Blocked polyisocyanates and their use in stoving lacquers

A polyisocyanate which has 1,2,4,-triazole-blocked isocyanate groups, a viscosity as a 60 wt. % solution in diethylene glycol mono-n-butyl ether acetate of at most 10,000 mPa.multidot.s at 23.degree. C., and a blocked isocyanate group content (calculated as NCO, molecular weight 42), based on solids, of 7 to 14 wt. %, and which is the reaction product of

• A) a polyisocyanate component having an NCO content of 12 to 24 wt. % selected from (i) lacquer polyisocyanates prepared from (cyclo)aliphatic diisocyanates and containing allophanate, biuret, isocyanurate, uretidione and/or urethane groups or (ii) mixtures of (i) with cycloaliphatic diisocyanates having a maximum molecular weight of 300, wherein at least 30 wt. % of the (cyclo)aliphatic diisocyanates present in component A) as lacquer polyisocyanates (i) or as mixtures (ii) are cycloaliphatic diisocyanates having methyl substituents and a maximum molecular weight of 222, with
• B) 50 to 80 equivalent-%, based on the isocyanate groups of component A), of a monofunctional blocking agent for isocyanate groups containing at least 90 wt. % of 1,2,4-triazole,
• C) 10 to 30 equivalent-%, based on the isocyanate groups of component A), of a polyester component having an OH number of 56 to 250 and containing at least one linear polyester diol and
• D) 0 to 20 equivalent-%, based on the isocyanate groups of component A), of a hydrazine derivative corresponding to the formula ##STR3## and/or
• H.sub.2 N--NH--CO--O--R--OH
• wherein
• R represents a saturated hydrocarbon residue having 2 to 5 carbon atoms in which at least 2 carbon atoms are arranged between the two oxygen atoms.