Novel latent catalysts for 2K-PUR systems

Polyurethane chemistry is established throughout the world in many coating, adhesive, sealant, foam and elastomer applications. This results essentially from the impressive variability of properties that can be achieved through the vast diversity and possible combinations of polyurethane raw materials. Although dibutyltin dilaurate (DBTL) is the most versatile metal catalyst in polyurethane reaction catalysis, its unfavorable toxicological profile and the changes in its classification and labeling are forcing the formulators to look for alternative catalysts. On the other hand, the constant need for increased productivity, i.e. faster curing systems, can only be achieved at the expense of a very short pot-life when using standard catalysts, e.g. DBTL. In the present paper, we show that we have successfully developed a smart way of meeting the two opposite requirements through the development of photo-latent metal catalysts. Since the latter will release the active catalyst only upon exposure to UV-light, the formulation will remain stable for a long time as long as it remains in the dark. Data showing the influence of UV-light exposure on the performance of these novel latent metal catalysts in a model two-component polyurethane coating are presented in comparison to the non-latent reference catalyst.