Preparation and evaluation of low migration oligomeric photoinitiators with a repeating photoactive site

UV-curing is an efficient, environmentally friendly technology used extensively for a variety of applications including food packaging. Its limitation is that small photoinitiator molecules may migrate into the foodstuff which, although not necessarily harmful, is undesirable and is subject to legislative requirements.In order to meet these requirements a variety of oligomeric photoinitiators based on benzophenone have ,been prepared. To maximise their photoinitiating capability these have been prepared with a repeat photoinitiating unit and it has been attempted to minimise the non-photoinitiating portion of the molecule.To evaluate migration a simple UV method of detecting and measuring migration has been developed and successfully validated.Twenty four oligomers with a repeat photoinitiating unit have been prepared with six of these shown to be low-migrating with a seventh capable of being used as a low migrating oligomeric photo initiator due to exhibiting a rapid speed of cure at low photoinitiator concentrations