The seams of food packaging versatility are being stretched to the bursting point as both regulators and consumers push packaging evolution in a fast-growing market, one that is seeing a growing demand for toxin-free, high-performance, food-safe inks. The million-dollar question, however, is whether the science of food-safe ink formulation is maturing quickly enough to adapt to business demands.
Water-based inks etch an indelible path to the future
The shift in ink formulation is moving from solvent-based inks — which release volatile organic compounds (VOCs) in the drying phase — to water-based inks, which are safer. The main driver behind the move? Consumers.
Consumers want a food package that's portable, heatable, freezable, grease resistant, graphically interesting, that doubles as a serving container, and more often today, one that they can compost, or at least recycle. In other words, food packaging is becoming more of an experience than simply a container that holds food. But that means there are more opportunities for the ink used in the packaging to come into contact with the food.
While solvent-based inks can be, and are, used in food packaging, using high-performance inks that are low in VOCs, and safer and more environmentally friendly, seems like a logical track for the packaging industry to take. So, what's standing in the way of an industry-wide adoption of water-based inks over traditional solvents?
Traditionally, printers and converters like to work with solvent-based inks because they perform quickly and efficiently in production environments. Conversely, when formulating water-based inks for print applications, some practical considerations need to be addressed.
Speed is king
Water-based inks have come a long way in terms of production-quality development. Where graphic integrity and adhesion to substrates used to be barriers to performance, formulators have made great advancements with water-based polymers.
"Solvent-based inks typically will grab onto a film substrate better, but we've worked hard to formulate water-based binders with comparable performance characteristics," notes Jennifer Rigney, Technical Specialist for Water-Based Products for Printing and Packaging, BASF.
Speed is still an issue though.
The goal is to have the speed and printability of the water-based inks on par with the solvents, but water's strength can also be its weakness.
"You're dealing with a very unique solvent, water; it's the only solvent used in printing that's tracked on the Weather Channel," said Steve Ems, Technical Account Manager, BASF. He's worked extensively with water-based formulations and observes that "drying speed is one of the main hurdles. Along with its high surface energy that can cause wetting issues on untreated and lower surface energy film substrates, water takes significantly more heat, energy and time to be driven off non-absorbent substrates. That's always going to be an issue in the conversion of solvent-based inks to water-based."
Resolubility performance presents a significant challenge, too.
In water-based inks, the polymer needs to be resoluble or have the ability to constantly re-wet on the printing press so the ink doesn't dry on the plate image, or in the anilox metering rolls. This is more difficult to achieve with water as compared to solvents. Solvent-based inks are built on resins that are soluble in a particular solvent or blend of solvents, and if properly monitored and maintained on press with the correct solvent blend, they will print very cleanly and quickly. Water-based inks use resins that in themselves are not soluble in the solvent of choice, water, but are made soluble with the choice of appropriate base. That makes monitoring the pH of a water-based ink on press a priority of press operators, as well as controlling the viscosity with water. If the formulation for resolubility is not accurate, the ink can begin to dry-in on the anilox cells or on the plate, less ink will be transferred, and color strength will be affected.
Hurry up and wait
Once the heavy lifting has been done with formulating and testing a new food-safe ink, it still must comply with FDA (Food and Drug Administration) regulations.
Even if an ink is not created specifically to be an ingredient in a packaged food, the FDA may consider it an indirect food additive. It isn't designed to be part of the food, but there is a recognition that there's potential for ink to come into contact with the food; components of the ink may migrate into the food and create the possibility of being ingested.
Everything in the ink formulation, including additives like the defoamer and the wetting agents, must be cleared for food contact. And that means copious testing and sometimes, lots of time.
Proactive formulators are keeping an open line of dialogue between their support staff and the FDA. Being available to answer questions, review test results and communicate effectively helps with understanding and keeping the ball in motion.
"We have dedicated regulatory staff who are very knowledgeable about requirements for FDA compliance. We work very closely with them to ensure the products we develop are suitable for food packaging. Great communication is invaluable when introducing new products," observes Rigney.
Even considering the approval delays, there are encouraging signs that the heavy investment of time, resources and patience into these new formulations will more than pay off in the long run.
Signs point to a sustainable materials future
More resources are now being used to develop polymers for food packaging inks from renewable resources, like soy, starch, biomass feedstocks and larch (to name just a few). Specialized acids can be incorporated to enhance moisture deflection and antimicrobial strength. High-quality print results and resolubility have been achieved using these renewable materials.
Read more about water versus solvent-based materials in the packaging industry