Hardening agent composition for thermosetting resin, epoxy resin composition, and fiber reinforced composite material

Abstract

To provide a curing agent composition for thermosetting resins capable of manufacturing an epoxy resin composition having a long service time and fast curability.SOLUTION: A curing agent composition for thermosetting resins comprises a curing agent A, a curing agent B and a curing agent C, in which the curing agent A is an aromatic polyamine having a substituent at each of two ortho positions to an amino group, the substituent is selected from an alkyl group, an aromatic group and a halogen group, the curing agent B is an aromatic polyamine that is liquid at 25°C, the curing agent C is an aromatic polyamine, and the aromatic polyamine is an aromatic polyamine that has only one an electron donating group at an ortho position relative to an amino group or does not have a substituent at an ortho position.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a curing agent composition for thermosetting resins, and more particularly to a curing agent composition for thermosetting resins that can produce an epoxy resin composition having a long pot life and rapid curing properties.

Background Art

[0002] Fiber-reinforced composite materials (hereinafter sometimes referred to as "FRP") are lightweight, high-strength, and high-rigidity, and are therefore used in a wide range of fields such as sports and leisure applications such as fishing rods and golf shafts, and industrial applications such as automobiles and aircraft. As a method for molding a composite material using a thermosetting resin as a matrix resin, there are a resin transfer molding (RTM) method in which a liquid resin composition is impregnated into a fiber-reinforced base material placed in a mold and cured to obtain a fiber-reinforced composite material, and a method of molding a prepreg (intermediate base material) in which a resin is previously impregnated into a fiber-reinforced base material and formed into a sheet shape, and the like are known.

[0003] In recent years, among them, in particular, the RTM molding method, which is a low-cost and highly productive manufacturing method that requires few steps for manufacturing fiber-reinforced composite materials and does not require expensive equipment such as an autoclave, has attracted attention. The composition of the matrix resin used in the RTM molding method mainly includes an epoxy resin and a curing agent, and optionally other additives. In order to obtain a cured product or a fiber-reinforced composite material having high mechanical properties, it is common to use an aromatic polyamine as the curing agent.

[0004] In the epoxy resin composition used in the RTM molding method, in order to prevent the curing agent from being filtered out when the epoxy resin composition is impregnated into the reinforcing fiber base material, the curing agent and additives are often stored and used in a state of being dissolved in the epoxy resin as the main agent. Such an epoxy resin composition in which a curing agent and additives are dissolved and mixed in the main epoxy resin is called a one-component epoxy resin composition.

[0005] In this one-component epoxy resin composition, since the curing agent is dissolved in the epoxy resin, the reaction between the epoxy resin and the curing agent is relatively likely to occur, and there is a problem that the shelf life of the epoxy resin composition is shortened. For this reason, the one-component epoxy resin composition had to be stored frozen.

[0006] To solve this problem, a two-component epoxy resin composition that is mixed immediately before using the epoxy resin and the curing agent has been studied. The two-component epoxy resin composition is composed of a main agent liquid containing an epoxy resin as a main component and a curing agent liquid (curing agent composition) containing a curing agent as a main component, and is an epoxy resin composition obtained by mixing these two liquids immediately before use.

[0007] In the two-component epoxy resin composition, since the main agent liquid and the curing agent liquid are mixed immediately before use, the ease of mixing is important. Although it is possible to use the curing agent used in the one-component epoxy resin composition as the curing agent for the two-component epoxy resin composition, as described in Patent Document 1, the aromatic polyamine curing agent used in the one-component epoxy resin composition is usually solid, and poor mixing with the main agent liquid is likely to occur. Therefore, it is desirable that the curing agent composition is liquid.

[0008] As epoxy resin compositions using a liquid aromatic polyamine as a curing agent, those described in Patent Documents 2 and 3 are known. However, the resin cured products obtained from the epoxy resin compositions described in Patent Documents 2 and 3 do not have sufficient mechanical properties such as elastic modulus and fracture toughness.

[0009] In the RTM method, in order to produce fiber-reinforced composite materials with high efficiency, rapid curability is required to shorten the resin curing time. Patent Document 4 proposes a two-component epoxy resin composition with rapid curability using a compound having two or more aromatic rings having phenolic hydroxyl groups. However, when a compound having a phenolic hydroxyl group is added to the epoxy resin composition, the viscosity of the resin composition increases rapidly due to its high reactivity, and the pot life in RTM molding becomes extremely short, making it difficult to impregnate a sufficient amount of resin into the reinforcing fiber base material. Therefore, fiber-reinforced composite materials produced using such epoxy resin compositions have many defects such as voids. As a result, there are problems such as a decrease in the compressive performance and damage tolerance of the fiber-reinforced composite material structure.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0011] Conventionally, there has been no two-component epoxy resin composition that has sufficient rapid curability to achieve high-level productivity of fiber-reinforced composite materials and can obtain a cured resin having heat resistance and mechanical properties required for industrial applications such as automobiles and aircraft, and a liquid curing agent composition for realizing the same.

[0012] An object of the present invention is to provide a curing agent composition for a thermosetting resin that can produce an epoxy resin composition having a long pot life and rapid curability. Further, an object of the present invention is to provide a curing agent composition for a thermosetting resin that becomes a uniform liquid at a temperature of 200° C. or lower by heating and can then maintain a uniform liquid state at room temperature for one week or more. The present invention further aims to provide a cured product of an epoxy resin composition and a fiber-reinforced composite material having high mechanical properties.

Means for Solving the Problems

[0013] That is, the present invention is a curing agent composition for a thermosetting resin containing curing agent A, curing agent B, and curing agent C, wherein curing agent A is an aromatic polyamine having substituents at two ortho positions with respect to an amino group, the substituents are selected from an alkyl group, an aromatic group, and a halogen group, curing agent B is an aromatic polyamine that is liquid at 25° C., and curing agent C is an aromatic polyamine that has only one electron-donating group at the ortho position with respect to the amino group or has no substituent at the ortho position.

Effects of the Invention

[0014] According to the present invention, it is possible to provide a curing agent composition for a thermosetting resin that can produce an epoxy resin composition having a long pot life and rapid curability. Further, it is possible to provide a curing agent composition for a thermosetting resin that becomes a uniform liquid at a temperature of 200° C. or lower by heating and can then maintain a uniform liquid state at room temperature for one week or more. The present invention can further provide a cured product of an epoxy resin composition and a fiber-reinforced composite material having high mechanical properties.

Modes for Carrying Out the Invention

[0015] Hereinafter, the present invention will be described in detail. Note that the fiber-reinforced composite material may be abbreviated as "FRP", and the carbon fiber-reinforced composite material may be abbreviated as "CFRP".

[0016] 〔Hardening agent composition for thermosetting resin〕 The hardening agent composition for thermosetting resin of the present invention is a hardening agent composition for thermosetting resin containing hardening agent A, hardening agent B, and hardening agent C. This hardening agent composition for thermosetting resin becomes a uniform liquid when heated to a temperature of 80 to 200°C.

[0017] The hardening agent composition for thermosetting resin of the present invention becomes a uniform liquid at a temperature of 80 to 200°C, and after raising the liquid temperature to 200°C and then lowering it to 25°C and allowing it to stand at 25°C for 1 week, it is a uniform liquid, preferably even after standing for another 2 weeks (total of 3 weeks of standing), and particularly preferably even after standing for a total of 1 month.

[0018] If the period in which it is in a uniform liquid state is less than 1 week after raising the liquid temperature to 200°C and then lowering it to 25°C and allowing it to stand at 25°C, it becomes difficult to handle it as a substantially liquid hardening agent composition for thermosetting resin, and poor mixing with the main agent liquid is likely to occur, which is not preferable.

[0019] In the hardening agent composition for thermosetting resin of the present invention, the total of hardening agent A, hardening agent B, and hardening agent C accounts for 70 to 100% by mass based on the total mass of the hardening agent composition for thermosetting resin. The hardening agent composition for thermosetting resin of the present invention may further contain other hardening agents and other components as long as it satisfies the above conditions.

[0020] 〔Hardening agent A〕 Hardening agent A is an aromatic polyamine having substituents at two ortho positions with respect to the amino group, and the substituents are selected from an alkyl group, an aromatic group, and a halogen group. Also, hardening agent A is solid at 25°C. By containing this hardening agent A, an epoxy resin cured product having excellent mechanical properties such as heat resistance, elastic modulus, and fracture toughness can be obtained when cured as a composition with an epoxy resin.

[0021] As the curing agent A, a compound represented by the following chemical formula (1) can be used as an aromatic polyamine having substituents at two ortho-positions with respect to the amino group.

[0022]

Chemical formula

[0023] However, in the above chemical formula (1), R1 to R4 are each independently any one of an aliphatic substituent, an aromatic substituent, an alkoxy group, and a halogen atom, and at least one substituent is any one of an aliphatic substituent having 1 to 6 carbon atoms, an aromatic substituent, and a halogen atom. X is any one of -CH2-, -CH(CH3)-, -C(CH3)2-, -S-, -O-, -SO2-, -CO-, -CONH-, -NHCO-, -C(=O)-, and -O-C(=O)-.

[0024] In the chemical formula (1), examples of the aliphatic substituent having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a neopentyl group, an n-hexyl group, and a cyclohexyl group. Examples of the aromatic substituent include a phenyl group and a naphthyl group. Examples of the aromatic substituent include a phenyl group and a naphthyl group.

[0025] The aromatic polyamine of the curing agent A is preferably an aromatic diamine, and among them, a 4,4'-diaminodiphenylmethane derivative is particularly preferable. Specific examples of this aromatic polyamine include compounds represented by the following chemical formulas (2) to (5). These may be used alone or in combination.

[0026]

Chemical formula

[0027] 〔Curing agent B〕 Hardener B is an aromatic polyamine that is liquid at 25°C. By containing this aromatic polyamine, a curing agent composition for a thermosetting resin that can maintain a liquid state at room temperature can be obtained.

[0028] As the aromatic polyamine of Hardener B, preferably a phenylenediamine derivative or a 4,4'-diaminodiphenylmethane derivative is used. As this aromatic polyamine, compounds represented by the following chemical formulas (6) or (7) can be exemplified.

[0029]

Chemical formula

[0030] However, in Chemical formula (6), R5 to R8 are each independently any one of a hydrogen atom, an aliphatic substituent, an alkoxy group, and a thioalkoxy group, and at least one substituent is either an aliphatic substituent having 1 to 6 carbon atoms or a thioalkoxy group.

[0031]

Chemical formula

[0032] However, in Chemical formula (7), R9 to R 10 are each independently any one of an aliphatic substituent, a methoxy group, an alkoxy group, and a thioalkoxy group.

[0033] As the aromatic polyamine used as Hardener B. Specifically, compounds represented by the following chemical formulas (8) to (12) can be exemplified. These may be used alone or in combination.

[0034]

Chemical formula

[0035] In the curing agent composition for thermosetting resins of the present invention, the mass ratio of curing agent A to curing agent B is preferably 1:99 to 99:1, more preferably 20:80 to 80:20, and particularly preferably 40:60 to 70:30. If the proportion of curing agent A is less than this, the mechanical properties such as heat resistance, elastic modulus, and fracture toughness of the resulting resin cured product tend to be insufficient, which is not preferable. On the other hand, if the proportion of curing agent A is more than this, it becomes difficult for the resulting curing agent composition for thermosetting resins to maintain a liquid state at room temperature, which is not preferable.

[0036] [Curing agent C] Curing agent C is an aromatic polyamine, and the aromatic polyamine is an aromatic polyamine having only one electron-donating group at the ortho position with respect to the amino group or having no substituent at the ortho position. The electron-donating group of the aromatic polyamine of curing agent C is preferably a methyl group, an ethyl group, a propyl group, an isopropyl group, a methoxy group, or an ethoxy group. By containing this curing agent C, the curing reaction of the resulting epoxy resin composition is promoted, and rapid curability can be imparted.

[0037] Examples of the curing agent C include 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 4,4'-thiodianiline, 4,4'-diamino-3,3'-dimethyldiphenylmethane, 1,1-bis(4-aminophenyl)cyclohexane, 3,3'-diaminobenzophenone, m-phenylenediamine, 2,4-diaminotoluene, 2,6-diaminotoluene, 2,4,6-trimethyl-1,3-phenylenediamine, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, o-dianisidine, 3,3',5,5'-tetramethylbenzidine. Among them, it is preferable to use 3,4'-diaminodiphenyl ether, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 2,6-diaminotoluene, m-phenylenediamine, and 3,4'-diaminodiphenyl ether, 1,3-bis(4-aminophenoxy)benzene, 2,6-diaminotoluene, m-phenylenediamine are more preferable.

[0038] The melting point of the curing agent C is preferably 200 °C or lower, more preferably 150 °C or lower, and particularly preferably 120 °C or lower. When the melting point exceeds 200 °C, it becomes difficult to obtain a liquid composition when the curing agent C is mixed with the curing agent A and the curing agent B, and it is likely to be difficult to keep the obtained curing agent composition for thermosetting resin in a liquid state at room temperature, which is not preferable. Also, the curing agent C is solid at 25 °C.

[0039] In the curing agent composition for thermosetting resins of the present invention, based on a total of 100 parts by mass of curing agent A and curing agent B, curing agent C is preferably contained in an amount of 1 to 43 parts by mass, more preferably 3 to 30 parts by mass, and particularly preferably 5 to 20 parts by mass. If the content is less than 1 part by mass, it becomes difficult to impart rapid curability to the resulting epoxy resin composition, which is not preferable. On the other hand, if it exceeds 43 parts by mass, the reactivity of the resulting epoxy resin composition becomes excessively high, and the pot life in RTM molding becomes extremely short, which is not preferable. In this case, it becomes difficult to impregnate a sufficient amount of resin into the reinforcing fiber base material, and the fiber-reinforced composite material produced using such an epoxy resin composition will have many defects such as voids, and the compression performance and damage tolerance of the fiber-reinforced composite material structure will deteriorate.

[0040] 〔Other Components〕 The curing agent composition for thermosetting resins of the present invention may further contain other components. For example, it may contain conductive particles, flame retardants, inorganic fillers, and internal release agents.

[0041] Examples of the conductive particles include conductive polymer particles such as polyacetylene particles, polyaniline particles, polypyrrole particles, polythiophene particles, polyisothianaphthene particles, and polyethylene dioxythiophene particles; carbon particles; carbon fiber particles; metal particles; and particles in which a core material made of an inorganic material or an organic material is coated with a conductive substance.

[0042] Examples of the flame retardant include phosphorus-based flame retardants. This phosphorus-based flame retardant may be any one containing a phosphorus atom in the molecule, and examples thereof include organic phosphorus compounds such as phosphate esters, condensed phosphate esters, phosphazene compounds, and polyphosphate salts, and red phosphorus.

[0043] Examples of the inorganic filler materials include aluminum borate, calcium carbonate, silicon carbonate, silicon nitride, potassium titanate, basic magnesium sulfate, zinc oxide, graphite, calcium sulfate, magnesium borate, magnesium oxide, and silicate minerals. In particular, it is preferable to use silicate minerals. As commercially available silicate minerals, THIXOTROPIC AGENT DT 5039 (manufactured by Huntsman Japan Co., Ltd.) can be mentioned.

[0044] Examples of the internal release agent include metal soaps, vegetable waxes such as polyethylene wax and carnauba wax, fatty acid ester-based release agents, silicone oils, animal waxes, and fluorine-based nonionic surfactants. Commercially available products of internal release agents include MOLD WIZ (registered trademark), INT1846 (manufactured by AXEL PLASTICS RESEARCH LABORATORIES INC.), Licowax S, Licowax P, Licowax OP, Licowax PE190, Licowax PED (manufactured by Clariant Japan), and stearyl stearate (SL-900A; manufactured by Riken Vitamin Co., Ltd.) can be exemplified.

[0045] [Method for producing a curing agent composition for a thermosetting resin] The curing agent composition for a thermosetting resin of the present invention can be produced by mixing curing agent A, curing agent B, curing agent C, and, if necessary, other components. The order of mixing is not limited.

[0046] The temperature of the composition during mixing is preferably 50 to 200°C, more preferably 50 to 150°C, and particularly preferably 80 to 120°C. If it exceeds 200°C, the added components may be thermally decomposed, which is not preferable. On the other hand, if it is less than 50°C, the solid curing agent A and curing agent C will not melt, and it will be difficult to melt into curing agent B, making it difficult to obtain a liquid curing agent composition for a thermosetting resin, which is not preferable.

[0047] Examples of the apparatus used for mixing the curing agents include a roll mill, a planetary mixer, a kneader, an extruder, a Banbury mixer, a mixing container equipped with stirring blades, and a horizontal mixing tank. The mixing may be carried out in the air or in an inert gas atmosphere.

[0048] When mixing in the atmosphere, it is preferable to carry out the mixing in an atmosphere where the temperature and humidity are controlled. In this case, for example, it is preferable to mix at a constant temperature controlled to 30°C or lower, or to mix in a low humidity atmosphere with a relative humidity of 50%RH or lower.

[0049] 〔Epoxy resin main agent〕 The epoxy resin main agent comprises an epoxy resin. The epoxy resin main agent may contain other optional components in addition to these. The content of the epoxy resin in the epoxy resin main agent is 30 to 100% by mass, preferably 50 to 100% by mass, based on the mass of the total epoxy resin main agent.

[0050] 〔Epoxy resin〕 The epoxy resin usable in the epoxy resin composition is not particularly limited, but tetraglycidyl-4,4'-diaminodiphenylmethane, tetraglycidyl-4,4'-diaminodiphenylsulfone, tetraglycidyl-3,3'-diaminodiphenylsulfone, tetraglycidyl-4,4'-diaminodiphenyl ether, tetraglycidyl-3,4'-diaminodiphenyl ether, and other tetrafunctional glycidylamine type epoxy resins, triglycidyl-m-aminophenol, triglycidyl-p-aminophenol, triglycidyl isocyanurate, and other trifunctional epoxy resins, diglycidylaniline and its derivatives such as diglycidyl-o-toluidine, diglycidyl-m-toluidine, diglycidyl-p-toluidine, diglycidyl-xylylidene diamine, diglycidyl-mesitylidene diamine, diglycidyl-anisidine, diglycidyl-phenoxyaniline, or diglycidyl-naphthylamine and its derivatives, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, resorcinol diglycidyl ether, 1,6-naphthalene diol diglycidyl ether, and other difunctional epoxy resins are exemplified. These epoxy resins may be used alone, or a plurality of epoxy resins may be mixed and used.

[0051] The epoxy resin may be synthesized as needed. Any method of synthesis may be used. For example, after reacting an epihalohydrin such as an aromatic diamine, aminophenol, diphenol, which are raw materials, with epichlorohydrin to obtain a halohydrin form, it is then obtained by subjecting it to a cyclization reaction using an alkaline compound.

[0052] Examples of the epihalohydrin include epichlorohydrin, epibromohydrin, epifluorohydrin and the like. Among these, from the viewpoints of reactivity and handleability, epichlorohydrin and epibromohydrin are particularly preferred.

[0053] The molar ratio of the aromatic diamine, aminophenol, diphenol, which are raw materials, to the epihalohydrin is preferably 1:1 to 1:30, more preferably 1:3 to 1:20. Examples of the solvent used during the reaction include alcohol solvents such as ethanol and n-butanol, ketone solvents such as methyl isobutyl ketone and methyl ethyl ketone, aprotic polar solvents such as acetonitrile and N,N-dimethylformamide, and aromatic hydrocarbon solvents such as toluene and xylene. The amount of the solvent used is preferably 1 to 10 times the mass of the aromatic diamine.

[0054] The reaction time is preferably 0.1 to 180 hours, more preferably 0.5 to 24 hours. The reaction temperature is preferably 20 to 100 °C, more preferably 40 to 80 °C.

[0055] Examples of the alkaline compound used during the cyclization reaction include sodium hydroxide and potassium hydroxide. The alkaline compound may be added as a solid or as an aqueous solution.

[0056] A phase transfer catalyst may be used during the cyclization reaction. Examples of the phase transfer catalyst include quaternary ammonium salts such as tetramethylammonium chloride, tetraethylammonium bromide, benzyltriethylammonium chloride, tetrabutylammonium hydrogen sulfate, phosphonium compounds such as tributylhexadecylphosphonium bromide, tributyldodecylphosphonium bromide, and crown ethers such as 18-crown-6-ether.

[0057] 〔Optional Component〕 In addition to the above epoxy resins, the epoxy resin base may contain a thermoplastic resin. The thermoplastic resin improves the fracture toughness and impact resistance of the resulting fiber-reinforced composite material. Such a thermoplastic resin may be dissolved in the curing agent composition for thermosetting resin during the production process of the curing agent composition for thermosetting resin.

[0058] Specific examples of the thermoplastic resin include polyethersulfone, polysulfone, polyetherimide, polycarbonate, etc. These may be used alone or in combination of two or more. The thermoplastic resin contained in the epoxy resin composition is particularly preferably polyethersulfone or polysulfone having a weight average molecular weight (Mw) in the range of 8000 to 100000 measured by gel permeation chromatography. If the weight average molecular weight (Mw) is 8000 or more, the impact resistance of the resulting FRP becomes sufficient, and if it is 100000 or less, an epoxy resin composition showing good handleability without significantly increasing the viscosity can be obtained. The molecular weight distribution of the epoxy resin-soluble thermoplastic resin is preferably uniform. In particular, the polydispersity (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably in the range of 1 to 10, and more preferably in the range of 1.1 to 5.

[0059] The thermoplastic resin preferably has a reactive group reactive with the epoxy resin or a functional group forming a hydrogen bond. Such a thermoplastic resin can improve the dissolution stability during the curing process of the epoxy resin. In addition, it can impart fracture toughness, chemical resistance, heat resistance, and wet heat resistance to the fiber-reinforced composite material obtained after curing.

[0060] As the reactive group having reactivity with the epoxy resin, a hydroxyl group, a carboxylic acid group, an imino group, an amino group, etc. are preferable. When using a polyethersulfone having a hydroxyl group at the terminal, it is more preferable because the resulting fiber-reinforced composite material is particularly excellent in impact resistance, fracture toughness, and solvent resistance.

[0061] The content of the thermoplastic resin contained in the curing agent composition for the thermosetting resin is appropriately adjusted according to the viscosity. From the viewpoint of impregnation into the fiber-reinforced base material, 0.1 to 10 parts by mass is preferable, and 0.5 to 5 parts by mass is more preferable with respect to 100 parts by mass of the curing agent composition for the thermosetting resin. When it is 0.1 part by mass or more, the resulting fiber-reinforced composite material exhibits sufficient fracture toughness and impact resistance. If the content of the thermoplastic resin is 10 parts by mass or less, the viscosity of the epoxy resin composition does not increase significantly, impregnation into the fiber-reinforced base material becomes easy, and the properties of the resulting fiber-reinforced composite material are improved.

[0062] The thermoplastic resin preferably contains a reactive aromatic oligomer having an amine terminal group (hereinafter, also simply referred to as "aromatic oligomer").

[0063] The epoxy resin composition is polymerized by the curing reaction of the epoxy resin and the curing agent during heat curing. By expanding the two-phase region due to the polymerization, the aromatic oligomer dissolved in the epoxy resin composition causes reaction-induced phase separation. By this phase separation, a two-phase structure of the cured epoxy resin and the aromatic oligomer becoming co-continuous is formed in the matrix resin. Further, since the aromatic oligomer has an amine terminal group, a reaction with the epoxy resin also occurs. Since each phase in this co-continuous two-phase structure is firmly bonded to each other, the solvent resistance is also improved.

[0064] This co-continuous structure absorbs an external impact on the fiber-reinforced composite material and suppresses crack propagation. As a result, the fiber-reinforced composite material produced using the epoxy resin composition containing the reactive aromatic oligomer having an amine terminal group has high impact resistance and fracture toughness.

[0065] As this aromatic oligomer, a polysulfone having a known amine terminal group or a polyethersulfone having an amine terminal group can be used. The amine terminal group is preferably a primary amine (-NH2) terminal group.

[0066] The aromatic oligomer incorporated into the epoxy resin composition preferably has a weight average molecular weight of 8,000 to 40,000 as measured by gel permeation chromatography. When the weight average molecular weight is 8,000 or more, the effect of improving the toughness of the matrix resin is high. Also, when the weight average molecular weight is 40,000 or less, processing advantages such as the viscosity of the resin composition not becoming too high and the resin composition being easily impregnated into the reinforcing fiber base material can be obtained.

[0067] As the aromatic oligomer, commercially available products such as "Virantage DAMS VW-30500 RP (registered trademark)" (manufactured by Solvay Specialty Polymers) can preferably be used.

[0068] The form of the thermoplastic resin before being incorporated into the curing agent composition for the thermosetting resin is not particularly limited but is preferably in particulate form. The particulate thermoplastic resin can be uniformly incorporated and dissolved in the resin composition.

[0069] A particulate rubber component may be incorporated into the main epoxy resin. In the present invention, particulate means being dispersed without dissolving in the main epoxy resin, and also constituting a dispersed island component in the resin cured product using the main epoxy resin.

[0070] The particulate rubber component improves the fracture toughness and impact resistance of the resin cured product and the fiber composite material. Examples of the particulate rubber component include silicone rubber, butadiene rubber, styrene-butadiene rubber, and methyl methacrylate-butadiene-styrene rubber.

[0071] The average particle diameter of the particulate rubber component is preferably 1 μm or less, more preferably 0.5 μm or less, and still more preferably 0.3 μm or less. The lower limit of the average particle diameter is not particularly limited, but is preferably 0.03 μm or more, more preferably 0.05 μm or more, and still more preferably 0.08 μm or more. When the average particle diameter exceeds 1 μm, in the impregnation step of the reinforcing fiber base material, the particulate rubber component is filtered on the surface of the reinforcing fiber base material, making it difficult to impregnate into the inside of the reinforcing fiber bundle. As a result, poor impregnation of the resin may occur, and the physical properties of the obtained fiber-reinforced composite material may deteriorate.

[0072] In the epoxy resin composition produced using the curing agent composition for thermosetting resins of the present invention and the epoxy resin main component, the content of the particulate rubber component is preferably 0.1 to 50% by mass, more preferably 0.5 to 20% by mass, and still more preferably 1 to 15% by mass, based on the total amount of the epoxy resin composition. When it is less than 0.1% by mass, the fracture toughness and impact resistance of the resin cured product and the fiber composite material are not sufficiently improved.

[0073] The particulate rubber component can also be used as a masterbatch highly dispersed in the epoxy resin. In this case, it becomes easy to highly disperse the rubber-like component in the epoxy resin composition.

[0074] Examples of commercially available particulate rubber components include MX-153 (a product in which 33% by mass of butadiene rubber is uniformly dispersed in a bisphenol A type epoxy resin, manufactured by Kaneka Corporation), MX-257 (a product in which 37% by mass of butadiene rubber is uniformly dispersed in a bisphenol A type epoxy resin, manufactured by Kaneka Corporation), MX-154 (a product in which 40% by mass of butadiene rubber is uniformly dispersed in a bisphenol A type epoxy resin, manufactured by Kaneka Corporation), MX-960 (a product in which 25% by mass of silicone rubber is uniformly dispersed in a bisphenol A type epoxy resin, manufactured by Kaneka Corporation), MX-136 (a product in which 25% by mass of butadiene rubber is uniformly dispersed in a bisphenol F type epoxy resin, manufactured by Kaneka Corporation), MX-965 (a product in which 25% by mass of silicone rubber is uniformly dispersed in a bisphenol F type epoxy resin, manufactured by Kaneka Corporation), MX-217 (a product in which 25% by mass of butadiene rubber is uniformly dispersed in a phenol novolac type epoxy resin, manufactured by Kaneka Corporation), MX-227M75 (a product in which 25% by mass of styrene butadiene rubber is uniformly dispersed in a bisphenol A novolac type epoxy resin, manufactured by Kaneka Corporation), MX-334M75 (a product in which 25% by mass of styrene butadiene rubber is uniformly dispersed in a brominated epoxy resin, manufactured by Kaneka Corporation), MX-416 (a product in which 25% by mass of butadiene rubber is uniformly dispersed in a tetrafunctional glycidylamine type epoxy resin, manufactured by Kaneka Corporation), MX-451 (a product in which 25% by mass of styrene butadiene rubber is uniformly dispersed in a trifunctional glycidylamine type epoxy resin, manufactured by Kaneka Corporation).

[0075] As other additives, conductive particles, flame retardants, inorganic fillers, and internal mold release agents may be blended with the epoxy resin main component.

[0076] Examples of the conductive particles include conductive polymer particles such as polyacetylene particles, polyaniline particles, polypyrrole particles, polythiophene particles, polyisothianaphthene particles, and polyethylene dioxythiophene particles; carbon particles; carbon fiber particles; metal particles; and particles in which a core material made of an inorganic material or an organic material is coated with a conductive substance.

[0077] Examples of the flame retardant include phosphorus-based flame retardants. The phosphorus-based flame retardants are not particularly limited as long as they contain a phosphorus atom in the molecule, and examples thereof include organic phosphorus compounds such as phosphate esters, condensed phosphate esters, phosphazene compounds, and polyphosphates, and red phosphorus.

[0078] Examples of the inorganic filler material include aluminum borate, calcium carbonate, silicon carbonate, silicon nitride, potassium titanate, basic magnesium sulfate, zinc oxide, graphite, calcium sulfate, magnesium borate, magnesium oxide, and silicate minerals. In particular, it is preferable to use silicate minerals. A commercially available product of silicate minerals includes THIXOTROPIC AGENT DT 5039 (manufactured by Huntsman Japan Co., Ltd.).

[0079] Examples of the internal release agent include metal soaps, vegetable waxes such as polyethylene wax and carnauba wax, fatty acid ester-based release agents, silicone oils, animal waxes, and fluorine-based nonionic surfactants. The blending amount of these internal release agents is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 2 parts by mass, based on 100 parts by mass of the epoxy resin. Within this range, the release effect from the mold is preferably exhibited.

[0080] Commercially available products of the internal release agent include "MOLD WIZ (registered trademark)" INT1846 (manufactured by AXEL PLASTICS RESEARCH LABORATORIES INC.), Licowax S, Licowax P, Licowax OP, Licowax PE190, Licowax PED (manufactured by Clariant Japan), and stearyl stearate (SL-900A; manufactured by Riken Vitamin Co., Ltd.).

[0081] [Manufacturing method of epoxy resin main agent] The epoxy resin main agent can be manufactured by mixing an epoxy resin and, if necessary, other optional components. The order of mixing these is not limited. Also, as the state of the epoxy resin composition, it may be in a one-component state in which each component is uniformly mixed, or it may be in a slurry state in which some components are dispersed as solids.

[0082] The method for producing the epoxy resin base is not particularly limited, and any conventionally known method may be used. The mixing temperature can be exemplified in the range of 40 to 200°C. When it exceeds 200°C, the self-polymerization reaction of the epoxy resin may partially proceed, resulting in a decrease in the impregnability to the reinforcing fiber base material, or the physical properties of the resin cured product produced using the obtained epoxy resin base may decrease. When it is less than 40°C, the viscosity of the epoxy resin base is high, and mixing may be substantially difficult. Preferably it is 50 to 100°C, and more preferably in the range of 50 to 90°C.

[0083] As the mixing mechanical device, conventionally known ones can be used. Specific examples include a roll mill, a planetary mixer, a kneader, an extruder, a Banbury mixer, a mixing container equipped with stirring blades, a horizontal mixing tank, etc. The mixing of each component can be carried out in the air or in an inert gas atmosphere. When mixing is carried out in the air, an atmosphere with controlled temperature and humidity is preferable. Although not particularly limited, for example, it is preferable to mix in an atmosphere with a constant temperature of 30°C or lower or a low humidity atmosphere with a relative humidity of 50%RH or lower.

[0084] 〔Epoxy Resin Composition〕 The epoxy resin composition comprises the curing agent composition for the thermosetting resin of the present invention and an epoxy resin base.

[0085] The epoxy resin composition preferably has a viscosity at 100 °C of 50 mPa·s or less, more preferably 30 mPa·s, and even more preferably 20 mPa·s. When the viscosity at 100 °C exceeds 50 mPa·s, it becomes difficult to impregnate the reinforcing fiber base material with the epoxy resin composition. As a result, voids and the like are likely to be formed in the obtained fiber-reinforced composite material, causing a deterioration in physical properties. Note that the relationship between viscosity and impregnability also depends on the configuration of the reinforcing fiber base material, and even outside the above viscosity range, impregnation of the reinforcing fiber base material may be good in some cases.

[0086] Also, the pot life of the epoxy resin composition varies depending on the molding conditions of the composite material. For example, when a large composite material is impregnated into a fiber base material at a relatively low impregnation pressure using a resin transfer molding method (RTM method), as the pot life, the time until the viscosity exceeds 50 mPa·s when held at 100 °C is preferably 60 minutes or more, more preferably 180 minutes or more, and even more preferably 300 minutes or more.

[0087] The total amount of the curing agent contained in the epoxy resin composition is an amount suitable for curing all the epoxy resins blended in the epoxy resin composition, and is appropriately adjusted according to the types of the epoxy resins and curing agents used. Specifically, the ratio of the number of total epoxy groups of the epoxy resin in the epoxy resin composition to the number of active hydrogens contained in the curing agent composition for thermosetting resins is preferably 0.7 to 1.3, more preferably 0.8 to 1.2, and particularly preferably 0.9 to 1.1. When the ratio of the number of active hydrogens is less than 0.7 or exceeds 1.3, the molar balance between the epoxy groups and the active hydrogens is disrupted, the crosslink density of the obtained resin cured product becomes insufficient, and the heat resistance and mechanical properties such as elastic modulus and fracture toughness decrease, which is not preferable.

[0088] According to the present invention, an epoxy resin composition can be obtained in which the DSC curing degree α represented by the following formula of the cured product obtained by curing at 180 °C for 30 minutes is 98% or more. α = (ΔH uncured - ΔH cured product) / ΔH uncured × 100 (However, ΔH is the heat of exotherm associated with the curing reaction confirmed when performing DSC measurement at a heating rate of 20°C per minute, ΔH uncured is the ΔH of the uncured epoxy resin composition, and ΔH cured product is the ΔH of the resin cured product.)

[0089] That is, the epoxy resin composition of the present invention is an epoxy resin composition in which the DSC curing degree α represented by the above formula of the cured product obtained by curing at 180°C for 30 minutes is 98% or more. By having the DSC curing degree α of 98% or more, excellent heat resistance and mechanical properties can be obtained, and changes in properties over time can be suppressed.)

[0090] [Epoxy resin cured product] The present invention also relates to an epoxy resin cured product obtained by curing the above epoxy resin composition.)

[0091] This resin cured product preferably has a glass transition temperature of 150°C or higher, more preferably 180°C or higher, and particularly preferably 200°C or higher. If it is less than 150°C, the heat resistance becomes insufficient when used for industrial applications, which is not preferable.) This epoxy resin cured product preferably has a glass transition temperature during water absorption of 120°C or higher, more preferably 140°C or higher.) If it is less than 120°C, the heat resistance becomes insufficient when used for industrial applications, which is not preferable.)

[0092] This resin cured product preferably has a flexural modulus measured by the JIS K7171 method of 3.0 GPa or higher, more preferably 3.3 GPa or higher, and particularly preferably 3.5 GPa or higher. If it is less than 3.0 GPa, the properties of the fiber-reinforced composite material obtained using the epoxy resin composition are likely to deteriorate, which is not preferable.)

[0093] [Fiber-reinforced composite material] The present invention also relates to a fiber-reinforced composite material comprising the above-mentioned cured epoxy resin and a fiber-reinforced base material. This fiber-reinforced composite material can be obtained by compounding and curing a fiber-reinforced base material and the epoxy resin composition of the present invention. As the fiber-reinforced base material, a carbon fiber-reinforced base material is preferably used. Curing can be carried out by heating.

[0094] As a method of compounding a fiber-reinforced base material and an epoxy resin composition, the fiber-reinforced base material and the epoxy resin composition may be compounded in advance. For example, they may be compounded during molding such as by the resin transfer molding method (RTM method), the hand lay-up method, the filament winding method, or the pultrusion method.

[0095] As a method for producing a fiber-reinforced composite material using the epoxy resin composition of the present invention, for example, the RTM method, the autoclave molding method, or the press molding method can be used. The epoxy resin composition of the present invention is particularly suitable for the RTM method. Here, the RTM method is a method of impregnating a fiber-reinforced base material disposed in a mold with a liquid epoxy resin composition and curing it to obtain a fiber-reinforced composite material. From the viewpoint of efficiently obtaining a fiber-reinforced composite material with a complex shape, the RTM method is a preferred molding method.

[0096] In the present invention, as the mold used in the RTM method, a closed mold made of a rigid material may be used, or an open mold of a rigid material and a flexible film (bag) may be used. In the latter case, the fiber-reinforced base material can be installed between the open mold of the rigid material and the flexible film. As the rigid material, for example, metals such as steel and aluminum, fiber-reinforced plastics (FRP), wood, gypsum, etc. can be used. As the material of the flexible film, for example, polyamide, polyimide, polyester, fluororesin, silicone resin, etc. can be used.

[0097] When using a closed mold of a rigid material in the RTM method, it is pressurized and clamped, and the epoxy resin composition is pressurized and injected. At this time, a suction port may be provided separately from the injection port and connected to a vacuum pump for suction. When suction is performed, the epoxy resin composition can be injected only by atmospheric pressure without using special pressurizing means. In this method, a large member can be manufactured by providing a plurality of suction ports and can be preferably used.

[0098] In the RTM method, when using an open mold of a rigid material and a flexible film, suction may be performed, and the epoxy resin may be injected only by atmospheric pressure without using special pressurizing means. In order to achieve good impregnation by injection only with atmospheric pressure, it is effective to use a resin diffusion medium. Further, a gel coat may be applied to the surface of the rigid material prior to the installation of the fiber-reinforced base material.

[0099] In the RTM method, after impregnating the fiber-reinforced base material with the epoxy resin composition, heat curing is performed. The mold temperature during heat curing is usually selected to be higher than the mold temperature at the time of injecting the epoxy resin composition. The mold temperature during heat curing is, for example, 80 to 200 °C. The time for heat curing is, for example, 1 minute to 20 hours. After the heat curing is completed, demolding is performed to take out the fiber-reinforced composite material. Thereafter, the obtained fiber-reinforced composite material may be heated at a higher temperature for post-curing. The temperature for post-curing is, for example, 150 to 200 °C, and the time is, for example, 1 minute to 4 hours.

[0100] The impregnation pressure when impregnating the fiber-reinforced base material with the epoxy resin composition by the RTM method may be appropriately determined in consideration of the viscosity and resin flow of the resin composition. The specific impregnation pressure is preferably 0.001 to 10 MPa, more preferably 0.01 to 1 MPa. When obtaining a fiber-reinforced composite material using the RTM method, the epoxy resin composition preferably has a viscosity at 100 °C of 50 mPa·s or less, more preferably 30 mPa·s, and even more preferably 20 mPa·s. When the viscosity at 100 °C exceeds 50 mPa·s, it becomes difficult to impregnate the fiber-reinforced base material with the epoxy resin composition.

[0101] In the RTM method, it is preferable that the curing agent composition for thermosetting resin of the present invention and the epoxy resin are mixed immediately before impregnation to produce an epoxy resin composition. The curing agent composition for thermosetting resin of the present invention has high reactivity with the epoxy resin, but when it is mixed immediately before impregnation to form an epoxy resin composition, an adequate amount of the epoxy resin composition can be impregnated into the reinforcing fiber base material before the viscosity of the epoxy resin composition increases. Therefore, the produced fiber-reinforced composite material does not contain defects such as voids and is excellent in compression performance and damage tolerance.

[0102] Thus, according to the present invention, a method for manufacturing a fiber-reinforced composite material is provided. That is, it is a method for manufacturing a fiber-reinforced composite material including a step of impregnating a fiber-reinforced base material with the epoxy resin composition of the present invention to obtain an impregnated base material, and a step of curing the impregnated base material obtained in the step.

[0103] In this manufacturing method, the step of impregnating the fiber-reinforced base material with the epoxy resin composition of the present invention to obtain an impregnated base material is a step of impregnating the fiber-reinforced base material disposed in a mold with the epoxy resin composition of the present invention to obtain an impregnated base material, and it is preferable that the step of curing the impregnated base material obtained in the step is a step of heat-curing the impregnated base material. And preferably, a step of preparing the epoxy resin composition of the present invention is included immediately before the step of impregnating the fiber-reinforced base material with the epoxy resin composition of the present invention to obtain an impregnated base material.

Examples

[0104] Hereinafter, the present invention will be described more specifically by way of examples. The components and evaluation methods used in the examples and comparative examples are described below.

[0105] 1. Raw materials of the epoxy resin composition (1) Curing agent (1-1) Curing agent A · 4,4'-Diamino-3,3'-diisopropyl-5,5'-dimethyldiphenylmethane (manufactured by Lonza, Lonzacure M-MIPA (product name), hereinafter abbreviated as "M-MIPA", melting point 70 °C, solid at 25 °C) · 4,4'-Diamino-3,3'-diethyl-5,5'-dimethyldiphenylmethane (manufactured by Kumiai Chemical Industry Co., Ltd., MED-J (product name), hereinafter abbreviated as "MED-J", melting point 76 °C, solid at 25 °C)

[0106] (1-2) Curing agent B · Diethyltoluenediamine (manufactured by Kumiai Chemical Industry Co., Ltd., Heart Cure 10 (product name), hereinafter abbreviated as "DETDA", liquid at 25 °C) · Dimethylthiotoluenediamine (manufactured by Kumiai Chemical Industry Co., Ltd., Heart Cure 30 (product name), hereinafter abbreviated as "DMTDA", liquid at 25 °C)

[0107] (1-3) Curing agent C · 3,4'-Diaminodiphenyl ether (manufactured by Teijin Chemicals, hereinafter abbreviated as "3,4'-DAPE", melting point 80 °C, solid at 25 °C) · 2,2-Bis[4-(4-aminophenoxy)phenyl]propane (manufactured by Tokyo Chemical Industry Co., Ltd., hereinafter abbreviated as "BAPP", melting point 129 °C, solid at 25 °C) · 1,3-Bis(4-aminophenoxy)benzene (manufactured by Tokyo Chemical Industry Co., Ltd., hereinafter abbreviated as "TPE-R", melting point 116 °C, solid at 25 °C) · 1,3-Bis(3-aminophenoxy)benzene (manufactured by Tokyo Chemical Industry Co., Ltd., hereinafter abbreviated as "APB", melting point 108 °C, solid at 25 °C) · 2,6-Diaminotoluene (manufactured by Tokyo Chemical Industry Co., Ltd., hereinafter abbreviated as "DAT", melting point 106 °C, solid at 25 °C) · m-Phenylenediamine (manufactured by Fujifilm Wako Pure Chemical Corporation, hereinafter abbreviated as "MPD", melting point 65 °C, solid at 25 °C)

[0108] (2) Epoxy resin · N,N-Diglycidyl-o-toluidine (manufactured by Nippon Kayaku Co., Ltd., GOT (product name), hereinafter abbreviated as "GOT") · N,N-Diglycidylaniline (GAN (product name) manufactured by Nippon Kayaku Co., Ltd., hereinafter abbreviated as "GAN") · Tetraglycidyl-3,4'-diaminodiphenyl ether This was synthesized by the method of Synthesis Example 1 below. Hereinafter, it is abbreviated as "3,4'-TGDDE".

[0109] 〔Synthesis Example 1〕 Synthesis of 3,4'-TGDDE 1110.2 g (12.0 mol) of epichlorohydrin was charged into a four-necked flask equipped with a thermometer, a dropping funnel, a condenser, and a stirrer. While purging with nitrogen, the temperature was raised to 70 °C, and 200.2 g (1.0 mol) of 3,4'-diaminodiphenyl ether dissolved in 1000 g of ethanol was added dropwise thereto over 4 hours. The mixture was further stirred for 6 hours to complete the addition reaction, and N,N,N',N'-tetrakis(2-hydroxy-3-chloropropyl)-3,4'-diaminodiphenyl ether was obtained. Subsequently, after lowering the temperature in the flask to 25 °C, 500.0 g (6.0 mol) of a 48% aqueous NaOH solution was added dropwise thereto over 2 hours and further stirred for 1 hour. After the cyclization reaction was completed, ethanol was distilled off, extraction was performed with 400 g of toluene, and washing was performed twice with 5% saline. When toluene and epichlorohydrin were removed from the organic layer under reduced pressure, 361.7 g (yield 85.2%) of a brown viscous liquid mainly composed of 3,4'-TGDDE was obtained.

[0110] (3) Particulate rubber component · MX-416 (MX-416 (product name) manufactured by Kaneka Corporation, a masterbatch in which a particulate rubber component is dispersed in a glycidylamine type tetrafunctional epoxy resin at a concentration of 25% by mass)

[0111] 2. Evaluation method (1) Characteristics of the curing agent composition (1-1) Preparation of the curing agent composition The curing agent was weighed at the ratio shown in the table and mixed using a stirrer at an appropriate temperature of 90 to 110 °C for 60 minutes to prepare a curing agent composition.

[0112] (1-2) Confirmation of Liquid Retention of Hardener Composition The hardener composition prepared in (1-1) was stored at room temperature for one week, and precipitation of solid components was visually confirmed. Those without precipitation were marked as "○", and those with observable precipitation were marked as "×".

[0113] (2) Properties of Resin Composition (2-1) Preparation of Epoxy Resin Composition The hardener composition prepared in (1-1), epoxy resin, and particulate rubber component were weighed at the ratios described in the table, and mixed at 80 °C for 60 minutes using a stirrer to prepare an epoxy resin composition. In the compositions described in the table, the epoxy groups of the epoxy resin and the active hydrogens of the hardener are equivalent.

[0114] (2-2) Initial Viscosity and Pot Life Viscosity measurement was carried out using a B-type viscometer TVB-15M manufactured by Toki Sangyo Co., Ltd. under the condition of 100 °C. The minimum measured value immediately after the start of measurement was taken as the initial viscosity, and the time when the viscosity reached 50 mPa·s was taken as the pot life.

[0115] (3) Properties of Resin Cured Product (3-1) Preparation of Resin Cured Product After degassing the epoxy resin composition prepared in (2-1) in vacuo, it was poured into a stainless mold set to a thickness of 4 mm by a 4-mm-thick silicone resin spacer. Curing was carried out at a temperature of 180 °C for 30 minutes to obtain a resin cured product with a thickness of 4 mm.

[0116] (3-2) Degree of Curing The degree of curing α was calculated using the following formula. α = (ΔH uncured - ΔH cured product) / ΔH uncured × 100 (However, ΔH is the heat of exotherm associated with the curing reaction confirmed when DSC measurement is carried out at a heating rate of 20 °C / min, ΔH uncured is the ΔH of the epoxy resin composition prepared in (2-1), and ΔH cured product is the ΔH of the resin cured product prepared in (3-1).)

[0117] (3-3) wet-Tg The glass transition temperature was measured in accordance with the SACMA 18R-94 method. Resin test specimens with dimensions of 50 mm × 6 mm × 2 mm were prepared. Using a pressure cooker (manufactured by Espec, HASTEST PC-422R8), the resin test specimens prepared under the conditions of 121 °C, 24 hours, and saturated water vapor were subjected to a water absorption treatment. Using a dynamic viscoelasticity measuring device Rheogel-E400 manufactured by UBM, under the conditions of a measurement frequency of 1 Hz, a heating rate of 5 °C / min, and a strain of 0.0167%, with the distance between chucks being 30 mm, the storage elastic modulus E' of the water-absorbed resin test specimens was measured from 50 °C to the rubber elastic region. logE' was plotted against temperature, and the temperature obtained from the intersection of the approximate straight line in the flat region of logE' and the approximate straight line in the region where E' transitions was recorded as the glass transition temperature (Tg).

[0118] (3-4) Resin flexural modulus The test was carried out in accordance with the JIS K7171 method. At that time, resin test specimens with dimensions of 80 mm × 10 mm × 4 mm (thickness h) were prepared. The distance between supports L was 16 × h (thickness), and a flexural test was performed at a test speed of 2 m / min to measure the flexural strength and flexural modulus.

[0119] (3-5) K1c The test was carried out in accordance with the ASTM D5045 method. At that time, resin test specimens with dimensions of 50 mm × 8 mm (width W) × 4 mm were prepared. The crack length a was adjusted so that 0.45 ≦ a / W ≦ 0.55. The crack length a was observed using an optical microscope on the fracture surface after the fracture test, and the length to the tip of the crack and the average value of the crack lengths on both surfaces of the test specimen were adopted.

[0120] [Example 1] (Preparation of curing agent composition) The curing agent was weighed at the ratios shown in the table and mixed at a temperature of 90 °C for 60 minutes using a stirrer to prepare a curing agent composition.

[0121] (Preparation of epoxy resin composition) The curing agent composition prepared above, the epoxy resin, and the particulate rubber component were weighed at the ratios described in the table and mixed at 80 °C for 60 minutes using a stirrer to prepare an epoxy resin composition. In the composition described in the table, the epoxy groups of the epoxy resin and the active hydrogens of the curing agent are equivalent.

[0122] (Preparation of resin cured product) After degassing the epoxy resin composition prepared above in vacuo, it was poured into a stainless mold set to a thickness of 4 mm by a 4-mm-thick silicone resin spacer. It was cured at a temperature of 180 °C for 30 minutes to obtain a resin cured product with a thickness of 4 mm.

[0123]

Table 1

[0124] The properties of the curing agent composition, the resin composition, and the resin cured product were shown in the table. The curing agent composition remained liquid for more than one week. The resin composition showed a low viscosity of 24 mPa·s at 100 °C, and the pot life was 120 min. The degree of cure α was 100%, indicating rapid curing properties. The wet-Tg of the resin cured product was 156 °C, the flexural modulus was 3.4 GPa, and K1c was 0.86 MPa·m 1 / 2 and showed high mechanical properties.

[0125] [Examples 2 to 22] The composition was changed as described in the table and carried out in the same manner as in Example 1. In the preparation of the epoxy resin composition, Examples 2 to 9 and Examples 15 to 22 were carried out at 90 °C, and Examples 10 to 14 were carried out at 110 °C. The properties of the curing agent composition, the resin composition, and the resin cured product were shown in the table. The curing agent composition remained liquid for more than one week. The resin composition showed a low viscosity of 32 mPa·s or less at 100 °C, and the pot life was 80 min or more. The degree of cure α was 100% in all cases, indicating rapid curing properties. The wet-Tg of the resin cured product was 150 °C or higher, the flexural modulus was 3.2 GPa or higher, and K1c was 0.81 MPa·m 1 / 2 and showed high mechanical properties as above.

[0126]

Table 2

[0127] 〔Examples 23 to 25〕 The composition was changed as described in the table and carried out in the same manner as in Example 1. In the preparation of the epoxy resin composition, Example 23 and Example 25 were carried out at 90 °C, and Example 24 was carried out at 110 °C. The properties of the curing agent composition, resin composition, and resin cured product are shown in the table. The curing agent composition maintained a liquid state for more than one week. The viscosity of the resin composition and the curing degree α were both 100%, indicating rapid curing properties. The wet-Tg of the resin cured product was 156 °C or higher, and the flexural modulus was 3.2 GPa or higher, showing high mechanical properties.

[0128]

Table 3

[0129] 〔Comparative Examples 1, 3, and 6〕 The composition was changed as described in the table and carried out in the same manner as in Example 1. The properties of the curing agent composition are shown in the table. Solids precipitated within one week in all cases.

[0130] 〔Comparative Examples 2, 4, and 5〕 The composition was changed as described in the table and carried out in the same manner as in Example 1. The properties of the resin cured product are shown in the table. In all cases, the curing degree α was less than 98, and the rapid curing property was insufficient.

Claims

1. A curing agent composition for a thermosetting resin, comprising curing agent A, curing agent B, and curing agent C, Curing agent A is a solid at 25°C and is an aromatic polyamine having substituents at two ortho positions with respect to the amino group. The substituents are selected from an alkyl group, an aromatic group, and a halogen group, and it is a 4,4'-diaminodiphenylmethane derivative, Curing agent B is an aromatic polyamine that is liquid at 25°C, Curing agent C is a solid at 25°C and is an aromatic polyamine having a melting point of 150°C or lower. The aromatic polyamine is an aromatic polyamine (excluding 4,4'-diaminodiphenylmethane derivatives) having only one electron-donating group at the ortho position with respect to the amino group or having no substituent at the ortho position. A curing agent composition for a thermosetting resin, characterized in that.

2. Based on the total mass of the curing agent composition for a thermosetting resin The total of curing agent A, curing agent B, and curing agent C accounts for 70 to 100% by mass, The mass ratio of curing agent A to curing agent B is 1:99 to 99:1, Curing agent C is 1 to 43 parts by mass with respect to 100 parts by mass in total of curing agent A and curing agent B The curing agent composition for a thermosetting resin according to claim 1.

3. The curing agent composition for a thermosetting resin according to claim 1 or 2, wherein the electron-donating group of the aromatic polyamine of curing agent C is a methyl group, an ethyl group, a propyl group, an isopropyl group, a methoxy group, or an ethoxy group.

4. The curing agent composition for a thermosetting resin according to any one of claims 1 to 3, wherein the aromatic polyamine of curing agent B is a phenylenediamine derivative or a 4,4'-diaminodiphenylmethane derivative.

5. It becomes a uniform liquid at a temperature of 80 to 200°C, and after raising the liquid temperature to 200°C and then lowering the temperature to 25°C and allowing it to stand at 25°C for 1 week, it is a uniform liquid. The curing agent composition for a thermosetting resin according to any one of claims 1 to 4. Claim 6 An epoxy resin composition containing a curing agent composition for a thermosetting resin and an epoxy resin base, wherein the curing agent composition for a thermosetting resin is the curing agent composition for a thermosetting resin according to any one of claims 1 to 5, and the ratio of the number of total epoxy groups in the epoxy resin composition to the number of active hydrogens contained in the curing agent composition for a thermosetting resin is 0.7 to 1.

3. Epoxy resin composition. Claim 7 The epoxy resin composition according to claim 6, wherein the DSC curing degree α represented by the following formula of the cured product obtained by curing at 180 ° C for 30 minutes is 98% or more. α = (ΔH uncured - ΔH cured product) / ΔH uncured × 100 (However, ΔH is the heat generation amount accompanying the curing reaction confirmed when performing DSC measurement at a temperature increase rate of 20 ° C / minute, ΔH uncured is ΔH of the uncured epoxy resin composition, and ΔH cured product is ΔH of the resin cured product.) Claim 8 An epoxy resin cured product obtained by curing the epoxy resin composition according to claim 6 or 7. Claim 9 A fiber-reinforced composite material containing the epoxy resin cured product according to claim 8 and a fiber-reinforced base material. Claim 10 The fiber-reinforced composite material according to claim 9, wherein the fiber-reinforced base material is a carbon fiber-reinforced base material.

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