JPH05228977A - Method and device for extrusion foam molding - Google Patents

Abstract

PURPOSE:To control the injection pressure of a foaming agent easily by opening a filler hole, from which a foaming agent such as a gas is injected into the cylinder of an extruder, to the surface of a screw shaft or the rear of the thread of a screw through the inside of the screw shaft. CONSTITUTION:A foaming-agent filler hole 2 is opened toward the surface of a screw shaft from the feed 2a of the axis of the screw shaft. Internal pressure by kneading material such as plastics in a cylinder is weakened on the surface of the screw shaft and brought to negative pressure or fine pressure on the rear of the thread 4a. Accordingly, there is no possibility that the filler hole 2 formed to the surface of the shaft or the rear of the thread is clogged by the kneading material even at the small injection pressure of a foaming agent, thus controlling injection pressure extremely easily.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion foam molding method and an apparatus therefor.

[0002]

2. Description of the Related Art When a foaming gas or a foaming agent (hereinafter referred to as a foaming material) is supplied between an extrusion screw of a thermoplastic resin extruder and an inner wall of a cylinder to extrude a porous synthetic resin, it has been conventionally performed. Cylinder 1 as shown in all FIGS.
A foam material injection port 2'is provided in the above, so that the material that has entered the cylinder from the raw material supply port 3 is injected into the place plasticized by the screw 4.

[0003]

The material being kneaded in the cylinder is pressurized by the screw. Therefore, in order to inject the foam material, it is necessary to inject at a pressure higher than the internal pressure of the cylinder. If the injection pressure is low, not only injection will not be possible, but the material inside will also work upside down from the injection port and block it. If the injection pressure is too high, the injection pressure is not limited to the injection position, and the material is supplied to the material supply port 3 or the extrusion port at the tip of the screw. The adjustment of the injection pressure and the cylinder internal pressure that changes depending on the rotation speed of the screw is delicate,
If the inlet is blocked, it will be troublesome. This invention made it a subject to develop the new injection system which eliminates the difficulty of the above-mentioned injection pressure control.

[0004]

In the extrusion foam molding method of the present invention, a foaming gas or a foaming agent is supplied between an extrusion screw of a thermoplastic resin extruder and an inner wall of a cylinder to extrude a porous synthetic resin. In the extrusion foam molding method for molding, the above-mentioned foaming gas or foaming agent is injected into the cylinder through the inside of the screw shaft and from the opening of the surface of the shaft or the rear surface of the screw thread.

The extrusion foam molding apparatus of the present invention is an extrusion foam molding apparatus for supplying a foaming gas or a foaming agent between an extrusion screw and an inner wall of a cylinder to extrude a porous synthetic resin. It is characterized in that it is provided with a supply path for the foaming gas or the foaming agent that passes through the shaft core, and an injection port that communicates with the supply path and is opened on the surface of the shaft or the back surface of the screw thread.

[0006]

The present invention breaks the conventional fixed concept that the foam material is always supplied from the injection port provided in the cylinder. By demonstrating that the difficulty of adjusting the conventional foam material injection pressure can be eliminated by providing the foam material injection port at the lowest pressure inside the cylinder. Specifically, the foam material injection port is provided on the surface of the screw shaft or on the back surface of the screw thread (on the back side of the raw material extrusion surface).

The kneading material inside the cylinder has a maximum internal pressure along the inner wall of the cylinder which receives the maximum reaction force, is weak on the surface of the screw shaft, and becomes negative pressure or minute pressure on the back surface of the screw thread. Therefore, even if the injection pressure of the foam material sent to the injection port provided on the shaft surface or the back of the screw thread is small, there is no fear that it will be blocked by the kneading material, and of course, the foam material will go around the high pressure part in the cylinder to an unnecessary place. Since it does not exist, the injection pressure control becomes extremely simple.

[0008]

FIG. 1 shows an embodiment of the present invention.
1 is a cylinder, 2 is a foam material injection port, 2a is a screw shaft 4
The foam material supply path communicating with the shaft core of 3, the raw material supply port 3, and the extrusion port die 5. 2 is a sectional view taken along the line XX in FIG. 1, showing a state in which the supply passage 2a of the screw shaft shaft core communicates with the inlet 2 on the screw shaft surface in the radial direction.

In FIG. 3, the injection port 2 is provided with a screw thread 4a.
It is sectional drawing of the Example provided in the back surface of FIG. The supply passage 2a passing through the shaft core in FIG. 1 is as it is, the passage in the radial direction toward the shaft surface is directed directly below the screw thread 4a, and is bent and passed to the injection port 2 on the back surface of the screw thread. It is tight.

[0010]

In the past, it was difficult to control the foam material injection pressure to the injection port provided in the cylinder, and it was not uncommon for the injection port to be clogged with a kneading material to stop the operation. And the countermeasure was advanced in the direction of improving the injection pressure control technology. The present inventor is not limited to such a conventional way of thinking, and as a result of advancing the principle research, it is difficult to control the injection pressure only by providing the foam material injection port on the surface of the screw shaft having the lowest cylinder internal pressure or the back surface of the screw thread. I made it unnecessary.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional explanatory view of an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line XX of FIG.

FIG. 3 is a sectional explanatory view of an embodiment different from the above.

FIG. 4 is an explanatory view of a vertical cross-sectional view of a conventional technique.

FIG. 5 is a cross sectional explanatory view of FIG. 4.

[Explanation of symbols]

 2 Foam material inlet 2a Foam material supply path 4 Screw 4a Screw screw thread

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[Procedure amendment]

[Submission date] March 18, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

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[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

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[0001]

This invention relates to plastics, rubbers,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion foam molding method for a thermoplastic elastomer and an apparatus for the same.

Claims (2)

[Claims] 1. A foaming gas or a foaming agent is supplied between an extrusion screw of a thermoplastic resin extruder and an inner wall of a cylinder,
In an extrusion foam molding method for extrusion molding a porous synthetic resin, the above-mentioned foaming gas or foaming agent is injected into the cylinder through the inside of the screw shaft, from the surface of the shaft or the opening on the back surface of the screw thread. Extrusion foam molding method. 2. An extrusion foam molding apparatus for supplying a foaming gas or a foaming agent between an extrusion screw and a cylinder inner wall to extrude a porous synthetic resin, wherein the extrusion screw is for foaming passed through a shaft core. An extrusion foam molding apparatus comprising: a supply path for gas or a foaming agent; and an injection port that communicates with the supply path and is opened on a surface of a shaft or a back surface of a screw thread.