Patent GB-906565-A (GB)
Title: Vinyl chloride-vinylidene chloride copolymer coatings
IPC: C08L27/06
Filed: 1959-01-14
Abstract: A solution suitable for producing baked coatings on metals comprises an organic solvent having dissolved therein a mixture of a major proportion of a vinyl chloride/vinylidene chloride copolymer and a minor proportion of a partially saponified vinyl chloride/vinyl fatty acid ester copolymer.  Solvents specified are benzene, toluene, xylene, ethyl or isopropyl benzene, mixed commercial aromatic hydrocarbon solvents, methyl ethyl or isobutyl ketone, cyclohexanone, isophorone, ethyl acetate and butyl propionate.  Up to 2 wt. per cent of an alcohol may be included to assist filtration.  Thermal stability of the vinyl-vinylidene chloride copolymer may be improved by including in the solution 1 to 8 wt. per cent based on the resins of a soluble etherified polyamine resin, e.g. those obtained by etherifying with a C3 to C8 primary saturated monohydric alcohol the condensation product of urea, melamine or benzoguanamine and a molar excess of formaldehyde.  Similarly 1 to 5 wt. per cent of a polyepoxide may also be added, several suitable classes of polyepoxides being described.  The solutions are used to form baked coatings on metal sheet, e.g. blackplate or electrotinplate, which coating may be a top coat over a prime coat.  Several suitable prime coating compositions are described the main categories being (i) oil soluble non heat hardening, resinous varnish heat bodied with an unsaturated drying oil; (ii) resins which have been heat reacted with an ethylenically unsaturated anhydride and a polyhydric aliphatic alcohol and then heat bodied with an unsaturated drying oil; (iii) epoxy resin modified condensation products of aldehydes with urea or phenol; and (iv) a copolymer of ethyl acrylate, methyl acrylate and glacial methacrylic acids.  The coated sheets may be shaped into tins.ALSO:A solution suitable for producing baked coatings on metals comprises an organic solvent having dissolved therein a mixture of a major proportion of a vinyl chloride/vinylidene chloride copolymer and a minor proportion of a partially saponified vinyl chloride/vinyl fatty acid ester copolymer the former containing 30 to 75 weight per cent vinyl chloride, being completely soluble in xylene at 25 weight per cent solids, and having a specific viscosity of 0,12 to 3,0 at 25 DEG  C. as a 0,4 weight per cent solution in nitro-benzene while the latter contains 80 to 92 weight per cent vinyl chloride and 2 to 10 weight per cent vinyl alcohol and has an average degree of unsaturation determined by a corrected iodine number between 2 and 10.  The unsaturation is achieved by alkali saponification, preferably in an anhydrous alcoholic medium, e.g. methanol containing an alkali metal hydroxide or alcoholate or a quaternary ammonium hydroxide. Solvents specified are benzene, toluene, xylene, ethyl or isopropyl benzene, mixed commercial aromatic hydrocarbon solvents, methyl ethyl or isobutyl ketone, cyclohexanone, isophorone, ethyl acetate and butyl propionate.  Up to 2 weight per cent of an alcohol may be included to assist filtration.  Thermal stability of the vinyl/vinylidene chloride copolymer may be improved by including in the solution 1 to 8 weight per cent based on the resins of a soluble etherified polyamine resin, e.g. those obtained by etherifying with a C3 to C8 primary saturated monohydric alcohol the condensation product of urea, melamine or benzoguanamine and a molar excess of formaldehyde. Similarly 1 to 5 weight per cent of a polyepoxide may also be added, several suitable classes of polyepoxides being described. The example describes the saponification of an 87/13 vinyl chloride/vinyl acetate copolymer and describes compositions containing the product and, for contrast, an acid-hydrolysed copolymer.  The properties of the compositions of the invention with or without the optional polyamine and polyepoxide resins are also described.  Baked coatings  The solutions are used to form baked coatings on metal sheet, e.g. blackplate or electrotinplate, which coating may be a top coat over a prime coat.  Several suitable prime coating compositions are described the main categories being (i) oil soluble non heat hardening, resinous varnish heat bodied with an unsaturated drying oil; (ii) resins which have been heat reacted with an ethylenically unsaturated anhydride and a polyhydric aliphatic alcohol and then heat bodied with an unsaturated drying oil; (iii) epoxy resin modified condensation products of aldehydes with urea or phenol; and (iv) a copolymer of ethyl acrylate, methyl acrylate p and glacial methacrylic acids.  The coated sheets may be shaped into tins.