JPS6041807B2 - flame retardant cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a reef cable, and its purpose is to prevent the conductor from being made of combustible rubber or plastic, such as polyethylene, polypropylene, ethylene, vinyl acetate copolymer, ethylene.・A thermoplastic resin such as an α-olefin copolymer, or a crosslinked product obtained by applying an organic peroxide or electron beam irradiation to a resin such as crosslinked polyethylene or ethylene propylene rubber is applied as an insulating coating layer, and the insulated wire In a cable in which a flame-retardant sheath made of a mixture mainly composed of flame-retardant vinyl chloride or chloroprene is provided around the outer circumference of a single core or the outer circumference of a multi-core twisted core, the above-mentioned insulator and/or twisted The object of the present invention is to provide a reef cable with improved flame retardancy and non-spreading properties by applying pulp-based paper or carbon paper on a multi-core fiber.

Conventionally used general cables, with some exceptions, are coated with flammable materials, mainly rubber and plastic, and are therefore easily flammable, so flame retardancy is desirable from a disaster prevention perspective.

On the other hand, flame retardant testing methods have traditionally been tested by Inlaid Power, Cable Engineers, and Association (
InsuiatedpowerCableEngine
ers Association) 519-18 (generally referred to as IPCEAS 19-18), etc., is a combustion test method for multi-stranded cables that simulates actual wiring. Electronics Engineers Inc. (TlleInst)
ituteElectricalandElectro
nicsEngineers) Inc.) 383 (hereinafter referred to as regular EE383), there was a case where the fire spread, so even in the case of multi-layer municipal construction, a reef cable with excellent flame retardant and non-flame spread properties is required. It's been requested. In general, two methods are known for making cables flammable: one is to impart flame retardancy to a combustible insulator, and the other is to improve the flame retardancy of a sheath material to protect the internal insulator from flames.
However, as is well known, in order to make insulator materials flame retardant, large amounts of halogen-based flame retardants, antimony oxide, aluminum hydroxide, and other fillers are added, which sacrifices the excellent electrical properties inherent to insulators. There are also problems that lead to increased prices. Therefore, it is preferable to improve the flame retardance of the cable by using the conventional insulator with excellent electrical properties and strengthening the flame retardance of the sheath material. Because rubber and plastic are extremely hot, once this insulator ignites and begins to burn, it is difficult to prevent the fire from spreading just by making the sheath flame-retardant, and in multi-strand installations, the fire continues to spread through cable groups. There is a risk of increasing the fire. In particular, in the combustion test method established by IEEE383, which is a combustion test method for multi-strand installation, cables other than cables whose sheaths have extremely high flame retardance will spread and fail, and in addition, the vertical duct combustion test (method) described below It turned out that everything would spread.
As a result of intensive investigation into the cause, the inventors of the present invention found that internal flammable insulators such as polyethylene, cross-linked polyethylene, etc. thermally decompose when heated, turning into a highly flammable low-molecular-weight molten liquid and forming a carbonized cable sheath. The fuel evaporates and ignites, creating a new source of fire.Furthermore, because the heat of combustion is extremely high, the combustion becomes intense despite the use of a flame-retardant sheath, and the fire eventually spreads to the entire cable. I found out that I can put it away.

It is difficult to obtain cables with excellent flame retardance by simply making the sheath highly flame retardant for cables that take on such a form of fire spread, and the present inventors have developed a cable that has a combustible insulator. The cable is coated with a sheath made of flame-retardant vinyl chloride or chloroprene, and has a structure in which paper or carbon paper is wound around an insulator and/or a multi-core structure made by twisting multiple insulated wire cores. The present invention was created based on the discovery that the spread of fire can be prevented by absorbing flammable low-molecular-weight liquid substances generated by thermal decomposition and preventing them from accumulating on the cable surface. It came to this.
Flame-retardant cables with a flame-resistant layer made of paper or carbon paper are IEEE38'SJ! ．． In the burning test method and vertical duct combustion test (method), the cable extinguished naturally without spreading, but when the cable was dismantled and the flame-resistant layer was observed, it remained in a strongly carbonized state after being steamed, and it also did not absorb decomposed liquid well. It has become clear that this method also prevents buildup on the cable surface. - An embodiment of the present invention will be described based on the drawings.

In FIGS. 1 to 4, 1 is a conductor, 2 is an insulating coating layer made of flammable rubber such as ethylene propylene rubber, polyethylene, crosslinked polyethylene, ethylene/vinyl acetate copolymer, polypropylene, or a plastic insulator; 3 is a flame-retardant sheath made of a mixture mainly composed of vinyl chloride or chloroprene, 4 is a chute or an inclusion such as paper, and 5 is a flame-resistant layer of paper or carbon paper. Figure 1 shows the cross section of a single-core cable. The figure shows an insulation coating layer 2 covered with a flame-resistant layer 5. Figure 2 shows a multi-core cable with three insulated wire cores, and each insulation coating layer 2 and the entire twisted structure are covered with a flame-resistant layer 3. FIG. 3 shows a multi-core cable in which only each insulating coating layer 2 is covered with a flame-resistant layer 3, and FIG. 4 shows a multi-core cable in which only the entire twisted structure is covered with a flame-resistant layer 3. FIG. 5 shows a conventional example of a single-core cable, and FIG. 6 shows a conventional example of a multi-core cable consisting of three twisted cores. Next, the IEEE383 combustion test method for cable multi-strand installation and the vertical duct combustion test (method) will be explained.

FIG. 7 shows an apparatus for the IEEE383 combustion test method, in which 6 is a tray with a length of 240 mm, a leaf width of 300 mm, and a depth of 75 mm, and both frames 7 are connected by an arm frame 8 at an appropriate interval. It is installed vertically. Cables A each having a length of 2400 f are lined up at intervals of 112 of the outer diameter of the cables A on the arm frame 8, making the width of the cable group 150 mm or more. A ribbon burner 9 is located horizontally at a height of 60 mm from the bottom of the tray 6 and 75 mm from the surface of the cable A, and the ribbon burner 9 burns the cable group for 20 minutes.

The pass/fail judgment for this test is if the cable group extinguishes itself without spreading the fire over the entire length of the tray 6 after the fire source is stopped 3. 8 and 9 show the apparatus for vertical duct combustion test (method), the tray 10 has a length of 3000 mm and a width of 30 mm.
0mm, depth 7 [hair is installed vertically, cable group is length I]
f3OO [Cable B outer diameter 11 with hair width 25 or more
They are arranged at two intervals and are laid in two rows in a staggered manner before and after the arm frame 8 of the tray 10.

As a fire source, a ribbon burner 9 compliant with IEEE383 was installed horizontally at a height of 600 m from the bottom of the tray 10 and 75 m from the surface of the cable B, and continued combustion for 12 minutes. 1
1 is a cylindrical vertical duct with a length of 225 mm, a width of 3 (6) mm, and a depth of 25 mm; the top 12 and bottom 13 of the duct 11 are open; and fix the tray 10 in the center of the vertical duct 11.

Pass/fail determination of the test is passed if the cable group naturally extinguishes without spreading the fire over the entire length of the tray after 12 minutes of combustion and the fire source is stopped. The IEEE383 combustion test method is well known as a test method that simulates actual wiring, but in actual wiring installation situation 1, cables are not only laid in a single tray but also in a closed duct. Because of this, a vertical duct combustion test (method) was established to simulate this.

In this vertical duct combustion test (method), compared to the IEEE383 method, the chimney effect of the duct appears, and the heat from the fire source does not diffuse and flows along the cable, and the duct is heated and the cable is further heated by the radiant heat. This is a test (method) with strict conditions as it promotes combustion. Table 1 is 6.6
The results of a combustion test are shown in which paper and carbon paper were wound to a thickness of 0.2 mm as a flame-resistant layer for a KV1C x 100 dCV cable.

According to the test results, those using paper or carbon for the flame resistant layer do not spread fire and extinguish naturally, but those without a flame resistant layer or using cotton tape completely burnt out, and as a flame resistant layer =
It turns out that paper and carbon paper are effective. Furthermore, carbon paper containing 5% or more of carbon is effective in view of the cable burnout length, but paper containing 20% or more of carbon has poor mechanical strength and reduces workability, making it impractical. Carbon paper containing 3% carbon or less and paper with no carbon additives have slightly inferior carbonization strength and decomposition product absorption, and have a slightly longer cable burnout length, but they are shown to have sufficient flame resistance.
In the present invention, paper refers to paper made from binders such as bulbs and starch, and carbon paper refers to paper containing carbon, and the carbon content is at most 20%, preferably 5 to 10%. Paper and carbon paper have a density of 0.
7gIc71 or higher is mainly used, and the higher the density, the better the flame retardancy, but there are problems such as the flexibility of the cable gradually decreases and wrinkles tend to occur during taping, reducing workability. . Note 1: Tray installation conditions The 5 cables and 2 flame-resistant layers are finished with a thickness of 0.1 mm by wrapping one layer around the heel.

3 The tensile strength is the value for a width of 15 mm and a thickness of 0.1 mm.

4 Flame-resistant layer characteristic evaluation: O excellent, Δ good, × poor In the high-voltage power cable of 6.6 KV or higher obtained by the present invention, carphone paper with a flame-resistant layer may be wound and shared as an external conductive layer, or If a reduction in partial discharge generation voltage is desired, a high-voltage cable with excellent flame retardancy can be obtained even if carbon paper is applied on the ordinary external conductive layer.

The flame-resistant layer according to the present invention has sufficient flame retardancy even when applied to communication cables and control instrumentation cables in addition to power cables.
It is clear that the cable is non-flammable.

The flame-retardant cable of the present invention has paper or carbon paper applied to the entire upper circumferential surface of a single-core cable, the entire upper circumferential surface of the insulator of a multi-core cable, or the entire circumferential surface of each insulator and multi-core cable. Since a flame-resistant layer is provided that absorbs the thermal decomposition products of the insulator, excellent flame retardancy and non-spreading properties are obtained, and the sheath material does not require high flame retardancy, which would lead to a decrease in mechanical properties. Furthermore, since it has a thin layer of flame-resistant structure, the outer diameter of the cable hardly changes, and since it uses conventional insulating materials, it maintains excellent electrical properties without deteriorating its electrical properties. It has the effect of being able to obtain a fire cable. Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Table 2 shows the combustion test results of Comparative Examples 1 and 2. Comparative example 1
is a conventional normal cable structure with various changes in the oxygen index (hereinafter referred to as LOI) of the sheath.
If I is 36 or less, IEEE383 method, vertical duct (
method) If both fail and the score is 40 or above, IEEE3
Although it passed the 83 method, the cable could not be said to have sufficient flame retardancy because the fire spread in vertical ducts (method). In addition, in Comparative Example 2, the sheath thickness of the cable in Comparative Example 1 was coated one inch thicker than the standard, and although the IEEE383 acceptable fire spread length was smaller, the vertical duct (method) had the same fire spread as in Comparative Example 1. However, these cables have a large outer diameter, which causes various problems in cable handling, and they are also expensive. Example 1 is carbon paper (8% carbon content)
) with a thickness of 0.24 f, and the cable has a sheath LOI of 30 or more, and its flame retardancy and non-spreading properties are clear from the test results, as shown by the IEEE 383 method, vertical duct ( Passes both combustion test methods (Act).
Example 2 shows the performance of a cable in which carbon-free paper was subjected to O-wetting as a flame-resistant layer, and although the burnout length was slightly larger than that of Example 1, it self-extinguished and passed both test methods. Example 3 is made of carbon paper (carbon content: 8%) with a thickness of 0A, which passes both test methods, has a short burnout length, and has even better flame retardancy than Example 1. . The method of applying the flame-resistant layer to the cable may be either by winding it or by attaching it to the outside. As described above, it is clear that the flame-retardant cable of the present invention satisfactorily passes the IEEE 383 combustion test method as well as the vertical duct combustion test (method), and does not spread fire even without imparting high flame retardancy to the sheath. BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 4 are longitudinal sectional front views showing one embodiment of the present invention, FIGS. 5 and 6 are longitudinal sectional front views of a conventional example, and FIG. 7 is a cable combustion test apparatus. Figure 8 is a front view of the apparatus in other combustion tests (methods), Figure 9 is a perspective view of
This is a sectional view taken along the line XX in the figure.

1...Conductor, 2...Insulating coating layer, 3...
...Flame retardant sheath, 4...Inclusion, 5...
...Flame-resistant layer, 6,10...Tray, 9...
...Ribbon burner, 11...Vertical duct.

Claims (1)

[Claims] 1. A flame-retardant sheath made of a mixture mainly composed of vinyl chloride or a synthetic resin such as chloroprene is placed around the outer periphery of a single insulated wire core or the outer periphery of a multi-core insulated wire core made of flammable rubber or plastic as an insulator, or a mixture mainly composed of vinyl chloride or a synthetic resin such as chloroprene. In the cable provided with the above, pulp-based paper or carbon paper is coated on the entire circumferential surface of the insulator, the entire circumferential surface of the twisted multicore, or the entire circumferential surface of both the insulator and the multicore. A flame-retardant cable characterized in that it is provided with a flame-resistant layer that absorbs thermal decomposition products of the insulator.