Poly(glycolic acid) for containers and films with reduced gas permeability

Abstract

Compositions of high molecular weight poly(hydroxy acid) polymer having good thermal stability and a weight average molecular weight of >100,000 by GPC. The compositions include one or more chain-terminator compounds/impurities which may be incorporated into the polymer and rendered harmless by the presence of appropriate amounts of bi-functional and multi-functional polymerization initiators. A process including first mixing glycolic acid and/or lactic acid (with chain-terminators), and a diol or di-acid initiator, and at least one multifunctional initiator to form a liquid monomer mixture in an agitated polycondensation reactor. Next, polycondensing to form a liquid reaction mixture comprising a pre-polymer having a weight average molecular weight of >10,000 by GPC, and greater than 80% by mole hydroxyl or carboxyl end-group termination, then crystallizing to form a first solid reaction mixture. Then, solid state polycondensing the solid reaction mixture to form a solid reaction mixture having a moisture level less than 50 ppm by weight. Then, mixing the solid reaction mixture with an appropriate reactive coupling agent in a melting and mixing extruder to couple and form the reaction mixture and form the final poly(hydroxy acid) polymer.