Flexible mineral-insulated fire-resistant power cable and method for producing the same

Abstract

The application discloses a flexible mineral insulation fireproof power cable and a preparation method thereof, and relates to the technical field of fireproof cables. The technical points of the application include at least one insulated cable core and an outer sheath wrapped outside the insulated cable core. The insulated cable core comprises a conductor and a flexible mineral insulation layer, a bidirectional spiral mineral fiber locking layer and a ceramizable elastic mineral layer which are sequentially arranged outside the conductor from inside to outside. The flexible mineral insulation layer comprises an interface mineralized mica tape wrapped outside the conductor. The interface mineralized mica tape is a composite mica tape in which a silicon-boron-aluminum oxygen network layer is formed in situ on the surface of a phlogopite paper and an alkali-free glass fiber base tape. Through the synergistic effect of the interface mineralized mica tape, the bidirectional spiral mineral fiber locking layer and the ceramizable elastic mineral layer, the cable has normal-temperature flexibility and high-temperature insulation integrity, and the contradiction between the insufficient flexibility of a traditional rigid mineral insulation cable and the loose layer-to-layer structure of a common mica tape cable in a fire scene is relieved.

Description

Technical Field

[0001] This invention relates to the field of fire-resistant cable technology, specifically to a flexible mineral-insulated fire-resistant power cable and its preparation method. Background Technology

[0002] Power cables are crucial transmission components in building power distribution systems, rail transit, data centers, petrochemical plants, underground utility tunnels, and public safety facilities. Under fire conditions, cables not only need to prevent the spread of flames but also need to maintain line integrity for a certain period to ensure the continuous operation of fire pumps, smoke extraction systems, emergency lighting, alarm systems, and critical control equipment. Therefore, the fire-resistant insulation reliability of fire-resistant power cables directly affects fire emergency response capabilities.

[0003] Existing fire-resistant cables typically employ magnesium oxide mineral insulation, mica tape wrapping, or ceramicizable polymer insulation. While magnesium oxide mineral-insulated cables offer high fire resistance, their overall structure is relatively rigid, with a large bending radius, resulting in limited ease of processing and installation, and restricting their adaptability to complex spatial wiring. Mica tape-wrapped fire-resistant cables offer better flexibility, but the mica tape layers rely primarily on mechanical overlap and resin bonding. Under the combined effects of flame impact, thermal expansion and contraction, water spray impact, or cable bending stress, interlayer loosening, crack propagation, or localized detachment can easily occur, reducing the continuity of the insulation barrier.

[0004] Ceramicizable silicone rubber materials possess rubber elasticity and electrical insulation properties at room temperature. At high temperatures, they can form a ceramicized residual layer through inorganic fillers and glassy phase flux components, thus making them suitable for use as insulation or sheathing in fire-resistant cables. However, when using ceramicizable silicone rubber extrusion layers alone, the residual ceramic layer often suffers from insufficient strength, poor bonding with the inner mica tape, and susceptibility to pulverization and detachment under bending or external impact after the polymer matrix thermally decomposes in a fire. Simply increasing the amount of inorganic filler added reduces the fluidity of the rubber compound during processing, affecting the cable's normal operating flexibility and extruded appearance.

[0005] Therefore, existing technologies still have shortcomings in balancing the cable's flexible laying performance, fire-resistant ceramic shell formation capability, insulation layer interface bonding strength, and high-temperature residual layer crack resistance. It is difficult to obtain a fire-resistant power cable that has both flexible mineral insulation characteristics and can form a continuous locked ceramic insulation barrier in a fire. Summary of the Invention

[0006] The purpose of this invention is to address the problems in the prior art, such as insufficient flexibility of magnesium oxide mineral-insulated cables, weak interlayer bonding of ordinary mica tape fire-resistant cables, easy pulverization and detachment of residual ceramic layers in ordinary ceramicizable silicone rubber, and insufficient insulation integrity in fire situations, by providing a flexible mineral-insulated fire-resistant power cable and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a flexible mineral-insulated fireproof power cable, comprising at least one insulated cable core and an outer sheath covering the outside of the insulated cable core, wherein the insulated cable core comprises a conductor and, from the inside out, a flexible mineral insulation layer, a bidirectional helical mineral fiber locking layer and a ceramicizable elastic mineral layer disposed on the outside of the conductor.

[0008] The flexible mineral insulation layer includes an interface mineralized mica tape wrapped around the outside of the conductor. This interface mineralized mica tape is a composite mica tape in which a silicon-boron-alumina network layer is formed in situ on the surface of phlogopite paper and alkali-free glass fiber substrate. This silicon-boron-alumina network layer improves the interfacial activity and heat-resistant adhesion of the mica tape surface at room temperature, and at high temperatures, it can sinter and bridge with the low-melting-point borosilicate glass phase and mineral fillers in the outer ceramicizable elastic mineral layer, thereby enhancing the bond between the mica layer and the ceramicized layer.

[0009] The bidirectional helical mineral fiber interlocking layer is disposed between the interface mineralized mica tape and the ceramicizable elastic mineral layer, with a portion of it embedded in the inner surface of the ceramicizable elastic mineral layer. This structure does not significantly weaken the cable flexibility at room temperature and can serve as a continuous skeleton in a fire to limit the cracking, peeling, and detachment of the ceramicized residue.

[0010] The ceramicizable elastic mineral layer is prepared from the following raw materials in parts by weight: 100 parts methyl vinyl silicone rubber, 5-15 parts vinyl MQ silicone resin, 18-35 parts fumed silica, 25-45 parts flaky mica powder, 10-25 parts acicular wollastonite, 12-28 parts low melting point borosilicate glass powder with a softening point of 430-560℃, 8-25 parts magnesium hydroxide, 2-8 parts hexagonal boron nitride, 1-6 parts borosilicate coupling prepolymer, and 0.8-3 parts vulcanizing agent.

[0011] Furthermore, the interface mineralized mica tape is spirally wrapped around the outside of the conductor with an overlap rate of 30%-55%, the thickness of the flexible mineral insulation layer is 0.25-1.20mm, and the thickness of the ceramicizable elastic mineral layer is 0.8-4.5mm.

[0012] Furthermore, the coating amount of the silicon-boron-aluminum oxide network layer is 0.8-4.0 g / m², and the molar ratio of Si, B, and Al in the silicon-boron-aluminum oxide network layer is 1:(0.08-0.25):(0.02-0.10).

[0013] Furthermore, the bidirectional helical mineral fiber locking layer is formed by the cross-wrapping of a first mineral fiber bundle and a second mineral fiber bundle, with the first mineral fiber bundle having an angle of 35°–55° with the cable axis and the second mineral fiber bundle having an angle of -35°–-55° with the cable axis.

[0014] Furthermore, the first mineral fiber bundle and the second mineral fiber bundle are each independently selected from basalt continuous fiber bundles, alumina silicate continuous fiber bundles, or high silica glass fiber bundles.

[0015] Furthermore, the flaky mica powder has a D50 of 5-20 μm and an aspect ratio of 20-80; the acicular wollastonite has an aspect ratio of 8-25; and the low-melting-point borosilicate glass powder has a D50 of 1.5-8 μm.

[0016] Furthermore, the borosilicate coupling prepolymer is obtained by dehydration condensation of hydroxyl-containing polydimethylsiloxane, boric acid or borate ester, and vinyltriethoxysilane at 80-120°C, and its number average molecular weight is 800-3000.

[0017] This invention also provides a method for preparing a flexible mineral-insulated fire-resistant power cable, comprising the following steps: S1. Preparation of interfacial mineralized mica tape: Plasma activation or corona activation is performed on phlogopite paper and alkali-free glass fiber substrate. Sol containing silicon source, boron source and aluminum source is coated on the surface of activated phlogopite paper and alkali-free glass fiber substrate. After drying and thermal densification treatment, interfacial mineralized mica tape with silicon-boron-aluminum oxide network layer on the surface is obtained. S2. Preparation of ceramic-type elastic mineral rubber compound: Flake mica powder, needle-shaped wollastonite, low-melting-point borosilicate glass powder, magnesium hydroxide and hexagonal boron nitride are dried and surface-treated with silane to obtain modified mineral filler; methyl vinyl silicone rubber, vinyl MQ silicone resin, fumed silica, modified mineral filler and borosilicate coupling prepolymer are mixed and then vulcanizing agent is added and mixed to obtain ceramic-type elastic mineral rubber compound; S3. Cable cabling: The interface mineralized mica tape is wrapped around the outside of the conductor to form a flexible mineral insulation layer. Mineral fiber bundles are wrapped around the outside of the flexible mineral insulation layer in opposite spiral directions to form a bidirectional spiral mineral fiber lock layer. Then, the ceramic elastic mineral rubber is extruded and vulcanized to form an insulated cable core. S4. Sheath Forming: An outer sheath is extruded onto the outside of one or more insulated cable cores, cooled, and wound up to obtain the flexible mineral-insulated fireproof power cable.

[0018] This invention constructs a multi-layered synergistic structure consisting of "interfacial mineralized mica tape—bidirectional spiral mineral fiber interlocking layer—ceramizable elastic mineral layer," enabling the cable to maintain the bending performance required for flexible mineral-insulated cables at room temperature, while forming a continuous mineral ceramicized insulation barrier in a fire. The silicon-boron-alumina network layer in the interfacial mineralized mica tape provides an active mineralized interface; low-melting-point borosilicate glass powder softens and wets the mica powder, wollastonite, and mineral fibers at lower temperatures; acicular wollastonite and bidirectional spiral mineral fibers together form a crack-resistant reinforcing skeleton; and borosilicate coupling prepolymers improve the interfacial bonding between the organosilicon matrix and the mineral filler, making the ceramicized residue formed in a fire denser, more continuous, and less prone to pulverization and peeling.

[0019] Compared with the prior art, the present invention provides a flexible mineral-insulated fireproof power cable and its preparation method, which has the following beneficial effects: through the synergistic effect of the interface mineralized mica tape, the bidirectional spiral mineral fiber locking layer and the ceramicizable elastic mineral layer, the cable has both normal temperature flexibility and high temperature insulation integrity, which alleviates the contradiction between the insufficient flexibility of traditional rigid mineral-insulated cables and the loose interlayer of ordinary mica tape cables in fire.

[0020] A silicon-boron-aluminum oxide network layer is formed in situ on the surface of the mica tape. This network layer can be sintered and bridged with the glass phase and silicate minerals in the ceramicizable elastic mineral layer at high temperature, thereby improving the bonding strength between the flexible mineral insulation layer and the outer ceramicized layer and reducing the risk of delamination under flame impact or water spray impact.

[0021] The bidirectional helical mineral fiber interlocking layer forms a cross-restraint skeleton in the axial and circumferential directions of the cable, which can limit the crack propagation and peeling of the ceramicized residue and improve the insulation reliability of the cable when it is subjected to bending, vibration or external force disturbance in a fire.

[0022] The ceramicizable elastic mineral layer is made of a compound of flaky mica powder, acicular wollastonite, low-melting-point borosilicate glass powder, magnesium hydroxide, hexagonal boron nitride and borosilicate coupling prepolymer, which enables the material to maintain extrudability and flexibility at room temperature, and form a ceramicized barrier with certain mechanical strength and electrical insulation at high temperature. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the cross-sectional structure of a flexible mineral-insulated fireproof power cable according to the present invention.

[0024] Figure 2 This is a microscopic SEM image of the ceramic-like elastic mineral layer of the present invention. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Please see Figure 1 and Figure 2 This invention provides a technical solution for a flexible mineral-insulated fire-resistant power cable and its preparation method: Preparation Example 1: Preparation of Interfacial Mineralized Mica Strips 1. Raw material composition: 100 parts of phlogopite paper; 45 parts of alkali-free glass fiber base tape; 12 parts of tetraethyl silicate; 2 parts of triethyl borate; 0.8 parts of aluminum isopropoxide; 1.5 parts of vinyltriethoxysilane; 80 parts of anhydrous ethanol; 12 parts of deionized water; and appropriate amount of glacial acetic acid.

[0027] 2. Preparation method: S1. Composite phlogopite paper with alkali-free glass fiber base tape to obtain mica base tape; S2. Perform corona treatment on the mica base strip, with the corona power controlled at 1.5kW and the treatment speed at 20m / min, to form activation sites on the surface of the mica base strip; S3. Mix tetraethyl silicate, triethyl borate, aluminum isopropoxide, vinyltriethoxysilane, anhydrous ethanol and deionized water, add glacial acetic acid to adjust the pH to 4.0, and stir at 35°C for 2 hours to obtain a silicon-boron-aluminum composite sol. S4. The silicon-boron-aluminum composite sol is coated onto the surface of the activated mica substrate, the wet film thickness is controlled to be 12 μm, dried at 100℃ for 5 min, and then thermally densified at 160℃ for 20 min to obtain an interface mineralized mica belt with a silicon-boron-aluminum oxide network layer on the surface.

[0028] The silicon-boron-aluminum oxide network layer coating of the interface mineralized mica belt has a coating amount of 2.1 g / m², and the molar ratio of Si, B, and Al is 1:0.16:0.06.

[0029] Preparation Example 2: Preparation of Borosilicate Coupling Prepolymer 1. Raw material composition: 100 parts of hydroxyl-terminated polydimethylsiloxane; 6 parts of boric acid; 12 parts of vinyltriethoxysilane; 0.05 parts of dibutyltin dilaurate; 80 parts of toluene.

[0030] 2. Preparation method: Hydroxyl-terminated polydimethylsiloxane, boric acid, vinyltriethoxysilane, and toluene were added to a reaction vessel and heated to 105°C under nitrogen protection. Dibutyltin dilaurate was then added, and the mixture was stirred for 4 hours. Small molecule water generated during the reaction was removed using a water separator. After the reaction was completed, toluene and unreacted small molecules were removed under reduced pressure to obtain a borosilicate coupling prepolymer. The obtained prepolymer was a pale yellow, transparent, viscous liquid with a number-average molecular weight of approximately 1500.

[0031] This borosilicate coupling prepolymer contains Si-O, B-O and vinyl structures that can participate in vulcanization or interfacial bonding, which can improve the interfacial bonding between the silicone rubber matrix and mineral fillers such as mica powder, wollastonite, and glass powder.

[0032] Example 1: Preparation of Flexible Mineral Insulated Fireproof Power Cable 1. Cable structure: The conductor is a Class VI tin-plated soft copper conductor with a nominal cross-sectional area of ​​10 mm². The flexible mineral insulation layer uses the interfacial mineralized mica tape obtained in Preparation Example 1, with an overlap rate of 45% and a wrapping thickness of 0.55 mm; The bidirectional helical mineral fiber interlocking layer uses continuous basalt fiber bundles. The first fiber bundle has an angle of 45° with the cable axis, and the second fiber bundle has an angle of -45° with the cable axis. The thickness of the ceramicizable elastic mineral layer is 1.8 mm; The outer sheath is made of low-smoke, halogen-free, flame-retardant polyolefin with a thickness of 1.6mm.

[0033] 2. Composition of the ceramicizable elastic mineral compound: 100 parts of methyl vinyl silicone rubber; 10 parts of vinyl MQ silicone resin; 25 parts of fumed silica; 35 parts of flake mica powder; 18 parts of acicular wollastonite; 20 parts of low-melting-point borosilicate glass powder; 15 parts of magnesium hydroxide; 5 parts of hexagonal boron nitride; 3 parts of the borosilicate coupling prepolymer obtained in Preparation Example 2; 1.5 parts of 2,5-dimethyl-2,5-di-tert-butylperoxyhexane.

[0034] Among them, the flaky mica powder has a D50 of 12 μm and an aspect ratio of 45; the acicular wollastonite has an aspect ratio of 15; and the low-melting-point borosilicate glass powder has a softening point of 500℃ and a D50 of 4 μm.

[0035] 3. Preparation method: S1. Dry the flake mica powder, needle wollastonite, low melting point borosilicate glass powder, magnesium hydroxide and hexagonal boron nitride at 110℃ for 3 hours, and cool them to below 60℃ for later use. S2. The dried mineral filler is put into a high-speed mixer, 1.2 parts of vinyltriethoxysilane are added, and the mixture is treated at 90℃ and 1000rpm for 15min to obtain the modified mineral filler. S3. Add methyl vinyl silicone rubber, vinyl MQ silicone resin and fumed silica to a mixer and mix at 95°C for 10 min; then add modified mineral filler and borosilicate coupling prepolymer and continue mixing at 100°C for 12 min to obtain the base compound. S4. Cool the base rubber compound to 55°C, add the vulcanizing agent, and pass it through a two-roll mill 8 times to obtain a ceramic-like elastic mineral rubber compound. S5. Wrap the interface mineralized mica tape around the outside of the sixth-class tin-plated soft copper conductor with a 45% overlap rate to form a flexible mineral insulation layer. S6. A continuous bundle of basalt fibers is wrapped around the outside of the flexible mineral insulation layer in opposite spiral directions to form a bidirectional spiral mineral fiber lock layer. S7. A ceramic-compatible elastic mineral rubber compound is extruded onto the outside of the bidirectional spiral mineral fiber interlocking layer using a rubber extruder. The extruder barrel temperature is 60℃, 70℃, 80℃, and 85℃ respectively, and the die head temperature is 85℃. Subsequently, it is continuously vulcanized at 180℃ for 8 minutes to form an insulated cable core. S8. Extrude a low-smoke, halogen-free, flame-retardant polyolefin sheath onto the outside of the insulated cable core, cool and wind it up to obtain a flexible mineral-insulated fireproof power cable.

[0036] Example 2: Preparation of a flexible mineral-insulated fireproof power cable, which is carried out with reference to Example 1, except that: the bidirectional helical mineral fiber locking layer is made of high silica glass fiber bundles, the first fiber bundle has an angle of 40° with the cable axis, the second fiber bundle has an angle of -40° with the cable axis, and other conditions are the same as in Example 1.

[0037] Example 3: Preparation of a flexible mineral-insulated fireproof power cable, which is carried out in accordance with Example 1, except that: the low melting point borosilicate glass powder is adjusted from 20 parts to 26 parts, and the acicular wollastonite is adjusted from 18 parts to 22 parts, while other conditions are the same as in Example 1.

[0038] Example 4: Preparation of a flexible mineral-insulated fireproof power cable, which was carried out in accordance with Example 1, except that the coating amount of the silicon-boron-aluminum oxide network layer in the interface mineralized mica tape was adjusted to 3.5 g / m², and other conditions were the same as in Example 1.

[0039] Comparative Example 1: The preparation of a fireproof power cable was carried out in accordance with Example 1, except that: ordinary phlogopite mica tape was used instead of interface mineralized mica tape, and the surface of ordinary phlogopite mica tape did not contain a silicon-boron-aluminum oxide network layer, and other conditions were the same as in Example 1.

[0040] Comparative Example 2: The preparation of a fireproof power cable was carried out in accordance with Example 1, except that a bidirectional helical mineral fiber locking layer was not provided, while other conditions were the same as in Example 1.

[0041] Comparative Example 3: The preparation of a fireproof power cable was carried out in accordance with Example 1, except that borosilicate coupling prepolymer was not added to the ceramic elastic mineral layer, and other conditions were the same as in Example 1.

[0042] Comparative Example 4: The preparation of a fireproof power cable was carried out in accordance with Example 1, except that low-melting-point borosilicate glass powder was not added to the ceramic elastic mineral layer, and other conditions were the same as in Example 1.

[0043] Performance testing 1. Bending performance: Repeatedly bend the cable according to the specified multiples of its outer diameter and observe whether the insulation layer cracks.

[0044] 2. Insulation resistance at room temperature: Test the insulation resistance of the cable at 20℃.

[0045] 3. Fire resistance integrity: Referring to the general test method for fire-resistant cables, the rated voltage is applied under a flame at 950℃ and the cable is continuously burned. Record whether breakdown occurs and the duration of energization.

[0046] 4. Compressive strength of ceramic residue: Take a sample of ceramic elastic mineral layer, calcine it at 950℃ for 90 min, and test the compressive strength of the residue after cooling.

[0047] 5. Insulation integrity after water spraying impact: After high-temperature burning, water spraying impact is performed to observe whether the insulation layer peels off over a large area and to test whether the insulation is maintained.

[0048] For detailed test results, please refer to Tables 1 and 2.

[0049] Table 1

[0050] Table 2

[0051] As shown in Table 1, the embodiment exhibits superior overall performance, maintaining normal temperature flexibility and high insulation resistance while preserving longer circuit integrity under 950°C flame conditions, and maintaining a high fire-resistant energizing time even after bending pretreatment. This demonstrates an effective synergy between the interface mineralized mica tape, the bidirectional helical mineral fiber interlocking layer, and the ceramicizable elastic mineral layer in this invention.

[0052] In Example 1, using a moderate amount of low-melting-point borosilicate glass powder, acicular wollastonite, and a bidirectional spiral mineral fiber interlocking layer, the cable showed no cracks or delamination after bending at room temperature, and formed a relatively complete ceramicized insulation barrier in a fire. In Example 3, increasing the content of low-melting-point borosilicate glass powder and acicular wollastonite further improved the compressive strength of the ceramicized residue, indicating that the softening sintering of the glass phase and the reinforcement of acicular minerals promote the strength of the residue. In Example 4, increasing the coating amount of the silicon-boron-aluminum oxide network layer of the interface mineralized mica tape resulted in no breakdown after spray impact, indicating that the mineralized interface can improve the bonding stability between the mica insulation layer and the outer ceramicized layer.

[0053] In contrast, Comparative Example 1 used ordinary phlogopite mica tape, lacking a silicon-boron-aluminum oxide network layer. In the fire, the bond between the mica tape and the outer ceramicized layer was insufficient, resulting in localized breakdown after spraying impact. Comparative Example 2 lacked a bidirectional helical mineral fiber interlocking layer, and the ceramicized residue lacked continuous skeletal constraint, making it prone to cracking and detachment after flame and bending disturbance. Comparative Example 3 did not use borosilicate coupling prepolymer, leading to decreased interfacial bonding between the mineral filler and the silicone rubber matrix, resulting in localized pulverization of the residue after burning. Comparative Example 4 did not add low-melting-point borosilicate glass powder, making it difficult to form effective sintering connections between the mineral fillers. The ceramicized residue was loose, and the fire-resistant electrical conduction time was significantly shortened. Comparative Example 5 used a unidirectional helical mineral fiber structure, which, while providing some reinforcement, could not simultaneously limit axial and circumferential crack propagation. Its fire resistance after bending and insulation retention after spraying impact were both weaker than the examples.

[0054] The above results demonstrate that the present invention provides a high-temperature sintering active interface through interface mineralized mica tape, a continuous crack-resistant skeleton through a bidirectional spiral mineral fiber locking layer, and a high-temperature ceramicized insulation barrier through a ceramicizable elastic mineral layer. The combined effect of these three elements is the key to achieving flexible mineral-insulated fireproof power cables that combine flexibility, fire-resistant line integrity, and ceramicized residual layer stability.

[0055] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A flexible mineral-insulated fire-resistant power cable, characterized in that: The cable includes at least one insulated cable core and an outer sheath covering the outside of the insulated cable core, characterized in that the insulated cable core includes a conductor and a flexible mineral insulation layer, a bidirectional helical mineral fiber locking layer and a ceramicizable elastic mineral layer disposed sequentially from the inside to the outside of the conductor. The flexible mineral insulation layer includes an interface mineralized mica tape wrapped around the outside of the conductor. The interface mineralized mica tape is a composite mica tape in which a silicon-boron-alumina network layer is formed in situ on the surface of phlogopite paper and alkali-free glass fiber base tape. A portion of the bidirectional helical mineral fiber locking layer is embedded in the inner surface of the ceramicizable elastic mineral layer; The ceramicizable elastic mineral layer is prepared from the following raw materials in parts by weight: 100 parts methyl vinyl silicone rubber, 5-15 parts vinyl MQ silicone resin, 18-35 parts fumed silica, 25-45 parts flaky mica powder, 10-25 parts acicular wollastonite, 12-28 parts low melting point borosilicate glass powder with a softening point of 430-560℃, 8-25 parts magnesium hydroxide, 2-8 parts hexagonal boron nitride, 1-6 parts borosilicate coupling prepolymer, and 0.8-3 parts vulcanizing agent.

2. The flexible mineral-insulated fire-resistant power cable according to claim 1, characterized in that: The interface mineralized mica tape is spirally wrapped around the outside of the conductor with an overlap rate of 30%-55%. The thickness of the flexible mineral insulation layer is 0.25-1.20 mm, and the thickness of the ceramicizable elastic mineral layer is 0.8-4.5 mm.

3. The flexible mineral-insulated fire-resistant power cable according to claim 1, characterized in that: The coating amount of the silicon-boron-aluminum oxide network layer is 0.8-4.0 g / m², and the molar ratio of Si, B and Al in the silicon-boron-aluminum oxide network layer is 1:0.08-0.25:0.02-0.

10.

4. The flexible mineral-insulated fire-resistant power cable according to claim 1, characterized in that: The surface of the interface mineralized mica strip also contains a vinyl silane coupling layer or an epoxy silane coupling layer, which is condensed and connected to the silicon-boron-aluminum oxide network layer.

5. A flexible mineral-insulated fire-resistant power cable according to claim 1, characterized in that: The bidirectional helical mineral fiber locking layer is formed by the cross-wrapping of a first mineral fiber bundle and a second mineral fiber bundle. The angle between the first mineral fiber bundle and the cable axis is 35° to 55°, and the angle between the second mineral fiber bundle and the cable axis is -35° to -55°. The first mineral fiber bundle and the second mineral fiber bundle are each independently selected from basalt continuous fiber bundles, alumina silicate continuous fiber bundles, or high silica glass fiber bundles.

6. A flexible mineral-insulated fire-resistant power cable according to claim 1, characterized in that: The flaky mica powder has a D50 of 5-20 μm and an aspect ratio of 20-80; the acicular wollastonite has an aspect ratio of 8-25; and the low-melting-point borosilicate glass powder has a D50 of 1.5-8 μm.

7. A flexible mineral-insulated fire-resistant power cable according to claim 1, characterized in that: The borosilicate coupling prepolymer is obtained by dehydration condensation of hydroxyl-containing polydimethylsiloxane, boric acid or borate ester, and vinyltriethoxysilane at 80-120°C, and has a number-average molecular weight of 800-3000.

8. A flexible mineral-insulated fire-resistant power cable according to claim 1, characterized in that: The conductor is a Class 5 or Class 6 soft copper conductor, and the outer surface of the conductor is provided with a tin-plated layer or a silane-containing anti-oxidation interface layer; the outer sheath is a low-smoke halogen-free flame-retardant polyolefin sheath, a ceramicizable silicone rubber sheath, or a double-layer sheath formed by combining a low-smoke halogen-free flame-retardant polyolefin inner sheath and a ceramicizable silicone rubber outer sheath.

9. A method for preparing a flexible mineral-insulated fire-resistant power cable according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Preparation of interfacial mineralized mica tape: Plasma activation or corona activation is performed on phlogopite paper and alkali-free glass fiber substrate. Sol containing silicon source, boron source and aluminum source is coated on the surface of activated phlogopite paper and alkali-free glass fiber substrate. After drying and thermal densification treatment, interfacial mineralized mica tape with silicon-boron-aluminum oxide network layer on the surface is obtained. S2. Preparation of ceramic-type elastic mineral rubber compound: Flake mica powder, needle-shaped wollastonite, low-melting-point borosilicate glass powder, magnesium hydroxide and hexagonal boron nitride are dried and surface-treated with silane to obtain modified mineral filler; methyl vinyl silicone rubber, vinyl MQ silicone resin, fumed silica, modified mineral filler and borosilicate coupling prepolymer are mixed and then vulcanizing agent is added and mixed to obtain ceramic-type elastic mineral rubber compound; S3. Cable cabling: The interface mineralized mica tape is wrapped around the outside of the conductor to form a flexible mineral insulation layer. Mineral fiber bundles are wrapped around the outside of the flexible mineral insulation layer in opposite spiral directions to form a bidirectional spiral mineral fiber lock layer. Then, the ceramic elastic mineral rubber is extruded and vulcanized to form an insulated cable core. S4. Sheath Forming: An outer sheath is extruded onto the outside of one or more insulated cable cores, cooled, and wound up to obtain the flexible mineral-insulated fireproof power cable.

10. The preparation method according to claim 9, characterized in that, In step S1, the sol containing silicon, boron and aluminum sources is prepared by mixing tetraethyl silicate, triethyl borate or boric acid, aluminum isopropoxide, vinyltriethoxysilane, ethanol and deionized water. The pH of the sol is 3.0-5.0, the drying temperature is 80-120℃, the thermal densification temperature is 130-180℃, and the treatment time is 10-40 min. In step S2, the mixing includes a first stage and a second stage. In the first stage, the mixing is carried out at 80-110℃ for 8-20 minutes. In the second stage, the vulcanizing agent is added at 40-65℃ and the mixture is passed through the vulcanizing agent 5-12 times. In step S3, the extrusion temperature of the ceramicizable elastic mineral rubber is 55-95℃, the vulcanization temperature is 150-200℃, and the vulcanization time is 3-15min.

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