000020: Process for the Preparation of Polymers of Dimeric Cyclic Esters

Polylactic acid (PLA) is growing rapidly in popularity as an alternative to petroleum-derived plastics. It is biodegradable thermoplastic and derived from renewable resources. Presently the preparation of crystalline materials requires enantiopure L-lactide where lactic acid is produced by microbial fermentation and the cyclic lactide monomer is made by oligomerization and catalytic dimerization. PLA is then produced from the lactide monomer by ring-opening polymerization. This process is costly weakening PLA\'s position as an alternative to less costly petroleum-derived plastics. Less costly production methods for preparing crystalline PLA are needed to reduce the cost of the material. Low costs would broaden PLA use as an alternative to petroleum-derived polymers. Description This invention provides a process that eliminates the need to prepare enantiopure D and L-lactic acid as a precursor for making PLA. The process involves direct synthesis of PLA from racemic lactide or polymendelide and the use of a racemic metal organic ligand polymer to catalyze the polymerization of racemic dimeric cyclic monomers to a polylactide sterocomplex. PLA made from this process is potentially less costly and has a higher melting temperature than PLA made from precursor enantiopure L-lactide. Benefits