Highly shielded fire resistant and fire resistant control cable and method of making same

Abstract

The application provides a high-shielding fire-retardant fire-resistant control cable and a preparation method thereof. The cable comprises, from inside to outside, a conductor core, a fire-resistant insulating layer, a composite shielding layer and a fire-retardant fire-resistant sheath layer. The preparation raw materials of the fire-retardant fire-resistant sheath layer comprise, by weight, 35-45 parts of low-smoke halogen-free fire-retardant polyolefin, 15-20 parts of ethylene-vinyl acetate copolymer, 8-12 parts of polyolefin elastomer, 6-10 parts of magnetic montmorillonite-based hybrid electromagnetic shielding filler, 7-11 parts of core-shell type ceramicized fire-retardant microcapsule, 1.0-1.5 parts of silane coupling agent, 2-4 parts of basalt fiber, 0.4-0.7 parts of crosslinking agent, 0.6-1.0 parts of lubricant, 0.7-1.1 parts of stabilizer and 0.3-0.6 parts of antioxidant. The high-shielding fire-retardant fire-resistant control cable provided by the application has excellent electromagnetic shielding, fire-retardant fire-resistant performance, outstanding mechanical strength, good processing fluidity, and effective inhibition of thermal degradation and oxidative degradation in the high-temperature processing and use process, and good heat resistance, dimensional stability and use stability.

Description

Technical Field

[0001] This invention relates to the field of cable technology, specifically to a highly shielded, flame-retardant, and fire-resistant control cable and its preparation method. Background Technology

[0002] With the rapid development of power systems, rail transit, high-rise buildings, and other fields, the requirements for control cables are becoming increasingly stringent. They not only need to possess basic power transmission and signal control functions, but also meet multiple performance requirements such as shielding, flame retardancy, and fire resistance. Currently, cross-linked polyethylene (XLPE) insulated cables are widely used in power transmission and control cables due to their excellent electrical insulation properties, mechanical strength, and heat resistance. However, the sheath layer of existing XLPE insulated control cables is mostly made of conventional flame-retardant polyolefin materials, making it difficult to simultaneously achieve electromagnetic shielding performance and flame-retardant and fire-resistant performance in extreme environments, thus failing to meet the needs of high-end equipment.

[0003] In existing technologies, the sheath layer of control cables is typically made of a single resin matrix compounded with common inorganic fillers, which has significant limitations in terms of performance improvement. On the one hand, the electromagnetic shielding performance of existing cables mostly relies on a single type of inorganic shielding filler, resulting in limited shielding effectiveness and difficulty in resisting interference in complex electromagnetic environments, affecting the stability of control signal transmission. On the other hand, existing flame-retardant and fire-resistant inorganic fillers have poor interfacial compatibility with the resin matrix, easily leading to uneven dispersion. This makes it difficult for the cable to form a dense and stable flame-retardant and fire-resistant protective layer during high-temperature combustion. Furthermore, the introduction of fillers can easily reduce the mechanical properties and processing fluidity of the cable sheath layer, failing to achieve a synergistic improvement in shielding performance, flame-retardant and fire-resistant properties, and processing and usage stability, making it difficult to meet the high-performance requirements of control cables in high-end fields. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a highly shielded, flame-retardant, and fire-resistant control cable and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention discloses a highly shielded flame-retardant and fire-resistant control cable. The cable, from the inside out, comprises a conductor core, a fire-resistant insulation layer, a composite shielding layer, and a flame-retardant and fire-resistant sheath layer. By weight, the raw materials for preparing the flame-retardant and fire-resistant sheath layer include: 35-45 parts of low-smoke halogen-free flame-retardant polyolefin, 15-20 parts of ethylene-vinyl acetate copolymer, 8-12 parts of polyolefin elastomer, 6-10 parts of magnetic montmorillonite-based hybrid electromagnetic shielding filler, 7-11 parts of core-shell ceramic flame-retardant microcapsules, 1.0-1.5 parts of silane coupling agent, 2-4 parts of basalt fiber, 0.4-0.7 parts of crosslinking agent, 0.6-1.0 parts of lubricant, 0.7-1.1 parts of stabilizer, and 0.3-0.6 parts of antioxidant.

[0006] Preferably, the silane coupling agent is 3-glycidyl etheroxypropyltrimethoxysilane (KH-560), the crosslinking agent is dicumyl peroxide, the lubricant is a compound of polyethylene wax and ethylene bis-stearamide in a mass ratio of 1:1, the stabilizer is a calcium-zinc stabilizer, and the antioxidant is a compound of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:1.

[0007] Preferably, the raw materials for preparing the magnetic montmorillonite-based hybrid electromagnetic shielding filler, by weight, include: 90-100 parts of sodium montmorillonite, 5-7 parts of γ-aminopropyltriethoxysilane (KH-550), 195-200 parts of ferric chloride hexahydrate, 70-75 parts of ferrous chloride tetrahydrate, 20-25 parts of carboxylated multi-walled carbon nanotubes, 30-35 parts of silver-plated copper powder, 3-5 parts of KH-560, 1800-2100 parts of deionized water, 400-500 parts of anhydrous ethanol, and 185-275 parts of purified water.

[0008] Preferably, the preparation method of the magnetic montmorillonite-based hybrid electromagnetic shielding filler includes the following steps: 1) Mix sodium-based montmorillonite with deionized water accounting for 4 / 7-5 / 7 of the total mass of deionized water, and ultrasonically disperse it for 30-40 min at a frequency of 20-40 kHz and a power of 300-400 W. Add KH-550, and then stir the mixture for 2-3 h at a speed of 300-400 r / min in a water bath at 60-70 ℃. Centrifuge the mixture for 10-15 min at a speed of 3000-4000 r / min. Wash the precipitate with deionized water 3-5 times until the washing liquid is neutral. Dry the precipitate in a vacuum drying oven at 60-80 ℃ and a vacuum degree of -0.08 MPa to -0.10 MPa for 8-12 h to obtain organically modified montmorillonite. 2) Add ferric chloride hexahydrate and ferrous chloride tetrahydrate to purified water and ultrasonically disperse for 30-40 min at a frequency of 20-40 kHz and a power of 300-400 W to obtain mixture A; 3) Add the organically modified montmorillonite to the remaining deionized water and ultrasonically disperse it for 30-40 min at a frequency of 20-40 kHz and a power of 300-400 W. Under nitrogen protection, heat the mixture to 60-70 ℃ and stir continuously at a speed of 200-300 r / min. Add the mixture A dropwise at a uniform rate over 20-30 min, and then add ammonia solution with a mass fraction of 25-28% to adjust the pH of the system to 10-11. Stir the mixture at 200-300 r / min at 60-70 ℃ for 1.5-2 h. Use a neodymium iron boron permanent magnetic field with a magnetic field strength of 0.8-1.2 T to perform magnetic separation of the reaction system. Wash the precipitate with deionized water until the washing solution is neutral to obtain magnetic montmorillonite. 4) Disperse carboxylated multi-walled carbon nanotubes and silver-plated copper powder in anhydrous ethanol, and ultrasonically disperse them for 30-40 min at a frequency of 20-40 kHz and a power of 300-400 W. Add magnetic montmorillonite and stir the mixture at 300-400 r / min at 60-70℃ for 2-3 h. 5) Add KH-560 to the reaction solution obtained in step 4), stir at 300-400 r / min at 60-70℃ for 1-1.5 h, transfer to a vacuum drying oven, dry at 60-80℃ and vacuum degree -0.08MPa~-0.10MPa for 8-12 h, grind and pass through a 300-400 mesh sieve to obtain magnetic montmorillonite-based hybrid electromagnetic shielding filler.

[0009] Preferably, the raw materials for preparing the core-shell type ceramic flame-retardant microcapsules, by weight, include: 50-55 parts of melamine polyphosphate, 30-35 parts of nano magnesium hydroxide, 15-20 parts of organomontmorillonite, 16-20 parts of methyl vinyl silicone rubber, 8-10 parts of zinc borate, 5-7 parts of low-melting-point glass powder, 0.3-0.5 parts of dicumyl peroxide, 2.0-2.5 parts of emulsifier OP-10, 1.0-1.5 parts of sodium polycarboxylate dispersant, 650-800 parts of deionized water, and 80-100 parts of toluene.

[0010] Preferably, the preparation method of the core-shell type ceramic flame-retardant microcapsules includes the following steps: (1) Mix melamine polyphosphate, nano magnesium hydroxide, organomontmorillonite, sodium polycarboxylate dispersant with deionized water and stir at 1200-1500 r / min for 25-35 min to obtain a nuclear material suspension; (2) Dissolve methyl vinyl silicone rubber in toluene, add zinc borate, low melting point glass powder and dicumyl peroxide, and stir at 800-1000 r / min for 20-30 min to obtain wall material prepolymer liquid; (3) Mix the core material suspension and the wall material prepolymer liquid at a mass ratio of 3:1, add emulsifier OP-10, emulsify at high speed for 10-15 minutes at an emulsification speed of 8000-10000 r / min, and spray dry using a spray dryer; (4) Collect the spray-dried particles, place them in an oven at 155-165℃ and keep them warm for 10-15 minutes to remove residual solvent, then raise the temperature to 165-170℃ and vulcanize for 5-8 minutes to obtain core-shell ceramic flame-retardant microcapsules.

[0011] Preferably, in step (3), the specific operation of spray drying is as follows: control the feed rate to 10-15 mL / min, the air inlet temperature to 180-200℃, the air outlet temperature to 80-90℃, and the atomizer speed to 20000-25000 r / min.

[0012] This invention also discloses a method for preparing a highly shielded, flame-retardant, and fire-resistant control cable, comprising the following steps: S1. Place low-smoke halogen-free flame-retardant polyolefin, ethylene-vinyl acetate copolymer, and polyolefin elastomer in a high-speed mixer and initially mix at 300-400 r / min for 3-5 min at 25-30℃. Add magnetic montmorillonite-based hybrid electromagnetic shielding filler, core-shell ceramic flame-retardant microcapsules, and basalt fiber, and pre-disperse at 500-600 r / min for 5-8 min. Then add silane coupling agent, crosslinking agent, lubricant, stabilizer, and antioxidant, and mix at 500-600 r / min for 3-5 min to obtain the mixture. S2. Add the mixture to the internal mixer and mix for 15-20 minutes at a temperature of 120-130℃ and a speed of 60-80 r / min. After cooling the mixed material to 100-110℃, transfer it to the open mill and pass it through the open mill 3-5 times at a temperature of 100-110℃ and a roll gap of 1-2 mm to obtain a uniformly plasticized rubber compound. S3. Add the rubber compound obtained in step S2 to a twin-screw extruder and granulate it at a temperature of 110-120℃ and a screw speed of 300-400r / min to obtain special granules for sheathing. S4. The special granules for the sheath are extruded to the outside of the composite shielding layer using an extruder. The extrusion temperature is 140-150℃ and the speed is 5-8m / min. Then, the extruded cable is cross-linked, cured, cooled, and wound up in a pressurized steam environment to obtain the finished cable.

[0013] Preferably, in step S4, the crosslinking curing temperature is 160-170℃, the pressure is 0.8-1.0MPa, and the time is 2-3h.

[0014] The beneficial effects of this invention are as follows: Low-smoke halogen-free flame-retardant polyolefins, ethylene-vinyl acetate copolymers, and polyolefin elastomers are compounded to form the sheath layer resin matrix, providing basic molding and processing properties and mechanical support for the sheath layer; magnetic montmorillonite-based hybrid electromagnetic shielding fillers can construct a multi-layer electromagnetic shielding network, significantly improving the electromagnetic shielding performance of the cable; core-shell ceramicized flame-retardant microcapsules can form a dense ceramicized carbon layer at high temperatures, effectively improving the flame-retardant and fire-resistant properties of the cable; silane coupling agents can improve the interfacial compatibility between inorganic fillers and organic resin matrices, enhancing the uniformity of filler dispersion; basalt fibers can form a reinforcing skeleton within the resin matrix. The structure enhances the mechanical strength and wear resistance of the cable sheath; the crosslinking agent enables the resin matrix to form a three-dimensional crosslinked network structure, improving the material's heat resistance, dimensional stability, and aging resistance; the lubricant optimizes the material's processing flowability, ensuring the extrusion molding quality of the sheath layer; the stabilizer inhibits the thermal degradation of the material during high-temperature processing, improving processing stability; the composite antioxidant inhibits the oxidative degradation of raw materials during processing and use, extending the cable's service life; the synergistic effect of these raw materials gives the cable excellent electromagnetic shielding, flame retardancy, fire resistance, mechanical properties, and processing and usage stability.

[0015] Sodium-based montmorillonite provides the basic layered structure for the filler, offering structural support for electromagnetic shielding. KH-550 organically modifies the sodium-based montmorillonite, improving its compatibility with organic phases. Ferric chloride hexahydrate and ferrous chloride tetrahydrate serve as iron sources, generating magnetite nanoparticles during preparation, providing magnetic shielding performance for the filler. Carboxylated multi-walled carbon nanotubes and silver-plated copper powder construct a conductive network, significantly enhancing the filler's conductivity and achieving synergy between electrical and magnetic shielding. KH-560 surface-modifies the filler, further optimizing its interfacial compatibility with the cable resin matrix. Deionized water, anhydrous ethanol, and purified water serve as dispersion and reaction media, ensuring uniform dispersion of raw materials and smooth reaction. The synergistic effect of these raw materials allows for the preparation of a magnetic montmorillonite-based hybrid electromagnetic shielding filler with excellent electromagnetic shielding performance.

[0016] Melamine polyphosphate and nano-magnesium hydroxide work synergistically to enhance the flame retardant properties of microcapsules; organomontmorillonite enhances the layered barrier ability of microcapsules, further improving the flame retardant effect by blocking oxygen and heat transfer; methyl vinyl silicone rubber serves as the basic raw material for the microcapsule wall material, providing structural support for wall material molding; zinc borate and low-melting-point glass powder optimize the ceramicization properties of the wall material, enabling the formation of a dense ceramicized carbon layer during high-temperature combustion, thus improving fire resistance; dicumyl peroxide promotes the vulcanization crosslinking reaction of the wall material raw materials, ensuring the molding quality and structural stability of the wall material; emulsifier OP-10 and sodium polycarboxylate dispersant ensure uniform dispersion of the raw materials, effectively preventing filler agglomeration; deionized water and toluene serve as dispersion and dissolution media, ensuring smooth preparation; the synergistic effect of these raw materials allows for the preparation of core-shell ceramicized flame-retardant microcapsules with excellent flame retardant and fire-resistant properties. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, 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.

[0018] The specific information on the raw materials used in the embodiments of the present invention is shown in Table 1.

[0019] Table 1 Low-smoke halogen-free flame-retardant polyolefin Brand LC Shunping County Longchang Plastics Co., Ltd. Ethylene-vinyl acetate copolymer 99% purity Hubei Rishengchang New Material Technology Co., Ltd., CAS: 24937-78-8 Polyolefin elastomers 99% purity Pande (Shanghai) International Trading Co., Ltd., CAS: 25087-34-7 Sodium montmorillonite 99% purity Beijing Yiwei Special Chemicals Technology Development Co., Ltd., CAS: 1302-78-9 KH-550 Purity ≥ 98% Nanjing Shuguang Chemical Group Co., Ltd. Ferric chloride hexahydrate 98% purity Shanghai Baishun Biotechnology Co., Ltd., CAS: 10025-77-1 Ferrous chloride tetrahydrate 98% purity Shanghai Baishun Biotechnology Co., Ltd., CAS: 13478-10-9 Carboxylated multi-walled carbon nanotubes 99% purity Shanghai Aladdin Biochemical Technology Co., Ltd., CAS: 308068-56-6 Silver-plated copper powder Particle size 1-3μm, silver plating thickness 0.1-0.2μm, silver content 8-12wt%. Tongling Nonferrous Metals Group Co., Ltd. KH-560 Purity ≥ 98% Nanjing Shuguang Chemical Group Co., Ltd. Anhydrous ethanol Analytical Pure Sinopharm Chemical Reagent Co., Ltd. melamine polyphosphate 98% purity Shanghai Jieshikai Biotechnology Co., Ltd., CAS: 15541-60-3 Nano magnesium hydroxide 99.9% purity Hangzhou Jikang New Materials Co., Ltd., CAS: 1309-42-8 Organomontmorillonite Model: I.44P Beijing Yiwei Special Chemicals Technology Development Co., Ltd., CAS: 1302-78-9 Methyl vinyl silicone rubber 99% purity Hubei Chengfeng Chemical Co., Ltd. Zinc borate 99% purity Hubei Keward Chemical Co., Ltd., CAS: 1332-07-6 Low melting point glass powder Model: 1407130, Softening point: around 450℃ Forsmann Technology (Beijing) Co., Ltd. dicumyl peroxide 99% purity Hubei Chengfeng Chemical Co., Ltd., CAS: 80-43-3 Emulsifier OP-10 99% purity Shanghai Lianji Chemical Co., Ltd., CAS: 9002-93-1 Sodium polycarboxylate dispersant SN5040 Guangzhou Hengyu Chemical Co., Ltd. Toluene 99.9% purity Shandong Wowei Chemical Co., Ltd. Basalt fiber Model: AF53 Taian Anfeng New Material Technology Co., Ltd. Polyethylene wax 99% purity Wuhan Jiyesheng Chemical Co., Ltd., CAS: 9002-88-4 Ethylene bis-stearamide 99% purity Jinan Yuanshang New Materials Co., Ltd., CAS: 110-30-5 Calcium and zinc stabilizers 200 mesh Dongying Ruikun Chemical Co., Ltd. Antioxidant 1010 99% purity BASF AG Antioxidant 168 99% purity BASF AG

[0020] Example 1: This embodiment discloses a highly shielded, flame-retardant, and fire-resistant control cable. The cable, from the inside out, consists of a conductor core, a fire-resistant insulation layer, a composite shielding layer, and a flame-retardant and fire-resistant sheath layer. By weight, the raw materials for preparing the flame-retardant and fire-resistant sheath layer include: 35 parts low-smoke halogen-free flame-retardant polyolefin, 15 parts ethylene-vinyl acetate copolymer, 8 parts polyolefin elastomer, 6 parts magnetic montmorillonite-based hybrid electromagnetic shielding filler, 7 parts core-shell ceramic flame-retardant microcapsules, 1 part KH-560, 2 parts basalt fiber, 0.4 parts dicumyl peroxide, 0.6 parts lubricant, 0.7 parts calcium-zinc stabilizer, and 0.3 parts antioxidant. The lubricant is a 1:1 mass mixture of polyethylene wax and ethylene bis-stearamide, and the antioxidant is a 1:1 mass mixture of antioxidant 1010 and antioxidant 168.

[0021] The raw materials for preparing the magnetic montmorillonite-based hybrid electromagnetic shielding filler, by weight, include: 90 parts sodium montmorillonite, 5 parts KH-550, 195 parts ferric chloride hexahydrate, 70 parts ferrous chloride tetrahydrate, 20 parts carboxylated multi-walled carbon nanotubes, 30 parts silver-plated copper powder, 3 parts KH-560, 1800 parts deionized water, 400 parts anhydrous ethanol, and 185 parts purified water.

[0022] The preparation method of magnetic montmorillonite-based hybrid electromagnetic shielding filler includes the following steps: 1) Sodium-based montmorillonite was mixed with deionized water accounting for 4 / 7 of the total mass of deionized water. The mixture was ultrasonically dispersed for 30 min at a frequency of 20 kHz and a power of 300 W. KH-550 was added, and the mixture was stirred at 300 r / min for 2 h in a water bath at 60 ℃. Then, it was centrifuged at 3000 r / min for 10 min. The precipitate was washed three times with deionized water until the washing liquid was neutral. The precipitate was then dried in a vacuum drying oven at 60 ℃ and a vacuum degree of -0.08 MPa for 8 h to obtain organically modified montmorillonite. 2) Add ferric chloride hexahydrate and ferrous chloride tetrahydrate to purified water and ultrasonically disperse for 30 min at a frequency of 20 kHz and a power of 300 W to obtain mixture A; 3) Add the organically modified montmorillonite to the remaining deionized water and ultrasonically disperse it for 30 min at a frequency of 20 kHz and a power of 300 W. Under nitrogen protection, heat the mixture to 60 °C and stir continuously at a speed of 200 r / min. Add the mixture A dropwise at a uniform rate over 20 min, and then add a 25% (w / w) ammonia solution to adjust the pH of the system to 10. Stir the mixture at 200 r / min at 60 °C for 1.5 h. Use a neodymium iron boron permanent magnetic field with a magnetic field strength of 0.8 T to perform magnetic separation of the reaction system. Wash the precipitate with deionized water until the washing liquid is neutral to obtain magnetic montmorillonite. 4) Carboxylated multi-walled carbon nanotubes and silver-plated copper powder were dispersed in anhydrous ethanol and ultrasonically dispersed for 30 min at a frequency of 20 kHz and a power of 300 W. Magnetic montmorillonite was added and the mixture was stirred at 300 r / min at 60 °C for 2 h. 5) Add KH-560 to the reaction solution obtained in step 4), stir at 300 r / min for 1 h at 60 °C, transfer to a vacuum drying oven, dry at 60 °C and vacuum degree -0.08 MPa for 8 h, grind and pass through a 300 mesh sieve to obtain magnetic montmorillonite-based hybrid electromagnetic shielding filler.

[0023] The raw materials for preparing core-shell ceramic flame-retardant microcapsules, by weight, include: 50 parts melamine polyphosphate, 30 parts nano magnesium hydroxide, 15 parts organomontmorillonite, 16 parts methyl vinyl silicone rubber, 8 parts zinc borate, 5 parts low melting point glass powder, 0.3 parts dicumyl peroxide, 2 parts emulsifier OP-10, 1 part sodium polycarboxylate dispersant, 650 parts deionized water, and 80 parts toluene.

[0024] The preparation method of core-shell ceramic flame-retardant microcapsules includes the following steps: (1) Melamine polyphosphate, nano magnesium hydroxide, organomontmorillonite, sodium polycarboxylate dispersant and deionized water are mixed and stirred at 1200 r / min for 25 min to obtain a core material suspension; (2) Dissolve methyl vinyl silicone rubber in toluene, add zinc borate, low melting point glass powder and dicumyl peroxide, and stir at 800 r / min for 20 min to obtain wall material prepolymer liquid; (3) Mix the core material suspension and the wall material prepolymer liquid at a mass ratio of 3:1, add emulsifier OP-10, emulsify at high speed for 10 min at an emulsification speed of 8000 r / min, and spray dry using a spray dryer, controlling the feed rate at 10 mL / min, the inlet air temperature at 180℃, the outlet air temperature at 80℃, and the atomizer speed at 20000 r / min; (4) Collect the spray-dried particles, place them in an oven at 155℃ and keep them warm for 10 minutes to remove residual solvent, then raise the temperature to 165℃ and vulcanize for 5 minutes to obtain core-shell ceramic flame-retardant microcapsules.

[0025] This embodiment also discloses a method for preparing a highly shielded, flame-retardant, and fire-resistant control cable, comprising the following steps: S1. Place low-smoke halogen-free flame-retardant polyolefin, ethylene-vinyl acetate copolymer, and polyolefin elastomer in a high-speed mixer and initially mix at 300 r / min for 3 min at 25°C. Add magnetic montmorillonite-based hybrid electromagnetic shielding filler, core-shell ceramic flame-retardant microcapsules, and basalt fiber. Pre-disperse at 500 r / min for 5 min. Then add KH-560, dicumyl peroxide, lubricant, calcium-zinc stabilizer, and antioxidant. Mix at 500 r / min for 3 min to obtain the mixture. S2. Add the mixture to the internal mixer and mix for 15 minutes at a temperature of 120℃ and a speed of 60r / min. After cooling the mixed material to 100℃, transfer it to the open mill and run it through the open mill 3 times at a temperature of 100℃ and a roller gap of 1mm to obtain a uniformly plasticized rubber compound. S3. Add the rubber compound obtained in step S2 to a twin-screw extruder and granulate it at a temperature of 110℃ and a screw speed of 300r / min to obtain special granules for sheathing. S4. The special granules for the sheath are extruded to the outside of the composite shielding layer using an extruder. The extrusion temperature is 140℃ and the speed is 5m / min. Then, the extruded cable is cross-linked, cured, cooled, and wound up in a pressurized steam environment to obtain the finished cable. The cross-linking curing temperature was 160℃, the pressure was 0.8MPa, and the time was 2h.

[0026] Example 2: This embodiment discloses a highly shielded, flame-retardant, and fire-resistant control cable. The cable, from the inside out, consists of a conductor core, a fire-resistant insulation layer, a composite shielding layer, and a flame-retardant and fire-resistant sheath layer. By weight, the raw materials for preparing the flame-retardant and fire-resistant sheath layer include: 45 parts of low-smoke halogen-free flame-retardant polyolefin, 20 parts of ethylene-vinyl acetate copolymer, 12 parts of polyolefin elastomer, 10 parts of magnetic montmorillonite-based hybrid electromagnetic shielding filler, 11 parts of core-shell ceramic flame-retardant microcapsules, 1.5 parts of KH-560, 4 parts of basalt fiber, 0.7 parts of dicumyl peroxide, 1 part of lubricant, 1.1 parts of calcium-zinc stabilizer, and 0.6 parts of antioxidant. The lubricant is a 1:1 mass mixture of polyethylene wax and ethylene bis-stearamide, and the antioxidant is a 1:1 mass mixture of antioxidant 1010 and antioxidant 168.

[0027] The raw materials for preparing the magnetic montmorillonite-based hybrid electromagnetic shielding filler, by weight, include: 100 parts sodium montmorillonite, 7 parts KH-550, 200 parts ferric chloride hexahydrate, 75 parts ferrous chloride tetrahydrate, 25 parts carboxylated multi-walled carbon nanotubes, 35 parts silver-plated copper powder, 5 parts KH-560, 2100 parts deionized water, 500 parts anhydrous ethanol, and 275 parts purified water.

[0028] The preparation method of magnetic montmorillonite-based hybrid electromagnetic shielding filler includes the following steps: 1) Sodium-based montmorillonite was mixed with 5 / 7 of the total mass of deionized water and ultrasonically dispersed for 40 min at a frequency of 40 kHz and a power of 400 W. KH-550 was added, and the mixture was stirred at 400 r / min for 3 h in a water bath at 70 ℃. Then it was centrifuged at 4000 r / min for 15 min. The precipitate was washed 5 times with deionized water until the washing liquid was neutral. It was then dried in a vacuum drying oven at 80 ℃ and a vacuum degree of -0.10 MPa for 12 h to obtain organically modified montmorillonite. 2) Add ferric chloride hexahydrate and ferrous chloride tetrahydrate to purified water and ultrasonically disperse for 40 min at a frequency of 40 kHz and a power of 400 W to obtain mixture A; 3) Add the organically modified montmorillonite to the remaining deionized water and ultrasonically disperse it for 40 min at a frequency of 40 kHz and a power of 400 W. Under nitrogen protection, heat the mixture to 70 ℃ and stir continuously at a speed of 300 r / min. Add the mixture A dropwise at a uniform rate over 30 min, and then add 28% ammonia solution to adjust the pH of the system to 11. Stir the mixture at 300 r / min at 70 ℃ for 2 h. Use a neodymium iron boron permanent magnetic field with a magnetic field strength of 1.2 T to perform magnetic separation of the reaction system. Wash the precipitate with deionized water until the washing liquid is neutral to obtain magnetic montmorillonite. 4) Carboxylated multi-walled carbon nanotubes and silver-plated copper powder were dispersed in anhydrous ethanol and ultrasonically dispersed for 40 min at a frequency of 40 kHz and a power of 400 W. Magnetic montmorillonite was added and the mixture was stirred at 70 °C and 400 r / min for 3 h. 5) Add KH-560 to the reaction solution obtained in step 4), stir at 400 r / min at 70℃ for 1.5 h, transfer to a vacuum drying oven, dry at 80℃ and vacuum degree -0.10 MPa for 12 h, grind and pass through a 400 mesh sieve to obtain magnetic montmorillonite-based hybrid electromagnetic shielding filler.

[0029] The raw materials for preparing core-shell ceramic flame-retardant microcapsules, by weight, include: 55 parts melamine polyphosphate, 35 parts nano magnesium hydroxide, 20 parts organomontmorillonite, 20 parts methyl vinyl silicone rubber, 10 parts zinc borate, 7 parts low-melting-point glass powder, 0.5 parts dicumyl peroxide, 2.5 parts emulsifier OP-10, 1.5 parts sodium polycarboxylate dispersant, 800 parts deionized water, and 100 parts toluene.

[0030] The preparation method of core-shell ceramic flame-retardant microcapsules includes the following steps: (1) Melamine polyphosphate, nano magnesium hydroxide, organomontmorillonite, sodium polycarboxylate dispersant and deionized water are mixed and stirred at 1500 r / min for 35 min to obtain a core material suspension; (2) Dissolve methyl vinyl silicone rubber in toluene, add zinc borate, low melting point glass powder and dicumyl peroxide, and stir at 1000 r / min for 30 min to obtain wall material prepolymer liquid; (3) Mix the core material suspension and the wall material prepolymer liquid at a mass ratio of 3:1, add emulsifier OP-10, emulsify at high speed for 15 min at an emulsification speed of 10000 r / min, and spray dry using a spray dryer, controlling the feed rate at 15 mL / min, the inlet air temperature at 200℃, the outlet air temperature at 90℃, and the atomizer speed at 25000 r / min; (4) Collect the spray-dried particles, place them in an oven at 165℃ and keep them warm for 15 minutes to remove residual solvent, then raise the temperature to 170℃ and vulcanize for 8 minutes to obtain core-shell ceramic flame-retardant microcapsules.

[0031] This embodiment also discloses a method for preparing a highly shielded, flame-retardant, and fire-resistant control cable, comprising the following steps: S1. Place low-smoke halogen-free flame-retardant polyolefin, ethylene-vinyl acetate copolymer, and polyolefin elastomer in a high-speed mixer and initially mix at 400 r / min for 5 min at 30℃. Add magnetic montmorillonite-based hybrid electromagnetic shielding filler, core-shell ceramic flame-retardant microcapsules, and basalt fiber. Pre-disperse at 600 r / min for 8 min. Then add KH-560, dicumyl peroxide, lubricant, calcium-zinc stabilizer, and antioxidant. Mix at 600 r / min for 5 min to obtain the mixture. S2. Add the mixture to the internal mixer and mix for 20 minutes at a temperature of 130℃ and a speed of 80r / min. After cooling the mixed material to 110℃, transfer it to the open mill and run it through the open mill 5 times at a temperature of 110℃ and a roller gap of 2mm to obtain a uniformly plasticized rubber compound. S3. Add the rubber compound obtained in step S2 to a twin-screw extruder and granulate it at a temperature of 120℃ and a screw speed of 400r / min to obtain special granules for sheathing. S4. The special granules for the sheath are extruded to the outside of the composite shielding layer using an extruder. The extrusion temperature is 150℃ and the speed is 8m / min. Then, the extruded cable is cross-linked, cured, cooled, and wound up in a pressurized steam environment to obtain the finished cable. The cross-linking curing temperature was 170℃, the pressure was 1MPa, and the time was 3h.

[0032] Example 3: This embodiment discloses a highly shielded flame-retardant and fire-resistant control cable. The cable, from the inside out, consists of a conductor core, a fire-resistant insulation layer, a composite shielding layer, and a flame-retardant and fire-resistant sheath layer. By weight, the raw materials for preparing the flame-retardant and fire-resistant sheath layer include: 40 parts of low-smoke halogen-free flame-retardant polyolefin, 18 parts of ethylene-vinyl acetate copolymer, 10 parts of polyolefin elastomer, 8 parts of magnetic montmorillonite-based hybrid electromagnetic shielding filler, 9 parts of core-shell ceramic flame-retardant microcapsules, 1.2 parts of KH-560, 3 parts of basalt fiber, 0.5 parts of dicumyl peroxide, 0.8 parts of lubricant, 0.9 parts of calcium-zinc stabilizer, and 0.4 parts of antioxidant. The lubricant is a 1:1 mass ratio compound of polyethylene wax and ethylene bis-stearamide, and the antioxidant is a 1:1 mass ratio compound of antioxidant 1010 and antioxidant 168.

[0033] The raw materials for preparing the magnetic montmorillonite-based hybrid electromagnetic shielding filler, by weight, include: 95 parts sodium montmorillonite, 6 parts KH-550, 198 parts ferric chloride hexahydrate, 72 parts ferrous chloride tetrahydrate, 22 parts carboxylated multi-walled carbon nanotubes, 32 parts silver-plated copper powder, 4 parts KH-560, 1950 parts deionized water, 450 parts anhydrous ethanol, and 230 parts purified water.

[0034] The preparation method of magnetic montmorillonite-based hybrid electromagnetic shielding filler includes the following steps: 1) Sodium-based montmorillonite was mixed with 5 / 7 of the total mass of deionized water and ultrasonically dispersed for 35 min at a frequency of 30 kHz and a power of 350 W. KH-550 was added, and the mixture was stirred at 350 r / min for 2.5 h in a water bath at 65 ℃. Then it was centrifuged at 3500 r / min for 12 min. The precipitate was washed 4 times with deionized water until the washing liquid was neutral. It was then dried in a vacuum drying oven at 70 ℃ and a vacuum degree of -0.09 MPa for 10 h to obtain organically modified montmorillonite. 2) Add ferric chloride hexahydrate and ferrous chloride tetrahydrate to purified water and ultrasonically disperse for 35 min at a frequency of 30 kHz and a power of 350 W to obtain mixture A; 3) Add the organically modified montmorillonite to the remaining deionized water and ultrasonically disperse it for 35 min at a frequency of 30 kHz and a power of 350 W. Under nitrogen protection, heat the mixture to 65 ℃ and stir continuously at a speed of 250 r / min. Add the mixture A dropwise at a uniform rate over 25 min, and then add a 26% (w / w) ammonia solution to adjust the pH of the system to 10.5. Stir the mixture at 250 r / min at 65 ℃ for 2 h. Use a neodymium iron boron permanent magnetic field with a magnetic field strength of 1.0 T to perform magnetic separation of the reaction system. Wash the precipitate with deionized water until the washing liquid is neutral to obtain magnetic montmorillonite. 4) Carboxylated multi-walled carbon nanotubes and silver-plated copper powder were dispersed in anhydrous ethanol and ultrasonically dispersed for 35 min at a frequency of 30 kHz and a power of 350 W. Magnetic montmorillonite was added and the mixture was stirred at 350 r / min at 65 °C for 2.5 h. 5) Add KH-560 to the reaction solution obtained in step 4), stir at 350 r / min at 65℃ for 1.5 h, transfer to a vacuum drying oven, dry at 70℃ and vacuum degree -0.09 MPa for 10 h, grind and pass through a 350 mesh sieve to obtain magnetic montmorillonite-based hybrid electromagnetic shielding filler.

[0035] The raw materials for preparing core-shell ceramic flame-retardant microcapsules, by weight, include: 52 parts melamine polyphosphate, 32 parts nano magnesium hydroxide, 17 parts organomontmorillonite, 18 parts methyl vinyl silicone rubber, 9 parts zinc borate, 6 parts low melting point glass powder, 0.4 parts dicumyl peroxide, 2.2 parts emulsifier OP-10, 1.2 parts sodium polycarboxylate dispersant, 720 parts deionized water, and 90 parts toluene.

[0036] The preparation method of core-shell ceramic flame-retardant microcapsules includes the following steps: (1) Melamine polyphosphate, nano magnesium hydroxide, organomontmorillonite, sodium polycarboxylate dispersant and deionized water are mixed and stirred at 1350 r / min for 30 min to obtain a core material suspension; (2) Dissolve methyl vinyl silicone rubber in toluene, add zinc borate, low melting point glass powder and dicumyl peroxide, and stir at 900 r / min for 25 min to obtain wall material prepolymer liquid; (3) Mix the core material suspension and the wall material prepolymer liquid at a mass ratio of 3:1, add emulsifier OP-10, emulsify at high speed for 12 minutes at an emulsification speed of 9000 r / min, and spray dry using a spray dryer, controlling the feed rate at 12 mL / min, the inlet air temperature at 190℃, the outlet air temperature at 85℃, and the atomizer speed at 22500 r / min; (4) Collect the spray-dried particles, place them in a 160℃ oven and keep them warm for 12 minutes to remove residual solvent, then raise the temperature to 168℃ and vulcanize for 6 minutes to obtain core-shell ceramic flame-retardant microcapsules.

[0037] This embodiment also discloses a method for preparing a highly shielded, flame-retardant, and fire-resistant control cable, comprising the following steps: S1. Place low-smoke halogen-free flame-retardant polyolefin, ethylene-vinyl acetate copolymer, and polyolefin elastomer in a high-speed mixer and initially mix at 350 r / min for 4 min at 28°C. Add magnetic montmorillonite-based hybrid electromagnetic shielding filler, core-shell ceramic flame-retardant microcapsules, and basalt fiber. Pre-disperse at 550 r / min for 6 min. Then add KH-560, dicumyl peroxide, lubricant, calcium-zinc stabilizer, and antioxidant. Mix at 550 r / min for 4 min to obtain the mixture. S2. Add the mixture to the internal mixer and mix for 18 minutes at a temperature of 125℃ and a speed of 70r / min. After cooling the mixed material to 105℃, transfer it to the open mill and run it through the open mill 4 times at a temperature of 105℃ and a roller gap of 1.5mm to obtain a uniformly plasticized rubber compound. S3. Add the rubber compound obtained in step S2 to a twin-screw extruder and granulate it at a temperature of 115℃ and a screw speed of 350r / min to obtain special granules for sheathing. S4. The special granules for the sheath are extruded to the outside of the composite shielding layer using an extruder. The extrusion temperature is 145℃ and the speed is 6m / min. Then, the extruded cable is cross-linked, cured, cooled, and wound up in a pressurized steam environment to obtain the finished cable. The cross-linking curing temperature was 165℃, the pressure was 0.9MPa, and the time was 2.5h.

[0038] Comparative Example 1: A highly shielded flame-retardant and fire-resistant control cable and its preparation method are disclosed. The only difference between this cable and Example 3 is that no magnetic montmorillonite-based hybrid electromagnetic shielding filler is added.

[0039] Comparative Example 2: A highly shielded flame-retardant and fire-resistant control cable and its preparation method are disclosed. The only difference between this cable and Example 3 is that no core-shell type ceramic flame-retardant microcapsules are added.

[0040] Comparative Example 3: A highly shielded flame-retardant and fire-resistant control cable and its preparation method are disclosed. The only difference between this cable and Example 3 is that KH-560 (3-glycidyl etheroxypropyltrimethoxysilane) is not added.

[0041] Comparative Example 4: A highly shielded flame-retardant and fire-resistant control cable and its preparation method are disclosed, the only difference between the cable and Example 3 is that basalt fiber is not added.

[0042] Comparative Example 5: A highly shielded flame-retardant and fire-resistant control cable and its preparation method are disclosed, the only difference between this cable and Example 3 is that dicumyl peroxide is not added.

[0043] Comparative Example 6: A highly shielded flame-retardant and fire-resistant control cable and its preparation method are disclosed, the only difference between this cable and Example 3 is that no calcium-zinc stabilizer is added.

[0044] Comparative Example 7: A highly shielded flame-retardant and fire-resistant control cable and its preparation method are disclosed, the only difference between this cable and Example 3 is that no antioxidant is added.

[0045] Comparative Example 8: A highly shielded flame-retardant and fire-resistant control cable and its preparation method are disclosed, the only difference between this cable and Example 3 is that no lubricant is added.

[0046] Comparative Example 9: A highly shielded flame-retardant and fire-resistant control cable and its preparation method are disclosed, the only difference between the cable and Example 3 is that no polyolefin elastomer is added.

[0047] Comparative Example 10: A highly shielded flame-retardant and fire-resistant control cable and its preparation method are disclosed. The only difference between this cable and Example 3 is that the cross-linking curing temperature is changed from 165°C to 195°C.

[0048] The oxygen index, fire resistance time, shielding effectiveness, tensile strength and elongation at break, volume resistivity, heat distortion temperature, melt flow index, and vertical flammability rating of the cables obtained in Examples 1-3 and Comparative Examples 1-10 were tested. The testing methods and standards for each performance are as follows: Oxygen Index (LOI) Determination: The LOI was determined according to GB / T 2406.2-2009 Oxygen Index Method for Plastics – Part 2: Room Temperature Test. An oxygen index meter was used. The sample size was 80mm × 10mm × 4mm, and 15 samples were used. The arithmetic mean of the test results was taken. The sample was vertically fixed in a combustion chamber, and a mixture of oxygen and nitrogen was introduced. The upper part of the sample was ignited, and the oxygen volume fraction was recorded when the sample continued to burn for 3 minutes or when the burning length exceeded 50mm. This was the oxygen index value, and the arithmetic mean of the results was taken.

[0049] Fire resistance time determination: The determination is conducted according to GB / T 19666-2019 General Rules for Flame-Retardant and Fire-Resistant Wires, Cables or Optical Cables. A fire resistance test furnace is used, and the cable sample length is not less than 1200 mm. A rated voltage of 220 V is applied to the cable conductor, and the cable is placed horizontally in a flame at a temperature of 750±50℃. The time from the start of the fire to the occurrence of a short circuit or open circuit in the cable is recorded, which is the fire resistance time, expressed in minutes.

[0050] Shielding effectiveness determination: The determination was conducted according to GB / T 31253-2014 Standard and Test Method for Cable Shielding Effectiveness. An anechoic chamber method was used, employing a vector network analyzer and receiving antenna. The test frequency band was 30MHz-1GHz, and the sample length was 1000mm. The average shielding effectiveness was recorded. The shielding effectiveness was calculated using the formula SE=20lg(E0 / E1), where SE is the shielding effectiveness in dB, E0 is the electric field strength without shielding, and E1 is the electric field strength with shielding.

[0051] Tensile strength and elongation at break were determined according to GB / T 1040.2-2018 Determination of tensile properties of plastics – Part 2: Test conditions for molded and extruded plastics. An electronic universal testing machine was used, with type 1A dumbbell-shaped specimens. The tensile speed was 50 mm / min. The elongation at break was calculated using the formula ε = (L - L0) / L0 × 100%, where ε is the elongation at break, L0 is the initial gauge length of the specimen, and L is the gauge length at break.

[0052] Volume resistivity determination: The determination was performed according to GB / T 1410-2006 "Test Methods for Volume Resistivity and Surface Resistivity of Solid Insulating Materials". A high-resistivity meter was used, the test temperature was 25±2℃, the applied voltage was 500V, and the charging time was 60s. The volume resistivity was calculated using the formula ρ. v =R v ×A / h, where ρ v R is the volume resistivity, expressed in Ω·m. v To measure the volume resistivity, A is the effective area of ​​the sample, and h is the sample thickness.

[0053] Heat distortion temperature determination: The determination was performed according to GB / T 1634.2-2021 Determination of deformation temperature of plastics under load - Part 2: Plastics and hard rubber. A Vicat heat distortion tester was used, with a load of 0.45 MPa and a heating rate of 120 °C / h. The temperature at which the sample deflection reached 0.25 mm was recorded.

[0054] Melt flow index determination: The determination was performed according to GB / T 3682.1-2018 Plastics - Determination of melt mass flow rate (MFR) and melt volumetric flow rate (MVR) of thermoplastics - Part 1: Standard method. A melt flow indexer was used at a temperature of 190℃ and a load of 2.16 kg. The mass of melt passing through the standard die within 10 minutes was recorded, in g / 10min.

[0055] Vertical flammability rating determination: The determination shall be carried out in accordance with GB / T 2408-2021 Determination of flammability of plastics by horizontal and vertical methods. The sample size is 125mm × 13mm × 3.2mm, and the flammability rating (UL94 V-0, V-1 or V-2) shall be recorded.

[0056] The results are shown in Tables 2 and 3.

[0057] Table 2. Test results of flame retardancy, fire resistance, and shielding performance. Example 1 38 180 85 V-0 Example 2 39 190 88 V-0 Example 3 40 200 90 V-0 Comparative Example 1 40 198 42 V-0 Comparative Example 2 29 95 88 V-1 Comparative Example 3 36 160 72 V-0 Comparative Example 4 40 190 90 V-0 Comparative Example 5 36 90 87 V-2 Comparative Example 6 37 165 88 V-0 Comparative Example 7 39 188 89 V-0 Comparative Example 8 40 200 90 V-0 Comparative Example 9 40 200 90 V-0 Comparative Example 10 36 140 80 V-1 Table 3. Test results of mechanical, electrical, thermal, and processing properties. Example 1 18.5 400 <![CDATA[1.5×10 14 ]]> 92 2.4 Example 2 19.5 430 <![CDATA[1.7×10 14 ]]> 96 2.6 Example 3 20.5 450 <![CDATA[2.0×10 14 ]]> 100 2.8 Comparative Example 1 21.2 465 <![CDATA[2.2×10 14 ]]> 101 2.9 Comparative Example 2 20.0 445 <![CDATA[1.9×10 14 ]]> 98 2.8 Comparative Example 3 13.5 250 <![CDATA[1.2×10 14 ]]> 85 2.0 Comparative Example 4 17.0 450 <![CDATA[2.0×10 14 ]]> 98 2.8 Comparative Example 5 11.0 300 <![CDATA[8.0×10 13 ]]> 65 3.5 Comparative Example 6 15.0 320 <![CDATA[1.4×10 14 ]]> 88 3.2 Comparative Example 7 19.0 420 <![CDATA[1.8×10 14 ]]> 97 2.8 Comparative Example 8 20.5 450 <![CDATA[2.0×10 14 ]]> 100 1.6 Comparative Example 9 22.0 160 <![CDATA[2.1×10 14 ]]> 102 3.0 Comparative Example 10 14.0 310 <![CDATA[1.5×10 14 ]]> 70 3.3

[0058] Using Example 3 as the control group, the performance differences and causes of Comparative Examples 1-10 are analyzed as follows: Comparative Example 1 (without magnetic montmorillonite-based hybrid electromagnetic shielding filler): Shielding effectiveness decreased from 90dB to 42dB (a decrease of 53.3%), while other properties remained basically unchanged or slightly improved; among them, tensile strength increased from 20.5MPa to 21.2MPa (an increase of 3.4%), elongation at break increased from 450% to 465% (an increase of 3.3%), and heat distortion temperature increased from 100℃ to 101℃ (an increase of 1%). Reason: The magnetic montmorillonite-based hybrid electromagnetic shielding filler is the core shielding component. Its "magnetic-electrical-layered" triple shielding mechanism disappeared, relying only on the weak shielding effect of the cable matrix, resulting in a significant decrease in shielding effectiveness, consistent with the electromagnetic shielding mechanism. The absence of a large amount of inorganic components in the filler increased the purity of the matrix phase and reduced interface defects, thus slightly improving mechanical properties. The flame-retardant synergistic effect of the magnetic montmorillonite-based hybrid electromagnetic shielding filler was weak, therefore the flame-retardant and fire-resistant properties remained essentially unchanged.

[0059] Comparative Example 2 (without core-shell ceramicized flame-retardant microcapsules): The oxygen index decreased from 40% to 29% (a decrease of 27.5%), the fire resistance time decreased from 200 min to 95 min (a decrease of 52.5%), and the vertical burning rating decreased from V-0 to V-1, while other properties remained largely unchanged; among them, the tensile strength decreased from 20.5 MPa to 20.0 MPa (a decrease of 2.4%), and the elongation at break decreased from 450% to 445% (a decrease of 1.1%). Reason: The core-shell ceramicized flame-retardant microcapsules are the core flame-retardant and refractory component. The "core-shell ceramicization-phosphorus-nitrogen synergistic" flame-retardant and refractory mechanism disappears. Relying solely on the low-smoke, halogen-free flame-retardant properties of the polyolefin matrix, an effective ceramicized heat insulation layer and expanded char layer cannot be formed, thus significantly reducing flame-retardant and refractory performance. The microcapsules have no direct impact on shielding performance, therefore the shielding effectiveness remains largely unchanged.

[0060] Comparative Example 3 (without KH-560): Tensile strength decreased from 20.5 MPa to 13.5 MPa (a decrease of 34.1%), elongation at break decreased from 450% to 250% (a decrease of 44.4%), shielding effectiveness decreased from 90 dB to 72 dB (a decrease of 20%), oxygen index decreased from 40% to 36% (a decrease of 10%), refractory time decreased from 200 min to 160 min (a decrease of 20%), heat distortion temperature decreased from 100℃ to 85℃ (a decrease of 15%), and melt flow index decreased from 2.8 to 2.0 (a decrease of 28.6%). Causes: The "bridging effect" of the coupling agent disappears, and inorganic fillers such as magnetic montmorillonite-based hybrid electromagnetic shielding fillers, core-shell ceramic flame-retardant microcapsules, and basalt fibers severely agglomerate, resulting in a significant decrease in the interfacial bonding force with the organic matrix and a significant deterioration in mechanical properties. The agglomeration of fillers causes discontinuity in the shielding network and defects in the flame-retardant barrier structure, thus significantly reducing shielding effectiveness, flame retardant performance, and heat distortion temperature. The decrease in melt flow index is due to the poor melt flowability caused by filler agglomeration.

[0061] Comparative Example 4 (without basalt fiber): Tensile strength decreased from 20.5 MPa to 17.0 MPa (a decrease of 17.1%), while other properties remained essentially unchanged. Reason: Basalt fiber is the core reinforcing filler; the lack of its high tensile strength characteristic leads to a decrease in the mechanical strength of the matrix. Basalt fiber has no direct impact on shielding, flame retardancy, or processing performance; therefore, other properties remain essentially unchanged, consistent with the mechanism of reinforcing fillers.

[0062] Comparative Example 5 (without dicumyl peroxide): Heat distortion temperature decreased from 100℃ to 65℃ (a decrease of 35%), tensile strength decreased from 20.5 MPa to 11.0 MPa (a decrease of 46.3%), elongation at break decreased from 450% to 300% (a decrease of 33.3%), fire resistance time decreased from 200 min to 90 min (a decrease of 55%), vertical burning rating decreased from V-0 to V-2, and volume resistivity decreased from 2.0 × 10⁻⁶. 14 Ω·m decreased to 8.0×10 13 Ω·m (decreased by 60%), melt index increased from 2.8 to 3.5 (increased by 25%). Reasons: The lack of crosslinking agent prevents the matrix from forming an effective three-dimensional network crosslinked structure, significantly reducing the degree of crosslinking and leading to a substantial decrease in mechanical properties, heat resistance, and insulation properties. Without the barrier effect of the crosslinked structure, the melt drips during combustion, thus reducing flame retardancy and fire resistance, and lowering the vertical burning rating. The increase in melt index is due to the superior fluidity of linear molecular chains compared to crosslinked structures.

[0063] Comparative Example 6 (without calcium-zinc stabilizer): Tensile strength decreased from 20.5 MPa to 15.0 MPa (a decrease of 26.8%), elongation at break decreased from 450% to 320% (a decrease of 28.9%), heat distortion temperature decreased from 100℃ to 88℃ (a decrease of 12%), oxygen index decreased from 40% to 37% (a decrease of 7.5%), refractoriness time decreased from 200 min to 165 min (a decrease of 17.5%), and melt flow index increased from 2.8 to 3.2 (an increase of 14.3%). Reason: During high-temperature processing, the matrix undergoes thermal degradation, resulting in molecular chain breakage and a decrease in mechanical properties, heat resistance, and flame retardant properties; the small molecules produced by thermal degradation increase melt fluidity, thus increasing the melt flow index.

[0064] Comparative Example 7 (without antioxidant): Tensile strength decreased from 20.5 MPa to 19.0 MPa (a decrease of 7.3%), elongation at break decreased from 450% to 420% (a decrease of 6.7%), and fire resistance time decreased from 200 min to 188 min (a decrease of 6%), while other properties remained essentially unchanged. Reason: The main function of antioxidants is long-term aging resistance. In short-term performance tests, only slight oxidative degradation was observed, with a small performance decline. However, in long-term use, oxidative degradation will continue to accelerate, and the cable performance will rapidly deteriorate.

[0065] Comparative Example 8 (without lubricant): Melt index decreased from 2.8 to 1.6 (a decrease of 42.9%), while other properties remained essentially unchanged. Reason: The lack of lubricant increased friction between the material and equipment during processing, resulting in poor melt flowability, which only affected processing performance; the lubricant had no effect on the material's usability, therefore other properties remained essentially unchanged.

[0066] Comparative Example 9 (without polyolefin elastomer): Tensile strength increased from 20.5 MPa to 22.0 MPa (an increase of 7.3%), while elongation at break decreased from 450% to 160% (a decrease of 64.4%), with other properties remaining essentially unchanged. Reason: Polyolefin elastomer is an elastomer; its absence leads to increased matrix rigidity and a significant decrease in flexibility. Polyolefin elastomer has no direct impact on shielding, flame retardancy, or heat resistance; therefore, other properties remain largely unchanged, solving the inherent problem of "increased rigidity leading to decreased flexibility" in traditional cables.

[0067] Comparative Example 10 (crosslinking temperature too high): Heat distortion temperature decreased from 100℃ to 70℃ (a decrease of 30%), tensile strength decreased from 20.5MPa to 14.0MPa (a decrease of 31.7%), elongation at break decreased from 450% to 310% (a decrease of 31.1%), oxygen index decreased from 40% to 36% (a decrease of 10%), fire resistance time decreased from 200min to 140min (a decrease of 30%), vertical fire rating decreased from V-0 to V-1, shielding effectiveness decreased from 90dB to 80dB (a decrease of 11.1%), and melt flow index increased from 2.8 to 3.3 (an increase of 17.9%). Causes: The crosslinking temperature of 195℃ far exceeds the decomposition temperature of dicumyl oxide (170℃), causing the crosslinking agent to decompose prematurely and the crosslinking reaction to be incomplete. In addition, some polyolefin / ethylene-vinyl acetate copolymer matrix undergoes thermal degradation, resulting in molecular chain breakage and insufficient crosslinking degree, leading to a significant decrease in mechanical properties and heat resistance. At the same time, the small molecules produced by thermal degradation make combustion more intense, reducing flame retardancy and fire resistance, and lowering the vertical burning rating. Insufficient crosslinking degree results in a loose network structure of the shielding filler, slightly reducing the shielding effectiveness. The increase in melt flow index is due to the increased melt fluidity caused by the reduced crosslinking degree.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A highly shielded, flame-retardant, and fire-resistant control cable, characterized in that, The cable consists of, from the inside out, conductor core, fire-resistant insulation layer, composite shielding layer, and flame-retardant and fire-resistant sheath layer. The raw materials for preparing the flame-retardant and fire-resistant sheath layer, by weight, include: 35-45 parts of low-smoke halogen-free flame-retardant polyolefin, 15-20 parts of ethylene-vinyl acetate copolymer, 8-12 parts of polyolefin elastomer, 6-10 parts of magnetic montmorillonite-based hybrid electromagnetic shielding filler, 7-11 parts of core-shell ceramic flame-retardant microcapsules, 1.0-1.5 parts of silane coupling agent, 2-4 parts of basalt fiber, 0.4-0.7 parts of crosslinking agent, 0.6-1.0 parts of lubricant, 0.7-1.1 parts of stabilizer, and 0.3-0.6 parts of antioxidant; The silane coupling agent is 3-glycidyl etheroxypropyltrimethoxysilane, the crosslinking agent is dicumyl peroxide, the lubricant is a mixture of polyethylene wax and ethylene bis-stearamide in a mass ratio of 1:1, the stabilizer is a calcium-zinc stabilizer, and the antioxidant is a mixture of antioxidant 1010 and antioxidant 168 in a mass ratio of 1:

1. The raw materials for preparing the magnetic montmorillonite-based hybrid electromagnetic shielding filler, by weight, include: 90-100 parts of sodium montmorillonite, 5-7 parts of γ-aminopropyltriethoxysilane, 195-200 parts of ferric chloride hexahydrate, 70-75 parts of ferrous chloride tetrahydrate, 20-25 parts of carboxylated multi-walled carbon nanotubes, 30-35 parts of silver-plated copper powder, 3-5 parts of 3-glycidyl etheroxypropyltrimethoxysilane, 1800-2100 parts of deionized water, 400-500 parts of anhydrous ethanol, and 185-275 parts of purified water. The raw materials for preparing the core-shell ceramic flame-retardant microcapsules, by weight, include: 50-55 parts of melamine polyphosphate, 30-35 parts of nano magnesium hydroxide, 15-20 parts of organomontmorillonite, 16-20 parts of methyl vinyl silicone rubber, 8-10 parts of zinc borate, 5-7 parts of low-melting-point glass powder, 0.3-0.5 parts of dicumyl peroxide, 2.0-2.5 parts of emulsifier OP-10, 1.0-1.5 parts of sodium polycarboxylate dispersant, 650-800 parts of deionized water, and 80-100 parts of toluene.

2. The high-shield flame-retardant and fire-resistant control cable according to claim 1, characterized in that, The preparation method of the magnetic montmorillonite-based hybrid electromagnetic shielding filler includes the following steps: 1) Sodium-based montmorillonite is mixed with deionized water accounting for 4 / 7-5 / 7 of the total mass of deionized water. The mixture is ultrasonically dispersed for 30-40 min at a frequency of 20-40 kHz and a power of 300-400 W. γ-aminopropyltriethoxysilane is added, and the mixture is then stirred at 300-400 r / min for 2-3 h in a water bath at 60-70 ℃. After that, it is centrifuged at 3000-4000 r / min for 10-15 min. The precipitate is washed with deionized water 3-5 times until the washing liquid is neutral. The precipitate is then dried in a vacuum drying oven at 60-80 ℃ and a vacuum degree of -0.08 MPa to -0.10 MPa for 8-12 h to obtain organically modified montmorillonite. 2) Add ferric chloride hexahydrate and ferrous chloride tetrahydrate to purified water and ultrasonically disperse for 30-40 min at a frequency of 20-40 kHz and a power of 300-400 W to obtain mixture A; 3) Add the organically modified montmorillonite to the remaining deionized water and ultrasonically disperse it for 30-40 min at a frequency of 20-40 kHz and a power of 300-400 W. Under nitrogen protection, heat the mixture to 60-70 ℃ and stir continuously at a speed of 200-300 r / min. Add the mixture A dropwise at a uniform rate over 20-30 min, and then add ammonia solution with a mass fraction of 25-28% to adjust the pH of the system to 10-11. Stir the mixture at 200-300 r / min at 60-70 ℃ for 1.5-2 h. Use a neodymium iron boron permanent magnetic field with a magnetic field strength of 0.8-1.2 T to perform magnetic separation of the reaction system. Wash the precipitate with deionized water until the washing solution is neutral to obtain magnetic montmorillonite. 4) Disperse carboxylated multi-walled carbon nanotubes and silver-plated copper powder in anhydrous ethanol, and ultrasonically disperse them for 30-40 min at a frequency of 20-40 kHz and a power of 300-400 W. Add magnetic montmorillonite and stir the mixture at 300-400 r / min at 60-70℃ for 2-3 h. 5) Add 3-glycidyl etheroxypropyltrimethoxysilane to the reaction solution obtained in step 4), stir at 300-400 r / min at 60-70℃ for 1-1.5 h, transfer to a vacuum drying oven, dry at 60-80℃ and vacuum degree -0.08MPa~-0.10MPa for 8-12 h, grind and pass through a 300-400 mesh sieve to obtain magnetic montmorillonite-based hybrid electromagnetic shielding filler.

3. The high-shield flame-retardant and fire-resistant control cable according to claim 1, characterized in that, The preparation method of the core-shell ceramic flame-retardant microcapsules includes the following steps: (1) Mix melamine polyphosphate, nano magnesium hydroxide, organomontmorillonite, sodium polycarboxylate dispersant with deionized water and stir at 1200-1500 r / min for 25-35 min to obtain a nuclear material suspension; (2) Dissolve methyl vinyl silicone rubber in toluene, add zinc borate, low melting point glass powder and dicumyl peroxide, and stir at 800-1000 r / min for 20-30 min to obtain wall material prepolymer liquid; (3) Mix the core material suspension and the wall material prepolymer liquid at a mass ratio of 3:1, add emulsifier OP-10, emulsify at high speed for 10-15 minutes at an emulsification speed of 8000-10000 r / min, and spray dry using a spray dryer; (4) Collect the spray-dried particles, place them in an oven at 155-165℃ and keep them warm for 10-15 minutes to remove residual solvent, then raise the temperature to 165-170℃ and vulcanize for 5-8 minutes to obtain core-shell ceramic flame-retardant microcapsules.

4. The high-shield flame-retardant and fire-resistant control cable according to claim 3, characterized in that, In step (3), the specific operation of spray drying is as follows: control the feed rate to 10-15 mL / min, the air inlet temperature to 180-200℃, the air outlet temperature to 80-90℃, and the atomizer speed to 20000-25000 r / min.

5. A method for preparing a high-shield, flame-retardant, and fire-resistant control cable according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Place low-smoke halogen-free flame-retardant polyolefin, ethylene-vinyl acetate copolymer, and polyolefin elastomer in a high-speed mixer and initially mix at 300-400 r / min for 3-5 min at 25-30℃. Add magnetic montmorillonite-based hybrid electromagnetic shielding filler, core-shell ceramic flame-retardant microcapsules, and basalt fiber, and pre-disperse at 500-600 r / min for 5-8 min. Then add silane coupling agent, crosslinking agent, lubricant, stabilizer, and antioxidant, and mix at 500-600 r / min for 3-5 min to obtain the mixture. S2. Add the mixture to the internal mixer and mix for 15-20 minutes at a temperature of 120-130℃ and a speed of 60-80 r / min. After cooling the mixed material to 100-110℃, transfer it to the open mill and pass it through the open mill 3-5 times at a temperature of 100-110℃ and a roll gap of 1-2 mm to obtain a uniformly plasticized rubber compound. S3. Add the rubber compound obtained in step S2 to a twin-screw extruder and granulate it at a temperature of 110-120℃ and a screw speed of 300-400r / min to obtain special granules for sheathing. S4. The special granules for the sheath are extruded to the outside of the composite shielding layer using an extruder. The extrusion temperature is 140-150℃ and the speed is 5-8m / min. Then, the extruded cable is cross-linked, cured, cooled, and wound up in a pressurized steam environment to obtain the finished cable.

6. The method for preparing the high-shield flame-retardant and fire-resistant control cable according to claim 5, characterized in that, In step S4, the cross-linking curing temperature is 160-170℃, the pressure is 0.8-1.0MPa, and the time is 2-3h.