JP5941747B2 - Method for producing regenerated carbon fiber and apparatus for producing regenerated carbon fiber - Google Patents

Description

  The present invention relates to a carbon fiber regeneration treatment method, and in particular, for producing a regenerated carbon fiber that can be reused as a raw material for a nonwoven fabric or the like by heating a carbon fiber reinforced plastic at a high temperature and removing a matrix component. The present invention relates to a carbon fiber regeneration treatment method.

  Carbon fiber is known as a material having excellent mechanical properties such as high strength and high elastic modulus, and is used as a filler component, and a carbon fiber reinforced plastic (CFRP: Carbon) using an epoxy resin or a polyester resin as a matrix component. Fiber Reinforced Plastic) is manufactured and widely used in various industrial fields including the aerospace industry.

  Carbon fiber reinforced plastics are mainly manufactured by producing a prepreg in which a resin of a matrix component is infiltrated into carbon fibers and firing the prepreg while pressing 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 the product itself such as an aircraft body has a large size, a large amount of the above-mentioned scrap material is generated, and the disposal thereof may be a problem. Carbon fiber reinforced plastic is a mixture of filler and matrix components with different properties as described above, and it is technically difficult to separate them for reuse (recycling) or reuse (reuse). And is not effective in terms of cost and energy efficiency. As a result, at present, most of the offcuts and unused prepreg generated during production 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.

Therefore, by the inventors of the present invention, the carbon fiber regeneration processing apparatus and the regeneration for selectively recovering the carbon fiber without degrading the mechanical properties by thermally removing only the matrix component from the carbon fiber reinforced plastic by thermal decomposition. Techniques relating to processing methods (see Patent Document 1 and Patent Document 2) have already been developed. According to this, a mesh-shaped belt conveyor is disposed in a regeneration processing section in which a slender tunnel-shaped regeneration processing space is constructed of a fireproof material, and the carbon fiber reinforced plastic is recycled using the belt conveyor. in addition to continuously supply, by heating the carbon fiber reinforced plastic in the heating region of the regeneration process in the space, only the matrix component such as e epoxy resin gasified by pyrolysis, the long carbon fibers (recycled carbon fiber) It can be recovered in a fibrous state. As a result, a large amount of carbon fiber reinforced plastic can be efficiently pyrolyzed, and regenerated carbon fiber can be produced.

  However, the above-described carbon fiber regeneration treatment apparatus and regeneration treatment method may cause problems in the following points. That is, the collected carbon fiber reinforced plastic mill ends have various shapes depending on the use site of the product. Therefore, a difference in shape causes a difference in heat transfer during pyrolysis, which may cause variations in heating conditions. As a result, when regenerated carbon fiber is produced from carbon fiber reinforced plastic using a regenerative processing apparatus having a continuous furnace, a part of the regenerated processing space becomes overheated and burns due to the difference in thermal characteristics. May not be sufficiently transmitted and some of the matrix components remain, resulting in unevenness in properties and quality of the obtained recycled carbon fiber. In particular, due to 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, a difference in heat transfer occurs, and the above-described problems are likely to occur.

  In addition, in the case of the conventional carbon fiber regeneration treatment method, the matrix component contained in the carbon fiber reinforced plastic is completely removed by pyrolysis, and a regenerated carbon fiber in which the residual ratio of the matrix component is 0% is generated. Was intended to be. 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. Therefore, when producing | generating regenerated carbon fiber using a regeneration processing apparatus, careful handling was needed so that it might not scatter in the heating area | region and cooling area | region of regeneration processing space. In addition, even when reused after collection, the handleability (handling property) of the regenerated carbon fiber may be a problem.

  Therefore, in view of the above circumstances, the present invention has an object to provide a carbon fiber regeneration processing method capable of efficiently recovering a regenerated carbon fiber from a carbon fiber reinforced plastic under a stable heating condition. .

In order to solve the above problems, a method for producing a regenerated carbon fiber according to the present invention is described as follows: “A carbon fiber reinforced plastic containing carbon fiber and a matrix component is used for a case-like heating cage in which each surface is formed of a breathable material. A bulk density filling step for filling the inside so as to have a predetermined bulk density inside, and a slender tunnel-shaped reclaim processing space is constructed inside by a refractory material, and an introduction port and a discharge port communicating with the reclaim processing space are provided. The heating cage transported by the heating cage transporting process of transporting the heating cage filled with the carbon fiber reinforced plastic to the reclaiming processing part opened respectively, and the heating removal unit provided in the heating region of the regeneration processing space heating the carbon fiber reinforced plastic inner and removed by heating to obtain a recycled carbon fibers by removing the matrix components of the regeneration space The cooling unit provided in the cooling zone of the conveyor downstream of the serial heating zones are mainly provided with a "cooling step of cooling while conveying the recycled carbon fiber has been heated removing the matrix component.

  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 carbon fiber regeneration treatment method 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, with respect to the thermal decomposition temperature (for example, about 850 ° C.) of the carbon fiber of the filler component, the epoxy resin of the matrix component is thermally decomposed even at a lower heating temperature (for example, about 400 ° C. to 600 ° C.), It has the property of gasifying. Therefore, in the carbon fiber reinforced plastic that has gradually reached the heating region of the regeneration treatment space (for example, the heating temperature is set to 500 ° C.), only the matrix component contained in the reaching process is liquefied (or vaporized) from the solid, Only the carbon fibers are discharged from the discharge port of the regeneration processing unit, and can be recovered as recycled carbon fibers.

Therefore, according to the method for producing regenerated carbon fiber of the present invention, the bulk density of the carbon fiber reinforced plastic introduced into the heating region of the regeneration processing space can be made constant by filling a heating cage of a specified size. Become. Thereby, it becomes possible to stabilize the heating conditions of the carbon fiber reinforced plastic, and the matrix component can be removed by heating in the regeneration processing space without unevenness.

Furthermore, the method for producing a regenerated carbon fiber of the present invention includes, in addition to the above-described configuration, “the heating and removing step converts a part of the matrix component of the carbon fiber reinforced plastic into fixed carbon by heating, and the fixed carbon It is also possible to produce the regenerated carbon fiber attached to the fiber surface.

Therefore, according to 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 can be converted to fixed carbon. Done. 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 method for producing a regenerated carbon fiber of the present invention includes, in addition to the above-described configuration, “the heating and removing step determines the residual carbon ratio of the fixed carbon relative to the initial weight of the matrix component contained in the carbon fiber reinforced plastic . , 0.5% by weight or more and 11.0% by weight or less of the matrix component may be removed by heating ”.

  Therefore, according to the carbon fiber regeneration treatment method of the present invention, the residual carbon ratio of the fixed carbon is adjusted to 0.5 wt% or more and 11.0 wt% or less. That is, 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 the regenerated carbon fiber. The properties as a fiber will be impaired, 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-described structure, the method for producing a regenerated carbon fiber of the present invention includes a “cutting step that is performed before the bulk density filling step and cuts the carbon fiber reinforced plastic into a predetermined size”. It doesn't matter if you do it.

Therefore, according to the method for producing regenerated carbon fiber of the present invention, by cutting the carbon fiber reinforced plastic into a predetermined cutting size in advance, the bulk at the time of filling the carbon fiber reinforced plastic into the heating cage in the bulk density filling step. It becomes easier to adjust the density. Here, the bulk density is not particularly limited, but may be set, for example, between 0.02 grams / cubic centimeter and 0.15 grams / cubic centimeter. By setting the bulk density in such a range, an appropriate gap is formed between the carbon fiber reinforced plastics, and the 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 according to the present invention includes, in addition to the above-described configuration, “a carbonization step that is carried out before the bulk density filling step, carbonization of the carbon fiber reinforced plastic in advance, and carbonization of the matrix component is further performed. And the heating cage may be filled with the carbonized carbon fiber reinforced plastic ".

Therefore, according to the method for producing regenerated carbon fiber of the present invention, a carbon fiber reinforced plastic filled in the heating cage is subjected to dry distillation treatment in advance. Here, the carbonization process is a process in which, for example, a carbon fiber reinforced plastic is put into a batch type heating furnace set to a heating temperature of 400 ° C. or higher and heated in an oxygen-free state (so-called “steaming”). The low-boiling substances and moisture contained in the carbon fiber reinforced plastic are gasified and carbonized by heating. This makes it possible to shorten the heat removal time of the matrix component contained in the carbon fiber reinforced plastic in the regeneration process of the regenerated carbon fiber performed after the fact. Furthermore, the carbonization of the carbon fiber reinforced plastic can be made constant by the carbonization process in advance, the heating conditions can be stabilized, and the energy efficiency of the regenerated carbon fiber using the reprocessing apparatus 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 from a carbon fiber reinforced plastic containing carbon fiber and a matrix component. The apparatus of the present invention is provided with a casing-like heating cage that is formed of a breathable material and has a surface that is filled with the carbon fiber reinforced plastic so as to have a predetermined bulk density. In addition, it has a mesh transport section for transporting the heating cage and a heat treatment space having an elongated tunnel shape, and a regeneration processing section for continuously heating the carbon fiber reinforced plastic to remove a part of the matrix component.

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 generated and recovered 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.

It is explanatory drawing which shows schematic structure of the regeneration processing apparatus used for the regeneration processing method of the carbon fiber of this embodiment. (A) a perspective view showing the configuration of the heating cage used in the regeneration processing apparatus, (b) a sectional view showing the configuration 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. It is. It is a flowchart which shows an example of the flow of the regeneration processing method of the carbon fiber of this embodiment.

  Hereinafter, a carbon fiber regeneration treatment method 1 (hereinafter simply referred to as “regeneration treatment method 1”) according to an embodiment of the present invention will be described with reference to FIGS. 1 to 3. Here, the regeneration processing method 1 of the present embodiment uses a regeneration processing apparatus 26 capable of continuously heating a carbon fiber reinforced plastic 25 (hereinafter simply referred to as “CFRP 25”) as shown in FIG. Shall be shown.

  Here, the regeneration processing device 26 will be described. The regeneration processing unit 3 in which a slender tunnel-shaped regeneration processing space 2 is constructed using a firebrick that is a fireproof material, and the regeneration processing unit 3 are penetrated. An endless mesh belt 4 arranged so as to support the mesh belt 4, a mesh transport unit 6 having a plurality of rotating rollers 5 that can rotate around the shaft, and the regeneration processing space 2 are divided into three regions. The regenerated carbon fiber 8 that has been divided and provided in the heating removal section 7 installed in the heating area HZ in the central area and the cooling area CZ downstream of the heating area HZ is gradually cooled to near room temperature. The CFRP 25 provided in the cooling unit 9 and the preheating area PZ on the upstream side of the heating area HZ and filled in the heating cage 10 is preliminarily added to a predetermined heating temperature before reaching the heating area HZ. A part of the regeneration processing unit 3 is opened so as to communicate with the preheating unit 11 and the preheating region PZ, and the residual gas component 12 including smoke and hydrocarbon gas generated in the preheating region PZ is preliminarily heated. The residual gas recovery unit 13 that sucks and recovers from the region PZ, and the residual gas combustion unit 15 that releases the recovered residual gas component 12 to the outside after being brought close to the flame of the burner B and recombusted in the combustion furnace 14. And mainly. 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 rotational drive that generates a rotational force for rotating the rotating roller 5 in addition to the configuration of the mesh belt 4 and the plurality of rotating rollers 5 already shown. This includes well-known components such as a motor for rotation and a rotation transmission mechanism for transmitting the rotational force to the rotating roller 5, and the details thereof 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, and a belt inner surface 20 of the upper belt 18. The heating elements 21 are arranged so as to face each other. As a result, current is supplied to the heating element 21 to generate resistance heat, thereby lowering 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. Heat can be applied from. It should be noted that a current supply unit for supplying a current to the heating element 21, a current adjusting mechanism for controlling the resistance heat generated by adjusting the supplied current value, and a plurality of locations in each of the preheating region PZ and the heating region HZ. The temperature measurement sensor, the oxygen concentration sensor, the carbon monoxide concentration sensor, and the like that measure the temperature at the position are provided, but are not shown here.

  On the other hand, the cooling unit 9 provided in the cooling zone CZ slowly cools the regenerated carbon fiber 8 that is regenerated by thermally decomposing the matrix components in the heating zone HZ, and the worker collects it when discharged from the discharge port 17. This is to lower the temperature to the extent possible. 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 regeneration processing device 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.

  Furthermore, as shown in FIG. 2, the heating cage 10 used in the regeneration processing device 26 is configured as a substantially rectangular parallelepiped housing. 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.

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

  Next, an example of the reproduction processing method 1 of the present embodiment using the reproduction processing device 26 will be described. Here, in the regeneration processing method 1 of the present embodiment, the CFRP 25 to be subjected to the regeneration processing is a milled material or the like (including a prepreg before firing) provided from a manufacturing factory that manufactures a product using a carbon fiber reinforced plastic. It is assumed that it is mainly a sheet. In addition, since the collected scraps and the like contain paper and other foreign matters, 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 regeneration treatment method 1 of this embodiment, the carbonization temperature by the carbonization carbonization apparatus is set to 550 ° C., and this is continued for 8 hours. As a result, the CFRP 25 is heated in an oxygen-free state in the carbonization furnace, whereby 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 to be about 12%. As a result, it becomes possible to stabilize the heating conditions for the subsequent heat removal of the matrix component. In addition, superheated steam may be added to the carbonization furnace during carbonization to increase the effect of carbonization.

  Although the carbonized CFRP 25 obtained by the carbonization step S1 has a smaller volume than that before the carbonization due to the generation of the hydrocarbon gas or the like, it still maintains the shape before the carbonization. Therefore, in order to fill the filling space 31 of the heating cage 10, the CFRP 25 is cut into a predetermined size (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. At this time, when the total filling amount of CFRP 25 is 1000 g, the bulk density of CFRP 25 is 0.08 grams / cubic centimeter by filling the cage body 29 so that the height from the cage bottom surface 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. In addition, since the chip-like CFRP 25 cut by the above-described cutting step S2 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). In addition, each heating element 21 of the heating removal unit 7 and the preheating unit 11 of the regeneration processing device 26 is preheated and adjusted so as to have a heating temperature and a temperature gradient set in the heating region HZ and the preheating region PZ. Has been. In addition, outside air is forcibly supplied from the air supply unit 22 of the cooling unit 9 toward the cooling region CZ.

  And the mesh conveyance part 6 is operated. Specifically, the rotating roller 5 that supports the mesh belt 4 is rotated, and the mesh belt 4 is driven accordingly. As a result, the upper belt 18 positioned 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, while the moving direction is reversed at the downstream end 4b. The lower belt 19 located on the lower side of the mesh belt 4 moves from the transport downstream side toward the transport upstream side. 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 regeneration processing device 26 used in the present embodiment, the furnace distance from the inlet 16 to the outlet 17 of the regeneration processing unit 3 is set to 26.5 m, while the upstream end 4a to the downstream end 4b. Is set to be 35.0 m. Therefore, the heating cage 10 is transported through the regeneration processing space 2 over 130 minutes until it is introduced from the introduction port 16 and discharged from the discharge port 17. Here, 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 residence 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, since the opening shape of the introduction port 16 and the cross-sectional shape of the heating cage 10 are formed so as to substantially match, the gap between the opening edge of the introduction port 16 and the cage surface 10a of the heating cage 10 is formed. Only a few voids are formed. For this reason, since only the minimum necessary amount of outside air or the like enters the regeneration processing space 2 from the inlet 16 side, it does not significantly affect the change in temperature gradient in the preheating region PZ. Further, as described above, 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 the same thermal effect is obtained. 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 region PZ of the regeneration processing space 2 from the introduction port 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). Here, as described above, 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.

  Thereafter, the heating cage 10 and the CFRP 25 that have reached the heating region HZ via the preheating region PZ are heated to remove the remaining carbide of the matrix component in the regeneration processing space 2 under an oxygen atmosphere (heating removal step S6). ). Here, the heating temperature of the heating region HZ is set to 550 ° C. in the present embodiment. At this time, the carbon fiber itself of the CFRP 25 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 generated. 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 temperature is set so as to reach the cooling zone CZ while the carbides of the matrix component are not completely removed. ing. That is, the carbide (fixed carbon) of the matrix component adheres to the fiber surface of the regenerated carbon fiber 8. In this embodiment, the residual carbon ratio of fixed carbon is set to be about 3%.

  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. In addition, since fixed carbon has adhered to the reproduction | regeneration carbon fiber 8, compared with what removed the matrix component completely, it does not scatter easily by the external air by the air supply part 22. FIG. 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. As a result, a part thereof is sucked from the intake duct 24 and discharged to the outside of the regeneration processing device 26. On the other hand, the remaining part reaches the heating zone HZ. At this time, the outside air contains oxygen and is consumed for an oxidation reaction for gasifying the carbide of the matrix component.

  Thereafter, the end of the regeneration processing space 2 is reached, and the sufficiently cooled regenerated carbon fiber 8 is discharged from the discharge port 17 (step S8). Here, 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 changes. There is nothing. 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 such fixed carbon does not affect the reuse.

  As described above, according to the regeneration processing method 1 of the present embodiment, the CFRP 25 to be regenerated is placed on the mesh belt on the upstream side of the transport and transported at a predetermined transport speed. By thermally decomposing leaving a part of the carbide, it is possible to selectively remove only the matrix component from the CFRP 25 and to regenerate 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. Note that, by controlling the bulk density of the CFRP 25 according to the regeneration processing 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. Here, 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 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 regeneration processing method 1 of the present embodiment, the carbonization process S1 is performed in advance on the CFRP 25 to be recycled, and the matrix component is carbonized to show a residual carbon ratio of about 12%. It is not limited to this, You may not perform 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 regeneration processing method 1 of the present embodiment, the transport cage 10 is transported to the regeneration processing space 2 using the mesh transport section 6 having the mesh belt 4, but is not limited to this. Alternatively, another roller hearth kiln or the like 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 reproduction processing method 1 of the present embodiment, the CFRP 25 is cut to a length of 50 mm. However, the present invention is not limited to this, and the cutting is performed to 3.5 mm to 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, the filler component of a nonwoven fabric, a heat insulating material, 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.

1 Regeneration treatment method (carbon fiber regeneration treatment method)
2 Regeneration processing space 3 Regeneration processing unit 7 Heat removal unit 8 Recycled carbon fiber 9 Cooling unit 10 Heating cage 16 Inlet 17 Outlet 25 CFRP (carbon fiber reinforced plastic)
26 Regeneration processing device 31 Filling space CZ Cooling zone HZ Heating zone PZ Preheating zone S1 Dry distillation step S2 Cutting step S3 Bulk density filling step S4 Heating cage conveying step S5 Preheating step S6 Heating removal step S7 Cooling step

JP 2008-285600 A JP 2008-285601 A JP 7-33904 A

Claims (6)

A method for producing a regenerated carbon fiber using a carbon fiber reinforced plastic containing carbon fiber and a matrix component ,
A bulk density filling step of filling the carbon fiber reinforced plastic so as to have a predefined bulk density in a casing-shaped heating cage in which each surface is formed of a breathable material;
The heat treatment material filled with the carbon fiber reinforced plastic is formed in the reclaim processing part in which a slender tunnel-shaped reclaim processing space is constructed inside by a refractory material, and an introduction port and a discharge port communicating with the reclaim processing space are respectively opened. A heating cage conveying step for conveying;
A heating and removing step of heating the carbon fiber reinforced plastic in the heating cage to be transported by a heating and removing unit provided in a heating region of the regeneration processing space, and removing the matrix component to obtain a recycled carbon fiber ;
The cooling unit provided in the cooling zone of the conveyor downstream of the heating region of the regeneration space, a cooling step of cooling while conveying the recycled carbon fiber has been heated removing the matrix component,
The manufacturing method of the regenerated carbon fiber characterized by comprising. The heating removal step includes
The converted to fixed carbon by heating a portion of the matrix component of the carbon fiber reinforced plastic, recycled carbon according to claim 1, wherein the fixed carbon and generates the recycled carbon fiber attached to the fiber surface A method for producing fibers . The heating removal step includes
Heat removal of the matrix component such 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 contained in the carbon fiber reinforced plastic. The method for producing a regenerated carbon fiber according to claim 2, wherein: 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,
Further comprising a carbonization step of carbonizing the carbon fiber reinforced plastic in advance and 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. An apparatus for producing regenerated carbon fiber using a carbon fiber reinforced plastic containing carbon fiber and a matrix component as a raw material,
Each surface is formed of a breathable material, and a housing-like heating cage that fills the carbon fiber reinforced plastic so as to have a predetermined bulk density;
A regenerative processing section that comprises a mesh transport section for transporting the heating cage and a heat treatment space having an elongated tunnel shape, and continuously heats the carbon fiber reinforced plastic to remove a part of the matrix component;
An apparatus for producing regenerated carbon fiber, comprising:

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