Sizing agent raw material composition, sizing agent and preparation method of sizing agent

Abstract

The invention relates to the technical field of sizing agents, in particular to a sizing agent raw material composition, a sizing agent and a preparation method of the sizing agent. The invention provides a sizing agent raw material composition, the composition comprises a graphene nanobelt solution, a nonionic surfactant, an alkali source and an epoxy resin emulsion, the composition is used for preparing a sizing agent, the composition has the advantages of small particle size, good stability and the like, after carbon fibers are sized, the interlayer shear force of the carbon fibers can be well improved, and the tensile strength of the carbon fibers is improved. The preparation method of the sizing agent is simple in process, mild in condition, low in cost and suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of sizing agents, and in particular to a sizing agent raw material composition and a sizing agent and a preparation method thereof. Background Art

[0002] Carbon fiber reinforced composite materials are increasingly used in aerospace, weapons and equipment, sports facilities, automobiles, energy and other industrial fields because of their advantages of light weight, high strength, strong impact resistance, fatigue resistance and corrosion resistance. In recent years, the production capacity of domestic carbon fiber has steadily increased, and high-performance carbon fiber composite materials have gradually replaced metal parts. However, during the production and processing of carbon fiber, it is easy to produce filaments and single filaments under the action of friction, thus reducing the strength of carbon fiber, and the interface properties between carbon fiber and matrix are also crucial to the performance of composite materials.

[0003] Using sizing agents to treat the surface of carbon fibers and form an organic film on the surface of carbon fibers can not only reduce wear and tear during processing and avoid the formation of hair, but also protect the clean and active surface after surface treatment and prevent the adsorption of dust and moisture in the air. Emulsion sizing agents are currently the most widely used sizing agents because they are safe and environmentally friendly, but the stability of emulsion sizing agents is not enough. The film formed by the sizing agent on the surface of carbon fibers is easily affected by the ambient temperature and humidity, affecting the bonding between carbon fibers and resins. The application of sizing agents in some high-performance carbon fiber fields is limited. The development of high-performance sizing agents has become an important link in the carbon fiber industry chain.

[0004] Graphene nanoribbons are one-dimensional nanoribbon-shaped graphene materials that combine the advantages of carbon nanotubes and graphene, with good dispersion, excellent conductivity, large specific surface area and excellent strength. Introducing graphene nanoribbons to the surface of carbon fiber through sizing agents can improve the surface properties of carbon fiber, thereby further enhancing the interface properties of composite materials.

[0005] Therefore, seeking a simple method for preparing a composite emulsion sizing agent modified with graphene nanoribbons will be beneficial to its in-depth research and promotion and application. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems of poor bonding between carbon fiber and resin, poor stability of sizing agent and the like in the prior art, and to provide a sizing agent raw material composition and a preparation method of the sizing agent. The sizing agent prepared by the sizing agent composition and the preparation method of the present invention has the advantages of small particle size and good stability, and can better improve the interlaminar shear force of the carbon fiber after sizing the carbon fiber. The preparation method of the sizing agent of the present invention has simple process, mild conditions, low cost and is suitable for industrial production.

[0007] In order to achieve the above-mentioned object, the first aspect of the present invention provides a sizing agent raw material composition, which comprises a graphene nanoribbon solution, a nonionic surfactant, an alkali source, and an epoxy resin emulsion.

[0008] The second aspect of the present invention provides a method for preparing a sizing agent, which is prepared using the formula of the raw material composition of the present invention, and the method comprises: (1) adding a nonionic surfactant and an alkali source to a graphene nanoribbon solution and mixing them to obtain a solution I; (2) adding the solution I to an epoxy resin emulsion and mixing them.

[0009] The third aspect of the present invention provides a sizing agent prepared by the preparation method of the present invention, wherein the particle size of the sizing agent is 100-300 nm, and the sizing agent does not break the emulsion or separate layers when left to stand for more than 30 days, and does not break the emulsion or separate layers when centrifuged at 3000 rpm for 1 minute.

[0010] Through the above technical solution, the present invention has the following beneficial effects:

[0011] The present invention proposes for the first time a sizing agent raw material composition, which comprises a graphene nanoribbon solution, a nonionic surfactant, an alkali source, and an epoxy resin emulsion. The composition is used for preparing a sizing agent and has the advantages of small particle size and good stability. After sizing carbon fiber, the interlaminar shear force of the carbon fiber can be improved. The preparation method of the present invention has the advantages of simple preparation process, mild conditions, low cost, etc., and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a scanning electron microscope image of the graphene nanoribbon synthesized in Example 1;

[0013] Figure 2 is the XPS graph of the graphene nanoribbon synthesized in Example 1;

[0014] Figure 3 This is an optical picture of the graphene nanoribbon composite emulsion sizing agent synthesized in Example 1. DETAILED DESCRIPTION

[0015] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0016] The invention provides a sizing agent raw material composition, which comprises a graphene nanoribbon solution, a nonionic surfactant, an alkali source and an epoxy resin emulsion.

[0017] In the present invention, the amount of the alkali source is used to make the pH value of the prepared sizing agent 9-13, preferably 9-10.

[0018] In the present invention, the amount of the graphene nanoribbon solution can be selected in a wide range, which is exemplified below but does not limit the scope of the present invention. For the present invention, the weight ratio of the graphene nanoribbon solution to the epoxy resin emulsion is preferably 0.1-10:1, preferably 0.1-1:1, and more preferably 0.5-1:1.

[0019] In the present invention, the dosage of the nonionic surfactant can be selected in a wide range. For the present invention, the preferred dosage is 1-20 mg / mL of graphene nanoribbon solution, and the more preferred dosage is 5-9 mg / mL of graphene nanoribbon solution.

[0020] In the present invention, the graphene nanoribbon solution has no special requirements. According to a preferred embodiment of the present invention, the graphene nanoribbon solution contains 0.5-2wt% of graphene nanoribbons, and the rest is solvent, and the solvent has no special requirements, such as water.

[0021] According to a preferred embodiment of the present invention, the graphene nanoribbon solution contains modified graphene nanoribbons and deionized water, and the modified graphene nanoribbons are at least one of graphene nanoribbons containing oxygen functional groups, graphene nanoribbons containing nitrogen functional groups and graphene nanoribbons containing sulfur functional groups, preferably graphene nanoribbons containing oxygen functional groups.

[0022] According to a preferred embodiment of the present invention, the oxygen-containing functional group preferably includes a hydroxyl group and / or a carboxyl group.

[0023] By adopting the above-mentioned preferred embodiment, the stability of the sizing agent can be further improved.

[0024] In the present invention, there is no special requirement for the nonionic surfactant. According to a preferred embodiment of the present invention, the nonionic surfactant is selected from at least one of Triton X-100, Triton X-114, Triton X-305 and Triton X-405. In the present invention, Triton X-100 is used as an example in the embodiment, but the present invention is not limited to this scope. By adopting the above preferred embodiment, the stability of the sizing agent can be further improved.

[0025] In the present invention, there is no special requirement for the alkali source. According to a preferred embodiment of the present invention, the alkali solution is selected from at least one of ammonia water, potassium hydroxide and sodium hydroxide. In the present invention, ammonia solution is used as an example in the examples, but the present invention is not limited to this scope.

[0026] In the present invention, there is no special requirement for the solid content of the epoxy resin emulsion. According to a preferred embodiment of the present invention, the solid content of the epoxy resin emulsion is 30-50wt%. By adopting the above preferred embodiment, the stability of the sizing agent can be further improved.

[0027] In the present invention, there is no special requirement for the source of the epoxy resin emulsion. According to a preferred embodiment of the present invention, the epoxy resin emulsion comprises: bisphenol A epoxy resin, emulsifier, and deionized water. By adopting the above preferred embodiment, the stability of the sizing agent can be further improved.

[0028] According to a preferred embodiment of the present invention, the epoxy resin emulsion comprises 30-50 wt % of bisphenol A epoxy resin, 1-10 wt % of emulsifier, and 40-70 wt % of water.

[0029] In the present invention, the emulsifier has a wide range of optional types. For the present invention, preferably, the emulsifier is at least one selected from Triton X-100, Triton X-114, Triton X-305 and Triton X-405, preferably X-100.

[0030] The present invention provides a method for preparing a sizing agent, which is prepared by adopting the formula of the raw material composition of the present invention. The method comprises: (1) adding a nonionic surfactant and an alkali source to a graphene nanoribbon solution and mixing them to obtain a solution I; and (2) adding the solution I to an epoxy resin emulsion and mixing them.

[0031] According to a preferred embodiment of the present invention, the preparation steps of the graphene nanoribbon solution include: first mixing carbon nanotubes with an acidic solution, second mixing with an oxidant a, third mixing with an oxidant b, first centrifuging, washing, second centrifuging, dialysis treatment of the centrifuge liquid, and using deionized water to determine the concentration to 0.1-2wt%.

[0032] In the present invention, the washing solvent is selected from deionized water, and the amount used can be adjusted according to actual operation.

[0033] In the present invention, the dialysis operation is to dialyze in deionized water for 3 days, and the deionized water is changed once a day. The concentration of the graphene nanoribbon solution after dialysis is set to 0.5-2wt% by adding water.

[0034] In the present invention, there is no special requirement for the acidic solution. According to a preferred embodiment of the present invention, the acidic solution is selected from at least one of concentrated sulfuric acid, concentrated nitric acid and concentrated hydrochloric acid. In the present invention, concentrated sulfuric acid is used as an example in the examples, but the present invention is not limited to this scope. By adopting the above preferred embodiments, the dispersibility of carbon nanotubes can be further improved.

[0035] In the present invention, there is no special requirement for the oxidant a. According to a preferred embodiment of the present invention, the oxidant a is selected from at least one of potassium permanganate, potassium chlorate and sodium permanganate. In the present invention, potassium permanganate is used as an exemplary embodiment in the examples, but the present invention is not limited to this scope. By adopting the above preferred embodiments, the yield of graphene nanoribbons can be further improved.

[0036] In the present invention, there is no special requirement for the oxidant b. According to a preferred embodiment of the present invention, the oxidant b is selected from aqueous hydrogen peroxide solution.

[0037] In the present invention, there is no special requirement for the solid content of the graphene nanoribbon solution. According to a preferred embodiment of the present invention, the solid content of the graphene nanoribbon solution is 0.01%-2wt%. By adopting the above preferred embodiment, the dispersibility of the graphene nanoribbon can be further improved.

[0038] In the present invention, there is no special requirement for the mass ratio of the carbon nanotubes to the volume ratio of the acidic solution. According to a preferred embodiment of the present invention, the mass ratio of the carbon nanotubes to the volume ratio of the acidic solution is 1g:(100-500mL). By adopting the above preferred embodiment, the dispersibility of the carbon nanotubes can be further improved.

[0039] In the present invention, there is no special requirement for the mass ratio of the carbon nanotubes to the volume ratio of the oxidant a. According to a preferred embodiment of the present invention, the mass ratio of the carbon nanotubes to the oxidant a is 1g:(3-15g). By adopting the above preferred embodiment, the yield of graphene nanoribbons can be further improved.

[0040] In the present invention, there is no special requirement for the volume ratio of the mass of the carbon nanotubes to the oxidant b. According to a preferred embodiment of the present invention, the volume ratio of the mass of the carbon nanotubes to the oxidant b is 1g:(1-20mL).

[0041] The present invention has no special requirements for carbon nanotubes, and commonly used carbon nanotubes can be applicable to the present invention.

[0042] In the present invention, the mixing conditions are all carried out under stirring conditions, and the speed can be adjusted by those skilled in the art according to actual operation.

[0043] In the present invention, in step (1), there is no special requirement for the first mixing condition.

[0044] According to a preferred embodiment of the present invention, the first mixing is ultrasonic mixing, and there is no special requirement for the time of the ultrasonic mixing, as long as the solution is evenly dispersed.

[0045] According to a preferred embodiment of the present invention, the first mixing temperature is 10-30°C.

[0046] According to a preferred embodiment of the present invention, the first mixing time is 30-120 minutes.

[0047] In the present invention, in step (1), there is no special requirement for the second mixing condition.

[0048] According to a preferred embodiment of the present invention, the second mixing temperature is 10-120°C, preferably 50-80°C.

[0049] According to a preferred embodiment of the present invention, the second mixing time is 60-300 min.

[0050] In the present invention, in step (1), there is no special requirement for the third mixing condition.

[0051] According to a preferred embodiment of the present invention, the third mixing temperature is 0-30°C.

[0052] According to a preferred embodiment of the present invention, the third mixing time is 5-20 minutes.

[0053] In the present invention, in step (1), there is no special requirement for the first centrifugation condition.

[0054] According to a preferred embodiment of the present invention, the first centrifugation temperature is 10-30°C.

[0055] According to a preferred embodiment of the present invention, the first centrifugation time is 5-20 min.

[0056] According to a preferred embodiment of the present invention, the first centrifugal rotation speed is 6000-10000 rpm.

[0057] In the present invention, in step (1), there is no special requirement for the second centrifugation condition.

[0058] According to a preferred embodiment of the present invention, the second centrifugation temperature is 10-30°C.

[0059] According to a preferred embodiment of the present invention, the second centrifugation time is 20-60 min.

[0060] According to a preferred embodiment of the present invention, the second centrifugal speed is 4000-8000 rpm.

[0061] In the present invention, after the first centrifugation operation, the supernatant is discarded and a small amount of deionized water is required for rinsing. There is no special requirement for the number of rinsing times, and those skilled in the art can adjust it according to actual operation.

[0062] In the present invention, after the second centrifugation operation, a dialysis step is also included, and the specific operation is: pouring the graphene nanoribbon solution into a dialysis bag, placing it in deionized water for 3 days, and changing the water once a day.

[0063] In the present invention, after the dialysis is completed, the concentration of the dialyzed graphene nanoribbon solution needs to be adjusted to 0.5-2wt% by adding water.

[0064] In the present invention, the solution I obtained in step (2) needs to be adjusted to pH=10 with aqueous ammonia.

[0065] In the present invention, there is no special requirement for the mixing conditions of solution I and epoxy emulsion in step (3). According to a preferred embodiment of the present invention, the mixing conditions are: mixing at 10000r for 20min.

[0066] The present invention provides a sizing agent prepared by the sizing agent preparation method. The sizing agent has a particle size of 100-300 nm, does not break the emulsion or separate layers when left to stand for more than 30 days, and does not break the emulsion or separate layers when centrifuged at 3000 rpm for 1 minute.

[0067] In the following examples, the epoxy resin model is E51;

[0068] The emulsifier is Triton X-100.

[0069] The diameter of the carbon nanotube raw material is 4-6nm.

[0070] Example 1

[0071] (1) Add 1g of carbon nanotubes to 150mL of concentrated sulfuric acid (98wt%), and ultrasonicate for 30min at room temperature (25℃) to make it uniformly dispersed. The obtained mixture was stirred at room temperature (25℃) for 1h, and then 5g of potassium permanganate was slowly added. After reacting for 1h, the temperature was raised to 70℃ and the reaction was continued for 2h. After the reaction was completed, the obtained graphene nanoribbon solution was carefully poured into 500mL of ice water containing 10mL of hydrogen peroxide (temperature 0℃, time 5min). Centrifugal separation, the centrifugal speed time is 8000r / min, the centrifugal time is 10min, after centrifugation, the supernatant is poured out, rinsed with a small amount of deionized water and continued to centrifuge. The centrifugal speed is 5000r / min, and the centrifugal time is 40min. Then the centrifuged graphene nanoribbon solution is poured into a dialysis bag. Dialyze in deionized water for 3 days, and change the water once a day. The concentration of the dialyzed graphene nanoribbon solution is fixed to 1wt% by adding water;

[0072] (2) taking 10 mL of graphene nanoribbon aqueous solution, adding 50 mg of Triton X-100 while stirring, and adjusting the solution to pH = 10 with ammonia water (25 wt %);

[0073] (3) Based on the total weight of the epoxy resin emulsion, 35% of epoxy resin E51 was added with 5% of emulsifier Triton X-100 and 60% of water, and the mixture was stirred at 10000r for 20 minutes. Then, the graphene nanoribbon aqueous solution was mixed with the epoxy resin emulsion to obtain a sizing agent, and the weight ratio of the graphene nanoribbon solution to the epoxy resin emulsion was 1:9.

[0074] The particle size of the sizing agent is 100-300 nm. It does not break the emulsion or separate after standing for more than 30 days, and does not break the emulsion or separate after centrifugation at 3000 rpm for 1 minute, which shows that the sizing agent of the present invention has the advantages of small particle size and high stability.

[0075] Figure 1 is a scanning electron microscope image of the graphene nanoribbon synthesized in this embodiment, and the model of the scanning electron microscope is FEI Quanta 450 FEG SEM; Figure 1 It can be seen that the structure of graphene nanoribbons is a ribbon-like layer structure.

[0076] Figure 2 is the full spectrum of the X-ray photoelectron spectroscopy (XPS) of the graphene nanoribbon synthesized in this example ( Figure 2 a) and C1s spectra ( Figure 2 b) The model of XPS is EscaLab 250Xi. Figure 2 a It can be seen that the elements in graphene nanoribbons are mainly carbon and oxygen. Figure 2 b shows that the oxygen-containing functional groups on graphene nanoribbons are mainly hydroxyl and carboxyl groups.

[0077] Figure 3 is an optical picture of the graphene nanoribbon composite emulsion sizing agent synthesized in this embodiment; Figure 3 It can be seen that the graphene nanoribbons are stably dispersed in the sizing agent.

[0078] Example 2

[0079] (1) Add 1g of carbon nanotubes to 150mL of concentrated sulfuric acid (98wt%), and ultrasonicate for 30min at room temperature (25℃) to make it uniformly dispersed. The obtained mixture was stirred at room temperature (25℃) for 1h, and then 3g of potassium permanganate was slowly added. After reacting for 1h, the temperature was raised to 70℃ and the reaction was continued for 2h. After the reaction was completed, the obtained graphene nanoribbon solution was carefully poured into 500mL of ice water containing 10mL of hydrogen peroxide (temperature 0℃, time 5min). Centrifugal separation, the centrifugal speed time is 8000r / min, the centrifugal time is 10min, after centrifugation, the supernatant is poured out, rinsed with a small amount of deionized water and continued to centrifuge. The centrifugal speed is 5000r / min, and the centrifugal time is 40min. Then the centrifuged graphene nanoribbon solution is poured into a dialysis bag. Dialyze in deionized water for 3 days, and change the water once a day. The concentration of the dialyzed graphene nanoribbon solution is fixed to 1wt% by adding water;

[0080] (2) taking 10 mL of graphene nanoribbon aqueous solution, adding 70 mg of Triton X-100 while stirring, and adjusting the solution to pH = 10 with ammonia water (25 wt %);

[0081] (3) Based on the total weight of the epoxy resin emulsion, 35% of the epoxy resin is added to 5% of the emulsifier and 60% of the water, and the mixture is stirred at 10000r for 20 minutes. Then, the graphene nanoribbon aqueous solution is mixed with the epoxy resin emulsion to obtain a sizing agent, and the weight ratio of the graphene nanoribbon solution to the epoxy resin emulsion is 3:7.

[0082] The particle size of the sizing agent is 100-300 nm. It does not break the emulsion or separate after standing for more than 30 days, and does not break the emulsion or separate after centrifugation at 3000 rpm for 1 minute, which shows that the sizing agent of the present invention has the advantages of small particle size and high stability.

[0083] Example 3

[0084] (1) Add 1g of carbon nanotubes to 150mL of concentrated sulfuric acid (98wt%), and ultrasonicate for 30min at room temperature (25℃) to make it uniformly dispersed. The obtained mixture was stirred at room temperature (25℃) for 1h, and then 15g of potassium permanganate was slowly added. After reacting for 1h, the temperature was raised to 70℃ and the reaction was continued for 2h. After the reaction was completed, the obtained graphene nanoribbon solution was carefully poured into 500mL of ice water containing 10mL of hydrogen peroxide (temperature 0℃, time 5min). Centrifugal separation, the centrifugal speed time is 8000r / min, the centrifugal time is 10min, after centrifugation, the supernatant is poured out, rinsed with a small amount of deionized water and continued to centrifuge. The centrifugal speed is 5000r / min, and the centrifugal time is 40min. Then the centrifuged graphene nanoribbon solution is poured into a dialysis bag. Dialyze in deionized water for 3 days, and change the water once a day. The concentration of the dialyzed graphene nanoribbon solution is fixed to 1wt% by adding water;

[0085] (2) taking 10 mL of graphene nanoribbon aqueous solution, adding 90 mg of Triton X-100 while stirring, and adjusting the solution to pH = 10 with ammonia water (25 wt %);

[0086] (3) Based on the total weight of the epoxy resin emulsion, 35% of the epoxy resin is added to 5% of the emulsifier and 60% of the water, and the mixture is stirred at 10000r for 20 minutes to obtain the epoxy resin emulsion, and then the graphene nanoribbon aqueous solution is mixed with the epoxy resin emulsion to obtain a sizing agent, and the weight ratio of the graphene nanoribbon solution to the epoxy resin emulsion is 2:8.

[0087] The particle size of the sizing agent is 100-300 nm. It does not break the emulsion or separate after standing for more than 30 days, and does not break the emulsion or separate after centrifugation at 3000 rpm for 1 minute, which shows that the sizing agent of the present invention has the advantages of small particle size and high stability.

[0088] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A sizing agent raw material composition, characterized in that: The composition comprises a graphene nanoribbon solution, a nonionic surfactant, an alkali source and an epoxy resin emulsion.

2. The composition according to claim 1, wherein The amount of the alkaline source is such that the pH value of the prepared sizing agent is 9-13; The weight ratio of the graphene nanoribbon solution to the epoxy resin emulsion is 0.1-10:1, preferably 0.1-1:1, and more preferably 0.5-1:1; The amount of the nonionic surfactant is 1-20 mg / mL of the graphene nanoribbon solution, preferably 5-9 mg / mL of the graphene nanoribbon solution; The graphene nanoribbon solution contains 0.5-2wt% of graphene nanoribbons, and the rest is solvent, and the solvent is water.

3. The composition according to claim 1 or 2, wherein The graphene nanoribbon solution contains modified graphene nanoribbons and deionized water, wherein the modified graphene nanoribbons are at least one of graphene nanoribbons containing oxygen functional groups, graphene nanoribbons containing nitrogen functional groups, and graphene nanoribbons containing sulfur functional groups, preferably graphene nanoribbons containing oxygen functional groups, and further preferably, the oxygen-containing functional groups include hydroxyl groups and / or carboxyl groups; Preferably, the concentration of the modified graphene nanoribbons is 0.5-2wt%; and / or The nonionic surfactant is selected from at least one of Triton X-100, Triton X-114, Triton X-305 and Triton X-405, preferably Triton X-100; and / or The alkaline source is selected from at least one of aqueous ammonia, sodium hydroxide and potassium hydroxide; and / or The epoxy resin emulsion is bisphenol A epoxy emulsion; and / or The solid content of the epoxy resin emulsion is 30-50wt%; The epoxy resin emulsion comprises 30-50 wt % of bisphenol A epoxy resin, 1-10 wt % of emulsifier and 40-70 wt % of water; Preferably, the emulsifier is at least one selected from Triton X-100, Triton X-114, Triton X-305 and Triton X-405, preferably X-100.

4. A method for preparing a sizing agent, characterized in that: The method is prepared by using the formula of the raw material composition according to any one of claims 1 to 3, comprising: (1) adding a nonionic surfactant and an alkali source to a graphene nanoribbon solution and mixing the mixture to obtain solution I; (2) Add solution I into the epoxy resin emulsion and mix them.

5. The preparation method according to claim 4, wherein: The preparation steps of the graphene nanoribbon solution include: first mixing carbon nanotubes with an acidic solution, second mixing with an oxidant a, third mixing with an oxidant b, first centrifuging, washing, second centrifuging, dialyzing the centrifuge liquid, and using deionized water to set the concentration to 0.1-2wt%.

6. The method of claim 5, wherein: The acidic solution is selected from at least one of concentrated sulfuric acid, concentrated nitric acid and concentrated phosphoric acid; and / or The oxidant a is selected from at least one of potassium permanganate, potassium chlorate and sodium permanganate; and / or The oxidant b is selected from hydrogen peroxide.

7. The method according to any one of claims 5 to 6, wherein: The ratio of the carbon nanotubes to the acidic solution is 1 g:(100-500 mL); and / or The ratio of the carbon nanotubes to the oxidant a is 1g:(3-15g); and / or The ratio of the carbon nanotubes to the oxidant b is 1 g:(1-20 mL).

8. The method according to any one of claims 5 to 7, wherein: The first mixing condition includes: Temperature 10-30°C; and / or Time: 30-120min; and / or The second mixing condition includes: Temperature 50-80°C; and / or Time: 60-300min; and / or The third mixing condition is: Temperature 0-30°C; and / or Time: 5-20 minutes.

9. The method according to any one of claims 5 to 8, wherein: The first centrifugation condition includes: Duration 5-20 minutes; and / or The speed is 6000-10000rpm; and / or The second centrifugation condition includes: Duration 20-60 minutes; and / or The rotation speed is 4000-8000rpm.

10. The sizing agent prepared by the preparation method according to any one of claims 4 to 9, wherein the particle size of the sizing agent is 100-300 nm, and the sizing agent does not break the emulsion or separate when left to stand for more than 30 days, and does not break the emulsion or separate when centrifuged at 3000 rpm for 1 minute.

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