Fiber-reinforced resin sheet and method for producing same

Abstract

The invention provides a fiber-reinforced resin sheet and a method for manufacturing the same. A fiber-reinforced resin sheet (1) is provided with: a resin base material (10) comprising a first thermoplastic resin layer (11), a second thermoplastic resin layer (12), and a third thermoplastic resin layer (13) which are laminated in the thickness direction and welded to each other; and reinforcing fibers (5) dispersed and contained in each of the first resin layer (11), the second resin layer (12), and the third resin layer (13) and oriented in the same direction in each of the layers. The thickness (T) of the fiber-reinforced resin sheet (1) is 20 llm or more and 200 [mu] m or less, and the average volume content of the reinforcing fibers (5) is 30% or more and 70% or less. Consequently, it is possible to provide a fiber-reinforced resin sheet which has a high content of reinforcing fibers and is unlikely to peel off the reinforcing fibers.

Description

Technical Field

[0001] The present invention relates to a fiber-reinforced resin sheet comprising a resin matrix containing reinforcing fibers. Background Art

[0002] As an example of a fiber-reinforced resin sheet, a fiber-reinforced resin sheet disclosed in Japanese Patent Publication No. 2022-103810 is known. The fiber-reinforced resin sheet of Japanese Patent Publication No. 2022-103810 is a fiber-reinforced resin sheet having a thickness of 30 to 65 μm, and includes: a thermoplastic resin film; and reinforcing fibers laminated on both sides of the resin film. The reinforcing fibers are laminated on both sides of the resin film in a manner that the volume content (Vf) relative to the fiber-reinforced resin sheet reaches 60 to 75% or more.

[0003] As described in the above-mentioned Japanese Patent Publication No. 2022-103810, when a relatively large amount of reinforcing fibers corresponding to a volume content of 60 to 75% are stacked on both sides of the resin film, there is a possibility that the resin film is not sufficiently impregnated into the reinforcing fibers. If the resin film impregnation into the reinforcing fibers is insufficient, there is a possibility that the reinforcing fibers may peel off from the resin film. Summary of the invention

[0004] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fiber-reinforced resin sheet having a high reinforcing fiber content and in which the reinforcing fibers are unlikely to be peeled off, and a method for producing the same.

[0005] As a technical solution for solving the above-mentioned problem, a fiber-reinforced resin sheet involved in one aspect of the present invention has a thickness of not less than 20 μm and not more than 200 μm, and includes: a resin substrate, comprising a first thermoplastic resin layer, a second resin layer and a third resin layer which are stacked in the thickness direction and fused to each other; and reinforcing fibers which are dispersed and contained in each layer of the first resin layer, the second resin layer and the third resin layer and are oriented in the same direction in each layer, wherein the average volume content of the reinforcing fibers is not less than 30% and not more than 70%.

[0006] A fiber-reinforced resin sheet according to another aspect of the present invention includes: a resin substrate formed of a sheet-shaped thermoplastic resin; and reinforcing fibers contained in the resin substrate at an average volume content of 30% or more and 70% or less in a state of being oriented in the same direction, wherein when the fiber-reinforced resin sheet is divided into five equal parts in the thickness direction, each range is defined as a first range, a second range, a third range, a fourth range, and a fifth range in order from one side surface to the other side surface of the resin substrate, the reinforcing fibers are contained in the resin substrate in such a manner that the volume content of the reinforcing fibers in the first range, the third range, and the fifth range is lower than the volume content of the reinforcing fibers in the second range and the fourth range.

[0007] In addition, another aspect of the present invention relates to a method for manufacturing a fiber-reinforced resin sheet, which includes: a first configuration step of configuring continuous first reinforcing fibers obtained by opening a fiber bundle between a first thermoplastic resin film and a second thermoplastic resin film; a second configuration step of configuring a third thermoplastic resin film from the opposite side of the first resin film in a manner facing the second resin film, and configuring continuous second reinforcing fibers obtained by opening a fiber bundle between the third resin film and the second resin film; and an impregnation step of softening the first resin film, the second resin film, and the third resin film by heating so that the first resin film, the second resin film, and the third resin film are impregnated into the first reinforcing fibers and the second reinforcing fibers.

[0008] According to the present invention, it is possible to provide a fiber-reinforced resin sheet having a high reinforcing fiber content and in which the reinforcing fibers are unlikely to be peeled off. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is a schematic cross-sectional view showing the structure of a fiber-reinforced resin sheet according to one embodiment of the present invention.

[0010] Figure 2 It is a side view schematically showing a production apparatus for producing the fiber-reinforced resin sheet.

[0011] Figure 3 It is a cross-sectional view schematically showing a state in which a fiber bundle is opened.

[0012] Figure 4 This is a table showing the characteristics of Examples and Comparative Examples of the present invention. DETAILED DESCRIPTION

[0013] [Structure of fiber-reinforced resin sheet]

[0014] Figure 11 is a schematic cross-sectional view showing the structure of a fiber-reinforced resin sheet 1 according to one embodiment of the present invention. As shown in the figure, the fiber-reinforced resin sheet 1 includes a resin substrate 10 formed of a sheet-like thermoplastic resin and reinforcing fibers 5 contained in the resin substrate 10. In other words, the fiber-reinforced resin sheet 1 is a thermoplastic composite material combining a thermoplastic resin and reinforcing fibers. Therefore, in the following description, the fiber-reinforced resin sheet 1 is appropriately referred to as a FRTP sheet 1.

[0015] FRTP sheet 1 is perpendicular to Figure 1 The sheet is a sheet having a specified size in the thickness direction D1 and the width direction D2 and having a length direction of the paper surface. Figure 1 The side in the thickness direction D1 above is "upper", Figure 1 The other side below the FRTP sheet 1 in the thickness direction D1 is “down”, but this does not limit the posture when using the FRTP sheet 1.

[0016] The resin substrate 10 includes a first thermoplastic resin layer 11, a second resin layer 12, and a third resin layer 13 laminated on each other. The first resin layer 11, the second resin layer 12, and the third resin layer 13 are laminated in this order from the top in the thickness direction D1 of the FRTP sheet 1.

[0017] The first to third resin layers 11 to 13 are fused to each other. That is, the lower surface 11b of the first resin layer 11 is fused to the upper surface 12a of the second resin layer 12, and the lower surface 12b of the second resin layer 12 is fused to the upper surface 13a of the third resin layer 13, so that the first to third resin layers 11 to 13 are bonded to each other and integrated. The resin substrate 10 is formed by the first to third resin layers 11 to 13 that are stacked and integrated in the thickness direction D1 as described above. The resin substrate 10 has a first surface S1 formed by the upper surface 11a of the first resin layer 11 located at the uppermost side and a second surface S2 formed by the lower surface 13b of the third resin layer 13 located at the lowermost side.

[0018] As the thermoplastic resin of the material of the resin substrate 10 (the first to third resin layers 11 to 13), that is, the base resin of the FRTP sheet 1, for example, polyamide (especially PA6, PAMXD6, PA9T, PA12), polyolefin, polyester, polyacetal, polyphenylene sulfide, polycarbonate, acrylic resin, acrylonitrile-butadiene-styrene copolymer (ABS), polyamide-imide, polysulfone, polyphenylsulfone, polyetherimide, polyethersulfone, polyetheretherketone (PEEK), polyetherketoneketone, polyimide, polyarylate, fluororesin, liquid crystal polymer, thermoplastic epoxy resin, etc. Alternatively, a polymer alloy in which two or more of these thermoplastic resins are mixed can also be used as the material of the first to third resin layers 11 to 13. In addition, the materials of the first to third resin layers 11 to 13 can be the same material as each other or different materials as long as they are thermoplastic resins including the above-mentioned material examples.

[0019] The thickness T of the FRTP sheet 1, that is, the distance from the first surface S1 to the second surface S2 of the resin substrate 10, is set to be 20 μm to 200 μm. In a preferred embodiment, the thickness T is preferably 30 μm to 150 μm, more preferably 40 μm to 100 μm.

[0020] The reinforcing fibers 5 are dispersed and contained in each of the first to third resin layers 11 to 13 of the resin base material 10. That is, the reinforcing fibers 5 include a fiber group contained in the first resin layer 11, a fiber group contained in the second resin layer 12, and a fiber group contained in the third resin layer 13. Furthermore, the reinforcing fibers 5 may include: a fiber group disposed at the boundary between the first resin layer 11 and the second resin layer 12 and contained in both the two resin layers 11 and 12; and a fiber group disposed at the boundary between the second resin layer 12 and the third resin layer 13 and contained in both the two resin layers 12 and 13.

[0021] As described above, the reinforcing fibers 5 are widely dispersed and arranged inside the resin base material 10. Although described in detail later, the distribution of the reinforcing fibers 5 has a non-uniformity in which the density of the fibers is uneven in the thickness direction D1.

[0022] The reinforcing fibers 5 are all perpendicular to Figure 1 The reinforcing fibers 5 are arranged in a manner extending in the direction of the paper surface of the FRTP sheet 1. That is, the reinforcing fibers 5 are continuous fibers oriented in the same direction inside the resin substrate 10. The orientation direction of the reinforcing fibers 5 (the direction perpendicular to the paper surface) is consistent with the length direction of the FRTP sheet 1. In other words, the reinforcing fibers 5 are included in the resin substrate 10 (each resin layer 11 to 13) in a state of being arranged in parallel along the length direction of the FRTP sheet 1.

[0023] As the reinforcing fiber 5, carbon fiber, glass fiber, ceramic fiber, aramid fiber, basalt fiber, PBO fiber (poly-p-phenylene benzobisoxazole fiber) and the like can be used. Among them, carbon fiber is conducive to improving the strength and corrosion resistance of the formed product. As carbon fiber, it is preferred to use a carbon fiber of a PAN (polyacrylonitrile) system with particularly high strength. When carbon fiber is used as the reinforcing fiber 5, its fiber diameter is preferably set to more than 5 μm and less than 12 μm.

[0024] The volume ratio of the reinforcing fiber 5 in the FRTP sheet 1, i.e., the volume of the reinforcing fiber 5 divided by the volume of the entire FRTP sheet 1, is the average volume content Vfa. The average volume content Vfa is set to be more than 30% and less than 70%. In the preferred technical solution, the average volume content Vfa of the reinforcing fiber 5 is preferably more than 30% and less than 65%, more preferably more than 30% and less than 60%.

[0025] For the FRTP sheet 1, the ratio of the area occupied by the voids in its cross section, i.e., the void ratio is small. Specifically, the void ratio of the FRTP sheet 1 is set to be 10% or less. In a preferred technical solution, the void ratio is preferably 5% or less, and more preferably 3% or less.

[0026] [Distribution of reinforcing fibers]

[0027] like Figure 1 As shown, the ranges when the FRTP sheet 1 is divided into five equal parts in the thickness direction D1 are defined as the first to fifth ranges R1 to R5 from the top. The first range R1 is a range including the first surface S1 (upper surface) of the resin substrate 10. The fifth range R5 is a range including the second surface S2 (lower surface) of the resin substrate 10. The second range R2 is a range adjacent to the lower side of the first range R1. The fourth range R4 is a range adjacent to the upper side of the fifth range R5. The third range R3 is a range located between the second range R2 and the fourth range R4 and including the center of the thickness direction D1 of the FRTP sheet 1. The thickness of the first to fifth ranges R1 to R5 is the value of the thickness T of the FRTP sheet 1 divided by 5, that is, T / 5. The reinforcing fiber 5 is included in the resin substrate 10 in a manner that a specific size relationship is established between the volume contents of the reinforcing fibers 5 in these first to fifth ranges R1 to R5.

[0028] Specifically, the volume content of the reinforcing fiber 5 contained in the first range R1 is the first content Vf1, the volume content of the reinforcing fiber 5 contained in the second range R2 is the second content Vf2, the volume content of the reinforcing fiber 5 contained in the third range R3 is the third content Vf3, the volume content of the reinforcing fiber 5 contained in the fourth range R4 is the fourth content Vf4, and the volume content of the reinforcing fiber 5 contained in the fifth range R5 is the fifth content Vf5. In this case, the third content Vf3 is smaller than both the second content Vf2 and the fourth content Vf4. In addition, the first content Vf1 and the fifth content Vf5 are both smaller than the third content Vf3. On the other hand, the first content Vf1 and the fifth content Vf5 are approximately equal, and the second content Vf2 and the fourth content Vf4 are approximately equal. That is, the magnitude relationship of the first to fifth contents Vf1 to Vf5 is established as shown in the following formula (1).

[0029] Vf2≈Vf4>Vf3>Vf1≈Vf5 (1)

[0030] As described above, in the present embodiment, the reinforcing fibers 5 are unevenly included in the resin substrate 10 in such a manner that the volume content (Vf1, Vf5) of the reinforcing fibers 5 in the first range R1 and the fifth range R5 including the surfaces S1 and S2 (upper and lower surfaces) of the resin substrate 10 is the lowest, the volume content (Vf2, Vf4) of the reinforcing fibers 5 in the second range R2 and the fourth range R4 separated by one layer from the surfaces S1 and S2 is the highest, and the volume content (Vf3) of the reinforcing fibers 5 in the central third range R3 is an intermediate value.

[0031] The volume content of the reinforcing fiber 5 in the first range R1 and the fifth range R5, that is, the first content Vf1 and the fifth content Vf5 are set to be greater than -30% and less than -1% with the difference between the average volume content Vfa of the reinforcing fiber 5 in the FRTP sheet 1. The difference (-30 to -1%) is the difference when the difference when the first content Vf1 (fifth content Vf5) is greater than the average volume content Vfa is set to a positive value, which is the value after the average volume content Vfa is subtracted from the first content Vf1 (fifth content Vf5). In other words, the first content Vf1 and the fifth content Vf5 are set to the average volume content Vfa plus -30 to -1%. In the preferred technical solution, the difference between the first content Vf1 (fifth content Vf5) and the average volume content Vfa is preferably greater than -25% and less than -3%, and more preferably greater than -20% and less than -5%.

[0032] The volume content of the reinforcing fiber 5 in the second range R2 and the fourth range R4, that is, the second content Vf2 and the fourth content Vf4 are set to be more than +1% and less than +25% with the difference between the average volume content Vfa of the reinforcing fiber 5 in the FRTP sheet 1. The difference (+1 to +25%) is the difference when the difference when the second content Vf2 (fourth content Vf4) is greater than the average volume content Vfa is set to a positive value, which is the value after the average volume content Vfa is subtracted from the second content Vf2 (fourth content Vf4). In other words, the second content Vf2 and the fourth content Vf4 are set to the average volume content Vfa plus +1 to +25%. In the preferred technical solution, the difference between the second content Vf2 (fourth content Vf4) and the average volume content Vfa is preferably more than +3% and less than +20%, and more preferably more than +5% and less than +15%.

[0033] The volume content of the reinforcing fiber 5 in the third range R3, that is, the third content Vf3 is set to a difference of more than -20% and less than +20% with the average volume content Vfa of the reinforcing fiber 5 in the FRTP sheet 1. The difference (-20 to +20%) is the difference when the difference when the third content Vf3 is greater than the average volume content Vfa is set to a positive value, and is the value after subtracting the average volume content Vfa from the third content Vf3. In other words, the third content Vf3 is set to the value of the average volume content Vfa plus -20 to +20%. In the preferred technical solution, the difference between the third content Vf3 and the average volume content Vfa is preferably more than -15% and less than +15%, more preferably more than -10% and less than +10%.

[0034] The numerical ranges of the first to fifth contents Vf1 to Vf5 and the average volume content Vfa described above can be summarized in Table 1 below.

[0035] Table 1

[0036]

[0037] [Manufacturing method]

[0038] The FRTP sheet 1 having the above-mentioned structure can be produced by the following production method. Figure 2 1 is a side view schematically showing a production device 20 for producing the FRTP sheet 1. The production device 20 shown in the figure includes a film roll 21, a fiber roll 22, a pair of heating rolls 25, and a pair of cooling rolls 26.

[0039] The film roll 21 includes a first film delivery roll 21A that delivers the first resin film 31, a second film delivery roll 21B that delivers the second resin film 32, and a third film delivery roll 21C that delivers the third resin film 33. The first resin film 31 is a first resin layer 11 ( Figure 1 ). The second resin film 32 is a strip-shaped resin film that is a prototype of the second resin layer 12 described above. The third resin film 33 is a strip-shaped resin film that is a prototype of the third resin layer 13 described above. The first to third resin films 31 to 33 are formed of appropriate thermoplastic resins corresponding to the materials of the first to third resin layers 11 to 13. The materials of the first to third resin films 31 to 33 may be the same thermoplastic resin or different thermoplastic resins.

[0040] The thickness of the first to third resin films 31 to 33 is set to be greater than 3 μm and less than 35 μm. In a preferred technical solution, the thickness of each resin film 31 to 33 is preferably greater than 5 μm and less than 20 μm, and more preferably greater than 7 μm and less than 15 μm. The thickness of each resin film 31 to 33 may be the same as or different from each other. In the case of making the thickness different, as an example, it can be considered to make the thickness of each of the first and third resin films 31 and 33 smaller than the thickness of the second resin film 32. In this case, the thickness of each of the first and third resin films 31 and 33 is preferably set to a value exceeding 45% of the thickness of the second resin film 32.

[0041] The fiber roller 22 includes a first fiber delivery roller 22A that delivers the first reinforcing fiber 41 and a second fiber delivery roller 22B that delivers the second reinforcing fiber 42. The first reinforcing fiber 41 and the second reinforcing fiber 42 are continuous fibers extending in their delivery direction (in other words, the length direction of each resin film 31 to 33), and are included in the above-mentioned resin films 31 to 33 during the manufacturing process to form the above-mentioned reinforcing fiber 5 ( Figure 1 ).

[0042] Fiber opening machines 23 and 24 are respectively arranged on the downstream sides of the first fiber delivery roller 22A and the second fiber delivery roller 22B. The fiber opening machine 23 (24) forms the first reinforcing fibers 41 (second reinforcing fibers 42) expanded into a thin strip by opening the fiber bundle FB received from the corresponding first fiber delivery roller 22A (22B) before fiber opening. As the fiber opening machine 23 (24), any mechanism that can perform such fiber opening treatment can be used, and various mechanisms such as a mechanism for beating and expanding the fiber bundle, a mechanism for blowing and expanding the fiber bundle, and a mechanism for applying ultrasonic waves to expand the fiber bundle can be used. In other words, the first fiber delivery roller 22A (second fiber delivery roller 22B) allows the fiber bundle FB to pass through the fiber opening machine 23 (24), thereby delivering the first reinforcing fibers 41 (second reinforcing fibers 42) in a strip shape after fiber opening to the downstream side.

[0043] like Figure 3 As shown in FIG. 1 , the width of the fiber bundle FB before fiber opening is W1, and the width of the first reinforcing fiber 41 (second reinforcing fiber 42) after fiber opening that has expanded into a strip shape is W2. Figure 3 In the case of a bundle having a circular cross section, the width W1 of the fiber bundle FB has the same meaning as the diameter. In the present embodiment, the fiber opening machine 23 (24) performs fiber opening in such a manner that the width W2 of the first reinforcing fiber 41 (the second reinforcing fiber 42) becomes 1.5 times or more and 6 times or less of the width W1 of the fiber bundle FB. That is, when the value obtained by dividing the width W2 by the width W1 is set as the fiber opening ratio, in the present embodiment, the fiber opening ratio is set to 1.5 times or more and 6 times or less. In a preferred embodiment, the fiber opening ratio is preferably 1.7 times or more and 5.5 times or less, and more preferably 2 times or more and 5 times or less.

[0044] The elements 31, 41, 32, 42, 33 fed from the film rolls 21 (21A to 21C) and the fiber rolls 22 (22A, 22B) are brought together so that the distances between them decrease as they go downstream, and they advance toward the heating roll 25. There is no particular limitation on the direction in which the elements are arranged. Figure 2 , a method of arranging the elements in the vertical direction, that is, a method of arranging the first resin film 31 at the uppermost side (arranging the third resin film 33 at the lowermost side) is illustrated. That is, the first resin film 31, the first reinforcing fiber 41, the second resin film 32, the second reinforcing fiber 42, and the third resin film 33 are sent toward the heating roller 25 in a state of being arranged in this order from the top, and are guided in a manner that the vertical intervals between each other become shorter as they approach the heating roller 25. According to this, a stacked body 100 in which the elements 31, 41, 32, 42, and 33 are stacked up and down is formed upstream of the heating roller 25. In addition, the process of forming the stacked body 100 in this order corresponds to the "first arrangement step" and the "second arrangement step" in the present invention.

[0045] As described above, in this embodiment, by the feeding action of the above-mentioned rollers 21 and 22, the first resin film 31 and the second resin film 32 are arranged to face each other in the vertical direction, and the first reinforcing fiber 41 is sandwiched between these first and second resin films 31 and 32. In addition, the third resin film 33 is arranged to face the second resin film 32 from the opposite side (below) of the first resin film 31, and the second reinforcing fiber 42 is sandwiched between these second and third resin films 32 and 33. According to this, the laminated body 100 in which the first resin film 31, the first reinforcing fiber 41, the second resin film 32, the second reinforcing fiber 42 and the third resin film 33 are stacked in this order from the top is formed. At the time when the laminated body 100 is formed, that is, before passing through the heating roller 25, the laminated body 100 is just a laminated body in which the layers are overlapped with each other, and the layers are not joined.

[0046] The laminate 100 is fed to the downstream side and introduced between a pair of heating rollers 25. The heating rollers 25 are high-temperature rollers heated by a heater (not shown). The laminate 100 is heated and pressurized by being sandwiched between the high-temperature heating rollers 25. The heating of the laminate 100 by the heating rollers 25 softens the first to third resin films 31 to 33. That is, the heating rollers 25 pressurize the laminate 100 in the thickness direction and heat the laminate 100 to a temperature at which each of the resin films 31 to 33 softens.

[0047] The heating and pressurization as described above press the first to third resin films 31 to 33 toward the first and second reinforcing fibers 41 and 42 while softening them. As a result, the first to third resin films 31 to 33 are impregnated into the first and second reinforcing fibers 41 and 42. That is, the softened first resin film 31 and the second resin film 32 are impregnated into the first reinforcing fiber 41 from top to bottom, and the softened second resin film 32 and the third resin film 33 are impregnated into the second reinforcing fiber 42 from top to bottom. In addition, the process of impregnating the reinforcing fibers 41 and 42 with each resin film 31 to 33 in this order corresponds to the "impregnation step" in the present invention.

[0048] The laminate 100 led out from the heating roller 25 is then introduced between a pair of cooling rollers 26. The cooling rollers 26 are low-temperature rollers cooled by a cooler (not shown). The laminate 100 is sandwiched between the low-temperature cooling rollers 26, thereby being cooled and pressurized. As a result, the softened first to third resin films 31 to 33 are solidified again, and the resin films 31 to 33 are bonded (fused) to each other. As a result, a single resin layer in which the first to third resin films 31 to 33 are integrated is formed, that is, the resin substrate 10 ( Figure 1 ).

[0049] In order to prevent the laminate 100 from sticking to the heating roller 25 or the cooling roller 26 , a release film or a release sheet may be disposed between the surface (resin film) of the laminate 100 and the rollers 25 and 26 .

[0050] After the above-mentioned treatment, the FRTP sheet 1 is manufactured. That is, the FRTP sheet 1 ( Figure 1). The first to third resin layers 11 to 13 are layers derived from the first to third resin films 31 to 33, and the reinforcing fibers 5 are a collection of the first and second reinforcing fibers 41 and 42. In other words, the first resin layer 11 is formed by the first resin film 31 that is softened and solidified, the second resin layer 12 is formed by the second resin film 32 that is softened and solidified, and the third resin layer 13 is formed by the third resin film 33 that is softened and solidified. In addition, the first reinforcing fibers 41 contained in the resin sandwiched between the first and second resin films 31 and 32 form the reinforcing fibers 5 in the upper half of the sheet, and the second reinforcing fibers 42 contained in the resin sandwiched between the second and third resin films 32 and 33 form the reinforcing fibers 5 in the lower half of the sheet.

[0051] In addition, based on the process of sandwiching two groups of reinforcing fibers 41 and 42 between three resin films 31 to 33, the density of the reinforcing fibers 5 naturally becomes low near the surfaces S1 and S2 (upper and lower surfaces) of the resin substrate 10 and in the central part of the resin substrate 10. In particular, the density of the reinforcing fibers 5 is greatly reduced near the surfaces S1 and S2 of the resin substrate 10. On the contrary, the density of the reinforcing fibers 5 increases near the positions corresponding to the boundaries of the resin films 31 to 33. The density of the reinforcing fibers 5 is constructed as shown in the above-mentioned formula (1) or the magnitude relationship of the first to fifth contents Vf1 to Vf5 shown in Table 1.

[0052] A winding roll 28 for winding up the FRTP sheet 1 is disposed on the downstream side of the cooling roll 26. That is, the FRTP sheet 1 is drawn out from the cooling roll 26 and then wound up by the winding roll 28 into a roll shape.

[0053] [Effects]

[0054] As described above, in the present embodiment, the first resin film 31, the first reinforcing fiber 41, the second resin film 32, the second second reinforcing fiber 42 and the third resin film 33 are stacked in this order, and the formed stacked body 100 is subjected to heating and other treatments by the heating roller 25, thereby manufacturing the FRTP sheet 1. The FRTP sheet 1 manufactured by this method has the characteristics of high content of reinforcing fibers and difficulty in peeling of reinforcing fibers.

[0055] That is, the first resin film 31 and the second resin film 32 disposed opposite to each other with the first reinforcing fiber 41 interposed therebetween are softened by heating, so that the first resin film 31 and the second resin film 32 are impregnated into the first reinforcing fiber 41. Similarly, the second resin film 32 and the third resin film 33 disposed opposite to each other with the second reinforcing fiber 42 interposed therebetween are softened by heating, so that the second resin film 32 and the third resin film 33 are impregnated into the second reinforcing fiber 42. Accordingly, a high-strength and high-quality FRTP sheet 1 including the first to third resin layers 11 to 13 corresponding to the first to third resin films 31 to 33 and the reinforcing fibers 5 contained in the respective resin layers 11 to 13 can be manufactured.

[0056] Specifically, since the first to third resin layers 11 to 13 that are fused to each other contain reinforcing fibers 5, respectively, the integrity of each resin layer 11 to 13 and the reinforcing fibers 5 can be improved, and the reinforcing fibers 5 can be prevented from peeling off from the resin layers 11 to 13. Therefore, even when a relatively thin FRTP sheet 1 having a thickness T of 20 to 200 μm is manufactured as in the present embodiment, a relatively large amount of reinforcing fibers 5 equivalent to a volume content (Vf) of 30 to 70% can be firmly maintained inside it. In addition, since the resin is fully impregnated into the reinforcing fibers 5, it is possible to suppress the generation of voids inside the FRTP sheet 1, and the void ratio of the FRTP sheet 1 can be reduced to less than 10%. And, when a thin and low void ratio FRTP sheet 1 containing a large amount of reinforcing fibers 5 is used to form a composite molded product, the strength of the composite molded product can be improved, and even a composite molded product of a relatively complex shape can be well formed. That is, according to the present embodiment, it is possible to manufacture a high-quality FRTP sheet 1 that contributes to improving the strength and formability of a composite molded product.

[0057] In addition, in the present embodiment, after the first resin film 31, the first reinforcing fiber 41, the second resin film 32, the second reinforcing fiber 42 and the third resin film 33 are stacked in this order, the formed stacked body 100 is heated together by the heating roller 25, so that the resin films 31 to 33 can be softened and impregnated into the reinforcing fibers 41 and 42 at the same time, which can improve the manufacturing efficiency of the FRTP sheet 1.

[0058] In addition, the method of the present embodiment of sandwiching the laminated body 100 of resin film 31~33 and reinforcing fiber 41,42 with heating roller 25 is conducive to thinning FRTP sheet 1, and easily improves the integrity of resin and fiber.Therefore, even when manufacturing the relatively thin FRTP sheet 1 with the thickness T of 20~200 μm as the present embodiment, also can firmly keep the relatively large amount of reinforcing fiber 5 equivalent to 30~70% average volume content Vfa in it.

[0059] In addition, in this embodiment, resin films with a thickness of 3 to 35 μm are used as the first to third resin films 31 to 33. Therefore, the FRTP sheet 1 including the resin films 31 to 33 can be sufficiently thinned and its thickness T can be within the desired value range (20 to 200 μm).

[0060] In addition, in the present embodiment, fibers obtained by opening the fiber bundle FB at an opening ratio of 1.5 to 6 times are used as the first reinforcing fibers 41 and the second reinforcing fibers 42. Therefore, the fully opened band-shaped first reinforcing fibers 41 and the second reinforcing fibers 42 can be included in each resin film 31 to 33, which can promote the thinning of the FRTP sheet 1.

[0061] In addition, the volume content (first, fifth content Vf1, Vf5) of the first range R1 and the fifth range R5 of the surface S1, S2 (upper and lower surfaces) of the FRTP sheet 1 of the present embodiment of the reinforcing fiber 5 is lower than the volume content (second, fourth content Vf2, Vf4) of the second range R2 and the fourth range R4 of the reinforcing fiber 5 separated by a distance from the surface S1, S2. According to the FRTP sheet 1, the resin component contained in the first range R1 and the fifth range R5 close to the surface can be relatively more, so that the reinforcing fiber 5 can be firmly bonded to the resin in the first range R1 and the fifth range R5, and the reinforcing fiber 5 can be prevented from peeling off from the surface S1, S2.

[0062] On the other hand, the volume contents of the reinforcing fibers 5 in the second range R2 and the fourth range R4 separated from the surfaces S1 and S2 (the second and fourth contents Vf2 and Vf4) are relatively high. Therefore, as described above, the proportion of the reinforcing fibers 5 near the surface (the first range R1 and the fifth range R5) can be suppressed to a low level, and the proportion of the reinforcing fibers 5 in the sheet as a whole can be increased, so that a relatively large amount of reinforcing fibers 5 equivalent to an average volume content Vfa of 30 to 70% can be contained in the sheet.

[0063] In addition, in the present embodiment, the volume content (the 3rd content Vf3) of the reinforcing fiber 5 in the 3rd range R3 farthest from the surface S1, S2 is only second to the volume content (the first, the fifth content Vf1, Vf5) of the reinforcing fiber 5 in the above-mentioned first range R1 and the 5th range R5 and low. In other words, the resin component contained in the first range R1 and the 5th range R5 near the surface S1, S2 and the 3rd range R3 of the center is more than the resin component contained in other second range R2 and the 4th range R4. Accordingly, the high layer (the second, the 4th range R2, R4) of the ratio of reinforcing fiber 5 can be sandwiched between the high layer (the first, the 3rd, the 5th range R1, R3, R5) of the ratio of resin, and the integrity of resin and fiber can be improved. Therefore, the high-strength and high-quality FRTP sheet 1 that firmly keeps the reinforcing fiber 5 inside can be obtained.

[0064] In addition, as a method for manufacturing the FRTP sheet 1, in the present embodiment, a method of respectively stacking the reinforcing fibers 41 and 42 between the three resin films 31 to 33 and heating them as described above is adopted, thereby being able to appropriately manufacture the FRTP sheet 1 of the above-mentioned structure in which the content of the reinforcing fiber 5 is different according to each range (the first to fifth ranges R1 to R5) in the thickness direction D1.

[0065] That is, according to the manufacturing method as described above, near the surface S1, S2 and the central part of the FRTP sheet 1, the ratio of resin naturally becomes more, and the ratio of fiber in the position outside it naturally becomes more. As a result, about the volume content of the reinforcing fiber 5 in each range (the first to the fifth range R1 to R5) divided into five equal parts in the thickness direction D1, the above-mentioned desired size relationship can be constructed, and the quality and strength of the FRTP sheet 1 can be improved.

[0066] [Example]

[0067] The results of actually manufacturing the FRTP sheet 1 by the method of the embodiment described above are shown as Examples 1 and 2. Figure 4 That is, the FRTP sheet 1 is manufactured under two conditions with different thicknesses of the first to third resin films 31 to 33 and the fiber opening ratios of the first and second reinforcing fibers 41 and 42, and the obtained results are respectively used as Examples 1 and 2. In Example 1, the thicknesses of the first to third resin films 31 to 33 are all set to 7 μm, and the fiber opening ratios of the first and second reinforcing fibers 41 and 42 are all set to 2. In Example 2, the thicknesses of the first to third resin films 31 to 33 are all set to 15 μm, and the fiber opening ratios of the first and second reinforcing fibers 41 and 42 are all set to 2.2. In Examples 1 and 2, polyamide 6 (PA6) is used as the material of the first to third resin films 31 to 33, and PAN (polyacrylonitrile) carbon fibers are used as the material of the first and second reinforcing fibers 41 and 42. The fiber diameter of the PAN carbon fibers used is 7 μm, the number of fibers is 12,000, and the fineness is 800 Tex.

[0068] Figure 4 Comparative Examples 1 and 2 are shown together. The materials of the first to third resin films 31 to 33 and the first and second reinforcing fibers 41 and 42 of Comparative Examples 1 and 2 are the same as those of Examples 1 and 2, but the film thickness or fiber opening ratio is different from that of Examples 1 and 2. Specifically, in Comparative Example 1, the fiber opening ratio of the first and second reinforcing fibers 41 and 42 is 1 (not fiber-opened). In Comparative Example 2, the thickness of the first to third resin films 31 to 33 is set to 50 μm, and the fiber opening ratio of the first and second reinforcing fibers 41 and 42 is set to 3.

[0069] like Figure 4As shown, in Examples 1 and 2, the membrane thickness and the fiber opening ratio are within the specified range of the above-mentioned embodiment (membrane thickness 3 to 35 μm, fiber opening ratio 1.5 to 6 times). As a result, the thickness (sheet thickness) T of the obtained FRTP sheet 1, the average volume content Vfa of the reinforcing fiber 5, and the porosity are also within the specified range of the above-mentioned embodiment (sheet thickness 20 to 200 μm, average volume content 30 to 70%, porosity 10% or less). Specifically, the sheet thickness T is 66.6 μm in Example 1 and 85.4 μm in Example 2. The average volume content Vfa is 68.5% in Example 1 and 47.3% in Example 2. The porosity is 0% in both Examples 1 and 2. In addition, no peeling (fuzzing) of the reinforcing fiber 5 was observed in Examples 1 and 2.

[0070] In contrast, in Comparative Examples 1 and 2, either the average volume content Vfa or the porosity is out of the above-specified range. Specifically, in Comparative Example 1, the average volume content Vfa is 80.9%, which is larger than the above-specified range (30 to 70%), and the porosity is 12%, which is larger than the above-specified range (10% or less). This is believed to be due to the use of unopened reinforcing fibers with an opening ratio of 1. In addition, in Comparative Example 2, the average volume content Vfa is 16.5%, which is smaller than the above-specified range. This is believed to be due to the use of a thicker resin film of 50 μm.

[0071] The above results confirm the advantages of the FRTP sheet 1 according to the above embodiment.

[0072] [Modifications]

[0073] In the above embodiment, after the five elements of the first resin film 31, the first reinforcing fiber 41, the second resin film 32, the second reinforcing fiber 42 and the third resin film 33 are stacked in this order, the stacked body 100 formed is heated all at once by the heating roller 25, but the heating method is not limited to this. For example, the stacked body in which only a part of the five elements are stacked may be heated first, and then the remaining elements may be stacked and heated again.

[0074] In the above embodiment, the volume content (third content Vf3) of the third range R3 is made greater than the volume content (first and fifth contents Vf1 and Vf5) of the first range R1 and the fifth range R5, and less than the volume content (second and fourth contents Vf2 and Vf4) of the second range R2 and the fourth range R4, but the third content Vf3 is at least less than the second and fourth contents Vf2 and Vf4, and the magnitude relationship with the first and fifth contents Vf1 and Vf5 is not particularly limited. For example, the third content Vf3 can be equal to the first and fifth contents Vf1 and Vf5, or it can be less than the first and fifth contents Vf1 and Vf5. However, when the third content Vf3 is made greater than the first and fifth contents Vf1 and Vf5 as in the above embodiment, the proportion of the resin contained in the first and fifth ranges R1 and R5 close to the surface can be maximized, thereby further reducing the possibility of the undesirable situation of the reinforcing fiber 5 peeling off from the sheet surface.

[0075] The same manufacturing method as the above-mentioned embodiment can also be applied to the case of manufacturing FRTP sheets with different number of plies. For example, the FRTP sheet with fewer plies than the above-mentioned embodiment can be manufactured by the same method as the above-mentioned embodiment, that is, the FRTP sheet containing reinforcing fibers inside the two resin layers. In this case, the reinforcing fibers of one layer are sandwiched between the two layers of resin films, and the laminate obtained thereby is heated, thereby manufacturing the FRTP sheet. Accordingly, the FRTP sheet including the first resin layer and the second resin layer and the reinforcing fibers dispersed in the two resin layers can be obtained.

[0076] [Summary]

[0077] A fiber-reinforced resin sheet according to one aspect of the present invention has a thickness of 20 μm or more and 200 μm or less, and includes: a resin substrate comprising a first thermoplastic resin layer, a second resin layer, and a third resin layer stacked in a thickness direction and fused to each other; and reinforcing fibers dispersed in each of the first resin layer, the second resin layer, and the third resin layer and oriented in the same direction in each layer, wherein the average volume content of the reinforcing fibers is 30% or more and 70% or less.

[0078] According to the present invention, since the three mutually fused resin layers contain reinforcing fibers, the integrity of each resin layer and the reinforcing fibers can be improved, and defects such as peeling of the reinforcing fibers from the resin layers can be prevented. Thus, a high-strength and high-quality fiber-reinforced resin sheet can be obtained, which has a relatively thin thickness of 20 to 200 μm but has a relatively large amount of reinforcing fibers corresponding to an average volume content of 30 to 70% firmly retained therein.

[0079] It is preferable that the ratio of voids to the cross-sectional area of ​​the fiber-reinforced resin sheet, that is, the void ratio, is 10% or less.

[0080] As described above, when the void ratio is reduced to 10% or less, the strength and quality of the fiber-reinforced resin sheet can be further improved.

[0081] Preferably, when the fiber-reinforced resin sheet is divided into five equal parts in the thickness direction, each range is defined as a first range, a second range, a third range, a fourth range and a fifth range in sequence from one side surface of the resin substrate to the other side surface, the reinforcing fiber is contained in the resin substrate in such a manner that the volume content of the reinforcing fiber in the first range, the third range and the fifth range is lower than the volume content of the reinforcing fiber in the second range and the fourth range.

[0082] In this embodiment, the volume content of the reinforcing fibers in the first range and the fifth range including the surface of the resin substrate is lower than the volume content of the reinforcing fibers in the second range and the fourth range away from the surface. When the resin component contained in the first range and the fifth range close to the surface is relatively large in this way, the reinforcing fibers can be firmly bonded to the resin in the first range and the fifth range, and the reinforcing fibers can be prevented from peeling off from the sheet surface.

[0083] On the other hand, the volume content of the reinforcing fibers in the second range and the fourth range separated from the surface is relatively high. Therefore, as described above, the proportion of the reinforcing fibers in the vicinity of the surface (the first range and the fifth range) can be relatively low while the proportion of the reinforcing fibers can be increased in the entire sheet, and a relatively large amount of reinforcing fibers corresponding to an average volume content of 30 to 70% can be contained in the resin base material.

[0084] Furthermore, since the volume content of the reinforcing fibers in the third range between the second range and the fourth range, that is, the central range, is relatively low, it is possible to sandwich layers with a high ratio of reinforcing fibers (the second and fourth ranges) between layers with a high ratio of resin (the first, third, and fifth ranges), thereby improving the integrity of the resin and the fibers. Thus, a high-strength and high-quality fiber-reinforced resin sheet can be obtained in which the reinforcing fibers are firmly held.

[0085] Preferably, the volume content of the reinforcing fiber in the first range and the fifth range is lower than the volume content of the reinforcing fiber in the third range.

[0086] In this aspect, the ratio of the resin contained in the first range and the fifth range close to the surface can be maximized, so that the possibility of the defect of the reinforcing fiber being peeled off from the resin base material can be further reduced.

[0087] Specifically, it is preferred that the volume contents of the reinforcing fibers in the first to fifth ranges have the following values ​​in relation to the average volume content of the entire sheet. That is, the volume contents of the reinforcing fibers in the first and fifth ranges are preferably values ​​of the average volume content plus -30 to -1%, the volume contents of the reinforcing fibers in the second and fourth ranges are preferably values ​​of the average volume content plus +1 to +25%, and the volume content of the reinforcing fibers in the third range is preferably values ​​of the average volume content plus -20 to +20%.

[0088] Another aspect of the present invention relates to a method for manufacturing a fiber-reinforced resin sheet, comprising: a first configuration step of configuring a first continuous reinforcing fiber obtained by opening a fiber bundle between a first thermoplastic resin film and a second thermoplastic resin film; a second configuration step of configuring a third thermoplastic resin film from the opposite side of the first resin film in a manner facing the second resin film, and configuring a second continuous reinforcing fiber obtained by opening a fiber bundle between the third resin film and the second resin film; and an impregnation step of softening the first resin film, the second resin film, and the third resin film by heating so that the first resin film, the second resin film, and the third resin film are impregnated into the first reinforcing fibers and the second reinforcing fibers.

[0089] According to this manufacturing method, a sheet similar to the above-mentioned fiber-reinforced resin sheet of the invention can be appropriately manufactured. That is, by heating and softening the first resin film and the second resin film arranged opposite to each other with the first reinforcing fiber sandwiched therebetween, the first resin film and the second resin film can be impregnated into the first reinforcing fiber. Similarly, by heating and softening the second resin film and the third resin film arranged opposite to each other with the second reinforcing fiber sandwiched therebetween, the second resin film and the third resin film can be impregnated into the second reinforcing fiber. As a result, a high-strength and high-quality fiber-reinforced resin sheet including three resin layers corresponding to the first to third resin films and the reinforcing fibers contained in the three resin layers can be manufactured.

[0090] Preferably, the impregnation step is a step of heating a laminate of each of the resin films and each of the reinforcing fibers formed through the first arrangement step and the second arrangement step.

[0091] In this technical solution, after the first resin film, the first reinforcing fiber, the second resin film, the second reinforcing fiber and the third resin film are stacked in this order, the formed stack is heated together. Therefore, each resin film can be softened and impregnated into each reinforcing fiber at the same time, which can improve the manufacturing efficiency of the fiber-reinforced resin sheet.

[0092] It is preferable that a resin film having a thickness of 3 μm or more and 35 μm or less be used as the first resin film, the second resin film, and the third resin film.

[0093] When the thickness of each resin film is set to 3 to 35 μm, the fiber-reinforced resin sheet including the resin film can be formed thinly, and the thickness can be within a desired value range (20 to 200 μm).

[0094] It is preferable that fibers opened to have a width 1.5 times or more and 6 times or less of the fiber bundle be used as the first reinforcing fibers and the second reinforcing fibers.

[0095] In this aspect, the first and second reinforcing fibers in a strip shape that are sufficiently opened can be contained in each resin film, and the thickness of the fiber-reinforced resin sheet can be accelerated.

Claims

1. A fiber-reinforced resin sheet, characterized in that: Having a thickness of 20 μm or more and 200 μm or less, and comprising: a resin substrate including a first thermoplastic resin layer, a second resin layer, and a third resin layer which are stacked in a thickness direction and fused to each other; and The reinforcing fibers are dispersed and contained in each of the first resin layer, the second resin layer and the third resin layer and are oriented in the same direction in each layer, wherein: The average volume content of the reinforcing fibers is 30% or more and 70% or less.

2. The fiber-reinforced resin sheet according to claim 1, characterized in that: The ratio of voids to the cross-sectional area of ​​the fiber-reinforced resin sheet, that is, the void ratio, is 10% or less.

3. The fiber-reinforced resin sheet according to claim 1 or 2, characterized in that: When the fiber-reinforced resin sheet is divided into five equal parts in the thickness direction, each range is defined as a first range, a second range, a third range, a fourth range and a fifth range in sequence from one side surface of the resin substrate to the other side surface, the reinforcing fiber is contained in the resin substrate in such a manner that the volume content of the reinforcing fiber in the first range, the third range and the fifth range is lower than the volume content of the reinforcing fiber in the second range and the fourth range.

4. The fiber-reinforced resin sheet according to claim 3, characterized in that: The volume content of the reinforcing fiber in the first range and the fifth range is lower than the volume content of the reinforcing fiber in the third range.

5. The fiber-reinforced resin sheet according to claim 4, characterized in that: The volume content of the reinforcing fiber in the first range and the fifth range is the average volume content plus a value of -30 to -1%, The volume content of the reinforcing fibers in the second range and the fourth range is the average volume content plus a value of +1 to +25%, The volume content of the reinforcing fiber in the third range is a value obtained by adding -20 to +20% to the average volume content.

6. A fiber-reinforced resin sheet, characterized in that include: A resin substrate formed of a sheet of thermoplastic resin; as well as The reinforcing fibers are contained in the resin matrix at an average volume content of 30% or more and 70% or less in a state of being oriented in the same direction, wherein When the fiber-reinforced resin sheet is divided into five equal parts in the thickness direction, each range is defined as a first range, a second range, a third range, a fourth range and a fifth range in sequence from one side surface of the resin substrate to the other side surface, the reinforcing fiber is contained in the resin substrate in such a manner that the volume content of the reinforcing fiber in the first range, the third range and the fifth range is lower than the volume content of the reinforcing fiber in the second range and the fourth range.

7. A method for manufacturing a fiber-reinforced resin sheet, characterized in that include: A first arrangement step of arranging continuous first reinforcing fibers obtained by opening a fiber bundle between a first thermoplastic resin film and a second thermoplastic resin film; A second arrangement step of arranging a third thermoplastic resin film from the opposite side of the first resin film so as to face the second resin film, and arranging a second continuous reinforcing fiber obtained by opening a fiber bundle between the third resin film and the second resin film; as well as The impregnation step softens the first resin film, the second resin film, and the third resin film by heating so that the first resin film, the second resin film, and the third resin film are impregnated into the first reinforcing fiber and the second reinforcing fiber.

8. The method for producing a fiber-reinforced resin sheet according to claim 7, wherein: The impregnation step is a step of heating the laminated body of each of the resin films and each of the reinforcing fibers formed through the first arrangement step and the second arrangement step.

9. The method for producing a fiber-reinforced resin sheet according to claim 7 or 8, characterized in that: As the first resin film, the second resin film, and the third resin film, resin films having a thickness of 3 μm or more and 35 μm or less are used.

10. The method for producing a fiber-reinforced resin sheet according to claim 7 or 8, characterized in that: As the first reinforcing fibers and the second reinforcing fibers, fibers opened to have a width 1.5 times or more and 6 times or less of the fiber bundle are used.

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