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FLEXO Magazine : March 2011
Technologies & Techniques significant renewable content that performs much like petroleum-based polymers. • Solvent-borne urethane resins based on bio-derived poly- ols, which result in polyurethane resins with significant bio-renewable content. Several versions closely offset both plasticizing and film-forming urethanes. Case study A case study in formulation using a common, water-based ink demonstrates the possibilities of bio-derived ink formula- tions. The ink used in this case study is typical of water-based inks used in flexible packaging; it is based on petroleum- derived polyacrylic resin and additives, uses standard organic and inorganic pigments and contains no bio-derived content. It is printed on clay-coated paper stock for multi-wall bag applications, and it may be overprinted with water-based or energy-cured overprint varnishes or used without overprint. The ink has excellent scuff resistance, a high coefficient of friction, and high heat resistance and it allows gluing to form bags. The goal of this exercise was to formulate two inks with significantly higher bio-derived content without affecting quality or performance. There were two formulation paths. Option 1 employed two new polyacrylics that contained bio-renewable monomers, both of which had a bio-renewable content of 35 percent—40 percent based on weight of dry resin. Option 2 used a 100 percent bio-renewable polysaccharide resin. Early tests showed that polysaccharide alone would not achieve the necessary wet-scuff resistance, so a modified rosin with 70 per- cent renewable content was chosen to enhance its properties. Table 1 summarizes the property results. Scuff, heated scuff, coefficient of friction and gloss were equal for all three inks. It is worth noting that the Option 2 ink offered better resolubility and clean-up on press than the standard and Op- tion 1 inks. Option 2 inks also had higher transfer on several flexographic presses, with better color and more ink delivered to the substrate. Wet scuff was the only property where the Option 2 ink did not equal the standard ink. The Option 2 inks had to be overprinted to achieve the exact wet-scuff perfor- mance of the standard ink. taBLe 1 – RenewaBLe InK PROPeRtIes COMPaRed tO standaRd ScuffHeatedScuffWetScuffCoFGlossResolubilityTransfer Option #1 = = = = = = = Option #2 = = < = = > > “=” – equal to “< ” – performed slightly less than “> ” – performed slightly better than Although the bio-derived content had been significantly increased in both Option 1 and Option 2, the inks differed little in performance. Table 2 summarizes the bio-content of all three inks in four common ink formats. “ Line Extender” represents the varnish used to blend pigment concentrates and cre- ate a finished ink for printing solid blocks of color. “ Line Ink” represents a finished ink used to print solid blocks of color. “Process Extender” represents the varnish used to blend with pigment concentrates to create a finished ink for process dots and screens. “ Process Inks” represents finished inks used for process dots and screens. The data in Table 2 is expressed in weight percentage based on the dry ink film. Both Option 1 and Option 2 inks have significantly more bio-renewable content than the standard ink. Up to 82 percent of the content in the Op- tion 2 ink was bio-derived, whereas no content in the standard ink was bio-derived. taBLe 2 – BIO-RenewaBLe COntent OF tHe dRy InK FILM Line Extender Line Ink Process Extender Process Ink Standard 0% 0% 0% 0% Option #1 9% 5% 25% 7% Option #2 43% 31% 82% 34% COnCLusIOn Ink plays a small role in the sustainability of a flexible package and accounts for a small percentage of a manufactured food product’s carbon footprint. However, formulators can significant- ly improve the renewability of printing inks by using renewable raw materials. These materials include additives, solvents and resins, some of which are completely bio-derived. The case study here illustrates how it is possible to formulate high-per- formance inks with significant bio-renewable content, but that is just the beginning. Current research in bio-fuel development ensures that new raw materials derived from plant and animal sources will continue to make their way to the market. n About the Author: Scot D. Pedersen, PhD, is a technical devel- opment manager at Siegwerk, USA Co., Des Moines, Iowa, where he manages the process development and techni- cal development labs, and works closely with the technical groups of raw material suppliers in developing new inks. He received his BS in chemistry in 1991 from Central University of Iowa in Pella, Iowa and completed his PhD in fluorinated organic polymer chemistry in 1996 at the University of Iowa. In 1998, he joined Color Converting Industries (now Siegwerk) in the R&D lab. He has worked on the development of solvent- borne, water-borne and radiation curable inks and coatings. He will further discuss renewable inks during his presenta- tion, “Improving the Environmental Impact of Printing Inks,” on Tuesday, May 3, in the Inks & Substrates Session of the 2011 FFTA Annual Forum in Indianapolis, Ind. FORUM 2011 SETTING THE PACE FOR FLEXO PACKAGING EXCELLENCE sPeaKeR 26 FLeXO march 2011 www.flexography.org Joncryl is a registered trademark of BASF Corporation functionality loves sustainability Navigating the waters of sustainability can be a challenge. Water-based inks and overprint varnishes based on our Joncryl® technology provide functionality, are economically attractive, and are eco-efficient. The functionality you need and the sustainability you want. At BASF, we create chemistry. basf.com/sustainability basf.com/sustainability 2011_BASF-Sustain_ad_Flexo_Print.pdf 1 2/25/2011 1:56:51 PM FLX_March11.indd 26 3/18/11 1:32 PM