Two step process for the preparation of thermoplastic polycarbonate

摘要

A 2-stage melt-transesterification process for the production of polycarbonate (PC) with a low degree of branching, comprising (1) addition of 10<-2> to 10<-8> mol (based on 1 mol diphenol) of a nitrogen or phosphorus base as catalyst to a mixture of diphenol and diaryl carbonate, heating the mixture to up to 290 degrees C at a pressure of from 100 Pa to atmospheric pressure with distillation of the monophenol produced, to give oligo-carbonate (OC) with an OH end group content of 10-35 mol%, and (2) polycondensation of OC at 240-340 (preferably 275-330, more preferably 280-310) degrees C and 1-50,000 Pa for 10-60 mins. in a self-cleaning high-viscosity reactor with a surface-related degree of self-cleaning of more than 95% and a free useful vol. of at least 50%.