Conductive carbon black, modification method thereof, high-voltage cable shielding material and high-voltage cable

Abstract

The invention relates to conductive carbon black, a modification method thereof, a high-voltage cable shielding material and a high-voltage cable. The modification method of the conductive carbon black comprises the following steps: mixing the conductive carbon black and an organic solvent, and carrying out swelling treatment; performing first heat treatment and second heat treatment on the swelling conductive carbon black; and performing post-treatment on the swelled conductive carbon black subjected to the second heat treatment to obtain the modified conductive carbon black with high carbon black oil absorption (DBP) and surface oxygen content of less than or equal to 0.5%. According to the method, through the synergistic effect of swelling treatment, first heat treatment, second heat treatment and post-treatment, oxygen-containing functional groups mainly including lactone oxygen and carboxyl oxygen in the conductive carbon black are effectively removed, the obtained modified conductive carbon black can keep a high DBP value, a high-quality channel can be provided for electron transmission, and the service life of the conductive carbon black is prolonged. The performance requirement of a high-voltage cable shielding material on the conductive filler can be met.

Description

Technical Field

[0001] The present application relates to the technical field of high-voltage cables, and in particular to a conductive carbon black and a modification method thereof, a high-voltage cable shielding material and a high-voltage cable. Background Art

[0002] Conductive carbon black is a special type of carbon black. Thanks to its nano-scale porous structure, conductive carbon black can provide a high-quality channel for the transmission of electrons. It has the advantages of good conductivity, easy processing and low price. It is widely used in various conductive products and is a common conductive filler selected for industrial production of high-voltage cable shielding materials.

[0003] According to the use of air in the production process, more oxygen-containing functional groups will be formed on the surface of conductive carbon black, which will reduce the stability and conductivity of conductive carbon black. Therefore, conductive carbon black often needs to be modified to reduce its surface oxygen content. However, traditional modification methods will destroy the intrinsic structure of conductive carbon black aggregates, which is manifested as a decrease in the carbon black oil absorption value (DBP) of conductive carbon black. It is difficult to obtain conductive carbon black with a lower oxygen content based on a higher DBP value, which restricts the further expansion of the use of conductive carbon black. Summary of the invention

[0004] Based on this, it is necessary to provide a modification method for conductive carbon black that can obtain a lower oxygen content while maintaining a higher DBP value of the conductive carbon black.

[0005] In a first aspect of the present application, a method for modifying conductive carbon black is provided, comprising the following steps:

[0006] The conductive carbon black is swelled in an organic solvent to prepare swollen conductive carbon black;

[0007] Under a protective gas atmosphere, subjecting the swollen conductive carbon black to a first heat treatment at 200° C. to 400° C.;

[0008] A reducing gas is introduced into the protective gas atmosphere, and the swollen conductive carbon black after the first heat treatment is subjected to a second heat treatment at 500° C. to 600° C.

[0009] In some embodiments, the first heat treatment comprises the following steps:

[0010] Raise the temperature to 200℃~400℃ at a heating rate of 2℃ / min~20℃ / min and keep it warm for 0.5h~6h.

[0011] In some embodiments, the second heat treatment comprises the following steps:

[0012] Raise the temperature to 500℃~600℃ at a heating rate of 10℃ / min~20℃ / min and keep it at this temperature for 0.5h~2h.

[0013] In some embodiments, the volume fraction of the reducing gas in the protective gas atmosphere is 5% to 15%.

[0014] In some embodiments, the flow rate of the reducing gas is 20-50 mL / min.

[0015] In some embodiments, the reducing gas comprises H 2 .

[0016] In some embodiments, the second heat treatment further comprises:

[0017] The conductive carbon black after the second heat treatment is mixed with an extraction solvent, and the mixture is subjected to microwave irradiation treatment.

[0018] In some embodiments, the volume mass ratio of the extraction solvent to the conductive carbon black after the second heat treatment is 30 mL / g to 50 mL / g.

[0019] In some embodiments, the extraction solvent includes one or more of methanol, diethylene glycol, and n-butanol.

[0020] In some embodiments, the frequency of the microwave irradiation treatment is 2 GHz to 3 GHz.

[0021] In some embodiments, the power of the microwave irradiation treatment is 500W~1000W.

[0022] In some embodiments, the microwave irradiation treatment time is 5 min to 10 min.

[0023] In some embodiments, the swelling treatment comprises: mixing the conductive carbon black and the organic solvent and then letting the mixture stand for 6 hours to 24 hours.

[0024] In some embodiments, the volume mass ratio of the organic solvent to the conductive carbon black is 20 mL / g to 50 mL / g.

[0025] In some embodiments, the organic solvent includes one or more of tetrahydrofuran, carbon disulfide, tetrachloroethylene and N-methylpyrrolidone.

[0026] In a second aspect of the present application, a modified conductive carbon black is provided, which is prepared by the modification method of the conductive carbon black.

[0027] In a third aspect of the present application, a high-voltage cable shielding material is provided, comprising the modified conductive carbon black.

[0028] In a fourth aspect of the present application, a high-voltage cable is provided, comprising the high-voltage cable shielding material.

[0029] In the above-mentioned modification method of conductive carbon black, the conductive carbon black is first subjected to a swelling treatment, so that the aggregate structure of the conductive carbon black can be stretched, and then the oxygen-containing functional groups in the conductive carbon black can be removed through the coordination of the first heat treatment and the second heat treatment, and the intrinsic structure of the conductive carbon black can be effectively protected, so that the conductive carbon black can obtain a lower oxygen content while maintaining a higher DBP value. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the steps of a conductive carbon black modification method in one embodiment of the present application.

[0031] Figure 2 This is a schematic diagram of the steps of a conductive carbon black modification method in another embodiment of the present application. DETAILED DESCRIPTION

[0032] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below. In the following description, many specific details are set forth 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 violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0033] In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In this application, "at least one" means more than one, such as one, two and more than two. "Multiple" or "several" means at least two, such as two, three, etc.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0035] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0036] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0037] In this application, "above" or "below" includes the number itself. For example, "1 below" includes 1.

[0038] The temperature parameters in the invention, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the precision range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0039] In the formation process of conductive carbon black graphite microcrystals, in order to achieve a saturated stable state, the active aromatic groups not only combine with each other, but also combine with oxygen-containing groups to form a large number of oxygen-containing functional groups on the surface. The role of oxygen-containing functional groups is equivalent to electron traps, which will hinder the movement of π electrons and reduce the conductivity of conductive carbon black. In addition, oxygen-containing functional groups can also react chemically with other compounds. For example, carboxyl and hydroxyl groups can react with acyl chlorides to form esterification products, thereby affecting the performance stability of conductive carbon black. After being compounded with polymer matrix resins, it will also reduce the electrical properties of cable shielding materials. Therefore, it is necessary to deoxidize the conductive carbon black to prepare conductive carbon black with low surface oxygen-containing functional groups (oxygen content ≤ 0.5%).

[0040] In order to solve the problem of excessive oxygen functional groups on the surface of activated carbon and coal, hydrogen thermal reduction treatment technology is currently often used. However, when it comes to the research field of conductive carbon black, traditional hydrogen thermal reduction technology will cause a certain degree of damage to the intrinsic structure of conductive carbon black, reduce the DBP value of conductive carbon black, and ultimately affect the performance of conductive carbon black.

[0041] See also Figure 1 , Figure 1 The present invention is a flowchart of the steps of the conductive carbon black modification method in one embodiment of the present invention. The conductive carbon black modification method includes the following steps:

[0042] The conductive carbon black is swelled in an organic solvent to prepare swollen conductive carbon black;

[0043] Under a protective gas atmosphere, subjecting the swollen conductive carbon black to a first heat treatment at 200° C. to 400° C.;

[0044] A reducing gas is introduced into the protective gas atmosphere, and the swollen conductive carbon black after the first heat treatment is subjected to a second heat treatment at 500° C. to 600° C.

[0045] In the modification method of the conductive carbon black of the present embodiment, the conductive carbon black is first subjected to a swelling treatment so that the aggregate structure of the conductive carbon black can be stretched. Then, the oxygen-containing functional groups in the conductive carbon black can be removed through the coordination of the first heat treatment and the second heat treatment. In addition, the intrinsic structure of the conductive carbon black can be effectively protected, so that the conductive carbon black can obtain a lower oxygen content while maintaining a higher DBP value.

[0046] Optionally, the raw materials for preparing the conductive carbon black include one or more of anthracene oil and coal tar.

[0047] Optionally, the preparation method of the conductive carbon black includes a furnace method, a tank method and a thermal cracking method, and the furnace method includes an oil furnace method.

[0048] Optionally, the average particle size of the conductive carbon black is 38 nm.

[0049] Optionally, the DBP value of the conductive carbon black is 145 mL / g.

[0050] Optionally, the conductive carbon black has an iodine absorption value of 72 g / kg.

[0051] Alternatively, a 325 mesh sieve residue of conductive carbon black includes 9 ppm of powder.

[0052] It can be understood that the oxygen-containing functional groups on the surface of conductive carbon black are studied by elemental analyzer and XPS, and combined with peak fitting, the types and relative contents of oxygen-containing functional groups of conductive carbon black can be obtained. The results show that the types of oxygen-containing functional groups of conductive carbon black include lactone group, carboxyl group, phenolic hydroxyl group, quinone group, carbonyl group, acid anhydride and ether bond, among which lactone group and carboxyl group have the highest content.

[0053] In some embodiments, the conductive carbon black has a surface oxygen content greater than 5%.

[0054] In some embodiments, the oxygen-containing functional groups on the surface of the conductive carbon black include lactone oxygen, carboxyl oxygen, phenolic hydroxyl oxygen, quinone oxygen, carbonyl oxygen, anhydride oxygen and ether oxygen.

[0055] In some embodiments, the oxygen-containing functional groups on the surface of the conductive carbon black are mainly lactone oxygen and carboxyl oxygen.

[0056] It can be understood that during the swelling process, the solvent molecules penetrate and diffuse into the aggregate structure of the conductive carbon black, breaking the hydrogen bonds between the oxygen-containing functional groups on the surface of the conductive carbon black, so that the aggregate structure of the conductive carbon black is fully stretched. The change in the aggregate structure of the conductive carbon black during the swelling process has an important influence on the decomposition of the oxygen-containing functional groups during the pyrolysis process.

[0057] In some embodiments, the organic solvent used for the swelling treatment includes one or more of tetrahydrofuran, carbon disulfide, tetrachloroethylene, and N-methylpyrrolidone.

[0058] Optionally, the volume mass ratio of the organic solvent to the conductive carbon black is 20 mL / g to 50 mL / g. Including but not limited to: 20 mL / g, 30 mL / g, 40 mL / g, 50 mL / g. The volume mass ratio of the organic solvent to the conductive carbon black refers to the ratio of the volume of the organic solvent to the mass of the conductive carbon black. For example, the volume mass ratio of the organic solvent to the conductive carbon black is 10 mL / g, which means that 10 mL of organic solvent is added to 1 g of conductive carbon black.

[0059] Optionally, the temperature of the swelling treatment is 15°C to 35°C, including but not limited to: 15°C, 20°C, 25°C, 30°C, 35°C.

[0060] Optionally, the duration of the swelling treatment is 6 h to 24 h, including but not limited to: 6 h, 10 h, 14 h, 18 h, 22 h, 24 h.

[0061] In some embodiments, the process further includes separating the mixture after the swelling treatment to remove the organic solvent or other impurities dissolved in the organic solvent to obtain swollen conductive carbon black.

[0062] Optionally, the separation process includes the following steps: centrifuging the mixture after the swelling process to use the solid phase as the swelling conductive carbon black. The centrifugal treatment conditions include: a rotation speed of 1000rad / min to 5000rad / min, including but not limited to: 1000rad / min, 3000rad / min, 5000rad / min; a time of 10min to 20min, including but not limited to: 10min, 15min, 20min.

[0063] Optionally, the first heat treatment comprises the following steps: placing the swollen conductive carbon black in a vacuum tube furnace, introducing protective gas at a rate of 2L / min~5L / min to exhaust the air in the vacuum tube, reducing the gas flow rate to 0.5L / min~1.5L / min, and heating the temperature to 200℃~400℃ at a heating rate of 2℃ / min~20℃ / min under a protective gas atmosphere, and maintaining the temperature for 0.5h~6h;

[0064] Optionally, the heating rate of the first heat treatment is 2°C / min to 20°C / min, including but not limited to: 2°C / min, 8°C / min, 12°C / min, 16°C / min, and 20°C / min.

[0065] Optionally, the temperature of the first heat treatment is 200°C~400°C, including but not limited to: 200°C, 250°C, 300°C, 350°C, 400°C.

[0066] Through qualitative and quantitative analysis of the surface oxygen-containing functional groups of conductive carbon black, it can be found that the content of lactone and carboxyl groups is relatively high, and their thermal stability is poorer than that of other oxygen-containing functional groups. Carboxyl groups generally begin to crack at 200°C, and ester groups have stronger thermal stability than carboxyl groups, which begin to crack at 300°C. Therefore, when the temperature of the first heat treatment is limited to between 200°C and 400°C, it can not only effectively remove most of the surface oxygen-containing functional groups, but also effectively avoid the destruction of the structure of the conductive carbon black aggregates.

[0067] Optionally, the time of the first heat treatment is 0.5h~6h, including but not limited to: 0.5h, 1h, 2h, 3h, 4h, 5h, 6h.

[0068] It is understandable that the DBP value of conductive carbon black is related to the heat treatment time. If the heat treatment time is too long, the damage to the intrinsic structure of the conductive carbon black will be magnified; if the heat treatment time is too short, it will not be possible to obtain conductive carbon black with a low oxygen content. Therefore, when the holding time of the first heat treatment is limited to between 0.5h and 6h, it can not only avoid the damage to the structure of the conductive carbon black aggregate during the heat treatment process, but also effectively remove the oxygen-containing functional groups on its surface.

[0069] Optionally, the protective gas used in the first heat treatment includes N 2 or Ar.

[0070] It can be understood that performing the first heat treatment under a protective gas atmosphere can prevent the conductive carbon black from surface oxidation, which is beneficial to ensuring the purity and electrical properties of the conductive carbon black.

[0071] Optionally, the initial ventilation rate of the protective gas is 2L / min~5L / min, including but not limited to: 2L / min, 3L / min, 4L / min, 5L / min.

[0072] Optionally, after the air in the vacuum tube is exhausted, the ventilation rate of the protective gas is 0.5L / min~1.5L / min, including but not limited to: 0.5L / min, 1L / min, 1.5L / min.

[0073] Optionally, the second heat treatment includes the following steps: placing the first heat-treated conductive carbon black in a vacuum tube furnace, introducing protective gas and reducing gas into the vacuum tube furnace, heating the temperature to 500°C~600°C at a heating rate of 10°C / min~20°C / min, keeping the temperature constant for 0.5h~2h, and then naturally cooling to room temperature.

[0074] Optionally, the reducing gas includes H 2 In the protective gas, the volume fraction of reducing gas is 5%~15%, including but not limited to: 5%, 10%, 15%; the flow rate is 20~50mL / min, including but not limited to: 20mL / min, 30mL / min, 40mL / min, 50mL / min.

[0075] Optionally, the shielding gas includes Ar, and the volume fraction is 85% to 95%, including but not limited to: 85%, 90%, 95%; the flow rate is 20 to 50 mL / min, including but not limited to: 20 mL / min, 30 mL / min, 40 mL / min, 50 mL / min.

[0076] It can be understood that after the swelling treatment and the first heat treatment, the carboxyl group and the ester group are converted into a more thermally stable CO bond, which is often difficult to remove by simple heat treatment. Therefore, a certain proportion of reducing gas and protective gas are mixed to improve the removal rate of oxygen-containing functional groups in an atmosphere including reducing gas.

[0077] Optionally, the temperature of the second heat treatment is 500°C~600°C, including but not limited to: 500°C, 520°C, 540°C, 560°C, 580°C, 600°C.

[0078] Optionally, the second heat treatment has a holding time of 0.5 h to 2 h, including but not limited to: 0.5 h, 1 h, 1.5 h, 2 h.

[0079] In some embodiments, after the second heat treatment, the method further includes a step of post-treating the swollen conductive carbon black subjected to the second heat treatment.

[0080] Optionally, the post-treatment step includes: mixing the conductive carbon black after the second heat treatment with the extraction solvent, and subjecting the mixture to microwave irradiation. Optionally, the microwave irradiation is performed under a protective gas atmosphere. Optionally, the irradiation frequency of the microwave irradiation is 2 GHz to 3 GHz, the microwave power is 500 W to 1000 W, and the irradiation time is 5 min to 10 min.

[0081] Optionally, the extraction solvent includes one or more of methanol, diethylene glycol and n-butanol.

[0082] Optionally, the volume mass ratio of the extraction solvent to the conductive carbon black is 30 mL / g to 50 mL / g, including but not limited to: 30 mL / g, 40 mL / g, and 50 mL / g.

[0083] In some embodiments, the protective gas atmosphere of the microwave irradiation treatment includes N 2 .

[0084] In N 2 Microwave irradiation treatment under the protection of can reduce the surface oxidation of conductive carbon black under microwave heating and the presence of oxidant, which is beneficial to ensure the purity and electrical properties of conductive carbon black.

[0085] Optionally, the frequency of the microwave irradiation treatment is 2 GHz to 3 GHz, including but not limited to: 2 GHz, 2.4 GHz, 2.8 GHz, and 3 GHz.

[0086] Optionally, the power of the microwave irradiation treatment is 500W~1000W, including but not limited to: 500W, 600W, 700W, 800W, 900W, 1000W.

[0087] Optionally, the microwave irradiation treatment time is 5 min to 10 min, including but not limited to: 5 min, 6 min, 7 min, 8 min, 9 min, 10 min.

[0088] It is understandable that the post-treated conductive carbon black suspension needs to be purified to remove the extraction solvent or other impurities dissolved in the extraction solvent, thereby obtaining purified modified conductive carbon black.

[0089] Optionally, the purification process comprises the following steps: washing the suspension containing the conductive carbon black with ethanol, washing with deionized water and drying.

[0090] Optionally, the drying conditions are: vacuum drying at 60°C to 80°C, including but not limited to: 60°C, 70°C, 80°C.

[0091] In a second aspect of the present application, a modified conductive carbon black is provided, which is obtained by the above-mentioned method for modifying the conductive carbon black.

[0092] In a third aspect of the present application, a high-voltage cable shielding material is provided, which contains the above-mentioned modified conductive carbon black.

[0093] In a fourth aspect of the present application, a high-voltage cable is provided, which contains the above-mentioned high-voltage cable shielding material.

[0094] The present application is further described in detail below in conjunction with specific embodiments.

[0095] 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; and the processes used, unless otherwise specified, are all routinely selected by those skilled in the art.

[0096] Among them, the specific parameters of conductive carbon black are as follows: the raw material oil is anthracene oil, and the preparation method is the traditional oil furnace method; the average particle size is 38nm, the oil absorption value is 145mL / g, the iodine absorption value is 72g / kg, the 325 mesh sieve residue is 9ppm, and the oxygen content is 6%.

[0097] Example 1

[0098] The modification method of the conductive carbon black of the present embodiment comprises the following steps:

[0099] (1) Swelling treatment: tetrachloroethylene was added to the conductive carbon black at a volume mass ratio of 20 mL / g, the mixture was stirred and evenly mixed, and then allowed to stand for 6 h. The mixture was centrifuged at a speed of 5000 rad / min for 10 min, and the upper layer of solvent was poured out to obtain swollen conductive carbon black.

[0100] (2) First heat treatment: The swollen conductive carbon black is placed in a vacuum tube furnace, and protective gas is introduced at a rate of 2.5 L / min to exhaust the air in the vacuum tube. The gas flow rate is reduced to 0.1 L / min, and the temperature is increased to 300 °C at a rate of 5 °C / min in an inert gas protective atmosphere, and the temperature is maintained at a constant temperature for 2 h;

[0101] (3) Second heat treatment: 8% volume fraction H2O2 is introduced into the vacuum tube furnace. 2 , heating to 600°C at a heating rate of 10°C / min, keeping the temperature constant for 0.5h and then cooling naturally to room temperature;

[0102] (4) Post-treatment: Methanol was added to the second heat-treated conductive carbon black at a volume mass ratio of 30 mL / g, and microwave irradiation was performed under the following conditions: irradiation frequency of 2.45 GHz, microwave power of 500 W, and irradiation time of 10 min. After microwave irradiation, the carbon black was first washed with ethanol and then with deionized water, and then vacuum dried at 60°C to obtain the modified conductive carbon black.

[0103] Example 2

[0104] The modification method of the conductive carbon black in this embodiment is basically the same as that in Embodiment 1, except that the holding time of the first heat treatment in step (2) is 6 hours.

[0105] Example 3

[0106] (1) Swelling treatment: tetrachloroethylene was added to the conductive carbon black at a volume mass ratio of 20 mL / g, the mixture was stirred and evenly mixed, and then allowed to stand for 6 h. The mixture was centrifuged at a speed of 5000 rad / min for 10 min, and the upper layer of solvent was poured out to obtain swollen conductive carbon black.

[0107] (2) First heat treatment: The swollen conductive carbon black is placed in a vacuum tube furnace, and protective gas is introduced at a rate of 2.5 L / min to exhaust the air in the vacuum tube. The gas flow rate is reduced to 0.1 L / min, and the temperature is increased to 400°C at a rate of 5°C / min in an inert gas protective atmosphere, and the temperature is maintained at a constant temperature for 2 h;

[0108] (3) Second heat treatment: 8% volume fraction H2O2 is introduced into the vacuum tube furnace. 2 , heating to 600°C at a heating rate of 10°C / min, keeping the temperature constant for 0.5h and then cooling naturally to room temperature;

[0109] (4) Post-treatment: Methanol was added to the second heat-treated conductive carbon black at a volume mass ratio of 30 mL / g, and microwave irradiation was performed under the following conditions: irradiation frequency of 2.45 GHz, microwave power of 500 W, and irradiation time of 10 min. After microwave irradiation, the carbon black was first washed with ethanol and then with deionized water, and then vacuum dried at 60°C to obtain the modified conductive carbon black.

[0110] Comparative Example 1

[0111] (1) Swelling treatment: tetrachloroethylene was added to the conductive carbon black at a volume mass ratio of 20 mL / g, the mixture was stirred and evenly allowed to stand for 6 h, and the mixture was centrifuged at a speed of 5000 rad / min for 10 min. The upper layer of solvent was poured out to obtain swollen conductive carbon black;

[0112] (2) Heating treatment: The swollen conductive carbon black was placed in a vacuum tube furnace, and an inert gas was introduced at a rate of 2.5 L / min to exhaust the air in the vacuum tube. The gas flow rate was reduced to 0.1 L / min, and 8% by volume H 2 , heating to 600°C at a heating rate of 10°C / min, keeping the temperature constant for 4h and then cooling naturally to room temperature;

[0113] (3) Post-treatment: Methanol was added to the second heat-treated conductive carbon black at a volume mass ratio of 30 mL / g, and microwave irradiation was performed under the following conditions: irradiation frequency of 2.45 GHz, microwave power of 500 W, and irradiation time of 10 min. After microwave irradiation, the carbon black was first washed with ethanol and then with deionized water, and then vacuum dried at 60°C to obtain the modified conductive carbon black.

[0114] Comparative Example 2

[0115] The modification method of the conductive carbon black in this comparative example is basically the same as that in Example 1, except that step (1) of swelling treatment is not included.

[0116] Test Case

[0117] The total oxygen content of the conductive carbon black was measured by an elemental analyzer, and the type and relative content of oxygen-containing functional groups of the conductive carbon black were obtained by XPS combined with peak fitting. In order to measure the structural damage of the conductive carbon black during the heat treatment process, the DBP absorption value of the conductive carbon black was tested to quantify its structure, and the results are shown in Table 1.

[0118] Table 1

[0119]

[0120] It can be seen from Examples 1 to 3 in Table 1 that in the first heat treatment stage, increasing the heat treatment time and temperature can increase the removal rate of oxygen-containing functional groups of conductive carbon black. Combined with Comparative Example 1, it can be found that although direct high-temperature heat treatment of conductive carbon black can reduce the total oxygen content of conductive carbon black, it will destroy the structure of conductive carbon black aggregates. Combined with Comparative Example 2, it is found that conductive carbon black can also remove some oxygen-containing functional groups without undergoing a swelling treatment process, but the deoxidation efficiency still cannot meet the requirements of conductive carbon black for oxygen content. In summary, the present application effectively removes oxygen-containing functional groups mainly composed of lactone oxygen and carboxyl oxygen in conductive carbon black through the synergistic effect of swelling treatment, first heat treatment, second heat treatment and post-treatment, and obtains modified conductive carbon black with low total oxygen content. The obtained modified conductive carbon black has a higher DBP value than the traditional modification method, can provide a high-quality channel for the transmission of electrons, and can meet the performance requirements of high-voltage cable shielding materials for conductive fillers.

[0121] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0122] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims, and the description may be used to interpret the content of the claims.

Claims

1. A method for modifying conductive carbon black, characterized in that: The following steps are involved: The conductive carbon black is swelled in an organic solvent to prepare swollen conductive carbon black; Under a protective gas atmosphere, subjecting the swollen conductive carbon black to a first heat treatment at 200° C. to 400° C.; A reducing gas is introduced into the protective gas atmosphere, and the swollen conductive carbon black after the first heat treatment is subjected to a second heat treatment at 500° C. to 600° C.

2. The method for modifying conductive carbon black according to claim 1, characterized in that: The first heat treatment comprises the following steps: Raise the temperature to 200℃~400℃ at a heating rate of 2℃ / min~20℃ / min and keep it warm for 0.5h~6h.

3. The method for modifying conductive carbon black according to claim 1, characterized in that: The second heat treatment comprises the following steps: Raise the temperature to 500℃~600℃ at a heating rate of 10℃ / min~20℃ / min and keep it at this temperature for 0.5h~2h.

4. The method for modifying conductive carbon black according to claim 1, characterized in that: The reducing gas meets one or more of the following characteristics: (1) In the protective gas atmosphere, the volume fraction of the reducing gas is 5% to 15%; (2) The flow rate of the reducing gas is 20-50 mL / min; (3) The reducing gas includes H2.

5. The method for modifying conductive carbon black according to claim 1, characterized in that: The second heat treatment further comprises: The conductive carbon black after the second heat treatment is mixed with an extraction solvent, and the mixture is subjected to microwave irradiation treatment.

6. The method for modifying conductive carbon black according to claim 5, characterized in that: The volume mass ratio of the extraction solvent to the conductive carbon black after the second heat treatment is 30 mL / g to 50 mL / g; and / or, The extraction solvent includes one or more of methanol, diethylene glycol and n-butanol; and / or, The frequency of the microwave irradiation treatment is 2 GHz to 3 GHz; and / or, The power of the microwave irradiation treatment is 500W to 1000W; and / or, The microwave irradiation treatment time is 5min to 10min.

7. The method for modifying conductive carbon black according to any one of claims 1 to 6, characterized in that: The swelling treatment satisfies one or more of the following characteristics: (1) The swelling treatment comprises: mixing the conductive carbon black and the organic solvent and leaving the mixture to stand for 6 hours to 24 hours; (2) The volume mass ratio of the organic solvent to the conductive carbon black is 20 mL / g to 50 mL / g; (3) The organic solvent includes one or more of tetrahydrofuran, carbon disulfide, tetrachloroethylene and N-methylpyrrolidone.

8. A modified conductive carbon black, characterized in that: The modified product is obtained by the modification method according to any one of claims 1 to 7.

9. A high voltage cable shielding material, characterized in that: Including the modified conductive carbon black as described in claim 8.

10. A high voltage cable, characterized in that: The high voltage cable shielding material comprises the high voltage cable shielding material as claimed in claim 9.

Images