No. 29 - Multi-Layer Blow Molding
Packaging innovator Toyo Seikan in Japan was an early pioneer of coextrusion blow molding.
Packaging innovator Toyo Seikan in Japan was an early pioneer of coextrusion blow molding. It developed a three-layer process in the early 1970s as a method of imparting barrier and potentially of using recycled and reground material. The technology eventually created opportunities in oxygen-sensitive food applications and later in multilayer fuel tanks. Toyo Seikan’s Lamicon process initially utilized EVOH between LDPE layers.
In 1975, Bekum in Germany introduced what is said to be the first commercial coextrusion blow molding machine. It produced three-layer structures with nylon as an outer barrier over a tie layer and either PE or PP for the inner layer. An early success was cosmetics tubes. By 1979, Bekum had sold 30 machines, 25 of them in Japan.
In 1977, Montedison in Italy revealed a special grade of polyvinyl alcohol (PVA) for polyolefin-based high-barrier containers. Montedison worked with Italian machine maker Comec, which produced coextrusion blow machines for production of three-layer bottles. At Interpack ’78, Krupp Kautex unveiled its coextrusion blow machine for nylon/PP bottles.
Another significant event was the development of a proprietary coex wheel system by American Can Co.’s plastics division in 1979-’80. The “Gamma” bottle from this machine became the first barrier food bottle to replace glass. Its debut was the six-layer PP/EVOH squeezable bottle for Heinz ketchup in 1983. About seven years later, the ketchup bottle moved to coinjection blow molding with PET instead of PP to enhance both clarity and recyclability.
A competing processor, Continental Can Co., licensed the Lamicon process from Toyo Seikan in the early 1980s and broke new ground in 1985 with the first squeezable plastic bottle for oil-based foods. The 15-oz Kraft Miracle Whip container was a six-layer PP/EVOH construction.
American Can broke more new ground with its coinjection blow molded five-layer Omni retortable plastic can of EVOH, tie layer with desiccant, and polyolefin. The technology was unveiled publicly in 1984 and the first commercial launch was for Hormel single-serve entrees in 1985.
The next step, in the mid-’90s, was coinjection stretch-blow molding of PET with a nylon or EVOH barrier. This effort was pioneered by Plastipak Packaging and Kortec Inc., both of which worked with Husky Injection Molding Systems on multi-layer preform production. Kortec’s technology has been commercialized for beer, juice, tea, milk, carbonated soft drinks, and tomato-based products.
Industrial coextrusion
Monolayer automotive fuel tanks emerged in the late 1960s. Initially, these HDPE tanks were sulfonated or fluorinated for barrier protection but as emission regulations stiffened in the 1980s, car makers looked to coextruded tanks as a solution. Europe was at the forefront of this trend, led by Germany’s Volkswagen and Kautex as the dominant machine supplier. Coex blow molding has since expanded into smaller fuel tanks for lawn and garden equipment and 1- to 5-gal gasoline storage containers.
Another breakthrough for coextrusion blow molding was in a non-barrier industrial use. In 1995, U.S. Coexcell in Maumee, Ohio, was reportedly the first to make three-layer 55-gal HDPE drums with a center layer of regrind made from used drums.
