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FLEXO Magazine : March 2011
Technologies & Techniques Increasing the Renewability of Flexographic Inks Additives, solvents, Resins, Hold secrets to sustainability By scot D. Pedersen, PhD Sustainable packaging has become a driving force in manufacturing. Corporations are increasing their focus on social responsibility, transparency and establish- ing higher consumer trust, and packaging is the most visible example of their efforts. There are eight criteria for defining a package as sustain- able. The package: • Should be beneficial, safe and healthy throughout its life cycle. • Must meet market criteria for performance and cost. • Should be sourced, manufactured, transported and recycled using renewable energy. • Must be manufactured using clean production technolo- gies and practices. • Should be made from materials that are healthy in all “ end-of-life” scenarios. • Should be designed to optimize the use of materials and energy. • Should be efficiently recovered and used in recycling. • Should maximize the use of renewable and recycled raw materials. The sustainability of any ink must be discussed in terms of the entire product life cycle. A study conducted by a European snack food manufacturer revealed that the ink used in product packaging comprised approximately 0.01percent of the total carbon footprint of the product’s entire life cycle. Likewise, the first serious evaluations of sustainability on packaging alone (not including the product contained within) have shown that printed ink constitutes less than 1 percent of a package’s car- bon footprint. Although it makes a minimal contribution to the weight of a package, ink is a significant part of the package’s appearance and therefore warrants attention. RenewabIlIty In PRIntIng Inks Ink formulators have begun to focus on using recycled and renewable raw materials when developing sustainable print- ing inks. Renewable raw materials come from bio-derived sources, such as plants and animals. Examples of renew- able or bio-derived sources include cotton, animal fats and proteins and new-growth forests. A brief discussion of ink composition is necessary to highlight specific areas of the industry ’s current work in developing renewable inks. All printing inks are similar in composition and contain three types of ingredients in addition to colorant. First, they contain a resin or polymer, sometimes referred to as the binder. The binder imparts the physical properties of the printing ink, such as gloss, adhesion, flexibil- ity, scuff resistance or heat resistance. The resin also carries and delivers the colorant. Second, all inks contain a solvent. Solvents dissolve the resin and disperse the colorant. They give the ink its viscosity and drying rate, two characteristics important for print quality, solvent retention and press speed. Third, all inks contain small amounts of additives to en- hance their performance. Additives include waxes to enhance the ink’s coefficient of friction and mar resistance; cross- linkers and adhesion promoters to improve heat resistance and adhesion; and other materials such as antioxidants, defoamers, silicone fluids, surfactants and dispersing aids. Figure 1 illustrates the basic composition of a printing ink. Solvents. Today ’s ink formulators have access to a wide variety of renewable raw materials for use in creat- ing solvents. For example, ethanol, which is 100 percent renewable, is produced from plant matter and can be used to make ethyl acetate, a solvent. Ethyl lactate is an ester derived from lactic acid and ethanol and FIgURe 1 – geneRiC inK CoMPosiTion 24 FLeXO MARCH 2011 www.flexography.org Carrying & Delivering Colorant • A package must meet eight criteria to be considered sustainable. • Recycled and renewable raw materials are crucial to the development of sustainable printing inks. • Ink formulators have a wide range of bio-renewable solvents, additives and resins from which to choose. • Inks made with significant amounts of bio-derived content perform as well as petroleum-based inks. FLX_March11.indd 24 3/18/11 1:32 PM