GB612605A - Improvements in or relating to coating compositions containing thermoplastic resins - Google Patents

Abstract

Coating compositions which on application to metal surfaces stratify into two layers each comprising a layer of one resinous constituent of the composition and the resin having more intense polarity being concentrated at the metal interface, comprise a solution in a volatile solvent of (a) a vinyl alcohol halide, or ester, or a lower aliphatic ester or nitrile or amide of acrylic or methacrylic acid polymer or copolymer, and (b) a non-oil modified, alkaline condensed, bifunctional, lower alkyl or lower aryl-substituted phenol-aldehyde resinoid of greater molecular polarity than (a) but compatible in solution therewith. The phenolic resinoids in question are alkaline condensed alkyl- or aryl-substituted phenols having only two reactive positions available in the benzene ring, e.g. o- and p-cresol, p-phenyl phenol, xylenols other than symmetrical xylenols. Molar ratios of aldehyde/phenolic compound should lie within 1.1/1 and 1.6/1 and in preparation heating times under reflux should be 3-7 hours and steam distillation for 30-120 mins. Proportion of (b) in the mixture may range from 1-40 per cent, but 20 per cent is preferred. A general formula for the monomers used in (a) is CH2=CRX and a list is given of radicals suitable for R and X. Preparation of the phenolic resinoids.-(1) 2 moles. o-cresol and 2.4 moles. formaldehyde are reacted in presence of 18 gs. 28 per cent ammonia and at 200-205 DEG F. The mixture is refluxed for 6 hours, and the upper aqueous layer separated, the resinous layer being steam distilled until clear and allowed to solidify or dissolved in acetone, methyl isobutyl ketone, isophorone, cyclohexanone or other ketone. Examples (2) to (7) describe the production of similar resins from amyl phenol, 1 : 4 : 3-xylenol-p-cresol mixture, o-cresol and a 210-215 DEG C. xylenol cut, p-phenyl phenol, and p-(o-sec. butyl phenyl) phenol. Preparation of the mixture.-A solution in xylol and methyl n-amyl ketone of a vinyl chloride (87 per cent) -vinyl acetate (13 per cent) copolymer is added with stirring to the resinoid of example (1) dissolved in xylol and methyl n-amyl ketone and the solution thinned to spraying consistency is sprayed on to tin plate and baked. Similar solutions are made up from vinyl chloride (75 per cent) methyl acrylate (25 per cent) copolymer and the resinoid of example (4); vinyl chloride (80 per cent) methyl methacrylate (5 per cent) copolymer and the resinoid of example (2).