WO2013168302A1

WO2013168302A1 - Manufacturing apparatus for regenerated carbon fiber, manufacturing process for regenerated carbon fiber, and regenerated carbon fiber

Info

Publication number: WO2013168302A1
Application number: PCT/JP2012/073762
Authority: WO
Inventors: 秀人板津; 肇神吉
Original assignee: カーボンファイバーリサイクル工業株式会社
Priority date: 2012-05-11
Filing date: 2012-09-10
Publication date: 2013-11-14
Also published as: JP2013237716A; JP5941747B2

Abstract

[Problem] To provide: an apparatus for manufacturing a regenerated carbon fiber having excellent handleability from a carbon fiber reinforced plastic (CFRP) as raw material; a process for manufacturing the regenerated carbon fiber; and a regenerated carbon fiber. [Solution] A carbon fiber manufacturing process (1) includes principally: a packing step (S3) for packing a heating cage (10) with a CFRP (25) in a prescribed bulk density; a heating cage conveying step (S5) for introducing the heating cage (10) into a regeneration treatment section (3) having a regeneration treatment space (2); a heating/removing step (S6) for heating the CFRP (25) in a heating/removing section provided in a heating zone and thereby removing the matrix components with a part thereof left as fixed carbon; and a cooling step (S7) for cooling the resulting regenerated carbon fiber (8) having fixed carbon adhering thereto. In the regenerated carbon fiber (8) manufactured by this manufacturing process with this manufacturing apparatus, the ratio of carbon remaining as fixed carbon is 0.5 to 11.0 wt%, said carbon being resulting from the matrix components of CFRP.

Description

Regenerated carbon fiber production apparatus, regenerated carbon fiber production method, and regenerated carbon fiber

The present invention relates to a regenerated carbon fiber production apparatus, a regenerated carbon fiber production method, and a regenerated carbon fiber. In particular, a carbon fiber reinforced plastic is heated at a high temperature to remove recycle carbon fibers that can be reused as a raw material for paper, nonwoven fabric, etc. by removing the matrix component, The present invention relates to a regenerated carbon fiber produced by these techniques.

Carbon fiber is known as a material having excellent mechanical properties such as high strength and high elastic modulus. Carbon fiber reinforced plastic (Carbon Fiber Reinforced Plastic, hereinafter also referred to as CFRP) is produced using this carbon fiber as a filler component and an epoxy resin or polyester resin as a matrix component. Carbon fiber is widely used in various industrial fields including aviation and space industries.

Carbon fiber reinforced plastic is mainly produced by producing a prepreg in which a matrix component resin is infiltrated into carbon fiber, and firing this prepreg while pressing it in an autoclave. In the manufacturing process of this carbon fiber reinforced plastic, many end materials are generated in addition to the product. In particular, when manufacturing a large-sized product such as an aircraft body, a large amount of the above-mentioned scrap material is generated. For this reason, disposal of the mill ends sometimes becomes a problem. As described above, carbon fiber reinforced plastics are a mixture of filler components and matrix components having different properties, and it is technically difficult to separate them for reuse (recycling) or reuse (reuse). The nature was high. Also, it was not effective in terms of cost and energy efficiency. As a result, at present, most of the scraps generated during production and unused prepregs are often disposed of by landfill or incineration. Furthermore, the carbon fiber reinforced plastic collected after the function as a product was also disposed of by landfill or the like.

By the inventors of the present invention, only the matrix components are removed from the carbon fiber reinforced plastic by thermal decomposition, and the carbon fibers are selectively recovered without deteriorating the mechanical properties. Techniques relating to processing methods (see Patent Document 1 and Patent Document 2) have already been developed. According to this, in the regeneration processing unit, a slender tunnel-shaped regeneration processing space is constructed of a fireproof material. A mesh belt conveyor is disposed in the regeneration processing unit. By continuously supplying carbon fiber reinforced plastic to the regeneration processing space using such a belt conveyor and heating the carbon fiber reinforced plastic in the heating region in the regeneration processing space, matrix components such as thermoplastic epoxy resin Only the gas can be gasified by pyrolysis, and the carbon fiber (regenerated carbon fiber) can be recovered in a long fiber state. As a result, a large amount of carbon fiber reinforced plastic can be efficiently pyrolyzed, and regenerated carbon fiber can be produced.

Patent Document 3 discloses a technique for recovering carbon fiber in a state where 68 to 80% of the plastic is removed by treating the carbon fiber reinforced plastic with superheated steam at 800 ° C. or higher. Patent Document 3 discloses a recovery device that includes a heater section that produces superheated steam, an introduction section that introduces the produced steam, and a holding section that holds carbon fiber reinforced plastic.

JP 2008-285601 A Japanese Patent No. 4949123 JP 2011-122032 A

However, the carbon fiber regeneration treatment apparatus and the regeneration treatment method described in Patent Document 1 and Patent Document 2 have the following problems. That is, the collected carbon fiber reinforced plastic end material has various shapes depending on the use part of the product. For this reason, a difference in shape causes a difference in heat transfer during pyrolysis, which may cause variations in heating conditions. As a result, regenerative carbon fiber is produced from carbon fiber reinforced plastic using a regenerative processing apparatus having a continuous furnace, and due to the difference in thermal characteristics, some of the regenerated processing space burns in an overheated state. Or, heat may not be sufficiently transferred, causing a problem such as a part of the matrix component remaining, and the properties and quality of the obtained regenerated carbon fiber may be biased. In particular, the heat transfer differs depending on the size of the contact area with the regeneration processing space due to the difference in the packing density (bulk density) of the carbon fiber reinforced plastic, and the above-mentioned problems are likely to occur.

In addition, the conventional carbon fiber regeneration treatment method completely removes the matrix component contained in the carbon fiber reinforced plastic by pyrolysis, and produces a regenerated carbon fiber in which the residual rate of the matrix component is 0%. Was aimed at. In the heating region of the regeneration processing space, the carbon fiber reinforced plastic is processed at a heating temperature and / or heating time that is more than necessary, so that the mechanical properties of the recovered recycled carbon fiber may be deteriorated. As a result, the use at the time of reuse and reuse may be limited. In addition, the regenerated carbon fiber from which the matrix component has been completely removed has a fluff-like aspect and has a small density, and thus may be easily scattered even by a slight wind. For this reason, when producing regenerated carbon fiber using a conventional reclaim processing apparatus, it is necessary to handle it carefully so as not to be scattered in the heating region and the cooling region of the regeneration processing space. In addition, even when reused after collection, the handleability (handling property) of the regenerated carbon fiber may be a problem.

On the other hand, in the carbon fiber recovery method disclosed in Patent Document 3, since 20 to 32% of the matrix component remains, the recovered carbon fiber maintains the form of the fiber bundle, but lacks flexibility. there is a possibility. For this reason, when the recovered carbon fibers are reused in a nonwoven fabric or the like, there is a high possibility that further processing is required.

In view of the above circumstances, an object of the present invention is to provide a technique for manufacturing a regenerated carbon fiber efficiently and at a low cost by processing a carbon fiber reinforced plastic under a stable heating condition. That is, an object of the present invention is to provide a regenerated carbon fiber suitable for processing, a production apparatus and a production method for the regenerated carbon fiber.

In order to solve the above-described problems, the carbon fiber manufacturing method of the present invention includes a bulk density filling step, a heating cage conveyance step, a heating removal step, and a cooling step. In the bulk density filling step, carbon fiber reinforced plastic containing carbon fibers and a matrix component is filled into a casing-shaped heating cage having each surface formed of a breathable material so as to have a predetermined bulk density. . In the heating cage transport process, a slender tunnel-shaped reclaim processing space is built inside with a fireproof material, and a carbon fiber reinforced plastic is placed in the reclaim processing section where the introduction port and discharge port communicating with the reclaim processing space are opened. Transport the filled heating cage. In the heat removal step, the carbon fiber reinforced plastic in the heating cage being conveyed is heated by a heat removal unit provided in the heating region of the regeneration processing space to remove the matrix component. In the cooling step, the regenerated carbon fiber from which the matrix component has been removed by heating is cooled while being conveyed by a cooling unit provided in the cooling area on the downstream side of the heating area of the regeneration processing space.

Here, the heating cage is a substantially rectangular parallelepiped housing in which each cage surface is formed of a breathable material such as a net (or hole), and the carbon fiber reinforced plastic to be heated in the filling space inside the cage. Can be filled. Since the heating cage is made of a breathable material, heat during heating can be efficiently transferred to the carbon fiber reinforced plastic, and further, the decomposition gas generated by the thermal decomposition of the matrix components inside the cage is heated. It has the function of quickly discharging out of the cage. The heating cage is configured using a metal material such as stainless steel. Further, a lid made of a breathable material such as a net is provided on the upper part of the housing, and the carbon fiber reinforced plastic can be closed inside the cage after filling is completed. Here, “bulk density” in the present invention is defined as a volume obtained by dividing the internal volume of the carbon fiber reinforced plastic filled in the filling space of the heating cage by the weight of the carbon fiber reinforced plastic. At this time, the internal volume of the carbon fiber reinforced plastic includes the volume of the gap between the carbon fiber reinforced plastics, the volume of the uneven surface of the carbon fiber reinforced plastic, and the volume of the gap between the carbon fiber reinforced plastic and the heating cage. It is. In addition, since it is difficult to accurately determine the inner volume of the carbon fiber reinforced plastic filled in the heating cage, in the present invention, the area of the bottom surface of the heating cage is multiplied by the filling height from the bottom surface of the cage. The internal volume of the carbon fiber reinforced plastic is calculated. That is, bulk density = weight of filled carbon fiber reinforced plastic / (bottom area of cage bottom surface × filling height).

On the other hand, the regeneration processing part is a structure in which a slender tunnel-shaped regeneration processing space is constructed inside using a fireproof material such as brick, and carbon fiber reinforced plastic is used in the heating region of the regeneration processing space. It is possible to produce regenerated carbon fiber by heating. At this time, the conveyance of the heating cage to the regeneration processing space can employ a conveyance unit such as a so-called “roller hearth kiln” in which a plurality of rollers are arranged in parallel, or a mesh conveyance unit that rotationally drives the mesh belt. It is.

The heat removal part is for heating the carbon fiber reinforced plastic conveyed in a state where the heating cage is filled in the regeneration processing space and thermally decomposing the matrix component. It is mainly composed by the body. Here, in the method for producing a regenerated carbon fiber of the present invention, the carbon fiber reinforced plastic to be treated uses, for example, a polyacrylonitrile-based carbon fiber (PAN-based carbon fiber) as a filler component, and an epoxy resin or the like as a matrix component. The one used can be assumed. In this case, the weight ratio of the matrix component in the carbon fiber reinforced plastic is generally about 60% by weight. Here, the thermal decomposition temperature of the carbon fiber of the filler component is, for example, around 850 ° C., whereas the epoxy resin of the matrix component is thermally decomposed even at a lower temperature (eg, around 400 ° C. to 600 ° C.). It has the property of gasifying. Therefore, the carbon fiber reinforced plastic that has gradually reached the heating region of the regeneration processing space (for example, the heating temperature is set to 500 ° C.), only the matrix component contained in the reaching process is vaporized from the solid, and carbon Only the fiber is discharged from the discharge port of the regeneration processing section, and it becomes possible to produce the regenerated carbon fiber.

Therefore, according to the method for producing a regenerated carbon fiber of the present invention, the bulk density of the carbon fiber introduced into the heating region of the regeneration processing space can be made constant by filling a heating cage of a prescribed size. Thereby, it becomes possible to stabilize the heating conditions of the carbon fiber, and the heating and removal of the matrix component can be carried out evenly in the regeneration processing space.

Further, in the heat removal step of the method for producing regenerated carbon fiber of the present invention, a part of the matrix component of the carbon fiber reinforced plastic is converted to fixed carbon by heating, and the regenerated carbon fiber having the fixed carbon attached to the fiber surface is produced. It can be set as the process to do.

Therefore, in the method for producing regenerated carbon fiber of the present invention, the matrix component of the carbon fiber is not completely removed from the fiber surface by the heat removal step, but a part of the matrix component is converted to fixed carbon. May be. Here, the fixed carbon is one in which, when the matrix component is gasified by heating and decomposes into carbon dioxide or the like, a part thereof is ashed and remains in the form of powder or the like. When this fixed carbon adheres to the fiber surface of the carbon fiber, the degree of entanglement (aggregation) between the respective regenerated carbon fibers increases, and it tends to be a lump like a bundle. Therefore, the possibility of being easily scattered by wind or the like is suppressed, and the handleability is improved. In addition, when the residual carbon rate of fixed carbon becomes high, it will function as a kind of binder which adhere | attaches regenerated carbon fiber, and the grade of a lump may become larger.

Furthermore, the heat removal step of the method for producing a regenerated carbon fiber of the present invention, the residual carbon ratio of the fixed carbon is 0.5 wt% or more based on the initial weight of the matrix component contained in the carbon fiber reinforced plastic, The matrix component is preferably removed by heating so that the content is 11.0% by weight or less.

According to the method for producing regenerated carbon fiber of the present invention, the residual carbon ratio of fixed carbon is adjusted to 0.5 wt% or more and 11.0 wt% or less. When the residual carbon ratio of the fixed carbon is lower than 0.5% by weight, the above-described improvement in handleability is difficult to be recognized, while the residual carbon ratio exceeding 11.0% by weight is a regenerated carbon fiber fiber. This will impair the properties of the product, making it unsuitable for reuse. Therefore, it is particularly preferable to adjust the content to 0.5 wt% or more and 11.0 wt% or less, more preferably 1.0 wt% or more and 5.0 wt% or less.

Furthermore, in addition to the above configuration, the method for producing a regenerated carbon fiber of the present invention may include a cutting step that is performed before the bulk density filling step. The cutting step is a step of cutting the carbon fiber reinforced plastic into a predetermined size.

By previously cutting the carbon fiber reinforced plastic into a predetermined cutting size, it becomes easy to adjust the bulk density when filling the heating cage with the carbon fiber reinforced plastic in the bulk density filling step. Here, the bulk density is not particularly limited, but may be set between 0.02 grams / cubic centimeter and 0.15 grams / cubic centimeter, for example. By setting the volume density within such a range, an appropriate void is formed in the carbon fiber reinforced plastic, and heat propagation in the heating region and the flow of the generated decomposition gas are also improved. Thereby, the heating conditions are stabilized, and the thermal decomposition treatment of the matrix component can be performed more efficiently. A cutting machine (crusher) for cutting the carbon fiber reinforced plastic is used.

Furthermore, the method for producing regenerated carbon fiber of the present invention may include a dry distillation step in addition to the above-described configuration. The carbonization step is a step performed before the bulk density filling step, and is a step of carbonizing the carbon fiber reinforced plastic in advance and carbonizing the matrix component. By providing the carbonization step, the heating cage is filled with carbonized carbon fiber reinforced plastic that has been previously carbonized.

Here, the carbonization process is, for example, putting carbon fiber reinforced plastic into a batch-type heating furnace set to a heating temperature of 400 ° C. or higher and heating it in an oxygen-free state (so-called “steaming”). . Low boiling point substances and moisture contained in the carbon fiber reinforced plastic are gasified and carbonized by heating. By the carbonization process, it is possible to shorten the heat removal time of the matrix component contained in the carbon fiber reinforced plastic in the subsequent manufacturing process. Furthermore, since carbonization of the carbon fiber reinforced plastic can be made constant in advance by the carbonization process, the heating conditions can be stabilized and the energy efficiency of the entire manufacturing process can be improved. In addition, you may implement the cutting process mentioned above with respect to the carbon fiber reinforced plastics after dry distillation.

The present invention also provides an apparatus for producing regenerated carbon fiber using carbon fiber reinforced plastic containing carbon fiber and a matrix component as a raw material. The manufacturing apparatus of the present invention includes a heating cage and a regeneration processing unit. Each surface of the heating cage is formed of a breathable material, and the heating cage is a housing-like cage filled with the carbon fiber reinforced plastic so as to have a predetermined bulk density. The regeneration processing unit includes a mesh transport unit that transports the heating cage and a heat treatment space having an elongated tunnel shape. The regeneration processing unit continuously heats the carbon fiber reinforced plastic to remove a part of the matrix component.

The present invention further provides a regenerated carbon fiber produced from a carbon fiber reinforced plastic containing carbon fiber and a matrix component. In the regenerated carbon fiber of the present invention, a part of the matrix component contained in the raw material carbon fiber reinforced plastic is converted to fixed carbon and remains on the surface. The regenerated carbon fiber of the present invention is characterized in that the residual carbon ratio of the fixed carbon is 0.5% by weight or more and 11.0% by weight or less based on the initial weight of the matrix component of the carbon fiber reinforced plastic.

As an effect of the present invention, a carbon fiber reinforced plastic can be filled in a heating cage and introduced into a regeneration processing section in a state in which the bulk density is adjusted to be constant, whereby a regenerated carbon fiber can be produced. Thereby, the thermal characteristics in the heating region can be made uniform, and the regenerated carbon fiber can be produced under stable heating conditions. Moreover, the handleability of the regenerated carbon fiber can be improved by leaving a part of the matrix component as fixed carbon. At this time, by adjusting the bulk density of the carbon fiber reinforced plastic, the residual carbon ratio of the fixed carbon can be easily adjusted.

The regenerated carbon fiber of the present invention has excellent characteristics such that the residual carbon ratio of the fixed carbon is not less than 0.5% by weight and not more than 11.0% by weight, maintaining mechanical properties and being difficult to scatter. ing. As a result, it is easy to handle and can be handled by a normal nonwoven fabric manufacturing apparatus or papermaking apparatus without any special additional processing.

It is explanatory drawing which shows schematic structure of the manufacturing apparatus used for the manufacturing method of the reproduction | regeneration carbon fiber of this embodiment. (A) A perspective view of a heating cage, (b) a sectional view of the heating cage, and (c) a schematic sectional view showing a state in which the heating cage is filled with carbon fiber reinforced plastic. is there. It is a flowchart which shows an example of the manufacturing method of the reproduction | regeneration carbon fiber of this embodiment.

Hereinafter, a carbon fiber manufacturing method 1 (hereinafter simply referred to as “manufacturing method 1”) according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. Here, in the manufacturing method 1 of the present embodiment, a carbon fiber reinforced plastic 25 (hereinafter simply referred to as “CFRP 25”) as shown in FIG. It will be shown about what is performed using (hereinafter, simply referred to as a manufacturing apparatus 26).

Here, the manufacturing apparatus 26 will be described. The manufacturing apparatus 26 includes a regeneration processing unit 3, a mesh belt 4, and a mesh transport unit 6. The regeneration processing unit 3 is constructed with a slender tunnel-shaped regeneration processing space 2 using refractory bricks, which are fire resistant materials. The mesh belt 4 is an endless belt arranged so as to penetrate the regeneration processing unit 3. The mesh transport unit 6 supports the mesh belt 4 and includes a plurality of rotating rollers 5 that can rotate around an axis. The regeneration processing space 2 is divided into three regions including a preheating unit 11, a heating removal unit 7, and a cooling unit 9. The heating removal unit 7 is installed in the heating area HZ in the center area. The cooling unit 9 is provided in the cooling zone CZ on the conveyance downstream side of the heating zone HZ, and gradually cools the produced regenerated carbon fiber 8 to near the room temperature. The preheating unit 11 is provided in the preheating area PZ on the upstream side of the conveyance of the heating area HZ, and preheats the CFRP 25 filled in the heating cage 10 to a predetermined heating temperature before reaching the heating area HZ. To do. The manufacturing apparatus 26 also includes a residual gas recovery unit 13 and a residual gas combustion unit 15. The residual gas recovery unit 13 is opened to a part of the regeneration processing unit 3 so as to communicate with the preheating region PZ, and reserve gas components 12 including smoke and hydrocarbon gas generated in the preheating region PZ are reserved. Suction and recovery from the heating zone PZ. The residual gas combustion unit 15 brings the recovered residual gas component 12 close to the flame of the burner B, re-combusts it in the combustion furnace 14, and then releases it to the outside. With this configuration, the CFRP 25 in the heating cage 10 placed on the mesh belt 4 is transported along the transport direction (the direction of arrow A in FIG. 1), and is introduced into the regeneration processing unit 3 on the upstream side of the transport. Are introduced into the regeneration processing space 2 and further discharged out of the regeneration processing space 2 through a discharge port 17 opened on the downstream side of the conveyance.

Here, in the regeneration processing space 2 between the introduction port 16 and the discharge port 17, three regions are set as described above. More specifically, for gradually heating the CFRP 25 in the heating cage 10 along a temperature gradient set in advance so as to reach a predetermined heating temperature (for example, 550 ° C.) from a temperature near room temperature. Preheated zone PZ and the heating temperature reached in the preheated zone PZ are set on the downstream side of the preheated zone PZ, and the heating temperature reached in the preheated zone PZ is kept as it is, and the CFRP 25 is heated to thermally decompose the matrix components to produce the regenerated carbon fiber 8 It is divided into three regions, namely, a heating region HZ for cooling and a cooling region CZ for cooling the regenerated carbon fiber 8 after the regeneration process to near the room temperature.

The mesh transport unit 6 having the mesh belt 4 made of a net-like member has a configuration of the mesh belt 4 and a plurality of rotating rollers 5 as already shown. In addition to this, the mesh conveyance unit 6 has a known configuration such as a rotation driving motor that generates a rotational force for rotating the rotation roller 5 and a rotation transmission mechanism for transmitting the rotation force to the rotation roller 5. The details are omitted here. The heating removal unit 7 and the preheating unit 11 are interposed between an upper belt 18 positioned on the upper side of the annular mesh belt 4 and a lower belt 19 positioned on the lower side. The heating elements 21 are respectively arranged so as to face the inner surface 20. The heating element 21 generates resistance heat when current is supplied. Heat can be applied from below to the heating cage 10 placed on the belt surface 18a of the upper belt 18 and conveyed to the preheating area PZ and the heating area HZ by the resistance heat of the heating element 21. The manufacturing apparatus 26 includes a current supply unit for supplying current to the heating element 21, a current adjustment mechanism that controls resistance heat generated by adjusting the supplied current value, and the preheating region PZ and the heating region HZ. Although provided with a temperature measurement sensor, an oxygen concentration sensor, a carbon monoxide concentration sensor, and the like that are installed at each of the plurality of locations and measure the temperature at the position, illustration is omitted here.

On the other hand, the cooling unit 9 provided in the cooling zone CZ gradually cools the regenerated carbon fiber 8 produced by thermally decomposing the matrix component in the heating zone HZ. The recycled carbon fiber 8 is cooled to a temperature at which the worker can collect the carbon fiber 8 when it is discharged from the discharge port 17. In the case of the present embodiment, an air supply unit 22 that forcibly supplies cold air (outside air) into the cooling region CZ from the vicinity of the discharge port 17 toward the upstream side of conveyance is provided. Furthermore, in the cooling region CZ of the regeneration processing unit 3, a plurality of communication ports 23 opened upward so as to communicate with the regeneration processing space 2 are opened, and the communication ports 23 and the intake duct 24 are connected. As a result, the forcedly supplied air is warmed by heat exchange by contacting the high-temperature regenerated carbon fiber 8 in the cooling zone CZ, and a part of the air (for example, about 60%) is connected to the communication port 23. In addition, the air is discharged to the outside of the manufacturing apparatus 26 through the intake duct 24, and the remaining air (for example, about 40%) flows to the heating region HZ on the upstream side of the conveyance.

The heating cage 10 used in the manufacturing apparatus 26 is configured as a substantially rectangular parallelepiped casing as shown in FIG. More specifically, a cage bottom surface portion 27 made of a square plate having a side of 47 cm and a cage side surface portion 28 made of four rectangular plates having a height of 15 cm suspended from the respective edges of the cage bottom surface portion 27 are provided. The cage main body 29 is mainly composed of a square plate having a side of 50 cm, and a cage lid portion 30 placed so as to cover the cage main body 29 from above. Here, the cage bottom surface portion 27 and the cage side surface portion 28 of the cage body 29 and the cage lid portion 30 are each made of a breathable material made of a mesh member.

The bulk density of the CFRP 25 can be calculated from the weight of the CFRP 25 filled in the filling space 31 and the height from the bottom surface portion 27 of the cage. The volume of the filling air 31 of the heating cage 10 is 47 cm × 47 cm × 15 cm = 33,135 cubic centimeters. Based on this, the bulk density = (weight of filled plastic) ÷ 33,135 × (cage (Height cm / 15 cm from the bottom surface portion). At this time, the CFRP 25 is filled evenly in the filling space 31, and the bulk density is calculated assuming that the height occupied in the filling space 31 is constant.

An example of the manufacturing method 1 of this embodiment using the manufacturing apparatus 26 will be described. The CFRP 25 to be subjected to the regeneration process in the manufacturing method 1 is a collection of scraps and the like (including prepregs before firing) extracted from the manufacturing process for manufacturing products using carbon fiber reinforced plastic. It assumes a sheet-like material. Since the collected scraps and the like contain paper and other contaminants, those that have been previously removed are used. Thereafter, the CFRP 25 is set in a carbonization furnace of a carbonization carbonization apparatus (not shown), and a low boiling point substance and a part of the matrix component contained in the CFRP 25 are carbonized (dry distillation process S1). Here, in the manufacturing method 1 of this embodiment, the carbonization temperature by a carbonization carbonization apparatus is set to 550 degreeC, and this is continued for 8 hours. When the CFRP 25 is heated in an oxygen-free state in the carbonization furnace, a low-boiling substance is volatilized, and a hydrocarbon gas such as methane or benzene is generated. Thereby, CFRP25 is carbonized. In the present embodiment, the carbon content of the carbonized CFRP 25 obtained by the carbonization step S1 is adjusted so as to be about 12%. As a result, the heating conditions for the subsequent heat removal of the matrix component can be stabilized. It becomes possible. In addition, superheated steam may be added to the carbonization furnace during carbonization to increase the effect of carbonization.

The carbonized CFRP 25 obtained in the carbonization step S1 has a smaller volume than before the carbonization due to the generation of the hydrocarbon gas and the like, but still maintains the shape before the carbonization. The carbonized CFRP 25 is cut into a predetermined size in order to fill the filling space 31 of the heating cage 10 (cutting step S2). In this embodiment, it cuts into 50 mm length by using the existing cutting machine. Thereafter, the filled CFRP 25 is filled in the filling space 31. For example, when the total filling amount of the CFRP 25 is 1000 g, the bulk density of the CFRP 25 is 0.08 grams / cubic centimeter (by filling the cage body 29 so that the height from the cage bottom portion 27 becomes 5.66 cm ( (Filling rate = about 38%) is adjusted (bulk density filling step S3, see FIG. 2 (c)). Then, the cage lid 30 is covered from above the cage body 29 to close the filling space 31. Thereby, it is possible to prevent the CFRP 25 or the regenerated carbon fiber 8 from being scattered in the reclaim processing space 2 due to vibrations or the like during conveyance by the mesh belt 4. Since the chip-like CFRP 25 cut by the cutting step S <b> 2 described above is large with respect to the mesh member such as the cage bottom surface portion 27 that constitutes the heating cage 10, the CFRP 25 does not spill out of the heating cage 10.

Next, the heating cage 10 filled with the CFRP 25 is placed on the mesh belt 4 in the vicinity of the introduction port 16 (see FIG. 1). The heating elements 21 of the heating removal unit 7 and the preheating unit 11 of the manufacturing apparatus 26 are preliminarily heated and adjusted to have heating temperatures and temperature gradients set in the heating region HZ and the preheating region PZ. . From the air supply section 22 of the cooling section 9, the outside air is forcibly supplied toward the cooling zone CZ.

The mesh transport unit 6 operates. Specifically, the mesh belt 4 is driven by the rotation of the rotating roller 5 that supports the mesh belt 4. The upper belt 18 located above the mesh belt 4 moves from the upstream end 4a on the upstream side of the conveyor belt toward the downstream end 4b on the downstream side. On the other hand, the moving direction is reversed at the downstream end 4b, and the lower belt 19 located on the lower side of the mesh belt 4 moves from the downstream side of the transport toward the upstream side of the transport. As a result, the heating cage 10 placed on the upper belt 18 of the mesh belt 4 moves in the horizontal direction (heating cage conveying step S4). Here, the moving speed of the mesh belt 4, that is, the conveying speed of the heating cage 10 is set to 12.2 m / h (≈0.20 m / min). In the manufacturing apparatus 26 used in the present embodiment, the distance in the furnace from the inlet 16 to the outlet 17 of the regeneration processing unit 3 is set to 26.5 m, while the entire length from the upstream end 4a to the downstream end 4b. Is set to be 35.0 m. As a result, the heating cage 10 is conveyed through the regeneration processing space 2 over 130 minutes until it is introduced from the inlet 16 and discharged from the outlet 17. Immediately after the mesh belt 4 on which one heating cage 10 is placed, another heating cage 10 is placed in close proximity. Therefore, 23.5 cases of the heating cage 10 per unit time can be processed at the transfer speed. At this time, if the conveyance speed is set low, the staying time in the regeneration processing space 2 of one heating cage 10 becomes long, and the working efficiency is remarkably lowered. On the other hand, if the conveyance speed is too high, the matrix component of the CFRP 25 filled in the heating cage 10 may be discharged from the discharge port 17 without being sufficiently thermally decomposed. Therefore, as described above, by setting the conveyance speed so as to advance about 12 m per hour, both problems of work efficiency and quality stability of the regenerated carbon fiber 8 can be solved.

In the present embodiment, the opening shape of the introduction port 16 and the cross-sectional shape of the heating cage 10 are substantially matched. Only a slight gap is formed between the opening edge of the inlet 16 and the cage surface 10 a of the heating cage 10. As a result, since only the minimum necessary amount of outside air or the like enters the regeneration processing space 2 from the inlet 16 side, the change in the temperature gradient in the preheating region PZ is hardly affected. In addition to this, by placing another heating cage 10 on the mesh belt 4 immediately after one heating cage 10, the amount of outside air flowing from the inlet port 16 is limited and at the same time, The heating cage 10 and the CFRP 25 having characteristics do not affect the temperature gradient in the preheating region PZ. As a result, stable heating up to the target heating temperature is possible.

The heating cage 10 introduced into the preheating area PZ of the regeneration processing space 2 from the inlet 16 of the regeneration processing unit 3 is heated by heat generated from the heating element 21 of the preheating unit 11 (preheating step S5). The CFRP 25 in the heating cage 10 is obtained by carbonizing a part of the matrix component in advance by the carbonization step S1. Therefore, the preliminary heating step S5 functions as a so-called “temperature raising step” in which the CFRP 25 in the heating cage 10 is heated to the heating temperature (= 550 ° C.) in the heating region HZ. However, a residual gas component 12 such as hydrocarbon gas or smoke may be generated from a part of the matrix component due to a substance not released in the dry distillation step S1. Therefore, the residual gas component 12 is recovered by the residual gas recovery unit 13 connected above the preheating zone PZ, and is burned completely in the burner B while supplying sufficient oxygen to the recovered residual gas component 12. Carbon dioxide and water can be generated, and these can be released into the atmosphere with a reduced impact on the natural environment.

The heating cage 10 and the CFRP 25 that have reached the heating zone HZ via the preheating zone PZ are heated in order to remove the remaining matrix component carbides by heating in the regeneration processing space 2 under an oxygen atmosphere (heating removal step S6). The heating temperature of the heating zone HZ is set to 550 ° C. in this embodiment. The carbon fiber itself of CFRP25 is not gasified in an oxygen atmosphere unless the heating temperature is 800 to 850 ° C. or higher. As a result, only the carbide derived from the matrix component is removed by heating by the oxidation reaction, and the regenerated carbon fiber 8 is produced. At this time, by adjusting the heating temperature in the heating zone HZ, the distance (length) of the heating zone HZ, and the conveyance speed, the regenerated carbon fiber 8 is moved to the cooling zone CZ while the carbide of the matrix component is not completely removed. To reach. That is, the carbide (fixed carbon) of the matrix component adheres to the fiber surface of the regenerated carbon fiber 8. In the present embodiment, the residual carbon ratio of the fixed carbon is set to be around 3% by weight.

Since the regenerated carbon fiber 8 that has reached the cooling zone CZ does not receive heat from the heating element 21 of the heating removal unit 7, it gradually releases heat while being conveyed along the mesh belt 4. It is cooled (cooling step S7). At this time, since the outside air is supplied from the downstream side of the conveyance by the air supply unit 22, the temperature of the regenerated carbon fiber 8 in contact with the outside air is further sharply lowered, and the cooling region CZ is set to be short. Even if it is a case, sufficient cooling effect can be acquired. Since the fixed carbon adheres to the regenerated carbon fiber 8, scattering by the outside air from the air supply section 22 is prevented as compared with the case where the matrix component is completely removed. The outside air sent to the cooling zone CZ is still in contact with the high-temperature regenerated carbon fiber 8 and is warmed by heat exchange. A part of the supplied outside air is sucked in the intake duct 24 and discharged to the outside of the manufacturing apparatus 26. On the other hand, a part of the remaining outside air reaches the heating zone HZ. This outside air contains oxygen and is consumed for the oxidation reaction for gasifying the carbide of the matrix component.

Thereafter, the regenerated carbon fiber 8 reaches the end of the reclaim processing space 2, is sufficiently cooled, and is discharged from the discharge port 17 (step S8). As described above, since the carbon fiber (regenerated carbon fiber 8) itself is not thermally decomposed at a heating temperature of about 550 ° C., the thickness or the like of the regenerated carbon fiber 8 in the heating cage 10 does not change. . Furthermore, since fixed carbon adheres to the fiber surface, the density is increased, and there is an advantage that the handleability is excellent compared to the case where the matrix component is completely removed. It should be noted that the presence of about 3% fixed carbon has no particular effect upon reuse.

As described above, according to the manufacturing method 1 of the present embodiment, the raw material CFRP 25 is placed on the mesh belt on the upstream side of the conveyance and conveyed at a predetermined conveyance speed. It is decomposed by heating, leaving a part of it. By thermal decomposition, it is possible to selectively remove only the matrix component from the CFRP 25 and to produce the regenerated carbon fiber 8 that is not easily scattered by wind or the like. Furthermore, before the introduction into the regeneration processing space 2, the heating in the regeneration processing space 2 is stabilized by filling the heating cage 10 so as to have a specified bulk density. As a result, the residual rate of fixed carbon can be stabilized. In the manufacturing method 1 of the present embodiment, the contact area between the CFRP 25 and oxygen (atmosphere) in the heat removal unit 7 can be adjusted by controlling the bulk density of the CFRP 25. The contact with oxygen at a high temperature increases the possibility of occurrence of problems such as loss due to gasification of the regenerated carbon fiber 8 or deterioration of mechanical properties of the regenerated carbon fiber 8. Therefore, the loss of the regenerated carbon fiber 8 and the like can be minimized by adjusting the contact area with oxygen.

The tensile strength of the regenerated carbon fiber 8 of this embodiment was verified. The tensile test was performed by a simple tensile test method based on JIS R 7606. The regenerated carbon fiber 8 produced according to this example has less variation in strength than the unused virgin carbon fiber, and has an average strength of 80% with respect to the virgin carbon fiber. It became clear that this is possible.

The present invention has been described with reference to preferred embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention as described below. And design changes are possible.

For example, in the production method 1 of the present embodiment, the carbonization process S1 was previously performed on the CFRP 25 to be regenerated, and the matrix component was carbonized to show a residual carbon ratio of about 12%. It is not limited, You may not implement such dry distillation process S1 as needed. That is, if the matrix component is gasified when the temperature is raised to the heating temperature in the preheating region PZ, the same effect as dry distillation can be obtained. Furthermore, although what cut | disconnects was shown in order to adjust the size of CFRP25 with which it fills after dry distillation process S1, it is not limited to this, You may implement before dry distillation process S1.

Furthermore, in the manufacturing method 1 of the present embodiment, the heating cage 10 is transported to the regeneration processing space 2 by using the mesh transport unit 6 having the mesh belt 4, but is not limited thereto. Any other roller hearth kiln may be used. However, when the heating element 21 is disposed below the heating cage 10 and heated as in the present embodiment, the mesh belt 4 is used to improve heat propagation and perform efficient heating. Can do. Moreover, in the manufacturing method 1 of this embodiment, although what cuts CFRP25 to 50 mm length was shown, it is not limited to this, It cuts to 3.5 mm-150 mm using a cutting machine, It doesn't matter. Thereby, it becomes possible to regenerate the regenerated carbon fiber 8 according to the reuse application. In addition, as a use of reuse, paper, a nonwoven fabric, a heat insulating material, the filler component of a novel carbon fiber reinforced plastic, etc. are assumed. Further, the cutting step S2 is not limited to one time. For example, when the fibers included in the CFRP 25 are knitted so as to cross, the cutting step S2 is performed twice or a plurality of times. You may do.

In the embodiment, CFRP containing an epoxy resin as a matrix component is exemplified, but the present invention is not limited to this. Examples of the resin used as the matrix component include a polypropylene resin, a polyethylene resin, a polymethyl methacrylate resin, a saturated polyester resin, and a polycarbonate resin as the thermoplastic resin in addition to the epoxy resin. Moreover, as a thermosetting resin, unsaturated polyester resin, a phenol resin, vinyl ester resin etc. can be illustrated other than an epoxy resin. When the CFRP containing a thermosetting resin as a matrix component is directly heated, there is a possibility that the CFRP is firmly fixed to the carbon fiber to be regenerated by a thermosetting reaction of the resin. Therefore, by gradually heating and gradually raising the temperature, gasification or combustion reaction can be caused, and the manufacturing method and manufacturing apparatus of this embodiment can be applied.

In the embodiment, the case where the residual carbon ratio of the CFRP processed in the carbonization step S1 is adjusted to 12% by weight is exemplified. However, the residual carbon ratio is adjusted in consideration of the type of the matrix component, the content of the matrix component in the CFRP, the shape of the CFRP, and the energy efficiency of the entire manufacturing method. In many cases, the residual carbon ratio of the CFRP processed in the carbonization step S1 is adjusted from about 10% by weight to about 12% by weight.

In the embodiment, the case where the residual carbon ratio of the regenerated carbon fiber is adjusted to 3% by weight is exemplified. However, the residual carbon ratio can be adjusted to 0.5 wt% or more and 11.0 wt% or less according to the intended use. Regenerated carbon fiber with a residual carbon ratio of 0.5% by weight or less may have insufficient mechanical strength due to a decrease in mechanical properties, and may not be in a fiber bundle state and may be scattered during production. . In addition, the regenerated carbon fiber having a residual carbon ratio of 11.5% by weight or more may not be flexible while maintaining the form of the fiber bundle.

1 Production method (Production method of recycled carbon fiber)
2 Regeneration processing space 3 Regeneration processing section 7 Heat removal section 8 Regenerated carbon fiber 9 Cooling section 10 Heating gauge 16 Inlet 17 Outlet 25 CFRP (carbon fiber reinforced plastic)
26 Manufacturing equipment 31 Filling space CZ Cooling area HZ Heating area PZ Preheating area S1 Dry distillation process S2 Cutting process S3 Bulk density filling process S4 Heating cage conveyance process S5 Preheating process S6 Heating removal process S7 Cooling process

Claims

A method for producing regenerated carbon fiber (8) using carbon fiber reinforced plastic (25) containing carbon fiber and a matrix component,
A bulk density filling step of filling the carbon fiber reinforced plastic (25) in a casing-like heating cage (10) formed with a breathable material so as to have a predetermined bulk density;
A regeneration processing space (2) having an elongated tunnel shape is constructed inside by a refractory material, and the introduction port (16) and the discharge port (17) communicating with the regeneration processing space (2) are opened. A heating cage transporting step for transporting the heating cage (10) filled with the carbon fiber reinforced plastic to the processing unit (3);
The carbon fiber reinforced plastic in the heating cage (10) to be transported is heated by the heating removal unit (7) provided in the heating region of the regeneration processing space (2) to remove the matrix component and regenerate. A heat removal step of obtaining carbon fibers (8);
The regenerated carbon fiber (8) from which the matrix component has been removed by heating is cooled while being transported by a cooling section (9) provided in a cooling region downstream of the heating region in the regeneration processing space (2). A cooling process;
A method for producing a regenerated carbon fiber (8), comprising:
The heating removal step includes
The part of the matrix component of the carbon fiber reinforced plastic (25) is converted into fixed carbon by heating, and the regenerated carbon fiber in which the fixed carbon adheres to the fiber surface is generated. The manufacturing method of the reproduction | regeneration carbon fiber of description.
The heating removal step includes
The residual carbon ratio of the fixed carbon (8) is 0.5% by weight or more and 11.0% by weight or less with respect to the initial weight of the matrix component contained in the carbon fiber reinforced plastic (40). The method for producing a regenerated carbon fiber according to claim 2, wherein the matrix component is removed by heating.
Carried out before the bulk density filling step,
The method for producing regenerated carbon fiber according to any one of claims 1 to 3, further comprising a cutting step of cutting the carbon fiber reinforced plastic into a predetermined size.
Carried out before the bulk density filling step,
The carbon fiber reinforced plastic (25) is carbonized in advance, further comprising a carbonization step of carbonizing the matrix component,
The method for producing regenerated carbon fiber according to any one of claims 1 to 4, wherein the carbonized carbon fiber reinforced plastic is filled in the heating cage (10).
An apparatus (26) for producing regenerated carbon fiber from carbon fiber reinforced plastic (25) containing carbon fiber and a matrix component,
Each surface is formed of a breathable material, and a housing-like heating cage (10) filled with the carbon fiber reinforced plastic so as to have a predetermined bulk density;
A mesh transport section (6) for transporting the heating cage (10) and a heat treatment space (2) having an elongated tunnel shape are provided, and the carbon fiber reinforced plastic is continuously heated to partly form the matrix component. A reproduction processing unit (3) for removing
An apparatus (26) for producing regenerated carbon fiber, comprising:
Regenerated carbon fiber (8) manufactured from carbon fiber reinforced plastic (40) containing carbon fiber and a matrix component,
A part of the matrix component of the carbon fiber reinforced plastic (40) is converted to fixed carbon and remains on the surface of the regenerated carbon fiber (8),
Regenerated carbon fiber characterized in that the residual carbon ratio of the fixed carbon is 0.5 wt% or more and 11.0 wt% or less with respect to the initial weight of the matrix component of the carbon fiber reinforced plastic (40). (8).