Patent GB-975328-A (GB)
Title: Can coating compositions
IPC: C09D167/08
Filed: 1961-02-07
Abstract: A coating composition suitable for coating the interior of tins comprises a solvent having dissolved therein at least 18% of two copolymers A and B in a weight ratio between 98.2 and 75.25 together with 2 to 10% (by weight of A+B) of an esterified aminoplast resin C. The solvent must comprise at least 75% of a liquid mononuclear aromatic hydrocarbon; copolymer A is a copolymer of 55 to 75% vinyl chloride with a C6- 24 diester of maleic, fumaric and/or chloromaleic acid which is completely soluble at 25% solids in toluene and has a relative viscosity of 1.3 to 1.7 as a 1% solution in cyclohexanone at 20 DEG C.; B is a copolymer of 60 to 92% vinylchloride with a vinyl fatty acid ester saponified to 2 to 10% vinyl alcohol content; and resin C is soluble in the solvent and is obtained by etherifying a condensate of urea, melamine or benzoguanamine and excess formaldehyde with a C3- 8 primary saturated monohydric alcohol. The solvent may contain up to 25% of a polar solvent e.g. ketones, esters, cyclic oxygen compounds, ether alcohols and their esters, nitrocompounds, amides and nitriles.  To obtain copolymers A having the specified properties (indicating low molecular weight) copolymerisation may be effected in the presence of 1 to 6.5% of a non-polymerising halohydrocarbon, many examples being given. Copolymers B should have a molecular weight of 5,000 to 20,000 and corrected iodine number 2 to 10. In examples the compositions are coated on primed electrolytic tinplate.  Primers specified are oleoresinous phenol aldehyde varnishes, epoxy resins mixed with a urea-formaldehyde and a phenol-formaldehyde resin, and copolymers of butadiene 1, 2-with styrene. Specification 883,070 is referred to.ALSO:A coating composition suitable for coating metal to be subsequently formed into tins comprises a solvent having dissolved therein at least 18% of two copolymers A and B in a weight ratio between 98,2 and 75,25 together with 2-10% (by weight of A+B) of an esterified aminoplast resin C.  The solvent must comprise at least 75% of a liquid mononuclear aromatic hydrocarbon; copolymer A is a copolymer of 55-75% vinyl chloride with a C6-24 diester of maleic, fumaric and/or chloromaleic acid which is completely soluble at 25% solids in toluene and has a relative viscosity of 1,3-1,7 as a 1% solution in cyclohexanone at 20  DEG C.; B is a copolymer of 60-92% vinyl-chloride with a vinyl fatty acid ester saponified to 2-10% vinyl alcohol content; and resin C is soluble in the solvent and is obtained by etherifying a condensate of urea, melamine or benzoguanamine and excess formaldehyde with a C3-8 primary saturated monohydric alcohol.  The solvent may contain up to 25% of a polar solvent, e.g. ketones, esters, cyclic oxygen compounds, ether alcohols and their esters, nitrocompounds, amides and nitriles. Copolymers B should have a molecular weight of 5000-20,000 and corrected iodine number of 2-10.  In examples the compositions are coated on primed electrolytic tinplate and baked.  Primers specified are oleoresinous phenol aldehyde varnishes, epoxy resins mixed with a ureaformaldehyde and a phenol-formaldehyde resin, and copolymers of butadiene-1,2 with styrene.  Specification 883,070 is referred to.