Extrusion System

The patented MRS Extrusion System offers completely new possibilities with regard to the efficient degassing and extrusion of polymer melts.

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.

Design
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.

Performance comparison
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.

Energy efficient
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.

The Online Viscometer was developed with the goal of achieving measurements which are comparable with laboratory results and to provide a system which provides these accurate values permanently and without influencing the process.

Reliable viscosity measurement
The Online Viscometer was developed with the goal of achieving measurements which are comparable with laboratory results and to provide a system which provides these accurate values permanently and without influencing the process.

The viscometer is fitted between two flange connections. The melt channel can be designed according to the customer´s specifications between D = 20 mm (0.8 inches) and D = 110 mm (4.3 inches). The unit includes the pump drive, the pump, pressure transducers, temperature sensors and the control and evaluation electronics. Electric or liquid/vapor heating is available (optional). The setting of process parameters, the evaluation and the display is realized via a user-friendly touch screen panel or alternatively can be integrated into an existing control system.

An easily exchangeable capillary permits the adaptation of the measuring device to different viscosities ranging from 1 mPas (0.01 poise) up to 20.000 Pas (200,000 poise). A subsequent change of the measuring range is also possible.

Due to the special melt channel design and precise fabrication, dead spots or edges in which shear and temperature sensitive polymers could possibly stagnate can be avoided. The very short dwell time also prevents accumulations of degraded material. A further innovative feature is the possibility of completely cleaning all parts in contact with the melt without interrupting or disturbing the production process.

Configuration
By means of a high precision metering gear pump, a small part of the polymer melt (max. 3 kg / h or 7 lbs / h) is separated from the main melt channel. This is pumped through a precisely manufactured slot capillary. The inlet and outlet pressures or the elastic properties which disturb the measurement are filtered out by means of length – optimized inlet and outlet zones in the capillaries for levelling out the laminar flow.

Advantages of the Online Viscometer VIS

• No measurable temperature increase in the rheometer thanks to ample flow channels.
• Short dwell time, no dead spots, no remnants or material left in the melt channels.
• Through measurement in the rectangular capillary cross section – no elastic properties are recorded.
• Very compact design, flexible adaptation to the existing melt pipe or extrusion line.
• Fast adaptation and change of the measuring range through an exchangeable capillary plate.
• Polymer bypass, therefore no melt losses.
• High-precision measurement of the melt temperature directly during the viscosity measurement.
• High measurement accuracy through use of special high-precision pressure transducers.
• Complete cleaning of all surfaces and channels in contact with the melt without interruption or shutting down of the production process.