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processing feature | High-temperature compounding


This BKG underwater pelletizer has an insulated closed water system to handle high- temperatures


require a longer distance to cool down from a high temperature. Cooling with a spray mist and an air belt is an alternative to a water bath that has been found to work well in Entek’s processing lab, notes Dean Elliott, laboratory manager at Entek Extruders. Trained maintenance personnel are important


because thermal expansion during processing changes the gaps in the pelletizer, notes Desio. There is a narrow window of optimal temperature, knife-blade speed, and roll pressure needed to make good pellets, he adds. While strand systems are widely used, die-face


pelletizers can now also be used due to technology advances in die-plate design, and suppliers note an increased interest in underwater, die-face systems for processing high-performance resins. Pelletizing high-temperature resins using underwa-


ter, die-face pelletizers requires specially designed systems, says Ralf Simon, managing director at BKG, a supplier of underwater pelletizer systems. The die-plate must be designed to minimize heat loss and maintain a good temperature distribution in the plate, and must be made of steel designed for higher temperature use. Insulation can be used to keep heat in


BKG demonstrates the improved temperature distribution of a die with thermal insulation (right) compared to one without (left)


the die, which prevents die freezing. In addition to die-plate design, the entire pelletizer


and screen-changer assembly must be designed to operate at higher temperatures using insulation, specially designed hydraulic cylinders, and cooling for some parts. Mark Tate, technical manager for underwater


pelletizer supplier Gala Industries, says that the company’s Heat Flux Die Plate technology combines surface-insulation methods and manufacturing techniques to reduce or eliminate die-hole freezing, and can therefore be used to pelletize high-temperature polymers. He notes that another possible concern when using


underwater pelletizing for high-temperature com- pounds is the resulting hot process water; Gala uses double-insulated tanks to ensure operator safety. Today’s systems from Gala come standard with coil heaters, which are more energy effi cient than earlier cartridge-heater technology and have improved conduc- tivity of heat into the die. “We have seen 30-60% reduction in energy use, which is particularly a benefi t when running higher temperatures,” says Tate.


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COMPOUNDING WORLD | December 2012


www.compoundingworld.com





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