Sumitomo Seika Chemicals Co., Ltd.

Ayaka Watanabe

Kimihiko Kondo

Junichi Takatori

Noriko Honda

One purpose of the present invention is to provide a water-absorbent resin having excellent water absorption characteristics and being capable of improving the shape-retaining characteristics of a water-absorbent material when used in the water-absorbent material. A water-absorbent resin obtained by performing reversed phase suspension polymerization of a water-soluble ethylenically unsaturated monomer in a hydrocarbon dispersion medium, using a radical polymerization initiator, said resin being capable of having both excellent absorption performance and shape retention in a water-absorbent material using the water-absorbent resin, as a result of fulfilling the conditions of: (1) having a water-retention capacity of physiological saline of at least 38 g/g; (2) having a water-absorption capacity of physiological saline under a load of 4.14 kPa of at least 15 ml/g; and (3) having a tan &#x3b4; of a 50-fold swollen gel of at least 2.10&#xd7;10.

Water-absorbent resin, water-absorbent material, and water-absorbent article

A method for producing a water-absorbent resin includes a polymerization step of polymerizing a polymerizable component containing a water-soluble ethylenically unsaturated monomer dissolved in water using a water-soluble azo-type radical polymerization initiator to obtain a reaction system including a water-absorbent resin precursor, and a dehydration step of removing water from the reaction system by heating. In the dehydration step, a water-soluble radical polymerization initiator is added to the reaction system at any first dehydration stage when the residual water rate calculated by the formula (1) is 50% or more, and a reducing substance is added to the reaction system at any second dehydration stage when the residual water rate decreases from that at the first dehydration stage by 10% or more. According to this production method, a water-absorbent resin having satisfactory water-absorption capacity can be produced while suppressing the content of residual monomers. 

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Saitama, Japan

Ayaka Watanabe