Preparation process of insulating rubber material for high-voltage distortion-resistant flexible cable

Abstract

The invention discloses a preparation process of an insulating rubber material for a high-voltage distortion-resistant flexible cable, and relates to the technical field of insulating rubber materials. The preparation process of the insulating rubber material for the cable comprises the steps of preparing the modified composite filler, preparing the modified nano barium sulfate and preparing the insulating rubber material. The rubber material is prepared from the following raw materials: ethylene propylene diene monomer, ethylene propylene rubber, an ethylene-vinyl acetate copolymer, a modified composite filler, dicumyl peroxide, triallyl cyanurate, a silane coupling agent A172, an anti-aging agent, an ultraviolet light absorber, paraffin oil, stearic acid, zinc oxide, modified nano barium sulfate and organic montmorillonite. The prepared insulating rubber material for the cable is excellent in electrical insulation property and high in mechanical property and aging resistance.

Description

Technical Field

[0001] This invention relates to the field of insulating rubber materials, specifically to a preparation process for insulating rubber materials for high-voltage torsion-resistant flexible cables. Background Technology

[0002] High-voltage torsion-resistant flexible cables are widely used in industrial equipment, mining machinery, hoisting machinery, electrical drag chains, and offshore wind power. Among them, there is an urgent need for 35kV-66kV cables for large-capacity wind turbines of 3.5MW and above. These cables connect the switch cabinet at the bottom of the tower to the transformer in the nacelle and need to withstand high-voltage electric fields and frequent torsion and bending for a long time. The comprehensive performance of the insulating rubber material directly determines the safety and service life of the cable.

[0003] Currently, most insulating rubber materials for cables are made from natural rubber and ethylene propylene rubber as base materials, combined with various fillers and additives, and prepared through conventional processes such as mixing, plasticizing, and vulcanization. However, existing processes have many shortcomings and cannot meet multiple performance requirements simultaneously. Inappropriate plasticizing temperature, uneven dispersion of mixing additives, and improper vulcanization parameters can lead to uneven cross-linking of the material, reducing insulation breakdown strength, flexibility, and tear resistance, and making it prone to cracking and aging under long-term torsion. Blindly adjusting the amount of additives can sacrifice insulation or torsion resistance, and may also cause problems such as copper wire adhesion. Existing technology with publication number CN119371740A discloses an ethylene propylene rubber insulating compound for power cables. This prior art uses ethylene propylene rubber and ethylene-vinyl acetate copolymer as base materials, combined with fillers such as silica and modified calcined clay, and improves electrical and mechanical properties through a mixing-granule preparation process. However, this prior art does not focus on improving torsion resistance, has insufficient high-voltage insulation performance, and cannot meet the insulation requirements of higher voltage level cables.

[0004] In summary, although the existing technical solutions have improved certain properties of insulating rubber materials for cables to some extent, the following technical problems still exist: insufficient electrical insulation performance, poor mechanical properties, and poor aging resistance. Summary of the Invention

[0005] In order to solve the above-mentioned problems in the prior art, the present invention provides a preparation process for insulating rubber material for high-voltage torsion resistant flexible cables, and achieves the following objective: to prepare insulating rubber material for cables with excellent electrical insulation properties, strong mechanical properties and aging resistance.

[0006] To achieve the above objectives, the following technical solution is adopted: A process for preparing insulating rubber material for high-voltage torsion-resistant flexible cables includes the steps of preparing modified composite filler, preparing modified nano-barium sulfate, and obtaining insulating rubber material.

[0007] The modified composite filler is prepared by mixing silane coupling agent A172, ammonium persulfate, and deionized water, stirring to obtain a reaction solution; mixing dried nano-kaolin and fumed silica evenly, adding methyl acrylate, heating, and stirring; then adding dropwise to the reaction solution and stirring; drying and pulverizing to obtain the modified composite filler.

[0008] Furthermore, the mass ratio of the silane coupling agent A172, ammonium persulfate, and deionized water is 10:(0.6-0.8):(30-40). The mass ratio of the nano-kaolin, fumed silica, methyl acrylate, and reaction solution is 90:(10-11):(5-6):(15-18). The drying process involves a temperature of 130-140℃ and a drying time of 3-4 hours.

[0009] Further, the modified composite filler is prepared as follows: Silane coupling agent A172, ammonium persulfate, and deionized water are mixed and stirred for 20-25 minutes at a speed of 300-400 rpm to obtain a reaction solution. Dry nano-kaolin and fumed silica are mixed evenly, methyl acrylate is added, and the mixture is heated to 40-50℃ and stirred for 20-30 minutes at a speed of 800-1000 rpm. Then, the reaction solution is added dropwise, controlling the temperature at 85-90℃ and the stirring speed at 1100-1200 rpm for 60-70 minutes. The mixture is then dried and pulverized to a particle size ≤5 μm to obtain the modified composite filler.

[0010] The modified nano-barium sulfate was prepared as follows: vinyltrimethoxysilane, anhydrous ethanol, and deionized water were mixed evenly, the pH of the mixture was adjusted, and the mixture was stirred; then nano-barium sulfate was added, and the reaction was stirred; the solid was collected by centrifugation, washed, dried, and ground to obtain pretreated nano-barium sulfate; the pretreated nano-barium sulfate was added to toluene and stirred; azobisisobutyronitrile and butyl acrylate were mixed and added, high-purity nitrogen was purged to remove oxygen, and the reaction was stirred under nitrogen protection; after the reaction was completed, the reaction solution was poured into methanol for precipitation, the solid was collected by filtration, washed, vacuum dried, and ground to obtain modified nano-barium sulfate.

[0011] Further, the mass ratio of vinyltrimethoxysilane, anhydrous ethanol, deionized water, and nano-barium sulfate is (8-12):(60-75):(20-25):100. The drying process involves a temperature of 70-80℃, a vacuum degree of 0.08-0.095MPa, and a drying time of 4-5 hours. The mass ratio of the pretreated nano-barium sulfate, toluene, azobisisobutyronitrile, and butyl acrylate is 10:(95-100):(0.1-0.15):(3-5). The vacuum drying process involves a temperature of 80-90℃, a vacuum degree of 0.09-0.095MPa, and a drying time of 6-8 hours.

[0012] Further, the preparation of modified nano-barium sulfate involves: mixing vinyltrimethoxysilane, anhydrous ethanol, and deionized water evenly; adjusting the pH of the mixture to 4-5 with glacial acetic acid; stirring at 300-400 rpm for 15-20 minutes; then adding nano-barium sulfate; heating to 60-70℃; stirring for 2-2.5 hours at 500-600 rpm; after the reaction, collecting the solid by centrifugation; washing with anhydrous ethanol 3-4 times; drying; and grinding through a 100-mesh sieve to obtain pretreated nano-barium sulfate. Pretreated nano-barium sulfate was added to toluene and stirred for 30-40 minutes at a speed of 1000-1200 rpm. Azobisisobutyronitrile and butyl acrylate were mixed and added to the mixture. High-purity nitrogen was introduced to remove oxygen, and the temperature was controlled at 70-80℃. The mixture was stirred for 4-6 hours under nitrogen protection. After the reaction was completed, the reaction solution was poured into methanol for precipitation. The solid was collected by filtration, washed 2-3 times with anhydrous methanol, vacuum dried, and ground until the particle size was ≤2μm to obtain modified nano-barium sulfate.

[0013] The insulating rubber material is prepared by: adding EPDM rubber, EPDM rubber, and ethylene-vinyl acetate copolymer to a mixer and masticating; adding paraffin oil and stearic acid and continuing masticating; sequentially adding zinc oxide, modified composite filler, organic montmorillonite, modified nano-barium sulfate, silane coupling agent A172, antioxidant, and ultraviolet absorber and continuing mixing; adding dicumyl peroxide and triallyl cyanurate and mixing to obtain a compound; transferring the compound to a two-roll mill, thin-passing, rolling, and triangular wrapping, and extruding the rubber sheet and placing it at room temperature to obtain a cured rubber sheet; adding the cured rubber sheet to an extruder, extruding it into an insulating layer shape, steam vulcanizing, cooling in a cold water bath, drying, and sizing to obtain the insulating rubber material.

[0014] Furthermore, the raw materials used are composed of the following parts by weight: 45-55 parts of EPDM rubber, 10-15 parts of EPDM rubber, 20-30 parts of ethylene-vinyl acetate copolymer, 30-40 parts of modified composite filler, 0.8-1.2 parts of dicumyl peroxide, 0.4-0.8 parts of triallyl cyanurate, 0.6-1 part of silane coupling agent A172, 1.2-1.5 parts of antioxidant, 0.3-0.5 parts of ultraviolet absorber, 3-5 parts of paraffin oil, 1-1.5 parts of stearic acid, 2-3 parts of zinc oxide, 2-4 parts of modified nano-barium sulfate, and 2-4 parts of organo-modified montmorillonite. The antioxidant is obtained by mixing antioxidant MB and antioxidant RD, with a mass ratio of antioxidant MB to antioxidant RD of (5-7):(6-8). The temperatures of each section of the extruder are as follows: feeding section 60-70℃, compression section 80-90℃, homogenization section 70-80℃, and die head temperature 90-100℃. The steam vulcanization process has the following parameters: vulcanization temperature 165-175℃, steam pressure 0.8-1.0 MPa, and vulcanization time 10-15 min. The temperature of the cooling water tank is 20-30℃.

[0015] Further, the insulating rubber material is prepared by: adding EPDM rubber, EPDM rubber, and ethylene-vinyl acetate copolymer to a mixer, setting the speed to 60-80 rpm and the temperature to 60-70℃, and plasticizing for 5-6 minutes; adding paraffin oil and stearic acid, and continuing plasticizing for 2-3 minutes; raising the temperature to 80-90℃, and sequentially adding zinc oxide, modified composite filler, organic montmorillonite, modified nano-barium sulfate, silane coupling agent A172, antioxidant, and ultraviolet absorber, and continuing to mix for 8-10 minutes after addition; cooling to below 70℃, adjusting the speed to 40-50 rpm, adding dicumyl peroxide and triallyl cyanurate, and mixing for 1.5-2 minutes to obtain the compound rubber. The mixed rubber is transferred to an open mill at a roller temperature of 50-60℃ and a roller gap of 0.5-1.0mm. It is passed through a thin mill 6-8 times, then the roller gap is adjusted to 3-5mm. The rubber is then rolled and formed into triangular loops 3-4 times each, producing a 2-4mm thick sheet. This sheet is left to stand at room temperature for 4-6 hours to obtain a cured rubber sheet. The cured rubber sheet is then added to an extruder at a screw speed of 20-30rpm to extrude an insulating layer shape. It is then steam-cured, cooled in a cold water bath, dried, and sized to obtain the insulating rubber material.

[0016] The beneficial effects of this invention are as follows: (1) In the modified composite filler of the present invention, methyl acrylate is inserted into the interlayer gaps of nano-kaolin to increase the interlayer spacing of kaolin. Coupling agent A172 is grafted onto the surface of kaolin and fumed silica, which promotes the uniform filling of the interlayer pores after the expansion of the spherical silica to form a dense three-dimensional insulating structure, providing a basis for the high voltage insulation performance of the material. After the coupling agent is hydrolyzed, it condenses with the hydroxyl groups on the filler surface through silanol groups, and grafts the vinyl active groups onto the filler surface. During the vulcanization stage, the vinyl groups undergo free radical copolymerization with the double bonds on the molecular chain of EPDM / EVA to achieve covalent bonding between the filler and the rubber, effectively improving the mechanical properties and torsional stability of the material.

[0017] The modified nano-barium sulfate surface has both vinyl and butyl acrylate side chains. During the vulcanization and compounding stages, the vinyl groups and the double bonds of the EPDM / EVA molecular chains undergo vulcanization covalent bonding. Due to the excellent compatibility of the butyl acrylate side chains with the EVA molecular chains, they can form physical entanglement with the EPDM molecular chains. This dual effect significantly improves the interfacial bonding force between the filler and the rubber matrix, further optimizing the torsion resistance.

[0018] Furthermore, the modified composite filler, consisting of flake kaolin, spherical silica, and modified nano-barium sulfate, forms a multi-scale, multi-morphological complementary structure that can uniformly fill the pores in the EPDM / EVA rubber matrix, making the matrix microstructure denser. This reduces charge migration channels and leakage gaps under high voltage, improves insulation performance, and enhances the material's torsion resistance and mechanical stability. Both fillers are chemically modified by grafting vinyl and acrylate side chains to form a unified active interface in the rubber matrix. During the vulcanization stage, they crosslink with the EPDM / EVA molecular chains to form an integrated crosslinked network, ensuring that the material maintains interfacial integrity during torsion, bending, and aging.

[0019] (2) The insulating rubber material for high-voltage torsion-resistant flexible cables of the present invention has excellent electrical insulation properties. The volume resistivity of the prepared insulating rubber material is 8.9 × 10⁻⁶. 15 -9.2×10 15 Ω·m, breakdown field strength is 38.8-41.5kV / mm.

[0020] (3) The insulating rubber material for high-voltage torsion resistant flexible cables of the present invention has excellent mechanical properties. The tensile strength of the prepared insulating rubber material is 43.2-44.8 MPa, and the elongation at break is 478-495%.

[0021] (4) The insulating rubber material for high-voltage torsion-resistant flexible cables of the present invention has excellent aging resistance. After ultraviolet aging, the tensile strength retention rate of the prepared insulating rubber material is 94.1-95.2%, and the volume resistivity retention rate is 95.3-96.1%; after thermal aging, the tensile strength retention rate is 96.5-96.9%, and the volume resistivity retention rate is 96.8-97.2%. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0023] Example 1: A preparation process for an insulating rubber material for high-voltage torsion-resistant flexible cables A preparation process for an insulating rubber material for high-voltage torsion-resistant flexible cables includes the following steps: Step 1: Preparation of modified composite fillers Mix silane coupling agent A172, ammonium persulfate, and deionized water, and stir for 20 minutes at a speed of 400 rpm to obtain a reaction solution.

[0024] The mass ratio of the silane coupling agent A172, ammonium persulfate, and deionized water is 10:0.6:30.

[0025] Dry nano-kaolin and fumed silica were mixed evenly, methyl acrylate was added, the temperature was raised to 40℃, and the mixture was stirred for 20 minutes at a speed of 1000 rpm. Then the reaction solution was added dropwise, the temperature was controlled at 85℃, the stirring speed was 1100 rpm, and the mixture was stirred for 70 minutes. After drying, the mixture was pulverized to a particle size ≤5μm to obtain the modified composite filler.

[0026] The mass ratio of the nano-kaolin, fumed silica, methyl acrylate, and reaction solution is 90:10:5:15.

[0027] The drying process involves a temperature of 130℃ and a drying time of 4 hours.

[0028] Step 2: Preparation of modified nano-barium sulfate Vinyltrimethoxysilane, anhydrous ethanol, and deionized water were mixed evenly, and the pH of the mixture was adjusted to 4 with glacial acetic acid. The mixture was stirred at 300 rpm for 20 min. Then, nano-barium sulfate was added, the temperature was raised to 60℃, and the mixture was stirred for 2 h at 600 rpm. After the reaction was completed, the solid was collected by centrifugation, washed three times with anhydrous ethanol, dried, and ground through a 100-mesh sieve to obtain pretreated nano-barium sulfate.

[0029] The mass ratio of vinyltrimethoxysilane, anhydrous ethanol, deionized water, and nano-barium sulfate is 8:60:20:100.

[0030] The drying process involves a temperature of 70°C, a vacuum of 0.08 MPa, and a drying time of 5 hours.

[0031] Pretreated nano-barium sulfate was added to toluene and stirred for 30 min at 1200 rpm. Azobisisobutyronitrile and butyl acrylate were mixed and added to the mixture. High-purity nitrogen was introduced to remove oxygen, and the temperature was controlled at 70℃. The mixture was stirred for 6 h under nitrogen protection. After the reaction was completed, the reaction solution was poured into methanol for precipitation. The solid was collected by filtration, washed twice with anhydrous methanol, vacuum dried, and ground until the particle size was ≤2 μm to obtain modified nano-barium sulfate.

[0032] The mass ratio of the pretreated nano-barium sulfate, toluene, azobisisobutyronitrile, and butyl acrylate is 10:95:0.1:3.

[0033] The vacuum drying process involves a temperature of 80°C, a vacuum level of 0.09 MPa, and a drying time of 8 hours.

[0034] Step 3: Obtaining the insulating rubber material Add EPDM rubber, EPDM rubber, and ethylene-vinyl acetate copolymer to a mixer, set the speed to 60 rpm and the temperature to 60℃, and masticate for 6 minutes; add paraffin oil and stearic acid, and continue masticating for 3 minutes; raise the temperature to 80℃, and add zinc oxide, modified composite filler, organic montmorillonite, modified nano barium sulfate, silane coupling agent A172, antioxidant, and ultraviolet absorber in sequence. After adding all the ingredients, continue mixing for 10 minutes; cool down to below 70℃, adjust the speed to 40 rpm, add dicumyl peroxide and triallyl cyanurate, and mix for 2 minutes to obtain the compound.

[0035] The raw materials used are composed of the following parts by weight: 45 parts EPDM rubber, 15 parts EPDM rubber, 20 parts ethylene-vinyl acetate copolymer, 40 parts modified composite filler, 0.8 parts dicumyl peroxide, 0.8 parts triallyl cyanurate, 0.6 parts silane coupling agent A172, 1.5 parts antioxidant, 0.3 parts ultraviolet absorber, 5 parts paraffin oil, 1 part stearic acid, 3 parts zinc oxide, 2 parts modified nano barium sulfate, and 4 parts organic montmorillonite.

[0036] The antioxidant is obtained by mixing antioxidant MB and antioxidant RD, with a mass ratio of antioxidant MB to antioxidant RD of 5:6.

[0037] The mixed rubber was transferred to an open mill at a roller temperature of 50°C and a roller gap of 0.5 mm. It was passed through a thin mill 6 times, then the roller gap was adjusted to 3 mm. The mixture was then rolled and triangularly wrapped 3 times each, producing a 2 mm thick sheet. This sheet was left to stand at room temperature for 4 hours to obtain a cured rubber sheet. The cured rubber sheet was then added to an extruder at a screw speed of 20 rpm to extrude an insulating layer shape. It underwent steam vulcanization, followed by cooling in a cold water bath, drying, and sizing to obtain the insulating rubber material.

[0038] The temperatures of each section of the extruder are as follows: feeding section 60℃, compression section 80℃, homogenization section 70℃, and die head temperature 90℃.

[0039] The steam vulcanization process involves a vulcanization temperature of 165°C, a steam pressure of 0.8 MPa, and a vulcanization time of 15 min.

[0040] The temperature of the cold water tank is 20°C.

[0041] Example 2: Preparation process of insulating rubber material for high-voltage torsion-resistant flexible cables A preparation process for an insulating rubber material for high-voltage torsion-resistant flexible cables includes the following steps: Step 1: Preparation of modified composite fillers Mix silane coupling agent A172, ammonium persulfate, and deionized water, and stir for 25 minutes at a speed of 400 rpm to obtain a reaction solution.

[0042] The mass ratio of the silane coupling agent A172, ammonium persulfate, and deionized water is 10:0.7:35.

[0043] Dry nano-kaolin and fumed silica were mixed evenly, methyl acrylate was added, the temperature was raised to 45℃, and the mixture was stirred for 25 minutes at a speed of 900 rpm. Then the reaction solution was added dropwise, the temperature was controlled at 85℃, the stirring speed was 1200 rpm, and the mixture was stirred for 65 minutes. After drying, the mixture was pulverized to a particle size ≤5μm to obtain the modified composite filler.

[0044] The mass ratio of the nano-kaolin, fumed silica, methyl acrylate, and reaction solution is 90:11:6:16.

[0045] The drying process involves a temperature of 135°C and a drying time of 3.5 hours.

[0046] Step 2: Preparation of modified nano-barium sulfate Vinyltrimethoxysilane, anhydrous ethanol, and deionized water were mixed evenly, and the pH of the mixture was adjusted to 4.5 with glacial acetic acid. The mixture was stirred at 400 rpm for 20 min. Then, nano-barium sulfate was added, the temperature was raised to 65℃, and the mixture was stirred for 2.5 h at 600 rpm. After the reaction was completed, the solid was collected by centrifugation, washed four times with anhydrous ethanol, dried, and ground through a 100-mesh sieve to obtain pretreated nano-barium sulfate.

[0047] The mass ratio of vinyltrimethoxysilane, anhydrous ethanol, deionized water, and nano-barium sulfate is 10:70:25:100.

[0048] The drying process was carried out at a temperature of 75°C, a vacuum of 0.09 MPa, and a drying time of 4.5 h.

[0049] Pretreated nano-barium sulfate was added to toluene and stirred for 35 min at 1100 rpm. Azobisisobutyronitrile and butyl acrylate were mixed and added to the mixture. High-purity nitrogen was introduced to remove oxygen, and the temperature was controlled at 75℃. The mixture was stirred for 5 h under nitrogen protection. After the reaction was completed, the reaction solution was poured into methanol for precipitation. The solid was collected by filtration, washed three times with anhydrous methanol, vacuum dried, and ground until the particle size was ≤2 μm to obtain modified nano-barium sulfate.

[0050] The mass ratio of the pretreated nano-barium sulfate, toluene, azobisisobutyronitrile, and butyl acrylate is 10:98:0.12:4.

[0051] The vacuum drying process involves a temperature of 85°C, a vacuum level of 0.09 MPa, and a drying time of 7 hours.

[0052] Step 3: Obtaining the insulating rubber material Add EPDM rubber, EPDM rubber, and ethylene-vinyl acetate copolymer to a mixer, set the speed to 70 rpm and the temperature to 65℃, and masticate for 6 minutes; add paraffin oil and stearic acid, and continue masticating for 3 minutes; raise the temperature to 85℃, and add zinc oxide, modified composite filler, organic montmorillonite, modified nano barium sulfate, silane coupling agent A172, antioxidant, and ultraviolet absorber in sequence. After adding all the ingredients, continue mixing for 10 minutes; cool down to below 70℃, adjust the speed to 50 rpm, add dicumyl peroxide and triallyl cyanurate, and mix for 2 minutes to obtain the compound.

[0053] The raw materials used are composed of the following parts by weight: 50 parts EPDM rubber, 13 parts EPDM rubber, 25 parts ethylene-vinyl acetate copolymer, 35 parts modified composite filler, 1 part dicumyl peroxide, 0.6 parts triallyl cyanurate, 0.8 parts silane coupling agent A172, 1.5 parts antioxidant, 0.4 parts ultraviolet absorber, 4 parts paraffin oil, 1.3 parts stearic acid, 2.5 parts zinc oxide, 3 parts modified nano barium sulfate, and 3 parts organic montmorillonite.

[0054] The antioxidant is obtained by mixing antioxidant MB and antioxidant RD, with a mass ratio of antioxidant MB to antioxidant RD of 6:7.

[0055] The mixed rubber was transferred to an open mill at a roller temperature of 55°C and a roller gap of 1.0 mm. It was passed through a thin mill 7 times, then the roller gap was adjusted to 4 mm. The mixture was then rolled and triangularly wrapped 4 times each, producing a 3 mm thick sheet. This sheet was left to stand at room temperature for 5 hours to obtain a cured rubber sheet. The cured rubber sheet was then added to an extruder at a screw speed of 30 rpm to extrude an insulating layer shape. It underwent steam vulcanization, followed by cooling in a cold water bath, drying, and sizing to obtain the insulating rubber material.

[0056] The temperatures of each section of the extruder are as follows: feeding section 65℃, compression section 85℃, homogenization section 75℃, and die head temperature 95℃.

[0057] The steam vulcanization process involves a vulcanization temperature of 170°C, a steam pressure of 0.9 MPa, and a vulcanization time of 15 min.

[0058] The temperature of the cold water tank is 25°C.

[0059] Example 3: Preparation process of insulating rubber material for high-voltage torsion resistant flexible cables A preparation process for an insulating rubber material for high-voltage torsion-resistant flexible cables includes the following steps: Step 1: Preparation of modified composite fillers Mix silane coupling agent A172, ammonium persulfate, and deionized water, and stir for 25 minutes at a speed of 300 rpm to obtain a reaction solution.

[0060] The mass ratio of the silane coupling agent A172, ammonium persulfate, and deionized water is 10:0.8:40.

[0061] Dry nano-kaolin and fumed silica were mixed evenly, methyl acrylate was added, the temperature was raised to 50℃, and the mixture was stirred for 30 minutes at a speed of 800 rpm. Then the reaction solution was added dropwise, the temperature was controlled at 90℃, the stirring speed was 1200 rpm, and the mixture was stirred for 60 minutes. After drying, the mixture was pulverized to a particle size ≤5μm to obtain the modified composite filler.

[0062] The mass ratio of the nano-kaolin, fumed silica, methyl acrylate, and reaction solution is 90:11:6:18.

[0063] The drying process involves a temperature of 140℃ and a drying time of 3 hours.

[0064] Step 2: Preparation of modified nano-barium sulfate Vinyltrimethoxysilane, anhydrous ethanol, and deionized water were mixed evenly, and the pH of the mixture was adjusted to 5 with glacial acetic acid. The mixture was stirred at 400 rpm for 15 min. Then, nano-barium sulfate was added, the temperature was raised to 70℃, and the mixture was stirred for 2.5 h at 500 rpm. After the reaction was completed, the solid was collected by centrifugation, washed four times with anhydrous ethanol, dried, and ground through a 100-mesh sieve to obtain pretreated nano-barium sulfate.

[0065] The mass ratio of vinyltrimethoxysilane, anhydrous ethanol, deionized water, and nano-barium sulfate is 12:75:25:100.

[0066] The drying process involves a temperature of 80°C, a vacuum of 0.095 MPa, and a drying time of 4 hours.

[0067] Pretreated nano-barium sulfate was added to toluene and stirred for 40 min at 1000 rpm. Azobisisobutyronitrile and butyl acrylate were mixed and added to the mixture. High-purity nitrogen was introduced to remove oxygen, and the temperature was controlled at 80℃. The mixture was stirred for 4 h under nitrogen protection. After the reaction was completed, the reaction solution was poured into methanol for precipitation. The solid was collected by filtration, washed three times with anhydrous methanol, vacuum dried, and ground until the particle size was ≤2 μm to obtain modified nano-barium sulfate.

[0068] The mass ratio of the pretreated nano-barium sulfate, toluene, azobisisobutyronitrile, and butyl acrylate is 10:100:0.15:5.

[0069] The vacuum drying process involves a temperature of 90°C, a vacuum level of 0.095 MPa, and a drying time of 6 hours.

[0070] Step 3: Obtaining the insulating rubber material Add EPDM rubber, EPDM rubber, and ethylene-vinyl acetate copolymer to a mixer, set the speed to 80 rpm and the temperature to 70℃, and masticate for 5 minutes; add paraffin oil and stearic acid, and continue masticating for 2 minutes; raise the temperature to 90℃, and add zinc oxide, modified composite filler, organic montmorillonite, modified nano barium sulfate, silane coupling agent A172, antioxidant, and ultraviolet absorber in sequence. After adding all the ingredients, continue mixing for 8 minutes; cool down to below 70℃, adjust the speed to 50 rpm, add dicumyl peroxide and triallyl cyanurate, and mix for 1.5 minutes to obtain the compound.

[0071] The raw materials used are composed of the following parts by weight: 55 parts EPDM rubber, 10 parts EPDM rubber, 30 parts ethylene-vinyl acetate copolymer, 30 parts modified composite filler, 1.2 parts dicumyl peroxide, 0.4 parts triallyl cyanurate, 1 part silane coupling agent A172, 1.2 parts antioxidant, 0.5 parts ultraviolet absorber, 3 parts paraffin oil, 1.5 parts stearic acid, 2 parts zinc oxide, 4 parts modified nano barium sulfate, and 2 parts organic montmorillonite.

[0072] The antioxidant is obtained by mixing antioxidant MB and antioxidant RD, with a mass ratio of antioxidant MB to antioxidant RD of 7:8.

[0073] The mixed rubber was transferred to an open mill at a roller temperature of 60℃ and a roller gap of 1.0mm. It was passed through a thin mill 8 times, then the roller gap was adjusted to 5mm, and the rubber was rolled and triangularly wrapped 4 times each, producing a 4mm thick sheet. This sheet was left to stand at room temperature for 6 hours to obtain a cured rubber sheet. The cured rubber sheet was then added to an extruder at a screw speed of 30rpm to extrude an insulating layer shape. It underwent steam vulcanization, followed by cooling in a cold water bath, drying, and sizing to obtain the insulating rubber material.

[0074] The temperatures of each section of the extruder are as follows: 70°C for the feeding section, 90°C for the compression section, 80°C for the homogenization section, and 100°C for the die head.

[0075] The steam vulcanization process involves a vulcanization temperature of 175°C, a steam pressure of 1.0 MPa, and a vulcanization time of 10 min.

[0076] The temperature of the cold water tank is 30°C.

[0077] Comparative Example 1 A preparation process for an insulating rubber material for high-voltage torsion-resistant flexible cables includes the following steps: Step 1: Preparation of modified nano-barium sulfate This step is the same as the "Preparation of Modified Nanobarium Sulfate" step in Example 2.

[0078] Step 2: Obtaining the insulating rubber material Based on the "preparation of insulating rubber material" step in Example 2, no modified composite filler is added, and the rest of the operations remain unchanged.

[0079] Comparative Example 2 A preparation process for an insulating rubber material for high-voltage torsion-resistant flexible cables includes the following steps: Step 1: Preparation of modified composite fillers This step is the same as the "Preparation of Modified Composite Filler" step in Example 2.

[0080] Step 2: Obtaining the insulating rubber material Based on the "preparation of insulating rubber material" step in Example 2, no modified nano barium sulfate is added, and the rest of the operations remain unchanged.

[0081] Example 4 Performance Test (a) The insulating rubber materials prepared in Examples 1-3 and Comparative Examples 1-2 were tested for electrical insulation performance. The volume resistivity was tested according to the test method specified in GB / T1410-2006; the power frequency breakdown field strength was tested according to the test method specified in GB / T 1695-2005. The specific test results are shown in Table 1.

[0082] Table 1 As shown in Table 1, the volume resistivity of the insulating rubber materials prepared in Examples 1-3 is 8.9 × 10⁻⁶. 15 -9.2×10 15 The dielectric constant is Ω·m, and the breakdown field strength is 38.8-41.5 kV / mm. Therefore, the insulating rubber material prepared in this invention exhibits excellent electrical insulation properties.

[0083] (ii) The mechanical properties of the insulating rubber materials prepared in Examples 1-3 and Comparative Examples 1-2 were tested according to the test methods specified in GB / T528-2009, including tensile strength and elongation at break. The specific test results are shown in Table 2.

[0084] Table 2 As shown in Table 2, the tensile strength of the insulating rubber materials prepared in Examples 1-3 is 43.2-44.8 MPa, and the elongation at break is 478-495%. This demonstrates that the insulating rubber materials prepared in this invention possess excellent mechanical properties.

[0085] (III) The insulating rubber materials prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to aging resistance tests. UV aging resistance tests were conducted according to the test methods specified in GB / T16422.3-2014, using method A, exposure cycle 1, and a test time of 1000 h. The tensile strength retention rate and volume resistivity retention rate were calculated. Heat aging resistance tests were conducted according to the test methods specified in GB / T2951.12-2008, with test conditions of 135℃ and 168 h. The tensile strength retention rate and volume resistivity retention rate were calculated. Specific test results are shown in Table 3.

[0086] Table 3 As shown in Table 3, the insulating rubber materials prepared in Examples 1-3 retained 94.1-95.2% of their tensile strength and 95.3-96.1% of their volume resistivity after UV aging; and 96.5-96.9% of their tensile strength and 96.8-97.2% of their volume resistivity after thermal aging. This demonstrates that the insulating rubber materials prepared in this invention possess excellent aging resistance.

[0087] The specific parameters of the raw materials used in this invention are as follows: The ethylene content of the EPDM rubber is 40-50%.

[0088] The ethylene propylene rubber used is model 4044.

[0089] The VA content of the ethylene-vinyl acetate copolymer is 18-28%.

[0090] The particle size of the nano-kaolin is ≤5μm.

[0091] The particle size of the fumed silica is 20-50 nm.

[0092] The nano-barium sulfate has a particle size of 30-100 nm.

[0093] The ultraviolet absorber used is UV-531.

[0094] The paraffin oil has a flash point ≥180℃ and a kinematic viscosity (40℃) ≥100 mmHg. 2 / s.

[0095] The stearic acid has a freezing point of 57-64℃ and an acid value of 194-212 mgKOH / g.

[0096] The zinc oxide has a particle size of 50-100 nm.

[0097] The organic montmorillonite used was Nanocor I.44P.

[0098] Obviously, there are many other possible implementation methods under the concept of this invention. It should be stated here that any changes made under the inventive concept of this invention will fall within the protection scope of this invention.

Claims

1. A preparation process for an insulating rubber material for high-voltage torsion-resistant flexible cables, characterized in that: The process includes the steps of preparing modified composite fillers, preparing modified nano-barium sulfate, and obtaining insulating rubber materials. The modified composite filler is prepared by mixing silane coupling agent A172, ammonium persulfate, and deionized water to obtain a reaction solution; mixing nano-kaolin and fumed silica, adding methyl acrylate, heating, and stirring; adding dropwise to the reaction solution and stirring; drying and pulverizing to obtain the modified composite filler. The preparation of modified nano-barium sulfate involves: mixing vinyltrimethoxysilane, anhydrous ethanol, and deionized water; adjusting the pH of the mixture; adding nano-barium sulfate; stirring the mixture to obtain pretreated nano-barium sulfate; adding the pretreated nano-barium sulfate to toluene; stirring the mixture; adding azobisisobutyronitrile and butyl acrylate; and reacting the mixture under nitrogen protection; pouring the reaction solution into methanol for precipitation; and filtering to collect the solid. The insulating rubber material obtained includes the following raw materials: ethylene propylene diene monomer (EPDM) rubber, ethylene propylene diene monomer (EPDM) rubber, ethylene-vinyl acetate copolymer, paraffin oil, stearic acid, zinc oxide, modified composite filler, organic montmorillonite, modified nano-barium sulfate, silane coupling agent A172, antioxidant, ultraviolet absorber, diisopropylbenzene peroxide, and triallyl cyanurate.

2. The preparation process of the insulating rubber material for high-voltage torsion-resistant flexible cables according to claim 1, characterized in that: In the step of preparing the modified composite filler, the mass ratio of silane coupling agent A172, ammonium persulfate, and deionized water is 10:(0.6-0.8):(30-40).

3. The preparation process of the insulating rubber material for high-voltage torsion-resistant flexible cables according to claim 1, characterized in that: The pH value of the mixture is adjusted by using glacial acetic acid to adjust the pH value to 4-5.

4. The preparation process of the insulating rubber material for high-voltage torsion-resistant flexible cables according to claim 1, characterized in that: The mass ratio of the nano-kaolin, fumed silica, methyl acrylate, and reaction solution is 90:(10-11):(5-6):(15-18).

5. The preparation process of the insulating rubber material for high-voltage torsion-resistant flexible cables according to claim 1, characterized in that: In the step of preparing modified nano-barium sulfate, the mass ratio of vinyltrimethoxysilane, anhydrous ethanol, deionized water, and nano-barium sulfate is (8-12):(60-75):(20-25):

100.

6. The preparation process of the insulating rubber material for high-voltage torsion-resistant flexible cables according to claim 1, characterized in that: The mass ratio of the pretreated nano-barium sulfate, toluene, azobisisobutyronitrile, and butyl acrylate is 10:(95-100):(0.1-0.15):(3-5).

7. The preparation process of the insulating rubber material for high-voltage torsion-resistant flexible cables according to claim 1, characterized in that: In the step of preparing the insulating rubber material, the raw materials used are in the following weight proportions: 45-55 parts of EPDM rubber, 10-15 parts of EPDM rubber, 20-30 parts of ethylene-vinyl acetate copolymer, 30-40 parts of modified composite filler, 0.8-1.2 parts of dicumyl peroxide, 0.4-0.8 parts of triallyl cyanurate, 0.6-1 part of silane coupling agent A172, 1.2-1.5 parts of antioxidant, 0.3-0.5 parts of ultraviolet absorber, 3-5 parts of paraffin oil, 1-1.5 parts of stearic acid, 2-3 parts of zinc oxide, 2-4 parts of modified nano-barium sulfate, and 2-4 parts of organo-modified montmorillonite.

8. The preparation process of the insulating rubber material for high-voltage torsion-resistant flexible cables according to claim 1, characterized in that: The antioxidant is obtained by mixing antioxidant MB and antioxidant RD, and the mass ratio of antioxidant MB to antioxidant RD is (5-7):(6-8).

9. The preparation process of the insulating rubber material for high-voltage torsion-resistant flexible cables according to claim 1, characterized in that: The insulating rubber material is prepared by: adding EPDM rubber, EPDM rubber, and ethylene-vinyl acetate copolymer to a mixer and masticating; adding paraffin oil and stearic acid and continuing masticating; sequentially adding zinc oxide, modified composite filler, organic montmorillonite, modified nano-barium sulfate, silane coupling agent A172, antioxidant, and ultraviolet absorber and continuing mixing; adding dicumyl peroxide and triallyl cyanurate and mixing to obtain a compound; transferring the compound to a two-roll mill, thin-passing, rolling, and triangular wrapping, and extruding the rubber sheet and placing it at room temperature to obtain a cured rubber sheet; adding the cured rubber sheet to an extruder, extruding it into an insulating layer shape, steam vulcanizing, cooling in a cold water bath, drying, and sizing to obtain the insulating rubber material.

10. The preparation process of the insulating rubber material for high-voltage torsion-resistant flexible cables according to claim 9, characterized in that: The steam vulcanization process involves a vulcanization temperature of 165-175℃, a steam pressure of 0.8-1.0MPa, and a vulcanization time of 10-15min.

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