A method for producing large-size tow carbon fibers by a filament combining process

Abstract

The application discloses a method for preparing large-size tow carbon fibers through filament combining, and the method comprises the following steps: S1, placing a plurality of small tow polyacrylonitrile-based carbon fibers containing a sizing agent in a desizing furnace under an inert gas atmosphere for desizing treatment, controlling the desizing temperature and the desizing time, and preparing small tow carbon fiber desizing filaments; S2, stacking and combining the prepared plurality of small tow desizing filaments to obtain large-size tow carbon fibers; and S3, sequentially performing water washing, water washing and drying, sizing, and sizing and drying on the large-size tow carbon fibers after the filament combining, and winding to prepare large-size tow carbon fiber products. The application can freely combine small tow carbon fibers and prepare different types of large-size carbon fiber products through filament combining, meets the differentiated market demands in different application fields, and reflects the flexibility and adaptability of the large-size tow product preparation.

Description

Technical Field

[0001] This invention patent relates to the field of carbon fiber material preparation technology, specifically a method for preparing large-size carbon fiber bundles by combining fibers. Background Technology

[0002] Carbon fiber is the main material in carbon fiber composites, possessing characteristics such as high strength, high modulus, and corrosion resistance, and is widely used in gas cylinders, wind power, photovoltaics, sports and leisure, and other fields. With the continuous development and innovation of the carbon fiber industry, advanced foreign carbon fiber companies have developed different types and properties of carbon fibers, including 6K, 12K, 24K, 36K, 48K, and other K types in terms of K number. Compared with foreign countries, my country's carbon fiber industry developed later. Currently, the high-performance and stable production types of carbon fibers are mainly concentrated in small tows (3K, 6K, 12K, and 24K). The preparation of high-performance, large-diameter tow carbon fibers is of great significance for meeting the differentiated needs of composite materials in various application fields.

[0003] Chinese Patent 202011081570.X discloses a spinning assembly for large-tow carbon fiber precursor and a method for preparing polyacrylonitrile-based large-tow carbon fiber precursor. The method includes: 1) obtaining a polyacrylonitrile polymer using an acrylonitrile aqueous suspension polymerization process, dissolving the polymer in a solvent, and obtaining a polyacrylonitrile spinning solution after degassing and filtering impurities; 2) using a spinning assembly for large-tow carbon fiber precursor, the spinning assembly consisting of a combined filter screen, a pre-distribution plate, a distribution plate, and a spinneret. This achieves uniform radial extrusion of the precursor solution on the spinneret surface, followed by solidification to obtain nascent fibers; 3) the nascent fibers undergo drawing, washing, hot drawing, pre-oiling, drying and densification, post-oiling, heat setting, and winding to obtain large-tow carbon fiber precursor. The spinning assembly involved solves the problem of uneven radial extrusion pressure on the spinneret surface after the diameter of the spinneret for large filament bundles above 24K is enlarged, which affects the fiber performance. It achieves no broken or drifting filaments on the spinneret surface of large filament bundles, and the fineness deviation of the filament is 0-3.0%, which improves the various performance indicators of the filament and the stable industrial production.

[0004] Chinese Patent 202111646223.1 discloses a 35K large-tow carbon fiber and its preparation method. The preparation method includes the following steps: 35K large-tow polyacrylonitrile copolymer fibers are placed in an oxidation furnace for pre-oxidation treatment in an air atmosphere to obtain 35K large-tow carbon fiber pre-oxidized fibers; the 35K large-tow carbon fiber pre-oxidized fibers are subjected to low-temperature carbonization treatment; the 35K large-tow carbon fiber pre-oxidized fibers after low-temperature carbonization treatment are subjected to high-temperature carbonization treatment; the 35K large-tow carbon fiber pre-oxidized fibers after high-temperature carbonization treatment undergo surface treatment, sizing, and drying to obtain 35K large-tow polyacrylonitrile carbon fiber; the prepared 35K large-tow polyacrylonitrile carbon fiber sample is impregnated and cured in a testing reagent, and then subjected to mechanical property testing. This 35K large-tow carbon fiber and its preparation method can effectively solve the core-sheath structure problem of large-tow pre-oxidation, improve the production efficiency of carbon fiber composite material applications, and reduce production costs. Summary of the Invention

[0005] This invention utilizes high-performance small-tow carbon fibers (3K, 6K, 12K, or 24K) with a stable domestic supply in terms of raw material selection. This solves the problems of difficulty in preparing large-grammage, large-tow polyacrylonitrile precursor fibers and the corresponding complexity of carbonization during the production of large-size tows. From the perspective of preparing carbon fiber tows of different sizes (30K, 36K, 48K, etc.), small tows can be freely combined and blended to prepare different types of products, adapting to differentiated market application needs. This invention offers flexibility and adaptability in product preparation, catering to the market and creating value.

[0006] The technical solution adopted in this invention is a method for preparing large-size carbon fiber bundles by combining fibers, which includes the following steps:

[0007] Step S1: Under an inert gas atmosphere, multiple bundles of small polyacrylonitrile-based carbon fibers containing sizing agent are placed in a desizing furnace for desizing treatment. The desizing temperature and desizing time are controlled to obtain desizing filaments of small bundle carbon fibers.

[0008] Step S2: The obtained multiple small filament bundles of desizing filaments are stacked and combined into the required large-size carbon fiber bundles.

[0009] Step S3: The large-size carbon fiber bundles after being combined are sequentially subjected to water washing, water washing and drying, sizing, and sizing and drying, and then wound to prepare the desired large-size carbon fiber bundle products.

[0010] The sizing agent in step S1 is an epoxy resin with a thermal decomposition temperature <600℃. The draw ratio of the desizing treatment in step S1 is 0.98 to 1.02, the draw ratio of the superimposed yarn in step S2 is 1.0 to 1.02, the draw ratio of the washing treatment in step S3 is 0.96 to 1.0, and the draw ratio of the drying treatment in step S3 is 1.0 to 1.02.

[0011] The preferred sizing agent is bisphenol A, with a thermal decomposition temperature of <380℃.

[0012] In step S1, four temperature gradient desizing furnaces are used. The temperature range inside the desizing furnace is 400-700℃, and the temperature gradient difference between each temperature zone is 50-100℃.

[0013] In step S1, the production speed of the desizing furnace is 8-10 m / min, and the desizing time is 0.5-1.0 min.

[0014] The water washing process in step S3 is a combination of ultrasonic and compressed air treatment.

[0015] The ultrasonic wave adopts a frequency-adjustable mode, preferably with an adjustable frequency of 25-30KHz.

[0016] The compressed air is introduced vertically upward from the bottom of the carbon fiber bundle, preferably at a pressure of 0.2 to 0.3 MPa.

[0017] In step S3, the drying process uses two series-connected contact drying rollers, with a heat source of 0.3-0.5 MPa saturated steam, and the moisture content of the carbon fiber is controlled to be below 0.1%.

[0018] A heat-conducting oil pressure roller is located directly above the second contact drying roller in series. The temperature is adjustable from room temperature to 150°C, and the pneumatic pressing pressure of the pressure roller is adjustable from 0.1 to 0.3 MPa. The combined large-size filament bundles are extruded and thermoformed.

[0019] Beneficial effects of the present invention

[0020] 1. This invention uses high-performance small-tow carbon fiber with stable domestic supply as raw material, eliminating the need to prepare large-grammage, large-tow polyacrylonitrile precursor fibers and the corresponding carbonization process.

[0021] 2. This invention uses four temperature gradient desizing furnaces. By matching the process parameters of desizing temperature and desizing time, the sizing agent carried in small tow carbon fiber products can be effectively removed.

[0022] 3. This invention employs a method of layering desizing fibers, using a combination of ultrasonic and compressed air washing, and then drying and extruding thermoforming. This method can effectively combine multiple small tows of carbon fiber together, meeting the differentiated market demands of different application fields and demonstrating the flexibility and adaptability in preparing large-scale tow products. Detailed Implementation

[0023] Comparative Example 1: Wet-spun 48K carbon fiber, tensile strength 4300MPa, tensile modulus 250GPa, elongation at break 1.7%, linear density 3200g / km.

[0024] Comparative Example 2: Wet-spun 48K carbon fiber, tensile strength 4480MPa, tensile modulus 234GPa, elongation at break 1.9%, linear density 3200g / km.

[0025] Example 1: Four dry-jet wet-spun 12K carbon fibers (product properties: tensile strength 4990MPa, tensile modulus 244GPa, elongation at break 2.0%, linear density 806g / km, sizing agent type bisphenol A, sizing content 1.09%) were used. The desizing furnace had four temperature zones set at 400℃ / 450℃ / 500℃ / 550℃, a production speed of 10m / min, a desizing time of 0.6min, a water washing ultrasonic frequency of 26KHz, and a compressed air pressure of 0. The saturated steam pressure of the contact drying roller is 0.3 MPa, the temperature of the heat transfer oil roller is 135℃, the pneumatic pressing pressure of the roller is 0.18 MPa, the draw ratio of the desizing treatment is 1.0, the draw ratio of the superimposed yarn is 1.0, the draw ratio of the water washing treatment is 0.96, the draw ratio of the sizing and drying treatment is 1.01, and the tensile strength of the 48K carbon fiber prepared by winding is 4450 MPa, the tensile modulus is 248 MPa, the elongation at break is 1.8%, and the linear density is 3212 g / km.

[0026] Example 2: Using two dry-jet wet-spun 24K carbon fibers (product properties: tensile strength 4970MPa, tensile modulus 238GPa, elongation at break 2.0%, linear density 1607g / km, sizing agent type bisphenol A, sizing content 1.08%), and using the same yarn preparation process, the resulting 48K carbon fibers had a tensile strength of 4440MPa, a tensile modulus of 247MPa, an elongation at break of 1.8%, and a linear density of 3204g / km.

[0027] Example 3: Using three dry-jet wet-spun 12K carbon fibers (product properties: tensile strength 4990MPa, tensile modulus 244GPa, elongation at break 2.0%, linear density 806g / km, sizing agent type bisphenol A, sizing content 1.09%), and using the same yarn preparation process, the resulting 36K carbon fibers had a tensile strength of 4678MPa, a tensile modulus of 248MPa, an elongation at break of 1.9%, and a linear density of 2420g / km.

[0028] Example 4: Using one dry-jet wet-spun 12K carbon fiber (product properties: tensile strength 4990MPa, tensile modulus 244GPa, elongation at break 2.0%, linear density 806g / km, sizing agent type bisphenol A, sizing content 1.09%) and one dry-jet wet-spun 24K carbon fiber (product properties: tensile strength 4970MPa, tensile modulus 238GPa, elongation at break 2.0%, linear density 1607g / km, sizing agent type bisphenol A, sizing content 1.08%), and employing the same yarn preparation process, the resulting 36K carbon fiber had a tensile strength of 4740MPa, a tensile modulus of 249MPa, an elongation at break of 1.9%, and a linear density of 2407g / km.

Claims

1. A method for preparing large-size carbon fiber bundles by combining fibers, characterized in that, The preparation method includes the following steps: Step S1: Under an inert gas atmosphere, multiple bundles of small tows of polyacrylonitrile-based carbon fibers containing sizing agent are placed in a desizing furnace for desizing treatment. The desizing temperature and desizing time are controlled to obtain desizing filaments of small tow carbon fibers. Step S2: The obtained multiple small filament bundles of desizing filaments are stacked and combined into the required large-size carbon fiber bundles; Step S3: The large-size towed carbon fibers after being combined are sequentially subjected to water washing, water washing and drying, sizing, and sizing and drying, and then wound to prepare the desired large-size towed carbon fiber product. The sizing agent in step S1 is an epoxy resin with a thermal decomposition temperature <600℃; the draw ratio of the desizing treatment in step S1 is 0.98~1.02; the draw ratio of the superimposed yarn in step S2 is 1.0~1.02; the draw ratio of the washing treatment in step S3 is 0.96~1.0; and the draw ratio of the drying treatment in step S3 is 1.0~1.

02. The sizing agent is bisphenol A type, with a thermal decomposition temperature of <380℃; In step S1, four temperature gradient desizing furnaces are used. The temperature range inside the desizing furnace is 400~700℃, and the temperature difference between each temperature gradient zone is 50~100℃.

2. The method for preparing large-size carbon fiber bundles by combining fibers according to claim 1, characterized in that: In step S1, the production speed of the desizing furnace is 8~10m / min, and the desizing time is 0.5~1.0min.

3. The method for preparing large-diameter carbon fiber bundles according to claim 1, characterized in that: The water washing process in step S3 is a combination of ultrasonic and compressed air treatment.

4. The method for preparing large-diameter carbon fiber bundles according to claim 3, characterized in that: The ultrasonic wave uses a frequency-adjustable mode, with an adjustable frequency of 25~30KHz.

5. The method for preparing large-diameter carbon fiber bundles according to claim 3, characterized in that: The compressed air is introduced vertically upward from the bottom of the carbon fiber bundle at a pressure of 0.2~0.3MPa.

6. The method for preparing large-diameter carbon fiber bundles according to claim 1, characterized in that: In step S3, the drying process uses two series-connected contact drying rollers, with a heat source of 0.3~0.5MPa saturated steam, and the moisture content of the carbon fiber is controlled to be below 0.1%.

7. The method for preparing large-diameter carbon fiber bundles according to claim 6, characterized in that: A heat-conducting oil pressure roller is located directly above the second contact drying roller in series. The temperature is adjustable from room temperature to 150°C, and the pneumatic pressing pressure of the pressure roller is adjustable from 0.1 to 0.3 MPa. The combined large-size filament bundles are extruded and thermoformed.