Process for isolating polycarbonates with CO.sub.2 under pressure

US5221731A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

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

Key dates

• Filing date: May 26, 1992
• Grant date: Jun 22, 1993
• Expiry date: May 26, 2012

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C08G64/403
• WIPO field: Macromolecular chemistry, polymers
• WIPO sector: Chemistry

Abstract

A continuous process for the isolation of polycarbonates from a solution of polycarbonate in methylene chloride at temperatures of 30.degree. to 80.degree. C. is disclosed. The process which yields polycarbonate in powder form having residual solvent content of less than 5% by weight, is characterized in that it entails the following steps: PA1 a) obtaining a solution of polycarbonate in methylene chloride containing 10 to 40 percent polycarbonate, said percent being relative to the total weight of the polycarbonate solution, PA1 b) mixing into said solution under pressures of 10 to 50 bar and at temperatures of 30.degree. to 50.degree. C. a fluid containing carbon dioxide resulting in a non-gelling polycarbonate/methylene/chloride/dioxide pressurized system, in which between 10 and 12% CO.sub.2 are dissolved, PA1 c) mixing said pressurized system in a two-component nozzle with additional fluid containing carbon dioxide under a pressure of 50 to 300 bar and at temperatures of 40.degree. to 150.degree. C., to cause rapid precipitation of polycarbonate in the form of solid particles, the quantitative ratio of CO.sub.2 to solution being between 1.0 and 15, preferably between 2.5 and 8…