JPH1040747A - Fire resistant wire - Google Patents

Abstract

(57) [Problem] To provide a fire-resistant electric wire capable of maintaining stable fire-resistance performance even at a high temperature. SOLUTION: In a fire-resistant electric wire having a fire-resistant layer formed by vertically attaching mica tape on a conductor, at least the outermost layer of the mica tape is pressed and wound with alumina yarn or silica yarn.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a refractory electric wire.

[0002]

2. Description of the Related Art Conventionally, a mica tape in which laminated mica is adhered to one side of a reinforcing material such as a plastic film or glass cloth has been used as a fireproof layer of a fireproof electric wire. Generally used fire-resistant electric wires have a fire-resistant layer in which a plurality of mica tapes are assembled on a conductor so that the mica surface faces the conductor, and an insulating layer such as plastic and a protective layer are sequentially provided outside the fire-resistant layer. It is a structure that was given.

[0003] When a mica tape is provided as a fire-resistant layer on a conductor, the mica tape is wound horizontally (gap winding, wrap winding) on the conductor, or vertically attached so as to wrap the mica tape around the conductor circumference. There is a method, but the method of longitudinally attaching is superior to the method of horizontal winding in that workability at the time of production of a fire-resistant wire is good, and scratches and cracks are less likely to occur on the mica tape during work. When a fireproof layer is formed by vertically applying mica tape, plastic or glass yarns may be wrapped around the outside of each layer of multiple mica tapes in order to prevent the mica tape to be vertically attached from opening. Is being done.

[0004]

The fire-resistant electric wire has a capability of supplying power for 30 minutes in the event of a fire as an emergency power supply cable. In addition to the general physical properties stipulated by the Electrical Appliance and Material Control Law and the like, fire-fighting It is required to satisfy the fire resistance standard (840 ° C, 30 minutes) stipulated in the Notification No. 7 of the Agency. There has been a demand for fire resistance that can withstand time tests. However, in a conventional fire-resistant electric wire having a fire-resistant layer obtained by holding and winding a vertically attached mica tape with a glass yarn, for example, when a fire resistance test is performed at 925 ° C. for 60 minutes, the glass yarn melts and becomes conductive. There is a problem that it penetrates into the layer of mica and lowers insulation.

[0005] Therefore, a fire-resistant electric wire in which the mica tape of the innermost layer on the conductor side is held down by a plastic yarn instead of a glass yarn out of a plurality of vertically attached mica tapes is considered. Plastic yarns are decomposed and burned out at high temperatures, and therefore do not have the inconvenience of glass yarns. However, if a plastic film is used as a reinforcing material that is bonded to the mica laminated to form the mica tape, not only the plastic yarn but also the plastic of the reinforcing material will be decomposed and burned off at high temperatures. And the mechanical strength of the refractory layer is extremely reduced.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a fire-resistant electric wire capable of maintaining stable fire-resistant performance even at a high temperature.

[0007]

That is, in the present invention, in a fire-resistant electric wire having a fire-resistant layer formed by vertically attaching a mica tape on a conductor, at least the outermost layer of the mica tape is held down by alumina yarn or silica yarn. A fire-resistant wire.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The alumina yarn of the present invention is preferably a bundle of 800 to 3000 single fibers having a diameter of 5 to 20 .mu.m, a twist number of 5 to 200 turns / m, and a fineness of 100 to 1000 g / 1000 m. Is appropriate. Alumina yarns are those containing SiO ₂ in addition to normal Al ₂ O _3, can be used, for example Al ₂ O ₃ 80%, those of SiO ₂ 20%.

The silica yarn is preferably a bundle of 300 to 2,000 single fibers having a diameter of 200 μm, the number of twists is 5 to 200 times / m, and the fineness is 80 to 1000 g / l.
000 m is appropriate. The silica yarn contains SiO ₂ as a main component, and may further contain Al ₂ O ₃ , Na ₂ O, or the like. For example, SiO ₂ 95.8
_{%, Al 2 O 3 4%} , is made of Na ₂ O0.2% can be used. The fibers may be surface-treated with silane or the like.

Alumina yarn and silica yarn have excellent heat resistance at high temperatures, and do not burn out or melt even after a fire resistance test at 925 ° C. for 60 minutes. Alumina yarn has no decrease in strength up to 1200 ° C, and silica yarn has no decrease in strength up to 1000 ° C. In addition, heating tests (alumina yarn, 10
00 ° C, 1000 hours, silica yarn, 700 ° C, 10
Before and after (00 hours), properties such as tensile strength, bending strength, corrosion resistance, and electrical insulation hardly change.

The alumina yarn and the silica yarn may be used after firing or before firing. Unfired alumina yarns and silica yarns are more flexible and more excellent in workability than those after firing, so that the workability when manufacturing a fire-resistant wire is good. In addition, since alumina yarn or silica yarn shrinks in the length direction when fired, a fire-resistant electric wire in which a fire-resistant layer is pressed and wound using unfired alumina yarn or silica yarn is fire-resistant due to shrinkage of the alumina yarn or silica yarn during heating. The effect of holding down the layer is improved, and the fire resistance is further improved.

In the fire-resistant electric wire of the present invention, at least the outermost layer of the vertically laid mica tape is a fire-resistant layer pressed and wound with the above-mentioned alumina yarn or silica yarn. May be pressed and wound by alumina yarn or silica yarn, but it is sufficient that at least the outermost layer is pressed and wound by alumina yarn. Other than the outermost layer, a plastic yarn such as a polypropylene yarn may be used.

[0013]

EXAMPLES The present invention will be specifically described below with reference to examples.

(Example 1) A mica surface of a 0.18 mm thick mica tape obtained by laminating a polyethylene film and laminated mica on a 2 mm diameter soft copper single wire conductor was vertically attached to the conductor side and fired. Alumina yarn (single fiber diameter 10 μm, 960 strands, 90 twists / m, fineness 2
00g / 1000m, component Al ₂ O ₃ 70%, SiO ₂ 3
(0%) was wound horizontally to hold the mica tape, and a mica tape similarly pressed and wound with alumina yarn was provided outside the mica tape to form a fire-resistant layer consisting of two vertically attached mica tapes. The outside of the refractory layer is extruded with polyethylene to form an insulated wire core provided with an insulating layer, and the three insulated wire cores are twisted with a polypropylene string as an intermediary, and pressed and wound with a polyester tape, followed by an ethylene resin composition. Was extruded into a sheath to produce a fire-resistant electric wire. FIG. 1 shows a schematic cross-sectional view of the obtained fireproof electric wire.

(Example 2) A fire-resistant electric wire was obtained in the same manner as in Example 1 except that the same alumina yarn as in Example 1 was used in an unfired state.

(Example 3) Sintered silica nano yarn (single fiber diameter 6 μm, 1100 twists, number of twists 150 times / m,
Fineness 170 g / 1000 m, components SiO ₂ 95%, Al ₂
A fire-resistant electric wire was obtained in the same manner as in Example except that O ₃ 4%, Na ₂ O 0.5% and other 0.5%) were used.

Example 4 A fire-resistant electric wire was obtained in the same manner as in Example 1, except that the same silica yarn as in Example 3 was used in an unfired state.

(Conventional example) A fire-resistant electric wire was obtained in the same manner as in Example 1 except that glass yarn was used instead of alumina yarn.

A fire resistance test (exposure test) according to Fire Service Agency No. 7, No. 3 was performed on the fire-resistant electric wires of Examples 1 to 4 and the conventional example. The heating conditions were 840 ° C. for 30 minutes and 925 ° C. for 60 minutes. Those that withstand the application of 600 V AC during heating were good, and those that withstand 1500 V AC for 1 minute after heating were good. In addition, during the above-mentioned heating, a fire-resistant electric wire having a resistance of 0.4 MΩ or more obtained by multiplying the insulation resistance between the ground and the core immediately before the end of the heating by the number of the cores on the non-ground side is used. ○, If the value obtained by multiplying the insulation resistance between the ground and the wire core immediately before the end of heating and the number of wires on the non-ground side is 0.4 MΩ or less, even if the device withstands the application of power during and after the heating, is x or less. Judged (low-pressure fire-resistant cable standards determined by the Electric Wire and Cable Association). Table 1 shows the results.

[0020]

[Table 1]

As shown in Table 1, the fire-resistant electric wires of Examples 1 to 4 have high insulation resistance values and good judgment results even under severe heating conditions of 925 ° C. and 60 minutes.

[0022]

The fire-resistant electric wire of the present invention uses alumina yarn or silica yarn which does not melt or decompose even at a high temperature as a holding material of a vertically-mounted mica tape which is a fire-resistant layer. Even at higher temperatures, stable electrical characteristics and mechanical strength can be maintained.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductor 2 Fireproof layer 3 Insulation layer 4 Interposition 5 Pressing tape 6 Sheath 7 Insulated wire core

Claims (2)

[Claims] 1. A fire-resistant electric wire having a fire-resistant layer formed by vertically attaching mica tape on a conductor, wherein at least the outermost layer of the mica tape is pressed and wound with alumina yarn or silica yarn. 2. The fire-resistant wire according to claim 1, wherein the alumina yarn or the silica yarn is unfired.