A cable insulation material

Abstract

The application discloses a cable insulation material, which comprises the following components in parts by weight: low-density polyethylene 40-60 parts, ethylene-vinyl acetate copolymer (EVA) 20-30 parts, composite anti-aging agent 2-5 parts, core-shell structure nano-composite modifier 5-10 parts, lubricant 1-2 parts, compatibilizer 3-8 parts, composite flame retardant 20-30 parts, nano-reinforcing agent 5-10 parts, and phenyl silane 2-4 parts. The core-shell structure modifier strengthens the interface bonding and cooperatively modifies the nano-reinforcing agent to disperse stress, so that the mechanical property and the high and low temperature resistance are improved. The composite anti-aging agent inhibits multi-path aging and improves the aging resistance. The material has excellent mechanical property, outstanding high and low temperature resistance and aging resistance, and meets the insulation quality and efficiency requirements of the cable in a complex use environment.

Description

Technical Field

[0001] This invention relates to the field of cable insulation materials, and in particular to a cable insulation material. Background Technology

[0002] Cable insulation materials are the core components that ensure the safe operation of cables. They must simultaneously possess excellent electrical insulation, mechanical strength, resistance to environmental aging, and processability.

[0003] Currently, mainstream cable insulation materials are based on polymers such as polyethylene (PE), cross-linked polyethylene (XLPE), polyvinyl chloride (PVC), and silicone rubber. However, while PVC has good processing performance and low cost, it has low heat resistance, releases toxic fumes when burning, and is environmentally unfriendly. PE / XLPE has excellent electrical properties, but its heat distortion temperature is limited; it melts and drips when exposed to fire, exacerbating the fire. Furthermore, while ordinary silicone rubber has excellent heat resistance and flexibility, its mechanical strength is low, its tear resistance is poor, and it quickly turns to ash under direct high-temperature flames, failing to maintain the integrity of the insulation structure and thus failing to meet the requirements of fire-resistant cables (which maintain circuit integrity in flames). Therefore, existing technologies often achieve fire resistance by adding a large amount of inorganic filler to silicone rubber to achieve ceramicization, but this has significant drawbacks: high filler content leads to poor mechanical properties at room temperature and difficulty in processing; the ceramic layer is porous and easily peels off, resulting in poor protective effect; pure methyl vinyl silicone rubber lacks sufficient heat resistance and arc resistance, while introducing phenyl silicone rubber sacrifices flexibility.

[0004] Therefore, there is an urgent need to develop a cable insulation material that combines resistance to high and low temperatures, long-term anti-aging properties, low cost, and easy processing. Summary of the Invention

[0005] The purpose of this invention is to provide a cable insulation material that combines resistance to high and low temperatures, long-term anti-aging properties, low cost, and easy processing.

[0006] This invention provides a cable insulation material comprising the following components in parts by weight: 40-60 parts of low-density polyethylene, 20-30 parts of ethylene-vinyl acetate copolymer (EVA), 2-5 parts of composite anti-aging agent, 5-10 parts of core-shell structure nanocomposite modifier, 1-2 parts of lubricant, 3-8 parts of compatibilizer, 20-30 parts of composite flame retardant, 5-10 parts of nano reinforcing agent, and 2-4 parts of phenylsilane.

[0007] As a preferred embodiment of the present invention, the VA content in the ethylene-vinyl acetate copolymer EVA is 15-25%.

[0008] As a preferred embodiment of the present invention, the composite anti-aging agent is a mixture of pentaerythritol ester, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and polypropylene adipate in a mass ratio of 2:1:0.5.

[0009] As a preferred embodiment of the present invention, the lubricant is calcium stearate.

[0010] As a preferred embodiment of the present invention, the compatibilizer is maleic anhydride-grafted polyethylene.

[0011] As a preferred technical solution of the present invention, the preparation method of the core-shell structured nanocomposite modifier is as follows: modified montmorillonite is dispersed in deionized water, and ultrasonically treated for 30-60 minutes under ultrasonic frequency of 20-40 Hz and ultrasonic temperature of 25-40℃. Boron nitride powder and coupling agent are added, and the mixture is stirred and reacted at 80-90℃ for 2-4 hours. After filtration, the mixture is dried at 60-80℃ for 12-20 hours and then pulverized to obtain the core-shell structured nanocomposite modifier.

[0012] As a preferred embodiment of the present invention, the modified montmorillonite is prepared by: dispersing sodium-based montmorillonite in 10-15 times its mass of deionized water and stirring to form a suspension; then sonicating at 300-500W and 25-30℃ for 30-60 minutes; after sonication, maintaining the temperature at 60-70℃ for 30 minutes to obtain an activated montmorillonite dispersion; weighing coupling agent KH550 at 5-15% of the mass of sodium-based montmorillonite; and then mixing coupling agent KH550 with a 50% ethanol solution at a mass ratio of 1:20-25. The pH was adjusted to 4-5 with glacial acetic acid, and the mixture was stirred for 15-30 min to obtain a hydrolyzed KH550 solution. The hydrolyzed KH550 solution was added to the activated montmorillonite dispersion and reacted at 75-85℃ for 2-4 h. After the reaction was completed, the mixture was cooled to room temperature, centrifuged at 8000-10000 rpm for 10-15 min, and the precipitate was collected. The precipitate was washed 2-3 times with a 50% ethanol solution and then dried in a vacuum drying oven at 60-80℃ for 12-24 h. After grinding through a 300-mesh sieve, modified montmorillonite was obtained.

[0013] As a preferred embodiment of the present invention, the mass ratio of the modified montmorillonite to deionized water is 1:20~30;

[0014] The mass ratio of the modified montmorillonite to boron nitride powder is 1:2~3;

[0015] The coupling agent is a titanate coupling agent, and the amount added is 1-3% of the total mass of modified montmorillonite and boron nitride.

[0016] As a preferred embodiment of the present invention, the composite flame retardant is a mixture of magnesium hydroxide, aluminum hydroxide and microcapsule red phosphorus in a mass ratio of 3:2:1, wherein the particle size of magnesium hydroxide and aluminum hydroxide is 1~5μm.

[0017] As a preferred embodiment of the present invention, the preparation method of the nano-reinforcing agent is as follows: Nano-calcium carbonate and deionized water are weighed at a mass ratio of 1:5-8, added to a high-speed disperser, and dispersed at 2000-3000 rpm for 20-30 minutes to obtain a nano-calcium carbonate dispersion; 2-5% by mass of silane coupling agent KH570 of nano-calcium carbonate is weighed and mixed with a 95% ethanol solution at a mass ratio of 1:10-15; the pH is adjusted to 5-6 using glacial acetic acid, and stirred at room temperature for 15-20 minutes. Hydrolysis was completed to obtain KH570 hydrolysate; the KH570 hydrolysate was slowly added dropwise to the nano-calcium carbonate dispersion, while the system temperature was raised to 60-70℃, and the reaction was stirred at 1500-2000 rpm for 1.5-2.5 h; after the reaction was completed, the mixture was centrifuged at 8000-10000 rpm for 10-15 min, the precipitate was collected, washed 2-3 times with deionized water, and then dried in a vacuum drying oven at 70-80℃ for 8-12 h. After grinding, it was passed through a 200-mesh sieve to obtain the nano-reinforcing agent.

[0018] As a preferred technical solution of the present invention, the method for preparing the cable insulation material includes the following steps: S1. Mixing and plasticizing: Low-density polyethylene, ethylene-vinyl acetate copolymer (EVA), composite flame retardant, compatibilizer and phenylsilane are added to a high-speed mixer and mixed at 80~90℃ for 10~15min. Then, a core-shell structured nanocomposite modifier, composite anti-aging agent, lubricant and nano reinforcing agent are added, and mixing is continued for 8~12min to obtain a premix; S2. Melt extrusion: The premix is ​​added to a twin-screw extruder, the screw speed is set to 100~150rpm, the extrusion temperature is 165~175℃, and after extrusion, cooling and pelletizing, the cable insulation material is obtained.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. The core-shell structured nanocomposite modifier in this invention uses modified montmorillonite as the core and boron nitride as the shell to synergistically improve the overall performance of cable insulation materials, resulting in superior insulation performance. The layered structure of modified montmorillonite hinders charge migration, while boron nitride combines high insulation and thermal conductivity. The combination of the two not only improves insulation resistance but also enhances heat dissipation, preventing localized overheating. Mechanical properties are enhanced, with the nanoscale core-shell structure exhibiting excellent dispersibility. After modification with a coupling agent, it has good compatibility with the matrix, strengthening tensile strength and impact resistance, and reducing material brittleness. Anti-aging and thermal stability are improved. Montmorillonite blocks oxygen and ultraviolet rays, while boron nitride is resistant to high temperatures, jointly delaying the aging process and extending service life. Furthermore, it has excellent processing adaptability. The core-shell structure avoids the agglomeration problem of traditional nanofillers and does not affect the melt flowability of the matrix, ensuring smooth processing such as extrusion granulation.

[0021] 2. This invention controls the content of low-density polyethylene (LDPE) and ethylene-vinyl acetate copolymer (EVA), with the VA content of EVA controlled at 15-25%. LDPE ensures the basic mechanical strength and insulation of the material, while EVA improves the flexibility of the material through flexible chain segments. The specific VA content range can avoid the decrease in thermal stability caused by excessive VA content.

[0022] 3. This invention comprises a composite anti-aging agent formulated from hindered phenolic antioxidant pentaerythritol ester, ultraviolet absorber 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, and anti-migration aid polypropylene adipate. The hindered phenolic antioxidant inhibits thermal oxidative degradation, the ultraviolet absorber shields ultraviolet light, and the anti-migration aid fixes the anti-aging agent through hydrogen bonding, preventing migration and precipitation, and extending anti-aging durability. Maleic anhydride-grafted polyethylene compatibilizer is added; its polar groups react with the surface functional groups of EVA and modified montmorillonite, optimizing the interfacial bonding force of each component. A lubricant (calcium stearate) is also added to improve the material's processing fluidity, making it suitable for industrial extrusion production.

[0023] 4. Nano-calcium carbonate modified with silane coupling agent KH570 is used as a nano-reinforcing agent. The nano-size results in a large specific surface area, and after dispersion, it bonds tightly with the interface of low-density polyethylene, EVA and other matrices, which can significantly enhance the tensile strength, elongation at break and impact resistance of the material. The nanoparticles can effectively disperse stress and absorb impact energy. After modification with KH570, the compatibility between inorganic nano-calcium carbonate and organic matrix is ​​greatly improved, avoiding agglomeration problems and ensuring the uniformity of mechanical properties of the material. At the same time, compared with other high-end reinforcing agents, nano-calcium carbonate is lower in cost, and the modified performance meets the standards, balancing performance and economy. Detailed Implementation

[0024] 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.

[0025] By constructing a core-shell structured nanocomposite modifier using modified montmorillonite as the core and boron nitride as the shell, the overall performance of cable insulation materials is synergistically improved, resulting in superior insulation performance. The layered structure of modified montmorillonite hinders charge migration, while boron nitride combines high insulation and thermal conductivity. The combination of the two not only increases insulation resistance but also improves heat dissipation, preventing localized overheating. Mechanical properties are enhanced, with the nanoscale core-shell structure exhibiting excellent dispersibility and good compatibility with the matrix after modification with a coupling agent. This strengthens tensile strength and impact resistance, reducing material brittleness. Anti-aging and thermal stability are improved, with montmorillonite blocking oxygen and ultraviolet radiation, and boron nitride resisting high temperatures, jointly delaying the aging process and extending service life. Furthermore, it exhibits excellent processing adaptability; the core-shell structure avoids the agglomeration problem of traditional nanofillers, does not affect the melt flowability of the matrix, and ensures smooth processing such as extrusion granulation.

[0026] By controlling the content of LDPE and EVA, and maintaining the VA content of EVA at 15-25%, the polar groups of VA can improve the compatibility of EVA with components such as composite flame retardants and nano-reinforcing agents, preventing agglomeration and ensuring uniform performance. Appropriate VA content can reduce the melt viscosity of the material, optimizing extrusion granulation processability; it also imparts flexibility to the material, preventing low-temperature brittleness and balancing mechanical and insulation properties. When VA > 25%, excessive polarity leads to a decrease in insulation resistance, violating the core requirements of insulation materials; the material's hygroscopicity increases, making it prone to aging with long-term use; mechanical strength (such as tensile strength) decreases, and excessive fluidity during melting easily leads to overflow problems during processing. When VA < 15%, EVA's performance is close to that of low-density polyethylene, lacking flexibility and prone to brittleness at low temperatures; poor compatibility with inorganic components leads to uneven flame retardant and reinforcing effects; high melt viscosity increases energy consumption during processing, easily causing uneven mixing and granulation difficulties.

[0027] Using nano-calcium carbonate as a base material, modified with silane coupling agent KH570, and uniformly dispersed through a specific process, the modified inorganic particles exhibit strong interfacial bonding with the organic matrix, along with fine particle size and large specific surface area. Its effects are significant: it enhances mechanical properties; the nano-size effect disperses stress and absorbs impact energy, greatly improving the material's tensile strength, elongation at break, and impact resistance; it optimizes compatibility; KH570 modification eliminates interfacial tension between inorganic and organic components, preventing agglomeration and ensuring uniformity in flame retardancy, anti-aging, and other properties; it provides synergistic effects, working synergistically with core-shell structured nanocomposite modifiers to enhance the overall structural stability of the material; it is suitable for processing, with good dispersibility that does not interfere with mixing, extrusion, and granulation processes, and its cost is lower than high-end reinforcing agents, balancing performance and economy.

[0028] This application provides a cable insulation material comprising the following components in parts by weight: 40-60 parts of low-density polyethylene, 20-30 parts of ethylene-vinyl acetate copolymer (EVA), 2-5 parts of composite anti-aging agent, 5-10 parts of core-shell structure nanocomposite modifier, 1-2 parts of lubricant, 3-8 parts of compatibilizer, 20-30 parts of composite flame retardant, 5-10 parts of nano reinforcing agent, and 2-4 parts of phenylsilane.

[0029] All raw materials used in this invention are commercially available.

[0030] Example 1: A cable insulation material comprising the following components in parts by weight: 60 parts of low-density polyethylene, 30 parts of ethylene-vinyl acetate copolymer (EVA), 5 parts of composite anti-aging agent, 10 parts of core-shell structure nanocomposite modifier, 2 parts of lubricant, 8 parts of compatibilizer, 30 parts of composite flame retardant, 10 parts of nano reinforcing agent, and 4 parts of phenylsilane.

[0031] The VA content in the ethylene-vinyl acetate copolymer EVA is 25%.

[0032] The composite anti-aging agent is composed of pentaerythritol ester, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and polypropylene adipate in a mass ratio of 2:1:0.5.

[0033] The lubricant is calcium stearate.

[0034] The compatibilizer is maleic anhydride-grafted polyethylene.

[0035] The composite flame retardant is a mixture of magnesium hydroxide, aluminum hydroxide and microencapsulated red phosphorus in a mass ratio of 3:2:1, wherein the particle size of magnesium hydroxide and aluminum hydroxide is 5μm.

[0036] The preparation method of the core-shell structured nanocomposite modifier is as follows: Modified montmorillonite is dispersed in deionized water, wherein the mass ratio of modified montmorillonite to deionized water is 1:30. After ultrasonic treatment at an ultrasonic frequency of 40 Hz and an ultrasonic temperature of 40 ℃ for 60 min, boron nitride powder (the mass ratio of modified montmorillonite to boron nitride powder is 1:3) and titanate coupling agent (the amount added is 3% of the total mass of modified montmorillonite and boron nitride) are added. The mixture is stirred and reacted at 90 ℃ for 4 h, filtered, and dried at 80 ℃ for 20 h. After drying, it is pulverized to obtain the core-shell structured nanocomposite modifier.

[0037] The preparation method of modified montmorillonite is as follows: Sodium-based montmorillonite is dispersed in 15 times its mass of deionized water and stirred into a suspension. Then, it is sonicated at 500W and 30℃ for 60 min. After sonication, it is kept at 70℃ for 30 min to obtain an activated montmorillonite dispersion. Coupling agent KH550 is weighed at 15% of the mass of sodium-based montmorillonite. Then, coupling agent KH550 is mixed with a 50% ethanol solution at a mass ratio of 1:25. The pH is adjusted to 5 with glacial acetic acid and stirred for 30 min to obtain a hydrolyzed KH550 solution. The hydrolyzed KH550 solution is added to the activated montmorillonite dispersion and reacted at 85℃ for 4 h. After the reaction, it is cooled to room temperature, centrifuged at 10000 rpm for 15 min, and the precipitate is collected. The precipitate is washed three times with a 50% ethanol solution and then dried in a vacuum drying oven at 80℃ for 24 h. After grinding through a 300-mesh sieve, modified montmorillonite is obtained.

[0038] The preparation method of the nano-reinforcing agent is as follows: Nano-calcium carbonate and deionized water are weighed at a mass ratio of 1:8 and added to a high-speed disperser. The mixture is dispersed at 3000 rpm for 30 min to obtain a nano-calcium carbonate dispersion. 5% (by mass) of silane coupling agent KH570 (by mass of nano-calcium carbonate) is weighed and mixed with a 95% ethanol solution at a mass ratio of 1:15. The pH is adjusted to 6 using glacial acetic acid, and the mixture is stirred at room temperature for 20 min to complete hydrolysis, yielding a KH570 hydrolysate. The KH570 hydrolysate is slowly added dropwise to the nano-calcium carbonate dispersion, while simultaneously raising the system temperature to 70℃ and stirring at 2000 rpm for 2.5 h. After the reaction, the mixture is centrifuged at 10000 rpm for 15 min, the precipitate is collected, washed three times with deionized water, dried in a vacuum drying oven at 80℃ for 12 h, and then ground through a 200-mesh sieve to obtain the nano-reinforcing agent.

[0039] A method for preparing cable insulation material includes the following steps:

[0040] S1. Mixing and Plasticizing: Low-density polyethylene, ethylene-vinyl acetate copolymer (EVA), composite flame retardant, compatibilizer and phenylsilane are added to a high-speed mixer and mixed at 90°C for 15 min. Then, core-shell structured nanocomposite modifier, composite anti-aging agent, lubricant and nano reinforcing agent are added and mixed for another 12 min to obtain a premix.

[0041] S2. Melt extrusion: The premixed material is added to a twin-screw extruder, the screw speed is set to 150 rpm, the extrusion temperature is 175℃, and after extrusion, cooling and pelletizing, cable insulation material is obtained.

[0042] Example 2: A cable insulation material comprising the following components in parts by weight: 40 parts low-density polyethylene, 20 parts ethylene-vinyl acetate copolymer EVA, 2 parts composite anti-aging agent, 5 parts core-shell structure nanocomposite modifier, 1 part lubricant, 3 parts compatibilizer, 20 parts composite flame retardant, 5 parts nano reinforcing agent, and 2 parts phenylsilane.

[0043] The VA content in the ethylene-vinyl acetate copolymer EVA is 15%.

[0044] The composite anti-aging agent is composed of pentaerythritol ester, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and polypropylene adipate in a mass ratio of 2:1:0.5.

[0045] The lubricant is calcium stearate.

[0046] The compatibilizer is maleic anhydride-grafted polyethylene.

[0047] The composite flame retardant is a mixture of magnesium hydroxide, aluminum hydroxide and microencapsulated red phosphorus in a mass ratio of 3:2:1, wherein the particle size of magnesium hydroxide and aluminum hydroxide is 1μm.

[0048] The preparation method of the core-shell structured nanocomposite modifier is as follows: Modified montmorillonite is dispersed in deionized water, wherein the mass ratio of modified montmorillonite to deionized water is 1:20. After ultrasonic treatment at an ultrasonic frequency of 20 Hz and an ultrasonic temperature of 25 ℃ for 30 min, boron nitride powder (the mass ratio of modified montmorillonite to boron nitride powder is 1:2) and titanate coupling agent (the amount added is 1% of the total mass of modified montmorillonite and boron nitride) are added. The mixture is stirred and reacted at 80 ℃ for 2 h, filtered, and dried at 60 ℃ for 12 h. After drying, it is pulverized to obtain the core-shell structured nanocomposite modifier.

[0049] The modified montmorillonite was prepared as follows: Sodium-based montmorillonite was dispersed in 10 times its mass of deionized water and stirred into a suspension. The suspension was then sonicated at 300W and 25℃ for 30 minutes. After sonication, the suspension was kept at 60℃ for 30 minutes to obtain an activated montmorillonite dispersion. Coupling agent KH550 was weighed at 5% of the sodium-based montmorillonite mass. KH550 was then mixed with a 50% ethanol solution at a mass ratio of 1:20. The pH was adjusted to 4 with glacial acetic acid, and the mixture was stirred for 15 minutes to obtain a hydrolyzed KH550 solution. The hydrolyzed KH550 solution was added to the activated montmorillonite dispersion and reacted at 75℃ for 2 hours. After the reaction, the mixture was cooled to room temperature, centrifuged at 8000 rpm for 10 minutes, and the precipitate was collected. The precipitate was washed twice with a 50% ethanol solution and then dried in a vacuum drying oven at 60℃ for 12 hours. After grinding through a 300-mesh sieve, modified montmorillonite was obtained.

[0050] The preparation method of the nano-reinforcing agent is as follows: Nano-calcium carbonate and deionized water are weighed at a mass ratio of 1:5 and added to a high-speed disperser. The mixture is dispersed at 2000 rpm for 20 min to obtain a nano-calcium carbonate dispersion. 2% (by mass) of silane coupling agent KH570 (by mass of nano-calcium carbonate) is weighed and mixed with a 95% ethanol solution at a mass ratio of 1:10. The pH is adjusted to 5 using glacial acetic acid, and the mixture is stirred at room temperature for 15 min to complete hydrolysis, yielding a KH570 hydrolysate. The KH570 hydrolysate is slowly added dropwise to the nano-calcium carbonate dispersion, while simultaneously raising the system temperature to 60℃ and stirring at 1500 rpm for 1.5 h. After the reaction, the mixture is centrifuged at 8000 rpm for 10 min, the precipitate is collected, washed twice with deionized water, dried in a vacuum drying oven at 70℃ for 8 h, and then ground through a 200-mesh sieve to obtain the nano-reinforcing agent.

[0051] A method for preparing cable insulation material includes the following steps:

[0052] S1. Mixing and Plasticizing: Low-density polyethylene, ethylene-vinyl acetate copolymer (EVA), composite flame retardant, compatibilizer and phenylsilane are added to a high-speed mixer and mixed at 80°C for 10 min. Then, core-shell structured nanocomposite modifier, composite anti-aging agent, lubricant and nano reinforcing agent are added and mixed for another 8 min to obtain a premix.

[0053] S2. Melt extrusion: The premixed material is added to a twin-screw extruder, the screw speed is set to 100 rpm, the extrusion temperature is 165℃, and after extrusion, cooling and pelletizing, cable insulation material is obtained.

[0054] Example 3: A cable insulation material comprising the following components in parts by weight: 50 parts low-density polyethylene, 25 parts ethylene-vinyl acetate copolymer (EVA), 4 parts composite anti-aging agent, 7 parts core-shell structure nanocomposite modifier, 1.5 parts lubricant, 5 parts compatibilizer, 25 parts composite flame retardant, 7 parts nano reinforcing agent, and 3 parts phenylsilane.

[0055] The VA content in the ethylene-vinyl acetate copolymer EVA is 20%.

[0056] The composite anti-aging agent is composed of pentaerythritol ester, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and polypropylene adipate in a mass ratio of 2:1:0.5.

[0057] The lubricant is calcium stearate.

[0058] The compatibilizer is maleic anhydride-grafted polyethylene.

[0059] The composite flame retardant is a mixture of magnesium hydroxide, aluminum hydroxide and microencapsulated red phosphorus in a mass ratio of 3:2:1, wherein the particle size of magnesium hydroxide and aluminum hydroxide is 3μm.

[0060] The preparation method of the core-shell structured nanocomposite modifier is as follows: Modified montmorillonite is dispersed in deionized water, wherein the mass ratio of modified montmorillonite to deionized water is 1:25. After ultrasonic treatment at an ultrasonic frequency of 30 Hz and an ultrasonic temperature of 35 ℃ for 45 min, boron nitride powder (the mass ratio of modified montmorillonite to boron nitride powder is 1:2.5) and titanate coupling agent (the amount added is 2% of the total mass of modified montmorillonite and boron nitride) are added. The mixture is stirred and reacted at 85 ℃ for 3 h, filtered, and dried at 70 ℃ for 16 h. After drying, it is pulverized to obtain the core-shell structured nanocomposite modifier.

[0061] The modified montmorillonite was prepared as follows: Sodium-based montmorillonite was dispersed in 12 times its mass of deionized water and stirred into a suspension. The suspension was then sonicated at 400W and 27℃ for 45 min. After sonication, the suspension was kept at 65℃ for 30 min to obtain an activated montmorillonite dispersion. Coupling agent KH550 was weighed at 10% of the sodium-based montmorillonite mass. KH550 was then mixed with a 50% ethanol solution at a mass ratio of 1:23. The pH was adjusted to 4.5 with glacial acetic acid, and the mixture was stirred for 23 min to obtain a hydrolyzed KH550 solution. The hydrolyzed KH550 solution was added to the activated montmorillonite dispersion and reacted at 80℃ for 3 h. After the reaction, the mixture was cooled to room temperature, centrifuged at 9000 rpm for 13 min, and the precipitate was collected. The precipitate was washed three times with a 50% ethanol solution and then dried in a vacuum drying oven at 70℃ for 18 h. After grinding through a 300-mesh sieve, modified montmorillonite was obtained.

[0062] The preparation method of the nano-reinforcing agent is as follows: Nano-calcium carbonate and deionized water are weighed at a mass ratio of 1:7 and added to a high-speed disperser. The mixture is dispersed at 2500 rpm for 25 min to obtain a nano-calcium carbonate dispersion. 3.5% (by mass) of silane coupling agent KH570 (by mass of nano-calcium carbonate) is weighed and mixed with a 95% ethanol solution at a mass ratio of 1:13. The pH is adjusted to 5.5 using glacial acetic acid, and the mixture is stirred at room temperature for 17 min to complete hydrolysis, yielding a KH570 hydrolysate. The KH570 hydrolysate is slowly added dropwise to the nano-calcium carbonate dispersion, while simultaneously raising the system temperature to 65℃ and stirring at 1750 rpm for 2 h. After the reaction, the mixture is centrifuged at 9000 rpm for 13 min, the precipitate is collected, washed three times with deionized water, dried in a vacuum drying oven at 75℃ for 10 h, and then ground through a 200-mesh sieve to obtain the nano-reinforcing agent.

[0063] A method for preparing cable insulation material includes the following steps:

[0064] S1. Mixing and Plasticizing: Low-density polyethylene, ethylene-vinyl acetate copolymer (EVA), composite flame retardant, compatibilizer and phenylsilane are added to a high-speed mixer and mixed at 85°C for 13 min. Then, core-shell structured nanocomposite modifier, composite anti-aging agent, lubricant and nano reinforcing agent are added and mixed for another 10 min to obtain a premix.

[0065] S2. Melt extrusion: The premixed material is added to a twin-screw extruder, the screw speed is set to 125 rpm, the extrusion temperature is 170℃, and after extrusion, cooling and pelletizing, cable insulation material is obtained.

[0066] Comparative Example 1:

[0067] The difference from Example 1 is that the core-shell structure nanocomposite modifier is removed.

[0068] Comparative Example 2:

[0069] The difference from Example 1 is that the nano-reinforcing agent is removed.

[0070] Comparative Example 3:

[0071] The difference from Example 1 is that the composite anti-aging agent is removed.

[0072] The cable insulation materials prepared in Examples 1, 2, and 3, and Comparative Examples 1, 2, and 3 were subjected to performance tests. Tensile strength, elongation at break, and the rate of change of tensile strength and elongation at break after being placed at 150°C for 7 days were tested according to standard GB / T1040.2-2022. Low-temperature embrittlement temperature was tested according to standard GB / T5470-2008. The test results are shown in Table 1.

[0073] Table 1: Performance Tests of Cable Insulation Materials Prepared in Examples and Comparative Examples

[0074]

[0075] As can be seen from the table, the cable insulation material prepared in the embodiment group of the present invention not only has better high-temperature stability and low-temperature embrittlement resistance than the comparative group, but also shows more outstanding performance in anti-aging properties and mechanical strength indicators such as tensile strength and elongation at break, fully demonstrating the synergistic effect of each key component in the formula.

[0076] The synergistic effect of core-shell structured nanocomposite modifiers, nano-reinforcing agents, and composite anti-aging agents significantly improves the overall performance of cable insulation materials. In the core-shell structured nanocomposite modifier, the core-shell structure formed by modified montmorillonite and boron nitride strengthens the interfacial bonding force, enhancing mechanical strength. Furthermore, the heat resistance of boron nitride and the structural stability of montmorillonite optimize high and low temperature resistance, preventing material brittleness or softening under sudden temperature changes. The nano-reinforcing agent, modified with KH570, exhibits excellent compatibility with the organic matrix. Its nano-size effect ensures uniform dispersion, effectively dispersing stress and absorbing impact energy, significantly enhancing tensile strength and elongation at break. The composite anti-aging agent, using a compound system including pentaerythritol esters, specifically inhibits various aging pathways such as high-temperature oxidation and photo-aging, delaying material degradation and maintaining mechanical and temperature stability during long-term use. The combination of these three components results in robust mechanical strength, a wider range of high and low temperature resistance, and longer anti-aging duration, achieving a balanced improvement in all performance aspects and adapting to the complex operating environments of cables.

[0077] In summary, the cable insulation material prepared by this invention combines resistance to high and low temperatures, long-term anti-aging properties, low cost, and ease of processing, making it suitable for cable laying in extreme environments.

[0078] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A cable insulation material, characterized by The components include the following parts by weight: low-density polyethylene 40-60 parts, ethylene-vinyl acetate copolymer EVA 20-30 parts, composite anti-aging agent 2-5 parts, core-shell structure nano-composite modifier 5-10 parts, lubricant 1-2 parts, compatibilizer 3-8 parts, composite flame retardant 20-30 parts, nano-reinforcing agent 5-10 parts, phenylsilane 2-4 parts; The composite anti-aging agent is a compound of pentaerythritol ester, 2-(2'-hydroxy-5'-methylphenyl) benzotriazole and polypropylene adipate with a mass ratio of 2:1:0.5; The preparation method of the core-shell structure nano-composite modifier is as follows: modified montmorillonite is dispersed in deionized water, and under the conditions of ultrasonic frequency of 20-40 Hz and ultrasonic temperature of 25-40 DEG C, ultrasonic treatment is carried out for 30-60 min, then boron nitride powder and coupling agent are added, stirring reaction is carried out at 80-90 DEG C for 2-4 h, then filtration is carried out, and under the conditions of temperature of 60-80 DEG C, drying is carried out for 12-20 h, then crushing is carried out, and the core-shell structure nano-composite modifier is obtained; The preparation method of the modified montmorillonite is as follows: sodium-based montmorillonite is dispersed in deionized water with a mass of 10-15 times of the sodium-based montmorillonite, and stirring is carried out to form a suspension, then ultrasonic treatment is carried out at 300-500 W and 25-30 DEG C for 30-60 min, and after the ultrasonic treatment, the activated montmorillonite dispersion is obtained by keeping the temperature at 60-70 DEG C for 30 min; the coupling agent KH550 is weighed according to 5-15% of the mass of the sodium-based montmorillonite, then the coupling agent KH550 is mixed with an ethanol solution with a mass concentration of 50% according to a mass ratio of 1:20-25, and the pH is adjusted to 4-5 by using glacial acetic acid, and stirring is carried out for 15-30 min to obtain the hydrolyzed KH550 solution; the hydrolyzed KH550 solution is added to the activated montmorillonite dispersion, and reaction is carried out at 75-85 DEG C for 2-4 h, then the reaction is cooled to room temperature, centrifugation is carried out at 8000-10000 rpm for 10-15 min, and then the precipitate is collected, the precipitate is washed with the ethanol solution with a mass concentration of 50% for 2-3 times, then drying is carried out in a vacuum drying oven at 60-80 DEG C for 12-24 h, and the modified montmorillonite is obtained by grinding through a 300-mesh sieve. The preparation method of the nano reinforcing agent is as follows: taking nano calcium carbonate and deionized water according to a mass ratio of 1:5-8, adding into a high-speed dispersion machine, dispersing at a rotation speed of 2000-3000 rpm for 20-30 min to obtain a nano calcium carbonate dispersion liquid; taking 2-5% of the nano calcium carbonate in mass of a silane coupling agent KH570, mixing with a 95% ethanol solution according to a mass ratio of 1:10-15, using glacial acetic acid to adjust the pH to 5-6, stirring at room temperature for 15-20 min to complete hydrolysis, obtaining a KH570 hydrolysis liquid; slowly dropping the KH570 hydrolysis liquid into the nano calcium carbonate dispersion liquid, at the same time, raising the system temperature to 60-70℃, stirring at a rotation speed of 1500-2000 rpm for 1.5-2.5 h; after the reaction is completed, centrifuging at 8000-10000 rpm for 10-15 min, collecting the precipitate, washing 2-3 times with deionized water, and then placing in a vacuum drying oven for drying at 70-80℃ for 8-12 h, grinding through a 200 mesh sieve, to obtain the nano reinforcing agent.

2. A cable insulation material according to claim 1, characterised in that The VA content in the ethylene-vinyl acetate copolymer EVA is 15-25%.

3. A cable insulation material according to claim 1, characterised in that The lubricant is calcium stearate; and the compatilizer is maleic anhydride grafted polyethylene.

4. The cable insulation material according to claim 1, characterized in that: The mass ratio of the modified montmorillonite to deionized water is 1:20-30; The mass ratio of the modified montmorillonite to boron nitride powder is 1:2-3; The coupling agent is a titanate coupling agent, and the addition amount is 1-3% of the total mass of the modified montmorillonite and the boron nitride.

5. A cable insulating material according to claim 1, wherein The composite flame retardant is a mixture of magnesium hydroxide, aluminum hydroxide and microcapsule red phosphorus in a mass ratio of 3:2:1, wherein the particle size of the magnesium hydroxide and the aluminum hydroxide is 1-5 μm.

6. A process for the preparation of a cable insulation material according to any one of claims 1 to 5, characterized in that The method comprises the following steps: S1. Mixing and plasticizing: adding low-density polyethylene, ethylene-vinyl acetate copolymer EVA, composite flame retardant, compatilizer and phenylsilane into a high-speed mixer, mixing at 80-90℃ for 10-15 min, and then adding core-shell structure nano composite modifier, composite anti-aging agent, lubricant and nano reinforcing agent, continuing to mix for 8-12 min to obtain a premix; S2. Melt extrusion: adding the premix into a twin-screw extruder, setting the screw rotation speed to 100-150 rpm, and setting the extrusion temperature to 165-175℃, and then extruding, cooling and pelletizing to obtain the cable insulation material.

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