Upstream side of the resistive element
The flight of the segment included in the resistive elements is twisted in a reverse-spiral fashion for pushing the material upstream, the material transferred from the upstream side accumulates in this section. Accordingly, the impregnation section having a high impregnation rate of the material is formed adjacent to the upstream side of the resistive element, whereby the front and rear spaces of the impregnation section are securely blocked from each other with pressure. Thus, the devolatilization segment section adjacent to the impregnation section is properly sealed.
Accordingly, the material transferred from the upstream side receives a flow-path resistance in the discharging member, such as a die, an orifice, a transfer pipe, or a filtration unit having a high flow-path resistance, whereby the impregnation section is formed adjacent to the upstream side of the discharging member. Thus, the front and rear spaces of the impregnation section are securely blocked from each other with pressure, whereby the devolatilization segment section adjacent to the impregnation section is properly sealed. The devolatilization segment section preferably includes a double-blade rotor segment including a pair of kneading flights which is projected in opposite directions from each other with respect to a diameter direction of the twin screw extruder. Furthermore, each of the kneading flights is preferably provided with a low tip and a high tip for facilitating the separation of the volatile component, the low tip having a large tip clearance with respect to an inner surface of at least one kneading chamber so as to enable a thin-film formation of the material on the inner surface, the high tip having a small tip clearance with respect to the inner surface of at least one kneading chamber so that the thin film of the material is scraped off the inner surface by the high tip.
Moreover, a pair of kneading screws respectively extends through the pair of kneading chambers in a rotatable fashion, the kneading screws being rotatable in the same direction and being meshed with each other. The double-blade rotor segments in the devolatilization segment section are connected in a continuous manner such that side surfaces of the kneading flights of the adjacent rotor segments with respect to an axial direction of said kneading screw do not have a step therebetween. The kneading flights of the adjacent rotor segments are connected such that they do not have a step therebetween, and grooves formed between the adjacent kneading flights extend continuously in the axial direction. Thus, the entire devolatilization segment section forms a smooth spiral. Since the grooves provided in the devolatilization segment section communicate with the vacuum suction hole, the volatile component evaporating from the material flows through a flow path defined by the grooves and is properly sucked into the vacuum suction hole so as to be released outward.