High-strength fireproof cable and preparation method thereof

Abstract

The invention relates to the field of cable materials, and particularly discloses a high-strength fireproof cable and a preparation method thereof.The high-strength fireproof cable comprises a conductor, an insulating layer, a flame-retardant layer and an outer sheath; the outer sheath material comprises the following raw materials: modified polyamide-imide resin, linear low-density polyethylene, amino modified carbon fiber, a styrene-maleic anhydride copolymer and genipin; the preparation method comprises the following steps: firstly, heating and mixing the modified polyamide-imide resin, the amino modified carbon fiber and the genipin, and then adding other raw materials for melt blending granulation to prepare the outer sheath; and sequentially assembling the conductor, the insulating layer, the flame-retardant layer and the outer sheath to obtain the high-strength fireproof cable. The fireproof cable has the advantages that the mechanical strength of the fireproof cable is kept under the long-term high-temperature condition, and the mechanical strength and the thermal aging performance of the cable are improved.

Description

Technical Field

[0001] The present application relates to the field of cable materials, and more specifically, to a high-strength fireproof cable and a preparation method thereof. Background Art

[0002] With the acceleration of global urbanization and the improvement of public safety awareness, fire-resistant cables are becoming increasingly important as key materials to ensure the safe operation of power systems and public safety. In particular, fire-resistant cables have become standard equipment in key infrastructure such as high-rise buildings, data centers, subway tunnels, and industrial facilities. These places place higher requirements on the fire resistance, high temperature resistance, and mechanical strength of cables, which has promoted the research and development and application of high-strength fire-resistant cables. In addition, the rapid development of new energy fields, such as new energy vehicle charging piles and smart grid transformation projects, has also placed higher requirements on the performance of fire-resistant cables.

[0003] Fireproof cables are generally composed of conductors, insulation layers, isolation layers and outer sheaths. The conductors are formed by winding multiple strands of metal materials to ensure good conductivity. The insulation layer is the key part of fireproof cables and is made of high-temperature, non-combustible refractory materials such as mica, ceramics, magnesium oxide, etc. These have high heat resistance and electrical properties, and can maintain the integrity of the cable in high temperature environments to prevent current leakage and short circuits.

[0004] The isolation layer is mainly used to enhance the fire resistance of the cable. It is usually made of inorganic mineral materials, which can effectively prevent the spread of flames and further protect the internal structure of the cable from damage. The outer sheath is the outermost layer of the fire-resistant cable. It is generally made of low-smoke and non-toxic plastic materials such as polyvinyl chloride or halogen-free, low-smoke, flame-retardant polyolefin materials, which can improve the corrosion resistance and electrical properties of the cable and reduce the toxic gases and smoke generated during a fire.

[0005] The fireproof cable produced by the above method has obvious deficiencies in handling extreme high temperatures and mechanical strength, especially when exposed to fire or heavy objects for a long time. The cable material ages and becomes brittle under long-term high temperature, which reduces the mechanical strength of the cable and makes it difficult to ensure the structural integrity of the cable. Summary of the invention

[0006] In order to improve the mechanical strength of fire-resistant cables under long-term high temperature conditions and to improve the mechanical strength and thermal aging performance of cables, the present application provides a high-strength fire-resistant cable and a preparation method thereof.

[0007] In the first aspect, the present application provides a high-strength fire-resistant cable, which adopts the following technical solution: A high-strength fireproof cable comprises a conductor, an insulating layer, a flame retardant layer and an outer sheath, wherein the outer sheath material comprises the following raw materials in parts by weight: 15-30 parts of modified polyamide-imide resin, 30-50 parts of linear low-density polyethylene, 5-10 parts of amino-modified carbon fiber, 10-20 parts of styrene-maleic anhydride copolymer and 1-3 parts of genipin; The modified polyamide-imide resin is prepared by subjecting the polyamide-imide resin to ring-opening treatment in alkali solution and then compositely modified with ethylenediamine and calcium lignin sulfonate.

[0008] By adopting the above technical scheme, the outer sheath in the present application is mainly composed of low-density polyethylene and modified polyamide-imide resin (PAI). The imide ring in the polyamide-imide resin has good thermal stability. The imide ring is opened in an alkali solution and modified with ethylenediamine to introduce a primary amine group. Then, under the action of genipin, it can form a cross-linked structure with the amino-modified carbon fiber, and can also form a bond with the styrene-maleic anhydride copolymer to enhance the cross-linking between the copolymer molecular chains and improve its high temperature resistance. In addition, the polyamide-imide resin is also modified with calcium lignin sulfonate, and the sulfonic acid group in the calcium lignin sulfonate can be modified with PAI. After AI is ring-opened, the amino group forms an ionic bond, and the hydroxyl group in calcium lignin sulfonate can also form a chemical bond with the amino group. Functional groups such as hydroxyl group and sulfonic acid group are also introduced into the PAI modified molecular chain, which can further interact with the maleic anhydride segment in the styrene-maleic anhydride copolymer to further improve the compatibility between PAI and polyethylene. In addition, the rigid aromatic ring structure introduced in calcium lignin sulfonate is dispersed in the PAI matrix. The benzene ring structure and sulfonic acid group in the calcium lignin sulfonate molecule can enhance the interaction between molecules at high temperature, inhibit the thermal motion of the polyethylene molecular chain, improve the high temperature resistance, and further improve its high temperature stability.

[0009] In addition, the addition of carbon fiber in the present application not only has better high temperature resistance, but also has better mechanical properties. Under continuous high temperature conditions, the carbon fiber acts as a reinforcing skeleton to withstand thermal stress, preventing the outer sheath from breaking due to high temperature and ensuring the integrity of the shape and structure of the outer sheath at high temperature; after its amino modification, it can form a cross-linking effect with modified polyamide-imide resin and styrene-maleic anhydride copolymer, thereby improving its high temperature stability and mechanical strength.

[0010] Linear low-density polyethylene also has certain heat resistance and high crystallinity. The crystalline area under high temperature conditions can stabilize the molecular structure and adapt to certain thermal stresses through slight sliding without destroying the structural integrity of the entire material. It provides certain flexibility and thermal buffering properties for the outer sheath. Moreover, as a polyolefin material, it improves the corrosion resistance and electrical properties of fire-resistant cables. The addition of styrene-maleic anhydride copolymer, in which maleic anhydride can form covalent bonds with amino groups in PAI, and the styrene chain segments have similar structures to polyethylene, can form good physical compatibility, thereby reducing the interfacial tension between the two through bridging action and improving the compatibility of PAI and polyethylene. Moreover, under the action of genipin, the primary amine introduced in PAI can form a chemical reaction with the amino groups and calcium lignin sulfonate introduced in the amino-modified carbon fiber, ultimately forming a cross-linked network structure, which ultimately has better high-temperature stability and mechanical properties.

[0011] Optionally, the modified polyamide-imide resin is prepared by the following method: 1) Add polyamide-imide resin to N-methylpyrrolidone and heat it to 60-70°C, stir and dissolve, then cool it to 30-40°C, drop a sodium hydroxide solution with a mass concentration of 0.1-0.8 mol / L, heat it to 40-50°C after the addition is complete, and stir and react for 2-3 hours; 2) Then, the temperature is raised to 70-80°C, ethylenediamine is added under stirring, and the reaction is carried out at this temperature for 1-2 hours. After the reaction is completed, the mixture is cooled to room temperature and the pH is adjusted to neutral. Then, methanol is added as a precipitant to precipitate the modified polyamide-imide resin, and then filtered, washed with alcohol, and dried to obtain ethylenediamine-modified polyamide-imide resin; 3) Mix calcium lignin sulfonate with ethanol aqueous solution to obtain calcium lignin sulfonate suspension, then add aminosilane coupling agent, heat to 50-60°C, stir and react for 20-40 minutes, and then dry to obtain pretreated calcium lignin sulfonate; 4) Mix the ethylenediamine modified polyamide-imide resin prepared in step 2) and the pretreated calcium lignin sulfonate prepared in step 3), add an antioxidant, then melt blend, add an initiator, react at 120-140° C. for 30-40 minutes, and cool to obtain a modified polyamide-imide resin.

[0012] By adopting the above technical scheme, the polyamide-imide resin is firstly dissolved, and then an alkali solution is added dropwise to open the imide ring. After the ring-opening reaction is returned, the temperature is raised and ethylenediamine is added, so that the carboxyl group generated after the ring-opening reacts with the primary amine in the ethylenediamine to form an amide bond, and the primary amine group is introduced into the molecular chain of the polyamide-imide resin to achieve the amination modification of the polyamide-imide resin. Then, the polyamide-imide resin is melt-blended with lignin cellulose treated with an aminosilane coupling agent, and an initiator is added to promote the condensation of the amino group in the polyamide-imide resin modified with the sulfonic acid group in the calcium lignin sulfonate, and the calcium lignin sulfonate is first treated with an aminosilane coupling agent. After the coupling agent treatment, the silane in the aminosilane coupling agent can be hydrolyzed to condense with the hydroxyl group of calcium lignin sulfonate, and form hydrogen bonds with the amino group after the ring opening of PAI. The silane coupling agent is introduced into the modified polyamide-imide resin, and its amino and ethoxy bifunctional groups are used to improve the combination of PAI and polyethylene. Moreover, after modification, it can form chemical bonds with amino-modified carbon fiber and calcium lignin sulfonate modified polyethylene to form a more complex network structure, thereby improving its temperature resistance and stability. At the same time, the carbon fiber can also make up for the loss of mechanical properties due to the introduction of the amino group. Finally, it still has excellent mechanical properties at high temperatures and maintains its structural integrity.

[0013] Optionally, during the preparation of the modified polyamide-imide resin, In step 1), the mass ratio of polyamide-imide resin to N-methylpyrrolidone is 1:(3-4), and the amount of sodium hydroxide solution added is 5-8wt% of the polyamide-imide resin; In step 2), the amount of ethylenediamine added is 8-15wt% of the amount of polyamide-imide resin added; In step 3), the ethanol aqueous solution is prepared by mixing ethanol and water in a mass ratio of 8-10:1, and the added mass ratio of calcium lignin sulfonate to the ethanol aqueous solution is 1:(4-6), and the added amount of aminosilane coupling agent is 5-10wt% of the calcium lignin sulfonate; In step 4), the mass ratio of ethylenediamine modified polyamide-imide resin to pretreated calcium lignin sulfonate is 1:(0.2-0.3), and the amount of antioxidant added is 0.5-1wt% of the ethylenediamine modified polyamide-imide resin, and the amount of initiator added is 1.5-3wt% of the ethylenediamine modified polyamide-imide resin.

[0014] Optionally, 3-5 parts by weight of maleic anhydride grafted polyethylene are also added to the raw material of the outer sheath.

[0015] By adopting the above technical scheme, the addition of maleic anhydride grafted polyethylene utilizes the carboxyl group of maleic anhydride to form an amide bond with the amino group in the modified polyamide-imide resin. At the same time, the grafted polyethylene segment is compatible with the polyethylene matrix, thereby improving the interfacial bonding strength between the two and improving the mechanical properties and high-temperature stability of the cable.

[0016] Optionally, the amino-modified carbon fiber is prepared by the following method: Carbon fiber pretreatment: The carbon fiber is immersed in concentrated nitric acid for immersion treatment, then washed and dried to obtain activated carbon fiber; Amination modification: The activated carbon fiber prepared is immersed in a γ-aminopropyltriethoxysilane solution, and after immersion for 1-2 hours, ethylenediamine is added, and the mixture is reacted at 100-120°C for 40-60 minutes, and then washed and dried to obtain amino-modified carbon fiber.

[0017] By adopting the above technical scheme, the carbon fiber is first immersed in concentrated nitric acid to activate the carbon fiber, and oxygen-containing functional groups such as hydroxyl and carboxyl groups are introduced on the surface of the carbon fiber. Then, when the activated carbon fiber is immersed in a γ-aminopropyltriethoxysilane solution, the silane coupling agent is hydrolyzed and condensed with the hydroxyl groups on the surface of the carbon fiber to achieve the modification of the silane coupling agent, and amino functional groups are introduced on the carbon fiber. Moreover, the introduction of ethylenediamine can introduce amino functional groups on the surface of the carbon fiber to achieve amino modification of the carbon fiber, so that cross-linking with the modified polyamide-imide resin can be achieved under the action of genipin.

[0018] Optionally, when preparing the amino-modified carbon fiber, in the carbon fiber pretreatment step, the mass concentration of concentrated nitric acid is 65-68%, and the concentrated nitric acid and water are mixed in a volume ratio of (3-4):1 and then immersed in the carbon fiber, and the carbon fiber is immersed in the concentrated nitric acid solution and then ultrasonically treated at 55-65° C. for 40-60 minutes; In the amination modification step, the γ-aminopropyltriethoxysilane solution is obtained by mixing γ-aminopropyltriethoxysilane and ethanol in a mass ratio of 1: (9-10), the added mass ratio of activated carbon fiber to the γ-aminopropyltriethoxysilane solution is 1: (5-6), and the impregnation temperature is 25-30°C. After the impregnation is completed, ethylenediamine is added, and the amount of ethylenediamine added is 8-15wt% of the activated carbon fiber, and the ethylenediamine is dissolved in 4-6 times the mass of water before being added.

[0019] Optionally, when the amino-modified carbon fiber is prepared, the amino-modified carbon fiber is further treated and then added: Nano-silica loading: Nano-silica is firstly treated by immersing in a 3-carboxypropyltriethoxysilane solution for modification, centrifugally washed and dried to obtain carboxylated nano-silica, and then the carboxylated nano-silica is mixed with a polyvinyl alcohol aqueous solution and sprayed on the obtained amino-modified carbon fiber, dried and cured to obtain modified carbon fiber loaded with nano-silica; Modification: The prepared modified carbon fiber loaded with nano-silica is immersed in a 1-butyl-3-methylimidazole dihydrogen phosphate ionic liquid solution, and then dried to obtain amino composite modified carbon fiber.

[0020] By adopting the above technical scheme, the nano-silica is firstly immersed in a 3-carboxypropyltriethoxysilane solution for modification treatment, and the silanol formed after the hydrolysis of 3-carboxypropyltriethoxysilane condenses with the hydroxyl group of the nano-silica to achieve silanization modification of the nano-silica, and carboxyl groups are introduced on the surface of the nano-silica, and then the nano-silica is sprayed and loaded on the amino-modified carbon fiber, so that the hydroxyl group on the surface of the nano-silica and the amino group on the surface of the carbon fiber form an amide bond, thereby improving the bonding strength between the two; Moreover, the amide bonds formed on the modified carbon fiber can form hydrogen bonds with the amino groups in PAI, and the hydroxyl groups on the surface of nano-silica can form a hydrogen bond network with the amino groups on the polyamide-imide resin, thereby improving the compatibility of the carbon fiber with the PAI and polyethylene systems. At the same time, the hydroxyl groups on the surface of nano-silica can also interact with PE through van der Waals forces, thereby improving the compatibility between PAI and polyethylene. In addition, the modified carbon fiber is subsequently treated with 1-butyl-3-methylimidazole dihydrogen phosphate ionic liquid for impregnation modification. The dihydrogen phosphate at the polar end can be combined with the amino and carboxylic acid groups of PAI through ionic bonds or hydrogen bonds, while the butyl chain of the imidazolium cation in the non-polar segment is compatible with the alkane chain segment of PE through van der Waals forces to form a molecular-level interface transition layer. Finally, the modified carbon fiber can not only have better compatibility with the system but also promote the compatibility of polyamide-imide resin and polyethylene, and has better comprehensive performance.

[0021] Optionally, during the post-treatment of the amino-modified carbon fiber, during the nano-silica loading process, the 3-carboxypropyl triethoxysilane solution is prepared by mixing 3-carboxypropyl triethoxysilane with ethanol and water in a mass ratio of 1: (6-8): (2-3), and the pH value of the 3-carboxypropyl triethoxysilane solution is adjusted to 4.5-6, the immersion temperature is 50-55° C., the immersion time is 40-60 min, and the addition mass ratio of the nano-silica to the 3-carboxypropyl triethoxysilane solution is 1: (8-10); The mass concentration of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 5-10wt%, and the carboxylated nano-silica and the polyvinyl alcohol aqueous solution are mixed in a mass ratio of 1: (3-4) to prepare a spraying liquid, and the spraying amount of the spraying liquid is 10-20wt% of the amount of amino-modified carbon fiber added; In the modification step, a 1-butyl-3-methylimidazole dihydrogen phosphate ionic liquid solution is prepared by mixing 1-butyl-3-methylimidazole dihydrogen phosphate with water and acetone in a mass ratio of 1: (8-10): (6-8), and the modified carbon fiber loaded with nano-silica is immersed in the 1-butyl-3-methylimidazole dihydrogen phosphate ionic liquid solution, the immersion temperature is 30-40° C., the immersion time is 30-40 min, and the immersion pressure is 0.6-0.8 MPa.

[0022] In a second aspect, the present application provides a method for preparing a high-strength fire-resistant cable, using the following technical solution: A method for preparing a high-strength fire-resistant cable comprises the following steps: S1. Firstly, the modified polyamide-imide resin, amino-modified carbon fiber and genipin are heated to 120-130° C., mixed for 20-30 minutes, and then the remaining raw materials are added for melt blending and granulation. The melting temperature is 180-210° C. to obtain an outer sheath; S2. Assemble the conductor, insulation layer, flame retardant layer and outer sheath in sequence to produce a high-strength fireproof cable.

[0023] In summary, this application has the following beneficial effects: 1. In the present application, the outer sheath is mainly composed of low-density polyethylene and modified polyamide-imide resin (PAI). The imide ring in the polyamide-imide resin has good thermal stability. The imide ring is opened in an alkaline solution and modified with ethylenediamine to introduce primary amine groups. Then, under the action of genipin, it can form a cross-linked structure with amino-modified carbon fiber, and can also form a bond with styrene-maleic anhydride copolymer, thereby enhancing the cross-linking between the copolymer molecular chains and improving its high temperature resistance. 2. In the present application, the polyamide-imide resin is modified by calcium lignin sulfonate, and the sulfonic acid group in the calcium lignin sulfonate can form an ionic bond with the amino group after the ring opening of PAI, and the hydroxyl group in the calcium lignin sulfonate can also form a chemical bond with the amino group. Functional groups such as hydroxyl and sulfonic acid groups are also introduced into the PAI modified molecular chain, which can further interact with the maleic anhydride segment in the styrene-maleic anhydride copolymer to further improve the compatibility between PAI and polyethylene. In addition, the rigid aromatic ring structure introduced in the calcium lignin sulfonate is dispersed in the PAI matrix. The benzene ring structure and sulfonic acid group in the calcium lignin sulfonate molecule can enhance the interaction between molecules at high temperature, inhibit the thermal motion of the polyethylene molecular chain, improve the high temperature resistance, and further improve its high temperature stability. DETAILED DESCRIPTION

[0024] The present application is further described in detail below in conjunction with the examples. It is particularly noted that if no specific conditions are specified in the following examples, the experiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be obtained from common commercial sources.

[0025] In the following preparation examples and embodiments, the polyamide-imide resin is selected from the polyamide-imide (PAI) resin powder Torlon 4000TF produced by Dongguan Tianzhihong Plastic Chemical Co., Ltd.; The linear low-density polyethylene is selected from the linear low-density polyethylene with the grade of M200024 produced by Shanghai Yuangao Plastic Technology Co., Ltd.; The styrene-maleic anhydride copolymer is a styrene-maleic anhydride copolymer of the brand Crayville Model 3000P produced by Shanghai Longti Chemical Co., Ltd.; Maleic anhydride grafted polyethylene is selected from Dongguan Taotao Plastic Raw Materials Co., Ltd. The brand is American DuPont brand 4288 maleic anhydride grafted polyethylene The following preparation examples are preparation examples of modified polyamide-imide resin and amino-modified carbon fiber. Preparation Example 1 A method for preparing a modified polyamide-imide resin comprises the following steps: 1) Add polyamide-imide resin to N-methylpyrrolidone and heat to 65°C, stir to dissolve, then cool to 35°C, drop 0.5 mol / L sodium hydroxide solution, heat to 45°C and stir to react for 2.5 hours after the addition is complete; The mass ratio of polyamide-imide resin to N-methylpyrrolidone is 1:3.5, and the amount of sodium hydroxide solution added is 6wt% of the polyamide-imide resin; 2) Then, the temperature was raised to 75°C, and ethylenediamine was added under stirring, the amount of ethylenediamine added was 10wt% of the amount of polyamide-imide resin added, and the reaction was carried out at this temperature for 1.5h. After the reaction was completed, the mixture was cooled to room temperature and the pH was adjusted to neutral. Then, methanol was added as a precipitant to precipitate the modified polyamide-imide resin, and then filtered, washed with alcohol, and dried to obtain ethylenediamine-modified polyamide-imide resin; 3) Mix calcium lignin sulfonate with an ethanol aqueous solution (ethanol and water are mixed in a mass ratio of 9:1) to obtain a calcium lignin sulfonate suspension, then add aminosilane coupling agent KH-550, heat to 55°C, stir and react for 30 minutes, and then dry to obtain pretreated calcium lignin sulfonate. The mass ratio of calcium lignin sulfonate to ethanol aqueous solution is 1:5, and the amount of aminosilane coupling agent added is 8wt% of the calcium lignin sulfonate; 4) The ethylenediamine modified polyamide-imide resin prepared in step 2) and the pretreated calcium lignin sulfonate prepared in step 3) are mixed in a mass ratio of 1:0.2, and then an antioxidant 1010 is added, and the antioxidant addition amount is 0.8wt% of the ethylenediamine modified polyamide-imide resin. Then, the mixture is melt-blended, and an initiator diisopropylbenzene peroxide is added, and the initiator addition amount is 2wt% of the ethylenediamine modified polyamide-imide resin. After reacting at 130° C. for 35 minutes, the mixture is melt-blended at 230° C. for 25 minutes, and cooled to obtain a modified polyamide-imide resin.

[0026] Preparation Example 2 A method for preparing a modified polyamide-imide resin comprises the following steps: 1) Add polyamide-imide resin to N-methylpyrrolidone and heat to 60°C, stir to dissolve, then cool to 30°C, drop 0.1 mol / L sodium hydroxide solution, heat to 40°C and stir to react for 3 hours after the addition is complete; The mass ratio of polyamide-imide resin to N-methylpyrrolidone is 1:3, and the amount of sodium hydroxide solution added is 5wt% of the polyamide-imide resin; 2) Then, the temperature was raised to 70°C, and ethylenediamine was added under stirring, the amount of ethylenediamine added was 8wt% of the amount of polyamide-imide resin added, and the reaction was carried out at this temperature for 2h. After the reaction was completed, the mixture was cooled to room temperature and the pH was adjusted to neutral. Then, methanol was added as a precipitant to precipitate the modified polyamide-imide resin, and then filtered, washed with alcohol, and dried to obtain ethylenediamine-modified polyamide-imide resin; 3) Mix calcium lignin sulfonate with an ethanol aqueous solution (ethanol and water are mixed in a mass ratio of 8:1) to obtain a calcium lignin sulfonate suspension, then add aminosilane coupling agent KH-550, heat to 50°C, stir and react for 40 minutes, and then dry to obtain pretreated calcium lignin sulfonate. The mass ratio of calcium lignin sulfonate to ethanol aqueous solution is 1:4, and the amount of aminosilane coupling agent added is 5wt% of the calcium lignin sulfonate; 4) The ethylenediamine modified polyamide-imide resin prepared in step 2) and the pretreated calcium lignin sulfonate prepared in step 3) are mixed in a mass ratio of 1:0.2, and an antioxidant 1010 is added, and the antioxidant addition amount is 0.5wt% of the ethylenediamine modified polyamide-imide resin. Then, the mixture is melt-blended, and an initiator diisopropylbenzene peroxide is added, and the initiator addition amount is 1.5wt% of the ethylenediamine modified polyamide-imide resin. After reacting at 120° C. for 40 minutes, the mixture is melt-blended at 220° C. for 20 minutes, and cooled to obtain a modified polyamide-imide resin.

[0027] Preparation Example 3 A method for preparing a modified polyamide-imide resin comprises the following steps: 1) Add polyamide-imide resin to N-methylpyrrolidone and heat to 70°C, stir to dissolve, then cool to 40°C, drop 0.8 mol / L sodium hydroxide solution, heat to 50°C and stir to react for 2h after the addition is complete; The mass ratio of polyamide-imide resin to N-methylpyrrolidone is 1:4, and the amount of sodium hydroxide solution added is 8wt% of the polyamide-imide resin; 2) Then, the temperature is raised to 80°C, and ethylenediamine is added under stirring, the amount of ethylenediamine added is 15wt% of the amount of polyamide-imide resin added, and the reaction is carried out at this temperature for 1 hour. After the reaction is completed, it is cooled to room temperature and the pH is adjusted to neutral. Then, methanol is added as a precipitant to precipitate the modified polyamide-imide resin, and then filtered, washed with alcohol, and dried to obtain ethylenediamine-modified polyamide-imide resin; 3) Mix calcium lignin sulfonate with an ethanol aqueous solution (ethanol and water are mixed in a mass ratio of 10:1) to obtain a calcium lignin sulfonate suspension, then add aminosilane coupling agent KH-550, heat to 60°C, stir and react for 20 minutes, and then dry to obtain pretreated calcium lignin sulfonate. The mass ratio of calcium lignin sulfonate to ethanol aqueous solution is 1:6, and the amount of aminosilane coupling agent added is 10wt% of the calcium lignin sulfonate; 4) The ethylenediamine modified polyamide-imide resin prepared in step 2) and the pretreated calcium lignin sulfonate prepared in step 3) are mixed in a mass ratio of 1:0.3, and then an antioxidant 1010 is added, and the antioxidant addition amount is 1wt% of the ethylenediamine modified polyamide-imide resin. Then, the mixture is melt-blended, and an initiator diisopropylbenzene peroxide is added, and the initiator addition amount is 3wt% of the ethylenediamine modified polyamide-imide resin. After reacting at 140° C. for 30 minutes, the mixture is melt-blended at 240° C. for 20 minutes, and cooled to obtain a modified polyamide-imide resin.

[0028] Preparation Example 4 A method for preparing a modified polyamide-imide resin is carried out according to the method in Preparation Example 1, except that step 3) is not performed, and an equal amount of pre-treated calcium lignin sulfonate in step 4) is replaced by calcium lignin sulfonate.

[0029] Comparative Preparation Example 1 A method for preparing a modified polyamide-imide resin is carried out according to the method in Preparation Example 1, except that step 3) and step 4) are not carried out, and the ethylenediamine-modified polyamide-imide resin prepared in step 2) is directly used as the modified polyamide-imide resin.

[0030] Preparation Example 5 A method for preparing amino-modified carbon fiber comprises the following steps: Step 1, carbon fiber pretreatment: concentrated nitric acid with a mass concentration of 68% and water are mixed in a volume ratio of 3:1 to prepare a concentrated nitric acid solution, and then the carbon fiber is immersed in the concentrated nitric acid solution and ultrasonically treated at 60°C for 50 minutes with an ultrasonic power of 500w, and then washed with water, washed with alkali, and dried after washing with water to obtain activated carbon fiber; Step 2, amination modification: γ-aminopropyltriethoxysilane and ethanol are mixed in a mass ratio of 1:9 to obtain a γ-aminopropyltriethoxysilane solution, and then the obtained activated carbon fiber is immersed in the γ-aminopropyltriethoxysilane solution, the added mass ratio of the activated carbon fiber to the γ-aminopropyltriethoxysilane solution is 1:5, and the immersion temperature is 25°C, and after immersion for 2 hours, ethylenediamine solution (obtained by dissolving ethylenediamine in 5 times the mass of water) is added, reacted at 110°C for 50 minutes, and then washed and dried to obtain amino-modified carbon fiber, and the amount of ethylenediamine added is 10wt% of the activated carbon fiber; Step 3, nano-silica loading: firstly, the nano-silica is immersed in a 3-carboxypropyltriethoxysilane solution (prepared by mixing 3-carboxypropyltriethoxysilane with ethanol and water in a mass ratio of 1:7:2 and adjusting its pH value to 5 by acetic acid) for modification, the immersion temperature is 50°C, the immersion time is 50min, and the addition mass ratio of the nano-silica to the 3-carboxypropyltriethoxysilane solution is 1:9, centrifugally washed and dried to obtain carboxylated nano-silica; Then, the carboxylated nano-silica and the polyvinyl alcohol aqueous solution with a mass concentration of 8wt% were mixed in a mass ratio of 1:3 to obtain a spray liquid, and the spray liquid was sprayed on the prepared amino-modified carbon fiber, and the spraying amount of the spray liquid was 15wt% of the amount of amino-modified carbon fiber added, the spraying distance was 22cm, the spraying pressure was 0.4MPa, and the spraying was divided into three times, each spraying interval was 5min, and after the spraying was completed, it was first dried at 60°C, and then vacuum dried and cured at 80°C to obtain a modified carbon fiber loaded with nano-silica; Step 4, modification: immersing the prepared modified carbon fiber loaded with nano-silica into a 1-butyl-3-methylimidazole dihydrogen phosphate ionic liquid solution (prepared by mixing 1-butyl-3-methylimidazole dihydrogen phosphate with water and acetone in a mass ratio of 1:9:7), and drying after immersion to obtain amino composite modified carbon fiber. The immersion temperature is 35°C, the immersion time is 35 minutes, and the immersion pressure is 0.7MPa.

[0031] Preparation Example 6 A method for preparing amino-modified carbon fiber comprises the following steps: Step 1, carbon fiber pretreatment: concentrated nitric acid with a mass concentration of 65% and water are mixed in a volume ratio of 3:1 to prepare a concentrated nitric acid solution, and then the carbon fiber is immersed in the concentrated nitric acid solution and ultrasonically treated at 55°C for 60 minutes with an ultrasonic power of 500w, and then washed with water, washed with alkali, and dried after washing with water to obtain activated carbon fiber; Step 2, amination modification: γ-aminopropyltriethoxysilane and ethanol are mixed in a mass ratio of 1:9 to obtain a γ-aminopropyltriethoxysilane solution, and then the obtained activated carbon fiber is immersed in the γ-aminopropyltriethoxysilane solution, the added mass ratio of the activated carbon fiber to the γ-aminopropyltriethoxysilane solution is 1:5, and the immersion temperature is 25°C, and after immersion for 2 hours, ethylenediamine solution (obtained by dissolving ethylenediamine in 4 times the mass of water) is added, reacted at 100°C for 60 minutes, and then washed and dried to obtain amino-modified carbon fiber, and the amount of ethylenediamine added is 8wt% of the activated carbon fiber; Step 3, nano-silica loading: firstly, the nano-silica is immersed in a 3-carboxypropyltriethoxysilane solution (prepared by mixing 3-carboxypropyltriethoxysilane with ethanol and water in a mass ratio of 1:6:2 and adjusting its pH value to 4.5 by acetic acid) for modification, the immersion temperature is 50°C, the immersion time is 60min, and the addition mass ratio of the nano-silica to the 3-carboxypropyltriethoxysilane solution is 1:8, centrifugally washed and dried to obtain carboxylated nano-silica; Then, the carboxylated nano-silica and a polyvinyl alcohol aqueous solution with a mass concentration of 5wt% were mixed in a mass ratio of 1:3 to obtain a spray liquid, and the spray liquid was sprayed on the prepared amino-modified carbon fiber, and the spraying amount of the spray liquid was 10wt% of the amount of amino-modified carbon fiber added, the spraying distance was 20cm, the spraying pressure was 0.4MPa, and the spraying was divided into three times, each spraying interval was 5min, and after the spraying was completed, it was first dried at 60°C, and then vacuum dried and cured at 80°C to obtain a modified carbon fiber loaded with nano-silica; Step 4, modification: immersing the prepared modified carbon fiber loaded with nano-silica into a 1-butyl-3-methylimidazole dihydrogen phosphate ionic liquid solution (prepared by mixing 1-butyl-3-methylimidazole dihydrogen phosphate with water and acetone in a mass ratio of 1:8:6), and drying after immersion to obtain amino composite modified carbon fiber. The immersion temperature is 30°C, the immersion time is 40 minutes, and the immersion pressure is 0.6MPa.

[0032] Preparation Example 7 A method for preparing amino-modified carbon fiber comprises the following steps: Step 1, carbon fiber pretreatment: concentrated nitric acid with a mass concentration of 65-68% and water are mixed in a volume ratio of 4:1 to prepare a concentrated nitric acid solution, and then the carbon fiber is immersed in the concentrated nitric acid solution and ultrasonically treated at 65°C for 40 minutes with an ultrasonic power of 500w, and then washed with water, washed with alkali, and dried after washing with water to obtain activated carbon fiber; Step 2, amination modification: γ-aminopropyltriethoxysilane and ethanol are mixed in a mass ratio of 1:10 to obtain a γ-aminopropyltriethoxysilane solution, and then the obtained activated carbon fiber is immersed in the γ-aminopropyltriethoxysilane solution, the added mass ratio of the activated carbon fiber to the γ-aminopropyltriethoxysilane solution is 1:6, and the immersion temperature is 30°C, and after immersion for 1h, ethylenediamine solution (obtained by dissolving ethylenediamine in 6 times the mass of water) is added, reacted at 120°C for 40min, and then washed and dried to obtain amino-modified carbon fiber, and the amount of ethylenediamine added is 15wt% of the activated carbon fiber; Step 3, nano-silica loading: firstly, the nano-silica is immersed in a 3-carboxypropyltriethoxysilane solution (prepared by mixing 3-carboxypropyltriethoxysilane with ethanol and water in a mass ratio of 1:8:3 and adjusting its pH value to 6 by acetic acid) for modification, the immersion temperature is 55°C, the immersion time is 40min, and the addition mass ratio of the nano-silica to the 3-carboxypropyltriethoxysilane solution is 1:10, centrifugally washed and dried to obtain carboxylated nano-silica; Then, the carboxylated nano-silica and a polyvinyl alcohol aqueous solution with a mass concentration of 10wt% were mixed in a mass ratio of 1:4 to obtain a spray liquid, which was sprayed on the prepared amino-modified carbon fiber. The spraying amount of the spray liquid was 20wt% of the amount of amino-modified carbon fiber added, the spraying distance was 25cm, the spraying pressure was 0.4MPa, and the spraying was performed three times, with an interval of 5min between each spraying. After the spraying was completed, it was first dried at 60°C, and then vacuum dried and cured at 80°C to obtain a modified carbon fiber loaded with nano-silica. Step 4, modification: immersing the prepared modified carbon fiber loaded with nano-silica into a 1-butyl-3-methylimidazole dihydrogen phosphate ionic liquid solution (prepared by mixing 1-butyl-3-methylimidazole dihydrogen phosphate with water and acetone in a mass ratio of 1:10:8), and drying after immersion to obtain amino composite modified carbon fiber. The immersion temperature is 40°C, the immersion time is 30 minutes, and the immersion pressure is 0.8 MPa.

[0033] Preparation Example 8 A method for preparing amino-modified carbon fiber is carried out according to the method in Preparation Example 5, except that the post-treatment steps of nano-silica loading in step three and modification in step four are not carried out, and the amino-modified carbon fiber obtained after amination modification in step two is directly added.

[0034] Preparation Example 9 A method for preparing amino-modified carbon fiber is carried out according to the method in Preparation Example 5, except that the nano-silica loading in step three is not carried out, and the amino-modified carbon fiber obtained after amination modification in step two is not subjected to the nano-silica loading treatment in step three, but is directly subjected to step four treatment to obtain amino-composite modified carbon fiber for application.

[0035] Preparation Example 10 A method for preparing amino-modified carbon fiber is carried out according to the method in Preparation Example 5, except that the modification treatment in step 4 is not performed, and the modified carbon fiber loaded with nano-silicon dioxide obtained in step 3 is directly used.

[0036] Example 1 A method for preparing a high-strength fire-resistant cable comprises the following steps: S1, 20kg of the modified polyamide-imide resin prepared in Preparation Example 1, 8kg of the amino-modified carbon fiber prepared in Preparation Example 5 and 2kg of genipin were first heated to 125°C, mixed for 25min, and then 40kg of linear low-density polyethylene and 15kg of styrene-maleic anhydride copolymer, 0.2kg of antioxidant 1010 and 0.2kg of ultraviolet absorber UV-327 were added and melt-blended and granulated by a twin-screw extruder, the melt temperature was 200°C, the screw speed was 100r / min, and an outer sheath was obtained; S2, using a copper core as a conductor and ceramic silicone rubber as an insulating layer, ceramic silicone rubber (model KT-TC8710 from Shanghai Kote New Materials Co., Ltd.) is extruded on the copper conductor as an insulating layer, and then nano magnesium hydroxide and aluminum hydroxide with a mass ratio of 3:1 are extruded on the insulating layer as flame retardants to form a flame retardant layer, and finally the outer sheath material prepared in step S1 is coated on the flame retardant layer by extrusion to form a fireproof cable.

[0037] Example 2 A method for preparing a high-strength fire-resistant cable comprises the following steps: S1, 15kg of the modified polyamide-imide resin prepared in Preparation Example 2, 5kg of the amino-modified carbon fiber prepared in Preparation Example 6 and 1kg of genipin were first heated to 120°C, mixed for 30min, and then 30kg of linear low-density polyethylene and 10kg of styrene-maleic anhydride copolymer, 0.1kg of antioxidant 1010 and 0.1kg of ultraviolet absorber UV-327 were added, and melt-blended and granulated by a twin-screw extruder, the melt temperature was 180°C, and the screw speed was 100r / min to obtain an outer sheath; S2, using a copper core as a conductor and ceramic silicone rubber as an insulating layer, ceramic silicone rubber (model KT-TC8710 from Shanghai Kote New Materials Co., Ltd.) is extruded on the copper conductor as an insulating layer, and then nano magnesium hydroxide and aluminum hydroxide with a mass ratio of 3:1 are extruded on the insulating layer as flame retardants to form a flame retardant layer, and finally the outer sheath material prepared in step S1 is coated on the flame retardant layer by extrusion to form a fireproof cable.

[0038] Example 3 A method for preparing a high-strength fire-resistant cable comprises the following steps: S1, 30kg of the modified polyamide-imide resin prepared in Preparation Example 3, 10kg of the amino-modified carbon fiber prepared in Preparation Example 7 and 3kg of genipin were first heated to 130°C, mixed for 20min, 50kg of linear low-density polyethylene and 20kg of styrene-maleic anhydride copolymer, 0.3kg of antioxidant 1010 and 0.3kg of ultraviolet absorber UV-327 were added, and melt blended and granulated by a twin-screw extruder, the melt temperature was 210°C, the screw speed was 100r / min, and an outer sheath was obtained; S2, using a copper core as a conductor and ceramic silicone rubber as an insulating layer, ceramic silicone rubber (model KT-TC8710 from Shanghai Kote New Materials Co., Ltd.) is extruded on the copper conductor as an insulating layer, and then nano magnesium hydroxide and aluminum hydroxide with a mass ratio of 3:1 are extruded on the insulating layer as flame retardants to form a flame retardant layer, and finally the outer sheath material prepared in step S1 is coated on the flame retardant layer by extrusion to form a fireproof cable.

[0039] Example 4 A method for preparing a high-strength fire-resistant cable is carried out according to the method in Example 1, except that the modified polyamide-imide resin in step S1 is the modified polyamide-imide resin prepared in Preparation Example 4.

[0040] Example 5 A method for preparing a high-strength fireproof cable is carried out according to the method in Example 1, except that 3 kg of maleic anhydride grafted polyethylene is added in step S1 while adding styrene-maleic anhydride copolymer.

[0041] Example 6 A method for preparing a high-strength fireproof cable is carried out according to the method in Example 1, except that 5 kg of maleic anhydride grafted polyethylene is added in step S1 while adding styrene-maleic anhydride copolymer.

[0042] Embodiment 7-9 A method for preparing a high-strength fireproof cable is carried out according to the method in Example 1, except that the amino-modified carbon fiber in step S1 is the amino-modified carbon fiber prepared in Preparation Examples 8-10.

[0043] Comparative Example 1 A method for preparing a high-strength fire-resistant cable is carried out according to the method in Example 1, except that the modified polyamide-imide resin in step S1 is the modified polyamide-imide resin prepared in Comparative Preparation Example 1.

[0044] Comparative Example 2 A method for preparing a high-strength fire-resistant cable is carried out according to the method in Example 1, except that in step S1, the modified polyamide-imide resin is replaced by an equal amount of polyamide-imide resin.

[0045] Comparative Example 3 A method for preparing a high-strength fire-resistant cable is carried out according to the method in Example 1, except that no modified polyamide-imide resin is added in step S1.

[0046] Comparative Example 4 A method for preparing a high-strength fire-resistant cable is carried out according to the method in Example 1, except that amino-modified carbon fiber is not added in step S1.

[0047] Comparative Example 5 A method for preparing a high-strength fire-resistant cable is carried out according to the method in Example 1, except that the amino-modified carbon fiber in step S1 is replaced by an equal amount of carbon fiber.

[0048] Comparative Example 6 A method for preparing a high-strength fire-resistant cable is carried out according to the method in Example 1, except that no styrene-maleic anhydride copolymer is added in step S1.

[0049] Comparative Example 7 A method for preparing a high-strength fire-resistant cable is carried out according to the method in Example 1, except that no genipin is added in step S1.

[0050] Performance Testing The tensile strength and elongation at break of the cables prepared in the examples and comparative examples of the present application were tested with reference to ISO 527-2 (2012), and the results are shown in Table 1 below. In addition, the cables were subjected to heat aging (150°C, 7d) with reference to IEC 60216, and the elongation at break and tensile strength properties were tested to characterize their heat aging properties. The test results are shown in Table 2 below.

[0051] Combined with the test results of Table 1 and Table 2 above, the cable prepared in the embodiment of the present application not only has excellent mechanical properties, but also maintains high mechanical properties after long-term heat treatment, has good heat aging performance, and has high mechanical strength under long-term high temperature conditions, ensuring the structural integrity of the cable. Combined with the test results of Example 1 and Example 4, when preparing the modified polyamide-imide resin, when calcium lignin sulfonate is used for modification, when it is directly added without silane modification, its performance is reduced compared with that in Example 1. Combined with the test results of Example 5 and Example 6, it can be seen that when maleic anhydride grafted polyethylene is also added to the outer sheath system, it can improve the compatibility between PAI and polyethylene, and is also conducive to forming a complex network cross-linking structure, and finally significantly improves its mechanical properties and heat aging performance.

[0052] Combined with the test results of Example 1 and Example 7, when preparing amino-modified carbon fiber in Example 7, it was only modified with a silane coupling agent, and was not loaded with nano-silica and ionic liquid treatment. It can be seen that its mechanical properties are significantly reduced, and the thermal aging performance is also significantly reduced. Combined with the test results in Example 8, when Example 8 is not loaded with nano-silica but directly treated with ionic liquid, its mechanical properties and thermal aging performance are improved compared with Example 7, but weaker than Example 1. Combined with the test results of Example 9, when amino-modified carbon fiber in Example 9 is treated with nano-silica but not with ionic liquid, its effect is still weaker than Example 1. When it is loaded with nano-silica, its roughness is used to realize the anchoring of modified carbon fiber and macromolecular resin structures such as PAI, which can significantly improve its mechanical properties and thermal aging performance. The modification of ionic liquid uses its chemical bonding to improve the compatibility between PAI and polyethylene, which helps to improve its mechanical properties and aging resistance.

[0053] Referring to the test results of Example 1 and Comparative Example 1, when the modified polyamide-imide resin in Comparative Example 1 is treated with only ethylenediamine modification without calcium lignin sulfonate modification, it can be seen that its mechanical properties are reduced and its thermal aging properties are also significantly reduced. The introduction of the benzene ring group modified by calcium lignin sulfonate and the introduction of the sulfonic acid group not only help to improve its thermal aging properties, but also improve its mechanical properties. Combined with the test results of Comparative Example 2, when the polyamide-imide resin is not modified, its mechanical properties and thermal aging properties are significantly reduced, and its compatibility with polyethylene is poor, resulting in poor performance. Combined with the test results of Comparative Example 3, when the modified polyamide-imide resin is not added to the outer sheath, its mechanical properties are significantly reduced and its thermal aging properties are also weak. Combined with the test results of Comparative Example 4, no ammonia is added. When the base modified carbon fiber is added, its mechanical properties are significantly reduced, and the thermal aging performance is also weak. The addition of modified polyamide-imide resin and amino modified carbon fiber in Example 1 of the present application can not only improve the initial mechanical properties of the cable, but also has good thermal aging performance, and maintains a high structural integrity under high temperature conditions. Combined with the test results of Comparative Example 5, when the carbon fiber in Comparative Example 5 is not amino-modified and added, although it itself helps to improve the mechanical properties, due to its poor compatibility with the system, its mechanical properties and thermal aging performance are weak. Referring to the test results of Comparative Examples 6 and 7, the addition of styrene-maleic anhydride copolymer helps to improve the system compatibility and thus improve the mechanical properties of the cable. In Comparative Example 7, genipin helps to form a cross-linked structure between the modified PAI and the amino modified carbon fiber, limits the displacement of polyethylene at high temperature, and improves its thermal aging performance.

[0054] In addition, the fire retardant performance of the cable prepared in the embodiment was tested according to the method required by GB / T 2406.2-2009, and the initial oxygen index test result was 35-38%, which showed good fire retardant performance.

[0055] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.

Claims

1. A high-strength fire-resistant cable, comprising a conductor, an insulating layer, a flame-retardant layer and an outer sheath, characterized in that: The outer sheath material is made from the following raw materials in parts by weight: 15-30 parts of modified polyamide-imide resin, 30-50 parts of linear low-density polyethylene, 5-10 parts of amino-modified carbon fiber, 10-20 parts of styrene-maleic anhydride copolymer and 1-3 parts of genipin; The modified polyamide-imide resin is prepared by subjecting the polyamide-imide resin to ring-opening treatment in alkali solution and then compositely modified with ethylenediamine and calcium lignin sulfonate.

2. A high-strength fireproof cable according to claim 1, characterized in that: The modified polyamide-imide resin is prepared by the following method: 1) Add polyamide-imide resin to N-methylpyrrolidone and heat it to 60-70°C, stir and dissolve, then cool it to 30-40°C, drop a sodium hydroxide solution with a mass concentration of 0.1-0.8 mol / L, heat it to 40-50°C after the addition is complete, and stir and react for 2-3 hours; 2) Then, the temperature is raised to 70-80°C, ethylenediamine is added under stirring, and the reaction is carried out at this temperature for 1-2 hours. After the reaction is completed, the mixture is cooled to room temperature and the pH is adjusted to neutral. Then, methanol is added as a precipitant to precipitate the modified polyamide-imide resin, and then filtered, washed with alcohol, and dried to obtain ethylenediamine-modified polyamide-imide resin; 3) Mix calcium lignin sulfonate with ethanol aqueous solution to obtain calcium lignin sulfonate suspension, then add aminosilane coupling agent, heat to 50-60°C, stir and react for 20-40 minutes, and then dry to obtain pretreated calcium lignin sulfonate; 4) Mix the ethylenediamine modified polyamide-imide resin prepared in step 2) and the pretreated calcium lignin sulfonate prepared in step 3), add an antioxidant, then melt blend, add an initiator, react at 120-140° C. for 30-40 minutes, and cool to obtain a modified polyamide-imide resin.

3. A high-strength fireproof cable according to claim 2, characterized in that: During the preparation of modified polyamide-imide resin, In step 1), the mass ratio of polyamide-imide resin to N-methylpyrrolidone is 1:(3-4), and the amount of sodium hydroxide solution added is 5-8wt% of the polyamide-imide resin; In step 2), the amount of ethylenediamine added is 8-15wt% of the amount of polyamide-imide resin added; In step 3), the ethanol aqueous solution is prepared by mixing ethanol and water in a mass ratio of 8-10:1, and the added mass ratio of calcium lignin sulfonate to the ethanol aqueous solution is 1:(4-6), and the added amount of aminosilane coupling agent is 5-10wt% of the calcium lignin sulfonate; In step 4), the mass ratio of ethylenediamine modified polyamide-imide resin to pretreated calcium lignin sulfonate is 1:(0.2-0.3), and the amount of antioxidant added is 0.5-1wt% of the ethylenediamine modified polyamide-imide resin, and the amount of initiator added is 1.5-3wt% of the ethylenediamine modified polyamide-imide resin.

4. A high-strength fireproof cable according to claim 1, characterized in that: 3-5 parts by weight of maleic anhydride grafted polyethylene are also added to the raw materials of the outer sheath.

5. A high-strength fireproof cable according to claim 1, characterized in that: The amino-modified carbon fiber is prepared by the following method: Carbon fiber pretreatment: The carbon fiber is immersed in concentrated nitric acid for ultrasonic treatment, then washed and dried to obtain activated carbon fiber; Amination modification: The activated carbon fiber prepared is immersed in a γ-aminopropyltriethoxysilane solution, and after immersion for 1-2 hours, ethylenediamine is added, and the mixture is reacted at 100-120°C for 40-60 minutes, and then washed and dried to obtain amino-modified carbon fiber.

6. A high-strength fireproof cable according to claim 5, characterized in that: When preparing amino-modified carbon fiber, in the carbon fiber pretreatment step, the mass concentration of concentrated nitric acid is 65-68%, and the concentrated nitric acid and water are mixed in a volume ratio of (3-4):1 and then immersed in the carbon fiber, and the carbon fiber is immersed in the concentrated nitric acid solution and then ultrasonically treated at 55-65° C. for 40-60 minutes; In the amination modification step, the γ-aminopropyltriethoxysilane solution is obtained by mixing γ-aminopropyltriethoxysilane and ethanol in a mass ratio of 1: (9-10), the added mass ratio of activated carbon fiber to the γ-aminopropyltriethoxysilane solution is 1: (5-6), and the impregnation temperature is 25-30°C. After the impregnation is completed, ethylenediamine is added, and the amount of ethylenediamine added is 8-15wt% of the activated carbon fiber, and the ethylenediamine is dissolved in 4-6 times the mass of water before being added.

7. A high-strength fireproof cable according to claim 5, characterized in that: When the amino-modified carbon fiber is prepared, the amino-modified carbon fiber is further treated and then added: Nano-silica loading: Nano-silica is firstly treated by immersing in a 3-carboxypropyltriethoxysilane solution for modification, centrifugally washed and dried to obtain carboxylated nano-silica, and then the carboxylated nano-silica is mixed with a polyvinyl alcohol aqueous solution and sprayed on the obtained amino-modified carbon fiber, dried and cured to obtain modified carbon fiber loaded with nano-silica; Modification: The prepared modified carbon fiber loaded with nano-silica is immersed in a 1-butyl-3-methylimidazole dihydrogen phosphate ionic liquid solution, and then dried to obtain amino composite modified carbon fiber.

8. A high-strength fireproof cable according to claim 7, characterized in that: During the post-treatment of amino-modified carbon fiber, during the nano-silica loading process, the 3-carboxypropyl triethoxysilane solution is prepared by mixing 3-carboxypropyl triethoxysilane with ethanol and water in a mass ratio of 1: (6-8): (2-3), and the pH value of the 3-carboxypropyl triethoxysilane solution is adjusted to 4.5-6, the immersion temperature is 50-55° C., the immersion time is 40-60 min, and the addition mass ratio of nano-silica to 3-carboxypropyl triethoxysilane solution is 1: (8-10); The mass concentration of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 5-10wt%, and the carboxylated nano-silica and the polyvinyl alcohol aqueous solution are mixed in a mass ratio of 1: (3-4) to prepare a spraying liquid, and the spraying amount of the spraying liquid is 10-20wt% of the amount of amino-modified carbon fiber added; In the modification step, a 1-butyl-3-methylimidazole dihydrogen phosphate ionic liquid solution is prepared by mixing 1-butyl-3-methylimidazole dihydrogen phosphate with water and acetone in a mass ratio of 1: (8-10): (6-8), and the modified carbon fiber loaded with nano-silica is immersed in the 1-butyl-3-methylimidazole dihydrogen phosphate ionic liquid solution, the immersion temperature is 30-40° C., the immersion time is 30-40 min, and the immersion pressure is 0.6-0.8 MPa.

9. A method for preparing a high-strength fire-resistant cable according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Firstly, the modified polyamide-imide resin, amino-modified carbon fiber and genipin are heated to 120-130° C., mixed for 20-30 minutes, and then the remaining raw materials are added for melt blending and granulation. The melting temperature is 180-210° C. to obtain an outer sheath; S2. Assemble the conductor, insulation layer, flame retardant layer and outer sheath in sequence to produce a high-strength fireproof cable.

Images