New technology from Imerys has allayed concerns about fluorocarbons and should be a particularly good fit for food-based applications
May 2008
By Martin Koepenick
It’s not enough to make superior grease-, vapor- and water-resistant hamburger wrappers, french fry containers or microwavable boxes if your existing barrier coating technology must go.
Back in the 1990s when new research revealed environmental and health concerns about fluorocarbons, this information led market leader 3M to end its profitable Scotchgard® and Scotchban® businesses in 2000. Its decision to stop production of perfluorooctanyl sulphonate and perfluorooctanoic acid sent shock waves into the marketplace, and was said to cost the company $200 million. For a wide range of industry segments, including paper, this meant that alternatives would be needed to meet customer, consumer and societal needs. The impending void created a sense of urgency to find new solutions.
Responding to this concern, an Imerys’ R&D team set out to find alternatives to fluorocarbons, and to tackle the issue of reducing the need for increasingly expensive extruded polymers at the same time. Says Tony Lyons, Director of R&D at Imerys Pigments for Paper, “Our quest for the perfect barrier pigment focused on a belief. Our calculations indicated that certain pigments could increase the path length through the coating for the permeating species, and therefore reduce transmission rate. By finding the ideal particle sizes and shapes, we could engineer a better ‘tortuous path’ or pigment barrier, so to speak, than ever before.”
A Global Search
The barrier coating team searched globally for this ideal barrier alternative, and consequently, zoomed in on some unusual platelets at two locations in the world. All kaolins, carbonates and talcs are not the same, especially when viewed on a nano-level. The discovery of these particular platelets would not have been possible only a few years ago.
Even though the Imerys barrier coating team knew that it was onto something, it appeared that the economic benefits fell short. As project leader Eddy Turner reveals, “In the beginning we were not thinking big enough. Fluorocarbon reduction and 3-4% extruded polymer substitution came up short on a practical basis for our potential customers and us. When we changed our mindset to 100% fluorocarbon elimination and 30-40% polymer reduction, the breakthrough potential was obvious. As we began trials to apply the bigger scale hyper-platy concept, we found that all barrier coating approaches – from metered size press to blade and curtain coating – even spray on at converters, performed above expectations, and at lower overall costs.”
The interview that follows aims to provide insights into the hyper-platy clay platform for water-based barrier coatings, and into the thinking of Imerys' Stage Gate approach to solving a serious problem, and introducing a new solution.
The Imerys “Break the Barrier Initiative” team includes Dave Bakshi, Chris Boothby, Dave Gittins, Phil Jones, Tony Lyons, Dan Panfil and Eddy Turner, together having more than a century of experience in minerals for paper and board applications.
What were your criteria for developing a new barrier coating?
Turner: We wanted to explore mineral options for an environmentally friendly, recyclable water-based coating technology. We aimed to reduce expensive extruded polymers, and find a clear path away from fluorocarbons.
You don’t simply decide to replace or adjust the ratios of film-forming polymers, including synthetic and natural latexes, starches, proteins and polyols, and expect an immediate perfect result. Pigments also typically include minerals such as kaolin, talc, mica or calcium carbonate. Additives can be thixotropes, stabilizers, antifoaming agents and waxes. That’s a lot to address and understand.
So where did you begin?
Lyons: We had reasons to believe that nano-thin platelets (nanotechnology deals with new discoveries at dimensions less than 100 nm) had the potential to effectively block oil, grease and water on the surface of paper and board, but we had no practical experience to prove it.
Our goal was to identify and then enhance pigments that could easily be substituted and applied with on-line and off-line paper coating processes, even at converting operations.
What was the reward you were seeking?
Panfil: Anyone who could cost effectively eliminate fluorocarbons and reduce extruded polymers without losing end product performance would win a lot of business.
Because of the 2015 ban on most fluorocarbon formulations, food applications such as wraps, containers, microwavable board, frozen food boxes all needed an alternative. That’s a sizeable array of applications.
How did you proceed with your research?
Turner: As we got into it the science, we discovered that very specific shapes and sizes were needed to compliment polymer films, especially in the absence of fluorocarbons. Based upon a global mine site review – segment by segment within our mineral locations – we identified some very unique platelets, which showed potential to be engineered into a potential breakthrough for barrier coatings. It was a long and challenging road to find the ideal ‘tortuous path’ barrier pigment, but we got there after many man-hours of intensive research.
Where do you go from here in terms of commercialization?
Turner: In fact, several years of effort have already prepared the way for the launch of an entire platform of shape engineered pigments platform for sustainable moisture, water, oil and grease barrier coating solutions. This means that paper and board producers can ramp up their exit from fluorocarbons, and reduce the cost of extruded polymers by substituting hyper-platy clays in the coating formulations. Fortunately, we have the ability to deliver sufficient quantities to meet market needs with current production capability and can easily expand with market growth.
Depending on a company’s coating approach, substitution of the nano-scale kaolin platelets works well with other additives in formulations for the metered size press, blade and curtain coating.
Panfil: Even though the fluorocarbon ban may seem a long way off, producers can move forward now, maintaining or raising performance with water-based barrier coatings (WBBC) for food applications such as wraps, containers, microwavable board, and frozen food boxes.
There’s no reason not to speed up the transition away from fluorocarbons, and to reformulate with lower percentages of extruded polymers, saving money and meeting sustainability needs sooner, rather than later.
Boothby: It’s important to remember that impermeability to water and other aqueous and non-aqueous fluids is what made fluorocarbon and extruded polymer technology a winning approach for paper and board makers.
However, with new research showing concerns about the potential toxicity of fluorocarbons, and with petroleum-based polymers continuing to spiral in price, there is no option but to change.
Fortunately, desired attributes in the sheet are not at risk. Combined with paper and board’s edge in biodegradability, recyclability, as well as printability to express branded images and eye appeal, the future looks bright for growth of market share against not-in-kind competition.
Gittins: What the hyper-platy mineral platform brings is the ability to protect paper’s market share, amplify the environmental advantage, and reduce the amount of costly polymeric coatings.
Do hyper-platy kaolins work better in some ways than fluorocarbons and extruded polymers?
Panfil: Compared with unfilled coatings, we are seeing improvements in barrier properties, optical properties, runnability, blocking resistance and cost effectiveness.
How would you summarize your progress in terms of sustainability and cost effectiveness?
Bakshi: We originally focused on the technical and commercial needs of our customers – to deliver an innovative solution that would be cost-effective. What we quickly discovered is that the industry is hugely concerned about the sustainability of their paper and board. The ability of the paper industry to produce a fluoro-chemical-free, film-free, and aluminum-free packaging material that is recyclable is a strong selling point.
Turner: We're excited with our new generation of hyper-platey products, and how well they are meeting important and emerging market requirements.
Martin Koepenick, mkoepen@earthlink.net, has written about innovations in papermaking for more than 25 years.
Pulp & Paper magazine is FREE to qualified subscribers. Click here to find out more.
