JP2000143720A - Production of water absorptive resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject resin, the gel constituting the resin rarely agglomerating with each other after it is polymerized, and being finely cuttable and efficiently dried when allowed to stand, by incorporating a specific water- containing gel with a surfactant and allowing it to stand for drying. SOLUTION: This resin is obtained by allowing (A) a water-containing gel of polymer which swells in the presence of water to stand and dry, after it is incorporated with (B) a surfactant at 0.005 to 1 wt.%, based on solids of the component A, preferably 0.05 to 0.5 wt.%. The substances useful for the component A include water-containing gels which swell in the presence of water, e.g. crosslinked starch/acrylate copolymer, polyacrylate, polysulfone and cellulose derivative. The preferable surfactants for the component B are nonionic ones, e.g. sorbitan monolaurate and ethylene oxide adduct of dimethylsiloxane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a water-absorbent resin. More specifically, the present invention relates to a production method which is excellent in drying efficiency in a drying step which requires the most energy during production of an absorbent resin.

[0002]

2. Description of the Related Art Several methods have conventionally been employed as a process for producing a water-absorbing resin. As a typical example, for example, a method in which acrylate is shredded with a double-arm kneader while polymerizing an aqueous solution, and dried with hot air, after polymerizing the acrylate with an aqueous solution, the polymer gel is shredded with a shredder, and hot air Drying or drying while crushing the gel with a drum dryer, after polymerizing acrylic acid in aqueous solution,
Neutralizing and shredding the polymer gel with a shredder, drying by crushing the gel with hot air drying or a drum dryer, removing a certain amount of water from a high concentration acrylate aqueous solution by heat during polymerization A method in which the polymer gel is shredded, and then the polymer gel is shredded and heated and dried, and a method in which the acrylate is polymerized by a reversed phase suspension polymerization method and, if necessary, the solvent and water are removed by heating under reduced pressure. Among these methods, particularly, and regarding, since the gel of the water-absorbent resin itself originally has tackiness, the shredded gels fuse together and adhere to each other during drying. As a result, there is a problem that the air permeability of the hot air is deteriorated and the drying efficiency is lowered.

[0003] As an example proposed for the purpose of increasing the drying efficiency of a hydrogel, a method in which a surfactant is added to a hydrogel containing an acid group obtained by aqueous solution polymerization and drying is performed while stirring with a rotor. (Japanese Unexamined Patent Publication No.
34134). However, this method does not mention an efficient drying method in a stationary state. In general, a method of drying in a stationary state is more advantageous in terms of both equipment cost and running cost. Therefore, there has been a demand for a technical breakthrough in increasing the drying efficiency when drying a hydrogel in a stationary state.

[0004]

In the process of drying a hydrous polymer gel in a static state, the polymer gel is insufficiently shredded, and after the shredding, the gels are fused to each other. Not only does it impede the ventilation of the hot air, it takes a long time to dry, but also because of the uneven drying state, it is not only difficult to grind to the desired particle size in the subsequent grinding process, but also a sticky undried product However, there is a problem that pulverization trouble is likely to occur due to mixing in the pulverization system.

[0005]

SUMMARY OF THE INVENTION In view of the above problems, the present inventors have found that there is little fusion between gels after polymerization, and the gel has excellent shredding properties, and can be dried efficiently in a static state. As a result of intensive studies to obtain a method for producing a water-absorbent resin, the present invention has been reached.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS That is, the present invention provides a method for producing a water-absorbent resin, which comprises adding a surfactant (B) to a water-containing gel (A) of a water-swellable polymer and drying the resultant in a stationary state. Is the law.

In the present invention, the water-containing gel (A) of the water-swellable polymer before drying includes, for example, a crosslinked product of a starch-acrylate copolymer, a salt of a starch-acrylic acid copolymer, Saponified starch-acrylonitrile copolymer, cross-linked polyacrylate, self-cross-linked polyacrylate, saponified cross-linked (meth) acrylate-vinyl acetate copolymer, isobutylene / maleic anhydride copolymer Cross-linked product, cross-linked polysulfonate, cross-linked polyacrylate / polysulfonate copolymer, cross-linked polyacrylic acid / polyacrylamide copolymer, hydrolyzate of cross-linked polyacrylamide, cross-linked polyacrylamide, cross-linked Examples include a hydrogel containing a water-swellable polymer such as polyvinylpyrrolidone and a crosslinked product of a cellulose derivative. Preferably, a polymerizable monomer containing a carboxylate and / or carboxylic acid capable of absorbing and retaining a large amount of liquid by ionic osmotic pressure and having little water separation even when a load or an external force is applied is used as a main component. Is a hydrous gel of a hydrophilic cross-linked polymer. In particular, in the polymer having a high degree of water absorption by reducing the degree of cross-linking, the adhesiveness of the gel is high, the gel is easily fused due to low elasticity, and it is difficult to shred, so the effect of the present invention Is more pronounced. The type of salt is not particularly limited, but is usually an alkali metal salt such as sodium or potassium.

[0008] The crosslinking agent (A) is not particularly limited as long as it is a crosslinking agent having an ethylenically unsaturated group and / or a reactive functional group and capable of obtaining a hydrogel crosslinked polymer. Specifically, for example, a compound having two or more ethylenically unsaturated groups [for example, N, N'-methylenebis (meth) acrylamide, ethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate Glycerin (di / tri) acrylate, trimethylolpropane triacrylate, triallylamine, triallyl cyanurate, triallyl isocyanurate, tetraallyloxyethane, pentaerythritol triallyl ether, etc.], ethylenically unsaturated groups and reactive functionalities Compounds having a reactive group (eg, glycidyl (meth) acrylate), compounds having two or more reactive functional groups [eg, ethylene glycol, diethylene glycol, glycerin, propylene glycol, diethanolamine, triethanolamine, etc.] Methylolpropane, polyethyleneimine, etc.], and two or more of these may be used in combination. Among these, preferred are N, N'-methylenebisacrylamide, trimethylolpropane triacrylate, tetraallyloxyethane, pentaerythritol triallyl ether, triallylamine, and ethylene glycol diacrylate. The amount of the crosslinking agent used is usually 0.001 to 5%, more preferably 0.05 to 2%, based on the total mass of the polymerizable monomer and the crosslinking agent. When the amount of the crosslinking agent is 0.0
If the content is less than 01%, it becomes a sol at the time of water absorption, and the water absorption / water retention ability, which is a function of the water absorbent resin, is reduced. Further, the drying property is very poor, and the productivity is inefficient. 5
%, On the contrary, the crosslinking becomes too strong and does not exhibit sufficient water absorption / water retention ability. Various additives, chain transfer agents (for example, thiol compounds, etc.), extenders and the like may be added to these polymerization systems.

The method for polymerizing the water-absorbing resin is not particularly limited, and examples thereof include an aqueous solution polymerization method and a reversed phase suspension polymerization method. Preferably, water is used as a main component, comprising a polymerizable monomer and a crosslinking agent. Is a method of radical polymerization. Polymerization concentration,
There are no particular limitations on the polymerization initiation temperature, the polymerization initiator in the case of radical polymerization, the presence or absence of heat removal during polymerization, and the polymerization conditions such as the polymerization apparatus, and known conditions can be applied.

The surfactant (B) in the present invention includes a nonionic surfactant, an anionic surfactant and an amphoteric surfactant. Preferred are nonionic surfactants. Examples of the nonionic surfactant include sorbitan lauric acid (mono / di) ester, sorbitan palmitic acid (mono / di) ester, sorbitan stearic acid (mono / di) ester, sorbitan oleic acid (mono / di) ester, Sorbitan coconut oil (mono / di) ester and their ethylene oxide adducts, polyoxyethylene sorbitan lauric acid (mono / di) ester, polyoxyethylene sorbitan palmitic acid (mono / di) ester, polyoxyethylene sorbitan stearic acid (Mono / di) ester, polyoxyethylene sorbitan oleic acid (mono / di) ester, polyoxyethylene lauric acid (mono / di) ester, polyoxyethylene stearic acid (mono / di) ester, polyoxyethylene oleic acid ( mono/ ) Ester, lauryl alcohol ethylene oxide adduct, oleyl alcohol ethylene oxide adduct, Macko alcohol ethylene oxide adduct, polyoxyethylene nonylphenyl ether, polyoxyethylene / polyoxypropylene block polymer, polydimethylsiloxane polyoxyethylene adduct, One or more selected from the group consisting of aliphatic or alicyclic alcohols having 4 or more carbon atoms, and a combination of these with an amphoteric surfactant or an anionic surfactant [however, (mono / di) Esters represent monoesters and / or diesters].

The amount of the active ingredient of the surfactant (B) relative to the water-swellable polymer hydrogel (A) is preferably determined by giving 0.005 to 1% by mass based on the solid content of (A). The condition is obtained. Preferably, it is 0.05 to 0.5%. When the amount is less than 0.005%, the effect of the present invention is poor, and when it exceeds 1%, the powder fluidity of the dried product is adversely affected, and the powder handling property as a water-absorbing resin is deteriorated. I do.

By providing the surfactant (B) to (A), the shredding property of the gel is improved, and the mechanism for suppressing the fusion of the gels is as follows. It is presumed that, because it has affinity with (A), the hydrophobic groups of (B) are oriented outward and fusion is suppressed. For this reason, in the case of a surfactant having extremely high hydrophilicity or a surfactant having extremely strong hydrophobicity, the present mechanism is unlikely to work. Therefore, the HLB of the surfactant is 4
To 15 are preferable, and 5 to 13 are more preferable. Also,
Among the hydrophilic groups, nonionic groups are particularly effective. HLB is a value calculated by the Oda method.

The application of (B) to (A) is preferably an aqueous solution or dispersion of (B), and the concentration of the solution of (B) is suitably from 0.01 to 10%. More preferably, it is 0.01 to 5%. When the solution concentration is lower than 0.01%, the amount of the solution (B) applied to the solution (A) is increased, so that the pure content of the solution (A) is reduced and the drying efficiency is rather deteriorated. If it exceeds 10%, the effect is poor because the solution (B) is not uniformly dispersed on the surface of (A).

As the solution (B), it is preferable to use a solution emulsified with an emulsifier in combination except for the case of self-dispersion. Also, a method of mechanically emulsifying and dispersing is suitably used, but in any case, the effect of the present invention is higher if uniformity is maintained until (B) is added to (A). (B) is added to (A) during the polymerization step of the water-swellable polymer and / or before the drying step.

The method of adding the solution (B) to the solution (A) is as follows.
There is a method in which (A) gets off with a spray or the like before, during, or after passing through the shredder. Either method can be adopted, but a method is preferred in which (B) is dispersed as uniformly as possible on the surface of (A) during the transfer of the gel to the drier after passing through the dryer. (B) When the gel is kneaded with a large shear after dropping the solution, (B) penetrates into the interior of (A) to reduce the effect, and more effect is required to obtain the effect of the present invention. Since (B) is required, it is preferable that a large share is not added after the uniform addition. (B) may be added both before and after passing through the shredder, or (B) may be added during polymerization.

(B) needs to have no more than two functional groups which react with the active ingredient of (A). In the case of having two or more reactive groups, (B) acts as a cross-linking agent and has a cross-linked structure stronger than the originally intended degree of cross-linking, resulting in a decrease in absorption performance.

The drying temperature of (A) to which (B) was added was 6
0-250 ° C is preferred. More preferably, 100 to
200 ° C. When the drying temperature is 60 ° C. or less, it takes a very long time to dry and is impractical.
If the temperature exceeds ℃, there is a possibility that a side reaction or decomposition of the resin may occur, resulting in a decrease in absorption performance.

As the shredding machine used for the shredding of (A), a conventionally known device can be used. Specific examples of the device include a double-arm kneader, an internal mixer (Banbury mixer), a self-cleaning mixer, a gear compound, a screw-type extruder, a screw-type kneader, and a minch machine. These shredders can be used in combination of two or more.

In a shredder, a neutralizing agent (eg, an aqueous solution of sodium hydroxide, sodium carbonate, etc.) for neutralizing acid groups contained in the water-swellable polymer in (A) is mixed, and Shredding and neutralization may be performed simultaneously. It is also possible to mix a crosslinking agent having two or more groups that react with the water-absorbing resin in the gel to cause a crosslinking reaction. If necessary,
As additives and extenders, residual monomer reducing agents (eg, sodium sulfite, hydrogen peroxide), antibacterial agents (eg, quaternary ammonium salt compounds, chlorhexidine compounds, metal salt antibacterial agents, etc.), preservatives, fragrances, Deodorants, colorants, fibrous materials, antioxidants, silica, zeolites, and the like can be added.

Examples of the apparatus for drying (A) to which (B) is added include: a parallel flow band dryer (tunnel dryer), a ventilation band dryer, a jet flow (nozzle jet) dryer, and a ventilation type dryer. And a box-type hot air dryer, and the heat source is not particularly limited. These dryers can be used in combination of two or more.

A water-absorbent resin obtained by adding (B) to (A), followed by drying, pulverization and particle size adjustment, and a surface-crosslinked water-absorbent resin near the particle surface are also included in the scope of the present invention. Surface cross-linking can be performed based on a known method.

[0022]

The present invention will be further described with reference to the following examples and comparative examples, but the present invention is not limited to these examples. The drying time, the angle of repose, and the amount of normal pressure absorption of the product obtained by crushing and sieving after drying were measured by the following methods.
Hereinafter, unless otherwise specified,% indicates mass%.

Time required for drying: The time required from when (A) was placed in the dryer until the water content became 5% or less was measured and defined as the required time for drying. The water content was calculated by measuring the mass of the dried product and calculating the difference from the mass of the gel before drying (the moisture content is known).

Angle of repose: Using a powder angle tester (manufactured by Hosokawa Micron Corporation), the angle of repose was measured according to the manual.

Normal pressure absorption: 1.00 g of a water-absorbing resin was placed in a 10 × 20 cm tee bag made of a 250-mesh nylon cloth, and an excess of normal saline (0.
(9% by mass aqueous sodium chloride solution) for 60 minutes, then suspended vertically and drained for 15 minutes to determine the increased weight, and this value was taken as the normal pressure absorption.

Production Example 1 of Water Absorbent Resin Gel In a 1-liter glass reaction vessel, 77 g of sodium acrylate, 23 g of acrylic acid, 0.3 g of N, N'-methylenebisacrylamide and 296 g of deionized water were charged and stirred. The temperature of the contents was maintained at 5 ° C. while mixing. After flowing nitrogen into the contents to reduce the amount of dissolved oxygen to 1 ppm or less, 1 g of a 1% aqueous solution of hydrogen peroxide, 1.2 g of a 0.2% aqueous solution of ascorbic acid and 2,2′-azobisamidinopropane dihydro Polymerization was started by adding and mixing 2.5 g of a 2% aqueous solution of chloride, followed by polymerization for about 5 hours to obtain a hydrogel polymer.

Production Example 2 of Water Absorbent Resin Gel A water-containing gel polymer was obtained in the same manner as in Production Example 1 of a water absorbent resin gel except that 0.3 g of N, N'-methylenebisacrylamide was changed to 0.1 g.

Production Example 3 of Water Absorbent Resin Gel A 1-liter glass reaction vessel was charged with 77 g of sodium acrylate, 23 g of acrylic acid, 0.4 g of N, N'-methylenebisacrylamide and 296 g of deionized water, and stirred. The temperature of the contents was maintained at 5 ° C. while mixing. After flowing nitrogen into the contents to reduce the amount of dissolved oxygen to 1 ppm or less, 1 g of a 1% aqueous solution of hydrogen peroxide, 1.2 g of a 0.2% aqueous solution of ascorbic acid and 2,2′-azobisamidinopropane dihydro Polymerization was initiated by adding and mixing 2.5 g of a 2% aqueous solution of chloride and 0.05 g of sorbitan monolaurate, followed by polymerization for about 5 hours to obtain a hydrogel polymer.

Production Example 4 of Water Absorbent Resin Gel Acrylic acid 100 was placed in a glass reactor having a capacity of 1 liter.
g, N, N'-methylenebisacrylamide (0.4 g) and deionized water (330 g) were charged, and the contents were kept at 5 ° C. while stirring and mixing. After injecting nitrogen into the contents to reduce the dissolved oxygen content to 1 ppm or less, 1% of hydrogen peroxide
1 g of aqueous solution, 1.2 g of 0.2% aqueous solution of ascorbic acid
Further, 2.5 g of a 2% aqueous solution of 2,2'-azobisamidinopropane dihydrochloride was added and mixed to start polymerization, and polymerization was carried out for about 5 hours to obtain a hydrogel polymer.

Example of Preparation of Surfactant Solution Surfactant solution (a): 1% aqueous solution of sorbitan monolaurate (HLB = 11.9) (forced stirring emulsification solution) Surfactant solution (b): dimethylsiloxane Ethylene oxide adduct (Shin-Etsu Silicone, KF-618
(Shin-Etsu Chemical Co., Ltd.), HLB = 14) 1% aqueous solution Surfactant solution (c): 2-ethylhexanol (HL
B = 6.7) 1% aqueous solution (10 mol of nonylphenol ethylene oxide adduct is added to 2-ethylhexanol at 20 wt% and emulsified) Surfactant solution (d): sorbitan monolaurate (HLB = 11.9) 0.1% aqueous solution (forced stirring emulsified solution) Surfactant solution (e): 10% aqueous solution of sorbitan monolaurate (HLB = 11.9) (forced stirring emulsified solution)

Examples 1 to 5 The hydrogel polymer obtained in Production Example 1 was cut into pieces having a size of 3 to 7 mm with an internal mixer, and then the surfactant solutions (a) to (e) were mixed with the hydrogel. 5% of the solid content was added, and this hydrogel was laminated to a thickness of about 5 cm,
It dried with the ventilation type band dryer (made by Inoue metal) at the conditions of ° C and the wind speed of 2.0m / sec. The obtained dried product is pulverized,
Water-absorbent resin (a ') by adjusting the particle size to 100 mesh
(E ') was obtained. Table 1 shows the results of these evaluations.

Example 6 A water-absorbent resin was prepared in the same manner as in Example 1 (a) except that the hydrogel polymer obtained in Production Example 2 was used in place of the hydrogel polymer. (F ′) was obtained.
Table 1 shows the results of the evaluation.

Example 7 A water-absorbent resin (g ') was obtained in the same manner as in Example 1 using the hydrogel polymer obtained in Production Example 3 of the water-absorbent resin gel without adding a surfactant. . Table 1 shows the results of the evaluation.

Example 8 To the hydrogel polymer obtained in Production Example 4, 114 g of a 35% aqueous sodium hydroxide solution was added and neutralized while kneading with an internal mixer. Next, the surfactant solution (a) was added, and a water-absorbent resin (h ′) was obtained in the same manner as in the examples below. Table 1 shows the results of the evaluation.

Example 9 A water-absorbent resin (i) was prepared in the same manner as in Example 1 (a) except that a surfactant solution was added during the chopping of the hydrogel polymer obtained in Production Example 1 with an internal mixer. ') Got.
Table 1 shows the results of the evaluation.

Example 10 A water-absorbent resin (j ') was obtained in the same manner as in Example 1 (a) except that the hydrogel polymer obtained in Production Example 1 was cut into pieces using a screw extruder. Table 1 shows the results of the evaluation.
Shown in

Comparative Examples 1 to 3 Hydrogel polymers obtained in Production Examples 1, 2 and 4
And after shredding to a size of 3 to 7 mm with an internal mixer, this hydrogel was laminated to a thickness of about 5 cm and
It dried with the ventilation type band dryer (made by Inoue metal) at 50 degreeC and the wind speed of 2.0 m / sec. Crush the dried product, 2
By adjusting the particle size to 0 to 100 mesh, comparative water absorbent resins (n ′), (o ′) and (p ′) were obtained. These evaluation results are also shown in Table 1.

[0038]

[Table 1]

[0039]

The method for producing an absorbent resin according to the present invention has the following features and effects. The water-absorbent resin of the present invention can be produced by ordinary water-absorbent resin production equipment, and does not require special equipment. Load during gel transfer is reduced. When the surfactant is added during the shredding of the gel, the load on the shredding machine is reduced. Since the drying is very efficient, the drying time is shortened, the energy cost can be reduced, and it is economical. Since the drying time is short, there is no side reaction, coloring or deterioration in quality due to overheating. As a result, a product with improved water absorption performance and little variation in quality can be obtained. Since uniform drying can be performed, there is little trouble in the pulverization system due to generation of undried material. The effects of increasing the water absorption rate of the product, reducing dust generation, reducing the angle of repose, improving the powder flowability, and improving the moisture absorption blocking resistance are obtained.

Due to the above effects, the water-absorbent resin obtained by the production method of the present invention is particularly suitable for disposable paper diapers (child and adult paper diapers). Also, other sanitary materials such as sanitary napkins, incontinent pads, breast milk pads, surgical underpads, puerperium mats,
Dressing materials for wound protection, pet sheets, etc.) and various absorbent sheets (for example, freshness preserving sheet, drip absorbing sheet, dew condensation preventing sheet, paddy rice seedling seedling sheet, concrete curing sheet, water running prevention sheet for cables, oil / water separation) Sheet, fire extinguishing sheet, etc.). Further, the application of the water-absorbing resin powder (eg, soil water retention agent, sludge solidifying agent, solidifying agent such as waste blood and aqueous waste liquid, portable urine gelling agent, battery electrolyte gelling agent, etc.) and water absorption It can also be used for applications where gels are applied (for example, chemical warmers, pulp materials, gel beds, artificial snow, gel-like fragrances, etc.).

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 4J100 AA06Q AG04Q AK01P AK01Q AK32P AL02P AM15P AM15Q AP01P AP01Q AQ08P BA03H BA16H BA56P BA56Q CA01 CA04 CA31 DA37 EA03 GC25 HA08 HA09 HA53 HC10 HC34 HC47 HC48 HC50 HC63

Claims (12)

[Claims] 1. A method for producing a water-absorbent resin, comprising adding a surfactant (B) to a water-containing gel (A) of a water-swellable polymer and drying it in a static state. 2. The method for producing a water-absorbent resin according to claim 1, wherein the amount of the active ingredient (B) is 0.005 to 1% by mass relative to the solid content in (A). 3. The method for producing a water-absorbent resin according to claim 1, wherein (B) is a nonionic surfactant. (B) is sorbitan lauric acid (mono / di) ester, sorbitan palmitic acid (mono / di)
Esters, sorbitan stearic acid (mono / di) ester, sorbitan oleic acid (mono / di) ester, sorbitan coconut oil (mono / di) ester, and ethylene oxide adducts thereof, polyoxyethylene sorbitan lauric acid (mono / di) ) Esters, polyoxyethylene sorbitan palmitic acid (mono / di) ester, polyoxyethylene sorbitan stearic acid (mono / di) ester, polyoxyethylene sorbitan oleic acid (mono / di) ester, polyoxyethylene lauric acid (mono / di) Di) ester, polyoxyethylene stearic acid (mono / di) ester, polyoxyethylene oleic acid (mono / di) ester, lauryl alcohol ethylene oxide adduct, oleyl alcohol ethylene oxide adduct, Macquaria Call ethylene oxide adducts,
One or more selected from the group consisting of polyoxyethylene nonyl phenyl ether, polyoxyethylene / polyoxypropylene block polymer, polydimethylsiloxane polyoxyethylene adduct, and aliphatic or alicyclic alcohols having 4 or more carbon atoms Mixture [however, (mono /
The di) ester represents a monoester and / or a diester], the method for producing a water-absorbent resin according to any one of claims 1 to 3. 5. The surfactant according to claim 1, wherein (B) is a surfactant having no more than two functional groups that react with the solid content in (A).
5. The method for producing a water-absorbent resin according to any one of 4. 6. The hydrophilic gel according to claim 1, wherein (A) is a hydrophilic crosslinked polymer having a polymerizable monomer containing a carboxylic acid salt and / or a carboxylic acid as a main component. Production method of water absorbent resin. 7. The process for producing a water-absorbent resin according to claim 1, wherein the crosslinking agent in (A) is a crosslinking agent having an ethylenically unsaturated group and / or a reactive functional group. 8. The use amount of the crosslinking agent in (A) is 0.001 to the total mass of the polymerizable monomer (A) and the crosslinking agent.
The method for producing a water-absorbent resin according to any one of claims 1 to 7, wherein the amount is from 5 to 5% by mass. 9. The method for producing a water-absorbent resin according to claim 8, wherein (B) is added to (A) during the polymerization step of the water-swellable polymer and / or before the drying step. 10. The water-absorbing material according to claim 1, wherein a crosslinking agent having two or more groups reactive with the functional group of the water-swellable polymer is mixed by a shredder to crosslink (A). Method of manufacturing resin. 11. An apparatus for drying (A) to which (B) has been added is a parallel flow band dryer (tunnel dryer), a ventilation band dryer, a jet flow (nozzle jet) dryer, or a rigid ventilation dryer. 1 selected from the group consisting of box-shaped hot air dryers
The method for producing a water-absorbent resin according to any one of claims 1 to 10, which is a seed or a combination of a plurality of these dryers. 12. The method for producing a water-absorbent resin according to claim 1, wherein the powder is dried, pulverized, and further subjected to surface crosslinking near the particle surface.