Composites and Prepregs

Abstract

To provide a composite material with both high heat resistance and impact resistance.SOLUTION: In a composite material consisting of a reinforced fiber and a cured product of a resin composition, the resin composition contains particles 1, particles 2 and a thermosetting resin, a ratio of average particle diameters of the particles 1 and the particles 2 (average particle diameter of the particles 2 / average particle diameter of the particles 1) is 10 to 1000, and the particles 1 and the particles 2 are contained in the cured product in a mutually contacting manner.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a composite material and a prepreg used in its production. More specifically, the present invention relates to a composite material having excellent heat resistance and impact resistance, and a prepreg used in the production of the composite material by curing. [Background technology]

[0002] In recent years, composite materials using carbon fiber, aromatic polyamide fiber, etc. as reinforcing agents have been widely used as structural materials for aircraft, etc., taking advantage of their high specific strength and specific rigidity. In epoxy resin-based prepregs, the combination of aromatic glycidylamine epoxy resin as the matrix resin and diaminodiphenyl sulfone curing agent has provided composite materials with excellent heat resistance, mechanical properties, dimensional stability, chemical resistance, and weather resistance. Bismaleimide resins and the like have been investigated as matrix resins to improve heat resistance, and are being applied to primary aircraft structural materials.

[0003] Although composite materials made from such thermosetting resin prepregs have been recognized to exhibit good performance, it has been pointed out that the matrix resin has low elongation and is brittle, resulting in poor toughness and impact resistance, and improvements have been sought. In particular, when these composite materials are used as primary aircraft structural materials, they may be subjected to external impacts such as pebbles being kicked up during takeoff and landing or tools being dropped during maintenance. To address this, it is necessary to improve impact resistance without sacrificing heat resistance, but this has been a difficult and important issue to resolve.

[0004] Patent Document 1 describes that a prepreg obtained from a uniform thermosetting resin / thermosetting resin component as a matrix resin can provide a molded product with improved impact resistance without impairing the heat resistance of the thermosetting resin. Patent Document 2 describes that a prepreg containing a large number of particles with bismaleimide resin as the main component can provide a durable composite material that can function at high temperatures for long periods of time. However, these methods still require improvement in impact resistance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 4-3770 [Patent Document 2] Patent No. 5746689 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a composite material that has both high heat resistance and impact resistance. [Means for solving the problem]

[0007] That is, the present invention is a composite material consisting of reinforcing fibers and a cured product of a resin composition, wherein the resin composition contains particles 1, particles 2, and a thermosetting resin, the ratio of the average particle diameters of particles 1 and particles 2 (average particle diameter of particles 2 / average particle diameter of particles 1) is 10 to 1000, and particles 1 and particles 2 are contained in the cured product in a manner in which they are in contact with each other. [Effects of the Invention]

[0008] According to the present invention, a composite material having both high heat resistance and impact resistance can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0009] The composite material and prepreg of the present invention will be described in detail below.

[0010] [1. Reinforced Fiber] Examples of reinforcing fibers that constitute the composite material of the present invention together with the resin composition include carbon fibers, glass fibers, aramid fibers, silicon carbide fibers, polyester fibers, ceramic fibers, alumina fibers, boron fibers, metal fibers, mineral fibers, rock fibers, and slag fibers. Among these reinforcing fibers, carbon fibers, glass fibers, aramid fibers, and silicon carbide fibers are preferred. Using these fibers allows for the production of lightweight, high-strength fiber-reinforced composite materials with good specific strength and specific modulus. Among carbon fibers, polyacrylonitrile-based carbon fibers (hereinafter referred to as PAN-based carbon fibers), which have excellent tensile strength, are particularly preferred.

[0011] When PAN-based carbon fibers are used as the reinforcing fibers, the tensile modulus is preferably 170 to 600 GPa, more preferably 220 to 450 GPa. The tensile strength is preferably 3920 MPa (400 kgf / mm 2 ) The use of PAN-based carbon fibers having this tensile modulus and tensile strength can improve the mechanical properties of fiber-reinforced composite materials.

[0012] From the viewpoint of processability, it is preferable to use the reinforcing fibers in a sheet form as a sheet-like reinforcing fiber substrate. Examples of this sheet-like reinforcing fiber substrate include a sheet-like reinforcing fiber substrate in which a large number of reinforcing fibers are aligned in one direction, a bidirectional woven fabric such as a plain weave or twill weave, a multiaxial woven fabric, a nonwoven fabric, a mat, a knit, a braid, and paper made from reinforcing fibers.

[0013] The thickness of the sheet-like reinforcing fiber substrate is preferably 0.01 to 3 mm, more preferably 0.1 to 1.5 mm. The basis weight of the sheet-like reinforcing fiber substrate is preferably 70 to 400 g / m 2 , and more preferably 100 to 300 g / m 2 is.

[0014] [2. Resin composition] The resin composition used in the present invention comprises particles 1, particles 2, and a thermosetting resin. The ratio of the average particle size of particles 1 to that of particles 2 (average particle size of particles 2 / average particle size of particles 1) is 10 to 1000, preferably 50 to 700, and more preferably 100 to 500. If this ratio is less than 10, particles 1 and 2 will not come into contact with each other, and if it exceeds 1000, impact resistance will decrease.

[0015] [2.1. Particle 1] From the viewpoint of ensuring contact between particles 1 and particles 2, the average particle size of particles 1 is preferably 1 nm to 10 μm, more preferably 10 nm to 1 μm, and particularly preferably 10 to 500 nm.

[0016] The average particle diameter of particles 1 is the average particle diameter obtained by observing the cross section of the cured resin composition using a scanning electron microscope or a transmission electron microscope and measuring the diameters of at least 50 particles 1. If the particles are not perfectly circular during observation, the maximum diameter of the particles is taken as the particle diameter. For example, if the particles are elliptical, the major axis is taken as the particle diameter.

[0017] Examples of particle 1 include silica particles, carbon nanotubes, and core-shell rubber particles, and from the viewpoint of ensuring contact between particle 1 and particle 2, core-shell rubber particles are preferred.

[0018] Specific examples of core-shell rubber particles are shown below. Core-shell (dendrimer) particles (the composition of which is described in US20100280151A1 (Nguyen et al., Toray Industries, Inc., 2010) in which an amine-branched polymer is grafted as a shell onto a core polymer polymerized from a polymerizable monomer having an unsaturated carbon-carbon bond), core-shell rubbery particles (the composition of which is described in EP1632533A1 and EP2123711A1 by Kaneka Corporation), and the "Kane Ace MX" product line of such particle / epoxy blends, in which the particles have a polymer core polymerized from a polymerizable monomer, such as butadiene, styrene, other unsaturated carbon-carbon bond monomers, or combinations thereof, and an epoxy-compatible polymer shell, generally polymethyl methacrylate, polyglycidyl methacrylate, polyacrylonitrile, or the like.

[0019] The "JSR SX" series of carboxylated polystyrene / polydivinylbenzene manufactured by JSR Corporation. "Kureha Paraloid" EXL-2655 (manufactured by Kureha Corporation), which is a butadiene alkyl methacrylate styrene copolymer; "Stafiloid" AC-3355 and TR-2122 (both manufactured by Takeda Pharmaceutical Company Limited), which are acrylate methacrylate copolymers; and "PARALOID" EXL-2611 and EXL-3387 (both manufactured by Rohm and Haas Company), which are butyl acrylate methyl methacrylate copolymers.

[0020] Core-shell rubber particles that can be found in the Kane Ace MX product line by Kaneka Corporation (e.g., MX416, MX125, MX156, MX150), materials that have a shell composition or surface chemistry similar to the Kane Ace MX materials, and materials that are compatible with the surface of particle 2 (which allows the material to form an aggregated structure around particle 2 when the resin composition cures).

[0021] The above are specific examples of core-shell rubber particles. When particles 1 are core-shell rubber particles, their content is preferably 0.1 to 30% by mass, more preferably 0.1 to 20% by mass, and particularly preferably 0.5 to 10% by mass, based on the total mass of the resin composition. If the content is less than 0.1% by mass, the effect on impact resistance is reduced, which is undesirable, while if it exceeds 30% by mass, the viscosity of the resin composition increases, which may significantly deteriorate the handleability, which is undesirable.

[0022] [2.2. Particle 2] From the viewpoint of exhibiting impact resistance, the average particle size of the particles 2 is preferably 10 nm to 100 μm, more preferably 100 nm to 100 μm, and particularly preferably 1 μm to 50 μm. The average particle size of the particles 2 is the median size measured on a volume basis by a laser diffraction / scattering method using a particle size measuring device.

[0023] Thermoplastic resin particles are used as the particles 2. Examples of thermoplastic resin particles include thermoplastic resin particles such as polyethersulfone, polysulfone, polyetherimide, and polyimide, with polyimide being preferred among them.

[0024] The content of the thermoplastic resin particles is preferably 0.1 to 30% by mass, more preferably 0.5 to 20% by mass, and particularly preferably 1 to 20% by mass, based on the total mass of the resin composition. If the content is less than 0.1% by mass, the effect on impact resistance will be small, which is undesirable, while if the content exceeds 30% by mass, the viscosity of the resin composition will increase, which may significantly deteriorate the handleability, which is undesirable.

[0025] [2.3. Thermosetting resin] As the thermosetting resin, a thermosetting resin is used, and among them, bismaleimide resin, cyanate ester resin, and epoxy resin are preferable. These may be used alone, in a mixture, or in the state of a pre-reacted product.

[0026] [2.3.1. Bismaleimide resin] An example of the bismaleimide resin (hereinafter also referred to as "BMI") is a bismaleimide resin represented by the following chemical formula (1).

[0027] [ka]

[0028] In chemical formula (1), R1 to R4 each independently represent a group selected from the group consisting of -H, -CH3, -C2H5, -C3H7, -F, -Cl, -Br, and I. X will be described later. X in chemical formula (1) represents a group selected from the group consisting of -CH2-, -CH(CH3)-, and -C(CH3)2-.

[0029] In the present invention, the bismaleimide resin may be either an aromatic bismaleimide or an aliphatic bismaleimide. In the present invention, the amount of aromatic bismaleimide relative to the total amount of bismaleimide resin contained in the resin composition is preferably 70% by mass or more. If it is less than 70% by mass, heat resistance will decrease.

[0030] In the present invention, the amount of the total bismaleimide resin relative to the total mass of the resin composition is preferably 0.1 to 30 mass%, more preferably 0.1 to 20 mass%, and particularly preferably 1 to 10 mass%. If it is less than 0.1 mass%, heat resistance will decrease, and if it exceeds 30 mass%, impact resistance will decrease.

[0031] [2.3.1.1. Aromatic bismaleimide resin] When the bismaleimide resin contains an aromatic ring structure (hereinafter also referred to as an "aromatic bismaleimide compound"), X in chemical formula (1) preferably has a structure represented by any of the following chemical formulas (2) to (8).

[0032] [ka]

[0033] [ka]

[0034] [ka]

[0035] [ka]

[0036] In chemical formula (5), R5 represents -CH2-, -C(CH3)2-, -O-, or -SO2-.

[0037] [ka]

[0038] In chemical formula (6), R5 represents -CH2-, -C(CH3)2-, -O-, or -SO2-. R6 to R9 each independently represent a group selected from the group consisting of -H, -CH3, -C2H5, -C3H7, -F, -Cl, -Br, and I.

[0039] [ka]

[0040] In chemical formula (7), R5 represents -CH2-, -C(CH3)2-, -O-, or -SO2-.

[0041] [ka]

[0042] In chemical formula (8), R 10 and R 11 each independently represents -CH2-, -C(CH3)2-, -O-, or -SO2-. In chemical formula (8), n is 0 to 0.5.

[0043] Examples of such aromatic bismaleimide compounds include N,N'-4,4'-diphenylmethane bismaleimide, N,N'-4,4'-diphenylether bismaleimide, N,N'-m-phenylene bismaleimide, N,N'-p-phenylene bismaleimide, N,N'-m-toluylene bismaleimide, N,N'-4,4'-biphenylene bismaleimide, N,N'-4,4'-(3,3'-dimethylbiphenylene)bismaleimide, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, N,N'-4,4'-diphenylsulfone bismaleimide, and N,N'-4,4'-benzophenone bismaleimide.

[0044] From the viewpoint of heat resistance after heat curing, N,N'-4,4'-diphenylmethane bismaleimide, N,N'-4,4'-diphenylether bismaleimide, N,N'-m-toluylene bismaleimide, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, 4-methyl-1,3-phenylene bismaleimide, N,N'-4,4'-diphenylsulfone bismaleimide, and N,N'-4,4'-benzophenone bismaleimide are preferred, and N,N'-4,4'-diphenylmethane bismaleimide, N,N'-4,4'-diphenylether bismaleimide, N,N'-m-toluylene bismaleimide, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, and 4-methyl-1,3-phenylene bismaleimide are particularly preferred. These aromatic bismaleimide compounds may be used alone or in combination of two or more.

[0045] [2.3.1.2. Aliphatic bismaleimide compounds] When the bismaleimide compound does not contain an aromatic ring structure (hereinafter also referred to as an "aliphatic bismaleimide compound"), X in chemical formula (1) preferably has a structure represented by any of the following chemical formulas (9) to (11).

[0046] [ka]

[0047] In the chemical formula (9), n is an integer of 10 or less, and is preferably 1, 2, 3, 4, or 6.

[0048] [ka]

[0049] [ka]

[0050] Examples of such aliphatic bismaleimide resins include 1,6'-bismaleimide-(2,2,4-trimethyl)hexane, hexamethylenediamine bismaleimide, N,N'-1,2-ethylene bismaleimide, N,N'-1,3-propylene bismaleimide, and N,N'-1,4-tetramethylene bismaleimide. 1,6'-bismaleimide-(2,2,4-trimethyl)hexane and hexamethylenediamine bismaleimide are particularly preferred. The aliphatic bismaleimide resins may be used alone or in combination of two or more.

[0051] When an aliphatic bismaleimide resin is contained, its content is preferably 3 to 30 mass %, more preferably 5 to 20 mass %, and particularly preferably 7 to 15 mass %, based on the total mass of the resin composition. If the content of the aliphatic bismaleimide resin is less than 3 mass %, it is undesirable because handleability tends to decrease. On the other hand, if it exceeds 30 mass %, it is undesirable because heat resistance tends to decrease.

[0052] [2.3.2. Cyanate ester resin] Examples of the cyanate ester resin include cyanate ester resins represented by the following chemical formula: NC-OA 1 -Y 1 -A 2 -O-CN

[0053] In the above chemical formula, Y 1 represents a divalent hydrocarbon group that is unsubstituted or substituted with a fluorine atom, a methyl group, or a cyanato group, -O-, -S-, or a single bond; A 1 and A 2 each independently represents an unsubstituted phenylene group or a phenylene group in which 1 to 4 hydrogen atoms on the ring are substituted with alkyl groups.

[0054] When a cyanate ester resin is contained, it is preferably contained in an amount of 1 to 80 mass %, more preferably 10 to 70 mass %, further preferably 20 to 60 mass %, and particularly preferably 30 to 60 mass %, based on the total mass of the resin composition. If it is contained in an amount of less than 1 mass %, heat resistance decreases, and if it exceeds 80 mass %, impact resistance decreases.

[0055] [2.3.3. Epoxy Resin] The epoxy resins that can be used include those exemplified below. Among these, epoxy resins containing aromatic groups are preferred, and epoxy resins containing either a glycidyl amine structure or a glycidyl ether structure are preferred. Alicyclic epoxy resins can also be suitably used.

[0056] Examples of epoxy resins containing a glycidylamine structure include tetraglycidyldiaminodiphenylmethane, N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-m-aminophenol, N,N,O-triglycidyl-3-methyl-4-aminophenol, and various isomers of triglycidylaminocresol.

[0057] Examples of epoxy resins containing a glycidyl ether structure include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, phenol novolac type epoxy resins, and cresol novolac type epoxy resins.

[0058] Furthermore, these epoxy resins may have a non-reactive substituent in the aromatic ring structure, etc., as necessary. Examples of the non-reactive substituent include alkyl groups such as methyl, ethyl, and isopropyl, aromatic groups such as phenyl, alkoxyl groups, aralkyl groups, and halogen groups such as chlorine and bromine.

[0059] The content of the epoxy resin in the thermosetting resin composition is preferably 1 to 30 mass %, more preferably 3 to 25 mass %, and particularly preferably 5 to 20 mass %, based on the total mass of the thermosetting resin composition. If the content is less than 1 mass %, the handleability of the prepreg used in producing the composite material tends to decrease, which is not preferred. On the other hand, if the content exceeds 30 mass %, the heat resistance tends to decrease, which is not preferred.

[0060] [2.3.4. Epoxy Resin-Soluble Thermoplastic Resin] The resin composition may further contain an epoxy resin-soluble thermoplastic resin in addition to the above-mentioned thermosetting resin. The epoxy resin-soluble thermoplastic resin adjusts the viscosity of the epoxy resin composition and improves the impact resistance of the resulting fiber-reinforced composite material.

[0061] An epoxy resin-soluble thermoplastic resin is a thermoplastic resin that can be partially or completely dissolved in an epoxy resin at or below the temperature at which a fiber-reinforced composite material is molded. Here, "partially soluble in an epoxy resin" means that when 10 parts by mass of a thermoplastic resin with an average particle size of 10 to 50 μm is mixed with 100 parts by mass of an epoxy resin and stirred at 190°C for 1 hour, the particles disappear or the particle size changes by 10% or more.

[0062] If the epoxy resin-soluble thermoplastic resin is not completely dissolved, it dissolves in the epoxy resin when heated during the epoxy resin curing process, thereby increasing the viscosity of the epoxy resin composition, thereby preventing the epoxy resin composition from flowing out of the prepreg due to a decrease in viscosity during the curing process. The epoxy resin-soluble thermoplastic resin is preferably a resin that dissolves in the epoxy resin at 190°C in an amount of 80 mass % or more.

[0063] Specific examples of epoxy resin-soluble thermoplastic resins include polyethersulfone, polysulfone, polyetherimide, polycarbonate, etc. These may be used alone or in combination of two or more. The epoxy resin-soluble thermoplastic resin contained in the epoxy resin composition is particularly preferably polyethersulfone or polysulfone having a weight-average molecular weight (Mw) in the range of 8,000 to 40,000. If the weight-average molecular weight (Mw) is less than 8,000, the impact resistance of the resulting fiber-reinforced composite material may be insufficient. If the weight-average molecular weight (Mw) is greater than 40,000, the viscosity may be significantly increased, significantly reducing handleability. It is preferable that the molecular weight distribution of the epoxy resin-soluble thermoplastic resin is uniform. In particular, the polydispersity (Mw / Mn), which is the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn), is preferably in the range of 1 to 10, more preferably 1.1 to 5.

[0064] The epoxy resin-soluble thermoplastic resin preferably has a reactive group reactive with the epoxy resin or a functional group capable of forming a hydrogen bond. Such an epoxy resin-soluble thermoplastic resin can improve the solubility stability of the epoxy resin during the curing process. Furthermore, it can impart toughness, chemical resistance, heat resistance, and moist heat resistance to the fiber-reinforced composite material obtained after curing.

[0065] Preferred reactive groups reactive with epoxy resins are hydroxyl groups, carboxylic acid groups, imino groups, amino groups, etc. Hydroxyl-terminated polyethersulfones are more preferred because the resulting fiber-reinforced composite materials are particularly excellent in impact resistance, fracture toughness, and solvent resistance.

[0066] The content of the epoxy resin-soluble thermoplastic resin in the resin composition is adjusted appropriately depending on the viscosity. From the viewpoint of prepreg processability, the content is preferably 5 to 90 parts by mass, more preferably 10 to 70 parts by mass, and even more preferably 20 to 50 parts by mass, per 100 parts by mass of the epoxy resin contained in the epoxy resin composition. If the content is less than 5 parts by mass, the impact resistance of the resulting fiber-reinforced composite material may be insufficient. If the content of the epoxy resin-soluble thermoplastic resin is high, the viscosity may increase significantly, which may significantly deteriorate the handleability of the prepreg.

[0067] The form of the epoxy resin-soluble thermoplastic resin is not particularly limited, but is preferably particulate. Particulate epoxy resin-soluble thermoplastic resins can be uniformly blended into the resin composition. In addition, the resulting prepreg has high moldability.

[0068] The average particle size of the epoxy resin-soluble thermoplastic resin is preferably 1 to 50 μm, and particularly preferably 3 to 30 μm. If the average particle size is less than 1 μm, the viscosity of the epoxy resin composition will increase significantly. This may make it difficult to add a sufficient amount of epoxy resin-soluble thermoplastic resin to the epoxy resin composition. If the average particle size exceeds 50 μm, it may be difficult to obtain a sheet of uniform thickness when processing the epoxy resin composition into a sheet. Furthermore, the dissolution rate in the epoxy resin will be slow, which is undesirable as it will result in non-uniformity in the resulting fiber-reinforced composite material.

[0069] [2.3.5. Other Additives] The resin composition may contain a curing accelerator, a flame retardant, an inorganic filler, and an internal mold release agent. Examples of the curing accelerator include dichlorophenyl dimethyl urea and dicyanamide.

[0070] Examples of flame retardants include phosphorus-based flame retardants, which are not particularly limited as long as they contain a phosphorus atom in the molecule, and examples thereof include organic phosphorus compounds such as phosphate esters, condensed phosphate esters, phosphazene compounds, and polyphosphates, as well as red phosphorus.

[0071] Examples of inorganic fillers include aluminum borate, calcium carbonate, silicon carbonate, silicon nitride, potassium titanate, basic magnesium sulfate, zinc oxide, graphite, calcium sulfate, magnesium borate, magnesium oxide, and silicate minerals. Silicate minerals are particularly preferred. Commercially available silicate minerals include THIXOTROPIC AGENT DT 5039 (manufactured by Huntsman Japan Co., Ltd.).

[0072] Examples of internal mold release agents include metal soaps, vegetable waxes such as polyethylene wax and carnauba wax, fatty acid ester-based mold release agents, silicone oil, animal wax, and fluorine-based nonionic surfactants. The amount of these internal mold release agents added is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 2 parts by mass, per 100 parts by mass of the epoxy resin. Within this range, the mold release effect from the mold is optimally exhibited.

[0073] Commercially available internal mold release agents include MOLD WIZ (registered trademark) INT1846 (manufactured by AXEL PLASTICS RESEARCH LABORATORIES INC.), Licowax S, Licowax P, Licowax OP, Licowax PE190, and Licowax PED (manufactured by Clariant Japan), and stearyl stearate (SL-900A; manufactured by Riken Vitamin Co., Ltd.).

[0074] [3. Prepreg] The prepreg of the present invention (hereinafter sometimes referred to as "the present prepreg") is a prepreg in which the above-mentioned resin composition is impregnated into a reinforcing fiber substrate.

[0075] The content of the resin composition in the prepreg is preferably 20 to 60% by mass, more preferably 30 to 50% by mass, based on the total mass of the reinforcing fiber substrate and the resin composition. If the content of the resin composition is less than 20% by mass, voids may occur inside the fiber-reinforced composite material produced using this prepreg. If the content of the resin composition exceeds 60% by mass, the content of the reinforcing fibers will be insufficient, and the strength of the resulting fiber-reinforced composite material will likely decrease.

[0076] The water absorption of the present prepreg is preferably 2 to 40%, more preferably 4 to 25%. In the present invention, water absorption is an index showing the void ratio in the prepreg, and a higher water absorption indicates a higher void ratio in the prepreg. When the water absorption is high, many voids are present in the prepreg, which deteriorates the handling properties during molding. Furthermore, voids are likely to remain in the produced fiber-reinforced composite material, which may adversely affect its mechanical properties. When the water absorption is low, few voids are present in the prepreg, which reduces drapeability. As a result, good molding processability (shape conformability) cannot be obtained.

[0077] 3.1. Prepreg manufacturing method The prepreg can be produced by impregnating the reinforcing fiber substrate with the resin composition. A known wet method or dry method can be used to impregnate the reinforcing fiber substrate with the resin composition. Since the wet method uses an organic solvent, it is necessary to remove the organic solvent after impregnation with the resin composition. Therefore, it is preferable to use the hot melt method, which is a dry method in which no organic solvent remains.

[0078] In the hot melt method, the resin composition and the stacked reinforcing fiber substrate are heated under pressure to reduce the viscosity of the resin composition and impregnate the reinforcing fiber substrate. When the reinforcing fiber substrate is a sheet-like material, it is preferable to stack a film-shaped resin composition on the reinforcing fiber substrate.

[0079] The resin composition can be formed into a film by a known method. For example, the resin composition can be formed into a film by casting it onto a support such as release paper or release film using a die coater, applicator, reverse roll coater, comma coater, knife coater, or the like. The temperature for producing the film is appropriately set depending on the viscosity of the resin composition. Generally, the temperature is preferably 60 to 130°C, more preferably 80 to 110°C. The thickness of the resin composition film is preferably 8 to 350 μm, and more preferably 10 to 200 μm.

[0080] The pressure conditions when the resin composition is impregnated into the reinforcing fiber substrate are adjusted appropriately depending on the composition and viscosity of the resin composition. The linear pressure is usually 0.98 to 245 N / cm, more preferably 19.6 to 147 N / cm. If the linear pressure is less than 0.98 N / cm, it is difficult to sufficiently impregnate the reinforcing fiber sheet with the resin composition. The pressure may be applied in one step or in multiple steps.

[0081] The heating temperature when the reinforcing fiber substrate is impregnated with the resin composition is adjusted appropriately depending on the viscosity of the resin composition. It is usually 70 to 160°C, and preferably 80 to 120°C. If the heating temperature is too low, the viscosity of the resin composition does not decrease, making it difficult to impregnate the reinforcing fiber substrate with the resin composition. If the heating temperature is too high, the curing reaction in the resin composition progresses, and the tackiness and drapeability of the prepreg tend to deteriorate.

[0082] The industrial production speed of the prepreg is not particularly limited, but in consideration of productivity, economy, and the like, in the case of continuous production, the speed is preferably 0.1 m / min or more, more preferably 1 to 50 m / min, and particularly preferably 2 to 20 m / min.

[0083] [3.2. How to use prepreg] The prepreg can be cured by known methods to produce a fiber-reinforced composite material, including conventional methods such as manual layup, automated tape layup (ATL), automated fiber placement, vacuum bagging, autoclave curing, non-autoclave curing, fluid-assisted processing, pressure-assisted processing, matched mold processing, simple press curing, presclave curing, or continuous band pressing.

[0084] For example, the prepreg can be laminated, pressurized to 0.2 to 1 MPa in an autoclave, and heated at 150 to 204°C for 1 to 8 hours to produce a molded fiber-reinforced composite material.

[0085] This prepreg uses a highly heat-resistant resin composition. Therefore, a fiber-reinforced composite material produced using this prepreg has a heat resistance of at least 150°C or higher. The cured resin composition constituting the fiber-reinforced composite material preferably has a glass transition temperature of 180 to 400°C, more preferably 200 to 350°C, as measured by a method in accordance with ASTM D7028.

[0086] The compressive strength after damage (CAI) of a fiber reinforced composite material produced using this prepreg is 100 to 500 MPa, and more preferably 150 to 400 MPa. The compressive strength after damage (CAI) refers to the compressive strength after damage (CAI) measured by a method conforming to SACMA SRM 2R-94, in which the material is compressed after an impact of 30.5 J.

[0087] The resin used in the present prepreg has a flexural modulus of elasticity of preferably 2.5 to 5.0 GPa, more preferably 3.0 to 4.0 GPa. The flexural modulus of elasticity of resin means a value obtained by a measurement method in accordance with JIS K7171.

[0088] The resin used in the present prepreg preferably has a resin flexural strength of 30 to 300 MPa, more preferably 50 to 300 MPa. The resin flexural modulus refers to a value obtained by a measurement method in accordance with JIS K7171.

[0089] The resin used in the present prepreg has a resin flexural elongation of preferably 1 to 30%, more preferably 3 to 20%. The resin flexural modulus refers to a value obtained by a measurement method in accordance with JIS K7171.

[0090] This prepreg has excellent storage stability, and maintains the same moldability as immediately after production even after at least 10 days have passed since production of this prepreg. Therefore, it is possible to produce fiber-reinforced composite materials that have high heat resistance and impact resistance even after a certain period of time has passed.

[0091] [4. Composite materials] The composite material of the present invention is obtained by curing the prepreg described above. In the composite material of the present invention, particles 1 and particles 2 are contained in the cured product of the thermosetting resin in a state where they are in contact with each other.

[0092] In the present invention, "contact" means that the components of particle 1 are distributed within 5 μm of the surface of particle 2. Particle 1 may be aggregated near the surface of particle 2. In the present invention, the contact state of particle 1 with particle 2 is observed using a microscope, and the contact ratio of particle 1 is determined as follows: First, 10 particles 2 are randomly selected from the image observed using the microscope, and the periphery of each particle 2 is approximated to a circle using image processing. Next, the ratio of the contact length of the components of particle 1 to the periphery of the approximated circle of each particle 2 (in other words, the ratio of the periphery of particle 1 located within 5 μm from the outer surface of particle 2 to the entire periphery of the approximated circle of particle 2) is determined, and the average value is taken as the average contact ratio. In the present invention, it is preferable that particles 1 are in contact with each other by an average of 5% or more, more preferably by 7% or more, and particularly preferably by 10% or more. [Example]

[0093] The present invention will be described in more detail below with reference to examples. 1. Raw materials The following materials were used as raw materials for the resin composition. (1) Particle 1, core-shell rubber particle KANE ACE MX-150 (product name) (masterbatch containing 40% by mass of polybutadiene rubber core-shell rubber particles, main component: bisphenol A epoxy resin, manufactured by Kaneka Corporation, average particle size of particle 1: 80 nm)

[0094] (2) Particle 2, thermoplastic resin AURUM PD450M (product name) (polyimide, manufactured by Mitsui Chemicals, Inc., average particle size 11 μm (11,000 nm)) VESTOSINT Terra 9158 (product name) (polyamide, manufactured by Daicel-Evonik Co., Ltd., average particle size 20 μm)

[0095] (3) Thermoplastic resin soluble in epoxy resin Sumikaexcel 5003P (product name) ground material (polyethersulfone, manufactured by Sumitomo Chemical Co., Ltd., average particle size 15 μm)

[0096] (4) Cyanate ester resin BT2160RX (product name) (cyanate ester resin, manufactured by Mitsubishi Gas Chemical Company, Inc.) BT2170 (product name) (a mixture of cyanate ester resin and bismaleimide resin (mass ratio 9:1), manufactured by Mitsubishi Gas Chemical Company, Inc.)

[0097] (5) Bismaleimide resin BT2170 (product name) (a mixture of cyanate ester resin and bismaleimide resin (mass ratio 9:1), manufactured by Mitsubishi Gas Chemical Company, Inc.) BMI-1100H (product name) (N,N'-4,4'-diphenylmethane bismaleimide, manufactured by Daiwa Chemical Industry Co., Ltd.)

[0098] (6) Epoxy resin YD-8125 (product name) (bisphenol A epoxy resin, manufactured by Nippon Steel Chemical & Material Co., Ltd.)

[0099] (7) Curing accelerator Preventol A6 (trade name) (dichlorophenyldimethylurea) manufactured by LANXESS (hereinafter abbreviated as "DCMU")

[0100] (8) Carbon fiber substrate Carbon fiber strand Tenax (registered trademark) IMS 65 E 23 24K 830tex (Teijin Limited, tensile strength: 5800 MPa, tensile modulus: 290 GPa) with a fiber mass per unit area of ​​190 g / m 2 A sheet-shaped reinforcing fiber substrate made by aligning carbon fibers in one direction so that

[0101] 2. Evaluation Method The composite materials were evaluated by the following methods. (1) Average particle size of particle 1 The average particle diameter of particles 1 (core-shell polymer particles) was determined by observing the cross section of the cured resin with a transmission electron microscope, measuring the maximum diameter of 50 randomly selected particles, and averaging the maximum diameters of each particle as the particle diameter.

[0102] (2) Average particle size of particle 2 Measurements were carried out on a volume basis using a particle size measuring device by the laser diffraction / scattering method, and the median diameter was taken as the average particle size.

[0103] (3) Impact resistance The prepreg is cut into squares with sides of 360 mm and laminated to form a laminate structure of [+45 / 0 / -45 / 90]. 3SA laminate was obtained. Using a conventional vacuum autoclave molding method, molding was performed for 2 hours under conditions of 0.59 MPa pressure and 180°C. After measuring the dimensions of each test piece, an impact test was performed using a drop weight impact tester (Instron Dynatup) to apply an impact energy of 30.5 J. After the impact, the damage area of ​​the test piece was measured using an ultrasonic flaw detector (Krautkramer SDS3600, HIS3 / HF).

[0104] (4) Contact of particle 1 with particle 2 The prepreg is cut into squares with sides of 360 mm and laminated to form a laminate structure of [+45 / 0 / -45 / 90]. 3S A laminate of the above formula was obtained. Using a conventional vacuum autoclave molding method, molding was performed for 2 hours under conditions of 0.59 MPa pressure and 180°C. The molded product was cut to appropriate dimensions (approximately 50 mm x 50 mm), and the cut surface was polished to obtain a test specimen for observation. The polished surface of the test specimen was observed using a microscope (KEYENCE VHX-5000), and the obtained image was processed to evaluate the contact of particle 1 with particle 2 according to the following criteria. The contact ratio of particle 1 with particle 2 was determined by randomly selecting 10 particles 2, determining the ratio of the contact length of the particle 1 component to the perimeter of the approximate circle around each particle 2, and calculating the average value. 〇: Particle 1 is in contact with particle 2 with a contact length of 5% or more of the perimeter of particle 2 ×: The contact length of particle 1 relative to the perimeter of particle 2 is less than 5%

[0105] Example 1 In a kneading machine, pulverized Sumikaexcel 5003P (5 parts by mass), an epoxy resin-soluble thermoplastic resin, was added to YD-8125 (20 parts by mass) and MX-150 (4 parts by mass), an epoxy resin containing core-shell rubber particles (particle 1), and the mixture was stirred using a planetary mixer at 120°C for 60 minutes until the Sumikaexcel 5003P was completely dissolved in the epoxy resin.The resin temperature was then cooled to below 80°C, and an epoxy resin composition was prepared. Then, using a roll mill, BT-2160RX (60 parts by mass), which is a cyanate ester resin, BT-2170 (20 parts by mass), which is a mixture of cyanate ester resin and bismaleimide resin, pulverized Sumikaexcel 5003P (35 parts by mass), AURUM PD450M (15 parts by mass, particle 2), and DCMU (0.4 parts by mass), which is a curing accelerator, were added to the above epoxy resin composition and kneaded together to prepare a resin composition.

[0106] The prepared resin composition was applied to a release paper using a film coater at a rate of 50 g / m 2 Next, two of the resin films prepared above were placed on both sides of an IMS65 carbon fiber sheet in which carbon fiber bundles were aligned in one direction. The carbon fiber sheet was impregnated with the resin composition by heating and pressurizing, and the carbon fiber weight was adjusted to 190 g / m. 2 A unidirectional prepreg with a matrix resin mass fraction of 35.0% was prepared.

[0107] The unidirectional prepreg was used to produce a composite material, and its impact resistance was evaluated. The resulting composite material had a damage area of ​​511 mm after impact. 2 and showed excellent impact resistance. When the contact of particle 1 with particle 2 in the above composite material was evaluated, it was observed that particle 1 was in contact with particle 2 over 20% of the perimeter of the obtained composite material.

[0108] Example 2 Resin compositions were prepared in the same manner as in Example 1, except that the amount of cyanate ester resin and the type of bismaleimide resin were changed to the amounts and types shown in Table 1. Furthermore, unidirectional prepregs were produced in the same manner as in Example 1.

[0109] The unidirectional prepreg was used to produce a composite material, and its impact resistance was evaluated. The resulting composite material had a damage area of ​​509 mm after impact. 2 The composite material was evaluated for contact between particle 1 and particle 2, and it was observed that particle 1 was in contact with particle 2 over 20% of its perimeter.

[0110] Example 3 A resin composition was prepared in the same manner as in Example 2, except that the amount of particles 2 was changed to the amount shown in Table 1. Furthermore, a unidirectional prepreg was produced in the same manner as in Example 1.

[0111] The unidirectional prepreg was used to produce a composite material, and its impact resistance was evaluated. The resulting composite material had a damage area of ​​511 mm after impact. 2 The composite material was evaluated for contact between particle 1 and particle 2, and it was observed that particle 1 was in contact with particle 2 over 20% of its perimeter.

[0112] Example 4 A resin composition was prepared in the same manner as in Example 2, except that the amount of particles 2 was changed to the amount shown in Table 1. Furthermore, a unidirectional prepreg was produced in the same manner as in Example 1.

[0113] The unidirectional prepreg was used to produce a composite material, and its impact resistance was evaluated. The resulting composite material had a damage area of ​​511 mm after impact. 2 The composite material was evaluated for contact between particle 1 and particle 2, and it was observed that particle 1 was in contact with particle 2 over 10% of its perimeter.

[0114] Example 5 A resin composition was prepared in the same manner as in Example 2, except that the amount of particles 1 was changed to the amount shown in Table 1. Furthermore, a unidirectional prepreg was produced in the same manner as in Example 1.

[0115] The unidirectional prepreg was used to produce a composite material, and its impact resistance was evaluated. The resulting composite material had a damage area of ​​520 mm after impact. 2 The composite material was evaluated for contact between particle 1 and particle 2. It was observed that particle 1 was in contact with particle 2 over 15% of its perimeter.

[0116] Comparative Example 1 In a kneading machine, pulverized Sumikaexcel 5003P (5 parts by mass), an epoxy resin-soluble thermoplastic resin, was added to YD-8125 (20 parts by mass), an epoxy resin, and the mixture was stirred using a planetary mixer at 120°C for 60 minutes until the Sumikaexcel 5003P was completely dissolved in the epoxy resin. The resin temperature was then cooled to below 80°C, preparing an epoxy resin composition.

[0117] Then, using a roll mill, BT-2160RX (60 parts by mass), which is a cyanate ester resin, BT-2170 (20 parts by mass), which is a mixture of cyanate ester resin and bismaleimide resin, pulverized Sumikaexcel 5003P (45 parts by mass), and DCMU (0.4 parts by mass), which is a curing accelerator, were added to the above resin and kneaded to prepare a resin composition.

[0118] The prepared resin composition was applied to a release paper using a film coater at a rate of 50 g / m 2 Next, two of the resin films prepared above were placed on both sides of an IMS65 carbon fiber sheet in which carbon fiber bundles were aligned in one direction. The carbon fiber sheet was impregnated with the resin composition by heating and pressurizing, and the carbon fiber weight was adjusted to 190 g / m. 2 A unidirectional prepreg with a matrix resin mass fraction of 35.0% was produced. The unidirectional prepreg was used to produce a composite material, and its impact resistance was evaluated. The resulting composite material had a damage area of ​​727 mm after impact. 2 It was.

[0119] Comparative Example 2 A resin composition was prepared in the same manner as in Comparative Example 1, except that the amounts of pulverized Sumikaexcel 5003P and core-shell rubber particles (particles 1) were changed to those shown in Table 1. Furthermore, a unidirectional prepreg was produced in the same manner as in Comparative Example 1. The unidirectional prepreg was used to produce a composite material, and its impact resistance was evaluated. The resulting composite material had a damage area of ​​1533 mm after impact. 2 It was.

[0120] Comparative Example 3 A resin composition was prepared in the same manner as in Comparative Example 1, except that the amounts of particles 2 and thermoplastic resin were changed to those shown in Table 1. Furthermore, a unidirectional prepreg was produced in the same manner as in Comparative Example 1. The unidirectional prepreg was used to produce a composite material, and its impact resistance was evaluated. The resulting composite material had a damage area of ​​575 mm after impact. 2 It was.

[0121] Comparative Example 4 A resin composition was prepared in the same manner as in Example 2, except that the type and amount of particles 2 were changed as shown in Table 1. Furthermore, a unidirectional prepreg was produced in the same manner as in Comparative Example 1. A composite material was manufactured using the unidirectional prepreg thus prepared. The contact between particle 1 and particle 2 in the obtained composite material was evaluated. It was found that the contact ratio between particle 1 and particle 2 was less than 5% of the perimeter of the obtained composite material. Furthermore, many voids were generated in the obtained composite material, and the test piece after the impact test was completely damaged.

[0122] [Table 1] [Industrial Applicability]

[0123] The composite material of the present invention can be used as a component for automobiles and aircraft, for example.

Claims

1. a composite material comprising reinforcing fibers and a cured product of a resin composition, the resin composition comprising particles 1, particles 2, and a thermosetting resin, the thermosetting resin comprising a cyanate ester resin and an epoxy resin, the cyanate ester resin content being 1 to 80 mass% based on the total mass of the resin composition, the epoxy resin content being 1 to 30 mass% based on the total mass of the thermosetting resin composition, the resin composition further comprising an epoxy resin-soluble thermoplastic resin, the ratio of the average particle diameters of particles 1 to 2 (average particle diameter of particles 2 / average particle diameter of particles 1) being 10 to 1000, particles 1 and 2 being contained in the cured product in a state where they are in contact with each other, particles 1 are core-shell rubber particles, and the shell composition of particles 1 is at least one selected from the group consisting of polymethyl methacrylate, polyglycidyl methacrylate, and polyacrylonitrile, and particles 2 are polyimide particles of a thermoplastic resin.

2. 2. The composite material according to claim 1, wherein the contact between particle 1 and particle 2 is an average contact length of 5% or more per total perimeter of any cross section of particle 2.

3. The composite material of claim 2 , wherein the thermosetting resin further comprises a bismaleimide resin.

4. 4. The composite material according to claim 3, wherein the content of the epoxy resin-soluble thermoplastic resin is 1 to 50 parts by mass per 100 parts by mass of the thermosetting resin.

5. 5. The composite material according to claim 1, wherein the epoxy resin-soluble thermoplastic resin has a glass transition temperature of 180° C. or higher.

6. The composite material according to any one of claims 1 to 5, wherein the content of particles 1 is 0.1 to 10 parts by mass relative to 100 parts by mass of the thermosetting resin.

7. A prepreg used in the production of the composite material according to claim 1, the prepreg comprising reinforcing fibers and a resin composition, the resin composition containing particles 1, particles 2, a thermosetting resin, and an epoxy resin-soluble thermoplastic resin, the ratio of the average particle diameters of particles 1 and particles 2 (average particle diameter of particles 2 / average particle diameter of particles 1) being 10 to 1000, and particles 1 and particles 2 being contained in the cured product in a manner such that they are in contact with each other.

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