Regeneration method of carbon fiber bundle and regenerator of carbon fiber bundle

Abstract

To provide a regeneration method of a carbon fiber bundle and a regenerator of a carbon fiber bundle, capable of heating an intermediate carbon fiber bundle and stably and efficiently decomposing a decomposition residue of a matrix resin.SOLUTION: A regeneration method of a carbon fiber bundle includes: a first heating step of heating a high-pressure hydrogen tank to decompose part of a matrix resin; a rolling-out step of rolling out an intermediate carbon fiber bundle with a decomposition residue of the matrix resin adhered thereto from a carbon fiber-reinforced resin layer that decomposes part of the matrix resin; a second heating step of heating the rolled-out intermediate carbon fiber bundle I using a tubular furnace 40 and decomposing a decomposition residue of the matrix resin to obtain a regenerated carbon fiber bundle R; and a winding-up step of winding up the regenerated carbon fiber bundle R. The tubular furnace 40 includes: a heating wire heater 43 configured to heat the intermediate carbon fiber bundle I; and a heat insulation lid 42 disposed at an inlet and an outlet and have a slit-like through hole that allows a passage of the intermediate carbon fiber bundle I.SELECTED DRAWING: Figure 5

Description

Technical Field

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

Background Art

[0002] In recent years, efforts to significantly reduce the generation of waste have been actively carried out through waste prevention, reduction, recycling, and reuse. Toward this realization, research and development on methods for recovering carbon fibers from carbon fiber reinforced resins have been conducted.

[0003] Patent Document 1 describes a method for recycling carbon fibers, which includes a step of thermally decomposing the resin in a carbon fiber reinforced resin molded article by a first heat treatment, and a step of pulling out and winding up the carbon fibers from the carbon fiber reinforced resin molded article after the first heat treatment. At this time, the winding-up step includes a step of thermally decomposing the resin residue adhering to the carbon fibers by a second heat treatment, and a step of applying a sizing agent to the carbon fibers after the second heat treatment. Further, the carbon fiber reinforced resin molded article is a tank including a liner and a carbon fiber reinforced resin layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when using the carbon fiber recycling method of Patent Document 1, when thermally decomposing the resin residue adhering to the carbon fibers by a second heat treatment, heat energy is released or outside air is mixed in. For this reason, it is difficult to stably and efficiently thermally decompose the resin residue adhering to the carbon fibers.

[0006] An object of the present invention is to provide a method for regenerating a carbon fiber bundle and a carbon fiber bundle regeneration apparatus capable of heating an intermediate carbon fiber bundle to stably and efficiently decompose decomposition residues of a matrix resin.

Means for Solving the Problems

[0007] (1) A method for regenerating a carbon fiber bundle from a structure having a hollow base material and a carbon fiber reinforced resin layer including a carbon fiber bundle and a matrix resin wound around the hollow base material, the method including: a first heating step of heating the structure 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 obtaining a regenerated carbon fiber bundle by heating the wound-out intermediate carbon fiber bundle using a tubular furnace to decompose the decomposition residues of the matrix resin; and a winding-up step of winding up the regenerated carbon fiber bundle, wherein the tubular furnace has a heater for heating the intermediate carbon fiber bundle and a lid installed at an inlet and an outlet and having a through-hole through which the intermediate carbon fiber bundle can pass.

[0008] (2) In the tubular furnace, there are a heating region where the intermediate carbon fiber bundle is heated and a non-heating region where the intermediate carbon fiber bundle is not heated, and the non-heating region exists between the heating region and the inlet and / or between the heating region and the outlet. The method for regenerating a carbon fiber bundle according to (1).

[0009] (3) The tubular furnace further has an introduction pipe for introducing an oxidizing gas into the heating region. The method for regenerating a carbon fiber bundle according to (2).

[0010] (4) The oxidizing gas is introduced along the surface of the intermediate carbon fiber bundle. The method for regenerating a carbon fiber bundle according to (3).

[0011] (5) The oxidative gas is introduced from the downstream side to the upstream side of the tubular furnace, and the method for regenerating the carbon fiber bundle according to (3) or (4).

[0012] (6) The introduction pipe is arranged such that the oxidative gas introduced into the heating region forms a turbulent flow, and the method for regenerating the carbon fiber bundle according to any one of (3) to (5).

[0013] (7) The through hole is slit-shaped and formed in the horizontal direction, and the method for regenerating the carbon fiber bundle according to any one of (1) to (6).

[0014] (8) The lid has a plurality of through holes formed therein, and the method for regenerating the carbon fiber bundle according to any one of (1) to (7).

[0015] (9) An apparatus for regenerating a carbon fiber bundle having a hollow substrate and a carbon fiber reinforced resin layer including a carbon fiber bundle wound around the hollow substrate and a matrix resin, the apparatus including a first heating unit that heats the structure to decompose a part of the matrix resin, a unwinding unit that unwinds 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 unwound intermediate carbon fiber bundle to decompose the decomposition residues of the matrix resin to obtain a regenerated carbon fiber bundle, and a winding unit that winds up the regenerated carbon fiber bundle, wherein the second heating unit includes a heater that heats the intermediate carbon fiber bundle and a lid that is installed at an inlet and an outlet and has a through hole formed therein through which the intermediate carbon fiber bundle can pass, and the apparatus is a tubular furnace for regenerating a carbon fiber bundle.

Advantages of the Invention

[0016] According to the present invention, it is possible to provide a method for regenerating a carbon fiber bundle and an apparatus for regenerating a carbon fiber bundle that can stably and efficiently decompose decomposition residues of a matrix resin by heating an intermediate carbon fiber bundle.

Brief Description of the Drawings

[0017]

Figure 1

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Figure 8

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0019] A method for regenerating a carbon fiber bundle according to an embodiment of the present invention is a method for regenerating a carbon fiber bundle from a structure having a hollow base material, a carbon fiber bundle wound around the hollow base material, and a carbon fiber reinforced resin layer containing a matrix resin. The structure is not particularly limited, and examples thereof include known high-pressure hydrogen tanks (types 2 to 4).

[0020] The carbon fibers constituting the carbon fiber bundle are not particularly limited, and 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, and examples thereof include thermosetting resins such as epoxy resins and thermoplastic resins.

[0021] Fig. 1 shows an example of a high-pressure hydrogen tank.

[0022] The high-pressure hydrogen tank T includes a liner L as a hollow substrate, a carbon fiber reinforced resin layer F including carbon fiber bundles wound around the liner L and a matrix resin, and caps C1 and C2 installed at both ends in the longitudinal direction. The material constituting the liner L is not particularly limited, and examples include metals such as aluminum and chromium molybdenum steel, and resins such as polyamide and polyethylene.

[0023] The manufacturing method of the high-pressure hydrogen tank T is not particularly limited, and examples include the filament winding method.

[0024] The method for regenerating carbon fiber bundles according to an embodiment of the present invention includes a first heating step of heating the high-pressure hydrogen tank T to decompose a part of the matrix resin, and a unwinding step of unwinding an intermediate carbon fiber bundle I to which decomposition residues of the matrix resin adhere from the carbon fiber reinforced resin layer in which a part of the matrix resin has decomposed. Further, the method for regenerating carbon fiber bundles according to an embodiment of the present invention further includes a second heating step of obtaining a regenerated carbon fiber bundle R by heating the unwound intermediate carbon fiber bundle I using a tubular furnace to decompose the decomposition residues of the matrix resin, and a winding step of winding up the regenerated carbon fiber bundle R. Here, the tubular furnace has a heater for heating the intermediate carbon fiber bundle I, and a lid installed at the inlet and outlet and having a through hole through which the intermediate carbon fiber bundle I can pass. Therefore, when the intermediate carbon fiber bundle I is heated using the tubular furnace to decompose the decomposition residues of the matrix resin, the release of thermal energy and the mixing of outside air are suppressed, and as a result, the decomposition residues of the matrix resin are decomposed stably and efficiently.

[0025] 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 start temperature of the matrix resin and equal to or lower than the flash point of the thermal decomposition 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 oxidation decomposition start temperature of the decomposition residue of the matrix resin and equal to or lower than the thermal decomposition start temperature of the carbon fiber. Thereby, overheating due to combustion of the thermal decomposition gas of the matrix resin and deterioration of the carbon fiber are suppressed.

[0026] When the matrix resin is an epoxy resin, for example, in the first step, heating is performed at a temperature of 330°C or higher and 360°C or lower, and in the second step, heating is performed at a temperature of 430°C or higher and 470°C or lower. In this case, examples of the thermal decomposition gas include bisphenol A and phenol.

[0027] Note that the heating temperature in the first heating step is not particularly limited as long as the carbon fiber bundle to which the decomposition residue of the matrix resin adheres can be unwound.

[0028] FIG. 2 shows a heat treatment furnace as an example of the first heating unit used in the first heating step.

[0029] The heat treatment furnace 10 has a heat treatment chamber 11 and a combustion chamber 12.

[0030] The heat treatment chamber 11 is a sealed space surrounded by an outer wall 11a and an inner wall 11b. Further, the heat treatment chamber 11 is provided with burners 11c at the upper part of the left outer wall 11a and the lower part of the right outer wall 11a in the drawing so that combustion gas flows into the inner wall 11b. Therefore, when gas fuel and air are mixed and burned by the burner 11c, the combustion gas convects inside the inner wall 11b and the temperature inside the inner wall 11b becomes stable.

[0031] The heat treatment chamber 11 is provided with a sealing door for accommodating the high-pressure hydrogen tank T on a part of the outer wall 11a and the inner wall 11b. Here, the high-pressure hydrogen tank T is placed on the heat insulating material 11d installed so as to penetrate the bottom surface of the inner wall 11b. Further, the load cell 11e as a mass detection unit is installed between the bottom surface of the outer wall 11a and the heat insulating material 11d, and detects the mass of the high-pressure hydrogen tank T in real time based on the amount of strain. As a result, since the heating conditions in the heat treatment chamber 11 are optimized, fluctuations in the decomposition amount of the matrix resin due to individual differences in the material, shape, etc. of the high-pressure hydrogen tank T are suppressed, and the management accuracy is improved. In addition, since it is not necessary to make the heating time in the heat treatment chamber 11 longer than necessary, it contributes to shortening the heating time and reducing the energy consumption.

[0032] Note that the mass detection unit may detect the amount of decrease in the mass of the high-pressure hydrogen tank T in real time. Further, the mass detection unit may be omitted as necessary.

[0033] The decomposition gas of the matrix resin generated inside the inner wall 11b is discharged from the exhaust port 11f formed at the upper part of the inner wall 11b in the figure, and then introduced into the combustion chamber 12 via the pipe 11g installed through the outer wall 11a.

[0034] The combustion chamber 12 is a sealed space surrounded by the outer wall 12a and the inner wall 12b. Further, the combustion chamber 12 is provided with a burner 12c at the central part of the left outer wall 12a in the figure so that the combustion gas flows into the inner wall 12b. On the other hand, after passing through the outer wall 12a, the pipe 11g penetrates inside and outside the inner wall 12b inside the outer wall 12a, and finally is connected to the upper left part of the inner wall 12b in the figure. At this time, 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 inside the inner wall 12b, and then introduced from the upper left part of the inner wall 12b and comes into contact with the combustion gas. As a result, the decomposition gas of the matrix resin is exhausted to the outside from the exhaust port 12d after combustion.

[0035] Fig. 3 shows an example of a rotating part that rotates the high-pressure hydrogen tank T inside the heat treatment chamber 11. Note that Figs. 3(a) and (b) are a cross-sectional view and a side view, respectively.

[0036] Since the rotating part 20 has a substantially horizontal rotation axis 21 passing through the wall W of the heat treatment chamber 11, in the figure, the temperature distribution of the carbon fiber reinforced resin layer F in the vertical direction is made uniform.

[0037] Note that the rotation axis 21 may be in a direction other than the substantially horizontal direction, for example, in a substantially vertical direction. When the rotation axis 21 is 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 an extent similar to the case where the rotation axis 21 is in the substantially horizontal direction.

[0038] The high-pressure hydrogen tank T is connected to the rotation axis 21 via a jig 22 with a flange and a rotation axis flange 23 that utilize the shapes of the bases C1 and C2. At this time, the jig 22 with a flange and the rotation axis flange 23 are fixed with, for example, bolts and nuts. Further, the high-pressure hydrogen tank T 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. Also, a motor for rotating the rotation axis 21 is installed outside the wall W of the heat treatment furnace 10, and a cooling jacket 27 is installed around the rotation axis 21.

[0039] Fig. 4 shows an example of a pay-out part used in the pay-out process. Note that Figs. 4(a) and (b) are a front view and a side view, respectively.

[0040] The unwinding unit 30 includes a rotary jig 31 that rotatably supports the high-pressure hydrogen tank T1 in which a part of the matrix resin has decomposed, and a motor 32 that rotates the high-pressure hydrogen tank T1. The rotational power of the motor 32 is transmitted to the rotary 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 arranged so that the intermediate carbon fiber bundle I is unwound outside the tangent line at the position where the intermediate carbon fiber bundle I of the high-pressure hydrogen tank T1 is unwound. Further, the rollers 34, 35, and 36 have a long axis so as to correspond to the unwinding of the intermediate carbon fiber bundle I in the longitudinal direction of the high-pressure hydrogen tank T1. Furthermore, a dancer roller 37 for controlling the unwinding tension is installed to absorb the difference in the unwinding amount per rotation due to the hoop winding and helical winding of the intermediate carbon fiber bundle I.

[0041] Note that a blade may be installed instead of the roller 34.

[0042] The heating temperature in the second heating step is preferably equal to or higher than the heating temperature in the first heating step. Thereby, the decomposition residue of the matrix resin adhering to the intermediate carbon fiber bundle I is likely to decompose. On the other hand, the heating temperature in the second heating step is preferably equal to or lower than the thermal decomposition start temperature of the carbon fiber. Thereby, the deterioration of the carbon fiber is suppressed.

[0043] Note that after performing a sizing step of sizing the recycled carbon fiber bundle R, the sized recycled carbon fiber bundle R may be wound up.

[0044] FIG. 5 shows an example 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.

[0045] As the second heating unit, the tubular furnace 40 is provided with a heat insulation cover 42 (see Fig. 6) having slit-shaped through holes S formed at both ends of the inlet and outlet, that is, both ends of the quartz tube 41, through which the intermediate carbon fiber bundle I with decomposition residues of the matrix resin adhering thereto can pass. Here, the slit-shaped through holes S are formed in the horizontal direction. Further, in the central portion of the quartz tube 41 of the tubular furnace 40, a heating wire heater 43, a heat insulating material 44, and a protective cover 45 are sequentially installed. Therefore, the intermediate carbon fiber bundle I is heated by the heating wire heater 43, and the decomposition residues of the matrix resin are decomposed, so that a regenerated carbon fiber bundle R is obtained.

[0046] In addition, when heating a plurality of intermediate carbon fiber bundles I, a heat insulation cover 42A (see Fig. 7) having a plurality of slit-shaped through holes S formed therein can be used. Further, the shape of the through holes formed in the heat insulation cover is not limited to a slit shape as long as the intermediate carbon fiber bundle I can pass through.

[0047] As shown in Fig. 8, in the tubular furnace 40, there are a heating region H where the intermediate carbon fiber bundle I is heated and a non-heating region N where the intermediate carbon fiber bundle I is not heated. That is, the heating wire heater 43 is wound around the quartz tube 41 constituting the heating region H, and the heating wire heater 43 is not wound around the quartz tube 41 constituting the non-heating region N. Here, the non-heating region N exists between the end portion on the inlet side of the quartz tube 41 and the heating region H and between the end portion on the outlet side of the quartz tube 41 and the heating region H. Therefore, due to the temperature difference between the heating region H and the non-heating region N, a natural convection vortex is generated, and as a result, the atmospheric gas in the heating region H stays.

[0048] The tubular furnace 40 is provided with an introduction pipe 46 for introducing an oxidizing gas into the heating region H. At this time, by introducing a minimum amount of oxidizing gas, carbon dioxide contained in the atmosphere gas in the stagnant heating region H is discharged, so that the composition and temperature of the atmosphere gas in the heating region H are maintained. Further, the oxidizing gas is introduced along the surface of the intermediate carbon fiber bundle I. Therefore, the fuzzing of the regenerated carbon fiber bundle R is suppressed. Furthermore, the oxidizing gas is introduced from the downstream side to the upstream side of the tubular furnace 40. Therefore, the decomposition residues of the trace amount of matrix resin adhering to the intermediate carbon fiber bundle I on the downstream side of the tubular furnace 40 are easily decomposed. The introduction pipe 46 is arranged along the upper surface of the quartz tube 41. Therefore, the oxidizing gas introduced into the heating region H forms a turbulent flow. At this time, in order for the oxidizing gas introduced into the heating region H to form a turbulent flow, the temperature of the oxidizing gas may be set to room temperature or the oxidizing gas may be intermittently introduced.

[0049] The oxidizing gas is not particularly limited as long as it is a gas that promotes the oxidation of the decomposition residues of the matrix resin adhering to the intermediate carbon fiber bundle I. For example, oxygen can be mentioned.

[0050] Note that the heating region H may be divided into a plurality of regions. Further, the introduction pipe 46 does not have to be arranged along the upper surface of the quartz tube 41.

[0051] The sizing unit 50 passes the regenerated carbon fiber bundle R through the sizing liquid 51. At this time, the sizing liquid 51 is heated by the heater 52. Further, the excessive coating of the sizing liquid 51 on the regenerated carbon fiber bundle R is prevented by the roller 53.

[0052] Note that, if necessary, a drying furnace may be installed to dry the regenerated carbon fiber bundle R.

[0053] The feeding mechanism 60 has feeder rollers 61, 62, and 63, and the linear velocity of the regenerated carbon fiber bundle R is controlled to a linear velocity that is easy to manage in the process by utilizing the friction between the feeder rollers 61, 62, and 63 and the regenerated carbon fiber bundle R.

[0054] 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, by controlling the torque of the winding motor 71, the winding tension of the recycled carbon fiber bundle R is controlled.

[0055] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments, and the above embodiments may be appropriately modified within the scope of the gist of the present invention. For example, as a structure other than the high-pressure hydrogen tank, a propeller shaft, a safety block, a low-friction roll, a rotor part of a spindle shaft motor, etc. may be used.

Explanation of Reference Numerals

[0056] 40 Tubular furnace 42, 42A Heat insulation lid 43 Electric heating wire heater 46 Introduction pipe C1, C2 Base F Carbon fiber reinforced resin layer H Heating region I Intermediate carbon fiber bundle L Liner N Non-heating region R Recycled carbon fiber bundle S Slit-shaped through hole T, T1 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, comprising: a first heating step of heating the structure 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 obtaining a regenerated carbon fiber bundle by heating the wound-out intermediate carbon fiber bundle using a tubular furnace to decompose the decomposition residues of the matrix resin; a winding-up step of winding up the regenerated carbon fiber bundle, wherein the tubular furnace has a heater for heating the intermediate carbon fiber bundle and a lid installed at an inlet and an outlet and having a through-hole formed therein through which the intermediate carbon fiber bundle can pass, the method for regenerating a carbon fiber bundle.

2. In the tubular furnace, there are a heating region where the intermediate carbon fiber bundle is heated and a non-heating region where the intermediate carbon fiber bundle is not heated, wherein the non-heating region exists between the heating region and the inlet and / or between the heating region and the outlet, the method for regenerating a carbon fiber bundle according to Claim 1.

3. The tubular furnace further has an introduction pipe for introducing an oxidizing gas into the heating region, the method for regenerating a carbon fiber bundle according to Claim 2.

4. The oxidizing gas is introduced along the surface of the intermediate carbon fiber bundle, the method for regenerating a carbon fiber bundle according to Claim 3.

5. The oxidizing gas is introduced from the downstream side to the upstream side of the tubular furnace, the method for regenerating a carbon fiber bundle according to Claim 3 or 4.

6. The introduction pipe is arranged such that the oxidizing gas introduced into the heating region forms a turbulent flow, the method for regenerating a carbon fiber bundle according to Claim 3 or 4.

7. The through-hole is slit-shaped and formed in the horizontal direction, the method for regenerating a carbon fiber bundle according to any one of Claims 1 to 4.

8. The lid has a plurality of the through-holes formed therein, the method for regenerating a carbon fiber bundle according to any one of Claims 1 to 4.

9. 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, a first heating unit that heats the structure to decompose a part of the matrix resin; a winding-out unit that winds out an intermediate carbon fiber bundle to which decomposition residues of the matrix resin adhere from the carbon fiber reinforced resin layer in which a part of the matrix resin has decomposed; a second heating unit that heats the wound-out intermediate carbon fiber bundle to decompose the decomposition residues of the matrix resin, thereby obtaining a regenerated carbon fiber bundle; a winding-up unit that winds up the regenerated carbon fiber bundle, and has The second heating unit is a tubular furnace having a heater that heats the intermediate carbon fiber bundle, and a lid that is installed at an inlet and an outlet and has a through hole through which the intermediate carbon fiber bundle can pass, for a carbon fiber bundle regeneration device.

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