JPH0917242A - Fire resistant cable and its manufacture - Google Patents

Abstract

PURPOSE: To provide the new fire resistant cable and its manufacture, which enhances its fire resistant characteristics in particular to a great extent. CONSTITUTION: A fire resistant layer 2 is formed over a conductor 1, and concurrently, its circumference is covered with an insulator 3 and a sheath 4. The fire resistant layer 2 comprises inorganic silicon resin impregnated in a synthesis laminated mica tape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fireproof cable used in a place where a high degree of safety is required, such as an underground mall of a building, and a method for manufacturing the fireproof cable.

[0002]

2. Description of the Related Art Generally, fire extinguishing equipment such as sprinklers and water sprayers, automatic fire alarms, emergency warning devices, and evacuation guidance installations such as guide lights are obligatory in buildings and underground malls as a safety measure in case of fire. These facilities include
Since it is necessary to protect the conductor from high heat in the event of a fire and to operate the above equipment for a certain period of time, and to prevent the spread of fire due to the combustion of the cable, fire resistant cables with excellent flame resistance and fire resistance are used. ing.

As a fireproof cable having such a function, for example, as shown in FIG. 2, a fireproof material such as glass mica or film mica is wound around a conductor 1 to form a fireproof layer 2, and the periphery thereof is formed. A typical structure is one in which an insulator 3 made of polyolefin such as polyethylene is formed, and a flame-retardant sheath 4 is further coated around the insulator 3. And the flame resistance of such a fireproof cable is JIS
-The flame retardancy level of C-3005 was 60%, and the flame-retardant level was the mainstream, but recently, with the increase in the height of buildings and the expansion and deepening of underground malls, I aimed at improving the safety in case of fire.
There has been an increasing demand for fire resistant cables with high flame retardance at a level that passes the vertical tray burning test of EEE383.

[0004]

By the way, in order to realize such high flame retardancy, the sheath 4 as shown in the drawing is used.
However, if the sheath 4 is made highly flame-retardant, the insulator 3 made of polyolefin such as polyethylene or cross-linked polyethylene will melt and fall in the fire resistance test according to JIS-A1304. Alternatively, there is a drawback that it becomes difficult to burn, carbonizes after being steamed, and as a result, the electrical characteristics of mica are significantly deteriorated. Furthermore, in the multi-core type fire resistant cable, the sheath carbonizes during the fire resistance exposure test, and then the combustibles such as the insulators and interpositions inside the cable are melted and gasified by the heat, and the internal pressure rises. When the cracks are generated and these decomposed products are blown to the surface of the sheath and then the sheath carbide is dropped, the temperature of the fire temperature curve defined in JIS-A1304 is far exceeded, and the sheath is dropped to expose the fireproof layer. , When the flame hits the refractory layer directly, since the natural laminated mica having a hydroxyl group has been conventionally used for this refractory layer, the crystal structure is changed by the chemical change of the hydroxyl group into water, and the insulation resistance is increased. There was an inconvenience that it decreased. Therefore, it is possible to increase the thickness of the refractory layer, but the thickness of the refractory layer is specified and there is a limit to that.

Therefore, the present invention has been devised in order to solve the above problems, and an object thereof is to significantly improve the fire resistance characteristics without adversely affecting the electric characteristics or increasing the thickness of the fire resistance layer. (EN) Provided is a novel fireproof cable and a manufacturing method thereof.

[0006]

In order to achieve the above object, the present invention provides a fire-resistant cable comprising a conductor, a fire-resistant layer formed on the conductor, and an insulator and a sheath around the fire-resistant layer. A synthetic mica tape made by bonding a lining material and synthetic mica is impregnated with an inorganicized silicone resin composed of a silicone resin and a filler.

The silicone resin used in the present invention is represented by the average formula of R _X SiO _{4 -X} (R: organic group represented by methyl group X: 1 or 2), and D unit (R ₂ Si
It is composed of a combination of O ₂ ) and T units (RSiO ₃ ), and the T units in this mineralized silicone resin must be 50 wt% or more.
This is because if it is 50 wt% or less, it is difficult to form a ceramic. Then, it is preferable that the varnish is dissolved in a solvent such as toluene or xylene.

On the other hand, as fillers added to this silicone resin, silica, alumina, mica powder, Al (O 2
H) ₃ , Mg (OH) _{2 and the} like, but mica powder is preferable from the viewpoint of ceramic strength. Examples of this mica powder include KAl ₂ (AlSi ₃ O ₁₀ ) (OH)
₂ , NaAl ₂ (AlSi ₃ O ₁₀ ) (OH) ₂ , KLi
Al (Si ₄ O ₁₀ ) F ₂ , KMg _2.5 (Si ₄ O ₁₀ ) F
₂ , KMg ₂ Li (Si ₄ O ₁₀ ) F _{2 and the} like, which are represented by chemical formulas. Although the amount of the filler added is not particularly limited, it is preferably in the range of 30 to 200 parts by weight with respect to 100 parts by weight of the silicone resin from the viewpoint of the effect and workability. In the case of silicone resin alone, it becomes brittle at high temperature, and the effect of insulation resistance and withstand voltage on the fire resistance characteristics is low. In particular, those with a small number of insulation wire cores or small conductor size can obtain sufficient fire resistance characteristics. I will not be able to. Further, as a method for forming a refractory layer containing such an inorganicized silicone resin, after applying the inorganicized silicone resin to a synthetic mica tape, the synthetic mica tape is wound around the conductor or the synthetic mica tape is wound directly on the conductor. After that, a method of applying on glass mica by a method such as dipping may be used.

Then, on the refractory layer, polyethylene,
After extrusion coating insulator such as cross-linked polyethylene,
Further, the flame-retardant cable of the present invention can be obtained by covering the flame-retardant sheath directly or through the intervening or pressing tape.

Examples of the resin composition constituting the insulator and the sheath include polyolefins such as polyethylene, ethylene vinyl acetate copolymer, ethylene methyl acrylate copolymer, ethylene acrylate copolymer, ethylene butene copolymer, ethylene propylene copolymer, etc. For the above, polyolefins such as polyethylene, ethylene butene copolymer, and ethylene propylene copolymer are preferable from the viewpoint of fire resistance. Further, if necessary, a cross-linking agent, a cross-linking aid, an antioxidant, a lubricant or the like may be added to these resin compositions, and the resin composition may be cross-linked with an electron beam or peroxide. good.

[0011]

The present inventors have conducted a study on the improvement of the fire resistance characteristics based on the above-mentioned combustion behavior, and as a result, have made a synthetic resin mica tape composed of a backing material and a synthetic resin mica stuck on the fire resistant layer, which is composed of silicone resin and filler. It has been found that the use of the impregnated mineralized silicone resin significantly improves the fire resistance.

That is, the conventional synthetic mica is one in which the hydroxyl group of natural mica is replaced with a fluorine group having a strong chemical bonding force, and its strong chemical bonding force makes it easy to crystallize even at high temperature. Has a stable crystal structure without being decomposed, and thus maintains high insulating properties even at high temperatures. However, these conventional synthetic mica are those bonded to a reinforcing material such as a plastic film typified by a polyethylene film or a natural fiber and a glass cloth by an organic or inorganic adhesive including a silicone resin, A large number of minute voids are formed between the mica and the interface of the reinforcing material and the laminated mica. Insulators, intervening substances, etc. are melted by heat into the voids, and a conductive decomposition product having a low molecular weight penetrates, It was supposed to significantly reduce the electrical characteristics. Therefore, as a result of studying to solve this problem, as described above, synthetic synthetic mica tape was impregnated with an inorganicized silicone resin consisting of a silicone resin and a filler, thereby forming a ceramic at high temperature and conducting decomposition into mica. It was found that it was effective in preventing the entry of materials and improving the fire resistance.

Further, the insulation resistance of the synthetic mica tape impregnated with the inorganicized silicone resin of the present invention at high temperature was examined in comparison with the synthetic mica that was not impregnated, and the heating curve of JIS-A1304 was followed by 840 after 30 minutes.
It was found that the insulation resistance at ° C was also increased by about one digit.
The reason for this is currently under study, but it is considered that the ceramicized layer functions as a heat insulating layer or prevents deterioration by blocking oxygen to mica, but details are unknown. By impregnating the inorganicized silicone resin composed of the silicone resin and the filler in this way, it was found that not only the infiltration of the conductive decomposition product is prevented but also the insulation resistance of the synthetic mica tape itself at high temperature is significantly improved.

[0014]

EXAMPLES Examples of the present invention will be described in detail below.

As shown in FIG. 1, first, two glass synthetic mica tapes impregnated with the composition shown in Table 1 were wound on a copper conductor 1 in a 1/5 wrap to form a refractory layer 2. An insulator core was formed by coating low density polyethylene as the insulator layer 3 on the top. Next, a holding tape 6 made of a phosphorus-containing tape is wound around the insulator core via an interposition 5, and a sheath having a composition shown in Table 2 is coated around the holding tape 6 to form six types of sample cables ( Examples 1-3 and comparative examples 1-3) were produced. Thereafter, these various sample cables were evaluated for flame retardancy and fire resistance, and the results are shown in Table 1. This flame retardance complies with the American Standard IEEE 383 vertical tray combustion test (VTFT), and 10 2.4m cables are vertically arranged and 0.6m to 70,000BTU below the cable.
/ H for 20 minutes, then remove the flame 1.8m
If the flame was self-extinguished at less than 1, the product passed the test and the product fired to 1.8 m or more was rejected. Regarding the fire resistance, the exposure test and the in-pipe test specified by the Fire and Heat Resistant Electric Wire Certification Operation Committee were performed according to the fire temperature curve defined in JIS-A1304.

[0016]

[Table 1]

[0017]

[Table 2]

As a result, as is clear from Table 1, all of Examples 1 to 3 within the scope of the present invention had flame retardance that passed VTFT and exhibited excellent fire resistance. On the other hand, Comparative Example 1 in which mica powder is not added,
Both Comparative Example 2 using ethylene vinyl acetate resin and Comparative Example 3 without treatment failed in the fire resistance test.

[0019]

In summary, according to the present invention, particularly excellent fire resistance characteristics are exhibited, so that reliability in case of fire is improved, and it is possible to greatly contribute to safety measures.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a multi-core fireproof cable according to the present invention.

FIG. 2 is a cross-sectional view showing an example of a conventional fireproof cable.

[Explanation of symbols]

 1 conductor 2 fireproof layer 3 insulator 4 sheath 5 interposer 6 holding tape

Claims (5)

[Claims] 1. A fire resistant cable comprising a conductor on which a fire resistant layer is formed, and an insulator and a sheath surrounding the fire resistant layer, wherein the fire resistant layer is formed by impregnating a synthetic laminated mica tape with an inorganicized silicone resin. Fireproof cable characterized by being. 2. The synthetic laminated mica tape is obtained by laminating a backing material and synthetic laminated mica, and
The fireproof cable according to claim 1, wherein the mineralized silicone resin comprises a silicone resin and a filler. 3. The fire resistant cable according to claim 1, wherein the T unit of the mineralized silicone resin is 50 wt% or more. 4. The fire resistant cable according to claim 2, wherein the filler is mica powder. 5. A synthetic mica tape is wound around a conductor, and an inorganicized silicone resin composed of a silicone resin and a filler is applied to the synthetic mica tape and dried, and then an insulator and a sheath are formed thereon. A method for manufacturing a fireproof cable, characterized by coating.