Method and device for producing carbon fiber sheet molding compound

Abstract

One of the main purposes of the present invention is to provide improvements pertaining to a method for producing a carbon fiber sheet molding compound.　This method for producing a carbon fiber sheet molding compound includes transferring a continuous carbon fiber bundle pulled out from a package to a chopper via a guide tube, performing loosening treatment of the continuous carbon fiber bundle prior to the passage thereof through the guide tube, cutting the continuous carbon fiber bundle by means of the chopper, dropping the chopped carbon fiber bundle thus generated onto a moving carrier film and thereby forming a random mat, and impregnating the random mat with a paste comprising a thermosetting resin composition.

Description

Carbon fiber sheet molding compound manufacturing method and carbon fiber sheet molding compound manufacturing device

[0001] The present invention relates primarily to a method and an apparatus for producing a carbon fiber sheet molding compound. This application claims priority based on Japanese Patent Application No. 2023-2937, filed with the Japan Patent Office on January 12, 2023, the contents of which are incorporated herein by reference.

[0002] Carbon fiber reinforced plastic (CFRP) is a composite material that uses carbon fiber as a reinforcing material. Due to its high strength and light weight, CFRP has recently been used in various transportation equipment components, including automobiles, ships, railway vehicles, manned aircraft, and unmanned aerial vehicles. One of the intermediate materials used in molding CFRP products is carbon fiber sheet molding compound (hereinafter also referred to as "CF-SMC"). CF-SMC is manufactured by forming a random mat from chopped carbon fiber bundles obtained by cutting continuous carbon fiber bundles into short pieces, and then impregnating the random mat with a paste of a thermosetting resin composition.

[0003] When producing a composite material reinforced with chopped carbon fiber bundles, a technique has been proposed in which continuous carbon fiber bundles are treated with a protruding roll before being cut with a chopper. When the continuous carbon fiber bundles are loosened by this treatment and then cut, a large number of chopped carbon fiber bundles with a smaller bundle size than the continuous carbon fiber bundles before being cut are produced, resulting in a high reinforcing effect (Patent Document 1). The bundle size of a carbon fiber bundle refers to the number of carbon fiber filaments that make up the carbon fiber bundle (the same applies hereinafter).

[0004] US Patent Application Publication No. 2012 / 0213997

[0005] One object of the present invention is to provide an improvement in a method for manufacturing a carbon fiber sheet molding compound. Another object of the present invention is to provide an improvement in an apparatus for manufacturing a carbon fiber sheet molding compound. The problems solved by each embodiment of the present invention may be explicitly or implicitly disclosed in this specification.

[0006] According to one aspect of the present invention, there is provided a method for producing a carbon fiber sheet molding compound, comprising: feeding a continuous carbon fiber bundle pulled out from a package to a chopper through a guide tube; subjecting the continuous carbon fiber bundle to a loosening treatment before passing it through the guide tube; dropping chopped carbon fiber bundles produced by cutting the continuous carbon fiber bundle with the chopper onto a running carrier film to form a random mat; and impregnating the random mat with a paste made of a thermosetting resin composition.

[0007] According to another aspect of the present invention, there is provided a method for producing a carbon fiber sheet molding compound, comprising: feeding a continuous carbon fiber bundle drawn out from a package to a chopper; subjecting the continuous carbon fiber bundle to a loosening treatment before cutting with the chopper; dropping chopped carbon fiber bundles produced by cutting the continuous carbon fiber bundle with the chopper onto a traveling carrier film to form a random mat; and impregnating the random mat with a paste made of a thermosetting resin composition, wherein the travel distance of the continuous carbon fiber bundle from the loosening treatment to the cutting with the chopper is more than 3 m.

[0008] According to yet another aspect of the present invention, there is provided a method for producing a carbon fiber sheet molding compound, comprising: cutting continuous carbon fiber bundles with a chopper, producing chopped carbon fiber bundles, and dropping the resulting chopped carbon fiber bundles onto a running carrier film to form a random mat; impregnating the random mat with a paste comprising a thermosetting resin composition; subjecting the continuous carbon fiber bundles to a loosening treatment before cutting with the chopper; and dispersing the chopped carbon fiber bundles with a rotationally driven dispersion roll before dropping them onto the carrier film.

[0009] According to yet another aspect of the present invention, there is provided a method for producing a carbon fiber sheet molding compound, comprising: cutting continuous carbon fiber bundles with a chopper, causing chopped carbon fiber bundles to fall onto a running carrier film to form a random mat; impregnating the random mat with a paste consisting of a thermosetting resin composition; and dividing the space into a plurality of regions along the T direction using at least one partition, into which the chopped carbon fiber bundles fall toward the carrier film, wherein the at least one partition is made of metal and is grounded.

[0010] According to yet another aspect of the present invention, there is provided an apparatus for manufacturing a carbon fiber sheet molding compound, comprising: a chopper arranged above a carrier film running path; a guide tube for passing a continuous carbon fiber bundle pulled out of a package and fed to the chopper; and a bundle loosener arranged upstream of the guide tube for loosening the continuous carbon fiber bundle.

[0011] According to yet another aspect of the present invention, there is provided an apparatus for manufacturing a carbon fiber sheet molding compound, comprising: a chopper arranged above a running path of a carrier film; and a bundle relaxer for loosening continuous carbon fiber bundles that are pulled out of a package and fed to the chopper, wherein the distance from the bundle relaxer to the chopper along the running path of the continuous carbon fiber bundles is greater than 3 m.

[0012] According to yet another aspect of the present invention, there is provided a carbon fiber sheet molding compound manufacturing apparatus having a chopper arranged above a carrier film running path, a bundle loosener for loosening continuous carbon fiber bundles fed to the chopper, and a rotationally driven dispersion roll for dispersing chopped carbon fiber bundles produced by cutting the continuous carbon fiber bundles with the chopper.

[0013] According to yet another aspect of the present invention, there is provided a carbon fiber sheet molding compound manufacturing device comprising: a chopper arranged above a carrier film running path; and at least one partition formed of metal and grounded, wherein the at least one partition divides a space into a plurality of regions along the T direction, into which chopped carbon fiber bundles produced by cutting continuous carbon fiber bundles with the chopper fall toward the running path.

[0014] In accordance with preferred embodiments, improvements are provided to a method or apparatus for producing carbon fiber sheet molding compounds.

[0015] FIG. 1 shows the configuration of a CF-SMC manufacturing apparatus according to one embodiment. FIG. 2 shows an example of a protrusion roll. FIG. 3 shows a gear pair consisting of two meshing spur gears with continuous carbon fiber bundles meshed therebetween. FIG. 4 shows a gear pair with the spacing between the gears widened to allow the splice between the continuous carbon fiber bundles to pass through. FIG. 5 shows a bundle relaxer in which only one continuous carbon fiber bundle is processed at a time by one gear pair. FIG. 6 shows the configuration of a chopper. FIG. 7 shows an example of a pin roll. FIG. 8 shows an example of a cage roll, showing the cage roll viewed from a direction parallel to the rotation axis. FIG. 9 shows the cage roll of FIG. 8 viewed from a direction perpendicular to the rotation axis. FIG. 10 shows a booth in which the main components of a pin roll-type dispersion roll are arranged. The running direction of the first carrier film is from left to right within the plane of the drawing. FIG. 11 shows a booth in which the main components of a pin roll-type dispersion roll are arranged. The running direction of the first carrier film is from the back to the front of the paper. Fig. 12 shows that the space into which chopped carbon fiber bundles, generated by cutting the continuous carbon fiber bundles with the chopper, fall is divided into multiple regions along the T direction by a partition arranged below the chopper. The running direction of the first carrier film is from the back to the front of the paper.

[0016] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. The dimensional ratios in the drawings are for the convenience of explanation and may differ from the actual ratios. Furthermore, the same components in the drawings will be indicated by the same reference numerals, and descriptions of overlapping components may be omitted.

[0017] 1. Method and Apparatus for Producing CF-SMC CF-SMC can be produced by a production method according to one embodiment of the present invention using, for example, a production apparatus whose basic configuration is shown in FIG. 1. The CF-SMC production apparatus 70 shown in FIG. 1 includes a bundle loosener BL, a guide tube GT, guide rolls GR, a chopper 1, a first coater 2a, a second coater 2b, and an impregnator 3. The chopper 1 is disposed above the travel path of the first carrier film 51. When the first carrier film 51 travels below the chopper 1, its surface is held horizontal. In this specification, the horizontal direction perpendicular to the travel direction of the first carrier film may be referred to as the T direction. In FIG. 1, the T direction is perpendicular to the plane of the paper.

[0018] A preferred embodiment of a CF-SMC manufacturing method will be described below, taking the case where the manufacturing apparatus shown in FIG. 1 is used as an example. First, a continuous carbon fiber bundle 10 is drawn out from a package P. The package P may use a bobbin or may not use a bobbin. The bundle size of the continuous carbon fiber bundle 10 is usually 12K or more, and may be 15K or more, 18K or more, 24K or more, 36K or more, 40K or more, 48K or more, etc. There is no particular upper limit to the bundle size of the continuous carbon fiber bundle 10, but it may be 200K or less, 150K or less, 100K or less, 80K or less, 60K or less, etc. Here, K is a symbol representing 1000, and for example, 12K means 12,000, 48K means 48,000, and 100K means 100,000.

[0019] The continuous carbon fiber bundle 10 drawn out from the package P is loosened by treatment with a bundle loosener BL before being passed through the guide tube GT. Loosening the carbon fiber bundle means weakening the bonds between the carbon fiber filaments that make up the bundle. In the carbon fiber bundle, the carbon fiber filaments are bonded to each other via a resin called a sizing agent, so the carbon fiber bundle can be loosened by applying an external mechanical force to partially break these bonds.

[0020] Chopped carbon fiber bundles obtained by cutting loosened continuous carbon fiber bundles contain many fibers with smaller bundle sizes than chopped carbon fiber bundles obtained by cutting the same continuous carbon fiber bundles without loosening them. This is because loosened continuous carbon fiber bundles tend to separate into multiple bundles when cut. As described in the aforementioned Patent Document 1, fine chopped carbon fiber bundles with smaller bundle sizes have a higher reinforcing effect when used in CFRP, and this is well known among those skilled in the art.

[0021] The bundle loosener according to one example may include a means for piercing the continuous carbon fiber bundle with protrusions. A typical example of such a means is a protrusion roll. As shown in FIG. 2, the protrusion roll 11 is a roll having a large number of protrusions 12 arranged on its outer periphery. Suitable examples of the protrusion roll include those described in the aforementioned Patent Document 1. The peripheral speed on the outer periphery of the protrusion roll is set to be approximately equal to the feed speed of the continuous carbon fiber bundle, for example, within a range of 0.9 to 1.1 times the feed speed. The wrap angle of the continuous carbon fiber bundle on the protrusion roll is preferably 30° or more, more preferably 60° or more, and even more preferably 90° or more. Sufficient tension is applied to the continuous carbon fiber bundle so that the protrusions are reliably pierced.

[0022] The arrangement pattern of the multiple protrusions on the surface of the protrusion-equipped roll preferably has periodicity in the circumferential and axial directions. The circumferential period is preferably 10 mm or less, more preferably 5 mm or less. The axial period is preferably 5 mm or less, more preferably 3 mm or less. There is no particular lower limit to each period, but it may be, for example, 1 mm or more.

[0023] A plurality of continuous carbon fiber bundles can be arranged in parallel to each other and supplied to a single protruding roll, and simultaneously subjected to a loosening treatment. The bundle loosener may further have a means for spreading the continuous carbon fiber bundles upstream or downstream of the means for piercing the continuous carbon fiber bundles with protrusions. Examples of the means for spreading the carbon fiber bundles include a spreader roll and a spreader bar.

[0024] An example bundle loosener may have a gear pair consisting of two gears meshing with each other. The two gears are preferably spur gears. As shown in FIG. 3 , when a continuous carbon fiber bundle 10 is meshed with a gear pair 14 consisting of two gears 13, 13, it is bent at a small radius, thereby partially destroying the bonds between the filaments mediated by the sizing agent and loosening the continuous carbon fiber bundle. The gear pair only needs to rotate passively and does not need to be connected to a power source to actively rotate it. Using this gear pair allows the continuous carbon fiber bundle to be bent at a small radius without applying any particular tension. In other words, the continuous carbon fiber bundle can be loosened easily without introducing a tension application mechanism.

[0025] The two gears constituting the gear pair may be made of polymer or metal. The tooth depth (the difference between the root radius and the crest radius) of each gear is, for example, 1 to 10 mm, and may be 2 to 5 mm. The length obtained by dividing the circumference of the crest circle of each gear by the number of teeth (the pitch between the teeth along the circumference of the crest circle) is, for example, 1 to 10 mm, and may be 3 to 7 mm. In one example, the tooth depth of each gear may be approximately 3.5 mm, and the length obtained by dividing the circumference of the crest circle by the number of teeth may be approximately 5 mm.

[0026] By splicing the end of a continuous carbon fiber bundle drawn from one package to the beginning of a continuous carbon fiber bundle drawn from the next package to be used, CF-SMC can be continuously produced without stopping the line every time a package becomes empty. However, the splice portion between the continuous carbon fiber bundles is thicker than the other portions and therefore cannot be meshed with the gear pair. Therefore, in a preferred example, as shown in Figure 4, the gap between the two gears 13, 13 that make up the gear pair 14 may be widened only when the splice portion 15 passes through.

[0027] As shown in Figure 5, it is preferable that one gear pair 14 processes only one continuous carbon fiber bundle 10 at a time. Therefore, in order to simultaneously perform the loosening process on N continuous carbon fiber bundles, it is preferable to install at least N gear pairs in the bundle loosener. In this way, when only the spliced ​​portion of one of the N continuous carbon fiber bundles passes through the bundle loosener at a certain timing, it is only necessary to widen the gap between the two gears that make up the gear pair that processes that continuous carbon fiber bundle.

[0028] An example of a debundler may apply sufficient tension to the continuous carbon fiber bundles and then pass them through a curved path formed by rollers and / or bars to debundle them. Such a debundler may also have the function of spreading the carbon fiber bundles.

[0029] Because the space between the downstream end of the guide tube GT and the chopper 1 is limited, installing the debundler BL there not only makes it inconvenient to adjust, maintain, inspect, and repair the debundler, but also makes it difficult to adjust, maintain, inspect, and repair the chopper. In contrast, there is often ample space upstream of the guide tube GT, so if the debundler is installed there, it is much easier to adjust, maintain, inspect, and repair the debundler BL. This is extremely important in a debundler that engages continuous carbon fiber bundles with gear pairs, when installing the same number of gear pairs as the number of continuous carbon fiber bundles to be processed. Because fiber filaments are less likely to break during the process of loosening continuous carbon fiber bundles, installing the debundler upstream of the guide tube does not exacerbate the problem of short carbon fiber filaments agglomerating in the guide tube and turning into cotton waste.

[0030] The continuous carbon fiber bundle 10 loosened by the bundle loosener BL is sent to the chopper 1 through the guide tube GT. There are no limitations on the material of the guide tube, and it may be a polymer or a metal. The length of the guide tube GT can be appropriately determined depending on the distance from the installation location of the bundle loosener BL to the chopper 1. In one example, the length of the guide tube may be 3 m or more, 5 m or more, or 7 m or more. This means that the travel distance of the continuous carbon fiber bundle 10 from the loosening process in the bundle loosener BL to being cut by the chopper 1, in other words, the distance from the bundle loosener BL to the chopper 1 along the travel path of the continuous carbon fiber bundle 10, may be more than 3 m, even more than 5 m, or even more than 7 m. There is no particular upper limit to the length of the guide tube, but in most cases, a length of 15 m or less or 10 m or less is sufficient. If the guide tube is longer than necessary, it becomes difficult to clean its interior.

[0031] As shown in Fig. 6 as an example, the chopper 1 comprises a receiving roll 22 that also serves as a feed roll, a pinch roll 23, and a cutter roll 24. The outer periphery of the receiving roll 22 is formed of rubber. The continuous carbon fiber bundle 10 is cut by being pressed against the receiving roll 22 by a blade 25 attached to the outer periphery of the cutter roll 24. The fiber length of the carbon fibers contained in the chopped carbon fiber bundle 20 is, for example, in the range of 5 to 100 mm, preferably in the range of 5 to 60 mm, and more preferably in the range of 10 to 30 mm.

[0032] Chopped carbon fiber bundles 20 produced when continuous carbon fiber bundles 10 are cut by a chopper 1 fall toward a traveling first carrier film 51. The fallen chopped carbon fiber bundles 20 form a random mat 30 on the first carrier film 51. A paste 41 of a thermosetting resin composition is applied to the upper surface of the first carrier film 51 by a first coater 2a, upstream of the location where the chopped carbon fiber bundles 20 fall. The viscosity of the paste is preferably adjusted to be within a range of 1 to 30 Pa·s at 25°C. A paste 42 having the same composition as the paste 41 is applied to the second carrier film 52 by a second coater 2b. A laminate 60 is formed by overlapping the first carrier film 51 and the second carrier film 52 with the random mat 30 sandwiched between them, with the surfaces coated with the pastes 41 and 42 facing each other.

[0033] The laminate 60 is compressed in the impregnation machine 3 and then wound onto a bobbin. In another example, the laminate 60 may be folded and stored in a container. When the laminate 60 is compressed in the impregnation machine 3, the random mat 30 is impregnated with the pastes 41 and 42. After impregnation, the pastes thicken to complete the CF-SMC. A thickener is usually blended into the pastes 41 and 42 so that the CF-SMC has an appropriate tack and hardness. The amount of thickener blended is adjusted so that the pastes 41 and 42 do not thicken too much before impregnation.

[0034] Examples of materials for the first carrier film and the second carrier film include polyolefins such as polyethylene and polypropylene, polyvinylidene chloride, vinyl chloride, and polyamide. The first carrier film and the second carrier film may each be a multilayer film. The first carrier film and the second carrier film may have a thickness, for example, in the range of 10 μm to 500 μm. The first carrier film and the second carrier film may have a width, for example, in the range of 0.5 m to 1.5 m.

[0035] In one example, a paste made of a thermosetting resin composition is formulated with a liquid epoxy resin, an epoxy curing agent, a thickener, and optional components. Examples of optional components include a low-profile agent, an internal mold release agent, a colorant, a flame retardant, and an antioxidant, as well as a modifier made of rubber, elastomer, or thermoplastic resin. In another example, a paste made of a thermosetting resin composition is formulated with at least one of a vinyl ester resin and an unsaturated polyester resin, along with a reactive diluent, a polymerization initiator, a thickener, and optional components. The reactive diluent is a liquid vinyl compound, examples of which include styrene and various (meth)acrylates. Examples of optional components include a polymerization inhibitor, a low-profile agent, an internal mold release agent, a colorant, a flame retardant, and an antioxidant, as well as a modifier made of rubber, elastomer, or thermoplastic resin.

[0036] The CF-SMC manufacturing method described above can be further modified as described below. In one modification, the chopped carbon fiber bundles may be dispersed using a rotationally driven dispersion roll before being dropped onto the first carrier film. The rotation axis of the dispersion roll is preferably parallel to the T direction. An example of a dispersion roll is a pin roll (also called a spike roll). As shown in an example in FIG. 7 , the main part 32 of the pin roll 31 has a structure in which multiple pins 34 protrude from the surface of a cylinder 33. The multiple pins 34 are all oriented perpendicular to the rotation axis. A shaft 35 passes through the center of the cylinder 33. When the pin roll 31 is rotated, the pins 34 of the main part 32 strike the chopped carbon fiber bundles.

[0037] Another example of a dispersion roll is a cage roll. As shown in Figures 8 and 9, the main part 37 of a cage roll 36 has a structure in which a plurality of rods 39 are stretched between a pair of disks 38, 38 that share a common rotation axis. The rods 39 can be replaced with rods with a non-round cross section, such as square bars or flat bars, or with taut wires. A shaft 40 passes through the center of each disk. When the cage roll is rotated, the rods in the main part strike the chopped carbon fiber bundles.

[0038] A feature of the dispersion roll common to both pin rolls and cage rolls is that the shape of the main part has n-fold rotational symmetry around the rotation axis (the central axis of the shaft), where n is a finite integer of 1 or more. n is preferably 3 or more and 72 or less, and may be 45 or less, 36 or less, or 24 or less. For example, n is 4 in the pin roll 31 shown in Fig. 7, and n is 6 in the cage roll 36 shown in Figs. 8 and 9. If a roll has this feature, even a roll other than a pin roll or a cage roll can apply physical impact to the chopped carbon fiber bundles when rotated.

[0039] When chopped carbon fiber bundles are dispersed using a rotating dispersion roll, the chopped carbon fiber bundles are physically broken down into smaller carbon fiber bundles. This effect is more pronounced if the continuous carbon fiber bundles are loosened before being cut with a chopper. On the other hand, physically striking chopped carbon fiber bundles in which the bonds between the fiber filaments have been weakened tends to generate fine carbon fiber dust that can float in the air. To prevent this carbon fiber dust from spreading, as shown in Figures 10 and 11, it is preferable to provide a booth 43 in which the main part of the dispersion roll 44 is located, provide an opening in the ceiling of the booth, and use a chute 45 to guide the chopped carbon fiber bundles into this opening. The arrow X in Figure 10 indicates the running direction of the first carrier film 51. The double-headed arrow T in Figure 11 indicates the T direction.

[0040] As shown in the example of Fig. 11, the width of the booth in the T direction is preferably narrower than the width of the first carrier film 51, but is not limited to this. The ends of the shafts of the dispersion rolls desirably protrude outside the booth through openings provided in the side walls of the booth (walls parallel to the running direction of the first carrier film). In the example of Fig. 11, bearings 46 supporting the dispersion roll 44 are disposed outside the booth 43, and substantially only the main part of the dispersion roll 44 is disposed inside the booth 43.

[0041] Furthermore, in order to prevent carbon fiber dust from escaping outside the booth, it is desirable to continue removing carbon fiber dust from inside the booth using a dust collector while CF-SMC is being produced. In the example of FIG. 10 , carbon fiber dust can be removed from inside the booth 43 using a dust collector 49 connected to the booth 43 via a hose 47. Although not limited to this, a suitable example of a dust collector is a dust collector equipped with a separator that separates dust from air using centrifugal force, i.e., a cyclone dust collector. A suction port connected to the dust collector is preferably provided on either or both of the wall surface of the booth and inside the booth. Carbon fiber dust that has leaked outside the booth may also be removed by the dust collector as needed.

[0042] The reasons why the spread of carbon fiber dust must be prevented include the following: - After being carried by air currents, carbon fiber dust can settle in specific locations and form cotton dust. If cotton dust gets mixed into random mats, it can cause poor impregnation. - Carbon fiber dust can contaminate the mechanical elements of SMC manufacturing equipment and interfere with their operation. - Carbon fiber dust can worsen the working environment in rooms where SMC manufacturing equipment is installed. - Because carbon fiber dust is conductive, it can interfere with the operation of electrical and electronic equipment attached to SMC manufacturing equipment and electrical and electronic equipment used in rooms where SMC manufacturing equipment is installed.

[0043] In another modified example, as shown in Fig. 12, the space into which chopped carbon fiber bundles, generated by cutting continuous carbon fiber bundles with the chopper 1, fall can be divided into a plurality of regions along the T direction by at least one partition 48 arranged below the chopper 1. Using a partition to prevent the chopped carbon fiber bundles from moving in the T direction while falling through this space is useful for making the basis weight of the random mat formed on the first carrier film uniform along the T direction. When the above-mentioned dispersing roll is arranged below the chopper, the adverse effect of the airflow generated by the rotation of the dispersing roll on the uniformity of the basis weight of the random mat can be reduced by arranging a partition below the dispersing roll.

[0044] When fibrous dust adheres to the partition due to static electricity, the adhered fibrous dust can aggregate and form lint. To prevent this, it is desirable to form the partition from metal and ground it. Suitable metals include aluminum alloys and stainless steel, with aluminum alloys being more preferable due to their high conductivity. If the partition is scratched, fibrous dust is more likely to become trapped in the scratch, which in turn makes it more likely to form lint. Since aluminum alloy plates are easily scratched, electroless nickel plating may be applied to increase the surface hardness and make them more resistant to scratches.

[0045] 2. Summary of Embodiments In summary, embodiments of the present invention include the following, but are not limited to these. [Embodiment 1] A method for producing a carbon fiber sheet molding compound, comprising: feeding a continuous carbon fiber bundle drawn from a package to a chopper through a guide tube; subjecting the continuous carbon fiber bundle to a loosening treatment before passing it through the guide tube; dropping chopped carbon fiber bundles produced by cutting the continuous carbon fiber bundle with the chopper onto a running carrier film to form a random mat; and impregnating the random mat with a paste made of a thermosetting resin composition. [Embodiment 2] The production method according to Embodiment 1, in which the loosening treatment comprises piercing the continuous carbon fiber bundle with protrusions. [Embodiment 3] The production method according to Embodiment 2, in which a protruding roll is used for the loosening treatment. [Embodiment 4] The production method according to any one of Embodiments 1 to 3, in which the loosening treatment comprises bending the continuous carbon fiber bundle. [Embodiment 5] The production method according to Embodiment 4, in which a gear pair consisting of two gears meshing with each other, each of which may be a spur gear, is used for the loosening treatment. [Embodiment 6] A production method according to any one of Embodiments 1 to 5, in which the chopped carbon fiber bundles are dispersed by a rotationally driven dispersion roll and then dropped onto the carrier film. [Embodiment 7] A production method according to Embodiment 6, further comprising: providing a booth and arranging a main part of the dispersion roll therein; and using a chute to guide the chopped carbon fiber bundles to an opening provided in the ceiling of the booth. [Embodiment 8] A production method according to Embodiment 6 or 7, further comprising: while dispersing the chopped carbon fiber bundles with the dispersion roll, removing fiber dust generated in association with the dispersion with a dust collector. [Embodiment 9] A production method according to Embodiment 7, further comprising: while dispersing the chopped carbon fiber bundles with the dispersion roll, removing fiber dust generated in association with the dispersion with a dust collector, and a suction port connected to the dust collector is provided in either or both of a wall surface of the booth and inside the booth.[Embodiment 10] A manufacturing method according to any one of embodiments 1 to 9, further comprising dividing a space into a plurality of regions along the T direction by at least one partition, into which the chopped carbon fiber bundles fall toward the carrier film. [Embodiment 11] A manufacturing method according to embodiment 10, wherein the at least one partition is made of metal and is grounded. [Embodiment 12] A manufacturing method according to any one of embodiments 1 to 11, wherein the length of the guide tube is 3 m or more, and may be 5 m or more or 7 m or more.

[0046] [Embodiment 13] A method for producing a carbon fiber sheet molding compound, comprising: feeding a continuous carbon fiber bundle drawn out from a package to a chopper, subjecting the continuous carbon fiber bundle to a loosening treatment before cutting with the chopper, dropping the chopped carbon fiber bundles produced by cutting the continuous carbon fiber bundle with the chopper onto a traveling carrier film to form a random mat, and impregnating the random mat with a paste made of a thermosetting resin composition, wherein the travel distance of the continuous carbon fiber bundle from the loosening treatment to cutting with the chopper is greater than 3 m, greater than 5 m, or greater than 7 m. [Embodiment 14] The production method according to Embodiment 13, wherein the loosening treatment comprises piercing the continuous carbon fiber bundle with protrusions. [Embodiment 15] The production method according to Embodiment 14, wherein a protruding roll is used for the loosening treatment. [Embodiment 16] The production method according to any of Embodiments 13 to 15, wherein the loosening treatment comprises bending the continuous carbon fiber bundle. [Embodiment 17] The production method according to embodiment 16, wherein a gear pair consisting of two gears meshing with each other, each of which may be a spur gear, is used for the loosening treatment. [Embodiment 18] The production method according to any of embodiments 13 to 17, wherein the chopped carbon fiber bundles are dispersed by a rotationally driven dispersion roll and then dropped onto the carrier film. [Embodiment 19] The production method according to embodiment 18, further comprising: providing a booth and arranging a main part of the dispersion roll therein; and using a chute to guide the chopped carbon fiber bundles to an opening provided in the ceiling of the booth. [Embodiment 20] The production method according to embodiment 18 or 19, further comprising: while dispersing the chopped carbon fiber bundles with the dispersion roll, removing fiber dust generated in association with the dispersion with a dust collector. [Embodiment 21] The production method according to embodiment 19, further comprising while dispersing the chopped carbon fiber bundles with the dispersion roll, removing fiber dust generated in association with the dispersion with a dust collector, wherein a suction port connected to the dust collector is provided in either or both of the wall of the booth and inside the booth.[Embodiment 22] The manufacturing method according to any one of embodiments 13 to 21, further comprising dividing a space into a plurality of regions along the T direction by at least one partition, into which the chopped carbon fiber bundles fall toward the carrier film. [Embodiment 23] The manufacturing method according to embodiment 22, wherein the at least one partition is made of metal and is grounded. [Embodiment 24] The manufacturing method according to any one of embodiments 13 to 23, wherein the continuous carbon fiber bundles are fed to the chopper through a guide tube, and the loosening treatment is performed on the continuous carbon fiber bundles before passing them through the guide tube.

[0047] [Embodiment 25] A method for producing a carbon fiber sheet molding compound, comprising: cutting continuous carbon fiber bundles with a chopper, dropping chopped carbon fiber bundles produced by cutting continuous carbon fiber bundles with a chopper onto a running carrier film to form a random mat, impregnating the random mat with a paste made of a thermosetting resin composition, loosening the continuous carbon fiber bundles before cutting with the chopper, and dispersing the chopped carbon fiber bundles with a rotationally driven dispersion roll before dropping them onto the carrier film. [Embodiment 26] The production method according to embodiment 25, further comprising providing a booth and arranging a main portion of the dispersion roll therein, and using a chute to guide the chopped carbon fiber bundles into an opening provided in the ceiling of the booth. [Embodiment 27] The production method according to embodiment 25 or 26, further comprising removing fiber dust generated as the chopped carbon fiber bundles are dispersed by the dispersion roll with a dust collector. [Embodiment 28] The manufacturing method according to embodiment 26, further comprising removing fiber dust generated by dispersing the chopped carbon fiber bundles with the dispersion roll using a dust collector, and a suction port connected to the dust collector is provided on either or both of the wall surface of the booth and the interior of the booth. [Embodiment 29] The manufacturing method according to any of embodiments 25 to 28, wherein the loosening treatment comprises piercing the continuous carbon fiber bundles with protrusions. [Embodiment 30] The manufacturing method according to embodiment 29, wherein a protruding roll is used for the loosening treatment. [Embodiment 31] The manufacturing method according to any of embodiments 25 to 30, wherein the loosening treatment comprises bending the continuous carbon fiber bundle. [Embodiment 32] The manufacturing method according to embodiment 31, wherein a gear pair consisting of two gears meshing with each other, each of which may be a spur gear, is used for the loosening treatment. [Embodiment 33] The manufacturing method according to any of embodiments 25 to 32, further comprising partitioning, by at least one partition, a space into which the chopped carbon fiber bundles fall toward the carrier film, into a plurality of regions along the T direction. [Embodiment 34] A manufacturing method according to embodiment 33, wherein the at least one partition is made of metal and is grounded.

[0048] [Embodiment 35] A method for producing a carbon fiber sheet molding compound, comprising: dropping chopped carbon fiber bundles produced by cutting continuous carbon fiber bundles with a chopper onto a running carrier film to form a random mat; impregnating the random mat with a paste made of a thermosetting resin composition; and partitioning a space into a plurality of regions along the T direction using at least one partition, into which the chopped carbon fiber bundles fall toward the carrier film, wherein the at least one partition is formed of metal and is grounded. [Embodiment 36] A production method according to embodiment 35, in which the chopped carbon fiber bundles are dispersed by a rotationally driven dispersion roll and then dropped onto the carrier film. [Embodiment 37] A production method according to embodiment 36, further comprising providing a booth in which a main portion of the dispersion roll and the at least one partition are disposed, and using a chute to guide the chopped carbon fiber bundles into an opening provided in the ceiling of the booth. [Embodiment 38] The manufacturing method according to embodiment 36 or 37, further comprising removing fiber dust generated in association with dispersing the chopped carbon fiber bundles with the dispersing roll using a dust collector. [Embodiment 39] The manufacturing method according to embodiment 37, further comprising removing fiber dust generated in association with dispersing the chopped carbon fiber bundles with the dispersing roll using a dust collector, wherein a suction port connected to the dust collector is provided on either or both of a wall surface of the booth and an interior of the booth. [Embodiment 40] The manufacturing method according to any of embodiments 35 to 39, further comprising subjecting the continuous carbon fiber bundles to a loosening treatment before cutting with the chopper. [Embodiment 41] The manufacturing method according to embodiment 40, wherein the loosening treatment comprises piercing the continuous carbon fiber bundle with protrusions. [Embodiment 42] The manufacturing method according to embodiment 41, wherein a protruding roll is used for the loosening treatment. [Embodiment 43] The manufacturing method according to any of embodiments 40 to 42, wherein the loosening treatment comprises bending the continuous carbon fiber bundles. [Embodiment 44] A manufacturing method according to embodiment 43, in which a gear pair consisting of two gears meshed with each other, each of which may be a spur gear, is used for the loosening process.

[0049] [Embodiment 45] A manufacturing apparatus for carbon fiber sheet molding compound, comprising: a chopper arranged above a running path of a carrier film; a guide tube for passing a continuous carbon fiber bundle drawn from a package and fed to the chopper; and a bundle relaxer arranged upstream of the guide tube for loosening the continuous carbon fiber bundle. [Embodiment 46] The manufacturing apparatus according to embodiment 45, wherein the bundle relaxer includes means for piercing the continuous carbon fiber bundle with protrusions. [Embodiment 47] The manufacturing apparatus according to embodiment 46, wherein the bundle relaxer includes a protrusion-equipped roll. [Embodiment 48] The manufacturing apparatus according to any of embodiments 45 to 47, wherein the bundle relaxer includes means for bending the continuous carbon fiber bundle. [Embodiment 49] The manufacturing apparatus according to embodiment 48, wherein the bundle relaxer includes a gear pair consisting of two gears meshing with each other, each of which may be a spur gear. [Embodiment 50] The manufacturing apparatus according to any one of Embodiments 45 to 49, further comprising a rotationally driven dispersion roll for dispersing chopped carbon fiber bundles produced by cutting the continuous carbon fiber bundles with the chopper. [Embodiment 51] The manufacturing apparatus according to Embodiment 50, in which a main part of the dispersion roll is disposed in a booth, and a chute is provided for guiding the chopped carbon fiber bundles to an opening provided in the ceiling of the booth. [Embodiment 52] The manufacturing apparatus according to Embodiment 51, in which a suction port connected to a dust collector is provided in either or both of a wall surface of the booth and inside the booth. [Embodiment 53] The manufacturing apparatus according to any one of Embodiments 45 to 52, in which at least one partition divides a space into a plurality of regions along the T direction, in which chopped carbon fiber bundles produced by cutting the continuous carbon fiber bundles with the chopper fall toward the traveling path. [Embodiment 54] The manufacturing apparatus according to Embodiment 53, in which the at least one partition is formed of metal and is grounded. [Embodiment 55] A manufacturing apparatus according to any one of embodiments 45 to 54, wherein the length of the guide tube is 3 m or more, and may be 5 m or more or 7 m or more.

[0050] [Embodiment 56] A manufacturing apparatus for carbon fiber sheet molding compound, comprising: a chopper arranged above a running path of a carrier film; and a bundle relaxer for loosening continuous carbon fiber bundles drawn from a package and fed to the chopper, wherein the distance from the bundle relaxer to the chopper along the running path of the continuous carbon fiber bundle is greater than 3 m, greater than 5 m, or greater than 7 m. [Embodiment 57] The manufacturing apparatus according to embodiment 56, wherein the bundle relaxer includes means for piercing protrusions into the continuous carbon fiber bundle. [Embodiment 58] The manufacturing apparatus according to embodiment 57, wherein the bundle relaxer includes a protruding roll. [Embodiment 59] The manufacturing apparatus according to any one of embodiments 56 to 58, wherein the bundle relaxer includes means for bending the continuous carbon fiber bundle. [Embodiment 60] The manufacturing apparatus according to embodiment 59, wherein the bundle relaxer includes a gear pair consisting of two gears meshing with each other, each of which may be a spur gear. [Embodiment 61] The manufacturing apparatus according to any one of Embodiments 56 to 60, further comprising a rotationally driven dispersion roll for dispersing chopped carbon fiber bundles produced by cutting the continuous carbon fiber bundles with the chopper. [Embodiment 62] The manufacturing apparatus according to Embodiment 61, in which a main part of the dispersion roll is disposed in a booth, and a chute is provided in an opening provided in the ceiling of the booth for guiding the chopped carbon fiber bundles. [Embodiment 63] The manufacturing apparatus according to Embodiment 62, in which a suction port connected to a dust collector is provided in either or both of a wall surface of the booth and inside the booth. [Embodiment 64] The manufacturing apparatus according to any one of Embodiments 56 to 63, in which at least one partition divides a space into a plurality of regions along the T direction, in which chopped carbon fiber bundles produced by cutting the continuous carbon fiber bundles with the chopper fall toward the traveling path. [Embodiment 65] The manufacturing apparatus according to Embodiment 64, in which the at least one partition is formed of metal and is grounded. [Embodiment 66] A manufacturing apparatus according to any one of embodiments 56 to 65, further comprising a guide tube for passing the continuous carbon fiber bundle sent to the chopper, and the bundle loosener is positioned upstream of the guide tube.

[0051] [Embodiment 67] A manufacturing apparatus for carbon fiber sheet molding compound, comprising: a chopper arranged above a running path of a carrier film; a bundle loosener for loosening continuous carbon fiber bundles fed to the chopper; and a rotationally driven dispersion roll for dispersing chopped carbon fiber bundles produced by cutting the continuous carbon fiber bundles with the chopper. [Embodiment 68] A manufacturing apparatus according to embodiment 67, in which the dispersion roll is arranged in a booth, and a chute is provided for guiding the chopped carbon fiber bundles into an opening provided in the ceiling of the booth. [Embodiment 69] A manufacturing apparatus according to embodiment 68, in which a suction port connected to a dust collector is provided in either or both of a wall surface of the booth and inside the booth. [Embodiment 70] A manufacturing apparatus according to any of embodiments 67 to 69, in which the bundle loosener includes means for piercing the continuous carbon fiber bundles with protrusions. [Embodiment 71] A manufacturing apparatus according to embodiment 70, in which the loosener includes a protruding roll. [Embodiment 72] A manufacturing apparatus according to any one of embodiments 67 to 71, wherein the loosening treatment includes a means for bending the continuous carbon fiber bundle. [Embodiment 73] A manufacturing apparatus according to embodiment 72, wherein the loosener includes a gear pair consisting of two gears meshing with each other, each of which may be a spur gear. [Embodiment 74] A manufacturing apparatus according to any one of embodiments 67 to 73, wherein at least one partition divides the space into a plurality of regions along the T direction, into which the chopped carbon fiber bundle falls toward the traveling path. [Embodiment 75] A manufacturing apparatus according to embodiment 74, wherein the at least one partition is made of metal and is grounded.

[0052] [Embodiment 76] A manufacturing apparatus for carbon fiber sheet molding compound, comprising a chopper arranged above a running path of a carrier film and at least one partition made of metal and grounded, wherein the at least one partition divides a space into a plurality of regions along the T direction, into which chopped carbon fiber bundles produced by cutting continuous carbon fiber bundles with the chopper fall toward the running path. [Embodiment 77] A manufacturing apparatus according to embodiment 76, further comprising a rotationally driven dispersion roll for dispersing the chopped carbon fiber bundles. [Embodiment 78] A manufacturing apparatus according to embodiment 77, wherein a main portion of the dispersion roll is arranged in a booth, and wherein a chute is provided for guiding the chopped carbon fiber bundles to an opening provided in the ceiling of the booth. [Embodiment 79] A manufacturing apparatus according to embodiment 78, wherein a suction port connected to a dust collector is provided in either or both of a wall surface of the booth and inside the booth. [Embodiment 80] A manufacturing apparatus according to any of embodiments 76 to 79, further comprising a bundle loosener for loosening the continuous carbon fiber bundles before cutting with the chopper. [Embodiment 81] A manufacturing apparatus according to embodiment 80, wherein the bundle relaxer includes a means for piercing protrusions into the continuous carbon fiber bundle. [Embodiment 82] A manufacturing apparatus according to embodiment 81, wherein the bundle relaxer includes a protruding roll. [Embodiment 83] A manufacturing apparatus according to any of embodiments 80 to 82, wherein the bundle relaxer includes a means for bending the continuous carbon fiber bundle. [Embodiment 84] A manufacturing apparatus according to embodiment 83, wherein the bundle relaxer includes a gear pair consisting of two gears meshing with each other, each of which may be a spur gear. [Embodiment 85] A manufacturing apparatus according to any of embodiments 45 to 84, wherein the carbon fiber sheet molding compound is obtained by impregnating a random mat consisting of chopped carbon fiber bundles with a paste consisting of a thermosetting resin composition.

[0053] [Embodiment 86] A manufacturing method according to any one of embodiments 1 to 44, further comprising, before forming the random mat on the carrier film, applying a portion of the paste to one side of the carrier film, overlaying another carrier film, having another portion of the paste applied to one side thereof, on the carrier film with the random mat sandwiched therebetween to form a laminate, and compressing the laminate for the impregnation. [Embodiment 87] A manufacturing method of a carbon fiber sheet molding compound using the manufacturing apparatus according to any one of embodiments 45 to 85.

[0054] 3. Experimental Results The results of an experiment conducted by the present inventors are described below. A random mat consisting of chopped carbon fiber bundles was deposited on a carrier film not coated with resin paste using a CF-SMC manufacturing device equipped with a disperser placed above the carrier film running path, a chopper placed above the disperser, multiple guide tubes for passing the continuous carbon fiber bundles to be sent to the chopper, and a pair of gears placed upstream of each guide tube. The procedure is described in more detail below.

[0055] Forty packages of bobbin-wound continuous carbon fiber bundles with 15,000 filaments were prepared. The continuous carbon fiber bundles drawn from each package were passed between two spur gears that make up a gear pair, and then sent to a chopper through a guide tube. The two spur gears in each gear pair were both made of SUS304, with a face width (the length of the teeth in the axial direction of the gears) of 20 mm, a tooth depth of 3.4 mm, a crest circle diameter of 48 mm, and a circumference of the crest circle divided by the number of teeth of 5.0 mm. No mechanism was provided to actively rotate the spur gears.

[0056] In each gear pair, the two spur gears were meshed with an axis distance of 46 mm. The continuous carbon fiber bundles meshed between the two spur gears were pulled by the chopper, causing the two spur gears to rotate passively. The guide tubes were polyethylene tubes with an outer diameter of 20 mm and an inner diameter of 14 mm, and their lengths ranged from 3 m to 6 m. Therefore, the travel distance of each continuous carbon fiber bundle from the time it was processed by the gear pair to the time it was cut by the chopper exceeded 3 m.

[0057] In the disperser, two pin rolls were arranged, each with a rotation axis parallel to the T direction. The two pin rolls had the same configuration, with a cylinder diameter of 120 mm and pins arranged on the cylinder periphery having a diameter and length of 3 mm and 20 mm, respectively. The pins were arranged periodically on the cylinder periphery, with a pin density of 1 cm ２ The number of pins per roll was 0.42. The distance between the rotation axes of the two pin rolls was 150 mm. The two pin rolls of the disperser were both rotated so that the pins on the side facing the other pin roller moved from top to bottom. The rotation speed of the two pin rolls was the same.

[0058] The continuous carbon fiber bundles were cut with a chopper so that the fiber length after cutting was about 1 inch (25.4 mm) to obtain chopped carbon fiber bundles. The chopped carbon fiber bundles were dispersed with a disperser and dropped onto a carrier film traveling at a linear speed of 5 m / min. The dropped chopped carbon fiber bundles were deposited on the carrier film to form a random mat. From the random mat, an area of ​​about 21 cm x 30 cm deposited near the center line of the carrier film was selected, and the weight of all chopped carbon fiber bundles (300 pieces or more) contained in that area was measured. The weight-average number of filaments calculated based on this weight measurement was defined as the average number of filaments of the chopped carbon fiber bundles in the random mat.

[0059] The average number of filaments in the chopped carbon fiber bundles in the random mats obtained by rotating the pin roll of the disperser at rotation speeds of 800 rpm, 1000 rpm, 1250 rpm, and 1500 rpm is shown in the following Table 1. Table 1 also shows the average number of filaments in the chopped carbon fiber bundles in the random mats formed in the same manner except that the continuous carbon fiber bundles were not treated with the gear pair.

[0060]

[0061] While the present invention has been described above with reference to specific embodiments, these embodiments are presented as examples and do not limit the scope of the present invention. Each embodiment described in this specification can be modified in various ways within the scope of the effects of the invention, and can be combined with features described in other embodiments within the scope of feasibility.

[0062] Carbon fiber sheet molding compounds manufactured using the manufacturing method or manufacturing apparatus according to the embodiment can be suitably used to manufacture CFRP parts for various transportation and industrial equipment, including, but not limited to, automobiles, ships, railroad vehicles, manned aircraft, and unmanned aerial vehicles.

[0063] REFERENCE SIGNS LIST 1 Chopper 2a First coater 2b Second coater 3 Impregnator 10 Continuous carbon fiber bundle 20 Chopped carbon fiber bundle 30 Random mat 41, 42 Paste 51 First carrier film 52 Second carrier film 60 Laminate BL Bundle relaxer GT Guide tube GR Guide roll

Claims

1. A chopped carbon fiber bundle is produced by cutting a continuous carbon fiber bundle with a chopper, and the chopped carbon fiber bundle is dropped onto a traveling carrier film to form a random mat; impregnating the random mat with a paste comprising a thermosetting resin composition; subjecting the continuous carbon fiber bundle to a loosening treatment before cutting by the chopper; Dispersing the chopped carbon fiber bundles by a rotating dispersing roll before dropping them onto the carrier film; Including, A method for producing a carbon fiber sheet molding compound, wherein the loosening process uses a gear pair consisting of two meshed gears, each of which may be a spur gear.

2. Providing a booth and disposing a main part of the dispersion roll therein; using a chute to guide the chopped carbon fiber bundles to an opening in the ceiling of the booth; The method of claim 1 further comprising:

3. The method according to claim 1 , further comprising removing fiber dust generated by dispersing the chopped carbon fiber bundles with a dust collector while dispersing the chopped carbon fiber bundles with the dispersing roll.

4. The method further includes removing fiber dust generated by dispersing the chopped carbon fiber bundles with a dust collector while dispersing the chopped carbon fiber bundles with the dispersion roll, The manufacturing method according to claim 2 , wherein a suction port connected to the dust collector is provided on either or both of a wall surface of the booth and inside the booth.

5. The method of claim 1 , wherein the loosening step comprises piercing the continuous carbon fiber bundle with a protrusion.

6. The method according to claim 5 , wherein a protruding roll is used for the loosening treatment.

7. The manufacturing method according to claim 1 , further comprising dividing a space in which the chopped carbon fiber bundles fall toward the carrier film into a plurality of regions along the T direction by at least one partition.

8. The method of claim 7 , wherein the at least one partition is made of metal and is grounded.

9. A chopper disposed above the running path of the carrier film; a bundle loosener for loosening the continuous carbon fiber bundles fed to the chopper; A dispersing roll that is driven to rotate for dispersing chopped carbon fiber bundles produced by cutting the continuous carbon fiber bundles with the chopper; having An apparatus for producing carbon fiber sheet molding compound, wherein the bundle releaser includes a gear pair consisting of two gears meshed with each other, each of which may be a spur gear.

10. The manufacturing apparatus according to claim 9, wherein the dispersion roll is disposed in a booth, and a chute is provided for directing the chopped carbon fiber bundles to an opening provided in a ceiling of the booth.

11. The manufacturing apparatus according to claim 10 , wherein a suction port connected to a dust collector is provided on either or both of a wall surface of the booth and inside the booth.

12. 10. The manufacturing apparatus of claim 9, wherein the bundle loosener includes means for piercing the continuous carbon fiber bundles with prongs.

13. The manufacturing apparatus of claim 12 , wherein the loosener comprises a protruding roll.

14. 10. The manufacturing apparatus according to claim 9, wherein a space in which the chopped carbon fiber bundles fall toward the traveling path is divided into a plurality of regions along the T direction by at least one partition.

15. The manufacturing apparatus of claim 14 , wherein the at least one partition is made of metal and is grounded.

16. 10. The manufacturing apparatus according to claim 9, wherein the carbon fiber sheet molding compound is obtained by impregnating a random mat made of chopped carbon fiber bundles with a paste made of a thermosetting resin composition.

17. applying a portion of the paste to one side of the carrier film prior to forming the random mat on the carrier film; Another carrier film having another portion of the paste applied to one side thereof is laminated on the carrier film with the random mat sandwiched therebetween to form a laminate; and The method of any one of claims 1 to 8, further comprising compressing the laminate for said impregnation.

18. A method for producing a carbon fiber sheet molding compound, using the production apparatus according to any one of claims 9 to 16.