Ultrahigh-voltage cable shielding material and preparation method thereof

Abstract

The invention discloses an ultrahigh-voltage cable shielding material and a preparation method thereof. The cable shielding material comprises the following raw materials: 70-96 parts of matrix resin; 10-30 parts of a modified conductive agent; 0.2 to 5 parts of an antioxidant; 0.1 to 3.5 parts of a lubricant; wherein the parts are parts by mass. Through modification of the conductive agent, the conductive effect is improved, and meanwhile, the surface smoothness of shielding material extrusion is improved. Meanwhile, a conventional cross-linking agent is replaced, gaseous decomposition products are reduced, the degassing time is shortened, and the production efficiency of cable enterprises is greatly improved.

Description

Technical Field

[0001] The present invention relates to a shielding material for cables, specifically to an extra-high voltage cable shielding material and a preparation method thereof. It belongs to the technical field of extra-high voltage cable material processing. Background Art

[0002] As an essential part of extra-high voltage cable materials, the stability and economy of extra-high voltage cable shielding materials are particularly important.

[0003] Ultra-smoothness is an important indicator in the extra-high voltage shielding material industry, requiring the surface of the shielding material to be ultra-smooth. The conductive filler used in conventional shielding materials is conductive carbon black, and its addition amount is generally controlled at 30wt%-40wt%. Its relatively high filling amount greatly increases the production cost. At the same time, it has strict requirements for processing equipment and it is difficult to ensure that the surface of the shielding material is smooth and defect-free. When there are protrusions or defects on the surface of the shielding layer, it will cause electric field concentration during the operation of the cable, leading to electric breakdown.

[0004] Cables using conventional cross-linking agents such as dicumyl peroxide for chemical cross-linking will produce volatile decomposition products such as methane during the cross-linking process, and a degassing step is required. Degassing is an extremely important process in the cable production process, and at the same time, the degassing process is the most time-consuming and energy-consuming process in cable production. Conventional chemically cross-linked extra-high voltage cables require degassing at 70°C for 7-15 days. The degassing time is too long, seriously affecting the production efficiency of cable enterprises.

[0005] In Patent CN 102257052 B, Daniel Nilsson et al. used maleimide compounds as cross-linking agents to prepare insulating materials and shielding materials. However, the conductive filler used in the prepared shielding material is furnace black with a content of 40wt%. This method has a complex process, and the surface protrusions cannot be effectively controlled, and it cannot meet the requirements of extra-high voltage shielding materials.

[0006] Through the modification of the conductive agent, the present invention improves the conductive effect and at the same time improves the surface smoothness of the extruded shielding material. At the same time, it also replaces the conventional cross-linking agent, reduces gaseous decomposition products, reduces the degassing time, and greatly improves the production efficiency of cable enterprises. Summary of the Invention

[0007] Aiming at the deficiencies of the existing preparation technology, the present invention provides an extra-high voltage cable shielding material and a preparation method thereof. By introducing a conductive agent material modified with maleimide compounds, replacing the use of traditional conductive carbon black, the uniform dispersion of the conductive filler is achieved, the generation of impurities and air gaps is reduced, and it fully meets the quality requirements of ultra-smooth extra-high voltage cable shielding materials. At the same time, maleimide compounds can also act as cross-linking agents, reducing the degassing time during the cable production process, and greatly improving the economy of cable production.

[0008] To achieve the above-mentioned invention object, the present invention provides the following technical solutions:

[0009] A super high voltage cable shielding material, the raw materials of the cable shielding material comprising:

[0010] 70 - 96 parts by mass of a matrix resin, preferably 83 - 91 parts by mass;

[0011] 10 - 30 parts by mass of a modified conductive agent, preferably 10 - 15 parts by mass;

[0012] 0.2 - 5 parts by mass of an antioxidant, preferably 0.5 - 2.5 parts by mass;

[0013] 0.1 - 3.5 parts by mass of a lubricant, preferably 0.2 - 0.5 parts by mass;

[0014] Wherein, the parts by mass are parts by mass.

[0015] Furthermore, 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 or EMA resin, and more preferably EBA resin.

[0016] Furthermore, the mass fraction of vinyl acetate monomer units in the ethylene - vinyl acetate copolymer is 15 - 30%, preferably 16 - 20%, and more preferably 16 - 19%; the mass fraction of butyl acrylate monomer units in the ethylene - butyl acrylate copolymer is 15 - 25%, preferably 16 - 20%, and more preferably 16 - 19%; the mass fraction of methyl acrylate monomer units in the ethylene - methyl acrylate copolymer is 15 - 25%, preferably 16 - 20%, and more preferably 16 - 19%.

[0017] Furthermore, the modified conductive agent is carbon black loaded with carbon nanotubes modified by enediyne compounds.

[0018] Furthermore, the preparation method of the modified conductive agent is as follows:

[0019] S1: Weigh 0.5 - 2 parts of carbon nanotubes and 20 - 30 parts of carbon black and place them in a reaction kettle, heat to 40 - 60 °C, introduce carbon dioxide and pressurize to 7 - 10 MPa, preferably the stirring time is 30 - 60 min, preferably the stirring speed is 400 - 600 r / min, and preferably let it stand for 5 - 10 min after completion to obtain carbon black loaded with carbon nanotubes, which is used as a conductive agent;

[0020] S2: Ultrasonically disperse the conductive agent in solvents such as N - methyl - 2 - pyrrolidone, ethylene glycol phenyl ether, or o - dichlorobenzene, preferably N - methyl - 2 - pyrrolidone; degas under vacuum conditions and heat to the reflux temperature to obtain a conductive agent solution;

[0021] S3: Slowly add the enediyne substance into the conductive agent solution for reaction, and finally wash, filter, and vacuum dry to obtain the modified conductive agent.

[0022] Preferably, the enediyne substance is a cis-enediyne compound, such as one of 1,2-diphenylethyne, 1,4-cyclohexadiene, and 4-tert-butyl-1,2-diphenylethyne, and preferably 1,2-diphenylethyne.

[0023] The conductive agent of the present invention uses carbon black loaded with carbon nanotubes, and grafts and modifies the conductive agent through an enediyne compound. At the same time, the Bergman cyclization reaction of the enediyne compound is used to abstract hydrogen to generate two free radicals. One free radical is directly grafted onto the surface of the carbon nanotube, and one forms a crosslinking site on the matrix resin, thereby acting as a crosslinking agent. By adding a small amount of this compound, the modification of the conductive agent is realized, the agglomeration of the conductive agent is reduced, and it also acts as a crosslinking agent, replacing the use of peroxide crosslinking agents. The reduction in the amount of crosslinking agent used can endow the shielding material with extremely excellent scorch resistance. Moreover, the loaded carbon black has excellent electrical conductivity and can replace the conductive carbon black widely used in the industry to achieve a similar conductive effect with a smaller filling amount, thereby reducing the generation of protrusions on the surface of the shielding material caused by carbon black impurities and agglomeration, achieving the purpose of ultra-smoothness. In addition, the reduction in the amount of crosslinking agent used can

[0024] shorten the degassing time in the cable production process, and the reduction in the use of processing aids enhances the thermal stability of the shielding material, which can support the application of the shielding material in the ultra-high voltage field.

[0025] Further, the preparation conditions include:

[0026] Preferably, the ultrasonic time for ultrasonic dispersion of the conductive agent in the solvent in S2 is 1 - 3 h.

[0027] Preferably, the ultrasonic temperature is 25 - 40 °C.

[0028] Preferably, the ultrasonic frequency is 40000 - 60000 Hz.

[0029] Further, the mass ratio of the conductive agent to the enediyne compound for preparing the modified conductive agent in S3 is 9 - 14:1, such as 14:1, 13:1, 12:1, 11:1, 10:1, and 9:1, preferably 10:1, the reaction temperature is 140 - 170 °C, and the reaction time is 11 - 13 h.

[0030] Further, the solvent used for washing in S3 is one of N-methylpyrrolidone, dimethylformamide, o-dichlorobenzene, and tetrahydrofuran, preferably tetrahydrofuran, and the filter membrane is a 220 nm polytetrafluoroethylene microporous membrane. The vacuum drying conditions are drying at 50 - 60 °C for 4 - 6 h.

[0031] Furthermore, the antioxidant is a commonly used primary antioxidant, such as 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.

[0032] Furthermore, the present invention also provides a method for preparing a super high voltage cable shielding material, comprising the following steps:

[0033] Adding the matrix resin, modified conductive agent, antioxidant, and lubricant into a reciprocating mixer for mixing, filtering through a screen changer, entering a melt pump for pressurized extrusion, and finally pelletizing and drying through an underwater pelletizing system. Continuously sampling and inspecting the materials for impurity detection, and finally packaging the finished product.

[0034] Furthermore, in the preparation method, the mixing part of the reciprocating mixer is a reciprocating single screw extruder. The feeding bin is equipped with an automatic loss-in-weight metering system, which can accurately control the addition of materials. Filtration is carried out through a filtration system in the molten state.

[0035] Compared with the prior art, the present invention has the following positive effects:

[0036] 1. By adding a conductive agent modified with a cis - dienediyne compound, uniform dispersion of the conductive filler is achieved during the preparation process, reducing the generation of impurities and air gaps, thereby avoiding the electric field concentration and breakdown phenomena caused by impurities and air gaps.

[0037] 2. The prepared shielding material has no protrusions above 50 μm and has super - smooth characteristics.

[0038] 3. It has excellent electrical conductivity, and the resistivity changes little with temperature.

[0039] 4. It replaces the traditional cross - linking agent, reducing the degassing time and energy consumption in the subsequent cable production process. Specific Embodiments

[0040] The present invention will be further described below in conjunction with embodiments, but the protection scope of the present invention is not limited to the embodiments, and should also include any other known changes within the scope of the claims of the present invention.

[0041] Reciprocating mixer: BUSS AG, Switzerland, model: MX - 30.

[0042] EBA: Dow Chemical Company, USA, the mass fraction of butyl acrylate monomer unit is 17%.

[0043] EVA: Dow Chemical Company, USA, the mass fraction of vinyl acetate monomer unit is 17%.

[0044] Carbon black: Cabot Corporation, VXC500.

[0045] Carbon nanotubes: Harbin Jinnak Technology.

[0046] Dienyne compounds: Jiuding Chemistry, 1,2-diphenylethyne, 4-tert-butyl-1,2-diethynylbenzene.

[0047] Polyethylene wax: EUROCERAS, CERALENE 691.

[0048] Antioxidant: Ciba Specialty Chemicals Switzerland, Antioxidant 300.

[0049] Mechanical property test: The test method is in accordance with ISO 527, ISO 178 and ISO 180 standards, and the Instron tensile tester INSTRON 5966 is used.

[0050] Density test: The test method is carried out in accordance with the provisions of GB / T 1033.1. Square specimens with a thickness of 2.0 ± 0.1 mm and a side length between 20 - 25 mm are used.

[0051] Thermal elongation: It should be carried out in accordance with the provisions of GB / T 2951.5, and the specimen preparation should be carried out in accordance with the provisions of GB / T 1040.2.

[0052] Volume resistivity: The volume resistivity at 23°C is measured in accordance with the provisions of GB / T 3048.3. The specimen should be conditioned in an environment with a temperature of 23 ± 3°C and a relative humidity of 50 ± 5% for at least 24 h. The volume resistivity at 90°C is measured in accordance with the provisions in Appendix A of GB / T 3048.3. The volume resistivity at 90°C after 7-day thermal aging at 135°C is measured in accordance with the provisions in Appendix A of GB / T 3048.3, and the thermal aging is carried out in accordance with the provisions of GB / T 2951.12.

[0053] Surface protrusions: It is carried out in accordance with the provisions in Appendix A of the standard Q / GDW 11883.2—2018. The resolution ability of the protrusion height of the detector should be better than 25 μm. Sampling and test standard: Class 1000 purification room.

[0054] Preparation Example 1

[0055] Preparation Example 1 of Modified Conductive Agent The preparation method is as follows: Weigh 1 part of carbon nanotubes and 25 parts of carbon black and place them in a reaction kettle. After tightening the kettle lid, heat it to 50 °C, introduce carbon dioxide to 8.5 MPa, and deposit through supercritical carbon dioxide. Stir for 40 min at a stirring speed of 500 r / min. After completion, let it stand for 5 min to obtain carbon black loaded with carbon nanotubes, which is used as a conductive agent. Disperse the conductive agent powder in N-methylpyrrolidone and ultrasonically disperse it for 1 h at an ultrasonic temperature of 35 °C and an ultrasonic frequency of 40 kHz. Centrifuge to obtain the supernatant. Degas the supernatant in a vacuum, then heat it to 160 °C, and slowly drip the solution of 1,2-diphenylethyne at a speed of 1 r / min with a peristaltic pump. The mass ratio of the enediyne compound to the conductive agent is 1:9, and react for 12 h. Wash and filter with tetrahydrofuran solvent, and the filter membrane is a 220-nm polytetrafluoroethylene microporous membrane. Dry it in a vacuum at 55 °C for 4 h to obtain the modified conductive agent.

[0056] Preparation Example 2

[0057] Preparation Example 2 of Modified Conductive Agent The preparation method is as follows: Weigh 0.5 part of carbon nanotubes and 30 parts of carbon black and place them in a reaction kettle. Heat it to 50 °C, introduce carbon dioxide to 8.5 MPa, and deposit through supercritical carbon dioxide. Stir for 40 min. After completion, let it stand for 5 min to obtain carbon black loaded with carbon nanotubes, which is used as a conductive agent. Disperse the conductive agent powder in N-methylpyrrolidone and ultrasonically disperse it for 1 h at an ultrasonic temperature of 35 °C and an ultrasonic frequency of 40 kHz. Centrifuge to obtain the supernatant. Degas the supernatant in a vacuum, then heat it to 160 °C, and slowly drip the solution of 1,2-diphenylethyne at a speed of 1 r / min with a peristaltic pump. The mass ratio of the enediyne compound to the conductive agent is 1:10, and react for 12 h. Wash and filter with tetrahydrofuran solvent, and the filter membrane is a 220-nm polytetrafluoroethylene microporous membrane. Dry it in a vacuum at 55 °C for 4 h to obtain the modified conductive agent.

[0058] Preparation Example 3

[0059] Preparation Example 3 of Modified Conductive Agent The preparation method is as follows: Weigh 2 parts of carbon nanotubes and 20 parts of carbon black and place them in a reaction kettle. Heat to 50 °C, pass carbon dioxide to 8.5 MPa, and use the supercritical carbon dioxide deposition method to stir for 40 min. After completion, let it stand for 5 min to obtain carbon black loaded with carbon nanotubes, which is used as a conductive agent. Disperse the conductive agent powder in N-methylpyrrolidone and perform ultrasonic dispersion for 1 h. The ultrasonic temperature is 35 °C; the ultrasonic frequency is 50 kHz, and then centrifuge to take the supernatant. Degas the supernatant under vacuum, then heat it to 160 °C, and slowly drip the solution of 1,2-diphenylacetylene at a speed of 1 r / min with a peristaltic pump. The mass ratio of the enediyne compound to the conductive agent is 1:14, and react for 12 h. Wash and filter with tetrahydrofuran solvent, and the filter membrane is a 220-nm polytetrafluoroethylene microporous membrane. Dry under vacuum at 55 °C for 4 h to obtain the modified conductive agent.

[0060] Preparation Example 4

[0061] Preparation Example 4 of Modified Conductive Agent The preparation method is as follows: Weigh 1 part of carbon nanotubes and 25 parts of carbon black and place them in a reaction kettle. After tightening the kettle lid, heat to 50 °C, pass carbon dioxide to 8.5 MPa, and use the supercritical carbon dioxide deposition method to stir for 40 min. After completion, let it stand for 5 min to obtain carbon black loaded with carbon nanotubes, which is used as a conductive agent. Disperse the conductive agent powder in N-methylpyrrolidone and perform ultrasonic dispersion for 1 h. The ultrasonic temperature is 35 °C; the ultrasonic frequency is 40 kHz, and then centrifuge to take the supernatant. Degas the supernatant under vacuum, then heat it to 160 °C, and slowly drip the solution of 1,2-diphenylacetylene at a speed of 1 r / min with a peristaltic pump. The mass ratio of the enediyne compound to the conductive agent is 1:12, and react for 12 h. Wash and filter with tetrahydrofuran solvent, and the filter membrane is a 220-nm polytetrafluoroethylene microporous membrane. Dry under vacuum at 55 °C for 4 h to obtain the modified conductive agent.

[0062] Example 1

[0063] This example provides a super high voltage cable shielding material. By weight, the cable shielding material includes 83 parts of EVA resin, 15 parts of modified conductive agent (Preparation Example 1), 1.5 parts of antioxidant 300, and 0.5 part of polyethylene wax.

[0064] This example provides a preparation method of a cable shielding material, including the following steps:

[0065] The EVA resin, modified conductive agent (Preparation Example 1), antioxidant 300 and polyethylene wax were added to a reciprocating mixer for mixing, filtered through a screen changer, extruded under pressure by a melt pump, granulated by an underwater granulation system and air-dried to obtain a resin composite material; the temperature of the mixing feeding section was 80°C, the melting section was 140°C, the plasticizing section was 150°C, the extrusion section was 160°C, and the screw speed was 300 rpm; during extrusion granulation, the head temperature was 160°C, the melt pressure was 7 - 7.5 MPa, the underwater pelletizing temperature was 45°C, and the air-drying temperature was 70°C. The materials were continuously sampled for impurity detection and finally packaged into finished products.

[0066] Example 2

[0067] This example provides a super high voltage cable shielding material. By weight, the cable shielding material includes 85 parts of EBA resin, 13 parts of modified conductive agent (Preparation Example 1), 1.6 parts of antioxidant 300 and 0.4 parts of polyethylene wax.

[0068] This example provides a preparation method for a super high voltage cable shielding material, which includes the following steps:

[0069] The EBA resin, modified conductive agent (Preparation Example 1), antioxidant 300 and polyethylene wax were added to a reciprocating mixer for mixing, filtered through a screen changer, extruded under pressure by a melt pump, granulated by an underwater granulation system and air-dried to obtain a resin composite material; the mixing temperature was 75°C in the feeding section, 140°C in the melting section, 155°C in the plasticizing section, 165°C in the extrusion section, and the screw speed was 320 rpm / min; during extrusion granulation, the head temperature was 160°C, the melt pressure was 7 - 7.5 MPa, the underwater pelletizing temperature was 40°C, and the air-drying temperature was 70°C. The materials were continuously sampled for impurity detection and finally packaged into finished products.

[0070] Example 3

[0071] This example provides a cable shielding material. By weight, the cable shielding material includes 88 parts of EBA resin, 10 parts of modified conductive agent (Preparation Example 1), 1.8 parts of antioxidant 300, and 0.2 parts of polyethylene wax.

[0072] This example provides a preparation method for a super high voltage cable shielding material, which includes the following steps:

[0073] The EBA resin, modified conductive agent (Preparation Example 1), antioxidant 300 and polyethylene wax were added to a reciprocating mixer for mixing, filtered through a screen changer, extruded under pressure by a melt pump, granulated by an underwater granulation system and air-dried to obtain a resin composite material; the temperature of the mixing feeding section was 80°C, the melting section temperature was 130°C, the plasticizing section temperature was 140°C, the extrusion section temperature was 160°C, and the screw speed was 300 rpm; during extrusion granulation, the head temperature was 160°C, the melt pressure was 7 - 7.5 MPa, the underwater pelletizing temperature was 45°C, and the air-drying temperature was 70°C. The materials were continuously sampled for impurity detection and finally packaged into finished products.

[0074] Example 4

[0075] This example provides a super high voltage cable shielding material. By weight, the cable shielding material includes 85 parts of EBA resin, 13 parts of modified conductive agent (Preparation Example 2), 1.5 parts of antioxidant 300 and 0.5 part of polyethylene wax.

[0076] This example provides a method for preparing a cable shielding material, including the following steps:

[0077] The EBA resin, modified conductive agent (Preparation Example 2), antioxidant 300 and polyethylene wax were added to a reciprocating mixer for mixing, filtered through a screen changer, extruded under pressure by a melt pump, granulated by an underwater granulation system and air-dried to obtain a resin composite material; the temperature of the mixing feeding section was 80°C, the melting section temperature was 140°C, the plasticizing section temperature was 150°C, the extrusion section temperature was 160°C, and the screw speed was 300 rpm; during extrusion granulation, the head temperature was 160°C, the melt pressure was 7 - 7.5 MPa, the underwater pelletizing temperature was 45°C, and the air-drying temperature was 70°C. The materials were continuously sampled for impurity detection and finally packaged into finished products.

[0078] Example 5

[0079] This example provides a super high voltage cable shielding material. By weight, the cable shielding material includes 85 parts of EBA resin, 13 parts of modified conductive agent (Preparation Example 3), 1.5 parts of antioxidant 300 and 0.5 part of polyethylene wax.

[0080] This example provides a method for preparing a cable shielding material, including the following steps:

[0081] The EBA resin, modified conductive agent (Preparation Example 3), antioxidant 300 and polyethylene wax were added to a reciprocating mixer for mixing, filtered through a screen changer, extruded under pressure by a melt pump, granulated by an underwater granulation system and dried by blowing air to obtain a resin composite material; the temperature of the mixing feeding section was 80°C, the melting section was 140°C, the plasticizing section was 150°C, the extrusion section was 160°C, and the screw speed was 300 rpm; during extrusion granulation, the head temperature was 160°C, the melt pressure was 7 - 7.5 MPa, the underwater pelletizing temperature was 45°C, and the blowing drying temperature was 70°C. The materials were continuously sampled for impurity detection and finally packaged into products.

[0082] Example 6

[0083] This example provides a super high voltage cable shielding material. By weight, the cable shielding material includes 85 parts of EBA resin, 13 parts of modified conductive agent (Preparation Example 4), 1.5 parts of antioxidant 300 and 0.5 part of polyethylene wax.

[0084] This example provides a preparation method for a cable shielding material, including the following steps:

[0085] The EBA resin, modified conductive agent (Preparation Example 4), antioxidant 300 and polyethylene wax were added to a reciprocating mixer for mixing, filtered through a screen changer, extruded under pressure by a melt pump, granulated by an underwater granulation system and dried by blowing air to obtain a resin composite material; the temperature of the mixing feeding section was 80°C, the melting section was 140°C, the plasticizing section was 150°C, the extrusion section was 160°C, and the screw speed was 300 rpm; during extrusion granulation, the head temperature was 160°C, the melt pressure was 7 - 7.5 MPa, the underwater pelletizing temperature was 45°C, and the blowing drying temperature was 70°C. The materials were continuously sampled for impurity detection and finally packaged into products.

[0086] Comparative Example

[0087] This comparative example provides a super high voltage cable shielding material. By weight, the cable shielding material includes 85 parts of EBA resin, 13 parts of conductive agent, 1.5 parts of antioxidant 300, 0.5 part of polyethylene wax and 1 part of di - tert - butyl peroxide diisopropylbenzene. The conductive agent is the unmodified conductive agent in Preparation Example 1. This comparative example provides a preparation method for a cable shielding material, including the following steps:

[0088] The EBA resin, conductive agent, antioxidant 300 and polyethylene wax were added to a reciprocating mixer for mixing, filtered through a screen changer, extruded under pressure by a melt pump, granulated by an underwater granulation system and dried by blowing air to obtain a resin composite material; the temperature of the mixing feeding section was 80°C, the melting section was 140°C, the plasticizing section was 150°C, the extrusion section was 160°C, and the screw speed was 300 rpm;

[0089] During extrusion granulation, the head temperature is 160 °C, the melt pressure is 7 - 7.5 MPa, the underwater pelletizing temperature is 45 °C, and the air-blowing drying temperature is 70 °C. The materials are continuously sampled for impurity detection, and finally packaged into finished products to obtain the cable shielding material.

[0090] The specimen preparation method adopts the particle molding method and is carried out according to the provisions in 6.2.1 of JB / T 10738-2007. The test pieces should be flat, smooth, with uniform thickness and no bubbles. The thickness of the test pieces should meet the requirements of each test item. The test standards are referred to Q / GDW11883.2—2018, and the standard values are as shown in the standards in the table. According to the standard requirements, the examples and comparative examples were tested, and the results are shown in Table 1.

[0091] Table 1 Main physical property parameters of each example and comparative example

[0092]

[0093] It can be seen from the data in Table 1 that the basic properties of the cable shielding materials prepared from the compositions in Examples 1 - 6 all meet the indicators specified in Q / GDW 11883.2—2018. Compared with Example 2, the mechanical properties of the comparative example are worse, the surface protrusions seriously do not meet the standards, and the degassing time is much higher than that of Examples 1 - 6. The reason is that the conductive agent is not modified, resulting in agglomeration and unable to be uniformly dispersed, thus leading to deterioration of various properties. The traditional peroxide cross-linking agent produces more small-molecule gaseous products after reaction, and the degassing time is slower.

[0094] From the above comparison, it can be seen that the extra-high voltage cable shielding material prepared by the present invention meets the extra-high voltage requirements, greatly reduces the number of surface protrusions of the shielding material, greatly improves the smoothness of the material, and greatly shortens the degassing time. At the same time, the cross-linking effect of the enediyne compound has no obvious difference from that of the ordinary peroxide cross-linking agent and can meet the usage requirements.

[0095] The above examples are only used to describe the preferred embodiments of the present invention, rather than limiting the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that various modifications or equivalent replacements made to the technical solutions of the present invention should fall within the protection scope determined by the claims of the present invention.

Claims

1. A kind of extra-high voltage cable shielding material, characterized in that, The raw materials of the cable shielding material include: 70-96 parts of matrix resin, preferably 83-91 parts; 10-30 parts of modified conductive agent, preferably 10-15 parts; 0.2-5 parts of antioxidant, preferably 0.5-2.5 parts; 0.1-3.5 parts of lubricant, preferably 0.2-0.5 parts; Wherein, the parts are parts by mass.

2. The extruded semi-conductive layer material for extra-high voltage cable according to claim 1, wherein The matrix resin includes 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 or EMA resin, and more preferably EBA resin.

3. The extruded semi-conductive layer material for extra-high voltage cable according to claim 2, wherein, The mass fraction of vinyl acetate monomer units in the ethylene-vinyl acetate copolymer is 15-30%, preferably 16-20%, and more preferably 16-19%; the mass fraction of butyl acrylate monomer units in the ethylene-butyl acrylate copolymer is 15-25%, preferably 16-20%, and more preferably 16-19%; the mass fraction of methyl acrylate monomer units in the ethylene-methyl acrylate copolymer is 15-25%, preferably 16-20%, and more preferably 16-19%.

4. The extruded semi-conductive layer material for extra-high voltage cable according to any one of claims 1 to 3, characterized in that, The modified conductive agent is carbon black loaded with carbon nanotubes modified by enediyne compounds.

5. The extruded semiconductive shielding compound according to claim 4, wherein The preparation method of the modified conductive agent includes the following steps: S1: Weigh 0.5-2 parts of carbon nanotubes and 20-30 parts of carbon black and place them in a reaction kettle, heat to 40-60 °C, introduce carbon dioxide and pressurize to 7-10 MPa, preferably the stirring time is 30-60 min, preferably the stirring speed is 400-600 r / min, and preferably let it stand for 5-10 min after completion to obtain carbon black loaded with carbon nanotubes, which is used as a conductive agent; S2: Ultrasonically disperse the conductive agent in a solvent, preferably the solvent is N-methylpyrrolidone, ethylene glycol phenyl ether or o-dichlorobenzene; degas under vacuum conditions and heat to the reflux temperature to obtain a conductive agent solution; S3: Slowly add enediyne substances to the conductive agent solution for reaction, and finally wash, filter, and vacuum dry to obtain the modified conductive agent. Preferably, the enediyne substance is a cis-enediyne compound, preferably one of 1,2-diphenylethyne and 4-tert-butyl-1,2-diphenylethyne, and further preferably 1,2-diphenylethyne.

6. The extruded semi-conductive layer shielding material for extra-high voltage cable according to claim 5, wherein In S2, the ultrasonic time for ultrasonically dispersing the conductive agent in the solvent is 1-3 h; the ultrasonic temperature is 25-40 °C; the ultrasonic frequency is 40000-60000 Hz.

7. The extruded semiconductive shielding compound for extra-high voltage cable according to claim 5 or 6, wherein In S3, the mass ratio of the conductive agent to the enediyne compound is 9-14:1, preferably 10-11:1; the reaction temperature is 140-170 °C, and the reaction time is 11-13 h.

8. The extruded semi-conductive layer shielding material for extra-high voltage cables according to any one of claims 5-7, characterized in that, In S3, the solvent used for washing is one of N-methylpyrrolidone, dimethylformamide, o-dichlorobenzene and tetrahydrofuran, preferably tetrahydrofuran, and the filter membrane for filtration is a 220 nm polytetrafluoroethylene microporous membrane.

9. The extruded semi-conductive shielding material for extra-high voltage cable according to any one of claims 1-8, characterized in that, The antioxidant is one or more of antioxidant 300, antioxidant 1010, and antioxidant 1076, preferably antioxidant 300; and / or, the lubricant is one or more of polyethylene wax, zinc stearate, and stearamide, preferably polyethylene wax.

10. The preparation method of the extra-high voltage cable shielding material according to any one of claims 1-9, characterized in that, It includes the following steps: Add the matrix resin, modified conductive agent, antioxidant and lubricant into a reciprocating mixer for mixing, filter through a screen changer, enter a melt pump for pressurized extrusion, and finally granulate and dry through an underwater pelletizing system; preferably, the mixing part of the reciprocating mixer is a reciprocating single-screw extruder, and the filtration is carried out through a filtration system in a molten state.

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