Carbon fiber and preparation method thereof, medical grade carbon fiber / polyether-ether-ketone composite material and application thereof

Abstract

The invention relates to a carbon fiber and a preparation method thereof, a medical carbon fiber / polyether-ether-ketone composite material and application thereof, and relates to the technical field of composite materials. The preparation method of the carbon fiber comprises the following steps: sequentially carrying out pre-oxidation, low-temperature carbonization, high-temperature carbonization, sizing, drying and winding on a carbon fiber precursor to obtain the carbon fiber, and in the low-temperature carbonization process, the atmosphere pressure in a low-temperature furnace is 10-30 Pa. By controlling the atmosphere pressure in the low-temperature furnace, silicon tar on the surface of the fiber is volatilized and discharged in time, silicon element residues on the surface of the fiber are reduced, the ash content of the carbon fiber is reduced, and impurities are reduced, so that the carbon fiber can meet the medical-grade requirement; moreover, the carbon fiber also has good mechanical properties, the tensile strength is greater than or equal to 6600MPa, and the tensile modulus is greater than or equal to 300GPa, so that the carbon fiber reinforced polyether-ether-ketone composite material prepared from the carbon fiber can be effectively applied to medical bearing implants.

Description

Technical Field

[0001] This application relates to the field of composite materials technology, and in particular to a carbon fiber and its preparation method, a medical-grade carbon fiber / polyetheretherketone composite material and its application. Background Technology

[0002] Carbon fiber, with its superior mechanical properties and lightweight characteristics, is hailed as the king of new materials in the 21st century and has wide applications in the national economy and society. Currently, the application of high-strength medium-modulus carbon fiber (tensile strength ≥4500MPa, elastic modulus ≥260GPa) is mainly concentrated in the aerospace field. Further development of carbon fiber applications in emerging fields such as new energy and biomedicine has broad market prospects.

[0003] In the clinical application of load-bearing medical implants, metal implants suffer from interference artifacts under radiotherapy / detection radiation. Furthermore, the mechanical properties of single-component polyetheretherketone (PEEK) resin are lower than those of metallic materials, failing to meet mechanical performance requirements. High-strength, medium-modulus carbon fiber reinforced PEEK composites possess excellent mechanical properties, along with radiation permeability and lightweight characteristics, effectively addressing these issues.

[0004] However, due to the large number of impurities generated on the fiber surface during the preparation process of carbon fiber, especially in the carbonization process, the carbon fiber prepared cannot meet the medical grade requirements (ash content ≤0.02%). Summary of the Invention

[0005] To address the problems existing in related technologies, the purpose of this application is to provide a carbon fiber and its preparation method, as well as a medical-grade carbon fiber / polyetheretherketone composite material, so that the carbon fiber can meet medical-grade requirements and can be applied to medical load-bearing implants.

[0006] In a first aspect, embodiments of this application provide a method for preparing carbon fiber, comprising the following steps: pre-oxidizing, low-temperature carbonizing, high-temperature carbonizing, sizing, drying, and winding carbon fiber in sequence to obtain carbon fiber; in the low-temperature carbonization process, the atmosphere pressure in the low-temperature furnace is 10Pa~30Pa.

[0007] In the above technical solution, this application sequentially pre-oxidizes, carbonizes at low temperature, carbonizes at high temperature, sizing, and dries the carbon fiber precursor, thereby giving the carbon fiber excellent mechanical properties. The tensile strength of the carbon fiber is ≥6600MPa, and the tensile modulus is ≥300GPa. Furthermore, by controlling the atmosphere pressure in the low-temperature furnace to 10Pa~30Pa during the low-temperature carbonization process, the silicon tar on the fiber surface is volatilized and discharged in a timely manner, reducing the residual silicon element on the fiber surface, reducing the ash content of the carbon fiber, and reducing impurities. As a result, the carbon fiber can meet the requirements for medical grade (ash content ≤0.02%), and the carbon fiber reinforced polyether ether ketone composite material prepared using this carbon fiber can be effectively applied to medical load-bearing implants.

[0008] In some implementations, the pre-oxidation, low-temperature carbonization, and high-temperature carbonization processes are carried out in a carbonization workshop. According to the GB50073-2001 standard, the overall cleanliness level of the carbonization workshop is Class 10,000, and the cleanliness level of the local winding process after high-temperature carbonization is Class 100. According to the "Cleanroom Design Code" (GB50073-2001), by controlling the cleanliness of the carbonization workshop to a level of 10,000, process pollution prevention can be achieved. By controlling the cleanliness of the local winding process to a level of 100, finished product anti-adsorption can be achieved, which is conducive to further reducing the ash content of carbon fiber and reducing impurities. In some embodiments, the temperature of the pre-oxidation process is 230°C to 260°C, the temperature of the low-temperature carbonization process is 500°C to 900°C, and the temperature of the high-temperature carbonization process is 1200°C to 1600°C. In the above technical solution, by controlling the pre-oxidation at low temperature, the low-temperature carbonization at medium temperature, and the high-temperature carbonization at high temperature respectively, the prepared carbon fibers have good mechanical properties. In some embodiments, the sizing process uses a low-heat-resistant sizing agent with a thermal decomposition temperature ≤250°C. In the aforementioned technical solutions, since the processing temperature of carbon fiber / polyetheretherketone (PEEK) composite materials is between 340℃ and 350℃, conventional carbon fiber epoxy resin sizing agents and thermoplastic resins often exhibit interfacial mismatch issues, necessitating desizing treatment. However, conventional epoxy sizing agents suffer from incomplete decomposition, leading to deterioration of the composite material's interfacial properties. This invention employs a low-heat-resistant sizing agent that can completely decompose, resolving the surface residue problem of carbon fiber sizing agents during processing. This improves the bonding ability between carbon fiber and the PEEK matrix resin, thereby enhancing the mechanical properties of the composite material.

[0009] In some embodiments, the low-heat-resistant sizing agent includes bisphenol A polyoxyethylene ether. In the above technical solution, bisphenol A polyoxyethylene ether can be completely decomposed during the processing of carbon fiber / polyetheretherketone composite material, solving the problem of surface residue of carbon fiber sizing agent during processing, improving the bonding ability between carbon fiber and polyetheretherketone matrix resin, thereby improving the mechanical properties of composite material. Furthermore, the bisphenol A polyoxyethylene ether can be at least one of BPE-15, BPE-16, and BPE-20.

[0010] In some embodiments, the content of low heat-resistant sizing agent in carbon fiber is 0.4% to 1.0%. In the above technical solution, the content of low heat-resistant sizing agent within a suitable range is conducive to the formation of a complete and continuous sizing film, which protects the carbon fiber, and is also conducive to its effective removal in subsequent processing, reducing residue. In some embodiments, the method for preparing carbon fiber precursor includes: using a dry-jet wet spinning process to draw and spin the polymer solution through a spinneret, and then sequentially subjecting the solidified fiber bundle to water washing at 20℃~30℃, water drawing at 50℃~70℃, oiling at 20℃~30℃, drying at 180℃~200℃, saturated steam drawing at 0.8MPa~1.0MPa, and drying at 120℃~150℃ to obtain carbon fiber precursor. In the above technical solution, by adopting the dry-jet wet spinning process and controlling the process parameters of each step within a suitable range, it is beneficial to further improve the mechanical properties of carbon fiber. Secondly, this application provides a carbon fiber prepared by the preparation method provided in the first aspect of this application; wherein the carbon fiber has a tensile strength ≥6600MPa, a tensile modulus ≥300GPa, and an ash content ≤0.02%.

[0011] In some embodiments, the fuzziness of the carbon fiber is ≤3mg / 50m. This low fuzziness indicates that the carbon fiber also possesses good abrasion resistance.

[0012] Thirdly, this application provides a medical-grade carbon fiber / polyetheretherketone composite material, including the carbon fiber and polyetheretherketone resin matrix provided in the second aspect of this application, wherein the mass percentage of carbon fiber is ≥60wt%, and the interlaminar shear strength of the medical-grade carbon fiber / polyetheretherketone composite material is ≥100MPa.

[0013] Fourthly, embodiments of this application provide an application of medical-grade carbon fiber / polyetheretherketone composite material in medical load-bearing implants. Detailed Implementation The following detailed description discloses the preparation method of the carbon fiber, the carbon fiber itself, the carbon fiber reinforced polyetheretherketone composite material, and embodiments thereof, but unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art.

[0014] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0015] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0016] As mentioned earlier, the current applications of high-strength medium-modulus carbon fibers (tensile strength ≥4500MPa, elastic modulus ≥260GPa) are mainly concentrated in the aerospace field. Further development of carbon fibers in emerging fields such as new energy and biomedicine holds broad market potential. However, the carbon fiber preparation process mainly includes precursor fiber forming, pre-oxidation, low-temperature carbonization, high-temperature carbonization, and sizing. In these processes, especially the low-temperature carbonization process, the fiber undergoes thermal decomposition, releasing a large amount of small-molecule pollutants (CO, CO2, CH4, etc.) and silicon tar. Simple cleaning alone cannot effectively remove these pollutants, resulting in carbon fibers with high ash content and numerous impurities. Existing technologies typically adjust the temperature, time, and tension of the low-temperature carbonization process, and / or subsequently perform chemical cleaning and surface treatment on the carbon fibers. However, these methods cannot effectively reduce the ash and impurities of the carbon fibers, thus failing to meet the requirements for medical-grade carbon fibers (ash content ≤0.02%).

[0017] Based on this, this application provides a method for preparing carbon fiber, including the following steps: pre-oxidizing, low-temperature carbonizing, high-temperature carbonizing, sizing, drying, and winding carbon fiber in sequence to obtain carbon fiber; in the low-temperature carbonization process, the atmosphere pressure in the low-temperature furnace is 10Pa~30Pa.

[0018] As an example, in the low-temperature carbonization process, the atmosphere pressure inside the low-temperature furnace can be any one of 10Pa, 12Pa, 15Pa, 20Pa, 25Pa, or 30Pa, or a range between any two.

[0019] The atmosphere inside the cryogenic furnace is an inert gas, such as nitrogen or argon. Preferably, the atmosphere inside the cryogenic furnace is high-purity nitrogen with an oxygen content of less than 5 ppm.

[0020] In this application, carbon fiber precursor is subjected to pre-oxidation, low-temperature carbonization, high-temperature carbonization, sizing and drying in sequence, so that the carbon fiber has good mechanical properties, with a tensile strength ≥6600MPa and a tensile modulus ≥300GPa.

[0021] Furthermore, by controlling the atmosphere pressure inside the low-temperature furnace to 10Pa~30Pa during the low-temperature carbonization process, under this low pressure, the volatile impurities generated by the pyrolysis of the precursor fiber (such as silane and siloxane tar) will form a huge concentration difference between a "high concentration area" (fiber surface) and a "low concentration area" (furnace space). Driven by the concentration gradient, the volatiles will diffuse from the fiber surface to the outside of the furnace at a faster rate (discharged by a vacuum pump), avoiding the re-attachment of impurities to the fiber due to "accumulation of volatiles inside the furnace". At low pressure, the boiling point of silicon tar is correspondingly reduced, allowing it to volatilize and be discharged in time during the low-temperature carbonization process, reducing the residual silicon element on the fiber surface, thereby reducing the ash content of the carbon fiber and reducing impurities, thus enabling the carbon fiber to meet medical-grade requirements.

[0022] This carbon fiber has good mechanical properties and meets medical-grade requirements. The carbon fiber reinforced polyether ether ketone composite material prepared using this carbon fiber can be effectively applied to medical load-bearing implants.

[0023] In some embodiments, the pre-oxidation, low-temperature carbonization and high-temperature carbonization processes are carried out in a carbonization workshop, the overall cleanliness level of the carbonization workshop is Class 10,000 (GB50073-2001), and the cleanliness level of the local winding process after high-temperature carbonization is Class 100 (GB50073-2001).

[0024] According to the "Cleanroom Design Code" (GB50073-2001), when the cleanliness level is Class 10,000, the number of dust particles (≥0.5μm) should be ≤352,000 / m³. 3Dust particle count (≥5μm) ≤2930 particles / m 3 Microbial limit (planktonic bacteria) ≤100 CFU / m³ 3 When the cleanliness level is Class 100, the number of dust particles (≥0.5μm) is ≤3520 / m². 3 Dust particle count (≥5μm) ≤29 particles / m 3 Microbial limit (planktonic bacteria) ≤5 CFU / m³ 3 By controlling the overall cleanliness level of the carbonization workshop to Class 10,000, it is beneficial to prevent dust from entering the furnace. The surface of the carbonized fiber after high-temperature carbonization is not yet protected by a sizing agent film layer and has high surface energy. By controlling the cleanliness level to Class 100, the adsorption of micro-dust can be effectively reduced, and the residual impurities can be reduced, thus minimizing their impact on ash content.

[0025] In some embodiments, the temperature of the pre-oxidation process is 230°C to 260°C, the temperature of the low-temperature carbonization process is 500°C to 900°C, and the temperature of the high-temperature carbonization process is 1200°C to 1600°C.

[0026] By controlling the pre-oxidation at low temperature, the low-temperature carbonization at medium temperature, and the high-temperature carbonization at high temperature respectively, the prepared carbon fibers exhibit excellent mechanical properties. It is understood that high-strength intermediate-modulus carbon fibers can be prepared by conventionally controlling the pre-oxidation, low-temperature carbonization, and high-temperature carbonization processes; this application does not specifically limit the specific methods used.

[0027] As an example, the pre-oxidation process can be carried out with a gradient temperature increase in the temperature range of 230℃ to 260℃, and the draw ratio is 0.97 to 1.0 times; the low-temperature carbonization process can be carried out with a gradient temperature increase in the temperature range of 500℃ to 900℃, and the draw ratio is 0.97 to 1.03 times; the high-temperature carbonization process can be carried out with a gradient temperature increase in the temperature range of 1200℃ to 1600℃, and the draw ratio is 0.97 to 1.0 times.

[0028] In some embodiments, the process may further include electrochemical surface treatment of the carbonized fibers after the high-temperature carbonization process.

[0029] Furthermore, the treatment medium for anodic electrochemical surface treatment is an acid, alkali, or salt electrolyte such as NaHCO3, NaOH, or H2SO4, and the surface treatment charge can be 10C / g to 50C / g.

[0030] Furthermore, two or more stages of electrochemical surface treatment can be used, with a treatment time of 30 to 90 seconds.

[0031] In some embodiments, the sizing process uses a low-heat-resistant sizing agent with a thermal decomposition temperature ≤250°C.

[0032] Since the processing temperature of carbon fiber / polyetheretherketone (PEEK) composites is between 340℃ and 350℃, conventional carbon fiber epoxy resin sizing agents and thermoplastic resins often exhibit interfacial mismatch, necessitating desizing. However, the thermal decomposition temperature of conventional epoxy sizing agents is typically above 350℃, leading to incomplete decomposition after desizing and consequently deteriorating the interfacial properties of the composite. This invention employs a low-heat-resistant sizing agent that can completely decompose, resolving the issue of surface residue from carbon fiber sizing agents during processing. This improves the bonding ability between carbon fiber and the PEEK matrix resin, thereby enhancing the mechanical properties of the composite.

[0033] In some embodiments, the low-heat-resistant sizing agent includes bisphenol A polyoxyethylene ether. Bisphenol A polyoxyethylene ether can be completely decomposed during the processing of carbon fiber / polyetheretherketone composites, solving the problem of surface residue of carbon fiber sizing agents during processing, improving the bonding ability between carbon fibers and the polyetheretherketone matrix resin, thereby improving the mechanical properties of the composite material. As an example, the bisphenol A polyoxyethylene ether can be at least one of BPE-15, BPE-16, and BPE-20. Specifically, the thermal decomposition temperature of BPE-15 is 225°C; the thermal decomposition temperature of BPE-16 is 231°C; and the thermal decomposition temperature of BPE-20 is 243°C.

[0034] In some embodiments, the content of low-heat-resistant sizing agent in carbon fiber is 0.4% to 1.0%. A suitable content of low-heat-resistant sizing agent facilitates the formation of a complete and continuous sizing film, protecting the carbon fiber, and also allows for effective removal during subsequent processing, reducing residue. As an example, the content of the low heat-resistant sizing agent is any one of 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, or a range between any two.

[0035] Understandably, the sizing process can be carried out using the conventional impregnation method, and this application does not specifically limit this. The content of the sizing agent can be obtained by the ignition method in GB / T 26752-2011 "Test Method for Sizing Agent Content of Carbon Fiber": ignite at 550℃±20℃ in air atmosphere until constant weight, and calculate the weight loss.

[0036] It should be noted that the preparation method of carbon fiber precursor is not specifically limited in the embodiments of this application, and conventional preparation methods can be used to obtain it.

[0037] In some embodiments, the method for preparing carbon fiber precursor includes: using a dry-jet wet spinning process to draw and spin a polymer solution through a spinneret; the solidified filament bundle is then sequentially subjected to water washing at 20°C~30°C, water drawing at 50°C~70°C, oiling at 20°C~30°C, drying at 180°C~200°C, saturated steam drawing at 0.8MPa~1.0MPa, and drying at 120°C~150°C to obtain carbon fiber precursor. By employing a dry-jet wet spinning process and controlling the process parameters of each step within a suitable range, it is beneficial to further improve the mechanical properties of carbon fiber.

[0038] In addition, this application embodiment also provides a carbon fiber prepared by the above preparation method, wherein the carbon fiber has a tensile strength ≥6600MPa, a tensile modulus ≥300GPa, and an ash content ≤0.02%.

[0039] For example, the tensile strength of carbon fiber is 6600MPa, 6650MPa, 6680MPa, 6700MPa, 6750MPa, etc.; the tensile modulus is 300GPa, 305GPa, 310GPa, 350GPa, etc.; and the ash content is 0.01%, 0.012%, 0.014%, 0.015%, 0.017%, 0.02%, etc.

[0040] The carbon fiber prepared in this application is a high-strength, medium-modulus carbon fiber, which has high tensile strength and tensile modulus, and low ash content, thus meeting the requirements for medical grade.

[0041] In some embodiments, the fuzziness of the carbon fiber is ≤3mg / 50m, such as 1mg / 50m, 1.5mg / 50m, 2mg / 50m, 2.5mg / 50m, or 3mg / 50m. A low fuzziness indicates that the carbon fiber also has good abrasion resistance.

[0042] In addition, this application embodiment also provides a medical-grade carbon fiber / polyetheretherketone composite material, including the above-mentioned carbon fiber and polyetheretherketone resin matrix, wherein the mass percentage of carbon fiber is ≥60wt%, and the interlaminar shear strength of the medical-grade carbon fiber / polyetheretherketone composite material is ≥100MPa.

[0043] As an example, in medical-grade carbon fiber / polyetheretherketone composite materials, the mass percentage of carbon fiber can be 60wt%, 61wt%, 62wt%, 65wt%, 70wt%, etc.; the interlaminar shear strength can be 100MPa, 101MPa, 103MPa, 105MPa, 110MPa, etc.

[0044] Understandably, medical-grade carbon fiber / polyetheretherketone composite materials can be prepared using conventional powder impregnation or suspension impregnation methods, and this application does not impose any specific limitations.

[0045] In addition, this application also provides an application of medical-grade carbon fiber / polyetheretherketone composite material in medical load-bearing implants.

[0046] As an example, this medical-grade carbon fiber / polyetheretherketone composite material can be used to manufacture spinal fusion devices, artificial joint prosthesis stems (hip / knee joints), bone defect repair scaffolds (weight-bearing bones), and trauma fixation devices (weight-bearing bone plates), etc.

[0047] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0048] Example 1 This embodiment provides a carbon fiber, the preparation method of which includes the following steps: (1) Preparation of carbon fiber precursor: The precursor is obtained by dry-jet wet spinning process through a polymer solution spinneret, followed by washing at 25°C, water drawing at 60°C, oiling at 25°C, drying at 190°C, drawing with saturated steam at 0.9MPa, and drying with hot rollers at 130°C.

[0049] (2) Preparation of carbon fiber: The carbon fiber precursor is subjected to pre-oxidation, low-temperature carbonization, high-temperature carbonization, partial winding, sizing, drying and finished winding in sequence to obtain carbon fiber.

[0050] The carbonization production workshop is maintained at a Class 10,000 cleanroom standard overall, with some winding processes at a Class 100 cleanroom standard. The pre-oxidation process operates at 230℃~260℃ with a draw ratio of 0.97. The low-temperature carbonization process operates at 500℃~900℃ with a draw ratio of 1.03, using a high-purity nitrogen atmosphere at a pressure controlled at 30Pa. The high-temperature carbonization process operates at 1200℃~1600℃ with a draw ratio of 0.98. The sizing process uses a low-heat-resistant sizing agent, bisphenol A polyoxyethylene ether (BPE-15, thermal decomposition temperature 225℃), with a sizing agent content of 0.7%.

[0051] Example 2 This embodiment provides a carbon fiber, the preparation method of which includes the following steps: (1) Preparation of carbon fiber precursor: The precursor is obtained by dry-jet wet spinning process through a polymer solution spinneret, followed by washing at 20℃, water drawing at 50℃, oiling at 20℃, drying at 180℃, saturated steam drawing at 0.8MPa, and hot roller drying at 120℃.

[0052] (2) Preparation of carbon fiber: The carbon fiber precursor is subjected to pre-oxidation, low-temperature carbonization, high-temperature carbonization, partial winding, sizing, drying and finished winding in sequence to obtain carbon fiber.

[0053] The carbonization production workshop is maintained at a Class 10,000 cleanroom standard overall, with some winding processes at a Class 100 cleanroom standard. The pre-oxidation process operates at 230℃~260℃ with a draw ratio of 1.0. The low-temperature carbonization process operates at 500℃~900℃ with a draw ratio of 0.97, using a high-purity nitrogen atmosphere at a pressure controlled at 25Pa. The high-temperature carbonization process operates at 1200℃~1600℃ with a draw ratio of 1.0. The sizing process uses a low-heat-resistant sizing agent, bisphenol A polyoxyethylene ether (BPE-15, thermal decomposition temperature 225℃), with a sizing agent content of 0.4%.

[0054] Example 3 This embodiment provides a carbon fiber, the preparation method of which includes the following steps: (1) Preparation of carbon fiber precursor: The precursor is obtained by dry-jet wet spinning process through a polymer solution spinneret, followed by washing at 30℃, water drawing at 70℃, oiling at 30℃, drying at 1200℃, saturated steam drawing at 1.0MPa, and hot roller drying at 120℃~150℃.

[0055] (2) Preparation of carbon fiber: The carbon fiber precursor is subjected to pre-oxidation, low-temperature carbonization, high-temperature carbonization, partial winding, sizing, drying and finished winding in sequence to obtain carbon fiber.

[0056] The carbonization production workshop is maintained at a Class 10,000 cleanroom standard overall, with some winding processes at a Class 100 cleanroom standard. The pre-oxidation process operates at 230℃~260℃ with a draw ratio of 1.0. The low-temperature carbonization process operates at 500℃~900℃ with a draw ratio of 0.97, using a high-purity nitrogen atmosphere at a pressure controlled at 20Pa. The high-temperature carbonization process operates at 1200℃~1600℃ with a draw ratio of 1.0. The sizing process uses a low-heat-resistant sizing agent, bisphenol A polyoxyethylene ether (BPE-16, thermal decomposition temperature 231℃), with a sizing agent content of 0.6%.

[0057] Example 4 This embodiment provides a carbon fiber, the preparation method of which includes the following steps: (1) Preparation of carbon fiber precursor: The precursor is obtained by dry-jet wet spinning process through a polymer solution spinneret, followed by washing at 25°C, water drawing at 60°C, oiling at 25°C, drying at 190°C, drawing with saturated steam at 0.9MPa, and drying with hot rollers at 140°C.

[0058] (2) Preparation of carbon fiber: The carbon fiber precursor is subjected to pre-oxidation, low-temperature carbonization, high-temperature carbonization, partial winding, sizing, drying and finished winding in sequence to obtain carbon fiber.

[0059] The carbonization production workshop is maintained at a Class 10,000 cleanroom standard overall, with some winding processes at a Class 100 cleanroom standard. The pre-oxidation process operates at 230℃~260℃ with a draw ratio of 0.98. The low-temperature carbonization process operates at 500℃~900℃ with a draw ratio of 0.99, using a high-purity nitrogen atmosphere at a pressure controlled at 15Pa. The high-temperature carbonization process operates at 1200℃~1600℃ with a draw ratio of 1.0. The sizing process uses a low-heat-resistant sizing agent, bisphenol A polyoxyethylene ether (BPE-16, thermal decomposition temperature 231℃), with a sizing agent content of 0.9%.

[0060] Example 5 This embodiment provides a carbon fiber, the preparation method of which includes the following steps: (1) Preparation of carbon fiber precursor: The precursor is obtained by dry-jet wet spinning process through a polymer solution spinneret, followed by washing at 25°C, water drawing at 60°C, oiling at 25°C, drying at 190°C, drawing with saturated steam at 0.9MPa, and drying with hot rollers at 140°C.

[0061] (2) Preparation of carbon fiber: The carbon fiber precursor is subjected to pre-oxidation, low-temperature carbonization, high-temperature carbonization, partial winding, sizing, drying and finished winding in sequence to obtain carbon fiber.

[0062] The carbonization production workshop is maintained at a Class 10,000 cleanroom standard overall, with some winding processes at a Class 100 cleanroom standard. The pre-oxidation process operates at 230℃~260℃ with a draw ratio of 0.98; the low-temperature carbonization process operates at 500℃~900℃ with a draw ratio of 0.99, using a high-purity nitrogen atmosphere at a pressure controlled at 10Pa; the high-temperature carbonization process operates at 1200℃~1600℃ with a draw ratio of 1.0; and the sizing process uses a low-heat-resistant sizing agent, bisphenol A polyoxyethylene ether (BPE-20, thermal decomposition temperature 243℃), with a sizing agent content of 1.0%.

[0063] Comparative Example 1 This comparative example provides a carbon fiber, the preparation method of which includes the following steps: (1) Preparation of carbon fiber precursor: The precursor is obtained by dry-jet wet spinning process through a polymer solution spinneret, followed by washing at 25°C, water drawing at 60°C, oiling at 25°C, drying at 190°C, drawing with saturated steam at 0.9MPa, and drying with hot rollers at 130°C.

[0064] (2) Preparation of carbon fiber: The carbon fiber precursor is subjected to pre-oxidation, low-temperature carbonization, high-temperature carbonization, partial winding, sizing, drying and finished winding in sequence to obtain carbon fiber.

[0065] The carbonization production workshop is maintained at a Class 10,000 cleanroom standard overall, with some winding processes at a Class 100 cleanroom standard. The pre-oxidation process operates at 230℃~260℃ with a draw ratio of 0.97. The low-temperature carbonization process operates at 500℃~900℃ with a draw ratio of 1.03, using a high-purity nitrogen atmosphere at a pressure controlled at 32 Pa. The high-temperature carbonization process operates at 1200℃~1600℃ with a draw ratio of 0.98. The sizing process uses a low-heat-resistant sizing agent, bisphenol A polyoxyethylene ether (BPE-15, thermal decomposition temperature 225℃), with a sizing agent content of 0.4%.

[0066] Comparative Example 2 This comparative example provides a carbon fiber, the preparation method of which includes the following steps: (1) Preparation of carbon fiber precursor: The precursor is obtained by dry-jet wet spinning process through a polymer solution spinneret, followed by washing at 25°C, water drawing at 60°C, oiling at 25°C, drying at 190°C, drawing with saturated steam at 0.9MPa, and drying with hot rollers at 130°C.

[0067] (2) Preparation of carbon fiber: The carbon fiber precursor is subjected to pre-oxidation, low-temperature carbonization, high-temperature carbonization, partial winding, sizing, drying and finished winding in sequence to obtain carbon fiber.

[0068] The carbonization production workshop is maintained at a Class 10,000 cleanroom standard overall, with some winding processes at a Class 100 cleanroom standard. The pre-oxidation process operates at 230℃~260℃ with a draw ratio of 0.97. The low-temperature carbonization process operates at 500℃~900℃ with a draw ratio of 1.03, using a high-purity nitrogen atmosphere at a pressure controlled at 5Pa. The high-temperature carbonization process operates at 1200℃~1600℃ with a draw ratio of 0.98. The sizing process uses a low-heat-resistant sizing agent, bisphenol A polyoxyethylene ether (BPE-15, thermal decomposition temperature 225℃), with a sizing agent content of 0.4%.

[0069] Comparative Example 3 This comparative example provides a carbon fiber, the preparation method of which includes the following steps: (1) Preparation of carbon fiber precursor: The precursor is obtained by dry-jet wet spinning process through a polymer solution spinneret, followed by washing at 25°C, water drawing at 60°C, oiling at 25°C, drying at 190°C, drawing with saturated steam at 0.9MPa, and drying with hot rollers at 130°C.

[0070] (2) Preparation of carbon fiber: The carbon fiber precursor is subjected to pre-oxidation, low-temperature carbonization, high-temperature carbonization, partial winding, sizing, drying and finished winding in sequence to obtain carbon fiber.

[0071] The carbonization production workshop is maintained at a Class 10,000 cleanroom standard overall, with some winding processes at a Class 100 cleanroom standard. The pre-oxidation process operates at 230℃~260℃ with a draw ratio of 0.97. The low-temperature carbonization process operates at 500℃~900℃ with a draw ratio of 1.03, using a high-purity nitrogen atmosphere at a pressure controlled at 32 Pa. The high-temperature carbonization process operates at 1200℃~1600℃ with a draw ratio of 0.98. The sizing process uses a low-heat-resistant sizing agent, bisphenol A polyoxyethylene ether (BPE-15, thermal decomposition temperature 225℃), with a sizing agent content of 1.1%.

[0072] Comparative Example 4 This comparative example provides a carbon fiber, the preparation method of which includes the following steps: (1) Preparation of carbon fiber precursor: The precursor is obtained by dry-jet wet spinning process through a polymer solution spinneret, followed by washing at 25°C, water drawing at 60°C, oiling at 25°C, drying at 190°C, drawing with saturated steam at 0.9MPa, and drying with hot rollers at 130°C.

[0073] (2) Preparation of carbon fiber: The carbon fiber precursor is subjected to pre-oxidation, low-temperature carbonization, high-temperature carbonization, partial winding, sizing, drying and finished winding in sequence to obtain carbon fiber.

[0074] The carbonization production workshop is maintained at a Class 10,000 cleanroom standard overall, with some winding processes at a Class 100 cleanroom standard. The pre-oxidation process operates at 230℃~260℃ with a draw ratio of 0.97. The low-temperature carbonization process operates at 500℃~900℃ with a draw ratio of 1.03, using a high-purity nitrogen atmosphere at a pressure controlled at 32 Pa. The high-temperature carbonization process operates at 1200℃~1600℃ with a draw ratio of 0.98. The sizing process uses a low-heat-resistant sizing agent, bisphenol A epoxy resin E44, with a thermal decomposition temperature of 272℃ and a sizing agent content of 0.4%.

[0075] Table 1 shows some of the preparation process parameters of carbon fiber in the above embodiments and comparative examples.

[0076] Table 1. Some process parameters for carbon fiber preparation

[0077] Performance testing and results analysis The carbon fibers prepared in Examples 1-5 and Comparative Examples 1-4 were desized in a desizing furnace at a temperature of 500°C for 30 seconds at a speed of 6 m / min. They were then washed and dried with distilled water. The desized carbon fibers were impregnated in a polyetheretherketone (PEEK) resin suspension for sizing. After heating and melting the PEEK resin on the surface, a prepreg was prepared. The prepreg was then cut, laid up, and molded to obtain a medical-grade carbon fiber / PEEK composite material.

[0078] The carbon fibers and medical-grade carbon fiber / polyetheretherketone composite materials prepared in the above examples and comparative examples were subjected to performance tests, and the test results are shown in Table 2. The specific test methods are as follows: 1. Carbon fiber (1) Tensile strength and tensile modulus The tensile strength and tensile modulus of carbon fiber were tested according to the GB / T3362-2017 test standard.

[0079] (2) Ash content Tested according to FZ / T 50044-2018 standard.

[0080] (3) Abrasion resistance (fuzziness) The carbon fiber to be tested is unwound by an unwinding mechanism and wound by a rewinding mechanism. The tension of the carbon fiber is controlled at 60N and the traction speed at 5m / min by a control system. The carbon fiber is then pulled through four friction rollers with an angle of 120° between adjacent sides and four friction rollers with an angle of 90° between adjacent sides. Next, the carbon fiber is pulled through polyester cotton, and the weight gain of the polyester cotton after passing through 50m of carbon fiber is measured.

[0081] 2. Medical-grade carbon fiber / polyetheretherketone composite material (1) Interlaminar shear strength According to the ASTM D2344 test standard, ten carbon fiber composite laminates were cut into specimens with a length × width × thickness of 12 mm × 4 mm × 2 mm. The interlaminar shear strength was then tested according to the test rate (1 mm / min) and the lower span (8 mm) parameters.

[0082] Table 2 Performance test results of carbon fiber and medical-grade carbon fiber / polyetheretherketone composites

[0083] As shown in Tables 1 and 2, the carbon fibers prepared in Examples 1-5 of this application all possess good mechanical properties, low ash content, and good wear resistance, with tensile strength ≥6600MPa, tensile modulus ≥300GPa, ash content ≤0.02%, and abrasion fuzz ≤3mg / 50m, meeting medical-grade requirements. The corresponding medical-grade carbon fiber / polyetheretherketone composite materials prepared also exhibit good mechanical properties, with interlaminar shear strength ≥100MPa.

[0084] The test results from Example 1 and Comparative Examples 1 and 2 show that both excessively high and low atmospheric pressure in the low-temperature furnace lead to a decrease in the mechanical properties of carbon fibers, an increase in ash content, and a decrease in abrasion resistance. This may be because when the atmospheric pressure is too high, the diffusion of small molecule contaminants and silicon tar generated by the pyrolysis of the fiber bundle is hindered, the discharge pressure increases, and these contaminants remain inside the fiber or coke on the fiber surface, forming defects. Conversely, when the atmospheric pressure is too low, the atmosphere inside the furnace is prone to instability, introducing external impurities and making the pyrolysis reaction incomplete.

[0085] The test results of Example 1 and Comparative Examples 3 and 4 show that when the atmospheric pressure in the low-temperature furnace is too high, the content of the sizing agent is too high, or a high-temperature resistant sizing agent is used, the interfacial properties of the composite material will deteriorate and the mechanical strength will decrease.

[0086] In summary, this application utilizes a dry-jet wet spinning process to prepare the precursor fiber, combined with controlled cleanliness levels and atmospheric pressure within a low-temperature furnace, and employs a low-heat-resistant sizing emulsion for surface sizing treatment, to obtain carbon fiber that meets the requirements for implantable medical applications. This carbon fiber possesses advantages such as high strength, high cleanliness, and significant weight reduction. The medical-grade carbon fiber / polyetheretherketone (PEEK) composite material prepared using this carbon fiber exhibits excellent mechanical properties and can be effectively used in the manufacture of load-bearing medical implants.

[0087] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for producing carbon fibers, characterized by, The method comprises the following steps: The carbon fiber precursor is sequentially subjected to pre-oxidation, low-temperature carbonization, high-temperature carbonization, sizing, drying and winding to obtain the carbon fiber; in the low-temperature carbonization process, the atmosphere pressure in the low-temperature furnace is 10 Pa to 30 Pa.

2. The production method according to claim 1, characterized by, The pre-oxidation, low-temperature carbonization and high-temperature carbonization processes are performed in a carbonization workshop, the overall cleanliness level of the carbonization workshop is 10,000 according to the GB50073-2001 standard, and the cleanliness level of the local winding process after the high-temperature carbonization treatment is 100.

3. The preparation method according to claim 1, characterized in that, The temperature of the pre-oxidation process is 230 DEG C to 260 DEG C, the temperature of the low-temperature carbonization process is 500 DEG C to 900 DEG C, and the temperature of the high-temperature carbonization process is 1200 DEG C to 1600 DEG C.

4. The preparation method according to claim 1, characterized in that, The sizing process uses a low-heat-resistant sizing agent, and the thermal decomposition temperature of the low-heat-resistant sizing agent is less than or equal to 250 DEG C.

5. The production method according to claim 4, characterized by, The low-heat-resistant sizing agent comprises bisphenol A polyoxyethylene ether.

6. The preparation method according to claim 4, characterized in that, The content of the low-heat-resistant sizing agent in the carbon fiber is 0.4% to 1.0%.

7. The preparation method according to claim 1, characterized in that, The preparation method of the carbon fiber precursor comprises: using a dry-jet wet spinning process to draw and spin the polymer solution through a spinneret, and then sequentially washing the formed fiber bundle in water at 20 DEG C to 30 DEG C, drawing the fiber bundle in water at 50 DEG C to 70 DEG C, oiling the fiber bundle at 20 DEG C to 30 DEG C, drying the fiber bundle at 180 DEG C to 200 DEG C, drawing the fiber bundle in saturated steam at 0.8 MPa to 1.0 MPa, and drying the fiber bundle at 120 DEG C to 150 DEG C to obtain the carbon fiber precursor.

8. A carbon fiber, characterized by, The carbon fiber is prepared by the preparation method according to any one of claims 1 to 7; wherein the tensile strength of the carbon fiber is greater than or equal to 6600 MPa, the tensile modulus of the carbon fiber is greater than or equal to 300 GPa, and the ash content of the carbon fiber is less than or equal to 0.02%.

9. A medical grade carbon fiber / polyether ether ketone composite material, characterized by, The medical-grade carbon fiber / polyether ether ketone composite material comprises the carbon fiber according to claim 8, and the mass fraction of the carbon fiber is greater than or equal to 60 wt%, and the interlaminar shear strength of the medical-grade carbon fiber / polyether ether ketone composite material is greater than or equal to 100 MPa.

10. Use of the medical-grade carbon fiber / polyether ether ketone composite material according to claim 9 in a medical load-bearing implant.

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