Method for preparing graphene composite fiber by using supercritical CO2 fluid and graphene composite fiber

Abstract

The invention discloses a method for preparing a graphene composite fiber by using a supercritical CO2 fluid and the graphene composite fiber. Comprising the following steps: step 1, mixing modified graphene, polyvinylpyrrolidone and polypropylene particles, stirring, melting, extruding and granulating to obtain graphene composite master batch; step 2, crushing and screening the graphene composite master batch, blending and stirring the graphene composite master batch and polypropylene powder, and carrying out melt spinning to obtain a nascent filament; then carrying out drafting, heat setting and winding operations to obtain modified fibers; and 3, putting the modified fiber into a supercritical fabric dyeing kettle, and carrying out supercritical CO2 fluid treatment to finally obtain the graphene composite fiber. The method has the beneficial effects that the fibers are treated by supercritical CO2 fluid, and uniform dispersion of internal components of the fibers is enhanced by utilizing unique solubility and permeability of the supercritical CO2 fluid; meanwhile, graphene is chemically modified in the fiber preparation process, functional groups are introduced, and the performance of the composite fiber is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of fiber materials, and specifically, relates to a method for preparing graphene composite fibers by using supercritical CO2 fluid and the graphene composite fibers. Background Art

[0002] With the rapid development of technology, the demand for high-performance fiber materials in the fields of aerospace, automotive manufacturing, electronic devices, medical protection, etc. is increasing day by day. Graphene, as a two-dimensional material with excellent mechanical, electrical, and thermal properties, is considered an ideal reinforcing phase for preparing high-performance composite fibers.

[0003] However, there are still many defects in the existing technologies. First, the dispersibility of graphene in the polymer matrix is poor, and it is easy to agglomerate, resulting in stress concentration inside the fiber and weakening its reinforcing effect. Second, the interfacial compatibility between graphene and the polymer is insufficient, and it is difficult to form an effective stress transfer mechanism. When the fiber is stressed, interfacial debonding is likely to occur, and the high-strength characteristics of graphene cannot be fully utilized. In addition, the traditional preparation process is complex, inefficient, costly, and often uses a large amount of organic solvents, causing environmental pollution. In terms of functionality, the existing fibers mainly focus on improving mechanical properties, but are insufficient in multifunctional properties such as antibacterial and flame retardant, and it is difficult to meet the requirements of fields such as medical protection and electronic devices.

[0004] Therefore, to solve the above problems, the present invention provides a method for preparing graphene composite fibers by using supercritical CO2 fluid. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the existing technologies, and provides a method for preparing graphene composite fibers by using supercritical CO2 fluid and the graphene composite fibers.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for preparing graphene composite fibers by using supercritical CO2 fluid, comprising the following steps:

[0008] Step 1: Mix modified graphene, polyvinylpyrrolidone, and polypropylene particles, stir for 1 - 2 h, and then melt-extrude and pelletize at 180 - 200 °C to obtain graphene composite masterbatch;

[0009] Step 2: Crush and screen the graphene composite masterbatch, blend and stir it with polypropylene powder for 2 - 3 h, transfer it to a spinning device, and obtain a nascent fiber through melt spinning; then perform stretching, heat setting, and winding operations to obtain modified fibers;

[0010] Step 3: Put the modified fiber into a supercritical fabric dyeing kettle for supercritical CO2 fluid treatment to finally obtain graphene composite fiber.

[0011] Preferably, the graphene composite masterbatch comprises the following components: by weight, 8 - 10 parts of modified graphene, 3 - 4 parts of polyvinylpyrrolidone, and 80 - 90 parts of polypropylene particles; the modified fiber comprises the following components: by weight, 10 - 12 parts of graphene composite masterbatch and 80 - 85 parts of polypropylene powder.

[0012] Preferably, the preparation process of the modified graphene is as follows:

[0013] S1: Mix 1 - tert - butoxycarbonylpiperazine, chloroacetyl chloride, triethylamine, and dichloromethane, stir and react at 0 °C for 4 - 5 h. Observe by thin - layer chromatography until the reaction is complete. After the reaction solution is extracted and washed, collect the organic phase, dry it to obtain intermediate A.

[0014] S2: Mix intermediate A, N,N - dimethylallylamine, and tetrahydrofuran, stir for 30 - 40 min, heat up to 40 - 50 °C, react for 1 - 2 h, cool, perform post - treatment, then transfer to acetonitrile, add 9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide and triethylamine, stir evenly, heat up to 80 - 90 °C, react for 3 - 4 h. After the reaction ends, cool to room temperature, filter and wash, then transfer to ethyl acetate, add concentrated hydrochloric acid, stir at room temperature for 1 - 2 h, perform post - treatment to obtain intermediate B.

[0015] S3: Mix intermediate B, graphene oxide, and N,N - dimethylformamide, ultrasonically stir for 30 - 40 min, add 1 - hydroxybenzotriazole, 1 - ethyl - 3 - (3 - dimethylaminopropyl)carbodiimide, and triethylamine, heat up to 80 - 90 °C, react for 3 - 4 h. After the reaction ends, cool to room temperature, wash and dry to obtain modified graphene.

[0016] In the scheme, 1 - tert - butoxycarbonylpiperazine and chloroacetyl chloride carry out an acylation reaction in the presence of triethylamine. Among them, chloroacetyl chloride is an acylation reagent, and its chlorine atom has high reaction activity. Under the condition that triethylamine is used as a base, the nitrogen atom of piperazine can attack the carbonyl carbon of chloroacetyl chloride to form an amide bond, thereby preparing intermediate A. The specific reaction equation is shown as follows:

[0017]

[0018] In the scheme, the tertiary amine nitrogen atom of N,N-dimethylallylamine has high nucleophilicity and can attack the chlorine atom contained in intermediate A to obtain a quaternary ammonium salt product. Then, the hydrogen atom in the P-H bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) can be attacked by the π electrons in the double bond contained in the quaternary ammonium salt product to form a new C-P bond. Finally, the tert-butoxycarbonyl (Boc) protecting group is removed under the action of concentrated hydrochloric acid to expose the amino group on the piperazine ring, obtaining intermediate B. The specific reaction equation is as follows:

[0019]

[0020] In the scheme, the amino group contained in intermediate B reacts with the carboxyl group on the surface of graphene oxide in the presence of 1-hydroxybenzotriazole (HOBT), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDCl), and triethylamine to graft the organic molecule onto the surface of graphene oxide, thereby realizing the modification of graphene.

[0021] More preferably, the raw materials of intermediate A include the following components: by weight, 16-18 parts of 1-tert-butoxycarbonylpiperazine, 10-12 parts of chloroacetyl chloride, 0.2-0.3 parts of triethylamine, and 60-70 parts of dichloromethane.

[0022] More preferably, the raw materials of intermediate A include the following components: by weight, 30-35 parts of intermediate A, 10-12 parts of N,N-dimethylallylamine, 80-85 parts of tetrahydrofuran, 80-85 parts of acetonitrile, 17-18 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1-2 parts of triethylamine, 40-50 parts of ethyl acetate, and 2-3 parts of concentrated hydrochloric acid.

[0023] More preferably, the raw materials of the modified graphene include the following components: by weight, 10-12 parts of intermediate B, 8-10 parts of graphene oxide, 60-70 parts of N,N-dimethylformamide, 1-2 parts of 1-hydroxybenzotriazole, 1-2 parts of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, and 0.3-0.4 parts of triethylamine.

[0024] More preferably, the parameters of the melt spinning are: temperature 250-300 °C, rate 1850-2000 m / min.

[0025] More preferably, the process parameters of the supercritical CO2 fluid treatment are: temperature 80-100 °C, pressure 10-20 MPa, time 30-40 min.

[0026] The beneficial effects of the present invention:

[0027] The present invention processes fibers through supercritical CO2 fluid, utilizes its unique solubility and permeability to enhance the uniform dispersion of internal components of the fibers; meanwhile, chemically modifies graphene during the fiber preparation process, introduces functional groups, and further improves the performance of the composite fibers. Specifically as follows:

[0028] Firstly: In the solution, N,N-dimethylallylamine reacts with intermediate A to generate a quaternary ammonium salt, which can undergo electrostatic adsorption with the negatively charged groups on the bacterial cell membrane, destroy the integrity of the cell membrane, cause the leakage of cell contents, thereby inhibiting the growth and reproduction of bacteria, and endowing the fibers with excellent antibacterial properties; subsequently, DOPO is introduced and combined through C-P bonds. The DOPO molecule contains phosphorus elements, which can decompose into phosphoric acid at high temperatures, promote the formation of a carbonized layer on the fiber surface, isolate oxygen and heat, and at the same time, the released water vapor dilutes the combustible gas, effectively inhibiting the combustion reaction, thereby significantly improving the thermal stability of the fibers;

[0029] Secondly: When the supercritical CO2 fluid processes the modified fibers, through plasticization, swelling and erosion effects, it changes the crystal structure, surface morphology and the motion state of molecular chain segments of the fibers, effectively improving the mechanical properties and thermal stability of the obtained graphene fibers. Specific Embodiments

[0030] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0031] Embodiment 1: A method for preparing graphene composite fibers using supercritical CO2 fluid, comprising the following steps:

[0032] Step 1: Mix 8 parts of modified graphene, 3 parts of polyvinylpyrrolidone, and 80 parts of polypropylene particles, stir for 1 h, and then melt-extrude and granulate at 180 °C to obtain graphene composite masterbatch;

[0033] Step 2: Crush and screen 10 parts of the graphene composite masterbatch, blend and stir it with 80 parts of polypropylene powder for 2 h, transfer it to a spinning device, and obtain a nascent filament through melt spinning (temperature 250 °C, rate 1850 m / min); then perform drawing, heat setting, and winding operations to obtain modified fibers;

[0034] Step 3: Place the modified fibers in a supercritical fabric dyeing instrument, perform supercritical CO2 fluid treatment (temperature 80 °C, pressure 10 MPa, time 30 min), and finally obtain graphene composite fibers;

[0035] The preparation process of the modified graphene is as follows:

[0036] S1: Mix 16 parts of 1-Boc-piperazine, 10 parts of chloroacetyl chloride, 0.2 part of triethylamine, and 60 parts of dichloromethane, stir and react at 0 °C for 4 h. Observe by thin-layer chromatography until the reaction is complete. After extraction and washing of the reaction solution, collect the organic phase, dry it, and obtain intermediate A;

[0037] S2: Mix 30 parts of intermediate A, 10 parts of N,N-dimethylallylamine, and 80 parts of tetrahydrofuran, stir for 30 min, heat up to 40 °C, react for 1 h, cool down, perform post-treatment, then transfer it to 80 parts of acetonitrile, add 17 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 1 part of triethylamine, stir evenly, heat up to 80 °C, react for 3 h. After the reaction is completed, cool down to room temperature, filter and wash, then transfer it to 40 parts of ethyl acetate, add 2 parts of concentrated hydrochloric acid, stir at room temperature for 1 h, perform post-treatment, and obtain intermediate B;

[0038] S3: Mix 10 parts of intermediate B, 8 parts of graphene oxide, and 60 parts of N,N-dimethylformamide, stir ultrasonically for 30 min, add 1 part of 1-hydroxybenzotriazole, 1 part of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, and 0.3 part of triethylamine, heat up to 80 °C, react for 3 h. After the reaction is completed, cool down to room temperature, wash, dry, and obtain modified graphene.

[0039] Example 2: A method for preparing graphene composite fibers by using supercritical CO2 fluid, comprising the following steps:

[0040] Step 1: Mix 10 parts of modified graphene, 4 parts of polyvinylpyrrolidone, and 90 parts of polypropylene particles, stir for 2 h, and then melt-extrude and granulate at 200 °C to obtain graphene composite masterbatch;

[0041] Step 2: Crush and screen 12 parts of the graphene composite masterbatch, blend and stir it with 85 parts of polypropylene powder for 3 h, transfer it to a spinning device, and obtain a nascent fiber by melt spinning (temperature 300 °C, rate 2000 m / min); then perform drawing, heat setting, and winding operations to obtain modified fibers;

[0042] Step 3: Put the modified fibers into a supercritical fabric dyeing kettle, perform supercritical CO2 fluid treatment (temperature 100 °C, pressure 20 MPa, time 40 min), and finally obtain graphene composite fibers;

[0043] The preparation process of the modified graphene is as follows:

[0044] S1: Mix 18 parts of 1-Boc-piperazine, 12 parts of chloroacetyl chloride, 0.3 part of triethylamine, and 70 parts of dichloromethane, stir and react at 0 °C for 5 h. Observe by thin-layer chromatography until the reaction is complete. After extraction and washing of the reaction solution, collect the organic phase, dry it to obtain intermediate A;

[0045] S2: Mix 35 parts of intermediate A, 12 parts of N,N-dimethylallylamine, and 85 parts of tetrahydrofuran, stir for 40 min, heat up to 50 °C, react for 2 h, cool down, perform post-treatment, then transfer to 85 parts of acetonitrile, add 18 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 2 parts of triethylamine, stir evenly, heat up to 90 °C, react for 4 h. After the reaction is completed, cool to room temperature, filter and wash, then transfer to 50 parts of ethyl acetate, add 3 parts of concentrated hydrochloric acid, stir at room temperature for 2 h, perform post-treatment to obtain intermediate B;

[0046] S3: Mix 12 parts of intermediate B, 10 parts of graphene oxide, and 70 parts of N,N-dimethylformamide, stir ultrasonically for 40 min, add 1 part of 1-hydroxybenzotriazole, 1 part of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, 0.3 part of triethylamine, heat up to 90 °C, react for 4 h. After the reaction is completed, cool to room temperature, wash and dry to obtain modified graphene.

[0047] Example 3: A method for preparing graphene composite fibers using supercritical CO2 fluid, comprising the following steps:

[0048] Step 1: Mix 9 parts of modified graphene, 3.5 parts of polyvinylpyrrolidone, and 85 parts of polypropylene particles, stir for 1.5 h, then melt and extrude and granulate at 190 °C to obtain graphene composite masterbatch;

[0049] Step 2: Crush and screen 11 parts of graphene composite masterbatch, blend and stir with 82.5 parts of polypropylene powder for 2.5 h, transfer to a spinning device, and obtain a nascent fiber through melt spinning (temperature 275 °C, rate 1925 m / min); then perform drawing, heat setting, and winding operations to obtain modified fibers;

[0050] Step 3: Place the modified fibers in a supercritical fabric dyeing kettle, perform supercritical CO2 fluid treatment (temperature 90 °C, pressure 15 MPa, time 35 min) to finally obtain graphene composite fibers;

[0051] The preparation process of the modified graphene is as follows:

[0052] S1: Mix 17 parts of 1 - tert - butoxycarbonylpiperazine, 11 parts of chloroacetyl chloride, 0.25 part of triethylamine, and 65 parts of dichloromethane, stir and react at 0 °C for 4.5 h. Observe by thin - layer chromatography until the reaction is complete. After the reaction solution is extracted and washed, collect the organic phase, dry it, and obtain intermediate A;

[0053] S2: Mix 32.5 parts of intermediate A, 11 parts of N,N - dimethylallylamine, and 82.5 parts of tetrahydrofuran, stir for 35 min, heat up to 45 °C, react for 1.5 h, cool down, perform post - treatment, then transfer it to 82.5 parts of acetonitrile, add 17.5 parts of 9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide and 1.5 parts of triethylamine, stir evenly, heat up to 85 °C, react for 3.5 h. After the reaction ends, cool it to room temperature, filter and wash, then transfer it to 45 parts of ethyl acetate, add 2.5 parts of concentrated hydrochloric acid, stir at room temperature for 1.5 h, perform post - treatment, and obtain intermediate B;

[0054] S3: Mix 11 parts of intermediate B, 9 parts of graphene oxide, and 65 parts of N,N - dimethylformamide, stir ultrasonically for 35 min, add 1 part of 1 - hydroxybenzotriazole, 1 part of 1 - ethyl - 3 - (3 - dimethylaminopropyl)carbodiimide, and 0.3 part of triethylamine, heat up to 85 °C, react for 3.5 h. After the reaction ends, cool it to room temperature, wash, dry, and obtain modified graphene.

[0055] Comparative Example 1: Do not use supercritical CO2 fluid for preparation, and the rest is the same as in Example 3. Specifically as follows:

[0056] Step 1: Mix 9 parts of modified graphene, 3.5 parts of polyvinylpyrrolidone, and 85 parts of polypropylene particles, stir for 1.5 h, then melt - extrude and pelletize at 190 °C to obtain graphene composite masterbatch;

[0057] Step 2: Crush and screen 11 parts of graphene composite masterbatch, blend and stir it with 82.5 parts of polypropylene powder for 2.5 h, transfer it to a spinning device, and obtain nascent filaments by melt spinning (temperature 275 °C, rate 1925 m / min); then perform stretching, heat setting, and winding operations to obtain graphene composite fibers;

[0058] The preparation process of the modified graphene is as follows:

[0059] S1: Mix 17 parts of 1 - tert - butoxycarbonylpiperazine, 11 parts of chloroacetyl chloride, 0.25 part of triethylamine, and 65 parts of dichloromethane, stir and react at 0 °C for 4.5 h. Observe by thin - layer chromatography until the reaction is complete. After the reaction solution is extracted and washed, collect the organic phase, dry it, and obtain intermediate A;

[0060] S2: Mix 32.5 parts of intermediate A, 11 parts of N,N-dimethylallylamine, and 82.5 parts of tetrahydrofuran, stir for 35 min, heat up to 45 °C, react for 1.5 h, cool down, perform post-treatment, and then transfer to 82.5 parts of acetonitrile. Add 17.5 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 1.5 parts of triethylamine, stir evenly, heat up to 85 °C, react for 3.5 h. After the reaction ends, cool to room temperature, filter and wash, then transfer to 45 parts of ethyl acetate, add 2.5 parts of concentrated hydrochloric acid, stir at room temperature for 1.5 h, perform post-treatment to obtain intermediate B;

[0061] S3: Mix 11 parts of intermediate B, 9 parts of graphene oxide, and 65 parts of N,N-dimethylformamide, stir ultrasonically for 35 min, add 1 part of 1-hydroxybenzotriazole, 1 part of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, and 0.3 part of triethylamine, heat up to 85 °C, react for 3.5 h. After the reaction ends, cool to room temperature, wash, and dry to obtain modified graphene.

[0062] Comparative Example 2: Do not modify graphene, and the rest is the same as in Example 3, specifically as follows:

[0063] Step 1: Mix 9 parts of graphene oxide, 3.5 parts of polyvinylpyrrolidone, and 85 parts of polypropylene particles, stir for 1.5 h, and then melt-extrude and granulate at 190 °C to obtain graphene composite masterbatch;

[0064] Step 2: Crush and screen 11 parts of graphene composite masterbatch, blend and stir with 82.5 parts of polypropylene powder for 2.5 h, transfer to a spinning device, and obtain a nascent fiber through melt spinning (temperature 275 °C, rate 1925 m / min); then perform drawing, heat setting, and winding operations to obtain modified fiber;

[0065] Step 3: Put the modified fiber into a supercritical fabric dyeing kettle and perform supercritical CO2 fluid treatment (temperature 90 °C, pressure 15 MPa, time 35 min) to finally obtain graphene composite fiber.

[0066] Detection test: (1) Detect the antibacterial properties of the graphene composite fibers obtained in the examples and comparative examples according to GB / T20944.3 "Evaluation of Antibacterial Properties of Textiles - Part 3: Oscillation Method" (select Escherichia coli as the strain); (2) Refer to GB / T14344-2008 "Test Method for Tensile Properties of Chemical Fiber Filaments" to measure the breaking strength of the graphene composite fibers obtained in the examples and comparative examples at 25 °C; (3) Refer to ASTM D-648 to test the heat distortion temperature of the graphene composite fibers obtained in the examples and comparative examples; the obtained data are shown in the following table:

[0067]

[0068] Table 1

[0069] Conclusion: Through supercritical CO2 fluid treatment and chemical modification of graphene, the comprehensive properties of graphene composite fibers are significantly improved. Experimental data shows that the fiber breaking strength of Example 3 reaches 1.32 N / tex, the heat distortion temperature reaches 126 °C, and the antibacterial rate against Escherichia coli is as high as 99.8%. Compared with Comparative Example 1 without supercritical treatment (breaking strength 0.88 N / tex, heat distortion temperature 102 °C, antibacterial rate 90.5%) and Comparative Example 2 without graphene modification (breaking strength 0.85 N / tex, heat distortion temperature 95 °C, antibacterial rate 80.8%), all performance indicators are significantly improved, indicating that the method of the present invention has significant advantages in enhancing the mechanical properties, thermal stability and antibacterial properties of the fibers and has good application prospects.

[0070] In the description of the specification, the description with reference to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0071] The above content is only an example and illustration of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined by the claims of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing graphene composite fibers using supercritical CO2 fluid, characterized in that: The following steps are involved: Step 1: Mix modified graphene, polyvinyl pyrrolidone and polypropylene particles, stir for 1-2 hours, and then melt-extrude and granulate at 180-200° C. to obtain a graphene composite masterbatch; Step 2: Grind and screen the graphene composite masterbatch, blend and stir with polypropylene powder for 2-3 hours, transfer to the spinning equipment, and obtain primary yarn by melt spinning; Then, the fiber is stretched, heat-set, and wound to obtain modified fiber. Step 3: Place the modified fiber into a supercritical fabric dyeing kettle and perform supercritical CO2 fluid treatment to finally obtain graphene composite fiber.

2. The method for preparing graphene composite fibers using supercritical CO2 fluid according to claim 1, characterized in that: The graphene composite masterbatch comprises the following components: 8-10 parts by weight of modified graphene, 3-4 parts of polyvinyl pyrrolidone, and 80-90 parts of polypropylene particles; The modified fiber comprises the following components: 10-12 parts by weight of graphene composite masterbatch and 80-85 parts of polypropylene powder.

3. The method for preparing graphene composite fibers using supercritical CO2 fluid according to claim 1, characterized in that: The preparation process of the modified graphene is: S1: 1-tert-butyloxycarbonylpiperazine, chloroacetyl chloride, triethylamine and dichloromethane were mixed and stirred at 0°C for 4-5 hours. The reaction was observed to be complete by thin layer chromatography. The reaction solution was extracted and washed, and the organic phase was collected and dried to obtain intermediate A; S2: Mix intermediate A, N,N-dimethylpropyleneamine and tetrahydrofuran, stir for 30-40 minutes, heat to 40-50°C, react for 1-2 hours, cool, post-treat, then transfer to acetonitrile, add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and triethylamine, stir evenly, heat to 80-90°C, react for 3-4 hours, cool to room temperature after the reaction, filter and wash, transfer to ethyl acetate, add concentrated hydrochloric acid, stir at room temperature for 1-2 hours, post-treat to obtain intermediate B; S3: Mix the intermediate B, graphene oxide and N,N-dimethylformamide, stir ultrasonically for 30-40 min, add 1-hydroxybenzotriazole, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and triethylamine, heat to 80-90°C, react for 3-4 h, cool to room temperature after the reaction, wash and dry to obtain modified graphene.

4. The method for preparing graphene composite fibers using supercritical CO2 fluid according to claim 3, characterized in that: The intermediate A raw material comprises the following components: by weight, 16-18 parts of 1-tert-butyloxycarbonylpiperazine, 10-12 parts of chloroacetyl chloride, 0.2-0.3 parts of triethylamine, and 60-70 parts of dichloromethane.

5. The method for preparing graphene composite fibers using supercritical CO2 fluid according to claim 3, characterized in that: The intermediate A raw material comprises the following components: by weight, 30-35 parts of intermediate A, 10-12 parts of N,N-dimethylpropyleneamine, 80-85 parts of tetrahydrofuran, 80-85 parts of acetonitrile, 17-18 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1-2 parts of triethylamine, 40-50 parts of ethyl acetate, and 2-3 parts of concentrated hydrochloric acid.

6. The method for preparing graphene composite fibers using supercritical CO2 fluid according to claim 3, characterized in that: The raw materials of the modified graphene include the following components: by weight, 10-12 parts of intermediate B, 8-10 parts of graphene oxide, 60-70 parts of N,N-dimethylformamide, 1-2 parts of 1-hydroxybenzotriazole, 1-2 parts of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, and 0.3-0.4 parts of triethylamine.

7. The method for preparing graphene composite fibers using supercritical CO2 fluid according to claim 1, characterized in that: The melt spinning parameters are: temperature 250-300° C., speed 1850-2000 m / min.

8. The method for preparing graphene composite fibers using supercritical CO2 fluid according to claim 1, characterized in that: The process parameters of the supercritical CO2 fluid treatment are: temperature 80-100°C, pressure 10-20MPa, and time 30-40min.

9. A graphene composite fiber obtained according to the method for preparing graphene composite fibers using supercritical CO2 fluid according to any one of claims 1 to 8.

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