Epoxy resin composition, adhesive, molding, molding material for fiber-reinforced composite material, and fiber-reinforced composite material

Abstract

To provide an epoxy resin composition that enables compatibility between storage stability of a curing agent and heat resistance of a cured product, and to provide a fiber-reinforced composite material formed from the epoxy resin composition.SOLUTION: An epoxy resin composition comprising the following components [A], [B], and [C], and satisfying conditions (i) and (ii): [A]: epoxy resin, [B]: curing agent having a thermally dissociable chemical bond in a molecule, and [C]: catalyst. (i) The epoxy resin composition contains 30 mass% or more of component [A] in 100 mass% of the epoxy resin composition. (ii) A ratio (H / E) of the number of moles of the thermally dissociable chemical bond in component [B] to the number of moles of epoxy groups in component [A] is 0.2 or more and 1.1 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an epoxy resin composition that is preferably used for aerospace components and general industrial applications, and to a molded article, a molding material for a fiber-reinforced composite material, and a fiber-reinforced composite material using the same. [Background technology]

[0002] Epoxy resin compositions are widely used as matrix resins in fiber-reinforced composite materials, taking advantage of their excellent heat resistance, adhesive properties, and mechanical strength. Traditionally, intermediate substrates such as prepregs, in which reinforcing fibers are pre-impregnated with matrix resin, have been widely used in the manufacture of fiber-reinforced composite materials due to their ease of transportation and shaping. However, in recent years, due to the demand for high productivity, methods such as resin transfer molding (RTM), which do not use intermediate substrates, are becoming more common.

[0003] In the RTM method, the resin is prepared at the time of injecting and impregnating the reinforcing fibers, so the base resin and curing agent are stored separately until use. Because the base resin and curing agent may be stored for long periods between production and use, it is essential that the components contained in each do not decompose or denature during storage. Furthermore, since the molded fiber-reinforced composite material is used in aerospace components and general industrial applications, it is also required to have the same heat resistance and mechanical properties as fiber-reinforced composite materials made from prepregs.

[0004] Patent Document 1 describes an epoxy resin composition using an isocyanate compound as a curing agent. The epoxy group and the isocyanate group are reacted to form an oxazolidone ring structure, resulting in a resin with excellent heat resistance and mechanical properties. A hardened product is obtained.

[0005] Patent Document 2 describes an epoxy resin composition and adhesive that use a liquid amine compound as a curing agent, thereby providing excellent storage stability of the curing agent. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2023 / 219007 [Patent Document 2] Japanese Patent Application Publication No. 2018-123336 Summary of the Invention [Problem to be solved by the invention]

[0007] The epoxy resin composition described in Patent Document 1 contains an isocyanate compound that is highly reactive with nucleophiles such as water and alcohol, and therefore the cured resin has excellent heat resistance and mechanical properties, but the storage stability of the curing agent is insufficient.

[0008] The epoxy resin composition described in Patent Document 2 has excellent storage stability of the curing agent due to the use of a liquid amine compound, but there is no description or suggestion about the heat resistance of the cured resin.

[0009] The present invention aims to overcome these drawbacks and provide an epoxy resin composition that can achieve both storage stability of the curing agent and heat resistance of the cured resin, a molding material for a fiber-reinforced composite material comprising said epoxy resin composition and reinforcing fibers, and a fiber-reinforced composite material obtained by thermally curing said molding material for a fiber-reinforced composite material. [Means for solving the problem]

[0010] As a result of intensive investigations aimed at solving the above problems, the present inventors have discovered an epoxy resin composition having the following constitution, and have completed the present invention. That is, the epoxy resin composition of the present invention has the following constitution. [1] An epoxy resin composition comprising the following components [A], [B], and [C], and satisfying the conditions (i) and (ii). [A]: Epoxy resin [B]: A curing agent having a thermally dissociable chemical bond in the molecule [C]:Catalyst (i) The epoxy resin composition contains 30% by mass or more of component [A] based on 100% by mass. (ii) The ratio (H / E) of the number of moles of thermally dissociable chemical bonds in component [B] to the number of moles of epoxy groups in component [A] is 0.2 or more and 1.1 or less. [2] The epoxy resin composition according to [1], which contains an onium salt and / or an inorganic salt as component [C]. [3] The epoxy resin composition according to [1] or [2], wherein the thermally dissociable chemical bond possessed by component [B] is at least one bond selected from the group consisting of a uretdione bond, a urethane bond, a urea bond, an allophanate bond, a carbodiimide bond, and an isocyanurate bond. [4] The epoxy resin composition according to any one of [1] to [3], wherein the thermally dissociable chemical bond possessed by component [B] is a uretdione bond. [5] Component [D]: The epoxy resin composition according to any one of [1] to [4], which contains a sulfonamide compound represented by formula (I) as an additive.

[0011] [ka]

[0012] (In formula (I), R1 represents a substituted or unsubstituted linear or branched alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group, or an aryl ring. R2 represents a hydrogen atom or a substituted or unsubstituted linear or branched alkyl group having 1 to 10 carbon atoms.) [6] An adhesive comprising the epoxy resin composition according to any one of [1] to [5]. [7] A molded article obtained by heat-curing the epoxy resin composition according to any one of [1] to [5]. [8] A molding material for a fiber-reinforced composite material, comprising the epoxy resin composition according to any one of [1] to [5] and reinforcing fibers. [9] A fiber-reinforced composite material comprising the molded article according to [7] and reinforcing fibers.

[10] A fiber-reinforced composite material obtained by thermosetting the molding material for a fiber-reinforced composite material according to [8]. [Effects of the Invention]

[0013] According to the present invention, an epoxy resin composition can be provided that can achieve both storage stability of the curing agent and heat resistance of the cured resin. DETAILED DESCRIPTION OF THE INVENTION

[0014] The epoxy resin composition of the present invention contains, as essential components, component [A]: an epoxy resin, component [B]: a curing agent having a thermally dissociable chemical bond in the molecule, and component [C]: a catalyst. First, these components will be described.

[0015] (Component [A]) Component [A] in the present invention is an epoxy resin. Such an epoxy resin is not particularly limited as long as it is a compound having an epoxy group in the molecule. Examples include bisphenol A type epoxy resin, bisphenol F type epoxy resin, and amine type epoxy resin. These epoxy resins may be used alone or in combination.

[0016] Commercially available bisphenol A epoxy resins include jER (registered trademark) 825 and jER (registered trademark) 828 (both manufactured by Mitsubishi Chemical Corporation), Epototo (registered trademark) YD-128, and Epototo (registered trademark) YD-8125 (both manufactured by Nippon Steel Chemical & Material Co., Ltd.).

[0017] Commercially available bisphenol F epoxy resins include, for example, jER (registered trademark) 806 and jER (registered trademark) 4004P (both manufactured by Mitsubishi Chemical Corporation), and EPICLON (registered trademark) 830 (manufactured by DIC Corporation).

[0018] Examples of the amine-type epoxy resin used in the present invention include tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, and diglycidylaniline.

[0019] Commercially available tetraglycidyldiaminodiphenylmethane products that can be used include "Sumiepoxy (registered trademark)" ELM434 (manufactured by Sumitomo Chemical Co., Ltd.) and "Araldite (registered trademark)" MY720 (manufactured by Huntsman Advanced Materials).

[0020] Commercially available triglycidylaminophenols include "Sumiepoxy (registered trademark)" ELM100 (manufactured by Sumitomo Chemical Co., Ltd.), "Araldite (registered trademark)" MY0500, "Araldite (registered trademark)" MY0600 (all manufactured by Huntsman Advanced Materials), and "jER (registered trademark)" 630 (manufactured by Mitsubishi Chemical Corporation).

[0021] Commercially available diglycidylaniline products that can be used include GAN (N,N-diglycidylaniline) and GOT (N,N-diglycidyl-o-toluidine) (both manufactured by Nippon Kayaku Co., Ltd.).

[0022] The epoxy resin composition of the present invention contains 30% by mass or more of component [A] based on 100% by mass of the epoxy resin composition. If the content of component [A] is less than 30% by mass, the heat resistance of the cured resin obtained by heat curing the epoxy resin composition of the present invention will be insufficient as a matrix resin for fiber-reinforced composite materials. Component [A] is preferably contained in an amount of 50% by mass or more, more preferably 70% by mass or more, based on 100% by mass of the epoxy resin composition.

[0023] (Component [B]) Component [B] in the present invention is a curing agent having a thermally dissociable chemical bond in the molecule. Such a curing agent is not particularly limited as long as it is a compound having a thermally dissociable chemical bond in the molecule, and may be composed of a single compound or multiple compounds. By including component [B], the epoxy resin composition of the present invention can achieve both the storage stability of the curing agent and the heat resistance of the cured resin, which were not possible with conventional curing agents.

[0024] The epoxy resin composition of the present invention may contain a curing agent other than component [B]. The curing agent other than component [B] is not particularly limited as long as it is a compound that can thermoset the epoxy resin, and examples thereof include amine compounds and derivatives thereof, acid anhydrides, imidazole and derivatives thereof, and isocyanate compounds.

[0025] Here, the storage stability of a curing agent can be evaluated by analyzing the decomposition or modification of the thermally dissociable chemical bond by a known chemical method when the curing agent is left to stand in an environment at a temperature of 25°C and a humidity of 50%. For example, when FT-IR is used, the evaluation can be performed using the ratio of the peak intensity after standing to the peak intensity before standing as an index, and the closer this ratio is to 100%, the better the storage stability can be said to be.

[0026] When evaluating the decomposition or modification of the thermally dissociable chemical bonds of component [B] by FT-IR, the ratio of the peak intensity after standing in the above environment to the peak intensity before standing is preferably 80% or more, more preferably 90% or more, and even more preferably 98% or more.

[0027] Examples of the thermally dissociable chemical bond in the present invention include a peroxide bond, a uretdione bond, a urethane bond, a urea bond, an allophanate bond, a biuret bond, a carbodiimide bond, an isocyanurate bond, etc. Component [B] may contain one or more of these bonds.

[0028] Examples of commercially available compounds having a peroxide bond in the molecule include di-tert-butyl peroxide, dicumyl peroxide, and benzoyl peroxide (all manufactured by Tokyo Chemical Industry Co., Ltd.).

[0029] Examples of compounds having a uretdione bond in the molecule include a dimer of tolylene diisocyanate (TDI), a dimer of diphenylmethane diisocyanate (MDI), a dimer of hexamethylene diisocyanate (HDI), and a dimer of isophorone diisocyanate (IPDI). Compounds containing a uretdione bond may be produced from a single isocyanate compound or from multiple isocyanate compounds. The number of uretdione bonds contained in the molecule is not particularly limited, as long as it is one or more.

[0030] Examples of compounds having a urethane bond in the molecule include reaction products of isocyanate compounds such as TDI, MDI, and HDI with alcohol compounds. Compounds containing urethane bonds may be produced from a single isocyanate compound or from multiple types of isocyanate compounds. The number of urethane bonds contained in the molecule is not particularly limited as long as it is one or more.

[0031] Examples of compounds having a urea bond in the molecule include reaction products of isocyanate compounds such as TDI, MDI, and HDI with amine compounds. Compounds containing urea bonds may be produced from a single isocyanate compound or from multiple types of isocyanate compounds. The number of urea bonds contained in the molecule is not particularly limited as long as it is one or more.

[0032] Examples of compounds having an allophanate bond in the molecule include compounds in which an isocyanate compound is added to a urethane bond derived from TDI, compounds in which an isocyanate compound is added to a urethane bond derived from MDI, and compounds in which an isocyanate compound is added to a urethane bond derived from HDI. Compounds containing allophanate bonds may be produced from a single urethane compound or multiple types of urethane compounds. Furthermore, the number of allophanate bonds contained in the molecule is not particularly limited as long as it is one or more.

[0033] Examples of compounds having a biuret bond in the molecule include compounds in which an isocyanate compound is added to a urea bond derived from TDI, compounds in which an isocyanate compound is added to a urea bond derived from MDI, and compounds in which an isocyanate compound is added to a urea bond derived from HDI. The compound containing a biuret bond may be produced from a single urea compound or multiple types of urea compounds. Furthermore, the number of biuret bonds contained in the molecule is not particularly limited as long as it is one or more.

[0034] Examples of compounds having a carbodiimide bond in the molecule include compounds obtained by decarboxylation and dimerization of TDI, compounds obtained by decarboxylation and dimerization of MDI, compounds obtained by decarboxylation and dimerization of HDI, and compounds obtained by decarboxylation and dimerization of IPDI. The compound containing a carbodiimide bond may be produced from a single isocyanate compound or from multiple isocyanate compounds. The number of carbodiimide bonds contained in the molecule is not particularly limited, as long as it is one or more.

[0035] Examples of compounds having an isocyanurate bond in the molecule include compounds obtained by trimerizing MDI, compounds obtained by trimerizing HDI, and compounds obtained by trimerizing IPDI. The compound containing an isocyanurate bond may be produced from a single isocyanate compound or from multiple types of isocyanate compounds. The number of isocyanurate bonds contained in the molecule is not particularly limited as long as it is one or more.

[0036] In the epoxy resin composition of the present invention, the thermally dissociable chemical bond contained in component [B] is preferably at least one bond selected from the group consisting of a uretdione bond, a urethane bond, a urea bond, an allophanate bond, a carbodiimide bond, and an isocyanurate bond, and more preferably a uretdione bond.

[0037] In the epoxy resin composition of the present invention, the ratio (H / E) of the number of moles of thermally dissociable chemical bonds in component [B] to the number of moles of epoxy groups in component [A] must be 0.2 or more and 1.1 or less. If H / E is less than 0.2, the thermal curing reaction does not proceed sufficiently, resulting in poor curing. If H / E is greater than 1.1, the crosslinked structure of the cured resin becomes non-uniform, and the heat resistance of the resulting cured resin is insufficient for use as a matrix resin for fiber-reinforced composite materials. H / E is preferably in the range of 0.4 to 0.9, and more preferably in the range of 0.5 to 0.8. If H / E is within this range, the resulting cured resin tends to have excellent heat resistance.

[0038] The number of moles of the thermally dissociable chemical bond in component [B] can be calculated by a known method. For example, in the case of a bond derived from an isocyanate compound, the isocyanate group content of the sample before and during heating is first measured by a titration method such as that described in JIS K 1603-1:2007, and the content (unit: mass%) of the thermally dissociable chemical bond is calculated based on the difference between the measured values. Then, the molar mass of the thermally dissociable chemical bond can be used to calculate the molar mass of the thermally dissociable chemical bond.

[0039] (Component [C]) Component [C] in the present invention is a catalyst that accelerates the thermosetting reaction of the epoxy resin composition. Component [C] is not particularly limited as long as it accelerates the thermosetting reaction of the epoxy resin composition.

[0040] Examples of catalysts preferably used in the present invention include heterocyclic amine compounds, imidazolium salts, onium salts, inorganic salts, etc. These catalysts may be used alone or in combination of two or more.

[0041] Commercially available heterocyclic amine compounds include Curazol (registered trademark) 2E4MZ, Curazol (registered trademark) 2MZA-PW, and Cureduct (registered trademark) P-0505 (all manufactured by Shikoku Chemical Industry Co., Ltd.), 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5-diazabicyclo[4.3.0]-5-nonene, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene, and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (all manufactured by Tokyo Chemical Industry Co., Ltd.).

[0042] Commercially available imidazolium salts that can be used include 1-ethyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium chloride, and 1-ethyl-3-methylimidazolium iodide (all manufactured by Tokyo Chemical Industry Co., Ltd.).

[0043] Commercially available onium salts that can be used include benzyltrimethylammonium bromide, tetrabutylammonium bromide, tetrabutylammonium iodide, and tetrapropylammonium bromide (all manufactured by Tokyo Chemical Industry Co., Ltd.), as well as "TBP-BB (registered trademark)," "TPP-PB (registered trademark)," and "TPP-MB (registered trademark)" (all manufactured by Hokko Sangyo Co., Ltd.).

[0044] Commercially available inorganic salts that can be used include sodium chloride, lithium chloride, lithium bromide, lithium iodide, and calcium iodide (all manufactured by Tokyo Chemical Industry Co., Ltd.).

[0045] Among these, onium salts and / or inorganic salts are preferred as component [C] in the present invention. Although there are no particular limitations on the content of component [C], the catalyst generally contained in the epoxy resin composition is preferably in the range of 0.01% by mass or more and 10.0% by mass or less, relative to 100% by mass of the epoxy resin composition.

[0046] (Component [D]) The epoxy resin composition of the present invention may contain component [D]: an additive, provided that the effects of the invention are not impaired. Examples of additives that can be used include tougheners, heat resistance improvers, diluents, solvents, flame retardants, thixotropic agents, and antifoaming agents. In particular, since high heat resistance is often required for fiber-reinforced composite materials, it is preferable that the epoxy resin composition of the present invention contain a heat resistance improver.

[0047] The heat resistance improver is not particularly limited as long as it can improve the heat resistance of the thermoset resin cured product, but for example, a sulfonamide compound represented by formula (I) can be used.

[0048] [ka]

[0049] (In formula (I), R1 represents a substituted or unsubstituted linear or branched alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group, or an aryl ring. R2 represents a hydrogen atom or a substituted or unsubstituted linear or branched alkyl group having 1 to 10 carbon atoms.)

[0050] Of the component [D], examples of commercially available compounds of formula (I) in which R2 is other than a hydrogen atom include N-methylmethanesulfonamide, N-ethylmethanesulfonamide, N-methylbenzenesulfonamide, N-ethylbenzenesulfonamide, and N-ethyl-p-chlorobenzenesulfonamide (all manufactured by Tokyo Chemical Industry Co., Ltd.), and Topsizer (registered trademark) No. 3 (N-ethyl-o / p-toluenesulfonamide) (manufactured by Fuji Amide Chemical Co., Ltd.).

[0051] Of the component [D], commercially available compounds of formula (I) in which R2 is a hydrogen atom include methanesulfonamide, benzenesulfonamide, p-chlorobenzenesulfonamide, phenylmethanesulfonamide, and cyclohexylsulfonamide (all manufactured by Tokyo Chemical Industry Co., Ltd.), Topsizer (registered trademark) No. 1S (p-toluenesulfonamide), Topsizer (registered trademark) No. 5 (o / p-toluenesulfonamide), and Orthoamide (o-toluenesulfonamide) (all manufactured by Fuji Amide Chemical Co., Ltd.).

[0052] The epoxy resin composition of the present invention preferably contains 20.0% by mass or less of additives, more preferably 10.0% by mass or less, and even more preferably 5.0% by mass or less, based on 100% by mass of the epoxy resin composition.

[0053] The epoxy resin composition of the present invention may be prepared using machines such as a kneader, a planetary mixer, a three-roll mill, or a twin-screw extruder. If uniform mixing is possible, the components may be mixed by hand using a beaker and a spatula.

[0054] The epoxy resin composition of the present invention has excellent adhesive properties as well as heat resistance, and therefore can be preferably used as an adhesive in the manufacture of aircraft, spacecraft, automobiles, ships, wind turbines, etc. The method of use as an adhesive is not particularly limited, and the epoxy resin composition may be applied directly to the bonding surface, or may be processed into a sheet or a solvent may be added to improve handleability before use.

[0055] The epoxy resin composition of the present invention can be used as a fiber-reinforced composite material by conjugating it with reinforcing fibers. The epoxy resin composition prepared by the above method can be heat-cured to form a molded product, which can then be conjugated with reinforcing fibers. Alternatively, the epoxy resin composition prepared by the above method can be conjugated with reinforcing fibers to form a molding material for a fiber-reinforced composite material, which can then be heat-cured to obtain a fiber-reinforced composite material containing the epoxy resin composition of the present invention as the matrix resin. The method for conjugating the epoxy resin composition with reinforcing fibers is not particularly limited, but examples include the RTM method, liquid composite molding method, sheet molding compound method, filament winding method, hand layup method, pultrusion method, and prepreg method.

[0056] In the method for producing a fiber-reinforced composite material using the epoxy resin composition of the present invention, the curing temperature of the epoxy resin composition is not particularly limited, but is preferably 23° C. to 200° C. The heat curing temperature does not need to be constant, and the temperature may be raised as appropriate to shorten the time required for heat curing.

[0057] The reinforcing fibers used in the fiber-reinforced composite material of the present invention are not particularly limited. Glass fibers, carbon fibers, aramid fibers, boron fibers, alumina fibers, silicon carbide fibers, etc. can be used, and two or more of these fibers may be mixed. From the viewpoint of obtaining a lightweight, highly rigid fiber-reinforced composite material, it is preferable to use carbon fibers or glass fibers.

[0058] The fiber-reinforced composite material of the present invention has excellent heat resistance and mechanical properties and can therefore be preferably used for many structural materials, including aircraft components such as fuselages, main wings, tails, moving surfaces, fairings, cowls, doors, seats, and interior materials; spacecraft components such as motor cases and main wings; artificial satellite components such as structures and antennas; automobile components such as outer panels, chassis, aerodynamic components, and seats; railway vehicle components such as structures and seats; and ship components such as hulls and seats. [Example]

[0059] The present invention will be explained in more detail below by showing examples, but the present invention is not limited to the descriptions of these examples.

[0060] <Materials used> Component [A]: Epoxy resin [A]-1 "jER (registered trademark)" 825 (manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 175 g / mol).

[0061] Component [B]: A curing agent having a thermally dissociable chemical bond within the molecule. [B]-1 Uretdione bond-containing compound prepared in Production Example 1 (uretdione bond content: 17% by mass) [B]-2 The uretdione bond-containing compound prepared in Production Example 2 (uretdione bond content: 24% by mass).

[0062] ·Component [C]: Catalyst [C]-1 Tetrabutylammonium bromide (Tokyo Chemical Industry Co., Ltd.) [C]-2 Lithium bromide (Tokyo Chemical Industry Co., Ltd.).

[0063] Component [D]: Additive [D]-1 PEG-300 (Sanyo Chemical Industries, Ltd.) [D]-2 p-Toluenesulfonamide (Tokyo Chemical Industry Co., Ltd.).

[0064] Other hardeners [E]-1 "Millionate (registered trademark)" NM (manufactured by Tosoh Corporation) [E]-2 “JEFFAMINE (registered trademark)” D-400 (manufactured by Huntsman).

[0065] ·others Toluene (ultra-dehydrated) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), tributylphosphine (manufactured by Tokyo Chemical Industry Co., Ltd.), "Coronate (registered trademark)" T-80 (manufactured by Tosoh Corporation).

[0066] <Method for preparing epoxy resin composition> A stainless steel beaker was charged with the specified amounts of component [A]: epoxy resin, component [B]: curing agent having a thermally dissociable chemical bond within the molecule, component [C]: catalyst, and component [D]: additive, and the components were mixed together until uniform, while heating as necessary to achieve compatibility, to obtain an epoxy resin composition. The resin composition was as shown in Table 1 or Table 2.

[0067] <Method for producing cured resin> The epoxy resin composition prepared according to the above <Method for preparing epoxy resin composition> was poured into an aluminum mold whose thickness was adjusted to 2 mm using a 2 mm Teflon (registered trademark) spacer. The mold was then heated at 180°C for 120 minutes to obtain a 2 mm thick cured resin plate.

[0068] <Method for evaluating the glass transition temperature (Tg) of cured resin> A test piece measuring 12.7 mm wide and 45 mm long was cut from the cured resin plate prepared according to the above <Method for Preparing Cured Resin>, and dynamic viscoelasticity measurements were performed using a dynamic viscoelasticity measuring device (ARES-G2: manufactured by TA Instruments) at a heating rate of 5°C / min, a frequency of 1 Hz, and a temperature range of 30 to 260°C. The glass transition temperature (Tg) was determined as the temperature at the intersection of the tangent drawn to the glassy state and the tangent drawn to the glass transition temperature region in the obtained graph of storage modulus vs. temperature.

[0069] <Evaluation of storage stability of curing agent> The curing agent was left to stand in a thermo-hygrostat chamber set at a temperature of 25°C and a humidity of 50% for 72 hours, after which FT-IR (ATR method) was performed using an FT-IR device (7000FT-IR: manufactured by Varian). When a compound having a uretdione bond in the molecule was used as the curing agent, the wave number was 2250 cm. -1 The peak at 1770 cm originates from the isocyanate group. -1 When "Millionate (registered trademark)" NM is used as the curing agent, there is a peak due to the uretdione bond near 3400 cm. When "JEFFAMINE (registered trademark)" D-400 is used as the curing agent, there is a peak due to the isocyanate group near 3400 cm. -1Analysis was conducted focusing on the peaks derived from amino groups in the vicinity. In the analysis, the closer the ratio of peak intensity after leaving the thermo-humidistat chamber to the peak intensity before leaving it was to 100%, the better the storage stability was judged to be. The results of the storage stability of various curing agents are shown in Table 3.

[0070] (Production Example 1) 50.7 g of Millionate (registered trademark) NM and 50 mL of toluene (ultra-dehydrated) were placed in a 300 mL eggplant-shaped flask, and the air inside the flask was then replaced with nitrogen. The solution was stirred using a magnetic stirrer until it became homogeneous, and then 250 μL of tributylphosphine was added dropwise using a micropipette. The reaction was allowed to proceed for 24 hours at 23°C with continued stirring. The white powder obtained by the reaction was washed with toluene (ultra-dehydrated), and the remaining tributylphosphine was removed. The mixture was then vacuum-dried for 24 hours in a vacuum dryer at 40°C to obtain a uretdione bond-containing compound. The uretdione bond content of the resulting uretdione bond-containing compound was measured and found to be 17% by mass.

[0071] (Production Example 2) 49.9 g of "Coronate (registered trademark)" T-80 and 50 mL of toluene (ultra-dehydrated) were placed in a 300 mL eggplant-shaped flask, and the air inside the flask was then replaced with nitrogen. The solution was stirred using a magnetic stirrer until it became homogeneous, and then 250 μL of tributylphosphine was added dropwise using a micropipette. The reaction was allowed to proceed for 24 hours at 23°C with continued stirring. The white powder obtained by the reaction was washed with toluene (ultra-dehydrated), and the remaining tributylphosphine was removed. The mixture was then vacuum-dried for 24 hours in a vacuum dryer at 40°C to obtain a uretdione bond-containing compound. The uretdione bond content of the resulting uretdione bond-containing compound was measured and found to be 24% by mass.

[0072] Example 1 An epoxy resin composition was prepared according to the above <Method for preparing epoxy resin composition> using 100 parts by mass of jER (registered trademark) 825 as component [A], 71.5 parts by mass of the uretdione group-containing compound prepared in Production Example 2 as component [B], and 2.8 parts by mass of tetrabutylammonium bromide as component [C].

[0073] The heat resistance of the cured resin of this epoxy resin composition was evaluated according to the above-mentioned <Method for evaluating the glass transition temperature (Tg) of cured resin>, and the result was a good value of 159° C. Furthermore, as shown in Table 3, the storage stability of the curing agent used was also good.

[0074] Examples 2 to 6 Epoxy resin compositions and cured resin products were prepared in the same manner as in Example 1, except that the components used were changed as shown in Table 1. The Tg of the epoxy resin compositions in each example was good, ranging from 129 to 170°C. Furthermore, as shown in Table 3, the storage stability of the curing agents used was also good.

[0075] (Comparative Example 1) An epoxy resin composition and a cured resin were prepared using the resin composition shown in Table 2 in the same manner as in Example 1. This epoxy resin composition did not contain component [B], but contained an isocyanate compound as a curing agent. As a result, although the Tg was a good value of 160°C, the storage stability of the curing agent was insufficient, as shown in Table 3.

[0076] (Comparative Example 2) An epoxy resin composition and a cured resin were prepared using the resin composition shown in Table 2 in the same manner as in Example 1. This epoxy resin composition did not contain component [B], but contained polyether polyamine as a curing agent. As a result, as shown in Table 3, the storage stability of the curing agent was excellent, but the Tg of the cured resin was 66°C, indicating insufficient heat resistance.

[0077] (Comparative Example 3) Using the resin compositions shown in Table 2, epoxy resin compositions and cured resins were prepared in the same manner as in Example 1. This epoxy resin composition did not contain component [C], and a cured resin could not be obtained by thermal curing.

[0078] Comparative Example 4 An epoxy resin composition and a cured resin were prepared using the resin composition shown in Table 2 in the same manner as in Example 1. The content of component [A] in this epoxy resin composition was less than 30 mass% of the total resin composition. As a result, the Tg of the obtained cured resin was 82°C, which indicated insufficient heat resistance.

[0079] (Comparative Example 5) An epoxy resin composition and a cured resin were prepared using the resin composition shown in Table 2 in the same manner as in Example 1. The epoxy resin composition had an H / E ratio of less than 0.2. As a result, a cured resin was obtained whose physical properties could not be evaluated. It is presumed that a sufficient crosslinked structure was not formed because there was not enough curing agent present.

[0080] (Comparative Example 6) An epoxy resin composition and a cured resin were prepared using the resin composition shown in Table 2 in the same manner as in Example 1. The epoxy resin composition had an H / E ratio of greater than 1.1. As a result, the cured resin had a Tg of 102°C, which indicated insufficient heat resistance.

[0081] [Table 1]

[0082] [Table 2]

[0083] [Table 3] [Industrial Applicability]

[0084] The present invention provides an epoxy resin composition that achieves both good storage stability of the curing agent and good heat resistance of the cured resin. Adhesives and fiber-reinforced composite materials made from the epoxy resin composition are suitable for use in aerospace components and general industrial structural components.

Claims

1. An epoxy resin composition comprising the following components [A], [B], and [C], and satisfying the conditions (i) and (ii). [A]: Epoxy resin [B]: a curing agent having a thermally dissociable chemical bond in the molecule [C]: Catalyst (i) The epoxy resin composition contains 30% by mass or more of component [A] based on 100% by mass of the composition. (ii) The ratio (H / E) of the number of moles of thermally dissociable chemical bonds in component [B] to the number of moles of epoxy groups in component [A] is 0.2 or more and 1.1 or less.

2. 2. The epoxy resin composition according to claim 1, comprising an onium salt and / or an inorganic salt as component [C].

3. 2. The epoxy resin composition according to claim 1, wherein the thermally dissociable chemical bond contained in component [B] is at least one bond selected from the group consisting of a uretdione bond, a urethane bond, a urea bond, an allophanate bond, a carbodiimide bond, and an isocyanurate bond.

4. 2. The epoxy resin composition according to claim 1, wherein the thermally dissociable chemical bond contained in component [B] is a uretdione bond.

5. Component [D]: The epoxy resin composition according to claim 1, which contains a sulfonamide compound represented by formula (I) as an additive. 【Chemical 1】 (In formula (I), R １ represents a substituted or unsubstituted linear or branched alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group, or an aryl ring. ２ represents a hydrogen atom or a substituted or unsubstituted straight-chain or branched alkyl group having 1 to 10 carbon atoms).

6. An adhesive comprising the epoxy resin composition according to any one of claims 1 to 5.

7. A molded article obtained by heat-curing the epoxy resin composition according to any one of claims 1 to 5.

8. A molding material for a fiber-reinforced composite material, comprising the epoxy resin composition according to any one of claims 1 to 5 and reinforcing fibers.

9. A fiber-reinforced composite material comprising the molded article according to claim 7 and reinforcing fibers.

10. A fiber-reinforced composite material obtained by thermosetting the molding material for a fiber-reinforced composite material according to claim 8.

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