Typical continuous kneading unit
Generally, a composite resin material, such as a plastic compound, is manufactured by injecting a polymeric resin material and a powdery additive into a barrel of a continuous kneading unit, and then extruding the two downstream while they are kneaded with a kneading screw extending through the barrel. Furthermore, a granulator, for example, is disposed adjacent to the downstream side of the continuous kneading unit, such that the granulator forms the composite resin material into pellets. A typical continuous kneading unit may either be a single kneading-screw type or a twin kneading-screw type. A twin-screw continuous kneading unit includes a barrel having therein a pair of left and right kneading chambers which communicate with each other; a pair of left and right kneading screws extending through the two respective kneading chambers in a rotatable fashion; and supply means connected to an upstream portion of the barrel for injecting a material into the kneading chambers.
Each of the kneading screws includes screw segments for transferring the material downstream, and rotor segments and kneading segments that knead the material while applying a large shearing force to the material. These segments are connected to each other in an axial direction of the kneading screw. For example, a twin-screw continuous kneading unit disclosed in Japanese Unexamined Patent Application Publication No. 2002-210731 has the structure described above, and is provided with a vacuum suction hole for forcibly removing volatile constituents and water from a material for the purpose of component adjustment. A gas suction operation through the vacuum vent creates a negative-pressure state in the kneading chambers, thereby enhancing devolatilization of the material and forcing the volatile components to be emitted outward through the vacuum vent. Twin-screw continuous kneading units that are equipped with a material-extruding function are generally called twin-screw extruders.
Specifically, a single screw extruder according to the present invention includes a barrel having a kneading chamber therein; a kneading screw comprising plural segments, said kneading screw extending through said kneading chamber in a rotatable fashion, said kneading screw being rotated so as to knead a material and to transfer the material from an upstream side of the extruder towards a downstream side of the extruder; a devolatilization segment section in said kneading screw, said devolatilization segment section being provided with a kneading flight twisted around said devolatilization segment section so as to transfer the material downstream, said kneading flight kneading the material while transferring the material downstream and separating a volatile component from the material; a feeding section disposed adjacent to a downstream side of said devolatilization segment section, said feeding section including a screw segment; a vacuum suction hole at a position corresponding to a position of said barrel where the feeding section is disposed, said vacuum suction hole communicating with a portion of said kneading chamber through which said devolatilization segment section extends.