Thermoforming warms to its green credibility
As a technology, thermoforming now has a surprisingly green story to tell. As Paul Gander reports, this is about energy efficiency as well as weight reduction.
Only a few years ago, plastics had a poor environmental reputation. That has begun to change, largely due to recycling initiatives involving plastic bottles and UK investment in this area.
But while other pack formats have had a slower start with recycling, equipment companies have paid more attention to energy efficiency and the overall sustainability profile of the technologies used to form those packs. Any technology with heat in its name, it might be supposed, would be off to a poor start in the energy efficiency stakes. But thermoforming equipment suppliers are now offering some interesting options in this area. The same is true for materials savings.
Of course, both types of saving are likely to have as much to do with operating costs as with sustainability. But with the supply chain scrutinising carbon footprint more closely than ever, converters and brand owners are eager to have greener practices.
As an equipment supplier, GN Europe focuses on machines suitable for thinner-walled packs of the type used in the food industry. Sales Director, Marek Nikiforov, says, ‘While the bigger, higheroutput machines of our competitors will typically have power requirements of between 50 and 70kw, GN machines are just 7.5kw. Energy efficiency wasn’t so important in the past, but now it’s starting to be a priority.’ Nikiforov is the first to point out that GN machines also have a lower output. But even if you ran two of these machines instead of one higher-output competitor system, Nikiforov says, you would still be making an energy saving.
Since most of a machine’s energy requirements are channelled into heat, this is where the savings can be made. With a polymer such as PET, GN uses direct as opposed to radiant heat. This means that in order to achieve the 120°C needed to form the sheet, the plates require heating to the same temperature. Where radiant heat is used, he argues, the plates may need to be heated as high as 400°C.
This energy efficiency is typified by GN’s 3021DX machine, which the company dubbed ‘the greenest thermoforming machine in the industry’ during the last K plastics show in Germany. The claim was based on a study commissioned from the Intertek consultancy. But the study did not focus exclusively on energy consumption. By leaving a minimal gap or using common-edge cutting between cavities, GN says it makes significant materials savings, too. This compares with the wide gap of up to 30mm between cavities that tool-makers are more often asked to provide for the sake of higher throughput. ‘The biggest single cost is material,’ says Nikiforov. ‘By being more material-efficient, you can reduce your total production costs by 10%.’
Meanwhile, to return to the other major cost and environmental impact, radiant heating tends to be used in higher-output machines, especially on polypropylene. But even where radiant heating is required, greater efficiency is possible. For instance, GN’s latest machine uses infrared heating rather than less efficient ceramic heaters.
But GN is not alone in focusing more on the various efficiencies possible in the production process. Other equipment suppliers have in the past tended to emphasise high output and final component quality. ‘But I’ve seen that many of them are talking about more efficient heaters than the traditional ceramic type,’ says Nikiforov.
Major suppliers such as Illig are understood to be developing more heatefficient options. Kiefel, another machinery company focused on high output, agrees that energy efficiency is increasingly a priority. But it sees this as a gradual evolutionary process, and one with several different parts to it. The efficiency of the heating elements themselves has risen by up to 15% over the past two years or so, says director for the packaging industry Erwin Wabnig. But as a machine builder, Kiefel says it is reliant on its component suppliers for this type of improvement.
Other efficiencies are the product of Kiefel’s own engineering, and are associated with higher rather than lower operating speeds. ‘By speeding up production, and moving the film more quickly, we are able to save energy on the heating side,’ says Wabnig. By halving the time taken by some operations, he estimates that heat energy savings of up to 5% can be made. ‘The next element to introduce is energy feedback where, as in a car, the energy used in braking can be fed back into acceleration,’ he adds.
Importantly, too, thermoforming system efficiencies in terms of both energy and scrap can often be combined with material reductions in the final pack. This is especially true when an operation moves from using pre-formed trays to a form-fillseal (FFS) type thermo-forming line.
While machine efficiencies can provide the supply chain with cost and carbon footprint reductions, a lighter pack gives retailers a visible and marketable sustainability benefit for their consumers.
As the latest figures for the second phase of the Courtauld Commitment demonstrate, packaging reduction continued during 2010 across the UK’s more important brands and retailers. ‘This trend is still there,’ says marketing manager at Multivac, Andrew Stark. ‘Users of semi-rigid packaging are asking, for instance, whether they can move to a flexible pack.’ Flexible skin-type packs can be thermoformed with or without a base tray.
But the Darfresh type skin-pack incorporating a base tray is already cutting materials weights for operations moving away from a preformed tray and lidding film. It also means that companies are shipping rolls of film rather than high volumes of rigid trays, Multivac argues. In the case of Darfresh for products such as fish, packaging weight reductions combine with other benefits. ‘You get better on-shelf presentation options, improved aesthetics from the point of view of blood and other fluids, an often longer shelf life than with modified atmosphere, and improved space efficiency in the supply chain,’ says Stark.
One further element of sustainability that is helping the thermoforming industry is the availability of greener materials. Omanbased Octal supplies direct-to-sheet PET (DPET) that avoids five particularly energy-intensive stages in the traditional sheet-forming process. This means it has a significantly lower carbon footprint than material from any of its competitors, says Octal.
In addition, by May 2012, Octal says that new facilities will have more than doubled its capacity in PET sheet and resin from 400,000 to 927,000 tonnes. As a part of this expansion, MD Nicholas Barakat says the company intends to build on the current 20,000 or so tonnes of recycled PET (rPET) it produces.
At Kiefel, Wabnig says that rPET first peaked as an issue in thermoforming around three years ago. ‘It will have an even bigger role in future, and is already influencing the development of the thermoforming process. For instance, it’s a tougher material than others, so you need more power in the cutting station.’
From the point of view of the energy and thermal efficiency of equipment, potential reductions in production waste, lightweighting options – particularly on FFS lines – and increasing use of recycled content, thermoforming has the opportunity to sell itself as a technology that takes its environmental responsibilities seriously.