Modified conductive carbon black and preparation method thereof, semiconductive shielding material and preparation method thereof, and high-voltage cable

Abstract

The invention relates to modified conductive carbon black and a preparation method thereof, a semiconductive shielding material and a preparation method thereof, and a high-voltage cable. According to the preparation method of the modified conductive carbon black, oxidation treatment is carried out on the conductive carbon black, so that the surface energy of the conductive carbon black is reduced, hydroxyl of the conductive carbon black is oxidized into carboxyl, richer reaction sites are provided for modification, and the modified conductive carbon black of which the surface is uniformly grafted with polyvinyl alcohol is obtained. The preparation method of the modified conductive carbon black is simple to operate and uniform in grafting effect, a uniform and stable polyvinyl alcohol layer can be formed on the surface of the conductive carbon black by means of hydrogen bonds and chemical bonds, and the obtained modified conductive carbon black has good dispersity in a polymer matrix and also has good electrical properties.

Description

Technical Field

[0001] This application relates to the field of cable materials, and particularly to a modified conductive carbon black and its preparation method, a semiconductive shielding material and its preparation method, and a high-voltage cable. Background Art

[0002] The structure of a power cable involves parts such as a metal conductor core, an insulating layer, a semiconductive shielding layer, and a sheath. In the structure of a power cable, the main function of the semiconductive shielding layer is to fill air gaps, form a smooth and uniform connection interface, and thus evenly distribute the electric field intensity on the surface of the core, reducing the phenomenon of tip discharge. Therefore, the degree of surface smoothness of the semiconductive shielding layer greatly affects the voltage level and service life of the power cable.

[0003] However, the conductive carbon black in the semiconductive shielding layer often agglomerates, resulting in an uneven structure of the shielding layer and a decrease in surface smoothness, thereby causing uneven electric field distribution, increasing the risk of tip discharge and partial discharge, and even damaging the insulation structure of the cable, significantly deteriorating the electrical performance of the semiconductive shielding layer, and reducing the withstand voltage strength and operating stability of the cable. Summary of the Invention

[0004] Based on this, it is necessary to provide a modified conductive carbon black with good electrical properties that is not easily agglomerated in a polymer matrix and its preparation method, a semiconductive shielding material and its preparation method, and a high-voltage cable.

[0005] In the first aspect of this application, a preparation method of a modified conductive carbon black is provided.

[0006] A preparation method of a modified conductive carbon black includes the following steps:

[0007] Performing an oxidation treatment on the conductive carbon black to obtain oxidized conductive carbon black;

[0008] Mixing the oxidized conductive carbon black with a polyvinyl alcohol solution to obtain a first slurry;

[0009] Heating the first slurry under a protective gas atmosphere.

[0010] In some embodiments, the oxidation treatment includes:

[0011] Dispersing the conductive carbon black in an oxidation solution, stirring at 60°C to 90°C for 1 h to 3 h, and performing solid-liquid separation to obtain the oxidized conductive carbon black, where the solute of the oxidation solution includes hydrogen peroxide and nitric acid.

[0012] In some embodiments, the preparation method of the modified conductive carbon black satisfies one or more of the following conditions:

[0013] (1) The solvent of the polyvinyl alcohol solution includes water;

[0014] (2) The mass concentration of polyvinyl alcohol in the polyvinyl alcohol solution is 5% - 10%;

[0015] (3) The heating temperature is 70°C - 120°C;

[0016] (4) The heating time is 2h - 6h.

[0017] In some embodiments, the mass ratio of the conductive carbon black to the polyvinyl alcohol is 10:(1 - 3).

[0018] In the second aspect of the present application, a modified conductive carbon black is provided.

[0019] A modified conductive carbon black is prepared by using the above - mentioned preparation method of the modified conductive carbon black.

[0020] In the third aspect of the present application, a semi - conductive shielding material is provided.

[0021] A semi - conductive shielding material, by mass, the raw materials for preparing the semi - conductive shielding material include:

[0022] Matrix resin 50 parts - 70 parts;

[0023] Modified conductive carbon black 20 parts - 30 parts;

[0024] Dispersant 0.5 parts - 2 parts;

[0025] Cross - linker 0.9 parts - 2 parts; and

[0026] Functional additive 1 part - 6 parts;

[0027] Among them, the modified conductive carbon black includes the above - mentioned modified conductive carbon black.

[0028] In some embodiments, the matrix resin includes ethylene - butyl acrylate copolymer; and / or

[0029] The dispersant includes one or more of ethylene bisstearamide and oleic acid amide; and / or

[0030] The functional additive includes one or more of lubricant and antioxidant; and / or

[0031] The cross - linker includes one or more of diisopropylbenzene peroxide and bis - tert - butyl peroxyisopropylbenzene.

[0032] In the fourth aspect of the present application, a preparation method of the above - mentioned semi - conductive shielding material is provided.

[0033] A preparation method of the above - mentioned semi - conductive shielding material includes the following steps:

[0034] Mix the modified conductive carbon black, the functional additive, the dispersant and the matrix resin to obtain a first mixture;

[0035] Mix the first mixture and the crosslinking agent, and heat and crosslink to obtain the semiconductive shielding material.

[0036] In some embodiments, the temperature of the heat crosslinking is 40°C to 80°C; and / or

[0037] The time of the heat crosslinking is 5 h to 12 h.

[0038] In the fifth aspect of the present application, a high-voltage cable is provided.

[0039] A high-voltage cable includes a conductor, an insulating layer, and a semiconductive shielding layer; the conductor is located inside the insulating layer, and the semiconductive shielding layer is located on at least one surface of the insulating layer; the semiconductive shielding layer is made of the above-mentioned semiconductive shielding material or the semiconductive shielding material prepared by the above-mentioned preparation method.

[0040] The preparation method of the modified conductive carbon black of the present application helps to remove active molecules such as hydroxyl groups, ester groups, and lactone groups on the surface of the conductive carbon black by oxidative pretreatment of the conductive carbon black, thereby reducing the surface energy of the conductive carbon black; at the same time, by oxidizing the hydroxyl groups of the conductive carbon black to carboxyl groups through oxidative pretreatment, it can also provide more abundant reaction sites for modification, which helps to improve the grafting efficiency of polyvinyl alcohol. The preparation method of the modified conductive carbon black of the present application is simple in operation and has a uniform grafting effect, and can form a polyvinyl alcohol layer with an average thickness of about 1 nm to 8 nm on the surface of the conductive carbon black. The obtained modified conductive carbon black has good dispersibility in the polymer matrix and good electrical properties.

[0041] The modified conductive carbon black of the present application can form a physical coating layer on the surface of the carbon black in the form of physical adsorption through the hydrogen bonds formed between the hydroxyl groups on the polyvinyl alcohol molecular chain and the carbon black; and further, through further chemical reactions, polyvinyl alcohol and conductive carbon black can form chemical bonds with more stable connections, which can further improve the stability of the modified conductive carbon black and its dispersibility in the polymer matrix. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative efforts.

[0043] Figure 1Schematic diagram of the modification of modified conductive carbon black in an embodiment of the present application.

[0044] Figure 2 TEM electron micrograph of the modified conductive carbon black in Example 3 of the present application. Detailed implementation manners

[0045] To make the above objects, features, and advantages of the present application more obvious and understandable, the following provides a detailed description of the specific implementation manners of the present application. Many specific details are set forth in the following description to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0046] In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically defined. In the present application, the meaning of "at least one" is more than one, such as one, two, and more than two. The meaning of "a variety of" or "several" is at least two, such as two, three, etc.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs. The terms used in the description of the present application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0048] When a numerical range is disclosed herein, the above range is considered continuous and includes the minimum and maximum values of the range, as well as each value therebetween. Further, when the range refers to an integer, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0049] If there is no special instruction, all steps of the present application can be carried out sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), indicating that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c) in sequence, or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0050] In this application, "above" or "below" both include the recited number. For example, 1 below includes 1.

[0051] The temperature parameter in this application, without special limitation, allows both constant temperature treatment and variation within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuation within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, ±1°C is allowed.

[0052] In the semiconductive shielding layer of a power cable, the agglomeration of conductive carbon black can lead to an uneven structure of the shielding layer and a decrease in surface smoothness, thereby causing uneven electric field distribution, increasing the risk of tip discharge and partial discharge. As the cable operates for a long time, such electric field defects will accelerate the aging of the insulating layer, shorten the service life of the cable, and even cause insulation breakdown faults under high-voltage loads, resulting in power transmission interruption or more serious safety accidents.

[0053] Based on this, the first aspect of this application provides a method for preparing modified conductive carbon black with good electrical properties that is not easily agglomerated in a polymer matrix.

[0054] The first aspect of this application provides a method for preparing modified conductive carbon black.

[0055] Exemplarily, please refer to Figure 1 , Figure 1 , which is a schematic diagram of the modification of modified conductive carbon black in an embodiment of this application. The method for preparing modified conductive carbon black includes the following steps:

[0056] Perform oxidation treatment on the conductive carbon black to obtain oxidized conductive carbon black;

[0057] Mix the oxidized conductive carbon black with a polyvinyl alcohol solution to obtain a first slurry;

[0058] Heat the first slurry in a protective gas atmosphere.

[0059] The above method for preparing modified conductive carbon black helps to remove active molecules such as hydroxyl groups, ester groups, and lactone groups on the surface of the conductive carbon black through oxidation pretreatment, thereby reducing the surface energy of the conductive carbon black; at the same time, oxidizing the hydroxyl groups of the conductive carbon black to carboxyl groups provides more abundant reaction sites for modification, which helps to obtain modified conductive carbon black with uniformly grafted polyvinyl alcohol on the surface. The method for preparing modified conductive carbon black in this application is simple to operate, has a high grafting rate, and the reaction degree is controllable. The obtained modified conductive carbon black has good dispersibility in the polymer matrix.

[0060] In some of these embodiments, the steps of the oxidation treatment include:

[0061] Disperse conductive carbon black in an oxidation solution, stir at 60°C to 90°C for 1h to 3h, and perform solid-liquid separation to obtain oxidized conductive carbon black. Optionally, the solute of the oxidation solution includes hydrogen peroxide and nitric acid.

[0062] In some embodiments, the mass ratio of the sum of the masses of hydrogen peroxide and nitric acid to the mass of conductive carbon black is (2 to 5):1. Optionally, the above mass ratio can be 2:1, 3:1, 4:1, 5:1, or other values within the range of (2 to 5):1.

[0063] In some embodiments, the oxidation solution includes a mixed solution of hydrogen peroxide with a volume fraction of 20% to 35% and 1 to 3 mol of nitric acid. Selecting the hydrogen peroxide aqueous solution with the above volume fraction helps to make the oxidation of conductive carbon black more thorough and reduce the impact on the intrinsic structure of conductive carbon black.

[0064] Optionally, the temperature of the oxidation treatment can be 60°C, 70°C, 80°C, 90°C, or other temperatures within the range of 60°C to 90°C. The time of the oxidation treatment can be 1h, 1.5h, 2h, 2.5h, 3h, or other times within the range of 1h to 3h. Maintaining the above time and temperature selection helps to make the oxidation of conductive carbon black more thorough and reduce the impact on the intrinsic structure of conductive carbon black.

[0065] In some embodiments, it further includes the step of washing the oxidized conductive carbon black:

[0066] Use deionized water to repeatedly wash the oxidized conductive carbon black until the filtrate is neutral, and dry at 60 to 80°C for 0.5h to 3h.

[0067] In some embodiments, after mixing the oxidized conductive carbon black with an aqueous solution of polyvinyl alcohol, pour it into a ball mill for further mechanical grinding and mixing, and grind at a rotation speed of 150 rpm to 300 rpm for 8h to 16h to obtain a first slurry.

[0068] Optionally, use a mixer to mix and granulate the first slurry. Granulate evenly.

[0069] Among them, the rotation speed of the mixer is 100 rpm to 140 rpm, the temperature is 20°C to 35°C, and the mixing time is 10 min.

[0070] In some embodiments, the protective gas includes one or more of nitrogen and argon. Heating in a protective gas atmosphere can avoid the influence of oxygen on the reaction and reduce the impurities of the product.

[0071] In some embodiments, before heating the first slurry, continuously introduce a protective gas to remove oxygen in the reaction system.

[0072] In some of these embodiments, after heating the first slurry in a protective gas atmosphere, it is washed with water and a precipitate product is obtained, and the precipitate product is dried under vacuum to obtain modified conductive carbon black.

[0073] In some of these embodiments, the solvent of the polyvinyl alcohol solution includes water.

[0074] In some of these embodiments, the mass concentration of the polyvinyl alcohol solution is 5% - 10%. Optionally, the mass concentration of the polyvinyl alcohol solution can be 5%, 6%, 7%, 8%, 9%, 10% or other concentrations within the range of 5% - 10%. Keeping the mass concentration of the polyvinyl alcohol solution within the above range helps to obtain a first slurry with good fluidity and uniform dispersion.

[0075] In some of these embodiments, the heating temperature of the first slurry in a protective gas atmosphere is 70°C - 120°C. Optionally, the heating temperature can be 70°C, 80°C, 90°C, 100°C, 110°C, 120°C or other temperatures within the range of 70°C - 120°C. Keeping the heating temperature within the above range helps to adjust the reaction rate to a suitable range and make the grafting more uniform.

[0076] In some of these embodiments, the heating time of the first slurry in a protective gas atmosphere is 2h - 6h. Optionally, the heating time can be 2h, 3h, 4h, 5h, 6h or other times within the range of 2h - 6h.

[0077] In some of these embodiments, the mass ratio of conductive carbon black to polyvinyl alcohol is 10:(1 - 3). Optionally, the mass ratio of conductive carbon black to polyvinyl alcohol can be 10:1, 10:2, 10:3 or other ratios within the range of 10:(1 - 3). Keeping the mass ratio of conductive carbon black to polyvinyl alcohol within the above range helps to form a polyvinyl alcohol modified layer with uniform grafting and appropriate thickness on the surface of the oxidized conductive carbon black.

[0078] In some of these embodiments, the conductive carbon black is a low-structured high-purity type conductive carbon black with an ash content < 0.1%.

[0079] In some of these embodiments, the DBP absorption value of the conductive carbon black is 130 mL / 100g - 150 mL / 100g.

[0080] In some of these embodiments, the degree of polymerization of the polyvinyl alcohol is from 1500 to 1800. The degree of polymerization of the polyvinyl alcohol can be 1500, 1600, 1650, 1700, 1750, 1800 or other values within the range of 1500 to 1800. Maintaining the degree of polymerization of the polyvinyl alcohol within the above range helps to form a polyvinyl alcohol modification layer with a relatively high grafting degree on the surface of the oxidized conductive carbon black, and can endow the first slurry with good processing fluidity.

[0081] In the second aspect of the present application, there is provided a modified conductive carbon black prepared by the preparation method of the above-mentioned modified conductive carbon black. For the above-mentioned modified conductive carbon black, through the hydrogen bonds formed between the hydroxyl groups on the polyvinyl alcohol molecular chain and the carboxyl groups on the carbon black surface, a physical coating layer can be formed on the carbon black surface in the form of physical adsorption; at the same time, through further chemical grafting reactions, the connection between the polyvinyl alcohol and the conductive carbon black becomes more stable, further improving the stability of the modified conductive carbon black and its dispersibility in the polymer matrix. Especially in an ultra-high voltage environment, the above-mentioned modified conductive carbon black still has a stable structure and excellent dispersibility.

[0082] In some of these embodiments, the modified conductive carbon black includes conductive carbon black and a polyvinyl alcohol layer located on at least a part of the surface of the conductive carbon black.

[0083] In some of these embodiments, the average thickness of the polyvinyl alcohol layer is from 1 nm to 8 nm. Optionally, the average thickness of the polyvinyl alcohol layer can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm or other values within the range of 1 nm to 8 nm. Maintaining the thickness of the polyvinyl alcohol layer within the above range helps to reduce the influence of the electron tunneling effect on the electrical properties of the conductive carbon black.

[0084] In the third aspect of the present application, there is provided a semi-conductive shielding material.

[0085] By mass, the raw materials for preparing the semi-conductive shielding material include:

[0086] 50 parts to 70 parts of matrix resin;

[0087] 20 parts to 30 parts of modified conductive carbon black;

[0088] 0.5 parts to 2 parts of dispersant;

[0089] 0.9 parts to 2 parts of cross-linking agent; and

[0090] 1 part to 6 parts of functional additives;

[0091] wherein, the modified conductive carbon black includes the above-mentioned modified conductive carbon black.

[0092] In the above-mentioned semiconductive shielding material, the modified conductive carbon black obtained by chemically grafting polyvinyl alcohol can not only improve the dispersion of the modified conductive carbon black in the polymer matrix, but also help to improve the fluidity and processing performance of the preparation raw materials, so that the preparation raw materials maintain a more stable melt state during the processing process.

[0093] In some of these embodiments, the matrix resin includes an ethylene-butyl acrylate copolymer. The coating layer of the modified conductive carbon black of the present application is polyvinyl alcohol, which is polar-matched with the ethylene-butyl acrylate copolymer, and the interfacial compatibility between the two is good, which helps to further improve the dispersion effect of the modified conductive carbon black in the matrix resin and further improve the surface smoothness of the semiconductive shielding material.

[0094] In some of these embodiments, the dispersant includes one or more of ethylene bisstearamide and oleic acid amide.

[0095] In some of these embodiments, the crosslinking agent includes one or more of diisopropylbenzene peroxide and bis(tert-butylperoxyisopropyl)benzene.

[0096] In some of these embodiments, the functional additives include one or more of lubricants and antioxidants. Optionally, the lubricant includes zinc stearate.

[0097] In the fourth aspect of the present application, a preparation method of the above-mentioned semiconductive shielding material is provided.

[0098] The preparation method of the semiconductive shielding material includes the following steps:

[0099] Mix the modified conductive carbon black, functional additives, dispersant and the matrix resin to obtain a first mixture;

[0100] Mix the first mixture and the crosslinking agent, and heat and crosslink to obtain the semiconductive shielding material.

[0101] In some of these embodiments, a mixer is used to mix the modified conductive carbon black, functional additives, dispersant and the matrix resin at room temperature. The rotation speed of the mixer is 100 rpm to 150 rpm, and the mixing time is 5 min to 20 min.

[0102] In some of these embodiments, after mixing the modified conductive carbon black, functional additives, dispersant and the matrix resin, it further includes the steps of melt blending, extruding and pelletizing the first mixture.

[0103] In some of these embodiments, a twin-screw extruder is used to melt blend and extrude the first mixture, the rotation speed is 80 rpm to 120 rpm, the extrusion temperature is 150 °C to 170 °C, and then discharging, mechanical compression, underwater pelletizing and drying are carried out.

[0104] In some of these embodiments, the crosslinking agent is subjected to grinding pretreatment. The crosslinking agent is ground using a grinder for 10 min or until it is uniform and has no obvious particles.

[0105] In some of these embodiments, the temperature for heat crosslinking is 40°C to 80°C.

[0106] In some of these embodiments, the time for heat crosslinking is 5 h to 12 h.

[0107] In the fifth aspect of the present application, a high-voltage cable is provided.

[0108] A high-voltage cable includes a conductor, an insulating layer, and a semiconductive shielding layer; the conductor is located inside the insulating layer, and the semiconductive shielding layer is located on at least one surface of the insulating layer. The semiconductive shielding layer is made of the above-mentioned semiconductive shielding material or the semiconductive shielding material prepared by the above-mentioned preparation method.

[0109] The following further describes the present application in detail with specific embodiments.

[0110] In the following specific embodiments and comparative examples, the raw materials used, unless otherwise specified, are all commercially available products; the instruments used, unless otherwise specified, are all commercially available products; the processes used, unless otherwise specified, are all conventional selections by those skilled in the art.

[0111] Example 1

[0112] This example provides a modified conductive carbon black and a semiconductive shielding material.

[0113] The preparation method of the modified conductive carbon black is as follows:

[0114] By mass, 10 parts of conductive carbon black (high-purity conductive carbon black, DBP absorption value 140 mL / 100 g, ash content < 0.1%) are dispersed in an oxidation solution (20 parts of hydrogen peroxide, 10 parts of nitric acid, and 70 parts of water), ultrasonically dispersed evenly, stirred in a water bath at 70°C for 2 h, and the magnetic stirring speed is 100 rpm. Subsequently, it is cooled to room temperature, filtered by suction, and the precipitate is repeatedly washed with deionized water until the filtrate is neutral. The precipitate is transferred into an oven at 80°C and dried for 1 h to obtain oxidized conductive carbon black.

[0115] The oxidized conductive carbon black is dispersed in an 8 wt% aqueous solution of polyvinyl alcohol containing 1 part of polyvinyl alcohol (degree of polymerization 1750), poured into a ball mill for further mechanical grinding and mixing, ground at 200 rpm for 12 h, then transferred to a mixer, mixed at 120 rpm for 10 min, and granulated to obtain a first slurry.

[0116] Add the first slurry into a container. After deoxygenating the reaction system, stir it under the protection of argon gas and react for 3 h in a 90 °C water bath. Wash the product with deionized water and vacuum-dry the precipitate to obtain modified conductive carbon black.

[0117] The preparation method of the semi-conductive shielding material is as follows:

[0118] By weight, the raw materials for preparing the semi-conductive shielding material are as follows:

[0119] Matrix resin: 65.5 parts;

[0120] Modified conductive carbon black: 30 parts;

[0121] Dispersant: 2 parts;

[0122] Functional additive: 1.5 parts; and

[0123] Crosslinking agent: 1 part.

[0124] Among them, the modified conductive carbon black is the modified conductive carbon black prepared in this example; the matrix resin is ethylene-butyl acrylate; the dispersant is ethylene bis-stearamide; the crosslinking agent is diisopropylbenzene peroxide; the functional additive contains 1 part of lubricant and 0.5 part of antioxidant. The lubricant is zinc stearate and the antioxidant is antioxidant 300.

[0125] Use a high-speed mixer to mix the matrix resin, conductive carbon black, dispersant, and functional additive evenly at room temperature of 25 °C, and then carry out melt blending and extrusion in a twin-screw extruder. After discharging, mechanical compression, underwater pelletizing, and drying in an oven, a first mixture is obtained; among them, the rotation speed of the high-speed mixer is 120 rpm and the mixing time is 10 min; the extrusion temperature of the twin-screw extruder is 160 °C and the rotation speed is 100 rpm.

[0126] Place the first mixture in a constant-temperature oven at 60 °C and dry for 4 h. Grind the crosslinking agent for 10 min using a grinder, and then mix the semi-conductive shielding material and the evenly ground crosslinking agent evenly, and keep it at a constant temperature in an oven at 60 °C for 8 h to obtain the semi-conductive shielding material.

[0127] Example 2

[0128] This example provides a modified conductive carbon black and a semi-conductive shielding material.

[0129] This example is basically the same as Example 1, except that when preparing the modified conductive carbon black, 2 parts of polyvinyl alcohol are used.

[0130] Example 3

[0131] This example provides a modified conductive carbon black and a semi-conductive shielding material. Please refer to Figure 2 , Figure 2TEM image of the modified conductive carbon black of this example, where the thickness of the polyvinyl alcohol layer is about 2 nm.

[0132] This example is basically the same as Example 1, except that: when preparing the modified conductive carbon black, 3 parts of polyvinyl alcohol are used.

[0133] Example 4

[0134] This example provides a modified conductive carbon black and a semi-conductive shielding material.

[0135] This example is basically the same as Example 1, except that: when preparing the modified conductive carbon black, 5 parts of polyvinyl alcohol are used.

[0136] Comparative Example 1

[0137] This comparative example provides a modified conductive carbon black and a semi-conductive shielding material.

[0138] This comparative example is basically the same as Example 1, except that: the conductive carbon black is not subjected to oxidation treatment.

[0139] Comparative Example 2

[0140] This comparative example provides a modified conductive carbon black and a semi-conductive shielding material.

[0141] This comparative example is basically the same as Example 1, except that: in an inert gas atmosphere, the first slurry is stirred at room temperature for 6 h to obtain the modified conductive carbon black.

[0142] Comparative Example 3

[0143] This comparative example provides a semi-conductive shielding material.

[0144] This comparative example is basically the same as Example 1, except that: conductive carbon black is used to replace the modified conductive carbon black.

[0145] Comparative Example 4

[0146] This comparative example provides a semi-conductive shielding material.

[0147] This comparative example is basically the same as Example 1, except that: in the raw materials for preparing the semi-conductive shielding material, unmodified conductive carbon black is used to replace the modified conductive carbon black, and no dispersant is added.

[0148] Test Example

[0149] The semi-conductive shielding materials obtained from the examples and comparative examples were hot-pressed in a flat vulcanizing machine for 15 min and cold-pressed for 6 min to prepare the semi-conductive shielding layer of the extra-high voltage cable, and their electrical and mechanical properties were measured. A strip-shaped semi-conductive shielding layer was prepared by a single-screw extruder, and the surface smoothness of the strip-shaped material was observed using an optical microscope. Five different test areas (1 cm 2 were selected, and the number of defects (protrusions or depressions) with two-dimensional dimensions exceeding 50 µm was counted. The test results of each property are shown in Table 1.

[0150] Table 1

[0151]

[0152] From the comparison between the examples and the comparative examples, it can be seen that the semi-conductive shielding materials added with modified conductive carbon black exhibited better mechanical properties, electrical properties, and surface smoothness, indicating that the modified conductive carbon black had excellent dispersion in the polymer matrix and formed a more developed conductive path. At the same time, the stress concentration points caused by filler agglomeration decreased, resulting in the optimization of the mechanical and electrical properties of the semi-conductive shielding material while the surface smoothness was also significantly improved, which was beneficial to improving the interfacial effect during the long-term use of the semi-conductive shielding material. It can be seen from Example 4 that as the addition amount of polyvinyl alcohol further increased, the mechanical and electrical properties of the semi-conductive shielding material prepared from the modified conductive carbon black did not change significantly, but the electrical properties decreased, and it was more significantly affected by temperature. It may be that more polyvinyl alcohol affected the electrical properties of the conductive carbon black network.

[0153] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0154] The above-described embodiments only represent several implementation manners of the present application. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the invention patent should be subject to the appended claims, and the specification can be used to explain the content of the claims.

Claims

1. A preparation method of modified conductive carbon black, characterized in that, It includes the following steps: Oxidize the conductive carbon black to obtain oxidized conductive carbon black; Mix the oxidized conductive carbon black with a polyvinyl alcohol solution to obtain a first slurry; Heat the first slurry in an atmosphere of protective gas.

2. The preparation method of the modified conductive carbon black according to claim 1, wherein, The oxidation treatment includes: Disperse the conductive carbon black in an oxidation solution, stir at 60°C to 90°C for 1 h to 3 h, perform solid-liquid separation to obtain the oxidized conductive carbon black; the solute of the oxidation solution includes hydrogen peroxide and nitric acid.

3. The preparation method of the modified conductive carbon black according to claim 1, characterized in that, The preparation method of the modified conductive carbon black satisfies one or more of the following conditions: (1) The solvent of the polyvinyl alcohol solution includes water; (2) The mass concentration of polyvinyl alcohol in the polyvinyl alcohol solution is 5% to 10%; (3) The temperature of the heating is 70°C to 120°C; (4) The time of the heating is 2 h to 6 h.

4. The preparation method of the modified conductive carbon black according to any one of claims 1 to 3, characterized in that, The mass ratio of the conductive carbon black to the polyvinyl alcohol is 10:(1 to 3).

5. A modified conductive carbon black, characterized in that, It is prepared by using the preparation method of the modified conductive carbon black according to any one of claims 1 to 4.

6. A semiconductive shielding material, characterized in that, By mass, the raw materials for preparing the semi-conductive shielding material include: 50 parts to 70 parts of matrix resin; 20 parts to 30 parts of modified conductive carbon black; 0.5 part to 2 parts of dispersant; 0.9 part to 2 parts of crosslinking agent; and 1 part to 6 parts of functional additive; Among them, the modified conductive carbon black includes the modified conductive carbon black according to claim 5.

7. The semi-conductive shielding material according to claim 6, characterized in that, The matrix resin includes ethylene-butyl acrylate copolymer; and / or The dispersant includes one or more of ethylene bisstearamide and oleic acid amide; and / or The functional additive includes one or more of lubricant and antioxidant; and / or The crosslinking agent includes one or more of diisopropylbenzene peroxide and bis(tert-butylperoxyisopropyl)benzene.

8. A method for preparing the semiconductive shielding material according to any one of claims 6 to 7, characterized in that, It includes the following steps: Mix the modified conductive carbon black, the functional additive, the dispersant and the matrix resin to obtain a first mixture; Mix the first mixture and the crosslinking agent, and heat and crosslink to obtain the semi-conductive shielding material.

9. The preparation method of the semi-conductive shielding material according to claim 8, characterized in that, The temperature of the heat crosslinking is 40°C to 80°C; and / or The time of the heat crosslinking is 5 h to 12 h.

10. A high-voltage cable, characterized in that, It includes a conductor, an insulating layer and a semi-conductive shielding layer; the conductor is located inside the insulating layer, and the semi-conductive shielding layer is located on at least one surface of the insulating layer; the semi-conductive shielding layer is made of the semi-conductive shielding material according to any one of claims 6 to 7 or the semi-conductive shielding material prepared by the preparation method according to any one of claims 8 to 9.

Images