Coating compsn. for forming metal-pigmented base coat - for clear top coat in wet-on-wet process contains polyurethane or polyurea elastomer, polyester, and etherified aminoplast polycondensate

摘要

Compsn. (I) contains metal pigments, organic solvent, conventional additives and auxiliaries, opt. other pigments, and binder (II) comprising (A) 20-60 % (all pts.wt.) one or more specified polyurethane and/or polyurea elastomers (B) 10-50% one or more specified polyesters (C) 5-25% polycondensate, partially etherified with monoalcohol, of melamine, benzoguanimine, and/or urea with HCHO, where in melamine-HCHO resins molar ratio M:F is 1:4.5-6 and in benzoguanamine or urea-HCHO resins molar ratio benzoguanamine or U:F is 1:2.5-4, (A)+(B)+(C) totalling 100%. Component (A) is prepd. from (A1) linear cpds. with terminal OH and/or prim. and/or sec. amino gps. (A2) aliphatic and/or cycloaliphatic di-isocyanates where mol.ratio (A1):(A2) = 0.8-1.5:1, while component (B) is prepd. from (B1) aromatic and aliphatic and/or cycloaliphatic polycarboxylic acids, 40-70 mol.% being aromatic, 60-30 mol.% being aliphatic and/or cyclo-aliphatic, and 0-5- mol.% total polycarboxylic acids being tricarboxylic (B2) polyols, where 20-60 mol.% polyols have 2 or 3 C and 40-80 mol.% have 4 or more C, at least 40 mol.% diols used have aliphatic side chains, 0-50 mol.% polyols are triols, and ratio (B1)/(B2) = n1-n2(F-2)/n2 = 1.05-1.5 n1 = no. mols. polyols n2 = no. mols. polycarboxylic acids F = mol. average of functionality of polycarboxylic acids. Prepn. of coatings, in which topcoat contg. metal pigment and (II) as binder is applied to form base layer followed by, after exposure to air, application in wet-on-wet process of a second coating compsn. (III) forming transparent top coat. Substrate coated with multilayer coating consisting of metal pigment-contg. base layer prepd. using a (II) and at least one transparent top layer. USE/ADVANTAGE - Prepn. of base layer in multilayer paint coating consisting of at least one base layer and at least one transparent top layer, e.g., for motor vehicle chassis. Base layers are readily printed over, even with high solids 1- or 2-component (III), show good compatibility, elasticity, and adhesion with less redissolving in wet-on-wet processes, and have good metallic effect and resistance to impact by ststs