Novel Printing Concept for Sustainable Packaging
An electron beam (EB) curing gravure printing process eliminates VOC emissions and reduces energy consumption.August 2010
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.
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).