WILLIAMSTON, MICH. — Clear, blow-molded bottles from lower-priced polypropylene preforms could win some applications away from PET, such as dry goods, uncarbonated water and some hot-fill packaging, according to Bekum America Corp.
Stretch blow molding PP “allows customers to make beautiful packages at a much lower price,” said Gary Carr, general sales manager of the Williamston company.
Blow molding grades of PP currently are about 60 percent of the price of PET bottle resin.
Bekum's new SB series can mold both types of bottles, PP and traditional PET. For polypropylene, the machine can run 1,000 bottles per hour, or 6,000 bottles on a six-cavity machine, Carr said. The SB is a two-step machine, meaning it blow molds preforms that have been molded on a separate injection press.
Bekum America's parent firm, Berlin-based Bekum Maschinenfabricken GmbH, showed the first SB stretch blow molder last year at K 2001. Carr said the company now is in full production at the Berlin factory.
PP has very good clarity and moisture barrier properties, Carr said. One weak point is PP's lack of barrier properties for oxygen or carbon dioxide. Carr said that means PP is not a good candidate for packaging carbonated beverages, such as sparkling water or soda.
The oxygen-barrier issue also could hold PP containers back from some hot-fill food uses. But Bekum engineers are researching ways to produce multilayer PP preforms and blown bottles — with a barrier layer of ethylene vinyl alcohol. “The real opportunity we see now could be the food market,” Carr said in an interview at Bekum America.
Bekum will present a paper on the new PP multilayer process during the Worldpak 2002 conference, June 23-28 at Michigan State University in East Lansing, Mich. Worldpak is sponsored by MSU's School of Packaging.
Carr said a key to Bekum's SB technology is tight control of the temperature of the PP preforms. Preforms are loaded on carriers and rotated through an infrared- heating oven. Preferential heating, with thread positioning, produces flat and oval containers. The machine also can produce wide-mouth PP bottles.
The SB also is Bekum's first all-electric blow molding machine.