JPH01218312A - Mold joint construction method for cable - Google Patents

Abstract

PURPOSE:To suppress the generation of voids and to prevent protruding and sharpened parts or the like from being generated by forming an inner edge part of an external semiconductive layer with a semiconductive composition thereafter heating a joint part wholely to be molded. CONSTITUTION:Conductor connection of cables F, F is performed, and winding a semiconductor tape on this connection part heating it to be melted and bridged, a bridged internal semiconductive layer 4 is formed. Thereafter in this part, an unbridged cross-linking agent-contained composite tape is wound, forming an insulator 6, and winding on its periphery the semiconductive tape, two-parts divided external part semiconductive layers 7, 8 are formed. Here suitably applying heat treatment, each external part semiconductive layers 7, 8, especially the part of an inside edge part 7a, sets its gelation factor to a range of 10-50%. On the external part semiconductive layers 7, 8 thus formed, further a retaining rape 10 is wound for retaining the layer, thereafter setting a metal mold for molding, the layer is guided to the final cross linking degree by pressure heating. By the method thus obtained, adhesiveness of the edge part and a shape holding quality are improved.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a mold joint construction method, and in particular improves the adhesion and shape retention of the two-divided edge of the outer semiconductive layer, This relates to a construction method that aims to improve breakdown voltage.

<Prior Art> Generally, an external semiconductive layer is provided at the mold joint part of a cable, for example, a Cv cable.
There are two types of external semiconductive layers: one that is continuous over the entire length of the joint part, and the other that is divided into two along the circumferential direction at appropriate parts and overlapped in a lap shape with their edges insulated. be.

The reason for adopting such a two-part method is that, for example, if a lightning strike current runs in the length direction of the cable through the outer semiconducting layer of the cable due to an accident such as a lightning strike, the outer semiconducting layer of the joint If a series of semiconducting layers are connected to the outer semiconducting layer of the cable, they will run the entire length of the cable, increasing the damage area of the cable. In,
This is because in order to block the flow of current, the outer semiconducting layer is separated by dividing into two parts in advance in order to limit the damage to the minimum range.

<Problems to be Solved by the Invention> However, when such a divided structure is adopted, stress such as electric field concentration tends to be concentrated on the edge of the external semiconducting layer, so it is difficult to select the edge composition material and the shape. Careful attention must be paid to molding, etc., and the configuration of the edges plays an important role in improving the breakdown voltage.

In fact, according to the tests and research conducted by the present inventors, voids may occur at the edges of the outer semiconducting layer, especially at the inner edges that go inside during wrapping, due to minute peeling, etc., or protrusions or pointed shapes may occur due to shape deformation. It has been found that if parts etc. are formed, electrical breakdown easily occurs due to this. In particular, in recent years, C■
Since cables are rapidly becoming higher in voltage, improvements in this respect are strongly desired.

Therefore, the inventors of the present invention conducted a deeper study and found that by forming at least the inner edge of the outer semiconducting layer with a composition having a degree of crosslinking (gel fraction) within a specific range, it is possible to form a molded resin insulator. It provides sufficient adhesion, suppresses the generation of voids due to micro-peeling, etc., and is resistant to shape deformation (
It has been found that protrusions, pointed parts, etc. are less likely to occur.

The present invention has been made from this perspective.

Means for Solving the Problems and Their Effects> The feature of the present invention is that the outer semiconductive layer coated on the outer periphery of the molded resin insulator is divided into two along the circumferential direction, and one At least the inner edge of the outer semiconductive layer is coated with a gel fraction of 10 to 50 at the mold joint portion of the cable where the edge goes inside and the other edge is overlapped in a lap shape while maintaining insulation. % of a semiconductive composition, and then the entire joint is heated and melted to be molded.

The composition of the outer semiconductive layer used in the present invention includes bases such as ethylene-ethyl acrylate copolymer (EEA), ethylene-vinyl acetate copolymer (EVA), and ethylene-acrylic acid copolymer (EAA). To the resin, conductive powder such as carbon or metal, and some crosslinking agents such as dicumyl peroxide (DCP), 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3,
Examples include those made by adding beef san and the like to 2.5-dimethyl-2,5-di(t-butylperoxy).

The amount of each of these components to be blended is approximately 10 to 70 parts by weight of the conductive powder and 0.2 to 1 part by weight of the crosslinking agent, based on 100 parts by weight of the base resin. When coated on a molded resin insulator as an external semiconducting layer, its gel fraction (110
(depending on the extraction method when immersed in xylene at ℃ for 24 hours) is adjusted so that it is in the range of 10 to 50%. This is because when the gel fraction is less than 10%, adhesion with the molded resin insulator is good, but the degree of crosslinking is insufficient, resulting in poor shape retention, resulting in crushed edges, protrusions, and sharp edges. This is because shape parts are likely to form (and may cause electrical damage).Also, if the gel fraction exceeds 50%, the shape retention is strengthened by a sufficient degree of crosslinking, but the mold resin This is because the adhesion with the insulator deteriorates, and voids are likely to occur at the edges due to minute peeling, etc., which also causes electrical breakdown.

Next, a specific example of the construction method of the present invention will be explained with reference to FIG.

In the figure, F and F are connected to each other. cable, J
is the main part.

In the construction method of the present invention, the covering portion (insulator, etc.) 2.2 of the reconnection end portion of the cables F and F to be connected is scraped off (pesticin ring treatment), exposed, and both grooves 1.1
The part is inserted into a cylindrical metal crimp sleeve 3 from both sides, and then the crimp sleeve 3 is crushed to first connect the conductors.

Next, wrap a semiconductive tape, for example, around the connection part of E.
The material is heated and melted to be crosslinked to form a crosslinked internal semiconductive layer 4. Of course, this internal semiconducting layer 4 is connected to the cable F and the internal semiconducting layer 5.5 on the F side.

Thereafter, an insulator 6 is formed by wrapping, for example, an uncrosslinked composition tape containing a crosslinking agent around this portion. In addition to this tape wrapping, in forming the insulator 6,
For example, an extrusion mold may be set in this portion, and molded resin may be extruded as the insulator 6 using a normal method.

A semiconductive tape is wrapped around the outer periphery of this insulator 6,
A two-part outer semiconductive layer 7.8 is formed. At this time, the edge 7a of one of the outer semiconductive layers 7 is placed inside,
The edge 8a of the other external semiconductive layer 8 is placed on top of this in a lap shape while maintaining insulation. At this time, it is necessary to set the gel fraction of each of the outer semiconductive layers 7, 8, especially the inner edge 7a, in the range of 10 to 50% as described above. is wrapped with a semiconductive tape having the above-mentioned composition and subjected to appropriate heat treatment to bring the degree of crosslinking to the above gel fraction, or the inner edge 7
It is also possible to form only the part corresponding to a in advance as one part, make this part have a gel fraction within the above range, and fit it.

The tip shape of this inner edge 7a is preferably as follows:
For example, as shown in Fig. 2, it is preferable to provide a smooth chamfer on the outward facing upper side.Of course, these outer semiconductive layers 7.8 are also connected to the cable F and the outer semiconductive layer 9.9 on the F side. .

On the outer semiconducting layer 7.8 formed in this way,
Further, the uncrosslinked or non-crosslinked film is heated under pressure at 180°C for 3 hours under a nitrogen gas pressure of 6 kg/cm'', for example. The sufficient insulator 6 and the outer semiconducting layer 7, 8 portions are melt-molded to reach the final degree of crosslinking (gel fraction 60-85%). Crosslinking is performed by migration of a crosslinking agent from the molded resin portion of the insulator 6.

In addition, during this molding, the outer semiconductive layer 7°8, especially the inner edge 7a, is made of a composition with the above-mentioned gel fraction (10 to 50%), so it has good adhesion to the insulator 6. Moreover, it does not lose its shape even under nitrogen gas pressure. Therefore, there is no generation of voids, protrusions, sharp parts, etc., and as a result, a high breakdown voltage can be obtained.

<Example> Compounds of each composition shown in Table 1 (Examples ■~■,
Comparative Examples 1 to 2) were extruded at 140° C. into a tape having a thickness of 0.1 mm and a width of 100 mm.

This tape is coated with Teflon and has an outer diameter of 120 mm.
The material was tightly wound on a mmφ iron mandrel to a thickness of 7 mm, and then a Teflon tape was wrapped 4 times in a 1/2 wrap over it, and crosslinked for 2 hours in an open environment at 160°C. The gel fraction at that time was as shown in Table 1.

Table 1 Semi-conductive composition pipes made in this way
□ was pulled out from the iron mandrel and a smooth chamfer was applied to the outward facing upper side as the inner edge part of the outer semiconducting layer as shown in FIG. 2 above.

On the other hand, the Cv cable (154Kvs) that you are trying to connect
1200mm”) coating at the connection end (insulator, etc.)
was scraped into a conical shape (penciling process), the conductors were connected with a crimp sleeve, and then semiconductive tape was wound to form an internal semiconductive layer, and tape molding was performed by heating.

Next, a polyethylene tape containing a cross-linking agent corresponding to the insulator part is wrapped around the mold shape, and then the above-mentioned pipe is wrapped around the appropriate part of the tape, for example, near the right end of the joint part, as shown in Figure 1 above. Attach the inner edge of the shape, wrap a semiconductive ERA tape containing a crosslinking agent in the left direction from above to form one outer semiconductive layer,
On top of the inner edge of the pipe shape, the edge is rolled up while maintaining insulation, and a semiconductive EEA tape also containing a crosslinking agent is applied.
Wrap the strip around the right conical portion to form the other outer semiconducting layer.

Further, a Teflon tape, for example, was wrapped thereon as a restraining tape, and the mold was cross-linked by heating under nitrogen gas pressure.

The AC breakdown voltage values of the joint parts thus prepared were investigated, and the results shown in Table 2 were obtained.

The experiment was conducted with two samples for each side (Examples I to ■, Comparative Examples ■ to ■).

From Table 2 above, in the case of the height measurement carried out in accordance with the present invention, a high AC breakdown voltage value was obtained, and the breakdown location occurred at a location other than the inner edge of the outer semiconducting layer. Improvement was confirmed. On the other hand, in the case of comparative height measurement, the AC breakdown voltage value is also low, and it can be seen that the breakdown occurs from the tip of the inner edge.

<Effects of the Invention> As is clear from the above description, according to the present invention, a composition having a specific gel fraction (10 to 50%) is used as the composition for the two-part edge of the outer semiconducting layer. Therefore, the adhesion and shape retention of this edge are greatly improved, and the occurrence of voids due to micro-peeling, protrusions, sharp parts, etc. due to shape deformation is minimized, making it possible to mold cables with excellent electrical properties. Joint construction method can be obtained.

[Brief explanation of the drawing]

Figure 1 is a schematic sectional view showing an example of the cable mold joint construction method according to the present invention, and Figure 2 is an enlarged view showing an example of the inner edge of the outer semiconducting layer used in the construction method of Figure 1. FIG. In the diagram, F, F...Cable, J...Joint part, 1.1...Conductor, 2.2...Sheathing part (insulator), 3...Crimp sleeve, 4...Inner semiconducting layer, 6...Mold resin insulator, 7.8...Outer semiconducting layer, 7a...Inner edge, 8a...Outer edge , 10...Pressure tape, patent applicant Fujikura Electric Wire Co., Ltd.

Claims (1)

[Claims] The outer semiconducting layer coated on the outer periphery of the molded resin insulator is divided into two along the circumferential direction, one edge is inside,
At least the inner edge of the outer semiconducting layer has a gel fraction of 10 to 10, at the mold joint part of the cable where the other edge is overlapped in a lap shape while maintaining insulation.
A mold joint construction method for a cable, characterized in that it is formed from a 50% semiconductive composition, and then the entire joint is heated and melted and molded.