Nippon Shokubai Co., Ltd.

Yoko Shirai

Kazushi Torii

Hiroyuki Ikeuchi

Sayaka Machida

Shigeru Sakamoto

Reiko Nakatsuru

Koji Tachi

Kunihiko Ishizaki

Kunihiki Ishizaki

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&#xb0; C. to 250&#xb0; C.; and (iv) carrying out a surface treatment to the particulate hydrogel crosslinked polymer thus dried.

Method for producing water absorbent polyacrylic acid (salt) resin powder, and water absorbent polyacrylic acid (salt) resin powder

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).

Production method for water-absorbing resin powder

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.

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Himeji, Japan

Yoko Shirai