46389), cross-linked polyacrylic acid partially neutralized product (JP-A-55-84304)
No.) etc. are known.

The performance required of the water-absorbent resin differs depending on the application to be used, but the desired properties of the water-absorbent resin for sanitary materials include an absorption capacity under high pressure when in contact with an aqueous liquid. , Fast absorption rate, large liquid permeability and the like. However, the relationship between these properties does not always show a positive correlation, and it has been difficult to improve these properties at the same time.

[0005] As an attempt to increase the absorption rate of a water-absorbing resin, for example, in order to increase the surface area, an attempt has been made to reduce the particle size, granulate or scaly. However, in general, when the water-absorbent resin is formed to have a small particle size, the water-absorbent resin particles form so-called "mamako" upon contact with the aqueous liquid, and the absorption rate is reduced. When the water-absorbent resin is formed in the granulated material, a phenomenon occurs in which the granulated material itself changes into a “mamako” state by contact with the aqueous liquid, and the absorption rate is rather reduced. When the water-absorbent resin is formed into flakes, the absorption rate is improved, but the absorption rate is not sufficient to induce gel blocking. The resulting water-absorbent resins are necessarily bulky and uneconomical because they require larger transportation and storage facilities.

Further, a technique has been proposed in which molecular chains near the surface of the water-absorbent resin are cross-linked to increase the cross-linking density of the surface layer, thereby preventing generation of mamako and improving the absorption rate. Such a technique is disclosed in, for example, Japanese Patent Application Laid-Open No. 57-44627.
No., JP-A-58-42602, JP-B-60-1869.
0, JP-A-58-180233, JP-A-59-62
665 and JP-A-61-16903. These techniques have provided some improvement in absorption rates. However, these water-absorbent resins actually contain a considerable proportion of fine powder finer than the desired optimum particle size. Therefore, even when such a water-absorbent resin is used, a sufficient absorption rate cannot be obtained, and a decrease in liquid permeability due to gel blocking occurs.

However, these water-absorbing resins have insufficient water absorption rates under no pressure and under pressure, are difficult to dry, and have a large load during pulverization.
In addition, there is a problem that the pore size is not uniform and the water-soluble component of the water-absorbent resin is large.

[0008]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a water-absorbing resin having a high water absorption rate and a method for producing the same.

Another object of the present invention is to provide a water-absorbent resin which has a high water absorption rate under no pressure and under pressure, is easy to dry, and has a small load during pulverization, and a method for producing the same. Still another object of the present invention is to provide a water-absorbent resin having a large amount of water absorption and a small amount of a water-soluble component of the water-absorbent resin, and a method for producing the same.

[0010]

The above object is achieved by the following (1).
(11) is achieved.

(1) In the presence of a fluorine-based surfactant,
A process for producing a water-absorbing resin having a high water absorption rate, comprising subjecting a mixture of a water-soluble unsaturated monomer and a crosslinkable monomer to aqueous solution copolymerization.

(2) The above (1), wherein the amount of the fluorinated surfactant is 0.0001 to 10 parts by weight per 100 parts by weight of the total amount of the water-soluble unsaturated monomer and the crosslinkable monomer. Method for producing a water-absorbent resin having a high water absorption rate.

(3) The water-soluble unsaturated monomer is (meth) acrylic acid (salt), 2- (meth) acryloylethanesulfonic acid (salt), 2- (meth) acrylamido-2-methylpropanoic acid (salt) ), (Meth) acrylamide and methoxypolyethylene glycol (meth) acrylate,
At least one selected from the group consisting of N, N-dimethylaminoethyl (meth) acrylate and quaternary compounds thereof;
The method for producing a high water absorption rate water absorbent resin according to the above (1) or (2), wherein

(4) The above-mentioned (1), wherein the water-soluble unsaturated monomer contains (meth) acrylic acid (salt) as an essential component.
The method for producing a water-absorbent resin having a high water absorption rate according to any one of (1) to (3).

(5) The crosslinkable monomer is a compound having two or more ethylenically unsaturated groups in one molecule.
The method for producing a water-absorbent resin having a high water absorption rate according to any one of (1) to (4).

(6) The method for producing a water-absorbent resin having a high water absorption rate according to any one of the above (1) to (5), wherein the aqueous solution copolymerization is carried out while foaming the obtained copolymer.

(7) The method for producing a water-absorbent resin having a high water absorption rate according to the above (6), wherein the foaming is carried out by introducing an inert gas into the aqueous solution.

(8) The method for producing a water-absorbent resin having a high water absorption rate according to the above (6), wherein the foaming is carried out by high-speed stirring of the aqueous solution.

(9) The method for producing a water-absorbent resin having a high water absorption rate according to the above (6), wherein the foaming is carried out by adding a foaming agent to the aqueous solution during the polymerization.

(10) A method for producing a water-absorbent resin having a high water-absorbing rate, wherein the water-absorbent resin according to any one of the above (1) to (9) is further treated with a surface crosslinking agent.

(11) A water-absorbent resin having a high water absorption rate produced by the method according to any one of the above (1) to (10).

[0022]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a highly water-absorbent resin characterized in that a mixture of a water-soluble unsaturated monomer and a crosslinkable monomer is copolymerized in an aqueous solution in the presence of a fluorine-containing surfactant. It is a manufacturing method of.

Examples of these water-soluble unsaturated monomers include (meth) acrylic acid, (anhydride) maleic acid, fumaric acid, crotonic acid, itaconic acid, 2- (meth) acryloylethanesulfonic acid, (Meth) acryloylpropanesulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid, styrenesulfonic acid, and other anionic monomers and salts thereof; (meth) acrylamide, N-substituted ( Meth) acrylamide, 2-
Hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, N-vinylpyrrolidone,
Nonionic hydrophilic group-containing monomers such as N-vinylacetamide; N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl (meth) Specific examples include amino group-containing unsaturated monomers such as acrylamide, and quaternized products thereof. In addition, in an amount that does not extremely impair the hydrophilicity of the obtained polymer, for example, acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, vinyl acetate, and propionic acid A hydrophobic monomer such as vinyl may be used. One or more of these can be selected and used as the monomer component. However, considering the water absorption properties of the finally obtained water absorbing material, (meth) acrylic acid (salt), 2- (meth) acryloylethanesulfonic acid (salt), 2- (meth) acrylamido-2-methylpropanesulfonic acid (salt),
One or more selected from the group consisting of (meth) acrylamide, methoxypolyethylene glycol (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate or a quaternary compound thereof are preferable, and (meth) acrylic acid (salt Is more preferable. In this case, 30 to 90 mol% of (meth) acrylic acid
Is most preferably neutralized with a basic substance.

Examples of the crosslinkable monomer include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, and polyethylene glycol di (meth) acrylate.
Acrylate, trimethylolpropane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate,
Pentaerythritol tetra (meth) acrylate,
N, N'-methylenebis (meth) acrylamide, triallyl isocyanurate, trimethylolpropanedi (meth) allyl ether, triallylamine, tetraallyloxyethane, glycerolpropoxytriacrylate, etc. Compounds having at least one compound; ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, polyglycerin, propylene glycol, 1,
4-butanediol, 1,5-pentanediol, 1,
Polyhydric alcohols such as 6-hexanediol, neopentyl alcohol, diethanolamine, tridiethanolamine, polypropylene glycol, polyvinyl alcohol, pentaerythritol, sorbit, sorbitan, glucose, mannitol, mannitol, sucrose, glucose; ethylene glycol diglycidyl ether; Polyglycidyl ethers such as polyethylene glycol diglycidyl ether and glycerin triglycidyl ether; haloepoxy compounds such as epichlorohydrin and α-methylchlorohydrin; polyaldehydes such as glutaraldehyde and glyoxal; polyamines such as ethylenediamine; Calcium, calcium chloride, calcium carbonate, calcium oxide, magnesium borax,
Hydroxides, halides, carbonates, oxides, borates such as borax, metals such as magnesium oxide, aluminum chloride, zinc chloride, nickel chloride, etc. And one or more of these can be used in consideration of reactivity. However, a compound having two or more ethylenically unsaturated groups in one molecule may be used. Most preferably, it is used as a crosslinking agent.

The ratio of the crosslinkable monomer used in the present invention is 0.00 0.00 parts by weight per 100 parts by weight of the water-soluble unsaturated monomer.
It is 1 to 2 parts by weight, preferably 0.005 to 1 part by weight. That is, when the amount is less than 0.001 part by weight, the ratio of the water-soluble component in the obtained water-absorbent resin is large, so that the water absorption under sufficient pressure may not be maintained. The crosslink density is too high,
The water absorption of the resulting water-absorbent resin may be insufficient.

There are various fluorine-based surfactants used in the present invention. For example, a fluorine-based surfactant is a perfluoroalkyl group in which hydrogen of a lipophilic group of a general surfactant is replaced with fluorine. The surface activity is much higher.

When the hydrophilic group of the fluorinated surfactant is changed,
4 types of anionic, nonionic, cationic and amphoteric
Although there are types, a fluorocarbon chain having the same structure is often used for the hydrophobic group. Moreover, the carbon chain which is a hydrophobic group can be used whether it is linear or branched. The following are typical fluorine-based surfactants.

Fluoroalkyl (C ₂ -C ₁₀ ) carboxylic acid, disodium N-perfluorooctanesulfonylglutamate, 3- [fluoroalkyl (C ₆ -C ₁₁ )
Oxy] -1-alkyl (C ₃ ~C ₄₎ sodium sulfonate, 3- [.omega.-fluoroalkanoyl (C ₆ ~
C ₈₎ -N- ethylamino] -1-sodium sulfonate, N-[3- (perfluorooctane sulfonamide) propyl] -N, N-dimethyl -N- carboxymethylene ammonium betaine, fluoroalkyl (C ₁₁ -C ₂₀₎ carboxylic acids, perfluoroalkyl carboxylic acids (C ₇ ~C _13), perfluorooctane sulfonic acid diethanolamide, perfluoroalkyl (C ₄ ~
C ₁₂₎ sulfonate (Li, K, Na), N-propyl-N-(2-hydroxyethyl) perfluorooctane sulfonamide, perfluoroalkyl (C ₆ -C ₁₀₎
Al Hong amidopropyl trimethyl ammonium salts, perfluoroalkyl (C ₆ -C ₁₀₎ -N- ethylsulfonyl glycine salt (K), phosphate bis (N- perfluorooctylsulfonyl -N- ethylamino ethyl), monoperfluoroalkyl Alkyl (C6 -C16) ethyl phosphate, perfluoroalkyl quaternary ammonium iodide (trade name: Florado FC-135, cationic fluorine-based surfactant manufactured by Sumitomo 3M Limited), perfluoroalkyl alkoxylate (trade name: Florard F
C-171, a nonionic surfactant manufactured by Sumitomo 3M Ltd.), and potassium perfluoroalkylsulfonic acid (trade names: Florade FC-95 and FC-98, an anionic surfactant manufactured by Sumitomo 3M Limited).

These fluorinated surfactants are used in a total amount of water-soluble unsaturated monomer and crosslinking monomer of 10%.
It is 0.0001 to 10 parts by weight, preferably 0.0003 to 5 parts by weight per 0 parts by weight. That is, 0.000
If the amount is less than 1 part by weight, a sufficient effect of increasing the water absorption rate may not be obtained. On the other hand, if the amount exceeds 10 parts by weight, the effect corresponding to the added amount may not be obtained, which is uneconomical. It is.

Conventionally, it has been known to use a surfactant other than a fluorine-based surfactant in aqueous solution polymerization, but such a known technique does not improve the water absorption rate at all.

To carry out the method of the present invention, the above-mentioned water-soluble unsaturated monomer, crosslinkable monomer and fluorine-containing surfactant are dissolved in an aqueous medium to prepare an aqueous monomer solution. A necessary amount of a polymerization initiator is added, and if necessary, the mixture is heated to a predetermined temperature to carry out aqueous solution copolymerization.

Then, the obtained hydrogel polymer is shredded as necessary, and further dried, and the resulting dried product is pulverized to obtain a high-water-absorbing-speed water-absorbing resin.

In the aqueous solution copolymerization of the water-soluble unsaturated monomer and the crosslinkable monomer, any of continuous polymerization and batch polymerization may be employed. It may be carried out under any normal pressure. The polymerization is preferably performed under a stream of an inert gas such as nitrogen, helium, argon, or carbon dioxide.

In the case of aqueous polymerization, it is more preferable that the radical polymerization initiator is previously dissolved or dispersed in the aqueous monomer solution. Specific examples of the radical polymerization initiator include azo compounds such as 2,2′-azobis (2-amidinopropane) dihydrochloride; ammonium persulfate, potassium persulfate, sodium persulfate, hydrogen peroxide, and hydrogen peroxide. Peroxides such as benzoyl oxide, cumene hydroperoxide and di-t-butyl peroxide; and the above peroxides and reducing agents such as sulfites, bisulfites, thiosulfates, formamidinesulfinic acid and ascorbic acid. And a redox initiator obtained by combining the above.
These radical polymerization initiators may be used alone or in combination of two or more.

The amount of the radical polymerization initiator used relative to the total amount of the water-soluble unsaturated monomer and the crosslinkable monomer depends on the combination of these monomers and the radical polymerization initiator. It is preferably in the range of 0.001 to 5 parts by weight, more preferably in the range of 0.01 to 1 part by weight, based on 100 parts by weight of the total amount of the unsaturated monomer and the crosslinkable monomer. When the use amount of the radical polymerization initiator is less than 0.001 part by weight, the amount of unreacted unsaturated monomers increases, and therefore, the amount of residual monomers in the obtained water-absorbing resin increases, which is preferable. Absent. On the other hand, if the amount of the radical polymerization initiator exceeds 5 parts by weight, the amount of water-soluble components in the obtained water-absorbing resin increases, which is not preferable.

The temperature at the start of polymerization depends on the type of radical polymerization initiator used, but is preferably in the range of 0 to 50 ° C., and more preferably in the range of 10 to 40 ° C. The polymerization temperature during the reaction depends on the type of radical polymerization initiator used, but is preferably in the range of 20 to 110 ° C, and more preferably in the range of 30 to 90 ° C. When the temperature at the start of polymerization or the polymerization temperature during the reaction is out of the above range, (a) the amount of residual monomers in the obtained water-absorbing resin increases, and (b) foaming by the blowing agent described below. If it is performed, it becomes difficult to control it. (C)
An excessive self-crosslinking reaction may proceed to cause inconvenience such as a decrease in the water absorption of the water-absorbing resin.

The reaction time may be set according to the combination of the unsaturated monomer, the crosslinking agent, the radical polymerization initiator, or the reaction conditions such as the reaction temperature, and is not particularly limited.

The aqueous solution polymerization according to the present invention can be carried out while foaming the obtained copolymer. Foaming can be performed by a known method. For example, a solution containing a carboxylic acid monomer or a water-soluble salt thereof and a crosslinking agent is prepared, a carbonate-based blowing agent and a polymerization initiator are added to the solution to form a carbonated monomer solution, and the solution is polymerized. A method of forming a microporous hydrogel, pulverizing and drying the microporous hydrogel, and treating the surface with a crosslinking agent to obtain a superabsorbent polymer (Japanese Patent Laid-Open No. 5-23737)
No. 8 and JP-A-7-185331), a method of producing a microporous water-absorbent resin by polymerizing a water-soluble monomer while dispersing a volatile organic compound such as toluene (US Pat.
No. 354,290), a water-insoluble foaming agent is dispersed in a reaction mixture comprising a water-soluble monomer, a cross-linking agent and a water-soluble solvent using a surfactant, then foamed, and the monomer and the cross-linking agent are further reacted. Methods for producing superabsorbent resins (U.S. Pat.
No. 38,766) A method for producing a superabsorbent water-absorbent resin by copolymerizing a water-soluble monomer and a crosslinking agent using an azo initiator having a 10-hour half-life of 30 to 120 ° C. (WO95 / 17455), a method of obtaining a water-absorbing resin by copolymerizing a water-soluble monomer and a crosslinking agent in the presence of a blowing agent comprising an acrylate complex of an azo compound (WO96 / 17884), and the like.

Further, foaming is performed by adding an inert gas to the aqueous solution,
For example, the reaction is performed by introducing an inert gas such as air of nitrogen or carbon dioxide, or by stirring the aqueous solution at a high speed. Foaming can also be performed by adding a foaming agent to the aqueous solution during polymerization.

Examples of such foaming agents include sodium carbonate, potassium carbonate, ammonium carbonate, magnesium carbonate, calcium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, ammonium hydrogen carbonate, magnesium hydrogen carbonate, calcium hydrogen carbonate, zinc carbonate, Examples thereof include carbonates such as barium carbonate, dry ice, water-soluble azo polymerization initiators such as azobisamidinopropane dihydrochloride, dicarboxylic acids such as malonic acid, and volatile organic solvents such as trichloroethane and trifluoroethane. When a foaming agent is added, the amount used is in the range of 0 to 5 parts by weight, more preferably 0 to 1 part by weight, per 100 parts by weight of the total amount of the water-soluble unsaturated monomer and the crosslinkable monomer. Is appropriate.

The above-mentioned hydrogel containing cells is broken up into fragments of about 0.1 mm to about 50 mm by a predetermined method during or after the reaction, if necessary. Next, in order to foam the foam more efficiently, the hydrogel containing cells is dried. In addition, foaming with a foaming agent can be performed not at the time of reaction but at the time of drying.

The drying temperature is not particularly limited, but may be, for example, in the range of 100 to 250 ° C., more preferably in the range of 120 to 200 ° C. The drying time is not particularly limited, but is preferably about 10 seconds to 5 hours. Prior to drying, the hydrogel resin may be neutralized, or may be further crushed and fragmented.

Drying methods include heating drying, hot air drying,
Various methods such as reduced-pressure drying, infrared drying, microwave drying, drum dryer drying, azeotropic dehydration with a hydrophobic organic solvent, and high-humidity drying using high-temperature steam can be employed, and are particularly limited. Not something. Of the drying methods exemplified above, hot air drying and microwave drying are more preferred. When microwaves are applied to the hydrogel containing bubbles,
Since the bubbles expand several times to several tens times, it is possible to obtain a water-absorbing resin with a further improved water absorption speed.

When the hydrogel containing bubbles is microwave-dried, the thickness of the crushed hydrogel is preferably 3 mm or more, more preferably 5 mm or more, and more preferably 10 mm or more. More preferred. When the hydrogel is subjected to microwave drying, it is particularly preferable to form the hydrogel into a sheet having the above thickness.

By the above-mentioned polymerization, that is, by the above-mentioned production method, the water-absorbing resin having a high water absorption rate according to the present invention can be easily obtained at low cost. The above water-absorbent resin has an average pore diameter in the range of 10 to 500 μm, more preferably 20 to 4 μm.
Within the range of 00 μm, more preferably 30 to 300 μm
, Most preferably in the range of 40 to 200 μm. The average pore diameter is determined by performing image analysis of a cross section of the dried water-absorbent resin using an electron microscope. That is, a histogram representing the pore size distribution of the water-absorbent resin is created by performing image analysis, and the number average of the pore sizes is calculated from the histogram, whereby the average pore size is obtained.

The water-absorbing resin obtained by the above method is
Since it is porous with a large number of pores inside and on its surface, under no pressure and under pressure, the liquid conducting space necessary for the aqueous liquid to migrate into the water absorbent resin is sufficiently secured. I have. Therefore, it is excellent in liquid permeability and diffusibility of the aqueous liquid, and can improve a water absorption rate, a water retention ability, and the like by a capillary phenomenon. Further, since the water-absorbent resin of the present invention is porous, even when the shape of the water-absorbent resin is particulate, it is possible to maintain liquid permeability when the aqueous liquid passes between the particles. . If the average pore diameter is smaller than 10 μm, there is a possibility that the liquid permeability and the diffusivity of the aqueous liquid may deteriorate. In addition, the average pore size is 50
If it is larger than 0 μm, the water absorption rate may not be sufficiently improved.

The water-absorbent resin may be treated with a surface cross-linking agent to form a covalent bond (secondary cross-link), thereby further increasing the cross-link density near the surface. The surface cross-linking agent is not particularly limited as long as it is a compound having a plurality of functional groups capable of forming a covalent bond by reacting with a carboxyl group of the water-absorbing resin. By treating the water-absorbent resin with a surface cross-linking agent, the liquid-permeability, water-absorption rate, water-absorption amount under pressure, and liquid-permeability of the water-absorbent resin are further improved.

As the surface cross-linking agent, specifically, for example, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, 1,3
-Propanediol, dipropylene glycol, 2,
3,4-trimethyl-1,3-pentanediol, polypropylene glycol, glycerin, polyglycerin,
2-butene-1,4-diol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,2-
Polyhydric alcohol compounds such as cyclohexanediol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-oxypropylene block copolymer, pentaerythritol, sorbitol; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether; Epoxy compounds such as glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether and glycidol; ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylene Hexamine, polyethylene Polyamine compounds such as imines and polyamide polyamines; haloepoxy compounds such as epichlorohydrin, epibromohydrin and α-methylepichlorohydrin; condensates of the above polyamine compounds with the above haloepoxy compounds; -Tolylene diisocyanate,
A polyvalent isocyanate compound such as hexamethylene diisocyanate; a polyvalent oxazoline compound such as 1,2-ethylenebisoxazoline; a silane coupling agent such as γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltrimethoxysilane; 3-dioxolan-2
-One, 4-methyl-1,3-dioxolan-2-one, 4,5-dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolan-2-one, -Ethyl-1,3-dioxolan-2-one, 4
-Hydroxymethyl-1,3-dioxolan-2-one, 1,3-dioxan-2-one, 4-methyl-1,
3-dioxan-2-one, 4,6-dimethyl-1,3
-Dioxan-2-one, 1,3-dioxoban-2-
Alkylene carbonate compounds such as on; and the like, but are not particularly limited thereto.

Among the surface cross-linking agents exemplified above, polyhydric alcohol compounds, epoxy compounds, polyvalent amine compounds, condensates of polyamine compounds and haloepoxy compounds, and alkylene carbonate compounds are more preferable.

These surface crosslinking agents may be used alone or in combination of two or more. When two or more surface crosslinking agents are used in combination, the solubility parameter (S
By combining the first surface cross-linking agent and the second surface cross-linking agent having different P values), it is possible to obtain a water-absorbing resin having even more excellent water-absorbing properties. The above-mentioned solubility parameter is a value generally used as a factor indicating the breadth of a compound.

The first surface cross-linking agent is a compound capable of reacting with the carboxyl group of the water-absorbent resin and having a solubility parameter of 12.5 (cal / cm ³ ) ^1/2 or more.
For example, glycerin and the like correspond. The second surface cross-linking agent can react with a carboxyl group of the water-absorbing resin,
A compound having a solubility parameter of less than 12.5 (cal / cm ³ ) ^1/2 , such as ethylene glycol diglycidyl ether.

The amount of the surface cross-linking agent used with respect to the water-absorbing resin depends on the combination of the water-absorbing resin and the surface cross-linking agent.
Within the range of 01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight.
It may be within the range of parts by weight. By using the surface cross-linking agent within the above range, the water absorbing properties for body fluids (aqueous liquids) such as urine, sweat, menstrual blood, etc. can be further improved. If the amount of the surface crosslinking agent is less than 0.01 parts by weight,
The crosslink density near the surface of the water-absorbent resin can hardly be increased. If the amount of the surface cross-linking agent is more than 5 parts by weight, the surface cross-linking agent becomes excessive, which is uneconomical and may make it difficult to control the cross-linking density to an appropriate value.

The treatment method when treating the water-absorbent resin with a surface crosslinking agent is not particularly limited. For example, a method of mixing a water-absorbing resin and a surface crosslinking agent without a solvent, a method of dispersing the water-absorbing resin in a hydrophobic solvent such as cyclohexane or pentane, and then mixing the surface crosslinking agent,
After dissolving or dispersing the surface crosslinking agent in the hydrophilic solvent,
A method of spraying or dropping the solution or dispersion onto the water-absorbent resin and mixing the solution or the dispersion may be used. The hydrophilic solvent is preferably water or a mixture of water and an organic solvent soluble in water.

Examples of the organic solvent include, for example, methyl alcohol, ethyl alcohol, n
-Propyl alcohol, iso-propyl alcohol,
n-butyl alcohol, iso-butyl alcohol, t
Lower alcohols such as -butyl alcohol; ketones such as acetone; ethers such as dioxane, ethylene oxide (EO) adduct of monohydric alcohol, and tetrahydrofuran; amides such as N, N-dimethylformamide and ε-caprolactam; And sulfoxides such as sulfoxide. These organic solvents may be used alone or in combination of two or more.

The amount of the hydrophilic solvent used for the water-absorbing resin and the surface cross-linking agent depends on the combination of the water-absorbing resin, the surface cross-linking agent and the hydrophilic solvent.
200 parts by weight or less, more preferably 0.1 part by weight based on parts by weight.
001 to 50 parts by weight, more preferably 0.1 to 50 parts by weight.
The amount may be in the range of from 50 to 50 parts by weight, particularly preferably in the range of from 0.5 to 20 parts by weight.

When the secondary crosslinking is carried out with the above-mentioned surface crosslinking agent, a heat treatment is carried out, if necessary, depending on the type of the surface crosslinking agent, so that the vicinity of the surface of the water-absorbent resin body is crosslinked. By performing the secondary crosslinking, it is possible to obtain a water-absorbent resin having an excellent absorption capacity under pressure.

The mixing device used for mixing the water-absorbing resin and the surface cross-linking agent preferably has a large mixing force in order to uniformly and surely mix the two. Examples of the mixing device include a cylindrical mixer, a double-walled conical mixer, a high-speed stirring mixer, a V-shaped mixer, a ribbon mixer, a screw mixer, and a fluidized furnace rotary desk type. Mixers, air-flow mixers, double-arm kneaders, internal mixers, pulverizing kneaders, rotary mixers, screw-type extruders and the like are preferred.

The treatment temperature and treatment time for treating the water-absorbent resin with the surface cross-linking agent may be appropriately selected and set according to the combination of the water-absorbent resin and the surface cross-linking agent, the desired crosslinking density, and the like. Although not particularly limited, for example, the processing temperature is preferably in the range of 0 to 250 ° C.

The above-mentioned water-absorbing resin may be further added to a deodorant, a fragrance, various inorganic powders, a foaming agent, a pigment, a dye, a hydrophilic short fiber, a plasticizer, an adhesive, a surfactant, if necessary. Fertilizers, oxidizing agents, reducing agents, water, salts, and the like may be added to impart various functions to the water-absorbing resin.

Examples of the inorganic powder include substances inert to aqueous liquids and the like, for example, fine particles of various inorganic compounds and fine particles of a viscous mineral. The inorganic powder preferably has an appropriate affinity for water and is insoluble or hardly soluble in water. Specifically, for example, metal oxides such as silicon dioxide and titanium oxide, silicic acids (salts) such as natural zeolite and synthetic zeolite, kaolin, talc, clay,
Bentonite and the like can be mentioned. Among them, silicon dioxide and silicic acid (salt) are more preferable, and silicon dioxide and silicic acid (salt) having an average particle diameter of 200 μm or less as measured by the Coulter counter method are more preferable.

The amount of the inorganic powder used for the water-absorbing resin is as follows:
Although it depends on the combination of the water-absorbent resin and the inorganic powder,
The amount may be in the range of 0.001 to 10 parts by weight, more preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the water absorbent resin. The mixing method of the water-absorbent resin and the inorganic powder,
There is no particular limitation, and for example, a dry blending method, a wet mixing method, or the like can be employed. However, it is preferable to employ a dry blending method.

The water-absorbent resin composition is compounded (combined) with a fibrous material such as pulp, for example.
It is an absorbent article.

Examples of the absorbent articles include sanitary materials (body fluid absorbent articles) such as disposable diapers, sanitary napkins, incontinence pads, wound protection materials and wound healing materials; absorbent articles such as urine for pets; Materials for civil engineering and construction such as water retention materials, water stop materials, packing materials, gel blisters, etc .; Food products such as drip absorbents, freshness retention materials, cold insulation materials; oil / water separation materials, dew condensation prevention materials,
Various industrial articles such as coagulants; agricultural and horticultural articles such as water retention materials such as plants and soil; and the like are not particularly limited. In addition, for example, a disposable diaper is formed by laminating a back sheet (back material) made of a liquid-impermeable material, the above-described water-absorbent resin composition, and a top sheet (surface material) made of a liquid-permeable material in this order. And a gather (elastic portion) or a so-called tape fastener or the like is attached to the laminate. Further, the disposable diaper also includes pants with a disposable diaper used when disciplining urination and defecation for infants.

The water absorbing resin thus obtained has a water absorption of 10 to 100 g / g, preferably 20 to 80 g / g.
g.

[0065]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the scope of the present invention is not limited to these Examples. Further,% in Examples and Comparative Examples means% by weight unless otherwise specified, and parts means parts by weight.

The amount of water absorbed, the rate of water absorption, and the amount of water-soluble components of the water-absorbing resin were measured by the following methods.

(1) Water Absorption of Water Absorbent Resin 0.2 g of the water absorbent resin is added to a tea bag type bag (6 cm × 6 c
m), heat-sealing the opening,
It was immersed in a 9% aqueous sodium chloride solution (physiological saline). After 60 minutes, the tea bag bag was pulled out and drained at 250 G for 3 minutes using a centrifuge, and then the weight W1 (g) of the bag was measured. The same operation was performed without using a water-absorbing resin, and the weight W0 (g) at that time was measured. The water absorption (g / g) was calculated from the weights W1 and W0 according to the following equation: water absorption (g / g) = (W1−W0) / weight (g) of the water-absorbing resin.

(2) Water Absorption Rate of Water Absorbing Resin A cylindrical polypropylene cup with an inner diameter of 50 mm and a height of 70 mm is filled with a water absorbing resin (600 μm in advance by a sieve).
A portion having a particle diameter in the range of ３００300 μm was collected and used as a sample. Next, 28 g of physiological saline was poured into the cup. Then, the time from when the physiological saline was poured to when the physiological saline was completely absorbed by the water-absorbent resin and disappeared was measured. The measurement was repeated three times, and the average value was taken as the water absorption rate (second).

(3) Amount of water-soluble component of water-absorbent resin 0.5 g of water-absorbent resin was dispersed in 1000 ml of deionized water, stirred for 16 hours, and filtered with a filter paper. Then, the obtained filtrate was titrated by colloid titration to determine the amount (%) of a water-soluble component in the water absorbent resin.

(Average Particle Diameter of Water Absorbent Resin) The average particle diameter is as shown below (850 μm, 600 μm, 30 μm).
(0 μm, 150 μm, 106 μm), the water absorbent resin was sieved and classified, and the residual percentage R was plotted on log probability paper, and the particle size corresponding to R = 50% was defined as the average particle size.

Example 1 153 parts of acrylic acid, 37% sodium acrylate 16
15 parts, 4.9 parts of polyethylene glycol (n = 8) diacrylate, 1.5 parts of a fluorinated anionic surfactant (trade name: Florade FC-95, manufactured by Sumitomo 3M Limited), and 710 parts of pure water An aqueous monomer solution was prepared. Remove the dissolved oxygen in the aqueous solution under a nitrogen stream,
Then, 10 parts of a 10% aqueous solution of sodium persulfate and 0.1 part of a 0.1% aqueous solution of sodium persulfate were added.
10 parts of a 4% L-ascorbic acid aqueous solution was added,
Polymerization was performed at 5 to 75 ° C for 3 hours. The hydrogel polymer obtained after the polymerization was shredded, and then dried in a hot-air dryer at 150 ° C. for 1 hour. The dried product is pulverized with a pulverizer,
The 50 μm sieved product was collected to obtain a water-absorbent resin (1) of the present invention having an average particle size of 440 μm. The water absorption amount, water absorption rate, and water-soluble component amount of the water absorbent resin (1) of the present invention were 36.7 g / g, 95 seconds, and 5.4%, respectively.

Example 2 153 parts of acrylic acid, 37% sodium acrylate 16
15 parts, 4.9 parts of polyethylene glycol (n = 8) diacrylate, 1.5 parts of a fluorinated nonionic surfactant (trade name: Florade FC-171, manufactured by Sumitomo 3M Limited), and 710 parts of pure water An aqueous monomer solution was prepared. Remove the dissolved oxygen in the aqueous solution under a nitrogen stream,
Then, 10 parts of a 10% aqueous solution of sodium persulfate and 0.1 part of a 0.1% aqueous solution of sodium persulfate were added.
10 parts of a 4% L-ascorbic acid aqueous solution was added,
Polymerization was performed at 5-75 ° C for 2 hours. After the polymerization, the hydrogel polymer obtained was shredded and then dried in a hot-air dryer at 150 ° C. for 1 hour. The dried product is pulverized with a pulverizer,
The 50 μm sieved product was collected to obtain a water-absorbent resin (2) of the present invention having an average particle size of 420 μm. The water absorption amount, water absorption speed and water-soluble component amount of the water-absorbent resin (2) of the present invention were 35.0 g / g, 90 seconds and 7.2%, respectively.

Example 3 153 parts of acrylic acid, 37% sodium acrylate 16
15 parts, 4.9 parts of polyethylene glycol (n = 8) diacrylate, 1.5 parts of a fluorinated cationic surfactant (trade name: Florard FC-135, manufactured by Sumitomo 3M Limited), and 710 parts of pure water An aqueous monomer solution was prepared. Remove the dissolved oxygen in the aqueous solution under a nitrogen stream,
Then 10 parts of a 10% aqueous sodium persulfate solution and 10 parts
10% aqueous sodium bisulfite solution at a temperature of 2
Polymerization was performed at 5 to 75 ° C for 3 hours. The hydrogel polymer obtained after the polymerization was shredded, and then dried in a hot-air dryer at 150 ° C. for 1 hour. The dried product is pulverized with a pulverizer,
A 50 μm sieve was collected to obtain a water-absorbent resin (3) of the present invention having an average particle diameter of 400 μm. The water absorption amount, water absorption rate and water-soluble component amount of the water-absorbent resin (3) of the present invention were 38.7 g / g, 98 seconds and 6.1%, respectively.

Example 4 153 parts of acrylic acid, 37% sodium acrylate 16
15 parts, 4.1 parts of polyethylene glycol (n = 8) diacrylate, 0.375 parts of a fluorinated cationic surfactant (trade name: Florade FC-135, manufactured by Sumitomo 3M Limited), and 0.75 parts of oxidized starch And pure water 71
An aqueous monomer solution containing 0 parts was prepared. Dissolved oxygen in the aqueous solution was removed while stirring the aqueous solution at a high speed under a nitrogen stream, and then 10 parts of a 10% aqueous sodium persulfate solution and 10 parts of a 10% aqueous sodium bisulfite solution were added under a high speed stirring, and the temperature was 25 to 75 ° C. For 3 hours. After the polymerization, the hydrogel polymer obtained was shredded and then cooled to 150 ° C.
For 1 hour in a hot air dryer. The dried product was pulverized with a pulverizer, and the material passed through a sieve having an opening of 850 μm was collected to obtain a water-absorbent resin (4) of the present invention having an average particle diameter of 200 μm. The water absorption amount, water absorption rate, and water soluble component amount of the water absorbent resin (4) of the present invention were 40.5 g / g, 27 seconds and 9, respectively.
8%.

Example 5 153 parts of acrylic acid, 37% sodium acrylate 16
15 parts, 4.8 parts of polyethylene glycol (n = 8) diacrylate, 0.0525 parts of a fluorinated cationic surfactant (trade name: Florade FC-135, manufactured by Sumitomo 3M Limited), and 710 parts of pure water An aqueous monomer solution was prepared. The dissolved oxygen in the aqueous solution is removed while stirring the aqueous solution at a high speed under a nitrogen stream.
10 parts of a 0% aqueous solution of sodium persulfate and 10 parts of a 10% aqueous solution of sodium bisulfite were added, and the temperature was 25 to 75.
The polymerization was carried out at room temperature for 2 hours. After the polymerization, the hydrogel polymer obtained was shredded and then dried in a hot-air dryer at 150 ° C. for 1 hour.
Dried for hours. The dried product is pulverized with a pulverizer, and the opening is 850.
The product having passed through the sieve having a size of μm was collected to obtain a water-absorbent resin (5) of the present invention having an average particle size of 320 μm. The water absorption amount, water absorption rate, and water-soluble component amount of the water absorbent resin (5) of the present invention were 36.0 g / g, 37 seconds, and 6.9%, respectively.

Example 6 100 parts of the water absorbent resin (4) of the present invention obtained in Example 4 was added to ethylene glycol diglycidyl ether (trade name: Denacol EX-810, manufactured by Nagase Kasei Co., Ltd.).
0.2 parts, pure water 9 parts, isopropyl alcohol 10 parts,
A crosslinker aqueous solution consisting of 2 parts of lactic acid and 0.02 part of polyoxyethylene sorbitan monostearate (trade name: Reodol TW-S120, manufactured by Kao Corporation) is added and mixed, and the mixture is heat-treated at 120 ° C. for 30 minutes, followed by the invention Water-absorbent resin (6) was obtained. Water absorption of the water absorbent resin (5) of the present invention,
The water absorption rate and the water-soluble component amount were 38.0 g /
g, 25 seconds and 6.7%.

Example 7 153 parts of acrylic acid, 37% sodium acrylate 16
15 parts, 4.9 parts of polyethylene glycol (n = 8) diacrylate, 1.5 parts of a fluorinated nonionic surfactant (trade name: Florade FC-171, manufactured by Sumitomo 3M Limited), and 710 parts of pure water An aqueous monomer solution was prepared. The dissolved oxygen in the aqueous solution was removed while stirring under a nitrogen stream, and then a 10% aqueous sodium persulfate solution was added.
And 10 parts of a 0.4% L-ascorbic acid aqueous solution were added, and polymerization was carried out at a temperature of 25 to 75 ° C. for 1 hour to obtain a shredded particulate hydrogel polymer. The obtained particulate hydrogel polymer was subjected to a hot air drying at 150 ° C. for 1 hour.
Dried for hours. The dried product is pulverized with a pulverizer, and the opening is 850.
The product having passed through the sieve having a size of μm was collected to obtain a water-absorbent resin (7) of the present invention having an average particle size of 420 μm. The water absorption amount, water absorption rate, and water-soluble component amount of the water-absorbent resin (7) of the present invention were 39.1 g / g, 90 seconds, and 4.0%, respectively.

Example 8 180 parts of acrylic acid, 37% sodium acrylate 19
An aqueous monomer solution containing 05 parts, 2.4 parts of polyethylene glycol (n = 8) diacrylate and 227 parts of pure water was prepared. While stirring, 600 parts of dry ice was added to remove dissolved oxygen in the solution and to dissolve carbon dioxide in the solution.

After the dry ice is completely dissolved, a fluorinated anionic surfactant (trade name: Florad FC-9)
5, manufactured by Sumitomo 3M Limited).
Subsequently, while maintaining the temperature of the solution at about 0 ° C., 12 parts of a 10% aqueous sodium persulfate solution, 5 parts of a 1% aqueous L-ascorbic acid solution and 1 part of a 1% aqueous Mohr salt solution were sequentially added with stirring.

Immediately after the addition of the initiator, the solution became cloudy and the polymerization started, and the stirring was stopped. After 20 minutes the temperature of the solution is 80
C. and the polymerization was continued for 20 minutes in a water bath at 60.degree. After the polymerization, a hydrogel containing bubbles was obtained, cut into a size of 5 mm square, and then dried in a hot air dryer at 160 ° C. for 1 hour. The dried product is pulverized with a pulverizer and the opening is 850 μm
Was filtered to obtain a water-absorbent resin (8) of the present invention having an average particle diameter of 400 μm. The water absorption amount, water absorption rate and water soluble component amount of the water absorbent resin (8) of the present invention are each 3
5.9 g / g, 60 seconds and 9.9%.

Comparative Example 1 153 parts of acrylic acid, 37% sodium acrylate 16
A monomer aqueous solution containing 15 parts, 4.9 parts of polyethylene glycol (n = 8) diacrylate, and 710 parts of pure water was prepared. The dissolved oxygen in the aqueous solution was removed while stirring under a nitrogen stream, and then a 10% aqueous sodium persulfate solution 1 was added.
0 parts and 10 parts of a 0.4% L-ascorbic acid aqueous solution were added, and the mixture was polymerized at a temperature of 25 to 75 ° C. for 3 hours to obtain a shredded particulate hydrogel polymer. The obtained particulate hydrogel polymer was dried in a hot air dryer at 150 ° C. for 1 hour. The dried product was pulverized with a pulverizer, and the material passed through a sieve having an opening of 850 μm was fractionated to obtain a comparative water absorbent resin (1) having an average particle diameter of 420 μm. The water absorption amount, water absorption rate and water-soluble component amount of the comparative water absorbent resin (1) were 37.0 g / g, 1
30 seconds and 4.9%.

Comparative Example 2 153 parts of acrylic acid, 37% sodium acrylate 16
A monomer aqueous solution containing 15 parts, 4.9 parts of polyethylene glycol (n = 8) diacrylate, and 710 parts of pure water was prepared. Dissolved oxygen in the aqueous solution was removed under a nitrogen stream, then 10 parts of a 10% aqueous sodium persulfate solution and 10 parts of a 10% aqueous sodium bisulfite solution were added, and polymerization was performed at a temperature of 25 to 75 ° C for 2 hours. The hydrogel polymer obtained after the polymerization was shredded, and then dried in a hot-air dryer at 150 ° C. for 1 hour. The dried product is pulverized by a pulverizer, and the material having passed through the sieve having an opening of 850 μm is fractionated to have an average particle diameter of 420 μm.
m of comparative water-absorbent resin (2) was obtained. The water absorption amount, water absorption rate and water-soluble component amount of the comparative water-absorbent resin (2) were 37.5 g / g, 112 seconds and 6.1%, respectively.

[0083]

According to the present invention, since the present invention is constituted as described above, the water absorption rate under no pressure and under pressure is high, the amount of water absorption is large, and the amount of water-soluble components is small. It can be suitably used for various applications that require water absorption or water retention, such as the field of sanitary materials, etc., the field of agriculture and horticulture, the food field such as keeping freshness, and the industrial field such as dew condensation prevention and cooling materials.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location C08F 220/06 MLR A61F 13/18 307A (72) Inventor Hideyuki Tahara 992 Nishioki, Okihama-shi, Abashiri-ku, Himeji-shi, Hyogo Address No. 1 Inside Nippon Shokubai

Claims (11)

[Claims] 1. A method for producing a water-absorbing resin having a high water absorption rate, comprising a step of subjecting a mixture of a water-soluble unsaturated monomer and a crosslinking monomer to aqueous solution copolymerization in the presence of a fluorine-containing surfactant. 2. The composition according to claim 1, wherein the amount of the fluorosurfactant is 0.0001 to 10 parts by weight per 100 parts by weight of the total amount of the water-soluble unsaturated monomer and the crosslinkable monomer. Water absorption rate A method for producing a water absorbent resin. 3. The water-soluble unsaturated monomer is (meth) acrylic acid (salt), 2- (meth) acryloylethanesulfonic acid (salt), or 2- (meth) acrylamido-2-methylpropanoic acid (salt). , (Meth) acrylamide and methoxypolyethylene glycol (meth) acrylate, N, N
The method for producing a water-absorbent resin having a high water absorption rate according to claim 1 or 2, wherein the resin is at least one member selected from the group consisting of -dimethylaminoethyl (meth) acrylate or a quaternary compound thereof. 4. The method for producing a water-absorbent resin having a high water absorption rate according to claim 1, wherein the water-soluble unsaturated monomer contains (meth) acrylic acid (salt) as an essential component. . 5. The method for producing a water-absorbent resin having a high water absorption rate according to claim 1, wherein the crosslinkable monomer is a compound having two or more ethylenically unsaturated groups in one molecule. . 6. The method for producing a water-absorbent resin having a high water absorption rate according to claim 1, wherein the aqueous solution copolymerization is carried out while foaming the obtained copolymer. 7. The method according to claim 6, wherein foaming is performed by introducing an inert gas into the aqueous solution. 8. The method according to claim 6, wherein the foaming is carried out by high-speed stirring of the aqueous solution. 9. The method according to claim 6, wherein the foaming is carried out by adding a foaming agent to the aqueous solution during the polymerization. 10. A method for producing a water-absorbent resin having a high water-absorbing rate, further comprising treating the water-absorbent resin according to claim 1 with a surface crosslinking agent. 11. A high water absorption rate water absorbent resin produced by the method according to claim 1.