POLYISOCYANATE BLOCKED WITH BLOCKING AGENT MIXTURE
(Cyclo)aliphatic polyisocyanates (I) are claimed, with a total content of 5-25 wt.% NCO gps., at least 95% of which are blocked with a blocking agent (II) contg. (A) 30-70 equiv.% 1,2,4-triazole; (B) 30-70 equiv.% 3,5-dimethylpyrazole and (C) 0-30 equiv.% blocking agents other than (A) and (B). (I)...
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Zusammenfassung: | (Cyclo)aliphatic polyisocyanates (I) are claimed, with a total content of 5-25 wt.% NCO gps., at least 95% of which are blocked with a blocking agent (II) contg. (A) 30-70 equiv.% 1,2,4-triazole; (B) 30-70 equiv.% 3,5-dimethylpyrazole and (C) 0-30 equiv.% blocking agents other than (A) and (B). (I) are produced by reacting (cyclo)aliphatic polyisocyanates with a NCO content of 7-30 wt.% (III) (opt. dissolved in paint solvents) with at least 95 equiv.% (II), w.r.t. the NCO gps. remaining after modifying up to 20 NCO equiv.% of the NCO gps. in (III) by isocyanate addn. reaction with carboxylic acid hydrazides contg. NCO-reactive gp(s). (IV) so that the final prod. (I) contains up to 5 wt.% units of formula -CO-NH-NH- (w.r.t. solid). The modification can be performed before, during and/or after the blocking reaction, which is carried out by adding the components of (II) in any sequence or as a mixt. |
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