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FLEXO Magazine : May 2011
Technologies & Techniques Comparing Flexography’s Plate and Screening Technologies for Functional Application of Oxygen Barrier Coatings Onto Film By Kasey Reed As most packaging is printed by way of flexography, and a fair amount of flexography is printed on films, it would be convenient to have a predictable way to improve functional barrier properties for packaged food prod- ucts through in-line coating. Because many of these new func- tional coatings need to be deposited in fairly thick structures onto different types of substrates, the application of the ink must be at high density. The goal of this research project is to compare three plate-screening and plate technologies for flexographic printing in order to discover the most functional application of printing oxygen barrier coatings onto films. The functionality of printing barriers in packaging is exceptionally beneficial. A manageable process of printing coatings onto films is useful for extending the life of products. My research looked at various smart packaging options available and the application methods of applying the barrier coating to films. Three popular forms of intelligent packaging investigated include sensors, scavengers and barriers. My research project focused on three different plate options, in- cluding DuPont Cyrel DFQ plate (control), a DuPont Cyrel DFQ with plate cell patterning (Treatment 1), and a MacDermid Epic capped plate (Treatment 2). The oxygen barrier coating tested was provided by Sun Chemical and was run on a 2 mil oriented polyproylene on Cal Poly ’s Mark Andy 2200 flexo- graphic press. Once the film was printed with the coating, it was tested using an Illinois instrument to evaluate the oxygen transmission rate of the materials, consequently identifying the most functional methods of barrier application. This research project addressed the question: What is the best plate technology (conventional, solid screening, or capped) to optimize the functionality of active materials, such as oxygen barrier coatings, when printed by flexo on filmic substrates? INTRODUCTION Intelligent packaging has come far in ensuring customer satisfaction. With ways of controlling oxygen, carbon dioxide, ethylene, moisture, odor and temperature, smart packaging can address many possible packaging problems. Whereas in- telligent packaging devices are narrowed down to the capabil- ity of sensing and providing information about the properties of the packaged food, active packaging includes components of packaging systems that have been deliberately included in or on the packaging material to enhance the performance of the package system (Kerry). Prior to deciding on the oxygen barrier ink as the focus for this research project, other intelligent pack- aging options were researched and considered. These include sensors, scavengers and, of course, barriers. A sensor is a device that detects or measures a physical property and records, indicates or otherwise responds to it (Kerry). An example of using sensors in smart packaging is the AgeLess Eye by Mitsubishi Gas Co. The AgeLess Eye is a colorimetrix redox dye-based indicator, in tablet form, placed inside a package to indicate the presence of oxygen in one glance (Mitsubishi). When exposed to oxygen, it turns blue, and it returns to its original pink appearance as soon as the oxygen is eliminated. A scavenger, in chemistry, is a substance added to a mixture to remove or inactivate impurities or unwanted reac- tion products. An example of this in packaging is an oxygen FIgURe 1. Close-up image of the digital file for the cell pattern plate. FIgURe 2. Close-up image of the actual mask for the cell pattern plate. www.flexography.org may 2011 FLeXO 143 The Benefits of Oxygen Barriers • The barrier works as a limit or boundary to restrain or keep out anything unwanted, and is designed to be impervious to gas migration. • There are two options for oxygen barrier coatings: Coating on press or purchasing a film that already has oxygen barrier properties. • With the right plate technology, similar oxygen bar- rier properties may be achieved in a more cost-effec- tive manner by printing an oxygen barrier coating in line, rather than purchasing pretreated films.
Sustainable Spring 2011