Mitsubishi Gas Chemical Company, Inc.

Yasuo Inaba

Masahiro Harada

Tsukasa Toki

A method for producing a copolyamide, which comprises (1) heating either one dicarboxylic acid selected from the group consisting of adipic acid and a mixture containing 40 mol % or more of adipic acid to a temperature higher than the melting point of adipic acid but lower than a temperature lower by 30.degree. C. than the melting point of the resulting copolyamide, (2) dropping a diamine comprising paraxylylene diamine and metaxylylene diamine into the heated dicarboxylic acid before a conversion of the dicarboxylic acid reaches 90 mol %, (3) stopping dropping of the diamine before the conversion of the dicarboxylic acid reaches 90 mol %, and dropping metaxylylene diamine or a diamine mixture of metaxylylene diamine and paraxylylene diamine in place of the diamine until a molar ratio of the total of the diamines to the total of the dicarboxylic acids becomes 0.97 to 1.03, and (4) heating a reaction system to a temperature higher than a temperature lower by 30.degree. C. than the melting point of the finally formed copolyamide before the conversion of the dicarboxylic acid reaches 95 mol %, and elevating the temperature of the reaction system to a temperature higher than the melting point of the finally formed copolyamide upon termination of dropping the diamine.

Copolyamide production method

A process for the production of a polyamide, which comprises polycondensing adipic acid prepared by nitric acid oxidation and containing 1 ppm by weight or less of a free mineral acid as an impurity with a diamine represented by formula (1)

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Hiratsuka, Japan

Yasuo Inaba