Isolation of polycarbonate with carbon dioxide

US5250658A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Hanns-Ingolf Paul · Leverkusen, DE
• Rolf Treckmann · Cologne, DE
• Gunther Weymans · Leverkusen, DE
• Jurgen Kirsch · Cologne, DE
• Wolfgang Herrig · Bensberg, DE

Key dates

• Filing date: Sep 4, 1992
• Grant date: Oct 5, 1993
• Expiry date: Sep 4, 2012

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C08J2369/00
• WIPO field: Macromolecular chemistry, polymers
• WIPO sector: Chemistry

Abstract

According to the invention, a special process for isolating polycarbonate from methylene chloride at temperatures of 30.degree. to 80.degree. C. in the form of a powder with residual solvent contents below 5% by weight is started up as a continuous process by starting up in a two-component nozzle, in which CO.sub.2 -containing fluid and the polymer solution are continuously combined, with a large excess of CO.sub.2 and then allowing the polycarbonate/methylene chloride/CO.sub.2 fluid system to pass through the gel-forming range of the polycarbonate/methylene chloride/CO.sub.2 phase diagram with continuous reduction of the CO.sub.2 throughput to a ratio of CO.sub.2 to organic solution of 4:1 to 2:1. The process started up in this way has a particularly long useful life.