Method for producing water-absorbent resin particles, water-absorbent resin particles, absorbent material and absorbent article

Abstract

There is provided a novel method for producing water-absorbent resin particles, the method being capable of producing water-absorbent resin particles having improved absorption performance (in particular, in terms of physiological saline retention capacity, physiological saline absorption capacity under a load of 4.14 kPa, and value of non-pressurization DW after 5 minutes). A method for producing water-absorbent resin particles by subjecting a water-soluble ethylenically unsaturated monomer to reversed phase suspension polymerization using a radical polymerization initiator, wherein the radical polymerization initiator comprises an azo compound as at least one radical polymerization initiator, wherein the reversed phase suspension polymerization comprises two or more stages of polymerization steps, wherein in a first-stage polymerization step, (a) an internal-crosslinking agent is used in an amount of 0.01 mmol or more and 0.11 mmol or less per mole of the water-soluble ethylenically unsaturated monomer used in first-stage polymerization, wherein in a second-stage polymerization step, (b) an internal-crosslinking agent is used in an amount of 0 mmol or more and 0.042 mmol or less per mole of the water-soluble ethylenically unsaturated monomer used in second-stage polymerization, and (c) the azo compound is used in an amount of 0.38 mmol or less per mole of the water-soluble ethylenically unsaturated monomer used in the second-stage polymerization, and wherein the method comprises a surface-crosslinking step after the second- or subsequent-stage polymerization step.

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