Process for the preparation of blocked isocyanates

摘要

A process for the preparation of blocked isocyanates by reaction of free isocyanates under water-free conditions with blocking agents containing acid hydrogen in the presence of basic catalysts, these being one or more alkali hydroxides, particularly lithium hydroxide. The process leads to yellowing-free products with a low alkali content which may be used as cross-linking agents for polyols, particularly in the lacquer sector.