Epoxy resin composition, resin film, prepreg, fiber-reinforced composite material, decomposition method of cured material, and decomposition product

Abstract

Described is a curable epoxy resin composition comprising the following components [A], [B] and [C], wherein the resin composition comprises a reaction product of components [A] and [B] as component [D], and optionally comprises component [B1] as component [B] included in component [D]; [A]: at least one epoxy resin; [B]: at least one amine compound; [C]: at least one curing agent different from component [B]; [B1]: at least one amine compound containing a structure represented by the following formula (I) or (II) in a molecule, wherein the cured epoxy resin composition has a viscosity suitable for handling, excellent reaction stability, and excellent reworkability and easy degradability after curing, which is useful for resin films, fiber-reinforced composites, prepregs formed by impregnating the curable epoxy resin composition into reinforcing fibers, and fiber-reinforced composites containing the curable epoxy resin composition and reinforcing fibers. Also described is a method of recycling a product comprising a cured epoxy resin composition and a fiber-reinforced composite, wherein the method comprises soaking the product in an acidic solvent at a temperature of 25 to 200°C under conditions to remove the cured epoxy resin from the product.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 572,228, filed March 30, 2024, and U.S. Provisional Application No. 63 / 755,746, filed February 7, 2025, the contents of which are incorporated herein by reference in their entirety for all purposes.

[0003] Invention Field

[0004] This invention relates to an epoxy resin composition that combines viscosity within a suitable operating range, excellent reaction stability, low exothermic heat generation during curing, and excellent reformability and biodegradability after curing. This epoxy resin composition can be used in a variety of applications, such as for resin films, fiber-reinforced composites, prepregs formed by impregnating the epoxy resin composition into reinforcing fibers, and fiber-reinforced composites containing both the epoxy resin composition and reinforcing fibers. The invention also relates to a method for recycling cured epoxy resin compositions present in a product, wherein the method comprises immersing the product in an acidic solvent at a temperature of 25 to 200°C under conditions sufficient to remove the cured epoxy resin from the product, and relates to the decomposition products obtained by said method. Background of the Invention

[0006] Fiber-reinforced composites, containing reinforcing fibers (such as carbon fiber or glass fiber) and matrix resins (such as epoxy or phenolic resins), have been widely used in fields such as aerospace, automotive, rail vehicles, shipbuilding, civil engineering and construction, and sporting goods due to their lightweight yet excellent mechanical properties, such as strength, rigidity, heat resistance, and corrosion resistance. For applications requiring high performance, fiber-reinforced composites containing continuous reinforcing fibers are a common choice. Carbon fiber, as the reinforcing fiber, exhibits excellent specific strength and specific modulus. As the matrix resin, thermosetting resins, particularly epoxy resins, are typically chosen, as they adhere to the carbon fibers and exhibit heat resistance, elastic modulus, chemical resistance, and low curing shrinkage.

[0007] However, due to the heat and chemical resistance inherent in its irreversible curing process, cured epoxy resins are difficult to degrade at the end of their lifespan, and the resin degradation products and reinforcing fibers are difficult to recycle. Therefore, most epoxy resins end up in landfills or are incinerated at temperatures of several hundred degrees Celsius. The challenge is to develop recycling methods that can reduce these negative environmental impacts and energy costs. Invention Overview

[0009] To facilitate the degradation of epoxy resins in acidic solvents, techniques for using components with readily degradable bonds in epoxy resin compositions have been described. WO 2013 / 184827 A1 describes epoxy resin compositions containing amine compounds with degradable bonds in the molecule. Furthermore, WO 2020 / 161538A1 describes epoxy resin compositions containing epoxy compounds with degradable bonds in the molecule. These techniques enable the previously difficult decomposition and recycling of cured epoxy resins in acetic acid solutions at relatively low temperatures.

[0010] On the other hand, when using these resin compositions as resin films, prepregs, or fiber-reinforced composites, it may be necessary or desirable to adjust the resin viscosity to a range suitable for the manufacturing process or operation during use, but such descriptions or suggestions are not found in these published documents. Generally, other components, such as thermoplastic resins, can be blended to adjust the viscosity of the epoxy resin composition; however, blending non-degradable high-molecular-weight components into the epoxy resin composition may undesirably impair the degradability of the easily degradable epoxy resin composition and may also make it difficult to recover degradation products.

[0011] WO2013 / 081058 A1 discloses a method for pre-reacting an epoxy resin with an amine compound to adjust the resin viscosity to a range suitable for manufacturing processes and operation during use. However, it does not consider achieving excellent reaction stability or low exothermic heat generation during curing, or the degradability and re-shapeability of the resulting cured product.

[0012] To address the aforementioned problems, the inventors have discovered a curable epoxy resin composition comprising the following components [A], [B], and [C], wherein the resin composition comprises the reaction product of components [A] and [B] (referred to as component [D]) and component [B1] contained in component [D]. [A]: At least one epoxy resin; [B]: At least one amine compound; [C]: At least one curing agent different from component [B]; [B1]: At least one amine compound containing a structure represented by formula (I) or (II).

[0013] , Another aspect relates to a curable epoxy resin composition comprising components [A], [B], and [C], wherein the resin composition contains the reaction product of components [A] and [B] (referred to as component [D]), wherein the rubber-state elastic modulus of the cured product obtained by DMA (Dynamic Mechanical Analysis) is 5.0 MPa or lower. [A]: At least one epoxy resin; [B]: At least one amine compound; [C]: At least one curing agent different from component [B].

[0014] Another aspect relates to a curable epoxy resin composition comprising the following components [A], [B] and [C], wherein the resin composition contains the reaction product of components [A] and [B] (defined as component [D]), wherein during the curing process of the composition, the curing calorific value, measured by differential scanning calorimetry (DSC) at a heating rate of 10 °C / min, is 240 J / g or lower; [A]: At least one epoxy resin; [B]: At least one amine compound; [C]: At least one curing agent different from component [B].

[0015] In one embodiment, the prepreg preform comprises a reinforcing fiber bundle impregnated with the epoxy resin composition disclosed herein.

[0016] In one embodiment, fiber-reinforced composite materials are obtained by curing the prepreg disclosed herein.

[0017] In one embodiment, the fiber-reinforced composite material comprises a cured epoxy resin product obtained by curing a mixture comprising the epoxy resin composition disclosed herein and reinforcing fibers.

[0018] In one embodiment, the resin film comprises the epoxy resin composition disclosed herein.

[0019] Another embodiment is a method for recycling a product comprising a cured epoxy resin composition and a fiber-reinforced composite material, wherein the method comprises immersing the cured product in an acidic solvent at a temperature of 25 to 200°C under conditions sufficient to remove the epoxy resin composition from the product, wherein the epoxy resin composition is formed from a curable epoxy resin composition comprising components [A], [B] and [C], wherein the resin composition comprises the reaction product of components [A] and [B] as component [D]. [A]: At least one epoxy resin; [B]: At least one amine compound; [C]: At least one curing agent different from component [B].

[0020] Another embodiment is a method for recycling a product containing a cured epoxy resin composition, wherein the method comprises immersing the product in an acidic solvent at a temperature of 25 to 200°C under conditions sufficient to remove the epoxy resin composition from the product, wherein the epoxy resin composition is formed from a curable epoxy resin composition comprising components [A], [B] and [C], and wherein the resin composition comprises the reaction product of components [A] and [B] as component [D], and wherein the curable epoxy resin composition comprises component [B1] as component [B] contained in component [D]. In one embodiment, resin decomposition products are obtained by the method disclosed herein.

[0021] In one embodiment, a fibrous material is obtained by the method disclosed herein.

[0022] Detailed description of the embodiments of the present invention

[0023] All publications, patents and patent applications cited in this specification are incorporated herein by reference in their entirety for all purposes.

[0024] The articles “a” and “an” are used in this document to refer to one or more (i.e., at least one) grammatical object of the article. For example, “a polymer resin” refers to one or more polymer resins. Any ranges referenced herein include end values. The terms “basically” and “approximately” are used to describe and take into account small fluctuations. For example, they can refer to a quantity or amount that differs from a specified value by less than or equal to ±5%.

[0025] Throughout this specification, the phrase "in one embodiment" or "an embodiment" means that a particular element, structure, or feature described in connection with that embodiment is included in at least one embodiment. Therefore, the appearance of the phrase "in one embodiment" or "in an embodiment" throughout this specification does not necessarily refer to the same embodiment. Furthermore, a particular element, structure, or feature may be combined in one or more embodiments in any suitable manner.

[0026] Unless otherwise specified, “room temperature” as used in this article refers to a temperature of 23°C.

[0027] The term “fiber-reinforced composite material” as used herein may be used interchangeably with the terms “fiber-reinforced compound,” “fiber-reinforced polymer material,” “fiber-reinforced polymer,” “fiber-reinforced plastic material,” and “fiber-reinforced plastic.”

[0028] This invention relates to an epoxy resin composition that combines viscosity within a suitable operating range, excellent reaction stability, low exothermic heat generation during curing, and excellent reformability and biodegradability after curing. This epoxy resin composition can be used in a variety of applications, such as for resin films, fiber-reinforced composites, prepregs formed by impregnating the epoxy resin composition into reinforcing fibers, and fiber-reinforced composites containing both the epoxy resin composition and reinforcing fibers. The invention also relates to a method for recycling cured epoxy resin compositions present in a product, wherein the method comprises immersing the product in an acidic solvent at a temperature of 25 to 200°C under conditions sufficient to remove the cured epoxy resin from the product, and relates to the decomposition products obtained by said method.

[0029] The epoxy resin composition, prepreg, and carbon fiber reinforced composite material of this disclosure are described in detail below.

[0030] Component [A]

[0031] Component [A] in this invention is an epoxy resin. The epoxy resin used in this invention is not limited to, but includes, for example, bisphenol epoxy resins (such as bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol AD ​​epoxy resin, bisphenol S epoxy resin, tetrabromobisphenol A brominated epoxy resin (such as tetrabromobisphenol A diglycidyl ether)), epoxy resins having a biphenyl skeleton, epoxy resins having a naphthalene skeleton, epoxy resins having a fluorene skeleton, epoxy resins having a dicyclopentadiene skeleton, phenolic novolac epoxy resin, and cresolnovolac epoxy resin. (resin), N,N,O-triglycidyl-m-aminophenol, N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-4-amino-3-methylphenol, N,N,N',N'-tetraglycidyl-4,4'-methylenediphenylamine, N,N,N',N'-tetraglycidyl-2,2'-diethyl-4,4'-methylenediphenylamine, N,N,N',N'-tetraglycidyl-m-phenylenediamine, N,N-diglycidylaniline, N,N,N-diglycidyl-o-toluidine, glycidylamine epoxy resin, resorcinol diglycidyl ether, and triglycidyl isocyanurate.

[0032] The epoxy resin used as component [A] is preferably a compound having two epoxy groups in its molecule. Having two epoxy groups prevents the crosslinking density of the resulting cured resin from becoming excessively high, and allows for the effects of this invention, such as excellent biodegradability and reformability, and also suppresses heat generation during the curing process. The epoxy resin used as component [A] can be blended with epoxy resins containing three or more epoxy groups in one molecule, or with epoxy resins containing one epoxy group in one molecule. These epoxy resins can be used alone or in combination.

[0033] Component [B]

[0034] Component [B] of this invention is an amine compound that acts as a curing agent in reaction with epoxy resin. This amine compound may be selected from, but is not limited to, aliphatic amines, aromatic amines, and mixtures thereof.

[0035] When component [B] is an aliphatic amine, the pre-reaction with component [A] described below can be readily carried out at low temperatures, which is preferred because it reduces energy costs. When component [B] is an aromatic amine, this is preferred because the resulting resin composition has excellent viscosity stability and the resulting cured material has excellent heat resistance and toughness.

[0036] When component [B] is a monoamine or diamine, this is preferred due to the excellent biodegradability of the resulting cured product. When component [B] is a trifunctional or higher polyamine, this is preferred because even with a small amount of pre-reactant, the viscosity of the epoxy resin composition can be effectively increased to a viscosity suitable for prepreg applications.

[0037] In a preferred embodiment of the invention, the resin composition comprises the following component [B1] as component [B] included in component [D].

[0038] [B1]: At least one amine compound containing in its molecule a structure represented by formula (I) or (II) below. .

[0039] By including component [B1], the structure represented by formula (I) or (II) above is incorporated into the cured product of the resulting epoxy resin. In this embodiment, [B1] is a subset of [B] such that the composition contains at least one amine compound [B], and at least one of the at least one amine compound [B] is [B1]. The cured product of this epoxy resin exhibits excellent degradability because this structure can be readily decomposed by treatment with an acid solution as described below. Here, depending on the type of component [B1] used, the reactivity with the epoxy resin (component [A]) may be too high, and the change in resin viscosity over time at the manufacturing process temperature (e.g., 60°C) of the resin film or prepreg blank may be too large, making the epoxy resin composition using it unsuitable for prepreg blank applications. To address this problem, the inventors have discovered that by using component [D], wherein component [B1] is pre-reacted with component [A], it is surprisingly possible to adjust the resin viscosity to a level suitable for the manufacturing process of resin films and prepreg blanks, while maintaining the excellent biodegradability of the cured product, and also improving the resin viscosity stability at 60°C.

[0040] Another form or aspect of the invention according to an exemplary embodiment is an epoxy resin composition in which component [B1] and component [A] are blended without prior reaction, each remaining unreacted. By blending component [B1] and component [A] without pre-reacting them, this epoxy resin composition can be suitably used in processes requiring relatively low resin viscosity, such as resin infusion applications, and the resulting resin-cured product or fiber-reinforced composite exhibits excellent reformability.

[0041] Component [B1] includes, but is not limited to, for example, 2-[2-(2-aminoethoxy)prop-2-oxy]ethylamine, 1,1'-(propane-2,2-diylbis(oxy))bis(propane-2-amine), 1,1'-(propane-2,2-diylbis(oxy))bis(butane-2-amine), 1,1'-(propane-2,2-diylbis(oxy))bis(2-methylpropane-2-amine), 2,2',2''-((methylsilanetriyl)tri(oxy))tri(propane-1-amine), 1,1',1''-((methylsilanetriyl)tri(oxy))tri(butane-2-amine), 1,1',1''-((methylsilanetriyl)tri(oxy))tri(2-methylpropane-2-amine) and, for example, WO2012071896 A1, WO2013184827 Amine compounds listed in A1, WO2015054698A1, WO2019240840A1 and WO2019240841A1. [B1] Amine compounds may be used alone or in combination.

[0042] Component [C]

[0043] Component [C] is a curing agent different from component [B] and can be selected according to the requirements of the application, as long as it is a compound that reacts with epoxy resin. When the epoxy resin composition contains component [D] as described below and does not contain unreacted component [B] separate from component [D], component [B] in component [D] has been pre-reacted and consumed, and the curing reaction of the resin composition proceeds through the reaction between component [C] (curing agent) and component [A] (epoxy resin). On the other hand, if the epoxy resin composition does not contain component [D] or contains unreacted component [B] separate from component [D], the curing reaction of the composition proceeds through competition between the reaction of component [B] with component [A] (epoxy resin) and the reaction of component [C] with component [A].

[0044] The curing agent may be selected from, for example, but not limited to, amine compounds, hydrazide compounds, phenolic compounds, thiols, acid anhydrides, isocyanate compounds, cyanate compounds, and mixtures thereof. These curing agents may be used alone or in combination of two or more.

[0045] When mixed with other components, they can be in powder or liquid form, or powder and liquid curing agents can be mixed together.

[0046] It is preferred to include an aromatic amine compound (referred to as [C1]) as component [C] of the present invention. Component [C1] is preferred because it provides excellent viscosity stability and high elastic modulus after curing of the epoxy resin composition. In this embodiment, [C1] is a subset of [C] such that the composition includes at least one curing agent [C], and at least one of the at least one curing agent [C] is [C1].

[0047] Examples of such aromatic amine compounds include, but are not limited to, m-phenylenediamine, diaminodiphenylmethane, diaminodiphenyl sulfone, m-phenylenediamine, (p-phenylenemethylene)diphenylamine, 4,4'-methylenebis[N-sec-butylaniline], N,N'-di-sec-butyl-p-phenylenediamine, diethyltoluenediamine, dimethylthiotoluenediamine, various derivatives thereof such as alkyl-substituted derivatives, and various isomers having an amino group at different positions.

[0048] Specific examples of suitable aromatic amine compounds include, but are not limited to, SEIKACURE-S (manufactured by Wakayama SeikaKogyo Co., Ltd.), ARADUR® 976-1, ARADUR® 9664-1, ARADUR® 9719-1 (all manufactured by Huntsman Corporation), 3,3'-DAS (manufactured by Mitsui Chemicals, Inc.), Primacure® M-DIPA and Primacure® M-MIPA (both manufactured by Arxada), Unilink 4200, and Unilink 4100 (both manufactured by DorfKetal Chemicals LLC).

[0049] Phenolic compounds (referred to as [C2]) are preferably included as component [C] of the present invention. Component [C2] is preferred because it provides excellent reactivity, viscosity stability, and high elastic modulus after curing of the epoxy resin composition.

[0050] Examples of such phenolic compounds include, but are not limited to, bisphenol derivatives, dihydroxybenzophenone derivatives, dihydroxybiphenyl derivatives, dihydroxybenzene derivatives, naphthol derivatives, and dihydroxynaphthalene derivatives.

[0051] Specific examples include 2,4-dihydroxybenzophenone, 4,4'-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-methylenebis(6-tert-butyl-4-ethylphenol), 4,4'-thiobis(6-tert-butyl-m-cresol), 4,4'-butylenebis(6-tert-butyl-m-cresol), bis(4-hydroxyphenyl) sulfone, 9,9'-bis(4-hydroxyphenyl)fluorene, 9,9-bis(3-methyl-4-hydroxyphenyl)fluorene, 9,9'-bis(3-allyl-4-hydroxyphenyl)fluorene, 4,4'-dihydroxybiphenyl, tetrabromobisphenol A, 4,4'-dihydroxydiphenyl ether, 4, 4'-Thiodiol, 2,2'-Dihydroxybiphenyl, 1,1'-Bi-2-naphthol, 4,4'-Methylenebis(2,6-di-tert-butylphenol), 2,2'-Dihydroxy-4,4'-dimethoxybenzophenone, 2,2'-Methylenebis[6-(1-methylcyclohexyl)-p-cresol], 2,2'-Methylenebis(6-tert-butyl-p-cresol), 2,5-Dihydroxyterephthalate, 1,4-Dihydroxyanthraquinone, 3,5-Di-tert-butylcatechol, tert-butylhydroquinone, methylhydroquinone, 2-Methylresorcinol, 1,6-Dihydroxynaphthalene, 2,3-Dihydroxynaphthalene, 1,3-Dihydroxynaphthalene, 3 3,3',3'-Tetramethyl-1,1'-spirobiindan-6,6'-diol, 3-(4-hydroxyphenyl)-1,1,3-trimethyl-5-indanol, cresolphthalein, fluorescein, 2',7'-dichlorofluorescein, 2,5-dihydroxy-1,4-benzoquinone, 3,3',5,5'-tetra-tert-butyl-[1,1'-biphenyl]-2,2'-diol, bis(4 2,2-diallyl-4,4'-bisphenol, 2,2'-diallylbisphenol A, 4,4'-sulfonylbis(2-allylphenol), 4-tert-butylcatechol, 2,5-di-tert-butylhydroquinone, 2,5-di-tert-pentylhydroquinone, 2,2'-methylenebis(6-cyclohexyl-p-cresol), 2,2'-methylenebis(6-tert-butyl-p-cresol), 4,4'-(3,3,5-trimethylcyclohexane-1,1-diyl)diol, and their various derivatives such as alkyl-substituted derivatives, as well as various isomers having phenolic groups at different positions.

[0052] A thiol compound (referred to as [C3]) is preferably included as component [C] of the present invention. Component [C3] is preferred because it provides excellent reactivity and high elastic modulus of the epoxy resin composition after curing.

[0053] Examples of such thiols include, but are not limited to, trimethylolpropane tris(3-mercaptobutyrate), 1,4-bis(3-mercaptobutyryloxy)butane, 1,3,5-tris[2-(3-mercaptobutyryloxy)ethyl]-1,3,5-triazine-2,4,6(1h,3h,5h)-trione, pentaerythritol tetra(3-mercaptobutyrate), 4,4'-thiobis(thiophenol), bismuthiol, 6-(dibutylamino)-1,3,5-triazine-2,4-dithiol, various derivatives thereof such as alkyl-substituted derivatives, and various isomers having thiols groups at different positions.

[0054] The component [C] of this invention is preferably a compound having two active hydrogen atoms in its molecule that react with epoxy resin. By having two active hydrogen atoms that react with epoxy resin, component [C] acts as a chain length extender and does not form crosslinking points in the resulting cured resin product, thus allowing the epoxy resin to be cured without compromising its biodegradability, which is an advantage of this invention. Furthermore, the resulting cured material exhibits excellent remolding properties and can suppress heat generation during the curing process. Examples of compounds having two active hydrogen atoms in their molecule that react with epoxy resin include monofunctional primary amine compounds, difunctional secondary amine compounds, difunctional phenolic compounds, monofunctional hydrazides, difunctional thiols, monofunctional anhydrides, difunctional isocyanates, difunctional cyanates, and mixtures thereof.

[0055] Furthermore, it is particularly preferred to use a compound having two epoxy groups in its molecule, which is also a component [A], as component [C] of the present invention. In this case, since the crosslinking points in the epoxy resin cured product formed by components [A], [B1], and [C] are formed only by component [B1], the resin cured product is particularly easy to decompose when the structure of formula (I) or (II) in component [B1] is decomposed by acid solution treatment. In other words, this structure can be effectively decomposed in a short time even at low temperatures or low acid concentrations, and the energy cost required for decomposition can be reduced.

[0056] Component [D]

[0057] Component [D] of the present invention is the reaction product of components [A] and [B]. As a form or aspect of the present invention, by including component [D], the epoxy resin composition of the present invention can have a viscosity suitable for the manufacturing process of resin films and prepreg blanks without blending with other components such as thermoplastic resins, thereby reducing costs and procedures in the production of epoxy resin compositions. Furthermore, by including component [D], a resin composition with excellent viscosity stability can be obtained compared to using component [B] alone, which has not reacted with component [A]. Moreover, since the heat generated by the curing of the epoxy resin composition can be reduced, the temperature rise of the component due to heat storage during the curing process of the resin and prepreg blank can be suppressed, and degradation due to thermal decomposition can be prevented. This is also desirable because even when molding components of different sizes and thicknesses, a cured material with uniform curing degree and minimal differences in physical properties can be obtained within the component.

[0058] The reaction products of components [A] and [B] can be obtained by heating a mixture of [A] and [B] blended in any ratio at the temperature at which the reaction takes place. When using this method, unreacted components [A] and [B] may remain in the reaction products, but there is no particular need to remove these residues. The heating temperature can be selected according to the type of components [A] and [B] used, but heating temperatures of 80°C or higher, 100°C or higher, 120°C or higher, 130°C or higher, 140°C or higher, or 160°C or higher are preferred. The higher the heating temperature in this range, the faster the reaction proceeds and the shorter the time it takes to obtain the reaction products. The preferred heating temperature is 200°C or lower, more preferably 180°C or lower. Heating temperatures in this range are ideal because they prevent undesirable thermal decomposition due to heating and also reduce the required energy costs.

[0059] In one embodiment of the invention, component [D] is the reaction product of component [A] and component [B1]. That is, component [D] has the structure of formula (I) or (II) in its molecule. This imparts excellent biodegradability to the resulting cured product.

[0060] The following describes specific, non-limiting examples of component [D] using chemical structural formulas. These chemical structures are examples and do not limit the scope of the invention. For example, when the bisphenol A epoxy resin listed in formula (III) is used as component [A] and the bifunctional amine listed in formula (IV) is used as component [B1], the four active hydrogens in component [B1] react with the epoxy groups in component [A] through the above-described pre-reaction procedure to form component [D] of formula (V). Although the chemical structure of component [D] obtained when all four active hydrogens in [B1] react is shown here, it is possible, for example, that only one, two, or three active hydrogens in [B1] react, and the system may contain unreacted active hydrogens in component [B1] and unreacted component [A]. Furthermore, component [D] may be an oligomer in which the terminal epoxy groups derived from component [A] have already reacted further with another component [B1] molecule in its chemical structure.

[0061] .

[0062] A preferred embodiment of the invention is a preparation method in which components [A] and [B] are pre-reacted to obtain component [D] as a reactant, and then component [C] is further blended to obtain an epoxy resin composition. The epoxy resin composition obtained by the above method is preferred because the resin viscosity stability at 60°C is improved, making the resin viscosity suitable for prepreg applications, and the heat generated during curing is also reduced.

[0063] Component [E]

[0064] Component [E] is a catalyst. It can be included in the epoxy resin composition to improve the reactivity of the epoxy resin and the curing agent for rapid curing and to enhance the heat resistance, toughness, and elongation of the cured product. As a catalyst, at least one selected from aromatic urea compounds, imidazole derivatives, and phosphorus compounds is preferred from the perspective of achieving storage stability and curability of the epoxy resin composition.

[0065] The aforementioned aromatic urea compounds include, for example, 3-phenyl-1,1-dimethylurea, 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, toluene dimethylurea, etc.

[0066] The aforementioned imidazole derivatives include, for example, 1-benzyl-2-methylimidazol, 1-benzyl-2-ethylimidazol, 1-cyanoethyl-2-methylimidazol, 1-cyanoethyl-2-ethyl-4-methylimidazol, 1-cyanoethyl-2-phenylimidazol, etc.

[0067] The aforementioned phosphorus compounds include, for example, triphenylphosphine, tri-o-tolylphosphine, tris(p-methoxyphenyl)phosphine, triphenylphosphine triphenylborane, tetraphenylphosphonium tetraphenylborate, etc.

[0068] The amount of component [E] relative to 100 parts by weight of epoxy resin is preferably 0.1 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more. The higher the amount of component [E] within this range, the better the curability of the epoxy resin composition. The amount of component [E] is preferably 5 parts by weight or less, 3 parts by weight or less, and 1.5 parts by weight or less per 100 parts by weight of epoxy resin. The lower the amount of component [E] within this range, the better the viscosity stability of the epoxy resin composition.

[0069] The resin composition of the present invention can be blended with thermosetting resin particles, thermoplastic resins soluble in epoxy resins, or inorganic fillers such as silica particles, carbon particles, clay, carbon nanotubes, graphene, and metal powders to a degree that does not impair the effects of the present invention.

[0070] As a thermoplastic resin, a thermoplastic resin having chemical bonds selected from carbon-carbon bonds, amide bonds, imide bonds, ester bonds, ether bonds, carbonate bonds, urethane bonds, thioether bonds, sulfone bonds, and / or carbonyl bonds in the main chain of the thermoplastic resin is preferred.

[0071] In addition, thermoplastic resins can also have a partially cross-linked structure and be crystalline or amorphous. In particular, suitable or preferred, at least one thermoplastic resin selected from polyamide, polycarbonate, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyallylate, polyester, polyamideimide, polyimide (including polyimides having a phenyltrimethylindane or phenylindane structure), polyetherimide, polysulfone, polyethersulfone, polyetherketone, polyetheretherketone, polyetheretherketone, polyaramid, polyethernitrile, polyvinylformal, and polybenzimidazole is mixed or dissolved in the epoxy resin composition.

[0072] In the resin composition of the present invention, it is preferred that the ratio of each component in component [D] satisfies (F1); (F1): ((moles of active hydrogen contained in component [B]) / moles of epoxy groups in component [A]) ≦0.4.

[0073] If the value of (moles of active hydrogen in component [B] / moles of epoxy groups in component [A]) is 0.4 or less, the viscosity of the epoxy composition will not become too high even if components [A] and [B] react fully, and it is suitable for mixing with other components. If the value of (moles of active hydrogen in component [B] / moles of epoxy groups in component [A]) is 0.1 or greater, the cured material is insoluble in organic solvents such as acetone, which is ideal because cured epoxy resins and fiber-reinforced composites are more resistant to these organic solvents in the operating environment.

[0074] In the resin composition of the present invention, it is preferred that the blending ratio of each component satisfies (F2); (F2): 0.5 ≦ (moles of active hydrogen contained in component [C] / moles of epoxy groups in component [A]).

[0075] If the value of (moles of active hydrogen contained in component [C] / moles of epoxy groups in component [A]) is 0.5 or greater, preferably 0.6 or greater, and even more preferably 0.7 or greater, the formation of a cross-linked structure in the epoxy resin cured material is appropriate, and a cured material with excellent toughness and solvent resistance is obtained, which can withstand the trimming of parts, etc. Furthermore, the rubber modulus of the cured material becomes sufficiently low, i.e., the cross-linking density becomes sufficiently low, which results in excellent reprocessing properties.

[0076] If the value of (moles of active hydrogen contained in component [C] / moles of epoxy groups in component [A]) is 0.9 or less, preferably 0.8 or less, the formation of cross-linked structures in the epoxy resin curing material is appropriate, and a curing material with excellent toughness and solvent resistance can be obtained, which can withstand the finishing of parts, etc.

[0077] In the resin composition of the present invention, it is preferred that the blending ratio of each component satisfies (F3); (F3): 0.8 ≦ ((moles of active hydrogen contained in component [B] + moles of active hydrogen contained in component [C]) / moles of epoxy groups in component [A]) ≦ 1.2.

[0078] If the value of ((moles of active hydrogen contained in component [B] + moles of active hydrogen contained in component [C]) / moles of epoxy groups in component [A]) is 0.8 or greater, preferably 0.9 or greater, then the formation of cross-linked structures in the epoxy resin cured material is appropriate, and a cured material with excellent toughness and solvent resistance is obtained, which can withstand the finishing of parts, etc.

[0079] If the value of ((moles of active hydrogen contained in component [B] + moles of active hydrogen contained in component [C]) / moles of epoxy groups in component [A]) is 1.2 or less, preferably 1.1 or less, then the formation of cross-linked structures in the epoxy resin cured material is appropriate, and a cured material with excellent toughness and solvent resistance is obtained, which can withstand the finishing of parts, etc.

[0080] The rubbery modulus of the cured material prepared by curing the epoxy resin composition of the present invention should be 5.0 MPa or lower in a dynamic viscoelasticity evaluation, more preferably 4.0 MPa or lower, 3.0 MPa or lower, 2.0 MPa or lower, and 1.0 MPa or lower. The rubbery modulus is said to be related to the crosslinking density of the cured epoxy resin material, and the lower the rubbery modulus within this range, the lower the crosslinking density of the cured material, which means that the cured material has a crosslinked structure with high deformability. Surprisingly, the inventors have found that when the dynamic viscoelastic modulus of the cured resin composition is within this range, the cured molded article or fiber-reinforced composite material exhibits excellent reformability. Reformability here refers to the ability of a cured molded article to be deformed in shape by press molding or other methods when reheated to a temperature above the glass transition temperature and to retain that deformed shape when the temperature is lowered to a temperature below the glass transition temperature.

[0081] The cured material cured from the epoxy resin composition of the present invention should have a storage modulus of 0.8 GPa or higher, more preferably 0.9 GPa or higher, and even more preferably 1.0 GPa or higher, at 40°C in a dynamic viscoelasticity evaluation. The higher the storage modulus within this range, the more rigid the cured material can be, and the wider its application range.

[0082] In the dynamic viscoelasticity evaluation, the ratio of storage modulus to rubber state modulus (storage modulus [Pa] / rubber state modulus [Pa] at 40°C) of the cured epoxy resin composition of the present invention should be 180 or greater, more preferably 200 or greater, 400 or greater, 600 or greater, 800 or greater, 1000 or greater, and 1500 or greater. A higher elastic modulus ratio within this outer range is more desirable because the cured material exhibits a high level of rigidity and reformability, which further expands its application range.

[0083] The rubber-state elastic modulus and storage modulus at 40°C of the cured epoxy resin composition of the present invention were measured in dynamic viscoelasticity evaluation as follows, according to the DMA measurement method in torsion mode as per ASTM D 5279. DMA measurements were performed on specimens 2.0 mm thick, 12.7 mm wide, and 50 mm long using an ARES (Actual Viscoelasticity Measurement Instrument) at a torsional vibration frequency of 1.0 Hz and a heating rate of 5.0°C / min within a temperature range of 40–280°C. The rubber-state elastic modulus and storage modulus at 40°C were then recorded. The rubber-state modulus is the storage modulus in the temperature region above the glass transition temperature, where the storage modulus has leveled off.

[0084] The initial viscosity of the epoxy resin composition of the present invention at 60°C is preferably 1.0 Pa·s or higher, more preferably 5.0 Pa·s, 10 Pa·s, 15 Pa·s, 20 Pa·s, 25 Pa·s, 30 Pa·s or higher. The initial viscosity of the epoxy resin composition of the present invention at 60°C is preferably less than 2000 Pa·s, more preferably less than 1000 Pa·s, 500 Pa·s, 400 Pa·s, 300 Pa·s, 200 Pa·s, 100 Pa·s or lower. Within this approximate range, the resin flow during the manufacturing process of the resin film and prepreg becomes suitable, and it is ideal to obtain resin films and prepregs with a uniform resin content. Furthermore, the handling properties of the resulting resin film or prepreg, such as tackiness and drape, are also ideal.

[0085] The viscosity of the epoxy resin composition after being held at 60°C for 2 hours should be 5.0 times or less of the initial viscosity at 60°C. More preferably, it is 4.0 times or less, 3.0 times or less, 2.0 times or less, 1.5 times or less, and 1.2 times or less. A smaller viscosity ratio within this approximate range is more desirable because it suppresses resin viscosity variations during the manufacturing process of the resin film and prepreg blank, and allows for the acquisition of resin films and prepreg blanks with uniform resin content. Furthermore, the chemical reaction is less likely to continue during prolonged storage of the resin film or prepreg blank, resulting in excellent storage stability.

[0086] The viscosity of the epoxy resin composition was measured using the following method. The complex viscosity η of the epoxy resin composition was measured using a viscoelastic measuring device (ARES, TAinstrument) and parallel plates with a plate spacing of 0.6 mm, at a torsional vibration frequency of 0.5 Hz and a measurement temperature of 60°C. 2 hours. The initial viscosity at 60°C and the viscosity after 2 hours are the initial viscosity and the viscosity after 2 hours at 60°C, respectively.

[0087] The epoxy resin compositions of the present invention preferably have a curing calorific value of less than 240 J / g, as measured by differential scanning calorimetry (DSC) at a heating rate of 10 °C / min, more preferably less than 230 J / g, 220 J / g, 190 J / g, 160 J / g, and 130 J / g. The smaller the curing calorific value within this approximate range, the more the resin or prepreg blank can suppress the temperature rise of the component due to heat storage during curing, thereby preventing degradation due to thermal decomposition. It is also desirable to obtain cured products with uniform curing degree and minimal differences in physical properties within the component, even when molding components of different sizes and thicknesses.

[0088] The curing calorific value of the epoxy resin composition of the present invention can be determined by the peak area of ​​the curing calorific value curve, which is obtained by increasing the temperature from room temperature at a rate of 10°C / min in a differential scanning calorimeter (DSC) according to ASTM D 3418-15.

[0089] A resin film is prepared by applying the epoxy resin composition alone to release paper or release film, or by impregnating a substrate with the epoxy resin composition.

[0090] Preferred examples of the base material include carbon fiber, graphite fiber, aramid fiber, glass fiber, thermoplastic resin fiber, etc. Glass fiber and thermoplastic resin fiber are particularly preferred. The resin film is manufactured by various known methods, such as a wet process (in which epoxy resin is dissolved in a solvent, such as methyl ethyl ketone or methanol, to reduce the viscosity of the resin, and the solution is applied to release paper or release film or impregnated into a base material), a method of heating epoxy resin to reduce the viscosity of the resin and applying the resin to release paper or release film, or a method of impregnating a base material.

[0091] The resulting resin film can be used as a surface resin layer to improve the surface quality of other components. It can also be used as an adhesive layer to bond other fiber-reinforced composites or between fiber-reinforced composites and other components.

[0092] The resin film of the present invention is preferably used in combination with the cured product of the epoxy resin or fiber-reinforced composite material of the present invention. This is because the entire cured material, including the resin film layer, has excellent biodegradability and is free of undissolved impurities after degradation. It is also ideal because the entire cured assembly, including the resin film layer, has excellent reformability. It is also preferable to use the resin film in combination with non-degradable cured conventional epoxy resin or fiber-reinforced composite material. This is because only the cured resin film layer is partially degradable and recyclable under mild acidic conditions, while the non-degradable cured conventional epoxy resin or fiber-reinforced composite material remains undegraded.

[0093] The resin weight in the resin membrane is preferably 30 g / m³. 2 Or greater, preferably 50 g / m 2 80 g / m 2 Or even higher. A higher resin weight results in fewer pinholes, and the epoxy resin composition can more uniformly cover the carrier, with a lower likelihood of tearing. On the other hand, the resin weight in the resin film is preferably 300 g / m³. 2 Or smaller, more preferably 200 g / m 2 150 g / m 2 Or even smaller. The lower the resin weight, the easier it is to improve the drape properties of the sheet-like intermediate substrate.

[0094] The prepreg blank of the present invention is prepared by impregnating reinforcing fibers with the epoxy resin composition as the matrix resin.

[0095] Preferred examples of reinforcing fibers include carbon fibers, graphite fibers, aramid fibers, glass fibers, etc., with carbon fibers being particularly preferred among these fibers. Prepreg blanks can be prepared by various commonly known methods, such as a wet method by dissolving a matrix resin in a solvent (e.g., methyl ethyl ketone and methanol) to reduce the resin viscosity, and then impregnating the reinforcing fiber bundles with that solution; or a hot-melt method by heating the matrix resin to reduce the resin viscosity, and then impregnating the reinforcing fiber bundles with that resin.

[0096] In the wet process, prepreg blanks are prepared by immersing carbon fiber bundles coated with sizing agents in a solution containing a matrix resin, then pulling up the reinforcing fiber bundles, and evaporating the solvent using an oven or other unit.

[0097] In the hot-melt method, the prepreg blank is prepared by either directly impregnating the reinforcing fiber bundles with a matrix resin whose viscosity is reduced by heating, or by preparing a coating film of the matrix resin composition on release paper or the like, then stacking the film on each or one side of the reinforcing carbon fiber bundles, and then applying heat and pressure to the film to impregnate the reinforcing fiber bundles with the matrix resin. The hot-melt method is superior to the wet method because there is no solvent residue in the prepreg blank.

[0098] The reinforcing fiber cross-sectional density of the prepreg can range from 50 to 1000 g / m². 2 For example, 100 to 1000 g / m 2 For example, 200 to 1000 g / m 2 If the cross-sectional density is at least 50 g / m³ 2 In molding fiber-reinforced composites, it may be possible to ensure the desired thickness by laminating only a small amount of prepreg preform, which simplifies the lamination process. On the other hand, if the cross-sectional density is no greater than 1000 g / m³... 2 The prepreg retains good drape. The reinforcing fiber mass fraction of the prepreg may be 40 to 90% by mass in some embodiments, 50 to 85% by mass in others, or even 60 to 80% by mass in still others. If the reinforcing fiber mass fraction is at least 40% by mass, there is sufficient fiber content to provide fiber-reinforced composites with excellent specific strength and specific modulus, and to prevent excessive heat generation during the curing process. If the reinforcing fiber mass fraction is no more than 90% by mass, resin impregnation of the reinforcing fibers reduces the risk of forming a large number of voids in the fiber-reinforced composite.

[0099] The prepreg blank of this invention is preferably characterized by containing unidirectionally oriented discontinuous carbon fibers. The discontinuity of the carbon fibers allows the prepreg blank to be stretched in the fiber direction to prevent bridging (fiber sticking out) during the surface forming process of the prepreg laminate and to suppress the formation of wrinkles and voids.

[0100] Furthermore, it is particularly desirable to use the epoxy resin compositions of the present invention as the matrix resin in prepregs characterized by unidirectional discontinuous carbon fibers. Although epoxy-cured materials with low crosslinking density inherently possess excellent reshaping properties, by using them as the matrix resin for fiber-reinforced composites containing unidirectional discontinuous carbon fibers, the restrictions on deformation in the fiber direction are relaxed compared to fiber-reinforced composites containing only continuous fibers, resulting in fiber-reinforced composites with excellent reshapeability even after curing. Moreover, by combining the epoxy resin curing materials of the present invention, which have excellent biodegradability, with the aforementioned discontinuous carbon fibers, the fiber material obtained after decomposing the fiber-reinforced composite has been processed into short fibers rather than continuous fibers. The recycled fiber material is desirable because it can be easily reprocessed for reuse in other applications, such as as filler for other materials or nonwoven materials, thereby simplifying the post-processing procedure.

[0101] Prepreg blanks characterized by containing unidirectional discontinuous carbon fibers can be manufactured by known methods. For example, they can be obtained by inserting a prepreg sheet containing unidirectional continuous fibers in the fiber direction into a roller cutter having blades arranged in a cylindrical shape and inserting intermittent straight incisions.

[0102] The method of forming fiber-reinforced composite materials using the prepregs of the present invention is illustrated by stacking prepreg blanks and thermosetting the matrix resin while applying pressure to the laminate.

[0103] The application of heat and pressure in the prepreg lamination and molding process can be achieved by using, as appropriate, press molding, autoclave molding, bagging molding, wrapping tape molding, internal pressure molding, etc.

[0104] Autoclave molding is a method in which prepreg preforms are laminated onto a tooling plate of a predetermined shape, covered with a bagging film, and then cured by applying heat and pressure while air is being extracted from the laminate. This method allows for precise control of fiber orientation and provides high-quality molding materials with excellent mechanical properties due to their extremely low porosity. The pressure applied during molding can be from 0.3 to 1.0 MPa, while the molding temperature can range from 90 to 300°C.

[0105] The wrapping tape method is a process in which a prepreg blank is wound around a mandrel or other core rod to form a tubular fiber-reinforced composite material. This method can be used to produce golf clubs, fishing rods, and other rod-shaped products. More specifically, the method involves using a wrapping tape made of thermoplastic film to wind around a mandrel onto the prepreg blank under tension to secure the prepreg blank and apply pressure. After the resin is cured by heating in a furnace, the mandrel is removed to obtain a tubular body. The tension used for winding the tape can be from 20 to 100 N. The molding temperature can be in the range of 80 to 300°C.

[0106] The internal pressure forming method involves placing a prepreg obtained by winding a prepreg around a thermoplastic resin tube or other internal pressure applicator into a metal mold. High-pressure gas is then introduced into the internal pressure applicator while the mold is heated to apply pressure, thereby molding the prepreg. This method can be used when forming objects with complex shapes, such as golf clubs, tennis rackets, or badminton rackets. The pressure applied during molding can range from 0.1 to 2.0 MPa. The molding temperature can range from room temperature to 300°C or from 120 to 275°C.

[0107] Fiber-reinforced composite materials made from the prepreg blanks of the present invention can have the Grade A surface described herein. The term "Grade A surface" refers to a surface exhibiting extremely high finish quality characteristics free from aesthetic flaws and defects.

[0108] Fiber-reinforced composites containing cured epoxy resin compositions obtained by curing the epoxy resin compositions described herein and reinforcing fibers are advantageously suited for sports applications, general industrial applications, and aerospace applications. Sports applications that advantageously utilize these materials include, but are not limited to, golf clubs, fishing rods, tennis or badminton rackets, hockey sticks, and ski poles. General industrial applications that advantageously utilize these materials include, but are not limited to, structural materials for vehicles (such as automobiles, bicycles, ships, and rail vehicles), drive shafts, leaf springs, windmill blades, pressure vessels, flywheels, paper rolls, roofing materials, cables, and repair / reinforcement materials.

[0109] The present invention provides a method for recycling a cured product of an epoxy resin composition and a fiber-reinforced composite material, wherein the method includes immersing the cured product in an acidic solvent, wherein the epoxy resin composition contains the following components [A], [B] and [C], and wherein the resin composition includes the reaction product of components [A] and [B] as component [D]; [A]: At least one epoxy resin; [B]: At least one amine compound; [C]: At least one curing agent different from component [B].

[0110] Examples are shown below, but are not limited to this method. In one embodiment, the cured product of the epoxy resin composition and the fiber-reinforced composite material is decomposed by an acidic solvent. The acidic solvent is a solvent containing a Lewis acid, such as an acid selected from hydrochloric acid, acetic acid, lactic acid, formic acid, propionic acid, citric acid, methanesulfonic acid, p-toluenesulfonic acid, sulfuric acid, benzoic acid, and phthalic acid.

[0111] The acid concentration in the acid solvent is preferably greater than 1% by volume, and more preferably greater than 5%, 10%, 15%, 20%, 25%, 30%, 40%, or 50% by volume. The higher the acid concentration, the more efficiently the epoxy resin composition and fiber-reinforced composite material decompose in a shorter time.

[0112] Furthermore, in one embodiment, the cured products of the epoxy resin composition and the fiber-reinforced composite material are prepared in the presence of a solvent selected from methanol, ethanol, ethylene glycol, isopropanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, water, and combinations thereof.

[0113] The acidic solution used in this method is preferably a mixture of acid and organic solvent. For example, dichloromethane, tetrahydrofuran, acetone, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone are used as organic solvents. The use of a mixed solvent of acid and these organic solvents increases the affinity of decomposition products for the solvent and promotes their diffusion into the solvent, resulting in more efficient decomposition.

[0114] In one embodiment, the cured product of the epoxy resin composition and fiber-reinforced composite material is decomposed by an acidic solution comprising 10% to 1000% of the volume of the epoxy resin composition contained therein.

[0115] The method for recycling cured products of epoxy resin compositions and fiber-reinforced composites is preferably carried out at a temperature of 25 to 150°C. More preferred temperature ranges are above 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, and 120°C. The higher the process temperature, the more rapidly the cured products of epoxy resin compositions and fiber-reinforced composites can be decomposed.

[0116] In one embodiment, the cured product of the epoxy resin composition and fiber-reinforced composite material is decomposed by heating in an acid solution for 10 minutes to 48 hours.

[0117] In some embodiments, the recycling method includes recovering the decomposition products of the cured epoxy resin product by filtration and / or precipitation. Filtration includes, for example, filtering the solution of the cured epoxy resin composition and fiber-reinforced composite material from the above-described method and recovering the contained fiber material. In precipitation, for example, the acid solution following the decomposition of the cured epoxy resin composition and fiber-reinforced composite material in the above-described method is neutralized with an alkaline compound to precipitate the resin decomposition products. Precipitation includes, for example, neutralizing the acid solution with an alkaline compound to precipitate the resin decomposition products.

[0118] The resin decomposition product of the present invention is a resin product obtained by decomposing the epoxy resin composition and the cured product of the fiber-reinforced composite material in the above method.

[0119] The degradation product of the present invention is a fiber material obtained by degrading fiber-reinforced composite materials in the above method.

[0120] In this specification, embodiments have been described in a manner that allows for clear and concise explanation; however, it is intended and understood that embodiments may be combined or separated in various ways without departing from the invention. For example, it is to be understood that all preferred features described herein apply to all aspects of the invention described herein.

[0121] Although the invention has been illustrated and described herein with reference to specific embodiments, the scope of the invention is not intended to be limited by these embodiments. Rather, various modifications may be made within the limits and scope of the equivalents of the claims without departing from the invention.

[0122] Example

[0123] Embodiments of the invention will now be described in more detail by way of examples. Various properties were measured using the methods described below. Unless otherwise stated, these properties were measured under environmental conditions including a temperature of 23°C and a relative humidity of 50%. Prepreg blanks were then manufactured from exemplary resins using a hot-melt prepreg method. The components used in the operational examples and comparative examples are as follows.

[0124] <Component [A]>

[0125] Epoxy Resin 1: EPON™ 825 (Bisphenol A type epoxy resin, manufactured by Miller-Stephenson Chemical Co., epoxy equivalent 187 g / eq); Epoxy Resin 2: ARALDITE® MY0816CH (ethylene oxide, 2,2'-[1,6-naphthylbis(oxymethylene)]bis-, manufactured by Huntsman Corporation, epoxy equivalent 148 g / eq); Epoxy Resin 3: EPICLON® 830 (Bisphenol F type epoxy resin, manufactured by DIC Corporation, epoxy equivalent 173 g / eq).

[0126] <Component [B]>

[0127] [B1] Amine 1: Recyclamine® R 501 (2,2-bis(2-amino-2-methylpropoxy)propane, manufactured by Aditya Birla Chemicals (Thailand) Limited., with an active hydrogen equivalent of 55 g / eq); [B1] Amine 2: Recyclamine® R 101 (2,2-bis(2-aminoethoxy)propane, manufactured by Aditya Birla Chemicals (Thailand) Limited., with an active hydrogen equivalent of 41 g / eq); [B1] Amine 3: Recyclamine® R 805 (1,1',1''-((methylsilyltriyl)tri(oxy))tri(2-methylprop-2-amine), manufactured by Aditya Birla Chemicals (Thailand) Limited., active hydrogen equivalent 51 g / eq); Amine 4: JEFFAMINE® T403 (trimethylolpropane (Propylidynetrimethanol), propoxylated, reaction product with ammonia, manufactured by Huntsman Corporation, active hydrogen equivalent 81 g / eq).

[0128] <Component [C]>

[0129] [C1] Amine 5: Unilink 4200 (manufactured by Everchem specialty chemicals, active hydrogen equivalent 155 g / eq); [C2] Phenol 1: Compimide® TM124 (2,2'-bis(3-allyl-4-hydroxyphenyl)propane, manufactured by Evonikindustries, active hydrogen equivalent 154 g / eq); [C2] Phenol 2: 4-tert-butylcatechol (manufactured by Tokyo Chemical Industry Co., Ltd., active hydrogen equivalent 83 g / eq); [C2] Phenol 3: 2,4-Dihydroxybenzophenone (manufactured by Tokyo Chemical Industry Co., Ltd., active hydrogen equivalent 107 g / eq); [C2] Phenol 4: tert-butylhydroquinone (manufactured by Tokyo Chemical Industry Co., Ltd., active hydrogen equivalent 83 g / eq); [C3] Thiol: Bismuthiol (manufactured by Tokyo Chemical Industry Co., Ltd., active hydrogen equivalent 75 g / eq).

[0130] <Component [E]>

[0131] Urea 1: DYHARD® UR200 (DCMU, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, manufactured by AlzChem LLC).

[0132] (1) Preparation of epoxy resin composition

[0133] The epoxy resin of component [A] and the amine compound of component [B] were placed in a kneader in the amounts and proportions shown in Table 1, and heated to 135°C while mixing. The mixture was then stirred for 90 minutes to allow them to pre-react, yielding a viscous liquid component [D]. The liquid was cooled to 70°C while stirring, and the hardener of component [C] was added. The liquid was cooled to 60°C while stirring, the catalyst of component [E] was added, and the mixture was stirred for an additional 10 minutes to obtain the epoxy resin composition.

[0134] (2) Preparation of epoxy resin cured products

[0135] The epoxy resin composition obtained in (1) was defoamed in a vacuum and then subjected to a 2 mm thick Teflon coating. TM The spacer is set in a mold with a thickness of 2 mm and cured to obtain a 2 mm thick sheet-like resin cured material. The curing conditions are either A or B below, depending on the curing agent used.

[0136] Curing conditions A: Ramp rate 1.7℃ / min, cured at 135℃ for 2 hours.

[0137] Curing condition B: Ramp rate 1.7℃ / min, cured at 180℃ for 2 hours.

[0138] (3) DMA (dynamic mechanical analysis) measurement of epoxy resin cured products

[0139] (2) The rubber-state elastic modulus and storage modulus at 40°C of the epoxy resin cured material obtained in the dynamic viscoelasticity assessment are as follows: Measured according to ASTM D 5279 DMA measurement method in torsion mode. DMA measurements were performed on specimens 2.0 mm thick, 12.7 mm wide, and 50 mm long using a viscoelasticity measuring apparatus (ARES, TA instrument) at a torsional vibration frequency of 1.0 Hz and a heating rate of 5.0°C / min within a temperature range of 40–280°C. The rubber-state elastic modulus and storage modulus at 40°C were read. The storage modulus at 140°C was used as the rubber-state modulus, which is above the glass transition temperature, where the storage modulus plateaus.

[0140] (4) Viscosity measurement of epoxy resin composition

[0141] According to ASTM D 4473-95a, the viscosity of the epoxy resin composition obtained in (1) at 60°C and the viscosity after holding at 60°C for 2 hours were measured using a dynamic viscoelasticity measuring device (ARES, manufactured by TA Instruments) equipped with parallel plates of diameter 40 mm (top) and 50 mm (bottom). The device was operated under the conditions of a parallel plate gap of 0.6 mm, an angular frequency of 10 rad / s, a strain of 10%, and a measurement temperature of 60°C.

[0142] (5) DSC (Differential Scanning Calorimeter) measurement of epoxy resin composition

[0143] The curing calorific value of the epoxy resin composition of the present invention is determined by the peak area of ​​the curing exothermic curve, which is obtained by heating approximately 3 μg of epoxy resin composition from room temperature at a rate of 10°C / min using a differential scanning calorimeter (Discovery DSC2500, TA instrument) according to ASTM D 3418-15.

[0144] (6) Degradability test of epoxy resin cured products

[0145] The biodegradability of the epoxy resin cured material was confirmed by the following method. Test pieces measuring 2.0 mm thick, 10.0 mm wide, and 20 mm long were cut from the epoxy resin cured material obtained in (2) and immersed in a 2:1 volume ratio mixture of 25% acetic acid and N-methylpyrrolidone in 12 ml. Solubility was rated "A" (good) when the epoxy resin cured material decomposed, and "B" (poor) when the epoxy resin cured material did not decompose and the solid remained in the solution.

[0146] (7) Preparation of carbon fiber reinforced composite materials

[0147] Use 129 g / m 2 The epoxy resin composition obtained in (2) is coated onto a carbon fiber fabric substrate (Toraycan). TM T400H-3K, fiber areal weight: 193 g / m² 2 A prepreg blank with a resin content of 40% by weight was obtained. The prepreg blank was cut into 10 cm square sheets and formed into 4-layer laminates in an autoclave under a pressure of 0.6 MPa and curing conditions A or B described above, to obtain a fiber-reinforced composite material with a thickness of approximately 1 mm.

[0148] (8) Reformability testing of carbon fiber reinforced composites

[0149] The reformability of fiber-reinforced composites was evaluated using the following method. Test pieces measuring 1.0 mm thick, 12.7 mm wide, and 50 mm long were cut from the fiber-reinforced composite obtained in (7) and heated in an oven to a temperature of 140°C. The test pieces were then removed from the oven and deformed by longitudinal twisting. Easily deformable specimens were classified as having reformability "A" (good), while specimens that were difficult to deform were classified as having reformability "B" (poor).

[0150] (9) Solvent resistance test of epoxy resin cured products

[0151] The solvent resistance of the epoxy resin cured material was tested using the following method. Test pieces measuring 2.0 mm thick, 10.0 mm wide, and 20 mm long were cut from the epoxy resin cured material obtained in (2) and immersed in acetone. After being kept at room temperature for 12 hours, the samples were evaluated at two levels: solvent resistance "A" (good) when the epoxy resin cured material remained solid without decomposition, and solvent resistance "B" (poor) when the epoxy resin cured material dissolved.

[0152] <Operation Example 1>

[0153] The epoxy resin composition was obtained by the method described in (1) at the ratios listed in Table 1. At this time, (F1): (Number of moles of active hydrogen in component [B]) / (Number of moles of epoxy groups in component [A]) = 0.3 (F2): (Number of moles of active hydrogen in component [C]) / (Number of moles of epoxy groups in component [A]) = 0.7 (F3): ((moles of active hydrogen contained in component [B]) + (moles of active hydrogen contained in component [C])) / (moles of epoxy groups in component [A]) = 1.0.

[0154] The storage modulus of the resin-cured material evaluated by method (3) at 40°C is 1.2 GPa, which is sufficient to obtain sufficiently high stiffness when used as a fiber-reinforced composite. The rubber modulus of elasticity of the resin-cured material at 140°C is 0.7 MPa, which is sufficiently low. In addition, the reformability evaluated by method (8) is A. The initial viscosity of the resin composition evaluated by method (4) at 60°C is 27 Pa·s, which is suitable for resin film and prepreg manufacturing processes. The ratio of viscosity after holding at 60°C for 2 hours to initial viscosity at 60°C is 1.4, indicating good stability. The curing heat of the resin composition evaluated by method (5) is 115 J / g, which is low enough to obtain a cured product with uniform properties. The decomposability of the resin-cured material evaluated by method (6) is “A”. The solvent resistance of the resin-cured material evaluated by method (8) is “A”.

[0155] <Operation Examples 2-4, 6-9>

[0156] Operational Examples 2-4 and 6-9 were evaluated in the same manner as Operational Example 1, except for the formulation ratios and curing conditions, the ratios of which are listed in Table 1. As shown in Table 1, good biodegradability, reformability, and solvent resistance were also obtained in Operational Examples 2-8.

[0157] <Operation Example 5>

[0158] Operational Example 5 was evaluated in the same manner as Operational Example 1, and the ratios are shown in Table 1. However, in Operational Example 5, a total of 15 parts of amine 1 were blended, of which 9 parts were blended with component A in a pre-reaction process to form component D, and the remaining 6 parts were blended without reaction. As shown in Table 1, good degradability, reformability, and solvent resistance were achieved in Operational Example 5.

[0159] <Comparative Examples 1-3>

[0160] Comparative Examples 1-3 were evaluated in the same manner as Operational Example 1, except that the ratios of the formulations were different, as listed in Table 1.

[0161] In Comparative Example 1, no pre-reactant corresponding to component [D] was used, and component [B1] was blended without pre-reacting with component [A]. Furthermore, the hardener of component [C] was not included. The rubber modulus of the resin-cured material evaluated by method (3) at 140°C was 7.2 MPa, and its reformability was worse than that of the operational example. The initial viscosity of the resin composition evaluated by method (4) at 60°C was 0.20 Pa·s. This viscosity is too low for the resin film and prepreg manufacturing process, and the resin did not maintain its shape at room temperature, resulting in significantly poor operating properties. The ratio of the viscosity after holding at 60°C for 2 hours to the initial viscosity at 60°C was 320, and the viscosity changed significantly during this process, resulting in uneven resin content per unit area in the resin film and prepreg, and the prepared prepreg was unstable because the reaction continued gradually during storage at room temperature, leading to continuous changes in operating properties. The prepared prepreg was unstable because the reaction continued gradually during storage at room temperature, leading to continuous changes in operation.

[0162] In Comparative Example 2, the amine compound corresponding to component [B] and the pre-reactant corresponding to component [D] were not used. All epoxy resins were cured with the curing agent corresponding to component [C], and the cured products had no crosslinking points. Therefore, the solvent resistance of the resin-cured products evaluated by the method in (8) was poor, and was rated as "B". In addition, the resin-cured material was brittle, and DMA measurement was not possible due to the difficulty in sample processing.

[0163] In Comparative Example 3, no pre-reactant corresponding to component [D] was used, and component [B] was blended without pre-reacting with component [A]. The rubber modulus of the resin-cured material evaluated by method (3) at 140°C was 8.3 MPa, and its remodeling properties were worse than those of the example. No blended component [B1] was used, and the degradability of the resin-cured material evaluated by method (6) was "B", which is poor.

[0164]

Claims

1. A curable epoxy resin composition comprising the following components [A], [B] and [C], wherein the curable epoxy resin composition includes the reaction product of components [A] and [B] as component [D], and wherein the curable epoxy resin composition includes the following component [B1] as component [B] contained in component [D]; [A]: At least one epoxy resin; [B]: At least one amine compound; [C]: At least one curing agent different from component [B]; [B1]: At least one amine compound containing in its molecule a structure represented by formula (I) or (II): 。 2. The curable epoxy resin composition according to claim 1, wherein when the curable epoxy resin composition is cured, the rubber modulus of the cured material, as measured by DMA (dynamic mechanical analysis), is 5.0 MPa or lower.

3. The curable epoxy resin composition according to claim 1, having a viscosity of 1.0 Pa·s or higher at 60°C.

4. The curable epoxy resin composition according to claim 1, having a curing heat value of 240 J / g or lower as measured by differential scanning calorimetry (DSC) at a heating rate of 10 °C / min.

5. The curable epoxy resin composition according to claim 1, wherein the blending ratio of components [A] and [B] in component [D] satisfies (F1): (F1): (number of moles of active hydrogen contained in component [B]) / (number of moles of epoxy groups in component [A]) ≦ 0.

4.

6. The curable epoxy resin composition according to claim 1, comprising component [C1] as said component [C], wherein [C1] is at least one aromatic amine compound.

7. The curable epoxy resin composition according to claim 1, comprising component [C2] as said component [C], wherein [C2] is at least one phenolic compound.

8. The curable epoxy resin composition according to claim 1, comprising component [C3] as said component [C], wherein [C3] is at least one thiol compound.

9. The curable epoxy resin composition according to claim 1, comprising component [C1] as component [C], wherein [C1] is at least one aromatic amine compound having two active hydrogen atoms in a molecule.

10. The curable epoxy resin composition according to claim 1, comprising component [C2] as component [C], wherein [C2] is at least one phenolic compound having two active hydrogen atoms in its molecule.

11. The curable epoxy resin composition according to claim 1, comprising component [C3] as component [C], wherein [C3] is at least one thiol compound having two active hydrogen atoms in a molecule.

12. The curable epoxy resin composition according to claim 1, wherein the blending ratio of components [C] and [A] satisfies (F2): (F2): 0.5 ≦ (moles of active hydrogen contained in component [C] / moles of epoxy groups in component [A]).

13. The curable epoxy resin composition according to claim 1, wherein the blending ratio of components [A], [B] and [C] satisfies (F3): (F3): 0.8 ≦ (moles of active hydrogen in component [B] + moles of active hydrogen in component [C]) / (moles of epoxy groups in component [A]) ≦ 1.

2.

14. The curable epoxy resin composition according to claim 1, wherein component [C] is a curing agent having two active hydrogen atoms in the molecule.

15. The curable epoxy resin composition according to claim 1, wherein component [A] is a bifunctional epoxy resin.

16. The curable epoxy resin composition according to claim 1, further comprising component [E]: [E]: At least one catalyst.

17. The curable epoxy resin composition according to claim 16, wherein the component [E] is at least one catalyst selected from aromatic urea compounds, imidazole derivatives and phosphorus compounds.

18. A curable epoxy resin composition formed from a curable epoxy resin composition containing the following components [A], [B] and [C], wherein the curable epoxy resin composition includes the reaction product of components [A] and [B] as component [D], and wherein the curable epoxy resin composition includes the following component [B1] as component [B] included in component [D]. [A]: At least one epoxy resin; [B]: At least one amine compound; [C]: At least one curing agent different from component [B]; [B1]: At least one amine compound containing in its molecule a structure represented by formula (I) or (II): ， In the dynamic viscoelasticity evaluation, the ratio of the storage modulus of the cured epoxy resin composition at 40°C to the rubber modulus of the cured epoxy resin composition (storage modulus [Pa] / rubber modulus [Pa] at 40°C) is 180 or greater.

19. The cured epoxy resin composition according to claim 18, wherein the ratio of the storage modulus of the cured epoxy resin composition at 40°C to the rubber modulus of the cured epoxy resin composition (storage modulus [Pa] / rubber modulus [Pa] at 40°C) in the dynamic viscoelasticity evaluation is 200 or greater.

20. The cured epoxy resin composition according to claim 18, wherein the ratio of the storage modulus of the cured epoxy resin composition at 40°C to the rubber modulus of the cured epoxy resin composition (storage modulus [Pa] / rubber modulus [Pa] at 40°C) in the dynamic viscoelasticity evaluation is 400 or greater.

21. The cured epoxy resin composition according to claim 18, wherein the ratio of the storage modulus of the cured epoxy resin composition at 40°C to the rubber modulus of the cured epoxy resin composition (storage modulus [Pa] / rubber modulus [Pa] at 40°C) in the dynamic viscoelasticity assessment is 600 or greater.

22. The cured epoxy resin composition according to claim 18, wherein the ratio of the storage modulus of the cured epoxy resin composition at 40°C to the rubber modulus of the cured epoxy resin composition (storage modulus [Pa] / rubber modulus [Pa] at 40°C) in the dynamic viscoelasticity assessment is 800 or greater.

23. The cured epoxy resin composition according to claim 18, wherein the ratio of the storage modulus of the cured epoxy resin composition at 40°C to the rubber modulus of the cured epoxy resin composition (storage modulus [Pa] / rubber modulus [Pa] at 40°C) in the dynamic viscoelasticity evaluation is 1000 or greater.

24. The cured epoxy resin composition according to claim 18, wherein the ratio of the storage modulus of the cured epoxy resin composition at 40°C to the rubber modulus of the cured epoxy resin composition (storage modulus [Pa] / rubber modulus [Pa] at 40°C) in the dynamic viscoelasticity evaluation is 1500 or greater.

25. A curable epoxy resin composition comprising components [A], [B] and [C], wherein the curable epoxy resin composition includes the reaction product of components [A] and [B] as component [D], and wherein the curable epoxy resin composition includes component [B1] as component [B] contained in component [D]. [A]: At least one epoxy resin; [B]: At least one amine compound; [C]: At least one curing agent different from component [B]; [B1]: At least one amine compound containing in its molecule a structure represented by formula (I) or (II): The viscosity of the curable epoxy resin composition after being held at 60°C for 2 hours is 5 times or less than the initial viscosity of the curable epoxy resin composition at 60°C.

26. The curable epoxy resin composition of claim 25, wherein the viscosity of the curable epoxy resin composition after being held at 60°C for 2 hours is 4 times or less the initial viscosity of the curable epoxy resin composition at 60°C.

27. The curable epoxy resin composition of claim 25, wherein the viscosity of the curable epoxy resin composition after being held at 60°C for 2 hours is 3 times or less the initial viscosity of the curable epoxy resin composition at 60°C.

28. The curable epoxy resin composition according to claim 25, wherein the viscosity of the curable epoxy resin composition after being held at 60°C for 2 hours is twice or less than the initial viscosity of the curable epoxy resin composition at 60°C.

29. The curable epoxy resin composition according to claim 25, wherein the viscosity of the curable epoxy resin composition after being held at 60°C for 2 hours is 1.5 times or less of the initial viscosity of the curable epoxy resin composition at 60°C.

30. The curable epoxy resin composition according to claim 25, wherein the viscosity of the curable epoxy resin composition after being held at 60°C for 2 hours is 1.2 times or less of the initial viscosity of the curable epoxy resin composition at 60°C.

31. A curable epoxy resin composition comprising components [A], [B] and [C], wherein the curable epoxy resin composition includes the reaction product of components [A] and [B] as component [D], and wherein, upon curing, the curable epoxy resin composition has a rubbery elastic modulus of 5.0 MPa or less obtained by DMA (Dynamic Mechanical Analysis); [A]: At least one epoxy resin; [B]: At least one amine compound; [C]: At least one curing agent different from component [B].

32. A curable epoxy resin composition comprising the following components [A], [B] and [C], wherein the curable epoxy resin composition includes the reaction product of components [A] and [B] as component [D], having a curing heat value of 240 J / g or less as measured by differential scanning calorimetry (DSC) at a heating rate of 10 °C / min; [A]: At least one epoxy resin; [B]: At least one amine compound; [C]: At least one curing agent different from component [B].

33. A curable epoxy resin composition comprising components [A], [B] and [C], wherein the curable epoxy resin composition comprises component [B1] as component [B], and wherein the blending ratio of components [C] and [A] satisfies (F2): (F2): 0.5 ≦ (moles of active hydrogen in component [C] / moles of epoxy groups in component [A]); [A]: At least one epoxy resin; [B]: At least one amine compound; [C]: At least one curing agent different from component [B]; [B1]: At least one amine compound having in its molecule a structure represented by formula (I) or (II).

34. The curable epoxy resin composition according to claim 33, comprising component [C1] as said component [C], wherein [C1] is at least one aromatic amine compound having two active hydrogen atoms in a molecule.

35. The curable epoxy resin composition according to claim 33, comprising component [C2] as said component [C], wherein [C2] is at least one phenolic compound having two active hydrogen atoms in its molecule.

36. The curable epoxy resin composition according to claim 33, comprising component [C3] as component [C], wherein [C3] is at least one thiol compound having two active hydrogen atoms in a molecule.

37. A curable epoxy resin composition formed from any one of claims 1 to 36.

38. A resin film comprising the cured epoxy resin composition according to claim 37.

39. A fiber-reinforced composite material comprising the cured epoxy resin and reinforcing fibers as described in claim 37.

40. An adhesive resin film comprising a curable epoxy resin composition according to any one of claims 1 to 36.

41. A prepreg blank comprising reinforcing fiber bundles impregnated with a curable epoxy resin composition according to any one of claims 1 to 36.

42. A fiber-reinforced composite material obtained by curing a prepreg blank according to claim 41.

43. A prepreg preform comprising a reinforcing fiber bundle impregnated with a curable epoxy resin composition according to any one of claims 1 to 36, wherein the prepreg preform contains unidirectionally oriented discontinuous carbon fibers.

44. A fiber-reinforced composite material obtained by curing a prepreg blank according to claim 43.

45. A method for recycling a product comprising a cured epoxy resin composition and a fiber-reinforced composite material, wherein the method comprises immersing the product in an acidic solvent at a temperature of 25 to 200°C under conditions sufficient to remove the cured epoxy resin composition from the product, wherein the cured epoxy resin composition is formed from a curable epoxy resin composition comprising components [A], [B] and [C], wherein the curable epoxy resin composition comprises a reaction product of components [A] and [B] as component [D], and wherein the curable epoxy resin composition comprises component [B1] as component [B] contained in component [D]. [A]: At least one epoxy resin; [B]: At least one amine compound; [C]: At least one curing agent different from component [B]; [B1]: At least one amine compound containing in its molecule a structure represented by formula (I) or (II): 。 46. ​​The method of claim 45, wherein a mixed solvent of acid and organic solvent is used.

47. A resin decomposition product obtained by the method according to claim 45 or claim 46.

48. A fibrous material recycled from a fiber-reinforced epoxy resin composite material decomposed by the method according to claim 45 or claim 46.

49. A method for recycling a product comprising a cured epoxy resin composition and a fiber-reinforced composite material, wherein the method comprises immersing the product in an acidic solvent at a temperature of 25 to 200°C under conditions sufficient to remove the cured epoxy resin composition from the product, wherein the cured epoxy resin composition is formed from a curable epoxy resin composition comprising components [A], [B] and [C], wherein the curable epoxy resin composition comprises component [B1] as component [B], and wherein the blending ratio of components [C] and [A] satisfies (F2): (F2): 0.5 ≦ (moles of active hydrogen contained in component [C] / moles of epoxy groups in component [A]); [A]: At least one epoxy resin; [B]: At least one amine compound; [C]: At least one curing agent different from component [B]; [B1]: At least one amine compound containing in its molecule a structure represented by formula (I) or (II): 。 50. The method of claim 49, wherein a mixed solvent of acid and organic solvent is used.

51. A resin decomposition product obtained by the method according to claim 49 or claim 50.

52. A fiber material recycled from a fiber-reinforced epoxy resin composite material decomposed by the method according to claim 49 or claim 50.

53. A method for recycling a product comprising a cured epoxy resin composition and a fiber-reinforced composite material according to any one of claims 39, 42 and 44, wherein the method comprises immersing the product in an acidic solvent at a temperature of 25 to 200°C under conditions sufficient to remove the cured epoxy resin composition from the product.

54. The method of claim 53, wherein a mixed solvent of acid and organic solvent is used.

55. A resin decomposition product obtained by the method according to claim 53.

56. A fiber material recycled from a fiber-reinforced epoxy resin composite material decomposed by the method according to claim 53.

57. The curable epoxy resin composition according to claim 1, wherein when the curable epoxy resin composition is cured at 135°C for 2 hours, the rubber modulus of the cured material, as measured by DMA (dynamic mechanical analysis), is 5.0 MPa or lower.

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