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Compounders know Entek as a supplier of twin-screw extruders (see NPE2015 preview, p. 76), but it’s also one of the world’s largest processors of battery-separator film. At a January open house in Lebanon, Ore.—where Entek builds both compounding machines and extrudes battery separators—visitors were given a tour of the firm’s newest and world’s largest line for producing lead-acid battery separators. Entek’s RhinoHide films are used in batteries for cars, forklifts, golf carts and other applications. The line’s been producing commercial film since last June.

The highly complex 350-ft-long line, Entek’s Line 11,  is equipped with a 133-mm twin-screw extruder (photo top) furnished by Entek’s machine-building sister company which, in fact, designed, built and commissioned all of the major line components except for the screen changer, die and oven. 

On the line, a custom feeding system doses a mixture of UHMWPE, silica, oil, and antioxidant to the extruder. After exiting the die, jet-black film passes through a roll stand, which forms a particular rib pattern. The film is then run through a bath to extract specific amounts of oil. It then makes multiple passes through an oven, after which it emerges a gray color (photo bottom). Then a vision-inspection system checks for pinholes larger than 25 microns before the film is slit to form separate lanes and wound.

In 2014, 625 million m² of lead-acid battery separators were sold worldwide. Entek; Polypore, Charlotte, N.C.;  and Microporous LLC, Piney Flats, Tenn. are said to have a combined 85% share of that market. The new line can produce material for more than 40 million batteries. Entek also has a battery-film plant in the U.K. Its total lead-acid separator-film capacity is 325 million m²/yr. Entek also makes separators for lithium-ion batteries.