Method for polytropically precipitating polyamide powder coating compositions where the polyamides have at least 10 aliphatically bound carbon atoms per carbonamide group

US4334056A · kind A · utility

Assignee

• Chemische Werke Huels Aktiengesellschaft · US

Inventors

• Klaus-Rudolf Meyer · Hattingen, DE
• Karl-Heinz Hornung · Marl, DE
• Rainer Feldmann · Marl, DE
• Hans-Jurgen Smigerski · Marl, DE

Key dates

• Filing date: Feb 20, 1980
• Grant date: Jun 8, 1982
• Expiry date: Feb 20, 2000

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C08J2377/00
• WIPO field: Macromolecular chemistry, polymers
• WIPO sector: Chemistry

Abstract

Polyamide powder coating compositions for the coating of metals at high temperatures are obtained by the precipitation method from polyamides having at least 10 aliphatically bound carbon atoms per carbonamide group, copolyamides having at least 70% of these polyamides and mixtures of homopolyamides and copolyamides having at least 70% of these polyamides. A. For the preparation of powder coating compositions useful in the fluidized bed coating method the polyamides with 10 or more carbon atoms and having a relative viscosity between 1.4 and 1.8 are added to at least twice the amount by weight of ethanol and while the mixture is being mechanically mixed in a closed vessel is converted into a solution at temperatures between 130.degree. and 150.degree. C. This solution is adjusted to a precipitation temperature of between 100.degree. and 125.degree. C. while avoiding the formation of local sub-cooling and is agitated under an inert gas atmosphere to suppress boiling. Without further heat supply, powders with a grain size distribution of at least 99.5% by weight between 40 and 250 microns are precipitated at a low angular speed of agitation. When the particle formation is terminated,…