JP2010113834A - Intercalation composition for cable, and rubber cable using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an intercalation composition for a cable, along with a rubber cable using the same, in which no electrical trouble occurs such as cracking and breakage of an insulator as well as intrusion of water, the intercalation material is easy to be peeled when processing a terminal, and a flame retarder with environment safety issues is not used to provide flame resistance. <P>SOLUTION: The intercalation composition for the cable contains polarized rubber, containing nitrile rubber and/or styrene butadiene rubber. The component composition ratio of the intercalation composition for cable is, in terms of mass ratio, 100/0 to 30/70 for (polarized rubber comprising nitrile rubber and/or styrene butadiene rubber)/(ethylene-based copolymer), while 100/0 to 30/70 for ((polarized rubber comprising nitrile rubber and/or styrene butadiene rubber)+(ethylene-based copolymer))/(ethylene propylene rubber). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a cable interposition composition and a rubber cable using the same.

  A rubber cable used at a low voltage to a high voltage (600 V to 33 kV) is required to have flexibility, bending resistance, wear resistance, and the like. Conventionally, such a rubber cable has a structure in which an intervening composition (full type or inner layer sheath) is coated on the outer periphery of a core (insulating core) provided with an insulator on a conductor for the purpose of preventing deformation and waterproofing. Have. In this production, a plurality of insulating cores are assembled according to the type of cable and the operating voltage, and an intervening rubber composition is formed on the gap and the outer layer by extrusion to form an intervening layer, and a protective sheath is further covered. Can be done. As the sheath material, a rubber material is applied according to required characteristics, use environment, and the like.

  The above-described intervening layer provided on the insulator or between the insulating layers is required to have appropriate adhesiveness and peelability in consideration of required characteristics at the time of terminal construction. Further, the insulator and the intervening layer need to prevent water from entering in order to stabilize the insulation performance when using the cable. For this reason, the same material is used for the insulator and the intervening layer to provide adhesiveness, while appropriate peelability is provided by applying or spraying an anti-adhesive agent on the insulator. If the coating amount of the anti-adhesive agent is too large, the adhesive strength will be weak, and the core in the cable will move easily due to repeated bending, twisting, and abrasion during use, resulting in cracks and breaks in the insulator. Electric troubles such as water intrusion occur. Moreover, when there is too little application | coating amount of a protective agent, both will adhere | attach firmly and the problem that it will become difficult to peel interposition at the time of the terminal construction of a core generate | occur | produces.

In addition, the rubber cable is required to have flame retardancy as a secondary disaster response in the event of a fire, and depending on the application of the product, conformity to the vertical VW-1 combustion test according to UL standard 1581-1080 may be required. On the other hand, conventional intervening materials include a composition using antimony as a halogen-based flame retardant and a flame retardant aid, but this has a problem in terms of environmental safety.
Therefore, the present invention is free from electrical troubles such as cracks, breaks, and water intrusion of the insulator, is easy to peel off the intervening layer appropriately at the time of terminal construction, and is environmentally safe when applying flame retardancy. An object of the present invention is to provide a composition for interposing a cable and a rubber cable using the same, which can avoid the use of a problematic flame retardant.

The above problems have been solved by the following invention.
(1) A cable intervening composition having a polar rubber composed of nitrile rubber and / or styrene butadiene rubber, wherein the component composition ratio in the cable intervening composition is a mass ratio (nitrile rubber and // Polar rubber made of styrene butadiene rubber) / (Ethylene copolymer) is 100/0 to 30/70, and ((Rubber rubber made of nitrile rubber and / or styrene butadiene rubber) + (Ethylene copolymer)) / (ethylene propylene rubber) is 100/0 to 30/70.
(2) The cable intermediate composition according to (1), wherein the ethylene propylene rubber is an ethylene / propylene copolymer and / or an ethylene / propylene / diene terpolymer.
(3) The composition for cable intervention according to (1) or (2), wherein the ethylene-based copolymer is an ethylene vinyl acetate copolymer or an ethylene ethyl acrylate copolymer.
(4) The vinyl acetate content of the ethylene vinyl acetate copolymer is 15 to 50% by mass, and the melt flow rate of the composition is 2 to 30 (g / 10 minutes) (3) The composition for cable interposition as described in 2.
(5) The ethyl acrylate content of the ethylene ethyl acrylate polymer is 15 to 50% by mass, and the melt flow rate of the composition is 2 to 30 (g / 10 minutes). The composition for cable intervention as described.

(6) A cable interposition composition described in any one of (1) to (5) is extruded and formed on an electric wire having an insulator coated around a metal conductor to form an intervening layer. The cable is characterized in that the outermost layer is extruded and covered with a sheath.
(7) The rubber cable according to (6), wherein the intervening layer and / or the sheath is crosslinked.
(8) The rubber cable according to (6) or (7), wherein the insulator is ethylene propylene rubber.
The “polar rubber” in the present invention refers to a rubber having an SP value larger than that of an ethylene-propylene rubber having a molecular structure assembled with only carbon and hydrogen atoms using a solubility parameter (SP value). The solubility parameter is the square root of the cohesive energy density of molecules and represents the magnitude of cohesive force between molecules.

  The composition for interposing a cable of the present invention has a good terminal workability without impairing the electrical performance because an appropriate peeling property can be obtained between the insulating rubber of the insulating core (for example, ethylene propylene rubber). Non-halogen flame retardant rubber cable. In addition, the composition and cable of the present invention have less adverse effects on the human body due to generation of toxic gas by the flame retardant even during combustion.

  FIG. 1 shows an example of the configuration of a cable according to the present invention. FIG. 1 is a cross-sectional view showing an embodiment of a preferred electric wire used as an insulated cable. An insulating layer 2 made of an insulator such as ethylene propylene rubber is provided on a conductor 1. An intervening layer containing acrylonitrile-butadiene copolymer rubber (NBR) and / or styrene-butadiene copolymer rubber (SBR) and ethylene copolymer (EVA and / or EEA), or an ethylene propylene rubber in this mixed composition The intervening layer 3 containing (EPDM and / or EPM) is extruded several layers, sequentially or simultaneously, and the coating and vulcanization process is repeated by a conventional method, and finally the sheath 4 is extruded to the outer layer. As the sheath material, an appropriate rubber material such as chloroprene rubber (CR), natural rubber (NR), or fluorine rubber (FKM) can be used according to the requirements for the product.

The materials used in the present invention will be described in detail below.
The acrylonitrile-butadiene copolymer rubber used for the cable-incorporating composition is a copolymer rubber of acrylonitrile (AN) and butadiene rubber (BR), and is classified from low nitrile to very high nitrile according to the acrylonitrile content (low Nitrile: less than 25% by mass, medium nitrile: 25-30% by mass, high nitrile: 30-42% by mass, extremely high nitrile: more than 42% by mass).
The styrene-butadiene rubber is a random copolymer of styrene and butadiene, and for example, those produced by emulsion polymerization (E-SBR) or solution polymerization (S-SBR) can be used. Also, a random copolymer of α-methylstyrene and butadiene (MSBR), vinylpyridine styrene butadiene rubber (PSBR), carboxylated styrene / butadiene copolymer rubber (XSBR), hydrogenated styrene / butadiene copolymer rubber (HSBR), etc. Can be used.

The solubility parameter (SP value) is often used as an indicator of the polarity of the polymer, but the acrylonitrile-butadiene copolymer rubber is 9.6, and the styrene-butadiene copolymer is compared to the SP value of 7.9 for ethylene propylene rubber. It can be seen that the rubber is as high as 8.6, and the compatibility with the ethylene propylene rubber is low.
Both acrylonitrile-butadiene rubber and styrene-butadiene copolymer rubber have inferior heat resistance compared to ethylene propylene rubber because butadiene rubber (BR) contains a double bond in the main chain. As a countermeasure, first, it is combined with ethylene vinyl acetate or ethylene ethyl acrylate resin or ethylene / propylene copolymer which is an olefin resin. Other measures include the use of hydrogenated acrylonitrile / butadiene copolymer rubber or hydrogenated styrene / hydrogenated styrene / hydrogenated styrene rubber to prevent the presence of double bonds by adjusting the type and amount of antioxidants and hydrogenation. Use of a butadiene copolymer rubber is mentioned. Acrylonitrile-butadiene copolymer rubber or styrene-butadiene copolymer rubber may be used in combination with an ethylene-based copolymer or further containing an ethylene / propylene / diene terpolymer or an ethylene / propylene copolymer.

Ethylene vinyl acetate and ethylene ethyl acrylate, which are ethylene-based copolymer resins with polarity, are compared to non-polar rubbers such as ethylene / propylene / diene terpolymers and ethylene / propylene copolymers, which are ethylene propylene rubbers. It is advantageous in terms of flame retardancy, and has an advantage that high flame retardancy can be imparted by a synergistic effect by adding metal hydrate.
As a result of various investigations on materials of the composition that forms an intervening layer having an appropriate releasability with respect to such an insulator (for example, made of ethylene propylene rubber), the present inventors have obtained acrylonitrile having polarity.・ Releasability is also possible with butadiene copolymer rubber and styrene / butadiene copolymer rubber, and more polar acrylonitrile / butadiene copolymer rubber, styrene / butadiene copolymer rubber and ethylene copolymer or this. It has been found that a more excellent effect can be obtained by using a blend of ethylene and propylene rubber.
In this case, for example, when an ethylene propylene rubber (for example, EPDM) used as an insulator is blended with a fatty acid or a metal salt thereof, a low molecular weight polyethylene wax, a fluorine-based release agent, or a silicone rubber, the insulating layer of the insulating core The adhesion becomes too strong and causes cohesive failure during the peel test. When ethylene vinyl acetate or ethylene ethyl acrylate is contained in ethylene propylene rubber, if the amount of vinyl acetate or ethyl acrylate is too small, cohesive failure occurs during the peel test, and if the amount of vinyl acetate or ethyl acrylate is too large, the material It tends to soften itself, has insufficient strength, and cannot be peeled due to material fracture.

By adding acrylonitrile-butadiene copolymer rubber and styrene-butadiene copolymer rubber at a predetermined ratio, the present inventors easily cause interfacial peeling from an insulator (for example, ethylene propylene rubber insulator). It has been found that an intervening layer exhibiting “peelability” can be obtained.
Moreover, when a predetermined amount of ethylene-based copolymer of ethylene vinyl acetate or ethylene ethyl acrylate is added to acrylonitrile-butadiene copolymer rubber or styrene-butadiene copolymer rubber, the peel strength and water barrier properties are further improved.
In the cable composition, when considering flame retardancy or heat resistance in addition to water shielding, an ethylene copolymer is added, or ethylene propylene diene ternary copolymer, which is an ethylene propylene rubber, is further added. It is preferable to contain a polymer and / or an ethylene / propylene copolymer. In other words, since the insulation core ethylene-propylene rubber insulator is coated, the above rubber inclusions can maintain the water-tight effect to prevent the intrusion of water and the like, and the mouth-peelability at the time of construction of the terminal, and are also environmentally friendly flame retardant. A highly intervening layer can be obtained.
The ethylene vinyl acetate and ethylene ethyl acrylate in the cable intermediate composition of the present invention show that when the vinyl acetate content and the ethyl acrylate content increase, the flame retardancy increases, but the mechanical properties tend to decrease. -If the flow rate (MFR) becomes too large, the material flows too much during extrusion molding, resulting in poor extrudability and insufficient strength during lip removal. From this point of view, the content of vinyl acetate or ethyl acrylate is preferably 15 to 50% by mass and MFR 2 to 30 (g / 10 min).

As the ethylene-propylene rubber that can be used as a component of the cable intermediate composition of the present invention, either an ethylene / propylene copolymer (EPM) or an ethylene / propylene / diene terpolymer (EPDM) can be used. is there. Examples of the third component contained in the ethylene / propylene / diene terpolymer include dicyclopentadiene (DCPD), ethylidene norbornene (ENB), and 1,4 hexadiene (1,4HD). It is not limited to. There are various commercially available ethylene propylene rubbers depending on the ethylene content and molecular weight, and these can also be selected and used as appropriate.
The ethylene propylene rubber that can be used as an insulator of the insulating core in the rubber cable of the present invention is the same as described above.

Hereinafter, embodiments of the present invention will be described in more detail.
In the present invention, ethylene propylene rubber (EPM and / or EPDM) can be contained as a material for the intervening layer as described above, and good physical properties can be obtained by peroxide crosslinking. In addition, ethylene polar copolymer of ethylene vinyl acetate or ethylene ethyl acrylate is used because it has polar polarity such as vinyl acetate and ethyl acrylate, has appropriate polarity, excellent filler acceptability, and flexibility. It has the characteristics. Here, the combination of ethylene propylene rubber and ethylene vinyl acetate (or ethylene ethyl acrylate) has strong adhesion to the ethylene propylene rubber insulator and is difficult to peel off, so polar acrylonitrile-butadiene copolymer rubber, styrene -Insulating layer (for example, made of ethylene propylene rubber insulator) by containing butadiene copolymer rubber together with ethylene propylene rubber and ethylene vinyl acetate and / or ethylene ethyl acrylate, or blended only with ethylene vinyl acetate (ethylene ethyl acrylate) ) And the peelability (appropriate peel strength).

In the rubber cable used for low voltage to high voltage (600V to 33kV) according to this embodiment, the insulator and the intervening layer are bonded (adhered) with an appropriate peel strength. The core and the intervening layer in the cable do not move even when subjected to rotation, and as a result, there is no infiltration of water even when a constant water pressure is applied to the cable. From this point, it is preferable that the adhesive force between the insulating layer made of the insulator and the intervening layer is basically about 10 to 50N.
There are also rubber cables that require flame resistance depending on the application of the product. For such applications, the above rubber or olefin resin has good filler acceptability even when a large amount of metal hydrate for imparting flame retardancy is added. Therefore, the lack of strength due to the addition of a large amount of filler is relatively small, and the intervening layer and the sheath can be easily peeled off when the terminal of the insulating core is constructed.

In the rubber composition for cable intervention of the present invention, the component composition ratio in the rubber composition for cable intervention is 100/0 of a rubber / ethylene copolymer having a polarity of nitrile rubber and / or styrene butadiene rubber. -30/70, and ((polar rubber made of nitrile rubber and / or styrene butadiene rubber) + (ethylene copolymer)) / (ethylene propylene rubber) may be 100 / 0-30 / 70 preferable. More preferably (nitrile rubber and / or styrene butadiene rubber) / (ethylene copolymer) is 70/30 to 30/70 by mass ratio.
Moreover, when ethylene propylene rubber (EPDM and / or EPM) is contained in these mixed compositions, the content of rubber having polarity of nitrile rubber and / or styrene butadiene rubber is preferably 50% by mass or more in the rubber component, As for ethylene propylene rubber (EPDM and / or EPM), 50 mass% or less is preferable.
Also, the polar rubber of nitrile rubber and / or styrene butadiene rubber can be a mixture with ethylene propylene rubber (ethylene / propylene / diene terpolymer and / or ethylene / propylene copolymer) only. It is.
Moreover, in the composition for cable intervention of this invention, it is preferable to add 50-250 mass parts of metal hydrate which is a flame retardant with respect to 100 mass parts of said base polymers. If the amount added is too small, sufficient flame retardancy may not be obtained, and if it is too large, the mechanical strength may decrease. The metal hydrate used here may be a surface-untreated one, or a surface treated with a fatty acid, a silane coupling agent or the like. Further, as a flame retardant aid, a flame retardant aid such as a phosphoric compound, a phosphorus compound such as red phosphorus, a silicone compound, a nitrogen compound, or a zinc compound can be appropriately added.
Furthermore, the coating layer (intervening layer, sheath) in the present invention is usually subjected to a crosslinking treatment at the time of coating or after coating. The intervening layer can be cross-linked by a conventional method, but in the case of sulfur vulcanization, co-crosslinking organic peroxide cross-linking is suitable because it causes problems such as discoloration reaction of the conductor.

When performing the crosslinking treatment, the type of the organic peroxide to be used is not particularly limited, but is appropriately selected according to the processing conditions at the time of compound kneading or extrusion production. As a method for crosslinking the sheath material, a suitable method for crosslinking the rubber material classified according to the use of the product is applied. Examples of the organic peroxide used for the crosslinking agent include dicumyl peroxide, 2,5-dimethyl-2,5-di (t-butyl peroxide) hexyne, and 1,3-bis- (t-butylperoxy). Isopropyl) benzene, 1,1, -bis (t-butylperoxy) cyclohexane and the like. As for the compounding quantity, 1-5 mass parts is preferable with respect to 100 mass parts of base resins.
The rubber cable of the present invention is more excellent in heat resistance due to the crosslinking treatment of the composition of the coating layer. As a method for crosslinking the coating layer, first, an ethylene propylene rubber composition is extruded on the outside of the conductor, coated and subjected to a vulcanization step as necessary, and then the rubber inclusion composition is formed in one or a plurality of layers, sequentially or a plurality of layers. It is common to extrude and coat at the same time, repeat the vulcanization process if necessary, extrude the sheath to the outermost layer, and then crosslink by heating at 160 to 200 ° C.
In addition to this, the rubber composition for cable interposition includes various additives used in the wire coating layer, for example, fillers, reinforcing agents such as carbon and silica, coloring agents, lubricants such as wax, and anti-aging. An agent, a crosslinking aid, and the like can be appropriately blended within a range that does not impair the object of the present invention.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto. In the examples, the mixing ratio indicating the composition was expressed by mass% based on the mass ratio.

  SBR and / or NBR and EVA which is an ethylene copolymer were blended to prepare first polymers of Formulation Examples A to G. These mixing ratios are shown in Table 1. The first polymers of Formulation Examples B to E are SBR and / or a mixture of NBR and EVA. On the other hand, the first polymers of Formulation Examples A, F, and G are SBR, NBR, or EVA alone.

Next, the 1st polymer of these compounding agents AG and EP rubber (EPM or EPDM) were blended, and the 2nd polymer of Examples 1-17 and comparative examples 1-6 was produced. These mixing ratios are shown in Table 2.

The second polymer of Examples 5-7, 9-11, 13-14, 16 and Comparative Example 1 is a mixture of SBR or NBR, EVA, and EP rubber.
The second polymer of Example 1 is SBR alone, the second polymer of Example 17 is NBR alone, and the second polymers of Examples 2 and 3 are a mixture of only SBR and EP rubber.
On the other hand, the second polymer of Comparative Example 1 is a mixture of SBR, EVA and EP rubber, but the blend of styrene-butadiene copolymer rubber is 10% by mass or less, and the second polymer of Comparative Example 2 is EVA and It becomes a mixture of only EP rubber, and the second polymer of Comparative Example 3 is EVA alone. In Comparative Examples 4 and 5, a fatty acid amide and a fluorine-based release agent are mixed with EP rubber as an anti-adhesive agent. Only in Comparative Example 6, a large amount of talc was applied to the surface of EP rubber.

Next, various additives shown in Table 3 are added to 100 parts by mass of each of the second polymers of Examples 1 to 17 and Comparative Examples 1 to 6, and Examples 1 to 17 and Comparative Examples 1 to 6 are interposed. Each composition was prepared.
In view of environmental safety, the flame retardant was only a metal hydrate and a non-halogen flame retardant material.

Each component shown in Tables 2 and 3 was kneaded with a Banbury mixer, and then a rubber intervening composition prepared by adding and kneading a crosslinking agent with an open roll machine was molded into a sheet.
1) VW-1 combustion test A combustion test was conducted in accordance with UL standard 1581-1080.
The rubber intervening composition prepared by kneading was extruded at 90 ° C., coated with a conductor, then pressure-crosslinked (vulcanized) with a molten salt (temperature: 200 ° C.), and used with a 1 × 3.5 SQ cable. . Each burning time is less than 60 seconds with 5 flame contacts, and a suitable range is that there is no ignition of absorbent cotton and no spread to the top.
2) Peeling strength A 2 mmt vulcanized sheet of EP rubber insulating material was prepared in advance, and a test sample was prepared with a pressure press at 160 ° C. for 30 minutes, overlaid with the prepared 2 mmt rubber intervening composition. did. (The applied pressure is 100 tons for a molded vulcanized sheet of 280 cm ² )
The vulcanized sheet was cut into a total length of 200 mm x a width of 25 mm (bonding location: 100 mm), and peeled in a 180 ° direction with respect to each test piece at a pulling speed of 50 mm / min by a shopper type tensile tester. The peel strength from the rubber-containing composition was determined, and the peeled state was observed.
Good adhesion with interfacial peeling (A), cohesive failure with thin cohesive layer but good adhesion (B), high cohesion with cohesive failure (C), strong adhesion with material destruction It was determined that peeling did not occur (D) and interface peeling, but the degree of adhesion was weak (E).

When the peel strength is within a range of 10N to 20N and the peel state is A (◎), when the peel strength is over 20N and 50N or less and the peel state is B (○), the peel strength is 5 In the range of over 10 and less than 10N, the peel state is A (Δ mark), and the peel strength is near 100N or higher and the peel state is C or D (× mark), it is interface peeling, but peeling The case where the strength was 5 N or less and the peeled state was E was also determined as (x mark).
These test results are shown in Table 4.

As shown in Table 4, each of the peel tests with the EP rubber insulating material using the intervening compositions of Examples 2 to 16 except for Examples 1 and 17 of SBR or NBR alone has an appropriate peel strength. Show. In Examples 1 and 17 of styrene / butadiene copolymer rubber or NBR alone, although the interfacial peeling occurs, the peel strength is less than 10N, and the adhesive strength is slightly small.
Example 2 having a blend ratio of SBR and EP rubber and a blend ratio of 50/50 by mass ratio, and Examples 4, 8 having blend ratios of SBR and EVA of 70/30, 50/50, and 30/70 by mass ratio 12, SBR, EVA and EP rubber mixture, but EP rubber is less than 10% by mass, Example 13, NBR / EVA blend ratio 50/50 is Example 15 with interfacial peeling and good adhesion It is.
In Examples 3, 7, and 11 having a high EP rubber mixing ratio, the adhesive force is slightly higher, but the intervening layer is an adhesion of a thin agglomerated layer and can be said to have good peel strength.
On the other hand, as shown in Table 5, Comparative Example 1 has a small amount of styrene / butadiene copolymer rubber as low as 6% by mass and a large amount of EP rubber as high as 80% by mass. Comparative Example 2 is a mixture of EVA and EP rubber only, and Comparative Example 3 is EVA alone, but both exhibit strong adhesive strength and material breakage. Moreover, what added the adhesion preventing agent of the comparative examples 4 and 5 to EP rubber also showed strong adhesive force, and resulted in material fracture. In Comparative Example 6, a large amount of talc was applied, but interface peeling occurred, but there was no adhesive force at all, or even about 2N, and the adhesive force was too weak.
As for flame retardancy, good flame retardancy is obtained in all the compositions containing only the aluminum hydroxide and magnesium hydroxide metal hydrates listed in Table 3.

It is a schematic sectional drawing which shows one embodiment of the covered electric wire using the composition of this invention.

Explanation of symbols

1 Conductor 2 Insulating layer 3 Intervening layer 4 Sheath layer

Claims (8)

  A composition for cable interposition having a polar rubber made of nitrile rubber and / or styrene butadiene rubber, wherein the component composition ratio in the cable interposition composition is expressed by mass ratio (nitrile rubber and / or styrene) Butadiene rubber, polar rubber) / (ethylene copolymer) is 100/0 to 30/70, and ((polar rubber composed of nitrile rubber and / or styrene butadiene rubber) + (ethylene A composition for interposing a cable, wherein the copolymer)) / (ethylene propylene rubber) is 100/0 to 30/70.   The composition for cable intervention according to claim 1, wherein the ethylene-propylene rubber is an ethylene-propylene copolymer and / or an ethylene-propylene-diene terpolymer.   The composition for cable intervention according to claim 1 or 2, wherein the ethylene-based copolymer is an ethylene vinyl acetate copolymer or an ethylene ethyl acrylate copolymer.   The vinyl acetate content of the ethylene vinyl acetate copolymer is 15 to 50% by mass, and the melt flow rate of the composition is 2 to 30 (g / 10 min). Composition for cable interposition.   The cable according to claim 3, wherein the ethyl acrylate content of the ethylene ethyl acrylate polymer is 15 to 50% by mass, and the melt flow rate of the composition is 2 to 30 (g / 10 minutes). Intervening composition.   An electric wire in which an insulator is coated around a metal conductor is formed by extruding the composition for interposing a cable according to any one of claims 1 to 5 to form an intervening layer, and extruding the outermost layer. A rubber cable that is molded and covered with a sheath.   The rubber cable according to claim 6, wherein the intervening layer and / or the sheath is crosslinked.   The rubber cable according to claim 6 or 7, wherein the insulator is ethylene propylene rubber.

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