JPS6264855A - Electrically conductive shielding compound and crosslinked polyethylene cable obtained by using the same - Google Patents

Abstract

PURPOSE:To provide an electrically conductive shielding compound for cross linked polyethylene cables, which has excellent initial and long-term insulating performances, by incorporating a softener such as mineral oil or a plasticizer and carbon black in a polynorbornene resin. CONSTITUTION:An electrically semi-conductive shielding compound for cross linked polyethylene-insulated power cables (hereinafter referred to as XLPE cable) is obtd. by incorporating a softener such as petroleum mineral oil which is lowly volatile and has a high b.p., or a plasticizer and carbon black in a polynorbornene resin. By using said compound, formation of harmful materials such as acids or bases which cause deterioration in insulation is prevented during a crosslinking reaction (a radical reaction) from a base material by mixing a large quantity of carbon black, and stable XLPE cables having excel lent initial and long-term insulating performances can be obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a semiconductive shielding compound for electrical cables, particularly cross-linked polyethylene insulated cables (hereinafter referred to as XLPE cables), and a cross-linked polyethylene cable using the same. Regarding.

[Prior Art] Conventionally, an inner semiconducting layer and an outer semiconducting layer have been used as conductor shielding and insulating shielding, respectively, for XLPE cables. Recently, conductive compounds that can be extruded are often used as members for the inner and outer semiconductive layers instead of conventional tape molds.

This conductive shielding compound is soft enough to be extruded after being filled with carbon black, and crosslinking must occur simultaneously with the cable insulation after extrusion, so the options are very limited. . Therefore, for many years, conductive shielding compounds for extrusion molding, for example, based on ethylene vinyl acetate copolymers (vinyl acetate content: 15 wt%, 20 wt%) have been used.

However, recent research by the present inventors has revealed that ethylene vinyl acetate copolymer (hereinafter referred to as EVA)
That's what it means. ) easily dissociates from the main chain during crosslinking with chemical crosslinking agents or radiation, generating strongly reactive acetate groups, which participate in diffusion radical crosslinking in XLPE, which is the main insulator. It has been found that the insulated cable may remain as free acetic acid, which reduces the dielectric breakdown performance of the insulated cable, and further causes insulation to deteriorate significantly when used under water.

Furthermore, it has been found that the copper conductor has harmful effects such as promoting oxidation and corrosion of the copper on the side in contact with the copper conductor.

[Problems to be solved by the invention] This invention has been made in view of the above points.
The purpose of the present invention is to provide a conductive shielding compound that eliminates the drawbacks of the prior art and a crosslinked polyethylene cable using the same, in order to manufacture a stable XLPE cable with excellent initial insulation performance and long-term insulation performance. 1 [Means and effects for solving the problems] This invention eliminates harmful substances such as acids or bases that cause insulation deterioration from the base material in which a large amount of carbon black is mixed during the crosslinking reaction, which is a radical reaction. The goal is to prevent it from happening.

As such substances, the present inventors have found that the most compatible are petroleum-based mineral oils with low volatility and high boiling points, or polynorbornene resins containing large amounts of softeners such as plasticizers. . Plasticizers such as paraffinic and naphthenic mineral oils, such as dioctyl sebacate, are absorbed in large quantities by polynorbornene resins, are stable during crosslinking reactions, do not generate harmful substances to insulators, and can be used in large quantities. can be filled with carbon black.

[Example] The present invention will be explained in detail below.

Each side uses polynorbornene resin as a base material to incorporate a large amount of carbon black during the crosslinking reaction, which is a radical reaction. Next, a formulation example will be shown.

Examples 1 to 3 Example 1 Example 2 Example 6 Polynorbornene resin ioo ioo
1 o.

Ethylene propylene terpolymer 20 2
0 20 Naphthenic petroleum 150 20
0 250 Bispheno-#A O,50,5
0.5 Zinc white 555 Lead stearate 1.0 1.0 1.0 Furnace carbon black 250 300
350 Volume resistivity: ρ (Ω-cm) 20tZ'
5. OXl[1'2.4X1031. DX103 The following example further contains a chemical crosslinking agent such as peroxide, sulfur, etc. in an amount necessary for the crosslinking reaction of the semiconductive extrusion layer.

5 Examples 4 to 6 Example 4 Actual flow example 5 Example 6 Polynorbornene resin 100 100
100 ethylene propylene terpolymer 20
20 20 naphthenic petroleum 150
200 250 screw 7, :c/-le A O
,50,50,5 Zinc white 555 Lead stearate i, o i, o i,
.

Furnace carbon black 250 3
00 350 dicumyl peroxide 3
3 3 Volume resistivity: ρ (Ω-cm) 20C5
, ox1o32.4x1031.0X1o3 Also, during the crosslinking reaction, which is a radical reaction, the volume resistivity is 105Ω-(
2) Contain the required amount of carbon black so as to have the following content.

Next, the structure of a 6KV class XLPE insulated vinyl sheathed cable using the conductive shielding compound of the above embodiment will be explained based on the drawings. For example, the surface of the conductor 1, which is a copper stranded wire, is extruded and coated with an internal semiconductive layer 2 as a conductor shield made of the conductive shielding compound of the above embodiment, and the soil is covered with a cross-linked polyethylene insulator (XLPE insulator) 3. do.

Furthermore, an external semiconductive layer 4 as an insulating shield made of the conductive compound of the above embodiment is extruded and coated thereon, a shielding layer 5 made of a copper tape wrapping layer, for example, is coated on top of this, and further on For example, a pressing layer 6 made of a cloth tape wrapping layer is disposed, and the pressing layer 6 is covered with a vinyl sheath 7, for example.

These inner and outer semiconductive layers 2.4 can be made by extrusion molding instead of the conventional tape molding, and are soft even after being filled with carbon black, and can be easily crosslinked at the same time as the cable insulator 3 after extrusion molding. can be manufactured.

Next, the initial AC breakdown voltage values and AC breakdown values after long-term water immersion and deterioration of the 6KV class XLPE insulated vinyl sheathed cables manufactured using the conductive compounds of the first to sixth embodiments of this invention are summarized in a table. show. This table shows the initial value of 1 for a conventional EVA (ethylene vinyl acetate) based XLPE cable.
It is shown as a value of 00.

Heat cycle: (90t? 10h on, 14h off)] As can be seen from the table above, in conventional EVA (ethylene vinyl acetate copolymer) based conductive compounds, during crosslinking with chemical crosslinking agents or radiation, A highly reactive acetic acid group is easily decoupled from the main chain, which participates in diffusion radical crosslinking in the crosslinked polyethylene insulator (XLPE), which is the main insulator, or remains as free acetic acid in the XLPE. However, in the sheathed cable using the conductive shielding compound of the present invention, the deterioration of insulation performance is clearly significantly improved.

The conductive compound of the present invention can be used not only as a material for semiconducting layers of power cables, but also as a material for shielding electronic devices.

[Effects of the Invention] As described above, the results obtained with the present invention can significantly reduce not only initial reliability but also the degree of insulation deterioration of power cables that require long-term reliability. Therefore, it is possible to prevent unexpected insulation breakdown accidents caused by deterioration of power cables over time, which is extremely effective in preventing damage caused by power outages in a highly information-oriented society where electricity is indispensable. Become something.

[Brief explanation of drawings]

The figure is a sectional view showing the structure of a crosslinked polyethylene insulated vinyl sheathed cable using the conductive shielding compound of the present invention. 1......Conductor 2...Inner semiconducting layer 3...XLPE insulator 4...Outer half Conductive layer patent applicant Hitachi Cable Co., Ltd. 7-λ Procedural amendment (Method) 2, Title of the invention Conductive shielding compound and racks using the same are also used for polyethylene cables 3, Relationship with the case of the person making the amendment Patent Applicant Address: 2-1-2 Marunouchi, 111-ku, Tokyo, Japan (512) Hitachi Cable Co., Ltd. 4, Agent: November 6, 1985 (Shipping date: November 26, 1985)
6. Subject of the amendment 7. Change "1. Title of the invention: conductive shielding compound and cross-linked polyethylene cable using the same" to "1. Title of the invention: conductive shielding compound" on page 1 of the statement of contents of the amendment. and cross-linked polyethylene cable using this”
I will correct it.

Claims (4)

[Claims] (1) A conductive shielding compound for cross-linked polyethylene cables, which contains polynorbornene resin, mineral oil, a softener such as a plasticizer, and carbon black. (2) The conductive shielding compound for crosslinked polyethylene cables according to claim 1, which contains a chemical crosslinking agent such as peroxide and sulfur in an amount necessary for the crosslinking reaction. (3) In a cross-linked polyethylene cable comprising a cross-linked polyethylene insulator on a conductor and a semi-conductive extruded layer on one or both of the inside and outside of the insulator, the semi-conductive extruded layer is made of polynorbornene resin. 1. A cross-linked polyethylene cable comprising mineral fat, a softening agent such as a plasticizer, and carbon black. (4) The crosslinked polyethylene cable according to claim 3, wherein the semiconductive extruded layer is crosslinked with a chemical crosslinking agent such as peroxide or sulfur.