Self-emulsifying degradable carbon fiber sizing agent, and preparation method and application thereof

Abstract

The application discloses a self-emulsifying degradable carbon fiber sizing agent and a preparation method and application thereof. Raw materials of the self-emulsifying degradable carbon fiber sizing agent include the following components in parts by weight: diglycidyl ester epoxy resin monomer 20-30 parts, fatty amine 1-3 parts, amine curing agent 5-10 parts, sodium p-aminobenzenesulfonate 1-3 parts, water 15-20 parts and acetone 20-30 parts. The self-emulsifying degradable carbon fiber sizing agent can significantly improve wear resistance of the carbon fiber and interface performance of a composite material, and can be degraded under mild conditions, and the carbon fiber recovered has good performance.

Description

Technical Field

[0001] This invention belongs to the field of carbon fiber sizing agent preparation technology, specifically relating to a self-emulsifying and biodegradable carbon fiber sizing agent, its preparation method, and its application. Background Technology

[0002] Carbon fiber reinforced composites have attracted much attention in aerospace, rail transportation, and new energy fields due to their advantages such as high specific strength and high specific modulus. They are mainly composed of carbon fiber reinforcement materials and resin matrix. Due to friction damage during carbon fiber processing and use, as well as interfacial bonding issues during composite molding, high-performance carbon fiber reinforced composites usually require a sizing process to form an organic layer on the surface that has wear resistance and compatibilization properties.

[0003] Carbon fiber sizing agents are mainly composed of resins, solvents, and other additives, with epoxy resin being one of the most widely used. However, because epoxy resin is a thermosetting resin, its cured three-dimensional cross-linked network makes the resulting products insoluble and difficult to degrade or recycle. Currently, desizing of sized carbon fibers can only be achieved through methods such as ablation and solvent soaking, which severely damages the surface of the high-value carbon fibers inside, affecting their secondary use. With the increasing demand for carbon fibers, the lack of green sizing agents and desizing technologies will result in significant economic and environmental losses.

[0004] In recent years, some studies have focused on developing biodegradable carbon fiber sizing agents. For example, patent CN202211637943.6 discloses a recyclable sizing agent for carbon fiber, its products, and applications. Its biodegradability is mainly achieved through dynamic Schiff base groups formed by aldehyde-containing epoxy resin and amine curing agents. Patent CN202111084936.3 discloses a biodegradable resin carbon fiber sizing agent, whose biodegradability is mainly achieved through the introduction of acetal, ketal, and triazine ring groups into the epoxy resin. However, the above-mentioned sizing agents all require the introduction of additional dynamic covalent bonds through synthetic reactions, making practical application difficult. Therefore, providing a simple and easy-to-use sizing agent is an urgent problem to be solved. Summary of the Invention

[0005] The main objective of this invention is to provide a self-emulsifying and biodegradable carbon fiber sizing agent, its preparation method, and its application, so as to overcome the shortcomings of the prior art.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] This invention provides a self-emulsifying biodegradable carbon fiber sizing agent. The raw materials of the self-emulsifying biodegradable carbon fiber sizing agent include the following components calculated by weight: 20-30 parts of diglycidyl ester epoxy resin monomer, 1-3 parts of fatty amine, 5-10 parts of amine curing agent, 1-3 parts of sodium p-aminobenzenesulfonate, 15-20 parts of water, and 20-30 parts of acetone.

[0008] This invention also provides a method for preparing the aforementioned self-emulsifying biodegradable carbon fiber sizing agent, comprising:

[0009] Sodium aminobenzoate is mixed with some water to form a sodium aminobenzoate solution;

[0010] Furthermore, diglycidyl ester epoxy resin monomer, amine curing agent, and fatty amine are dissolved in acetone and stirred to react. Then, the sodium aminobenzoate solution is added and the reaction is continued with stirring. Finally, the remaining water is added to prepare a self-emulsifying biodegradable carbon fiber sizing agent.

[0011] The present invention also provides a sizing method, which includes: passing carbon fibers through the aforementioned self-emulsifying biodegradable carbon fiber sizing agent at a rate of 0.5~1m / min, and then drying them to obtain sized carbon fibers; preferably, the drying temperature is 80~120℃ and the time is 5~10min.

[0012] The present invention also provides sized carbon fibers prepared by the aforementioned sizing method.

[0013] The embodiments of the present invention also provide the use of the aforementioned self-emulsifying biodegradable carbon fiber sizing agent or sizing carbon fiber in the preparation of carbon fiber reinforced composite materials for wind power, automobiles, aerospace, sports equipment or military applications.

[0014] This invention also provides a method for recovering carbon fibers from sized carbon fibers, comprising:

[0015] The sized carbon fiber is mixed with acid or alkali and solvent and heated at 25~200℃ to degrade it, thereby realizing the recycling of carbon fiber; wherein the sized carbon fiber includes the aforementioned sized carbon fiber.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] (1) The present invention uses commercially available epoxy resin as the main component directly, without the need for additional emulsifiers. The surface of the sized carbon fiber has abundant epoxy groups, active groups and hydrogen bond groups. After sizing, it can be easily degraded under mild conditions and high-quality carbon fiber can be recycled.

[0018] (2) The sizing agent provided by the present invention can significantly improve the wear resistance of carbon fiber and the interfacial properties of composite material, and can be degraded under mild conditions, and the recycled carbon fiber retains good properties. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figures 1a-1b These are scanning electron microscope images of carbon fibers before and after recycling in Embodiment 1 of the present invention. Detailed Implementation

[0021] In view of the deficiencies of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention. This invention uses commercially available epoxy resin as the main component directly, without the need for additional emulsifiers. The resulting sized carbon fiber has abundant epoxy groups, active groups and hydrogen bond groups on its surface, and after sizing, it can be easily degraded under mild conditions, thus achieving the recycling of high-quality carbon fiber.

[0022] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Specifically, as one aspect of the technical solution of the present invention, the raw materials of a self-emulsifying biodegradable carbon fiber sizing agent include the following components calculated by weight: 20-30 parts of diglycidyl ester epoxy resin monomer, 1-3 parts of fatty amine, 5-10 parts of amine curing agent, 1-3 parts of sodium p-aminobenzenesulfonate, 15-20 parts of water and 20-30 parts of acetone.

[0024] In some preferred embodiments, the self-emulsifying biodegradable carbon fiber sizing agent has a structure as shown in formula (I):

[0025]

[0026] Formula (I)

[0027] Among them, R1 is derived from diglycidyl ester epoxy resin monomer, R2 is derived from amine curing agent, and R3 is derived from fatty amine.

[0028] Specifically, R1, R2, and R3 correspond to the main structure of the diglycidyl ester epoxy resin monomer, the main structure of the polyamide / polyetheramine curing agent, and the aliphatic amine alkyl chain, respectively.

[0029] In some preferred embodiments, the diglycidyl ester epoxy resin monomer includes any one or more combinations of 1,2-cyclohexanedicarboxylic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, adipate diglycidyl ester, and dimeric acid diglycidyl ester, and is not limited thereto.

[0030] In some preferred embodiments, the aliphatic amine includes, but is not limited to, C2-C18 aliphatic alkane primary amines and / or C2-C18 aliphatic alkane secondary amines.

[0031] In some preferred embodiments, the amine curing agent includes, but is not limited to, polyamides and / or polyetheramines.

[0032] In some preferred embodiments, the molecular weight of the amine curing agent is less than or equal to 2000.

[0033] In some preferred embodiments, the water is deionized water.

[0034] Another aspect of the present invention provides a method for preparing the aforementioned self-emulsifying biodegradable carbon fiber sizing agent, comprising:

[0035] Sodium aminobenzoate is mixed with some water to form a sodium aminobenzoate solution;

[0036] Furthermore, diglycidyl ester epoxy resin monomer, amine curing agent, and fatty amine are dissolved in acetone and stirred to react. Then, the sodium aminobenzoate solution is added and the reaction is continued with stirring. Finally, the remaining water is added to prepare a self-emulsifying biodegradable carbon fiber sizing agent.

[0037] In some preferred embodiments, the preparation method specifically includes:

[0038] Diglycidyl ester epoxy resin monomer, amine curing agent, and fatty amine are dissolved in acetone and stirred at 25-60°C for 1-2 hours. Then, the sodium aminobenzoate solution is added and stirred at 25-60°C for 1-2 hours until emulsification forms an emulsion.

[0039] In addition, the remaining water is added to the emulsion to prepare a self-emulsifying biodegradable carbon fiber sizing agent.

[0040] In some more specific embodiments, the preparation method of the self-emulsifying biodegradable carbon fiber sizing agent includes:

[0041] (1) Dissolve diglycidyl ester epoxy resin monomer, amine curing agent and fatty amine in acetone and stir at 25~60℃ for 1~2 hours;

[0042] (2) Dissolve sodium p-aminobenzoate in a portion of deionized water to obtain a mixed solution. Add the mixed solution to the stirred system prepared in step 1, and continue stirring at 25-60°C for 1-2 hours until the system emulsifies;

[0043] (3) Continue to add the remaining deionized water to the above emulsion to dilute it, and obtain a self-emulsifying biodegradable carbon fiber sizing agent containing sulfonate groups.

[0044] Another aspect of the present invention provides a sizing method, which includes: passing carbon fibers through the aforementioned self-emulsifying biodegradable carbon fiber sizing agent at a rate of 0.5~1m / min, followed by drying treatment to obtain sized carbon fibers.

[0045] Furthermore, the drying process is carried out at a temperature of 80~120℃ (preferably 100℃) for 5~10 minutes.

[0046] In some more specific embodiments, the sizing method of the self-emulsifying biodegradable carbon fiber sizing agent includes: pouring the aforementioned self-emulsifying biodegradable carbon fiber sizing agent into a sizing tank, passing the carbon fiber through the sizing tank at a speed of 0.5~1m per minute, then drying the solvent in an oven at 100°C for 5~10 minutes, and finally winding it up to obtain sized carbon fiber.

[0047] Another aspect of the present invention provides sized carbon fibers prepared by the aforementioned sizing method.

[0048] Another aspect of the present invention provides the use of the aforementioned self-emulsifying biodegradable carbon fiber sizing agent or sizing carbon fiber in the preparation of carbon fiber reinforced composite materials for wind power, automobiles, aerospace, sports equipment or military applications.

[0049] Another aspect of the present invention provides a method for recovering carbon fibers from sized carbon fibers, comprising:

[0050] The sized carbon fiber is mixed with acid or alkali and solvent and heated at 25~200℃ to degrade it, thereby realizing the recycling of carbon fiber; wherein the sized carbon fiber includes the aforementioned sized carbon fiber.

[0051] In some preferred embodiments, the mass ratio of the sized carbon fiber, acid or alkali, and solvent is 1~10:1~10:50~80, but is not limited thereto. In some preferred embodiments, the acid includes, but is not limited to, hydrohalic acids, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, trifluoroacetic acid, methanesulfonic acid, p-toluenesulfonic acid, benzoic acid, etc.

[0052] In some preferred embodiments, the alkali includes, but is not limited to, sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia monohydrate, amines containing C1 to C20, etc.

[0053] In some preferred embodiments, the solvent includes, but is not limited to, acetone, butanone, ethyl acetate, propyl acetate, butyl acetate, dichloromethane, chloroform, diethyl ether, tetrahydrofuran, dioxane, dimethyl sulfoxide, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, C1-C20 alcohols, etc.

[0054] In some preferred embodiments, the degradation time is 1 to 48 hours, but is not limited thereto.

[0055] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0056] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0057] Example 1

[0058] Weigh 25 parts of diglycidyl 1,2-cyclohexanedicarboxylate, 2 parts of octadecylamine, and 6 parts of polyamide curing agent (brand name 651), and dissolve them in 25 parts of acetone. Stir at 40°C for 1.5 hours. Separately weigh 2 parts of sodium p-aminobenzenesulfonate and dissolve it in 8 parts of deionized water. Pour the resulting solution into the stirring system and continue stirring at 50°C for 1.2 hours. Then, add 8 parts of deionized water to dilute, obtaining a self-emulsifying and biodegradable carbon fiber sizing agent containing sulfonate groups.

[0059] The prepared carbon fiber sizing agent was poured into a sizing tank, and T800S carbon fiber was passed through the sizing tank at a speed of 0.6 m / min. The carbon fiber was then placed in an oven and dried at 100°C for 6 minutes. After winding, the sized carbon fiber was obtained. The monofilament tensile strength of the obtained sized carbon fiber was 6080 MPa, and the abrasion resistance was 1684 cycles.

[0060] The prepared sized carbon fibers were desized in a 1M hydrochloric acid / methanol system at 50°C for 5 hours. The tensile strength of the recovered carbon fibers was 5845 MPa. Scanning electron microscopy observations of the carbon fibers before and after recovery are shown below. Figures 1a-1b As shown.

[0061] Example 2

[0062] Weigh 28 parts of diglycidyl tetrahydrophthalate, 3 parts of dodecylamine, and 7 parts of polyetheramine curing agent (brand name D230), and dissolve them in 28 parts of acetone. Stir at 25°C for 2 hours. Separately weigh 3 parts of sodium p-aminobenzenesulfonate and dissolve them in 9 parts of deionized water. Pour the resulting solution into the stirring system and continue stirring at 25°C for 2 hours. Then, add 9 parts of deionized water to dilute, obtaining a self-emulsifying and biodegradable carbon fiber sizing agent containing sulfonate groups.

[0063] The prepared carbon fiber sizing agent was poured into a sizing tank, and T800S carbon fiber was passed through the sizing tank at a speed of 0.8 m / min. It was then placed in an oven and dried at 110℃ for 5 minutes. After winding, the sized carbon fiber was obtained. The monofilament tensile strength of the obtained sized carbon fiber was 6035 MPa, and the abrasion resistance was 1723 cycles.

[0064] The prepared sized carbon fibers were desized in a 1M potassium hydroxide / ethylene glycol system at 60°C for 6 hours, and the tensile strength of the single filament of the recovered carbon fibers was 5853 MPa.

[0065] Example 3

[0066] Weigh 30 parts of diglycidyl dimerase, 3 parts of hexadecylamine, and 6 parts of polyamide curing agent (brand name 650), and dissolve them in 30 parts of acetone. Stir at 55°C for 1.8 hours. Separately weigh 3 parts of sodium p-aminobenzenesulfonate and dissolve it in 10 parts of deionized water. Pour the resulting solution into the stirring system and continue stirring at 60°C for 1 hour. Then, add 10 parts of deionized water to dilute, thus obtaining a self-emulsifying and biodegradable carbon fiber sizing agent containing sulfonate groups.

[0067] The prepared carbon fiber sizing agent was poured into a sizing tank, and T800S carbon fiber was passed through the sizing tank at a speed of 1 m / min. It was then placed in an oven and dried at 100℃ for 6 minutes. After winding, the sized carbon fiber was obtained. The monofilament tensile strength of the obtained sized carbon fiber was 6012 MPa, and the abrasion resistance was 1646 cycles. This sized carbon fiber could be desized in a 5M acetic acid / ethanol system at 80℃ for 8 hours, and the monofilament tensile strength of the recycled carbon fiber was 5834 MPa.

[0068] Example 4

[0069] Weigh 20 parts of diglycidyl hexahydrophthalate, 1 part of decylamine, and 6 parts of polyetheramine curing agent (brand name D400), and dissolve them in 20 parts of acetone. Stir at 45°C for 1.5 hours. Separately weigh 1 part of sodium p-aminobenzenesulfonate and dissolve it in 7 parts of deionized water. Pour the resulting solution into the stirring system and continue stirring at 45°C for 1.5 hours. Then add 8 parts of deionized water to dilute, obtaining a self-emulsifying biodegradable carbon fiber sizing agent containing sulfonate groups.

[0070] The prepared carbon fiber sizing agent was poured into a sizing tank, and T800S carbon fiber was passed through the sizing tank at a speed of 0.5 m / min. The carbon fiber was then placed in an oven and dried at 80°C for 10 minutes. After winding, the sized carbon fiber was obtained. The monofilament tensile strength of the obtained sized carbon fiber was 6021 MPa, and the abrasion resistance was 1751 cycles.

[0071] The prepared sized carbon fibers were desized in a 1M ethylenediamine / dioxane system at 25°C for 12 hours, and the tensile strength of the single filament of the recovered carbon fibers was 5896 MPa.

[0072] Comparative Example 1

[0073] In this comparative example, 1,2-cyclohexanedicarboxylic acid diglycidyl ester in Example 1 was replaced with 1,4-cyclohexanediethanol diglycidyl ether, while the other components, contents, and operations remained unchanged.

[0074] The obtained sized carbon fiber has a single filament tensile strength of 5987 MPa and an abrasion resistance of 1540 cycles. This sized carbon fiber could not be desized in a 1M hydrochloric acid / methanol system at 50℃ for 48 hours, thus preventing carbon fiber recycling.

[0075] Comparative Example 2

[0076] In this comparative example, tetrahydrophthalic acid diglycidyl ester in Example 2 was replaced with 1,4-cyclohexanediethanol diglycidyl ether, while the other components, contents, and operations remained unchanged.

[0077] The obtained sized carbon fiber has a single filament tensile strength of 5912 MPa and an abrasion resistance of 1521 cycles. This sized carbon fiber could not be desized in a 1M potassium hydroxide / ethylene glycol system at 50°C for 48 hours, thus preventing carbon fiber recycling.

[0078] Comparative Example 3

[0079] The method is the same as in Example 1. Compared with Example 1, this comparative example lacks octadecylamine and replaces it with an equal part by weight of diglycidyl 1,2-cyclohexanedicarboxylate. The other components, contents and operations remain unchanged.

[0080] The obtained sized carbon fiber had a single filament tensile strength of 5903 MPa and an abrasion resistance of 1139 cycles. The sized carbon fiber was desized in a 1M hydrochloric acid / methanol system at 50°C for 5 hours, and the recovered carbon fiber had a single filament tensile strength of 5791 MPa.

[0081] Comparative Example 4

[0082] This comparative example differs from Example 1 in that it lacks sodium p-aminobenzenesulfonate, which is replaced by an equal part by weight of diglycidyl 1,2-cyclohexanedicarboxylate, while the other components, contents, and operations remain unchanged.

[0083] The obtained sized carbon fiber had a single filament tensile strength of 5894 MPa and an abrasion resistance of 1087 cycles. After desizing in a 1M hydrochloric acid / methanol system at 50°C for 10 hours, the recovered carbon fiber had a single filament tensile strength of 5658 MPa.

[0084] Comparative Example 5

[0085] Compared with Example 1, this comparative example replaces the polyamide curing agent (brand name 651) with a common isoflurane diamine curing agent, while the other components, contents and operations remain unchanged.

[0086] The obtained sized carbon fiber had a single filament tensile strength of 5915 MPa and an abrasion resistance of 1311 cycles. After desizing in a 1M hydrochloric acid / methanol system at 50°C for 5 hours, the recovered carbon fiber had a single filament tensile strength of 5784 MPa. The performance of Examples 1-4 and Comparative Examples 1-5 is summarized in Table 1.

[0087] Table 1 Performance test results of Examples 1-4 and Comparative Examples 1-5

[0088] name raw carbon fiber Tensile strength (MPa) of sized carbon fiber monofilament Tensile strength (MPa) of recycled carbon fiber monofilaments Wear resistance cycles (times) Example 1 T800S (5880 MPa) 6080 5845 1684 Example 2 T800S (5880 MPa) 6035 5853 1723 Example 3 T800S (5880 MPa) 6012 5834 1646 Example 4 T800S (5880 MPa) 6021 5896 1751 Comparative Example 1 T800S (5880 MPa) 5987 Non-recyclable 1540 Comparative Example 2 T800S (5880 MPa) 5912 Non-recyclable 1521 Comparative Example 3 T800S (5880 MPa) 5903 5791 1139 Comparative Example 4 T800S (5880 MPa) 5894 5658 1087 Comparative Example 5 T800S (5880 MPa) 5915 5784 1311

[0089] Example 5

[0090] The carbon fibers obtained in Example 1 were laid flat in a mold, and a commercially available E51 epoxy resin AB adhesive system was poured into the mold. The mixture was impregnated at 80°C for 30 minutes to obtain a carbon fiber prepreg. The prepreg was further hot-pressed on a flatbed hot press at a pressure of 85 MPa, and cured at 90°C for 3 hours, 115°C for 1.5 hours, and 140°C for 3 hours, respectively, to obtain a carbon fiber composite material. The resulting composite material had a tensile strength of 882 MPa, a flexural strength of 914 MPa, and an interlaminar shear strength of 104 MPa.

[0091] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0092] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A self-emulsifying and biodegradable carbon fiber sizing agent, characterized in that, The raw materials of the self-emulsifying biodegradable carbon fiber sizing agent include the following components by weight: 20-30 parts of diglycidyl ester epoxy resin monomer, 1-3 parts of fatty amine, 5-10 parts of amine curing agent, 1-3 parts of sodium p-aminobenzenesulfonate, 15-20 parts of water and 20-30 parts of acetone. The self-emulsifying and biodegradable carbon fiber sizing agent has the structure shown in Formula (I): ； Formula (I); Among them, R1 is derived from diglycidyl ester epoxy resin monomer, R2 is derived from amine curing agent, and R3 is derived from fatty amine.

2. The self-emulsifying biodegradable carbon fiber sizing agent according to claim 1, characterized in that: The diglycidyl ester epoxy resin monomer includes any one or more combinations of 1,2-cyclohexanedicarboxylic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, adipate diglycidyl ester, and dimeric acid diglycidyl ester.

3. The self-emulsifying biodegradable carbon fiber sizing agent according to claim 1, characterized in that: The fatty amines include C2-C18 fatty alkane primary amines and / or C2-C18 fatty alkane secondary amines.

4. The self-emulsifying biodegradable carbon fiber sizing agent according to claim 1, characterized in that: The amine curing agent includes polyamide and / or polyetheramine; and / or, the molecular weight of the amine curing agent is less than or equal to 2000.

5. The method for preparing the self-emulsifying biodegradable carbon fiber sizing agent according to any one of claims 1-4, characterized in that, include: Sodium p-aminobenzenesulfonate is mixed with some water to form a sodium p-aminobenzenesulfonate solution; Furthermore, diglycidyl ester epoxy resin monomer, amine curing agent, and fatty amine are dissolved in acetone and stirred to react. Then, the sodium p-aminobenzenesulfonate solution is added and the reaction is continued with stirring. Finally, the remaining water is added to prepare a self-emulsifying biodegradable carbon fiber sizing agent.

6. The preparation method according to claim 5, characterized in that, Specifically, it includes: Diglycidyl ester epoxy resin monomer, amine curing agent, and fatty amine are dissolved in acetone and stirred at 25-60°C for 1-2 hours. Then, the sodium p-aminobenzenesulfonate solution is added and stirred at 25-60°C for 1-2 hours until emulsification forms an emulsion. In addition, the remaining water is added to the emulsion to prepare a self-emulsifying biodegradable carbon fiber sizing agent.

7. A sizing method, characterized in that, include: Carbon fibers are passed through the self-emulsifying biodegradable carbon fiber sizing agent according to any one of claims 1-4 at a rate of 0.5-1 m / min, and then dried to obtain sized carbon fibers; wherein the drying temperature is 80-120°C and the time is 5-10 min.

8. A sized carbon fiber prepared by the sizing method of claim 7.

9. The use of the self-emulsifying biodegradable carbon fiber sizing agent according to any one of claims 1-4 or the sizing carbon fiber according to claim 8 in the preparation of carbon fiber reinforced composite materials for wind power, automobiles, sporting goods or military applications.

10. A method for recovering carbon fiber from sized carbon fiber, characterized in that, include: The sized carbon fiber is mixed with acid or alkali and solvent and heated at 25~200°C to degrade it, thereby realizing the recycling of carbon fiber; wherein the sized carbon fiber includes the sized carbon fiber of claim 8.

11. The method according to claim 10, characterized in that: The mass ratio of the sized carbon fiber, acid or alkali, and solvent is 1~10:1~10:50~80.

12. The method according to claim 10, characterized in that: The acid includes any one or more combinations of hydrohalic acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, trifluoroacetic acid, methanesulfonic acid, p-toluenesulfonic acid, and benzoic acid; and / or, the base includes any one or more combinations of sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonia monohydrate, and amines containing C1 to C20; and / or, the solvent includes any one or more combinations of acetone, butanone, ethyl acetate, propyl acetate, butyl acetate, dichloromethane, chloroform, diethyl ether, tetrahydrofuran, dioxane, dimethyl sulfoxide, acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, and alcohols containing C1 to C20.

13. The method according to claim 10, characterized in that: The degradation time is 1 to 48 hours.

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