Method for manufacturing short fiber oriented rubber or synthetic resine and expansion die for extrusion molding

Abstract

A method comprises steps of extruding rubber or synthetic resin mixed with short fiber from a mold opening 6 of sectionally annular and molding a cylindrical body of rubber or synthetic resin with short fiber oriented in predetermined direction. And the mold opening 6 is passed through with an expansion portion 9 whose diameter expands in extrusion direction, and a flow passage width Wi of an inlet portion 6i of the mold opening, a flow passage width Wo of an outlet portion 6o, and radiuses Ri and Ro of the inlet portion 6i and the outlet portion 6o respectively that are coaxial with the mold opening satisfy a relation of Wo/Wi<Ro/Ri. And value of Ro/Ri is adjusted within a scope of 2≦Ro/Ri≦8 by changing the radius Ri of the inlet portion according to mechanical property in circumferential direction of the cylindrical body to be molded, so that orientation of the short fiber is adjusted.

Dependencies are inferred from the claim text.