| abstract |
(57) [Summary] [Problem] To produce a polyester from a lactone by a ring-opening polymerization reaction with energy saving, simply and efficiently. [Solution] In the following general formula I Ln (OSO 2 R 1) (OSO 2 R 2) (OSO 2 R 3) ยทยทยท I ( formula as catalyst for ring opening polymerization of lactones, R 1, R 2, R 3 is A polyester is produced from a lactone by using a rare earth metal compound represented by a perfluoroalkyl group which may be the same or different, and Ln represents a rare earth metal. |