Patent GB-972169-A (GB)
IPC: B05D1/18
Abstract: 972,169. Coating surfaces electro-phoretically. GLIDDEN CO. Aug. 7, 1962 [Aug. 18, 1961; March 28, 1962 ; April 10, 1962 (2); June 15, 1962], No. 30151/62. Heading C7B. Surfaces as anodes are coated electrophoretically using a film forming substance dispersed in an aqueous medium, the binder used being partially soluble in water, but water insoluble when heated in a final baking stage of the coated surface, the binder present being up to 35% of total weight of liquid and preferably 3-20%, and the liquid being of viscosity not greater than 200 times that of water and preferably below 30 times. The binder used consists of a synthetic carboxylic acid resin at least partly neutralized with ammonia, or a water-soluble amino compound. Preferably the anolyte is separated from the catholyte by an ionic permeable diaphragm through which N-compounds formed pass to the catholyte and are drawn off to prevent pH value rising unduly. Alternatively the N- compounds may be neutralized by adding low molecular polybasic acid, e.g. a polymer of polyenoic acid. The resin is formed by reacting a siccative oil, e.g. linseed, dehydrated castor oil and like oils, or thin fatty acids with acrylic olefinic acid, e.g. maleic, crotonic, phthalic acids or their anhydrides or an aldehyde or ester, e.g. acrolein or vinyl acetate. Preferably the resin is further reacted with a vinyl monomer, e.g. vinyl toluene, styrene, or acrylonitrile. Alkyd resins modified with acrylic or vinyl polymers may also be used. Such resins should have an "electrical equivalent weight" of 1000 to 20,000. This is defined and is based on the amount of resin deposited per unit of electricity relative to a silver deposition unit. The resin is then partly neutralized by treating with ammonia, hydroxy amines, or polyamines, e.g. ethanolamine, hydroxylamine, hexanol amine, diethylene triamine, alkylene oxide-polyamine products, but preferably diisopropanol amine. The product can be dispersed in water alone or after heating to 200-260 ‹C. with non-heat-reactive phenolic resins, but coumarone/indene, cyclopentadiene and other resins are referred to. Pigments, and solubilizing agents, e.g. naphtha, pine oil, glycerine or glycols, and sulphonated compounds as emulsifying agents, may be added. Many examples are given, e.g. linseed oil heated with maleic anhydride, cooled, product reacted with vinyl toluene and a little ditertiary butyl peroxide. Product heated with oil-soluble phenolic resin (amyl phenol-formaldehyde). The product reduced with water and neutralized with diisopropanolamine. The diluted prdouct was electrolytically applied at 11-25 A.S.M. and 19-33V. rising finally to 250V. The coated surface was then washed, dried, and cured by heating at 190 ‹C. The surfaces coated include metals, e.g. phosphated steel, in the form of articles, wire, tube, or plate, or salt-impregnated paper. An apparatus is described in which the paint suspension is pumped upwards through a central anode zone, surrounded by a metal screen covered by a permeable diaphragm in the catholyte zone through which a current of water passes scavenging the N-compounds and keeping the pH value down to about 7À3. Specification 407,957 and U.S.A. Specifications 2,188,883, 2,188,885, 2,188,888, 2,188,890, 2,262,923, 2,285,646, 2,286,466, 2,298,914, 2,369,683, 2,384,846, 2,502,606, 2,634,256, 2,678,934, 2,731,481 and 2,820,711 are referred to.