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A clever strategy for plastic beer bottles

Michigan Brewing sees great potential for beer in plastic when the target market is tightly focused. Custom-labeled bottles for a casino, for instance, have found a receptive audience.

Michigan Brewing unveiled its Cherry Creek brand in plastic at the Traverse City Cherry Festival.
Michigan Brewing unveiled its Cherry Creek brand in plastic at the Traverse City Cherry Festival.

Beer in a plastic bottle is a concept that has more than its share of doubters. But even the doubters allow that such a container could appeal to certain niche markets. Take these two, for example: a Michigan casino and a week-long festival in the self-proclaimed Cherry Capital of the U.S.

These are the targets selected by Michigan Brewing for the plastic beer bottles it launched this summer. The five-year-old microbrewery, based in Webberville, MI, worked closely with Amcor PET Technologies (Mississauga, Ontario, Canada) to develop its 16-oz multilayer bottle and 28-mm plastic threaded closure.

“We’re looking first and foremost at venues where plastic bottles have an advantage,” says brewery president Bob Mason. “Plastic for beer is going to happen sooner or later anyway, so we decided to seize the opportunity early when the chance presented itself.”

An added incentive was Amcor’s willingness to take on Michigan Brewing as a partner. As Mason puts it, “Amcor is helping us a lot with the pricing as well as the technology.”

Weighs in at 39 g

The last time Amcor made news with a plastic bottle was this past March when it supplied quantities for an Anheuser-Busch test that lasted only a few weeks. The bottle used by Michigan Brewing is similar to A-B’s. Weighing 39 g, the coinjection stretch/blow-molded bottle has a three-layer structure of polyethylene terephthalate/oxygen absorber/PET. The central oxygen absorbing layer is BP Amoco’s (Chicago, IL) Amosorb® 3000. Amber colorant is added during preform molding.

The 28-mm injection-molded polypropylene closure, from Bericap North America (Burlington, Ontario, Canada), also has an oxygen absorber. A barrier layer in the bottle sidewall is unnecessary, says Amcor’s Kirby Losch, thanks to the bottle’s design and the way Amcor blow molds it. “We do something along the lines of heat setting,” is about as specific as Losch gets.

Whatever it is, it helps keep oxygen out and carbon dioxide in long enough for a 90-day shelf life. It should be pointed out, though, that Michigan Brewing keeps the plastic bottle at temperatures below 50°F during storage and distribution.

Adjusting the filling line to accept the plastic bottle was fairly easy, says Mason. A used four-head rotary capper was installed, and the 16-head rotary filler used for glass bottles was modified.

“Unlike our glass bottle, we can’t evacuate ambient air from the plastic bottle because the sidewalls would collapse,” says Mason. “So we modified the double pre-evacuation system. We pressurize the plastic bottle with carbon dioxide, and the vacuum channel opens to purge the bottle of ambient atmosphere. Only then does the filling valve open.”

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