Epoxy resin composition for RTM, cured resin, fiber-reinforced composite material, and method for producing same

Abstract

The present invention addresses the problem of providing: a resin composition which has both viscosity stability during injection and rigidity during mold release; the present invention relates to an epoxy resin composition for RTM having an excellent balance among the modulus of elasticity under wet heat, the heat resistance when wet, and the fracture toughness, and a large and high-Vf fiber-reinforced composite material formed from the epoxy resin composition, and more particularly, to a resin composition for RTM having an excellent balance among the modulus of elasticity under wet heat, the heat resistance when wet, and the fracture toughness. [Solution] The epoxy resin composition for RTM contains an epoxy resin and a curing agent component, the epoxy resin contains the following components [A] and [C], the curing agent component contains components [B], and the components [A] and [A] contain 50-85 parts by mass of the components [A] and [A] per 100 parts by mass of the epoxy resin. [B] is a curing agent that is liquid at 150 DEG C. [C] is an aniline-type epoxy resin represented by formula (I). (In formula (I), R1 and R2 each represent at least one selected from among aliphatic hydrocarbon groups having 1-4 carbon atoms, n is an integer of 0-4, m is an integer of 0-5, when n or m is 2 or more, R1 and R2 may be the same as or different from each other, and X represents-O-or-S-. > # imgabs0 #

Description

Technical Field

[0001] The present invention relates to an RTM epoxy resin composition, a resin cured product, a fiber-reinforced composite material using the RTM epoxy resin composition and the resin cured product, and a method for manufacturing the same, which can be suitably used in aerospace components and general industrial applications. Background Art

[0002] Epoxy resin compositions exhibit excellent characteristics such as high heat resistance, adhesiveness, and mechanical strength, and are widely used as matrix resins for fiber-reinforced composite materials. Fiber-reinforced composite materials are manufactured by integrating reinforcing fibers and a matrix resin. As manufacturing methods thereof, there are a method of laminating and molding prepregs in which reinforcing fibers and a matrix resin are impregnated in advance, a method of injecting a low-viscosity matrix resin into a shaped reinforcing fiber substrate and curing it, and the like. Generally, the method using an intermediate substrate such as a prepreg is widely used in the industrial and aerospace fields because it exhibits high mechanical properties, but has the disadvantage that manufacturing processes such as the production and shaping of prepregs take time.

[0003] In recent years, the demand for high productivity has also increased in applications such as structural materials for aircraft and automobiles. There is a demand for technologies for producing large composite parts at high speed and obtaining fiber-reinforced composite materials having high mechanical properties and heat resistance. Therefore, in injection molding methods such as resin transfer molding (RTM method), there is an increasing demand for fiber-reinforced composite materials that can also be applied to molding methods that eliminate the time loss of temperature rise and fall by injecting and curing at a certain temperature and exhibit excellent characteristics.

[0004] In an injection molding method in which injection is carried out to molding at a certain temperature, in order to obtain a large fiber-reinforced composite material, the matrix resin has a low viscosity in the injection process. In addition, in order not to deform during demolding, the Tg after curing must be higher than the mold temperature during molding (hereinafter sometimes referred to as the mold temperature). In addition, in order to use fiber-reinforced composite materials for primary structural materials such as aircraft applications, it is desired to have an elastic modulus, heat resistance, and fracture toughness under humid heat in a well-balanced manner. In order to balance the elastic modulus and heat resistance under humid heat and at the same time make the matrix resin have a low viscosity, there is a method of mixing a large amount of polyfunctional and low-molecular-weight epoxy resins. However, since the crosslinking density of the resin cured product is too high, there are problems of a decrease in fracture toughness and a decrease in the impact resistance of the fiber-reinforced composite material. In addition, since the low-molecular-weight epoxy resin component volatilizes during the molding process, there is a problem that the fiber volume fraction (Vf) of the molded product decreases and it is difficult to exhibit mechanical properties. Therefore, it is desired to establish a resin design technology that can balance the viscosity stability during injection and the rigidity during demolding, and obtain a large and high-Vf fiber-reinforced composite material by injection molding without impairing the elastic modulus, heat resistance, and fracture toughness under humid heat.

[0005] In Patent Document 1, a technique is disclosed in which a tetrafunctional epoxy resin and a curing agent are used in combination with 4,4'-methylenebis(isopropyl-6-methylaniline) to improve the rigidity during demolding, and the fracture toughness of the resin cured product is improved by containing core-shell rubber particles.

[0006] In Patent Document 2, an epoxy resin composition is disclosed which is blended with N,N-diglycidyl-4-phenoxyaniline having low volatility, can provide a prepreg capable of obtaining a molded product with few voids, and there are also general examples such as the resin transfer molding method that can be used.

[0007] Prior Art Documents

[0008] Patent Documents

[0009] Patent Document 1: International Publication No. 2020 / 008847

[0010] Patent Document 2: International Publication No. 2010 / 109929 Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] Although the epoxy resin composition described in Patent Document 1 is excellent in rigidity and fracture toughness during demolding, it is not suitable for cases where a higher elastic modulus of the resin cured product is required.

[0013] The epoxy resin composition described in Patent Document 2 has a high water absorption rate, insufficient elastic modulus and glass transition temperature (Tg) under humid heat conditions. In addition, it has a high viscosity and poor impregnability, and it is difficult to apply to the RTM method.

[0014] An object of the present invention is to provide an RTM epoxy resin composition, a resin cured product, and a fiber-reinforced composite material using the RTM epoxy resin composition and the resin cured product, which improve the disadvantages of the prior art.

[0015] Means for Solving the Problems

[0016] The inventors of the present invention conducted in-depth research to solve the above problems, and as a result, found an RTM epoxy resin composition having the following structure, thus completing the present invention. That is, the RTM epoxy resin composition of the present invention is composed of the following.

[0017] [1]. An RTM epoxy resin composition containing an epoxy resin and a curing agent component, containing the following Component A and Component C as the epoxy resin, containing Component B as the curing agent component, and containing 50 to 85 parts by mass of the Component A in 100 parts by mass of the epoxy resin,

[0018] A: Tetrafunctional glycidylamine type epoxy resin,

[0019] B: A curing agent that is liquid at 150°C

[0020] C: An aniline-type epoxy resin represented by formula (I)

[0021]

[0022] In formula (I), R 1 and R 2 each independently represent at least one selected from aliphatic hydrocarbon groups having 1 to 4 carbon atoms, n is an integer from 0 to 4, m is an integer from 0 to 5, and when n or m is 2 or more, R 1 and R 2 may be the same or different, and X represents -O- or -S-.

[0023] [2]. The RTM epoxy resin composition according to [1], which contains tetraglycidyl diaminodiphenylmethane as component A.

[0024] [3]. The RTM epoxy resin composition according to [1] or [2], which contains methylene bisaniline as component B.

[0025] [4]. The RTM epoxy resin composition according to any one of [1] to [3], which contains 4,4'-methylenebis(isopropyl-6-methylaniline) as component B.

[0026] [5]. The RTM epoxy resin composition according to any one of [1] to [4], which contains 75 to 100 parts by mass of component B per 100 parts by mass of the curing agent component.

[0027] [6]. The RTM epoxy resin composition according to any one of [1] to [5], which further contains 1 to 10 parts by mass of core-shell rubber particles as component D based on 100 parts by mass of the epoxy resin.

[0028] [7]. The RTM epoxy resin composition according to any one of [1] to [6], the mass reduction rate of which is 3.0% by mass or less when heated at 150°C for 30 minutes.

[0029] [8]. For the RTM epoxy resin composition according to any one of [1] to [7], when the viscosity of the RTM epoxy resin composition after being held at temperature T1 for 30 minutes is denoted as η30 and the Tg of the RTM epoxy resin composition after being held at temperature T1 for 120 minutes is denoted as Tg 120 There is a temperature range of T1 that satisfies both formula 1 and formula 2 and is 5°C or more,

[0030] η 30 ≤100 cps Formula 1

[0031] Tg 120 ≥T1 formula 2.

[0032] [9]. The epoxy resin composition for RTM as described in [8], the highest temperature satisfying the formula 1 is above 165 °C.

[0033]

[10] . A resin cured product is obtained by curing the epoxy resin composition for RTM according to any one of [1] to [9].

[0034]

[11] . A fiber-reinforced composite material is composed of the resin cured product described in

[10] and a reinforcing fiber substrate.

[0035]

[12] . The fiber-reinforced composite material as described in

[11] , the reinforcing fiber substrate is a carbon fiber substrate.

[0036]

[13] . A method for manufacturing a fiber-reinforced composite material, injecting the epoxy resin composition for RTM according to any one of [1] to [9] into a reinforcing fiber substrate disposed in a mold heated to 70 °C or higher and 190 °C or lower, impregnating it, and curing it in the mold.

[0037]

[14] . The method for manufacturing a fiber-reinforced composite material as described in

[13] , the reinforcing fiber substrate is a carbon fiber substrate.

[0038] Advantages of the Invention

[0039] According to the present invention, it is possible to provide an epoxy resin composition for RTM with excellent balance of elastic modulus, heat resistance and fracture toughness of the resin cured product in a humid and hot environment. In addition, the epoxy resin composition for RTM of the present invention can balance the viscosity stability during injection and the rigidity during demolding while maintaining the above characteristics, and has little volatility, so it can be well used as an epoxy resin composition for RTM suitable for manufacturing large-sized and high-Vf fiber-reinforced composite materials by injection molding from injection to curing at a certain temperature. Detailed Embodiments

[0040] The epoxy resin composition for RTM of the present invention contains an epoxy resin and a curing agent component. As the epoxy resin, it contains component [A] a tetrafunctional glycidylamine type epoxy resin and component [C] an aniline type epoxy resin represented by formula (I). As the curing agent component, it contains component [B] a curing agent that is liquid at 150 °C as an essential component. First, these components will be described.

[0041] (Component [A])

[0042] The epoxy resin composition for RTM of the present invention needs to contain 50 to 85 parts by mass of component [A] in 100 parts by mass of the epoxy resin. When 50 to 85 parts by mass of component [A] is contained in 100 parts by mass of the epoxy resin, the epoxy resin cured product exhibits high heat resistance and excellent elastic modulus under humid heat conditions. When the amount of component [A] is less than 50 parts by mass, it is impossible to balance the viscosity stability during injection and the rigidity during demolding, and an epoxy resin cured product with low heat resistance will be obtained. When the amount of component [A] exceeds 85 parts by mass, an epoxy resin cured product with a low elastic modulus under humid heat conditions will be obtained. From the viewpoint of the above effects, the blending amount of component [A] is preferably in the range of 60 parts by mass or more and 80 parts by mass or less.

[0043] Examples of the component [A] include tetraglycidyl diaminodiphenylmethane, tetraglycidyl diaminodiphenyl sulfone, etc. From the viewpoint of improving the balance between the viscosity stability during injection and the rigidity during demolding, tetraglycidyl diaminodiphenylmethane is preferably used.

[0044] As the above-mentioned tetraglycidyl diaminodiphenylmethane, "Sumiepoxy (registered trademark)" ELM-434, "Sumiepoxy (registered trademark)" ELM-434VL (both manufactured by Sumitomo Chemical Co., Ltd.), YH434L (manufactured by Nippon Steel Chemical & Material Co., Ltd.), "jER (registered trademark)" 604 (manufactured by Mitsubishi Chemical Corporation), "Araldite (registered trademark)" MY720, "Araldite (registered trademark)" MY721 (both manufactured by Huntsman Japan K.K.), etc. can be used.

[0045] As the above-mentioned tetraglycidyl diaminodiphenyl sulfone, TG3DAS (manufactured by Konishi Chemical Industry Co., Ltd.), etc. can be used.

[0046] (Component [C])

[0047] The epoxy resin composition for RTM of the present invention must contain component [C] which is an aniline type epoxy resin represented by formula (I).

[0048] Formula 1

[0049]

[0050] (In formula (I), R 1 and R 2 each represent at least one selected from aliphatic hydrocarbon groups having 1 to 4 carbon atoms. n is an integer of 0 to 4, and m is an integer of 0 to 5. When n or m is 2 or more, R 1 can be the same or different, and R 2 can be the same or different. X represents -O- or -S-.)

[0051] In the case of containing component [C], an epoxy resin cured product with a good balance between fracture toughness and elastic modulus under humid heat can be obtained. In the case of not containing component [C], an epoxy resin cured product with a low elastic modulus will be obtained. In addition, component [C] is preferably contained in an amount of 10 to 50 parts by mass, more preferably 20 to 40 parts by mass, per 100 parts by mass of the epoxy resin. When the amount of component [C] is 10 parts by mass or more, an epoxy resin cured product having a sufficient elastic modulus under humid heat can be obtained. In addition, when the amount of component [C] is 50 parts by mass or less, the viscosity stability during injection and the rigidity during demolding can be taken into account.

[0052] Examples of component [C] include diglycidyl p-phenoxyaniline, diglycidyl-4-(4-methylphenoxy)aniline, diglycidyl-4-(4-tert-butylphenoxy)aniline, and diglycidyl-4-(4-phenoxyphenoxy)aniline. Among them, diglycidyl p-phenoxyaniline with a small molecular weight (n = 0, m = 0, X = -O-) can exhibit the characteristic of low viscosity and is well used in the resin injection process.

[0053] Examples of the diglycidyl p-phenoxyaniline include "TOREP (registered trademark)" A-204E (manufactured by Toray Fine Chemical Co., Ltd.).

[0054] (Component [D])

[0055] In the case of the RTM epoxy resin composition of the present invention, when the epoxy resin is 100 parts by mass, it preferably contains 1 to 10 parts by mass, more preferably 3 to 6 parts by mass, of core-shell rubber particles as component [D]. When component [D] is contained in the above range, the fracture toughness can be improved without impairing the elastic modulus of the epoxy resin cured product, and thus a fiber-reinforced composite material excellent in compressive properties and impact resistance can be obtained. When the blending amount of component [D] is less than 1 part by mass, an epoxy resin cured product with sufficient fracture toughness may not be obtained. When the blending amount of component [D] exceeds 10 parts by mass, the viscosity of the RTM epoxy resin composition increases, and the elastic modulus of the epoxy resin cured product may be insufficient.

[0056] As the component [D], examples include "KANE ACE (registered trademark)" MX-125, "KANE ACE (registered trademark)" MX-150, "KANE ACE (registered trademark)" MX-154, "KANE ACE (registered trademark)" MX-257, "KANE ACE (registered trademark)" MX-267, "KANE ACE (registered trademark)" MX-416, "KANE ACE (registered trademark)" MX-451 (the above are manufactured by Kaneka Corporation), "PARALOID (registered trademark)" EXL-2655, "PARALOID (registered trademark)" EXL-2668 (the above are manufactured by Dow Chemical Company), and the like.

[0057] (Component [B])

[0058] The RTM epoxy resin composition of the present invention needs to contain a curing agent that is liquid at 150°C as component [B]. Here, the curing agent is a curing agent for the epoxy resin contained in the RTM epoxy resin composition of the present invention, and is a compound having an active group capable of reacting with an epoxy group. As the curing agent that is liquid at 150°C, specifically, for example, imidazoles such as 2-methylimidazole and 2-ethyl-4-methylimidazole, acid anhydrides such as phthalic anhydride and maleic anhydride, aliphatic amines such as isophorone diamine and m-phenylenediamine, and aromatic amines such as alkylbenzene diamine and methylene bisaniline can be cited. Among them, from the viewpoint of imparting excellent mechanical properties to the resin cured product, aromatic amines are preferred. By containing a curing agent that is liquid at 150°C, the viscosity of the RTM epoxy resin composition is reduced, and it is easy to inject and impregnate the reinforcing fiber base material in RTM molding.

[0059] As the component [B], alkylbenzene diamine and methylene bisaniline are preferred, and methylene bisaniline is more preferred.

[0060] The alkylbenzene diamine is an aromatic amine compound having one or more alkyl groups and two amino groups on the benzene ring, and toluene diamines such as diethyltoluene diamine and dimethylthiotoluene diamine are preferably used. By using alkylbenzene diamine as the curing agent, the viscosity of the RTM epoxy resin composition can be suppressed, and at the same time, an epoxy resin cured product having excellent elastic modulus can be obtained.

[0061] Commercially available products of such alkylphenylenediamine include "jER Cure (registered trademark)" WA (manufactured by Mitsubishi Chemical Corporation), "Ethacure (registered trademark)" 100 (manufactured by Albemarle Corporation), "Heart Cure (registered trademark)" 10 (manufactured by Kumiai Chemical Industry Co., Ltd.), "Lonzacure (registered trademark)" DETDA80 (manufactured by Lonza), "Ethacure (registered trademark)" 300 (manufactured by Albemarle Corporation), "Heart Cure (registered trademark)" 30 (manufactured by Kumiai Chemical Industry Co., Ltd.), etc.

[0062] This methylene bisaniline is an aromatic amine compound formed by linking two aniline compounds through a methylene bridge, and various substituents may also be present on each benzene ring. By using methylene bisaniline as a curing agent for epoxy resin, a resin cured product with excellent low water absorption and fracture toughness can be obtained.

[0063] As such methylene bisaniline, it is preferable to use 4,4'-methylenebis(isopropyl-6-methylaniline) (M-MIPA), methylenebis(diethylaniline) (M-DEA), methylenebis(chlorodiethylaniline) (M-CDEA), methylene(methylethylaniline)-(chlorodiethylaniline) (M-MEACDEA), etc. Among them, when 4,4'-methylenebis(isopropyl-6-methylaniline) is used, it becomes an RTM epoxy resin composition with a good balance between the viscosity stability during injection and the rigidity during demolding. In addition, it is particularly preferable in terms of obtaining an epoxy resin cured product with an excellent balance between elastic modulus and fracture toughness.

[0064] Commercially available products of methylene bisaniline include MDA-220 (manufactured by Mitsui Chemicals, Inc.), "Lonzacure (registered trademark)" M-MIPA, "Lonzacure (registered trademark)" M-DEA, "Lonzacure (registered trademark)" M-CDEA, "Lonzacure (registered trademark)" M-DIPA (all of the above are manufactured by Lonza), "Kayhard (registered trademark)" A-A (PT) (manufactured by Nippon Kayaku Co., Ltd.), etc.

[0065] This component [B] is preferably contained in an amount of 75 to 100 parts by mass per 100 parts by mass of the curing agent component. When the component [B] is contained within the above range, it becomes an RTM epoxy resin composition with a good balance between the viscosity stability during injection and the rigidity during demolding.

[0066] The mass reduction rate of the RTM epoxy resin composition of the present invention when heated at 150°C for 30 minutes is preferably 3.0% by mass or less, more preferably 1.5% by mass or less. By being within this range, a fiber-reinforced composite material with a high Vf and excellent mechanical properties can be obtained by suppressing the volatilization of the resin component during the molding process.

[0067] The mass reduction rate of the RTM epoxy resin composition is obtained by putting about 2 g of the RTM epoxy resin composition into an aluminum cup with an inner diameter of 50 mm, weighing it with an electronic balance, heating it in a forced-air oven set at 150°C for 30 minutes, taking it out and cooling it to room temperature, and then weighing it again to calculate the mass reduction rate of the epoxy resin.

[0068] The temperature range of T1 that preferably satisfies both Formula 1 and Formula 2 for the RTM epoxy resin composition of the present invention is 5°C or higher, more preferably 10°C or higher. Formula 1 is a formula related to the viscosity stability during injection. By maintaining the RTM epoxy resin composition at temperature T1 for 30 minutes, the viscosity η 30 Within this range, it is easy to inject into the reinforcing fiber substrate during RTM molding. Formula 2 is a formula related to the rigidity during demolding. By maintaining the RTM epoxy resin composition at temperature T1 for 120 minutes, the Tg, Tg 120 Within this range, it has sufficient rigidity to prevent deformation during demolding. By having a temperature range of T1 that satisfies both Formula 1 and Formula 2 of 5°C or higher, injection, curing, and demolding can be carried out at a certain temperature, thereby achieving molding with excellent productivity.

[0069] η 30 ≤100 cps Formula 1

[0070] Tg 120 ≥T1 Formula 2.

[0071] The viscosity η of the RTM epoxy resin composition after maintaining it at temperature T1 for 30 minutes 30 is measured for the RTM epoxy resin composition using a dynamic viscoelasticity measuring device (Discovery HR-2, manufactured by TA Instruments) under the measurement mode: parallel plate (25 mmφ, gap 1.0 mm), temperature T1, shear rate: 100 s -1 conditions. The higher the temperature T1, the easier the reaction of the RTM epoxy resin composition proceeds, and the higher the viscosity after 30 minutes. Therefore, if the highest temperature that satisfies Formula 1 is known, it can also be considered that Formula 1 is satisfied at temperatures below this temperature.

[0072] The Tg, Tg of the RTM epoxy resin composition after maintaining it at temperature T1 for 120 minutes 120It is the value of the midpoint where an inflection point appears when measured under the conditions of a measurement range of 30 to 280 °C and a heating rate of 3 °C / min after giving a heat history of 120 minutes at a certain temperature T1 using DSC (DSC25, manufactured by TA Instruments). The higher the temperature T1, the higher the Tg of the epoxy resin cured product. Therefore, if the lowest temperature satisfying Equation 2 is known, it can be considered that Equation 2 is also satisfied even above this temperature.

[0073] Therefore, the temperature range that satisfies both Equation 1 and Equation 2 can be calculated from the difference between the highest temperature satisfying Equation 1 and the lowest temperature satisfying Equation 2.

[0074] The RTM epoxy resin composition of the present invention preferably has a highest temperature satisfying Equation 1 of 165 °C or higher. By satisfying this condition, the difference between the injection temperature and the curing temperature becomes smaller, and molding with less time required for heating and excellent productivity can be achieved.

[0075] For the RTM epoxy resin composition of the present invention, the elastic modulus in wet heat of the cured product obtained by curing the RTM epoxy resin composition at 180 °C for 2 hours is preferably 3.1 GPa or higher, more preferably 3.2 GPa or higher. By satisfying the above range, a fiber-reinforced composite material showing higher compressive strength with holes in wet heat can be obtained.

[0076] The elastic modulus in wet heat of the resin cured product is obtained by impregnating a test piece with a thickness of 2.0 mm, a width of 10 mm, and a length of 60 mm in boiling water for 48 hours, using an Instron universal testing machine (manufactured by Instron Corporation), setting the span to 32 mm, the crosshead speed to 10 mm / min, and performing three-point bending at a high temperature environment (82 °C) according to JIS K7171 (1994).

[0077] As a method for measuring the compressive strength with holes in wet heat of the fiber-reinforced composite material, first, a rectangle is cut out from the fiber-reinforced composite material with a length of 304.8 mm along the 0° direction and a length of 38.1 mm along the 90° direction, and a circular hole with a diameter of 6.35 mm is opened in the center to obtain a test piece. For this test piece, after impregnating it in warm water at 72 °C for 14 days, it is measured using an Instron universal testing machine (manufactured by Instron Corporation) at a high temperature environment (82 °C) according to ASTM-D6484. The compressive strength with holes in wet heat obtained by the above method is preferably 240 MPa or higher.

[0078] The RTM epoxy resin composition of the present invention preferably has a K1c of 1.0 MPa·m 0.5 or higher for the cured product obtained by curing the epoxy resin composition at 180 °C for 2 hours, and more preferably 1.2 MPa·m0.5 As described above, by satisfying the above ranges, a fiber-reinforced composite material with few microcracks can be obtained.

[0079] The K1c of the cured resin was obtained by machining a test piece with a thickness of 6.0 mm into the test piece shape described in ASTM D5045-99 and then performing a SENB test according to ASTM D5045-99.

[0080] Here, a microcrack refers to a tiny crack of about several tens of μm that occurs in a fiber-reinforced composite material used for aircraft applications, and it is known that it is likely to occur when repeatedly exposed to an environment where the temperature changes from a high temperature of about 70°C to a low temperature of about -50°C. When the matrix resin in the fiber-reinforced composite material changes from a high temperature of about 70°C to a low temperature atmosphere of about -50°C, the matrix resin itself wants to shrink, but since it is surrounded by reinforcing fibers that hardly shrink, it cannot shrink. As a result, there is tensile stress (thermal residual stress) inside the matrix resin itself. If repeated, environmental fatigue accumulates, and sometimes microcracks are generated inside the fiber-reinforced composite material. This phenomenon is particularly significant in the resin-rich part, and microcracks also occur frequently in the resin-rich part. In the state where microcracks occur, if environmental fatigue is applied again, the microcracks further grow into larger cracks, and finally, these large cracks may reduce the mechanical properties of the fiber-reinforced composite material.

[0081] As a specific calculation method for the number of microcracks, after exposing to the environmental conditions shown in the following steps a, b, and c using a commercially available thermo-hygrostat and environmental test machine, cut out a width of 25 mm from the longitudinal center ±10 mm of the test piece, grind the cut surface as the observation surface, observe the observation surface with a commercially available microscope at a magnification of 200 times, and measure the number of generated cracks to obtain the result.

[0082] a. Expose for 12 hours in an environment of 49°C and 95% / RH using a commercially available thermo-hygrostat.

[0083] b. After exposure, transfer to a commercially available environmental test machine. First, expose in an environment of -54°C for 1 hour. Then, heat up to 71°C at a heating rate of 10°C ± 2°C / minute. After heating, maintain at 71°C for 5 minutes ± 1 minute, then cool down to -54°C at a cooling rate of 10°C ± 2°C / minute, and maintain at -54°C for 5 minutes ± 1 minute. Define one cycle as heating from -54°C to 71°C and then cooling down to -54°C, and repeat this cycle 200 times.

[0084] c. Define the sum of the environmental exposure in the above thermo-hygrostat and the cycles in the environmental test machine as one module, and repeat 5 modules.

[0085] From the viewpoint of long-term durability of the fiber-reinforced composite material, the number of microcracks observed in the above method is preferably 10 or less, more preferably 5 or less.

[0086] In the present invention, the ratio (Mh / Me) of the number of moles of active hydrogen (Mh) in 100 parts by mass of the curing agent component to the number of moles of active epoxy groups (Me) in 100 parts by mass of the epoxy resin is preferably in the range of 1.0 to 1.4, and more preferably in the range of 1.1 to 1.3. By setting it in this range, both the elastic modulus during wet heat and the fracture toughness can be achieved.

[0087] The number of moles of active epoxy groups (Me) in 100 parts by mass of the epoxy resin refers to the sum of the number of moles of active groups of each epoxy resin, and is represented by the following formula.

[0088] Me=(mass of epoxy resin A / epoxy equivalent of epoxy resin A)+(mass of epoxy resin B / epoxy equivalent of epoxy resin B)+…+(mass of epoxy resin W / epoxy equivalent of epoxy resin W).

[0089] The number of moles of active hydrogen (Mh) in 100 parts by mass of the curing agent component is the sum of the values ​​obtained by dividing the mass of each curing agent by the active hydrogen equivalent of each curing agent, and is represented by the following formula.

[0090] Mh=(mass of curing agent A / active hydrogen equivalent of curing agent A)+(mass of curing agent B / active hydrogen equivalent of curing agent B)+…+(mass of curing agent W / active hydrogen equivalent of curing agent W).

[0091] The epoxy resin composition for RTM of the present invention has a wet heat flexural modulus of 82° C. (E 82 ) and the flexural modulus of elasticity (E 23 ) is a characteristic that is difficult to reduce. As this indicator, E 82 With E 23 The ratio (E 82 / E 23 ) to represent the retention rate, E 82 / E 23 It is preferably 0.75 or more, and more preferably 0.80 or more.

[0092] The epoxy resin composition for RTM used in the present invention may contain an epoxy resin (component [E]) different from component [A] or [C] as the epoxy resin, within the range not losing the effects of the present invention.

[0093] Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, phenol novolac type epoxy resin, triglycidyl p-aminophenol type epoxy resin, dicyclopentadiene type epoxy resin, biphenyl type epoxy resin, phenol aralkyl type epoxy resin, naphthalene type epoxy resin, etc. They can be used alone or in combination of multiple types. Dicyclopentadiene type epoxy resin and naphthalene type epoxy resin are preferably used in terms of the balance between elastic modulus and fracture toughness. Particularly preferably used is dicyclopentadiene type epoxy resin. In addition to the effect of reducing the water absorption rate of the epoxy resin cured product, it can also improve the fracture toughness of the resin cured product.

[0094] In the preparation of the RTM epoxy resin composition of the present invention, mechanical devices such as a kneader, a planetary mixer, a three-roll mill, and a twin-screw extruder can also be used for mixing. As long as uniform mixing can be achieved, a beaker and a spatula can also be used for manual mixing.

[0095] The RTM epoxy resin composition of the present invention exhibits viscosity stability at relatively high temperatures, has excellent impregnation characteristics for the reinforcing fiber substrate, and has a Tg that easily rises at relatively low temperatures, and has excellent rigidity during demolding. Therefore, it is particularly suitable for the RTM process that proceeds from injection to curing at a certain temperature. The RTM process is a method of setting a reinforcing fiber substrate or a preform in a mold, injecting a liquid matrix resin into the mold, impregnating it into the reinforcing fibers, and then curing the matrix resin to obtain a fiber-reinforced composite material as a molded product. The temperature at which the matrix resin (RTM epoxy resin composition) is injected in the manufacturing method of the fiber-reinforced composite material using the RTM epoxy resin composition of the present invention is not particularly limited. It is preferable to set the reinforcing fiber substrate in a mold preheated to 70°C to 190°C and inject the RTM epoxy resin composition of the present invention. By preheating the mold, the RTM epoxy resin composition has a lower viscosity, and the injection time is shortened, so the mass productivity is excellent. In addition, the thermal curing temperature does not need to be the same as the injection temperature, and the temperature can be appropriately increased to shorten the time required for thermal curing.

[0096] In the present invention, the mold used in the RTM process can be a closed mold made of a rigid material, or an open mold made of a rigid material and a flexible film (bag). In the latter case, the reinforcing fiber substrate can be set between the open mold made of a rigid material and the flexible film. As the rigid material, various existing materials such as metals such as steel and aluminum, fiber reinforced plastics (FRP), wood, and gypsum can be used. The material of the flexible film can be polyamide, polyimide, polyester, fluororesin, silicone resin, etc.

[0097] The reinforcing fibers used for the reinforcing fiber base material used in the fiber-reinforced composite material of the present invention are not particularly limited, and glass fibers, carbon fibers, aramid fibers, boron fibers, alumina fibers, silicon carbide fibers, etc. can be used. Two or more of these fibers can also be used in combination. From the viewpoint of obtaining a lightweight and high-rigidity fiber-reinforced composite material, carbon fibers are preferably used.

[0098] Since the fiber-reinforced composite material of the present invention has excellent mechanical properties, compressive strength under humid heat, and impact resistance, it can be well used for various structural materials such as aircraft parts such as fuselage, main wing, tail wing, moving wing, fairing, engine cover, car door, seat, interior material, spacecraft parts such as motor housing, main wing, artificial satellite parts such as frame, antenna, automobile parts such as outer panel, chassis, aerodynamic parts, seat, railway vehicle parts such as frame, seat, ship parts such as hull, seat.

[0099] Examples

[0100] Examples are shown below to more specifically illustrate the present invention, but the present invention is not limited to the descriptions of these examples.

[0101] The components used in this example are as follows.

[0102] <Used materials>

[0103] (1) Epoxy resin

[0104] · Component [A]: Tetrafunctional glycidylamine type epoxy resin

[0105] [A]-1 "Sumiepoxy (registered trademark)" ELM434VL (tetraglycidyl diaminodiphenylmethane) (manufactured by Sumitomo Chemical Co., Ltd.)

[0106] [A]-2 "Araldite (registered trademark)" MY721 (tetraglycidyl diaminodiphenylmethane) (manufactured by Huntsman Co., Ltd.)

[0107] [A]-3 "Sumiepoxy (registered trademark)" ELM434 (tetraglycidyl diaminodiphenylmethane) (manufactured by Sumitomo Chemical Co., Ltd.)

[0108] [A]-4 TG3DAS (diaminodiphenyl sulfone type epoxy resin) (manufactured by Konishi Chemical Co., Ltd.).

[0109] · Component [B]: A curing agent that is liquid at 150 °C

[0110] [B]-1: "jER Cure (registered trademark)" WA (diethyltoluenediamine) (manufactured by Mitsubishi Chemical Co., Ltd.) (liquid at room temperature)

[0111] [B] - 2: "Ethacure (registered trademark)" 300 (dimethylthiotoluenediamine) (manufactured by Albemarle Corporation) (liquid at room temperature)

[0112] [B] - 3: "Lonzacure (registered trademark)" M - MIPA (4,4'-methylenebis(2 - isopropyl - 6 - methylaniline)) (manufactured by Lonza) (melting point: 72°C).

[0113] Component [C]: Aniline - type epoxy resin represented by formula (I)

[0114] [C] - 1 "TOREP (registered trademark)" A - 204E (diglycidyl p - phenoxyaniline) (manufactured by Toray Fine Chemical Co., Ltd.).

[0115] · Component [D]: Core - shell rubber particles

[0116] [D] - 1 "Kane Ace (registered trademark)" MX - 416 (75% by mass of glycidylamine - type epoxy resin and 25% by mass of butadiene - based core - shell rubber particles).

[0117] · Component [E]: Other epoxy resins

[0118] [E] - 1 "EPICLON (registered trademark)" HP - 7200L (dicyclopentadiene - type epoxy resin) (manufactured by DIC Corporation)

[0119] [E] - 2 "EPICLON (registered trademark)" HP - 7200H (dicyclopentadiene - type epoxy resin) (manufactured by DIC Corporation)

[0120] [E] - 3 "EPICLON (registered trademark)" HP - 4770 (naphthalene - type epoxy resin) (manufactured by DIC Corporation)

[0121] [E] - 4 "EPICLON (registered trademark)" 830 (bisphenol F - type epoxy resin) (manufactured by DIC Corporation)

[0122] [E] - 5 "jER (registered trademark)" 630 (triglycidyl p - aminophenol) (manufactured by Mitsubishi Chemical Corporation)

[0123] [E] - 6 GAN (glycidylaniline) (manufactured by Nippon Kayaku Co., Ltd.).

[0124] · Other curing agent components

[0125] [G] - 1: "Seika Cure (registered trademark)" S (4,4'-diaminodiphenyl sulfone) (manufactured by Seika Corporation) (melting point: 170 - 173°C, solid at 150°C).

[0126] <Method for Preparing Epoxy Resin Composition for RTM>

[0127] Add components other than component [B] and other curing agent components in a stainless steel cup, heat to 60 - 150 °C, and mix properly until all components are compatible to obtain the epoxy main agent liquid. Put component [B] and other curing agent components in another container, heat as needed to make them compatible to obtain the curing agent liquid. Mix a specified amount of the epoxy main agent liquid and the curing agent liquid, and knead for 3 minutes with a planetary mixer to obtain the epoxy resin composition for RTM. The composition of the epoxy resin composition is shown in Tables 1 - 4.

[0128] <Evaluation Method for Mass Reduction Rate of Epoxy Resin Composition for RTM at 150 °C>

[0129] Put about 2 g of the epoxy resin composition for RTM obtained in the above <Method for Preparing Epoxy Resin Composition for RTM> into an aluminum cup with an inner diameter of 50 mm, weigh it with an electronic balance, then heat it in a forced-air oven (DKM400, manufactured by Yamato Scientific Co., Ltd.) set at 150 °C for 30 minutes, take it out and cool it to room temperature, and then weigh it again. Calculate the mass reduction rate of the resin based on the mass difference before and after.

[0130] <Epoxy Resin Composition for RTM η 30 Evaluation Method>

[0131] Use a dynamic viscoelasticity measuring device (Discovery HR-2, manufactured by TA Instruments), in the measurement mode: parallel plate (25 mm φ, gap 1.0 mm), temperature T1, shear rate: 100 s -1 Under the conditions, measure the complex viscosity η0 of the epoxy resin composition for RTM obtained according to the above <Method for Preparing Epoxy Resin Composition for RTM>, and take the value after 30 minutes as the η of the epoxy resin composition for RTM 30 .

[0132] <Tg of Epoxy Resin Composition for RTM 120 Evaluation Method>

[0133] Use DSC (DSC25, manufactured by TA Instruments), after giving a heat history of 120 minutes to the epoxy resin composition for RTM obtained according to the above <Method for Preparing Epoxy Resin Composition for RTM> at a certain temperature T1, measure under the conditions of measurement temperature: 30 - 280 °C, heating rate: 3 °C / min, and use the midpoint at the inflection point as the value of Tg 120 .

[0134] <Flexural modulus of the resin cured product (23 °C, 50% RH): E 23 Evaluation method>

[0135] The RTM epoxy resin composition obtained according to the above <Preparation method of RTM epoxy resin composition> is degassed in vacuo, and then cured at 180 °C for 2 hours in a mold with a thickness of 2 mm set by a 2-mm-thick Teflon spacer to obtain a plate-shaped resin cured product with a thickness of 2 mm. A test piece with a width of 10 mm and a length of 60 mm is cut out from the resin cured product, and using an Instron universal testing machine (manufactured by Instron Corporation), with a span of 32 mm and a crosshead speed of 10 mm / min, according to JIS K 7171 (1994), three-point bending is performed at room temperature (23 °C, 50% RH) to measure the flexural modulus (23 °C, 50% RH). At this time, the number of specimens n = 6, and the average value is used as the flexural modulus E 23 value.

[0136] <Flexural modulus of the resin cured product (humid heat 82 °C): E 82 Evaluation method>

[0137] A resin cured product is obtained by the same method as the above <Evaluation method of flexural modulus of resin cured product (23 °C, 50% RH): E 23 After cutting out a test piece with a width of 10 mm and a length of 60 mm, it is immersed in boiling water for 48 hours. The taken-out test piece is used with an Instron universal testing machine (manufactured by Instron Corporation), with a span of 32 mm and a crosshead speed of 10 mm / min, and according to JIS K 7171 (1994), three-point bending is performed at a high temperature environment (82 °C) to measure the flexural modulus (humid heat 82 °C). At this time, the number of specimens n = 6, and the average value is used as the flexural modulus E 82 value.

[0138] <Evaluation method of fracture toughness value K1c of resin cured product>

[0139] The RTM epoxy resin composition obtained according to the above <Preparation method of RTM epoxy resin composition> is degassed in vacuo, and then cured at 180 °C for 2 hours in a mold with a thickness of 6 mm set by a 6-mm-thick Teflon spacer to obtain a plate-shaped resin cured product with a thickness of 6 mm. After processing the obtained resin cured product into the test piece shape described in ASTM D5045-99, the SENB test is carried out according to ASTM D5045-99. At this time, the number of specimens n = 10, and the average value is used as the K1c value.

[0140] <Manufacture of reinforced fiber substrate with non-woven fabric>

[0141] On one side of a plain weave fabric (fiber weight per unit area: 285 g / m 2 ) composed of carbon fiber "Torayca (registered trademark)" T700G-12K-31E as a reinforcing fiber, a non-woven fabric composed of polyamide 12 (fiber weight per unit area: 6 g / m 2 ) is attached. Then, the non-woven fabric is welded by using a far-infrared heater to obtain a reinforced fiber base material with a non-woven fabric on one side surface.

[0142] <Fabrication of Fiber Reinforced Composite Material>

[0143] The reinforced fiber base material with a non-woven fabric obtained according to the above <Fabrication of Reinforced Fiber Base Material with Non-woven Fabric> is cut into 400 mm × 400 mm in such a way that the fiber directions are 0° / 90° and 45° / -45°. The cut reinforced fiber base material with a non-woven fabric is laminated in the mold in a structure of [(45° / -45°) / (0° / 90°)] 4 layers. Then, the mold is heated to 110°C, and the RTM epoxy resin composition obtained according to the above <Preparation Method of RTM Epoxy Resin Composition> and preheated to 110°C in advance is injected into the mold. Then, the temperature is raised to 180°C at a rate of 1.5°C per minute and cured at 180°C for 2 hours to obtain a fiber reinforced composite material.

[0144] <Evaluation Method for Porous Compressive Strength (Wet Heat 82°C) of Fiber Reinforced Composite Material: OHC 82 >

[0145] A rectangular test piece is cut from the fiber reinforced composite material obtained according to the above <Fabrication of Fiber Reinforced Composite Material> by cutting 304.8 mm along the 0° direction and 38.1 mm along the 90° direction, and a circular hole with a diameter of 6.35 mm is opened in the center. After immersing the test piece in warm water at 72°C for 14 days, using an Instron universal testing machine (manufactured by Instron Corporation), according to ASTM-D6484, the porous compressive strength (wet heat 82°C) is measured in a high-temperature environment (82°C). At this time, the number of specimens n = 5, and the average value is used as the value of OHC 82 .

[0146] <Evaluation Method for Number of Microcracks in Fiber Reinforced Composite Material>

[0147] A test piece with a width of 75 mm and a length of 50 mm is cut from the fiber reinforced composite material obtained according to the above <Fabrication of Fiber Reinforced Composite Material> in such a way that the length direction is the same as the 0° direction. Using a commercially available thermostatic and humidity-controlled chamber and environmental testing machine, the obtained test piece is exposed to the environmental conditions shown in the following steps a, b, and c.

[0148] a. Expose for 12 hours in an environment of 49 °C and 95% / RH using a commercially available thermo-hygrostat chamber.

[0149] b. After exposure, transfer to a commercially available environmental test chamber. First, expose for 1 hour in an environment of -54 °C. Then, increase the temperature to 71 °C at a heating rate of 10 °C ± 2 °C per minute. After heating, hold at 71 °C for 5 minutes ± 1 minute, then cool to -54 °C at a cooling rate of 10 °C ± 2 °C per minute, and hold at -54 °C for 5 minutes ± 1 minute. Define one cycle as the process of heating from -54 °C to 71 °C and then cooling back to -54 °C, and repeat this cycle 200 times.

[0150] c. Define the total of the environmental exposure in the above thermo-hygrostat chamber and the cycles in the environmental test chamber as 1 module, and repeat 5 modules.

[0151] Cut out test pieces with a width of 25 mm along the 0°, 45°, and 90° directions from the test pieces that have undergone the above environmental exposure. Grind the cut surface as the observation surface, and observe the observation surface with a commercially available microscope at a magnification of 200 times to measure the number of cracks generated.

[0152] Hereinafter, the production methods of the samples in each example, the resin cured product characteristics, and the measurement results of the resin uncured product characteristics will be described.

[0153] (Example 1)

[0154] As the epoxy resin, use 70 parts by mass of "Sumiepoxy (registered trademark)" ELM-434VL (Component [A]), 15 parts by mass of "TOREP (registered trademark)" A-204E (Component [C]), 20 parts by mass of "Kane Ace (registered trademark)" MX-416 (Component [D] and Component [A]), and 78.0 parts by mass of "Lonzacure (registered trademark)" M-MIPA (Component [B]), and prepare an RTM epoxy resin composition according to the above <Preparation method of RTM epoxy resin composition>.

[0155] For this RTM epoxy resin composition, according to the above <Evaluation method for flexural modulus of resin cured product (23 °C, 50% RH): E 23 > and <Evaluation method for flexural modulus of resin cured product (humid heat 82 °C): E 82 >, obtain the flexural properties. As a result, E 23 is 4.05 GPa, E 82 is 3.10 GPa, E 82 / E 23was 0.77, showing good elastic modulus under humid heat conditions. In addition, according to the above <Evaluation method for fracture toughness value of resin cured product>, the fracture toughness value was evaluated, and the result was 1.24 MPa·m 0.5 , excellent.

[0156] In addition, according to the above <Evaluation method for mass reduction rate of RTM epoxy resin composition at 150 °C>, the mass reduction rate was evaluated, and the result was 0.8 mass%.

[0157] In addition, according to the above <Evaluation method for η 30 of RTM epoxy resin composition> for η 30 was evaluated. As a result, the highest temperature of T1 satisfying Equation 1 was 165 °C, which was high enough. According to the above <Evaluation method for Tg 120 of RTM epoxy resin composition> for Tg 120 was evaluated. As a result, the lowest temperature of T1 satisfying Equation 2 was 150 °C, and a wide temperature range of T1 satisfying both Equation 1 and 2 existed, up to 15 °C.

[0158] (Examples 2 to 15)

[0159] Except that the resin compositions were changed as shown in Tables 1 and 2 respectively, RTM epoxy resin compositions and resin cured products were prepared by the same method as in Example 1.

[0160] The humid heat and room temperature elastic moduli and fracture toughness values of the RTM epoxy resin compositions of each example were evaluated, and good physical properties were obtained at all levels. In addition, the mass reduction rate after 150 °C for 30 minutes of each example was less than 3.0 mass%, and a temperature range of T1 satisfying both Equation 1 and 2 existed for more than 5 °C.

[0161] (Comparative Example 1)

[0162] For the RTM epoxy resin composition shown in Table 3, the RTM epoxy resin composition was prepared by the same method as in Example 1.

[0163] For this RTM epoxy resin composition, according to the above <Flexural elastic modulus of resin cured product (23 °C, 50% RH): E 23 evaluation method> and <Flexural elastic modulus of resin cured product (humid heat 82 °C): E 82 evaluation method>, the bending characteristics were obtained. As a result, E 23 was as high as 4.13 GPa, but E 82 was insufficient, being 2.97 GPa, and E 82 / E 23 was 0.72. In addition, according to the above <η of RTM epoxy resin composition30 Evaluation method of > for η 30 was evaluated, and the highest temperature of T1 satisfying Equation 1 was 160 °C, which was slightly insufficient.

[0164] (Comparative Example 2)

[0165] For the RTM epoxy resin composition shown in Table 3, the RTM epoxy resin composition was prepared in the same manner as in Example 1.

[0166] For this RTM epoxy resin composition, according to the above <η of the RTM epoxy resin composition 30 Evaluation method of > for η 30 was evaluated, and the highest temperature of T1 satisfying Equation 1 was high enough, at 175 °C. However, according to the above <Tg of the RTM epoxy resin composition 120 Evaluation method of > for Tg 120 was evaluated, and there was no T1 satisfying Equation 2, that is, there was no temperature range of T1 that simultaneously satisfied Equations 1 and 2.

[0167] (Comparative Example 3)

[0168] For the RTM epoxy resin composition shown in Table 3, the RTM epoxy resin composition was prepared in the same manner as in Example 1.

[0169] For this RTM epoxy resin composition, according to the above <Flexural modulus of the resin cured product (23 °C, 50% RH): E 23 Evaluation method of > and <Flexural modulus of the resin cured product (damp heat 82 °C): E 82 Evaluation method of >, the flexural properties were obtained. As a result, E 23 was as high as 3.90 GPa, but E 82 was insufficient, at 2.87 GPa, and E 82 / E 23 was 0.74. In addition, according to the above <Evaluation method of the fracture toughness value of the resin cured product>, the fracture toughness value was evaluated, and the result was 0.95 MPa·m 0.5 , which was insufficient.

[0170] In addition, according to the above <Evaluation method of the mass reduction rate of the RTM epoxy resin composition at 150 °C>, the mass reduction rate was evaluated, and the result was as high as 4.0 mass%. In addition, according to the above <η of the RTM epoxy resin composition 30 Evaluation method of > for η 30 was evaluated, and the highest temperature of T1 satisfying Equation 1 was 155 °C, which was slightly insufficient.

[0171] (Comparative Example 4)

[0172] For the RTM epoxy resin composition shown in Table 3, the RTM epoxy resin composition was prepared in the same manner as in Example 1.

[0173] For this RTM epoxy resin composition, the mass reduction rate was evaluated according to the above <Evaluation Method for the Mass Reduction Rate of the RTM Epoxy Resin Composition at 150 °C>, and the result was as high as 3.5% by mass. In addition, according to the above <Evaluation Method for η 30 of the RTM epoxy resin composition>, η 30 was evaluated, and the highest temperature of T1 that satisfied Formula 1 was 160 °C, which was slightly insufficient.

[0174] (Comparative Example 5)

[0175] For the RTM epoxy resin composition shown in Table 3, the RTM epoxy resin composition was prepared in the same manner as in Example 1.

[0176] Regarding the RTM epoxy resin composition, according to the above <Flexural Modulus of the Resin Cured Product (Wet Heat at 82 °C): E 82 Evaluation Method>, the flexural properties were obtained. As a result, E 82 was insufficient, being 3.01 GPa. In addition, according to the above <Evaluation Method for the Mass Reduction Rate of the RTM Epoxy Resin Composition at 150 °C>, the mass reduction rate was evaluated, and the result was as high as 7.0% by mass. In addition, according to the above <Evaluation Method for η 30 of the RTM epoxy resin composition>, η30 was evaluated. As a result, the highest temperature of T1 that satisfied Formula 1 was less than 135 °C, and according to the above <Evaluation Method for Tg 120 of the RTM epoxy resin composition>, Tg 120 was evaluated. As a result, the lowest temperature of T1 that satisfied Formula 2 was 135 °C, and the temperature range of T1 that satisfied both Formulas 1 and 2 was less than 0 °C.

[0177] (Comparative Example 6)

[0178] For the RTM epoxy resin composition shown in Table 3, the RTM epoxy resin composition was prepared by the method described in Example 3 of Patent Document 2 (International Publication No. 2010 / 109929).

[0179] For this RTM epoxy resin composition, according to the above <Flexural Modulus of the Resin Cured Product (23 °C, 50% RH): E 23 Evaluation Method> and <Flexural Modulus of the Resin Cured Product (Wet Heat at 82 °C): E 82 Evaluation Method>, the flexural properties were obtained. As a result, E 23 was as high as 4.20 GPa, but E 82 was insufficient, being 3.00 GPa, E82 / E 23 was 0.71. In addition, according to the above <Evaluation method for fracture toughness value of resin cured product>, the fracture toughness value was evaluated, and the result was very low, 0.60 MPa·m 0.5 .

[0180] In addition, according to the above <Evaluation method for η 30 of RTM epoxy resin composition> for evaluating η 30 , there was no T1 satisfying Formula 1, and the injection stability was poor. In addition, according to the above <Tg 120 of RTM epoxy resin composition> for evaluating Tg 120 , there was no T1 satisfying Formula 2, that is, there was no temperature range of T1 that simultaneously satisfied Formulas 1 and 2.

[0181] (Comparative Example 7)

[0182] For the RTM epoxy resin composition shown in Table 3, the RTM epoxy resin composition was prepared by the method described in Example 10 of Patent Document 1 (International Publication No. 2020 / 008847).

[0183] Regarding the RTM epoxy resin composition, the flexural properties were obtained according to the above <Flexural modulus of elasticity of resin cured product (humid heat 82°C): E 82 evaluation method>, and the result of E 82 was as low as 2.97 GPa.

[0184] In addition, according to the above <Evaluation method for η 30 of RTM epoxy resin composition> for evaluating η 30 , the highest temperature of T1 satisfying Formula 1 was 160°C, which was slightly insufficient.

[0185] The fiber-reinforced composite material properties of each example are as follows.

[0186] (Example 1’)

[0187] For the RTM epoxy resin composition shown in Table 4, the fiber-reinforced composite material was prepared according to the above <Production of fiber-reinforced composite material>.

[0188] For this fiber-reinforced composite material, the perforated compressive strength was obtained according to the above <Perforated compressive strength of fiber-reinforced composite material (humid heat 82°C): OHC 82 evaluation method>, and the result of OHC 82It is 241 MPa, showing excellent compression characteristics under hygrothermal conditions. In addition, the number of microcracks was evaluated according to the above <Evaluation Method for the Number of Microcracks in Fiber Reinforced Composites>, and the result showed excellent microcrack resistance characteristics, which was 4.

[0189] (Examples 4', 7', 14', 15')

[0190] Except that the resin compositions were changed as shown in Table 4 respectively, fiber reinforced composites were fabricated and evaluated in the same manner as in Example 1. For the OHC of the fiber reinforced composites of each example 82 , the number of microcracks was evaluated, and the results showed excellent compression characteristics and microcrack resistance characteristics under hygrothermal conditions at all levels.

[0191] (Comparative Example 3')

[0192] For the resin composition shown in Table 4, a fiber reinforced composite was fabricated according to the above <Fabrication of Fiber Reinforced Composites>.

[0193] For this fiber reinforced composite, the perforated compression strength was obtained according to the above <Evaluation Method for the Perforated Compression Strength of Fiber Reinforced Composites (Hygrothermal 82 °C): OHC 82 . Since the elastic modulus of this epoxy resin composition under hygrothermal conditions is low, the OHC 82 is 224 MPa, and the compression characteristics are insufficient. In addition, when evaluating the number of microcracks according to the above <Evaluation Method for the Number of Microcracks in Fiber Reinforced Composites>, since the fracture toughness of this epoxy resin composition is low, multiple microcracks were generated, and there were 12.

[0194] (Comparative Example 6')

[0195] For the resin composition shown in Table 4, a fiber reinforced composite was fabricated according to the above <Fabrication of Fiber Reinforced Composites>. Since the resin viscosity of this epoxy resin composition is high, injection could not be completed within 30 minutes. For this fiber reinforced composite, the perforated compression strength was obtained according to the above <Evaluation Method for the Perforated Compression Strength of Fiber Reinforced Composites (Hygrothermal 82 °C): OHC 82 . Since the elastic modulus of this epoxy resin composition under hygrothermal conditions is low, the OHC 82 is 234 MPa, and the compression characteristics are insufficient. In addition, when evaluating the number of microcracks according to the above <Evaluation Method for the Number of Microcracks in Fiber Reinforced Composites>, since the fracture toughness of this epoxy resin composition is low, multiple microcracks were generated, and there were 23.

[0196]

[0197]

[0198]

[0199]

[0200] In addition, the unit of each component in the table is parts by mass.

[0201] Industrial applicability

[0202] The epoxy resin composition for RTM of the present invention can provide an epoxy resin cured product having low viscosity, low volatility, and high elastic modulus and fracture toughness under humid heat. The fiber-reinforced composite material composed of the epoxy resin composition also has excellent compression characteristics and impact resistance under humid heat, and thus can be well used for aerospace components and structural components for general industrial use.

Claims

1. An epoxy resin composition for RTM, which contains an epoxy resin and a curing agent component. As the epoxy resin, it contains the following Component A and Component C, and as the curing agent component, it contains Component B. And in 100 parts by mass of the epoxy resin, 50 to 85 parts by mass of the Component A is contained. A: A tetrafunctional glycidylamine type epoxy resin B: A curing agent that is liquid at 150 °C C: An aniline type epoxy resin represented by the formula (I) In formula (I), R 1 and R 2 each independently represent at least one selected from aliphatic hydrocarbon groups having 1 to 4 carbon atoms, n is an integer of 0 to 4, m is an integer of 0 to 5, and when n or m is 2 or more, R 1 and R 2 may be the same or different from each other, and X represents -O- or -S-.

2. The epoxy resin composition for RTM according to claim 1, which contains tetraglycidyl diaminodiphenylmethane as Component A.

3. The epoxy resin composition for RTM according to claim 1, which contains methylene bisaniline as Component B.

4. The epoxy resin composition for RTM according to claim 1, which contains 4,4'-methylenebis(isopropyl-6-methylaniline) as Component B.

5. The epoxy resin composition for RTM according to claim 1, which contains 75 to 100 parts by mass of Component B in 100 parts by mass of the curing agent component.

6. The epoxy resin composition for RTM according to claim 1, further contains 1 to 10 parts by mass of core-shell rubber particles as Component D when the epoxy resin is 100 parts by mass.

7. The epoxy resin composition for RTM according to claim 1, the mass reduction rate when heated at 150 °C for 30 minutes is 3.0% by mass or less.

8. The viscosity of the epoxy resin composition for RTM after holding the epoxy resin composition for RTM at temperature T1 for 30 minutes is denoted as η30, and the Tg of the epoxy resin composition for RTM after holding it at temperature T1 for 120 minutes is denoted as Tg 120 When there is a temperature range of T1 that satisfies both Formula 1 and Formula 2 and is more than 5 °C η 30 ≤ 100 cps formula 1 Tg 120 ≥ T1 formula 2.

9. The epoxy resin composition for RTM according to claim 8, the maximum temperature satisfying the formula 1 is 165 °C or higher.

10. A resin cured product, which is obtained by curing the epoxy resin composition for RTM according to claim 1.

11. A fiber reinforced composite material, which is composed of the resin cured product according to claim 10 and a reinforcing fiber base material.

12. The fiber reinforced composite material according to claim 11, the reinforcing fiber base material is a carbon fiber base material.

13. A method for manufacturing a fiber reinforced composite material, injecting the epoxy resin composition for RTM according to claim 1 into a reinforcing fiber base material disposed in a mold heated to 70 °C or higher and 190 °C or lower, impregnating it, and curing it in the mold.

14. The method for manufacturing a fiber reinforced composite material according to claim 13, the reinforcing fiber base material is a carbon fiber base material.

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