Mitsubishi Chemical Corporation

Mitsubishi Kasei Corporation

Hiroaki Yamaoka

Hiroshi Noguchi

Takayuki Ohta

Atsushi Kasai

Shiho Sano

Junichi Gotoh

Keiko Miyazaki

Takayuku Ota

Aliphatic polyester copolymers, which have molecular weights high enough for practical use and which are excellent in thermal stability, tensile strength and moldability, and which are biodegradable as well, are provided, which are produced by a process comprising effecting polycondensation of an aliphatic diol and an aliphatic dicarboxylic acid in the presence of an aliphatic monohydroxymonocarboxylic acid in a specific amount and of a catalyst comprising a germanium compound.

Production of aliphatic copolyesters

A copolymer having repeating units of the following formula (I) and repeating units of the formula (II), wherein the ration of (I) to (II) is within a range of from 10:90 to 90:10 by weight ratio, and the number average molecular weight is at least 1,000, or the intrinsic viscosity .eta..sub.inh is at least 0.02: ##STR1## wherein A is a polyester unit having a polymerization degree of from 2 to 200, R.sup.3 is a bivalent organic group having an ester, urethane or ketone bond, and R.sup.4 is a hydrogen atom or a methyl group, ##STR2## wherein R.sup.5 is a hydrogen atom or a methyl group, and X is a substituent having functionality.

Copolymer and composition containing the copolymer

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Yokohama, Japan

Hiroaki Yamaoka