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FLEXO Magazine : March 2011
Technologies & Techniques can be used alone as a solvent or combined with another sol- vent that comes from biological sources. These novel blends can dry as quickly as petroleum-based solvents, such as propylene glycol methyl ether acetate and isopropyl alcohol. Additives. Bio-renewable additives provide eco-friendly alternatives to traditional additives. For example, surface modifiers, such as carnauba wax and fatty acid amides, are high in bio-derived content and can be used in place of Fischer-Tropsch and polyethylene (PE) waxes. Several plasticizers and print aids are highly renewable, as well. For example, soy lecithin, which is 100 percent bio- derived, has long been used as a print additive in flexog- raphy. Vegetable oils and fatty acid esters have historically been used as plasticizers, and modifying them has resulted in new materials that perform as well as their petroleum-based counterparts. Several bio-derived defoamers have recently come onto the market. These defoamers have low to medium amounts of bio-derived content, and their performance is similar to that of petroleum-based defoamers. Last but not least are additives created with recycled wax. These are mostly PE and polytetrafluoroethylene waxes recycled from other industries. Their molecular weights and particle size are corrected during recycling to make the waxes suitable for use in printing inks. Resins. Several of the resins traditionally used in printing inks are high in bio-renewable content and contribute to the formulation of inks with excellent gloss, adhesion and flex- ibility. Current options include: • Nitrocellulose, ethyl cellulose, cellulose acetate pro- pionate and cellulose acetate butyrate—the cellulosic resins—based on cellulose derived from cotton or wood pulp. These resins enhance printing inks because of their pigment-grinding capability and their mar and heat resistance. • Polyamides, based on fatty acids isolated from tall oil derived from wood pulp. • Modified rosin esters derived in part from wood pulp. • Shellac, a flexible, alcohol-soluble resin isolated from the secretions of the lac beetle. • Alcohol- and water-soluble protein resins derived from soybeans. • Polysaccharide resins, which are useful in ink formula- tions because they exhibit good solubility in a wide range of solvents. • Newly developed versions of polylactic acid polymers, which have limited solubility in alcohol but show prom- ise in their ability to grind pigment and develop color strength. • Polyacrylic resins based on a combination of renewable and petroleum monomers, which result in a polymer with www.flexography.org march 2011 FLeXO 25 FLX_March11.indd 25 3/18/11 1:32 PM