Burning-resistant flexible mineral fireproof cable and preparation method thereof

Abstract

The invention discloses a firing-resistant flexible mineral fireproof cable and a preparation method thereof. The cable comprises a metal tube sheath cable core. Two mineral flame-retardant powder mud layers, namely a first mineral flame-retardant powder mud layer and a second mineral flame-retardant powder mud layer, are arranged on the outer side of the metal tube sheath cable core from inside to outside; the first mineral flame-retardant powder mud layer is a muddy mixture prepared by adding water into a ceramic reaction powder raw material; the second mineral flame-retardant powder mud layer is a glass batch raw material; the ceramic phase generation temperature of the ceramic reaction powder raw material of the first mineral flame-retardant powder mud layer is higher than the glass transition temperature of the vitrification reaction powder raw material of the second mineral flame-retardant powder mud layer. According to the invention, under continuous high temperature, the first mineral powder mud layer is protected by the second mineral powder mud layer in the viscoelastic state, a complete ceramic reaction is carried out, a ceramic layer with a compact structure is formed, the hardness and fireproof performance of the cable body are improved, the structural stability of the flexible mineral fireproof cable is maintained, and the cable failure is avoided.

Description

Technical Field

[0001] This invention belongs to the field of cables, and more specifically, relates to a heat-resistant flexible mineral fireproof cable and its preparation method. Background Technology

[0002] Flexible mineral-insulated cables are a type of special cable with excellent fire resistance and high-temperature resistance, making them suitable for locations with extremely high safety requirements, such as high-rise buildings, subways, and nuclear power plants. Flexible mineral-insulated cables are mainly composed of multi-strand copper wires, mica tape mineral insulation wrapping, dense filling with alkali-free glass fiber, a copper tube sheath longitudinally wrapped and welded with copper tape, mineral flame-retardant powder, and an outer sheath.

[0003] Mineral fire-retardant mortar with good flame-retardant properties is made by mixing ceramization reaction powder raw materials with water to form a plastic mortar, and then forming a mineral fire-retardant mortar layer through a screw extruder, such as the flexible mineral fire-resistant cable and its preparation method provided in Chinese patent document CN119742113A. The ceramization reaction of the powder occurs during sintering at high temperature, thereby protecting the internal cable core structure and maintaining the cable's performance under extreme conditions such as fires.

[0004] However, in the event of a fire or other incident, the flames directly scorch the cable, causing the local temperature to rapidly reach over 400°C, or even maintain a sustained high temperature environment of 1000°C. This can lead to the peeling off of the mineral flame-retardant powder and outer sheath. Once the mineral powder layer peels off, the structure of the flexible mineral fire-resistant cable cannot remain intact, affecting its flame-retardant performance and potentially causing the entire cable to fail. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a heat-resistant flexible mineral fire-resistant cable and its preparation method. The purpose is to composite a vitrified mineral fire-retardant powder layer with a ceramicized mineral fire-retardant powder layer. As the mineral powder gradually sinters during the ceramicization reaction, the viscoelastic vitrified mineral layer maintains overall structural stability, resisting and preventing localized high temperatures caused by flame burning, thus avoiding deconstruction and extending the cable's normal operating time under fire or other extreme high-temperature conditions. This solves the technical problem of existing cables failing due to the peeling of the mineral fire-retardant powder layer under flame burning or extreme / localized high-temperature environments.

[0006] To achieve the above objectives, according to one aspect of the present invention, a burn-resistant flexible mineral fireproof cable is provided, comprising a metal tube sheath cable core. The outer side of the metal tube sheathed cable core has two layers of mineral flame retardant powder mud from the inside out, namely the first mineral flame retardant powder mud layer and the second mineral flame retardant powder mud layer. The first mineral flame-retardant powder mud layer is a mud-like mixture made by adding water to ceramic reaction powder raw materials; The second mineral flame-retardant powder mud layer is a glass batching material; The ceramic phase formation temperature of the ceramicized reactive powder raw material in the first mineral flame retardant powder mud layer is higher than the glass transition temperature of the glass-transformed reactive powder raw material in the second mineral flame retardant powder mud layer.

[0007] Preferably, in the heat-resistant flexible mineral fireproof cable, the glass compound raw material contains more than 30% by mass of quartz powder.

[0008] Preferably, the heat-resistant flexible mineral fireproof cable contains sodium silicate with a mass fraction of more than 15% in the glass compound raw materials.

[0009] Preferably, the heat-resistant flexible mineral fireproof cable contains wollastonite powder and perlite powder in its glass compound; the mass ratio of quartz powder, sodium silicate, wollastonite powder and perlite powder is (3.5~4.5):(1.5~2.5):(2.5~3.5):1.

[0010] Preferably, the scorch-resistant flexible mineral fireproof cable uses a ceramicized reactive powder as its raw material, which is a mixture of metal hydroxide and sodium silicate, wherein the mass fraction of sodium silicate is between 25% and 70%.

[0011] Preferably, in the burn-resistant flexible mineral fireproof cable, the metal hydroxide is magnesium hydroxide or aluminum hydroxide.

[0012] Preferably, the first mineral flame-retardant powder layer of the scorching-resistant flexible mineral fireproof cable has a thickness of 2mm to 4mm, and the second mineral flame-retardant powder layer has a thickness of 1mm to 3mm.

[0013] Preferably, in the scorch-resistant flexible mineral fireproof cable, a mineral fiber fireproof insulation tape is wrapped between the first mineral flame-retardant powder layer and the second mineral flame-retardant powder layer.

[0014] According to another aspect of the present invention, a method for preparing the ignition-resistant flexible mineral fire-resistant cable is provided, comprising the following steps: The pre-proportioned ceramic reaction powder raw materials are mixed with water to form a mud-like mixture, and then extruded onto the outside of the metal tube sheath cable core to form the first mineral mud layer. The glass batching material with a preset ratio is mixed with water to form a mud-like mixture, which is then extruded to the outside of the first mineral powder mud layer and dried to remove moisture, forming the second mineral powder mud layer.

[0015] Preferably, in the preparation method of the scorch-resistant flexible mineral fireproof cable, a mineral fiber fireproof insulation tape is wrapped around the outside of the first mineral powder layer.

[0016] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: The scorch-resistant flexible mineral fire-resistant cable provided by this invention has two layers of mineral flame-retardant powder mud with different compositions. The inner first mineral flame-retardant powder mud layer is made of ceramization reaction powder raw material, and the outer second mineral flame-retardant powder mud layer is made of glass compound raw material. The ceramic phase formation temperature of the ceramization reaction powder raw material in the first mineral flame-retardant powder mud layer is higher than the glass transition temperature of the glass transition reaction powder raw material in the second mineral flame-retardant powder mud layer. When subjected to high-temperature scorching, the first mineral flame-retardant powder mud layer undergoes a ceramization reaction and gradually sinters, while the outer second mineral flame-retardant powder mud layer undergoes a glass transition to form a viscoelastic state, maintaining the overall structural stability and preventing the peeling off of the first mineral flame-retardant powder mud layer with local agglomeration. Under continuous high temperatures, the scorch-resistant flexible mineral fire-resistant cable provided by this invention allows the first mineral powder mud layer to undergo a complete ceramization reaction under the protection of the viscoelastic second mineral powder mud layer, forming a dense ceramization layer, improving the cable's hardness and fire resistance, maintaining the structural stability of the flexible mineral fire-resistant cable, and preventing cable failure. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the cross-sectional structure of the burn-resistant flexible mineral fireproof cable provided by the present invention; Figure 2 This is a cross-sectional photograph of the burn-resistant flexible mineral fireproof cable provided in Embodiment 1 of the present invention; Figure 3 This is a cross-sectional photograph of the burn-resistant flexible mineral fireproof cable provided in Embodiment 2 of the present invention.

[0018] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1 is a metal tube sheath cable core, 11 is a conductor, 12 is a mica tape insulation layer, 13 is a mineral insulation filling layer, 14 is a metal tube sheath, 2 is a first mineral flame retardant powder layer, 3 is a second mineral flame retardant powder layer, 4 is an outer sheath, and 5 is a mineral fiber fireproof insulation tape. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0020] The fire-resistant flexible mineral fireproof cable provided by this invention, such as... Figure 1As shown, it includes a metal tube sheathed cable core, two layers of mineral flame retardant powder mud on the outside of the metal tube sheathed cable core from the inside out, namely the first mineral flame retardant powder mud layer and the second mineral flame retardant powder mud layer, and an outer sheath. The metal-sheathed cable core includes conductors, a mineral insulation filling layer, and a metal sheath. The conductors are generally stranded copper wires, composed of multiple strands of copper conductors, with a mica tape insulation layer wrapped around the outside. The mineral insulation filling layer of the cable core is generally filled with alkali-free glass fiber; to improve cabling and insulation performance, it can be wrapped with insulating tape. The metal sheath can be a corrugated aluminum sheath or a copper sheath. Some metal-sheathed cables have a support skeleton on the outside of the metal sheath, generally extruded from a high-molecular organic material. The support skeleton serves to improve the mechanical strength and toughness of the cable and, through different shapes, better fix the mineral powder layer. However, at high temperatures, the support skeleton softens, loses its supporting function, and even increases in fluidity, causing the mineral powder layer to peel off before it is fully ceramicized, making it even more difficult to maintain the integrity of the cable structure. Therefore, in a preferred embodiment of the present invention, the organic support skeleton in the cable core is eliminated to further ensure the structural integrity and electrical performance of the cable at high temperatures (above 950°C).

[0021] The first mineral flame-retardant powder mud layer is a mud-like mixture of ceramic reaction powder raw materials and water; the second mineral flame-retardant powder mud layer is a glass compound raw material. The ceramic phase formation temperature of the ceramicized reactive powder raw material in the first mineral flame retardant powder mud layer is higher than the glass transition temperature of the glass-transformed reactive powder raw material in the second mineral flame retardant powder mud layer.

[0022] The high-temperature environment generated by flame burning not only causes a rapid temperature rise but is also likely to develop locally. Under localized flame burning, the mineral flame-retardant mortar experiences a rapid localized temperature rise, releasing free water and water of crystallization within the mortar, producing water vapor. This water vapor will impact the outer sheath, causing bulging and perforation, and localized peeling of the outer sheath and mineral flame-retardant mortar. Once the localized fireproof structure of the cable is damaged, the entire cable will become inoperable.

[0023] The ceramic phase formation temperature refers to the critical temperature range in which the ceramic reaction powder raw materials undergo a core phase transformation and form a stable ceramic crystal structure during heat treatment. The glass transition temperature refers to the initial temperature at which the glass batch raw materials begin to melt upon heating. When the flexible mineral fire-resistant cable is in a continuous high-temperature environment, the first mineral flame-retardant powder layer and the second mineral flame-retardant powder layer maintain a relatively synchronous temperature rise. The second mineral powder layer is located on the outside of the concentric nested structure of the fire-resistant cable, and its temperature rises relatively faster. Before the first mineral flame-retardant powder layer has undergone a core phase transformation and formed a stable ceramic crystal structure, the second mineral powder layer begins to melt, forming a viscoelastic outer layer that wraps around the first mineral powder layer. This ensures that the second mineral powder layer undergoes overall ceramicization to form a structurally stable protective layer, significantly improving the cable body's hardness and fire resistance, thereby maintaining the overall structure at high temperatures. Without the protection of a viscoelastic second mineral powder layer, if high temperatures increase the fluidity of the polymer outer sheath and cause it to lose its inherent structural maintenance ability, the first mineral powder layer will be unable to maintain its structure during the ceramization core phase transition. As the ceramization raw material powder gradually sinters, some ceramization agglomerates, and before a complete tubular ceramization structure is formed, these agglomerates may detach, leading to the inability to maintain the overall cable structure. The metal tube cable core will then be directly exposed to high temperatures, unable to maintain reliable electrical performance, rendering it unusable. Therefore, the coordinated phase transition process of the ceramization reactive powder raw material in the first mineral powder layer and the melting process of the glass transition reactive powder raw material in the second mineral powder layer are crucial for maintaining the integrity of the cable structure.

[0024] The ceramic reaction powder raw material for the first mineral flame-retardant powder layer can be a general-purpose ceramic fire-retardant mineral powder layer, commonly a mixture of metal hydroxide and sodium silicate. The metal hydroxide is often magnesium hydroxide or aluminum hydroxide, and the ceramic phase formation temperature is in the range of 600℃ to 1200℃. In the preferred embodiment of this invention, no organic support skeleton is provided inside the first mineral flame-retardant powder layer. Therefore, the viscosity of the first mineral flame-retardant powder layer needs to be relatively high to ensure good forming during production. This requires a certain proportion of sodium silicate. However, sodium silicate absorbs a lot of water when mixed with water, and will first dehydrate to form water vapor during the high-temperature ceramic reaction. The large amount of water vapor generated can cause bulging of the outer sheath, local gaps in the second mineral powder layer, and vibration of the first mineral powder layer. These phenomena exacerbate the overall instability risk of the cable structure. Experiments show that when the mass fraction of sodium silicate in the ceramicizing reaction powder raw material is between 25% and 70% (a mixture of metal hydroxide and sodium silicate), a relatively balanced processing performance and acceptable water content can be achieved, forming a first mineral flame-retardant powder layer with a thickness of 2mm to 4mm. The water content in the first mineral flame-retardant powder layer is preferably minimized while meeting the processing viscosity requirements of the mud-like mixture. The water addition process uses an optimized solid-liquid ratio to ensure the minimum amount of water required for extrusion performance, that is, using as little water as possible to mix the first mineral flame-retardant powder layer as the ceramicizing reaction powder raw material for extrusion molding.

[0025] To ensure that the ceramicized reactive powder raw materials can form a mud-like mixture using as little water as possible, a first mineral flame-retardant mud layer is prepared by wrapping it with tape after extrusion to maintain its shape. Preferably, a mineral fiber fire-resistant insulating tape is used. Commonly used mineral fiber fire-resistant insulating tapes include brucite mineral fibers, quartz fibers, and zirconium-containing ceramic fiber paper, all of which possess fire-resistant and insulating properties. Furthermore, the fibrous structure allows water vapor generated during the dehydration of the ceramicized powder raw materials to disperse through the fiber structure into the viscoelastic second mineral mud layer, forming fine bubbles. This prevents the formation of large, concentrated water vapor bubbles that could cause localized rupture of the second mineral mud layer, thus minimizing the risk of peeling off both the first and second mineral mud layers.

[0026] The glass batching material contains at least 30% quartz powder by mass, serving as the base material for the glass batching, typically between 35% and 45%. Additionally, to lower the glass transition temperature, it preferably contains 15% to 25% sodium silicate (calculated as anhydrous sodium silicate) and an appropriate amount of wollastonite, usually 25% to 35%. Furthermore, the second mineral flame-retardant powder layer provided by this invention is a glass batching material with added perlite powder. Perlite contains bound water (2% to 6%), which releases water vapor at 100–400°C, expanding in volume to form a porous structure. The water vapor further promotes the adhesion of the sodium silicate gel, optimizing pore uniformity. When the water vapor released at the high temperature of the first mineral flame-retardant powder layer enters the second mineral powder layer, it is more easily dispersed into fine bubbles through the porous structure formed by the perlite, rather than agglomerating into larger bubbles, thus helping to stabilize the structure of the second mineral powder layer.

[0027] The preferred mass ratio of quartz powder, sodium silicate, wollastonite powder, and perlite powder is (3.5~4.5):(1.5~2.5):(2.5~3.5):1. With the presence of water vapor, the glass transition temperature is between 400℃ and 500℃. Perlite releases bound water, sodium silicate partially hydrolyzes, wollastonite hydrolyzes to generate CaO, and quartz melts more rapidly.

[0028] The extrusion processing performance of the second mineral powder layer stems from the adhesive state of sodium silicate after absorbing water. The extrusion processing performance of the second mineral powder layer is relatively poor, with the thickness of the extruded first mineral flame-retardant powder layer ranging from 1mm to 3mm. To prevent excessive water vapor in the second mineral powder layer under heating conditions, which could compromise its stability, a heating and drying process is necessary to remove moisture. Ingeniously, the heating and drying of sodium silicate causes the second mineral powder layer to enter a compacted state, and the high-temperature dried surface is more suitable for the outer sheath extrusion process.

[0029] The outer sheath covers and fixes the inorganic mineral powder layer. The outer sheath is made of flame-retardant high-molecular thermoplastic material, preferably a low-smoke halogen-free sheath.

[0030] The method for preparing a heat-resistant flexible mineral fire-resistant cable provided by the present invention is characterized by comprising the following steps: The pre-proportioned ceramic reaction powder raw materials are mixed with water to form a mud-like mixture, and then extruded onto the outside of the metal tube sheath cable core to form the first mineral mud layer. A preferred embodiment is to wrap a mineral fiber fireproof and insulating strip around the outside of the first mineral powder layer.

[0031] The glass batching material with a preset ratio is mixed with water to form a mud-like mixture, which is then extruded to the outside of the first mineral powder mud layer and dried to remove moisture, forming the second mineral powder mud layer.

[0032] A polymer sheath is formed by extruding a polymer material on the outside of the second mineral powder layer, and after cooling and shaping, an outer sheath is formed, thus obtaining the scorch-resistant flexible mineral fireproof cable.

[0033] The following is an example: The scorching-resistant flexible mineral fireproof cable provided in the embodiment has the following basic structure: Figure 1 As shown, it includes a metal tube sheathed cable core, two layers of mineral flame retardant powder mud on the outside of the metal tube sheathed cable core from the inside out, namely the first mineral flame retardant powder mud layer and the second mineral flame retardant powder mud layer, and an outer sheath. The metal tube sheathed cable core includes a conductor, a mineral insulation filling layer, and a metal tube sheath; the conductor is made of copper conductor stranded wire, which is made of multiple strands of copper conductor stranded together, and the outside of the copper conductor is wrapped with a mica tape insulation layer; the mineral insulation filling layer of the cable core is made of alkali-free glass fiber filled with wrapped insulation tape; the metal tube sheath can be a corrugated aluminum sheath.

[0034] The first mineral flame-retardant powder mud layer is a mud-like mixture of ceramic reaction powder raw materials and water. The ceramic reaction powder raw materials of the first mineral flame-retardant powder mud layer are a mixture of common metal hydroxides and sodium silicate. The metal hydroxides are often magnesium hydroxide and aluminum hydroxide. The ceramic phase formation temperature of the mixture of magnesium hydroxide and sodium silicate is 550-800℃, and that of the mixture of aluminum hydroxide and sodium silicate is in the range of 800℃ to 1200℃.

[0035] When the mass fraction of sodium silicate in the ceramic reaction powder raw material is between 25% and 70%, a first mineral flame-retardant powder mud layer with a thickness of 2 mm to 4 mm is formed.

[0036] Mineral fiber fireproof insulation tape, with quartz fiber wrapping layer selected.

[0037] The second mineral flame-retardant powder slurry layer is a glass batching material, which is a mixture of quartz powder, sodium silicate, wollastonite powder, and perlite powder. The mass ratio of quartz powder, sodium silicate, wollastonite powder, and perlite powder is (3.5~4.5):(1.5~2.5):(2.5~3.5):1, and the glass transition temperature is between 500℃ and 650℃. The thickness is between 1mm and 3mm.

[0038] The outer sheath covers and fixes the inorganic mineral powder mud layer, and is a low-smoke halogen-free sheath.

[0039] The method for preparing the ignition-resistant flexible mineral fire-resistant cable provided in the embodiments is as follows: The pre-proportioned ceramic reaction powder raw materials are mixed with water to form a mud-like mixture, and then extruded onto the outside of the metal tube sheath cable core to form the first mineral mud layer; the water mixing process adopts an optimized solid-liquid ratio to ensure the minimum amount of water required for extrusion performance.

[0040] A mineral fiber fireproof insulation tape is wrapped around the outside of the first mineral powder layer. In this embodiment, a quartz fiber wrapping layer is used as the mineral fiber fireproof insulation tape.

[0041] The glass batch material with a preset ratio is mixed with water to form a mud-like mixture, and then extruded to the outside of the first mineral powder mud layer. The second mineral powder mud layer is formed by drying and removing moisture in an oven set in front of the inlet of the outer sheath extruder.

[0042] A polymer sheath is formed by extruding a polymer material on the outside of the second mineral powder layer, and after cooling and shaping, an outer sheath is formed, thus obtaining the scorch-resistant flexible mineral fireproof cable.

[0043] The cross-sectional structural diagram of Example 1 is shown below. Figure 2 As shown, the cross-sectional structural diagram of Example 2 is as follows. Figure 3 As shown.

[0044] The prepared cable was subjected to a burning test. The test method and procedure were in accordance with standard BS6387:2013. The specific parameters were: the fire temperature was (1200-1250)℃, the fire time was 180 min, and the flame temperature was increased by approximately 200-250℃. The cable specifications, composition, and burning test results provided in the example are shown in Table 1.

[0045] Table 1. Cable specifications and performance of examples and comparative models

[0046] Experiments show that, compared to single-layer flexible mineral fireproof cables with the same total thickness of mineral powder mud layers, the mineral flexible fireproof cable with ceramicized and vitrified double-layer mineral flame-retardant powder mud layers provided by this invention can maintain the integrity of the cable structure under high-temperature flame burning environment, thereby ensuring electrical performance.

[0047] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A heat-resistant flexible mineral fireproof cable, characterized in that, Including metal-coated cable cores; The outer side of the metal tube sheathed cable core has two layers of mineral flame retardant powder mud from the inside out, namely the first mineral flame retardant powder mud layer and the second mineral flame retardant powder mud layer. The first mineral flame-retardant powder mud layer is a mud-like mixture made by adding water to ceramic reaction powder raw materials; The second mineral flame-retardant powder mud layer is a glass batching material; The ceramic phase formation temperature of the ceramicized reactive powder raw material in the first mineral flame retardant powder mud layer is higher than the glass transition temperature of the glass-transformed reactive powder raw material in the second mineral flame retardant powder mud layer.

2. The fire-resistant flexible mineral fireproof cable as described in claim 1, characterized in that, The glass batch material contains more than 30% quartz powder by mass.

3. The fire-resistant flexible mineral fireproof cable as described in claim 2, characterized in that, The glass batch material contains sodium silicate with a mass fraction of 15% or more.

4. The fire-resistant flexible mineral fireproof cable as described in claim 3, characterized in that, The glass batch contains wollastonite powder and perlite powder; the mass ratio of quartz powder, sodium silicate, wollastonite powder and perlite powder is (3.5~4.5):(1.5~2.5):(2.5~3.5):

1.

5. The fire-resistant flexible mineral fireproof cable as described in claim 1, characterized in that, The raw material for the ceramicization reaction powder is a mixture of metal hydroxide and sodium silicate, wherein the mass fraction of sodium silicate is between 25% and 70%.

6. The fire-resistant flexible mineral fireproof cable as described in claim 5, characterized in that, The metal hydroxide is magnesium hydroxide or aluminum hydroxide.

7. The fire-resistant flexible mineral-resistant cable as described in claim 1, characterized in that, The thickness of the first mineral flame-retardant powder mud layer is 2mm to 4mm, and the thickness of the second mineral flame-retardant powder mud layer is 1mm to 3mm.

8. The fire-resistant flexible mineral fireproof cable as described in claim 1, characterized in that, A mineral fiber fireproof insulation tape is wrapped between the first mineral flame-retardant powder mud layer and the second mineral flame-retardant powder mud layer.

9. The method for preparing the ignition-resistant flexible mineral fire-resistant cable as described in any one of claims 1 to 8, characterized in that, Includes the following steps: The pre-proportioned ceramic reaction powder raw materials are mixed with water to form a mud-like mixture, and then extruded onto the outside of the metal tube sheath cable core to form the first mineral mud layer. The glass batching material with a preset ratio is mixed with water to form a mud-like mixture, which is then extruded to the outside of the first mineral powder mud layer and dried to remove moisture, forming the second mineral powder mud layer.

10. The method for preparing the ignition-resistant flexible mineral fire-resistant cable as described in claim 9, characterized in that, Mineral fiber fireproof insulation tape is wrapped around the outside of the first mineral powder layer.

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