Minimizing Ink Migration to Build Brand Trust

With most Americans consuming meals at home over the past year due to the COVID-19 pandemic, a spotlight has been turned on food packaging safety protocols. Packaging companies play a big part in ensuring that the food products the public eats are free of potentially harmful or unwanted substances.

Low migration ink products also perform an important role in the production of safe food packaging materials. By design, these inks are formulated to eliminate the potential transfer of substances from the printed packaging onto the edible product inside.

George Fuchs, director of regulatory affairs and technology for the National Association of Printing Ink Manufacturers (NAPIM) notes that it is important to remember that each ink system must be specifically formulated for the intended conditions of use, including the type of package, printing process, and substrate.

“Brands and consumer product groups continue to show strong interest in the safety of their food packaging,” Fuchs says. “Many ink companies invest in the development and formulation of inks that are designed to reduce the potential for migration through packaging substrates.”

Legislators, non-governmental organizations, brand owners, converters, and consumers are all becoming more aware of the packaging ink migration topic, resulting in the demand for low migration ink products to grow steadily, says Peter Walther, regional head of product safety and regulation for ink supplier Siegwerk USA.

“However, it is not enough to only provide the suitable inks — the ink supply has to go hand-in-hand with adequate communication, information, and education so that each member of the downstream supply chain can perform its own compliance work,” he says.

Fuchs, of NAPIM, states that the regulatory environment for non food-contact inks can be complex and vary widely among regions and countries.

“Most countries, including the U.S., continue to review guidance and regulations covering printing ink on the external side of food packaging as technical and toxicity information and understanding evolves,” he explains. “In my view, all members of the food packaging supply chain — regardless of the print process used — need to understand that they are part of the process necessary to ensure the safety of a food package.”

Package structure, substrate selection, print process, ink systems, and other variables all play a vital role in packaging safety, Fuchs says.

For packaging companies invested in inkjet printing technology, the application of low migration ink is becoming a bigger issue, points out Tom Molamphy, Siegwerk USA’s inkjet sales and technology manager for North America. He sees inkjet printing becoming a strong player in all the packaging market spaces — even as a viable candidate for printing of primary packaging.

Siegwerk is among multiple ink suppliers that provide low-migration solutions for package printing. Image courtesy of Siegwerk.

“UV-based low migration inkjet inks are becoming more common for secondary food packaging (non-primary and non-direct food contact) and pharma applications where migration is a concern,” Molamphy explains. “For primary food packaging — such as flexible packaging — it’s likely that water-based inkjet inks will be the chosen solution where migration is a primary concern, and the ink volume/cost is a bigger driver. Water-based piezo inkjet ink solutions are a big focus for most of the major inkjet ink manufacturers.”

When it comes time to cure low migration inks, John Kilbo, Siegwerk USA’s regional technical manager, narrow web, describes UV inks as a matrix of varying molecule sizes that change with the level of irradiation and cure applied.

“A certain portion of this matrix needs to be bound together to prevent setoff, for example a roll-to-roll pouch printing outside to inside while in the roll form,” Kilbo says. “There is always setoff and migration but depending how well vitrified the system is will then determine whether certain migration limits can be met.”

Additionally, Kilbo contends that it is not always the UV intensity levels that disrupt cure, as heat or chill roller settings can often lead to positive or negative impacts.

“UV starts the reaction, but temperature of the web drives the kinetics behind it and has to be monitored,” Kilbo says. “Always the hotter the better until film distortion and maintaining register come into play. One of the advantages in LED versus UV is it pulls off much of the extra IR heat coming from the lamps and allows chill rollers to increase in temperature and carry an overall warmer web, which then speeds the underlying chain growth further or faster than in UV.”

Evan Benbow, VP, product technology and solutions for ink supplier Wikoff Color Corp., sees some recent industry trends that are applicable to energy-curable inks.

“With the numerous reclassifications of previously suitable photo-initiators, our inks must constantly evolve to stay current,” Benbow says. “There is also a greater focus on the impurities present in ink raw materials and products generated during the manufacture or application of our products. These are commonly referred to as non-intentionally added substances.”

Benbow adds that while offset migration — ink transfer from the printed side of packaging to the food contact side — is one of the primary modes of migration, converters cannot assume that migration through the substrate will not occur. As an example, Benbow points out that an ink suitable for one packaging substrate might not have the same migration profile when used with another substrate.

“Packaging companies must also know the conditions of use of the package, as elevated temperatures in the filling, storage, or use of the package can influence migration,” Benbow says. “One of the major challenges with different printing processes is the amount of ink being applied to the substrate. At higher ink film thicknesses, the amount of potential migrants increases and could be demonstrated — through a worst case calculation — to be not of concern at lower ink film weights, but the opposite could be true at a thicker ink film.”

Benbow maintains that advisable best practices will always be unique to each converter. However, packaging companies must perform due diligence with suppliers to create a standard of transparency in the supply chain regarding the materials involved in the production of the final package, he says.

“As an ink company, we will supply a statement of composition (SoC) to our customers so that they can perform a risk assessment in regard to materials that have the potential to migrate,” Benbow states. “Beyond performing a similar exercise with their other suppliers, it is up to the converter to ensure good manufacturing practices are followed to ensure no contaminants are being introduced on-site. Pending the outcome of the risk assessment, a migration test may be necessary to ensure compliance.”

Additionally, packaging companies must have strong internal production standards to ensure that the same protocol is followed for every qualified job, Benbow adds.

“An uncured ink can also exhibit some telltale signs through a physical property evaluation of the printed article, which can indicate troubles ahead,” he says.

Fuchs shares that the safety of food packaging, including the development of low or lower migration inks, will continue to need to have a robust emphasis going forward by all parties involved in the food packaging space.

“Regulatory agencies in all geographic regions will also continue to study and understand these complex systems in an effort to develop guidance and regulations for this market,” he says.