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Basic Study on Drsk Type Extruders
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Funatsu, Kazumori / Kajiwara, Toshihisa / Minoda, Takeshi / Ohga, Yoshinori
Although screw extruders have been used for the production of films, pipes, sheets and many other kinds of plastic products, there is still room for improvement. The melting process has an important role in extruders. According to the results of computer simulations on the melting process in a single screw extruder, the melting rate of a polymer solid bed will increase strongly if the heat transfer surface can be enlarged. For ordinary screw extruders, it is very difiicult to increase the heat transfer surface using the conventional screw geometry. Therefore, a disk type extruder was assembled as a modification to a single screw extruder. A trial apparatus was examined from various aspects. In this disk type extruder polymeric materials flow by relative motion between a fixed spiral plate where a rectangular channel was cut spirally from the center to the circumference and a moving flat plate. Usage of two surfaces of these plates for heating was very effective in increasing the melting rates. The extruder could extrude materials at rates less than 95g Emin-1 and under pressures less than 9.5 MPa. At higher pressures, the extruder developed leaks through the circumference. The leakage could probably be prevented by cooling the first turn of the channel sufficiently to keep the materials from melting.. From the residence time distribution measured under steady extrusion, it was clear that there is circulation flow over flights. Mixing may thus be enhanced by longer shear loading by circulatory flow in the extruder.
Key words: Disk type extruder / Meltingproces / Mixing / Residence time distribution