Process for the production of oxymethylene copolymer molding compositions with a low content of residual formaldehyde

US4225703A · kind A · utility

Assignee

• Deutsche Gold- und Silber-Scheideanstalt Vormals Roessler

Inventors

• Herbert Amann · Hanau, DE
• Gerhard Morlock · Hanau, DE
• Hellmut Trautwein · Hasselroth, DE

Key dates

• Filing date: Sep 11, 1979
• Grant date: Sep 30, 1980
• Expiry date: Sep 11, 1999

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C08G2/28
• WIPO field: Macromolecular chemistry, polymers
• WIPO sector: Chemistry

Abstract

Oxymethylene copolymers molding compositions with low portions of residual formaldehyde are produced by heating the polymerizate melts treated with chemical stabilizers in an apparatus in which there are continuously presented new polymerizate surfaces under reduced pressure. The heating of the polymerizate melt takes place in a thin layer evaporator for highly viscous media during an average residence time of 30 to 120 seconds at an average rate of shear between 500 and 2000 s.sup.-1 and at a pressure P.sub.abs of at most 150 mbar. The escaping gases and vapors are drawn off countercurrent to the polymerizate melt.