Patent ID: 6777385
Filing Date: 2004-08-17
Classification: C08F

Abstract:
A production process for a low-molecular (meth)acrylic acid (salt)-based polymer, which comprises the step of polymerizing an aqueous solution of at least one monomer component of a high concentration in the presence of an alkaline substance under conditions where polymerization catalysts are used, wherein: 100 to 95 mol % of the at least one monomer component is a monoethylenically unsaturated monocarboxylic acid (salt) monomer (a) having 3 to 6 carbon atoms; and 0 to 5 mol % of the at least one monomer component is a monoethylenically unsaturated monomer (b) copolymerizable with the monomer (a) (wherein the total of (a) and (b) is 100 mol %); and wherein: a persulfate salt and hydrogen peroxide are used together as the polymerization catalysts; and the entirety of the alkaline substance as used is set not to be more than 99 mol % of the amount which is necessary for neutralizing all acid groups of the at least one monomer component; the monomer (a) is added to the reaction system by substantially continuously drop-wise adding not less than 70 weight % of the entirety of said monomer (a), and the monomer (b) is added to the reaction system by substantially continuously drop-wise adding not less than 70 weight % of the entirety of said monomer (b), and the dropwise addition of the hydrogen peroxide is completed at the latest 10 minutes earlier than the completion time of the dropwise addition of the at least one monomer component.