Ant termite flame-retardant crosslinked polyethylene insulated high-voltage power cable and preparation method thereof

Abstract

This invention relates to the field of high-voltage power cable technology, and discloses a termite-resistant and flame-retardant cross-linked polyethylene insulated high-voltage power cable and its preparation method. The insulated high-voltage power cable of this invention comprises, from the inside out, a conductor core, a conductor shielding layer, an insulation layer, an insulation shielding layer, a metal shielding layer, and a protective layer. The protective layer comprises the following raw materials in parts by weight: 45-65 parts polypropylene, 3-7 parts EPDM rubber, 1-2 parts EPDM rubber grafted with maleic anhydride, 3-8 parts modified flame retardant, 0.3-1 part antioxidant 1010, 1-3 parts termite repellent, 0.5-1 part light stabilizer 770, 1-1.5 parts calcium stearate, 1-2 parts tributyl acetylacetonate, and 0.2-0.5 parts glyceryl monostearate. The termite repellent of this invention can significantly improve the long-term termite resistance of the cable and is also environmentally friendly; the modified flame retardant can optimize the flame-retardant performance of the protective layer and effectively delay the spread of flame.

Description

Technical Field

[0001] This invention relates to the field of high-voltage power cable technology, specifically to a termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable and its preparation method. Background Technology

[0002] High-voltage power cables are core equipment in power transmission networks, responsible for long-distance, high-capacity power transmission. They are crucial infrastructure connecting the power generation and consumption sides, ensuring the safe and stable operation of the main power grid. They are widely used in power transmission channels from new energy bases, cross-sea transmission lines, and high-voltage power supply systems for large industrial and mining enterprises. Cross-linked polyethylene (XLPE) insulated high-voltage power cables are currently the mainstream cable type in the high-voltage transmission field. Compared to traditional paper-insulated cables, XLPE insulated high-voltage cables have significant advantages such as low dielectric loss, high current carrying capacity, and ease of maintenance, making them the preferred cable type for high-voltage transmission projects worldwide. However, in actual engineering applications, the laying environment of high-voltage cables is complex and diverse. Especially in the hot and humid regions of southern my country, where termites are prevalent, the cable outer sheath faces the risk of biological damage from termite attacks. Termites can gradually erode the metal sheath and insulation structure by gnawing at the outer sheath, causing insulation dampness, electric field distortion, and ultimately electrical breakdown, even leading to large-scale regional power outages. Currently, commonly used chemical protection agents are mostly small-molecule termite repellents. However, under long-term high-temperature operation and outdoor exposure to sun and rain, these agents are prone to migration, precipitation, and photothermal decomposition. In addition, the cable itself poses a safety hazard of flammability and fire hazards. Termite repellency and flame retardancy have become key bottlenecks restricting the long-term safe operation of high-voltage cross-linked polyethylene insulated cables in complex environments.

[0003] Patent application number 202310680328.1 discloses an environmentally friendly ant and rodent-proof cable, which achieves its ant and rodent-proof effect by adding azadirachtin and capsaicin to the cable's protective layer. However, the organic small molecules have poor compatibility with the polymer matrix and are prone to migration and precipitation in complex outdoor environments, failing to meet the long-term service life requirements of the cable. Patent application number 202510977474.X discloses an ant-proof flame-retardant cable and its preparation method, using magnesium hydroxide and aluminum hydroxide as flame retardants for the cable's protective layer. However, inorganic flame retardants have low flame-retardant efficiency and are prone to affecting the mechanical properties of the material, easily agglomerating and affecting the flame-retardant durability. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions: A termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable comprises, from the inside out, a conductor core, a conductor shielding layer, an insulation layer, an insulation shielding layer, a metal shielding layer, and a protective layer; The core consists of 7 stranded copper wires; The insulating layer is made of cross-linked polyethylene insulating material; Both the conductor shielding layer and the insulating shielding layer are made of ethylene-vinyl acetate copolymer material; The metal shielding layer is formed by a conductive metal strip made of aluminum spirally wrapped around an insulating shielding layer. The protective layer comprises the following raw materials in parts by weight: 45-65 parts polypropylene, 3-7 parts EPDM rubber, 1-2 parts EPDM rubber grafted with maleic anhydride, 3-8 parts modified flame retardant, 0.3-1 part antioxidant 1010, 1-3 parts termite repellent, 0.5-1 part light stabilizer 770, 1-1.5 parts calcium stearate, 1-2 parts tributyl acetylacetonate, and 0.2-0.5 parts glyceryl monostearate. The ant repellent is prepared by the following steps: Step A1: Mix natural capsaicin, 1,3-dibromopropane and acetonitrile, then add anhydrous potassium carbonate, and reflux at 80°C for 36 h. After the reaction is complete, cool to room temperature, extract with ethyl acetate, wash with saturated sodium chloride solution, dry, concentrate under reduced pressure and purify to obtain intermediate product 1. Furthermore, the ratio of natural capsaicin, 1,3-dibromopropane, acetonitrile, anhydrous potassium carbonate, ethyl acetate, and saturated sodium chloride solution is 0.1-0.3 mol: 0.3-0.9 mol: 200-600 mL: 0.3-0.9 mol: 300-600 mL: 400-700 mL; In step A1, natural capsaicin and 1,3-dibromopropane undergo a nucleophilic substitution reaction, introducing a bromine group into the system and providing reaction conditions for the subsequent quaternization reaction. Natural capsaicin is one of the active ingredients in chili peppers and has the characteristics of low toxicity, environmental friendliness, and biodegradability. Capsaicin-like substances have both contact and stomach poison effects on termites. They can be directly contacted or ingested by termites, interfering with their nervous system function and causing paralysis or death.

[0006] Step A2: Mix intermediate product 1, dodecyl dimethyl tertiary amine and acetonitrile, reflux at 80°C for 36 h, after the reaction is completed, cool to room temperature, concentrate under reduced pressure, and wash three times with methyl tert-butyl ether to obtain intermediate product 2. Furthermore, the ratio of intermediate product 1, dodecyl dimethyl tert-amine, acetonitrile, and methyl tert-butyl ether is 0.08-0.16 mol: 0.24-0.48 mol: 200-300 mL: 150-300 mL; In step A2, intermediate 1 and dodecyl dimethyl tertiary amine undergo a quaternization reaction, introducing a hydrophobic alkyl long chain into the system, providing favorable conditions for subsequent inclusion by cyclodextrin. The resulting quaternary ammonium salt structure can disrupt the insect cell membrane structure, causing ants to avoid or even die after contact.

[0007] Step A3: Dissolve hydroxypropyl-β-cyclodextrin in deionized water to obtain a saturated solution of hydroxypropyl-β-cyclodextrin. Separately, mix intermediate product 2 with anhydrous ethanol, heat in a water bath to 65°C, and add the saturated solution of hydroxypropyl-β-cyclodextrin dropwise while stirring. After stirring for 3 hours, stop heating, stir in a water bath until room temperature, evaporate by rotary evaporation, filter, concentrate, and freeze dry to obtain the ant repellent. Furthermore, the ratio of hydroxypropyl-β-cyclodextrin, deionized water, intermediate 2, and anhydrous ethanol is 0.18-0.24 mol: 600-800 mL: 0.06-0.08 mol: 500-600 mL; In step A3, hydroxypropyl-β-cyclodextrin forms an inclusion complex with intermediate product 2. The long-chain alkyl group in intermediate product 2 endows natural capsaicin with good flexibility and hydrophobicity, which can form a size match with the hydrophobic cavity of cyclodextrin, thereby improving the host-guest inclusion efficiency. Cyclodextrin encapsulates the ant-repellent molecules in the hydrophobic cavity through hydrophobic interactions, forming a stable inclusion complex. This allows the ant-repellent active ingredient to release its activity slowly, maintaining the long-term ant-repellent effect of the cable, while also improving its thermal stability and avoiding decomposition and volatilization losses during processing.

[0008] The modified flame retardant is prepared by the following steps: Step B1: Mix 3-aminopropyltriethoxysilane, furfural and anhydrous ethanol, stir and reflux at 75°C for 3 hours, then lower the temperature to 70°C, add phosphoric acid, and continue stirring for 3 hours. After the reaction is complete, cool to room temperature and dry under vacuum to obtain silicic acid-furan coupling agent. Furthermore, the molar ratio of 3-aminopropyltriethoxysilane, furfural, anhydrous ethanol, and phosphoric acid is 0.04-0.1 mol: 0.04-0.1 mol: 400-500 mL: 0.04-0.1 mol; In step B1, 3-aminopropyltriethoxysilane and furfural first undergo an aldehyde-amine condensation reaction, followed by an addition reaction with phosphoric acid, introducing siloxane into the system and providing reaction conditions for the subsequent grafting reaction. The introduced phosphorus-containing structure is decomposed into acidic substances such as metaphosphoric acid and pyrophosphoric acid at high temperature, which promotes the dehydration and carbonization of polypropylene molecular chains, forming a dense and expanded carbon layer that can insulate against heat and oxygen and inhibit the release of combustibles. The furanyl group has excellent carbonization performance and can undergo cross-linking and carbonization at high temperature, thereby improving the char formation of the polymer. In addition, the nitrogen and phosphorus elements in the structure can form more stable nitrogen-carbon and phosphorus-carbon cross-linked structures, which helps to form a stable and dense carbon layer.

[0009] Step B2: Mix attapulgite and deionized water, sonicate for 8 minutes, centrifuge, repeat 3 times, freeze for 24 hours, grind and sieve, dry the ground attapulgite, then mix with toluene, heat to 110°C under nitrogen protection, stir, reflux for 30 minutes, then add silicon-based phosphoric acid-furan coupling agent solution dropwise, continue the reaction for 1 hour, then centrifuge, wash, and vacuum dry to obtain the modified flame retardant; Furthermore, the ratio of attapulgite, deionized water, toluene, and silicic acid-furan coupling agent solution is 3g: 500-600mL: 60-70mL: 40-80mL; Furthermore, the silicon-based phosphoric acid-furan coupling agent solution is prepared by mixing silicon-based phosphoric acid-furan coupling agent and anhydrous ethanol at a volume ratio of 0.01-0.03 mol: 40-80 mL; In step B2, a silicon-based phosphoric acid-furan coupling agent is grafted onto the surface of attapulgite. Attapulgite is rich in magnesium and aluminum, and at high temperatures, a thermally stable oxide char layer mainly composed of magnesium oxide and aluminum oxide is generated on its surface. This char layer has heat insulation and oxygen barrier functions, and can also improve the mechanical properties of the polymer matrix. It works synergistically with phosphorus, nitrogen, and furan groups to construct an organic-inorganic composite system, significantly enhancing the density and anti-dripping ability of the char layer. At the same time, it improves the compatibility between the inorganic filler and the matrix, and enhances the flame retardant properties of the material.

[0010] A method for preparing a termite-resistant and flame-retardant cross-linked polyethylene insulated high-voltage power cable includes the following steps: Step S1: Using an extruder, a conductor shielding layer is extruded and deposited on the outer periphery of the wire core, and an insulating layer is extruded and deposited on the outer periphery of the conductor shielding layer to form an insulating layer; Step S2: Extrude and deposit an insulating shielding layer on the outer periphery of the insulating layer, and then wrap an aluminum conductive metal strip around the outer periphery of the insulating shielding layer in a spiral to obtain a metal shielding layer. Step S3: Weigh the protective layer raw materials according to the weight proportions, stir and mix the weighed raw materials evenly for 8-15 minutes, extrude and deposit them on the outer periphery of the metal shielding layer to obtain the protective layer, anneal after extrusion, the extrusion temperature is 180-210℃, and the termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable is obtained.

[0011] The beneficial effects of this invention are: The termite-resistant and flame-retardant cross-linked polyethylene insulated high-voltage power cable of this invention can be widely used in various high-voltage power transmission scenarios such as outdoor high-voltage power transmission and distribution, municipal underground pipelines, and rail transit. In the production of the cable protective layer, the addition of the termite repellent and modified flame retardant prepared in this invention endows the cable with dual core protective properties: on the one hand, it significantly improves the product's long-term termite resistance, effectively repelling and blocking termites from gnawing and damaging the cable, avoiding major safety hazards such as insulation layer damage and high-voltage leakage caused by biological erosion, while also being environmentally friendly and not polluting the surrounding water and soil environment; on the other hand, it optimizes the flame-retardant properties of the protective layer, significantly reducing the material's heat release rate, effectively delaying flame spread and inhibiting the release of toxic and harmful fumes, ensuring the cable's line integrity and emergency power supply capability in fire scenarios. Compared with existing technologies, this invention, through the synergistic compounding and system optimization of the termite repellent and modified flame retardant, simultaneously achieves the dual core functions of highly efficient and environmentally friendly termite resistance and high-level flame retardancy without sacrificing the mechanical processing performance of the cable protective layer, and has broad application prospects in the field of high-voltage power transmission.

[0012] The termite repellent of this invention first utilizes a nucleophilic substitution reaction between natural capsaicin and 1,3-dibromopropane. Natural capsaicin is one of the active ingredients in chili peppers, characterized by low toxicity, environmental friendliness, and biodegradability. Capsaicin-like substances have both contact and stomach poison effects on termites, allowing them to enter the termite body through direct contact or ingestion, interfering with their nervous system function and leading to paralysis or death. Subsequently, a quaternization reaction occurs with dodecyl dimethyl tertiary amine. The resulting quaternary ammonium salt structure can disrupt the insect cell membrane structure, causing termites to avoid contact or even die. Finally, an inclusion complex is formed with hydroxypropyl-β-cyclodextrin. The long-chain alkyl group imparts good flexibility and hydrophobicity to natural capsaicin, allowing it to form a size match with the hydrophobic cavity of cyclodextrin, improving the host-guest inclusion efficiency. Cyclodextrin encapsulates the termite repellent molecules within the hydrophobic cavity through hydrophobic interactions, forming a stable inclusion complex. This allows the termite repellent active ingredient to release its activity slowly, maintaining the long-term termite-repelling effect of the cable, while also improving its thermal stability and avoiding decomposition and volatilization losses during processing.

[0013] The modified flame retardant of this invention first utilizes 3-aminopropyltriethoxysilane and furfural to undergo an aldehyde-amine condensation reaction, followed by an addition reaction with phosphoric acid. The introduced phosphorus-containing structure is decomposed into acidic substances such as metaphosphoric acid and pyrophosphoric acid at high temperatures, which promotes the dehydration and carbonization of polypropylene molecular chains, forming a dense and expanded carbon layer that can insulate against heat and oxygen, and inhibit the release of combustibles. The furanyl group has excellent carbonization performance and can undergo cross-linking and carbonization at high temperatures, thereby improving the char formation of the polymer. In addition, the nitrogen and phosphorus elements in the structure can form more stable nitrogen-carbon and phosphorus-carbon cross-linked structures, which helps to form a stable and dense carbon layer. Subsequently, it is grafted onto the surface of attapulgite. Attapulgite is rich in magnesium and aluminum. At high temperatures, a thermally stable oxide char layer mainly composed of magnesium oxide and aluminum oxide is generated on its surface, which has the functions of heat insulation and oxygen barrier. It can also improve the mechanical properties of the polymer matrix. It works synergistically with phosphorus, nitrogen and furan groups to construct an organic-inorganic composite system, which significantly enhances the density and anti-dripping ability of the char layer. At the same time, it improves the compatibility between inorganic fillers and matrix and improves the flame retardant properties of the material. Detailed Implementation

[0014] 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.

[0015] Example 1: The ant repellent was prepared by the following steps: Step A1: Mix natural capsaicin, 1,3-dibromopropane, and acetonitrile, then add anhydrous potassium carbonate, and reflux at 80°C for 36 hours. After the reaction is complete, cool to room temperature, extract with ethyl acetate, wash with saturated sodium chloride solution, dry, concentrate under reduced pressure, and purify to obtain intermediate product 1. The ratio of natural capsaicin, 1,3-dibromopropane, acetonitrile, anhydrous potassium carbonate, ethyl acetate, and saturated sodium chloride solution is 0.1 mol: 0.3 mol: 200 mL: 0.3 mol: 300 mL: 400 mL. Step A2: Mix intermediate product 1, dodecyl dimethyl tertiary amine and acetonitrile, reflux at 80°C for 36 h. After the reaction is complete, cool to room temperature, concentrate under reduced pressure, and wash three times with methyl tert-butyl ether to obtain intermediate product 2. The ratio of intermediate product 1, dodecyl dimethyl tertiary amine, acetonitrile and methyl tert-butyl ether is 0.08 mol: 0.24 mol: 200 mL: 150 mL. Step A3: Dissolve hydroxypropyl-β-cyclodextrin in deionized water to obtain a saturated hydroxypropyl-β-cyclodextrin solution. Separately, mix intermediate product 2 and anhydrous ethanol, heat in a water bath to 65°C, and add the saturated hydroxypropyl-β-cyclodextrin solution dropwise while stirring. After stirring for 3 hours, stop heating, stir in a water bath until room temperature, rotary evaporate, filter, concentrate, and freeze dry to obtain the ant repellent. The ratio of hydroxypropyl-β-cyclodextrin, deionized water, intermediate product 2, and anhydrous ethanol is 0.18 mol: 600 mL: 0.06 mol: 500 mL.

[0016] The modified flame retardant is prepared by the following steps: Step B1: Mix 3-aminopropyltriethoxysilane, furfural, and anhydrous ethanol, and stir and reflux at 75°C for 3 hours. Then, lower the temperature to 70°C, add phosphoric acid, and continue stirring for 3 hours. After the reaction is complete, cool to room temperature and dry under vacuum to obtain a silanized phosphoric acid-furan coupling agent. The molar ratio of 3-aminopropyltriethoxysilane, furfural, anhydrous ethanol, and phosphoric acid is 0.04 mol: 0.04 mol: 400 mL: 0.04 mol. Step B2: Mix attapulgite and deionized water, sonicate for 8 minutes, centrifuge, repeat 3 times, freeze for 24 hours, grind and sieve, dry the ground attapulgite, then mix with toluene, heat to 110℃ under nitrogen protection, stir, reflux for 30 minutes, then add silicon-based phosphoric acid-furan coupling agent solution dropwise, continue the reaction for 1 hour, then centrifuge, wash, and vacuum dry to obtain the modified flame retardant. The ratio of attapulgite, deionized water, toluene, and silicon-based phosphoric acid-furan coupling agent solution is 3g:500mL:60mL:40mL. The silicon-based phosphoric acid-furan coupling agent solution is prepared by mixing silicon-based phosphoric acid-furan coupling agent and anhydrous ethanol at a ratio of 0.01mol:40mL.

[0017] Example 2: The ant repellent was prepared by the following steps: Step A1: Mix natural capsaicin, 1,3-dibromopropane, and acetonitrile, then add anhydrous potassium carbonate, and reflux at 80°C for 36 hours. After the reaction is complete, cool to room temperature, extract with ethyl acetate, wash with saturated sodium chloride solution, dry, concentrate under reduced pressure, and purify to obtain intermediate product 1. The ratio of natural capsaicin, 1,3-dibromopropane, acetonitrile, anhydrous potassium carbonate, ethyl acetate, and saturated sodium chloride solution is 0.2 mol: 0.6 mol: 400 mL: 0.6 mol: 4500 mL: 550 mL. Step A2: Mix intermediate product 1, dodecyl dimethyl tertiary amine and acetonitrile, reflux at 80°C for 36 h. After the reaction is complete, cool to room temperature, concentrate under reduced pressure, and wash three times with methyl tert-butyl ether to obtain intermediate product 2. The ratio of intermediate product 1, dodecyl dimethyl tertiary amine, acetonitrile and methyl tert-butyl ether is 0.12 mol: 0.36 mol: 250 mL: 225 mL. Step A3: Dissolve hydroxypropyl-β-cyclodextrin in deionized water to obtain a saturated hydroxypropyl-β-cyclodextrin solution. Separately, mix intermediate product 2 and anhydrous ethanol, heat in a water bath to 65°C, and add the saturated hydroxypropyl-β-cyclodextrin solution dropwise while stirring. After stirring for 3 hours, stop heating, stir in a water bath until room temperature, rotary evaporate, filter, concentrate, and freeze dry to obtain the termite repellent. The ratio of hydroxypropyl-β-cyclodextrin, deionized water, intermediate product 2, and anhydrous ethanol is 0.21 mol: 700 mL: 0.07 mol: 550 mL.

[0018] The modified flame retardant is prepared by the following steps: Step B1: Mix 3-aminopropyltriethoxysilane, furfural, and anhydrous ethanol, and stir and reflux at 75°C for 3 hours. Then, lower the temperature to 70°C, add phosphoric acid, and continue stirring for another 3 hours. After the reaction is complete, cool to room temperature and dry under vacuum to obtain a silanized phosphoric acid-furan coupling agent. The molar ratio of 3-aminopropyltriethoxysilane, furfural, anhydrous ethanol, and phosphoric acid is 0.07 mol: 0.07 mol: 450 mL: 0.07 mol. Step B2: Mix attapulgite and deionized water, sonicate for 8 minutes, centrifuge, repeat 3 times, freeze for 24 hours, grind and sieve, dry the ground attapulgite, then mix with toluene, heat to 110℃ under nitrogen protection, stir, reflux for 30 minutes, then add silicon-based phosphoric acid-furan coupling agent solution dropwise, continue the reaction for 1 hour, then centrifuge, wash, and vacuum dry to obtain the modified flame retardant. The ratio of attapulgite, deionized water, toluene, and silicon-based phosphoric acid-furan coupling agent solution is 3g:550mL:65mL:60mL. The silicon-based phosphoric acid-furan coupling agent solution is prepared by mixing silicon-based phosphoric acid-furan coupling agent and anhydrous ethanol at a ratio of 0.02mol:60mL.

[0019] Example 3: The ant repellent was prepared by the following steps: Step A1: Mix natural capsaicin, 1,3-dibromopropane, and acetonitrile, then add anhydrous potassium carbonate, and reflux at 80°C for 36 hours. After the reaction is complete, cool to room temperature, extract with ethyl acetate, wash with saturated sodium chloride solution, dry, concentrate under reduced pressure, and purify to obtain intermediate product 1. The ratio of natural capsaicin, 1,3-dibromopropane, acetonitrile, anhydrous potassium carbonate, ethyl acetate, and saturated sodium chloride solution is 0.3 mol: 0.9 mol: 600 mL: 0.9 mol: 600 mL: 700 mL. Step A2: Mix intermediate product 1, dodecyl dimethyl tertiary amine and acetonitrile, reflux at 80°C for 36 h. After the reaction is complete, cool to room temperature, concentrate under reduced pressure, and wash three times with methyl tert-butyl ether to obtain intermediate product 2. The ratio of intermediate product 1, dodecyl dimethyl tertiary amine, acetonitrile and methyl tert-butyl ether is 0.16 mol: 0.48 mol: 300 mL: 300 mL. Step A3: Dissolve hydroxypropyl-β-cyclodextrin in deionized water to obtain a saturated hydroxypropyl-β-cyclodextrin solution. Separately, mix intermediate product 2 and anhydrous ethanol, heat in a water bath to 65°C, and add the saturated hydroxypropyl-β-cyclodextrin solution dropwise while stirring. After stirring for 3 hours, stop heating, stir in a water bath until room temperature, rotary evaporate, filter, concentrate, and freeze dry to obtain the ant repellent. The ratio of hydroxypropyl-β-cyclodextrin, deionized water, intermediate product 2, and anhydrous ethanol is 0.24 mol: 800 mL: 0.08 mol: 600 mL.

[0020] The modified flame retardant is prepared by the following steps: Step B1: Mix 3-aminopropyltriethoxysilane, furfural, and anhydrous ethanol, and stir and reflux at 75°C for 3 hours. Then, lower the temperature to 70°C, add phosphoric acid, and continue stirring for another 3 hours. After the reaction is complete, cool to room temperature and dry under vacuum to obtain a silanized phosphoric acid-furan coupling agent. The molar ratio of 3-aminopropyltriethoxysilane, furfural, anhydrous ethanol, and phosphoric acid is 0.1 mol: 0.1 mol: 500 mL: 0.1 mol. Step B2: Mix attapulgite and deionized water, sonicate for 8 minutes, centrifuge, repeat 3 times, freeze for 24 hours, grind and sieve, dry the ground attapulgite, then mix with toluene, heat to 110℃ under nitrogen protection, stir, reflux for 30 minutes, then add silicon-based phosphoric acid-furan coupling agent solution dropwise, continue the reaction for 1 hour, then centrifuge, wash, and vacuum dry to obtain the modified flame retardant. The ratio of attapulgite, deionized water, toluene, and silicon-based phosphoric acid-furan coupling agent solution is 3g:600mL:70mL:80mL. The silicon-based phosphoric acid-furan coupling agent solution is prepared by mixing silicon-based phosphoric acid-furan coupling agent and anhydrous ethanol at a ratio of 0.03mol:80mL.

[0021] Example 4: A method for preparing a termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable, comprising the following steps: The protective layer comprises the following raw materials in parts by weight: 45 parts polypropylene, 3 parts EPDM rubber, 1 part EPDM rubber grafted with maleic anhydride, 3 parts modified flame retardant prepared in Example 1, 0.3 parts antioxidant 1010, 1 part termite repellent prepared in Example 1, 0.5 parts light stabilizer 770, 1 part calcium stearate, 1 part acetylsic acid tributyl ester, and 0.2 parts glyceryl monostearate. Step S1: Using an extruder, a conductor shielding layer is extruded and deposited on the outer periphery of the wire core, and an insulating layer is extruded and deposited on the outer periphery of the conductor shielding layer to form an insulating layer; Step S2: Extrude and deposit an insulating shielding layer on the outer periphery of the insulating layer, and then wrap an aluminum conductive metal strip around the outer periphery of the insulating shielding layer in a spiral to obtain a metal shielding layer. Step S3: Weigh the protective layer raw materials according to the weight proportions, stir and mix the weighed raw materials evenly for 8 minutes, extrude and deposit them on the outer periphery of the metal shielding layer to obtain the protective layer, anneal after extrusion, the extrusion temperature is 180℃, and the termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable is obtained.

[0022] Example 5: A method for preparing a termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable, comprising the following steps: The protective layer comprises the following raw materials in parts by weight: 55 parts polypropylene, 5 parts EPDM rubber, 1.5 parts EPDM rubber grafted with maleic anhydride, 5 parts modified flame retardant prepared in Example 2, 0.6 parts antioxidant 1010, 2 parts termite repellent prepared in Example 2, 0.8 parts light stabilizer 770, 1.5 parts calcium stearate, 1.5 parts tributyl acetylacetic acid, and 0.4 parts glyceryl monostearate. Step S1: Using an extruder, a conductor shielding layer is extruded and deposited on the outer periphery of the wire core, and an insulating layer is extruded and deposited on the outer periphery of the conductor shielding layer to form an insulating layer; Step S2: Extrude and deposit an insulating shielding layer on the outer periphery of the insulating layer, and then wrap an aluminum conductive metal strip around the outer periphery of the insulating shielding layer in a spiral to obtain a metal shielding layer. Step S3: Weigh the protective layer raw materials according to the weight proportions, stir and mix the weighed raw materials evenly for 12 minutes, extrude and deposit them on the outer periphery of the metal shielding layer to obtain the protective layer, anneal after extrusion, and the extrusion temperature is 200℃ to obtain the termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable.

[0023] Example 6: A method for preparing a termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable, comprising the following steps: The protective layer comprises the following raw materials in parts by weight: 65 parts polypropylene, 7 parts EPDM rubber, 2 parts EPDM rubber grafted with maleic anhydride, 8 parts modified flame retardant prepared in Example 3, 1 part antioxidant 1010, 3 parts termite repellent prepared in Example 3, 1 part light stabilizer 770, 1.5 parts calcium stearate, 2 parts acetylsic acid tributyl ester, and 0.5 parts glyceryl monostearate. Step S1: Using an extruder, a conductor shielding layer is extruded and deposited on the outer periphery of the wire core, and an insulating layer is extruded and deposited on the outer periphery of the conductor shielding layer to form an insulating layer; Step S2: Extrude and deposit an insulating shielding layer on the outer periphery of the insulating layer, and then wrap an aluminum conductive metal strip around the outer periphery of the insulating shielding layer in a spiral to obtain a metal shielding layer. Step S3: Weigh the protective layer raw materials according to the weight proportions, stir and mix the weighed raw materials evenly for 15 minutes, extrude and deposit them on the outer periphery of the metal shielding layer to obtain the protective layer, anneal after extrusion, the extrusion temperature is 210℃, and the termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable is obtained.

[0024] Comparative Example 1: This comparative example is an insulated high-voltage power cable. The difference between this example and Example 6 is that natural capsaicin is used instead of the termite repellent prepared in Example 3. All other aspects are the same.

[0025] Comparative Example 2: This comparative example is an insulated high-voltage power cable. The difference between this example and Example 6 is that magnesium hydroxide is used instead of the modified flame retardant prepared in Example 3. All other aspects are the same.

[0026] Comparative Example 3: This comparative example is an insulated high-voltage power cable. The difference between this example and Example 6 is that natural capsaicin is used instead of the termite repellent prepared in Example 3, and magnesium hydroxide is used instead of the modified flame retardant prepared in Example 3. All other aspects are the same.

[0027] The protective layer raw materials from Examples 4-6 and Comparative Examples 1-3 were mixed evenly, melt-extruded into test samples, and then their performance was tested. Tensile strength: The test was conducted according to the test method in GB / T 1040.1-2018, using an injection-molded dumbbell-shaped tensile standard specimen, with a tensile speed of 50 mm / min. ‑1 Tested under constant temperature conditions of 23℃; Bending strength: The test was conducted according to the test method in GB / T 9341-2008, using a molded elongated standard specimen, with a deflection of 6 mm and a test speed of 2 mm / min. ‑1 Tested under constant temperature conditions of 23℃; Impact performance: The impact strength of the cantilever beam was tested according to the method of GB / T 1843-2008. A long strip standard specimen was used for injection molding, and a V-shaped notch was punched in using a notch sample making machine within 4 hours after injection molding. A pendulum with appropriate energy was selected, and the test was conducted under a constant temperature of 23℃. Oxygen index: The oxygen index was tested according to Method B in GB / T 2406.2-2009; Flame retardancy rating: Tested according to the method in GB / T 2408-2021; Termite resistance test: The termite infestation level was tested according to the experimental group method in JB / T 10696.9-2011 "Mechanical and physical and chemical properties test methods for wires and cables - Part 9: Termite test". Three samples were taken for each test.

[0028] The test results are shown in Table 1: Table 1: Performance Test Results As can be seen from Table 1, the cross-linked polyethylene insulated high-voltage power cable protective layer prepared by this invention possesses excellent mechanical properties. The tensile strength of the examples is above 51 MPa, the flexural strength is above 58 MPa, and the impact strength is above 32 KJ / m. 2 As shown in Example 6 and Comparative Example 1, the termite repellent prepared by this invention improves the termite resistance of the cable protective sheath, effectively repelling and blocking termites from gnawing and damaging the cable. As shown in Example 6 and Comparative Example 2, the modified flame retardant prepared by this invention improves the flame retardant and mechanical properties of the protective sheath. This is because the organic-inorganic composite flame retardant improves the compatibility between the inorganic filler and the polymer matrix. In summary, this invention demonstrates that the cross-linked polyethylene insulated high-voltage power cable prepared by this invention possesses excellent termite resistance and flame retardant capabilities.

[0029] The above content is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the scope defined by the inventive concept, they should all fall within the protection scope of the present invention.

Claims

1. A termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable, characterized in that, From the inside out, it includes the wire core, conductor shielding layer, insulation layer, insulation shielding layer, metal shielding layer, and protective layer; The protective layer comprises the following raw materials in parts by weight: 45-65 parts polypropylene, 3-7 parts EPDM rubber, 1-2 parts EPDM rubber grafted with maleic anhydride, 3-8 parts modified flame retardant, 0.3-1 part antioxidant 1010, 1-3 parts termite repellent, 0.5-1 part light stabilizer 770, 1-1.5 parts calcium stearate, 1-2 parts tributyl acetylacetonate, and 0.2-0.5 parts glyceryl monostearate. The ant repellent is prepared by the following steps: Step A1: Mix natural capsaicin, 1,3-dibromopropane and acetonitrile, then add anhydrous potassium carbonate, and reflux at 80°C for 36 h. After the reaction is complete, cool to room temperature, extract with ethyl acetate, wash with saturated sodium chloride solution, dry, concentrate under reduced pressure and purify to obtain intermediate product 1. Step A2: Mix intermediate product 1, dodecyl dimethyl tertiary amine and acetonitrile, reflux at 80°C for 36 h, after the reaction is completed, cool to room temperature, concentrate under reduced pressure, and wash three times with methyl tert-butyl ether to obtain intermediate product 2. Step A3: Dissolve hydroxypropyl-β-cyclodextrin in deionized water to obtain a saturated solution of hydroxypropyl-β-cyclodextrin. Separately, mix intermediate product 2 with anhydrous ethanol, heat in a water bath to 65°C, and add the saturated solution of hydroxypropyl-β-cyclodextrin dropwise while stirring. After stirring for 3 hours, stop heating, stir in a water bath until room temperature, evaporate by rotary evaporation, filter, concentrate, and freeze dry to obtain the ant repellent.

2. The termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable according to claim 1, characterized in that, In step A1, the ratio of the amounts of natural capsaicin, 1,3-dibromopropane, acetonitrile, anhydrous potassium carbonate, ethyl acetate, and saturated sodium chloride solution is 0.1-0.3 mol: 0.3-0.9 mol: 200-600 mL: 0.3-0.9 mol: 300-600 mL: 400-700 mL.

3. The termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable according to claim 1, characterized in that, In step A2, the ratio of intermediate product 1, dodecyl dimethyl tert-amine, acetonitrile, and methyl tert-butyl ether is 0.08-0.16 mol: 0.24-0.48 mol: 200-300 mL: 150-300 mL.

4. The termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable according to claim 1, characterized in that, In step A3, the ratio of hydroxypropyl-β-cyclodextrin, deionized water, intermediate product 2, and anhydrous ethanol is 0.18-0.24 mol: 600-800 mL: 0.06-0.08 mol: 500-600 mL.

5. The termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable according to claim 1, characterized in that, The modified flame retardant is prepared by the following steps: Step B1: Mix 3-aminopropyltriethoxysilane, furfural and anhydrous ethanol, stir and reflux at 75°C for 3 hours, then lower the temperature to 70°C, add phosphoric acid, and continue stirring for 3 hours. After the reaction is complete, cool to room temperature and dry under vacuum to obtain silicic acid-furan coupling agent. Step B2: Mix attapulgite and deionized water, sonicate for 8 minutes, centrifuge, repeat 3 times, freeze for 24 hours, grind and sieve, dry the ground attapulgite, then mix with toluene, heat to 110°C under nitrogen protection, stir, reflux for 30 minutes, then add silicon-based phosphoric acid-furan coupling agent solution dropwise, continue the reaction for 1 hour, then centrifuge, wash, and vacuum dry to obtain the modified flame retardant.

6. The termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable according to claim 5, characterized in that, In step B1, the ratio of 3-aminopropyltriethoxysilane, furfural, anhydrous ethanol, and phosphoric acid is 0.04-0.1 mol: 0.04-0.1 mol: 400-500 mL: 0.04-0.1 mol.

7. The termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable according to claim 5, characterized in that, In step B2, the ratio of attapulgite, deionized water, toluene, and silicic acid-furan coupling agent solution is 3g: 500-600mL: 60-70mL: 40-80mL.

8. A termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable according to claim 5, characterized in that, In step B2, the silicon-based phosphoric acid-furan coupling agent solution is prepared by mixing silicon-based phosphoric acid-furan coupling agent and anhydrous ethanol at a ratio of 0.01-0.03 mol: 40-80 mL.

9. A termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable according to claim 1, characterized in that, The core consists of seven stranded copper wires. The insulation layer is made of cross-linked polyethylene insulation material. Both the conductor shielding layer and the insulation shielding layer are made of ethylene-vinyl acetate copolymer material. The metal shielding layer is made of aluminum conductive metal strips spirally wrapped around the insulation shielding layer.

10. A method for preparing a termite-resistant and flame-retardant cross-linked polyethylene insulated high-voltage power cable according to any one of claims 1-9, characterized in that, The method for preparing the insulated high-voltage power cable comprises the following steps: Step S1: Using an extruder, a conductor shielding layer is extruded and deposited on the outer periphery of the wire core, and an insulating layer is extruded and deposited on the outer periphery of the conductor shielding layer to form an insulating layer; Step S2: Extrude and deposit an insulating shielding layer on the outer periphery of the insulating layer, and then wrap an aluminum conductive metal strip around the outer periphery of the insulating shielding layer in a spiral to obtain a metal shielding layer. Step S3: Weigh the protective layer raw materials according to the weight proportions, stir and mix the weighed raw materials evenly for 8-15 minutes, extrude and deposit them on the outer periphery of the metal shielding layer to obtain the protective layer, anneal after extrusion, the extrusion temperature is 180-210℃, and the termite-proof and flame-retardant cross-linked polyethylene insulated high-voltage power cable is obtained.