PROCESS FOR PRODUCING B-BUTYROLACTONE HOMOPOLYMER OR COPOLYMER

The object of the invention is to provides a process in which a high-molecular-weight -butyrolactone homopolymer or copolymer being biodegradable, absorbable into the living body, useful as a functional polymeric material and superior in physical characteristics is produced with high yield and good productivity. This object is solved by a process for producing the homopolymer or copolymer of the invention, which comprises ring-opening polymerization of sole -butyrolactone subjected previously to acid removal and dehydration treatment, or of said -butyrolactone with other lactones, in the presence of a tin compound represented by the following formula (1) and/or formula (2): 1 wherein R 1 and R 2 and R 4 to R 7 independently represent an alkyl group containing 1 to 12 carbon atoms which may have a branched chain, or a cycloalkyl group containing 5 to 7 carbon atoms, or a phenyl or naphthyl group which may have a substituent group, R 3 represents an alkylene group containing 2 to 12 carbon atoms which may have a substituent group, a cyclopentane-1,2-ylene group or a cyclohexane-1,2-ylene group, and n is an integer of 1 to 10.