At a part of the screw main body at which the kneading portion is provided, conveyance portions, a barrier portion and a path are provided at a plurality of places. At least one of the places, the path is provided inside the screw main body, and includes an entrance and an exit. The entrance is opened in such a manner that the raw material whose pressure is enhanced by being restricted in conveyance by the barrier portion flows into the entrance. The path is formed in such a manner that the raw material flowing into the path from the entrance flows toward the exit in a direction opposite to the direction of conveyance.

At a part of the screw main body at which the kneading portion is provided, conveyance portions, a barrier portion and a path are provided at a plurality of places. At least one of the places, the path is provided inside the screw main body, and includes an entrance and an exit. The entrance is opened in such a manner that the raw material whose pressure is enhanced by being restricted in conveyance by the barrier portion flows into the entrance. The path is formed in such a manner that the raw material flowing into the path from the entrance flows toward the exit in a direction opposite to the direction of conveyance.

An extruder is disclosed including: a barrel; and a screw provided with a helical groove; wherein the screw comprises a dewatering portion comprising a first portion, and a second portion at a location downstream from the first portion; wherein, at the dewatering portion, clearance between the groove and the barrel decreases as one proceeds downstream; and wherein clearance reduction ratio at the first portion is greater than clearance reduction ratio at the second portion.

An extruder is disclosed including: a barrel; and a screw provided with a helical groove; wherein the screw comprises a dewatering portion comprising a first portion, and a second portion at a location downstream from the first portion; wherein, at the dewatering portion, clearance between the groove and the barrel decreases as one proceeds downstream; and wherein clearance reduction ratio at the first portion is greater than clearance reduction ratio at the second portion.

A kneading method includes conveying a raw material along a conveyance path; and increasing the raw material in pressure by restricting a conveyer from conveying the raw material by a barrier, causing the raw material with an increased pressure to flow into a passage from an inlet located at the conveyer, circulating the raw material having flowed into the passage to an outlet in the same direction as the conveying direction of the conveyer, and causing the raw material having circulated in the passage to flow out from the outlet to the outer circumference of a screw body. The raw material includes a polypropylene-based resin composition containing polypropylene and olefin rubber.

Provided is a flexible tube production apparatus capable of shortening the length of a resin layer in which the mixing ratio between two kinds of resins changes. The flexible tube production apparatus includes: two extruders extruding resins different from each other; two valves provided corresponding to the two extruders, respectively; a kneading mechanism kneading the resins supplied from the two extruders via the two valves; a die extruding the resins kneaded by the kneading mechanism; and a control device controlling the two valves to switch from a first state where one extruder and the kneading mechanism communicate with each other and communication between the other extruder and the kneading mechanism is cut off, to a second state where the other extruder and the kneading mechanism communicate with each other and communication between the one extruder and the kneading mechanism is cut off, when the flexible tube is extruded.

This concerns a screw pump for the extrusion of plastic materials, which is extremely compact and so it can be inserted in-line in a plastic material filtration system, encapsulating within it a duct parallel to the axis of the screw.

An extruder screw conveying raw materials while kneading them includes a screw main body, conveyance portions, barrier portions, and paths. The conveyance portions convey the raw materials in an axial direction. The paths each include an entrance and an exit. The raw materials, the conveyance of which is limited by the barrier portions, flow in from the entrance. The raw materials flowing in from the entrance flow through the paths in the same direction as a conveyance direction of the conveyance portions. The exit is opened in the outer circumferential surface of the screw main body at a position outside the conveyance portions in which the entrance is opened.

An extruder screw conveying raw materials while kneading them includes a screw main body, conveyance portions, barrier portions, and paths. The conveyance portions convey the raw materials in an axial direction. The paths each include an entrance and an exit. The raw materials, the conveyance of which is limited by the barrier portions, flow in from the entrance. The raw materials flowing in from the entrance flow through the paths in the same direction as a conveyance direction of the conveyance portions. The exit is opened in the outer circumferential surface of the screw main body at a position outside the conveyance portions in which the entrance is opened.

An extruder screw conveying raw materials while kneading them includes a screw main body, conveyance portions, barrier portions, and paths. The conveyance portions convey the raw materials in an axial direction. The paths each include an entrance and an exit. The raw materials, the conveyance of which is limited by the barrier portions, flow in from the entrance. The raw materials flowing in from the entrance flow through the paths in an opposite direction to a conveyance direction. The exit is opened in the outer circumferential surface of the screw main body at a position outside the conveyance portions in which the entrance is opened.