Polyether based polyurethane coating compositions

A coating composition comprises a mixture of, or the reaction product of an organic polyisocyanate and a polyhydroxy polyether containing at least two terminal hydroxyl groups in which linking between such hydrocarbon radicals as are present in the polyether is solely provided by molecular groupings of the formula in which the aromatic ring may be further substituted by up to 4 additional -CH2O- groups attached to different ring carbon atoms or by other substituents and/or may be part of a condensed ring system. Suitable polyethers can be prepared by the condensation of 1,3- or 1,4-xylylene glycol or 1,4-dimethanol naphthalene, or by reacting 1,3- or 1,4-xylylene chloride, 1,4-dichloromethyl naphthalene or p,p1-dichloromethyl diphenyl ether with polyalcohols in the presence of a caustic potash solution, or by the processes of Specifications 877,913 and 889,633. Suitable di- and tri-isocyanates are listed. Also mentioned are their polymerization products, and reaction products of polyisocyanates with polyhydric alcohols or phenols, malonic esters or imines. The molar ratio of NCO/OH may be between about 1:0,5 and about 1:2. Suitable solvents are aromatic hydrocarbons, ethyl or butyl acetate, acetone, cyclohexanone and glycol monomethyl ether acetate. The polyethers may also be modified by reaction with epoxides such as phenyl glycidyl ether, 1,4-butylene glycol diglycidyl ether and the reaction product of 2 mols. of 1,4-butylene glycol diglycidyl ether with 1 mol. of 4,41-dihydroxy diphenyl methane. To the lacquer solution may be added an accelerator or retarder a tertiary amine, mineral acid, carboxylic acid, sulphonic acid, acid chloride or organic metallic compounds, and also a dye, pigment, filler or flow agent. In examples coating compositions are prepared of a reaction product of 1 mol. of trimethylolpropane and 3 mols. of toluene diisocyanate and (1) a polyhydroxyl compound obtained by condensing 2,4-dimethyl-1,5-xylylene glycol dimethyl ether and trimethylol-propane, ethyl acetate and a flow agent comprising a 10% polyvinyl ether solution in ethyl, butyl and methyl glycol acetates and toluene; (2) and (3) as polyhydroxy compound the condensation product of trimethylol propane with the product obtained by decomposing a xyleneformaldehyde resin with methanol at 150 DEG C. is used; (4) the polyhydroxy compound of (2) is modified by reaction with a diepoxide from 2 mols. of 1,4-butylene glycol diglycidyl ether and 1 mol. of 4,41-