Parameters Affecting Extractables Cationic Uv-Cured Coatings In Cardboard Application

Cationic UV-curabl e clear coatings based on epoxy formul ati ons used for
example as overprint varnishes have been commercially available for several.
years. These coatings have received acceptance mainly because of their
odourlessness which makes them ideally suited for applications
where odour would otherwise present a major drawback. These applications
include food and pet food packaging as well as other high quality packaging
such as cardboard substrates for cosmetics or pharmaceuticals.

Besides odourlessness additional advantages of cationic UV epoxy
coatings are low skin irritation and low sensitization potential of uncured
formulations, and also a low level of migratable components in properly cured
coating films, the latter being an important aspect of consumer safety in
food packaging  [1]. Although direct food contact of UV coatings in general is
not intended migrants are nevertheless an area of considerable concern
because of a potential mass transfer from the outside to the inside of a
coated substrate which will be in direct contact with food. It is for this
reason that future European Conniuni ty Chemicals Legislation apparently
intends to cover all radi ati on curable coati ngs for i ndi rect food contact
under EEC Directive 90/128/EEC by including their raw materials in the
Directive's positive lists [2].

This paper reports on some critical parameters affecting extractable and
hence potentially migratáble residues from pigment—coated cardboard to which
a cationic UV varnish has been applied. Emphasis is placed especially on
substrate pretreatment and UV coating composition, in order to minimize,
extractable residues along with increasing coating reactivity.