JP2000011772A - Fire-resistant electric cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fire-resistant electric cable, holding excellent high- temperature insulating properties and voltage-withstand characteristics even at a temperature as high as 925 deg.C when it is exposed to the heat of fire for a long time, in the same way as a single-wire conductor is used, although a stranded-wire conductor is used. SOLUTION: A fire-resistant cable 1 is made up by coating, with an insulation layer 4 and a sheath 5, in order, a fire-resistant core having, on a linear conductor, a fire-resistant layer 3 made of a cross-linked silicone rubber mixed with, at least, aluminum hydroxide powder and mica powder, and preferably, the aluminum hydroxide powder is mixed by 3 to 100 wt. portions with the silicone rubber of 100 wt. portions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is capable of withstanding use for a long time even when exposed to high heat or flame due to a fire or the like.
The present invention relates to a fire-resistant electric wire having a synthetic resin insulating layer.

[0002]

2. Description of the Related Art Generally, in places where many people gather, such as theaters and department stores, when an emergency such as a fire occurs, it is necessary to safely guide people in the hall to an emergency exit. In such a case, even if the emergency exit guide light itself is not destroyed, if the power transmission wire is exposed to high heat, flame, etc., the wire may short-circuit in a short time and the power transmission may stop. There is. However, since the emergency exit guide light is required to be lit for a certain period of time, the electric wire for supplying power to the emergency exit guide light does not break the insulation even when exposed to high heat, flame, etc. It must be possible to supply.

A refractory wire used for such a purpose has a structure as shown in FIG. 1 (for example, Japanese Patent Publication No. 63-11721). That is, the fire-resistant electric wire 1 is formed by forming a fire-resistant layer 3 on the outer periphery of a conductor 2, covering the outer periphery with an insulating layer 4 made of polyethylene, and further covering the outer periphery with a sheath 5. The refractory layer 3 of the refractory wire 1 is made of a mica sheet formed by bonding a mica layer to a base film such as a glass fiber cloth or a polyethylene film, and has a thickness of about 0.01 to 0.2 mm. And the like.

[0004] Such fire-resistant electric wires have a fire resistance certification standard specified by the Fire and Disaster Management Agency Notification No. 7 (the insulation resistance immediately after heating to 840 ° C for 30 minutes is 0.4 MΩ or more, the insulation withstand voltage is 1500 V, and the withstand voltage is 1 minute. In order to satisfy condition (2), the above-mentioned two or three refractory tapes are wound by １ ／ to ４ overlap or wound vertically, so that the thickness of the refractory layer is 300 to 1200 μm. When the sheath is coated on the refractory layer, the electric wire becomes thicker, and not only the flexibility is poor but also the weight cannot be reduced, and there is a problem that the handleability is poor.

Therefore, in recent years, a method of forming a refractory layer of a ceramic film on a conductor by using a dipping method in which the conductor is immersed in a coating solution containing ceramic particles and a silicone-based resin and run (for example, Japanese Patent Publication No. 63-3
No. 7922). However, this method can provide general heat-resistant insulation and withstand voltage characteristics, but the insulation and withstand voltage characteristics at a high temperature of 840 ° C. or higher, which are fire resistance certification standards according to the Fire Service Agency Notification No. 7 above. Was not enough to satisfy

Further, in order to conform the heat resistance of the fire-resistant electric wire to the fire resistance certification standard notified by the Fire and Disaster Management Agency, the above-mentioned dipping method is improved, and a methylphenyl silicone resin, a diluent, a silane coupling agent and 3 μm A fire-resistant electric wire formed by dipping a conductor into a mixture of talc having the following particle size to form a fire-resistant layer, further covering the fire-resistant layer with an insulator such as polyethylene, and further covering a sheath. Has also been proposed (JP-A-7-105733).

However, when a highly flexible stranded wire conductor is used for applications requiring workability, not only the thickness of the refractory layer becomes non-uniform but also the smoothness of the surface is lost. There is a problem that the withstand voltage characteristic of the electric wire is reduced. Therefore,
There has been proposed a fire-resistant wire provided with a fire-resistant layer in which a conductor is coated with a compound of a silicone polymer mixed with a platinum-based crosslinking agent and a ceramic agent (Japanese Patent Application Laid-Open No. 9-237527).
issue). However, such a refractory layer has fire resistance performance under a static combustion test, but tends to collapse due to insufficient strength of the ceramic layer after combustion, and may not show sufficient fire resistance performance for practical use. .

Accordingly, the present inventor has provided a mica tape layer in which a fire-resistant tape made of a laminated mica sheet is wound on a fire-resistant rubber layer made of a crosslinked silicone rubber filled with powdered mica having a specific property. A refractory wire having a two-layered refractory layer has been invented and a patent application has been filed (Japanese Patent Application No. 9-200052). However, even with these improved techniques, the step of winding the fire-resistant tape complicates the manufacturing process of the fire-resistant wire, and also has problems in the workability of the fire-resistant wire.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is not necessary to wrap a fire-resistant tape, to use a stranded conductor or a single-wire conductor. Similarly, another object of the present invention is to provide a fire-resistant electric wire capable of maintaining excellent fire-resistant insulation characteristics and withstand voltage characteristics.

[0010]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
On a linear conductor, a refractory wire core provided with a refractory layer made of a crosslinked silicone rubber containing at least an aluminum hydroxide powder and a mica powder, the insulating layer and the sheath are sequentially coated. This can be achieved by the featured refractory wire. In the fire-resistant electric wire of the present invention, the amount of the aluminum hydroxide powder in the crosslinked silicone rubber constituting the fire-resistant layer is preferably 3 to 100 parts by weight with respect to 100 parts by weight of the silicone rubber. The refractory insulation and withstand voltage characteristics when the refractory layer is exposed to high heat are improved.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A fire-resistant electric wire according to the present invention has a structure essentially similar to that of a conventional fire-resistant electric wire as shown in FIG. It is made of a crosslinked silicone rubber containing at least a powder. The refractory layer 3 is covered with an insulating layer 4 made of polyethylene, and the outer periphery thereof is further covered with a sheath 5.

In the refractory wire of the present invention, the silicone rubber used for forming the refractory layer is preferably HTV.
A so-called millable type silicone rubber such as that described above can be used, but the material is not limited to this as long as it can cover the linear conductor with a desired thickness. Examples of such silicone rubber include polymers containing a functional group such as dimethyl, methylvinyl, methylphenylvinyl, and methylfluoroalkyl.

Examples of the crosslinking agent blended in the silicone rubber include organic peroxides such as dicumyl peroxide, dibenzoyl peroxide, di-2,4, dichlorobenzoyl peroxide, and t-butyl perbenzoate. Things and
Platinum-based cross-linking catalysts and the like can be mentioned, and such cross-linking agents can be appropriately selected according to the type of silicone rubber used and desired cross-linking conditions. When a platinum-based catalyst is used in combination with the above-mentioned cross-linking agent, it has a remarkable effect on improving the fire resistance of the electric wire. However, any platinum-catalyst that is generally used for cross-linking silicone rubber can be used. The amounts of these vulcanizing agents and platinum-based catalysts can be appropriately determined. Usually, the amount of the vulcanizing agent is in the range of 1 to 3% by weight, and the amount of the platinum-based catalyst is 0.1 to 10% by weight based on silicone rubber.
Preferably it is in the range of 0.5% by weight.

The silicone rubber used to form the refractory layer of the refractory wire of the present invention contains a heat-resistant inorganic filler. As such an inorganic filler, among silicic fillers and the like, mica powder is particularly preferable, and mica powder having a particle size (average particle size) of 50 μm or more is particularly preferable. The particle size distribution is preferably such that the maximum particle size does not exceed 2.5 mm from the viewpoint of uniform dispersion.
The amount of the mica powder to be blended is desirably 250 parts by weight or less, preferably 10 to 200 parts by weight, per 100 parts by weight of the silicone rubber. The amount of mica powder is 1
When the amount is less than 0 parts by weight, the effect of improving the fire resistance is not large, and when the amount is more than 250 parts by weight, the withstand voltage characteristics are impaired.

In order to improve the strength of the ceramic refractory layer formed by burning and decomposing the silicone rubber, aluminum hydroxide powder as a modifier is blended with the silicone rubber filled with mica powder as described above. Is done. Such aluminum hydroxide powder has a particle size (average particle size) of 0.5 to
It is preferably about 100 μm, and the compounding amount is insufficient when the amount is too small, and when the amount is too large,
Since the processability when coating the silicone rubber on the conductor is reduced, 5 to 10 parts by weight per 100 parts by weight of the silicone rubber are used.
Suitably, it is in the range of 0 parts by weight.

The silicone rubber used in the present invention may be added with a silicone oil or the like, if necessary, in order to avoid a decrease in extrusion processability due to an increase in the amount of fillers and modifiers. it can. The amount of the silicone oil used as the processing aid is not particularly limited, but is generally used in the range of about 3 to 35 parts by weight per 100 parts by weight of the silicone rubber. When the amount is less than the above range, the smoothness of the refractory layer is lost, and when the amount exceeds 25 parts by weight, electric characteristics at high temperatures tend to be unstable.

Further, in order to improve the kneading processability, stearic acid can be added to the silicone rubber used in the present invention in addition to the silicone oil. The amount of such stearic acid is preferably 0.1 to 25 parts by weight per 100 parts by weight of silicone rubber. If the amount is less than this, kneading processability cannot be improved, and 25
Exceeding the parts by weight does not improve the kneading processability and also loses the smoothness of the refractory layer, which is not preferred.

A flame retardant can be added to such a silicone rubber in order to further enhance fire resistance. The flame retardant is not particularly limited, but preferably does not generate a halogen compound during combustion. For example, a powder of a metal hydroxide such as magnesium hydroxide or the like, or a boric acid compound such as zinc borate is preferably used. The amount of the flame retardant is 0.1% by weight per 100 parts by weight of the silicone polymer.
It is preferably about 10 to 10 parts by weight.

The rubber composition based on the silicone rubber as described above is extrusion-coated on a linear conductor composed of a single wire or a stranded wire, and then guided to a heating device to form a crosslinked system used for the silicone rubber composition. Cured under the crosslinking conditions corresponding to
A fire-resistant core is obtained.

Such a refractory core may be bundled into a plurality of cores as required, or may be covered with an insulating layer while keeping a single core. This insulating layer is formed by extrusion-coating an insulating synthetic resin composition using a conventional technique.
As such a synthetic resin composition, for example, polyethylene,
An olefin-based resin composition such as polypropylene is preferably used. The refractory wire covered with such an insulating layer may be further bundled as necessary to form a multi-core,
Alternatively, the fire-resistant electric wire of the present invention can be obtained by keeping a single core or by arranging a plurality of them in parallel and extruding and coating a protective sheath or the like thereon.

[0021]

EXAMPLES XE21-B5881 (methyl vinyl silicone) manufactured by Toshiba Silicone Co., Ltd. as silicone rubber (SR), and TC- manufactured by Toshiba Silicone Co., Ltd. as cross-linking agent (CA).
8. Silicone oil (SO) and stearic acid (SA) as processing aids, mica powders (M) having different particle sizes as shown in Table 1 as inorganic fillers, and mica powders with different particle sizes as shown in Table 1 as modifiers Different aluminum hydroxides (AH
O), magnesium carbonate (MC) as a control for the modifier
And magnesium hydroxide were blended and kneaded according to the blending in Table 2 to prepare a silicone rubber composition for a fire-resistant layer.

[0022]

[Table 1] M-1: Japanese mica, Kirara, particle size 40 µm, particle size 5
45 μm M-2: Japanese mica, Kirara, particle size 52 μm, particle size 10
６０60 μm M-3: Japanese mica, Kirara, particle size 500 μm, particle size 1
50-1130 μm AHO-1: Showa Denko, Heidilite H-10 AHO-2: Showa Denko, Heidilite H-40

[0023]

[Table 2]

On the other hand, a stranded copper conductor having a cross section of 2 mm ² (diameter 1.
8 mm), each of the above silicone rubber compositions was coated at an extrusion temperature of 60 ° C. by an extruder, and further coated for 20 minutes
After passing through a 0 ° C. tubular vulcanizing device, each has a diameter of 2.6 mm.
Was obtained. These fire-resistant cores were extrusion-coated with a polyethylene insulating layer to form insulated wires having a diameter of 4.5 mm. Thereafter, a polyethylene sheath was further extrusion-coated to obtain fire-resistant electric wires each having an outer diameter of 12.5 mm. Further, for comparison, a refractory reinforcing layer of a mica sheet was wound around a 2.6 mm diameter core coated with a silicone rubber composition not containing aluminum hydroxide as a modifier to form a 3.0 mm diameter refractory core. And coated with a polyethylene insulating layer to obtain a diameter of 4.5.
After forming an insulated wire having a diameter of 1 mm, a refractory wire according to the prior art having an outer diameter of 12.5 mm, which was further coated with a polyethylene sheath by extrusion, was also manufactured.

An appearance inspection and a flexibility test were performed on a sample of the refractory core obtained by removing the sheath and the insulating coating from each of the refractory wires thus obtained. In addition, the samples cut out from the refractory wire were tested for insulation properties at room temperature and withstand voltage properties at room temperature, and insulation properties and withstand voltage properties when heated to 840 ° C in 30 minutes, and the test results were summarized. Table 2 also shows the results. In addition, these test methods and criteria are as follows.

(1) Appearance Inspection The surface of the refractory layer of the wire core sample was visually inspected. (2) Flexibility The core sample was wound around a mandrel having a diameter of 10 mm.

(3) Room temperature insulation A vertical 300 mounted vertically on a carriage that can enter and exit the heating furnace.
mm, 300mm wide and 10mm thick pearlite plate,
A refractory electric wire sample having a length of 1.3 m was horizontally attached and fixed using soft copper wires each having a diameter of 1.6 mm at two positions 20 cm apart from each other at the center. At both ends of a bundle of two 40 cm long soft copper wires having a diameter of 1.6 mm are wound around the center of the mounting position at an interval of about 13 mm, and a 1.3 m long fireproof wire is wound around the center of the soft copper wire. A load equivalent to twice the weight of the electric wire was applied. Then, a DC voltage of 500 V was applied between the wire core conductor and the fixed wire, and the insulation resistance at room temperature was measured.

(4) Room Temperature Withstand Voltage Following the above-mentioned room temperature insulation property measurement, a commercial AC voltage of 1500 V was applied between the core conductor and the fixed wire, and the one that did not cause dielectric breakdown in one minute was evaluated as ○. , And those that were not were marked as x.

(5) 840 ° C. Insulation After performing the above-mentioned normal temperature withstand voltage measurement, the bogie on which the sample of the refractory wire was mounted was introduced into the heating furnace, and while the commercial AC voltage of 600 V was continuously applied, the heating furnace was heated. 840 in 30 minutes
The temperature was raised to ° C. In this state, 5
A DC voltage of 00 V was applied to measure the insulation resistance.
Those having a resistance value of 4 MΩ or more were evaluated as ○, and those having no resistance were evaluated as ×.

(6) 840 ° C. Withstand Voltage Following the above-mentioned 840 ° C. insulation measurement, a commercial AC voltage of 1500 V was applied between the conductor and the fixed wire. , And those that were not were marked as x.

According to the test results shown in Table 2, mica powder, especially mica powder having a particle size of 50 μm or more, was compounded up to 200 parts by weight per 100 parts by weight of silicone rubber, and aluminum hydroxide was used as a modifier. 5-100
A fire-resistant electric wire coated with a rubber composition compounded in a range of parts by weight and provided with a fire-resistant layer formed by cross-linking has excellent fire resistance performance without providing a fire-resistant reinforcing layer made of mica sheet. I understand.

[0032]

The fire-resistant electric wire according to the present invention is provided with a fire-resistant layer comprising a crosslinked silicone rubber containing at least mica powder as a fire-resistant inorganic filler and aluminum hydroxide as a modifier. Even if the fire-resistant reinforcing layer made of a sheet is not provided, the fire-proof characteristics conforming to the fire resistance certification standard of the Fire Service Agency Notification No. 7 are provided, and the production efficiency is greatly improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a structure of a conventional fire-resistant electric wire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fireproof electric wire 2 Conductor 3 Fireproof layer 4 Insulating layer 5 Sheath

Claims (5)

[Claims] An insulating layer and a sheath are sequentially coated on a refractory wire core having a refractory layer made of a crosslinked silicone rubber in which at least aluminum hydroxide powder and mica powder are blended on a linear conductor. A fire-resistant electric wire characterized by being made. 2. The fire-resistant electric wire according to claim 1, wherein the aluminum hydroxide powder is mixed in an amount of 3 to 100 parts by weight based on 100 parts by weight of the silicone rubber. 3. The refractory wire according to claim 1, wherein the mica powder has a particle size of 50 μm or more. 4. The fire-resistant wire according to claim 1, wherein the mica powder is blended in an amount of 250 parts by weight or less based on 100 parts by weight of the silicone rubber. 5. The refractory wire according to claim 1, wherein silicone oil or stearic acid is blended as a processing aid.