Patent GB-833122-A (GB)
Title: Improvements in or relating to the coating of metal surfaces
IPC: B05D7/16
Filed: 1958-01-13
Abstract: A metal article, e.g. an automobile body, had as an undercoat a baked layer of an alkyd resin formed by the reaction of (1) a dicarboxylic acid component comprising 25 to 100% mole. of hexachloroendomethylenetetrahydrophthalic acid or anhydride and 0 to 75% mole. of at least one unsubstituted benzene or acrylic dicarboxylic acid or anhydride, (2) at least one polyol and (3) at least one oil component in the form of tall oil, a semi-drying oil, a drying oil or a fatty acid derivable from such an oil. Pigments and various modifiers may be included.  The alkyd resin may be applied to the metal by flow, dip, spray, brush or roller coating and then baked at 150 DEG  to 200 DEG  C. for 60 to 15 minutes. The topcoat may be of a polymethylmethacrylate lacquer (e.g. as described in Specifications 763,158 or 807,895) or of a nitrocellulose lacquer, either of which may be sprayed on the baked undercoat.  The metal may first be primed by treatment with a conventional rust inhibitor (e.g. "Bonderite"-Registered Trade Mark).ALSO:An undercoat for metal surfaces comprises an alkyd resin which is the reaction product of (1) a dicarboxylic acid of which 25-100 mol. per cent is chlorendic acid; (2) a polyol; and (3) an oil component in the form of tall oil, a semidrying oil, a drying oil or a fatty acid derivable from any of such oils; the alkyd having an acid number of less than 50, unreacted hydroxyl groups equivalent to 0.5-5% of glycerol based on the weight of the resin and an oil length of 20 to 45.  The other dicarboxylic acid may be phthalic, isophthalic, terephthalic, adipic, sebacic or azelaic acid.  The polyol may be glycerine, pentaerythritol, mannitol, sorbitol, trimethylol ethane, trimethylol propane, ethylene glycol or cyclohexane diol.  The semi-drying or drying oil may be soybean, menhaden, codliver, dehydrated castor, tung, oiticica, linseed or perilla oil.  The alkyd is made by heating the components at below 200 DEG  C. and there may be added during or after the polyesterification a solvent, e.g. benzene, toluene, xylene, decane, naphtha, cyclohexane, butyl acetate, methyl isobutyl ketone or butyl ether.  Paints are made by mixing the alkyd with a solvent, a pigment (e.g. a metal oxide, hydroxide, chromate, silicate, sulphide, sulphate or carbonate; carbon black, an organic dyestuff or its lake or metal flakes) and, if desired, an inhibitor, dispersing agent or flow control agent.  In examples, alkyds are made from (a) chlorendic acid together with phthalic and/or adipic acid, (b) glycerol or a mixture thereof with ethylene glycol or pentaerythritol and (c) tall oil and/or dehydrated castor oil.  Paints are made comprising (1) the alkyd resin, mineral spirits, toluene, high-boiling naphtha, calcium carbonate, zinc chromate, carbon black, phenyl-alphanaphthylamine and copper naphthenate; (2) the alkyd resin, xylene, mineral spirits, petroleum naphtha, barytes, iron oxide, calcium silicate, cresol, soya lecithin and lithographing oil.  The alkyd resin undercoat is applied to a metal surface and an overcoat then applied based on a polymethyl methacrylate lacquer or a nitrocellulose lacquer (see Group III).  The overcoat may comprise polymethyl methacrylate, benzyl butyl phthalate, fatty amine treated montmorillonite clay, titanium dioxide, phthalocyanine blue, toluene and xylene. Specifications 763,158 and 807,895 are referred to.