Extruder screw, extruder, and extrusion method

An extruder screw comprising:

• a transfer portion continuously conveying supplied materials;
• a melting and mixing portion continuously melting and mixing the conveyed materials;
• and
• a kneading portion continuously kneading raw materials obtained by melting and mixing the materials,
• wherein
• the transfer portion, the melting and mixing portion, and the kneading portion are provided in a screw main body rotating about a straight axis, and
• a conveyance portion conveying the raw materials, a barrier portion limiting conveyance of the raw materials, and a path through which the raw material flows are provided at places, at a part of the screw main body in which the kneading portion is provided, and
• wherein in at least one of the places,
• the path is provided inside the screw main body and comprises an entrance and an exit,
• the entrance is opened in an outer circumferential surface of the screw main body in the conveyance portion to urge the raw materials having the conveyance limited by the barrier portion to increase pressure on the raw materials, to flow into the entrance,
• the path is configured to urge the raw materials flowing from the entrance to flow toward the exit in a same direction as a direction of the conveyance of the conveyance portion, and
• the exit is opened in the circumferential surface of the screw main body, at a position displaced from the conveyance portion in which the entrance is opened.