Coperion GmbH, Stuttgart, Germany, has invented a device consisting of a multi-shaft screw extruder, two metering devices, separate infeed openings and a controller that is capable of alternately making colored and uncolored pellets simply and economically without complex cleaning measures.
Traditionally, an extruder used for pelletizing exclusively produces either colored or uncolored plastic pellets to avoid contaminating natural pellets with colorant, according to the company’s patent application. “On account of only a single multi-shaft screw extruder being required, the complexity in terms of machine technology is significantly reduced,” the application states.
The screws are configured so they are self-cleaning by meshing tightly together and also scraping the internal wall of the barrel housing.
Patent application 20190168418; published June 6
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