Abstract: Copolycarbonates containing such structural units as birefringence-reducing or “soft block” units are prepared by conducting a reaction, such as melt polymerization or equilibration, between a precursor polycarbonate and a monomer, polycarbonate oligomer or high molecular weight polycarbonate which is a source of other structural units. The crystallinity of the resulting precursor copolycarbonate or one of the reagents employed in its preparation is enhanced and the precursor copolycarbonate is subjected to solid state polymerization.

Abstract: Polymerization of polycarbonates is performed by first enhancing the crystallinity of a precursor polycarbonate, such as an oligomer, by contact in pellet form with an alkanol in the liquid or vapor state as non-solvent, and then conducting solid state polymerization in a stream of inert gas such as nitrogen. The solid state polymerization operation includes a stage of heating at a constant temperature in the range of about 215-225° C., optionally combined with a first heating stage at a constant temperature in the range of about 180-190° C. The method is adaptable to continuous operation and produces a polycarbonate having a number average molecular weight, as determined by gel permeation chromatography relative to polystyrene, of at least 15,000.

Abstract: Solid state polymerization of polycarbonates and polyesters is preceded by a step of contacting particles of an amorphous precursor polymer with a particulate material, typically a crystallized polycarbonate, which prevents adherence of the precursor polymer particles to each other. It is then possible to perform the solid state polymerization step without crystallizing the precursor polymer.