All photos courtesy of Comexi
Until recently, packaging printing was dominated by solvent-based ink technologies, applied with flexo or rotogravure technology, requiring solvent recovery systems or solvent incinerators. Nowadays, these technologies are under strong social and political pressure. Alternatives must be developed and implemented globally, so environmental goals can be reached.
There is a huge spectrum of possibilities to get rid of solvents when printing flexo. The difficulty is making the right choice between them. Each has its pros and cons. In the case of water-based inks, we know how they are applied and what the machine does with them, but when we go to curable inks, there are still a lot of questions about behavior, inking systems, doctor blades, ink temperature, trapping, etc.
Non-curable inks (water-based) are the “easiest” or “most obvious” alternatives to solvent inks, as they do not require big investments or changes to existing equipment. One flexo machine that today is printing with solvent-based inks can be easily switched over to print water-based inks with low investment, even if a reduction in printing speed is necessary due to drying capabilities.
Curable inks, or hybrid inks, are more difficult, as they require a high investment to adapt the curing equipment (electron beams or UV lamps) and inking systems in an existing machine. When we talk about curable inks, we need to differentiate between existing technologies:
- UV-curable inks are widely used in label printing, but not so much in packaging because of the presence of photoinitiators. The combination of the high, concentrated power of UV LED lamps and low-migration inks has re-awakened interest
- At present, no electron beam technology is being used widely, but in the last four to five years, changes in solvent regulation and the involvement of some brand owners in solventless printing have generated interest. This has opened the gate for two electron beam ink technologies to appear that can help make the definitive switch to curable inks. Both were developed by well-known ink manufacturers
- Hybrid inks—a mixture of water-based inks and curable inks—are quite easy to use because they print like normal water-based inks. Once passed through an electron beam and cured, they have most of the properties of curable inks—resistance, brilliance, etc.
[perfectpullquote align=”full” cite=”” link=”” color=”#e2de68″ class=”” size=””]”The old rule, ‘simple product, simple machine,’ does not apply anymore.”[/perfectpullquote]
Presses Meet Protocol
Efficiency contributes to sustainability. Emphasis is on high print quality, fast job changes and short to medium run lengths. Reduction of setup waste and obsolete stock are seen as definitive, sustainable advantages of any press.
Converters have always faced the difficult challenge of achieving high productivity while maintaining exceptional quality. The former is the driver to competitive prices while the latter is increasing rapidly because of the high standards of added-value packaging components.
What is the right technology to get rid of solvents? In which machine do printers need to invest? A clever solution is a machine fully adapted to print solvent inks, water-based inks and electron beam curable inks. Comexi’s F2 hybrid press serves as an example. Such machines allow printers to print with solvent inks and begin testing different technologies until they identify one that best suits their needs.
An upcoming trend is the growing use of energy-curable ink, more specifically electron beam. When it comes to migration risk, electron beam ink systems have a clear food safety advantage over UV-curable systems that contain significant amounts of photoinitiators.
An electron beam curing system is robust and color blind, turning the polymeric inks from fluid into a solid state in a fraction of a second. Once cured, these inks match perfectly to an increased use of solvent-free adhesives.
In certain aspects, electron beam curable ink systems are actually considered more sustainable than water-based systems, which require serious energy levels in order to vaporize all the water from the ink and maintain reasonable press speed.
An additional advantage and contribution to sustainable printing is the suitability of a press to work with 7-color process, also known as expanded gamut (EG). Running with EG dramatically reduces ink stock and the risk of obsolete inks, and requires a minimum of ink changes. Electron beam inks do not dry or cure in the roller train and can even be left over the weekend. This contributes directly to lighter cleaning requirements, and a reduction in both ink consumption and ink waste.
Coating & Laminating, Too
High-performance solventless adhesives, already a reality for many applications, offer simple, low added-value structure that has evolved to become among the most advanced final products. The old rule, “simple product, simple machine,” does not apply anymore. Nowadays, new products with aluminum, thick structures, pouches and high added-value end products are produced in solventless machines.
New generation laminators are capable of running as fast as 1,312 fpm and 1,640 fpm with minimum power consumption. Tension control perfected through dancer rollers has been standardized and the same can be said of the fully motorized coating side. To achieve the highest efficiency and quality control, a coating weight sensor can obtain measurements inline. This way, converters can measure and adjust the coating weight, reducing the final amount of packaging adhesive, making the laminating process more economical as well as environmentally friendly. Thanks to this motorization, the cleaning process has quickened to 10 minutes, reducing the amount of solvents used. The sleeve in the metering roller brings flexo dosing quality and the fastest changeover time on the market—less than two minutes!
Today’s solventless laminators deal with thick, multilayer structures and are configurable with one, two or three non-stop turret winders; this avoids continuous stops in production. Typically, a standard thick structure of 100-μm. will halt the production every 20 minutes, decreasing the production up to 25 percent in reel changeover.
With everything controlled by the latest state-of-the-art electronics and software, integrating all peripheral equipment into a single converting line affords production traceability. All this turns an environmental and sustainable solution like solventless into an extremely profitable alternative for all kinds of packaging.
With the advent of Industry 4.0—the Internet of Things (IoT)—helping to control and analyze production, things are getting better and better. An online platform generates automatic key performance indicators (KPIs) and reports—all of which are accessible from everywhere and every device, making for a 24/7 tool to see real online production, as well as historical data and future machine demands.
Being eco-friendly and having total traceability of the jobs has never been easier! Mission accomplished! This is better packaging for a greener world.
About the Authors: Jordi Puig Vilà, technical director BU flexo, is a mechanical engineer. He holds an MBA from the University of Girona.
Carles Rodríguez i Nieto, global brand manager – lamination, has 15 years’ experience in international sales and marketing, and seven with Comexi. He has overseen several markets: Asia, Australia, Africa and the Middle East, and now leads Comexi’s global marketing efforts for lamination. He has a master’s in engineering and an executive MBA.
Adelbert Schoonman, R&D manager, application development for BU-Offset holds a degree in mechanical engineering and management of product development. He has more than 15 years’ experience in design and development roles in web offset. He has been with Comexi for more than eight years.
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