A screw includes a screw main body, a conveyance portion conveying a raw material, and a passage provided in the screw main body. The passage includes a first passage element, a second passage element, and a third passage element. The screw main body has a plurality of cylindrical bodies arranged in an axial direction of the rotating shaft. At least a portion of the conveyance portion is formed on outer peripheral surfaces of the cylindrical bodies adjacent to each other, and the passage is formed in the cylindrical body so as to cross over between the adjacent cylindrical bodies.

The invention relates to a low pressure extruder (3) for manufacturing a low density plastic composite material, characterized in that, the volume between the cylinder and the screw per unit length is not decreased along the direction from the hopper to the die in order that the mixture is extruded at low pressure in the melted state out of the cylinder of the extruder; the die is heated by the heater to maintain the melted state of the material in order not to create resistance to the flow in the process of pushing the material mixture out of the cylinder of the extruder. Furthermore, the present invention provides a method and equipment for manufacturing this material.

The invention relates to a low pressure extruder (3) for manufacturing a low density plastic composite material, characterized in that, the volume between the cylinder and the screw per unit length is not decreased along the direction from the hopper to the die in order that the mixture is extruded at low pressure in the melted state out of the cylinder of the extruder; the die is heated by the heater to maintain the melted state of the material in order not to create resistance to the flow in the process of pushing the material mixture out of the cylinder of the extruder. Furthermore, the present invention provides a method and equipment for manufacturing this material.

A conveyance portion, a barrier portion, and a path are provided at places of a screw main body in which a kneading portion is provided. In 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 to urge the raw materials having the conveyance limited by the barrier portion to increase pressure on the raw materials, to flow in the entrance. The raw materials flowing from the entrance flow through the path in the same direction as a conveyance direction of the conveyance portion.

A conveyance portion, a barrier portion, and a path are provided at places of a screw main body in which a kneading portion is provided. In 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 to urge the raw materials having the conveyance limited by the barrier portion to increase pressure on the raw materials, to flow in the entrance. The raw materials flowing from the entrance flow through the path in the same direction as a conveyance direction of the conveyance portion.

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 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.

A conveyance portion, a barrier portion, and a path are provided at places of a portion of a screw main body in which a kneading portion is provided. In at least one of the places, an entrance is opened to cause raw materials, conveyance of which is limited by a barrier portion to increase pressure on the raw materials, to flow in. The raw materials flowing in from the entrance flow through the path in the opposite direction to a conveyance direction of the conveyance portion. An exit is opened in an outer circumferential surface of the screw main body at a position outside the conveyance portion in which the entrance is opened.