Process for the preparation of thermoplastic polycarbonates

US5340905A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

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

Key dates

• Filing date: Feb 3, 1994
• Grant date: Aug 23, 1994
• Expiry date: Feb 3, 2014

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C08G64/14
• WIPO field: Macromolecular chemistry, polymers
• WIPO sector: Chemistry

Abstract

A two step solvent-free process for the preparation of polycarbonates having a low degree of branching is disclosed. Accordingly, the process comprise PA1 (i) transesterifying in the melt, at temperatures of from 80.degree. to 250.degree. C. and under atmospheric pressure and for a time of up to five hours of diphenols and carbonic acid diaryl esters in the presence of a catalyst to form an oligocarbonate having a weight average molecular weight of from 8,000 to 18,000 and an OH-end group content of from 25 to 50%, and PA1 (ii) polycondensing of said oligocarbonate at temperatures of from 250.degree. C. to 295.degree. C. and pressures of from <500 mbar to 0. 01 mbar, said catalyst being present in an amount of 10.sup.-1 to 10.sup.-8 tool of a catalyst per tool of diphenol, said catalyst being at least one member selected from the group consisting of quaternary ammonium compounds and quaternary phosphonium compounds.