JPH0720657B2 - Extruder for coating foamed resin - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extrusion device for covering foamed resin.

[0002]

2. Description of the Related Art Foaming agent or gas (hereinafter referred to as foaming material)
A method has been developed in which is injected into the middle part of a screw cylinder of an extruder, mixed with a synthetic resin inside, thoroughly kneaded, and then extruded into a foamed resin, and immediately coating the wire. The foaming resin for coating is particularly homogeneous and is not put into practical use unless fine bubbles are arranged therein, and therefore various measures have been taken. For example, Japanese Examined Patent Publication No. 57-87344 “Extrusion Mixer” is provided with a concave surface opposed to a large number of concave surfaces on the inner circumference of an extrusion screw cylinder on a screw peripheral surface having no screw groove to increase the kneading ratio, and Japanese Examined Patent Publication No. As in the case of continuous extrusion equipment for cellular resin, short axial peaks and troughs are provided around the screw axis to intermittently inject the foam material, or in addition, notches in the reverse screw direction are added to the multi-thread screw flight. Various measures have been taken, such as putting it in and interrupting the screw flight many times.

[0003]

The present inventor has conducted an experimental study on the conventional technique and found that the method of providing the concave surfaces (referred to as cavities) on the inner circumference of the cylinder and the outer circumference of the screw as the mixing section is lengthened. Although this method is an excellent method that can obtain a good kneading result, it has a drawback that a large pressure drop is required to lengthen the mixing section. Another preferable method is to insert a notch in the reverse screw direction in the flight of the multi-screw screw, which gives excellent kneading results, but in this case as well, it is necessary to lengthen the mixing part to some extent. However, there is a fatal defect for coating a foamed resin that cannot be used when fine bubbles are required. The present invention has an object to develop, if these conventional techniques are properly combined, the defects may be complemented to each other, and as a result, a satisfactory resin foam may be obtained.

[0004]

The extruding device for coating a foamed resin of the present invention is a synthetic resin extruding device having an injecting portion for a foaming agent or gas in the middle of a screw cylinder, and receives the blowing agent or gas from the injecting portion. The screw-cylinder mixing section for kneading the resin faces the multiple thread section in which the multi-thread screw flight is provided with a notch in the reverse screw direction, and a large number of concave surfaces on the inner circumference of the cylinder that are provided behind or intersecting with the multiple thread section. And a cavity portion provided with a concave surface on the peripheral surface of the screw without a screw groove, wherein the screw of the injection portion is a single-screw or multi-screw single screw, the screw groove is deeper than the other portion, and is located immediately downstream of the injection hole. In addition, it is characterized by a plurality of rod-shaped protrusions, which are the same height as the screw flights or slightly lower, and are erected in the radial direction. In addition, it is recommended that the rod-shaped projections standing in the radial direction stand radially along one or a few planes perpendicular to the screw axis or stand in a reverse thread direction within one screw groove.

[0005]

The present invention, from among many prior arts, combines the above-mentioned method of forming a notch in the reverse screw direction with the above-mentioned multi-thread screw flight and the cavity method, thereby making a rough kneading by the former divided blades. It was confirmed that the action and the careful action of the inward and outward concave surfaces for shearing the mating together compensate for the disadvantages and enable precise kneading sufficient for coating the foamed resin in a short section. Conventionally, the groove of the screw near the injection hole is deepened to facilitate injection, but since the resin is not completely filled there, the gas for bubbles does not mix with the resin and spreads in the front-back direction of the screw. However, there was a dislike that the injection pressure became high and the extrusion varied. The rod-shaped projection of the present invention does not cause the above problems because the foam material just injected is immediately kneaded with the resin and captured.

[0006]

1 and 2 show a screw (cylinder not shown) according to an embodiment of the present invention and an injection hole 2 in a foam material injection portion for the screw. As in the past, the screw groove of the injection part is deeper than the others. The feature of the present invention is that the screw tip portion has a multi-threaded portion 3 in which a multi-threaded screw flight is provided with a notch in the reverse screw direction, and a cavity portion having a large number of concave surfaces facing a concave surface (cavity) on the inner circumference of a cylinder (not shown). 4 are adjacent to each other or intersect with each other, and a plurality of rod-shaped projections 6 that are slightly lower than the height of the screw flight 5 are provided in the deep thread groove of the injection portion 1 in the radial direction. 1 in FIG.
Although it is a multiple screw, the injection part 1 in Fig. 2 is different only in that it is a multiple screw. Conventionally, it was general that a large number of rod-shaped projections standing on the circumferential surface of the screw were made to stand in the mixing portion at the tip of the screw. On the other hand, in the present invention, only a plurality of foam materials are arranged near the foam material injection hole 2. The reason is that precise kneading is not possible no matter how many rod-shaped projections are lined up, but a small number of rod-shaped projections are effective to stir the material and increase the contact area with the foam material.

The material containing the foaming material is pushed and pushed between the feeding section, the screw of the compression section, and the cylinder so as to be kneaded, and reaches the mixing section peculiar to the present invention. In the mixing section, first, the multi-thread section 3 in which the multi-thread screw flight is provided with a notch in the reverse screw direction is subjected to a rough kneading action. As described above, a material containing fine-grained uniform bubbles cannot be made in the multi-strand portion 3. However, it is extremely effective for uniform homogenization as a whole, and achieves its purpose in a short section to feed the material to the subsequent cavity portion 4. The cavity portion 4 cannot be efficiently homogenized like the multi-strand portion 3, but is optimal for precision kneading into fine-grained bubbles so that it can be used for coating a foamed resin. This is because the materials are intertwined between the inner and outer concave surfaces and sheared. However, since there is no screw flight, there is no feeding action, and the longer the cavity portion 4, the greater the burden on the feeding screw portion.

In the mixing section of the present invention, the foamed material is kneaded efficiently by the multi-threaded section 3 having a feeding action, rough-finished in mechanical work, and then fed into the cavity section 4 for precision kneading. , That is, precision finishing. Therefore, the cavity portion 4 can be remarkably shorter than the conventional one. Preliminary kneading suffices for the multi-thread part 3 as well, so that it is short, and when both are combined, the precision mixing part is shorter and has higher performance than the conventional one.

In FIGS. 3 and 5, the rod-shaped projections 1 do not stand on one plane or a few planes as in FIGS. 1, 2, 4, and 6, but are arranged in one screw groove in the reverse screw direction. It is an example. Further, in FIG. 4, the screw flight 5 is provided with a cut 7 so that the rows of the protrusions 1 arranged in the same plane pass through the cut 7. FIGS. 5 and 6 show an embodiment in which projections 6 are lined up or passed through a slit 7 as shown in FIGS. FIG. 7 shows an example of an annular dam 8 that prevents the foam material from moving backward.
FIG. 8 also shows an example of the diaphragm mechanism 9. The protrusion 1 is omitted.

[0010]

INDUSTRIAL APPLICABILITY As a result of experimental research on various proposals relating to a conventional foamed resin extrusion apparatus, the present invention is excellent in kneading efficiency, but is not suitable for precision kneading for coating foamed resin. A multi-part section and a cavity section, which is optimal for precision kneading but which does not have a feeding function and is not efficient, were selected as a composite mixing section that extends the advantages of each and compensates for the disadvantages. Also, a rod-shaped projection on the screw near the foam material injection hole. As a result of this provision, both efficiency and product quality of this type of extrusion device have been improved.

[Brief description of drawings]

FIG. 1 is an explanatory view of a screw and an injection hole position according to an embodiment of the present invention.

FIG. 2 is an explanatory view of another embodiment of the same.

FIG. 3 is an explanatory view of an embodiment of a rod-shaped projection near the injection part.

FIG. 4 is an explanatory diagram of another embodiment of the same.

FIG. 5 is an explanatory view of an embodiment of a multi-screw screw of the same.

FIG. 6 is an explanatory view of another embodiment.

FIG. 7 is an explanatory diagram of the same loop dam.

FIG. 8 is an explanatory view of a diaphragm mechanism of the above.

[Explanation of symbols]

 2 Injection hole 3 Multi-stripe part 4 Cavity 6 Rod-shaped protrusion

Claims (2)

[Claims] 1. A synthetic resin extruder having a foaming agent or gas injection section in the middle of a screw cylinder, wherein the screw cylinder mixing section for kneading the resin that has received the foaming agent or gas from the injection section is a multi-thread screw flight. A multi-threaded portion provided with a notch in the reverse screw direction, and a cavity portion which is provided so as to follow or intersect with this, a concave surface facing a number of concave surfaces on the inner circumference of the cylinder provided on the screw circumferential surface without a screw groove. The screw of the injection part is a single-threaded or multi-threaded single screw, the thread groove is deeper than the other part, and a plurality of rod-shaped projections at the same height as the screw flight or slightly lower than the screw flight are provided at the position immediately downstream of the injection hole. An extruding device for coating a foamed resin, characterized in that it stands upright in the radial direction. 2. The device according to claim 1, wherein the rod-shaped projections standing in the radial direction stand radially along one or a few planes perpendicular to the screw axis, or in one screw groove in the reverse screw direction. An extrusion device for coating a foamed resin, which is characterized by standing side by side.