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Article | March 31, 1996
Cap and liner top Tree Top's switch to PET
Changing from glass to heat-set PET boosts sales of apple juice and cider by 60% on 1-gal bottles. PP closure and EVA liner provide tamper-evidence and eliminate labor-intensive cap inspection.
Sealing solution Adjustments in filling and capping machinery were also necessary to accommodate PET bottles. As Tree Top gained experience with the PET bottles it increased speeds to match those achieved with glass: roughly 80/min with the 1-gal size 140 to 160/min on the 1/2-gal. Tree Top modified an existing filling machine for PET bottles. This machine uses air to keep the bottle rigid during hot filling thereby avoiding bottle collapse. Graham Packaging (York PA) is the primary bottle supplier with Johnson Controls (Manchester MI) serving as an alternate provider at this time. Graham injection-molds a preform from PET resin then stretch/blow-molds the preform into the finished bottles. An in-line station on Graham's stretch/blow-molding machine performs the heat-set function that permits hot-filling by Tree Top. Maintaining tolerances on the bottle's finish is critical to Tree Top. "We wanted to see if we could still use our in-line capper that we had used to put a metal cap onto our prior glass bottle for the PET bottle without having to buy an additional capping machine" says Robbins. To do this Tree Top enlisted Sun Coast. "To enable the PET bottle to accommodate the closure we knew we would only need to redesign the bottle's neck finish" says Peter Lennox vp of sales and marketing for Sun Coast. "Graham Packaging was easily able to handle our neck design modifications." The in-line capper uses what Robbins calls a "multi-lead" finish. This multi-lead thread has three leads rather than one continuous thread. "To use a continuous-thread we would have had to purchase a rotary capper. That would have been costly. "But what we found out was that in order to get the proper closure application to the bottle we still had to add a machine to apply additional torque after the closure was applied on the in-line capper" he continues. Tree Top's addition of a capper from Surekap (Winder GA) "cost us about $320 less than it would have to purchase a new rotary capper" Robbins estimates. Improved tamper-evidence The neck finish permits application of the new closure which provides much greater tamper-evidence compared with the metal closure/glass bottle combination. "When we had glass bottles the only tamper-evidence we had was to check if the button on the metal cap was in an up or down position" says Robbins. "If product is jostled in transit or if a consumer twists it on the shelf the bottle could lose its vacuum and its tamper-evidence. That presents a safety concern. When we went to plastic bottles we looked at tamper-evident bands but we didn't feel they were completely effective. With the new closure we know the consumer is getting a fresh product." From a production standpoint Robbins estimates that "the industry average for defective packages coming off the capper ranges from 2 percent to 4 percent. With the new cap and liner combination we were able to reduce capper misapplications to less than 1 percent and virtually eliminate any spoilage problems." Looking at the economics of the switch to plastic Robbins admits unit costs for the PET bottle runs about 3¢ more than glass on the 1-gal size and 5¢ more on the 1/2 gal. Also shelf life for the PET bottle is only one year as opposed to two for glass. "There's no oxygen transfer with glass as there is in PET" says Robbins. Despite those drawbacks Tree Top couldn't be happier with its decision to move to PET especially since adding the new closure/liner. "The added PET bottle costs are more than offset with our sales increases at warehouse outlets that began stocking our product" says Robbins. "We're giving our customers the lightweight tamper-evident containers they want and we're able to get the reliability and high production speeds we need" he continues. There are other benefits as well. "We still have a clear bottle that lets the consumer see our product. And we're working with bottle manufacturers and local governments to develop programs to get the bottles back for recycling too." Tree Top operates five production facilities four in Washington another in California. These facilities produce more than 900 product varieties in all sold primarily west of the Mississippi River. The success of its move from glass to plastic on 1- and 1/2-gal apple juice and cider could set a precedent. "We're extremely pleased with the results" says Robbins. "And we're looking at moving some of our other juices into plastic. We also co-pack for some other companies who are beginning to move out of glass and into plastic particularly on the 64-ounce size."
Since the 1940's Selah WA-based Tree Top packaged its apple juice and cider products in glass bottles. Despite the traditional appeal of glass warehouse clubs stocking Tree Top favored lighter-weight plastic to make it easier for consumers to carry the bottles. In early '94 Tree Top began to accommodate customer wishes. Initially it converted 1-gal bottles to heat-set stretch/blow-molded bottles of polyethylene terephthalate. A polypropylene bale handle was added to ease handling. The filled bottle weighs about 8 lb down from nearly 12 lb in glass. The switch to PET on 1/2-gal bottles was made last autumn. A pinch grip makes it easy for consumers to pick up and pour from this smaller bottle. The change has paid off handsomely most notably in the larger size where sufficient time has passed to make a viable comparison. "Our gallon sales have gone up 60%" says Jim Robbins Tree Top's directorof quality assurance. "We've been able to pick up warehouse and club store business that we did not have before because of the PET package." The switch wasn't without its challenges. "We hot-fill at 185 degrees on one line at our Selah plant" Robbins explains. "We had to make sure there was a really good heat set to avoid deformed bottles. Capping also proved difficult with our 48-mm finish." Most vexing however was that "a closure and ethylene vinyl acetate liner combination didn't work as anticipated" he recalls. "EVA has a tendency to shrink around heat. Even though the liner was oversized to make up for the shrinkage and stay inside the cap properly it either moved or shrunk too much. In some instances it even fell into the product in which case we wound up with no seal on the product." This "false seal" led to extensive downtime to adjust capping equipment. It also created the potential for product spoilage as apple juice provides a good medium for mold and yeast growth. "We couldn't afford to ship any gallons that weren't sealed properly so we had to do a 100% product sort which is slow labor-intensive and costly" Robbins notes. To solve its dilemma Tree Top worked with Sun Coast Closures (Sarasota FL). Sun Coast recommended a 48-mm PP closure from Tri-Seal Intl. (Blauvelt NY). Tri-Seal's F-8268 liner combines a core of foamed PP and EVA copolymer to provide high heat resistance and hold the liner in place without distortion during hot filling. The closure added in mid-'95 also includes a breakaway band that provides tamper-evidence. The consistent seal quality of the new closure/liner combination eliminated the need for a crew of operators to conduct the product sort necessary for PET bottles using the earlier cap and liner. That provided a one-time labor savings of about $50.
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