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Article | February 28, 2006
Unilever was not the only beneficiary of the change from foil to metallized film. Its converter, American Packaging Corp.
of Rochester NY anticipates potential cost reductions and efficiency improvements as a result of the change. “As you would expect with any change from something we have been doing for a long time we went through a learning curve” says technical director Larry Webb. “The transition was relatively easy however and our operators were able to learn the new procedures pretty quickly. We are now up to the same level of efficiency as we were with foil and expect to see further improvements as we get more familiar with the process.”
APC first prints the paper substrate on a 6- 8- or 10-color press. The paper is 20# 30# or 35# clay-coated one side or two and printed gravure or offset in up to seven colors for pouches sold uncartoned at retail. Paper used for pouches sold in folding cartons are typically printed in one color flexo. The printed paper exits the press in 50+”-wide 40+”-dia rolls. APC then uses a tandem lamination process with two extruders positioned in line one after the other. “The first extruder laminates the paper to the metallized side of the film using a hot polymer adhesive to form a paper/PE/metal/BOPP laminate structure” says Webb. The laminated film is then cooled on a chill drum and automatic instrumentation measures its gauge to make sure it is correct. “The second extruder applies a hot polymer sealant coating to the corona-treated side of the OPP film and its gauge is measured a second time” Webb explains. “In other words the first step is extrusion lamination and the second is extrusion coating.”
Although the two-step process requires higher precision and more attention to detail than simple foil lamination it does offer several advantages. “For one thing because it is only 50 ga in thickness the metallized film delivers more square feet per pound. For another because of Toray’s proprietary ultra-high surface energy (UHSE) and its advanced metallizing technology we don’t have to worry about the metal delaminating from the OPP film during high-temperature extrusion” says Webb.
“On the other hand metallized film is more prone to scratching than foil so the consistency of the metallization is critical. Fortunately with this film we don’t have to worry about that because Toray does a really good job of meeting ultra-tight specifications.”
The net result in Webb’s opinion is a demonstrably superior laminate which is shipped to Unilever in 21” diameter rolls. “It really is no more difficult to produce than foil although it requires more testing” he says. “Oriented films are inherently more tear- and puncture-resistant than even thicker blown films. If Unilever did not provide the small notch at the top of the pouch for example the package would be so strong the consumer would not be able to tear the package open but would need a knife or a pair of scissors.”
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