JPH09194598A - Granulation of high water absorbing resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To granulate the subject resin excellent in water absorbing force under load, useful as a sanitary article, a water retaining agent for soil, by reacting a high water absorbing resin with a cross-linking agent in the presence of water-insoluble inorganic powder and water and adding water during rise in temperature and the cross-linking reaction. SOLUTION: A reactor is charged with acrylic acid, is neutralized by dripping a solution, obtained by dissolving sodium hydroxide in water, with stirring under cooling and oxygen in the system is replaced with bubbling nitrogen. 1% aqueous solution of ammonium persulfate and 0.5% aqueous solution of N,N'-methylenebisacrylamide are added to the system, polymerization is carried out at 60 deg.C for 1 hour and contents are taken out from the reactor, cut into small pieces, dried at 100 deg.C for 2 hours and then ground by a grinder to give the objective high water absorbing resin. Then the high water absorbing resin is cross-linked by adding a cross-linking agent (e.g. ethylene glycol dimethacrylate, etc.), water-insoluble inorganic powder (e.g. talc) and water and further adding water during rise in temperature and the cross-linking reaction to give the objective high water absorption resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for granulating a highly water-absorbent resin, and more particularly to a method for granulating a highly water-absorbent resin which is excellent in water absorption capacity and water absorption under load.

[0002]

BACKGROUND OF THE INVENTION Super absorbent polymers are useful as a body fluid absorbent for absorbing and preventing leakage of body fluids in sanitary products. In addition, a water retention agent for soil, a seed coating agent, a water blocking agent, a thickener, It is used for anti-condensation agents, desiccants, humidity control agents, etc. However, these super absorbent resins are
When water is absorbed, particles stick to each other, uniform water absorption is impeded, water does not diffuse throughout the water-absorbent resin, and the water absorption capacity decreases, and the water absorption capacity under load, which is important for sanitary material applications, is low. Some have.

As a technique for improving these drawbacks, a method of adding a polyhydric alcohol or its oxyalkylene ether to a highly water-absorbent resin (JP-A-58-183754),
A method in which a superabsorbent resin is crosslinked by absorbing a crosslinking agent and water in the presence of an inorganic powder (JP-A-60-16395).
No. 6), sucrose fatty acid ester is added to the superabsorbent resin, and a crosslinking agent is used in the presence of water to crosslink (JP-A-3-28203). Water and inorganic substances are added to the superabsorbent resin. A method in which a crosslinking agent is crosslinked in a hydrophilic inert solvent in the presence of powder (JP-A-60-147475), and a crosslinking agent dispersed in a hydrophobic organic solvent in the presence of a surfactant is hydrophobic. Of adding a superabsorbent resin dispersed in a water-soluble organic solvent to a suspension (JP-A-1-207327), the content of the organic solvent in the presence of a surfactant in advance,
By mixing a super absorbent polymer and an inorganic powder, the water content of which is specified,
Then, a method of drying (Japanese Patent Laid-Open No. 2-284927), the water content is defined, and water is further added during the crosslinking reaction,
A method of continuing the cross-linking reaction (Japanese Patent Laid-Open No. 3-195705), a powdery inorganic substance is added to a super absorbent polymer in the presence of water and a surfactant in an inert solvent, and then water and the inert solvent are distilled off. A method of leaving (Japanese Patent Publication No. 6-43500) is known.

[0004]

However, with the technique disclosed in Japanese Patent Laid-Open No. 183754/1983, a decrease in water absorption under load cannot be avoided, and in Japanese Patent Laid-Open No. 60-639.
56, JP-A-3-28203, and JP-A-6-28203.
In the disclosed technology of 0-147475, since the crosslinking is performed in the presence of a large amount of water, the superabsorbent resin absorbs part of the water, and the effect of adding the crosslinking agent cannot be sufficiently obtained.
As a result, there is a drawback that the water absorption capacity under load is reduced, and further, JP-A-1-207327 and JP-A-2-2849.
27, JP-A-3-195705, and JP-B-6.
Even with the disclosed technique, the effect of sufficiently improving water absorption under load cannot be obtained, and there is a demand for a granulation method of a highly water-absorbent resin having a large water-absorbing capacity and an excellent water-absorbing power under load. Of.

[0005]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that a superabsorbent resin is crosslinked in the presence of a crosslinking agent, a water-insoluble inorganic powder and water. Upon granulation, it was found that by adding more water at the time of temperature rise and / or during the cross-linking reaction, the water absorption capacity is large and the water absorption is good even under load, and the present invention has been completed. It was

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below.
The superabsorbent resin to be the subject of the present invention is not specified as long as it has a carboxylate group in the molecule, but specifically has a carboxylate group and absorbs a large amount of water in water to swell. A resin that forms a hydrogel. Here, the carboxylate group means a carboxyl group or a carboxylate group. Various resins are known as such a resin, for example, a hydrolyzate of a starch-acrylonitrile graft copolymer, a neutralized product of a starch-acrylic acid graft polymer, an acrylic acid ester-vinyl acetate copolymer. Saponified product, hydrolyzate of acrylonitrile copolymer or acrylamide copolymer, crosslinked polyvinyl alcohol modified product, self-crosslinking polyacrylic acid neutralized product, polyacrylic acid salt crosslinked product, crosslinked isobutylene-maleic anhydride copolymer Examples thereof include, but are not limited to, a highly water-absorbent resin composed of a polyacrylate cross-linked product and a cross-linked polyvinyl alcohol-modified product.

The highly water-absorbent resin composed of the crosslinked polyacrylic acid salt is usually obtained by polymerizing a monomer composed of a mixture of (meth) acrylic acid and a water-soluble salt of (meth) acrylic acid. Examples of the water-soluble salt include sodium salt, potassium salt, ammonium salt and the like. The mixing ratio of (meth) acrylic acid and the water-soluble salt of (meth) acrylic acid is preferably selected from the range of 10/90 to 50/50 in terms of molar ratio. If it deviates from this range, the absorption characteristics of the resulting superabsorbent polymer will deteriorate. A mixture of (meth) acrylic acid and a water-soluble salt of (meth) acrylic acid is
It is usually obtained by partially neutralizing (meth) acrylic acid with an alkali such as sodium hydroxide, potassium hydroxide or ammonia. In addition to these monomers, other vinyl monomers such as (meth) acrylic acid ester, unsaturated sulfonic acid or its salt, (meth) acrylamide,
A small amount of (meth) acrylonitrile, vinyl ester, vinyl ether, etc. can be used together.

In carrying out the polymerization, any known method can be adopted, and any of aqueous solution polymerization (static polymerization), emulsion polymerization (reverse phase emulsion polymerization), suspension polymerization (reverse phase suspension polymerization) and the like can be used. Although possible, reverse phase suspension polymerization or static polymerization is preferable. The polymerization method will be described more specifically below. When carrying out reverse phase suspension polymerization, an aqueous solution containing (meth) acrylic acid, a water-soluble salt of (meth) acrylic acid, preferably a crosslinking agent such as a polyfunctional vinyl monomer is dispersed in an organic solvent that is insoluble in water. Polymerization is performed in the presence of a radical polymerization initiator. At that time, it is possible to improve the stability of the polymerization by coexisting a known dispersion stabilizer or surfactant. As the organic solvent, cyclohexane,
Alicyclic hydrocarbons such as cyclopentane, n-pentane, n
Examples thereof include aliphatic hydrocarbons such as -hexane, n-heptane and ligroin, and aromatic hydrocarbons such as benzene, toluene and xylene. Judging from the melting point, boiling point, price, and industrial availability of the solvent, n-heptane and cyclohexane are the most practical. It is suitable that the polymerization temperature is 50 to 90 ° C. and the polymerization time is 0.5 to 5 hours. After completion of the polymerization, the superabsorbent resin is obtained by filtering the produced particles, washing and drying according to a conventional method.

Next, in order to carry out static polymerization, water, (meth) acrylic acid, water-soluble salt of (meth) acrylic acid and radical polymerization initiator are uniformly mixed, and no stirring or kneading is performed thereafter. Polymerization is carried out, and the obtained solid is pulverized and dried. Industrially, the above uniform mixed solution is put in a bucket conveyor, supplied on a belt having weirs at both ends, supplied in a tube, or charged in a container having an arbitrary shape and 40 After kneading at a temperature of about 100 ° C for 0.03 to 5 hours, polymerization is allowed to proceed while keeping no mixing. The resin solid matter having reached a predetermined polymerization rate is cut to a size of a pellet or a particle size smaller than that, pulverized and dried. It is desirable to continuously perform this series of operations.

In carrying out the above-mentioned polymerization method, the polymerization initiator used is an azonitrile such as azobisisobutyronitrile; an alkyl peroxide such as t-butyl peroxide or cumene hydroperoxide; di- Dialkyl peroxides such as t-butyl peroxide; amyl peroxides such as acetyl peroxide, lauroyl peroxide, stearoyl peroxide, benzoyl peroxide; t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t
Examples include peroxyesters such as butyl peroxypivalate; ketone peroxides such as methyl ethyl ketone peroxide and cyclohexanone peroxide; hydrogen peroxide solution; ammonium persulfate; potassium persulfate; and cerium salts. The amount of the initiator added is about 200 to 5000 ppm based on the total amount of (meth) acrylic acid and the water-soluble salt of (meth) acrylic acid.

During the reverse phase suspension polymerization, it is practical to add a surfactant to keep the system stable.
Examples of the activator include polyoxyethylene alkyl ether, polyoxyethylene acyl ester, polyoxyethylene sorbitan fatty acid ester, sorbitan fatty acid ester, oxyethyleneoxypropylene block copolymer, sucrose fatty acid ester, higher alcohol sulfate ester salt, and alkylbenzene sulfone. A nonionic surfactant such as an acid salt or polyoxyethylene sulfate, or an anionic surfactant is used alone or in combination. Further, in order to exert a high water absorbing property, a water-soluble crosslinking agent (different from a crosslinking agent having two or more functional groups capable of reacting with a carboxylate group) is usually used together during polymerization.

The water-soluble crosslinking agent is 10 to 2 relative to the total amount of (meth) acrylic acid and (meth) acrylic acid water-soluble salt.
000 ppm, preferably 50 to 1000 ppm is used, and as an example of such a water-soluble crosslinking agent, N, N '
-Methinebis (meth) acrylamide, N-methylol (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, glycerin tri (meth) acrylate, glycerin (meth) acrylate, (Meth) acrylic acid polyvalent metal salt, trimethylolpropane tri (meth) acrylate, triallylamine, triallyl cyanurate, triallyl isocyanurate, triallyl phosphate, glycidyl (meth) acrylate,
Examples thereof include ethylene glycol diglycidyl ether, glycerin tri (di) glycidyl ether, polyethylene glycol diglycidyl ether, and polyglycerol polyglycidyl ether.

Further, the superabsorbent resin comprising a crosslinked polyvinyl alcohol-modified product has a maleic acid monoester content of 0.2 to 15 mol% and a saponification degree of 70 to 100 mol% vinyl acetate-maleic acid monoester. It can be obtained by irradiating the saponified copolymer with an electron beam or radiation of 0.1 to 50 Mrads in a water-containing state, or by heat treatment at 100 ° C. or higher.

The cross-linking agent used in the present invention is capable of reacting with the carboxylate group present in the superabsorbent resin modified according to the present invention, preferably other than this, a hydroxyl group, a sulfone group, an amino group and the like. It is a cross-linking agent having two or more functional groups, and such a cross-linking agent can be used without particular limitation. As the cross-linking agent,
For example, diglycidyl ether compounds, haloepoxy compounds, aldehyde compounds, isocyanate compounds and the like can be mentioned. Among these, for example (poly)
Diglycidyl ether compounds such as ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, and (poly) glycerin diglycidyl ether are suitable, and among these, diethylene glycol diglycidyl ether is a carboxy in the superabsorbent resin. Most suitable because of its reactivity with the rate group.

Specific examples of the haloepoxy compound include epichlorohydrin, epibromohydrin, α-methylepochlorohydrin, etc., aldehyde compounds such as glutaraldehyde and glyoxal, and isocyanate compounds such as 2,4-triphenyl. Examples thereof include rendi diisocyanate and hexamethylene diisocyanate. The amount of the crosslinking agent used is preferably 0.001 to 1 part by weight, more preferably 0.005 to 0.1 part by weight, relative to 100 parts by weight of the water-free superabsorbent resin.
Parts by weight. If the amount of the cross-linking agent used is less than 0.001 part by weight, the effect of addition will be small, and if it exceeds 1 part by weight, excessive crosslinking will be carried out and the water absorption amount will be significantly reduced, such being undesirable.

Examples of the water-insoluble inorganic powder used in the present invention include silicon dioxide, aluminum oxide, titanium dioxide, talc, bentonite, zeolite and other metal oxides, but silicon dioxide is preferably used. Further, these water-insoluble inorganic powders are preferably fine particles that can be adsorbed on the surface of the highly water-absorbent resin, and the preferable particle diameter is 200 μm or less, particularly preferably 10 μm.
0 μm or less. If the particle diameter exceeds 200 μm, the amount of free water-insoluble inorganic powder that is not adsorbed on the surface of the super absorbent polymer increases, which is not preferable. The specific surface area of the water-insoluble inorganic powder is preferably 30 m ² / g or more, more preferably 100 m ² / g or more. Specific surface area is 30
If it is less than m ² / g, adsorption to the surface of the super absorbent polymer is poor,
Granule improvement effect is small and not preferable. The amount of the water-insoluble inorganic powder used is preferably 0.005 to 2 parts by weight, and particularly preferably 0.05 to 1 part by weight, based on 100 parts by weight of the water-free superabsorbent resin. When the amount of the water-insoluble inorganic powder used is less than 0.005 part by weight, a sufficient granulation improving effect cannot be obtained, and when it exceeds 2 parts by weight, free water-insoluble inorganic powder increases, which is not preferable.

Next, the granulation method of the super absorbent polymer of the present invention will be specifically described. The present invention is a super absorbent polymer as a crosslinking agent,
A water-insoluble inorganic powder, which is characterized in that water is further added at the time of temperature rise and / or during the crosslinking reaction in carrying out the granulation by causing the crosslinking reaction in the presence of water. The addition order of the water-insoluble inorganic powder is not particularly limited, and it may be added in any order, or may be added in a lump, but after the crosslinking agent is added to the super absorbent polymer from the viewpoint of its mixing property. It is preferable to add a water-insoluble inorganic powder, and such a method will be described in more detail below.

The super absorbent polymer used may be used in a dry state, but is preferably used in a water containing state. The water content is preferably 3 to 50% by weight. If the water content is less than 3% by weight, it is difficult to carry out the crosslinking efficiently, and if it exceeds 50% by weight, the super absorbent polymer agglomerates.
As a lump, it is difficult to perform uniform crosslinking. The water content is more preferably 18 to 35% by weight. Examples of the method of obtaining the water-absorbing superabsorbent resin include a method of adding water to the superabsorbent resin, a method of containing water during the production of the superabsorbent resin, and the like, and a method of adding water to the superabsorbent resin. As, as long as it is a method of adding as uniformly as possible to the super absorbent polymer, it is not particularly limited, specifically, it may be added by spraying or steaming, in an organic solvent containing super absorbent resin. In addition, an organic solvent in which water is dispersed may be added.
Further, as a method for obtaining a superabsorbent resin which contains water uniformly when it is made to contain water during the production of the superabsorbent resin, preferably the superabsorbent resin powder containing water obtained by reverse phase suspension polymerization is subjected to azeotropic dehydration. There is a method of adjusting the water content within the above range by distilling off the water with. It goes without saying that the amount of water contained in the superabsorbent resin is included in the amount of water required for the granulation of the present invention.

A cross-linking agent is added to the above super absorbent polymer, but it is preferable to add the cross-linking agent uniformly.
It is preferable that the organic solvent liquid containing a crosslinking agent is added to the superabsorbent polymer, the mixture is uniformly mixed and stirred, and then the organic solvent is distilled off to uniformly add the crosslinking agent. The content of the crosslinking agent in the solvent is preferably 20 to 100 parts by weight with respect to 100 parts by weight of the super absorbent polymer. It is desirable to distill off the organic solvent under reduced pressure and low temperature in order to suppress the crosslinking reaction.
The temperature is suitably selected from the range of 0 to 250 torr and the temperature of 20 to 50 ° C.

Next, the water-insoluble inorganic powder is added. The addition may be carried out directly. However, considering the dispersibility of the powder, the water-insoluble inorganic powder should be added after being uniformly dispersed in water. preferable. When the water-insoluble inorganic powder is added as an aqueous dispersion, 100 to 5000 parts by weight of water is preferably added to 100 parts by weight of the water-insoluble inorganic powder, and more preferably 1000 to 3000 parts by weight of water is added. . If the amount of water is less than 100 parts by weight, the aqueous dispersion becomes difficult to handle, and if it exceeds 5000 parts by weight, the amount of added water becomes excessive, which is not preferable.

As a device for mixing the dispersion liquid of the water-insoluble inorganic powder or the super absorbent polymer, the cross-linking agent, (the water dispersion liquid of the water-insoluble inorganic powder) and water, a well-known mixing device can be used without limitation. As a mixing device that can be suitably used, for example, a high-speed rotating paddle type mixer, a double-arm type kneader, a conical screw mixer, etc. can be mentioned.

Next, the temperature is raised to start the cross-linking reaction to carry out granulation. The reaction temperature is 50 to 100.
C. is preferable, more preferably 60 to 80.degree. C., and the reaction time is preferably 20 to 240 minutes, more preferably 30 to 120 minutes. In the present invention, as described above, water is added at the time of heating during the crosslinking reaction and / or at the time of crosslinking reaction after the temperature is raised. The addition at 70 ° C. or lower is preferable, and more preferably at 60 ° C. or lower, water is added in total amount or in divided portions. In the case of divided addition, water is preferably added in two portions. In that case, the first / second time is 20-
80% by weight / 80 to 20% by weight.

When the residual amount of the cross-linking agent reaches 25 to 80% by weight of the compounding amount, it is 5 with respect to 100 parts by weight of the super absorbent polymer.
Add -20 parts by weight of water in one portion or in several portions. Water is preferably added in two portions. In that case, the distribution is 20-80% by weight for the first / second times / 80-20
% By weight.

The highly water-absorbent resin obtained by such a method has a high absorption capacity and an excellent water absorption capacity under load, and is used as a sanitary material such as a paper diaper and a sanitary napkin, a water retention agent for soil, and a seed coating agent. It can be widely used as a water-stopping agent, a thickener, an anti-condensation agent, a desiccant, a humidity control agent and the like.

[0025]

EXAMPLES The present invention will be specifically described below with reference to examples. In the examples, “part” and “%” are based on weight unless otherwise specified. In addition, the evaluation of the super absorbent polymer was performed according to the following procedure.

Example 1 5 l equipped with a stirrer, a reflux condenser and a nitrogen gas introducing tube
After 400 g of acrylic acid was charged into a separable flask, 530 g of water was added with 179 of sodium hydroxide 179 having a purity of 95%.
The solution in which g was dissolved was added dropwise with stirring and cooling to neutralize.
Nitrogen bubbling was performed for 30 minutes to replace oxygen in the system.
Next, 4 g of a 1% ammonium persulfate aqueous solution which had been subjected to nitrogen bubbling in advance and 2 g of a 0.5% N, N′-methylenebisacrylamide aqueous solution were added, and after sufficiently mixing, stirring was stopped. When the flask was immersed in a 60 ° C warm bath to start polymerization without stirring, the internal temperature returned to 60 ° C after reaching a maximum of 80 ° C after 10 minutes. Further, this temperature was maintained for 1 hour and then cooled to room temperature to terminate the polymerization. Remove the contents from the flask and cut into small pieces,
After drying at 100 ° C. for 2 hours, it was ground with a grinder and sieved to obtain 520 g of a highly water-absorbent resin having a particle diameter of 350 to 74 μm. 190 g of the super absorbent polymer (water content 22.5%),
As a crosslinking agent, 300 ppm of a bifunctional alicyclic epoxy compound with respect to the super absorbent polymer (trade name "Denacol EX-
314 "manufactured by Nagase Kasei Co., Ltd. and 76 g of cyclohexane were charged into a 1-liter twin-arm kneader, and after stirring 76 g of cyclohexane at 210 torr at 45 ° C., the mixture was mixed for 60 minutes. After that, 14.7 g of water (10% with respect to the super absorbent polymer) and 0.80 g (0.5% by weight) of water-insoluble inorganic powder are stirred using a stirrer, then added as a dispersion liquid and heated. This initiated the crosslinking reaction. It became 60 ° C. in 15 minutes after the start of the reaction.
40 minutes after the start of the crosslinking reaction, the residual amount of the crosslinking agent is 52
At the time of reaching the weight%, 10.3 g of water (7% based on the super absorbent polymer) was added. 40 minutes later, 10.3 g of water was added when the remaining amount of the crosslinking agent reached 22% by weight of the blended amount.
(7% based on superabsorbent resin) was added. While stirring in a kneader under atmospheric pressure, it was dried at 80 ° C. for 1 hour, and then statically dried at 110 ° C. for 3 hours to obtain about 160 g of a highly water-absorbent resin granule having a water content of 5%. It was The water absorption capacity and the water absorption capacity under load of the obtained granules of the super absorbent polymer were measured.

(Water absorption capacity) 0.2 g (in a dried state) of a granule of a highly water-absorbent resin was put into a 500 ml beaker, and 60 g of physiological saline (0.9% sodium chloride aqueous solution) or pure water 2
00 g was added, the mixture was lightly stirred with a glass rod, allowed to stand at room temperature for 1 hour, filtered with a 325-mesh wire net, the weight of the gel after filtration was measured, and the water absorption capacity was determined by the following formula. Water absorption capacity (g / g) = [gel weight after filtration (g) -0.2
(g)] / 0.2 (g)

(Water absorption capacity under load) A 50 ml capacity burette with a branch attached to a branch pipe and a glass filter funnel with an inner diameter of 55 mmφ are connected by a tube with an inner diameter of 6 mmφ, and the upper surface of the glass filter and the center of the burette branch pipe are connected. They were placed side by side so that the positions would be the same height, and left. The buret was filled with artificial urine, and the top of the buret was sealed with a rubber stopper. On a glass filter of a funnel with a glass filter, put 0.25 g of a super absorbent polymer granules through a non-woven fabric, and a cylindrical weight 45 having a bottom diameter of 54 mmφ on it.
A weight of 3 g was placed so that a load of 20 g / cm ² was applied to the super absorbent polymer on the glass filter. On the other hand, a tube (6 mmφ) was attached to the tip of the funnel with a glass filter, and a burette with a branch of 50 ml was placed vertically at the other end of the tube so that the upper surface of the glass filter and the center position of the branch pipe of the buret were at the same height. , Put artificial urine.
Leave for 60 minutes in this state to absorb water (ml)
/ G) was measured. The results are shown in Table 1.

Example 2 A highly water-absorbent resin produced in the same manner as in Example 1 was charged with a cross-linking agent and cyclohexane in a 1-liter twin-arm kneader, the cyclohexane was distilled off, and then the mixture was mixed with water.2. 8
g (2% with respect to super absorbent polymer) and 0.16 g (0.1
(% By weight) of the water-insoluble inorganic powder was stirred in the same manner as in Example 1, then added as a dispersion and the temperature was raised to start the crosslinking reaction. It became 60 ° C. in 15 minutes after the start of the reaction.
40 minutes after the start of the crosslinking reaction, the residual amount of the crosslinking agent is 48
At the time of reaching the weight%, 10.3 g of water (7% based on the super absorbent polymer) was added. 40 minutes later, 10.3 g of water was added when the remaining amount of the crosslinking agent reached 30% by weight of the blended amount.
(7% based on superabsorbent resin) was added. While stirring in a kneader under atmospheric pressure, it was dried at 80 ° C. for 1 hour, and then statically dried at 110 ° C. for 3 hours to obtain about 160 g of a highly water-absorbent resin granule having a water content of 5%. It was The water absorption capacity and the water absorption capacity under load of the obtained granules of the super absorbent polymer were measured in the same manner as in Example 1.

Example 3 A superabsorbent resin produced in the same manner as in Example 1 contained 300 ppm of a bifunctional epoxy compound as a cross-linking agent with respect to the superabsorbent resin (trade name "Denacol EX-314", Nagase Kasei Kogyo). (Manufactured by Co., Ltd.) and cyclohexane were charged into a double-arm kneader having a volume of 1 liter, cyclohexane was distilled off, and then mixed, and then 14.7 g of water (1 for the super absorbent polymer).
(0%) and 0.8 g (0.5% by weight) of the water-insoluble inorganic powder were stirred in the same manner as in Example 1, then added as a dispersion and the temperature was raised to start the crosslinking reaction. After starting the reaction
It reached 60 ° C. in 15 minutes. 40 minutes after the start of the cross-linking reaction, water 1
0.3 g (7% based on the super absorbent resin) was added. 40 minutes after that, the remaining amount of the crosslinking agent is 35% by weight of the blended amount.
10.3g of water (7% for super absorbent polymer)
%) Was added. While stirring in a kneader under atmospheric pressure,
Dry at 80 ° C for 1 hour, then dry by static drying for 11 hours.
This was carried out at 0 ° C. for 3 hours to obtain about 160 g of a granulated body of a super absorbent polymer having a water content of 5%. The water absorption capacity and the water absorption capacity under load of the obtained granules of the super absorbent polymer were measured in the same manner as in Example 1.

Example 4 The procedure of Example 1 was repeated except that when the water-insoluble inorganic powder was added in Example 1, the same amount of water-insoluble inorganic powder was added and then the same amount of water was added. About 160 g of a granulated body of a super absorbent polymer having a rate of 5% was obtained. The water absorption capacity and the water absorption capacity under load of the obtained granules of the super absorbent polymer were measured in the same manner as in Example 1.

Example 5 The same procedure as in Example 1 was carried out except that 20.6 g of water was added all at once 10 minutes after the initiation of the crosslinking reaction (during heating), and no water was added thereafter. About 160 g of a granulated body of a super absorbent polymer having a water content of 5% was obtained. The water absorption capacity and the water absorption capacity under load of the obtained granules of the super absorbent polymer were measured in the same manner as in Example 1.

Comparative Example 1 The same procedure as in Example 1 was carried out except that no crosslinking agent was used, to obtain about 160 g of granules of a super absorbent polymer having a water content of 5%. The water absorption capacity and the water absorption capacity under load of the obtained granules of the super absorbent polymer were measured in the same manner as in Example 1.

Comparative Example 2 The same procedure as in Example 1 was carried out except that the aqueous dispersion of the water-insoluble inorganic powder was not used, and 40 minutes after the initiation of the crosslinking reaction, the residual amount of the crosslinking agent was 53% by weight of the blended amount. Water 1
0.3 g (7% based on the super absorbent resin) was added. 40 minutes after that, the remaining amount of the crosslinking agent is 28% by weight of the blended amount.
10.3g of water (7% for super absorbent polymer)
%) Was added. About 160 g of granules of a super absorbent polymer having a water content of 5% were obtained. The water absorption capacity and the water absorption capacity under load of the obtained granules of the super absorbent polymer were measured in the same manner as in Example 1.

Comparative Example 3 The same procedure as in Example 1 was repeated except that 231 g (water content 36.5%) was used as the highly water-absorbent resin and the two times of water addition carried out during the crosslinking reaction was omitted. About 160 g of a granulated body of a super absorbent polymer having a rate of 5% was obtained. The water absorption capacity and the water absorption capacity under load of the obtained granules of the super absorbent polymer were measured in the same manner as in Example 1.

[0036]

[Table 1]

[0037]

INDUSTRIAL APPLICABILITY In the present invention, when granulation is carried out by crosslinking reaction of a super absorbent polymer in the presence of a crosslinking agent, a water-insoluble inorganic powder, and water, water is further added during heating and / or during the crosslinking reaction. Since it is added, it is possible to produce a granulated body of a highly water-absorbent resin, which is excellent in water absorption ability and water absorption under load.

Claims (3)

[Claims] 1. When granulating the superabsorbent resin by a crosslinking reaction in the presence of a crosslinking agent, a water-insoluble inorganic powder and water, further water is added at a temperature rise and / or during the crosslinking reaction. A granulation method for a super absorbent polymer characterized. 2. The method for granulating a super absorbent polymer according to claim 1, wherein a water-insoluble inorganic powder is allowed to coexist as an aqueous dispersion. 3. The method for granulating a highly water-absorbent resin according to claim 1, wherein water to be further added during the crosslinking reaction is dividedly added.