Fresh Ink

Sun Chemical Introduces Wet Trapping EC Inks for Flexo


Sun Chemical Ink (GPI) unveiled WetFlex EC, a new flexographic printing process that utilizes UniQure inks, Sun Chemical’s innovative line of wet-trapping UV and EB inks for the flexographic printing process.
“This unique flexo ink technology has the potential to revolutionize the Common Impression (CI) flexo printing process as it exists today,” said Mike McGovern, director, sales and marketing for energy curable products.
“Printers have told us that the CI-flexo process could be made more efficient,” said Chris Morrissey, vice president, sales and marketing. “Sun Chemical listened and then dedicated its considerable resources to finding an innovative answer to customer needs with this new ink technology.”
The WetFlex EC process can completely eliminate the need for inter-station curing while printing multicolor jobs on a non-absorbent substrate, said Dr. Subh Chatterjee, director, energy curable R&D.
 “With the new process, colors simply trap over each other from one printing station to the next without smearing,” Dr. Chatterjee said. “These are energy curable inks that do not contain any VOCs. The only requirement is to have an electron beam unit or a set of UV lamps after the last printing unit to dry the printed matter.”
Energy curable inks dry virtually instantaneously when exposed to EB energy or light from a UV lamp. It is relatively easy to wet trap two colors on a porous substrate, as solvent or water from the inks simply absorbs into the substrate. However, for printing on nonabsorbent substrates such as films, an external UV or EB energy source eliminates the ink volatile from the first down color and increases the viscosity or tack so the ink does not transfer back or contaminate the next color being printed.
Under current systems, EB flexo technology requires usage of UV flexo inks, semi-drying them with inter-station UV lamps and then completely curing them by exposing them to EB after the final printing station. The UniQure ink technology removes this fundamental limitation by allowing multiple colors to trap over one another on a nonabsorbent substrate without requiring an energy source in between the print stations.
This is the revolutionary aspect of the process, Dr. Chatterjee said. An EB unit or UV lamp at the end of the CI-flexo press is the only energy source required to instantly cure the printed image and render it fit for further processing. There are no restrictions on sequence or number of colors for any multi-color printing process. The printing speed can be as high as 1000 feet per minute, he added.
According to Mr. McGovern, the largest impact could be in printing for flexible packaging, where the new process could open the door to many converting opportunities that were thought to be unattainable.
For example, he said, an existing converter with a conventional flexo CI press might adopt WetFlex EC process with the minimal investment of adding an in-line EB unit or UV station after the final station. Multiple inter-station dryers, with their high-energy consumption, would no longer be required. Accordingly, incinerators could be shut down or eliminated, depending on the penetration of the WetFlex EC technology into the pressroom or the plant. The net impact for converters would be economic savings in terms of energy and environmental regulation costs.
Since UV flexo inks have higher viscosity than solvent or water-based flexo inks, they also offer improved dot structures, Dr. Chatterjee said, resulting in improved print quality. Furthermore, he added, since no heat is involved in the overall process, improved registration of thermally sensitive films is likely.
Since inter-station drying would no longer be needed, Mr. McGovern said the design of presses with common impression cylinders could be simplified. New presses could have a smaller footprint, allowing better space management in the pressroom. Potentially, these presses also could be more economical, reducing capital required for expansion, he said.
Converters working to comply with environmental regulations might install an EB unit at the end of an existing press to eliminate VOCs, said Dr. Chatterjee. For jobs where lamination is a requirement, Dr. Chatterjee said, an in-line EB lamination unit could be used.