Semiconductive rubber belt, and process for producing the same
An object of the present invention is to provide a semiconductive rubber belt wherein a variation in the electric resistance is decreased, in particular, in the belt circumferential direction so that high-quality images can be formed, and a process for producing the same. In order to achieve the object, in a case where on any single straight line extended in the belt circumferential direction, the maximum value of the molecular orientation ratio correction value MOR-C of the semiconductive rubber belt, the minimum value thereof, and the average thereof are set to satisfy a specified relationship.
1. A process for producing a seamless semiconductive rubber belt having a volume resistivity of 10 4 to 10 12 Ωcm, comprising:
an extruding step of using an extruder equipped with a crosshead having an inner cylinder section wherein a spiral flow type groove is made to plasticize an unvulcanized rubber composition having a scorch time t 5 of 10 to 18 minutes, and extruding the composition through the extruder,
an unvulcanized rubber belt molding step of shifting, inside the inner cylinder section, a cylindrical mold in a direction substantially orthogonal to the extrusion direction of the unvulcanized rubber composition in the extruder while making the unvulcanized rubber composition into a layer form and allowing the layer-form unvulcanized rubber composition to cover the outside surface of the cylindrical mold, thereby yielding an unvulcanized rubber belt, molded body, and
a vulcanizing step of vulcanizing the unvulcanized rubber belt molded body, thereby yielding the semiconductive rubber belt.
2. The process for producing the semiconductive rubber belt according to claim 1 , wherein the ratio between the maximum outside diameter d of the inner cylinder section and the outside diameter e of a discharging opening in the section (the die contraction ratio) satisfies the following: 0.2≦e/d≦0.8, and further the shift speed of the cylindrical mold is 1 m/minute or less in the unvulcanized rubber belt molding step.