JPS61165903A - Vulcanized ep rubber 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 Field of the Invention The present invention relates to a vulcanized EPP rubber insulating layer capeple having an outer semiconducting layer on a vulcanized EPP rubber edge.

[Prior Art] When connecting or processing the terminals of a power cable having an external semiconductive layer, the external semiconductive layer must be removed without damaging the insulator, and conventional methods have required the skill and labor of the operator. I was relying on it.

Therefore, the development of an easy-to-peel external semiconducting layer that is easy to install has been an important issue for cable manufacturers.

Regarding electrical cables using cross-linked polyethylene as an insulator, cross-linked polyethylene itself is non-polar and has the property of resisting adhesion to other materials, so it is relatively easy to develop an external semiconductive layer that is easy to peel off.

However, in the case of vulcanized EP rubber insulating capacity cables made of ethylene-propylene copolymer or ethylene-propylene-diene terpolymer, vulcanized EPP rubber contains many fillers,
Because it contains additives, it has polarity and has the property of adhering well to other materials, making it extremely difficult to develop an external semiconducting layer that is easy to peel off.

Conventionally, chloroprene rubber and chlorosulfonated polyethylene5. The use of highly polar polymer materials, such as ethylene/vinyl acetate copolymers with extremely high vinyl acetate concentrations, has been proposed, but many of them have problems with heat resistance stability and extrusion processability, and are not fully satisfactory. There was nothing to go on.

[Problems to be solved by the invention] The object of the present invention is to provide a vulcanized EP rubber insulating power capsule whose external semiconducting layer can be peeled off very easily during construction.

[Means for solving the problems] The vulcanized EP rubber insulating power cable of the present invention, ethylene
- A vulcanized EP rubber insulated power cable in which the insulator is formed of a resin composition mainly composed of a propylene copolymer or an ethylene-propylene-diene terpolymer and has an external semiconductive layer on the outer periphery of the insulated power cable. The outer semiconductive layer is made of an ethylene/vinyl acetate copolymer with a vinyl acetate content of 50% by weight or more, and an ethylene/vinyl acetate copolymer with a vinyl acetate content of 50% by weight or more.
Acrylate graft mixture with ethylene/vinyl acetate copolymer obtained by grafting 5 to 30% by weight of acrylic acid or methacrylic acid ester onto vinyl acetate copolymer 1
It is characterized in that it is formed from a resin composition containing 40 parts by weight or more of conductive carbon black per 00 parts by weight.

In order to realize an external semiconducting layer that can be easily peeled off from the insulator, the inventors investigated various materials with high polarity and good heat resistance stability. It has been found that an acrylate graft-ethylene/vinyl acetate copolymer obtained by graft-polymerizing a vinyl copolymer with an ester of acrylic acid or methacrylic acid to a content of 5 to 30% by weight is suitable for this purpose. .

In other words, the conventional material, ethylene/vinyl acetate copolymer, lacks thermal stability because the acetoxy groups are easily released as acetic acid at high temperatures. When polymerized, the above-mentioned ester is chemically bonded to the acetoxy group, making it difficult for acetic acid to be eliminated and improving thermal stability.

However, it has been found that when such a prescription is followed, the strength of the outer semiconductive layer decreases during peeling, making it easier to tear.

Thus, in the present invention, it has been found that the tear strength of the outer semiconductive layer can be improved by mixing an ethylene/vinyl acetate copolymer with the acrylate graft-ethylene/vinyl acetate copolymer.

That is, the ethylene/vinyl acetate copolymer itself has a sufficiently high tear strength, and therefore, it is best from the viewpoint of compatibility to mix it with the acrylate graft-ethylene/vinyl acetate copolymer.

In the present invention, the mixing ratio of the ethylene/vinyl acetate copolymer and the acrylate graft-ethylene/vinyl acetate copolymer is not particularly limited, but if a large amount of the ethylene/vinyl acetate copolymer is mixed, the heat resistance will decrease. Therefore, the weight ratio is ethylene/vinyl acetate copolymer/acrylate graft - ethylene/vinyl acetate copolymer =
The range of 5/95 to 30/70 is preferable.

In the present invention, the ethylene/vinyl acetate copolymer that is the base of the acrylate grafted ethylene/vinyl acetate copolymer, and the ethylene/vinyl acetate copolymer mixed with the 7 acrylate grafted ethylene/vinyl acetate copolymer are used. For the combination, it is necessary to use a material having a vinyl acetate content of 50% by weight or more, and if it is less than this, peeling of the semiconducting layer from the insulator will be insufficient.

In addition, the amount of ester of acrylic acid or methacrylic acid grafted onto the ethylene/vinyl acetate copolymer is 5
It is necessary to keep the amount in the range of ~30% by weight; if it is less than 5% by weight, the heat resistance will be poor, and if it exceeds 30% by weight, the flexibility will be impaired.

Acrylate grafted ethylene/vinyl acetate copolymer is produced by adding a suspension aid to an aqueous dispersion of ethylene/vinyl acetate copolymer obtained by copolymerizing vinyl acetate and ethylene that previously contained an organic peroxide. After the addition, the temperature is raised to a temperature higher than the decomposition temperature of the organic peroxide to cause appropriate crosslinking, and then an acrylate monomer is added to perform graft polymerization. At this time, it is desirable that the ethylene/vinyl acetate copolymer be obtained by emulsion polymerization.

As the carbon black for imparting conductivity, conductive carbon blacks such as acetylene black, furnace black, and Ketjen black can be used alone or in combination. The blending amount is 40 parts by weight or more per 100 parts by weight of the mixture of acrylate graft-ethylene/vinyl acetate copolymer and ethylene/vinyl acetate copolymer, and if it is less than this, sufficient conductivity cannot be imparted.

As mentioned above, the composition containing acrylate graft-ethylene/vinyl acetate copolymer, ethylene/vinyl acetate copolymer, and conductive carbon black as essential components contains an organic peroxide, and is crosslinked after molding. It is preferable.

In this case, the crosslinking agent is dicumyl peroxide,
1,3-bis-(t-butylperoxy-isopropyl)-benzene, 2,5-dimethyl-2,5-di(t-
butylperoxy)-hexyne, 2,5-dimethyl-2
, 5-di(t-butylperoxy)-hexyne-3 and the like.

In addition, in the present invention, lubricants such as stearic acid and its metal salts and paraffin wax, crosslinking aids such as zinc white, triallylisocyanurate, and trimethylolpropane trimethacrylate, and 4,4'-thiobis(3-methyl-
6-t-butylphenol), 2,2,4-trimethyl-
Dihydroquinoline polymer, N,N'-diphenyl-p
phenylenediamine, 2-mercaptobezimidal,
Antioxidants for rubber or polyopine, such as zinc salts thereof, may be added as appropriate.

In the present invention, the vulcanized EP rubber insulator is not particularly limited, but it is preferably based on ethylene/propylene rubber with an ethylene content of 60% by weight or more, which is commonly used for electric wires and cables.

EPPb0 vulcanization is preferably carried out with dicumyl peroxide, and inorganic fillers such as clay, other vulcanization aids, antioxidants, processing aids, etc. may be blended as appropriate.

[Example 1] The compositions shown on each side of Table 1 were kneaded in a Banbury mixer, and then a crosslinking agent was added to prepare a conductive composition.

An insulator formed by extrusion coating EPPb0 to a thickness of 5 mm on a copper stranded wire conductor with a conductor area of 150 ml. The above conductive composition was extruded and coated on the same to a thickness of 0.7 M, and then nitrogen gas was used as a heat medium. Vulcanization was carried out in a dry crosslinking cylinder. After that, copper tape for insulation shielding, vinyl sheath, etc. were applied to complete the cable.

Table 2 shows the evaluation results for the cable thus obtained.

Note that the evaluation was performed as follows.

The ease of peeling of the external semiconductive layer was determined by measuring the peel strength according to the AEIG standard, and it was determined that the peel strength was 1.8 Ny/1/2" to 4° OKg.
/l/2'' range, it is passed.

Flexibility is judged from the extent of elongation of the outer semiconducting layer peeled from the cable, and if the elongation is 100% or more, it is passed.

The volume resistivity is measured at room temperature and is passed if it is 5×10 Ωcm or less.

The heat resistance stability was evaluated as good if the semiconductive layer had a residual elongation of 75 to 125% after being heat aged at 135° C. for 7 days.

The tear strength was determined by measuring a 1m thick sheet of the same composition as the cable in accordance with ASTM standards, and the tear strength was 0.7'j/c.
A value of m or more was considered good.

From Table 2, Examples 1 to 6 within the scope of the present invention all exhibit good peelability, flexibility, volume resistivity, and heat resistance stability, and are fully satisfactory as semiconducting layers for power cables. It is.

Comparative Example 1 is a case where an ethylene/vinyl acetate copolymer is used alone, and the heat resistance stability is poor.

Comparative Example 2 uses an ethylene/vinyl acetate copolymer grafted with methyl methacrylate alone, and has poor tear strength.

Comparative Example 3 has methyl methacrylate grafted in an amount exceeding the range defined by the present invention, and has low elongation and poor flexibility.

Comparative Example 4 is a case where the amount of methyl methacrylate is less than the range of the present invention, and the heat resistance stability is poor. Comparative Example 5 uses an acrylate graft-ethylene/vinyl acetate copolymer mixture obtained by grafting metal acrylate onto an ungrooved ethylene/vinyl acetate copolymer with a vinyl acetate content of 50% by weight. Too big.

In Comparative Example 6, the content of carbon black is less than the content specified in the present invention, and the volume resistivity is too high.

[Effects of the Invention] As explained above, the present invention provides a well-balanced external semiconductor that has excellent peelability from an insulator, as well as excellent heat resistance stability, tear strength, flexibility, and conductivity. It is possible to realize a vulcanized EP rubber insulation capacitor having a layer.

Claims (1)

[Claims] (1) Vulcanized EP rubber insulated power cable with an insulator formed from a resin composition mainly composed of an ethylene-propylene copolymer or an ethylene-propylene-diene terpolymer, and an external semiconductive layer on the outer periphery of the insulator. In the above, the outer semiconductive layer is made of ethylene having a vinyl acetate content of 50% by weight or more.
Vinyl acetate copolymer and acrylate graft-ethylene/vinyl acetate copolymer obtained by graft polymerizing 5 to 30% by weight of an ester of acrylic acid or methacrylic acid to an ethylene/vinyl acetate copolymer having a vinyl acetate content of 50% by weight or more. A vulcanized EP rubber insulated power cable, characterized in that it is formed from a resin composition containing 40 parts by weight or more of conductive carbon black based on 100 parts by weight of the mixture.