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FLEXO Magazine : October 2013
Smart Value: State-of-the-ar t today may not be competitive tomorrow. Technology is advancing at an exponential pace pushing conver ters’ demands for quicker ROI. Stay ahead of the curve with European component quality equipment at a lower investment. * Value = Affordable Euroflex Flexo CI 8 /10c Press * High Speed 1500+ f.p .m . * Shor t & Long Runs * Mono-block Frame * Fully Ser vo * Auto Pre-register & Impression * Auto Wash System Call 630-681-2521 firstname.lastname@example.org www.kymcamerica.com The laminating industry was born through the use of printing technologies to “calibrate” the amount of adhesive layered on a substrate. It is used with paper, cellophane, polymers, foil and foams. The most common application for lamination, based on the number of installations, is print protection. It is used from the simplest packaging application to the most complex multi- layer compound. Laminating print involves trapping the printed layer be- tween two layers of substrates. The first layer is the printed one and the second layer, a transparent film, is applied above the printed layer to protect it from scratches and other me- chanical, chemical or UV damages. By properly combining the specific characteristics of dif- ferent webs, lamination evolved into a technology capable of producing multi-layer compounds that feature the combined characteristics of all the involved substrates: • Light Barrier • Gas Barrier • Mechanical Strength • Puncture Resistance • Chemical Resistance In a typical flexible substrate compound it is possible to generate a combination of layers to formulate a package tuned to the specific characteristics of a given product or specific application. LAMinAtion LeXicon Before a substrate is laminated, it must be coated. Coat- ing means depositing an adhesive on a substrate that is not rigid. Coating is closely related to print. This is also true for adhesives. Adhesives, for most applications, are very similar to inks. While in printing technology the goal is to layer pigments on a substrate, in lamination the goal is to layer a resin on a sub- strate. It is important to focus on the way the resin is handled and deposited in a proper amount on a substrate. There are two main families of inks: low viscosity and high viscosity. In low viscosity inks, the pigments are dispersed or dis- solved into a vehicle. The vehicle is a liquid that is temporar- ily used to lower the viscosity of the ink pigments, making it possible for them to be handled and dosed on a typical low viscosity ink printing press (flexo or roto). The vehicle—specif- ically water or a combination of solvents—is then evaporated in an oven. The same process works for adhesives, with resin used instead of pigment. High viscosity inks consist of formulations made by practi- cally 100 percent solid, and no vehicle—The entire compound is made of pigments. These inks are very thick and difficult to dose. They are used on offset presses, where a multi-roller printing head will properly dose the ink. This also applies to adhesives. A 100 percent solid adhesive is high viscosity and requires a multi-roller coating head to be handled. The coated substrate, or primary material, and the lami- nated substrate, or secondary material, are combined in a lamination nip. The lamination nip is a motorized, temper- ature-controlled pressure nip where adhesion between the two substrates is achieved by pressing the two webs, with adhesive in the middle, through a supporting chromed roller and a rubber-covered pressure roller. How It Works: The deposition process is not the easiest thing to explain. So, how exactly is it done? Early on, deposition was used for an array of applications, from adhesion to waterproofing. Then, with the development of the vehicle technology—the ability to dilute or disperse a resin into a liquid—it expanded into other applications. Coat- ing technology was born primarily by soaking a substrate in oil or melted wax. The need to control the amount of coating influenced the continued evolution and it improved side-by- side with the rotary press. New substrates like cellophane and synthetic polymers led to the final expansion of the technology to the multiple applications we know today. The process of coating can be simplified into a few steps: • Handling a layer of a substrate • Bringing it into a coating station • Applying a substance to it • Properly calibrating the amount of coating Coating technology is influenced by the substance to be coated. There are a variety of alternative coating head designs that allow for proper handling. The main goal is to properly dose the applied quantity. It was the mastering of the ability to apply a substance to a substrate that led to lamination. Coating Weight: Dosing introduces one of the most impor- tant variables: coating weight. Unlike print, the target is not to achieve a specific color density; rather, it is the amount of adhesive layered that matters. The amount of adhesive will influence some specific technical factors in the lamination process, primarily bond. Bond can be defined as the characteristic of an adhesive to bind two substrates together. Coating weight has an influence on bond and an excess can negatively influence optics. Optics is a characteristic of lamination that defines the visual quality and influence of a laminating process, involving at least one transparent substrate. The goal, obviously, is to achieve a crystal clear result. Any interference generated by excess adhesive, a non-uniformly layered adhesive or other factor, will negatively influence optics. Coating weight is usually referred to as pounds per ream or grams per square meter. The weight can be adjusted by al- tering the coating head design or percentage of solids, which LAMinAtor’s LAnguAge • Coating: Depositing an adhesive on a non-rigid substrate • Vehicle: A liquid used to temporarily lower the viscosity of the ink pigments in order to allow them to be handled and dosed on a low viscosity ink printing press • Bond: The adhesive trait that binds two substrates together • Optics: The term that refers to the visual quality of a laminate 38 FLeXo OCTOBER 2013 www.flexography.org