| 摘要 |
PROBLEM TO BE SOLVED: To obtain a high-molecular-weight water-soluble polymer reduced in a content of insolubles resulting from a crosslinking reaction and a content of unreacted monomer remaining after the reaction by polymerizing a water-soluble monomer in the presence of a plurality of azoic polymerization initiators, a reductant, and a polyvalent metal salt. SOLUTION: A water-soluble monomer is polymerized in the presence of 1-1,000 ppm of an azoic polymerization initiator, 30-2,000 ppm of an azoic polymerization initiator having a 10-hr half-life temperature higher than that of the former initiator by at least 5 deg.C, 1-200 ppm of a reductant selected from a hydrogensulfite and a sulfite, and 0.01-50 ppm (in terms of the metallic ions) of a salt of a polyvalent metal selected from iron, copper, manganese, and cerium or a mixture thereof. The water-soluble monomer used is exemplified by a cationic monomer, an anionic monomer, or a nonionic monomer. The polymerization process used is desirably aqueous solution polymerization. The total concentration of the respective monomers is 25-60 wt.%, the polymerization temperature is 0-35 deg.C, and the polymerization time is desirably 0.1-30 hr.
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