| abstract |
PURPOSE: To obtain a hydrogel having fine particle size and excellent filtration characteristics, by polymerizing an α,β-unsaturated carboxylic acid monomer, etc. using a W/O-type reverse-phase suspension polymerization in the presence of a nonionic surface active agent, and adding a powdery inorganic substance after the completion of polymerization. n CONSTITUTION: An α,β-unsaturated carboxylic acid monomer (preferably acrylic acid or methacrylic acid) and/or its alkali metal salt is polymerized by the W/O- type reverse-phase suspension polymerization using 0.1W20wt% of a nonionic surface active agent (preferably sorbitan monostearate, etc.) as a dispersing agent. When the polymerization ratio has reached ≥40%, or after the completion of the polymerization, and before the separation of the reaction medium, powder of water-insoluble inorganic material (preferably alumina, silica, etc. having particle diameter of ≤100μ) is added to the slurry in an amount of preferably 0.2W100% to obtain the objective hydrogel composed of coagulated particles having a particle diameter of 0.1W3mm. n EFFECT: The recovered hydrogel can be disintegrated easily to the primary particles having a particle diameter of 5W50μ. n COPYRIGHT: (C)1984,JPO&Japio |