Method for recycling fiber-reinforced composite material and method for producing fiber-reinforced composite material

Abstract

This method for recycling a fiber-reinforced composite material containing a resin and reinforcing fibers comprises: a step for obtaining a treatment liquid (18) by mixing a resin-dissolving solvent (15) with a recycled raw material (14) made of a fiber-reinforced composite material and containing, as reinforcing fibers, fibers having a fiber length of at least 50 μm; and a fiber separation step for passing the treatment liquid (18) through a filter (12b) having an opening size of 10-500 μm to thereby selectively separate, from the reinforcing fibers, long fibers (18a) having a length equal to or greater than the opening size of the filter (12b).

Description

Method for recycling fiber-reinforced composite material and method for producing fiber-reinforced composite material

[0001] The present disclosure relates to a method for recycling a fiber-reinforced composite material and a method for producing a fiber-reinforced composite material.

[0002] Patent Document 1 discloses a method for recycling waste fiber-reinforced composite materials that have increased strength by mixing fibers into resin. First, a dissolving step is performed, in which the waste fiber-reinforced composite material is subjected to dissolving treatment using a solvent having high solubility for the resin. Next, a fiber-resin separation step is performed, in which the resin containing the solvent is separated from the fibers. Subsequently, a resin-solvent separation step is performed, in which the resin containing the solvent is separated into the solvent and the resin. Finally, a fiber / resin recycling and recovery step is performed, in which the fibers and the resin separated in the fiber-resin separation step are separately recovered.

[0003] Japanese Unexamined Patent Application Publication No. 2019-104861

[0004] Incidentally, fibers taken out by recycling methods are sometimes reused as raw materials for fiber-reinforced composite materials and the like. However, fibers taken out by conventional recycling methods have a broad distribution of fiber lengths, resulting in large variations in fiber length. Therefore, when fibers taken out by a recycling method are reused by being blended again into resin or the like, it is necessary to perform treatments such as sieving on the taken-out fibers. That is, when the taken-out fibers are reused, their usability is inferior.

[0005] A method for recycling a fiber-reinforced composite material according to a first aspect of the present disclosure is a method for recycling a fiber-reinforced composite material containing a resin and reinforcing fibers, comprising the steps of: obtaining a treatment liquid by mixing a recycled raw material made of the fiber-reinforced composite material, which contains, as the reinforcing fibers, at least fibers having a fiber length of 50 µm or more, with a solvent that dissolves the resin; and a fiber separation step of passing the treatment liquid through a filter having an opening of 10 µm or more and 500 µm or less, thereby selectively separating long fibers having a length equal to or larger than the opening of the filter among the reinforcing fibers.

[0006] A method for recycling fiber-reinforced composite materials according to a second aspect of the present disclosure is a method for recycling fiber-reinforced composite materials including a resin and reinforcing fibers, comprising: a step of obtaining a processing liquid by mixing a recycling raw material consisting of the fiber-reinforced composite material and the reinforcing fibers having a fiber length of at least 50 μm with a solvent for dissolving the resin; a fiber separation step of selectively separating long fibers from the reinforcing fibers that are greater than or equal to the mesh opening of the filter by passing the processing liquid through a filter with a mesh opening of 10 μm to 500 μm; and a resin separation step of recovering the liquid component including the resin by separating the solid component and liquid component contained in the processing liquid that has passed through the filter.

[0007] A method for manufacturing a fiber-reinforced composite material according to a first aspect of this disclosure comprises manufacturing a recycled fiber-reinforced composite material using the reinforcing fibers obtained from the recycled raw material by the fiber-reinforced composite material recycling method according to the first aspect.

[0008] A method for manufacturing a fiber-reinforced composite material according to a second aspect of the present disclosure comprises manufacturing a recycled fiber-reinforced composite material using the reinforcing fibers and resin obtained from the recycled raw materials by the fiber-reinforced composite material recycling method according to the second aspect.

[0009] Figure 1 shows a schematic diagram of a recycling apparatus for implementing the fiber-reinforced composite material recycling method of the first embodiment. Figure 2 shows a schematic diagram of the first filtration section in the second state of the recycling apparatus for implementing the fiber-reinforced composite material recycling method of the first embodiment.

[0010] Hereinafter, with reference to Figures 1 and 2, an embodiment of the recycling method for fiber-reinforced composite materials according to this disclosure (hereinafter referred to as the "recycling method") will be described. As shown in Figure 1, the recycling method of this embodiment is carried out using a recycling device 10 comprising a mixing tank 11, a first filtration section 12, and a second filtration section 13.

[0011] (Mixing Tank 11) The mixing tank 11 is filled with recycled material 14 and a solvent 15 that dissolves the resin in the recycled material 14. The recycled material 14 is introduced via a recycled material input pipe 16. The solvent 15 is introduced via a solvent input pipe 17. The mixing tank 11 is equipped with a stirring blade 11a for mixing the recycled material 14 and the solvent 15. After the recycled material 14 and the solvent 15 are mixed, the first processed liquid 18 obtained by dissolving the resin in the recycled material 14 in the solvent 15 is transported to the first filtration section 12 via a pipe 19. The pipe 19 is provided with a stopcock (not shown) near the connection point with the mixing tank 11.

[0012] (First Filtration Section 12) The first filtration section 12 comprises a cylindrical frame 12a and a filter 12b attached to a slit portion cut out in the axial direction on the outer surface of the frame 12a. The frame 12a is housed inside the pipe 19 such that its axis is perpendicular to the linear filtration flow direction X of the pipe 19, and is also installed so as to be able to rotate about the axis. In the first filtration section 12, the inner surface of the pipe 19 is molded so as to be able to contact and slide with the outer surface of the frame 12a. A branch pipe 20 is attached that branches off in a direction substantially perpendicular to the filtration flow direction X of the pipe 19.

[0013] As shown in Figure 1, when the frame 12a is in the first state, the first filtration section 12 has a main passage formed by the filtration fluid flow direction X, in which the fluid flows linearly from the upstream side of the piping 19 to the second filtration section 13.

[0014] As shown in Figure 2, when the frame 12a is in the second state, the first filtration section 12 forms a branch passage in the branch fluid flow direction Y, where the fluid flows from the upstream side of the piping 19 from the main passage to the branch pipe 20.

[0015] The lower limit of the mesh opening of filter 12b is 10 μm or more, preferably 50 μm or more. When the lower limit of the mesh opening is 10 μm or more, relatively long reinforcing fibers can be selected and captured from among the reinforcing fibers contained in the recycled material 14. The upper limit of the mesh opening of filter 12b is 500 μm or less, preferably 300 μm or less. When the upper limit of the mesh opening is 500 μm or less, longer reinforcing fibers can be selected and recovered from among the reinforcing fibers contained in the recycled material 14. Also, when the upper limit of the mesh opening is 500 μm or less, reinforcing fibers in the range of high reusability can be efficiently recovered from among the reinforcing fibers contained in the recycled material 14. The mesh opening of the filter indicates the dimension of the gap in the mesh, and can be determined by (25.4 mm / mesh) - wire diameter (mm), which is the number of wires per inch (25.4 mm) and the wire diameter. The material of filter 12b is not particularly limited, but metal, glass, etc. are preferably used from the viewpoint of strength, chemical resistance, etc.

[0016] When the frame 12a is in the first state, the first processing liquid 18 passes through the filter 12b located on the main passage, and then long reinforcing fibers 18a with a fiber length greater than or equal to the mesh opening of the filter 12b are captured on the surface of the filter 12b. As a result, the second processing liquid 21, which contains short reinforcing fibers that were not filtered by the filter 12b and the solvent 15, is passed through from the back surface of the filter 12b.

[0017] The frame 12a has a first liquid passage hole 12c formed on its circumferential surface opposite to the filter 12b. The second treatment liquid 21 flows out of the frame 12a through the first liquid passage hole 12c and then flows toward the second filtration section 13 located downstream of the piping 19. In the first state, since the frame 12a does not have a liquid passage hole on the branch pipe 20 side, the second treatment liquid 21 does not flow into the branch pipe 20.

[0018] The flow path formed in the first filtration section 12 is formed by a frame 12a and comprises a main passage in which a filter 12b is arranged, and a branch passage provided branching off from the main passage. The flow path formed in the first filtration section 12 further includes a switching mechanism that switches between a first state in which the second processed liquid 21 supplied by passing through the filter 12b does not flow into the branch passage, and a second state in which fluid flows into the branch passage.

[0019] (Switching Mechanism) As shown in Figures 1 and 2, the frame 12a is rotated 90 degrees clockwise around its axis in the direction of arrow A1 by the switching mechanism, thereby switching from a first state in which the processed liquid is directed toward the second filtration section 13 to a second state in which it is directed toward the branch pipe 20.

[0020] In the second state, the frame 12a has a second fluid passage hole 12d formed on its circumferential surface that contacts the upstream interior of the pipe 19. The fluid flowing into the frame 12a from the second fluid passage hole 12d on the upstream side of the pipe 19 is configured to pass through the filter 12b and then the branch pipe 20 in sequence. In the second state, the frame 12a is in a position where there are no fluid passage holes in the direction of the second filtration section 13, so no fluid passes in the direction of the second filtration section 13. In the first state, the fluid passed from the front side to the back side of the filter 12b, but in the second state, the fluid passes in the opposite direction, from the back side to the front side of the filter 12b.

[0021] (Second Filtration Section 13) A second filtration section 13 is provided in the piping 19 downstream of the first filtration section 12. In the second filtration section 13, a packing material 13a having a predetermined particle size is held in a column 13b which serves as a packing section.

[0022] As the second processing liquid 21 passes through the second filtration section 13, short fibers 21a, which are reinforcing fibers with short fiber lengths, are captured by a filtration action that separates the solid and liquid components of the filler 13a. The lower limit of the average particle diameter of the filler 13a is set as appropriate, but is preferably 0.25 μm or more, more preferably 0.50 μm or more. When the lower limit of the average particle diameter is 0.25 μm or more, short reinforcing fibers with short fiber lengths that were not filtered in the first filtration section 12 can be efficiently recovered while ensuring liquid permeability. The upper limit of the average particle diameter of the filler 13a is set as appropriate, but is preferably 100 μm or less, more preferably 80 μm or less. When the upper limit of the average particle diameter is 100 μm or less, short reinforcing fibers with short fiber lengths can be efficiently recovered. The average particle diameter of the filler 13a is the value (D50) measured by the laser diffraction / scattering method.

[0023] Specific examples of the filler 13a include silica, Celite, activated carbon, etc. These are selected as appropriate depending on the purpose and application. Furthermore, one type may be used alone, or two or more types may be used in combination. Additives such as colorants derived from recycled raw materials 14 dispersed in the second processing liquid 21 are captured by the adsorption action of the filler 13a. After the second processing liquid 21 passes through the second filtration section 13, a third processing liquid 22 containing solvent 15 and resin components derived from recycled raw materials 14 is generated. The third processing liquid 22 is recovered in a recovery device (not shown) located downstream of the piping 19.

[0024] (Recycling Method) The recycling method using the above-described recycling apparatus 10 first involves preparing a first processing liquid 18 by mixing the recycled raw material 14 with a solvent 15 for dissolving the resin. Next, a fiber separation step is performed to separate the long fibers 18a by passing the first processing liquid 18 through a filter 12b. Furthermore, a resin separation step is performed to recover a third processing liquid 22 containing resin derived from the recycled raw material 14 by separating the solid components and liquid components contained in the second processing liquid 21 that has passed through the filter 12b.

[0025] (Process for preparing the processing solution) The process for preparing the first processing solution 18 is carried out in the mixing tank 11. After mixing the recycled material 14 and the solvent 15, the mixture is stirred for a predetermined time with the stirring blade 11a. As a result, the resin in the recycled material 14 is dissolved in the solvent 15 and the reinforcing fibers are suspended in the first processing solution 18. The mixing ratio of the recycled material 14 and the solvent 15, the mixing temperature, and the mixing time can be appropriately set according to the type of recycled material 14 and the solvent 15, the physical properties of the obtained first processing solution 18, etc. For example, the mixing ratio of the recycled material 14 and the solvent 15 is set to 10 to 30 parts by mass of solvent for every 1 part by mass of resin in the recycled material 14.

[0026] The recycled material 14 consists of a fiber-reinforced composite material and includes reinforcing fibers, at least 50 μm in length. Such recycled material improves the reusability of recovered fibers. The upper limit of the fiber length of the reinforcing fibers in the recycled material 14 is not particularly limited, but 5000 μm or less is preferred. Such recycled material improves the reusability of recovered fibers. In particular, the recovered reinforcing fibers can be reused in many molded products, such as automobile parts.

[0027] The fiber length distribution of reinforcing fibers varies depending on the type of original product and molding method of the recycled material 14. In this embodiment, the recycled material 14 contains at least fibers with a relatively long fiber length of 50 μm or more, and may also contain reinforcing fibers with a fiber length of less than 50 μm. The recycling method of this disclosure further uses a filter 12b having a predetermined mesh opening to remove reinforcing fibers with a fiber length less than the predetermined mesh opening and selectively separate reinforcing fibers with a fiber length equal to or greater than the mesh opening.

[0028] The reinforcing fibers included in the fiber-reinforced composite material are not particularly limited, but include inorganic fibers and solvent-insoluble organic fibers, and more specifically, glass fibers, carbon fibers, cellulose fibers, wood fibers, etc. The fiber diameter of the reinforcing fibers is not particularly limited, but for example, it is between 5 μm and 20 μm.

[0029] Specific examples of resins constituting the fiber-reinforced composite material include, for example, polyethylene resin, polyolefin resins such as polypropylene resin, polyamide resin, polyurethane resin, polycarbonate resin, polyester resin, polyimide resin, polyether ester resin, and polyacrylic resin. In order to improve the solubility of the recycled material 14 in the solvent 15, it is preferable that the recycled material 14 be subjected to processing such as crushing, shredding, or cutting to a predetermined size within a range that does not significantly affect the length of the reinforcing fibers contained therein.

[0030] The type of solvent 15 is appropriately determined depending on the type of resin constituting the recycled raw material 14. Examples of solvents 15 include cyclic ether organic solvents, aromatic alcohols, aromatic hydrocarbons, aromatic halogenated hydrocarbons, aromatic halogenated organic solvents, aromatic organic solvents, aliphatic halogenated hydrocarbons, ketone organic solvents, acid or alkali solvents, etc. More specifically, the following combinations of resin and solvent are exemplified.

[0031] When the resin is polycarbonate resin, applicable solvents include, for example, cyclic ether organic solvents such as 1,3-dioxolane and tetrahydrofuran, and mixtures thereof. When the resin is polyamide resin, applicable solvents include, for example, aromatic alcohols including benzyl alcohol and 2-phenoxyethanol, acid solutions containing hydrochloric acid and sulfuric acid in cyclic ether organic solvents such as 1,4-dioxane and tetrahydrofuran, alkaline aqueous solutions containing sodium hydroxide, and mixtures thereof.

[0032] When the resin is a polyolefin resin such as polyethylene resin or polypropylene resin, applicable solvents include, for example, aromatic hydrocarbons such as benzene, toluene, and xylene, aromatic halogenated hydrocarbons such as orthodichlorobenzene, and mixtures thereof.

[0033] When the resin is a polyester resin, applicable solvents include, for example, aromatic halogenated organic solvents such as orthochlorophenol, aromatic organic solvents such as phenol and cresol, and mixtures thereof.

[0034] When the resin is acrylic resin, applicable solvents include, for example, aliphatic halogenated hydrocarbons such as chloroform and methylene chloride, ketone-based organic solvents such as acetone and methyl ethyl ketone, and mixtures thereof.

[0035] The original uses of the recycled raw materials 14 are not particularly limited, but examples include transportation equipment such as automobile parts, machine parts, building materials, daily necessities, and ELV materials, PCR materials, PIR materials obtained from them.

[0036] Among these, at least one selected from ELV material, PCR material, and PIR material, which have polypropylene as the main component, is preferred from the viewpoint of excellent environmental properties due to recycling. Furthermore, in the case of such recycled raw materials, a solvent whose main component is xylene is preferred from the viewpoint of excellent resin solubility. The main component refers to xylene accounting for 50% by mass or more of the total solvent.

[0037] The first processing liquid 18 obtained as described above is sent to the first filtration section 12 through the piping 19 by opening a stopcock (not shown). (Fiber separation process) The fiber separation process is carried out in the first filtration section 12. When the frame 12a is in the first state, the first processing liquid 18 is passed through a filter 12b with a mesh size of 10 μm to 500 μm, which is placed on the main passage. By passing the first processing liquid 18 through the filter 12b, long fibers 18a of the reinforcing fibers that are longer than the mesh size of the filter 12b are selectively separated on the surface of the filter 12b. At that time, the second processing liquid 21 containing short fibers, which are reinforcing fibers with a shorter fiber length that were not filtered by the filter 12b, and the solvent 15 flows out from the back surface of the filter 12b. Note that because the reinforcing fibers are needle-thin, some of the long fibers longer than the mesh size may pass through the filter 12b without being captured. Therefore, the recovered reinforcing fibers tend to have a relatively larger fiber length than the mesh opening of the filter 12b. For example, if the mesh opening of the filter 12b is 300 μm, most of the reinforcing fibers with a fiber length of 600 μm or less will pass through the filter 12b, while reinforcing fibers with a fiber length of 800 μm or more tend to be captured by the filter 12b. Taking this into consideration, the mesh opening of the filter 12b is set so that a large amount of reinforcing fibers with the desired fiber length are captured.

[0038] As shown in Figure 1, the second processing liquid 21 flows out of the frame 12a through the first liquid passage hole 12c and then flows toward the second filtration section 13 located downstream of the piping 19 along the filtration liquid passage direction X.

[0039] As shown in Figures 1 and 2, the long fibers 18a recovered on the surface of the filter 12b move into the branch pipe 20 that constitutes the branching path after the frame 12a is switched to the second state by the switching mechanism of the first filtration section 12. The switching by the switching mechanism is performed by rotating the frame 12a, which is in the first state, by 90 degrees in the direction of arrow A1, that is, clockwise. This switches the fluid from the first state, in which it flows along the filtration fluid flow direction X toward the second filtration section 13, to the second state, in which it flows along the branching fluid flow direction Y toward the branch pipe 20.

[0040] In the first state of the frame 12a, the fluid was flowing from the front side to the back side of the filter 12b. In the second state of the frame 12a, the fluid is flowing in the opposite direction, from the back side to the front side of the filter 12b. As a result, the long fibers 18a remaining on the surface of the filter 12b are moved into the branch pipe 20 by the switching mechanism, and then moved by the fluid to a fiber recovery mechanism (not shown) further downstream, where they are recovered. After the long fibers 18a are recovered, the frame 12a is switched from the second state to the first state by the switching mechanism.

[0041] As shown in Figure 2, the frame 12a is rotated 90 degrees in the direction of arrow A2, i.e., counterclockwise, by the switching mechanism, thereby switching from a second state in which the fluid flows toward the branch pipe 20 to a first state in which it flows toward the second filtration section 13. As a result, the long fibers 18a are captured again by the filter 12b in the same manner. The switching mechanism ensures that the capture of the long fibers 18a by the filter 12b and the recovery of the long fibers 18a by the branch pipe 20 are performed continuously. The recovered long fibers 18a are dried as needed and then reused for various purposes.

[0042] (Resin Separation Process) The resin separation process is performed in the second filtration section 13. The resin separation process is a process of separating the solid components and liquid components contained in the second processing liquid 21 that has passed through the filter 12b. As a result, short fibers 21a with short fiber lengths that were not captured by the filter 12b are separated, and a third processing liquid 22 containing resin derived from recycled raw materials 14 is generated. Since the packing material 13a has a predetermined particle size, when it passes through the liquid, it exhibits a filtering effect that separates the solid components and liquid components of the packing material 13a. As a result, the short fibers 21a, which are the solid components, are captured on the upper surface of the packing material 13a in the column 13b.

[0043] Furthermore, additives such as colorants derived from the recycled raw materials 14 that are dispersed in the second processing liquid 21 are captured by the adsorption action of the filler 13a. After the second processing liquid 21 passes through the second filtration section 13, a third processing liquid 22 containing a solvent and resin components derived from the recycled raw materials 14 is generated. The third processing liquid 22 is recovered in a recovery device (not shown) located downstream of the piping 19.

[0044] The third treatment liquid 22 containing the recovered solvent and resin component is subjected to separation treatment of the solvent and the resin component by a known method. Examples of the method for separating the resin component include removal of the solvent by heating such as distillation treatment, precipitation treatment using a poor solvent, and the like. The obtained solvent may be reused in the recycling method. The obtained resin component may be reused for various applications after being dried if necessary.

[0045] (Method for producing fiber-reinforced composite material) The long fibers 18a and resin component obtained from the recycled raw material 14 by the above recycling method can be applied to appropriate uses. Since long fibers 18a from which those having short fiber lengths have been removed, a recycled fiber-reinforced composite material may be produced by reapplying the long fibers 18a to a fiber-reinforced composite material. The resin used for the fiber-reinforced composite material is appropriately selected from known resins according to the purpose, application, and the like.

[0046] Furthermore, a recycled fiber-reinforced composite material may be produced by using the long fibers 18a obtained from the recycled raw material 14 and the resin component in combination. It is preferable that the recycled raw material 14 and the recycled fiber-reinforced composite material are applied to the same use. The application is not particularly limited, and examples include transportation equipment such as automobile parts, mechanical parts, construction materials, daily necessities, and the like. Examples of automobile parts include bumpers, glove boxes, and the like.

[0047] The recycling method of the present embodiment will be described in further detail based on the following examples. Note that the recycling method is not limited to the configuration described in the Examples section. (First Example) The recycling method of the first example is implemented using the recycling apparatus 10. In this case, the filter 12b used was a metal filter with an opening of 300 µm. Activated carbon having an average particle diameter of 1 µm was used as the filler 13a. Further, as the recycled raw material 14, a fiber-reinforced composite material molded from a polypropylene resin containing 30% by mass of glass fibers as reinforcing fibers was used. As a result of measurement by an optical microscope, the fiber length distribution of the reinforcing fibers was 200 µm to 2000 µm.

[0048] First, a recycled raw material 14 crushed to a predetermined size and xylene as a solvent 15 were introduced into a mixing tank 11 at a mass ratio of 1:30. A first treatment liquid 18 was obtained by stirring at 120°C for 30 minutes. The first treatment liquid 18 was passed through the filter 12b of the first filtration unit 12 and the filler 13a of the second filtration unit 13 in order. The first filtration unit 12, the second filtration unit 13, and the piping 19 were placed in an environment at a temperature of 120°C.

[0049] As a result of measuring the fiber length distribution of the reinforced fibers collected on the surface of the filter 12b by optical microscopy, the fiber length distribution was 800 µm to 2000 µm. Further, as a result of measuring the fiber length distribution of the reinforced fibers collected on the upper surface of the filler 13a by optical microscopy, the fiber length distribution was 200 µm to 600 µm. It was confirmed that long fibers of a predetermined size can be selectively recovered from the reinforced fibers contained in the recycled raw material.

[0050] (First Comparative Example) In contrast to the recycling method of the first example, a recycling apparatus in which the filter 12b was omitted was used. Other procedures were performed in the same manner as in the first example.

[0051] As a result of measuring the fiber length distribution of the reinforced fibers collected on the upper surface of the filler 13a by optical microscopy, the fiber length distribution was 200 µm to 2000 µm. It was confirmed that almost all of the reinforced fibers in the recycled raw material were collected on the upper surface of the filler 13a.

[0052] (Second Comparative Example) In contrast to the recycling method of the first example, a recycling apparatus in which filter paper (No. 2, manufactured by Advantec Toyo Kaisha, Ltd.) with an opening of 7 µm was disposed instead of the filter 12b was used. Other configurations and procedures are the same as those of the first example.

[0053] As a result of measuring the fiber length distribution of the reinforced fibers collected on the upper surface of the filter paper by optical microscopy, the fiber length distribution was 200 µm to 2000 µm. No reinforced fibers were collected on the upper surface of the filler 13a. It was confirmed that almost all of the reinforced fibers in the recycled raw material were collected on the upper surface of the filter paper.

[0054] It has been confirmed that the recycling method described herein selectively yields highly reusable long fibers. (Effects of this embodiment) The effects of the recycling method or the method for manufacturing fiber-reinforced composite materials of this embodiment will be described below.

[0055] (1) As a recycling method, first a step is carried out to obtain a first processing liquid 18 by mixing a recycled raw material 14 containing fibers with a fiber length of at least 50 μm as reinforcing fibers with a solvent 15 for dissolving resin. Next, a fiber separation step is carried out to selectively separate long fibers 18a from the reinforcing fibers that are longer than the mesh opening of the filter 12b by passing the first processing liquid 18 through a filter 12b with a mesh opening of 10 μm or more and 500 μm or less.

[0056] According to the above configuration, long fibers 18a, whose fiber length is greater than or equal to the mesh opening of the filter 12b, can be selectively separated and recovered from the reinforcing fibers contained in the recycled raw material 14. As a result, reinforcing fibers with relatively uniform fiber lengths can be obtained, thereby improving the utilization characteristics of the recovered reinforcing fibers.

[0057] (2) In the second filtration section 13, a resin separation step is performed to recover the third treatment liquid 22, which is the liquid component containing resin, by separating the solid component consisting mainly of short fibers contained in the second treatment liquid 21 from the liquid component containing solvent and resin.

[0058] According to the above configuration, only the liquid component can be extracted from the second processing solution 21. This makes it possible to remove short reinforcing fibers from the processing solution after it has passed through the filter 12b. The third processing solution 22, which contains resin, can be easily processed.

[0059] (3) The resin separation step in the second filtration section 13 is performed by passing the material through a column 13b containing a packing material 13a having an average particle size of 0.25 μm or more and 100 μm or less. With the above configuration, short reinforcing fibers can be removed from the second processing liquid 21, and only the liquid component can be efficiently and reliably extracted. In addition, the third processing liquid 22 containing the resin can be efficiently recovered while the liquid is passing through.

[0060] (4) The packing material 13a in the second filtration section 13 is at least one selected from silica, Celite, and activated carbon. With the above configuration, additives such as colorants dispersed in the second processing liquid 21 can be removed. This improves the quality of the final resin obtained.

[0061] (5) The fiber separation process is performed by flowing the first processing liquid 18 through a flow path formed by a frame 12a in which the filter 12b is arranged. The flow path comprises a main passage in which the filter 12b is arranged, a branch pipe 20 for recovering long fibers 18a, and a switching mechanism that switches between a first state in which the second processing liquid 21 supplied to the flow path does not flow into the branch pipe 20 and a second state in which it flows into the branch pipe 20.

[0062] With the above configuration, the long fibers 18a separated from the first processing liquid 18 can be easily and efficiently recovered from the flow path onto the filter 12b. Furthermore, the switching mechanism allows for continuous and efficient filtration of the long fibers 18a on the filter 12b and recovery of the long fibers 18a in the branch pipe 20.

[0063] (6) When the recycled material 14 is at least one selected from ELV material, PCR material, and PIR material, which are mainly composed of polypropylene, an aromatic hydrocarbon whose main component is xylene is used as the solvent 15.

[0064] According to the above configuration, the recycling process of the recycled raw material 14 can be carried out at low cost and in a short time. This improves the environmental characteristics of the recycled material. (7) The method for manufacturing the recycled fiber-reinforced composite material is carried out using the long fibers 18a obtained from the recycled raw material 14 by the recycling method of the above embodiment.

[0065] According to the above configuration, the reinforcing fibers used in the original product can be applied. Furthermore, reinforcing fibers with more uniform fiber lengths can be used. Therefore, when the recycled fiber-reinforced composite material is applied to the same product as the recycled raw material 14, it is possible to manufacture a fiber-reinforced composite material that is close to or better than the performance of the original product.

[0066] (8) The method for manufacturing the recycled fiber-reinforced composite material is carried out using long fibers 18a obtained from the recycled raw material 14 and resin. According to the above configuration, the reinforcing fibers and resin used in the original product are combined and applied. Therefore, since the compatibility between the reinforcing fibers and the matrix resin is good, it is possible to manufacture a fiber-reinforced composite material that is closer to the performance of the original product. In addition, since the recycling rate can be improved, the environmental characteristics can be further improved.

[0067] (9) The recycled raw material 14 and the recycled fiber-reinforced composite material are automobile parts. According to the above configuration, it is possible to obtain automobile parts made of recycled fiber-reinforced composite material that has excellent quality characteristics and whose performance is closer to that of the original product. In addition, the recycling rate of automobile parts can be improved, thereby improving environmental characteristics.

[0068] (Another example of this embodiment) The above embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0069] In the above embodiment, the fiber separation step selectively separates long fibers 18a that are longer than or equal to the mesh opening of the filter 12b. However, it is assumed that some short fibers shorter than the mesh opening of the filter 12b may be captured due to the accumulation of long fibers on the filter 12b. The recovered reinforcing fibers are included in this disclosure if they provide a sharper fiber length distribution than the fiber length distribution of the reinforcing fibers in the recycled raw material.

[0070] In the above embodiment, the preparation of the first treatment liquid 18 obtained by mixing the recycled material 14 and the solvent 15 may be carried out by stirring, ultrasonic treatment, shaking treatment, or the like.

[0071] - In the above embodiment, each processing liquid may be transported by a pump or the like (not shown), or by gravity. - In the above embodiment, in the first filtration section 12 or the second filtration section 13, an outlet for taking out the filtered reinforced fibers to the outside may be formed on the outer surface of the piping 19.

[0072] In the above embodiment, a pressure sensor, a flow sensor, etc., may be provided in the upstream piping 19 in order to determine whether or not the long fibers 18a can be recovered by switching the switching mechanism.

[0073] In the above embodiment, the recovery of long fibers 18a in the branch pipe 20 in the second state of the switching mechanism is preferably carried out by flowing a new solvent in order to maintain the quality of the recovered long fibers 18a. From the viewpoint of operational efficiency, it may also be carried out by flowing the first processing liquid 18 as is in the branch liquid flow direction Y.

[0074] - In the above embodiment, the first filtration unit 12 may employ other known continuous filtration mechanisms, such as a disc-shaped rotating filter. - In the above embodiment, the filter 12b may be provided at the connection point between the mixing tank 11 and the piping 19. With this configuration, the long fibers 18a can be recovered in the mixing tank 11.

[0075] - In the above embodiment, two or more filters with different mesh sizes may be placed in the main passage to obtain fractions of two or more reinforcing fibers with different fiber lengths. - In the above embodiment, if only long fibers 18a are to be recovered, the second filtration section 13 may be omitted.

[0076] In the above embodiment, the second filtration section 13 may be performed by a filter, as long as it can separate the solid components and liquid components contained in the second processing liquid 21.

Claims

1. A method for recycling a fiber-reinforced composite material containing resin and reinforcing fibers, comprising: a step of obtaining a processing liquid by mixing a recycling raw material consisting of the fiber-reinforced composite material and containing reinforcing fibers having a fiber length of at least 50 μm with a solvent for dissolving the resin; and a fiber separation step of selectively separating long fibers from the reinforcing fibers that are longer than the mesh opening of the filter by passing the processing liquid through a filter with a mesh opening of 10 μm to 500 μm.

2. A method for recycling a fiber-reinforced composite material according to claim 1, further comprising a resin separation step of recovering the liquid component containing the resin by separating the solid component and the liquid component contained in the processing liquid that has passed through the filter.

3. The method for recycling a fiber-reinforced composite material according to claim 2, wherein the resin separation step includes passing the processed liquid that has passed through the filter through a filling section that holds a filler having an average particle size of 0.25 μm or more and 100 μm or less.

4. The fiber separation step is performed by flowing the processing liquid through a flow path in which the filter is arranged, and the flow path comprises: a main passage in which the filter is arranged; a branch passage branching off from the main passage for recovering the reinforcing fibers remaining on the filter; and a switching mechanism for switching between a first state in which the fluid supplied to the flow path does not flow into the branch passage and a second state in which the fluid flows into the branch passage, according to any one of claims 1 to 3.

5. The method for recycling fiber-reinforced composite materials according to any one of claims 1 to 4, wherein the recycled raw material is at least one selected from polypropylene-based ELV material, PCR material, and PIR material, and the solvent is mainly xylene.

6. A method for producing a fiber-reinforced composite material, comprising producing a recycled fiber-reinforced composite material using the reinforcing fibers obtained from the recycled raw material by the method for recycling a fiber-reinforced composite material described in any one of claims 1 to 5.

7. A method for producing a fiber-reinforced composite material, comprising producing a recycled fiber-reinforced composite material using the reinforcing fibers and resin obtained from the recycled raw materials by the method for recycling fiber-reinforced composite materials described in claim 2.

8. The method for manufacturing a fiber-reinforced composite material according to claim 6 or 7, wherein the recycled raw material and the recycled fiber-reinforced composite material are automobile parts.

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