Preparation method of high-strength and high-modulus polyacrylonitrile-based precursor, polyacrylonitrile-based precursor and application

Abstract

The invention discloses a preparation method of a high-strength and high-modulus polyacrylonitrile-based precursor, the polyacrylonitrile-based precursor and application of the polyacrylonitrile-based precursor. The preparation method of the high-strength and high-modulus polyacrylonitrile-based precursor comprises a steam drafting step, and the relationship between the steam drafting inlet speed and the steam drafting outlet precursor tension meets the following relational expression: y is greater than or equal to 0.0024 x + 0.2975 and less than or equal to-1.9 * 10 <-5 > x < 2 > + 0.0043 x + 0.3487, y represents the tension of a single fiber at the steam drafting outlet, and the unit is cN; x represents the steam drafting inlet speed, and the unit is m / min. The method provided by the invention well solves the problems of excessive broken filaments and poor mechanical properties of the carbon fiber in the process of preparing the carbon fiber from the polyacrylonitrile-based precursor under the existing conditions, and can be well used in the industrial production of the polyacrylonitrile fiber for the high-strength and high-modulus carbon fiber.

Description

Technical Field

[0001] The present invention relates to the technical field of polyacrylonitrile spinning, and in particular to a preparation method of high-strength and high-modulus polyacrylonitrile-based precursor, the polyacrylonitrile-based precursor and applications thereof. Background Art

[0002] Carbon fiber boasts exceptional properties of high strength, high modulus, and lightweight. Its use as a reinforcing fiber in composite materials has garnered significant attention in fields such as aerospace and new energy, becoming a crucial strategic material for the development of national defense, military industry, and the national economy. Carbon fiber can be categorized into three types based on its raw material: polyacrylonitrile, asphalt, and viscose. Polyacrylonitrile-based carbon fiber, due to its readily available raw material and excellent overall mechanical properties, has become the primary component of carbon fiber, accounting for over 90% of global carbon fiber production.

[0003] The production of carbon fiber can be divided into two main processes: carbon fiber precursor preparation and precursor oxidation and carbonization, involving thousands of process control points. The carbon fiber precursor is the key to its performance. The structure and defects of the precursor are inherited into the carbon fiber during the oxidation and carbonization process, irreversibly affecting its structure and properties.

[0004] The production of carbon fiber precursor requires a series of steps including coagulation, hot water drawing, washing, oiling, drying, steam drawing, and heat setting. Among them, steam drawing is an important step in the preparation of polyacrylonitrile-based carbon fiber precursor, which determines the key structures of the precursor, such as orientation and crystallinity. Chinese patents CN111088543A and CN116024680A disclose a method for preparing polyacrylonitrile-based carbon fiber precursor, which respectively reduces the fuzzing phenomenon and improves the performance of carbon fiber by controlling the tension on each fiber during steam drawing and the steam pressure during steam drawing; however, the mechanical properties of the former still need to be improved, while the number of fuzzy fibers in the latter is still relatively large. During the steam drawing process, the precursor is subjected to a large drawing and the speed increases rapidly. At this time, the groove structure on the surface of the precursor obtained by wet spinning will increase the friction between the filaments and increase the surface defects, which is not conducive to the subsequent oxidation and carbonization process in the carbon fiber preparation process, and ultimately hinders the improvement of the mechanical properties of the carbon fiber. Summary of the Invention

[0005] To address the existing problems of excessive fuzz and poor mechanical properties of polyacrylonitrile-based precursor fibers during carbon fiber production, the present invention provides a method for preparing high-strength, high-modulus polyacrylonitrile-based precursor fibers, as well as polyacrylonitrile-based precursor fibers and their applications. The method effectively addresses this issue and can be used in the industrial production of polyacrylonitrile fibers for high-strength, high-modulus carbon fibers.

[0006] One of the objects of the present invention is to provide a method for preparing high-strength and high-modulus polyacrylonitrile-based precursor yarn, comprising a steam drawing step, wherein the relationship between the steam drawing inlet velocity and the steam drawing outlet precursor yarn tension satisfies the following relationship:

[0007] 0.0024x+0.2975≤y≤-1.9×10 -5 x 2 +0.0043x+0.3487

[0008] Wherein, y represents the tension of a single fiber at the outlet of steam drawing, in cN; x represents the inlet velocity of steam drawing, in m / min.

[0009] In a preferred embodiment of the present invention,

[0010] The steam drawing inlet speed is 5-80 m / min, preferably 8-65 m / min.

[0011] In a preferred embodiment of the present invention,

[0012] The steam pressure (unit MPa) a for steam drawing is 0.15-0.18 times of the drawing ratio (unit times) b, preferably 0.15-0.17 times, more preferably 0.15-0.16 times, wherein the drawing ratio is 1.5-3.0 times, preferably 1.8-2.7 times.

[0013] The present invention has developed the above-mentioned relationship through extensive experimental research. By ensuring that the tension of a single fiber at the steam drawing exit and the steam drawing inlet velocity during steam drawing conform to the relationship expressed by this formula, the problem of excessive fuzz and poor mechanical properties of the carbon fibers produced by polyacrylonitrile-based precursors under existing conditions in the prior art can be effectively solved.

[0014] In a preferred embodiment of the present invention,

[0015] The preparation method adopts a wet spinning process, preferably including the steps of subjecting the polyacrylonitrile stock solution to coagulation molding, coagulation drawing, hot water drawing, water washing, oiling, drying and densification, steam drawing, and steam heat setting to obtain the high-strength and high-modulus polyacrylonitrile-based precursor.

[0016] In a preferred embodiment of the present invention,

[0017] The polyacrylonitrile stock solution has a polyacrylonitrile solid content of 10-40%, preferably 17-22%, and / or an intrinsic viscosity of the stock solution of 1.0-5.0 dL / g, preferably 1.7-2.5 dL / g.

[0018] In a preferred embodiment of the present invention,

[0019] The coagulation and drawing process includes at least three stages; preferably,

[0020] In the coagulation and drawing, the temperature of each coagulation and drawing is 25-95° C., preferably 30-80° C., more preferably 30-70° C., and / or the total drawing ratio is 1.5-3.5, preferably 1-2.

[0021] In a preferred embodiment of the present invention,

[0022] The hot water drawing comprises at least 3 stages; and / or,

[0023] The temperature of the hot water drawing is 90-100°C, preferably 95-99°C; preferably,

[0024] The total stretching ratio of the hot water stretching is greater than or equal to 3.5 times, preferably greater than or equal to 4.5 times, and the third hot water stretching ratio is greater than or equal to 1.3 times, preferably 1.6-2.7 times.

[0025] In a preferred embodiment of the present invention,

[0026] The oiling and drying densification are at least two stages; and / or,

[0027] The drying and densification temperature is 90-150°C without applying stretching. Preferably, the drying and densification temperature is 100-140°C.

[0028] In a preferred embodiment of the present invention,

[0029] The number of strands in a single bundle of the high-strength and high-modulus polyacrylonitrile-based precursor yarn is 1,000-320,000.

[0030] In the above technical solution, other aspects of the polyacrylonitrile-based precursor preparation method are not particularly limited. It can be prepared from a polyacrylonitrile stock solution commonly used in the art through a spinning process commonly used in the art. The polyacrylonitrile stock solution and the spinning process are not particularly limited. The polyacrylonitrile used in this application can be a polyacrylonitrile homopolymer or a polyacrylonitrile copolymer. The polyacrylonitrile copolymer can be prepared from a comonomer commonly used in the art. For example, but not limited to, the polyacrylonitrile comonomer is a vinyl-containing monomer, and the comonomer is preferably one or more of acrylates, vinyl esters, acrylamides, sulfonates, carboxylic acids, and ammonium salts.

[0031] The second object of the present invention is to provide a polyacrylonitrile-based precursor obtained by the preparation method of one of the objects of the present invention.

[0032] The third object of the present invention is to provide a high-strength and high-modulus carbon fiber, which is prepared from the polyacrylonitrile-based precursor described in the second object of the present invention; preferably, the high-strength and high-modulus carbon fiber is obtained by subjecting the polyacrylonitrile precursor to steps including pre-oxidation, carbonization, and graphitization.

[0033] The preparation process of the high-strength and high-modulus carbon fiber is not particularly limited, and can be prepared from polyacrylonitrile-based precursors through pre-oxidation, carbonization, and graphitization processes commonly used in the art.

[0034] In a preferred embodiment of the present invention,

[0035] The pre-oxidation temperature is 180-300° C.; and / or,

[0036] The carbonization is divided into low-temperature carbonization and high-temperature carbonization; preferably, the temperature of the low-temperature carbonization is 300-700°C; and / or, the temperature of the high-temperature carbonization is 1000-1500°C; and / or,

[0037] The graphitization temperature is 2200-2800°C.

[0038] By adopting the technical solution of the present invention, the number of fiber filaments at the graphite furnace outlet every 30 hours during the carbon fiber preparation process can be counted by online camera, which can be as low as 8. The tensile strength of the prepared carbon fiber can be as high as 5.82GPa, and the modulus can be as high as 380GPa, achieving good technical results. DETAILED DESCRIPTION

[0039] The present invention will be described in detail below with reference to specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0040] In the present invention, the tension value borne by the fiber during the saturated steam drawing process is obtained by measuring the tension of the filament bundle between the front and rear drawing rollers of the supported steam drawing machine using a handheld tension meter; the test standard for the linear density of carbon fiber precursor is GB / T 14343, and the test standard for the mechanical properties of carbon fiber multifilament is GB / T 3362-2017; the number of filaments at the outlet of the graphite furnace during the carbon fiber preparation process is obtained by counting the number of filaments for 10 hours using an online camera.

[0041] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present invention are all disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0042] The polyacrylonitrile in the spinning solution used in Example 1 of the present invention is a polyacrylonitrile copolymer, which is obtained by polymerization with reference to Example 1 of Chinese Patent CN110684149A; the preparation process of other examples and comparative examples is the same as that of Example 1 of Chinese Patent CN110684149A, except that the mass ratio of the added acrylonitrile, itaconic acid and sodium methyl propylene sulfonate is changed.

[0043] [Example 1]

[0044] Preparation of polyacrylonitrile-based precursor: Wet spinning technology was used, and the intrinsic viscosity of the spinning solution used was 2.5 dL / g and the solid content was 18%. The spinning solution is precisely measured and filtered by a metering pump, extruded through a 3000-hole spinneret, and sequentially enters four coagulation baths of dimethyl sulfoxide aqueous solution for coagulation at temperatures of 35°C, 55°C, 60°C, and 70°C, with a total draw ratio of 2.0 and concentrations of 85%, 67%, 53%, and 39%, respectively. It then undergoes three-stage hot water drawing at temperatures of 95°C, 96°C, and 99°C, with draw ratios of 1.84, 2.15, and 2.68, respectively. After oiling, it undergoes a two-stage drying and densification treatment without drawing, at temperatures of 115°C and 125°C, respectively. The steam drawing inlet speed is 40m / min, the steam pressure is 0.375MPa, and the draw ratio is 2.5 times. At this time, the steam drawing outlet tow tension is 1320cN, and the tension of a single fiber is 0.44cN. Finally, after heat setting and winding, high-strength and high-modulus polyacrylonitrile carbon fiber precursor is obtained.

[0045] Preparation of high-strength and high-modulus carbon fiber: the obtained raw silk is passed through four pre-oxidation temperature zones in sequence, with temperatures of 180℃, 240℃, 270℃, and 300℃, and draw ratios of 1.01, 1.0, 1.0, and 0.99, respectively, and stays in each temperature zone for 40 minutes; then it is carbonized at a low temperature of 700℃, with a draw ratio of 1.03 and a residence time of 20 minutes; it is carbonized at a high temperature of 1500℃, with a draw ratio of 1.04 and a residence time of 20 minutes; finally, it is graphitized at 2500℃, and finally, after surface treatment, water washing, sizing, drying at 120℃ and collecting, high-strength and high-modulus carbon fiber is obtained.

[0046] The number of hair fibers at the outlet of the graphite furnace was counted by an online camera. The number of hair fibers in the fiber was 15 every 30 hours. The tensile strength of the carbon fiber was 5.82 GPa and the modulus was 380 GPa.

[0047] [Example 2]

[0048] Preparation of polyacrylonitrile-based precursor: Wet spinning technology was used, and the spinning solution used (the mass ratio of acrylonitrile:itaconic acid:sodium methyl propylene sulfonate in the polyacrylonitrile copolymer was 90:8:2) had an intrinsic viscosity of 2.0 dL / g and a solid content of 19%. The spinning solution is precisely measured and filtered by a metering pump, extruded through a 6000-hole spinneret, and sequentially enters four coagulation baths of dimethyl sulfoxide aqueous solution for coagulation at temperatures of 30°C, 50°C, 55°C, and 60°C, with a total draw ratio of 1.95 and concentrations of 85%, 67%, 53%, and 39%, respectively. It then undergoes three-stage hot water drawing at temperatures of 97°C, 98°C, and 99°C, with draw ratios of 1.65, 1.90, and 2.25, respectively. After oiling, it undergoes a two-stage drying and densification treatment without drawing, at temperatures of 118°C and 120°C, respectively. The steam drawing inlet speed is 35m / min, the steam pressure is 0.3MPa, and the draw ratio is 2.0 times. At this time, the steam drawing outlet tow tension is 2580cN, and the tension of a single fiber is 0.43cN. Finally, after heat setting and winding, high-strength and high-modulus polyacrylonitrile carbon fiber precursor is obtained.

[0049] Preparation of high-strength and high-modulus carbon fiber: the obtained raw silk is passed through four pre-oxidation temperature zones in sequence, with temperatures of 180℃, 240℃, 270℃, and 300℃, and draw ratios of 1.01, 1.0, 1.0, and 0.99, respectively, and stays in each temperature zone for 40 minutes; then it is carbonized at a low temperature of 480℃, with a draw ratio of 1.03 and a residence time of 20 minutes; it is carbonized at a high temperature of 1400℃, with a draw ratio of 1.04 and a residence time of 20 minutes; finally, it is graphitized at 2500℃, and finally, after surface treatment, water washing, sizing, drying at 120℃ and collecting, high-strength and high-modulus carbon fiber is obtained.

[0050] The number of hair fibers at the outlet of the graphite furnace was counted by an online camera. The number of hair fibers in the fiber was 18 every 30 hours. The tensile strength of the carbon fiber was 5.79 GPa and the modulus was 378 GPa.

[0051] [Example 3]

[0052] Preparation of polyacrylonitrile-based precursor: Wet spinning technology was used, and the spinning solution used (polyacrylonitrile copolymer, the mass ratio of acrylonitrile:itaconic acid:sodium methyl propylene sulfonate was 90:7:3) had an intrinsic viscosity of 1.9 dL / g and a solid content of 17%. The spinning solution is precisely measured and filtered by a metering pump, extruded through a 320,000-hole spinneret, and sequentially enters four coagulation baths containing dimethyl sulfoxide aqueous solution for coagulation at temperatures of 35°C, 60°C, 65°C, and 75°C, with a total draw ratio of 1.2 and concentrations of 85%, 67%, 53%, and 39%, respectively. The solution then undergoes three-stage hot water drawing at temperatures of 95°C, 96°C, and 97°C, with draw ratios of 1.35, 1.65, and 1.85, respectively. After oiling, the solution undergoes a two-stage drying and densification treatment without drawing, at temperatures of 130°C and 140°C, respectively. The steam drawing inlet speed is 8 m / min, the steam pressure is 0.27 MPa, and the draw ratio is 1.8 times. At this time, the steam drawing outlet tow tension is 108,800 cN, and the tension of a single fiber is 0.34 cN. Finally, the high-strength and high-modulus polyacrylonitrile carbon fiber precursor is obtained after heat setting and winding.

[0053] Preparation of high-strength and high-modulus carbon fiber: the obtained raw silk is passed through four pre-oxidation temperature zones in sequence, with temperatures of 180℃, 240℃, 270℃, and 300℃, and draw ratios of 1.01, 1.0, 1.0, and 0.99, respectively, and stays in each temperature zone for 40 minutes; then it is carbonized at a low temperature of 480℃, with a draw ratio of 1.03 and a residence time of 20 minutes; it is carbonized at a high temperature of 1400℃, with a draw ratio of 1.04 and a residence time of 20 minutes; finally, it is graphitized at 2500℃, and finally, after surface treatment, water washing, sizing, drying at 120℃ and collecting, high-strength and high-modulus carbon fiber is obtained.

[0054] The number of hair fibers at the graphite furnace outlet was counted by an online camera. The number of hair fibers in the fiber was 32 every 30 hours. The tensile strength of the carbon fiber was 5.68 GPa and the modulus was 365 GPa.

[0055] [Example 4]

[0056] Preparation of polyacrylonitrile-based precursor: Wet spinning technology was used, and the spinning solution used (the mass ratio of acrylonitrile:itaconic acid:sodium methyl propylene sulfonate in the polyacrylonitrile copolymer was 90:6:4) had an intrinsic viscosity of 1.7 dL / g and a solid content of 22%. The spinning solution is precisely measured and filtered by a metering pump, extruded through a 96,000-hole spinneret, and sequentially enters four coagulation baths containing dimethyl sulfoxide aqueous solution for coagulation at temperatures of 40°C, 60°C, 65°C, and 70°C, with a total draw ratio of 1.35 and concentrations of 85%, 67%, 53%, and 39%, respectively. The solution then undergoes three-stage hot water drawing at temperatures of 96°C, 97°C, and 98°C, with draw ratios of 1.60, 1.75, and 1.85, respectively. After oiling, the solution undergoes a two-stage drying and densification treatment without drawing, at temperatures of 135°C and 145°C, respectively. The steam drawing inlet speed is 10 m / min, the steam pressure is 0.27 MPa, and the draw ratio is 1.8 times. At this time, the steam drawing outlet tow tension is 33,600 cN, and the tension of a single fiber is 0.35 cN. Finally, the high-strength and high-modulus polyacrylonitrile carbon fiber precursor is obtained after heat setting and winding.

[0057] Preparation of high-strength and high-modulus carbon fiber: the obtained raw silk is passed through four pre-oxidation temperature zones in sequence, with temperatures of 180℃, 240℃, 270℃, and 300℃, and draw ratios of 1.01, 1.0, 1.0, and 0.99, respectively, and stays in each temperature zone for 40 minutes; then it is carbonized at a low temperature of 480℃, with a draw ratio of 1.03 and a residence time of 20 minutes; it is carbonized at a high temperature of 1400℃, with a draw ratio of 1.04 and a residence time of 20 minutes; finally, it is graphitized at 2500℃, and finally, after surface treatment, water washing, sizing, drying at 120℃ and collecting, high-strength and high-modulus carbon fiber is obtained.

[0058] The number of hair fibers at the outlet of the graphite furnace was counted by an online camera. The number of hair fibers in the fiber was 28 every 30 hours. The tensile strength of the carbon fiber was 5.59 GPa and the modulus was 360 GPa.

[0059] [Example 5]

[0060] Preparation of polyacrylonitrile-based precursor: Wet spinning technology was used, and the spinning solution used (the mass ratio of acrylonitrile:itaconic acid:sodium methyl propylene sulfonate in the polyacrylonitrile copolymer was 95:4:1) had an intrinsic viscosity of 2.2 dL / g and a solid content of 20%. The spinning solution is precisely measured and filtered by a metering pump, extruded through a 48,000-hole spinneret, and sequentially enters four coagulation baths of dimethyl sulfoxide aqueous solution for coagulation at temperatures of 30°C, 45°C, 55°C, and 65°C, with a total draw ratio of 1.45 and concentrations of 85%, 67%, 53%, and 39%, respectively. It then undergoes three-stage hot water drawing at temperatures of 95°C, 97°C, and 99°C, with draw ratios of 1.55, 1.85, and 2.05, respectively. After oiling, it undergoes a two-stage drying and densification treatment without drawing, at temperatures of 135°C and 150°C, respectively. The steam drawing inlet speed is 25m / min, the steam pressure is 0.3MPa, and the draw ratio is 2.0 times. At this time, the steam drawing outlet tow tension is 19,200cN, and the tension of a single fiber is 0.4cN. Finally, after heat setting and winding, high-strength and high-modulus polyacrylonitrile carbon fiber precursor is obtained.

[0061] Preparation of high-strength and high-modulus carbon fiber: the obtained raw silk is passed through four pre-oxidation temperature zones in sequence, with temperatures of 180℃, 240℃, 270℃, and 300℃, and draw ratios of 1.01, 1.0, 1.0, and 0.99, respectively, and stays in each temperature zone for 40 minutes; then it is carbonized at a low temperature of 480℃, with a draw ratio of 1.03 and a residence time of 20 minutes; it is carbonized at a high temperature of 1400℃, with a draw ratio of 1.04 and a residence time of 20 minutes; finally, it is graphitized at 2500℃, and finally, after surface treatment, water washing, sizing, drying at 120℃ and collecting, high-strength and high-modulus carbon fiber is obtained.

[0062] The number of hair fibers at the outlet of the graphite furnace was counted by an online camera. The number of hair fibers in the fiber was 22 every 30 hours. The tensile strength of the carbon fiber was 5.63 GPa and the modulus was 371 GPa.

[0063] [Example 6]

[0064] Preparation of polyacrylonitrile-based precursor: Wet spinning technology was used, and the spinning solution used (the mass ratio of acrylonitrile:itaconic acid:sodium methyl propylene sulfonate in the polyacrylonitrile copolymer was 97:2:1) had an intrinsic viscosity of 2.4 dL / g and a solid content of 21%. The spinning solution is precisely measured and filtered by a metering pump, extruded through a 12,000-hole spinneret, and sequentially enters four coagulation baths containing dimethyl sulfoxide aqueous solution for coagulation at temperatures of 30°C, 50°C, 70°C, and 75°C, with a total draw ratio of 1.55 and concentrations of 85%, 67%, 53%, and 39%, respectively. The solution then undergoes three-stage hot water drawing at temperatures of 96°C, 96°C, and 99°C, with draw ratios of 1.45, 1.65, and 1.75, respectively. After oiling, the solution undergoes a two-stage drying and densification treatment without drawing, at temperatures of 125°C and 135°C, respectively. The steam drawing inlet speed is 15m / min, the steam pressure is 0.38MPa, and the draw ratio is 2.5 times. At this time, the steam drawing outlet tow tension is 4080cN, and the tension of a single fiber is 0.34cN. Finally, after heat setting and winding, high-strength and high-modulus polyacrylonitrile carbon fiber precursor is obtained.

[0065] Preparation of high-strength and high-modulus carbon fiber: the obtained raw silk is passed through four pre-oxidation temperature zones in sequence, with temperatures of 180℃, 240℃, 270℃, and 300℃, and draw ratios of 1.01, 1.0, 1.0, and 0.99, respectively, and stays in each temperature zone for 40 minutes; then it is carbonized at a low temperature of 480℃, with a draw ratio of 1.03 and a residence time of 20 minutes; it is carbonized at a high temperature of 1400℃, with a draw ratio of 1.04 and a residence time of 20 minutes; finally, it is graphitized at 2500℃, and finally, after surface treatment, water washing, sizing, drying at 120℃ and collecting, high-strength and high-modulus carbon fiber is obtained.

[0066] The number of hair fibers at the outlet of the graphite furnace was counted by an online camera. The number of hair fibers in the fiber was 8 every 30 hours. The tensile strength of the carbon fiber was 5.54 GPa and the modulus was 373 GPa.

[0067] [Comparative Example 1]

[0068] Preparation of polyacrylonitrile-based precursor: Wet spinning technology was used, and the spinning solution used (obtained by polymerization according to Example 1 of Chinese patent CN110684149A) had an intrinsic viscosity of 2.5 dL / g and a solid content of 18%. The spinning solution is precisely measured and filtered by a metering pump, extruded through a 3000-hole spinneret, and sequentially enters four coagulation baths of dimethyl sulfoxide aqueous solution for coagulation at temperatures of 35°C, 55°C, 60°C, and 70°C, with a total draw ratio of 2.0 and concentrations of 85%, 67%, 53%, and 39%, respectively. It then undergoes three-stage hot water drawing at temperatures of 95°C, 96°C, and 99°C, with draw ratios of 1.84, 2.15, and 2.68, respectively. After oiling, it undergoes a two-stage drying and densification treatment without drawing, at temperatures of 115°C and 125°C, respectively. The steam drawing inlet speed is 40m / min, the steam pressure is 0.27MPa, and the draw ratio is 2.5 times. At this time, the steam drawing outlet tow tension is 1740cN, and the tension of a single fiber is 0.58cN. Finally, after heat setting and winding, high-strength and high-modulus polyacrylonitrile carbon fiber precursor is obtained.

[0069] Preparation of high-strength and high-modulus carbon fiber: the obtained raw silk is passed through four pre-oxidation temperature zones in sequence, with temperatures of 180℃, 240℃, 270℃, and 300℃, and draw ratios of 1.01, 1.0, 1.0, and 0.99, respectively, and stays in each temperature zone for 40 minutes; then it is carbonized at a low temperature of 700℃, with a draw ratio of 1.03 and a residence time of 20 minutes; it is carbonized at a high temperature of 1500℃, with a draw ratio of 1.04 and a residence time of 20 minutes; finally, it is graphitized at 2500℃, and finally, after surface treatment, water washing, sizing, drying at 120℃ and collecting, high-strength and high-modulus carbon fiber is obtained.

[0070] The number of hair fibers at the outlet of the graphite furnace was counted by an online camera. The number of hair fibers in the fiber was 35 every 30 hours. The tensile strength of the carbon fiber was 5.27 GPa and the modulus was 352 GPa.

[0071] [Comparative Example 2]

[0072] Preparation of polyacrylonitrile-based precursor: Wet spinning technology was used, and the spinning solution used (obtained by polymerization according to Example 1 of Chinese patent CN110684149A) had an intrinsic viscosity of 2.5 dL / g and a solid content of 18%. The spinning solution is precisely measured and filtered by a metering pump, extruded through a 3000-hole spinneret, and sequentially enters four coagulation baths of dimethyl sulfoxide aqueous solution for coagulation at temperatures of 35°C, 55°C, 60°C, and 70°C, with a total draw ratio of 2.0 and concentrations of 85%, 67%, 53%, and 39%, respectively. It then undergoes three-stage hot water drawing at temperatures of 95°C, 96°C, and 99°C, with draw ratios of 1.84, 2.15, and 2.68, respectively. After oiling, it undergoes a two-stage drying and densification treatment without drawing, at temperatures of 115°C and 125°C, respectively. The steam drawing inlet speed is 40m / min, the steam pressure is 0.35MPa, and the draw ratio is 2.5 times. At this time, the steam drawing outlet tow tension is 1050cN, and the tension of a single fiber is 0.35cN. Finally, after heat setting and winding, high-strength and high-modulus polyacrylonitrile carbon fiber precursor is obtained.

[0073] Preparation of high-strength and high-modulus carbon fiber: the obtained raw silk is passed through four pre-oxidation temperature zones in sequence, with temperatures of 180℃, 240℃, 270℃, and 300℃, and draw ratios of 1.01, 1.0, 1.0, and 0.99, respectively, and stays in each temperature zone for 40 minutes; then it is carbonized at a low temperature of 700℃, with a draw ratio of 1.03 and a residence time of 20 minutes; it is carbonized at a high temperature of 1500℃, with a draw ratio of 1.04 and a residence time of 20 minutes; finally, it is graphitized at 2500℃, and finally, after surface treatment, water washing, sizing, drying at 120℃ and collecting, high-strength and high-modulus carbon fiber is obtained.

[0074] The number of hair fibers at the graphite furnace outlet was counted by an online camera. The number of hair fibers in the fiber was 55 every 30 hours. The tensile strength of the carbon fiber was 5.24 GPa and the modulus was 349 GPa.

[0075] [Comparative Example 3]

[0076] Preparation of polyacrylonitrile-based precursor: Wet spinning technology was used, and the spinning solution used (polyacrylonitrile copolymer was the same as in Example 2) had an intrinsic viscosity of 2.0 dL / g and a solid content of 19%. The spinning solution is precisely measured and filtered by a metering pump, extruded through a 6000-hole spinneret, and sequentially enters four coagulation baths of dimethyl sulfoxide aqueous solution for coagulation at temperatures of 30°C, 50°C, 55°C, and 60°C, with a total draw ratio of 1.95 and concentrations of 85%, 67%, 53%, and 39%, respectively. It then undergoes three-stage hot water drawing at temperatures of 97°C, 98°C, and 99°C, with draw ratios of 1.65, 1.90, and 2.25, respectively. After oiling, it undergoes a two-stage drying and densification treatment without drawing, at temperatures of 118°C and 120°C, respectively. The steam drawing inlet speed is 35m / min, the steam pressure is 0.55MPa, and the draw ratio is 3.0 times. At this time, the steam drawing outlet tow tension is 2880cN, and the tension of a single fiber is 0.48cN. Finally, after heat setting and winding, high-strength and high-modulus polyacrylonitrile carbon fiber precursor is obtained.

[0077] Preparation of high-strength and high-modulus carbon fiber: the obtained raw silk is passed through four pre-oxidation temperature zones in sequence, with temperatures of 180℃, 240℃, 270℃, and 300℃, and draw ratios of 1.01, 1.0, 1.0, and 0.99, respectively, and stays in each temperature zone for 40 minutes; then it is carbonized at a low temperature of 480℃, with a draw ratio of 1.03 and a residence time of 20 minutes; it is carbonized at a high temperature of 1400℃, with a draw ratio of 1.04 and a residence time of 20 minutes; finally, it is graphitized at 2500℃, and finally, after surface treatment, water washing, sizing, drying at 120℃ and collecting, high-strength and high-modulus carbon fiber is obtained.

[0078] The number of hair fibers at the graphite furnace outlet was counted by an online camera. The number of hair fibers in the fiber was 34 every 30 hours. The tensile strength of the carbon fiber was 5.07 GPa and the modulus was 347 GPa.

[0079] [Comparative Example 4]

[0080] Preparation of polyacrylonitrile-based precursor: Wet spinning technology was used, and the spinning solution used (polyacrylonitrile copolymer was the same as in Example 6) had an intrinsic viscosity of 2.4 dL / g and a solid content of 21%. The spinning solution is precisely measured and filtered by a metering pump, extruded through a 12,000-hole spinneret, and sequentially enters four coagulation baths containing dimethyl sulfoxide aqueous solution for coagulation at temperatures of 30°C, 50°C, 70°C, and 75°C, with a total draw ratio of 1.55 and concentrations of 85%, 67%, 53%, and 39%, respectively. The solution then undergoes three-stage hot water drawing at temperatures of 96°C, 96°C, and 99°C, with draw ratios of 1.45, 1.65, and 1.75, respectively. After oiling, the solution undergoes a two-stage drying and densification treatment without drawing, at temperatures of 125°C and 135°C, respectively. The steam drawing inlet speed is 15m / min, the steam pressure is 0.27MPa, and the draw ratio is 2.5 times. At this time, the steam drawing outlet tow tension is 5040cN, and the tension of a single fiber is 0.42cN. Finally, the high-strength and high-modulus polyacrylonitrile carbon fiber precursor is obtained after heat setting and winding.

[0081] Preparation of high-strength and high-modulus carbon fiber: the obtained raw silk is passed through four pre-oxidation temperature zones in sequence, with temperatures of 180℃, 240℃, 270℃, and 300℃, and draw ratios of 1.01, 1.0, 1.0, and 0.99, respectively, and stays in each temperature zone for 40 minutes; then it is carbonized at a low temperature of 480℃, with a draw ratio of 1.03 and a residence time of 20 minutes; it is carbonized at a high temperature of 1400℃, with a draw ratio of 1.04 and a residence time of 20 minutes; finally, it is graphitized at 2500℃, and finally, after surface treatment, water washing, sizing, drying at 120℃ and collecting, high-strength and high-modulus carbon fiber is obtained.

[0082] The number of hair fibers at the outlet of the graphite furnace was counted by an online camera. The number of hair fibers in the fiber was 51 every 30 hours. The tensile strength of the carbon fiber was 4.68 GPa and the modulus was 340 GPa.

[0083] [Comparative Example 5]

[0084] Preparation of polyacrylonitrile-based precursor: Wet spinning technology is used, and the intrinsic viscosity of the spinning solution used (the mass ratio of acrylonitrile: itaconic acid: sodium methyl propylene sulfonate in the polyacrylonitrile copolymer is 98:1:1) is 3.5dL / g, and the solid content is 18%. The spinning solution is accurately measured and filtered by a metering pump, extruded through a 6000-hole spinneret, and sequentially enters four coagulation baths of dimethyl sulfoxide aqueous solution for coagulation. The temperatures are 26°C, 30°C, 40°C, and 50°C, respectively, with a total draft ratio of 1.32 and concentrations of 85%, 67%, 53%, and 39%, respectively; then it undergoes four levels of hot water drawing at temperatures of 95°C, 96°C, 97°C, and 99°C, with draft ratios of 1.38, 1.40, and 1.60, respectively. 1.40, 1.48, 1.50; after oiling, two-stage drying and densification treatment is carried out without stretching, and the temperatures are 110℃ and 120℃ respectively; the steam stretching inlet speed is 25m / min, the steam pressure is 0.3MPa, and the stretching ratio is 2.5 times. At this time, the steam stretching outlet bundle tension is 3000cN, and the tension of a single fiber is 0.5cN; finally, after heat setting and winding, high-strength and high-modulus polyacrylonitrile carbon fiber precursor is obtained.

[0085] Preparation of high-strength and high-modulus carbon fiber: the obtained raw silk is passed through four pre-oxidation temperature zones in sequence, with temperatures of 180℃, 240℃, 270℃, and 300℃, and draw ratios of 1.01, 1.0, 1.0, and 0.99, respectively, and stays in each temperature zone for 40 minutes; then it is carbonized at a low temperature of 480℃, with a draw ratio of 1.03 and a residence time of 20 minutes; it is carbonized at a high temperature of 1400℃, with a draw ratio of 1.04 and a residence time of 20 minutes; finally, it is graphitized at 2800℃, and finally, after surface treatment, water washing, sizing, drying at 120℃ and collecting, high-strength and high-modulus carbon fiber is obtained.

[0086] The number of hair fibers at the outlet of the graphite furnace was counted by an online camera. The number of hair fibers in the fiber was 150 every 30 hours. The tensile strength of the carbon fiber was 4.56 GPa and the modulus was 345 GPa.

[0087] It can be seen from Example 1 and Comparative Examples 1-2 that under the same conditions, the relationship between the steam drawing inlet velocity and the steam drawing outlet yarn tension during the steam drawing process in Comparative Examples 1-2 does not satisfy the following relationship: 0.0024x+0.2975≤y≤-1.9×10 -5 x 2 +0.0043x+0.3487, so the number of hairs is significantly increased compared with Example 1, and the mechanical properties of the carbon fiber are also reduced compared with Example 1;

[0088] It can be seen from the comparison between Example 2 and Comparative Example 3, and between Example 6 and Comparative Example 4 that under the same conditions, only when the relationship between the steam drawing inlet velocity and the steam drawing outlet yarn tension during the steam drawing process satisfies the relationship of the present invention (0.0024x+0.2975≤y≤-1.9×10 -5 x 2 +0.0043x+0.3487) can more effectively reduce the number of hairs and improve the mechanical properties of carbon fiber.

[0089] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

[0090] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of conflict, the definitions in this specification shall prevail.

[0091] When this specification uses the prefix "well known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, the objects introduced by the prefix include those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become generally recognized in the art to be suitable for similar purposes.

[0092] The endpoints and any values ​​of the ranges disclosed in this application document 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 each range, the endpoint values ​​of each range and a separate point value, and the separate point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0093] In the context of this specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

[0094] Moreover, any embodiment described herein may be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas thus formed shall be deemed as part of the original disclosure or original record of the present invention, and shall not be regarded as new content that has not been disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

Claims

1. A method for preparing high-strength and high-modulus polyacrylonitrile-based precursor yarn, comprising a steam drawing step, wherein the relationship between the steam drawing inlet velocity and the steam drawing outlet precursor yarn tension satisfies the following relationship: 0.0024x+0.2975≤y≤-1.9×10 -5 x 2 +0.0043x+0.3487 in, y represents the tension of a single fiber at the outlet of steam drawing, in cN; x represents the inlet speed of steam drawing, in m / min.

2. The preparation method according to claim 1, wherein: The steam drawing inlet speed is 5-80 m / min, preferably 8-65 m / min.

3. The preparation method according to claim 1, wherein: The steam pressure (unit MPa) a for steam drawing is 0.15-0.18 times of the drawing ratio (unit times) b, wherein the drawing ratio is 1.5-3.0 times, preferably 1.8-2.7 times.

4. The preparation method according to any one of claims 1 to 3, wherein: The preparation method adopts a wet spinning process, preferably including the steps of subjecting the polyacrylonitrile stock solution to coagulation molding, coagulation drawing, hot water drawing, water washing, oiling, drying and densification, steam drawing, and steam heat setting to obtain the high-strength and high-modulus polyacrylonitrile-based precursor.

5. The preparation method according to claim 4, wherein: The polyacrylonitrile stock solution has a polyacrylonitrile solid content of 10-40%, preferably 17-22%, and / or an intrinsic viscosity of the stock solution of 1.0-5.0 dL / g, preferably 1.7-2.5 dL / g.

6. The preparation method according to claim 4, wherein: The coagulation and drawing process includes at least three stages; preferably, In the coagulation and drawing, the temperature of each coagulation and drawing is 25-95° C., preferably 30-80° C., and / or the total drawing ratio is 1.5-3.5, preferably 1-2.

7. The preparation method according to claim 4, wherein: The hot water drawing comprises at least 3 stages; and / or, The temperature of the hot water drawing is 90-100°C, preferably 95-99°C; preferably, The total stretching ratio of the hot water stretching is greater than or equal to 3.5 times, preferably greater than or equal to 4.5 times, and the third hot water stretching ratio is greater than or equal to 1.3 times, preferably 1.6-2.7 times.

8. The preparation method according to claim 4, wherein: The oiling and drying densification are at least two stages; and / or, The drying and densification temperature is 90-150°C without applying stretching. Preferably, the drying and densification temperature is 100-140°C.

9. The preparation method according to claim 1, wherein: The number of strands in a single bundle of the high-strength and high-modulus polyacrylonitrile-based precursor yarn is 1,000-320,000.

10. A polyacrylonitrile-based precursor obtained by the preparation method according to any one of claims 1 to 9.

11. A high-strength and high-modulus carbon fiber prepared from the polyacrylonitrile-based precursor according to claim 10; preferably, the high-strength and high-modulus carbon fiber is obtained by subjecting the polyacrylonitrile precursor to steps including pre-oxidation, carbonization, and graphitization.

12. The high-strength and high-modulus carbon fiber according to claim 11, wherein: The pre-oxidation temperature is 180-300° C.; and / or, The carbonization is divided into low-temperature carbonization and high-temperature carbonization; preferably, the temperature of the low-temperature carbonization is 300-700°C; and / or, the temperature of the high-temperature carbonization is 1000-1500°C; and / or, The graphitization temperature is 2200-2800°C.