the invention relates to a method of preparing a polyisocyanate with at least one uretdione group by oligomerizing part of the isocyanate groups of isophorone diisocyanate in the presence of a catalyst which accelerates the dimerization of isocyanate groups , wherein the oligomerization catalyst comprises a saline compound comprising from 10 to 100 wt . % of 1 , 2 , 3 - and / or 1 , 2 , 4 - triazolate structures in the anion , and the products prepared by this method .