New, Isocyanate-free routes to Blocked Isocyanates from the non-toxic chemical Carbonyl BisCaprolactam (ALLINCO~(~R))

摘要

Here we describe novel and simple methods to make a wide range of blocked isocyanates (BI's) from carbonyl biscaprolactam (CBC, ALLINCO~(~R)). BI's are a major class of crosslinkers in powder coatings, which are among the strongest growing areas of paints, due to the environmental and economical benefits. Crosslinkers are an indispensable part of these solvent-free coatings since they are responsible for the network formation. ALLINCO is a non-toxic chemical, while the current method to make BI's requires phosgene or isocyanates, chemicals suspected of health hazards. In one method ALLINCO reacts quantitatively with primary amines to form BI's. Every compound containing one or more primary amines can so be converted into the corresponding BI's. Remarkably, it is shown in another method that ALLINCO also gives BI's with alcohols. Chemicals with one or more primary alcohol groups are transformed with ALLINCO into BI's as well! ALLINCO has an extremely high selectivity. Amino alcohols, for instance 3-amino-1-propanol, react exclusively via the amine group with ALLINCO, while the alcohol remains unaffected. Similar high selectivity is shown in the reaction of compounds containing primary and secondary amino groups. In this case solely the primary amino groups react with ALLINCO, leaving the secondary amine unaffected. In both cases, either the alcohol group or the secondary amino group is still available to introduce other functionalities in addition to the BI group. This is illustrated by the preparation of rotaxanes.