×

Process for devolatilization

  • US 5,932,691 A
  • Filed: 12/05/1997
  • Issued: 08/03/1999
  • Est. Priority Date: 12/05/1997
  • Status: Expired due to Fees
First Claim
Patent Images

1. A process for the devolatilization of a thermoplastic polymer containing gaseous impurities in an apparatus having a melting zone, a mixing zone, and a reduced pressure zone, comprising:

  • (a) adding a gaseous blowing agent to the mixing zone;

    (b) melting the polymer in the melting zone;

    (c) mixing the molten polymer and blowing agent in the mixing zone under sufficient pressure to maintain the blowing agent in the mixture;

    (d) at a temperature sufficient for expansion, expanding the gaseous blowing agent in the reduced pressure zone wherein the blowing agent in its expanded state develops froth cells in the molten polymer;

    (e) in the reduced pressure zone, reducing the pressure at the surface of the molten polymer in a sufficient amount to remove essentially all of the gaseous impurities;

    (f) optionally, repeating steps (c), (d), and (e) at least once; and

    (g) recovering the polymer in an essentially unfoamed state.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×