JPS606049B2 - Manufacturing method of plastic insulated wire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a plastic insulated wire by continuously extrusion coating a compound containing a crosslinking agent over a long period of time.

More specifically, it is a method for manufacturing a plastic insulated wire that does not generate scorch (early scorch) even after long-term continuous operation. When extruding plastics, an extruder equipped with a breaker plate as shown in FIG. 1 has conventionally been used. In this extruder, 1 is a screw, 2
is the cylinder, 3 is the breaker plate, 4 is the supplied plastic, 5 is its passage, and 6 is the crosshead. The plastic passage 5 of this conventional breaker plate 3 had approximately the same diameter on the inlet and outlet sides and was straight. Normally, when manufacturing cross-linked polyethylene insulated wire using the breaker plate shown in Figure 1, if continuous operation exceeds 10 hours, scorch will occur in the extruder and the surface of the extrudate may become rough. ,
Or there may be large particles attached.

It also leads to a decrease in the amount of extrusion. For this reason, about 100 hours after starting, the extruder had to be stopped, cleaned, and then restarted, resulting in poor workability. Furthermore, as mentioned above, when the extrusion rate decreases, there is also a manufacturing problem in that the thickness of the insulator becomes thinner from the middle. After various investigations into the causes of such conventional problems, we found that in Fig. 1, the retention of the crosslinking agent-containing compound, that is, the plastic, was particularly significant near the tip 7 of the screw 1, and that depending on the type of extruder or manufacturing conditions, ,
It also accumulates near the pipe wall of the cylinder 2, and furthermore, it accumulates at the center #L of the breaker plate 3 and before and after it, and a dead zone occurs at the outlet side wall portion 8 of the breaker plate, which also causes plastic It was found that this was due to scorch occurring due to stagnation.

Therefore, the present inventors have already solved this problem by enlarging the plastic passage in the breaker plate at least once along the plastic flow, thereby eliminating breaker marks (due to the orientation of molecules passing through the breaker plate). An invention (Tokukai 1970-70803) that can significantly reduce the opaque ring-like striped pattern (which is presumed to be an opaque ring-like striped pattern) and thereby can be expected to greatly improve the electrical properties, especially the dielectric breakdown properties, of plastic insulated wires. Based on what we have discovered, this also leads to a reduction in plastic buildup near the screw tips and cylinder walls, while structurally eliminating the dead zone of the breaker plate itself, resulting in no scorch even after more than 100 hours of continuous operation. We provide a method for manufacturing plastic insulated wires that causes almost no generation of
As we continued our research, we discovered areas for further improvement. The present invention has been made from the above viewpoint, and its gist is that the plastic passage is expanded at least once on the outlet side of the breaker plate of the extruder, and The opening ratio of the inlet side and the outlet side of the entire breaker plate is set within a predetermined range, and at the same time, a taper portion of a predetermined length is provided on the inlet side of each hole, or at the same time as this taper portion is provided, the center D hole is Or, the outermost hole is formed larger than the other holes to make it easier for plastic to flow into the breaker plate, and at the same time, to more effectively eliminate the accumulation of plastic in front and behind the breaker plate to prevent the occurrence of scorch. The point is that I did it like this.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 2 is a schematic diagram showing an example of a breaker plate used in the present invention, and plastic flows in the direction of the arrow in the figure. The passages 15 of the plastic 14 in the individual holes of this breaker plate 13 are enlarged midway. That is, a tapered step portion 15a is formed in the middle. Note that, from the viewpoint of plastic flow, the stepped portion 15a preferably has a tapered shape, but may have other shapes such as a rounded shape or a right-angled shape. At this time, breaker plate 1
3, the diameter of the breaker plate 13 is c, and the plastic passage 1 is
5, the diameter on the inlet side is a, and the diameter on the outlet side is b, and the opening rate (%) on the inlet side is a2 x random number 0 ri XI.

Table C25 is ○, and the opening rate (%) on the exit side is expressed as x number of holes x) XC2100.

In the present invention, the porosity on the inlet side is set to 10 to 30.
%, and the opening ratio on the outlet side is preferably in the range of 40 to 65%. Here, each of these porosity ratios represents the front surface of the breaker plate, in other words, the ratio of each hole to the total amount of plastic extruded by the screw onto this surface, and that value is the value on the inlet side. So 4・
A larger flow rate on the outlet side means that the flow velocity of the plastic flowing through the plastic passage is faster on the inlet side and slower on the outlet side. The reason for setting the value in the above range is that if the porosity is set at 10% to 30% on the inlet side, the porosity of the conventional breaker plate (Fig. 1) is generally about 350 to 40%. %, but it is quite small, and because of this, the flow velocity of plastic passing through the breaker plate is considerably faster (approximately twice) than that of the conventional one on the inlet side, and the retention of plastic on the inlet side is effective. In other words, if the plastic flows smoothly on the inlet side of the breaker plate, stagnation becomes less likely to occur on the breaker plate as a whole, and scorch can be prevented.
However, if the porosity is too small (less than 10%), the pressure (back pressure) of the molten plastic inside the cylinder will become too high, which is undesirable, and if it exceeds 30%, it will become almost the same as the conventional one. This is because it is not desirable. Also,
The reason why the opening ratio on the outlet side is increased to 40-65% compared to the conventional one (both the inlet and outlet sides are the same, about 35-40% as mentioned above) is because the overall breaker plate This is to adjust the flow resistance to the plastic so that it does not become too large. Another reason is that by increasing the pore ratio on the exit side, the dead zone consisting of the wall surface portion between the holes is made smaller, and scorch is prevented from occurring there. However, the separability rate is 4
If it is less than 0%, due to the relationship with the porosity on the entrance side, etc.
If the flow resistance becomes too large and exceeds 65%,
This is because the flow velocity on the outlet side becomes extremely low, which is undesirable, and also causes problems in machining the breaker plate and problems in terms of mechanical strength. In the breaker plate 13, according to the present invention, a tapered portion 15b is formed on the entrance side of the plastic passage 15 of each hole.

By making the inlet side funnel-shaped in this way, it becomes easier for the plastic 14 to flow into the breaker plate 13, so the accumulation of plastic on the front surface of the breaker plate is more effectively removed compared to a configuration without a tapered part. be done. Therefore, the occurrence of scorch is prevented. However, when the length of the passage on the entrance side is d,
If the length d' of the tapered portion 15b is too short, the effect of facilitating the inflow can hardly be expected; on the other hand, if it is too long, the hole diameter a, which has the function of drawing in the plastic at the point where the flow velocity is highest, becomes too short. The length d' of the tapered portion 15b is approximately 0.5 mm, although it varies depending on the size and wall thickness of the breaker plate and the size of the plastic passage.
It is preferable to set it to about 5 to 3 ribs. FIG. 3 is a schematic diagram showing another example of the breaker plate used in the present invention. A narrower portion 15a is provided on the entrance side of each hole, and at the same time, the plastic passage 15' in the center hole is formed larger than the surrounding plastic passage 15. It has been done.

That is, the diameter a'' on the inlet side and the flea b'' on the outlet side are respectively made larger to be equal to the expansion ratio (b2/a2) of the surrounding plastic passage 15. The reason why the plastic passage 15' in the center hole is formed to be large is to further reduce the flow resistance in the center portion of the breaker plate. This makes it possible to remove particularly large plastic buildup near the tip of the screw more effectively than in the case where all the holes have the same size, and to prevent the occurrence of scorch. In addition, in the plastic passage 15' having such a large diameter, in addition to the hollow hole, depending on the type of extruder or manufacturing conditions, a considerable amount of plastic may accumulate near the pipe wall of the cylinder, so if necessary, It may also be formed in the outermost hole to remove stagnation and prevent the occurrence of scorch.

When plastic insulated wires were manufactured using the breaker plate configured as described above, as mentioned above, the plastic easily flowed into the inlet side of the breaker plate, and the flow velocity of the plastic at the inlet side was far and Since the flow resistance at the center hole or the outermost hole is small and there is almost no dead zone, there is no accumulation of plastic before and after the breaker plate. It was confirmed that no scorch occurred at all.

The continuous operation time is now approximately three times longer than before. In addition, problems such as a decrease in extrusion amount and roughness of the surface due to the occurrence of scorch have almost disappeared. Also,
In Figure 2 or Figure 3, Kong Peng a, a'' and b,
The length distribution of the portion b'' and the number of holes (n) need to be determined in consideration of the geometrical resistance of the entire breaker plate, that is, the resin pressure immediately before the breaker plate.

Although the above description has mainly been given to the case of an insulator, this apparatus can be similarly used in the formation of an outer sheath and inner and outer semiconducting layers.

Furthermore, it can be used in conjunction with a crosslinking device to carry out steam crosslinking, silicone oil crosslinking, gas crosslinking, silane crosslinking, and the like. Various plastic materials can be used, such as polyolefins such as polyethylene, polyvinyl chloride, and synthetic rubbers such as ethylene-propylene rubber (EPR, EPDM) and butyl rubber.

In either case, it is best to select the porosity on the inlet side in the range of 10 to 30% and the porosity on the outlet side in the range of 40 to 65%. Since it is sufficient that the passage of the plastic passage is expanded at least once on the outlet side, there are various methods other than providing one step in the plastic passage in the plater plate as shown in Fig. 2. For example, a two-stage structure in which the plastic passage in the breaker plate is expanded twice is possible.

Next, an example will be described.

Example 1 Using the breaker plates shown in Fig. 2, a-4.2 side, a'-6.6 side, b-6.6 side small, c-150 Yanagi small, d-10 side, d '-1 side, e-28 side, e'-6 willow, number of holes (n) -271, nominal cross-sectional area 40 ga 2
The conductor is extruded and coated with polyethylene containing a cross-linking agent, *
Subsequently, a 6-board V cross-linked polyethylene insulated wire was manufactured by gas cross-linking.

At this time, the porosity ratio on the inlet side was 21.2%, and the porosity ratio on the outlet side was 52.5%. Also, for comparison, the breaker plate shown in Figure 1 (hole diameter 5 holes, hole length 38 holes,
A similar crosslinked polyethylene insulated wire was produced using the same conditions except that the number of holes (n) was 391. In addition, the continuous operation time is 10 feeding hours in each case. In these wires, amber (a foreign substance that has scorched and turned into a rust color) and black (a foreign substance that has further changed color and turned black) in the insulator.
The results of examining the density are shown in Table 1.

From Table 1, it can be seen that when the breaker plate according to the present invention is used, there are significantly fewer foreign substances that have changed color to lees color or black due to scorch, compared to the conventional one.

Example 2 Using the breaker plate shown in Fig. 3, a-4.2 side, a'-6.6 rib ◇, b-6.6 side, c-150 side, d-10 leg, d '-1 willow, e-28 ribs, e'-6 secret (however, the center hole is on the a'-6.3 side 'a'-9.9
Yanagigu, *b''-9.9 jobs, clid, d'9 e, e'
(same) Number of holes (n) - 271 A conductor with a nominal cross section of 40 x 2 was coated with polyethylene containing a crosslinking agent by extrusion, and then gas crosslinking was performed to produce a 6-V crosslinked polyethylene insulated wire.

At this time, the porosity on the inlet side was 21.3%, and the porosity on the outlet side was 52.7. The continuous operation time is 10 hours. Table 2 shows the results of examining the densities of amber and black in the insulator for this wire.

From Table 2, it can be seen that in the present invention, in addition to providing a portion of the taper on the entrance side of each hole, by forming the plastic passage in the center hole to be larger than the others, it is possible to more effectively prevent the occurrence of scorch.

Example 3 Using the breaker plate shown in Fig. 2, a
- 4.2 side, a' - 6.6 legs, b - 6.6 ribs, c
-150 skin, d-10 willow, d'-1 side, e-28 side,
e'-16 fences (however, the center holes are a, a', b, c, d',
e' is the same, d-5 side, e-33 side) "Number of holes (n) -
Under 271 conditions, polyethylene containing a crosslinking agent was coated by extrusion on a conductor having a nominal cross-sectional area of 40 mm, and then gas crosslinking was performed to produce a 6-board V cross-linked polyethylene insulated wire.

At this time, the porosity on the inlet side was 21.2%, and the porosity on the outlet side was 52.5%. The continuous operation time is 10 feeding hours. Table 3 shows the results of examining the densities of amber and black in the insulation of this electric wire.

Table 3 From Table 3, according to the present invention, when the entrance ratios on the inlet side and the outlet side are equal, the same effect can be obtained even if the internal structure of the center hole (length distribution of d and e) is slightly different. Recognize.

In each of the above examples, the same screen mesh was used in each case.

As is clear from the above detailed description, in the method for manufacturing a plastic insulated wire of the present invention, the plastic passage in each hole of the breaker plate is expanded at least once on the outlet side, and The porosity of the hole and the porosity of the outlet side are kept within a predetermined range, and a tapered part is provided on the entrance side of each hole, or at the same time as a taper part is provided, the center hole and/or the outermost hole are made larger than the others. This makes it easier for plastic to flow into the breaker plate, and reduces the accumulation of plastic in front and behind the breaker plate, especially in the center hole of the breaker plate and before and after it, near the tip of the sari screw, and near the cylinder pipe wall. Because it is effectively removed, there is almost no scorch occurring before and after the breaker plate, which allows for longer continuous operation times than before, and significantly reduces problems such as reduced extrusion volume and rough surfaces. can.

Brief explanation of the drawings Figure 1 shows a conventional screw;
Schematic representations of cylinders, conventional breaker plates and crossheads. FIGS. 2 and 3 are schematic representations of each breaker plate used in the method of the present invention.

13, 13'...Breaker plate, 14...Plastic, 15, 15'...Plastic passage, 15b,
15'b... Part of Napa.

Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. When producing an insulated wire by extruding and coating a conductor with plastic using an extruder, the passage of the plastic in each hole of the breaker plate of the extruder is enlarged at least once on the exit side thereof. configuration, and the aperture ratio on the inlet side is 10 to 30% and the aperture ratio on the outlet side is 40%.
65% and further includes the use of an extruder in which a tapered portion of a predetermined length is formed on the entrance side of each hole to prevent scorching of a compound containing a crosslinking agent. 2. When manufacturing an insulated wire by extruding and coating a conductor with plastic using an extruder, the plastic passage in each hole of the breaker plate of the extruder is expanded at least once on the exit side, and The porosity on the outlet side is 10 to 30%, and the porosity on the exit side is 40%.
~65%, and further formed a tapered part of a predetermined length on the entrance side of each hole, and at the same time, by using an extruder that formed the center hole or the center hole and the outermost hole larger than the other holes. A method for producing a plastic insulated wire characterized by preventing scorch of a compound containing a crosslinking agent.