JP2002075072A - Water impermeable tape and water impermeable power cable using the same - Google Patents

Abstract

(57) [Problem] To provide a water-shielding tape which suppresses an increase in contact resistance at the interface between an aluminum foil and a semiconductive film, and further has excellent adhesiveness and water-proof performance between the aluminum foil and the semiconductive film; The use of this tape provides a water-proof power cable that has excellent water-blocking performance, maintains stable electrical characteristics over a long period of time, and has a long service life. A plastic film is laminated on one surface of an aluminum foil and a conductive adhesive layer having a lower melting point than a base resin of the semiconductive film is formed on the other surface of the aluminum foil. Tape 10 formed by laminating the semiconductive film 18 by thermocompression bonding
And an impermeable power cable provided with an impermeable layer using the impermeable tape 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water impermeable tape and a water impermeable power cable using the same.

[0002]

2. Description of the Related Art When a power cable is exposed to a high electric field for a long time under flooding, water trees and the like are generated in an insulating layer, insulation is deteriorated, electric characteristics are deteriorated, and stable use for a long time becomes difficult. In addition, it also causes dielectric breakdown and shortens the cable life. Therefore, in order to prevent water from entering the core for the high-voltage power cable from the outside, the use of a simple water-blocking structure has recently been expanded.

[0003] In this water-blocking type power cable, an inner semiconductive layer, an insulating layer such as cross-linked polyethylene, an outer semiconductive layer are provided on a conductor, and a metal shielding layer such as a copper tape or a copper wire is provided as necessary. Lead on the power cable core with
A water-shielding structure which is basically composed of a metal foil such as an aluminum foil laminated on one side with a plastic film as a reinforcing body for the metal foil, and a semi-conductive film laminated on the other side by thermocompression bonding. The tape is provided with a simple water-impervious layer by vertically attaching the semiconductive film to the cable core side, and further provided with an anticorrosive layer of plastic such as PVC.

[0004]

As the metal foil of the water-impervious tape used for the simple water-impervious layer, lead foil excellent in fatigue characteristics has been mainly used, but in recent years, considering the environmental load, Aluminum foil has been used. However, the water-impermeation tape using this aluminum foil, as the heating temperature at the time of thermocompression bonding of the semiconductive film to the aluminum foil increases, the contact resistance at the interface between the aluminum foil and the semiconductive film increases, There is a problem that the volume resistivity in the thickness direction of the water impermeable tape is increased. The cause of the increase in the contact resistance at the interface is that, due to the difference in the coefficient of thermal expansion between the aluminum foil and the semiconductive film, current flows through the interface between the aluminum foil and the semiconductive film during cooling after thermocompression bonding of both. This is considered to be because microvoids that hinder the formation are generated, but as the thermocompression bonding temperature increases, the shrinkage of the semiconductive film during cooling increases, and the number of microvoids generated at the interface increases. When the contact resistance increases, the conduction state between the aluminum foil and the external semiconductive layer or the metal shielding layer of the power cable core deteriorates, and an abnormal voltage such as a lightning surge or a switching surge enters the water-impermeable power cable. At this time, a potential difference is generated between the aluminum foil and the external semiconductive layer or the metal shielding layer, and a discharge is generated between the two and a hole is formed in the aluminum foil, so that the water shielding tape cannot maintain the water shielding performance.

In order to solve such a problem, when a semiconductive film is thermocompression-bonded to an aluminum foil, the thermocompression bonding temperature is lowered so that the contact resistance at the interface between the aluminum foil and the semiconductive film does not increase. It is also conceivable to do so. Then, the adhesive strength between the aluminum foil and the semiconductive film is reduced, and the aluminum foil is peeled off from the semiconductive film due to the thermal expansion and contraction repeatedly applied to the power cable, and the aluminum foil is likely to wrinkle and crack. This causes a problem that the water blocking performance is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a water-shielding tape which suppresses an increase in contact resistance at an interface between an aluminum foil and a semiconductive film, and further has excellent adhesiveness and water-shielding performance. It is an object of the present invention to provide a water-impervious power cable that has excellent water-impermeability by using a tape, maintains stable electrical characteristics for a long period of time, and has a long life.

[0007]

In order to achieve the above-mentioned object, a water-impervious tape of the present invention comprises a laminate of at least a plastic film on one surface of an aluminum foil and a semiconductive film on the other surface of the aluminum foil. The semiconductive film is laminated by thermocompression bonding via a conductive adhesive layer having a lower melting point than the base resin of the conductive film.

[0008] With the above configuration, when the semiconductive film is laminated on the other surface of the aluminum foil, the conductive adhesive layer is melted at a temperature lower than the temperature at which the base resin of the semiconductive film is melted. Then, the aluminum foil and the semiconductive film are heat-sealed, and the aluminum foil and the semiconductive film are firmly adhered to each other. Since the temperature at which the semiconductive film is thermocompression-bonded to the aluminum foil is relatively low, an increase in the contact resistance at the interface between the aluminum foil and the semiconductive film is suppressed.

Therefore, the volume resistivity in the thickness direction of the water-impervious tape does not increase, and when this water-impervious tape is used as the water-impervious layer of the power cable, the aluminum foil and the metal shield layer of the core for the power cable are used. And a good conduction state is maintained. Therefore, even if an abnormal voltage such as a lightning surge or a switching surge enters the water-shielded power cable, no potential difference occurs between the aluminum foil and the external semiconductive layer or the metal shielding layer. Does not occur, cracks or holes are not formed in the aluminum foil, and the water-blocking tape can maintain good water-blocking performance.

Also, even if a semiconductive film is thermocompression-bonded to an aluminum foil at a low temperature and laminated integrally, the aluminum foil and the semiconductive film adhere to each other with a larger adhesive force to the conductive adhesive layer. Even if the water impermeable tape is pulled, bent, etc., the aluminum foil and the semiconductive film do not peel off, the aluminum foil does not wrinkle or crack, and the water impermeable performance can be maintained well over a long period of time. it can.

Further, in the water impermeable power cable of the present invention, it is preferable that a water impermeable layer is provided on the power cable core by covering the water impermeable tape with the semiconductive film facing the cable core. Features.

Since the cable of the present invention is provided with a water-blocking layer using a water-blocking tape having excellent water-blocking performance as described above, it is possible to suppress the insulation deterioration of the cable for a long period of time and obtain stable electrical characteristics. And maintain cable life.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory cross-sectional view of a water impermeable tape 10 according to the present invention. The waterproofing tape 10 of the present invention
On one surface of the aluminum foil 12, a plastic film 14 as a reinforcing body for the aluminum foil 12 and, if necessary, for example, improving the adhesion between the cable and the anticorrosive layer,
In order to increase the water barrier, the adhesive film layer 16 is laminated, and the other surface of the aluminum foil 12 is lower than the base resin of the semiconductive film 18 in the calorimetric measurement by DSC (differential scanning calorimeter). The semiconductive film 18 is laminated by thermocompression bonding via a conductive adhesive layer 20 having a crystal melting point.

The aluminum foil 12 is formed by molding aluminum or its alloy material into a foil shape. If it is too thin, pinholes are likely to occur, and if it is too thick, flexibility becomes poor. Therefore, there is a problem that it is not easy to provide a water impermeable layer.
Those having a thickness of about 0 μm are suitable.

The plastic film 14 is usually laminated on the aluminum foil 12 with an adhesive, for example, a polyester film such as a polyethylene terephthalate film (PET film), a polyvinyl chloride film, a polyimide film, a polycarbonate film and the like. And its thickness is preferably about 15 to 200 μm. For the adhesive film layer 16, a hot melt film having thermoplasticity is used.
Are laminated by, for example, thermocompression bonding using a heating roll.

The semiconductive film 18 is made of, for example, ethylene ethyl acrylate copolymer (EEA), ethylene ethyl methacrylate copolymer (EMA), ethylene vinyl acetate copolymer (EVA), ethylene acrylic acid copolymer (EAA). ) Or a mixture of two or more of them, or a resin obtained by blending each of the above copolymers or a mixture thereof with various polyethylenes as a base resin, and imparting a predetermined amount of conductivity thereto. A semiconductive plastic film formed into a film with a thickness of about 0.03 to 0.2 mm from a resin composition containing an agent, for example, carbon black such as acetylene black, graphite, or the like is used. The semiconductive film 18 desirably has a characteristic that the volume resistivity is 1 × 10 ⁴ Ω · cm or less and the melting point by DSC is 80 to 120 ° C.

The conductive adhesive layer 20 is made of, for example, a polyester containing a conductivity-imparting agent such as carbon black,
Polyolefin-based, polyurethane-based hot-melt adhesive films and adhesive paints having the same volume resistivity as the semiconductive film are used. In the case of a paint, it is desirable to apply the paint to the contact surface of the aluminum foil 12 or the semiconductive film 18 in advance. Conductive adhesive layer 2
As for 0, one having a lower melting point than the base resin of the semiconductive film 18 is appropriately selected. Semiconductive film 18
Are laminated on the other surface of the aluminum foil with the conductive adhesive layer 20 interposed therebetween and thermocompression-bonded with a heating roll or the like.

The water impermeable tape 10 of the present invention has the above-described configuration. With such a configuration, the aluminum foil 12
When the semiconductive film 18 is laminated on the other surface of the aluminum foil 12, the conductive adhesive layer 20 melts at a temperature lower than the temperature at which the base resin of the semiconductive film 18 melts.
And the semiconductive film 18 are thermally fused, and the aluminum foil 12 and the semiconductive film 18 are firmly adhered to each other. And
Since the temperature at which the semiconductive film 18 is thermocompression-bonded to the aluminum foil 12 is relatively low, the aluminum foil 12 and the semiconductive film 1
8 suppresses an increase in contact resistance at the interface.

Therefore, when the water-impervious tape 10 is used for the water-impervious layer of a power cable, good conduction between the aluminum foil 12 and the metal shield layer of the power cable core is maintained. Even if an abnormal voltage such as a lightning surge or switching surge enters the cable, there is no potential difference between the aluminum foil and the external semiconductive layer or metal shielding layer. The water-shielding performance of the tape 10 can be favorably maintained.

Next, a water impermeable power cable using the water impermeable tape 10 will be described with reference to FIG.
In FIG. 2, reference numeral 22 denotes a power cable core, on which a conductor 24 is provided with an inner semiconductive layer 26, a plastic insulator layer 28 such as cross-linked polyethylene, and an outer semiconductive layer 30;
Further, a metal shielding layer 32 made of a copper tape, a copper wire, or the like is provided. Further, a water barrier layer 34 is provided on the power cable core 22, and a corrosion protection layer 36 made of plastic such as PVC is provided thereon. As shown in FIG. 1, the water-blocking layer 34 is formed by laminating the plastic film 14 and the adhesive film layer 16 on one surface of the aluminum foil 12,
A water-shielding tape 10 formed by thermocompression bonding the semiconductive film 18 on the other surface of the aluminum foil 12 via a conductive adhesive layer 20 having a lower melting point than the base resin of the semiconductive film 18. Is formed by placing the semiconductive film 18 on the power cable core 22 side and vertically covering the core 22. The impermeable power cable of the present invention is configured as described above. Such a water impermeable power cable is excellent in bending resistance and can maintain stable electrical characteristics for a long period of time.

[0021]

(Example 1) Aluminum foil 12 having a thickness of 50 μm
The plastic film 14 having a thickness of 5
In an AL / PET laminated tape in which a 0 μm PET film is preliminarily laminated, an adhesive film layer 16 is further formed on the plastic film 14 (PET film).
A polyester hot melt adhesive tape (Sumitomo Chemical's Bondfast VC40) having a thickness of 50 μm
On the other surface of the aluminum foil 12, a conductive adhesive layer 20 having a thickness of 50 μm and a crystal melting point of
Polyester hot melt adhesive film having a volume resistivity of 1.5 × 10 ¹ Ω · cm (15 parts of acetylene black added to 100 parts of NAC ACE GB-301 manufactured by Nippon Unicar. Tensile strength 15 MPa, (Elongation: 50%), and as the semiconductive film 18, a semiconductive EEA resin film (DPJJ manufactured by Nippon Unicar) having a thickness of 100 μm, a crystal melting point by DSC of 94 ° C., and a volume resistivity of 3 × 10 ³ Ω · cm. Material 100 of -9169
15 parts of acetylene black. (Tensile strength: 20 MPa, elongation: 40%) were overlapped, and the layers were laminated by thermocompression bonding with a heating roll at 100 ° C., to thereby produce a waterproof tape 10 as a prototype. When the volume resistivity in the thickness direction of the water impermeable tape 10 was measured, it was 8 × 10 ⁴ Ω · c
m, the adhesive force between the aluminum foil 12 and the semiconductive film 18 is 6.0 N / 10 mm width and a sufficient adhesive force is obtained;
Also, an increase in contact resistance at the interface between the aluminum foil 12 and the semiconductive film 18 was able to be suppressed low.

(Comparative Example) On a plastic film (PET film) of an AL / PET laminated tape having the same dimensions, composition and properties as described in Example 1, a polyester hot melt adhesive tape (Sumitomo Chemical) Bondfast VC40) and the same dimensions as above, without the conductive adhesive layer on the other side of the aluminum foil.
A semi-conductive EEA resin film, which is a semi-conductive film having a composition and characteristics, was overlaid and laminated by thermocompression bonding with a heating roll at 160 ° C. to produce a water-blocking tape. When the volume resistivity in the thickness direction of this water-impervious tape was measured, it was significantly increased to 7 × 10 ¹⁰ Ω · cm. This indicates that the contact resistance at the interface between the aluminum foil 12 and the semiconductive film 18 has significantly increased. Further, the adhesive force between the aluminum foil 12 and the semiconductive film 18 was also 5.0 N / 10 mm width.

[0023]

As described above, the water-impervious tape of the present invention has at least one plastic film laminated on one surface of the aluminum foil and has a lower surface than the base resin of the semiconductive film on the other surface of the aluminum foil. Since the semiconductive film was laminated by thermocompression bonding via a conductive adhesive layer having a melting point, when the semiconductive film was laminated on the other surface of the aluminum foil, the base resin of the semiconductive film was melted. The conductive adhesive layer melts at a temperature lower than the temperature at which the aluminum foil and the semiconductive film are thermally fused, and the aluminum foil and the semiconductive film are firmly adhered to each other. Since the temperature for thermocompression bonding of the film is relatively low, it is possible to suppress an increase in contact resistance at the interface between the aluminum foil and the semiconductive film.

Therefore, when this water-impervious tape is used for the water-impervious layer of a power cable, good conduction between the aluminum foil and the metal shield layer of the power cable core is maintained. Even if an abnormal voltage such as a lightning surge or switching surge enters, there is no potential difference between the aluminum foil and the external semiconductive layer or metal shielding layer, and no discharge occurs.Therefore, cracks, holes, etc. do not occur in the aluminum foil. In addition, the water-shielding tape can maintain good water-shielding performance.

Further, even when a semiconductive film is thermocompression-bonded to an aluminum foil at a low temperature and laminated integrally, the aluminum foil and the semiconductive film are firmly adhered to each other by the conductive adhesive layer. Even if the water tape is pulled or bent, the aluminum foil and the semiconductive film do not peel off. For this reason, wrinkles and cracks do not occur in the aluminum foil, and the water barrier performance can be maintained satisfactorily for a long period of time.

Next, in the water impermeable power cable of the present invention, a water impermeable layer is provided on the power cable core by covering the water impermeable tape with its semiconductive film facing the cable core. Therefore, the water blocking performance of the water blocking layer is improved, the insulation deterioration of the cable is suppressed over a long period of time, the stable electrical characteristics are maintained, and the life of the cable can be extended.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view showing one embodiment of a water impermeable tape according to the present invention.

FIG. 2 is an explanatory sectional view showing one embodiment of a water-blocking type power cable according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Waterproof tape 12 Aluminum foil 14 Plastic film 16 Adhesive film layer 18 Semiconductive film 20 Conductive adhesive layer 22 Power cable core 24 Conductor 26 Inner semiconductive layer 28 Insulator layer 30 External semiconductive layer 32 Metal shielding Layer 34 Waterproof layer 36 Anticorrosion layer

Claims (2)

[Claims] At least one plastic film is laminated on one surface of an aluminum foil, and the other surface of the aluminum foil is provided with a conductive adhesive layer having a melting point lower than that of a base resin of the semiconductive film. A water-blocking tape characterized by laminating conductive films by thermocompression bonding. 2. A water-blocking type power cable, wherein a water-blocking layer is provided on the power cable core by covering the water-blocking tape with its semiconductive film facing the cable core.