Cylindrical extruding die and method for producing seamless tube

A method for producing an electrically conductive seamless tube containing a thermoplastic resin serving as a binder and an electrically conductive filler dispersed in the thermoplastic resin, the method comprising the steps of:

• (1) preparing an electrically conductive resin composition containing a thermoplastic resin and an electrically conductive filler;
• (2) preparing a cylindrical extruding die comprising a cylindrical slit, a plurality of circumferential distribution channels communicating with the slit and configured to distribute the resin composition that is plasticized in a helical direction toward the slit, and a plurality of lead-in paths configured to lead the plasticized resin composition into the plurality of circumferential distribution channels, each of the plurality of lead-in paths containing a line mixer;
• (3) introducing the plasticized resin composition into the plurality of lead-in paths of the cylindrical extruding die toward the plurality of circumferential distribution channels;
• (4) introducing the plasticized resin composition that has flowed through the plurality of lead-in paths into the plurality of circumferential distribution channels toward the slit;
• and
• (5) introducing the plasticized resin composition that has flowed through the plurality of circumferential distribution channels into the slit and extruding the plasticized resin composition from an outlet of the slit into a cylindrical shape,
• wherein
• the step (3) comprises a step of interchanging the plasticized resin composition flowing through the plurality of lead-in paths between a flow near a wall of the plurality of lead-in paths and a flow in a radial center of the plurality of lead-in paths by the line mixers disposed in the plurality of lead-in paths,
• the plurality of lead-in paths has a circular cross section.