PURPOSE: To obtain a biodegrdable plastic being homogeneous and having sufficient strengths by subjecting a cyclic ester and a cyclic amide to a ring-opening copolymerization reaction and removing excessive monomer, water, etc., by evacuating the reaction vessel.
CONSTITUTION: A cyclic ester such as β-propiolactone, β-valerolactone or - caprolactone and a cyclic amide such as 2-pyrrolidone, 2-piperidone or - caprolactam are subjected to a ring-opening copolymerization reaction to produce a biodegradable plastic comprising a polyester amide copolymer composed of polyester blocks and polyamide blocks randomly bonded to each other. After the above polymerization reaction, the polymerization and purification are performed by removing excessive monomers and water from the reaction vessel by evacuation to obtain a biodegradable plastic which need not be purified with a solvent. By adding acetic acid to the reaction mixture after the polymerization reaction, the formed polymer can be decolored.
KOBAYASHI YOSHIKAZU
AZUMA TAKASHI
