A flame-retardant and fireproof high-voltage cable for new energy vehicles and its preparation method

Abstract

This invention discloses a flame-retardant and fire-resistant high-voltage cable for new energy vehicles and its preparation method, relating to the field of high-voltage cable technology. The high-voltage cable comprises, from the inside out, a cable core, an insulating sleeve, and an outer sheath. The outer sheath is made from the following components by weight: 80-95 parts polyethylene, 10-15 parts EPDM rubber, 7-10 parts compatibilizer, 10-12 parts flame retardant, 1-2 parts peroxide, 0.2-0.5 parts photoinitiator, and 2-4 parts stabilizer. The polyethylene comprises high-density polyethylene, low-density polyethylene, and modified high-density polyethylene in a mass ratio of (64-76):(7.5-8.5):(8.5-10.5). The outer sheath prepared according to this application, when applied to high-voltage cables, can effectively improve the flame-retardant and fire-resistant properties and mechanical properties of the high-voltage cables.

Description

Technical Field

[0001] This invention relates to the field of high-voltage cable technology, specifically a flame-retardant and fire-resistant high-voltage cable for new energy vehicles and its preparation method. Background Technology

[0002] With the rapid development of the new energy vehicle industry, high-voltage cables, as key components of power systems and batteries, have seen their development drive research into the outer sheaths of high-voltage cables. Common outer sheath materials are generally low-density polyethylene (LDPE) and polyvinyl chloride (PVC). However, PVC releases toxic gases when burned, and LDPE's mechanical properties are insufficient to meet the requirements of new energy vehicle outer sheaths. High-density polyethylene (HDPE), on the other hand, is chlorine-free and possesses excellent resistance to deformation and other mechanical properties, making it an important base material for new energy vehicle outer sheaths.

[0003] In the existing technology, the outer sheath of high-voltage cables with high-density polyethylene as the main body still has many shortcomings: On the one hand, conventional high-voltage cable outer sheaths mainly use a single high-density polyethylene as the base material, but its flame retardancy is insufficient, and it is easy to catch fire and burn under conditions such as vehicle short circuits and overloads, causing safety risks; on the other hand, a large amount of flame retardant is usually added to improve the flame retardant performance of the outer sheath, but the excessive introduction of flame retardant often destroys the molecular chain structure of the base material, resulting in a significant reduction in the mechanical properties of the protective sheath, which cannot meet the mechanical requirements of high-voltage cable outer sheaths in actual use, and it is difficult to balance flame retardancy and mechanical properties.

[0004] In summary, solving the above problems and providing a flame-retardant and fireproof high-voltage cable for new energy vehicles is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a flame-retardant and fireproof high-voltage cable for new energy vehicles and its preparation method, so as to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A flame-retardant and fire-resistant high-voltage cable for new energy vehicles, wherein the high-voltage cable comprises, from the inside out, a cable core, an insulating sleeve, and an outer sheath; the outer sheath is made of the following components by weight: 80-95 parts polyethylene, 10-15 parts EPDM rubber, 7-10 parts compatibilizer, 10-12 parts flame retardant, 1-2 parts peroxide, 0.2-0.5 parts photoinitiator, and 2-4 parts stabilizer.

[0007] More preferably, the polyethylene includes high-density polyethylene, low-density polyethylene and modified high-density polyethylene in a mass ratio of (64~76):(7.5~8.5):(8.5~10.5).

[0008] In a more optimized manner, the modified high-density polyethylene is prepared by mixing high-density polyethylene, dicumyl peroxide, hydroxyethyl methacrylate phosphate, and alkenyl DOPO, and then melt-extruding at 160~180°C to obtain modified high-density polyethylene.

[0009] In a more optimized manner, the raw materials for the modified high-density polyethylene, by weight, consist of: 8-10 parts high-density polyethylene, 0.1-0.2 parts dicumyl peroxide, 0.5-0.7 parts hydroxyethyl methacrylate phosphate, and 0.3-0.5 parts alkenyl DOPO.

[0010] In a more optimized manner, the flame retardant comprises alkenyl DOPO and rare earth modified nitrogen heterocycles in a mass ratio of (9~10):(1~2).

[0011] A more optimized method for preparing the alkenyl DOPO is as follows: 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide is added to N,N-dimethylformamide; under a nitrogen atmosphere, the mixture is heated to 80-85°C and stirred until homogeneous; the mixture is cooled, sodium hydroxide is added, followed by 1,4-dichlorobenzyl and phenyl 4-chloroacrylate; the mixture is reacted at 65-75°C for 5-7 hours, and then filtered, washed, and dried to obtain alkenyl DOPO.

[0012] In the preparation of alkenyl DOPO, 10-(2,5-dihydroxyphenyl)-9-oxa-10-phosphaphenanthrene-10-oxide generates phenoxy anions under the action of sodium hydroxide alkaline catalyst. Then, the anions undergo nucleophilic substitution reactions with chlorine atoms in the structures of 1,4-dichlorobenzyl and 4-chloroacrylate, respectively, to obtain alkenyl DOPO.

[0013] More preferably, the raw material of the alkenyl DOPO includes the following components by weight: 8-12 parts of 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide, 50-60 parts of N,N-dimethylformamide, 1-3 parts of sodium hydroxide, 0.5-0.7 parts of 1,4-dichlorobenzyl, and 0.3-0.5 parts of 4-chloroacrylate.

[0014] A more optimized method for preparing the rare earth-modified nitrogen heterocycle is as follows: Tetraazacyclododecane and allyl glycidyl ether were added to ethanol and stirred at 78-80°C for 2-3 days under a nitrogen atmosphere. After cooling, lanthanum chloride hexahydrate was added and stirred at 60-70°C for 7-9 hours. The mixture was then filtered, washed, and dried to obtain rare earth modified nitrogen heterocycles.

[0015] In the preparation of rare earth modified nitrogen heterocycles, the hydrogen atom on the secondary amine group in the tetraazacyclododecane structure undergoes a ring-opening nucleophilic addition reaction with the epoxy group of allyl glycidyl ether to generate an alkenyl nitrogen heterocycle. Furthermore, the alkenyl nitrogen heterocycle molecule coordinates with the lanthanum ion in lanthanum chloride hexahydrate, thereby introducing the rare earth lanthanum ion into the nitrogen heterocycle skeleton to obtain a rare earth modified nitrogen heterocycle.

[0016] In a more optimized manner, the raw material for the rare earth modified nitrogen heterocycle includes the following components: by weight, 0.5 to 1.5 parts of tetraazacyclododecane, 2.5 to 3 parts of allyl glycidyl ether, and 0.5 to 1.5 parts of lanthanum chloride hexahydrate.

[0017] A method for preparing a flame-retardant and fire-resistant high-voltage cable for new energy vehicles includes the following steps: Step 1: Mix polyethylene, EPDM rubber, compatibilizer, flame retardant, stabilizer, peroxide, and photoinitiator evenly to obtain the outer sheath material; Step 2: (1) Twist several cable core materials in the same direction to form a cable core, and set an insulating sleeve on its outside; (2) Melt and extrude the outer sheath material through a twin-screw extruder at a temperature of 155~170℃ to form an outer sheath, and wrap the outside; irradiate with ultraviolet light to obtain a high-voltage cable.

[0018] Compared with the prior art, the beneficial effects of the present invention are: the present application uses high-density polyethylene as the main body, and by introducing alkenyl DOPO and rare earth modified nitrogen heterocycles as flame retardants, the flame retardancy of the outer sheath is effectively improved. At the same time, the introduction of modified high-density polyethylene improves the compatibility between the matrices and the dispersibility of the flame retardant. (1) Regarding the improvement of flame retardant performance, this invention uses alkenyl DOPO and rare earth modified nitrogen heterocycles to form a nitrogen-phosphorus synergistic flame retardant system, which effectively enhances the flame retardant performance. Among them, the phosphorus group contained in alkenyl DOPO can effectively release phosphorus-containing free radicals to inhibit combustion at high temperature. At the same time, the phosphoric acid substances produced by its thermal decomposition can promote the char formation of the material and form a carbon barrier. However, due to the disadvantages of single alkenyl DOPO, such as the loose carbon layer structure that is easy to crack and the limited duration of gas phase flame retardant effect, rare earth modified nitrogen heterocycles are further introduced. Compared with ordinary metal salts, such as typical zinc salts and iron salts, the rare earth ions in its structure have higher thermal stability, and the oxides produced by its decomposition have higher strength, which can fill the carbon layer to make the carbon layer denser. At the same time, it not only decomposes to produce non-combustible gas to dilute the concentration of combustible gas, but also works synergistically with alkenyl DOPO to enhance the flame retardant effect. It can also adsorb smoke particles and reduce the release of toxic gases. Furthermore, the alkenyl group at the end of the alkenyl DOPO can be cross-linked and fixed in the polymer three-dimensional network by ultraviolet light, which not only makes itself uniformly dispersed, but also makes the flame retardant elements such as nitrogen and lanthanum in the rare earth modified nitrogen heterocycle uniformly dispersed in the cross-linked network, avoiding the migration and precipitation of flame retardant molecules, thus further enhancing the flame retardant effect.

[0019] (2) Regarding the improvement of mechanical properties, the present invention introduces modified high-density polyethylene into the outer sheath material formulation to improve the dispersion uniformity of each component, thereby effectively enhancing the mechanical properties. Among them, the modified high-density polyethylene is grafted with phosphorus-containing polar segments, which effectively enhances its interfacial compatibility with alkenyl DOPO and rare earth modified nitrogen heterocycles, and can effectively improve the dispersion uniformity of both in polyethylene and EPDM rubber matrix, avoiding stress concentration caused by uneven dispersion between components, thereby reducing the decay of mechanical properties; in addition, the ratio between alkenyl DOPO and rare earth modified nitrogen heterocycles needs to be clearly defined, and alkenyl DOPO should be used as the main flame retardant: because in the outer sheath material formulation, the alkenyl group in the alkenyl DOPO structure can participate in the construction of cross-linking network, and at the same time provide a dispersion environment for rare earth modified nitrogen heterocycles, forming a continuous dispersion environment, so that the rare earth modified nitrogen heterocycle particles are uniformly dispersed in the cross-linking network, ensuring that stress is uniformly transmitted in the matrix molecular chain, and avoiding the decrease in the mechanical properties of the substrate due to the addition of flame retardants. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In the following embodiments, the parts are by weight. It should be noted that there are no special restrictions on the manufacturers of the raw materials involved in this invention. Exemplary examples include: high-density polyethylene (ExxonMobil HMA-018), low-density polyethylene (ExxonMobil LD100AC), hydroxyethyl methacrylate phosphate (CAS: 52628-03-2), 1,4-dichlorobenzyl (CAS: 623-25-6), phenyl 4-chloroacrylate (CAS: 13633-87-9), tetraazacyclododecane (CAS: 294-90-6), allyl glycidyl ether (CAS: 106-92-3), lanthanum chloride hexahydrate (CAS: 17272-45-6), ethylene propylene diene monomer (EPDM) rubber (grade: 3092PM), and maleic anhydride-grafted ethylene-vinyl acetate copolymer (grade: Dow Fusabond). C190), 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide (CAS: 99208-50-1), 1-hydroxycyclohexylphenyl ketone (CAS: 947-19-3), and other products without special requirements are commercially available.

[0022] Pre-preparation: I. Preparation of alkenyl DOPO: 10 parts of 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide were added to 55 parts of N,N-dimethylformamide; under a nitrogen atmosphere, the mixture was heated to 80°C and stirred until homogeneous; the mixture was cooled, and 2 parts of sodium hydroxide, 0.6 parts of 1,4-dichlorobenzyl, and 0.4 parts of 4-chloroacrylate were added; the mixture was reacted at 70°C for 6 hours, filtered, washed, and dried to obtain alkenyl DOPO.

[0023] II. Preparation of modified high-density polyethylene: 9 parts of high-density polyethylene, 0.15 parts of dicumyl peroxide, 0.6 parts of hydroxyethyl methacrylate phosphate, and 0.4 parts of alkenyl DOPO were mixed and melt-extruded at 160°C to obtain modified high-density polyethylene.

[0024] III. Preparation of rare earth modified nitrogen heterocycles: 1 part of tetraazacyclododecane and 2.7 parts of allyl glycidyl ether were added to 50 parts of ethanol. The mixture was stirred at 79°C for 3 days under a nitrogen atmosphere. After cooling, 1 part of lanthanum chloride hexahydrate was added and stirred at 65°C for 8 hours. The mixture was then filtered, washed, and dried to obtain rare earth modified nitrogen heterocycles.

[0025] Example 1: A method for preparing a flame-retardant and fireproof high-voltage cable for new energy vehicles, specifically including the following steps: Step 1: Mix 88 parts polyethylene (composed of 70.5 parts high-density polyethylene, 8 parts low-density polyethylene, and 9.5 parts modified high-density polyethylene), 13 parts EPDM rubber, 8.5 parts compatibilizer (maleic anhydride-grafted ethylene-vinyl acetate copolymer), 11 parts flame retardant (composed of 9.5 parts alkenyl DOPO and 1.5 parts rare earth modified nitrogen heterocyclic compounds), and 3 parts stabilizer (antioxidant 1010) at 150°C until homogeneous. Cool down, then add 1.5 parts peroxide (dicumyl peroxide) and 0.3 parts photoinitiator (1-hydroxycyclohexylphenyl ketone) sequentially. Stir until homogeneous at 90°C to obtain the outer sheath material. Step 2: (1) Twist several cable core materials in the same direction to obtain a cable core, and set an insulating sleeve on its outside; (2) Melt and extrude the outer sheath material through a twin-screw extruder at a temperature of 160°C to form the cable outer sheath, wrap the outside, and irradiate with ultraviolet light to obtain a high-voltage cable.

[0026] Example 2: A method for preparing a flame-retardant and fireproof high-voltage cable for new energy vehicles, specifically including the following steps: Step 1: Mix 80 parts polyethylene (composed of 64 parts high-density polyethylene, 7.5 parts low-density polyethylene, and 8.5 parts modified high-density polyethylene), 10 parts EPDM rubber, 7 parts compatibilizer (maleic anhydride-grafted ethylene-vinyl acetate copolymer), 10 parts flame retardant (composed of 9 parts alkenyl DOPO and 1 part rare earth modified nitrogen heterocyclic compound), and 2 parts stabilizer (antioxidant 1010). Set the temperature to 140℃ and stir until homogeneous. Cool down, then add 1 part peroxide (dicumyl peroxide) and 0.2 parts photoinitiator (1-hydroxycyclohexylphenyl ketone) in sequence. Stir until homogeneous at 90℃ to obtain the outer sheath material. Step 2: (1) Twist several cable core materials in the same direction to obtain a cable core, and set an insulating sleeve on its outside; (2) Melt and extrude the outer sheath material through a twin-screw extruder at a temperature of 160°C to form the cable outer sheath, wrap the outside, and irradiate with ultraviolet light to obtain a high-voltage cable.

[0027] Example 3: A method for preparing a flame-retardant and fireproof high-voltage cable for new energy vehicles, specifically including the following steps: Step 1: Mix 95 parts polyethylene (composed of 76 parts high-density polyethylene, 8.5 parts low-density polyethylene, and 10.5 parts modified high-density polyethylene), 15 parts EPDM rubber, 10 parts compatibilizer (maleic anhydride-grafted ethylene-vinyl acetate copolymer), 12 parts flame retardant (composed of 10 parts alkenyl DOPO and 2 parts rare earth modified nitrogen heterocyclic compounds), and 4 parts stabilizer (antioxidant 1010). Set the temperature to 160℃ and stir until homogeneous. Cool down, then add 2 parts peroxide (dicumyl peroxide) and 0.5 parts photoinitiator (1-hydroxycyclohexylphenyl ketone) in sequence. Stir until homogeneous at 90℃ to obtain the outer sheath material. Step 2: (1) Twist several cable core materials in the same direction to obtain a cable core, and set an insulating sleeve on its outside; (2) Melt and extrude the outer sheath material through a twin-screw extruder at a temperature of 160°C to form the cable outer sheath, wrap the outside, and irradiate with ultraviolet light to obtain a high-voltage cable.

[0028] Comparative Example 1: Based on Example 1, the flame retardant composition was adjusted, and a single alkenyl DOPO was added to prepare the outer sheath material. The rest remained the same as in Example 1. The specific steps are as follows: Step 1: Mix 88 parts polyethylene (composed of 70.5 parts high-density polyethylene, 8 parts low-density polyethylene, and 9.5 parts modified high-density polyethylene), 13 parts EPDM rubber, 8.5 parts compatibilizer (maleic anhydride-grafted ethylene-vinyl acetate copolymer), 11 parts flame retardant (alkenyl DOPO), and 3 parts stabilizer (antioxidant 1010) at 150°C until homogeneous. Cool down, then add 1.5 parts peroxide (dicumyl peroxide) and 0.3 parts photoinitiator (1-hydroxycyclohexylphenyl ketone) sequentially. Stir until homogeneous at 90°C to obtain the outer sheath material. Step 2: (1) Twist several cable core materials in the same direction to obtain a cable core, and set an insulating sleeve on its outside; (2) Melt and extrude the outer sheath material through a twin-screw extruder at a temperature of 160°C to form the cable outer sheath, wrap the outside, and irradiate with ultraviolet light to obtain a high-voltage cable.

[0029] Comparative Example 2: Based on Example 1, the flame retardant composition was adjusted, and a single rare earth-modified nitrogen heterocycle was added to prepare the outer sheath material. The rest remained the same as in Example 1. The specific steps are as follows: Step 1: Mix 88 parts polyethylene (composed of 70.5 parts high-density polyethylene, 8 parts low-density polyethylene, and 9.5 parts modified high-density polyethylene), 13 parts EPDM rubber, 8.5 parts compatibilizer (maleic anhydride-grafted ethylene-vinyl acetate copolymer), 11 parts flame retardant (rare earth modified nitrogen heterocyclic), and 3 parts stabilizer (antioxidant 1010) at 150°C until homogeneous. Cool down, then add 1.5 parts peroxide (dicumyl peroxide) and 0.3 parts photoinitiator (1-hydroxycyclohexylphenyl ketone) sequentially. Stir until homogeneous at 90°C to obtain the outer sheath material. Step 2: (1) Twist several cable core materials in the same direction to obtain a cable core, and set an insulating sleeve on its outside; (2) Melt and extrude the outer sheath material through a twin-screw extruder at a temperature of 160°C to form the cable outer sheath, wrap the outside, and irradiate with ultraviolet light to obtain a high-voltage cable.

[0030] Comparative Example 3: Based on Example 1, the flame retardant ratio was adjusted, and 1.5 parts of alkenyl DOPO and 9.5 parts of rare earth modified nitrogen heterocyclic compounds were added to prepare the outer sheath material. The rest remained the same as in Example 1. The specific steps are as follows: Step 1: Mix 88 parts polyethylene (composed of 70.5 parts high-density polyethylene, 8 parts low-density polyethylene, and 9.5 parts modified high-density polyethylene), 13 parts EPDM rubber, 8.5 parts compatibilizer (maleic anhydride-grafted ethylene-vinyl acetate copolymer), 11 parts flame retardant (composed of 1.5 parts alkenyl DOPO and 9.5 parts rare earth modified nitrogen heterocyclic compounds), and 3 parts stabilizer (antioxidant 1010) at 150°C until homogeneous. Cool down, then add 1.5 parts peroxide (dicumyl peroxide) and 0.3 parts photoinitiator (1-hydroxycyclohexylphenyl ketone) sequentially. Stir until homogeneous at 90°C to obtain the outer sheath material. Step 2: (1) Twist several cable core materials in the same direction to obtain a cable core, and set an insulating sleeve on its outside; (2) Melt and extrude the outer sheath material through a twin-screw extruder at a temperature of 160°C to form the cable outer sheath, wrap the outside, and irradiate with ultraviolet light to obtain a high-voltage cable.

[0031] Comparative Example 4: Based on Example 1, the composition of the outer sheath material was adjusted, wherein modified polyethylene was replaced with high-density polyethylene, while the rest remained the same as in Example 1. The specific steps are as follows: Step 1: Mix 88 parts polyethylene (composed of 80 parts high-density polyethylene and 8 parts low-density polyethylene), 13 parts EPDM rubber, 8.5 parts compatibilizer (maleic anhydride-grafted ethylene-vinyl acetate copolymer), 11 parts flame retardant (composed of 9.5 parts alkenyl DOPO and 1.5 parts rare earth modified nitrogen heterocyclic compounds), and 3 parts stabilizer (antioxidant 1010) at 150°C until homogeneous. Cool down, then add 1.5 parts peroxide (dicumyl peroxide) and 0.3 parts photoinitiator (1-hydroxycyclohexylphenyl ketone) sequentially. Stir until homogeneous at 90°C to obtain the outer sheath material. Step 2: (1) Twist several cable core materials in the same direction to obtain a cable core, and wrap an insulation layer around the outside of the cable core; (2) Melt and extrude the outer sheath material through a twin-screw extruder at a temperature of 160°C to form a cable outer sheath, which is wrapped around the insulation layer of the cable core, and then ultraviolet light is introduced to irradiate it to obtain a high-voltage cable.

[0032] Comparative Example 5: Based on Example 1, the composition of the outer sheath material was adjusted, wherein the rare earth modified nitrogen heterocycle was replaced with zinc sulfate, and the rest remained the same as in Example 1. The specific steps are as follows: Step 1: Mix 88 parts polyethylene (composed of 70.5 parts high-density polyethylene, 8 parts low-density polyethylene, and 9.5 parts modified high-density polyethylene), 13 parts EPDM rubber, 8.5 parts compatibilizer (maleic anhydride-grafted ethylene-vinyl acetate copolymer), 11 parts flame retardant (composed of 9.5 parts alkenyl DOPO and 1.5 parts zinc sulfate), and 3 parts stabilizer (antioxidant 1010) at 150°C until homogeneous. Cool down, then add 1.5 parts peroxide (dicumyl peroxide) and 0.3 parts photoinitiator (1-hydroxycyclohexylphenyl ketone) sequentially. Stir until homogeneous at 90°C to obtain the outer sheath material. Step 2: (1) Twist several cable core materials in the same direction to obtain a cable core, and set an insulating sleeve on its outside; (2) Melt and extrude the outer sheath material through a twin-screw extruder at a temperature of 160°C to form the cable outer sheath, wrap the outside, and irradiate with ultraviolet light to obtain a high-voltage cable.

[0033] Performance test 1: (1) Flame retardancy test: In accordance with GB / T2406.2-2009 "Determination of burning behavior of plastics by oxygen index method", the burning phenomenon of the outer sheath was observed using an oxygen index meter to determine the critical oxygen index value; (2) Mechanical property test: In accordance with GB / T1040.1-2025 "Determination of tensile properties of plastics", an electronic universal tensile testing machine was used with a tensile speed of 50 mm / min to test the tensile properties of the outer sheath; the obtained data are shown in the table below.

[0034] Table 1

[0035] Conclusion: Comparing the performance test data of Examples 1-3, it can be seen that the prepared cables and cable sheaths possess excellent flame retardancy and mechanical properties. The modified high-density polyethylene, through grafting hydroxyethyl methacrylate phosphate and a small amount of alkenyl DOPO, introduces polar groups into the matrix, enhancing its compatibility with alkenyl DOPO and rare-earth modified nitrogen heterocycles, promoting uniform dispersion. Simultaneously, the alkenyl groups in the alkenyl DOPO are fixed in the cross-linked network, effectively maintaining flame retardant efficiency and material stability. Furthermore, the lanthanum ions in the rare-earth modified nitrogen heterocycles catalyze the graphitization of the carbon layer, improving the condensed phase barrier effect, forming an effective synergy with the gas-phase flame retardant effect of the alkenyl DOPO. Through optimized proportioning, the flame retardancy is significantly improved while maintaining the material's mechanical properties.

[0036] Comparing Example 1 with Comparative Examples 1-5, the test data in Table 1 shows that: Comparative Example 1 uses only alkenyl DOPO, and the lack of rare earth modified nitrogen heterocycles results in an insignificant flame retardant effect in the condensed phase, leading to a significant decrease in the oxygen index; Comparative Example 2 uses only rare earth modified nitrogen heterocycles, lacking the gas-phase free radical capture effect of alkenyl DOPO and the fixing function of the alkenyl crosslinking network for the flame retardant, resulting in decreased flame retardant efficiency and poor dispersion stability, and consequently, reduced mechanical properties; Comparative Example 3 suffers from an imbalance in the ratio of alkenyl DOPO to rare earth modified nitrogen heterocycles, failing to form a sufficient crosslinking network, causing flame retardant agglomeration and stress concentration, leading to a decrease in both flame retardant and mechanical properties; Comparative Example 4 replaces modified high-density polyethylene with polyvinyl chloride, resulting in decreased compatibility and dispersibility of the formulation system, leading to a decrease in the uniformity of flame retardant dispersion, and consequently, a decrease in the oxygen index and tensile strength; Comparative Example 5 uses conventional metal salts to replace rare earth modified nitrogen heterocycles, and because the thermal stability of zinc ions and the strength of their decomposition product oxides are inferior to those of rare earth ions, the flame retardant performance of the material decreases. In summary, by using modified polyethylene as a polar compatibility bridging component, combined with the nitrogen-phosphorus synergistic flame retardancy of alkenyl DOPO and rare earth modified nitrogen heterocycles, the flame retardant performance can be effectively improved while ensuring the mechanical properties of the material.

[0037] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A flame-retardant and fireproof high-voltage cable for new energy vehicles, characterized in that: The high-voltage cable consists of a cable core, an insulating sleeve, and an outer sheath from the inside out. The outer sheath is made of the following components by weight: 80-95 parts polyethylene, 10-15 parts EPDM rubber, 7-10 parts compatibilizer, 10-12 parts flame retardant, 1-2 parts peroxide, 0.2-0.5 parts photoinitiator, and 2-4 parts stabilizer. The polyethylene includes high-density polyethylene, low-density polyethylene, and modified high-density polyethylene in a mass ratio of (64~76):(7.5~8.5):(8.5~10.5). The modified high-density polyethylene is prepared by mixing high-density polyethylene, dicumyl peroxide, hydroxyethyl methacrylate phosphate, and alkenyl DOPO, and then melting and extruding the mixture at 160~180℃ to obtain modified high-density polyethylene. The flame retardant comprises alkenyl DOPO and rare earth modified nitrogen heterocycles in a mass ratio of (9~10):(1~2); The alkenyl DOPO is prepared as follows: 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide is added to N,N-dimethylformamide; under a nitrogen atmosphere, the mixture is heated to 80-85°C and stirred until homogeneous; the mixture is cooled, sodium hydroxide is added, followed by 1,4-dichlorobenzyl and phenyl 4-chloroacrylate; the mixture is reacted at 65-75°C for 5-7 hours, and then filtered, washed, and dried to obtain alkenyl DOPO. The method for preparing the rare earth modified nitrogen heterocycle is as follows: tetrazahexacyclododecane and allyl glycidyl ether are added to ethanol and stirred at 78~80℃ for 2~3 days under a nitrogen atmosphere. Cool down, add lanthanum chloride hexahydrate, stir at 60-70℃ for 7-9 hours, filter, wash, and dry; Rare earth-modified nitrogen heterocycles were obtained.

2. The flame-retardant and fireproof high-voltage cable for new energy vehicles according to claim 1, characterized in that: The modified high-density polyethylene raw materials, by weight, consist of: 8-10 parts high-density polyethylene, 0.1-0.2 parts dicumyl peroxide, 0.5-0.7 parts hydroxyethyl methacrylate phosphate, and 0.3-0.5 parts alkenyl DOPO.

3. The flame-retardant and fireproof high-voltage cable for new energy vehicles according to claim 1, characterized in that: The raw materials of the alkenyl DOPO include the following components: by weight, 8-12 parts of 10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide, 50-60 parts of N,N-dimethylformamide, 1-3 parts of sodium hydroxide, 0.5-0.7 parts of 1,4-dichlorobenzyl, and 0.3-0.5 parts of 4-chloroacrylate.

4. The flame-retardant and fireproof high-voltage cable for new energy vehicles according to claim 1, characterized in that: The raw material for the rare earth modified nitrogen heterocycle includes the following components: by weight, 0.5-1.5 parts tetraazacyclododecane, 2.5-3 parts allyl glycidyl ether, and 0.5-1.5 parts lanthanum chloride hexahydrate.

5. The method for preparing a flame-retardant and fireproof high-voltage cable for new energy vehicles according to claim 1, characterized in that: Includes the following steps: Step 1: Mix polyethylene, EPDM rubber, compatibilizer, flame retardant, stabilizer, peroxide, and photoinitiator evenly to obtain the outer sheath material; Step 2: (1) Twist several cable core materials in the same direction to form a cable core, and set an insulating sleeve on its outside; (2) Melt and extrude the outer sheath material through a twin-screw extruder at a temperature of 155~170℃ to form an outer sheath, and wrap the outside; irradiate with ultraviolet light to obtain a high-voltage cable.

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