Ultra-high purity polycarbonates having good inherent color and thermal resistance and a device and a method for producing the same

US10435507B2 · kind B2 · utility

Assignee

• Covestro Deutschland AG · DE

Inventors

• Thomas Koenig · Leverkusen, DE
• Joerg Kirchhoff · Cologne, DE
• Michael Bierdel · Leverkusen, DE
• Klemens Kohlgrueber · Kürten, DE
• Johann Rechner · Krefeld, DE
• Ing. Johan Vaes · Kalmthout, BE
• Johan Vanden Eynde · Zwijnaarde, BE
• Frank Bruynseels · Dendermonde, BE
• Bert Ruytinx · Halen, BE

Key dates

• Filing date: Oct 20, 2017
• Grant date: Oct 8, 2019
• Expiry date: Feb 7, 2038

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B29K2069/00
• WIPO field: Other special machines
• WIPO sector: Mechanical engineering

Abstract

The invention relates to polycarbonates with extremely low residual levels of volatile constituents and thermal degradation products, and also improved optical properties, especially Yellowness Index (YI) and good thermal stability, from solvent-containing polymer melts. The invention further relates to an apparatus and a process for preparing these polycarbonates with the aid of a devolatilizing extruder with at least three devolatilizing zones, and zones for introducing entraining agent into dispersion are present upstream of at least three devolatilizing zones.