A method for producing an ultrahigh-strength ultrahigh-modulus carbon fiber

Abstract

The application relates to the technical field of carbon fiber production, in particular to a preparation method of super-high-strength super-high-modulus carbon fiber. The preparation method of the super-high-strength super-high-modulus carbon fiber comprises the following steps: first, preparing super-high-molecular-weight polyacrylonitrile by adopting a water-phase suspension method; then, preparing high-viscosity homogeneous spinning stock solution containing UHMWPAN by adopting a solution polymerization method; then, preparing fine denier and high-orientation polyacrylonitrile filaments by adopting a dry-wet spinning method and through multi-stage drafting; finally, preparing T1100-grade carbon fiber through pre-oxidation and carbonization. The preparation method provided by the application realizes the synthesis of T1100 super-high-strength super-high-modulus carbon fiber grade, achieves the purpose of localization of the super-high-strength super-high-modulus carbon fiber, and can meet the use requirements in high-end fields such as aerospace and national defense and military industry.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber production technology, and in particular to a method for preparing ultra-high strength and ultra-high modulus carbon fiber. Background Technology

[0002] Domestically, T300 and T700 carbon fibers have been industrialized, but T700 production is still mainly based on 12K. In addition, T800 and M40J carbon fibers have also achieved engineered production. Internationally, in the latest technological advancements, carbon fiber companies such as Toray Industries of Japan and Hexcel of the United States have continuously strengthened their research and development of key technologies, successively achieving large-scale production and commercialization of ultra-high-strength carbon fibers such as T1000GB, T1100GJ, and T1200, which can be mainly used in aerospace, defense, and other fields.

[0003] Domestic companies such as Zhongfu Shenying and Hengshen have made some breakthroughs in the preparation technology of T1000-grade carbon fiber, but large-scale stable production has not yet been fully achieved. Overall, in high-end fields such as aerospace and defense, the quality and stability of domestic carbon fiber products are unsatisfactory, and the quality of carbon fiber cannot meet the application requirements of these fields. Therefore, there is an urgent need for a method for preparing ultra-high strength and ultra-high modulus carbon fiber. Summary of the Invention

[0004] To address the issues of poor quality and stability in existing domestically produced carbon fibers, this invention provides a method for preparing ultra-high strength and ultra-high modulus carbon fibers.

[0005] The present invention provides a method for preparing ultra-high strength and ultra-high modulus carbon fibers, which is achieved through the following technical solution:

[0006] A method for preparing ultra-high strength and ultra-high modulus carbon fiber includes the following steps:

[0007] S1, ultra-high molecular weight polyacrylonitrile was prepared by aqueous suspension method;

[0008] S2 is a high-viscosity homogeneous spinning solution containing UHMWPAN, prepared by solution polymerization using ultra-high molecular weight polyacrylonitrile, azobisisobutyronitrile, acrylonitrile and methyl 3-amide-3-butenoate as raw materials.

[0009] S3, the high-viscosity homogeneous spinning solution in S2 is subjected to dry-jet wet spinning, multi-stage water washing and stretching, oiling and drying, two-stage steam stretching, and heat setting to obtain fine denier, highly oriented carbon fiber precursor.

[0010] S4 is used to prepare T1100 grade carbon fiber through pre-oxidation and carbonization.

[0011] Preferably, in step S1, ultra-high molecular weight polyacrylonitrile (UHMWPA) is prepared using an aqueous suspension method: polyvinyl alcohol (PVA) aqueous solution is used as a dispersant, azobisisobutyronitrile (AIBN) as an initiator, and acrylonitrile AN and methyl 3-amido-3-butenoate (ABM) are used as monomers. The mass ratio of acrylonitrile AN to methyl 3-amido-3-butenoate (ABM) is (98.8–99.2):(0.8–1.2). The monomer concentration is 22–26 wt%, the initiator accounts for 0.01–0.04 wt% of the total monomer mass, and the PVA content in the PVA aqueous solution is 0.2–0.5 wt%. The weight-average molecular weight is 1.4 × 10⁻⁶. 6 ~1.9×10 6 g / mol of ultra-high molecular weight polyacrylonitrile.

[0012] The preparation method provided by this invention realizes the synthesis of T1100 ultra-high strength and ultra-high modulus carbon fiber, achieving the goal of domestic production of ultra-high strength and ultra-high modulus carbon fiber, which can meet the needs of high-end fields such as aerospace and defense.

[0013] Preferably, the specific steps for preparing ultra-high molecular weight polyacrylonitrile by aqueous suspension in S1 are as follows:

[0014] S1.1, add 320 parts of a polyvinyl alcohol (PVA) aqueous solution with a PVA concentration of 0.2-0.5 wt% to the polymerization reactor and stir at 85±2℃ for 3-5 hours until it is completely dissolved;

[0015] S1.2, cool to 50-70℃, add accurately measured acrylonitrile AN, methyl 3-amide-3-butenoate ABM, and azobisisobutyronitrile AIBN, and polymerize under nitrogen protection for 10-15 hours;

[0016] S1.3, after the reaction was completed, the product was filtered, washed with water, and dried to obtain a weight-average molecular weight of 1.4 × 10⁻⁶. 6 ~1.9×10 6 g / mol of ultra-high molecular weight polyacrylonitrile.

[0017] In the aqueous suspension polymerization process for synthesizing ultra-high molecular weight polyacrylonitrile (UHMWPA), acrylonitrile (AN) and methyl 3-amido-3-butenoate (ABM) are used as mixed monomers. Copolymerization of an appropriate amount of methyl 3-amido-3-butenoate (ABM) can improve the flexibility of the PAN molecular chain, enhance spinning processability, and increase the uniformity of the precursor fiber structure. Water-soluble polyvinyl alcohol (PVA) is used in the suspension polymerization system to prevent monomer droplet / particle aggregation and ensure stable particle dispersion. Deionized water serves as the suspension phase, transferring heat, controlling temperature, and isolating the polymerized particles. Thermal decomposition of azobisisobutyronitrile (AIBN) generates free radicals, initiating free radical polymerization of the AN / ABM monomers. A low initiator dosage (0.01-0.04 wt% of AIBN) is beneficial for obtaining UHMWPA products.

[0018] Preferably, the specific steps for preparing the high-viscosity homogeneous spinning solution containing UHMWPAN by solution polymerization in step S2 are as follows:

[0019] S2.1, take 80-100 parts of the ultra-high molecular weight polyacrylonitrile prepared in S1 and 480-600 parts of dimethyl sulfoxide (DMSO) and add them to the polymerization reactor. Heat and stir to completely dissolve the ultra-high molecular weight polyacrylonitrile in DMSO.

[0020] S2.2, the temperature is adjusted to 50-70℃, using azobisisobutyronitrile (AIBN) as the initiator, acrylonitrile (AN) and methyl 3-amido-3-butenoate (ABM) as monomers, the mass ratio of acrylonitrile (AN) to methyl 3-amido-3-butenoate (ABM) is (98.8~99.2):(0.8-1.2), the monomer concentration is 22-26wt%, and the initiator accounts for 0.01-0.04wt% of the total monomer mass. Under nitrogen protection, the polymerization reaction is carried out at 50-70℃ and 60-240rpm for 20-26h.

[0021] S2.3, after the polymerization reaction is completed, is filtered, vacuum de-singed, and de-bubbled to obtain a high-viscosity homogeneous spinning solution.

[0022] Preferably, the parameters for dry-jet wet spinning in S3 are as follows: the polymer content in the high-viscosity homogeneous spinning solution is 18-29 wt%, the spinning solution temperature is 8-62℃, the air section distance is 5±0.5 mm, the DMSO content in the coagulation bath is 45-70 wt%, the coagulation bath temperature is 4-6℃, and the coagulation time is 0.5-2 min.

[0023] Preferably, the multi-stage washing and stretching process in S3 is as follows: the nascent fiber is stretched 6-12 times in the coagulation bath, the hot water stretching temperature is 60-95 ℃, the hot water stretching ratio is 3-5 times, the drying temperature is 140-160 ℃, the steam stretching ratio is 3-5 times, and the heat setting temperature is 130±5 ℃.

[0024] Preferably, the two-stage steam stretching process in S3 is as follows: steam stretching of 3-5 times is carried out under the conditions of saturated steam pressure of 0.3-0.4MPa and steam chamber temperature of 125-135℃.

[0025] More preferably, the steam stretching is a two-stage steam stretching, with the first-stage steam stretching being 1.6-2.4 times and the second-stage steam stretching being 1.2-3.4 times.

[0026] Preferably, the oil drying process in S3 is as follows: the drying temperature is 150±5℃, two-stage hot air drying, and the total drying time is 4-6 minutes.

[0027] Preferably, the heat setting process in S3 is as follows: temperature is 130±2℃, setting tension is 5±0.5N, heat setting time is 230-250s, and shrinkage rate is ≤2%.

[0028] The finished filaments prepared by S3 have a single filament diameter of 7.5~8.5μm, an orientation degree of 93%~95%, and a single filament strength ≥6.5cN / dtex.

[0029] Preferably, the pre-oxidation process in S4 is as follows: the finished yarn after heat setting is subjected to pre-oxidation treatment in seven temperature zones: 180±5℃, 200±5℃, 220±5℃, 240±5℃, 250±5℃, 260±5℃, and 270±5℃. During the stabilization process, the roller speed is 140-160mm / min, and the total residence time is 130-150min, thereby obtaining pre-oxidized fiber.

[0030] Preferably, the carbonization process in S4 is as follows: the pre-oxidized fiber is placed in a nitrogen atmosphere and subjected to continuous low-temperature carbonization, high-temperature carbonization, and graphitization treatments, with a total carbonization time of 4-6 minutes; the low-temperature carbonization temperature range is 400-800℃, and the low-temperature carbonization draw ratio is 14-16%; the high-temperature carbonization temperature range is 1000-1400℃, and the high-temperature carbonization draw ratio is -3 to -1%; the semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, with a graphitization temperature of 2600±50℃ and a graphitization tension of 6-10N, and the semi-finished carbon fiber is subjected to graphitization treatment for 10-20 seconds to prepare T1100 grade carbon fiber, wherein the diameter of the T1100 grade carbon fiber is 7~9μm, the orientation degree is ≥94.5%, the strength is ≥6.1GPa, and the modulus is ≥390GPa.

[0031] The T1100 grade carbon fiber prepared by the above technical solution has a diameter of 7~9μm, an orientation degree of ≥94.5%, a strength of ≥6.1GPa, and a modulus of ≥390GPa.

[0032] More preferably, in the S4 carbonization process, the semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, the graphitization temperature is 2600℃, the graphitization tension is 10N, and the semi-finished carbon fiber is graphitized for 15s to prepare T1100 grade carbon fiber.

[0033] The T1100 grade carbon fiber prepared by the above technical solution has a diameter of 7~9μm, an orientation degree of ≥94.5%, a strength of ≥6.2GPa, and a modulus of ≥410GPa.

[0034] In summary, this invention has the following advantages: By introducing UHWMPAN and bifunctional comonomers, fine denier and highly oriented polyacrylonitrile precursor fibers are prepared through multi-stage high-ratio drawing. The effects of the introduction of UHWMPAN and bifunctional comonomers on the orientation, crystallinity, and porosity of the precursor fibers are studied in detail. Through synergistic research on the microscopic molecular structure and macroscopic morphological structure of the fibers, the mechanism by which ultra-high molecular weight polymers enhance the performance of the precursor fibers is revealed (UHWMPAN long-chain entanglement network inhibits slippage, MMPA amide / ester group synergistic plasticization + promotes cyano cyclization; multi-stage drawing induces high axial orientation of molecular chains, resulting in more complete crystallization and reduced porosity), thus obtaining a controllable preparation method for high-performance carbon fiber precursor fibers. Detailed Implementation

[0035] To further understand the inventiveness and technical advancements of this invention, the preferred embodiments of this invention will be discussed in detail below with reference to examples and comparative examples.

[0036] Example: A method for preparing ultra-high strength and ultra-high modulus carbon fiber, comprising the following steps:

[0037] S1. Ultra-high molecular weight polyacrylonitrile (UHMWPA) was prepared by an aqueous suspension method: using polyvinyl alcohol (PVA) aqueous solution as a dispersant, azobisisobutyronitrile (AIBN) as an initiator, and acrylonitrile AN and methyl 3-amido-3-butenoate (ABM) as monomers. The mass ratio of acrylonitrile AN to methyl 3-amido-3-butenoate (ABM) was (98.8–99.2):(0.8–1.2), the monomer concentration was 22–26 wt%, the initiator accounted for 0.01–0.04 wt% of the total monomer mass, and the PVA content in the PVA aqueous solution was 0.2–0.5 wt%. A weight-average molecular weight of 1.4 × 10⁻⁶ was obtained by the aqueous suspension method. 6 ~1.9×10 6 g / mol of ultra-high molecular weight polyacrylonitrile, specifically,

[0038] S1.1, add 320 parts of a polyvinyl alcohol (PVA) aqueous solution with a PVA concentration of 0.2-0.5 wt% to the polymerization reactor and stir at 85±2℃ for 3-5 hours until it is completely dissolved;

[0039] S1.2, cool to 50-70℃, add accurately measured acrylonitrile AN, methyl 3-amide-3-butenoate ABM, and azobisisobutyronitrile AIBN, and polymerize under nitrogen protection for 10-15 hours;

[0040] S1.3, after the reaction was completed, the product was filtered, washed with water, and dried to obtain a weight-average molecular weight of 1.4 × 10⁻⁶. 6 ~1.9×10 6 g / mol of ultra-high molecular weight polyacrylonitrile;

[0041] S2, using ultra-high molecular weight polyacrylonitrile, azobisisobutyronitrile, acrylonitrile, and methyl 3-amide-3-butenoate as raw materials, yields a high-viscosity homogeneous spinning solution containing UHMWPAN via solution polymerization:

[0042] S2.1 Take 80-100 parts of the ultra-high molecular weight polyacrylonitrile prepared in S1 and 480-600 parts of dimethyl sulfoxide (DMSO) and add them to the polymerization reactor. Heat the reactor to 50±1℃ and let it swell for 3-6 hours. Adjust the temperature to 75±1℃ and stir at 60-240 rpm for 6-12 hours to completely dissolve the ultra-high molecular weight polyacrylonitrile in DMSO.

[0043] S2.2, the temperature is adjusted to 50-70℃, azobisisobutyronitrile (AIBN) is used as the initiator, acrylonitrile (AN) and methyl 3-amido-3-butenoate (ABM) are used as monomers, the mass ratio of acrylonitrile (AN) and methyl 3-amido-3-butenoate (ABM) is (98.8~99.2):(0.8-1.2), the monomer concentration is 22-26wt%, and the initiator accounts for 0.01-0.04wt% of the total monomer mass. The polymerization reaction is carried out under nitrogen protection at 50-70℃ and 60-240rpm for 20-26h.

[0044] S2.3, after the polymerization reaction is completed, a high-viscosity homogeneous spinning solution is obtained by filtration, vacuum degassing, and defoaming.

[0045] S3, the high-viscosity homogeneous spinning solution in S2 is subjected to dry-jet wet spinning, multi-stage water washing and stretching, oiling and drying, two-stage steam stretching, and heat setting to obtain fine denier, highly oriented carbon fiber precursor.

[0046] The parameters for dry-jet wet spinning are as follows: the polymer content in the high-viscosity homogeneous spinning solution is 18-29 wt%, the spinning solution temperature is 60±2℃, the air section distance is 5±0.5 mm, the DMSO content in the coagulation bath is 45-70 wt%, the coagulation bath temperature is 5±1℃, and the coagulation time is 0.5-2 min.

[0047] The multi-stage washing and stretching process is as follows: the nascent fiber is stretched 6-12 times in the coagulation bath, the hot water stretching temperature is 60-95 ℃, the hot water stretching ratio is 3-5 times, the drying temperature is 140-160 ℃, the steam stretching ratio is 3-5 times, and the heat setting temperature is 130±5℃.

[0048] The specific oiling and drying process is as follows: the drying temperature is 150±5℃, two-stage hot air drying, and the total drying time is 4-6 minutes.

[0049] The two-stage steam drawing process is as follows: steam drawing is carried out at a saturated steam pressure of 0.3-0.4 MPa and a steam chamber temperature of 125-135℃ for 3-5 times;

[0050] The heat setting process is as follows: temperature is 130±2℃, setting tension is 5±0.5N, heat setting time is 230-250s, shrinkage rate is ≤2%, and the single filament diameter of the finished yarn after heat setting is 7.5~8.5μm, the orientation degree is 93%~95%, and the single filament strength is ≥6.5cN / dtex.

[0051] S4, prepared as T1100 grade carbon fiber through pre-oxidation and carbonization:

[0052] The pre-oxidation process is as follows: the finished yarn after heat setting is subjected to pre-oxidation treatment in seven temperature zones: 180±5℃, 200±5℃, 220±5℃, 240±5℃, 250±5℃, 260±5℃, and 270±5℃. During the stabilization process, the roller speed is 140-160mm / min and the total residence time is 130-150min. Pre-oxidized fiber is obtained, and a stable heat-resistant annular trapezoidal structure is formed on the fiber.

[0053] The carbonization process is as follows: Pre-oxidized fibers are placed in a nitrogen atmosphere and subjected to continuous low-temperature carbonization, high-temperature carbonization, and graphitization treatments, with a total carbonization time of 4-6 minutes. The low-temperature carbonization temperature range is 400-800℃, and the draw ratio is 15±1%. The high-temperature carbonization temperature range is 1000-1400℃. The semi-finished carbon fibers after high-temperature carbonization are then placed in an ultra-pure nitrogen atmosphere, with a graphitization temperature of 2550-2650℃ and a graphitization tension of 6-10N, for 10-20 seconds to prepare T1100 grade carbon fibers. The prepared T1100 grade carbon fibers have a diameter of 7-9 μm, an orientation degree ≥94.5%, a strength ≥6.0 GPa, and a modulus ≥390 GPa, meeting the requirements of high-end applications in aerospace and defense industries.

[0054] Example 1: A method for preparing ultra-high strength and ultra-high modulus carbon fiber, comprising the following steps:

[0055] S1, ultra-high molecular weight polyacrylonitrile was prepared by an aqueous suspension method, as detailed below:

[0056] S1.1, 320 parts of a 0.25wt% polyvinyl alcohol PVA aqueous solution were added to a polymerization reactor and stirred at 85°C for 4.0 h to completely dissolve the PVA in deionized water to obtain polyvinyl alcohol PVA water-soluble solution;

[0057] S1.2, polyvinyl alcohol (PVA) was dissolved in water and cooled to 60°C. Accurately metered acrylonitrile AN, methyl 3-amido-3-butenoate (ABM), and azobisisobutyronitrile (AIBN) were added, wherein the mass ratio of acrylonitrile AN to methyl 3-butenoate (ABM) was 99:1, the total concentration of acrylonitrile AN and methyl 3-butenoate (ABM) as monomers was 25 wt%, and AIBN accounted for 0.015 wt% of the total monomer mass. The polymerization reaction was carried out for 12 hours under nitrogen protection, maintaining 60°C and stirring at 100 rpm.

[0058] S1.3, after the reaction was completed, the product was filtered, washed with water, and dried to obtain a weight-average molecular weight of 1.72 × 10⁻⁶. 6 g / mol of ultra-high molecular weight polyacrylonitrile;

[0059] S2, using ultra-high molecular weight polyacrylonitrile, azobisisobutyronitrile, acrylonitrile, and methyl 3-amide-3-butenoate as raw materials, yields a high-viscosity homogeneous spinning solution containing UHMWPAN via solution polymerization:

[0060] S2.1, take 100 parts of the ultra-high molecular weight polyacrylonitrile prepared in S1 and 600 parts of dimethyl sulfoxide (DMSO) and add them to the polymerization reactor. Heat the reactor to 50°C and let it swell for 4.0 h. Adjust the temperature to 75°C and stir at 120 rpm for 8 h to completely dissolve the ultra-high molecular weight polyacrylonitrile in DMSO.

[0061] S2.2, with the temperature adjusted to 60℃, using azobisisobutyronitrile (AIBN) as the initiator, acrylonitrile (AN) and methyl 3-amido-3-butenoate (ABM) as monomers, the mass ratio of acrylonitrile (AN) to methyl 3-amido-3-butenoate (ABM) was 99:1, the total concentration of acrylonitrile (AN) and methyl 3-amido-3-butenoate (ABM) as monomers was 25wt%, and AIBN accounted for 0.015wt% of the total monomer mass. The polymerization reaction was carried out for 24 hours under nitrogen protection at 60℃ and 120rpm.

[0062] S2.3 After the polymerization reaction is completed, the solution is filtered, vacuum depolymerized, and degassed to obtain a high-viscosity homogeneous spinning solution with a polymer content of 23.6 wt%.

[0063] S3, the high-viscosity homogeneous spinning solution in S2 is subjected to dry-jet wet spinning, multi-stage water washing and stretching, oiling and drying, two-stage steam stretching, and heat setting to obtain fine denier, highly oriented carbon fiber precursor.

[0064] The parameters for dry-jet wet spinning are as follows: the polymer content in the high-viscosity homogeneous spinning solution is 23.6 wt%, the spinning solution temperature is 60 ℃, the air section distance is 5.0 mm, the DMSO content in the coagulation bath is 60 wt%, the coagulation bath temperature is 5 ℃, and the coagulation time is 1.0 min.

[0065] The multi-stage washing and stretching process is as follows: the nascent fiber is stretched 12 times in the coagulation bath, then stretched 1.4 times in a first-stage hot water stretching temperature of 75℃, stretched 1.4 times in a second-stage hot water stretching temperature of 85℃, and stretched 1.9 times in a third-stage hot water stretching temperature of 95℃, with a total hot water stretching multiple of 3.8 times;

[0066] The specific oiling and drying process is as follows: two-stage hot air drying at a drying temperature of 150℃ for 6 minutes;

[0067] The two-stage steam drawing process is as follows: two-stage steam drawing is carried out under the conditions of saturated steam pressure of 0.35MPa and steam chamber temperature of 138.2℃. The first stage steam drawing is 2.2 times, the fiber bundle stays for 8s, the second stage steam drawing is 1.8 times, and the total steam drawing multiple is 4.0 times.

[0068] The heat setting process is as follows: temperature is 130℃, setting tension is 5N, heat setting time is 4min, shrinkage rate is 1.52%, and the finished yarn after heat setting has a single filament diameter of 7.5μm, an orientation degree of 94.8%, and a single filament strength of 6.63cN / dtex.

[0069] S4, prepared as T1100 grade carbon fiber through pre-oxidation and carbonization:

[0070] The pre-oxidation process is as follows: the finished yarn after heat setting is pre-oxidized in seven temperature zones of 180℃, 200℃, 220℃, 240℃, 250℃, 260℃ and 270℃. During the stabilization process, the roller speed is 150mm / min and the total residence time is 140min to obtain pre-oxidized fiber.

[0071] The carbonization process is as follows: Pre-oxidized fibers are placed in a nitrogen atmosphere and subjected to continuous low-temperature carbonization, high-temperature carbonization, and graphitization treatments. The temperature interval for the low-temperature carbonization zones is 100℃, and the low-temperature carbonization zones are divided into five zones: 300℃, 400℃, 500℃, 600℃, and 700℃. The draw ratio for low-temperature carbonization is +15%, the tension is 2500 cN, and the low-temperature carbonization time is 2.5 min. The temperature interval for the high-temperature carbonization zones is 50℃, and the high-temperature carbonization zones consist of eight carbonization zones. The carbonization temperatures were 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, and 1350℃, with a high-temperature carbonization draw ratio of -1.5%, a tension of 3500cN, and a carbonization time of 3.0 min. The semi-finished carbon fibers after high-temperature carbonization were then placed in an ultra-pure nitrogen atmosphere, graphitized at 2600℃ with a graphitization tension of 10N, and graphitized for 15 s to prepare T1100 grade carbon fibers. The resulting carbon fiber monofilaments were fine in denier, had good uniformity, and showed no obvious stranding / adhesion; the surface was smooth and dense, with only very shallow axial texture (due to multi-stage drawing), and no large grooves, pores, or flaking defects. This indicates that the UHWMPAN long-chain + bifunctional monomer synergy resulted in uniform solidification and significantly fewer surface defects than conventional PAN precursor fibers.

[0072] The difference between Example 2 and Example 1 is that in the carbonization process, the semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, the graphitization temperature is 2600℃, the graphitization tension is 6N, and the semi-finished carbon fiber is graphitized for 10s to prepare T1100 grade carbon fiber.

[0073] The difference between Comparative Example 1 and Example 1 is that in the carbonization process, the semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, the graphitization temperature is 2600℃, the graphitization tension is 2N, and the semi-finished carbon fiber is graphitized for 20s to prepare T1100 grade carbon fiber.

[0074] The difference between Comparative Example 2 and Example 1 is that in the carbonization process, the semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, the graphitization temperature is 2400℃, the graphitization tension is 2N, and the semi-finished carbon fiber is graphitized for 10s to prepare T1100 grade carbon fiber.

[0075] The difference between Comparative Example 3 and Example 1 is that in the carbonization process, the semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, the graphitization temperature is 2400℃, the graphitization tension is 6N, and the semi-finished carbon fiber is graphitized for 15s to prepare T1100 grade carbon fiber.

[0076] The difference between Comparative Example 4 and Example 1 is that in the carbonization process, the semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, the graphitization temperature is 2400℃, the graphitization tension is 10N, and the semi-finished carbon fiber is graphitized for 20s to prepare T1100 grade carbon fiber.

[0077] The difference between Comparative Example 5 and Example 1 is that in the carbonization process, the semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, the graphitization temperature is 2800℃, the graphitization tension is 10N, and the semi-finished carbon fiber is graphitized for 10s to prepare T1100 grade carbon fiber.

[0078] The difference between Comparative Example 6 and Example 1 is that in the carbonization process, the semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, the graphitization temperature is 2800℃, the graphitization tension is 2N, and the semi-finished carbon fiber is graphitized for 15s to prepare T1100 grade carbon fiber.

[0079] The difference between Comparative Example 7 and Example 1 is that in the carbonization process, the semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, the graphitization temperature is 2800℃, the graphitization tension is 6N, and the semi-finished carbon fiber is graphitized for 20s to prepare T1100 grade carbon fiber.

[0080] Table 1: Performance parameters of T1100 grade carbon fiber in Examples 1-2 and Comparative Examples 1-7

[0081] Example 1 7.2 95.3 6.23 412 Example 2 7.3 94.5 6.15 396 Comparative Example 1 7.1 93.7 5.79 385 Comparative Example 2 7.4 90.8 5.82 364 Comparative Example 3 7.5 91.3 5.97 388 Comparative Example 4 7.5 92.1 5.71 391 Comparative Example 5 7.0 93.9 5.48 421 Comparative Example 6 7.1 92.7 5.62 417 Comparative Example 7 7.0 93.3 5.53 420

[0082] Based on Examples 1-2 and Comparative Examples 1-7, and referring to Table 1, it can be seen that the T1100 grade carbon fiber prepared by placing the semi-finished carbon fiber in an ultra-pure nitrogen atmosphere, with a graphitization temperature of 2600℃ and a graphitization tension of 6-10N for 10-15s exhibits the best overall performance. This results in a diameter of 7-9 μm, an orientation degree ≥94.5%, a strength ≥6.1 GPa, and a modulus ≥390 GPa. More preferably, a graphitization temperature of 2600℃, a graphitization tension of 10N, and a graphitization treatment of 15s for the semi-finished carbon fiber yields the best strength and modulus properties.

[0083] The difference between Example 3 and Example 1 is as follows: The carbonization process is as follows: The pre-oxidized fiber is placed in a nitrogen atmosphere and subjected to continuous low-temperature carbonization, high-temperature carbonization, and graphitization treatments. The low-temperature carbonization temperature interval is 150°C, and the low-temperature carbonization temperature zone is divided into four carbonization temperature zones: 300°C, 450°C, 650°C, and 800°C. The low-temperature carbonization draw ratio is +15%, the tension is 2500 cN, and the low-temperature carbonization time is 2.5 min. The high-temperature carbonization temperature interval is 100°C. The carbonization temperature range consists of six zones: 1000℃, 1100℃, 1200℃, 1300℃, 1400℃, and 1500℃. The high-temperature carbonization draw ratio is -1.5%, the tension is 3500cN, and the high-temperature carbonization time is 3.0min. The semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, with a graphitization temperature of 2600℃ and a graphitization tension of 10N. The semi-finished carbon fiber is then graphitized for 15s to prepare T1100 grade carbon fiber.

[0084] The difference between Example 4 and Example 1 is as follows: The carbonization process is as follows: The pre-oxidized fiber is placed in a nitrogen atmosphere and subjected to continuous low-temperature carbonization, high-temperature carbonization, and graphitization treatments. The low-temperature carbonization temperature interval is 150°C, and the low-temperature carbonization temperature zone is divided into four carbonization temperature zones: 300°C, 450°C, 650°C, and 800°C. The low-temperature carbonization draw ratio is +15%, the tension is 2500 cN, and the low-temperature carbonization time is 2.5 min. The high-temperature carbonization temperature interval is... The high-temperature carbonization process is divided into four zones: 1000℃, 1200℃, 1400℃, and 1600℃. The high-temperature carbonization draw ratio is -1.5%, the tension is 3500cN, and the high-temperature carbonization time is 3.0min. The semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, with a graphitization temperature of 2600℃ and a graphitization tension of 10N. The semi-finished carbon fiber is then graphitized for 15s to prepare T1100 grade carbon fiber.

[0085] The difference between Comparative Example 8 and Example 1 is as follows: The carbonization process is as follows: The pre-oxidized fiber is placed in a nitrogen atmosphere and subjected to continuous low-temperature carbonization, high-temperature carbonization, and graphitization treatments. The low-temperature carbonization temperature interval is 200°C, and the low-temperature carbonization temperature zone is divided into four carbonization temperature zones: 300°C, 500°C, 700°C, and 900°C. The low-temperature carbonization draw ratio is +15%, the tension is 2500 cN, and the low-temperature carbonization time is 2.5 min. The high-temperature carbonization temperature interval is 50°C, and the high-temperature carbonization temperature zone is divided into three carbonization temperature zones: 1000°C, 1400°C, and 1650°C. The high-temperature carbonization draw ratio is -1.5%, the tension is 3500 cN, and the high-temperature carbonization time is 2.5 min. The semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, and the graphitization temperature is 2600°C, the graphitization tension is 10 N, and the semi-finished carbon fiber is graphitized for 15 s to prepare T1100 grade carbon fiber.

[0086] The difference between Comparative Example 9 and Example 1 is as follows: The carbonization process is as follows: The pre-oxidized fiber is placed in a nitrogen atmosphere and subjected to continuous low-temperature carbonization, high-temperature carbonization, and graphitization treatments. The low-temperature carbonization temperature interval is 200°C, and the low-temperature carbonization temperature zone is divided into four carbonization temperature zones: 300°C, 500°C, 700°C, and 900°C. The low-temperature carbonization draw ratio is +15%, the tension is 2500 cN, and the low-temperature carbonization time is 2.5 min. The high-temperature carbonization temperature interval is 50°C, and the high-temperature carbonization temperature zone is divided into three carbonization temperature zones: 1000°C, 1400°C, and 1650°C. The high-temperature carbonization draw ratio is -1.0%, the tension is 4500 cN, and the high-temperature carbonization time is 2.5 min. The semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, and the graphitization temperature is 2600°C, the graphitization tension is 10 N, and the semi-finished carbon fiber is graphitized for 15 s to prepare T1100 grade carbon fiber.

[0087] The difference between Comparative Example 10 and Example 1 is as follows: The carbonization process is as follows: The pre-oxidized fiber is placed in a nitrogen atmosphere and subjected to continuous low-temperature carbonization, high-temperature carbonization, and graphitization treatments. The low-temperature carbonization temperature interval is 200°C, and the low-temperature carbonization temperature zone is divided into four carbonization temperature zones: 300°C, 500°C, 700°C, and 900°C. The low-temperature carbonization draw ratio is +15%, the tension is 2500 cN, and the low-temperature carbonization time is 2.5 min. The high-temperature carbonization temperature interval is 50°C, and the high-temperature carbonization temperature zone is divided into three carbonization temperature zones: 1000°C, 1500°C, and 1750°C. The high-temperature carbonization draw ratio is -1.5%, the tension is 3500 cN, and the high-temperature carbonization time is 2.5 min. The semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, and the graphitization temperature is 2600°C, the graphitization tension is 10 N, and the semi-finished carbon fiber is graphitized for 15 s to prepare T1100 grade carbon fiber.

[0088] Table 2: Performance parameters of T1100 grade carbon fiber in Examples 1, 3-4 and Comparative Examples 8-10

[0089] Example 1 7.2 95.3 6.23 412 Example 3 7.2 94.9 6.12 403 Example 4 7.3 94.5 6.04 392 Comparative Example 8 7.3 94.7 5.83 295 Comparative Example 9 7.4 95.3 6.10 308 Comparative Example 10 7.2 94.1 5.64 315

[0090] Based on Examples 1, 3-4, and Comparative Examples 8-9, and in conjunction with Table 2, the carbonization process is as follows: the pre-oxidized fiber is placed in a nitrogen atmosphere and subjected to continuous low-temperature carbonization, high-temperature carbonization, and graphitization treatments, with a total carbonization time of 4-6 minutes; the low-temperature carbonization temperature interval is 50-100℃, and the draw ratio of low-temperature carbonization is 1%; the high-temperature carbonization temperature interval is 50-200℃, and the draw ratio of high-temperature carbonization is -1 to -0.5%. The prepared T1100 grade carbon fiber has relatively superior strength and modulus properties.

[0091] The difference between Example 5 and Example 1 is as follows: The multi-stage water washing and stretching process is as follows: the nascent fiber is stretched 11 times in the coagulation bath, then stretched 1.6 times in the first stage of hot water stretching at a hot water stretching temperature of 75°C, stretched 1.6 times in the second stage of hot water stretching at a hot water stretching temperature of 85°C, and stretched 1.8 times in the third stage of hot water stretching at a hot water stretching temperature of 95°C. The total multiple of hot water stretching is 5.0 times.

[0092] The specific oiling and drying process is as follows: two-stage hot air drying at a drying temperature of 150℃ for 6 minutes;

[0093] The two-stage steam drawing process is as follows: two-stage steam drawing is carried out under the conditions of saturated steam pressure of 0.35MPa and steam chamber temperature of 138.2℃. The first stage of steam drawing is 2.0 times, and the fiber bundle stays for 8s. The second stage of steam drawing is 2.5 times, and the total steam drawing multiple is 4.5 times.

[0094] The heat setting process is as follows: the temperature is 130℃, the setting tension is 5N, the heat setting time is 4min, the shrinkage rate is 1.39%, the single filament diameter of the finished yarn after heat setting is 7.2μm, the orientation degree is 95.3%, and the single filament strength is 6.83cN / dtex. All other steps are the same.

[0095] The difference between Comparative Example 6 and Example 1 is that the multi-stage water washing and stretching process is as follows: the nascent fiber is stretched 10 times in the coagulation bath, then stretched 1.2 times in a first-stage hot water stretching temperature of 75°C, stretched 1.2 times in a second-stage hot water stretching temperature of 85°C, and stretched 2.6 times in a third-stage hot water stretching temperature of 95°C, with a total hot water stretching multiple of 4.0 times;

[0096] The specific oiling and drying process is as follows: two-stage hot air drying at a drying temperature of 150℃ for 6 minutes;

[0097] The two-stage steam drawing process is as follows: two-stage steam drawing is carried out under the conditions of saturated steam pressure of 0.35MPa and steam chamber temperature of 138.2℃. The first stage steam drawing is 1.8 times, the fiber bundle stays for 8s, the second stage steam drawing is 2.7 times, and the total steam drawing multiple is 4.5 times.

[0098] The heat setting process is as follows: the temperature is 130℃, the setting tension is 5N, the heat setting time is 4min, the shrinkage rate is 1.46%, the single filament diameter of the finished yarn after heat setting is 7.4μm, the orientation degree is 94.9%, and the single filament strength is 6.53cN / dtex. All other steps are the same.

[0099] The difference between Comparative Example 11 and Example 1 is that the multi-stage washing and stretching process is as follows: the nascent fibers are stretched 9 times in the coagulation bath, and then stretched 3.0 times in a single hot water stretching process at a hot water stretching temperature of 60°C.

[0100] The specific oiling and drying process is as follows: two-stage hot air drying at a temperature of 140℃ for 6 minutes;

[0101] The two-stage steam drawing process is as follows: two-stage steam drawing is carried out under the conditions of saturated steam pressure of 0.35MPa and steam chamber temperature of 138.2℃. The first stage steam drawing is 1.6 times, the fiber bundle stays for 8s, the second stage steam drawing is 1.8 times, and the total steam drawing multiple is 3.4 times.

[0102] The heat setting process is as follows: the temperature is 130℃, the setting tension is 5N, the heat setting time is 4min, the shrinkage rate is 1.89%, the single filament diameter of the finished yarn after heat setting is 8.5μm, the orientation degree is 91.1%, and the single filament strength is 5.45cN / dtex. All other steps are the same.

[0103] The difference between Comparative Example 12 and Example 1 is that the multi-stage washing and stretching process is as follows: the nascent fibers are stretched 9 times in the coagulation bath, and then stretched 5.0 times in hot water at a temperature of 95°C.

[0104] The specific oiling and drying process is as follows: two-stage hot air drying at a temperature of 160℃ for 6 minutes;

[0105] The two-stage steam drawing process is as follows: two-stage steam drawing is carried out under the conditions of saturated steam pressure of 0.35MPa and steam chamber temperature of 138.2℃. The first-stage steam drawing is 2.6 times, the fiber bundle stays for 8s, the second-stage steam drawing is 1.9 times, and the total steam drawing multiple is 4.5 times.

[0106] The heat setting process is as follows: the temperature is 130℃, the setting tension is 5N, the heat setting time is 4min, the shrinkage rate is 2.32%, the diameter of the finished yarn after heat setting is 7.8μm, the orientation degree is 94.1%, the tensile stress is relatively large, a small number of yarns have fuzz, and the yarn strength is 6.13cN / dtex. The remaining steps are the same.

[0107] Table 3: Performance parameters of T1100 grade carbon fiber in Examples 1, 5-6 and Comparative Examples 11-12

[0108] Example 1 7.2 95.3 6.23 412 Example 5 7.0 96.0 6.30 423 Example 6 7.0 95.6 6.25 408 Comparative Example 11 7.3 92.5 5.78 365 Comparative Example 12 7.4 94.7 5.92 389

[0109] As can be seen from Examples 1, 5-6 and Comparative Examples 11-12 and Table 3, the preparation process S3 in this invention can ensure that the prepared carbon fibers have the advantages of high strength and high modulus.

[0110] In summary, this invention introduces UHWMPAN and bifunctional comonomers to prepare fine denier, highly oriented polyacrylonitrile precursor fibers through multi-stage high-ratio drawing. The effects of the introduction of UHWMPAN and bifunctional comonomers on the orientation, crystallinity, and porosity of the precursor fibers are studied in detail. Through synergistic research on the microscopic molecular structure and macroscopic morphological structure of the fibers, the mechanism by which ultra-high molecular weight polymers enhance the performance of the precursor fibers is revealed (UHWMPAN's long-chain entanglement network inhibits slippage; MMPA's amide / ester groups synergistically plasticize and promote cyano cyclization; multi-stage drawing induces high axial orientation of the molecular chains, resulting in more complete crystallization and reduced porosity). This provides a controllable method for preparing high-performance carbon fiber precursor fibers.

[0111] It should be noted that this specific embodiment is merely an explanation of the technical solution of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A method for preparing ultra-high strength and ultra-high modulus carbon fiber, characterized in that: Includes the following steps: S1, ultra-high molecular weight polyacrylonitrile was prepared by aqueous suspension method; S2 is prepared by solution polymerization of ultra-high molecular weight polyacrylonitrile, azobisisobutyronitrile, acrylonitrile, and methyl 3-amide-3-butenoate to obtain a high-viscosity homogeneous spinning solution containing UHMWPAN. S3, the high-viscosity homogeneous spinning solution in S2 is subjected to dry-jet wet spinning, multi-stage water washing and stretching, oiling and drying, two-stage steam stretching, and heat setting to obtain fine denier, highly oriented carbon fiber precursor. S4 is used to prepare T1100 grade carbon fiber through pre-oxidation and carbonization.

2. The method for preparing ultra-high strength and ultra-high modulus carbon fiber according to claim 1, characterized in that: S1 involves preparing ultra-high molecular weight polyacrylonitrile (UHMWPA) using an aqueous suspension method: polyvinyl alcohol (PVA) aqueous solution is used as a dispersant, azobisisobutyronitrile (AIBN) as an initiator, and acrylonitrile AN and methyl 3-amido-3-butenoate (ABM) as monomers. The mass ratio of acrylonitrile AN to methyl 3-amido-3-butenoate (ABM) is (98.8–99.2):(0.8–1.2). The monomer concentration is 22–26 wt%, the initiator accounts for 0.01–0.04 wt% of the total monomer mass, and the PVA content in the PVA aqueous solution is 0.2–0.5 wt%. The UHMWPA obtained by the aqueous suspension method has a weight-average molecular weight of 1.4 × 10⁻⁶. 6 ~1.9×10 6 g / mol of ultra-high molecular weight polyacrylonitrile.

3. The method for preparing ultra-high strength and ultra-high modulus carbon fiber according to claim 2, characterized in that: The specific steps for preparing ultra-high molecular weight polyacrylonitrile using the aqueous suspension method in S1 are as follows: S1.1, add 320 parts of a polyvinyl alcohol (PVA) aqueous solution with a PVA concentration of 0.2-0.5 wt% to the polymerization reactor and stir at 85±2℃ for 3-5 hours until it is completely dissolved; S1.2, cool to 50-70℃, add accurately measured acrylonitrile AN, methyl 3-amide-3-butenoate ABM, and azobisisobutyronitrile AIBN, and polymerize under nitrogen protection for 10-15 hours; S1.3, after the reaction was completed, the product was filtered, washed with water, and dried to obtain a weight-average molecular weight of 1.4 × 10⁻⁶. 6 ~1.9×10 6 g / mol of ultra-high molecular weight polyacrylonitrile.

4. The method for preparing ultra-high strength and ultra-high modulus carbon fiber according to claim 1, characterized in that: The specific steps for preparing the high-viscosity homogeneous spinning solution containing UHMWPAN by solution polymerization in S2 are as follows: S2.1, take 80-100 parts of the ultra-high molecular weight polyacrylonitrile prepared in S1 and 480-600 parts of dimethyl sulfoxide (DMSO) and add them to the polymerization reactor. Heat and stir to completely dissolve the ultra-high molecular weight polyacrylonitrile in DMSO. S2.2, the temperature is adjusted to 50-70℃, using azobisisobutyronitrile (AIBN) as the initiator, acrylonitrile (AN) and methyl 3-amido-3-butenoate (ABM) as monomers, the mass ratio of acrylonitrile (AN) to methyl 3-amido-3-butenoate (ABM) is (98.8~99.2):(0.8-1.2), the monomer concentration is 22-26wt%, and the initiator accounts for 0.01-0.04wt% of the total monomer mass. Under nitrogen protection, the polymerization reaction is carried out at 50-70℃ and 60-240rpm for 20-26h. S2.3, after the polymerization reaction is completed, is filtered, vacuum de-singed, and de-bubbled to obtain a high-viscosity homogeneous spinning solution.

5. The method for preparing ultra-high strength and ultra-high modulus carbon fiber according to claim 1, characterized in that: The parameters for dry-jet wet spinning in S3 are as follows: the polymer content in the high-viscosity homogeneous spinning solution is 18-29 wt%, the spinning solution temperature is 58-62℃, the air section distance is 5±0.5 mm, the DMSO content in the coagulation bath is 45-70 wt%, the coagulation bath temperature is 4-6℃, and the coagulation time is 0.5-2 min.

6. The method for preparing ultra-high strength and ultra-high modulus carbon fiber according to claim 5, characterized in that: The multi-stage washing and stretching process in S3 is as follows: the nascent fiber is stretched 6-12 times in the coagulation bath, the hot water stretching temperature is 60-95 ℃, the hot water stretching ratio is 3-5 times, the drying temperature is 140-160 ℃, the steam stretching ratio is 3-5 times, and the heat setting temperature is 130±5 ℃.

7. The method for preparing ultra-high strength and ultra-high modulus carbon fiber according to claim 1, characterized in that: The two-stage steam drawing process in S3 is as follows: steam drawing is carried out at a saturated steam pressure of 0.3-0.4 MPa and a steam chamber temperature of 125-135℃ for 3-5 times.

8. The method for preparing ultra-high strength and ultra-high modulus carbon fiber according to claim 1, characterized in that: The specific oiling and drying process in S3 is as follows: the drying temperature is 150±5℃, two-stage hot air drying, and the total drying time is 4-6 min; the specific heat setting process in S3 is as follows: the temperature is 130±2℃, the setting tension is 5±0.5N, the heat setting time is 230-250s, the shrinkage rate is ≤2%, and the single filament diameter of the finished yarn after heat setting is 7.5~8.5μm, the orientation degree is 93%~95%, and the single filament strength is ≥6.5cN / dtex.

9. The method for preparing ultra-high strength and ultra-high modulus carbon fiber according to claim 8, characterized in that: The pre-oxidation process in S4 is as follows: the finished yarn after heat setting is subjected to pre-oxidation treatment in seven temperature zones: 180±5℃, 200±5℃, 220±5℃, 240±5℃, 250±5℃, 260±5℃, and 270±5℃. During the stabilization process, the roller speed is 140-160mm / min, and the total residence time is 130-150min, thus obtaining pre-oxidized fiber.

10. The method for preparing ultra-high strength and ultra-high modulus carbon fiber according to claim 9, characterized in that: The carbonization process in S4 is as follows: the pre-oxidized fiber is placed in a nitrogen atmosphere and subjected to continuous low-temperature carbonization, high-temperature carbonization, and graphitization treatments, with a total carbonization time of 4-6 minutes; the low-temperature carbonization temperature range is 400-800℃, and the draw ratio of low-temperature carbonization is 14-16%; the high-temperature carbonization temperature range is 1000-1400℃, and the draw ratio of high-temperature carbonization is -3 to -1%; the semi-finished carbon fiber after high-temperature carbonization is placed in an ultra-pure nitrogen atmosphere, with a graphitization temperature of 2600±50℃ and a graphitization tension of 6-10N, and the semi-finished carbon fiber is subjected to graphitization treatment for 10-20 seconds to prepare T1100 grade carbon fiber. The T1100 grade carbon fiber has a diameter of 7~9μm, an orientation degree ≥94.5%, a strength ≥6.1GPa, and a modulus ≥390GPa.