2 Stage prodn. of aromatic polycarbonate without using phosgene - by precondensation of di:phenol and di:alkyl carbonate and further condensation of oligomer

摘要

2-Stage prodn. of aromatic polycarbonates (I) without using COCl2 involves (1) reacting diphenol(s) (II) with dialkyl carbonate(s) (III) to give aromatic oligocarbonates (IV) with mainly alkyl carbonate end gps., with liberation of alcohol(s); and (2) further condensn. to (I) at higher temp. The claims also cover (I) produced in this way. In stage (1), (II) and (III) are reacted, pref. in the presence of organo-Sn catalyst, to give partly crystalline (IV), which are purified if necessary. In (2), condensn. is carried out in the solid phase. (III) are derived from 1-4 C alcohols; and (II) consist of at least 80 mole-% bisphenol A. (IV) have relative soln. viscosity (RSV) values of 1.02-1.18, pref. 1.06-1.09. USE/ADVANTAGE - (I) are useful for making semifinished prods., mouldings and films, e.g. for use in the electrical industry and vehicle construction. The need to use a special solvent in the prepn. of (IV) can be avoided by using a large excess of (III).