EPOXY RESIN COMPOSITION, MOLDING MATERIAL FOR FIBER-REINFORCED COMPOSITE MATERIAL, AND FIBER-REINFORCED COMPOSITE MATERIAL

Abstract

The purposes of the present invention are: to provide an epoxy resin composition having excellent impregnation into reinforcing fibers, excellent shapability under low-temperature conditions after thickening, and excellent heat resistance after curing; to provide a molding material for a fiber-reinforced composite material, said molding material having excellent shapability during handling and excellent fluidity during press molding; and to provide a fiber-reinforced composite material having excellent heat resistance and bending strength. To achieve the abovementioned purposes, the present invention provides an epoxy resin composition containing all of the following components (A)-(D), wherein: the content of the component (A), in terms of 100 mass % of the total mass of the epoxy resin composition, is 30-95 mass %; and the ratio Wc/Wd of the content We of the component (C) to the content Wd of the component (D) is 0.01-10. Component (A) is an epoxy resin; component (B) is a curing agent; component (C) is a diisocyanate compound having consecutive double bonds, an alicyclic structure or a heterocyclic structure; and component (D) is a polyisocyanate compound excluding the component (C).

Claims

1. An epoxy resin composition comprising all of the following components (A) to (D): component (A): an epoxy resin; component (B): a hardener; component (C): a diisocyanate compound having consecutive double bonds, an alicyclic structure, or heterocyclic structure; and component (D): a polyisocyanate compound excluding the component (C), wherein a content of the component (A) is 30% by mass or more and 95% by mass or less per 100% by mass of a total mass of the epoxy resin composition, and a ratio Wc/Wd of a content We of the component (C) to a content Wd of the component (D) is 0.01 or more and 10 or less.

2. The epoxy resin composition according to claim 1, wherein a viscosity at 30? C. of the component (C) is 10 mPa.Math.s or more and 1,000 mPa.Math.s or less.

3. The epoxy resin composition according to claim 1, wherein the component (C) has, in a molecule, the following chemical structure: C?C?C or N?C?N.

4. The epoxy resin composition according to claim 1, wherein the component (C) has a linear structure.

5. The epoxy resin composition according to claim 1, wherein the component (D) is a polyisocyanate compound having 3 or more and 10 or less isocyanate groups in one molecule.

6. The epoxy resin composition according to claim 1, wherein both the component (C) and the component (D) are aromatic isocyanate compounds.

7. The epoxy resin composition according to claim 1, further comprising the following component (E): component (E): at least one compound selected from the group consisting of a quaternary ammonium salt, a phosphonium salt, an imidazole compound, and a phosphine compound.

8. The epoxy resin composition according to claim 1, wherein a reaction onset temperature is 5? C. or higher and 80? C. or lower.

9. The epoxy resin composition according to claim 1, wherein a thickened resin obtained by holding the epoxy resin composition at 40? C. for 24 hours has a viscosity at 30? C. of 100 Pa.Math.s or more and 30,000 Pa.Math.s or less, and the thickened resin has a viscosity at 130? C. of 1 Pa.Math.s or more and 100 Pa.Math.s or less.

10. The epoxy resin composition according to claim 1, wherein the component (A) is a hydroxy-containing epoxy resin that is liquid at 30? C.

11. The epoxy resin composition according to claim 1, wherein the component (B) is dicyandiamide or a derivative of dicyandiamide.

12. A molding material for a fiber-reinforced composite material, the molding material comprising the epoxy resin composition according to claim 1 and a reinforcing fiber.

13. The molding material for a fiber-reinforced composite material according to claim 12, wherein the reinforcing fiber is a carbon fiber.

14. A fiber-reinforced composite material comprising a cured product of the molding material for a fiber-reinforced composite material according to claim 12.

Description

EXAMPLES

[0081] Hereinafter, the epoxy resin composition, the molding material for a fiber-reinforced composite material, and the fiber-reinforced composite material of the present invention will be described in more detail with reference to examples.

<Resin Raw Materials>

[0082] The following resin raw materials were used to prepare the epoxy resin compositions of the examples and comparative examples. The numerical value of each component in the column of Epoxy resin composition in the tables indicates the content, and the unit (parts) is parts by mass unless otherwise specified.

1. Component (A): An Epoxy Resin

[0083] Epotohto (registered trademark) YD128 (manufactured by NIPPON STEEL & SUMIKIN CHEMICAL CO., LTD.): Liquid bisphenol A epoxy resin (hydroxyl group equivalent: 1,250 g/mol) [0084] jER (registered trademark) 154 (manufactured by Mitsubishi Chemical Corporation): Phenol novolac epoxy resin (no hydroxyl group) [0085] jER (registered trademark) 1001 (manufactured by Mitsubishi Chemical Corporation): Solid bisphenol A epoxy resin (hydroxyl group equivalent: 313 g/mol) SR-DGE (manufactured by Sakamoto Yakuhin Kogyo Co., Ltd.): Diglycerol epoxy (hydroxyl group equivalent: 435 g/mol) [0086] DENACOL (registered trademark) EX-614 (manufactured by Nagase ChemteX Corporation): Sorbitol epoxy resin (hydroxyl group equivalent: 229 g/mol).

2. Component (B): A Hardener

[0087] jERcure (registered trademark) DICY7 (manufactured by Mitsubishi Chemical Corporation): Dicyandiamide. 3. Component (C): a diisocyanate compound having consecutive double bonds, an alicyclic structure, or heterocyclic structure [0088] Desmodur (registered trademark) N 3400 (manufactured by Sumika Covestro Urethane Co., Ltd.): HDI uretdione [0089] Desmodur (registered trademark) I (manufactured by Sumika Covestro Urethane Co., Ltd.): Isophorone diisocyanate [0090] Desmodur (registered trademark) W (manufactured by Sumika Covestro Urethane Co., Ltd.): Dicyclohexylmethane-4,4-diisocyanate [0091] Lupranate (registered trademark) MM-103 (manufactured by BASF INOAC Polyurethanes Ltd.): Carbodiimide-modified MDI.

4. Component (D): A Polyisocyanate Compound Excluding the Component (C)

[0092] Sumidur (registered trademark) N 3300 (manufactured by Sumika Covestro Urethane Co., Ltd.): HDI isocyanate [0093] Lupranate (registered trademark) M20S (manufactured by BASF INOAC Polyurethanes Ltd.): Polymeric MDI (polymethylene polyphenyl polyisocyanate) [0094] Lupranate (registered trademark) MI (manufactured by BASF INOAC Polyurethanes Ltd.): Monomeric MDI (diphenylmethane diisocyanate) [0095] Lupranate (registered trademark) MP102 (manufactured by BASF INOAC Polyurethanes Ltd.): Urethane-modified MDI [0096] Coronate (registered trademark) T-100 (manufactured by Tosoh Corporation): TDI.
5. Component (E): At Least One Compound Selected from the Group Consisting of a Quaternary Ammonium Salt, a Phosphonium Salt, an Imidazole Compound, and a Phosphine Compound [0097] Tetrabutylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) [0098] Tetraphenylphosphonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.).

<Preparation of Epoxy Resin Compositions>

[0099] Epoxy resin compositions were prepared by mixing the components with the contents (parts by mass) shown in the tables.

<Measurement of Viscosity of Epoxy Resin Compositions Immediately after Preparation>

[0100] The specimen to be measured, while being held at 30? C., was subjected to the measurement according to JIS 28803 (1991), Viscosity measurement method using circular cone-flat plate type rotary viscometer using an E-type viscometer equipped with a standard cone rotor (1?34?R24). The E-type viscometer used was TVE-30H manufactured by TOKIMEC INC. The specimen used was an epoxy resin composition immediately after preparation.

<Measurement of Reaction Onset Temperature of Epoxy Resin Compositions Immediately after Preparation>

[0101] The specimen to be measured was used to measure the change in the calorific value of the epoxy resin composition when the temperature was changed at intervals of 10? C. in a temperature range of 20? C. to 130? C. and kept constant at each temperature stage. The measurement was performed using a differential calorimeter DSC 25 manufactured by TA. In the obtained exothermic curve, temperatures at which the maximum calorific value was kept for 5 minutes or shorter were determined. The lowest temperature among the temperatures was defined as the reaction onset temperature.

<Measurement of Shapability at 10? C. of Epoxy Resin Compositions after Thickening>

[0102] The specimen to be measured was shaped by hand according to a hat-shaped mold and then left for 5 minutes. At this time, the specimen that had its form maintained without being peeled off from the mold for more than 5 minutes was referred to as A, the specimen that had its form maintained without being peeled off from the mold for 1 minute or more and 5 minutes or less was referred to as B, and the specimen that had its form maintained without being peeled off from the mold for less than 1 minute, the specimen that fractured, or the specimen that failed to retain its shape was referred to as C. Herein, as the hat shape, an aluminum mold having a total length of 300 mm, a total height of 40 mm, a top surface width of 40 mm, a flange width of 22 mm, and a radius of a curvature portion of 15 mm was used.

<Measurement of Viscosity of Epoxy Resin Compositions after Thickening>

[0103] Using a DMA (ARES manufactured by TA Instruments), the specimen to be measured was placed on a stage heated to 30? C., and the viscosity of the sample was measured while ramping the temperature at 10? C./min. The specimen used was an epoxy resin composition that was obtained by mixing the components and held at 40? C. for 24 hours. For example, the viscosity at 30? C. refers to the viscosity at the point when the specimen reached 30? C., and the viscosity at each temperature was measured in the same manner.

<Production of Cured Resins>

[0104] Each epoxy resin composition prepared in <Preparation of epoxy resin compositions> was defoamed in a vacuum, and then injected into a mold set to a thickness of 2 mm with a 2-mm thick TEFLON (registered trademark) spacer. The epoxy resin composition was cured at a temperature of 140? C. for 2 hours to give a cured resin having a thickness of 2 mm.

<Measurement of Glass Transition Temperature Tg of Cured Resins>

[0105] A test piece having a width of 12.7 mm and a length of 40 mm was cut out from the cured resin, and Tg was measured using DMA (ARES manufactured by TA Instruments). The measurement conditions included a temperature ramp rate of 5? C./min. The temperature at the inflection point of the storage modulus G obtained in the measurement was defined as Tg.

<Measurement of Bending Strength of Cured Resins>

[0106] The bending strength of the cured resin obtained as described above was measured according to JIS K7074: 1988. 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 a measurement by a 3-point bending test using an Instron universal testing machine (manufactured by Instron). Measurement was performed at a crosshead speed of 5 mm/min with a span of 80 mm using an indenter having a diameter of 5 mm and supporting points having a diameter of 2 mm to measure the bending strength. From measurement values of 5 samples, the converted values were calculated, and the average of the converted values was determined as the bending strength.

<Production of SMCs>

[0107] Torayca (registered trademark) T700S-12K (manufactured by Toray Industries, Inc.) was used as a carbon fiber. The continuous carbon fiber strands were cut at a desired angle, and the bundle assemblies of the carbon fibers were scattered so as to be uniformly dispersed to produce a discontinuous carbon fiber nonwoven fabric having an isotropic fiber orientation. A rotary cutter was used as a cutting device. A distance between blades was 30 mm. A basis weight of the discontinuous carbon fiber nonwoven fabric was 1 kg/m2. The discontinuous carbon fiber nonwoven fabric was sandwiched between polyethylene films coated with the epoxy resin composition so that the weight content of the carbon fiber of SMC to be obtained was 50%, and pressed with a roller to be impregnated with the epoxy resin composition, thereby obtaining a sheet-like SMC precursor. The SMC precursor was held at 40? C. for 24 hours to thicken the resin, thereby obtaining SMC.

<Measurement of Shapability at 10? C. of SMCs>

[0108] The specimen to be measured was shaped by hand according to a hat-shaped mold and then left for 5 minutes. At this time, the specimen that had its form maintained without being peeled off from the mold for more than 5 minutes was referred to as A, the specimen that had its form maintained without being peeled off from the mold for 1 minute or more and 5 minutes or less was referred to as B, and the specimen that had its form maintained without being peeled off from the mold for less than 1 minute, the specimen that fractured, or the specimen that failed to retain its shape was referred to as C. Herein, as the hat shape, an aluminum mold having a total length of 300 mm, a total height of 40 mm, a top surface width of 40 mm, a flange width of 22 mm, and a radius of a curvature portion of 15 mm was used.

Examples 1 to 18

[0109] Resin compositions were prepared according to the preparation of resin compositions described above using the components of the types and contents (parts by mass) shown in Table 1, and the reaction onset temperature and the viscosity at 30? C. were measured. In addition, each epoxy resin composition was held at 40? C. for 24 hours to be thickened, and then the viscosities at 30? C. and 130? C. were measured, and the shapability was measured under the conditions of 10? C. Further, a cured resin of the epoxy resin composition and SMC were produced using the epoxy resin composition before thickening. The reaction onset temperature of the epoxy resin composition immediately after preparation was 80? C. or lower, and the viscosity at 30? C. was 5.0 Pa.Math.s or less. The viscosity at 30? C. after thickening was 100 Pa.Math.s or more, the viscosity at 130? C. after thickening was 1 Pa.Math.s or more and 100 Pa.Math.s or less, the shapability under the conditions of 10? C. was B or more, and the shapability under low temperature conditions was excellent. The cured resin obtained by curing the epoxy resin composition had a Tg of 120? C. or higher and a bending strength of 110 MPa or more. The shapability under the conditions of 10? C. of SMC containing the epoxy resin composition was B or more.

Comparative Example 1

[0110] A resin composition, a cured resin of an epoxy resin composition, and SMC were produced in the same manner as in Examples 1 to 18 except that the components of the types and contents (parts by mass) shown in Table 2 were used, and various measurements were performed. The epoxy resin composition immediately after preparation had a reaction onset temperature of 100? C., which was inadequate, and the viscosity at 30? C. was 5.0 Pa.Math.s or less. The viscosity at 30? C. after thickening was 120 Pa.Math.s, which was good, but the viscosity at 130? C. after thickening was 0.3 Pa.Math.s, which was poor. The shapability under the conditions of 10? C. was C, which indicated that the shapability under low temperature conditions was poor. The cured resin obtained by curing the epoxy resin composition had a Tg of 115? C., which was poor, and had a bending strength of 108 MPa, which indicated that the mechanical properties were poor. The shapability under the conditions of 10? C. of SMC containing the epoxy resin composition was C.

Comparative Example 2

[0111] A resin composition, a cured resin of an epoxy resin composition, and SMC were produced in the same manner as in Examples 1 to 18 except that the components of the types and contents (parts by mass) shown in Table 2 were used, and various measurements were performed. The epoxy resin composition immediately after preparation had a reaction onset temperature of 90? C., which was inadequate, and the viscosity at 30? C. was 5.0 Pa.Math.s or less. The viscosity at 30? C. after thickening was 1,590 Pa.Math.s, which was good, but the viscosity at 130? C. after thickening was 0.7 Pa.Math.s, which was poor. The shapability under the conditions of 10? C. was C, which indicated that the shapability under low temperature conditions was poor. The cured resin obtained by curing the epoxy resin composition had a Tg of 110? C., which was poor, and had a bending strength of 107 MPa, which indicated that the mechanical properties were poor. The shapability under the conditions of 10? C. of SMC containing the epoxy resin composition was C.

Comparative Example 3

[0112] A resin composition, a cured resin of an epoxy resin composition, and SMC were produced in the same manner as in Examples 1 to 18 except that the components of the types and contents (parts by mass) shown in Table 2 were used, and various measurements were performed. The epoxy resin composition immediately after preparation had a reaction onset temperature of 90? C., which was inadequate, and the viscosity at 30? C. was 5.0 Pa.Math.s or less. However, the viscosity at 30? C. and the viscosity at 130? C. after thickening were 0.4 Pa.Math.s and 0.02 Pa s, respectively, both which were poor. The shapability under the conditions of 10? C. was C, which indicated that the shapability under low temperature conditions was poor. The cured resin obtained by curing the epoxy resin composition had a Tg of 106? C., which was poor, and had a bending strength of 80 MPa, which indicated that the mechanical properties were poor. The shapability under the conditions of 10? C. of SMC containing the epoxy resin composition was C.

Comparative Example 4

[0113] A resin composition, a cured resin of an epoxy resin composition, and SMC were produced in the same manner as in Examples 1 to 18 except that the components of the types and contents (parts by mass) shown in Table 2 were used, and various measurements were performed. The epoxy resin composition immediately after preparation had a reaction onset temperature of 130? C., which was inadequate, and the viscosity at 30? C. was 5.0 Pa.Math.s or more, which was inadequate. The viscosity at 30? C. and the viscosity at 130? C. after thickening were 2 Pa.Math.s and 0.01 Pa.Math.s, respectively, both which were poor. The shapability under the conditions of 10? C. was C, which indicated that the shapability under low temperature conditions was poor. The cured resin obtained by curing the epoxy resin composition had a Tg of 80? C., which was poor, and had a bending strength of 87 MPa, which indicated that the mechanical properties were poor. The shapability under the conditions of 10? C. of SMC containing the epoxy resin composition was C.

Comparative Example 5

[0114] A resin composition, a cured resin of an epoxy resin composition, and SMC were produced in the same manner as in Examples 1 to 18 except that the components of the types and contents (parts by mass) shown in Table 2 were used, and various measurements were performed. The epoxy resin composition immediately after preparation had a reaction onset temperature of 80? C., which was good, and the viscosity at 30? C. was 5.0 Pa s or less. The viscosity at 30? C. after thickening was 140 Pa.Math.s, which was good, but the viscosity at 130? C. after thickening was 0.4 Pa.Math.s, which was also poor. The shapability under the conditions of 10? C. was C, which indicated that the shapability under low temperature conditions was poor. The cured resin obtained by curing the epoxy resin composition had a Tg of 117? C., which was poor, and had a bending strength of 109 MPa, which indicated that the mechanical properties were poor. The shapability under the conditions of 10? C. of SMC containing the epoxy resin composition was C.

Comparative Example 6

[0115] A resin composition, a cured resin of an epoxy resin composition, and SMC were produced in the same manner as in Examples 1 to 18 except that the components of the types and contents (parts by mass) shown in Table 2 were used, and various measurements were performed. The epoxy resin composition immediately after preparation had a reaction onset temperature of 100? C., which was inadequate, and the viscosity at 30? C. was 5.0 Pa.Math.s or less. The viscosity at 30? C. and the viscosity at 130? C. after thickening were 80 Pa.Math.s and 0.1 Pa.Math.s, respectively, both which were poor. The shapability under the conditions of 10? C. was C, which indicated that the shapability under low temperature conditions was poor. The cured resin obtained by curing the epoxy resin composition had a Tg of 108? C., which was poor, and had a bending strength of 100 MPa, which indicated that the mechanical properties were poor. The shapability under the conditions of 10? C. of SMC containing the epoxy resin composition was C.

TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Epoxy resin Component YD128 80 60 60 60 60 60 composition (A) 154 20 20 20 20 20 1001 SR-DGE 20 EX-614 20 20 20 20 20 Component DICY7 10 10 10 10 10 10 (B) Component Desmodur N 3400 10 10 (C) Desmodur I 10 Desmodur W 10 MM103 10 10 Component Sumidur N 3300 10 10 10 10 10 (D) M20S 10 MI MP102 T-100 Component Tetrabutylammonium (E) bromide Tetraphenylphosphonium bromide Resin Immediately Reaction onset 80 80 70 70 70 80 composition after temperature (? C.) preparation Viscosity at 30? C. 4.8 4.2 2.1 2.3 2.6 2.0 [Pa .Math. s] After Shapability at 10? C. B B A A A A thickening Viscosity at 30? C. 9400 33000 28000 17000 13000 24000 [Pa .Math. s] Viscosity at 130? C. 11 12 7 18 3 13 [Pa .Math. s] After Glass transition 124 130 123 127 130 135 curing temperature [? C.] Bending strength [MPa] 119 113 118 121 132 134 SMC After Shapability at 10? C. B B B B B B thickening Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Epoxy resin Component YD128 60 60 60 60 60 60 composition (A) 154 20 20 20 20 20 1001 20 SR-DGE EX-614 20 20 20 20 20 20 Component DICY7 10 10 10 10 10 10 (B) Component Desmodur N 3400 (C) Desmodur I Desmodur W MM103 10 10 10 2 18 10 Component Sumidur N 3300 10 (D) M20S 18 2 MI 10 MP102 10 T-100 10 Component Tetrabutylammonium (E) bromide Tetraphenylphosphonium bromide Resin Immediately Reaction onset 70 70 70 80 60 70 composition after temperature (? C.) preparation Viscosity at 30? C. 2.0 2.2 2.1 2.0 1.9 2.6 [Pa .Math. s] After Shapability at 10? C. A A A A A A thickening Viscosity at 30? C. 9200 11000 13000 32000 9800 43000 [Pa .Math. s] Viscosity at 130? C. 1 8 4 23 11 86 [Pa .Math. s] After Glass transition 122 120 124 140 133 130 curing temperature [? C.] Bending strength [MPa] 120 123 117 138 132 132 SMC After Shapability at 10? C. B B B B B A thickening Example 13 Example 14 Example 15 Example 16 Example 17 Example 18 Epoxy resin Component YD128 70 70 70 70 70 70 composition (A) 154 1001 SR-DGE 20 20 20 20 20 20 EX-614 10 10 10 10 10 10 Component DICY7 10 10 10 10 10 10 (B) Component Desmodur N 3400 (C) Desmodur I Desmodur W MM103 10 20 5 25 20 20 Component Sumidur N 3300 (D) M20S 10 5 20 3 5 5 MI MP102 T-100 Component Tetrabutylammonium 3 10 (E) bromide Tetraphenylphosphonium 5 bromide Resin Immediately Reaction onset 60 50 50 40 30 40 composition after temperature (? C.) preparation Viscosity at 30? C. 1.3 1.1 1.8 1.0 1.3 1.2 [Pa .Math. s] After Shapability at 10? C. A A A A A A thickening Viscosity at 30? C. 1500 600 900 820 1200 980 [Pa .Math. s] Viscosity at 130? C. 36 5 14 12 2 3 [Pa .Math. s] After Glass transition 133 130 142 131 123 128 curing temperature [? C.] Bending strength [MPa] 134 136 144 139 131 137 SMC After Shapability at 10? C. A A A A A A thickening

TABLE-US-00002 TABLE 2 Comparative Comparative Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Epoxy resin Component YD128 60 60 10 100 70 70 composition (A) 154 20 20 1001 20 SR-DGE 30 30 EX-614 20 Component DICY7 10 10 10 2 10 10 (B) Component Desmodur N 3400 80 3 (C) Desmodur I Desmodur W MM103 20 Component Sumidur N 3300 (D) M20S MI 20 MP102 20 T-100 20 Component Tetrabutylammonium (E) bromide Tetraphenylphosphonium bromide Resin Immediately Reaction onset 100 90 90 130 80 100 properties after temperature (? C.) preparation Viscosity at 30? C. 2.8 2.5 0.7 6.0 1.1 1.4 [Pa .Math. s] After Shapability at 10? C. C C C C C C thickening Viscosity at 30? C. 120 1590 0.4 2 140 80 [Pa .Math. s] Viscosity at 130? C. 0.3 0.7 0.02 0.01 0.4 0.1 [Pa .Math. s] After Glass transition 115 110 106 80 117 108 curing temperature [? C.] Bending strength [MPa] 108 107 80 87 109 100 SMC After Shapability at 10? C. C C C C C C thickening