Bayer Aktiengesellschaft

Renate Wilms

Wolfgang Alewelt

Silke Kratschmer

Lothar Bunzel

A transesterification process for producing polyester is disclosed. In a first stage of the process there is heated, in an inert gas atmosphere, a first mixture containing at least one dihydroxy compound and at least one diaryl carbonate to form an oligocondensate. In a second stage there is added to the oligocondensate at least one dicarboxylic acid to form a second mixture. The second mixture is heated to a temperature not higher than 290&deg; C. in the presence of a quaternary onium compound as catalyst to form polyester carbonate. Hydroxyaryl formed throughout the process is distilled-off under reduced pressure.

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Krefeld, Germany

Renate Wilms