JPS5935776B2 - extrusion molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a screw-type extrusion molding machine for thermoplastic resins, and in particular to screw cooling thereof.

In general, screw cooling involves creating a hollow space inside the screw around the center shaft, passing a double pipe through it, and circulating a cooling medium such as water or oil from the inner pipe to the outer pipe for temperature control. It is carried out by

Conventionally, screw cooling was mainly done to prevent flow marks, and as shown in Fig. 1, a double tube consisting of an inner tube 2 and an outer tube 3 was inserted to cool only the feed section of the screw 1. Then, as shown in Figure 3, insert two double tubes up to the tip of screw 1, and then screw screw 1.
In most cases, cooling is applied to the tip of the tube.

However, when only the feed section of the screw is cooled, although the crosstalk effect due to the shallow groove effect can be improved, the discharge amount generally decreases and surging often occurs.

In addition, when cooling to the tip of the screw, it prevents over-kneading of the raw material resin at the tip of the screw, which is more effective in reducing flow marks than when cooling only the feed section, but due to the structure of the cooling device, This also resulted in a reduction in discharge volume and surging.

The object of the present invention is to perform screw cooling of only the portions that require cooling without impairing extrudability.

Furthermore, the present invention aims not only at countering flow marks, which is the main purpose of conventional screw cooling, but also at preventing thermal deterioration of the resin caused by long-term stagnation caused by resin wrapping around the screw.

In order to achieve this objective, the present invention uses FIGS. 3 and 4.
As shown in the figure, a double tube consisting of an inner tube 2 for supplying a cooling medium and an outer tube 3 for returning the cooling medium is inserted into a hollow part inside the screw 1, and the screw 1 needs to be cooled. A bulging portion 4 is formed in the outer tube 3 only at that portion, and extends to the extent that it comes into contact with the inner wall of the screw 1.

The diameter of other parts of the outer tube 3 is small, and a heat insulating material is interposed between the outer tube 3 and the inner wall of the screw 1.

Here, the heat insulating material may be one in which an air layer is interposed between the inner wall of the screw 1 and the outer tube 3 using a three-point support 5 or a ring support, or one in which glass wool or the like is interposed. You can.

Further, a three-point support 6 or a perforated ring support is interposed between the inner tube 2 and the outer tube 3.

Next, the present invention will be explained in detail.

When extruding ABC resin with a rubber content of 20% by weight or more using a single-screw vent type extruder with a cylinder inner diameter of 120ψ, the resin temperature is usually 230±, although it depends on the screw specifications.
It becomes 20℃.

In a vent type screw, the conveyance of molten resin at the vent part does not depend on pressure conveyance, but depends on the function of the screw conveyor by flight, so at the resin temperature mentioned above, ABS resin remains in the vent part for a long period of time (10 hours or more). This caused deterioration, and resin deterioration foreign matter was generated in the extruded product, resulting in a defective product.

Therefore, the outer tube of the double tube was bulged so that only the vent portion could be cooled using the apparatus described in FIGS. 3 and 4.

As a result, even when the extruder was operated continuously for more than 500 hours, no resin-retaining and deteriorating foreign matter was generated.

Further, although the resin temperature at this time was 230° C., no change in resin temperature due to screw cooling was observed, and there were no developing defects such as surging or insufficient deaeration.

The cooling medium used was tap water, and the water temperature on the inlet side was 15.
℃, the water temperature on the outlet side was 40℃, and the water amount was 37/death.

As described above, the present invention enables screw cooling of only desired portions in a thermoplastic resin extrusion molding machine.

In addition, the cooling part can be changed simply by replacing the double pipe without removing the screw from the cylinder barrel.
Changing the cooling section by changing the resin or grade can be done by simply stopping the extruder.

Furthermore, since the cooling portion can be set at a desired length and position with respect to the entire length of the screw, problems in extrusion due to cooling the screw are less likely to occur, and the industrial value of the present invention is extremely great.

A brief description of the drawing.

1 and 2 are plan views of the screw in a conventional extrusion molding machine, FIG. 3 is a sectional view of the screw in the present invention, and FIG. 4 is a sectional view taken along line A-A' in FIG. 3. .

1 is the screw, 2 is the inner tube, 3 is the outer tube, and 4 is the expansion.

Haribe, 5 supports 3 points.

Claims (1)

[Claims] 1 Consisting of an inner tube that supplies the cooling medium and an outer tube that returns the cooling medium, both are connected at the tip of the screw or in the middle 2
A cooling device in which a heavy pipe is inserted into a hollow part inside the screw, a heat insulating material is interposed between the inner wall of the screw and the outer pipe, and the outer pipe is expanded to the extent that it comes into contact with the inner wall of the screw in the part where screw cooling is required. Extrusion molding machine equipped with