Patent ID: 8697832
Filing Date: 2014-04-15
Classification: C08G

Abstract:
1. A process for preparing lactic acid polymers having high crystallinity and molecular weight, the process comprising melt polymerization of a lactide to form prepolymers having active end groups followed by solid state polymerization of the prepolymers, wherein the melt polymerization is carried out in the presence of a catalyst system comprising a lactide, an organic metal-oxo compound and a polycondensed pre-formed lactic acid oligomer, the metal to oligomer ratio in the catalyst system being in the range of 0.1 to 10, and wherein the residual lactide monomer left after the melt polymerization is removed by heating the reaction mixture under reduced pressure, in the temperature range of 98° C. to a temperature less than the melting point of the prepolymer, such that during the solid state polymerization, the prepolymers react with each other to yield lactic acid polymers whose molecular weight is 3 to 9 times higher than the molecular weight of the prepolymer.