Patent GB-1450961-A (GB)
Title: Containers
IPC: B65D25/34
Filed: 1973-10-30
Abstract: 1450961 Coated containers AMERICAN CAN CO 30 Oct 1973 [7 Nov 1972] 50426/73 Heading B2E [Also in Division B8] A can body is fabricated by bending into tubular form a metal blank 11, which is provided on that side forming the exterior body face with a heat-cured pigmented epoxy resin decorative coating 13, and bonding the overlapped blank side edges with a linear super polyamide adhesive 18 having an inherent viscosity of 0.4, said coating extending into the seam and constituting an interface between the adhesive and metal blank surface. The coating comprises as a non-volatile vehicle an epoxide having, before curing, an epoxide equivalent of from 425 to 6000 and an average molecular weight of from 1000 to 4000 and coreactive components to form a cured epoxy resin, and a pigment. The coating comprises 40-65 parts by weight of pigment to 60-35 parts by weight of non-volatile vehicle. The pigment may be titanium dioxide, colloidal silica, zinc oxide, or aluminium paste or powder. The epoxy resin may be an epoxy-phenolic, epoxyester or an epoxy-amino resin. Suitable epoxyester resins may be derived by reacting an epoxy ether with a saturated or unsaturated fatty acid derived from linseed oil, soya, caster oil, tall oil or simple fatty acids or mixtures thereof. Suitable epoxy-amino resins may be derived by the reaction of an epoxy ether, e.g. diglycidyl ether of bis-phenol A, with aminocontaining resins such as melamine, triazine, or urea formaldehyde. Suitable epoxy-phenolic resins include the reaction products of polyhydricphenols (e.g. allyl ether of polymethylol phenol, polymethylol tertiary butyl phenol, or polymethol p-phenylphenol) with epichlorohydrin. The epoxy-ester, epoxy-amino or epoxy-phenolic resins may be modified through further reaction with melamine, urea formaldehyde resins or combinations thereof. Solvents for the non-volatile vehicle and pigment may comprise alcohols, ketones, ethes or esters and mixtures thereof (with or without blending aryl or aralkyl hydrocarbons). The metal sheet blank is coated with the resin composition and bakedat a temperature of at least 300‹F to drive off the volatile component. The thus coated sheet may then be printed as desired and varnished. The other side of the blank forming the interior can face is coated with a pigmented or non-pigmented epoxy base coating 19, which may be as described above or formed by an epoxy-urea formaldehyde coating. The internal coating preferably, includes a different colouring pigment, such as gold tartrazine lake pigment, to that in the external coating. The coated blank has a linear superpolyamide adhesive applied to the inner coating 19 along a marginal side edge, and is then lapped around a mandrel, the adhesive heated, and the overlapped blank side edges pressed together between chilled supports to form a bonded seam. Suitable examples of super polyamides are polypentamethylene sebacamide, polyhexamethylene adipamide, polyhexamethylene sebacamide, poly-m-phenylene sebacamide, 6-amino-caproic acid polymers, 7-amino-heptanoic acid polymers, 11-amino undecanoic acid polymers, and 12-amino-stearic acid polymers and polyamides derived from the reaction of polymeric fat acids with organic diamines, triamines, or titramines. The blank may be of aluminium or of low carbon steel with or without an external plating of aluminium, chromium, cobalt, nickel, or tin.