Spinning solution for single-walled carbon nanotube fibers, preparation method and application

Abstract

The present invention discloses a spinning solution for single-walled carbon nanotube fibers, a preparation method, and applications. The spinning solution for single-walled carbon nanotube fibers comprises oleum, single-walled carbon nanotubes, and poly(arylene oxadiazole), wherein the mass of the single-walled carbon nanotubes is 1%-2% of the mass of the oleum, and the mass of the poly(arylene oxadiazole) is 0.1%-1% of the mass of the oleum. The present invention uses oleum and poly(ethylene glycol) diol (POD) as a dispersion solution, utilizes the strong oxidizing ability of the strong acid and the π-π bond action of the POD to improve the monodispersity of the carbon nanotubes. Simultaneously, utilizing the properties of the POD conductive polymer, the inter-tube resistance of the carbon nanotube composite fiber is reduced, while the spinnability of the spinning solution is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon nanotube fibers, and in particular to a spinning solution for single-walled carbon nanotube fibers, a preparation method and applications. Background Art

[0002] Carbon nanotube fibers, with their light weight, high strength, corrosion resistance, low density, strong flexibility, and excellent electrical and thermal conductivity, are crucial building blocks for the development of high-tech industries such as aerospace, new energy, and high-end equipment manufacturing. Micron-scale carbon nanotube conductive fibers, constructed from single-walled and double-walled carbon nanotubes, offer lightweight, high strength, corrosion resistance, low density, and excellent electrical conductivity. They are expected to replace traditional metallic conductive materials and represent an important development direction for new high-performance conductive fiber materials.

[0003] There are three main methods for preparing carbon nanotube fibers, namely floating catalytic spinning, array spinning, and wet spinning. Wet spinning technology evolved from traditional soluble polymer spinning technology and is the easiest to achieve large-scale production. At the same time, this method uses single-walled carbon nanotubes as raw materials, and the fibers prepared have good electrical conductivity and have a specific conductivity comparable to that of copper. Therefore, it is most suitable as a method for preparing lightweight, highly conductive carbon nanotube fibers. However, the lightweight, highly conductive carbon nanotube fibers currently prepared by wet spinning have not yet reached the optimal assembly state due to factors such as the length, defect structure, and preparation process of the carbon nanotubes. They have low density and unsatisfactory orientation, resulting in large intertube interface resistance, making it difficult to form a good electron transfer path in one step. The charge transfer efficiency between tubes is low, which limits the performance of its electrical properties. The relevant performance indicators are all less than 10% of their theoretical values, seriously affecting the application and development of carbon nanotube fibers.

[0004] Currently, improving the conductive properties of carbon nanotube fibers primarily involves manipulating their structure, reducing intertube resistance, increasing the number of charge carriers within the fiber, and combining them with other conductive materials to form composite fibers. As the fundamental building block of the fiber, the structure of the carbon nanotube itself significantly influences its conductivity. Previous studies have shown that single-walled carbon nanotubes with a larger aspect ratio exhibit lower interfacial resistance and higher fiber conductivity during liquid crystal spinning. However, high aspect ratio carbon nanotubes are more susceptible to entanglement, which not only affects the orientation but also the continuity of the carbon nanotube fibers. Therefore, achieving uniform dispersion in strongly acidic dispersions is currently a challenge. Furthermore, carbon nanotube fibers prepared by dry and wet spinning inevitably contain pores and gaps, resulting in a high electrical resistance even after densification.

[0005] In view of this, this application is hereby filed. Summary of the Invention

[0006] The purpose of the present invention is to provide a spinning solution, preparation method and application for single-walled carbon nanotube fibers. Using fuming sulfuric acid / polyaryl oxadiazole solution as a dispersion liquid for carbon nanotubes and a spinning aid for dry and wet spinning processes is beneficial for obtaining single-walled carbon nanotube fibers with high orientation and high density, and further helps to improve the conductivity of the single-walled carbon nanotube fibers.

[0007] The present invention is achieved in that:

[0008] In a first aspect, the present invention provides a spinning solution for single-walled carbon nanotube fibers, comprising fuming sulfuric acid, single-walled carbon nanotubes, and polyaromatic oxadiazole, wherein the mass of the single-walled carbon nanotubes is 1%-2% of the mass of the fuming sulfuric acid, and the mass of the polyaromatic oxadiazole is 0.1%-1% of the mass of the fuming sulfuric acid.

[0009] In an optional embodiment, the concentration of the fuming sulfuric acid is 2wt%-70wt%;

[0010] and / or, the aspect ratio of the single-walled carbon nanotube is 10,000-100,000;

[0011] and / or, the mass ratio of the single-walled carbon nanotubes to the poly(arylene oxadiazole) is (3-20):1;

[0012] and / or, the intrinsic viscosity of the polyarylene oxadiazole is 3-6 dL / g;

[0013] And / or, the viscosity of the spinning solution for the single-walled carbon nanotube fibers is 120-300 Pa·S.

[0014] In a second aspect, the present invention provides a method for preparing the spinning solution for single-walled carbon nanotube fibers described in the aforementioned embodiment, comprising: adding single-walled carbon nanotubes to fuming sulfuric acid and dispersing the single-walled carbon nanotubes in the fuming sulfuric acid, then adding polyarylene oxadiazole and stirring until the dispersion exhibits a graphite luster, thereby obtaining the spinning solution for single-walled carbon nanotube fibers.

[0015] In an optional embodiment, the method further comprises pretreatment: mixing agglomerated single-walled carbon nanotubes, water, and ethanol to obtain a mixture, breaking up the single-walled carbon nanotubes in the mixture using a wall breaking machine, then sequentially performing solid-liquid separation, drying, and removing amorphous carbon and impurities, and then adding the single-walled carbon nanotubes from which the amorphous carbon and impurities have been removed into fuming sulfuric acid;

[0016] Preferably, the impurity removal comprises: soaking the dried product in a hydrogen peroxide solution and a hydrochloric acid solution in sequence at 50° C.-70° C. and performing solid-liquid separation, and then heating the product at 350° C.-450° C. for 3 h-5 h.

[0017] In an optional embodiment, the preparation of polyarylene oxadiazole is also included:

[0018] Dissolving hydrazine sulfate and a reaction monomer in fuming sulfuric acid, then heating and sequentially performing prepolymerization and polycondensation to obtain a reaction liquid, and removing air and free SO3 from the reaction liquid to obtain the polyarylene oxadiazole;

[0019] Preferably, the reactive monomer is at least one of terephthalic acid, isophthalic acid, 4,4-biphenyl dicarboxylic acid and 4,4'-diphenyl ether dicarboxylic acid.

[0020] In an optional embodiment, the preparation of polyarylene oxadiazole satisfies at least one of the following:

[0021] A. the molar ratio of the hydrazine sulfate to the total molar amount of terephthalic acid and isophthalic acid is 1-1.1:1;

[0022] B. The prepolymerization temperature is 80-90°C and the time is 2.5-3.5h;

[0023] C. The temperature of polycondensation is 115-125℃ and the time is 1.5-2.5h.

[0024] In a third aspect, the present invention provides a method for spinning single-walled carbon nanotube fibers, comprising:

[0025] The single-walled carbon nanotube fiber described in the above embodiment is extruded into the air section using a syringe, then enters sulfuric acid, ethanol or acetone for the first stretching, and then enters water for the second stretching to obtain the fiber. The residual sulfuric acid in the fiber is removed, and then it is dried to obtain the single-walled carbon nanotube fiber.

[0026] In an optional embodiment, the spinning method satisfies at least one of the following:

[0027] a. The extrusion rate of the single-walled carbon nanotube fiber spinning solution is 0.13 ml / min -0.15 ml / min, and the pore size of the syringe outlet is 50μm-380μm;

[0028] b. The height of the air segment is 10 mm-50 mm;

[0029] c. The first stretching rate is 1.8m / S-3m / S;

[0030] d. The second stretching rate is 2.5m / s-3.5m / s;

[0031] e. The fiber was soaked in water for 1 h to remove residual sulfuric acid;

[0032] f. The fibers from which sulfuric acid has been removed are dried at 100° C. for 2 h to obtain the single-walled carbon nanotube fibers.

[0033] In a fourth aspect, the present invention provides a single-walled carbon nanotube fiber obtained by the spinning method described in the aforementioned embodiment.

[0034] The present invention has the following beneficial effects:

[0035] The present invention uses fuming sulfuric acid and POD as dispersion liquid, utilizes the strong oxidizing ability of strong acid and the π-π bond effect of POD to improve the monodispersity effect of carbon nanotubes; at the same time, utilizes the characteristics of POD conductive polymer to reduce the inter-tube resistance of carbon nanotube fibers and improve the spinnability of spinning solution.

[0036] The present invention adopts dry-wet spinning technology, introduces an air layer, and utilizes gravity to achieve highly oriented arrangement of carbon nanotubes.

[0037] The present invention adopts dilute sulfuric acid as the coagulation bath, which is conducive to realizing its industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0039] Figure 1 Schematic diagram of the dry-wet spinning process in Example 1;

[0040] Figure 2 This is a light microscope image of the spinning solution prepared in Example 1;

[0041] Figure 3 This is a polarizing microscope image of the spinning solution prepared in Example 1;

[0042] Figure 4 This is a light microscope image of the single-walled carbon nanotube fiber prepared in Example 1;

[0043] Figure 5 This is an SEM image of the single-walled carbon nanotube fiber prepared in Example 1. DETAILED DESCRIPTION

[0044] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0045] An embodiment of the present invention provides a spinning solution for single-walled carbon nanotube fibers, comprising fuming sulfuric acid, single-walled carbon nanotubes, and polyoxadiazole, wherein the mass of the single-walled carbon nanotubes is 1%-2% of the mass of the fuming sulfuric acid, and the mass of the polyoxadiazole is 0.1%-1% of the mass of the fuming sulfuric acid.

[0046] In the embodiment of the present invention, fuming sulfuric acid is used as a solvent, which is beneficial to the dispersion of single-walled carbon nanotubes.

[0047] Polyaryl oxadiazole (POD) is a main chain conjugated n-type conductive polymer containing an oxadiazole ring with excellent electronic and ionic conductivity. As a typical rigid chain polymer, it has a strong π-π stacking effect and can exist stably in fuming sulfuric acid. It can also be used as a conductive filler material, dispersant and spinning aid, thereby realizing the dry and wet spinning preparation of single-walled carbon nanotube fibers.

[0048] The present invention uses an oleum / polyarylene oxadiazole solution as a dispersant, which can inhibit the agglomeration of single-walled carbon nanotubes and facilitate the dispersion of the single-walled carbon nanotubes. On the one hand, the polyarylene oxadiazole conjugated n-type conductive polymer is used as an intertube filler. By utilizing its special conductivity and strong π-π stacking effect, it not only reduces the intertube resistance and realizes an electron path, but also forms a strong force with the carbon nanotube walls, weakening the interaction force between the tube walls, thereby achieving the purpose of high dispersion of the carbon nanotubes. On the other hand, the polyarylene oxadiazole is used as a spinning aid to increase the viscosity of the carbon nanotube dispersion, thereby facilitating the wet and dry spinning of the carbon nanotube / polyarylene oxadiazole / oleum spinning solution.

[0049] In an optional embodiment, the concentration of the fuming sulfuric acid is 2 wt %-70 wt %.

[0050] In an optional embodiment, the single-walled carbon nanotubes have an aspect ratio of 10,000 to 100,000. Single-walled carbon nanotubes with a larger aspect ratio are beneficial for improving the electrical conductivity of the fiber. However, single-walled carbon nanotubes with a larger aspect ratio are difficult to disperse in conventional solvents. In this application, due to the presence of poly (arylene oxadiazole) / oleum, single-walled carbon nanotubes with a larger aspect ratio can achieve a good dispersion effect.

[0051] In an optional embodiment, the mass ratio of the single-walled carbon nanotubes to the poly(arylene oxadiazole) is (3-20):1; a reduced proportion of poly(arylene oxadiazole) is beneficial to improving the conductive properties of the single-walled carbon nanotube fibers; however, if the proportion of poly(arylene oxadiazole) is too low, the viscosity of the spinning solution is too low, which is not conducive to dry-wet spinning. At the same time, the effect of weakening the force between the walls of the single-walled carbon nanotubes is reduced, which is not conducive to the monodispersity of the carbon nanotubes.

[0052] In an optional embodiment, the intrinsic viscosity of the polyarylene oxadiazole is 3-6 dL / g. Polyarylene oxadiazole with a larger molecular weight can reduce the amount of polyarylene oxadiazole used while maintaining the viscosity of the spinning solution for single-walled carbon nanotube fibers within a desired range.

[0053] In an optional embodiment, the viscosity of the spinning solution for the single-walled carbon nanotube fibers is 120-300 Pa·S. Too low a viscosity is not conducive to spinning, while too high a viscosity results in an excessively high POD content in the spinning solution, which is not conducive to improving the conductive properties of the single-walled carbon nanotube fibers.

[0054] An embodiment of the present invention also provides a method for preparing the spinning solution for single-walled carbon nanotube fibers described in the aforementioned embodiment, comprising: adding single-walled carbon nanotubes to fuming sulfuric acid and dispersing the single-walled carbon nanotubes in the fuming sulfuric acid, then adding polyaryl oxadiazole and stirring until the dispersion exhibits a graphite luster, thereby obtaining the spinning solution for single-walled carbon nanotube fibers.

[0055] In an optional embodiment, a pretreatment is further included: agglomerated single-walled carbon nanotubes, water and ethanol are mixed to obtain a mixture, the single-walled carbon nanotubes in the mixture are broken up by using a wall breaking machine, followed by solid-liquid separation, drying and removal of amorphous carbon and impurities, and then the single-walled carbon nanotubes without amorphous carbon and impurities are added to fuming sulfuric acid.

[0056] In an optional embodiment, the impurity removal includes: soaking the dried product in a hydrogen peroxide solution and a hydrochloric acid solution at 50°C-70°C in sequence and performing solid-liquid separation, and then heating the product at 350°C-450°C for 3h-5h. Among them, hydrogen peroxide, as an oxidant, can oxidize and remove some impurities, and hydrochloric acid is beneficial to the dissolution of metal ions in the product. The soaking time can be specifically as low as 6-24h. In an optional embodiment, the preparation of polyaromatic oxadiazole is also included: dissolving hydrazine sulfate and reaction monomers in fuming sulfuric acid, then heating and sequentially performing prepolymerization and polycondensation to obtain a post-reaction liquid, removing air and free SO3 in the post-reaction liquid to obtain the polyaromatic oxadiazole;

[0057] Preferably, the reactive monomer is at least one of terephthalic acid, isophthalic acid, 4,4-biphenyl dicarboxylic acid and 4,4'-diphenyl ether dicarboxylic acid.

[0058] In an optional embodiment, the preparation of polyarylene oxadiazole satisfies at least one of the following:

[0059] A. the total molar ratio of the hydrazine sulfate to the reaction monomer is 1-1.1:1;

[0060] B. The prepolymerization temperature is 80-90°C and the time is 2.5-3.5h;

[0061] C. The temperature of polycondensation is 115-125℃ and the time is 1.5-2.5h.

[0062] In the present application, the POD structures produced by polymerization of different monomers are different, and the π-π forces between the molecules are also different. In addition, adjusting the preparation conditions of the polyarylene oxadiazole is beneficial to regulating the intrinsic viscosity of the prepared polyarylene oxadiazole.

[0063] An embodiment of the present invention further provides a spinning method for single-walled carbon nanotube fibers, comprising:

[0064] The single-walled carbon nanotube fiber described in the above embodiment is extruded into the air section using a syringe, then enters sulfuric acid, ethanol or acetone for the first stretching, and then enters water for the second stretching to obtain the fiber, and the residual sulfuric acid and water in the fiber are removed to obtain the single-walled carbon nanotube fiber.

[0065] By introducing air segments during the spinning process, the carbon nanotubes are highly oriented under the action of gravity, realizing a macroscopic preparation process of lightweight, highly conductive carbon nanotube composite fibers with high orientation, high density and continuity, which is conducive to obtaining single-walled carbon nanotube fibers with better conductive properties.

[0066] In the present application, sulfuric acid, ethanol or acetone is used as the coagulation bath, which is conducive to large-scale industrial application. The concentration of sulfuric acid can be 10-50wt%.

[0067] In an optional embodiment, the spinning method satisfies at least one of the following:

[0068] a. The extrusion rate of the single-walled carbon nanotube fiber spinning solution is 0.13 ml / min -0.15 ml / min, and the pore size of the syringe outlet is 50μm-380μm.

[0069] b. The height of the air segment is 10 mm-50 mm; by regulating the height of the air segment, the orientation and close packing of the gravity-induced carbon nanotube spinning solution can be regulated.

[0070] c. The drawing rate of the first drawing is 1.8 m / s-3 m / s.

[0071] d. The second stretching rate is 2.5 m / s-3.5 m / s; regulating the difference between the extrusion rate and the stretching rate is conducive to achieving high orientation and high density of single-walled carbon nanotubes.

[0072] e. Soak the fiber in water for 1 hour to remove residual sulfuric acid.

[0073] f. The fibers from which sulfuric acid has been removed are dried at 100° C. for 2 h to obtain the single-walled carbon nanotube fibers.

[0074] An embodiment of the present invention further provides a single-walled carbon nanotube fiber obtained by the spinning method described in the above embodiment.

[0075] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0076] Example 1

[0077] This embodiment provides a spinning method for single-walled carbon nanotube fibers, comprising:

[0078] 1. Pretreatment of single-walled carbon nanotubes

[0079] The agglomerated single-walled carbon nanotubes were placed in a wall-breaking machine, and water and ethanol were added to break them up and break them up. The mixed liquid was then filtered and placed in a freeze dryer for freeze drying. The freeze-dried single-walled carbon nanotubes were then immersed in a hydrogen peroxide solution and a hydrochloric acid solution for 24 hours each. After filtration and drying, they were placed in a muffle furnace and heated at 400°C for 4 hours to remove the amorphous carbon and impurities inside the single-walled carbon nanotubes.

[0080] 2. Preparation of POD

[0081] A one-step, three-stage polycondensation method was used. 17.07 g of hydrazine sulfate, 20.76 g of terephthalic acid, and 5.3 g of isophthalic acid were dissolved in 150 mL of fuming sulfuric acid in a 250 mL three-necked flask equipped with a mechanical stirrer. The temperature was raised to 85°C, the prepolymerization temperature, and the reaction was allowed to proceed for 3 hours. The temperature was then raised to 120°C, the polycondensation temperature, and the reaction was continued for 2 hours. The original solution was vacuum degassed to remove free SO₃ and set aside.

[0082] 3. Preparation of Spinning Dope

[0083] 50g of 20% fuming sulfuric acid was placed in a 250mL three-necked flask, and single-walled carbon nanotubes (1% by weight of fuming sulfuric acid) were added. The single-walled carbon nanotubes were dispersed using a high-speed stirrer. Then, polyarylene oxadiazole (1% by weight of fuming sulfuric acid) was added and stirred until the dispersion showed a graphite luster. The spinning solution of single-walled carbon nanotubes / polyarylene oxadiazole was obtained. The optical microscopy and polarizing microscopy images are shown below. Figure 2 and Figure 3 As shown, after the stirring is terminated, the spinning solution is allowed to stand for degassing. The aspect ratio of the single-walled carbon nanotubes is 100,000, the intrinsic viscosity of the polyoxadiazole is 6 dL / g, and the viscosity of the spinning solution is 300 Pa·s.

[0084] 4. Dry and wet spinning process

[0085] like Figure 1As shown, the single-walled carbon nanotube / POD spinning solution was transferred to a syringe, and a micro-pump syringe was used to control the extrusion rate to 0.13 ml / min. The syringe aperture was 200 μm, and the solution was injected vertically into the air segment with a height of 50 mm. The solution then entered a T-shaped coagulation bath filled with dilute sulfuric acid and was stretched once through a winding device at a rate of 3 m / s. The solution then entered water for a second stretch at a rate of 3.5 m / s. The collection reel speed was the same as the second stretch speed. The collected fibers were soaked in water for 1 hour to remove the residual sulfuric acid in the fibers, and then dried in an oven at 100°C for 2 hours. The diameter of the single-walled carbon nanotube fibers was 0.1 mm, as shown in the figure. Figure 4 The SEM images of the fibers are shown in Figure 5 shown.

[0086] Example 2:

[0087] This embodiment provides a spinning method for single-walled carbon nanotube fibers, comprising:

[0088] 1. Pretreatment of single-walled carbon nanotubes

[0089] The agglomerated single-walled carbon nanotubes are placed in a wall-breaking machine, and water and ethanol are added to break them up and break them up. The mixed liquid is then filtered and placed in a freeze dryer for freeze drying. The freeze-dried single-walled carbon nanotubes are then immersed in a hydrogen peroxide solution and a hydrochloric acid solution for 24 hours each. After filtration and drying, the single-walled carbon nanotubes are placed in a muffle furnace and heated at 400°C for 4 hours to remove the amorphous carbon and impurities inside the single-walled carbon nanotubes.

[0090] 2. Preparation of POD

[0091] A one-step, three-stage polycondensation method was used. 17.07 g of hydrazine sulfate, 20.76 g of terephthalic acid, and 5.3 g of isophthalic acid were dissolved in 150 mL of fuming sulfuric acid in a 250 mL three-necked flask equipped with a mechanical stirrer. The temperature was raised to 85°C, the prepolymerization temperature, and the reaction was allowed to proceed for 3 h. The temperature was then raised to 120°C, the polycondensation temperature, and the reaction was continued for 2 h. The reaction was terminated and the original solution was vacuum degassed to remove free SO₃ before use.

[0092] 3. Preparation of Spinning Dope

[0093] 50g of 20% fuming sulfuric acid was placed in a 250mL three-necked flask. Single-walled carbon nanotubes (0.75g) were added at a concentration of 1.5% by weight of the fuming sulfuric acid. The SWNTs were dispersed using a high-speed blender. Polyarylene oxadiazole (0.25g) was then added at a concentration of 0.5% by weight of the fuming sulfuric acid and stirred continuously until the dispersion exhibited a graphite sheen. This yielded a SWNT / polyarylene oxadiazole spinning solution. After stirring, the solution was allowed to stand for degassing. The SWNTs had an aspect ratio of 50,000, the polyarylene oxadiazole had an intrinsic viscosity of 4.5 dL / g, and the viscosity of the spinning solution was 200 Pa·s.

[0094] 4. Dry and wet spinning process

[0095] The SWCNT / POD spinning solution was transferred to a syringe and extruded at a rate of 0.13 ml / min using a microfluidic pump syringe. The solution was then injected vertically into a 30mm air segment. The solution then entered a T-shaped coagulation bath filled with dilute sulfuric acid. The solution was then drawn through a winding device at a rate of 2.5 m / s. The solution then entered water for a secondary draw at a rate of 3 m / s. The collection reel had the same rate as the secondary draw. The collected fibers were then soaked in water for 1 hour to remove any residual sulfuric acid. The fibers were then dried in a 100°C oven for 2 hours. The resulting SWCNT fibers had a diameter of 0.1 mm.

[0096] Example 3:

[0097] This embodiment provides a spinning method for single-walled carbon nanotube fibers, comprising:

[0098] 1. Pretreatment of single-walled carbon nanotubes

[0099] The agglomerated single-walled carbon nanotubes are placed in a wall-breaking machine, and water and ethanol are added to break them up and break them up. The mixed liquid is then filtered and placed in a freeze dryer for freeze drying. The freeze-dried single-walled carbon nanotubes are then immersed in a hydrogen peroxide solution and a hydrochloric acid solution for 24 hours each. After filtration and drying, the single-walled carbon nanotubes are placed in a muffle furnace and heated at 400°C for 4 hours to remove the amorphous carbon and impurities inside the single-walled carbon nanotubes.

[0100] 2. Preparation of POD

[0101] A one-step, three-stage polycondensation method was used. 17.07 g of hydrazine sulfate, 20.76 g of terephthalic acid, and 5.3 g of isophthalic acid were dissolved in 150 mL of fuming sulfuric acid in a 250 mL three-necked flask equipped with a mechanical stirrer. The temperature was raised to 85°C, the prepolymerization temperature, and the reaction was allowed to proceed for 3 h. The temperature was then raised to 120°C, the polycondensation temperature, and the reaction was continued for 2 h. The reaction was terminated and the original solution was vacuum degassed to remove free SO₃ before use.

[0102] 3. Preparation of Spinning Dope

[0103] 50g of 20% fuming sulfuric acid was placed in a 250mL three-necked flask. Single-walled carbon nanotubes (SWCNTs) were added at a ratio of 2% by weight of the fuming sulfuric acid. The SWCNTs were dispersed using a high-speed blender. Polyarylene oxadiazole (POX) was then added at a ratio of 0.1% by weight of the fuming sulfuric acid and stirred until the dispersion exhibited a graphite sheen. This yielded a SWCNT / POX spinning dope. After stirring, the flask was allowed to stand for degassing. The SWCNTs had an aspect ratio of 10,000, the POX had an intrinsic viscosity of 3 dL / g, and the viscosity of the spinning dope was 120 Pa·s.

[0104] 4. Dry and wet spinning process

[0105] The SWCNT / POD spinning solution was transferred to a syringe and extruded at a rate of 0.13 ml / min using a microfluidic pump syringe. The solution was then injected vertically into an air segment with a height of 10 mm. The solution then entered a T-shaped coagulation bath filled with dilute sulfuric acid and was drawn through a winding device at a rate of 2 m / s. The solution then entered water for a secondary draw at a rate of 2.5 m / s. The collection reel speed was the same as the secondary draw rate. The collected fibers were then soaked in water for 1 hour to remove any residual sulfuric acid. The fibers were then dried in a 100°C oven for 2 hours. The diameter of the SWCNT fibers was 0.1 mm.

[0106] Examples 4-9 and Comparative Examples 1-3:

[0107] This embodiment provides a spinning method for single-walled carbon nanotube fibers. The only difference from Example 1 is the composition of the spinning solution. The composition of the spinning solutions in Examples 4-9 and Comparative Examples 1-3 is shown in Table 1.

[0108] Table 1

[0109]

[0110] Example 10

[0111] This embodiment provides a spinning method for single-walled carbon nanotube fibers, which differs from Example 1 only in that the aspect ratio of the single-walled carbon nanotubes is 5000.

[0112] Examples 11-17 and Comparative Examples 4-7:

[0113] This embodiment provides a spinning method for single-walled carbon nanotube fibers, which differs from Example 1 only in the air segment height, coagulation bath solvent, extrusion rate, primary drawing rate, and secondary drawing rate. The air segment height, extrusion rate, primary drawing rate, and secondary drawing rate in Examples 11-17 and Comparative Examples 4-7 are shown in Table 2.

[0114] Table 2

[0115]

[0116] Example 19

[0117] This comparative example provides a spinning method for single-walled carbon nanotube fibers, which differs from Example 1 only in that terephthalic acid is replaced by 4,4-biphenyldicarboxylic acid or 4,4'-biphenyl ether dicarboxylic acid in an equal molar ratio.

[0118] Example 20

[0119] This comparative example provides a spinning method for single-walled carbon nanotube fibers, which differs from Example 1 only in that the intrinsic viscosity of the prepared POD is adjusted to 3 dg / L, so that the viscosity of the spinning solution in step 3 is 150 Pa·S.

[0120] The tensile strength and electrical conductivity of the single-walled carbon nanotube fibers prepared in the above examples and comparative examples were measured, and the results are shown in Table 3.

[0121] Table 3

[0122]

[0123] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A spinning solution for single-walled carbon nanotube fibers, characterized in that: The invention comprises fuming sulfuric acid, single-walled carbon nanotubes and polyaromatic oxadiazole, wherein the mass of the single-walled carbon nanotubes is 1%-2% of the mass of the fuming sulfuric acid, and the mass of the polyaromatic oxadiazole is 0.1%-1% of the mass of the fuming sulfuric acid; The concentration of the fuming sulfuric acid is 2wt%-70wt%, the aspect ratio of the single-walled carbon nanotubes is 10,000-100,000, the mass ratio of the single-walled carbon nanotubes to polyarylene oxadiazole is (3-20):1, the intrinsic viscosity of the polyarylene oxadiazole is 3-6 dL / g, and the viscosity of the spinning solution for the single-walled carbon nanotube fibers is 120-300 Pa·s.

2. A method for preparing a spinning solution for single-walled carbon nanotube fibers according to claim 1, characterized in that: include: Single-walled carbon nanotubes are added to fuming sulfuric acid and dispersed in the fuming sulfuric acid, and then polyarylene oxadiazole is added and stirred until the dispersion exhibits graphite luster, thereby obtaining the spinning solution for the single-walled carbon nanotube fibers.

3. The method for preparing a spinning solution for single-walled carbon nanotube fibers according to claim 2, wherein: The method also includes pretreatment: mixing agglomerated single-walled carbon nanotubes, water and ethanol to obtain a mixture, using a wall breaking machine to break up the single-walled carbon nanotubes in the mixture, then sequentially performing solid-liquid separation, drying and removing amorphous carbon and impurities, and then adding the single-walled carbon nanotubes from which the amorphous carbon and impurities have been removed into fuming sulfuric acid.

4. The method for preparing a spinning solution for single-walled carbon nanotube fibers according to claim 3, wherein: The removal of amorphous carbon and impurities includes: soaking the dried product in a hydrogen peroxide solution and a hydrochloric acid solution in sequence at 50-70° C. and performing solid-liquid separation, and then heating the product at 350-450° C. for 3-5 hours.

5. The method for preparing a spinning solution for single-walled carbon nanotube fibers according to claim 3, wherein: The method also includes the preparation of polyarylene oxadiazole: dissolving hydrazine sulfate and reaction monomers in fuming sulfuric acid, then heating to sequentially perform prepolymerization and polycondensation to obtain a reaction liquid, and removing air and free SO3 in the reaction liquid to obtain the polyarylene oxadiazole.

6. The method for preparing a spinning solution for single-walled carbon nanotube fibers according to claim 5, characterized in that: The reactive monomer is at least one of terephthalic acid, isophthalic acid, 4,4-biphenyl dicarboxylic acid and 4,4'-diphenyl ether dicarboxylic acid.

7. The method for preparing a spinning solution for single-walled carbon nanotube fibers according to claim 5, characterized in that: The preparation of polyarylene oxadiazole satisfies at least one of the following: A. the total molar ratio of the hydrazine sulfate to the reaction monomer is 1-1.1:1; B. The prepolymerization temperature is 80-90°C and the time is 2.5-3.5h; C. The temperature of polycondensation is 115-125℃ and the time is 1.5-2.5h.

8. A method for spinning single-walled carbon nanotube fibers, characterized in that: include: The single-walled carbon nanotube fiber according to claim 1 is extruded into the air segment using a syringe, then placed in sulfuric acid, ethanol or acetone for the first stretching, and then placed in water for the second stretching to obtain the fiber, and the residual sulfuric acid in the fiber is removed, and then dried to obtain the single-walled carbon nanotube fiber.

9. The spinning method of single-walled carbon nanotube fibers according to claim 8, characterized in that: The spinning method satisfies at least one of the following: a. The extrusion rate of the single-walled carbon nanotube fiber spinning solution is 0.13 ml / min -0.15 ml / min, and the pore size of the syringe outlet is 50μm-380μm; b. The height of the air segment is 10 mm-50 mm; c. The first stretching rate is 1.8m / s-3m / s; d. The second stretching rate is 2.5m / s-3.5m / s; e. The fiber was soaked in water for 1 h to remove residual sulfuric acid; f. The fibers from which sulfuric acid has been removed are dried at 100° C. for 2 h to obtain the single-walled carbon nanotube fibers.

10. A single-walled carbon nanotube fiber, characterized in that: Obtained by the spinning method according to claim 8 or 9.

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