Epoxy resin composition, prepreg, and fiber-reinforced composite material

Abstract

A cured resin product obtained by curing the epoxy resin composition containing an epoxy resin of the present invention for two hours at 180°C has a thermal diffusivity at 25°C, measured based on ASTM E1461-01 (2001), of from 0.17 mm2 / s to less than 0.30 mm2 / s and a 600°C char production rate in air of from 20% to less than 50%. The present invention provides: an epoxy resin composition that, by being cured, is capable of yielding a cured resin product having prominent char-forming effects and thermal conductivity as well as exceptional mechanical properties; and a prepreg as well as an exceptionally fire-resistant fiber-reinforced composite material in which this epoxy resin composition is used.

Description

Epoxy resin composition, prepreg and fiber-reinforced composite material

[0001] The present invention relates to an epoxy resin composition, a prepreg, and a fiber-reinforced composite material having excellent fire resistance.

[0002] Composite materials, which use reinforcing fibers such as carbon fiber or glass fiber and a thermosetting resin such as epoxy resin or phenolic resin as a matrix resin, are used in a wide range of applications, from sports and leisure goods such as fishing rods and tennis and badminton rackets to various industrial equipment, civil engineering and construction, and aerospace. However, the thermosetting resins used in most composite materials are flammable and can cause fires. Therefore, flame-retardant composite materials are required, particularly for structural materials such as aircraft and vehicles, to prevent accidents caused by ignition and combustion. In addition, flame-retardant materials are required for electronic and electrical equipment to prevent internal heat generation that could ignite and burn the housings or components, leading to accidents.

[0003] Methods for making composite materials flame retardant include a method of promoting char formation in the matrix resin to suppress the diffusion of decomposition gases that occur when the resin is thermally decomposed, and a method of suppressing the decomposition of the resin in the early stages of combustion by the heat absorption effect of an inorganic filler containing a heat-absorbing agent.

[0004] To promote char formation in matrix resins, additives that make the material less flammable, known as flame retardants, are often added. Phosphorus compounds are commonly used as flame retardants, and several phosphorus compounds are used industrially. It is believed that phosphorus compounds convert to polyphosphoric acid, which has a dehydrating and carbonizing effect, during combustion, thereby promoting char formation. Flame retardant technologies using such phosphorus compounds include adding additive-type flame retardants such as red phosphorus or phosphate esters to epoxy resin compositions, and using reactive flame retardants that contain phosphorus atoms in their molecules and react with resins to introduce phosphorus atoms into the crosslinked structure.

[0005] Metal hydroxides are generally used as heat-absorbing agents and are used industrially.

[0006] Furthermore, Patent Document 1 reports a technology for obtaining a cured resin product that has excellent viscosity stability and char formation promoting effects as well as excellent mechanical properties, by using a flame retardant technology that uses a resin composition containing a reactive diluent having a specific structure and an amine-based curing agent containing a phosphorus atom having a specific structure.

[0007] Patent Document 2 reports a technique for obtaining a fire-resistant resin containing an epoxy resin containing a phosphorus atom having a specific structure.

[0008] Patent Document 3 reports a flame-retardant resin containing a specific epoxy resin, red phosphorus, and aluminum hydroxide, and a technique for obtaining a fire-resistant fiber-reinforced composite material using the same.

[0009] Re-listed Patent Publication No. 2019-082595 JP 2016-510355 A International Publication No. 2021-153644

[0010] In structural materials for aircraft, vehicles, and the like, it is advantageous to reduce the thickness of the material due to the demand for weight reduction to reduce fuel consumption. However, the thinner the material, the more likely flames will spread vertically during combustion. When using the phosphorus-based flame retardants and inorganic fillers described in the above patent documents, it was difficult to obtain sufficient fire resistance in thin materials.

[0011] An object of the present invention is to provide an epoxy resin composition from which a fiber-reinforced composite material having excellent mechanical properties and excellent fire resistance can be obtained, as well as a prepreg and a fiber-reinforced composite material using the same.

[0012] In the present invention, it has been discovered that by using a cured resin that has a high char formation-promoting effect and thermal conductivity as the matrix resin of a fiber-reinforced composite material, a fiber-reinforced composite material with excellent fire resistance and mechanical properties can be provided due to the synergistic effect of suppressing the diffusion of decomposition gases and promoting heat dissipation in the thickness direction.

[0013] The epoxy resin composition of the present invention is an epoxy resin composition containing an epoxy resin, and the cured resin obtained by curing at a temperature of 180°C for 2 hours has a thermal diffusivity at 25°C of 0.17 mm as measured in accordance with ASTM E1461-01 (2001).２ / s or more 0.30mm ２ / s or less, and the char generation rate at 600°C in air is 20% or more and less than 50%.

[0014] Such an epoxy resin composition preferably contains an inorganic filler made of boron nitride or graphite as a component other than the epoxy resin.

[0015] The prepreg of the present invention is a prepreg obtained by impregnating reinforcing fibers with the above-mentioned epoxy resin composition.

[0016] Furthermore, the fiber-reinforced composite material of the present invention is a fiber-reinforced composite material obtained by curing the above-mentioned prepreg, or a fiber-reinforced composite material containing a cured resin obtained by curing the above-mentioned epoxy resin composition and reinforcing fibers, and the fiber-reinforced composite material has a thickness of 0.5 mm or more and less than 2 mm.

[0017] The present invention makes it possible to provide an epoxy resin composition that can be cured to give a cured resin product having high char-forming effect, thermal conductivity, and excellent mechanical properties, as well as a prepreg using the same.The present invention also makes it possible to provide a fiber-reinforced composite material having excellent mechanical properties and fire resistance.

[0018] The epoxy resin composition of the present invention has a thermal diffusivity of 0.17 mm at 25°C for a cured resin obtained by curing the epoxy resin composition at 180°C for 2 hours. ２ / s or more 0.30mm ２ When the thermal diffusivity is in this range, heat dissipation in the thickness direction is sufficiently promoted, and a fiber-reinforced composite material with excellent fire resistance can be obtained. Here, the thermal diffusivity is the thermal diffusivity in the thickness direction when the cured resin is measured in accordance with the standard ASTM E1461-01 (2001). The lower limit of the thermal diffusivity is preferably 0.18 mm ２ / s or more, more preferably 0.19 mm ２ / s or more. Most preferably, the thermal diffusivity is 0.20 mm ２ / s or more 0.30mm ２ / s or less.

[0019] Furthermore, the epoxy resin composition of the present invention has a char generation rate at 600°C in air of 20% or more but less than 50% for the cured resin product obtained. When the char generation rate is within this range, thermal diffusion of decomposition gases is sufficiently suppressed, allowing for the production of a fiber-reinforced composite material with excellent fire resistance. Here, the char generation rate at 600°C in air refers to the percentage of thermal decomposition residue remaining when the cured resin product reaches 600°C when heated from room temperature at a heating rate of 10°C / min in an air atmosphere using a thermogravimetric analyzer. The lower limit of the char generation rate is preferably 25% or more, more preferably 30% or more. Most preferably, the char generation rate is 35% or more but less than 50%.

[0020] In this way, when a resin composition having a high thermal diffusivity and a high char generation rate after curing is used as the matrix resin of a fiber-reinforced composite material, a synergistic effect is obtained between the effect of suppressing the thermal diffusion of decomposition gases by promoting char formation and the heat dissipation effect in the thickness direction, improving the fire resistance of the fiber-reinforced composite material.

[0021] Furthermore, the fiber-reinforced composite material of the present invention is a fiber-reinforced composite material comprising a cured epoxy resin and reinforcing fibers, and the cured resin has a thermal diffusivity of 0.17 mm at 25°C as measured in accordance with ASTM E1461-01 (2001). ２ / s or more 0.30mm ２ / s or less, the 600°C char generation rate in air is 20% or more and less than 50%, and the thickness of the fiber reinforced composite material is 0.5 mm or more and less than 2 mm.

[0022] In structural members for aircraft, vehicles, and the like, it is necessary to reduce the thickness of the material in order to reduce weight, but when the thickness is reduced, there is a concern that the flame will tend to spread vertically in the vertical burning test required for structural members. In contrast, the fiber-reinforced composite material of the present invention has an excellent heat dissipation effect in the thickness direction, and therefore can exhibit the effect of improving fire resistance even when the material thickness is within the above-mentioned range.

[0023] The epoxy resin composition of the present invention preferably contains, in addition to the epoxy resin, an inorganic filler made of boron nitride or graphite as component [A].

[0024] Of these, the inorganic filler made of graphite is more preferable, as the addition of such an inorganic filler improves the thermal conductivity of the resin.

[0025] Specific examples of component [A] include flake boron nitride, spherical graphite, flake graphite, and flake graphite. Among these, flake graphite is particularly preferred because it is highly graphitized and has high thermal conductivity. These boron nitride and graphite components [A] may be used alone as the inorganic filler, or both may be used in combination. It is also possible to use a mixture of two or more types of boron nitride, graphite, or a combination of both.

[0026] The volume average particle size of component [A] in the present invention, as determined by a particle size distribution analyzer using a laser diffraction method, is preferably 10 nm to 100 μm, and more preferably 1 μm to 20 μm, in order to obtain high thermal conductivity and mechanical properties.

[0027] The content of component [A] in the present invention is preferably 0.5% by mass to 50% by mass of the total epoxy resin composition, from the viewpoint of obtaining high thermal conductivity and mechanical properties, and more preferably 1% by mass to 10% by mass.

[0028] The epoxy resin composition of the present invention preferably further comprises, as component [B], at least one amine curing agent selected from the group consisting of an amine curing agent having a structure represented by the following general formula (1), an amine curing agent having a structure represented by the following general formula (2), and an amine curing agent having a structure represented by the following general formula (3). Addition of such an amine curing agent to the epoxy resin composition promotes char formation. It also functions as a curing agent for the epoxy resin, resulting in a cured product with a high degree of cure.

[0029]

[0030] In general formula (1), R １ represents a hydrocarbon group having 1 to 4 carbon atoms.

[0031]

[0032] In general formula (2), R ２represents a hydrogen atom or an amino group.

[0033] In general formula (1), R １ When the number of carbon atoms in R is reduced, the hydrophobicity of the amine-based curing agent having the structure represented by general formula (1) decreases, and the moisture absorption resistance of the resulting cured resin may decrease. １ Preferably, the number of carbon atoms is 4.

[0034] Examples of hydrocarbon groups having 1 to 4 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, and tert-butyl groups.

[0035]

[0036] In general formula (3), R ３ ~R ６ represents one selected from a hydrogen atom and an aliphatic hydrocarbon group having 1 to 4 carbon atoms, and n represents 1 to 4.

[0037] Examples of the aliphatic hydrocarbon group having 1 to 4 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an isobutyl group, and a tert-butyl group.

[0038] In general formula (3), R ３ ~R ６ When the number of carbon atoms in R increases, the molecular chain of the aliphatic hydrocarbon group becomes longer, which may result in a decrease in the flame retardancy and mechanical properties of the cured resin product and fiber-reinforced composite material obtained by curing the epoxy resin composition of the present invention. ３ ~R ６ is preferably a hydrogen atom or a group having one carbon atom, i.e., a methyl group. ３ ~R ６ do not all need to be the same.

[0039] Examples of the amine-based curing agent having a structure represented by general formula (1) of component [B] in the present invention include bis(4-aminophenyl)ethylphosphine oxide, bis(3-aminophenyl)ethylphosphine oxide, bis(2-aminophenyl)ethylphosphine oxide, bis(4-aminophenyl)n-propylphosphine oxide, bis(3-aminophenyl)n-propylphosphine oxide, bis(4-aminophenyl)isopropylphosphine oxide, bis(3-aminophenyl)isopropylphosphine oxide, bis(4-aminophenyl)n-butylphosphine oxide, bis(3-aminophenyl)n-butylphosphine oxide, bis(4-aminophenyl)isobutylphosphine oxide, and bis(3-aminophenyl)isobutylphosphine oxide.

[0040] Examples of the amine-based curing agent having the structure represented by the general formula (2) include tris(4-aminophenyl)phosphine oxide, tris(3-aminophenyl)phosphine oxide, tris(2-aminophenyl)phosphine oxide, bis(4-aminophenyl)phenylphosphine oxide, and bis(3-aminophenyl)phenylphosphine oxide.

[0041] Examples of the amine-based curing agent having the structure represented by the general formula (3) include R ３ ~R ６ Biphenylaralkyl aromatic amine (BAN, manufactured by Nippon Kayaku Co., Ltd.) in which R is a hydrogen atom, and ３ ~R ６ and biphenylaralkyl aromatic amines (BXN, manufactured by Nippon Kayaku Co., Ltd.) in which the aryl group is a methyl group.

[0042] Among these, tris(3-aminophenyl)phosphine oxide or bis(3-aminophenyl)phenylphosphine oxide is preferably used because of its excellent mechanical properties and heat resistance, with the latter being more preferably used.

[0043] The content of component [B] in the present invention is preferably 10 to 100 parts by mass, and more preferably 25 to 100 parts by mass, per 100 parts by mass of the total epoxy resin, from the viewpoint of ensuring the viscosity stability of the resin composition and the flame retardancy and mechanical properties of the resulting cured product and fiber-reinforced composite material.

[0044] In the present invention, when an amine-based curing agent having a structure represented by general formula (1) or (2) is used as component [B], a phosphorus atom content of 0.1 to 5.0 mass% in the epoxy resin composition is preferred, since this allows the resulting cured product and fiber-reinforced composite material to achieve both flame retardancy and mechanical properties. The phosphorus atom content is preferably 0.3 to 4.0 mass%. The phosphorus atom content (mass%) here is calculated by dividing the mass (g) of phosphorus atoms in the total epoxy resin composition by the mass (g) of the total epoxy resin composition × 100. The mass of phosphorus atoms is obtained by calculating the mass of phosphorus atoms per molecule of the compound of component [B] from the atomic weight of the phosphorus atoms, and multiplying this by the number of molecules of the compound of component [B] contained in the total epoxy resin composition, calculated from the number of moles.

[0045] The epoxy resin composition of the present invention may also contain a curing agent other than the above-mentioned component [B]. The curing agent referred to here is a curing agent for epoxy resins, a compound having an active group capable of reacting with epoxy groups. Examples of curing agents other than component [B] include dicyandiamide, aromatic polyamines, aminobenzoic acid esters, various acid anhydrides, phenol novolac resins, cresol novolac resins, polyphenol compounds, imidazole derivatives, aliphatic amines, tetramethylguanidine, thiourea adduct amines, carboxylic acid anhydrides such as methylhexahydrophthalic anhydride, carboxylic acid hydrazides, carboxylic acid amides, polymercaptans, and Lewis acid complexes such as boron trifluoride ethylamine complex. Among these, the use of aromatic polyamines as curing agents facilitates the production of cured epoxy resins with good heat resistance. In particular, the use of various isomers of diaminodiphenyl sulfone, such as 4,4'-diaminodiphenyl sulfone and 3,3'-diaminodiphenyl sulfone, among aromatic polyamines, facilitates the production of cured epoxy resins with good heat resistance.

[0046] The content of the curing agent other than the component [B] is preferably 90 parts by mass or less relative to 100 parts by mass of the total amount of the curing agents including the component [B] and the curing agents other than the component [B], since this makes it easier to ensure the flame retardancy of the resulting cured product and fiber-reinforced composite material.

[0047] The epoxy resin composition of the present invention may contain a bifunctional glycidylamine-type epoxy resin as component [C] in order to impart excellent flame retardancy and mechanical properties to the resulting cured resin. Among these, an aniline-based compound is preferably used. It is particularly preferred to use the epoxy resin component [C] represented by the following general formula (4) as the aniline-based compound, since it allows the resulting cured resin to have excellent heat resistance, flame retardancy, and mechanical properties.

[0048]

[0049] In general formula (4), R ７ represents one selected from a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, a halogen atom, an acyl group, a trifluoromethyl group, and a nitro group. X represents a hydrogen atom or a substituent having a ring structure of 4 or more members. Examples of the substituent having a ring structure of 4 or more members include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a phenoxy group, a 1-naphthoxy group, a 2-naphthoxy group, a biphenyl group, a phenylsulfonyl group, and a benzyl group. R ７ When R is an aliphatic hydrocarbon group, the number of highly flammable methylene groups increases as the number of carbon atoms increases. ７ is preferably a hydrogen atom or a methyl group. ７ It is also preferable that X is a halogen atom such as Br or Cl. X is preferably a substituent having one benzene ring, from the viewpoint that as the number of carbon atoms increases, the viscosity of the resin composition increases, which may make it difficult to handle, and from the viewpoint of flame retardancy.

[0050] Specific examples of component [C] include monoamine-type epoxy resins such as N,N-diglycidylaniline, N,N-diglycidyl-o-toluidine, N,N-diglycidyl-m-toluidine, N,N-diglycidyl-p-toluidine, N,N-diglycidyl-2,3-xylidine, N,N-diglycidyl-2,4-xylidine, N,N-diglycidyl-3,4-xylidine, and N,N-diglycidyl-4-phenoxyaniline. Of these, N,N-diglycidylaniline and N,N-diglycidyl-4-phenoxyaniline are particularly preferred due to their excellent flame retardancy and mechanical properties. These epoxy resins of component [C] may be used alone or in combination of two or more.

[0051] The content of component [C] in the present invention is preferably 10 to 60 parts by mass, more preferably 25 to 40 parts by mass, per 100 parts by mass of the total epoxy resin, in order to ensure excellent heat resistance and mechanical properties.

[0052] The epoxy resin composition of the present invention may also contain the following epoxy resins in addition to the above-mentioned component [C]. First, examples of difunctional or less glycidyl ether epoxy resins include bisphenol-type epoxy resins such as bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol AD-type epoxy resins, and bisphenol S-type epoxy resins, as well as epoxy resins having a biphenyl skeleton, epoxy resins having a naphthalene skeleton, and epoxy resins having a dicyclopentadiene skeleton. Next, examples of trifunctional epoxy resins include aminophenol-type epoxy resins such as N,N,O-triglycidyl-m-aminophenol, N,N,O-triglycidyl-p-aminophenol, and N,N,O-triglycidyl-4-amino-3-methylphenol. Examples of tetrafunctional epoxy resins include diamine-type epoxy resins such as N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-2,2'-diethyl-4,4'-diaminodiphenylmethane, and N,N,N',N'-tetraglycidyl-m-xylylenediamine.

[0053] The epoxy resin composition of the present invention may further contain a thermoplastic resin soluble in the epoxy resin composition as component [D] to control the tackiness of the resulting prepreg, control the resin flowability when the epoxy resin composition is impregnated into reinforcing fibers, and impart toughness to the resulting fiber-reinforced composite material. The thermoplastic resin of component [D] is preferably a thermoplastic resin having a polyaryl ether skeleton. Specific examples include polysulfone, polyphenylsulfone, polyethersulfone, polyetherimide, polyphenylene ether, polyetheretherketone, and polyetherethersulfone. These thermoplastic resins having a polyaryl ether skeleton may be used alone or in combination as appropriate. Among these, polyethersulfone and polyetherimide are preferred because they can impart toughness to the resulting fiber-reinforced composite material without reducing its heat resistance or mechanical properties.

[0054] The amount of component [D] in the present invention is preferably 5 to 40 parts by mass, more preferably 10 to 35 parts by mass, and even more preferably 14 to 30 parts by mass, per 100 parts by mass of the total epoxy resin. By setting the amount of component [D] in this range, it is possible to ensure a balance between the viscosity of the epoxy resin, the tackiness of the resulting prepreg, and the mechanical properties of the resulting fiber-reinforced composite material.

[0055] When the epoxy resin composition of the present invention is used as a matrix resin for a prepreg, the viscosity of the epoxy resin composition at 80°C is preferably in the range of 0.5 to 200 Pa·s from the viewpoint of tack and drape of the prepreg. If the viscosity at 80°C is less than 0.5 Pa·s, excessive resin flow is likely to occur during molding of the fiber-reinforced composite material, resulting in greater variation in the basis weight of the reinforcing fibers. On the other hand, if the viscosity at 80°C exceeds 200 Pa·s, it becomes difficult for the epoxy resin composition to impregnate the reinforcing fibers during prepreg production, which makes it more likely that voids will form in the resulting fiber-reinforced composite material and reduces the strength of the fiber-reinforced composite material. The viscosity at 80°C referred to here is determined by the following method. That is, a dynamic viscoelasticity measuring device such as ARES (manufactured by TA Instruments Japan) is used, and flat parallel plates with a diameter of 40 mm are used. The epoxy resin composition is placed between the upper and lower plates so that the distance between the plates is 1 mm. After confirming that the temperature has reached 40°C, measurement is carried out in a torsion mode (angular frequency: 3.14 rad / s) with a simple temperature increase rate of 1.5°C / min, and the complex viscosity η* is determined when the temperature reaches 80°C.

[0056] In order to improve the impact resistance of the resulting fiber-reinforced composite material, the epoxy resin composition according to the present invention preferably contains, as component [E], particles whose main component is a thermoplastic resin (thermoplastic resin particles). Such thermoplastic resin particles are insoluble in the epoxy resin composition and remain as particles even after the epoxy resin composition is prepregged and then converted into a fiber-reinforced composite material. Note that, as used herein, "particles whose main component is a thermoplastic resin" refers to particles whose thermoplastic resin content is the highest among the components constituting the particles, and also includes thermoplastic resin particles consisting solely of a thermoplastic resin.

[0057] Polyamide is the most preferred material for thermoplastic resin particles, and among polyamides, polyamide 12, polyamide 6, polyamide 11, polyamide 66, polyamide 6 / 12 copolymer, and polyamide semi-IPN with epoxy resin (semi-IPN polyamide) are preferred. Using particles composed of epoxy resin and semi-IPN polyamide can impart excellent heat resistance and impact resistance to the prepreg. Here, IPN is an abbreviation for interpenetrating polymer network, a type of polymer blend in which the blend component polymers are crosslinked polymers, and the different crosslinked polymers are partially or completely entangled with each other to form a multiple network structure. Semi-IPN is a structure in which a crosslinked polymer and a linear polymer form a multi-network structure. Semi-IPN thermoplastic resin particles can be obtained, for example, by dissolving a thermoplastic resin and a thermosetting resin in a common solvent, mixing them uniformly, and then reprecipitation. For example, semi-IPN polyamide particles can be obtained by the method described in Example 1 of JP-A No. 1-104624.

[0058] The shape of these thermoplastic resin particles may be spherical, non-spherical, or porous, but spherical particles are preferred because they do not reduce the flow characteristics of the resin, provide excellent viscoelasticity, and have no starting points for stress concentration, thereby providing high impact resistance. Commercially available polyamide particles include SP-500, SP-10, TR-1, TR-2, 842P-48, 842P-80, and "Trepar (registered trademark)" TN (all manufactured by Toray Industries, Inc.), and "Orgasol (registered trademark)" 1002D, 2001UD, 2001EXD, 2002D, 3202D, 3501D, and 3502D (all manufactured by Arkema). These polyamide particles may be used alone or in combination.

[0059] The epoxy resin composition of the present invention may contain components other than those described above, such as a coupling agent, thermosetting resin particles, or inorganic fillers such as silica gel, carbon black, clay, carbon nanotubes, graphene, carbon particles, and metal powder, within the scope of not impairing the effects of the present invention.

[0060] The prepreg of the present invention is obtained by impregnating reinforcing fibers with the epoxy resin composition of the present invention. That is, the above-mentioned epoxy resin composition is used as a matrix resin, and this epoxy resin composition is composited with reinforcing fibers. Preferred examples of reinforcing fibers include carbon fibers, graphite fibers, aramid fibers, and glass fibers. Of these, carbon fibers are particularly preferred in terms of mechanical properties. Commercially available carbon fibers include "TORAYCA (registered trademark)" T700SC-24K, "TORAYCA (registered trademark)" T800SC-24K, and "TORAYCA (registered trademark)" T1100GC-24K (all manufactured by Toray Industries, Inc.).

[0061] The prepreg of the present invention can be produced by various known methods, such as a wet method, a hot melt method, etc. Among these, the hot melt method is preferred because it is easy to achieve the effects of the present invention.

[0062] The hot melt method is a method in which the viscosity of a matrix resin is reduced by heating without using a solvent, and the matrix resin is then impregnated into the reinforcing fibers. Hot melt methods include a method in which the matrix resin, which has been reduced in viscosity by heating, is directly impregnated into the reinforcing fibers, and a method in which the matrix resin is first applied to a release paper or the like to produce a release paper sheet with a resin film, which is then placed on both sides or one side of the reinforcing fibers, and the matrix resin is impregnated into the reinforcing fibers by heating and pressurizing.

[0063] In the prepreg of the present invention, the weight of the reinforcing fiber is 100 to 1000 g / m ２ It is preferable that the reinforcing fiber basis weight is 100 g / m ２ If the weight of the reinforcing fibers is less than 1000 g / m, it is necessary to increase the number of layers to obtain a predetermined thickness when molding the fiber-reinforced composite material, which may make the layering work complicated. ２If the fiber mass content exceeds 40%, the drapeability of the prepreg tends to deteriorate. The fiber mass content of the prepreg is preferably 40 to 90% by mass, and more preferably 50 to 80% by mass. If the fiber mass content is less than 40% by mass, the resin ratio is too high, which may prevent the advantages of the excellent mechanical properties of the reinforcing fibers from being fully utilized, and may result in an excessively high heat generation during curing of the fiber-reinforced composite material. If the fiber mass content exceeds 90% by mass, impregnation with the resin may be insufficient, resulting in the resulting fiber-reinforced composite material having many voids.

[0064] The prepreg of the present invention may be in any form, such as a unidirectional (UD) prepreg, a woven fabric prepreg, or a nonwoven fabric prepreg such as a sheet molding compound.

[0065] A first aspect of the fiber-reinforced composite material of the present invention is a fiber-reinforced composite material obtained by curing the prepreg of the present invention. Such a fiber-reinforced composite material can be obtained, for example, by laminating the prepreg of the present invention in a predetermined form and then applying heat and pressure to cure the matrix resin. Here, known methods such as autoclave molding, press molding, bagging molding, wrapping tape molding, and internal pressure molding can be used to apply heat and pressure.

[0066] A second aspect of the fiber-reinforced composite material of the present invention is a fiber-reinforced composite material comprising a cured resin obtained by curing the epoxy resin composition of the present invention and reinforcing fibers. Such a fiber-reinforced composite material can be obtained by a method in which a reinforcing fiber substrate is directly impregnated with a liquid epoxy resin and cured, without using a prepreg. Specifically, such a fiber-reinforced composite material can be obtained by, for example, a resin transfer molding method, a filament winding method, a pultrusion method, or a hand layup method.

[0067] The thickness of the fiber-reinforced composite material of the present invention is 0.5 mm or more and less than 2 mm, preferably 0.5 mm or more and less than 1 mm. If the thickness of the fiber-reinforced composite material is less than 0.5 mm, flames tend to propagate more easily in the vertical direction of the material, and fire resistance tends to deteriorate. On the other hand, if the thickness is 2 mm or more, the weight of the component becomes too large, and the structural component cannot be sufficiently lightened. Furthermore, if the material is too thick, flames tend to propagate less easily in the vertical direction even without using the fiber-reinforced composite material of the present invention, and the fire resistance effect of the fiber-reinforced composite material of the present invention cannot be fully utilized. In other words, the fiber-reinforced composite material of the present invention is characterized by having sufficient fire resistance even when the thickness is thin.

[0068] Furthermore, the fiber-reinforced composite material of the present invention preferably has a surface burn length of 10 mm or more and less than 50 mm, more preferably 10 mm or more and less than 46 mm, in a JIS T8022 flame spread test (Method A (surface ignition), 50 seconds of flame contact). Furthermore, the back surface damage length is preferably 10 mm or more and less than 60 mm, more preferably 10 mm or more and less than 56 mm. The surface burn length here refers to the maximum vertical length of the region where the resin has decomposed on the surface on the flame side of the measured sample, and this region does not include the sooted portion. Furthermore, the back surface damage length here refers to the maximum vertical length of the discolored region on the surface opposite the flame side of the measured sample. When the surface burn length and back surface damage length are within these ranges, the vertical propagation of flame is sufficiently suppressed, making it possible to exhibit excellent fire resistance for use as structural members for aircraft, vehicles, etc.

[0069] The upper and lower limits of the above-mentioned ranges can be combined in any way.

[0070] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. Materials used in the examples and comparative examples of the present invention are listed below.

[0071] <Component [A]: Boron nitride or graphite> Flake boron nitride (Platelets 003, manufactured by 3M Japan Ltd.) Flake graphite (BF-3AK (volume average particle size 3 μm), manufactured by Chuetsu Graphite Industries Co., Ltd.) Flake graphite (CBR (volume average particle size 18 μm), manufactured by Chuetsu Graphite Industries Co., Ltd.).

[0072] <Component [B]: Amine-based curing agent having a structure represented by general formula (2)> Bis(3-aminophenyl)phenylphosphine oxide (BAPPO, manufactured by Katayama Chemical Industry Co., Ltd.) Tris(3-aminophenyl)phosphine oxide (TAPPO, manufactured by Katayama Chemical Industry Co., Ltd.) <Component [B]: Amine-based curing agent having a structure represented by general formula (3)> Biphenylaralkyl-type aromatic amine (BAN) Biphenylaralkyl-type aromatic amine (BXN) <Curing agents other than component [B]> 4,4'-Diaminodiphenyl sulfone (Seikacure S, manufactured by Wakayama Seika Kogyo Co., Ltd.).

[0073] <Component [C]: Epoxy resin having a structure represented by general formula (4)> N,N-diglycidylaniline (GAN, manufactured by Nippon Kayaku Co., Ltd.) N,N-diglycidyl-4-phenoxyaniline (TOREP A-204E, manufactured by Toray Fine Chemical Co., Ltd.) <Epoxy resins other than component [C]> Bisphenol A epoxy resin ("jER (registered trademark)" 825, manufactured by Mitsubishi Chemical Corporation) N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane ("Araldite (registered trademark)" MY721, manufactured by Huntsman Advanced Materials) N,N,O-triglycidyl-p-aminophenol ("Araldite (registered trademark)" MY510, manufactured by Huntsman Advanced Materials).

[0074] <Component [D]: Thermoplastic Resin> Polyethersulfone ("VIRANTAGE (registered trademark)" VW-10700RFP, manufactured by Solvay Advanced Polymers) Polyetherimide ("ULTEM (registered trademark)" EXUM9990, manufactured by SABIC).

[0075] <Component [E]: Particles mainly composed of thermoplastic resin> Polyamide particles ("Trepar (registered trademark)" TN, manufactured by Toray Industries, Inc.) <Other components> Red phosphorus ("Novared (registered trademark)" 120UF, manufactured by Rinkagaku Kogyo Co., Ltd.) Carbon fiber ("Torayca (registered trademark)" T800SC-24K, manufactured by Toray Industries, Inc.).

[0076] (1) Method for Preparing Epoxy Resin Compositions: An inorganic filler corresponding to component [A], an epoxy resin, a thermoplastic resin corresponding to component [D], and other additives were added to a kneading device in the amounts listed in Tables 1 to 4, and the mixture was heated to 140°C or higher and kneaded under heat to dissolve the thermoplastic resin [D]. The resin composition in the kneading device was then cooled to 80°C or lower, and component [B] and curing agents other than component [B] were added to the kneading device in the amounts listed in Tables 1 to 4 and stirred to obtain an epoxy resin composition. When particles primarily composed of component [E] thermoplastic resin were used, the resin composition in the kneading device was cooled to 80°C or lower, and then added to the kneading device and stirred before adding the curing agent.

[0077] (2) Measurement of Char Formation Rate of Cured Resin The measurement of char formation rate by thermogravimetry (TGA) was carried out as follows.

[0078] The epoxy resin composition prepared in (1) was degassed in a vacuum and then cured under specified curing conditions in a mold set to a thickness of 2 mm using a 2 mm Teflon (registered trademark) spacer to obtain a 2 mm-thick cured epoxy resin product. Flame retardancy was evaluated using a thermogravimetric TG-DSC (PerkinElmer STA6000 system). A test piece weighing approximately 10 mg was cut from the cured epoxy resin product and simply heated at a rate of 10°C / min in air. The char generation rate (%) at 600°C was used as an index of flame retardancy. The char generation rate here is a value calculated by dividing the mass (g) of the thermal decomposition residue at 600°C by the mass (g) of the cured epoxy resin product before measurement by 100.

[0079] (3) Measurement of Thermal Diffusivity of Cured Resin The thermal diffusivity was measured as follows.

[0080] The cured epoxy resin product prepared in (2) was cut into a 10 mm x 10 mm square, and the surface was blackened using Blackguard Spray (manufactured by Fine Chemical Japan Co., Ltd.) to prepare a measurement sample. The thermal diffusivity of the sample at 25°C was measured using a thermal diffusivity measuring device LFA467 HyperFlash (manufactured by NETZSCH) in accordance with ASTM E1461-01 (2001).

[0081] (4) Evaluation of Mechanical Properties of Cured Resin Products Evaluation of mechanical properties of cured resin products was carried out as follows.

[0082] The cured epoxy resin product prepared in (2) was cut into a 10 mm × 60 mm square test piece, and a three-point bending test was performed on the test piece in accordance with JIS K7171 (2006) using an Instron 5565 universal testing machine (manufactured by Instron Corporation) under the conditions of a crosshead speed of 2.5 mm / min, a span length of 40 mm, an indenter diameter of 10 mm, and a fulcrum diameter of 4 mm, to measure the flexural modulus.

[0083] (5) Viscosity Measurement of Epoxy Resin Composition The viscosity of the epoxy resin composition was measured using an ARES-G2 dynamic viscoelasticity analyzer (manufactured by TA Instruments Inc.) Using flat parallel plates with a diameter of 40 mm, the epoxy resin composition was placed between the upper and lower plates at a distance of 1 mm, and after confirming that the temperature had reached 40°C, the viscosity was measured in a torsion mode (angular frequency: 3.14 rad / s) with a simple temperature increase rate of 1.5°C / min.

[0084] (6) Evaluation of Flame Retardancy of Carbon Fiber Reinforced Composite Material (Flame Propagability Test) Three layers of UD prepreg were laminated in a [0 / 90 / 0] configuration, and the laminate was heated in an autoclave at a pressure of 6 kg / cm. ２ The temperature was increased to 180°C at a rate of 1.7°C / min, and the temperature was maintained at 180°C for 2 hours under a pressure of 6 kg / cm ２ A sample measuring 200 mm long x 160 mm wide (approximately 0.6 mm thick) was cut out from this composite material, and the surface burn length and backside damage length were determined after contact with a flame for 50 seconds according to JIS T8022 flame spread test (Method A (surface ignition)).

[0085] (Examples 1 to 14, Comparative Examples 1 to 5) Epoxy resin compositions were prepared by the above-mentioned (1) Method for preparing an epoxy resin composition, using the components in the ratios (parts by mass) shown in Tables 1 to 3. The resulting epoxy resin compositions were cured at 180°C for 2 hours, and the char formation rate and thermal diffusivity of the resulting cured resins were measured. The evaluation results are shown in Tables 1 to 3.

[0086]

[0087]

[0088]

[0089] Example 15 In a kneading device, 9.5 parts by mass of flake graphite (component [A]), 35 parts by mass of N,N-diglycidylaniline (GAN) (component [C]), 65 parts by mass of tetraglycidyldiaminodiphenylmethane (epoxy resin other than component [C]), and 19 parts by mass of "VIRANTAGE (registered trademark)" VW-10700RFP (component [D]) were kneaded and dissolved, and then 28 parts by mass of bis(3-aminophenyl)phenylphosphine oxide (BAPPO) (component [B]) and 33 parts by mass of 4,4'-diaminodiphenyl sulfone were added and kneaded to prepare a primary resin composition. This primary resin composition did not contain particles (component [E]) mainly composed of a thermoplastic resin. The viscosity of the resulting primary resin composition at 80°C was 15.5 Pa·s. The resulting primary resin composition was coated using a knife coater with a resin basis weight of 29 g / m. ２ This primary resin film was set in a prepreg making machine, and unidirectionally aligned carbon fibers (weight per unit area: 190 g / m) were coated on a release paper. ２ ) and impregnated with the primary resin composition to obtain a primary prepreg. Next, a secondary resin composition was prepared by adding "Trepar (registered trademark)" TN (particles (component [E]) mainly composed of thermoplastic resin) to the primary resin composition so that the epoxy resin composition of the final prepreg would be the blending amount shown in Table 4. The secondary resin composition was applied using a knife coater to a resin basis weight of 20 g / m. ２The resulting prepreg was coated on release paper with a coating of 100% cellulose acetate and 100% cellulose acetate to prepare a secondary resin film. This secondary resin film was then laminated onto both sides of the primary prepreg to obtain the final prepreg. The surface burn length and backside damage length of the resulting prepreg were measured according to the method described in (6) Flame Retardancy Evaluation (Flame Spread Test) of Carbon Fiber Reinforced Composite Materials above. The results are shown in Table 4.

[0090] The char formation rate and thermal diffusivity of the cured resin were measured according to the methods described above. The results are shown in Table 4.

[0091] Comparative Example 6 A prepreg was produced in the same manner as in Example 15, except that the amount of flake graphite (component [A]) in Example 15 was set to 0 parts by mass, and the mass percentages of "Trepar (registered trademark)" TN (particles composed mainly of thermoplastic resin (component [E])) and "VIRANTAGE (registered trademark)" VW-10700RFP (component [D]) in the total resin composition were constant as shown in Table 4. The surface burn length and back surface damage length of the obtained prepreg were measured according to the method described in (6) Flame retardancy evaluation of carbon fiber reinforced composite material (flame spread test) above. The results are shown in Table 4.

[0092] The char formation rate and thermal diffusivity of the cured resin were measured according to the methods described above. The results are shown in Table 4.

[0093] Comparative Example 7 A prepreg was produced in the same manner as in Example 15, except that the composition shown in Table 4 was used so that the blending amount of bis(3-aminophenyl)phenylphosphine oxide (BAPPO) (component [B]) in Example 15 was 0 parts by mass, the mass percentages of flake graphite (component [A]), "Trepar (registered trademark)" TN (particles mainly composed of thermoplastic resin (component [E])), and "VIRANTAGE (registered trademark)" VW-10700RFP (component [D]) in the total resin composition were constant, and the ratio H / E of the number of moles of active hydrogen (H) in the curing agent to the number of moles of epoxy groups (E) in the epoxy resin was constant. The viscosity of the resulting primary resin composition at 80°C was 9.1 Pa s. The surface burn length and backside damage length of the resulting prepreg were measured according to the method described in (6) Flame Retardancy Evaluation of Carbon Fiber Reinforced Composite Materials (Flame Spread Test) above. The results are shown in Table 4.

[0094] The char formation rate and thermal diffusivity of the cured resin were measured according to the methods described above. The results are shown in Table 4.

[0095]

Claims

1. An epoxy resin composition comprising an epoxy resin, The epoxy resin composition was cured at 180°C for 2 hours to obtain a cured resin product. Thermal diffusivity at 25°C measured according to ASTM E1461-01 (2001) is 0.17 mm ２ / s or more 0.30mm ２ / s or less, and the char generation rate at 600°C in air is 20% or more and less than 50%.

2. 2. The epoxy resin composition according to claim 1, comprising, as component [A], an inorganic filler made of boron nitride or graphite.

3. 3. The epoxy resin composition according to claim 2, wherein component [A] is an inorganic filler made of graphite having a volume average particle size of 1 μm to 20 μm.

4. An epoxy resin composition as described in claim 3, wherein component [A] is an inorganic filler consisting of graphite having a volume average particle size of 1 μm to 3 μm.

5. 4. The epoxy resin composition according to claim 1 or 3, comprising, as component [B], at least one amine-based curing agent selected from the group consisting of an amine-based curing agent having a structure represented by general formula (1), an amine-based curing agent having a structure represented by general formula (2), and an amine-based curing agent having a structure represented by general formula (3); 【Chemistry 1】 In general formula (1), R １ represents a hydrocarbon group having 1 to 4 carbon atoms; 【Chemistry 2】 In general formula (2), R ２ represents a hydrogen atom or an amino group; 【Transformation 3】 In general formula (3), R ３ ~R ６ represents one selected from a hydrogen atom and an aliphatic hydrocarbon group having 1 to 4 carbon atoms, and n represents 1 to 4.

6. The epoxy resin composition according to claim 1 or 3, further comprising a component [C]: a difunctional glycidylamine-type epoxy resin.

7. The epoxy resin composition according to claim 6, wherein the component [C] has a structure represented by the following general formula (4): 【Chemistry 4】 In general formula (4), R ７ represents one selected from a hydrogen atom, a hydrocarbon group having 1 to 4 carbon atoms, a halogen atom, an acyl group, a trifluoromethyl group, and a nitro group; X represents a hydrogen atom or a substituent having a ring structure of four or more members.

8. 7. The epoxy resin composition according to claim 6, wherein the content of component [C] is 10 to 60 parts by mass per 100 parts by mass of the total amount of epoxy resins.

9. The epoxy resin composition according to claim 1 or 3, further comprising 5 to 40 parts by mass of a thermoplastic resin as component [D], per 100 parts by mass of the total amount of the epoxy resins.

10. 4. The epoxy resin composition according to claim 1, further comprising particles containing a thermoplastic resin as a main component as component [E].

11. A prepreg obtained by impregnating reinforcing fibers with the epoxy resin composition according to claim 1 or 3.

12. A fiber-reinforced composite material obtained by curing the prepreg according to claim 11.

13. A fiber-reinforced composite material comprising a cured resin obtained by curing the epoxy resin composition according to claim 1 or 3 and reinforcing fibers.

14. A fiber-reinforced composite material comprising a cured epoxy resin and reinforcing fibers, The thermal diffusivity of the cured resin at 25°C measured according to ASTM E1461-01 (2001) is 0.17 mm ２ / s or more 0.30mm ２ / s or less, And the 600 ° C. char generation rate in air is 20% or more and less than 50%, A fiber-reinforced composite material having a thickness of 0.5 mm or more and less than 2 mm.

15. 15. The fiber-reinforced composite material according to claim 14, wherein the cured epoxy resin contains, as component [A], an inorganic filler made of boron nitride or graphite.

16. A fiber-reinforced composite material as described in claim 15, wherein component [A] is an inorganic filler consisting of graphite having a volume average particle size of 1 μm to 20 μm.

17. A fiber-reinforced composite material as described in claim 16, wherein component [A] is an inorganic filler consisting of graphite having a volume average particle size of 1 μm to 3 μm.

18. A fiber-reinforced composite material according to claim 14 or 16, further comprising component [D] thermoplastic resin in an amount of 5 to 40 parts by mass per 100 parts by mass of the total amount of epoxy resin.

19. 17. The fiber-reinforced composite material according to claim 14 or 16, wherein the cured epoxy resin product is obtained from an epoxy resin composition comprising, as component [B], at least one amine-based curing agent selected from the group consisting of an amine-based curing agent having a structure represented by general formula (1), an amine-based curing agent having a structure represented by general formula (2), and an amine-based curing agent having a structure represented by general formula (3):

20. 17. The fiber-reinforced composite material according to claim 14 or 16, wherein the surface burning length in a JIS T8022 flame spread test (method A (surface ignition), 50 seconds of flame contact) is 10 mm or more and less than 50 mm, and the back surface damage length is 10 mm or more and less than 60 mm.