GB1115453A - Internally coated metal container - Google Patents

Abstract

A substantially mercaptan-free composition comprises an interpolymer of 2 to 20% by weight of an ethylenically unsaturated carboxylic acid amide and 50 to 98% by weight of a vinyl aromatic monomer and/or an alkyl ester of an ethylenically unsaturated carboxylic acid, the interpolymer having at least some of the hydrogen atoms attached to the amido groups from the amide replaced by the structure R.CH.OR1 where R is hydrogen or a hydrocarbon radical, and R1 is a radical derived by removing the hydroxyl group from a monohydric alcohol. An ethylenically unsaturated nitrile, an ethylenically unsaturated carboxylic acid, an epoxy resin may also be included in the interpolymer. The interpolymer may be produced from a mercaptan-free reaction mixture containing a catalytic amount of alpha, alpha-azobis (isobutyronitrile). The included polyepoxide should have an epoxide equivalent of 100 to 1000 and may be polyglycidyl ether of a polyhydric compound, e.g. the condensation product of bisphenol A and epichlorohydrin, or epoxylated novolacs. Other polyhydric compounds which may be used to produce the polyepoxide are bis-4-hydroxy-phenyl-2,2-butane and pentaerythritol, and other oxirano compounds such as 1-chloro-2,3-epoxy butane may be used. The coating compositions used in the examples include colorants such as those certified for beverage liners by the Food and Drug Administration. Compositions disclosed comprise (a) 575 parts of an interpolymer of acrylamide, methacrylic acid, styrene, ethyl acrylate, 34 parts of a Bisphenol A-epichlorohydrin condensation product having an epoxide equivalent of 450 to 525, 48 parts toluene; (b) 222.5 parts of the interpolymer of (a), 2 parts of a thermoplastic hydrocarbon resin based on cyclo-pentadiene, 12 parts toluene, (c) 575 parts of an interpolymer of acrylamide, methacrylic acid, styrene, 34 parts of the polyepoxide of (a), 48 parts toluene; in the interpolymers used, the amide groups were reacted with formaldehyde and butanol. The interpolymers were prepared by polymerizing the corresponding monomers in a mixture of butanol and aromatic hydrocarbons using azobis-isobutyronitrile as catalyst.ALSO:A metal container suitable for packaging beverages or food has its internal surface coated with a single cured layer of a substantially mercaptan-free composition comprising an interpolymer of 2 to 20 per cent by weight of an ethylenically unsaturated carboxylic acid amide and 50 to 98 per cent by weight of a vinyl aromatic monomer and/or an alkyl ester of an ethylenically unsaturated carboxylic acid, the interpolymer having at least some of the hydrogen atoms attached to the amido groups from the amide replaced by the structure: R.CH.OR1 where R is hydrogen or a hydrocarbon radical, and R1 is a radical derived by removing the hydroxyl group from a monohydric alcohol. An ethylenically unsaturated nitrile, an ethylenically unsaturated carboxylic acid, an epoxy resin may also be included in the interpolymer. The amide may be acrylamide, methacrylamide, itaconic acid diamine, alpha-ethyl acrylamide, crotonamide, fumaric acid diamide, maleic acid diamide and other amides of alpha, beta-ethylenically unsaturated carboxcylic acids containing up to 10 carbon atoms, maleuric acid and esters, and imide derivatives such as N - carbamyl maleimide. The alkyl esters of an ethylenically unsaturated carboxylic acid may be esters of "acrylic acid", maleic and fumaric acid, and examples of various esters are given. By "acrylic acid" is meant acrylic acid, methacrylic and similar alpha-substituted acrylic acids. The vinyl aromatic monomer may be styrene, vinyl toluene, mono- and di-substituted chlorostyrenes, alpha-methyl styrene. The included ethylenically unsaturated carboxylic acids may be acrylic, methacrylic, maleic, crotonic and ethacrylic acid and monoesters of dicarboxylic acids. The included ethylenically unsaturated nitrile may be acrylonitile, methacrylonitrile, ethacrylonitrile. Methods of making the interpolymers are described. The interpolymer may be produced from a mercapton-free reaction mixture containing a catalytic amount of alpha, alpha-azobis (iso butyronitrile). The included polyepoxide should have an epoxide equivalent of 100 to 1000 and may be a polyglycidyl ether of a polyhydric compound, e.g. the condensation product of bisphenol A and epichlorohydrin, or epoxylated novolacs. Other polyhydric compounds which may be used to produce the polyepoxide are bis - 4 - hydroxy - phenyl - 2,2 - butane and pentacrythritol, and other oxirano compounds such as 1 - chloro - 2,3 - epoxy butane may be used. The metal may be steel, aluminium, tin plate. The compositions may be applied by spraying, roll coating, brushing, or dipping. In spray application, two spray coatings may be applied, either wet on wet or with a short drying interval. After application the coatings are cured by heating. The coating compositions used in the Examples include one containing a colourant comprising a hydrocarbon resin based on cyclopentadiene. Other colourants such as those certified for beverage liners by the Food and Drug Administration may be used. Compositions disclosed comprise (a) 575 parts of an interpolymer of acrylamide, methacrylic acid, styrene, ethyl acrylate, 34 parts of a Bisphenol A-epichlorohydrin condensation product having an epoxide equivalent of 450 to 525, 48 parts toluene; (b) 222.5 parts of the interpolymer of (a), 2 parts of a thermoplastic hydrocarbon resin based on cyclo-penadiene, 12 parts toluene, (c) 575 parts of an interpolymer of acrylamide, methacrylic acid, styrene, 34 parts of the polyepoxide of (a), 48 parts toluene.