Next Generation Low Migration Photoinitiators
Michael Kiehnel, Julia Volk, BCH Brühl
Abstract: The formulation of low migration UV inks and varnishes is often a challenge for the formulator. Although many commercial photoinitiators are available for various types of light sources, most conventional photoinitiators are prone to migrate from the cured coating. There are polymeric versions available, but in addition to the lower reactivity they cause restrictions in formulation, mainly due to their high viscosity. Since the photoinitiator is a key component in the formulation of UV-inks and -coatings, there is a need for photoinitiators, which effectively work and do not migrate into the packed material maintaining a freedom in formulation. An alternative to polymeric photoinitiators are functionalized photoinitiators, which are incorporated into the polymeric networks upon curing, hence decreasing migration potential, while having a minor impact on the viscosity. Combining both elements of a type II photoinitiator pushes reactivity even higher. Their higher reactivity gives the formulator more opportunities in designing UV curing systems and facilitates the formulation of low migration inks and coatings.