JPS6353648B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a watertight and airtight electric cable with good terminal exit properties.

Recently, juute or polypropylene string, which has long been used as an intervening material between the insulated core and sheath of an electric cable, has been used to improve the watertightness and airtightness of electric cables along their length. Instead of fibrous inclusions such as, a method has been adopted in which a mixture of polyvinyl chloride, attacking polypropylene, butyl rubber, etc. is fully interposed by extrusion molding. However, in the method using a mixture of polyvinyl chloride, attacking polypropylene, butyl rubber, etc., this mixture is highly adhesive and adheres excessively to the insulated wire core or sheath, making it difficult to remove the mixture from the air. This made it difficult to connect electrical cables, and there was a drawback that it was difficult to pull out the insulated wire core when connecting the terminals of electrical cables.

There is also a method of interposing a mixture consisting mainly of attack polypropylene and a large amount of inorganic filler, but in this method, the mixture does not have the ability to retain its shape and is brittle, so it does not fill the above-mentioned voids. I had the inconvenience of not being able to do that.

This invention was made in view of the above circumstances,
The purpose is to provide an electric cable with excellent watertightness, airtightness, and easy terminal exit, and is made of at least one type of rubber selected from the group consisting of natural rubber and ethylene propylene rubber and attractive polypropylene as an intervening material. It is characterized by using a mixture consisting of and an inorganic filler.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

The drawing shows an example of the electric cable of the present invention, and reference numeral 1 in the figure indicates the electric cable of the present invention. This electric cable 1 has three insulated wire cores 2,
2, 2, a sheath 3 that covers these insulated wire cores 2, 2, 2, and an admixture 4 that is interposed in the space formed by the sheath 3 and the insulated wire cores 2, 2, 2. ing. The insulated wire core 2 includes a metal conductor 5 made of copper, aluminum, etc., and a material made of polyvinyl chloride, polyethylene, crosslinked polyethylene, butyl rubber, chlorosulfonated polyethylene, etc. provided on the outside of the metal conductor 5 by an extrusion coating method or the like. Insulator 6
However, considering the watertightness and airtightness of the electric cable 1, polyvinyl chloride,
It is desirable to form the insulator 6 from polyethylene or crosslinked polyethylene.

The sheath 3 is formed on the insulated wire cores 2, 2, 2 by an extrusion coating method or the like, and polyvinyl chloride, polyethylene, nitrile rubber, chloroprene rubber, etc. are used, but the sheath 3 is also used for electrical cables. From the viewpoint of watertightness and airtightness (1), it is preferable to use polyvinyl chloride or polyethylene.

Mixture 4 includes one or more rubbers selected from the group consisting of natural rubber and ethylene propylene rubber, attacking polypropylene, calcium carbonate, talc, clay, titanium oxide, silica,
It consists of an inorganic filler such as alumina,
The blending amounts of these components are 5 to 20% by weight of rubber, 5 to 20% by weight of attacking polypropylene, and 60 to 90% by weight of inorganic filler. The amount of rubber and attack polypropylene is 5.
If the rubber content is less than 20% by weight, the mixture will not retain its shape and will become crumbly, making it impossible to fill the above-mentioned void. If the rubber content exceeds 20% by weight, the admixture will become too sticky and will not adhere to the sheath 3 or the insulated wire core 2. It is too sticky and inconvenient, and the attack polypropylene is 20
If the amount exceeds % by weight, the cohesive force of the mixture decreases, making it easy to tear off, which is inconvenient. The mixture 4 having such a composition has excellent watertightness and airtightness, as well as appropriate shape retention and adhesiveness, and is suitable as an inclusion.

Next, an example of a method for manufacturing the electric cable 1 of the present invention will be explained. First, an insulator 6 is provided on the metal conductor 5 by an extrusion coating method to form an insulated wire core 2, and three insulated wire cores 2 are twisted together to form a twisted wire core. On the other hand, a mixture raw material prepared by blending appropriate amounts of one or more rubbers selected from the group consisting of natural rubber and ethylene propylene rubber, attacking polypropylene, and an inorganic filler may be prepared using a mixer such as a ribbon mixer. Mix. Next, the mixed mixture raw materials are fed to an extruder equipped with a crosshead die, the mixture is deposited on the twisted wire cores, and the twisted insulated wire cores are twisted so as to have a circular cross-sectional shape. Fill it thoroughly with the mixture. Then, a sheath 4 is formed on the twisted insulated wire core provided with the mixture 4 by an extrusion coating method, and the intended electric cable 1 is obtained.

In the electric cable 1 of the present invention constructed as described above, the mixture 4 interposed in the space between the insulated wire cores 2, 2, 2 and the sheath 3 has appropriate shape retention and adhesiveness. Moreover, since it has excellent watertightness and airtightness, the above-mentioned void can be completely filled, preventing deformation of the cable 1 and exhibiting excellent watertightness and airtightness. Also, during the terminal opening work, the mixture 4 may be removed from the sheath 3 or the insulated wire cores 2, 2, 2.
Since it does not adhere excessively to the surface and can be easily removed from the space, it is easy to remove the terminal. Furthermore, when polyethylene or polyvinyl chloride is used for the sheath 3 and polyvinyl chloride, polyethylene, or cross-linked polyethylene is used for the insulator 6, the adhesion of the mixture 4 to the sheath 3 and the insulated wire cores 2, 2, 2 is particularly low. This makes it possible to obtain excellent opening properties and further improve watertightness and airtightness.

As explained above, in the electric cable of the present invention, one or more types of inclusions selected from the group consisting of natural rubber and ethylene propylene rubber are used as inclusions interposed in the cavity formed by the sheath and the insulated wire core. Since it uses a mixture consisting of rubber, attacking polypropylene, and an inorganic filler, this mixture has appropriate shape retention and adhesiveness, so it is possible to use the mixture in the above-mentioned space. It is possible to fully fill the electric cable without leaving anything behind, prevent deformation of the electric cable, and allow the mixture to be easily removed from the terminal without excessively adhering to the sheath or insulated wire core. Further, since the mixture has high watertightness and airtightness and at the same time sufficiently fills the above-mentioned voids, it has the advantage of improving the watertightness and airtightness of the electric cable itself.

[Brief explanation of the drawing]

The drawing is a sectional view showing an example of the electric cable of the present invention. 1... Electric cable, 2... Insulated wire core, 3...
Sheath, 4...admixture.

Claims (1)

[Claims] 1. an insulated wire core, a sheath covering the insulated wire core,
An electric cable having an inclusion interposed in a cavity formed by an insulated wire core and a sheath, the inclusion being one or more rubbers selected from the group consisting of natural rubber and ethylene propylene rubber;
An electric cable characterized by using a mixture of attacking polypropylene and an inorganic filler.