Novel Printing Concept for Sustainable Packaging

With recent advances in waterborne energy curing resin technology, an elec-
tron beam (EB) curing gravure printing process has been developed which allows elimination of VOC emissions and reduces energy consumption while providing outstanding aesthetics, chemical, physical, and functional properties. These inks can run on existing gravure presses already using EB technology for varnishes at costs that are competitive with current solvent-based printing.

Gravure application

EB curing provides the means for addressing the shortcomings of aqueous gravure inks. Novel UV-cured, water-based polyurethane resins designed originally for use in different coating formulations, attracted the attention of IdeOn LLC, a New Jersey-based company specializing in UV and EB curable products. "Gravure provides great quality and performance, but the emissions issue is becoming prohibitive," notes Dr. Subh Chatterjee, managing partner of the company. "We are looking to take this technology to a new level in order to gain that performance, but in a sustainable, truly VOC-free manner with a noticeably reduced carbon footprint."

IdeOn has partnered with Connecticut-based Amgraph Packaging to develop and test water-based EB gravure inks and printing processes. According to CEO Kenneth A. Fontaine, "Our goal in working with IdeOn is to develop completely VOC-free inks that still provide the high level of performance that gravure inks are known for."

The two companies used waterborne UV resins offered by Cytec Industries, a supplier of UV/EB curable systems for a wide variety of ink and coating applications. Nearly 20 different water-based resin dispersions were evaluated for their drying speed, curing properties, and scuffability, with several meeting the desired performance requirements. The best resins appeared to be polyurethanes (aliphatic or aromatic) or polyurethane/acrylic co-poplymers.

The new inks were formulated with viscosities of 20-30 cps, levels similar to those for solvent-based systems. A low and consistent viscosity level throughout the printing process is important in gravure printing to obtain good ink release from the cells and transfer to the surface, especially at the high press speeds common for this printing method. Minimum flocculation was observed even at very low stress levels (< 1 Pa) for yellow, magenta, and cyan inks, while the black ink showed some flocculation tendency, but it disappeared at slightly higher stress levels (~2.5 Pa).

Evaluation of the required dose of EB energy also provided positive results. Different cyan inks were applied over polyethylene terephthalate (PET) film, dried and cured. It was determined that the amount of EB energy required is similar to that used in other EB printing applications (10–30 kGy).

Results are in

During field printing tests conducted at Amgraph, initial formulations of EB cured inks (CMYK, cyan, magenta, yellow, and black) were found to have desirable and consistent optical print densities and solvent resistance at different press speeds (500, 750, and 800+ feet per minute) and a moderate EB dose (20 kGy). Solvent rubs (isopropyl alcohol) generally fell in the range of 30–40 for the individual colors and approximately 60 for the four-color trap, which is a significant improvement over typical water-based inks (typically only 1–2 IPA rubs). Furthermore, the color came up quickly and the cured inks had much higher gloss compared to waterborne alternatives, according to Amgraph's director of R&D Sean Evans.

Still work to be done

IdeOn and Amgraph continue working to further optimize the printing performance and expand the scope of applicability for their new EB gravure printing technology toward different substrates. Ultimately they plan to offer a package of different colored inks including white, and are exploring EB solutions for other applications such as in-line EB laminating adhesives and overprint varnishes. The expectation is that the technology will be commercialized in 2011. IdeOn plans to license the new EB Gravure printing process to other ink formulators on a worldwide basis beginning in 2011-2012. pP

Authors:

Mikhail Laksin, VP Technology, IdeOn LLC, Hillsborough, N.J.
Ken Fontaine Jr., President & CEO, Amgraph Packaging Inc., Versailles, Conn.
Sean Evans, Director R&D, Amgraph Packaging Inc., Versailles, Conn.
Jo Grosman, Global Marketing Manager Graphic Arts, Cytec Industries Inc., Woodland Park, N.J.