Process for preparing a coating with improved resistance to yellowing and the resulting coating.

摘要

The present invention relates to process for preparing a coated substrate having improved resistance to yellowing which comprises coating a substrate with a one-component coating composition containing a) a blocked polyisocyanate which is the reaction product of a polyisocyanate with an oxime or lactam blocking agent for isocyanate groups and b) a compound containing at least two isocyanate-reactive groups, provided that component a) and/or component b) contains the group, -CO-(R)N-N(R)-CO-, wherein R represents hydrogen or an optionally substituted hydrocarbon radical, in an amount of 0.01 to 5% by weight, based on the solids content of components a) and b), by applying the one-component coating composition wet-on-wet to a coating composition containing acid groups and/or melamine resins which has previously been applied to the substrate or by adding a melamine resin to the one-component coating composition prior to applying it to the substrate, which may optionally have been precoated. The present invention also relates to the coated substrate having improved resistance to yellowing prepared by this process.