Flexible mineral insulated fireproof cable

Abstract

The invention discloses a flexible mineral insulated fireproof cable, and belongs to the technical field of fireproof cables, the flexible mineral insulated fireproof cable comprises four parallel copper conductors, a silicone rubber mineral insulating layer is wrapped outside the copper conductors, a mica tape wrapping layer is wrapped outside the silicone rubber mineral insulating layer, and a filling layer is arranged outside the mica tape wrapping layer. The outer side of the filling layer is wrapped by an armor layer, and an outer sheath is arranged outside the armor layer. According to the invention, the brucite mineral fibers are modified to prepare the silicone rubber mineral insulating layer, so that the mechanical property of the cable is improved, the structural damage caused by stress concentration is avoided, the structural integrity of the cable is guaranteed, the flexibility of the cable is enhanced, and the cable is not easy to break or damage the internal structure in the bending process; the modified brucite fiber can effectively resist abrasion, the service life of the cable is prolonged, the modified brucite fiber has better compatibility with the silicone rubber and the filler, and the cable added with the modified brucite fiber has excellent fireproof and flame-retardant properties.

Description

Technical Field

[0001] The invention belongs to the technical field of fireproof cables, and in particular relates to a flexible mineral insulated fireproof cable. Background Art

[0002] Mineral insulated fireproof cables, as key materials in the field of power transmission and distribution, play a vital role in modern buildings, industrial facilities and various places with strict requirements on fire safety. Its main function is to maintain the integrity and normal power supply of the line in extreme situations such as fire, and provide reliable power guarantee for personnel evacuation, fire rescue and continuous operation of important equipment.

[0003] At present, in the preparation process of mineral insulated fire-resistant cables, the method of directly adding inorganic mineral flame retardant materials is generally adopted. Due to the large difference in the physical and chemical properties between inorganic mineral flame retardant materials and cable matrix materials, it is difficult to evenly disperse them in the matrix during processing, and agglomeration is prone to occur. Not only does it lead to the unevenness of the internal structure of the cable, affecting the overall performance of the cable, but it may also form weak points in local areas, reducing the fire resistance and service life of the cable. Secondly, inorganic mineral flame retardant materials will migrate to the outside of the layer where they are located. During the long-term use of the cable, affected by factors such as temperature changes, electric field effects, and mechanical vibrations, inorganic mineral flame retardant materials will gradually migrate from their original location to the outer layer of the cable. This migration phenomenon will change the distribution of flame retardant materials inside the cable, destroy the originally designed flame retardant structure, and thus weaken the fire resistance of the cable. Summary of the invention

[0004] In view of the above situation, in order to overcome the defects of the prior art, the present invention modifies the brucite mineral fiber and applies it to the preparation of the silicone rubber mineral insulation layer, thereby effectively solving the problem of uneven dispersion and migration of inorganic mineral flame retardant materials in the cable matrix, and improving the mechanical properties, insulation properties and fire retardant properties of the cable.

[0005] In order to achieve the above-mentioned purpose, the following technical scheme is adopted: the present invention provides a flexible mineral insulated fire-resistant cable, comprising four parallel copper conductors, the outer side of the copper conductor is wrapped with a silicone rubber mineral insulation layer, the outer side of the silicone rubber mineral insulation layer is wrapped with a mica tape wrapping layer, the outer side of the mica tape wrapping layer is provided with a filling layer, the outer side of the filling layer is wrapped with an armor layer, and the outer side of the armor layer is provided with an outer sheath.

[0006] The silicone rubber mineral insulation layer comprises, by weight, 60-80 parts of silicone rubber, 2-5 parts of vulcanizing agent, 30-40 parts of filler and 8-12 parts of modified brucite fiber.

[0007] Wherein, the modified brucite fiber is prepared by the following steps: S1. Dispersing brucite fiber in 0.1-0.5 mol / L acetic acid solution, reacting at 50°C for 2h to obtain a brucite fiber dispersion, dissolving (2,6-dichlorobenzenesulfonylamino)-acetic acid in DMF to obtain an intercalation modification solution, slowly dropping the intercalation modification solution into the brucite fiber dispersion, stirring at 80°C for 5-8h, and then stirring at room temperature for 24-48h. After the reaction is completed, filtering, washing the filter cake 3 times with DMF, and then washing the filter cake 3 times with deionized water, and vacuum drying at 80°C for 12-18h to obtain intercalation modified brucite fiber; S2. 3-mercaptopropionic acid was added to anhydrous ethanol, and the intercalated modified brucite fiber was added and stirred for 15 minutes, and then a photoinitiator and divinyl-terminated polydimethylsiloxane were added, and the mixture was irradiated with 365nm ultraviolet light, and reacted at room temperature for 3-6h, filtered, and the filter cake was washed with toluene for 3 times, and vacuum dried at 80°C for 12-18h to obtain the grafted silane intercalated modified brucite fiber; S3. Add the grafted silane intercalation modified brucite fiber to anhydrous ethanol, stir to make it evenly dispersed, then slowly add diglycerol borate, continue stirring for 15 minutes, then drop triethylamine, react at 70°C for 3-5 hours, after the reaction is completed, cool the reaction solution to room temperature, filter, wash the filter cake three times with anhydrous ethanol, and dry it in a vacuum drying oven at 50°C for 24-36 hours to obtain the modified brucite fiber product.

[0008] Preferably, in step S1, the mass ratio of brucite fiber to acetic acid solution is 1:10-15.

[0009] Preferably, in step S1, the mass ratio of (2,6-dichlorobenzenesulfonylamino)-acetic acid to DMF is 1:8-10.

[0010] Preferably, in step S1, the mass ratio of the intercalation modification solution to the brucite fiber dispersion is 1:5-8.

[0011] Preferably, in step S2, the mass ratio of 3-mercaptopropionic acid, anhydrous ethanol, intercalated modified brucite fiber, photoinitiator and divinyl-terminated polydimethylsiloxane is 1:20-35:5-10:0.05-0.2:3-5.

[0012] Preferably, in step S3, the mass ratio of anhydrous ethanol, grafted silane intercalated modified brucite fiber, boric acid diglyceride and triethylamine is 30:5-10:1-5:1-3.

[0013] Preferably, the photoinitiator is one of Irgacure 2959, Irgacure 184, Irgacure 369, Irgacure 500 and Irgacure651.

[0014] Preferably, the molecular weight of the silicone rubber is 300,000-450,000.

[0015] Preferably, the vulcanizing agent is a combination of one or more of tert-butyl perbenzoate, di-tert-butyl peroxide, bis(2,4-dimethylbenzene) and bis(2,5-dimethylbenzene).

[0016] Preferably, the filler is a combination of white carbon black and calcium carbonate in a mass ratio of 5:1-3.

[0017] Preferably, the specific surface area of ​​the white carbon black is 150-200m 2 / g.

[0018] Preferably, the filling layer is fire-resistant mineral wool; the armor layer is galvanized steel strip; and the outer sheath is low-smoke halogen-free cross-linked polyethylene material.

[0019] The beneficial effects of the present invention are: (1) The present invention improves the compression, flexural and abrasion resistance of the cable by modifying the brucite mineral fiber to form a silicone rubber mineral insulation layer, avoids structural damage caused by stress concentration, thereby ensuring the structural integrity of the cable in a complex environment, and enhancing the flexibility of the cable, making it less likely to break or have internal structural damage during bending. The physical properties of the modified brucite fiber can effectively resist wear and tear, extend the service life of the cable, and the modified brucite fiber has better compatibility with silicone rubber and filler. The cable with the modified brucite fiber has excellent fire retardancy, and the cable can form a stable thermal insulation layer at high temperature to prevent rapid heat transfer and slow down the combustion rate. (2) Since (2,6-dichlorobenzenesulfonylamino)-acetic acid is difficult to react with brucite fiber, the present invention first reacts brucite fiber with acetic acid, and then replaces acetic acid with (2,6-dichlorobenzenesulfonylamino)-acetic acid based on the principle of strong acid replacing weak acid, thereby intercalating the brucite fiber. The intercalation treatment increases the brucite interlayer spacing, making the internal structure of the brucite fiber more loose and porous, thereby providing more space for heat absorption and dispersion; (3) The present invention introduces divinyl-terminated polydimethylsiloxane into the surface of brucite through a mercapto-ene click reaction, and connects brucite with diglycerol borate through the divinyl-terminated polydimethylsiloxane as a bridge. The prepared modified brucite fiber has a synergistic flame retardant effect of multiple elements including silicon, nitrogen, sulfur and boron. Silicon can form a glassy protective film at high temperature, nitrogen can decompose to produce non-flammable gas, sulfur can generate sulfur-containing compounds during combustion, promote the formation of a carbon layer, and enhance the stability of the carbon layer. Boron can melt at a relatively low temperature and cover the surface of the cable, thereby playing a role in heat insulation and oxygen isolation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic structural diagram of a flexible mineral insulated fireproof cable of the present invention; Figure 2 The mechanical properties test results of the silicone rubber mineral insulation layer in the flexible mineral insulated fire-resistant cable of the present invention; Figure 3 The insulation performance test results of the silicone rubber mineral insulation layer in the flexible mineral insulated fire-resistant cable of the present invention; Figure 4 The fire retardant performance test results of a flexible mineral insulated fire retardant cable of the present invention are shown in FIG.

[0021] Legend: 1. Copper conductor; 2. Silicone rubber mineral insulation layer; 3. Mica tape wrapping layer; 4. Filling layer; 5. Armor layer; 6. Outer sheath.

[0022] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0024] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein may be applied to the present invention. The preferred implementation methods and materials described herein are for demonstration purposes only and are not intended to limit the content of this application.

[0025] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are purchased from commercial channels unless otherwise specified. Example 1

[0026] A flexible mineral insulated fireproof cable comprises four parallel copper conductors, the outer side of the copper conductor is wrapped with a silicone rubber mineral insulation layer, the outer side of the silicone rubber mineral insulation layer is wrapped with a mica tape wrapping layer, the outer side of the mica tape wrapping layer is provided with a filling layer, the outer side of the filling layer is wrapped with an armor layer, and the outer side of the armor layer is provided with an outer sheath.

[0027] The silicone rubber mineral insulation layer comprises, by weight, 60 parts of silicone rubber, 2 parts of vulcanizing agent, 30 parts of filler and 8 parts of modified brucite fiber.

[0028] The modified brucite fiber is prepared by the following steps: S1. Disperse brucite fiber in 0.1 mol / L acetic acid solution, the mass ratio of brucite fiber to acetic acid solution is 1:10, react at 50°C for 2h to obtain brucite fiber dispersion, dissolve (2,6-dichlorobenzenesulfonylamino)-acetic acid in DMF, the mass ratio of (2,6-dichlorobenzenesulfonylamino)-acetic acid to DMF is 1:8, obtain intercalation modification solution, slowly dropwise add the intercalation modification solution to the brucite fiber dispersion, the mass ratio of intercalation modification solution to brucite fiber dispersion is 1:5, stir at 80°C for 5h, then stir at room temperature for 24h, filter after the reaction, wash the filter cake 3 times with DMF, then wash the filter cake 3 times with deionized water, and vacuum dry at 80°C for 12h to obtain intercalation modified brucite fiber; S2. 3-mercaptopropionic acid was added to anhydrous ethanol, the mass ratio of 3-mercaptopropionic acid, anhydrous ethanol, intercalated modified brucite fiber, photoinitiator and divinyl-terminated polydimethylsiloxane was 1:20:5:0.05:3, the intercalated modified brucite fiber was added and stirred for 15 minutes, and then the photoinitiator Irgacure 2959 and divinyl-terminated polydimethylsiloxane were added, irradiated with 365nm ultraviolet light, reacted at room temperature for 3h, filtered, and the filter cake was washed with toluene for 3 times, and vacuum dried at 80℃ for 12h to obtain grafted silane intercalated modified brucite fiber; S3. Add grafted silane intercalation modified brucite fiber to anhydrous ethanol, the mass ratio of anhydrous ethanol, grafted silane intercalation modified brucite fiber, diglycerol borate and triethylamine is 30:5:1:1, stir to make it evenly dispersed, then slowly add diglycerol borate, continue stirring for 15 minutes, then add triethylamine dropwise, react at 70°C for 3 hours, after the reaction is completed, cool the reaction solution to room temperature, filter, wash the filter cake three times with anhydrous ethanol, and dry it in a vacuum drying oven at 50°C for 24 hours to obtain the modified brucite fiber product.

[0029] The molecular weight of the silicone rubber is 300,000, the vulcanizing agent is tert-butyl perbenzoate, the filler is a combination of white carbon black and calcium carbonate in a mass ratio of 5:1, and the specific surface area of ​​the white carbon black is 150 m² / g; the filling layer is fire-resistant mineral wool; the armor layer is galvanized steel strip; and the outer sheath is a low-smoke halogen-free cross-linked polyethylene material. Example 2

[0030] A flexible mineral insulated fireproof cable comprises four parallel copper conductors, the outer side of the copper conductor is wrapped with a silicone rubber mineral insulation layer, the outer side of the silicone rubber mineral insulation layer is wrapped with a mica tape wrapping layer, the outer side of the mica tape wrapping layer is provided with a filling layer, the outer side of the filling layer is wrapped with an armor layer, and the outer side of the armor layer is provided with an outer sheath.

[0031] The silicone rubber mineral insulation layer comprises, by weight, 80 parts of silicone rubber, 5 parts of vulcanizing agent, 40 parts of filler and 12 parts of modified brucite fiber.

[0032] The modified brucite fiber is prepared by the following steps: S1. Disperse brucite fiber in 0.5 mol / L acetic acid solution, the mass ratio of brucite fiber to acetic acid solution is 1:15, react at 50°C for 2h to obtain brucite fiber dispersion, dissolve (2,6-dichlorobenzenesulfonylamino)-acetic acid in DMF, the mass ratio of (2,6-dichlorobenzenesulfonylamino)-acetic acid to DMF is 1:10, obtain intercalation modification solution, slowly dropwise add the intercalation modification solution to the brucite fiber dispersion, the mass ratio of intercalation modification solution to brucite fiber dispersion is 1:8, stir at 80°C for 8h, then stir at room temperature for 48h, filter after the reaction, wash the filter cake 3 times with DMF, then wash the filter cake 3 times with deionized water, and vacuum dry at 80°C for 18h to obtain intercalation modified brucite fiber; S2. 3-mercaptopropionic acid was added to anhydrous ethanol, the mass ratio of 3-mercaptopropionic acid, anhydrous ethanol, intercalated modified brucite fiber, photoinitiator and divinyl-terminated polydimethylsiloxane was 1:35:10:0.2:5, the intercalated modified brucite fiber was added and stirred for 15 minutes, and then the photoinitiator Irgacure 651 and divinyl-terminated polydimethylsiloxane were added, irradiated with 365nm ultraviolet light, reacted at room temperature for 6h, filtered, and the filter cake was washed 3 times with toluene, and vacuum dried at 80℃ for 18h to obtain grafted silane intercalated modified brucite fiber; S3. Add grafted silane intercalation modified brucite fiber to anhydrous ethanol, the mass ratio of anhydrous ethanol, grafted silane intercalation modified brucite fiber, diglycerol borate and triethylamine is 30:10:5:3, stir to make it evenly dispersed, then slowly add diglycerol borate, continue stirring for 15 minutes, then add triethylamine dropwise, react at 70°C for 5 hours, after the reaction is completed, cool the reaction solution to room temperature, filter, wash the filter cake 3 times with anhydrous ethanol, and dry it in a vacuum drying oven at 50°C for 36 hours to obtain the modified brucite fiber product.

[0033] The molecular weight of the silicone rubber is 450,000; the vulcanizing agent is a combination of di-tert-butyl peroxide, bis(2,4-dimethyl-1-nitropropene) and bis(2,5-dimethyl-1-nitropropene) in a mass ratio of 1:1:2; the filler is a combination of white carbon black and calcium carbonate in a mass ratio of 5:3, and the specific surface area of ​​the white carbon black is 200 m² / g; the filling layer is refractory mineral wool; the armor layer is galvanized steel strip; and the outer sheath is a low-smoke halogen-free cross-linked polyethylene material. Example 3

[0034] A flexible mineral insulated fireproof cable comprises four parallel copper conductors, the outer side of the copper conductor is wrapped with a silicone rubber mineral insulation layer, the outer side of the silicone rubber mineral insulation layer is wrapped with a mica tape wrapping layer, the outer side of the mica tape wrapping layer is provided with a filling layer, the outer side of the filling layer is wrapped with an armor layer, and the outer side of the armor layer is provided with an outer sheath.

[0035] The silicone rubber mineral insulation layer comprises, by weight, 70 parts of silicone rubber, 3.5 parts of vulcanizing agent, 35 parts of filler and 10 parts of modified brucite fiber.

[0036] The modified brucite fiber is prepared by the following steps: S1. Disperse brucite fiber in 0.3 mol / L acetic acid solution, the mass ratio of brucite fiber to acetic acid solution is 1:12.5, react at 50°C for 2h to obtain brucite fiber dispersion, dissolve (2,6-dichlorobenzenesulfonylamino)-acetic acid in DMF, the mass ratio of (2,6-dichlorobenzenesulfonylamino)-acetic acid to DMF is 1:9, obtain intercalation modification solution, slowly dropwise add the intercalation modification solution to the brucite fiber dispersion, the mass ratio of intercalation modification solution to brucite fiber dispersion is 1:6.5, stir at 80°C for 6.5h, then stir at room temperature for 36h, filter after the reaction, wash the filter cake 3 times with DMF, then wash the filter cake 3 times with deionized water, and vacuum dry at 80°C for 15h to obtain intercalation modified brucite fiber; S2. 3-mercaptopropionic acid was added to anhydrous ethanol, the mass ratio of 3-mercaptopropionic acid, anhydrous ethanol, intercalated modified brucite fiber, photoinitiator and divinyl-terminated polydimethylsiloxane was 1:27.5:7.5:0.125:4, the intercalated modified brucite fiber was added and stirred for 15 minutes, and then the photoinitiator Irgacure 369 and divinyl-terminated polydimethylsiloxane were added, irradiated with 365nm ultraviolet light, reacted at room temperature for 4.5h, filtered, and the filter cake was washed with toluene for 3 times, and vacuum dried at 80℃ for 15h to obtain grafted silane intercalated modified brucite fiber; S3. Add grafted silane intercalation modified brucite fiber to anhydrous ethanol, the mass ratio of anhydrous ethanol, grafted silane intercalation modified brucite fiber, diglycerol borate and triethylamine is 30:7.5:3:2, stir to make it evenly dispersed, then slowly add diglycerol borate, continue stirring for 15 minutes, then add triethylamine dropwise, react at 70°C for 4 hours, after the reaction is completed, cool the reaction solution to room temperature, filter, wash the filter cake 3 times with anhydrous ethanol, and dry it in a vacuum drying oven at 50°C for 30 hours to obtain the modified brucite fiber product.

[0037] The molecular weight of the silicone rubber is 380,000; the vulcanizing agent is a combination of tert-butyl perbenzoate and di-tert-butyl peroxide in a mass ratio of 1:2; the filler is a combination of white carbon black and calcium carbonate in a mass ratio of 5:2, and the specific surface area of ​​the white carbon black is 175 m² / g.

[0038] Comparative Example 1 In this comparative example, brucite fiber is dispersed in deionized water with an equal amount of acetic acid solution, and reacted at 50° C. for 2 h to obtain a brucite fiber dispersion. The remaining steps are the same as those in Example 3.

[0039] Comparative Example 2 This comparative example uses an equal amount of intercalated modified brucite fiber to replace the modified brucite fiber product, and the rest is the same as Example 3.

[0040] Comparative Example 3 In this comparative example, an equal amount of grafted silane intercalated modified brucite fiber is used to replace the modified brucite fiber product, and the rest is the same as Example 3.

[0041] Results Analysis (1) Cable performance test The flexible mineral insulated fire resistant cables prepared in the embodiments and comparative examples were subjected to the following tests: Mechanical properties test: The tensile strength of the silicone rubber mineral insulation layer in each embodiment and comparative example before and after aging was tested according to the measurement method in GB / T 5013-2008. The aging conditions were: constant temperature at 110°C for 7 days. The results are shown in Table 1. Figure 2 .

[0042] Insulation performance test: The silicone rubber mineral insulation layer in each embodiment and comparative example was cut into standard strips, and then the resistivity of the strips was tested according to the measurement method in GB / T 1692-2008. The test voltage was 1000V. The results are shown in Figure 3 .

[0043] Depend on Figure 2 It can be seen that the silicone rubber mineral insulation layer of Examples 1-3 has high tensile strength before and after aging and shows good aging resistance. The brucite fiber after multi-step modification of the present invention may have better toughness and strength. It is more tightly combined with the silicone rubber matrix to form a more integrated structure. When subjected to tensile stress, it can effectively disperse stress and prevent stress concentration, so that the entire insulation layer shows a higher bearing capacity. The modified brucite fiber has better compatibility with silicone rubber and filler, which forms a more uniform and continuous structure in the insulation layer, reducing weak points that may be generated due to incompatibility between materials. Weak points are easy to become the starting point of cracks when stretched, and good compatibility ensures the integrity of the insulation layer structure, thereby improving the tensile strength.

[0044] Depend on Figure 3 It can be seen that the strips made of the silicone rubber mineral insulation layer of Examples 1-3 have high resistivity and show excellent insulation. The good compatibility of the modified brucite fiber with silicone rubber, filler and other components in the insulation layer, as well as its special microstructure and chemical composition, make it difficult for charges to be conducted therein. Therefore, the silicone rubber mineral insulation layer in Examples 1-3 has better insulation.

[0045] (2) Cable fire retardant performance test The flexible mineral insulated fire-resistant cables prepared in each embodiment and comparative example were tested for their fire retardant properties: Oxygen index measurement: The cables prepared in each embodiment and comparative example were subjected to oxygen index measurement according to the standard of GB / T 2406.2-2009. The results are shown in Figure 4 .

[0046] from Figure 4 It can be seen from the results that the oxygen index of the cables of Examples 1-3 is higher than that of the comparative example, which indicates that the cables prepared by the present invention have more excellent fire retardant properties. The main reason is that the modified brucite fiber in the examples plays an important role. In the preparation process, the synergistic flame retardant effect of multiple elements is introduced through multi-step modification. The silicon element can form a glassy protective film at high temperature to effectively block heat and oxygen; the nitrogen element decomposes to produce non-combustible gas, which can dilute the oxygen concentration in the combustion environment; the sulfur element promotes the formation of the carbon layer and enhances the stability of the carbon layer; the boron element melts at a lower temperature and covers the cable surface, which plays a role in heat insulation and oxygen isolation.

[0047] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0048] The present invention and its implementation methods are described above, which is not restrictive. The drawings are only one of the implementation methods of the present invention, and the actual application is not limited thereto. In short, if ordinary technicians in the field are inspired by it and design methods and embodiments similar to the technical solution without creativity without departing from the purpose of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A flexible mineral insulated fire-resistant cable, characterized in that: It comprises four parallel copper conductors, the outer side of the copper conductor is wrapped with a silicone rubber mineral insulation layer, the outer side of the silicone rubber mineral insulation layer is wrapped with a mica tape wrapping layer, the outer side of the mica tape wrapping layer is provided with a filling layer, the outer side of the filling layer is wrapped with an armor layer, and the outer side of the armor layer is provided with an outer sheath; The silicone rubber mineral insulation layer comprises, by weight, 60-80 parts of silicone rubber, 2-5 parts of vulcanizing agent, 30-40 parts of filler and 8-12 parts of modified brucite fiber; The modified brucite fiber is prepared by the following steps: S1. Dispersing brucite fiber in 0.1-0.5 mol / L acetic acid solution, reacting at 50°C for 2h to obtain a brucite fiber dispersion, dissolving (2,6-dichlorobenzenesulfonylamino)-acetic acid in DMF to obtain an intercalation modification solution, slowly dropping the intercalation modification solution into the brucite fiber dispersion, stirring at 80°C for 5-8h, and then stirring at room temperature for 24-48h. After the reaction is completed, filtering, washing the filter cake 3 times with DMF, and then washing the filter cake 3 times with deionized water, and vacuum drying at 80°C for 12-18h to obtain intercalation modified brucite fiber; S2. 3-mercaptopropionic acid was added to anhydrous ethanol, and the intercalated modified brucite fiber was added and stirred for 15 minutes, and then a photoinitiator and divinyl-terminated polydimethylsiloxane were added, and the mixture was irradiated with 365 nm ultraviolet light, and reacted at room temperature for 3-6 hours, filtered, and the filter cake was washed with toluene for 3 times, and vacuum dried at 80° C. for 12-18 hours to obtain the grafted silane intercalated modified brucite fiber; S3. Add the grafted silane intercalation modified brucite fiber to anhydrous ethanol, stir to make it evenly dispersed, then slowly add diglycerol borate, continue stirring for 15 minutes, then drop triethylamine, react at 70°C for 3-5 hours, after the reaction is completed, cool the reaction solution to room temperature, filter, wash the filter cake three times with anhydrous ethanol, and dry it in a vacuum drying oven at 50°C for 24-36 hours to obtain the modified brucite fiber product.

2. A flexible mineral insulated fire resistant cable according to claim 1, characterized in that: In step S1, the mass ratio of brucite fiber to acetic acid solution is 1:10-15; In step S1, the mass ratio of (2,6-dichlorobenzenesulfonylamino)-acetic acid to DMF is 1:8-10; In the step S1, the mass ratio of the intercalation modification solution to the brucite fiber dispersion is 1:5-8.

3. A flexible mineral insulated fire resistant cable according to claim 2, characterized in that: In the step S2, the mass ratio of 3-mercaptopropionic acid, anhydrous ethanol, intercalated modified brucite fiber, photoinitiator and divinyl-terminated polydimethylsiloxane is 1:20-35:5-10:0.05-0.2:3-5.

4. A flexible mineral insulated fire resistant cable according to claim 3, characterized in that: In the step S3, the mass ratio of anhydrous ethanol, grafted silane intercalation modified brucite fiber, boric acid diglyceride and triethylamine is 30:5-10:1-5:1-3.

5. A flexible mineral insulated fire resistant cable according to claim 4, characterized in that: The photoinitiator is one of Irgacure 2959, Irgacure 184, Irgacure 369, Irgacure 500 and Irgacure 651.

6. A flexible mineral insulated fire resistant cable according to claim 5, characterized in that: The molecular weight of the silicone rubber is 300,000-450,000.

7. A flexible mineral insulated fire resistant cable according to claim 6, characterized in that: The vulcanizing agent is a combination of one or more of tert-butyl perbenzoate, di-tert-butyl peroxide, bis(2,4-dimethylbenzene) and bis(2,5-dimethylbenzene).

8. A flexible mineral insulated fire resistant cable according to claim 7, characterized in that: The filler is a combination of white carbon black and calcium carbonate in a mass ratio of 5:1-3.

9. A flexible mineral insulated fire resistant cable according to claim 8, characterized in that: The specific surface area of ​​the white carbon black is 150-200m 2 / g.

10. A flexible mineral insulated fire resistant cable according to claim 9, characterized in that: The filling layer is fire-resistant mineral wool; the armor layer is galvanized steel strip; and the outer sheath is low-smoke halogen-free cross-linked polyethylene material.

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