GB1086999A - Improvements in or relating to a paint composition for rubber - Google Patents

Abstract

A coating composition for rubber comprises a polyester derived from (a) at least one aliphatic dicarboxylic acid and at least one aromatic dicarboxylic acid amounting to 5-30 mol. per cent of the total acid, and (b) a mixture of di-and/or tri-functional alcohols of which 10-80 mol. per cent is a di- or tri-functional alcohol containing a b ,g -alkenyloxy group or an equivalent glycidyl compound, the overall ratio of OH:COOH being 1-1.17:1, or a polyurethane derived from said polyester when component (b) is used in excess by reaction with a diisocyanate equivalent to the excess OH groups, together with sulphur, a vulcanization accelerator, a pigment and a diluent solvent. Suitable components for the polyester are (a) adipic, succinic and sebacic acids; phthalic anhydride, isophthalic and terephthalic acids; carboxyl-ended polyesters and polylactones, and (b) ethylene glycol, di- and tri-ethylene glycols, propylene glycol, trimethylolethane, trimethylolpropane, hexane triol and glycerol or unsaturated fatty acid monoglycerides, hydroxy -terminated polyesters, polyethers or polylacton diols, and hydroxy-terminated diisocyanate prepolymers of these; a - and b -allyloxypropane diol, trimethylolpropane monoallyl ether and allyl glycidyl ether. Suitable diisocyanates include toluene diisocyanate, diphenylmethane diisocyanate and NCO-terminated prepolymer of these with hydroxy-polymers, e.g. e -caprolactone polyester of M.W. 600-1200 or a polyether glycol of M.W. 400-1200, using 1.5-2 moles diisocyanate per mole of polymer. The sulphur may amount to 2-15 wt. per cent of the polymer vehicle, and the preferred accelerator is mercaptobenzthiazole. In Examples diethylene glycol and a -allyloxypropane diol or trimethylolpropane monoallyl ether or allyl glycidyl ether and, optionally, dehydrated castor oil monoglyceride are heated with adipic acid and phthalic anhydride or isophthalic acid to give polyesters. In Example 4, the diethylene glycol is pre-reacted with some diphenylmethane diisocyanate. In Examples 1, 3, 5 and 6, the polyester is further reacted with toluene diisocyanate, diphenylmethane diisocyanate or prepolymer from 2 mols. of the latter with 1 mol. of poly-e -caprolactone. Coating compositions contain solutions of these polymers in ethyl acetate or ethoxyethyl acetate mixed with ethyl and/or butyl acetate and/or butoxyethanol and sulphur, mercaptobenzthiazole, stearic acid, zinc white, rutile or anatase TiO2 or carbon black and, optionally, dehydrated silicic acid or zinc diethyl dithiocarbamate.ALSO:A coating composition for rubber comprises a polyester derived from (a) at least one aliphatic dicarboxylic acid and at least one aromatic dicarboxylic acid, the latter amounting to 5-30 mol % of the total acid, and (b) a mixture of diols and/or triols of which 10-80 mol % is a diol or triol (or equivalent glycidyl compound) containing a b :g -alkenyloxy group, the overal ratio of OH:COOH being 1.0-1.7:1, or a polyurethane derived from a polyisocyanate and said polyester when excess OH is present, together with sulphur (e.g. 2-15 wt % of the polymer), a vulcanization accelerator (e.g. mercaptobenzthiazole) a pigment and a diluent solvent. (see Division C3). In Examples polyesters are derived from diethylene glycol, a -allyloxypropane diol or trimethylolpropane monoallyl ether or glycidyl allyl ether, and, optionally, dehydrated castor oil monoglyceride, with adipic acid and phthalic anhydride or isophthalic acid. These may further be reacted with toluene diisocyanate, diphenylmethane diisocyanate or prepolymers thereof. The product polyesters and polyurethanes are dissolved in ether alcohols and acetates and mixed with sulphur, mercaptobenzthiazole, stearic acid, zinc white, rutile or anatase TiO2 or C black and, optionally, dehydrated silicic acid or zinc diethyl dithiocarbamate. The coating compositions are coated onto vulcanized rubber and cured.