Method for manufacturing fiber-reinforced resin sheets

Abstract

To provide a method for manufacturing fiber-reinforced resin sheets with reduced fiber bundling in the width direction using a double belt press apparatus.SOLUTION: The invention includes a first step of aligning fibers A in one direction, a second step of conveying the fibers toward rollers 22 and 24 provided at one end of either a lower endless belt 21 or an upper endless belt 23 so that the rollers circulate in the same direction as the aligned fibers, and conveying thermoplastic resin films B and C toward a double belt press device 20, a third step of heating the thermoplastic resin films to obtain a sheet D integrated with the fibers, and a fourth step of taking up the integrated sheet with a take-up device 14. The method for manufacturing a fiber-reinforced resin sheet is characterized in that the integrated sheet is positioned either below a surface of the lower endless belt facing the upper endless belt or above a surface of the upper endless belt facing the lower endless belt.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a fiber-reinforced resin sheet. [Background technology]

[0002] Fiber-reinforced resin sheets containing fibers and resin have been widely used as molding intermediates and molded products because of their excellent processability and impact resistance. In particular, molding intermediates are called stampable sheets, and the final molded products can be obtained by cutting the stampable sheet into a predetermined shape, placing the cut sheet in a mold, heating and pressurizing it, and then cooling it.

[0003] Such molding intermediates have conventionally been produced by melting a powder, film, or sheet of a thermoplastic resin onto a mat (e.g., chopped strand mat) or aligned product of reinforcing fibers (e.g., glass fibers, carbon fibers) at a temperature at least higher than the softening point or melting point of the thermoplastic resin, and impregnating the thermoplastic resin with the reinforcing fibers.

[0004] As molding intermediates, fiber-reinforced resin sheets, which are lightweight yet highly rigid and strong, have attracted attention from the perspectives of energy and environmental issues. In particular, fiber-reinforced resin sheets using thermoplastic resins as matrix resins have excellent processability and impact resistance, and are being considered for application in the construction and automotive fields. For use in these fields, molding intermediates are required to be large in size from the perspective of the shape of the final molded product. When using a double-belt press, the longitudinal direction is not restricted by the device, making it suitable for producing large molding intermediates.

[0005] The following is a method for manufacturing a molding intermediate (prepreg) using a double belt press.

[0006] Patent Document 1 discloses a method for producing a thermoplastic resin prepreg in which a double belt press is used to heat and pressurize reinforcing fiber bundles and a thermoplastic resin to impregnate the reinforcing fiber bundles with the thermoplastic resin, and by controlling the zero shear viscosity of the thermoplastic resin at a predetermined position, tow cracking of the prepreg is reduced. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-224297 Summary of the Invention [Problem to be solved by the invention]

[0008] From the viewpoint of improving the physical properties of the prepreg, it is preferable that the fiber bundles are distributed in the width direction on the prepreg. However, it has been found that even when the prepreg manufacturing apparatus disclosed in Patent Document 1 is used, multiple fiber bundles gather closely together in the width direction on the prepreg. When multiple fiber bundles gather in the width direction on the prepreg, areas where there is not enough fiber are generated, resulting in uneven physical properties depending on the area of ​​the prepreg, which is insufficient from the viewpoint of physical properties. Therefore, there is a demand for a fiber-reinforced resin sheet in which fiber gathering in the width direction is reduced.

[0009] The present invention has been made in consideration of the above circumstances, and its object is to provide a fiber-reinforced resin sheet in which fiber aggregation in the width direction is reduced when a fiber-reinforced resin sheet is manufactured using a double belt press device. It is to obtain a fiber-reinforced resin sheet. [Means for solving the problem]

[0010] That is, the present invention includes the following inventions. [1] A manufacturing method for manufacturing a fiber-reinforced resin sheet containing fibers and a thermoplastic resin using a double belt press device, wherein the double belt press device is provided with an upper endless belt and a lower endless belt, and the upper and lower endless belts have a structure in which they are wound around rollers provided at one end and the other end of the double belt press device and run in a circular motion, and the first step aligns the fibers in one direction using a unidirectional aligning device, and the second step conveys the fibers discharged from the unidirectional aligning device toward a roller provided at one end of either the lower endless belt or the upper endless belt, which is arranged to run in a circular motion in the same direction as the aligned fibers, and then conveys the fibers toward the double belt press device. A method for producing a fiber-reinforced resin sheet, comprising: a second step of transporting a thermoplastic resin film; a third step of heating the thermoplastic resin film in the double belt press device to obtain an integrated sheet in which the thermoplastic resin film and the fibers are integrated; and a fourth step of taking up the integrated sheet discharged from the other end of the double belt press device with a take-up device, wherein the fibers transported from the alignment device to the one end and the integrated sheet transported from the other end to the take-up device are both located below the surface of the lower endless belt that faces the upper endless belt, or both are located above the surface of the upper endless belt that faces the lower endless belt. [2] The manufacturing method described in [1] above, which includes, in the third step, a step of heating and pressurizing the thermoplastic resin film and the fibers, and then cooling them to integrate the thermoplastic resin film and the fibers. [3] The manufacturing method according to [2] above, wherein the molding temperature during heating is at least 60°C higher than the lower of the melting point and the glass transition temperature of the thermoplastic resin. [4] The manufacturing method according to any one of [1] to [3] above, which comprises, before the first step, a step of opening a roving fiber bundle having a length of 100 mm or more. [5] The method according to any one of the above [1] to [4], wherein the thickness of the thermoplastic resin film is 10 μm to 250 μm. [6] The method according to any one of the above [1] to [5], wherein in the fiber reinforced resin sheet, the mass ratio of the fibers to the thermoplastic resin is 95 / 5 to 30 / 70. [Effects of the Invention]

[0011] By using the manufacturing method of the present invention, it is possible to obtain a fiber-reinforced resin sheet in which the aggregation of fibers in the width direction is reduced. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a schematic side view of a fiber-reinforced resin sheet manufacturing apparatus used in the examples of the present invention. [Figure 2] FIG. 2 is a schematic top view showing a aligning device used in an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The manufacturing method of the present invention is a manufacturing method for manufacturing a fiber-reinforced resin sheet containing fibers and a thermoplastic resin by integrating a thermoplastic resin film and fibers using a double belt press device.

[0014] The double belt press used in the manufacturing method of the present invention has an upper endless belt and a lower endless belt, which are wound around rollers provided at one end and the other end of the double belt press and run in a circular motion. The upper endless belt and the lower endless belt are provided so as to be approximately horizontal.

[0015] The manufacturing method of the present invention includes a first step of aligning fibers in one direction using an aligning device, a second step of conveying the fibers discharged from the aligning device toward a roller provided at one end of one of the lower endless belt and the upper endless belt arranged to travel in the same direction as the aligned fibers and conveying a thermoplastic resin film toward the double belt press device, a third step of heating the thermoplastic resin film in the double belt press device to obtain an integrated sheet integrating the thermoplastic resin film and the fibers, and a fourth step of taking up the integrated sheet discharged from the other end of the double belt press device with a take-up device. Note that, hereinafter, the roller to which the fibers discharged from the aligning device are conveyed in the second step is referred to as the front roller.

[0016] [Thermoplastic resin film] The thermoplastic resin film is not particularly limited and may be a flat sheet or an embossed sheet, but is preferably a flat sheet. When it is a flat sheet, the thickness of the thermoplastic resin film is preferably 10 μm to 250 μm, and more preferably 20 μm to 100 μm. Furthermore, a sheet-like material made of a woven or nonwoven thermoplastic resin fabric may be used as the thermoplastic resin film, but from the viewpoint of heat transfer to the thermoplastic resin film, it is preferable that the sheet does not have voids.

[0017] The thermoplastic resin is not particularly limited, and can be selected depending on the application of the molded article and the desired properties of the molded article. Examples of thermoplastic resins include polyolefin resins such as polyethylene and polypropylene; polyamide resins such as polyamide 6, polyamide 12, polyamide 66, and polyamide 46; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polyether ketone resins; polyphenylene sulfide resins; polyetherimide resins; and polycarbonate resins. In this specification, the term "based" refers to modified resins, and for example, polyolefin resins include not only polyolefin resins but also modified polyolefin resins obtained by modifying polyolefin resins.

[0018] The thermoplastic resin is preferably a polyolefin resin from the viewpoints of low cost, flowability during molding, water resistance, hot water resistance, chemical resistance, etc. Among polyolefin resins, polypropylene resins are more preferred from the viewpoint of easy availability, and acid-modified polypropylene resins are even more preferred from the viewpoint of adhesiveness to fibers.

[0019] From the viewpoints of abrasion resistance, oil resistance, and long-term heat resistance, a polyamide-based resin may be used as the thermoplastic resin, and from the viewpoints of heat resistance, mechanical strength, creep characteristics, chemical resistance, and oil resistance, a polyester-based resin may be used as the thermoplastic resin.

[0020] [fiber] The type of fiber is not particularly limited, and examples include inorganic fibers such as carbon fiber, glass fiber, and basalt fiber; metal fibers such as boron fiber, titanium fiber, and steel fiber; organic fibers such as aramid, polyamide, and polyester; and natural fibers such as cotton, hemp, and flax. Among these, inorganic fibers are preferred, and from the viewpoints of cost and the elastic modulus and mechanical strength of the resulting molded product, at least one of carbon fiber and glass fiber is more preferred, and carbon fiber is even more preferred.

[0021] When a fiber bundle is used, the fiber bundle generally has a round shaft shape consisting of thousands to tens of thousands of single fibers. Therefore, even if the fiber bundle is impregnated with a resin, the impregnation of the resin is insufficient. Therefore, when a fiber bundle is used, it is necessary to perform at least one of an unwinding process and a spreading process on the fiber bundle before the first process of aligning the fibers using a aligning device, thereby reducing the number of fiber bundles in the thickness direction and spreading the fiber bundle into a thin band. When a fiber bundle is used, it is preferable to use a roving fiber bundle having a length of 100 mm or more from the viewpoint of productivity. Note that when the fiber or fiber bundle is in a state that is easy to impregnate with a resin, such as a single fiber or a fiber bundle spread into a thin band, the fiber or fiber bundle may be introduced into the aligning device without performing the unwinding process and the spreading process.

[0022] The unwinding process refers to unwinding the fiber bundle from the roving fiber bundle, and the spreading process refers to spreading the unwound round-shape fiber bundle into a thin strip. Since it is sufficient if the fiber bundle is spread into a thin strip (flat shape) before the fibers are aligned in the first process, spreading is not necessary if the number of fiber bundles in the thickness direction is reduced due to tension applied during unwinding and the fiber bundle has become a thin strip.

[0023] When fiber-spreading is performed, the fiber bundle is continuously spread to form a thin, band-like, continuous fiber bundle (hereinafter referred to as spread fiber bundle). The method of spreading is not particularly limited as long as the fiber bundle is spread into a thin band-like shape, and the fiber bundle may be spread by beating, by blowing air, or by applying ultrasonic waves.

[0024] In this specification, "fiber" includes not only single fibers but also spread fiber bundles. Furthermore, in this specification, "spread" includes not only fibers spread by the spreading step, but also fibers spread into a thin band shape by only the unwinding step without the spreading step.

[0025] [1st step] In the first step, the fibers are aligned in one direction using an alignment device. If the fibers are transported to the double-belt press without being aligned, uneven fiber distribution in the width direction occurs. As a result, the fibers may be damaged by rubbing against each other during or immediately after transport to one of the endless belts. If damaged, the physical properties of the resulting fiber-reinforced resin sheet, such as impact resistance, may be reduced. Furthermore, the fibers may gather in the width direction, which may prevent the fiber bundles from maintaining their open state, especially when using spread fiber bundles.

[0026] When at least one of unwinding and spreading is performed on the fiber bundle, it is preferable to provide a paralleling device near the spreading device (or the unwinding device if spreading is not performed) to prevent damage caused by rubbing of the fibers in the spread fiber bundle against each other.

[0027] The aligning device may be any device capable of aligning the fibers in one direction, and may align the fibers in one direction using, for example, a comb-shaped or uneven guide, or may align the fibers in one direction using a groove provided in the aligning device. By aligning the fibers in one direction, the possibility of the fibers gathering in the width direction when producing a fiber-reinforced resin sheet can be reduced.

[0028] An example of a paralleling device is shown below, but the device is not limited to the one described below as long as it can align the fibers in one direction, prevent the fibers from gathering in the width direction, and allow the fibers to pass through the paralleling device stably.

[0029] Fig. 2 shows an example of an alignment device that aligns fibers in one direction using a guide. The alignment device 13 in Fig. 2 includes a guide 3 having a plurality of annular protrusions 2 provided at equal intervals in the axial direction of the rod-shaped object 1. The fiber bundle A discharged from the fiber-spreading device 12 is aligned by passing between adjacent annular protrusions 2. The axial direction of the rod-shaped object 1 and the axial direction of the front roller are the same. Also, in Fig. 2, the fiber bundle A discharged from the fiber-spreading device 12 is transported to the alignment device 13, but the fiber bundle A discharged from the unwinding device may be transported directly to the alignment device 13 without passing through the fiber-spreading device 12.

[0030] The sizes of the rod-shaped object 1 and the annular protrusion 2 depend on the type of fiber and the number of filaments, and are not particularly limited as long as the fiber bundle A can be aligned, the fiber bundle A does not gather in the width direction, and the fiber bundle A can pass through the alignment device 13 stably. For example, the rod-shaped object 1 is cylindrical and has a diameter of 0.1 to 5 mm, preferably 0.5 to 3 mm. For example, the annular protrusion 2 is annular and has a diameter of 0.2 to 20 mm, preferably 0.5 to 15 mm. The interval between adjacent annular protrusions 2 is preferably 3 mm to 30 mm, more preferably 5 mm to 15 mm.

[0031] The fibers discharged from the alignment device are transported toward the front roller of the double belt press device. However, if the distance between the alignment device and the front roller is too great, the tension on the fibers may cause the fibers to bunch up in the width direction. In particular, when spread fiber bundles are used, the distance between the fiber bundles is likely to be uneven, which may prevent the fiber bundles from remaining dispersed in the width direction and cause them to bunch up. Therefore, the distance between the position where the fibers contact in the alignment device and the position where the fibers contact on the front roller is preferably 40 cm or less, more preferably 20 cm or less, and even more preferably 10 cm or less. Note that the "position where the fibers contact on the alignment device" refers to the position closest to the front roller among the positions where the fibers contact on the alignment device, and the "position where the fibers contact on the front roller" refers to the position closest to the alignment device among the positions where the fibers contact on the front roller.

[0032] [Second process] In the second step, the fibers discharged from the arranging device are transported toward the front roller.

[0033] The fibers discharged from the alignment device are conveyed so as to contact the front roller, and the wrap angle at the front roller with which the fibers contact is preferably 30 to 150°, more preferably 60 to 135°. The wrap angle can be adjusted by the position of the alignment device (the height relative to the front roller and the distance between the position where the fibers contact the alignment device and the position where the fibers contact the front roller). Note that the wrap angle refers to the angle between a line connecting the center point of the front roller and the start point where the fibers contact the front roller, and a line connecting the center point of the front roller and the end point where the contact between the fibers and the front roller ends, when the front roller is viewed from a cross section perpendicular to the axial direction.

[0034] If the wrap angle is smaller than 30°, the contact pressure of the fibers on the endless belt will be low, which may cause the fiber bundles arranged by the drawing device to become distorted.If the wrap angle is larger than 150°, the fibers may be excessively bent or the contact pressure of the fibers may become too high, which may cause damage to the fibers.

[0035] The drum diameter of the rollers provided at one end and the other end of the double belt press device is preferably 800 mm or more. By making the diameter 800 mm or more, the fibers are in contact with the front roller for a certain period of time, and the contact pressure of the fibers sufficiently fixes the fibers, making it difficult for the fibers to gather in the width direction. The location of the alignment device is automatically determined by the drum diameter of the front roller, the wrap angle, and the distance between the position where the fibers contact the alignment device and the front roller.

[0036] In the second step, the thermoplastic resin film is conveyed toward a double belt press device. The thermoplastic resin film may be conveyed toward a roller provided at one end of the lower endless belt or toward a roller provided at one end of the upper endless belt. That is, the fiber and the thermoplastic resin film may be conveyed toward the same roller or toward different rollers. When conveying multiple thermoplastic resin films, all of the thermoplastic resin films may be conveyed toward the same roller or toward both rollers. In the case of a double belt press device in which the roller provided at one end of the lower endless belt and the roller provided at one end of the upper endless belt are misaligned and there is a section in the front where only one of the lower endless belt and the upper endless belt is present, the thermoplastic resin film may be conveyed toward the endless belt located behind the roller.

[0037] From the viewpoint of making it difficult for the fibers to gather in the width direction, it is preferable to introduce a thermoplastic resin film on both the lower and upper sides of the fibers. However, depending on the melt viscosity of the thermoplastic resin film and the fiber volume content of the desired fiber-reinforced resin sheet, the thermoplastic resin film may be introduced only on the lower or upper side of the fibers.

[0038] The thermoplastic resin film can be transported to the double belt press device using a known method, for example, by unwinding the thermoplastic resin film from a roll on which it is wound and transporting it toward the desired transport position.

[0039] [3rd step] In the third step, the thermoplastic resin film is heated in a double belt press to obtain an integrated sheet in which the thermoplastic resin film and the fibers are integrated. While the thermoplastic resin film provided above or below the fibers is conveyed from one end to the other end (from front to rear) of the double belt press, the thermoplastic resin film is heated to soften or melt, and the thermoplastic resin is impregnated into the fibers.

[0040] The third step preferably includes a step of heating and pressurizing the thermoplastic resin film and fibers, followed by cooling to integrate the thermoplastic resin film and fibers. By applying pressure while heating and increasing the temperature, air bubbles contained in the integrated sheet can be removed, improving the quality of the integrated sheet. Furthermore, by solidifying the thermoplastic resin by cooling, the handleability of the integrated sheet can be improved.

[0041] The heating method is not particularly limited, but for example, a heating roller can be provided behind one end of the double belt press device, or a fluid can be passed through the double belt press device, thereby heating the heating roller or fluid and transmitting thermal energy to the endless belt. Alternatively, the endless belt itself may be heated without using a heating roller or fluid. Known methods for heating the roller or fluid can be used, such as direct heating with an electric heater or indirect heating with high-frequency induction heating.

[0042] From the viewpoint of continuously and efficiently impregnating the fibers with the thermoplastic resin, the molding temperature of the thermoplastic resin during heating is preferably at least 60°C higher than the lower of the melting point or glass transition temperature of the thermoplastic resin, more preferably 70 to 100°C higher than the lower of the melting point or glass transition temperature of the thermoplastic resin, and even more preferably 70 to 100°C higher than the melting point of the thermoplastic resin.

[0043] The method of applying pressure is not particularly limited, and examples include a method of transmitting pressure to the belts by providing a roller at a position behind one end of the double belt press device or by flowing a fluid inside the double belt press device.

[0044] When applying pressure using rollers, it is difficult to maintain a constant surface pressure on the passing integrated sheet, so adjusting the clearance between the upper and lower endless belts in the pressure application area is important. If the clearance between the upper and lower endless belts is too wide, the endless belts will not make sufficient contact with the passing integrated sheet, which may result in uneven impregnation of the thermoplastic resin into the fibers. On the other hand, if the clearance between the upper and lower endless belts is too narrow, the endless belts will make excessive contact with the integrated sheet passing between them, which may result in the softened or molten thermoplastic resin spreading excessively in the width direction of the device or flowing backward. Therefore, when applying pressure using rollers, the clearance between the upper and lower endless belts is preferably 1 to 10 times, and more preferably 3 to 5 times, the thickness of the fiber-reinforced resin sheet (target sheet thickness).

[0045] The cooling method is not particularly limited, and examples thereof include known methods such as air cooling, water cooling, and oil cooling. The cooling temperature is not particularly limited and can be determined appropriately based on the balance with the production rate, but it is sufficient that the integrated sheet is sufficiently solidified when it is discharged from the double belt press apparatus. It is preferable that the temperature of the integrated sheet when it is discharged from the other end of the double belt press apparatus is lower than the lower of the melting point or the glass transition temperature. By lowering the temperature of the integrated sheet below the lower of the melting point or the glass transition temperature, the integrated sheet can be sufficiently solidified.

[0046] It is preferable to continue to apply pressure to the integrated sheet during heating and cooling, as this also promotes impregnation of the thermoplastic resin into the fibers.

[0047] The pressurization time in the double belt press is preferably 30 to 540 seconds, more preferably 60 to 360 seconds. The cooling time in the double belt press is preferably 10 to 180 seconds, more preferably 20 to 120 seconds. When the pressurization time and cooling time in the double belt press are within the above ranges, the thermoplastic resin is heated over time before the thermoplastic resin and fibers reach the other end of the double belt press, and then solidifies over time. This allows the thermoplastic resin to be efficiently impregnated throughout the fibers, and the fibers to be sufficiently impregnated with the thermoplastic resin. The conveying speed of the double belt press is not particularly limited as long as the pressurization time and cooling time are within the above ranges. However, it is preferably 0.05 to 5 m / min, more preferably 0.1 to 3 m / min. The lengths of the pressurization section and cooling section in the double belt press are not particularly limited, and are preferably set to satisfy the above conveying time and conveying speed.

[0048] [4th step] In the fourth step, the integrated sheet discharged from the other end of the double belt press device is taken up by a take-up device. By taking up the integrated sheet with the take-up device, a fiber-reinforced resin sheet is obtained. The fibers conveyed from the aligning device to one end and the integrated sheet conveyed from the other end to the take-up device are both positioned below the surface of the lower endless belt facing the upper endless belt, or both positioned above the surface of the upper endless belt facing the lower endless belt. By positioning the fibers conveyed from the aligning device to one end and the integrated sheet conveyed from the other end to the take-up device in the above positions, it is possible to reduce the accumulation of fibers in the width direction within the integrated sheet. The take-up device can be, for example, a device composed of one or more take-up rollers, but is not particularly limited as long as it is a device capable of taking up the integrated sheet.

[0049] The position of the take-up device differs depending on whether the front roller in the second step is a roller provided at one end of the lower endless belt or a roller provided at one end of the upper endless belt. When the front roller is a roller provided at one end of the lower endless belt, the take-up device is provided below the surface of the lower endless belt of the double belt press apparatus that faces the upper endless belt so that both the fibers conveyed from the aligning device to one end and the integrated sheet conveyed from the other end to the take-up device are located below the surface of the lower endless belt that faces the upper endless belt. When the front roller is a roller provided at one end of the upper endless belt, the take-up device is provided so that the position at which the integrated sheet is taken up by the take-up device is located above the surface of the upper endless belt that faces the lower endless belt, and both the fibers conveyed from the aligning device to one end and the integrated sheet conveyed from the other end to the take-up device are located above the surface of the upper endless belt that faces the lower endless belt. From the viewpoint of reducing the concentration of fibers in the width direction within the integrated sheet, it is preferable that the fibers transported from the alignment device to one end and the integrated sheet transported from the other end to the take-up device are both located below the surface of the lower endless belt facing the upper endless belt.

[0050] The angle between the horizontal plane and the sheet transported from the other end to the take-up device is preferably 5 to 40°, more preferably 10 to 35°. The fiber arrangement in the integrated sheet before and after take-up may differ depending on the take-up method, but by setting the angle between the horizontal plane and the sheet transported from the other end to the take-up device within the above range, the fiber arrangement at one end can be maintained while transporting the sheet to the take-up device, and fiber concentration in the width direction within the integrated sheet can be reduced. As mentioned above, the fiber arrangement in the integrated sheet before and after take-up may differ depending on the take-up method, so in this specification, only the integrated sheet after take-up by the take-up device in the fourth step is referred to as the fiber-reinforced resin sheet.

[0051] 1 shows an example of a schematic side view of a fiber-reinforced resin sheet manufacturing apparatus, but is not limited to the illustrated embodiment. In addition, FIG. 1 shows an embodiment in which the fibers transported from the aligning device to one end and the integrated sheet transported from the other end to the take-up device are both located below the surface of the lower endless belt that faces the upper endless belt. Also, in FIG. 1, one end of the lower endless belt is located forward of one end of the upper endless belt. First, the fiber bundle A is loaded onto the unwinding device 11. Next, the fiber bundle A discharged from the unwinding device 11 is transported to the spreading device 12 to spread the fiber bundle A. Thereafter, the fiber bundle A spread by the spreading device 12 is transported to the arranging device 13 so as to be dispersed in the width direction. The spread fiber bundle A passes through a guide provided in the arranging device 13, whereby the spread fiber bundle A is aligned in one direction. The aligned fiber bundle A is transported toward a roller (front roller) 22 provided at one end of a lower endless belt 21 of a double belt press device 20. The thermoplastic resin film B is transported toward the front roller 22, and the thermoplastic resin film C is transported toward a roller 24 provided at one end of an upper endless belt 23. As a result, a laminate is formed in which the fiber bundle A is sandwiched between the thermoplastic resin film B and the thermoplastic resin film C. Thermoplastic resin film B, fiber bundle A, and thermoplastic resin film C are conveyed from the front (one end) to the rear (other end) of the double belt press device. During conveyance, thermoplastic resin films B and C are heated and softened or melted in a temperature-raising section (heating section) 25, and an integrated sheet D is obtained in which thermoplastic resin film B, fiber bundle A, and thermoplastic resin film C are integrated. Thereafter, integrated sheet D is cooled in a cooling section 26 provided behind the temperature-raising section 25 to solidify the thermoplastic resin. Finally, the integrated sheet D discharged from the rear (other end) of the double belt press device is taken up by a take-up device 14 provided below the surface of the lower endless belt 21 located at the other end that faces the upper endless belt 23. The angle (take-up angle) between the horizontal plane and the sheet transported from the other end to the take-up device is indicated by θ.

[0052] [Fiber reinforced resin sheet] The fiber reinforced resin sheet obtained by the manufacturing method of the present invention preferably has a mass ratio of fiber to thermoplastic resin of 95 / 5 to 30 / 70, more preferably 85 / 15 to 40 / 60. By setting the mass ratio within the above range, it is easy to achieve both the impregnation of the resin into the fibers in the fiber reinforced resin sheet and improvements in the strength, rigidity, etc. of the fiber reinforced resin sheet.

[0053] The thickness of the fiber-reinforced resin sheet obtained by the production method of the present invention is preferably 50 to 400 μm, more preferably 70 to 200 μm. By setting the thickness within the above range, it is possible to improve production efficiency and also improve the impregnation of the resin into the fibers in the fiber-reinforced resin sheet.

[0054] The width of the fiber-reinforced resin sheet obtained by the manufacturing method of the present invention is limited by the width of the endless belt of the double belt press device, and is preferably about 20 to 80 mm narrower than the width of the endless belt, more preferably about 40 to 60 mm narrower. The width of the fiber-reinforced resin sheet is, for example, 100 to 500 mm, and preferably 200 to 400 mm.

[0055] Furthermore, the fiber reinforced resin sheet may contain additives such as a heat deterioration inhibitor, an antioxidant, and an ultraviolet absorber, as needed.

[0056] [Strip-shaped sheet] The fiber-reinforced resin sheet obtained by the manufacturing method of the present invention can also be further molded into a molded product of a predetermined shape. From the viewpoint of improving handleability during molding when forming into a molded product, the fiber-reinforced resin sheet may be cut in the longitudinal direction into strip-shaped sheets. Specifically, in the cutting process, the fiber-reinforced resin sheet is slit in the width direction to a predetermined width using a slitting device to form a tape, and the tape-shaped fiber-reinforced resin sheet can be further cut in the longitudinal direction to form strip-shaped sheets. Cutting is usually performed using a fan cutter, but is not particularly limited.

[0057] The size of the strip-shaped sheet is not particularly limited, but can be, for example, 5 to 100 mm in length and 4 to 60 mm in width. By setting the length and width within the above ranges, handling during molding into a molded product can be improved. The thickness of the strip-shaped sheet is the same as the thickness of the fiber-reinforced resin sheet before cutting. [Example]

[0058] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples. Furthermore, modifications can be made within the scope of the above and below-described aims, and all such modifications are within the technical scope of the present invention.

[0059] The state of collection of fiber bundles in the width direction of the obtained fiber reinforced resin sheet was visually confirmed. A: The fiber bundles are less concentrated in the width direction than in the fiber-reinforced resin sheet obtained in Example 5, and almost no concentration of multiple fiber bundles is observed in the width direction. B: The aggregation state is the same as that of the fiber reinforced resin sheet obtained in Example 5, and a small amount of aggregation of multiple fiber bundles is observed in the width direction. C: There is more fiber bundle aggregation in the width direction than in the fiber reinforced resin sheet obtained in Example 5, and many aggregations of multiple fiber bundles in the width direction are observed throughout the sheet

[0060] The state of damage to the fibers in the obtained fiber-reinforced resin sheet was visually confirmed. A: The damage is the same as that of the fiber-reinforced resin sheet obtained in Example 5, and the fibers are hardly damaged. B: More fiber damage is observed than in the fiber-reinforced resin sheet obtained in Example 5

[0061] Example 1 A fiber-reinforced resin sheet was produced using roving carbon fiber (TR700, 800 tex, 12,000 f manufactured by Toray Industries, Inc.) as the fiber and an acid-modified polypropylene film with a thickness of 40 μm and a melting point of 165°C manufactured by Asahi Techno Industries Co., Ltd. as the thermoplastic resin film, using the manufacturing apparatus shown in Figure 1. The outline of the double belt press device is as follows: Device total length: 7500mm Length of the press part of the lower endless belt: 5220 mm Length of the press part of the upper endless belt: 4000mm Endless belt width: 500mm Heating part total length: 2250mm Cooling section total length: 750mm Press method: 750 kg load on the press part of the upper endless belt

[0062] First, 48 carbon fiber bundles were loaded onto the unwinding device. The carbon fiber bundle discharged from the unwinding device was transported to the spreading device, and the fiber bundles spread by the spreading device were transported so as to be dispersed across the entire width direction of the alignment device shown in Figure 2. The spread fiber bundles were aligned in one direction by passing through a guide equipped with annular protrusions, each 11 mm in diameter and 1.5 mm wide, spaced 11 mm apart in the axial direction of a cylindrical rod with a diameter of 1.5 mm, which was attached to the alignment device. The spreading device and alignment device were installed so that the height of the fiber bundles discharged from each device was the same as the height of the center of the roller (front roller) attached to one end of the lower endless belt. The distance between the position where the carbon fiber bundles contact in the guide of the alignment device and the position where the carbon fiber bundles contact in the front roller was 2 cm. The aligned carbon fiber bundle was conveyed toward the front roller, and two acid-modified polypropylene films were conveyed toward the front roller so as to sandwich the carbon fiber bundle. The wrap angle at the front roller with which the carbon fiber bundle came into contact was 90°. The rollers provided at one end and the other end of the upper and lower endless belts of the double belt press device all had a drum diameter of 1000 mm. In the heating section of the double belt press, the acid-modified polypropylene film and the carbon fiber bundle were heated and pressurized to form an integrated sheet, which was then cooled. The conveying speed of the double belt press was 2 m / min, the gap (clearance) between the upper and lower endless belts was 0.5 mm, and the temperature of the heating section was set to 250 °C. In the cooling section, the integrated sheet was cooled by air. Finally, the integrated sheet discharged from the other end of the lower endless belt was taken up by a take-up device. The take-up device was installed so that the angle between the horizontal plane and the sheet transported from the other end to the take-up device was 15°. The obtained fiber-reinforced resin sheet was 300 mm wide, 150 μm thick, and had a mass ratio of carbon fiber to acid-modified polypropylene resin of 67 / 33. The obtained fiber-reinforced resin sheet had carbon fibers uniformly arranged in the sheet width direction, and almost no damage to the carbon fibers was observed. Furthermore, there were no problems with the double belt press associated with damage to the carbon fiber bundles, and operability was extremely good.

[0063] (Examples 2 to 6, Comparative Examples 1 to 3) A fiber-reinforced resin sheet was produced by the manufacturing method described in Example 1, except that the positions of the spreading device, the aligning device, and the take-up device were adjusted so that the distance between the position where the carbon fiber bundle contacts the guide of the aligning device and the position where the carbon fiber bundle contacts the front roller, the embrace angle, and the take-up angle were set to the conditions shown in Table 1.

[0064] In Comparative Example 1, in which the take-up device was installed higher than the lower endless belt, the positional deviation of the fibers was remarkable not only near the other end of the lower endless belt but also near one end, and as a result, a large amount of fiber aggregation was observed in the width direction of the fiber-reinforced resin sheet. Comparative Examples 2 and 3, in which the height of the position where the integrated sheet was taken up by the take-up device was the same as that of the lower endless belt, also showed similar results to Comparative Example 1.

[0065] [Table 1] [Explanation of symbols]

[0066] 1: Rod-shaped object 2: Ring-shaped protrusion 3: Guide 11:Unwinding device 12: Spreading device 13: Alignment device 14: Take-off device 20: Double belt press device 21: Lower endless belt 22: Roller (front roller) provided at one end of the lower endless belt 23: Upper endless belt 24: Roller provided at one end of the upper endless belt 25: Heating section 26: Cooling section A: Fiber bundle B, C: Thermoplastic resin film D: Integrated sheet

Claims

1. A manufacturing method for manufacturing a fiber reinforced resin sheet containing fibers and a thermoplastic resin using a double belt press device, the double belt press device includes an upper endless belt and a lower endless belt, and the upper and lower endless belts are wound around rollers provided at one end and the other end of the double belt press device and run in a circular motion; a first step of aligning the fibers in one direction using an aligning device; a second step of conveying the fibers discharged from the alignment device toward a roller provided at one end of either the lower endless belt or the upper endless belt, the roller being disposed so as to travel in the same direction as the aligned fibers, and conveying the thermoplastic resin film toward the double belt press device; a third step of increasing the temperature of the thermoplastic resin film in the double belt press device to obtain an integrated sheet in which the thermoplastic resin film and the fibers are integrated; a fourth step of taking up the integrated sheet discharged from the other end of the double belt press device with a take-up device, A method for manufacturing a fiber-reinforced resin sheet, characterized in that the fibers transported from the alignment device to one end and the integrated sheet transported from the other end to the take-up device are both located below the surface of the lower endless belt facing the upper endless belt, or both are located above the surface of the upper endless belt facing the lower endless belt.

2. The manufacturing method according to claim 1 , wherein the third step comprises a step of heating and pressurizing the thermoplastic resin film and the fibers, and then cooling the thermoplastic resin film and the fibers to integrate them.

3. 3. The method according to claim 2, wherein the molding temperature during heating is at least 60° C. higher than the lower of the melting point and the glass transition temperature of the thermoplastic resin.

4. The manufacturing method according to claim 1 or 2, further comprising, before the first step, a step of opening a roving fiber bundle having a length of 100 mm or more.

5. 3. The method according to claim 1, wherein the thickness of the thermoplastic resin film is 10 μm to 250 μm.

6. The manufacturing method according to claim 1 or 2, wherein the mass ratio of the fiber to the thermoplastic resin in the fiber reinforced resin sheet is 95 / 5 to 30 / 70.

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