GB1335545A - Treatment of electrophoretic deposition bath - Google Patents

Abstract

1335545 Electro-phoretic coating P P G INDUSTRIES Inc 27 Nov 1970 [1 Dec 1969 9 Dec 1969] 56434/70 Heading C7B Dragout loss on an article, electrocoated in an aqueous electrophoretic deposition bath 1 comprising ionically solubolised synthetic resin while controlling the composition of the bath, is reduced by rinsing the article with water e.g. at station 10 or 14 so that the rinse containing dragout is returned to the bath, and subjecting at least a portion of the bath to ultrafiltration, e.g. in a microporous or diffusive (gel) ultrafilter 4, which removes water and preferably solute of relatively low M.W. (amine, alkali metal ion, phosphate, chromate, sulphate, chloride, silicate and dissolved CO 2 ) but retains the resin; such aqueous effluent may be employed, e.g. through line 3 via valves 6, 9 or 13, as rinsing agent for the electrocoated article. Preferably the ultrafilter is an anisotropic membrane through which the aqueous effluent is forced under a pressure of between 2 and 150 psi. The resin may be solubilised polybasic or polyacid resin, e.g. a polycarboxylic acid resin in which the base is an amine or KOH. The articles being coated may be of Fe, steel, Cu, Zn, brass, Sn, Ni, Cr, Al or impregnated paper. Many examples of resins which include reaction products of (semi) drying oil fatty acid esters with dicarboxylic acid or anhydride are specified. Pigments, such as lead silicate, MnO 2 , anthracite and SrCrO 4 , and antifoaming, suspending and wetting agents may be included. Specifications 1335546, 1301515, 1149153 and 1112062 are referred to.