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Drying, Curing & UV


New sustainable applications in drying, curing & UV technology


By Jonathan Sexton, marketing manager, Sun Chemical W


hile solvent-based is still the drying method of choice for many flexible packaging converters, some


industry observers are reporting a shift towards energy-cured inks and processes, such as UV LED and EB (electron beam), to address productivity and sustainability demands – for example, VOCs (volatile organic compounds) released from solvent- based inks from presses without containment systems can contribute to climate change. In addition to potentially lower solvent emissions, solvent-free drying systems can meet many of the current market demands such as run length reduction and high-quality printing. UV LED is a well-established,


environmentally sound curing alternative within the commercial print market which is now penetrating the narrow web label space. In some instances, it is even expanding into flexible packaging markets. UV curing works as a photopolymerisation process that uses UV energy to cure the ink via the use of photoinitiators that produce free radicals to crosslink monomers and oligomers. UV LED lamps avoid the use of mercury found in traditional UV, while using less energy than standard UV and solvent- based methods. They offer better register and more stable and consistent printing, particularly on low grammage, thin and heat sensitive materials, due to the lack of heat emission from the UV LEDs onto the substrate. Sun Chemical has ranges of non- food and migration-compliant, offset and flexo UV LED inks available for packaging. These inks can be used on a variety of substrates, including films, foil, paper and other speciality substrates. Electron beam (EB) curing inks are another alternative to solvent-based evaporative drying, delivering excellent


14 October 2020


print quality and productivity with wet-on- wet printing and a single curing unit at the end of the press. A key advantage of EB curing inks is that, unlike UV inks, they don’t require photoinitiators, as the electron beam is powerful enough to polymerize the ink. This is an added benefit, especially as some photoinitiators have been subject to supply chain disruption and health and safety reclassification in recent years. As the inks are cured in a single unit, the need for multiple large drying ovens is eliminated, reducing energy use. Containing on average 30 percent of bio-renewable carbon content, Sun Chemical’s SunBeam Advance 5 (for offset EB) also offers a further sustainability benefit. As they don’t contain photoinitiators, EB


inks eliminate one potential source of ink component migration into food packaging. This makes them ideal for food and pharmaceutical packaging. Furthermore, EB curing, particularly in offset printing, offers faster set-up time and greater uptime, which better suits the demands of short-run work. With EB processes, expanded color gamut printing can also be used to run a press more efficiently due to the limited ink change downtime. As with UV LED, EB curing runs cooler than traditional UV curing, which makes it a good option for thin plastic and film substrates for food packaging. Despite all of these benefits, while a


growing number of companies in the industry are starting to use EB and LED curing in flexible packaging, it is important to note that this is still a developing area. UV and EB inks can be used successfully


for many applications but it can be a challenge to achieve the adhesion of solvent-based inks across a wide range of substrates. Care is required in substrate selection as well as careful testing of high-


performance applications, such as lamination. Nevertheless, an increasing number of converters are investing in these technologies as they are facing increasing demand for short-run work, for which solvent-based gravure printing may not be economical due to relatively high set-up costs. For long run, high speed printed filmic packaging however, traditional solvent- based printing is still the most economical and polyvalent solution. Those opting to use UV and EB inks tend


to be companies focusing on sustainable solutions and those specializing in short run lengths. Another way in which Sun Chemical is assisting converters moving away from solvent-based printing is via water-based inks. In addition to a wide range of water-based inks for paper and filmic packaging, Sun Chemical’s SunVisto AquaGreen water-based inks are formulated with significantly high levels of bio- renewable resin content, making them a high sustainability printing option. However, it is important to note that


sustainability within flexible packaging printing is not just about reducing certain types of solvent-free printing. Sun Chemical is also actively developing solutions in multiple ink technologies for paper printing, deinking and higher bio renewable content, including more sustainable solvent based solutions. Overall, for the reasons outlined, UV, EB


curing along with traditional solvent-based drying all have a role to play depending on the company requirements. Life cycle analyses which quantify carbon emissions are complex, so converters should be mindful to assess their own business when exploring what solution is best for them, their customers, and the environment.


usunchemical.com convertermag.com


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