JPH07276470A - Water foaming resin extrusion molding method - Google Patents

Abstract

PURPOSE:To mix easily water with a molten resin by forming an injection passage protruding inwardly into a cylinder and injecting water from a protrud ed section into the molten synthetic resin. CONSTITUTION:A water injection passage 3 is opened at the end of an protruded section 3a extending further inwardly in a cylinder 1. A half-molten resin pushed forward by the rotation of a screw 2 is pressed to the inner periphery of the cylinder 1 formed to be hard to slide while sliding on a press surface 1 and moved toward the downstream direction without revolving together. The inner periphery of the cylinder 1 is only one friction face to prevent the co-revolution of the resin with a screw, and the pressed resin is pushed aside by the protruded section 3a of the injection passage, and water is injected therein. This method is optimum as the injection method for mixing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-foam resin extrusion molding method in which a synthetic resin is foamed with water and extruded.

[0002]

2. Description of the Related Art In a water-foam resin extrusion molding method using water, when a synthetic resin is extruded by an extruder, water is externally added to a plasticized resin in a cylinder, and the mixture is kneaded and extruded. In order to form a fine and uniform foam structure, various methods have been added to the kneading method of the added water and the molten resin. However, the method of supplying water from the outside is constant, and all are injected from the injection passage that penetrates the cylinder wall from the outside to the inside at a pressure that overcomes the internal pressure in the cylinder.

The relationship between the injection pressure and the cylinder internal pressure is delicate. If the injection pressure is too strong, water will spread along the inner wall of the cylinder from the raw material supply port to the extrusion port, and if it is too weak, the resin will flow back into the injection path. , May block the injection channel. In addition, since the injection passage opens on the inner surface of the cylinder, water collects along the inner surface of the cylinder, but it is difficult to take this water into the molten resin with ordinary screw flight. Is required, which complicates the structure.

[0004]

As described above, the prior art is as follows.
Since water was being injected into the injection passage that was open on the inner surface of the cylinder, water was collected along the inner circumference of the cylinder or spread laterally, and the mixing means was devised to take it into the resin quickly. However, the present inventors have wondered whether there is a problem in the water injection method. Isn't it easier to mix water into the molten resin by improving the water injection method? The improvement of the injection method was taken up as the subject of this invention.

[0005]

In the water-foam resin extrusion molding method of the present invention, a water injection passage that penetrates the cylinder wall from the outside to the inside is provided in the middle of a cylinder containing a screw of a synthetic resin extruder. In a water-foam resin extrusion molding method in which water injected from there and synthetic resin in the cylinder are mixed and extruded by the rotation of a screw shaft in the cylinder, the injection passage is further extended to protrude inward of the cylinder, It is characterized in that water is injected from the protruding portion into the molten synthetic resin.

[0006]

[Function] As is obvious from the point of view, in the past, water that came out of the injection path that opened in the inner circumference of the cylinder pushed away the molten resin and either runs along the inner circumference of the cylinder or accumulates. is there. According to this invention, if the injection path is extended inward of the cylinder and water is injected into the molten resin, water is injected into the area where the inwardly protruding injection path separates the resin. Water is easily mixed in.

[0007]

1 and 2 show an embodiment of a water injection path in the water-foamed resin extrusion molding method of the present invention. Reference numeral 1 is a screw cylinder, 2 is a screw, and 3 is a water injection path. While the conventional injection passage 3'of FIG. 5 is open to the inner peripheral surface of the cylinder 1, the injection passage 3 of the present invention is opened to the tip of the protrusion 3a extending further inward of the cylinder 1. is doing. Although not shown, the semi-molten resin pushed forward by the rotation of the screw 2 is the screw flight 2 which is made smoothly.
It slides on the pressing surface of a and is pressed against the inner circumference of the cylinder 1 which is made to slip, and moves in the downstream direction without rotating together.

The inner circumference of the cylinder 1 is the only friction surface that prevents the resin from co-rotating with the screw, and the protrusion 3a of the injection path of the present invention scrapes away the resin to be pressed, and injects water into it. Of. This is an ideal injection method for mixing.

3 and 4 also show an embodiment of the injection path of the present invention, the protrusion 3a of this injection path extends deeper inward of the cylinder 1, and therefore the screw flight 2a.
A notch 4 is provided through which the protruding portion 3a passes. Further, in this example, the injection path 3 is bent in the protruding portion 3a and opens toward the downstream side (right side in the drawing). Therefore, the protruding portion 3a of the injection path pushes the resin by the back surface of the opening surface, and water is injected into the separated portion. Although the two embodiments of the foam material injection path peculiar to the present invention have been described above, the protruding portion 3a of the injection path is described.
The length, shape, outlet position, orientation, etc. should be appropriately designed according to the operating conditions.It is easy to provide multiple injection path protrusions in the cylinder, or to provide multiple openings for each protrusion. Conceivable.

[0010]

According to the present invention, the means for supplying water to the foamed resin extrusion molding machine breaks the conventional fixed concept which was always limited to the injection passage opening to the inner peripheral surface of the extrusion cylinder. Furthermore, we opened a new method that extends inward and injects water from the protruding part. This is a slight change in structure, but it is an extremely large improvement in operation.

That is, since the inner peripheral surface of the cylinder is a place where the resin inside is pressed and proceeds downstream along this, by providing a protruding portion of the water injection path here, the flow of the resin can be separated by It will be disturbed and water will be injected into it. Conventionally, the water that has flowed out of the injection channel pushes the resin that advances along the inner circumference of the cylinder toward the inside of the cylinder,
The value of the present invention can be clearly understood in comparison with the injection method that allowed the particles to be accumulated in the gap between the inner wall and the resin or moved back and forth along the inner wall. It is not necessary to explain the difference between supplying water to the outside of the resin and mixing it, or supplying the water while the resin is being divided and mixing.However, since the present invention opens the injection passage in the protrusion of the cylinder inner wall, , The position, direction and number of the openings can be freely selected.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part of an embodiment of the present invention.

FIG. 2 is a transverse sectional view of the same.

FIG. 3 is a longitudinal sectional view of a main part of another embodiment of the present invention.

FIG. 4 is a transverse sectional view of the same.

FIG. 5 is a cross-sectional view showing a conventional technique.

[Explanation of symbols]

 3 Foam material injection path 3a Projection

Claims (1)

[Claims] 1. A water injection passage that penetrates the cylinder wall from the outside to the inside is provided in the middle of a cylinder containing a screw of a synthetic resin extruder, and the water injected from there and the synthetic resin in the cylinder are provided in the cylinder. In the water-foam resin extrusion molding method in which mixing and extruding are performed by the rotation of the screw shaft in the inside, the injection passage is further extended to protrude inward of the cylinder,
A water-foam resin extrusion molding method, which comprises injecting water into the molten synthetic resin from the protruding portion.