A fire-resistant cable and a method for preparing the same

Abstract

The invention relates to a fire-resistant cable and a preparation method thereof, and belongs to the technical field of cables. The invention uses metal copper, high-density polyethylene, ethylene-vinyl acetate copolymer, plasticizer, antioxidant and self-made flame retardant as raw materials to prepare a fire-resistant cable. The invention first heats the metal copper until it is molten and then performs heat preservation treatment, then cools the metal copper liquid and casts it into wire under nitrogen protection conditions, performs heat preservation and toughening treatment on the copper wire, then adds the copper wire into water for rapid cooling and draws a stranded wire at room temperature to obtain a core material, and finally uniformly mixes the high-density polyethylene and ethylene-vinyl acetate copolymer, plasticizer, antioxidant and flame retardant in the raw materials, heats and melts them, and extrudes and coats them on the surface of the cable core material through an extruder to obtain a fire-resistant cable. The cable prepared by the invention has good toughness, and the cable protective sheath wrapped outside has good impact resistance, good heat resistance and flame retardancy, and good safety performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of cables, and in particular, relates to a fire-resistant cable and a preparation method thereof. Background Art

[0002] With the rapid development of the new energy vehicle industry, the safety performance requirements for cables are becoming higher and higher. New energy vehicles usually use high voltage charging, so the cables need to withstand higher voltages and larger currents, which will cause the cables to be at high operating temperatures for a long time, and the risk of combustion will also be greatly increased. Therefore, cables used in the new energy vehicle field need to have better flame retardant properties. In addition, since cables in the new energy vehicle industry need to be frequently bent and stretched during use, they also need to have good flexibility and wear resistance.

[0003] Polyethylene material has excellent tensile and bending strength, good flexibility, excellent heat resistance and cold resistance, and can maintain stable performance in a wide temperature range. It is an ideal cable material. However, due to its own chemical properties, the flame retardant performance of polyethylene material is poor. Based on this, the present invention provides a fire-resistant cable and a preparation method thereof to prepare a polyethylene cable with good flame retardancy. Summary of the invention

[0004] The object of the present invention is to provide a fire-resistant cable and a preparation method thereof, so as to solve the problems mentioned in the above background technology.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A fire-resistant cable, comprising the following raw materials in parts by weight: 70-80 parts of metallic copper, 4-7 parts of high-density polyethylene, 16-21 parts of ethylene-vinyl acetate copolymer, 0.24-0.3 parts of plasticizer, 0.16-0.2 parts of antioxidant, and 0.54-0.6 parts of flame retardant;

[0007] A method for preparing a fire-resistant cable comprises the following steps:

[0008] The first step is to weigh the raw materials according to the mass proportions: 70-80 parts of metallic copper, 4-7 parts of high-density polyethylene, 16-21 parts of ethylene-vinyl acetate copolymer, 0.24-0.3 parts of plasticizer, 0.16-0.2 parts of antioxidant, and 0.54-0.6 parts of flame retardant;

[0009] The second step is to heat the copper metal to a temperature of 1200°C-1360°C, and then heat-insulate the copper metal. Then, the temperature of the copper metal liquid is lowered to 1100°C, and the copper metal liquid is cast into wire under nitrogen protection.

[0010] Step 3: When the temperature of the copper wire obtained in the second step drops to 550°C-600°C, it is subjected to heat preservation and toughening treatment, and then the copper wire is naturally cooled to 360°C, added into water for rapid cooling, and subjected to wire drawing treatment at room temperature to obtain the finished copper wire;

[0011] Step 4: Twisting the finished copper wires obtained in the step 3 to obtain a cable core material;

[0012] The fifth step is to uniformly mix high-density polyethylene, ethylene-vinyl acetate copolymer, plasticizer, antioxidant and flame retardant and heat them to 170°C-200°C, and continuously extrude and wrap the molten liquid on the surface of the cable core material obtained in the fourth step through an extruder to obtain a fire-resistant cable.

[0013] Furthermore, the plasticizer is one of dioctyl phthalate, diisononyl phthalate, and diisodecyl phthalate.

[0014] Furthermore, the antioxidant is 2,6-di-tert-butylphenol.

[0015] Furthermore, the time condition of the heat preservation treatment in the second step is 70min-90min, the specification of the casting molding in the second step is Ф20mm-30mm, and the casting speed is 60mm / min-90mm / min.

[0016] Furthermore, in the third step, the time of the heat preservation and toughening treatment is 2h-4h, and the specification after wire drawing is Ф0.3mm-0.4mm.

[0017] Furthermore, in the fourth step, the specification of the twisted wire is 15-20 finished copper wires per strand.

[0018] Furthermore, in the fifth step, the extrusion speed of the extruder is 180m / min-200m / min.

[0019] Furthermore, the flame retardant is prepared by the following steps:

[0020] Step 1, 3,4-dihydroxybenzaldehyde, 3-aminopropyltriethoxysilane, dimethyl phosphite, iodine, and cyclopentyl methyl ether were mixed in a three-necked flask, magnetic stirring was turned on, and the mixture was reacted at room temperature for 4 hours. After the reaction was completed, a saturated sodium bicarbonate solution was added to the three-necked flask for washing, and the mixture was extracted with dichloromethane. The organic layer was dried and dichloromethane was removed by rotary evaporation to obtain an intermediate 1;

[0021] Step 2, mix the intermediate 1, vinyl ethyl ether and imidazole hydrochloride in a three-necked flask, install a condenser and a thermometer, start magnetic stirring, and react at a temperature of 40°C-50°C for 3h-4h. After the reaction is completed, add saturated sodium bicarbonate solution to the three-necked flask for washing, extract with dichloromethane, dry the organic layer and remove dichloromethane by rotary evaporation to obtain intermediate 2;

[0022] Step 3, the intermediate 2, phosphorus oxychloride, aluminum trichloride, and N-methylpyrrolidone are mixed in a three-necked flask, a condenser and a thermometer are installed, magnetic stirring is turned on, and the reaction is carried out at a temperature of 80°C-90°C for 6h-8h. After the reaction is completed, the excess phosphorus oxychloride is removed by rotary evaporation, and the remaining solid is washed with deionized water and dried to obtain a flame retardant.

[0023] Furthermore, the amount ratio of 3,4-dihydroxybenzaldehyde, 3-aminopropyltriethoxysilane, dimethyl phosphite, iodine and cyclopentyl methyl ether used in step 1 is 0.1 mol: 0.11 mol-0.12 mol: 0.11 mol-0.12 mol: 0.06 mol-0.07 mol: 100 mL-120 mL.

[0024] Furthermore, the usage ratio of intermediate 1, vinyl ethyl ether and imidazole hydrochloride used in step 2 is 0.08 mol: 0.08 mol-0.1 mol: 0.04 mol-0.05 mol.

[0025] Furthermore, the amount ratio of intermediate 2, phosphorus oxychloride, aluminum chloride and N-methylpyrrolidone used in step 3 is 0.05 mol: 0.15 mol: 0.02 g: 2 mL.

[0026] Beneficial effects of the present invention:

[0027] 1) The present invention uses metallic copper, high-density polyethylene, ethylene-vinyl acetate copolymer, plasticizer, antioxidant, and homemade flame retardant as raw materials to prepare a fire-resistant cable. The present invention first heats the metallic copper until it is molten and then performs heat preservation treatment, then cools the metallic copper liquid and casts it into wire under nitrogen protection conditions, performs heat preservation and toughening treatment on the copper wire, then adds the copper wire into water for rapid cooling and draws and twists it at room temperature to obtain a core material, and finally uniformly mixes the high-density polyethylene and ethylene-vinyl acetate copolymer, plasticizer, antioxidant, and flame retardant in the raw materials, heats and melts them, and extrude and coat them on the surface of the cable core material through an extruder to obtain a fire-resistant cable. The preparation method of the present invention performs heat preservation treatment on the metallic copper during its melting stage, so that the residual solid phase in the metallic copper liquid can be fully melted and thus has good fluidity, and performs heat preservation and toughening on the high-temperature copper wire, thereby eliminating the internal stress of the copper wire and effectively improving the toughness of the copper wire. At the same time, the present invention adopts ethylene-vinyl acetate and high-density polyethylene to prepare the cable protective sheath, and the obtained fire-resistant cable has good flexibility and impact resistance.

[0028] 2) The present invention uses 3,4-dihydroxybenzaldehyde, 3-aminopropyltriethoxysilane and dimethyl phosphite as raw materials, and uses the aldehyde group of 3,4-dihydroxybenzaldehyde and the amino group of 3-aminopropyltriethoxysilane to react with dimethyl phosphite under the catalytic action of elemental iodine to produce a Kabachnik-Fields reaction to obtain an intermediate 1, and then uses intermediate 1 and vinyl ethyl ether as raw materials, and uses the imino group of intermediate 1 to react with the double bond of vinyl ethyl ether to produce an intermediate 2, and finally uses intermediate 2 and phosphorus oxychloride as raw materials, and uses the intermediate 2 to react with the double bond of vinyl ethyl ether to produce an intermediate 2. The phenolic hydroxyl group of intermediate 2 undergoes a substitution reaction with phosphorus oxychloride under the catalytic action of aluminum chloride to obtain a flame retardant. The flame retardant of the present invention has a double-ended phosphate structure and has better flame retardant properties than conventional flame retardants. It can form a heat-insulating and oxygen-insulating protective carbon layer at high temperatures to prevent the base cable from contacting with open flames, thereby protecting the cable. In addition, the flame retardant of the present invention also has a rigid benzene ring structure, which can increase the intermolecular meso resistance after being embedded in the polymer chain, thereby enhancing the heat resistance of the polymer shell, so that the prepared cable has better performance.

[0029] 3) The cable prepared by the present invention has good toughness, the cable protective sheath wrapped outside has good impact resistance, good heat resistance and flame retardancy, and good safety performance. DETAILED DESCRIPTION

[0030] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0031] A flame retardant is prepared by the following steps:

[0032] Step 1, 0.1 mol 3,4-dihydroxybenzaldehyde, 0.11 mol 3-aminopropyltriethoxysilane, 0.11 mol dimethyl phosphite, 0.06 mol iodine, and 100 mL cyclopentyl methyl ether were mixed in a three-necked flask, magnetic stirring was turned on, and the mixture was reacted at room temperature for 4 hours. After the reaction was completed, a saturated sodium bicarbonate solution was added to the three-necked flask for washing, and the mixture was extracted with dichloromethane. The organic layer was dried and dichloromethane was removed by rotary evaporation to obtain an intermediate 1;

[0033] Step 2, 0.08 mol of intermediate 1, 0.08 mol of vinyl ethyl ether and 0.04 mol of imidazole hydrochloride were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the mixture was reacted at 40°C for 3 hours. After the reaction was completed, a saturated sodium bicarbonate solution was added to the three-necked flask for washing, and the mixture was extracted with dichloromethane. The organic layer was dried and dichloromethane was removed by rotary evaporation to obtain intermediate 2;

[0034] Step 3, 0.05 mol of intermediate 2, 0.15 mol of phosphorus oxychloride, 0.02 g of aluminum chloride, and 2 mL of N-methylpyrrolidone were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the reaction was carried out at a temperature of 80°C for 6 hours. After the reaction was completed, excess phosphorus oxychloride was removed by rotary evaporation, and the remaining solid was washed with deionized water and dried to obtain a flame retardant. Example 2

[0035] A flame retardant is prepared by the following steps:

[0036] Step 1, 0.1 mol 3,4-dihydroxybenzaldehyde, 0.115 mol 3-aminopropyltriethoxysilane, 0.115 mol dimethyl phosphite, 0.065 mol iodine, and 110 mL cyclopentyl methyl ether were mixed in a three-necked flask, magnetic stirring was turned on, and the mixture was reacted at room temperature for 4 hours. After the reaction was completed, a saturated sodium bicarbonate solution was added to the three-necked flask for washing, and the mixture was extracted with dichloromethane. The organic layer was dried and dichloromethane was removed by rotary evaporation to obtain intermediate 1;

[0037] Step 2, 0.08 mol of intermediate 1, 0.09 mol of vinyl ethyl ether and 0.045 mol of imidazole hydrochloride were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the mixture was reacted at 45°C for 3.5 hours. After the reaction was completed, a saturated sodium bicarbonate solution was added to the three-necked flask for washing, and the mixture was extracted with dichloromethane. The organic layer was dried and dichloromethane was removed by rotary evaporation to obtain intermediate 2;

[0038] Step 3, 0.05 mol of intermediate 2, 0.15 mol of phosphorus oxychloride, 0.02 g of aluminum chloride, and 2 mL of N-methylpyrrolidone were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the reaction was carried out at a temperature of 85°C for 7 hours. After the reaction was completed, excess phosphorus oxychloride was removed by rotary evaporation, and the remaining solid was washed with deionized water and dried to obtain a flame retardant. Example 3

[0039] A flame retardant is prepared by the following steps:

[0040] Step 1, 0.1 mol 3,4-dihydroxybenzaldehyde, 0.12 mol 3-aminopropyltriethoxysilane, 0.12 mol dimethyl phosphite, 0.07 mol iodine, and 120 mL cyclopentyl methyl ether were mixed in a three-necked flask, magnetic stirring was turned on, and the mixture was reacted at room temperature for 4 hours. After the reaction was completed, a saturated sodium bicarbonate solution was added to the three-necked flask for washing, and the mixture was extracted with dichloromethane. The organic layer was dried and dichloromethane was removed by rotary evaporation to obtain intermediate 1;

[0041] Step 2, 0.08 mol of intermediate 1, 0.1 mol of vinyl ethyl ether and 0.05 mol of imidazole hydrochloride were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the mixture was reacted at 50°C for 4 hours. After the reaction was completed, a saturated sodium bicarbonate solution was added to the three-necked flask for washing, and the mixture was extracted with dichloromethane. The organic layer was dried and dichloromethane was removed by rotary evaporation to obtain intermediate 2;

[0042] Step 3, 0.05 mol of intermediate 2, 0.15 mol of phosphorus oxychloride, 0.02 g of aluminum chloride, and 2 mL of N-methylpyrrolidone were mixed in a three-necked flask, a condenser and a thermometer were installed, magnetic stirring was turned on, and the reaction was carried out at a temperature of 90°C for 8 hours. After the reaction was completed, excess phosphorus oxychloride was removed by rotary evaporation, and the remaining solid was washed with deionized water and dried to obtain a flame retardant. Example 4

[0043] A fire-resistant cable, comprising the following raw materials in parts by mass: 70 parts of metallic copper, 4 parts of high-density polyethylene, 16 parts of ethylene-vinyl acetate copolymer, 0.24 parts of dioctyl phthalate, 0.16 parts of 2,6-di-tert-butylphenol, and 0.54 parts of the flame retardant obtained in Example 1;

[0044] A method for preparing a fire-resistant cable comprises the following steps:

[0045] The first step is to weigh the raw materials by mass: 70 parts of metallic copper, 4 parts of high-density polyethylene, 16 parts of ethylene-vinyl acetate copolymer, 0.24 parts of dioctyl phthalate, 0.16 parts of 2,6-di-tert-butylphenol, and 0.54 parts of the flame retardant obtained in Example 1;

[0046] The second step is to heat the copper metal to 1200°C and keep it warm for 70 minutes, then lower the temperature of the copper metal liquid to 1100°C and cast it into a copper wire with a specification of 20 mm at a speed of 60 mm / min under nitrogen protection;

[0047] Step 3: When the temperature of the copper wire obtained in the second step drops to 550°C, it is kept for 2 hours for toughening treatment, then the copper wire is naturally cooled to 360°C, added into water for rapid cooling, and stretched into a 0.3mm Ф finished copper wire at room temperature;

[0048] Step 4: Twisting 15 finished copper wires obtained in the step 3 to obtain a cable core material;

[0049] The fifth step is to uniformly mix high-density polyethylene, ethylene-vinyl acetate copolymer, dioctyl phthalate, 2,6-di-tert-butylphenol, and the flame retardant obtained in Example 1, and heat to 170°C, and continuously extrude the molten liquid at a speed of 180m / min through an extruder to wrap it on the surface of the cable core material obtained in the fourth step to obtain a fire-resistant cable. Example 5

[0050] A fire-resistant cable, comprising the following raw materials in parts by mass: 80 parts of metallic copper, 7 parts of high-density polyethylene, 21 parts of ethylene-vinyl acetate copolymer, 0.24 parts of diisononyl phthalate, 0.16 parts of 2,6-di-tert-butylphenol, and 0.54 parts of the flame retardant obtained in Example 2;

[0051] A method for preparing a fire-resistant cable comprises the following steps:

[0052] The first step is to weigh 80 parts of metallic copper, 7 parts of high-density polyethylene, 21 parts of ethylene-vinyl acetate copolymer, 0.24 parts of diisononyl phthalate, 0.16 parts of 2,6-di-tert-butylphenol, and 0.54 parts of the flame retardant obtained in Example 2 according to their mass fractions;

[0053] The second step is to heat the copper metal to 1280°C and keep it warm for 80 minutes, then lower the temperature of the copper metal liquid to 1100°C and cast it into a copper wire with a specification of 25 mm at a speed of 75 mm / min under nitrogen protection;

[0054] Step 3: When the temperature of the copper wire obtained in the second step drops to 575°C, it is kept for 3 hours for toughening treatment, then the copper wire is naturally cooled to 360°C, added into water for rapid cooling, and stretched into a 0.35mm Ф finished copper wire at room temperature;

[0055] Step 4: Twisting the 17 finished copper wires obtained in the step 3 to obtain a cable core material;

[0056] The fifth step is to uniformly mix high-density polyethylene, ethylene-vinyl acetate copolymer, plasticizer, 2,6-di-tert-butylphenol, and the flame retardant obtained in Example 2, and heat to 185°C. The molten liquid is continuously extruded and wrapped on the surface of the cable core material obtained in the fourth step at a speed of 190m / min through an extruder to obtain a fire-resistant cable. Example 6

[0057] A fire-resistant cable, comprising the following raw materials in parts by mass: 70 parts of metallic copper, 4 parts of high-density polyethylene, 16 parts of ethylene-vinyl acetate copolymer, 0.3 parts of diisodecyl phthalate, 0.2 parts of 2,6-di-tert-butylphenol, and 0.6 parts of the flame retardant obtained in Example 3;

[0058] A method for preparing a fire-resistant cable comprises the following steps:

[0059] The first step is to weigh the raw materials by mass: 70 parts of metallic copper, 4 parts of high-density polyethylene, 16 parts of ethylene-vinyl acetate copolymer, 0.3 parts of diisodecyl phthalate, 0.2 parts of 2,6-di-tert-butylphenol, and 0.6 parts of the flame retardant obtained in Example 3;

[0060] The second step is to heat the copper metal to 1360°C and keep it warm for 90 minutes, then lower the temperature of the copper metal liquid to 1100°C and cast it into a copper wire with a specification of 30 mm at a speed of 90 mm / min under nitrogen protection;

[0061] Step 3: When the temperature of the copper wire obtained in the second step drops to 600°C, keep it for 4 hours for toughening treatment, then naturally cool the copper wire to 360°C, add it into water for rapid cooling and stretch it into a 0.4mm finished copper wire at room temperature;

[0062] Step 4: Twisting the 20 finished copper wires obtained in the step 3 to obtain a cable core material;

[0063] The fifth step is to uniformly mix high-density polyethylene, ethylene-vinyl acetate copolymer, diisodecyl phthalate, 2,6-di-tert-butylphenol, and the flame retardant obtained in Example 3, and heat them to 200°C. The molten liquid is continuously extruded and wrapped on the surface of the cable core material obtained in the fourth step at a speed of 200m / min through an extruder to obtain a fire-resistant cable.

[0064] Comparative Example 1

[0065] A fire-resistant cable, comprising the following raw materials in parts by mass: 70 parts of metallic copper, 4 parts of high-density polyethylene, 16 parts of ethylene-vinyl acetate copolymer, 0.3 parts of diisodecyl phthalate, and 0.2 parts of 2,6-di-tert-butylphenol;

[0066] A method for preparing a fire-resistant cable comprises the following steps:

[0067] The first step is to weigh the raw materials according to their mass fractions: 70 parts of metallic copper, 4 parts of high-density polyethylene, 16 parts of ethylene-vinyl acetate copolymer, 0.3 parts of diisodecyl phthalate, and 0.2 parts of 2,6-di-tert-butylphenol;

[0068] The second step is to heat the copper metal to 1360°C and keep it warm for 90 minutes, then lower the temperature of the copper metal liquid to 1100°C and cast it into a copper wire with a specification of 30 mm at a speed of 90 mm / min under nitrogen protection;

[0069] Step 3: When the temperature of the copper wire obtained in the second step drops to 600°C, keep it for 4 hours for toughening treatment, then naturally cool the copper wire to 360°C, add it into water for rapid cooling and stretch it into a 0.4mm finished copper wire at room temperature;

[0070] Step 4: Twisting the 20 finished copper wires obtained in the step 3 to obtain a cable core material;

[0071] The fifth step is to uniformly mix high-density polyethylene, ethylene-vinyl acetate copolymer, diisodecyl phthalate and 2,6-di-tert-butylphenol and heat them to 200°C, and to continuously extrude the molten liquid at a speed of 200m / min through an extruder to wrap it on the surface of the cable core material obtained in the fourth step to obtain a fire-resistant cable.

[0072] Comparative Example 2

[0073] This comparative example is a commercially available YJV type cross-linked polyethylene insulated cable.

[0074] The fire resistance performance of a fire-resistant cable in Examples 4-6 and Comparative Example 1 and the commercially available cable in Comparative Example 2 were tested respectively. The insulation layer outside the cable was cut 15 cm and placed vertically and burned for 10 seconds with a 1000W flamethrower. The burning was then stopped and the time the flame continued to burn was recorded. The burn loss rate was calculated according to the state of the cable before and after burning, and the loss state of the insulation layer after burning was observed. The test results are shown in Table 1:

[0075] Table 1

[0076] ;

[0077] It can be seen from Table 1 that the fire-resistant cable of the present invention in Examples 4-6 has much better fire-resistant performance than commercially available cables and can be quickly extinguished when exposed to open flames, while the fire-resistant cable in Comparative Example 1 has poor flame retardant performance because the flame retardant prepared by the present invention is not added. In summary, the fire-resistant cable of the present invention has excellent flame retardant performance and good safety, and can be widely used in the field of new energy vehicles.

[0078] A fire-resistant cable and a preparation method thereof provided by the present invention are introduced in detail above. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enables any technician in the field to practice the present invention, including manufacturing and using any device or system, and implementing any combination method. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made to the present invention without departing from the principles of the present invention. In particular, as long as there is no structural conflict, the various features in the embodiments disclosed in the present invention can be used in combination with each other in any way. The fact that these combinations are not exhaustively described in this specification is only for the purpose of omitting space and saving resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A fire-resistant cable, characterized in that: The invention comprises the following raw materials in parts by weight: 70-80 parts of metallic copper, 4-7 parts of high-density polyethylene, 16-21 parts of ethylene-vinyl acetate copolymer, 0.24-0.3 parts of plasticizer, 0.16-0.2 parts of antioxidant, and 0.54-0.6 parts of flame retardant; Wherein, the flame retardant is prepared by the following steps: Step 1, 3,4-dihydroxybenzaldehyde, 3-aminopropyltriethoxysilane, dimethyl phosphite, iodine and cyclopentyl methyl ether are mixed in a container, stirred evenly, and reacted at room temperature for 4 hours to obtain intermediate 1; Step 2, intermediate 1, vinyl ethyl ether and imidazole hydrochloride are mixed in a container, stirred evenly, and reacted at a temperature of 40°C-50°C for 3h-4h to obtain intermediate 2; Step 3: Mix the intermediate 2, phosphorus oxychloride, aluminum trichloride and N-methylpyrrolidone in a container, stir evenly, and react at a temperature of 80° C. to 90° C. for 6 h to 8 h to obtain a flame retardant.

2. A fire-resistant cable according to claim 1, characterized in that: The amount ratio of 3,4-dihydroxybenzaldehyde, 3-aminopropyltriethoxysilane, dimethyl phosphite, iodine and cyclopentyl methyl ether used in step 1 is 0.1 mol: 0.11 mol-0.12 mol: 0.11 mol-0.12 mol: 0.06 mol-0.07 mol: 100 mL-120 mL.

3. A fire-resistant cable according to claim 1, characterized in that: The usage ratio of intermediate 1, vinyl ethyl ether and imidazole hydrochloride used in step 2 is 0.08 mol: 0.08 mol-0.1 mol: 0.04 mol-0.05 mol.

4. A fire-resistant cable according to claim 1, characterized in that: The amount ratio of intermediate 2, phosphorus oxychloride, aluminum chloride and N-methylpyrrolidone used in step 3 is 0.05 mol: 0.15 mol: 0.02 g: 2 mL.

5. A method for preparing a fire-resistant cable according to any one of claims 1 to 4, characterized in that: The method comprises the following preparation steps: The first step is to weigh the raw materials according to the mass proportions: 70-80 parts of metallic copper, 4-7 parts of high-density polyethylene, 16-21 parts of ethylene-vinyl acetate copolymer, 0.24-0.3 parts of plasticizer, 0.16-0.2 parts of antioxidant, and 0.54-0.6 parts of flame retardant; The second step is to heat the copper metal to a temperature of 1200°C-1360°C, and then heat-insulate the copper metal. Then, the temperature of the copper metal liquid is lowered to 1100°C, and the copper metal liquid is cast into wire under nitrogen protection. Step 3: When the temperature of the copper wire obtained in the second step drops to 550°C-600°C, it is subjected to heat preservation and toughening treatment, and then the copper wire is naturally cooled to 360°C, added into water for rapid cooling, and subjected to wire drawing treatment at room temperature to obtain the finished copper wire; Step 4: Twisting the finished copper wires obtained in the step 3 to obtain a cable core material; The fifth step is to uniformly mix high-density polyethylene, ethylene-vinyl acetate copolymer, plasticizer, antioxidant and flame retardant and heat them to 170°C-200°C, and continuously extrude and wrap the molten liquid on the surface of the cable core material obtained in the fourth step through an extruder to obtain a fire-resistant cable.

6. The method for preparing a fire-resistant cable according to claim 5, characterized in that: The plasticizer is one of dioctyl phthalate, diisononyl phthalate and diisodecyl phthalate, and the antioxidant is 2,6-di-tert-butylphenol.

7. The method for preparing a fire-resistant cable according to claim 5, characterized in that: The time condition of the heat preservation treatment in the second step is 70min-90min, the specification of the casting molding in the second step is Ф20mm-30mm, and the casting speed is 60mm / min-90mm / min.

8. The method for preparing a fire-resistant cable according to claim 5, characterized in that: In the third step, the time of heat preservation and toughening treatment is 2h-4h, and the specification after wire drawing is Ф0.3mm-0.4mm.

9. The method for preparing a fire-resistant cable according to claim 5, characterized in that: The specification of the stranded wire in the fourth step is 15 to 20 finished copper wires per strand.

10. The method for preparing a fire-resistant cable according to claim 5, characterized in that: In the fifth step, the extrusion speed of the extruder is 180m / min-200m / min.