Carbon fiber bundle regeneration method and carbon fiber bundle regeneration device

Abstract

The present invention provides a method for regenerating a carbon fiber bundle from a structure having a hollow base material and a carbon fiber reinforced resin layer containing a carbon fiber bundle and a matrix resin wrapped around the hollow base material, the carbon fiber bundle regeneration method comprising: a treating step for performing a deforming treatment or a fracture treatment on the hollow base material so that a space is formed at least partially between the hollow base material and the carbon fiber reinforced resin layer; a first heating step for heating the structure of which the hollow base material has been subjected to the deforming treatment or the fracture treatment to decompose a portion of the matrix resin; an unwinding step for unwinding an intermediate carbon fiber bundle with adhering decomposition residue of the matrix resin from the carbon fiber reinforced resin layer in which a portion of the matrix resin has decomposed; a second heating step for heating the unwound intermediate carbon fiber bundle to decompose the decomposition residue of the matrix resin and thereby obtain a regenerated carbon fiber bundle; and a winding step for winding the regenerated carbon fiber bundle.

Description

Carbon fiber bundle recycling method and carbon fiber bundle recycling device

[0001] The present invention relates to a method and an apparatus for recycling carbon fiber bundles.

[0002] In recent years, efforts to significantly reduce waste generation through waste prevention, reduction, recycling, and reuse have become increasingly active. To achieve this, research and development is being conducted on methods for recovering carbon fiber from carbon fiber reinforced resins.

[0003] Patent Document 1 describes a carbon fiber recycling method including a step of pyrolyzing the resin in a carbon fiber reinforced resin molded product by a first heat treatment and a step of drawing out and winding the carbon fiber from the carbon fiber reinforced resin molded product after the first heat treatment. The winding step includes a step of pyrolyzing the resin residue adhering to the carbon fiber by a second heat treatment and a step of applying a sizing agent to the carbon fiber after the second heat treatment. The carbon fiber reinforced resin molded product is a tank including a liner and a carbon fiber reinforced resin layer.

[0004] Japanese Patent Application Laid-Open No. 2022-15366

[0005] However, when the carbon fiber recycling method of Patent Document 1 is applied to a case where there is a large difference in linear expansion between the carbon fiber reinforced resin layer and the liner, the expansion force of the liner is applied to the carbon fibers when the resin in the carbon fiber reinforced resin layer is pyrolyzed by the first heat treatment, resulting in damage to the carbon fibers. In addition, the carbon fibers are compressed, which reduces the handleability when pulling out the carbon fibers.

[0006] An object of the present invention is to provide a method and an apparatus for recycling carbon fiber bundles that can suppress damage to intermediate carbon fiber bundles and improve the handling properties when unwinding the intermediate carbon fiber bundles, even if there is a large difference in linear expansion between a carbon fiber reinforced resin layer and a hollow substrate.

[0007] (1) A method for recycling carbon fiber bundles from a structure having a hollow substrate and a carbon fiber reinforced resin layer containing carbon fiber bundles and a matrix resin wound around the hollow substrate, the method comprising: a processing step of deforming or destructing the hollow substrate so as to form a space at least partially between the hollow substrate and the carbon fiber reinforced resin layer; a first heating step of heating the structure in which the hollow substrate has been deformed or destructed to decompose a portion of the matrix resin; an unwinding step of unwinding an intermediate carbon fiber bundle having decomposition residues of the matrix resin adhering thereto from the carbon fiber reinforced resin layer in which a portion of the matrix resin has been decomposed; a second heating step of heating the unwinding intermediate carbon fiber bundle to decompose the decomposition residues of the matrix resin to obtain a recycled carbon fiber bundle; and a winding step of winding up the recycled carbon fiber bundle.

[0008] (2) The method for recycling carbon fiber bundles according to (1), wherein the hollow substrate contains a metal.

[0009] (3) The method for regenerating a carbon fiber bundle according to (2), wherein the processing step is a step of twisting the hollow substrate.

[0010] (4) The method for regenerating carbon fiber bundles according to (2), wherein the processing step is a step of electromagnetically forming the hollow substrate.

[0011] (5) The method for regenerating a carbon fiber bundle according to (2), wherein the processing step is a step of embrittling the hollow substrate using a liquid metal.

[0012] (6) An apparatus for recycling carbon fiber bundles from a structure having a hollow substrate and a carbon fiber reinforced resin layer containing carbon fiber bundles and a matrix resin wound around the hollow substrate, the apparatus comprising: a processing unit that deforms or destroys the hollow substrate so as to form a space at least partially between the hollow substrate and the carbon fiber reinforced resin layer; a first heating unit that heats the structure in which the hollow substrate has been deformed or destroyed to decompose a portion of the matrix resin; an unwinding unit that unwinds an intermediate carbon fiber bundle having decomposition residues of the matrix resin adhering thereto from the carbon fiber reinforced resin layer in which a portion of the matrix resin has been decomposed; a second heating unit that heats the unwound intermediate carbon fiber bundle to decompose the decomposition residues of the matrix resin to obtain a recycled carbon fiber bundle; and a winding unit that winds up the recycled carbon fiber bundle.

[0013] According to the present invention, it is possible to provide a method and an apparatus for recycling carbon fiber bundles that can suppress damage to intermediate carbon fiber bundles and improve the handling properties when unwinding the intermediate carbon fiber bundles, even if there is a large difference in linear expansion between the carbon fiber reinforced resin layer and the hollow substrate.

[0014] FIG. 4 is a cross-sectional view showing an example of a high-pressure hydrogen tank. FIG. 5 is a schematic view showing an example of a processing unit used in the processing step. FIG. 6 is a schematic view showing another example of a processing unit used in the processing step. FIG. 7 is a schematic view showing another example of a processing unit used in the processing step. FIG. 8 is a view showing an example of a first heating unit used in the first heating step. FIG. 9 is a view showing a rotation unit that rotates the high-pressure hydrogen tank in the heat treatment chamber of FIG. 4. FIG. 10 is a view showing an example of an unwinding unit used in the unwinding step. FIG. 11 is a view showing an example of an unwinding unit used in the unwinding step. FIG. 12 is a schematic view showing examples of a second heating unit, a sizing unit and a winding unit used in the second heating step, the sizing step and the winding step.

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] A method for recycling carbon fiber bundles according to one embodiment of the present invention is a method for recycling carbon fiber bundles from a structure having a hollow substrate and a carbon fiber reinforced resin layer containing carbon fiber bundles and a matrix resin wound around the hollow substrate. The structure is not particularly limited, but examples thereof include known high-pressure hydrogen tanks (Types 2 to 4).

[0017] The carbon fibers constituting the carbon fiber bundle are not particularly limited, but examples thereof include polyacrylonitrile (PAN)-based carbon fibers and pitch-based carbon fibers. Here, the carbon fibers constituting the carbon fiber bundle are long fibers. The fiber length of the carbon fibers is not particularly limited, but is, for example, 1 m or more. The matrix resin is not particularly limited, but examples thereof include thermosetting resins such as epoxy resins and thermoplastic resins.

[0018] FIG. 1 shows an example of a high-pressure hydrogen tank.

[0019] The high-pressure hydrogen tank T has a liner L as a hollow substrate, a carbon fiber reinforced resin layer F containing carbon fiber bundles and a matrix resin wound around the liner L, and mouthpieces C1, C2 installed at both ends in the longitudinal direction. The material constituting the liner L is not particularly limited, but examples include metals such as aluminum and chromium molybdenum steel, and resins such as polyamide and polyethylene.

[0020] The method for manufacturing the high-pressure hydrogen tank T is not particularly limited, but may be, for example, a filament winding method.

[0021] A method for recycling carbon fiber bundles according to one embodiment of the present invention includes a processing step of deforming or destructing the liner L so as to form a space at least partially between the liner L and the carbon fiber reinforced resin layer F, and a first heating step of heating the high-pressure hydrogen tank in which the liner L has been deformed or destructed to decompose a portion of the matrix resin. The method for recycling carbon fiber bundles according to one embodiment of the present invention further includes an unwinding step of unwinding an intermediate carbon fiber bundle I having decomposition residues of the matrix resin adhering thereto from the carbon fiber reinforced resin layer F in which a portion of the matrix resin has been decomposed, a second heating step of heating the unwound intermediate carbon fiber bundle I to decompose the decomposition residues of the matrix resin to obtain a recycled carbon fiber bundle R, and a winding step of winding up the recycled carbon fiber bundle R. Therefore, even if there is a large difference in linear expansion between the carbon fiber reinforced resin layer F and the liner L, the expansion force of the liner L is prevented from being applied to the carbon fiber bundle when a portion of the matrix resin is decomposed, and as a result, damage to the intermediate carbon fiber bundle I is suppressed. Furthermore, the carbon fiber bundles are less likely to be compacted, which improves the handling properties when unwinding the intermediate carbon fiber bundle I. Furthermore, the release of decomposition products of the matrix resin and heat exchange are promoted, which shortens the processing time of the first heating step and improves the homogeneity of the decomposition residues of the matrix resin.

[0022] The method for deforming or destructively processing the liner L is not particularly limited, but examples include a method for twisting the liner L, a method for electromagnetically forming the liner L, and a method for embrittling the liner L using liquid metal.

[0023] FIG. 2 shows a twisting machine as an example of a processing unit used in the processing step.

[0024] The twisting machine 100 has a base 101 that holds the side of the high-pressure hydrogen tank T, a chuck 102 that secures the nozzle C1 of the high-pressure hydrogen tank T, and a chuck 103 that secures the nozzle C2 of the high-pressure hydrogen tank T. Here, the chuck 103 is connected to a motor 106 via gears 104 and 105, and can rotate about a rotation axis 107. Therefore, when the motor 106 is operated, the chuck 103 rotates about the rotation axis 107, thereby twisting the liner L of the high-pressure hydrogen tank T and forming a space at least partially between the liner L and the carbon fiber reinforced resin layer F.

[0025] The twisting machine 100 may be provided with a sliding mechanism so that the chuck 102 and / or the chuck 103 can slide in the length direction of the high-pressure hydrogen tank T, if necessary.

[0026] 3A and 3B show an electromagnetic forming machine as another example of a processing unit used in the processing step, in which Figs. 3A and 3B are a front view and a side view, respectively.

[0027] The electromagnetic forming machine 200 has a frame-shaped member 201 arranged over the entire outer peripheral surface of the high-pressure hydrogen tank T, a forming coil 202 arranged inside the frame-shaped member 201, and wiring 203 connected to the forming coil 202. A switch and a capacitor are installed in the wiring 203. Therefore, when the switch is closed, a large current flows from the charged capacitor to the forming coil 202, causing an induced current to flow in the liner L. As a result, an electromagnetic force is generated between the magnetic field generated by the large current flowing in the forming coil 202 and the induced current flowing in the liner L, causing the liner L to deform inward and forming a space at least partially between the liner L and the carbon fiber reinforced resin layer F.

[0028] It is also possible to arrange the frame-shaped member 201 on a portion of the outer peripheral surface of the high-pressure hydrogen tank T and perform the process of electromagnetically forming a portion of the liner L multiple times.

[0029] When using a liquid metal to embrittle the liner L, the liquid metal may be filled into the high-pressure hydrogen tank T using a known device, or the high-pressure hydrogen tank T may be immersed in the liquid metal. The liquid metal is not particularly limited as long as it can embrittle the liner L, but an example of the liquid metal is gallium.

[0030] Before the liner L is deformed or destroyed, the mouthpieces C1 and C2 may be removed from the high-pressure hydrogen tank T, if necessary.

[0031] The first heating step preferably includes a first step of decomposing the matrix resin at a temperature equal to or higher than the thermal decomposition initiation temperature of the matrix resin and equal to or lower than the flash point of the pyrolysis gas of the matrix resin, and a second step of decomposing the matrix resin decomposed in the first step at a temperature equal to or higher than the thermal oxidative decomposition initiation temperature of the decomposition residue of the matrix resin and equal to or lower than the thermal decomposition initiation temperature of the carbon fiber, thereby suppressing overheating due to combustion of the pyrolysis gas of the matrix resin and deterioration of the carbon fiber.

[0032] When the matrix resin is an epoxy resin, for example, in the first step, the resin is heated at a temperature of 330° C. or higher and 360° C. or lower, and in the second step, the resin is heated at a temperature of 430° C. or higher and 470° C. In this case, examples of pyrolysis gases include bisphenol A and phenol.

[0033] The heating temperature in the first heating step is not particularly limited as long as it is possible to unwind the carbon fiber bundle with the decomposition residue of the matrix resin adhering to the carbon fibers.

[0034] FIG. 4 shows a heat treatment furnace as an example of the first heating section used in the first heating step.

[0035] The heat treatment furnace 10 has a heat treatment chamber 11 and a combustion chamber 12 .

[0036] The heat treatment chamber 11 is an enclosed space surrounded by an outer wall 11a and an inner wall 11b. Burners 11c are provided above the outer wall 11a on the left side and below the outer wall 11a on the right side in the drawing so that combustion gas flows into the inner wall 11b. When gas fuel and air are mixed and burned by the burners 11c, the combustion gas convects within the inner wall 11b, stabilizing the temperature within the inner wall 11b.

[0037] The heat treatment chamber 11 has a sealed door installed on a portion of the outer wall 11a and inner wall 11b for accommodating a high-pressure hydrogen tank T1 whose liner L has been deformed or destroyed. The high-pressure hydrogen tank T1 is placed on a thermal insulator 11d installed so as to penetrate the bottom surface of the inner wall 11b. A load cell 11e serving as a mass detector is installed between the bottom surface of the outer wall 11a and the thermal insulator 11d and detects the mass of the high-pressure hydrogen tank T1 in real time based on the amount of strain. This optimizes the heating conditions in the heat treatment chamber 11, suppressing variations in the amount of decomposition of the matrix resin due to individual differences in the material, shape, etc., constituting the high-pressure hydrogen tank T1, and improving management accuracy. Furthermore, since the heating time in the heat treatment chamber 11 does not need to be longer than necessary, this contributes to shortening the heating time and reducing energy consumption.

[0038] The mass detector may detect the amount of mass loss in the high-pressure hydrogen tank T1 in real time. If necessary, the mass detector may be omitted.

[0039] The decomposition gas of the matrix resin generated within the inner wall 11b is discharged from an exhaust port 11f formed at the top of the inner wall 11b in the figure, and then introduced into the combustion chamber 12 via a pipe 11g installed to penetrate the outer wall 11a.

[0040] The combustion chamber 12 is an enclosed space surrounded by an outer wall 12a and an inner wall 12b. A burner 12c is provided in the center of the outer wall 12a (left side of the figure) so that combustion gas flows into the inner wall 12b. Meanwhile, the pipe 11g penetrates the outer wall 12a, then penetrates the inside and outside of the inner wall 12b within the outer wall 12a, and finally connects to the upper left of the inner wall 12b. While passing through the pipe 11g inside the inner wall 12b, the decomposition gas of the matrix resin is heated by the combustion gas flowing within the inner wall 12b, and then introduced from the upper left of the inner wall 12b and comes into contact with the combustion gas. After combustion, the decomposition gas of the matrix resin is exhausted to the outside through the exhaust port 12d.

[0041] 5A and 5B show an example of a rotating unit that rotates the high-pressure hydrogen tank T1 in the heat treatment chamber 11. Note that Fig. 5A and Fig. 5B are a cross-sectional view and a side view, respectively.

[0042] The rotating part 20 has a rotation axis 21 extending in a substantially horizontal direction that penetrates the wall W of the heat treatment chamber 11, so that the temperature distribution of the carbon fiber reinforced resin layer F in the vertical direction in the drawing is made uniform.

[0043] The rotation shaft 21 may be oriented in a direction other than the substantially horizontal direction, for example, the rotation shaft 21 may be oriented in the substantially vertical direction. When the rotation shaft 21 is oriented in the substantially vertical direction, the temperature distribution of the carbon fiber reinforced resin layer F in the heat treatment chamber 11 is made uniform to the same extent as when the rotation shaft 21 is oriented in the substantially horizontal direction.

[0044] The high-pressure hydrogen tank T1 is connected to the rotating shaft 21 via a flanged jig 22 and a rotating shaft flange 23 that utilize the shapes of the mouthpieces C1 and C2. At this time, the flanged jig 22 and the rotating shaft flange 23 are fixed with, for example, bolts and nuts. The high-pressure hydrogen tank T1 is placed on a pedestal 24, and a bearing 25 is installed on the pedestal 24. Furthermore, a heat insulating material 26 is installed inside the wall W of the heat treatment furnace 10. Furthermore, a motor that rotates the rotating shaft 21 is installed outside the wall W of the heat treatment furnace 10, and a cooling jacket 27 is installed around the rotating shaft 21.

[0045] An example of an unwinding unit used in the unwinding process is shown in Figures 6A and 6B, which are a front view and a side view, respectively.

[0046] The unwinding section 30 has a rotating jig 31 that rotatably supports the high-pressure hydrogen tank T2 in which part of the matrix resin has decomposed, and a motor 32 that rotates the high-pressure hydrogen tank T2. The rotational power of the motor 32 is transmitted to the rotating jig 31 via a belt 33. As a result, the intermediate carbon fiber bundle I is unwound via rollers 34, 35, and 36. At this time, the roller 34 is positioned so that the intermediate carbon fiber bundle I is unwound outside the tangent line at the position where the intermediate carbon fiber bundle I is unwound from the high-pressure hydrogen tank T2. Furthermore, the rollers 34, 35, and 36 have long axes that correspond to the unwinding of the intermediate carbon fiber bundle I in the longitudinal direction of the high-pressure hydrogen tank T2. Furthermore, a dancer roller 37 that controls the unwinding tension is provided to absorb the difference in the unwinding amount per rotation between hoop winding and helical winding of the intermediate carbon fiber bundle I.

[0047] It should be noted that blades may be installed instead of the rollers 34. Furthermore, since the liner L of the high-pressure hydrogen tank T2 is subjected to deformation processing or destruction processing, the intermediate carbon fiber bundle I may be unwound in a state in which it is placed on the particles without using the unwinding section 30.

[0048] The heating temperature in the second heating step is preferably equal to or higher than the heating temperature in the first heating step. This facilitates decomposition of the decomposition residue of the matrix resin adhering to the intermediate carbon fiber bundle I. On the other hand, the heating temperature in the second heating step is preferably equal to or lower than the thermal decomposition starting temperature of the carbon fiber. This suppresses deterioration of the carbon fiber.

[0049] After the sizing step of sizing the recycled carbon fiber bundle R, the sized recycled carbon fiber bundle R may be wound up.

[0050] FIG. 7 shows an example of the second heating section, sizing section, and winding section used in the second heating step, sizing step, and winding step.

[0051] The tubular furnace 40, serving as the second heating section, has a quartz tube 41 and, at both ends thereof, insulating covers 42 formed with through-holes through which the intermediate carbon fiber bundle I, to which the decomposition residue of the matrix resin adheres, can pass. The tubular furnace 40 also has an electric heating wire 43, an insulating material 44, and a protective cover 45 sequentially disposed in the center of the quartz tube 41. Therefore, by passing an electric current through the electric heating wire 43, the intermediate carbon fiber bundle I is heated, and the decomposition residue of the matrix resin is decomposed, thereby obtaining a recycled carbon fiber bundle R. At this time, the temperature distribution within the tubular furnace 40 is made uniform, and heating of anything other than the intermediate carbon fiber bundle I is suppressed.

[0052] The sizing unit 50 passes the recycled carbon fiber bundles R through a sizing solution 51. At this time, the sizing solution 51 is heated by a heater 52. In addition, a roller 53 prevents the sizing solution 51 from being applied excessively to the recycled carbon fiber bundles R.

[0053] If necessary, a drying oven may be installed to dry the recycled carbon fiber bundles R.

[0054] The feeding mechanism 60 has feeder rollers 61, 62, and 63, and by utilizing the friction between the feeder rollers 61, 62, and 63 and the recycled carbon fiber bundle R, the linear speed of the recycled carbon fiber bundle R is controlled to a linear speed that is easy to manage in the process.

[0055] The winding unit 70 includes a winding motor 71 for winding the recycled carbon fiber bundle R around the paper core P, and a slide roller 72 for traverse-winding the recycled carbon fiber bundle R. At this time, the winding tension of the recycled carbon fiber bundle R is controlled by controlling the torque of the winding motor 71.

[0056] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and the above embodiments may be modified as appropriate within the scope of the present invention. For example, a propeller shaft, a safety block, a low-friction roll, a rotor portion of a spindle shaft motor, etc. may be used as a structure other than a high-pressure hydrogen tank.

[0057] 100 Twisting machine 200 Electromagnetic forming machine C1, C2 Die cap F Carbon fiber reinforced resin layer I Intermediate carbon fiber bundle L Liner R Recycled carbon fiber bundle T, T1, T2 High-pressure hydrogen tank

Claims

1. A method for regenerating a carbon fiber bundle from a structure having a hollow substrate, and a carbon fiber reinforced resin layer including a carbon fiber bundle and a matrix resin wound around the hollow substrate, the method comprising: a processing step of deforming or destroying the hollow substrate so that a space is formed in at least a part between the hollow substrate and the carbon fiber reinforced resin layer; a first heating step of heating the structure in which the hollow substrate has been deformed or destroyed to decompose a part of the matrix resin; a winding-out step of winding out an intermediate carbon fiber bundle having decomposition residues of the matrix resin attached thereto from the carbon fiber reinforced resin layer in which a part of the matrix resin has been decomposed; a second heating step of heating the wound-out intermediate carbon fiber bundle to decompose the decomposition residues of the matrix resin to obtain a regenerated carbon fiber bundle; and a winding-up step of winding up the regenerated carbon fiber bundle.

2. The method for regenerating a carbon fiber bundle according to claim 1, wherein the hollow substrate contains a metal.

3. The method for regenerating a carbon fiber bundle according to claim 2, wherein the processing step is a step of twisting the hollow substrate.

4. The method for regenerating a carbon fiber bundle according to claim 2, wherein the processing step is a step of electromagnetic forming the hollow substrate.

5. The method for regenerating a carbon fiber bundle according to claim 2, wherein the processing step is a step of embrittling the hollow substrate using liquid metal.

6. An apparatus for regenerating a carbon fiber bundle from a structure having a hollow substrate, and a carbon fiber reinforced resin layer including a carbon fiber bundle and a matrix resin wound around the hollow substrate, the apparatus comprising: a processing unit that deforms or destroys the hollow substrate so that a space is formed in at least a part between the hollow substrate and the carbon fiber reinforced resin layer; a first heating unit that heats the structure in which the hollow substrate has been deformed or destroyed to decompose a part of the matrix resin; a winding-out unit that winds out an intermediate carbon fiber bundle having decomposition residues of the matrix resin attached thereto from the carbon fiber reinforced resin layer in which a part of the matrix resin has been decomposed; a second heating unit that heats the wound-out intermediate carbon fiber bundle to decompose the decomposition residues of the matrix resin to obtain a regenerated carbon fiber bundle; and a winding-up unit that winds up the regenerated carbon fiber bundle.

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