EPOXY RESIN COMPOSITION, PREPREG, AND FIBER-REINFORCED COMPOSITE MATERIAL

Abstract

The purpose of the present invention is to provide: an epoxy resin composition capable of giving cured resins which combine flexural modulus with flexural strain on a high level and have excellent heat resistance; a prepreg comprising the epoxy resin composition and reinforcing fibers; and a fiber-reinforced composite material obtained by curing the prepreg and excellent especially in terms of 0° and 90° bending strength. An embodiment of the epoxy resin composition of the present invention for achieving such purpose is an epoxy resin composition which comprises the following components [A], [B], and [C] and satisfies a specific requirement. Component [A]: a trifunctional amine type epoxy resin. Component [B]: a bisphenol F type epoxy resin which is solid at 25° C. Component [C]: an aromatic amine compound.

Claims

1. An epoxy resin composition comprising: a component [A] being a trifunctional amine type epoxy resin; a component [B] being a bisphenol F type epoxy resin being solid at 25° C.; and a component [C] being an aromatic amine compound, wherein all of a condition 1, a condition 2, and a condition 3 described below are satisfied, the condition 1 being that a resin cured product produced by reacting the epoxy resin composition at 180° C. for 120 minutes has a flexural modulus of 4.4 GPa or more, the condition 2 being that the resin cured product produced by reacting the epoxy resin composition at 180° C. for 120 minutes has a bending strength of 190 MPa or more, and the condition 3 being that an average epoxy equivalent of the component [A] (Ea) and an average epoxy equivalent of the component [B] (Eb) satisfy Formula (1) described below:
6≤Eb/Ea≤10  (1).

2. An epoxy resin composition comprising: a component [A] being a trifunctional amine type epoxy resin; a component [B] being a bisphenol F type epoxy resin being solid at 25° C.; and a component [C] being an aromatic amine compound, wherein all of a condition 4, a condition 5, and a condition 6 described below are satisfied, the condition 4 being that a resin cured product produced by reacting the epoxy resin composition at 180° C. for 120 minutes has a bending strain amount of 6% or more, the condition 5 being that an average epoxy equivalent of the component [B] is 600 to 1,000 g/eq, and the condition 6 being that the resin cured product produced by reacting the epoxy resin composition at 180° C. for 120 minutes has a glass transition temperature X (° C.) and a storage elastic modulus in a rubber state Y (MPa), the glass transition temperature and the storage elastic modulus determined by dynamic viscoelasticity measurement and satisfying Formula (2) described below:
0.087X−6≤Y≤≤0.087X−4  (2).

3. An epoxy resin composition comprising: a component [A] being a trifunctional amine type epoxy resin; a component [B] being a bisphenol F type epoxy resin being solid at 25° C.; and a component [C] being an aromatic amine compound, wherein a condition 5 and a condition 7 described below are satisfied, the condition 5 being that an average epoxy equivalent of the component [B] is 600 to 1,000 g/eq, and the condition 7 being that a resin cured product produced by reacting the epoxy resin composition at 180° C. for 120 minutes has a storage elastic modulus in a rubber state Y (MPa) determined by dynamic viscoelasticity measurement and has an active group mole number in 100 parts by mass of all epoxy resins (Ma), the storage elastic modulus and the active group mole number satisfying Formula (3) described below:
1,100≤Y/Ma≤2,000  (3).

4. The epoxy resin composition according to claim 1, wherein all of a condition 4, a condition 5, and a condition 6 described below are satisfied, the condition 4 being that the resin cured product produced by reacting the epoxy resin composition at 180° C. for 120 minutes has a bending strain amount of 6% or more, the condition 5 being that the average epoxy equivalent of the component [B] is 600 to 1,000 g/eq, and the condition 6 being that the resin cured product produced by reacting the epoxy resin composition at 180° C. for 120 minutes has a glass transition temperature X (° C.) and a storage elastic modulus in a rubber state Y (MPa), the glass transition temperature and the storage elastic modulus determined by dynamic viscoelasticity measurement and satisfying Formula (2) described below:
0.087X−6≤Y≤0.087X−4  (2).

5. The epoxy resin composition according to claim 1, wherein a condition 5 and a condition 7 described below are satisfied, the condition 5 being that the average epoxy equivalent of the component [B] is 600 to 1,000 g/eq, and the condition 7 being that the resin cured product produced by reacting the epoxy resin composition at 180° C. for 120 minutes has a storage elastic modulus in a rubber state Y (MPa) determined by dynamic viscoelasticity measurement and has an active group mole number in 100 parts by mass of all epoxy resins (Ma), the storage elastic modulus and the active group mole number satisfying Formula (3) described below:
1,100≤Y/Ma≤2,000  (3).

6. The epoxy resin composition according to claim 4, wherein a condition 7 described below is satisfied, the condition 7 being that the resin cured product produced by reacting the epoxy resin composition at 180° C. for 120 minutes has the storage elastic modulus in a rubber state Y (MPa) determined by dynamic viscoelasticity measurement and has an active group mole number in 100 parts by mass of all epoxy resins (Ma), the storage elastic modulus and the active group mole number satisfying Formula (3) described below:
1,100≤Y/Ma≤2,000  (3).

7. An epoxy resin composition comprising: a component [A] being a trifunctional amine type epoxy resin; a component [E] being a sorbitol type epoxy resin; and a component [F] being dicyandiamide or a derivative of dicyandiamide, wherein all of a condition 8, a condition 9, and a condition 10 described below are satisfied, the condition 8 being that a resin cured product produced by reacting the epoxy resin composition at 130° C. for 90 minutes has a flexural modulus of 4.3 GPa or more, the condition 9 being that the resin cured product produced by reacting the epoxy resin composition at 130° C. for 90 minutes has a bending strength of 190 MPa or more, and the condition 10 being that the epoxy resin composition includes the component [A] and the component [E] at a total content of 40 parts by mass or more based on 100 parts by mass of all epoxy resins in the epoxy resin composition.

8. The epoxy resin composition according to claim 1, wherein the component [A] is an aminophenol type epoxy resin.

9. The epoxy resin composition according to claim 1, wherein the component [A] is included at a content of 50 to 80 parts by mass based on 100 parts by mass of all the epoxy resins.

10. The epoxy resin composition according to claim 1, wherein the component [B] is included at a content of 20 to 40 parts by mass based on 100 parts by mass of all the epoxy resins.

11. The epoxy resin composition according to claim 1, wherein the component [C] is 3,3′-diaminodiphenylsulfone.

12. The epoxy resin composition according to claim 7, wherein the component [E] is included at a content of 20 to 40 parts by mass based on 100 parts by mass of all the epoxy resins.

13. The epoxy resin composition according to claim 7, wherein a component [D]-1 and/or a component [D]-2 described below is included as a component [D], the component [D]-1 being a naphthalene type epoxy resin and the component [D]-2 being an isocyanuric acid type epoxy resin.

14. The epoxy resin composition according to claim 7, wherein a thermoplastic resin is included as a component [H].

15. The epoxy resin composition according to claim 14, wherein the thermoplastic resin is polyether sulfone.

16. A prepreg comprising: the epoxy resin composition according to claim 1; and a reinforcing fiber.

17. A fiber-reinforced composite material comprising the prepreg according to claim 16 that is cured.

18. The epoxy resin composition according to claim 2, wherein the component [A] is an aminophenol type epoxy resin.

19. The epoxy resin composition according to claim 3, wherein the component [A] is an aminophenol type epoxy resin.

20. The epoxy resin composition according to claim 4, wherein the component [A] is an aminophenol type epoxy resin.

Description

EXAMPLES

[0154] Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to the description in Examples.

[0155] The components used in Examples are as follows.

[0156] <Material Used> [0157] Component [A]: trifunctional amine type epoxy resin

[0158] Component [A]-1 “Araldite (registered trademark)” MY0500 (aminophenol type epoxy resin, manufactured by Huntsman Advanced Materials LLC.),

[0159] Component [A]-2 “Araldite (registered trademark)” MY0600 (aminophenol type epoxy resin, manufactured by Huntsman Advanced Materials LLC.). [0160] Component [B]: bisphenol F type epoxy resin being solid at 25° C.

[0161] Component [B]-1 “Epotohto (registered trademark)” YDF-2001 (manufactured by Tohto Kasei Co., Ltd.),

[0162] Component [B]-2 “jER (registered trademark)” 4004P (manufactured by Mitsubishi Chemical Corporation),

[0163] Component [B]-3 “Epotohto (registered trademark)” YDF-2004 (manufactured by Tohto Kasei Co., Ltd.),

[0164] Component [B]-4 “Epotohto (registered trademark)” YDF-2005RD (manufactured by Tohto Kasei Co., Ltd.),

[0165] Component [B]-5 “jER (registered trademark)” 4007P (manufactured by Mitsubishi Chemical Corporation),

[0166] Component [B]-6 “jER (registered trademark)” 4010P (manufactured by Mitsubishi Chemical Corporation). [0167] Component [C]: aromatic amine compound

[0168] Component [C]-1 SEIKACURE-S (4,4′-diaminodiphenylsulfone, manufactured by SEIKA CORPORATION),

[0169] Component [C]-2 3,3′DAS (3,3′-diaminodiphenylsulfone, manufactured by Mitsui Fine Chemicals, Inc.),

[0170] Component [C]-3 “Lonzacure (registered trademark)” M-MIPA (4,4′-methylenebis(2-isopropyl-6-methylaniline), manufactured by Lonza),

[0171] Component [C]-4 “jERCURE (registered trademark)” W (diethyltoluenediamine, manufactured by Mitsubishi Chemical Corporation). [0172] Component [D]-1: naphthalene type epoxy resin

[0173] “EPICLON” HP-4032D (manufactured by DIC Corporation). [0174] Component [D]-2: isocyanuric acid type epoxy resin

[0175] “TEPIC”-S (manufactured by Nissan Chemical Corporation). [0176] Component [E]: sorbitol type epoxy resin

[0177] “DENACOL (registered trademark)” EX-614B (manufactured by Nagase ChemteX Corporation). [0178] Component [F]: dicyandiamide or its derivative

[0179] DICY7 (manufactured by Mitsubishi Chemical Corporation). [0180] Component [G]: another epoxy resin

[0181] Component [G]-1 GAN (diglycidylaniline type epoxy resin, manufactured by Nippon Kayaku Co., Ltd.),

[0182] Component [G]-2 “SUMI-EPDXY (registered trademark)” ELM434 (diaminodiphenylmethane type epoxy resin, manufactured by SUMITOMO CHEMICAL COMPANY, LIMITED),

[0183] Component [G]-3 TG3DAS (diaminodiphenylsulfone type epoxy resin, manufactured by Konishi Chemical Ind. Co., Ltd.),

[0184] Component [G]-4 “jER (registered trademark)” 828 (bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation),

[0185] Component [G]-5 “jER (registered trademark)” 1001 (bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation),

[0186] Component [G]-6 “jER (registered trademark)” 1004 (bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation),

[0187] Component [G]-7 “jER (registered trademark)” 154 (phenol novolac type epoxy resin, manufactured by Mitsubishi Chemical Corporation),

[0188] Component [G]-8 “EPICLON (registered trademark)” 830 (bisphenol F type epoxy resin, manufactured by Dainippon Ink and Chemicals, Incorporated),

[0189] Component [G]-9 “EPICLON (registered trademark)” 807 (bisphenol F type epoxy resin, manufactured by Dainippon Ink and Chemicals, Incorporated),

[0190] Component [G]-10 NER-7604 (polyfunctional bisphenol F type epoxy resin, manufactured by Nippon Kayaku Co., Ltd.),

[0191] Component [G]-11 EHPE-3150 (solid alicyclic epoxy resin, manufactured by Daicel Corporation),

[0192] Component [G]-12 AER-4152 (oxazolidone ring type epoxy resin, manufactured by Asahi Kasei E-Materials Corporation). [0193] Component [H]: thermoplastic resin

[0194] Component [H]-1 “VINYLEC (registered trademark)” K (polyvinyl formal, manufactured by JNC CORPORATION),

[0195] Component [H]-2 “VINYLEC (registered trademark)” E (polyvinyl formal, manufactured by JNC CORPORATION),

[0196] Component [H]-3 “SUMIKAEXCEL (registered trademark)” PES2603P (polyether sulfone, manufactured by SUMITOMO CHEMICAL COMPANY, LIMITED),

[0197] Component [H]-4 “SUMIKAEXCEL (registered trademark)” PES5003P (polyether sulfone, manufactured by SUMITOMO CHEMICAL COMPANY, LIMITED),

[0198] Component [H]-5 “Virantage (registered trademark)” VW-10700RFP (polyether sulfone, manufactured by Solvay). [0199] Component [I]: curing accelerator

[0200] DCMU99 (3-(3,4-dichlorophenyl)-1,1-dimethylurea, manufactured by Hodogaya Chemical Co., Ltd.).

[0201] <Method of Measuring Average Epoxy Equivalent of Epoxy Resin>

[0202] A component [A] or a component [B] was weighed so as to be about 300 mg and put into a glass beaker, and 10 mL of chloroform was further added. The mixture was stirred with a magnetic stirrer until the weighed component was dissolved in the chloroform. To the resulting solution, 20 mL of acetic acid was added, then 10 mL of tetraethylammonium bromide-acetic acid solution (0.4 g/mL acetic acid) was added, and the mixture was stirred. An electrode was immersed in the resulting solution, potentiometric titration was performed with a perchloric acid-acetic acid standard solution (0.1 mol/L), and the average epoxy equivalents of the component [A] and the component [B] were calculated in accordance with JIS K7236 (2001). The average epoxy equivalents are as shown in Tables 1, 2, 6, and 7. Note that in the present description, the word “Table 1” refers to Table 1-1 and Table 1-2. The same applies to the words “Table 2”, “Table 6”, and “Table 7”.

[0203] <Method of Preparing Epoxy Resin Composition>

[0204] Into a kneader, predetermined amounts of components were put other than a component [C] aromatic amine compound, a component [F] another curing agent, and a component [I] curing accelerator, the temperature was raised to 60 to 150° C., and the mixture was appropriately kneaded until the components were compatible. That is, the temperature was raised to a temperature at which the components were compatible depending on the composition in each of Examples and Comparative Examples, and as a result, it was possible to make the components compatible at a temperature in the range of 60 to 150° C. concerning all the compositions. The temperature was lowered to 60° C., then the component [C], or the component [F] and the component [I] were added, and the mixture was kneaded at 60° C. for 30 minutes to obtain an epoxy resin composition. The epoxy resin composition is as shown in Tables 1 to 8.

[0205] <Method of Evaluating Bending Characteristic of Epoxy Resin Cured Product>

[0206] An uncured resin composition was degassed in vacuum and then cured at a temperature of 180° C. or 130° C. depending on the kind of the curing agent for 2 hours in a mold that was set to have a thickness of 2 mm with a 2 mm thick “Teflon (registered trademark)” spacer to obtain a plate-shaped resin cured product having a thickness of 2 mm. In the case of using a curing agent that is not used in Examples and Comparative Examples, the curing temperature is appropriately selected from temperatures higher than the temperature at which the exothermic peak appears in the differential scanning calorimetry. From the resin cured product, a test piece having a width of 10 mm and a length of 60 mm was cut out, three-point bending was performed using an Instron universal testing machine (manufactured by Instron) with a span of 32 mm at a crosshead speed of 10 mm/min in accordance with JIS K7171 (1994), and the flexural modulus, the bending strain, and the bending strength were measured. At this time, the values measured for the number of the samples n=6 were employed as the values of the flexural modulus, the bending strain, and the bending strength.

[0207] <Method of Evaluating Glass Transition Temperature and Storage Elastic Modulus of Epoxy Resin Cured Product>

[0208] An uncured resin composition was degassed in vacuum and then cured at a temperature of 180° C. or 130° C. depending on the kind of the curing agent for 2 hours in a mold that was set to have a thickness of 2 mm with a 2 mm thick “Teflon (registered trademark)” spacer to obtain a plate-shaped resin cured product having a thickness of 2 mm. In the case of using a curing agent that is not used in Examples and Comparative Examples, the curing temperature is appropriately selected from temperatures higher than the temperature at which the exothermic peak appears in the differential scanning calorimetry. From the resin cured product, a test piece having a width of 12.7 mm and a length of 45 mm was cut out, and measurement was performed using a dynamic viscoelasticity measurement device (ARES W/FCO: manufactured by TA Instruments) with the test piece that was set on a solid twisting jig at a temperature rise rate of 5° C./min, a frequency of 1 Hz, and a strain amount of 0.08% in a temperature range of 40 to 260° C. At this time, in the obtained graph of the storage elastic modulus and the temperature, the temperature at the intersection of the tangent line drawn in the glass state and the tangent line drawn in the glass transition temperature region was regarded as the glass transition temperature. In the obtained graph of the storage elastic modulus and the temperature, the storage elastic modulus at a temperature higher than the glass transition temperature by 50° C. was regarded as the storage elastic modulus in a rubber state.

[0209] <Method of Preparing Prepreg>

[0210] The epoxy resin composition obtained in accordance with <Method of Preparing Epoxy Resin Composition> described above was applied to release paper using a knife coater to prepare two resin films having a predetermined basis weight. The basis weight of the resin film was adjusted to be 39 g/m2. Next, the obtained two resin films were stacked on both faces of the carbon fiber “TORAYCA (registered trademark)” T700S-12K-60E (manufactured by Toray Industries, Inc., basis weight: 150 g/m.sup.2) arranged in one direction in a sheet shape, the resulting product was heated under pressure at a temperature of 110° C. and a pressure of 2 MPa to impregnate the carbon fiber with the epoxy resin composition, and a unidirectional prepreg was obtained. The fiber mass content of the obtained prepreg was 67%.

[0211] <Method of Measuring Composite Property>

[0212] (1) Bending Strength in 0° Direction of CFRP

[0213] The fiber directions of the unidirectional prepregs prepared by <Method of Preparing Prepreg> described above were aligned, 13 plies of the unidirectional prepregs were stacked and molded with an autoclave at a temperature of 180° C. or 130° C. for 2 hours under a pressure of 0.6 MPa at a temperature rise rate of 1.7° C./min to prepare a unidirectional CFRP having a thickness of 2 mm. From this laminated plate, a test piece was cut out so as to have a width of 15 mm and a length of 100 mm, and was subjected to three-point bending using an Instron universal testing machine (manufactured by Instron) in accordance with JIS K7017 (1988). Measurement was performed at a crosshead speed of 5.0 mm/min with a span of 80 mm using an indenter having a diameter of 10 mm and supporting points having a diameter of 4 mm to measure the bending strength. The bending strength in the 0° direction was measured for 6 samples, the measured value was converted into a value at which the fiber mass content was 60% by mass, and the average of the converted values was determined as the bending strength in the 0° direction.

[0214] (2) Bending Strength in 90° Direction of CFRP

[0215] A unidirectional CFRP was prepared in the same manner as in (1) described above. From the obtained unidirectional laminated plate having a thickness of 2 mm, a test piece was cut out so as to have a width of 15 mm and a length of 60 mm, and was subjected to three-point bending using an Instron universal testing machine (manufactured by Instron) in accordance with JIS K7017 (1988). Measurement was performed at a crosshead speed of 1.0 ram/min with a span of 40 mm using an indenter having a diameter of 10 mm and supporting points having a diameter of 4 mm to measure the bending strength. The bending strength in the 90° direction was measured for 6 samples, the measured value was converted into a value at which the fiber mass content was 60% by mass, and the average of the converted values was determined as the bending strength in the 90° direction.

[0216] (3) Method of Evaluating Interlaminar Toughness Value G.sub.1c

[0217] The fiber directions of the unidirectional prepregs prepared by <Method of Preparing Prepreg> described above were aligned, 13 plies of the unidirectional prepregs were stacked, and 2 pairs of laminated bodies were prepared. “TOYOFLON (registered trademark)” E (manufactured by Toray Industries, Inc.) was sandwiched between the laminated bodies along the fiber direction for 40 mm from the end portion, and the resulting product was molded with an autoclave at a temperature of 180° C. or 130° C. for 2 hours under a pressure of 0.6 MPa at a temperature rise rate of 1.7° C./min to prepare a unidirectional CFRP having a thickness of 3 mm. In the case of using a curing agent that is not used in Examples and Comparative Examples, the curing temperature is appropriately selected from temperatures higher than the temperature at which the exothermic peak appears in the differential scanning calorimetry. From the laminated plate, a test piece was cut out so as to have a width of 20 mm and a length of 200 mm, an aluminum block was adhered, so as to be perpendicular to the fiber direction, to the end portion where the film was inserted, and a double cantilever beam test was performed using an Instron universal testing machine (manufactured by Instron) in accordance with JIS K7086 (1993). The measurement was performed at a crosshead speed of 1.0 mm/min to measure the fracture toughness value. The fracture toughness value was measured for 6 samples, and the average of the measured values was determined as G.sub.1c.

[0218] (4) Method of Evaluating Interlaminar Toughness Value G.sub.1c

[0219] A CFRP was prepared in the same manner as described in (3) Method of Evaluating G.sub.1c above. From this laminated plate, a test piece was cut out so as to have a width of 20 mm and a length of 400 mm, and was subjected to an end notched flexure test by three-point bending using an Instron universal testing machine (manufactured by Instron) in accordance with JIS K7086 (1993). Measurement was performed at a crosshead speed of 0.5 mm/min with a span of 100 mm using an indenter having a diameter of 10 mm and supporting points having a diameter of 4 mm to measure the fracture toughness value. The fracture toughness value was measured for 6 samples, and the average of the measured values was determined as G.sub.2c.

Example 1

[0220] An epoxy resin composition was prepared in accordance with <Method of Preparing Epoxy Resin Composition> described above using, as an epoxy resin, 10 parts by mass of “Araldite (registered trademark)” MY0500, 45 parts by mass of “Araldite (registered trademark)” MY0600, 18 parts by mass of “Epotohto (registered trademark)” YDF-2004, 10 parts by mass of “SUMI-EPDXY (registered trademark)” ELM434, and 17 parts by mass of EPICLON (registered trademark) 830, 41.5 parts by mass of SEIKACURE-S as an aromatic amine compound, and 5.0 parts by mass of “VINYLEC (registered trademark)” K as a thermoplastic resin.

[0221] The average epoxy equivalents of the component [A] and the component [B] were measured in accordance with <Method of Measuring Average Epoxy Equivalent of Epoxy Resin>, and as a result, the average epoxy equivalent of the component [A] was 117 g/eq and that of the component [B] was 980 g/eq. The value of average epoxy equivalent of component [B]/average epoxy equivalent of component [A] shown in Formula (1) was 8.4.

[0222] Using this epoxy resin composition, the bending characteristics of the epoxy resin cured product were obtained. The epoxy resin cured product was cured at 180° C. in accordance with <Method of Evaluating Bending Characteristic of Epoxy Resin Cured Product>. As a result, the flexural modulus was 4.7 GPa, the bending strength was 205 MPa, and the bending strain amount was 6.9%.

[0223] The glass transition temperature and the storage elastic modulus in a rubber state were measured in accordance with <Method of Evaluating Glass Transition Temperature and Storage Elastic Modulus of Epoxy Resin Cured Product>, and as a result, the glass transition temperature was 175° C., and the storage elastic modulus in a rubber state was 10.0 MPa. In the relationship between the glass transition temperature (X) and the storage elastic modulus in a rubber state (Y) shown in Formula (2) (Formula (2): 0.087X−6≤Y≤0.087X−4), X=175° C., and therefore, 9.2≤Y≤11.2, so that the storage elastic modulus in a rubber state of the epoxy resin cured product satisfied the range shown in Formula (2).

[0224] The storage elastic modulus in a rubber state was measured in accordance with <Method of Evaluating Glass Transition Temperature and Storage Elastic Modulus of Epoxy Resin Cured Product>, and as a result, the storage elastic modulus in a rubber state was 10.0 MPa, and the ratio of the storage elastic modulus in a rubber state (Y) to the active epoxy group mole number in 100 parts by mass of all the epoxy resins (Ma) (Y/Ma) shown in Formula (3) was 1,489.

[0225] From the obtained epoxy resin composition, a prepreg having a fiber mass content of 67% by mass was prepared in accordance with <Method of Preparing Prepreg>, and 13 plies of the obtained prepregs were stacked and cured at 180° C. to prepare a unidirectional fiber-reinforced composite material (CFRP).

[0226] The mechanical properties of the CFRP were measured, and the results were good that the bending strength in the 0° direction was 1,810 MPa and the bending strength in the 90° direction was 132 MPa.

[0227] The interlaminar toughness of the CFRP was evaluated, and as a result, G.sub.1c showed a good value of 520 J/m.sup.2 and G.sub.2c showed a good value of 610 J/m.sup.2.

Examples 2 to 15

[0228] An epoxy resin composition, a prepreg, a resin cured product, and a CFRP were prepared in the same manner as in Example 1 except that the resin composition was changed as shown in Tables 1 and 2, and the bending characteristics of the resin cured product, average epoxy equivalent of component [B]/average epoxy equivalent of component [A] (Formula (1)), the relationship between the glass transition temperature and the storage elastic modulus in a rubber state (Formula (2)), and the relationship 1100≤Y/Ma≤2000 (Formula (3)) were obtained. As a result, all of Formulae (1) to (3) were satisfied.

[0229] The bending characteristics and the CFRP properties of the epoxy resin composition in each Example were evaluated, and as a result, good physical properties were obtained at all levels.

Examples 16 to 38

[0230] An epoxy resin composition and a prepreg were prepared in the same manner as in Example 1 except that the resin composition was changed as shown in Tables 3 to 5. An epoxy resin cured product was obtained by curing at 130° C. in accordance with <Method of Evaluating Bending Characteristic of Epoxy Resin Cured Product> described above, and a CFRP was obtained in accordance with <Method of Evaluating Composite Property> described above.

[0231] The bending characteristics and the CFRP properties of the epoxy resin composition in each Example were evaluated, and as a result, good physical properties were obtained at all levels.

Comparative Example 1

[0232] Using the resin composition shown in Table 6-1, an epoxy resin composition and a prepreg were prepared in the same manner as in Example 1.

[0233] The value in Formula (1) was 20.1, and the bending characteristics of the epoxy resin cured product were obtained. The epoxy resin cured product was cured at 130° C. in accordance with <Method of Evaluating Bending Characteristic of Epoxy Resin Cured Product>. As a result, the flexural modulus of the resin cured product was 4.5 GPa, and the bending strength was as low as 180 MPa.

[0234] The glass transition temperature and the storage elastic modulus in a rubber state were obtained in the same manner as in Example 1. The relationship shown in Formula (2) was examined using this epoxy resin cured product. As a result, Formula (2) was not satisfied, the glass transition temperature was 93° C., and the bending strain amount was as low as 4.3%. Furthermore, the relationship shown in Formula (3) was examined using this epoxy resin cured product, and as a result, Formula (3) was not satisfied.

[0235] From the obtained epoxy resin composition, a prepreg having a fiber mass content of 67% by mass was prepared in accordance with <Method of Preparing Prepreg>, and 13 plies of the obtained prepregs were stacked and cured at 130° C. to prepare a unidirectional fiber-reinforced composite material (CFRP).

[0236] The mechanical properties of the CFRP were measured. As a result, the bending strength in the 0° direction was 1,701 MPa, the bending strength in the 90° direction was 113 MPa, and the bending strength in the 90° direction was low.

[0237] Furthermore, the interlaminar toughness of the CFRP was evaluated, and the results were insufficient that G.sub.1c was 228 J/m.sup.2 and G.sub.2c was 483 J/m.sup.2.

Comparative Examples 2 to 3

[0238] Using the resin composition shown in Table 6-1, an epoxy resin composition, a prepreg, a resin cured product, and a CFRP were prepared in the same manner as in Comparative Example 1, and the bending characteristics of the resin cured product, the relationships shown in Formulae (2) and (3), and the properties of the CFRP were obtained. Each epoxy resin composition includes no component [B]. Because each resin cured product did not satisfy the relationships shown in Formulae (2) and (3), the resin cured product had low flexural modulus and insufficient heat resistance. Furthermore, the bending characteristics and the interlaminar toughness value of the CFRP were insufficient.

Comparative Example 4

[0239] Using the resin composition shown in Table 6-2, an epoxy resin composition, a prepreg, a resin cured product, and a CFRP were prepared in the same manner as in Comparative Example 1, and the bending characteristics of the resin cured product, the relationships shown in Formulae (2) and (3), and the properties of the CFRP were obtained. The epoxy resin composition includes no component [B]. The resin cured product did not satisfy the relationships shown in Formulae (2) and (3), and the glass transition temperature was 170° C. The flexural modulus was as low as 3.7 GPa, the bending strain amount was as low as 5.8%, and the bending strength was as low as 181 MPa. The bending strength in the 0° direction and the 90° direction and the interlaminar toughness value of the CFRP were also low.

Comparative Example 5

[0240] Using the resin composition shown in Table 6-2, an epoxy resin composition, a prepreg, a resin cured product, and a CFRP were prepared in the same manner as in Comparative Example 1, and the bending characteristics of the resin cured product, the relationships shown in Formulae (2) and (3), and the properties of the CFRP were obtained. The epoxy resin composition includes no component [B], and includes 40 parts by mass of bisphenol F being liquid at 25° C. The resin cured product did not satisfy the relationships shown in Formulae (2) and (3), and the flexural modulus, the bending strain amount, and the bending strength were insufficient. Furthermore, the bending strength in the 90° direction of the CFRP was as low as 98 MPa, and the interlaminar toughness value was also insufficient.

Comparative Example 6

[0241] Using the resin composition shown in Table 6-2, an epoxy resin composition, a prepreg, a resin cured product, and a CFRP were prepared in the same manner as in Comparative Example 1, and the bending characteristics of the resin cured product, the relationships shown in Formulae (2) and (3), and the properties of the CFRP were obtained. In the epoxy resin composition, the average epoxy equivalent of the component [B] is 2,273 g/eq, and the resin cured product does not satisfy the relationships shown in Formulae (2) and (3). The flexural modulus of the resin cured product was 4.5 GPa, and the bending strength was as low as 180 MPa, so that the CFRP had an insufficient bending strength in the 90° direction of 89 MPa.

[0242] Furthermore, the interlaminar toughness of the CFRP was evaluated, and the results were insufficient that G.sub.1c was 199 J/m.sup.2 and G.sub.2c was 365 J/m.sup.2.

Comparative Example 7

[0243] Using the resin composition shown in Table 7-1, an epoxy resin composition, a prepreg, a resin cured product, and a CFRP were prepared in the same manner as in Comparative Example 1, and the bending characteristics of the resin cured product, the relationships shown in Formulae (2) and (3), and the properties of the CFRP were obtained. In the epoxy resin composition, the average epoxy equivalent of the component [B] was 4,190 g/eq, and the resin cured product did not satisfy Formulae (2) and (3). Therefore, the bending strain amount was low, and the bending strength in the 0° direction and the 90° direction and the interlaminar toughness value of the CFRP were insufficient.

Comparative Example 8

[0244] Using the resin composition shown in Table 7-1, an epoxy resin composition, a prepreg, a resin cured product, and a CFRP were prepared in the same manner as in Comparative Example 1, and the bending characteristics of the resin cured product, the relationships shown in Formulae (2) and (3), and the properties of the CFRP were obtained. In the epoxy resin composition, the average epoxy equivalent of the component [B] was 480 g/eq, the resin cured product did not satisfy Formulae (2) and (3), the flexural modulus was insufficient, and the bending strength in the 0° direction and the 90° direction and the interlaminar toughness value of the CFRP were also low. The heat resistance was also insufficient.

Comparative Example 9

[0245] Using the resin composition shown in Table 7-1, an epoxy resin composition, a prepreg, a resin cured product, and a CFRP were prepared in the same manner as in Comparative Example 1, and the bending characteristics of the resin cured product, the relationships shown in Formulae (2) and (3), and the properties of the CFRP were obtained. The epoxy resin composition includes no component [B], and includes 40 parts by mass of a bisphenol A type epoxy resin being solid at 25° C. The resin cured product did not satisfy the relationships shown in Formulae (2) and (3), and had a high glass transition temperature of 180° C. and a low flexural modulus of 4.0 GPa. The bending strength in the 0° direction and the 90° direction and the interlaminar toughness value of the CFRP were also insufficient.

Comparative Example 10

[0246] Using the resin composition shown in Table 7-2, an epoxy resin composition, a prepreg, a resin cured product, and a CFRP were prepared in the same manner as in Comparative Example 1, and the bending characteristics of the resin cured product, the relationships shown in Formulae (2) and (3), and the properties of the CFRP were obtained. The epoxy resin composition includes no component [B], and includes 30 parts by mass of a bisphenol A type epoxy resin being solid at 25° C. The resin cured product did not satisfy Formulae (2) and (3), and did not satisfy Formula (1). The flexural modulus and the bending strength were low. The bending strength and the interlaminar toughness value of the CFRP were also insufficient.

Comparative Example 11

[0247] Using the resin composition shown in Table 7-2, an epoxy resin composition, a prepreg, a resin cured product, and a CFRP were prepared in the same manner as in Comparative Example 1, and the bending characteristics of the resin cured product, the relationships shown in Formulae (2) and (3), and the properties of the CFRP were obtained. The epoxy resin composition includes no component [A], and includes 60 parts by mass of ELM434 being a tetrafunctional glycidyl amine type epoxy resin. The resin cured product did not satisfy the relationships shown in Formulae (1) and (2), and had a high glass transition temperature of 190° C., a low flexural modulus of 4.0 GPa, and a low bending strength of 160 MPa. The bending strength and the interlaminar toughness value of the CFRP were also insufficient.

Comparative Examples 12 and 13

[0248] Using the resin composition shown in Table 8, a resin cured product and a CFRP were prepared in the same manner as in Example 16, and the bending characteristics were evaluated.

[0249] Because no component [E] was included in Comparative Example 12, the flexural modulus and the strain were insufficient, and the bending strength was also insufficient.

[0250] In Comparative Example 13, no component [A] was included, and the flexural modulus was insufficient. As a result, the bending strength was also insufficient. The physical properties in the 0° direction and the 90° direction of the CFRP were also low.

Comparative Example 14

[0251] Using the resin composition shown in Table 8, a resin cured product and a CFRP were prepared in the same manner as in Example 16, and the bending characteristics were evaluated. In the resin composition, the total content of the component [A] and the component [E] was less than 40 parts by mass, and both the flexural modulus and the strain were insufficient, so that the bending strength was insufficient. The bending characteristics of the CFRP were also insufficient.

Comparative Example 15

[0252] Using the resin composition shown in Table 8, a resin cured product and a CFRP were prepared in the same manner as in Example 16, and the bending characteristics were evaluated. Both the flexural modulus and the strain were insufficient, so that the bending strength was insufficient. The bending characteristics of the CFRP were also insufficient.

Comparative Example 16

[0253] Using the resin composition shown in Table 8, a resin cured product and a CFRP were prepared in the same manner as in Example 16, and the bending characteristics were evaluated. The balance between the flexural modulus and the strain was poor, and the bending strength was insufficient. The bending characteristics of the CFRP were also insufficient.

TABLE-US-00001 TABLE 1-1 Exam- Exam- Exam- Exam- Component ple 1 ple 2 ple 3 ple 4 Component [A] “Araldite ®”MY0500 Aminophenol type epoxy resin 10 trifunctional amine “Araldite ®”MY0600 45 55 60 65 type epoxy resin Component [B] “jER ®”4004P Bisphenol F type epoxy resin bisphenol F type “Epotohto ®”YDF2004 18 18 22 22 epoxy resin being solid at 25° C. Component [G] GAN Difunctional glycidyl amine type 8 5 another epoxy resin epoxy resin “SUMI-EPOXY ®”ELM434 Tetrafunctional glycidyl amine 10 TG3DAS type epoxy resin “EPICLON ®”830 Bisphenol F type epoxy resin 17 27 10 8 Component [D]-2 “TEPIC ®”-S Isocyanuric acid type epoxy resin isocyanuric acid type epoxy resin Component [C] SEIKACURE-S 4,4′-diaminodiphenylsulfone 41.5 aromatic amine 3,3′-DAS 3,3′-diaminodiphenylsulfone 40 40.5 41 compound “Lonzacure ®”M-MIPA 4,4′-methylenebis(2-isopropyl-6- methylaniline) Component [H] “VINYLEC ®”K Polyvinyl formal 5 5 5 5 thermoplastic resin “SUMIKAEXCEL ®”PES5003P Polyether sulfone Average epoxy equivalent of component [B] (g/eq) 980 980 980 980 Average epoxy equivalent of component [A] (g/eq) 117 118 118 118 Formula (1): average epoxy equivalent of component [B]/average epoxy equivalent of 8.4 8.3 8.3 8.3 component [A] (Eb/Ea) Active group mole number in epoxy resin/active hydrogen mole number of component 1.00 1.00 1.00 1.00 [C] (Ma/Mc) Resin cured product Glass transition temperature (° C.): X 175 175 170 172 properties Storage elastic modulus in rubber state (MPa): Y 10.0 10.5 10.0 10.1 Formula (2): 0.087X − 6 ≤ Y ≤ 0.087X − 4 9.2 ≤ 9.2 ≤ 8.8 ≤ 9.0 ≤ Y ≤ 11.2 Y ≤ 11.2 Y ≤ 10.8 Y ≤ 11.0 Formula (3): Storage elastic modulus in rubber state/ 1489 1627 1529 1529 active group mole number in epoxy resin (Y/Ma) Flexural modulus (GPa) 4.7 4.9 5.0 5.2 Bending strength (MPa) 205 215 225 230 Bending strain (%) 6.9 7.0 7.1 7.2 Composite properties Bending strength in 0° direction (MPa) 1810 1871 1860 1920 Bending strength in 90° direction (MPa) 132 162 153 157 G.sub.1C (J/m.sup.2) 520 547 550 523 G.sub.2C (J/m.sup.2) 610 672 730 670

TABLE-US-00002 TABLE 1-2 Exam- Exam- Exam- Exam- Component ple 5 ple 6 ple 7 ple 8 Component [A] “Araldite ®”MY0500 Aminophenol type epoxy resin 15 15 15 15 trifunctional amine “Araldite ®”MY0600 30 30 30 30 type epoxy resin Component [B] “jER ®”4004P Bisphenol F type epoxy resin 18 bisphenol F type “Epotohto ®”YDF2004 18 18 18 epoxy resin being solid at 25° C. Component [G] GAN Difunctional glycidyl amine type 7 another epoxy resin epoxy resin “SUMI-EPOXY ®”ELM434 Tetrafunctional glycidyl amine TG3DAS type epoxy resin 10 10 10 10 “EPICLON ®”830 Bisphenol F type epoxy resin 22 22 20 22 Component [D]-2 “TEPIC ®”-S Isocyanuric acid type epoxy resin 5 5 5 isocyanuric acid type epoxy resin Component [C] SEIKACURE-S 4,4′-diaminodiphenylsulfone aromatic amine 3,3′-DAS 3,3′-diaminodiphenylsulfone compound “Lonzacure ®”M-MIPA 4,4′-methylenebis(2-isopropyl-6- 55 48 51 27.5 methylaniline) Component [H] “VINYLEC ®”K Polyvinyl formal thermoplastic resin “SUMIKAEXCEL ®”PES5003P Polyether sulfone 4 4 4 4 Average epoxy equivalent of component [B] (g/eq) 980 980 850 980 Average epoxy equivalent of component [A] (g/eq) 116 116 116 116 Formula (1): average epoxy equivalent of component [B]/average epoxy equivalent of 8.4 8.4 7.3 8.4 component [A] (Eb/Ea) Active group mole number in epoxy resin/active hydrogen mole number of component 0.93 1.07 1.00 1.07 [C] (Ma/Mc) Resin cured product Glass transition temperature (° C.): X 157 150 169 150 properties Storage elastic modulus in rubber state (MPa): Y 8.0 7.4 9.4 7.3 Formula (2): 0.087X − 6 ≤ Y ≤ 0.087X − 4 7.7 ≤ 7.1 ≤ 8.7 ≤ 7.1 ≤ Y ≤ 9.7 Y ≤ 9.1 Y ≤ 10.7 Y ≤ 9.1 Formula (3): Storage elastic modulus in rubber state/ 1213 1122 1432 1107 active group mole number in epoxy resin (Y/Ma) Flexural modulus (GPa) 4.4 4.5 4.5 4.5 Bending strength (MPa) 196 193 205 195 Bending strain (%) 6.1 6.0 6.7 6.1 Composite properties Bending strength in 0° direction (MPa) 1750 1727 1781 1790 Bending strength in 90° direction (MPa) 131 133 130 127 G.sub.1C (J/m.sup.2) 512 497 510 495 G.sub.2C (J/m.sup.2) 597 581 607 590

TABLE-US-00003 TABLE 2-1 Exam- Exam- Exam- Exam- Component ple 9 ple 10 ple 11 ple 12 Component [A] “Araldite ®”MY0500 Aminophenol type epoxy resin 15 15 15 15 trifunctional amine “Araldite ®”MY0600 30 30 30 30 type epoxy resin Component [B] “jER ®”4004P Bisphenol F type epoxy resin 18 18 18 bisphenol F type “Epotohto ®”YDF2004 18 epoxy resin being solid at 25° C. Component [G] GAN Difunctional glycidyl amine type 7 7 7 another epoxy resin epoxy resin TG3DAS Tetrafunctional glycidyl amine 10 10 10 10 type epoxy resin “EPICLON ®”830 Bisphenol F type epoxy resin 20 20 20 22 Component [D]-2 “TEPIC ®”-S Isocyanuric acid type epoxy resin 5 isocyanuric acid type epoxy resin Component [C] SEIKACURE-S 4,4′-diaminodiphenylsulfone 37.0 45.0 41.0 aromatic amine 3,3′-DAS 3,3′-diaminodiphenylsulfone compound “jER ®”CURE W Diethyltoluenediamine 29.2 Component [H] “VINYLEC ®”K Polyvinyl formal thermoplastic resin “SUMIKAEXCEL ®”PES5003P Polyether sulfone 4 4 4 4 Average epoxy equivalent of component [B] (g/eq) 850 850 850 980 Average epoxy equivalent of component [A] (g/eq) 116 116 116 116 Formula (1): average epoxy equivalent of component [B]/average epoxy equivalent of 7.3 7.3 7.3 8.4 component [A] (Eb/Ea) Active group mole number in epoxy resin/active hydrogen mole number of component 1.00 1.10 0.90 1.00 [C] (Ma/Mc) Resin cured product Glass transition temperature (° C.): X 157 155 167 175 properties Storage elastic modulus in rubber state (MPa): Y 9.0 7.6 8.7 10.5 Formula (2): 0.087X − 6 ≤ Y ≤ 0.087X − 4 7.7 ≤ 7.5 ≤ 8.5 ≤ 9.2 ≤ Y ≤ 9.7 Y ≤ 9.5 Y ≤ 10.5 Y ≤ 11.2 Formula (3): Storage elastic modulus in rubber state/ 1371 1158 1326 1593 active group mole number in epoxy resin (Y/Ma) Flexural modulus (GPa) 4.5 4.7 4.4 4.5 Bending strength (MPa) 200 198 195 208 Bending strain (%) 6.4 6.0 6.1 6.9 Composite properties Bending strength in 0° direction (MPa) 1775 1801 1760 1780 Bending strength in 90° direction (MPa) 131 135 125 139 G.sub.1C (J/m.sup.2) 513 520 510 541 G.sub.2C (J/m.sup.2) 618 640 622 630

TABLE-US-00004 TABLE 2-2 Exam- Exam- Exam- Component ple 13 ple 14 ple 15 Component [A] “Araldite ®”MY0500 Aminophenol type epoxy resin trifunctional amine “Araldite ®”MY0600 80 40 20 type epoxy resin Component [B] “jER ®”4004P Bisphenol F type epoxy resin 40 25 bisohenol F type “Epotohto ®”YDF2004 10 epoxy resin being solid at 25° C. Component [G] GAN Difunctional glycidyl amine 20 5 another epoxy resin type epoxy resin TG3DAS Tetrafunctional glycidyl amine type epoxy resin “EPICLON ®”830 Bisphenol F type epoxy resin 10 20 Component [D]-2 “TEPIC ®”-S Isocyanuric acid type epoxy resin 25 isocyanuric acid type epoxy resin Component [C] SEIKACURE-S 4,4′-diaminodiphenylsulfone 31.0 aromatic amine 3,3′-DAS 3,3′-diaminodiphenylsulfone 46.5 37 compound “jER ®”CURE W Diethyltoluenediamine Component [H] “VINYLEC ®”K Polyvinyl formal 5 5 thermoplastic resin “SUMIKAEXCEL ®”PES5003P Polyether sulfone 4 Average epoxy equivalent of component [B] (g/eq) 980 850 850 Average epoxy equivalent of component [A] (g/eq) 118 118 118 Formula (1): average epoxy equivalent of component [B]/average epoxy equivalent of 8.3 7.2 7.2 component [A] (Eb/Ea) Active group mole number in epoxy resin/active hydrogen mole number of component 1.00 1.09 1.01 [C] (Ma/Mc) Resin cured product Glass transition temperature (° C.): X 173 140 185 properties Storage elastic modulus in rubber state (MPa): Y 9.2 6.3 11.9 Formula (2): 0.087X − 6 ≤ Y ≤ 0.087X − 4 9.1 ≤ Y ≤ 11.1 6.2 ≤ Y ≤ 8.2 10.1 ≤ Y ≤ 12.1 Formula (3): Storage elastic modulus in rubber state/ 1230 1156 1966 active group mole number in epoxy resin (Y/Ma) Flexural modulus (GPa) 5.1 4.5 4.5 Bending strength (MPa) 200 194 194 Bending strain (%) 6.0 6.0 6.1 Composite properties Bending strength in 0° direction (MPa) 1900 1760 1782 Bending strength in 90° direction (MPa) 135 133 127 G.sub.1C (J/m.sup.2) 510 528 529 G.sub.2C (J/m.sup.2) 642 600 613

TABLE-US-00005 TABLE 3 Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Component ple 16 ple 17 ple 18 ple 19 ple 20 ple 21 ple 22 ple 23 Component [A] “Araldite ®”MY0500 Aminophenol type 40 50 trifunctional amine “Araldite ®”MY0600 epoxy resin 30 70 50 50 40 50 type epoxy resin Component [E] “DENACOL ®”EX-614B Sorbitol type 10 10 10 10 35 35 50 50 sorbitol type epoxy epoxy resin resin Component [B] “Epotohto ®”YDF2001 Bisphenol F type 15 15 bisphenol F type epoxy resin epoxy resin being “jER ®”4007P 10 10 solid at 25° C. Component [G] “jER ®”828 Bisphenol A type 20 another epoxy resin epoxy resin “EPICLON ®”830 Bisphenol F type 60 20 20 20 epoxy resin “jER ®”154 Phenol novolac 20 type epoxy resin Component [F] DICY7 Dicyandiamide 8.3 10.1 9.0 9.1 7.2 7.4 9.1 8.9 dicyandiamide or its derivative Component [I] DCMU99 Dichloro- 5.4 6.5 6.0 5.9 4.7 4.8 6.0 5.8 curing accelerator dimethylurea Total content of component [A] and component [E] 40 80 60 60 75 75 100 100 Resin cured product Flexural modulus (GPa) 4.3 4.9 4.4 4.5 4.4 4.4 5 4.6 properties Bending strength (MPa) 190 194 195 195 194 196 205 199 Bending strain (%) 6.9 5.0 6.3 6.2 6.7 6.7 6.6 6.7 Glass transition temperature (° C.) 125 153 150 154 131 117 126 136 Composite properties Bending strength in 0° direction (MPa) 1751 1863 1760 1770 1770 1765 1880 1800 Bending strength in 90° direction (MPa) 137 130 133 137 140 141 148 140

TABLE-US-00006 TABLE 4 Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Component ple 24 ple 25 ple 26 ple 27 ple 28 ple 29 ple 30 ple 31 Component [A] “Araldite ®”MY0600 Aminophenol type 50 70 50 50 50 70 80 70 trifunctional amine epoxy resin type epoxy resin Component [E] “DENACOL ®”EX-614B Sorbitol type 25 20 40 40 40 10 10 20 sorbitol type epoxy epoxy resin resin Component [D]-1 “EPICLON ®”HP-4032D Naphthalene type 20 10 naphthalene type epoxy resin epoxy resin Component [D]-2 “TEPIC ®”-S Isocyanuric acid 10 isocyanuric acid type epoxy resin type epoxy resin Component [B] “Epotohto ®”YDF2001 Bisphenol F type 10 bisphenol F type epoxy resin epoxy resin being solid at 25° C. Component [G] “EPICLON ®”830 Bisphenol F type 25 10 10 another epoxy resin epoxy resin “jER ®”154 Phenol novolac 10 type epoxy resin Component [F] DICY7 Dicyandiamide 9.1 10.0 9.1 8.7 9.1 10.3 11.0 10.2 dicyandiamide or its derivative Component [I] DCMU99 Dichloro- 6.0 6.5 6.0 5.7 5.9 6.7 7.1 6.6 curing accelerator dimethylurea Total content of component [A] and component [E] 75 90 90 90 90 80 90 90 Resin cured product Flexural modulus (GPa) 4.8 5.0 4.9 4.9 4.9 5.0 5.4 5.1 properties Bending strength (MPa) 203 203 201 205 199 192 194 210 Bending strain (%) 6.3 5.7 5.9 6.0 6.0 5.4 5.0 6.0 Glass transition temperature (° C.) 124 147 129 124 133 162 175 155 Composite properties Bending strength in 0° direction (MPa) 1862 1900 1887 1890 1880 1910 2050 1910 Bending strength in 90° direction (MPa) 142 143 140 141 137 135 140 147

TABLE-US-00007 TABLE 5 Exam- Exam- Exam- Exam- Exam- Exam- Exam- Component ple 32 ple 33 ple 34 ple 35 ple 36 ple 37 ple 38 Component [A] “Araldite ®”MY0500 Aminophenol type 50 trifunctional amine “Araldite ®”MY0600 epoxy resin 50 60 50 50 50 60 type epoxy resin Component [E] “DENACOL  ®”EX-614B Sorbitol type 25 20 40 25 25 25 40 sorbitol type epoxy epoxy resin resin Component [D]-1 “EPICLON ®”HP-4032D Naphthalene type 25 10 25 25 25 naphthalene type epoxy resin epoxy resin Component [D]-2 “TEPIC ®”-S Isocyanuric acid 20 isocyanuric acid type epoxy resin type epoxy resin Component [F] DICY7 Dicyandiamide 9.5 10.6 9.3 9.3 9.5 9.5 9.5 dicyandiamide or its derivative Component [H] “SUMIKAEXCEL ®”PES2603P Polyether sulfone 20 20 thermoplastic resin “VINYLEC ®”K Polyvinyl formal 10 Component [I] DCMU99 Dichloro- 6.2 6.9 6.1 6.1 6.2 6.2 6.2 curing accelerator dimethylurea Total content of component [A] and component [E] 75 80 90 75 75 75 100 Resin cured product Flexural modulus (GPa) 4.9 5.4 4.9 4.7 4.3 4.8 5.0 properties Bending strength (MPa) 225 208 222 213 195 203 195 Bending strain (%) 6.5 5.0 6.4 6.5 6.0 6.6 6.0 Glass transition temperature (° C.) 145 171 136 153 141 144 136 Composite properties Bending strength in 0° direction (MPa) 1880 1910 1893 1850 1790 1870 1904 Bending strength in 90° direction (MPa) 143 140 137 135 141 158 151

TABLE-US-00008 TABLE 6-1 Compar- Compar- Compar- ative ative ative Exam- Exam- Exam- Component ple 1 ple 2 ple 3 Component [A] “Araldite ®”MY0500 Aminophenol type epoxy resin 50 trifuncticnal amine “Araldite ®”MY0600 15 type epoxy resin Component [B] “jER ®”4007P Bisphenol F type epoxy resin 30 bisphenol F type epoxy resin being solid at 25° C. Component [G] “jER ®”828 Bisphenol A type epoxy resin 10 46 another epoxy resin “jER ®”1001 45 “EPICLON ®”830 Bisphenol F type epoxy resin 20 10 NER-7604 Polyfunctional bisphenol 25 type epoxy resin EHPE3150 Alicyclic epoxy resin 25 AER4152 Oxazolidone ring type 15 9 epoxy resin Component [C] SEIKACURE-S 4,4′′-diaminodiphenylsulfone aromatic amine 3,3′-DAS 3,3′-diaminodiphenylsulfone compound Component [H] “VINYLEC ®”K Polyvinyl formal 2 1 thermoplastic resin “VINYLEC ®”E Polyvinyl formal 3 “Virantage ®”VW- Polyether sulfone 10700RFP Component [F] DICY7 Dicyandiamide 6.2 10 5 dicyandiamide or its derivative Component [I] DCMU99 Dichlorodimethylurea 2 7 1.5 curing accelerator Average epoxy equivalent of component [B] (g/eq) 2273 0 0 Average epoxy equivalent of component [A] (g/eq) 113 118 0 Formula (1): average epoxy equivalent of component [B/average epoxy equivalent of 20.1 0.0 0.0 component [A] (Eb/Ea) Active group mole number in epoxy resin/active hydrogen mole number of component 1.11 0.58 0.86 [C] (Ma/Mc) Resin cured product Glass transition temperature (° C.): X 93 140 128 properties Storage elastic modulus in rubber state (MPa): Y 5.9 4.9 9.0 Formula (2): 0.087X − 6 ≤ Y ≤ 0.087X − 4 2.1 ≤ Y ≤ 4.1 6.2 ≤ Y ≤ 8.2 5.1 ≤ Y ≤ 7.1 Formula (3): Storage elastic modulus in rubber state/ 1027 1007 2502 active group mole number in epoxy resin (Y/Ma) Flexural modulus (GPa) 4.5 4.1 3.0 Bending strength (MPa) 180 180 131 Bending strain (%) 4.3 7.4 7.0 Composite properties Bending strength in 0° direction (MPa) 1701 1615 1420 Bending strength in 90° direction (MPa) 113 101 112 G.sub.1C (J/m.sup.2) 228 270 227 G.sub.2C (J/m.sup.2) 483 428 354

TABLE-US-00009 TABLE 6-2 Compar- Compar- Compar- ative ative ative Exam- Exam- Exam- Component ple 4 ple 5 ple 6 Component [A] “Araldite ®”MY0500 Aminophenol type epoxy resin trifuncticnal amine “Araldite ®”MY0600 100 60 50 type epoxy resin Component [B] “jER ®”4007P Bisphenol F type epoxy resin 30 bisphenol F type epoxy resin being solid at 25° C. Component [G] “jER ®”828 Bisphenol A type epoxy resin another epoxy resin “jER ®”1001 “EPICLON ®”830 Bisphenol F type epoxy resin 40 20 NER-7604 Polyfunctional bisphenol type epoxy resin EHPE3150 Alicyclic epoxy resin AER4152 Cxazolidone ring type epoxy resin Component [C] SEIKACURE-S 4,4′-diaminodiphenylsulfone 88 aromatic amine 3,3′-DAS 3,3′-diaminodiphenylsulfone 54.5 34.5 compound Component [H] “VINYLEC ®”K Polyvinyl formal 4 thermoplastic resin “VINYLEC ®”E Polyvinyl formal “Virantage ®”VW- Polyether sulfone 19 10700RFP Component [F] DICY7 Dicyandiamide dicyandiamide or its derivative Component [I] DCMU99 Dichlorodimethylurea curing accelerator Average epoxy equivalent of component [B] (g/eq) 0 0 2273 Average epoxy equivalent of component [A] (g/eq) 118 118 118 Formula (1): average epoxy equivalent of component [B]/average epoxy equivalent of 0.0 0.0 19.3 component [A] (Eb/Ea) Active group mole number in epoxy resin/active hydrogen mole number of component 0.96 0.53 1.00 [C] (Ma/Mc) Resin cured product Glass transition temperature (° C.): X 170 182 158 properties Storage elastic modulus in rubber state (MPa): Y 8.0 7.1 5.5 Formula (2): 0.087X − 6 ≤ Y ≤ 0.087X − 4 8.8 ≤ Y ≤ 10.8 3.8 ≤ Y ≤ 11.8 7.7 ≤ Y ≤ 9.7 Formula (3): Storage elastic modulus in rubber state/ 944 951 989 active group mole number in epoxy resin (Y/Ma) Flexural modulus (GPa) 3.7 4.3 4.5 Bending strength (MPa) 181 181 180 Bending strain (%) 5.8 5.8 5.0 Composite properties Bending strength in 0° direction (MPa) 1510 1675 1667 Bending strength in 90° direction (MPa) 107 98 89 G.sub.1C (J/m.sup.2) 242 218 199 G.sub.2C (J/m.sup.2) 421 312 365

TABLE-US-00010 TABLE 7-1 Compar- Compar- Compar- ative ative ative Exam- Exam- Exam- Component ple 7 ple 8 ple 9 Component [A] “Araldite ®”MY0500 Aminophenol type epoxy resin 10 trifuncticnal amine “Araldite ®”MY0600 50 50 50 type epoxy resin Component [B] “Epotohto ®”YDF2001 Bisphenol F type epoxy resin 30 bisphenol F type “Epotohto ®”YDF2004 epoxy resin being “jER ®”4010P 30 solid at 25° C. Component [G] “SUMI-EPOXY ®”ELM434 Tetrafunctional glycidyl another epoxy resin amine type epoxy resin “jER ®”1001 Bisphenol A type epoxy resin “jER ®”1004 40 “EPICLON ®”830 Bisphenol F type epoxy resin 20 20 Component [C] SEIKACURE-S 4,4′-diaminodiphenylsulfone 34.5 aromatic amine 3,3′-DAS 3,3′-diaminodiphenylsulfone 34 37.4 compound Component [H] “VINYLEC ®”K Polyvinyl formal 2 1 4 thermoplastic resin “SUMIKAEXCEL ®”PES5003P Polyether sulfone Average epoxy equivalent of component [B] (g/eq) 4190 480 0 Average epoxy equivalent of component [A] (g/eq) 118 118 117 Formula (1): average epoxy equivalent of component [B]/average epoxy equivalent of 35.5 4.1 0.0 component [A] (Eb/Ea) Active group mole number in epoxy resin/active hydrogen mole number of component 1.00 1.00 1.00 [C] (Ma/Mc) Resin cured product Glass transition temperature (° C.): X 160 143 180 properties Storage elastic modulus in rubber state (MPa): Y 5.9 5.7 14.3 Formula (2): 0.087X − 6 ≤ Y ≤ 0.087X − 4 7.9 ≤ Y ≤ 9.9 6.4 ≤ Y ≤ 8.4 9.7 ≤ Y ≤ 11.7 Formula (3): Storage elastic modulus in rubber state/ 1073 942 2574 active group mole number in epoxy resin (Y/Ma) Flexural modulus (GPa) 4.4 4.3 4.0 Bending strength (MPa) 175 180 170 Bending strain (%) 4.7 5.1 4.7 Composite properties Bending strength in 0° direction (MPa) 1670 1665 1550 Bending strength in 90° direction (MPa) 90 97 89 G.sub.1C (J/m.sup.2) 230 220 240 G.sub.2C (J/m.sup.2) 460 476 466

TABLE-US-00011 TABLE 7-2 Compar- Compar- ative ative Exam- Exam- Component ple 10 ple 11 Component [A] “Araldite ®”MY0500 Aminophenol type epoxy resin 10 trifuncticnal amine “Araldite ®”MY0600 50 type epoxy resin Component [B] “Epotohto ®”YDF2001 Bisphenol F type epoxy resin bisphenol F type “Epotohto ®”YDF2004 30 epoxy resin being “jER ®”4010P solid at 25° C. Component [G] “SUMI-EPOXY ®”ELM434 Tetrafunctional glycidyl 60 another epoxy amine type epoxy resin resin “jER ®”1001 Bisphenol A type epoxy resin 30 “jER ®”1004 “EPICLON ®”830 Bisphenol F type epoxy resin 10 10 Component [C] SEIKACURE-S 4,4′-diaminodiphenylsulione 38 aromatic amine 3,3′-DAS 3,3′-diaminodiphenylsulfone 40 compound Component [H] “VINYLEC ®”K Polyvinyl formal 5 thermoplastic “SUMIKAEXCEL ®”PES5003P Polyether sulfone 8 resin Average epoxy equivalent of component [B] (g/eq) 0 0 Average epoxy equivalent of component [A] (g/eq) 117 0 Formula (1): average epoxy equivalent of component [B]/average epoxy equivalent of 0.0 0.0 component [A] (Eb/Ea) Active group mole number in epoxy resin/active hydrogen mole number of component 0.98 0.95 [C] (Ma/Mc) Resin cured product Glass transition temperature (° C.): X 175 190 properties Storage elastic modulus in rubber state (MPa): Y 15.3 15.6 Formula (2): 0.087X − 6 ≤ Y ≤ 0.087X − 4 9.2 ≤ Y ≤ 11.2 10.5 ≤ Y ≤ 12.5 Formula (3): Storage elastic modulus in rubber state/ 2411 2681 active group mole number in epoxy resin (Y/Ma) Flexural modulus (GPa) 4.2 4.0 Bending strength (MPa) 170 160 Bending strain (%) 4.9 4.2 Composite properties Bending strength in 0° direction (MPa) 1590 1531 Bending strength in 90° direction (MPa) 88 85 G.sub.1C (J/m.sup.2) 235 240 G.sub.2C (J/m.sup.2) 455 460

TABLE-US-00012 TABLE 8 Compar- Compar- Compar- Compar- Compar- ative ative ative ative ative Exam- Exam- Exam- Exam- Exam- Component ple 12 ple 13 ple 14 ple 15 ple 16 Component [A] “Araldite ®”MY0500 Aminophenol type 50 trifunctional amine “Araldite ®”MY0600 epoxy resin 40 20 type epoxy resin Component [E] “DENACOL ®”EX-614B Sorbitol type 40 15 sorbitol type epoxy resin epoxy resin Component [B] “jER ®”4007P Bisphenol F type 30 bisphenol F type epoxy resin epoxy resin being solid at 25° C. Component [G] “jER ®”828 Bisphenol A type 10 another epoxy resin “jER ®”1002 epoxy resin 12 “EPICLON ®”830 Bisphenol F type 60 60 65 20 “jER ®”807 epoxy resin 16 NER-7604 Polyfunctional bisphenol type epoxy resin EHPE3150 Alicyclic epoxy resin AER4152 Oxazolidone 45 ring type epoxy resin GOT N,N′-diglycidyl- 3 o-toluidine Component [F] DICY7 Dicyandiamide 8.7 7.0 7.8 5.0 6.3 dicyandiamide or its derivative Component [H] “VINYLEC ®”E Polyvinyl formal thermoplastic YP-70 Bisphenol A/ 4 resin bisphenol F copolymerization type phenoxy resin Component [I] DCMU99 Dichloro- 5.8 4.5 5.1 3.0 2.0 curing dimethylurea accelerator Total content of component [A] and component [E] 40 40 35 — 50 Resin cured product Flexural modulus (GPa) 4.2 3.8 4.0 3.4 4.5 properties Bending strength (MPa) 170 163 170 161 178 Bending strain (%) 5.4 6.6 6.2 7.0 4.5 Glass transition temperature (° C.) 133 95 115 141 133 Composite properties Bending strength in 0° direction (MPa) 1613 1589 1593 1670 1820 Bending strength in 90° direction (MPa) 91 100 94 102 85

[0254] The unit of each component in Tables is parts by mass.

INDUSTRIAL APPLICABILITY

[0255] The epoxy resin composition according to the present invention achieves both the high elastic modulus and the high bending strain at a high level, and provides a resin cured product having excellent heat resistance, so that the fiber-reinforced composite material in which the epoxy resin composition is used has excellent bending strength in the 0° direction and excellent bending strength in the 90° direction. As a result, the weight of the fiber-reinforced composite material can be reduced, therefore, the degree of freedom in structural design is increased, and it is expected that the possibility of application to various structures is expanded.