Coating medium, the use thereof, and a process for multilayer coating

A styrene-free coating medium, comprising;

• A) one or more copolymers containing hydroxyl groups, comprising;
• a1) 8-12% by weight of one or more vinyl esters of alpha,alpha,dialkyl-substituted, branched, aliphatic saturated monocarboxylic acids,
• a2) 32-42% by weight of one or more hydroxyalkyl esters of (meth) acrylic acid,
• a3) 25-40% by weight of one or more alkyl esters of (meth)acrylic acid,
• a4) 12-24% by weight of one or more unsubstituted or substituted cycloalkyl esters of (meth)acrylic acid, and
• a5) 2-4% by weight of (meth)acrylic acid,
• with a hydroxyl number of 100-160 mg KOH/g, an acid number of 10-50 mg KOH/g, a number average molecular weight (Mn) of 1000 to 3000 g/mole and a glass transition temperature (Tg) of 30.degree.-80.degree. C.,
• B) one or more polyisocyanates in a quantitative proportion such that 0.5 to 2 isocyanate groups are allotted to one hydroxyl group of component A), and
• C) one or more solvents and optionally one or more members selected from the group consisting of pigments and extenders;
• wherein the styrene-free coating medium has a solids content of 50 to 65%, by weight.