| 摘要 |
A process for polymerizing lactide and up to 20 mole percent of another lactone is disclosed. The cayalysts used have the formula MZ3 wherein M is scandium, yttrium, bismuth, a lanthanide series rare earth metal or a mixture thereof and the Zs are independently the same or different highly coordinating ligands. The preferred metals M are lanthanum, cerium, praseodymium and neodymium with lanthanum being especially preferred. The preferred ligands are betadiketones, betaketoesters and malonate anions with the betadiketones such as 2,2,6,6-tetramethyl-3,5-heptanedionates being especially preferred.
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