JPH07173296A - Production of water-absorptive material, and water-absorptive article - Google Patents

Abstract

PURPOSE:To obtain a water-absorptive material excellent in water absorption, speed of water absorption, and safety by irradiating water-absorptive resin particles agglomerated in plane form with actinic radiation. CONSTITUTION:Water-absorptive resin particles (e.g. particles of a poly(meth) acrylic acid or poly(meth)acrylamide) agglomerated in plane form are irradiated with actinic radiation (e.g. ultraviolet rays, electron beams or radiation). It is desirable to obtain the water-absorptive resin particles agglomerated in plane form through the step of casting a particulate water-absorptive resin into a plane form with a thickness of about 0.3-5 mm on a support and the step of adding at least one of water and steam in an amount of 10-150 pts.wt. based on 100 pts.wt. water-absorptive resin [or adding water and polyhydric alcohol (e.g. ethylene glycol) respectively in amounts of 3-30 pts.wt. and 5-50 pts.wt. based on 100 pts.wt. water-absorptive resin] while keeping the state of a plane obtained in the first step.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing a water absorbent material and a water absorbent article. More specifically, the present invention relates to a method for producing a water-absorbing material that absorbs and swells water-based liquid such as water or body fluid to a high degree, and a water-absorbing article. More specifically, such as sanitary napkins, sanitary / medical products such as disposable diapers, which are excellent in absorption amount, absorption speed and safety, and extremely excellent in energy cost, freshness preservation of vegetables and meat or drip absorption sheets, etc. The present invention relates to a water absorbent article that can be suitably used in fields requiring water absorption and water retention, such as the fields of agriculture and forestry.

The water-absorbent material can be used by itself or
It is useful as a water absorbent article such as a sanitary material, a dew condensation absorbing sheet, a water retention agent for agriculture and horticulture, a water blocking agent for civil engineering, medical sheets, a freshness-keeping agent for foods, and a drip absorbent for foods.

[0003]

2. Description of the Related Art As a water-absorbent resin, a polyacrylic acid partially neutralized crosslinked product, a saponified product of an acrylic ester-vinyl acetate copolymer, a crosslinked polyvinyl alcohol modified product, a crosslinked isobutylene-maleic anhydride copolymer, and starch. A hydrolyzate of an acrylonitrile graft polymer, a starch-acrylic acid graft polymer, a partially crosslinked polyethylene oxide and the like are known, and the water-absorbent resin is a sanitary napkin, an absorbent material for a sanitary material such as a paper diaper, or the like. Agricultural and horticultural fields,
It is used in a wide range of applications such as water retention agents and dehydration agents in the field of civil engineering.

The water-absorbent resin used is generally in the form of powder or particles, and in many cases it is actually used, it is sandwiched with paper, mixed with pulp and subjected to pressure-bonding treatment such as embossing, or thermoplastic resin. It is used by changing the shape such as sheet or film by performing compounding such as fusion sealing.

Conventionally, various proposals have been made for applying a water-absorbent resin to a base material to carry out fixing treatment and making it into a sheet form for use. These can be roughly classified into a method in which a water-absorbent resin is manufactured and then formed into a sheet, and a method in which the water-absorbent resin is simultaneously manufactured and formed into a sheet. The former method includes a method (A) in which a water-absorbent resin powder is applied to a base material in a sheet shape to perform fixing treatment, and a method (B) in which a fibrous water-absorbent resin is formed into a sheet. In the method (B), obtaining the fibrous water-absorbent resin is costly, and the water-absorbent sheet to be obtained has a low water-absorbing ability and is not so general.

As the fixing treatment of the method (A), a water-absorbent resin powder is sprinkled on a base sheet, another sheet is superposed on the powder, and the base sheet and the water-absorbent resin powder are mixed. A method of embossing or a method of giving a small amount of water to the water-absorbent resin powder so as to realize firm adhesion to the base sheet (for example, USP3959596, JP-A-51-40497, JP-A-54-123293). JP-A-54-141099 and JP-A-58-3645.
No. 2) or a resin binder to achieve fixation between the water absorbent resin powder and the substrate sheet (for example, JP-A-58-101047 and JP-A-4-504).
234, USP5128082) and the like. Further, Japanese Patent Application Laid-Open No. 1-230671 proposes a method for immobilizing a water absorbent resin by combining a water absorbent resin with an aqueous liquid to form a hydrate.

However, these methods for obtaining a sheet-shaped water absorbent material have some problems.
For example, the complexing process of the base material and the water absorbent resin powder is complicated, productivity is low, the working environment is bad such as dust, and the strength or flexibility of the resulting water absorbent material is insufficient. It was Further, since the amount of water-absorbent resin per unit area cannot be increased, the water-absorbent material obtained has a small water-absorption amount or a low water-absorption rate. When the amount of the water-absorbent resin per unit area was increased, the resulting water-absorbent material became hard and the water-absorbent resin powder spilled out from the water-absorbent material. On the other hand, for the purpose of improving the detachment of the water-absorbent resin from the base material, several methods have been proposed for simultaneously producing the water-absorbent resin and forming the sheet by directly polymerizing monomers on the base material sheet. . For example, JP-A-6
0-149609, JP-A-62-53309, JP-A-62-62829 and JP-A-62-97979. However, all of these methods have the following drawbacks. That is, there is a high possibility that a polymerization initiator used for polymerization, other additives, and a relatively large amount of monomers will remain. When the safety of these substances is a concern, it becomes a problem when the product is used for sanitary applications or food applications. In addition, it was difficult to control the reaction and productivity was low. Further, the obtained sheet-shaped water-absorbing material had swelling restriction due to the base material and had insufficient water-absorbing performance, or was inferior in so-called soft feeling in terms of flexibility.

[0008]

Problem to be Solved by the Invention EP-A-44362
No. 7, proposes a water-absorbent article in which the amount of the water-absorbent resin is increased by using the water-absorbent resin having an increased water absorption rate. However, when there is little or no fibrous matrix that has served to immobilize the particulate water-absorbing resin as proposed in EP-A-443627, the water-absorbing property in the water-absorbing article is reduced. It is expected that problems such as resin migration and bias will occur. Until the time when the water-absorbent resin fulfills its functions of absorbing and swelling, a new device for fixing the resin at a predetermined position is required. Furthermore, when it is attempted to use the water absorbent resin as a dry powder, since it is fine, there are many leaks and airborne particles, and it is extremely difficult to handle. This greatly impedes stable operation in mechanical mass production.

[0009] WO 91/15362 proposes a porous absorbent polymer macrostructure which can take the form of a sheet, film, strip or the like. This has a high water absorption rate and can retain its geometric shape even after absorbing liquid, and can solve the problems of the above-mentioned conventional techniques. However, it is necessary to use an interparticle cross-linking agent as an essential component and react this, which complicates the production process and lowers the productivity.

On the other hand, a technique of irradiating a water absorbent resin with an active energy ray such as an electron beam or a radiation is disclosed in JP-A-63-4.
It is publicly known such as 3930 and JP-A-59-129232. However, since the water-absorbent resin obtained by these methods is in the form of particles, the above-mentioned problems associated with the particulate water-absorbent resin still remain.

There is a need for compact and thin water absorbent articles having good water absorption and water absorbent materials for obtaining the same. Has a sufficient water absorption rate, a high water absorption rate,
There has been a long-awaited demand for a water-absorbent material capable of immobilizing a water-absorbent resin at a desired position before and after absorbing the liquid.

Various water-absorbent resin particles are known to be applied to water-absorbent articles using the water-absorbent resin particles as an absorbent material. For example, Japanese Patent Publication No. 57-56561 discloses an absorbent material containing dried water-absorbent resin particles. In JP-A-59-204956, there is 10
An absorbent structure is disclosed which comprises a compressed mixture of dried water-absorbent resin particles having a water content of up to wt% and ground pulp. Japanese Patent Application Laid-Open No. 57-73051 discloses an immobilized absorbent composition comprising a liquid polyhydroxy compound and dry water-absorbent resin particles. JP-A-56-
131683 and JP-A-58-131133 disclose water-absorbent articles obtained by softening dry water-absorbent resin particles with water, applying the particles to a substrate, and then drying. Japanese Unexamined Patent Publication No. 1-230671 discloses a water-absorbing material comprising a mixture of dry water-absorbing resin particles and an aqueous liquid. Furthermore, JP-A-4-236203 discloses a water-absorbent article containing a sheet-like hydrogel obtained by polymerization.

However, the water-absorbent articles known so far have some problems. For example, when focusing on the dried water-absorbing polymer that constitutes the main component of the absorbent material of these water-absorbing articles, the water-absorbing cross-linking obtained by polymerizing an aqueous liquid of a monomer that can be converted into a water-absorbing polymer by polymerization. A step of drying the water content of the polymer to 20% or less, which is a water content range that can be handled as a powder, and a crushing or crushing step for forming powder particles are essential, and a large amount of energy is required for that. In addition to increasing the cost of the resulting water-absorbent polymer, deterioration of the polymer inevitably occurs in the drying step for reducing the water content to 20% or less, and the amount of soluble components in the polymer increases. It was sometimes unfavorable in terms of various absorption characteristics.

On the other hand, when attention is paid to a water-absorbent article containing a dried water-absorbent resin, when the dry water-absorbent resin is inserted into a target absorbent article, the water-absorbent article in a dry state which is unfavorable to the working environment is desired. Processes and equipment for handling resin particles are required, and in order to immobilize dried water-absorbent resin particles as absorbent materials in water-absorbent articles, further processes such as softening / drying with water and compression are required. Therefore, the complexity of the process of obtaining the water-absorbent article and the apparatus has not been solved. Japanese Unexamined Patent Publication (Kokai) No. 4-236203 suggests, as a method for solving these problems, to directly insert a sheet-shaped hydrogel-like water-absorbing crosslinked polymer obtained under specific polymerization conditions into an absorbent article. The sheet-shaped water-containing gel-like water-absorbing cross-linked polymer has a smaller surface area than the powder-like water-absorbing cross-linked polymers known so far, so that the water absorption rate is slow, and the surface area is increased to a film-like shape. Molding operation was required. Liquid transfer space between water-absorbing polymers that have swollen even if they are film-formed,
Due to the lack of the swelling permissible space, the water absorbent article obtained had insufficient absorption amount and water absorption rate, and was not satisfactory in terms of flexibility.

Therefore, an object of the present invention is to provide a novel method for producing a water absorbent material and a water absorbent article.

Another object of the present invention is to have good water absorbency (water absorption rate and water absorption amount), and to fix the water absorbent resin at a desired position before and after the liquid absorption and to obtain an arbitrary size. Another object of the present invention is to provide a method for producing a water-absorbent material which can be cut into a sword or a shape and which is highly safe. Still another object of the present invention is to provide a simple and highly productive production method for obtaining the water-absorbent material, and easy control of product performance. Another object of the present invention is to provide a compact and thin water absorbent article using the absorbent material. Still another object of the present invention is to have good water absorption properties, be compact and thin, and have no migration of the water-absorbent polymer, even if the water-absorbent polymer is contained in a large amount in the absorbent material, It is intended to provide a water absorbent article which is flexible and excellent in economical efficiency.

[0017]

These various objects are achieved by a method for producing a water-absorbing material, which comprises irradiating surface-aggregated water-absorbing resin particles with an active energy ray.

According to the present invention, the water-absorbent resin particles aggregated in a plane flow in a plane with (a1) the particulate water-absorbent resin regulated to a thickness of about 0.3 to 5 mm on a support. And (b1) at least one kind selected from the group consisting of water and steam per 100 parts by weight of the water-absorbent resin while maintaining the surface state obtained in the step (a1).
The method for producing the water-absorbing material is obtained through a step of adding at a ratio of 0 to 150 parts by weight.

In the present invention, further, the water-absorbent resin particles aggregated into a plane form (a2) the particulate water-absorbent resin on a support,
Water is added to 100 parts by weight of the water-absorbent resin while maintaining the surface state obtained in the step (b2) of controlling the thickness to about 0.3 to 5 mm and flowing in a plane. 3 to 3
The method for producing the water-absorbing material is the one obtained through the step of adding 0 parts by weight and polyhydric alcohol in a ratio of 5 to 50 parts by weight.

According to the present invention, the step of mixing the water-absorbent resin particles agglomerated in a plane with (a3) the polyhydric alcohol in an amount of 1 to 10 parts by weight relative to 100 parts by weight of the particulate water-absorbent resin, b3) a step of dry-mixing the mixture obtained in the step (a3) and the hydrophilic fiber at a ratio of 1 to 30 parts by weight of the hydrophilic fiber to 100 parts by weight of the water absorbent resin in the mixture, and (c3 ) A method for producing the water-absorbing material as described above, which is obtained by subjecting the mixture obtained in the step (b3) to a sheet-like air-paper-making process.

Further, in the present invention, the water-absorbent resin particles aggregated in a plane form are added to the sheet-like material obtained through the above-mentioned steps in water and water vapor per 100 parts by weight of the water-absorbent resin in the sheet-like material. The method for producing the water-absorbing material is obtained by adding at least one selected from the group consisting of 10 to 150 parts by weight.

According to the present invention, the water-absorbent resin particles aggregated in a plane form are mixed with (a4) 100 parts by weight of the particulate water-absorbent resin and 1 to 10 parts by weight of a polyhydric alcohol. b4) The above-mentioned water-absorbent material, which is obtained through a step of spreading the mixture obtained in the step (a4) on a support in a planar manner while controlling the thickness to about 0.3 to 5 mm. It is a manufacturing method.

In the present invention, further, the water-absorbent resin particles aggregated in a plane shape are treated with water to 100 parts by weight of the water-absorbent resin in the sheet body while maintaining the surface state obtained through the above-mentioned steps. And the method for producing the water-absorbing material, which is obtained by adding at least one selected from the group consisting of and steam at a ratio of 10 to 150 parts by weight.

The present invention is also the method for producing the water-absorbent material, wherein the water-absorbent resin particles aggregated in a plane form contain 10 to 70% by weight of water based on the total weight. Further, the present invention is a water-absorbent resin particles obtained by molding a water-absorbent resin particle that is aggregated in a plane form, obtained by polymerization, and further capable of absorbing water, in the form of particles, a water-containing gel polymer. Is a manufacturing method.

In the present invention, the water-absorbent resin particles agglomerated in a plane are obtained by the polymerization of (a5) and are capable of further absorbing water. The step of forming the sheet in a planar shape by regulating to 0.3 to 20 mm and (b5) keeping the surface state obtained in the step (a5), the water content with respect to the total weight of the hydrogel polymer is at least 10. The method for producing the water-absorbing material, which is obtained through a step of reducing the content by weight to form an aggregate of a water-containing gel polymer having a water content of 20 to 70% by weight. The present invention further provides that the hydrogel polymer has a particle size of 50 to 2000 μm.
Is a method for producing the water-absorbing material, which has an average particle diameter in dry conversion. The present invention is also the method for producing the water absorbent material, wherein the active energy ray is at least one selected from the group consisting of gamma rays and electron rays.

These objects are also achieved by a water-absorbent article characterized in that the water-absorbent material obtained by the above-mentioned manufacturing method is housed inside a bag body having at least one side formed of a water-permeable sheet. To be done.

[0027]

The water-absorbent resin particles used in the present invention are not particularly limited as long as they are particulates of water-absorbent resin and absorb water or an aqueous liquid to cause volume expansion. It is obtained by polymerizing a saturated monomer. Examples of these water-soluble unsaturated monomers include (meth) acrylic acid, (anhydrous) maleic acid, fumaric acid, crotonic acid,
Itaconic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2
Anionic monomer such as (meth) acrylamide-2-methylpropanesulfonic acid, vinylsulfonic acid, styrenesulfonic acid and salts thereof; (meth) acrylamide, N-
Nonionic hydrophilic group-containing monomers such as substituted (meth) acrylamide, 2-hydroxyethyl methacrylate, 2-hydroxypropyl (meth) acrylate, methoxy polyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate; N; Specific examples include amino group-containing unsaturated monomers such as N-dimethylaminopropyl methacrylate, N, N-dimethylaminoethyl (meth) acrylate, and N, N-dimethylaminopropyl (meth) acrylamide, and their quaternized products. I can list them.

Further, an amount of acrylic acid ester such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, vinyl acetate, etc., in an amount that does not extremely hinder the hydrophilicity of the obtained polymer. Hydrophobic monomers such as vinyl propionate may also be used. As the monomer component, one kind or two or more kinds can be selected and used from these, but considering various water absorption characteristics of the finally obtained water-absorbing material, (meth) acrylic acid (salt) , 2- (meth) acryloylethanesulfonic acid (salt), 2- (meth) acrylamido-2-methylpropanesulfonic acid (salt), (meth) acrylamide, methoxypolyethyleneglycol (meth) acrylate,
One or more selected from the group consisting of N, N-dimethylaminoethyl (meth) acrylate or a quaternary compound thereof is preferable. Those containing (meth) acrylic acid (salt) as an essential component are more preferable. In this case, it is most preferable that 30 to 90 mol% of (meth) acrylic acid is neutralized with a basic substance. The water absorption capacity of the water-absorbent resin is a value measured by the Tea Bag method in physiological saline, and is 20
It is preferable to have about 60 / g. The proportion of the uncrosslinked component, that is, the water-soluble component in the water absorbent resin is preferably 20% by weight or less, more preferably 10% by weight or less, and further preferably 5% by weight or less.

The water-absorbent resin used in the present invention may be a self-crosslinking resin obtained without using a crosslinking agent, but a water-absorbing resin having a polymerizable unsaturated group and / or a reactive functional group can be obtained. It may be obtained by using the resin particles in such a range that the various characteristics reach the above-mentioned criteria.

Examples of these cross-linking agents include N, N
′ -Methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate, glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, triallylamine, triallyl cyanurate, triallyl isocyanurate, glycidyl meta Acrylate, (poly) ethylene glycol,
Diethylene glycol, (poly) glycerin, propylene glycol, diethanolamine, trimethylolpropane, pentaerythritol, (poly) ethylene glycol diglycidyl ether, (poly) glycerol polyglycidyl ether, epichlorohydrin, ethylenediamine, polyethyleneimine, (poly) aluminum chloride, sulfuric acid Specific examples include aluminum, calcium chloride, magnesium sulfate, and the like, and one or more of them can be used in consideration of reactivity.

In order to obtain a water-absorbent resin, the above-mentioned monomer components are polymerized in the presence of a hydrophilic polymer such as starch, cellulose or polyvinyl alcohol to form a graft bond or a complex simultaneously with the polymerization. Good.

Upon polymerization of these monomer components, as a polymerization initiator, ammonium persulfate, potassium persulfate, hydrogen persulfate, t-butyl hydroperoxide, 2,2'-azobis-amidinopropane dihydrochloride, etc. The water-soluble radical polymerization initiator may be used. The polymerization method is not particularly limited, and for example, known methods such as bulk polymerization, aqueous solution polymerization and reverse phase suspension polymerization may be used.

These water-absorbent resins are used alone or in the form of a mixture of two or more water-absorbent resins.

The shape of the water-absorbent resin particles used in the present invention is not particularly limited. It may be in the form of flakes obtained by drying with a drum, or may be in the form of irregular shapes obtained by crushing a lump of resin. Further, it may have a spherical shape obtained by reverse phase suspension polymerization. Generally, particles obtained by reverse phase suspension polymerization have a dispersant or a surfactant on the surface thereof, and in the case of such particles,
It may be preferred to use in the present invention after removing the dispersant or surfactant, or after adding additional milling. Further, the shape of the particles may have a major axis or a minor axis such as a rod shape or a fibrous shape.

The water-absorbent resin particles used in the present invention may be in any particle form as long as the object of the present invention can be achieved, and the size thereof is not particularly limited. In order to obtain a water-absorbing material having a high water absorption rate, it is preferable that substantially no particles larger than 1000 μm are contained, and it is more preferable that substantially no particles larger than 850 μm are contained. Generally, the water absorption rate can be increased by reducing the average particle diameter of the water absorbent resin particles. However, if the content of particles of 150 μm or less is increased, inconvenience may occur in terms of handleability, and so-called gel blocking phenomenon tends to occur easily.

The water-absorbent resin particles used in the present invention may preferably have a narrow particle size distribution. Ie 600μ
The proportion of m to 150 μm is 80% by weight or more, more preferably 90% by weight or more, or the proportion of 300 μm to 150 μm is 80% by weight or more. More preferably, by using the water-absorbent resin particles having a particle size distribution of 90% by weight or more, the water-absorbent material obtained may have good water-absorption rate and good shape retention after liquid absorption.

In the present invention, it is preferable to use, as the water-absorbent material having a high water-absorption rate, a water-absorbent resin particle having a large water absorption capacity under load. The method for measuring the water absorption capacity under load will be described later, but it is preferable to absorb 0.9 wt% saline at least 20 ml / g under a load of at least 20 g / cm ² . Those that absorb at least 24 ml / g of water are more preferred, and those that absorb at least 28 ml / g are even more preferred. The water-absorbent material obtained by using the water-absorbent resin particles having a water absorption capacity under this load larger than a specific value has a particularly excellent water absorption rate. The water-absorbent resin particles having a large water absorption capacity under such a load can be obtained, for example, by subjecting the surface of the water-absorbent resin particles described below to a crosslinking treatment.

The water-absorbent resin particles used in the present invention may preferably be surface-crosslinked. Water-absorbing resin particles and a cross-linking agent having a group capable of reacting with at least two functional groups of the particles are mixed and reacted, and treated to increase the cross-linking density in the vicinity of the surface of the water-absorbing resin particles. By using the water-soluble resin particles, it is possible to obtain a water-absorbing material having a particularly high water-absorption rate. For water-absorbent resin particles,
For example, a method using a polyhydric alcohol as a cross-linking agent (JP-A-58-180233 and JP-A-61-16903).
No.), polyvalent glycidyl compounds, polyvalent aziridine compounds,
A method using a polyvalent amine compound or a polyvalent isocyanate compound (JP-A-59-189103), a method using glyoxal (JP-A-52-117393), a method using a polyvalent metal (JP-A-51-136588). , JP-A-61-257235, JP-A-62-7745), and a method using a silane coupling agent (JP-A-61-211).
No. 305, JP-A-61-252212, JP-A-61-
264006), a method using an epoxy compound and a hydroxy compound (JP-A-2-132103), and a method using an alkylene carbonate (DE-A-4020780).
The surface-crosslinked water-absorbent resin particles can be obtained by performing a known surface treatment such as 9). In addition, a method in which an inert inorganic powder is present during the crosslinking reaction (Japanese Patent Laid-Open No. 6-58242)
0-163956, JP-A-60-255814),
Method of allowing dihydric alcohol to exist (Japanese Patent Laid-Open No. 1-2920)
No. 04), a method of allowing water and an ether compound to be present (JP-A-2-153903), and the like.

The water-absorbent resin particles used in the present invention may contain auxiliary components such as water-insoluble fine particles, a surfactant and short fibers in an amount that does not inhibit aggregation. Inclusion of these auxiliary components may act to increase the water absorption rate of the water absorbent material of the present invention. For example, as the surfactant, polyoxyethylene alkyl ether,
Polyoxyethylene alkylphenol ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene acyl ester,
Examples thereof include oxyethylene oxypropylene block copolymer and sucrose fatty acid ester. As the water-insoluble inorganic fine particles, mica, pyrophyllite, kaolinite, halcite, and other similar clay minerals and Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.) mainly composed of silicon dioxide particles having an average particle size of 50 μm or less. In addition, fine particle silica such as Carplex # 80 (manufactured by Shionogi Co., Ltd.) can be used. As the water-insoluble organic fine particles, carbon black,
Examples include activated carbon and pulp powder. Among them, fine particle silica is preferable because it has a large effect of increasing the water absorption rate. The amount of these auxiliary components used is 0.1 to 10 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the water absorbent resin.
5 parts by weight, most preferably 0.5 to 2 parts by weight. If the weight exceeds 10 parts by weight, the effect cannot be obtained in proportion to the amount used, but the water absorption amount is decreased, and in some cases, formation of aggregates is difficult. To do. If the amount used is less than 0.1 part by weight, the use effect cannot be obtained.

In the present invention, the water-absorbent resin particles are irradiated with active energy rays in a state where they are aggregated in a plane. At this time, the water content of the water-absorbent resin particles is not particularly limited, with respect to the total weight of the water-containing water-absorbent resin particles, 10 ~
It preferably contains 70% by weight of water. By irradiating the planar aggregates of the water-absorbent resin particles having the water content in this range with active energy rays, a flexible water-absorbent material can be obtained. At a water content outside the range,
The resulting absorbent material may have poor shape retention during liquid absorption. The water content is more preferably 15 to 60% by weight, and further preferably 20 to 50% by weight.

In the present invention, the term “planar aggregation” means a state in which a large number of originally independent water-absorbent resin particles are brought into physical contact to form a planar aggregate. That is, instead of being in an aggregated state via a third substance such as an adhesive or a fibrous base material, the water-absorbent resin particles are directly adhered to each other to form a continuous aggregated state. There is something.

In the present invention, the term "agglomerated in a plane" means that the water-absorbent resin particles are directly adhered to each other to form an agglomerated state, and can be handled as a physically integrated body. It is a thing.

For example, a state in which water-absorbent resin particles having a water content of 15% are dispersed in a mold of a certain size placed on a plane is different from the state in which the water-absorbent resin particles are aggregated in a plane as referred to in the present invention. .. Physically, it is a large number of independent water-absorbent resin particles.

In the present invention, the term “planar” means that at least a part of the surface has a continuous surface, and may be, for example, a surface having one or a plurality of through holes of any shape. It may be wavy or pleated. Further, it may have a strip shape, a string shape, or a strip shape. One side (front or back) is preferably 5c
m ² or more, more preferably 10 cm ² or more, and further preferably 15 cm ² or more.

In the present invention, the active energy rays have high energy such as ultraviolet rays, electron rays, and radiation. Among them, those having high permeability are preferable, gamma rays or electron rays are preferable, and gamma rays are more preferable.

In the production method of the present invention, the irradiation dose of the active energy rays is determined by the water content of the water-absorbent resin, the type of resin,
Or, depending on the irradiation atmosphere, generally 1 to
Range of 1000 kGy, preferably 10-500 kGy
The absorbed dose is in the range of. When the dose exceeds 1000 kGy, the water absorption amount of the obtained water absorbent material tends to be too small, whereas when the dose is less than 1 kGy, the shape retention of the obtained water absorbent material after absorbing the liquid may deteriorate.

In one of the preferred embodiments of the present invention, the water-absorbent resin particles aggregated in a plane form (a1) a particulate water-absorbent resin on a support, and the thickness is regulated to about 0.3 to 5 mm. And (b1) water and / or steam at a ratio of 15 to 150 parts by weight relative to 100 parts by weight of the water-absorbent resin while maintaining the surface state obtained in the step (b1) and the step (a1). It is obtained through the adding step.

In step (a1), the thickness is about 0.3 m.
If it is less than m, it tends to be difficult to spread the particulate water-absorbent resin in a plane, or the strength of the resulting absorbent material tends to be low, resulting in poor handleability. In addition, the amount of water-absorbent resin per unit area decreases, and the water-absorbing rate of the resulting water-absorbent material decreases. In order to achieve such a thickness, it is generally 200 g / m ² or more, preferably 250 g / m ² or more, and more preferably 300 g / m ^2.
Water-absorbent resin particles of m ² or more are required. On the other hand, when the thickness exceeds about 5 mm, it takes a significantly long time to obtain a water-absorbent resin that is aggregated in a plane by adding water and / or steam, or the water-absorbing rate of the obtained water-absorbing material is high. Instead, it gets smaller. The preferable thickness of the particulate water absorbent resin is 0.5 to 3 mm.

In the step (b1), adding water and / or water vapor to the water-absorbent resin particles, the thickness of which has been regulated and spread while maintaining the surface state, means that the water-absorbent resin particles are substantially sheared. This means adding water and / or steam in a state of not being covered, and for example, a method of spraying water on the water-absorbent resin particles which have been spread on the support with the thickness regulated to about 0.3-5 mm. , A method of applying saturated steam, a method of holding a support on which water-absorbent resin particles are spread in an atmosphere having a relative humidity of 50% or more, and the like. If the contact between the water-absorbent resin particles and water is non-uniform, a uniform planar aggregate may not be obtained, but after contact with water,
To prevent water from splashing, for example, seal it, preferably 30
When it is left to stand at a temperature of ℃ or more, a homogeneous sheet-like aggregate is obtained. When water is added to the water-absorbent resin particles, if a shearing force, such as mixing and agitating the water-absorbent resin particles and water, is applied, the water-absorbing rate of the resulting water-absorbent material decreases, which is not preferable. When such an operation is performed, the water absorbent resin particles tend to be lumpy. It is difficult to form this lump into the planar aggregate which is the object of the present invention. For example, using an extruder or the like, it is not impossible to mold this lump into a planar aggregate, but such an operation not only requires a great deal of energy, but also water-absorbent resin particles In some cases, the adhesion between the adhered particles disappears and the adhered particles are integrated with each other. The water absorbing material thus obtained tends to have a significantly reduced water absorption rate.

In step (b1), the amount of water added to the water-absorbent resin particles is 100 parts by weight of the water-absorbent resin particles.
The amount is 10 to 150 parts by weight. If the amount of water exceeds 150 parts by weight, the content of the water absorbent resin in the water absorbent material becomes low,
The water absorption amount of the obtained water absorbent material becomes low and the strength of the water absorbent material becomes weak. On the other hand, if the amount of water is less than 10 parts by weight, the strength of the water-absorbent material obtained will be weak, and a flexible absorbent material cannot be obtained. A more preferable amount of water is in the range of 20 to 100 parts by weight, and most preferably in the range of 30 to 80 parts by weight, based on 100 parts by weight of the water absorbent resin particles.

The water used in the present invention is distilled water,
It may be ion-exchanged water, tap water, industrial pure water, or the like, and may be an inorganic or organic substance dissolved or dispersed in these waters.

In another preferred embodiment of the present invention, the surface-aggregated water-absorbent resin particles are (a1) the particulate water-absorbent resin on a support and have a thickness of about 0.3 to 5 mm, preferably 3 to 30 parts by weight of water per 100 parts by weight of the water absorbent resin while maintaining the surface state obtained in the step (b2) step (a2) in which the step is regulated to 0.5 to 3 mm and the surface is spread. Parts and polyhydric alcohol in a ratio of 5 to 50 parts by weight.

Step (a2) is the same operation as step (a1) described above.

In the step (b2), adding water and a polyhydric alcohol to the water-absorbent resin whose thickness has been regulated and spread while maintaining its surface state means that the water-absorbent resin particles have substantially no shearing force. This means adding water and a polyhydric alcohol in a state where the water-absorbing resin particles are spread on the support while controlling the thickness to about 0.3 to 5 mm and spraying an aqueous solution of the polyhydric alcohol. A method of spraying the polyhydric alcohol, then applying saturated steam or maintaining it in an atmosphere having a relative humidity of 50% or more, a method of spraying water and then spraying the polyhydric alcohol, and the like. Preferred is a method of spraying an aqueous solution of a polyhydric alcohol.

In the step (b2), the amount of water and polyhydric alcohol added to the water absorbent resin particles is 100
3 to 30 parts by weight of water and 5 to 50 parts by weight of polyhydric alcohol are used with respect to parts by weight. By adding water and polyhydric alcohol in the amounts and ratios within this range, it is possible to obtain a water absorbing material that does not lose its flexibility even in a low humidity atmosphere. It is more preferable to add 5 to 20 parts by weight of water and 5 to 30 parts by weight of polyhydric alcohol. It is more preferable that the weight ratio of the polyhydric alcohol and the water is 1 or more. When the value of this ratio is smaller than 1, the flexibility of the resulting water-absorbent material in a low humidity atmosphere may decrease.

Examples of the polyhydric alcohol used in the present invention include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol,
1,3-propanediol, dipropylene glycol,
2,2,4-trimethyl-1,3-pentadiol, polypropylene glycol, glycerin, polyglycerin, 2-butene-1,4-diol, 1,4-butanediol, 1,5-pentanediol, 1,6 -Hexanediol, 1,2-cyclohexanedimethanol, 1,
Examples thereof include polyhydric alcohols such as 2-cyclohexanol, trimethylolpropane, diethanolamine, triethanolamine, polyoxypropylene, oxyethyleneoxypropylene block copolymer, pentaerythritol and sorbitol. Suitable examples include glycerin, polyglycerin, ethylene glycol, diethylene glycol, triethylene glycol and 1,3-propanediol. Among them, glycerin,
Ethylene glycol, diethylene glycol and polyglycerin are preferred.

In another preferred embodiment of the present invention, the surface-aggregated water-absorbent resin particles have a proportion of 1 to 10 parts by weight of a polyhydric alcohol to 100 parts by weight of the particulate water-absorbent resin (a3). Step (b3) of mixing, and the mixture obtained in step (a3) and the hydrophilic fiber are mixed with water-absorbent resin 1 in the mixture.
It is obtained through a step of dry-mixing hydrophilic fibers in an amount of 1 to 30 parts by weight with respect to 00 parts by weight, and a step (c3) of air-paper-making the mixture obtained in step (b3) into a sheet. .

As the polyhydric alcohol used in the step (a3), the above-mentioned polyhydric alcohol can be used.

In the step (a3), the water absorbent resin particles 1
The amount of polyhydric alcohol relative to 100 parts by weight is 1 to 10 parts by weight, preferably 1 to 6 parts by weight, more preferably 1.5 to
5 parts by weight. It is necessary that a specific amount of polyhydric alcohol is present near the surface of the water absorbent resin particles. 2 above
The mixing method of the components is not particularly limited, and a conventionally known mixer or kneader, for example, a horizontal cylinder type mixer, a V type mixer,
Double cylinder type mixer, ribbon type mixer, cone type screw mixer, high speed fluid type mixer, rotary disk type mixer, air flow stirring type mixer, gravity drop mixing machine, stirring type mixing machine and kneader etc. Can be used and mixed. When the amount of the polyhydric alcohol is less than 1 part by weight, the uniformity of the mixing is deteriorated when the hydrophilic fiber and the mixture of the water absorbent resin particles and the polyhydric alcohol are mixed in the next step (b3). Alternatively, the hydrophilic fiber and the water-absorbent resin particles have a low affinity, and a large amount of the water-absorbent resin particles fall out of the mixture. On the other hand, when the amount of the polyhydric alcohol is 10 parts by weight or more, the mixture obtained by mixing the hydrophilic fiber and the mixture of the water-absorbent resin particles and the polyhydric alcohol in the next step (b3) is strongly aggregated. And the handleability at the time of pneumatic papermaking in the step (c3) is deteriorated.

The mixture obtained in step (a3) is further dry mixed with 1 to 30 parts by weight of hydrophilic fibers in step (b3). Examples of the hydrophilic fibers used in the present invention include wood pulp fibers such as mechanical pulp, chemical pulp, semi-chemical pulp and dissolving pulp from wood, and artificial cellulose fibers such as rayon and acetate. In addition to these hydrophilic fibers, some synthetic fibers such as nylon, polyester, and polyolefin may be used. A preferred hydrophilic fiber is wood pulp fiber. The amount of the hydrophilic fibers to be mixed is 1 to 30 parts by weight, preferably 2 to 10 parts by weight, based on 100 parts by weight of the water absorbent resin particles. When the amount of the hydrophilic fibers is less than 1 part by weight, when the hydrophilic fibers are mixed with the mixture of the water-absorbent resin particles and the polyhydric alcohol, not only the uniformity of mixing decreases but also the mixture falls out of the mixture. The water-absorbent resin particles increase. On the other hand, when the amount of the hydrophilic fibers is 30 parts by weight or more, the content of the water-absorbent resin per unit volume is lowered, and the favorable water-absorption property (water-absorption rate and water-absorption amount) which is the object of the present invention is obtained.
It is not preferable for obtaining a water absorbent material having Also, because of the sublime hydrophilic fibers, the thickness of the resulting water-absorbent material is large.

The step (b3) is carried out, for example, by metering an air flow containing the hydrophilic fiber and an air flow containing the mixture of the water absorbent resin particles and the polyhydric alcohol onto the wire screen. At this time, the mixture of the hydrophilic fibers and the water-absorbent resin particles and the polyhydric alcohol is mixed by the turbulent flow generated by the two kinds of air streams. Alternatively, in an air stream containing hydrophilic fibers, a method of supplying and mixing a mixture of water-absorbent resin particles and polyhydric alcohol may be used, and the hydrophilic fibers and the mixture of water-absorbent resin particles and polyhydric alcohol may be directly mixed. Alternatively, a method of stirring and mixing may be used.

The mixture obtained in step (b3) is formed into a sheet by air papermaking in step (c3). In the present invention, the air-making can be carried out by using an ordinary apparatus made for air-making the hydrophilic fibrous web. The mixture obtained in step (b3) is placed on an air stream and deposited on a wire screen to form a sheet-like material.

The sheet material obtained through the above steps may be compressed to a density of 0.2 to 1.0 g / cm ³ .
By compressing the sheet-shaped material, the morphological stability of the sheet-shaped matrix composed of the water-absorbent resin particles-hydrophilic fibers is improved, and the shape retention of the resulting water-absorbent material before and after liquid absorption is further improved. The compression is performed, for example, by passing between rolls adjusted to obtain a sheet having a desired density. At this time, as a roll,
By using embossing rolls having various patterns, it is possible to perform embossing simultaneously with compression. Also, a method using a press or a roller press can be adopted.

The density of the sheet material is 0.2 to 1.0 g /
cm ³ , preferably in the range of 0.3 to 0.8 g / cm ³ . When the density is less than 0.2 g / cm ³ , not only the mechanical strength of the water-absorbing material is small and handling becomes difficult, but also the shape retention after liquid absorption may be deteriorated. On the other hand, when the density is compressed to 1.0 g / cm ³ or more, not only the flexibility of the water absorbent material is lost but also the water absorption speed may be decreased.

The thickness of the sheet material is preferably 0.3 to 10 mm, more preferably 0.5 to 5 mm. The thickness is 0.
If it is less than 3 mm, the strength of the resulting water-absorbent material is low and the handleability is poor. In addition, the amount of water-absorbent resin per unit area is too small, and the water absorption rate is also small. On the other hand, when the thickness exceeds 10 mm, it is not preferable for obtaining the water absorbent material for providing the compact and thin water absorbent article which is the object of the present invention.

Mixing the water absorbent resin powder and the hydrophilic fiber,
The technology of making this into a sheet is known. However,
In the conventional technique, consideration was given to avoid the water absorbent resin particles from approaching each other as much as possible, and therefore, the content of the water absorbent resin particles was about 50% by weight at most. With such a low content, the thin water-absorbent material aimed at by the present invention cannot secure a sufficient water absorption. In addition, simply by listing the content of the water-absorbent resin particles, as described above,
It was impossible to make a sheet-shaped water absorbent material. In another preferred embodiment of the present invention, the water-absorbent resin particles aggregated in a plane form are added to the sheet-shaped product obtained through the above steps (a3) to (c3) to absorb water in the sheet-shaped product. Resin 1
It is obtained by adding water and / or steam (moisture) to 100 parts by weight of 10 to 150 parts by weight. By adding water to the sheet-like material, the shape retention of the resulting water-absorbent material before and after liquid absorption is improved, and the water absorption speed is also increased. Examples of the method for adding water include a method of spraying water on a sheet, a method of applying saturated steam, and a method of holding the sheet in an atmosphere having a relative humidity of 50% or more. If the contact between the sheet and the water is uneven and it is necessary to make it uniform, after contact with the water,
Do not remove water (eg, seal) and leave it for a while (preferably at a temperature of 30 ° C or higher),
A homogeneous sheet is obtained.

The amount of water and / or steam added to the sheet material is 10 to 150 parts by weight, preferably 10 to 100 parts by weight, and more preferably 20 parts by weight, relative to 100 parts by weight of the water absorbent resin in the sheet material. -80 parts by weight.
If the amount of water exceeds 150 parts by weight, the content of the water-absorbent resin in the sheet-like material will be low, the water-absorbent amount of the obtained water-absorbent material will be low, and the strength of the water-absorbent material obtained will be weak. On the other hand, if the amount of water is less than 10 parts by weight, the result of adding water cannot be obtained.

In another preferred embodiment of the present invention, the surface-aggregated water-absorbent resin particles have a proportion of 1 to 10 parts by weight of polyhydric alcohol to 100 parts by weight of the particulate water-absorbent resin (a4). It is obtained through the step of mixing and (b4) the step of spreading the mixture obtained in step (a4) in a planar manner on the support while controlling the thickness to about 0.3 to 5 mm.

As the polyhydric alcohol used in the step (a4), the above-mentioned polyhydric alcohol can be used.

In the step (a4), the water-absorbent resin particles 1
The amount of the polyhydric alcohol relative to 100 parts by weight is 1 to 10 parts by weight, preferably 1 to 6 parts by weight, more preferably 1.5 to
5 parts by weight. The mixing method of the above two components is not particularly limited, and a conventionally known mixer or kneader, for example, a horizontal cylindrical mixer, a V-shaped mixer, a double cylindrical mixer, a ribbon-type mixer, a conical screw mixer. Machine, high-speed flow type mixer, rotary disk type mixer, air flow stirring type mixer, gravity drop mixer,
It can be mixed using a stirring type mixer, a kneader and the like. When the amount of the polyhydric alcohol is less than 1 part by weight, the shape retention of the resulting water-absorbent material before and after liquid absorption becomes poor. On the other hand, when the amount of the polyhydric alcohol is 10 parts by weight or more, it becomes difficult to regulate the thickness in the next step (b4) and spread the water in a planar manner, and the water absorption amount of the resulting water-absorbing material is increased. It may decrease.

In the step (b4), the mixture obtained in the step (a4) is spread on the support in a plane shape with its thickness regulated. At this time, by using the above-mentioned auxiliary component together, the fluidity of the mixture obtained in the step (a4) may be improved, and the operation of spreading the mixture in a planar state may be facilitated.

In the step (b4), the thickness that spreads is
It is about 0.3-5 mm. If the thickness is less than about 0.3 mm, it tends to be difficult to spread the particulate water-absorbent resin in a plane, or the strength of the resulting water-absorbent material tends to be low, resulting in poor handleability. In addition, the amount of water-absorbent resin per unit area decreases, and the water-absorbing rate of the resulting water-absorbent material decreases. On the other hand, if the thickness exceeds about 5 mm, the water absorption rate of the resulting water absorbent material may rather decrease.

In another preferred embodiment of the present invention, the water-absorbent resin particles aggregated in a plane form have the above-mentioned (a4) to (b4).
Water and / or steam (moisture) was added to the sheet-like body obtained through each of the steps in an amount of 10 to 150 parts by weight with respect to 100 parts by weight of the water-absorbent resin in the sheet-like body. It is a thing. By adding water to the sheet, the shape retention of the water-absorbent material obtained before and after liquid absorption is improved, and the water absorption rate is also increased. Also, a highly flexible water-absorbing material can be obtained. Examples of the method of adding water include a method of spraying water on a sheet, a method of applying saturated steam, and a method of holding a sheet in an atmosphere having a relative humidity of 50% or more. When the contact between the sheet and the water is non-uniform and it is necessary to make it uniform, the water should not be skipped (for example, sealed) after the contact with the water and left for a while (preferably 30). Homogeneous sheet-like bodies are obtained by applying a temperature of ℃ or more).

The amount of water and / or steam (moisture) added to the sheet obtained through the steps (a4) to (b4) is based on 100 parts by weight of the water-absorbent resin in the sheet. 10
˜150 parts by weight, preferably 10 to 100 parts by weight, more preferably 20 to 80 parts by weight. When the amount of water exceeds 150 parts by weight, the water-absorbent resin content in the sheet becomes low, the water-absorbent material obtained has a low water-absorption amount, and the water-absorbent material obtained has low strength. On the other hand, 10
If the amount of water is less than parts by weight, the effect of adding water cannot be obtained.

Another preferred embodiment of the present invention is that the water-absorbent resin particles aggregated in a plane form a water-absorbable, particulate, hydrogel polymer obtained by polymerization,
It was obtained. The hydrogel polymer in the present invention means a polymer in which a hydrophilic polymer is in a state of absorbing an aqueous liquid and swelling. Usually, the water content with respect to the total weight of the water-containing gel polymer becomes a gel state at about 30% by weight or more, and the preferable water content when carrying out the production method of the present invention is 30 to 90% by weight, More preferably, it is in the range of 40 to 80% by weight. If the water content is less than 30% by weight, the strength of the resulting water-absorbent material may be reduced, while if the water content exceeds 90% by weight, the handleability of the hydrogel polymer tends to be poor. Not only that, the particulate hydrogel polymer tends to be integrated, and the water absorption property (water absorption rate and water absorption amount) of the resulting water absorbent material may be low.

The water-containing gel polymer of the present invention is capable of absorbing further water and is in the form of particles. Further, the term "capable of absorbing water" means that when the hydrogel polymer comes into contact with water, the hydrogel polymer absorbs water and causes volume expansion. Preferably, it has the ability to absorb at least 3 times the weight of water of the hydrogel polymer.

The particle shape is a shape of an individual unit. The unit may be an aggregate. The shape can have, for example, a shape such as a cubic shape, a rod shape, a polyhedron, a spherical shape, a round shape, a square shape, an irregular shape, an irregular shape having a random size, a needle shape, a flake shape, or a fibrous shape. .
Preferably, it is an irregular shape having a random size or a spherical shape having a uniform particle size.

The hydrogel polymer in the present invention may have a wide range of particle size distribution, but it is preferable that it has a specific particle size distribution and size. In a preferred embodiment of the present invention, the hydrogel polymer has an average particle diameter in the dry conversion range of 50 to 2000 μm. Also preferably 5 mm or more, more preferably 3 m
It does not substantially contain a hydrogel polymer having a size of m or more. The method for measuring the average particle size in terms of dry matter is described in the test method of Examples in this specification. If the average particle size in terms of dryness exceeds 2000 μm, the surface area of the hydrogel polymer is generally small, and the water absorption rate of the resulting water absorbent material tends to be small. On the other hand, if the average particle size in terms of dryness is less than 50 μm, the handleability of the hydrogel polymer tends to deteriorate. The average particle size in terms of dryness is more preferably in the range of 50 to 1500 μm, further preferably in the range of 50 to 1000 μm, and most preferably in the range of 50 to 600 μm.

The hydrogel polymer in the present invention is obtained by polymerization. That is, the hydrated gel-like polymer obtained in the polymerization step is used as the hydrated gel-like polymer in the production method of the present invention without going through an intentional drying step, a pulverization step of the dried product and the like. Conventionally, a water-absorbent resin as a water-absorbent material is generally obtained by polymerizing an aqueous liquid of a monomer component containing an ethylenically unsaturated monomer that becomes a hydrogel by polymerization to obtain a hydrogel polymer. The hydrated gel polymer has been dried, pulverized and processed into a powder form. The method for producing a water-absorbing material of the present invention is a method of directly absorbing the water-containing gel-like polymer obtained in the polymerization step without going through a drying step or a pulverization step of a dried product which was conventionally considered to be an essential step. It is provided to be used as a raw material of a material.

The monomer component that becomes a hydrogel by polymerization is generally a water-soluble ethylenically unsaturated monomer, examples of which include (meth) acrylic acid, (anhydrous) maleic acid, fumaric acid, Crotonic acid, itaconic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, styrenesulfonic acid, etc. Anionic monomers and salts thereof; (meth) acrylamide, N-substituted (meth) acrylamide, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate,
Nonionic hydrophilic group-containing monomers such as polyethylene glycol (meth) acrylate; N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-dimethylaminopropyl Specific examples thereof include amino group-containing unsaturated monomers such as (meth) acrylamide and quaternized products thereof. In addition, an amount of acrylic acid ester such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, vinyl acetate, propionic acid, etc., in an amount that does not extremely hinder the hydrophilicity of the obtained polymer. Hydrophobic monomers such as vinyl may be used.
As the monomer, one kind or two or more kinds can be selected and used from these, but considering various water absorption characteristics of the finally obtained water-absorbing material, (meth) acrylic acid (salt), 2 -(Meth) acryloylethanesulfonic acid (salt), 2- (meth) acrylamido-2-methylpropanesulfonic acid (salt), (meth) acrylamide, methoxypolyethylene glycol (meth) acrylate,
One or more selected from the group consisting of N, N-dimethylaminoethyl (meth) acrylate or a quaternary compound thereof is preferable, and one containing (meth) acrylic acid (salt) as an essential component is more preferable. In this case, it is most preferable that 30 to 90 mol% of (meth) acrylic acid is neutralized with a basic substance.

In polymerizing these monomer components,
The method of initiating polymerization is a method using a polymerization initiator, radiation,
There is a method using active energy rays such as electron rays, ultraviolet rays or electromagnetic rays and there is no particular limitation, but a free radical polymerization initiator is generally used. For example, ammonium persulfate,
Inorganic peroxides such as potassium persulfate and hydrogen peroxide; Organic peroxides such as t-butyl hydroperoxide, benzoyl peroxide and cumene hydroperoxide; 2,2 ′
-Azobis (N, N'-dimethyleneisobutylamidine) or a salt thereof, 2,2'-azobis (2-amidinopropane) or a salt thereof, an azo compound such as 4,4'-azobis-4-cyanovaleric acid; And a redox initiator in which a reducing agent such as sulfite, bisulfite, and ascorbic acid is combined with a peroxide. The amount of these polymerization initiators used is usually 0.001 to 5% by weight, preferably 0.01 to 1% by weight, based on the monomer components.

In polymerizing these monomer components, starch, cellulose, chitin, polyvinyl alcohol,
By polymerizing the monomer component in the presence of a hydrophilic polymer such as polyethylene glycol, a graft bond or a complex may be formed simultaneously with the polymerization.

The hydrogel polymer of the present invention may be a self-crosslinking type polymer obtained without using a crosslinking agent,
It may be one obtained by using a cross-linking agent having an ethylenically unsaturated group and / or a reactive functional group within a range in which the water absorbing performance of the resulting water absorbent material reaches a desired standard. These crosslinking agents are not particularly limited as long as they can be polymerized with the above-mentioned ethylenically unsaturated monomer to obtain a hydrogel polymer. Specific examples include N, N'-methylenebis (meth) acrylamide, (poly) ethylene glycol (meth) acrylate, glycerin tri (meth) acrylate, trimethylolpropane (meth) acrylate, triallylamine, triary. Lucyanurate, triallyl isocyanurate, glycidyl (meth)
Acrylate, (poly) ethylene glycol, diethylene glycol, (poly) glycerin, propylene glycol, diethanolamine, trimethylolpropane,
Pentaerythritol, (poly) ethylene glycol diglycidyl ether, (poly) glycerol, polyglycidyl ether, epichlorohydrin, ethylenediamine, polyethyleneimine, (poly) aluminum chloride,
Aluminum sulfate, calcium chloride, magnesium sulfate and the like can be mentioned, and one or more of them can be used in consideration of reactivity. Among these, N, N'-methylenebis (meth) acrylamide, (poly) ethylene glycol di (meth) acrylate and trimethylolpropane tri (meth) acrylate are preferable. The amount of these cross-linking agents used is usually 0.001 to 2 mol%, preferably 0.
It is from 0 to 1 mol%.

The polymerization method for obtaining the hydrogel polymer in the present invention is not particularly limited, and a conventionally known polymerization method can be used. Usually, it is possible to carry out a polymerization method such as an aqueous solution polymerization method or a reverse phase suspension polymerization method. As the aqueous solution polymerization method, for example, a method in which an aqueous solution of a monomer component is put in a mold and polymerized (JP-A-55-133,413), and a hydrous gel polymer produced inside can be subdivided A method of polymerizing an aqueous solution of a monomer component using a polymerization machine such as a kneader having a different stirring shaft (JP-A-57-34,101, etc.) and the like can be mentioned. The latter polymerization method is more preferable in that a particulate hydrogel polymer can be obtained in the polymerization step.
As the reverse phase suspension polymerization method, for example, a method of suspending an aqueous solution of a monomer component in a hydrophobic organic solvent and polymerizing it in the presence of a dispersant (Japanese Patent Publication No. 54-30,710, JP-A-56). -1
47,806 and JP-A-59-140,202). In the reverse phase suspension polymerization method, spherical hydrogel polymer particles are generally obtained, and the particulate hydrogel polymer used in the production method of the present invention can be obtained.

The water-containing gel-like polymer obtained by the aqueous solution polymerization method may be in the form of a lump, and in some cases, a step of molding into particles is necessary in order to obtain the water-containing gel-like polymer used in the production method of the present invention. is there. As a method for molding the hydrogel polymer obtained by the polymerization into a desired particulate hydrogel polymer, a conventionally known method can be used. For example, shearing force may be applied to the hydrogel polymer to pulverize it into particles. Specific devices for applying shearing force to the hydrogel polymer include, for example, screw-type extruders such as meat chopper and (mechanical) pressure kneaders, internal mixers, kneaders such as Banbury mixers, and the like. it can.

The hydrogel polymer used in the present invention may contain auxiliary components such as water-insoluble fine particles, surfactants and short fibers in an amount that does not hinder the molding and aggregation in the next step. These auxiliary components may act to increase the water absorption rate of the resulting water-absorbent material or to facilitate the molding of the hydrogel polymer. For example, as the surfactant, polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether,
Examples thereof include sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene acyl ester, oxyethyleneoxypropylene block copolymer, and sucrose fatty acid ester. The water-insoluble inorganic fine particles include mica, pyrophyllite, kaolinite, halcite, and other similar clay minerals and Aerosil 200 (manufactured by Nippon Aerosil Co., Ltd.) mainly composed of silicon dioxide particles having an average particle size of 50 μm or less. ) And Carplex # 80 (manufactured by Shionogi Co., Ltd.). Examples of the water-insoluble organic fine particles include carbon black, activated carbon and pulp powder. Among them, fine particle silica is preferable because it has a large effect of increasing the water absorption rate. The amount of these auxiliary components used is 1
It is 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, and most preferably 0.5 to 2 parts by weight with respect to 00 parts by weight. If the weight exceeds 10 parts by weight, the effect cannot be obtained in proportion to the amount used, but the water absorption amount is decreased, and in some cases, formation of aggregates is difficult. To do. If the amount used is less than 0.1 part by weight, the use effect cannot be obtained.

The production method of the present invention comprises molding a water-absorbable, particulate, water-containing gel-like polymer obtained by polymerization, and irradiating the obtained aggregate with an active energy ray. The method for molding the hydrogel polymer is not particularly limited. For example, ordinary methods such as embossing, extrusion and rolling can be mentioned. Alternatively, a method of filling a container, mold, bag or the like having a desired shape with the hydrogel polymer may be used. The fresh hydrous gel-like polymer obtained by polymerization usually has a temperature of about 40 to 90 ° C. due to the heat of polymerization, and aggregates can also be obtained by allowing these to cool in a stacked state.

The shape to be molded is not particularly limited.
For example, sheet, tape, mat, rod, string,
A plate shape, a column shape, a spherical shape, an amorphous shape, or the like can be appropriately selected according to the use and purpose. Moreover, there is no particular limitation on the size, length, and width.

The production method of the present invention comprises irradiating the aggregate of the hydrous gel polymer obtained by the above-mentioned molding with an active energy ray. By irradiating with active energy, it is possible to obtain a water-absorbing material excellent in shape retention after absorbing liquid, in addition to water absorption and flexibility. That is, when the volume of the water-absorbent material increases by absorbing liquid, it is possible to impart a property of expanding to a shape similar to that of the shape before absorbing liquid. This allows the water-absorbent resin that constitutes the water-absorbent material to be fixed at a desired position even after absorbing the liquid. Further, it is possible to obtain a water-absorbing material having a small amount of residual monomer and water-soluble content which are not desired to be contained in the water-absorbing material.

In another preferred embodiment of the present invention, the water-absorbent resin particles agglomerated in a plane are obtained by the polymerization of (a5), and further water-absorbable, particulate, hydrogel polymer is used as a support. The total weight of the water-containing gel-like polymer while maintaining the surface state obtained in the step of (a5) in which the step of controlling the thickness to about 0.3 to 20 mm and molding the sheet into a sheet shape is carried out. It is obtained by the process of reducing the water content by at least 10% by weight to form an aggregate of the hydrogel polymer having a water content of 20 to 70% by weight. The method for molding the hydrogel polymer into a planar shape is not particularly limited. For example, a method of spraying the hydrogel polymer on a support which is transferred in a certain direction, a method of putting the hydrogel polymer in a mold and spreading the hydrogel polymer while flattening it, and the like can be adopted.

In the present invention, the term "planar" means a state in which a large number of originally independent particulate hydrogel polymers are brought into physical contact with each other to form planar aggregates. That is, instead of being in an agglomerated state via a third substance such as an adhesive or a fibrous base material, a continuous agglomerate is formed by direct contact between hydrogel polymer particles. It is in the state of doing. Further, it is sufficient that at least a part thereof has a continuous surface, and for example, a surface having one or a plurality of through holes having an arbitrary shape may be used. It may be waved or pleated. Further, it may have a strip shape, a string shape, or a strip shape. Preferably, one side (front side or back side) is 5 cm ² or more,
More preferably 10 cm ² or more, still more preferably 15 cm ^2.
It has an area of not less than cm ² .

In the present invention, the hydrogel polymer is molded into a sheet with the thickness regulated to about 0.3 to 20 mm. If the thickness is less than about 0.3 mm, the strength of the resulting water-absorbent material will be low and the handleability will be poor. On the other hand, when the thickness exceeds 20 mm, the resulting water-absorbent material becomes thick, which is not preferable as the water-absorbent material for providing the compact and thin water-absorbent article for the purpose of the present invention. Preferably, the regulated thickness is about 0.5-10 mm, more preferably about 0.5-5 mm.

Production method of the present invention, step (b5) step (a5)
The water content with respect to the total weight of the water-containing gel-like polymer is reduced by at least 10% by weight while maintaining the surface state obtained in the above step, and the water-containing gel-like polymer aggregates have a water content of 20 to 70 weight%. Reducing the water content of the water-containing gel-like polymer while maintaining the surface state obtained in the step (a5), which comprises the step of It means that the water content of the hydrogel polymer is reduced without adding the water. For example, as the support, a material having low adhesion to the hydrogel polymer is selected, and the hydrogel polymer on the support is heated and dried with hot air, steam, a heater, or the like, on the same support. Examples thereof include a method of immersing the hydrous gel polymer in a hydrophilic organic solvent for dehydration, and a method of applying a high-frequency electric field to the hydrous gel polymer on the same support to perform dielectric heating drying. On this occasion,
When the adhesiveness between the support and the hydrous gel polymer is large, when the hydrous gel polymer loses water and contracts, the surface hydrous gel polymer is distorted, and the hydrous gel polymer is Aggregation may be insufficient and the strength of the resulting water absorbent material may be reduced. Examples of the support having low adhesion to the hydrogel polymer include a support whose surface is covered with a non-adhesive material such as a fluororesin.

In the step (b5), the water-containing gel-like polymer is reduced in the water content with respect to the total weight by at least 10% by weight to form an aggregate of the water-containing gel-like polymer having the water content of 20 to 70% by weight. When the decrease in water content is less than 10% by weight, the water-containing gel-like polymers are not sufficiently aggregated with each other, and the strength of the resulting water-absorbent material is reduced. Preferably 15
.About.70 wt.%, More preferably 20-60 wt.% Water content reduction.

The water-containing gel polymer aggregate obtained by reducing the water content has a water content of 20 to 70% by weight. If the water content is less than 20% by weight, not only the water-absorbing material obtained will have small flexibility, but also the water absorption rate will be small. On the other hand, if the water content exceeds 70% by weight, the strength of the water absorbent material obtained will be low. Water content of preferably 25 to 60% by weight, more preferably
The water content is 30 to 50% by weight.

The water content of the obtained water-absorbent material is preferably uniform in the water-absorbent material from the viewpoint of flexibility. In order to obtain a uniform water-absorbing material, it is necessary to reduce the water content of the hydrogel polymer in the surface state uniformly. If the thickness of the hydrous gel polymer increases, it tends to be difficult to uniformly reduce the water content. From this point as well, the thickness of the hydrogel polymer in the step (a5) is preferably 20 mm or less. Moreover, the method of uniformly reducing the water content is
Among the above-mentioned methods, a method of applying a high-frequency electric field to the hydrogel polymer and subjecting it to dielectric heating and drying is preferable. Also in the method of heating and drying with hot air, it is possible to uniformly reduce the water content by using hot air having a high dew point and a relatively low temperature. It is preferable that the hydrogel polymer is contacted with a gas containing at least water vapor and having a dew point of 50 to 100 ° C. at a temperature of 80 to 150 ° C.

The present invention is a method for producing a water-absorbing material, which comprises irradiating the surface-aggregated water-absorbing resin particles with active energy rays. By irradiating with active energy rays, it is possible to obtain a water-absorbing material which is excellent not only in flexibility but also in shape retention after absorbing liquid. That is, when absorbing the liquid to increase the volume of the water-absorbing material, it is possible to impart a property of expanding to a shape similar to the shape before absorbing the liquid. As a result, the water-absorbent resin forming the water-absorbent material can be fixed at a desired position even after absorbing the liquid.

The water-absorbing material obtained by the production method of the present invention has a good water-absorbing property (water-absorption rate and water-absorption amount), and is a water-absorbing resin before and after absorbing water or an aqueous liquid such as body fluid. Can be fixed at a desired position. The details of the method of measuring the water absorption rate will be described later, but the time for completely absorbing water by applying a certain amount of artificial urine to a water absorbent material having a predetermined area is defined as the water absorption rate. It has been found that increasing this water absorption rate is important in reducing the amount of wood pulp fluff used and producing small and thin water absorbent articles.

The water-absorbent material obtained by the production method of the present invention has supple flexibility when it contains water or a polyhydric alcohol. The details of the method of measuring the flexibility will be described later, but the flexibility of the present invention is an index indicating the flexibility of the water absorbent material and the difficulty of generating fine powder particles when an external force is applied. If the softness is insufficient, a hard and rugged feel may be increased, and the product may become unusable, or the water-absorbent material may collapse and the water-absorbent resin particles may fall off.

By disposing a water-permeable sheet on at least one surface of the water-absorbent material obtained by the production method of the present invention, a water-absorbent article which is a laminated water-absorbent material can be obtained. In such a laminated water-absorbing material, the water-permeable sheet may be arranged on at least one side of the water-absorbing material, but may be arranged on both sides, and in some cases, the water-permeable sheet on one side and the other side. A water impermeable sheet may be provided. Such a laminated water-absorbent material can be obtained simply by stacking a water-permeable sheet or a water-impermeable sheet on the water-absorbent material, but may be embossed if necessary. Also,
Such a laminated water absorbent material can also be obtained by forming the water absorbent material on a water permeable sheet or a water impermeable sheet. In this case, these sheets may be sandwiched and the periphery thereof may be adhered with an adhesive, or each material may be selected and joined by a known method such as heat sealing or ultrasonic fusion.

Examples of the water-permeable sheet include regenerated cellulosic non-woven fabric, cotton-like pulp, rayon, cotton card web, paper and the like, and those having a structure that easily permeates water are preferable. Examples of the water-impermeable sheet include nylon, polyethylene, polypropylene, polyester, polystyrene, and polyvinyl chloride films.

The water-absorbing material obtained by the production method of the present invention, a water-soluble polymer, a deodorant, a fragrance, a drug, a plant growth aid, a bactericide, a fungicide, a foaming agent, a pigment, carbon black, and activated carbon. It is also possible to add a new function to the resulting water-absorbent material by combining it with a short fiber or the like.

The water-absorbent material obtained by the production method of the present invention can be combined with cellulose fiber or its web, synthetic fiber or its web, etc. to form a water-absorbent article suitable as a water-absorbing layer such as sanitary materials. it can. For example, to obtain a water-absorbent article, such as a method of sandwiching the water-absorbent material between paper, a nonwoven fabric or a mat made of cellulose fiber or synthetic fiber, a method of blending the cellulose fiber and a strip of the water-absorbent material, etc. Any known means can be selected as appropriate. The water-absorbent article thus obtained exhibits a water-absorbing performance equal to or higher than that of the conventional one, although it is thinner and more compact than the conventional water-absorbent article.

The water-absorbent material and the water-absorbent article obtained by the production method of the present invention have good water absorbency (water absorption rate and water absorption amount), and before and after absorbing water or an aqueous liquid such as body fluid. Since the water-absorbent resin can be immobilized at a desired position, it is not necessary to incorporate the water-absorbent resin into the fibrous matrix at a relatively low concentration as in the conventional water-absorbent resin particles in order to prevent gel blocking. It can be incorporated in relatively high concentrations in sexual articles. By using the water absorbent material obtained by the production method of the present invention, a water absorbent article having a (substantially dry) water absorbent resin content of about 50 to 98% by weight based on the total weight of the water absorbent article is produced. It will be possible. Preferably about 60-95
%, More preferably about 70-95% by weight water absorbent resin content. Even if a water absorbent article having such a high resin concentration is prepared, the water absorbent material of the present invention is used in the production step of the water absorbent article, in the packaging step and in the transportation step, to move the water absorbent resin in the water absorbent article and There is no spillage of the water-absorbent resin, and there is no migration of the water-absorbent resin even after absorbing the aqueous liquid. In addition, there is no dust.

The water-absorbent article of the present invention is a water-absorbent article in which the water-absorbent material obtained by the above-mentioned manufacturing method is housed inside a bag body having at least one side formed of a water-permeable sheet. Sanitary materials such as incontinence pads, disposable diapers, sanitary napkins, tampons, etc., which are currently on the market, or water-condensation absorbent sheets, water-retaining materials for concentrated gardening, water-stopping agents for civil engineering, medical sheets, food freshness-maintaining materials, foods It is suitable for use as a water-absorbing article for products such as drip absorbents for automobiles. Most of such water-absorbent articles are composed of a water-permeable sheet on the front surface, a water-impermeable leak-proof sheet on the back surface, and a water-absorbing layer located therebetween. By using a water-absorbent article containing the water-absorbent material obtained by the production method of the present invention inside, significantly thinner than conventional products, despite being compact,
It is possible to make products that exhibit water absorption performance equivalent to or better than conventional products.

INDUSTRIAL APPLICABILITY The water absorbent article of the present invention is suitable for absorbing many fluids such as body fluids such as urine and menstrual blood as well as juices of foods such as meat, fish or fruits and vegetables, and diapers and incontinence. It is applicable to products such as articles, pad pads, sanitary napkins, sanitary articles such as tampons and towels, bandages, food freshness-retaining materials, food drip absorbents.

[0107]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

Reference Example 1 Synthesis Example of Water-Absorbent Resin Particles (A) A stainless steel kneader with a jacket having an internal capacity of 10 liters and two sigma type blades was used, which consisted of 75 mol% sodium acrylate and 25 mol% acrylic acid. 5500 g of monomer aqueous solution (monomer concentration 38%) and trimethylolpropane triacrylate 3.1 as a crosslinking agent
g (0.045 mol% with respect to the monomer) were charged, and nitrogen gas was blown into the reaction system to replace the atmosphere in the reaction system with nitrogen. 30 on the jacket
The mixture was heated with warm water of ℃, and while rotating and stirring the sigma type blade at 40 rpm, 2.8 g of sodium persulfate as a polymerization initiator and 0.1 g of L-ascorbic acid were added to initiate polymerization. The polymerization reaction was carried out for 30 minutes. After completion of the reaction, the finely divided particulate hydrogel polymer was spread on a wire net having an opening of 0.3 mm and dried at 150 ° C. for 90 minutes. The resulting dried product (ppA) is crushed using a hammer mill, and water-absorbent resin particles (pA) passing through 850 μm
Got 100 parts by weight of the water-absorbent resin particles (pA) and 0.5 parts by weight of glycerin, 1 part by weight of water, and 2 parts by weight of isopropanol were mixed, and the resulting mixture was placed in an oil bath (195 ° C.). Put in a pickled bowl. The mixture was heat-treated for 45 minutes in a bowl with stirring to obtain water-absorbent resin particles (A) having a particle size of 850 μm. The ratio of the water-absorbent resin particles (A) that passed through 150 μm was 13% by weight. The water absorption capacity under load of the water absorbent resin particles (A) was 25 ml / g.

[1] Water absorption capacity under load of water-absorbent resin particles The water absorption capacity under load is measured using the apparatus shown in FIG.
The upper opening 2 of the buret 1 is capped 3 and the measuring table 4 and the air opening 5 are attached.
Is set to a high level. Diameter 7 at the center of the measuring table 4
Place the filter paper 7 on the 0 mm glass filter 6. On the other hand, the non-woven fabric 8 is fixed to the lower end of the support cylinder 10 having a diameter of 55 mm, and 0.2 g of the water-absorbent resin particles 11 is placed on the non-woven fabric 8.
Disperse evenly and apply a load 9 of 20 g / cm ² . This non-woven fabric 8-water-absorbent resin particles-load 9 together with the supporting cylinder 10 is placed on the filter paper 7 on the glass filter 6,
Amount of 0.9% by weight saline solution absorbed over a period of time (Am
1) was measured, and the water absorption capacity under load was determined according to the following mathematical formula 1.

Water absorption capacity under load (ml / g) = A (ml) /0.2 (g) (1) Example 1 100 parts by weight of water absorbent resin particles (A) and water-insoluble fine particle silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) and 1 part by weight were uniformly mixed. The resulting mixture 39
g was evenly spread on a mold of 150 × 300 mm, and 19 g of water was applied to the water absorbent resin particles (A) by spraying with a spray. The entire form was sealed in a polyethylene bag and left at 45 ° C. for 16 hours to obtain a flexible sheet-shaped water absorbent material (a) having a thickness of 2 mm. The obtained water absorbent material (A) was treated with an absorbed dose of 25 kGy using a gamma ray irradiation device. The water absorbent material (1) thus obtained was evaluated by the following method. The water absorbent material (1) had a large flexibility (softness of 180 degrees or more), and the water absorbent resin particles did not fall off, and could be handled as an integrated sheet. In addition, 100 × on a petri dish with a diameter of 150 mm
When 100 mm of the water-absorbent material (1) was put and 100 ml of 0.9 wt% saline was poured, the saline was satisfactorily absorbed and gelled. Furthermore, the shape retention after absorbing the liquid was excellent.

[2] Flexibility A water-absorbent material having a width of at least 2 cm is placed on a horizontal plane, and a straight line that roughly divides the area of the water-absorbent material into two equal parts is centered, and about half of the water-absorbent material is placed on the plane. It was rotated slowly while keeping it. At that time, the degree of flexibility was defined as the angle from the horizontal plane at which the rotation started when the water-absorbent material was substantially cracked. The larger this angle, the greater the flexibility. Further, when performing the above operation, the degree of falling of the water-absorbent resin particles from the water-absorbent material was observed.

[3] Shape retention after absorption of liquid [0112] A 100 x 100 mm water-absorbing material was placed in a petri dish having a diameter of 150 mm, and 100 ml of 0.9 wt% saline was poured. When the shape of the swollen water-absorbent material after absorbing liquid was substantially similar to the shape of the water-absorbing material before absorbing liquid, the shape retention after absorbing liquid was regarded as good. Also, pick up the edge of the absorbed water-absorbing material and lift up the whole water-absorbing material.
The shape retention after absorbing the liquid was excellent.

Comparative Example 1 The procedure of Example 1 was repeated to obtain water-absorbent resin particles (A) 10
A mixture consisting of 0 parts by weight and 1 part by weight of Aerosil 200 was obtained. Water was added by spraying using a spray while stirring the mixture to obtain water absorbent resin particles (Comparative A) having a water content of 16%. Spread 39 g of water-absorbent resin particles (comparative A) evenly on a mold frame of 150 x 300 mm, thickness about 2 mm
Molded into. Using a gamma ray irradiation device for this, 2
It was processed with an absorbed dose of 5 kGy. The obtained products were water-absorbent resin particles that were independent of each other, and could not be handled as an integrated sheet.

Example 2 100 parts by weight of water-absorbent resin particles (A) and water-insoluble fine particle silica (Sipernat 22S, manufactured by Tegusa Co., Ltd.)
0.5 parts by weight were uniformly mixed. The resulting mixture 27
g uniformly on a 150 × 300 mm mold, and 8.1 g of a 50% by weight aqueous solution of diethylene glycol is sprayed onto the mold to give a flexible sheet-shaped water-absorbing material (a) with a thickness of about 1.2 mm. Obtained. Obtained water absorbent material (a)
Was treated with a gamma ray irradiation apparatus at an absorbed dose of 45 kGy. The water absorbent material (2) thus obtained was evaluated in the same manner as in Example 1. The water absorbent material (2) had a large flexibility (softness of 180 degrees or more), and the water absorbent resin particles did not fall off, and could be handled as an integrated sheet-like material. In addition, 100 × on a petri dish with a diameter of 150 mm
When 100 mm of the water-absorbent material (2) was put and 100 ml of 0.9 wt% saline was poured, the saline was satisfactorily absorbed and gelled. Further, the shape retention after absorbing the liquid was good.

Example 3 100 parts by weight of the water-absorbent resin particles (A) and 1 part by weight of water-insoluble fine particle silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) were uniformly mixed, and the resulting mixture and glycerin were mixed. 2 parts by weight were mixed uniformly. A mixture (K1) comprising the resulting water-absorbent resin particles, Aerosil and glycerin, and 6 parts by weight of pulverized pulp based on 100 parts by weight of the water-absorbent resin particles (A) in the mixture (K1), Dry-mix in a mixer and air-form on a wire screen using a batch-type air-making machine.
A web having a size of 50 × 300 mm and a basis weight of 763 g / m ² was obtained. The obtained web is applied at a pressure of 5.0 kg / cm ² for 15
After being compressed for a minute, a flexible sheet-shaped water absorbent material (c) having a thickness of 1.3 mm was obtained. The obtained water absorbent material (c) was treated with a gamma ray irradiation device at an absorbed dose of 25 kGy. The water absorbent material (3) thus obtained was evaluated in the same manner as in Example 1. The water absorbent material (3) has flexibility (softness 18
(0 degree or more), the water-absorbent resin particles hardly fell off, and could be handled as an integrated sheet-like product. In addition, 100 Petri dish with a diameter of 150 mm
0.9% by weight with 100% water absorbent material (3)
When 100 ml of saline was poured, the saline was well absorbed and gelled. Furthermore, the shape retention after absorbing the liquid was excellent.

Example 4 The web obtained in Example 3 was sprayed with water to give 40 parts by weight of water to 100 parts by weight of the water-absorbent resin particles (A) in the web, and the size was 150 ×. A flexible sheet-shaped water absorbent material (D) having a thickness of 300 mm, a basis weight of 1043 g / m ² , and a thickness of 2.5 mm was obtained. The obtained water absorbent material (d) was treated with an absorbed dose of 25 kGy using a gamma ray irradiation device. The water absorbent material (4) thus obtained was evaluated in the same manner as in Example 1. The water absorbent material (4) had a large flexibility (softness of 180 degrees or more), and the water absorbent resin particles did not fall off, and could be handled as an integrated sheet-like material. In addition, 100 × on a petri dish with a diameter of 150 mm
When 100 mm of the water-absorbing material (4) was put and 100 ml of 0.9% by weight saline was poured, the saline was satisfactorily absorbed and gelled. Furthermore, the shape retention after absorbing the liquid was excellent.

Example 5 100 parts by weight of the water-absorbent resin particles (A) and 1 part by weight of water-insoluble particulate silica (Aerosil 200, manufactured by Nippon Aerosil Co., Ltd.) were uniformly mixed, and the resulting mixture and glycerin were mixed. 6 parts by weight were mixed uniformly. 39 g of the mixture (K2) consisting of the water-absorbent resin particles, Aerosil and glycerin thus obtained was evenly spread on a mold of 150 × 300 mm, and this was left in a thermo-hygrostat at 45 ° C. and 80% relative humidity to give 18 g. Was added to the mixture (K2).
A flexible sheet-shaped water absorbent material (e) having a thickness of about 2 mm was obtained. The water absorbent material (e) thus obtained was treated with a gamma ray irradiation device at an absorbed dose of 30 kGy. The water absorbent material (5) thus obtained was evaluated in the same manner as in Example 1.
The water absorbent material (5) had a large flexibility (softness of 180 degrees or more), and the water absorbent resin particles did not fall off, and could be handled as an integrated sheet-like material. Further, when a 100 × 100 mm water-absorbent material (5) was placed in a petri dish having a diameter of 150 mm and 100 ml of 0.9 wt% saline was poured, the saline was satisfactorily absorbed and gelled. Furthermore, the shape retention after absorbing the liquid was excellent.

Example 6 The water-absorbent resin particles (A) were classified to 300 μm to 212 μm.
Water-absorbent resin particles (B) having a size of m were obtained. 40 g of the water-absorbent resin particles (B) were spread evenly on a mold of 150 × 300 mm, and 12 g of water was applied to the water-absorbent resin particles (B) by spraying with a spray. A flexible sheet-shaped water absorbent material (f) having a thickness of about 1.5 mm was obtained. The obtained water absorbent material (f) was treated with a gamma ray irradiation device at an absorbed dose of 25 kGy. The water absorbent material (6) thus obtained was evaluated in the same manner as in Example 1. The water absorbent material (6) had a large flexibility (softness of 180 degrees or more), and the water absorbent resin particles did not fall off, and could be handled as an integrated sheet. Further, 100 × 100 mm of the water-absorbent material (6) was put into a petri dish having a diameter of 150 mm, and
When 100 ml of 9 wt% saline was poured, the saline was absorbed well and gelled. Furthermore, the shape retention after absorbing the liquid was excellent.

Reference Example 2 Synthesis Example of Water-Absorbent Resin Particles (C) In a 500 ml cylindrical separable flask, 8.6 g of sodium salt of 2-sulfoethyl methacrylate, 75 mol% of acrylic acid neutralized with sodium salt was added. 35.
A monomer aqueous solution containing 4 g, 0.07 g of trimethylolpropane triacrylate as a crosslinking agent (0.06 mol% based on the monomer) and 69 g of water was charged. Nitrogen substitution in the reaction system was performed under stirring, and the temperature of the aqueous monomer solution was adjusted to 3
The temperature was 0 ° C. Then, a 10% sodium persulfate aqueous solution of 0.
5 g and 0.4 g of 0.5% L-ascorbic acid were added, and the stirring was stopped to start the polymerization. 15 after initiation of polymerization
In minutes, the temperature in the system rose to 72 ° C. After confirming that the temperature inside the system started to drop, heat the polymerization system externally and
Held for hours. The hydrous gel polymer obtained is subdivided,
It was dried at 150 ° C. for 90 minutes. Obtained dried product (pp
C) is crushed by a roll mill, then classified, and 600-
Water-absorbent resin particles (C) of 150 μm were obtained. The water absorption capacity under load of the water absorbent resin particles (C) was 20 ml / g.

Example 7 100 parts by weight of the water absorbent resin particles (C) and 5 parts by weight of ethylene glycol were uniformly mixed. 38 g of the obtained mixture
Uniformly spread over a 150 × 300 mm mold, and leave this in a thermo-hygrostat at 45 ° C. and 80% relative humidity for 4.5
g of water was given to the mixture. A flexible sheet-shaped water absorbent material (g) having a thickness of about 1.5 mm was obtained. The water-absorbent material (K) thus obtained was treated with an absorbed dose of 30 kGy using a gamma ray irradiation device. The water absorbent material (7) thus obtained was evaluated in the same manner as in Example 1. The water-absorbent material (7) had a large flexibility (flexibility of 120 degrees or more), almost no falling of the water-absorbent resin particles, and could be handled as an integral sheet-like material. Further, when a 100 × 100 mm water-absorbent material (7) was placed in a petri dish having a diameter of 150 mm and 100 ml of 0.9 wt% saline was poured, the saline was satisfactorily absorbed and gelled. Further, the shape retention after absorbing the liquid was good.

Reference Example 3 Synthesis Example of Water-Absorbent Resin Particles (D) 472 g of an aqueous solution of a monomer consisting of 25 mol% of acrylic acid and 75 mol% of sodium acrylate (concentration of monomer: 30)
% By weight), 0.16 g of polyethylene glycol diacrylate (average degree of polymerization of polyethylene glycol part 8) as a cross-linking agent (0.02 mol% based on monomer), and 0.19 g of sodium persulfate as a polymerization initiator. Was added, and the mixture was stirred and dissolved at room temperature. Further, nitrogen gas was blown in to expel dissolved oxygen. On the other hand, 1000 ml of cyclohexane and 4 g of the surfactant sorbitan monostearate were charged in a 2000 ml flask equipped with a reflux condenser in which the system was replaced with nitrogen in advance, and the surfactant was dissolved at 40 to 45 ° C. while stirring at 250 rpm. Then, the above-mentioned aqueous monomer solution containing a polymerization initiator was added dropwise and suspended. When the bath temperature was raised and kept at 55 ° C., the internal temperature rose sharply and reached the polymerization peak temperature of 72 ° C. after 10 minutes. Then, the bath temperature was raised, the internal temperature was kept at 70 ° C., and the reaction was carried out for 100 minutes. The suspension of the obtained polymer was separated by filtration, and the separated particulate hydrogel polymer was placed in a vacuum dryer. Cyclohexane and water were removed at a temperature of 80 to 90 ° C to obtain particulate water-absorbent resin particles (D) having an average particle diameter of about 80 µm.

Example 8 The same operation as in Example 6 was repeated except that the water absorbent resin particles (D) were used in place of the water absorbent resin particles (B) in Example 6, and the thickness was about 1.5 mm. A flexible sheet-shaped water-absorbing material (K) was obtained. Obtained water absorbent material (h)
Was treated with a gamma ray irradiation device at an absorbed dose of 25 kGy. The water absorbent material (8) thus obtained was evaluated in the same manner as in Example 1. The water absorbent material (8) had a large flexibility (softness of 180 degrees or more), and the water absorbent resin particles did not fall off, and could be handled as an integrated sheet-like material. In addition, 100 × on a petri dish with a diameter of 150 mm
When 100 mm of the water absorbent material (8) was put and 100 ml of 0.9 wt% saline was poured, the saline was absorbed well and gelled. Furthermore, the shape retention after absorbing the liquid was excellent.

Example 9 The water absorbent material (1) obtained in Example 1 was treated with 150 × 30.
It was sandwiched by two sheets of 0 mm paper (basis weight 15 g / m ² ) to prepare a laminated sheet (1). On the other hand, the center of a waterproof sheet made of polyethylene film of a commercially available disposable diaper ping-pong pants L size (Shiseido Co., Ltd.) was cut in the longitudinal direction to remove an absorbent body made of a water-absorbent resin, a cotton-like pulp and a water-absorbent paper. The above-mentioned laminated sheet (1) was incorporated in the chassis of the disposable diaper thus obtained, and the cut of the waterproof sheet was closed with an adhesive tape. While the thickness of commercially available disposable diapers was about 7 mm,
The water absorbent article (1) obtained had a thickness of about 2.5 mm. It also had great flexibility. When the water absorbent article (1) was evaluated by the following method, it absorbed 360 ml of saline solution and showed a sufficient water absorption capacity as a disposable diaper.

[4] Method for evaluating water-absorbent article A baby model equipped with a urinary tract was prepared based on an infant weighing 10 kg. The water absorbent article (1) prepared in Example 9 was mounted on the baby model, and 0.9 wt% saline was discharged at a rate of 60 ml / 10 sec. The same urination operation was performed after 30 minutes, and urine leakage was evaluated by the amount of saline solution absorbed until the saline solution leaked from the absorbent article.

Example 10 In Example 1, an electron beam irradiation apparatus (TYPE CB250 / 15 / 180L, manufactured by Iwasaki Electric Co., Ltd.) was used instead of the gamma ray irradiation apparatus for the water absorbent material (A), and an absorbed dose of 20 kGy was used. The operation of Example 1 was repeated except that the treatment was carried out in step 1 to obtain a water absorbent material (9). The water absorbent material (9) had a large flexibility (softness of 180 degrees or more), and the water absorbent resin particles did not fall off, and could be handled as an integrated sheet-like material. In addition, 100 × on a petri dish with a diameter of 150 mm
When 100 mm of the water-absorbent material (9) was put and 100 ml of 0.9 wt% saline was poured, the saline was satisfactorily absorbed and gelled. Furthermore, the shape retention after absorbing the liquid was excellent.

Example 11 In Example 6, an electron beam irradiation apparatus (TYPE CB250 / 15 / 180L, manufactured by Iwasaki Electric Co., Ltd.) was used instead of the gamma ray irradiation apparatus for the water absorbent material (f), and an absorbed dose of 30 kGy was used. The operation of Example 6 was repeated except that the treatment was carried out in step 1 to obtain a water absorbent material (10). The water absorbent material (10) had a large flexibility (softness of 180 degrees or more), and the water absorbent resin particles did not fall off, and could be handled as an integrated sheet. In addition, 100 × on a petri dish with a diameter of 150 mm
0.9% by weight containing 100 mm of water absorbing material (10)
When 100 ml of saline was poured, the saline was well absorbed and gelled. Furthermore, the shape retention after absorbing the liquid was excellent.

Example 12 The absorption dose of 30 kGy was obtained by using an electron beam irradiation apparatus (TYPE CB250 / 15 / 180L, manufactured by Iwasaki Electric Co., Ltd.) in place of the gamma ray irradiation apparatus for the water absorbent material (K) in Example 8. The procedure of Example 8 was repeated except that the water-absorbing material (11) was obtained. The water absorbent material (11) had a large flexibility (softness of 180 degrees or more), and the water absorbent resin particles did not fall off, and could be handled as an integrated sheet-like material. In addition, 100 × on a petri dish with a diameter of 150 mm
0.9% by weight containing 100 mm of water absorbing material (11)
When 100 ml of saline was poured, the saline was well absorbed and gelled. Furthermore, the shape retention after absorbing the liquid was excellent.

Example 13 In Example 9, except that the water absorbent material (1) obtained in Example 10 was used instead of the water absorbent material (1).
The operation of Example 9 was repeated to obtain a highly flexible water absorbent article (2) having a thickness of 2.5 mm. When the obtained water absorbent article (2) was evaluated in the same manner as in Example 9,
It absorbed 360 ml of saline and showed a sufficient absorption capacity as a disposable diaper.

Example 14 The procedure of Example 9 was repeated, except that the water absorbent material (11) obtained in Example 12 was used instead of the water absorbent material (1) in Example 9, and the thickness, 2.5 mm,
A highly flexible water-absorbent article (3) was obtained. The water absorbent article (3) thus obtained was evaluated in the same manner as in Example 9, and it absorbed 360 ml of saline solution and showed a sufficient absorption capacity as a disposable diaper.

Example 15 Commercially available polyacrylate-based water-absorbent fiber (trade name: F.I.
S. A. (Type 101, manufactured by Allied Colloid Co., Ltd.) 20 parts by weight are pneumatically formed on a mold with a mesh screen of 10 cm × 30 cm to have a thickness of 10 mm and a size of 10 cm × 3.
A water-absorbent fibrous web having a density of 0 cm and a density of 0.06 g / cm ³ was prepared. Then, this one, 30 ℃, relative humidity 90%
The water-absorbent fibers are partially bonded directly by holding them in a thermo-hygrostat set to the conditions of above, adjusting the water content to 15% by weight, and further compressing them to a density of 0.1 g / cm ^3. Then, a water-absorbent fiber web in which the water-absorbent fibers were aggregated in a plane was obtained. Using this gamma ray irradiation device, 25kG
It was treated with an absorbed dose of y to obtain a water absorbent material (12). The water absorbent material (12) had a large flexibility (softness of 180 degrees or more), and the water absorbent fiber did not fall off, and could be handled as an integrated sheet-like material. Also, diameter 1
When 100 × 100 mm of the water absorbent material (12) was put in a 50 mm petri dish and 100 ml of 0.9 wt% saline was poured, the saline was well absorbed and gelled. Furthermore, the shape retention of the absorbing liquid was excellent.

Example 16 In a 2.5 liter double-arm kneader, with stirring, 956 g of a 37% aqueous sodium acrylate solution, 113 g of an 80% aqueous acrylic acid solution and methylenebisacrylamide (0.1 g) were added.
A monomer aqueous solution consisting of 8 g was charged, and under a nitrogen atmosphere, 1
50 g of a 0% aqueous solution of ammonium persulfate and 20 g of a 10% aqueous solution of sodium hydrogen sulfite were added, and polymerization was carried out with stirring. After the polymerization, the obtained finely divided hydrogel is dried in a drier at 180 ° C., pulverized, and a 20-mesh wire mesh passing product is fractionated to have an average particle diameter of 400 μm and a bulk specific gravity of 0.
3 g / ml of powdery water-absorbent resin particles were obtained. 25 g of the water-absorbent resin particles obtained and 1.5 g of glycerin were mixed, and the mixture was further thickened, 2.5 mm, and size 10 cm.
It is molded into a sheet shape of × 22 cm, and the sheet-shaped molded product is
The sheet was kept in a thermo-hygrostat set at 50 ° C. and 90% relative humidity for 20 minutes to absorb 4 g of water to obtain a sheet-shaped water-absorbent material in which water-absorbent resin particles were aggregated in a plane. . Using a gamma ray irradiation device to the obtained water-absorbing material,
It was treated with an absorbed dose of 25 kGy to obtain a water absorbent material (13). The water absorbent material (13) had a large flexibility (softness of 180 degrees or more), and the water absorbent resin particles did not fall off, and could be handled as an integrated sheet.
Also, a petri dish with a diameter of 150 mm is 100 x 100 mm
Water absorbent material (13) of 0.9 wt% saline solution
When 00 ml was poured, the saline solution was absorbed well and gelled. Furthermore, the shape retention after absorbing the liquid was excellent.

Reference Example 4 Synthetic Example of Hydrous Gel Polymer (A) Mechanical mechanical kneader made of stainless steel with an internal capacity of 75 liters, a hydraulic pressure cover, two Z-shaped blades, a jacket and a thermometer ( Kurimoto Steel Co., Ltd.), 30 kg of an aqueous solution of a monomer consisting of 70 mol% sodium acrylate and 30 mol% acrylic acid (monomer concentration 34 wt%), and N, N'-methylene as a crosslinking agent. Bisacrylamide 1
2.6 g (0.07 mol% with respect to the monomer) was added, and nitrogen gas was blown into the reaction system to replace it with nitrogen. 14 g of sodium persulfate as a polymerization initiator and 0.6 g of L-ascorbic acid were added to the jacket while heating the jacket with warm water of 30 ° C. and rotating and stirring the Z-shaped blade at 40 rpm. Polymerization was started 1 minute after the addition of the polymerization initiator, and the polymerization peak temperature of 82 ° C. was reached 12 minutes later, and a particulate hydrogel polymer was obtained. The warm water temperature of the jacket was raised to 70 ° C., the hydraulic device was operated, and the pressure cover was lowered onto the hydrous gel polymer. The hydraulic pressure was adjusted so that a surface pressure of about 0.4 kg / cm ² was applied to the hydrogel polymer, and the rotary stirring with a Z-shaped blade was continued for 20 minutes under the load. After the reaction was completed, a particulate hydrogel polymer (A) was obtained. The obtained water-containing gel polymer (A) was evaluated by the following method. The average particle diameter of the water-containing gel polymer (A) in dry conversion was 250 μm, and the water content was 65% by weight. It was

[5] Average particle size of the particulate hydrous gel polymer in terms of dryness: 25 g of the sampled particulate hydrous gel polymer (solid content α% by weight) was added to a 20% by weight sodium chloride aqueous solution 12
It was put in 00 g and the stirrer chip was rotated at 300 rpm and stirred for 60 minutes. After stirring, sieve (opening 9.5 mm, 2.0 mm, 0.85 mm, 0.60
mm, 0.30 mm, 0.15 mm, and 0.075
mm) with the above dispersion liquid, and further 6 from the top of the sieve.
A 20% by weight sodium chloride aqueous solution (000 g) was slowly poured to classify the particulate hydrogel polymer. The classified hydrogel polymer particles on each sieve were thoroughly drained and then weighed. The mesh size of the sieve was calculated according to the following formula 1 so that the solid content of the particulate hydrous gel polymer was 10:
0% by weight equivalent (dry conversion) sieve opening R (10
It was converted to 0). R (100) and the ratio of the weight of the water-containing gel-like polymer placed on the screen to the total weight of the water-containing gel-like polymer after the classification and draining operations were plotted on a logarithmic probability paper. From the obtained graph, the openings of the sieve were read so that the proportion on the sieve was 50% by weight, and this was taken as the average particle diameter of the particulate hydrous gel polymer in terms of dryness.

[0134]

[Equation 1]

R (100): sieve opening when converted to a particulate hydrogel polymer having a solid content of 100% by weight
(Mm) w: total weight of hydrous gel polymer after classification and draining
(G) γ: mesh size of sieve classified hydrogel polymer swollen in 20% sodium chloride aqueous solution (mm) [6] water content of particulate hydrogel polymer sampled particulate hydrogel weight The combined product (5 g) was spread on a petri dish and dried at 180 ° C. for 120 minutes. The water content of the particulate hydrogel polymer was determined according to the following mathematical formula 2.

[0136]

[Equation 2]

B1: Weight of particulate hydrogel polymer after drying (g) Example 17 Reference Example 3 was prepared on a flat polytetrafluoroethylene plate.
25 g of the hydrous gel polymer (A) obtained in
It was molded into a thickness of about 4 mm and a size of 100 × 100 mm.
This was placed in a household microwave oven and partially dried for 5 minutes to obtain a sheet-shaped water-absorbing material (ke) in which particulate hydrogel polymer was aggregated. The water content of the obtained water-absorbent material (ke) was 35% by weight, and it was possible to handle it as an integrated sheet. Further, the flexibility (flexibility of 180 degrees or more) was large, and the polymer did not fall off. The water-absorbent material (K) was treated with an absorbed dose of 25 kGy using a gamma ray irradiation device. The water absorbent material (14) thus obtained was evaluated by the test methods described below and in Example 1. The water content of the water absorbent material (14) is 3
It was 4% by weight, and could be handled as an integrated sheet. Further, the flexibility (flexibility of 180 degrees or more) was large, and the polymer did not fall off. Also, put the water-absorbent material (14) in a petri dish having a diameter of 150 mm,
When 100 ml of 0.9 wt% saline was poured, the saline satisfactorily absorbed and gelled. The shape retention after absorbing the liquid was excellent.

[7] Water Content of Water-Absorbing Material 5 g of the sampled water-absorbing material was put in a petri dish, and 1
It was dried at 80 ° C. for 120 minutes. The water content of the water absorbent material was calculated according to the following mathematical formula 3.

[0139]

[Equation 3]

C1: Weight of Water-Absorbing Material after Drying (g) Comparative Example 2 The procedure of Example 17 was repeated except that the partial drying treatment in the microwave oven was carried out for 10 minutes.
A sheet-shaped comparative water-absorbing material (2c) in which the particulate hydrous gel polymer was aggregated was obtained. The obtained comparative water absorbent material (2
c) was evaluated by the same test method as in Example 17.
The comparative water absorbent material (2c) had a water content of 14% by weight and could be handled as an integrated sheet. However, it was not flexible (flexibility of 5 degrees or less), and when it was forcibly bent, many polymer particles fell out. Further, when the comparative water-absorbent material (2c) was put in a petri dish having a diameter of 150 mm and 100 ml of 0.9 wt% saline was poured, the initial water absorption rate was low, but the saline was absorbed and gelled.

Comparative Example 3 The procedure of Example 17 was repeated except that the partial drying treatment with a microwave oven was carried out for 2 minutes. The hydrogel polymer was not aggregated and integrated, but was a discrete particulate hydrogel polymer. The water content of the hydrogel polymer after the treatment was 60% by weight.

Reference Example 5 Synthesis Example of Hydrous Gel Polymer (B) 472 g of an aqueous solution of a monomer consisting of 25 mol% of acrylic acid and 75 mol% of sodium acrylate (concentration of monomer: 30)
% By weight), 0.39 g of polyethylene glycol diacrylate (average degree of polymerization of polyethylene glycol part 8) as a cross-linking agent (0.05 mol% based on the monomer), and 0.19 g of sodium persulfate as a polymerization initiator. Was added, and the mixture was stirred and dissolved at room temperature. 1000 ml of cyclohexane and sorbitan monostearate 4 were placed in a 2000 ml flask equipped with a reflux condenser in which the inside of the system was replaced with nitrogen.
40 g to 45 ° C. while stirring at 220 rpm
To dissolve the surfactant. Then, the above-mentioned aqueous monomer solution containing a polymerization initiator was added dropwise and suspended. When the bath temperature was raised and kept at 55 ° C., polymerization started, and after 10 minutes, the polymerization peak temperature of 72 ° C. was reached. The bath temperature was raised and the internal temperature was kept at 70 ° C. to carry out a reaction for 100 minutes. The suspension of the obtained polymer was filtered to obtain a particulate hydrogel polymer (B). When the obtained hydrogel polymer (B) was evaluated by the same method as in Reference Example 4, the hydrogel polymer (B) had an average dry particle size of about 100 μm and a water content of 70. % By weight.

Example 18 Reference example 4 on a flat polytetrafluoroethylene plate
19 g of the particulate water-containing gel polymer (A) obtained in step 2 was spread and molded into a thickness of about 3 mm and a size of 100 × 100 mm. This was placed in a drier in which hot air consisting of steam-air mixed gas having a temperature of 105 ° C and a dew point of 85 ° C was circulated, and after 8 minutes, a sheet-shaped water-absorbing material (co) in which particulate hydrogel polymers were aggregated. Got The water absorbing material (K) had a water content of 27% by weight and could be handled as an integrated sheet. Further, the flexibility was large (flexibility of 180 degrees or more), and the polymer did not fall off. The water-absorbent material (K) was used as an electron beam irradiation device (TYPE CB250 / 15/18
0 L, manufactured by Iwasaki Electric Co., Ltd.) was used and the absorbed dose was 30 kGy. The obtained water absorbent material (15) was used in Example 1
It evaluated by the same test method as 7. Water absorbent material (1
The water content of 5) was 26% by weight, and it could be handled as an integrated sheet. Further, the flexibility was large (flexibility of 180 degrees or more), and the polymer did not fall off. Further, when the water-absorbent material (15) was put in a petri dish having a diameter of 150 mm and 100 ml of 0.9 wt% saline was poured, the saline was satisfactorily absorbed and gelled. The shape retention product after absorbing the liquid was excellent.

Example 19 In Example 17, 13 g of hydrous gel polymer (B)
Was used, except that the molding thickness of the hydrous gel polymer was about 2 mm and the partial drying treatment in a microwave oven was 3.5 minutes, and the procedure of Example 17 was repeated to obtain a sheet in which the particulate hydrogel polymer was aggregated. A water-absorbing material having a shape of (a) was obtained.

The above water-absorbent material (SA) was treated with a gamma ray irradiation device at an absorbed dose of 35 kGy. The water absorbent material (16) thus obtained was evaluated by the same test method as in Example 17. The water content of the water absorbent material (16) is 38.
It was a weight%, and could be handled as an integrated sheet-like material. Further, the flexibility (flexibility of 180 degrees or more) was large, and the polymer did not fall off. Also, diameter 1
Put the water-absorbent material (16) in a 50 mm petri dish,
When 100 ml of 9 wt% saline was poured, the saline was absorbed well and gelled. The shape retention after absorbing the liquid was excellent.

Example 20 The hydrogel polymer (B) obtained in Reference Example 5 at a temperature of about 70 ° C. was filled in a cylindrical container made of paper having a diameter of 9 cm and allowed to cool overnight at room temperature. An aggregate of the hydrogel polymer (B) having a thickness of 20 mm was obtained. The obtained aggregate was treated with a gamma ray irradiation device at an absorbed dose of 100 kGy.
The water content of the obtained water absorbent material (17) was 68% by weight, the elasticity was large, and the hydrous gel polymer did not fall off.
It could be treated as a unitary mass. Further, 0.9 wt% saline solution was well absorbed and swollen. The shape retention after absorbing the liquid was excellent.

Example 21 In Example 19, the water absorbing material (SA) was replaced with a gamma ray irradiating device and an electron beam irradiating ray (TYPE CB250 / 15 / 180L, manufactured by Iwasaki Electric Co., Ltd.) was used, and an absorbed dose of 40 kGy. The operation of Example 19 was repeated except that the treatment was carried out in step 19 to obtain a water absorbent material (18). The water content of the water absorbent material (18) is 37.
It was a weight%, and could be handled as an integrated sheet-like material. Greater flexibility (flexibility 1
80 degrees or more), and the polymer did not fall off. Also, diameter 1
When 100 × 100 mm water-absorbent material (18) was put in a 50 mm petri dish and 100 ml of 0.9 wt% saline was poured, the saline was well absorbed and gelled. Furthermore, the shape retention after absorbing the liquid was excellent.

Example 22 In Example 18, 90 g of the hydrogel polymer (A) was used.
The procedure of Example 18 was repeated except that the above was molded into a size of 150 × 300 mm to obtain a sheet-shaped water absorbent material (19) that had been subjected to electron beam irradiation treatment. The water absorbent material (19) thus obtained was evaluated by the same test method as in Example 17. The water absorbent material (19) had a water content of 31% by weight and could be handled as an integrated sheet. Further, the flexibility (flexibility of 180 degrees or more) was large, and the polymer did not fall off. On the other hand, the center of a waterproof sheet made of a polyethylene film of a commercially available disposable diaper Pinpin Bantz L size (made by Shiseido Co., Ltd.) was cut in the longitudinal direction to remove the liquid absorbent composed of the water absorbent resin, the cotton-like pulp and the water absorbent paper. A water-absorbent material (19) was incorporated in the chassis of the disposable diaper thus obtained, and the cut of the waterproof material sheet was closed with an adhesive tape to obtain a water-absorbent article (3). The resulting water absorbent article (3) was thin, supple and had a good feel. The water absorbent article (3) thus obtained was evaluated in the same manner as in Example 9 to find 3
It was possible to absorb 60 ml of saline.

[0149]

The water-absorbent material obtained by the production method of the present invention has high safety because it does not contain impurities, has high flexibility, has good water-absorption (water-absorption rate and water-absorption amount), and Because of its excellent shape retention before and after liquid absorption,
It can be used for various purposes for absorbing water or absorbing moisture. For example, water absorption layer of sanitary material, dew condensation water absorption sheet,
Applications include water-retaining materials for concentrated horticulture, water-stopping agents for civil engineering, mechanical sheets, freshness-retaining materials for foods, drip absorbents for foods, water-absorbing agents for sundries, and the like. In addition, the production method of the present invention makes it possible to produce the above water-absorbent material very easily and inexpensively with high productivity. The water-absorbing material obtained by the production method of the present invention has good water-absorbing property, and the water-absorbing article of the present invention having the water-absorbing material stored therein has a water-absorbing performance equal to or higher than that of a conventional water-absorbing article. It is thin and compact while having it. It is also highly flexible and fits well on the object of use, making it easy to use.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a device for measuring water absorption magnification under load used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Burette, 2 ... Upper end of burette, 3 ... Stopper, 4 ... Measuring stand, 5 ... Air intake, 6 ... Glass filter, 7 ... Filter paper 8 ... Nonwoven fabric 9 ... Load, 10 ... Support cylinder 11 ... Water absorbent resin particle.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area // C08L 33/02 LHR

Claims (13)

[Claims] 1. A method for producing a water-absorbing material, which comprises irradiating active-energy rays to the water-absorbing resin particles that have been aggregated in a plane. 2. The water-absorbent resin particles aggregated in a plane form are
1) Particulate water-absorbent resin on a support with a thickness of about 0.3
A step of regulating to ~ 5 mm and spreading in a plane, and (b1)
While maintaining the surface state obtained in the step (a1), at least one selected from the group consisting of water and steam is added in a proportion of 10 to 150 parts by weight to 100 parts by weight of the water absorbent resin. The method for producing a water absorbent material according to claim 1, which is obtained through steps. 3. The water-absorbent resin particles aggregated in a plane are
2) Particulate water-absorbent resin on a support, thickness of about 0.3
A step of regulating to ~ 5 mm and spreading in a plane, and (b2)
Obtained through a step of adding 3 to 30 parts by weight of water and 5 to 50 parts by weight of polyhydric alcohol to 100 parts by weight of the water absorbent resin while maintaining the surface state obtained in the step (a2). The method for producing a water absorbent material according to claim 1, wherein the water absorbent material is produced. 4. The water-absorbent resin particles aggregated in a plane are
3) A step of mixing polyhydric alcohol in an amount of 1 to 10 parts by weight with respect to 100 parts by weight of the particulate water absorbent resin, (b3).
A step of dry-mixing the mixture obtained in the step (a3) and the hydrophilic fiber at a ratio of 1 to 30 parts by weight of the hydrophilic fiber to 100 parts by weight of the water absorbent resin in the mixture; and (c
3) The method for producing a water-absorbing material according to claim 1, which is obtained through a step of pneumatically forming the mixture obtained in the step (b3) into a sheet. 5. The sheet-shaped product obtained by the steps according to claim 4, wherein the surface-aggregated water-absorbent resin particles are added to 100 parts by weight of the water-absorbent resin in the sheet-shaped product. The method for producing a water absorbent material according to claim 1, wherein the water absorbent material is obtained by adding at least one selected from the group consisting of and steam at a ratio of 10 to 150 parts by weight. 6. The water-absorbent resin particles that are aggregated in a plane are
4) A step of mixing the polyhydric alcohol in an amount of 1 to 10 parts by weight with respect to 100 parts by weight of the particulate water absorbent resin, and (b)
4) It is obtained through a step of spreading the mixture obtained in the step (a4) on a support on a support while controlling the thickness to about 0.3 to 5 mm and spreading it in a plane. The method for producing the water-absorbent material of. 7. The water-absorbent resin particles that are aggregated in a planar state, while maintaining the surface state obtained through the steps of claim 6, relative to 100 parts by weight of the water-absorbent resin in the planar body. The method for producing a water absorbent material according to claim 1, wherein the water absorbent material is obtained by adding at least one selected from the group consisting of water and water vapor at a ratio of 10 to 150 parts by weight. 8. The method for producing a water-absorbing material according to claim 1, wherein the water-absorbent resin particles aggregated in a plane form contain 10 to 70% by weight of water based on the total weight. 9. The water-absorbent resin particles that are aggregated in a plane are obtained by molding a water-absorbable, particulate, hydrogel polymer obtained by polymerization. A method for producing the water-absorbing material as described above. 10. The water-absorbent resin particles aggregated in a plane form,
(A5) A water-absorbable, particulate hydrogel polymer obtained by polymerization is placed on a support, and the thickness thereof is about 0.3 to
A step of forming the sheet in a plane shape with a regulation of 20 mm and (b5)
While maintaining the surface state obtained in the step (a5), the water content relative to the total weight of the water-containing gel polymer is at least 1.
The method for producing a water-absorbing material according to claim 9, which is obtained through a step of reducing the content by 0% by weight to form an aggregate of a hydrogel polymer having a water content of 20 to 70% by weight. 11. The hydrogel polymer is 50 to 200.
The method for producing a water absorbent material according to claim 9, wherein the water absorbent material has an average particle diameter in dry conversion of 0 μm. 12. The method for producing a water absorbent material according to claim 1, wherein the active energy ray is at least one selected from the group consisting of gamma rays and electron rays. 13. A water absorbing material, characterized in that the water absorbent material obtained by the manufacturing method according to any one of claims 1 to 12 is housed inside a bag body having at least one surface side formed of a water permeable sheet. Sex goods.