Process for the production of thermoplastic polycarbonates

US5373082A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Hermann Kauth · Krefeld, DE
• Steffen Kuhling · Meerbusch, DE
• Wolfgang Alewelt · Krefeld, DE
• Dieter Freitag · Krefeld, DE

Key dates

• Filing date: Nov 19, 1993
• Grant date: Dec 13, 1994
• Expiry date: Nov 19, 2013

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C08G64/30
• WIPO field: Macromolecular chemistry, polymers
• WIPO sector: Chemistry

Abstract

A process for the production of polycarbonates by melt transesterification is disclosed. Accordingly, polycarbonate waste is dissolved in monophenols and at an elevated temperature and in the presence of a catalyst degraded to yield oligocarbonates, diaryl carbonates and diphenols. Following the optional separation of fillers and other additives there is produced by partial recondensation and the distillation of monophenol a higher viscosity oligocarbonate having a OH and aryl carbonate terminal groups and a weight average molecular weight of 8000 to 18000, the oligocarbonate thus produced is then polycondensed to form a polycarbonate resin.