Fiber-reinforced resin sheet, fiber-reinforced composite material, and molded article

Abstract

The present invention provides a fiber-reinforced resin sheet able to yield a fiber-reinforced composite material having excellent strength. This fiber-reinforced resin sheet includes: a resin film comprising a resin composition containing a poly(phenylene sulfide) resin; and a plurality of reinforcing fibers layered on the resin film in a state whereby the fiber direction is aligned in a single direction. The resin composition contains an epoxy resin at a quantity of 1-20 parts by mass relative to 100 parts by mass of the poly(phenylene sulfide) resin.

Description

Fiber-reinforced resin sheets, fiber-reinforced composite materials and molded products

[0001] The present invention relates to a fiber-reinforced resin sheet as an intermediate material used as a material for a wide range of applications, and to a fiber-reinforced composite material and a molded article using the same.

[0002] Fiber-reinforced composite materials (FRP: Fiber Reinforced Plastics) are lightweight and have excellent mechanical properties. Therefore, fiber-reinforced composite materials are widely used in vehicle-related parts such as automobiles and motorcycles, aircraft-related parts, ship-related parts, electrical and electronic components, electronic device housings, medical equipment, building materials, furniture, home appliances, sporting goods, and the like. Fiber-reinforced composite materials are manufactured using an intermediate material, i.e., a prepreg (hereinafter also referred to as a "fiber-reinforced resin sheet"), in which a reinforcing material made of long fibers (continuous fibers) such as reinforcing fibers is impregnated (or laminated) into a matrix resin. Specifically, a fiber-reinforced composite material or a molded product containing the same can be obtained by stacking multiple fiber-reinforced resin sheets and heating and curing them, or heating and cooling them to solidify them.

[0003] On the other hand, polyphenylene sulfide resin (hereinafter also referred to as "PPS resin") is known as one of the high-performance engineering plastics, also known as "super engineering plastics," among thermoplastic resins. PPS resin is in high demand in various industrial fields due to its excellent flame retardancy, heat resistance, chemical resistance, etc. By compounding PPS resin with reinforcing fibers, it is expected that a fiber-reinforced composite material can be obtained that exhibits the excellent properties inherent to PPS resin and excellent mechanical properties such as tensile strength and flexural strength. However, in reality, fiber-reinforced composite materials using PPS resin have lower strength than fiber-reinforced composites using other resins as matrix resins. This is due to the low interfacial shear strength between the PPS resin and the reinforcing fibers, resulting in poor adhesion between the two in the composite. Therefore, technologies have been developed to improve the interfacial shear strength between resin compositions containing PPS resin and reinforcing fibers in order to obtain superior strength fiber-reinforced composite materials.

[0004] For example, Patent Document 1 describes a fiber-reinforced composite material that is primarily excellent in tensile strength and may contain a polyarylene resin as a thermoplastic resin. Specifically, Patent Document 1 describes a fiber-reinforced composite material that may contain a polyarylene resin as a thermoplastic resin (A), and contains, as an adhesive compound (B), a compound having two or more structures in one molecule that are at least one type of structure selected from the group consisting of a carbodiimide structure, a urea structure, and a urethane structure, and in which the abundance ratio Rb of the adhesive compound (B) satisfies a predetermined condition.

[0005] JP 2015-110747 A

[0006] An object of the present invention is to provide a fiber-reinforced resin sheet from which a fiber-reinforced composite material having excellent strength can be obtained.

[0007] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention.

[0008] A fiber-reinforced resin sheet according to a first aspect of the present invention is a fiber-reinforced resin sheet including: a resin film made of a resin composition containing a polyphenylene sulfide resin; and a plurality of reinforcing fibers laminated to the resin film with the fibers oriented in the same direction, wherein the resin composition includes 1 part by mass or more and 20 parts by mass or less of an epoxy resin per 100 parts by mass of the polyphenylene sulfide resin.

[0009] A fiber-reinforced composite material according to a second aspect of the present invention includes a plurality of the fiber-reinforced resin sheets according to the first aspect, and the plurality of fiber-reinforced resin sheets are stacked in a thickness direction.

[0010] A molded article according to a third aspect of the present invention includes the fiber-reinforced composite material according to the second aspect.

[0011] Fig. 1 is a schematic cross-sectional view of an example of a fiber reinforced resin sheet in this embodiment. Fig. 2 is a schematic cross-sectional view of another example of a fiber reinforced resin sheet in this embodiment. Fig. 3 is a schematic cross-sectional view of a laminated chopped sheet, which is an example of a fiber reinforced composite material in this embodiment.

[0012] In the fiber-reinforced composite material described in Patent Document 1, the adhesive compound (B) is localized around the reinforcing fibers, thereby increasing the interfacial shear strength between the matrix resin of the PPS resin and the reinforcing fibers, and thereby increasing the tensile strength of the fiber-reinforced composite material.

[0013] However, it would be preferable to improve the interfacial shear strength between a resin composition (matrix resin) containing a PPS resin and reinforcing fibers by a simpler method than the complicated method described in Patent Document 1. Furthermore, fiber-reinforced composite materials using PPS resin are in high demand. Therefore, further improvements in strength, such as tensile strength, of such fiber-reinforced composite materials beyond those of conventional techniques are desired.

[0014] The present inventors have conducted extensive research into fiber-reinforced resin sheets that can produce fiber-reinforced composites with excellent strength. As a result, they have found that in a fiber-reinforced resin sheet that includes a resin film made of a resin composition containing a PPS resin and a plurality of reinforcing fibers laminated to the resin film, the interfacial shear strength between the resin composition and the reinforcing fibers can be improved by including an epoxy resin in a predetermined amount relative to the PPS resin. Furthermore, they have found that improving the interfacial shear strength between the resin composition and the reinforcing fibers ultimately results in a fiber-reinforced composite with excellent strength, particularly tensile strength.

[0015] As described above, according to the present invention, it is possible to provide a fiber-reinforced resin sheet from which a fiber-reinforced composite material having excellent strength, particularly excellent tensile strength, can be obtained.

[0016] In this specification, "the fiber-reinforced composite material has excellent strength" means that, due to an improvement in the interfacial shear strength between the resin composition and the reinforcing fibers, the fiber-reinforced composite material obtained using the resin composition has high strength, particularly tensile strength, and excellent mechanical properties.

[0017] Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present invention.

[0018] <Fiber Reinforced Resin Sheet> 1. Configuration of Fiber Reinforced Resin Sheet First, the configuration of the fiber reinforced resin sheet in this embodiment will be described.

[0019] FIG. 1 shows a schematic cross-sectional view of an example of a fiber-reinforced resin sheet in this embodiment. In FIG. 1, the respective symbols represent a fiber-reinforced resin sheet 1, a resin film 2, and reinforcing fibers 3, respectively. As shown in FIG. 1, the fiber-reinforced resin sheet 1 in this embodiment includes a resin film 2 made of a resin composition containing a PPS resin, and a plurality of reinforcing fibers 3 laminated on the resin film 2. The plurality of reinforcing fibers 3 are laminated on the resin film 2 with their fiber directions oriented in the same direction. Specifically, the plurality of reinforcing fibers 3 can be laminated on the resin film 2 with their fiber directions approximately parallel to the longitudinal direction of the fiber-reinforced resin sheet 1 and oriented in the same direction.

[0020] Here, in this specification, "reinforcing fibers are laminated on a resin film" includes the meanings of "reinforcing fibers are laminated after at least a portion of each reinforcing fiber is fused, adhered, or pressure-bonded to the resin film" and "reinforcing fibers are impregnated in the resin film over approximately half or almost the entirety of each reinforcing fiber." The specific meaning of "lamination" varies depending on the physical properties of the resin film, the physical properties and shape of the reinforcing fibers, the type of treatment performed for lamination, and the treatment conditions. In other words, "lamination" in this specification means that when laminating the reinforcing fibers and the resin film, they may be subjected to heating, cooling, and / or pressure treatment as necessary.

[0021] 2 shows a schematic cross-sectional view of another example of a fiber-reinforced resin sheet according to the present embodiment. In FIG. 2, the reference symbols indicate a fiber-reinforced resin sheet 1, a resin film 2A, a resin film 2B, and reinforcing fibers 3, respectively. As shown in FIG. 2, the fiber-reinforced resin sheet 1 includes not only a resin film 2A made of a resin composition containing a PPS resin and a plurality of reinforcing fibers 3 laminated on the resin film 2, but also another resin film 2B made of a resin composition containing a PPS resin laminated on the plurality of reinforcing fibers 3. That is, the plurality of reinforcing fibers 3 may be sandwiched and laminated between two resin films 2A and 2B made of a resin composition containing a PPS resin, with the fiber directions of the fibers being approximately parallel to the longitudinal direction of the fiber-reinforced resin sheet 1 and oriented in the same direction.

[0022] Hereinafter, each component included in the fiber reinforced resin sheet will be described.

[0023] [Resin Film] The resin film is a film made of a resin composition containing a PPS resin. Hereinafter, each component contained in the resin composition, the physical properties of the resin composition, and a method for producing the resin film will be described.

[0024] (PPS Resin) The resin composition contains a PPS resin as a main resin. When the resin composition contains a PPS resin, a fiber-reinforced resin sheet can be produced from which a fiber-reinforced composite material having excellent properties in terms of flame retardancy, heat resistance, chemical resistance, dimensional stability, rigidity, etc. can be obtained.

[0025] PPS resin is a polymer mainly containing repeating units represented by the following structural formula (1): From the viewpoint of flame retardancy, heat resistance, etc., the PPS resin preferably contains 70 mol % or more, and more preferably 90 mol % or more, of repeating units represented by the following structural formula (1).

[0026]

[0027] The PPS resin may be composed of one or more repeating units represented by the following structural formula (2) in an amount of about 30 mol % or less of the repeating units.

[0028] The mass average molecular weight of the PPS resin is not particularly limited, but may be, for example, about 10,000 to 80,000. Specifically, the mass average molecular weight of the PPS resin may be appropriately set within a range that does not impair the effects of improving the interfacial shear strength and providing a fiber-reinforced composite material with excellent strength (particularly excellent tensile strength) in this embodiment.

[0029] The weight average molecular weight of the PPS resin can be measured by size exclusion chromatography (hereinafter also referred to as "SEC"). In SEC, the weight average molecular weight of the PPS resin is calculated as a weight average molecular weight converted into polystyrene.

[0030] The melt flow rate of the PPS resin (measured at a temperature of 315°C and a load of 5 kg) is not particularly limited, but may be, for example, about 100 g / 10 min to 200 g / 10 min. Specifically, the melt flow rate of the PPS resin may be appropriately set within a range that does not impair the effects of improving the interfacial shear strength and providing a fiber-reinforced composite material with excellent strength (particularly excellent tensile strength) in this embodiment.

[0031] The melting point of the PPS resin is not particularly limited as long as it does not impair the effects of improving interfacial shear strength and providing a fiber-reinforced composite material with excellent strength (particularly excellent tensile strength) in this embodiment. For example, the melting point of the PPS resin is preferably 260°C to 280°C, and more preferably 270°C to 280°C. When the melting point of the resin is within this range, a resin film can be formed well without reducing melt moldability and thermal stability. In this specification, the melting point of the PPS resin can be measured based on JIS K7121:2012.

[0032] Such PPS resins can be synthesized by any method known to those skilled in the art. For example, PPS resins can be obtained by a method in which an alkali metal sulfide and an organic dihalogen compound are polymerized in a polar organic solvent. Examples of alkali metal sulfides that can be used include sodium sulfide, lithium sulfide, potassium sulfide, and mixtures thereof.

[0033] Furthermore, any commercially available PPS resin known to those skilled in the art may be used. As a commercially available PPS resin, an unreinforced grade PPS resin is preferred. Examples of commercially available unreinforced grade PPS resins include "W214A" (manufactured by Polyplastics Co., Ltd.), "TORELINA A900" (manufactured by Toray Industries, Inc.), "B-06P" (manufactured by Tosoh Corporation), "ASPEX-PPS" (manufactured by Aspect Corporation), "DSP-B100," "Primef 4010," "Primef 7002," and "Primef 7010" (all manufactured by DIC Corporation).

[0034] The content of the PPS resin in the resin composition is not particularly limited as long as the condition for the content of the epoxy resin relative to the PPS resin described below is satisfied. For example, the PPS resin may be contained in the resin composition in an amount of about 83 to 99 parts by mass per 100 parts by mass of the resin composition.

[0035] (Epoxy Resin) The resin composition contains an epoxy resin in a predetermined range of amount. When the resin composition contains a predetermined amount of epoxy resin, the interfacial shear strength between the resin composition containing PPS resin and the reinforcing fiber can be increased. As a result, a fiber-reinforced resin sheet can be produced that can provide a fiber-reinforced composite material with excellent strength (especially excellent tensile strength).

[0036] The type of epoxy resin is not particularly limited as long as it can provide the fiber-reinforced composite material of this embodiment with improved interfacial shear strength and therefore excellent strength (particularly excellent tensile strength). Specific types of epoxy resins include, for example, bisphenol F epoxy resin, bisphenol A epoxy resin, bisphenol S epoxy resin, and phenol novolac epoxy resin.

[0037] Of these, the epoxy resin preferably contains one or more resins selected from bisphenol A epoxy resins and bisphenol F epoxy resins. When the epoxy resin contains one or more resins, the interfacial shear strength between the resin composition and the reinforcing fibers is more reliably increased, and therefore a fiber-reinforced composite material having excellent tensile strength can be more reliably obtained.

[0038] These epoxy resins may be used alone or in combination of two or more.

[0039] The epoxy equivalent of the epoxy resin is not particularly limited as long as it does not impair the effect of improving the interfacial shear strength and providing a fiber-reinforced composite material with excellent strength (particularly tensile strength) in this embodiment. For example, the epoxy equivalent of the epoxy resin is preferably 100 g / eq to 250 g / eq, and more preferably 150 g / eq to 200 g / eq.

[0040] Such epoxy resins, such as bisphenol A epoxy resins and bisphenol F epoxy resins, may be any commercially available product known to those skilled in the art. For example, commercially available bisphenol A epoxy resins include "EPICLON 850" (registered trademark) (manufactured by DIC Corporation), "JER (registered trademark) 825" (manufactured by Mitsubishi Chemical Corporation), "RE-310S" (manufactured by Nippon Kayaku Co., Ltd.), and "ADEKA RESIN EP-4400" (manufactured by ADEKA Corporation). For example, commercially available bisphenol F epoxy resins include "EPICLON 830" (registered trademark) (manufactured by DIC Corporation), "JER 807" (manufactured by Mitsubishi Chemical Corporation), "RE-304S" (manufactured by Nippon Kayaku Co., Ltd.), and "ADEKA RESIN EP-4901E" (manufactured by ADEKA Corporation). Furthermore, examples of commercially available epoxy resins other than bisphenol A type and bisphenol F type include "EXA-1514" (manufactured by DIC Corporation), "EXA-1517" (manufactured by DIC Corporation), and "RE-305" (Nippon Kayaku Co., Ltd.).

[0041] In this embodiment, the content of the epoxy resin in the resin composition is 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of PPS resin. When the resin composition contains 1 part by mass or more of the epoxy resin per 100 parts by mass of PPS resin, the interfacial shear strength between the resin composition containing the PPS resin and the reinforcing fiber can be increased. As a result, a fiber-reinforced resin sheet can be produced that provides a fiber-reinforced composite material with excellent strength, particularly excellent tensile strength. Furthermore, when the resin composition contains 20 parts by mass or less of the epoxy resin per 100 parts by mass of PPS resin, a resin film made of the resin composition can be well molded, and the fiber-reinforced resin sheet of this embodiment can be produced using the resin film.

[0042] The content of the epoxy resin is preferably 1.5 parts by mass or more, more preferably 2.0 parts by mass or more, even more preferably 2.5 parts by mass or more, and particularly preferably a value selected from the group consisting of 3.0 parts by mass, 3.5 parts by mass, 4.0 parts by mass, 4.5 parts by mass, and 5.0 parts by mass or more, relative to 100 parts by mass of the PPS resin. The content of the epoxy resin is preferably 18 parts by mass or less, more preferably 16 parts by mass or less, even more preferably 14 parts by mass, and particularly preferably a value selected from the group consisting of 12 parts by mass, 10 parts by mass, 8 parts by mass, and 7 parts by mass or less, relative to 100 parts by mass of the PPS resin.

[0043] Furthermore, when the resin composition contains not only an epoxy resin but also a polycarbodiimide (described later), the content of the epoxy resin in the resin composition is preferably greater than the content of the polycarbodiimide in the resin composition. By containing the epoxy resin in a larger amount than the polycarbodiimide in the resin composition, the interfacial shear strength between the resin composition containing the PPS resin and the reinforcing fiber can be significantly increased. As a result, a fiber-reinforced resin sheet can be produced that can provide a fiber-reinforced composite material with significantly excellent strength, particularly significantly excellent tensile strength.

[0044] (Polycarbodiimide) The resin composition preferably contains polycarbodiimide. When the resin composition contains polycarbodiimide, the interfacial shear strength between the resin composition containing PPS resin and the reinforcing fiber can be further increased. As a result, a fiber-reinforced resin sheet can be produced that can provide a fiber-reinforced composite material having superior strength, particularly superior tensile strength.

[0045] The polycarbodiimide is not particularly limited, but examples thereof include aliphatic polycarbodiimides, aromatic polycarbodiimides, etc. Among these, from the viewpoint of reactivity with PPS resin, the polycarbodiimide is preferably an aliphatic polycarbodiimide.

[0046] Aliphatic polycarbodiimides have the general formula: -N=C=N-R １ - (wherein, R １ represents a divalent organic group of an alicyclic compound such as cyclohexylene, or a divalent organic group of an aliphatic compound such as methylene, ethylene, propylene, or methylethylene) as a main constituent unit. Specifically, the aliphatic polycarbodiimide is a homopolymer or copolymer containing preferably 70 mol % or more of the repeating unit, more preferably 90 mol % or more of the repeating unit, and even more preferably 95 mol % or more of the repeating unit.

[0047] Aromatic polycarbodiimides are represented by the general formula: -N=C=N-R ２ - (wherein, R ２ represents a divalent organic group of a cyclic unsaturated compound such as benzene, toluene, xylene, biphenyl, naphthalene, anthracene, etc.) as a main constituent unit. Specifically, the aromatic polycarbodiimide is a homopolymer or copolymer containing preferably 70 mol % or more of the repeating unit, more preferably 90 mol % or more of the repeating unit, and even more preferably 95 mol % or more of the repeating unit.

[0048] The carbodiimide equivalent of the polycarbodiimide is not particularly limited as long as it does not impair the effects of improving the interfacial shear strength and providing a fiber-reinforced composite material with excellent strength (particularly tensile strength) in this embodiment. For example, the carbodiimide equivalent is preferably 100 to 600, more preferably 200 to 450, and even more preferably 250 to 350.

[0049] The polycarbodiimide may be in a powder form or a liquid form. The polycarbodiimide is preferably in a powder form from the viewpoints of ease of handling, ease of mixing with PPS resin and / or epoxy resin, etc. When the polycarbodiimide is in a powder form, its average particle size is preferably about 5 μm to 1500 μm, although there are no particular limitations thereon.

[0050] Such polycarbodiimides can be synthesized by any method known to those skilled in the art. For example, aliphatic polycarbodiimides can be synthesized by reacting an organic polyisocyanate in the presence of a catalyst that promotes the carbodiimidization reaction of isocyanate groups.

[0051] Furthermore, any commercially available polycarbodiimide known to those skilled in the art may be used. Examples of commercially available polycarbodiimides include "HMV-5A" and "HMV-8CA" (both manufactured by Nisshinbo Chemical Inc.), "UcarlnkXL-29SE," "UcarlnkXL-20," "UcarlnkXL-25SE," and "UcarlnkXL-27HS" (all manufactured by Union Carbide Corporation). More specific examples of polycarbodiimides include poly(tricarbodiimide), poly(1,4-tetramethylenecarbodiimide), poly(1,6-hexamethinecarbodiimide), poly(1,3-cyclohexylenecarbodiimide), and poly(4,4'-methylenebiscyclohexylcarbodiimide).

[0052] When the resin composition contains polycarbodiimide, the content of polycarbodiimide in the resin composition is not particularly limited as long as it satisfies the condition for the content of epoxy resin relative to the PPS resin described above and does not impair the effects of improving the interfacial shear strength and providing a fiber-reinforced composite material with excellent strength (particularly tensile strength) in this embodiment.

[0053] Specifically, when the resin composition contains polycarbodiimide, the content of polycarbodiimide is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, even more preferably 1.0 parts by mass or more, and particularly preferably a value selected from the group consisting of 1.2 parts by mass, 1.4 parts by mass, 1.6 parts by mass, 1.8 parts by mass, and 2.0 parts by mass or more, relative to 100 parts by mass of PPS resin. Furthermore, the content of polycarbodiimide is preferably 7 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 4 parts by mass or less, and particularly preferably a value selected from the group consisting of 3.5 parts by mass, 3.0 parts by mass, and 2.5 parts by mass or less, relative to 100 parts by mass of PPS resin.

[0054] However, as described above, from the viewpoint of further enhancing the effects of this embodiment, it is preferable that the content of polycarbodiimide in the resin composition be less than the content of epoxy resin in the resin composition. More specific conditions are that when the resin composition contains not only an epoxy resin but also a polycarbodiimide, the content of the epoxy resin is preferably 2 to 4 parts by mass per 100 parts by mass of PPS resin, the content of the polycarbodiimide is preferably 1 to 3 parts by mass per 100 parts by mass of PPS resin, and the content of the epoxy resin is preferably greater than the content of polycarbodiimide. Furthermore, it is even more preferable that the content of the epoxy resin is 2.5 to 3.5 parts by mass per 100 parts by mass of PPS resin, the content of the polycarbodiimide is 1.5 to 2.5 parts by mass per 100 parts by mass of PPS resin, and the content of the epoxy resin is greater than the content of polycarbodiimide.

[0055] (Other Additives) The resin film may contain any additive known to those skilled in the art, as necessary, within a range that does not impair the effects of improving the interfacial shear strength and providing a fiber-reinforced composite material with excellent strength (particularly tensile strength) in this embodiment. For example, the resin film may contain additives such as antioxidants, light stabilizers, and weather resistance improvers to improve the storage stability of the resin film and prevent discoloration or deterioration of the cured product.

[0056] Examples of other additives include thermosetting elastomers, flame retardants (e.g., phosphorus-containing polyamide resins, red phosphorus, phosphazene compounds, phosphates, phosphate esters, etc.), silicone oils, wetting and dispersing agents, antifoaming agents, defoamers, natural waxes, synthetic waxes, metal salts of straight-chain fatty acids, acid amides, esters, paraffins, and other mold release agents, crystalline silica, fused silica, calcium silicate, alumina, calcium carbonate, talc, barium sulfate, and other powders, metal oxides, metal hydroxides, glass fibers, carbon nanotubes, fullerenes, and other inorganic fillers, carbon fibers, cellulose nanofibers, and other organic fillers, red iron oxide, and other colorants, silane coupling agents, conductive materials, slip agents, leveling agents, polymerization inhibitors, such as hydroquinone monomethyl ether, and ultraviolet absorbers. These additives can be used alone or in combination of two or more.

[0057] (Physical properties of resin composition) In this embodiment, the interfacial shear strength (MPa) between the resin composition containing the above-mentioned components and the reinforcing fiber can be 54 MPa or more, preferably 60 MPa or more, and more preferably 70 MPa or more. Therefore, a fiber-reinforced composite material manufactured using a fiber-reinforced resin sheet obtained using a resin film made of the resin composition and reinforcing fiber has excellent strength, particularly tensile strength.

[0058] In this specification, the term "interfacial shear strength (of a resin composition)" refers to the interfacial shear strength measured by the microdroplet method using a composite interfacial property evaluation device, as will be described in detail in the examples below.

[0059] (Method for producing resin film) The method for producing the resin film is not particularly limited, and the resin film can be produced by any method known to those skilled in the art. For example, after preparing a resin composition by appropriately heating and mixing the weighed components, the resin composition can be subjected to roll coating, reverse coating, comma coating, knife coating, die coating, gravure coating, melt extrusion molding, solution casting, T-die method, calendaring method, etc. to produce a resin film. In addition, by using a co-extrusion method or a lamination method, the thickness of the resin film can be increased, or resin films with different resin compositions can be laminated.

[0060] The thickness of the resin film is preferably 7 μm or more and 50 μm or less. When the thickness of the resin film is 7 μm or more, when a fiber-reinforced resin sheet is molded, not only is it possible to obtain sufficiently excellent strength, but also superior properties such as flame retardancy and heat resistance derived from the PPS resin. Furthermore, the shape of the fiber-reinforced resin sheet can be well maintained. When the thickness of the resin film is 50 μm or less, when the fiber-reinforced resin sheet is molded, the fiber-reinforced resin sheet has good moldability.

[0061] The thickness of the resin film is more preferably 10 μm or more, even more preferably 13 μm or more, and particularly preferably 15 μm or more, and more preferably 30 μm or less, even more preferably 25 μm or less, and particularly preferably 20 μm or less.

[0062] [Multiple Reinforcing Fibers] The multiple reinforcing fibers are laminated on the resin film with the fibers oriented in the same direction. The multiple laminated reinforcing fibers are multiple reinforcing fibers opened from reinforcing fiber bundles.

[0063] In this specification, the phrase "a state in which the fiber directions (of a plurality of reinforcing fibers) are oriented in the same direction" means a state in which the fiber directions of the respective reinforcing fibers extend in substantially parallel directions.

[0064] The reinforcing fiber material is not particularly limited, and may be appropriately selected from any fiber known to those skilled in the art as a reinforcing fiber for forming a fiber-reinforced resin sheet, depending on the application. Specific examples include carbon fiber, aramid fiber, glass fiber, boron fiber, alumina fiber, silicon nitride fiber, and basalt fiber. Among these, carbon fiber, aramid fiber, glass fiber, boron fiber, alumina fiber, and silicon nitride fiber are preferred from the viewpoints of specific strength and specific elasticity. Furthermore, carbon fiber is more preferred from the viewpoint of improving the strength and corrosion resistance of fiber-reinforced composite materials manufactured using the fiber-reinforced resin sheet. PAN (polyacrylonitrile)-based carbon fiber, which has particularly high strength, is even more preferred. When carbon fiber is used as a reinforcing fiber, it may be surface-treated with a metal. Note that the reinforcing fibers opened from these reinforcing fiber bundles can be used alone or in combination of two or more types as long as they are oriented in the same direction.

[0065] 2. Method for Manufacturing Fiber-Reinforced Resin Sheet The fiber-reinforced resin sheet in this embodiment can be manufactured, for example, by the method described below.

[0066] First, a plurality of reinforcing fibers (specifically, a plurality of continuous reinforcing fibers) are arranged on one or both surfaces of the resin film produced by the above-described method so that the fiber direction is oriented in the same direction. Then, the plurality of reinforcing fibers arranged on the resin film are subjected to heating, cooling, and / or pressure treatment as necessary to laminate and integrate the resin film and the plurality of reinforcing fibers. As a result, the fiber-reinforced resin sheet of this embodiment can be obtained.

[0067] From the viewpoint of obtaining higher strength and excellent handling during processing, it is preferable that the plurality of reinforcing fibers are laminated on both sides of the resin film (see FIG. 1). Alternatively, the fiber-reinforced resin sheet in this embodiment may include two or more resin films, with a plurality of reinforcing fibers laminated on one resin film, and another resin film may be disposed on the surface of the resin film on which the plurality of reinforcing fibers are laminated. That is, the fiber-reinforced resin sheet may be formed so that a plurality of reinforcing fibers are sandwiched between two or more resin films (see FIG. 2).

[0068] 3. Physical Properties of Fiber-Reinforced Resin Sheet Furthermore, the physical properties of the fiber-reinforced resin sheet in this embodiment will be described.

[0069] In the fiber-reinforced resin sheet of this embodiment, the volume fraction Vf of the reinforcing fibers relative to the fiber-reinforced resin sheet is preferably 20% or more and 70% or less. When the volume fraction Vf of the reinforcing fibers is 20% or more, the fiber-reinforced resin sheet is sufficiently reinforced by the reinforcing fibers, and a fiber-reinforced composite material superior in tensile strength, bending strength, etc. can be obtained. When the volume fraction Vf of the reinforcing fibers is 70% or less, the fiber-reinforced resin sheet has good moldability, and a fiber-reinforced composite material excellent in flame retardancy, heat resistance, etc., which are properties derived from PPS resin, can be obtained.

[0070] The volume fraction Vf of the reinforcing fibers is more preferably 30% or more, even more preferably 35% or more, and particularly preferably 40% or more. The volume fraction Vf of the reinforcing fibers is more preferably 65% ​​or less, even more preferably 60% or less, and particularly preferably 55% or less.

[0071] The volume fraction Vf of the reinforcing fibers can be adjusted within the above range by appropriately controlling not only the type and thickness of the reinforcing fibers, the fiber width in which the reinforcing fibers are oriented, the thickness of the resin film, etc., but also the temperature and pressure applied during the production of the fiber-reinforced resin sheet. In this specification, the volume fraction Vf of the reinforcing fibers can be measured by a combustion method.

[0072] The thickness of the fiber reinforced resin sheet in this embodiment is preferably 20 μm or more and 80 μm or less. The thickness of the fiber reinforced resin sheet is more preferably 25 μm or more, even more preferably 30 μm or more, and particularly preferably 35 μm or more. The thickness of the fiber reinforced resin sheet is more preferably 70 μm or less, even more preferably 60 μm or less, and particularly preferably 50 μm or less.

[0073] By setting the thickness of the resin film and the volume fraction Vf of the reinforcing fibers within a predetermined range and making the thickness of the sheet as thin as possible within the above range, the resin film and the reinforcing fibers are laminated together after being fused to each other over most of the surface. As a result, when a fiber-reinforced composite material is constructed using the fiber-reinforced resin sheet, the strength of the reinforcing fibers and improved interfacial shear strength can be fully demonstrated. Furthermore, when stress is applied to the fiber-reinforced composite material obtained from the fiber-reinforced resin sheet, delamination is less likely to occur and the fiber-reinforced composite material also has excellent fatigue properties. Furthermore, the thinner the sheet, the better the moldability of the fiber-reinforced resin sheet.

[0074] The thickness of the fiber reinforced resin sheet is also affected by the thickness of the resin film, but can be adjusted within the above range by appropriately controlling the temperature, pressure, etc. applied during the production of the fiber reinforced resin sheet.

[0075] By using the fiber-reinforced resin sheet of this embodiment as an intermediate material, a fiber-reinforced composite material having excellent strength, particularly tensile strength, can be obtained. Furthermore, the fiber-reinforced composite material obtained in this manner also has excellent flame retardancy, heat resistance, and other properties derived from PPS resin. Furthermore, the fiber-reinforced resin sheet has good moldability due to its relatively thin thickness. Therefore, the fiber-reinforced resin sheet of this embodiment is suitable for use as a material for producing molded products that require high strength, such as tensile strength, and excellent flame retardancy and heat resistance. Furthermore, with the fiber-reinforced resin sheet of this embodiment, multiple fiber-reinforced resin sheets can be stacked while minimizing voids to form a variety of shapes at high density. Therefore, molded products of various types and shapes can ultimately be produced.

[0076] Furthermore, as another form of the fiber reinforced resin sheet in this embodiment, a fiber reinforced resin chopped material (hereinafter also referred to as "chopped material") can be mentioned. The chopped material is produced by shredding a fiber reinforced resin sheet and can be suitably used to produce a fiber reinforced composite material described in the embodiment described later.

[0077] The chopped material is preferably obtained by chopping the above-mentioned fiber reinforced resin sheet into rectangles having short sides of 2 mm to 20 mm and long sides of 10 mm to 40 mm (or preferably formed by chopping into rectangles). That is, like the fiber reinforced resin sheet before chopping, the chopped material includes a resin film made of a resin composition containing PPS resin and a plurality of reinforcing fibers laminated on the resin film.

[0078] <Fiber-reinforced composite material> As the fiber-reinforced composite material of the present embodiment, for example, two specific embodiments can be mentioned, which will be described in detail below.

[0079] The fiber-reinforced composite material of the first embodiment includes a plurality of fiber-reinforced resin sheets of the above-described embodiment, which are stacked in the thickness direction. As described above, the fiber-reinforced composite material of the first embodiment has excellent strength. Furthermore, the fiber-reinforced composite material also has excellent flame retardancy, heat resistance, and other properties derived from PPS resin.

[0080] Here, in this specification, "fiber reinforced resin sheets (or chopped materials) are stacked" means "fiber reinforced resin sheets (or chopped materials) are stacked after being bonded, fused, adhered, or pressure-bonded at least in part to each other." The specific meaning of such "stacking of fiber reinforced resin sheets (or chopped materials)" varies depending on the physical properties and shape of the fiber reinforced resin sheets (or chopped materials), the type of processing performed for stacking, and the processing conditions. In other words, in this specification, "stacking of fiber reinforced resin sheets (or chopped materials)" means that when stacking the fiber reinforced resin sheets or chopped materials, the sheets (or chopped materials) may be subjected to heating, cooling, and / or pressure processing as necessary.

[0081] The plurality of fiber-reinforced resin sheets to be laminated may be cut into pieces or the like as needed to fit the shape of the desired fiber-reinforced composite material, and then laminated. The number of fiber-reinforced resin sheets to be laminated is not particularly limited, and may be appropriately set according to the size of the desired fiber-reinforced composite material, etc.

[0082] Multiple fiber-reinforced resin sheets can be stacked in the thickness direction with the fiber direction of the reinforcing fibers in any direction. For example, multiple fiber-reinforced resin sheets can be stacked in the thickness direction with the fiber directions of the reinforcing fibers in the same direction. Alternatively, multiple fiber-reinforced resin sheets can be stacked in the thickness direction with the fiber directions of the reinforcing fibers having an angle difference in a two-dimensional plane.

[0083] As an example of the former, multiple fiber-reinforced resin sheets may be stacked in the thickness direction so that the fiber directions of the reinforcing fibers are aligned in the same direction with an angular difference of approximately 0°. As an example of the latter, multiple fiber-reinforced resin sheets may be stacked in the thickness direction so that the fiber directions of the reinforcing fibers are aligned in four axial directions with an angular difference of 45°. In other words, multiple fiber-reinforced resin sheets may be stacked in the thickness direction so that the fiber directions of the reinforcing fibers are aligned in four axial directions of 0°, 45°, −45°, and 90° in a two-dimensional plane. By stacking the fiber-reinforced resin sheets in such a fiber direction, the tensile strength and flexural strength along each fiber direction can be improved, and the strength of the fiber-reinforced composite material as a whole can be effectively improved. In this case, it is preferable that 4 × n fiber-reinforced resin sheets (n is an integer greater than or equal to 1) are stacked in the thickness direction. Alternatively, multiple fiber-reinforced resin sheets may be stacked in the thickness direction in a state where the fiber directions of the reinforcing fibers are two-dimensionally random (quasi-isotropic).

[0084] The fiber-reinforced composite material of the second embodiment includes a plurality of the chopped materials described above, which are stacked in the thickness direction. As described above, the fiber-reinforced composite material of the second embodiment also has excellent strength and excellent properties such as flame retardancy and heat resistance derived from the PPS resin.

[0085] In such a fiber-reinforced composite material, multiple chopped materials may be stacked in the thickness direction with the fiber directions of the reinforcing fibers in any direction, but it is preferable that the multiple chopped materials are stacked in a state where the fiber directions of the reinforcing fibers are two-dimensionally random (quasi-isotropic).

[0086] Figure 3 shows a schematic cross-sectional view of a laminated chopped sheet, which is an example of a fiber-reinforced composite material. In Figure 3, each symbol represents a chopped material C and a laminated chopped sheet CS, respectively. As shown in Figure 3, the laminated chopped sheet CS is formed by stacking multiple chopped materials C in the thickness direction. Specifically, the laminated chopped sheet CS is formed by integrating multiple stacked chopped materials C. t is the thickness of the laminated chopped sheet CS. The thickness t of the laminated chopped sheet CS can be controlled by appropriately adjusting the number of stacked chopped materials C.

[0087] <Molded Article> The molded article of this embodiment includes the fiber-reinforced composite material of the above-described embodiment.

[0088] The molded article may be any molded article of any shape that can be produced using the fiber reinforced composite material of the above-described embodiments by any molding method known to those skilled in the art.

[0089] The method for producing the molded product is not particularly limited, but examples thereof include the following production method. First, the laminated chopped sheet described in the above embodiment is cut into plates of a predetermined size, and multiple sheets are prepared. Next, the multiple prepared laminated chopped sheets are stacked in the thickness direction and placed in a mold such as a heat press. After that, the stacked multiple laminated chopped sheets are subjected to a heating and / or pressure treatment and, if necessary, a cooling treatment. A molded product can be produced by such a method.

[0090] The above-described manufacturing method can produce molded articles with excellent strength, particularly excellent tensile strength, and excellent flame retardancy, heat resistance, and other properties derived from the PPS resin. In addition, the method using the above-described laminated chopped sheet allows multiple chopped materials to be stacked in a state where the fiber orientation of the reinforcing fibers is two-dimensionally random (quasi-isotropic), as previously mentioned. This reduces the possibility of the reinforcing fibers being shredded when the laminated chopped sheet is pressed, and promotes the flow of the resin during press processing, thereby increasing the shape freedom of the molded article. This allows the reinforcing effect of the reinforcing fibers to be exerted isotropically, while allowing molded articles of various shapes to be molded without any problems.

[0091] As described above, the molded article of this embodiment contains the fiber-reinforced composite material of the above-described embodiment, and therefore has excellent strength, such as tensile strength, and also excellent flame retardancy and heat resistance. Therefore, the molded article of this embodiment is suitable for use in, for example, vehicle-related parts such as automobiles and motorcycles, aircraft-related parts, marine-related parts, electrical and electronic parts, electronic device housings, medical equipment, building materials, furniture, home appliances, sporting goods, and the like, which require excellent strength, particularly tensile strength, and excellent flame retardancy and heat resistance. More specifically, the molded article of this embodiment is suitable for use in, for example, vehicle-related parts such as safety belt parts, instrument panels, console boxes, pillars, roof rails, fenders, bumpers, door panels, roof panels, hood panels, trunk lids, door mirror stays, spoilers, hood louvers, wheel covers, hubcaps, garnishes, intake manifolds, fuel pumps, engine coolant joints, windshield washer nozzles, wipers, battery peripheral parts, wire harness connectors, lamp housings, lamp reflectors, lamp sockets, and the like. Furthermore, for example, as building materials, they can be suitably used for walls, roofs, ceiling-related parts of civil engineering buildings, window-related parts, heat-insulating material-related parts, floor-related parts, seismic isolation and vibration-damping material-related parts, lifeline-related parts, etc.

[0092] As described above, this specification discloses various aspects of the technology, the main aspects of which are summarized below.

[0093] A fiber-reinforced resin sheet according to a first aspect of the present invention is a fiber-reinforced resin sheet including a resin film made of a resin composition containing a polyphenylene sulfide resin, and a plurality of reinforcing fibers laminated to the resin film with the fiber directions oriented in the same direction, wherein the resin composition includes 1 part by mass or more and 20 parts by mass or less of an epoxy resin per 100 parts by mass of the polyphenylene sulfide resin.

[0094] A fiber reinforced resin sheet according to a second aspect of the present invention is the fiber reinforced resin sheet according to the first aspect, wherein the resin composition includes polycarbodiimide.

[0095] A fiber reinforced resin sheet according to a third aspect of the present invention is the fiber reinforced resin sheet according to the second aspect, wherein the content of the epoxy resin in the resin composition is greater than the content of the polycarbodiimide.

[0096] A fiber reinforced composite material according to a fourth aspect of the present invention includes a plurality of fiber reinforced resin sheets according to any one of the first to third aspects, and the plurality of fiber reinforced resin sheets are stacked in the thickness direction.

[0097] A molded article according to a fifth aspect of the present invention comprises the fiber-reinforced composite material according to the fourth aspect.

[0098] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0099] In this example, various resin compositions were prepared by adding varying amounts of epoxy resin (bisphenol F epoxy resin and bisphenol A epoxy resin) and / or polycarbodiimide to PPS resin. Resin films were then produced using the prepared resin compositions, and film formability was evaluated. Next, the interfacial shear strength was measured and evaluated using the prepared resin compositions. Furthermore, test pieces of fiber-reinforced composites were produced using resin films made from the prepared resin compositions, and their tensile strength was measured and evaluated.

[0100] First, the materials of the resin compositions in each example and comparative example, the method for preparing the resin compositions, the method for evaluating film formability, and the method for measuring and evaluating interfacial shear strength will be described in detail below.

[0101] <Materials of Resin Composition> The materials used in preparing the resin compositions in each Example and Comparative Example and shown in Table 1 are as follows: PPS resin (polyphenylene sulfide resin): "W214A" manufactured by Polyplastics Co., Ltd. (melting point: 280°C) Bis-F type epoxy resin (bisphenol F type epoxy resin): "EPICLON 830" (registered trademark) manufactured by DIC Corporation (epoxy equivalent: 165 g / eq to 177 g / eq) Bis-A type epoxy resin (bisphenol A type epoxy resin): "EPICLON 850" (registered trademark) manufactured by DIC Corporation (epoxy equivalent: 184 g / eq to 194 g / eq) Polycarbodiimide: "HMV-5CA" manufactured by Nisshinbo Chemical Inc. (carbodiimide equivalent: 310, powder form)

[0102] <Method for preparing resin composition> The resin compositions were prepared by blending a bis-F type epoxy resin (liquid), a bis-A type epoxy resin (liquid), and / or a polycarbodiimide (powder) with a PPS resin that had been heated and melted at 300°C in the content ratios shown in Table 1 below for each example and comparative example.

[0103] <Method for Evaluating Film Formability> To evaluate the film formability of the resin composition, a film was produced by the following method. Specifically, resin pellets of the resin composition in each Example and Comparative Example prepared by the method described above were molded into a film having a thickness of 20 μm using an extruder equipped with a T-die. The film formability in each Example and Comparative Example was evaluated according to the following criteria. Evaluation criteria: A: Easy to form into a film (no gas and / or foreign matter is generated during film formation, and the appearance is good). B: Film formable (gas and / or foreign matter is generated during film formation, and a film can be formed, although the appearance is poor). C: Impossible to form into a film (a film cannot be formed).

[0104] <Method for measuring and evaluating interfacial shear strength> The interfacial shear strength (MPa) between a resin composition containing PPS resin and reinforcing fibers was measured by the microdroplet method using a composite interface property evaluation device ("MODEL HM410", manufactured by Toei Sangyo Co., Ltd.). The size of the resin composition containing PPS resin used in each example and comparative example was a resin ball diameter of about 50 μm. The reinforcing fiber used was "TORAYCA (registered trademark) T700SC-24000" (manufactured by Toray Industries, Inc.). The interfacial shear strength between the resin composition containing PPS resin and reinforcing fibers measured in each example and comparative example was evaluated according to the following criteria. Evaluation criteria: AA: Interfacial shear strength is 70 MPa or more A: Interfacial shear strength is 60 MPa or more and less than 70 MPa B: Interfacial shear strength is 54 MPa or more and less than 60 MPa C: Interfacial shear strength is less than 54 MPa

[0105] Next, a method for preparing test pieces of fiber-reinforced composite materials using resin films made of the resin compositions in each Example and Comparative Example, and a method for measuring and evaluating the tensile strength of the test pieces of the fiber-reinforced composite materials will be described in detail below.

[0106] <Method for Preparing Fiber-Reinforced Composite Test Pieces> To evaluate the tensile strength of fiber-reinforced composite materials, test pieces of two types of fiber-reinforced composite materials with different fiber lamination states were prepared by the following method. Specifically, first, a fiber-reinforced resin composite sheet was prepared as an intermediate material for preparing the fiber-reinforced composite test pieces. First, a 20 μm-thick resin film was molded from the resin composition of each Example and Comparative Example using the same method as described above. Using the molded resin film and carbon fiber (manufactured by Toray Industries, Inc., "TORAYCA," grade: T-700 (PAN-based carbon fiber), fiber diameter: 7 μm, filament count: 12K, fineness: 800 tex) as the reinforcing fiber, a fiber-reinforced resin composite sheet was prepared by laminating the carbon fiber bundles, which had been opened to a width of 44 mm, onto the resin film melted at 260°C. The prepared fiber-reinforced resin composite sheet had the opened carbon fiber bundles laminated and integrated on both sides of the resin film.

[0107] The first type of test piece was a fiber-reinforced composite test piece prepared by stacking the sheets so that the fiber angle difference was approximately 0°. Specifically, the obtained fiber-reinforced resin composite sheet was first cut into a size suitable for insertion into a mold. Then, 24 sheets were stacked so that the carbon fiber angle difference of the cut fiber-reinforced resin composite sheets was approximately 0°. The stacked sheets were then placed into a mold and heat-pressed at 300°C and 2 MPa for 30 minutes. The detailed heat-pressing conditions were 10 minutes of preheating, 10 minutes of heating, and 10 minutes of cooling. The fiber-reinforced composite was then removed from the mold. The obtained fiber-reinforced composite was cut into a size of 25 mm (length in the minor axis direction) × 250 mm (length in the major axis direction) × 1 mm (thickness), to obtain a fiber-reinforced composite test piece with a fiber angle difference of approximately 0°.

[0108] The second type of test piece was a fiber-reinforced composite test piece laminated in a two-dimensionally random fiber orientation (quasi-isotropic). Specifically, the obtained fiber-reinforced resin composite sheet was first cut into a size suitable for insertion into a mold. Then, 48 sheets were stacked so that the carbon fiber orientation of the cut fiber-reinforced resin composite sheets was quasi-isotropic. The laminated sheets were then placed into a mold and heat-pressed at 300°C and 2 MPa for 30 minutes. The detailed heat-pressing conditions were 10 minutes of preheating, 10 minutes of heating, and 10 minutes of cooling. The fiber-reinforced composite was then removed from the mold. The obtained fiber-reinforced composite was cut into a size of 25 mm (minor axis length) × 250 mm (major axis length) × 2 mm (thickness), to obtain a test piece of a fiber-reinforced composite with quasi-isotropic fiber orientation.

[0109] <Method for measuring and evaluating tensile strength of test pieces of fiber-reinforced composite material> The tensile strength of test pieces of fiber-reinforced composite material prepared by the method described above was measured using a universal testing machine "68FM-100" manufactured by Instron Japan Co., Ltd. Specifically, test pieces of fiber-reinforced composite material with a fiber angle difference of approximately 0° were measured using the universal testing machine in accordance with JIS K 7165:2008. Test pieces of fiber-reinforced composite material with a quasi-isotropic fiber direction were measured using the universal testing machine in accordance with JIS K 7164:2005. The tensile strength of test pieces of fiber-reinforced composite material with a fiber angle difference of approximately 0° and a quasi-isotropic fiber direction measured in each example and comparative example was evaluated according to the following criteria. Evaluation criteria: A: The tensile strength at an angle difference of approximately 0° is 2400 MPa or more and the quasi-isotropic tensile strength is 910 MPa or more. B: The tensile strength at an angle difference of approximately 0° is 2100 MPa or more and less than 2400 MPa and the quasi-isotropic tensile strength is 810 MPa or more and less than 910 MPa. C: The tensile strength at an angle difference of approximately 0° is less than 2100 MPa and / or the quasi-isotropic tensile strength is less than 810 MPa.

[0110] The content ratio of the resin composition in each example and each comparative example, the physical properties of the resin composition (film formability and interfacial shear strength), and the physical properties of the fiber-reinforced composite material (tensile strength of a test piece with a fiber angle difference of approximately 0° and a quasi-isotropic fiber direction) are summarized in the following Table 1. In the following Table 1, "-" means that the component was not contained in the composition or that measurement was not possible because a film could not be formed.

[0111]

[0112] <Discussion> As shown in Table 1 above, the film formability of the resin compositions of Examples 1 to 8 was rated B or higher, meaning that films could be easily formed or could be formed into films. Furthermore, the interfacial shear strength between the resin compositions and the reinforcing fibers of Examples 1 to 8 was also rated B or higher, which was improved compared to the interfacial shear strength of the resin compositions of Comparative Examples 1, 3, and 4. Accordingly, the tensile strength of the fiber-reinforced composites of Examples 1 to 8 was also rated B or higher, which was improved compared to the tensile strength of the fiber-reinforced composites of Comparative Examples 1, 3, and 4.

[0113] In particular, Examples 4, 5, and 7, in which both epoxy resin (bis-F type epoxy resin or bis-A type epoxy resin) and polycarbodiimide were added in a suitable balance, tended to have higher interfacial shear strengths of the resin compositions and higher tensile strengths of the fiber-reinforced composites. Furthermore, among these, Examples 4 and 7, in which the epoxy resin content was higher than the polycarbodiimide content, showed significantly higher interfacial shear strengths and higher tensile strengths of the fiber-reinforced composites.

[0114] Thus, when a fiber-reinforced resin sheet is produced using a resin composition with high interfacial shear strength with the reinforcing fibers, and a fiber-reinforced composite material is produced using the fiber-reinforced resin sheet, the tensile strength of the fiber-reinforced composite material increases with the improvement in interfacial shear strength. It is naturally expected that similar effects will be obtained when the fiber-reinforced composite material is used to produce a molded product. Furthermore, it is expected that fiber-reinforced composite materials and molded products using the fiber-reinforced resin sheet will also have excellent flame retardancy, heat resistance, and other properties inherent to PPS resin.

[0115] On the other hand, the resin composition of Comparative Example 1, which contained an excessive amount of bis-F epoxy resin, had a low viscosity and could not form a film. This means that even if such a resin composition is used, it is not possible to produce a fiber-reinforced resin sheet in which reinforcing fibers are laminated on a resin film. Therefore, the tensile strength of the fiber-reinforced composite material in Comparative Example 1 was not measured or evaluated.

[0116] The resin composition of Comparative Example 3, to which only polycarbodiimide was added, had a lower interfacial shear strength with the reinforcing fibers than the resin composition of Example 1, to which the same amount of bis-F type epoxy resin was added. Accordingly, the tensile strength of the fiber-reinforced composite material of Comparative Example 3 was also lower than that of the fiber-reinforced composite material of Example 1. Similarly, even when a molded article is made using the fiber-reinforced composite material of Comparative Example 3, it is naturally expected that the tensile strength will be lower than that of the molded article made using the fiber-reinforced composite material of Example 1.

[0117] The resin composition of Comparative Example 4, which contained a small amount of bis-F type epoxy resin, had a significantly lower interfacial shear strength with the reinforcing fibers than the resin composition of Example 1. Accordingly, the tensile strength of the fiber-reinforced composite material of Comparative Example 4 was also lower than the tensile strength of the fiber-reinforced composite material of Example 1. Similarly, even when a molded article is made using the fiber-reinforced composite material of Comparative Example 4, it is naturally expected that the tensile strength will be lower than the tensile strength of the molded article made using the fiber-reinforced composite material of Example 1.

[0118] This application is based on Japanese Patent Application No. 2024-147437 filed on August 29, 2024, the contents of which are incorporated herein by reference.

[0119] The embodiments and examples disclosed herein should be understood to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0120] According to an embodiment of the present invention, a fiber-reinforced resin sheet can be provided that can produce a fiber-reinforced composite material having excellent strength, particularly excellent tensile strength. Such fiber-reinforced composite materials with excellent mechanical properties are in high demand and are suitable for use in a wide range of fields, such as vehicle-related parts for automobiles, motorcycles, etc., aircraft-related parts, ship-related parts, electrical and electronic parts, electronic device housings, medical equipment, building materials, furniture, home appliances, and sporting goods.

Claims

1. A fiber-reinforced resin sheet comprising a resin film made of a resin composition containing polyphenylene sulfide resin and a plurality of reinforcing fibers laminated to the resin film with the fibers oriented in the same direction, wherein the resin composition contains 1 to 20 parts by mass of an epoxy resin per 100 parts by mass of the polyphenylene sulfide resin.

2. The fiber-reinforced resin sheet according to claim 1, wherein the resin composition contains polycarbodiimide.

3. A fiber-reinforced resin sheet according to claim 2, wherein the content of the epoxy resin in the resin composition is greater than the content of the polycarbodiimide.

4. A fiber-reinforced composite material comprising a plurality of fiber-reinforced resin sheets according to any one of claims 1 to 3, the plurality of fiber-reinforced resin sheets being stacked in the thickness direction.

5. A molded article comprising the fiber-reinforced composite material of claim 4.

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