JPS6021453B2 - flame retardant cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to a chicken-burning cable that has excellent flame resistance.

In recent years, there has been a demand for cables to pass particularly strict standards from the standpoint of fireproofing, and multifaceted testing, research, and development have been carried out, and numerous cables have been proposed and put into practical use. ing.

Conventionally, the standard for determining the flame retardancy of this type of flame-retardant cable is the combustion test according to the JIS standard2, but in this test, a single flame-retardant cable is exposed to a flame and the combustion results are determined. Met.

The Institute of Electronics Engineers (mEE) standard for low-voltage power cables and control cables that are recently installed in multiple strips is 3 ÷ 197.
Vertical tray flammability tests (as shown in Figure 4) have been carried out, and various so-called flame-retardant cables have been developed that are compatible with these tests. According to this test, it was specified that a large number of cables would be arranged in a row at intervals of 0.5 times the outer diameter of the cables, and that the lower ends of the cables would be exposed to intense flame for 20 minutes. The criteria for judgment are that the fire does not spread and that the fire extinguishes naturally. By the way, in recent years, large-capacity power plants and huge plant facilities have installed more cables than expected, and when these cables are exposed to flames in the event of a disaster, the above-mentioned combustion test of a single cable is not enough. I can't help but worry that the performance that has been judged will have serious consequences that cannot be predicted at all.

Furthermore, since the above-mentioned mEE standard test is different from actual cable installation, it is difficult to make sufficient predictions for actual disaster occurrences 5 based only on the judgments of this test. In other words, under such harsh conditions that when cables burn, the combustion heat influences each other due to reflection, a group of cables installed in multiple strands is exposed to flames, and once they are combusted, a large amount of heat is generated due to the combustion of the cables themselves. Zero heat generation may cause other cables to burn, resulting in mutual interference, resulting in an extremely dangerous situation that would be completely inconceivable considering the flame retardancy of a single cable or the flame retardancy of a small group of cables. It is expected. Therefore, the inventor installed a multi-strand cable in a full-scale vertical sealed duct that would be expected to be used in the power plant or Wataru plant mentioned above, and conducted a test that will be described in detail later, in which a powerful flame was applied to the cable from the bottom of the duct. As a result, it was confirmed that the above-mentioned concerns actually occur, that is, serious consequences that could not be predicted with conventional hammer cables were confirmed.
In general, elutriation cables used in power plants or plants are further elutriated by using jute, inorganic fibers such as glass fibers, asbestos, or non-combustible chute as an intervening material between multi-core insulated conductors. A structure in which a pressure tape is wrapped around the outer periphery and the outer periphery is covered with a flame-retardant sheath is used, and the results of the high-level flame resistance tests conducted by the above-mentioned inventors of this Hinamune cable were almost satisfactory. It was confirmed that this was not possible.

We also considered using a flame-retardant rubber mixture as an intervening material to increase the gap between the insulated conductor and the jacket, but we were unable to obtain satisfactory results. As a result of extensive studies regarding the severe flame resistance of flame-retardant cables, the inventors decided to insert a rod-shaped object made of flame-retardant rubber or flame-retardant plastic as the above-mentioned inclusion, and to further The present invention was completed based on the discovery that a surprising improvement in flame resistance can be obtained by providing a protective layer based on an inorganic or cellulose material. That is, the present invention provides a multi-core cable in which necessary inclusions are interposed between multi-core insulated conductors and the outer periphery is covered with a flame-retardant sheath, in which flame-retardant rubber or flame-retardant plastic is used as the inclusion. The second invention is a flame-retardant cable characterized by having a rod-like material interposed therein.
In the intervening type cape 3, an inclusion made of a stick of flame-retardant rubber or flame-retardant plastic is interposed between insulated conductors, and a protective layer based on an inorganic or cellulose material is provided around the outer periphery. It is a fuel cable.

3. In this invention, it is not possible to clearly explain why the use of rod-shaped objects as the inclusions exhibits the above-mentioned excellent flame-proofing effect. However, based on the observation of many combustion test results, the following four facts are clearly recognized.

(i) For example, in the case of conventional materials using jute, glass fiber or asbestos as inclusions, if the outer sheath burns and falls off due to strong flames, it simply decomposes or remains as it is, making it look like a mere combustible material. As a result, flames can freely enter through the gaps and cause combustion to occur in the insulation.

Once the insulation began to burn, the flames became more and more intense, and it was safe to say that there was no way to deal with the fire. There are cables that have heat-shielding tape, such as metal tape, wrapped tightly around the inside of the outer sheath to prevent combustion from spreading to the insulating material covered by the plate. It is torn apart by the thermal expansion ZO of the core and the pressure of the pyrolysis gas, and this becomes a gap for the flame to enter, resulting in the same result as (i) above.
There is almost no heat shielding effect. In contrast, in the rod-like object of the present invention, the rod-like objects are quickly fused to each other after the outer sheath falls off, completely surrounding the internal insulated conductor to prevent flame from entering.

In addition, if there is a protective layer, this layer becomes ashes and acts synergistically with the above-mentioned effects of the internal rods as a fireproofing and heat insulating material, preventing the intrusion of flames and retarding the rise in temperature. As a result, the above-mentioned surprising flame resistance effect is produced. Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is 3 consisting of a conductor 3 with an insulator 2.
This is the core of the book, and numeral 4 is a rod-shaped intervening member that is attached to the core 1 and is unique to this invention. Then, the outer periphery of the core body 1 and the rod-shaped object 4 is wrapped with a pressure tape 5, and further the outer periphery is covered with a flame-retardant sheet 6. An example of applying this invention to a high voltage cable is shown in FIG.

In the figure, 10' is a conductor, 110 is an insulating layer, and 12 is the rod-shaped inclusion mentioned above. Next, 13 is jute which is conventionally used as an insert, 14 is a conductive cloth, 15 is a copper tape, 16 is the above-mentioned protective layer, and 17 is a flame-retardant sheath. The above is an example, and the cable may have a structure in which another semiconducting layer or a metal shielding layer is provided on the functional core of the cable. Although there are no particular limitations on the cross-sectional shape and diameter of the rod-like objects as the above-mentioned inclusions in the present invention, it is clear that the rod-like objects are likely to be moderately hostile to each other and form a protective layer that prevents the intrusion of flames. 1 to 200 items in area 2
It is preferable to use the longest body, preferably 2 to 10 proboscis.

In particular, it is preferable to use materials with circular cross sections and different diameters sewn together as shown in the figure, in order to appropriately fill the void. The base materials for this rod include polychloroprene, chlorinated polyethylene, chlorosulfonated polyethylene, polysiloxane, EP rubber, polybutadiene, styrene-butadiene rubber, etc., and various fillers and key fuels used for rubber are used. Flame-retardant plastics are used, such as flame-retardant rubber blended with , or flame-retardant plastics blended with a flame retardant and a base material such as polyvinyl chloride, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, or polystyrene.

It is necessary that the elutriation degree of such a material is 24 or more, particularly preferably 30 or more in terms of oxygen index Z, and the flame retardant should be appropriately selected and blended. The filling rate for filling the gap between the wire core and the outer sheath by using the above-mentioned rod-shaped object as an inclusion is 20J to 90%, and particularly preferably 40 to 90%.
It is 70%.

If the filling rate is below this lower limit, there is a risk that the effects of the present invention may not be obtained due to insufficient inclusions, and if it exceeds the upper limit, there is a concern that the sheath may be torn due to thermal expansion due to flames, and both are undesirable. Furthermore, the gap between the inclusions 2 can be appropriately filled with other fibrous inclusions such as jute, glass fiber, and asbestos. Next, the material for the outer sheath is selected from the materials used for the rod-shaped object described above.
However, it is preferable that the flame retardance is 27 or more, particularly preferably 35 or more in terms of oxygen index.

Furthermore, this outer sheath may be made of a knitted structure made of fibers or inorganic fibers such as asbestos, in combination with the flame-retardant rubber or flame-retardant plastic. Next, as the protective layer in the present invention, a material based on an inorganic material or a cellulose-based material is used, but a material obtained by cutting a cellulose-based woven fabric such as cotton cloth into a tape shape and wrapping it is most suitable.

Materials made of polyester, polyamide, etc. as a base material tend to lose their shape when exposed to flames, even if a rod-like object is interposed therebetween, and are not suitable for the purpose of the present invention. Such cotton cloth is preferably a thick, loosely bound product with a roughness of 0.5 or more, preferably 0.8 or more, specifically a so-called canvas, and the rubberized tape is made of a semiconductor-conductive rubber mixture. A conductive cloth coated with a flame-retardant rubber mixture can be used as appropriate.

Furthermore, inorganic materials include asbestos paper, glass mica paper, glass cloth, etc., and these are wrapped around the wire 0 and the twisted outer circumference of the rod-shaped object to a thickness of 0.9 or more.
It is preferable to layer more than one layer. As is clear from the above description and the embodiments described later, when a multi-stranded cable is exposed to a flame, the rod-like object of the inclusion appropriately ignites and is insulated from the flame. It has the effect of protecting electric wires and demonstrating surprising flame resistance, and its industrial value is extremely large.

The present invention will be specifically explained below with reference to Examples.

Example 1 and Comparative Examples 1 to 3 A cross-linked polyethylene insulation layer was provided on the copper wire on the side 2 of the cross-section 38, and a conductive cloth and steel tape were wrapped thereon, and a diameter of about 16
Rib 6. Three wire cores for the gunwale and nine rods each made of scaled polychlorinated pinyl with an oxygen index of 43 and having a diameter of 3 and 5 legs are twisted together as shown in Figure 1, and then A pressure tape was wound around the cable, and polyvinyl chloride having an oxygen index of 43 was extruded and coated thereon to a thickness of 2.8 yen to obtain a cable.

For comparison, a cable with glass fiber interposed in the same part instead of the above rod-like material (Comparative Example 1), a cable with jute interposed with the same non-combustible treatment (Comparative Example 2), and a cable with chloroprene rubber as the base material were used. A cable (3) enriched by extrusion of the mixture was obtained.

The outer diameter of each of these cables is 42 mm. Each of these 3h long cables has a cross section of 500 legs x 500 skins.
Eight of them were installed in a vertical closed duct with a height of about 1 ridge, and a burner flame (flame length about 1 m) with an energy of 87,500 Keal/hr was applied from the bottom end of the duct for 20 minutes to perform a combustion test. The burner was turned off and the afterflame of the cable was examined and the height of damage to the cable sheath caused by the flame was measured.The results are shown in the table below. According to the results in the table above, it is clear that the cable of the present invention has significantly superior flame resistance compared to the comparative example.

Since all of the Comparative Examples 1 to 3 passed the combustion test according to the American Institute of Electrical Engineers Standard 383 (lEEE383), it is clear that the products of the present invention have significantly improved combustion characteristics. it is obvious. Examples 2 to 5 and Comparative Examples 4 to 7 High voltage cables as shown in FIG. 2 were obtained as follows.

In other words, the figure shows three wire cores made of copper wire with a cross-sectional side of 38 and a cross-linked polyethylene insulating layer with a thickness of 4.0, and three rod-shaped rods made of flammable polyvinyl chloride with an oxygen index of 43 and having a diameter of 8. Twist the pieces together as shown, fill in the gaps with jute, wrap a conductive cloth layer and an electrical shielding layer made of mild steel tape around the outer periphery, and wrap around it a 0.9-inch thick, 75-side thick rubberized cotton tape. 1
The outermost layer was extruded and coated with polyvinyl chloride having an oxygen index of 43 to a thickness of 2.8 mm to obtain a cable with a diameter of 45 ribs (Example 2). In addition, similar cables were obtained by changing the filling rate of the core rods as shown in the following table (Table 2 and 3), such as increasing the number of the twills on two sides.

Furthermore, the above-mentioned gauze rubber drawing tape was wrapped 2/3 times to give an average of 3
A cable was obtained in the same manner except that it was wound in layers (Same 4).

For comparison, cables were obtained in which the rods of Example 2 were not used and the inclusions included only jute (Comparative Example 4), glass fiber only (Comparative Example 5), and a combination of both (Comparative Example 6).

Furthermore, in place of the flame retardant rubberized cotton tape of Example 2, 0.15
A cable of Comparative Example 7 was obtained by winding flame-retardant polyester tapes of average side thickness in layers so as to have the same winding thickness.

Each of these cables was subjected to a combustion test in the same manner as in Example 1, and the results are shown in the following table.

According to the results shown in the table above, it was clear that the product of the present invention was superior to the comparative product in that the afterflame time was approximately zero and there was less damage to the outer skin.

Further, in Comparative Example 7, in which a plastic tape was used instead of a cotton tape as a protective layer, the effects of the present invention could not be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of the Hinenen cable of the present invention, and FIG. 2 is a cross-sectional view of an example of a pond applied to a pressure-resistant cable. 1, 10... Conductor, 2, 11... Insulating layer, 4, 12
...rod-shaped object, 6,17 flame-retardant sheath, 16...protective layer. Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. A multi-core cable in which necessary inclusions are interposed between multi-core insulated conductors and the outer periphery is covered with a flame-retardant sheath, wherein the inclusion is made of flame-retardant rubber or flame-retardant sheath. A flame-retardant cable characterized by having a rod-like object made of plastic interposed therein. 2. In the multi-core interposed cable according to item 1, an inclusion made of a stick of flame-retardant rubber or flame-retardant plastic is interposed between the insulated conductors, and a protective layer made of an inorganic or cellulose material as a base material is provided on the outer periphery of the inclusion. A flame-retardant cable characterized by being provided with.