Patent GB-865304-A (GB)
Title: Process for coating metals and compositions useful therein
IPC: C09D133/10
Filed: 1959-04-02
Abstract: A coating composition for protecting metals comprises a film forming aqueous dispersion of (1) an aqueous latex of an acrylic polymer consisting essentially of at least 50% of an alkyl methacrylate having from 1 to 12 carbon atoms in the alkyl group and a complementary amount of at least one other copolymerizable monomer selected from alkyl methacrylates, alkyl acrylates, vinyl esters, acrylonitrile, styrene and vinylidene chloride, said acrylic polymer when in the form of said latex without modification not being film-forming at temperatures below 40 DEG C. and (2) uniformly distributed throughout said latex from 5 to 50% of a plasticizer, the plasticizer concentration being sufficient to import film formability to said latex at the aforesaid temperatures.  The alkyl methacrylate may be the methyl, ethyl, butyl, hexyl, 2-ethyl-hexyl, decyl, or dodecyl ester.  The comonomer may be butyl, ethyl or 2-ethylhexyl acrylate and ternary or quaternary polymers may be used.  The polymer may contain a small proportion of acrylic or methacrylic acid.  The copolymers may be prepared using a copolymerizable compound as the principal emulsifier, e.g. compounds of the-type:- <FORM:0865304/IV (a)/1> where R is hydrogen, halogen or an orgnaic radical, Q is a bivalent organic radical and M is hydrogen, ammonium or a metal. Other copolymerizable emulsifiers may be vinylbenzene sulphonate, acryloyl taurine and methacryloyl taurine.  The plasticizer may be 2-(2-butoxyethoxy) ethyl acetate, 1-phenoxy-2-propanol, hexylene glycol, high boiling aromatic fractions, n-butyl benzyl phthalate, butyl phthalyl butyl glycolate, triethylene glycol di-2-ethyl butyrate or bis (dimethylbenzyl) citrate.  The composition may contain pigments and usual stabilizers and additives such as titanium dioxide, water soluble methyl cellulose, sodium salts of high polymeric carboxylic acids, antifoaming agents and emulsifying agents.  The compositions may be applied to articles made from any of the common structural metals which may be primed or the coating composition may be used as the primer coating.ALSO:Metals are coated with a polymer coating by applying a film of an aqueous dispersion of an acrylic polymer consisting essentially of at least 50% of an alkyl methacrylate and a complementary amount of at least one other comonomer, said polymer latex without modification not being film forming at temperatures below 40 DEG C., together with 5 to 50% of a plasticizer, the plasticizer concentration being sufficient to impart film formability to said latex below 40 DEG C., and then drying and fusing said coating into a continuous film.  The alkyl methacrylate may be the methyl, ethyl, butyl or other alkyl ester up to the dodecyl ester.  The comonomer is selected from alkyl methacrylates, alkyl acrylates, vinyl esters, acrylonitrile, styrene and vinylidene chloride.  The plasticizer may be 2-(2-butoxyethoxy) ethyl acetate, 1-phenoxy-2-propanol, hexylene glycol, high boiling aromatic fractions, n-butyl benzyl phthalate, butyl phthalyl butyl glycolate, triethylene glycol di-2-ethyl butyrate or bis (dimethylbenzyl) citrate.  The composition may also contain pigments and usual stabilizers and additives such as titanium dioxide, water soluble methyl cellulose, antifoaming agents and emulsifying agents. Articles made from any of the common structural metals may be coated with the above compositions such as those made from aluminium, magnesium alloy, tin plate or ferrous metals and alloys, e.g. the various irons and steels, and may be car bodies, farm machinery, outdoor signs, metal furniture or household appliances.  The article to be coated preferably has a surface which has been primed, e.g. with an epoxy or conjugated diolefine primer, or phosphatised although the above composition may also be used as the primer coating.  The compositions may be applied by conventional methods such as roller coating, brushing, spraying and dipcoating with the viscosity adjusted accordingly. Examples are given.