Preparation method and device of high-strength carbon fiber precursor

Abstract

The invention relates to the technical field of polyacrylonitrile-based carbon fibers, and discloses a preparation method and device of a high-strength carbon fiber precursor, and the preparation method comprises the following steps: spraying a spinning solution through a spinneret plate, carrying out coagulating bath drafting to obtain a nascent fiber, carrying out water washing drafting, oiling and drying, carrying out first air interlacing, and carrying out steam drafting to obtain the high-strength carbon fiber precursor. And carrying out secondary air interlacing after steam drafting to finally obtain the carbon fiber precursor. Two-time air interlacing is adopted, the densification degree of dried nascent fibers is improved through first-time air interlacing, meanwhile, broken filaments and miscellaneous filaments in tows are removed, the breaking strength of the nascent fibers is improved, the nascent fibers can bear large drafting during steam drafting, after drafting is completed, second-time air interlacing is carried out, and the densification degree of the nascent fibers is improved. The interlacing degree of the tows is further improved, and the number of broken filaments in the fibers is reduced, so that the 12k carbon fiber precursor with higher strength and less broken filaments is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of polyacrylonitrile-based carbon fibers, and in particular to a method and device for preparing high-strength carbon fiber precursors. Background Art

[0002] Carbon fiber is a new type of material with excellent properties such as low density, high strength, high modulus, high temperature resistance and corrosion resistance. It can be used as a reinforcement material for high-performance composite materials and as a functional material. It is widely used in aerospace, construction, machinery, sports equipment and entertainment products. Among them, polyacrylonitrile (PAN) is the most promising precursor for the preparation of high-performance carbon fibers. PAN-based carbon fibers prepared with PAN as raw material have a simple production process, high carbon yield and good overall performance. Its output exceeds 90% of the world's total carbon fiber material output value, occupying a mainstream position in the current carbon fiber industry production.

[0003] In recent years, my country's carbon fiber production technology and product quality have made great progress, especially enterprises have entered a stage of rapid development. However, the current carbon fiber products generally have the problem of high hair rate, which has limited the application of carbon fiber and restricted the quality improvement of the carbon fiber industry. The higher the orientation, crystallinity and clustering of the precursor, the lower the hair rate of the carbon fiber product. In the precursor production process, the steam drawing process is a key link. In this process, a large amount of hair or even broken hair will be generated, which makes the precursor not have the properties of high orientation, high crystallinity and high clustering. The presence of precursor hair will become a heat concentration point during carbonization pre-oxidation, resulting in uneven pre-oxidation of nearby monofilaments, which will not only form carbon fiber hair itself, but also increase the performance difference of monofilaments between carbon fiber bundles. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method and device for preparing high-strength carbon fiber precursor.

[0005] In order to achieve the above-mentioned purpose, the technical solution of the present invention is: a method for preparing high-strength carbon fiber precursor, in which the spinning solution is ejected through a spinneret, and the primary fiber is obtained by drawing in a coagulation bath, and then the fiber is washed and drawn, oiled, and dried, and then air-entangled for the first time, and then steam-drawn, and after steam drawing, air-entangled for the second time, and finally the carbon fiber precursor is obtained.

[0006] Furthermore, in the spinning solution, the solid content of polyacrylonitrile is 19 to 20 wt %, the solvent used in the spinning solution is dimethyl sulfoxide (DMSO), and the rotational viscosity is 70,000 to 120,000 cp.

[0007] Furthermore, the steam drawing pressure is 3 to 5 bar and the temperature is 140 to 170°C.

[0008] Furthermore, the DMSO concentration in the coagulation bath is 30-40 wt % and the temperature is 4°C.

[0009] Furthermore, the drawing ratio of the coagulation bath is 2 to 2.5 times, the water washing drawing ratio is 2 to 2.5 times, and the steam drawing ratio is 3 to 4 times.

[0010] Another technical solution of the present invention is: a device for realizing the preparation method of the high-strength carbon fiber precursor, wherein the primary fiber is washed, stretched, oiled, and dried and then conveyed along the conveying direction of the carbon fiber, including a first air entanglement device, a first guide roller group, a steam drawing box, a second guide roller group and a second air entanglement device arranged in sequence.

[0011] Furthermore; the number of the first air intertwining devices and the second air intertwining devices is the same, and the total number and pressure of the first air intertwining devices and the second air intertwining devices increase with the increase of the number of spindles of the spun fibers in the coagulation bath. When the number of spindles increases by n, the total number of the first air intertwining devices and the second air intertwining devices increases by n / 3, the pressure of the first air intertwining device increases by 0.5×n / 3bar, and the pressure of the second air intertwining device increases by 2×n / 3bar, where 6≤n≤78.

[0012] Furthermore, the steam pressure of the steam drawing box and the steam drawing pipe increase as the number of the first air interweaving devices increases. If n first air interweaving devices are added, n steam drawing pipes in the steam drawing box will increase, and the steam pressure will increase by 4n, where 1≤n≤26.

[0013] Furthermore, the steam drawing box steam drawing pipe pressure is 3-5bar, the temperature is 140-170 ℃.

[0014] Furthermore, the drying adopts multiple groups of steam hot rollers for drying, the temperature of the first group of steam hot rollers is greater than or equal to 160°C and less than or equal to 180°C; the temperature of the last group of steam hot rollers is greater than or equal to 120°C and less than or equal to 140°C, and the temperature of the steam hot rollers from the first group to the last group is stepped down.

[0015] Furthermore, the first air intertwining device, the second air intertwining device and the drawing tube in the steam drawing box are arranged in the horizontal direction, the support rollers of the first guide roller group and the second guide roller group are arranged in the horizontal direction respectively, and the speed of each group of guide rollers is the same. By changing the speed of the first guide roller group and the second guide roller group, the multiple of the fiber in steam drawing is changed.

[0016] Furthermore, each air intertwining device is sequentially arranged with the coagulation bath spindle and the steam drawing box in a central axis, and the coagulation bath spun fibers can pass through the central axis through the air intertwining device and the steam drawing tube threading channel, and ensure that each fiber does not contact each other.

[0017] The beneficial effects of the present invention are as follows: the present invention adopts two air interlacing processes. The first air interlacing improves the densification degree of the spun fibers after drying, and at the same time removes the fuzz and debris inside the filament bundle, thereby improving the breaking strength of the spun fibers and enabling the spun fibers to withstand a larger stretch during steam stretching. After the stretching is completed, the second air interlacing is performed to further improve the degree of interlacing of the filament bundle and reduce the number of fuzz in the fiber, thereby obtaining a 12k carbon fiber precursor with higher strength and less fuzz. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a diagram of a device for preparing high-strength carbon fiber precursor of the present invention;

[0019] Figure 2 yes Figure 1 Schematic diagram of the middle steam pull pipe structure. DETAILED DESCRIPTION

[0020] The air intertwining device of the present invention adopts the intertwining device of carbon fiber bundles in the patent application number CN202410836119.6.

[0021] like Figure 1 and Figure 2 As shown: A preparation device for high-strength carbon fiber precursor, the primary fiber 6 is washed, stretched, oiled, and dried and then conveyed along the carbon fiber conveying direction, including a first air intertwining device 1, a first wire guide roller group 2, a steam drawing box 3, a second wire guide roller group 4 and a second air intertwining device 5 which are arranged in sequence.

[0022] The number of the first air intertwining devices 1 and the second air intertwining devices 5 is the same. The total number and pressure of the first air intertwining devices 1 and the second air intertwining devices 5 increase with the increase in the number of spindles of the spun fibers in the coagulation bath. When the number of spindles increases by n, the total number of the first air intertwining devices 1 and the second air intertwining devices 5 increases by n / 3, the pressure of the first air intertwining device 1 increases by 0.5×n / 3bar, and the pressure of the second air intertwining device 5 increases by 2×n / 3bar, where 6≤n≤78.

[0023] The steam pressure of the steam drawing box 3 and the steam drawing pipe 302 increase as the number of the first air intermingling devices 1 increases. If the number of the first air intermingling devices 1 increases by n, the number of the steam drawing pipe 302 in the steam drawing box 3 increases by n, and the steam pressure increases by 4n, where 1≤n≤26.

[0024] The drying is carried out by using multiple groups of steam hot rollers, and the temperatures of the steam hot rollers from the first group to the last group are gradually reduced in a step-by-step manner.

[0025] The first air intertwining device 1, the second air intertwining device 5 and the drawing tube 302 in the steam drawing box 3 are arranged in the horizontal direction, and the support rollers of the first godet roller group 2 and the second godet roller group 4 are respectively arranged in the horizontal direction. The speed of each group of godet rollers is the same. By changing the speed of the first godet roller group 2 and the second godet roller group 4, the multiple of steam drawing of the fiber can be changed.

[0026] Each air intertwining device is sequentially on a central axis with the coagulation bath spindle position and the steam drawing tube 302 in the steam drawing box 3. The coagulation bath nascent fibers can pass through the air intertwining device and the threading channel 301 of the steam drawing tube 302 through this central axis, and ensure that each fiber does not contact each other.

[0027] Example 1: A method for preparing high-strength carbon fiber precursor

[0028] (1) A dry-jet wet spinning process is adopted to eject the spinning solution through a spinneret. The solid content of polyacrylonitrile in the spinning solution is 19.3 wt %. The solvent used in the spinning solution is DMSO with a rotational viscosity of 80,000 cp. After being ejected, the spinning solution enters a coagulation bath to obtain spun fibers 6. The DMSO concentration in the coagulation bath is 34 wt % and the temperature is 4°C. The drafting multiple of the coagulation bath is 2.2. The number of spindles of the spun fibers 6 in the coagulation bath is 18 and the glue application amount is 86.31 kg / h.

[0029] (2) The spun fiber 6 was washed, stretched, oiled, and dried, and the spinning speed was controlled to be 180 m / min, wherein the washing stretching was 2.3 times, the fiber was soaked in oil for 1.6 m, and dried using four groups of steam hot rollers, a total of 15 steam hot rollers, and the temperature of the steam hot rollers from the first group to the last group was stepped down, with the drying temperature of the first group being 180°C and the drying temperature of the last group being 160°C.

[0030] (3) The dried spun fibers 6 enter the first air interlacing device 1, and are then guided to the steam drawing unit of the steam drawing box 3 through the first guide roller group 2. Each bundle of spun fibers 6 is drawn through the corresponding steam drawing tube 302, and then passed through the second guide roller group 4 and the second air interlacing device 5 to obtain 12k carbon fiber precursor; wherein the steam drawing is 3.5 times, the number of the first air interlacing device 1 and the second air interlacing device 5 are respectively 3, the pressure of the first air interlacing device is 3 bar, the pressure of the second air interlacing device 5 is 12 bar, the number of steam drawing tubes 302 in the steam drawing box 3 is 3, the steam pressure of the steam drawing box 3 is 12 bar, the pressure of the steam drawing tube 302 is 4 bar, and the temperature is 150°C.

[0031] The total drafting ratio in the production of 12k carbon fiber precursor is 22 times, the yarn breakage frequency is 10 times / day, and the DMSO residue in the yarn is 300ppm.

[0032] Finally, the raw silk is subjected to pre-oxidation, low-temperature carbonization, high-temperature carbonization, surface treatment, drying, sizing, and drying to obtain carbon fiber, as shown in (Xu Lianghua, Cao Weiyu, Hu Liangquan. Polyacrylonitrile-based carbon fiber. National Defense Industry Press, 2018.).

[0033] Comparative Example 1: A method for preparing carbon fiber precursor

[0034] The difference from Example 1 is that the second air intertwining device 5 is not used. The specific method is as follows:

[0035] (1) Same as step (1) in Example 1.

[0036] (2) Same as step (2) in Example 1.

[0037] (3) The dried spun fibers 6 enter the first air interlacing device 1, and are then guided to the steam drawing unit of the steam drawing box 3 through the first guide roller group 2. Each bundle of spun fibers 6 is drawn through the corresponding steam drawing tube 302, and finally passes through the second guide roller group 4 to obtain 12k carbon fiber precursor; wherein the steam drawing is 3.5 times, there are 3 first air interlacing devices 1, the pressure of the first air interlacing device is 3 bar, there are 3 steam drawing tubes 302 in the steam drawing box 3, the steam pressure of the steam drawing box 3 is 12 bar, the pressure of the steam drawing tube 302 is 4 bar, and the temperature is 150°C.

[0038] The total drafting ratio in the production of 12k carbon fiber precursor is 22 times, the yarn breakage frequency is 15 times / day, and the DMSO residue in the yarn is 500ppm.

[0039] Finally, the precursor is subjected to pre-oxidation, low-temperature carbonization, high-temperature carbonization, surface treatment, drying, sizing, and drying to obtain carbon fibers, as in Example 1 with reference to the literature.

[0040] Comparative Example 2: A method for preparing carbon fiber precursor

[0041] The difference from Example 1 is that the first air convolution device 1 and the second air convolution device 5 are not used. The specific method is as follows:

[0042] (1) Same as step (1) in Example 1.

[0043] (2) Same as step (2) in Example 1.

[0044] (3) The dried spun fibers 6 are guided to the steam drawing unit of the steam drawing box 3 through the first guide roller group 2, and each bundle of spun fibers 6 is drawn through the corresponding steam drawing tube 302, and finally passes through the second guide roller group 4 to obtain 12k carbon fiber precursor; wherein the steam drawing is 3.5 times, there are 3 steam drawing tubes 302 in the steam drawing box 3, the steam pressure of the steam drawing box 3 is 12 bar, the pressure of the steam drawing tube 302 is 4 bar, and the temperature is 150°C.

[0045] The total drafting ratio in the production of 12k carbon fiber precursor is 22 times, the yarn breakage frequency is 20 times / day, and the DMSO residue in the yarn is 500ppm.

[0046] Finally, the precursor is subjected to pre-oxidation, low-temperature carbonization, high-temperature carbonization, surface treatment, drying, sizing, and drying to obtain carbon fibers, as in Example 1 with reference to the literature.

[0047] Comparative Example 3: A method for preparing carbon fiber precursor

[0048] The difference from Example 1 is that the first air intertwining device 1 is not used. The specific method is as follows:

[0049] (1) Same as step (1) in Example 1.

[0050] (2) Same as step (2) in Example 1.

[0051] (3) The dried spun fibers 6 are guided to the steam drawing unit of the steam drawing box 3 through the first guide roller group 2, and each bundle of spun fibers 6 is drawn through the corresponding steam drawing pipe 302, and then passed through the second guide roller group 4 and the second air intertwining device 5 to obtain 12k carbon fiber precursor; wherein the steam drawing is 3.5 times, there are 3 second air intertwining devices 5, the pressure of the second air intertwining device 5 is 12 bar, there are 3 steam drawing pipes 302 in the steam drawing box 3, the steam pressure of the steam drawing box 3 is 12 bar, the pressure of the steam drawing pipe 302 is 4 bar, and the temperature is 150°C.

[0052] The total drafting ratio in the production of 12k carbon fiber precursor is 22 times, the yarn breakage frequency is 20 times / day, and the DMSO residue in the yarn is 500ppm.

[0053] Finally, the precursor is subjected to pre-oxidation, low-temperature carbonization, high-temperature carbonization, surface treatment, drying, sizing, and drying to obtain carbon fibers, as in Example 1 with reference to the literature.

[0054] The precursors obtained in Example 1 and Comparative Examples 1-3 were tested for performance parameters, including linear density, linear density CV value, single fiber fineness, fineness CV value, breaking strength, elongation at break, oil content, and DMSO content for the precursors; and modulus, tensile strength, tensile strength CV value, and hairiness for the carbon fibers. The results are shown in Table 1.

[0055] Table 1

[0056] project unit Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Nominal fineness dtex 1.12 1.12 1.12 1.12 Line density g / m 1.351 1.349 1.356 1.356 Linear density CV value ％ 1.51 2.26 2.76 3.12 Fineness dtex 1.122 1.119 1.115 1.124 Fineness CV value ％ 3.79 4.27 4.42 4.66 Breaking strength cN / dtex 8.5 8.3 8 8 Elongation at break ％ 15 13 10 13 Oil content ％ 1 1 1 1 DMSO residue ppm 300 500 500 500 Modulus GPa 260 260 260 260 tensile strength MPa 5500 5300 5000 5100 Tensile strength CV value ％ 1.5 1.5 1.5 1.5 Hairiness mg / 50m 0.6 2 10 5

[0057] As shown in Table 1, the 12k carbon fiber precursor prepared by the present invention has high breaking strength and crystallinity. At the same time, the precursor is completely entangled inside and has no hairy or stray fibers. The higher the crystallinity of the carbon fiber precursor, the better the density of the precursor structure, the more stable the structure during the carbonization process, and the higher the tensile strength and initial modulus of the final carbon fiber, and the lower the hairiness.

[0058] The breaking strength of the 12k carbon fiber precursor prepared by Example 1 reaches 8.5 cN / dtex, the elongation at break is 15%, the tensile strength of the carbon fiber obtained by the carbonization process is 5500 MPa, and the hairiness is only 0.6 mg / 50 m, that is, the mechanical properties of the obtained carbon fiber are excellent.

[0059] Example 2

[0060] The differences from Example 1 are as follows: the solid content of polyacrylonitrile in the spinning solution is 19.3 wt %, the number of coagulation bath spindles is 24, the glue application rate is 115.08 kg / h, and a total of 8 first and second air intertwining devices are used.

[0061] Example 3

[0062] The differences from Example 1 are as follows: the solid content of polyacrylonitrile in the spinning solution is 19.3 wt %, the number of coagulation bath spindles is 30, the sizing rate is 143.85 kg / h, and a total of 10 first and second air entanglement devices are used.

[0063] Example 4

[0064] The differences from Example 1 are as follows: the solid content of polyacrylonitrile in the spinning solution is 19.3 wt %, the number of coagulation bath spindles is 36, the glue application rate is 172.62 kg / h, and a total of 12 first and second air entanglement devices are used.

[0065] Example 5

[0066] The differences from Example 1 are as follows: the solid content of polyacrylonitrile in the spinning solution is 19.3 wt %, the number of coagulation bath spindles is 42, the glue application rate is 201.39 kg / h, and a total of 14 first and second air intertwining devices are used.

[0067] Example 6

[0068] The differences from Example 1 are as follows: the solid content of polyacrylonitrile in the spinning solution is 19.3 wt %, the number of coagulation bath spindles is 48, the glue application rate is 230.16 kg / h, and a total of 16 first and second air intertwining devices are used.

[0069] Example 7

[0070] The differences from Example 1 are as follows: the solid content of polyacrylonitrile in the spinning solution is 19.3 wt %, the number of coagulation bath spindles is 54, the sizing rate is 258.94 kg / h, and a total of 18 first and second air entanglement devices are used.

[0071] Example 8

[0072] The differences from Example 1 are as follows: the polyacrylonitrile solid content in the spinning solution is 19.3 wt %, the number of coagulation bath spindles is 60, the sizing rate is 287.71 kg / h, and a total of 20 first and second air entanglement devices are used.

[0073] Example 9

[0074] The differences from Example 1 are as follows: the solid content of polyacrylonitrile in the spinning solution is 19.3 wt %, the number of coagulation bath spindles is 66, the glue application rate is 316.48 kg / h, and a total of 22 first and second air entanglement devices are used.

[0075] Example 10

[0076] The differences from Example 1 are as follows: the solid content of polyacrylonitrile in the spinning solution is 19.3 wt %, the number of coagulation bath spindles is 72, the glue application rate is 345.25 kg / h, and a total of 24 first and second air entanglement devices are used.

[0077] The present invention tested the properties of the 12k precursor and carbon fiber of Examples 2 to 10, and the results are shown in Table 2 below:

[0078] Table 2

[0079]

[0080] As can be seen from Table 2, the 12k carbon fiber precursor in the present invention has a linear density of 1.34-1.35g / m, a breaking strength of 8.4-9.7cN / dtex, an elongation at break of 11.4-13.1%, an oil content of 1.0-1.1%, a fineness CV value of 5%, and a DMSO content of less than 500ppm. Carbon fiber: modulus of 256-263GPa, tensile strength of 5387-5505MPa, tensile strength CV value of 1.1-2.2%, and hairiness of 0.2-1.3mg / 50m. That is, the 12k carbon fiber precursor and carbon fiber prepared by the present invention have good mechanical properties, low hairiness, low oil content, small fineness CV value and tensile strength CV value, and stable performance.

[0081] In addition, the 12k carbon fiber precursor produced by the present invention has good linear density stability, and the product has high uniformity and stability, which is conducive to large-scale production by enterprises.

[0082] The above-described embodiments are only preferred solutions of the present invention and are not intended to limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solutions described in the claims.

[0083] In the description of the present invention, it should be understood that the terms indicating orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings and are only used to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they cannot be understood as limiting the present invention.

Claims

1. A method for preparing high-strength carbon fiber precursor, characterized in that: The spinning solution is ejected from the spinneret and drawn in a coagulation bath to obtain the primary fiber, which is then washed and drawn, oiled, and dried. The fiber is then air-entangled for the first time, then steam-drawn, and after steam-drawn, air-entangled for the second time to finally obtain the carbon fiber precursor.

2. The method for preparing high-strength carbon fiber precursor according to claim 1, characterized in that: In the spinning solution, the solid content of polyacrylonitrile is 19-20 wt %, the solvent used in the spinning solution is dimethyl sulfoxide, and the rotational viscosity is 70,000-120,000 cp.

3. The method for preparing high-strength carbon fiber precursor according to claim 1, wherein: The steam drawing pressure is 3-5 bar, and the temperature is 140-170°C.

4. The method for preparing high-strength carbon fiber precursor according to claim 1, characterized in that: The DMSO concentration in the coagulation bath is 30-40 wt %, and the temperature is 4° C.

5. The method for preparing high-strength carbon fiber precursor according to claim 1, wherein: The drafting ratio of the coagulation bath is 2 to 2.5 times, the drafting ratio of the water washing is 2 to 2.5 times, and the drafting ratio of the steam is 3 to 4 times.

6. A device for implementing the method for preparing high-strength carbon fiber precursor according to any one of claims 1 to 5, characterized in that: After being washed, drawn, oiled and dried, the raw fibers are transported in the direction of the carbon fibers and sequentially comprised of a first air entanglement device, a first godet roller group, a steam drawing box, a second godet roller group and a second air entanglement device.

7. The device according to claim 6, characterized in that: The number of the first air intertwining devices and the second air intertwining devices is the same. The total number and pressure of the first air intertwining devices and the second air intertwining devices increase with the increase in the number of spindles of the spun fibers in the coagulation bath. When the number of spindles increases by n, the total number of the first air intertwining devices and the second air intertwining devices increases by n / 3, the pressure of the first air intertwining device increases by 0.5×n / 3, and the pressure of the second air intertwining device increases by 2×n / 3, where 6≤n≤78.

8. The device according to claim 7, characterized in that: The steam pressure of the steam drafting box and the steam drafting pipe increase as the number of the first air interweaving devices increases. If the number of the first air interweaving devices increases by n, the number of the steam drafting pipes in the steam drafting box increases by n, and the steam pressure increases by 4n, where 1≤n≤26.

9. The device according to claim 7, characterized in that: The steam drawing box has a steam drawing pipe pressure of 3-5 bar and a temperature of 140-170°C.

10. The device according to claim 6, characterized in that: The drying is carried out using multiple groups of steam hot rollers, the temperature of the first group of steam hot rollers is greater than or equal to 160°C and less than or equal to 180°C; the temperature of the last group of steam hot rollers is greater than or equal to 120°C and less than or equal to 140°C, and the temperatures of the steam hot rollers from the first group to the last group are gradually reduced.

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