Method for continuously preparing high-conductivity carbon nanotube fiber tows by uniformly propelling high-quality liquid crystal solution through air pressure

Abstract

The invention relates to the technical field of controllable preparation of carbon nanotube fiber tows, in particular to a method for continuously preparing high-conductivity carbon nanotube fiber tows by uniformly propelling a high-quality liquid crystal solution through air pressure. A high-quality carbon nanotube liquid crystal spinning solution serves as a raw material and is placed in a charging kettle, the liquid crystal spinning solution is pressed into an acetone coagulating bath through a porous spinneret plate by means of uniform air pressure generated by an air compressor, and then high-conductivity carbon nanotube fiber tows are continuously prepared through a winding device. According to the method, the technical bottleneck of continuous spinning of the high-performance carbon nanotube fiber tows at present is broken through, and continuous preparation of the high-orientation-degree and high-conductivity carbon nanotube fiber tows is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of controllable preparation of carbon nanotube fiber bundles, and in particular to a method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly propelling a high-quality liquid crystal solution with air pressure. Background Art

[0002] Carbon nanotubes have excellent electrical, thermal and mechanical properties, and their theoretical conductivity is as high as 10 8 S·m -1 , thermal conductivity 3000W·m -1 ·K -1 , the tensile strength can reach 100GPa. Therefore, the macroscopic carbon nanotube fiber composed of carbon nanotubes is regarded as an ideal next-generation conductive fiber material, and is expected to be used in many fields such as flexible sensors, high-performance cables, artificial muscles, etc. However, so far, carbon nanotube fibers have not yet been applied on a large scale. The main reason is that the yield of carbon nanotube fibers is low and the size of carbon nanotube fibers is at the micron level, which cannot meet the application requirements in most cases. Therefore, how to improve the carbon nanotube fiber spinning technology, increase the yield of carbon nanotube fibers, and prepare high-performance carbon nanotube fiber bundles is the key to realizing its large-scale application.

[0003] At present, the preparation methods of carbon nanotube fibers are mainly divided into dry spinning and wet spinning, and dry spinning can be further divided into array spinning and floating catalyst chemical vapor deposition direct spinning. The array spinning method is to first grow a vertical array of super-aligned carbon nanotubes on a substrate, and then extract the carbon nanotubes from one end of the array. Under the action of the van der Waals force between the tubes, the carbon nanotubes are connected end to end to form continuous fibers (Document 1: Jiang K, Li Q, Fan S. Nature, 2002 (6909).). The floating catalyst chemical vapor deposition direct spinning is to directly extract the carbon nanotubes generated in the high temperature reaction zone and spin them into continuous carbon nanotube fibers (Document 2: Zhu, HW Science, 2002, 296 (5569): 884-886.). Wet spinning is to mix the pretreated carbon nanotubes with chlorosulfonic acid in a certain proportion to form a uniform liquid crystal spinning solution, and then squeeze the spinning solution into a coagulation bath to form carbon nanotube fibers (Document 3: Vigolo B, Penicaud A, Coulon C, Sauder, C., Pailler, R., Journet, C, Bernier B, Poulin B. Science. 2000, 290 (5495), 1331-1334). Compared with dry spinning, the carbon nanotubes in wet-spun fibers are more closely arranged and have stronger interactions between tubes, which is suitable for the production of high-performance fibers. At the same time, wet spinning draws on the spinning technology of chemical fibers in industrial production and has a more complete technical system. Therefore, wet spinning has significant advantages in the industrialization of carbon nanotube fibers.

[0004] However, the wet spinning technology for preparing carbon nanotube fibers reported in the literature is all single-filament technology, with a fiber diameter of about 20 microns. This small diameter single carbon nanotube fiber limits its practical application scenarios, so there is an urgent need to develop a method for continuously preparing carbon nanotube fiber bundles. At present, there are no technical reports on the continuous preparation of carbon nanotube fiber bundles. The main reason is that it is extremely challenging to simultaneously prepare fiber bundles with high orientation, good continuity, and no sticking phenomenon.

[0005] In summary, in order to realize the practical application of carbon nanotube fibers, it is urgently necessary to develop a method for continuously preparing high-conductivity carbon nanotube fiber bundles. Summary of the invention

[0006] The purpose of the present invention is to provide a method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly propelling high-quality liquid crystal solutions with air pressure, breaking through the technical bottleneck of continuous preparation of carbon nanotube fiber bundles, and utilizing the stable, adjustable, and uniform propulsion power provided by an air compressor, combined with the high viscosity of high-quality, large aspect ratio carbon nanotube liquid crystal spinning solution, to achieve continuous preparation of high-conductivity carbon nanotube fiber bundles.

[0007] The technical solution of the present invention is:

[0008] A method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly advancing high-quality liquid crystal solution with air pressure, wherein high-quality carbon nanotube liquid crystal spinning solution is used as raw material, is placed in a charging kettle, and the liquid crystal spinning solution is pressed into an acetone coagulation bath through a porous spinneret by using uniform air pressure generated by an air compressor, and then the high-conductivity carbon nanotube fiber bundles are continuously prepared through a winding device; the viscosity of the high-quality carbon nanotube liquid crystal spinning solution is ≥3000cp, the aspect ratio of the carbon nanotubes in the carbon nanotube liquid crystal spinning solution is ≥15000, and the Raman spectrum I G / I D Ratio ≥80.

[0009] The method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly advancing high-quality liquid crystal solution with air pressure, and the device for continuously preparing high-conductivity carbon nanotube fiber bundles include an air compressor, a charging kettle, a porous spinneret, a coagulation bath and a winding device, and the specific structure is as follows: the top of the closed charging kettle is connected to the air compressor through a pipeline, the bottom of the charging kettle is connected to the porous spinneret through a pipeline, the porous spinneret is placed in the coagulation bath below the charging kettle, and one end of the winding device is arranged in the coagulation bath and corresponds to the spinning direction of the porous spinneret.

[0010] The method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly advancing high-quality liquid crystal solution with air pressure adopts the uniform pressure generated by the air compressor to press the high-quality carbon nanotube liquid crystal spinning solution out of the charging kettle, which is beneficial to the efficient use of the charging kettle volume and the continuous preparation of high-conductivity carbon nanotube fiber bundles, and reduces the residual carbon nanotube liquid crystal spinning solution in the wet spinning system. The air compressor pressure is 20 to 200 MPa.

[0011] In the method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly advancing high-quality liquid crystal solution with air pressure, the number of holes and inner diameter of the porous spinneret are adjustable, the number of holes is 5 to 50, and the inner diameter of the holes is 80 to 120 μm.

[0012] In the method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly advancing high-quality liquid crystal solutions with air pressure, the winding rate of the winding device is adjustable. By adjusting the rate and the pressure of the air compressor, a stretching effect is exerted on the fibers, which helps to orient the carbon nanotubes in the fibers.

[0013] The method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly advancing high-quality liquid crystal solution with air pressure has 5 to 50 high-conductivity carbon nanotube fiber bundles, a single fiber diameter of 10 to 25 μm, a bundle diameter of 50 to 400 μm, and no length restriction.

[0014] The method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly advancing high-quality liquid crystal solution with air pressure, and the Raman spectrum of the high-conductivity carbon nanotube fiber bundles G / I D ratio ≥70, electrical conductivity up to 10MS / m, and tensile strength up to 4 GPa.

[0015] The design concept of the present invention is:

[0016] The present invention utilizes the characteristics of high-quality, large aspect ratio carbon nanotube liquid crystal spinning solution, which has high viscosity and is easy to form, and uses an air compressor to provide uniform and stable propulsion pressure on a porous spinning plate, so that the high-quality carbon nanotube liquid crystal spinning solution in a charging kettle is uniformly extruded through a porous spinneret into an acetone coagulation bath, and the high-viscosity, oriented liquid crystal spinning solution is further oriented and densified under the extrusion and shearing action of the spinneret holes, and multiple fibers sprayed from the spinneret are respectively double-diffused and solidified in the coagulation bath, and the solidified multiple fibers are simultaneously stretched in the same direction by a winding device, and are stranded to form a carbon nanotube fiber bundle before the liquid outlet surface, and finally are collected by the winding device to obtain a high-conductivity carbon nanotube fiber bundle.

[0017] The advantages and beneficial effects of the present invention are:

[0018] 1. The present invention utilizes an air compressor to provide uniform and stable propulsion pressure, combined with the high viscosity characteristics of high-quality, large aspect ratio carbon nanotube liquid crystal solutions, to break through the technical bottleneck of continuous preparation of high-performance carbon nanotube fiber bundles, and realizes the continuous preparation of high-orientation, high-conductivity carbon nanotube fiber bundles.

[0019] 2. The present invention introduces an air compressor as a power source for extruding the single-walled carbon nanotube liquid crystal spinning solution from the charging kettle, and its pressure is continuously adjustable; and compared with the traditional piston feeding method, it is not limited by the size of the charging kettle, which is conducive to increasing the size of the charging kettle, thereby realizing the continuous preparation of carbon nanotube fiber bundles; at the same time, due to the permeability of the gas, it is conducive to reducing the residual spinning solution in the wet spinning system and improving the utilization rate of the material.

[0020] 3. The present invention can prepare high quality (the intensity ratio of the G peak to the D peak in the Raman spectrum is I G / I D The conductivity of carbon nanotube fiber bundles (value ≥70) reaches the highest performance of single fiber (10MS / m).

[0021] 4. The preparation method of the high-conductivity carbon nanotube fiber bundle developed by the present invention can be applied to continuous production and is easy to achieve large-scale preparation. It is expected to be important in the fields of high-performance cables, flexible sensors, aerospace, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of a device for uniformly advancing high-quality liquid crystal solution by air pressure to continuously prepare high-conductivity carbon nanotube fiber bundles. In the figure, 1-support, 2-charging kettle, 3-air compressor, 4-porous spinneret, 5-coagulation bath, 6-winding device.

[0023] Figure 2 This is the Raman spectrum of the carbon nanotube liquid crystal spinning solution prepared in Example 1. In the figure, the horizontal axis Raman shift is the Raman shift (cm -1 ), the vertical axis Intensity is the relative intensity (au).

[0024] Figure 3 This is an optical photograph of the carbon nanotube fiber bundle prepared in Example 1.

[0025] Figure 4 This is a scanning electron microscope photograph of the carbon nanotube fiber bundle prepared in Example 1, with a scale of 50 μm.

[0026] Figure 5 This is a scanning electron microscope photograph of the carbon nanotube fiber bundle prepared in Example 1, with a scale of 100 μm. DETAILED DESCRIPTION

[0027] like Figure 1 As shown, the device for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly advancing high-quality liquid crystal solution with air pressure of the present invention mainly comprises a support 1, a charging kettle 2, an air compressor 3, a porous spinneret 4, a coagulation bath 5, and a winding device 6. The specific structure is as follows: a charging kettle 2 is installed on the support 1, the top of the closed charging kettle 2 is connected to the air compressor 3 through a pipeline, the bottom of the charging kettle 2 is connected to the porous spinneret 4 through a pipeline, the porous spinneret 4 is placed in the coagulation bath 5 below the charging kettle 2, and one end of the winding device 6 is arranged in the coagulation bath 5 and corresponds to the spinning direction of the porous spinneret 4. When in use, the uniform and stable advancing air pressure provided by the air compressor 3 is used as a power source to extrude the high-quality carbon nanotube liquid crystal spinning solution in the charging kettle 2 through the porous spinneret 4 into the acetone coagulation bath 5, and the fiber is coagulated in the coagulation bath 5 and collected by the winding device 6 to obtain a high-conductivity fiber bundle.

[0028] In the specific implementation process, the present invention provides a method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly pushing high-quality liquid crystal solution with air pressure (device diagram as shown in FIG. Figure 1 ), including the following steps:

[0029] (1) mixing carbon nanotubes with a large aspect ratio with chlorosulfonic acid in a certain proportion, adding the mixture to a high-speed mixer for stirring and dispersion, and obtaining a high-quality carbon nanotube liquid crystal spinning solution; preferably, the viscosity of the high-quality carbon nanotube liquid crystal spinning solution is 3000-6000cp, the aspect ratio of the carbon nanotubes in the carbon nanotube liquid crystal spinning solution is 30000-80000, and the Raman spectrum I G / I D Ratio 80~120, mass fraction of carbon nanotubes 0.5~3.0wt% 。

[0030] (2) Add the obtained carbon nanotube liquid crystal spinning solution into a charging kettle, and squeeze the spinning solution evenly into an acetone coagulation bath through a porous spinneret under the air pressure of an air compressor.

[0031] (3) Under the directional stretching action of the winder, the fiber bundles are solidified, self-assembled and stranded in a coagulation bath to obtain high-conductivity carbon nanotube fiber bundles.

[0032] The technical solution of the present invention will be clearly and completely described below in conjunction with embodiments.

[0033] Example 1

[0034] In this embodiment, a method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly propelling a high-quality liquid crystal solution with air pressure includes the following steps:

[0035] (1) 630 mg of high-quality carbon nanotubes were mixed with 30 ml of chlorosulfonic acid, and then the mixture was mixed and dispersed in a high-speed mixer at a speed of 3500 r / min for 10 min to obtain a carbon nanotube liquid crystal spinning solution with a mass fraction of 1.2 wt %, a viscosity of 5600 cp, a carbon nanotube aspect ratio of 75000, and a Raman I G / I D The ratio is 105( Figure 2 ).

[0036] (2) The carbon nanotube liquid crystal spinning solution prepared in step (1) is transferred to a charging kettle, and a spinneret with 10 holes and an inner diameter of 100 μm is selected, and the air compressor pressure is set to 30 MPa. The carbon nanotube liquid crystal spinning solution in the charging kettle is squeezed into an acetone coagulation bath through the porous spinneret, and the spinning line is coagulated in the coagulation bath. The coagulated carbon nanotube fibers are self-assembled and stranded and collected by a winding device to obtain a continuous carbon nanotube fiber bundle ( Figure 3 ).

[0037] The structure and performance of the prepared carbon nanotube fiber bundle were characterized, and the fiber scanning electron microscope photo ( Figure 4 ) showed that the diameter of the carbon nanotube fiber bundle was ~70 μm, which was composed of multiple fiber filaments ( Figure 5 ), Raman spectroscopy I G / I D The ratio is 90, and the conductivity of the fiber bundle measured by the four-wire method is 10MS / m, and the tensile strength is 4GPa.

[0038] Example 2

[0039] In this embodiment, a method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly propelling a high-quality liquid crystal solution with air pressure includes the following steps:

[0040] (1) Step (1) is the same as step (1) in Example 1, except that the carbon nanotube raw material is used instead. The prepared carbon nanotube liquid crystal spinning solution has a viscosity of 4200 cp, an aspect ratio of the carbon nanotubes of 52000, and a Raman spectrum G / D ratio of 95.

[0041] (2) Step (2) is the same as step (2) in Example 1, except that the air compressor pressure is changed to 50 MPa, the number of spinneret holes is 50, and the inner diameter is 80 μm.

[0042] The structure and properties of the prepared carbon nanotube fiber bundles were characterized. Scanning electron microscope photos showed that the diameter of the carbon nanotube fiber bundles was 250 μm. Raman spectra G / I D The ratio is 75, and the electrical conductivity of the fiber bundle measured by the four-wire method is 4.8MS / m, and the tensile strength is 2GPa.

[0043] Example 3

[0044] In this embodiment, a method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly propelling a high-quality liquid crystal solution with air pressure includes the following steps:

[0045] (1) Step (1) is the same as step (1) in Example 1, except that the carbon nanotube raw material is replaced with the carbon nanotube liquid crystal spinning solution having a viscosity of 3000 cp, an aspect ratio of the carbon nanotube of 35000, and a Raman I G / I D The value is 85.

[0046] (2) Step (2) is the same as step (2) in Example 1, except that the air compressor pressure is changed to 80 MPa, the number of spinneret holes is 20, and the inner diameter is 120 μm.

[0047] The structure and performance of the prepared carbon nanotube fiber bundles were characterized. Scanning electron microscope photos show that the diameter of the carbon nanotube fiber bundles is 150 μm, and the Raman spectrum I G / I D The ratio is 72, and the conductivity of the fiber bundle measured by the four-wire method is 2MS / m, and the tensile strength is 1.2GPa.

[0048] Comparative Example 1:

[0049] In this comparative example, the method for preparing a carbon nanotube fiber bundle using a low-quality carbon nanotube liquid crystal solution comprises the following steps:

[0050] (1) Step (1) is the same as step (1) in Example 1, except that the carbon nanotube raw material is replaced with the carbon nanotube liquid crystal spinning solution having a viscosity of 1700 cp, an aspect ratio of the carbon nanotube of 8000, and a Raman I G / I D The value is 30.

[0051] (2) Step (2) is the same as step (2) in Example 1.

[0052] The structure and performance of the prepared carbon nanotube fiber bundles were characterized. Scanning electron microscope photos show that the diameter of the carbon nanotube fiber bundles is ~85μm, and Raman spectrum I G / I D The ratio is 22, and the conductivity of the fiber bundle measured by the four-wire method is 0.7MS / m, and the tensile strength is 0.5GPa.

[0053] Comparative Example 2:

[0054] In this comparative example, the method for preparing carbon nanotube fiber bundles by using a conventional piston feeding method includes the following steps:

[0055] (1) Step (1) is the same as step (1) in Example 1.

[0056] (2) The obtained liquid crystal spinning solution was transferred to an injection syringe, and the extrusion rate was set to 0.12 mL / min. The rest was the same as step (2) in Example 1.

[0057] The structure and performance of the prepared carbon nanotube fiber bundles were characterized. Scanning electron microscope photos show that the diameter of the carbon nanotube fiber bundles is 70 μm, and Raman spectrum I G / I D The ratio is 90, and the conductivity of the fiber bundle is 9.8MS / m and the tensile strength is 4GPa measured by the four-wire method. However, due to the limitation of the injection syringe volume (10mL), it is difficult to achieve the continuous preparation of carbon nanotube fiber bundles.

[0058] In summary, the present invention utilizes an air compressor as the power source for extruding the liquid crystal spinning solution from the porous spinneret, and combines the high spinnability of high-quality carbon nanotube liquid crystal spinning solution to break through the technical bottleneck of carbon nanotube fiber bundle preparation, and realizes the continuous spinning of highly oriented and high-density carbon nanotube fiber bundles, and the optimal performance reaches the highest performance of single fibers reported in the literature. The implementation results show that the Raman spectrum I of the high conductivity carbon nanotube fiber bundle obtained by the present invention is G / I D The ratio can reach above 70 and up to 90, the electrical conductivity can reach above 2MS / m and up to 10MS / m, and the tensile strength at break can reach above 1.2GPa and up to 4GPa.

[0059] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly advancing a high-quality liquid crystal solution under air pressure, characterized in that: High-quality carbon nanotube liquid crystal spinning solution is used as raw material, which is placed in a charging kettle, and the liquid crystal spinning solution is pressed into an acetone coagulation bath through a porous spinneret using the uniform air pressure generated by an air compressor, and then continuously prepared through a winding device to form a high-conductivity carbon nanotube fiber bundle; The viscosity of high-quality carbon nanotube liquid crystal spinning solution is ≥3000cp, the aspect ratio of carbon nanotubes in the carbon nanotube liquid crystal spinning solution is ≥15000, Raman spectrum I G / I D Ratio ≥80.

2. A method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly propelling a high-quality liquid crystal solution with air pressure according to claim 1, characterized in that: The device for continuously preparing high-conductivity carbon nanotube fiber bundles includes an air compressor, a charging kettle, a porous spinneret, a coagulation bath and a winding device, and the specific structure is as follows: the top of the closed charging kettle is connected to the air compressor through a pipeline, the bottom of the charging kettle is connected to the porous spinneret through a pipeline, the porous spinneret is placed in the coagulation bath below the charging kettle, and one end of the winding device is arranged in the coagulation bath and corresponds to the spinning direction of the porous spinneret.

3. The method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly propelling high-quality liquid crystal solution with air pressure according to claim 1, characterized in that: The high-quality carbon nanotube liquid crystal spinning solution is pressed out of the charging kettle with uniform pressure generated by an air compressor, which is beneficial to the efficient use of the charging kettle volume and the continuous preparation of high-conductivity carbon nanotube fiber bundles, and the reduction of residual carbon nanotube liquid crystal spinning solution in the wet spinning system. The air compressor pressure is between 20 and 200 MPa.

4. A method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly propelling a high-quality liquid crystal solution with air pressure according to claim 1, characterized in that: The number of holes and inner diameter of the porous spinneret are adjustable, the number of holes is 5 to 50, and the inner diameter of the holes is 80 to 120 μm.

5. The method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly propelling high-quality liquid crystal solutions with air pressure according to claim 1, characterized in that: The winding speed of the winding device is adjustable. By adjusting the speed and the pressure of the air compressor, a stretching effect is exerted on the fiber, which is helpful for the orientation of the carbon nanotubes in the fiber.

6. A method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly propelling a high-quality liquid crystal solution with air pressure according to any one of claims 1 to 5, characterized in that: The number of high-conductivity carbon nanotube fiber bundles is 5 to 50, the diameter of a single fiber is 10 to 25 μm, the diameter of the bundle is 50 to 400 μm, and the length is not limited.

7. A method for continuously preparing high-conductivity carbon nanotube fiber bundles by uniformly propelling a high-quality liquid crystal solution with air pressure according to any one of claims 1 to 5, characterized in that: Raman Spectra of High Conductivity Carbon Nanotube Fiber Tows I G / I D ratio ≥70, electrical conductivity up to 10MS / m, and tensile strength up to 4GPa.

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