Überzugsmittel für transparente Decklackschichten und deren Verwendung bei Verfahren zur Herstellung von Mehrschichtüberzügen

摘要

The invention concerns coating agents based on (meth) acrylate copolymers with hydroxyl groups and blocked urethane prepolymers with carboxyl groups, as well as crosslinking agents and the usual additives and solvents for paints, the coating agents being particularly suitable for the production of a transparent finishing coat in a multi-coat coating. The coating agents proposed contain binders made from: A) 5.0 to 40.0 % by wt. of urethane prepolymers with carboxyl groups and having an OH-number from 0 to 80, an acid number from 5 to 50 and a molecular weight from 500 to 5,000, the prepolymers being obtained by reacting together: a1) 10 to 50 mol % of alkane diols or cycloalkane diols, a2) 10 to 30 mol % of polycarboxylic acids or anhydrides, a3) 0 to 30 mol % of polyols with at least three OH-groups, a4) 0 to 20 mol % of hydroxycarboxylic acids with at least one hydroxyl group and at least one carboxyl group, a5) 10 to 40 mol % of aliphatic, cycloaliphatic and/or arylaliphatic di- and/or polyisocyanates and a6) 10 to 40 mol % of monofunctional NCO-blocking agents, B) 30.0 to 70.0 % by wt. of hydroxy-group-containing (meth) acrylate copolymers with a molecular weight from 2,000 to 20,000, an acid number from 1 to 50 and an OH-number from 30 to 200, C) 0 to 50.0 % by wt. of polyesters which hydroxyl groups and having an OH-number from 40 to 200 and D) 5.0 to 40.0 % by wt. of additional crosslinking agents.