A type of ultra-high voltage DC shielding material and its preparation method

Abstract

This invention discloses an ultra-high voltage direct current (UHVDC) shielding material and its preparation method. The shielding material, by weight, comprises the following raw materials: 65-80 parts of matrix resin, preferably 70-80 parts; 15-25 parts of carbon black-MXene-ionic liquid composite conductive agent, preferably 18-23 parts; 0.2-5 parts of antioxidant, preferably 0.5-2.5 parts; 1-2 parts of lubricant, preferably 1-1.5 parts; and 0.5-2 parts of crosslinking agent, preferably 0.8-1.2 parts. This invention improves conductivity and reduces the amount of carbon black by introducing MXene-ionic liquid to modify superconducting carbon black, achieving uniform dispersion of the conductive filler. This reduces the generation of surface protrusions and improves the surface smoothness of the shielding material. Simultaneously, due to the synergistic conductive effect of the ionic liquid and MXene, the PTC effect of the shielding material is reduced, and the generation of space charge is decreased.

Description

Technical Field

[0001] This invention relates to the field of cable material processing technology, specifically to an ultra-high voltage DC shielding material and its preparation method. Background Technology

[0002] Ultra-high voltage direct current (UHVDC) transmission is characterized by long distance, large capacity, and low cost, and is widely used in the field of submarine cables. Shielding material, as an indispensable component of UHVDC cables, is particularly important for its stability and economy. UHVDC shielding materials are required to possess characteristics such as ultra-smoothness, low PTC effect, and reduced space charge generation, thereby ensuring the stable operation of the DC cable over a long period.

[0003] Conductive carbon black has a high surface energy and specific surface area, making it prone to agglomeration. Carbon black agglomeration is a significant factor affecting the surface smoothness of ultra-high voltage shielding materials. In CN116120655A, ionic liquids were used to modify conductive carbon black, solving the protrusion problem caused by carbon black agglomeration and improving surface smoothness; however, the impact on space charge generation was not addressed. Space charge refers to the charge accumulated inside or at the interface of a dielectric, which can disturb the electric field distribution and potentially lead to cable breakdown. In dielectrics, space charge generation may originate from the uneven distribution of charge carriers, such as the capture and release of electrons, holes, or ions; therefore, reducing space charge generation is also crucial. Summary of the Invention

[0004] The main objective of this invention is to provide an ultra-high voltage direct current (UHVDC) shielding material and its preparation method. By introducing MXene-ionic liquid to modify superconducting carbon black, the conductivity is improved, the amount of carbon black used is reduced, and uniform dispersion of conductive filler is achieved, thereby reducing the generation of surface protrusions and improving the surface smoothness of the shielding material. Simultaneously, due to the synergistic conductivity effect of the ionic liquid and MXene, the PTC effect of the shielding material is reduced, and the generation of space charge is decreased.

[0005] To achieve one aspect of the above objectives, the present invention employs the following technical solution: an ultra-high voltage DC shielding material, comprising the following raw materials by mass parts:

[0006] The matrix resin comprises 65-80 parts, preferably 70-80 parts;

[0007] 15-25 parts of carbon black-MXene-ionic liquid composite conductive agent, preferably 18-23 parts;

[0008] Antioxidant 0.2-5 parts, preferably 0.5-2.5 parts;

[0009] 1-2 parts of lubricant, preferably 1-1.5 parts;

[0010] The crosslinking agent is 0.5 to 2 parts, preferably 0.8 to 1.2 parts;

[0011] The carbon black-MXene-ionic liquid composite conductive agent is carbon black modified with MXene and imidazole conductive ionic liquid.

[0012] In some specific embodiments, the matrix resin comprises one or more of ethylene-vinyl acetate copolymer (EVA), ethylene-butyl acrylate copolymer (EBA), ethylene-methyl acrylate copolymer (EMA), and ethylene-ethyl acrylate copolymer (EEA), preferably EBA resin or EMA resin, and more preferably EBA resin.

[0013] In some specific embodiments, the mass fraction of vinyl acetate monomer units in the ethylene-vinyl acetate copolymer is 15-30%, preferably 16-20%, more preferably 16-19%; the mass fraction of butyl acrylate monomer units in the ethylene-butyl acrylate copolymer is 15-25%, preferably 16-20%, more preferably 16-19%; and the mass fraction of methyl acrylate monomer units in the ethylene-methyl acrylate copolymer is 15-25%, preferably 16-20%, more preferably 16-19%.

[0014] In some specific embodiments, the imidazole-based conductive ionic liquid is 1-vinyl-3-butylimidazolium tetrafluoroborate or 1-butyl-3-methylimidazolium tetrafluoroborate.

[0015] In some specific embodiments, the preparation method of the carbon black-MXene-ionic liquid composite conductive agent includes the following steps:

[0016] 1) MXene and ionic liquid are heated under stirring to react. The reactants are pulverized and separated to obtain a solid, which is then dried to obtain ionic liquid modified MXene.

[0017] 2) Mix the ionic liquid-modified MXene obtained in step 1) with carbon black to obtain a dispersion, and grind the dispersion to obtain a carbon black-MXene-ionic liquid composite conductive agent.

[0018] In some specific embodiments, in step 1), the mass ratio of MXene to ionic liquid is 5-6:1-1.5, exemplarily 5:1, 5.5:1, 6:1, 5:1.5, 5.5:1.5, 6:1.5, etc.

[0019] In some specific embodiments, the stirring conditions in step 1) include: stirring time of 40-60 min and stirring speed of 400-600 r / min, exemplarily 400 r / min, 450 r / min, 500 r / min, 550 r / min, 600 r / min, etc.

[0020] In some specific embodiments, in step 1), the heating temperature is 120-170℃, exemplarily 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, etc.

[0021] In some specific embodiments, in step 1), the reaction is carried out in a microwave reactor, and the pulverization process is carried out in a cell disruptor, preferably with a pulverization time of 30-50 min and a vibration frequency of 50-80 kHz.

[0022] In some specific embodiments, in step 1), centrifugation is carried out in a centrifuge, and the centrifugation conditions include: a centrifugation speed of 8000-10000 r / min and a centrifugation time of 5-10 min.

[0023] In some specific implementations, the drying conditions in step 1) include: a drying temperature of 80-90°C and a drying time of 8-10 hours.

[0024] In some specific embodiments, in step 2), ionic liquid-modified MXene and carbon black are dispersed in an organic solvent, and a dispersant is added to obtain a dispersion solution.

[0025] Preferably, the solvent is one or more of ethylene glycol monobutyl ether and diethylene glycol monobutyl ether, and the dispersant is one or more of polyvinylpyrrolidone and polyvinyl alcohol.

[0026] Preferably, the mass ratio of carbon black: ionic liquid modified MXene: solvent: dispersant is 1:3-8:90-95:1-3.

[0027] In some specific embodiments, in step 2), the ionic liquid-modified MXene and carbon black are ultrasonically dispersed in an organic solvent. Preferably, the ultrasonic time is 1 to 3 hours, the ultrasonic temperature is 25 to 40°C, and the ultrasonic frequency is 40,000 to 60,000 Hz.

[0028] In some specific embodiments, in step 2), the grinding method is selected from one of ball milling, vibratory milling, air jet milling, stirring milling, planetary ball milling, and high-pressure roller milling, with ball milling being preferred.

[0029] In some specific implementations, the ball milling conditions include: a ball milling speed of 200-300 r / min and a ball milling time of 1-2 h.

[0030] In a preferred embodiment, the preparation method of the carbon black-MXene-ionic liquid composite conductive agent includes the following steps:

[0031] S1: Take 5-6 parts of MXene and 1-1.5 parts of ionic liquid and place them in a microwave reactor. Heat to 120-170℃. The preferred stirring time is 40-60 min and the preferred stirring speed is 400-600 r / min. Then treat with a cell disruptor for 30-50 min. The preferred vibration frequency is 50-80 kHz. Centrifuge at 8000-10000 r / min for 5-10 min. Take the supernatant and add dichloromethane and ethanol respectively. Centrifuge for 15-20 min. Keep the solid. Repeat 2-3 times. Place the obtained black solid in a vacuum drying oven and dry at 80-90℃ for 8-10 h to obtain ionic liquid modified MXene.

[0032] S2: The ionic liquid-modified MXene and carbon black prepared in S1 are ultrasonically dispersed in an organic solvent, and a dispersant is added. The preferred solvent is ethylene glycol monobutyl ether or diethylene glycol monobutyl ether, and the preferred dispersant is polyvinylpyrrolidone or polyvinyl alcohol. The preferred mass ratio of carbon black: ionic liquid-modified MXene: solvent: dispersant is 1:3-8:90-95:1-3. The treated dispersion is ball-milled in a ball mill at 200-300 r / min for 1-2 h to obtain a carbon black-MXene-ionic liquid composite conductive agent.

[0033] In some specific embodiments, the antioxidant is one or more of antioxidant 300, antioxidant 1010, and antioxidant 1076, preferably antioxidant 300; the lubricant is one or more of polyethylene wax, zinc stearate, and stearamide, preferably polyethylene wax; and the crosslinking agent is one or more of dicumyl peroxide and bis-tert-butyl dicumyl peroxide.

[0034] Another aspect of the present invention provides a method for preparing ultra-high voltage DC shielding material, comprising the following steps:

[0035] The matrix resin, carbon black-MXene-ionic liquid composite conductive agent, antioxidant and lubricant are mixed, filtered, extruded and granulated, dried, and then a crosslinking agent is added for post-absorption to obtain the shielding material.

[0036] In some specific embodiments, the mixing is carried out in a reciprocating mixer, wherein the mixing section of the reciprocating mixer is a reciprocating single-screw extruder, and the molten material processed in the reciprocating mixer is filtered by a filtration system.

[0037] In some specific embodiments, the crosslinking agent is atomized and then added for post-absorption. Preferably, the temperature of the post-absorption process is 60-80°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, etc., and the time of the post-absorption process is 1-3 hours.

[0038] Compared with existing technologies, this invention has the following advantages: The ultra-high voltage DC shielding material provided by this invention, by mass, comprises the following raw materials: 65-80 parts of matrix resin; 15-25 parts of carbon black-MXene-ionic liquid composite conductive agent; 0.2-5 parts of antioxidant; 1-2 parts of lubricant; and 0.5-2 parts of crosslinking agent. The carbon black is spherical and easily forms grape-like aggregates after processing; MXene is a two-dimensional layered conductive material with a layered crystal structure. The conductivity of MXene originates from the metal layers in its layered structure, which provide free electrons, giving the material metallic conductivity. Furthermore, the large interlayer distance of MXene facilitates the insertion and extraction of ions and molecules, thus affecting its conductivity; the ionic liquid can generate current and conduct electricity through the migration of cations and anions.

[0039] This invention introduces MXene-ionic liquid-modified carbon black material, reducing the amount of traditional carbon black used, improving the material's processing performance, and achieving uniform dispersion of conductive fillers. This reduces the formation of surface protrusions, thus avoiding electric field concentration and breakdown caused by impurities and air gaps, and improving the surface smoothness of the shielding material. Simultaneously, the layered structure of MXene and the botryoidal structure of carbon black interact to form a bipolar conductive network, resulting in a complete electronic conductive network structure. Furthermore, the introduction of the ionic liquid allows for ion migration between MXene layers, enabling synergistic conduction between electrons and ions, improving the overall conductivity of the conductive agent and reducing the PTC effect of the shielding material. The introduction of a diversified conductor (carbon black-MXene-ionic liquid composite) also reduces space charge generation.

[0040] Specifically, the mechanism by which MXene-grafted ionic liquids suppress space charge may involve the following aspects:

[0041] 1. Electronic conductivity: The high electronic conductivity of the MXene layer can provide a fast electron migration path, helping to balance the charge distribution inside the material and reduce the space charge effect caused by the accumulation of electrons or holes.

[0042] 2. Ionic conductivity: The ionic conductivity of ionic liquids ensures that ions migrate rapidly under the influence of an electric field, preventing the formation of localized charge accumulation within the dielectric. The rapid ionic response helps maintain charge balance, thereby suppressing the formation of space charge.

[0043] 3. Reduced interfacial polarization: The interfacial effect between MXene and ionic liquid can reduce interfacial polarization because the ionic liquid can wet the MXene surface, reduce charge traps at the interface, and thus reduce the formation of space charge.

[0044] 4. Chemical stability: The chemical stability of ionic liquids can prevent MXene from degrading under harsh environments, maintain its good conductivity, and thus continuously suppress the generation of space charge.

[0045] 5. Enhanced dielectric properties: MXene-grafted ionic liquid composites may exhibit enhanced dielectric properties, which helps to better manage the distribution of charge carriers and reduce the accumulation of space charge.

[0046] 6. Capture and release of charge carriers: The layered structure of MXene and the ions in the ionic liquid can work together to reduce the capture and release time of charge carriers in the material and avoid the formation of persistent space charge.

[0047] Other features and advantages of the present invention will be described in detail through the following specific embodiments. Detailed Implementation

[0048] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are shown in the examples, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0049] The raw materials, instruments, and testing methods used in the embodiments of the present invention are described below. For details not described in detail, please refer to the prior art.

[0050] Reciprocating mixer: Swiss BUSS AG, model: MX-30.

[0051] EBA: Dow Chemical Company, USA, with a butyl acrylate monomer unit mass fraction of 17%.

[0052] Carbon black: DENKA, acetylene carbon black.

[0053] MXene: Beike New Materials Co., Ltd., Ti3C2T x .

[0054] Ionic liquids: Qiyue Biotechnology, 1-vinyl-3-butylimidazolium tetrafluoroborate; Shandong Daike Biotechnology Co., Ltd., 1-butyl-3-methylimidazolium tetrafluoroborate;

[0055] Polyethylene wax: Honeywell, AC-617A.

[0056] Antioxidant: Ciba Specialty Chemicals, Switzerland, Antioxidant 300.

[0057] BIPB: Arkema.

[0058] Mechanical property testing: The testing methods are in accordance with ISO 527, ISO 178 and ISO 180 standards, using the INSTRON 5966 tensile tester.

[0059] Density test: The test method shall be performed in accordance with GB / T 1033.1. A square specimen with a thickness of 2.0±0.1 mm and a side length of 20-25 mm shall be used.

[0060] Heat extension: It shall be performed in accordance with GB / T 2951.5, and the sample preparation shall be performed in accordance with GB / T 1040.2.

[0061] Volume resistivity: The volume resistivity at 23℃ shall be determined in accordance with GB / T 3048.3, and the sample shall be acclimated in an environment with a temperature of 23±3℃ and a relative humidity of 50±5% for no less than 24 hours. The volume resistivity at 90℃ shall be determined in accordance with Appendix A of GB / T 3048.3. The volume resistivity at 90℃ after 7 days of heat aging at 135℃ shall be determined in accordance with Appendix A of GB / T 3048.3, and the heat aging shall be performed in accordance with GB / T 2951.12.

[0062] Surface protrusions: Compliance with Appendix A of Q / GDW 11883.2—2018 standard; the detector is an SSA testing device from OCS; the protrusion height resolution should be better than 25 μm. Sampling and testing standards: Class 100 cleanroom.

[0063] Space charge: The pulse-electroacoustic (PEA) method was used for testing, employing a solid-dielectric space charge testing system built by Shanghai Jiao Tong University. The semiconductive electrodes used the shielding materials from the examples and comparative studies, and the insulating layer was LE0550DC from Borealis. FEF parameters were introduced to characterize the space charge. Where v peak It is the peak height (mV) of the ground electrode signal voltage when a high voltage U = 40kV is applied; v peak,cal At a low voltage U where there is no space charge cal The peak height of the ground electrode signal voltage (mV) during calibration measurements at (kV). When stray charges are near the ground electrode, the electric field will be higher than the calculated field assuming no space charge, i.e., FEF > 1. Conversely, when like charges are present, the field is lower, i.e., FEF < 1. The optimal value is FEF = 1, indicating that space charge has no effect on the ground electrode electric field. The closer the FEF value is to 1, the less space charge is generated.

[0064] Preparation Example 1

[0065] Five parts by weight of MXene and one part by weight of 1-vinyl-3-butylimidazolium tetrafluoroborate ionic liquid were placed in a microwave reactor and heated to 150°C. The mixture was stirred at 500 rpm for 60 min. Subsequently, the mixture was treated with a cell disruptor for 30 min at a vibration frequency of 80 kHz. The mixture was centrifuged at 10000 rpm for 10 min, and the supernatant was collected and centrifuged in portions with dichloromethane and ethanol for 20 min each. The solid was retained, and this process was repeated three times. The resulting black solid was dried in a vacuum drying oven at 90°C for 8 h to obtain ionic liquid-modified MXene.

[0066] The prepared ionic liquid-modified MXene and acetylene carbon black were ultrasonically dispersed in ethylene glycol monobutyl ether solvent at 35℃, ultrasonic frequency of 50000Hz, and ultrasonication time of 2h. Polyvinylpyrrolidone was then added, wherein the mass ratio of superconducting carbon black: ionic liquid-modified MXene: ethylene glycol monobutyl ether solvent: polyvinylpyrrolidone was 1:5:92:2. The treated dispersion was ball-milled at 300 r / min for 2h to obtain a carbon black-MXene-ionic liquid composite conductive agent.

[0067] Preparation Example 2

[0068] Six parts by weight of MXene and 1.5 parts by weight of 1-vinyl-3-butylimidazolium tetrafluoroborate ionic liquid were placed in a microwave reactor and heated to 170°C. The mixture was stirred at 500 rpm for 60 min. Subsequently, the mixture was treated with a cell disruptor for 30 min at a vibration frequency of 80 kHz. The mixture was centrifuged at 10000 rpm for 10 min, and the supernatant was collected and centrifuged in portions with dichloromethane and ethanol for 20 min each. The solid was retained, and this process was repeated three times. The resulting black solid was dried in a vacuum drying oven at 90°C for 8 h to obtain ionic liquid-modified MXene.

[0069] The prepared ionic liquid-modified MXene and acetylene carbon black were ultrasonically dispersed in ethylene glycol monobutyl ether solvent at 35℃, ultrasonic frequency of 50000Hz, and ultrasonication time of 2h. Polyvinylpyrrolidone was then added, wherein the mass ratio of superconducting carbon black: ionic liquid-modified MXene: ethylene glycol monobutyl ether solvent: polyvinylpyrrolidone was 1:5:92:2. The treated dispersion was ball-milled at 300 r / min for 2h to obtain a carbon black-MXene-ionic liquid composite conductive agent.

[0070] Preparation Example 3

[0071] Five parts by weight of MXene and one part by weight of 1-vinyl-3-butylimidazolium tetrafluoroborate ionic liquid were placed in a microwave reactor and heated to 150°C. The mixture was stirred at 500 rpm for 60 min. Subsequently, the mixture was treated with a cell disruptor for 30 min at a vibration frequency of 80 kHz. The mixture was centrifuged at 10000 rpm for 10 min, and the supernatant was collected and centrifuged in portions with dichloromethane and ethanol for 20 min each. The solid was retained, and this process was repeated three times. The resulting black solid was dried in a vacuum drying oven at 90°C for 8 h to obtain ionic liquid-modified MXene.

[0072] The prepared ionic liquid-modified MXene and acetylene carbon black were ultrasonically dispersed in ethylene glycol monobutyl ether solvent at 35℃, ultrasonic frequency of 50000Hz, and ultrasonication time of 2h. Polyvinylpyrrolidone was then added, wherein the mass ratio of superconducting carbon black: ionic liquid-modified MXene: ethylene glycol monobutyl ether solvent: polyvinylpyrrolidone was 1:5:93:1. The treated dispersion was ball-milled at 300 r / min for 2h to obtain a carbon black-MXene-ionic liquid composite conductive agent.

[0073] Preparation Example 4

[0074] Five parts by weight of MXene and one part by weight of 1-vinyl-3-butylimidazolium tetrafluoroborate ionic liquid were placed in a microwave reactor and heated to 150°C. The mixture was stirred at 600 rpm for 60 min. Subsequently, the mixture was treated with a cell disruptor for 50 min at a vibration frequency of 80 kHz. The mixture was centrifuged at 10000 rpm for 10 min, and the supernatant was collected and centrifuged in portions with dichloromethane and ethanol for 20 min each. The solid was retained, and this process was repeated three times. The resulting black solid was dried in a vacuum drying oven at 90°C for 8 h to obtain ionic liquid-modified MXene.

[0075] The prepared ionic liquid-modified MXene and acetylene carbon black were ultrasonically dispersed in ethylene glycol monobutyl ether solvent at 35℃, ultrasonic frequency of 50000Hz, and ultrasonication time of 2h. Polyvinylpyrrolidone was then added, wherein the mass ratio of superconducting carbon black: ionic liquid-modified MXene: ethylene glycol monobutyl ether solvent: polyvinylpyrrolidone was 1:5:92:2. The treated dispersion was ball-milled at 300 r / min for 2h to obtain a carbon black-MXene-ionic liquid composite conductive agent.

[0076] Preparation Example 5

[0077] Five parts by weight of MXene and one part by weight of 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid were placed in a microwave reactor and heated to 150°C. The mixture was stirred at 500 rpm for 60 min. Subsequently, the mixture was treated with a cell disruptor for 30 min at a vibration frequency of 80 kHz. The mixture was centrifuged at 10000 rpm for 10 min, and the supernatant was collected and centrifuged in portions with dichloromethane and ethanol for 20 min each. The solid was retained, and this process was repeated three times. The resulting black solid was dried in a vacuum drying oven at 90°C for 8 h to obtain ionic liquid-modified MXene.

[0078] The prepared ionic liquid-modified MXene and acetylene carbon black were ultrasonically dispersed in ethylene glycol monobutyl ether solvent at 35℃, ultrasonic frequency of 50000Hz, and ultrasonication time of 2h. Polyvinylpyrrolidone was then added, wherein the mass ratio of superconducting carbon black: ionic liquid-modified MXene: ethylene glycol monobutyl ether solvent: polyvinylpyrrolidone was 1:5:92:2. The treated dispersion was ball-milled at 300 r / min for 2h to obtain a carbon black-MXene-ionic liquid composite conductive agent.

[0079] Example 1

[0080] This embodiment provides an ultra-high voltage cable shielding material, which, by weight, comprises 76 parts EBA resin, 22 parts carbon black-MXene-ionic liquid composite conductive agent (preparation example 1), 0.5 parts antioxidant 300, 1.5 parts polyethylene wax and 1 part BIPB.

[0081] This embodiment provides a method for preparing cable shielding material, including the following steps:

[0082] (1) EBA resin, carbon black-MXene-ionic liquid composite conductive agent (preparation example 1), antioxidant 300 and polyethylene wax were added to a reciprocating mixer for mixing, filtered in a screen changer, extruded under pressure by a melt pump, and the melt was granulated through an underwater granulation system and dried by forced air to obtain a resin composite material; the mixing and feeding section temperature was 80°C, the melting section temperature was 180°C, the plasticizing section temperature was 190°C, the extrusion section temperature was 190°C, and the screw speed was 300 rpm; in the extrusion granulation, the die head temperature was 200°C, the melt pressure was 7~7.5MPa, the underwater pelletizing temperature was 40°C, and the forced air drying temperature was 60°C.

[0083] (2) The BIPB crosslinking agent is atomized and then introduced into a shaking tank for post-absorption with the granules obtained in step (1). The mixture is kept at 70°C for 24 hours to ensure complete absorption of the crosslinking agent. The material is continuously sampled for impurity testing, and finally packaged to obtain the cable shielding material.

[0084] Example 2

[0085] This embodiment provides an ultra-high voltage cable shielding material, which, by weight, comprises 76 parts EBA resin, 22 parts carbon black-MXene-ionic liquid composite conductive agent (preparation example 2), 0.5 parts antioxidant 300, 1.5 parts polyethylene wax and 1 part BIPB.

[0086] This embodiment provides a method for preparing cable shielding material, including the following steps:

[0087] (1) EBA resin, carbon black-MXene-ionic liquid composite conductive agent (preparation example 2), antioxidant 300 and polyethylene wax were added to a reciprocating mixer for mixing, filtered in a screen changer, extruded under pressure by a melt pump, and the melt was granulated through an underwater granulation system and dried by forced air to obtain a resin composite material; the mixing and feeding section temperature was 80°C, the melting section temperature was 180°C, the plasticizing section temperature was 190°C, the extrusion section temperature was 190°C, and the screw speed was 300 rpm; in the extrusion granulation, the die head temperature was 200°C, the melt pressure was 7-7.5 MPa, the underwater pelletizing temperature was 40°C, and the forced air drying temperature was 60°C.

[0088] (2) The BIPB crosslinking agent is atomized and then introduced into a shaking tank for post-absorption with the granules obtained in step (1). The mixture is kept at 70°C for 24 hours to ensure complete absorption of the crosslinking agent. The material is continuously sampled for impurity testing, and finally packaged to obtain the cable shielding material.

[0089] Example 3

[0090] This embodiment provides an ultra-high voltage cable shielding material, which, by weight, comprises 76 parts EBA resin, 22 parts carbon black-MXene-ionic liquid composite conductive agent (preparation example 3), 0.5 parts antioxidant 300, 1.5 parts polyethylene wax and 1 part BIPB.

[0091] This embodiment provides a method for preparing cable shielding material, including the following steps:

[0092] (1) EBA resin, carbon black-MXene-ionic liquid composite conductive agent (preparation example 3), antioxidant 300 and polyethylene wax were added to a reciprocating mixer for mixing, filtered in a screen changer, extruded under pressure by a melt pump, and the melt was granulated through an underwater granulation system and dried by forced air to obtain a resin composite material; the mixing and feeding section temperature was 80°C, the melting section temperature was 180°C, the plasticizing section temperature was 190°C, the extrusion section temperature was 190°C, and the screw speed was 300 rpm; in the extrusion granulation, the die head temperature was 200°C, the melt pressure was 7-7.5 MPa, the underwater pelletizing temperature was 40°C, and the forced air drying temperature was 60°C.

[0093] (2) The BIPB crosslinking agent is atomized and then introduced into a shaking tank for post-absorption with the granules obtained in step (1). The mixture is kept at 70°C for 24 hours to ensure complete absorption of the crosslinking agent. The material is continuously sampled for impurity testing, and finally packaged to obtain the cable shielding material.

[0094] Example 4

[0095] This embodiment provides an ultra-high voltage cable shielding material, which, by weight, comprises 76 parts EBA resin, 22 parts carbon black-MXene-ionic liquid composite conductive agent (preparation example 4), 0.5 parts antioxidant 300, 1.5 parts polyethylene wax and 1 part BIPB.

[0096] This embodiment provides a method for preparing cable shielding material, including the following steps:

[0097] (1) EBA resin, carbon black-MXene-ionic liquid composite conductive agent (preparation example 4), antioxidant 300 and polyethylene wax were added to a reciprocating mixer for mixing, filtered in a screen changer, extruded under pressure by a melt pump, and the melt was granulated through an underwater granulation system and dried by forced air to obtain a resin composite material; the mixing and feeding section temperature was 80°C, the melting section temperature was 180°C, the plasticizing section temperature was 190°C, the extrusion section temperature was 190°C, and the screw speed was 300 rpm; in the extrusion granulation, the die head temperature was 200°C, the melt pressure was 7-7.5 MPa, the underwater pelletizing temperature was 40°C, and the forced air drying temperature was 60°C.

[0098] (2) The BIPB crosslinking agent is atomized and then introduced into a shaking tank for post-absorption with the granules obtained in step (1). The mixture is kept at 70°C for 24 hours to ensure complete absorption of the crosslinking agent. The material is continuously sampled for impurity testing, and finally packaged to obtain the cable shielding material.

[0099] Example 5

[0100] This embodiment provides an ultra-high voltage cable shielding material, which, by weight, comprises 80 parts EBA resin, 18 parts carbon black-MXene-ionic liquid composite conductive agent (Preparation Example 1), 0.5 parts antioxidant 300, 1.5 parts polyethylene wax, and 1 part BIPB.

[0101] This embodiment provides a method for preparing ultra-high voltage cable shielding material, including the following steps:

[0102] (1) EBA resin, carbon black-MXene-ionic liquid composite conductive agent (preparation example 1), antioxidant 300 and polyethylene wax were added to a reciprocating mixer for mixing, filtered in a screen changer, extruded under pressure by a melt pump, and the melt was granulated through an underwater granulation system and dried by forced air to obtain a resin composite material; the mixing temperature was 75°C in the feeding section, 180°C in the melting section, 190°C in the plasticizing section, and 200°C in the extrusion section, and the screw speed was 320 rpm / min; in the extrusion granulation, the die head temperature was 200°C, the melt pressure was 7-7.5 MPa, the underwater pelletizing temperature was 40°C, and the forced air drying temperature was 60°C.

[0103] (2) The BIPB crosslinking agent is atomized and then introduced into a shaking tank for post-absorption with the granules obtained in step (1). The mixture is kept at 70°C for 24 hours to ensure complete absorption of the crosslinking agent. The material is continuously sampled for impurity testing, and finally packaged to obtain the cable shielding material.

[0104] Example 6

[0105] This embodiment provides an ultra-high voltage cable shielding material, which, by weight, comprises 73 parts EBA resin, 25 parts carbon black-MXene-ionic liquid composite conductive agent (Preparation Example 1), 0.5 parts antioxidant 300, 1.5 parts polyethylene wax, and 1 part BIPB.

[0106] This embodiment provides a method for preparing ultra-high voltage cable shielding material, including the following steps:

[0107] (1) EBA resin, carbon black-MXene-ionic liquid composite conductive agent (preparation example 1), antioxidant 300 and polyethylene wax were added to a reciprocating mixer for mixing, filtered in a screen changer, extruded under pressure by a melt pump, and the melt was granulated through an underwater granulation system and dried by forced air to obtain a resin composite material; the mixing temperature was 75°C in the feeding section, 180°C in the melting section, 190°C in the plasticizing section, and 200°C in the extrusion section, and the screw speed was 320 rpm / min; in the extrusion granulation, the die head temperature was 200°C, the melt pressure was 7-7.5 MPa, the underwater pelletizing temperature was 40°C, and the forced air drying temperature was 60°C.

[0108] (2) The BIPB crosslinking agent is atomized and then introduced into a shaking tank for post-absorption with the granules obtained in step (1). The mixture is kept at 70°C for 24 hours to ensure complete absorption of the crosslinking agent. The material is continuously sampled for impurity testing, and finally packaged to obtain the cable shielding material.

[0109] Example 7

[0110] This embodiment provides an ultra-high voltage cable shielding material, which, by weight, comprises 76 parts EBA resin, 22 parts carbon black-MXene-ionic liquid composite conductive agent (preparation example 5), 0.5 parts antioxidant 300, 1.5 parts polyethylene wax and 1 part BIPB.

[0111] This embodiment provides a method for preparing cable shielding material, including the following steps:

[0112] (1) EBA resin, carbon black-MXene-ionic liquid composite conductive agent (preparation example 1), antioxidant 300 and polyethylene wax were added to a reciprocating mixer for mixing, filtered in a screen changer, extruded under pressure by a melt pump, and the melt was granulated through an underwater granulation system and dried by forced air to obtain a resin composite material; the mixing and feeding section temperature was 80°C, the melting section temperature was 180°C, the plasticizing section temperature was 190°C, the extrusion section temperature was 190°C, and the screw speed was 300 rpm; in the extrusion granulation, the die head temperature was 200°C, the melt pressure was 7~7.5MPa, the underwater pelletizing temperature was 40°C, and the forced air drying temperature was 60°C.

[0113] (2) The BIPB crosslinking agent is atomized and then introduced into a shaking tank for post-absorption with the granules obtained in step (1). The mixture is kept at 70°C for 24 hours to ensure complete absorption of the crosslinking agent. The material is continuously sampled for impurity testing, and finally packaged to obtain the cable shielding material.

[0114] Comparative Example

[0115] This comparative example provides an ultra-high voltage cable shielding material, which, by weight, comprises 62.5 parts EBA resin, 35 parts conductive carbon black, 1 part antioxidant 300, 1.5 parts polyethylene wax, and 1 part BIPB. The conductive carbon black is commercially available Cabot carbon black VXC500. This comparative example also provides a method for preparing the cable shielding material, comprising the following steps:

[0116] EBA resin, conductive carbon black, antioxidant 300, and polyethylene wax are added to a reciprocating mixer for mixing, filtered in a screen changer, and extruded under pressure by a melt pump. The melt is granulated through an underwater granulation system and then dried by forced air to obtain a resin composite material. The mixing and feeding section temperature is 80℃, the melting section temperature is 160℃, the plasticizing section temperature is 180℃, the extrusion section temperature is 190℃, and the screw speed is 300 rpm. During extrusion granulation, the die head temperature is 200℃, the melt pressure is 7-7.5 MPa, the underwater pelletizing temperature is 40℃, and the forced air drying temperature is 70℃. The material is continuously sampled for impurity testing, and finally packaged to obtain the cable shielding material.

[0117] The sample preparation method adopted was particle molding, in accordance with the provisions of 6.2.1 in JB / T 10738-2007. The sample should be flat, smooth, uniform in thickness, and free of air bubbles. The thickness of the sample should meet the requirements of each test item. The testing standard was based on Q / GDW11883.2—2018, and the standard values ​​are shown in the table. Tests were conducted on the examples and comparative examples according to the standard requirements, and the results are shown in Table 1.

[0118] Table 1. Main physical properties of each embodiment and comparative example.

[0119]

[0120]

[0121] As can be seen from the data in Table 1, the basic properties of the cable shielding materials prepared by the compositions in Examples 1-7 all met the indicators specified in Q / GDW 11883.2—2018. Compared with the examples, the mechanical properties of the comparative examples deteriorated, and the surface protrusions seriously failed to meet the standards. This was because the conductive carbon black could not be uniformly dispersed, resulting in poor performance. Compared with Example 1, Example 2 showed a slight increase in the amount of ionic liquid, and the resistance increased slightly. This was because the reduction in the MXene layered structure led to an incomplete formation of the conductive network. In Example 3, the amount of dispersant used was reduced, resulting in poorer mechanical properties of the material and the appearance of small protrusions. This was because the conductive agent was not completely dispersed and agglomerated. In Example 4, the rotation speed of Preparation Example 4 was increased, and the cell pulverizer grinding time was increased, resulting in increased resistance and an increasing trend in the FEF parameter. This was because the preparation conditions were harsh, and the composite conductive agent structure began to be destroyed. In Example 5, the amount of composite conductive agent was reduced, and in Example 6, the amount of composite conductive agent was increased. Their performance was within the standard range. In Example 7, the preparation example 5 used 1-butyl-3-methylimidazolium tetrafluoroborate imidazolium ionic liquid, and all the effects were within the standard range.

[0122] As can be seen from the above comparison, the ultra-high voltage cable shielding material prepared by this invention meets the requirements of ultra-high voltage, significantly reduces the number of surface protrusions, greatly improves the smoothness of the material, enhances its conductivity, and reduces the PTC effect. Simultaneously, the use of composite conductive agents reduces the generation of space charge.

[0123] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A type of ultra-high voltage DC shielding material, characterized in that, It is made from the following ingredients by weight: 65-80 parts of matrix resin; 15-25 parts of carbon black-MXene-ionic liquid composite conductive agent; Antioxidant 0.2-5 parts; 1-2 parts lubricant; Crosslinking agent 0.5~2 parts; The carbon black-MXene-ionic liquid composite conductive agent is carbon black modified with MXene and imidazole conductive ionic liquid; The preparation method of the carbon black-MXene-ionic liquid composite conductive agent includes the following steps: 1) MXene and ionic liquid are heated under stirring to react. The reactants are then pulverized and separated to obtain a solid, which is then dried to obtain ionic liquid-modified MXene. 2) Mix the ionic liquid-modified MXene obtained in step 1) with carbon black in a solution to obtain a dispersion. Grind the dispersion to obtain a carbon black-MXene-ionic liquid composite conductive agent. In step 1), the mass ratio of MXene to ionic liquid is 5-6:1-1.5; In step 2), the dispersion obtained by mixing ionic liquid-modified MXene and carbon black in a solution is as follows: ionic liquid-modified MXene and carbon black are dispersed in an organic solvent, and a dispersant is added. The mass ratio of carbon black, ionic liquid-modified MXene, organic solvent, and dispersant is 1:3-8:90-95:1-3.

2. The ultra-high voltage DC shielding material according to claim 1, characterized in that, It is made from the following ingredients by weight: 70-80 parts of matrix resin; 18-23 parts of carbon black-MXene-ionic liquid composite conductive agent; Antioxidant 0.5~2.5 parts; 1 to 1.5 parts of lubricant; Crosslinking agent 0.8~1.2 parts.

3. The ultra-high voltage DC shielding material according to claim 1, characterized in that, The matrix resin comprises one or more of the following: ethylene-vinyl acetate copolymer (EVA), ethylene-butyl acrylate copolymer (EBA), ethylene-methyl acrylate copolymer (EMA), and ethylene-ethyl acrylate copolymer (EEA). The mass fraction of vinyl acetate monomer units in the ethylene-vinyl acetate copolymer is 15-30%; the mass fraction of butyl acrylate monomer units in the ethylene-butyl acrylate copolymer is 15-25%; and the mass fraction of methyl acrylate monomer units in the ethylene-methyl acrylate copolymer is 15-25%.

4. The ultra-high voltage DC shielding material according to claim 3, characterized in that, The matrix resin is EBA resin or EMA resin; The mass fraction of butyl acrylate monomer units in the ethylene-butyl acrylate copolymer is 16-20%; the mass fraction of methyl acrylate monomer units in the ethylene-methyl acrylate copolymer is 16-20%.

5. The ultra-high voltage DC shielding material according to claim 4, characterized in that, The matrix resin is EBA resin; The mass fraction of butyl acrylate monomer units in the ethylene-butyl acrylate copolymer is 16-19%.

6. The ultra-high voltage DC shielding material according to claim 1, characterized in that, In step 1), the stirring conditions include: stirring time of 40-60 min, stirring speed of 400-600 r / min, and heating temperature of 120-170℃. In step 1), the reaction is carried out in a microwave reactor, and the pulverization process is carried out in a cell disruptor for 30-50 minutes with a vibration frequency of 50-80 kHz. In step 1), the drying conditions include: a drying temperature of 80-90℃ and a drying time of 8-10h.

7. The ultra-high voltage DC shielding material according to claim 1, characterized in that, In step 2), the organic solvent is one or more of ethylene glycol monobutyl ether and diethylene glycol monobutyl ether, and the dispersant is one or more of polyvinylpyrrolidone and polyvinyl alcohol. In step 2), the ionic liquid-modified MXene and carbon black are ultrasonically dispersed in an organic solvent. The ultrasonic time is 1-3 hours, the ultrasonic temperature is 25-40°C, and the ultrasonic frequency is 40000-60000 Hz.

8. The ultra-high voltage DC shielding material according to claim 7, characterized in that, In step 2), the grinding method is ball milling; the conditions for ball milling include: ball milling speed of 200-300 r / min and ball milling time of 1-2 h.

9. The ultra-high voltage DC shielding material according to any one of claims 1-8, characterized in that, The preparation method of the carbon black-MXene-ionic liquid composite conductive agent includes the following steps: S1: Take 5-6 parts of MXene and 1-1.5 parts of ionic liquid and place them in a microwave reactor. Heat to 120-170 ℃, stir for 40-60 min, and stir at 400-600 r / min. Then treat with a cell disruptor for 30-50 min, vibrate at 50-80 kHz, and centrifuge at 8000-10000 r / min for 5-10 min. Take the supernatant, add dichloromethane and ethanol respectively, and centrifuge for 15-20 min. Keep the solid and repeat 2-3 times. Place the obtained black solid in a vacuum drying oven and dry at 80-90 ℃ for 8-10 h to obtain ionic liquid modified MXene. S2: The ionic liquid-modified MXene and carbon black prepared in S1 are ultrasonically dispersed in an organic solvent, and a dispersant is added. The organic solvent is one of ethylene glycol monobutyl ether and diethylene glycol monobutyl ether, and the dispersant is one of polyvinylpyrrolidone and polyvinyl alcohol. The mass ratio of carbon black: ionic liquid-modified MXene: solvent: dispersant is 1:3-8:90-95:1-3. The treated dispersion is ball-milled in a ball mill at 200-300 r / min for 1-2 h to obtain carbon black-MXene-ionic liquid composite conductive agent.

10. The ultra-high voltage DC shielding material according to claim 1, characterized in that, The antioxidant is one or more of antioxidant 300, antioxidant 1010, and antioxidant 1076; the lubricant is one or more of polyethylene wax, zinc stearate, and stearamide; and the crosslinking agent is one or more of dicumyl peroxide and bis-tert-butyldicumyl peroxide.

11. The ultra-high voltage DC shielding material according to claim 10, characterized in that, The antioxidant is antioxidant 300; the lubricant is polyethylene wax.

12. The method for preparing the ultra-high voltage DC shielding material according to any one of claims 1-11, characterized in that, Includes the following steps: The matrix resin, carbon black-MXene-ionic liquid composite conductive agent, antioxidant and lubricant are mixed, filtered, extruded and granulated, dried, and then a crosslinking agent is added for post-absorption to obtain the shielding material.

13. The method for preparing the ultra-high voltage DC shielding material according to claim 12, characterized in that, The mixing is carried out in a reciprocating mixer, the mixing section of which is a reciprocating single-screw extruder, and the molten material processed in the reciprocating mixer is filtered by a filtration system. The crosslinking agent is atomized and then added for post-absorption. The temperature of the post-absorption process is 60~80℃, and the time of the post-absorption process is 1~3 h.

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