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: 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: 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: A method for producing a water-absorbing resin comprises circulation of the water-absorbing resin in a predetermined amount in a pulverization step before a surface cross-linking step. At least a part of a classified polymer is supplied again to the same or a different pulverization step before the surface cross-linking step, wherein the circulation pulverization ratio in the pulverization step, represented by the following equation, is 1.10 to 1.50: (Circulation pulverization ratio)=(total supply amount of the water-absorbing resin to the pulverization step)/(total discharge amount of the water-absorbing resin at the drying step) wherein (total supply amount of the water-absorbing resin to the pulverization step)=(total discharge amount of the water-absorbing resin at the drying step)+(amount of the classified polymer supplied again to the same or a different pulverization step).

Abstract: The present invention provides a method for producing a water-absorbing resin powder. The method includes a polymerization step, a drying step, a pulverization step, a classification step, and a surface cross-linking step. It further includes an additional step, performed before the surface cross-linking step, in which at least part of the classified polymer is supplied again to the same or a different pulverization step. The circulation pulverization ratio in the pulverization step is higher than 1.50.

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: [PROBLEM] It is an object of the present invention to enhance and stabilize properties of a water-absorbing resin, for example, damage resistance or water-absorbing speed, by a simple and convenient method without requiring change of raw materials or expensive facility investment, in a large scale production method for the water-absorbing resin. [MEANS FOR SOLVING THE PROBLEM] It is solved by circulation of the water-absorbing resin in a predetermined amount or more in the pulverization step before the surface cross-linking step. That is, at least a part of the classified polymer is supplied again to the same or different pulverization step, before the surface cross-linking step, wherein circulation pulverization ratio in the pulverization step, represented by the following equation is larger than 1.

Abstract: [PROBLEM] It is an object of the present invention to enhance and stabilize properties of a water-absorbing resin, for example, damage resistance or water-absorbing speed, by a simple and convenient method without requiring change of raw materials or expensive facility investment, in a large scale production method for the water-absorbing resin. [MEANS FOR SOLVING THE PROBLEM] It is solved by circulation of the water-absorbing resin in a predetermined amount or more in the pulverization step before the surface cross-linking step. That is, at least a part of the classified polymer is supplied again to the same or different pulverization step, before the surface cross-linking step, wherein circulation pulverization ratio in the pulverization step, represented by the following equation is 1.10 to 1.