JP2014214169A - Two liquid type epoxy resin composition for fiber reinforced composite material and fiber reinforced composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two liquid type epoxy resin composition: excellent in workability during resin preparation, viscosity stability of a resin composition at low temperature and impregnating ability by holding low viscosity during injection into reinforced fibers; and capable of hardening itself in a short time during molding and providing a fiber reinforced composite material high in dimensional accuracy, and a fiber reinforced composite material using the same.SOLUTION: The two liquid type epoxy resin composition for fiber reinforced composite materials includes the components of following [A]-[D], where an acid dissociation constant pKa of each compound corresponding to the component [C] is 10.2 or more and 13 or less, and the component [D] is a liquid at normal temperature or a solid having a melting point of 90°C or less. [A] is epoxy resin, [B] is acid anhydride, [C] is a compound having a hydroxyphenyl structure, and [D] is an organic phosphorous compound or an imidazole derivative.

Description

  The present invention relates to a two-component epoxy resin composition used for a fiber-reinforced composite material, a curing agent solution used for a two-component epoxy resin composition, and a fiber-reinforced composite material using the same.

  Fiber reinforced composite materials composed of reinforced fibers and matrix resins can be designed using the advantages of reinforced fibers and matrix resins, so the applications are expanded to aerospace, sports, general industrial fields, etc. .

  As the reinforcing fiber, glass fiber, aramid fiber, carbon fiber, boron fiber or the like is used. As the matrix resin, either a thermosetting resin or a thermoplastic resin is used, but a thermosetting resin that can be easily impregnated into the reinforcing fiber is often used. As the thermosetting resin, epoxy resin, unsaturated polyester resin, vinyl ester resin, phenol resin, bismaleimide resin, cyanate resin and the like are used.

  For the production of the fiber reinforced composite material, a prepreg method, a hand layup method, a filament winding method, a pultrusion method, an RTM (Resin Transfer Molding) method, or the like is applied.

  In recent years, environmental regulations for automobiles have become more stringent worldwide, and domestic and overseas automobile manufacturers have been working to reduce the weight of the vehicle body, which affects fuel efficiency. Carbon fiber composite materials that are half the weight of iron and about 70% of aluminum The application of is being studied actively. Various members for automobiles are required to have high rigidity and strength characteristics as well as weight reduction, and often have a three-dimensional complicated shape. Therefore, the RTM method capable of dealing with complicated shapes using high-rigidity and high-strength carbon fibers as continuous fibers is a promising forming method. The RTM method is to close the mold after placing the reinforcing fiber base in the mold, inject the resin from the resin injection port, impregnate the reinforcing fiber, harden the resin, open the mold and take out the molded product This is a method for obtaining a fiber-reinforced composite material. Here, productivity is a major issue for the spread of carbon fiber composite materials in automobiles, which becomes a barrier and is only slightly adopted in some luxury cars.

  In the hand lay-up method, filament winding method, pultrusion method, and RTM method, a two-component epoxy resin composition is often used from the viewpoint of moldability. The two-pack type epoxy resin composition is composed of a main agent liquid containing an epoxy resin as a main component and a hardener liquid containing a curing agent as a main component, and two liquids of the main agent liquid and the hardener liquid are mixed immediately before use. It is the epoxy resin composition obtained by this. On the other hand, an epoxy resin composition in which all components including a main agent and a curing agent are mixed together is called a one-pack type epoxy resin composition. In the case of a one-pack type epoxy resin composition, since the curing reaction proceeds during storage, frozen storage is required. In addition, a solid component having low reactivity is often selected as the curing agent component, and in order to impregnate the reinforcing fiber with the one-pack type epoxy resin composition, it is not necessary to use a press roll or the like at high pressure. Must not. In the two-pack type epoxy resin composition, both the main agent liquid and the curing agent liquid are liquid, so that the mixture obtained by mixing the main agent liquid and the curing agent liquid can also be made into a low-viscosity liquid, and the reinforcing fiber It becomes easy to impregnate. Further, since the main agent liquid and the curing agent liquid are stored separately, long-term storage is possible without any particular limitation on the storage conditions.

  For example, in this RTM method, in order to realize the productivity at a high level as described above, not only the curing time of the resin is short, but also the following four conditions must be satisfied at once. Specifically required. First, when mixing and preparing resin raw materials, the two liquids are both low in viscosity and close to the viscosity level, so that mixing workability is excellent. Secondly, the resin composition after mixing and preparation should be stable in that the increase in viscosity is suppressed for a long time when kept at a low temperature. Third, the resin composition has a low viscosity during the resin injecting step to the reinforcing fiber base, and the impregnation property is excellent by suppressing an increase in viscosity during the injecting step. Fourth, sufficient high-speed curing in the low temperature region around 100 ° C can simplify the molding equipment, eliminate the need for heat resistance of secondary materials, etc., and reduce costs, and the temperature difference between the curing temperature and room temperature. The surface smoothness of the molded product is excellent by being able to reduce the heat shrinkage derived from the. Fifth, during the demolding process after molding, the resin has reached sufficient rigidity due to curing, can be smoothly demolded without causing distortion, and further undergoes distortion and deformation even after the painting process. It is that high dimensional accuracy can be obtained in the molded product without any problem.

  In response to these problems, the use of a combination of an acid anhydride and phenol novolac as a curing agent suppresses the generation of formalin and provides a molded product having excellent rigidity, and is therefore suitable as a sheet molding compound material for building materials. A resin composition is disclosed (Patent Document 1). However, this material does not have sufficient rapid curability in a low temperature region.

  Furthermore, by using an epoxy resin composition in which an acid anhydride is combined as a curing agent and an organic phosphorus compound is combined as a catalyst, an epoxy resin composition having an excellent balance between low viscosity retention time and curing time under a constant temperature condition around 100 ° C The thing is disclosed (patent document 2). However, there has been a problem that high-speed curability is not sufficient, and the rigidity of the resin at the time of demolding is not sufficient, and the dimensional accuracy may be lowered.

  In addition, by using an epoxy resin composition that combines a phenol curing agent as a curing agent and a small amount of carboxylic acid anhydride as a catalyst auxiliary material, an electrical material that has achieved high heat resistance, high toughness, and high adhesion to copper foil at once. An epoxy resin composition is disclosed (Patent Document 3), but this also does not have sufficient high-speed curability, requires a solvent, and is not suitable for use as a molded product.

  In this way, RTM molding or the like can be made into a high cycle (shortening the time required for one molding cycle and increasing the molding cycle to be executed within a certain period of time), which is necessary for realizing a high level of productivity. There has never been a two-pack type epoxy resin composition that has all the requirements.

JP 2002-12649 A International Publication No. 2007/125759 Pamphlet Special table 2009-521666

  The object of the present invention is to improve the disadvantages of the prior art, to improve the workability during resin preparation, to improve the viscosity stability at low temperatures of the resin composition, and to maintain the low viscosity when injected into the reinforcing fiber and impregnation Another object of the present invention is to provide a two-pack type epoxy resin composition, a curing agent liquid, and a fiber reinforced composite material using the same, which give a fiber reinforced composite material that is excellent in the above-described properties and is cured in a short time during molding.

In order to solve the above problems, the two-pack type epoxy resin composition for fiber-reinforced composite material of the present invention has the following configuration. That is, the acid dissociation constant pKa of at least one of the compounds corresponding to the component [C], which includes the following components [A] to [D], is 10.2 to 13, and the component [D] Is a two-pack type epoxy resin composition for fiber-reinforced composite materials which is liquid at normal temperature or solid with a melting point of 130 ° C. or lower.
[A] epoxy resin [B] acid anhydride [C] compound having hydroxyphenyl structure [D] organophosphorus compound or imidazole derivative

  In such a two-component resin composition for fiber-reinforced composite materials, component [C] is preferably a compound having an electron-donating substituent on a carbon atom of a hydroxyphenyl structure.

  In such a two-component resin composition for fiber-reinforced composite material, the mass blending ratio of component [B] and component [C] is preferably 99: 1 to 65:35.

  In such a two-component resin composition for fiber-reinforced composite material, component [A] is preferably a bisphenol A type epoxy resin.

  In such a two-component resin composition for fiber-reinforced composite materials, component [B] is preferably an acid anhydride having an alicyclic structure.

  Such a two-component resin composition for fiber-reinforced composite material has a cure index determined by dielectric measurement under constant temperature holding of 10% and 90%, respectively, when the times are t10 and t90 (unit: minutes), It is preferable that t10 and t90 have a specific temperature T that satisfies 0.5 ≦ t10 ≦ 4, 0.5 ≦ t90 ≦ 9, and 1 <t90 / t10 ≦ 2.5.

  Such a two-component resin composition for fiber-reinforced composite materials preferably has a viscosity at 25 ° C. of 0.1 to 2.5 Pa · s.

  Such a two-component resin composition for fiber-reinforced composite material is obtained by mixing a main agent liquid composed of component [A] and a curing agent liquid composed of components [B], [C], and [D]. Is preferred.

  Such a two-component resin composition for fiber-reinforced composite materials preferably has a viscosity of 0.05 to 1.8 Pa · s at 25 ° C. of the curing agent solution.

  Moreover, in order to solve the said subject, the fiber reinforced composite material of this invention has the following structure. That is, it is a fiber-reinforced composite material obtained by combining and curing the above-described two-component epoxy resin composition for fiber-reinforced composite material and reinforcing fibers.

  In such a fiber-reinforced composite material, the reinforcing fiber is preferably a carbon fiber.

  According to the present invention, the workability at the time of resin preparation is excellent, the viscosity stability of the resin composition at low temperature is excellent, the low viscosity is maintained at the time of injection into the reinforcing fiber, the impregnation is excellent, and the molding time is short. It becomes possible to provide a fiber composite material which is cured and has high dimensional accuracy with high productivity.

The preferred embodiments of the present invention will be described below.
First, the epoxy resin composition according to the present invention will be described.

The epoxy resin composition according to the present invention includes the following components [A] to [D], and the acid dissociation constant pKa of at least one compound corresponding to the component [C] is 10.2 or more and 13 or less. And the component [D] is a liquid at a normal temperature or a solid having a melting point of 130 ° C. or lower and is a two-pack type epoxy resin composition for fiber-reinforced composite materials.
[A] epoxy resin [B] acid anhydride [C] compound having hydroxyphenyl structure [D] organophosphorus compound or imidazole derivative

  Component [A] in the present invention is an epoxy resin. An epoxy resin means a compound having two or more epoxy groups in one molecule.

  Specific examples of the component [A] in the present invention include an aromatic glycidyl ether obtained from a phenol having a plurality of hydroxyl groups, an aliphatic glycidyl ether obtained from an alcohol having a plurality of hydroxyl groups, a glycidyl amine obtained from an amine, and an oxirane ring. Examples thereof include epoxy resins and glycidyl esters obtained from carboxylic acids having a plurality of carboxyl groups.

  Examples of the aromatic glycidyl ether that can be used as the component [A] in the present invention include diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol AD, diglycidyl ether of bisphenol S, etc. Diglycidyl ether obtained from bisphenol, polyglycidyl ether of novolak obtained from phenol or alkylphenol, diglycidyl ether of resorcinol, diglycidyl ether of hydroquinone, diglycidyl ether of 4,4'-dihydroxybiphenyl, 4,4'- Diglycidyl ether of dihydroxy-3,3 ′, 5,5′-tetramethylbiphenyl, diglycidyl ether of 1,6-dihydroxynaphthalene, 9,9′-bis Reacting diglycidyl ether of 4-hydroxyphenyl) fluorene, triglycidyl ether of tris (p-hydroxyphenyl) methane, tetraglycidyl ether of tetrakis (p-hydroxyphenyl) ethane, diglycidyl ether of bisphenol A and bifunctional isocyanate And diglycidyl ether having an oxazolidone skeleton obtained in the above manner.

  Examples of the aliphatic glycidyl ether that can be used as the component [A] in the present invention include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol, diglycidyl ether of 1,4-butanediol, 1,6- Diglycidyl ether of hexanediol, diglycidyl ether of neopentyl glycol, diglycidyl ether of cyclohexanedimethanol, diglycidyl ether of glycerin, triglycidyl ether of glycerin, diglycidyl ether of trimethylolethane, triglycidyl ether of trimethylolethane , Diglycidyl ether of trimethylolpropane, triglycidyl ether of trimethylolpropane, tetraglycidyl ether of pentaerythritol, Diglycidyl ethers of mosquito hydro bisphenol A, diglycidyl ethers of dodeca hydro bisphenol F and the like.

  Examples of the glycidylamine that can be used as the component [A] in the present invention include diglycidylaniline, diglycidyltoluidine, triglycidylaminophenol, tetraglycidyldiaminodiphenylmethane, tetraglycidylxylylenediamine, and halogen and alkyl substitution thereof. Body and hydrogenated products.

  Examples of the epoxy resin having an oxirane ring that can be used as the component [A] in the present invention include vinylcyclohexene dioxide, dipentene dioxide, 3,4-epoxycyclohexanecarboxylic acid 3,4-epoxycyclohexylmethyl, and adipine. Examples include acid bis (3,4-epoxycyclohexylmethyl), dicyclopentadiene dioxide, bis (2,3-epoxycyclopentyl) ether, oligomer of 4-vinylcyclohexene dioxide, and the like.

  Examples of the glycidyl ester that can be used as the component [A] in the present invention include diglycidyl phthalate, diglycidyl terephthalate, diglycidyl hexahydrophthalate, and diglycidyl dimer.

  Among them, diglycidyl ether of a bisphenol compound, that is, a bisphenol type epoxy resin, particularly a bisphenol A type epoxy resin, balances the viscosity of the resin composition with the heat resistance of the resulting cured resin and mechanical properties such as elastic modulus. Since it is excellent, it is preferably used as the component [A] in the present invention. The component [A] is desirably contained in the total epoxy resin in an amount of 60 to 100% by mass, and particularly desirably 80 to 100% by mass.

  Such a bisphenol A type epoxy resin preferably has a repeating unit number in the range of 0 to 0.2, and more preferably in the range of 0 to 0.1. The number of repeating units corresponds to n in the chemical structural formula of the bisphenol A type epoxy resin usually represented by the following [Chemical Formula 1]. When the number of repeating units exceeds 0.2, the viscosity of the epoxy resin composition increases and the impregnation property to the reinforcing fibers is deteriorated, and the heat resistance of the obtained fiber-reinforced composite material may be insufficient.

  The bisphenol A type epoxy resin preferably has an epoxy equivalent in the range of 170 to 220, and more preferably in the range of 170 to 195. Such an epoxy equivalent generally has a relationship such that it increases as the number of repeating units increases and decreases as it decreases. When the epoxy equivalent is less than 170, low molecular weight impurities may be contained, which may lead to deterioration of the surface quality due to volatilization during molding. Moreover, when this epoxy equivalent exceeds 220, while the viscosity of an epoxy resin composition rises and the impregnation property to a reinforced fiber deteriorates, the rigidity of the fiber reinforced composite material obtained may become inadequate.

  Component [B] in the present invention is an acid anhydride, specifically a carboxylic acid anhydride, and more specifically, one carboxylic acid anhydride group capable of reacting with an epoxy group of an epoxy resin per molecule. It refers to a compound having the above and acts as a curing agent for epoxy resin.

  Component [B] in the present invention may be an acid anhydride having an aromatic ring but not having an alicyclic structure such as phthalic anhydride, or an aromatic ring or fatty acid such as succinic anhydride. An acid anhydride having no cyclic structure may be used, but an acid anhydride having an alicyclic structure may be used from the viewpoint of heat resistance and mechanical properties of a cured product, since it is a low-viscosity liquid and easy to handle. It is effective to be used, and among them, those having a cycloalkane ring or a cycloalkene ring are preferable. Specific examples of the acid anhydride having such an alicyclic structure include hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyldihydronadic acid anhydride, 1,2,4,5-cyclopentane. Tetracarboxylic dianhydride, 1,2,3,6-tetrahydrophthalic anhydride, methyl-1,2,3,6-tetrahydrophthalic anhydride, nadic anhydride, methyl nadic anhydride, bicyclo [ 2,2,2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 4- (2,5-dioxotetrahydrofuran-3-yl) -3-methyl-1,2 , 5,6-tetrahydrophthalic anhydride. Among them, those selected from hexahydrophthalic anhydride, tetrahydrophthalic anhydride, nadic anhydride and their alkyl-substituted types are the viscosity of the resin composition, the heat resistance of the resulting cured resin, and the elastic modulus. Therefore, it is preferably used as component [B] in the present invention. Even when an acid anhydride having an alicyclic structure is used as the component [B], the epoxy resin composition according to the present invention contains an acid anhydride having no alicyclic structure. Also good.

  Component [C] in the present invention is a compound having a hydroxyphenyl structure. Specifically, the compound [C] has a structure containing phenol represented by [Chemical Formula 2] in the chemical structure of the compound, and serves as a curing agent for an epoxy resin. Works.

  This component [C] has an acid dissociation constant pKa of 10.2 or more among compounds corresponding to the component [C] from the viewpoint of the characteristics required for the resin composition for RTM described later. (Hereinafter, the component [C] having an acid dissociation constant pKa of 10.2 or more and 13 or less may be referred to as a component [C *]). The acid dissociation constant pKa of the component [C] is Ka = [H3O +] [B −] / [BH] (wherein [H3O +] is the hydrogen ion concentration and [BH] is the component [C] The concentration [B-] represents the concentration of the conjugate base from which the component [C] has released a proton), and is determined according to pKa = -logKa. The measurement method of pKa can be calculated from the concentration of the relevant substance and the hydrogen ion concentration by measuring the hydrogen ion concentration using, for example, a pH meter.

  As the component [C], a single compound or a plurality of compounds may be used. When a single compound is used, the acid dissociation constant pKa of the compound is 10.2 or more and 13 or less. When a plurality of compounds are used, it is necessary that at least one compound has an acid dissociation constant pKa of 10.2 or more and 13 or less.

  When only the compound having an acid dissociation constant pKa of less than 10.2 is used as the compound corresponding to component [C], the reason is unknown, but the viscosity stability of the resin composition at a low temperature of about 40 ° C. Remarkably decreases and thickens. When a compound corresponding to component [C] is not used or only a compound corresponding to component [C] having an acid dissociation constant pKa greater than 13 is used, curing is performed while maintaining a low viscosity for a long time. The property required for the resin composition for RTM that the time to completion can be shortened does not appear.

  Component [C] is usually a low molecular weight compound from the viewpoint of ease of preparation and viscosity stability at low temperatures. The low molecular weight compound here means a compound having a molecular weight of 1000 or less.

  As the component [C] in the present invention, a compound having a hydroxyphenyl structure and having an acid dissociation constant pKa of 10.2 or more and 13 or less may be used. When there is an electron donating substituent, the electron density in the benzene ring increases and the electron density of the lone pair in the oxygen atom of the hydroxyl group also increases, so the acidity decreases and the acid dissociation constant pKa increases. In a single compound, the acid dissociation constant pKa tends to be 10.2 or more and 13 or less. Examples of electron donating substituents include alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, hydroxyl, methoxy Group, amino group, phenyl group and the like. Examples of the component [C] having these substituents on the benzene ring in the hydroxyphenyl structure include o-cresol (pKa = 10.28, molecular weight 108.14), 2,4-dimethylphenol (pKa = 10 .6, molecular weight 122.16), 2,6-dimethylphenol (pKa = 10.59, molecular weight 122.16), o-ethylphenol (pKa = 10.2, molecular weight 122.16), 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane (pKa = 10.8, molecular weight 284.39), 4,4′-methylenebis (2,6-dimethylphenol) (pKa = 10.8, molecular weight 256. 34), 4,4′-methylenebis (2,6-di-tert-butylphenol) (pKa = 11.6, molecular weight 424.66), 4-aminophenone (PKa = 10.3, molecular weight 109.13), p-methoxyphenol (pKa = 10.2, molecular weight 124.14), 4-tert-octylphenol (pKa = 10.33, molecular weight 206.32) and the like. It is done.

  Of these components [C] having an electron-donating substituent on the carbon atom of the hydroxyphenyl structure, a compound in which the substituent is an alkyl group is preferable from the viewpoint of ease of handling and mechanical properties of the cured product. Further, as in [Chemical Formula 3], when the alkyl group of this substituent is ortho to the hydroxyl group, the alkyl group itself becomes a steric hindrance to the dissociation of the hydroxyl group, the pKa increases, and the resin composition is easy to handle. It is preferable from the viewpoint of viscosity stability.

  Surprisingly, by using the component [C *] in combination with the component [B] as the curing agent in the present invention, it is surprisingly possible to maintain a low viscosity at a molding temperature while being excellent in viscosity stability at a low temperature. The characteristic requested | required of the resin composition for RTM that the time to completion of hardening can be shortened maintaining is expressed. Although the reason for this is unknown, it is considered that the component [C *] functions not only as a curing agent but also as a catalyst for the component [B]. At the same time, when the component [B] and the component [C *] are mixed, gelation or the like due to the reaction between them does not occur, the storage stability is excellent, and the curing agent liquid is appropriately thickened by mixing. ] Tends to be easy to mix.

  The mass mixing ratio [B]: [C *] of the component [B] and the component [C *] in the present invention is preferably 99: 1 to 65:35, and is 99: 1 to 81:19. Is more preferable. When [B]: [C *] is more than 99: 1, the time required for curing may become longer and productivity may be reduced. On the other hand, when [B]: [C *] is more than 65:35, the heat resistance of the cured product may decrease.

  The blending amount of component [B] and component [C *] in the present invention includes the total number of acid anhydride groups in component [B], the total number of hydroxyl groups in component [C *] (H), and component [A]. The ratio of the total number of epoxy groups (E) in all epoxy resins, the H / E ratio is preferably a blending amount satisfying the range of 0.8 to 1.1, and the blending satisfying the range of 0.85 to 1.05 The amount is more preferable, and the blending amount satisfying the range of 0.9 to 1.0 is more preferable. When the H / E ratio is less than 0.8, the polymerization between the excessively existing epoxy resins proceeds and the physical properties of the cured product are deteriorated. When the H / E ratio exceeds 1.1, the concentration of the reaction point of the system decreases due to the excessive curing agent component, the reaction rate decreases, and sufficient high-speed curability cannot be exhibited.

  The epoxy resin composition according to the present invention needs to contain an organophosphorus compound or an imidazole derivative as component [D], which acts as a curing accelerator for rapid curing. This component [D] needs to have a melting point of 130 ° C. or lower from the viewpoint of handling properties and high-speed curability in the molding temperature range, and is preferably liquid at room temperature or has a melting point of 90 ° C. or lower. . Although the detailed mechanism of the organophosphorus compound and imidazole derivative is not clear, the progress of the reaction is suppressed at the early stage of the curing reaction of the epoxy resin composition, and the time for maintaining the low viscosity becomes longer. Since the reaction rate is sufficiently high and the curing time can be shortened, it is preferably used as a curing accelerator in the present invention. The compounding amount of the component [D] in the present invention is preferably 5 to 25 parts by mass, more preferably 10 to 20 parts by mass with respect to 100 parts by mass of the total epoxy resin including the component [A]. When the amount of the component [D] is less than 5 parts by mass, the time required for curing becomes long and sufficient high-speed curability cannot be exhibited in many cases. On the other hand, when the amount of the component [D] is more than 25 parts by mass, the time for maintaining the low viscosity is shortened and it is often difficult to impregnate the reinforcing fibers.

  Specific examples of the organic phosphorus compound in the present invention include tributylphosphine (liquid at normal temperature), trioctylphosphine (liquid at normal temperature), tricyclohexylphosphine (melting point 82 ° C.), triphenylphosphine (melting point 80 ° C.), tribenzylphosphine. (Melting point 99 ° C), tri-o-tolylphosphine (melting point 124 ° C), tri-m-tolylphosphine (melting point 98 ° C), diphenylcyclohexylphosphine (melting point 60 ° C), 1,3-bis (diphenylphosphino) propane (Melting point 64 ° C.).

Specific examples of the imidazole derivative in the present invention include imidazole (melting point 89 ° C), 2-ethylimidazole (melting point 80 ° C), 2-undecylimidazole (melting point 72 ° C), 2-heptadecylimidazole (melting point 89 ° C), 1,2-dimethylimidazole (liquid at room temperature), 2-ethyl-4-methylimidazole (liquid at room temperature), 1-benzyl-2-phenylimidazole (liquid at room temperature), 1-benzyl-2-methylimidazole (room temperature) And 1-cyanoethyl-2-methylimidazole (liquid at room temperature).
The epoxy resin composition according to the present invention preferably has a viscosity at 25 ° C. of 0.1 to 2.5 Pa · s, and more preferably 0.1 to 2.0 Pa · s. This is because by setting the viscosity to 2.5 Pa · s or less, the viscosity at the molding temperature can be lowered, the injection time into the reinforcing fiber base is shortened, and the cause of non-impregnation can be prevented. In addition, by setting the viscosity to 0.1 Pa · s or more, the viscosity at the molding temperature does not become too low, and pits that are generated by entraining air when injected into the reinforcing fiber base can be prevented, and the impregnation is uneven. This is because it is possible to prevent the occurrence of the unimpregnated region.

  The viscosity in this invention is calculated | required by measuring the viscosity immediately after preparation of an epoxy resin composition based on the measuring method using the cone-plate type rotational viscometer in ISO 2884-1 (1999), for example. Examples of the measuring device include TVE-33H type manufactured by Toki Sangyo Co., Ltd.

In the epoxy resin composition according to the present invention, when the time when the cure index obtained by dielectric measurement under constant temperature holding is 10% and 90% is t10 and t90, respectively, t10 and t90 are the following three. It is preferable to have a specific temperature T that satisfies the relational expression.
0.5 ≦ t10 ≦ 4 (Formula 1)
0.5 ≦ t90 ≦ 9 (Formula 2)
1 <t90 / t10 ≦ 2.5 (Expression 3)
(Here, t10 represents the time (minutes) from the start of measurement at the temperature T until the cure index reaches 10%, and t90 represents the time (minutes) from the start of measurement to the cure index reaching 90%. .)

  Dielectric measurement cannot be uniquely associated with viscosity and elastic modulus, but is useful for obtaining a curing profile of a thermosetting resin that changes from a low viscosity liquid to a high elastic modulus amorphous solid. In the dielectric measurement, a curing profile is obtained from a change over time in ion viscosity (equivalent resistivity) calculated from a complex dielectric constant measured by applying a high-frequency electric field to a thermosetting resin.

  As the dielectric measurement device, for example, an MDE-10 cure monitor manufactured by Holometrix-Micromet can be used. As a measuring method, first, a Viton O-ring with an inner diameter of 32 mm and a thickness of 3 mm is installed on the lower surface of the programmable mini press MP2000 with a TMS-1 inch type sensor embedded in the lower surface, and the press temperature is set to a predetermined temperature T. To do. Next, the epoxy resin composition is poured inside the O-ring, the press is closed, and the time change of the ionic viscosity of the resin composition is followed. Dielectric measurement is performed at frequencies of 1, 10, 100, 1000, and 10000 Hz, and the logarithm Log (σ) of ion viscosity independent of frequency is obtained by using software (Umetric) attached to the apparatus.

The cure index at the time required for curing t was determined by (Equation 4), and the time for the cure index to reach 10% was t10, and the time for the cure index to reach 90% was t90.
Cure index = {log (αt) −log (αmin)} / {log (αmax) −log (αmin)} × 100 (Equation 4)
Cure index: (Unit:%)
αt: Ionic viscosity at time t (unit: Ω · cm)
αmin: minimum value of ion viscosity (unit: Ω · cm)
αmax: Maximum value of ion viscosity (unit: Ω · cm).

  Tracking the ionic viscosity by dielectric measurement is relatively easy even if the curing reaction is fast. In addition, the ionic viscosity can be measured after gelation, and it increases with the progress of curing and saturates as the curing is completed. Therefore, not only the initial viscosity change but also the progress of the curing reaction is tracked. Can also be used. The value obtained by standardizing the logarithm of the ionic viscosity so that the minimum value is 0% and the saturation value (maximum value) is 100% is called the cure index, and describes the curing profile of the thermosetting resin. Used to do. If the time for the cure index to reach 10% is used as an index related to the speed of the initial viscosity increase, and the time for the cure index to reach 90% is used as an index related to the curing time, the initial viscosity increase is small and short. Preferred conditions can be described because they can be cured in time.

  To summarize the meaning of the above three relational expressions in the present invention, t10 proportional to the time (flowable time) at which the epoxy resin composition can flow at a specific temperature T is 0.5 minutes or more and 4 minutes or less (Formula 1). ), The curing of the epoxy resin composition is almost completed and the time t90 proportional to the time when the mold can be removed (demoldable time) is 0.5 minutes or more and 9 minutes or less (Formula 2). The ratio of moldable time and flowable time is greater than 1 and not more than 2.5 (Equation 3). That is, in the above range, when t10 is large, the epoxy resin composition is easily impregnated into the reinforcing fiber base, and when t90 is small, it means that the epoxy resin composition is cured quickly. Therefore, t90 / t10 is 1 The smaller one is more preferable in the range of 2.5 or less.

  In consideration of the balance with the molding temperature described later, the molding temperature (heat curing temperature) of the epoxy resin composition, that is, the specific temperature T is preferably in the range of 90 to 130 ° C. By setting the range of the specific temperature T to 90 to 130 ° C., the time required for curing can be shortened, and at the same time, the thermal shrinkage after demolding can be relaxed to obtain a fiber-reinforced composite material with good surface quality. Can do.

  The two-pack type epoxy resin composition of the present invention first comprises a main agent liquid containing the epoxy resin as component [A] as a main component, and a curing agent containing the curing agents as components [B] and [C] as main components. It is obtained by mixing the liquid with the above-mentioned mixing amount and mixing the main agent liquid and the curing agent liquid so that the above-mentioned mixing amount is obtained immediately before use. The component [D] described above may be blended in either the main agent solution or the curing agent solution, but is more preferably contained in the curing agent solution. Other ingredients may be formulated into either base material liquid, the sclerosant liquid may be used in admixture with either or both advance.

  It is preferable that the hardening | curing agent liquid for fiber reinforced composite materials of this invention consists of component [B], [C], [D]. The viscosity of the fiber reinforced composite material curing agent solution at 25 ° C. is preferably 0.05 to 1.8 Pa · s, and more preferably 0.05 to 0.7 Pa · s. By setting the viscosity of the curing agent liquid to 1.8 Pa · s or less, the viscosity of the resin composition at the molding temperature can be lowered, the injection time into the reinforcing fiber base can be shortened, and the cause of unimpregnation can be prevented. Because. Moreover, by setting the viscosity of the curing agent liquid to 0.05 Pa · s or more, the viscosity of the resin composition at the molding temperature does not become too low, and pits generated by entraining air when injected into the reinforcing fiber base are prevented. This is because generation of an unimpregnated region caused by uneven impregnation can be prevented.

  The main agent liquid and the curing agent liquid should be heated separately before mixing, and mixing with a mixer immediately before use, such as pouring into a mold, to obtain an epoxy resin composition, It is preferable from the viewpoint of the pot life of the resin.

  The two-component epoxy resin composition of the present invention and the reinforcing fiber are combined and cured to obtain the fiber-reinforced composite material of the present invention. The molding method of the fiber reinforced composite material of the present invention is not particularly limited, but a two-component type such as a hand lay-up method, a filament winding method, a pultrusion method, an RTM (Resin Transfer Molding) method, or the like. A molding method using a resin is preferably used. Among these, the RTM molding method is particularly preferably used from the viewpoints of productivity and the shape freedom of the molded body. In the RTM molding method, a reinforcing fiber composite material is obtained by injecting a resin into a reinforcing fiber base disposed in a mold and curing the resin.

  Taking the RTM molding method as an example, a method for producing the fiber-reinforced composite material of the present invention will be described. First, as described above, the epoxy resin composition according to the present invention is obtained. In the fiber-reinforced composite material of the present invention, the heated epoxy resin composition is injected into a reinforcing fiber base disposed in a mold heated to a specific temperature T, impregnated, and cured in the mold. Preferably, it is manufactured by.

  The temperature at which the epoxy resin composition is heated is determined from the relationship between the initial viscosity of the epoxy resin composition and the increase in viscosity from the viewpoint of impregnation into the reinforcing fiber substrate, and is preferably 30 to 70 ° C., more preferably 50 ~ 60 ° C.

  In addition, in the method for producing such a fiber reinforced composite material, a mold having a plurality of injection ports is used, and the epoxy resin composition is injected from a plurality of injection ports simultaneously or sequentially with a time difference. It is preferable to select appropriate conditions according to the fiber-reinforced composite material to obtain flexibility in adapting to molded bodies having various shapes and sizes. The number and shape of such injection ports are not limited, but in order to enable injection in a short time, it is better that there are more injection ports, and the arrangement is a position where the flow length of the resin can be shortened according to the shape of the molded product. Is preferred.

  The injection pressure of the epoxy resin composition is usually 0.1 to 1.0 MPa, and VaRTM (Vacuum Assist Resin Transfer Molding) method of injecting the resin composition by vacuum suction in the mold can be used. And from the point of economical efficiency of equipment, 0.1-0.6 MPa is preferable. Even when pressure injection is performed, it is preferable to suck the inside of the mold in vacuum before injecting the resin composition, because generation of voids is suppressed.

  In the fiber-reinforced composite material of the present invention, glass fibers, aramid fibers, carbon fibers, boron fibers, and the like are preferably used as the reinforcing fibers. Among these, carbon fiber is preferably used because it is lightweight and a fiber-reinforced composite material having excellent mechanical properties such as strength and elastic modulus can be obtained.

  The reinforcing fiber may be either a short fiber or a continuous fiber, or both may be used in combination. In order to obtain a high Vf fiber-reinforced composite material, continuous fibers are preferred.

  In the fiber reinforced composite material of the present invention, the reinforcing fiber may be used in the form of a strand, but a reinforcing fiber base material obtained by processing the reinforcing fiber into a form such as a mat, a woven fabric, a knit, a braid, or a unidirectional sheet is preferable. Used. Among them, a woven fabric which is easy to obtain a high Vf fiber-reinforced composite material and excellent in handleability is preferably used.

The ratio of the net volume of the reinforcing fibers to the apparent volume of the fabric is defined as the fabric filling rate. The filling rate of the woven fabric is obtained from the weight per unit area W (unit: g / m ² ), the thickness t (unit: mm), and the density ρf (unit: g / cm ³ ) of the reinforcing fiber by the formula of W / (1000 t · ρf). It is done. The fabric weight and thickness are determined in accordance with JIS R 7602 (1995). The higher the woven fabric filling rate, the easier it is to obtain a fiber reinforced composite material having a high Vf. Therefore, the woven fabric filling rate is 0.10 to 0.85, preferably 0.40 to 0.85, more preferably 0.50. It is preferable to be within a range of ˜0.85.

In order for the fiber-reinforced composite material of the present invention to have a high specific strength or specific elastic modulus, the fiber volume content Vf is preferably in the range of 40 to 85%, preferably 45 to 85%. In addition, the fiber volume content Vf of a fiber reinforced composite material said here is a value defined and measured by the following based on ASTM D3171 (1999), and is an epoxy resin with respect to a reinforced fiber base material. It refers to the state after the composition is injected and cured. That is, the measurement of the fiber volume content Vf of the fiber reinforced composite material can be expressed by the following formula from the thickness h of the fiber reinforced composite material.
Fiber volume content Vf (%) = (Af × N) / (ρf × h) / 10 (Formula 5)
Af: fiber base material one · 1 m ² per weight (g ^{/ m} 2)
N: Number of laminated fiber substrates (sheets)
ρf: density of reinforcing fiber (g / cm ³ )
h: Thickness (mm) of the fiber reinforced composite material (test piece).

In addition, when the weight Af per fiber substrate / m ² , the number N of laminated fiber substrates, and the density ρf of reinforcing fibers are not clear, a combustion method or a nitric acid decomposition method based on JIS K 7075 (1991), The fiber volume content of the fiber reinforced composite material is measured by any of the sulfuric acid decomposition methods. As the density of the reinforcing fiber used in this case, a value measured based on JIS R 7603 (1999) is used.

  A specific method for measuring the thickness h of the fiber-reinforced composite material is not particularly limited as long as the thickness of the fiber-reinforced composite material can be measured correctly, but is described in JIS K 7072 (1991). As described above, it is preferable to measure with a micrometer as defined in JIS B 7502 (1994) or with a precision equivalent to or better than this. If the fiber reinforced composite material has a complicated shape and cannot be measured, cut out a sample (a sample with a certain shape and size for measurement) from the fiber reinforced composite material and measure it. May be.

  One preferred form of the fiber-reinforced composite material of the present invention is a veneer. Further, as another preferred form, a sandwich structure in which a single plate-like fiber reinforced composite material is disposed on both surfaces of the core material, a hollow structure in which the periphery is covered with a single plate-like structure, or a single plate-like fiber Examples include a so-called canapé structure in which a reinforced composite material is disposed on one side of a core material.

  Core materials for sandwich and canapé structures include honeycomb cores made of aluminum or aramid, foam cores such as polyurethane, polystyrene, polyamide, polyimide, polyvinyl chloride, phenol resin, acrylic resin, epoxy resin, balsa, etc. Examples include wood. Among them, a foam core is preferably used as the core material because a lightweight fiber-reinforced composite material can be obtained.

  Since the fiber-reinforced composite material of the present invention is lightweight and has excellent mechanical properties such as strength and elastic modulus, it is preferably used for structural members and outer panels of aircrafts, space satellites, industrial machines, railway vehicles, ships, automobiles, etc. It is done. Moreover, since it is excellent also in a color tone, surface quality, and dimensional accuracy, it is preferably used especially for an automobile outer plate.

  Hereinafter, the epoxy resin composition of the present invention will be described in more detail by way of examples.

<Resin raw material>
In order to obtain the resin composition of each Example, the following resin raw materials were used. In addition, the unit of the content rate of the resin composition in Tables 1 and 2 means “part by mass” unless otherwise specified.
1. Epoxy resin “Epototo” (registered trademark) YD-128 (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.): bisphenol A type epoxy resin, epoxy equivalent 189
"Epototo" (registered trademark) YDF-170 (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.): bisphenol F type epoxy resin, epoxy equivalent 170
"Celoxide" (registered trademark) 2021P (manufactured by Daicel Corporation): alicyclic epoxy resin, epoxy equivalent 137
2. Acid anhydride / HN-5500 (manufactured by Hitachi Chemical Co., Ltd.): Methylhexahydrophthalic acid anhydride / “Kayahard” (registered trademark) MCD (manufactured by Nippon Kayaku Co., Ltd.): Methyl nadic acid anhydride Compound having hydroxyphenyl structure: 4,4′-methylenebis (2,6-di-tert-butylphenol) (manufactured by Tokyo Chemical Industry Co., Ltd.): pKa11.6, molecular weight 424.66
2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane “Bis26X-A” (Honshu Chemical Industry Co., Ltd.): pKa10.8, molecular weight 284.39
・ 4,4′-methylenebis (2,6-dimethylphenol) (manufactured by Tokyo Chemical Industry Co., Ltd.): pKa10.8, molecular weight 256.34
4-aminophenol (manufactured by Tokyo Chemical Industry Co., Ltd.): pKa 10.3, molecular weight 109.13
2,6-di-tert-butyl-p-cresol “H-BHT” (manufactured by Honshu Chemical Industry Co., Ltd.): pKa12.2, molecular weight 220.35
Phenol novolac resin “H-4” (manufactured by Meiwa Kasei Co., Ltd.): pKa9.8
・ 4,4′-methylenediphenol “bisphenol F” (manufactured by Wako Pure Chemical Industries, Ltd.): pKa 9.6, molecular weight 200.23
4). Curing accelerator, triphenylphosphine “TPP” (manufactured by Kei-I Kasei Co., Ltd.) Melting point 80 ° C.
・ Tri-o-tolylphosphine “TOTP” (Hokuko Chemical Co., Ltd.) Melting point: 124 ° C.
“CURESOL” (registered trademark) 12DMZ (manufactured by Shikoku Chemicals Co., Ltd.): 1,2-dimethylimidazole Liquid at room temperature “CUREZOL” (registered trademark) 2PZ (manufactured by Shikoku Chemicals Co., Ltd.): 2-phenyl Imidazole Melting point 140 ° C

<Preparation of epoxy resin composition>
An epoxy resin was blended at a blending ratio described in Tables 1 and 2 to obtain a main agent liquid. In the compounding ratios shown in Tables 1 and 2, acid anhydride, a compound having a hydroxyphenyl structure, and a curing accelerator were blended to obtain a curing agent solution. Using these main agent liquid and curing agent liquid, an epoxy resin composition was prepared by blending at a blending ratio described in Tables 1 and 2.

<Measurement of viscosity of main agent liquid, curing agent liquid, resin composition>
The viscosity immediately after the preparation of the epoxy resin composition was measured in accordance with a measurement method using a conical plate type rotational viscometer in ISO 2884-1 (1994). A TVE-30H type manufactured by Toki Sangyo Co., Ltd. was used as the apparatus. Here, the rotor was 1 ° 34 ′ × R24, and the sample amount was 1 cm ³ . Immediately after the preparation of the epoxy resin composition, the viscosity at T1 ° C. was compared with the viscosity after 20 minutes at T1 ° C. to evaluate the viscosity stability (however, T1 ° C. was 30 ° C. in Example 2 and Example 8, In Example 15, it was set to 60 ° C., and in other examples / comparative examples, it was set to 40 ° C.).

<Dielectric measurement>
Dielectric measurements were taken to follow the cure of the resin. As a dielectric measurement device, an MDE-10 cure monitor manufactured by Holometrix-Micromet was used. A Viton O-ring with an inner diameter of 32 mm and a thickness of 3 mm was installed on the lower surface of the programmable mini press MP2000 with a TMS-1 inch type sensor embedded in the lower surface, and the temperature of the press was T2 ° C (however, T2 ° C 110 ° C., 140 ° C. in Example 15 and 120 ° C. in the other examples and comparative examples), the epoxy resin composition was poured inside the O-ring, the press was closed, and the ion of the resin composition was The change in viscosity over time was followed. Dielectric measurement was performed at frequencies of 1, 10, 100, 1000, and 10000 Hz, and logarithm Log (α) of frequency independent ion viscosity was obtained using the attached software.

Next, the cure index was obtained by (Equation 4), and the ratio t90 / t10 of the time t90 when the cure index reached 90% with respect to the time t10 when the cure index reached 10% was obtained.
Cure index = {log (αt) −log (αmin)} / {log (αmax) −log (αmin)} × 100 (Expression 4)
Cure index: (Unit:%)
αt: Ionic viscosity at time t (unit: Ω · cm)
αmin: minimum value of ion viscosity (unit: Ω · cm)
αmax: Maximum value of ion viscosity (unit: Ω · cm).

<Creating a cured resin plate>
A copper spacer having a thickness of 2 mm, in which a square with a side of 50 mm was cut out, was placed on the lower surface of the press device, the press temperature was set to 120 ° C., the epoxy resin composition was poured inside the spacer, and the press was closed. After 20 minutes, the press was opened to obtain a cured resin plate.

<Measurement of glass transition temperature Tg of cured resin>
A test piece having a width of 12.7 mm and a length of 40 mm was cut out from the cured resin plate and subjected to torsional DMA measurement using a rheometer (ARES manufactured by TA Instruments). The measurement conditions are a heating rate of 5 ° C./min. The temperature at the inflection point of the storage elastic modulus G ′ obtained by the measurement was defined as Tg.

<Production of fiber-reinforced composite material>
As the fiber reinforced composite material for the mechanical test, one produced by the following RTM molding method was used.
Carbon fiber woven fabric CO6343 (carbon fiber: T300-3K, organization: plain weave, basis weight: 198 g / m ² , manufactured by Toray Industries, Inc.) is used as a reinforcing fiber in a mold having a plate-like cavity of 350 mm × 700 mm × 2 mm. Nine sheets were stacked in the tee and clamped with a press. Next, the inside of the mold held at 100 ° C. (molding temperature) is reduced to atmospheric pressure −0.1 MPa by a vacuum pump and heated to 50 ° C. in advance, and the main resin solution and curing of the epoxy resin composition The agent solution was mixed using a resin injection machine and injected at a pressure of 0.2 MPa. Twenty minutes after the start of injection of the epoxy resin composition, the mold was opened and demolded to obtain a fiber-reinforced composite material.

<Resin mixing workability>
The workability in resin mixing during the production of the fiber reinforced composite material was compared and evaluated in the following three stages. When preparing a hardener solution, a mixture that is easily mixed by stirring with a spatula is good. A solid component that remains as a lump, but that is stirred and mixed for a while with a spatula. ) Was determined to be bad, even if it was stirred with a fair or spatula, the solid components remained and could not be mixed.

<Resin impregnation of reinforcing fiber>
The impregnation property in the resin injection process in the production of the fiber reinforced composite material was compared and evaluated in the following three stages. If the void amount in the molded product is less than 1%, it is good that there is substantially no void, and no resin-impregnated portion is observed in the appearance of the molded product, but the void amount in the molded product is 1% or more The product was designated as fair, and the appearance of the molded product with a resin non-impregnated part as bad was designated as bad.
The amount of voids in the molded product is a value obtained by observing a smoothly polished cross-section of the molded product with a tilt-down optical microscope and calculating the area ratio of voids in the molded product.

<Demolding workability of fiber reinforced composite material>
The workability in the demolding process during the production of the fiber reinforced composite material was compared and evaluated in the following three stages. When the mold is opened and the molded product is peeled off from the mold with a spatula, it is good that it can be easily demolded without resistance, but there is resistance, but the molded product can be demolded without plastic deformation (for demolding work) Fair because it takes time, it is inferior to good in practical use), and it was judged as bad if it was difficult to remove or if the molded product was plastically deformed during removal.

(Examples 1 to 15)
As described above, an epoxy resin composition was prepared, and viscosity measurement and dielectric measurement were performed. Further, using the prepared epoxy resin composition, a cured resin plate and a fiber reinforced composite material were prepared as described above.

  As shown in Tables 1 and 2, the epoxy resin composition of the present invention maintains a low viscosity state even when held at a low temperature T1 ° C. Moreover, since the flowable time represented by t10 at T2 ° C. is long, the impregnation property and the filling property to the reinforcing fiber at the time of molding are excellent. Furthermore, since the demoldable time represented by t90 at T2 ° C. is short, the value of t90 / t10 at the same temperature is sufficiently small, which is effective for shortening the molding time in the molding of fiber reinforced composite materials. I understand that there is. In addition, since the Tg of the cured resin exceeds the molding temperature (120 ° C.), it can be easily removed without deformation when the molded product is taken out from the mold.

(Comparative Examples 1-4)
As described above, an epoxy resin composition was prepared, and viscosity measurement and dielectric measurement were performed. Further, using the prepared epoxy resin composition, a cured resin plate and a fiber reinforced composite material were prepared as described above.

  As shown in Tables 1 and 2, an epoxy resin composition outside the scope of the present invention has not obtained satisfactory characteristics. In Comparative Example 1, since an imidazole derivative having a melting point higher than 130 ° C. was used as component [D], it was difficult to prepare a curing agent solution, and the curing time was longer than in Examples, and the productivity during molding was high. Inferior. In Comparative Example 2, since the component [C] is not included, the curing time is longer than in the Example, and the productivity at the time of molding is inferior. In Comparative Examples 3 and 4, since the component [C] having an acid dissociation constant pKa of less than 10.2 is used, thickening at a low temperature of 40 ° C. is remarkably inferior in viscosity stability. The impregnation of is poor.

  As described above, the epoxy resin composition of the present invention is suitable for molding a fiber reinforced composite material, and a fiber reinforced composite material excellent in appearance and surface quality can be obtained in a short time with high productivity by the RTM method. . In addition, the epoxy resin composition of the present invention is excellent in molding a fiber-reinforced composite material having a large shape, and is particularly suitable for application to automobile members.

  The epoxy resin composition of the present invention has excellent workability during resin preparation, excellent viscosity stability at low temperatures of the resin composition, cures in a short time during molding, and gives a high-grade fiber-reinforced composite material. A high-quality fiber-reinforced composite material can be provided with high productivity by the RTM method or the like. As a result, the application of fiber-reinforced composite materials for automobiles is especially advanced, and it can be expected to contribute to the improvement of fuel economy and the reduction of greenhouse gas emissions by further reducing the weight of automobiles.

Claims (12)

The acid dissociation constant pKa of at least one compound that includes the following components [A] to [D] and corresponds to the component [C] is 10.2 to 13, and the component [D] is normal temperature And a two-pack type epoxy resin composition for fiber-reinforced composite materials which is liquid or solid with a melting point of 130 ° C. or lower.
[A] epoxy resin [B] acid anhydride [C] compound having hydroxyphenyl structure [D] organophosphorus compound or imidazole derivative The two-pack type epoxy resin composition for fiber-reinforced composite materials according to claim 1, wherein component [C] is a compound having an electron-donating substituent on a carbon atom of a hydroxyphenyl structure. The fiber-reinforced composite material 2 according to claim 1 or 2, wherein the mass blending ratio of the component [B] and the component [C] having an acid dissociation constant pKa of 10.2 to 13 is 99: 1 to 65:35. Liquid epoxy resin composition. The two-pack type epoxy resin composition for fiber-reinforced composite materials according to any one of claims 1 to 3, wherein the component [A] is a bisphenol A type epoxy resin. The two-pack type epoxy resin composition for fiber-reinforced composite materials according to any one of claims 1 to 4, wherein component [B] is an acid anhydride having an alicyclic structure. The two-pack type epoxy resin composition for fiber-reinforced composite materials according to any one of claims 1 to 5, wherein the cure index has a specific temperature T satisfying the following formulas (a) to (c).
0.5 ≦ t10 ≦ 4 (a)
0.5 ≦ t90 ≦ 9 (b)
1 <t90 / t10 ≦ 2.5 (c) The two-pack type epoxy resin composition for fiber-reinforced composite materials according to any one of claims 1 to 6, wherein the viscosity at 25 ° C is 0.1 to 2.5 Pa · s. The two-component liquid for fiber-reinforced composite material according to any one of claims 1 to 7, wherein a main agent solution comprising component [A] and a curing agent solution comprising components [B], [C] and [D] are mixed. Type epoxy resin composition. The two-pack type epoxy resin composition for fiber-reinforced composite materials according to claim 8, wherein the viscosity of the curing agent liquid at 25 ° C is 0.05 to 1.8 Pa · s. The hardening | curing agent liquid for fiber reinforced composite materials used for the two-pack type epoxy resin composition for fiber reinforced composite materials of Claim 8 or 9. A fiber-reinforced composite material obtained by combining and curing the two-component epoxy resin composition for fiber-reinforced composite material according to any one of claims 1 to 9 and a reinforcing fiber. The fiber-reinforced composite material according to claim 11, wherein the reinforcing fibers are carbon fibers.