Patent ID: 6838543
Filing Date: 2005-01-04
Classification: C08G

Abstract:
1. A process for producing polycarbonates by reacting a monomeric carbonate component with at least one diphenol or dialcohol in the presence of a transesterification catalyst, wherein the molten components are mixed with the transesterification catalyst by stirring and a transesterification product is produced, which is polycondensated, wherein for polycondensation the transesterification product is passed through a preliminary reactor, at least one intermediate reactor and one final reactor, said reactors being connected in series and each having a substantially horizontal driven shaft with stirrers attached thereto, the polycarbonate being withdrawn from the final reactor, each reactor having in its interior a ratio of the horizontal length L to the diameter D of 1.2:1 to 10:1 the preliminary reactor and the final reactor each having a dwell time of the melt of 5 minutes to 30 minutes, the temperature in the preliminary reactor being maintained in the range from 220 to 300° C. and the temperature in the final reactor being maintained in the range from 240 to 350° C., with vapors being withdrawn from each reactor, the pressure in the preliminary reactor being maintained in the range from 100 to 900 mbar and the pressure in the final reactor being maintained in the range from 0.1 to 50 mbar.