Understanding Low Migration Inks In Packaging

Though there have been some new potato chip flavors showing up on shelves lately, one that is unlikely to join the ranks of cappuccino or mango salsa is that of ink. The thought of getting a mouthful of ink when taking a bite out of a favorite snack may seem farfetched, but as food package printers know, it's not always easy to keep ink on its side of a package and the food on the other.

Many ink suppliers manufacture and market low-migration inks with the idea that when applied to a substrate, the ink will not pass through to the other side, causing unwanted contamination. But when printing a job that requires low-migration properties, there's far more to consider than just loading up the press with a low-migration ink.

What makes low migration?

In general, the term low migration ink refers to ink formulated without use of raw materials that have been recognized as ones that could pass through a substrate. Yet because there are so many different combinations of inks, printing processes, and end uses, each job needs to have an element of customization to make sure the proper ink is used.

Kristin Adams, the marketing manager for Collins InkJet, explains that when a customer requests a low migration ink, it's not as simple as just handing over a pre-made can of exactly what the customer needs. There's a substantial amount of research, testing and communication throughout the supply chain that must occur before any packaging is completed and shipped.

"We typically take guidance from our customers, such as 'Here's what we're printing on and here are the guidelines we need to adhere to,' " Adams says. "We'll research those guidelines and formulate the inks to meet whatever approval they're seeking. The term low-migration actually defines the selection of materials as well as the ink. So regardless of how an ink is formulated, the ink alone cannot be considered low-migration until it's actually applied to a specific substrate."

While it falls on the ink supplier to manufacture the ink that will be used on the final project, it's up to the converter to ensure good manufacturing practices are being used throughout the job. Primarily, understanding print speeds and the curing process are the keys to making sure the low-migration ink serves its intended purpose.

According to Frank Roman, the flexo product manager at Zeller+Gmelin, an ink can work properly when cured at a certain speed, but fail when cured at another. Roman says this is due to dwell time, or how long an ink can remain on a substrate before it's dried.

"You've got to do your homework," Roman states. "You have to set up your QC procedures and also make sure your inks are fully cured. If they're not cured, you're obviously open to a liability."

What needs low-migration?

In addition to food, many pharmaceuticals, personal care products, child and baby care products, beverages, and tobacco products require inks with low-migration properties.

Gregory Pace, Ph.D., is the manager of regulatory affairs and product stewardship for Sun Chemical. He explains that when evaluating low-migration inks, it is necessary to consider the entire packaging unit. For example, in addition to understanding the substrate, product, and end use, Pace says the proximity of ink to product is also important.

"It has to be a functional barrier," Pace says. "In other words it has to function to protect the food from anything on the outside environment outside of that primary package that could affect the food in any way. No chemical from anywhere in that packaging can become part of the food product and have an unintended effect."

Critical communication along the supply chain

Because there are numerous steps in the low-migration packaging process, the responsibility of ensuring the ink and packaging are functioning as they should does not necessarily fall to one party. The ink suppliers need to ensure the correct formulation is being used, and that the printer or converter is educated on the ink and is using the appropriate product. The printer/converter needs to be sure his or her quality control system is in place and that the ink is being properly cured.

With all of these moving parts, constant communication is critical to ensuring successful application of the ink.

"It's a long process and we need to work really closely together—all converters, printers, and ink manufacturers," Adams says. "We can make a low-migration ink that will be low migration on material A, but won't be low migration on material B."

Though it is up to the entire supply chain to make sure the final packaging is up to code, Renee Schouten, corporate marketing manager for INX International Ink, says final culpability tends to fall on the company sending the packaging into the marketplace.

"The most important thing to remember is the responsibility for compliance of packaging does not lie with one single individual member of the packaging supply chain," Schouten says. "It is on the ownership of all stakeholders, including the package designer, printer/converter, and material suppliers. Ultimate responsibility for ensuring compliance rests with the company placing the packaging in the market."

Testing, testing

Even if all of the involved parties have done their homework and research, testing the application is not only a responsible best practice, but also can be part of a regulation.

Adams recalls an instance in which Collins InkJet had formulated an ink to be used on a medical device. Despite all of the work that went into constructing the proper ink, the product was far from being able to go straight to market.

"We had done all of our due diligence, come up with a finalized ink, and the OEM had delivered the system and had it all up and running," Adams says. "They still had to run on that product for one full year before they got FDA approval. It wasn't just the ink and it wasn't just the printer. It was the whole process from start to finish."

According to Pace, the testing not only provides a determination as to whether or not the ink, substrate and product are working well together, but can also help determine where any concerns may lie. In some instances, he says, the problem might not be in the ink at all.

"In paperboard, we would want to know, is that chemical coming from an additive that's in the pulping and paper manufacturing?," Pace explains. "Or is it an additive that's coming from the multi-layered polyboard itself, which is both plastic and paper? Or is it coming from the printing inks?"

The future of low migration

With much of the attention in low-migration packaging devoted to the curing process, the Flint Group is focusing on inks that can be cured using LED, which can be easier to control than UV.

Tom Hammer, Flint Group's narrow web product manager in the United States says the company introduced a series of low-migration LED curable inks at Labelexpo 2014 in Chicago. The EkoCure ANCORA series is the first commercially available low migration ink, specifically designed for UV LED curing.

"LED is definitely here to change our industry forever, and now we've introduced products that can be used for food packaging that can be cured by LED lamps."

No matter how the inks are cured though, communications, attention to details, and involving all the stakeholders will help ensure your low migration inks stay put. pP

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