Extrusion process

• US 6,767,956 B2
• Filed: 03/11/2003
• Issued: 07/27/2004
• Est. Priority Date: 03/02/2000
• Status: Expired due to Term

• Current Assignee: AKZO Nobel Coatings Incorporated (Nouryon BV)
• Original Assignee: Imperial Chemical Industries PLC (IMPERIAL CHEMICAL INDUSTRIES)
• Inventors: Choudhery, Riaz Ahmad, Downing, Stephen Barry, Murray, Kenneth Andrew, Southgate, David John
• Primary Examiner(s): THEXTON, MATTHEW
• Application Number:
  US10/220,376
• Publication Number:
  US 20030176564A1
• Time in Patent Office: 504 Days
• Field of Search: 366/77, 523/348, 523/319, 523/322, 523/323, 524/502-536, 524/582, 524/586, 524/604, 524/605
• US Class Current: 524/582
• CPC Class Codes: B29C 48/022 characterised by the choice of material
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/405 Intermeshing co-rotating screws
• CPC Class Codes: B29K 2067/00 Use of polyesters or derivatives thereof, as moulding material
• CPC Class Codes: C08J 2323/02 not modified by chemical after treatment
• CPC Class Codes: C08J 2367/02 Polyesters derived from dicarboxylic acids and dihydroxy compounds; C08J2367/06 takes precedence
• CPC Class Codes: C08J 3/05 from solid polymers

Abstract

A process for producing an aqueous dispersion of a polymer in an aqueous medium having a viscosity below 10 Pa.s, in which the polymer is dispersed in an aqueous medium in an extruder at a temperature above 100° C., the pressure inside the extruder being maintained above atmospheric pressure so that the aqueous medium does not boil inside the extruder.

Claims

1. A process for producing a dispersion of a polymer in an aqueous medium in which the polymer is dispersed in an aqueous medium in an extruder at a temperature above 100°

C. in an extruder having an outlet wherein the pressure in the extruder is maintained above atmospheric so that the aqueous medium does not boil characterized by maintaining the pressure above atmospheric for the extruder at the outlet with a pressurized collection vessel and wherein aqueous dispersion from the extruder has at least 25% by weight of the aqueous medium where the aqueous medium has less than 40% by weight of organic solvent and wherein the aqueous dispersion enters the outlet and pressurized collection vessel at a pressure above atmospheric so that the aqueous medium does not boil and is subjected to the action of a cooling zone to lower the temperature of the aqueous dispersion to below 100°

C. to have an aqueous dispersion with a viscosity below 10 Pa.s.

2. A process according to claim 1 which is carried out at a temperature of from 5 to 150°

C. above the melting point of the polymer.

3. A process according to claim 2 in which the extruder is a continuous twin screw extruder.

4. A process according to claim 2 in which the polymer is a crystalline polyester or polyolefin.

5. A process according to claim 4 in which the polymer is a crystalline polyester.

6. A process according to claim 2 in which the polymer has a melting point above 130°

C.

7. A process as claimed in claim 1 in which the aqueous medium also comprises a dispersant for the polymer.

8. A process as claimed in claim 7 in which the dispersant is at least partially hydrolysed polyvinyl alcohol.