Modification method of conductive carbon black, ultrahigh-voltage cable semi-conductive shielding material and preparation method of ultrahigh-voltage cable semi-conductive shielding material

Abstract

The invention relates to the technical field of ultrahigh-voltage cable preparation, in particular to a modification method of conductive carbon black, an ultrahigh-voltage cable semi-conductive shielding material and a preparation method of the ultrahigh-voltage cable semi-conductive shielding material, and the modification method comprises the following steps: A, adding polyethyleneimine into a solvent, and performing ultrasonic dispersion and heating to obtain dispersion liquid; b, uniformly mixing conductive carbon black powder with the dispersion liquid in the step A, granulating and drying to obtain modified conductive carbon black; the ultrahigh-voltage cable semi-conductive shielding material has excellent electrical performance and mechanical performance, the processing process has the advantages of being simple in process, reliable in preparation, excellent in performance and the like, large-scale production is facilitated, and the ultrahigh-voltage cable semi-conductive shielding material has very high practical and popularization value in actual cable manufacturing.

Description

Technical Field

[0001] The invention relates to the technical field of ultra-high voltage cable preparation, and in particular to a method for modifying conductive carbon black, an ultra-high voltage cable semi-conductive shielding material and a preparation method thereof. Background Art

[0002] As the core component of cables with medium and high voltage levels and above, the semi-conductive shielding layer has the functions of homogenizing the electric field, eliminating interface gaps between layers, and weakening electrical stress concentration that damages insulation. Its material properties directly affect the service life of the cable.

[0003] Conductive carbon black, as a key component of semi-conductive shielding materials, determines the key properties of shielding materials such as electrical, mechanical, thermal, processability, and surface finish. However, conductive carbon black has a small particle size, a large specific surface area, and strong van der Waals forces between particles. In addition, it has few surface active functional groups and low surface polarity, so it is very easy to form large-sized agglomerates in the matrix resin, making it difficult to disperse. On the one hand, poor dispersion of conductive carbon black will affect the formation of the conductive network in the composite material, causing the conductive properties of the material to deteriorate. On the other hand, the agglomeration of conductive carbon black will bring about problems such as increased protrusions on the interface of the shielding layer. The protrusions at the semi-conductive shielding-insulation interface will be further amplified under high voltage, causing local electric field distortion, and even further evolution to cause local insulation breakdown, affecting the service life of the cable and posing great safety hazards to the construction of cross-regional power networks. Therefore, how to improve the dispersion of conductive carbon black in the matrix is ​​a key issue that must be solved in the preparation of domestic ultra-high voltage cable shielding materials.

[0004] In order to solve the problem of difficult dispersion of conductive carbon black, there are currently two commonly used technical means. One is to graft polar groups on the surface of carbon black to increase the surface polarity of carbon black; the other is to use a dispersing agent to coat the surface of carbon black to reduce the surface energy of carbon black. Although the grafting modification technology has a high dispersion efficiency, the grafting method is complicated, and the required cost and process are not suitable for actual factory processing and production. Dispersing agent coating modification has been put into industrial application, but due to the low utilization rate of dispersing agents and poor coating effect on the surface of carbon black, the efficiency of improving the actual dispersion of carbon black is not high; and excessive addition of dispersing agents will affect the intrinsic structure of carbon black due to the insulation of the agent itself, and deteriorate the mechanical and electrical properties of semi-conductive shielding materials.

[0005] Publication number "CN112542590A" discloses an easily dispersible carbon black conductive agent and its preparation method and use: first, oxidize the native carbon black to obtain oxidized carbon black; then introduce acyl chloride groups on the surface of the oxidized carbon black to obtain chlorinated carbon black; finally, react the chlorinated carbon black with carboxymethyl cellulose to graft carboxymethyl cellulose on the surface of the carbon black, which is beneficial to prevent the agglomeration of carbon black and form a lithium-ion battery slurry with good dispersion of the conductive agent. The carboxymethyl cellulose used in this method has good solubility in water, which can prevent the agglomeration of carbon black, thereby reducing the internal resistance of the battery and improving the rate performance. However, this method still has certain problems: (1) The grafting uniformity cannot be determined, and the dispersion stability of the conductive slurry is difficult to ensure; (2) The oxygen-containing groups on the surface of carbon black increase after oxidation, which may destroy the π-π conjugated structure of carbon black and affect the intrinsic conductivity of carbon black; (3) The preparation process is complicated and is not conducive to actual factory production.

[0006] Publication number "CN118440519B" also discloses a method for preparing highly dispersible carbon black, in which carbon black is ground to obtain carbon black powder of suitable fineness, and then a double adsorption layer is formed on the surface of the carbon black powder through ultrasonic treatment of a first mixed amino acid solution, a first dispersant, a second mixed amino acid solution, and a second dispersant, thereby greatly improving the dispersibility of the carbon black. However, the dispersants used in this method, such as fatty acid polyoxyethylene esters and polyether polymer dispersant S-100, are all insulating polymers. Although the double-layer coating improves the dispersibility of carbon black, there is also the problem that the insulating coating layer is too thick to hinder the electron tunneling effect between carbon blacks, which affects the practical application of carbon black.

[0007] In summary, the existing processing technology for dispersing conductive carbon black has problems such as complicated process or low dispersant efficiency, and a large amount of dispersant coating affecting the conductivity. It is urgent to propose a method that is simple to prepare, effective in dispersion and does not affect the intrinsic conductive properties of carbon black. Summary of the invention

[0008] In order to solve the above technical problems, embodiments of the present invention provide a method for modifying conductive carbon black, a semi-conductive shielding material for ultra-high voltage cables and a preparation method thereof.

[0009] To achieve the above object, the embodiments of the present invention adopt the following technical solutions:

[0010] In one aspect, the present invention provides a method for modifying conductive carbon black, comprising the following steps:

[0011] A. adding polyethyleneimine into a solvent, dispersing by ultrasonication and heating to obtain a dispersion;

[0012] B. Mix the conductive carbon black powder with the dispersion in step A, and then granulate and dry to obtain the modified conductive carbon black.

[0013] In some embodiments, in step A, the structural formula of the polyethyleneimine is as follows:

[0014] Wherein n is 10, and the mass ratio of the polyethyleneimine to the solvent is (0.5-1):1000.

[0015] In some embodiments, in step A, the solvent is deionized water, the power of the ultrasonic dispersion is 400w, the time is 15-20min, and the heating temperature is 40-70°C.

[0016] In some embodiments, in step B, the mass ratio of the conductive carbon black to the dispersion is 1:1, and the granulation is carried out using a stirring tooth wet granulator with a stirring tooth linear speed of 10 to 15 m / s, and the rotation speed is controlled at 350 to 450 rpm.

[0017] On the other hand, the present invention provides a semi-conductive shielding material for ultra-high voltage cables, which comprises the following raw materials, in parts by weight: 32 to 34 parts of conductive carbon black, 63.4 to 65.4 parts of matrix resin, 1 part of lubricant, 0.5 part of antioxidant and 0.9 to 1 part of cross-linking agent, wherein the conductive carbon black is the conductive carbon black prepared by the modification method described in any one of claims 1 to 4.

[0018] In some embodiments, the base resin is ethylene butyl acrylate and / or ethylene ethyl acrylate.

[0019] In some embodiments, the crosslinking agent is di-tert-butyl peroxyisopropylbenzene and / or diisopropylbenzene peroxide, the lubricant is zinc stearate, and the antioxidant is 4,4'-thiobis(6-tert-butyl-3-methylphenol).

[0020] In another aspect, the present invention provides a method for preparing a semi-conductive shielding material for an ultra-high voltage cable, comprising the following steps:

[0021] S1, mixing conductive carbon black, lubricant, antioxidant and base resin, and drying to obtain a mixture;

[0022] S2, melt-kneading the mixture obtained in S1 in a twin-screw extruder, with an extrusion temperature of 160-200° C. and a main engine speed of 80-140 rpm, and pelletizing and drying the extrudate to obtain pellets;

[0023] S3, drying the pellets obtained in S2, grinding the cross-linking agent and mixing it with the pellets, and drying to obtain the ultra-high voltage cable semi-conductive shielding material.

[0024] In some embodiments, in S1, the mixing stirring speed is 100-120 rpm, the mixing time is 30-60 min, the drying temperature is 60° C., and the drying time is 4 h.

[0025] In some embodiments, in S3, the pellets are dried at 70°C for 6 hours, and the cross-linking agent is mixed with the pellets and dried at 60°C for 10 hours.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] In order to increase the apparent density of conductive carbon black, reduce pollution and save transportation costs, the powdered conductive carbon black is usually wet granulated in the later stage of conductive carbon black production. Under the action of the high-speed rotating agitator shaft, the powdered conductive carbon black is subjected to centrifugal force to form an empty vortex in the granulator and thrown to the wall of the granulator barrel. Granulation water is injected to eliminate the surface gas and wet the particles of conductive carbon black. After the conductive carbon black aggregates are wetted, they are bonded to form nuclei under the action of the binder. At present, the mainstream process uses molasses or lignin sulfonate as the binder of granulation water, but excessive binder will lead to the production of hard particles, which greatly reduces the dispersibility of granulated conductive carbon black in the matrix. Replacing the binder with a high-efficiency dispersant in the wet granulation stage can not only simplify the process and realize the functional integration of dispersion-bonding, but also introduce a trace amount of high-efficiency dispersant to coat and modify the carbon black in the degassing and wetting stage. Based on the dual action mechanism of electrostatic-steric hindrance of the dispersant used, it ensures that the conductive carbon black is not affected. The conductive ability is not affected while achieving efficient dispersion.

[0028] (1) The present invention uses polyethyleneimine dispersion to replace traditional granulation water in the conductive carbon black wet granulation stage, and promotes the powdered conductive carbon black to discharge the gas attached to the surface through the rapid rotation of the stirring teeth, and highly infiltrates and fuses with the dispersion, thereby improving the utilization efficiency of the dispersant. It not only realizes the simplification of the production process and the integration of the dispersion-bonding functions, but also has a significant dispersion efficiency, which can reduce the amount of dispersant used and avoid the situation where the addition of excessive dispersant coating affects the conductive carbon black's conductivity.

[0029] (2) The conductive carbon black modified with polyethyleneimine in the present invention has two dispersion mechanisms: electrostatic effect and steric hindrance. The -NH 2 After hydrolysis, the -COOH groups on the surface of the conductive carbon black are positively charged. When the dispersion liquid replaces the granulation water, the -COOH on the surface of the conductive carbon black can form a stable solvation layer with the -NH 2 Tight adsorption is formed through electrostatic action, and a double electric layer structure is formed on the surface of the conductive carbon black, and the electrostatic repulsion prevents the adjacent conductive carbon black particles from approaching and agglomerating.

[0030] Compared with conventional cationic dispersants such as hexadecyltrimethylammonium bromide (CTAB), polyethyleneimine has a larger molecular weight, a longer molecular chain, and a large number of -NH 2On the one hand, it can have a stronger short-range steric hindrance effect, which can effectively overcome the electrostatic force and van der Waals force between adjacent conductive carbon black particles and inhibit the re-agglomeration of conductive carbon black particles; on the other hand, it can form hydrogen bonds with the -OH on the surface of conductive carbon black, enhance the compatibility of carbon black particles and the dispersed matrix, and make the dispersion performance more excellent.

[0031] (3) The ultra-high voltage cable semi-conductive shielding material of the present invention has excellent electrical and mechanical properties, and the processing process has the advantages of simple process, reliable preparation, excellent performance, etc. It is convenient for large-scale production and has high practical and promotion value in actual cable manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the dispersion mechanism diagram of polyethyleneimine modified conductive carbon black;

[0033] Figure 2 The particle size distribution diagram of the modified conductive carbon black of Comparative Example 1, Comparative Example 2, Comparative Example 4 and Example 1;

[0034] Figure 3 This is a transmission electron microscope image of the modified conductive carbon black in Example 1. DETAILED DESCRIPTION

[0035] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in some embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments provided by the present disclosure, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present disclosure.

[0036] Example 1

[0037] Step 1: Take 100g of deionized water, add 0.1g of polyethyleneimine (PEI) and perform ultrasonic treatment at an ultrasonic power of 400w for 20min, and heat to 70°C to obtain a dispersion;

[0038] Step 2: Add 100-mesh conductive carbon black powder and dispersion liquid at a mass ratio of 1:1 into a stirring tooth wet granulator and stir at high speed;

[0039] Step 3: The conductive carbon black is degassed, soaked, bonded, granulated, compacted, and polished in the granulator barrel, wherein the stirring tooth linear speed is 15 m / s and the rotation speed is 450 rpm;

[0040] Step 4: drying the granulated conductive carbon black to obtain modified conductive carbon black, wherein the drying temperature is 120° C. and the drying time is 12 h; applying the modified conductive carbon black to a semi-conductive shielding material for ultra-high voltage cables, which includes 63.4 g of ethylene-butyl acrylate, 34 g of modified conductive carbon black, 1 g of a cross-linking agent, 1 g of a lubricant, and 0.5 g of an antioxidant, wherein the lubricant is zinc stearate, the antioxidant is 4,4'-thiobis(6-tert-butyl-3-methylphenol), and the cross-linking agent is di-tert-butyl peroxyisopropylbenzene;

[0041] Step 5: mixing the modified conductive carbon black, antioxidant, lubricant and ethylene-butyl acrylate in a mixer at 100 rpm for 45 min, and drying in an oven at 60° C. for 4 h to obtain a mixture;

[0042] Step 6: melt-knead the obtained mixture in a twin-screw extruder at an extrusion temperature of 160° C. and a main engine speed of 120 rpm. The extrudate is pelletized and dried to obtain pellets;

[0043] Step 7: Place the pellets in an oven at 70°C for 6 hours, mix the crosslinking agent with the pellets for 10 minutes, and place them in an oven at 60°C for 10 hours to allow the crosslinking agent to be fully absorbed to obtain a cable shielding material.

[0044] Example 2

[0045] The difference between Example 2 and Example 1 is:

[0046] The polyethyleneimine in step 1 is 0.05 g and the deionized water is 100 g.

[0047] Example 3

[0048] The difference between Example 3 and Example 1 is:

[0049] In step 4, the modified conductive carbon black is 33 g and the ethylene-ethyl acrylate is 64 g.

[0050] Example 4

[0051] The difference between Example 4 and Example 1 is:

[0052] In step 4, the modified conductive carbon black is 34 g and the ethylene-butyl acrylate is 65 g.

[0053] Example 5

[0054] The difference between Example 5 and Example 1 is:

[0055] In step 4, the modified conductive carbon black is 34 g and the ethylene-butyl acrylate is 65.4 g.

[0056] Comparative Example 1

[0057] The difference between Comparative Example 1 and Example 1 is:

[0058] The polyethyleneimine in step 1 was replaced with sodium polyacrylate (PAA), with a molecular weight of 5000 and a density of 1.32 g / cm 3 .

[0059] Comparative Example 2

[0060] The difference between Comparative Example 2 and Example 1 is:

[0061] The polyethyleneimine in step 1 was replaced by polyvinylpyrrolidone (PVP), with a molecular weight of 5500 and a density of 1.144 g / cm 3 .

[0062] Comparative Example 3

[0063] The difference between Comparative Example 3 and Example 1 is:

[0064] The polyethyleneimine in step 1 was replaced with ethylene bis stearamide (EBS), molecular weight 593, density 0.97 g / cm 3 , EBS mass is 2g, deionized water 100g.

[0065] Comparative Example 4

[0066] The difference between Comparative Example 4 and Example 1 is:

[0067] In step 1, no polyethyleneimine is included.

[0068] Comparative Example 5

[0069] The difference between Comparative Example 5 and Example 1 is:

[0070] The polyethyleneimine in step 1 was replaced with hexadecyltrimethylammonium bromide (CTAB), with a molecular weight of 364.5 and a density of 1.11 g / cm 3 , CTAB mass is 2g, deionized water is 100g.

[0071] Performance Testing

[0072] (1) Weigh 0.01 g of the modified conductive carbon black of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 4 respectively, add them into a dropper, add 30 mL of deionized water, place them in an ultrasonic crusher and disperse them at a speed of 120 rpm for 1 min, take 10 mL of the upper layer liquid into a new dropper, add deionized water to 30 mL, and continue ultrasonic dispersion for 1 min. Repeat the dilution and dispersion cycle until the concentration of the conductive carbon black dispersion is 1×10 -6 g / mL. Take the diluted conductive carbon black dispersion and measure each sample three times at 25°C, and take the average value. The test results are shown in Table 1.

[0073] (2) The ultra-high voltage cable semi-conductive shielding material obtained in Examples 1 to 2 and Comparative Examples 1 to 5 was placed in a flat vulcanizer and hot-pressed and cross-linked at 180°C for 15 minutes to obtain an ultra-high voltage cable semi-conductive shielding material sheet, and its electrical properties and mechanical properties were measured. The volume resistivity and mechanical properties data are shown in Table 2.

[0074] Table 1. Average particle size of conductive fillers in Examples and Comparative Examples

[0075] Test items Average particle size / nm Standard Deviation Example 1 566.93 15.42 Comparative Example 1 736.03 20.74 Comparative Example 2 650.50 37.52 Comparative Example 4 664.80 54.35

[0076] Table 1 shows that the average particle size of the conductive carbon black agglomerates of polyethyleneimine (high molecular weight cationic dispersant) used in Example 1 is significantly smaller than that of the anionic dispersants, nonionic dispersants and no dispersants of the same molecular weight used in Comparative Examples 1, 2 and 4; Figure 2 The particle size distribution diagram of Example 1 is more intuitive, and the particle size distribution of Example 1 is the most concentrated, and the peak value of the concentrated particle size is the smallest, while the three comparative examples still have large particle size agglomerates in the range of 1000-10000nm, so there are peaks on the particle size distribution curve. The above all reflect that PEI has a significant improvement on the dispersion of conductive carbon black, which is because there are a large number of -NH 2 , -NH- and other groups can better play a short-range steric hindrance role in the polar matrix resin, inhibit the re-agglomeration of conductive carbon black in the matrix, thereby reducing the particle size of conductive carbon black agglomerates at the molecular level, and then applied to cable semi-conductive shielding materials to improve the surface finish of the material.

[0077] The specific mechanism of action is shown in the figure Figure 1 As shown in the figure, the conductive carbon black modified by polyethyleneimine in the present invention has two dispersion mechanisms: electrostatic effect and steric hindrance. 2 After hydrolysis, the -COOH groups on the surface of the conductive carbon black are positively charged. When the dispersion liquid replaces the granulation water, the -COOH on the surface of the conductive carbon black can form a stable solvation layer with the -NH 2 Tight adsorption is formed through electrostatic action, and a double electric layer structure is formed on the surface of the conductive carbon black, and the electrostatic repulsion prevents the adjacent conductive carbon black particles from approaching and agglomerating.

[0078] Table 2. Conductive properties and mechanical properties of examples and comparative examples

[0079]

[0080] It can be seen from Table 2 that the semiconductive shielding material prepared by the present invention exhibits excellent mechanical properties and conductive properties. Example 1 has the best comprehensive electrical and mechanical properties, with resistivities of 20.85Ω·cm and 132.28Ω·cm at 23°C and 90°C, respectively, a tensile strength of 19.05MPa, and an elongation at break of 252.60%.

[0081] Example 1 has a more significant dispersion improvement effect than Comparative Examples 1, 2, 3, 4 and 5. This is because PEI has a dual dispersion mechanism of electrostatic action and steric hindrance. The conductive carbon black is negatively charged due to the properties of the surface groups. Driven by the electrostatic force, the cationic PEI after hydrolysis is more easily adsorbed on the surface of the conductive carbon black particles and forms a protective layer of the same charge than the anionic PAA and non-ionic PVP and EBS. Figure 3 As shown, a PEI coating layer is formed on the surface of the modified conductive carbon black particles in Example 1, which hinders the approach of adjacent conductive carbon blacks.

[0082] The PAA in Comparative Example 1 is electronegative after hydrolysis. Due to the repulsion of like charges, the adsorption and coating effect on the conductive carbon black with the same electronegativity is poor, and the dispersion improvement effect on the conductive carbon black is limited; the PVP in Comparative Example 2 only relies on the hydrophobic / hydrophilic interaction of the surface groups of the conductive carbon black and the molecular binding to achieve coating. Although it has a certain coating effect, it is not as stable as the PEI dispersion effect. Therefore, when the addition amount of dispersants (PEI, PAA, PVP) and the molecular weight level are equivalent, the dispersion efficiency of PEI is more significant.

[0083] The large molecular weight PEI has a long molecular chain and has a stronger steric hindrance than the conventional industrial dispersant EBS in comparative example 3, which can overcome the electrostatic force and van der Waals force between adjacent conductive carbon black particles and inhibit the re-agglomeration of conductive carbon black. The CTAB in comparative example 5 has a similar electrostatic adsorption mechanism to the PEI in embodiment 1, but due to the low molecular weight and short molecular chain of CTAB, the extremely weak steric resistance makes the dispersion system less stable. When the dispersant (CTAB) in comparative example 5 is added at a higher content, the electrical and mechanical properties of the shielding material sample obtained are still weaker than those of the same type of cationic dispersant PEI; by comparing comparative examples 3 and As shown in Comparative Example 5, the amount of EBS and CTAB added is 20 times the amount of PEI added in Example 1, but the electrical and mechanical properties of Example 1 are still better than those of Comparative Examples 3 and 5, indicating that PEI only needs to be added in a trace amount to achieve excellent dispersion effect, avoiding the situation where the addition of excessive dispersant coating affects the conductivity of conductive carbon black; the situation of no dispersion in Comparative Example 4 shows that the dispersion effect of conductive carbon black has a significant impact on electrical properties, and it is difficult to ensure the development of a good conductive network of conductive carbon black in the shielding material only through the physical dispersion of the screw, so it is very necessary to add a dispersant to assist the dispersion of conductive carbon black. In Example 2, the amount of PEI added is only half of that in Example 1, so the electrical properties are poorer than those of Comparative Examples 1, 2, 3, and 5, but there is still a significant improvement in electrical and mechanical properties compared with Comparative Example 4 without a dispersant.

[0084] In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

[0085] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for modifying conductive carbon black, characterized in that: The following steps are involved: A. adding polyethyleneimine into a solvent, dispersing by ultrasonication and heating to obtain a dispersion; B. Mix the conductive carbon black powder with the dispersion in step A, and then granulate and dry to obtain the modified conductive carbon black.

2. The modification method according to claim 1, characterized in that: In step A, the structural formula of the polyethyleneimine is as follows: Wherein n is 10, and the mass ratio of the polyethyleneimine to the solvent is (0.5-1):1000.

3. The modification method according to claim 1, characterized in that: In step A, the solvent is deionized water, the power of the ultrasonic dispersion is 400W, the time is 15-20min, and the heating temperature is 40-70°C.

4. The modification method according to claim 1, characterized in that: In step B, the mass ratio of the conductive carbon black to the dispersion is 1:1, and the granulation adopts a stirring tooth wet granulator with a stirring tooth linear speed of 10 to 15 m / s and a rotation speed controlled at 350 to 450 rpm.

5. Ultra-high voltage cable semi-conductive shielding material, characterized in that: The present invention comprises the following raw materials in parts by weight: 32-34 parts of conductive carbon black, 63.4-65.4 parts of base resin, 1 part of lubricant, 0.5 part of antioxidant and 0.9-1 part of cross-linking agent. The conductive carbon black is the conductive carbon black prepared by the modification method according to any one of claims 1 to 4.

6. The ultra-high voltage cable semi-conductive shielding material according to claim 5, characterized in that: The matrix resin is ethylene-butyl acrylate and / or ethylene-ethyl acrylate.

7. The ultra-high voltage cable semi-conductive shielding material according to claim 5, characterized in that: The cross-linking agent is di-tert-butyl peroxyisopropylbenzene and / or diisopropylbenzene peroxide, the lubricant is zinc stearate, and the antioxidant is 4,4'-thiobis(6-tert-butyl-3-methylphenol).

8. A method for preparing a semi-conductive shielding material for an ultra-high voltage cable as claimed in any one of claims 5 to 7, characterized in that: The following steps are involved: S1, mixing conductive carbon black, lubricant, antioxidant and base resin, and drying to obtain a mixture; S2, melt-kneading the mixture obtained in S1 in a twin-screw extruder, with an extrusion temperature of 160-200° C. and a main engine speed of 80-140 rpm, and pelletizing and drying the extrudate to obtain pellets; S3, drying the pellets obtained in S2, grinding the cross-linking agent and mixing it with the pellets, and drying to obtain the ultra-high voltage cable semi-conductive shielding material.

9. The preparation method according to claim 8, characterized in that: In S1, the mixing stirring speed is 100-120 rpm, the mixing time is 30-60 min, the drying temperature is 60° C., and the drying time is 4 h.

10. The preparation method according to claim 8, characterized in that: In S3, the pellets are dried at 70°C for 6 hours, and the cross-linking agent is mixed with the pellets and dried at 60°C for 10 hours.

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