Flexo - the key to sustainability in package printing
As far as environmental perceptions are concerned, 2018 can be regarded as a pivotal year. The scale of the damage to the climate from greenhouse gas emissions and plastic waste is becoming apparent, bringing with it a profound change in attitudes: consumers are shunning non-recyclable packaging and demanding government to outlaw their use.
Hardly a week goes by without being confronted by harrowing images or alarming studies: consider the marine life choked by bags and netting, floating islands of rubbish and beaches strewn with decades-old litter, as well as reports of carcinogenic microplastics permeating the food chain.
Plastic can take centuries for plastic to break down – scientists estimate that it will take up to 450 years(1) for plastic bottles to disappear - and yet every year, between 5 and 13 million tonnes are added to the oceans(2). PET, the most commonly used material for plastic bottles, is being recycled at rate of only seven percent: brand owners generally do not consider the material in its recycled state to be clear enough, and there are simply not enough facilities to keep up with the dramatic surge in consumption. Attention has also turned to the poor recyclability of disposable paper cups, as a high proportion of them contain a polypropylene lining that very few waste-handling facilities(3) have the capability to process.
New statistics from the European Parliament suggest that bottles and lids account for a fifth of all marine litter in EU waters, so it is no wonder that the packaging and quick-service restaurant industries have become targets for criticism.
Government legislation is being passed to curb plastic use and encourage more responsible consumer habits: Kenya introduced a ban on the production and sale of plastic bags in 2017, and its success is inspiring at least four other African nations(4) to follow suit. The European parliament voted overwhelmingly for a complete ban on various single-use plastic products such as cutlery, plates and straws, effective from 2021.
There is also an urgency to act at a global level to reduce carbon dioxide emissions that, at 38bn tonnes annually, is far greater than the planet’s photosynthesising plants and rocks can absorb. This has already led to a rise of global surface temperatures by 0.8°C since the start of the industrial age – and a rise of 2°C is as much as the world can adapt to without long-term devastating consequences(5). In this context, this summer’s forest fires in the Arctic circle can only be seen as a prelude.
Innovation offers growth opportunities for paperboard packaging
Faced with a consumer backlash, brand owners and retailers are realizing that sustainability is not just a matter of saving costs – reputations are at stake. It is imperative that market players look closely at materials and processes that minimize the environmental burden.
It is encouraging to see global market leaders investing heavily in finding eco-friendlier alternatives to plastic disposable cups, lids and containers.
Starbucks is investing in research to develop fully recyclable cups(6), using biodegradable plastic, while Tetra Pak is developing paper straws and caps made from a polyethylene byproduct of sugar cane(7). Water-based polymer coatings have been developed that can safely dissolve when the carton cup or plate is repulped, so it can be sorted with regular paper.
These developments make paper and carton packaging a practical and economically viable alternative to plastic for a variety of liquid food and dairy segments, as well as for secondary packaging.
Flexo for lower emissions and lower waste
The switch to carton packaging makes it possible to use printing and converting processes that produce lower levels of emissions and waste. Gravure and offset processes tend to use inks with relatively high solvent content, and involve costly tooling and engraving processes with high carbon footprints. Flexo offers significant sustainability advantages compared with other printing processes, with eco-friendlier water-based inks, recyclable polymer plates and sleeves, and emerging LED-UV curing technologies.
Thanks to advances in press and ancillary technologies, flexography is becoming a greener and ‘leaner’ process, requiring less energy and water, while generating less material waste and emissions.
Inline flexo is beneficial for fast water-based printing because a longer web path between printing stations is possible, making unit-to-unit drying possible, and thus cleaner colour printing.
Air drying systems
The key to high-performance, sustainable drying of flexo inks lies with using air velocity at the lowest possible temperature, while recycling as much air and energy as possible. Reducing drying temperature in turn reduces energy requirements and eliminates the need for chill rollers afterwards.
Drying speeds and energy efficiency are optimised by situating the fan that applies the air and pressure inside the drying hood, shortening the distance from the fan to the air nozzle. This enables heat and noise to be contained within the head and provide better insulation.
The optimum air velocity – temperature combination varies according to factors such as the thickness of the ink coverage, substrate type, web speed, and time spent in the drying unit. TRESU’s research and development specialists have worked to devise energy-conserving drying systems for numerous printing applications, often in partnership with substrate manufacturers. Additionally, power consumption and CO2 emission levels from a hot air drying system are only 25 percent as much as those associated with UV-curing.
Optimising energy efficiency
An important energy and emission-reducing factor is the ability to recycle energy. Efficient energy consumption is achieved with a gas-heating solution and a software design where servo motors run at relatively low power. Drying units recycle a high proportion of the air inside the dryer and, from the exhausted air, much of the energy is recycled by a central heat exchange module. In the case of TRESU drying systems, up to 80 per cent of the air inside the dryer can be recycled.
Chilling systems safely extract heat from the press to external condensers, which can return the energy to the incoming cold fresh air. The chilling system’s ‘split system’ design does not interfere with the printing process or place additional demands on the facility’s existing heating, ventilation or air-conditioning systems. In this way, up to 60 per cent of the exhaust energy can be recycled.
Reducing material waste
Today’s inline flexo machines feature advanced controls and ancillary equipment to ensure stable printing at faster speeds with minimal substrate or ink waste.
Automated register controls and spectral colour measurement systems enable the press to meet tight targets at the beginning of the production run, limiting startup waste to within the length of the press. Web controls also reduce waste, by holding register as the press ramps up at the start, and when it reduces speed at the end of the production run.
Automating ink supply
Automated ink supply systems provide the solution for reducing ink waste - as well as clean printing at high speed, elimination of leakage and increased machine uptime.
A supply system works harmoniously with a chamber doctor blade that features a rubber seal system, creating an enclosed environment that stops leakage, emissions and any opportunity for the ink to react with the atmosphere.
Automating characteristics like viscosity, pH value and ink temperature is an effective way of reducing waste. The ink supply system automatically regulates flow rate, pressure and viscosity, as it feeds ink to the chamber. In turn, the chamber feeds ink to the cells of the rotating anilox roll. Exactly the right pressure is maintained so there is a constant presence of ink between the blade and the anilox roll during production, stopping air bubbles from entering. In turn, this ensures blister-free printing, throughout the production run, at speeds of up to 800 metres per minute.
After the production run, the supply systems can perform automatic ink changes. They return almost all the ink remaining in the chamber to the bucket, cleaning without human intervention in minutes. At TRESU we have helped packaging converters achieve ink yield improvements of 30 per cent, by modernising their presses with an enclosed ink flow, featuring the F10 iCon supply system. Ink supply systems and circulators are also available for handling water-based, UV-curable and solvent coating media with relatively large particles and higher viscosity.
The enclosed chamber system enables more economical use of water for cleaning. First, with no leakage, the environment surrounding the press is likely to be cleaner. Second, carbon fibre chamber surfaces repel the ink enabling thorough cleaning with less water. There also self-cleaning chambers, such as TRESU’s MaxiPrint Concept, feature nozzles that jet water at high pressure, economising further on cleaning water.
Stable systems make flexo viable for more jobs
By incorporating the drying, ancillary and automated control systems, described above into an inline flexo press, therefore, stable printing is possible, at speed, with minimal defects or waste. This means flexo can achieve high definition up to at least 70 lines/cm with precision, not only faster, but at a lower unit cost.
With its lower emissions and the flexibility to include sophisticated converting processes, water-based flexo becomes the process of choice for numerous applications that were once only possible with gravure or offset. Examples include simulations of metallic foil to double sided coatings that protect the carton against moisture and grease.
A printing press should be an investment that brings returns for 20 years or more. There is a great responsibility to give careful consideration to the machine specification, because over such a long lifespan, this makes a big difference to the converter’s overall environmental – and financial - performance.
Undoubtedly, there is also a financial incentive to implement sustainable processes and practices, because the reduced consumption of materials, logistics, manual input and energy they bring results in lower cost-to-print and, in turn, greater profitability.
Arguably though, there is a yet greater motivation for the packaging value chain to care about how they affect the environment, than the profitability of the production line – important though it is.
Brand owners increasingly recognize that their market success and relevance depends on a good reputation for sustainability, among more socially aware consumers. They also face increasing pressure from a growing number of ‘ethical’ investors(9), as well as politicians, who see more stringent environmental legislation as a vote-winner. We can thus expect packaging buyers to look more closely at the environmental record of their suppliers.
With a modern inline flexo press, a packaging supplier is well-placed to show leadership in this area: it provides the flexibility to compete for short and long production runs, and the opportunity to contribute to a sustainable value chain as a “Green Technology Ambassador”.
(1) ‘How long does it take trash to decompose?’ – 4ocean.com, 20th January, 2018:
(2) ‘Rethinking the future of plastics’ – Ellen MacArthur Foundation, 2016: https://www.ellenmacarthurfoundation.org/assets/downloads/EllenMacArthurFoundation_TheNewPlasticsEconomy_15-3-16.pdf See also ‘Turn down the heat’ (first publication) World Bank, 2012: http://www.worldbank.org/en/topic/climatechange/publication/turn-down-the-heat
(3) ‘Call to step up coffee cup recycling in battle on plastic waste’ – Financial Times, 27th January, 2018:
(4) ‘Eight months on, is the world’s most drastic bag ban working?’ - The Guardian, 25th April, 2018: https://www.theguardian.com/world/2018/apr/25/nairobi-clean-up-highs-lows-kenyas-plastic-bag-ban
(5) ‘European Geosciences Union: Act strongly before 2035 to keep warming below 2°C’ – Sciencedaily.com, August 30th, 2018: https://www.sciencedaily.com/releases/2018/08/180830084818.htm
(6) ‘Starbucks commits $10m to decade-old pledge for fully recyclable cup – Packagingnewsco.uk, 22nd March, 2018: https://www.packagingnews.co.uk/news/markets/coffee-and-paper-cups/starbucks-commits-10m-decade-old-pledge-fully-recyclable-cup-22-03-2018
(7) ‘Caps from sugar cane’ – Tetra Pak:
(8) ‘Technology allows for wider coffee cup recycling’ – Pulp and Paper Canada, 25th May, 2018: https://www.pulpandpapercanada.com/news/technology-allows-for-wider-coffee-cup-recycling-1100001178
(9) ‘Busting the myths about ethical investing’ - George Salmon, Hargreaves Landsdown, 20 September, 2018: https://www.hl.co.uk/news/articles/busting-the-myths-around-ethical-investing See also ‘Sustainable investment joins the mainstream – The Economist, 25th November, 2017: https://www.economist.com/finance-and-economics/2017/11/25/sustainable-investment-joins-the-mainstream
To understand the spread of plastic waste around the globe’s oceans, visit:
Studies have long shown that environmental and social concerns are strong purchasing drivers, with consumers willing to pay more for products with an environmentally friendly package.