Abstract: Provided is a method for producing a particulate water absorbing agent, the method including the steps of: a polymerization step of polymerizing an acrylic acid (salt)-based aqueous monomer solution so as to obtain a crosslinked hydrogel polymer; a drying step of drying the crosslinked hydrogel polymer so as to obtain a dried polymer; a classification step of classifying a polymer subjected to classification so as to obtain a water-absorbing resin powder having a specific particle size; and a surface-crosslinking step of surface-crosslinking the water-absorbing resin powder that is not surface crosslinked, wherein the classification step is carried out at least either or both of before and/or after the surface-crosslinking step but after said drying step, and wherein a hole shape of a classification sieve used in the classification step is an irregular polygonal or non-circular.

Abstract: A particulate water absorbing agent having a polyacrylic acid (salt)-based water-absorbing resin as a main component, being surface-crosslinked and satisfying physical properties (1) to (3) below: (1) a proportion of particles with a particle diameter of not less than 150 ?m and less than 850 ?m is not less than 90% by weight; (2) an elastic modulus index (EMI) of particles with a particle diameter of not less than 500 ?m and less than 600 ?m is not less than 5500; and (3) a recovery rate defined as Rec.CRC/CRC is 1.05 to 1.20, the particulate water absorbing agent being particularly useful for absorbent articles.

Abstract: An object of the invention is to provide a technique in which a decrease in physical properties is suppressed or consumer complaints are diminished. A method for filling a particulate water absorbing agent includes a filling step of filling a particulate water absorbing agent into a filling container and a vibrating step of vibrating the filling container at the outside of the filling container, the vibrating step being conducted at least one time between the start and the end of the filling step, in which a vibration condition in the vibrating step satisfies the following conditions (a) and (b): (a) vibration by a vibrating body in contact with the filling container has a vertical directional component and a vibrational angle is within 90°±30°; and (b) total amplitude at no load and a vibration frequency at no load of the vibrating body are set so as to satisfy Equation 1-1 and Equation 2 or Equation 1-2 and Equation 2.

Abstract: To provide a water-absorbing resin composition having both a high centrifuge retention capacity (CRC) and a sufficient urine resistance and a method for producing such a water-absorbing resin composition, an aspect of the present invention is a water-absorbing resin composition having the following properties: (1) A centrifuge retention capacity (CRC) being not less than 35 g/g; (2) A post-degradation-test one-hour eluted soluble component being not more than 19% by mass; (3) An absorbency against pressure 0.7 psi (AAP0.7) being not less than 10 g/g; and (4) A content of a water-absorbing resin in dust being not more than 300 ppm with respect to a total mass of the water-absorbing resin composition.

Abstract: An object of the present invention is to provide a method for producing water absorbent resin powder in which permeability potential (SFC) is improved while a water absorbing rate (FSR) is being kept. The method is a method for producing water absorbent polyacrylic acid (salt) resin powder including the steps of: (i) polymerizing an acrylic acid (salt) monomer aqueous solution; (ii) during or after the step of (i), performing gel grinding of a hydrogel crosslinked polymer obtained by the polymerization, wherein the hydrogel crosslinked polymer has resin solid content of 10 wt % to 80 wt %, and the gel grinding is carried out with gel grinding energy (GGE) of 18 [J/g] to 60 [J/g]; (iii) drying a particulate hydrogel crosslinked polymer obtained by the gel grinding, wherein the drying is performed at 150° C. to 250° C.; and (iv) carrying out a surface treatment to the particulate hydrogel crosslinked polymer thus dried.

Abstract: Provided is a water absorbent resin that is useful to sanitary materials such as a disposable diaper, a sanitary napkin, and a blood absorbent for medical use each having a higher liquid permeability and a higher water absorbing speed. Further provided is a water absorbent resin powder that is useful to sanitary materials such as a disposable diaper, a sanitary napkin, and a blood absorbent for medical use each having increased in absorbency of a liquid and in heat retaining property. A gel grinding device to be used to produce a water absorbent resin, includes: a screw; a feed opening; an extrusion opening; a porous plate; and a barrel, the barrel including a return preventing member provided on an inner surface thereof, and the return preventing member satisfying at least one of specific parameters.

Abstract: Provided is a water absorbent resin that is useful to sanitary materials such as a disposable diaper, a sanitary napkin, and a blood absorbent for medical use each having a higher liquid permeability and a higher water absorbing speed. Further provided is a water absorbent resin powder that is useful to sanitary materials such as a disposable diaper, a sanitary napkin, and a blood absorbent for medical use each having increased in absorbency of a liquid and in heat retaining property. A gel grinding device to be used to produce a water absorbent resin, includes: a screw; a feed opening; an extrusion opening; a porous plate; and a barrel, the barrel including a return preventing member provided on an inner surface thereof, and the return preventing member satisfying at least one of specific parameters.

Abstract: To provide water-absorbing resin powder particularly useful for a sanitary article, water-absorbing resin powder containing a polyacrylic acid (salt)-based water-absorbing resin as a main component is surface-crosslinked, and satisfies (1) to (3) below: (1) a proportion of a water absorbent resin powder having a particle size of not less than 150 ?m and less than 850 ?m is not less than 90 weight %; (2) a water absorption time according to a vortex method is not more than 42 seconds; and (3) an elastic modulus index (600-500) is not less than 5500.

Abstract: A method for producing a polyacrylic acid (salt)-based water absorbent resin, sequentially including the steps of: storing or producing acrylic acid; mixing acrylic acid containing a polymerization inhibitor with water, a crosslinking agent, and optionally, a basic composition, and/or neutralizing them, to prepare an aqueous monomer solution; polymerizing the aqueous monomer solution; drying an obtained water-containing gel-like crosslinked polymer; and optionally carrying out surface crosslinking, wherein the acrylic acid containing the polymerization inhibitor has a water content of not higher than 1,000 ppm (by mass; the same applies hereinafter), and/or the aqueous monomer solution has a formic acid content of 1 to 700 ppm, relative to the monomer.

Abstract: The present invention provides a particulate water-absorbing agent which has an excellent fluid retention capacity under pressure and an excellent liquid permeability. Each of the following values of the particulate water-absorbing agent of the present invention falls within a certain range: a ratio represented by “centrifuge retention capacity/Ln (water-soluble component amount)”; a molecular weight distribution of the water-soluble component; a weight average molecular weight after a hydrolysis treatment; and a branching density after the hydrolysis treatment.

Abstract: The purpose of the present invention is to provide a particulate water absorbing agent having both a high water absorption multiplying factor and a high water absorption rate and a method for manufacturing the same. The present invention is a particulate water absorbing agent for which CRC is 30 to 50 g/g, wherein the weight average particulate diameter (D50) is 200-600 ?m, and the DRC index given by the following formula is a specific value (for example, 43, 30, or 20) or less: DRC index=(49?DRC5min [g/g])/(D50 [?m]/1000).

Abstract: The purpose of the present invention is to provide a water absorbent agent having a high water absorption multiplying factor with which stickiness after absorbing liquid can be reduced when used as a hygienic material, and a method for manufacturing the same. The present invention is a method for manufacturing a water absorbent agent that has a centrifuge retention capacity (CRC) of 30 g/g or greater, comprising of subjecting an aqueous solution of a monomer that includes an acrylic acid (salt) to a polymerization step, a drying step, and a surface crosslinking step, wherein the method includes a step for adding ?-hydroxycarboxylic acid (salt) before the drying step.

Abstract: An object of the present invention is to provide a water absorbent resin which attains high liquid permeability and water absorbing speed, and which does not have problems of coloring and odor. The water absorbent resin includes: (A) a water absorbent resin particle having a carboxyl group; (B) a covalent surface crosslinking agent in which the number of carbons is not more than 10; (C) 0.001 mass % to 0.2 mass % of a water-soluble or water-dispersible polymer whose Log P is not less than 1.0; and (D) 0.001 mass % to 1 mass % of a water-soluble polyvalent cation. The water absorbent resin has not less than 20 g/g of a fixed height absorption (FHA) at a height of 20 cm.

Abstract: The present invention provides polyacrylic acid (salt)-based water-absorbing resin powder having an excellent fluid retention capacity under pressure, an excellent water absorption speed, and an excellent liquid permeability and a method for producing the polyacrylic acid (salt)-based water-absorbing resin powder. The earlier-described objects are attained by: a method for producing water-absorbing resin powder which includes adding an inorganic compound to a crosslinked hydrogel polymer obtained in a polymerization step of polymerizing a polyacrylic acid (salt) and performing crushing in specific gel-crushing conditions; and the resultant water-absorbing resin powder.

Abstract: A particulate water absorbing agent having a polyacrylic acid (salt)-based water-absorbing resin as a main component, being surface-crosslinked and satisfying physical properties (1) to (3) below: (1) a proportion of particles with a particle diameter of not less than 150 ?m and less than 850 ?m is not less than 90% by weight; (2) an elastic modulus index (EMI) of particles with a particle diameter of not less than 500 ?m and less than 600 ?m is not less than 5500; and (3) a recovery rate defined as Rec.CRC/CRC is 1.05 to 1.20, the particulate water absorbing agent being particularly useful for absorbent articles.

Abstract: The present invention provides a particulate water-absorbing agent which has an excellent fluid retention capacity under pressure and an excellent liquid permeability. Each of the following values of the particulate water-absorbing agent of the present invention falls within a certain range: a ratio represented by “centrifuge retention capacity/Ln (water-soluble component amount)”; a molecular weight distribution of the water-soluble component; a weight average molecular weight after a hydrolysis treatment; and a branching density after the hydrolysis treatment.

Abstract: Provided is a method for producing a particulate water absorbing agent, the method including the steps of: a polymerization step of polymerizing an acrylic acid (salt)-based aqueous monomer solution so as to obtain a crosslinked hydrogel polymer; a drying step of drying the crosslinked hydrogel polymer so as to obtain a dried polymer; a classification step of classifying a polymer subjected to classification so as to obtain a water-absorbing resin powder having a specific particle size; and a surface-crosslinking step of surface-crosslinking the water-absorbing resin powder that is not surface crosslinked, wherein the classification step is carried out at least either or both of before and/or after the surface-crosslinking step but after said drying step, and wherein a hole shape of a classification sieve used in the classification step is an irregular polygonal or non-circular.

Abstract: To provide water-absorbing resin powder particularly useful for a sanitary article, water-absorbing resin powder containing a polyacrylic acid (salt)-based water-absorbing resin as a main component is surface-crosslinked, and satisfies (1) to (3) below: (1) a proportion of a water absorbent resin powder having a particle size of not less than 150 ?m and less than 850 ?m is not less than 90 weight %; (2) a water absorption time according to a vortex method is not more than 42 seconds; and (3) an elastic modulus index (600-500) is not less than 5500.

Abstract: Provided is a water absorbent resin that is useful to sanitary materials such as a disposable diaper, a sanitary napkin, and a blood absorbent for medical use each having a higher liquid permeability and a higher water absorbing speed. Further provided is a water absorbent resin powder that is useful to sanitary materials such as a disposable diaper, a sanitary napkin, and a blood absorbent for medical use each having a smaller amount of return of a liquid and a higher heat retaining property. A gel grinding device to be used to produce a water absorbent resin, includes: a screw; a feed opening; an extrusion opening; a porous plate; and a barrel, the screw including: a rotating shaft; and a flight, and the screw satisfying at least one of specific parameters.

Abstract: Provided is a water-absorbing agent which is less likely to cause gel blocking and is suitable for a sanitary product and an absorbent article each being thin and containing a large amount of a water-absorbing agent, and which, while maintaining or hardly losing the other physical properties (a fluid retention capacity and a bulk specific gravity) of the water-absorbing agent, simultaneously achieves a high water absorbing speed (e.g., FSR), a high fluid retention capacity under load, high liquid permeability, and salt tolerance. The water-absorbing agent is a polyacrylic acid (salt)-based water-absorbing agent whose surface and its vicinity are crosslinked by an organic surface crosslinking agent, characterized by satisfying the following (A)-(D): (A) Free Swell Rate (FSR) of at least 0.