Abstract: A process produces a cationic polymer having a cholesterol-lowering activity, which the process includes a step for subjecting a water-soluble monomer component essentially including a cationic monomer to aqueous polymerization so that the viscosity of a polymerization reaction solution is 1,000 cps or more and less than 300,000 cps at the point of time when a polymerization rate reaches 90%, a step for continuing the polymerization until the polymerization rate exceeds 95%, a step for ultrafiltrating the obtained aqueous polymer, a step for concentrating the ultrafiltration treated solution under reduced pressure at a temperature of the solution lower than 100° C., and a step for drying the concentrated solution under a specific condition. The production process can attain both the safety as a drug and a satisfactory production efficiency.

Abstract: A method of drying a viscous solution containing a (meth)acrylic acid-based polymer or copolymer containing (meth)acrylic acid and/or a salt thereof as a monomer unit, the degree of neutralization of the acid group contained in the polymer being not more than 50 mol %, wherein the method comprises subjecting the solution to, or passing the solution through, a drying zone, in the form of a line, so that the solvent in the solution is removed.

Abstract: A specially defined amount of hydrogen peroxide is used as a polymerization catalyzer; a specially defined amount and a specially defined kind of a polyvalent metal ion is used; and a specially defined amount of an alkaline substance is used, in order to polymerize a monomer component consisting essentially of only maleic acid, or a monomer component composed of maleic acid and another water-soluble ethylenically unsaturated monomer, in a specially defined proportion in water, whereby a maleic acid polymer salt, preferably a copolymer salt, of improved biodegradability is produced. The maleic acid polymer salt obtained is superior in biodegradability, has a low residual monomer content, and is useful as a detergent builder and as a scale inhibitor, etc.