Molding material, fiber-reinforced composite material, and method for manufacturing fiber-reinforced composite material

Abstract

To provide a prepreg capable of obtaining a fiber-reinforced composite material in a uniform cured state, even when using a thick prepreg having a large basis weight of a reinforced fiber.SOLUTION: A molding material in which a reinforcing fiber base material is impregnated with an epoxy resin composition containing an epoxy resin, an epoxy resin curing agent, and a fluorine-containing polyether surfactant having a melting point of 25°C. or higher. Alternatively, a molding material in which a reinforcing fiber base material is impregnated with an epoxy resin composition containing an epoxy resin and an epoxy resin curing agent, wherein in the epoxy resin composition, a fluorine-containing polyether surfactant having a polyethylene oxide chain and a group derived from a hexafluoropropylene trimer is blended, and a ratio (Nx / Ny) of the average number of moles of ethylene oxide in the polyethylene oxide chain Nx to the number of moles Ny of groups derived from the hexafluoropropylene trimer is 10 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a molding material, a fiber-reinforced composite material, and a method for producing a fiber-reinforced composite material. [Background technology]

[0002] Fiber-reinforced composite materials containing reinforcing fibers and a matrix resin are widely used in industrial applications such as automobiles due to their excellent mechanical properties, and their range of applications has been expanding in recent years. For example, a sheet-like prepreg in which reinforcing fibers are impregnated with a matrix resin composition is known as a molding material for obtaining the fiber-reinforced composite material. A fiber-reinforced composite material can be obtained by molding a prepreg laminate in which multiple prepregs are stacked under heat and pressure. As the matrix resin composition, thermosetting resin compositions containing phenolic resin, melamine resin, bismaleimide resin, unsaturated polyester resin, epoxy resin, etc. are often used because of their excellent impregnation properties and heat resistance. Of these, epoxy resin compositions are widely used because they provide fiber-reinforced composite materials with excellent heat resistance and moldability and higher mechanical strength. Furthermore, solid curing agents are often used as curing agents for the epoxy resins used in combination with them, due to their storage stability. Patent Document 1 discloses that the use of an epoxy resin composition containing a powder curing agent with reduced particle size satisfies the demands associated with high-speed automated manufacturing systems (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2018-532014 Summary of the Invention [Problem to be solved by the invention]

[0004] In the prepreg production process in which matrix resin is impregnated into reinforcing fibers, the curing agent and filler may not penetrate well into the reinforcing fiber bundle, remaining near the surface of the reinforcing fiber bundle or becoming uneven inside the fiber bundle. This results in locally different cured states of the matrix resin, leading to problems such as reduced mechanical properties and poor appearance. One object of the present invention is to provide a prepreg that can produce a fiber-reinforced composite material in a uniform cured state, even when using a thick prepreg with a large reinforcing fiber weight. [Means for solving the problem]

[0005] The present invention includes the following embodiments [1] to

[12] .

[0006] [1] A molding material in which a reinforcing fiber substrate is impregnated with an epoxy resin composition containing an epoxy resin, an epoxy resin curing agent, and a fluorine-containing polyether surfactant having a melting point of 25°C or higher. [2] The molding material according to [1], wherein the fluorine-containing polyether surfactant contains a compound having a polyethylene oxide chain. [3] The molding material according to [2], wherein the average number of moles of ethylene oxide per molecule of the compound having a polyethylene oxide chain in the fluorine-containing polyether surfactant is 20 or more. [4] The molding material according to any one of [1] to [3], wherein the fluorine-containing polyether surfactant contains a compound having a perfluoroalkenyl group. [5] The molding material according to [4], wherein the perfluoroalkenyl group is a group derived from hexafluoropropylene trimer. [6] The molding material according to any one of [1] to [5], wherein the fluorine-containing polyether surfactant has a polyethylene oxide chain and a group derived from a hexafluoropropylene trimer, and the ratio (Nx / Ny) of the average number of moles of ethylene oxide in the polyethylene oxide chain, Nx, to the number of moles of the group derived from the hexafluoropropylene trimer, Ny, is 10 or more. [7] The molding material according to any one of [1] to [6], wherein the content of the component (C) is 0.05 to 1 part by mass per 100 parts by mass of the component (A). [8] A molding material in which a reinforcing fiber substrate is impregnated with an epoxy resin composition containing an epoxy resin and an epoxy resin curing agent, wherein the epoxy resin composition is blended with a fluorine-containing polyether surfactant having a polyethylene oxide chain and a group derived from a hexafluoropropylene trimer, and the ratio (Nx / Ny) of the average number of moles of ethylene oxide in the polyethylene oxide chain, Nx, to the number of moles of the group derived from the hexafluoropropylene trimer, Ny, is 10 or more. [9] The molding material according to any one of [1] to [8], wherein the reinforcing fibers contained in the reinforcing fiber substrate are continuous fibers.

[10] The molding material according to any one of [1] to [9], wherein the reinforcing fibers contained in the reinforcing fiber substrate are carbon fibers.

[11] A fiber-reinforced composite material, which is a cured product of the molding material according to any one of [1] to

[10] .

[12] A method for producing a fiber-reinforced composite material, which comprises press-molding the molding material according to any one of [1] to

[10] . [Effects of the Invention]

[0007] According to the molding material of the present invention, even when a thick prepreg having a large basis weight of reinforcing fiber bundles is used, a fiber-reinforced plastic in a uniform cured state can be obtained. In addition, a molding material having excellent curability and storage stability can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Molding material] One embodiment of the present invention is a molding material in which a reinforcing fiber substrate is impregnated with an epoxy resin composition containing an epoxy resin, epoxy resin curing agent particles, and a fluorinated polyether surfactant having a melting point of 25°C or higher. The fluorinated polyether surfactant can promote the impregnation of solids such as epoxy resin curing agent particles and fillers. Having a melting point of 25°C or higher for the fluorinated polyether surfactant can suppress a decrease in the dispersion aid performance of solid particles due to bleed-out of the surfactant in the resin film during the hot-melt film method described below. Therefore, when a reinforcing fiber substrate is impregnated with a matrix resin composition to produce a prepreg, the solids can penetrate between the reinforcing fibers without being unevenly distributed on the reinforcing fiber surfaces. Therefore, when the prepreg is cured, a fiber-reinforced composite material in a uniformly cured state can be obtained. Examples of molding materials include unidirectional prepreg, cross prepreg, SMC, and tow prepreg. Unidirectional prepreg is preferred as the molding material because it allows the impregnation properties of the epoxy resin composition to be easily exhibited.

[0009] (Epoxy resin composition) The epoxy resin composition contains an epoxy resin, epoxy resin curing agent particles, and a fluorine-containing polyether surfactant having a melting point of 25°C or higher. The epoxy resin composition can be used as a matrix resin composition for a molding material, which is an intermediate material used in the production of fiber-reinforced composite materials, and is particularly suitable as a matrix resin composition for unidirectional prepregs. The epoxy resin composition preferably cures within 7 minutes at 140°C, more preferably within 7 minutes at 140°C. The viscosity of the epoxy resin composition at 30°C is 10 3 ~10 6 Pa·s is preferred, 10 4 ~10 5 The viscosity of the epoxy resin composition is more preferably Pa·s. The viscosity of the epoxy resin composition is a value measured using a rheometer under the following conditions. Plate used: 25φ parallel plate Plate gap: 0.5 mm Measurement frequency: 10rad / sec Stress: 300Pa

[0010] The epoxy resin is not particularly limited, and examples thereof include liquid epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol AD ​​type epoxy resin, epoxy resin having a naphthalene skeleton, epoxy resin having an oxazolidone ring structure, resorcinol type epoxy resin, hydroquinone type epoxy resin, catechol type epoxy resin, dihydroxynaphthalene type epoxy resin, biphenyl type epoxy resin, tetramethylbiphenyl type epoxy resin, phenol novolac type epoxy resin, cresol type epoxy resin, cresol novolac type epoxy resin, triphenylmethane type epoxy resin, and tetraphenylethane type epoxy resin. resins, dicyclopentadiene-type epoxy resins, dicyclopentadiene-phenol addition reaction type epoxy resins, phenol aralkyl-type epoxy resins, naphthol novolac-type epoxy resins, naphthol aralkyl-type epoxy resins, naphthol-phenol co-condensed novolac-type epoxy resins, naphthol-cresol co-condensed novolac-type epoxy resins, aromatic hydrocarbon formaldehyde resin-modified phenolic resin-type epoxy resins, biphenyl-modified novolac-type epoxy resins, tetrabromobisphenol A-type epoxy resins, brominated phenol novolac-type epoxy resins, glycidyl amine-type epoxy resins, glycidyl ether-type epoxy resins, and urethane-modified epoxy resins. Among these, bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, biphenyl type epoxy resins, dicyclopentadiene type epoxy resins, epoxy resins having a naphthalene skeleton, epoxy resins having an oxazolidone ring structure, phenol novolac type epoxy resins, cresol type epoxy resins, glycidyl amine type epoxy resins, glycidyl ether type epoxy resins, modified products of these epoxy resins, and brominated epoxy resins are preferred.

[0011] Bisphenol A type epoxy resins are more preferred in terms of good heat resistance and chemical resistance of the fiber reinforced composite material. Bisphenol F type epoxy resins are more preferred in terms of high elastic modulus of the fiber reinforced composite material. Examples of suitable epoxy resins include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol C diglycidyl ether, bisphenol E diglycidyl ether, bisphenol Z diglycidyl ether, bisphenol S diglycidyl ether, bisphenol AD ​​diglycidyl ether, bisphenol acetophenone diglycidyl ether, bisphenol trimethylcyclohexane diglycidyl ether, bisphenol fluorene diglycidyl ether, tetramethyl bisphenol A diglycidyl ether, tetramethyl bisphenol F diglycidyl ether, tetra-t-butyl bisphenol A diglycidyl ether, and tetramethyl bisphenol A diglycidyl ether. Examples of suitable epoxy resins include bifunctional epoxy resins such as phenol S diglycidyl ether, trifunctional epoxy resins such as aminophenol triglycidyl ether, triglycidyl aminophenol, triglycidyl aminocresol, triazine-modified, trishydroxyphenylmethane triglycidyl ether, trimethylolpropane triglycidyl ether, cresol novolac, and phenol novolac, and polyfunctional epoxy resins such as diaminodiphenylmethane tetraglycidyl ether, tetraglycidyl xylene diamine, tetraglycidyl bisaminomethylcyclohexane, tetraglycidyl glycoluril, cresol novolac, and phenol novolac. From the viewpoint of achieving an excellent balance between toughness and heat resistance of the cured product, bifunctional epoxy resins are preferred.

[0012] From the viewpoint of ease of handling of the prepreg, the epoxy resin is preferably contained in an amount of 50 parts by mass or more, more preferably 80 parts by mass or more, per 100 parts by mass of the epoxy resin composition, and may be contained in an amount of 100 parts by mass or less, or 95 parts by mass or less, per 100 parts by mass of the epoxy resin composition.

[0013] The epoxy resin curing agent particles can be selected according to the mechanical properties (flexural strength, flexural modulus), storage stability, and curing temperature and time of the fiber-reinforced composite material (cured product). The epoxy resin curing agent may be in various forms, such as a microcapsule type or a modified form. The epoxy resin curing agent particles may be any that can cure epoxy resins, including amines, guanidines, acid anhydrides (e.g., carboxylic acid anhydrides), phenols (e.g., novolac resins), mercaptans, Lewis acid amine complexes, onium salts, imidazoles, and ureas. The epoxy resin curing agent particles preferably exist as solid particles in the epoxy resin at an ambient temperature of 25°C. This is because they have low reactivity with epoxy resins at 25°C and excellent storage stability. The epoxy resin curing agent particles preferably become liquid in a curing temperature range of 120 to 190°C. Dicyandiamide or imidazoles are preferred as the epoxy resin curing agent particles, as they can achieve both a long pot life and good reactivity during curing. From the viewpoint of adhesion between the reinforcing fibers and the matrix resin and heat resistance, it is more preferable to use dicyandiamide in combination with an imidazole that is solid at 25°C. Examples of amines include aromatic amines such as diaminodiphenylmethane and diaminodiphenylsulfone, aliphatic amines, thiourea-added amines, and derivatives, isomers, and modifications thereof. Examples of guanidines include dicyandiamide, tetramethylguanidine, and derivatives thereof. Examples of dicyandiamide derivatives include those obtained by bonding dicyandiamide to various compounds such as epoxy resins, vinyl compounds, acrylic compounds, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. One type of dicyandiamide derivative may be used alone, or two or more types may be used in combination. The dicyandiamide derivative may be used in combination with dicyandiamide. Preferable imidazole compounds include those in which the hydrogen atom at the 5-position of 1H-imidazole is substituted with a hydroxymethyl group and the hydrogen atom at the 2-position is substituted with a phenyl group or a toluyl group. Specific examples include 2-phenyl-4,5-bis(hydroxymethyl)imidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4-benzyl-5-hydroxymethylimidazole, 2-p-toluyl-4-methyl-5-hydroxymethylimidazole, 2-m-toluyl-4-methyl-5-hydroxymethylimidazole, 2-m-toluyl-4,5-bis(hydroxymethyl)imidazole, and 2-p-toluyl-4,5-bis(hydroxymethyl)imidazole. Preferable imidazole compounds include those having a triazine ring in the molecule, because they have high storage stability at room temperature in epoxy resin compositions and a fast curing rate. Specific examples include 2,4-diamino-6-[2-(2-methyl-1-imidazolyl)]ethyl-s-triazine. Examples of ureas include 3-phenyl-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 2,4-bis(3,3-dimethylureido)toluene, and 1,1'-(4-methyl-1,3-phenylene)bis(3,3-dimethylurea). The content of the epoxy resin curing agent is preferably 1 to 20 parts by mass, more preferably 3 to 10 parts by mass, per 100 parts by mass of the epoxy resin, from the viewpoints of curing speed and suppression of water absorption.

[0014] A fluorinated polyether surfactant having a melting point of 25°C or higher can promote the impregnation of epoxy resin curing agent particles or other solid components in the step of impregnating a reinforcing fiber substrate with a resin composition. In particular, in the hot melt method described below, a fluorinated polyether surfactant having a melting point of 25°C or higher is effective in improving the dispersibility of solid particles such as epoxy resin curing agent particles and fillers in the resin composition, the coatability of a sheet made of the resin composition, and the impregnation of the resin and solid particles in the sheet made of the resin composition into the reinforcing fiber substrate. Examples of the fluorine-containing surfactant include anionic fluorine-containing surfactants, cationic fluorine-containing surfactants, amphoteric fluorine-containing surfactants, and nonionic fluorine-containing surfactants. Among these, nonionic fluorine-containing surfactants are preferred from the viewpoint of sufficiently improving the coatability of the resin composition while sufficiently ensuring the dispersibility of solid components such as the curing agent and filler in the resin composition. The fluorine-containing surfactant preferably contains a compound having a perfluoroalkenyl group or a perfluoroalkyl group (hereinafter, both will be abbreviated as Rf group), and more preferably contains a compound having a perfluoroalkenyl group. The Rf group is preferably a group derived from hexafluoropropylene (HFP) trimer. The presence of the Rf group can sufficiently improve the coatability of the resin composition while also sufficiently increasing the dispersibility of the curing agent and filler in the resin composition.

[0015] Examples of groups derived from HFP trimers include groups obtained by removing one fluorine atom from HFP or a dimer or trimer obtained by oligomerization of HFP. The fluorine-containing surfactant preferably contains a compound having a polyether chain. The polyether chain is more preferably a polyethylene oxide chain, since this can increase the impregnation rate of solid particles into the reinforcing fibers. From the viewpoints of dispersibility and fluidity of the added solid particles, the average number of moles of ethylene oxide (EO) added is preferably 10 or more, more preferably 20 or more, and even more preferably 22 or more. From the viewpoints of dispersibility and fluidity of the added solid particles, the average number of moles of ethylene oxide (EO) added is preferably 60 or less, more preferably 50 or less.

[0016] The fluorine-containing surfactant preferably contains a compound having a structure represented by the following formula (1).

[0017] [ka] ...Formula (1) In formula (1), R 1 is a perfluoroalkenyl group, R2 represents a hydrogen atom, an acetal group, an aldehyde group, an amino group, a carboxyl group, a methacryloyl group, an allyl group, an alkyl group having 1 to 10 carbon atoms, a halogen atom, or a perfluoroalkenyl group, and m represents 1 to 60. 2 is preferably a hydrogen atom or a perfluoroalkenyl group.

[0018] To promote impregnation, the epoxy resin composition preferably contains a fluorine-containing polyether surfactant having a polyethylene oxide chain and a group derived from a hexafluoropropylene trimer. The ratio (Nx / Ny) of the average number of moles of ethylene oxide in the polyethylene oxide chain, Nx, to the number of moles of the group derived from the hexafluoropropylene trimer, Ny, is preferably 10 or more, more preferably 20 or more, because this balance between the excluded volume effect of the ethylene oxide chain and the cohesive force of HFP is considered to contribute to promoting the impregnation of the solid particles of the curing agent. The ratio (Nx / Ny) is preferably 60 or less, more preferably 40 or less, from the viewpoint of preventing the polyethylene oxide chain from being added in excessive amounts and suppressing deterioration of the rigidity and heat resistance of the resin composition. The fluorine-containing polyether surfactant is not particularly limited, and examples thereof include Ftergent 251, Ftergent 222F, and Ftergent 245F manufactured by Neos Corporation.

[0019] The content of the fluorine-containing polyether surfactant relative to 100 parts by mass of the epoxy resin is preferably 0.01 part by mass or more, more preferably 0.05 part by mass or more, from the viewpoint of improving impregnation ability, and is preferably 2 parts by mass or less, more preferably 1 part by mass or less, from the viewpoint of improving adhesive strength at the interface.

[0020] The epoxy resin composition may further contain other components as needed within the range that does not impair the effects of the present invention. Examples of other components include a curing accelerator, an inorganic filler, an organic pigment, and an inorganic pigment. Examples of inorganic fillers include calcium carbonate, aluminum hydroxide, clay, barium sulfate, magnesium oxide, glass powder, hollow glass beads, and silica.

[0021] The epoxy resin composition may be prepared, for example, by simultaneously mixing the components. Alternatively, a masterbatch may be prepared in advance by appropriately dispersing an epoxy resin curing agent, a fluorinated polyether surfactant, and the like in an epoxy resin, and then the composition may be prepared using this masterbatch. Furthermore, if the temperature in the system increases due to shear heat generated during kneading, the temperature can be prevented from increasing during kneading by adjusting the kneading speed or by water-cooling the kneading vessel. Examples of kneading equipment include a mortar mixer, an attritor, a planetary mixer, a dissolver, a three-roll mill, a kneader, a universal mixer, a homogenizer, a homogenizer dispenser, a ball mill, and a bead mill. Two or more kneading equipment may be used in combination.

[0022] (Reinforced fiber base material) Examples of reinforcing fibers constituting the reinforcing fiber substrate include carbon fibers (including graphite fibers; the same applies hereinafter), aramid fibers, silicon carbide fibers, alumina fibers, boron fibers, tungsten carbide fibers, and glass fibers. From the viewpoint of the mechanical properties of the fiber-reinforced composite material, carbon fibers or glass fibers are preferred, and carbon fibers are particularly preferred. The reinforcing fibers may be long fibers (continuous fibers) or short fibers having a length of, for example, 0.01 to 30 cm. From the viewpoint of strength development of the fiber-reinforced composite material, the carbon fibers may have a tensile elongation of 1.5% or more.

[0023] Examples of the form of the reinforcing fiber substrate include a sheet-like form in which continuous fibers are aligned in one direction (unidirectional sheet); a form in which continuous fibers are woven in the warp and weft directions (woven fabric); a form in which tows are aligned in one direction and held together with weft yarns (auxiliary yarns) (non-crimp fabric); a form in which multiple sheets of reinforcing fibers in which continuous fibers are aligned in one direction are stacked so that the fiber directions are different and fastened together with auxiliary yarns (multiaxial warp knit); and nonwoven fabric. Among these, unidirectional sheets, woven fabrics, non-crimp fabrics, and multiaxial warp knits are preferred from the viewpoint of ease of prepreg production. From the viewpoint of strength expression of the resulting fiber-reinforced composite material, unidirectional sheets are more preferred.

[0024] The weight of the reinforcing fiber substrate is, for example, 50 g / m 2 More than 2000g / m 2 In order to easily obtain a prepreg that is well impregnated with the matrix resin composition, the weight of the reinforcing fiber substrate is preferably 50 g / m or less. 2 More than 600g / m 2 Less than 50 g / m is more preferable. 2 More than 300g / m 2 The following is even more preferred:

[0025] (Method of manufacturing molding material) The molding material can be produced by impregnating a reinforcing fiber substrate with a matrix resin composition. For example, a predetermined amount of epoxy resin composition is applied to the surface of release paper or the like, a reinforcing fiber substrate is then applied to the surface, and the reinforcing fiber substrate is then passed through a pressure roll to impregnate the matrix resin composition, thereby obtaining a molding material. Alternatively, a molding material can be obtained by applying a predetermined amount of matrix resin composition to a reinforcing fiber substrate, and then sandwiching the reinforcing fiber substrate between release papers or the like as needed, and passing through a pressure roll to impregnate the reinforcing fiber substrate with the matrix resin composition.

[0026] (fiber reinforced composite materials) A fiber-reinforced composite material is a cured product obtained by curing a molding material. A fiber-reinforced composite material can be produced by heating and pressurizing the above-mentioned molding material to cure it. The fiber-reinforced composite material obtained by curing the above-mentioned molding material has the property of being easily coated because the fluorine-containing polyether surfactant is also present on the surface. Methods for producing a fiber-reinforced composite material include autoclave molding, vacuum bag molding, and press molding. When using the above-mentioned molding material, it is preferable to produce a fiber-reinforced composite material by press molding (heat-pressure molding) the molding material, as this improves mold releasability and increases productivity. When producing a fiber-reinforced composite material by press molding, it is preferable to include a step of sandwiching a preform preformed using a prepreg or a prepreg laminate obtained by laminating prepregs as the molding material in a mold previously adjusted to a molding temperature and heating and pressurizing it. The molding temperature (temperature inside the mold) during press molding is preferably 100 to 170°C, more preferably 130 to 150°C. A molding temperature within the above range results in a reinforced fiber composite material with high storage stability and dimensional stability. In press molding, the molding material or a preform thereof is preferably heated at the above molding temperature and under a pressure of 1 to 15 MPa for 1 to 20 minutes to cure the epoxy resin composition, and then molded. The molding time is more preferably 10 minutes or less, and even more preferably 5 minutes or less.

[0027] When a fiber-reinforced composite material is produced by press molding, the glass transition temperature of the cured fiber-reinforced composite material, particularly G'-Tg, determined as the temperature at which the storage modulus (G') begins to decrease, is preferably higher than the temperature inside the mold during molding. This prevents deformation of the fiber-reinforced composite material when it is removed from the mold after press molding. For example, a fiber-reinforced composite material produced by clamping a prepreg, in which a reinforcing fiber substrate is impregnated with an epoxy resin composition, between a mold preheated to 140°C, applying a pressure of 1 MPa, and holding the mold for 5 minutes preferably has a G'-Tg of 150°C or higher. Here, G'-Tg is the temperature at the intersection of the linear approximation of the flat region of logG' and the linear approximation of the region where logG' rapidly decreases when the storage modulus (G') obtained by dynamic viscoelasticity measurement using a rheometer is measured at a frequency of 1 Hz and a heating rate of 5°C / min, and then logG' is plotted against temperature. This is the glass transition temperature obtained by dynamic viscoelasticity measurement of the cured product. [Example]

[0028] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following descriptions.

[0029] [90 degree bending strength] The molded plates obtained in each Example and Comparative Example were cut using a wet diamond cutter to a length (perpendicular to the fibers) of 63 mm x width (parallel to the fibers) of 12.7 mm, and the end faces were polished with #1000 sandpaper to prepare test specimens. A three-point bending test was performed on the test specimens using a universal testing machine (Instron, Instron 5565, analysis software: Bluehill) in accordance with ASTM D790 under the conditions of indenter R: 5.0, L / D: 16, and crosshead speed (calculated based on the specimen thickness) (0.89 to 0.94 mm / min), and the 90-degree bending strength was calculated.

[0030] The components used in this example are listed below. (Component (A)) jER828: Bisphenol A epoxy resin (product name "jER 828", epoxy equivalent 189, manufactured by Mitsubishi Chemical Corporation). YD-952: Oxazolidone ring-containing epoxy resin (product name "YD-952", epoxy equivalent 336, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.). YDPN-638: Phenol novolac epoxy resin (product name "YDPN-638", epoxy equivalent 180, manufactured by DIC Corporation).

[0031] (Component (B)) 1400F: Dicyandiamide (product name "Dicyanex 1400F", manufactured by Air Products). 2MZA-PW: 2,4-diamino-6-(2'-methylimidazolyl-(1'))-ethyl-s-triazine (product name "Curezol (registered trademark) 2MZA-PW", manufactured by Shikoku Chemical Industries, Ltd.).

[0032] (Component (C)) Ftergent 250: (product name "Ftergent 250", α-perfluorononenyloxy-ω-methylpolyethylene oxide, average EO molar number: 22, Mw: 1,800, manufactured by Neos Corporation). Ftergent 245F: (product name "Ftergent 245F", α,ω-perfluoroalkenyl polyoxyethylene ether, average EO molar number: 45, manufactured by Neos Corporation). (Other fluorine-containing polyether surfactants) Ftergent 251: (product name "Ftergent 251", perfluoroalkenyl polyoxyethylene ether, average EO molar number: 8, Mw: 1,500, liquid at room temperature, manufactured by Neos Corporation). FTX-218: (Product name "FTX-218", diglycerin ethylene oxide adduct perfluorononenyl ether, average EO mole number: 18, liquid at room temperature, manufactured by Neos Corporation). (thermoplastic resin) PES 5003P: Polyethersulfone (product name "Sumikaexcel PES 5003P", weight average molecular weight approximately 42,000 g / mol, manufactured by Sumitomo Chemical Co., Ltd.). (reinforced fiber) Carbon fiber bundle X-1: Product name "TR 50S15L", manufactured by Mitsubishi Chemical Corporation, tensile strength: 4.9 GPa, tensile modulus: 235 GPa, tensile elongation: 2.09%, number of filaments: 15,000, basis weight: 1.00 g / m 2 .

[0033] [Example 1] 10.8 parts by weight of jER828 (component (A)), 2.4 parts by weight of 1400F (component (B)), and 6 parts by weight of 2MZA-PW were mixed and kneaded using a three-roll mill to obtain a curing agent masterbatch. Next, 23.5 parts by weight of jER828 (component (A)) and 3 parts by weight of PES 5003P (thermoplastic resin) were mixed in a flask and heated to 150°C while stirring using a three-one motor to completely dissolve the PES 5003P. Next, 42.5 parts by weight of YD-952 (component (A)) and 25 parts by weight of YDPN-638 were added to the flask, and the mixture was dissolved at 100°C to obtain a resin mixture. The resin mixture was heated to 60°C, and 1 part by weight of the curing agent masterbatch and Ftergent 250 (component (C)) were added. The mixture was kneaded using a three-one motor to obtain an epoxy resin composition.

[0034] Using a multi-coater (Hirano Tecseed Co., Ltd., M-500 model), the obtained epoxy resin composition was applied onto release paper at 60°C to obtain two resin films. Carbon fiber bundles X-1 were wound onto the resin-coated surface of one of the resin films using a drum winding, and another resin film was placed on top to sandwich the carbon fiber bundles X-1, and the epoxy resin composition was impregnated into the carbon fiber bundles X-1. The release paper from one side of the resin film was peeled off and a polyethylene film (protective film) was attached to obtain a unidirectional prepreg. The basis weight of the carbon fiber bundles in the obtained unidirectional prepreg was 250 g / m 2 The resin content was 30.0% by mass.

[0035] The obtained unidirectional prepreg was cut to a size of 298 mm (parallel to the fibers) x 298 mm (orthogonal to the fibers), the release paper and protective film were peeled off, and five unidirectional prepregs were stacked so that the fiber directions of adjacent unidirectional prepregs on top and bottom were perpendicular to each other to form a prepreg laminate. After cleaning the surface of the mold, the prepreg laminate was placed in a mold heated to 140°C and press-molded under the following conditions: a surface pressure of 4 MPa on the prepreg laminate, a molding temperature of 140°C, and a molding time of 5 minutes, to obtain a flat fiber-reinforced composite material.

[0036] [Examples 2 to 5, Comparative Examples 1 to 3] An epoxy resin composition was prepared and a unidirectional prepreg was produced in the same manner as in Example 1, except that the composition was changed as shown in Table 1. A prepreg laminate was also produced in the same manner as in Example 1, to obtain a fiber-reinforced composite material. [Reference example] The composition was changed as shown in Table 1, and the weight of the carbon fiber bundle in the unidirectional prepreg was 200 g / m 2 A prepreg laminate was produced in the same manner as in Example 1, except for the above change, and a fiber-reinforced composite material was obtained.

[0037] [Table 1]

[0038] As shown in Table 1, the fiber-reinforced composite materials of Examples 1 to 5 exhibited higher 90-degree bending strength and bending strain than the comparative example. This suggests that the high bending properties were achieved because the curing agent component was sufficiently impregnated into the interior of the prepreg. In Comparative Examples 1 and 2, the melting points of the fluorine-containing polyether surfactants or the average number of moles of EO / the average number of moles of HFP were lower and the 90° bending was poor compared to Examples 1 to 5. This suggests that the powder was not uniformly dispersed or impregnated into the reinforcing fiber bundles insufficiently. In Comparative Example 3, no fluorine-containing polyether surfactant was contained, and the 90° bending strength was inferior to that of Examples 1 to 5. In Comparative Example 3, the carbon fiber bundle basis weight was 250 g / m 2 The weight of the carbon fiber bundle in the reference example is 200 g / m 2The 90° bending strength was lower than that of the Reference Example. This indicates that the carbon fiber basis weight affects the state of the reinforced fiber composite material, and a possible problem is thought to be the difference in the curing state of the matrix resin caused by the difference in the impregnation state of the curing agent component. Examples 1 to 5 showed a 90° bending strength superior to that of the Reference Example. This suggests that the impregnation state of the curing agent component was improved. [Industrial Applicability]

[0039] According to the molding material of the present invention, even when a thick prepreg having a large basis weight of reinforcing fibers is used, a fiber-reinforced plastic in a uniform cured state can be obtained. Therefore, the molding material can be used as a structural material for aircraft, vehicles such as automobiles, ships, structural materials for buildings, etc., sporting goods such as golf shafts, fishing rods, and tennis rackets, and general industrial goods such as windmills and rolls.

Claims

1. A molding material in which a reinforcing fiber substrate is impregnated with an epoxy resin composition containing an epoxy resin, an epoxy resin curing agent, and a fluorinated polyether surfactant having a melting point of 25°C or higher, wherein the fluorinated polyether surfactant contains a compound having a polyethylene oxide chain.

2. 2. The molding material according to claim 1, wherein the average number of moles of ethylene oxide per molecule of the compound having a polyethylene oxide chain in the fluorine-containing polyether surfactant is 20 or more.

3. The molding material according to claim 1 or 2, wherein the fluorine-containing polyether surfactant comprises a compound having a perfluoroalkenyl group.

4. The molding material according to claim 3 , wherein the perfluoroalkenyl group is a group derived from hexafluoropropylene trimer.

5. 5. The molding material according to claim 1, wherein the fluorine-containing polyether surfactant has a polyethylene oxide chain and a group derived from a hexafluoropropylene trimer, and the ratio (Nx / Ny) of the average number of moles of ethylene oxide in the polyethylene oxide chain, Nx, to the number of moles of the group derived from the hexafluoropropylene trimer, Ny, is 10 or more.

6. The molding material according to any one of claims 1 to 5, wherein the content of the fluorine-containing polyether surfactant is 0.05 to 1 part by mass per 100 parts by mass of the epoxy resin.

7. A molding material in which a reinforcing fiber substrate is impregnated with an epoxy resin composition containing an epoxy resin and an epoxy resin curing agent, wherein the epoxy resin composition is blended with a fluorine-containing polyether surfactant having a polyethylene oxide chain and a group derived from a hexafluoropropylene trimer, and the ratio (Nx / Ny) of the average number of moles of ethylene oxide in the polyethylene oxide chain, Nx, to the number of moles of the group derived from the hexafluoropropylene trimer, Ny, is 10 or more.

8. The molding material according to any one of claims 1 to 7, wherein the reinforcing fibers contained in the reinforcing fiber substrate are continuous fibers.

9. The molding material according to any one of claims 1 to 8, wherein the reinforcing fibers contained in the reinforcing fiber substrate are carbon fibers.

10. A fiber-reinforced composite material, which is a cured product of the molding material according to any one of claims 1 to 9.

11. A method for producing a fiber-reinforced composite material, comprising press-molding the molding material according to any one of claims 1 to 9.

Images