Method and device for producing sheet prepreg

Abstract

To provide a technology useful for producing CF-SMC, for accelerating impregnation of a carbon fiber mat with a matrix resin to increase a line speed, or for enabling use of a resin composition having a high viscosity at room temperature as a matrix resin.SOLUTION: There is provided a method for producing a sheet prepreg, comprising: applying a thermosetting resin paste; conveying a plurality of short carbon fiber bundles 20 by a belt conveyor 140, dropping a resulting material from a discharge end onto a first carrier film 41, thereby depositing a carbon fiber mat 30 on a surface of the first carrier film 41 on which a thermosetting resin paste is applied; impregnating the carbon fiber mat with the thermosetting resin paste; and heating the short carbon fiber bundles 20 with a heater 150 while conveying a resulting material with the belt conveyor 140.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention mainly relates to a method for producing a sheet prepreg, and particularly to a method for producing a sheet prepreg using carbon fiber (CF). The present invention also relates to a sheet prepreg production apparatus that can be suitably used for producing the sheet prepreg. [Background technology]

[0002] CF-SMC is a type of carbon fiber prepreg, and in its manufacturing process, long carbon fiber bundles are cut with a chopper into short carbon fiber bundles, which are then dropped onto a moving carrier film to form a carbon fiber mat. In the production of CF-SMC, studies have been conducted on the method of increasing the line speed by promoting the impregnation of the carbon fiber mat with the matrix resin and on the method of heating the matrix resin during impregnation to reduce its viscosity in order to enable the use of a resin composition with a high room temperature viscosity as the matrix resin (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 106585 Summary of the Invention [Problem to be solved by the invention]

[0004] If the temperature of the short carbon fiber bundles dropped onto the carrier film is not increased, the temperature of the matrix resin applied to the carrier film surface will drop when the carbon fiber mat is deposited on top of it, and the heating effect of the matrix resin will not be fully achieved. When short carbon fiber bundles cut by a chopper are dropped directly onto a carrier film, the drop time is short, so it is difficult to sufficiently increase the temperature by heating the short carbon fiber bundles while they are falling.

[0005] The main object of the present invention is to provide a technique useful for producing CF-SMC, for promoting impregnation of a carbon fiber mat with a matrix resin to increase the line speed, or for enabling the use of a resin composition having a high viscosity at room temperature as a matrix resin. In this specification, problems that can be solved by each embodiment of the present invention may be explicitly or implicitly disclosed. [Means for solving the problem]

[0006] Preferred embodiments of the present invention include, but are not limited to, the following. [1] A method for manufacturing a sheet prepreg, comprising: applying a thermosetting resin paste to each of a surface of a first carrier film and a second carrier film; transporting a plurality of short carbon fiber bundles on a belt conveyor and then dropping them from an outlet end of the belt conveyor onto the first carrier film, thereby depositing a carbon fiber mat on the surface of the first carrier film on which the thermosetting resin paste has been applied; bonding the second carrier film to the first carrier film with the carbon fiber mat therebetween so that the surfaces on which the thermosetting resin paste has been applied face each other to form a laminate; pressurizing the laminate to impregnate the carbon fiber mat with the thermosetting resin paste; and heating the plurality of short carbon fiber bundles with a heater while they are transported on the belt conveyor. [2] The method for producing a sheet prepreg described in [1], wherein a space including at least a discharge end of the belt conveyor and a carbon fiber mat deposition section, which is a section where the carbon fiber mat is deposited on the first carrier film, is maintained at a higher temperature than the surrounding area. [3] a first coater for applying a thermosetting resin paste to a first carrier film; a second coater for applying a thermosetting resin paste to a second carrier film; a belt conveyor having a discharge end for conveying a plurality of short carbon fiber bundles and then dropping them from the discharge end onto the first carrier film to deposit a carbon fiber mat on the surface of the first carrier film on which the thermosetting resin paste has been applied; a heater for heating the short carbon fiber bundles transported by the belt conveyor; a lamination machine for laminating the second carrier film to the first carrier film with the carbon fiber mat sandwiched therebetween such that the surfaces coated with the thermosetting resin paste face each other to form a laminate; an impregnation machine for impregnating the carbon fiber mat with the thermosetting resin paste by pressing the laminate; A sheet prepreg manufacturing apparatus comprising: Effect of the Invention

[0007] The present invention provides a technique that is useful in producing CF-SMC, for promoting impregnation of a carbon fiber mat with a matrix resin to increase the line speed, or for enabling the use of a resin composition having a high viscosity at room temperature as a matrix resin. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a CF-SMC manufacturing apparatus. [Diagram 2] FIG. 2 is a schematic diagram showing a pin-roll type dispersion roll disposed below a chopper. [Diagram 3] FIG. 3 is a schematic diagram of a basket-type dispersion roll. [Figure 4] FIG. 4 is a schematic diagram of the belt conveyor from the discharge section to the carbon fiber mat depositing section as viewed from the conveying direction of the belt conveyor. [Diagram 5] FIG. 5 is a schematic diagram showing the area from the discharge portion of the belt conveyor to the carbon fiber mat depositing portion as viewed from a direction perpendicular to the conveying direction of the belt conveyor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] One embodiment of the present invention relates to a method for producing an SMC, comprising the following steps (i) to (v): (i) Applying a thermosetting resin paste to the surface of each of the first carrier film and the second carrier film. (ii) depositing a carbon fiber mat on the surface of the first carrier film on which the thermosetting resin paste has been applied by feeding a plurality of short carbon fiber bundles onto the first carrier film from the discharge end of the belt conveyor; (iii) laminating the second carrier film to the first carrier film with the carbon fiber mat therebetween such that the surfaces having the thermosetting resin paste applied thereto face each other to form a laminate; (iv) pressing the laminate to impregnate the carbon fiber mat with the thermosetting resin paste. (v) heating the plurality of short carbon fiber bundles with a heater while being transported by the belt conveyor.

[0010] 1.CF-SMC manufacturing equipment FIG. 1 shows a conceptual diagram of a CF-SMC production apparatus that can be preferably used when producing an SMC using the above-described production method according to the embodiment. Referring to FIG. 1, a CF-SMC production apparatus 100 includes a first coater 110, a second coater 120, a chopper 130, a belt conveyor 140, a heater 150, and an impregnation machine 160. The first coater 110 is used to apply the first resin paste 51 to the first carrier film 41 to form a first resin paste layer 51L on one surface of the first carrier film 41. The second coater 120 is used to apply the second resin paste 52 to the second carrier film to form a second resin paste layer 52L on one surface of the second carrier film .

[0011] The chopper 130 is of a type also used in conventional CF-SMC manufacturing equipment, and includes a cutter roll 131 , a receiving roll (rubber roll) 132 , and a guide roll 133 . The rotation axes of the cutter roll 131, the receiving roll 132, and the guide roll 133 are all parallel to the T direction of the belt conveyor 140. The T direction is the width direction of the conveying path of the belt conveyor 140, that is, the width direction of the conveying belt that constitutes the conveying path, and is usually horizontal. The chopper 130 is disposed above the conveying path of the belt conveyor 140 .

[0012] In one embodiment, as shown in FIG. 2, a dispersing roll 134 for dispersing the short carbon fiber bundles 20 (chopped carbon fiber bundles) dropping from the chopper 130 may be disposed below the chopper. The rotation axis of the dispersing roll 134 is parallel to the T direction of the belt conveyor 140. The structure and number of the dispersing roll 134 are not limited to those shown in the figure. The dispersing roll 134 shown in FIG. 2 is a pin roll type, but may be a cage type as shown in FIG. 3. Although not shown, the pin roll type dispersing roll has a cylinder and a plurality of pins arranged on the circumferential surface of the cylinder. The cage type dispersing roll 134 (cage roll) shown in FIG. 3 has a structure in which a plurality of wires or rods 134c are stretched between a pair of disks 134b sharing a rotation axis 134a. The number of dispersing rolls is not limited to one, and may be two or more. The dispersing roll is usually a rigid body, and is preferably formed of a metal (including an alloy).

[0013] The short carbon fiber bundles 20 fall onto the conveying path of the belt conveyor 140 below the chopper 130, and are conveyed by the belt conveyor 140 toward its discharge end. The discharge end of belt conveyor 140 is disposed above the running path of first carrier film 41. The T direction of belt conveyor 140 and the width direction of first carrier film 41 running on the running path are parallel to each other.

[0014] The running direction of the first carrier film 41 is preferably horizontal below the discharge end of the belt conveyor 140. In other words, below the discharge end of the belt conveyor 140, the upper surface of the first carrier film 41 is preferably maintained horizontal. A laminating machine 170 is disposed upstream of the impregnating machine 160, which gradually brings the first carrier film 41 and the second carrier film 42 closer to each other and laminates them together. The laminating machine 170 laminates the first carrier film 41 and the second carrier film 42 together to form a laminate 60. In the laminate 60, the first resin paste layer 51L, the carbon fiber mat 30, and the second resin paste layer 52L are sandwiched between the first carrier film 41 and the second carrier film 42. In order to sandwich and transport the laminate 60 between two conveyor belts from above and below, the impregnating machine 160 includes two belt conveyors, one above the other, and a roll for pressing the laminate 60 together with the conveyor belts.

[0015] The heater 150 heats the short carbon fiber bundles 20 transported by the belt conveyor 140. In Fig. 1, the heater is disposed above the transport path to heat the transported short carbon fiber bundles 20 from above, but the heater may be disposed below the transport path to heat the transported short carbon fiber bundles 20 from below, or may be disposed above and below the transport path to heat the transported short carbon fiber bundles 20 from above and below. The heating method of the heater 150 is not particularly limited, but examples include a hot air heater, an infrared heater, etc. A plurality of heating methods may be used in combination as the heater 150. For example, a hot air heater and an infrared heater may be used in combination as the heater 150 and appropriately arranged.

[0016] 2. Manufacturing method of SMC The procedure for manufacturing an SMC using the manufacturing method according to the embodiment will be described below using the CF-SMC manufacturing apparatus described in 1 above as an example. First, the long carbon fiber bundle 10 is drawn from a fiber package prepared in advance. The long carbon fiber bundle 10 may be drawn from a bobbin package attached to a creel by external drawing, or may be drawn from a package from which the bobbin has been removed by internal drawing. The long carbon fiber bundle 10 may be partially split into a plurality of sub-bundles in advance.

[0017] A plurality of long carbon fiber bundles 10 are aligned in parallel to each other and supplied to a chopper 130 . The long carbon fiber bundle 10 is cut to a predetermined length by the chopper 130 to become a short carbon fiber bundle 20. The predetermined length is preferably within a range of 10 to 60 mm, and may typically be 0.5 inches (about 1.3 cm), 1 inch (about 2.5 cm), 2 inches (about 5.1 cm), etc., but is not limited thereto.

[0018] The short carbon fiber bundles 20 fall onto the conveying path of the belt conveyor 140 below the chopper 130 and are conveyed toward the discharge end of the belt conveyor 140. While being conveyed by the belt conveyor 140, the short carbon fiber bundle 20 is heated by the heater 150. The temperature of the heated short carbon fiber bundle 20 may be 40° C. or more and less than 50° C., 50° C. or more and less than 60° C., 60° C. or more and less than 70° C., 70° C. or more and less than 80° C., 80° C. or more and less than 90° C., 90° C. or more and less than 100° C., 100° C. or more and less than 110° C., or 110° C. or more and less than 120° C. The temperature of the short carbon fiber bundle 20 dropped onto the belt conveyor 140 and heated can be measured by, for example, a thermocouple or a radiation thermometer.

[0019] The temperature of the short carbon fiber bundles 20 can be controlled by the output of the heater 150, the heating time, and the density of the short carbon fiber bundles 20 on the belt conveyor 140. The heating time is the time required for each of the short carbon fiber bundles 20 to pass through the area heated by the heater 150, and is determined by the length of the area along the conveying direction of the belt conveyor and the conveying speed. When the space in which the belt conveyor 140 can be installed is narrow, the conveying speed can be reduced to ensure sufficient heating time even if the conveying path is short.

[0020] When the running speed of the transport belt is relatively slow, for example, equal to or slower than the running speed of the first carrier film, a mat of piled up short carbon fiber bundles 20 is accumulated on the transport belt. When heating such a mat, if the conveyor belt has a mesh structure and hot air is blown weakly from both above and below the conveyor path, not only the surface of the mat but also its inside can be heated. In an alternative example, a suction nozzle may be installed so as to reduce the pressure below the transport path to prevent the short carbon fiber bundles from flying around, while a heater wire may be placed above the transport path to blow hot air onto the mat from above.

[0021] When the running speed of the conveyor belt is increased so that the short carbon fiber bundles 20 do not pile up thickly on the belt, particularly when the short carbon fiber bundles 20 do not overlap each other, the short carbon fiber bundles 20 can be sufficiently heated by the heater 150 installed only above the conveying path. In this case, the heater 150 may be an infrared heater or a hot air heater, or both may be used in combination. When a hot air heater is used, it is preferable that the conveying belt is a mesh belt and hot air is blown from the upper surface side of the conveying belt. Additionally or alternatively, a reduced pressure may be applied underneath the mesh belt to keep the short carbon fiber bundles from flying around.

[0022] As shown in FIG. 4, the short carbon fiber bundles 20 fall from the discharge end of the belt conveyor 140, and a carbon fiber mat 30 made of the short carbon fiber bundles 20 is deposited on the first carrier film 41 running below the discharge end.

[0023] In a preferred embodiment, a space (inside the dashed line in FIG. 5) including at least the discharge end X of the belt conveyor 140 and the carbon fiber mat depositing portion Y where the carbon fiber mat 30 is deposited on the first carrier film 41 is kept at a higher temperature than the surrounding area. This makes it possible to prevent the short carbon fiber bundles 20 from being cooled during the fall and the temperature from decreasing too much.

[0024] One method for maintaining the space inside the dashed line in Figure 5 at a higher temperature than the surrounding area is to surround the space with boards or sheets to isolate it from outside air to the greatest extent possible, and then supply warm air into the space. This space may be extended so that the heater 150 and the area where the short carbon fiber bundles 20 on the belt conveyor 140 are heated by the heater 150 are also included in this space.

[0025] Before the carbon fiber mat 30 is deposited, a first resin paste 51 is applied to one side of the first carrier film 41 unrolled from a roll by using a first coater 110 . The first resin paste 51 is a thermosetting resin composition, and its base resin is, but is not limited to, for example, vinyl ester resin (also called epoxy acrylate resin), unsaturated polyester resin, epoxy resin, polyimide resin, maleimide resin, or phenol resin. A mixed resin of vinyl ester resin and unsaturated polyester resin may be used as the base resin. The first resin paste 51 may contain, as necessary, a hardener, a polymerization inhibitor, a thickener, a reactive diluent, a low-shrinkage agent, a flame retardant, an antibacterial agent, and the like.

[0026] In a separate process, a second resin paste 52 made of a thermosetting resin composition having the same composition as the first resin paste 51 is applied to one side of a second carrier film 42 using a second coater 120 . The second carrier film 42 is superimposed on the first carrier film 41 having the carbon fiber mat 30 placed thereon, with the surface on which the second resin paste layer 52L is formed facing down, by a laminating machine 170. The laminate 60 thus formed is pressurized by an impregnating machine 160, whereby the carbon fiber mat 30 is impregnated with the first resin paste 51 and the second resin paste 52, to form a resin-impregnated carbon fiber mat.

[0027] By heating the short carbon fiber bundles 20 with the heater 150, the temperature of the carbon fiber mat 30 increases, preventing the first resin paste 51 and the second resin paste 52 from becoming highly viscous due to a decrease in temperature due to contact with the carbon fiber mat 30. The temperature of the carbon fiber mat 30 dropped onto the first resin paste layer 51L may be 40° C. or more and less than 50° C., 50° C. or more and less than 60° C., 60° C. or more and less than 70° C., 70° C. or more and less than 80° C., 80° C. or more and less than 90° C., 90° C. or more and less than 100° C., 100° C. or more and less than 110° C., 110° C. or more and less than 120° C., etc. The temperature can be measured using a non-contact measurement method, for example, a radiation thermometer. In a preferred embodiment, the first resin paste layer 51L and the second resin paste layer 52L may be heated by a heater (not shown).

[0028] The resin-impregnated carbon fiber mat is wound up on a bobbin while being sandwiched between the first carrier film 41 and the second carrier film 42. The resin-impregnated carbon fiber mat wound up on the bobbin is thickened as necessary and then shipped as CF-SMC.

[0029] In the above example, the first resin paste 51 and the second resin paste 52 stored in the first coater 110 and the second coater 120, respectively, can be heated or kept warm as needed, and the laminate 60 transported by the impregnation machine 160 can be heated or kept warm as needed. The first resin paste 51 and the second resin paste 52 can also be heated or kept warm in a stage before being supplied to the coaters by an appropriate method as needed.

[0030] In a preferred example, the laminate 60 (the resin-impregnated carbon fiber mat sandwiched between the first carrier film 41 and the second carrier film 42) may be cooled before being wound around a bobbin. By cooling, the start of the curing reaction of the thermosetting resin composition can be reliably prevented, and the thermosetting resin composition that does not penetrate into the short carbon fiber bundles 20 and exists in the gaps between the short carbon fiber bundles 20 becomes highly viscous, so that it can be prevented from being squeezed out to the outside of the carbon fiber mat 30. Cooling may be performed until the temperature of the laminate 60 falls to room temperature, but is not limited thereto, and may be performed to such an extent that the above-mentioned object can be achieved. Examples of cooling methods include, but are not limited to, forced air cooling using a fan and contact with a cooling roll. Forced air cooling and a cooling roll may be used in combination.

[0031] In one example, the long carbon fiber bundle 10 supplied toward the chopper 130 may be additionally heated. However, if the long carbon fiber bundle 10 is heated to the extent that the sizing agent is softened, the short carbon fiber bundle 20 will stick to the rubber roll of the chopper 130, so there is a limit to the temperature. In an alternative embodiment, instead of cutting long carbon fiber bundles to produce short carbon fiber bundles with a chopper installed in the CF-SMC manufacturing equipment, short carbon fiber bundles produced in advance by cutting long carbon fiber bundles in a separate process or by other methods may be supplied onto the conveying path of the belt conveyor. [Industrial Applicability]

[0032] CF-SMC is used to mold CFRP (carbon fiber reinforced plastic) products, for example, by compression molding. CFRP products that can be manufactured using CF-SMC are diverse, including parts for aircraft, automobiles, ships, and other types of transportation equipment, as well as sporting goods and leisure goods. [Explanation of symbols]

[0033] 10...long carbon fiber bundle, 20...short carbon fiber bundle, 30...carbon fiber mat, 41...first carrier film, 42...second carrier film, 51...first resin paste, 51L...first resin paste layer, 52...second resin paste, 52L...second resin paste layer, 60...laminated body, 100...CF-SMC manufacturing apparatus, 110...first coater, 120...second coater, 130...chopper, 131...cutter roll, 132...receiving roll, 133...guide roll, 134...dispersing roll, 134a...rotating shaft, 134b...disk, 134c...wire or rod, 140...belt conveyor, 150...heater, 160...impregnation machine, 170...lamination machine, X...discharge end of belt conveyor, Y...carbon fiber mat deposition section

Claims

1. 1. A method for producing a sheet prepreg, comprising: applying a thermosetting resin paste to a surface of each of a first carrier film and a second carrier film; transporting a plurality of short carbon fiber bundles on a belt conveyor and then dropping them from a discharge end of the belt conveyor onto the first carrier film, thereby depositing a carbon fiber mat on the surface of the first carrier film on which the thermosetting resin paste has been applied; bonding the second carrier film to the first carrier film with the carbon fiber mat sandwiched therebetween so that the surfaces on which the thermosetting resin paste has been applied face each other to form a laminate; pressurizing the laminate to impregnate the carbon fiber mat with the thermosetting resin paste; and heating the plurality of short carbon fiber bundles with a heater while they are transported on the belt conveyor.

2. 2. The method for producing a sheet prepreg according to claim 1, wherein a space including at least a discharge end of the belt conveyor and a carbon fiber mat deposition portion where the carbon fiber mat is deposited on the first carrier film is maintained at a higher temperature than the surrounding area.

3. a first coater for applying a thermosetting resin paste to a first carrier film; a second coater for applying a thermosetting resin paste to a second carrier film; a belt conveyor having a discharge end for conveying a plurality of short carbon fiber bundles and then dropping them from the discharge end onto the first carrier film to deposit a carbon fiber mat on the surface of the first carrier film on which the thermosetting resin paste has been applied; a heater for heating the short carbon fiber bundles transported by the belt conveyor; a lamination machine for laminating the second carrier film to the first carrier film with the carbon fiber mat sandwiched therebetween such that the surfaces coated with the thermosetting resin paste face each other to form a laminate; an impregnation machine for impregnating the carbon fiber mat with the thermosetting resin paste by pressing the laminate; A sheet prepreg manufacturing apparatus comprising:

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