Ultrahigh-temperature-resistant mineral insulated fireproof cable and preparation method thereof

Abstract

The invention belongs to the technical field of cable preparation, and particularly relates to an ultrahigh-temperature-resistant mineral insulated fireproof cable and a preparation method thereof. The fireproof insulating material is prepared by compounding the ethylene propylene rubber, the polycarbonate, the polytetrafluoroethylene, the antimony trioxide, the modified magnesium oxide and the plasticizer, and the materials can absorb a large amount of heat in the combustion process, so that the temperature of the materials is reduced, and the combustion speed is delayed; meanwhile, a compact protection layer is formed, oxygen is prevented from entering, and the fireproof performance of the cable is remarkably improved; besides, the mineral insulating layer prepared from kaolin, an ethylene-vinyl acetate copolymer, quartz powder and an ethylene-acrylic acid-maleic anhydride copolymer can form a stable ceramic structure at a high temperature, so that the effects of heat insulation and fire prevention are achieved. Therefore, the mineral insulation fireproof cable prepared by using the fireproof insulation material and the mineral insulation layer avoids the damage of the internal structure under the ultrahigh temperature condition, and the performance is more excellent.

Description

Technical Field

[0001] The present invention belongs to the technical field of cable preparation, and particularly relates to a mineral insulated fireproof cable resistant to ultra-high temperature and a preparation method thereof. Background Art

[0002] In recent years, with the steady growth of the economy and the continuous advancement of the industrialization and urbanization processes, the wire and cable industry has achieved efficient development and is widely used in fields such as electric power, communication, industrial automation, construction, and transportation.

[0003] As a kind of power cable, mineral insulated cable has excellent properties such as high safety, waterproof and fireproof, anti-corrosion, and large current-carrying capacity, but there are still defects. For example, both the conductor and the sheath of the mineral insulated cable are made of copper, and the modified magnesium oxide powder filled inside becomes hard after high-temperature sintering, resulting in the overall cable being relatively rigid, with a large bending radius and being difficult to lay in complex shapes. With the refined regulation of the market, people's performance requirements for cable materials in all aspects are also more stringent. How to optimize the performance of mineral insulated cables in all aspects is an urgent need for social development. Summary of the Invention

[0004] The purpose of the present invention is to provide a mineral insulated fireproof cable resistant to ultra-high temperature and a preparation method thereof, with excellent performance and resistance to ultra-high temperature.

[0005] The present invention provides a fireproof insulating material for cables. Calculated by mass fraction, the insulating material includes the following components:

[0006] 40 - 50 parts of ethylene-propylene rubber, 10 - 20 parts of polycarbonate, 1 - 5 parts of antimony trioxide, 5 - 10 parts of modified magnesium oxide, 2 - 3 parts of plasticizer;

[0007] The volume ratio of dioctyl phthalate and dibutyl phthalate in the plasticizer is 1:0.1 - 0.2.

[0008] Preferably, the preparation method of the modified magnesium oxide includes:

[0009] Mix an aqueous solution of MgCl2 and an aqueous solution of polyethylene glycol to obtain a mixture;

[0010] Mix the mixture, ammonia water, and graphite powder and perform ultrasonic stirring to obtain a sol;

[0011] Mix the sol and carbon fiber evenly and dry in vacuum at room temperature to obtain modified magnesium oxide.

[0012] Preferably, the volume ratio of the aqueous solution of MgCl2 and the aqueous solution of polyethylene glycol is 9 - 10:1;

[0013] The molar concentration of the aqueous solution of MgCl2 is 1.5 - 2 mol / L;

[0014] The mass concentration of the polyethylene glycol aqueous solution is 2%-3%.

[0015] Preferably, when performing ultrasonic stirring, the volume-mass ratio of the mixture, ammonia water, and graphite powder is 100-110 mL: 50-55 mL: 0.8-1 g;

[0016] The molar concentration of the ammonia water is 0.5-0.8 mol / L;

[0017] Preferably, the parameters of the ultrasonic stirring include: power of 650-700 w, stirring speed of 250-300 r / min, and temperature of 82-88 °C.

[0018] Preferably, the mass ratio of the sol to the carbon fiber is 100:4-5.

[0019] The present invention provides an application of the fireproof and insulating material described in the above technical solution in improving the high-temperature resistance performance of cables.

[0020] The present invention provides a mineral insulated fireproof cable resistant to ultra-high temperatures, and the mineral insulated fireproof cable includes: a core conductor, a fireproof insulation layer made of the fireproof and insulating material described in the above technical solution, a mineral insulation layer, an aluminum tape, and a sheath.

[0021] The present invention provides a mineral insulated fireproof cable resistant to ultra-high temperatures. In terms of parts by mass, the mineral insulation layer includes the following raw materials: 50-60 parts of kaolin, 25-30 parts of ethylene-vinyl acetate copolymer, 10-15 parts of quartz powder, and 7-8 parts of ethylene-acrylic acid-maleic anhydride copolymer.

[0022] The present invention provides a preparation method of the mineral insulated fireproof cable described in the above technical solution, and the steps include:

[0023] Wrapping a fireproof insulation layer made of the fireproof and insulating material described in the above technical solution around the surface of the core conductor to obtain an insulated core;

[0024] Stranding several of the insulated cores, extruding a mineral insulation layer on its surface, and then wrapping the mineral insulation layer with an aluminum tape;

[0025] Extruding a sheath on the surface of the aluminum tape to obtain a mineral insulated fireproof cable.

[0026] Beneficial effects:

[0027] The present invention provides a fireproof insulating material dedicated for cables. In parts by mass, the insulating material comprises the following components: 40-50 parts of ethylene-propylene rubber, 10-20 parts of polycarbonate, 1-5 parts of antimony trioxide, 5-10 parts of modified magnesium oxide, and 2-3 parts of plasticizer; the volume ratio of dioctyl phthalate to dibutyl phthalate in the plasticizer is 1:0.1-0.2. The raw materials are compounded in specific proportions in the present invention. During the combustion process, the above materials will absorb a large amount of heat, reduce the temperature of the materials, and delay the combustion speed; at the same time, a dense protective layer will be formed to prevent oxygen from entering, significantly improving the fireproof performance of the cables.

[0028] The present invention also provides a mineral insulating layer made of kaolin, ethylene-vinyl acetate copolymer, quartz powder, and ethylene-acrylic acid-maleic anhydride copolymer. The above raw materials interact with each other to form a stable ceramization structure at high temperatures, playing a role in heat insulation and fire prevention. Therefore, the mineral insulated fireproof cable prepared by using the above fireproof insulating material and mineral insulating layer avoids the damage of the internal structure under ultra-high temperature conditions and has more excellent performance. Specific Embodiments

[0029] In the present invention, unless otherwise specified, the materials, equipment, and methods used are all conventional selections.

[0030] To further illustrate the present invention, the solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they cannot be understood as limiting the protection scope of the present invention.

[0031] Example 1

[0032] A method for preparing a mineral insulated fireproof cable resistant to ultra-high temperatures, the steps are as follows:

[0033] (1) Prepare the fireproof insulating material: In parts by mass, the fireproof insulating material comprises the following raw materials: 50 parts of ethylene-propylene rubber, 15 parts of polycarbonate, 3 parts of antimony trioxide, 5 parts of modified magnesium oxide, and 2 parts of plasticizer; the plasticizer is obtained by mixing dioctyl phthalate and dibutyl phthalate according to a volume ratio of 1:0.2;

[0034] The preparation method of the modified magnesium oxide is as follows:

[0035] A 2mol / L MgCl2 aqueous solution and a 2% polyethylene glycol aqueous solution are mixed evenly according to a volume ratio of 10:1 to obtain a mixture;

[0036] Mix a mixture, ammonia water with a molar concentration of 0.5 mol / L, and graphite powder (the particle size of the graphite powder < 10 μm) in a ratio of 100 mL: 50 mL: 0.8 g, and ultrasonically stir the above mixture evenly at 700 w, 88 °C, and 300 r / min to obtain a sol;

[0037] Mix the sol and carbon fiber (fiber length is 40 nm, diameter is 2 nm) evenly according to a mass ratio of 100:5 to obtain a wet gel; Dry the wet gel at 12 Pa and room temperature in vacuum for 6 d to obtain modified magnesium oxide.

[0038] (2) Prepare a mineral insulation layer: By mass, the mineral insulation layer includes the following raw materials: 50 parts of kaolin, 30 parts of ethylene-vinyl acetate copolymer, 10 parts of quartz powder, and 8 parts of ethylene-acrylic acid-maleic anhydride copolymer;

[0039] Mix the above raw materials of the mineral insulation layer in a conventional manner and set aside.

[0040] (3) Prepare a mineral-insulated fire-resistant cable with ultra-high temperature resistance:

[0041] Wrap the fire-resistant insulation layer made of the fire-resistant insulation material in (1) around the surface of a multi-strand stranded copper conductor to obtain an insulated wire core; Stranded several insulated wire cores, extrude the mineral insulation layer in (2) on its surface, and then wrap the mineral insulation layer with an aluminum strip; Extrude a copper sheath on the surface of the aluminum strip to obtain a mineral-insulated fire-resistant cable.

[0042] Example 2

[0043] A method for preparing a mineral-insulated fire-resistant cable with ultra-high temperature resistance, the steps are as follows:

[0044] (1) Prepare a fire-resistant insulation material: By mass, the fire-resistant insulation material includes the following raw materials: 45 parts of ethylene-propylene rubber, 15 parts of polycarbonate, 3 parts of antimony trioxide, 10 parts of modified magnesium oxide, and 2 parts of plasticizer; Among them, the plasticizer is obtained by mixing dioctyl phthalate and dibutyl phthalate according to a volume ratio of 1:0.1.

[0045] The preparation method of the modified magnesium oxide is as follows:

[0046] Mix an aqueous solution of MgCl2 with a molar concentration of 2 mol / L and an aqueous solution of polyethylene glycol with a mass concentration of 2% in a volume ratio of 10:1 evenly to obtain a mixture;

[0047] Mix the mixture, ammonia water with a molar concentration of 0.5 mol / L, and graphite powder (the particle size of the graphite powder < 10 μm) in a ratio of 100 mL: 50 mL: 0.8 g, and ultrasonically stir the above mixture evenly at 700 w, 88 °C, and 300 r / min to obtain a sol;

[0048] Mix the sol and carbon fiber (fiber length is 40 nm and diameter is 2 nm) evenly according to a mass ratio of 100:5 to obtain a wet gel; dry the wet gel at 12 Pa under vacuum at room temperature for 6 days to obtain modified magnesium oxide.

[0049] (2) Prepare the mineral insulation layer: By mass fraction, the mineral insulation layer includes the following raw materials: 50 parts of kaolin, 30 parts of ethylene-vinyl acetate copolymer, 10 parts of quartz powder, and 8 parts of ethylene-acrylic acid-maleic anhydride copolymer;

[0050] Mix the above raw materials of the mineral insulation layer in a conventional manner and set aside.

[0051] (3) Prepare a mineral-insulated fire-resistant cable resistant to ultra-high temperature:

[0052] Wrap a fire-resistant insulation layer made of the fire-resistant insulation material in (1) around the surface of a multi-stranded copper conductor to obtain an insulated wire core; twist several insulated wire cores together, extrude the mineral insulation layer in (2) on its surface, and then wrap the mineral insulation layer with an aluminum strip; extrude a copper sheath on the surface of the aluminum strip to obtain a mineral-insulated fire-resistant cable.

[0053] Example 3

[0054] A method for preparing a mineral-insulated fire-resistant cable resistant to ultra-high temperature, the steps are as follows:

[0055] (1) Prepare the fire-resistant insulation material: By mass fraction, the fire-resistant insulation material includes the following raw materials: 50 parts of ethylene-propylene rubber, 15 parts of polycarbonate, 3 parts of antimony trioxide, 5 parts of modified magnesium oxide, and 2 parts of plasticizer; the plasticizer is obtained by mixing dioctyl phthalate and dibutyl phthalate according to a volume ratio of 1:0.2.

[0056] The preparation method of the modified magnesium oxide is as follows:

[0057] Mix an aqueous solution of MgCl2 with a molar concentration of 2 mol / L and an aqueous solution of polyethylene glycol with a mass concentration of 2% evenly according to a volume ratio of 9:1 to obtain a mixture;

[0058] Mix the mixture, ammonia water with a molar concentration of 0.5 mol / L, and graphite powder (the particle size of the graphite powder < 10 μm) according to 100 mL:50 mL:1 g, and ultrasonically stir the above mixture evenly at 700 w, 86 °C, and 300 r / min to obtain a sol;

[0059] Mix the sol and carbon fiber (fiber length is 40 nm and diameter is 2 nm) evenly according to a mass ratio of 100:5 to obtain a wet gel; dry the wet gel at 12 Pa under vacuum at room temperature for 6 days to obtain modified magnesium oxide.

[0060] (2) Preparation of mineral insulation layer: By mass, the mineral insulation layer comprises the following raw materials: 50 parts of kaolin, 30 parts of ethylene-vinyl acetate copolymer, 10 parts of quartz powder, and 8 parts of ethylene-acrylic acid-maleic anhydride copolymer;

[0061] Mix the above raw materials of the mineral insulation layer in a conventional manner and set aside.

[0062] (3) Preparation of mineral insulation fire-resistant cable resistant to ultra-high temperature:

[0063] Wrap a fire-insulating layer made of the fire-insulating material in (1) around the surface of a multi-stranded copper conductor to obtain an insulated wire core; Stranded several insulated wire cores together, extrude the mineral insulation layer in (2) on their surface, and then wrap the mineral insulation layer with an aluminum strip; Extrude a copper sheath on the surface of the aluminum strip to obtain a mineral insulation fire-resistant cable.

[0064] Comparative Example 1

[0065] A method for preparing a mineral insulation fire-resistant cable resistant to ultra-high temperature, the steps are as follows:

[0066] The difference from Example 1 is only in step (1), specifically:

[0067] Preparation of fire-insulating material: By mass, the fire-insulating material comprises the following raw materials: 50 parts of ethylene-propylene rubber, 15 parts of polycarbonate, 3 parts of antimony trioxide, 15 parts of magnesium oxide, 2 parts of plasticizer; The plasticizer is obtained by mixing dioctyl phthalate and dibutyl phthalate in a volume ratio of 1:0.2.

[0068] Comparative Example 2

[0069] The difference from Example 1 is only in step (1), specifically:

[0070] Preparation of fire-insulating material: By mass, the fire-insulating material comprises the following raw materials: 50 parts of ethylene-propylene rubber, 15 parts of polycarbonate, 3 parts of alumina, 5 parts of modified magnesium oxide, 2 parts of plasticizer; The plasticizer is obtained by mixing dioctyl phthalate and dibutyl phthalate in a volume ratio of 1:0.2.

[0071] Comparative Example 3

[0072] The difference from Example 1 is only in step (1), specifically:

[0073] Preparation of fireproof insulating material: By mass, the fireproof insulating material comprises the following raw materials: 50 parts of ethylene-propylene rubber, 15 parts of polycarbonate, 3 parts of antimony trioxide, 5 parts of modified magnesium oxide, and 2 parts of plasticizer; wherein the plasticizer is obtained by mixing dioctyl phthalate and dibutyl phthalate in a volume ratio of 0.5:0.2.

[0074] Comparative Example 4

[0075] The difference from Example 1 is only in step (1), specifically:

[0076] By mass, the fireproof insulating material comprises the following raw materials: 50 parts of ethylene-propylene rubber, 15 parts of polycarbonate, 3 parts of antimony trioxide, 5 parts of modified magnesium oxide, and 2 parts of plasticizer; wherein the plasticizer is dioctyl phthalate.

[0077] Comparative Example 5

[0078] The difference from Example 1 is only in step (2), specifically:

[0079] Preparation of mineral insulating layer: By mass, the mineral insulating layer comprises the following raw materials: 60 parts of kaolin, 30 parts of ethylene-vinyl acetate copolymer, 10 parts of quartz powder, and 8 parts of tetrachlorobisphenol A;

[0080] Mix the above raw materials of the mineral insulating layer in a conventional manner and set aside.

[0081] Comparative Example 6

[0082] The difference from Example 1 is only in step (1), specifically:

[0083] The preparation method of modified magnesium oxide is as follows:

[0084] Mix an aqueous solution of MgCl2 with a molar concentration of 2 mol / L and absolute ethanol in a volume ratio of 10:1 to obtain a mixture;

[0085] Mix the mixture, ammonia water with a molar concentration of 0.5 mol / L, and graphite powder (the particle size of the graphite powder < 10 μm) in a ratio of 100 mL:50 mL:2 g, and ultrasonically stir the above mixture evenly at 700 w, 88 °C, and 300 r / min to obtain a sol;

[0086] Mix the sol and carbon fiber (fiber length is 40 nm and diameter is 2 nm) evenly in a mass ratio of 100:5 to obtain a wet gel; dry the wet gel at 12 Pa and room temperature in vacuum for 6 d to obtain modified magnesium oxide.

[0087] Comparative Example 7

[0088] The difference from Example 1 is only in step (1), specifically:

[0089] The preparation method of modified magnesium oxide is as follows:

[0090] After uniformly mixing an aqueous solution of MgCl2 with a molar concentration of 2 mol / L and an aqueous solution of polyethylene glycol with a mass concentration of 2% according to a volume ratio of 10:1, a mixture is obtained;

[0091] Mix the mixture, aqueous ammonia with a molar concentration of 0.5 mol / L, and graphite powder (the particle size of the graphite powder < 10 μm) according to 100 mL:50 mL:0.8 g, and ultrasonically stir the above mixture evenly at 700 w, 88 °C, and 300 r / min to obtain a sol; dry the sol at 12 Pa and room temperature in vacuum for 6 days to obtain modified magnesium oxide.

[0092] Comparative Example 8

[0093] The difference from Example 1 is only in step (1), specifically:

[0094] The preparation method of modified magnesium oxide is as follows:

[0095] After uniformly mixing an aqueous solution of MgCl2 with a molar concentration of 2 mol / L and an aqueous solution of polyethylene glycol with a mass concentration of 2% according to a volume ratio of 10:1, a mixture is obtained;

[0096] Mix the mixture and aqueous ammonia with a molar concentration of 0.5 mol / L according to 100 mL:50 mL, and ultrasonically stir the above mixture evenly at 700 w, 88 °C, and 300 r / min to obtain a sol;

[0097] Mix the sol and carbon fiber (fiber length is 40 nm and diameter is 2 nm) evenly according to a mass ratio of 100:5 to obtain a wet gel; dry the wet gel at 12 Pa and room temperature in vacuum for 6 days to obtain modified magnesium oxide.

[0098] Application Example 1

[0099] Conduct fire resistance performance and high temperature resistance performance tests on the mineral insulated fire-resistant cables prepared in Examples 1 - 3 and Comparative Examples 1 - 8. According to the description in GB / T 19216.21 - 2003 "Cable and Optical Fiber Line Integrity Combustion Test", test the fire exposure time and fire exposure temperature when the line remains intact at the rated voltage of 0.6 / 1 KV. The results are shown in Table 1.

[0100] Table 1 Detection Results of Cables in Different Treatments

[0101] Treatment Exposure time (min) Exposure temperature (°C) Example 1 190 1200 Example 2 195 1250 Example 3 185 1232 Comparative Example 1 135 952 Comparative Example 2 167 960 Comparative Example 3 126 968 Comparative Example 4 150 954 Comparative Example 5 134 985 Comparative Example 6 170 970 Comparative Example 7 138 990 Comparative Example 8 105 980

[0102] Combined with the data in Table 1, it can be seen that the mineral insulated fire-resistant cables prepared in Examples 1-3 have good ultra-high temperature resistance and fire resistance, and can still maintain the integrity of the cables for a long time under ultra-high temperature conditions of 1200-1250°C.

[0103] Application Example 2

[0104] According to BS 687 "Fire resistance test method for cable integrity under fire conditions", the mineral insulated fire resistant cables prepared in Examples 1-3 and Comparative Examples 1-8 (each cable has an outer diameter of 19-20 mm) were subjected to integrity tests, specifically including:

[0105] Fire resistance test: under the impact of flame at 950℃±40℃ for 180min, during which the voltage does not exceed 600 / 1000V. If the fuse does not break or the bulb goes out during the test, it means it has passed;

[0106] Vibration fire resistance test: In the experimental environment of 950±40℃, use 600 / 1000V, withstand continuous temperature, supply fire and withstand knocking vibration for 15 minutes. If the fuse does not break or the bulb goes out during the test, it means it has passed. The results are shown in Table 1.

[0107] Table 1 Experimental results in different treatments

[0108] Treatment Fire resistance test Vibration fire resistance test Example 1 Passed Passed Example 2 Passed Passed Example 3 Passed Passed Comparative Example 1 Passed Passed Comparative Example 2 Failed Passed Comparative Example 3 Failed Passed Comparative Example 4 Passed Failed Comparative Example 5 Passed Passed Comparative Example 6 Failed Failed Comparative Example 7 Passed Failed Comparative Example 8 Passed Failed

[0109] It can be seen from the data in Table 2 that the mineral insulated fire resistant cables prepared in Examples 1-3 can all pass the simple fire resistance test and the fire resistance vibration test; while when the fireproof insulation material components or the mineral insulation layer components are adjusted in the comparative example, the fire resistance test or the vibration fire resistance test may fail; although the mineral insulated fire resistant cables prepared in Comparative Examples 1 and 5 can all pass the simple fire resistance test and the fire resistance vibration test, it can be seen from the data in Table 1 that their fire resistance and high temperature resistance are poor.

[0110] In summary, the present invention compounds EPDM, polycarbonate, polytetrafluoroethylene, antimony trioxide, modified magnesium oxide, and plasticizer in a specific ratio. During the combustion process of the composite, the above materials will absorb a large amount of heat, reduce the temperature of the material, and slow down the combustion rate; at the same time, a dense protective layer will be formed to prevent oxygen from entering, significantly improving the fire resistance of the cable; in addition, a mineral insulation layer made of kaolin, ethylene-vinyl acetate copolymer, quartz powder, and ethylene-acrylic acid-maleic anhydride copolymer can form a stable ceramic structure at high temperature, which plays a role in heat insulation and fire prevention. Therefore, the mineral insulated fireproof cable prepared by using the above fireproof insulation material and mineral insulation layer avoids damage to the internal structure under ultra-high temperature conditions, and has better performance.

[0111] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on these embodiments without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A fireproof insulating material dedicated for cables, characterized in that, In parts by mass, the insulating material comprises the following components: 40 - 50 parts of ethylene - propylene rubber, 10 - 20 parts of polycarbonate, 1 - 5 parts of antimony trioxide, 5 - 10 parts of modified magnesium oxide, 2 - 3 parts of plasticizer; In the plasticizer, the volume ratio of dioctyl phthalate to dibutyl phthalate is 1:0.1 - 0.

2.

2. The fireproof and insulating material according to claim 1, characterized in that, The preparation method of the modified magnesium oxide comprises: Mixing an aqueous solution of MgCl2 and an aqueous solution of polyethylene glycol to obtain a mixture; Mixing the mixture, ammonia water and graphite powder and carrying out ultrasonic stirring to obtain a sol; Mixing the sol with carbon fiber evenly and drying at room temperature under vacuum to obtain modified magnesium oxide.

3. The fireproof and insulating material according to claim 2, characterized in that, The volume ratio of the aqueous solution of MgCl2 to the aqueous solution of polyethylene glycol is 9 - 10:1; The molar concentration of the aqueous solution of MgCl2 is 1.5 - 2 mol / L; The mass concentration of the aqueous solution of polyethylene glycol is 2% - 3%.

4. The fireproof and insulating material according to claim 2, characterized in that, When carrying out ultrasonic stirring, the volume - mass ratio of the mixture, ammonia water and graphite powder is 100 - 110 mL:50 - 55 mL:0.8 - 1 g; The molar concentration of the ammonia water is 0.5 - 0.8 mol / L.

5. The fireproof and insulating material according to claim 2 or 4, characterized in that, The parameters of the ultrasonic stirring include: power is 650 - 700 w, stirring speed is 250 - 300 r / min, and temperature is 82 - 88 °C.

6. The fireproof and insulating material according to claim 2, characterized in that, The mass ratio of the sol to the carbon fiber is 100:4 - 5.

7. Application of the fire - resistant insulating material according to any one of claims 1 - 6 in improving the high - temperature resistance performance of a cable.

8. A mineral insulated fire-resistant cable resistant to ultra-high temperatures, characterized in that, The mineral - insulated fire - resistant cable comprises: a core conductor, a fire - resistant insulating layer made of the fire - resistant insulating material according to claim 1 or 2, a mineral - insulating layer, an aluminum tape and a sheath.

9. A mineral insulated fire-resistant cable resistant to ultra-high temperatures, characterized in that, In parts by mass, the mineral - insulating layer comprises the following raw materials: 50 - 60 parts of kaolin, 25 - 30 parts of ethylene - vinyl acetate copolymer, 10 - 15 parts of quartz powder and 7 - 8 parts of ethylene - acrylic acid - maleic anhydride copolymer.

10. The preparation method of the mineral insulated fireproof cable according to claim 8 or 9, characterized in that, The steps are as follows: Wrapping a fire - resistant insulating layer made of the fire - resistant insulating material according to claim 1 or 2 around the surface of the core conductor to obtain an insulated core; Stranding a plurality of the insulated cores and extruding a mineral - insulating layer on their surfaces, and then wrapping the mineral - insulating layer with an aluminum tape; Extruding a sheath on the surface of the aluminum tape to obtain a mineral - insulated fire - resistant cable.