PRODUCTION OF LIGHT-COLOR URETDIONE POLYISOCYANATE

PROBLEM TO BE SOLVED: To obtain a malodor-free light-color uredione polyisocyanate by oligomerizing part of the isocyanate groups of a diisocyanate in the presence of a specified catalyst and a tri-substituted phosphite stabilizer and removing unreacted diisocyanate from the reaction mixture. SOLUTION: Part of the isocyanate groups of a diisocyanate having aliphatically and/or alicyclically bonded isocyanate group are oligomerized in the presence 0.01-5 wt.% catalyst which catalyzes the dimerization of isocyanate groups and 0.01-10 wt.% tri-substituted phosphite stabilizer of the formula [where R to R are each an ether group or a linear or branched aliphatic group optionally containing a 18C or lower aromatic(aliphatic) group, provided that R and R together with the P atom and two O atoms may form a heterocyclic five- or six-members ring; at least one of the substituents R to R is a 6-18C aromatic group or a 9-18C linear or branched aliphatic group], a catalyst poison is optionally added to the reaction mixture to stop the oligomeration at a degree of oligomeration of 10-60%, and the resultant reaction mixture is subjected to film evaporation to remove unreacted monomer therefrom.