GB1131023A - Improvements in or relating to electrophoretic painting - Google Patents

Abstract

1,131,023. Electro-phoretic painting. GOODLASS WALL & CO. Ltd. Dec. 30, 1965, No. 55163/65. Heading C7B. The invention of Specification 1, 027,813 is modified in that the aqueous dispersion of pigmented resin, for electro-phoretically depositing a pigmented resin film on a metal object using either D. C. or A. C. is replenished by adding further quantities of resin without further base or water. Preferably the resin is added in a non-aqueous liquid vehicle such as a mixture of a polar and a non-polar solvent. The polar solvent may be an alcohol or alcohol ether, e.g. isopropanol, butanol, butyl carbitol, cyclohexanol, benzyl alcohol, or monoethyl or -butyl ether of (di) ethylene glycol; the non-polar solvent may be an aromatic or a cyclic hydrocarbon, e. g. xylene, naphtha or pine oil. Initially, an aqueous dispersion of pigmented resin may be prepared by adding the equivalent amount of triethanolamine (as base) for a 10% solids emulsion to an emulsion of a homogeneous paint base made by mixing TiO 2 pigment, lampblack, barytes, zinc phosphate, vinyl toluenated alkyd resin and mixed solvent; subsequently, sufficient paint base as above without any triethanolamine may be added after electro-phoretic deposition to obtain a 10% solids emulsion. The alkyd resin may be prepared by reacting dehydrated castor oil fatty acids, trimellitic anhydride, propylene glycol, copolymerizing with vinyl toluene and methyl propanoic acid in presence of di-tertiary butyl peroxide, and thinning to 75% solids with a mixed solvent of butyl carbitol and pine oil. Alternatively, the resin may be a vinyl toluenated maleic modified oil prepared from maleic anhydride and linseed oil. The metal object to be coated may be a phosphated mild steel panel.