Mitsubishi Chemical Corporation

Seiichiro Iida

Kiichi Itoh

Kiichi Ito

Sueichi Kato

A process for producing a highly water-absorptive polymer, which comprises suspending an aqueous solution containing a water-soluble polymerizable monomer and an optional crosslinking agent into droplets in a hydrophobic organic solvent in the presence of a dispersant and a water-soluble radical polymerization initiator, and allowing the water-soluble polymerizable monomer to polymerize in the droplets, wherein the dispersant is a phosphoric ester surface active agent represented by the following general formula [I]: ##STR1## wherein R.sup.1 represents an alkyl or alkylaryl group having 8 to 30 carbon atoms, R.sup.2 represents OH group or a group of the formula --(CH.sub.2 CH.sub.2 O).sub.m --OR.sup.1, and m and n are an integer of 1 to 30, and the aqueous solution is successively fed to the hydrophobic organic solvent so that the droplets of different polymerization degrees can be present in the solvent.

Highly water-absorptive polymer and process for producing the same

A method of preparing a water-soluble resin, which comprises the steps of: subjecting an aqueous solution of a first water-soluble ethylenically unsaturated monomer to a first-stage water-in-oil type of reverse-phase suspension polymerization using a water-soluble radical polymerization initiator in a hydrophobic organic solvent in the presence of an emulsifier and optionally a crosslinking agent, thereby forming a slurry containing hydrous polymer gel particles; adding to said slurry a nonionic or anionic surface active agent having an HLB of at least 7 and higher than that of said emulsifier and an aqueous solution of a second water-soluble ethylenically unsaturated monomer so as to absorb the aqueous solution of the second monomer in said hydrous polymer gel particles; and carrying out a second-stage polymerization of said second monomer.

Growing community of inventors

Yokkaichi, Japan

Seiichiro Iida