| 摘要 |
The invention concerns a basecoat/clearcoat in which the basecoat composition used contains a polyurethane resin as a film-forming material. The polyurethane resin is made by first preparing an intermediate product from (A) a mixture of 10-90 mol% of linear polyetherdiols and 90-10 mol% of polyesterdiols, (B) diisocyanates, (C) compounds containing two groups which react with isocyanate groups, at least some of these compounds having a group capable of forming an anion. The free isocyanate groups of this intermediate product are subsequently reacted with (D) polyols containing at least three hydroxyl groups, and the reaction product thus obtained is then converted into an aqueous phase. Whereby a) the polyesterdiol is made from diols and an acid component consisting of 60-100 % by weight of aliphatic dicarbonic acids with not more than 18 C-atoms and of 40-0 % by weight of aliphatic dicarbonic acids with 2 to 18 C-atoms, b) the ratio by equivalents of the NCO-groups to the sum of the OH-groups in (A) and the reactive groups in (C) is 2:a to 1.05:1, c) the ratio by equivalents of the OH-groups in component (D) to the NCO-groups in the intermediate product is 0.5:1 to 4:1. |
