Process for the preparation of aqueous dispersions containing both blocked polyisocyanates and polyhydroxyl compounds

摘要

The present invention is directed to a process for the preparation of an aqueous dispersion containing both a blocked polyisocyanate and a polyhydroxyl compound by reacting an aqueously dispersed polyisocyanate having an isocyanate content of at least 12% by weight, based on the weight of the polyisocyanate, with a monofunctional blocking agent which is more reactive with isocyanate groups than water at an equivalent ratio of monofunctional blocking groups to isocyanate groups of 0.5:1 to 2:1 in the presence of a polyhydroxyl compound which is either water soluble or water dispersible, wherein the polyhydroxyl compound is present in an amount which is sufficient to provide an equivalent ratio of hydroxyl groups to blocked isocyanate groups of 0.6:1 to 1.25:1.