JPS59181416A - Crosslinked polyolefine insulated power cable - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an electric cable in which a crosslinked polyolefin insulator and an outer semiconducting layer are in close contact with each other, and an outer semiconducting layer is provided that can be easily peeled off as needed. It relates to polyolefin insulated cables, especially high voltage cables.

Conventionally, materials obtained by mixing polyethylene, ethylene/vinyl acetate copolymer, or ethylene/ethyl acrylate copolymer with a conductive filler have often been used as external semiconductive materials for crosslinked polyolefin insulated high voltage cables. However, since these materials are in complete contact with the adjacent crosslinked polyolefin insulation layer, there is a problem in that it is extremely difficult to separate the two layers when performing cable connection or terminal construction.

As a solution to this problem, ``ichikagupuru'' has been proposed in which the outer semiconducting layer is made of vinyl chloride grafted ethylene/vinyl acetate copolymer, chlorinated polyethylene, or vinyl acetate/ethylene copolymer with a high vinyl acetate content ( For example, JP 55-765 (1B, JP 54-9714
, JP-A-51-53286, JP-A-52-, N875
).

However, although these materials for the outer semiconducting layer have a high content of vinyl acetate or chlorine, which imparts polar groups, to improve releasability, they have the disadvantage of poor cold resistance. In addition, cross-linked polyethylene cables with semiconducting layers made of these materials can be heated to temperatures above 200'C to improve productivity.
When cross-linked at a high temperature of
0T: When heated above 0T, there is a problem that the peelability deteriorates and the shielding copper tape on the external semiconductive layer becomes discolored due to corrosion. Since these phenomena are further accelerated when water vapor is used as a heating medium, it is presumed that they are caused by the effects of decomposition products such as organic acids and inorganic acids produced by thermal decomposition or hydrolysis.

Recently, there has been an increasing demand for high-performance tape tape, which not only has excellent peelability but also has an external semiconductive layer that can withstand high-temperature cross-linking and steam cross-linking and does not cause corrosion of the copper tape. .

The inventors of the present invention have found that the present invention has excellent electrical properties, cold resistance, oil resistance, and extrusion processability, and also has good peelability and copper corrosion resistance.
・As a result of various studies to provide an electric cable with a lip-type external semiconducting layer, we found that an acrylic monomer was polymerized under grafting conditions to a vinyl acetate/ethylene copolymer. The inventors discovered that the above-mentioned problems could be solved by using a semiconductive composition prepared by adding a conductive filler, a crosslinking agent, etc. to a modified vinyl acetate/ethylene copolymer for the outer semiconductive layer, which led to the present invention. Ta.

That is, the present invention provides a conductor in which a semiconducting layer is formed on an insulator made of an olefinic polymer extrusion coated on a conductor, and the semiconducting layer has a solubility coefficient (sp fig) 8.6-94, Mooney viscosity 10-
40. It is made by blending a conductive filler and a crosslinking agent with an acrylic grafted vinyl acetate/ethylene copolymer with a thermal decomposition initiation temperature of 315°C or higher. Crosslinking aids, anti-aging agents, processing aids, etc. are added as necessary. Provided is a crosslinked polyolefin insulating capeple made of a semiconductive composition containing other additives as appropriate.

The composition forming the semiconductive layer of the electrical cable in the present invention has excellent electrical properties, cold resistance, oil resistance, extrusion processability, etc., and is excellent in releasability from the l-bond insulator and copper corrosion resistance.

The acrylic grafted vinyl acetate/ethylene copolymer (hereinafter referred to as graft copolymer) used in the present invention has good peelability from olefinic polymers that are constituent materials of the insulator, such as polyethylene and ethylene/propylene copolymers. In order to obtain this, it is necessary that the sp value is between 8.6 and 94. If the 8p value is less than 8.6, the peelability from the insulator will be poor, and if it is more than 94, the cold resistance will be poor, which does not meet the object of the present invention. Note that the sp value of polyethylene is Z9.

The Mooney viscosity of the graft copolymer is required to be 10 to 40 from the viewpoint of peelability, copper corrosion resistance, and moldability.

If the Mooney viscosity is less than 10, the peelability and copper corrosion resistance will be poor, and if it exceeds 40, the moldability will be poor.

Further, the thermal decomposition temperature of the graft copolymer must be 315°C or higher. If the temperature is less than 615°C, copper corrosion will occur when cross-linking occurs at a high temperature of 230°C or higher or with water vapor.

In addition, the vinyl acetate/ethylene copolymer which is the main component of the graft copolymer has a vinyl acetate content of 5.
A copolymer having a Mooney viscosity of 5 to 40 is preferred.

The graft component of the graft copolymer of the present invention is obtained by graft polymerizing an acrylic monomer, and such acrylic monomers include (meth)acrylic acid, 6-methyl (meth)acrylate, and (meth)acrylic acid. Examples include ethyl acid, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and acrylonitrile.

Olefins such as ethylene and propylene, vinyl acetate,
Vinyl esters such as vinyl propionate, styrenes, etc. may also be used in combination as long as they do not impede the effects of the present invention, and one or more of these may be mixed. Vinyl chloride or styrene alone is not preferred from the viewpoint of copper corrosion.

The amount of the graft component varies depending on the sp value of the monomer, but is preferably 5 to 50% of the graft copolymer.

Further, rubbers or plastics such as chlorinated polyethylene, acrylic rubber, ethylene/propylene rubber, ethylene copolymer, and polystyrene may be used in combination with the graft copolymer to the extent that the effects of the present invention are not impaired.

Acetylene black, furnace black, Ketjen black, etc. are commonly used as conductive fillers, and the addition end is 20 to 1 part by weight per 100 parts by weight of the graft copolymer.
00 parts by weight is sufficient.

As a crosslinking agent, dicumyl peroxide, 1,6-bis(1-butylperoxy isopropyl)benzene, 2
Organic peroxides such as 5-dimethyldi(t-butyl peroxy)hexyne-3 are common. In addition to the addition of a crosslinking agent, crosslinking by irradiation with high energy radiation such as an electron beam may also be used as the crosslinking means.

In addition, examples of the olefin polymer used in the insulating layer of the power cable of the present invention include polyethylene, ethylene, etc.
It consists of a polymer such as a propylene copolymer and a crosslinking agent. This insulating layer is usually crosslinked simultaneously with the crosslinking of the semiconducting composition coated thereon.

The high voltage r-pull of the present invention is, for example, as shown in FIG.
An inner semiconducting layer 2 made of polyethylene containing carbon, an insulator 6, and an outer semiconducting layer 4 are sequentially extruded and coated on the conductor 1, and a shielding copper tape 5, a holding tape 6, and a sheath 7 are applied thereon. has been done. These semiconducting layers 2, 4
In order to prevent insulation deterioration due to corona discharge, it is necessary that the insulator 3 be in close contact with the insulator 3 without any gaps.

Since the electric cable of the present invention uses a specific material as the outer semiconducting layer, the adhesion between the semiconducting layer and the insulating layer is appropriate, and the cables are insulated from the outer semiconducting layer when connecting cables. It is easy to peel off from the body layer.

On the other hand, in the case of electrical cables that have an outer semiconducting layer made of conventionally used materials, the outer semiconducting layer adheres moderately to the insulator and cannot be peeled off. After scraping, the surface of the insulator must be smoothed using sandpaper or the like, which requires a lot of time and skill.

Next, in order to clarify the characteristics of the present invention, examples will be given to specifically explain the present invention. Note that all parts in Examples and Comparative Examples indicate parts by weight.

Examples 1 to 3, Comparative Examples 1 to 4 33KV cross-linked polyethylene insulating vinyl sheath electrical cable (100m♂
×1 core) was molded using an extruder, and then a prototype was produced by steam crosslinking.

Table 1 shows the physical properties of the cables of Examples and Comparative Examples.

The testing methods for various physical properties are shown below.

0 solubility coefficient (ap value) Encyclopedia of Polymer 5
science and Technology(Will
The Polymer 8 p-value according to EY Inter 5cjence (published by Co., Ltd.) was used. The 8p value of the copolymer was calculated assuming additivity depending on the composition ratio.

10-0 Peelability According to IPCEA S-66-524, length 30c
A cut of 12.7 mm (X inch) was made in the outer semiconductive layer of a sample cable of 1.0 m, and a peel test was carried out at a speed of 750 m/min with a tensile tester perpendicular to the cable axis. A peel strength of 0.5 to 2.5 kli+ was considered good.

0 Volume Specific Resistivity Volume specific resistance was measured using a sample cable with a length of 30 cTl according to IPCEA S-66-524.

O copper tape corrosion test A sample cable from which the sheath layer had been removed was cut out and placed in a hot air dryer adjusted to 105°C for 30 days for an accelerated test. The state of discoloration due to corrosion was visually observed.

The evaluation criteria are that the same plate as Comparative Example 2 is good, and the following is bad;
Measurement was carried out according to JIS K-6301 using the sheets obtained from press crosslinking 1 to 1 for 15 minutes at 0''C.
-15°C or lower was considered to be a pass.

To extrude into extrudable cables, the formulation shown in Table 1 was subjected to a Prabender blast graph at 160°C
The torque was tracked under the conditions of 5 Dr, p, m, and the time until it reached the first largest peak was measured as the vulcanization time. It was considered good if the vulcanization time was 15 minutes or more.

Under these conditions, scorch will not occur even under practical extrusion molding conditions.

0 muni viscosity Measured according to JIS K-6300.

O thermal decomposition onset temperature was measured using a differential thermometer under the following conditions. The temperature at which the weight was reduced by 1% was defined as the thermal decomposition start temperature.

Atmosphere Nitrogen gas 601/min Heating rate: 20℃/min Sample amount 10±1～ / 13-

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially exploded perspective view of the power cable of the present invention. 1...Conductor 2...-Inner semiconducting layer 6...Insulator 4...
External semiconductive layer 5... Shielding steel tape 6... Four presser tape 7... Sheath layer agent Patent attorney Masaru Takahashi 15- Figure 1

Claims (1)

[Claims] In an electric capule in which an external semiconducting layer is formed on an insulating layer made of an olefinic polymer, the semiconducting layer has a solubility coefficient of 846 to 9.4, a Mooney viscosity of 10 to 40, and a thermal decomposition initiation temperature of 615°C. A crosslinked polyolefin insulating cape caple comprising a semiconductive composition prepared by blending the above acrylic grafted vinyl acetate/ethylene copolymer with a conductive filler, a crosslinking agent, and other additives if necessary.