| 摘要 |
The present invention is directed to a process for the preparation of modified polyisocyanates containing uretdione and isocyanurate groups by the oligomerization of a portion of the isocyanate groups of organic diisocyanates containing (cyclo)aliphatically-bound isocyanate groups in the presence of organic phosphines of catalysts followed by termination of the oligomerization reaction at the desired degree of oligomerization by the addition of a catalyst poison and removal, by distillation, of at least a portion of the excess, unreacted starting diisocyanate, characterized in that a) about 0.1 to 10% of the isocyanate groups present in the starting diisocyanate are converted into urethane groups by the addition of at least one alcohol before and/or during the oligomerization reaction, and b) the distillation residue obtained after removal of the excess starting diisocyanate is heated to temperatures of at least 50.degree.C in the presence of 100 to 10,000 ppm, based on the weight of the distillation residue, of a peroxide. The present invention is also directed to the polyisocyanates containing uretdione and isocyanurate groups obtained by this process and their use, optionally in blocked form, as the isocyanate component in two-component polyurethane coatings.
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