JPH0229612Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to an improved metal-conductive rubber or plastic laminate tape.

(Prior art) The inventors created a structure in which a water-blocking layer was provided by covering the conductor and/or cable core vertically with a tape laminated with conductive rubber or plastic film on at least one side of metal foil. Rubber or plastic insulated cables were proposed. As shown in Figure 1, the above laminated tape for a water-blocking layer is made by coating 50 to 120 weight parts of conductive carbon black in a base range of 100 parts by weight on at least one side of a metal foil 1 such as lead foil, aluminum foil, or copper foil. The conductive rubber or plastic film 2 is laminated and integrated to make it conductive.

A method of forming a water-blocking layer by wrapping a tape made by laminating metal foil and conductive rubber or plastic film (hereinafter referred to as metal laminate tape) on a cable conductor or/and cable core is a method that Since the metal laminate tape is formed by vertically wrapping or horizontally winding, there is always an overlapping part, and electric cables having such an overlapping part have the disadvantage that electric field concentration and electric field irregularity are likely to occur in this part.

(Purpose of the invention) The present invention is a metal laminate tape, that is, a metal foil, which has a function of preventing the occurrence of electric field concentration and electric field irregularities at the overlapping portions of the tapes as described above when used as a water-shielding layer forming material for cables. The object of the present invention is to provide a composite tape comprising a conductive rubber or plastic film and a conductive rubber or plastic film.

(Summary of the invention) As shown in Fig. 2, the composite tape of the present invention has a conductive rubber or plastic layer 2 having an electrical resistance of 10 ¹ to ^{10 8} Ω-cm on both sides of a metal foil 1, and at least one of them. This composite tape is characterized by having a rubber or plastic layer 3 with a dielectric constant of 3 to 8 and a volume resistivity of 10 ⁸ to ^{10 16} Ω-cm provided on the surface, and such a composite tape can be used in the conventional manner. If a rubber or plastic layer 3 (hereinafter referred to as an electric field relaxation layer) having a dielectric constant of 3 to 8 is vertically or horizontally wound toward the insulating layer side of the cable to form a water-blocking layer, the electric field relaxation layer 3 can be It exhibits an electric field relaxation effect, and thus prevents electric field concentration from occurring at the overlapped portion of the tape even under high stress.

The conductive rubber or plastic used in the present invention includes low, medium, and high density polyethylene, polypropylene, polybutene-1, polymethylpentene, ethylene-propylene copolymer, ionomer, ethylene-ethyl acrylate copolymer,
Conductive carbon in base polymers such as ethylene-vinyl acetate copolymer, chlorinated polyethylene, chlorosulfonated polyethylene, polyvinyl chloride, natural rubber, butadiene rubber, isoprene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, styrene-butadiene rubber, etc. A material having a volume resistivity of 10 ¹ to 10 ⁸ Ω-cm by appropriately blending black, metal powder, etc. is used.

In addition, the dielectric constant is 3 to 8 and the volume resistivity is 10 ⁸ to
10 ¹⁶ Ω-cm rubber or plastic is a high dielectric constant material in the above-mentioned base polymer.
_Tio2 , _Sio2 , _BaTiO3 , Cas, _LiNbO3 , _LiTaO3
are appropriately blended, and conductive carbon black, metal powder, etc. are suitably blended as necessary so that the dielectric constant and volume resistivity of the composition fall within the above ranges.

The electrical properties of both the above compositions are 10 ¹ to 10 for the former.
The reason for having a volume resistivity of 10 ⁸ Ω-cm was determined from the viewpoint of use for forming a water-blocking layer on the conductor of an electric cable or on the cable core, and the latter is based on the above. In addition to this reason, the relative permittivity is determined to be within the range of 3 to 8 for the purpose of obtaining an electric field relaxation effect.

A method of laminating the above two types of compositions and metal foil is to laminate a conductive rubber or plastic layer and a metal foil.
For the purpose of improving the interfacial smoothness and adhesion of the electric field relaxation layer having a dielectric constant of ~8, it is desirable to coextrude these two types of compositions into a two-layer laminated film and integrate it with the metal foil.

In addition, the thickness of the metal foil used in this invention is 20 μ~
The thickness of the conductive rubber or plastic layer and the electric field relaxation layer are 50μ to 200μ each.
from the viewpoint of flexibility of the resulting composite tape, and lead foil is most preferred because of its excellent flexibility and chemical resistance.

(Example) Next, examples of the composite tape of the present invention will be shown.

Example 1 A composition containing 100 parts by weight of ethylene-vinyl acetate copolymer and 10 parts by weight of conductive carbon black (relative dielectric constant 6, volume resistivity 10 ¹³ Ω-cm) and 100 parts by weight ethylene-vinyl acetate copolymer A composition containing 60 parts by weight of conductive carbon black (volume resistivity 10 ⁴ Ω-cm) was coextruded into two layers each having a thickness of 50 μm to prepare a two-layer laminated film with a thickness of 100 μm. did. Next, the two-layer laminated film described above was placed on both sides of a 50 μm thick lead foil so that the conductive plastic layer faced the lead foil, and the two were bonded together to obtain the composite tape of the present invention.

Example 2 Low density polyethylene 100 as electric field relaxation layer material
A composition containing 75 parts by weight of titanium oxide (relative permittivity 7, volume resistivity 10 ¹⁶ Ω-cm) was used, and as a conductive plastic layer material, 100 parts by weight of low-density polyethylene and 50 parts by weight of conductive carbon were used. Using a composition containing (volume resistivity 10 ⁶ Ω-cm),
In addition, a lead foil with a thickness of 20 μm was used as the metal foil, and Example 1
A similar composite tape was obtained in the same manner as above.

Example 3 100 parts by weight of ethylene-propylene rubber and 30% barium titanate (BaTiO ₃ ) as the material for the electric field relaxation layer.
A film having a thickness of 50 μm was prepared using the composition (relative permittivity: 5, volume resistivity: 10 ¹⁵ Ω-cm) containing parts by weight.

A conductive plastic film having a thickness of 50 μm was prepared using a composition (volume resistivity: 10 ⁷ Ω-cm) containing 100 parts by weight of ethylene ethyl acrylate (EEA) and 40 parts by weight of conductive carbon black.

Next, the above-mentioned conductive plastic film was laminated on both sides of a 50 μm thick lead foil, and the above-mentioned electric field relaxation layer film was further laminated on one side to prepare a composite film of the present invention.

Comparative Example 1 In Example 1, a conductive layer of 50μ was applied to both sides of the lead foil.
A composite film was prepared by laminating only EVA film.

Comparative Example 2 In Example 2, 50μ conductive PE was applied on both sides of the lead foil.
A composite film was prepared by laminating only films.

Comparative Example 3 In Example 3, conductivity of 50μ was applied to both sides of the lead foil.
A composite film was prepared by laminating only EEA film.

Next, using the composite films prepared in Examples 1 to 3 and Comparative Examples 1 to 3 above, an overlapping portion was formed using two of each composite film, and a 1 mm thick crosslinked low-density polyethylene film was placed on the overlapping portion. The sheets were placed and the whole was integrated, and an impulse fracture test was conducted on the resulting integrated sheet containing the mutually overlapping parts of the composite tapes.

Note that the composite sheet obtained in Example 3 was integrated with the electric field relaxation layer facing the polyethylene sheet side.

Further, a ball-flat plate electrode was used as the electrode during the impulse destruction test.

The obtained results showed that the fracture values of the composite films of Examples 1 to 3 were 20 to 40% higher than those of the composite films of Comparative Examples 1 to 3.

It should be noted that the destruction phenomenon occurred first at the overlapping edge of the composite tape in all samples.

(Effects of the invention) As is clear from the examples, even when the composite tape of the present invention is used in a wound manner, electric field concentration does not occur in the overlapped portions of the tapes, and it has high destructive properties.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view of a conventional metal foil conductive rubber or plastic composite tape, and FIG. 2 is a cross-sectional explanatory view of the composite tape of the present invention. 1... Metal foil, 2... Conductive rubber or plastic layer, 3... Electric field relaxation material layer.

Claims (1)

[Scope of claims for utility model registration] (1) Both sides of the metal foil have a volume resistivity of 10 ¹ to 10 ⁸ Ω
- cm of conductive rubber or plastic layer, and on at least one side thereof a rubber or plastic layer with a dielectric constant of 3 to 8 and a volume resistivity of 10 ⁸ to 10 ¹⁶ Ω-cm. A composite tape characterized by: (2) The composite tape according to claim 1, wherein the metal foil is lead foil.