NOVEL LACQUER POLYISOCYANATE, MANUFACTURE AND USE IN THERMOSETTING TWO-COMPONENT POLYURETHANE LACQUER AS ISOCYANATE COMPONENT

摘要

The present invention relates to lacquer polyisocyanates which contain about 0 to 8% free isocyanate groups, about 10 to 28% blocked isocyanate groups and about 2 to 10% of the structural units, -NH-NH-CO-O, all percentages based on the weight of the polyisocyanates, but excluding the weight of the blocking agent. Also provided is a process for preparing these polyisocyanates which comprises reacting about 10 to 30 mol % of the isocyanate groups of an organic polyisocyanate with reaction products which have (i) alcoholic hydroxyl groups and (ii) structural units of the formula, -O-CO-NH-NH-CO-O-, and/or of the formula H2N-NH-CO-O-, with the formation of urethane groups and optionally groups corresponding to the formula, -NH-NH-CO-O-, and reacting about 50 to 90 mol % of the isocyanate groups of the organic polyisocyanate with a blocking agent. The reaction products containing alcoholic hydroxyl groups are obtained by reacting 1 mol of hydrazine or of hydrazine hydrate with about 1 to 2 mols of a cyclic carbonate. A final object of the present invention is the use of the new lacquer polyisocyanates as the isocyanate component in thermosetting, two-component polyurethane lacquers.