Process for the production of polycarbonate
View Patent ↗A process for the isolation of polycarbonate produced by the interfacial polymerization process is disclosed. Accordingly, the process entails (a) evaporating the organic solvent from the solution that contains solvent and polycarbonate to obtain a material system that contains 90 to 99.95% polycarbonate, the percent being relative to the weight of the system, and (b) passing the material system through inlet openings of a separating vessel to obtain a plurality of streams of polycarbonate, on entry into the inlet openings said material system being supersaturated with volatile constituents to an extent of at least 1 bar and having a temperature of 250° to 340° C. and a flow rate of 0.1 to 20 kg/hour, and (c) degassing the streams in the separating vessel wherein the pressure is 0.1 to 20 mbar to effect degassing of the polycarbonate.
1. In the process for producing polycarbonate by interfacial polymerization the improvement comprising
(a) evaporating the organic solvent from the solution that comprises solvent and polycarbonate to obtain a melt that contains 90 to 99.95% polycarbonate, the percent being relative to the weight of the melt, and
(b) passing the melt through inlet openings of a separating vessel to obtain a plurality of streams of polycarbonate, on entry into the inlet openings said melt being supersaturated with volatile constituents to an extent of at least 1 bar and having a temperature of 250° to 340° C. and a flow rate of 0.1 to 20 kg/hour, and
(c) degassing the streams in the separating vessel wherein the pressure is 0.1 to 20 mbar to effect degassing of the polycarbonate and
(d) obtaining polycarbonate containing less than 250 ppm of volatile constituents.
2. The process of claim 1 wherein a foaming agent is mixed into the melt before passing the melt through the inlet openings of the separating vessel according to step (b).
3. The process of claim 2 wherein the foaming agent is completely dissolved in the system before (b).
4. The process of claim 1 wherein the residence time of the streams in the separating vessel is at most 10 minutes.
5. The process of claim 1 wherein the separating vessel includes at least one substantially horizontally arranged guide element.
6. The process of claim 1 wherein the melt is heated or cooled between steps (a) and (b) and/or (b) and (c).
7. The process of claim 1 wherein the melt is heated after passing through the inlet openings.