US Patent 7091302 Process for the preparation of polycarbonate

The invention describes a process for the preparation of polycarbonate. The process includes(a) transesterifying at least one aromatic dihydroxyaryl compound and a diaryl carbonate in the melt in the presence of a catalyst,(b) mixing the melt obtained in step (a) with a foaming agent(c) passing the mixture at 250 to 340° C. through inlet openings of a separating vessel at a rate of 0.1 to 20 kg/hour, to obtain a plurality of streams of foamed polycarbonate and degassing the streams of foamed polycarbonate in the separating vessel wherein the pressure is 0.1 to 20 mbar.