The premise behind ink is a simple one: stored in a receptacle, the liquid is then ejected through the nib of a ballpoint pen, and applied to a surface to dry and leave an indelible mark. For most people, that is the end of the process. Packaging companies, however, have to consider whether the inks used will leak harmful chemicals into the items they have sealed into their respective containers. To safeguard consumers, regulatory bodies in the EU and US have passed numerous laws that restrict the use of certain inks in packaging on grounds of excessive toxicity.
UV curable inks facilitate compliance with these laws. Having been in use for some years, they are a firm favourite among food packaging manufacturers. It is to that end that Rahn introduced its GENOPOL range. Polymeric photoinitiators with a high-molecular weight, this line easily meets the demands for low migration and reduced odour, while maintaining a favourable toxicology.
"Most of our product range is suitable for packaging inks," says Roger Küng, head of operations at Rahn. "When it comes to food packaging for indirect contact, odour and the potential migration of mobile components are a concern for every formulator, independent of the curing mechanism. With UV-curing inks and coatings, the main focus is on photoinitiators that are usually of low molecular weight and have a tendency to migrate, either through the substrate or via reverse-side migration."
UV/EB has been Rahn's area of expertise for over 30 years. "Our company's philosophy is based on a high level of customer support, combined with cuttingedge technical data and up-to-date health, safety and regulatory information," explains Küng. "The productdevelopment laboratory identifies new chemistries and solutions for our customers. This enables us to create customer-specific solutions and broader marketdriven products."
It should therefore be no surprise that health and safety remains a prime concern. According to EuPIA guidelines, a target migration limit of 'no concern' - equal to 10ppb for non-evaluated substances with molecular weight below 1,000Da - is consistent with other food-contact materials. If a packaging solution does not meet these requirements, it must be redesigned with lower migration products developed, or toxicological data must be obtained to demonstrate that the intended use is acceptable.
Ink manufacturers and converters must conduct real-life migration studies to ensure compliance with legislation and guidelines. However, experience shows that it is possible to formulate and convert inks and coatings with GENOPOL products that result in migration levels below 50ppb of residual photoinitiator, thus conforming fully with guidelines and regulations. This has also been verified by downstream users such as Nestlé.
Furthermore, Rahn is continuously working to improve existing GENOPOL products and extend the product range in the future.
"In recent years, subjects such as product safety, environmental exposure and compliance with legal restraints have become more and more important," explains Küng. Rahn GENOPOL products assure the health and safety of consumers, according to Article 3 of the European directive 1935/2004. "As a responsible supplier, Rahn has created a special department to deal with these challenges. The main task of this job is to gather all available national and international information, process it according to the industry, and make it available to customers and users."
All in all, Rahn's strategy has always remained clear. "In the product development and application areas, we support our clients with more than three decades of experience in radiation curing," says Küng. "Above all, we have a customer-focused and service-oriented approach. Joint projects with customers are always welcome, and tailor-made solutions are the strength of our organisation."