Epoxy resin composition, prepreg and fiber-reinforced composite material

Abstract

The present invention addresses the problem of providing an epoxy resin composition having an excellent elastic modulus, strength, and tackiness and a prepreg and a fiber-reinforced composite material that use the epoxy resin composition.　The present invention is an epoxy resin composition including the following components [A]-[C], wherein the epoxy resin composition includes 20-40 mass% (inclusive) of an isocyanurate epoxy resin as component [A-1] among 100 mass% of component [A]. [A]: epoxy resin, [B]: dicyandiamide, [C]: polysulfone having a weight average molecular weight of 15,000-25,000 (inclusive)

Description

[Technical Field]

[0001] The present invention relates to an epoxy resin composition, and a prepreg and a fiber-reinforced composite material using the epoxy resin composition. [Background technology]

[0002] Fiber-reinforced composite materials using carbon fibers, aramid fibers, or other reinforcing fibers have been widely used, taking advantage of their high specific strength and specific modulus, in structural materials for aircraft and automobiles, sports applications such as tennis rackets, golf shafts, fishing rods, bicycles, and housings, and general industrial applications. Methods for producing fiber-reinforced composite materials include stacking multiple prepregs, which are sheet-like molding materials in which reinforcing fibers are impregnated with an uncured resin composition, followed by heat curing, and resin transfer molding, in which a liquid resin is poured onto reinforcing fibers placed in a mold and then heat cured. Among these methods, the prepreg method offers the advantage of being able to precisely control the orientation of the reinforcing fibers and allowing for a high degree of freedom in designing the laminate structure, making it easy to obtain high-performance fiber-reinforced composite materials. Thermosetting resins are primarily used as the resin composition for these prepregs from the perspectives of heat resistance and productivity, with epoxy resins being preferred from the perspective of mechanical properties such as adhesion to reinforcing fibers. Dicyandiamide is often used as a curing agent due to the excellent mechanical properties and heat resistance of the resulting cured products.

[0003] In recent years, improvements in various physical properties have been required for the application of fiber-reinforced composite materials to golf shafts, fishing rods, bicycles, automotive components, industrial components, and other applications requiring further weight reduction. For example, prepregs used in cylindrical molded articles such as golf shafts and fishing rods require high surface tackiness to prevent the prepreg from peeling off when formed into a cylindrical shape. The tackiness of such prepregs is affected by the viscosity characteristics of the resin composition used in combination with the reinforcing fibers, and in order to achieve good tackiness, it is necessary to adjust the viscosity of the resin composition to a certain value or higher by techniques such as blending a thermoplastic resin with an epoxy resin.

[0004] Furthermore, in order to achieve excellent bending strength in a cylindrical molded body, the fiber-reinforced composite material used must have high compressive strength and tensile strength, which in turn requires improving the elastic modulus and strength of the epoxy resin used.Patent documents 1 and 2 disclose a method of blending an isocyanuric acid-type epoxy resin as a method for achieving excellent elastic modulus in an epoxy resin.

[0005] Furthermore, when fiber-reinforced composite materials are applied to various applications, there is an increasing trend to place prepregs using woven fiber substrates on the surface to create a cross stitch design. This means that matrix resins are now required to have not only tackiness and the mechanical properties of the cured product, but also low colorability of the cured product and the appearance quality of the fiber-reinforced composite material. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-20004 [Patent Document 2] International Publication No. 2017 / 047225 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the resin composition used in Patent Document 1, the incorporation of a thermoplastic resin sometimes reduces the strength of the cured epoxy resin. Similarly, in the resin composition used in Patent Document 2, the incorporation of a thermoplastic resin sometimes reduces the strength of the cured epoxy resin. Thus, it has traditionally been extremely difficult to achieve both excellent tackiness in a prepreg and the elastic modulus and strength of the resin. Furthermore, Patent Documents 1 and 2 do not take into consideration the appearance quality of the resulting cured resin or fiber-reinforced composite material.

[0008] An object of the present invention is to provide an epoxy resin composition that provides a cured product with excellent elastic modulus and strength, a prepreg that uses the epoxy resin composition and has high tackiness, and a fiber-reinforced composite material that has excellent appearance quality. [Means for solving the problem]

[0009] The present invention employs the following means to solve the above problems: Namely, the present invention is an epoxy resin composition containing the following components [A] to [C], wherein, relative to 100% by mass of the component [A], the component [A-1] is an isocyanuric acid-type epoxy resin in an amount of 20% by mass to 40% by mass. [A]: Epoxy resin [B]: Dicyandiamide [C]: Polysulfone having a weight average molecular weight of 15,000 or more and 25,000 or less.

[0010] The present invention also relates to a prepreg comprising the epoxy resin composition of the present invention and reinforcing fibers.

[0011] The present invention also relates to a fiber-reinforced composite material comprising a cured product of the epoxy resin composition of the present invention and reinforcing fibers. [Effects of the Invention]

[0012] According to the present invention, it is possible to obtain an epoxy resin composition which exhibits excellent elastic modulus and strength when cured, a prepreg which uses the epoxy resin composition and has high tackiness, and a fiber-reinforced composite material which exhibits excellent appearance quality. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described in detail below. In the present invention, the term "not less than" means that the value is equal to or greater than the indicated value. The term "not more than" means that the value is equal to or smaller than the indicated value.

[0014] The resin composition of the present invention contains components [A] to [C] as essential components. In the present invention, the term "component" refers to a compound contained in the composition.

[0015] The component [A] in the present invention is an epoxy resin, which can provide thermosetting properties.

[0016] The epoxy resin of component [A] may have one epoxy group per molecule, but it is preferable to include one having two or more epoxy groups per molecule, because the cured product obtained by heat-curing the resin composition has a high glass transition temperature and high heat resistance. These epoxy resins may be used alone or in appropriate combinations.

[0017] Examples of the epoxy resin of component [A] include diaminodiphenylmethane-type, diaminodiphenylsulfone-type, aminophenol-type, bisphenol-type, meta-xylenediamine-type, 1,3-bisaminomethylcyclohexane-type, isocyanurate-type, hydantoin-type, phenol novolac-type, orthocresol novolac-type, trishydroxyphenylmethane-type, and tetraphenylolethane-type epoxy resins.

[0018] Commercially available bisphenol A epoxy resins include, for example, EPON (registered trademark) 825 (manufactured by Mitsubishi Chemical Corporation), Epiclon (registered trademark) 850 (manufactured by DIC Corporation), Epotohto (registered trademark) YD-128 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), and DER-331 and DER-332 (all manufactured by The Dow Chemical Company).

[0019] Commercially available bisphenol F epoxy resins include, for example, Araldite (registered trademark) GY282 (manufactured by Huntsman Advanced Materials), jER (registered trademark) 806, jER (registered trademark) 807, and jER (registered trademark) 1750 (all manufactured by Mitsubishi Chemical Corporation), Epicron (registered trademark) 830 (manufactured by DIC Corporation), and Epotohto (registered trademark) YD-170 (manufactured by Nippon Steel Chemical & Material Co., Ltd.).

[0020] It is important that component [A] contains an isocyanuric acid type epoxy resin as component [A-1]. Isocyanuric acid type epoxy resins have an isocyanuric acid skeleton in the molecule, and this resin can improve the elastic modulus of the cured product.

[0021] It is important that the content of component [A-1] is 20% by mass or more and 40% by mass or less of component [A-1] per 100% by mass of component [A]. By setting the content of component [A-1] to 20% by mass or more, an epoxy resin cured product with excellent elastic modulus can be obtained. Furthermore, by setting the content of component [A-1] to 40% by mass or less, it is possible to prevent the precipitation of component [A-1] in the epoxy resin composition, resulting in non-uniformity, and the precipitation of component [A-1] after curing, which would result in a loss of strength, and it also provides excellent appearance quality for the resulting fiber-reinforced composite material. Furthermore, by setting the content of component [A-1] to 30% by mass or more and 35% by mass or less, the resulting epoxy resin cured product has a particularly excellent balance between elastic modulus and strength.

[0022] The component [A-1] is preferably a trifunctional isocyanuric acid type epoxy resin. When the component [A-1] is trifunctional, having three epoxy groups in the molecule, it is possible to obtain a cured epoxy resin product with an excellent balance between elastic modulus and strength.

[0023] Commercially available isocyanuric acid type epoxy resins include, for example, "TEPIC (registered trademark)"-S (trifunctional), "TEPIC (registered trademark)"-G (trifunctional), "TEPIC (registered trademark)"-L (trifunctional), "TEPIC (registered trademark)"-HP (trifunctional), "TEPIC (registered trademark)"-VL (trifunctional), "TEPIC (registered trademark)"-UC (hexafunctional), "TEPIC (registered trademark)"-PAS B22 (2.2 functional), "TEPIC (registered trademark)"-PAS B26L (2.6 functional) (all manufactured by Nissan Chemical Industries, Ltd.), and "Araldite (registered trademark)" PT9810 (trifunctional) (manufactured by Huntsman Advanced Materials). These may be used alone or in appropriate combinations.

[0024] The component [A] preferably contains a trifunctional or higher glycidylamine-type epoxy resin as the component [A-2] in an amount of 20 to 60 mass % of 100 mass % of the component [A]. By containing 20 to 60 mass %, more preferably 30 to 40 mass %, of the component [A-2], the resulting epoxy resin cured product has a particularly excellent balance between elastic modulus and strength.

[0025] Examples of tri- or higher functional glycidylamine type epoxy resins include diaminodiphenylmethane type, diaminodiphenylsulfone type, aminophenol type epoxy resins, etc. These may be used alone or in appropriate combination.

[0026] Commercially available diaminodiphenylmethane epoxy resins include ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), Araldite (registered trademark) MY720 (manufactured by Huntsman Advanced Materials Co., Ltd.), Araldite (registered trademark) MY721 (manufactured by Huntsman Advanced Materials Co., Ltd.), Araldite (registered trademark) MY9512 (manufactured by Huntsman Advanced Materials Co., Ltd.), Araldite (registered trademark) MY9663 (manufactured by Huntsman Advanced Materials Co., Ltd.), Epotohto (registered trademark) YH-434 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), and jER (registered trademark) 604 (manufactured by Mitsubishi Chemical Corporation).

[0027] Commercially available diaminodiphenyl sulfone type epoxy resins include TG3DAS (manufactured by Mitsui Fine Chemicals, Inc.).

[0028] Commercially available aminophenol-type epoxy resins include ELM120 (manufactured by Sumitomo Chemical Co., Ltd.), ELM100 (manufactured by Sumitomo Chemical Co., Ltd.), jER (registered trademark) 630 (manufactured by Mitsubishi Chemical Corporation), Araldite (registered trademark) MY0500 (manufactured by Huntsman Advanced Materials Co., Ltd.), Araldite (registered trademark) MY0510 (manufactured by Huntsman Advanced Materials Co., Ltd.), Araldite (registered trademark) MY0600 (manufactured by Huntsman Advanced Materials Co., Ltd.), and Araldite (registered trademark) MY0610 (manufactured by Huntsman Advanced Materials Co., Ltd.).

[0029] Preferably, component [A] contains 10% by mass or more and 40% by mass or less of component [A-3], a bisphenol-type epoxy resin that is solid at 25°C, relative to 100% by mass of component [A]. By including 10% by mass or more, more preferably 30% by mass or more, of component [A-3], the resin viscosity of the resin composition at 25°C increases, resulting in excellent tackiness of the resulting prepreg. Furthermore, by keeping the content of component [A-3] at 40% by mass or less, the elastic modulus of the resulting epoxy resin cured product is excellent, and the appearance quality of the resulting fiber-reinforced composite material is also excellent.

[0030] Commercially available products of the component [A-3] include "jER (registered trademark)" 1001 (manufactured by Mitsubishi Chemical Corporation), "jER (registered trademark)" 1002 (manufactured by Mitsubishi Chemical Corporation), "jER (registered trademark)" 1003 (manufactured by Mitsubishi Chemical Corporation), "jER (registered trademark)" 1004 (manufactured by Mitsubishi Chemical Corporation), "jER (registered trademark)" 1007 (manufactured by Mitsubishi Chemical Corporation), "jER (registered trademark)" 1009 (manufactured by Mitsubishi Chemical Corporation), "jER (registered trademark)" 1010 (manufactured by Mitsubishi Chemical Corporation), "jER (registered trademark)" 4004P (manufactured by Mitsubishi Chemical Corporation), "jER (registered trademark)" 4005P (manufactured by Mitsubishi Chemical Corporation), "jER (registered trademark)" 4007P (manufactured by Mitsubishi Chemical Corporation), "jER (registered trademark)" 4010P (manufactured by Mitsubishi Chemical Corporation). These may be used alone or in appropriate combination.

[0031] Furthermore, component [A] preferably contains 60% by mass or more of a component that is solid at 25° C., based on 100% by mass of component [A]. By containing 60% by mass or more of a component that is solid at 25° C., the resin viscosity of the epoxy resin composition at 25° C. becomes appropriate, and the resulting prepreg has excellent tackiness.

[0032] The epoxy resin composition of the present invention contains dicyandiamide as component [B]. Dicyandiamide is excellent in imparting high mechanical properties and heat resistance to cured epoxy resins, and functions as a curing agent that forms the main skeleton of the cured epoxy resin. Dicyandiamide also imparts excellent storage stability to the epoxy resin composition.

[0033] Commercially available dicyandiamide products include DICY7 (manufactured by Mitsubishi Chemical Corporation) and DICY15 (manufactured by Mitsubishi Chemical Corporation).

[0034] The content of dicyandiamide in the epoxy resin composition of the present invention is preferably an amount such that the active hydrogen groups of dicyandiamide are 0.2 to 1.2 equivalents relative to the total number of epoxy groups in component [A]. By using dicyandiamide in an amount calculated as active hydrogen groups relative to epoxy groups of 0.2 to 1.2 equivalents, more preferably 0.3 to 1.0 equivalents, and even more preferably 0.4 to 0.7 equivalents, it is possible to obtain a cured epoxy resin product with an excellent balance between heat resistance and mechanical properties.

[0035] The epoxy resin composition of the present invention contains, as component [C], polysulfone having a weight-average molecular weight of 15,000 or more and 25,000 or less. In the present invention, component [C] is necessary for improving the tackiness of the prepreg without impairing the elastic modulus and strength of the epoxy resin cured product and the appearance quality of the cured product.

[0036] This is because the constituent element [A-1], which is an essential component of the present invention, has a highly polar isocyanuric acid skeleton and therefore tends to have lower compatibility with thermoplastic resins compared to other epoxy resins, such as glycidylamine-type epoxy resins. Therefore, when polyvinyl formal or polyethersulfone with a weight-average molecular weight of more than 25,000, which are used as viscosity modifiers, are blended to adjust the viscosity of the epoxy resin composition to an appropriate level, the epoxy resin and the thermoplastic resin may undergo coarse phase separation after curing, resulting in a significant decrease in resin strength.

[0037] The inventors have discovered that using polysulfone with a weight-average molecular weight of 25,000 or less as the thermoplastic resin provides excellent compatibility between the thermoplastic resin and the epoxy resin containing component [A-1]. This allows the epoxy resin composition to form a homogeneous phase without phase separation, or to form a fine phase-separated structure composed mainly of the epoxy resin and the thermoplastic resin, without impairing the elastic modulus or strength of the cured epoxy resin. Furthermore, by controlling the weight-average molecular weight of the polysulfone to 25,000 or less, excessive viscosity changes upon dissolution in the epoxy resin can be suppressed, preventing deterioration in the handleability of the resin during prepreg production. Furthermore, the resulting fiber-reinforced composite material has excellent appearance. Furthermore, by controlling the weight-average molecular weight of the polysulfone to 15,000 or more, the viscosity of the epoxy resin can be adjusted even with a small amount, thereby improving the tackiness of the prepreg without impairing the elastic modulus or strength of the cured epoxy resin. Furthermore, it is preferable that the weight average molecular weight of the component [C] is 15,000 or more and 22,000 or less, since this provides a good balance between the modulus of elasticity and strength of the cured product, the tackiness of the prepreg, and the appearance quality of the fiber-reinforced composite material.

[0038] Examples of commercially available products of the component [C] include "Virantage (registered trademark)" VW-10700RFP (manufactured by Solvay Advanced Polymers, Ltd.) and "Sumikaexcel (registered trademark)" PES2603P (manufactured by Sumitomo Chemical Co., Ltd.).

[0039] The content of component [C] in the epoxy resin composition of the present invention is preferably 2 to 15 parts by mass, more preferably 5 to 12 parts by mass, and even more preferably 8 to 12 parts by mass, of component [C] per 100 parts by mass of component [A]. By setting the blending amount of component [C] within this range, it is possible to prevent the components [A], [B], and [C] from coarsely separating into phases after curing, and the elastic modulus, strength, and lightness index L of the obtained cured resin product can be improved. * The tack of the prepreg is also particularly excellent.

[0040] The epoxy resin composition of the present invention may contain a thermoplastic resin other than the component [C] to the extent that the physical properties are not impaired.

[0041] The epoxy resin composition of the present invention may contain a curing accelerator in order to control the curing rate. Examples of the curing accelerator include urea compounds and imidazole compounds. Urea compounds are particularly preferred in terms of the storage stability of the epoxy resin composition.

[0042] Examples of the urea compound include aromatic urea compounds such as 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 3-(4-chlorophenyl)-1,1-dimethylurea, phenyldimethylurea, and toluenebisdimethylurea. Among these, toluenebisdimethylurea is preferred because the resulting epoxy resin composition has excellent fast curing properties and strength.

[0043] Commercially available aromatic urea compounds include DCMU99 (manufactured by Hodogaya Chemical Co., Ltd.) and toluene bisdimethylurea "Omicure (registered trademark)" U-24M (manufactured by CVC Thermoset Specialties).

[0044] The epoxy resin composition of the present invention was kept at 90°C for 60 minutes, and then cured at 135°C for 120 minutes. The cured product was in the form of a 2 mm thick plate, and the L * a * b * Lightness index L in color system * The lightness index L of the cured product is preferably 15 or more, more preferably 20 or more, and even more preferably 30 or more. * When the amount is within this range, coloration of the surface of the obtained fiber-reinforced composite material and coloration of resin pools present in the stitches of the fiber woven fabric substrate become less noticeable, resulting in a fiber-reinforced composite material with excellent appearance quality.

[0045] Brightness index L of cured resin *can be controlled by changing the type and blending ratio of each component contained in the resin composition and the weight-average molecular weight of the component [C]. Examples of methods for increasing the value of L* include reducing the blending amount of the component [A-1], reducing the blending amount of the component [A-3], reducing the blending amount of the component [C], and reducing the weight-average molecular weight of the component [C].

[0046] The epoxy resin composition of the present invention has excellent elastic modulus, strength, and elongation, and is therefore suitable for use as a matrix resin in fiber-reinforced composite materials. That is, the fiber-reinforced composite materials of the present invention comprise a cured product of the epoxy resin composition of the present invention and reinforcing fibers.

[0047] Methods for obtaining fiber-reinforced composite materials include methods in which reinforcing fibers are impregnated with a resin composition during the molding process, such as hand layup, RTM, filament winding, and pultrusion, and methods in which a prepreg in which reinforcing fibers have already been impregnated with a resin composition is molded by autoclave or press molding. Among these, it is preferable to prepare a prepreg from an epoxy resin composition and reinforcing fibers in advance, as this allows precise control of the fiber arrangement and resin ratio and maximizes the properties of the composite material. That is, the prepreg of the present invention is composed of the epoxy resin composition of the present invention and reinforcing fibers.

[0048] Preferred examples of the reinforcing fibers used in the prepreg and fiber-reinforced composite material of the present invention include carbon fiber, graphite fiber, aramid fiber, and glass fiber, with carbon fiber being particularly preferred. The shape and arrangement of the reinforcing fibers are not limited, and fiber structures such as unidirectionally aligned long fibers, single tows, woven fabrics, knitted fabrics, and braided cords can be used. Two or more types of carbon fiber, glass fiber, aramid fiber, boron fiber, PBO fiber, high-strength polyethylene fiber, alumina fiber, and silicon carbide fiber can also be used in combination as the reinforcing fibers.

[0049] Specific examples of carbon fibers include acrylic, pitch, and rayon carbon fibers, and acrylic carbon fibers having particularly high tensile strength are preferably used.

[0050] The carbon fiber may be in the form of twisted yarn, untwisted yarn, or non-twisted yarn, but in the case of twisted yarn, the filaments constituting the carbon fiber are not oriented parallel to one another, which can cause a decrease in the mechanical properties of the resulting carbon fiber reinforced composite material. Therefore, untwisted yarn or non-twisted yarn is preferably used, as it provides a good balance between the formability and strength properties of the carbon fiber reinforced composite material.

[0051] The carbon fiber preferably has a tensile modulus of 200 GPa or more and 440 GPa or less. The tensile modulus of carbon fiber is affected by the crystallinity of the graphite structure that constitutes the carbon fiber, and the higher the crystallinity, the higher the modulus. This range is preferable because it achieves a high level of balance between the rigidity and strength of the carbon fiber reinforced composite material. A more preferred modulus is 230 GPa or more and 400 GPa or less, and even more preferably 260 GPa or more and 370 GPa or less. Here, the tensile modulus of carbon fiber is a value measured in accordance with JIS R7608 (2008).

[0052] The prepreg of the present invention can be produced by various known methods. For example, the prepreg can be produced by a hot melt method in which a resin composition is heated to reduce its viscosity and then impregnated into reinforcing fibers without using an organic solvent.

[0053] In addition, in the hot melt method, a resin composition whose viscosity has been reduced by heating can be directly impregnated into the reinforcing fibers, or a release paper sheet with a resin film can be first prepared by coating the resin composition on release paper or the like, and then a resin film can be placed on both sides or one side of the reinforcing fibers, and the resin composition can be impregnated into the reinforcing fibers by heating and pressurizing.

[0054] The content of reinforcing fibers in the prepreg is preferably 30% by mass or more and 90% by mass or less. By setting it to 30% by mass or more, more preferably 35% by mass or more, and even more preferably 65% ​​by mass or more, the advantages of a fiber-reinforced composite material, such as excellent specific strength and specific modulus, can be easily obtained. In addition, when molding the fiber-reinforced composite material, excessive heat generation during curing can be prevented. On the other hand, by setting it to 90% by mass or less, more preferably 85% by mass or less, the generation of voids in the composite material due to insufficient resin impregnation can be prevented. In addition, the tackiness of the prepreg can be maintained.

[0055] The fiber-reinforced composite material of the present invention can be produced, for example, by laminating the prepregs of the present invention described above in a predetermined form and curing the resin by applying pressure and heat. Methods for applying heat and pressure include press molding, autoclave molding, bagging molding, wrapping tape molding, and internal pressure molding.

[0056] The fiber-reinforced composite material of the present invention can be widely used in aerospace applications, general industrial applications, and sports applications. More specifically, in general industrial applications, it is suitable for use in structures such as automobiles, ships, and railway vehicles. In sports applications, it is suitable for use in golf shafts, fishing rods, and tennis and badminton rackets. [Example]

[0057] The present invention will be described in detail below with reference to examples. However, the scope of the present invention is not limited to these examples. The unit "parts" used in the composition ratios means parts by mass unless otherwise noted. Furthermore, measurements of various characteristics (physical properties) were carried out in an environment of 23°C and 50% relative humidity unless otherwise noted.

[0058] <Various evaluation methods> The epoxy resin compositions of each example were measured using the following measurement methods.

[0059] (1) Three-point bending test of cured resin The uncured resin composition was degassed in a vacuum and then placed in a mold set to a thickness of 2 mm using a 2 mm Teflon spacer. The temperature was raised from 30°C at a rate of 1.7°C / min, held at 90°C for 60 minutes, and then raised at a rate of 2.0°C / min to 135°C for 120 minutes to obtain a 2 mm thick cured resin plate. Test pieces measuring 10 mm wide and 60 mm long were cut from the cured resin and subjected to three-point bending according to JIS K7171 (1994) using an Instron universal testing machine (manufactured by Instron Corporation) with a span of 32 mm, a crosshead speed of 2.5 mm / min, and six samples. The average values ​​of the strength and modulus of elasticity were recorded as the bending strength and the bending modulus of the cured resin, respectively.

[0060] (2) Viscosity measurement of resin composition The viscosity of the resin composition was measured using a dynamic viscoelasticity apparatus (TA Instruments "ARES"-G2). The upper and lower measuring jigs were flat parallel plates with a diameter of 25 mm. The epoxy resin composition was set so that the distance between the upper and lower jigs was 1 mm, and then the measurement was performed in torsion mode (measurement frequency: 0.5 Hz). The temperature was raised from 20°C to 30°C at a rate of 1°C / min, and the complex viscoelastic modulus at 25°C was taken as the viscosity of the resin composition at 25°C.

[0061] (3) Measurement of the brightness index of cured resin The uncured resin composition was degassed in a vacuum, and then placed in a mold set to a thickness of 2 mm using a 2 mm Teflon (registered trademark) spacer. The temperature was raised from 30°C at a rate of 1.7°C / min, held at 90°C for 60 minutes, and then raised at a rate of 2.0°C / min to 135°C for 120 minutes to cure the composition, yielding a 2 mm thick plate-shaped cured resin. A test piece measuring 10 mm wide and 60 mm long was cut from this cured resin, and the lightness index L was measured using a multi-light source spectrophotometer MSC-P (manufactured by Suga Test Instruments Co., Ltd.) by the transmission method. * was measured.

[0062] (4) Prepreg tack evaluation The tackiness when the prepregs were overlapped in an environment of 25°C was evaluated using the following four levels of A to D. A: The adhesive strength is very strong and the handling during lamination is extremely good. B: Strong adhesive strength and good handling when stacked C: The adhesive strength is weak, but there is no problem with handling when stacking. D: The adhesive strength is very weak, peeling occurs easily when laminating, and handling is insufficient.

[0063] <Materials used in Examples and Comparative Examples> (1) Component [A-1]: Isocyanuric acid type epoxy resin "TEPIC (registered trademark)"-S (trifunctional isocyanuric acid type epoxy resin, epoxy equivalent: 100 g / eq, solid at 25°C, manufactured by Nissan Chemical Industries, Ltd.) "TEPIC (registered trademark)"-PAS B26L (2.6-functional isocyanuric acid type epoxy resin, epoxy equivalent: 138 g / eq, liquid at 25°C, manufactured by Nissan Chemical Industries, Ltd.).

[0064] (2) Component [A-2]: Trifunctional or higher glycidylamine epoxy resin Araldite® MY0500 (aminophenol-type epoxy resin, epoxy equivalent: 118 g / eq, liquid at 25°C, manufactured by Huntsman Advanced Materials, Inc.) Araldite® MY0600 (aminophenol-type epoxy resin, epoxy equivalent: 118 g / eq, liquid at 25°C, manufactured by Huntsman Advanced Materials, Inc.) "Araldite (registered trademark)" MY721 (aminophenol type epoxy resin, epoxy equivalent: 120 g / eq, liquid at 25°C, manufactured by Huntsman Advanced Materials, Inc.).

[0065] (3) Component [A-3]: bisphenol-type epoxy resin that is solid at 25°C jER (registered trademark) 4004P (bisphenol F type epoxy resin, epoxy equivalent: 880 g / eq, solid at 25°C, manufactured by Mitsubishi Chemical Corporation).

[0066] (4) Component [A] not belonging to the above: epoxy resin jER (registered trademark) 828 (bisphenol F type epoxy resin, epoxy equivalent: 189 g / eq, liquid at 25°C, manufactured by Mitsubishi Chemical Corporation).

[0067] (5) Component [B]: Dicyandiamide DICY7 (dicyandiamide, manufactured by Mitsubishi Chemical Corporation).

[0068] (6) Component [C]: Polysulfone having a weight-average molecular weight of 15,000 or more and 25,000 or less "Virantage (registered trademark)" VW-10700RFP (polyethersulfone, weight average molecular weight: 21,000, manufactured by Solvay Advanced Polymers, Inc.) "Sumikaexcel (registered trademark)" PES2603P (polyethersulfone, weight average molecular weight: 16,000, manufactured by Sumitomo Chemical Co., Ltd.).

[0069] (7) Component [C']: Other thermoplastic resins · “Virantage (registered trademark)” VW-30500RP (polysulfone, weight average molecular weight: 14000, manufactured by Solvay Advanced Polymers Co., Ltd.) "Sumikaexcel (registered trademark)" PES5003P (polyethersulfone, weight-average molecular weight: 47,000, manufactured by Sumitomo Chemical Co., Ltd.) "Vinylec (registered trademark)" K (polyvinyl formal, weight average molecular weight: 50,000, manufactured by JNC Corporation).

[0070] (8) Curing accelerator "Omicure®" U-24M (2,4-toluenebis(dimethylurea), manufactured by CVC Thermoset Specialties) DCMU99 (3-(3,4-dichlorophenyl)-1,1-dimethylurea, manufactured by Hodogaya Chemical Industry Co., Ltd.).

[0071] (9) Carbon fiber "TORAYCA (registered trademark)" T1100G-24K (24,000 fibers, tensile modulus: 324 GPa, density: 1.8 g / cm 3 , manufactured by Toray Industries, Inc.

[0072] Example 1 (Preparation of Resin Composition) A resin composition was prepared by the following method.

[0073] A kneading apparatus was charged with 35 parts of TEPIC (registered trademark)-S as the component [A-1], 35 parts of Araldite (registered trademark) MY0500 as the component [A-2], 30 parts of jER (registered trademark) 4004P as the component [A-3], and 10 parts of Virantage (registered trademark) VW-10700RP as the component [C], and the temperature was raised to 150°C while kneading. After kneading at 150°C for 60 minutes, the temperature was lowered to 55 to 65°C, and 7 parts of DICY7 as the component [B] and 2 parts of Omicure (registered trademark) U-24M as a curing accelerator were added and kneaded for 30 minutes to obtain a resin composition.

[0074] At this time, the component that was solid at 25°C accounted for 65% by mass of 100% by mass of the component [A].

[0075] The obtained resin composition was subjected to a three-point bending test, and the elastic modulus was 4.7 GPa and the strength was 190 MPa. Compared with Comparative Examples 2, 3, and 4 (not containing the component [C]) described later, superior elastic modulus and strength were obtained. In addition, the resin viscosity was 1.8 × 10 5 The viscosity was Pa·s, which was suitable for prepreg applications. * The value was 23, and the appearance quality was also excellent.

[0076] (Prepreg production) The resin composition obtained above was applied onto a release paper using a knife coater to give a resin basis weight of 21 g / m 2 Next, two resin films with a fiber basis weight of 125 g / m were prepared. 2 Two sheets of the resin film were placed on both sides of the carbon fibers, which were aligned in one direction to form a sheet, and the carbon fibers were impregnated with the epoxy resin composition under heating and pressure at a temperature of 110°C and a maximum pressure of 1 MPa to obtain a prepreg. The tack evaluation of the produced prepreg was graded A, and the handleability of the prepreg was extremely good.

[0077] <Examples 2 to 13> Resin compositions and prepregs were obtained in the same manner as in Example 1, except that the ingredients were blended according to the blending ratios in Tables 1 and 2.

[0078] The results of various measurements in the examples are shown in Tables 1 and 2. Even when the formulation of the resin composition was changed as in Examples 2 to 13, the elastic modulus, strength, and appearance quality of the cured resin were excellent, and the tackiness of the prepreg did not pose any problems in handling.

[0079] <Comparative Examples 1 to 6> A resin composition and a prepreg were obtained in the same manner as in Example 1, except that the ingredients were blended according to the blending ratios in Table 2.

[0080] In Comparative Example 1, no substance equivalent to the component [C] was blended. Comparing Comparative Example 1 with Example 1, it is clear that blending the component [C] prevents the resin viscosity from becoming too low, and improves the tackiness of the prepreg.

[0081] In Comparative Example 2, "Virantage (registered trademark)" VW-30500RP was blended in place of component [C]. "Virantage (registered trademark)" VW-30500RP does not satisfy the requirement that the weight-average molecular weight be 15,000 or more and 25,000 or less. Comparing Example 1 and Comparative Example 2, it can be seen that the strength of the cured resin is dramatically improved by adjusting the weight-average molecular weight of component [C] to 15,000 or more and 25,000 or less.

[0082] In Comparative Example 3, "Sumikaexcel (registered trademark)" PES5003P was blended in place of component [C]. "Sumikaexcel (registered trademark)" PES5003P does not meet the requirement of a weight-average molecular weight of 15,000 or more and 25,000 or less. Comparing Example 1 and Comparative Example 3, it can be seen that the strength of the cured resin is dramatically improved by adjusting the weight-average molecular weight of component [C] to 15,000 or more and 25,000 or less. Furthermore, in Comparative Example 3, the lightness index L * The number increased to 10, and the coloring became more noticeable.

[0083] In Comparative Example 4, "Vinylec (registered trademark)" K was blended in place of component [C]. Comparing Example 1 and Comparative Example 4, it is clear that the strength of the cured resin is dramatically improved by using polysulfone having a weight-average molecular weight of 15,000 or more and 25,000 or less as component [C].

[0084] In Comparative Example 5, the blending ratio of the component [A-1] to the component [A] is 15 mass %. Comparing Example 1 and Comparative Example 5, it is found that the elastic modulus and strength of the resin are excellent when the component [A-1] is contained in an amount of 20 mass % to 40 mass % of the component [A] (100 mass %).

[0085] In Comparative Example 6, the compounding ratio of component [A-1] to component [A] was 45% by mass. When the obtained resin composition was left to stand at room temperature, a large amount of solid matter precipitated and solidified, making it unsuitable as a matrix resin for prepreg, and the resin viscosity and prepreg tack could not be measured. Comparing Example 1 and Comparative Example 6, it was found that by including 20% ​​by mass or more and 40% by mass or less of component [A-1] in 100% by mass of component [A], the strength and brightness index L of the resin were improved. * It is clear that the

[0086] [Table 1]

[0087] Table 2

Claims

1. An epoxy resin composition comprising the following components [A] to [C]: In 100% by mass of the component [A], the component [A-1] contains 20% by mass or more and 40% by mass or less of a trifunctional isocyanuric acid type epoxy resin, and the component [A-2] contains 15% by mass or more of a trifunctional or higher functional glycidylamine type epoxy resin. Epoxy resin composition. [A]: Epoxy resin [B]: Dicyandiamide [C]: Polysulfone having a weight average molecular weight of 15,000 or more and 25,000 or less

2. 2. The epoxy resin composition according to claim 1, wherein the epoxy resin composition is maintained at 90°C for 60 minutes and then cured at 135°C for 120 minutes to produce a 2 mm thick plate-shaped cured product, which has a lightness index L* of 15 or more in the L*a*b* color system measured by a transmission method.

3. 3. The epoxy resin composition according to claim 1, comprising 2 parts by mass or more and 15 parts by mass or less of the component [C] per 100 parts by mass of the component [A].

4. 4. The epoxy resin composition according to claim 1, wherein the component [A-2] is a tri- or higher functional glycidyl amine-type epoxy resin in an amount of 20% by mass to 60% by mass, based on 100% by mass of the component [A].

5. 5. The epoxy resin composition according to claim 1, wherein the component [A-3] is a bisphenol epoxy resin that is solid at 25°C in an amount of 10% by mass or more and 40% by mass or less, relative to 100% by mass of the component [A].

6. 6. The epoxy resin composition according to claim 1, wherein, relative to 100% by mass of the component [A], 60% by mass or more of a component that is in a solid form at 25°C is contained.

7. A prepreg comprising the epoxy resin composition according to any one of claims 1 to 6 and reinforcing fibers.

8. A fiber-reinforced composite material comprising a cured product of the epoxy resin composition according to any one of claims 1 to 6 and reinforcing fibers.

Images