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FLEXO Magazine : March 2009
TECHNOLOGIES & TECHNIQUES A line of water-based flexographic inks has been developed through the use of rosin ester technology. Rosin ester resin solu- tion was used to replace 40-50 percent of acrylic resin solution in the formulations. These inks showed improvement in certain ink properties and print characteristics, above those of acrylic- only based inks. In no case were they inferior to the conventional acrylic-based inks. For instance, pigment loading was reduced in many cases, which allowed for increased press speeds of about 25 percent. At the same time, driers on the press could run at 75 percent capacity instead of 100 percent, thus saving energy. These two results were unexpected benefits resulting from the chemis- try associated with the organic source of the resin. Bronzing and ghosting were practically eliminated while ink transfer, adhesion, coverage, wet traps and heat resistance improved noticeably. Other properties, such as gloss, viscosity and pH stability, resolu- bilityfrewetting, water resistance, plate and anilox roll wash-up performed at the same levels as the conventionalloo-percent acrylic inks. No detrimental effects have been observed. WHAT IS ECO-FRIENDLY? Water-based flexo inks, by their nature, are the most environ- mentally and ecologically friendly printing inks in use today. In order to comply with environmental requirements, all water- based flexo inks, whether they are made with conventional acryl- ics, soy or rosin ester, should not use any banned substances, no produce no volatile organic compounds (VOCs), and contain no hazardous air pollutants (HAPs) or heavy metals. Pine rosin esters do not contain any heavy metals, the so-called CONEG (Coalition of Northeastern Governors) metals, which include lead, cadmium, mercury and hexavalent chromium. CONEG-which has now changed its name to Toxics in Packaging Clearing House (TPCH}-introduced legislation limit- ing the use of these four heavy metals in packaging and packag- ing components. The TPCH law states that the sum of incidental concentration levels of lead, cadmium, mercury and hexavalent chromium present in any package or package component does not exceed looppm (parts per million) by weight. Furthermore, in cases where the regulated metals are present below the limit stated above (looppm), these regulated metals cannot have been intentionally added during the manufacturing process. In the past, inks may have contained TPCH heavy metals. Many ink manufacturers used lead-, cadmium-, chromium- and, occasionally, mercury-based pigments. As the health hazards as- sociated with even very small amounts of heavy metals came to light, the pigment industry developed new colorants, mostly organic pigments, as replacements. Basically, all heavy metal con- taining pigments have been replaced, so inks that are formulated today are free of these metals, and the content is well below the looppm aggregate contaminant level, as required by the TPCH regulations. Chemical analysis by ICP (Inductively Coupled Plasma Spectroscopy) that was carried out on conventional water- based inks has shown that no lead or cadmium were present. If any minute amounts of lead and cadmium were present in these inks, they were under the detection limit of the ICP method. Furthermore, no mercury or hexavalent chromium would be ex- pected to be present, based on the types of pigments used in the inks. Although exact figures can- not be obtained at this time, it is estimated that about three gallons of oil, used to make acrylics derived from petro- leum, can be saved per 55gal drum of ink, by replacing acrylics with rosin esters. Photo courtesy BCM Inks. MARCH 2009 - www.flexography.org FLEXO
Sustainable Winter 2009