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Through thick and thin

While supporting the demand for sustainable solutions the printing ink sector isn’t allowing functionality to be swept aside in a deluge of greenwash, reports Sam Cole

According to a recent industry report commissioned by Smithers Pira, the application of eco-friendly inks is set to increase from €5.8 billion in 2009 to nearly €7.2 billion in 2014, with a strong compound annual growth rate of 4.5%. Even allowing for this covering anything from replacing solvent with water-based manufacture, using vegetable pigments or effecting the simple reduction of volatile organic compounds (VOCs), that represents a significant share of a global market valued at about €11 billion last year.

And yet, how many hoops does the printing ink supply chain have to clamber through in order to be seen to be green – or indeed does it actually have any need to? Retail packaging is very much at the sharp end of consumer concerns about food safety – as was graphically evidenced just last year with the focus on the potential migration of mineral-oils inherent within recycled cartonboard fibre. While newspaper ink was swiftly tagged as the villain of the piece, relatively overlooked in the general mêlée of populist panic was the irony of unintended consequences, in this case attributable to an intrinsically eco-friendly solution – recycled board.

In response to the problem – and irrespective of question marks over degrees of toxicity or even the slightest risk to human health – Hubergroup has led its competitors in developing a range of mineral oil-free ink formulations.

Reducing the risks

Incorporating 80% of renewable raw materials, the Munich-based supplier’s Corona MGA and Natura GA inks for offset carton applications have been specifically developed to eliminate the requirement for a functional barrier film or any other mechanism to pre-empt migration of mineral oils from the board to the contents.

While the chemistry is sound, the desired result is not necessarily guaranteed, agrees Hubergroup corporate communications director Robert Doerffel. “Although Corona ink contains no ingredient that’s in conflict with regulations issued by Swiss Ordinance or EuPIA, eliminating the mineral oil is only going to make the ink formulation environmentally friendly if virgin fibre is used rather than recycled board.

“We want to give printers the option of a risk-free ink. Making all formulations mineral oil-free would ultimately remove them from the paper recycling chain, within which web offset inks, for example, can contain 20-30% of mineral oil derivatives. The cleaning-up process has to start somewhere, so why not right now?”

Self-evidently, the more development work that goes into a formulation, the more expensive the end product is likely to be. However, that shouldn’t act as a deterrent, says Doerffel. “As volume grows, the price difference will shrink. In the end the ink only represents between 1-3% of the cost of a packaging, so the overall impact is relatively insignificant.“

Unless a highly decorative effect has been specified, the likelihood is that ink will have a similarly small-scale impact upon the total weight and composition of any given packaging application – in eco-friendly terms, of particular significance within a biopolymer compostable solution, points out Sun Chemical’s technical director of packaging (Europe), Paul Hunt.

“As long as the ink printed onto any pack represents less than 5% of the overall weight, we know that it won’t interfere with plant growth; in other words, it’s perfectly safe to compost along with the substrate.

“That’s just as well, since the problem with going the totally sustainable route is the inevitable limitation on colorants, most of the natural ones, for example, being not resistant to light. Indeed, most of the pigments used today in food packaging are pretty much self-selecting because they’ve been proved to be light and heat fast. Natural pigments are that much weaker, so if you have a pack with any degree of shelf-life then you are more or less bound to work within a very tight colour gamut

“If packaging was generally going to be printed, converted, used and discarded within a matter of just a few days then it could be quite feasible to select natural pigments – but in terms of the modern supply chain that just wouldn’t be feasible, since in reality products need to remain stable on-shelf for six to twelve months or longer. That very much limits the options you’ve got. So, broadly speaking, as long as there’s not much of it, it really doesn’t signify what the ink is made of.”

And what with some colours containing a higher than average level of toxicity – the copper element that occurs naturally in cyan blue and black – the inevitable conclusion is that the only truly eco-friendly ink formulation might just as well be invisible; a commercial oxymoron in effect, given that the overriding requirement of any ink is to deliver text and graphics that are not only fit for purpose, but that physically sell the product on-shelf.

In general terms, for food packaging, no inks are designed specifically for recycling; not least since some substrates, irrespective of what’s printed on them, aren’t designed to withstand the waste recovery process – which in itself has a sketchy track record when it comes to managing separation and de-inking; particularly with flexibles.

Although something that could be easily de-inked and uncured might only represent the most eco-friendly solution on paper, the reality is that solvent-based UV cured inks are selected for a wide range of packaging applications because they meet time, cost and performance criteria. Sun Chemical’s recently introduced SunUno Solimax, for example, is a solvent-based solution capable of fulfilling a multiple number of surface printing and laminated applications that can be run equally as well on either flexo or gravure presses.

Closing the gap

Water-based formulations that are more intrinsically eco-friendly could fulfil a greater range of packaging applications. Now is the right time for converters to reassess their options, says Flint Group’s paper packaging technology manager Marc Los. “Because our new generation of water-based inks for flexible packaging is based on a self cross-linking binder technology, it shows excellent printability and improved properties compared with traditional water-based systems.

“Drying speeds are also catching up with solvent-based; not least by printing with lower anilox volumes, resulting in lower film weights, which again once wasn’t always possible with the traditional water-based ink systems for film. For example, at Drupa we were able to run 500m/min in 4-colour+ white inks on a Comexi F2 flexo machine using low volume aniloxes (420 l/cm 4.0g/m2) resulting in prints with excellent trapping properties and dot formation.”

With discussions on legislation, and the wish for sustainable solutions ruling against the use of solvents likely to gather momentum, the decision could be taken out of the industry’s hands; indeed, Los estimates that 10% of the Flint Group’s total water-based sales is already outside the traditional area of absorbent substrates, and will go higher as a result of committed supply chain collaboration.

In the meantime, Flint Group’s Premo Film SXS water-based flexo ink series for surface printing on polyolefin films – based on a self cross-linking technology that enables the ink film to have very good adhesion to non-absorbent substrates such as OPP and PE – is also available for compostable packaging, including end-use applications such as carrier bags and deep freeze packaging.

Water-based PremoFilm SXS flexo ink PremoFilm SXS Low migration mineral-oil free ink for offset printed cartons Low migration SunUno Solimax solvent-based ink for flexo and gravure Solimax

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Flint Group
Sun Chemical