Sumitomo Naugatuck Co., Ltd.

Hisao Usami

Saburo Mishiba

Junkoh Hyoda

Akira Uchida

Akira Watanabe

A process for preparing a copolymer latex by polymerization of at least one aliphatic conjugated diene monomer, at least one ethylenically unsaturated carboxylic acid monomer and at least one monoolefinic monomer copolymerizable with them in a weight proportion of 19.5-80:0.5-10:10-80, characterized in that (a) a mixture of the whole amount of the aliphatic conjugated diene monomer, the whole amount of the ethylenically unsaturated carboxylic acid monomer and a portion of the monoolefinic monomer, the combined amount of them being from 45 to 99% by weight on the basis of the total amount of the starting monomers, is subjected to emulsion polymerization, and (b) after or while the remainder of the monoolefinic monomer in an amount of from 1 to 55% by weight on the basis of the total amount of the starting monomers is added to the reaction mixture, the further emulsion polymerization is carried out.

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Izumi, Japan

Hisao Usami