Sheet-shaped intermediate substrate and fiber-reinforced composite material

Abstract

To provide a sheet-like intermediate substrate formed by impregnating or coating a metal foil or mesh with an epoxy resin composition excellent in the light resistance, and excellent in the handleability (tackiness) at room temperature.SOLUTION: A sheet-like intermediate substrate formed by applying a constituent element [B] onto a surface of the following constituent element [A]. [A] metal meh or metal foil, [B] an epoxy resin composition containing at least (I) to (IV), relative to 100 pts.mass of a total epoxy resin, 90 to 100 pts.mass of (I), 15 to 75 pts.mass of (II), 20 to 75 pts.mass of (III), and 0.1 to 10 pts.mass of (IV). (I) A nonaromatic epoxy resin. (II) A pigment having an average particle size of 0.1 to 10 μm. (III) A nonaromatic thermoplastic resin. (IV) A cationic curing agent or an anionic curing agent.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a sheet-like intermediate substrate excellent in handling properties at room temperature, in which an epoxy resin composition excellent in light resistance is impregnated or coated on a metal foil or mesh.

Background Art

[0002] For products that require high structural performance such as aircraft structural members, windmill blades, automobile outer panels, and computer applications such as IC trays and laptop computer casings, prepregs produced by impregnating reinforcing fibers such as carbon fibers with thermosetting resins such as epoxy resins are often used. In recent years, there has been an increasing demand to improve the conductivity of prepregs and impart functions such as antistatic properties and lightning resistance to the fiber-reinforced composite materials obtained by curing the prepregs. On the other hand, the conductivity of carbon fibers themselves is not very high, and it has been necessary to integrally combine a highly conductive metal or the like separately. In addition, fiber-reinforced composite materials obtained by curing general prepregs have low light resistance (UV resistance), and deteriorate and deform when the surface is exposed to light.

[0003] Patent Document 1 discloses a conductive sheet material as a surface protection film for fiber-reinforced composite materials. Further, Patent Document 2 discloses a combination of an epoxy resin containing no aromatic ring, a carboxylic anhydride also containing no aromatic ring, and an ultraviolet absorber as a resin composition having UV resistance. Non-aromatic epoxy generally has properties such as low molecular weight, weak intermolecular interaction, low viscosity, and easy volatilization.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the technology disclosed in Patent Document 1, the epoxy resin composition used as the film material contains an aromatic ring and has a problem of poor UV resistance. Further, in the technology disclosed in Patent Document 2, since a carboxylic anhydride is applied as a curing agent for the epoxy resin composition, there is a problem that the degree of freedom in design is low in order to control the handleability suitable for films and sheet materials, the resin flow, and the volatilization during curing.

[0006] Therefore, it is an issue to realize a surface protection film that can reduce the working process of integrating with metal or the like in a special manner to impart conductivity to the fiber-reinforced composite material only by attaching it to the surface of the prepreg serving as the base material, and can prevent the deterioration of the fiber-reinforced composite material due to UV and prevent defects during coating.

Means for Solving the Problems

[0007] The present invention has the following configuration in order to solve such problems. That is, the sheet-like intermediate base material of the present invention is formed by applying component [B] to the surface of the following component [A]. [A] Metal mesh or metal foil [B] An epoxy resin composition containing at least (I) to (IV), which contains 90 to 100 parts by mass of (I), 15 to 75 parts by mass of (II), 20 to 75 parts by mass of (III), and 0.1 to 10 parts by mass of (IV) with respect to 100 parts by mass of the total epoxy resin. (I) Non-aromatic epoxy resin (II) Pigment having an average particle size of 0.1 to 10 μm (III) Non-aromatic thermoplastic resin (IV) Cation curing agent or anion curing agent.

[0008] Further, the fiber-reinforced composite material of the present invention is formed by integrating the cured product of the above sheet-like intermediate base material with the fiber-reinforced composite material precursor.

Effects of the Invention

[0009] According to the present invention, a sheet-like intermediate substrate excellent in handleability (tackiness) at room temperature can be provided, in which an epoxy resin composition excellent in light resistance is impregnated or coated on a metal foil or mesh.

Embodiments for Carrying Out the Invention

[0010] The sheet-like intermediate substrate of the present invention has the following configuration. That is, it is a sheet-like intermediate substrate in which component [B] is applied to the surface of the following component [A]. [A] Metal mesh or metal foil [B] An epoxy resin composition containing at least (I) to (IV), and containing 90 to 100 parts by mass of (I), 15 to 75 parts by mass of (II), 20 to 75 parts by mass of (III), and 0.1 to 10 parts by mass of (IV) with respect to 100 parts by mass of the total epoxy resin. (I) Non-aromatic epoxy resin (II) Pigment having an average particle size of 0.1 to 10 μm (III) Non-aromatic thermoplastic resin (IV) Cationic curing agent or anionic curing agent.

[0011] Component [A] according to the present invention is a metal mesh or foil. Metals generally have conductivity. Examples of metals having conductivity include copper, silver, platinum, palladium, nickel, lead, tin, aluminum, titanium, and alloys using them.

[0012] The metal foil of component [A] used in the present invention may have holes or cuts, and there is no particular limitation on the weaving method of the metal mesh. For example, there are plain weave, twill weave, satin weave, plain basket weave, twill basket weave, satin basket weave, etc.

[0013] Component [B] used in the present invention is an epoxy resin composition containing at least (I) to (IV) shown below.

[0014] (I) is a non-aromatic epoxy resin. Here, "aromatic" means those containing aromatic hydrocarbons or unsaturated heterocyclic compounds in the chemical structure, and the rest are "non-aromatic". That is, the non-aromatic epoxy resin refers to an epoxy resin that does not contain an aromatic hydrocarbon group or an unsaturated heterocycle in the chemical structure.Examples of non-aromatic epoxy resins include alicyclic epoxy resins (epoxy resins containing cycloalkane rings), such as tetrahydroindene diepoxide, vinyl cyclohexene oxide, (3’,4’-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate, dipentene dioxide, bis(3,4-epoxycyclohexylmethyl) adipate, dicyclopentadiene dioxide, bis(2,3-epoxycyclopentyl) ether, 1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol, tetrakis-(3-cyclohexenylmethyl) modified epsilon-caprolactone of epoxidized butanetetracarboxylic acid, bi-7-oxabicyclo[4.1.0]heptane, dodecahydrobisphenol A diglycidyl ether, dodecahydrobisphenol F diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, hexahydrophthalic acid diglycidyl ester, hexahydroterephthalic acid diglycidyl ester, diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane (common name: hydrogenated bisphenol A type liquid epoxy resin). Specific examples of epoxy resins containing neither an aromatic ring, an amine nitrogen atom, a cycloalkane ring, nor a cycloalkene ring include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol glycidyl ether, 1,6-hexanediol diglycidyl ether, neopentylene glycol diglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, 1,4-bis(2-oxiranyl)butane, pentaerythritol polyglycidyl ether. Specific examples of monofunctional epoxy compounds (epoxy compounds containing only one oxirane ring) containing neither an aromatic ring nor an amine nitrogen atom include 4-tert-butyl glycidyl ether, butyl glycidyl ether, 1-butene oxide, 1,2-epoxy-4-vinylcyclohexane, 2-ethylhexyl glycidyl ether, and the like.

[0015] From the perspective of heat resistance, alicyclic epoxy resins are preferably used as the non-aromatic epoxy resins.

[0016] Commercially available products can be used as the above non-aromatic epoxy resins. For example, "Celloxide (registered trademark)" 2021P, "Celloxide (registered trademark)" 8010, "Celloxide (registered trademark)" 2000, "Epolead (registered trademark)" GT401, "Celloxide (registered trademark)" 2081, EHPE3150 (manufactured by Daicel Chemical Industries, Ltd.), THI-DE (manufactured by JXTG Energy Corporation), TTA21, AAT15, TTA22 (manufactured by Sankyo Chemical Co., Ltd.), Ex-121, Ex-211, Ex-212, Ex-313, Ex-321, Ex-411 (manufactured by Nagase ChemteX Corporation), "Epolite (registered trademark)" 4000 (manufactured by Kyoeisha Chemical Co., Ltd.), ST-3000, ST-4000 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), YX8000 (manufactured by Mitsubishi Chemical Corporation), EPALOY5000 (manufactured by Huntsman), etc.

[0017] By using at least two types of the above non-aromatic epoxy resins, the reactivity of the epoxy resin composition can be controlled, and a good balance between the rapid curing property and the pot life of the epoxy resin composition can be obtained.

[0018] By containing 90% by mass or more of the above non-aromatic epoxy resin in the entire epoxy resin composition, high light resistance (UV resistance) can be obtained.

[0019] (II) is a pigment (average particle size: 0.1 to 10 μm). Examples of the pigment include barium sulfate, zinc sulfide, titanium oxide, molybdenum red, cadmium red, chromium oxide, titanium yellow, cobalt green, cobalt blue, ultramarine blue, barium titanate, carbon black, iron oxide, red phosphorus, copper chromate, and the like. When the average particle size of the pigment is 0.1 to 10 μm, preferably 0.1 to 5 μm, more preferably 0.3 to 5 μm, an epoxy resin composition having high UV shielding properties can be obtained. Here, the average particle size is measured using LA-950 (manufactured by Horiba, Ltd.) using the laser diffraction scattering method. As the dispersion medium, the volume conversion result measured using "Araldite (registered trademark)" GY282 (component: bisphenol F type epoxy resin, manufactured by Huntsman Japan Co., Ltd.) is adopted as the particle size distribution measurement result, and the particle size (median diameter) at 50% in the cumulative curve of the obtained particle size distribution is taken as the average particle size.

[0020] By including 15 to 75 parts by mass, preferably 25 to 55 parts by mass, more preferably 30 to 50 parts by mass of the above pigment with respect to 100 parts by mass of the total epoxy resin contained in the epoxy resin composition, a good balance between the light shielding property and the tack property of the resin cured product can be obtained.

[0021] (III) is a non-aromatic thermoplastic resin. Here, "aromatic" means those containing aromatic hydrocarbons or unsaturated heterocyclic compounds in the chemical structure, and the rest are "non-aromatic". That is, the non-aromatic thermoplastic resin refers to a thermoplastic resin that does not contain an aromatic hydrocarbon group or an unsaturated heterocycle in its chemical structure. Examples of the non-aromatic thermoplastic resin include polyvinyl alcohol, polyvinyl acetal, polyvinyl formal, polyvinyl acetoacetal, polyvinyl butyral, polyvinyl acetate, hydrogenated bisphenol A - pentaerythritol phosphite polymer, hydrogenated terpene, hydrogenated terpene phenol, and the like.

[0022] Polyvinyl alcohol, polyvinyl formal, polyvinyl butyral, polyvinyl acetoacetal, and polyvinyl acetate, which have particularly high solubility in non-aromatic epoxy resins, are preferred in that they can easily adjust the viscosity of the epoxy resin composition. Polyvinyl acetoacetal and polyvinyl butyral are more preferred because they can improve the elongation of the cured epoxy resin composition. Here, the elongation refers to the bending strain (%) when the cured epoxy resin composition is bent at three points in a predetermined shape.

[0023] These non-aromatic thermoplastic resins are preferably those that can be dissolved in the non-aromatic epoxy resin of (I). For example, when at least 10 parts by mass of the powder of the thermoplastic resin is added to 100 parts by mass of the epoxy resin of (I) and kneaded at 100 to 120 °C for 1 hour, those in which the weight loss of the powder of the thermoplastic resin is observed compared to the start are considered soluble. The weight loss being observed means that it becomes so small that it is optically unobservable, or that when the remaining powder is recovered, a mass reduction of 10% or more is observed compared to the start. From the viewpoint of dissolving in the epoxy resin, the powder of the thermoplastic resin preferably has an average particle size of 100 μm or less obtained by at least the laser diffraction method. Also, when the average particle size is larger than 100 nm, it is preferable such as being easy to suppress aggregation during storage and easy to stir into the epoxy resin.

[0024] In addition, when the molecular weight of these non-aromatic thermoplastic resins is 5000 to 70000 g / mol, preferably 7000 to 65000 g / mol, and more preferably 10000 to 60000 g / mol, a good balance between the uniformity of dissolution in the epoxy resin composition and the resin flow suppression effect can be obtained. Here, the molecular weight means the weight average molecular weight in terms of polystyrene by gel permeation chromatography using HLC-8420GPC (manufactured by Tosoh Corporation).

[0025] As the above non-aromatic thermoplastic resin, commercially available products can be used. For example, "J-POVAL (registered trademark)" (manufactured by Nippon Vinyl Poval Co., Ltd.), "Vinilec (registered trademark)" (manufactured by JNC Corporation), "Esrec (registered trademark)" (manufactured by Sekisui Chemical Co., Ltd.), "Ultra-Sen (registered trademark)" (manufactured by Tosoh Corporation), JPH-3800 (manufactured by Johoku Chemical Industry Co., Ltd.), YS Polyster UH130 (manufactured by Yasuhara Chemical Co., Ltd.), etc. can be mentioned.

[0026] By containing the above non-aromatic thermoplastic resin in an amount of 20 to 75 parts by mass, preferably 30 to 65 parts by mass, more preferably 30 to 55 parts by mass, based on 100 parts by mass of the total epoxy resin contained in the epoxy resin composition, a sheet-like intermediate substrate having good tack characteristics can be obtained.

[0027] (IV) is a cationic curing agent or an anionic curing agent. Examples of the cationic curing agent include 1-naphthylmethylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate, 2-methylbenzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate, benzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate, dimethyl-p-acetoxyphenylsulfonium hexafluoroantimonate, diaryliodonium salt, boron trifluoride piperidine, boron trifluoride monoethylamine, diaryliodonium salt, sulfonium salt, etc.

[0028] As the cationic curing agent, commercially available products can be used. For example, "ADEKA OPTON (registered trademark)" CP-77, "ADEKA OPTON (registered trademark)" CP-66 (manufactured by ADEKA CORPORATION), CI-2639, CI-2624 (Nippon Soda Co., Ltd.), "SUN AID (registered trademark)" SI-60, "SUN AID (registered trademark)" SI-80, "SUN AID (registered trademark)" SI-100, "SUN AID (registered trademark)" SI-150, "SUN AID (registered trademark)" SI-B4, "SUN AID (registered trademark)" SI-B5 (manufactured by Sanshin Chemical Industry Co., Ltd.), TA-100, IK-1PC(80) (manufactured by San-Apro Ltd.), boron trifluoride piperidine, boron trifluoride monoethylamine (manufactured by Stella Chemifa Corporation), etc. can be mentioned. The cationic curing agent is preferably a photo-thermal cationic curing agent or a thermal cationic curing agent. A photo-thermal cationic curing agent refers to a substance that generates reactivity by applying light with a certain wavelength or less such as ultraviolet rays or visible light or heat at a certain temperature or higher, and a thermal cationic curing agent refers to a substance that generates reactivity by heat. Using a photo-thermal cationic curing agent is preferable because it can be cured in a variety of environments, and in the case of a thermal cationic curing agent, high storage stability can be obtained by temperature control, so it is preferable.

[0029] Examples of the anionic curing agent include phosphorus hexafluoride, antimony hexafluoride, arsenic hexafluoride, tin hexachloride, iron tetrachloride, bismuth pentachloride, niobium hexachloride, etc.

[0030] By using two types of the above curing agents, the reactivity of the epoxy resin composition can be controlled, and a good balance between the fast curability and the pot life of the epoxy resin composition can be obtained.

[0031] The above curing agent is contained in an amount of 0.5 to 10 parts by mass, preferably 1 to 5 parts by mass, more preferably 1 to 3 parts by mass, based on 100 parts by mass of the total epoxy resin contained in the epoxy resin composition, so that fast curability can be achieved and a good balance among the resin flow during molding, the volatile amount, the fast curability, the pot life, and the UV resistance can be obtained.

[0032] Also, component [B] in the present invention can contain a (V) thixotropy-imparting agent. Examples of the thixotropy-imparting agent include silicon dioxide, magnesium silicon sodium fluoride hydroxide oxide, alkyl quaternary ammonium salts, synthetic hectorite, viscosity minerals, modified bentonite, and mixed systems of mineral and organically modified bentonite, etc.

[0033] As the above thixotropy-imparting agent, commercially available products can be used. Examples include fumed silica (“Aerosil (registered trademark)” (manufactured by Nippon Aerosil Co., Ltd.)), “OPTIGEL (registered trademark)”, “OPTIBENT (registered trademark)”, “GARAMITE (registered trademark)”, “LAPONITE (registered trademark)”, “TIXOGEL (registered trademark)”, “CRAYTONE (registered trademark)”, “CLOISITE (registered trademark)” (manufactured by BYK Co., Ltd.), “Somasif (registered trademark)” ME-100, micro mica MK (manufactured by Katakura Koppu Agri Co., Ltd.), etc.

[0034] By containing the above thixotropy-imparting agent in an amount of 0.1 to 20 parts by mass, preferably 0.5 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the total epoxy resin contained in the epoxy resin composition, a good balance between the resin flow suppression effect during molding and the tack characteristics can be obtained.

[0035] Furthermore, component [B] in the present invention can contain a (VI) curing aid. Examples of the curing aid include 4-hydroxyphenyldimethylsulfonium = methyl sulfate, 4-(methylthio)phenol, etc.

[0036] As the above curing aid, commercially available products can be used. Examples include “Sun-Aid (registered trademark)” SI-S, “Sun-Aid (registered trademark)” S-ME (manufactured by Sanshin Chemical Industry Co., Ltd.), etc.

[0037] By including the above-mentioned curing aid in an amount of 0.1 to 10 parts by mass, preferably 0.1 to 5 parts by mass, more preferably 0.1 to 2.5 parts by mass, based on 100 parts by mass of the total epoxy resin contained in the epoxy resin composition, a good balance between the rapid curability and the pot life of the epoxy resin composition can be obtained.

[0038] Component [B] (VII) in the present invention may contain rubber. Examples of the rubber include natural rubber, diene rubber, non-diene rubber and the like. Examples of the diene rubber include styrene-butadiene rubber, isoprene rubber, butadiene rubber, chloroprene rubber, acrylonitrile-butadiene rubber and the like. Examples of the non-diene rubber include butyl rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, urethane rubber, silicone rubber, fluororubber and the like. As the inclusion in the epoxy resin composition in the present invention, non-diene rubber is preferable. Among them, ethylene-propylene rubber, ethylene-propylene-diene rubber, silicone rubber, and fluororubber, which do not have double bonds in the polymer main chain, are particularly preferable because they have high light resistance and little influence on the light resistance of the epoxy resin composition in the present invention. Further, as the shape of the rubber, a powder form is particularly preferable because it has excellent dispersibility in the epoxy resin composition.

[0039] The content of the above-mentioned rubber is preferably 5 to 50 parts by mass based on 100 parts by mass of the total epoxy resin. When the content of the rubber is 5 parts by mass or more based on 100 parts by mass of the total epoxy resin, the resin flow suppression effect and the elongation of the cured epoxy resin composition are excellent, so that the effect of preventing cracks after coating can be obtained. When the content is 50 parts by mass or less, the adhesion to the sheet-like intermediate substrate in the present invention is excellent, which is preferable.

[0040] Commercially available products can be used as the above rubber. Examples include KMP-598, KMP-600, KMP-601, KMP-602, KMP-605 (manufactured by Shin-Etsu Chemical Co., Ltd.), "Cevian (registered trademark)" (manufactured by Daicel Miraiz Co., Ltd.), JSR N215SL, JSR N222SH, JSR N238H, JSR N241H, JSR N250S, PN30A, PN20HA, N280 (manufactured by JSR Corporation), etc.

[0041] The sheet-like intermediate substrate of the present invention is generally attached to the outermost surface of uncured prepregs, RTM materials, or resin film infusion (RFI) materials (also referred to as "fiber-reinforced composite material precursors" in the present invention) that are used in fiber-reinforced composite materials, and can be cured together by heat in the attached state. Here, the prepreg is a fiber-reinforced composite material precursor obtained by impregnating reinforcing fibers with a thermosetting resin such as an epoxy resin. The RTM material is a fiber-reinforced composite material precursor obtained by laminating a reinforcing fiber substrate in a mold and injecting a liquid thermosetting resin into it to impregnate the reinforcing fiber substrate. The RFI material refers to a fiber-reinforced composite material precursor obtained by stacking and laminating a thermosetting resin film on a reinforcing fiber substrate and impregnating the reinforcing fiber substrate with the thermosetting resin by heating and pressing. By curing, the cured product of the sheet-like intermediate substrate covers the surface of the fiber-reinforced composite material precursor after curing, and an integrated fiber-reinforced composite material can be obtained. As the reinforcing fibers in the fiber-reinforced composite material precursor, various carbon fibers, graphite fibers, glass fibers, aramid fibers, etc. are preferably used.

[0042] The sheet-like intermediate substrate of the present invention is formed by impregnating or coating a metal foil or metal mesh serving as a support with an epoxy resin composition which is a thermosetting resin. The epoxy resin composition may be impregnated or coated only on one side of the metal foil or metal mesh, or may be impregnated or coated on both sides. By having the epoxy resin composition present only on one side, it is difficult to be picked up by hand during attachment of the sheet-like intermediate substrate, making it easy to handle. On the other hand, by having the epoxy resin composition present on both sides, it has tack on both sides, so there is an advantage that it is easy to attach not only to the fiber-reinforced composite material precursor serving as the base material but also to the tool surface. Also, the epoxy resin composition may be present in the holes / cuts of the metal foil or in the meshes of the mesh.

[0043] The sheet-like intermediate substrate of the present invention can be manufactured by various methods. For example, a wet method in which the epoxy resin composition is dissolved in an organic solvent selected from acetone, methyl ethyl ketone, methanol, etc. to lower the viscosity and then impregnated into the metal foil or metal mesh, or a hot melt method in which the epoxy resin composition is heated to lower the viscosity without using an organic solvent and then impregnated into the metal foil or metal mesh. The sheet-like intermediate substrate can be manufactured by such methods.

[0044] In the wet method, the metal foil or metal mesh is immersed in a liquid containing the epoxy resin composition and then pulled up, and the organic solvent is evaporated using an oven or the like to obtain the sheet-like intermediate substrate.

[0045] The hot melt method includes a method of directly impregnating the metal foil or metal mesh with the epoxy resin composition whose viscosity has been lowered by heating, or first preparing a release paper sheet with a resin film (hereinafter sometimes referred to as "resin film") obtained by once coating the epoxy resin composition on a release paper or the like, and then overlapping the resin film on the metal foil or metal mesh from both sides or one side of the metal foil or metal mesh and heating and pressurizing to impregnate the metal foil or mesh with the epoxy resin composition. Such methods can be used.

[0046] As a method for manufacturing the sheet-like intermediate base material of the present invention, it is preferable to use a hot melt method in which an epoxy resin composition without residual organic solvent is impregnated into a metal foil or a metal mesh. The width of the sheet-like intermediate base material of the present invention is not particularly limited, and a wide sheet with a width exceeding 1 m may be manually pasted, or it may be pasted using an automatic laminating device as a tape with a width of 1 inch or less.

[0047] It is possible to produce a sheet-like intermediate base material using a pre-cured resin film. The pre-curing can be carried out by heating, light irradiation, etc. Heating can be performed by an oven, an IR heater, bringing the release paper surface of the resin film into contact with a hot plate, etc. The temperature of the oven, furnace, IR heater, or hot plate during pre-curing is preferably 40 to 200 °C. When the temperature is 40 °C or higher, the pre-curing time can be shortened, and when it is 200 °C or lower, the resin film can be uniformly pre-cured. The wavelength of the light when pre-curing is performed by irradiating the resin film with light is not particularly limited, but ultraviolet light of 100 to 400 nm, which is absorbed by a general photoinitiator, is more preferable. Depending on the curing temperature and the illuminance of ultraviolet / visible light, it is preferable to pre-cure over 0.005 to 24 hours from the viewpoint of film uniformity. Curing by light or heat may be carried out until the fluidity of the resin film surface disappears, or the degree of curing may be arbitrarily adjusted to leave a certain degree of fluidity. After impregnating the resin film into a separate support, the resin film with the support may be impregnated into a metal foil or mesh to produce a sheet-like intermediate base material.

[0048] The sheet-like intermediate base material of the present invention preferably has 5 to 300 g / m of metal foil or metal mesh per unit area. 2 When the amount of such metal foil or metal mesh is 5 g / m or more, it is difficult to break as a support for the epoxy resin composition, and the handleability becomes easy, so the work becomes easy. On the other hand, when the amount of metal foil or metal mesh is 300 g / m or less, the drapeability of the sheet-like intermediate base material is likely to be improved. 2 2

[0049] ​​ The content of the metal foil or metal mesh in the sheet-like intermediate substrate of the present invention is preferably 1 to 80% by mass, more preferably 3 to 60% by mass, and still more preferably 5 to 30% by mass. When the content of the metal foil or metal mesh is 1% by mass or more, the amount of the resin does not become too large, and it is easy to obtain the handling advantages of the sheet-like intermediate substrate excellent in specific strength and specific modulus. Also, when molding with the fiber-reinforced composite material, the balance between the heat generation during resin curing and the heat dissipation by the metal is preferable. Further, when the content of the metal foil or metal mesh is 80% by mass or less, poor impregnation of the resin hardly occurs, and the possibility of void generation in the sheet-like intermediate substrate after molding is reduced.

[0050] The basis weight of component [B] is preferably 30 to 300 g / m 2 It is preferable that the basis weight of component [B] is 30 g / m 2 When it is 30 g / m or more, there are no pinholes and it is possible to uniformly cover the support with the epoxy resin composition, and it is difficult to break. On the other hand, when the basis weight of component [B] is 300 g / m 2 When it is 300 g / m or less, the drapeability of the sheet-like intermediate substrate is likely to be improved.

[0051] As a method for molding the sheet-like intermediate substrate of the present invention, it is preferable to attach it to the outermost surface of the fiber-reinforced composite material precursor and cure it together. The sheet-like intermediate substrate of the present invention described above is attached to the outermost surface of the fiber-reinforced composite material precursor in a predetermined form, pressurized and heated to cure the resin, and a fiber-reinforced composite material can be produced. Here, as a method for applying heat and pressure, for example, a press molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, an internal pressure molding method, etc. are adopted.

Examples

[0052] Hereinafter, the present invention will be described in detail with reference to examples. However, the scope of the present invention is not limited to these examples. Also, the measurement of various properties was carried out in an environment of a temperature of 23°C and a relative humidity of 50% unless otherwise noted.

[0053] <Materials used in Examples and Comparative Examples> (1) Component [A]: Metal foil or metal mesh · Pure copper (C1020, manufactured by Takeuchi Metal Foil Powder Industry Co., Ltd.).

[0054] (2) Aromatic epoxy resin · Bisphenol A type epoxy resin (“jER (registered trademark)” 828, manufactured by Mitsubishi Chemical Corporation), epoxy equivalent: 175 (g / eq.).

[0055] (3) Component [B] (I) Non-aromatic epoxy resin · (3’,4’-Epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate (“Celoxide (registered trademark)” 2021P, manufactured by Daicel Corporation), epoxy equivalent: 136 (g / eq.) · 1,2-Epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol (“EHPE3150”, manufactured by Daicel Corporation) · Epoxidized butanetetracarboxylic acid tetrakis-(3-cyclohexenylmethyl) modified epsilon-caprolactone (“Epolead (registered trademark)” GT401, manufactured by Daicel Corporation) · Diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane (YX8000, manufactured by Mitsubishi Chemical Corporation).

[0056] (4) Component [B] (II) Pigment · Titanium oxide (rutile type) (“Ti-Pure (registered trademark)” R-960, manufactured by Kemira Co., Ltd., average particle size 0.5 μm).

[0057] (5) Component [B] (III) Non-aromatic thermoplastic resin · Polyvinyl formal (“Vinylec (registered trademark)” K, manufactured by JNC Corporation, calculated molecular weight 40000 - 54000 g / mol) · Polyvinyl acetal (“Esrec (registered trademark)” KS-10, manufactured by Sekisui Chemical Co., Ltd., calculated molecular weight 17000 g / mol) · Polyvinyl butyral (“Esrec (Registered Trademark)” BX-L, manufactured by Sekisui Chemical Co., Ltd., calculated molecular weight 18,000 g / mol).

[0058] (6) Component [B] (IV) Cationic curing agent · Dimethyl-p-acetoxyphenylsulfonium hexafluoroantimonate “Sun Aid (Registered Trademark)” SI-150, manufactured by Sanshin Chemical Industry Co., Ltd. · Benzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate “Sun Aid (Registered Trademark)” SI-100, manufactured by Sanshin Chemical Industry Co., Ltd.).

[0059] (7) Component [B] (V) Thixotropy-imparting agent · Fumed silica (“AEROSIL (Registered Trademark)” RY200S, manufactured by Nippon Aerosil Co., Ltd.) · Alkylammonium clay (“GARAMITE (Registered Trademark)” 1958, manufactured by BYK Co., Ltd.).

[0060] (8) Component [B] (VI) Curing aid · 4-Hydroxyphenyldimethylsulfonium = methyl sulfate (“Sun Aid (Registered Trademark)” SI-S, manufactured by Sanshin Chemical Industry Co., Ltd.) · 4-(Methylthio)phenol (“Sun Aid (Registered Trademark)” S-ME, manufactured by Sanshin Chemical Industry Co., Ltd.).

[0061] (9) Acid anhydride · Mixture of 4-methylhexahydrophthalic anhydride and hexahydrophthalic anhydride (“Ricacid (Registered Trademark)” MH-700, manufactured by Shin Nippon Rika Co., Ltd.) Acid anhydride equivalent: 163 (g / eq.).

[0062] (10) Component [B] (VII) Rubber · Silicone rubber powder (KPM-601, manufactured by Shin-Etsu Chemical Co., Ltd.).

[0063] <Epoxy resin composition, method for producing sheet-like intermediate substrate, and evaluation method> The epoxy resin compositions of each example and comparative example were measured by the following method.

[0064] (1) Preparation of epoxy resin composition An epoxy resin corresponding to component [B](I) described in Tables 1 to 6 (aromatic epoxy in Examples 30 and Comparative Examples 1 and 8), a pigment corresponding to component [B](II), and if necessary, a thixotropic agent as component [B](V) and a rubber as component [B](VII) were put into a three-roll mill and mixed at an arbitrary roll rotation speed to obtain a powder mixture precursor. The powder mixture precursor and a thermoplastic resin corresponding to component [B](III) described in Tables 1 to 6 were put into a mixer, and heat mixing was performed to dissolve the thermoplastic resin. Then, while continuing kneading, the temperature was lowered to 60°C or lower, and a cationic curing agent as component [B](IV) described in Tables 1 to 6 (anhydride in Comparative Example 9) and if necessary, a curing aid as component [B](VI) were added and stirred to obtain an epoxy resin composition.

[0065] (2) Method for producing a sheet-like intermediate substrate The epoxy resin composition prepared in (1) above was coated on release paper to prepare a resin film with a predetermined resin basis weight. This resin film was set in a sheet-like intermediate substrate production machine, a metal foil was overlapped on the resin film, and heat and pressure were applied to impregnate the epoxy composition into the metal foil (single-sided impregnation), and a sheet-like intermediate substrate with a metal foil basis weight of 89.4 g / m 2 , and a resin basis weight of 100 g / m 2 was prepared. The metal foil used was brass (C2680R-EH, manufactured by Takeuchi Metal Foil Powder Industry Co., Ltd.).

[0066] (3) Method for evaluating the tackiness of the sheet-like intermediate substrate The sheet-shaped intermediate substrate prepared in (2) above was cut into a 10 cm square, and a prepreg (T800S / 3900-2B (manufactured by Toray Industries, Inc.)) used for a 15 cm square fiber-reinforced composite material was placed on the lower side, and the 10 cm square sheet-shaped intermediate substrate was placed on the upper side and overlapped. A 10 cm square stainless steel plate (400 g) with an adhesive tape attached was placed on the upper side of the overlapped sheet-shaped intermediate substrate and held for 30 seconds. Then, when the stainless steel plate was lifted, when the sheet-shaped intermediate substrate peeled off from the prepreg and was divided into two sheets, if the epoxy resin composition used for the sheet-shaped intermediate substrate remained on the prepreg, the tackiness was judged as "poor", and if the epoxy resin composition used for the sheet-shaped intermediate substrate did not remain, the tackiness was judged as "good".

[0067] (4) Adhesion of sheet-shaped intermediate substrate The sheet-shaped intermediate substrate prepared in (2) above was cut into a 10 cm square and attached to an aluminum plate of an arbitrary size (larger than 10 cm square). A 10 cm square stainless steel plate (400 g) that had been subjected to a release treatment by spraying Die Free GA-3000 (manufactured by Daikin Industries, Ltd.) from above was placed on it and held for 30 seconds. Then, the stainless steel plate was lifted, and with the sheet-shaped intermediate substrate attached to the aluminum plate, the aluminum plate was leaned at a 90° angle around the ground axis. After 24 hours, if the sheet-shaped intermediate substrate was attached to the aluminum plate, the adhesion was judged as "good", and if it was partially peeled off, it was judged as "poor".

[0068] (5) Method for measuring the heat generation peak temperature of the sheet-shaped intermediate substrate Using a differential scanning calorimeter (DSC Q2500, manufactured by TA Instruments), the exothermic curve of the sheet-shaped intermediate substrate was obtained in a nitrogen atmosphere at a heating rate of 5°C / min. In the obtained exothermic curve, the temperature at the peak of the exothermic peak with an exothermic amount of 100 mW / g or more was calculated as the exothermic peak temperature. When there are two or more exothermic peaks with an exothermic amount of 100 mW / g or more, the temperature at the peak of the peak on the low-temperature side was calculated as the exothermic peak temperature of the DSC in the present invention. Regarding the evaluation of rapid curability, in Tables 1 to 4, an exothermic peak temperature of 100°C or less was denoted as A, more than 100°C and 120°C or less as B, more than 120°C and 140°C or less as C, and more than 140°C as D.

[0069] (6) Measurement of the volatile content of the sheet-shaped intermediate substrate The sheet-shaped intermediate substrate prepared in (2) above was cut out into an 8 cm square, the mass of the 8 cm square sheet-shaped intermediate substrate was measured (mass: W1), and it was placed in an oven at 180°C for 1 hour while placed on the release paper. Then, the sheet-shaped intermediate substrate and the release paper were taken out of the oven, left in a desiccator for 30 minutes, and then the mass of the sheet-shaped intermediate substrate was measured (mass: W2). Using the mass (W3) of one 8 cm square of the metal foil or mesh used for the sheet-shaped intermediate substrate, the volatile content [%] in the present invention was calculated by the following calculation formula. {(W1 - W3) - (W2 - W3)} / (W1 - W3)×100 [%] When the calculated volatile content was 5% or less, it was regarded as "good", and when it exceeded 5%, it was regarded as "bad".

[0070] (7) Measurement of the resin flow amount of the sheet-shaped intermediate substrate The sheet-shaped intermediate substrate produced in the above (2) was cut into 10 cm squares, four 10 cm square sheet-shaped intermediate substrates were laminated, and the mass of the laminate was measured (W4). It was sandwiched between two release films cut into 15 cm squares, and further sandwiched between two 10 cm square metal plates (one plate weighing 400 g), and then molded in an autoclave in this state (180 °C for 2 hours under 6 atmospheres, heating rate 1.7 °C / min). After molding, the cured product of the sheet-shaped intermediate substrate protruding from the 10 cm square metal plate was removed, and the mass of the cured laminate of the 10 cm square sheet-shaped intermediate substrate was measured (mass: W5). Using the mass (W6) of four 10 cm squares of the metal foil or mesh used for the sheet-shaped intermediate substrate, it was calculated as the resin flow rate [%] in the present invention according to the following calculation formula. {(W4 - W6) - (W5 - W6)} / (W4 - W6)×100 [%] The resin flow rate of 5% or less was designated as A, more than 5% and 10% or less as B, more than 10% and 15% or less as C, and more than 15% as D.

[0071] (8) UV irradiation test of the sheet-shaped intermediate substrate The sheet-shaped intermediate substrate produced in the above (2) was cut into 5 cm squares, and the sheet-shaped intermediate substrate cut into 5 cm squares was cured in an oven at 180 °C for 2 hours under the condition of a heating rate of 1.7 °C / min. Using a metering weather meter (manufactured by Suga Test Instruments Co., Ltd., model M6T), UV light with an irradiation wavelength of 300 - 400 nm was irradiated on the surface of the cured sheet-shaped intermediate substrate with an integrated illuminance of 1.55 kW / m 2 and an integrated intensity of 1000 kJ / m 2 (approximate value of the amount of ultraviolet rays in Japan (summer) for one month). If the color of the cured sheet-shaped intermediate substrate did not visually change before and after irradiation, the UV resistance was rated as "good", and if it discolored, the UV resistance was rated as "poor".

[0072] (9) Resin amount of the prepreg mixed into the sheet-shaped intermediate substrate during the molding process The sheet-shaped intermediate substrate produced in the above (2) was cut into 5 cm squares, and eight 5 cm square sheet-shaped intermediate substrates were laminated so that the continuous fiber prepreg became pseudo-isotropic (lamination structure: [+45° / 0° / -45° / 90°] sOne sheet was attached to the outermost surface of the resulting product, and in that state, the sheet-like intermediate substrate side of the composite material formed in an autoclave at 6 atm, 180 °C for 2 hours with a heating rate of 1.7 °C / min was subjected to IR measurement by the ATR method (FT / IR-4000, manufactured by JASCO Corporation, prism: diamond, measurement wavelength: 400~4000 cm -1 , number of integrations: 16 times). The peak at 1715 cm -1 indicating an ester was normalized, and by evaluating the value of the peak at 1592 cm -1 indicating the benzene ring due to the cured resin used in the prepreg, it becomes possible to evaluate the amount of the resin used in the prepreg mixed with the sheet-like intermediate substrate during the molding process and exposed to the surface of the fiber-reinforced composite material. If the value of the peak at 1592 cm -1 indicating the benzene ring due to the cured resin used in the prepreg is 0.6 or less, it was determined that the UV resistance of the surface of the fiber-reinforced composite material is good. Also, in Examples 31 to 41 and Comparative Examples 10 to 11, IR measurement by the ATR method was carried out in the same manner as above, and normalization using the peak at 1715 cm -1 indicating an ester was not performed, and the value of the peak at 1592 cm -1 indicating the benzene ring due to the cured resin used in the fiber-reinforced composite material precursor was evaluated. In this case, if the value of the peak at 1592 cm -1 indicating the benzene ring due to the cured resin used in the fiber-reinforced composite material precursor is 1.0 or less, it was determined that the UV resistance of the surface of the fiber-reinforced composite material is good.

[0073] (10) Measurement of pot life The viscosity of the epoxy resin composition used for the sheet-like intermediate substrate was measured using a dynamic viscoelasticity apparatus ARES-2KFRTN1-FCO-STD (manufactured by TA Instruments). After setting the epoxy resin composition using parallel plates with a diameter of 40 mm for the upper and lower measurement jigs so that the distance between the upper and lower jigs is 1 mm, the measurement was performed in a torsion mode (measurement frequency: 0.5 Hz). The viscosity η * 2 at 65 °C for 2 minutes was measured, and the viscosity η * x at any time after holding at 65 °C for 2 hours was measured, and the thickening ratio at that time was η* x ÷η * It was determined from 2. The time until the obtained thickening magnification reached 3 was defined as the pot life.

[0074] (11) Bending test of the epoxy resin composition after curing After degassing the uncured epoxy resin composition in a vacuum, using a 2 mm thick spacer made of "Teflon (registered trademark)", it was set in a mold so as to have a thickness of 2 mm and cured at a temperature of 180 °C for 2 hours. The obtained epoxy resin cured product with a thickness of 2 mm was cut into a width of 10 ± 0.1 mm and a length of 60 ± 1 mm to obtain test pieces. Using an Instron universal testing machine (manufactured by Instron), three-point bending with a span of 32 mm was carried out in accordance with JIS-K7171 (1994), and the elastic modulus and bending strain (elongation) were measured. The number of measurements was N = 6, and the average value was obtained.

[0075] <Examples 1 to 29 and Comparative Example 1> In Examples 1 to 29, as component [B](I), only (3’,4’-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate, or a combination of an epoxy resin with an adduct of 2,2-bis(hydroxymethyl)-1-butanol and 1,2-epoxy-4-(2-oxiranyl)cyclohexane, or an epoxy-modified butanetetracarboxylic acid tetrakis-(3-cyclohexenylmethyl) modified epsilon-caprolactone was used. For the sheet-like intermediate substrate cured by the UV resistance test using the epoxy resin composition, no discoloration was observed in the UV resistance test, and good results were obtained. On the other hand, Comparative Example 1 containing an aromatic epoxy resin showed discoloration, indicating low UV resistance.

[0076] <Examples 1 to 2> In Examples 1 and 2, the types of component [B](IV) were changed and compared. As a result, when benzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate was used as the cationic curing agent, the curing speed was higher than when an iodonium salt was used as the cationic curing agent, and there was a tendency to suppress all of volatility, resin flow, and the resin amount of the prepreg mixed into the sheet-like intermediate substrate during the molding process. On the other hand, it was shown that the pot life decreased.

[0077] Also, Examples 1 to 2 used only non-aromatic epoxy resins and obtained high UV resistance. On the other hand, when only aromatic epoxy was used as the epoxy resin as in Comparative Example 1, it was shown that the UV resistance was poor.

[0078] <Examples 2 to 3, 6, 21, 26 to 27, Comparative Examples 4 and 5> In Examples 2 to 3, the types of component [B](III) were changed and compared. As a result, it was shown that when polyvinyl formal was used as compared with polyvinyl acetoacetal, the effect of suppressing the resin flow amount was higher. Also, in Examples 2, 21 and Examples 3, 6, the addition amounts of polyvinyl formal and polyvinyl acetoacetal were changed respectively, and it was shown that the effect of suppressing the resin flow amount improved as both increased.

[0079] Also, in Examples 26 to 27, when the amounts of polyvinyl formal, a non-aromatic thermoplastic resin as component [B](III), were 20 parts by mass and 75 parts by mass respectively, it was shown that both sheet-like intermediate substrates had good tack characteristics and adhesiveness.

[0080] On the other hand, as shown in Comparative Example 4, when the addition amount of component [B](III) was too small at 10 parts by mass compared with the non-aromatic epoxy resin, the tack characteristics were judged to be poor because resin remained on the prepreg after peeling the sheet-like intermediate substrate from the prepreg. Also, as shown in Comparative Example 5, when the addition amount of component [B](III) was excessive at 80 parts by mass compared with the non-aromatic epoxy resin, the adhesiveness was insufficient and the adhesiveness was judged to be poor.

[0081] <Examples 3 to 5, 30, Comparative Example 8> In Example 3, 100 parts by mass of (3’,4’-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate was used for component [B](I). On the other hand, with respect to 70 parts by mass of (3’,4’-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate, in Example 4, 30 parts by mass of the 1,2-epoxy-4-(2-oxiranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol was added, and in Example 5, 30 parts by mass of epoxybutanetetracarboxylic acid tetrakis-(3-cyclohexenylmethyl) modified epsilon-caprolactone was added respectively. As a result, the tack characteristics and adhesiveness of the sheet-like intermediate base material in Examples 3 to 5 were good, and the UV resistance was also good. Therefore, it was shown that a sheet-like intermediate base material with good physical properties can be obtained both when using a single compound and when using a plurality of non-aromatic epoxies.

[0082] Also, in Example 30, 90 parts by mass of a non-aromatic epoxy resin and 10 parts by mass of an aromatic epoxy resin were used in combination, and as a result of the UV resistance evaluation, it was judged to be good. Therefore, it was shown that the UV resistance is good in the case of an epoxy resin composition containing 10 parts by mass of an aromatic epoxy resin among all the epoxy resins contained in the epoxy resin composition.

[0083] On the other hand, in Comparative Example 8, 80 parts by mass of a non-aromatic epoxy resin and 20 parts by mass of an aromatic epoxy resin were used in combination, and as a result of the UV resistance evaluation, it was judged to be poor. Therefore, it was shown that the UV resistance is poor in the case of an epoxy resin composition containing 20 parts by mass of an aromatic epoxy resin among all the epoxy resins contained in the epoxy resin composition.

[0084] <Examples 1, 2, 7 to 10, Comparative Examples 6, 7> In Example 7, the amount of the iodonium salt, which is the cationic curing agent of component [B](IV), was increased as compared with Example 1. While the fast-curing property of the epoxy resin composition of Example 7 increased as compared with Example 1, the pot life decreased, but it was shown that the effects of suppressing the volatile amount and the resin flow amount were high.

[0085] Similarly, in Example 8, the amount of benzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate, which is the cationic curing agent of component [B](IV), was increased as compared with Example 2. The fast-curing property of the epoxy resin composition of Example 8 increased as compared with Example 2, while the pot life decreased, but it was shown that the effects of suppressing the volatile amount and the resin flow amount were high.

[0086] In Examples 9 to 10, two types of dimethyl-p-acetoxyphenylsulfonium hexafluoroantimonate and benzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate, which are the cationic curing agents of component [B](IV), were used in combination as curing agents. In Example 9, the fast-curing property decreased as compared with Example 8, while an increase in the pot life was observed. In Example 10, the amount of methyl-p-acetoxyphenylsulfonium hexafluoroantimonate was increased from Example 9. In Example 10, the fast-curing property improved as compared with Example 9, and the pot life decreased. Therefore, it was shown that the balance between the fast-curing property and the pot life of the epoxy resin composition can be controlled by the addition ratio of the cationic curing agent of component [B](IV) and, when two types are added, by the mixing ratio.

[0087] In Comparative Example 6, 0.05 part of dimethyl-p-acetoxyphenylsulfonium hexafluoroantimonate, which is the cationic curing agent of component [B](IV), was added. Comparative Example 6 had low fast-curing property, and it was determined that the volatile amount and the resin amount of the prepreg mixed into the sheet-like intermediate base material during the molding process were defective.

[0088] On the other hand, in Comparative Example 7, 15 parts by mass of benzylmethyl p-hydroxyphenylsulfonium hexafluoroantimonate was added. Although the rapid curability was high, the pot life was significantly reduced. In addition, the evaluation of the resin amount of the prepreg mixed into the sheet-like intermediate substrate during the molding process was determined to be poor. Further, in Comparative Example 7, after UV irradiation of 1000 kJ / m 2 discoloration of the cured sheet-like intermediate substrate was observed, indicating that the UV resistance of the sheet-like intermediate substrate was low.

[0089] <Examples 11 to 12, Examples 28 to 29, Comparative Examples 2 and 3> In Examples 11 to 12, the amount of titanium oxide in Component [B](II) was changed for comparison. As a result, Example 12 with a larger amount of titanium oxide had a lower rapid curability and an improved pot life compared to Example 11, indicating that the reactivity of the epoxy resin composition can be controlled by the amount of titanium oxide. Also, it was shown that Example 12 with a larger amount of titanium oxide had a higher effect of suppressing the resin amount of the prepreg mixed into the sheet-like intermediate substrate during the molding process than Example 11.

[0090] In Examples 28 to 29, the amount of titanium oxide in Component [B](II) was 15 parts by mass and 75 parts by mass, respectively. It was shown that Example 29 had a lower rapid curability and a higher effect of suppressing the volatile amount compared to Example 28. Also, both of them were judged to have good UV resistance and the resin amount of the prepreg mixed into the sheet-like intermediate substrate during the molding process.

[0091] When 10 parts by mass of titanium oxide in Component [B](II) was added as in Comparative Example 2, the resin amount of the prepreg mixed into the sheet-like intermediate substrate during the molding process increased and was judged to be defective.

[0092] Also, when 100 parts by mass of titanium oxide in Component [B](II) was added as in Comparative Example 3, the rapid curability was poor and the volatile amount after 1 hour at 180°C was judged to be defective.

[0093] <Examples 8, 13 to 15> In Examples 13 to 15, a curing aid for Component [B](VI) was applied. In Example 13, as Component [B](VI), 0.2 part of the curing aid 4-hydroxyphenyldimethylsulfonium = methyl sulfate was applied, and as a result, an improvement in the pot life compared to Example 8 was observed. Further, in Example 15, the amount of 4-hydroxyphenyldimethylsulfonium = methyl sulfate was increased to 1.0 part, and as a result, a further improvement in the pot life was observed compared to Example 13. Similarly, in Example 14, the type of the curing aid for Component [B](VI) was changed to 4-(methylthio)phenol, and 0.2 part was applied, and as a result, an improvement in the pot life was observed compared to Example 8. Further, Examples 13 to 15 were judged to be good in terms of all of volatility, UV resistance, and the resin amount of the prepreg incorporated into the sheet-like intermediate base material during the molding process.

[0094] <Examples 8, 16 to 18> In Examples 16 to 18, a thixotropy-imparting agent for Component [B](V) was applied. In Examples 16 to 17, 4 parts each of fumed silica and alkylammonium clay were applied to Example 8, and the effects of suppressing the resin flow amount and the resin amount of the prepreg incorporated into the sheet-like intermediate base material during the molding process were shown without impairing the tackiness, adhesiveness, rapid curability, and UV resistance. Further, in Example 18, 4 parts each of fumed silica and alkylammonium clay were applied to Example 8, and it was shown that the effects of suppressing the resin flow amount and the resin amount of the prepreg incorporated into the sheet-like intermediate base material during the molding process were higher when compared with Examples 17 and 18.

[0095] <Examples 8, 19 to 20> In Examples 19 to 20, both a thixotropy-imparting agent for Component [B](V) and a curing aid for Component [B](VI) were applied. Compared with Example 8, it was shown that there was an effect of suppressing the resin flow amount and the resin amount of the prepreg incorporated into the sheet-like intermediate base material during the molding process, and further that the pot life was excellent.

[0096] <Examples 21 to 25> In Examples 21 to 25, all of the components [B] (I) to (VI) were applied. In Examples 21 to 22, the amount of titanium oxide as component [B] (II) and the amount of non-aromatic thermoplastic resin as component [B] (III) were changed, and furthermore, the type of curing aid as component [B] (VI) was changed. In Example 22 where the contents of titanium oxide and polyvinyl formal were high, it was shown that the effect of suppressing the resin flow amount of the contrast resin in Example 21 and the resin amount of the prepreg mixed into the sheet-like intermediate substrate during the molding process was high. In Examples 23 to 25, as a result of changing the content of polyvinyl formal which is a non-aromatic thermoplastic resin as component [B] (III) and the combination of the types of thixotropy imparting agents as component [B] (V), when the content of polyvinyl formal was high and two types of thixotropy imparting agents were used, it was shown that the effect of suppressing the resin flow amount and the resin amount of the prepreg mixed into the sheet-like intermediate substrate during the molding process was high.

[0097] <Comparative Example 9> In Comparative Example 9, an acid anhydride was applied to a non-aromatic epoxy resin curing agent. However, since the acid anhydride has a low viscosity and needs to be contained in a large amount compared to component [B] (IV), the viscosity of the epoxy resin composition was too low. The epoxy resin composition was applied onto the release paper of the support, but the resin flowed down from the release paper due to its own weight, so it was impossible to produce the target resin film.

[0098] <Examples 8, 31 to 41, Comparative Examples 10 to 11> In Examples 31 to 33, diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane was used as the non-aromatic epoxy resin of Component [B](I), and one kind each of polyvinyl formal, polyvinyl acetoacetal, and polyvinyl butyral was used as the non-aromatic thermoplastic resin of Component [B](III). A decrease in the elastic modulus and an improvement in the flexural strain were observed in the cured products of the epoxy resin compositions in the order of Examples 31, 32, and 33. Also, when Example 31 was compared with Example 8, the exothermic peak temperature was lower in Example 31 while showing a high pot life. Therefore, it was shown that the reactivity can be controlled by changing the type of Component [B](I), and the balance between rapid curability and pot life, that is, the effect of suppressing the resin flow amount during the molding process and the resin amount of the prepreg mixed into the sheet-like intermediate base material, and the processability can be adjusted.

[0099] In Examples 34 to 35, silicone rubber powder of Component [B](VII) rubber was used. An increase in the content of Component [B](VII) showed a decrease in the cured elastic modulus, an improvement in the flexural strain, and an effect of suppressing the resin flow amount of the epoxy resin composition. On the other hand, when Component [B](VII) was excessive as in Comparative Example 10, the adhesiveness was determined to be poor. When Component [B](VII) was too small as in Comparative Example 10, a sufficient resin flow amount suppressing effect was not observed, and the resin amount of the prepreg mixed into the sheet-like intermediate base material during the molding process became excessive and was determined to be defective.

[0100] In Examples 36 to 37, two types of non-aromatic epoxy resins of component [B](I), i.e., (3’,4’-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate and diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane, were used. Comparing Examples 31, 36 to 37, it was shown that the higher the content of (3’,4’-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate, the lower the exothermic peak temperature, and the resin flow amount and the resin amount of the prepreg mixed into the sheet-like intermediate base material during the molding process were suppressed. Example 8 using only one type of (3’,4’-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate as component [B](I) was excellent in rapid curability, and Examples using two types of component [B](I) were excellent in rapid curability. Example 31 using only one type of diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane was shown to be excellent in pot life. When using the above two types as in Examples 36 to 37, it is possible to achieve both excellent rapid curability and excellent pot life. Therefore, by using two types of non-aromatic epoxy resins of component [B](I), the reactivity of the epoxy resin composition can be controlled, and the balance between rapid curability and pot life, i.e., the suppression effect of the resin flow amount during the molding process and the resin amount of the prepreg mixed into the sheet-like intermediate base material, and the processability can be adjusted. Here, comparing Examples 8 and 31, it was shown that the flexural strain of the cured epoxy resin was higher in Example 31 using diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane than in Example 8 using (3’,4’-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate as the non-aromatic epoxy resin of component [B](I). Comparing Examples 36 to 37, it was shown that the higher the proportion of diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane used as the non-aromatic epoxy resin of component [B](I), the higher the flexural strain of the cured epoxy resin.

[0101] In Example 38, (3’,4’-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate was used for the non-aromatic epoxy resin of Component [B](I), and in Example 39, (3’,4’-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate and diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane were used. In both cases, 4-hydroxyphenyldimethylsulfonium = methyl sulfate was used as the curing aid of Component [B](VI). Comparing Example 38 with Example 31 and Example 39 with Example 37, it was shown that in Examples 38 and 39, the exothermic peak temperature was improved respectively, and the reactivity of the epoxy resin composition could be controlled by the inclusion of Component [B](VI).

[0102] In Example 40, (3’,4’-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate was used for the non-aromatic epoxy resin of Component [B](I), and in Example 41, (3’,4’-epoxycyclohexane)methyl 3,4-epoxycyclohexanecarboxylate and diglycidyl ether of 2,2-bis(4-hydroxycyclohexyl)propane were used. In both cases, fumed silica as the thixotropic agent of Component [B](V), 4-hydroxyphenyldimethylsulfonium = methyl sulfate as the curing aid of Component [B](VI), and silicone rubber powder of Component [B](VII) rubber were used. Comparing Example 40 with Example 31 and Example 41 with Example 37, it was shown that in Examples 40 and 41, the inclusion of Component [B](VI) further improved the pot life of the epoxy resin composition respectively. Also, comparing Example 40 with Example 38 and Example 41 with Example 39, in Examples 40 and 41, while maintaining the effect of improving the pot life by the inclusion of Component [B](VI) and Component [B](VII), the resin flow amount was suppressed, and the resin amount of the prepreg mixed into the sheet-like intermediate base material during the molding process was also suppressed.

[0103]

Table 1

[0104]

Table 2

[0105]

Table 3

[0106]

Table 4

[0107]

Table 5

[0108]

Table 6

Claims

1. A sheet-like intermediate substrate in which component [B] is applied to the surface of the following component [A]. [A] A metal mesh or a metal foil [B] An epoxy resin composition containing at least (I) to (IV), wherein 90 to 100 parts by mass of (I), 15 to 75 parts by mass of (II), 20 to 75 parts by mass of (III), and 0.1 to 10 parts by mass of (IV) are contained per 100 parts by mass of the total epoxy resin. (I) A non-aromatic epoxy resin (II) A pigment having an average particle diameter of 0.1 to 10 μm (III) At least one non-aromatic thermoplastic resin selected from the group consisting of polyvinyl alcohol, polyvinyl formal, polyvinyl butyral, polyvinyl acetoacetal, and polyvinyl acetate (IV) A cationic curing agent or an anionic curing agent

2. The sheet-like intermediate substrate according to claim 1, wherein a non-aromatic compound is contained in an amount of 90% by mass or more based on the entire epoxy resin composition of component [B].

3. The sheet-like intermediate substrate according to claim 1 or 2, wherein the non-aromatic epoxy resin (I) is an alicyclic epoxy resin.

4. The sheet-like intermediate substrate according to any one of claims 1 to 3, wherein component [B] further contains (V) a thixotropy-imparting agent.

5. The sheet-like intermediate substrate according to any one of claims 1 to 4, wherein component [B] further contains (VI) a curing aid.

6. The sheet-like intermediate substrate according to any one of claims 1 to 5, wherein component [B] contains at least two types of non-aromatic epoxy (I).

7. The sheet-like intermediate substrate according to any one of claims 1 to 6, wherein for the epoxy resin composition of component [B], the temperature of the exothermic peak of DSC is 80 to 120°C.

8. The sheet-like intermediate substrate according to any one of claims 1 to 7, wherein the amount of resin flow is 20% or less.

9. The sheet-like intermediate substrate according to any one of claims 1 to 8, wherein the volatile content is 10% or less.

10. The sheet-like intermediate substrate according to any one of claims 1 to 9, wherein component [A] is a copper mesh, a copper foil, an aluminum mesh, or an aluminum foil.

11. The sheet-like intermediate substrate according to any one of claims 1 to 10, containing two or more types of (IV) cationic polymerization curing agents.

12. The sheet-like intermediate substrate according to any one of claims 1 to 11, wherein component [B] is impregnated or applied to one or both surfaces of component [A].

13. A fiber-reinforced composite material in which a cured product of the sheet-like intermediate base material according to any one of claims 1 to 12 is integrated with a fiber-reinforced composite material precursor.

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