A method for making polycarbonate substantially free of diaryl carbonate.

摘要

A method for making polycarbonate comprises: (a) adding phosgene to a bisphenol under interfacial reaction conditions at pH 10-12 in the presence of a phase transfer catalyst; (b) lowering the pH to 8.0-9.0 and adding phosgene until about 2 mole % excess has been added; (c) introducing to the mixt. a phenolic chain-stopper; (d) raising the pH to 10-12; and (e) eliminating any excess chloroformate gps. in the resulting mixt. In step (a), the amt. of catalyst used is effective until 1-70 mole % of phosgene has been added, based on the total moles of available arylhydroxyl of the bisphenol. In step (b), the excess phosgene is adequate to generate chloroformate end gps. capable of reacting with available bisphenol OH gps. and those of the phenolic chain-stopper to give a polycarbonate having a predetermined molecular wt. The resultant polycarbonate is free of diarylcarbonate.