A carbon fiber precursor with a special cross-section, a carbon fiber with a special cross-section, and a preparation method

Abstract

The application provides a shaped cross-section carbon fiber precursor, a shaped cross-section carbon fiber and a preparation method, and relates to the technical field of carbon fibers. The preparation method of the shaped cross-section carbon fiber precursor comprises the following steps: extruding a spinning dope through a spinneret with a shaped hole according to a preset spinning rate to form a dope fine stream; making the dope fine stream pass through an air layer with a preset height and then enter a coagulation bath to be coagulated and formed at a first preset temperature to obtain a nascent fiber; and performing post-treatment on the nascent fiber to obtain the shaped cross-section carbon fiber precursor. The shaped degree of the spinneret with the shaped hole is 0.2-0.8. The preset spinning rate is 15.00-25.00 m / min. The preset height is 1.5-4.5 mm. The concentration of the coagulation bath is 30-70 wt%. The first preset temperature is 5-55 DEG C. The shaped cross-section carbon fiber prepared from the polyacrylonitrile-based precursor according to the application has the characteristics of high specific surface area, high compactness and low skin-core ratio.

Description

Technical Field

[0001] This application relates to the field of carbon fiber technology, and in particular to a carbon fiber precursor with irregular cross-section, a carbon fiber with irregular cross-section, and a preparation method thereof. Background Technology

[0002] Polyacrylonitrile-based carbon fiber is produced by spinning polyacrylonitrile spinning solution to obtain polyacrylonitrile-based carbon fiber precursor, which is then carbonized. Polyacrylonitrile-based carbon fiber precursor can be prepared using three main spinning technologies: dry spinning, wet spinning, and dry-jet wet spinning. Dry-jet wet spinning combines the characteristics of dry and wet spinning. In this method, the spinning solution is ejected through a spinneret and passes through an air layer, causing the solvent in the spinning solution to evaporate rapidly, forming a dense, uniform, and fine-structured filament. Then, it passes through a coagulation bath, where the solvent and water undergo bidirectional diffusion and phase separation to solidify the filament into a high-density, smooth, groove-free filament structure.

[0003] Dry-jet wet spinning can produce fibers with smoother surfaces and better mechanical properties, and can reduce fiber voids and surface collapse caused by solidification. However, due to the strong electronegativity of the cyano group in polyacrylonitrile and the large intermolecular and chain forces, the spinning solution is sensitive to the shearing action of the irregular pores and is prone to breakage, which makes the application of dry-jet wet spinning in polyacrylonitrile irregular cross-section carbon fibers difficult. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a carbon fiber precursor with irregular cross-section, carbon fiber with irregular cross-section, and a preparation method, which can produce polyacrylonitrile-based precursors with different irregular cross-sections. The carbon fiber with irregular cross-section prepared from the polyacrylonitrile-based precursor has the characteristics of high specific surface area, high density, and low core-sheath ratio.

[0005] According to the first aspect of this application, a method for preparing irregularly shaped cross-section carbon fiber precursor is provided, comprising:

[0006] The spinning solution is extruded through a spinneret with irregularly shaped holes at a preset spinning rate to form a fine stream of the solution;

[0007] The original liquid is passed through an air layer at a preset height and then enters a coagulation bath, where it is solidified at a first preset temperature to obtain nascent fibers.

[0008] The nascent fibers are post-processed to obtain carbon fiber precursors with irregular cross-sections;

[0009] The irregularity of the spinneret with irregularly shaped holes is 0.2-0.8;

[0010] The preset spinneret rate is 15.00-25.00 m / min;

[0011] The preset height is 1.5-4.5mm;

[0012] The concentration of the coagulation bath is 30-70 wt%, and the first preset temperature is 5-55℃.

[0013] In some embodiments of this application, when the irregularity of the spinneret with irregular holes is 0.2-0.4, the preset height is 3.6-4.5 mm, the concentration of the coagulation bath is 40-50 wt%, and the first preset temperature is 5-10 °C.

[0014] When the irregularity of the spinneret with irregular holes is 0.41-0.6, the preset height is 2.0-3.5 mm, the concentration of the coagulation bath is 40-50 wt%, and the first preset temperature is 5-10℃.

[0015] When the irregularity of the spinneret with irregular holes is 0.61-0.8, the preset height is 2.2-3.0 mm, the concentration of the coagulation bath is 40-50 wt%, and the first preset temperature is 5-10℃.

[0016] In some embodiments of this application, the spinneret with irregularly shaped holes has a thickness of 5-15 mm, a hole spacing of 1-3 mm, a number of holes of 1-5 k, a length-to-diameter ratio of 1-10:1, and a design pressure of 10-30 MPa.

[0017] In some embodiments of this application, when the irregularity of the spinneret with irregular holes is 0.2-0.4, the aspect ratio of the irregular holes is 4.5-6.5:1;

[0018] When the irregularity of the spinneret with irregular holes is 0.41-0.6, the aspect ratio of the irregular holes is 2-4:1;

[0019] When the irregularity of the spinneret with irregular holes is 0.61-0.8, the aspect ratio of the irregular holes is 7-9:1.

[0020] In some embodiments of this application, the step of post-processing the nascent fibers to obtain irregularly shaped cross-section carbon fiber precursors includes:

[0021] The nascent fibers are washed with desalinated water, stretched with hot water, oiled, dried, and stretched with steam before being wound and collected to obtain the carbon fiber precursor with the irregular cross-section.

[0022] The temperature of the demineralized water washing is 20-35℃, and the draw ratio is 1-1.5;

[0023] The temperature of the hot water stretching is 60-80℃, and the stretching ratio is 1-2.0;

[0024] The drying temperature is 100-185℃;

[0025] The steam stretching pressure is 0.30-0.80 MPa, and the steam stretching ratio is 3.0-5.0 times;

[0026] The winding speed for winding and taking in the yarn is 350-500 m / min.

[0027] According to a second aspect of this application, a carbon fiber precursor with an irregular cross-section is provided, which is prepared by the above-described method for preparing carbon fiber precursor with an irregular cross-section.

[0028] According to a third aspect of this application, a method for preparing irregular cross-section carbon fiber is provided, wherein the irregular cross-section carbon fiber precursor is subjected to carbonization treatment to obtain irregular cross-section carbon fiber.

[0029] The carbonization process includes:

[0030] The irregularly shaped cross-section carbon fiber precursor is subjected to gradient heating under a first preset condition to perform pre-oxidation treatment, thereby obtaining pre-oxidized carbon fiber.

[0031] The pre-oxidized carbon fiber is subjected to carbonization treatment at a first temperature under a second preset condition to obtain low-temperature carbonized carbon fiber.

[0032] The low-temperature carbonized carbon fiber is subjected to a second temperature carbonization treatment under a third preset condition to obtain high-temperature carbonized carbon fiber, wherein the second temperature is higher than the first temperature.

[0033] In some embodiments of this application, the first preset conditions include: a temperature of 200-300℃ and a pre-oxidation stretching ratio of 0.9-1.05 times;

[0034] The second preset conditions include: a temperature of 320-800℃, a heating rate of 40-100℃ / min, and a stretching ratio of 1.0-1.1.

[0035] The third preset conditions include: a temperature of 1000-1800℃, a heating rate of 100-150℃ / min, and a stretching ratio of 0.95-1.05.

[0036] In some embodiments of this application, when the irregularity of the spinneret with irregular holes is 0.2-0.4, the gradient temperature of the first preset condition is 210-220℃, 220-240℃, and 246-260℃.

[0037] When the irregularity of the spinneret with irregular holes is 0.41-0.6, the gradient temperature of the first preset condition is 205-215℃, 215-235℃, and 236-245℃.

[0038] When the irregularity of the spinneret with irregular holes is 0.61-0.8, the gradient temperature of the first preset condition is 200-210℃, 210-230℃, and 230-235℃.

[0039] According to a fourth aspect of this application, a carbon fiber with an irregular cross-section is provided, which is prepared by the above-described method for preparing carbon fiber with an irregular cross-section.

[0040] The technical solution provided in this application can include the following beneficial effects: By adjusting the parameters of the spinning process and the spinning process, this application can produce carbon fiber precursor with high anisotropy and high anisotropy forming rate. The carbon fiber with anisotropy prepared from the carbon fiber precursor has the characteristics of large specific surface area, high anisotropy, low carbonization temperature, short spinning time, high density, low core-sheath ratio and high mechanical strength.

[0041] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0042] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0043] Figure 1 This is a flowchart illustrating a method for preparing irregularly shaped cross-section carbon fiber precursor according to an exemplary embodiment.

[0044] Figure 2 This is a schematic diagram of a spinneret with irregularly shaped holes in the form of a "six-pointed star" according to an exemplary embodiment.

[0045] Figure 3 This is a schematic diagram of a spinneret with Y-shaped orifices, according to an exemplary embodiment.

[0046] Figure 4 This is a schematic diagram of a spinneret with triangular orifices, according to an exemplary embodiment.

[0047] Figure 5 This is a flowchart illustrating a method for preparing irregularly shaped carbon fibers according to an exemplary embodiment. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0049] This application provides a method for preparing irregularly shaped cross-section carbon fiber precursor, including spinning, spinning, and post-treatment. By adjusting various parameters of the spinning and spinning processes, the preset spinning rate is 15.00-25.00 m / min, the preset height is 1.5-4.5 mm, the concentration of the coagulation bath is 30-70 wt%, and the first preset temperature is 5-55℃. In this way, irregularly shaped cross-section carbon fibers with an irregularity of 0.2-0.8 can be obtained, and they have a high irregularity forming rate. The irregularly shaped cross-section carbon fibers prepared from this precursor have the characteristics of high specific surface area, high density, and low core-sheath ratio.

[0050] In one exemplary embodiment, reference is made to Figure 1 This application provides a method for preparing irregularly shaped cross-section carbon fiber precursor, comprising:

[0051] S100. The spinning solution is extruded through a spinneret with irregularly shaped holes at a preset spinning rate to form a fine stream of the solution; wherein, the irregularity of the spinneret with irregularly shaped holes is 0.2-0.8; and the preset spinning rate is 15.00-25.00 m / min.

[0052] Irregular fiber cross-sections significantly alter various fiber properties, particularly the mechanical properties of the fibers and their composites. Furthermore, irregularly shaped fibers have a large specific surface area, which, when used as two-dimensional reinforcement materials, not only enhances the bond between the fiber and the matrix but also allows for a larger filler ratio, thus substantially improving the overall performance of the composite material.

[0053] The irregular shape effect of irregularly shaped fibers can be characterized by irregularity degree, which is calculated as (1 - radius of the inscribed circle of the irregular cross-section / radius of the circumscribed circle of the irregular cross-section). A higher irregularity degree indicates a greater irregular shape effect. Irregularity degree is mainly affected by fiber forming and setting effects. In the spinning process, the spinning rate is one of the factors affecting the forming effect. If the spinning rate is too low, the liquid stream is prone to breakage; if the spinning rate is too high, the process becomes unstable. In step S100, a spinneret with an irregularity degree of 0.2-0.8 is used. By adjusting the preset spinning rate to 15.00-25.00 m / min, rapid spinning can be achieved, facilitating rapid forming.

[0054] For example, the preset spinneret rate can be 15.00 m / min, 15.67 m / min, 15.98 m / min, 16.56 m / min, 17.43 m / min, 18.11 m / min, 19.65 m / min, 20.43 m / min, 21.39 m / min, 22.76 m / min, 23.09 m / min, 24.41 m / min, or 25.00 m / min.

[0055] The spinning solution is prepared by the following method: using acrylonitrile as the first monomer, adding a second monomer, and performing solution polymerization in an organic solvent to obtain the spinning solution;

[0056] The second monomer includes one of acrylic acid, methyl acrylate, methyl methacrylate, and isobutyl methacrylate;

[0057] Organic solvents include one of dimethyl sulfoxide, dimethylformamide, and dimethylacetamide;

[0058] The second monomer is 2-6% of the sum of the first and second monomers;

[0059] The solid content of the resulting spinning solution was 20-22 wt%.

[0060] For example, the spinning solution is prepared by the following method: using 94-98 wt% acrylonitrile as the first monomer and 2-6 wt% methyl acrylate as the second monomer, free radical solution polymerization is carried out in dimethyl sulfoxide to obtain a polymer; the polymer is subjected to monomer removal and degassing treatment, and filtered to obtain a spinning solution with a solid content of 20-22 wt%.

[0061] S200: The original liquid is allowed to pass through an air layer of a preset height and then enter the coagulation bath, where it is coagulated and formed at a first preset temperature to obtain nascent fibers; wherein, the preset height is 1.5-4.5mm; the concentration of the coagulation bath is 30-70wt%; and the first preset temperature is 5-55℃.

[0062] In the spinning process, the air layer height is another factor affecting the forming effect. Matching the spinning rate and the air layer height during spinning is a key means to mitigate the breakage of irregularly shaped filaments due to uneven stress. With a constant spinning rate, if the air layer height is too low, fluctuations in the coagulation bath surface will cause the plate surface to contact the liquid surface and absorb water; if the air layer height is too high, filament breakage or tangling will occur. In step S200, the air layer height is set between 1.5-4.5 mm to facilitate rapid forming. For example, the preset height can be 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm, 4.0 mm, or 4.5 mm.

[0063] The concentration gradient effect of the coagulation bath has a significant impact on the fiber cross-section. A low coagulation bath concentration leads to a higher concentration gradient effect, which easily causes deformation of the spindle cross-section. By adjusting the concentration of the coagulation bath, the nascent fiber can maintain the shape of the orifice expansion during extrusion. By adjusting the temperature of the coagulation bath, rapid setting can be achieved, thereby improving the density of the nascent fiber. The organic solvent in the coagulation bath can be the same as the organic solvent in the spinning solution, for example, both being dimethyl sulfoxide. Exemplarily, the concentration of the coagulation bath is 30wt%, 40wt%, 45wt%, 50wt%, 60wt%, 65wt%, or 70wt%; the first preset temperature can be 5℃, 10℃, 15℃, 25℃, 35℃, 45℃, or 55℃.

[0064] In this process, the original liquid stream solidifies at a first preset temperature, and a draw ratio of 1-2 times is applied to obtain nascent fibers. For example, the draw ratio can be 1, 1.1, 1.3, 1.5, 1.7, or 2 times.

[0065] S300: The nascent fibers are post-processed to obtain carbon fiber precursors with irregular cross-sections.

[0066] In step S300, the post-treatment of the nascent fibers can improve their density, thereby enhancing the mechanical properties of the irregular cross-section carbon fiber precursor.

[0067] In an exemplary embodiment, when the irregularity of the spinneret with irregular holes is 0.2-0.4, the preset height is 3.6-4.5 mm, the concentration of the coagulation bath is 40-50 wt%, and the first preset temperature is 5-10 °C;

[0068] When the irregularity of the spinneret with irregular holes is 0.41-0.6, the preset height is 2.0-3.5mm, the concentration of the coagulation bath is 40-50wt%, and the first preset temperature is 5-10℃.

[0069] When the irregularity of the spinneret with irregular holes is 0.61-0.8, the preset height is 2.2-3.0 mm, the concentration of the coagulation bath is 40-50 wt%, and the first preset temperature is 5-10℃.

[0070] Dry-jet wet spinning technology can effectively improve the mechanical properties and spinning speed of polyacrylonitrile-based carbon fibers. However, under the influence of surface tension, the forming process of the spinning solution with viscoelastic properties after passing through shaped spinnerets is much more complex than that after passing through circular spinnerets. The spinning solution undergoes extrusion and expansion after passing through shaped spinnerets. Due to the differences in the structure of the shaped spinnerets (i.e., the difference in the degree of irregularity), the shear force on the spinning solution is uneven, which can easily lead to the breakage of the fine strands. In this embodiment, according to the different degrees of irregularity of the spinneret, under a certain spinning rate, the height of the air layer during spinning is adjusted to facilitate rapid forming, thereby reducing the breakage of the shaped fine strands due to uneven stress. Furthermore, by adjusting the concentration of the coagulation bath, the nascent fibers are kept in the shape of the orifice expansion during extrusion. By adjusting the temperature of the coagulation bath, rapid setting is achieved, thereby improving the density of the nascent fibers.

[0071] The irregularly shaped orifices of the spinneret can be leaf-shaped, annular, triangular, star-shaped, multi-hole-shaped, hexagonal, Y-shaped, pentagonal, cross-shaped, etc. For example, when the irregularity of the spinneret's orifices is 0.2-0.4, the orifice shape can be... Figure 2 The "six-pointed star" shape shown indicates that the carbon fiber with a "six-pointed star" cross-section possesses ultra-high density and specific surface area, making it widely applicable to resin-based composites and carbon / carbon composites. When the irregularity of the spinneret with irregularly shaped orifices is 0.41-0.6, the orifice shape of the spinneret can be... Figure 3 The "Y"-shaped carbon fiber shown exhibits high filler ratio and microwave absorption performance, making it suitable for preparing microwave absorbing materials, electromagnetic shielding materials, and radar absorbing materials. When the irregularity of the spinneret with irregularly shaped holes is 0.61-0.8, the hole shape of the spinneret can be... Figure 4 The "triangle" shape shown has the advantages of high strength and low cost, and can be applied to functional materials, structural materials and stealth weapons.

[0072] Understandably, to facilitate rapid prototyping, in addition to adjusting the air layer height, the preset spinneret rate can also be adjusted during the spinneret process. For example, when the irregularity of the spinneret with irregular orifices is 0.2-0.4, the preset spinneret rate is 17.85-20.24 m / min; when the irregularity of the spinneret with irregular orifices is 0.41-0.6, the preset spinneret rate is 15.25-15.96 m / min; and when the irregularity of the spinneret with irregular orifices is 0.61-0.8, the preset spinneret rate is 15.55-16.36 m / min.

[0073] For example, in one embodiment, when the irregularity of the spinneret with irregular holes is 0.2-0.4, the preset spinneret rate is 17.85 m / min, the preset height is 3.6 mm, the concentration of the coagulation bath is 40 wt%, and the first preset temperature is 5 °C.

[0074] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.2-0.4, the preset spinneret rate is 18.00 m / min, the preset height is 4.0 mm, the concentration of the coagulation bath is 45 wt%, and the first preset temperature is 6 °C.

[0075] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.2-0.4, the preset spinneret rate is 20.24 m / min, the preset height is 4.5 mm, the concentration of the coagulation bath is 50 wt%, and the first preset temperature is 10 °C.

[0076] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.41-0.6, the preset spinneret rate is 15.25 m / min, the preset height is 2.0 mm, the concentration of the coagulation bath is 40 wt%, and the first preset temperature is 5 °C.

[0077] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.41-0.6, the preset spinneret rate is 15.55 m / min, the preset height is 2.8 mm, the concentration of the coagulation bath is 45 wt%, and the first preset temperature is 7 °C.

[0078] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.41-0.6, the preset spinneret rate is 15.96 m / min, the preset height is 3.5 mm, the concentration of the coagulation bath is 50 wt%, and the first preset temperature is 10 °C.

[0079] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.61-0.8, the preset spinneret rate is 15.55 m / min, the preset height is 2.2 mm, the concentration of the coagulation bath is 40 wt%, and the first preset temperature is 5 °C.

[0080] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.61-0.8, the preset spinneret rate is 16.00 m / min, the preset height is 2.6 mm, the concentration of the coagulation bath is 45 wt%, and the first preset temperature is 8 °C.

[0081] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.61-0.8, the preset spinneret rate is 16.36 m / min, the preset height is 3.0 mm, the concentration of the coagulation bath is 50 wt%, and the first preset temperature is 10 °C.

[0082] In one exemplary embodiment, the spinneret with irregularly shaped holes has a thickness of 5-15 mm, a hole spacing of 1-3 mm, a number of holes of 1-5 k, a length-to-diameter ratio of 1-10:1 for the irregularly shaped holes, and a design pressure of 10-30 MPa.

[0083] In this embodiment, by designing the structure of the spinneret and adjusting parameters such as hole spacing, number of holes, and aspect ratio of irregular holes, production efficiency can be improved while reducing problems such as wire tangling and wire breakage.

[0084] For example, in one embodiment, the spinneret with irregularly shaped holes has a thickness of 5 mm, a hole spacing of 1 mm, a number of holes of 1 k, a length-to-diameter ratio of 1:1 for the irregularly shaped holes, and a design pressure of 10 MPa.

[0085] In one embodiment, the spinneret with irregularly shaped holes has a thickness of 10 mm, a hole spacing of 2 mm, a number of holes of 3 k, a length-to-diameter ratio of 5:1 for the irregularly shaped holes, and a design pressure of 20 MPa.

[0086] In one embodiment, the spinneret with irregularly shaped holes has a thickness of 15 mm, a hole spacing of 3 mm, a number of holes of 5 k, a length-to-diameter ratio of 10:1 for the irregularly shaped holes, and a design pressure of 30 MPa.

[0087] The spinneret is made of one of the following materials: Hastelloy C276, 316L alloy, 1Cr18Ni9Ti austenitic stainless steel, AISI316, AISI630, etc., and the plate diameter is 150-200mm. For example, the plate diameter can be 150mm, 180mm, or 200mm.

[0088] In an exemplary embodiment, when the irregularity of the spinneret with irregularly shaped holes is 0.2-0.4, the aspect ratio of the irregularly shaped holes is 4.5-6.5:1;

[0089] When the irregularity of the spinneret with irregular holes is 0.41-0.6, the length-to-diameter ratio of the irregular holes is 2-4:1;

[0090] When the irregularity of the spinneret with irregular holes is 0.61-0.8, the length-to-diameter ratio of the irregular holes is 7-9:1.

[0091] The aspect ratio of an irregularly shaped orifice refers to the ratio of the length to the diameter of the orifice in a spinneret. The aspect ratio is adjusted according to the degree of irregularity of the orifice in the spinneret.

[0092] For example, when the irregularity of the spinneret with irregular holes is 0.2-0.4, the aspect ratio of the irregular holes can be 4.5:1, 5:1, or 6.5:1;

[0093] When the irregularity of the spinneret with irregularly shaped holes is 0.41-0.6, the aspect ratio of the irregularly shaped holes is 2:1, 3:1, or 4:1.

[0094] When the irregularity of the spinneret with irregular holes is 0.61-0.8, the length-to-diameter ratio of the irregular holes can be 7:1, 8:1, or 9:1.

[0095] In one exemplary embodiment, the nascent fibers are post-processed to obtain carbon fiber precursors with irregular cross-sections, including:

[0096] The nascent fibers are washed with desalinated water, stretched with hot water, oiled, dried, and stretched with steam before being wound and taken up to obtain carbon fiber precursors with irregular cross-sections.

[0097] The temperature for desalination washing is 20-35℃, and the draw ratio is 1-1.5;

[0098] The temperature for hot water stretching is 60-80℃, and the stretching ratio is 1-2.0;

[0099] The drying temperature is 100-185℃;

[0100] The steam stretching pressure is 0.30-0.80 MPa, and the steam stretching ratio is 3.0-5.0 times;

[0101] The winding speed for winding and take-up is 350-500 m / min.

[0102] In this embodiment, by washing the nascent fibers with desalinated water, impurities such as dimethyl sulfoxide in the coagulation bath can be removed. After washing the nascent fibers with desalinated water, hot water drawing, oiling, drying, and steam drawing can improve the density of the resulting shaped cross-section carbon fiber precursor. By adjusting the drawing ratio of each process, a high shaped cross-section carbon fiber precursor can be maintained.

[0103] Among them, the water washing tank during desalination is of grade 3-7; the hot water stretching has 1-3 sections; the oil is a composite oil composed of amino-modified silicone oil, polyether-modified silicone oil, epoxy-modified silicone oil and other surfactants, with an oil concentration of 1.0-2.0 wt%; and the drying roller is of grade 3-7.

[0104] For example, in one embodiment, the nascent fibers are washed with desalinated water, stretched with hot water, oiled, dried, stretched with steam, and then wound up to obtain carbon fiber precursor with an irregular cross-section.

[0105] The temperature for desalination was 20℃, and the draw ratio was 15.

[0106] The hot water stretching temperature was 60℃, and the stretching ratio was 1.

[0107] The drying temperature is 100℃;

[0108] The steam stretching pressure is 0.30 MPa, and the steam stretching ratio is 3.0.

[0109] The winding speed for winding and take-up is 350 m / min.

[0110] In one embodiment, the nascent fibers are washed with desalinated water, stretched with hot water, oiled, dried, and stretched with steam before being wound and taken up to obtain carbon fiber precursor with an irregular cross-section.

[0111] The temperature for desalination was 30℃, and the draw ratio was 1.2.

[0112] The hot water stretching temperature was 70℃, and the stretching ratio was 1.5.

[0113] The drying temperature is 145℃;

[0114] The steam stretching pressure is 0.60 MPa, and the steam stretching ratio is 4.5.

[0115] The winding speed for winding and take-up is 420 m / min.

[0116] In one embodiment, the nascent fibers are washed with desalinated water, stretched with hot water, oiled, dried, and stretched with steam before being wound and taken up to obtain carbon fiber precursor with an irregular cross-section.

[0117] The temperature for desalination was 35℃, and the draw ratio was 1.5.

[0118] The hot water stretching temperature was 80℃, and the stretching ratio was 2.0.

[0119] The drying temperature is 185℃;

[0120] The steam stretching pressure is 0.80 MPa, and the steam stretching ratio is 5.0.

[0121] The winding speed for winding and take-up is 500 m / min.

[0122] In one exemplary embodiment, reference is made to Figure 5 This application provides a method for preparing irregular cross-section carbon fiber, wherein the irregular cross-section carbon fiber precursor is carbonized to obtain irregular cross-section carbon fiber.

[0123] Carbonization treatment includes:

[0124] S400. The irregular cross-section carbon fiber precursor is subjected to gradient heating under the first preset conditions to perform pre-oxidation treatment and obtain pre-oxidized carbon fiber.

[0125] Due to their unique surface morphology, irregularly shaped cross-section fibers often result in excessively high core-sheath ratios when using conventional pre-oxidation methods. In step S400, a gradient heating method is employed. During the pre-oxidation process, oxygen can more easily penetrate into the core, which alleviates the radial non-uniformity of the fibers, improves the consistency of the pre-oxidized filaments, and further reduces the core-sheath ratio of the carbon fibers. On the other hand, it increases the reaction rate, reduces the fiber travel distance, and shortens the reaction time, enabling rapid carbon fiber preparation and reducing production costs.

[0126] S500. The pre-oxidized carbon fiber is subjected to carbonization treatment at a first temperature under a second preset condition to obtain low-temperature carbonized carbon fiber.

[0127] In step S500, the carbonization process at the first temperature can transform the structure of the carbon fiber into a graphite structure, thereby reducing structural defects in the carbon fiber.

[0128] S600. The low-temperature carbonized carbon fiber is subjected to a second temperature carbonization treatment under a third preset condition to obtain high-temperature carbonized carbon fiber, wherein the second temperature is higher than the first temperature.

[0129] In step S600, the carbonization process at a second temperature allows the carbon fiber structure to further transform into a graphite structure at a higher carbonization temperature, thereby improving the mechanical properties of the carbon fiber.

[0130] In an exemplary embodiment, the first preset conditions include: a temperature of 200-300°C and a pre-oxidation stretching ratio of 0.9-1.05 times;

[0131] The second preset conditions include: temperature of 320-800℃, heating rate of 40-100℃ / min, and stretching ratio of 1.0-1.1 times;

[0132] The third preset conditions include: temperature of 1000-1800℃, heating rate of 100-150℃ / min, and stretching ratio of 0.95-1.05.

[0133] For example, in one embodiment, the first preset conditions include: increasing the temperature according to a gradient of 200°C, 220°C, and 240°C, with a pre-oxidation stretching ratio of 0.9 times;

[0134] The second preset conditions include: a temperature of 320℃, a heating rate of 40℃ / min, and a stretching ratio of 1.0.

[0135] The third preset conditions include: a temperature of 1000℃, a heating rate of 100℃ / min, and a stretching ratio of 0.95.

[0136] In one embodiment, the first preset conditions include: increasing the temperature according to a gradient of 220°C, 240°C, and 260°C, with a pre-oxidation stretching ratio of 1.0.

[0137] The second preset conditions include: a temperature of 450℃, a heating rate of 70℃ / min, and a stretching ratio of 1.05.

[0138] The third preset conditions include: a temperature of 1500℃, a heating rate of 120℃ / min, and a stretching ratio of 1.0.

[0139] In one embodiment, the first preset conditions include: increasing the temperature according to a gradient of 240°C, 260°C, and 280°C, with a pre-oxidation stretching ratio of 1.05 times;

[0140] The second preset conditions include: a temperature of 800℃, a heating rate of 100℃ / min, and a stretching ratio of 1.1.

[0141] The third preset conditions include: a temperature of 1800℃, a heating rate of 150℃ / min, and a stretching ratio of 1.05.

[0142] In an exemplary embodiment, when the irregularity of the spinneret with irregular holes is 0.2-0.4, the gradient temperature of the first preset condition is 210-220°C, 220-240°C, and 246-260°C.

[0143] When the irregularity of the spinneret with irregular holes is 0.41-0.6, the gradient temperature of the first preset condition is 205-215℃, 215-235℃, and 236-245℃.

[0144] When the irregularity of the spinneret with irregular holes is 0.61-0.8, the gradient temperature of the first preset condition is 200-210℃, 210-230℃, and 230-235℃.

[0145] Excessively high pre-oxidation temperatures can lead to excessively high core-sheath ratios in carbon fibers, while excessively low temperatures can result in insufficient pre-oxidation. In this embodiment, the pre-oxidation temperature is adjusted according to the irregularity of the spinneret's orifices to obtain carbon fibers with superior performance.

[0146] For example, in one embodiment, when the irregularity of the spinneret with irregular holes is 0.2-0.4, the gradient temperature of the first preset condition is 210°C, 220°C, and 246°C.

[0147] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.2-0.4, the gradient temperature of the first preset condition is 215°C, 230°C, and 250°C.

[0148] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.2-0.4, the gradient temperature of the first preset condition is 220°C, 240°C, and 260°C.

[0149] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.41-0.6, the gradient temperature of the first preset condition is 205°C, 215°C, and 236°C.

[0150] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.41-0.6, the gradient temperature of the first preset condition is 210°C, 225°C, and 235°C.

[0151] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.41-0.6, the gradient temperature of the first preset condition is 215°C, 235°C, and 245°C.

[0152] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.61-0.8, the gradient temperature of the first preset condition is 200°C, 210°C, and 230°C.

[0153] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.61-0.8, the gradient temperature of the first preset condition is 205°C, 220°C, and 232°C.

[0154] In one embodiment, when the irregularity of the spinneret with irregular holes is 0.61-0.8, the gradient temperature of the first preset condition is 210°C, 230°C, and 235°C.

[0155] To more clearly explain the technical solution of this application, this application provides specific embodiments of the preparation method of irregular cross-section carbon fibers. The beneficial effects of selecting the above-mentioned range of process parameters will be explained through specific experimental data provided in the specific embodiments.

[0156] The spinning solutions in the following examples and comparative examples were prepared using the following methods:

[0157] Using 96 wt% acrylonitrile as the first monomer and 4 wt% methyl acrylate as the second monomer, a polymer was obtained by free radical solution polymerization in dimethyl sulfoxide solution. After monomer removal and degassing treatment, the polymer was sent to a 1 μm secondary filter for further treatment. The refined product was then used to obtain the spinning solution. The spinning solution was pressurized and transported to the spinning unit, and then passed through a 0.5 μm wick filter for later use.

[0158] The oil is a water-based latex emulsion containing amino-modified silicone oil, polyether-modified silicone oil, antistatic agents, and emulsifiers.

[0159] Example 1: A method for preparing irregularly shaped carbon fiber, comprising the following steps:

[0160] (1) Spinning: The spinning solution is extruded through a spinneret with irregularly shaped spinneret holes at a spinning rate of 18.00 m / min to form a fine stream of the solution; wherein, the material of the spinneret is Hastelloy, the irregularity of the irregularly shaped holes of the spinneret is 0.35, the diameter of the plate is 190 mm, the number of holes is 3k, the cross-section of the irregularly shaped holes is "hexagram", the hole spacing is 2.2 mm, and the length-to-diameter ratio of the irregularly shaped holes is 5:1.

[0161] (2) Spinning: The raw liquid is fed through an air layer and then enters a coagulation bath for coagulation and molding. At the same time, a draw ratio of 1.5 is applied to obtain nascent fibers. The height of the air layer is 4.0 mm, the concentration of the coagulation bath is 45 wt%, and the temperature of the coagulation bath is 5 °C.

[0162] (3) Post-treatment: The nascent fibers are desalinated in multiple stages at 33-36℃ to remove the solvent; after washing in the desalinated water, they are heated in hot water at 60-80℃ and simultaneously stretched by 1.3 times; after hot water stretching, the washed fibers are passed through an oil bath with a concentration of 1.10%; the oiled fibers are dried and densified by drying rollers at a temperature of 100-185℃, with 25 drying rollers and a drying roller pressure of 0.55MPa; the dried fiber bundles are steam stretched with a saturated steam pressure of 0.45MPa and a steam stretching ratio of 3.55 times; the fibers are wound and taken up at a winding speed of 400m / min to obtain carbon fiber filaments with irregular cross sections.

[0163] (4) The irregular cross-section carbon fiber precursor is subjected to gradient heating at 220℃, 240℃ and 260℃, and the pre-oxidation stretching ratio is 0.99 times to carry out pre-oxidation treatment to obtain pre-oxidized carbon fiber.

[0164] (5) Place the pre-oxidized carbon fiber in a low-temperature carbonization furnace, maintain the temperature at 600℃, the heating rate at 40℃ / min, and the stretching ratio at 1.0 times to obtain low-temperature carbonized carbon fiber.

[0165] (6) Place the low-temperature carbonized carbon fiber in a high-temperature carbonization furnace, maintain the temperature at 1500℃, the heating rate at 150℃ / min, and the stretching ratio at 1.05 times to obtain high-temperature carbonized carbon fiber, i.e., irregular cross-section carbon fiber.

[0166] Example 2: A method for preparing irregularly shaped carbon fiber, comprising the following steps:

[0167] (1) Spinning: The spinning solution is extruded through a spinneret with irregularly shaped spinneret holes at a spinning rate of 18 m / min to form a fine stream of the solution; wherein, the material of the spinneret is Hastelloy, the irregularity of the irregularly shaped holes of the spinneret is 0.52, the diameter of the plate is 190 mm, the number of holes is 3k, the cross-section of the irregularly shaped holes is "Y" shaped, the hole spacing is 2.2 mm, and the length-to-diameter ratio of the irregularly shaped holes is 3:1.

[0168] (2) Spinning: The raw liquid is fed through an air layer and then enters a coagulation bath for coagulation and molding. At the same time, a draw ratio of 1.1 is applied to obtain nascent fibers. The height of the air layer is 3.0 mm, the concentration of the coagulation bath is 45 wt%, and the temperature of the coagulation bath is 5 °C.

[0169] (3) Post-treatment: The nascent fibers are desalinated in multiple stages at 33-36℃ to remove the solvent; after washing in the desalinated water, they are heated in hot water at 60-80℃ and simultaneously stretched by 1.3 times; after hot water stretching, the washed fibers are passed through an oil bath with a concentration of 1.10%; the oiled fibers are dried and densified by drying rollers at a temperature of 100-185℃, with 25 drying rollers and a drying roller pressure of 0.55MPa; the dried fiber bundles are steam stretched with a saturated steam pressure of 0.45MPa and a steam stretching ratio of 3.55 times; the fibers are wound and taken up at a winding speed of 400m / min to obtain carbon fiber filaments with irregular cross sections.

[0170] (4) The irregular cross-section carbon fiber precursor is subjected to gradient heating at temperatures of 215℃, 235℃ and 245℃, and the pre-oxidation stretching ratio is 0.98 times to carry out pre-oxidation treatment and obtain pre-oxidized carbon fiber.

[0171] (5) Place the pre-oxidized carbon fiber in a low-temperature carbonization furnace, maintain the temperature at 600℃, the heating rate at 40℃ / min, and the stretching ratio at 1.0 times to obtain low-temperature carbonized carbon fiber.

[0172] (6) Place the low-temperature carbonized carbon fiber in a high-temperature carbonization furnace, maintain the temperature at 1500℃, the heating rate at 150℃ / min, and the stretching ratio at 1.01 times to obtain high-temperature carbonized carbon fiber, i.e., irregular cross-section carbon fiber.

[0173] Example 3: A method for preparing irregularly shaped carbon fiber, comprising the following steps:

[0174] (1) Spinning: The spinning solution is extruded through a spinneret with irregularly shaped spinneret holes at a spinning rate of 18.00 m / min to form a fine stream of the solution; wherein, the material of the spinneret is Hastelloy, the irregularity of the irregularly shaped holes of the spinneret is 0.74, the diameter of the plate is 190 mm, the number of holes is 3k, the cross-section of the irregularly shaped holes is "triangular", the hole spacing is 2.2 mm, and the length-to-diameter ratio of the irregularly shaped holes is 8:1.

[0175] (2) Spinning: The raw liquid is fed through an air layer and then enters a coagulation bath for coagulation and molding. At the same time, a draw ratio of 1.8 is applied to obtain nascent fibers. The height of the air layer is 2.5 mm, the concentration of the coagulation bath is 45 wt%, and the temperature of the coagulation bath is 5 °C.

[0176] (3) Post-treatment: The nascent fibers are desalinated in multiple stages at 33-36℃ to remove the solvent; after washing in the desalinated water, they are heated in hot water at 60-80℃ and simultaneously stretched by 1.3 times; after hot water stretching, the washed fibers are passed through an oil bath with a concentration of 1.10%; the oiled fibers are dried and densified by drying rollers at a temperature of 100-185℃, with 25 drying rollers and a drying roller pressure of 0.55MPa; the dried fiber bundles are steam stretched with a saturated steam pressure of 0.45MPa and a steam stretching ratio of 3.55 times; the fibers are wound and taken up at a winding speed of 400m / min to obtain carbon fiber filaments with irregular cross sections.

[0177] (4) The irregular cross-section carbon fiber precursor is subjected to gradient heating at temperatures of 200℃, 210℃ and 230℃, and the pre-oxidation stretching ratio is 0.98 times to carry out pre-oxidation treatment and obtain pre-oxidized carbon fiber.

[0178] (5) Place the pre-oxidized carbon fiber in a low-temperature carbonization furnace, maintain the temperature at 600℃, the heating rate at 40℃ / min, and the stretching ratio at 1.0 times to obtain low-temperature carbonized carbon fiber.

[0179] (6) Place the low-temperature carbonized carbon fiber in a high-temperature carbonization furnace, maintain the temperature at 1500℃, the heating rate at 150℃ / min, and the stretching ratio at 1.01 times to obtain high-temperature carbonized carbon fiber, i.e., irregular cross-section carbon fiber.

[0180] To more clearly explain the technical solution of this application, this application also provides examples 4-24 of the preparation method of irregular cross-section carbon fiber, wherein the process parameters of examples 4-24 are shown in Tables 1-3.

[0181] It should be noted that, apart from the process parameters listed in Tables 1-3, the process parameters of Examples 4-10 are basically the same as those of Example 1, the process parameters of Examples 11-17 are basically the same as those of Example 2, and the process parameters of Examples 18-24 are basically the same as those of Example 3.

[0182] Table 1. Process parameters for preparing irregularly shaped carbon fibers in Examples 1-10

[0183]

[0184] Table 2. Process parameters for preparing irregularly shaped carbon fibers in Examples 11-17

[0185]

[0186]

[0187] Table 3. Preparation process of irregular cross-section carbon fibers in Examples 18-24

[0188]

[0189] Comparative Example 1: A method for preparing carbon fiber with a circular cross-section, comprising the following steps:

[0190] (1) Spinning: The spinning solution is extruded through a spinneret with circular spinneret holes at a spinning rate of 20.00 m / min to form a fine stream of the solution; wherein, the material of the spinneret is Hastelloy, the diameter of the plate is 190 mm, the number of holes is 3k, the hole spacing is 2.2 mm, and the length-to-diameter ratio of the spinneret holes is 3:1.

[0191] (2) Spinning: The raw liquid is fed through an air layer and then enters a coagulation bath for coagulation and molding. At the same time, a draw ratio of 1.6 is applied to obtain nascent fibers. The height of the air layer is 3.0 mm, the concentration of the coagulation bath is 45 wt%, and the temperature of the coagulation bath is 5 °C.

[0192] (3) Post-treatment: The nascent fibers are desalinated in multiple stages at 33-36℃ to remove the solvent; after washing in the desalinated water, they are heated in hot water at 60-80℃ and simultaneously stretched by 1.3 times; after hot water stretching, the washed fibers are passed through an oil bath with a concentration of 1.10%; the oiled fibers are dried and densified by drying rollers at a temperature of 100-185℃, with 25 drying rollers and a drying roller pressure of 0.55MPa; the dried fiber bundles are steam stretched with a saturated steam pressure of 0.45MPa and a steam stretching ratio of 3.55 times; the fibers are wound and taken up at a winding speed of 400m / min to obtain carbon fiber filaments with irregular cross sections.

[0193] (4) The irregular cross-section carbon fiber precursor is heated at 270°C and the pre-oxidation stretching ratio is 0.98 times to carry out pre-oxidation treatment to obtain pre-oxidized carbon fiber.

[0194] (5) Place the pre-oxidized carbon fiber in a low-temperature carbonization furnace, maintain the temperature at 600℃, the heating rate at 40℃ / min, and the stretching ratio at 1.0 times to obtain low-temperature carbonized carbon fiber.

[0195] (6) Place the low-temperature carbonized carbon fiber in a high-temperature carbonization furnace, maintain the temperature at 1500℃, the heating rate at 150℃ / min, and the stretching ratio at 1.01 times to obtain high-temperature carbonized carbon fiber, i.e., circular cross-section carbon fiber.

[0196] Performance testing

[0197] The properties of the carbon fibers prepared by Examples 1-24 and Comparative Example 1 were tested according to the following method, and the test results are recorded in Table 4.

[0198] The heterogeneity morphology rate is calculated using the following formula:

[0199]

[0200] Where S is the irregular forming rate; X0 is the irregularity of the irregular spinneret; X i The cross-sectional irregularity of the irregular fiber is tested for the i-th time.

[0201] Tensile strength and tensile modulus of elasticity: The tests were conducted according to the methods in GB / T 3362-2017 "Test Method for Tensile Properties of Carbon Fiber Multifilament".

[0202] Table 4. Carbon fiber performance test table for Examples 1-24 and Comparative Example 1

[0203]

[0204]

[0205] As can be seen from Tables 1-4, Examples 1-24 and Comparative Example 1, the irregular cross-section carbon fibers prepared by the method of this application have a high irregular cross-section forming rate. Compared with circular cross-section carbon fibers, irregular cross-section carbon fibers have superior tensile strength and tensile modulus.

[0206] As can be seen from Tables 1-4, changes in the cross-sectional shape of the irregular holes, the air layer height, the concentration of the coagulation bath, the coagulation bath temperature, and the pre-oxidation temperature all have a certain impact on the irregular shape formation rate, core-sheath ratio, tensile strength, and tensile modulus of carbon fibers with irregular cross-sections.

[0207] When the irregularity of the spinneret orifice is 0.2-0.4, the aspect ratio of the irregular orifice is 4.5-6.5:1, the air layer height is 3.6-4.5mm, the coagulation bath concentration is 40-50wt%, the coagulation bath temperature is 5-10℃, and the pre-oxidation temperature is 210-220℃—220-240℃—246-260℃, the resulting irregularly shaped carbon fiber has a higher irregularity forming rate, tensile strength, tensile elastic modulus, and lower core-sheath ratio.

[0208] When the irregularity of the spinneret orifice is 0.41-0.6, the aspect ratio of the orifice is 2-4:1, the air layer height is 2.0-3.5 mm, the coagulation bath concentration is 40-50 wt%, the coagulation bath temperature is 5-10℃, and the pre-oxidation temperature is...

[0209] At temperatures of 205-215℃—215-235℃—236-245℃, the resulting irregularly shaped carbon fibers exhibit high irregularity rate, tensile strength, tensile elastic modulus, and low core-sheath ratio.

[0210] When the irregularity of the spinneret orifice is 0.61-0.8, the aspect ratio of the orifice is 7-9:1, the air layer height is 2.2-3.0 mm, the coagulation bath concentration is 40-50 wt%, the coagulation bath temperature is 5-10℃, and the pre-oxidation temperature is...

[0211] At temperatures of 200-210℃—210-230℃—230-235℃, the resulting irregularly shaped carbon fibers exhibit higher irregularity rate, tensile strength, tensile elastic modulus, and lower core-sheath ratio.

[0212] In summary, the irregularly shaped carbon fibers prepared by the method of this application have the advantages of high irregularity and low core-sheath ratio. When used as a reinforcing material, they not only enhance the bonding force between the fiber and the matrix, but also have a large filling ratio, which can significantly improve the overall performance of the composite material.

[0213] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0214] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit it. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing irregularly shaped cross-section carbon fiber precursor, characterized in that, include: The spinning solution is extruded through a spinneret with irregularly shaped holes at a preset spinning rate to form a fine stream of the solution; The original liquid is passed through an air layer at a preset height and then enters a coagulation bath, where it is solidified at a first preset temperature to obtain nascent fibers. The nascent fibers are post-processed to obtain carbon fiber precursors with irregular cross-sections; The irregularity of the spinneret with irregular holes is 0.2-0.8; the irregularity = 1 - radius of the inscribed circle of the irregular cross section / radius of the circumscribed circle of the irregular cross section; The preset spinneret rate is 15.00-25.00 m / min; The preset height is 1.5-4.5mm; The concentration of the coagulation bath is 30-70 wt%, and the first preset temperature is 5-55℃; When the irregularity of the spinneret with irregular holes is 0.2-0.4, the preset height is 3.6-4.5 mm, the concentration of the coagulation bath is 40-50 wt%, the first preset temperature is 5-10℃, and the aspect ratio of the irregular holes is 4.5-6.5:

1. When the irregularity of the spinneret with irregular holes is 0.41-0.6, the preset height is 2.0-3.5mm, the concentration of the coagulation bath is 40-50wt%, the first preset temperature is 5-10℃, and the aspect ratio of the irregular holes is 2-4:

1. When the irregularity of the spinneret with irregular holes is 0.61-0.8, the preset height is 2.2-3.0 mm, the concentration of the coagulation bath is 40-50 wt%, the first preset temperature is 5-10℃, and the aspect ratio of the irregular holes is 7-9:

1.

2. The method for preparing irregularly shaped cross-section carbon fiber precursor according to claim 1, characterized in that, The spinneret with irregularly shaped holes has a thickness of 5-15 mm, a hole spacing of 1-3 mm, a hole count of 1-5 k, and a design pressure of 10-30 MPa.

3. The method for preparing irregularly shaped cross-section carbon fiber precursor according to claim 1, characterized in that, The process of post-processing the nascent fibers to obtain irregularly shaped cross-section carbon fiber precursor includes: The nascent fibers are washed with desalinated water, stretched with hot water, oiled, dried, and stretched with steam before being wound and collected to obtain carbon fiber precursors with irregular cross-sections. The temperature of the desalination washing is 20-35℃, and the draw ratio is 1-1.5; The temperature of the hot water stretching is 60-80℃, and the stretching ratio is 1-2.0; The drying temperature is 100-185℃; The steam stretching pressure is 0.30-0.80 MPa, and the steam stretching ratio is 3.0-5.0 times; The winding speed for winding and taking in the yarn is 350-500 m / min.

4. A type of irregularly shaped cross-section carbon fiber precursor, characterized in that, It is prepared by the preparation method described in any one of claims 1-3.

5. A method for preparing carbon fibers with irregular cross-sections, characterized in that, The irregular cross-section carbon fiber precursor described in claim 4 is carbonized to obtain irregular cross-section carbon fiber. The carbonization process includes: The irregularly shaped cross-section carbon fiber precursor is subjected to gradient heating under a first preset condition to perform pre-oxidation treatment, thereby obtaining pre-oxidized carbon fiber. The pre-oxidized carbon fiber is subjected to carbonization treatment at a first temperature under a second preset condition to obtain low-temperature carbonized carbon fiber. The low-temperature carbonized carbon fiber is subjected to a second temperature carbonization treatment under a third preset condition to obtain high-temperature carbonized carbon fiber, wherein the second temperature is higher than the first temperature.

6. The method for preparing irregularly shaped cross-section carbon fibers according to claim 5, characterized in that, The first preset conditions include: a temperature of 200-300℃ and a pre-oxidation stretching ratio of 0.9-1.05 times; The second preset conditions include: a temperature of 320-800℃, a heating rate of 40-100℃ / min, and a stretching ratio of 1.0-1.

1. The third preset conditions include: a temperature of 1000-1800℃, a heating rate of 100-150℃ / min, and a stretching ratio of 0.95-1.

05.

7. The method for preparing irregularly shaped cross-section carbon fibers according to claim 6, characterized in that, When the irregularity of the spinneret with irregular holes is 0.2-0.4, the gradient temperature of the first preset condition is 210-220℃, 220-240℃, and 246-260℃. When the irregularity of the spinneret with irregular holes is 0.41-0.6, the gradient temperature of the first preset condition is 205-215℃, 215-235℃, and 236-245℃. When the irregularity of the spinneret with irregular holes is 0.61-0.8, the gradient temperature of the first preset condition is 200-210℃, 210-230℃, and 230-235℃.

8. A carbon fiber with an irregular cross-section, characterized in that, It is prepared by the preparation method described in any one of claims 5-7.

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