Large-tow carbon fiber sizing method and device

Abstract

The invention discloses a large-tow carbon fiber sizing method and device, and relates to the technical field of carbon fibers. Large-tow carbon fibers are treated by a first-stage dynamic tension control unit, an ultrasonic-assisted sizing tank unit, a second-stage dynamic tension control unit, a quantitative extrusion unit and a pre-drying and winding unit in sequence, and a low-tension infiltration-high-tension distribution dynamic tension process is adopted. Macroscopic distribution of the slurry on the section of the tow is actively regulated and controlled in a mechanical mechanical mode, and complementation with ultrasonic microcosmic action is formed; the ultrasonic cavitation effect is utilized to effectively break the air barrier in the large tow, so that the sizing agent is ensured to directly reach the core part of the tow, and the dry core phenomenon is eliminated. According to the sizing method provided by the invention, the sizing uniformity of the large-tow carbon fibers can be remarkably improved, the interface performance of the carbon fibers is favorably improved, and the fluffing amount is reduced.

Description

Technical Field

[0001] This invention relates to the field of carbon fiber technology, and more specifically, to a method and apparatus for sizing large-tow carbon fibers. Background Technology

[0002] In the sizing process of carbon fiber, the uniform coating of the sizing agent (or "bundling agent" or "impregnating agent") is crucial, as it directly affects the interfacial bonding performance between carbon fiber and resin matrix, the mechanical properties of subsequent composite materials, and the amount of fuzz during processing.

[0003] In existing technologies, the traditional impregnation-extrusion roller sizing method is effective for small tow carbon fibers (such as 3K and 12K). However, when applied to large tow carbon fibers (48K and above), due to the large number and dense arrangement of their internal monofilaments, the following drawbacks exist: (1) The outer monofilaments of the filament bundle are more likely to come into contact with and be coated with the sizing agent, while the inner monofilaments are difficult to be effectively penetrated by the sizing agent due to capillary action and fluid resistance, forming a "dry core" phenomenon. (2) The extrusion roller can only apply pressure to the entire filament bundle, and cannot promote the uniform distribution of the sizing agent at the microscale inside the filament bundle, resulting in uneven sizing thickness on the surface of the single filament; (3) Traditional equipment applies a relatively constant tension along the entire sizing path, which cannot be dynamically adjusted according to the needs of the sizing agent wetting stage, which is not conducive to the sizing material penetrating into the interior.

[0004] Uneven distribution of the sizing agent will lead to weak interfacial regions in the subsequent preparation of composite materials from large-tow carbon fibers, severely affecting the full realization of their performance. Therefore, it is urgent to solve the technical problem of uneven wetting and coating of the sizing agent on the individual filaments inside large-tow carbon fibers.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a method and apparatus for sizing large-tow carbon fibers, aiming to solve the technical problem of uneven wetting and coating of sizing agent on the individual filaments inside large-tow carbon fibers.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides a method for sizing large-tow carbon fiber, wherein the large-tow carbon fiber sizing device includes a first-stage dynamic tension control unit, an ultrasonic-assisted sizing tank unit, a second-stage dynamic tension control unit, a quantitative extrusion unit, and a pre-drying and winding unit arranged sequentially along the traveling direction of the carbon fiber filament bundle. The steps are as follows: Pre-relaxation and initial impregnation: The tension of the large tow carbon fiber entering the ultrasonic-assisted sizing tank unit is adjusted to T1 by the first-stage dynamic tension control unit; Ultrasonic enhanced penetration: Large tow carbon fibers are immersed in sizing agent in an ultrasonic-assisted sizing tank unit and undergo ultrasonic treatment at the same time; Dynamic tension-assisted redistribution: After the large tow carbon fibers leave the ultrasonic-assisted sizing tank unit, the tension is increased to T2 by the second-stage dynamic tension control unit and maintained at the tension of T2. Quantitative control and curing: After passing through the second-stage dynamic tension control unit, the material enters the quantitative extrusion unit, where the amount of slurry applied is regulated by extrusion; after passing through the quantitative extrusion unit, the material enters the pre-drying and winding unit to cure the slurry.

[0008] In an optional implementation, T1 ranges from 25cN to 35cN, and T2 ranges from 90cN to 110cN; And / or, the specifications for large-tow carbon fibers are 48K-96K.

[0009] In an optional embodiment, the metering extrusion unit includes a metering extrusion roller pair to remove excess slurry by extrusion, thereby controlling the slurry application rate to be 0.8wt%-1.5wt%.

[0010] In an optional implementation, the tension of T2 is maintained for 1m-3m before entering the quantitative extrusion unit.

[0011] In an optional embodiment, the ultrasonic-assisted sizing tank unit includes a sizing tank for holding the sizing agent, and ultrasonic transducers are provided on both sides and the bottom of the sizing tank.

[0012] In an optional implementation, the vibration frequency range of the ultrasonic transducer is controlled to be 15kHz-100kHz, and the power density is 0.2W / cm². 2 -1.0W / cm 2 The ultrasound time is 1s-10s.

[0013] In an optional embodiment, the first-stage dynamic tension control unit includes a first guide roller assembly and a first-stage dynamic tension controller, which controls the tension applied to the carbon fiber by the first guide roller assembly.

[0014] In an optional implementation, both the first-stage dynamic tension control unit and the second-stage dynamic tension control unit employ a closed-loop controlled servo motor-driven guide roller system.

[0015] In an optional implementation, during the pre-drying and winding process, the drying temperature is controlled at 110℃-130℃ and the drying time is 30s-180s.

[0016] In a second aspect, the present invention provides an apparatus for implementing any of the large-tow carbon fiber sizing methods described above, comprising: a first-stage dynamic tension control unit, an ultrasonic-assisted sizing tank unit, a second-stage dynamic tension control unit, a quantitative extrusion unit, and a pre-drying and winding unit arranged sequentially along the traveling direction of the carbon fiber filament bundle. Both the first-stage dynamic tension control unit and the second-stage dynamic tension control unit include a guide roller assembly and a controller for controlling the tension applied by the guide roller assembly; The ultrasonic-assisted sizing tank unit includes a sizing tank for holding sizing agent, and an ultrasonic transducer is installed on the tank body of the sizing tank. The quantitative extrusion unit includes a quantitative extrusion roller pair, which removes excess slurry by extrusion to control the slurry application rate; The pre-drying and rewinding unit includes a pre-drying oven.

[0017] The present invention has the following beneficial effects: A smaller tension T1 is applied by the first-stage dynamic tension control unit, making the filament bundle easier to unfold and initially wet in a relaxed state; sizing is performed simultaneously by the ultrasonic-assisted sizing tank unit, with the high-frequency vibration of ultrasound directly acting on the filament bundle and sizing agent flowing through the tank. The ultrasonic cavitation effect effectively breaks down air barriers inside the large filament bundle, ensuring the sizing agent reaches the core of the filament bundle and eliminating the "dry core" phenomenon; a higher tension is applied by the second-stage dynamic tension control unit, making the filament bundle compact and promoting the microscopic redistribution of sizing agent among the filaments through the "squeeze-suction" effect; sizing is controlled by a quantitative extrusion unit; and drying, curing, and winding are performed by a pre-drying and winding unit. Large-tow carbon fibers are processed sequentially through a first-stage dynamic tension control unit, an ultrasonic-assisted sizing tank unit, a second-stage dynamic tension control unit, a quantitative extrusion unit, and a pre-drying and winding unit. The process employs a "low-tension impregnation-high-tension distribution" dynamic tension technology, which actively controls the macroscopic distribution of the sizing material across the fiber tow cross-section through mechanical means. This complements the ultrasonic microscopic action, significantly improving the sizing uniformity of large-tow carbon fibers, which is beneficial for improving the interfacial properties of carbon fibers and reducing fuzzing. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This invention provides a structural schematic diagram of a large-tow carbon fiber sizing device.

[0020] Icons: 001-First-stage dynamic tension control unit; 002-Ultrasonic-assisted sizing tank unit; 003-Second-stage dynamic tension control unit; 004-Quantitative extrusion unit; 005-Pre-drying and winding unit; 101-First guide roller group; 102-First-stage dynamic tension controller; 103-Sizing tank; 104-Second-stage dynamic tension controller; 105-Quantitative extrusion roller pair; 106-Pre-drying oven. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention 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.

[0022] like Figure 1 As shown, this embodiment of the invention provides a sizing device for large tow carbon fibers, including a first-stage dynamic tension control unit 001, an ultrasonic-assisted sizing tank unit 002, a second-stage dynamic tension control unit 003, a quantitative extrusion unit 004, and a pre-drying and winding unit 005 arranged sequentially along the traveling direction of the carbon fiber tow. The large tow carbon fibers are processed through the above five units in sequence to complete the sizing process.

[0023] The first-stage dynamic tension control unit 001 is located before the ultrasonic-assisted sizing tank unit 002. It applies a low, adjustable first preset tension T1 to the fiber bundle before it enters the sizing tank, making the fiber bundle easier to unwind and initially wet in a relaxed state. In some embodiments, the first-stage dynamic tension control unit 001 includes a first guide roller group 101 and a first-stage dynamic tension controller 102. The first-stage dynamic tension controller 102 controls the tension applied to the carbon fiber by the first guide roller group 101. Specifically, the controller has a conventional structure and can adjust parameters such as rotation speed of its respective guide roller group.

[0024] The ultrasonic-assisted sizing tank unit 002 includes a sizing tank 103 for holding the sizing agent, and at least one array of ultrasonic transducers (not shown) immersed in the sizing agent. The high-frequency vibrations emitted by the ultrasonic transducer array directly act on the filament bundle and sizing agent flowing through the tank.

[0025] The second-stage dynamic tension control unit 003 applies a high, adjustable second preset tension T2 (T2>T1) to the sizing bundle, so that the bundle is in a compact state, and the "squeeze-suction" effect promotes the microscopic redistribution of the sizing material among the monofilaments. The second-stage dynamic tension control unit 003 includes a second-stage dynamic tension controller 104 and a corresponding guide roller assembly, and uses the second-stage dynamic tension controller 104 to control the tension applied to the carbon fiber by the corresponding guide roller assembly.

[0026] Specifically, the controller has the structure of an existing controller, capable of adjusting parameters such as rotational speed of its respective guide roller group. Both the first-stage dynamic tension control unit 001 and the second-stage dynamic tension control unit 003 employ closed-loop controlled servo motor-driven guide roller systems, which can monitor and precisely adjust the yarn tension in real time.

[0027] The quantitative extrusion unit 004, located after the second-stage dynamic tension control unit 003, is used to precisely control the amount of sizing agent adhering to the entire fiber bundle. The quantitative extrusion unit 004 includes a quantitative extrusion roller pair 105, which removes excess sizing agent through precision metering rollers to obtain a precise and consistent sizing rate. In actual operation, the force exerted by the quantitative extrusion roller pair 105 on the carbon fiber can be adjusted by the concentration of the sizing agent in the sizing tank 103. A larger force can be applied when the sizing agent concentration is higher, and a smaller force can be applied when the sizing agent concentration is lower. The magnitude of the force exerted by the quantitative extrusion roller pair 105 can be linearly controlled empirically, and the specific parameters are not limited. For example, the sizing agent concentration X is directly proportional to the force F, i.e., F = aX + b, where a is a positive number.

[0028] The pre-drying and winding unit 005 includes a pre-drying oven 106, which dries the carbon fiber coated with sizing agent to achieve curing. After drying, the product enters the winding process to complete the sizing operation.

[0029] This invention provides a method for sizing large-tow carbon fibers, the steps of which are as follows: S1, Pre-relaxation and initial infiltration The tension of the large tow carbon fibers entering the ultrasonic-assisted sizing tank unit 002 is adjusted to T1 by the first-stage dynamic tension control unit 001, so that the large tow carbon fibers enter the sizing tank with a lower tension T1. This state is conducive to the physical looseness of the tow, creating space for the sizing agent to initially enter the gaps between the tow fibers.

[0030] In some embodiments, the specifications of the large-tow carbon fiber are 48K-96K. The apparatus and method provided in this embodiment of the invention are applicable to large-tow carbon fibers of different specifications (48K and above), and have good adaptability to sizing agents of different viscosities and compositions. T1 ranges from 25cN to 35cN, such as 25cN, 28cN, 30cN, 33cN, 35cN, etc.

[0031] S2, Ultrasonic Enhanced Penetration Large-tow carbon fibers are immersed in sizing agent in ultrasonic-assisted sizing tank unit 002 and undergo ultrasonic treatment simultaneously. The cavitation effect generated by high-frequency vibration produces and collapses microbubbles inside the fiber bundle and on the surface of the individual filaments, strongly breaking the gas-liquid interface and driving away the bubbles. At the same time, micro-jet and shear effects directly impact the surface of the individual filaments, forcing the sizing agent to overcome resistance and penetrate into the core of the fiber bundle, achieving preliminary uniform wetting of the surface of the individual filaments.

[0032] In some embodiments, the ultrasonic-assisted sizing tank unit 002 includes a sizing tank 103 for holding the sizing agent. Ultrasonic transducers are provided on both sides and the bottom of the sizing tank 103 to further enhance the wetting effect. The ultrasonic cavitation effect can effectively break through the air barrier inside the large filament bundle, ensuring that the sizing agent reaches the core of the filament bundle directly and eliminating the "dry core" phenomenon.

[0033] Furthermore, the vibration frequency range of the ultrasonic transducer is controlled to be 15kHz-100kHz, such as 15kHz, 20kHz, 30kHz, 40kHz, 50kHz, 60kHz, 70kHz, 80kHz, 90kHz, 100kHz, etc. The power density is 0.2W / cm². 2 -1.0W / cm 2 For example, it can be 0.2W / cm 2 0.3W / cm 2 0.4W / cm 2 0.5W / cm 2 0.6W / cm 2 0.7W / cm 2 0.8W / cm 2 0.9W / cm 2 1.0W / cm 2 The ultrasound duration is 1s-10s, such as 1s, 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, 10s, etc.

[0034] S3, Dynamic Tension-Assisted Redistribution After the large tow of carbon fibers leaves the ultrasonic-assisted sizing tank unit 002, the tension is increased to T2 using the second-stage dynamic tension control unit 003 and maintained at T2. The tension of the sizing-carrying tow is rapidly increased from T1 to T2. During this process, the overall cross-section of the tow contracts, creating a "squeezing" effect on the internal sizing material; simultaneously, due to changes in capillary pressure, some sizing material is "drawn back" from the outside to the inside. This "squeezing-drawing" effect induced by controllable tension changes significantly promotes the uniform redistribution of the sizing material along the cross-sectional direction of the tow.

[0035] In some embodiments, T2 ranges from 90cN to 110cN, such as 90cN, 95cN, 100cN, 105cN, 110cN, etc. After maintaining the tension of T2 for 1m-3m (such as 1.0m, 1.5m, 2.0m, 2.5m, 3.0m, etc.), it enters the quantitative extrusion unit 004 to ensure a uniform distribution of the slurry in the cross-sectional direction of the filament bundle.

[0036] The embodiments of the present invention employ a dynamic tension process of "low tension wetting - high tension distribution", which actively controls the macroscopic distribution of the slurry in the cross section of the filament bundle through mechanical means, complementing the ultrasonic microscopic effect.

[0037] S4. Quantitative Control and Curing After passing through the second-stage dynamic tension control unit 003, the slurry enters the quantitative extrusion unit 004, where excess slurry is removed by precision metering rollers to achieve a precise and consistent slurry application rate. After passing through the quantitative extrusion unit 004, the slurry enters the pre-drying and winding unit 005 to solidify.

[0038] In some embodiments, the quantitative extrusion unit 004 includes a quantitative extrusion roller pair 105, which removes excess slurry by extrusion to control the slurry rate to be 0.8wt%-1.5wt%, such as 0.8wt%, 0.9wt%, 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, etc.

[0039] In some embodiments, drying is performed using a pre-drying oven 106, with the drying temperature controlled at 110℃-130℃, such as 110℃, 115℃, 120℃, 125℃, 130℃, etc.; and the drying time is 30s-180s, such as 30s, 50s, 80s, 100s, 130s, 150s, 180s, etc.

[0040] It should be noted that the sizing method optimized by this invention can significantly improve the uniformity of sizing, and ultimately improve the interfacial properties of large-tow carbon fiber composites by about 10%-30% and reduce the amount of fuzz by more than 50%.

[0041] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0042] Example 1 This embodiment provides a method for sizing large-tow carbon fibers, employing... Figure 1 The device in the middle processes the data, and the steps are as follows: 48K large-tow carbon fiber is used, along with an epoxy resin sizing agent (model EP51).

[0043] The filament bundle passes through the first guide roller group 101, and the tension T1 of it entering the sizing tank 103 is precisely controlled by the first-stage dynamic tension controller 102 to be 30cN.

[0044] The filament bundle is immersed in the sizing agent in sizing tank 103. Simultaneously, three sets of ultrasonic transducers (frequency 40kHz, power density 0.5W / cm³) arranged on both sides and the bottom of the tank are activated. 2 The duration of the ultrasound treatment is approximately 2 seconds.

[0045] After the slurry-carrying fiber bundle leaves the slurry tank 103, the tension of the bundle is immediately increased to T2=100cN by the second-stage dynamic tension controller 104, and the bundle is maintained at this tension for about 2 meters to complete the dynamic redistribution of the slurry.

[0046] The filament bundle is then passed through a metering extrusion roller pair 105 with a precisely positioned gap (applied tension of 110 cN) to control the sizing rate at 1.20 ± 0.20 wt%.

[0047] Finally, the filament bundles are placed in a pre-drying oven 106 at 120°C and left for about 1 minute to initially solidify the slurry.

[0048] The carbon fibers prepared in this embodiment were observed by scanning electron microscopy, which showed that after sizing, the carbon fiber monofilaments were clearly separated, the surface sizing film was continuous and uniform, and there were no exposed points; the shear strength was 81.3 MPa, and the fuzzing weight was 3.0 mg / 50 m.

[0049] Example 2 This embodiment provides a method for sizing large-tow carbon fibers, employing... Figure 1 The device in the middle processes the data, and the steps are as follows: 48K large-tow carbon fiber is used, along with bismaleimide resin-type sizing agent (model BMI-5100).

[0050] The filament bundle passes through the first guide roller group 101, and the tension T1 of it entering the sizing tank 103 is precisely controlled by the first-stage dynamic tension controller 102 to be 30cN.

[0051] The filament bundle is immersed in the sizing agent in sizing tank 103. Simultaneously, three sets of ultrasonic transducers (frequency 50kHz, power density 0.5W / cm²) arranged on both sides and the bottom of the tank are activated.2 The duration of the ultrasound treatment is approximately 3 seconds.

[0052] After the slurry-carrying fiber bundle leaves the slurry tank 103, the tension of the bundle is immediately increased to T2=100 cN by the second-stage dynamic tension controller 104, and the bundle is maintained at this tension for about 2 meters to complete the dynamic redistribution of the slurry.

[0053] The filament bundle is then passed through a metering extrusion roller with a precisely positioned gap (applied tension of 105 cN) to control the sizing rate at 1.00 ± 0.20 wt%.

[0054] Finally, the filament bundles are placed in a pre-drying oven 6 at 160°C and left for about 1 minute to initially solidify the slurry.

[0055] The carbon fibers prepared in this embodiment were observed by scanning electron microscopy, which showed that after sizing, the carbon fiber monofilaments were clearly separated, the surface sizing film was continuous and uniform, and there were no exposed points; the shear strength was 75.3 MPa, and the fuzzing weight was 5.1 mg / 50m.

[0056] Example 3 This embodiment provides a method for sizing large-tow carbon fibers, employing... Figure 1 The device in the middle processes the data, and the steps are as follows: 60K large-tow carbon fiber is used, along with an epoxy resin sizing agent (model EP51).

[0057] The filament bundle passes through the first guide roller group 101, and the tension T1 of it entering the sizing tank 103 is precisely controlled by the first-stage dynamic tension controller 102 to be 30 cN.

[0058] The filament bundle is immersed in the sizing agent in the sizing tank 103. At the same time, three sets of ultrasonic transducers (frequency 30 kHz, power density 0.5 W / cm²) arranged on both sides and the bottom of the tank are activated. The ultrasonic treatment time is approximately 2 seconds.

[0059] After the slurry-carrying fiber bundle leaves the slurry tank 103, the tension of the bundle is immediately increased to T2=100cN by the second-stage dynamic tension controller 104, and the bundle is maintained at this tension for about 2 meters to complete the dynamic redistribution of the slurry.

[0060] The filament bundle is then passed through a metering extrusion roller pair 105 with a precisely positioned gap (with an applied tension of 115) to control the sizing rate at 1.20 ± 0.20 wt%.

[0061] Finally, the filament bundles are placed in a pre-drying oven 106 at 120°C and left for about 1 minute to initially solidify the slurry.

[0062] The carbon fibers prepared in this embodiment were observed by scanning electron microscopy, which showed that after sizing, the carbon fiber monofilaments were clearly separated, the surface sizing film was continuous and uniform, and there were no exposed points; the shear strength was 78.0 MPa, and the fuzzing weight was 6.4 mg / 50 m.

[0063] Example 4 The only difference from Example 1 is that T2 = 70cN.

[0064] The results showed that after sizing, the carbon fiber monofilaments adhered to each other, and there were sizing agent protrusions on the surface; the layer shear strength was 59.5 MPa, and the fuzzing amount was 13.5 mg / 50 m.

[0065] Example 5 The only difference from Example 1 is that T2 = 150 cN.

[0066] The results showed that the carbon fiber monofilaments were exposed after sizing and were prone to breakage; the shear strength was 41.7 MPa and the fuzzing weight was 18.3 mg / 50 m.

[0067] Comparative Example 1 48K large-tow carbon fiber and epoxy resin sizing agent (same as in Example 1) were used. The carbon fiber was sized using a traditional impregnation and extrusion method, with the following specific steps: The large-tow carbon fiber was passed through a sizing impregnation tank, and excess adhesive was removed by extrusion rollers, controlling the sizing rate to be 1.20±0.20 wt%. It was then placed in a pre-drying oven at 120℃ for about 1 minute to pre-cure the sizing agent.

[0068] Scanning electron microscopy revealed that the carbon fiber monofilaments adhered after sizing; the shear strength was 70.7 MPa and the fuzzing weight was 9.6 mg / 50 m.

[0069] Comparative Example 2 48K large-tow carbon fiber and epoxy resin sizing agent (same as in Example 1) were used. The carbon fiber was sized using a traditional impregnation and extrusion method, with the following specific steps: The large-tow carbon fiber was passed through a sizing impregnation tank, and excess adhesive was removed by extrusion rollers, controlling the sizing rate to be 1.00±0.20 wt%. It was then placed in a pre-drying oven at 160℃ for about 1 minute to pre-cure the sizing agent.

[0070] Scanning electron microscopy revealed that the carbon fiber monofilaments exhibited adhesion and insufficient sizing after sizing; the lamellar shear strength was 65.4 MPa, and the fuzzing weight was 11.8 mg / 50 m.

[0071] Comparative Example 3 The only difference from Example 1 is that the three sets of ultrasonic transducers arranged on the slurry tank 103 are not activated.

[0072] The results showed that the carbon fiber monofilaments were slightly adhered after sizing, and the surface sizing film was continuous and uniform; the layer shear strength was 75.8 MPa, and the fuzzing amount was 7.8 mg / 50 m.

[0073] Comparative Example 4 The only difference from Example 1 is that both T1 and T2 are 30cN.

[0074] The results showed that the carbon fiber monofilaments were severely adhered after sizing; the layer shear strength was 41.4 MPa and the fuzzing amount was 17.2 mg / 50 m.

[0075] Comparative Example 5 The only difference from Example 1 is that both T1 and T2 are 100cN.

[0076] The results showed that the carbon fiber monofilaments were severely exposed after sizing, indicating insufficient sizing; the shear strength was 33.7 MPa, and the fuzzing amount was 22.1 mg / 50 m.

[0077] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for sizing large-tow carbon fibers, characterized in that, The large-tow carbon fiber sizing device includes a first-stage dynamic tension control unit, an ultrasonic-assisted sizing tank unit, a second-stage dynamic tension control unit, a quantitative extrusion unit, and a pre-drying and winding unit arranged sequentially along the direction of carbon fiber filament travel. The steps are as follows: Pre-relaxation and initial impregnation: The tension of the large tow carbon fiber entering the ultrasonic-assisted sizing tank unit is adjusted to T1 by the first-stage dynamic tension control unit; Ultrasonic enhanced penetration: The large tow carbon fibers are immersed in the sizing agent in the ultrasonic-assisted sizing tank unit and undergo ultrasonic treatment at the same time; Dynamic tension-assisted redistribution: After the large tow carbon fibers leave the ultrasonic-assisted sizing tank unit, the tension is increased to T2 by the second-stage dynamic tension control unit and maintained at the tension of T2. Quantitative control and curing: After passing through the second-stage dynamic tension control unit, the material enters the quantitative extrusion unit, where the amount of sizing is adjusted by extrusion. After passing through the quantitative extrusion unit, the slurry enters the pre-drying and winding unit to solidify.

2. The method for sizing large-tow carbon fibers according to claim 1, characterized in that, The range of T1 is 25cN-35cN, and the range of T2 is 90cN-110cN; And / or, the specifications of the large tow carbon fibers are 48K-96K.

3. The method for sizing large-tow carbon fibers according to claim 1, characterized in that, The quantitative extrusion unit includes a quantitative extrusion roller pair, which removes excess slurry by extrusion to control the slurry application rate to 0.8wt%-1.5wt%.

4. The method for sizing large-tow carbon fibers according to claim 1 or 3, characterized in that, After maintaining the tension of T2 for 1m-3m, it enters the quantitative extrusion unit.

5. The method for sizing large-tow carbon fibers according to claim 1, characterized in that, The ultrasonic-assisted sizing tank unit includes a sizing tank for holding the sizing agent, and ultrasonic transducers are provided on both sides and the bottom of the sizing tank.

6. The method for sizing large-tow carbon fibers according to claim 5, characterized in that, The vibration frequency range of the ultrasonic transducer is controlled to be 15kHz-100kHz, and the power density is 0.2W / cm². 2 -1.0W / cm 2 The ultrasound time is 1s-10s.

7. The method for sizing large-tow carbon fibers according to claim 1, characterized in that, The first-stage dynamic tension control unit includes a first guide roller assembly and a first-stage dynamic tension controller, which controls the tension applied to the carbon fiber by the first guide roller assembly.

8. The method for sizing large-tow carbon fibers according to claim 1 or 7, characterized in that, Both the first-stage dynamic tension control unit and the second-stage dynamic tension control unit employ a closed-loop controlled servo motor-driven guide roller system.

9. The method for sizing large-tow carbon fibers according to claim 1, characterized in that, During the pre-drying and winding process, the drying temperature is controlled at 110℃-130℃ and the drying time is 30s-180s.

10. An apparatus for implementing the sizing method for large-tow carbon fibers according to any one of claims 1-9, characterized in that, include: The first-stage dynamic tension control unit, the ultrasonic-assisted sizing tank unit, the second-stage dynamic tension control unit, the quantitative extrusion unit, and the pre-drying and winding unit are arranged sequentially along the direction of carbon fiber bundle travel. Both the first-stage dynamic tension control unit and the second-stage dynamic tension control unit include a guide roller assembly and a controller for controlling the tension applied by the guide roller assembly; The ultrasonic-assisted sizing tank unit includes a sizing tank for holding sizing agent, and an ultrasonic transducer is provided on the tank body of the sizing tank. The quantitative extrusion unit includes a quantitative extrusion roller pair, which removes excess slurry by extrusion to control the slurry application rate; The pre-drying and winding unit includes a pre-drying oven.

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