A method for producing polyacrylonitrile carbon fiber precursor

Abstract

The application provides a polyacrylonitrile carbon fiber precursor preparation method, which comprises the following steps: forming a series of primary fibers in a transition coagulation state in a coagulation bath; slowly coagulating the series of primary fibers in the transition coagulation state through a fiber bundle conditioning device to form a series of coagulation fibers, wherein the fiber bundle conditioning device is outside the coagulation bath, and the fiber bundle conditioning device comprises a positioning guide rod, and each fiber bundle is guided and coagulated under the limiting action of each guide groove of the positioning guide rod; and performing post-treatment on the series of coagulation fibers to obtain a series of polyacrylonitrile carbon fiber precursors. The application effectively avoids the occurrence of the hairiness and broken filament phenomenon caused by the mutual adhesion of the fiber bundles on adjacent spinning positions due to the lack of necessary traction and guidance at the outlet of the coagulation bath, and further reduces the CV value of the linear density of the precursors; meanwhile, the volume of the corresponding coagulation bath does not need to be designed to be too large, which is convenient for production operation and reduces the occupation of the production space to a certain extent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polyacrylonitrile carbon fiber precursor preparation, and particularly relates to a polyacrylonitrile carbon fiber precursor preparation method. BACKGROUND

[0002] Polyacrylonitrile carbon fiber is a kind of composite material main reinforcing body, which has high specific strength, high specific modulus, low density, corrosion resistance and other excellent properties, and is widely used in aerospace, aviation, wind power, high-pressure gas cylinder, building reinforcement and sports goods and other fields of national economy. Due to the long-term high cost of polyacrylonitrile carbon fiber production, it is difficult to meet the growing industrial demand. With the continuous expansion of the application field of high-performance fibers and their composites in China, the high performance, quality stability and low cost of carbon fiber will be the mainstream direction of the development of domestic carbon fiber and its composite material technology in the future.

[0003] The production cost of polyacrylonitrile carbon fiber is mainly related to the cost of raw and auxiliary materials, process flow setting, energy consumption utilization rate and production capacity scale and other factors. At present, the main means to reduce the cost of polyacrylonitrile carbon fiber are: producing large-tow carbon fiber, using low-cost precursors such as lignin, expanding the production scale of single line, etc. Research shows that with the increase of production scale and output, the production cost of carbon fiber shows a downward trend.

[0004] In the development of large-scale carbon fiber production technology, problems such as unstable product quality, many hair balls and high scrap rate often occur, and the designed production capacity cannot be realized in time, resulting in poor process application performance of carbon fiber products. For carbon fiber precursor, the main means to expand the production scale include increasing the spinning speed and increasing the number of spinning positions. With the increase of spinning speed, the residence time of nascent fiber in the coagulation bath becomes shorter. The existing technology realizes the equivalent by lengthening the coagulation bath immersion length or adjusting the coagulation bath parameters, which leads to the problems of too large coagulation bath tank volume, poor nascent fiber density and other adverse consequences. With the increase of the number of spinning positions, the existing technology is prone to cause the problems of fiber adhesion between adjacent spinning positions, many broken filaments and large CV value of the prepared precursor linear density. SUMMARY

[0005] Therefore, the present application provides a polyacrylonitrile carbon fiber precursor preparation method, which can solve the technical problems of the existing technology, such as the adhesion of fibers between adjacent spinning positions in the coagulation bath, many broken filaments, and large CV value of the prepared precursor linear density.

[0006] In order to solve the above problems, the present application provides a polyacrylonitrile carbon fiber precursor preparation method, which comprises the following steps:

[0007] Spinning and solidifying process: the polyacrylonitrile spinning dope is formed into spinning streams through a series of metering devices and a spinning assembly, the spinning streams pass through an air section and enter a coagulation bath to undergo phase separation and form a series of primary fibers in a transition coagulation state, and the series of primary fibers travel in the coagulation bath for a first target length of time;

[0008] Tow arrangement process: the series of primary fibers in the transition coagulation state are slowly coagulated through a tow arrangement device to form a series of coagulated fibers, the length of time for which the fiber tow travels in the tow arrangement device is not less than a second target length of time, and the second target length of time is greater than the first target length of time, the tow arrangement device is outside the coagulation bath, and the tow arrangement device includes a positioning guide rod, and each fiber tow is guided and coagulated under the limiting action of each guide groove of the positioning guide rod;

[0009] Post-processing process: the series of coagulated fibers are subjected to post-processing to obtain a series of polyacrylonitrile carbon fiber precursors.

[0010] In some embodiments, the spinning stream spinning speed is not less than 10 m / min.

[0011] In some embodiments, the solvent concentration C1 of the liquid outside the primary fibers at the tow inlet of the tow arrangement device and the solvent concentration C2 of the liquid outside the coagulated fibers at the tow outlet of the tow arrangement device are obtained, and the difference (C2-C1) between C2 and C1 is obtained, and when the difference (C2-C1) is greater than a preset concentration difference A, the spinning stream spinning speed is reduced.

[0012] In some embodiments, 0.5%≤A≤2%.

[0013] In some embodiments, the first target length of time is 3.5 s to 6.0 s, and the second target length of time is 20 s to 125 s; and the number of spinning positions in the spinning and solidifying process is not less than 60.

[0014] In some embodiments, the tow arrangement device further includes a deflection roller corresponding to each spinning position, and each deflection roller guides each primary fiber drawn out of the coagulation bath to the guide groove of the positioning guide rod at a preset angle in the horizontal plane.

[0015] In some embodiments, the preset angle is 90°; and / or, the tow arrangement device further includes a plying guide rod, the plying guide rod is located at the outlet end of the tow arrangement device, and the plying guide rod has plying grooves on the top surface, and each plying groove can combine a preset number of fiber tows into one.

[0016] In some embodiments, the centerline deviation angle of each fiber tow combined in each plying groove is not greater than 1°.

[0017] In some embodiments, the tow arrangement device further comprises a plurality of support godets, and each of the positioning guide rods is alternately arranged with each of the support godets along the pulling direction of the fiber tow.

[0018] In some embodiments, the tow arrangement device further comprises a plurality of liquid receiving trays, each of the liquid receiving trays is arranged below the lower region of each of the support godets, positioning guide rods and plying guide rods.

[0019] The polyacrylonitrile carbon fiber precursor preparation method provided by the application has the following beneficial effects:

[0020] The spinning stream of each spinning position (corresponding to the number of spinning assemblies) first enters the coagulation bath to undergo phase separation coagulation to form a series of primary fibers in a transition coagulation state, and the series of primary fibers in the transition coagulation state are further pulled out of the coagulation bath to the tow arrangement process to realize final coagulation into a series of coagulation fibers through plying guidance. That is, after the spinning stream undergoes phase separation in the coagulation bath to realize preliminary coagulation, it can be pulled into the tow arrangement device to rely on slow coagulation for a longer time, which can significantly reduce the residence time of the fiber tow in the coagulation bath, effectively avoid the occurrence of pilling and broken filament phenomenon caused by the mutual adhesion of the tows on adjacent spinning positions due to the lack of necessary traction guidance at the outlet of the coagulation bath, and further reduce the CV value of the precursor linear density. At the same time, the volume of the corresponding coagulation bath does not need to be designed too large, which is convenient for production operation and to a certain extent reduces the occupation of production space and the amount of solution used.

[0021] By real-time detection of the solvent concentration of the outer surface liquid of the fiber tow at the inlet and outlet of the tow arrangement device, the size relationship between the difference in solvent concentration of the outer surface liquid before and after the fiber tow enters and exits the tow arrangement device and the preset concentration difference can be used to determine whether the solvent content in the fiber tow meets the standard. If it is less than the preset concentration difference A, it means that the solvent content meets the standard, and the compactness of the finally prepared carbon fiber precursor will also be within a relatively optimal range. Otherwise, it means that the compactness of the finally prepared carbon fiber precursor is poor. At this time, the spinning stream jetting speed is reduced, the residence time of the primary fiber in the coagulation bath is increased to a certain extent, and the coagulation time of the fiber tow in the tow arrangement device is further reduced, thereby ensuring the sufficient diffusion and separation of the solvent in the fiber tow.

[0022] The parallel and spaced primary fibers introduced from the coagulation bath are deflected by 90 degrees by the deflection rollers corresponding to each spinning position respectively, and then introduced into the fiber bundle arrangement device, so that the spacing between the primary fiber bundles is shortened after being deflected by the preset angle, that is, the spacing between the spinning positions is not limited, and only the fiber bundles in the transition coagulation state or even the coagulation state are required to be prevented from contacting each other, the space occupied by the fiber bundle running can be reduced by deflecting the fiber bundle traction running path, especially when the number of spinning positions is large, the demand for operation space can be significantly reduced, thereby facilitating the demand for large-scale spinning operation. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. The drawings in the following description are only exemplary, and other embodiments can be derived from the provided drawings without creative labor for those skilled in the art.

[0024] Figure 1 is a schematic diagram of the steps of the polyacrylonitrile carbon fiber precursor preparation method of the embodiment of the present application;

[0025] Figure 2 is a top view structural schematic diagram of the fiber bundle arrangement device used in the polyacrylonitrile carbon fiber precursor preparation method of the embodiment of the present application, only part of the primary fibers and part of the deflection rollers are shown in the diagram;

[0026] Figure 3 is an axial structure electron microscope diagram of the polyacrylonitrile carbon fiber precursor (T800 grade carbon fiber precursor) prepared in the embodiment 1 of the present application;

[0027] Figure 4 is an axial structure electron microscope diagram of the polyacrylonitrile carbon fiber precursor (T700 grade carbon fiber precursor) prepared in the embodiment 2 of the present application.

[0028] The reference signs are:

[0029] 11, positioning guide rod; 12, deflection roller; 13, plying guide rod; 14, supporting godet. DETAILED DESCRIPTION

[0030] Clearly, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one example embodiment is merely illustrative in nature and is in no way limiting to the present application and its applications or uses. Based upon the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of the present application.

[0031] In the description of the present application, it should be understood that the orientation words such as "front, back, up, down, left, right", "transverse, vertical, perpendicular, horizontal" and "top, bottom" and the like indicated orientation or position relationship are generally based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, without the contrary description, these orientation words do not indicate and imply that the indicated device or element must have a particular orientation or be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation to the protection scope of the present application; the orientation words "inner, outer" refer to the inner and outer relative to the contour of each component.

[0032] For the convenience of description, spatial relative terms such as "over", "above", "upper surface", "upper" and the like can be used herein to describe the spatial position relationship of one device or feature with other devices or features as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device described in the drawings. For example, if the device in the drawings is inverted, the device described as "above" or "over" other devices or structures will be positioned "below" or "under" other devices or structures. Thus, the example term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90° or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0033] In addition, it should be noted that the use of "first", "second" and the like to define parts is only for the convenience of distinguishing the corresponding parts, and the above words have no special meaning unless otherwise stated, therefore it cannot be understood as a limitation to the protection scope of the present application.

[0034] Referring to Figures 1 to 4 As shown, according to the embodiments of the present application, a polyacrylonitrile carbon fiber precursor preparation method is provided, comprising the following steps:

[0035] Spinning and coagulation process: The polyacrylonitrile spinning solution is passed through a series of metering devices (not shown in the figure) and then through a spinneret assembly (not shown in the figure) to form a spinning stream. The spinning stream passes through an air section and enters a coagulation bath where phase separation occurs, forming a series of nascent fibers in a transitional coagulation state. The series of nascent fibers are drawn and traveled in the coagulation bath for a first target time. The aforementioned transitional coagulation state is a state before the complete coagulation state. Specifically, it means that the bidirectional diffusion of solvent and coagulant in the nascent filament (i.e., nascent fiber) is in a transitional state and has not yet reached diffusion equilibrium. The filament drawn out in this state can continue to undergo bidirectional diffusion at a lower rate to achieve uniform coagulation and shaping of the nascent filament, ensuring the density within the monofilament and the consistency between monofilaments.

[0036] Tow finishing process: The series of nascent fibers in the transitional solidification state are passed through a tow finishing device (such as...) Figure 2 The fiber bundles are slowly solidified to form a series of solidified fibers. The fiber bundles are pulled and traveled within the fiber bundle finishing device for a time not less than the second target time, and the second target time is greater than the first target time. The fiber bundle finishing device is located outside the solidification bath. The fiber bundle finishing device includes a positioning guide rod 11. Each fiber bundle is guided and solidified under the limiting action of each guide groove (not shown in the figure, not labeled) on the positioning guide rod 11. It is understood that the number of the aforementioned guide grooves is the same as the number of spinning positions, that is, the same as the number of strands of the nascent fiber. Specifically, when the number of strands of the nascent fiber is 60, the number of guide grooves on one positioning guide rod 11 is also 60. Each guide groove is arranged at equal intervals along the length direction of the positioning guide rod 11 and forms an equal width positioning with the series of nascent fibers. In a specific embodiment, the equal width spacing of each guide groove is 15mm to 25mm, which can prevent the spacing from being too large, wasting space and increasing costs. If the spacing is too small, the fibers are prone to twisting and uneven force, which is not conducive to improving the uniformity of fiber structure and performance.

[0037] Post-processing: The series of coagulated fibers are post-processed to obtain a series of polyacrylonitrile carbon fiber precursors. Specifically, the series of coagulated fibers are sequentially washed, oiled, dried and densified, and steam-drawn to obtain polyacrylonitrile carbon fiber precursors. It should be noted that the "series" in the aforementioned series of nascent fibers and series of coagulated fibers refers to a relatively large number of strands in the fiber bundle, generally not less than 60 strands. In this case, the number of spinning positions in the spinneret coagulation process is not less than 60.

[0038] In the technical solution, the spinning streams of each spinning position (corresponding to the number of jetting assemblies) first enter the coagulation bath to undergo phase separation coagulation to form a series of primary fibers in a transition coagulation state, and the series of primary fibers in the transition coagulation state are further pulled to a tows finishing process outside the coagulation bath to realize final coagulation into a series of coagulated fibers through strand guiding. That is, after the spinning streams undergo phase separation in the coagulation bath to realize preliminary coagulation, the spinning streams can be pulled to the tow finishing device to realize slow coagulation for a longer time, which can significantly reduce the residence time of the fiber tows in the coagulation bath. The occurrence of the pilling and broken filament phenomenon caused by the mutual adhesion of the tows on adjacent spinning positions due to the lack of necessary traction guidance at the outlet of the coagulation bath is effectively avoided, thereby reducing the CV value of the raw filament linear density. At the same time, slow coagulation effectively improves the structural uniformity of the skin and core of the primary fiber, thereby reducing the CV value of the mechanical properties of the raw filament. At the same time, the volume of the corresponding coagulation bath does not need to be designed to be too large, which is convenient for production operation, reduces the occupation of production space and the amount of solution used to a certain extent, and reduces the production cost.

[0039] In some embodiments, the spinning stream jetting speed is not less than 10 m / min, which prevents the primary fiber from completely coagulating during the residence in the coagulation bath, resulting in a large structural difference between the skin and core of the primary fiber formed at a faster diffusion rate, thereby making the prepared carbon fiber raw filament have poor compactness and poor uniformity of structure and performance. In addition, a slower jetting speed is also not conducive to improving the spinning production efficiency and is not conducive to the industrialization of spinning. A faster jetting speed can not only improve the production capacity but also reduce the time cost.

[0040] In some embodiments, the solvent concentration C1 of the liquid outside the primary fiber at the tow inlet of the tow finishing device and the solvent concentration C2 of the liquid outside the coagulated fiber at the tow outlet of the tow finishing device are obtained, and the difference (C2-C1) between C2 and C1 is obtained. When the difference (C2-C1) is greater than a preset concentration difference A, the spinning stream jetting speed is reduced. It can be understood that the spinning stream jetting speed after reduction should also meet the requirement of not being less than 10 m / min.

[0041] In the technical solution, the solvent concentration of the external liquid of the fiber tow is detected in real time at the fiber tow inlet and outlet of the fiber tow arrangement device, and the size relationship between the difference of the solvent concentration of the external liquid before and after the fiber tow enters and exits the fiber tow arrangement device and the preset concentration difference is used to determine whether the solvent content in the fiber tow meets the standard. If the difference is less than the preset concentration difference A, it means that the solvent content meets the standard, and the compactness of the final prepared carbon fiber precursor is also within a relatively optimal range. Otherwise, it means that the compactness of the final prepared carbon fiber precursor is poor. In this case, the spinning stream jet speed is reduced, the residence time of the nascent fiber in the coagulation bath is increased to a certain extent, and the coagulation time of the fiber tow in the fiber tow arrangement device is further reduced, thereby ensuring sufficient diffusion of the solvent in the fiber tow.

[0042] In a specific embodiment, 0.5%≤A≤2%, that is, in this embodiment, in order to ensure the compactness of the final prepared carbon fiber tow, when the difference 0.5%≤(C2-C1)≤2%, it means that the pulling speed of the nascent fiber is within a reasonable range. When the difference (C2-C1) > 2%, it means that the pulling speed of the nascent fiber is too fast, which results in insufficient residence time of the nascent fiber in the coagulation bath and the fiber tow arrangement device, and the solvent in the fiber tow is not fully diffused and separated, and the compactness of the final prepared carbon fiber tow is deviated. When the difference (C2-C1) < 0.5%, it means that the pulling speed of the nascent fiber is too slow or the residence time of the nascent fiber in the coagulation bath is too long, which results in low production efficiency and is not conducive to reducing production cost.

[0043] The specifications of the aforementioned spinning assembly can be 3K, 4K, or 6K, which can be reasonably selected according to actual production needs.

[0044] In a feasible embodiment, the first target time length is 3.5s-6.0s, and the second target time length is 20s-125s, that is, the residence time of the fiber in the fiber arrangement device is much longer than the residence time of the fiber in the coagulation bath, which can significantly reduce the volume of the coagulation bath and the amount of reagent solution in the coagulation bath, facilitating production operation and reducing production cost.

[0045] For details, please refer to Figure 2 As shown in the drawings, in some embodiments, the fiber arrangement device further comprises a deflection roller 12 arranged one-to-one corresponding to each spinning position. Each deflection roller 12 horizontally guides the nascent fiber drawn out of the coagulation bath by each spinning position to the guide groove of the positioning guide rod 11 after being deflected by a preset angle. The aforementioned preset angle is generally 90°-93°, and is preferably 90°.

[0046] In the technical solution, each nascent fiber introduced from the coagulation bath is deflected 90° by the deflection roller 12 corresponding to each spinning position and then introduced into the fiber bundle arrangement device. In this way, the parallel and spaced nascent fiber bundles introduced from the coagulation bath can shorten the distance between each other after being deflected by a preset angle. That is, the distance between the spinning positions does not need to be limited, and only the fiber bundles in the transition coagulation state or even the coagulation state need to be ensured not to contact each other. The deflection of the fiber bundle traction path can reduce the space occupied by the fiber bundle, especially when there are many spinning positions, which can significantly reduce the demand for operation space, thereby facilitating the demand for large-scale spinning operation. When the deflection angle is 90°, the space occupied by the fiber bundle can be minimized.

[0047] It should be noted that, with the Figure 2 position as the reference, the nascent fibers formed by each spinning position are pulled and run from top to bottom. After passing through the corresponding deflection roller 12, the corresponding nascent fibers are deflected 90° and pulled and run from left to right. It can be understood that, in order to ensure that each nascent fiber is still in a parallel and spaced state after deflection, the arrangement positions of each deflection roller 12 are also different in the up-down direction of the Figure 2

[0048] In a preferred embodiment, the fiber bundle arrangement device further comprises a plying guide rod 13. The plying guide rod 13 is located at the outlet end of the fiber bundle arrangement device. The top surface of the plying guide rod 13 has plying grooves (not shown and not referenced in the figure). Each plying groove can combine a preset number of fiber bundles into one, thereby meeting the demand for different plying numbers.

[0049] In a preferred embodiment, the aforementioned positioning guide rod 11 and the plying guide rod 13 are specifically fixed different structures. That is, the guide grooves on the aforementioned positioning guide rod 11 and the plying grooves of the plying guide rod 13 are only needed to be constructed on the top surface of the rod body. In this way, the installation space of the positioning guide rod 11 and the plying guide rod 13 can be effectively reduced. For example, when the aforementioned positioning guide rod 11 and the plying guide rod 13 are both driven rotatable structures, it is necessary to set annular guide grooves and plying grooves in the circumferential direction of the rod body, which will increase the diameter of the rod body and occupy the installation space.

[0050] In some embodiments, the center line deviation angle of each fiber bundle plying in each plying groove is not greater than 1°, which can further reduce the overall width of the fiber bundle arrangement device (that is, the distance between the left and right sides of the fiber bundle arrangement device). Figure 2 ​(The vertical height of the indicated position) further reduces the occupation of the working space; and / or, the stranding guide rod 13 has at least two rods, each stranding guide rod 13 is arranged sequentially at intervals along the traction direction of the fiber bundle. In a specific embodiment, the width of the stranding groove upstream in the traction direction is greater than the width of the stranding groove downstream. This can form a gradual gradient stranding of the fiber bundles in each stranding groove, ensuring that the deflection angle of each fiber bundle is small, which can further reduce the occurrence of friction, fuzzing or even fiber breakage between the surface of the fiber bundle and the stranding groove.

[0051] In some embodiments, the fiber bundle finishing device further includes multiple support guide rollers 14, and multiple positioning guide rods 11. The support guide rollers 14 and the positioning guide rods 11 are alternately arranged at intervals along the traction direction of the fiber bundle to provide reliable support for the traction of the fiber bundle within the finishing device. In a specific embodiment, the support guide rollers 14 are either passive rollers or stationary rollers, preferably stationary rollers, with a diameter of φ40mm-80mm.

[0052] In one specific embodiment, the drafting ratio of the nascent fibers in the fiber bundle finishing device is 0.99-1.05 to prevent the fiber bundle from being too loose and unable to operate if the drafting is too small, or from being too loose and causing the fiber bundle to easily pull and produce fuzz or breakage; the operating temperature of the fiber bundle finishing device is 10℃-30℃.

[0053] In some embodiments, the fiber bundle finishing device further includes multiple liquid receiving trays (not shown in the figure), each of which is correspondingly disposed in the area below each of the supporting guide rollers 14, positioning guide rods 11 and stranding guide rods 13, so as to recover the liquid formed when the fiber bundles come into contact with the corresponding rods or rollers. In a specific embodiment, each of the aforementioned liquid receiving trays is connected to a coagulation bath through corresponding pipelines, so that the solution collected therein can be returned to the coagulation bath for reuse, thereby saving production costs.

[0054] Furthermore, the solidified fibers formed in the aforementioned preparation method have a crystallinity of 20%-30%, a tensile strength ≥100MPa, and an elongation ≥230%; the polyacrylonitrile carbon fiber precursor prepared using the aforementioned preparation method of the present invention has a crystallinity of 60%-80%, a linear density CV value ≤0.6%, and a bulk density ≥1.18g / cm³. 3 Tensile strength ≥ 600 MPa, tensile strength CV value ≤ 2.0%, elongation ≥ 7%, elongation CV value ≤ 2.0%.

[0055] The preparation method of the present invention is further illustrated below with reference to several embodiments:

[0056] Example 1

[0057] The embodiment prepares polyacrylonitrile carbon fiber precursor, and the number of spinning positions is 80. The specific steps are as follows:

[0058] 1. Spinning and coagulation process: the polyacrylonitrile spinning dope with a viscosity of 120 Pa.s passes through 80 metering devices and then through a 3K spinning pack to form a spinning stream, and the spinning speed is 10 m / min. The spinning stream passes through an air section of 6 mm and then enters a coagulation bath with a DMSO (dimethyl sulfoxide) concentration of 35% and a temperature of 5°C to undergo phase separation, the residence time of the coagulation bath is 5.7 s, and 80 bundles of primary fibers in a transition coagulation state are formed.

[0059] 2. Bundle arrangement process: the 80 bundles of primary fibers in a transition coagulation state are deflected by 90° through a bundle arrangement device. The support godet 14 is a stationary roller with a diameter of φ40 mm. The equal-width spacing of the positioning guide rod 11 is 20 mm. The temperature of the bundle arrangement device is 20°C, the draft ratio is 1.00, the residence time of the primary fibers is 40-119.8 s, and the residence time of each adjacent primary fiber bundle increases by 1.4 s. The DMSO solvent concentration (C2) of the liquid around the coagulation fibers at the outlet of the bundle arrangement process is 36.25%, the solvent concentration (C1) of the liquid around the primary fibers at the inlet is 35.63%, and the difference between C2 and C1 is 0.62%.

[0060] The 80 bundles of primary fibers become 20 bundles of 12K coagulation fibers through the plying guide rod 13. The primary fibers pass through the plying guide rod 13 with an angle of 0.55° from the center line. The crystallinity of the coagulation fibers is 28.5%, the tensile strength is 141 MPa, and the elongation is 280%.

[0061] Post-treatment process: the obtained coagulation fibers are subjected to water washing treatment at a gradient temperature of 40-60°C, hot water drafting treatment at a gradient temperature of 85-90°C, oiling (oil concentration 2.5%), drying and densification treatment (temperature 120-140°C), and steam drafting treatment (pressure 0.6 MPa) to obtain polyacrylonitrile carbon fiber precursor. The prepared polyacrylonitrile carbon fiber precursor has a crystallinity of 76.3%, a linear density CV value of 0.5%, a bulk density of 1.183 g / cm 3 , a tensile strength of 780 MPa, a tensile strength CV value of 1.56%, an elongation of 8.2%, and an elongation CV value of 1.60%.

[0062] Example 2

[0063] The embodiment prepares polyacrylonitrile carbon fiber precursor, and the number of spinning positions is 72. The specific steps are as follows:

[0064] 1. Spinning and solidification process: the polyacrylonitrile spinning dope with viscosity of 120 Pa.s passes through 72 metering devices and then through 4K spinning pack to form spinning streams, the spinning speed is 14.5 m / min. The spinning streams pass through 6 mm air section and then enter the coagulation bath with DMSO concentration of 35% and temperature of 5°C to undergo phase separation, the residence time of the coagulation bath is 4.1 s, and 72 bundles of nascent fibers in transition solidification state are formed.

[0065] 2. Bundle arrangement process: the 72 bundles of nascent fibers in transition solidification state are deflected by 90° through the bundle arrangement device. The support godet 14 is a stationary roller with diameter of φ60 mm. The equal-width spacing of the positioning guide rod 11 is 25 mm. The temperature of the bundle arrangement device is 20°C, the draft ratio is 1.02, the residence time of the nascent fibers is 26.8-93.5 s, the residence time of each adjacent bundle of nascent fibers is increased by 0.967 s in turn, the DMSO solvent concentration (C2) of the liquid around the solidification fibers at the outlet of the bundle arrangement process is 36.62%, the solvent concentration (C1) of the liquid around the nascent fibers at the inlet is 35.43%, and the difference between C2 and C1 is 1.19%.

[0066] The 72 bundles of nascent fibers become 24 bundles of 12K solidification fibers through the plying guide rod 13. The nascent fibers pass through the plying guide rod 13 with an angle of 0.67° from the center line. The crystallinity of the solidification fibers is 26.4%, the tensile strength is 120 MPa, and the elongation is 290%.

[0067] Post-processing process: the obtained solidification fibers are subjected to water washing treatment at gradient temperature of 40-60°C, hot water drafting treatment at gradient temperature of 85-90°C, oiling (concentration of oil agent is 2.5%), drying and densification treatment (temperature is 130-160°C), and steam drafting treatment (pressure is 0.6 MPa) to obtain polyacrylonitrile carbon fiber precursor. The polyacrylonitrile carbon fiber precursor has a crystallinity of 73.6%, a linear density CV value of 0.45%, a bulk density of 1.181 g / cm3, a tensile strength of 630 MPa, a tensile strength CV value of 1.68%, an elongation of 8.1%, and an elongation CV value of 1.70%.

[0068] Those skilled in the art can easily understand that the advantageous technical features of the above-mentioned modes can be freely combined and superimposed without conflict.

[0069] The above merely describes preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application. The above merely describes preferred embodiments of the present application and is not used to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for producing a polyacrylonitrile carbon fiber precursor, characterized by, It comprises the following steps: Spinning and solidification process: the polyacrylonitrile spinning dope is formed into spinning streams through a series of metering devices and a spinning assembly, the spinning streams pass through an air section and enter a coagulation bath to undergo phase separation and form a series of primary fibers in a transition coagulation state, and the series of primary fibers travel in the coagulation bath for a first target length of time; Tow arrangement process: the series of primary fibers in the transition coagulation state are slowly coagulated through a tow arrangement device to form a series of coagulated fibers, the fiber tow travels in the tow arrangement device for a length of time not less than a second target length of time, the second target length of time is greater than the first target length of time, the tow arrangement device is outside the coagulation bath, the tow arrangement device comprises a positioning guide rod (11), and each fiber tow is guided and coagulated under the limiting action of each guide groove of the positioning guide rod (11); Post-treatment process: the series of coagulated fibers are post-treated to obtain a series of polyacrylonitrile carbon fiber precursors.

2. The polyacrylonitrile carbon fiber precursor production method according to claim 1, characterized by, The spinning stream spinning speed is not less than 10 m / min.

3. The polyacrylonitrile-based carbon fiber precursor production method according to claim 2, characterized by, The solvent concentration C1 of the outer surface liquid of the primary fiber at the tow inlet of the tow arrangement device and the solvent concentration C2 of the outer surface liquid of the coagulated fiber at the tow outlet of the tow arrangement device are obtained, and the difference (C2-C1) between C2 and C1 is obtained, when the difference (C2-C1) is greater than a preset concentration difference A, the spinning stream spinning speed is reduced.

4. The polyacrylonitrile-based carbon fiber precursor production method according to claim 3, characterized by, 0.5％≤A≤2％。 5. The polyacrylonitrile-based carbon fiber precursor production method according to claim 1, wherein The first target length of time is 3.5 s to 6.0 s, and the second target length of time is 20 s to 125 s; the number of spinning positions in the spinning and solidification process is not less than 60.

6. The polyacrylonitrile-based carbon fiber precursor production method according to claim 1, wherein The tow arrangement device further comprises a deflection roller (12) corresponding to each spinning position, each deflection roller (12) deflects each primary fiber drawn out of the coagulation bath by a preset angle in the horizontal plane and then guides it into the guide groove of the positioning guide rod (11).

7. The polyacrylonitrile-based carbon fiber precursor production method according to claim 6, wherein The preset angle is 90°; and / or, the tow arrangement device further comprises a plying guide rod (13), the plying guide rod (13) is located at the outlet end of the tow arrangement device, the top surface of the plying guide rod (13) has plying grooves, and each plying groove can combine a preset number of fiber tows into one.

8. The polyacrylonitrile-based carbon fiber precursor production method according to claim 7, wherein The centerline deviation angle of each fiber tow in each plying groove is not greater than 1°.

9. The polyacrylonitrile-based carbon fiber precursor production method according to claim 7, wherein The tow arrangement device further comprises a plurality of support godets (14), and the positioning guide rod (11) has a plurality of roots, each support godet (14) and each positioning guide rod (11) are alternately arranged along the direction of travel of the fiber tow.

10. The polyacrylonitrile-based carbon fiber precursor production method according to claim 9, wherein The tow arrangement device further comprises a plurality of liquid receiving discs, each liquid receiving disc is arranged below each support godet (14), positioning guide rod (11) and plying guide rod (13).

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