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Compounding equipment at K presents not so much new technology as new modifications or combinations of equipment to improve output and conserve space. For example, Battenfeld Extrusionstechnik, part of SMS Plastics Technology in Germany (U.S. office is American Maplan in McPherson, Kan.), mounts a planetary-roller extruder over either a second planetary roller or a twin-screw metering device. Typically, a planetary extruder is paired with a single-screw extruder for applications like PVC calendering. Battenfeld says the new combos work well for heat-sensitive wood-flour compounds, where the planetary roller offers more controlled cooling.

Another multi-screw device has grown much bigger since it was first introduced at K'98. The so-called ring extruder from 3+ Extruder GmbH in Germany (represented by Century Extruders, Traverse City, Mich.) has a circle of 12 screws, each originally of 1.125-in. diam. Since then, the company has sold units with screws of up to 4.7-in. diam. and is designing a lab model of 0.75 in. The biggest model runs at a recycling plant in Germany.

Twin-screws for foam

Some equipment makers are touting twin-screw extruders as more efficient ways to compound and extrude foamed PS board and foamed PE film. Leistritz AG (U.S. office in Edison, N.J.) modifies a twin-screw to foam and cool in one extruder by installing a high-pressure injection pump to inject liquid or gas into the barrel.

Berstorff (U.S. office in Florence, Ky.) has also modified a twin-screw extruder to foam and cool in one unit by using low-energy pumping elements that add less heat. Berstorff also combines a twin-screw compounder with a single-screw cooling extruder in its new Schaumtandex ZE/KE system, boosting output of PS foam board from 1700 lb/hr with conventional tandem single-screws to 3000 lb/hr with a twin/single combo.

More twin-screw news

Coperion (U.S. headquarters in Ramsey, N.J.), the new firm that combines Werner & Pfleiderer and Buss, will show two new developments. Coperion W&P will unveil a higher output twin-screw extruder, while Coperion Buss shows what's said to be a cost-effective kneader with higher output.

Davis-Standard Corp. in Pawcatuck, Conn., has developed a new screw geometry for the pumping zone of a corotating twin-screw for in-line compounding and extrusion. The new geometry is said to improve pressure stability by increasing leakage flow, reducing the effect of resin variations and improving quality.
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Author:Schut, Jan H.
Publication:Plastics Technology
Date:Sep 1, 2001
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