How to Safe Using UV Flexo Inks
UV flexo ink now has new technology when applicable using in food package, bu the mean of reducing the photoinitiator quantity in flexo ink, while increasing its ability to eliminate risks of migration of non-cured free radicals. Some major suppliers of low-migration UV flexo inks have pass the safety tests. However its risk and uncertainty still exists in most brands with traditional packaging converters.
Cationic UV inks are opposite to free radical inks as polymerization process is fully complete once started, so can be make it for 24 hours delay until its full polymerization, hence it will avoid migrate during its post curing time inside the reel. Curing speed are different with free radical inks, which the later on is higher and its efficiency is related to the working environment. Some of packaging converters already tested and have shown the possibility of such application, and have successful trial on adopt cationic UV flexo inks in niche short run food packaging markets, with its perfect adhesion, high print quality and reduced waste.
Another obstacle to full polynerization is oxygen, which is broken by UV radiation in the lamp head. This will interrupt and chain of polymerization inside the ink and leaves some light molecules free to migrate. Innert UV dryer substitute ambient air in the lamp housing with an inert gas, this will help reduce the oxygen effect. All in all, full polymerization, less quantity of photoinitiator, higher curing speeds and limited ink migration have been experimented.
The high cost, feeders, pipers inside the environmental during production and etc obstacles are highly limited adoption of its technology in some UV offset applications for food packaging. While low migration free radical UV flexo ink is preferred by mostly UV Flexo ink suppliers. It is still preventing adoption of process among very limited food packaging.
Edit by Vikas
Print Series Team
5 March, 2012
