Kontinuierliche Herstellung von Elastomercompounds auf gleichsinnig rotierenden Zweischneckenextrudern

摘要

The co-rotating twin screw extruder has been used for the continuous preparation and mixing of high viscosity material for more than fifty years. Its most important area of operation is thermoplastics including thermoplastic elastomers. Its modular construction and multiple degrees of freedom in process design enable the twin screw extruder to be easily adapted to various processing requirements. Its technical reliability and high economic efficiency in its classical areas of use led early on to considerations of employing the twin screw extruder for elastomer compounds as well. These are traditionally produced discontinuously in internal mixers. Scientific studies on laboratory plants show that it is fundamentally possible to produce erosslinkable elastomer compounds on twin screw extruders. There has also been some initial positive experience on an industrial scale. The main advantages of the continuous over discontinious mixing lie in the steady mode of operation, which gives constant product quality and uniform low energy consumption. The quality of a continuous mixing process is decisively dependent on the accuracy of the raw material dosing. Most additives are available as free flowing dry bulk material or liquid and can be dosed to the mixing process with typical gravimetric solids dispensing equipment and pumps available on the market. Dosing the rubber, however, often presents difficulties. Granulated rubber is usually expensive and tends to agglomerate. A system comprising a single screw extruder combined with a gear wheel pump is available, with which roughly cut up rubber bales or strips can be fed to a twin screw extruder both reliably and economically.