UV Curing Properties of Polyalkyleneglycol modified Amine Synergists and Ketonic Photoinitiators with Acrylate S

The presence of Type I and Type II initiators and their degradation products in cured films
can have a deleterious effect e.g. they can cause blooming thereby destroying the finish of
the fllm.(l) In some cases the low molecular weight degradation products are odorous and
consequently impart an unacceptable smell to the finished product (2). The presence of low
molecular weight, volatile species in the curing formulation can lead to fogging of the optics
in the curing chamber. A further drive to reduce the number of migrateable species (which
usually are of low molecular weight) is the impending legislation relating to materials which
are in contact with food where very low levels of migrateables will have to be achieved (3).

Efforts to overcome the outlined problems in the field of photoinitiator chemistry have been
directed at producing polymeric and polymerisable initiators (4). Many of the polymeric
initiators have been shown to possess lower reactivity than their monomeric counterparts
and also their addition to formulations leads to an increase in viscosity (5). Whilst the
polymerisable initiators do not suffer from these deficiencies these compounds are never
fully incorporated into the coatings and consequently the unpolymerised materials
contribute to the number of migrateables (6).

In an earlier paper we outlined an alternative approach in which the photoinitiator is
derivatised with a low molecular weight polymer side chain (7). This side-chain, will if it
contains readily abstractable C-H bonds, undergo crosslinking reactions which will lead to
its incorporation into the coating via crosslinking. The side chain will also reduce the
mobility/migrateability of the initiator in the cured coating due to increased physical
entanglement. Another feature that can be built in using the polymer side chain is increased