Patent ID: 8403554

Claim:
A screw for an extruder, comprising: a feeding portion, a kneading portion, and an extruding portion arranged in sequence along the length of the screw, from upstream to downstream in the direction of conveyance of material by the rotation of the screw, wherein the feeding portion and the extruding portion are each comprised of a screw element; the kneading portion including a kneading segment, the kneading segment having at least two kneading elements, each kneading element comprising either a kneading disk segment or a rotor segment with two kneading tip portions or more, for kneading the material to be kneaded, the kneading portion having a kneading element at each end thereof along the length of the screw; and a bearing segment provided within said kneading portion and upstream of the screw element of said extruding portion, wherein said bearing segment is provided with at least two axially spaced bearing elements, each bearing element having only one tip portion in the circumferential direction, wherein the tip portions of the bearing elements are uniformly angularly spaced in the rotational direction of the screw, wherein the rotational outer diameter of each bearing element of said bearing segment is uniform over the entire length of the bearing element of said bearing segment in the axial direction of the screw, and wherein the length of each of the bearing elements in the axial direction of the screw is set to 0.2D (D: rotational outer diameter of said bearing segment) or more.