GB1301515A - - Google Patents

Abstract

1301515 Electrophoretic coating P P G INDUSTRIES Inc 8 April 1970 [9 April 1969] 16547/70 Heading C7B The composition of an electro-deposition bath, comprising a synthetic vehicle resin ionically solubilized or dispersed in an aqueous medium, is controlled by subjecting at least a portion of the bath to ultra-filtration to selectively remove solvent and solute below a given M.W. (e.g. that of the vehicle resin), viz. water and organic solvent with excess base or acid counter-ion used to solubilize the resin, deleterious metal, chromate, phosphate, chloride or sulphate ions, and dissolved CO 2 , using a pressurized gas or hydraulic pressure in contact with the ultrafilter, which may be microporous or diffusive e.g. a gel membrane. The bath may comprise a polycarboxylic acid resin solubilized by a water-soluble base e.g. amine or KOH, or a polybasic resin solubilized by a water-soluble acid, for continuously electro-coating conductive objects, as anode or cathode respectively, e.g. of Fe, steel, Cu, Zn, brass, Sn, Ni, Cr, Al or impregnated paper. The coating may be air-dried or baked after rinsing. Preferably the vehicle resin includes a reaction product or adduct of a (semi) drying oil fatty acid ester with a dicarboxylic acid or anhydride, with or without another ethylenically unsaturated monomer. Many examples are specified. USA Specifications 3366563 and 3369983 and Specification 1112062 are referred to. Alternatively, the coating composition may comprise neutralized copolymers of hydroxyalkyl esters of unsaturated carboxylic acids,unsaturated carboxylic acids and at least one other ethylenically unsaturated monomer along with an amine-aldehyde condensation product. Examples are specified. USA Specification 3403088 is referred to. An alkylamine vehicle resin may be used. Or the composition may comprise mixed esters of a resinous polyol e.g. containing oxirane rings; Specification 1149153 is referred to. Pigments, e.g. Fe oxide, Pb silico chromate, Sr chromate, C black, TiO 2 , talc, BaSO 4 , Cd yellow or red, phthalocyanine blue, chrome yellow, toluidine red and/or hydrated Fe oxide; dispersing or surface active agents, e.g. aliphatic naphthenic and/or aromatic hydrocarbons, dialkyl ethers of glycols or pine oil; antioxidants, e.g. O-amylphenol or cresol; and wetting or foaming agents, may be included in the coating composition.