Aqueous polyisocyanate crosslinking agents modified with hydroxycarboxylic acids and pyrazole-based blocking agents

Abstract From the Canadian patent

The present invention relates to aqueous or water dilutable blocked polyisocyanates containing, a) a polyisocyanate component and based on the equivalents of, isocyanate groups b) 60 to 85 equivalent % of a pyrazole blocking agent c) 15 to 40 equivalent % of a monohydroxycarboxylic acid to impart hydrophilic properties and, d) 0 to 15 equivalent % of a difunctional chain extender containing OH and/or NH2 groups, wherein the amounts of a) to d) are selected so that the equivalent ratio of NCO groups of component a) to isocyanate-reactive groups of components b), c) and d) is 1:0.8 to 1:1.2. The present invention also relates to a process for preparing these polyisocyanate crosslinking agents …