| 摘要 |
The present invention relates to a process for preparing blocked polyisocyanates wherein at least 50 mole % of the NCO groups have been blocked with sterically hindered phenols by reacting a) one or more organic polyisocyanates with b) one or more sterically hindered phenols in the presence of c) at least one catalyst selected from i) heterocyclic amines in which at least one nitrogen atom is part of an aliphatic, olefinic or aromatic ring, ii) tetraorganoammonium and tetraorganophosphonium salts of weak acids (pk<SUB>a</SUB>>=2.0), with nitrogen- and/or phosphorus-attached aliphatic, cycloaliphatic, araliphatic and/or aromatic radicals, and iii) zinc(II) compounds. The present invention also relates to the resulting blocked polyisocyanates and to their use for producing coatings, adhesives or sealants suitable for contact with foods and/or drinking water.
|
