Removal of acid from cathodic electrocoating baths by electrodialysis

US4883573A · kind A · utility

Assignee

• BASF SE

Inventors

• Hartwig Voss · Bischofswerda, DE
• Thomas Bruecken · Dortmund, DE

Key dates

• Filing date: Dec 9, 1987
• Grant date: Nov 28, 1989
• Expiry date: Dec 9, 2007

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C25D13/24
• WIPO field: Surface technology, coating
• WIPO sector: Chemistry

Abstract

Acid is removed from cathodic electrocoating baths by a process in which electroconductive substrates are coated with cationic resins present in the form of aqueous dispersions, at least a portion of the coating bath being subjected to an ultrafiltration where the ultrafiltration membrane retains the cationic resin to form an ultrafiltrate which contains water, solvent, low molecular weight substances and ions and at least a portion of the ultrafiltrate is recycled into the coating bath, and at least a portion of the ultrafiltrate is subjected to a special electrodialysis treatment before being returned into the electrocoating bath.