JPH081070Y2 - Resin extrusion equipment - Google Patents

Description

[Detailed description of the device] [Industrial applications]

The present invention relates to a resin extruding apparatus useful for extruding a resin such as rubber or plastic containing an additive such as a crosslinking agent.

[Prior art]

Conventionally, a two-stage extrusion method is adopted, and for example, as shown in FIG. 5, when a plastic resin such as polyethylene is mixed with an additive such as a cross-linking agent or an antioxidant, the first extruder 1 is provided with a filter unit 2 , A crosshead 4 forming a connecting part is connected via a cooling part 3 or the like, and a plastic resin supplied from the first extruder 1 is supplied with the additive press-fitting device 5 connected to the crosshead 4 as desired. A quantity of additive is pressed in and mixed, and the mixed plastic resin is mixed with the second
A method has been already proposed in which, for example, the electric wire conductor 8 is extruded and covered with a plastic resin as an insulator 9 from the head portion 7 of the second extruder 6 by introducing the plastic resin into the extruder 6.

[Problems to be solved by the device]

In such a resin extruder system, the second extruder 6
In the part, for example, as shown in FIG.
Cross-linking agent 10 pressed in from is supplied in a form surrounded by resin 11 and kneaded.At this time, a strong stirring force (kneading force) is immediately applied from the resin supply port side of extruder cylinder 12. However, there was a problem that scorch (premature cross-linking) occurred in the relevant part when kneading was performed with the above method. That is, in the resin supply part, the resin is cut between the screw crest part and the cylinder inner wall, and the liquid crosslinking agent
It is considered that 10 leaks and the crosslinking agent 10 stays and is not dispersed, so that the crosslinking is locally promoted. Therefore, as shown in FIG. 6, the height of the screw thread portion 14a of the resin supply port portion of the kneading screw 13 is made lower than the screw thread portion 14b of the other portion by, for example, about 1.5 pitch, so that the resin breaks as much as possible. It is intended to prevent the resin from being cut. However, this time, as a new problem, the above-mentioned high thread portion 14
It was found that scorch is generated in a portion (region A) slightly advanced from the base end where b starts to the tip end direction. The reason for this is considered as follows. In the case of this screw 13, at the low thread portion 14a,
Since there is a slight gap between the inner wall surface of the cylinder 12 and
Although the resin 11 advances beyond the ridges, there is almost no gap between the high screw ridges 14b and the inner wall surface of the cylinder 12, so the resin 11 slows down. On the other hand, this screw
In 13, the liquid cross-linking agent 10 is dispersed in the resin 11 to some extent in the portion where the height of the mountain portion changes, but there is still a liquid lump, so the flow of the resin 11 slows down. When strong stirring and kneading are usually performed in the part, the cross-linking agent 10 in the liquid mass causes sliding on the screw surface and stays, so that scorch is generated in the part, Be done. In view of such conventional circumstances, the present invention provides a resin extruder using an extruder having a screw shape in which an additive such as a cross-linking agent is well dispersed and kneaded over the entire length of the screw. To do.

[Means for Solving the Problems]

The resin extruder of the present invention is such that the first extruder extrudes a resin such as rubber or plastic that does not contain an additive such as a cross-linking agent, and the cross-linking agent is added to the resin at the connecting portion with the second extruder. In a resin extrusion apparatus in which additives such as the above are pressed and mixed, and the mixture is kneaded and extruded by a second extruder, the resin extruder is rotatably inserted into the cylinder of the second extruder and has a spiral thread. A mixing portion is provided in the substantially central portion of the screw, and the height of the screw thread portion from the mixing portion to the resin supply port side is lower than that of the screw thread portion from the mixing portion to the tip side of the screw. .

[Action]

In the resin extrusion device of the present invention, the height of the screw thread portion is lowered in a considerably long region from the mixing portion provided in the substantially central portion of the screw to the resin supply port side, and the terminal end becomes the mixing portion immediately. Therefore, good additive dispersion kneading is performed, and scorch generation and the like can be effectively suppressed.

【Example】

FIG. 1 shows one embodiment of the screw of the second extruder used in the resin extruder according to the present invention. In the screw 13A of the second extruder 6, the cylinder 12
From the resin supply port 12a side of the
The height of the screw thread portion 14a up to 5 is set to the mixing portion 15
To the tip side of the screw 13A, the screw thread portion 14b is made lower than the thread portion 14b, and a small gap is provided between the screw thread portion 14A and the inner wall surface of the cylinder. On the other hand, the screw thread portion 14 in the tip direction from the mixing portion 15
The height of b is the normal height. The other components of the resin extrusion device are the same as those of the resin extrusion device of FIG. 5 described above. The mixing portion 15 is not particularly limited, but for example, as shown in FIGS. 2 to 4, while providing an annular groove 15b in the central circumferential direction of a large diameter portion 15a slightly thicker than the thread forming portion, In the axial direction of the outer circumference of the left and right large-diameter portions 15a, a large number of independent small grooves 15c ... With slightly deviated engraving positions are provided. Therefore, in the case of this screw 13A, the resin 11 supplied from the resin supply port 12a of the cylinder 12 and this resin 11
The liquid additive 10 such as a cross-linking agent contained in the resin supply port 12a to the mixing section 15 has a relatively low stirring force because the screw thread 14a of the screw 13A in the area is low in height. Since the resin 11 is agitated and flows over the screw thread portion 14a, it is conveyed to the mixing portion 15 at a high flow rate. That is, during this period, although the dispersion of the additive 10 is insufficient,
It is carried out almost uniformly without being locally unevenly distributed, and the occurrence of scorch is effectively prevented. Then, when it reaches the mixing section 15, each groove in this section
Due to the action of 15b, 15c ..., the resin 11 and the additive 10 are agitated more finely.
In the screw thread portion 14b having a normal height from the tip end 15 side, stronger stirring and kneading are performed, so that the additive 10 is almost completely dispersed in the resin 11. The resin 11 in which the additive 10 is completely dispersed is extrusion-coated by the second extruder 6 as an insulator such as a wire conductor. In addition, in the above-mentioned embodiment, the case was applied to the second extruder 6, but the present invention is not limited to this, and a single extruder or an extruder containing an additive-containing resin other than the crosslinking agent is used. It can also be applied to.

[Effect of device]

As described above, in the resin extrusion device of the present invention, the height of the screw thread portion is lowered in a considerably long region from the mixing portion of the screw provided in the substantially central portion of the screw to the resin supply port side, and the end thereof is immediately mixed. Since it is made into a part, the stirring force is appropriately suppressed during this time, and the resin flows smoothly over the mountain part,
Additive leakage due to resin breakage or resin breakage and reduction in flow rate are effectively prevented, good additive dispersion kneading is performed, and scorch is effectively suppressed.

[Brief description of drawings]

FIG. 1 is a partial vertical sectional view showing an embodiment of a second extruder in a resin extruder according to the present invention, and FIG. 2 is a vertical sectional view of a mixing portion of a screw of the extruder shown in FIG. FIG. 3 is a plan view of the mixing section of FIG. 2, and FIG. 4 is IV-I of FIG.
FIG. 5 is a cross-sectional view taken along the line V, FIG. 5 is a schematic explanatory view of a resin extrusion apparatus using a general two-stage extrusion method, and FIG. 6 is a vertical sectional view showing a conventional extruder in the resin extrusion apparatus of FIG. In the figure, 1 ... first extruder, 4 ... crosshead, 6 ... second
Extruder, 10 ... Additive, 11 ... Resin, 12 ... Cylinder, 12a ... Resin supply port, 13A ... Screw, 14a ... Low thread part, 14b ... High thread part, 15 ... … The mixing department,

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-108609 (JP, A) JP-A-60-21228 (JP, A) Jitsukaihei 2-34226 (JP, U)

Claims (1)

[Scope of utility model registration request] 1. A first extruder extrudes a resin such as rubber or plastic containing no additive such as a cross-linking agent, and an additive such as a cross-linking agent is pressed into the resin at a connecting portion with a second extruder. , In a resin extruder for kneading and extruding the mixture with a second extruder, the screw is rotatably inserted into the cylinder of the second extruder and has a screw thread having a spiral shape at substantially the center. A resin extruding device, wherein a mixing portion is provided and the height of a screw thread portion from the mixing portion to the resin supply port side is made lower than that of a screw thread portion from the mixing portion to the tip end side of the screw.