Multistage melt polymerization of bisphenol‐A and diphenyl carbonate to polycarbonate

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Abstract
A multistage melt polycondensation of bisphenol‐A and carbonate has been studied experimentally using LiOH·H2O catalyst. The reaction process consists of batch and semi‐batch periods with different temperature and pressure conditions. It was observed that a small amount of diphenyl carbonate lost from the reaction mixture by vaporization had little effect on the molecular weight in the batch reaction period but the efficiency of subsequent low‐pressure semibatch polycondensation was affected by the change in the mol ratio of the phenyl carbonate group to the hydroxyl end group. A molecular species model developed for the multistage process was used to analyze the kinetics of the polycondensation process. The composition of the reaction mixture was analyzed of HPLC and compared with model simulations. In particular, the effect of evaporative loss of diphenyl carbonate on the progress of reaction is discussed in detail. © 1993 John Wiley & Sons, Inc.