Twin screw extruder system.

Twin screw extrusion systems are said to continuously mix and devolatilize polymers with fillers and additives in combination with direct wire coating extrusion. A key component in the equipment package is a 10 to 1 L/D single screw pump front end attachment that is designed to build and stabilize pressure to the wire coating, or alternative die. The single screw pump is directly mated at a 90 [degrees] angle to facilitate pressure generation at its inlet, and the barrel uses liquid cooling for controlled heat transfer capabilities. Single screw pumps may be preferred to a gear pump attachment, particularly for formulations that cannot withstand filtration, or that are heat sensitive, according to the company. Typically, the system uses a PLC-based closed loop pressure feedback that analyzes inputs from key points in the system, makes numerical calculations, and applies corrections to the screw rpms and feed rate to maintain the single screw pump inlet pressure at a user definable set point. This allows the back-pressure for the twin screw extruder to be held constant at the inlet of the single screw pump, which provides for consistent shear and mixing. With a steady melt delivery to the single screw pump, the discharge flow and pressure to the die will be uniform, which results in a dimensionally stable part, according to the company. (Leistritz)

Circle 105 on card