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UV/EB curing is widely known as an "environmentally friendly" technology since they
are 100% solids formulations that cure without the emission of volatile organic
compounds (VOCs). The attraction from an environmental point of view has been further
enhanced as a result of a study that shows that UV/EB coated paper may be easily
recycled. As a method for reducing pollution, UV/EB curing is very attractive. However,
one thing that still clouds the perceived "friendliness" of this technology are concerns
with the health hazards associated with acrylate monomers. In the United States, these
concerns have !ed to government restrictions on the use of new acrylate monomers.2
In the United Kingdom, several acrylate monomers have been voluntarily excluded from
use in the printing industry.3 Since many existing acrylate monomers are still generally
regarded as safe when properly handled,4 most users have little incentive to change
their formulations. Therefore, the replacement of acrylate monomers will depend on the
development of safer technologies that can also compete with acrylate monomers on
a cost/performance basis.
One way to reduce the use of acrylate diluent monomers is by the development of water
borne UV/EB formulations. In these systems, water is used to reduce the viscosity of the
less hazardous acrylate oligomers. Although water based formulations offer several
potential advantages, they may be offset by the necessity to remove water prior to
UV/EB cure. The water flash-off step requires energy and space which defeat some of
the basic advantages of 100% reactive systems.
Several reports of non-acrylate UV/EB curing chemistry have appeared in recent years.
The cationic curing of cycloaliphatic epoxies has found use in a number of applications.
Cycloaliphatic epoxies are generally used because they offer unique performance
properties, not because they are non-acrylate.6 The cationic curing of natural epoxidzed
plant oils appears to offer the most advanced environmentally friendly chemistry.7
However, practical cost and performance of this chemistry has not yet been
demonstrated. The cationic curing of vinyl ether monomers and oligomers offers the
potential for very fast cure speeds.8 However, the cost of these materials may hinder
their use in many applications. One attractive use of vinyl ethers appears to be as a
reactive diluent in radical/cationic hybrid systems.9
