MRS Extrusion Concept
The patented MRS Extrusion System offers completely new possibilities with regard to the efficient degassing and extrusion of polymer melts. Additionally, this system also offers excellent dispersion performance for the introduction of gases and / or all forms of additives.
The MRS extruder is based on the conventional single screw extruder, but is equipped with a multiple screw section, for optimum devolatilisation. The polymer melt is delivered into a large single screw drum. The drum contains 8 small extruder barrels, parallel to the main screw axis. Installed in these small extruder barrels are the “satellite” screws, which are driven by a ring gear in the main barrel. The satellite screws rotate in the opposite direction to the main screw while they rotate around the screw axis. This disproportionately increases the surface exchange of the polymer melt. So that the volatiles can be freely evacuated, the MRS extruder is equipped with a large opening for venting (exposing the full length of the satellite screws) which is completely under vacuum. This provides excellent and unrestricted access to the polymer melt, the surface of which is constantly replaced at an extremely high rate by the action of the satellite screws in the multiple screw section. Further, precise control of the melt temperature is possible as the temperatures of all the surfaces in contact with the melt can be controlled accurately.
Thanks to its Multi Rotation Section, the surface area – and the surface area exchange rate – available for devolatilization are far greater than in other extrusion systems available on the market.
The surface area of the steel parts in contact with the melt is exchanged at a rate of more than 25 times greater than with a co-rotating twin screw extruder. Due to the opposite rotation direction and high speed of the satellite screws, the polymer surface area is increased by a factor of 100 compared to a single screw extruder and a factor of 40 compared to a twin screw extruder.
The specific energy requirement of the MRS system is typically 15 to 25 % less than for conventional technologies as it needs neither pre-drying nor powerful vacuum systems. Compared with the single screw extruder when processing PET, pre-treatment of the material in the form of drying and crystallizing can be avoided thereby saving operating and maintenance costs along with energy savings.
The MRS also has a lower energy consumption when compared with corotating twin screw extruders. In the case of PET processing, there are additional savings with the MRS as this system requires neither a powerful vacuum system ( < 5 mbar) nor partial pre-drying of the material.
Furthermore, the MRS delivers sufficient pressure that in most cases, a melt pump is not necessary to boost the pressure.