JPH07312123A - Coaxial cable - Google Patents

Abstract

PURPOSE:To provide a coaxial cable provided with flame resistance and a high void ratio. CONSTITUTION:A skin layer 2 of polyethylene resin is provided on an outer circumference of a center conductor 1, a polyethylene resin pipe 3 is disposed on its outer circumference, and foam insulation of foam particles of vinylidene chloride in which fluoro-gas is enclosed is filled between the pipe 3 and the skin layer 2 to form an insulation layer 4. On an outer circumference of the pipe 3, brading of strands of tin-plated soft copper is provided to form an outer conductor 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coaxial cable excellent in flame retardancy and electric conductivity (dielectric constant).

[0002]

2. Description of the Related Art Conventionally, in order to reduce the transmission loss of a coaxial cable, a coaxial cable having a foam layer provided by chemical foaming or gas foaming on the outer periphery of a center conductor has been used. In recent years, a foamed layer having a higher porosity (foaming degree of 80% or more) has been demanded, but the mechanical strength is lowered, the electrical characteristics are deteriorated by the decomposition residue of the foaming agent, and the foaming gas is generated. There is a problem that the adhesiveness between the foam layer and the central conductor is deteriorated due to. Therefore, a coaxial cable having a hollow plastic body or a hollow insulating particle, which has been prepared in a separate process in advance, as an insulating layer, has been devised instead of foaming the foamed layer in the manufacturing process (actual flat cable 2). -41331 gazette, Unexamined-Japanese-Patent No. 3-114108 reference).

[0003]

[Problems to be Solved by the Invention] The former case, Kaikaihei 2-41
Japanese Patent No. 331 discloses a hollow plastic body of several microns to several tens of microns, which is produced by sending air into a polyethylene-based plastic body. Also,
The latter Japanese Patent Laid-Open No. 3-114108 discloses foamed particles and hollow plastic spheres obtained by foaming a plastic material such as polyethylene or polystyrene with an ADCA organic foaming agent or a petroleum low boiling point solvent. For these hollow plastic bodies and hollow insulating particles, flammable resins such as polyethylene are used. In order to make a coaxial cable using a flammable resin as an insulating layer flame-retardant, it is necessary to thicken the sheath made of a flame-retardant resin provided on the outer circumference of the outer conductor. However, when the sheath is made thick, there are problems that the outer diameter of the coaxial cable becomes large and the flexibility is lost, and the weight of the cable increases and the workability of installation is deteriorated.

In view of the above problems, an object of the present invention is to provide a coaxial cable having flame retardancy and high porosity.

[0005]

A coaxial cable of the invention according to claim 1 is a coaxial cable in which an insulating layer made of a foamed insulating material is provided around a central conductor, and an outer conductor is provided on the outer periphery of the insulating layer. It is characterized in that the foamed insulator is made of vinylidene chloride resin.

Further, in the coaxial cable of the invention according to the second aspect of the present invention, there is provided a foamed insulator of a coaxial cable in which an insulating layer made of a foamed insulating material is provided around a central conductor, and an outer conductor is provided on an outer periphery of the insulating layer. It is characterized in that it is made of vinylidene chloride resin in which bubbles are filled with fluoro gas.

The foamed insulator used in the present invention foams particles containing vinylidene chloride resin as a main component to form a large number of bubbles in the particles, or a substantially spherical vinylidene chloride particle with a gas. It is composed of a hollow body which is enclosed and expanded to have a hollow portion inside, or a crushed product of a foam having a predetermined size, but is not particularly limited as long as it is a vinylidene chloride resin particle having a large porosity. The reason for using vinylidene chloride resin here is that vinylidene chloride resin is excellent in flame retardancy and self-extinguishing property, and even if the porosity is increased, the flame retardancy and mechanical strength of the coaxial cable are not easily reduced. is there.

According to the second aspect of the invention, the use of the foamed insulation material in which the fluorogas is enclosed in the bubbles is because the fluorogas is excellent in the electric insulation property and the electric dielectric property.
This is because the gas is characterized by being non-corrosive and non-flammable.
As a method of enclosing the fluorogas in the foamed insulator, the insulating resin which is the main component of the foamed insulator is foamed with the fluorogas, and the generated closed cells are filled with the fluorogas.

Further, a foamed insulating material containing a vinylidene chloride resin in which fluorogas is enclosed as a main component is particularly preferable, because the vinylidene chloride resin has excellent mechanical strength, and therefore some external force is applied to the foamed insulating material. Even if the bubbles are blown, the bubbles are not destroyed and the closed bubbles are kept, and the encapsulated fluoro gas does not leak to the outside and exhibits excellent dielectric properties.

The insulating layer formed by the foamed insulating material of the present invention has a high porosity. The desirable porosity is 50 to
80%. This is because if the porosity is less than 50%, the coaxial cable has insufficient dielectric properties, and if it exceeds 80%, it becomes difficult to maintain the closed cells, and the gas retention capability is reduced.

[0011]

In the present invention, the vinylidene chloride resin is used for the foamed insulating material of the insulating layer to make the coaxial cable flame-retardant, and the use of the foamed insulating material in which the fluorogas is enclosed in the air bubbles further enhances the insulating property. .

[0012]

EXAMPLE An example of the present invention will be described below. Diameter 2.1
A 0.1 mm-thick skin layer 2 made of polyethylene resin (Mirason 3530, trade name of Mitsui Petrochemical Co., Ltd.) was provided on the outer periphery of the central conductor 1 made of a 7 mm tin-plated annealed copper wire. Furthermore, the inner diameter is 6.57mm and the thickness is 0.2mm
Polyethylene resin (Millason 3530) pipe 3 is placed, and a gap between the pipe 3 and the skin layer 2 is a foamed insulator made of vinylidene chloride resin foamed particles in which fluorogas is sealed (Cellmore filler 36 times Asahi Kasei Corp. Company brand name)
Was filled in to form the insulating layer 4. Further, the outer circumference of the pipe 3 is braided with a tin-plated annealed copper stranded wire to form the outer conductor 5, and the outer conductor 5 has a thickness of 0.1 mm made of polyvinyl chloride resin (TG4244, a product name of Riken Vinyl Industry Co., Ltd.). Sheath 6 was covered.

[Comparative Example 1] In the above-mentioned example, a foamed polyethylene resin (WN-
866 Nippon Unicar Co., Ltd.) is extruded into an elongated shape while being foamed by the decomposition gas of the foaming agent and has a diameter of 1 mm.
Comparative Example 1 was a coaxial cable filled with foamed spheres formed by strand cutting.

[Comparative Example 2] A foamed extruded layer (foaming rate: 45%) of a foamed polyethylene resin (WN-866, a product of Nippon Unicar Co., Ltd.) was used as the insulating layer, and the same coaxial cable as that of Example was used as a comparative example. It was set to 2.

The weight of each of the above Examples and Comparative Examples 1 and 2 was measured, and an underwater capacitance (underwater C), a vertical combustion test (VW-1) and a vertical tray test were conducted. The vertical burning test was performed according to UL subject 1581, and the vertical tray test was performed according to IEEE standard 383. Then, the underwater capacitance is, as shown in FIG.
The electric wire 11 was grounded in water, and measurement was performed using a device in which the electric wire 11 was provided with the guard electrodes 12, 12 and the measuring electrode 13. First, a voltage was applied to the electric wire 11 from the guard electrodes 12 and 12, and the capacitance was measured by the measurement circuit 14 connected to the measurement electrode 13. The results are shown in Table 1.

[0016]

[Table 1] It can be seen that this example has a lighter weight than that of the comparative example, is excellent in insulation, and is hard to burn. In the vertical burning test of the comparative example, the cotton burned and the flag was burnt down. Also, the vertical tray test was burnt down in 10 minutes.

[0017]

According to the present invention, since vinylidene chloride resin is used, flame retardance can be achieved without providing a thick sheath, so that flexibility is reduced without increasing weight. There is nothing. Further, as in the second aspect of the present invention, if the fluoro gas is further enclosed in the bubbles, the dielectric characteristics can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a coaxial cable of the present invention.

FIG. 2 is a schematic diagram showing a device for measuring an underwater capacitance.

[Explanation of symbols]

 1 ... Central conductor 2 ... Skin layer 3 ... Pipe 4 ... Insulating layer 5 ... Outer conductor 6 ... Sheath

Front page continuation (72) Inventor Mitsuo Ito 2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa Showa Electric Wire & Cable Co., Ltd. (72) Inventor Hiroshi Nakamura 2-chome, Oda-e, Kawasaki-ku, Kanagawa No. 1 In Showa Electric Wire & Cable Co., Ltd. (72) Inventor Gen Tanimoto 2-1-1, Oda Sakae, Kawasaki-ku, Kawasaki City, Kanagawa Prefecture Sakae 2-1-1 No. 1 Showa Cable Denki Co., Ltd. (72) Inventor Zhang Higashinari 2-1-1, Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa Kanagawa Prefecture (72) Inventor Murase Chika Kanagawa 2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Showa Electric Wire & Cable Co., Ltd. (72) Inventor Keiko Shiraishi 2-1-1, Odae Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa

Claims (2)

[Claims] 1. A coaxial cable in which an insulating layer made of a foamed insulating material is provided around a central conductor, and an outer conductor is provided at the outer periphery of the insulating layer, wherein the foamed insulating material is made of vinylidene chloride resin. Characteristic coaxial cable. 2. A coaxial cable in which an insulating layer made of a foamed insulating material is provided around a central conductor, and an outer conductor is provided at the outer periphery of the insulating layer, wherein the foamed insulating material has a fluorogas enclosed in bubbles. A coaxial cable characterized by being made of vinylidene chloride resin.