SURFACE-COATING COMPOSITIONS

1,221,289. Surface-coating compositions. REICHHOLD - ALBERT - CHEMIE A.G. 28 April, 1969 [10 May, 1968], No. 21563/69. Headings C3P and C3R. [Also in Division B2] Surface-coating compositions comprise as binder a mixture of (A) 60-94% by weight (based on the binder) of a hydroxyl-containing copolymer produced from a monomer mixture comprising (a) 20-70% by weight of styrene or vinyl toluene, (b) 10-50% by weight of a C 1 - C 4 -monohydric alcohol ester of methacrylic acid, (c) 5-30% by weight of a C 1 -C 4 -hydroxyalkyl acrylate or methacrylate and (d) an aliphatic, heterocyclic or aromatic mono- or poly-mercaptan in an amount such that component (A) contains 0À1-5% by weight of -SH groups; (B) 1-20% by weight of a polyhydroxy compound of the formula in which R 1 and R 3 are each H, CH 3 - or -CH 2 -(O-CH 2 .CHCH 3 ) n -OH, R 2 is -CH 2 -(O-CH 2 .CHCH 3 ) n -OH or and R 4 is a group as defined for R 2 or CH 3 -H 2 -, with the proviso that R 4 is not CH 3 -CH 2 - when R 1 and R 3 are H or CH 2 -, and n is from 1-30; and (C) 5-30% by weight of an organic polyisocyanate. Preferably, the binder includes an organometallic compound (e.g. dimethyltin dichloride, dibutyltin dilaurate, or tin or zinc octoate) and/or a tertiary amine (e.g. triethylamine, triethylenediamine or N-methylmorpholine). Component A is preferably derived additionally from up to 30% by weight of a C 1 -C 8 monohydric alcohol ester of acrylic acid. The mercaptan constituent of component A may be an alkyl mercaptan, a polymethylenedimercaptan, methyl or ethyl mercaptoacetate, α - mercaptopropionic acid, 2 - mercaptothiazoline, 2 - mercapto - benzimidazole or 2,5 - dimercapto - 1,3,4 - thiadiazole. Preferred as component B are reaction products of glycerine or trimethylol-propane with propylene oxide (n being from 10-30). The polyisocyanate C may be an aliphatic, cycloaliphatic or aromatic di- or tri-isocyanate, a reaction product of a polyhydric alcohol (e.g. trimethylolpropane) with a polyisocyanate (e.g. toluylene-diisocyanate), a trimerized or polymerized isocyanate, or, preferably, a reaction product of water (1 mol.) and hexamethylene-diisocyanate (3 mols.). Component A is prepared by polymerizing the appropriate monomers and mercaptan in an organic solvent in the presence of a catalyst, e.g. benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, di-t-butyl peroxide or azoisobutyric acid dinitrile; the solvent-containing product obtained can then be combined with components B and C to