Abstract: The invention provides a novel method for producing a water-absorbent resin comprising: subjecting at least one water-soluble ethylenic unsaturated monomer to reversed-phase suspension polymerization in a petroleum hydrocarbon dispersion medium, the reversed-phase suspension polymerization being conducted using a 0.00005 to 0.00016 mole of water-soluble azo initiator for radical polymerization per mole of the water-soluble ethylenic unsaturated monomer in the presence of 0.000015 to 0.00015 mole of hypophosphorous compound per mole of the water-soluble ethylenic unsaturated monomer. According to the method, the environmental impact can be lessened by reducing the amount of petroleum hydrocarbon dispersion medium released to the outside of the system, and the method makes it possible to obtain a water-absorbent resin having a high water-retention capacity and water-absorption capacity under a load, and a small content of water soluble component at the same time.

Abstract: A water-absorbent sheet composition containing a structure in which an absorbent layer containing a water-absorbent resin and an adhesive is sandwiched with two or more sheets of hydrophilic nonwoven fabrics, wherein the water-absorbent sheet composition has a structure in which the absorbent layer is separated in divided parts of a primary absorbent layer and a secondary absorbent layer with a water-permeable substrate having a water permeability index of from 20 to 90, and wherein the water-absorbent resin is contained in the absorbent layer in an amount of from 100 to 1000 g/m2. The water-absorbent sheet composition of the present invention exhibits some excellent effects that the water-absorbent sheet composition is capable of accomplishing thinning and avoidance of gel blocking phenomenon and liquid leakage, while obtaining basic properties as a water-absorbent sheet composition at a high level, even for a water-absorbent sheet composition containing a very small amount of pulps.

Abstract: The invention provides a novel method for producing a water-absorbent resin comprising: subjecting at least one water-soluble ethylenic unsaturated monomer to reversed-phase suspension polymerization in a petroleum hydrocarbon dispersion medium, the reversed-phase suspension polymerization being conducted using a 0.00005 to 0.00016 mol of water-soluble azo initiator for radical polymerization per mol of the water-soluble ethylenic unsaturated monomer in the presence of 0.000015 to 0.00015 mol of hypophosphorous compound per mol of the water-soluble ethylenic unsaturated monomer. According to the method, the environmental impact can be lessened by reducing the amount of petroleum hydrocarbon dispersion medium released to the outside of the system, and the method makes it possible to obtain a water-absorbent resin having a high water-retention capacity and water-absorption capacity under a load, and a small content of water soluble component at the same time.

Abstract: A water-absorbent sheet structure comprising a structure in which an absorbent layer containing a water-absorbent resin and an adhesive is sandwiched with nonwoven fabrics from an upper side and a lower side of the absorbent layer, wherein the water-absorbent sheet structure has a structure in which the absorbent layer is separated in divided parts of a primary absorbent layer and a secondary absorbent layer with a fibrous substrate having a void ratio of from 91 to 99%, and wherein the water-absorbent resin is contained in an amount of from 100 to 1,000 g/m2, and wherein the adhesive is contained in a proportion of 0.05 to 2.0 times the amount of the water-absorbent resin contained (mass basis).

Abstract: A water-absorbent sheet structure comprises a structure in which an absorbent layer containing a water-absorbent resin and an adhesive is sandwiched with nonwoven fabrics from an upper side and a lower side of the absorbent layer, wherein the water-absorbent resin is contained in an amount of from 100 to 1,000 g/m2, and wherein the water-absorbent resin has a water-retention capacity of saline solution of from 15 to 50 g/g, and wherein the water-absorbent sheet structure has a peeling strength of from 0.05 to 3.0 N/7 cm. The water-absorbent sheet structure of the present invention exhibits some effects that a water-absorbent sheet structure has excellent shape retaining ability even when the structure is thin, so that the water-absorbent sheet structure does not undergo deformation of the form before liquid absorption or after the absorption, and is capable of sufficiently exhibiting absorbent properties.

Abstract: Process for preparing a water-absorbent resin comprising carrying out a reversed-phase suspension polymerization in multi-steps of two or more steps. The water-absorbent resin is prepared by subjecting a water-soluble ethylenically unsaturated monomer to the reversed phase suspension polymerization. This process for preparing a water-absorbent resin involves adding an aminocarboxylic acid compound to at least one step in the second and subsequent steps to carry out the polymerization reaction. The resulting water-absorbent resin can be suitably used in a hygienic material. The water-absorbent resin has a high degree of water-retention, including a high degree of water absorption under pressure. It also has a high water absorption rate, and contains only a small amount of water-soluble substances.

Abstract: A water-absorbent sheet composition (51) comprising a structure in which an absorbent layer comprising a water-absorbent resin and an adhesive is sandwiched with two or more sheets of hydrophilic nonwoven fabrics (57), wherein the water-absorbent sheet composition has a structure in which the absorbent layer is fractionated into a primary absorbent layer (53) and a secondary absorbent layer (54), and wherein the water-absorbent sheet composition satisfies (1) the median particle size of the water-absorbent resin (52) used in the primary absorbent layer and the median particle size of the water-absorbent resin (54) used in the secondary absorbent layer are from 100 to 600 ?m; (2) the water absorption rate of saline solution of the water-absorbent resin used in the primary absorbent layer is from 20 to 70 seconds; (3) the water absorption rate of saline solution of the water-absorbent resin used in the secondary absorbent layer is from 1 to 20 seconds; and (4) (the water absorption rate of saline solution of th

Abstract: A water-absorbent sheet composition containing a structure in which an absorbent layer containing a water-absorbent resin and an adhesive is sandwiched with two or more sheets of hydrophilic nonwoven fabrics, wherein the water-absorbent sheet composition has a structure in which the absorbent layer is separated in divided parts of a primary absorbent layer and a secondary absorbent layer with a water-permeable substrate having a water permeability index of from 20 to 90, and wherein the water-absorbent resin is contained in the absorbent layer in an amount of from 100 to 1000 g/m2. The water-absorbent sheet composition of the present invention exhibits some excellent effects that the water-absorbent sheet composition is capable of accomplishing thinning and avoidance of gel blocking phenomenon and liquid leakage, while obtaining basic properties as a water-absorbent sheet composition at a high level, even for a water-absorbent sheet composition containing a very small amount of pulps.

Abstract: A water-absorbent sheet composition comprising a structure in which a water-absorbent resin and a hot melt adhesive are sandwiched with two or more sheets of hydrophilic nonwoven fabrics, wherein the hydrophilic nonwoven fabrics have a basis weight of 25 g/m2 or more, and wherein the water-absorbent resin is contained in an amount of from 200 to 400 g/m2, and wherein the hot melt adhesive is contained in an amount of from 0.10 to 0.50 times that of the amount of the water-absorbent resin contained (based on weight). According to the present invention, a water-absorbent sheet composition which has sufficient absorbency without undergoing deformation of shape after liquid absorption, while being thin in style can be provided.

Abstract: A water-absorbent sheet composition comprising a structure in which a water-absorbent resin and a hot melt adhesive are sandwiched with two or more sheets of hydrophilic nonwoven fabrics, wherein the hydrophilic nonwoven fabrics have a basis weight of 30 g/m2 or more, and wherein the water-absorbent resin is contained in an amount of from 10 to 150 g/m2, and wherein the hot melt adhesive is contained in an amount of from 0.10 to 1.0 time that of the amount of the water-absorbent resin contained (based on weight). The water-absorbent sheet composition of the present invention exhibits some excellent effects that the sheet composition has sufficient absorbency not only for a liquid having a low viscosity but also a liquid having a high viscosity, without undergoing deformation of shape before or after liquid absorption, while being thin in style.

Abstract: [Problems] To provide a process for preparing a water-absorbent resin which can be suitably used in a hygienic material, the water-absorbent resin having a large amount of water-retention, a large amount of water absorption under pressure, a high water absorption rate, and a small amount of water-soluble substance. [Solving Means] A process for preparing a water-absorbent resin comprising carrying out a reversed phase suspension polymerization in multi-steps of two or more steps when the water-absorbent resin is prepared by subjecting a water-soluble ethylenically unsaturated monomer to the reversed phase suspension polymerization, said process for preparing a water-absorbent resin being characterized by adding an aminocarboxylic acid compound to at least one step in the second and subsequent steps, to carry out the polymerization reaction.