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Flexo Sustainable : End of Year 2008
Humble beginnings For practical purposes and for the benefit of those who consider themselves “green” when it comes to soy knowledge, we should first distinguish two very different types of soy inks: offset versus flexographic inks. Traditionally, soy oil inks have been widely utilized in the offset printing process. Inks made from soybean oil were developed in the 1980’s at the request of the Newspaper Association of America as an alternative to petroleum based inks. Looking for a more reliable and cost-effective method of printing, they found it in soybean oil. It was noted that after being slightly refined, soybean oil had an innate clearness to it, much more so than petrochemical or other vegetable oils. This soybean oil was then blended with pigments, resins, waxes and—Presto!—a new ink system was created that offered better economics, brighter colors and contained less volatile organic compounds (VOCs). It is by all accounts a true success story. This article, however, will focus on flexographic water-based “soy inks.” These inks differ from lithographic soy inks in that rather than being composed primarily from soy oil; they instead contain a soy protein vehicle that has been integrated into a waterbased formula. This vehicle, which is a result of a chemical modification of a soybean protein, helps to serve as a carrier for the pigment and binder to the substrate. In order to fully understand this, we should refer back to the basic elements of a water-based flexographic ink: resin (binder), pigment, and a small amount of property-enhancing additives such as wax, all dispersed in water. In a water-based soy ink, a soy protein vehicle replaces a portion of the resin system (generally acrylic), essentially becoming homogeneous with that system. It is important to make this distinction because a lot of the reputed advantages of soy inks come from a comparison of soy oil inks to petroleum-based inks. When comparing water-based soy inks to standard acrylic inks, their dominant counterpart in flexography, we see a much different picture. Our focus, therefore, will be to illustrate the impact of incorporating soy protein into a water-based flexographic ink. Many of you are probably curious as to why these inks are called “soy inks” if their primary ingredient is not soy. For all the benefits provided by a soy protein, it alone does not have the binding properties required to be the basis of a flexographic ink formula. However, if soy protein is formulated into an ink in conjunction with an appropriate resin package, the benefits can be plentiful. With this understanding, the American Soybean Association (ASA) allows licensees to apply its certification seal to a water-based flexographic ink that meets the following requirements: the finished ink must include at least 15 percent of a vehicle that is comprised of at least 20 percent soy protein. When incorporating an appropriate amount of soy vehicle (20 percent in this case), the visual difference becomes minimal. www. f le xomag.com Year end 2008 Sustainable FLEXO 5