GB939212A - Thermosetting surface-coating compositions - Google Patents

Abstract

Coating compositions which may be applied to substrates by brushing, spraying, dipping or roller coating, followed by drying and curing by baking, if desired with the addition of an acidic catalyst, comprise organic solvent solutions of a compatible mixture of at least one thermosetting alkylated aminoplast resin, a polyepoxide, and a thermoplastic copolymer of one or more hydroxyalkyl esters of monoethylenically a ,b -unsaturated carboxylic acids, which esters may contain in the hydroxy alkyl moiety thereof, in addition to the hydroxyl group, a second hydroxyl group, a halogen atom or a nitrile group, and one or more copolymerizable monoethylenically unsaturated compounds containing a CH2=C< group, which latter compound or compounds constitute a major proportion by weight of the copolymer (see Group IVa). The compositions may be used for coating metals, wood, ceramics, brick, stone and concrete surfaces, e.g. as finishing topcoats for automobiles or for the decoration of tin cans or other canisters; they are particularly suitable for the finishing of household appliances, such as stoves and refrigerators, because of their resistance to modern detergents. Examples describe the production of glossy coatings on "Bonderized" (Registered Trade Mark) steel panels. Specifications 518,057, 579,698 and 939,211 are referred to.ALSO:A thermosetting coating composition comprises a compatible mixture of at least one thermosetting alkylated aminoplast resin, a polyepoxide, and a thermoplastic copolymer of one or more hydroxyalkyl esters of monoethylenically a ,b -unsaturated carboxylic acids, which esters may contain in the hydroxy alkyl moiety thereof, in addition to the hydroxyl group, a second hydroxyl group, a halogen atom or a nitrile group, and one or more copolymerizable monoethylenically unsaturated compounds containing a CH2=C< group, which latter compound or compounds constitute a major proportion by weight of the copolymer. The alkylated aminoplast may be one obtained by alkylation with an alkanol having 1 to 8 carbon atoms or cyclohexanol, of a condensate of an aldehyde, particularly formaldehyde, with urea, N,N1-ethylene urea, dicyandiamide or an aminotriazine; alkylated aminoplasts used in the examples are butylated or methylated methylol melamine, butylated urea-formaldehyde condensate and butylated benzoguanamine-formaldehyde condensate. The polyepoxides contemplated are those which contain at least two epoxy groups, those used in the examples being condensation products of epichlorhydrin with glycerine, ethylene glycol, 4,41-isopropylidene-bisphenol or a mixture of ethylene glycol and diethylene glycol. The hydroxyalkyl ester may be 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 6-hydroxyhexyl, -8 hydroxyoctyl or 10-hydroxydecyl acrylate or methacrylate, 4-hydroxybutyl acrylate, 5-hydroxyamyl or 7-hydroxyheptyl acrylate or crotonate, 9-hydroxynonyl acrylate, 6-hydroxyhexyl or 10-hydroxydecyl crotonate, di(2-hydroxyethyl), di(4-hydroxybutyl), di(6-hydroxyhexyl) or di(10-hydroxydecyl) maleate or fumarate, di(9-hydroxynonyl) maleate, 2,3-dihydroxypropyl acrylate, 3,5-dihydroxyamyl crotonate, 6,10-dihydroxydecyl methacrylate, di-2,6-dihydroxyhexyl maleate or di-2-chloro-7-hydroxyheptyl fumarate. The other monoethylenically unsaturated compounds which may be used include esters of acrylic or methacrylic acid with cyclohexanol, benzyl alcohol or alkanols having 1 to 18 carbon atoms, acrylonitrile, methacrylonitrile, styrene, vinyl toluene, or a -methyl styrene. The copolymer preferably also contains from 1 to 4% of a monoethylenically, a ,b -unsaturated carboxylic acid such as acrylic, methacrylic, itaconic, maleic, fumaric, aconitic, citraconic or crotonic acid. The copolymers are preferably prepared by solution polymerization in a solvent such as xylene in the presence of an initiator such as an azo catalyst, t-butyl peracetate, benzoyl peroxide, t-butyl hydroperoxide or cumene hydroperoxide. The coating composition may be prepared by dissolving the copolymer, the aminoplast and the polyepoxide in a solvent such as those specified in Specification 939,211, and pigments referred to in that specification may also be added. Specifications 518,057 and 579,698 also are referred to.