Crushing method for CFRP waste material, and method of manufacturing CFRP crushing material

Abstract

To provide a crushing method for a CFRP waste material, in which a crushed piece with a high content percentage of a carbon fiber suitable for manufacture of a carbon fiber assembly can be easily produced, when used to crush the CFRP waste material containing the carbon fiber with a filament length of 100 mm or more.SOLUTION: A crushing method for a CFRP waste material includes crushing a CFRP waste material while circulating it within a crushing chamber of a biaxial shear crusher. The thickness of a crushing blade possessed by the biaxial shear crusher can also be 15 mm or more, and can also be 30 mm or less. The biaxial shear crusher can also have a hopper for throwing the CFRP waste material into the crushing chamber. During crushing, dust produced within the crushing chamber can also be removed by a dust collector.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention mainly relates to a method for crushing CFRP waste materials and a method for producing crushed CFRP materials. [Background technology]

[0002] CFRP (Carbon Fiber Reinforced Plastic), a fiber-reinforced plastic made with carbon fiber, is a lightweight material with excellent mechanical properties that is suitable for parts in automobiles, ships, railway vehicles, manned aircraft, unmanned aerial vehicles, and other transportation equipment, and its importance has been increasing in recent years. The carbon fiber manufacturing process consumes a significant amount of energy, so it is desirable to recover and reuse the carbon fibers contained in used CFRP products.

[0003] A method for producing recycled carbon fibers has been proposed (Patent Document 1), which includes primary crushing of CFRP waste material, followed by secondary crushing to obtain CFRP crushed fragments, removing powder contained in the CFRP crushed fragments using a powder removal device, removing matrix resin components from the de-powdered CFRP fragments by thermal decomposition to obtain recycled carbon fibers, and classifying the recycled carbon fibers.

[0004] It has been reported that short carbon fibers and water in which a resin has been dispersed are mixed by stirring and then dried to produce granulated carbon fiber aggregates that can be fed into a kneader using a feeder (Patent Document 2). It has been reported that short recycled carbon fibers were extracted from waste CFRP produced using carbon fiber sheet molding compound (CF-SMC) and bundled to obtain a carbon fiber aggregate that can be used as a reinforcing material for sheet prepregs (Patent Document 3).

[0005] It is known that a dual shaft shear shredder can achieve fine crushing by repeatedly crushing the material to be crushed using a closing damper that opens and closes at the discharge outlet (Patent Document 4). The purpose of the shredder disclosed in Patent Document 4 is to crush waste before it is fed into a waste incinerator. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-127040 [Patent Document 2] International Publication No. 2022 / 265100 [Patent Document 3] International Publication No. 2022 / 265099 [Patent Document 4] Japanese Patent Application Publication No. 2017-131832 Summary of the Invention [Problem to be solved by the invention]

[0007] The CFRP waste produced using CF-SMC contains only short cut carbon fibers, so by simply removing the resin matrix, recycled carbon fibers can be obtained that can be used directly to produce carbon fiber aggregates. In contrast, to obtain recycled carbon fibers suitable for producing carbon fiber assemblies from CFRP waste containing long carbon fibers with filament lengths of 100 mm or more, such as CFRP waste produced using UD prepregs, it is necessary to crush the CFRP waste before removing the resin matrix. This is because it is not easy to cut long recycled carbon fibers to the desired length after extracting them from the CFRP waste, and the method of cutting the fibers without controlling the cutting length and then classifying them with a sieve is not practical because a large amount of dust is generated during cutting.

[0008] The object of the present invention is to provide a method for crushing CFRP waste, which, when used to crush CFRP waste containing carbon fibers with a filament length of 100 mm or more, is likely to produce fragments with a high carbon fiber content suitable for producing carbon fiber aggregates. Another object of the present invention is to provide a method for producing CFRP crushed material with a high carbon fiber content suitable for producing carbon fiber aggregates from CFRP waste material containing carbon fibers with a filament length of 100 mm or more. In this specification, problems that can be solved by each embodiment of the present invention may be explicitly or implicitly disclosed. [Means for solving the problem]

[0009] In one aspect of the present invention, there is provided a method for crushing CFRP waste materials, which comprises crushing the CFRP waste materials while circulating them in a crushing chamber of a biaxial shear crusher.

[0010] In another aspect of the present invention, there is provided a method for producing crushed CFRP material, which comprises crushing CFRP waste material containing carbon fibers with a filament length of 100 mm or more while circulating the material in a crushing chamber of a biaxial shear crusher. This method may preferably further comprise separating the crushed pieces obtained by the crushing into at least three classes based on their size, and removing pieces included in at least the classes at both ends. [Effects of the Invention]

[0011] According to one embodiment, a method for crushing CFRP waste is provided which, when used to crush CFRP waste containing carbon fibers with a filament length of 100 mm or more, is likely to produce fragments with a high carbon fiber content suitable for producing carbon fiber aggregates. According to another embodiment, there is provided a method for producing CFRP crushed material with a high carbon fiber content suitable for producing carbon fiber aggregates from CFRP waste material containing carbon fibers with a filament length of 100 mm or more. [Brief explanation of the drawings]

[0012] [Figure 1] Figure 1 shows a cross-sectional plan view of a twin-shaft shear crusher. [Figure 2] FIG. 2 shows a side cross-sectional view of the twin-shaft shear crusher with the bottom plate and lid closed. [Figure 3] Figure 3 shows a longitudinal cross-sectional view of the twin-shaft shear crusher with the bottom plate and lid closed. [Figure 4] FIG. 4 shows a longitudinal cross-sectional view of the twin-shaft shear crusher with the bottom plate in the closed position. [Figure 5] FIG. 5 shows how a 40-ply prepreg laminate is folded in three. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of the present invention will be described below. 1. Method for crushing CFRP waste One embodiment of the present invention relates to a method for crushing CFRP waste materials.

[0014] 1.1. CFRP waste Typical examples of CFRP waste in this specification include CFRP extracted from discarded CFRP-using products (e.g., transportation equipment, industrial equipment, sports and leisure goods, etc.) and CFRP discarded as defective or surplus products at CFRP product manufacturing plants. Thermoplastic carbon fiber prepreg waste is also an example of CFRP waste. Examples of thermoplastic carbon fiber prepreg waste include scraps generated during the manufacturing process of CFRP products using thermoplastic carbon fiber prepreg, as well as scraps, defective products, and surplus products generated in thermoplastic carbon fiber prepreg manufacturing plants.

[0015] Further examples of CFRP waste include cured thermosetting carbon fiber prepreg waste. Examples of thermosetting carbon fiber prepreg waste include offcuts generated during the manufacturing process of CFRP products, as well as offcuts, rejects, and surplus products generated in thermosetting carbon fiber prepreg manufacturing plants. There is no limitation on the method for curing the waste thermosetting carbon fiber prepreg, and a heat treatment furnace may be used, or the waste may simply be left indoors or outdoors for a long period of time. Thermosetting carbon fiber prepregs that have hardened during storage and become unusable can also be included in this type of CFRP waste.

[0016] The crushing method according to the embodiment can be preferably used to crush CFRP waste materials containing carbon fibers with a filament length of 100 mm or more. For example, CFRP waste containing carbon fibers with a filament length of 100 mm or more is generated when CFRP-using products containing the following CFRPs are manufactured or when they become unnecessary.

[0017] CFRP obtained by curing a thermosetting carbon fiber prepreg containing carbon fibers with a filament length of 100 mm or more. For example, carbon fiber UD prepreg, carbon fiber fabric prepreg, and carbon fiber tow prepreg may contain carbon fibers with a filament length of 100 mm or more. CFRP manufactured by the RTM or VaRTM methods. · CFRP manufactured using the filament winding method. CFRP manufactured using the pultrusion method. - Thermoplastic CFRP containing carbon fibers with a filament length of 100 mm or more.

[0018] The cured waste of carbon fiber UD prepreg, carbon fiber fabric prepreg, or carbon fiber tow prepreg is often CFRP waste containing carbon fiber with a filament length of 100 mm or more.

[0019] 1.2. Crushing method The method for crushing CFRP waste materials according to the embodiment includes crushing the CFRP waste materials while circulating them in a crushing chamber of a biaxial shear crusher. The basic structure of the twin-shaft shear crusher used in this method will be described below with reference to Figures 1 to 3. Figures 1, 2 and 3 are a plan cross-sectional view, a side cross-sectional view and a longitudinal cross-sectional view of the twin-shaft shear crusher, respectively.

[0020] As shown in Fig. 1, the twin-shaft shear crusher 100 has a main shaft 1 and a driven shaft 2 arranged parallel to each other. The main shaft 1 and the driven shaft 2 are rotatably supported at both ends by bearings 3. Both bearings 3 are fixed to a casing 4. A shaft 1a connected to one end of the main shaft 1 is connected to a drive shaft 7 of an electric motor 6 via a coupling 5. A spur gear 8 is mounted on the shaft 1a and meshes with a spur gear 9 provided on one end of the driven shaft 2. When the electric motor 6 is operated to rotate the main shaft 1, the driven shaft 2 rotates in the opposite direction to the main shaft 1, as shown in Figure 3.

[0021] Disk-shaped crushing blades 10 and spacers 11 are alternately mounted on the main shaft 1. Similarly, disk-shaped crushing blades 10 and spacers 11 are alternately mounted on the slave shaft 2. The crushing blades 10 on the main shaft 1 and the crushing blades 10 on the slave shaft 2 all have the same thickness. The thickness of the crushing blades 10 is not limited, but is usually 15 mm or more. The main shaft 1 and the slave shaft 2 are arranged so that the side surface of the crushing blade 10 on the main shaft 1 and the side surface of the crushing blade 10 on the slave shaft 2 overlap in a state of close contact.

[0022] As shown in FIG. 3, a plurality of claws 10a are provided at regular intervals on the outer periphery of each crushing blade 10. One of the roles of the claws 10a is to draw the CFRP waste material to be crushed between the main shaft 1 and the slave shaft 2. The CFRP waste material drawn between the main shaft 1 and the slave shaft 2 is sheared and crushed by the crushing blades 10. Another role of the claws 10a is to pull up the crushed CFRP waste that has fallen onto the bottom plate 12 again through the gaps between the main shaft 1 and the driven shaft 2 and the casing 4. Due to this function of the claws 10a, the CFRP waste that has been fed into the biaxial shear crusher 100 circulates within the crushing chamber R surrounded by the casing 4, bottom plate 12, and lid 13, and is repeatedly sheared and crushed. The crushing chamber R may be configured so that the CFRP waste material can be sheared and crushed by the crushing blades 10 while circulating therein, and for example, the lid 13 may be omitted.

[0023] The bottom plate 12 is connected to the casing 4 via a hinge (not shown) and can be opened and closed. The CFRP waste is crushed with the bottom plate 12 closed, and when crushing is complete, the bottom plate 12 is opened while the main shaft 1 and the slave shaft 2 are still rotating, and the crushed CFRP pieces are dropped into a container (not shown) installed below the crushing chamber R.

[0024] The lid 13 is connected to the casing 4 via a hinge so that it can be opened and closed, or is removable. The lid 13 is opened when the CFRP waste material is fed into the crushing chamber R. For safety reasons, it is preferable to close the lid 13 to make the crushing chamber R a closed space while the CFRP waste material is being crushed. Making the crushing chamber R a closed space while crushing CFRP waste is also useful for preventing the leakage of dust generated during crushing from deteriorating the working environment in the room where the biaxial shear crusher 100 is installed. This dust contains carbon fibers, which may cause damage to electrical and electronic equipment, as carbon fibers are electrically conductive.

[0025] In one example, an air intake port connected to a dust collector may be provided on the lid 13, so that dust generated in the crushing chamber R while the CFRP waste is being crushed can be removed by the dust collector. In addition to providing an air intake port connected to a dust collector on the lid 13, or instead of providing an air intake port connected to a dust collector on the lid 13, a suction nozzle connected to a dust collector may be installed in the crushing chamber R. By using a dust collector, it is possible to effectively prevent dust generated during crushing from leaking out of the crushing chamber R.

[0026] In a modified example, instead of using the lid 13, as shown in Fig. 4, a hopper 14 having an inlet 14a may be fixed to the top of the housing 4. Since CFRP waste can be fed into the crushing chamber R only through the hopper 14, safety is improved. Preferably, the input port 14a is of an openable / closable type. In other words, a door (not shown) is provided at the input port 14a. When the door of the input port 14a is closed, the crushing chamber R becomes part of a closed space consisting of the crushing chamber R and the hopper internal space S.

[0027] Circulating the CFRP waste material within the crushing chamber R during crushing is extremely effective in reducing the amount of large fragments that cannot pass through a round hole with the same diameter as the thickness of the crushing blade 10. For example, when the thickness of the crushing blade 10 is 30 mm, circulating the CFRP waste material within the crushing chamber R during crushing significantly reduces the amount of large fragments that cannot pass through a round hole with a diameter of 30 mm. Moreover, advantageously, even if the CFRP waste material is circulated in the crushing chamber R, if the circulation time is short, the amount of small CFRP fragments generated will not increase significantly.

[0028] Among the fragments contained in the crushed material obtained by crushing CFRP waste containing carbon fibers with a filament length of 100 mm or more using the biaxial shear crusher 100, for example, between fragments that can pass through a round hole with a diameter of 30 mm and fragments that cannot, the former is thought to have a higher content of carbon fibers with a filament length of 30 mm or less (the proportion of carbon fibers with a filament length of 30 mm or less out of the total carbon fibers contained). Similarly, between fragments that can pass through a round hole with a diameter of 20 mm and fragments that cannot, the former is thought to have a higher content of carbon fibers with a filament length of 20 mm or less.

[0029] Therefore, recycled carbon fibers with a high content of carbon fibers with filament lengths of 30 mm or less can be recovered from CFRP crushed material obtained by crushing CFRP waste containing carbon fibers with filament lengths of 100 mm or more so as to produce many crushed fragments that can pass through a round hole with a diameter of 30 mm. Similarly, recycled carbon fiber with a high content of carbon fiber with a filament length of 20 mm or less can be recovered from the CFRP crushed material obtained by crushing the same CFRP waste material so as to produce many crushed pieces that can pass through a round hole with a diameter of 20 mm.

[0030] With the exception of continuous carbon fibers, carbon fibers with too long filament lengths, for example, carbon fibers with filament lengths of 100 mm or more, are difficult to industrially use as reinforcing materials for fiber-reinforced resins. In contrast, carbon fibers with filament lengths of 30 mm or less are suitable as raw materials for carbon fiber aggregates that can be used as reinforcing materials for sheet prepregs. From this viewpoint, the thickness of the crushing blade 10 is preferably 30 mm or less, and may be 25 mm or less, or 20 mm or less.

[0031] The crushed material obtained by crushing CFRP waste containing carbon fibers with a filament length of 100 mm or more using the biaxial shear crusher 100 includes fragments that can pass through a round hole with a diameter of about half the thickness of the crushing blade 10. The proportion of such fragments in the total weight of the crushed material begins to increase with the circulation time once the circulation time of the CFRP waste in the crushing chamber exceeds a certain limit. This means that if the circulation time is set appropriately, the biaxial shear crusher 100 can efficiently produce crushed material with a high carbon fiber content and a filament length less than half the thickness of the crushing blade 10.

[0032] In order to obtain CFRP crushed material in a short time with a high proportion of crushed pieces that can pass through a round hole of diameter D (mm) in the total weight, it is advantageous to use a crushing blade 10 with a thickness close to the diameter D (mm) of the round hole. For example, if you want to obtain CFRP crushed material in a shorter time, with a high proportion of crushed fragments that can pass through a 10 mm diameter round hole in the total weight, it is more advantageous to use a 25 mm thick crushing blade than a 30 mm thick crushing blade, and it is even more advantageous to use a 20 mm thick crushing blade, and it is even more advantageous to use a 15 mm thick crushing blade.

[0033] 2. Manufacturing method for crushed CFRP material One embodiment of the present invention relates to a method for producing crushed CFRP material. The manufacturing method of the embodiment for CFRP crushed material includes a crushing step of crushing CFRP waste material containing carbon fibers with a filament length of 100 mm or more, and preferably further includes a sorting step of selecting some of the crushed pieces obtained in the crushing step.

[0034] 2.1.Crushing process In the crushing step, the crushing method for CFRP waste described in 1. above is used. That is, CFRP waste containing carbon fibers with a filament length of 100 mm or more is crushed while circulating it in the crushing chamber of a biaxial shear crusher. As described above, the thickness of the crushing blades provided in the biaxial shear crusher is usually 15 mm or more, and preferably 30 mm or less, and may be 25 mm or less or 20 mm or less. For example, when producing CFRP crushed material in which the proportion of crushed pieces that can pass through a round hole with a diameter of 15 mm or less is high in the total weight, the thickness of the crushing blade is preferably 25 mm or less, more preferably 20 mm or less, and even more preferably 15 mm.

[0035] 2.2.Sorting process In the sorting step, the crushed pieces obtained in the crushing step are divided into at least three classes based on their size, and further, pieces included in at least the two end classes are removed.

[0036] The sieve used to separate the crushed pieces into at least three sizes is not particularly limited. In one example, the sieve may be a punched metal sieve with holes of the same shape and size regularly arranged. The holes may be round, rectangular, or other polygonal.

[0037] For example, both are punched metals with round holes, each with a diameter of D A , D B , D C (However, D A <D B <D CWhen crushed fragments are classified using sieves A, B, and C (sieves A, B, and C), the crushed fragments are divided into four groups: group G1 consisting of crushed fragments that pass through sieve A; group G2 consisting of crushed fragments that do not pass through sieve A but pass through sieve B; group G3 consisting of crushed fragments that do not pass through sieve B but pass through sieve C; and group G4 consisting of crushed fragments that do not pass through sieve C. In the sorting process, at least the crushed fragments included in group G1 and group G4 of the four groups are removed. Therefore, the crushed fragments selected in this process may be only the crushed fragments included in group G2, or only the crushed fragments included in group G3, or may be crushed fragments included in either group G2 or group G3.

[0038] For example, D A If the length of the filament is 10 mm, removing the fragments contained in the fragment group G1 means removing fragments with a high carbon fiber content and filament lengths of less than 10 mm. For example, D C If the length of the filament is 30 mm, removing the fragments contained in the fragment group G4 means removing fragments with a high carbon fiber content and a filament length of more than 30 mm. For example, D B If the filament length is 20 mm, removing the fragments contained in fragment group G3 and the fragments contained in fragment group G4 means removing fragments with a high carbon fiber content and a filament length of more than 20 mm.

[0039] As can be seen from the above example, by carrying out the sorting process, it is possible to obtain CFRP crushed material in which the proportion of crushed pieces with a high content of carbon fibers having the desired filament length in the total weight is high.

[0040] In order for carbon fibers dispersed in a resin to be highly effective as a reinforcing material, it is desirable for the filament length to be 3 mm or more. However, for example, if the carbon fibers are mixed into a thermoplastic resin using a kneader during use, they will be cut and shortened during the kneading process, so the filament length before use is preferably 5 mm or more, and more preferably 10 mm or more. To separate out fragments with a high carbon fiber content and filament lengths of 5 mm or more, the CFRP fragments can be classified using a sieve, for example, a punched metal with round holes of 5 mm diameter, and the fragments that pass through the sieve can be removed. Similarly, to separate out fragments with a high carbon fiber content and filament lengths of 10 mm or more, the CFRP fragments can be classified using a sieve, such as a punched metal sieve with round holes 10 mm in diameter, and the fragments that pass through the sieve can be removed.

[0041] As a raw material for a spindle-shaped carbon fiber aggregate suitable for feeding to a kneader using a feeder, carbon fibers having a filament length of 15 mm or less are preferred, and carbon fibers having a filament length of 12 mm or less are more preferred. For example, if you want to separate out fragments with a high carbon fiber content and filament lengths of 15 mm or less, you can use a punched metal sieve with round holes 15 mm in diameter to classify the CFRP fragments, and then remove the fragments that do not pass through the sieve. Similarly, if you want to separate out fragments with a high carbon fiber content and filament lengths of 12 mm or less, you can use a punched metal sieve with round holes 12 mm in diameter to classify the CFRP fragments, and then remove the fragments that do not pass through the sieve.

[0042] The debris removed in the sorting process can be used for other purposes. In the above example, the fragments contained in the fragment group G4 may be removed in the sorting process and then returned to the crushing process again to be crushed together with CFRP waste material containing carbon fibers with a filament length of 100 mm or more.

[0043] 3. Manufacturing method of recycled carbon fiber The crushed CFRP material obtained by using the method for crushing CFRP waste materials according to the embodiment or the method for producing crushed CFRP material according to the embodiment can be preferably used as a raw material for recycled carbon fibers.

[0044] To produce recycled carbon fibers from crushed CFRP materials, the resin matrix may be removed from the crushed CFRP materials by using a conventionally known method, such as the following method.

[0045] According to Japanese Patent Laid-Open No. 6-99160, carbon fibers can be recovered by treating CFRP in a gas atmosphere with an oxygen concentration in the range of 3 to 18% by volume and a temperature in the range of 300 to 600°C without combustion. According to Japanese Patent Laid-Open No. 7-33904, carbon fibers can be recovered by dry distilling CFRP and then treating it at an oxygen concentration in the range of 0.1 to 25% by volume and at a temperature in the range of 300 to 1000°C without burning it. According to Japanese Patent Laid-Open No. 7-118440, when CFRP is dry distilled at a temperature in the range of 300 to 1000°C, a carbon fiber aggregate is formed in which a large number of carbon fibers are bound together by the thermal decomposition product (residue) of the thermosetting resin.

[0046] For example, the resin matrix of CFRP may be decomposed and removed by a semiconductor thermal activation method using an oxide semiconductor such as chromium oxide, titanium oxide, zinc oxide, vanadium oxide, tungsten oxide, molybdenum oxide, cobalt oxide, iron oxide, or copper oxide. For specific procedures for removing the resin matrix from CFRP by the semiconductor thermal activation method, see, for example, International Publication No. 2022 / 050281.

[0047] In one example, the resin matrix of CFRP may be decomposed using subcritical or supercritical fluids, and any resin residue that cannot be removed by this method can be removed by heat treatment in an oxidizing atmosphere. In one example, the resin matrix of CFRP can be decomposed and removed by microwave heating.

[0048] 4. Manufacturing method of fiber assembly Recycled carbon fibers can be produced using the CFRP crushed material obtained using the embodiment's method for crushing CFRP waste materials or the embodiment's method for manufacturing CFRP crushed material as raw materials, and the recycled carbon fibers can be used to produce a fiber aggregate. Specifically, a binder-containing liquid is added to and mixed with dried raw fiber material containing recycled carbon fiber to form a wet fiber aggregate, and then the wet fiber aggregate is dried to obtain the fiber aggregate. In the recycled carbon fiber used as the raw material, it is preferable that the filaments are not bonded to each other, but very loose bonding is acceptable.

[0049] The dried raw fiber material may contain only recycled carbon fiber, or may contain recycled carbon fiber together with thermoplastic resin fiber having a filament length similar to that of the recycled carbon fiber. The preferred liquid component contained in the binder-containing liquid is water. The strong surface tension of water causes a capillary effect that causes the fiber filaments in the raw fiber to aggregate, thereby forming a fiber aggregate.

[0050] A suitable example of the binder contained in the binder-containing liquid is a sizing agent that is commonly used in the production of carbon fibers, and a suitable example of the binder liquid is an aqueous dispersion of such a sizing agent. There is no limitation on the method for mixing the dried raw fiber material with the binder-containing liquid, but stirring is preferred for efficient mixing in a short time. For stirring, a stirring mixer for powders known as a Henschel mixer can be preferably used.

[0051] When the recycled carbon fiber contains a large amount of carbon fibers with a filament length of 5 mm or more and 30 mm or less, needle-shaped, spindle-shaped or wire-shaped carbon fiber aggregates suitable as reinforcing materials for sheet prepregs can be obtained. When recycled carbon fibers contain a large amount of carbon fibers with a filament length of 1 mm or more and 15 mm or less, and particularly when they contain a large amount of carbon fibers with a filament length of 12 mm or less, spindle-shaped carbon fiber aggregates that can be fed into a kneader using a feeder are easily formed. For example, WO 2022 / 210591 discloses a procedure for producing spindle-shaped carbon fiber aggregates.

[0052] 5. Summary of embodiments Embodiments of the present invention include, but are not limited to, the following:

[0053] [Embodiment 1] A method for crushing CFRP waste materials, which includes crushing CFRP waste materials while circulating them in the crushing chamber of a biaxial shear crusher. [Embodiment 2] The crushing method according to embodiment 1, wherein the thickness of the crushing blades of the biaxial shear crusher is 15 mm or more. [Embodiment 3] A crushing method according to embodiment 2, wherein the thickness of the crushing blade is 30 mm or less. [Embodiment 4] A crushing method according to embodiment 2, wherein the thickness of the crushing blade is 25 mm or less. [Embodiment 5] A crushing method according to embodiment 2, wherein the thickness of the crushing blade is 20 mm or less. [Embodiment 6] A crushing method according to any one of embodiments 1 to 5, wherein the biaxial shear crusher has a hopper for feeding the CFRP waste material into the crushing chamber. [Embodiment 7] A crushing method according to any one of embodiments 1 to 6, wherein the crushing chamber is a closed space or a part of a closed space during the crushing. [Embodiment 8] A crushing method according to any one of embodiments 1 to 7, wherein dust generated in the crushing chamber during the crushing is removed by a dust collector. [Embodiment 9] A method for producing crushed CFRP material, comprising crushing CFRP waste material containing carbon fibers with a filament length of 100 mm or more using a crushing method according to any one of embodiments 1 to 8. [Embodiment 10] A method for producing recycled carbon fibers, comprising producing crushed CFRP material using the manufacturing method of embodiment 9, and recovering carbon fibers from the crushed CFRP material. [Embodiment 11] A method for producing a carbon fiber bundle aggregate, comprising producing recycled carbon fibers using the method according to embodiment 10, mixing the recycled carbon fibers with a binder-containing liquid, and then drying the mixed fibers. [Embodiment 12] Use of a biaxial shear crusher in a method for crushing CFRP waste, wherein the biaxial shear crusher has a crushing chamber, and the crushing method involves crushing the CFRP waste while circulating it within the crushing chamber. [Embodiment 13] The use according to embodiment 12, wherein the thickness of the crushing blade of the biaxial shear crusher is 15 mm or more. [Embodiment 14] The use according to embodiment 13, wherein the thickness of the crushing blade is 30 mm or less. [Embodiment 15] The use according to embodiment 13, wherein the thickness of the crushing blade is 25 mm or less. [Embodiment 16] The use according to embodiment 13, wherein the thickness of the crushing blade is 20 mm or less. [Embodiment 17] The use according to any one of embodiments 12 to 16, wherein the biaxial shear crusher has a hopper for feeding the CFRP waste material into the crushing chamber. [Embodiment 18] The use according to any one of embodiments 12 to 17, wherein the crushing chamber can be a closed space or a part of a closed space. [Embodiment 19] The use according to any one of embodiments 12 to 18, wherein the CFRP waste material contains carbon fibers with a filament length of 100 mm or more.

[0054] [Embodiment 20] A method for producing CFRP crushed material, which includes crushing CFRP waste material containing carbon fibers with a filament length of 100 mm or more while circulating it in the crushing chamber of a biaxial shear crusher. [Embodiment 21] A manufacturing method according to embodiment 20, wherein the thickness of the crushing blades of the biaxial shear crusher is 15 mm or more. [Embodiment 22] A manufacturing method according to embodiment 21, wherein the thickness of the crushing blade is 30 mm or less. [Embodiment 23] A manufacturing method according to embodiment 21, wherein the thickness of the crushing blade is 25 mm or less. [Embodiment 24] A manufacturing method according to embodiment 21, wherein the thickness of the crushing blade is 20 mm or less. [Embodiment 25] A manufacturing method according to any one of embodiments 20 to 24, wherein the biaxial shear crusher has a hopper for feeding the CFRP waste material into the crushing chamber. [Embodiment 26] A manufacturing method according to any one of embodiments 20 to 25, wherein the crushing chamber is a closed space or a part of a closed space during the crushing. [Embodiment 27] A manufacturing method according to any one of embodiments 20 to 26, wherein dust generated in the crushing chamber during the crushing is removed by a dust collector. [Embodiment 28] A manufacturing method according to any of embodiments 20 to 27, further comprising dividing the crushed fragments obtained by the crushing into at least three classes based on their size, and then removing those that fall within at least the two end classes. [Embodiment 29] A method for producing recycled carbon fibers, comprising producing crushed CFRP material using the production method according to any one of embodiments 20 to 28, and recovering carbon fibers from the crushed CFRP material. [Embodiment 30] A method for producing a carbon fiber bundle aggregate, comprising producing recycled carbon fiber using the method of embodiment 29, mixing the recycled carbon fiber with a binder-containing liquid, and then drying the recycled carbon fiber. [Embodiment 31] A production system for crushed CFRP materials, comprising: a biaxial shear crusher capable of crushing CFRP waste materials while circulating them within a crushing chamber; and at least two types of sieves for separating the crushed pieces obtained by crushing the CFRP waste materials with the biaxial shear crusher into at least three classes based on their size. [Embodiment 32] A production system according to embodiment 31, in which the thickness of the crushing blades of the biaxial shear crusher is 15 mm or more. [Embodiment 33] A production system according to embodiment 32, wherein the thickness of the crushing blade is 30 mm or less. [Embodiment 34] A production system according to embodiment 32, wherein the thickness of the crushing blade is 25 mm or less. [Embodiment 35] A production system according to embodiment 32, wherein the thickness of the crushing blade is 20 mm or less. [Embodiment 36] A production system according to any one of embodiments 31 to 35, wherein the biaxial shear crusher has a hopper for feeding the CFRP waste material into the crushing chamber. [Embodiment 37] A production system according to any one of embodiments 31 to 36, wherein the crushing chamber can be a closed space or a part of a closed space. [Embodiment 38] The production system according to any one of embodiments 31 to 37, further comprising a dust collector for removing dust generated in the crushing chamber during operation of the biaxial shear crusher. [Embodiment 39] A production system according to any one of embodiments 31 to 38, used to produce CFRP crushed material by crushing CFRP waste material containing carbon fibers with a filament length of 100 mm or more.

[0055] 6. Experimental Results The results of the experiments conducted by the present inventors are described below. To prepare the simulated CFRP waste material for the experiment (hereinafter simply referred to as "simulated waste material"), a thermosetting carbon fiber UD prepreg, Pyrofil (registered trademark) TR350C100S (carbon fiber weight 100 g / m) manufactured by Mitsubishi Chemical Corporation, was used. 2 , resin content 25wt%, prepreg weight 133g / m 2 , thickness 0.083 mm) was used.

[0056] First, 40 sheets of UD prepreg cut to 100 cm x 30 cm were stacked together so that the longitudinal direction coincided with the fiber direction to form a laminate. Next, as shown in Figure 5, this laminate was folded into thirds so that the folds were perpendicular to the fiber direction. This folded 40-ply prepreg laminate was cured at 90°C for 3 hours to produce simulated waste material.

[0057] The three simulated waste materials were crushed using a biaxial shear crusher. The crusher used was a Helios Co., Ltd. variable particle size crusher 60ET, equipped with crushing blades 25 mm thick and 300 mm in diameter, and the bottom of the crushing chamber was openable. The rotation speed of the high-speed shaft was set to 11 rpm, and the rotation speed of the low-speed shaft was set to 9 rpm, and three simulated waste materials were placed one by one into the crushing chamber and crushed.

[0058] When the simulated waste material was placed in the crushing chamber with the bottom closed, the circulatory crushing time was set to three values: 60 seconds, 90 seconds, and 150 seconds. Here, the circulatory crushing time refers to the time from when the third simulated waste material was placed in the crushing chamber to when the bottom of the crushing chamber was opened. In all cases, the simulated waste material circulated within the crushing chamber and was repeatedly subjected to shear crushing until the bottom of the crushing chamber was opened.

[0059] The CFRP crushed materials obtained when the circulation crushing time was 0 seconds, i.e., when the simulated waste material was put into the crushing chamber with the bottom of the crushing chamber open and crushed, and when the simulated waste material was crushed using the three circulation crushing times mentioned above, were classified into the following four groups of crushed fragments using three types of punched metal sieves with round hole diameters of 10 mm, 20 mm, and 30 mm, respectively. First fragment group: A group consisting of fragments that pass through the first sieve. Second fragment group: A group consisting of fragments that do not pass through the first sieve but pass through the second sieve. Third fragment group: A group consisting of fragments that do not pass through the second sieve but pass through the third sieve. Fourth fragment group: A group consisting of fragments that do not pass through the third sieve. However, the first sieve is a punched metal with round holes having a diameter of 10 mm, the second sieve is a punched metal with round holes having a diameter of 20 mm, and the third sieve is a punched metal with round holes having a diameter of 30 mm.

[0060] The weight composition ratio of the crushed material changed as shown in Table 1 depending on the circulation crushing time.

[0061] [Table 1]

[0062] The CFRP fragments contained in the second group of fragments were selected from the crushed material obtained after a 90-second circulating crushing time. These fragments were then dry-distilled at 700°C for 0.5 hours, and then held at 600°C for 1 hour in an atmosphere containing 21% oxygen, thereby thermally decomposing and removing the resin matrix, and cotton-like recycled carbon fibers were obtained.

[0063] 400 g of this recycled carbon fiber was mixed with 320 g of an aqueous dispersion of a sizing agent for carbon fiber using a stirring granulator to produce a wet carbon fiber aggregate. This wet carbon fiber aggregate was dried at 120°C for 2 hours to obtain a carbon fiber aggregate. Most of the obtained carbon fiber aggregates were 35 mm or less in length and had a needle-like or wire-like shape. [Industrial Applicability]

[0064] Recycled carbon fibers recovered from CFRP waste can be used as a reinforcing material for fiber-reinforced resins.

Claims

1. A method for crushing CFRP waste materials, comprising crushing the CFRP waste materials while circulating them in a crushing chamber of a biaxial shear crusher.

2. The crushing method according to claim 1, wherein the thickness of the crushing blades of the biaxial shear crusher is 15 mm or more.

3. 3. The crushing method according to claim 2, wherein the thickness of the crushing blade is 30 mm or less.

4. 3. The crushing method according to claim 2, wherein the thickness of the crushing blade is 25 mm or less.

5. 3. The crushing method according to claim 2, wherein the thickness of the crushing blade is 20 mm or less.

6. The crushing method according to any one of claims 1 to 5, wherein the biaxial shear crusher has a hopper for feeding the CFRP waste material into the crushing chamber.

7. The method according to any one of claims 1 to 6, wherein the crushing chamber is a closed space or a part of a closed space during the crushing.

8. The crushing method according to any one of claims 1 to 7, wherein dust generated in the crushing chamber during the crushing is removed by a dust collector.

9. A method for producing crushed CFRP material, comprising crushing CFRP waste material containing carbon fibers with a filament length of 100 mm or more using the crushing method according to any one of claims 1 to 8.

10. A method for producing recycled carbon fibers, comprising: producing crushed CFRP material by the method according to claim 9; and recovering carbon fibers from the crushed CFRP material.

11. A method for producing a carbon fiber bundle aggregate, comprising: producing recycled carbon fibers by the method according to claim 10; mixing the recycled carbon fibers with a binder-containing liquid; and then drying the mixed carbon fibers.

12. A use of a biaxial shear crusher in a method for crushing CFRP waste materials, the biaxial shear crusher having a crushing chamber, and the crushing method crushing the CFRP waste materials while circulating them in the crushing chamber.

13. The use according to claim 12, wherein the thickness of the crushing blades of the twin-shaft shear crusher is 15 mm or more.

14. 14. The use according to claim 13, wherein the thickness of the crushing blade is 30 mm or less.

15. 14. The use according to claim 13, wherein the thickness of the crushing blade is 25 mm or less.

16. 14. The use according to claim 13, wherein the thickness of the crushing blade is 20 mm or less.

17. The use according to any one of claims 12 to 16, wherein the biaxial shear crusher has a hopper for feeding the CFRP waste material into the crushing chamber.

18. Use according to any of claims 12 to 17, wherein the crushing chamber can be a closed space or part of a closed space.

19. The use according to any one of claims 12 to 18, wherein the CFRP waste material contains carbon fibers with a filament length of 100 mm or more.

20. A method for producing crushed CFRP material, comprising crushing CFRP waste material containing carbon fibers with a filament length of 100 mm or more while circulating the material in a crushing chamber of a biaxial shear crusher.

21. The manufacturing method according to claim 20, wherein the thickness of the crushing blades of the biaxial shear crusher is 15 mm or more.

22. 22. The manufacturing method according to claim 21, wherein the thickness of the crushing blade is 30 mm or less.

23. 22. The manufacturing method according to claim 21, wherein the thickness of the crushing blade is 25 mm or less.

24. 22. The manufacturing method according to claim 21, wherein the thickness of the crushing blade is 20 mm or less.

25. The manufacturing method according to any one of claims 20 to 24, wherein the biaxial shear crusher has a hopper for feeding the CFRP waste material into the crushing chamber.

26. The method according to any one of claims 20 to 25, wherein the crushing chamber is a closed space or part of a closed space during the crushing.

27. The manufacturing method according to any one of claims 20 to 26, wherein dust generated in the crushing chamber during the crushing is removed by a dust collector.

28. The manufacturing method according to any one of claims 20 to 27, further comprising separating the crushed pieces obtained by the crushing into at least three classes based on their size, and removing pieces included in at least the classes at both ends.

29. A method for producing recycled carbon fibers, comprising: producing CFRP crushed material using the production method according to any one of claims 20 to 28; and recovering carbon fibers from the CFRP crushed material.

30. 30. A method for producing a carbon fiber bundle aggregate, comprising: producing recycled carbon fibers by the method according to claim 29; mixing the recycled carbon fibers with a binder-containing liquid; and then drying the mixed carbon fibers.

31. A production system for crushed CFRP materials, comprising: a biaxial shear crusher capable of crushing CFRP waste materials while circulating them in a crushing chamber; and at least two types of sieves for separating the crushed pieces obtained by crushing the CFRP waste materials with the biaxial shear crusher into at least three classes based on their size.

32. The production system according to claim 31, wherein the thickness of the crushing blades of the biaxial shear crusher is 15 mm or more.

33. 33. The production system according to claim 32, wherein the thickness of the crushing blade is 30 mm or less.

34. 33. The production system according to claim 32, wherein the thickness of the crushing blade is 25 mm or less.

35. 33. The production system according to claim 32, wherein the thickness of the crushing blade is 20 mm or less.

36. The production system according to any one of claims 31 to 35, wherein the biaxial shear crusher has a hopper for feeding the CFRP waste material into the crushing chamber.

37. A production system according to any one of claims 31 to 36, wherein the crushing chamber can be a closed space or a part of a closed space.

38. The production system according to any one of claims 31 to 37, further comprising a dust collector for removing dust generated in the crushing chamber during operation of the biaxial shear crusher.

39. A production system according to any one of claims 31 to 38, used to produce CFRP crushed material by crushing CFRP waste material containing carbon fibers with a filament length of 100 mm or more.

Images