Patent ID: 9061269
Filing Date: 2015-06-23
Classification: A61L,B01J,C08F

Abstract:
1. A method for producing a water-absorbent resin by a reversed-phase suspension polymerization method, the method comprising: step 1 of dispersing a first aqueous solution containing a partially neutralized product (A) of a water-soluble ethylenically unsaturated monomer having acid groups in the molecule in a petroleum-type hydrocarbon dispersion medium in the presence of a dispersing agent, and then polymerizing the resulting dispersion to obtain a slurry containing primary particles of a polymer, and step 2 of adding a second aqueous solution containing a partially neutralized product (B) of a water-soluble ethylenically unsaturated monomer having acid groups in the molecule to the slurry obtained in step 1, and then polymerizing the resulting mixture to obtain a slurry in which the primary particles are agglomerated, and a drying step of removing the petroleum-type hydrocarbon dispersion medium and moisture from the slurry obtained in step 2, wherein the dispersing agent is at least one member selected from the group consisting of a surfactant and a polymer-type dispersing agent, and a molar neutralization degree X of the partially neutralized product (A) is set larger than a molar neutralization degree Y of the partially neutralized product (B), and a difference between the molar neutralization degree X and the molar neutralization degree Y is set to 5% or more.