GB1296987A - - Google Patents

Abstract

1296987 Electro-phoretic coating IMPERIAL CHEMICAL INDUSTRIES Ltd 15 May 1970 [23 May 1969] 26428/69 Heading C7B A conductive article, particularly a hollow vessel e.g. petrol tank, is coated immersed in a dispersion of ionized film-forming material and counter-ion, with an electrical current passed between the article and a counter-electrode contacting the dispersion, by joining regions of the dispersion which are electrically inaccessible to the counter-electrode, e.g. hollows, cavities or recesses, to the other regions by an ionconducting bridge which is impermeable to the ionized film-forming material but permeable to ions of opposite sign e.g. the counter-ion to improve the coating of surfaces adjacent such electrically inaccessible regions. The bridge may comprise an ion-exchange rod, bar or tube protected by a casing of higher mechanical strength, e.g. of ion exchange membrane, dialysis membrane such as of regenerated cellulose or polypropylene, or mesh, porous or perforated plastic sheet; or comprise an electrolyte or polyelectrolyte such as including an alkali metal hydroxide or salt e.g. 5% aqueous KOH solution or organic salts e.g. K phenol sulphonate, enclosed in an elongated casing permeable to counter-ion (or constructed of PVC having at opposite ends areas permeable to counter-ion) e.g. comprising an ion exchanger such as a cation exchange membrane. The counter-ion of the (poly) electrolyte in the bridge may be the same as or different from that of the dispersion. The ion exchangers may include sulphonated styrene/ divinylbenzene copolymers or chloromethylated and aminated cross-linked polystyrene, or condensation products of phenolsulphonates or quanidinium salts with formaldehyde. The dispersion may be a solution, colloidal suspension, emulsion or solid particle suspension of acrylic (co) polymers, alkyd and epoxy resins, maleinized oils or fatty acid esters of polyols, in an aqueous medium at least partially neutralized with ammonia, an amine, NaOH or KOH, or phosphoric acid, where appropriate; pigments, fillers and plasticisers may also be present. Specification 1106979 is referred to.