Patent ID: 6399739
Filing Date: 2002-06-04
Classification: C08G

Abstract:
A method for making a polycarbonate comprising structural units derived from at least one dihydroxy aromatic compound and at least one diaryl carbonate, said method comprising the following steps:Step (I) selecting a desired molecular weight and percent endcap of the product polycarbonate; Step (II) consulting a computerized process model to obtain a starting molar ratio of diaryl carbonate to dihydroxy aromatic compound; Step (III) charging an amount of dihydroxy aromatic compound and diaryl carbonate in the molar ratio indicated by the process model to a reactor to form a reaction mixture, said reactor being an element of said process model; and Step (IV) heating at a temperature and pressure indicated by the process model in the presence of a transesterification catalyst while distilling from the reactor a mixture comprising by-product hydroxy aromatic compound and diaryl carbonate to provide a polycarbonate having an effective molar ratio of diaryl carbonate to dihydroxy aromatic compound and having the desired molecular weight and percent endcapping.