Patent ID: 8378033

Claim:
A method of producing water-absorbent resin particles in which a median particle size of primary particles (d) and a median particle size of secondary particles (D) satisfy the relationship of the formula, 5d/3+150<D<5d+150, comprising: (1) subjecting a first water-soluble ethylenically unsaturated monomer to a first reversed phase suspension polymerization reaction, in a petroleum hydrocarbon solvent, in the presence of a surfactant as a first dispersion stabilizer and a polymeric dispersing agent as a second dispersion stabilizer, to give spherical primary particles having a median particle size (d) of from 30 to 130 μm, wherein the surfactant is at least one member selected from the group consisting of sucrose fatty acid esters and polyglycerol fatty acid esters; (2) cooling the polymerization reaction solution, to precipitate the surfactant and the polymeric dispersing agent; and (3) carrying out a second reversed phase suspension polymerization reaction by adding to the polymerization reaction solution a second water-soluble ethylenically unsaturated monomer to agglomerate the primary particles, to give secondary particles having a median particle size (D) of from 200 to 500 μm, and wherein the water-absorbent resin particles in an agglomerated form have a retention rate of the particle size of 80% or more after particle collision test, and wherein the polymeric dispersing agent is a maleic anhydride-modified ethylene-propylene copolymer.