JP2012131849A - Epoxy resin composition, epoxy resin cured product, prepreg and fiber-reinforced composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition which is low in viscosity and excellent in impregnation properties into between reinforcing fibers by improving defects of the prior art to form a resin cured product which has both excellent elastic modulus and toughness and also is excellent in toughness in a high-temperature range, and to provide a prepreg and a fiber-reinforced composite material using the epoxy resin composition.SOLUTION: The epoxy resin composition includes: the following epoxy resin [A], epoxy resin [B], epoxy resin [C] and hardener [D] in a predetermined mixing ratio. [A] Bisphenol F-type epoxy resin having a number average molecular weight of 2,000 to 20,000; [B] Trifunctional or more amine type epoxy resin; [C] Bisphenol type epoxy resin having a number average molecular weight of 300 to 500; [D] Dicyandiamide or a derivative thereof.

Description

  The present invention relates to an epoxy resin composition preferably used as a matrix resin of a fiber-reinforced composite material suitable for sports applications and general industrial applications, a prepreg using the same as a matrix resin, and these epoxy resin compositions and prepregs. It is related with the fiber reinforced composite material obtained by this.

  Fiber reinforced composite materials using carbon fibers or aramid fibers as reinforcing fibers make use of their high specific strength and specific elastic modulus to make structural materials such as aircraft and automobiles, sports such as tennis rackets, golf shafts and fishing rods. -Widely used for general industrial purposes.

  In the method of manufacturing the finely reinforced composite material, a prepreg that is a sheet-like intermediate material in which reinforcing fibers are impregnated with an uncured matrix resin is used. A resin transfer molding method, in which a liquid resin is poured into the arranged reinforcing fibers and heat-cured, is used.

  Among these production methods, the method using a prepreg has an advantage that it is easy to obtain a high-performance fiber-reinforced composite material because the orientation of the reinforcing fibers can be strictly controlled and the design freedom of the laminated structure is high. As the matrix resin used for the prepreg, a thermosetting resin is mainly used from the viewpoint of heat resistance and productivity, and an epoxy resin is preferably used from the viewpoint of mechanical properties such as adhesion to reinforcing fibers. .

  The epoxy resin has a higher elastic modulus than the thermoplastic resin, but is inferior in toughness, so that the impact resistance of the fiber-reinforced composite material is insufficient. In addition, there is a problem that defects such as cracks and cracks are likely to occur not only when the fiber reinforced composite material is used but also in a processing process that is exposed to a high temperature environment such as painting or baking.

  Conventionally, as a method for improving the toughness of an epoxy resin, a method in which a rubber component or a thermoplastic resin having excellent toughness is blended to form a phase separation structure with the epoxy resin has been tried. However, these methods have problems such as a decrease in elastic modulus and heat resistance, deterioration in processability due to thickening, and a decrease in quality such as generation of voids. For example, by adding a block copolymer consisting of styrene-butadiene-methyl methacrylate or butadiene-methyl methacrylate, a fine phase separation structure is stably formed in the curing process of the epoxy resin, and the toughness of the epoxy resin is increased. A method of greatly improving is disclosed (Patent Document 1). Furthermore, a method of forming a fine phase separation structure while improving the elastic modulus by blending a specific amine type epoxy is disclosed (Patent Document 2). However, such a high molecular weight thermoplastic resin has a large thickening effect of the epoxy resin, which may deteriorate the processability, and may cause a decrease in the elastic modulus resulting from the blending of the thermoplastic resin. There was a tendency that the balance between rate and toughness was not sufficiently obtained.

  On the other hand, several methods for improving the balance between elastic modulus and toughness that do not rely on rubber components and thermoplastic resins have been proposed. For example, a method of expressing a high elastic modulus by combining a high elastic modulus and high elongation bisphenol F type epoxy resin with an amine type epoxy resin having a high elastic modulus is disclosed (Patent Document 3). However, even in this case, the resin toughness was not sufficient.

  In contrast, a phase separation structure is formed by combining a diglycidyl ether type epoxy resin having a molecular weight of 1500 or more, a diglycidyl ether type epoxy resin having a molecular weight in the range of 500 to 1200, and an amine type epoxy resin. And a method for obtaining a cured resin having an excellent balance between elastic modulus and toughness is disclosed (Patent Document 4). However, in this case, the viscosity of the resin composition is high, the impregnation property to the reinforcing fibers may be insufficient, and the resin toughness in a high temperature environment is insufficient, so that the high temperature environment of about 80 ° C. to 100 ° C. In the exposed processing process, cracks may occur in the fiber-reinforced composite material.

International Publication No. 2006/075153 Pamphlet International Publication No. 2008/143044 Pamphlet JP 2009-074009 A International Publication No. 2009/107697 Pamphlet

  An object of the present invention is to overcome the problems of the prior art, and further, an epoxy resin composition having a low viscosity and excellent impregnation into reinforcing fibers, a high elastic modulus and high toughness, particularly in high temperature toughness. An object of the present invention is to provide an excellent cured epoxy resin, prepreg, and a fiber-reinforced composite material having excellent static strength characteristics and impact resistance, and excellent crack resistance.

  As a result of intensive studies to solve the above problems, the present inventors have found an epoxy resin composition having the following constitution, and have completed the present invention. That is, this invention consists of the following structures.

(I) An epoxy resin composition containing the following [A] to [D] at a blending ratio satisfying the following formulas (1) to (5).
[A] Bisphenol F type epoxy resin having a number average molecular weight in the range of 2000 to 20000 [B] Trifunctional or higher amine type epoxy resin [C] Bisphenol type epoxy resin having a number average molecular weight in the range of 300 to 500 [D ] Dicyandiamide or a derivative thereof 0.2 ≦ A / (A + B + C + E) ≦ 0.6 (1)
0.2 ≦ B / (A + B + C + E) ≦ 0.6 (2)
0.15 ≦ C / (A + B + C + E) ≦ 0.5 (3)
0.01 ≦ D / (A + B + C + E) ≦ 0.1 (4)
0 ≦ E / (A + B + C + E) ≦ 0.2 (5)
(In each formula, A, B, C and D are the masses of [A], [B], [C] and [D], respectively, and E is an epoxy resin other than [A], [B] and [C]. Mass).

(II) The storage elastic modulus G ′ _{75 ° C.} , G ′ _{100 ° C.} , and G ′ _{120 °} C. at 75 ° C., 100 ° C., and 120 ° C. after curing at 130 ° C./2 hours are in the relationship of the following formula. Epoxy resin composition.

1.3 (GPa) ≦ G ′ _{75 ° C.} ≦ 1.8 (GPa) (i)
1.3 ≦ G ′ _{75 °} C./G ′ _{100 ° C.} ≦ 7.0 (ii)
0.08 (GPa) ≦ G ′ _{120 ° C.} ≦ 0.8 (GPa) (iii).

  (III) The epoxy resin composition according to any one of (I) and (II), wherein [B] is a trifunctional aminophenol type epoxy resin.

  (IV) The epoxy resin composition according to any one of (I) to (III), wherein [C] is a bisphenol F-type epoxy resin.

(V) The epoxy resin composition according to any one of (I) to (IV), including the following [F] at a blending ratio that satisfies the following formula (6).
[F] Thermoplastic resin soluble in epoxy resin 0.01 ≦ F / (A + B + C + E) ≦ 0.1 (6)
(In the formula, A, B, C and E are the masses of [A], [B], [C] and [E], respectively, and E is an epoxy resin other than [A], [B] and [C]. mass)
(VI) The epoxy resin composition according to any one of (I) to (V), wherein the complex viscosity at 80 ° C. is in the range of 0.1 to 200 (Pa · s).

  (VII) A cured epoxy resin obtained by curing the epoxy resin composition according to any one of (I) to (VI), wherein the phase-separated structure has at least a [A] rich phase and a [B] rich phase. The epoxy resin hardened | cured material whose structural period is 0.01-5 micrometers.

  (VIII) A prepreg comprising the epoxy resin composition according to any one of (I) to (VI) and a reinforcing fiber.

  (IX) A fiber-reinforced composite material comprising the cured epoxy resin described in (VII) and reinforcing fibers.

  (X) A fiber-reinforced composite material obtained by curing the prepreg described in (IX).

  According to the present invention, it is possible to provide an epoxy resin composition having a low viscosity and excellent impregnation into reinforcing fibers, and a cured epoxy resin product having a high elastic modulus and high toughness, particularly excellent toughness in a high temperature range. Moreover, the fiber-reinforced composite material comprising the cured epoxy resin of the present invention has both excellent static strength characteristics and impact resistance, and can avoid occurrence of cracks in the processing step.

It is a figure which shows an ideal G'-temperature curve.

An embodiment of the present invention is an epoxy resin composition containing the following [A] to [D] at a blending ratio that satisfies the following formulas (1) to (4).
[A] Bisphenol F type epoxy resin having a number average molecular weight in the range of 2000 to 20000 [B] Trifunctional or higher amine type epoxy resin [C] Bisphenol type epoxy resin having a number average molecular weight in the range of 300 to 500 [D ] Epoxy resin curing agent 0.2 ≦ A / (A + B + C + E) ≦ 0.6 (1)
0.2 ≦ B / (A + B + C + E) ≦ 0.6 (2)
0.15 ≦ C / (A + B + C + E) ≦ 0.5 (3)
0.02 ≦ D / (A + B + C + E) ≦ 0.5 (4)
0 ≦ E / (A + B + C + E) ≦ 0.2 (5)
(In each formula, A, B, C and D are the masses of [A], [B], [C] and [D], respectively, and E is an epoxy resin other than [A], [B] and [C]. Mass).

  In such an epoxy resin composition, the above formulas (1) to (5) represent the following. That is, in the epoxy resin composition, as the epoxy resin, [A] bisphenol F type epoxy resin having a number average molecular weight in the range of 2000 to 20000, [B] trifunctional or higher amine type epoxy resin, [C] number average molecular weight It is essential to include a bisphenol-type epoxy resin in the range of 300 to 500, [D] an epoxy resin curing agent, [A], [B], [C] and other epoxy resins [E] (hereinafter referred to as “E”) [A] is 20 to 60 parts by mass, [B] is 20 to 60 parts by mass out of 100 parts by mass of the total epoxy resin, and [C] is 100 parts by mass of the total epoxy resin. It is necessary to include 15 to 40 parts by mass of the part and 1 to 10 parts by mass of [D] out of 100 parts by mass of the total epoxy resin. Moreover, epoxy resin [E] other than [A], [B], and [C] needs to be 20 mass parts or less out of 100 mass parts in all the epoxy resins.

  The inventors of the present invention have the resin composition having the specific content ratio so that the epoxy resin of each of [A] and [B] is a main component in the curing reaction process while exhibiting a homogeneous compatibility state before the curing reaction. A fine phase separation structure is formed, thereby having both the static strength characteristic that is a feature of the [B] component and the impact resistance that is a feature of the [A] component, and a high temperature of about 80 ° C. to 100 ° C. It has been found that a fiber-reinforced composite material with less cracking, that is, excellent in crack resistance can be obtained in a processing step exposed to the environment. This crack resistance is brought about by the fact that the phase containing [A] as a main component ([A] rich phase) is in the rubber region in the high temperature environment of the processing step.

  As an embodiment of the cured resin obtained by curing such an epoxy resin composition, it has a phase separation structure having [A] rich phase and [B] rich phase, and the phase separation structure period is 0.01 to The thing which is 5 micrometers is mentioned, and it becomes possible to make an elastic modulus and toughness compatible by having such a phase-separation structure.

  In the resin composition of the present invention, [A] to [C] are uniformly compatible, but as the molecular weight of both increases during the curing reaction during molding, [A] rich phase and [B] rich A phase structure having the [A] rich phase and the [B] rich phase is formed by so-called reaction-induced phase separation that causes phase separation in the phase. In the present invention, the phase separation structure refers to a structure in which phases mainly composed of different components have a structural period of 0.01 μm or more. On the other hand, the state of being uniformly mixed at the molecular level is referred to as a compatible state, and in the present invention, when the phase mainly composed of different components has a phase separation structure period of less than 0.01 μm, It shall be regarded as a molten state. Whether or not the phase separation structure is exhibited can be determined by an electron microscope, a phase-contrast optical microscope, and various other methods.

  As one preferable embodiment of the cured epoxy resin of the present invention, the cured epoxy resin has a phase separation structure having [A] rich phase and [B] rich phase, and the structural period is 0.01 to 5 μm. Is mentioned. Here, the structural period of phase separation is defined as follows. The phase separation structure includes a two-phase continuous structure and a sea-island structure. In the case of a two-phase continuous structure, a straight line of a predetermined length is drawn on the micrograph, the intersection of the straight line and the phase interface is extracted, the distance between adjacent intersections is measured, and the number average value of these is the structure period And The predetermined length is set as follows based on a micrograph. When the structural period is expected to be on the order of 0.01 μm (0.01 μm or more and less than 0.1 μm), a photograph is taken at a magnification of 20,000 times, and a length of 20 mm randomly on the photograph (a length of 1 μm on the sample) ) Refers to a selection of three. Similarly, if the phase separation structure period is expected to be on the order of 0.1 μm (0.1 μm or more and less than 1 μm), take a picture at a magnification of 2,000 times, If the phase separation structure period is expected to be on the order of 1 μm (1 μm or more and less than 10 μm), the photograph is taken at a magnification of 200 times. In the photograph, three 20 mm lengths (100 μm length on the sample) are selected at random. If the measured phase separation structure period is out of the expected order, the corresponding length is measured again at the magnification corresponding to the corresponding order, and this is adopted. In the case of a sea-island structure, the shortest distance between the island phase and the island phase shall be used even if the island phase is elliptical, indefinite, or a circle or ellipse of two or more layers.

  Another preferable embodiment of the cured epoxy resin of the present invention has a sea-island structure with [A] rich phase and [B] rich phase, and the island phase has a diameter of 0.01 to 5 μm. A certain epoxy resin hardened material is mentioned. Here, the diameter of the island phase indicates the size of the island phase in the sea-island structure, and is a number average value in a predetermined region. When the island phase is elliptical, the major axis is taken, and when it is indefinite, the diameter of the circumscribed circle is used. In the case of a circle or ellipse having two or more layers, the diameter of the outermost layer circle or the major axis of the ellipse is used. In the case of the sea-island structure, the major axis of all island phases existing in a predetermined region is measured, and the number average value thereof is set as the phase separation size.

  Depending on the content ratio of [A] and [B], the structure period may not reflect the quality of the epoxy resin cured product, but the island phase diameter may reflect the properties and may be preferable. Specifically, when the content of [A] is small, the diameter of the island phase tends to reflect the characteristics.

  As described above, when measuring the structural period of the phase separation and the diameter of the island phase, a micrograph of a predetermined region is taken. The predetermined area is set as follows based on a micrograph. When the phase separation structure period is expected to be on the order of 0.01 μm (0.01 μm or more and less than 0.1 μm), a photograph is taken at a magnification of 20,000 times, and an area of 4 mm square on the photograph (0. (2 μm square area) refers to an area selected from three locations. Similarly, when the phase separation structure period is expected to be on the order of 0.1 μm (0.1 μm or more and less than 1 μm), a photograph is taken at a magnification of 2,000 times, and a 4 mm square region (on the sample) (2 μm square area) refers to an area selected from three locations. Similarly, when the phase separation structure period is expected to be on the order of 1 μm (1 μm or more and less than 10 μm), a photograph is taken at a magnification of 200 times, and an area of 4 mm square on the photograph (an area of 20 μm square on the sample) is taken. It shall be said. If the measured phase separation structure period is out of the expected order, the corresponding region is measured again at the magnification corresponding to the corresponding order, and this is adopted.

  The phase separation structure of the cured resin product can be observed with a scanning electron microscope or a transmission electron microscope. You may dye | stain with osmium etc. as needed. Dyeing can be performed by a usual method.

  The structural period and the diameter of the island phase are more preferably in the range of 0.01 to 5 μm, and still more preferably in the range of 0.08 to 1 μm. When the structural period is 0.01 μm or more, the toughness of the cured product at room temperature and high temperature can be sufficiently secured, and when the structural period is 5 μm or less, the fiber-reinforced composite material obtained by using it When the phase separation structure period becomes smaller than the inter-yarn region, and a fiber-reinforced composite material is obtained, a sufficient toughness improving effect can be exhibited.

  The epoxy resin composition of the present invention induces phase separation by blending each component so as to satisfy the above-mentioned conditions, but for embodiments such as the component of the epoxy resin composition of the present invention, This will be described in more detail below.

  As [A] in such an epoxy resin composition, a bisphenol F type epoxy resin having a number average molecular weight in the range of 2000 to 20000 is within a range satisfying the formula (1), that is, 20 to 60 out of 100 parts by mass of all epoxy resins. It is necessary to contain a mass part, and it is preferable to contain 25-50 mass parts among 100 mass parts of all the epoxy resins. When it is less than 20 parts by mass, it is difficult for the cured product to form a phase separation structure, and the toughness is insufficient and the crack resistance is insufficient. When the amount exceeds 60 parts by mass, the cured product has an insufficient elastic modulus and insufficient heat resistance, which may cause distortion or deformation during molding or use of the fiber-reinforced composite material.

0.2 ≦ A / (A + B + C + E) ≦ 0.6 (1)
When the number average molecular weight of [A] is less than 2000, it is difficult for the cured product to form a phase-separated structure, resulting in insufficient toughness and insufficient crack resistance. When the number average molecular weight of [A] exceeds 20000, the phase separation structure of the cured product becomes coarse, the impact resistance and crack resistance of the fiber reinforced composite material are insufficient, and the viscosity of the resin composition increases. The impregnation property is insufficient.

  The number average molecular weight of the epoxy resin in the present invention is determined by GPC (Gel Permeation Chromatography) using, for example, a polystyrene standard sample. For an epoxy resin having a known epoxy equivalent, the product of the epoxy equivalent and the number of epoxy functional groups is used. The calculated numerical value shall be used.

  Examples of such commercial products of bisphenol F type epoxy resin include jER4007P, jER4010P (manufactured by Mitsubishi Chemical Corporation), and the like.

  As [B] in such an epoxy resin composition, it is necessary to contain a tri- or higher functional amine-type epoxy resin in an amount of 20 to 60 parts by mass out of 100 parts by mass of the total epoxy resin, It is preferable to contain 25-50 mass parts. When it is less than 20 parts by mass, the elastic modulus of the cured product is insufficient, and it is difficult to form a phase separation structure, resulting in insufficient toughness and crack resistance. Moreover, when it exceeds 60 mass parts, the elongation of hardened | cured material will become inadequate and toughness will run short.

  As such an amine type epoxy resin, for example, tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, triglycidylaminocresol, tetraglycidylxylylenediamine, halogens thereof, alkyl-substituted products, hydrogenated products, and the like can be used. .

  Examples of the tetraglycidyldiaminodiphenylmethane include “Sumiepoxy (registered trademark)” ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), YH434L (manufactured by Tohto Kasei Co., Ltd.), and “jER (registered trademark)” 604 (Mitsubishi Chemical Corporation). , "Araldide (registered trademark)" MY720, MY721 (manufactured by Huntsman Advanced Materials) and the like can be used. As triglycidylaminophenol or triglycidylaminocresol, “Sumiepoxy (registered trademark)” ELM100, ELM120 (manufactured by Sumitomo Chemical Co., Ltd.), “Araldide (registered trademark)” MY0500, MY0510, MY0600 (Huntsman Advanced Materials) And “jER (registered trademark)” 630 (manufactured by Mitsubishi Chemical Corporation), etc. can be used. As tetraglycidylxylylenediamine and hydrogenated products thereof, “TETRAD (registered trademark)”-X, “TETRAD (registered trademark)”-C (manufactured by Mitsubishi Gas Chemical Co., Inc.) and the like can be used.

  Among them, a trifunctional aminophenol type epoxy resin such as triglycidylaminophenol or triglycidylaminocresol is particularly preferably used because a low-viscosity epoxy resin composition is easily obtained and a high elastic modulus is easily obtained.

  As [C] in such an epoxy resin composition, it is necessary to contain a bisphenol type epoxy resin having a number average molecular weight in the range of 300 to 500 of 15 to 50 parts by mass out of 100 parts by mass of all epoxy resins. It is preferable to contain 20-40 mass parts among 100 mass parts of epoxy resins. Since [C] is compatible with both [A] and [B] epoxy resins, the affinity between [A] rich phase and [B] rich phase is increased, and the phase separation structure period is reduced to a size of 5 μm or less. can do.

  Here, when the number average molecular weight of [C] is less than 300, volatilization in the resin preparation or molding process becomes a problem, the compatibilizing effect becomes insufficient, the phase separation structure becomes coarse, and the fiber reinforced composite material The impact resistance and crack resistance are insufficient. Further, when the number average molecular weight exceeds 500, the [C] component is easily incorporated into the [A] rich phase, and the glass transition temperature of the [A] rich phase becomes higher than necessary. Impact resistance and crack resistance are insufficient.

  Moreover, when content of [C] is less than 15 mass parts, a phase-separation structure will become coarse and sufficient impact resistance cannot be exhibited when it is set as a fiber reinforced composite material. Moreover, when it exceeds 50 mass parts, a phase-separation structure is not formed in hardened | cured material, and the impact resistance and crack resistance of a fiber reinforced composite material become inadequate.

  Since the phase separation structure period is determined by the balance between the phase separation formation rate and the curing reaction rate, the appropriate content of [C] is 15 to 50 parts by mass depending on the amount of the curing agent and the curing conditions. Adjust appropriately within the range.

  As the bisphenol type epoxy resin used in [C], bisphenol A type, bisphenol F type, bisphenol AD type, bisphenol S type, or halogens, alkyl-substituted products, hydrogenated products, etc. of these bisphenol type epoxy resins are used. The number average molecular weight is obtained by GPC (Gel Permeation Chromatography) using, for example, a polystyrene standard sample, as in [A]. For an epoxy resin having a known epoxy equivalent, the epoxy equivalent and the number of epoxy functional groups The numerical value calculated from the product shall be used.

  Examples of commercially available diglycidyl ether type epoxy resins having a number average molecular weight of 300 to 500 that can be suitably applied as the main component of [C] include the following. Examples of commercially available bisphenol A type epoxy resins include jER825, jER826, jER827, jER828 (above, “jER”: registered trademark, manufactured by Mitsubishi Chemical Corporation). Examples of commercially available hydrogenated bisphenol A type epoxy resins include Denacol EX-252 (manufactured by Nagase ChemteX Corporation, “Denacol” is a registered trademark of the company), ST3000 (manufactured by Toto Kasei Co., Ltd.), and the like. Examples of commercially available bisphenol F-type epoxy resins include jER806, jER807 (manufactured by Mitsubishi Chemical Corporation), and Epc830 (manufactured by DIC Corporation).

  Among the above, the component [C] is particularly preferably a bisphenol F-type epoxy resin because of its low viscosity and a good balance between elastic modulus and toughness.

  [D] Dicyandiamide or a derivative thereof in the present invention is a kind of epoxy resin curing agent, and has an excellent balance of elastic modulus and elongation, and also has excellent storage stability of the resin composition. It can be used suitably. Such a dicyandiamide derivative is obtained by bonding various compounds to dicyandiamide, and includes a reaction product with an epoxy resin, a reaction product with a vinyl compound or an acrylic compound.

  The blending amount of [D] needs to be 1 to 10 parts by mass with respect to 100 parts by mass of the epoxy resin in the epoxy resin composition from the viewpoint of heat resistance and mechanical properties, and may be 2 to 8 parts by mass. It is preferable. If it is less than 1 part by mass, the cured product has insufficient crosslinking density, so that the elastic modulus is insufficient and the mechanical properties may be inferior. When it exceeds 10 mass parts, the crosslinked density of hardened | cured material becomes high, a plastic deformation capability becomes small, and it may be inferior to impact resistance.

  In addition, blending dicyandiamide or a derivative thereof as a powder into the resin as [D] is preferable from the viewpoint of storage stability at room temperature and viscosity stability during prepreg formation. When dicyandiamide or a derivative thereof is blended into the resin as a powder, the average particle size is preferably 10 μm or less, and more preferably 7 μm or less. When it exceeds 10 μm, for example, when used for prepreg applications, when impregnating the resin composition into the reinforcing fiber bundle by heating and pressing, dicyandiamide or a derivative thereof may not enter the reinforcing fiber bundle and may remain on the surface of the fiber bundle. is there.

  Examples of commercially available dicyandiamide include DICY-7 and DICY-15 (manufactured by Mitsubishi Chemical Corporation).

  Dicyandiamide may be used alone or in combination with a dicyandiamide curing catalyst or other epoxy resin curing agent. Examples of dicyandiamide curing catalysts to be combined include ureas, imidazoles, Lewis acid catalysts, and epoxy resin curing agents include aromatic amine curing agents, alicyclic amine curing agents, and acid anhydride curing agents. Can be mentioned. Examples of commercially available ureas include DCMU99 (manufactured by Hodogaya Chemical Co., Ltd.), Omicure 24, Omicure 52, Omicure 94 (above CVC Specialty Chemicals, Inc.). Examples of commercially available imidazoles include 2MZ, 2PZ, and 2E4MZ (manufactured by Shikoku Kasei Co., Ltd.). Lewis acid catalysts include boron trifluoride / piperidine complex, boron trifluoride / monoethylamine complex, boron trifluoride / triethanolamine complex, boron trichloride / octylamine complex, etc. Is mentioned.

  In addition, in the epoxy resin composition of the present invention, [A] to [C] for the purpose of improving workability by adjusting viscoelasticity when uncured or improving the elastic modulus and heat resistance of the cured resin. The epoxy resin [E] other than the above may be added in a range satisfying the formula (5), that is, in an amount of 20 parts by mass or less of 100 parts by mass of the total epoxy resin. [E] may be added in a combination of not only one type of epoxy resin but also a plurality of types.

0 ≦ E / (A + B + C + E) ≦ 0.2 (5)
Specific examples of the epoxy resin of [E] include, for example, bisphenol type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, resorcinol type epoxy resin, phenol aralkyl type epoxy resin, dicyclopentadiene type epoxy resin, biphenyl. Examples thereof include an epoxy resin having a skeleton, a urethane-modified epoxy resin, an aliphatic epoxy resin, and an alicyclic epoxy resin.

  Commercial products of phenol novolac type epoxy resins include “Epicoat (registered trademark)” 152, “Epicoat (registered trademark)” 154 (manufactured by Mitsubishi Chemical Corporation), “Epicron (registered trademark)” N-740, “ Epicron (registered trademark) "N-770", "Epiclon (registered trademark)" N-775 (manufactured by DIC Corporation), and the like.

  Examples of commercially available cresol novolac epoxy resins include “Epicron (registered trademark)” N-660, “Epicron (registered trademark)” N-665, “Epicron (registered trademark)” N-670, and “Epicron (registered trademark)”. “N-673”, “Epicron (registered trademark)” N-695 (above, manufactured by DIC Corporation), EOCN-1020, EOCN-102S, EOCN-104S (above, manufactured by Nippon Kayaku Co., Ltd.) It is done.

  Specific examples of the resorcinol type epoxy resin include “Denacol (registered trademark)” EX-201 (manufactured by Nagase ChemteX Corporation).

  Commercially available dicyclopentadiene type epoxy resins include “Epicron (registered trademark)” HP7200, “Epicron (registered trademark)” HP7200L, “Epicron (registered trademark)” HP7200H (above, manufactured by DIC Corporation), Tactix558 (Huntsman) Advanced Materials Co., Ltd.), XD-1000-1L, XD-1000-2L (Nippon Kayaku Co., Ltd.).

  Commercially available epoxy resins having a biphenyl skeleton include “Epicoat (registered trademark)” YX4000H, “Epicoat (registered trademark)” YX4000, “Epicoat (registered trademark)” YL6616 (manufactured by Mitsubishi Chemical Corporation), NC -3000 (manufactured by Nippon Kayaku Co., Ltd.).

  Examples of commercially available urethane and isocyanate-modified epoxy resins include AER4152 (produced by Asahi Kasei E-Materials Co., Ltd.) having an oxazolidone ring and ACR1348 (produced by Asahi Denka Co., Ltd.).

The epoxy resin composition of the present invention has a storage elastic modulus G ′ of _{75 ° C.} , G ′ of _{100 ° C.} , and G ′ of _{120 °} C. at 75 ° C., 100 ° C., and 120 ° C. after curing at 130 ° C./2 hours. It is preferable that it is the relationship of (iii).

1.3 (GPa) ≦ G ′ _{75 ° C.} ≦ 1.8 (GPa) (i)
1.3 ≦ G ′ _{75 °} C./G ′ _{100 ° C.} ≦ 7.0 (ii)
0.08 (GPa) ≦ G ′ _{120 ° C.} ≦ 0.8 (GPa) (iii)
More preferably, storage elastic moduli G ′ _{75 ° C.} , G ′ _{100 ° C.} , G ′ _{120 °} C. at 75 ° C., 100 ° C., 120 ° C. after curing at 130 ° C./2 hours are represented by the following formulas (i ′) to (iii ′): ) Is preferable.

1.4 (GPa) ≦ G ′ _{75 ° C.} ≦ 1.6 (GPa) (i ′)
1.4 ≦ G ′ _{75 °} C./G ′ _{100 ° C.} ≦ 6.0 (ii ′)
0.12 (GPa) ≦ G ′ _{120 ° C.} ≦ 0.6 (GPa) (iii ′)
After curing at 130 ° C./2 hours is a typical molding condition of a prepreg, the temperature is raised from room temperature at 1.5 ° C./minute, and then heated and cured at 130 ° C. for 2 hours to reach room temperature at 3 ° C./minute. Refers to the state of the cured resin obtained by lowering the temperature.

  In addition, the storage elastic modulus (G ′) in the present invention is a dynamic viscoelasticity measuring device such as ARES (manufactured by TA Instruments), for example, with a heating rate of 5 ° C./min, a frequency of 1 Hz, and a strain amount of 0.1%. It is obtained under measurement conditions.

The fiber reinforced composite material using the epoxy resin composition of the present invention may be used and stored in a considerably high temperature range such as under the hot sun in the summer, and in that case, in order to ensure sufficient static strength characteristics, G ′ _{75 ° C.} is preferably a certain level or higher. On the other hand, in the processing step of such a fiber reinforced composite material, [A] since the rich phase is in a rubber state, sufficient crack resistance can be expressed, so G ′ _{100 ° C.} is less than a certain level compared to G ′ _{75 ° C.} It is preferable that Furthermore, it is preferable that G ′ _{120 ° C.} is not less than a certain level so that the fiber-reinforced composite material does not warp or deform during the demolding operation after molding.

  The G′-temperature curve of the cured epoxy resin of the present invention has the shape shown in FIG. 1 so that the above formulas (i) to (iii), preferably the above formulas (i ′) to (iii ′) are all satisfied. Ideal to take. This ideal G′-temperature curve can be realized by the following mechanism. At 75 ° C., the [A] rich phase and the [B] rich phase both have a sufficiently high G ′ because they are in the glass state, and in the temperature range of 75 ° C. to 100 ° C., the glass transition of the [A] rich phase occurs. As a result, G ′ drops to a predetermined level. Furthermore, in the temperature range from 100 ° C. to 120 ° C., the [B] rich phase maintains the glass state, thereby avoiding a significant decrease in G ′ at 120 ° C., and in the temperature range exceeding 120 ° C., the [B] rich phase It is a mechanism that G ′ is greatly lowered for the first time by entering the glass transition.

When the G ′ _{75 ° C.} of the epoxy resin composition is 1.3 GPa or more, the static strength characteristics of the fiber-reinforced composite material obtained using the epoxy resin composition can be sufficiently ensured. On the other hand, when the G ′ _{75 ° C.} of the epoxy resin composition is 1.8 GPa or less, the toughness of the cured resin can be ensured, and the impact resistance of the fiber-reinforced composite material obtained using the resin can be sufficiently ensured. be able to. In addition, by _{G '75 ℃ / G' 100} ℃ epoxy resin composition is 1.3 or more, can be well expressed crack resistance of the fiber-reinforced composite material using the same. On the other hand, when G ′ _{75 °} C./G ′ _{100 ° C.} of the epoxy resin composition is 7.0 or less, warping and deformation can be avoided during the demolding operation after molding the fiber-reinforced composite material. Further, when G ′ _{120 ° C.} of the epoxy resin composition is 0.08 or more, it is possible to avoid warping and deformation at the time of demolding after molding of the fiber-reinforced composite material. On the other hand, when the G ′ _{120 ° C.} of the epoxy resin composition is 0.8 or less, the toughness of the cured resin can be secured, and the impact resistance of the fiber-reinforced composite material using the resin can be sufficiently secured. it can.

The cured epoxy resin of the present invention has a resin toughness at 90 ° C. of 550 J / m ² or more in the sense that it can avoid the occurrence of cracks and the like in the fiber reinforced composite material in a processing step exposed to a high temperature environment. Is more preferable, and 600 J / m ² or more is more preferable. In addition, the resin toughness described here refers to the energy release rate G _IC obtained according to ASTM D5045 (1999).

In addition, the epoxy resin composition of the present invention has [F] epoxy resin in order to control viscoelasticity and improve tack and drape characteristics of prepreg, and to improve mechanical properties such as impact resistance of fiber reinforced composite materials. It is preferable to add the soluble thermoplastic resin in a range satisfying the formula (6), that is, in a blending amount of 1 to 10 parts by mass with respect to 100 parts by mass of the total epoxy resin.
0.01 ≦ F / (A + B + C + E) ≦ 0.1 (6)
Among these, a thermoplastic resin having a hydrogen bonding functional group that can be expected to improve the adhesion between the resin and the reinforcing fiber is more preferably used. Examples of the hydrogen bonding functional group include an alcoholic hydroxyl group, an amide bond, and a sulfonyl group.

  Examples of the thermoplastic resin having an alcoholic hydroxyl group include polyvinyl acetal resins such as polyvinyl formal and polyvinyl butyral, polyvinyl alcohol, phenoxy resin, and thermoplastic resins having an amide bond such as polyamide, polyimide, polyvinyl pyrrolidone, and heat having a sulfonyl group. Examples of the plastic resin include polysulfone such as polyethersulfone. Polyamide, polyimide and polysulfone may have a functional group such as an ether bond and a carbonyl group in the main chain. The polyamide may have a substituent on the nitrogen atom of the amide group.

  In particular, polyvinyl formal and polyethersulfone can be suitably used because they are excellent in compatibility with the epoxy resin and can be blended while ensuring a phase separation structure of an appropriate size between [A] and [B]. Examples of commercially available polyvinyl formal include “Denka Formal (registered trademark)” (manufactured by Denki Kagaku Kogyo Co., Ltd.) and “Vinylec (registered trademark)” (manufactured by Chisso Corporation). Also, commercially available polyethersulfone products are “Sumika Excel (registered trademark)” PES5200P, “Sumika Excel (registered trademark)” PES4700P, “Sumika Excel (registered trademark)” PES3600P, “Sumika Excel (registered trademark)” PES5003P ( As mentioned above, Sumitomo Chemical Co., Ltd.) etc. are mentioned.

  Commercially available thermoplastic resins that are soluble in epoxy resins and have hydrogen-bonding functional groups include polyvinyl acetal resins such as Denkabutyral and “Denka Formal (registered trademark)” (manufactured by Denki Kagaku Kogyo Co., Ltd.), “Vinylec” (Registered trademark) "(manufactured by Chisso Corporation)," UCAR (registered trademark) "PKHP (manufactured by Union Carbide) as the phenoxy resin, and" Macromelt (registered trademark) "(manufactured by Henkel Hakusui Co., Ltd.) as the polyamide resin “Amilan (registered trademark)” CM4000 (manufactured by Toray Industries, Inc.), “Ultem (registered trademark)” (manufactured by General Electrics) as polyimide, “Matrimid (registered trademark)” 5218 (manufactured by Ciba), and polysulfone “Victrex (registered trademark)” (manufactured by Mitsui Chemicals, Inc.), “UDEL ( Recorded trademark) "(manufactured by Union Carbide Corporation), as polyvinylpyrrolidone," Luviskol (registered trademark) "(BASF Japan Ltd. can be exemplified, Ltd.).

  In addition, the acrylic resin has high compatibility with the epoxy resin, and is preferably used for controlling the viscoelasticity. Commercially available acrylic resins include “Dynar (registered trademark)” BR series (Mitsubishi Rayon Co., Ltd.), “Matsumoto Microsphere (registered trademark)” M, M100, M500 (Matsumoto Yushi Seiyaku Co., Ltd.) ) And the like.

  For preparing the epoxy resin composition of the present invention, a kneader, a planetary mixer, a three-roll extruder, a twin-screw extruder, or the like is preferably used. After the epoxy resin component is added and kneaded, the temperature of the epoxy resin mixture is raised to an arbitrary temperature of 130 to 180 ° C. while stirring, and the remaining components other than the curing agent and the curing catalyst are dissolved or dispersed in the epoxy resin mixture. Thereafter, while stirring, the temperature is preferably lowered to 100 ° C. or lower, more preferably 80 ° C. or lower, and a curing agent and a curing catalyst are added and kneaded and dispersed. This method is preferably used because an epoxy resin composition having excellent storage stability can be obtained.

  The epoxy resin composition of the present invention comprises a cured epoxy resin obtained by curing the epoxy resin composition, a prepreg for a fiber reinforced composite material using the cured epoxy resin and a cured product thereof, and a cured epoxy resin and a reinforced fiber substrate. It can be used as a reinforced fiber composite material combined.

  When the epoxy resin composition of the present invention is used as a prepreg matrix resin, the viscosity at 80 ° C. is preferably from 0.1 to 200 Pa · s, more preferably from the viewpoint of processability such as tack and drape. It is desirable to be in the range of 5 to 100 Pa · s, more preferably 1 to 50 Pa · s. When the viscosity at 80 ° C. is 0.1 Pa · s or more, the shape of the prepreg can be maintained, the resin flow during molding hardly occurs, and variations in the reinforcing fiber content are reduced. When the viscosity at 80 ° C. is 200 Pa · s or less, fading is suppressed in the film-forming step of the epoxy resin composition, and the impregnation property to the reinforcing fibers is excellent.

Viscosity here refers to, for example, a dynamic viscoelasticity measuring device such as ARES (manufactured by TA Instruments), using a parallel plate with a diameter of 40 mm, and according to measurement conditions of a heating rate of 2 ° C./min, a frequency of 0.5 Hz, and a gap of 1 mm. It refers to the obtained complex viscosity η ^* .

  From the epoxy resin composition of the present invention, the curing temperature and curing time for obtaining a cured product are not particularly limited, depending on the curing agent and catalyst to be blended, cost and productivity, mechanical properties of the resulting cured product, It can be appropriately selected from the viewpoints of heat resistance, quality and the like. For example, in a curing agent system in which dicyandiamide and DCMU are combined, it is preferable to cure at a temperature of about 130 ° C. for about 2 hours.

  Here, the resin bending elastic modulus of the cured product is measured using a sample obtained as follows, using a universal testing machine (Instron), the span length is 32 mm, and the crosshead speed is 2.5 mm. / Min., Measured by 3-point bending according to JIS K7171 (1994), and obtained as an average value of the number of samples n = 5. A sample for measuring the resin flexural modulus of the cured product was obtained by defoaming an uncured epoxy resin composition in a vacuum and in a mold set to a thickness of 2 mm by a 2 mm thick “Teflon (registered trademark)” spacer. The plate-like cured product without voids is obtained by curing under the predetermined curing conditions, and this is cut into a width of 10 mm and a length of 60 mm with a diamond cutter.

  Moreover, the resin toughness measurement of hardened | cured material was measured according to ASTM D5045 (1999) using the universal tester (made by Instron) using the sample obtained as follows, and the average value of the number of samples n = 5 Shall be obtained as The resin toughness measurement sample of the cured product is predetermined in a mold set to a thickness of 6 mm with a 6 mm thick “Teflon (registered trademark)” spacer after defoaming the uncured epoxy resin composition in vacuum. A plate-like cured product without voids is obtained by curing under the curing conditions described above, and this is cut into a width of 12.7 mm and a length of 150 mm with a diamond cutter, and a pre-crack of 5 to 7 mm is introduced from one end in the width direction. did. The initial precrack was introduced into the test piece by applying a razor blade cooled to liquid nitrogen temperature to the test piece and applying an impact to the razor with a hammer.

  The reinforcing fiber used in the present invention is not particularly limited, and glass fiber, carbon fiber, aramid fiber, boron fiber, alumina fiber, silicon carbide fiber and the like are used. Two or more of these fibers may be mixed and used. Among these, it is preferable to use carbon fibers from which a lightweight and highly rigid fiber-reinforced composite material can be obtained. Among these, carbon fibers having a tensile modulus of 100 to 900 GPa are preferable, and carbon fibers having a tensile modulus of 200 to 800 GPa are more preferable.

  When such a high elastic modulus carbon fiber is combined with the epoxy resin composition of the present invention, the effects of the present invention tend to be particularly prominent.

  The form of the reinforcing fiber is not particularly limited, and for example, a long fiber aligned in one direction, a tow, a woven fabric, a mat, a knit, a braid, a short fiber chopped to a length of less than 10 mm, and the like are used. As used herein, long fibers refer to single fibers or fiber bundles that are substantially continuous for 10 mm or more. A short fiber is a fiber bundle cut to a length of less than 10 mm. In particular, an array in which reinforcing fiber bundles are aligned in a single direction is most suitable for applications that require a high specific strength and specific elastic modulus. Arrangements are also suitable for the present invention.

  The prepreg of the present invention is obtained by impregnating a fiber base material with the epoxy resin composition of the present invention. Examples of the impregnation method include a wet method in which the epoxy resin composition is dissolved in a solvent such as methyl ethyl ketone and methanol to lower the viscosity and impregnation, and a hot melt method (dry method) in which the viscosity is reduced by heating and impregnation. it can.

  The wet method is a method in which the reinforcing fiber is immersed in a solution of the epoxy resin composition and then lifted and the solvent is evaporated using an oven or the like. The hot melt method directly applies the epoxy resin composition whose viscosity has been reduced by heating. A method of impregnating reinforcing fibers, or a film in which an epoxy resin composition is once coated on a release paper or the like is prepared, and then the films are laminated from both sides or one side of the reinforcing fibers and heated and pressed to form reinforcing fibers. This is a method of impregnating a resin. The hot melt method is preferable because substantially no solvent remains in the prepreg.

The prepreg preferably has a reinforcing fiber amount of 70 to 200 g / m ² per unit area. When the amount of the reinforcing fibers is 70 g / m ² or more, it is not necessary to increase the number of laminated layers in order to obtain a predetermined thickness when forming the fiber reinforced composite material, and the operation is simplified. On the other hand, when the amount of reinforcing fibers is 200 g / m ² or less, the prepreg drapability tends to be improved. The fiber mass content is preferably 60 to 90% by mass, and is usually used in the range of 65 to 85% by mass. When the fiber mass content is 60% by mass or more, the ratio of the resin is preferable, and the advantages of the fiber reinforced composite material having excellent specific strength and specific modulus can be obtained. Can be suppressed. In addition, when the fiber mass content is 90% by mass or less, the impregnation property of the resin is improved, and the obtained composite material has few voids.

  After shaping and / or laminating the prepreg, the composite material according to the present invention is produced by a method of heat-curing the resin while applying pressure to the shaped product and / or laminate.

  As a method for applying heat and pressure, a press molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, an internal pressure molding method, or the like can be appropriately used.

  The autoclave molding method is a method of laminating a prepreg on a tool plate of a predetermined shape, covering with a bagging film, pressurizing and heat-curing while degassing the inside of the laminate, and the fiber orientation can be precisely controlled, Further, since the generation of voids is small, a molded article having excellent mechanical properties and high quality can be obtained.

  The wrapping tape method is a method of winding a prepreg around a mandrel or other core metal to form a tubular body made of a fiber-reinforced composite material, and is a method suitable for producing a rod-shaped body such as a golf shaft or fishing rod. . More specifically, a prepreg is wound around a mandrel, a wrapping tape made of a thermoplastic film is wound around the outside of the prepreg for fixing and applying pressure, and the resin is heated and cured in an oven, and then a cored bar. This is a method for extracting a tube to obtain a tubular body.

  Also, the internal pressure molding method is to set a preform in which a prepreg is wound on an internal pressure applying body such as a tube made of a thermoplastic resin in a mold, and then introduce a high pressure gas into the internal pressure applying body to apply pressure. At the same time, the mold is heated and molded. This method is preferably used when molding a complicated shape such as a golf shaft, a bad, a racket such as tennis or badminton.

  The fiber reinforced composite material using the cured product of the epoxy resin composition of the present invention as a matrix resin is suitably used for sports applications, general industrial applications, and aerospace applications. More specifically, in sports applications, it is preferably used for golf shafts, fishing rods, tennis and badminton racket applications, stick applications such as hockey, and ski pole applications. Furthermore, in general industrial applications, it is used as a structural material for moving bodies such as automobiles, ships and railway vehicles, drive shafts, leaf springs, windmill blades, pressure vessels, flywheels, paper rollers, roofing materials, cables, and repair and reinforcement materials. Preferably used. Suitable for aerospace applications such as aircraft primary structural materials such as main wings, tail wings and floor beams, secondary structural materials such as flaps, ailerons, cowls, fairings and interior materials, rocket motor cases and satellite structural materials Used for.

  The static strength characteristics of the fiber reinforced composite material in the present invention are compared with dynamic strength characteristics obtained by impact tests, fatigue tests, and the like, and compressive strength, bending strength, tensile strength in the fiber direction or non-fiber direction. Strength and the like. In general, the compressive strength in the fiber direction tends to be a destructive factor of the fiber reinforced composite material, so that it is particularly required to have a sufficient strength level.

  The tubular body made of fiber-reinforced composite material obtained by curing the prepreg of the present invention into a tubular shape can be suitably used for golf shafts, fishing rods and the like.

  Hereinafter, the present invention will be described in more detail with reference to examples. Various physical properties were measured by the following methods. These physical properties were measured in an environment at a temperature of 23 ° C. and a relative humidity of 50% unless otherwise specified.

(1) Preparation of epoxy resin composition In a kneader, a predetermined amount of components other than the curing agent and the curing accelerator are added, and while kneading, the temperature is increased to 160 ° C. A viscous liquid was obtained. After the temperature was lowered while kneading to 80 ° C., a predetermined amount of a curing agent and a curing accelerator were added and kneaded to obtain an epoxy resin composition. The raw material compounding ratios of the examples and comparative examples are as shown in Table 1. Further, the contents of [A], [B], [C], “D”, [E] and [F] in the obtained epoxy resin composition are as shown in Table 1. In each table, EEW represents an epoxy equivalent.

  The epoxy equivalent, the average number of epoxy groups, etc. of each raw material used for preparing each epoxy resin composition are as shown below.

<Epoxy resin ([A])>
-Bisphenol F type epoxy resin ("jER (registered trademark)" 4007P, epoxy equivalent: 2270, manufactured by Mitsubishi Chemical Corporation)
-Bisphenol F type epoxy resin ("jER (registered trademark)" 4010P, epoxy equivalent: 4400, manufactured by Mitsubishi Chemical Corporation).

<Epoxy resin ([B])>
Triglycidyl-m-aminophenol ("Sumiepoxy (registered trademark)" ELM120, epoxy equivalent: 118, trifunctional, manufactured by Sumitomo Chemical Co., Ltd.)
Triglycidyl-p-aminophenol (“Araldide (registered trademark)” MY0510, epoxy equivalent: 101, trifunctional, manufactured by Huntsman Advanced Materials)
Tetraglycidyl diaminodiphenyl methane (“Sumiepoxy (registered trademark)” ELM434, manufactured by Sumitomo Chemical Co., Ltd., epoxy equivalent: 125)
<Epoxy resin ([C])>
・ Bisphenol F type epoxy resin ("Epiclon (registered trademark)" 830, epoxy equivalent: 170, manufactured by DIC Corporation)
<Other epoxy resins ([E])>
-Bisphenol A type epoxy resin ("jER (registered trademark)" 828, epoxy equivalent: 189, bifunctional, manufactured by Mitsubishi Chemical Corporation)
-Bisphenol A type epoxy resin ("jER (registered trademark)" 834, epoxy equivalent: 250, bifunctional, manufactured by Mitsubishi Chemical Corporation)
-Bisphenol F type epoxy resin ("Epototo (registered trademark)" YDF2001, epoxy equivalent: 475, bifunctional, manufactured by Tohto Kasei Co., Ltd.)
-Bisphenol A type epoxy resin ("jER (registered trademark)" 1009, epoxy equivalent: 2850, bifunctional, manufactured by Mitsubishi Chemical Corporation)
<Curing agent ([D])>
Dicyandiamide (curing agent, DICY-7, manufactured by Mitsubishi Chemical Corporation).

<Other ingredients ([F] and others)>
・ "Vinylec (registered trademark)" PVF-K (polyvinyl formal), manufactured by Chisso Corporation)
DCMU99 (3- (3,4-dichlorophenyl) -1,1-dimethylurea, curing accelerator, manufactured by Hodogaya Chemical Co., Ltd.)

(2) Number average molecular weight measurement of epoxy resin An epoxy resin is dissolved in THF at a concentration of 0.1 mg / ml, polystyrene is obtained using HLC-8220GPC (manufactured by Tosoh Corporation), and UV-8000 (254 nm) as a detector. The relative molecular weight was measured using a standard sample. TSK-G4000H (manufactured by Tosoh Corporation) was used for the column, and measurement was performed at a flow rate of 1.0 ml / min and a temperature of 40 ° C. The mass ratio of the molecular weight of the epoxy resin contained was calculated from the area ratio.

(3) Viscosity measurement of epoxy resin composition The viscosity of the epoxy resin composition was measured using a dynamic viscoelasticity measuring device ARES (manufactured by TA Instruments), a parallel plate having a diameter of 40 mm, and a temperature increase rate of 2 ° C / min. The temperature was simply raised, and the value at 80 ° C. of the complex viscosity (η ^* ) obtained under the measurement conditions of a frequency of 0.5 Hz and a gap of 1 mm was adopted.

(4) Flexural modulus of cured epoxy resin After defoaming the uncured resin composition in a vacuum, 130 mm in a mold set to a thickness of 2 mm with a 2 mm thick Teflon (registered trademark) spacer. It was cured at a temperature of 0 ° C. for 2 hours to obtain a cured resin having a thickness of 2 mm. From this cured resin, a test piece having a width of 10 mm and a length of 60 mm was cut out, an Instron universal tester (Instron) was used, the span length was 32 mm, and the crosshead speed was 2.5 mm / min. Three-point bending was performed according to JIS K7171 (1994) to obtain a flexural modulus. The number of samples was set to n = 5, and the average value was compared.

(5) Measurement of storage elastic modulus (G ′) of cured epoxy resin A test piece having a width of 10 mm and a length of 40 mm was cut out from the cured resin product having a thickness of 2 mm obtained in (4) above, and dynamic viscoelasticity measurement was performed. A torsional mode DMA test was performed using an apparatus ARES (manufactured by TA Instruments). Specifically, using a Torsion Rectangler for Geometry, the storage elastic modulus (G ′) is measured under the measurement conditions of a temperature rising rate of 5 ° C./min, a frequency of 1 Hz, and a strain amount of 0.1%, and 75 ° C., 100 G ′ at 120 ° C. and 120 ° C. was extracted.

(6) Measurement of toughness (G _IC ) of cured epoxy resin The uncured epoxy resin composition was degassed in vacuum, and then set to a thickness of 6 mm using a 6 mm thick Teflon (registered trademark) spacer. Unless otherwise specified in the mold, it was cured at a temperature of 130 ° C. for 2 hours to obtain a cured resin product having a thickness of 6 mm. This cured resin was cut at 12.7 × 150 mm to obtain a test piece. Using an Instron universal testing machine (manufactured by Instron), processing of the test piece and a three-point bending test were performed according to ASTM D5045 (1999). The initial precrack was introduced into the test piece by applying a razor blade cooled to liquid nitrogen temperature to the test piece and applying an impact to the razor with a hammer. The stress intensity factor K _IC was measured, and the energy release rate G _IC was obtained from this value and the tensile elastic modulus E and Poisson's ratio ν obtained separately by a tensile test of the cured resin, according to the following equation. The number of measurements was n = 5, and the average value was adopted.
G _IC = (1−ν ² ) K _IC ² / E
Here, the tensile test of the cured resin is performed by quantifying the amount of strain with a strain gauge on a test piece having a width of 10 ± 0.1 mm and a length of 100 ± 0.1 cm from a cured resin plate having a thickness of 2 ± 0.1 mm. Tensile measurement was performed by the method described above to determine the tensile modulus E and Poisson's ratio ν.

  The above test was performed under a normal temperature environment and a 90 ° C. heating environment.

(7) Measurement of structural period of cured epoxy resin After the resin cured product obtained in (4) above is dyed, it is sliced and a transmission electron image is obtained under the following conditions using a transmission electron microscope (TEM). did. As the staining agent, OsO ₄ and RuO ₄ were properly used according to the resin composition so that the morphology was sufficiently contrasted.
Apparatus: H-7100 transmission electron microscope (manufactured by Hitachi, Ltd.)
・ Acceleration voltage: 100 kV
-Magnification: 10,000 times Thereby, the structural period of the [A] rich phase and the [B] rich phase was observed. Depending on the types and ratios of [A] and [B], the phase separation structure of the cured product forms a two-phase continuous structure or a sea-island structure, and was measured as follows. In Table 1, the phase structure period of the resin cured product is as shown in the phase structure size (μm) column.

  In the case of a two-phase continuous structure, a straight line of a predetermined length is drawn on the micrograph, the intersection of the straight line and the phase interface is extracted, the distance between adjacent intersections is measured, and the number average value of these is the structure period It was. The predetermined length was set as follows based on a micrograph. When the structural period is expected to be on the order of 0.01 μm (0.01 μm or more and less than 0.1 μm), a photograph is taken at a magnification of 20,000 times, and a length of 20 mm randomly on the photograph (a length of 1 μm on the sample) ) Select three, and in the same way, if the phase separation structure period is expected to be on the order of 0.1 μm (0.1 μm or more and less than 1 μm), take a photograph at a magnification of 2,000 times, and randomly on the photo When three 20mm lengths (10μm length on the sample) are selected and the phase separation structure period is expected to be on the order of 1μm (1μm or more and less than 10μm), a photograph is taken at a magnification of 200x and random on the photograph 3 pieces having a length of 20 mm (length of 100 μm on the sample) were selected. If the measured phase separation structure period was out of the expected order, the corresponding length was measured again at the magnification corresponding to the corresponding order and adopted.

  In the case of the sea-island structure, the number average value of the distance between the island phase and the island phase existing in a predetermined region is defined as the structure period. The shortest distance between the island phase and the island phase was used when the island phase was an ellipse, an indeterminate shape, or a circle or ellipse with two or more layers. The predetermined region was set as follows based on a micrograph. When the distance between particles is expected to be on the order of 0.01 μm (0.01 μm or more and less than 0.1 μm), a photograph is taken at a magnification of 20,000 times, and a 4 mm square area on the photograph (0.2 μm on the sample) In the same way, if the distance between the particles is expected to be on the order of 0.1 μm (0.1 μm or more and less than 1 μm), the photograph is taken at a magnification of 2,000 times. Randomly select 3 areas of 4 mm square (2 μm square area on the sample), and if the phase separation structure period is expected to be on the order of 1 μm (1 μm or more and less than 10 μm), take a picture at a magnification of 200 times, Then, a 4 mm square area (20 μm square area on the sample) was randomly selected. If the measured phase separation structure period was out of the expected order, the corresponding region was measured again at a magnification corresponding to the corresponding order and adopted.

  In the case of the sea-island structure, the major axis of all the island phases existing in a predetermined region was measured, and the number average value of these was obtained as the island phase diameter. When the island phase is an ellipse, an indeterminate shape, or a circle or ellipse of two or more layers, the diameter of the outermost circle or the major axis of the ellipse was used. The predetermined region was set as follows based on a micrograph. When the diameter of the island phase is expected to be on the order of 0.01 μm (0.01 μm or more and less than 0.1 μm), a photograph is taken at a magnification of 20,000 times, and a 20 mm square region (1. Similarly, if the island phase diameter is expected to be on the order of 0.1 μm (0.1 μm or more and less than 1 μm), a photograph is taken at a magnification of 2,000 times. If you randomly select 3 areas of 20 mm square (10 μm square area on the sample) and phase separation structure period is expected to be on the order of 1 μm (1 μm or more and less than 10 μm), take a photo at a magnification of 200 times, A 20 mm square area (100 μm square area on the sample) was randomly selected on the photograph. If the measured phase separation structure period was out of the expected order, the corresponding region was measured again at a magnification corresponding to the corresponding order and adopted.

Example 1
As shown in Table 1, 35 parts by mass of jER4007P as [A], 35 parts by mass of MY0510 as [B], 30 parts by mass of Epc830 as [C], 5 parts by mass of DICY-7 as curing agent [D], An epoxy resin composition was prepared using 3 parts by mass of Vinylec K as [F] and 3 parts by mass of DCMU99 as a curing aid. The obtained cured resin formed a fine phase separation structure and had good mechanical properties.

(Example 2)
As shown in Table 1, 55 parts by mass of jER4007P as [A], 20 parts by mass of MY0510 as [B], 25 parts by mass of Epc830 as [C], 5 parts by mass of DICY-7 as the curing agent [D], An epoxy resin composition was prepared using 3 parts by mass of Vinylec K as [F] and 3 parts by mass of DCMU99 as a curing aid. Although the obtained resin composition had a high viscosity and there was concern about the impregnation property to the reinforcing fiber, a cured resin product having excellent resin toughness at room temperature and 90 ° C. was obtained.

(Example 3)
As shown in Table 1, 20 parts by mass of jER4007P as [A], 55 parts by mass of MY0510 as [B], 25 parts by mass of Epc830 as [C], 5 parts by mass of DICY-7 as the curing agent [D], An epoxy resin composition was prepared using 3 parts by mass of Vinylec K as [F] and 3 parts by mass of DCMU99 as a curing aid. Compared with Example 1, the obtained resin cured product was at a level at which there is no problem although the resin toughness at room temperature and 90 ° C. was slightly lowered.

Example 4
As shown in Table 1, 40 parts by mass of jER4007P as [A], 45 parts by mass of MY0510 as [B], 15 parts by mass of Epc830 as [C], 5 parts by mass of DICY-7 as curing agent [D], An epoxy resin composition was prepared using 3 parts by mass of Vinylec K as [F] and 3 parts by mass of DCMU99 as a curing aid. The obtained cured resin formed a slightly larger phase separation structure period as compared with Example 1, and the resin toughness at room temperature was slightly lowered, but it was at a level with no problem.

(Example 5)
As shown in Table 1, 25 parts by mass of jER4007P as [A], 30 parts by mass of MY0510 as [B], 45 parts by mass of Epc830 as [C], 5 parts by mass of DICY-7 as curing agent [D], An epoxy resin composition was prepared using 3 parts by mass of Vinylec K as [F] and 3 parts by mass of DCMU99 as a curing aid. The obtained resin cured product had a low G ′ _{75 °} C./G ′ _{100 ° C.} of 1.4, which was an acceptable level although the resin toughness at 90 ° _C. was lower than that in Example 1. .

(Example 6)
As shown in Table 1, 30 parts by mass of jER4010P as [A], 40 parts by mass of ELM434 as [B], 15 parts by mass of Epc830 as [C], 15 parts by mass of YDF2001 as [E], and curing agent [D ], 5 parts by mass of DICY-7, 3 parts by mass of Vinylec K as [F], and 3 parts by mass of DCMU99 as a curing aid were used to prepare an epoxy resin composition. The obtained cured resin was at a level with no problem although the flexural modulus was slightly lowered as compared with Example 1.

(Example 7)
As shown in Table 1, 30 parts by mass of jER4010P as [A], 40 parts by mass of ELM434 as [B], 30 parts by mass of jER828 as [C], 5 parts by mass of DICY-7 as the curing agent [D], An epoxy resin composition was prepared using 3 parts by mass of Vinylec K as [F] and 3 parts by mass of DCMU99 as a curing aid. The obtained cured resin was at an acceptable level, although the flexural modulus decreased compared to Example 1.

(Example 8)
As shown in Table 1, 40 parts by mass of jER4010P as [A], 40 parts by mass of ELM120 as [B], 20 parts by mass of Epc830 as [C], 5 parts by mass of DICY-7 as curing agent [D], An epoxy resin composition was prepared using 3 parts by mass of Vinylec K as [F] and 3 parts by mass of DCMU99 as a curing aid. The obtained cured resin was excellent in flexural modulus and resin toughness at 90 ° C.

(Comparative Example 1)
As shown in Table 1, 100 parts by mass of ELM120 as [B], 5 parts by mass of DICY-7 as curing agent [D], 3 parts by mass of Vinylec K as [F], and 3 parts by mass of DCMU99 as a curing aid Used to prepare an epoxy resin composition. The obtained cured resin was uniform without phase separation and had a very high flexural modulus but a very low resin toughness. Furthermore, the viscosity at 80 ° C. of the epoxy resin composition was as low as 0.01 Pa · s, and there was concern about the shape retention of the prepreg.

(Comparative Example 2)
As shown in Table 1, 50 parts by mass of jER4007P as [A], 50 parts by mass of ELM120 as [B], 5 parts by mass of DICY-7 as curing agent [D], and 3 parts by mass of Vinylec K as [F] An epoxy resin composition was prepared using 3 parts by mass of DCMU99 as a curing aid. The obtained cured resin formed a coarse phase separation structure, and the resin toughness at room temperature and 90 ° C. was insufficient.

(Comparative Example 3)
As shown in Table 1, 20 parts by mass of jER4007P as [A], 25 parts by mass of ELM120 as [B], 55 parts by mass of jER828 as [C], 5 parts by mass of DICY-7 as the curing agent [D], An epoxy resin composition was prepared using 3 parts by mass of Vinylec K as [F] and 3 parts by mass of DCMU99 as a curing aid. The obtained cured resin was uniform without phase separation, and resin toughness at room temperature and 90 ° C. was insufficient.

(Comparative Example 4)
As shown in Table 1, 10 parts by mass of jER4010P as [A], 70 parts by mass of ELM120 as [B], 20 parts by mass of Epc830 as [C], 5 parts by mass of DICY-7 as the curing agent [D], An epoxy resin composition was prepared using 3 parts by mass of Vinylec K as [F] and 3 parts by mass of DCMU99 as a curing aid. The obtained cured resin was uniform without phase separation, and resin toughness at room temperature and 90 ° C. was insufficient.

(Comparative Example 5)
As shown in Table 1, 40 parts by mass of jER4007P as [A], 40 parts by mass of Epc830 as [C], 20 parts by mass of jER834 as [E], 5 parts by mass of DICY-7 as a curing agent [D], An epoxy resin composition was prepared using 3 parts by mass of Vinylec K as [F] and 3 parts by mass of DCMU99 as a curing aid. The obtained resin cured product was uniform without phase separation, resin toughness at 90 ° C. was insufficient, and flexural modulus was extremely low.

(Comparative Example 6)
As shown in Table 1, 35 parts by mass of ELM120 as [B], 30 parts by mass of Epc830 as [C], 35 parts by mass of jER1009 as [E], 5 parts by mass of DICY-7 as the curing agent [D], An epoxy resin composition was prepared using 3 parts by mass of Vinylec K as [F] and 3 parts by mass of DCMU99 as a curing aid. The obtained cured resin had a low G ′ _{75 °} C./G ′ _{100 ° C.} of 1.2, and the resin toughness at 90 ° C. was insufficient.

(Comparative Example 7)
An epoxy resin composition was prepared with a resin composition equivalent to that of Example 9 of Patent Document 4. The obtained cured resin had a low G ′ _{75 °} C./G ′ _{100 ° C.} of 1.2, and the resin toughness at 90 ° C. was insufficient.

(Comparative Example 8)
As shown in Table 1, an epoxy resin composition was prepared in the same manner as in Example 1 except that jER4007P as [A] was replaced with jER4004P. The obtained cured resin had a low G ′ _{75 °} C./G ′ _{100 ° C.} of 1.2, and the resin toughness G _IC at 90 ° C. was insufficient.

  The epoxy resin composition of the present invention provides a cured product with excellent toughness at room temperature and high temperature range while having a high room temperature elastic modulus, so it has excellent static strength characteristics and impact resistance, and also has crack resistance. An excellent fiber-reinforced composite material can be obtained. As a result, in addition to improving the performance and weight of fiber reinforced composite materials, processability is improved and the degree of freedom in material composition and shape is improved. In various fields, fiber reinforced composites can be used from existing materials such as metals. It is expected to contribute to the replacement of materials.

Claims (10)

An epoxy resin composition containing the following [A] to [D] at a blending ratio satisfying the following formulas (1) to (5).
[A] Bisphenol F type epoxy resin having a number average molecular weight in the range of 2000 to 20000 [B] Trifunctional or higher amine type epoxy resin [C] Bisphenol type epoxy resin having a number average molecular weight in the range of 300 to 500 [D ] Dicyandiamide or a derivative thereof 0.2 ≦ A / (A + B + C + E) ≦ 0.6 (1)
0.2 ≦ B / (A + B + C + E) ≦ 0.6 (2)
0.15 ≦ C / (A + B + C + E) ≦ 0.5 (3)
0.01 ≦ D / (A + B + C + E) ≦ 0.1 (4)
0 ≦ E / (A + B + C + E) ≦ 0.2 (5)
(In each formula, A, B, C and D are the masses of [A], [B], [C] and [D], respectively, and E is an epoxy resin other than [A], [B] and [C]. Mass) The epoxy according to claim 1, wherein the storage elastic moduli G ′ _{75 ° C.} , G ′ _{100 ° C.} , and G ′ _{120 °} C. at 75 ° C., 100 ° C., and 120 ° C. after curing at 130 ° C./2 hours are in the relationship of the following formulas: Resin composition.
1.3 (GPa) ≦ G ′ _{75 ° C.} ≦ 1.8 (GPa) (i)
1.3 ≦ G ′ _{75 °} C./G ′ _{100 ° C.} ≦ 7.0 (ii)
0.08 (GPa) ≦ G ′ _{120 ° C.} ≦ 0.8 (GPa) (iii). The epoxy resin composition according to claim 1 or 2, wherein [B] is a trifunctional aminophenol type epoxy resin. The epoxy resin composition according to any one of claims 1 to 3, wherein [C] is a bisphenol F-type epoxy resin. The epoxy resin composition in any one of Claims 1-4 containing the following [F] with the compounding ratio which satisfy | fills following formula (6).
[F] Thermoplastic resin soluble in epoxy resin 0.01 ≦ F / (A + B + C + E) ≦ 0.1 (6)
(In the formula, A, B, C and E are the masses of [A], [B], [C] and [E], respectively, and E is an epoxy resin other than [A], [B] and [C]. mass) The epoxy resin composition according to claim 1, wherein the complex viscosity at 80 ° C. is in the range of 0.1 to 200 (Pa · s). A cured epoxy resin obtained by curing the epoxy resin composition according to any one of claims 1 to 6, which has a phase separation structure having at least a [A] rich phase and a [B] rich phase, and the structure Epoxy resin cured product having a period of 0.01 to 5 μm. A prepreg comprising the epoxy resin composition according to claim 1 and reinforcing fibers. A fiber-reinforced composite material comprising the cured epoxy resin according to claim 7 and reinforcing fibers. A fiber-reinforced composite material obtained by curing the prepreg according to claim 8.

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