Only for 12,90 EUR
Continuous production of elastomer compounds on co-rotating twin-screw extruders
von Dr.-Ing. Dietmar Becker, Dipl.-Ing. Dieter Mayer
For more than fifty years, the co-rotating twin-screw extruder has been used for
continuous processing and mixing highly viscous products. Thermoplastic polymers, including thermoplastic elastomers, are its most important area of application. Its modular construction and various degrees of freedom in process configuration enable the twin-screw extruder to be easily adapted to different processing tasks.
Its technical reliability and high economic efficiency in its classical areas of operation led early on to considerations of using the twin-screw extruder for the continuous production of elastomer compounds as well. These are traditionally produced discontinuously in internal mixers. Scientific investigations on laboratory machines show that it is fundamentally possible to produce crosslinkable elastomer compounds on twin-screw extruders.
Furthermore, first the positive experiences have already been
gained on industrial scale. Basically the main advantages of continuous compared with the discontinuous mixing process, lie in the steady mode of operation, which leads to a constant product quality and a constant low power consumption. The quality of a continuous mixing process is critically dependent on the accuracy of the raw material feed. Most additives are available as free flowing bulk material or as liquid.
They can easily be fed to the mixing process with commercially available gravimetric solid dosing units and pumps. In contrast, dosing rubber often causes difficulties. Granulated elastomers are often expensive and tend to agglomerate. A system consisting of a single-screw extruder and a gear pump has recently become available, with which roughly chopped bale rubber or rubber strip can be fed into a twin-screw extruder both reliably and economically.