JPH07276463A - Method and device for water foaming resin extrusion molding - Google Patents

Abstract

PURPOSE:To make easy the control of injection pressure of water into a cylinder of a water foaming resin extrusion molding machine. CONSTITUTION:In a water foaming extrusion molding device for feeding water between an extrusion screw shaft 4 and the inner wall of a cylinder 1 and extrusion molding a porous foamed product, a water feed line 6 is formed inside the extrusion screw shaft 3 and a feed hole 7 communicating with the feed line and opened on the surface of the extrusion screw shaft or on the rear face of a thread of the extrusion screw shaft.

Description

Detailed Description of the Invention

[0001]

This invention relates to plastics, rubbers,
The present invention relates to a water foam extrusion molding method for foaming a thermoplastic elastomer or the like with water and extruding the same, and an apparatus therefor.

[0002]

2. Description of the Related Art When a porous foamed product is extruded by supplying water between an extrusion screw of a thermoplastic resin extruder and an inner wall of a cylinder, conventionally, as shown in FIGS. A water injection port 2 is provided in the cylinder, and water is supplied to the place where the material that has entered the cylinder from the raw material supply port 3 is plasticized by the extrusion screw shaft 4.

[0003]

The material being kneaded in the cylinder is pressurized by the extrusion screw shaft. Therefore, in order to inject water, it must be injected at a pressure higher than the internal pressure of the cylinder. If the injection pressure is low, not only injection is not possible, but the material inside goes upside down from the injection port and the injection port is blocked. If the injection pressure is too high, the water does not remain at the injection position but flows to the material supply port 3 or the extrusion port at the tip of the extrusion screw shaft. The adjustment of the injection pressure and the cylinder internal pressure that changes depending on the rotation speed of the extrusion screw shaft is delicate, and when the injection port is closed, the molding work must be interrupted and the troublesome work of opening the injection port must be performed. This invention has made it a subject to develop a new injection method that eliminates the difficulty of controlling the injection pressure of water as described above.

[0004]

The water foam extrusion molding method of the present invention is a water foam extrusion molding method in which water is supplied between an extrusion screw shaft of an extruder and an inner wall of a cylinder to extrude a porous foam product. The method is characterized in that water is injected into the cylinder through the inside of the extrusion screw shaft, through the surface of the shaft or the opening on the back surface of the extrusion screw thread.

The water foam extrusion molding apparatus of the present invention is a water foam extrusion molding apparatus for supplying water between an extrusion screw shaft and an inner wall of a cylinder to extrude a porous foam product, and the inside of the extrusion screw shaft. In addition, a water supply path and a supply hole communicating with the water supply path and opened on the surface of the extrusion screw shaft or the back surface of the screw thread of the extrusion screw shaft are provided.

[0006]

The present invention breaks the conventional fixed concept that water is always supplied from the inlet provided in the cylinder. It has been demonstrated that if water is injected into the lowest pressure location inside the cylinder, the difficulty of adjusting the conventional water injection pressure can be eliminated. Specifically, water is supplied to the inside of the cylinder from the surface of the extrusion screw shaft or from the back surface of the screw thread of the extrusion screw shaft (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 extrusion screw shaft, and is a negative pressure or a slight pressure on the rear surface of the screw thread of the extrusion. Therefore, even if the injection pressure of water supplied to the surface of the extrusion screw shaft or the back surface of the screw thread is small, there is no risk of it being blocked by the kneading material, and of course, the water will go around the high pressure part in the cylinder to an unnecessary place. Since there is no danger of going there, the control of the injection pressure becomes extremely easy.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention.
Is a cylinder, 3 is a raw material supply port, 4 is an extrusion screw shaft,
Reference numeral 5 is a die for the extrusion port at the front end of the cylinder, and the screw shaft 4 has a water supply path 6 from the rear end to the middle along the shaft center.
At the front end of this supply passage, as shown in FIG. 2, there is provided an extrusion screw shaft 4 and a supply hole 7 opening to the surface in the radial direction. Further, as shown in FIG. 3, the supply hole 7 may be provided from the front end of the water supply passage 6 to the back surface of the screw thread 8 of the extrusion screw shaft. The supply hole 7 is preferably provided so as to supply water to a portion where the material that has entered the cylinder from the raw material supply port 3 is plasticized by the rotation of the extrusion screw shaft.

[0009]

In the past, it was difficult to control the injection pressure of water into 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. Then, the countermeasure was advanced in the direction of improving the injection pressure control technique. The present inventor is not limited to such a conventional way of thinking, and as a result of proceeding with the theoretical research, it is only necessary to provide the water supply port on the surface of the extrusion screw shaft having the lowest cylinder internal pressure or on the back surface of the screw thread of the extrusion screw shaft. Eliminating the difficult control of water injection pressure.

[Brief description of drawings]

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

FIG. 2 is an enlarged sectional view taken along line XX of FIG.

FIG. 3 is an enlarged cross-sectional view of an embodiment different from FIG.

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

5 is an enlarged cross-sectional view taken along line XX of FIG.

[Explanation of symbols]

 1 Cylinder 3 Raw Material Supply Port 4 Extrusion Screw Shaft 6 Water Supply Channel 7 Water Supply Port 8 Extrusion Screw Shaft Thread

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Claims (2)

[Claims] 1. A water foaming extrusion molding method for forming a porous foamed product by supplying water between an extrusion screw shaft of an extruder for extruding plastic, rubber, a thermoplastic elastomer and the like and an inner wall of a cylinder. A water foam extrusion molding method, wherein water is injected into the cylinder through the inside of the extrusion screw shaft and from the surface of the shaft or the back surface of the screw thread of the extrusion screw shaft. 2. A water foam extrusion molding apparatus for supplying water between an extrusion screw shaft and an inner wall of a cylinder to extrude a porous foam product, wherein a water supply passage is provided inside the extrusion screw shaft, A water-foaming extrusion molding apparatus for plastics, rubber thermoplastic elastomers, etc., characterized in that a supply hole is provided which is open to the surface of the extrusion screw shaft or the back surface of the screw thread of the extrusion screw shaft, which is connected to the supply passage.