Mesoporous carbon modified conductive asphalt and preparation method thereof

Abstract

The present application relates to a kind of mesoporous carbon modified conductive asphalt and its preparation method, the conductive asphalt at least includes following weight parts of each raw material: base asphalt 100-120 parts;Conductive fiber 0.5-2 parts;Surface modified mesoporous carbon 0.5-2 parts;Coupling agent 0.3-0.8 parts.Step preparation is as follows: S1.corresponding weight parts of base asphalt is heated and melted, keep temperature between 145-165 DEG C, under the condition of stirring, corresponding weight parts of surface modified mesoporous carbon is added, fully stirred and mixed, and keep warm for standby;S2.at room temperature, corresponding weight parts of coupling agent is diluted with deionized water to diluent, corresponding weight parts of conductive fiber is added to diluent and stirred to slurry;S3.the slurry of S2 is poured into S1, fully stirred, mixed, and obtained.The advantage is that conductive fiber and surface modified mesoporous carbon are used as conductive phase to modify asphalt, and ideal conductive performance can be obtained with less addition amount.

Description

Technical Field

[0001] This invention relates to the field of asphalt modification technology, specifically to a mesoporous carbon-modified conductive asphalt and its preparation method. Background Technology

[0002] Asphalt concrete is an insulator and lacks electrical conductivity. In recent years, to enhance the functionality of asphalt pavements, researchers have incorporated graphite into asphalt concrete to impart a certain degree of conductivity. However, to form conductive pathways within the asphalt concrete, the amount of graphite added needs to be continuously increased. When the conductivity of the asphalt concrete is satisfied, excessive graphite content, coupled with poor lubrication and bonding between graphite and asphalt, leads to a decline in the pavement performance of the asphalt concrete, failing to meet road requirements. Besides graphite, current research indicates that graphene is also an effective conductive additive for conductive asphalt and conductive asphalt concrete. However, both graphite and graphene have poor bonding with asphalt, and even with coupling agents, effective bonding of the components cannot be guaranteed. Therefore, the resulting conductive asphalt and conductive asphalt concrete still fail to meet road requirements in terms of overall performance such as conductivity, softening point, and strength. Furthermore, the improvement in the conductivity of asphalt by graphene is mainly due to its large specific surface area and good conductivity, allowing it to form a conductive network in asphalt concrete with a relatively small dosage. The more graphene layers a graphene has, the smaller its specific surface area, resulting in better economics and a simpler fabrication process. Conversely, the fewer graphene layers a graphene has, the larger its specific surface area, resulting in poorer economics and a more complex fabrication process. Graphene with a monolayer content of over 99% has a specific surface area of ​​2620 nm. 2 While the price is around 1 / g, it is higher than that of gold, making it impractical for large-scale engineering applications. In other words, from a cost perspective, simply adding high-quality single-layer or few-layer graphene to obtain conductive asphalt is not a realistic option.

[0003] Ordered mesoporous carbon is a novel type of porous carbon material with a structure and properties distinct from other carbon materials. It possesses a highly ordered pore structure, large specific surface area and pore volume, narrow and tunable pore size distribution, high mechanical strength, good electrical conductivity, and excellent thermal stability and chemical inertness. Current research and applications of mesoporous carbon mainly focus on separation and adsorption, catalysis, sensing, energy storage, capacitors, and fuel cells, but there are no reports of its successful application in conductive asphalt. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a mesoporous carbon modified conductive asphalt and its preparation method, aiming to apply mesoporous carbon to the preparation of conductive asphalt and overcome the shortcomings of the poor comprehensive performance of conductive asphalt prepared by graphite or graphene.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: a mesoporous carbon modified conductive asphalt, which includes at least the following raw materials in parts by weight: 100-120 parts of base asphalt; 0.5-2 parts of conductive fiber; 0.5-2 parts of surface-modified mesoporous carbon; and 0.3-0.8 parts of coupling agent.

[0006] Based on the above technical solution, the present invention can also make the following further specific choices.

[0007] Specifically, the surface-modified mesoporous carbon is mesoporous carbon with graphene and graphene oxide grown in situ on its surface.

[0008] Specifically, the surface-modified mesoporous carbon is prepared by the following method: A reaction vessel is placed in an ice-water bath, and then an appropriate amount of concentrated sulfuric acid is added to the reaction vessel. Under stirring, an appropriate amount of mesoporous carbon powder and sodium nitrate powder are added to the reaction vessel, followed by the slow addition of an appropriate amount of potassium permanganate. The temperature of the reaction solution in the reaction vessel is controlled below 20°C. After stirring for 10-15 minutes, the temperature is raised to 25-32°C, and stirring is continued for 30-45 minutes. An appropriate amount of deionized water is added, and the temperature is controlled at 25-32°C. The reaction continues for 30-45 minutes, and hydrogen peroxide is added to terminate the reaction. The mixture is then filtered and washed while hot to obtain mesoporous carbon with graphene oxide grown in situ on its surface. The filter cake is redissolved in deionized water to obtain a mixed solution. Under stirring, an appropriate amount of hydrazine hydrate is added to the mixed solution, and the temperature is raised to 90-95°C. The reaction continues for 30-40 minutes to partially reduce the graphene oxide on the surface of the mesoporous carbon. The mixture is then filtered, and the filter cake is placed in a vacuum drying oven at 60-70°C for thorough drying to obtain the final product.

[0009] The optimal ratio of concentrated sulfuric acid, mesoporous carbon powder, sodium nitrate powder, and potassium permanganate is 30-35 mL: 0.5-1 g: 0.5 g: 3 g. The volume of deionized water added for the first time should be 4-5 times the volume of the initial concentrated sulfuric acid added, and the volume of deionized water added for the second time should be 10-15 times the volume of the initial concentrated sulfuric acid added.

[0010] Optimal, the mass of hydrazine hydrate is 0.1-0.2 times the mass of the initially added mesoporous carbon.

[0011] Specifically, the base asphalt is coal tar pitch, petroleum asphalt, or natural asphalt.

[0012] Specifically, the conductive fiber is carbon fiber, metal fiber, or conductive polymer fiber.

[0013] Specifically, the coupling agent is a silane coupling agent, preferably KH550 or KH560.

[0014] Furthermore, the present invention also provides a method for preparing the above-mentioned mesoporous carbon-modified conductive asphalt, which includes the following steps:

[0015] S1. Heat and melt the corresponding weight parts of base asphalt, keeping the temperature between 145-165℃. Under stirring conditions, add the corresponding weight parts of surface-modified mesoporous carbon to the molten base asphalt, stir and mix thoroughly to obtain a mixture, and keep it warm for later use.

[0016] S2. Dilute the corresponding weight parts of coupling agent with deionized water at room temperature to obtain a diluted solution, and add the corresponding weight parts of conductive fiber to the diluted solution and stir to obtain a slurry.

[0017] S3. Under stirring conditions, pour the slurry of S2 into S1 which is in a heat-insulating state, stir thoroughly, and mix well to obtain mesoporous carbon modified conductive asphalt.

[0018] Specifically, in S2, the ratio of coupling agent to deionized water is 1g:1000-2000mL. In S1 and S3, thorough stirring means stirring at 1000-1500 rpm for 8-15 minutes, and then stirring at 2000-3000 rpm for 25-30 minutes.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] Conductive fibers and surface-modified mesoporous carbon are used to modify asphalt. Surface-modified mesoporous carbon has both good conductivity and good self-lubricating dispersion properties, which can be well dispersed in asphalt. At the same time, it works synergistically with conductive fibers to form a relatively complete conductive network in conductive asphalt, ensuring that ideal conductivity is achieved with a small amount of addition.

[0021] Graphene oxide is grown in situ on the surface of surface-modified mesoporous carbon, and then partially reduced to graphene by hydrazine hydrate or other methods. That is, both graphene oxide and graphene are distributed on the surface of the surface-modified mesoporous carbon. After modification, the mesoporous carbon becomes bloated and its specific surface area is further increased. The graphene oxide on the surface improves the hydrophilicity, compatibility, wettability and surface activity of the mesoporous carbon, which facilitates its subsequent interaction with water, coupling agents and conductive fibers in the slurry. This allows the coupling agent to better connect the mesoporous carbon to the matrix asphalt and to the conductive fibers. The graphene on the surface allows the mesoporous carbon to maintain good conductivity while also having a certain degree of self-lubrication, which is beneficial for its own dispersion and the dispersion of other components (conductive fibers and coupling agents), thus ensuring that the conductive asphalt has good overall performance.

[0022] The preparation method of surface-modified mesoporous carbon is simple, and its production cost is significantly lower than that of single-layer or few-layer graphene. Therefore, the production cost of conductive asphalt modified with surface-modified mesoporous carbon in this invention is low, economical, and easy to promote and use. Detailed Implementation

[0023] The principles of the present invention will be further described in detail below with reference to specific embodiments. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0024] To avoid unnecessary details, unless otherwise specified, all raw materials used in the following examples are commercially available products, and all methods used are conventional methods unless otherwise specified.

[0025] The mesoporous carbon used in this invention can be a commercially available product or can be prepared by oneself from waste asphalt or base asphalt. The preparation method is described in Chinese invention patents CN113213453A and CN114604849A, which disclose mesoporous carbon materials and their preparation methods. This method uses waste asphalt as raw material and can obtain low-cost mesoporous carbon.

[0026] The surface-modified mesoporous carbon used in the following examples was prepared by the following method:

[0027] Place the reaction vessel in an ice-water bath, then add an appropriate amount of concentrated sulfuric acid. Under stirring, add an appropriate amount of mesoporous carbon powder and sodium nitrate powder, followed by a slow addition of potassium permanganate. Control the temperature of the reaction solution in the reaction vessel to below 20℃. After stirring for 10-15 minutes, raise the temperature to 25-32℃ and continue stirring for 30-45 minutes. Add an appropriate amount of deionized water, control the temperature at 25-32℃, and continue the reaction for 30-45 minutes. Add hydrogen peroxide to terminate the reaction. Filter and wash while hot to obtain mesoporous carbon with graphene oxide growing in situ on the surface. Redissolve the filter cake in deionized water to obtain a mixed solution. Under stirring, add an appropriate amount of hydrazine hydrate to the mixed solution, raise the temperature to 90-95℃, and continue the reaction for 30-40 minutes to partially reduce the graphene oxide on the surface of the mesoporous carbon. Filter and place the filter cake in a vacuum drying oven at 60-70℃ to dry thoroughly. The ratio of concentrated sulfuric acid, mesoporous carbon powder, sodium nitrate powder, and potassium permanganate was 30 mL: 0.5 g: 0.5 g: 3 g. The volume of deionized water added initially was four times the volume of the initial concentrated sulfuric acid, and the volume of deionized water added second time was 15 times the volume of the initial concentrated sulfuric acid. The mass of hydrazine hydrate was 0.1-0.2 times the mass of the initial mesoporous carbon. By strictly controlling the reaction time, temperature conditions, and material dosage, the surface modification of mesoporous carbon was ensured to first involve relatively complete oxidation of the surface, followed by a certain degree of reduction, thus ensuring the coexistence of surface-oxidized graphene and graphene.

[0028] In the above preparation process, the intermediate product after the first filtration and washing was characterized by FT-IR. It can be seen that the characteristic peaks of the oxygen-containing groups, which represent carboxyl, hydroxyl and epoxy groups, are significantly enhanced, indicating that graphene oxide was generated by in-situ oxidation on the surface. When the product after reduction with hydrazine hydrate was characterized, the characteristic peaks of the oxygen-containing groups could still be seen in the spectrum, but they were significantly weakened compared with those before treatment with hydrazine hydrate. This indicates that the graphene oxide on the surface-modified mesoporous carbon was partially reduced to graphene, that is, the surface of the surface-modified mesoporous carbon simultaneously possesses graphene oxide and graphene.

[0029] Example 1

[0030] A mesoporous carbon-modified conductive asphalt, the raw materials and their weight parts are as follows:

[0031] 100 parts of base pitch (coal tar pitch); 1 part of conductive fiber (3mm short-cut carbon fiber filament); 1 part of surface-modified mesoporous carbon; 0.5 parts of coupling agent (KH-560).

[0032] The specific preparation method includes the following steps:

[0033] S1. Heat and melt the corresponding weight parts of base asphalt, keeping the temperature between 145-165℃. Under stirring conditions, add the corresponding weight parts of surface-modified mesoporous carbon to the molten base asphalt. First, stir at a speed of 1000-1200 rpm for 10-15 minutes, then stir at a speed of 2000-2500 rpm for 25-30 minutes. Stir thoroughly to obtain a mixture, and keep it warm for later use.

[0034] S2. Dilute the corresponding weight parts of coupling agent with deionized water at room temperature to obtain a diluted solution. The ratio of coupling agent to deionized water is 1g:1500mL. Add the corresponding weight parts of conductive fiber to the diluted solution and stir to mix well to obtain a slurry.

[0035] S3. Under stirring conditions, pour the slurry of S2 into S1, stir at a speed of 1000-1200 rpm for 10-15 minutes, and then stir at a speed of 2000-2500 rpm for 25-30 minutes. Stir thoroughly and mix evenly to obtain mesoporous carbon modified conductive asphalt.

[0036] Example 2

[0037] A mesoporous carbon-modified conductive asphalt, the raw materials and their weight parts are as follows:

[0038] 110 parts of base pitch (coal tar pitch); 0.5 parts of conductive fiber (3mm chopped carbon fiber filament); 2 parts of surface-modified mesoporous carbon; 0.8 parts of coupling agent (KH-560).

[0039] The specific preparation method includes the following steps:

[0040] S1. Heat and melt the corresponding weight parts of base asphalt, keeping the temperature between 145-165℃. Under stirring conditions, add the corresponding weight parts of surface-modified mesoporous carbon to the molten base asphalt. First, stir at a speed of 1200-1500 rpm for 10-15 minutes, and then stir at a speed of 2500-3000 rpm for 25-30 minutes. Stir thoroughly to obtain a mixture, and keep it warm for later use.

[0041] S2. Dilute the corresponding weight parts of coupling agent with deionized water at room temperature to obtain a diluted solution. The ratio of coupling agent to deionized water is 1g:1500mL. Add the corresponding weight parts of conductive fiber to the diluted solution and stir to mix well to obtain a slurry.

[0042] S3. Under stirring conditions, pour the slurry of S2 into S1, stir at a speed of 1200-1500 rpm for 8-15 minutes, and then stir at a speed of 2500-3000 rpm for 25-30 minutes. Stir thoroughly and mix evenly to obtain mesoporous carbon modified conductive asphalt.

[0043] Example 3

[0044] A mesoporous carbon-modified conductive asphalt, the raw materials and their weight parts are as follows:

[0045] 120 parts of base pitch (coal tar pitch); 0.5 parts of conductive fiber (3mm chopped carbon fiber filament); 0.5 parts of surface-modified mesoporous carbon; 0.3 parts of coupling agent (KH-560).

[0046] The specific preparation method includes the following steps:

[0047] S1. Heat and melt the corresponding weight parts of base asphalt, keeping the temperature between 145-165℃. Under stirring conditions, add the corresponding weight parts of surface-modified mesoporous carbon to the molten base asphalt. First, stir at a speed of 1000-1200 rpm for 8-10 minutes, then stir at a speed of 2000-2500 rpm for 25-30 minutes. Stir thoroughly to obtain a mixture, and keep it warm for later use.

[0048] S2. Dilute the corresponding weight parts of coupling agent with deionized water at room temperature to obtain a diluted solution. The ratio of coupling agent to deionized water is 1g:2000mL. Add the corresponding weight parts of conductive fiber to the diluted solution and stir to mix well to obtain a slurry.

[0049] S3. Under stirring conditions, pour the slurry of S2 into S1, stir at a speed of 1000-1200 rpm for 8-10 minutes, and then stir at a speed of 2000-2500 rpm for 25-30 minutes. Stir thoroughly and mix evenly to obtain mesoporous carbon modified conductive asphalt.

[0050] Example 4

[0051] A mesoporous carbon-modified conductive asphalt, the raw materials and their weight parts are as follows:

[0052] 100 parts of base asphalt (petroleum asphalt); 1 part of conductive fiber (3mm polyacetylene short filament); 1 part of surface-modified mesoporous carbon; 0.5 parts of coupling agent (KH-560).

[0053] The specific preparation method includes the following steps:

[0054] S1. Heat and melt the corresponding weight parts of base asphalt, keeping the temperature between 145-165℃. Under stirring conditions, add the corresponding weight parts of surface-modified mesoporous carbon to the molten base asphalt. First, stir at a speed of 1000-1200 rpm for 10-15 minutes, then stir at a speed of 2000-2500 rpm for 25-30 minutes. Stir thoroughly to obtain a mixture, and keep it warm for later use.

[0055] S2. Dilute the corresponding weight parts of coupling agent with deionized water at room temperature to obtain a diluted solution. The ratio of coupling agent to deionized water is 1g:1500mL. Add the corresponding weight parts of conductive fiber to the diluted solution and stir to mix well to obtain a slurry.

[0056] S3. Under stirring conditions, pour the slurry of S2 into S1, stir at a speed of 1000-1200 rpm for 10-15 minutes, and then stir at a speed of 2000-2500 rpm for 25-30 minutes. Stir thoroughly and mix evenly to obtain mesoporous carbon modified conductive asphalt.

[0057] Example 5

[0058] A mesoporous carbon-modified conductive asphalt, the raw materials and their weight parts are as follows:

[0059] 100 parts of base bitumen (petroleum bitumen); 1 part of conductive fiber (3mm polypyrrole short filament); 1 part of surface-modified mesoporous carbon; 0.5 parts of coupling agent (KH-560).

[0060] The specific preparation method includes the following steps:

[0061] S1. Heat and melt the corresponding weight parts of base asphalt, keeping the temperature between 145-165℃. Under stirring conditions, add the corresponding weight parts of surface-modified mesoporous carbon to the molten base asphalt. First, stir at a speed of 1000-1200 rpm for 10-15 minutes, then stir at a speed of 2000-2500 rpm for 25-30 minutes. Stir thoroughly to obtain a mixture, and keep it warm for later use.

[0062] S2. Dilute the corresponding weight parts of coupling agent with deionized water at room temperature to obtain a diluted solution. The ratio of coupling agent to deionized water is 1g:1500mL. Add the corresponding weight parts of conductive fiber to the diluted solution and stir to mix well to obtain a slurry.

[0063] S3. Under stirring conditions, pour the slurry of S2 into S1, stir at a speed of 1000-1200 rpm for 10-15 minutes, and then stir at a speed of 2000-2500 rpm for 25-30 minutes. Stir thoroughly and mix evenly to obtain mesoporous carbon modified conductive asphalt.

[0064] Comparative Example 1

[0065] Compared with Example 1, this comparative example only lacks the surface-modified mesoporous carbon component when preparing conductive asphalt.

[0066] Comparative Example 2

[0067] Compared with Example 1, this comparative example only lacks the conductive fiber component when preparing conductive asphalt.

[0068] Comparative Example 3

[0069] Compared with Example 1, this comparative example uses commercially available mesoporous carbon instead of surface-modified mesoporous carbon in the preparation of conductive asphalt.

[0070] To verify the conductivity of the mesoporous carbon-modified conductive asphalt provided by this invention, the cured test specimens corresponding to the conductive asphalts prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were tested according to the "Test Methods for Volume Resistivity and Surface Resistivity of Solid Insulating Materials" (GB / T 1410-2006 / IEC 60093:1980). The results are shown in the table below:

[0071]

[0072] As shown in the table above, the surface-modified mesoporous carbon and conductive fibers in the mesoporous carbon-modified conductive asphalt provided by this invention have a synergistic effect on enhancing the conductivity of asphalt; the surface modification of mesoporous carbon also has a significant effect on enhancing the conductivity of asphalt. By modifying the surface of mesoporous carbon and then using it together with conductive fibers as the conductive phase of asphalt, this invention can ensure that relatively ideal conductivity is achieved with a small amount of conductive phase addition.

[0073] Furthermore, to verify the comprehensive performance of the mesoporous carbon-modified conductive asphalt provided by this invention in other aspects, the conductive asphalts prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were tested according to the methods in the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTGE20-2011). The results are shown in the table below:

[0074] Group Example 1 Example 2 Example 3 Example 4 Example 5 Penetration (25℃, dmm) 73.2 74.8 71.3 68.4 65.7 Softening point (°C) 49.6 48.5 46.7 79.5 76.8 Ductility (10℃, cm) 26.1 25.7 24.4 22.8 23.5

[0075] As can be seen from the table above, the mesoporous carbon modified conductive asphalt provided by this invention has good comprehensive performance in terms of penetration, softening point and ductility, and meets the requirements for use.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A mesoporous carbon-modified conductive bitumen, characterized in that, At least the following raw materials by weight parts: matrix pitch 100-120 parts; conductive fiber 0.5-2 parts; surface modified mesoporous carbon 0.5-2 parts; coupling agent 0.3-0.8 parts, the surface modified mesoporous carbon is mesoporous carbon with graphene and graphene oxide grown in-situ on the surface.

2. The mesoporous carbon modified conductive bitumen according to claim 1, characterized in that, The surface modified mesoporous carbon is prepared by the following method: placing a reaction container in an ice water bath, then adding an appropriate amount of concentrated sulfuric acid to the reaction container, adding an appropriate amount of mesoporous carbon powder and sodium nitrate powder to the reaction container under stirring conditions, then slowly adding an appropriate amount of potassium permanganate, controlling the temperature of the reaction liquid in the reaction container below 20℃, after stirring for 10-15min, heating to 25-32℃, continuing to stir for 30-45min, adding an appropriate amount of deionized water, controlling the temperature at 25-32℃, continuing to react for 30-45min, adding hydrogen peroxide to terminate the reaction, hot filtering and washing to obtain mesoporous carbon with graphene oxide grown in-situ on the surface, dissolving the filter cake in deionized water to obtain a mixed solution, under stirring conditions, adding an appropriate amount of hydrazine hydrate to the mixed solution, heating to 90-95℃, and continuing to react for 30-40min to partially reduce the graphene oxide on the surface of the mesoporous carbon, filtering, and drying the filter cake in a vacuum drying oven at 60-70℃ to obtain the surface modified mesoporous carbon.

3. The mesoporous carbon modified conductive bitumen according to claim 2, characterized in that, The amount ratio of concentrated sulfuric acid, mesoporous carbon powder, sodium nitrate powder and potassium permanganate is 30-35mL:0.5-1g:0.5g:3g, the volume of the first added deionized water is 4-5 times the volume of the initially added concentrated sulfuric acid, and the volume of the second added deionized water is 10-15 times the volume of the initially added concentrated sulfuric acid.

4. The mesoporous carbon modified conductive bitumen of claim 2, wherein, The mass of hydrazine hydrate is 0.1-0.2 times the mass of the initially added mesoporous carbon.

5. The mesoporous carbon modified conductive bitumen of claim 1, wherein, The matrix pitch is coal tar pitch, petroleum pitch or natural pitch.

6. The mesoporous carbon modified conductive bitumen of claim 1, wherein, The conductive fiber is carbon fiber, metal fiber or conductive polymer fiber.

7. The mesoporous carbon-modified conductive bitumen according to any one of claims 1 to 6, characterized in that, The coupling agent is a silane coupling agent.

8. A method for preparing the mesoporous carbon-modified conductive bitumen according to any one of claims 1 to 7, characterized by, The method comprises the following steps: S1. Heating and melting the corresponding weight parts of matrix pitch, keeping the temperature between 145-165℃, under stirring conditions, adding the corresponding weight parts of surface modified mesoporous carbon to the molten matrix pitch, thoroughly stirring and mixing to obtain a mixture, and keeping warm for standby use; S2. Diluting the corresponding weight parts of coupling agent with deionized water at room temperature to obtain a diluent, and adding the corresponding weight parts of conductive fiber to the diluent and stirring to obtain a slurry; S3. Under stirring conditions, pouring the slurry of S2 into the mixture of S1, thoroughly stirring and mixing, to obtain mesoporous carbon modified conductive pitch.

9. The method of claim 8, wherein the mesoporous carbon-modified conductive pitch is prepared by the steps of: The amount ratio of coupling agent to deionized water in S2 is 1g:1000-2000mL, and the thorough stirring in S1 and S3 means first stirring at a speed of 1000-1500rpm for 8-15min, and then stirring at a speed of 2000-3000rpm for 25-30min.

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