Process for the continuous production of large tow carbon fibers and large tow carbon fibers

Abstract

The present application relates to the technical field of large-tow carbon fiber production, and in particular to large-tow carbon fiber and a method for continuously producing large-tow carbon fiber, and discloses a large-tow fiber, which comprises large-tow filaments and carbon fibers connected alternately, wherein the large-tow filaments and the carbon fibers are connected by a weaving knot method. By using this connection method, the end of the large-tow filaments in a box can be connected to the end of the adjacent large-tow filaments in a box, and the knot is firm, and the breaking strength of the knot is greater than 140,000 cN. By using the weaving knot method to connect the ends of the large-tow filaments, the continuous production of the large-tow carbon fiber can be realized, the number of times of winding around the roller is reduced, the production safety is high, the stable production time is improved, the amount of waste filaments is reduced, the production cost is reduced, and the production efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of large-tow carbon fiber production, and particularly relates to large-tow carbon fiber and a method for continuously producing large-tow carbon fiber. BACKGROUND

[0002] Carbon fiber is an inorganic fiber with a carbon main chain structure formed by the pyrolysis and carbonization of polyacrylonitrile at high temperature, and the carbon content is higher than 90%. Carbon fiber has many excellent properties, and the main advantages are high strength and modulus, low density, good fatigue resistance, etc. Among them, large-tow carbon fiber generally refers to a fiber bundle with a number greater than or equal to 48K. Compared with small-tow carbon fiber, large-tow carbon fiber can use low-cost PAN fiber, and under the same production conditions, the single-line capacity of carbon fiber can be greatly improved, realizing low-cost production, and to a large extent breaking the application limitations caused by the high price of carbon fiber, which is suitable for large-scale industrial application. The main purpose of the oxidation of the precursor is to make the cyclization and intermolecular cross-linking of the linear polyacrylonitrile (PAN) macromolecular chain into a heat-resistant network ladder structure.

[0003] CN217968442U discloses a carbon fiber continuous production furnace threading and splicing device, relating to the technical field of splicing equipment, specifically a carbon fiber continuous production furnace threading and splicing device, comprising a mounting seat, one side of the mounting seat is fixedly connected with a splicing box, both sides of the splicing box are fixedly connected with control sleeves, the upper surface of the splicing box is provided with a connecting groove, the inner side wall of the connecting groove is provided with a sliding groove, and the sliding groove is internally and slidably connected with a downward pressing splicing assembly. When the old yarn and the new yarn are overlapped to the lower side of the downward pressing block, the operator can lift the control rod upward from both sides of the device to push the pressing rod downward to press the downward pressing block, thereby achieving the effect of pressing the old yarn and the new yarn at high temperature by the anti-adhesion pressing block. However, the knot connection by rapid pressing may result in insufficient or unstable knot strength, which cannot guarantee continuous production, and in addition, the high temperature pressing by the oxidation furnace in this patent may result in high temperature of the operating equipment, which has operation safety risks.

[0004] CN217263957U relates to the technical field of filament bundle multi-point filament connection, specifically to a new type of multi-point filament bundle air joint device. It includes a multi-point air joint, a joint device rack and a joint operation table. The multi-point air joint contains multiple filament clamps, and the upper and lower sides of the fiber joint groove are provided with air injection holes. Each filament clamp is provided with an air inlet switch, and the multi-point air joint is provided with a compressed air distributor. The joint device rack is provided with a storage rack for storing multiple limiting fixing rods. The rack is provided with a linear guide rail, a sliding block and an air cylinder for controlling the forward and backward movement of the joint operation table. Two original filament bundles are placed on the joint operation table, and the two bundles are stacked together. The joint operation table is moved into the filament clamp of the multi-point air joint through the linear guide rail pneumatically or manually. The original filament bundles pass through multiple fiber joint grooves and continuously connect the bundles during the movement of the operation table. However, this patent requires multiple air joints to work simultaneously, which is difficult to ensure that the air pressure of each air joint is stable and consistent, resulting in some connection points not meeting the connection requirements, and thus the strength of the entire knot is insufficient. SUMMARY

[0005] The purpose of the present application is to overcome the problems of existing technology, such as direct laying of original long filaments in the box for production, unfirm connection of the end heads of adjacent two boxes of original filaments, loosening or breaking of the connection between the end heads of adjacent two boxes of original filaments, easy oxidation around the roller, and inability to realize continuous production of large filament carbon fibers. The present application provides a large filament carbon fiber and a continuous production method of large filament carbon fiber. The continuous production method of large filament carbon fiber using the large filament carbon fiber including alternately connected large filament original filaments and carbon fibers realizes continuous production of large filament carbon fiber, reduces the number of winding rollers, improves production safety, increases stable production time, reduces the amount of waste filaments, reduces production cost, and improves production efficiency.

[0006] To achieve the above-mentioned purpose, the present application provides a large filament carbon fiber, which includes alternately connected large filament original filaments and carbon fibers. The large filament original filaments and the carbon fibers are connected by a textile knot. The knot head after knotting of adjacent large filament original filaments not only does not loosen or fall off during oxidation, but also does not produce smoke and fire due to heat accumulation and overheating at the connection, ensuring that the head and tail of adjacent two boxes of original filaments can be connected tightly. The original filaments can smoothly pass through the oxidation furnace, low-temperature carbonization furnace, high-temperature carbonization furnace, surface treatment, washing, sizing, drying and winding production processes in sequence.

[0007] In the present application, the operation steps of the textile knot knotting are as follows (knotting is completed as shown in Figure 1 , and the specific steps are demonstrated as Figure 2 :

[0008] Step 1: Cross the end of the pre-oxidized large tow with the end of the carbon fiber by 75° and leave 7 cm of the two ends at the two crossing points respectively, and then press the end of the pre-oxidized large tow on the end of the carbon fiber.

[0009] Step 2: Wrap the end of the carbon fiber around the end of the pre-oxidized large tow outwardly and press the end from the crossing position, that is, make the end of the carbon fiber wrap to form a loop, and then pass the end of the pre-oxidized large tow into the loop while pulling the end of the pre-oxidized large tow and the end of the carbon fiber.

[0010] In the present application, the length of the knot tail left after the connection of the respective ends of the large tow and the carbon fiber is not particularly limited, and according to a preferred embodiment of the present application, the length of the knot tail left after the connection of the large tow and the carbon fiber by the weaving knot is 8-25 cm, preferably 13-20 cm. By using the foregoing preferred embodiment, the safety and stability of the knot in the production process through the oxidation furnace, the low-temperature carbonization furnace and the high-temperature carbonization furnace can be further improved.

[0011] In the present application, the K number of the carbon fiber can be selected according to the prior art, and according to a preferred embodiment of the present application, the K number of the carbon fiber is 180-250 K, preferably 200-230 K. By using the foregoing preferred embodiment, the connection stability of the large tow and the carbon fiber can be further improved, and the connection part will not be loose or broken.

[0012] According to a preferred embodiment of the present application, the respective ends of the large tow and the carbon fiber are connected by a weaving knot.

[0013] According to a preferred embodiment of the present application, the connected end of the large tow is subjected to an oxidation treatment.

[0014] In the present application, the number of times of the connection of the large tow and the carbon fiber alternately is not limited and can be selected according to the need.

[0015] The large-tow carbon fiber with the characteristics of the application can achieve the purpose of the application, and the specific preparation steps and processes thereof can be selected and adjusted as needed. According to a preferred embodiment of the application, the application provides a continuous production method of a large-tow carbon fiber, which comprises the following steps: S1. Pre-oxidizing one end of a large-tow precursor, connecting the end of the pre-oxidized large-tow precursor with the end of a carbon fiber by a weaving knot, and repeating the connection of the weaving knot according to the needs of continuous production; S2. After the connection of the weaving knot is completed, performing oxidation, low-temperature carbonization, high-temperature carbonization, surface treatment, washing, sizing, drying, and winding and collecting the yarn. Through the continuous production method, the continuous production of the large-tow carbon fiber can be achieved, the number of roll winding is reduced, the production safety is high, the stable production time is improved, the amount of waste yarn is reduced, the production cost is reduced, the production efficiency is improved, and the risk of fire caused by excessive heat accumulation at the connection of the precursor end is avoided, thereby reducing the production cost and improving the production efficiency. Thus, the continuous production of the large-tow carbon fiber can be effectively achieved.

[0016] In the application, after the step S1 and before the step S2, the two ends of the large-tow precursor are laid on a tension frame, the precursor is tensioned and fixed, the tension frame is placed in a pre-oxidation furnace, and the ends of the precursor are pre-oxidized. This step has no special requirements and can be performed according to the prior art, which will not be described in detail herein.

[0017] In the application, after the ends of the large-tow precursor are pre-oxidized in the step S1, a cooling step is needed. The cooling time and method have no special requirements and can be performed according to the prior art, and the precursor only needs to be cooled to room temperature.

[0018] In the application, after the knot connection is completed in the step S2, the precursor is oxidized, low-temperature carbonized, high-temperature carbonized, surface treated, washed, sized, dried, and wound and collected. The specific steps and operating conditions have no special requirements and can be performed according to the prior art, which will not be described in detail herein.

[0019] According to a preferred embodiment of the application, the weaving knot in the step S1 comprises: folding the ends of the pre-oxidized large-tow precursor in a cross shape to form a first loop, inserting the end of the carbon fiber from below the first loop, and then winding downward at the cross of the precursor end to form a second loop, and then inserting from above into the first loop and tensioning.

[0020] In the application, in the step S1, after the ends of the large-tow precursor are crossed, the crossing angle needs to be controlled to be 70-80 degrees, and each of the two ends needs to be exposed by 7 cm.

[0021] In the application, the winding connection can be continuously performed, and the specific winding times are determined according to the needs and actual working conditions.

[0022] By adopting the foregoing preferred embodiment, the breaking strength of the joint at the connection between the precursor and the carbon fiber can be further improved, and the joint is stable and not loose.

[0023] In the present application, the step S1 further comprises reserving a length of the pre-oxidized end of the large tow precursor before the pre-oxidation of the large tow precursor. The reserved length is not particularly limited, and according to one preferred embodiment of the present application, the reserved length of the pre-oxidized end of the large tow precursor before the pre-oxidation is 100-180 cm, preferably 140-170 cm. By adopting the foregoing preferred embodiment, the length of the pre-oxidized precursor can be further ensured to meet the length requirement for connection with the carbon fiber.

[0024] In the present application, the length of the tail of the joint after knotting of the connection end of the pre-oxidized large tow precursor and the carbon fiber is not particularly limited, and according to one preferred embodiment of the present application, the length of the tail of the joint after knotting of the connection end of the pre-oxidized large tow precursor and the carbon fiber is 8-25 cm, preferably 13-20 cm. By adopting the foregoing preferred embodiment, the safety and stability of the joint during the production process through the oxidation furnace, the low-temperature carbonization furnace and the high-temperature carbonization furnace can be further improved.

[0025] In the present application, the pre-oxidation times of the large tow precursor are not particularly limited.

[0026] According to one preferred embodiment of the present application, the pre-oxidation of the large tow precursor is completed in two stages, including first pre-oxidation and second pre-oxidation.

[0027] According to one preferred embodiment of the present application, the temperature of the second pre-oxidation is 10-30℃ higher than that of the first pre-oxidation.

[0028] In the present application, the conditions for the first pre-oxidation of the large tow precursor can be selected conventionally in the art.

[0029] According to one preferred embodiment of the present application, the temperature for the first pre-oxidation of the large tow precursor is 210-260℃, preferably 230-250℃.

[0030] According to one preferred embodiment of the present application, the time for the first pre-oxidation of the large tow precursor is 10-60 min, preferably 30-45 min.

[0031] By adopting the foregoing preferred embodiment, the oxidation reaction of the precursor can be further effectively and rapidly carried out.

[0032] In the present application, the conditions for the second pre-oxidation of the large tow precursor can be selected conventionally in the art.

[0033] According to a preferred embodiment of the present application, the second pre-oxidation temperature of the large-tow precursor is 238-270 DEG C, preferably 245-265 DEG C.

[0034] According to a preferred embodiment of the present application, the second pre-oxidation time of the large-tow precursor is 10-60 min, preferably 30-45 min.

[0035] By using the preferred embodiment described above, the precursor can be further ensured to complete the cyclization and dehydrogenation reactions, and through intramolecular cyclization and intermolecular crosslinking, the linear macromolecular chain of the PAN-based precursor is converted into a heat-resistant ladder macromolecular structure.

[0036] The present application provides the large-tow carbon fiber prepared by the continuous production method of the large-tow carbon fiber.

[0037] As shown in Figure 1 the schematic diagram of the connection of the respective end of the large-tow precursor and the carbon fiber by the textile knot method; wherein, Figure 1 1 is the end of the large-tow precursor after the pre-oxidation treatment; and 2 is the carbon fiber.

[0038] By the technical solution described above, the present application has the following beneficial effects:

[0039] The present application first proposes a large-tow carbon fiber, which comprises large-tow precursors and carbon fibers connected alternately, and the large-tow precursors and the carbon fibers are connected by the textile knot method. By the connection method described in the present application, the end of the large-tow precursor in the packing box can be connected with the end of the adjacent large-tow precursor in the packing box, and the knot is firm and the breaking strength of the knot is above 140000 cN.

[0040] The knot of the adjacent large-tow precursor after the knotting described in the present application does not loosen or fall off during the oxidation process, and the knot connection does not produce smoke and fire due to heat accumulation and overheating, so that the knot of the adjacent large-tow precursor can be connected tightly. The large-tow precursor can smoothly pass through the oxidation furnace, the low-temperature carbonization furnace, the high-temperature carbonization furnace, the surface treatment, the washing, the sizing, the drying and the winding production processes in sequence.

[0041] In the preferred embodiment of the present application, the large-tow precursor and the carbon fiber connected by the textile knot method can realize the continuous production of the large-tow carbon fiber, reduce the number of winding rollers, improve the production safety, increase the stable production time, reduce the amount of waste silk, reduce the production cost and improve the production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is a schematic diagram of the textile knot connection of the precursor and the carbon fiber;

[0043] Figure 2 This is a step-by-step demonstration diagram showing how raw silk and carbon fiber are knotted. Detailed Implementation

[0044] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0045] This invention proposes for the first time a large-tow carbon fiber, comprising alternating large-tow precursor fibers and carbon fibers. The large-tow precursor fibers and carbon fibers are connected by a weaving knot. Using the connection method described in this invention, in continuous production, the ends of the large-tow precursor fibers in the boxed packaging can be connected to the ends of the adjacent large-tow precursor fibers in the boxed packaging through carbon fibers. Not only are the knots strong, but the breaking strength of the knots reaches more than 140,000 cN.

[0046] The present invention will be described in detail below through embodiments. In the following embodiments, the knot breaking strength parameter was measured using the GB / T19975-2005 test method for tensile properties of high-strength fiber filaments. In the present invention, the knot breaking strength data is the average value of three knot tests conducted in actual operation; the oxidation furnace pass rate, low-temperature carbonization furnace pass rate, and high-temperature carbonization furnace pass rate were calculated using the following methods:

[0047] Oxidation furnace throughput = (Number of nodes that successfully pass through the oxidation furnace / Total number of nodes entering the oxidation furnace) * 100%

[0048] Low-temperature carbonization furnace throughput = (Number of nodes that successfully pass through the low-temperature carbonization furnace / Total number of nodes entering the low-temperature carbonization furnace) * 100%

[0049] High-temperature carbonization furnace throughput = (Number of nodes that successfully pass through the high-temperature carbonization furnace / Total number of nodes entering the high-temperature carbonization furnace) * 100%

[0050] The raw material for the silk is a commercially available product of brand SF from Sinopec Shanghai Petrochemical Co., Ltd.

[0051] In the following examples and comparative examples, the oxidation furnace, low-temperature carbonization furnace, high-temperature carbonization furnace, surface treatment, washing, sizing, drying, and winding / dewinding processes all operate under the same conditions: (Details are as follows:)

[0052] Oxidation furnace: The oxidation process is carried out in four temperature zones for a total time of 60 minutes. The draw ratios between the four heating temperature zones are 1.26, 0.99, 0.98, and 0.96, respectively. The temperatures of the four temperature zones in the embodiments and comparative examples of this invention are shown in Table 1.

[0053] Low temperature carbonization furnace: the low temperature carbonization production process is carried out in a low temperature carbonization furnace divided into 6 heating temperature zones. The pre-oxidized yarn at the outlet of the oxidation furnace enters the low temperature carbonization furnace through a traction device, and low temperature carbonization is carried out with nitrogen as the medium to produce low temperature carbonized yarn. The temperatures of the 6 heating temperature zones are 470℃, 540℃, 610℃, 670℃, 740℃ and 790℃ respectively. The yarn runs in the low temperature carbonization furnace, and the draft ratio is controlled to be 1.06. The total residence time in the low temperature carbonization furnace is 1.2 minutes.

[0054] High temperature carbonization furnace: the high temperature carbonization production process is carried out in a high temperature carbonization furnace divided into 5 heating temperature zones. The yarn at the outlet of the low temperature carbonization furnace enters the high temperature carbonization furnace through a traction device, and high temperature carbonization is carried out with nitrogen as the medium to produce high temperature carbonized yarn. The temperatures of the 5 heating temperature zones are 1100℃, 1390℃, 1470℃, 1490℃ and 1400℃ respectively. The yarn runs in the high temperature carbonization furnace, and the draft ratio is controlled to be 0.76. The total residence time in the high temperature carbonization furnace is 1.2 minutes.

[0055] Surface treatment: the surface treatment production process is that the yarn at the outlet of the high temperature carbonization furnace enters the surface treatment tank through a traction device, and ammonium bicarbonate aqueous solution is used as the electrolyte. The voltage is 18V, the electrolyte concentration is 10%, and the residence time of the yarn in the electrolyte is 60 seconds.

[0056] Water washing: the yarn at the outlet of the surface treatment tank enters the water washing tank for water washing. The water washing flow is 2800L / hour, and the water washing temperature is 50℃.

[0057] Sizing: commercially available K7 epoxy emulsion sizing agent is used for impregnation sizing of unsized carbon fibers. The time is 20s, and the temperature is 25℃.

[0058] Drying: horizontal hot air drying is carried out at a drying temperature of 100℃.

[0059] Winding and collecting yarn: the carbon fibers after sizing and drying are wound and collected using a carbon fiber winding machine to produce finished carbon fibers.

[0060] In the following implementation, the yarn head and the yarn tail are the two end heads of the yarn, and the K number of the large tow precursor yarn and the carbon fiber is the same in the same example. Other parameters are shown in Table 2.

[0061] Example 1

[0062] The K number of the carbon fiber and the large tow precursor yarn in this example is 200K.

[0063] S1. Pre-oxidation of yarn head and yarn tail:

[0064] The length of the head and tail of each box of raw silk is reserved, and the length of the head and tail of the raw silk is 140 cm. The head and tail of each box of raw silk is laid on the tension frame, the raw silk is tensioned and fixed, the tension frame is put into the pre-oxidation furnace, and the head of 140 cm of the head and tail of the raw silk is pre-oxidized. The pre-oxidation is divided into two stages, the first stage of oxidation is at an oxidation temperature of 230 DEG C for 30 min, and the second stage of oxidation is at an oxidation temperature of 245 DEG C for 30 min.

[0065] S2. The knotting operation steps of the head and tail are as follows (the completed knot is shown in Figure 1 , and the specific step-by-step demonstration is shown in Figure 2 . The left is the pre-oxidized large tow raw silk, and the right is the carbon fiber):

[0066] Step 1: The head of the pre-oxidized large tow raw silk is crossed with the head of the carbon fiber at an angle of 75 DEG, and 7 cm of the head of the pre-oxidized large tow raw silk is reserved at the two crossing positions. Then the head of the pre-oxidized large tow raw silk is pressed on the head of the carbon fiber.

[0067] Step 2: The head of the pre-oxidized large tow raw silk is pressed on the head of the carbon fiber. The head of the pre-oxidized large tow raw silk is pressed on the head of the carbon fiber.

[0068] S3. The above knot is twisted and connected in turn, and then subjected to oxidation, low-temperature carbonization, high-temperature carbonization, surface treatment, washing, sizing, drying and winding.

[0069] The implementation effect of this embodiment is shown in Table 3.

[0070] Example 2

[0071] The K number of the carbon fiber and the large tow raw silk of this embodiment is 220K.

[0072] S1. Pre-oxidation of the head and tail of the raw silk:

[0073] The length of the head and tail of each box of raw silk is reserved, and the length of the head and tail of the raw silk is 155 cm. The head and tail of each box of raw silk is laid on the tension frame, the raw silk is tensioned and fixed, the tension frame is put into the pre-oxidation furnace, and the head and tail of the raw silk is pre-oxidized. The pre-oxidation is divided into two stages, the first stage of oxidation is at an oxidation temperature of 243 DEG C for 40 min, and the second stage of oxidation is at an oxidation temperature of 260 DEG C for 40 min.

[0074] S2. The steps of the knotting operation of the yarn head and the yarn tail are as follows (the completed knotting is shown in Figure 1 , and the specific steps are shown in Figure 2 , in which the left side is the pre-oxidized large tow precursor, and the right side is the carbon fiber:

[0075] Step 1: Cross the end of the pre-oxidized large tow precursor with the end of the carbon fiber by 75°, and leave 7 cm of each end at the two crossing positions, and then press the end of the pre-oxidized large tow precursor on the end of the carbon fiber.

[0076] Step 2: Wrap the end of the carbon fiber around the end of the pre-oxidized large tow precursor outward from the crossing position, and press the end of the carbon fiber to form a loop, and then pass the end of the pre-oxidized large tow precursor into the loop, and pull the end of the pre-oxidized large tow precursor and the end of the carbon fiber tightly to complete the knotting.

[0077] S3. Twist the above knot, and then sequentially perform oxidation, low-temperature carbonization, high-temperature carbonization, surface treatment, washing, sizing, drying, and winding.

[0078] The implementation effect of this example is shown in Table 3.

[0079] Example 3

[0080] The K number of the carbon fiber and the large tow precursor in this example is 230K.

[0081] S1. Pre-oxidation of the yarn head and the yarn tail:

[0082] A certain length of the yarn head and the yarn tail of each box of precursor is reserved, and the length of the yarn head and the yarn tail is 170 cm. The yarn head and the yarn tail of each box of precursor are respectively laid on a tension frame, the precursor is pulled tightly and fixed, the tension frame is placed into a pre-oxidation furnace, and the yarn head and the yarn tail of the precursor are pre-oxidized. The pre-oxidation is divided into two stages, the first stage of oxidation is at an oxidation temperature of 250℃ for 45 min, and the second stage of oxidation is at an oxidation temperature of 265℃ for 45 min.

[0083] S2. The steps of the knotting operation of the yarn head and the yarn tail are as follows (the completed knotting is shown in Figure 1 , and the specific steps are shown in Figure 2 , in which the left side is the pre-oxidized large tow precursor, and the right side is the carbon fiber:

[0084] Step 1: Cross the end of the pre-oxidized large tow precursor with the end of the carbon fiber by 75°, and leave 7 cm of each end at the two crossing positions, and then press the end of the pre-oxidized large tow precursor on the end of the carbon fiber.

[0085] Step 2: winding the end of the carbon fiber around the end of the pre-oxidized large tow precursor outwardly and out of the end of the pre-oxidized large tow precursor from the above end crossing position, pressing the end of the pre-oxidized large tow precursor, so that the end of the carbon fiber is wound to form a loop, the end of the pre-oxidized large tow precursor is inserted into the above loop, and the end of the pre-oxidized large tow precursor is pulled tight with the end of the carbon fiber, and the knot is completed; after the knot is completed, the two ends of the knot are pulled tight, and the excess ends of the filaments are cut, and the length of the knot tail left is 20 cm, and the subsequent pre-oxidized end of the large tow precursor and the end of the carbon fiber are alternately connected in sequence.

[0086] S3. twisting the above knot, and then sequentially performing oxidation, low-temperature carbonization, high-temperature carbonization, surface treatment, washing, sizing, drying, and winding.

[0087] The implementation effect of this embodiment is shown in Table 3.

[0088] Example 4

[0089] All operation steps are the same as those in Example 1, except that the process parameter values of the K number of the carbon fiber and the large tow precursor, the pre-oxidation temperature and the pre-oxidation residence time of the two sections, the length of the filament ends, the number of strands of the filaments and the carbon fiber, and the length of the knot tail left after the knot of the filament ends is not within the preferred range of the present application. Specifically, as shown in Table 2.

[0090] The implementation effect of this embodiment is shown in Table 3.

[0091] Example 5

[0092] All operation steps are the same as those in Example 1, except that the process parameter values of the K number of the carbon fiber and the large tow precursor, the pre-oxidation temperature and the pre-oxidation residence time of the two sections, the length of the filament ends, the number of strands of the filaments and the carbon fiber, and the length of the knot tail left after the knot of the filament ends is not within the preferred range of the present application. Specifically, as shown in Table 2.

[0093] The implementation effect of this embodiment is shown in Table 3.

[0094] Example 6

[0095] All operation steps and conditions are the same as those in Example 1, except that the K number of the carbon fiber and the large tow precursor is 170K, which is not within the preferred range of the present application.

[0096] The implementation effect of this embodiment is shown in Table 3.

[0097] Example 7

[0098] All operation steps and conditions are the same as those in Example 1, except that the length of the knot tail left after the knot of the filament ends is 23 cm, which is not within the preferred range of the present application.

[0099] The implementation effect of this example is shown in Table 3.

[0100] Example 8

[0101] All operating steps and conditions are the same as in Example 1, except that the original wire head and tail are pre-oxidized, the pre-oxidation is divided into two stages, the temperature and time of the second stage of oxidation are not within the preferred range of the present application, the first stage of oxidation is at an oxidation temperature of 223°C for 28 minutes, and the second stage of oxidation is at an oxidation temperature of 240°C for 28 minutes.

[0102] The implementation effect of this example is shown in Table 3.

[0103] Example 9

[0104] All operating steps and conditions are the same as in Example 1, except that the length of the large tow original wire at one end is 128 cm, which is not within the preferred range of the present application.

[0105] The implementation effect of this example is shown in Table 3.

[0106] Comparative Example 1

[0107] All conditions are the same as in Example 1, except that the large tow carbon fiber only includes 200K large tow original wire connected alternately, and does not include 200K carbon fiber.

[0108] The implementation effect of this example is shown in Table 3.

[0109] Comparative Example 2

[0110] All conditions are the same as in Example 1, except that the connection method of 200K large tow original wire and 200K carbon fiber is a barrel knot tying method, the original wire head of one box and the original wire tail of the adjacent box are stacked together in parallel, the stacked tow is wound around a loop, the head and tail are pulled tight through the loop, and the excess knot tail is cut off.

[0111] The implementation effect of this example is shown in Table 3.

[0112] Table 1

[0113]

[0114] Table 2

[0115]

[0116] Table 3

[0117]

[0118] As can be seen from the results in Table 3, in the carbon fiber production process using the large-tow carbon fiber and the embodiment of the continuous production splicing method of large-tow carbon fiber, the end of the adjacent filaments can be firmly connected together, the breaking strength of the joint reaches 140000 CN or more, and the joint can smoothly pass through the oxidation furnace, the low-temperature carbonization furnace and the high-temperature carbonization furnace, the oxidation furnace passing rate is 100%, the low-temperature carbonization furnace passing rate is 100%, the high-temperature carbonization furnace passing rate is 100%, and the implementation effect is good.

[0119] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the present application and fall within the protection scope of the present application.

Claims

1. A continuous production method of large-tow carbon fibers, characterized by, The method comprises the following steps: S1. One end of the large-tow precursor is pre-oxidized, and the end of the pre-oxidized large-tow precursor is connected to the end of the carbon fiber by a weaving knot, and the above-mentioned weaving knot connection is repeated according to the needs of continuous production, wherein the K number of the carbon fiber is 180-250K; S2. After the weaving knot connection is completed, oxidation, low-temperature carbonization, high-temperature carbonization, surface treatment, washing, sizing, drying, and winding are performed; The weaving knot connection in step S1 comprises: folding the end of the pre-oxidized large-tow precursor in a cross shape to form a first loop, inserting the end of the carbon fiber from below the first loop, and then winding down at the cross of the end of the large-tow precursor to form a second loop, and then inserting from above into the first loop and tightening; Before the pre-oxidation, in step S1, the length of the end of the large-tow precursor reserved for pre-oxidation is 100-180 cm; After the large-tow precursor is connected to the carbon fiber by the weaving knot, the length of the tail of the weaving knot is 8-25 cm; The pre-oxidation is performed in two stages, including first pre-oxidation and second pre-oxidation, wherein The conditions of the first pre-oxidation comprise: a temperature of 210-260℃; a time of 10-60 min; The conditions of the second pre-oxidation comprise: a temperature of 238-270℃; a time of 10-60 min; The temperature of the second pre-oxidation is 10-30℃ higher than that of the first pre-oxidation.

2. The method of claim 1, wherein, Before the pre-oxidation, in step S1, the length of the end of the large-tow precursor reserved for pre-oxidation is 140-170 cm.

3. The method of claim 1, wherein, After the large-tow precursor is connected to the carbon fiber by the weaving knot, the length of the tail of the weaving knot is 13-20 cm.

4. The method according to any one of claims 1-3, wherein The conditions of the first pre-oxidation comprise: a temperature of 230-250℃; and / or a time of 30-45 min; and / or The conditions of the second pre-oxidation comprise: a temperature of 245-265℃; and / or a time of 30-45 min.

5. The method of any of claims 1-3, wherein, The K number of the carbon fiber is 200-230K.

6. The large-tow carbon fiber prepared by the continuous production method of the large-tow carbon fiber according to any one of claims 1-5, wherein the large-tow carbon fiber comprises large-tow precursors and carbon fibers connected alternately, the large-tow precursors and the carbon fibers are connected by a weaving knot, and the length of the tail of the weaving knot is 8-25 cm after the large-tow precursors and the carbon fibers are connected by the weaving knot, and the K number of the carbon fiber is 180-250K.

7. The large-tow carbon fiber according to claim 6, wherein the length of the tail of the weaving knot is 13-20 cm after the large-tow precursors and the carbon fibers are connected by the weaving knot.

8. The large-tow carbon fiber according to claim 6, wherein the K number of the carbon fiber is 200-230K.

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