Polyacrylonitrile-based carbon fiber and method for producing the same

Abstract

The application relates to a polyacrylonitrile-based carbon fiber and a preparation method thereof, wherein the preparation method of the polyacrylonitrile-based carbon fiber comprises the following steps: sequentially performing unwinding treatment, pre-oxidation treatment, low-temperature carbonization treatment, high-temperature carbonization treatment and surface treatment on polyacrylonitrile fibers to obtain the polyacrylonitrile-based carbon fiber; and before the pre-oxidation treatment, the fiber tows after the unwinding treatment are sequentially subjected to first-time turning treatment through a first turning roller and second-time turning treatment through a second turning roller; the parameters of the first-time turning treatment are as follows: a turning angle is 10-40 DEG, the fiber tows run along a first direction for 5-20 m, and a tension applied to the fiber tows is 500-1500 cN; the parameters of the second-time turning treatment are as follows: a turning angle is 10-40 DEG, the fiber tows run along a second direction for 5-20 m, and a tension applied to the fiber tows is 1000-1500 cN; and the first direction and the second direction are opposite directions. The application is mainly used for avoiding fiber tow abrasion and improving tension control precision.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon fiber, in particular to a polyacrylonitrile-based carbon fiber and a preparation method thereof. BACKGROUND

[0002] In the production process of carbon fiber, turning generally exists in the processes such as pre-oxidation furnace and carbonization furnace. Through turning, the carbon fiber tows can be transported along a reasonable path between different production equipment, so that the layout of each equipment is more compact, the production space occupation is reduced, and the site utilization rate is improved. In addition, reasonable turning can avoid sudden or uneven changes in tow tension, and ensure the stable stress of carbon fiber in production, which is crucial for ensuring the quality and performance of carbon fiber, and can make the performance indicators such as strength and modulus more stable and consistent. At the same time, smooth turning can reduce production abnormalities such as tows, crossing, twisting, winding, broken wires, etc., avoid production interruption, realize stable and continuous production, improve production efficiency, and reduce production cost.

[0003] The existing turning technologies mainly include: (1) guide roller turning technology: guide rollers are arranged in pre-oxidation furnace, carbonization furnace and other equipment, and the carbon fiber tows are turned along a predetermined path by changing the position and angle of the guide rollers; (2) pulley turning technology: the direction of the tows is changed by the rotation of the pulley, which is similar to the guide roller, but the rotation of the pulley is more flexible, which can reduce the friction between the tows and the turning device, and is often used in production links with high requirements for tow tension and surface quality; (3) airflow turning technology: the carbon fiber tows are turned by airflow, and the tows are turned as required by controlling the direction, speed and pressure of the airflow, which has the advantages of flexible turning and little damage to the tows, but the equipment is complex, the cost is high, and the process control is strict.

[0004] However, the inventors of the present application found that the above-mentioned turning technologies at least have the following technical problems:

[0005] (1) There is friction between the turning device such as guide roller and pulley and the tows, and if the turning process control is not reasonable, it is easy to cause the surface of the tows to be abraded and hairy, thereby affecting the performance and appearance quality of the carbon fiber.

[0006] (2) The existing turning technologies are difficult to accurately control the tension of the tows, and the tension is easy to fluctuate during the turning process, which affects the quality and production stability of the carbon fiber. For the production of high-performance carbon fiber, insufficient control precision of the tension will reduce the performance indicators of the product.

[0007] (3) The adaptability of some turning technologies to carbon fiber tows of different specifications and materials is poor. For example, a turning device works well when processing small tow carbon fiber, but when processing large tow carbon fiber, it may have problems such as poor turning, uneven tension, etc.

[0008] (4) For the air flow diversion and other more complex technology, the equipment maintenance cost is high, and professional personnel are needed to maintain and repair, which increases the production cost and technical difficulty of enterprises. SUMMARY

[0009] Therefore, the present application provides a polyacrylonitrile-based carbon fiber and a preparation method thereof, which mainly aims to avoid fiber tow abrasion and improve the control accuracy of tension.

[0010] To achieve the above-mentioned purpose, the present application mainly provides the following technical solutions:

[0011] In one aspect, the embodiment of the present application provides a preparation method of a polyacrylonitrile-based carbon fiber, wherein the preparation method of the polyacrylonitrile-based carbon fiber comprises the following steps:

[0012] The polyacrylonitrile fiber is sequentially subjected to unwinding treatment, pre-oxidation treatment, low-temperature carbonization treatment, high-temperature carbonization treatment and surface treatment to obtain a polyacrylonitrile-based carbon fiber; wherein

[0013] Before the pre-oxidation treatment, the fiber tow after the unwinding treatment is sequentially subjected to first turning treatment by a first turning roller and second turning treatment by a second turning roller; wherein the fiber tow is gathered by the first turning treatment and the second turning treatment;

[0014] The parameters of the first turning treatment are as follows: the turning angle is 10-40°, the fiber tow runs along a first direction for 5-20 m, and the tension applied to the fiber tow is 500-1500 cN;

[0015] The parameters of the second turning treatment are as follows: the turning angle is 10-40°, the fiber tow runs along a second direction for 5-20 m, and the tension applied to the fiber tow is 1000-1500 cN;

[0016] The first direction and the second direction are opposite directions.

[0017] Preferably, the first direction is the direction in which the fiber tow runs upward, and the second direction is the direction in which the fiber tow runs downward.

[0018] Preferably, the fiber tow after the unwinding treatment is arranged in groups on the groove roller; wherein the spacing between the two adjacent groups of fiber tow is 20-40 mm; and the inter-fiber spacing of the fiber tow in each group is 8-8.5 mm.

[0019] Preferably, after the first and second turning treatments, the distance between the two adjacent groups of fiber tows is reduced from 20-40mm to 0-5mm, and the distance between the fibers in each group is reduced from 8-8.5mm to 7-7.5mm.

[0020] Preferably, after the low-temperature carbonization treatment and before the high-temperature carbonization treatment, the fiber tows after the low-temperature carbonization treatment are sequentially subjected to a third turning treatment by a third turning roller and a fourth turning treatment by a fourth turning roller, wherein the fiber tows are gathered by the third and fourth turning treatments.

[0021] The parameters of the third turning treatment are as follows: the turning angle is 5-20°, and the tension applied to the fiber tows is 500-1000cN.

[0022] The parameters of the fourth turning treatment are as follows: the turning angle is 5-20°, and the tension applied to the fiber tows is 1500-3000cN.

[0023] Preferably, after the third and fourth turning treatments, the distance between the two adjacent groups of fiber tows remains unchanged, and the distance between the fibers in each group is reduced from 7-7.5mm to 5-5.5mm.

[0024] Preferably, after the high-temperature carbonization treatment and before the surface treatment, the fiber tows after the high-temperature carbonization treatment are sequentially subjected to a fifth turning treatment by a fifth turning roller and a sixth turning treatment by a sixth turning roller, wherein the fiber tows are expanded by the fifth turning treatment, and gathered by the sixth turning treatment.

[0025] The parameters of the fifth turning treatment are as follows: the turning angle is 20-50°, and the tension applied to the fiber tows is 2000-3000cN.

[0026] The parameters of the sixth turning treatment are as follows: the turning angle is 2-10°, and the tension applied to the fiber tows is 2000-3000cN.

[0027] Preferably, after the fifth and sixth turning treatments, the distance between the two adjacent groups of fiber tows is increased from 0-5mm to 15-20mm, and the distance between the fibers in each group is increased from 5-5.5mm to 6.5-7mm.

[0028] Preferably, the first and second turning rollers are groove rollers.

[0029] Preferably, the third deflection roller and the fourth deflection roller are grooved rollers;

[0030] Preferably, the fifth deflection roller and the sixth deflection roller are grooved rollers;

[0031] Preferably, the depth of the wire channel on the grooved roller is 1-5 mm;

[0032] Preferably, the grooved roller comprises a first end portion, a second end portion, and a wire running portion between the first end portion and the second end portion; the wire channel is arranged on the wire running portion; the first end portion and the second end portion of the grooved roller are 10-50 mm higher than the wire running portion.

[0033] Preferably, after the deflection treatment, the distance between the two sides of the fiber tows and the inner wall of the pre-oxidation furnace is 30-100 mm; and / or

[0034] Preferably, after the deflection treatment, the distance between the two sides of the fiber tows and the inner wall of the high-temperature carbonization furnace is 30-100 mm; and / or

[0035] Preferably, after the deflection treatment, the distance between the fiber tows and the inner wall of the surface treatment device is 30-100 mm; and / or

[0036] Preferably, the pre-oxidation treatment temperature is 220-270℃; and / or

[0037] Preferably, the low-temperature carbonization treatment temperature is 350-800℃; and / or

[0038] Preferably, the high-temperature carbonization treatment temperature is 1000-1500℃; and / or

[0039] Preferably, the mass concentration of the electrolyte used in the surface treatment is 2-8%.

[0040] Preferably, after the surface treatment, water washing, sizing, and drying treatment are further included; preferably, the conductivity of the water used in the water washing treatment is ≤200 μs / cm; the concentration of the sizing solution used in the sizing treatment is 1-2.5 wt%; the drying treatment temperature is 200-240℃.

[0041] In another aspect, the embodiments of the present application provide a polyacrylonitrile-based carbon fiber, wherein the polyacrylonitrile-based carbon fiber is prepared by the preparation method of the polyacrylonitrile-based carbon fiber according to any one of the above embodiments;

[0042] Preferably, the polyacrylonitrile-based carbon fiber has a hairiness amount ≤0.4 g / km; the CV value of the batch tensile strength of the polyacrylonitrile-based carbon fiber is ≤2%, the CV value of the linear density is ≤0.8%, and the CV value of the sizing amount is ≤3%.

[0043] Compared with the prior art, the polyacrylonitrile-based carbon fiber and the preparation method thereof have at least the following beneficial effects:

[0044] In one aspect, the preparation method of the polyacrylonitrile-based carbon fiber provided by the embodiment of the present application designs two-stage turning (i.e., first turning treatment and second turning treatment) after the unwinding treatment and before the pre-oxidation treatment, and controls the turning angle, running distance and tension range applied to the fiber tows during the turning treatment. It should be noted that in the above scheme, the turning angle and tension of the first turning treatment and the second turning treatment are matched, and the running distance is controlled to achieve turning take-up, so as to avoid tow fuzzing caused by excessive tension or turning. The embodiment reserves an adjustment range for tension control, so as to avoid fiber index differences and different specifications of fibers caused by substandard tension control accuracy and adaptability problems. In addition, the turning rollers and path turning used in the embodiment avoid high maintenance costs caused by airflow turning.

[0045] Further, the preparation method of the polyacrylonitrile-based carbon fiber provided by the embodiment of the present application designs two-stage turning (third turning treatment and fourth turning treatment) after the low-temperature carbonization treatment and before the high-temperature carbonization treatment. In this embodiment, the turning angle and tension of the turning treatment are matched to achieve take-up, so as to avoid tow fuzzing caused by excessive tension or turning, and at the same time, an adjustment range is reserved for tension control, so as to avoid fiber index differences and different specifications of fibers caused by substandard tension control accuracy and adaptability problems.

[0046] Further, the preparation method of the polyacrylonitrile-based carbon fiber provided by the embodiment of the present application further designs two-stage turning (fifth turning treatment and sixth turning treatment) after the high-temperature carbonization treatment and before the surface treatment. In this embodiment, the turning angle and tension of the turning treatment are matched to achieve take-up, so as to avoid tow fuzzing caused by excessive tension or turning, and at the same time, an adjustment range is reserved for tension control, so as to avoid fiber index differences and different specifications of fibers caused by substandard tension control accuracy and adaptability problems.

[0047] In another aspect, the polyacrylonitrile-based carbon fiber provided by the embodiment of the present application is prepared by the above-mentioned preparation method of the polyacrylonitrile-based carbon fiber, and therefore, the overall appearance qualification rate of the polyacrylonitrile-based carbon fiber is high.

[0048] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application and to implement the content of the description, the following will describe the preferred embodiments of the present application in detail. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 A schematic diagram of the third time turning treatment of two groups of fiber tows in the embodiment. In the figure, Figure 1 In the figure: 1: turning angle; 2: fiber tows; 3: third time turning roller; 4: fiber running direction. DETAILED DESCRIPTION

[0050] In order to further illustrate the technical means and effects taken by the present application to achieve the predetermined object, the following describes the specific embodiments, structures, features and effects according to the present application in detail. In the following description, different "an embodiment" or "embodiments" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0051] Embodiment 1

[0052] The embodiment provides a preparation method of polyacrylonitrile-based carbon fiber, and the preparation method of the polyacrylonitrile-based carbon fiber comprises the following steps: sequentially performing unwinding treatment, pre-oxidation treatment, low-temperature carbonization treatment, high-temperature carbonization treatment and surface treatment on polyacrylonitrile fiber (original fiber) to obtain polyacrylonitrile-based carbon fiber; wherein before the pre-oxidation treatment, the fiber tows after the unwinding treatment are sequentially subjected to first time turning treatment through a first time turning roller and second time turning treatment through a second time turning roller; wherein the parameters of the first time turning treatment are as follows: the turning angle is 10-40°, the fiber tows run along a first direction for 5-20 m, and the tension applied to the fiber tows is 500-1500 cN; wherein the parameters of the second time turning treatment are as follows: the turning angle is 10-40°, the fiber tows run along a second direction for 5-20 m, and the tension applied to the fiber tows is 1000-1500 cN; wherein the first direction and the second direction are two opposite directions.

[0053] Preferably, the first direction is the upward running direction (ascending) of the fiber tows, and the second direction is the downward running direction (descending) of the fiber tows.

[0054] Preferably, the fiber tows after the unwinding treatment are arranged horizontally in groups on the groove roller; wherein the spacing between the two adjacent groups of fiber tows is 20-40 mm; and the spacing between the fiber tows in each group is 8-8.5 mm.

[0055] Preferably, after the fiber tows after the unwinding treatment are subjected to the first time turning treatment and the second time turning treatment, the spacing between the two adjacent groups of fiber tows is reduced from 20-40 mm to 0-5 mm; and the spacing between the fiber tows in each group is reduced from 8-8.5 mm to 7-7.5 mm, so as to reduce the effective space of the equipment design and reduce the cost.

[0056] The polyacrylonitrile-based carbon fiber preparation method provided in the embodiment designs two-stage turning (i.e., first turning treatment and second turning treatment) after the unwinding treatment and before the pre-oxidation treatment, and controls the turning angle, running distance, and tension range applied to the fiber tows during the turning treatment. It should be noted that the embodiment matches the turning angle and tension of the first turning treatment and the second turning treatment, and controls the running distance to achieve convergence, thereby avoiding tow fuzzing caused by excessive tension or turning. The embodiment reserves a range for tension control, thereby avoiding fiber index differences and different specifications of fibers caused by poor tension control accuracy and adaptability problems. In addition, the turning rollers and path turning used in the embodiment avoid the high maintenance costs caused by airflow turning.

[0057] For the first turning treatment, the "turning angle" is described as follows: the turning angle of the fiber tows in all groups is controlled within the range of 10-40°, but the turning angles of the fiber tows in different groups can be different, and are specifically determined according to the required spacing. The same applies to the second turning treatment, the third turning treatment, the fourth turning treatment, the fifth turning treatment, and the sixth turning treatment.

[0058] Embodiment 2

[0059] Preferably, the polyacrylonitrile-based carbon fiber preparation method provided in the embodiment further comprises, after the low-temperature carbonization treatment and before the high-temperature carbonization treatment: making the fiber tows after the low-temperature carbonization treatment sequentially pass through a third turning roller for third turning treatment and a fourth turning roller for fourth turning treatment. The parameters of the third turning treatment are as follows: the turning angle is 5-20°, and the tension applied to the fiber tows is 500-1000 cN. The parameters of the fourth turning treatment are as follows: the turning angle is 5-20°, and the tension applied to the fiber tows is 1500-3000 cN.

[0060] The turning angle of the embodiment is described as follows: as shown in FIG. 2, two groups of fiber tows 2 start running along a first fiber running direction 4, and then are turned after passing through a third turning roller 3, wherein, Figure 1 the turning angle of the fiber tows on the left is 5-10°, Figure 1 the turning angle of the fiber tows on the right is 10-15°, and the turning angles of the two groups of fiber tows are both within the range of 5-20°, and the distance between the two groups of fiber tows becomes smaller after turning. Figure 1

[0061] ​It should be noted that if the low-temperature carbonization furnace is a vertical furnace, it needs to run upward in the third time of turning and downward in the fourth time of turning; if the low-temperature carbonization furnace is a horizontal furnace, it does not need to.

[0062] Preferably, the fiber tows after the low-temperature carbonization treatment are subjected to the third time of turning, the fourth time of turning, and the spacing between the two adjacent groups of fiber tows remains unchanged; the spacing between the fibers in each group is reduced from 7-7.5 mm to 5-5.5 mm, so as to reduce the effective space of the equipment design, reduce the cost, and adapt to the double-layer high-temperature carbonization furnace.

[0063] Here, the embodiment further designs two stages of turning (the third time of turning and the fourth time of turning) after the low-temperature carbonization treatment and before the high-temperature carbonization treatment. The embodiment matches the turning angle and tension of the turning treatment to realize the contraction of the fiber tows, which can avoid the fiber tow abrasion caused by excessive tension or turning, and reserves the adjustment range for tension control, avoids the fiber index difference caused by the substandard tension control accuracy, and solves the adaptability problem of different specifications of fibers.

[0064] Embodiment 3

[0065] Preferably, the embodiment provides a preparation method of polyacrylonitrile-based carbon fiber. Compared with the above-mentioned embodiments, the embodiment is subjected to the fifth time of turning by the fifth turning roller and the sixth time of turning by the sixth turning roller after the high-temperature carbonization treatment and before the surface treatment. The fifth time of turning expands the fiber tows, and the sixth time of turning contracts the fibers. The parameters of the fifth time of turning are as follows: the turning angle is 20-50°, and the tension applied to the fiber tows is 2000-3000 cN. The parameters of the sixth time of turning are as follows: the turning angle is 2-10°, and the tension applied to the fiber tows is 2000-3000 cN.

[0066] Preferably, the fiber tows after the high-temperature carbonization treatment are subjected to the fifth time of turning and the sixth time of turning, the spacing between the two adjacent groups of fiber tows is increased from 0-5 mm to 15-20 mm, and the spacing between the fibers in each group is increased from 5-5.5 mm to 6.5-7 mm.

[0067] It should be noted that if the high-temperature carbonization furnace is a vertical furnace, it needs to run upward in the fifth time of turning and downward in the sixth time of turning; if the high-temperature carbonization furnace is a horizontal furnace, it does not need to.

[0068] In this embodiment, two-stage turning (fifth turning treatment, sixth turning treatment) is designed after high-temperature carbonization treatment and before surface treatment. In this embodiment, the turning angle and tension of the turning treatment are matched to achieve expansion, which can avoid fiber abrasion caused by excessive tension or turning, and reserves an adjustment range for tension control, avoiding fiber index differences and different specifications of fiber adaptability caused by substandard tension control accuracy.

[0069] In summary, the turning treatment of embodiment-embodiment 3 is as follows: the first and second turning treatments before pre-oxidation treatment are to achieve expansion and make the fiber tows closely arranged. After entering the pre-oxidation treatment, the efficiency can be improved, the space can be reduced when designing the pre-oxidation furnace, and the cost can be reduced. The third and fourth turning treatments after low-temperature carbonization are to cooperate with the double-layer high-temperature carbonization furnace. The advantage of the double-layer high-temperature carbonization furnace is that more fiber tows can be run, and the efficiency is higher. The turning treatment after high-temperature carbonization treatment is to expand the width, which is beneficial to the uniformity of surface treatment and the processability of carbon fiber.

[0070] Embodiment 4

[0071] Preferably, the embodiment provides a preparation method of polyacrylonitrile-based carbon fiber. Compared with the above embodiments, the embodiment is further designed as follows:

[0072] The turning rollers are groove rollers. Specifically, the first and second turning rollers are groove rollers; the third and fourth turning rollers are groove rollers; and the fifth and sixth turning rollers are groove rollers.

[0073] In this embodiment, a preparation method of polyacrylonitrile-based carbon fiber is provided, which only needs to use groove rollers for turning. On the one hand, it avoids the high maintenance cost caused by airflow turning. On the other hand, the turning angle and tension of the turning treatment are matched to achieve expansion / contraction by using groove rollers, so as to avoid fiber abrasion caused by excessive tension or turning, and reserves an adjustment range for tension control, to avoid fiber index differences and different specifications of fiber adaptability caused by substandard tension control accuracy.

[0074] Preferably, the groove depth of the groove roller is 1-5 mm. Preferably, the groove roller includes a first end portion, a second end portion, and a wire running portion between the first end portion and the second end portion. The wire channel is arranged on the wire running portion. The first end portion and the second end portion of the groove roller are 10-50 mm higher than the wire running portion. Through the above design, the fiber tows can be prevented from sliding out of the groove roller during turning (the height of the two end portions and the wire running portion of the existing groove roller is consistent).

[0075] Embodiment 5

[0076] Preferably, the present embodiment provides a preparation method of polyacrylonitrile-based carbon fiber, compared with the above embodiment, the present embodiment is further designed as follows:

[0077] After the fiber tows after the unwinding treatment are subjected to the turning treatment and then enter the pre-oxidation furnace, the distance between the two sides of the fiber tows and the inner wall of the pre-oxidation furnace is 30-100 mm. After the fiber tows after the low-temperature carbonization treatment are subjected to the turning treatment and then enter the high-temperature carbonization furnace, the distance between the two sides of the fiber tows and the inner wall of the high-temperature carbonization furnace is 30-100 mm. After the fiber tows after the high-temperature carbonization treatment are subjected to the turning treatment and then enter the surface treatment device, the distance between the fiber tows and the inner wall of the surface treatment device is 30-100 mm. Here, through the above design, the difference in the performance indexes of the fibers can be avoided, and the CV value of the performance indexes between different spinning positions in the same batch can be reduced.

[0078] Preferably, the temperature of the pre-oxidation treatment is 220-270℃; the temperature of the low-temperature carbonization treatment is 350-800℃; the temperature of the high-temperature carbonization treatment is 1000-1500℃; and the concentration of the electrolyte used in the surface treatment is 2-8%. It should be noted that, after matching the turning treatment technology of the above embodiment, the range value of each process is reduced, and energy saving and cost reduction are achieved. For example, before matching the above turning technology, under the same conditions, the pre-oxidation temperature needs to be set to 250-300℃ to prepare fibers with comparable performance indexes, and after matching the turning technology of the present embodiment, the pre-oxidation temperature of 220-270℃ can meet the requirements.

[0079] After the surface treatment, water washing, sizing and drying treatment are further included. Preferably, the conductivity of the water used in the water washing treatment is ≤200 μs / cm; the concentration of the sizing liquid used in the sizing treatment is 1-2.5 wt%; and the temperature of the drying treatment is 200-240℃. It should be noted that, after the above turning treatment, for example, under the same sizing concentration and drying temperature, better sizing and drying effects can be achieved. Because the turning treatment directly affects the spacing, arrangement and filament width between the fiber tows between different spinning positions, and directly affects the treatment effect and uniformity of each process.

[0080] Embodiment 6

[0081] Preferably, the present embodiment provides a polyacrylonitrile-based carbon fiber, wherein the polyacrylonitrile-based carbon fiber of the present embodiment is prepared by the preparation method of the polyacrylonitrile-based carbon fiber of any one of the above embodiments, so that the appearance of the polyacrylonitrile-based carbon fiber of the present embodiment is qualified, the hairiness amount is controlled at a relatively optimal level (hairiness amount ≤0.4 g / km), and the indexes are stable (the CV value of the tensile strength of the polyacrylonitrile-based carbon fiber in the same batch ≤2%, the CV value of the linear density ≤0.8%, and the CV value of the sizing amount ≤3%).

[0082] The present application is further illustrated by the following specific experimental embodiments.

[0083] Experimental Example 1

[0084] The experimental example provides a preparation method of polyacrylonitrile-based carbon fiber. The fiber is turned before pre-oxidation treatment, high-temperature carbonization treatment and surface treatment, so that the fiber tows are turned along a predetermined path, and fiber fuzzing and uneven tension are avoided. The method mainly includes the following steps:

[0085] Unwinding treatment: the polyacrylonitrile fiber (original fiber) is subjected to unwinding treatment, and after unwinding, the fiber tows are arranged in groups on the groove roller.

[0086] First turning treatment and second turning treatment: the fiber tows after unwinding treatment are sequentially subjected to first turning treatment by the first turning roller and second turning treatment by the second turning roller; wherein the parameters of the first turning treatment are as follows: the turning angle of the first group of fiber tows is 20° (amplitude), and the turning angle of the second group of fiber tows is 10° (amplitude); the fiber tows rise by 10 m, and the tension applied to the first group and the second group of fiber tows is 1000 cN and 800 cN respectively; wherein the parameters of the second turning treatment are as follows: the turning angle of the first group of fiber tows is 20° (amplitude), and the turning angle of the second group of fiber tows is 10° (amplitude), the fiber tows descend by 10 m, and the tension applied to the first group and the second group of fiber tows is 1000 cN and 800 cN respectively. Here, through the first turning treatment and the second turning treatment, the distance between the two adjacent groups of fiber tows is reduced from 20-40 mm to 0-5 mm; and the distance between the fiber tows in each group is reduced from 8-8.5 mm to 7-7.5 mm.

[0087] Pre-oxidation treatment: the fiber tows after unwinding treatment are subjected to pre-oxidation treatment (the temperature of pre-oxidation treatment is 220-270°C) after turning treatment; wherein the distance between the two sides of the fiber tows and the inner wall of the pre-oxidation furnace is about 50 mm.

[0088] Low-temperature carbonization treatment: the fiber tows after low-temperature carbonization treatment are subjected to low-temperature carbonization treatment at 350-800°C.

[0089] Third time turning treatment, fourth time turning treatment: make the fiber tows after low-temperature carbonization treatment pass through the third turning roller for third time turning treatment and the fourth turning roller for fourth time turning treatment in turn; wherein, the parameters of the third time turning treatment are as follows: the turning angle of the first group of fiber tows is 5° (narrowing), the turning angle of the second group of fiber tows is 10° (narrowing), and the tension applied to the first group and the second group of fiber tows is 800 cN and 900 cN respectively; wherein, the parameters of the fourth time turning treatment are as follows: the turning angle of the first group of fiber tows is 5° (narrowing), the turning angle of the second group of fiber tows is 10° (narrowing), and the tension applied to the first group and the second group of fiber tows is 1500 cN and 2000 cN respectively. After the third time turning treatment and the fourth time turning treatment of the fiber tows after low-temperature carbonization treatment, the distance between the two adjacent groups of fiber tows remains unchanged; the distance between the fibers in each group is reduced from 7-7.5 mm to 5-5.5 mm.

[0090] High-temperature carbonization treatment: after the fiber tows after low-temperature carbonization treatment pass through the turning treatment and enter the high-temperature carbonization furnace, high-temperature carbonization treatment is carried out (the temperature of the high-temperature carbonization treatment is 1000-1500 °C), and the distance between the two sides of the fiber tows and the inner wall of the high-temperature carbonization furnace is about 50 mm.

[0091] Fifth time turning treatment, sixth time turning treatment: make the fiber tows after high-temperature carbonization treatment pass through the fifth turning roller for fifth time turning treatment and the sixth turning roller for sixth time turning treatment in turn; wherein, the parameters of the fifth time turning treatment are as follows: the turning angle of the first group of fiber tows is 20° (widening), the turning angle of the second group of fiber tows is 50° (widening), and the tension applied to the first group and the second group of fiber tows is 2000 cN and 3000 cN respectively; wherein, the parameters of the sixth time turning treatment are as follows: the turning angle of the first group of fiber tows is 2° (narrowing), the turning angle of the second group of fiber tows is 10° (narrowing), and the tension applied to the first group and the second group of fiber tows is 2000 cN and 3000 cN respectively. After the fifth time turning treatment and the sixth time turning treatment of the fiber tows after high-temperature carbonization treatment, the distance between the two adjacent groups of fiber tows is increased from 0-5 mm to 15-20 mm, and the distance between the fibers in each group is increased from 5-5.5 mm to 6.5-7 mm.

[0092] Surface treatment: after the fiber tows after high-temperature carbonization treatment pass through the turning treatment and enter the surface treatment device, surface treatment is carried out (the mass concentration of the electrolyte is 3%); wherein, the distance between the fiber tows and the inner wall of the surface treatment device is about 50 mm.

[0093] Finally, after water washing treatment (water conductivity is 200 μs / cm), sizing treatment (the concentration of sizing liquid is 1.5wt%), drying (the temperature is 200℃), winding, polyacrylonitrile-based carbon fiber is obtained.

[0094] In addition, it should be noted that the deflection roller of the embodiment adopts a groove roller, and the wire path depth of the groove roller is 2mm; preferably, the groove roller comprises a first end portion, a second end portion, and a wire running portion between the first end portion and the second end portion; wherein the wire path is arranged on the wire running portion; wherein the first end portion and the second end portion of the groove roller are 50mm higher than the wire running portion.

[0095] The polyacrylonitrile-based carbon fiber prepared in the embodiment has a smooth outer surface, and the actual measured hairiness is 0.37g / km; the CV value of the tensile strength of the batch is ≤2%, the CV value of the linear density is ≤0.8%, and the CV value of the sizing amount is ≤3%. The comprehensive qualified rate of batch indexes, fixed length, and appearance is 92%.

[0096] Experimental embodiment 2

[0097] The experimental embodiment provides a preparation method of polyacrylonitrile-based carbon fiber, which deflects the fiber before pre-oxidation treatment, high-temperature carbonization treatment, and surface treatment, so that the fiber tows are deflected according to a predetermined path, and fiber pilling and uneven tension are avoided. The method mainly comprises the following steps:

[0098] Unwinding treatment: the polyacrylonitrile fiber (original wire) is subjected to unwinding treatment, and after unwinding, the fiber tows are arranged in groups on the groove roller.

[0099] First deflection treatment and second deflection treatment: the fiber tows after the unwinding treatment are subjected to first deflection treatment by the first deflection roller and second deflection treatment by the second deflection roller; wherein the parameters of the first deflection treatment are as follows: the deflection angle of the first group of fiber tows is 20° (amplitude), the deflection angle of the second group of fiber tows is 10° (amplitude), the fiber tows rise by 15m, and the tension applied to the first group and the second group of fiber tows is 1500cN and 800cN respectively; wherein the parameters of the second deflection treatment are as follows: the deflection angle of the first group of fiber tows is 30° (amplitude), the deflection angle of the second group of fiber tows is 40° (amplitude), the fiber tows descend by 15m, and the tension applied to the first group and the second group of fiber tows is 1200cN and 1500cN respectively. Here, the spacing between the two adjacent groups of fiber tows is reduced from 20-40mm to 0-5mm by the first deflection treatment and the second deflection treatment; and the inter-fiber spacing of each group of fiber tows is reduced from 8-8.5mm to 7-7.5mm.

[0100] Pre-oxidation treatment: the fiber tows after the unwinding treatment enter a pre-oxidation furnace for pre-oxidation treatment (the temperature of the pre-oxidation treatment is 220-270°C) after the turning treatment; wherein the distance between the two sides of the fiber tows and the inner wall of the pre-oxidation furnace is about 50mm.

[0101] Low-temperature carbonization treatment: the fiber tows after the low-temperature carbonization treatment are subjected to 400-700°C low-temperature carbonization treatment.

[0102] Third and fourth turning treatments: the fiber tows after the low-temperature carbonization treatment are subjected to third and fourth turning treatments in sequence by a third turning roller and a fourth turning roller respectively; wherein the parameters of the third turning treatment are as follows: the turning angles of the first and second groups of fiber tows are 5° (amplitude reduction) and 10° (amplitude reduction) respectively, and the tensions applied to the first and second groups of fiber tows are 500cN and 800cN respectively; wherein the parameters of the fourth turning treatment are as follows: the turning angles of the first and second groups of fiber tows are 15° (amplitude reduction) and 20° (amplitude reduction) respectively, and the tensions applied to the first and second groups of fiber tows are 2000cN and 3000cN respectively. After the third and fourth turning treatments, the distance between the two adjacent groups of fiber tows remains unchanged, and the distance between the fibers in each group is reduced from 7-7.5mm to 5-5.5mm.

[0103] High-temperature carbonization treatment: the fiber tows after the low-temperature carbonization treatment enter a high-temperature carbonization furnace for high-temperature carbonization treatment (the temperature of the high-temperature carbonization treatment is 1000-1500°C) after the turning treatment, and the distance between the two sides of the fiber tows and the inner wall of the high-temperature carbonization furnace is about 50mm.

[0104] Fifth and sixth turning treatments: the fiber tows after the high-temperature carbonization treatment are subjected to fifth and sixth turning treatments in sequence by a fifth turning roller and a sixth turning roller respectively; wherein the parameters of the fifth turning treatment are as follows: the turning angles of the first and second groups of fiber tows are 20° (amplitude expansion) and 40° (amplitude expansion) respectively, and the tensions applied to the first and second groups of fiber tows are 2000cN and 2500cN respectively; wherein the parameters of the sixth turning treatment are as follows: the turning angles of the first and second groups of fiber tows are 2° (amplitude reduction) and 10° (amplitude reduction) respectively, and the tensions applied to the first and second groups of fiber tows are 2000cN and 3000cN respectively. After the fifth and sixth turning treatments, the distance between the two adjacent groups of fiber tows is increased from 0-5mm to 15-20mm, and the distance between the fibers in each group is increased from 5-5.5mm to 6.5-7mm.

[0105] Surface treatment: the fiber tows after high-temperature carbonization treatment enter the surface treatment device for surface treatment (the mass concentration of the electrolyte is 4%) after the deflection treatment; wherein, the distance between the fiber tows and the inner wall of the surface treatment device is about 50 mm.

[0106] Finally, after washing treatment (the conductivity of the water is 200 μs / cm), sizing treatment (the concentration of the sizing liquid is 1.5 wt%), drying (the temperature is 200 °C), and winding, the polyacrylonitrile-based carbon fiber is obtained.

[0107] In addition, it should be noted that: the deflection roller of the embodiment adopts a groove roller, and the depth of the wire channel on the groove roller is 5 mm; preferably, the groove roller comprises a first end portion, a second end portion, and a wire running portion between the first end portion and the second end portion; wherein, the wire channel is arranged on the wire running portion; wherein, the first end portion and the second end portion of the groove roller are 50 mm higher than the wire running portion.

[0108] The polyacrylonitrile-based carbon fiber prepared in the embodiment has a smooth outer surface, the actually measured hairiness is 0.34 g / km, the CV value of the batch tensile strength is 1.5%, the CV value of the linear density is 0.5%, the CV value of the sizing amount is 3%, and the comprehensive qualified rate of the batch indexes / appearance / constant length is 94%.

[0109] Comparative Example 1

[0110] Comparative Example 1 provides a method for preparing a polyacrylonitrile-based carbon fiber, which is different from Experimental Example 1 in that the parameters of the first deflection treatment and the second deflection treatment are different, and the others are the same.

[0111] The parameters of the first deflection treatment of Comparative Example 1 are as follows: the deflection angle of the first group of fiber tows is 50° (amplitude), the deflection angle of the second group of fiber tows is 60° (amplitude), the fiber tows rise by 22 m, and the tension applied to the first group and the second group of fiber tows is 3000 cN and 4000 cN, respectively; the parameters of the second deflection treatment are as follows: the deflection angle of the first group of fiber tows is 50° (amplitude), the deflection angle of the second group of fiber tows is 60° (amplitude), the fiber tows descend by 22 m, and the tension applied to the first group and the second group of fiber tows is 3000 cN and 4000 cN, respectively. After the first deflection treatment and the second deflection treatment of the fiber tows after the unwinding treatment, the spacing between the adjacent two groups of fiber tows is reduced from 20-40 mm to 0-3 mm; and the inter-fiber spacing of each group of fiber tows is reduced from 8-8.5 mm to 5-5.5 mm.

[0112] In this case, during the first and second turning processes of Comparative Example 1, the fiber turning angle and tension are too large, the unwound fiber is prone to lint winding, the actual lint amount is 0.87 g / km, the CV value of the tensile strength of the carbon fiber batch prepared in Comparative Example 1 is 6%, the CV value of the linear density is 7%, the CV value of the sizing amount is 6%, and the comprehensive qualified rate of the index, length, and appearance is 75%.

[0113] Comparative Example 2

[0114] Comparative Example 2 provides a method for preparing polyacrylonitrile-based carbon fiber, which is different from Experimental Example 1 in that Comparative Example 2 only performs a first turning process (take-up) after high-temperature carbonization and before surface treatment. The parameters are as follows: the turning angle of the first group of fiber tows is 10° (take-up), the turning angle of the second group of fiber tows is 20° (take-up), and the tension applied to the first and second groups of fiber tows is 1000 cN and 2000 cN, respectively.

[0115] In this case, during the surface treatment of Comparative Example 2, the fiber gap at each station is insufficient, which is prone to hooking and forming large pieces of winding fiber, ultimately resulting in a comprehensive qualified rate of the index, length, and appearance of the prepared carbon fiber batch of 65%, and an actual lint amount of 1.54 g / km.

[0116] Comparative Example 3

[0117] Comparative Example 3 provides a method for preparing polyacrylonitrile-based carbon fiber, which is different from Experimental Example 1 in that the parameters of the six turning processes of Comparative Example 3 and Experimental Example 1 are different.

[0118] In Comparative Example 3, the turning process parameters are designed as follows:

[0119] The parameters of the first turning process are as follows: the turning angle of the first group of fiber tows is 50° (take-up), the turning angle of the second group of fiber tows is 60° (take-up), the fiber tows rise by 10 m, and the tension applied to the first and second groups of fiber tows is 2000 cN and 3000 cN, respectively. The parameters of the second turning process are as follows: the turning angle of the first group of fiber tows is 50° (take-up), the turning angle of the second group of fiber tows is 60° (take-up), the fiber tows descend by 10 m, and the tension applied to the first and second groups of fiber tows is 2000 cN and 3000 cN, respectively. Through the first and second turning processes, the distance between the two adjacent groups of fiber tows is reduced from 20-40 mm to 0-4 mm, and the distance between the fibers within each group is reduced from 8-8.5 mm to 6-6.5 mm.

[0120] The parameters of the third time of the steering treatment are as follows: the steering angle of the first group of fiber tows is 25° (contracted), the steering angle of the second group of fiber tows is 30° (contracted), the tension applied to the first group and the second group of fiber tows is 1500 cN and 2000 cN respectively; the parameters of the fourth time of the steering treatment are as follows: the steering angle is 25° (contracted), the tension applied to the fiber tows is 3500 cN. The inter-fiber spacing of the fiber tows in each group is reduced from 6-6.5 mm to 4-4.5 mm

[0121] The parameters of the fifth time of the steering treatment are as follows: the steering angle of the first group of fiber tows is 50° (expanded), the steering angle of the second group of fiber tows is 60° (expanded), the tension applied to the first group and the second group of fiber tows is 3500 cN and 4000 cN respectively; the parameters of the sixth time of the steering treatment are as follows: the steering angle of the first group of fiber tows is 10° (expanded), the steering angle of the second group of fiber tows is 20° (expanded), the tension applied to the first group and the second group of fiber tows is 3500 cN and 4000 cN respectively. After the high-temperature carbonization treatment, the inter-group spacing of the two adjacent groups of fiber tows is increased from 0-4 mm to 15-20 mm, and the inter-fiber spacing of the fiber tows in each group is increased from 4-4.5 mm to 6.5-7 mm.

[0122] In the Comparative Example 2, the fiber is prone to produce fuzz and broken strands during operation due to the excessively large steering angle, the polyacrylonitrile-based carbon fiber prepared has fuzz and hair balls on the outer surface, the actual measured hairiness amount is 2.89 g / km, the CV value of the tensile strength of the batch is 8%, the CV value of the linear density is 7%, and the CV value of the sizing amount is 10%. The comprehensive qualified rate of the batch indexes, the fixed length and the appearance is 50%.

[0123] In summary, the polyacrylonitrile-based carbon fiber and the preparation method thereof provided by the embodiments of the present application can realize the steering of the carbon fiber tows along the predetermined path by the bipolar steering treatment of the fiber tows before the pre-oxidation treatment, before the high-temperature carbonization treatment and before the surface treatment, and matching the corresponding steering treatment parameters, so that the fiber fuzzing and the uneven tension are avoided.

[0124] The above description is only the preferred embodiments of the present application, and does not limit the present application in any form. Any simple modification, equivalent change and modification made according to the technical essence of the present application to the above embodiments still belongs to the scope of the technical solutions of the present application.

Claims

1. A method for preparing polyacrylonitrile-based carbon fiber, characterized in that, The preparation method of the polyacrylonitrile-based carbon fiber includes the following steps: Polyacrylonitrile fibers were subjected to unwinding, pre-oxidation, low-temperature carbonization, high-temperature carbonization, and surface treatment in sequence to obtain polyacrylonitrile-based carbon fibers; among which, Before the pre-oxidation treatment, the unwound fiber bundle is sequentially passed through the first turning roller for a first turning treatment and through the second turning roller for a second turning treatment; wherein, the fiber bundle is wound up through the first turning treatment and the second turning treatment. The parameters for the first turning process are as follows: the turning angle is 10~40°, the fiber bundle runs along the first direction for 5~20m, and the tension applied to the fiber bundle is 500~1500cN; The parameters for the second turning process are as follows: the turning angle is 10~40°, the fiber bundle runs along the second direction for 5~20m, and the tension applied to the fiber bundle is 1000~1500cN; Wherein, the first direction and the second direction are two opposite directions; Specifically, after the low-temperature carbonization treatment and before the high-temperature carbonization treatment: the fiber bundle after the low-temperature carbonization treatment is sequentially passed through the third turning roller for a third turning treatment and through the fourth turning roller for a fourth turning treatment; wherein, the fiber bundle is wound up through the third turning treatment and the fourth turning treatment. The parameters for the third turning process are as follows: the turning angle is 5~20°, and the tension applied to the fiber bundle is 500~1000cN; The parameters for the fourth turning process are as follows: the turning angle is 5~20°, and the tension applied to the fiber bundle is 1500~3000cN; Specifically, after the high-temperature carbonization treatment and before the surface treatment: the fiber bundles after the high-temperature carbonization treatment are sequentially passed through the fifth turning roller for the fifth turning treatment and through the sixth turning roller for the sixth turning treatment; wherein, the fiber bundles are expanded through the fifth turning treatment; and the fiber bundles are contracted through the sixth turning treatment. The parameters for the fifth turning process are as follows: the turning angle is 20~50°, and the tension applied to the fiber bundle is 2000~3000cN; The parameters for the sixth turning process are as follows: the turning angle is 2~10° and the tension applied to the fiber bundle is 2000~3000cN.

2. The method for preparing polyacrylonitrile-based carbon fiber according to claim 1, characterized in that, The first direction is the direction in which the fiber bundle moves upward, and the second direction is the direction in which the fiber bundle moves downward.

3. The method for preparing polyacrylonitrile-based carbon fiber according to claim 1, characterized in that, The unwound fiber bundles are arranged in groups on the grooved roller; wherein... The spacing between two adjacent groups of fiber bundles is 20~40mm; the spacing between the fiber bundles within each group is 8~8.5mm.

4. The method for preparing polyacrylonitrile-based carbon fiber according to claim 1, characterized in that, After the unwinding process, the fiber bundles undergo a first turning process and a second turning process. The spacing between two adjacent groups of fiber bundles is reduced from 20-40 mm to 0-5 mm; the spacing between the fiber bundles in each group is reduced from 8-8.5 mm to 7-7.5 mm.

5. The method for preparing polyacrylonitrile-based carbon fiber according to claim 1, characterized in that, After the low-temperature carbonization treatment, the fiber bundles undergo a third and fourth reversal treatment, and the spacing between two adjacent groups of fiber bundles remains unchanged; the spacing between the fiber bundles in each group decreases from 7~7.5mm to 5~5.5mm.

6. The method for preparing polyacrylonitrile-based carbon fiber according to any one of claims 1, characterized in that, After the high-temperature carbonization treatment, the fiber undergoes a fifth and sixth turning treatment, and the spacing between two adjacent groups of fiber bundles increases from 0-5 mm to 15-20 mm, while the spacing between the fiber bundles within each group increases from 5-5.5 mm to 6.5-7 mm.

7. The method for preparing polyacrylonitrile-based carbon fiber according to claim 1, characterized in that, The first and second steering rollers are grooved rollers.

8. The method for preparing polyacrylonitrile-based carbon fiber according to claim 7, characterized in that, The third and fourth steering rollers are grooved rollers.

9. The method for preparing polyacrylonitrile-based carbon fiber according to claim 7, characterized in that, The fifth and sixth steering rollers are grooved rollers.

10. The method for preparing polyacrylonitrile-based carbon fiber according to claim 7, characterized in that, The depth of the thread path on the grooved roller is 1~5mm.

11. The method for preparing polyacrylonitrile-based carbon fiber according to claim 10, characterized in that, The grooved roller includes a first end, a second end, and a feeding section located between the first end and the second end; wherein the thread path is disposed on the feeding section; wherein the first end and the second end of the grooved roller are 10~50mm higher than the feeding section.

12. The method for preparing polyacrylonitrile-based carbon fiber according to claim 1, characterized in that, After unwinding and reorientation, the fiber bundles enter the pre-oxidation furnace with a distance of 30-100 mm between both sides of the fiber bundle and the inner wall of the pre-oxidation furnace; and / or After low-temperature carbonization, the fiber bundles are redirected and then enter the high-temperature carbonization furnace. The distance between the two sides of the fiber bundles and the inner wall of the high-temperature carbonization furnace is 30~100mm; and / or After high-temperature carbonization, the fiber bundles are redirected and then enter the surface treatment device. The distance between the fiber bundles and the inner wall of the surface treatment device is 30~100mm; and / or The temperature of the pre-oxidation treatment is 220~270℃; and / or The low-temperature carbonization treatment is performed at a temperature of 350~800℃; and / or The high-temperature carbonization treatment is carried out at a temperature of 1000~1500℃; and / or The mass concentration of the electrolyte used in the surface treatment is 2-8%.

13. The method for preparing polyacrylonitrile-based carbon fiber according to claim 1, characterized in that, The surface treatment process includes water washing, sizing, and drying. The water used for the water washing process has a conductivity of ≤200 μs / cm. The sizing solution used for the sizing process has a concentration of 1~2.5 wt%. The drying process is carried out at a temperature of 200~240℃.

14. A polyacrylonitrile-based carbon fiber, characterized in that, The polyacrylonitrile-based carbon fiber is prepared by the method for preparing polyacrylonitrile-based carbon fiber according to any one of claims 1-13; Wherein, the hairiness of the polyacrylonitrile-based carbon fiber is ≤0.4g / km; Among them, the batch tensile strength CV value of polyacrylonitrile-based carbon fiber is ≤2%, the linear density CV value is ≤0.8%, and the sizing amount CV value is ≤3%.

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