Method for the manufacture of polymer products from cyclic esters

Claim 1

Method of manufacturing a polymer product from cyclic monomers comprising the steps of: combining the cyclic monomers and a catalyst in a mixing chamber to form a mixture, injecting the mixture, under pressure, into a cavity of a mold having at least two parts, which mold is heated to a temperature above the melting temperature of the monomers, whereby the monomers polymerize allowing the polymerization to take place in the mold for 30 to 200 hours to obtain a degree of polymerization greater than 95% and an intrinsic viscosity of the polymer product greater than 8, opening the mold to remove the product from the mold, wherein the cyclic monomers are selected from the lactone group consisting of lactide, glycolide, ε-caprolactone, dioxanone, 1,4-dioxane-2,3-dione, beta-propiolactone, tetramethylglycolide, beta-butyrolactone, gamma-butyrolactone, pivalolactone, and the cyclic carbonate group consisting of trimethylene carbonate, 2,2-dimethyltrimethylene carbonate, and mixtures thereof, and wherein the catalyst is tin cotoate, antimony trifluoride, zinc powder, dibutyl tin oxide, tin oxalate or a compound according to Formula I: ##STR2## M being a metal ion and n being a number between 1 and 4, equal to the valence of the metal ion, and R 1 and R 2 being, independently of one another, an alkyl, aryl or cycloaliphatic group, and R 3 being an alkyl, aryl or cycloaliphatic group, or a hydrogen atom.