Epoxy resin curing agent, epoxy resin composition and its cured product, fiber-reinforced composite material, and wind turbine blade.

Abstract

The present invention provides an epoxy resin curing agent comprising: a component (a1), a polyether polyamine; a component (a2), an aliphatic polyamine having an alicyclic structure; and a component (a3), an aliphatic polyamine having an aromatic ring. Also provided are: an epoxy resin composition and a cured product thereof; a fiber-reinforced composite containing the cured product of the epoxy resin composition and reinforcing fibers; and a wind power generation blade.

Description

[Technical Field]

[0001] The present invention relates to an epoxy resin curing agent, an epoxy resin composition and its cured product, a fiber-reinforced composite material comprising the cured product of the epoxy resin composition and reinforcing fibers, and a wind turbine blade comprising the fiber-reinforced composite material. [Background technology]

[0002] Fiber-reinforced plastics (FRPs) are attracting attention as a metal substitute due to their extremely high modulus of elasticity and strength. Demand for FRPs is expected to accelerate, particularly in automotive structural materials, wind turbine blades, pressure vessels, and aerospace applications. Consequently, demand for reinforcing fibers and matrix resins such as epoxy resins used in FRPs has also increased in recent years.

[0003] Incidentally, since the molding methods for FRP differ for automotive structural materials, wind turbine blades, pressure vessels, and aerospace applications, the required properties for the matrix resin used in FRP also differ depending on the application. For example, wind turbine blades are now being molded using infusion molding, Va-RTM (Vacuum Assist Resin Transfer Molding), or Light-RTM methods. In these methods, for example, reinforcing fibers are pre-placed in a mold consisting of an upper mold made of film or FRP and a lower mold. The mold is then vacuumed, and an epoxy resin composition, which will serve as the matrix resin, is filled at atmospheric pressure to impregnate the reinforcing fibers. Subsequently, the epoxy resin is cured to form the mold. In infusion molding, Va-RTM, and Light-RTM molding methods, due to the characteristics of these molding processes, it usually takes several tens of minutes to fill the mold with the epoxy resin composition, which is a mixture of epoxy resin and epoxy resin curing agent. Therefore, the epoxy resin compositions used in these molding methods are required to have a long pot life.

[0004] Epoxy resin compositions for wind turbine blade applications are also known, and isophorone diamine and polyamine compounds with a polyether skeleton are used as epoxy resin curing agents. For example, Patent Document 1 discloses an epoxy resin composition for wind turbine blades that has low viscosity and high processing performance, which comprises an epoxy resin of a predetermined composition and a curing agent containing polyetheramine curing agent D230, isophorone diamine IPDA, and tertiary amine accelerator K54, each in predetermined ranges.

[0005] Patent Document 2 also discloses a blend containing an epoxy resin component comprising one or more epoxy resins selected from the group of aromatic epoxy resins and / or cyclic aliphatic epoxy resins, a cyclic carbonate having 1 to 10 carbon atoms, and one or more predetermined reactive diluents, each in a predetermined range; and a curing agent comprising one or more polyalkoxy polyamines, one or more further amines selected from the group of aromatic, aryl aliphatic, cyclic aliphatic, heterocyclic, and aliphatic polyamines having at least 3 carbon atoms and having at least 4 reactive NH functional groups in primary and / or secondary amino groups, and a predetermined catalyst, each in a predetermined range, wherein the ratio of the amine equivalents in the curing agent to the total amount of epoxy resin and cyclic carbonate in the epoxy resin component is within a specific range. The blend is described as having sufficient fluidity for the Va-RTM method, curing completely in a short time, and meeting mechanical requirements (e.g., high tensile strength, elongation at break, and bending resistance, as well as thermal stability required for use in large fiber-reinforced components) for the manufacture of large fiber-reinforced components, particularly rotor blades for wind power plants. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Chinese Patent Application Publication No. 104151780 Specification [Patent Document 2] Special Publication No. 2015-511264 [Overview of the project] [Problems that the invention aims to solve]

[0007] As mentioned above, epoxy resin compositions used in molding by methods such as Va-RTM require a long pot life. Furthermore, for epoxy resin compositions used as the matrix resin for FRP, it is important that a highly elastic FRP can be obtained. Furthermore, for wind turbine blades used offshore, excellent saltwater resistance is also desired. However, the technologies disclosed in Patent Documents 1 and 2 have found it difficult to satisfy all of these required characteristics.

[0008] The object of the present invention is to provide an epoxy resin curing agent, an epoxy resin composition and its cured product, a fiber-reinforced composite material containing the cured product of the epoxy resin composition and reinforcing fibers, and a wind turbine blade, which can provide an epoxy resin composition suitable for molding wind turbine blades that have a long pot life and are highly elastic and have excellent saltwater resistance by the Va-RTM method or the like. [Means for solving the problem]

[0009] The inventors have found that the above problems can be solved by an epoxy resin curing agent containing a polyether polyamine, an aliphatic polyamine having an alicyclic structure, and an aliphatic polyamine having an aromatic ring. In other words, the present invention relates to the following. [1] An epoxy resin curing agent containing component (a1): polyether polyamine, component (a2): aliphatic polyamine having an alicyclic structure, and component (a3): aliphatic polyamine having an aromatic ring. [2] An epoxy resin composition comprising an epoxy resin and the epoxy resin curing agent described in [1] above. [3] A cured product of the epoxy resin composition described in [2] above. [4] A fiber-reinforced composite material comprising a cured product of the epoxy resin composition described in [3] above and reinforcing fibers. [5]A wind power blade including the fiber reinforced composite material described in [4] above.

Advantages of the Invention

[0010] According to the epoxy resin curing agent of the present invention, a pot life is long, and the epoxy resin composition suitable for shaping a wind power blade by methods, such as Va-RTM method, can be provided. The wind power blade obtained by using this epoxy resin composition is highly elastic and excellent in salt water resistance.

Embodiments for Carrying Out the Invention

[0011] [Epoxy Resin Curing Agent] The epoxy resin curing agent of the present invention contains polyether polyamine (a1), an aliphatic polyamine (a2) having an alicyclic structure, and an aliphatic polyamine (a3) having an aromatic ring. Since the epoxy resin curing agent of the present invention has the above-described configuration, the epoxy resin composition suitable for shaping a wind power blade having a long pot life, high elasticity, and excellent salt water resistance by methods, such as Va-RTM method, can be provided.

[0012] Although the reason why the epoxy resin curing agent of the present invention exhibits the above-described effects is not clear, it is presumed as follows. Polyether polyamine (a1) (hereinafter also referred to as "component (a1)") is a curing agent component having a low viscosity and capable of realizing a long pot life. On the other hand, since the curing rate is slow and the Tg of the cured product of the obtained epoxy resin composition also tends to be low, there are production problems such as difficulty in curing unless under high temperature conditions. An aliphatic polyamine (a2) having an alicyclic structure (hereinafter also referred to as "component (a2)") is also a curing agent component capable of realizing a long pot life. Component (a2) tends to have a higher viscosity as compared with polyether polyamine (a1), but improves the Tg of the cured product of the obtained epoxy resin composition and makes it easier to achieve high elasticity. Furthermore, the epoxy resin curing agent of the present invention contains an aliphatic polyamine (a3) ​​having an aromatic ring (hereinafter also referred to as "component (a3)"), which suppresses the excessive reduction in curing speed caused by components (a1) and (a2) that enable a long pot life. In addition, it is believed that the crystallinity-improving effect derived from the structure of component (a3) ​​provides an improved saltwater resistance effect that could not be achieved with components (a1) and (a2) alone.

[0013] <Component (a1): Polyether polyamine> The epoxy resin curing agent of the present invention contains a polyether polyamine as component (a1). The polyether polyamine used in the present invention is preferably a compound having a polyether structure and two or more amino groups containing at least one active hydrogen, from the viewpoint of exhibiting its function as an epoxy resin curing agent component. "Amino group containing active hydrogen" refers to an amino group in which at least one hydrogen atom is directly bonded to the nitrogen atom of the amino group. Examples of polyether polyamines include linear polyether polyamines and cyclic polyether polyamines. From the viewpoint of having low viscosity suitable for molding by the Va-RTM method, availability, and cost-effectiveness, linear polyether polyamines are preferred as component (a1).

[0014] Component (a1) is more preferably a linear polyetherdiamine from the viewpoint of having low viscosity suitable for molding by the Va-RTM method and achieving a long pot life. Even more preferably, component (a1) is a polyoxyalkylenediamine represented by the following general formula (1). H2N-(R 1 O) n -R 2 -NH2(1) (In formula (1), R 1 n is an alkylene group with 2 to 6 carbon atoms. 1 O) The average number of repetitions in units, and a number greater than 1. 1 They may all be the same or they may be different. 2is a divalent group having 2 to 12 carbon atoms.)

[0015] R in formula (1) 1 is preferably an alkylene group having 2 to 4 carbon atoms, more preferably an alkylene group having 2 to 3 carbon atoms. Specific examples of R 1 include an ethylene group, a propylene group, a trimethylene group, a tetramethylene group, a butylene group, an isobutylene group, a pentamethylene group, a hexamethylene group, etc. Preferably, it is one or more selected from the group consisting of an ethylene group, a propylene group, a trimethylene group, a tetramethylene group, a butylene group, and an isobutylene group. More preferably, it is one or more selected from the group consisting of an ethylene group, a propylene group, and a trimethylene group. Even more preferably, it is one or more selected from the group consisting of an ethylene group and a propylene group. Even more preferably, it is a propylene group.)

[0016] n in formula (1) is the average number of repetitions of the (R 1 O) unit. From the viewpoint of having a low viscosity suitable for molding by the Va-RTM method and achieving a long pot life, it is preferably 1.5 to 100, more preferably 1.5 to 50, even more preferably 2 to 30, even more preferably 2 to 20, even more preferably 2 to 10, even more preferably 2 to 6.)

[0017] R in formula (1) 2 is preferably a divalent linear aliphatic group having 2 to 12 carbon atoms, more preferably 2 to 8 carbon atoms, and even more preferably 2 to 4 carbon atoms. Specific examples of R 2 include an ethylene group, a propylene group, a trimethylene group, a tetramethylene group, a butylene group, an isobutylene group, a pentamethylene group, a hexamethylene group, a heptamethylene group, an octamethylene group, an ethylhexylene group, a nonamethylene group, a decamethylene group, an undecamethylene group, a dodecamethylene group, etc. Among these, R 2Preferably, it is one or more selected from the group consisting of ethylene group, propylene group, trimethylene group, tetramethylene group, butylene group, isobutylene group, pentamethylene group, hexamethylene group, heptamethylene group, octamethylene group, and ethylhexylene group; more preferably, one or more selected from the group consisting of ethylene group, propylene group, trimethylene group, tetramethylene group, butylene group, and isobutylene group; even more preferably, one or more selected from the group consisting of ethylene group, propylene group, and trimethylene group; and even more preferably, propylene group.

[0018] Component (a1) is preferably one or more selected from the group consisting of polyoxyethylenediamine, polyoxypropylenediamine, and polyoxyethylene-polyoxypropylenediamine, more preferably one or more selected from the group consisting of polyoxypropylenediamine and polyoxyethylene-polyoxypropylenediamine, and even more preferably polyoxypropylenediamine, from the viewpoint of having low viscosity suitable for molding by the Va-RTM method and achieving a long pot life. The average number of repeating oxyalkylene units in polyoxyethylenediamine, polyoxypropylenediamine, and polyoxyethylene-polyoxypropylenediamine is preferably 1.5 to 100, more preferably 1.5 to 50, even more preferably 2 to 30, even more preferably 2 to 20, even more preferably 2 to 10, and even more preferably 2 to 6, from the viewpoint of having low viscosity suitable for molding by the Va-RTM method and achieving a long pot life.

[0019] Component (a1) is more preferably a polyoxyalkylenediamine represented by the following general formula (1-1). [ka] (In equation (1-1), n1, n2, and n3 are the average number of repetitions, and n1+n3>1 and n2≧0.) The sum of n1, n2, and n3 in formula (1-1), (n1+n2+n3), is preferably 1.5 to 100, more preferably 1.5 to 50, even more preferably 2 to 30, even more preferably 2 to 20, even more preferably 2 to 10, and even more preferably 2 to 6. In formula (1-1), n2 is preferably 0 to 50, more preferably 0 to 30, even more preferably 0 to 20, and even more preferably 0.

[0020] Component (a1) is more preferably a polyoxypropylenediamine represented by the following general formula (1-2). [ka] (In equation (1-2), n is the average number of repetitions and is a number greater than 1.) In formula (1-2), n is preferably 1.5 to 100, more preferably 1.5 to 50, even more preferably 2 to 30, even more preferably 2 to 20, even more preferably 2 to 10, and even more preferably 2 to 6, from the viewpoint of having low viscosity suitable for molding by the Va-RTM method and achieving a long pot life.

[0021] A commercially available polyether polyamine can also be used as component (a1). Examples of commercially available polyether polyamines include the JEFFAMINE D series (polyoxypropylenediamine, D-230, D-400, D-2000, D-4000) and the JEFFAMINE ED series (ED-600, ED-900, ED-2003) (all manufactured by Huntsman).

[0022] <Component (a2): Aliphatic polyamine having an alicyclic structure> The epoxy resin curing agent of the present invention contains an aliphatic polyamine having an alicyclic structure as component (a2). Component (a2) is an aliphatic polyamine having an alicyclic structure and not containing an aromatic ring, from the viewpoint of achieving a long pot life.

[0023] Component (a2) only needs to have at least one alicyclic structure, preferably 1 to 3, more preferably 1 to 2, and even more preferably only 1 from the viewpoint of low viscosity suitable for molding by the Va-RTM method.

[0024] Examples of alicyclic structures in component (a2) include cycloalkane rings, cycloalkene rings, bicycloalkane rings, bicycloalkene rings, and tricycloalkane rings. Among these, cycloalkane rings are preferred, more preferably cycloalkane rings having 5 to 8 carbon atoms, and even more preferably cyclohexane rings.

[0025] Component (a2) is preferably an aliphatic polyamine having at least one amino group directly bonded to an alicyclic structure, from the viewpoint of achieving a long pot life and obtaining a cured product with high Tg and high elasticity.

[0026] Component (a2) is preferably a diamine from the viewpoint of obtaining a highly elastic cured product.

[0027] Specific examples of component (a2) include isophorone diamine, mensendiamine, norbornanediamine, tricyclodecanediamine, adamantanediamine, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,2-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-3,6-diethylcyclohexane, 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane (bis(4-amino-3-methylcyclohexyl)methane), 3,3',5,5'-tetramethyl-4,4'-diaminodicyclohexylmethane, 4,4'-diaminodicyclohexylmethane, etc., and one or more of these can be used. Among the above, from the viewpoint of having low viscosity suitable for molding by the Va-RTM method, achieving a long pot life, and obtaining a cured product with high Tg and high elasticity, component (a2) is preferably one or more selected from the group consisting of isophorone diamine, mensendiamine, norbornanediamine, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, and 1,4-diamino-2-methylcyclohexane, more preferably one or more selected from the group consisting of isophorone diamine, mensendiamine, and norbornanediamine, and even more preferably isophorone diamine.

[0028] <Component (a3): Aliphatic polyamine having an aromatic ring> The epoxy resin curing agent of the present invention contains an aliphatic polyamine having an aromatic ring as component (a3). Because component (a3) ​​has an aromatic ring, it can impart saltwater resistance to the cured epoxy resin composition. Furthermore, because component (a3) ​​is an aliphatic polyamine that does not have an amino group directly bonded to the aromatic ring, it is easy to achieve low viscosity suitable for molding by the Va-RTM method.

[0029] Component (a3) ​​only needs to have at least one aromatic ring, preferably 1 to 3, more preferably 1 to 2, and even more preferably only 1, from the viewpoint of low viscosity suitable for molding by the Va-RTM method.

[0030] Component (a3) ​​is preferably a diamine from the viewpoint of having low viscosity suitable for molding by the Va-RTM method. More preferably, component (a2) is a diamine represented by the following general formula (2). [ka] (In formula (2), R 11 and R 12 Each of these is an alkylene group with 1 to 6 carbon atoms.

[0031] R in equation (2) 11 and R12 Each of these is independently an alkylene group, preferably having 1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms. 11 and R 12 Specific examples include methylene group, ethylene group, propylene group, trimethylene group, tetramethylene group, butylene group, isobutylene group, pentamethylene group, hexamethylene group, etc. Preferably, one or more selected from the group consisting of ethylene group, trimethylene group, and tetramethylene group; more preferably, one or more selected from the group consisting of methylene group, ethylene group, and trimethylene group; and even more preferably, a methylene group.

[0032] Specific examples of component (a3) ​​include orthoxylylenediamine, metaxylylenediamine (MXDA), and paraxylylenediamine (PXDA), 1,2-bis(aminoethyl)benzene, 1,3-bis(aminoethyl)benzene, 1,4-bis(aminoethyl)benzene, 1,2-bis(aminopropyl)benzene, 1,3-bis(aminopropyl)benzene, and 1,4-bis(aminopropyl)benzene, and one or more of these can be used. Among the above, xylylenediamine is preferred as component (a3) ​​from the viewpoint of improving the saltwater resistance of the cured epoxy resin composition. Among xylylenediamines, one or more selected from the group consisting of metaxylylenediamine and paraxylylenediamine are preferred from the viewpoint of improving the saltwater resistance of the cured epoxy resin composition, and metaxylylenediamine alone or a mixture of metaxylylenediamine and paraxylylenediamine are more preferred from the viewpoint of low viscosity suitable for molding by the Va-RTM method, and metaxylylenediamine is even more preferred. When component (a3) ​​is a mixture of metaxylylenediamine and paraxylylenediamine, the mass ratio of metaxylylenediamine to paraxylylenediamine is preferably 99 / 1 to 50 / 50, more preferably 99 / 1 to 60 / 40, and even more preferably 99 / 1 to 75 / 25, from the viewpoint of low viscosity and improved saltwater resistance.

[0033] Furthermore, the polyamines relating to components (a1) to (a3) ​​can be used after at least a portion of them have been modified. Examples of modified polyamines relating to components (a1) to (a3) ​​include Mannich modified products, epoxy modified products, Michael adducts, Michael adduct-polycondensate products, styrene modified products, and polyamide modified products of the polyamine.

[0034] <Content> From the viewpoint of providing an epoxy resin composition suitable for molding wind turbine blades that have a long pot life, high elasticity, and excellent saltwater resistance by methods such as Va-RTM, the content of components (a1) to (a3) ​​in the epoxy resin curing agent of the present invention is preferably as follows.

[0035] The content of component (a1) in the epoxy resin curing agent is preferably 60 to 90% by mass, more preferably 65 to 85% by mass, and even more preferably 65 to 75% by mass. The content of component (a2) in the epoxy resin curing agent is preferably 2 to 30% by mass, more preferably 5 to 25% by mass, and even more preferably 10 to 25% by mass. The content of component (a3) ​​in the epoxy resin curing agent is preferably 1 to 25% by mass, more preferably 5 to 20% by mass, and even more preferably 5 to 15% by mass.

[0036] Furthermore, a preferred combination of the content of components (a1) to (a3) ​​in the epoxy resin curing agent is a content of 60 to 90% by mass for component (a1) and a total content of 10 to 40% by mass for components (a2) and (a3). A more preferred combination is a content of 65 to 85% by mass for component (a1) and a total content of 15 to 35% by mass for components (a2) and (a3). An even more preferred combination is a content of 65 to 75% by mass for component (a1) and a total content of 25 to 35% by mass for components (a2) and (a3).

[0037] The total content of components (a1) to (a3) ​​in the epoxy resin curing agent is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and also 100% by mass or less.

[0038] The ratio of the content of component (a3) ​​to the total content of component (a2) and component (a3) ​​in the epoxy resin curing agent is preferably 0.15 to 0.70, more preferably 0.20 to 0.55, and even more preferably 0.25 to 0.45, as a mass ratio [(a3) / {(a2)+(a3)}], from the viewpoint of improving the saltwater resistance of the cured epoxy resin composition.

[0039] <Other ingredients> The epoxy resin curing agent of the present invention may contain known curing agents other than components (a1) to (a3). Among the above, curing agents other than components (a1) to (a3) ​​include polyamine compounds having two or more amino groups in the molecule, or modified versions thereof. Examples of such polyamine compounds include linear aliphatic polyamine compounds such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexamethylenediamine, 2-methylpentamethylenediamine, and trimethylhexamethylenediamine; aromatic polyamine compounds such as phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, and diethyltoluenediamine; and polyamine compounds having a heterocyclic structure such as N-aminoethylpiperazine and N,N'-bis(aminoethyl)piperazine. Modified versions of such polyamine compounds include Mannich modified products, epoxy modified products, Michael adducts, Michael adduct-polycondensates, styrene modified products, and polyamide modified products of the above compounds. These can be used individually or in combination of two or more.

[0040] From the viewpoint of efficiently exhibiting the effects of the present invention, if the epoxy resin curing agent of the present invention contains curing agents other than components (a1) to (a3), the content of these curing agents is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 10% by mass or less, even more preferably 5% by mass or less, and even more preferably 1% by mass or less, relative to the total amount of the epoxy resin curing agent of the present invention. The lower limit is 0% by mass.

[0041] [Epoxy resin composition] The epoxy resin composition of the present invention contains an epoxy resin and the epoxy resin curing agent of the present invention. In this specification, "epoxy resin" means a component used as the main component of the epoxy resin composition.

[0042] <Epoxy resin> Any epoxy resin having a glycidyl group that can react with the active hydrogen in the epoxy resin curing agent of the present invention can be used as the epoxy resin. From the viewpoint of obtaining a highly elastic cured product, it is preferable to use an epoxy resin that contains an aromatic ring or alicyclic structure in its molecule.

[0043] An epoxy resin containing an aromatic ring in its molecule can be any resin containing at least one aromatic ring and at least two epoxy groups. The aromatic ring may be a monoring or a fused ring, and examples include, but is not limited to, a benzene ring, a naphthalene ring, anthracene ring, and a tetracene ring. Among these, a benzene ring and a naphthalene ring are preferred, and a benzene ring is more preferred.

[0044] Preferred epoxy resins containing aromatic rings in their molecules include, for example, bisphenol-type epoxy resins such as bisphenol A-type epoxy resin, bisphenol E-type epoxy resin, and bisphenol F-type epoxy resin; biphenol-type epoxy resins; phenol novolac-type epoxy resins; and resorcinol-type epoxy resins. Among the above, one or more selected from the group consisting of bisphenol-type epoxy resins and biphenol-type epoxy resins are more preferred, and from the viewpoint of obtaining a highly elastic cured product, the epoxy resin represented by the following general formula (3) is even more preferred. [ka] (In formula (3), R 31 ~R 34 Each of these is an alkyl group having 1 to 6 carbon atoms, and each of p, q, r, and s is an integer from 0 to 4. 31 , multiple R 32 , multiple R 33 , and multiple R 34 They may all be the same, or they may be different from one another. 1 and Y 2 Each of these is independently a single bond, -CH2-, -CH(CH3)-, or -C(CH3)2-. 35 (The compound is -CH2CH(OH)- or -CH(OH)CH2-. m represents the average number of repeating units, ranging from 0 to 2.0.) R 31 ~R 34 It is preferably an alkyl group having 1 to 4 carbon atoms, and more preferably one or more selected from the group consisting of a methyl group, an ethyl group, an isopropyl group, and a t-butyl group. p, q, r, and s are preferably integers between 0 and 2, more preferably 0 or 1, and even more preferably all 0. Y 1 and Y 2 It is preferably -CH2- or -C(CH3)2-, and more preferably -C(CH3)2-. Furthermore, from the viewpoint of obtaining a highly elastic cured product, m is preferably 0 to 1.0, more preferably 0.01 to 0.5, even more preferably 0.01 to 0.2, and even more preferably 0.01 to 0.15.

[0045] Among the above, a bisphenol A type epoxy resin represented by the following formula (3-1) is more preferable. [ka] In the above formula, R 35 And m is the same as above. Epoxy resins may be used individually or in combination of two or more types.

[0046] The epoxy resin may further contain a reactive diluent from the viewpoint of obtaining a low-viscosity epoxy resin composition suitable for molding by the Va-RTM method, and from the viewpoint of improving workability. Examples of reactive diluents include low molecular weight compounds having at least one epoxy group, such as aromatic monoglycidyl ethers like phenyl glycidyl ether and cresyl glycidyl ether; alkyl monoglycidyl ethers like butyl glycidyl ether, hexyl glycidyl ether, octyl glycidyl ether, decyl glycidyl ether, lauryl glycidyl ether, and tetradecyl glycidyl ether; and diglycidyl ethers of aliphatic diols such as 1,3-propanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, and 1,6-hexanediol diglycidyl ether. The above-mentioned reactive diluents can be used individually or in combination of two or more.

[0047] The epoxy equivalent of the epoxy resin is preferably 400 g / equivalent or less, more preferably 300 g / equivalent or less, even more preferably 250 g / equivalent or less, and even more preferably 220 g / equivalent or less, from the viewpoint of suppressing the low viscosity of the epoxy resin composition and an excessive decrease in the curing rate. The lower limit is not particularly limited, but when the epoxy resin contains a bisphenol A type epoxy resin represented by formula (3-1), it is preferably 170 g / equivalent or more.

[0048] From the viewpoint of obtaining a low-viscosity epoxy resin composition suitable for molding by the Va-RTM method, the viscosity of the epoxy resin at a temperature of 30°C is preferably 20,000 mPa·s or less, more preferably 15,000 mPa·s or less, even more preferably 10,000 mPa·s or less, even more preferably 5,000 mPa·s or less, even more preferably 3,000 mPa·s or less, even more preferably 2,000 mPa·s or less, and even more preferably 1,500 mPa·s or less. There is no particular lower limit to the viscosity of the epoxy resin at a temperature of 30°C, but it is usually 5 mPa·s or more. The viscosity of epoxy resin can be measured using an E-type viscometer, specifically by the method described in the examples.

[0049] <Other ingredients> The epoxy resin composition of the present invention may further contain, depending on the application, other components such as fillers, plasticizers and other modifying components, thixotropes and other flow-adjusting components, pigments, leveling agents, tackifiers, and elastomer fine particles.

[0050] <Content> The ratio of epoxy resin to epoxy resin curing agent in the epoxy resin composition of the present invention is such that the ratio of the number of active hydrogens in the epoxy resin curing agent to the number of epoxy groups in the epoxy resin (number of active hydrogens in the epoxy resin curing agent / number of epoxy groups in the epoxy resin) is preferably 1 / 0.5 to 1 / 2, more preferably 1 / 0.75 to 1 / 1.5, and even more preferably 1 / 0.8 to 1 / 1.2. This ratio only needs to be within the above range in the end, and may be constant during molding of the epoxy resin composition or may be varied during molding.

[0051] From the viewpoint of obtaining the effects of the present invention, the total content of epoxy resin and epoxy resin curing agent in the epoxy resin composition is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more, and also 100% by mass or less.

[0052] Furthermore, from the viewpoint of low viscosity suitable for molding by the Va-RTM method and achieving a long pot life, it is preferable that the epoxy resin content in the epoxy resin composition is 65 to 85% by mass, the epoxy resin curing agent content is 15 to 35% by mass, and the total content of epoxy resin and epoxy resin curing agent in the epoxy resin composition is 80 to 100% by mass. More preferably, the epoxy resin content in the epoxy resin composition is 70 to 80% by mass, the epoxy resin curing agent content is 20 to 30% by mass, and the total content of epoxy resin and epoxy resin curing agent in the epoxy resin composition is 80 to 100% by mass.

[0053] <Viscosity> The viscosity of the epoxy resin composition of the present invention at a temperature of 30°C is preferably 5,000 mPa·s or less, more preferably 3,000 mPa·s or less, even more preferably 2,000 mPa·s or less, even more preferably 1,000 mPa·s or less, even more preferably 800 mPa·s or less, and even more preferably 600 mPa·s or less, from the viewpoint of low viscosity suitable for molding by the Va-RTM method. There is no particular lower limit to the viscosity of the epoxy resin composition at a temperature of 30°C, but it is usually 5 mPa·s or more. The viscosity of the epoxy resin composition can be measured using an E-type viscometer, similar to the viscosity of the epoxy resin itself, and specifically, it can be measured by the method described in the examples.

[0054] <Pot Life> The epoxy resin composition of the present invention has a long pot life. Specifically, the time it takes for the viscosity to reach 0.3 Pa·s at a temperature of 50°C is preferably 2500 seconds or more, more preferably 3000 seconds or more, and even more preferably 3200 seconds or more. The pot life of the epoxy resin composition can be measured specifically by the method described in the examples.

[0055] <Method for preparing epoxy resin composition> There are no particular restrictions on the method for preparing the epoxy resin composition. It can be prepared by mixing an epoxy resin curing agent, epoxy resin, and other components as needed using known methods and apparatus. There are no particular restrictions on the mixing order of the components contained in the epoxy resin composition. The epoxy resin curing agent may be prepared first and then mixed with the epoxy resin, or the components (a1) to (a3) ​​constituting the epoxy resin curing agent, as well as the other components, may be mixed simultaneously with the epoxy resin. From the viewpoint of avoiding gelation before use, it is preferable to bring the components of the epoxy resin composition into contact and mix them immediately before use. The temperature when mixing the components of the epoxy resin composition can be appropriately adjusted according to the viscosity of the epoxy resin, but from the viewpoint of suppressing viscosity increase, it is preferably 120°C or lower, more preferably 100°C or lower, and from the viewpoint of miscibility of the epoxy resin, it is preferably 30°C or higher, more preferably 50°C or higher. The mixing time is preferably in the range of 0.1 to 15 minutes, more preferably 0.2 to 10 minutes, and even more preferably 0.5 to 5 minutes.

[0056] [Cured product] The cured product of the epoxy resin composition of the present invention (hereinafter also simply referred to as "the cured product of the present invention") is obtained by curing the epoxy resin composition of the present invention described above by a known method. The curing conditions for the epoxy resin composition are appropriately selected according to the application and form, and are not particularly limited. The form of the cured product of the present invention is not particularly limited and can be selected according to the application. For example, when the epoxy resin composition is used as a paint, the cured product of the composition is usually in the form of a film. However, from the viewpoint of effectively exhibiting the effects of the present invention, it is preferable that the cured product of the present invention be the matrix resin of the fiber-reinforced composite material described later.

[0057] [Fiber-reinforced composite material] The fiber-reinforced composite material (FRP, hereinafter also referred to as "composite material") of the present invention comprises a cured product of the epoxy resin composition and reinforcing fibers. The fiber-reinforced composite material can be obtained by impregnating the reinforcing fibers with the epoxy resin composition and then curing the composition.

[0058] <Reinforced Fiber> Examples of reinforcing fibers include glass fibers, carbon fibers, aramid fibers, boron fibers, and metal fibers. One type of reinforcing fiber may be used alone, or two or more types may be used in combination. Among these, from the viewpoint of using the resulting composite material in wind turbine blades, it is preferable that the reinforcing fibers be one or more types selected from the group consisting of glass fibers and carbon fibers. Carbon fibers may be manufactured using rayon or polyacrylonitrile (PAN) as raw materials, or they may be manufactured by spinning pitch from petroleum or coal. Furthermore, recycled carbon fibers made from recycled carbon fiber scraps or recycled carbon fiber reinforced polymer (CFRP) from which the resin has been removed can also be used.

[0059] While reinforcing fibers can take the form of short fibers or continuous fibers, continuous fibers are preferred from the viewpoint of impregnating them with the epoxy resin composition and molding the composite material by the Va-RTM method. Furthermore, continuous fibers and short fibers can be used in combination. Continuous fibers can take various forms, such as simply monofilaments or multifilaments arranged in one direction or alternately in an intersecting manner, fabrics such as knitted or woven materials, nonwoven fabrics, or mats. Of these, the forms of monofilaments, fabrics, nonwoven fabrics, or mats are preferred, with the form of fabric being more preferred.

[0060] The number of filaments in a continuous fiber is typically in the range of 500 to 100,000, preferably 5,000 to 80,000, and more preferably 10,000 to 70,000.

[0061] The fineness of the continuous fibers is preferably 20 to 4,500 tex, and more preferably 50 to 4,000 tex. Within this fineness range, impregnation with resin components is easy, and highly elastic composite materials are readily obtainable. The fineness can be determined by calculating the weight of a continuous fiber of any length and converting it to the weight per 1,000 m.

[0062] The average fiber diameter of the reinforcing fibers is preferably 1 to 100 μm, more preferably 3 to 50 μm, and even more preferably 4 to 20 μm. When the average fiber diameter is within this range, processing is easy, and highly elastic composite materials are readily available. The average fiber diameter of the reinforcing fibers is determined by randomly selecting 50 or more fibers using a scanning electron microscope (SEM), observing and measuring them, and then calculating the average fiber diameter.

[0063] The fiber-reinforced composite material may further contain a foaming agent in addition to the cured epoxy resin composition and reinforcing fibers. There are no particular restrictions on the foaming agent, but examples include foaming agents made from resin materials such as polyvinyl chloride resin, polyurethane resin, polystyrene resin, polyolefin resin, acrylic resin, phenolic resin, polymethacrylimide resin, and epoxy resin.

[0064] The fiber volume content (Vf) of the fiber-reinforced composite material is preferably 20% or more, more preferably 30% or more, and even more preferably 35% or more, from the viewpoint of obtaining a highly elastic composite material. Furthermore, from the viewpoint of moldability, processability, and lightweight properties of the composite material, it is preferably 90% or less, more preferably 80% or less, even more preferably 70% or less, and even more preferably 60% or less. The fiber volume content of the fiber-reinforced composite material can be determined specifically by the method described in the examples.

[0065] <Application> The epoxy resin composition and fiber-reinforced composite material of the present invention can be suitably used in wind turbine blades. Other applications of the fiber-reinforced composite material of the present invention include automotive structural materials and building materials.

[0066] <Method for manufacturing fiber-reinforced composite materials> There are no particular limitations on the method for producing the fiber-reinforced composite material of the present invention, but from the viewpoint of avoiding curing of the epoxy resin composition during the manufacturing process, it is preferable to mix the epoxy resin curing agent and the epoxy resin immediately before molding, and then impregnate and cure the reinforcing fibers. In particular, from the viewpoint of manufacturing wind turbine blades made of fiber-reinforced composite material, it is preferable that the fiber-reinforced composite material and the wind turbine blades have a process of being molded by the Va-RTM method. By manufacturing the composite material by the Va-RTM method using the epoxy resin curing agent and epoxy resin composition of the present invention, which have a long pot life, wind turbine blades can be manufactured with high productivity.

[0067] The Va-RTM method can be used to produce the composite, for example, by following the procedure below. First, reinforcing fibers are placed inside a pair of upper and lower molds and sealed, and the inside of the molds is depressurized. Next, the epoxy resin, which is the main component of the epoxy resin composition, and the epoxy resin curing agent are filled into separate tanks and sent to a mixer to be mixed. The epoxy resin composition prepared in this way is injected into the molds to impregnate the reinforcing fibers, and then the epoxy resin is cured.

[0068] In the above process, the temperature at which the epoxy resin composition is injected into the mold or impregnated into the reinforcing fibers is preferably 30 to 120°C, more preferably 50 to 100°C. When the epoxy resin curing agent and the epoxy resin are supplied from separate tanks and mixed immediately before molding, the temperature at which the epoxy resin curing agent and the epoxy resin are mixed can also be set individually. The temperature during mixing of the epoxy resin curing agent is preferably 5 to 30°C, more preferably 10 to 25°C, from the viewpoint of suppressing viscosity increase. The temperature during mixing of the epoxy resin can be appropriately adjusted according to the viscosity of the epoxy resin, but is preferably 30 to 120°C, more preferably 50 to 100°C. The above temperatures may be kept constant during molding or may be varied during molding. The impregnation time of the epoxy resin composition into the reinforcing fibers varies depending on the shape of the fiber-reinforced composite material, but from the viewpoint of moldability and productivity, it is preferably 10 to 120 minutes, more preferably 10 to 60 minutes.

[0069] The curing temperature of the epoxy resin composition is preferably 50 to 200°C, more preferably 50 to 150°C, and even more preferably 50 to 120°C. The curing temperature may be constant during molding or may be varied during molding. If the curing temperature is 50°C or higher, the epoxy resin will cure sufficiently, and if it is 200°C or lower, the cost of adjusting the mold temperature will be low. The curing time of the epoxy resin composition can be appropriately selected according to the curing temperature, etc., but from the viewpoint of moldability and productivity, it is preferably 0.5 to 24 hours, more preferably 1 to 18 hours.

[0070] [Wind turbine blades] The present invention also provides a wind turbine blade comprising the fiber-reinforced composite material. Since at least a portion of the wind turbine blade is composed of a fiber-reinforced composite material comprising a cured epoxy resin composition and reinforcing fibers, it is highly elastic and has excellent saltwater resistance. When a portion of a wind turbine blade is made of the fiber-reinforced composite material of the present invention, it is preferable that at least the outer surface of the wind turbine blade is made of the fiber-reinforced composite material, from the viewpoint of exhibiting saltwater resistance. The wind turbine blade may also be made solely of the fiber-reinforced composite material of the present invention. The wind turbine blades of the present invention can be formed, for example, using the Va-RTM method described above in the method for manufacturing fiber-reinforced composite materials. Wind turbine blades may be molded as a single unit. Alternatively, they can be manufactured by molding two or more components made of fiber-reinforced composite material and then bonding these components together with an adhesive or the like. [Examples]

[0071] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Various measurements and evaluations were performed according to the following methods.

[0072] (viscosity) The viscosity of the main epoxy resin and epoxy resin composition was measured at 30°C using an E-type viscometer, "TVE-22H type viscometer, cone plate type" (manufactured by Toki Sangyo Co., Ltd.).

[0073] (Pot life evaluation) The pot life of the epoxy resin composition was evaluated by the following method. The viscosity of the epoxy resin composition was measured at 50°C using a rheometer (TA Instruments). Measurements were taken every 10 seconds, and the time it took for the viscosity to reach 0.3 Pa·s is shown in the table. A longer time to reach 0.3 Pa·s indicates a longer pot life.

[0074] (Fiber volume content in fiber-reinforced composite materials) The fiber volume content (Vf(%)) in the fiber-reinforced composite material was calculated using the following formula. Vf(%) = {Mass of reinforcing fiber (g) / Specific gravity of reinforcing fiber} ÷ [{Mass of reinforcing fiber (g) / Specific gravity of reinforcing fiber} + {Mass of solids of impregnated epoxy resin composition (g) / Specific gravity of solids of epoxy resin composition}] × 100

[0075] (Flexural strength and flexural modulus of fiber-reinforced composite materials) The fiber-reinforced composite materials obtained in the examples described later were cut to create test specimens measuring 80 mm x 15 mm x 2 mm thick, which were then used for measurement. Using an Autograph (manufactured by Shimadzu Corporation), bending tests were conducted in accordance with ISO 178 under conditions of room temperature (23°C) and a test speed of 5 mm / min to measure bending strength and bending modulus.

[0076] (Bending strength retention rate after salt spray test) Test specimens of fiber-reinforced composite material used for measuring flexural strength were placed in a salt spray tester (STP-90, manufactured by Suga Test Instruments Co., Ltd., chamber temperature 35°C) and continuously sprayed with salt water (5% by mass concentration) for one month. Subsequently, the test specimens were dried at 60°C for 15 hours, and then the flexural strength was measured using the same method as described above. The flexural strength before the salt spray test was denoted as A (MPa), and the flexural strength after the salt spray test was denoted as B (MPa). The flexural strength retention rate was calculated using the following formula. A higher flexural strength retention rate indicates superior salt water resistance. Flexural strength retention rate after salt spray test (%) = B / A × 100

[0077] Examples 1-5 and Comparative Examples 1-3 (Preparation of epoxy resin curing agents and epoxy resin compositions) Polyoxypropylenediamine ("JEFFAMINE D-230", manufactured by Huntsman), component (a1), isophoronediamine (IPDA, manufactured by EVONIK), and component (a3), metaxylylenediamine (MXDA, manufactured by Mitsubishi Gas Chemical Co., Ltd.) were mixed in the proportions shown in the table to obtain an epoxy resin curing agent. Furthermore, this epoxy resin curing agent and the main component, bisphenol A type liquid epoxy resin "jER811" (manufactured by Mitsubishi Chemical Corporation), were blended and mixed so that the ratio of the number of active hydrogens in the epoxy resin curing agent to the number of epoxy groups in the main component epoxy resin (number of active hydrogens in the epoxy resin curing agent / number of epoxy groups in the epoxy resin) was 1 / 1, thereby preparing an epoxy resin composition.

[0078] (Fabrication of fiber-reinforced composite materials) The prepared epoxy resin composition was impregnated into a 16cm x 16cm plain weave glass cloth (roving cloth "ERW320-554A", manufactured by Central Glass Fiber Co., Ltd., 0.3mm thick) by Va-RTM molding at room temperature to produce a prepreg. The prepreg was then held in a 60°C hot air dryer for 15 hours to heat-cur the epoxy resin composition, producing a 2mm thick glass fiber reinforced composite. The volume content Vf of glass fibers in the composite is as shown in the table.

[0079] The epoxy resin compositions and composite materials obtained by the above method were evaluated using the method described above. The results are shown in Table 1. Note that the amounts of each ingredient listed in the table are all amounts of the active ingredient. In this embodiment, if the pot life of the epoxy resin composition is 3200 seconds or more, and the flexural strength retention rate of the fiber-reinforced composite material after a salt spray test is 92% or more, it will be determined that both a long pot life and salt water resistance have been achieved.

[0080] [Table 1]

[0081] The ingredients used in the table are as follows: <Main component: epoxy resin> jER811: Bisphenol A type liquid epoxy resin "jER811", manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 186 g / equivalent, viscosity at 30°C: 1100 mPa·s <Epoxy resin curing agent components> (a1) JEFFAMINE D-230: Polyoxypropylenediamine "JEFFAMINE D-230" represented by the following general formula, manufactured by Huntsman, n=2.5 in the general formula. [ka] (a2) IPDA: Isophorone diamine, manufactured by EVONIK. • (a3) ​​MXDA: Metaxylylenediamine, manufactured by Mitsubishi Gas Chemical Co., Ltd. <Reinforced Fiber> • GF: Plain weave glass cloth, roving cloth "ERW320-554A", manufactured by Central Glass Fiber Co., Ltd., unit weight: 320g / m 2 Silane-based treatment, 0.3mm thickness

[0082] Table 1 shows that the epoxy resin composition containing the epoxy resin curing agent according to the present invention has a long pot life. Furthermore, the fiber-reinforced composite material using the cured epoxy resin composition as the matrix resin is more elastic and has better saltwater resistance compared to Comparative Example 1. In contrast, in this comparative example, either the pot life of the epoxy resin composition or the saltwater resistance of the fiber-reinforced composite material using the cured epoxy resin composition as the matrix resin was inferior. [Industrial applicability]

[0083] The epoxy resin curing agent of the present invention provides an epoxy resin composition with a long pot life and suitable for molding wind turbine blades by methods such as Va-RTM. Wind turbine blades obtained using this epoxy resin composition are highly elastic and have excellent saltwater resistance.

Claims

1. An epoxy resin curing agent containing component (a1): polyether polyamine, component (a2): aliphatic polyamine having an alicyclic structure, and component (a3): aliphatic polyamine having an aromatic ring, The above component (a3) ​​is xylylenediamine, The epoxy resin curing agent contains 60 to 90% by mass of component (a1), and the total content of components (a2) and (a3) ​​is 10 to 40% by mass. An epoxy resin curing agent wherein the ratio of the content of component (a3) ​​to the total content of component (a2) and component (a3) ​​in the epoxy resin curing agent is 0.20 to 0.55 as a mass ratio [(a3) / {(a2) + (a3)}].

2. The epoxy resin curing agent according to claim 1, wherein the component (a1) is polyoxypropylenediamine.

3. The epoxy resin curing agent according to claim 1, wherein the component (a2) is isophorone diamine.

4. An epoxy resin composition comprising an epoxy resin and an epoxy resin curing agent according to any one of claims 1 to 3.

5. The epoxy resin composition according to claim 4, wherein the epoxy resin content in the epoxy resin composition is 65 to 85% by mass, the epoxy resin curing agent content is 15 to 35% by mass, and the total content of the epoxy resin and the epoxy resin curing agent in the epoxy resin composition is 80 to 100% by mass.

6. A cured product of the epoxy resin composition according to claim 4.

7. A fiber-reinforced composite material comprising a cured product of the epoxy resin composition according to claim 6 and reinforcing fibers.

8. The fiber-reinforced composite material according to claim 7, wherein the reinforcing fiber is one or more selected from the group consisting of glass fibers and carbon fibers.

9. A wind turbine blade comprising the fiber-reinforced composite material described in claim 7.

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