JP2001035267A - Fire resisting wire and fire resisting cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce crackings of a fire resisting layer in burning and improve and stabilize the fire resisting characteristic by coating a conductor with a silicone polymer composition, having fine powder of mica mixed therein as a fire resisting layer, and extruding an insulator thereon so as to cover it. SOLUTION: A conductor 2 is covered with a fire resisting layer 12 formed of a silicone polymer composition having fine powder of mica mixed therein. An insulator 4 is extruded onto the fire resisting layer 12, to form a fire resisting wire 13. Otherwise, the insulator 4 is further covered with a sheath to constitute a fire resisting cable. The silicone polymer composition constituting the fire resisting layer 12 is formed by mixing, to 100 pts.wt. of silicone polymer, about 50-300 pts.wt. of a fine powder of mica and 0 to about 20 pts.wt. of an inorganic fiber material. The fine powder of mica preferably has a particle size of 150 μm or less and a thickness of 10 μm or less. As the inorganic fiber material, alumina fiber of glass fiber may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fire-resistant cable capable of improving fire resistance and maintaining stable fire resistance when exposed to high heat or flame due to a fire or the like.

[0002]

2. Description of the Related Art In a theater or a department store where a large number of people gather, in the event of a fire or the like, evacuation guide lights such as emergency exit lights are used to safely guide people in the hall to an emergency exit. It is required that the lamp be kept lit for a certain period of time for completion. Therefore, for fire-resistant cables used for the wiring of fire-extinguishing equipment, alarm equipment, and evacuation equipment for fire-resistant objects, etc., the Japan Electric Wire & Cable Makers Association has voluntarily established its own certification standards for fire-resistant cables, etc. The quality of materials is being ensured. A conventional fire-resistant electric wire has a configuration as shown in FIG. That is, in the fire-resistant electric wire 1, an inorganic powder such as mica or alumina is mixed around the conductor 2 and coated with a silicone polymer which is turned into a ceramic during combustion to form a fire-resistant layer 3, and an olefin is formed on the fire-resistant layer 3. It is configured by covering an insulator 4 made of a system resin.

A conventional fire-resistant cable has a configuration as shown in FIG. 5 in the case of a single-core fire-resistant cable. That is, the fire-resistant cable 5 is formed by mixing an inorganic powder such as mica and alumina around the outer periphery of the conductor 2 and coating a silicone polymer which is turned into a ceramic during combustion to form a fire-resistant layer 3. It is configured by covering a sheath 6 on an insulator 4 made of a system resin. Further, in the case of a conventional fireproof cable, in the case of a multicore fireproof cable, FIG.
(Three-core fire-resistant stranded electric wire is shown in the figure). That is, in the fire-resistant cable 7, an inorganic powder such as mica or alumina is mixed around the outer periphery of the conductor 2,
A fireproof layer 3 is formed by coating a silicone polymer which becomes a ceramic during combustion, and two or more fireproof insulation cores 8 formed by coating an insulator 4 made of an olefin resin on the fireproof layer 3 Interposition 9, presser tape 10 formed by twisting, olefin resin mixed with inorganic filler
And sheath 11 formed of polyolefin resin
(For example, Japanese Utility Model Publication No. 3-2657).
No. 1).

Accordingly, when these fire-resistant electric wires and cables are exposed directly to a flame in the event of a fire, the silicone polymer constituting the fire-resistant layer 3 is ceramicized, and this ceramicization secures the shape retention and electrical insulation. I have.

[0005]

However, in such conventional fire-resistant electric wires and cables, when exposed to high temperatures, the thermal expansion between inorganic powder such as mica and alumina and the silicone polymer. Cracks (cracks) may occur in the refractory layer at the time of combustion due to a difference in the rate or shrinkage rate, and the fire resistance may be reduced or stable fire resistance may not be obtained.

Accordingly, in recent years, a method has been proposed in which an inorganic fiber material such as alumina fiber and a glass powder which softens at about 800 ° C. are kneaded into a silicone polymer composition. The amount of the inorganic substance added to the material is increased, which causes a reduction in workability and a loss in flexibility of the cable.

It is an object of the present invention to reduce the occurrence of cracks in the refractory layer during combustion and to improve and stabilize the refractory properties.

[0008]

According to a first aspect of the present invention, there is provided a fire-resistant electric wire according to the first aspect of the present invention, wherein a fire-resistant layer is formed by coating a silicone polymer composition containing fine powdered mica on a conductor as a fire-resistant layer. An insulator is extruded and coated on the refractory layer. The refractory layer is obtained by mixing fine powder mica with a silicone polymer. The mica of the fine powder has a good dispersibility in the silicone polymer, has a function of reducing cracks generated in the silicone polymer composition during combustion, and improving and stabilizing fire resistance. The silicone polymer may be of any type as long as it is capable of forming a ceramic during combustion, and the type thereof is not particularly limited. With this configuration, according to the invention described in claim 1,
The amount of the inorganic substance added to the silicone polymer composition can be suppressed or eliminated, and the fire resistance can be improved and the fire resistance can be stabilized without lowering the workability or impairing the flexibility of the electric wire.

In order to achieve the above object, the fire-resistant wire according to claim 2 is characterized in that the silicone polymer composition is used in an amount of 50 to 100 parts by weight of the silicone polymer and 50 to 100 parts by weight of fine powder mica.
It is composed of 300 parts by weight and 0 to 20 parts by weight of an inorganic fiber material. The amount of the mica of the fine powder to be blended in the silicone polymer composition was set to 50 to 300 parts by weight with respect to 100 parts by weight of the silicone polymer. This is because not only is it not possible to expect an improvement in cracking, but also it is not possible to obtain the effect of reducing the occurrence of cracks in the ceramic refractory layer during combustion. In addition, the compounding amount of the fine powder mica is 3
Even if it is added in excess of 00 parts by weight, the fire resistance performance is not improved compared to the amount of mica in the fine powder to be added, the workability is reduced, the production cost is increased, and the flexibility of the electric wire is increased Is to be reduced. The amount of the mica in the fine powder is preferably 100 to 200 parts by weight based on 100 parts by weight of the silicone polymer. The inorganic fiber material is, for example, alumina fiber, glass fiber, or the like. Then, the silicone polymer composition contains inorganic fiber material in an amount of 0-2.
It is composed of 0 parts by weight. The amount of the inorganic fiber material is 0 to 2 with respect to 100 parts by weight of the silicone polymer.
The reason that the amount was 0 parts by weight is that the compounding amount of the inorganic fiber material is 0 parts by weight,
That is, it is not necessary to mix them at all.
When the blending amount of the inorganic fiber material is 0 parts by weight, that is, when the inorganic fiber material is not blended at all, the improvement of the fire resistance property and the stabilization of the fire resistance property are achieved by the mixing of the fine powder mica. The reason why the inorganic fiber material is blended is that by blending the inorganic fiber material, a higher synergistic effect between the fine powder and the mica can be used to improve the fire resistance and stabilize the fire resistance. The reason why the amount of the inorganic fiber material is set to 20 parts by weight or less with respect to 100 parts by weight of the silicone polymer is that when the amount of the inorganic fiber material is more than 20 parts by weight with respect to 100 parts by weight of the silicone polymer, This is because the fire resistance performance is not improved compared to the amount of the inorganic fiber material to be blended, and the workability is reduced, and the production cost is increased. According to the invention as set forth in claim 2 by having such a configuration, the amount of the inorganic substance added to the silicone polymer composition can be suppressed or eliminated, without reducing the workability or impairing the flexibility of the electric wire. The fire resistance can be improved and the fire resistance can be stabilized.

In order to achieve the above object, a fire-resistant electric wire according to claim 3 is characterized in that fine powdered mica has a particle size of 150 μm.
Hereinafter, it is composed of mica powder having a thickness of 10 μm or less. The fine powder mica blended in the silicone polymer composition forming the refractory layer is composed of mica powder having a particle size of 150 μm or less and a thickness of 10 μm or less. 100μm or less, thickness 5μm
What consists of the following mica powders is good. With this configuration, according to the invention described in claim 3,
The amount of the inorganic substance added to the silicone polymer composition can be suppressed or eliminated, and the fire resistance can be improved and the fire resistance can be stabilized without lowering the workability or impairing the flexibility of the electric wire.

In order to achieve the above object, the fireproof cable according to the present invention is characterized in that a conductor is coated with a silicone polymer composition containing fine powdered mica as a fireproof layer. An insulator is extruded and coated, and a flame-retardant olefin-based resin is extruded on the insulator to form a sheath layer. The refractory layer is obtained by mixing fine powder mica with a silicone polymer. The mica of the fine powder has a good dispersibility in the silicone polymer, has a function of reducing cracks generated in the silicone polymer composition during combustion, and improving and stabilizing fire resistance. The silicone polymer may be of any type as long as it is capable of forming a ceramic during combustion, and the type thereof is not particularly limited. According to the invention as set forth in claim 4, the amount of the inorganic substance added to the silicone polymer composition can be suppressed or eliminated, and the workability is not reduced and the flexibility of the electric wire is not impaired. The fire resistance can be improved and the fire resistance can be stabilized.

In order to achieve the above object, a fireproof cable according to the present invention is characterized in that a silicone polymer composition containing fine powdered mica is coated on a conductor as a fireproof layer, and the fireproof cable is coated on the fireproof layer. Twist two or more refractory insulated core wires composed by extruding and covering an insulator, interposing an inclusion,
It is constructed by winding a holding tape and covering the outermost layer with a sheath made of a flame-retardant olefin resin. The refractory layer is obtained by mixing fine powder mica with a silicone polymer. The mica of the fine powder has a good dispersibility in the silicone polymer, has a function of reducing cracks generated in the silicone polymer composition during combustion, and improving and stabilizing fire resistance. This silicone polymer is
What is necessary is just to have the property of ceramicizing at the time of combustion, and the type is not particularly limited. The inclusions are provided between the refractory insulated wires so that the cable has a substantially circular cross section when two or more refractory insulated wires are twisted. As this inclusion, paper, jute, PP defibrated yarn or the like is generally used. Polyester non-woven fabric,
Nylon nonwoven fabric, polypropylene, polyester tape, glass tape, paper tape, ceramic paper, and the like.
The flame-retardant olefin resin that constitutes the sheath is an olefin resin containing a metal hydroxide (magnesium hydroxide, aluminum hydroxide, etc.).
Examples include polyethylene, polypropylene, and polybutylene. According to the invention as set forth in claim 5, by having such a configuration, it is possible to suppress or eliminate the amount of the inorganic substance added to the silicone polymer composition, without lowering the workability or impairing the flexibility of the electric wire. The fire resistance can be improved and the fire resistance can be stabilized.

[0013] To achieve the above object, a fire-resistant cable according to claim 6 is characterized in that the silicone polymer composition is mixed with 100 parts by weight of the silicone polymer and 5 fine mica powders.
It is composed of 0 to 300 parts by weight and 0 to 20 parts by weight of an inorganic fiber material. The amount of the mica of the fine powder to be blended in the silicone polymer composition was set to 50 to 300 parts by weight with respect to 100 parts by weight of the silicone polymer. This is because not only is it not possible to expect an improvement in cracking, but also it is not possible to obtain the effect of reducing the occurrence of cracks in the ceramic refractory layer during combustion. Further, even if the compounding amount of the mica of the fine powder exceeds 300 parts by weight, the fire resistance performance is not improved compared to the amount of the mica of the fine powder to be mixed, and the processability is reduced, This is because the manufacturing cost increases and the flexibility of the cable decreases. The inorganic fiber material is, for example, alumina fiber, glass fiber, or the like. Then, the silicone polymer composition contains inorganic fiber material in an amount of 0-2.
It is composed of 0 parts by weight. The amount of the inorganic fiber material is 0 to 2 with respect to 100 parts by weight of the silicone polymer.
The reason that the amount was 0 parts by weight is that the compounding amount of the inorganic fiber material is 0 parts by weight,
That is, it is not necessary to mix them at all.
When the blending amount of the inorganic fiber material is 0 parts by weight, that is, when the inorganic fiber material is not blended at all, the improvement of the fire resistance property and the stabilization of the fire resistance property are achieved by the mixing of the fine powder mica. The reason why the inorganic fiber material is blended is that by blending the inorganic fiber material, a higher synergistic effect between the fine powder and the mica can be used to improve the fire resistance and stabilize the fire resistance. The reason why the amount of the inorganic fiber material is set to 20 parts by weight or less with respect to 100 parts by weight of the silicone polymer is that when the amount of the inorganic fiber material is more than 20 parts by weight with respect to 100 parts by weight of the silicone polymer, This is because the fire resistance performance is not improved compared to the amount of the inorganic fiber material to be blended, and the workability is reduced, and the production cost is increased. According to the invention as set forth in claim 6 by having such a configuration, the amount of the inorganic substance added to the silicone polymer composition can be suppressed or eliminated, without lowering the workability and impairing the flexibility of the electric wire. The fire resistance can be improved and the fire resistance can be stabilized.

In order to achieve the above object, a refractory cable according to claim 7 is characterized in that fine powdered mica is used for the refractory cable.
The mica powder having a thickness of 10 μm or less and having a thickness of 10 μm or less was used. The fine powder mica blended in the silicone polymer composition forming the refractory layer has a particle size of 150 μm.
Below, it is composed of mica powder having a thickness of 10 μm or less, but optimally, the particle size is 100 μm or less and the thickness is 5 μm.
m or less mica powder is preferred. According to the invention as set forth in claim 7, the amount of the inorganic substance added to the silicone polymer composition can be suppressed or eliminated, and the workability is not reduced and the flexibility of the electric wire is not impaired. The fire resistance can be improved and the fire resistance can be stabilized.

[0015]

Embodiments of the present invention will be described below. FIG. 1 shows one embodiment of a fire-resistant wire according to the present invention. In the figure, on the conductor 2,
A refractory layer 12 composed of a silicone polymer composition containing fine powdered mica is coated, and an insulator 4 is extruded and coated on the refractory layer 12 to form a refractory wire 1.
3 are formed. The silicone polymer composition constituting the refractory layer 12 is formed by mixing 50 to 300 parts by weight of fine powder mica and 0 to 20 parts by weight of an inorganic fiber material with respect to 100 parts by weight of the silicone polymer. . And
The fine powder mica mixed with the silicone polymer is a mica powder having a particle size of 150 μm or less and a thickness of 10 μm or less, and most preferably a particle size of 100 μm or less and a thickness of 5 μm.
The following mica powder is blended. The inorganic fiber material is, for example, alumina fiber, glass fiber, or the like.

FIG. 2 shows an embodiment of a fireproof cable according to the present invention. The fireproof cable in FIG. 2 is a single-core fireproof cable. In the figure, a conductor 2 is covered with a refractory layer 12 composed of a silicone polymer composition containing fine powdered mica, on which an insulator 4 is extruded and coated. I have. Further, a sheath 14 is coated on the insulator 4 to form a fire-resistant cable 15.

FIG. 3 shows another embodiment of the fireproof cable according to the present invention. The fireproof cable in FIG. 3 is a multi-core fireproof cable (in FIG. 3, a three-core cable). In the figure, on the conductor 2,
A refractory layer 12 composed of a silicone polymer composition containing fine powdered mica is coated, and an insulator 4 is extrusion-coated on the refractory layer 12. Further, a sheath 14 is coated on the insulator 4 to form a fire-resistant insulated core 16. This fireproof insulated core 16
Are interposed between the refractory insulated wire cores 16 so that the cable 17 has a substantially circular cross section, and a holding tape 18 is wound. A sheath 19 made of a flame-retardant olefin-based resin is coated on the press-wrap tape 18 (outermost layer) to form a fire-resistant cable 20.
Is configured.

The silicone polymer composition constituting the refractory layer 12 comprises 50 to 300 parts by weight of fine powder mica and 0 to 300 parts by weight of an inorganic fiber material based on 100 parts by weight of the silicone polymer.
It is constituted by mixing 20 parts by weight. The fine powder mica mixed with the silicone polymer has a particle size of 150.
A mica powder having a thickness of 10 μm or less and a mica powder having a particle size of 100 μm or less and a thickness of 5 μm or less is optimally blended. In addition, the inorganic fiber material, for example,
Alumina fiber, glass fiber and the like. The inclusions 17 are provided between the refractory insulated cores 16 so that the cable becomes substantially circular in cross section when two or more (three in FIG. 3) insulated refractory insulated cores 16 are twisted. , Paper, jute,
PP defibrated yarn or the like is generally used. Holding tape 1
No. 8 includes polyester nonwoven fabric, nylon nonwoven fabric, polypropylene, polyester tape, glass tape, paper tape, ceramic paper and the like. The flame-retardant olefin-based resin constituting the sheath 19 is an olefin-based resin containing a metal hydroxide (such as magnesium hydroxide or aluminum hydroxide). Examples of the olefin-based resin include polyethylene, polypropylene, and polybutylene.

[0019]

EXAMPLES Hereinafter, specific examples of the silicone polymer composition constituting the fire-resistant layer used in the fire-resistant electric wire and the fire-resistant cable according to the present invention will be described in comparison with conventional examples and comparative examples. In addition, the mica powder blended in each comparative example and the conventional example is
The average particle size is 250 μm and the average thickness is 15 μm.

Example 1 Example 1 is based on 100 parts by weight of the silicone polymer.
It comprises 50 parts by weight of fine mica powder.

Example 2 Example 2 is based on 100 parts by weight of the silicone polymer.
It is constituted by mixing 200 parts by weight of fine powder mica powder.

Example 3 Example 3 is based on 100 parts by weight of the silicone polymer.
It is composed of 300 parts by weight of fine mica powder.

Example 4 Example 4 is based on 100 parts by weight of the silicone polymer.
It is composed of 200 parts by weight of fine mica powder and 20 parts by weight of alumina fiber.

Example 5 Example 5 is based on 100 parts by weight of the silicone polymer.
It is composed of 150 parts by weight of fine mica powder and 10 parts by weight of alumina fiber.

Example 6 Example 6 is based on 100 parts by weight of the silicone polymer.
It is composed of 150 parts by weight of fine mica powder and 5 parts by weight of alumina fiber.

Example 7 Example 7 is based on 100 parts by weight of the silicone polymer.
It is composed of 100 parts by weight of fine powder mica powder and 20 parts by weight of alumina fiber.

Example 8 Example 8 is based on 100 parts by weight of the silicone polymer.
It is composed by mixing 50 parts by weight of fine mica powder and 20 parts by weight of alumina fiber.

Comparative Example 1 Comparative Example 1 was based on 100 parts by weight of the silicone polymer.
It is composed of 200 parts by weight of mica powder and 50 parts by weight of alumina fiber.

Comparative Example 2 Comparative Example 2 was based on 100 parts by weight of the silicone polymer.
200 parts by weight of mica powder, 20 parts by weight of alumina fiber,
It is constituted by blending 20 parts by weight of soda-lime glass.

Comparative Example 3 Comparative Example 3 was based on 100 parts by weight of the silicone polymer.
200 parts by weight of mica powder, 50 parts by weight of alumina fiber,
It is composed of 30 parts by weight of soda-lime glass.

Conventional Example 1 Conventional Example 1 is based on 100 parts by weight of the silicone polymer.
It is constituted by mixing 250 parts by weight of mica powder.

Examples 1 to 8 and Comparative Examples 1 to 8
3. Tables 1 and 2 show the characteristic test results of the characteristics of fire-resistant cables using each of the silicone polymer compositions based on the conventional examples.

[0033]

[Table 1]

[Table 2] The material workability in Table 1 relates to the kneadability, and was evaluated by the torque when kneading and extruding at 30 rpm using a 20 mm extruder.・ M is “△”, 10kg ・ m
"X".

Regarding fire resistance, JIS A 130
4 Heated for 30 minutes was tested according to the fire temperature curve. The test method was based on JCMA Test No. 1010. Regarding the size of generated cracks, those with a crack length of 10 mm or more are "large", and those with a crack length of 5 mm or more.
Those with a crack length of less than 5 mm were regarded as “small” and those with a crack length of less than 5 mm were regarded as “small”.

Looking at the comparison results, in all of Examples 1 to 8, the material workability was “『 ”, the cable flexibility was“ ○ ”, and the fire resistance was“ ○ ”. Regarding the magnitude of the generated crack, all of Examples 1 to 8 are “small”. In addition, it can be seen from Examples 1 to 8 that sufficient characteristics can be obtained even when the amount of the fine mica powder is reduced by blending the alumina fiber. This indicates that the blending amount of alumina fiber (inorganic fiber material) can be reduced by blending the fine mica powder with the silicone polymer.

Looking at the conventional examples, those obtained by mixing a conventional silicone polymer with an inorganic powder such as mica have a material processing property of “△”, cable flexibility of “『 ”, and fire resistance of“ × ”. The size of the generated crack is "large".

Regarding Comparative Examples 1 to 3 in which fine mica powder was not blended, the material processability was all “△”.
As for the cable flexibility, Comparative Example 3 was “△”, and the fire resistance performance was “』 ”in Comparative Example 3, but Comparative Examples 1 and 2 were“ △ ”. ] Has become.

From the comparison of Examples 1 to 8, Comparative Examples 1 to 3, and Conventional Example 1, it is clear that the compounding of the fine mica powder improves the respective properties.

[0039]

Since the present invention is configured as described above, it has the following effects.

According to the first aspect of the present invention, the amount of the inorganic substance added to the silicone polymer composition can be suppressed or eliminated, and the fire resistance can be improved without lowering the workability or impairing the flexibility of the electric wire. Improvement and stabilization of fire resistance can be achieved.

According to the second aspect of the present invention, the amount of the inorganic substance added to the silicone polymer composition can be suppressed or eliminated, and the fire resistance can be improved without lowering the workability or impairing the flexibility of the electric wire. In addition, the fire resistance can be stabilized.

According to the third aspect of the present invention, the amount of the inorganic substance added to the silicone polymer composition can be suppressed or eliminated, and the fire resistance can be improved without lowering the workability or impairing the flexibility of the electric wire. In addition, the fire resistance can be stabilized.

According to the fourth aspect of the present invention, the amount of the inorganic substance added to the silicone polymer composition can be suppressed or eliminated, and the fire resistance can be improved without lowering the workability or impairing the flexibility of the electric wire. In addition, the fire resistance can be stabilized.

According to the fifth aspect of the present invention, the amount of the inorganic substance added to the silicone polymer composition can be suppressed or eliminated, and the fire resistance can be improved without lowering the workability or impairing the flexibility of the electric wire. In addition, the fire resistance can be stabilized.

According to the sixth aspect of the invention, the amount of the inorganic substance added to the silicone polymer composition can be suppressed or eliminated, and the fire resistance can be improved without lowering the workability or impairing the flexibility of the electric wire. In addition, the fire resistance can be stabilized.

According to the seventh aspect of the present invention, the amount of the inorganic substance added to the silicone polymer composition can be suppressed or eliminated, and the fire resistance can be improved without lowering the workability or impairing the flexibility of the electric wire. In addition, the fire resistance can be stabilized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a fire-resistant wire according to the present invention.

FIG. 2 is a sectional view showing an embodiment of a fire-resistant cable according to the present invention.

FIG. 3 is a sectional view showing another embodiment of the fireproof cable according to the present invention.

FIG. 4 is a sectional view showing a conventional fire-resistant electric wire.

FIG. 5 is a sectional view showing a conventional single-core fireproof cable.

FIG. 6 is a sectional view showing a conventional three-core fireproof cable.

[Explanation of symbols]

 2 ……………… Conductor 4 ………………………… Insulator 12 ……………………… Fireproof layer 13 …… ……………………………………………………………………… Sheath 15,20 ……………………………… Fireproof cable 16 ……………………………. … Fireproof insulated core wire 17… Inclusion 18 …………………………

Claims (7)

[Claims] 1. A fire-resistant electric wire characterized in that a silicone polymer composition containing fine powdered mica is coated on a conductor as a refractory layer, and an insulator is extruded and coated on the refractory layer. . 2. The silicone polymer composition according to claim 1, wherein 50 parts of fine mica is added to 100 parts by weight of the silicone polymer.
The fire-resistant electric wire according to claim 1, wherein the fire-resistant electric wire is formed by blending 0 to 300 parts by weight and 0 to 20 parts by weight of an inorganic fiber material. 3. The fine powdered mica has a particle size of 150 μm.
The refractory wire according to claim 1 or 2, which is mica powder having a thickness of 10 m or less. 4. A silicone polymer composition containing fine powdered mica mixed on a conductor as a refractory layer, an insulator is extruded on the refractory layer, and a flame-retardant olefin is coated on the insulator. A fire-resistant cable formed by extruding a resin to form a sheath layer. 5. A fire-resistant insulated core composed of a conductor coated with a silicone polymer composition containing fine powdered mica as a fire-resistant layer, and extruding and covering an insulator on the fire-resistant layer. A fire-resistant cable comprising a plurality of twisted wires, an intervening member interposed therebetween, a holding tape wound thereon, and an outermost layer covered with a sheath made of a flame-retardant olefin resin. 6. The silicone polymer composition according to claim 1, wherein 50 parts of fine mica is added to 100 parts by weight of the silicone polymer.
The fire-resistant cable according to claim 4 or 5, wherein the fire-resistant cable is formed by blending 0 to 300 parts by weight and 0 to 20 parts by weight of an inorganic fiber material. 7. The fine powdered mica has a particle size of 150 μm.
The fire-resistant cable according to claim 4, 5 or 6, which is mica powder having a thickness of 10 m or less.