High-temperature and high-speed heat treatment device for conductive continuous fiber and method for recovering continuous recycled carbon fiber using same

Abstract

The present invention relates to: a heat treatment device capable of generating an induction heating effect in a conductive material having a continuous fiber form, which does not have a closed loop form, or even if it does, cannot be imparted with a heat treatment effect by the induction heating due to its low electrical resistance, through a closed loop that is formed by transferring the conductive material while bringing the conductive material into contact with a conductive roller 120; and a method for recovering a unidirectional carbon fiber, in which an impregnating resin has been completely removed from a waste carbon fiber product, by using the heat treatment device.

Description

High-temperature high-speed heat treatment apparatus for conductive continuous fibers and method for recovering continuous recycled carbon fibers using the same

[0001] The present invention relates to a high-temperature high-speed heat treatment apparatus for conductive continuous fibers (200) and a method for recovering continuous regenerated carbon fibers using the same. More specifically, the invention relates to a high-temperature high-speed heat treatment apparatus for conductive continuous fibers (200) that enables induction heating treatment for conductive continuous fibers (200) that are aligned in one direction and cannot form a closed circuit on their own, and a method for recovering continuous regenerated carbon fibers using the same.

[0002] When electrically conductive materials (metals, carbon fibers, Oxi-PAN, etc.) are placed in an electromagnetic field, eddy currents are formed due to their intrinsic properties, and when a closed circuit is formed, a heating effect occurs due to the intrinsic resistance of the material, and a heating method utilizing these characteristics is called induction heating.

[0003] The aforementioned induction heating technology is capable of selectively and uniformly heating only specific areas and reaching the desired temperature at high speed, resulting in high heating efficiency. Furthermore, it is environmentally friendly as it does not require the combustion of fossil fuels, and is therefore utilized in various industries, including the recovery process of recycled carbon fibers.

[0004] However, there is a problem in that the range of materials to which the heat treatment technology for electrically conductive materials using the aforementioned induction heating can be applied is limited.

[0005] First, since induction heating utilizes the principle that Joule heating generated by induced current and resistance raises the temperature, the efficiency of induction heating is high in materials with moderately high internal resistance, such as materials with a high iron (Fe) content or carbon fibers with a closed circuit, even if they are conductive; however, heat generation may be insufficient in cases where the resistance is too low, such as in non-ferrous metals (aluminum, copper, titanium) or ceramics.

[0006] In addition, since induction heating is generated by the continuous flow of eddy currents, continuous fiber-shaped materials that cannot form a closed loop have a problem in that even if eddy currents are formed by electromagnetic induction as shown in the left diagram of Fig. 1, they are continuously discharged into the atmosphere and heating does not occur.

[0007] In this regard, the right side of Fig. 1 is a thermal image showing the temperature change after applying an electromagnetic field to a unidirectional carbon fiber, which is a type of continuous fiber, and it can be confirmed that the temperature of the carbon fiber did not rise.

[0008] Therefore, in order to perform heating by the induction heating method, the material must be capable of forming a closed circuit on its own, such as in the form of a plate, structure, or rod for metals, or carbon fiber fabric (2D), preform (3D), or nonwoven fabric (Random Orientation) for organic materials.

[0009] If induction heating is to be performed on a continuous fiber-shaped material, a method may be considered in which a circular closed circuit is formed by connecting the ends of the fibers as shown in Fig. 2, or a square closed circuit is formed by cross-linking a conductive material between two strands of continuous fibers.

[0010] As related prior art, International Patent Publication No. 2023-091572 (published May 25, 2023) discloses a method for recycling carbon fiber composites in which carbon fibers are recovered by decomposing the matrix of the composite material through local induction heating of the carbon fibers using an electromagnetic field generated by applying a direct current or alternating current to the composite material containing carbon fibers.

[0011] However, the heating method according to the above patent document is not an induction heating method based on electromagnetic induction, but rather a resistance heating method using a DC power source after constructing a closed circuit by connecting both ends of the waste carbon fiber material to a power source through silver paste and copper tape. Therefore, in order to apply it to unidirectional carbon fibers, the power source must be directly connected to both ends of the conductive material, and consequently, there is a limitation in that it can only be performed in a configuration where the heating is cut into units of a predetermined length.

[0012] Therefore, research is needed on a heating device and a heating method capable of performing non-contact induction heating via electromagnetic induction without cutting continuous fibers aligned in a single direction, such as unidirectional (UD) carbon fibers, carbon fiber intermediates (Towpreg, Tape), and metal conductive fibers.

[0013] [Prior Art Literature]

[0014] [Patent Literature]

[0015] (Patent Document 1) International Patent Publication No. 2023-091572 (Published May 25, 2023)

[0016] The problem to be solved by the present invention is to provide a heat treatment device capable of generating an induction heating effect for a conductive material in the form of a continuous fiber that does not inherently have a closed-loop shape, or even if it does, cannot obtain a heat treatment effect by induction heating due to low electrical resistance.

[0017] In addition, the problem to be solved by the present invention is to provide a method for recovering recycled carbon fibers from waste carbon fiber products using the heat treatment device.

[0018] To achieve the above technical objective, the present invention discloses a high-temperature, high-speed heat treatment apparatus for conductive continuous fibers, comprising: a chamber (110); one or more winders for transporting a conductive continuous fiber (200) into the chamber (110); a plurality of cylindrical conductive rollers (120) installed horizontally inside the chamber (110), and a plurality of conductive rollers (120) provided at predetermined intervals in the vertical direction; and an induction coil provided respectively on the front and rear sides of the chamber (110) and applying a magnetic field to the conductive continuous fiber (200) transported by the conductive roller set; wherein the conductive continuous fiber (200) is transported upward by contacting the conductive rollers (120) to form a closed circuit, and the eddy current formed by the induction coil generates Joule heating.

[0019] According to one embodiment, the high-temperature high-speed heat treatment device for the conductive continuous fiber may include an inert gas inlet formed at the bottom of the chamber (110); and a gas outlet formed at the top of the chamber (110).

[0020] According to one embodiment, the distance between the induction coil and the conductive continuous fiber (200) may be 5 mm to 20 mm.

[0021] According to one embodiment, the alternating current applied to the induction coil has a frequency of 150 to 300 kHz, and the power may be 1000 to 5000 W.

[0022] According to one embodiment, there may be two or more transport paths through which the conductive continuous fiber (200) in contact with the conductive roller (120) is introduced into the chamber (110).

[0023] According to one embodiment, a plurality of conductive roller sets installed vertically within the chamber (110) are included at predetermined intervals, a partition wall is installed between the conductive roller sets, and the induction coils may be installed on both sides of the partition wall.

[0024] In addition, the present invention discloses a method for recovering unidirectional carbon fibers, characterized by comprising: (a) a step of drawing out unidirectional carbon fibers; (b) a step of transporting the unidirectional carbon fiber drawn out by step (a) to contact a conductive roller (120); and (c) a step of applying an electromagnetic field to the unidirectional carbon fiber contacted by step (b) to generate an eddy current.

[0025] According to one embodiment, step (c) can be performed in an inert gas atmosphere.

[0026] According to one embodiment, the unidirectional carbon fiber can be heated to a range of 500 to 1200 ℃.

[0027] The high-temperature high-speed heat treatment device for a conductive continuous fiber (200) according to the present invention has the advantage that induction heating can be performed by forming a closed circuit at a location where the conductive continuous fiber (200), which has low induction heating efficiency, comes into contact with a conductive roller (120), and since the conductive continuous fiber (200) is continuously transported along the location where the closed circuit is formed, uniform heat treatment is performed over the entire conductive continuous fiber (200). Furthermore, by utilizing a non-contact heating means using electromagnetic induction by an induction coil, the conductive continuous fiber (200) can be transported into the device without the need to cut it to a predetermined length or size, thereby enabling collective heat treatment.

[0028] In addition, the method for recovering unidirectional carbon fibers according to the present invention can be performed by a high-temperature, high-speed heat treatment device for the conductive continuous fiber (200), and can completely remove impregnated resins, etc. remaining on the unidirectional carbon fibers recovered by a conventional process, and can suppress diameter reduction or physical property deterioration due to oxidation during the heat treatment process.

[0029] Figure 1 is a diagram showing the current flow and temperature change when unidirectional carbon fibers are exposed to an electromagnetic field.

[0030] FIG. 2 is a diagram showing an exemplary form of a closed circuit for producing an induction heating effect on a continuous fiber and the temperature change when a unidirectional carbon fiber with a closed circuit constructed according to each exemplary form is exposed to an electromagnetic field.

[0031] FIG. 3 is a diagram illustrating an exemplary perspective view of a high-temperature, high-speed heat treatment apparatus for a conductive continuous fiber (200) according to the present invention.

[0032] FIG. 4 is a simplified diagram showing the left side view (left) and front view (right) of a high-temperature high-speed heat treatment device for a conductive continuous fiber (200) according to the present invention.

[0033] Figure 5 is a graph and photograph showing the diameter and surface condition of unidirectional carbon fibers according to Example 1 and Comparative Example 1.

[0034] Figure 6 is a graph showing the tensile strength test results for unidirectional carbon fibers according to Example 1, Example 2 and Comparative Example 1.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by a skilled expert in the art to which the present invention pertains. In general, the nomenclature used herein is well known and commonly used in the art.

[0036] Throughout this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0037] In each drawing of the present invention, the sizes or dimensions of the structures are depicted enlarged or reduced compared to the actual size to ensure clarity of the invention, and known configurations are omitted to reveal characteristic configurations, so the invention is not limited to the drawings.

[0038] In describing the principles of a preferred embodiment of the present invention in detail, if it is determined that a specific description of related known functions or configurations could unnecessarily obscure the essence of the present invention, such detailed description is omitted.

[0039] Throughout this specification, 'conductive continuous fiber (200)' refers to a material comprising one or more strands of electrically conductive fibers that are continuously arranged in the same direction without crosslinking between the fibers and cannot independently form a closed circuit, and may be, for example, one or more of unidirectional (UD) carbon fibers, carbon fiber intermediates (towpreg), or metal wires. In the case of the unidirectional (UD) carbon fibers or carbon fiber intermediates (towpreg), the surface may be impregnated with resin, and the material may be a polymer resin such as epoxy resin, nylon resin, or polypropylene resin. According to an embodiment, the conductive continuous fiber (200) may be provided in a reel form, and the end of the conductive continuous fiber (200) unwound from the reel may be fed into the high-temperature high-speed heat treatment device for the conductive continuous fiber (200) according to the present invention, and heat treatment may be performed.

[0040] To achieve the above goal, the present invention,

[0041] A high-temperature, high-speed heat treatment apparatus for a conductive continuous fiber (200) is disclosed, comprising: a chamber (110); one or more winders for transporting a conductive continuous fiber (200) into the chamber; a plurality of cylindrical conductive rollers (120) installed horizontally inside the chamber (110), and a plurality of conductive roller sets having a plurality of conductive rollers (120) arranged vertically at predetermined intervals; and an induction coil each provided on the inner side of the front and rear portions of the chamber (110) and applying a magnetic field to the conductive continuous fiber (200) transported by the conductive roller set; wherein the conductive continuous fiber (200) is transported upward by contacting the conductive rollers (120) to form a closed circuit, and the eddy current formed by the induction coil generates Joule heating.

[0042] One embodiment of the high-temperature high-speed heat treatment device for the above-mentioned conductive continuous fiber (200) can be shown as in FIG. 3 and FIG. 4, and the present invention will be described in more detail below with reference to the drawings.

[0043] In the high-temperature high-speed heat treatment device (100) for the above-mentioned conductive continuous fiber (200), the chamber (110) is configured to form a sealed space in which heat treatment by induction heating of the conductive continuous fiber (200) takes place, and the front and rear portions of the chamber may be provided with an openable front door (111) and a rear door (112), and the interior can be opened to check the interior when necessary for maintenance, etc.

[0044] In the present invention, doors may be installed on both the front and rear sides, or on only one side, depending on the necessity; furthermore, if the chamber design does not require a door, it is acceptable not to install one. For the sole purpose of explaining the present invention, the following description focuses on the case where doors are installed on both the front and rear sides, but is not limited thereto.

[0045] In the chamber (110), the front door (111) may include an insertion hole into which a conductive continuous fiber (200) can be introduced, and the rear door (112) may include an discharge hole into which the conductive continuous fiber (200) that has undergone heat treatment can be discharged and recovered.

[0046] The chamber (110) may be made of a conventional material capable of withstanding the high-temperature environment generated by induction heating. For example, it is preferable to use a non-conductive material or a non-ferrous metal that does not absorb the magnetic field generated by the induction coil (130) described later, but is not limited thereto. Additionally, an insulating material may be provided inside the chamber (110) to increase heating efficiency.

[0047] In the high-temperature high-speed heat treatment device (100) for the above-mentioned conductive continuous fiber (200), a winder (not shown) corresponds to a configuration for transporting the conductive continuous fiber (200) into the chamber (110), and the conductive continuous fiber (200) after heat treatment is completed can be continuously transported out of the chamber (110).

[0048] The above winder may use any known conveying device that allows the conductive continuous fiber (200) to be continuously conveyed into the chamber (110) without limitation, such as a reel holder that fixes a reel on which the conductive continuous fiber (200) is wound before heat treatment; a rewinder that rewinds the conductive continuous fiber (200) unwound from the reel when it is heat-treated; and a rotary motor that drives the rewinder; but is not limited thereto.

[0049] According to an embodiment, the winder may additionally be equipped with electronic control means such as a console and a memory, and accordingly, the driving speed of the winder and the conveying speed of the conductive continuous fiber (200) can be controlled.

[0050] In the high-temperature high-speed heat treatment device (100) for the above-mentioned conductive continuous fiber (200), the conductive roller set is configured such that a plurality of cylindrical conductive rollers (120) are installed horizontally inside the chamber (110), and a plurality of conductive rollers (120) are provided at predetermined intervals in the vertical direction, and one or more conductive roller sets may be installed at predetermined intervals.

[0051] The conductive roller (120) is a cylindrical structure made of a conductive material and forms a path for the conductive continuous fiber (200) to move within the chamber (110), while simultaneously serving to support the path so that it can move steadily. The conductive continuous fiber (200) can be transported upward while making contact sequentially starting from the conductive roller (120) located at the bottom.

[0052] In order to maintain a constant distance from the induction coil (130) described later, the conductive roller (120) is preferably arranged in a line from the bottom to the top of the chamber (110) as exemplarily illustrated in FIG. 4, but is not limited thereto and can be arranged in any variety so that the user can move along a desired path.

[0053] The high-temperature high-speed heat treatment device (100) for a conductive continuous fiber (200) according to the present invention is characterized by the technical feature that the conductive roller (120) simultaneously conveys two or more conductive continuous fibers (200, 200') along the longitudinal direction, and the two or more conductive continuous fibers (200, 200') are conveyed side by side along the path while sequentially contacting the conductive roller (120), thereby forming one or more closed circuits (300) in the form of a bridge as shown in FIG. 2, which consists of a conductive continuous fiber (200) - a lower conductive roller (120) - a conductive continuous fiber (200') - an upper conductive roller (120').

[0054] At this time, since the two or more conductive continuous fibers (200, 200') are continuously conveyed through the winder, induction heating proceeds during the time that the two or more conductive continuous fibers (200, 200') rise inside the chamber (110) and come into contact with the conductive roller (120), and accordingly, the entire section of the two or more conductive continuous fibers (200, 200') is heated continuously and uniformly, which corresponds to the technical features of the present invention.

[0055] The above two or more conductive continuous fibers (200, 200') can be transported by being lifted by the conductive roller in various paths to maximize the contact area with the conductive roller (120).

[0056] For example, contact can be made to rise across the space between the lower conductive roller (120) and the upper conductive roller (120'). For instance, as illustrated in the left side view in FIG. 4(a), a conductive continuous fiber (200) wound around the lower conductive roller (120) and rising from the left side of the roller can make contact with the upper conductive roller (120') by winding into the right side of the upper conductive roller (120') across the space between the lower conductive roller (120) and the upper conductive roller (120'). This is merely an example and is not limited thereto, and the conductive continuous fiber (200) can be raised while making contact with a plurality of conductive rollers in various ways.

[0057] A ball bearing may be provided in the center of the conductive roller (120), and accordingly, the conductive roller (120) can assist in the smooth transport of the conductive continuous fiber (200) by rotating the ball bearing around the central axis.

[0058] The conductive material constituting the conductive roller (120) may be any non-ferrous metal material capable of withstanding the heating temperature of two or more conductive continuous fibers (200, 200'), such as one or more of copper, aluminum, and titanium.

[0059] In the high-temperature high-speed heat treatment device (100) for the conductive continuous fiber (200), the induction coil (130), which is respectively provided on the inner side of the front and rear portions of the chamber (110), is configured to induce the formation of an eddy current inside the conductive continuous fiber (200) by forming a magnetic field on both sides of the conductive continuous fiber (200) that is transported upward along a path provided by the conductive roller (120).

[0060] The above eddy current can be conducted along the fiber direction of the conductive continuous fiber (200) toward both ends, and circulates in a closed circuit (300) formed by contact between the conductive continuous fiber (200) and the conductive roller (120), and in the process, Joule heating is generated by the intrinsic resistance of the conductive continuous fiber (200).

[0061] As the temperature of the conductive continuous fiber (200) rises due to the above-mentioned Joule heat, the conductive continuous fiber (200) may undergo heat treatment, and during this process, impurities such as impregnated resin or oxide that may be present on the surface may be removed by combustion, vaporization, or thermal decomposition.

[0062] Since the present invention generates eddy currents by electromagnetic induction of the induction coil (130) installed on the front and rear sides of the chamber (110), unlike general resistance heating, there is no need for the power supply to be directly connected to the conductive continuous fiber (200), and since the conductive continuous fiber (200) being transported can be heated for a certain amount of time, there is an advantage that continuous and uniform induction heating can be performed over the entire conductive continuous fiber (200).

[0063] Meanwhile, the induction coil (130) may be provided in the front door (111) and the rear door (112), and may be installed and arranged in any shape capable of generating electromagnetic induction in the conductive continuous fiber (200) present on the transport path of the conductive continuous fiber (200) within the chamber (110), such as in a planar spiral or a current-crossing shape. FIG. 4 illustrates an exemplary induction coil (130) provided in a planar spiral shape on the inner side of the front door (111) and the rear door (112).

[0064] It is desirable that the distance between the conductive continuous fiber (200) and the adjacent induction coil (130) be 5 mm to 20 mm in order to provide a transport space for the conductive continuous fiber (200) and at the same time maximize the efficiency of electromagnetic induction.

[0065] In addition, the induction coil (130) may be connected to a power supply unit to apply alternating current, and the frequency and power of the alternating current may be appropriately adjusted in consideration of heating efficiency and the stability of heat treatment. According to a preferred embodiment, the alternating current may have a frequency of 150 to 300 kHz and a power of 1000 to 5000 W, but is not limited thereto.

[0066] In addition, regarding the pattern of the induction coil (130), if it is provided in a planar spiral shape, the number of turns of the coil may be 1 to 5 turns.

[0067] The temperature of the conductive continuous fiber (200) heated by the induction coil (130) can be individually set according to the material of the conductive continuous fiber (200) and the purpose of the heat treatment. For example, in the case of waste carbon fiber, it is preferable to have a temperature of 500 to 1200°C for effective thermal decomposition of foreign substances, and in the case of metal fiber, it is preferable to have it heated in the range of 600 to 800°C to improve hardness through structural deformation of the metal material.

[0068] In addition, the high-temperature high-speed heat treatment device (100) for a conductive continuous fiber (200) according to the present invention may additionally include an inert gas inlet; and a gas outlet.

[0069] The above-mentioned inert gas inlet (not shown) is preferably provided at the bottom of the chamber (110), and by introducing an inert gas (400) into the chamber (110) through the inert gas inlet, the heat treatment process by induction heating of the conductive continuous fiber (200) can be performed in an inert gas environment. This prevents oxidation of the conductive continuous fiber (200), such as carbon fiber, during the induction heating process.

[0070] The above inert gas (400) may be a known inert gas that does not react with the conductive continuous fiber (200) at high temperatures, such as one or more of nitrogen, argon, and helium.

[0071] The above gas outlet (420) discharges exhaust gas (410) formed inside the chamber (110) to the outside of the chamber (110), and the exhaust gas (410) may contain impurities such as vaporized or thermal decomposition products of an impregnating resin attached to the surface of an inert gas (400) and a conductive continuous fiber (200).

[0072] According to the embodiment, the gas outlet (420) may additionally include a configuration such as a filter that separates inert gas (400) and impurities from the exhaust gas (410).

[0073] In addition, the high-temperature high-speed heat treatment device (100) for a conductive continuous fiber (200) according to the present invention may include two or more sets of conductive rollers (120) according to an embodiment, and two or more conductive continuous fibers (200) may be introduced into a chamber (110) for each set of conductive rollers (120).

[0074] In this regard, FIG. 4 illustrates an exemplary high-temperature, high-speed heat treatment device (100) for conductive continuous fibers (200), wherein conductive rollers (120) are arranged in two rows in a vertical direction, i.e., a set of two conductive rollers (120). FIG. 4 shows that two or more conductive continuous fibers (200, 200') are conveyed along the conductive rollers (120) provided in the left row, but if necessary, it is possible to heat treat by separately conveying two or more conductive continuous fibers (200, 200') to the conductive rollers (120) provided in the right row.

[0075] Accordingly, each of the two or more conductive continuous fibers (200, 200') conveyed through each conductive roller (120) can be heat-treated individually.

[0076] More specifically, each of the two or more conductive continuous fibers (200, 200') conveyed by each of the sets of conductive rollers (120) may be the same or different from each other, and the winding speed of the winder that winds each of the two or more conductive continuous fibers (200, 200') may also be the same or different from each other. Accordingly, it is possible to perform induction heating optimized for each of the different types of conductive continuous fibers (200, 200') individually in a single device, and it is possible to perform induction heating at different speeds and temperatures even when the same conductive continuous fiber (200, 200') is fed.

[0077] In the case where two or more sets of conductive rollers (120) are provided as described above, a partition wall may be additionally provided within the chamber (110) to separate the space between the two or more sets of conductive rollers (120), and induction coils (130) may also be provided on both sides of the partition wall.

[0078] As illustrated in the above Fig. 4, when there are two or more transfer paths formed by the conductive roller (120), one side (left side) of the conductive roller (120) can maintain a close distance from the induction coil (130), but the opposite side (right side) is far from the induction coil (130), so the effect of induction heating may be reduced even though a closed circuit (300) is formed.

[0079] Accordingly, by providing a partition (not shown) that separates the transfer path as described above and an induction coil (130) on one or both sides of the partition, the closed circuit (300) provided on the opposite side of the conductive roller (120) can also be brought close to the induction coil (130) to maximize the induction heating effect.

[0080] In addition, the present invention discloses a method for recovering unidirectional carbon fibers, characterized by comprising: (a) a step of drawing out unidirectional carbon fibers from a waste carbon fiber product; (b) a step of transporting the carbon fibers drawn out by step (a) to contact a conductive roller (120); and (c) a step of applying an electromagnetic field to the carbon fibers contacted by step (b) to generate eddy currents.

[0081] The above method for recovering recycled carbon fibers corresponds to a method capable of recovering high-quality recycled carbon fibers by completely removing impregnating resins, etc. that were not completely removed from the surface of waste carbon fibers recovered by conventional technology through an induction heating method, and each step is described in detail below in chronological order.

[0082] The above step (a) corresponds to the step of preparing waste carbon fibers that serve as raw materials for recycled carbon fibers recovered according to the present invention.

[0083] The waste carbon fiber product in step (a) above may be, for example, a hydrogen pressure vessel made of unidirectional carbon fiber, and the process of drawing out the carbon fiber may use a conventional carbon fiber recovery process without limitation, in which carbon fibers are separated from a matrix composed of resin by acid treatment or heat treatment and then drawn out. The unidirectional carbon fiber recovered according to step (a) above may be in the form of carbon fiber yarn or a strip in which a plurality of carbon fiber yarns arranged side by side are fixed by an impregnation resin, and the impregnation resin may remain on the surface.

[0084] Step (b) above corresponds to a step of forming a closed circuit by contacting the unidirectional carbon fiber recovered by Step (a) above with a conductive roller (120). As previously mentioned, the unidirectional carbon fiber is a type of conductive continuous fiber (200) and, by itself, cannot form a closed circuit, so the induction heating efficiency by electromagnetic induction is very low. However, by contacting it with the conductive roller (120) as described above, a closed circuit can be formed, and induction heating by electromagnetic induction can occur. In Step (b), detailed information regarding the shape, structure, and arrangement of the conductive roller (120) for forming the closed circuit is the same as previously mentioned, so it is omitted to avoid duplication.

[0085] Step (c) above corresponds to a step of performing induction heating by generating eddy currents by electromagnetic induction in the unidirectional carbon fiber in which a closed circuit is formed by Step (b), and as Step (c) is performed, impurities such as impregnating resin remaining on the surface of the unidirectional carbon fiber can be removed by thermal decomposition or vaporization by the induction heating.

[0086] In step (c) above, it is preferable that the unidirectional carbon fiber be continuously transported using a configuration such as a winder, and the electromagnetic induction may be generated by an induction coil connected to an alternating current.

[0087] The eddy current generated by the above electromagnetic induction can be conducted along the unidirectional carbon fiber and can generate heat by circulating through the closed circuit formed by step (b).

[0088] At this time, the heating temperature in step (c) above is preferably 500 to 1200 ℃ in terms of the thermal decomposition efficiency of foreign substances present on the surface of carbon fiber waste.

[0089] According to the embodiment, it is preferable that step (c) be performed in an inert gas atmosphere to prevent oxidation of the carbon fiber, and the type of inert gas is the same as that mentioned in the preceding embodiment.

[0090] Steps (b) and (c) above can be performed using a high-temperature high-speed heat treatment device (100) for a conductive continuous fiber (200) according to the preceding embodiment, and since the induction heating treatment process of a unidirectional carbon fiber by the high-temperature high-speed heat treatment device (100) for the conductive continuous fiber (200) is the same as previously mentioned, it is omitted to avoid duplication.

[0091]

[0092] The present invention will be described in more detail below with reference to examples and comparative examples. However, it will be obvious to those skilled in the art that these examples are intended to explain the present invention more specifically and that the scope of the present invention is not limited by them.

[0093] (Example)

[0094] Example 1

[0095] After transferring the T300 carbon fiber towpreg impregnated with epoxy resin into the chamber (110) of the high-temperature high-speed heat treatment device for the conductive continuous fiber (200) according to the present invention through a winder (110), an alternating current of 150 to 300 A at a frequency of 180 kHz was applied to an induction coil to perform high-frequency induction heating on the recycled carbon fiber, and the output was adjusted in the range of 2500 to 5000 W. The high-frequency alternating current was applied for 5 seconds, and it was confirmed through thermal imaging that the temperature of the carbon fiber rose to 1000℃. After the induction heating was performed as described above, the recycled carbon fiber (IH-Recycled Carbon Fiber from Epoxy Composition, rCF) transferred outside the chamber (110) was recovered.

[0096] Example 2

[0097] In the above Example 1, the carbon fiber towpreg was carried out in the same manner as in Example 1, except that it was impregnated with PA6 polyamide resin, to prepare the recovered carbon fiber (IH-Recycled Carbon Fiber from PA6 Composition).

[0098] Comparative Example 1

[0099] A T300 carbon fiber towpreg (Virgin Carbon Fiber, vCF) was prepared before heat treatment according to Example 1 above.

[0100]

[0101] Experimental Example 1: Confirmation of Surface Condition According to Induction Heat Treatment

[0102] The diameter of the towpreg according to Example 1 and Comparative Example 1 was measured, and the result is shown in FIG. 5(a). According to FIG. 5(a), it can be confirmed that the diameter of the recycled carbon fiber according to Example 1 does not show a significant difference compared to the diameter of the recycled carbon fiber according to Comparative Example 1.

[0103] In addition, the surface condition of the carbon fibers according to Example 1 and Comparative Example 1 was shown in FIG. 5(b). According to FIG. 5(b), in the case of Comparative Example 1 (Virgin Carbon Fiber), it can be seen that the fibers are surrounded by epoxy resin and that all fibers are physically bonded by the epoxy resin. In contrast, in the case of Example 1 (IH-Recycled Carbon Fiber), the recovered carbon fibers exhibited a smooth surface in which no epoxy resin or pyrolysis byproducts (char) were present.

[0104]

[0105] Experimental Example 2: Changes in physical properties due to induction heat treatment

[0106] Tensile tests were performed on the carbon fibers according to Example 1, Example 2, and Comparative Example 1, and the results are shown in Fig. 6. Fig. 6(a) shows the tensile modulus expressed in GPa, and Fig. 6(b) shows the tensile strength expressed in MPa. According to Fig. 6, it can be confirmed that the tensile modulus and tensile strength of the recycled carbon fibers according to Example 1 and Example 2 are at a level almost equivalent to the tensile strength of the carbon fiber according to Comparative Example 1.

[0107] Through the above experimental example, it can be confirmed that the high-temperature high-speed heat treatment apparatus for conductive continuous fibers (200) according to the present invention and the method for recovering recycled carbon fibers using the same can cleanly remove various impregnating resins present on the surface, and that during this process, no reduction in diameter due to oxidation or deterioration of physical properties due to damage to the fiber surface occurs.

[0108]

[0109] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto and can be implemented with various modifications within the scope of the claims, the detailed description of the invention, and the attached drawings, and it is obvious that such modifications also fall within the scope of the present invention.

[0110] [Explanation of the symbol]

[0111] 100: High-temperature, high-speed heat treatment device for conductive continuous fibers

[0112] 110: Chamber

[0113] 111: Front door

[0114] 112: Rear door

[0115] 120: Conductive roller

[0116] 130: Induction coil

[0117] 200, 200': Conductive continuous fiber

[0118] 300: Closed circuit

[0119] 400: Inert gas

[0120] 410: Exhaust gas

[0121] 420: Gas outlet

[0122] The high-temperature, high-speed heat treatment apparatus for conductive continuous fibers according to the present invention and the method for recovering continuous recycled carbon fibers using the same have the advantage of performing uniform heat treatment over the entire conductive continuous fiber. Furthermore, since a non-contact heating means using electromagnetic induction by an induction coil is utilized, the conductive continuous fibers can be transported into the apparatus for batch heat treatment without the need to cut them to a predetermined length or size, thus demonstrating industrial applicability.

Claims

1. Chamber (110); One or more winders for transporting a conductive continuous fiber (200) into the chamber (110); A plurality of cylindrical conductive rollers (120) are installed horizontally inside the chamber (110), and a conductive roller set is provided with a plurality of conductive rollers (120) arranged vertically at predetermined intervals; and It includes an induction coil that is respectively provided on the inner side of the front and rear portions of the chamber (110) and applies a magnetic field to a conductive continuous fiber (200) conveyed by the conductive roller set; A high-temperature, high-speed heat treatment device for conductive continuous fibers, characterized in that the conductive continuous fiber (200) is transported upward while in contact with a conductive roller (120) forming a closed circuit, and the eddy current formed by the induction coil generates Joule heating.

2. In Paragraph 1, An inert gas inlet formed at the bottom of the chamber (110); and A high-temperature, high-speed heat treatment apparatus for conductive continuous fibers, characterized by including a gas outlet formed at the top of the chamber (110).

3. In Paragraph 1, A high-temperature, high-speed heat treatment apparatus for conductive continuous fibers, characterized in that the distance between the induction coil and the conductive continuous fiber (200) is 5 mm to 20 mm.

4. In Paragraph 1, A high-temperature, high-speed heat treatment apparatus for conductive continuous fibers, characterized in that the alternating current applied to the induction coil has a frequency of 150 to 300 kHz and a power of 1000 to 5000 W.

5. In Paragraph 1, A high-temperature, high-speed heat treatment apparatus for conductive continuous fibers, characterized in that there are two or more transport paths through which a conductive continuous fiber (200) in contact with the conductive roller (120) is introduced into a chamber (110).

6. In Paragraph 1, A set of conductive rollers installed vertically within the chamber (110) includes a plurality of rollers at predetermined intervals. A partition is installed between the above sets of conductive rollers, and A high-temperature, high-speed heat treatment apparatus for conductive continuous fibers, characterized in that the induction coils are installed on both sides of the partition wall. 7.(a) A step of drawing out unidirectional carbon fibers; (b) a step of transporting the unidirectional carbon fiber drawn out by step (a) above to contact a conductive roller (120); and (c) a step of generating eddy currents by applying an electromagnetic field to the unidirectional carbon fiber that has come into contact with the conductive roller (120) by the above step (b); characterized by comprising a method for recovering unidirectional carbon fibers.

8. In Paragraph 7, The above step (c) is characterized by being performed in an inert gas atmosphere, Method for recovering unidirectional carbon fibers.

9. In Paragraph 7, A method for recovering unidirectional carbon fibers, characterized in that the unidirectional carbon fibers are heated to a range of 500 to 1200 ℃.

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