Twin screw extruder type batch mixers
Twin screw extruder type batch mixers
A twin screw extruder type batch mixer that is comprised of two screws parallel to each other with the distance between the two screw center lines being larger or equal than the half of the sum of two screw diameters and the two screws conveying material in the opposite direction during mixing and reacting stage and the same direction during charging and discharging stages; and a barrel casing completely enclosing said screws which can run clockwise and counter-clockwise independently.
Another shortcoming with a internal mixer is in tts use in evaluating materials for an extrusion process. One of the major uses of a laboratory internal mixer is to test the processibility of thermoplastics, thermosets and elastomers, and transfer the information to a continuous sheet production extruder process such as extrusion. As both the geometry of a internal mixer and mixing mechanism are different from those of a screw extruder, it is often difficult to predict extrusion results from information learnt through a batch internal mixer study. Scott and Macosko (Scott, C. E. and Macosko, C. W., Polymer Engineering and Science, 33, 1065, 1993) developed a batch mixer named the recirculating screw mixer(RSM) based on single screw extrusion technology. The mixing mechanism in RSM is more representative of that in a continuous single screw extruder and thus results obtained are more meaningful in scale up for continuous single screw extrusion operation.
However, a single screw extruder and RSM do not have very good mixing capabilities. More polymer mixing and reaction processes are performed in twin screw extruders which have much better mixing capabilities. Thus a twin screw type batch mixer should provide not only a good batch mixer but also a tool with which useful information which can be easily transformed to continuous twin screw extruder can be learnt.
A twin screw extruder type batch mixer that is comprised of two screws parallel to each other with the distance between the two screw center lines being larger or equal than the half of the sum of two screw diameters and the two screws conveying material in the opposite direction during mixing and reacting stage and the same direction during charging and discharging stages; and a barrel casing completely enclosing said screws which can run clockwise and counter-clockwise independently.
Another shortcoming with a internal mixer is in tts use in evaluating materials for an extrusion process. One of the major uses of a laboratory internal mixer is to test the processibility of thermoplastics, thermosets and elastomers, and transfer the information to a continuous sheet production extruder process such as extrusion. As both the geometry of a internal mixer and mixing mechanism are different from those of a screw extruder, it is often difficult to predict extrusion results from information learnt through a batch internal mixer study. Scott and Macosko (Scott, C. E. and Macosko, C. W., Polymer Engineering and Science, 33, 1065, 1993) developed a batch mixer named the recirculating screw mixer(RSM) based on single screw extrusion technology. The mixing mechanism in RSM is more representative of that in a continuous single screw extruder and thus results obtained are more meaningful in scale up for continuous single screw extrusion operation.
However, a single screw extruder and RSM do not have very good mixing capabilities. More polymer mixing and reaction processes are performed in twin screw extruders which have much better mixing capabilities. Thus a twin screw type batch mixer should provide not only a good batch mixer but also a tool with which useful information which can be easily transformed to continuous twin screw extruder can be learnt.