JPS6333324Y2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to fire-resistant electric wires, particularly fire-resistant electric wires used in emergency power circuits of firefighting equipment. Recently, buildings are becoming more and more high-rise,
Along with this, fire prevention measures for buildings are becoming more and more important. The first thing to do is to prevent fires,
When a fire occurs, it is important to minimize the damage caused by it. First of all, it is necessary to ensure that the activation devices of each fire-fighting equipment installed in the building, the receivers of motorized automatic fire alarm equipment, evacuation guide lights, and emergency exit indicator lights are activated at the same time as a fire occurs. It is necessary that the system can continue to operate reliably for a predetermined period of time (for example, until the people inside the building evacuate from the building). For this purpose, the electric wires used for circuit wiring to each of the above-mentioned facilities must have characteristics that can sufficiently withstand even in a high-temperature atmosphere during a fire. For example, the Fire and Disaster Management Agency of the Ministry of Home Affairs has established strict fire resistance standards for this type of electric wire and has legislated that they must pass these standards. In other words, when a wire placed in a refractory furnace is exposed or has a conduit attached and heated for 30 minutes according to the indoor fire temperature curve specified in JISA1302, and immediately after that, the wire is measured with a 500V DC insulation resistance meter. This value must be 0.4MΩ or more. In addition, when an AC voltage of 1500V is applied between the wires immediately after heating, the wires must withstand this for 1 minute, and the length of wire fire extension must be within 150 mm from the inner wall of the furnace. Conventionally, this type of fire-resistant electric wire has been made of a fire-resistant insulating layer (for example, an inorganic material such as mica powder or mica scales and a support such as glass, asbestos, or plastic tape) on a conductor such as a copper wire, or a wire made of these and silicone rubber. A synthetic resin insulating layer made of polyethylene and a synthetic resin insulating layer made of polyethylene are sequentially formed to form an insulated wire core, and the insulated wire core of the fireproof wire is twisted using an inclusion as necessary, and then The basic structure is a sheath layer made of synthetic resin, and almost all commercially available fire-resistant electric wires use soft polyvinyl chloride resin as the sheath material. When this soft polyvinyl chloride resin is exposed to a temperature above a certain decomposition temperature, it begins to decompose thermally, starting with the elimination of hydrogen chloride. 581
Since it contains a large amount of hydrogen chloride (mg/g), the generated hydrogen chloride gas not only corrodes peripheral equipment but also has a negative effect on the human body, especially under high temperatures such as during a fire. There was a risk that the hydrogen chloride gas would penetrate the fireproof insulation layer of the fireproof wires and deteriorate the original function of the fireproof wires. On the other hand, when flame-retardant polyolefin resin such as flame-retardant polyethylene is used as a sheath material, polyolefin resin does not contain any halogen atoms in its molecular structure, so even if it is made flame-retardant by using a halogen-based flame retardant, for example. The amount of hydrogen halide generated in the event of a fire is significantly smaller than that of polyvinyl chloride resins, and the above-mentioned danger can be said to be considerably reduced. However, if flame-retardant polyethylene is used, However, the disadvantage is that the spread of fire in electric wires is generally greater than that of soft polyvinyl chloride resins, and it is often difficult to meet the fire resistance standards set by the Fire and Disaster Management Agency of the Ministry of Home Affairs, mentioned above. The inventors took advantage of flame-retardant polyolefin resin's ability to generate a small amount of hydrogen halide during combustion, and sheathed various flame-retardant polyolefin resins with the aim of reducing the spread of fire in electric wires. As a result of research on the combustion of fire-resistant electric wires,
This is what led us to this idea. That is, the gist of the present invention is that in a refractory electric wire in which a refractory insulating layer 2 is provided on a conductor 1, the outermost sheath layer 4 of the refractory electric wire has an oxygen index of 24.
In the above, the thermal deformation rate at 105℃ is 65% or less, and the content of inorganic powder is 30 parts by weight (resin content).
The present invention is a fire-resistant electric wire characterized in that it is formed from a flame-retardant, crystalline polyethylene resin composition having a composition of 100 parts by weight or less. In general, in fire-resistant electric wires, the synthetic resin insulating layer and inclusions of the insulated wire core are either not flame-retardant at all, or are flame-retardant only to a much milder extent than the sheath layer. The former is typically made of polyethylene. Further, as the inclusion, polypropylene split fibers or the like are usually used. From an economic point of view, it is desirable to use the above materials without flame retardant treatment. So to speak, easily flammable materials are usually used.
Therefore, when fire-resistant wires are exposed to fire according to the fire resistance test method specified by the Fire and Disaster Management Agency, once the sheath layer is destroyed by a strong fire, the spread of fire to the wires is caused by the combustion of the synthetic resin or inclusions in the insulation layer. As a result, the temperature of the insulating layer becomes higher than that of the sheath layer due to heat conduction from the conductor, and the melting and thermal decomposition of the insulating layer precedes.As a result, the sheath layer opens in a floppy shape, and the insulation layer spreads through this. This occurs as the synthetic resin inclusions in the layer first burn while melting and dripping, and then the edges of the sheath layer, which have become flabby, melt and droop as they burn and fall. In general, the fire spread of synthetic resins is determined by the oxygen index (defined in JISK7201-1976), which is a measure of flame retardancy.
However, in the above-mentioned fire spread mode of the fire-resistant electric wire, the relationship with the oxygen index of the flame-retardant polyolefin resin forming the sheath layer is not uniform, and the above-mentioned unevenness of the sheath layer It was discovered that the degree of shape retention of the shaped ends plays a major role in the fire spread of fire-resistant wires. In other words, even if the above-mentioned resins have the same oxygen index, those that easily sag during combustion are significantly inferior in terms of fire spread. Based on the above phenomenon, we investigated various flame-retardant polyolefin resins and found that a flame-retardant, crystalline polyethylene resin composition with an oxygen index of 24 or more and a thermal deformation rate of 65% or less at 105°C. However, we have found empirically that fire-resistant electric wires with a sheath layer can pass the fire-resistance test set by the Fire and Disaster Management Agency of the Ministry of Home Affairs. Here, the thermal deformation rate at 105℃ is JISC3005−
The value is measured according to the heating deformation test method specified in Section 23 of the 1977 "Plastic Electric Wire Test Method", and is a value measured in accordance with the heating deformation test method specified in Section 23 of the 1977 "Test Method for Plastic Electric Wires". 4Kg in thickness direction under test temperature
The rate of change in thickness after applying a load of Defined as thickness (mm) x 100. In this invention, crystalline polyethylene resin is
Crystalline ethylene homopolymers such as high-density, medium-density, and low-density polyethylene, crystalline ethylene copolymers containing olefins such as butene-1 as a comonomer, and copolymerizable compounds such as vinyl acetate and ethyl acrylate. and ethylene, and may be a mixture of two or more of these. As is clear from the above-mentioned uses, fire-resistant electric wires are often routed over concrete surfaces within buildings during construction, so it is preferable that the sheath layer has excellent resistance to damage. Crystalline polyethylene resin has excellent scratch resistance during construction. In addition, these may be filled with inorganic fillers such as calcium carbonate, silica, clay, and magnesium hydroxide within a range that does not impair the properties of the sheath material. At this time, the total content of inorganic powder shall be 30 parts by weight or less (based on 100 parts by weight of resin content). Additionally, it is common practice to add processing aids such as antioxidants, lubricants, and pigments. The oxygen index of these crystalline polyethylene resins alone is in the range of 18 to 22, and is almost the same when an inorganic filler is added to these resins in an amount of 30 parts by weight or less.
Further, crosslinking treatment such as chemical crosslinking or electron beam irradiation crosslinking is an effective means for improving the thermal deformation rate. In the present invention, flame retardancy is imparted to the crystalline polyethylene resin by adding a so-called flame retardant. That is, for example, flame retardants such as halogen flame retardants, boric acid flame retardants, phosphorus flame retardants, silicone flame retardants, or combinations of these with flame retardant aids such as antimony trioxide, or aluminum hydroxide, hydroxide, etc. This is achieved by the combined use of hydrated metal oxides such as magnesium, and two or more of these flame retardants may be used in combination. Specific examples of flame-retardant, crystalline polyethylene resin compositions selected from the flame-retardant, crystalline polyethylene resins obtained as described above and used in the present invention are shown below. It goes without saying that the invention is not limited to these. [Example 1] Low density polyethylene (NUC9025 Nippon Unicar Co., Ltd. product) 100 parts by weight Chlorinated polyethylene (Daisorak U-303
Osaka Soda Co., Ltd. product) 10 parts by weight Halogen flame retardant (DBDPE Toyo Soda Co. product) 10 parts by weight Halogen flame retardant (Dechlorane Plus 575 Stauffer Chemical product) 15 parts by weight Antimony trioxide 10 parts by weight Water Aluminum oxide (Higilite H-42M
Showa Denko Co., Ltd. product) 15 parts by weight Oxygen index of the above composition = 25 Thermal deformation rate (105°C) = 20% Example 1 As shown in Figure 2, on the annealed copper stranded wire 1 with a cross-sectional area of 38 mm ² , the thickness was A fireproof layer 2 with a thickness of 0.7mm is formed by wrapping three 0.13mm polyethylene mica tapes so that 1/2 of their widths overlap, and on top of that a low-density layer with a density of 0.92 and a melt index of 1.0. Three insulated wire cores made of extruded density polyethylene coated to a thickness of 1.2 mm and provided with an insulating layer were twisted together with polypropylene split fibers 5 interposed therebetween, and a 0.05 mm thick nylon tape 6 was pressed and wound thereon. The fire-resistant electric wire of the present invention was obtained by extrusion coating the flame-retardant polyethylene resin of [Example 1] described in the text as a sheath 4 to a thickness of 1.8 mm on the outside thereof. The fire resistance performance of this fire resistant wire was measured based on the fire resistance test standards shown in Table 1, and the results are shown in Table 2. Comparative Example For comparison, a refractory electric wire was obtained in the same manner as in Example 1 using the following composition having an oxygen index of 28 and a thermal deformation rate of 73% as a sheath material. The fireproof performance of this fireproof electric wire was measured in the same manner as in Example 1. As shown in Table 2, the wire failed in terms of fire spread. Comparative Example Composition Ethylene-Vinyl Acetate Copolymer (Evaflex EV360 Mitsui Polychemical Co., Ltd. product)
70 parts by weight low-density polyethylene (Yukalon HE-30 Mitsubishi Yuka Co., Ltd. product) 30 parts by weight halogen flame retardant (FG-3000 Teijin Ltd. product)
20 parts by weight Antimony trioxide 10 parts by weight Aluminum hydroxide (Higilite H-42M
Showa Denko Co., Ltd. product) 80 parts by weight Oxygen index of the above composition = 28 Heat distortion rate (105°C) = 73%

[Table] However, fire resistance test with conduit

[Table] Example 2 As shown in Figure 2, five pieces of polyethylene mica tape with a thickness of 0.13 mm were wrapped around an annealed copper stranded wire 1 with a cross-sectional area of 3.5 mm ² so that 1/2 of the width overlapped. A fireproof layer 2 with a thickness of 1.2 mm was formed, and on top of that, three insulated wire cores were coated with an insulating layer made by extruding low-density polyethylene with a density of 0.92 and a melt index of 1.0 to a thickness of 0.8 mm. Polypropylene split fiber 5
A nylon tape 6 with a thickness of 0.05 mm is wrapped around it, and a sheath 4 with the following composition is made of high-density polyethylene (Shorex 4002E).
Showa Denko Co., Ltd. product) 100 parts by weight Halogen flame retardant (DBDPE Toyo Soda Co., Ltd. product) 30 parts by weight Antimony trioxide 15 parts by weight Carbon black 3 parts by weight flame retardant polyethylene resin extruded to a thickness of 1.5 mm The fire-resistant electric wire of the present invention was obtained by coating. The above composition had an oxygen index of 24 and a thermal deformation rate (105°C) of 3%. The fire resistance performance of this fire resistant electric wire was measured based on the fire resistance test standards shown in Table 1, and the results were as shown in Table 3. Example 3 and Comparative Example As shown in Figure 2, five layers of polyethylene mica tape with a thickness of 0.13 mm were wrapped around an annealed copper stranded wire 1 with a cross-sectional area of 3.5 mm ² so that 1/2 of the width overlapped. A fireproof layer 2 with a thickness of 1.2 mm was formed, and on top of that, three insulated wire cores were coated with an insulating layer made by extruding low-density polyethylene with a density of 0.92 and a melt index of 1.0 to a thickness of 0.8 mm. Polypropylene split fiber 5
A nylon tape 6 with a thickness of 0.05 mm is wrapped around it, and the following composition is used as a sheath 4 on the outside. ) 100 parts by weight halogen flame retardant (FG3000 Teijin Kasei Ltd. product)
30 parts by weight antimony trioxide 15 parts by weight carbon black 3 parts by weight flame retardant polyethylene resin was extrusion coated to a thickness of 1.5 mm. Thereafter, the wire was uniformly irradiated with an electron beam of 20 Mrad using an electron beam with an acceleration energy of 1.0 MeV to obtain a refractory electric wire of Example 3. In the comparative example, a flame-retardant polyethylene resin having the same composition was only extruded and coated to a thickness of 1.5 mm, and no electron beam irradiation was performed. of the above composition
After 20 Mrad electron beam irradiation (gel fraction = 65%), the oxygen index is 24 and thermal deformation rate (105℃) = 25%, and without irradiation, the oxygen index is 24 and thermal deformation rate (105℃) is 71%. It was hot. The fire resistance performance of these fire resistant wires was measured based on the fire resistance test standards shown in Table 1, and the results are shown in Table 3.

[Table] As is clear from Examples 2 and 3, the thermal deformation rate (105°C) of the comparative example exceeds 65%, so it does not satisfy the fire resistance properties, but by applying electron beam irradiation,
The thermal deformation rate was able to achieve the requirement of 65% or less, and excellent fire resistance properties were obtained. As is clear from the examples above, the fire-resistant electric wire of the present invention has excellent fire-resistant properties, and is even more resistant to damage caused to the sheath layer during construction, so its practical value is extremely high. It is something.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the fireproof electric wire of the present invention, and FIG. 2 is a sectional view of another embodiment. DESCRIPTION OF SYMBOLS 1... Conductor, 2... Fireproof insulating layer, 3... Flammable synthetic resin layer, 4... Sheath layer, 5... Flammable intervening layer, 6... Presser tape.

Claims (1)

[Scope of utility model registration request] Twisting a desired number of insulated wire cores on an insulated wire core for a fireproof electric wire in which a fireproof insulating layer and a flammable electrical insulation layer are provided on a conductor, or using flammable inclusions as necessary. In a fire-resistant electric wire formed by applying a sheath layer on a combined twisted wire core, the outermost sheath layer of the fire-resistant electric wire has an oxygen index of 24 or more, a thermal deformation rate of 65% or less at 105°C, and is made of inorganic powder. A fire-resistant electric wire characterized in that it is formed from a flame-retardant crystalline polyethylene resin composition having a content of 30 parts by weight or less (based on 100 parts by weight of resin content).