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In the early days of radiation curing, it was discovered
that the monomers or reactive diluents have irritant
properties. This sometimes resulted in severe skin- and
eye irritation for workers, V especially printers, working
with these materials. As a result, the labelling of these
products (see table I in the next section) was regulated
on-EEC-level in Annex I. In the UK, the use of these
products was excluded from use in printing inks and
'varnishes according to a recommendation of the
Society of British Printing Ink Manuqctures and they
were listed in a so-called exclusion list 2.
Skin- and eye irritation in those days used to be
expressed in terms of the DRAIZE test'. The DRAIZE
skin irritation test is a particularly severe test in that
the product to be tested is applied on two sites on the
skin of the test animal (rabbit) of which one is abraded.
Since then, several improvements were implemented in
acrylate monomer production. V Toxic solvents V like
benzene were removed from the production process. In
addition, product V purity was significantly improved
:resulting in diminished low molecular byproducts. Last
VVbut not least the level of residual acrylic acid and
:residual solvents was dramatically reduced.
At least as important as these product improvements
was the fact that the raw material suppliers to the UVand
EB-curing industry reacted to the alarming
discovery of severe skin- and eye irritation of the first
generation acrylate monomers with the development of
intrinsically low irritancy products. This lead to the
development of monomers like TPGDA and GPTA,
that were only mildly irritant in the DRAIZE skinirrItation
test andV as a result replaced monomers like-
1,6-hexanediol diacrylate, triethylene glycol diacrylate,
trimethyloipropane triacrylate, pentaerythritol
triacrylate and pentaerythritol tetraacrylate in many
applications, especially in printing inks and overprint
varnishes (in line and off line).
