A method for regenerating carbon fibers in a resin-based composite material

Abstract

The application discloses a method for regenerating carbon fibers in resin-based composite materials, which comprises the following steps: (1) adding water into a heated water storage tank to generate water vapor; (2) opening corresponding control valves to allow the water vapor to enter a gas storage tank; (3) pressurizing the water vapor in the gas storage tank to a required pressure; (4) opening a gas outlet valve of the corresponding gas storage tank to allow high-temperature and high-pressure water vapor in the corresponding gas storage tank to enter a decomposition tank containing resin-based composite materials to decompose the resin-based composite materials into a mixture; and (5) opening a second control valve connected to a discharge pipe of the decomposition tank to allow the treated mixture in the decomposition tank to enter a cooler. The method does not need any chemical additives, the carbon fibers are surrounded by water vapor during the whole treatment process, and there are no problems such as oxidation of the carbon fibers during pyrolysis, and the emissions do not need special treatment, so that the method is a green and environment-friendly technology.

Description

Technical Field

[0001] This invention relates to the field of resin composite material recycling and reuse, and more specifically to a method for regenerating carbon fibers in resin-based composite materials. Background Technology

[0002] Fiber-reinforced resin-based composites are multiphase materials composed of organic resins, such as epoxy resin, polyester resin, and phenolic resin, combined with fiber (carbon fiber, glass fiber, aramid fiber, etc.) or particulate (silicon carbide, alumina, etc.) reinforcing phases through specific composite processes. The matrix resin provides bonding, protection, and load transfer, while the reinforcing phase imparts excellent properties such as high strength and high modulus. The synergistic effect of these two components allows resin-based composites to possess a variety of superior properties, exhibiting unique advantages in numerous fields. They are a crucial class of materials in modern materials science, providing an ideal material basis for lightweight mechanical structure design and finding wide application in aerospace, automotive, and marine engineering.

[0003] The resins commonly used in resin-based composites are epoxy resins and unsaturated polyester resins. Commonly used types include thermosetting resins, thermoplastic resins, and various modified or blended matrices. Thermosetting resins can only be heated and molded once, curing during processing to form an infusible and insoluble network of cross-linked polymers, thus they cannot be recycled. Thermoplastic resins can dissolve in solvents, soften and melt into a viscous liquid upon heating, and harden upon cooling. The resin matrix of composite materials is primarily thermosetting resin, especially epoxy resin. Thermosetting resin matrices possess a stable three-dimensional cross-linked network, exhibiting infusibility and insolubility. This makes the recycling of composite material waste more complex than simpler methods like injection molding or extrusion for thermoplastic resin-based composites, and recycling at the end of their service life is quite challenging. On the one hand, traditional incineration and landfill methods pollute the environment and consume land resources; on the other hand, the manufacturing technology for high-performance carbon fibers (content above 60 wt%) in composite material waste is demanding and costly, making it highly valuable for recycling. Therefore, it is essential to find green, non-toxic, and sustainable methods to achieve full recycling of carbon fibers and resin matrices in composite materials.

[0004] Currently, the recycling methods for thermosetting resin-based composite materials mainly include several novel recycling technologies such as direct recycling, pyrolysis recycling, and chemical solvent swelling recycling. Direct recycling involves mechanically crushing and sorting the thermosetting resin composite material, then utilizing the non-metallic particles according to their properties, primarily as fillers in new composite materials. The main problem is the low mechanical properties of products made from recycled materials. Pyrolysis recycling involves heating the thermosetting resin composite material to decompose it in an inert gas or air, then separating the oil-gas mixture and fillers such as fibers from the decomposition products. The advantages of pyrolysis are low pollution emissions and the ability to obtain some energy during the process, improving energy recovery efficiency. Pyrolysis methods can be mainly divided into high-temperature pyrolysis, microwave-promoted pyrolysis, and fluidized bed-assisted pyrolysis. In general pyrolysis, the strength of recycled fibers in thermosetting resin composite waste decreases by about 20%. Chemical solvent recycling refers to the degradation and recycling of thermosetting resin composite waste by breaking the chemical bonds between polymers under the action of heat and catalysts. These mainly include supercritical / subcritical fluid methods and alcoholysis methods. Supercritical fluid methods involve treating waste materials using fluids at their respective temperature and pressure critical points. The liquid media used include water, alcohols, and carbon dioxide in a supercritical state. Because supercritical fluids are fluid and have gas-like diffusivity, they can penetrate into the interior of thermosetting resin composites, causing polymer decomposition. Alcoholysis involves placing epoxy resin in an alcohol solvent (ethylene glycol, propylene glycol, etc.). Under heating conditions, the epoxy resin and the alcohol solvent undergo a dynamic bond exchange reaction (reaction temperature 140–200℃), degrading the resin into oligomers that completely dissolve in the alcohol solvent.

[0005] In summary, the direct recycling method is relatively simple, but the resulting particles have poor mechanical properties, and their suitability as fillers depends on the application scenario.

[0006] Currently, the most commercially viable method for recycling composite materials is pyrolysis, which requires harsh conditions such as high temperature (300–800℃), high pressure (4–27 MPa), and strong acids / alkalis (sodium hydroxide, potassium hydroxide, nitric acid). This results in high equipment requirements, high recycling costs, and significant loss of fiber performance. Incomplete matrix decomposition is also common during pyrolysis, leading to matrix residues on the recycled fibers and a large number of byproducts. Chemical solvent recycling is less efficient and requires strict control over the process. Regenerated carbon fibers can only be used to produce lower-quality resin-based composites. Given the high cost of carbon fibers in resin-based composites, achieving green, non-toxic, and sustainable full recycling of carbon fibers is crucial for closed-loop remanufacturing and reuse. Therefore, a simple and cost-effective method for recycling carbon fiber composite materials is needed. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for regenerating carbon fibers in resin-based composite materials. It requires no chemical additives, and the carbon fibers are surrounded by water vapor throughout the entire process, avoiding problems such as carbon fiber oxidation during pyrolysis. The emissions do not require special treatment, making it a green and environmentally friendly technology.

[0008] The solution of the present invention to the aforementioned technical problem is:

[0009] A method for regenerating carbon fibers in a resin-based composite material, comprising the following steps:

[0010] (1) Add water to the heating storage tank and heat it to produce steam;

[0011] (2) Open the corresponding control valve, and water vapor enters the gas storage tank;

[0012] (3) Pressurize the water vapor in the gas storage tank to the required pressure;

[0013] (4) Open the gas outlet valve of the corresponding gas storage tank so that the high temperature and high pressure water vapor of the corresponding gas storage tank is introduced into the decomposition tank containing the resin-based composite material to decompose the resin-based composite material into a mixture.

[0014] (5) Open the second control valve connected to the discharge pipe of the decomposition tank so that the mixture processed by the decomposition tank is introduced into the cooler;

[0015] (6) After the mixture in the cooler is cooled, the small particles and water are in the lower part of the cooler, while the large carbon fiber particles accumulate in the filter sleeve of the cooler. After a certain period of time, they are removed to obtain the carbon fiber material.

[0016] In step (3), water vapor is pressurized to 50 to 350 bar in the gas storage tank.

[0017] The temperature of the water vapor in step (1) is between 200°C and 800°C.

[0018] In step (4), the decomposition time of the resin-based composite material in the decomposition tank is 20 to 60 minutes.

[0019] Furthermore, the cooler is air-cooled or water-cooled, with an inlet temperature of 600 to 650°C and an outlet temperature of approximately 50°C.

[0020] The cooler's outlet is connected to a return pipe, and the outlet of the return pipe is connected to the return gas connection pipe of the heating water storage tank.

[0021] The heated water storage tank includes an outer tank and an inner tank. The inner tank is inserted into the outer tank. Multiple bottom support blocks are fixed to the bottom surface of the bottom plate of the inner tank. The bottom surface of the bottom support blocks is fixed to the top surface of the bottom plate of the outer tank. An annular support ring is fixed to the upper outer wall of the inner tank. The outer wall of the annular support ring is welded and fixed to the upper inner wall of the outer tank.

[0022] A spirally wound heating tube is fixed to the lower part of the inner tank. The electrical connection part at the bottom end of the heating tube extends out of the bottom outer wall of the inner tank, and its end extends out of the outer wall of the outer tank.

[0023] An annular support ring is fixed on the inner side wall of the middle part of the inner tank. The filter screen groove is inserted into the annular support ring. A radially extending edge is formed on the outer side wall of the top of the filter screen groove, which presses against the top surface of the annular support ring. The filter screen groove covers the middle through hole of the annular support ring.

[0024] The top plate of the inner tank is connected to a middle exhaust pipe, a water inlet pipe, and a return gas connection pipe. The top of the outer tank is fixed with a top cover plate. The upper parts of the middle exhaust pipe, water inlet pipe, and return gas connection pipe extend out of the middle through hole of the top cover plate. An upper support frame is fixed to the top surface of the top cover plate. A conveying pump is fixed to the top surface of the top plate of the upper support frame. The inlet end of the conveying pump is connected to the inlet of the middle exhaust pipe.

[0025] The outstanding effects of this invention are:

[0026] Compared with existing technologies, it requires no chemical additives. Throughout the entire process, the carbon fiber is surrounded by water vapor, eliminating problems such as carbon fiber oxidation during pyrolysis. The emissions do not require special treatment, making it a green and environmentally friendly technology. Attached Figure Description

[0027] Figure 1 This is a partial structural schematic diagram of the present invention;

[0028] Figure 2 yes Figure 1 A magnified view of a portion of the image;

[0029] Figure 3 yes Figure 1 A magnified view of another part;

[0030] Figure 4 yes Figure 1 There are also some enlarged partial images;

[0031] Figure 5 yes Figure 1 A magnified view of part four;

[0032] Figure 6 This is a partial top view of all the gas storage tanks. Detailed Implementation

[0033] For example, see below. Figures 1 to 6 As shown, a method for regenerating carbon fibers in a resin-based composite material is described. In this embodiment, all electrical components are electrically connected to the controller of the main control cabinet via electrical connection lines, and the operation is controlled by the controller. This is a conventional structure and will not be described in detail here.

[0034] In this embodiment, it includes a heated water storage tank 10, a gas storage tank 20, a decomposition tank 30, and a cooler 40.

[0035] The heated water storage tank 10 includes an outer tank 11 and an inner tank 12. The inner tank 12 is inserted into the outer tank 11. Multiple bottom support blocks are fixed to the bottom surface of the bottom plate of the inner tank 12. The bottom surface of the bottom support blocks is fixed to the top surface of the bottom plate of the outer tank 11. An annular support ring 13 is fixed to the upper outer side wall of the inner tank 12. The outer side wall of the annular support ring 13 is welded and fixed to the upper inner side wall of the outer tank 11. A pressure sensor and a temperature sensor are fixed to the top plate of the inner tank 12. The sensing ends of the pressure sensor and the temperature sensor extend into the inner tank 12, and they can sense the temperature and pressure of the water vapor in the inner tank 12.

[0036] The lower part of the inner tank 12 is fixed with a spirally wound heating tube 14. The electrical connection part of the bottom end of the heating tube 14 extends out of the bottom outer wall of the inner tank 12, and its end extends out of the outer wall of the outer tank 11 and is electrically connected to the control board of the main control cabinet through an electrical connection line, so that the operation is controlled by the main control cabinet.

[0037] An annular support ring is fixed on the inner side wall of the inner tank 12. The filter screen trough 15 is inserted into the annular support ring. A radially extending edge is formed on the top outer side wall of the filter screen trough 15, which presses against the top surface of the annular support ring. The filter screen trough 15 covers the central through hole of the annular support ring. The filter screen trough 15 can filter solid particles in liquid water or gas poured into the inner tank 12, making it difficult for them to enter the lower part of the inner tank 12.

[0038] The inner tank 12 has a central exhaust pipe 121, a water inlet pipe 122, and a return gas connection pipe 123 connected to the middle of its top plate. The outer tank 11 has a top cover plate 111 fixed to its top. The upper parts of the central exhaust pipe 121, water inlet pipe 122, and return gas connection pipe 123 extend out of the central through-hole of the top cover plate 111. An upper support frame 112 is fixed to the top surface of the top cover plate 111. A delivery pump 113 is fixed to the top surface of the top plate of the upper support frame 112. The inlet end of the delivery pump 113 is connected to the inlet of the central exhaust pipe 121. The end of the return air connection pipe 123 is connected to the air outlet of the cooler 40 through the connection pipe. In use, the water inlet pipe 122 is connected to the control valve of the water outlet pipe of the external water inlet device. By opening the external control valve, the external water liquid can enter the inner tank 12 (the water liquid is pure water). The water liquid can be heated by the heating pipe 14 to generate water vapor. Its temperature is generally above 200°C, but does not exceed 800°C. The most preferred temperature is 600°C to 650°C. For example, the temperature in this embodiment is about 620°C.

[0039] The outer tank 11 provides insulation for the inner tank 12.

[0040] Furthermore, the outlet end of the delivery pump 113 is connected to an output exhaust connection pipe 114, and the bottom plate of the output exhaust connection pipe 114 is connected to multiple air outlet connectors. The air outlet end of the air outlet connector is connected to a control valve, and the air outlet of the control valve is connected to the air inlet end of the corresponding air storage tank 20.

[0041] In this embodiment, multiple gas storage tanks 20 are inserted into the same heat-insulating outer shell. A mesh heat insulation block (which is a high-temperature resistant ceramic plate) is fixed on the top surface of the bottom plate of the heat-insulating outer shell. An upper support plate is fixed on the upper inner side wall of the heat-insulating outer shell. Multiple through holes are formed on the upper support plate. The gas storage tanks 20 are inserted into the corresponding through holes, with their bottom surfaces pressed against the top surface of the mesh heat insulation block, and their outer side walls tightly attached to or close to the inner side walls of the corresponding through holes.

[0042] Furthermore, the top of the gas storage tank 20 is connected to a corresponding gas outlet valve, and the outlet of the gas outlet valve is connected to the same delivery pipe 1. The outlet of the delivery pipe 1 is connected to the upper air inlet hole of the side plate of the decomposition tank 30. Each gas storage tank 20 is fixed with a pressure sensor on its top plate. The sensing end of the pressure sensor extends into the gas storage tank 20 to sense the pressure of the water vapor injected into it. It is generally above 50 bar, but does not exceed 350 bar. In this embodiment, it is 200 bar.

[0043] Furthermore, the decomposition tank 30 includes a main tank body, with a central annular ring fixed on the inner side wall of the middle part of the main tank body. A mesh inner cylinder 31 made of a perforated plate is inserted into the central annular ring, and the radially extending edge formed on the outer side wall of the top of the inner cylinder 31 presses against the top surface of the central annular ring. The top plate of the main tank body is a detachable plate, on which a pressure sensor and a temperature sensor are fixed. The sensing ends of the sensors extend into the main tank body, which can sense the temperature and pressure inside the main tank body.

[0044] Before use, open the top plate of the main tank and pour the resin-based composite material to be decomposed into the mesh inner cylinder 31;

[0045] An exhaust connector 32 is connected to the outer wall of the middle part of the side plate of the decomposition tank 30. The exhaust port of the exhaust connector 32 is connected to a control valve. The exhaust port of the control valve is connected to the air inlet of the top plate of the cooler 40 through a connecting pipe.

[0046] The cooler 40 includes a vertical cylindrical shell section 41, the bottom of which is welded and fixed to a rectangular lower shell 42 at the bottom. The bottom end of the vertical cylindrical shell section 41 communicates with and is aligned with a through hole in the middle of the top plate of the rectangular lower shell 42. A discharge through hole 4 is formed in the middle of the bottom plate of the rectangular lower shell 42. A discharge valve is connected to the bottom surface of the bottom plate of the rectangular lower shell 42 corresponding to the discharge through hole 43. A perforated plate is fixed on the lower inner sidewall of the vertical cylindrical shell section 41. A vertical exhaust pipe 44 is fixed in the middle of the perforated plate. The bottom end of the vertical exhaust pipe 44 extends out of the bottom surface of the perforated plate, and the top end of the vertical exhaust pipe 44 is inserted into the vertical cylindrical shell section 41. The top end of the vertical exhaust pipe 44 extends out of the top surface of the top cover plate 411 through the middle hole of the top cover plate 411. A filter screen sleeve is fixed to the bottom surface of the top cover plate 411. The outer side wall of the filter screen sleeve is close to or tightly attached to the inner side wall of the vertical cylindrical shell part 41. The bottom surface of the filter screen sleeve is pressed against the top surface of the perforated plate. An air inlet hole is formed on the top cover plate 411, which is the air inlet. An air inlet connector is fixed to the top surface of the top cover plate 411. The air inlet connector communicates with the air inlet hole. A sealing sleeve is fixed to the inner side wall of the middle hole of the top cover plate 411. The outer side wall of the vertical exhaust pipe 44 is pressed against the inner side wall of the sealing sleeve.

[0047] An outer protective sleeve 412 is fixed on the outer side wall from the upper part to the middle part of the vertical cylindrical shell 41. Multiple annular rings arranged vertically are welded and fixed on the inner side wall of the outer protective sleeve 412. A through hole is formed on the left side of one annular ring, and a through hole is formed on the right side of the next adjacent annular ring. All annular rings are arranged in this manner. A feed head is connected to the upper side plate of the outer protective sleeve 412, and a discharge head is connected to the lower side plate of the outer protective sleeve 412.

[0048] When in use, the above structure can be connected to the air outlet pipe of the ventilation equipment at the feed head, in which case air cooling is used. It can also be water-cooled. When water-cooled, the feed head is connected to the water outlet pipe of the water cooling equipment (both the water cooling equipment and the ventilation equipment are existing conventional structures, which will not be described in detail here), and the discharge pipe is connected to the return water pipe. This structure allows the water or air to be introduced to exchange heat with the vertical cylindrical shell part 41, so that the material inside can condense.

[0049] A pusher cylinder is fixed to the middle of the left side wall of the rectangular lower housing 42 (it is connected to the pneumatic system via a connecting pipe and operates through the pneumatic system). The right end of the pusher rod of the pusher cylinder extends out of the inner side wall of the left side plate of the rectangular lower housing 42 and is fixed with a pusher plate. The front and rear side walls of the pusher plate are close to or adjacent to the front and rear inner side walls of the rectangular lower housing 42. A scraper is fixed to the bottom surface of the pusher plate, and the bottom surface of the scraper is close to the top surface of the bottom plate of the rectangular lower housing 42. The right side plate of the rectangular lower housing 42 is a detachable plate, which is fixed to the right end of the rectangular lower housing 42 by screws. A sealing ring is clamped between the right side plate and the right end of the rectangular lower housing 42. The top end of the vertical exhaust pipe 44 is an air outlet, which is connected to the return air connection pipe 123 via a connecting pipe.

[0050] The processing method in this embodiment:

[0051] (1) Add water to the heating storage tank 10. It enters the inner tank 12 through the water inlet pipe 122 and is heated by the heating pipe 14 to form water vapor. At the same time, the temperature and pressure of the inner tank 12 are sensed by the corresponding pressure sensor and temperature sensor.

[0052] (2) When the temperature reaches the required level, such as 650℃, the control valve of the corresponding gas storage tank 20 is opened by the controller, and the water vapor is introduced into the corresponding gas storage tank 20 by the operation of the delivery pump 113 (wherein, the delivery pump 113 can be a pneumatic booster pump).

[0053] (3) Pressurize the water vapor in the gas storage tank 20 to the required pressure, that is, continuously supply it until the pressure sensor of the gas storage tank 20 senses that the pressure reaches 250 bar. At this time, the corresponding control valve is closed.

[0054] (4) Open the outlet valve of the pre-filled gas storage tank 20 to allow the high-temperature, high-pressure steam from the corresponding gas storage tank 20 to enter the decomposition tank 30 containing the resin-based composite material, causing the resin-based composite material to decompose and form a mixture. The steam stays in the decomposition tank 30 for 20 to 60 minutes. If the residence time is too long, the carbon fibers will remain at a high temperature for an extended period, causing quality changes. If the residence time is too short, the resin will remain on the carbon fibers, resulting in incomplete separation. In this embodiment, the time is controlled at 45 minutes.

[0055] (5) After the decomposition time is reached, open the second control valve connected to the discharge pipe of the decomposition tank 30 so that the mixture processed by the decomposition tank 30 is introduced into the cooler 40.

[0056] (6) After the mixture in the cooler 40 is cooled, the small particles and water are in the lower part of the cooler 40, that is, they fall into the rectangular lower shell 42 through the perforated plate. The large carbon fiber material accumulates in the filter sleeve of the cooler 40. After a certain period of time, the second control valve can be closed, the upper cover plate 411 at the vertical cylindrical shell part 41 can be separated from it, and it can be lifted so that the filter sleeve can be lifted. After it is separated from the upper cover plate 411, the carbon fiber in the filter sleeve can be taken out.

[0057] At the same time, it can open the discharge valve of the discharge through hole 43 at regular intervals to discharge the condensed water and resin particles. After a certain period of time, the right side plate can be disassembled and pushed by the push rod of the push cylinder to push the push plate to the right, pushing out the material on the bottom plate of the rectangular lower shell 42, which is very convenient.

[0058] The inlet temperature of cooler 40 is 600 to 650°C, and the outlet temperature is approximately 50°C. This embodiment uses an air-cooled ventilation system, which can employ a fan for air delivery.

[0059] Furthermore, in step (3), water vapor is pressurized to 50 to 350 bar in the gas storage tank 20. Preferably, the water vapor is pressurized to 80 bar or more, but not exceeding 300 bar, and more preferably, the water vapor is pressurized to 100 bar to 250 bar.

[0060] Furthermore, the temperature of the water vapor in step (1) is between 200°C and 800°C. Preferably, the temperature of the water vapor is above 500°C but not exceeding 700°C. More preferably, the temperature of the water vapor is between 500°C and 700°C, and most preferably, the temperature is between 600°C and 650°C.

[0061] The outlet of the cooler 40 is connected to a return pipe, and the outlet of the return pipe is connected to the return gas connection pipe 123 of the heating water storage tank 10.

[0062] According to the method of this embodiment, recycled carbon fibers can be used to manufacture composite materials. Recycled carbon fibers exhibit improved wetting and interfacial bonding characteristics when forming composite materials. These characteristics are improved compared to virgin carbon fibers, allowing composite materials made from recycled carbon fibers to have the same mechanical properties as composite materials made from virgin carbon fibers.

[0063] Composite materials were manufactured using different carbon fibers, and their mechanical properties were compared. The comparison processes are as follows:

[0064] Comparative Example 1: Weigh 48.5g of epoxy resin solution, add 10ml of ethyl acetate and stir magnetically until completely dissolved. Place the mixture in a 100℃ vacuum drying oven and evacuate to remove the ethyl acetate solvent and eliminate air bubbles. After cooling to room temperature, add 6.7g of tetraethylenepentamine and stir magnetically for 5 minutes. Cast the mixture manually into a polytetrafluoroethylene mold coated with a release agent. The curing process is as follows: 90℃ / 1h + 130℃ / 3h + 180℃ / 2h. After curing, remove the specimen and leave it at room temperature for 24h, denoted as EP. According to the test method of GB / T 2567-2008, the tensile strength is 48.56±1.8MPa, the flexural strength is 84.58±2.7MPa, the impact strength is 2.87KJ / m2, and the glass transition temperature is 89.9℃.

[0065] Comparative Example 2: Weigh 48.5g of epoxy resin solution, add 10ml of ethyl acetate and stir magnetically until completely dissolved. Weigh 1.5g of recycled carbon fiber and add it to the epoxy resin in small batches, stirring for 4 hours to ensure uniform dispersion. Place the mixture in a 100℃ vacuum drying oven and evacuate to remove the ethyl acetate solvent and eliminate air bubbles. After cooling to room temperature, add 6.7g of tetraethylenepentamine and stir magnetically for 5 minutes. Cast the mixture manually into a polytetrafluoroethylene mold coated with a release agent. The curing process is as follows: 90℃ / 1h + 130℃ / 3h + 180℃ / 2h. After curing, remove the sample and leave it at room temperature for 24 hours, denoted as EP-R (epoxy resin: carbon fiber = 97.0: 3.0). According to the test method of GB / T 2567-2008, the tensile strength is 70.97±1.7MPa, the flexural strength is 126.54±3.4MPa, and the impact strength is 5.57KJ / m. 2 Its glass transition temperature is 137.7℃.

[0066] Comparative Example 3: Weigh 48.5g of epoxy resin solution, add 10ml of ethyl acetate and stir magnetically until completely dissolved. Weigh 1.5g of raw carbon fiber and add it to the epoxy resin in small batches, stirring for 4 hours to ensure uniform dispersion. Place the mixture in a 100℃ vacuum drying oven and evacuate to remove the ethyl acetate solvent and eliminate air bubbles. After cooling to room temperature, add 6.7g of tetraethylenepentamine and stir magnetically for 5 minutes. Cast the mixture manually into a polytetrafluoroethylene mold coated with a release agent. The curing process is as follows: 90℃ / 1h + 130℃ / 3h + 180℃ / 2h. After curing, remove the sample and leave it at room temperature for 24 hours, denoted as EP-O (epoxy resin: carbon fiber = 97.0: 3.0). The tensile strength was 73.78±1.5MPa, the flexural strength was 129.46±3.3MPa, and the impact strength was 5.60KJ / m², as determined by the test method of GB / T 2567-2008.2 Its glass transition temperature is 137.8℃.

[0067] These comparative examples demonstrate that the addition of carbon fibers significantly improves the mechanical properties of the composite material. In particular, composite materials made with recycled carbon fibers exhibit the same mechanical properties as those made with virgin carbon fibers.

[0068] Finally, the above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also fall within the scope of the present invention, and the patent protection scope of the present invention should be defined by the claims.

Claims

1. A method for regenerating carbon fibers in a resin-based composite material, characterized in that: It includes the following steps: (1) Add water to the heating storage tank (10) and heat it to produce steam; (2) Open the control valve of the corresponding gas storage tank (20) and water vapor enters the gas storage tank (20); (3) Pressurize the water vapor in the gas storage tank (20) to the required pressure; (4) Open the gas outlet valve of the corresponding gas storage tank (20) so that the high temperature and high pressure water vapor of the corresponding gas storage tank (20) is introduced into the decomposition tank (30) containing the resin-based composite material to decompose the resin-based composite material into a mixture. (5) Open the second control valve connected to the discharge pipe of the decomposition tank (30) so that the mixture processed by the decomposition tank (30) is introduced into the cooler (40); (6) After the mixture in the cooler (40) is cooled, the small particles and water are in the lower part of the cooler (40), and the large particles of carbon fiber material accumulate in the filter sleeve of the cooler (40). After a certain period of time, it is taken out to obtain carbon fiber material.

2. The method for regenerating carbon fibers in a resin-based composite material according to claim 1, characterized in that: In step (3), water vapor is pressurized to 50 to 350 bar in the gas storage tank (20).

3. The method for regenerating carbon fibers in a resin-based composite material according to claim 1, characterized in that: The temperature of the water vapor in step (1) is between 200°C and 800°C.

4. The method for regenerating carbon fibers in a resin-based composite material according to claim 1, characterized in that: In step (4), the decomposition time of the resin-based composite material in the decomposition tank (30) is 20 to 60 minutes.

5. The method for regenerating carbon fibers in a resin-based composite material according to claim 1, characterized in that: The cooler (40) is air-cooled or water-cooled, with an inlet temperature of 600 to 650°C and an outlet temperature of about 50°C.

6. The method for regenerating carbon fibers in a resin-based composite material according to claim 1, characterized in that: The outlet of the cooler (40) is connected to a return pipe, and the outlet of the return pipe is connected to the return gas connection pipe of the heating water storage tank (10).

7. The method for regenerating carbon fibers in a resin-based composite material according to claim 1, characterized in that: The heated water storage tank (10) includes an outer tank (11) and an inner tank (12). The inner tank (12) is inserted into the outer tank (11). Multiple bottom support blocks are fixed on the bottom surface of the bottom plate of the inner tank (12). The bottom surface of the bottom support blocks is fixed on the top surface of the bottom plate of the outer tank (11). An annular support ring (13) is fixed on the upper outer side wall of the inner tank (12). The outer side wall of the annular support ring (13) is welded and fixed on the upper inner side wall of the outer tank (11). The lower part of the inner tank (12) is fixed with a spirally wound heating tube (14). The electrical connection part of the bottom end of the heating tube (14) extends out of the bottom outer wall of the inner tank (12), and its end extends out of the outer wall of the outer tank (11).

8. The method for regenerating carbon fibers in a resin-based composite material according to claim 7, characterized in that: An annular support ring is fixed on the inner side wall of the middle part of the inner tank (12). The filter screen groove (15) is inserted into the annular support ring. A radially extending edge is formed on the outer side wall of the top of the filter screen groove (15), which presses against the top surface of the annular support ring. The filter screen groove (15) covers the middle through hole of the annular support ring. The top plate of the inner tank (12) is connected to the middle of the middle exhaust pipe (121), the water inlet pipe (122) and the return gas connection pipe (123). The top of the outer tank (11) is fixed with a top cover plate (111). The upper part of the middle exhaust pipe (121), the water inlet pipe (122) and the return gas connection pipe (123) extends out of the middle through hole of the top cover plate (111). The top surface of the top cover plate (111) is fixed with an upper support frame (112). The top surface of the top plate of the upper support frame (112) is fixed with a delivery pump (113). The inlet end of the delivery pump (113) is connected to the inlet of the middle exhaust pipe (121).

9. The method for regenerating carbon fibers in a resin-based composite material according to claim 7, characterized in that: The outlet end of the delivery pump (113) is connected to an output exhaust connection pipe (114), and the bottom plate of the output exhaust connection pipe (114) is connected to multiple air outlet connectors. The air outlet end of the air outlet connector is connected to a control valve, and the air outlet of the control valve is connected to the air inlet end of the corresponding air storage tank (20). The top of the gas storage tank (20) is connected to the gas outlet end, and a corresponding gas outlet valve is connected to the gas outlet of the gas outlet valve. The gas outlet of the gas outlet valve is connected to the same conveying pipe (1). The gas outlet end of the conveying pipe (1) is connected to the upper air inlet hole of the side plate of the decomposition tank (30). The decomposition tank (30) is equipped with a mesh inner cylinder (31), and a resin-based composite material is placed in the mesh inner cylinder (31); An exhaust connector (32) is connected to the outer wall of the middle part of the side plate of the decomposition tank (30). The exhaust port of the exhaust connector (32) is connected to a control valve. The exhaust port of the control valve is connected to the air inlet of the top plate of the cooler (40) through a connecting pipe.

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