JPH04349311A - Flame retardant electric cable - Google Patents

Abstract

PURPOSE:To provide a flame retarding electric cable so that a gas upon the burning of a sheath is interrupted and the electric continuity between respective wires can be prevented. CONSTITUTION:A sheath is formed on aggregates such that; conductors 1 are coated with internal and external insulating layers 2 and 3 made of an organic polymer and an organic aromatic polymer respectively and the resulting single aggregates or collected plural aggregates are stranded. The internal insulating layers 2 are made of either an insulating substance, the melting point mp of which is 155 deg.C or less, or an elastomer containing no melting point; the external insulating layers 3 being made of an insulating substance, mp or Tg of which exceeds 155 deg.C; the sheath 4 being made of an insulating substance, melting paint mp of which is 155 deg.C or less, or of an elastomer which has no melting point.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electric cables widely used for electrical and communication purposes, and more particularly to flame-retardant electric cables using polyolefin as an insulator.

0002

2. Description of the Related Art As shown in FIG. 3, a conventional flame-retardant electric cable is constructed by forming an insulating layer 101 of cross-linked polyethylene or non-cross-linked polyethylene on a conductor 100.
It is known that a sheath 102 containing a metal hydroxide is coated on the outside of a plurality of wires in which an insulating layer 101 is formed on a metal hydroxide. Insulating layer 1
The melting point (mp) of 01 is 150°C or less for polyethylene.

0003

[Problems to be Solved by the Invention] In the conventional example having the insulating layer 101 made of cross-linked polyethylene, when the sheath 102 is burned, the cross-linked polyethylene of the insulating layer 101 maintains its shape because it is cross-linked, but the sheath combustion gas (H2 O,NO2
, CO, CO2, etc.) diffuse into cross-linked polyethylene,
The drawback was that the insulation function deteriorated, leading to short circuits.

[0004] Therefore, an object of the present invention is to provide a flame-retardant electric cable that can block gas (water vapor, etc.) during combustion from the outside (sheath) and prevent electrical conduction between wires. do.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an insulating material having a melting point (mp) of 155° C. or less on a conductor directly or through another insulating material, or mp or glass transition temperature (Tg
), either one of which is coated with an organic aromatic polymer whose temperature exceeds 155°C to form an outer insulating layer, and a single or plural fibers having this inner and outer insulating layer are collected or twisted together, and then directly or otherwise A sheath is formed by extrusion coating a flame-retardant mixture containing an organic polymer and a metal hydroxide, which is an insulator with a melting point mp of 155°C or less, or an elastomer with no melting point, through an insulator. This is what I did.

[0006]

[Function] In the present invention, when a plurality of wires are covered with a sheath, the mp or Tg is 155°C.
When the sheath burns, the outer insulating layer (organic aromatic polymer) of each wire is melted and integrated, and this melted and integrated material blocks gas when the sheath is burned. Therefore, electrical continuity (short circuit) between the lines is prevented.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, a conductor 1 consisting of a single copper conductor wire or a stranded copper conductor wire plated with tin, nickel, silver, etc.
The inner insulating layer 2 is formed by extrusion coating an organic polymer, such as polyethylene, which is an insulator having a melting point (mp) of 155° C. or less or an elastomer having no melting point, and then crosslinking it. In addition to polyethylene, organic polymers include ethylene/propylene copolymer, ethylene/butene copolymer, ethylene/vinyl acetate copolymer,
At least one ethylene/ethyl acrylate copolymer
It may consist of a polyolefin composition containing 20-80 parts by weight of seeds. In addition, the ethylene-propylene copolymer and ethylene-butene copolymer contained in the polyolefin composition also include copolymers containing terpolymers, and in the case of copolymers containing terpolymers, the copolymers include A terpolymer containing a diene component as a third component may also be used. As the diene component, 1,4-hexadiene, dicyclopentadiene, and ethylidenenorbornene are preferably used. Furthermore, since the polyolefin of the inner insulating layer 2 contains 20 to 80 parts by weight of a copolymer and is crosslinked, heat deformability and melting/decomposition at high temperatures can be significantly prevented. When the amount of the copolymer is less than 20 parts by weight, there is little effect of preventing heat deformation and foaming at high temperatures, and when it exceeds 80 parts by weight, the copolymer has poor hardness at room temperature and becomes easily deformed. As a method for crosslinking the insulating layer 2, irradiation crosslinking is preferred. Although the inner insulating layer 2 is formed directly on the conductor 1 in FIG. 1, it may be formed on the conductor 1 via another insulator.

[0009] Outside the inner insulating layer 2 thus formed, an outer insulating layer 3 made of an organic aromatic polymer is formed directly or via another insulator. This outer insulating layer 3 is m
Organic aromatic polymers with either p or glass transition temperature (Tg) exceeding 155°C, such as polyetherketone (PEK), polyetheretherketone (PEEK), polycarbonate (PC), polyphenylene oxide (PPO), Etherimide (PE
I) etc. are preferably used.

A plurality of conductors 1 with inner and outer insulating layers 2 and 3 formed thereon are collected or twisted together, and the outside of the conductor 1 is directly or through another insulator, and is made of an insulator with an mp of 155° C. or less, or or an organic polymer that is an elastomer without a melting point, such as ethylene vinyl acetate (E
VA) and a metal hydroxide (for example Mg(OH)2) is extrusion coated to form the sheath 4. Such a sheath 4 can also be formed on the outer insulating layer 3 of a single wire.

Next, production examples 1 to 3 of the present invention and comparative example 1
Table 1 shows the results of testing for flame retardancy (IEEE383 standard) and line-to-line short circuit time.

0012

[Table 1]

In Table 1, the sheath 4 in both the production example and the comparative example had EEA=50 parts by weight, ethylene acrylic elastomer=50 parts by weight, organic peroxide=2.5 parts by weight, and Mg(OH)2= 120 parts by weight of the mixture was used. As is clear from this table, in the IEE383VTFT test, there was not much difference between the manufacturing example of the present invention and the comparative example, but there was a significant difference in the time required to reach short circuit. For flame retardant electrical cables, IEEE38
It is common to evaluate cables by vertical tray combustion tests according to 3 standards, etc., but this relates to self-extinguishing properties determined simply by how long the cable burns. However, in the event of an actual fire, there are other considerations besides just how flame-retardant the cable is.
In order to function as a cable, that is, to stably supply electricity and information, the electrical insulation properties of the material are important.
The time required to reach the short circuit shown in Table 1 is important. In this respect, all of Production Examples 1 to 3 of the present invention are different from Comparative Examples 1 to 3.
It can be seen that this is a significant improvement over 4.

[0014] By adding a radiation-resistant additive to the sheath 4, together with the fact that the outer insulating layer 3 is made of an aromatic polymer, the radiation resistance is improved. Aromatic polymers themselves have excellent radiation resistance.

[0015]

As explained above, according to the present invention, the inner insulating layer is an insulator with a mp of 155°C or less or an elastomer with no melting point, and the outer insulating layer is
is an organic aromatic polymer with a mp or Tg of over 155°C, and the sheath is an insulator with a mp of 155°C or less;
Alternatively, since it is an elastomer with no melting point, the outer insulation layer of each wire melts and integrates when the sheath burns (see Figure 2).
This integrated layer can block the passage of gas to the inner insulating layer and prevent contact between the conductors of each line, that is, short circuit.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a preferred embodiment of the invention.

FIG. 2 is a sectional view of the cable shown in FIG. 1 during combustion.

FIG. 3 is a sectional view showing a conventional cable.

FIG. 4 is a sectional view of a conventional cable during combustion.

[Explanation of symbols]

1 Conductor 2 Inner insulation layer 3 Outer insulation layer 4 Sheath

Claims (1)

[Claims] Claim 1: Extrusion coating of an organic polymer which is an insulator with a melting point (mp) of 155° C. or lower, or an elastomer having no melting point, directly or through another insulator on the conductor (1). An organic aromatic polymer having either a melting point (mp) or a glass transition temperature (Tg) exceeding 155°C is coated on the outside of the cross-linked insulating layer (2) directly or via another insulator to insulate the outside. A layer (3) is formed, and a melting point mp of 155 is applied directly or through another insulating material to the outside of a single or plural fibers collected or twisted together having the inner and outer insulating layers (2, 3).
A flame retardant, characterized in that the sheath (4) is formed by extrusion coating of a flame retardant mixture containing an organic polymer and a metal hydroxide, which is an insulator or an elastomer with no melting point below ℃. sex electrical cable.