BLOCKED POLYISOCYANATE AND ITS PRODUCTION

(Cyclo)aliphatic polyisocyanates partly or completely blocked with malonate esters are claimed, with a free NCO content of not more than 4%, derived from (A) di-isocyanates of formula OCN-R-NCO (I), where R = 6-14C (cyclo)aliphatic hydrocarbylene; and (B) polyisocyanate-isocyanurates of formula (II), where n = 1-3; with a wt. ratio of (A):(B) = (100-0):(0-100); with (C) blocking agents of formula (III), where R = 1-10C alkyl or tert.-Bu. Also claimed is the prepn. of these blocked polyisocyanates by reacting (A) and/or (B) with (C) in the presence of a catalyst. Pref. component (A) is isophorone di-isocyanate (IPDI), hexamethylene di-isocyanate (HDI) or 2,4,4(2,2,4)-trimethyl-HDI. Component (B) comprises isocyanurates of IPDI or HDI. Component (C) is methyl, ethyl, propyl, isopropyl, butyl or 2-ethylhexyl tert.-butyl malonate, or di-tert.-butyl malonate.