JPH09278900A - Hydrophilic resin and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrophilic resin having a high absorption rate under pressure and showing excellent performances (water-absorbing properties) when used as e.g. a sanitary material even when it contains a hydrophilic polymer in a high concentration and to provide a process for producing the same. SOLUTION: A hydrophilic polymer is mixed with a powdery modifier prepared by converting a liquid modifier into a powder, and the resulting mixture is optionally heated to obtain a hydrophilic resin which shows excellent performances (water-absorbing properties) even when the concentration of the hydrophilic polymer is high. Examples of the methods for converting the liquid modifier into the powdery modifier include one comprising mixing the liquid modifier with a water-insoluble compound and one comprising cooling the liquid modifier to a temperature equal to or lower than its melting point.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hydrophilic resin and a method for producing the same. More specifically, the present invention relates to a hydrophilic resin preferably used for sanitary materials such as paper diapers (disposable diapers), sanitary napkins, so-called incontinence pads, etc., and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, sanitary materials such as disposable diapers, sanitary napkins and so-called incontinence pads have been used as constituent materials thereof.
BACKGROUND ART Water absorbent resins for the purpose of absorbing body fluids are widely used. Further, the water-absorbent resin is not only a hygienic material but also a wide range of applications as a constituent material such as a soil water retention material for the purpose of retaining water and a drip absorbent for the purpose of absorbing drip generated from food and the like. Is used for.

Examples of the above water-absorbent resin include cross-linked polyacrylic acid partially neutralized products, hydrolyzed products of starch-acrylonitrile graft polymer, neutralized products of starch-acrylic acid graft polymer, vinyl acetate-acrylic. Known are saponified products of acid ester copolymers, hydrolyzed products of acrylonitrile copolymers or acrylamide copolymers, crosslinked products thereof, and crosslinked products of cationic monomers.

The properties that the water-absorbent resin should have include high absorption capacity when contacted with an aqueous liquid such as body fluid, excellent absorption rate, liquid permeability, gel strength of swelling gel, and aqueous liquid. For example, suction force for sucking water from the base material can be used. However, these characteristics do not always show a positive correlation. For example, as the absorption capacity increases, the absorption rate, liquid permeability, gel strength, etc. decrease. Therefore, conventionally, a method of cross-linking the vicinity of the surface of the water-absorbent resin has been performed as a method of making (improving) the balance of the above-mentioned various properties favorable.

As a method of cross-linking with a cross-linking agent, for example, a method of using a polyhydric alcohol (Japanese Patent Application Laid-Open No. 5 (1999) -58242)
8-180233, JP-A-61-16903), polyvalent glycidyl compounds and polyvalent aziridine compounds,
Method using polyvalent amine or polyvalent isocyanate (JP-A-59-189103), method using glyoxal (JP-A-52-117393), method using polyvalent metal compound (JP-A-51-136588). Bulletin,
JP-A-61-257235 and JP-A-62-774.
5), a method using a silane coupling agent (JP-A-61-211305, JP-A-61-25221).
No. 2, JP-A-61-264006), a method of using an epoxy compound and a hydroxy compound (JP-A-2).
-132103), a method using alkylene carbonate (German Patent No. 4,020,780) and the like have been proposed.

Various methods have also been proposed in which the crosslinking agent is more evenly distributed on the surface of the water-absorbent resin in order to uniformly cross-link the surface of the water-absorbent resin. For example, when a cross-linking agent is added to a water-absorbent resin, an inert inorganic powder is allowed to coexist (JP-A-60-163956, JP-A-60-255814), and a dihydric alcohol is allowed to coexist. (JP-A-1-292004), a method of coexisting an ether compound (JP-A-2-153903), an alkylene oxide adduct of a monohydric alcohol,
Method of coexisting organic acid salt, lactam, etc. (European Patent No. 5
55,692) and the like.

[0007]

However, although the above-mentioned conventional method can make (improve) the balance of various properties which the water-absorbent resin should have to some extent, it is practically sufficient. It is hard to say that the balance can be improved. For example, in recent years, in sanitary materials, while the amount of water-absorbent resin used has increased, it has tended to be made thinner. However, in consideration of various characteristics desired for the constituent material of the sanitary material, that is, the water-absorbent resin used for the absorber, the conventional method described above cannot provide a practical balance. have. Therefore, there is a demand for a method capable of improving the balance of various properties to a practically sufficient state, that is, a method capable of achieving further high quality of the water absorbent resin.

For example, in an absorbent body containing a large amount of a water-absorbent resin, that is, a high concentration, properties generally desired for the water-absorbent resin include absorption capacity under pressure and water retention capacity. Absorption characteristics under pressure, or JP-A-5-961
No. 59, proposes a binding property and shape retention property during water absorption between water-absorbent resin particles, a binding property and shape retention property during absorption of an absorbent body composed of a water-absorbent resin and cellulose fibers, Etc. However, in order to further improve the absorption characteristics under pressure, the above-mentioned conventional method is insufficient. Further, when the method described in JP-A-5-96159 is adopted, there are disadvantages such that the water-absorbent resin falls off from the absorber during water absorption and the water-absorbent resin moves inside the absorber. Although it can be suppressed, it is difficult to improve the absorption capacity under pressure depending on the type of the water absorbent resin. Furthermore, after producing the water absorbent resin,
There is also a problem that the binding property of the water-absorbent resin deteriorates with the lapse of time until the water-absorbent resin is used.

The present invention has been made in view of the above conventional problems, and an object thereof is to have excellent absorption characteristics under pressure, such as absorption capacity under pressure and water retention capacity, and for example, hygiene. When used as a material or the like, a hydrophilic resin (water absorbing agent composition) capable of exhibiting excellent performance (absorption property) even if the weight% (resin concentration) of the hydrophilic polymer (water absorbing resin) is increased, And to provide a manufacturing method thereof.

Another object of the present invention is that it has excellent absorption characteristics under pressure, and that the hydrophilic polymer (water-absorbent resin) does not easily fall off from the absorber during absorption of water, and after production,
It is intended to provide a hydrophilic resin (water-absorbing agent composition) whose binding property does not change with time during use, and a method for producing the same.

[0011]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the inventors of the present application have made extensive studies on a hydrophilic polymer and a method for producing the same. As a result, a hydrophilic resin containing a hydrophilic polymer (for example, a water-absorbent resin) and a powdered modifier obtained by pulverizing a liquid modifier has an excellent balance of various properties and achieves the above object. I found that I can.
In addition, the hydrophilic resin can be easily obtained by a production method including a mixing step of mixing the hydrophilic polymer and the pulverizing modifier, and a heating step of heating the mixture as necessary. The present invention has been completed and the present invention has been completed.

That is, in the method for producing a hydrophilic resin according to the first aspect of the present invention, in order to solve the above-mentioned problems, a hydrophilic polymer and a pulverizing modifier obtained by pulverizing a liquid modifying agent are used. It is characterized by mixing. In order to solve the above-mentioned problems, the method for producing a hydrophilic resin according to a second aspect of the present invention is the method for producing a hydrophilic resin according to the first aspect.
It is characterized in that it is carried out by mixing a liquid modifier with a particulate water-insoluble compound. In order to solve the above-mentioned problems, the method for producing a hydrophilic resin according to a third aspect of the present invention is the method for producing a hydrophilic resin according to the first aspect. It is characterized in that it is performed by cooling to solidify. The method for producing a hydrophilic resin of the invention according to claim 4 is the method for producing a hydrophilic resin according to any one of claims 1 to 3, wherein a hydrophilic polymer and It is characterized in that a mixture of the powdering modifier is heated. The method for producing a hydrophilic resin of the invention according to claim 5 is the method for producing a hydrophilic resin according to any one of claims 1 to 3, wherein a hydrophilic polymer and The method is characterized in that a liquid or gaseous aqueous liquid is added to a mixture of the pulverizing modifier, and then the mixture is heated. The method for producing a hydrophilic resin of the invention according to claim 6 is the method for producing a hydrophilic resin according to any one of claims 1 to 5, wherein the hydrophilic polymer is the hydrophilic polymer. Is a water-absorbent resin having an acid group. In order to solve the above-mentioned problems, the method for producing a hydrophilic resin of the invention according to claim 7 is the method according to claims 1-6.
In the method for producing a hydrophilic resin according to any one of
The liquid modifier is characterized by containing a crosslinking agent.
In order to solve the above-mentioned problems, the method for producing a hydrophilic resin according to claim 8 is the method for producing a hydrophilic resin according to claim 7, wherein the crosslinking agent has a weight average molecular weight of 2,
It is characterized by containing 000 or more polyvalent amines.
In order to solve the above-mentioned problems, the powdered modification agent of the invention according to claim 9 is characterized by containing a liquid modification agent capable of reacting with an acid group and a particulate water-insoluble compound. In order to solve the above-mentioned problems, the powdered modifying agent of the invention of claim 10 is characterized in that, in the powdered modifying agent of claim 9, the liquid modifying agent contains a crosslinking agent.

In the conventional method, for example, when the water-absorbent resin is surface-crosslinked with a crosslinking agent, the crosslinking agent alone or its aqueous solution is mixed with the water-absorbent resin. Normal,
The cross-linking agent and its aqueous liquid are liquid at room temperature, and the cross-linking agent and the water absorbent resin have high affinity. Therefore, immediately after mixing the two, the cross-linking agent is absorbed by the water-absorbent resin,
Alternatively, the reaction between the crosslinking agent and the water absorbent resin may be started. Therefore, it is difficult to uniformly distribute the cross-linking agent on the surface of the water absorbent resin, and it is difficult to uniformly perform the surface cross-linking treatment.

On the other hand, according to the method of the present invention, the hydrophilic resin is produced by mixing the hydrophilic polymer and the powdered modifier obtained by powderizing the liquid modifier. Therefore, for example, when the powdering modifier is a mixture of a liquid modifier and a particulate water-insoluble compound, the liquid modifier in the powdering modifier is, for example, the surface of the water-insoluble compound and / Or inside. That is, according to the method of the present invention, the liquid modifier can be mixed with the hydrophilic polymer in a substantially solid state. Therefore, according to the above method, as compared with the case of mixing the liquid modifier and the hydrophilic polymer, the hydrophilic polymer and the liquid modifier, that is, the powdered modifier are uniformly mixed. You can In addition, in the mixture of the hydrophilic polymer and the powdering modifier, the hydrophilic polymer and the liquid modifier are separately present. That is, when the liquid modifier is pulverized and used as the powder modifier, the liquid modifier is immediately absorbed by the hydrophilic polymer even if the hydrophilic polymer and the powder modifier are mixed. Alternatively, the reaction between the modifier contained in the liquid modifier and the hydrophilic polymer is not started. Then, for example, when the hydrophilic resin is allowed to absorb an aqueous liquid, or when the hydrophilic resin is heated, for example, the hydrophilic polymer and the modifier contained in the liquid modifier come into contact with each other,
The hydrophilic polymer can be uniformly modified.

Also, when a powdered modifier obtained by cooling a liquid modifier below its melting point to solidify is used as the powdered modifier, the liquid modifier is substantially solid. In the state, it can be uniformly mixed with the hydrophilic polymer. Also in this case, since the liquid modifier forms a powdered modifier, in the hydrophilic resin, the hydrophilic polymer and the modifier in the liquid modifier are separately present until the reaction, There is nothing to do. Then, when the powdering modifier is melted, the hydrophilic polymer and the modifier react with each other, and the hydrophilic polymer is modified (for example, when the liquid modifier is a cross-linking agent, , Surface cross-linking treatment).

As described above, according to the above manufacturing method,
The hydrophilic polymer can be uniformly modified and the timing of the modification can be controlled. Therefore, according to the above-mentioned manufacturing method, various characteristics that are exhibited by modification, such as absorption capacity under pressure, can be improved. Therefore, according to the above method, a hydrophilic resin having an excellent balance of various properties can be easily obtained. Further, in particular, when the liquid modifier is a cross-linking agent containing a polyvalent amine, at the time of use, when the hydrophilic resin absorbs the aqueous liquid, the binding force between the hydrophilic polymer particles and the above-mentioned absorber Shape retention is expressed. Furthermore, when a cross-linking agent containing a polyvalent amine or the like is used as the liquid modifier, it is possible to control the timing of the reaction between the hydrophilic polymer particles due to the polyvalent amine, so that various properties including gel breaking force can be controlled. It is possible to more effectively prevent the deterioration of the characteristics due to aging.

In order to solve the above problems, the hydrophilic resin of the invention according to claim 11 is characterized in that it contains a hydrophilic polymer and a powdered modifier obtained by powderizing a liquid modifier. There is.

According to the above structure, the liquid modifier is powdered to form the powdered modifier. Therefore, the liquid modifier in the powdered modifier is contained in the hydrophilic resin in a substantially solid state. Further, since the liquid modifier forms a powdered modifier, in the hydrophilic resin, until used, the hydrophilic polymer and the modifier contained in the liquid modifier are present separately, It does not react. On the other hand, when the hydrophilic resin absorbs an aqueous liquid, or when the hydrophilic resin is heated, for example, the hydrophilic polymer and the modifier contained in the liquid modifier are brought into contact with each other to react, The functional polymer is modified (for example, surface crosslinking treatment is performed when the modifying agent is a crosslinking agent). Therefore, since the hydrophilic polymer can be uniformly modified and the timing of the modification can be controlled, it is possible to prevent deterioration of various properties developed by the modification due to aging. In particular, when the liquid modifier is a cross-linking agent containing a polyvalent amine or the like, it is possible to control the timing of ionic cross-linking of the hydrophilic polymer by the polyvalent amine or the like, and thus the above-mentioned changes in various properties over time. Can be prevented more effectively.

Therefore, according to the above-mentioned constitution, the absorbent polymer has excellent absorption characteristics under pressure, such as absorption capacity under pressure and water retention capacity, and, when it is used for sanitary materials, hydrophilic polymer ( For example, it is possible to provide a hydrophilic resin capable of exhibiting excellent performance (absorption property) even when the weight% (resin concentration) of the water-absorbent resin) is increased. Further, according to the above configuration, excellent absorption characteristics under pressure, the hydrophilic polymer (for example, the water-absorbent resin) is less likely to fall off from the absorber during water absorption, and after production, before use During the period
It is possible to provide a hydrophilic resin whose binding property does not change with time.

Since the hydrophilic resin according to the present invention has excellent absorption characteristics, it is intended to absorb body fluids. Sanitary materials such as jigs, wound protection materials, and wound healing materials; drip absorbents and freshness-maintaining materials for absorbing drip generated from foods and the like;
It can be suitably used for a wide range of applications such as a soil water retention material for water retention; a water blocking material.

The present invention will be described in detail below. The hydrophilic polymer contained in the hydrophilic resin according to the present invention is not particularly limited as long as it has a functional group, but the hydrophilic polymer in which the functional group is an acid group, especially water-absorbing property Resins are more preferred.

As the hydrophilic polymer having an acid group, for example, a water-absorbing crosslinked polymer containing a carboxyl group is suitable. The water-absorbing cross-linked polymer is, for example, (co) a hydrophilic unsaturated monomer containing acrylic acid or a salt thereof as a main component.
It is obtained by polymerizing (hereinafter, simply referred to as polymerization). Examples of the water-absorbing crosslinked polymer include crosslinked polyacrylic acid partially neutralized products (US Pat. No. 4,625,00).
1, US Pat. No. 4,654,039, US Pat. No. 5,250,640, US Pat. No. 5,275,773.
No. 4, European Patent No. 456, 136, etc.), a partially neutralized product of a starch-acrylic acid graft polymer (US Pat. No. 4,
076, 663), isobutylene-maleic acid copolymer (U.S. Pat. No. 4,389,513), vinyl acetate-
Saponified Acrylic Acid Copolymer (US Pat. No. 4,12,12)
4,748), acrylamide (co) polymer hydrolysates (US Pat. No. 3,959,569), acrylonitrile polymer hydrolysates (US Pat. No. 3,935,0).
Known water-absorbent resins such as No. 99). Among the water-absorbing crosslinked polymers, polyacrylic acid crosslinked polymers are more preferable. In the crosslinked polymer of polyacrylic acid salt, 50 mol% to 90 mol% of the acid groups in the crosslinked polymer are neutralized with, for example, an alkali metal salt, an ammonium salt, an amine salt or the like. Is more preferable.

The above-mentioned hydrophilic unsaturated monomer may contain an unsaturated monomer other than acrylic acid or its salt (hereinafter referred to as other monomer), if necessary. Specific examples of other monomers include methacrylic acid, maleic acid, vinyl sulfonic acid, styrene sulfonic acid, and 2
-(Meth) acrylamido-2-methylpropanesulfonic acid, 2- (meth) acryloylethanesulfonic acid, 2
Anionic unsaturated monomer such as (meth) acryloylpropanesulfonic acid and salts thereof; acrylamide, methacrylamide, N-ethyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-isopropyl (meth ) Acrylamide, N, N-dimethyl (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth)
Acrylate, polyethylene glycol mono (meth) acrylate, vinyl pyridine, N-vinyl pyrrolidone,
N-acryloylpiperidine, N-acryloylpyrrolidine, and other nonionic hydrophilic group-containing unsaturated monomers;
N-dimethylaminoethyl (meth) acrylate, N,
N-diethylaminoethyl (meth) acrylate, N,
N-dimethylaminopropyl (meth) acrylate,
Examples thereof include cationic unsaturated monomers such as N, N-dimethylaminopropyl (meth) acrylamide and quaternary salts thereof, but are not particularly limited. When used in combination with these other monomers, the amount used is preferably less than 50 mol% of the entire hydrophilic unsaturated monomer,
Less than mol% is more preferred.

The hydrophilic polymer obtained by polymerizing the hydrophilic unsaturated monomer has a carboxyl group. When obtaining the hydrophilic polymer, it is desirable to introduce a crosslinked structure inside by using an internal crosslinking agent. The above-mentioned internal cross-linking agent is
The compound is not particularly limited as long as it is a compound having a plurality of polymerizable unsaturated groups and / or reactive groups in one molecule. That is, the internal cross-linking agent may be a compound having a plurality of substituents in one molecule that copolymerize and / or react with the hydrophilic unsaturated monomer. The hydrophilic unsaturated monomer is
It may be composed of a self-crosslinking compound that forms a crosslinked structure without using an internal crosslinking agent.

Specific examples of the internal crosslinking agent include N, N'-methylenebis (meth) acrylamide,
(Poly) ethylene glycol di (meth) acrylate,
(Poly) propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane di (meth) acrylate,
Glycerin tri (meth) acrylate, glycerin acrylate methacrylate, ethylene oxide modified trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, triallyl Allyl phosphate, triallyl amine, poly (meth) allyloxy alkane, (poly) ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ethylene glycol, polyethylene glycol, propylene glycol, glycerin, pentaerythritol, ethylenediamine, polyethyleneimine, glycidyl (meth) ) Acrylics and the like are mentioned, but not limited thereto. These internal crosslinking agents may be used alone or in combination of two or more. And
Among the internal crosslinking agents exemplified above, by using an internal crosslinking agent having a plurality of polymerizable unsaturated groups in one molecule, it is possible to further improve the absorption characteristics and the like of the resulting hydrophilic polymer (water-absorbent resin). You can

The amount of the internal cross-linking agent used is more preferably in the range of 0.005 mol% to 3 mol% and more preferably 0.01 mol% to 1.5 mol% with respect to the hydrophilic unsaturated monomer. The range is more preferable. When the amount of the internal cross-linking agent used is less than 0.005 mol% or more than 3 mol%, a water-absorbent resin having desired absorption characteristics may not be obtained as a hydrophilic polymer. There is.

When a hydrophilic polymer is obtained by polymerizing a hydrophilic unsaturated monomer, starch, a starch derivative, cellulose, a cellulose derivative, polyvinyl alcohol, polyacrylic acid (salt) is used in the reaction system. ), Polyacrylic acid (salt)
A hydrophilic polymer such as a crosslinked product; a chain transfer agent such as hypophosphorous acid (salt); and the like may be added.

The method for polymerizing the hydrophilic unsaturated monomer is not particularly limited, and known methods such as aqueous solution polymerization, reverse phase suspension polymerization, bulk polymerization, precipitation polymerization and the like can be adopted. . Among these, from the viewpoint of ease of control of the polymerization reaction and the performance of the resulting hydrophilic polymer, a method of polymerizing a hydrophilic unsaturated monomer in an aqueous solution, that is, an aqueous solution polymerization and a reverse phase suspension polymerization, More preferable. The reaction conditions such as reaction temperature and reaction time may be appropriately set according to the type of hydrophilic unsaturated monomer, and are not particularly limited. As a polymerization method for aqueous solution polymerization or reversed-phase suspension polymerization, known polymerization methods (for example, US Pat.
001, US Pat. No. 4,769,427, US Pat. No. 4,873,299, US Pat. No. 4,093,77.
6, U.S. Pat. No. 4,367,323, U.S. Pat. No. 4,446,261, U.S. Pat. No. 4,683,274.
U.S. Pat. No. 4,690,996, U.S. Pat. No. 4,
721, 647, U.S. Pat. No. 4,738,867,
U.S. Pat. No. 4,748,076).

When polymerizing the hydrophilic unsaturated monomer,
For example, potassium persulfate, ammonium persulfate, sodium persulfate, t-butyl hydroperoxide, hydrogen peroxide, 2,2′-azobis (2-amidinopropane)
Radical polymerization initiators such as dihydrochlorides; active energy rays such as ultraviolet rays and electron rays; and the like can be used. When using an oxidizing radical polymerization initiator, for example, sodium sulfite, sodium hydrogen sulfite, ferrous sulfate,
Redox polymerization may be carried out in combination with a reducing agent such as L-ascorbic acid. The amount of these polymerization initiators used is 0.001 mol% to 2 mol% with respect to the hydrophilic unsaturated monomer.
Is preferable, and the range of 0.01 mol% to 0.5 mol% is more preferable.

The hydrophilic polymer obtained by the above-mentioned polymerization method may have various shapes such as irregular crushed shape, spherical shape, scale shape, fibrous shape, granular shape, rod shape, substantially spherical shape, and flat shape. The particle size of the hydrophilic polymer may be adjusted by an operation such as classification, if necessary. The average particle size of the hydrophilic polymer is preferably in the range of 200 μm to 600 μm. The average particle size is within the above range, and the ratio of particles having a particle size of less than 150 μm is 1
A hydrophilic polymer having a content of 0% by weight or less is more preferable, and a hydrophilic polymer having a ratio of the particles of 5% by weight or less is further preferable. When the average particle diameter of the water absorbent resin is out of the above range, it may be difficult to obtain a water absorbent resin having excellent absorption characteristics as a hydrophilic polymer.

In the present invention, the liquid modifier means a liquid modifier in a state where the modifier is added to the hydrophilic polymer. As the liquid modifier, the modifier itself may be liquid, or a modifier solution or dispersion obtained by dissolving or dispersing the modifier in a suitable solvent.
That is, the liquid modifier is not particularly limited as long as it contains a modifier and is liquid when added to the hydrophilic polymer.

The modifier is not particularly limited as long as it is a compound capable of reacting with the functional group of the hydrophilic polymer. In the present invention, the modification means that the structure and physical properties of the hydrophilic polymer are changed by contacting and reacting the hydrophilic polymer with the modifier. Specifically, the modification means, for example, a crosslinking treatment (secondary crosslinking treatment) or the like. In addition, as the reaction between the hydrophilic polymer and the modifier,
Specifically, for example, crosslinking reaction, addition reaction, substitution reaction,
Shows esterification reaction and the like.

As the above-mentioned modifier, a compound having a plurality of functional groups (that is, polyfunctional) in one molecule which reacts with a functional group of a hydrophilic polymer, and a functional group of a hydrophilic polymer are reacted. A compound having one functional group (that is, monofunctional) in one molecule can be mentioned. Among these modifiers, compounds having a plurality of functional groups that react with the functional groups of the hydrophilic polymer in one molecule are preferable.

In the above modifier, the compound having a plurality of functional groups which react with the functional group of the hydrophilic polymer in one molecule includes a crosslinking agent (surface crosslinking agent). When the functional group of the hydrophilic polymer is a carboxyl group, as a suitable crosslinking agent, specifically, for example, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, Tetraethylene glycol, tetrapropylene glycol, polyethylene glycol, polypropylene glycol, 1,
3-propanediol, 2,2,4-trimethyl-1,
3-pentanediol, glycerin, polyglycerin,
2-butene-1,4-diol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 2,4-pentanediol, 1,6-hexanediol, 2,5-hexane Diol, 1,2-cyclohexanedimethanol, 1,2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethylene-
Polyhydric alcohols such as oxypropylene block copolymer, pentaerythritol, sorbitol; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, propylene glycol di Polyvalent epoxides such as glycidyl ether, polypropylene glycol diglycidyl ether and glycidol; polyamines such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyallylamine and polyethyleneimine; 1,3-dioxolane- Two
-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
-Alkylene carbonates such as dioxan-2-one;
Polyhydric isocyanates such as 2,4-tolylene diisocyanate and hexamethylene diisocyanate; polyvalent oxazoline compounds such as 1,2-ethylenebisoxazoline; epichlorohydrin, epibromohydrin, α-methylepichlorohydrin, etc. Known surface cross-linking agents such as haloepoxides; polyvalent metal compounds such as hydroxides and chlorides of polyvalent metals such as zinc, calcium, magnesium, aluminum, iron, zirconium; It is not limited. One of these crosslinking agents may be used alone, or two or more thereof may be used in combination.

Of the above-exemplified crosslinking agents, crosslinking agents containing at least one compound selected from the group consisting of polyhydric alcohols, polyepoxides, polyamines, and alkylene carbonates are more preferable.

Among the polyvalent amines, a polyvalent amine having a weight average molecular weight (Mw) of 2,000 or more (hereinafter referred to as a high molecular weight polyvalent amine) is more preferable, and a weight average molecular weight of 10,000 to 10 is obtained. High molecular weight polyamines in the range of 1,000,000 are particularly preferred. When the weight average molecular weight of the high-molecular-weight polyvalent amine is less than 2,000, the binding property and shape retention property during water absorption between the hydrophilic polymer particles in the resulting hydrophilic resin, the hydrophilic resin and the cellulose fiber ( For example, there is a possibility that the binding property and shape retention property of the absorber formed of paper, crushed pulp, etc.) when absorbing water may be insufficient.

When the crosslinking agent contains a high molecular weight polyvalent amine, for example, when the hydrophilic resin, that is, the hydrophilic polymer in the hydrophilic resin absorbs the aqueous liquid, it is treated with the hydrophilic polymer. The high-molecular-weight polyvalent amine is brought into contact with and reacts with each other to generate a binding force between the hydrophilic polymer particles and a shape-retaining force of the absorber. As described above, according to the present invention, since the timing of the reaction between the hydrophilic polymer and the high molecular weight polyvalent amine can be controlled, it is possible to more effectively prevent the deterioration of the binding property due to aging. You can When a high molecular weight polyvalent amine is used as a cross-linking agent, the hydrophilic polymer may have its surface portion subjected to surface cross-linking treatment by a known surface cross-linking method or the method described in the present invention. Good.

Examples of the high molecular weight polyvalent amine include (1) homopolymers of monoallylamine derivatives and homopolymers of diallylamine derivatives; (2) copolymers of two or more monoallylamine derivatives, and two types. Copolymers of the above diallylamine derivatives, copolymers of monoallylamine derivatives and diallylamine derivatives; (3) Copolymers of monoallylamine derivatives and / or diallylamine derivatives with dialkyldiallylammonium salts; (4) Tertiary amino Homopolymer of unsaturated carboxylic acid derivative having a group (hereinafter referred to as unsaturated carboxylic acid derivative a); (5) Copolymer of two or more kinds of unsaturated carboxylic acid derivative a; (6) Unsaturated carboxylic acid Derivative a and the unsaturated carboxylic acid derivative a
A quaternary ammonium salt obtained by protonating and / or alkylating a tertiary amino group possessed by the above (hereinafter, referred to as quaternary ammonium salt) and / or a copolymer with a dialkyldiallylammonium salt; (7) Unsaturated Tertiary copolymer of carboxylic acid derivative a, quaternary ammonium salt and / or dialkyldiallylammonium salt, and vinyl monomer copolymerizable with these monomers; (8) unsaturated carboxylic acid, and A polymer obtained by copolymerizing an unsaturated carboxylic acid and an unsaturated monomer copolymerizable therewith to obtain a copolymer, and then reacting a carboxyl group of the copolymer with an alkyleneimine; (9) poly Alkyleneimine; (10) Polyalkyleneimine / epihalohydrin resin; (11) Polyalkylenepolyamine; (12) (2-methacryloyloxyethyl) ethyleneimine Body, (2-methacryloyloxyethyl) ethyleneimine, and a copolymer of an unsaturated monomer copolymerizable with the (2-methacryloyloxyethyl) ethyleneimine; (13) polyamide polyamine; (14) polyamide amine・ Epihalohydrin resin; (1
5) Mannich reaction modified product of polyacrylamide, Mannich reaction modified product of polymethacrylamide; (16) Polyvinylamine, vinylamine, and copolymer of unsaturated monomer copolymerizable with the vinylamine; (17) Dicyandiamide -Diethylenetriamine polycondensate; and the like.

As such a high molecular weight polyvalent amine,
More specifically, for example, polyallylamine, polydiallylamine, poly (N-alkylallylamine), poly (alkyldiallylamine), monoallylamine-diallylamine copolymer, N-alkylallylamine-monoallylamine copolymer, monoallylamine- Dialkyldiallylammonium salt / copolymer, diallylamine-
Dialkyldiallylammonium salt / copolymer, polydimethylaminoethyl acrylate, polydiethylaminoethyl acrylate, polydimethylaminoethyl acrylamide, linear polyethyleneimine, branched polyethyleneimine, polyethylenepolyamine, polypropylenepolyamine, polyamidepolyamine, polyetherpolyamine , Polyvinylamine, polyamide polyamine
Examples include epichlorohydrin resin and polyamidine. In addition, an aminated modified product obtained by reacting polyacrylamide or polymethacrylamide with formaldehyde and diethylamine can also be mentioned. Further, the high molecular weight polyvalent amine may be completely neutralized or partially neutralized with an acidic compound.

In the above modifier, the compound having one functional group in one molecule which reacts with the functional group of the hydrophilic polymer is, for example, pentanol, hexanol, heptanol, Compounds having a hydroxyl group such as octanol, decanol, alkoxy polyethylene glycol, lactic acid, ethyl lactate; 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, butyl glycidyl ether, 2-methyloctyl glycidyl ether, allyl glycidyl ether,
Compounds having an epoxy group such as glycidyl (meth) acrylate; methylamine, ethylamine, diethylamine, triethylamine, n-propylamine, isopropylamine, diisopropylamine, 3-methoxypropylamine, 3-ethoxypropylamine, 3- (2
-Ethylhexyloxy) propylamine, 3- (dibutylamino) propylamine, n-butylamine, t-
Compounds having an amino group such as butylamine, sec-butylamine, diisobutylamine, 2-ethylhexylamine, di-2-ethylhexylamine, and tri-n-octylamine, and salts thereof; cationic surface active agents having an amino group Agents, salts thereof, and the like, but are not limited to these compounds. These compounds may be used alone or in combination of two or more. Furthermore, in the modifier according to the present invention, a compound having a plurality of functional groups in one molecule and a compound having one functional group in a molecule may be used in combination.

The amount of the modifier used for the hydrophilic polymer is
Depending on the composition of the hydrophilic polymer, the kind of the hydrophilic polymer, the combination of the hydrophilic polymer and the modifier, the use of the hydrophilic resin, etc., the solid content of the hydrophilic polymer is 100 parts by weight. , 0.001 to 10 parts by weight is more preferable, and 0.01 to 5 parts by weight is further preferable. By setting the amount of the modifier used within the above range, as a hydrophilic resin, the absorption characteristics under pressure, and
It is possible to obtain a water absorbing agent having excellent binding properties and shape retention. When the amount of the modifier used exceeds 10 parts by weight, a part of the modifier is wasted, which is uneconomical, and the modifier is present in excess, so that the desired modifying effect is obtained. May not be obtained. For example, when the modifier is a cross-linking agent, if the cross-linking agent is present in excess, the cross-linking density becomes too high, and the absorption capacity decreases. On the other hand, when the amount of the modifier used is less than 0.001 part by weight, it may be difficult to obtain the desired modifying effect.

Examples of the solvent used when the liquid modifier according to the present invention contains a solvent include water, hydrophilic organic solvents, and mixed solvents thereof.
That is, when the liquid modifier is a solution or dispersion of the modifier, the liquid modifier can be easily obtained by dissolving or dispersing the modifier in, for example, water and / or a hydrophilic organic solvent. You can The concentration of the modifying agent when it is used as a solution or dispersion is not particularly limited.

Specific examples of the hydrophilic organic solvent include methyl alcohol, ethyl alcohol, n
-Propyl alcohol, isopropyl alcohol, n-
Lower alcohols such as butyl alcohol, isobutyl alcohol, t-butyl alcohol; ketones such as acetone; ethers such as dioxane and tetrahydrofuran;
Examples include amides such as N, N-dimethylformamide; sulfoxides such as dimethyl sulfoxide;
There is no particular limitation.

In the present invention, the method for obtaining the powdered modifier by pulverizing the liquid modifier is not particularly limited. For example, the liquid modifier is mixed with a particulate water-insoluble compound. Method; cooling the liquid modifier below its melting point; and the like.

The particulate water-insoluble compound may be any compound which is inert to the reaction between the hydrophilic polymer and the modifier and does not adversely affect the various properties of the resulting hydrophilic resin. It is not particularly limited.

Specific examples of the above water-insoluble compound include silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, zinc oxide, talc, calcium phosphate, barium phosphate, silicic acid, silicates, clay, diatomaceous earth, Inorganic powder such as zeolite, bentonite, kaolin, hydrotalcite, perlite, isolite, activated clay, silica sand, silica stone, strontium ore, fluorite, bauxite; polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyamide, melamine resin, poly Examples thereof include organic powders such as methyl methacrylate, modified starch, powdered cellulose, ethyl cellulose, sawdust, activated carbon, and tea leaves; particulate water-absorbent resin; but are not particularly limited. These water-insoluble compounds may be used alone or in combination of two or more. Among the above-exemplified water-insoluble compounds, fine-grained inorganic powder is more preferable, and fine-grained clay is further preferable. The particle size of the water-insoluble compound is 1,000μ.
m or less is preferable, 500 μm or less is more preferable, 1
It is more preferably 00 μm or less.

The ratio of the liquid modifier to the water-insoluble compound in the powdering modifier is determined by the kind of the liquid modifier, the kind of the water-insoluble compound, the combination of the liquid modifier and the water-insoluble compound, or the use of the hydrophilic resin. The ratio of the liquid modifier (that is, the modifier or its solution or dispersion) to 1 part by weight to 100 parts by weight of the water-insoluble compound,
It is more preferably set within the range of 1,000 parts by weight, and even more preferably set within the range of 10 parts by weight to 500 parts by weight. When the proportion of the liquid modifier exceeds 1,000 parts by weight, the hydrophilic resin tends to be in the form of slurry. When the hydrophilic resin is in the form of a slurry, the liquid modifier is absorbed by the hydrophilic polymer immediately after mixing the hydrophilic polymer and the powdering modifier, or the liquid modifier and the hydrophilic polymer are mixed. The reaction with the coalescence is started. Therefore, it becomes difficult to uniformly distribute the liquid modifier on the surface of the hydrophilic polymer, and it may not be possible to obtain a desired modifying effect. For example, when the modifier is a cross-linking agent, it may be difficult to obtain a water-absorbing agent having excellent absorption properties under pressure, as well as binding properties and shape retention properties as a hydrophilic polymer. On the other hand, if the proportion of the liquid modifier is less than 1 part by weight, it may be difficult to obtain the desired modifying effect.

The mixing method of mixing the liquid modifier and the water-insoluble compound is not particularly limited, and for example, a method of simply mixing the modifier and the water-insoluble compound; a solution or dispersion of the modifier, A method of mixing with a water-insoluble compound; and the like. When the solution or dispersion of the modifier and the water-insoluble compound are mixed, for example, a method of spraying or dropping the above-mentioned solution or dispersion on the water-insoluble compound and then mixing the two are generally used. Target.

The mixing device used for mixing the liquid modifier and the water-insoluble compound is, for example, a cylinder type mixer, a screw type mixer, a screw type extruder, a turbulizer, a Nauter type mixer, Examples thereof include a V-shaped mixer, a ribbon mixer, a double-arm kneader, a fluid mixer, an airflow mixer, a rotary disk mixer, a roll mixer, and a tumbling mixer. The mixing speed may be high speed or low speed. When the liquid modifier is used as a modifier solution or dispersion, water and / or a hydrophilic organic solvent may be removed, if necessary, after mixing with the water-insoluble compound.

The powdered modifier according to the present invention can be obtained by mixing the liquid modifier and the water-insoluble compound.
The powdering modifier is preferably in the form of particles. Normal,
The particle size of the powdering modifier is 1/2 or less, preferably 1/5 or less of the average particle size of the hydrophilic polymer. When producing the powdered modifier, for example, depending on the application of the hydrophilic resin, the kind and particle size of the water-insoluble compound, and the mixing conditions of the water-insoluble compound and the liquid modifier are appropriately selected. do it. As a result, the hydrophilic polymer can be modified more uniformly, and a powdering modifier which can more easily control the timing of the modification can be obtained.

A powdered modifier can also be obtained by cooling the liquid modifier below its melting point to solidify it.

In the present invention, the mixing method of mixing the hydrophilic polymer and the powdering modifier is not particularly limited. Examples of the mixing device used when mixing the two include the mixing device exemplified above. The mixing speed may be high speed or low speed.

According to the present invention, it is possible to uniformly mix the modifier with the hydrophilic polymer by performing the mixing step of mixing the hydrophilic polymer with the powdered modifier.
This makes it possible to easily obtain a hydrophilic resin having an excellent balance of various properties. In addition, if necessary, after performing the above-mentioned mixing step, by performing a heat treatment (heating step) for heating the obtained mixture, the reaction between the hydrophilic polymer and the modifier can be efficiently performed. it can. Further, if necessary, after performing the above-mentioned mixing step, to the obtained mixture, a liquid or gaseous aqueous liquid is added, and then,
The hydrophilic polymer and the modifier can be efficiently reacted with each other by performing the heat treatment as necessary. That is, when the hydrophilic polymer is modified with a powdering modifier, specifically, the hydrophilic polymer and the powdering modifier are mixed, and if necessary, an aqueous liquid is added and / or Alternatively, the hydrophilic polymer may be brought into contact with the modifier constituting the powdering modifier by using an appropriate means such as heating.

Specific examples of the liquid or gaseous aqueous liquid include water, water vapor, a mixed solution of water and a hydrophilic organic solvent, and the like. Examples of the hydrophilic organic solvent include, but are not limited to, the compounds exemplified above. When a covalent bond is formed by the reaction between the modifier and the hydrophilic polymer, for example, when the modifier is a polyhydric alcohol, a polyepoxide, an alkylene carbonate or the like, the hydrophilic polymer and the powder. By adding the aqueous liquid to a mixture with a body-modifying agent,
As the hydrophilic resin, it is possible to obtain a water absorbing agent having a more excellent absorption property under pressure. In this case, the amount of water in the aqueous liquid used depends on the composition of the hydrophilic polymer, the average particle size, the composition of the powdering modifier used, the use of the hydrophilic resin, and the like. It is preferably 10 parts by weight or less, more preferably 1 part by weight to 5 parts by weight, based on 100 parts by weight of the solid content of the combined product. Similarly, the amount of the hydrophilic organic solvent in the aqueous liquid to be used is generally preferably 10 parts by weight or less, and preferably 0.1 parts by weight to 5 parts by weight, based on 100 parts by weight of the solid content of the hydrophilic polymer. The range of parts by weight is more preferable. The addition method of adding the aqueous liquid is not particularly limited.

The processing temperature for the heat treatment is
Although it depends on the type of the powdering modifier used, 80 ° C or higher is more preferable, 100 ° C to 230 ° C is more preferable, and 160 ° C to 220 ° C is particularly preferable.
By performing the heat treatment, the surface of the hydrophilic polymer is modified. When the treatment temperature is lower than 80 ° C., it may be difficult to uniformly modify the hydrophilic polymer. Therefore, when a water absorbing agent is obtained as the hydrophilic resin, it is more excellent in absorption property under pressure. It may be difficult to obtain such a water absorbing agent. Further, since the heat treatment takes time, there is a possibility that productivity of the hydrophilic resin may be reduced. The heat treatment can be performed using a general dryer or heating furnace. Examples of the dryer include a groove-type mixing dryer, a rotary dryer, a desk dryer, a fluidized-bed dryer, a flash dryer, and an infrared dryer. still,
It is also possible to perform heat treatment while mixing the hydrophilic polymer and the powdering modifier. That is, the mixing step and the heat treatment can be performed in parallel.

As described above, the hydrophilic resin according to the present invention has a constitution including the hydrophilic polymer and the powdered modifier obtained by powderizing the liquid modifier. According to the above configuration, the liquid modifier is powdered to form the powdered modifier. Therefore, the liquid modifier is contained in the hydrophilic resin in a substantially solid state. In addition, since the liquid modifier forms a powdered modifier, the water-absorbent resin and the modifier contained in the liquid modifier are present separately in the hydrophilic resin until they are used. There is nothing to do. On the other hand, when the hydrophilic resin absorbs, for example, an aqueous liquid, or when the hydrophilic resin is heated, for example, the water-absorbent resin and the modifier contained in the liquid modifier are brought into contact with each other to react, resulting in hydrophilicity. The polymer is modified (for example, surface cross-linking treatment when the modifier is a cross-linking agent). Therefore, the hydrophilic polymer can be uniformly modified and the timing of the modification can be controlled. Therefore, the above-mentioned hydrophilic resin can improve various characteristics such as absorption capacity under pressure which are exhibited by modification, and can prevent deterioration of various characteristics such as gel breaking force due to aging. .

Therefore, according to the above constitution, the absorption characteristics under pressure, such as the absorption capacity and water retention capacity under pressure, are excellent, and when used for sanitary materials, the hydrophilic polymer It is possible to provide a hydrophilic resin capable of exhibiting excellent performance (absorption property) even if the weight% (resin concentration) is increased. In the hydrophilic resin, that is, the water-absorbent resin, a liquid-conducting space for moving the aqueous liquid between the water-absorbent resin particles is ensured even under pressure. Therefore, even when the amount of the hydrophilic polymer used is 50% by weight or more, the above liquid guiding space is ensured even under pressure.

Further, according to the above constitution, the absorption property under pressure is excellent, the hydrophilic polymer is less likely to fall off from the absorber at the time of absorbing water, and during the period after the production until the use. It is possible to provide a hydrophilic resin whose binding property does not change with time. In particular, when the liquid modifier is a cross-linking agent containing a polyvalent amine or the like, the above effects can be more remarkably exhibited.

The hydrophilic resin according to the present invention is used in combination with, for example, cellulose fibers such as paper and crushed pulp. The hydrophilic resin according to the present invention is excellent in diffusibility of an aqueous liquid and has little leakage even under pressure,
Moreover, since it has excellent absorption properties, for example, for the purpose of absorbing body fluids, for example, disposable diapers and sanitary napkins, jigs for incontinence such as so-called incontinence pads, wound protection materials, wound healing Suitable for a wide range of applications such as sanitary materials such as materials; drip absorbents and freshness-retaining materials for absorbing drip generated from foods; soil water-retaining materials for water retention; be able to.

The method for producing a hydrophilic resin according to the present invention comprises:
As described above, the hydrophilic polymer is mixed with the powdered modifier obtained by powderizing the liquid modifier. The above pulverization is performed by, for example, a method of mixing a liquid modifier with a particulate water-insoluble compound or a method of cooling the liquid modifier below its melting point to solidify it. Further, the method for producing a hydrophilic resin according to the present invention is a method of heating a mixture of a hydrophilic polymer and a powdering modifier as described above. Furthermore, the method for producing a hydrophilic resin according to the present invention,
As described above, this is a method in which a liquid or gaseous aqueous liquid is added to a mixture composed of a hydrophilic polymer and a powdering modifier, and then the mixture is heated. As the hydrophilic polymer,
For example, a water absorbent resin having an acid group may be mentioned. Also,
Examples of the liquid modifier include a cross-linking agent.

According to the above method, the hydrophilic resin is produced by mixing the hydrophilic polymer with the powdered modifier obtained by powderizing the liquid modifier. Therefore, for example, when the powdering modifier is a mixture of a liquid modifier and a particulate water-insoluble compound, the liquid modifier in the powdering modifier is, for example, the surface of the water-insoluble compound and / Or inside. Therefore, according to the above method, the liquid modifier can be uniformly mixed with the hydrophilic polymer in a substantially solid state. Therefore, according to the above method, the hydrophilic polymer and the liquid modifier, that is, the powdered modifier are uniformly mixed, as compared with the case where the liquid modifier is directly mixed with the hydrophilic polymer. be able to. In addition, in the mixture of the hydrophilic polymer and the powdering modifier, the hydrophilic polymer and the liquid modifier are separately present. That is, when the liquid modifier is pulverized and used as the powder modifier, the liquid modifier is immediately absorbed by the hydrophilic polymer even if the hydrophilic polymer and the powder modifier are mixed. Alternatively, the reaction between the modifier contained in the liquid modifier and the hydrophilic polymer is not started. Then, when the hydrophilic resin is allowed to absorb an aqueous liquid, or when the hydrophilic resin is heated, for example, the hydrophilic polymer and the modifier contained in the liquid modifier come into contact with each other, and the hydrophilic polymer The coalescence can be uniformly modified.

When a powdered modifier obtained by cooling a liquid modifier below its melting point and solidifying is used as the powdered modifier, the liquid modifier is substantially solid. In the state, it can be mixed with the hydrophilic polymer. Also in this case, since the liquid modifier forms the powdered modifier, the hydrophilic polymer and the modifier contained in the liquid modifier are present separately in the hydrophilic resin until they are used. However, it does not react. Then, when the powdered modifier is melted, the hydrophilic polymer and the modifier contained in the liquid modifier react with each other, and the hydrophilic polymer is modified (for example, the liquid modifier is crosslinked). When it is an agent, it is surface-crosslinked. The method for melting the powdering modifier is not particularly limited, and various methods such as heat treatment can be adopted.

As described above, according to the above manufacturing method,
The hydrophilic polymer can be uniformly modified and the timing of the modification can be controlled. Therefore,
According to the above-mentioned production method, for example, when the liquid modifier is a polyhydric alcohol, a polyvalent epoxide, an alkylene carbonate, etc., it is possible to improve various characteristics that are exhibited by the modification, such as the absorption capacity under pressure. it can. Also,
In particular, when the liquid modifier is a cross-linking agent containing a polyvalent amine or the like, at the time of use, when the hydrophilic resin absorbs the aqueous liquid, the binding force between the hydrophilic polymer particles and the above-mentioned absorber Shape retention is expressed. Furthermore, when a cross-linking agent containing a polyvalent amine or the like is used as the liquid modifier, it is possible to control the timing of the reaction between the hydrophilic polymer particles due to the polyvalent amine or the like, so that the gel breaking force and the like are included. It is possible to more effectively prevent the above characteristics from being deteriorated due to changes with time. Therefore, according to the method described above, the hydrophilic resin having an excellent balance of various properties can be easily obtained.

[0064]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples, but the present invention is not limited thereto. In the following description, “part” means “part by weight” and “%” unless otherwise specified.
Indicates "% by weight". Further, various performances (physical properties) of these hydrophilic polymers or hydrophilic resins after treatment (these may be collectively referred to as a water absorbing agent) were measured by the following methods.

(A) Absorption capacity 0.2 g of a water absorbing agent is used as a non-woven bag (60 mm × 60 mm)
And then immersed in a 0.9% aqueous sodium chloride solution (physiological saline) at room temperature. Pull up the bag after 60 minutes,
After draining using a centrifuge at 250 G for 3 minutes, the weight W ₁ (g) of the bag was measured. Further, the same operation was performed without using the water absorbing agent, and the weight W ₀ (g) at that time
Was measured. Then, from these weights W ₁ · W ₀ , the following equation, absorption capacity (g / g) = (weight W ₁ (g) −weight W
_The absorption capacity (g / g) was calculated according to ₀ (g)) / weight of water-absorbing agent (g).

(B) Absorption capacity under load First, the measuring apparatus used for measuring the absorption capacity under load will be briefly described below with reference to FIG.

As shown in FIG. 1, the measuring device is a balance 1
And a container 2 having a predetermined capacity mounted on the balance 1, an outside air suction pipe 3, a conduit 4, a glass filter 6, and a measuring unit 5 mounted on the glass filter 6. I have. The container 2 has an opening 2a at the top and an opening 2b at the side surface thereof.
The outside air suction pipe 3 is fitted into the opening a, and the conduit 4 is attached to the opening 2b. Further, the container 2 contains a predetermined amount of artificial urine 11. The artificial urine 11 described above contains sodium sulfate 0.2%, potassium chloride 0.2%, magnesium chloride hexahydrate 0.05%, calcium chloride dihydrate 0.025%, ammonium dihydrogen phosphate 0. 085
%, Diammonium hydrogen phosphate 0.015%. Further, the lower end of the outside air suction pipe 3 is submerged in the artificial urine 11. The glass filter 6 has a diameter of 70 mm. And container 2
And the glass filter 6 is in communication with each other by means of a conduit 4. Furthermore, the upper surface of the glass filter 6 is
It is fixed at a position where the height is equal to the lower end of the outside air suction pipe 3.

The measuring unit 5 comprises a filter paper 7 and a supporting cylinder 8.
And a wire mesh 9 attached to the bottom of the support cylinder 8 and a weight 10. Then, the measuring unit 5 places the filter paper 7 and the support cylinder 8 (that is, the wire mesh 9) on the glass filter 6 in this order, and places the weight 10 inside the support cylinder 8, that is, on the wire mesh 9. It has been. Support cylinder 8
Has an inner diameter of 60 mm. The wire net 9 is made of stainless steel and is formed to have a JIS standard of 400 mesh (mesh size: 38 μm). Then, a predetermined amount of the water absorbing agent (hydrophilic resin) is evenly spread on the wire net 9. The weight of the weight 10 is adjusted so that a load of 50 g / cm ² can be uniformly applied to the wire net 9, that is, the water absorbing agent.

The absorption capacity under pressure was measured using the measuring apparatus having the above-mentioned structure. The measuring method will be described below.

First, a predetermined preparatory operation such as putting a predetermined amount of artificial urine 11 into the container 2 and fitting the outside air suction pipe 3 into the container 2 was performed. Next, the filter paper 7 is placed on the glass filter 6.
Was placed. On the other hand, in parallel with these placing operations, 0.9 g of the water absorbing agent was evenly spread inside the supporting cylinder 8, that is, on the metal net 9, and the weight 10 was placed on the water absorbing agent.

Then, on the filter paper 7, the wire net 9, that is, the support cylinder 8 on which the water absorbing agent and the weight 10 were placed was placed.

The weight W ₂ (g) of the artificial urine 11 absorbed by the water absorbing agent was measured for 60 minutes from the time when the support cylinder 8 was placed on the filter paper 7 using the balance 1.

Then, from the above weight W _{2, according} to the following formula: absorption capacity under pressure (g / g) = weight W ₂ (g) / weight of water absorbing agent (g) The absorption capacity (g / g) was calculated.

(C) Gel breaking force: 25.3 inside a supporting cylinder having an inner diameter of 50 mm and a height of 13 mm.
g of artificial urine and 0.84 g of a water absorbing agent were put therein, and the water absorbing agent was allowed to absorb the artificial urine to obtain a gel. The composition of the artificial urine is as described in (b) Absorption capacity under pressure. Then, the supporting cylinder is placed on a measuring table having an opening with a diameter of 20 mm in the central part so that the center of the supporting cylinder coincides with the center of the measuring table, and The breaking force was measured. The measurement of the breaking force is
Neo card meter (manufactured by Aitechno Co., Ltd .; model M)
-302) was used under the conditions of a pressure-sensitive shaft diameter of 8 mm and a pressure-sensitive shaft descending speed of 0.36 cm / sec. The breaking force refers to the minimum force required to break the elastic body, that is, the gel inside the supporting cylinder, with respect to the limit of the elastic force.

(D) Gel Breaking Force and Retention after Acceleration Test for Decreasing Gel Breaking Force 0.84 g of a water-absorbing agent was added at 40 ° C. and relative humidity of 90% for 24 hours.
It was left for 48 hours or 48 hours (gel rupture strength reduction acceleration test; hereinafter simply referred to as reduction acceleration test). Then, the gel rupture force was measured using the water absorbing agent after the deterioration acceleration test. That is, 0.84 g of the water absorbing agent and 25.3 g of artificial urine were put into a support cylinder having an inner diameter of 50 mm and a height of 13 mm, and the water absorbing agent absorbed the artificial urine to obtain a gel. The breaking force of the gel was measured according to the method (c) above.

The retention rate (%) is a gel rupture force when a deterioration promoting test is carried out by leaving the water absorbing agent at 40 ° C. and a relative humidity of 90% for 48 hours, and when the deterioration promoting test is not carried out. When the gel breaking force of the water-absorbing agent is B, the ratio of A to B is expressed as a percentage.

Next, a method for producing the water absorbent resin used in this example will be shown in a reference example. [Reference Example 1] 5,500 g of a 39 wt% aqueous solution of sodium acrylate (hydrophilic unsaturated monomer) having a neutralization ratio of 75 mol%
Then, 3.59 g of trimethylolpropane triacrylate as an internal cross-linking agent was dissolved into a reaction solution. Next, the reaction solution was degassed under a nitrogen gas atmosphere for 30 minutes. Then, the above reaction solution was supplied to a reactor formed by attaching a lid to a stainless steel double-arm kneader with a jacket having an internal volume of 10 L and having two sigma type blades, and the system was maintained while maintaining the reaction solution at 30 ° C. The atmosphere was replaced with nitrogen gas. Subsequently, while stirring the reaction solution, 2.4 g of ammonium persulfate as a polymerization initiator and 0.1 g of L-ascorbic acid were used.
When 2 g was added, the polymerization started after about 1 minute. Then, polymerization was carried out at 30 ° C. to 80 ° C., and 60 minutes after the polymerization was started, the reaction was terminated and the hydrogel polymer was taken out.

The obtained hydrogel polymer was subdivided into particles each having a diameter of about 5 mm. This finely divided hydrogel polymer was spread on a 50-mesh wire mesh,
Hot air drying was performed for 0 minutes. Then, the dried product is pulverized using a vibration mill, and further passed through a 20-mesh wire net for classification to obtain an average particle diameter of 400 μm and
A water absorbent resin precursor was obtained in which the proportion of particles having a particle size of less than 106 μm was 5% by weight.

A surface crosslinking agent solution comprising 100 parts of the water-absorbent resin precursor obtained, 0.5 part of glycerin as a crosslinking agent, 3 parts of water, and 0.75 part of isopropyl alcohol as a hydrophilic organic solvent. Were mixed. 2 of the above mixture
By performing heat treatment at 00 ° C. for 35 minutes, a water absorbent resin (a) as a hydrophilic polymer was obtained. The average particle diameter of the resulting water absorbent resin (a) is 400 μm, and the particle diameter is 1
The proportion of particles smaller than 06 μm was 3%.

Reference Example 2 3.56 g of polyethylene glycol diacrylate as an internal cross-linking agent was dissolved in 5,500 g of a 33% by weight aqueous solution of sodium acrylate (hydrophilic unsaturated monomer) having a neutralization ratio of 75 mol%. To obtain a reaction solution. Next, this reaction liquid was degassed under a nitrogen gas atmosphere, and then 2.4 g of sodium persulfate as a polymerization initiator and 0.12 g of L-ascorbic acid were added to carry out polymerization while stirring. When the polymerization was completed, the obtained hydrogel-like crosslinked polymer was further subdivided and dried in a hot air dryer at 150 ° C. until the water content of the hydrogel-like crosslinked polymer was 5% or less. Then, the dried product is pulverized by using a roll granulator and further passed through a 20-mesh wire net to be classified to obtain an average particle diameter of 400.
A water-absorbent resin (b) as a particle-shaped crosslinked polymer having a particle size of μm, that is, a hydrophilic polymer was obtained. The proportion of particles having a particle diameter of less than 106 μm in the water absorbent resin (b) was 3% by weight.

Example 1 First, a crosslinking agent (liquid modifier)
As a 50% aqueous solution of polyethyleneimine having a weight average molecular weight of 70,000 (trade name: Epomin P-1050;
3 parts by weight of Nippon Shokubai Co., Ltd. and 9 parts of aluminum oxide as a water-insoluble compound (average particle diameter 80 μm) were stirred and mixed to obtain a powdering modifier (1) having an average particle diameter of 80 μm. .

Next, with respect to 100 parts of the water absorbent resin (a) obtained in Reference Example 1 above, 1 part of the above powdering modifier (1) was added.
Two parts were added and mixed. Then the mixture is heated at 90 ° C. for 2 hours.
Hot air drying was performed for 0 minutes. The obtained dried product is classified with a wire net having an opening of 840 μm to obtain a passing product,
A hydrophilic resin was obtained as the water absorbing agent (1). The various performances of this water absorbing agent (1) were measured by the above methods. The results are summarized in Table 1.

Example 2 First, 500 μl of pearlite (volcanic rock particles in which the total amount of SiO ₂ and Al ₂ O ₃ accounts for 80% or more of all the components) as a water-insoluble compound is used.
The product was classified by a wire mesh having m openings to obtain a passing product. Then, 5 parts of this passing product and 5 parts of a 30% aqueous solution of polyethyleneimine having a weight average molecular weight of 70,000 as a cross-linking agent (liquid modifier) (trade name Epomin P-1000; manufactured by Nippon Shokubai Co., Ltd.) are stirred. Then, the powdered modifier (2) having an average particle diameter of 200 μm was obtained by mixing.

Next, with respect to 100 parts of the water absorbent resin (a) obtained in Reference Example 1 above, 1 part of the above powdering modifier (2) was added.
0 parts was added and mixed. Then, the mixture was mixed with 840 μm.
A hydrophilic resin was obtained as a water absorbing agent (2) by classifying with a wire mesh having m openings to obtain a passing product. The performances of this water absorbing agent (2) were measured by the above methods. The results are summarized in Table 1. The water absorbing agent is crosslinked by water absorption during use, that is, in the measurement of various performances in this example.

Example 3 First, a crosslinking agent (liquid modifier)
A 30% aqueous solution of polyethyleneimine having a weight average molecular weight of 70,000 (trade name: Epomin P-1000;
5 parts of Nippon Shokubai Co., Ltd. and powdered polyethylene (trade name: Flowsen UF-1.
Content of particles having a particle diameter of 5, 75 μm or less 99.
9% or more; 5 parts by Sumitomo Seika Chemicals Co., Ltd.) was stirred and mixed to obtain a powdering modifier (3).

Next, with respect to 100 parts of the water absorbent resin (a) obtained in Reference Example 1 above, 1 part of the above powdering modifier (3) was added.
0 parts was added and mixed. Then, the mixture was mixed with 840 μm.
A hydrophilic resin was obtained as a water-absorbing agent (3) by classifying with a wire net having openings of m to obtain a passing product. The various performances of this water absorbing agent (3) were measured by the methods described above. The results are summarized in Table 1. The water absorbing agent is crosslinked by water absorption during use, that is, in the measurement of various performances in this example.

Comparative Example 1 100 parts of the water-absorbent resin (a) obtained in Reference Example 1 was added to a crosslinking agent (liquid modifier).
A 30% aqueous solution of polyethyleneimine having a weight average molecular weight of 70,000 (trade name: Epomin P-1000;
(Manufactured by Nippon Shokubai Co., Ltd.) 5 parts were added and mixed. afterwards,
The mixture was hot air dried at 90 ° C. for 20 minutes. The dried product was classified with a wire mesh having an opening of 840 μm to obtain a passing product, whereby a treated hydrophilic polymer was obtained as a comparative water absorbing agent (1). The performances of this comparative water absorbent (1) were measured by the above-mentioned methods. The results are summarized in Table 1.

[0088]

[Table 1]

Example 4 First, 0.1 part of ethylene glycol diglycidyl ether as a cross-linking agent (modifying agent) and isopropyl alcohol 2 as a hydrophilic organic solvent.
Part and 1 part of hydrophilic fine particle silicon dioxide (trade name Aerosil 200; manufactured by Nippon Aerosil Co., Ltd.) as a water-insoluble compound by stirring and mixing to obtain a powdering modifier (4) having an average particle diameter of 10 μm. Got

Next, with respect to 100 parts of the water-absorbent resin (b) obtained in Reference Example 2 above, the powdering modifier (4) above was added.
After adding and mixing 3.1 parts, 5 parts of water was further mixed. Then, the resulting mixture was heated at 180 ° C. for 25 minutes,
After the heat treatment, the product was classified with a wire net having an opening of 840 μm to obtain a passing product, thereby obtaining a crosslinked hydrophilic resin as a water absorbing agent (4). The various performances of this water absorbing agent (4) were measured by the methods described above. Table 2 summarizes the results.

Example 5 1 part of glycerin as a cross-linking agent (modifying agent), 1 part of isopropyl alcohol as a hydrophilic organic solvent, and hydrophilic particulate silicon dioxide as a water-insoluble compound (trade name: Carplex 22S). 1 part of Shionogi Pharmaceutical Co., Ltd.) was stirred and mixed to obtain a powdering modifier (5) having an average particle diameter of 20 μm.

Next, with respect to 100 parts of the water absorbent resin (b) obtained in Reference Example 2 above, the powdering modifier (5) 3 above was added.
After adding and mixing 1 part, 3 parts of water was further mixed. Then, after heating the resulting mixture at 200 ° C. for 40 minutes,
By classifying with a wire net having an opening of 840 μm and obtaining a passing product, a hydrophilic resin after crosslinking was obtained as a water absorbing agent (5). The various properties of this water absorbing agent (5) were measured by the above-mentioned methods. Table 2 summarizes the results.

Example 6 A liquid modifier was obtained by stirring and mixing 0.1 part of ethylene glycol diglycidyl ether as a crosslinking agent (modifier) and 7 parts of water.
The liquid modifier is cooled at −20 ° C. for 12 hours to make the liquid modifier solid, and then pulverized to classify with a wire net having a 2 mm hole to obtain a passing product, thereby pulverizing and modifying. The agent (6) was obtained.

Next, with respect to 100 parts of the water absorbent resin (b) obtained in Reference Example 2 above, the powdering modifier (6) above was added.
7.1 parts were added and mixed. Then, the obtained mixture was heat-treated at 140 ° C. for 30 minutes, and then classified with a wire netting having 840 μm pores to obtain a passing product, thereby obtaining a hydrophilic resin after crosslinking as a water absorbing agent (6). It was The various properties of this water absorbing agent (6) were measured by the methods described above. Table 2 summarizes the results.

Comparative Example 2 Various properties of the water absorbent resin (b) obtained in Reference Example 2 above as the comparative water absorbent (2) were measured by the above methods. Table 2 summarizes the results.

Comparative Example 3 With respect to 100 parts of the water absorbent resin (b) obtained in Reference Example 2 above, 0.1 part of ethylene glycol diglycidyl ether as a crosslinking agent (modifying agent) and a hydrophilic organic compound were used. Isopropyl alcohol 2 as a solvent
Parts and 5 parts of water were mixed. After that, the obtained mixture was heat-treated at 180 ° C. for 25 minutes, and then classified with a wire net having an opening of 840 μm to obtain a passing product. A hydrophilic polymer was obtained. The performances of this comparative water absorbent (3) were measured by the above-mentioned methods. Table 2 summarizes the results.

Comparative Example 4 100 parts of the water-absorbent resin (b) obtained in Reference Example 2 above, 1 part of glycerin as a crosslinking agent (modifying agent), and 1 part of isopropyl alcohol as a hydrophilic organic solvent. And 3 parts of water were mixed. Then, the obtained mixture was heated at 200 ° C. for 40 minutes, and then heat-treated, and then classified with a wire netting having an opening of 840 μm to obtain a passing product. To obtain a hydrophilic polymer. The properties of this comparative water absorbent (4) were measured by the above-mentioned methods. Table 2 summarizes the results.

Comparative Example 5 A comparative water absorbing agent was obtained in the same manner as in Example 6, except that the liquid modifier was not pulverized. That is, first, 0.1 parts of ethylene glycol diglycidyl ether as a crosslinking agent (modifying agent) and 7 parts of water were stirred and mixed to obtain a liquid modifying agent (5).

Next, to 100 parts of the water absorbent resin (b) obtained in Reference Example 2 above, 7.1 parts of the above liquid modifier was added and mixed. Then, the obtained mixture was heat-treated at 140 ° C. for 30 minutes, and then classified by a wire net having 840 μm pores to obtain a passing product, which was cross-linked as a comparative water-absorbing agent (5). A hydrophilic polymer was obtained. The performances of this comparative water absorbent (5) were measured by the above-mentioned methods. Table 2 summarizes the results.

[0100]

[Table 2]

As is clear from the results shown in Table 1, the hydrophilic resin of the present invention comprises a hydrophilic polymer having a functional group,
By including the powdered modifying agent obtained by powderizing the liquid modifying agent, the gel breaking force was high and the retention rate was high even after the deterioration promoting test. From this, it is understood that the hydrophilic resin of the present invention does not change its binding property with time during the period from the production to the use. This is due to the following reasons. In other words, since the liquid modifier forms a powdered modifier, the hydrophilic polymer and the modifier in the liquid modifier must exist and react separately in the hydrophilic resin until they are used. There is no. Then, when the hydrophilic resin absorbs the aqueous liquid, for example, the hydrophilic polymer and the modifier in the liquid modifier are brought into contact with each other to react with each other, and the hydrophilic polymer is modified. Therefore, since the hydrophilic polymer can be uniformly modified and the timing of the modification can be controlled, it is possible to prevent deterioration of various properties developed by the modification due to aging. As described above, the hydrophilic resin of the present invention can more effectively prevent the deterioration of the above-mentioned various characteristics due to the change with time. Further, as is clear from the results of Table 1 and Table 2, the hydrophilic resin of the present invention was modified (surface cross-linking) after the powdering modifier was uniformly mixed with the hydrophilic polymer. It had excellent absorption characteristics under pressure.

[0102]

As described above, the method for producing a hydrophilic resin according to claim 1 of the present invention comprises the step of mixing the hydrophilic polymer with the powdered modifier obtained by powderizing the liquid modifier. Is. As described above, the method for producing a hydrophilic resin according to claim 2 of the present invention is the same as the method for producing a hydrophilic resin according to claim 1, wherein the powdering is performed by converting the liquid modifier into a particulate water-insoluble compound. This is a configuration performed by mixing. The method for producing a hydrophilic resin according to claim 3 of the present invention is as described above.
The method for producing a hydrophilic resin according to claim 1, wherein the pulverization is performed by cooling the liquid modifier below its melting point to solidify it. As described above, the method for producing a hydrophilic resin according to claim 4 of the present invention is as described above.
In the method for producing a hydrophilic resin according to any one of
This is a constitution in which a mixture of a hydrophilic polymer and a powdering modifier is heated. As described above, the method for producing the hydrophilic resin according to the fifth aspect of the present invention is the method for producing the hydrophilic resin according to any one of the first to third aspects, wherein the hydrophilic polymer and the powder are used. The composition is such that a liquid or gaseous aqueous liquid is added to a mixture of the body-modifying agent, and then the mixture is heated. The method for producing a hydrophilic resin according to claim 6 of the present invention is
As described above, in the method for producing a hydrophilic resin according to any one of claims 1 to 5, the hydrophilic polymer is a water-absorbent resin having an acid group. Claim 7 of the present invention
The method for producing a hydrophilic resin of the described invention, as described above,
The method for producing a hydrophilic resin according to any one of claims 1 to 6, wherein the liquid modifier includes a crosslinking agent. As described above, the method for producing a hydrophilic resin according to claim 8 of the present invention is the method for producing a hydrophilic resin according to claim 7, wherein the crosslinking agent has a weight average molecular weight of 2,0.
This is a configuration containing a polyvalent amine of 00 or more. As described above, the powdered modification agent of the invention according to claim 9 of the present invention is a composition containing a liquid modification agent capable of reacting with an acid group and a particulate water-insoluble compound. As described above, the powdered modification agent according to the tenth aspect of the present invention is the powdered modification agent according to the ninth aspect, wherein the liquid modification agent contains a crosslinking agent.

According to the above constitution, since the hydrophilic polymer and the powdered modifier obtained by powderizing the liquid modifier are mixed,
The liquid modifier can be mixed with the hydrophilic polymer in a substantially solid state. Therefore, as compared with the case where the liquid modifier and the hydrophilic polymer are mixed, the hydrophilic polymer and the liquid modifier, that is, the powdered modifier can be uniformly mixed. Further, since the hydrophilic polymer and the liquid modifier are present separately, even if the hydrophilic polymer and the powdered modifier are mixed, the liquid modifier is immediately absorbed by the hydrophilic polymer,
Alternatively, the reaction between the modifier and the hydrophilic polymer is not started. Then, the hydrophilic polymer can be uniformly modified at the time when the hydrophilic resin absorbs the aqueous liquid, or at the time when the hydrophilic resin is heated, for example. Therefore, the timing of the denaturation can be controlled. Therefore, according to the above configuration, it is possible to easily obtain the hydrophilic resin having an excellent balance of various characteristics.

Further, the hydrophilic resin according to claim 11 of the present invention has a constitution containing the hydrophilic polymer and the powdered modifying agent obtained by powderizing the liquid modifying agent as described above.

According to the above structure, the liquid modifier is powdered to form the powdered modifier. Therefore, the liquid modifier is contained in the hydrophilic resin in a substantially solid state. Further, since the liquid modifier forms a powdered modifier, in the hydrophilic resin,
Until used, the hydrophilic polymer and the liquid modifier are present separately and do not react. On the other hand, when the hydrophilic resin absorbs, for example, an aqueous liquid, or when the hydrophilic resin is heated, for example, the hydrophilic polymer and the modifier in the liquid modifier are brought into contact with each other to react, and the hydrophilic polymer is Be denatured. Therefore, the hydrophilic polymer can be uniformly modified and the timing of the modification can be controlled. Therefore, for example, the absorption capacity under pressure, various properties exhibited by the modification, the gel breaking force, etc. can be improved. It is possible to prevent the deterioration of various characteristics including the above due to aging.

Therefore, according to the above constitution, the absorbent polymer has excellent absorption characteristics under pressure, such as absorption capacity under pressure and water retention capacity, and when it is used as a hygienic material, the hydrophilic polymer It is possible to provide a hydrophilic resin capable of exhibiting excellent performance (absorption property) even if the weight% (resin concentration) is increased. Further, according to the above configuration, excellent absorption characteristics under pressure, the hydrophilic polymer is less likely to fall off from the absorber at the time of water absorption, and, after the production, during the period until use, its binding It is possible to provide a hydrophilic resin whose properties do not change with time.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a measuring device used for measuring a water absorption capacity under pressure, which is one of the performances of a hydrophilic resin in the present invention.

[Explanation of symbols]

 1 Balance 2 Container 3 Outside Air Suction Pipe 4 Conduit 5 Measuring Section 6 Glass Filter 7 Filter Paper 8 Support Cylinder 9 Wire Mesh 10 Weight 11 Artificial Urine

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area C08K 5/109 KAS C08K 5/17 KAY 5/17 KAY 9/00 KCM 9/00 KCM C08L 33 / 02 LHR C08L 33/02 LHR 101/14 LTB 101/14 LTB A61F 13/18 307A (72) Inventor Yoshihiko Masuda 1 992, Nishi-oki, Hamaji-ku, Himeji-shi, Hyogo 1

Claims (11)

[Claims] 1. A method for producing a hydrophilic resin, which comprises mixing a hydrophilic polymer and a powdered modifier obtained by powderizing a liquid modifier. 2. The method for producing a hydrophilic resin according to claim 1, wherein the pulverization is performed by mixing a liquid modifier with a particulate water-insoluble compound. 3. The method for producing a hydrophilic resin according to claim 1, wherein the pulverization is carried out by cooling the liquid modifier below its melting point to solidify it. 4. The method for producing a hydrophilic resin according to claim 1, wherein a mixture of the hydrophilic polymer and the powdering modifier is heated. 5. A liquid or gaseous aqueous liquid is added to a mixture of a hydrophilic polymer and a pulverizing modifier, and the mixture is heated.
The method for producing a hydrophilic resin according to item. 6. The method for producing a hydrophilic resin according to claim 1, wherein the hydrophilic polymer is a water absorbent resin having an acid group. 7. The method for producing a hydrophilic resin according to claim 1, wherein the liquid modifier contains a crosslinking agent. 8. The cross-linking agent has a weight average molecular weight of 2,000.
The method for producing a hydrophilic resin according to claim 7, wherein the method comprises 0 or more polyvalent amine. 9. A powdered modifying agent comprising a liquid modifying agent capable of reacting with an acid group and a particulate water-insoluble compound. 10. The powdered modifier according to claim 9, wherein the liquid modifier contains a crosslinking agent. 11. A hydrophilic resin comprising a hydrophilic polymer and a powdered modifier obtained by powderizing a liquid modifier.