JPS6224887Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a thin film material for electrical cables that has excellent flexibility and can provide chemical resistance as well as waterproof and moisture-proof properties to electrical cables. Conventionally, in electric cables in which the insulator layer is made of rubber or plastic material, semiconducting layers are provided on the conductor and the insulator in order to alleviate potential gradients. The first requirement for this semiconducting layer is that it has conductivity suitable for electric field relaxation, which is its original purpose, but it also has sufficient general properties such as strength and flexibility. It is necessary to have the following. Furthermore, recently, electrical cables have been increasingly used in harsh environments, and as a result, semiconducting layers used in electrical cables are required to be waterproof, moisture-proof, and chemical-resistant. It's coming. Conventionally, it has been difficult to obtain thin materials such as semiconductive synthetic resin films that are excellent in waterproofness, moistureproofness, chemical resistance, and flexibility for the following reasons. (1) It is known that a semiconductive composition can ^be obtained by blending conductive carbon with a thermoplastic resin.
In order to obtain a semiconductive composition having a volume resistivity of 10 ⁴ Ω-cm, a large amount of carbon, such as 80 to 150 parts by weight, must be added to 100 parts by weight of the resin. The thin sheets obtained by processing a semiconductive composition containing a large amount of carbon into thin sheets such as films and tapes have mechanical properties such as tensile strength, low temperature brittleness,
The flexibility was so poor that it could not be put to practical use. (2) Thermoplastic resin itself has excellent water-shielding properties and chemical resistance, but when exposed to special chemicals or in harsh environments, its ability to shield water and chemicals over a long period of time deteriorates, resulting in its waterproof, moisture-proof, and chemical-resistant properties. etc. functions will be lost. Furthermore, if a thermoplastic resin is used as a fabric and coated with a conductive mixture, the waterproof, moisture-proof, chemical-resistant properties, etc. will be slightly improved, but the complete waterproof, moisture-proof, and chemical-resistant properties that are the objective of this invention will not be achieved. It was difficult to obtain. In the present invention, as a result of extensive research aimed at improving these drawbacks, we have discovered a conductive thin film material that has particularly excellent chemical resistance. That is, in the present invention, on one or both sides of the lead film,
A flexible semiconductive thin film made of rubber or plastic is attached.
And preferably, the volume resistivity in the thickness direction is 10 ⁰ to 10 ⁴ to alleviate the potential gradient of the electric cable.
It is to set it to Ω-cm. In addition, the volume resistivity is 10 ⁰
If the volume resistivity is less than ¹⁰⁴ Ω-cm, the flexibility will be significantly reduced and it will be difficult to obtain a thin film with the desired strength. If the tanδ of the cable
cause of deterioration such as partial discharge and partial discharge.
Undesirable. In this invention, the thickness of the semiconductive thin film is 0.05~
Approximately 3 mm, the base materials include low, medium, and high density polyethylene, polypropylene, polyamide, polybutene-1, polymethylpentene, ethylene propylene copolymer, ionomer, ethylene-ethyl acrylate copolymer, and ethylene-acetic acid. Vinyl-vinyl chloride graft copolymer, chlorinated polyethylene, chlorosulfonated polyethylene,
Using plastic or rubber elastic bodies such as plasticized polyvinyl chloride, ABS resin, vinyl acetate resin, acrylic resin, natural rubber, butadiene rubber, isoprene rubber, chloroprene rubber, acrylonitrile-butadiene rubber, styrene-butadiene rubber, etc. A film made of a semiconductive mixture with a volume resistivity of 10 ⁰ to ^{10 4} Ω-cm by mixing carbon black into a base material, or a fibrous material made of these materials, such as cloth. It is made by coating the body with a conductive mixture. Note that the carbon black is not particularly limited, and it is preferable to use conductive carbon such as Ketchen Black EC (trade name) manufactured by Akzo of the Netherlands. In this case, the volume resistivity of the semiconductive thin film is usually 10 ⁰ to ^{10 4} Ω-cm.
It has the following. In addition, although a lead film is attached to this thin substrate, the reason why we chose to use lead film in particular is that lead has excellent water-shielding properties and chemical resistance compared to aluminum, copper, and stainless steel, as well as lead It adapts well to the outer surface of a round cross-section like a cable core, and even if there are minute irregularities on the surface, it can follow and adhere closely to it. In contrast, aluminum and stainless steel have a semi-conducting property in the presence of moisture. This is because contact with the conductive carbon black in the conductive composition causes corrosion, making it impossible to maintain water-shielding and chemical-resistant functions for a long period of time. In addition, in order to attach the semiconductive thin film to the above-mentioned lead film, both of them may be attached as is or with a conductive adhesive interposed between them. In the former case, the surface of the lead film may be embossed. By applying this, the semiconductive thin film can be easily brought into close contact by pressing with a hot roll. Next, the present invention will be explained in detail based on the drawings. As shown in the drawing, lead film (thickness 0.05mm x width
200 mm x length 500 m) 1, semi-conductive thin film material (thickness 0.1 mm x width 200 mm x length 500 m) 2 made of polyamide base fabric coated with conductive butyl rubber,
A product bonded with isocyanate adhesive 3 (Example 1), consisting of ethylene-ethyl acrylate copolymer mixed with Kettien Black EC on both sides of a lead film (thickness 0.05 mm x width 200 mm x length 500 m). A conductive thin film for an electric cable was obtained by directly bonding a conductive film (thickness: 0.1 mm) using a hot roll (Example 2). For comparison with the thin film of the present invention, the above-mentioned polyamide cloth alone (Comparative Example 1), aluminum (Comparative Example 2), stainless steel film (Comparative Example 3),
On both sides of the copper film (Comparative Example 4), a semiconductive film (0.1 mm thick) made by mixing the ethylene-ethyl acrylate copolymer with carbon black (Ketting Black EC) was pasted to form a comparative conductive thin film. The results of measuring the mechanical properties and volume resistivity of the conductive thin film of the present invention and the above polyamide cloth alone are shown in Table 1. Each is placed vertically on a 50φ aluminum pipe (wall thickness 1.5 mm), with lead caps applied to both ends, and the joints between the thin sheets and the joints between the thin sheets and the lead caps are completely sealed with epoxy resin. Finally, corrosion resistance test samples were prepared. These samples were mixed with 1% NaOH, 1% NaCl, and 1%
After being immersed in H ₂ SO ₄ and left for 1 hour, 100 hours, and 1000 hours, they were taken out and the corrosion changes of the Al pipes were evaluated. The results are shown as corrosion protection percentage (100−
Corrosion rate (%) is shown in Table 2. The corrosion protection rate test method is based on the following formula. Corrosion protection rate % = (1 - weight change before and after corrosion test / weight before corrosion test) x 100

[Table] As is clear from the above table, it was shown that the volume resistivity was lowered and the volume resistivity was excellent by attaching polyamide cloth or semiconductive film to the lead film.

【table】

[Table] As is clear from the above table, the conductive thin film of the present invention has the following effects. (1) Without increasing the amount of conductive carbon black (usually 30 to 70 parts by weight of carbon black per 100 parts by weight of resin or rubber), the excellent conductive properties of the bonded lead film can improve the volume resistivity. can be lowered. (2) Since the lead film maintains its waterproof, moisture-proof, and chemical-resistant functions, it has excellent water-proofing and chemical resistance that are stable over a long period of time. (3) Due to the bonded structure of lead film and semiconductive thin film, only a small amount of conductive carbon black is required, and excellent flexibility can be achieved by appropriately selecting the thickness of the lead film. I can do it. (4) Mechanical properties can be significantly improved by using lead film. As detailed above, the conductive thin film of the present invention has excellent chemical resistance and other properties, so it can be used on the outside of insulators or conductors such as electric wires and cables, or on the inside of anti-corrosion layers, as well as being waterproof. It is extremely useful when applied as a conductive water-shielding layer having moisture-proof properties, or as a water-shielding tape for connection parts, terminal parts, etc. of electric wires and cables.

[Brief explanation of drawings]

The drawing is a sectional view showing an example of the conductive thin film for electric cables of the present invention. 1... Lead film, 2, 2... Semiconductive thin film, 3
…glue.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A conductive thin film for electric cables made by attaching a flexible semiconductive thin film based on rubber or plastic to one or both sides of a lead film. . (2) A utility model according to claim 1, characterized in that the volume resistivity in the thickness direction of the conductive thin film for electric cables is in the range of 10 ⁰ Ω-cm to 10 ⁴ Ω-cm. Conductive thin film for electrical cables.