Epoxy resin composition

Abstract

To provide an epoxy resin composition which exhibits sufficient breaking strength and exhibits improved strain (elongation) at break.SOLUTION: The epoxy resin composition contains the following components: (A) a bi- or higher functional aromatic epoxy resin; (B) a monoepoxy compound; (C) a first amine-based curing agent which is solid at 25°C by itself; (D) a second amine-based curing agent which is liquid at 25°C by itself; and (E) an accelerator. The ratio E2 / E1 of the total number E2 of epoxy groups derived from the monoepoxy compound to the total number E1 of epoxy groups derived from the bi- or higher functional aromatic epoxy resin is 0.04 or more and 0.25 or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an epoxy resin composition. In particular, the present invention relates to an epoxy resin composition for use in a prepreg, and further to an epoxy resin composition for use in a tow prepreg for producing a pressure vessel. [Background technology]

[0002] Epoxy resin compositions are used, for example, in the production of fiber-reinforced composite materials (also called composites) consisting of reinforcing fibers and a matrix resin, and are particularly used as materials for tow prepregs for pressure vessels.

[0003] A pressure vessel is a vessel designed to store gas or liquid at a specific pressure different from atmospheric pressure. In recent years, with the spread of fuel cell vehicles, development of pressure vessels with sufficient performance for in-vehicle use and hydrogen stations has been progressing.

[0004] The pressure vessel has, for example, an inner frame (liner) made of metal or resin and an outer layer made of carbon fiber reinforced composite material (CFRP).

[0005] As a method for manufacturing such a pressure vessel, in addition to a method in which resin is applied to carbon fiber and then the fiber is wound around a liner, there is also a method in which carbon fiber (especially tow prepreg) to which resin has already been applied is wound around a liner and then subjected to a heat curing treatment.

[0006] Patent Document 1 discloses a tow prepreg containing a specific epoxy resin composition and reinforcing fibers. This document describes the production of a fiber-reinforced composite material using the tow prepreg, and describes that this fiber-reinforced composite material can be suitably used for high-pressure containers filled with hydrogen gas, such as those used in fuel cells.

[0007] Patent Document 2 describes a curable resin composition containing as essential components a bisphenol-type epoxy resin (A), an aliphatic epoxy resin having an average of two or more epoxy groups in the molecule (B), dicyandiamide or a derivative thereof (C), and a solid aromatic urea compound (D). This document also describes a tow prepreg obtained by compounding reinforcing fibers with the curable resin composition.

[0008] Patent Document 3 discloses a tow prepreg made by impregnating a reinforcing fiber bundle with a specific epoxy resin composition. The epoxy resin composition contains an epoxy resin having no hydroxyl group in the chemical structure of the main component, a liquid aromatic amine, and a toughening agent. The tow prepreg is said to be suitable for use in the manufacture of hollow containers and cylinders made of fiber-reinforced composite materials.

[0009] The invention according to Patent Document 4 aims to provide a method for curing an epoxy resin composition for a fiber-reinforced composite material, which is particularly suitable for the filament winding method. This document describes a fiber-reinforced composite material containing an epoxy resin composition containing an epoxy resin, a specific urethane-modified epoxy resin, dicyandiamide, and a specific curing accelerator as essential components, and reinforcing fibers.

[0010] Patent Document 5 discloses an epoxy resin composition for fiber-reinforced composite materials used in pressure vessels, etc., and describes that the rubber-state elastic modulus of the cured product of this epoxy resin composition in a dynamic viscoelasticity evaluation is 10 MPa or less. It also describes the addition of a specific phenyl glycidyl ether to the epoxy resin composition, which results in a fiber-reinforced composite material having an appropriate curing rate and excellent tensile strength utilization rate. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 2020 / 250957 [Patent Document 2] Patent Publication No. 2021-161242 [Patent Document 3] JP 2021-116403 A [Patent Document 4] Patent Publication No. 2021-161239 [Patent Document 5] JP 2017-119861 A Summary of the Invention [Problem to be solved by the invention]

[0012] As described above, in recent years, the requirements for pressure vessels have been increasing, for example, there is a demand for larger vessels and further improved pressure resistance.

[0013] In a pressure vessel, the strength in the tensile direction of the fiber-reinforced composite material (e.g., carbon fiber-reinforced composite material) used in the pressure vessel is important from the viewpoint of enduring the pressure (expansion pressure) applied from inside the vessel. If the tensile strength of the fiber-reinforced composite material is improved, it becomes possible to store more gas in the pressure vessel, and it also becomes possible to reduce the amount of composite material required to store a certain amount of gas.

[0014] Fiber-reinforced composite materials manufactured using conventional prepregs (especially tow prepregs) often have insufficient mechanical properties (especially pressure resistance). In particular, when a fiber-reinforced composite material manufactured from conventional tow prepregs is used for a pressure vessel, it may not be able to meet the high requirements for the pressure vessel (especially for larger size and improved pressure resistance).

[0015] Here, it is considered that the resin constituting the fiber-reinforced composite material needs to have a relatively high strength so as not to break even under high stress, and also needs to have a high breaking strain (elongation) to suppress the expansion of the break due to local stress concentration.

[0016] However, it has been difficult for conventional epoxy resin compositions to satisfy both excellent breaking strain (elongation) and sufficient strength, and furthermore, it has been difficult to provide an epoxy resin composition that satisfies these requirements and is also excellent in terms of impregnation property and pot life.

[0017] Therefore, an object of the present invention is to provide an epoxy resin composition which exhibits sufficient breaking strength and improved breaking strain (elongation). In particular, an object of the present invention is to provide an epoxy resin composition which exhibits sufficient breaking strength, impregnation property, and pot life (storage property) and improved breaking strain (elongation).

[0018] The present disclosure also aims to provide a prepreg having such an epoxy resin composition, and to provide a method of manufacturing a pressure vessel from such a prepreg. [Means for solving the problem]

[0019] The object of the present invention can be achieved by the following aspects of the present invention. <Aspect 1> Contains: (A) Difunctional or higher aromatic epoxy resin (B) Monoepoxy compound (C) a first amine-based curing agent that is a solid by itself at 25°C (D) a second amine-based curing agent that is liquid by itself at 25°C (E) Accelerator An epoxy resin composition comprising: a ratio E2 / E1 of a total number E1 of epoxy groups derived from the difunctional or higher aromatic epoxy resin to a total number E2 of epoxy groups derived from the monoepoxy compound is 0.04 or more and 0.25 or less; Epoxy resin composition. <Aspect 2> 2. The epoxy resin composition according to claim 1, wherein a ratio A2 / A1 of a total number A1 of active hydrogens derived from the first amine curing agent to a total number A2 of active hydrogens derived from the second amine curing agent is 0.20 or greater and 1.50 or less. <Aspect 3> 3. The epoxy resin composition according to claim 1 or 2, wherein the monoepoxy compound is an aliphatic monoepoxy compound and / or an aromatic monoepoxy compound. <Aspect 4> 4. The epoxy resin composition of embodiment 3, wherein the monoepoxy compound is an aliphatic monoepoxy compound. <Aspect 5> 5. The epoxy resin composition according to claim 3 or 4, wherein the aliphatic monoepoxy compound is at least one selected from butyl glycidyl ether, 2-ethylhexyl glycidyl ether, and glycidyl lauryl ether. <Aspect 6> 4. The epoxy resin composition of claim 3, wherein the aromatic monoepoxy compound is at least one selected from styrene oxide and phenyl glycidyl ether. <Aspect 7> 7. The epoxy resin composition according to any one of Aspects 1 to 6, wherein the first amine-based curing agent is at least one selected from dicyandiamide and its derivatives. <Aspect 8> The epoxy resin composition according to any one of Aspects 1 to 7, wherein the second amine-based curing agent is a compound having an aromatic ring. <Aspect 9> The epoxy resin composition according to any one of Aspects 1 to 8, wherein the second amine-based curing agent is at least one selected from diethyltoluenediamine and its derivatives. <Aspect 10> 10. The epoxy resin composition according to any one of Aspects 1 to 9, wherein the accelerator is at least one selected from 1,1'-(4-methyl-1,3-phenylene)bis(3,3-dimethylurea) and derivatives thereof. <Aspect 11> The epoxy resin composition according to any one of aspects 1 to 10, wherein the di- or higher functional aromatic epoxy resin is a bisphenol A type epoxy resin. <Aspect 12> A prepreg comprising reinforcing fibers and the epoxy resin composition according to any one of aspects 1 to 11 impregnated into the reinforcing fibers. <Aspect 13> 13. A prepreg according to embodiment 12 for a pressure vessel. <Aspect 14> 14. The prepreg of claim 12 or 13, wherein the reinforcing fibers are carbon fibers. <Aspect 15> A prepreg according to any one of aspects 12 to 14, which is a tow prepreg, is wound around a substrate to form an intermediate; and heat-curing the intermediate body; Including, A method for manufacturing a pressure vessel. Effect of the Invention

[0020] According to the present invention, it is possible to provide an epoxy resin composition that exhibits sufficient breaking strength and improved breaking strain (elongation). In particular, according to the present invention, it is possible to provide an epoxy resin composition that exhibits sufficient breaking strength, impregnation property, and pot life, as well as improved breaking strain (elongation).

[0021] Furthermore, according to the present invention, it is possible to provide a prepreg having such an epoxy resin composition, and to provide a method for producing a pressure vessel from such a prepreg. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] <Prepreg> The epoxy resin composition according to the present invention comprises: (A) Difunctional or higher aromatic epoxy resin (B) Monoepoxy compound (C) a first amine-based curing agent that is a solid by itself at 25°C (D) a second amine-based curing agent that is liquid by itself at 25°C (E) Accelerator Including, The ratio E2 / E1 of the total number E1 of epoxy groups derived from di- or higher-functional aromatic epoxy resins to the total number E2 of epoxy groups derived from monoepoxy compounds is 0.04 or more and 0.25 or less.

[0023] As a result of extensive investigations, the present inventors discovered that a resin exhibiting sufficient compressive strength and excellent compressive elongation can be obtained when the composition contains, in addition to a bifunctional or higher aromatic epoxy resin (component A) and a specific proportion of a monoepoxy compound (component B), a first amine-based curing agent (component C) that is a solid by itself at 25° C., a second amine-based curing agent (component D) that is a liquid by itself at 25° C., and an accelerator (component E), and thus arrived at the present invention. The epoxy resin composition according to the present invention is particularly excellent in storage stability (pot life) and impregnation into reinforcing fibers.

[0024] Although there is no intention to be limited by theory, it is believed that by adopting such a component composition, the crosslink density during curing treatment is optimized, and as a result, a resin that shows sufficient compressive strength and very excellent compressive elongation is obtained. More specifically, it is believed that the presence of multiple curing agents (components C and D) with different reaction temperatures and molecular sizes in the system causes the molecular crosslink structure generated by the reaction to have a rough and dense structure, which appropriately distributes stress. Furthermore, it is believed that the monoepoxy compound contributes to achieving both elongation and strength by controlling the crosslink density and filling the free volume (gaps in the crosslinks) of the molecules present in the system. In particular, when an aliphatic epoxy with weak cohesive strength is used, it is believed that nanovoids are formed during deformation of the resin, dispersing stress, thereby achieving higher physical properties. Furthermore, it is believed that excellent effects can be obtained in terms of impregnation and pot life by using curing agents (components C and D) with different physical properties.

[0025] <Epoxy resin composition>

[0026] (ratio E2 / E1) In the epoxy resin composition according to the present disclosure, the ratio E2 / E1 of the total number E1 of epoxy groups derived from difunctional or higher aromatic epoxy resins to the total number E2 of epoxy groups derived from monoepoxy compounds is 0.04 or more and 0.25 or less. Without intending to be limited by theory, it is believed that by having the ratio E2 / E1 of difunctional or higher aromatic epoxy resins to monoepoxy compounds in the epoxy resin composition in this range, it is possible to achieve both high levels of compressive elongation and compressive strength.

[0027] The above ratio E2 / E1 may be 0.05 or more, 0.06 or more, or 0.07 or more, and / or 0.24 or less, 0.22 or less, 0.20 or less, or 0.18 or less.

[0028] The total number of epoxy groups is calculated as the sum of the epoxy groups of all epoxy components contained in the resin composition. i is the epoxy equivalent Eq (g / eq) of a specific epoxy component contained in the epoxy resin composition and the mass W of a specific epoxy component contained in the epoxy resin composition. i (g) can be calculated from (N i =W i / Eq). The epoxy equivalent is a value measured in accordance with JIS K7236.

[0029] (Component A: Difunctional or higher aromatic epoxy resin) The epoxy resin composition contains a di- or higher functional aromatic epoxy resin. The di- or higher functional aromatic epoxy resin is particularly a di-functional aromatic epoxy resin.

[0030] Examples of bifunctional epoxy resins include bisphenol type epoxy resins (e.g., bisphenol A type epoxy resins, bisphenol F type epoxy resins, and bisphenol S type epoxy resins), ethylene glycol diglycidyl ether type epoxy resins, neopentyl glycol diglycidyl ether type epoxy resins, 1,4-butanediol diglycidyl ether type epoxy resins, 1,6-hexanediol diglycidyl ether type epoxy resins, 1,7-heptanediol diglycidyl ether type epoxy resins, 1,8-octanediol diglycidyl ether type epoxy resins, cyclohexanedimethanol diglycidyl ether, polyethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether. These may be used alone or in combination of two or more.

[0031] Examples of aromatic epoxy resins having three or more functionalities include N,N,N',N'-tetraglycidyl diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-m-aminophenol, N,N,O-triglycidyl-3-methyl-4-aminophenol, triglycidyl aminocresol, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether type epoxy resin, diglycerol polyglycidyl ether, pentaerythritol tetraglycidyl ether type epoxy resin, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, etc. These may be used alone or in combination of two or more.

[0032] The di- or higher functional aromatic epoxy resin (component A) is particularly preferably a bisphenol A type epoxy resin.

[0033] The content of the di- or higher functional aromatic epoxy resin is preferably 60 to 95 mass %, more preferably 70 to 90 mass %, and particularly preferably 75 to 85 mass %, based on the total mass of the epoxy resin composition.

[0034] (Component B: monoepoxy compound) The epoxy resin composition includes a monoepoxy compound.

[0035] The monoepoxy compounds include aliphatic monoepoxy compounds and aromatic monoepoxy compounds.

[0036] The aliphatic monoepoxy compound is preferably at least one selected from butyl glycidyl ether, 2-ethylhexyl glycidyl ether, and glycidyl lauryl ether.

[0037] Aromatic monoepoxy compounds include styrene oxide, and phenyl glycidyl ether and combinations thereof.

[0038] The aliphatic monoepoxy compound and the aromatic monoepoxy compound may be appropriately combined or used according to the desired physical properties. In one preferred embodiment, the monoepoxy compound is an aliphatic monoepoxy compound. It is considered that the aliphatic monoepoxy compound is more advantageous than the aromatic monoepoxy compound in terms of elongation and impregnation. In particular, the advantages of the aliphatic monoepoxy compound include low viscosity and low surface energy, which can bring about more advantageous effects than aromatic compounds in terms of impregnation into the fiber substrate.

[0039] In another embodiment of the present disclosure, the monoepoxy compound is an aromatic monoepoxy compound. Aromatic monoepoxy compounds may be more advantageous than aliphatic monoepoxy compounds in terms of heat resistance, elastic modulus, and the like.

[0040] The content of the monoepoxy compound is preferably from 1 to 20 mass %, more preferably from 1.5 to 15 mass %, and particularly preferably from 2 to 10 mass %, based on the total mass of the epoxy resin composition.

[0041] (Component C: First amine-based curing agent) The epoxy resin composition includes a first amine-based curing agent. The first amine-based curing agent is a solid at 25°C by itself.

[0042] The first amine-based curing agent that is a solid by itself at 25° C. includes dicyandiamide and its derivatives, as well as imidazole derivatives and diaminodiphenyl sulfone.

[0043] The first amine-based curing agent is preferably at least one selected from dicyandiamide and its derivatives.

[0044] The content of the first amine-based curing agent is preferably 0.5 to 12 mass%, more preferably 1 to 8 mass%, particularly preferably 2 to 7 mass%, based on the total mass of the epoxy resin composition.

[0045] (Component D: Second amine-based hardener) The epoxy resin composition includes a second amine-based curing agent. The second amine-based curing agent is liquid at 25°C by itself.

[0046] Examples of the second amine-based curing agent that is liquid at 25° C. include diethyltoluenediamine and its derivatives, as well as isophoronediamine, metaphenylenediamine, diaminodiphenylmethane, bis(paraaminocyclohexyl)methane, 3,3′-dimethylenedi(cyclohexylamine), and norbornanediamine.

[0047] The second amine-based curing agent is preferably a compound having an aromatic ring. It is believed that using a compound having an aromatic ring as the second amine-based curing agent contributes to achieving both high strength and heat resistance.

[0048] The second amine-based curing agent is preferably at least one selected from diethyltoluenediamine and its derivatives.

[0049] The content of the second amine curing agent is preferably 2 to 20 mass %, more preferably 3 to 15 mass %, and particularly preferably 4 to 10 mass %, based on the total mass of the epoxy resin composition.

[0050] (ratio A2 / A1) In a preferred embodiment of the present disclosure, the ratio A2 / A1 of the total number A1 of active hydrogens derived from the first amine curing agent to the total number A2 of active hydrogens derived from the second amine curing agent is 0.20 or more and 1.50 or less.

[0051] The ratio A2 / A1 is more preferably 0.25 or more, 0.30 or more, 0.35 or more, 0.40 or more, 0.45 or more, or 0.50 or more, and / or 1.40 or less, 1.30 or less, or 1.20 or less.

[0052] By setting the ratio A2 / A1 within the above range, it is possible to obtain an optimal balance between handling properties and storage properties.

[0053] The smaller the ratio A2 / A1, the more excellent the storage stability of the composition can be. In one embodiment according to the present disclosure, the ratio A2 / A1 is 0.20 to 0.90, 0.25 to 0.70, 0.25 to 0.50, or even 0.30 to 0.40.

[0054] Moreover, the larger the ratio A2 / A1, the more excellent the impregnation property of the composition can be. In another embodiment according to the present disclosure, the ratio A2 / A1 is 0.40 to 1.50, or further 0.60 to 1.30.

[0055] Without intending to be limited by theory, it is believed that because the first amine-based hardener (corresponding to A1), which is solid at room temperature, has latent properties, compositions containing a large amount of this component have high storage stability. On the other hand, it is believed that the addition of the second amine-based hardener (corresponding to A2), which is liquid, reduces the viscosity of the resin and improves its ability to be impregnated into the fibers.

[0056] (H T / E T ) In the epoxy resin composition, the total number of epoxy groups derived from difunctional or higher aromatic epoxy resins and monoepoxy compounds (E T ) and the total number of active hydrogens derived from the first and second amine-based curing agents (H T ) compared to H T / E T is preferably less than 1.0, more preferably 0.4 or more and less than 1.0, and particularly preferably 0.5 to 0.9. T / E T is 0.65 to 0.85, or even 0.70 to 0.80. In this case, particularly good physical properties (particularly strength) may be obtained. T / E T When the value is relatively high, the physical properties (particularly strength) of the cured product obtained from the epoxy resin composition can be improved.

[0057] (Component E: Accelerator) The epoxy resin composition may contain an accelerator (curing accelerator).

[0058] The curing accelerator includes urea compounds, particularly aromatic urea compounds (aromatic urea compounds). Specific examples thereof include 3-(3,4-dichlorophenyl)-1,1-dimethylurea, 1,1'-(4-methyl-1,3-phenylene)bis(3,3-dimethylurea), N-phenyl-N',N'-dimethylurea, N-(4-chlorophenyl)-N',N'-dimethylurea, N-(3,4-dichlorophenyl)-N',N'-dimethylurea, N-(3-chloro-4-methylphenyl)-N',N'-dimethylurea, N-(3-chloro-4-ethylphenyl)-N',N'-dimethylurea, N-(3-chloro-4-methoxyphenyl)-N',N'-dimethylurea, N-(4-methyl-3-nitrophenyl)-N',N'-dimethylurea, 2,4-bis(N',N'-dimethylureido)toluene, and methylene-bis(p-N',N'-dimethylureidophenyl). Among these, 3-(3,4-dichlorophenyl)-1,1-dimethylurea and 1,1'-(4-methyl-1,3-phenylene)bis(3,3-dimethylurea) are preferred. These may be used alone or in combination of two or more.

[0059] The accelerator is particularly preferably at least one selected from 1,1'-(4-methyl-1,3-phenylene)bis(3,3-dimethylurea) and its derivatives.

[0060] The content of the accelerator in the epoxy resin composition is preferably 0.5 to 5 mass %, more preferably 1 to 4 mass %, and particularly preferably 1.5 to 3 mass %, based on the total mass of the epoxy resin composition.

[0061] (Other Ingredients) The epoxy resin composition according to the present disclosure may contain other components such as rubber-like particle compounds, thermoplastic resins, defoamers, leveling agents, flame retardants, flame retardant assistants, and pigments, within the scope of not impairing the effects of the present invention. The other components are preferably 10% by mass or less, 5% by mass or less, or even 1% by mass or less, based on the epoxy resin composition. Examples of rubber-like particle compounds include silicone rubber, butadiene rubber, styrene butadiene rubber, methyl methacrylate-butadiene-styrene rubber, butadiene nitrile rubber and modified products thereof, and core-shell type rubber. The rubber-like particle compounds may be used alone or in combination of two or more kinds.

[0062] (Content of each ingredient) In one embodiment according to the present disclosure, the epoxy resin composition contains each of components A to E in an amount within the following ranges relative to the total mass of the epoxy resin composition: (A) 60 to 95% by mass of difunctional or higher aromatic epoxy resin (B) 1 to 20 mass% of a monoepoxy compound (C) 0.5 to 12 mass% of a first amine-based curing agent (D) 2 to 20% by mass of a second amine-based curing agent (E) 0.5 to 5 mass % of an accelerator.

[0063] In a preferred embodiment according to the present disclosure, the epoxy resin composition contains each of the components A to E in an amount within the following ranges relative to the total mass of the epoxy resin composition: (A) 70 to 90% by mass of a difunctional or higher aromatic epoxy resin (B) 1.5 to 15 mass% of a monoepoxy compound (C) 1 to 8 mass% of a first amine-based curing agent (D) 3 to 15% by mass of a second amine-based curing agent (E) 1 to 4 mass % of an accelerator.

[0064] In a more preferred embodiment of the present disclosure, the epoxy resin composition contains each of the components A to E in an amount within the following ranges relative to the total mass of the epoxy resin composition: (A) 75 to 85% by mass of difunctional or higher aromatic epoxy resin (B) 2 to 10 mass% of a monoepoxy compound (C) 2 to 7 mass% of a first amine-based curing agent (D) 4 to 10% by mass of a second amine-based curing agent (E) 1.5 to 3 mass % of an accelerator.

[0065] (Production of Epoxy Resin Composition) The method for obtaining the epoxy resin composition is not particularly limited, and the composition can be produced by a known method. The epoxy resin composition can be obtained, for example, by uniformly kneading the above-mentioned components A to E and, if necessary, other components in a predetermined content.

[0066] As the kneading device, for example, a planetary mixer, a three-roll mill, a universal mixer, a homogenizer, a homodispenser, a ball mill, a bead mill, an extruder, a heating roll, a kneader, a roller mixer, a Banbury mixer, etc. can be used.

[0067] (Compressive strength and elongation) Preferably, the epoxy resin composition according to the present disclosure exhibits a compressive strength of 270 MPa or more and a compressive elongation of 50% or more when a sample cured at 130°C for 1 hour is cut into a sample measuring 10 mm x 10 mm x 4 mm and measured in accordance with JIS 7181.

[0068] <Prepreg> The present disclosure also encompasses a prepreg. The prepreg comprises a reinforcing fiber and an epoxy resin composition according to the present disclosure. In particular, the prepreg comprises a reinforcing fiber and an epoxy resin composition according to the present disclosure impregnated into the reinforcing fiber. The prepreg is in particular a prepreg for a pressure vessel, in particular a tow prepreg.

[0069] The method for producing the prepreg (particularly the tow prepreg) is not particularly limited. For example, the prepreg (particularly the tow prepreg) can be produced by impregnating reinforcing fibers with the epoxy resin composition having the properties according to the present invention.

[0070] One embodiment of the method for producing the prepreg according to the present invention comprises the steps of: Providing reinforcing fibers and an epoxy resin composition according to the present disclosure; and Impregnating reinforcing fibers with the epoxy resin composition according to the present disclosure. Includes.

[0071] The method of impregnating the reinforcing fiber with the epoxy resin composition is not particularly limited. For example, there may be mentioned a method of immersing the reinforcing fiber in a solution containing the epoxy resin composition and then removing the solvent, a method of impregnating the reinforcing fiber with an epoxy resin composition whose viscosity has been reduced by heating, and a method of overlapping a layer of the reinforcing fiber with a film-like epoxy resin composition and heating and pressurizing the layer to impregnate the reinforcing fiber.

[0072] The fiber volume content of the reinforcing fibers in the prepreg may be 45 to 80% by volume relative to the entire prepreg, and may be 50% by volume or more, 55% by volume or more, 60% by volume or more, or 65% by volume or more, and / or 75% by volume or less, or 70% by volume or less.

[0073] <Tow prepreg> The tow prepreg may include a reinforcing fiber bundle and an epoxy resin composition. The reinforcing fiber bundle may have a configuration in which reinforcing fiber filaments are aligned in one direction. The tow prepreg may be produced by a known method.

[0074] <Reinforced fiber> The form of the reinforcing fibers that can be used in the prepreg (particularly the tow prepreg) and the manufacturing method thereof is not particularly limited, but may be in the form of a bundle of reinforcing fiber filaments (so-called "tow") or in the form of a sheet, particularly in the form of a sheet in which reinforcing fiber bundles are aligned in one direction. The reinforcing fibers may be in the form of a fabric, such as a plain weave, twill weave, or satin weave.

[0075] Examples of reinforcing fibers include glass fibers, aramid fibers, carbon fibers, boron fibers, alumina fibers, and silicon carbide fibers.

[0076] The reinforcing fibers are particularly carbon fibers, and examples of the carbon fibers include polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, and rayon-based carbon fibers.

[0077] <Carbon fiber> In order to obtain high composite material properties, the carbon fiber preferably has a strand tensile strength of 4000 MPa or more, a strand tensile modulus of elasticity of 200 GPa or more and 400 GPa or less, and a filament number of 6000 to 75000. More preferred ranges are a strand tensile strength of 5000 MPa or more, a strand tensile modulus of elasticity of 225 GPa or more and 400 GPa or less, and a filament number of 12000 to 60000. By setting the modulus to 225 GPa or more, the rigidity of the composite material can be ensured, and by setting it to 400 GPa or less, the properties of the composite material in the non-fiber direction can be maintained well. From this viewpoint, the carbon fiber is preferably polyacrylonitrile-based.

[0078] The single fiber diameter of the reinforcing fiber (diameter of a single fiber) is not particularly limited, but may be, for example, 10 μm or less. Preferably, the reinforcing fiber has a single fiber diameter of less than 8.0 μm. The lower limit of the single fiber diameter may be, for example, 1.0 μm. The diameter of the reinforcing fiber can be obtained by averaging the diameters of 30 or more reinforcing fibers measured using images obtained using an electron microscope or the like.

[0079] <Fiber-reinforced composite materials> By subjecting the prepreg according to the present disclosure to a heat curing treatment, a fiber reinforced composite material, in particular a molded article having a fiber reinforced composite material, can be produced. More specifically, a molded article of a fiber reinforced composite material can be obtained by optionally laminating the prepreg or optionally wrapping it around a substrate and then heat curing the prepreg. The fiber reinforced composite material is in particular a carbon fiber reinforced composite material.

[0080] (Pressure vessel manufacturing method) For example, a pressure vessel can be manufactured by winding the tow prepreg according to the present disclosure around a substrate to form an intermediate body, and then subjecting the intermediate body to a heat curing treatment. The pressure vessel has a structure in which a liner as an inner shell is covered with a layer of a fiber-reinforced composite material.

[0081] A method for manufacturing a pressure vessel according to the present disclosure includes: Winding a tow prepreg according to the present disclosure around a substrate to form an intermediate body; and This intermediate is subjected to a heat curing treatment. Includes.

[0082] The substrate may be made of metal or resin. The substrate is preferably a liner (or core) made of metal or resin.

[0083] The temperature of the heat curing treatment is preferably 80° C. to 250° C., more preferably 110° C. to 200° C., and further preferably 120° C. to 150° C. The time of the heat curing treatment may be 30 minutes to 30 hours, and may also be 10 to 20 hours.

[0084] The fiber volume content of the reinforcing fibers in the fiber reinforced composite material may be 45 to 80 volume % relative to the entire fiber reinforced composite material, and this volume content may be 50 volume % or more, 55 volume % or more, 60 volume % or more, or 65 volume % or more, and / or 75 volume % or less, or 70 volume % or less. EXAMPLES

[0085] The present invention will now be described in more detail with reference to the following examples, which are not intended to limit the present application.

[0086] <<Measurement and evaluation methods>> In the examples and comparative examples, physical properties were measured and evaluated as follows.

[0087] <Fracture energy, upper yield point, compressive strength, compressive elongation> Regarding the epoxy resin composition, the fracture energy, upper yield point, compressive strength, and compressive elongation were measured by carrying out a compression test in accordance with the test standard JIS7181.

[0088] The test specimens (resin test specimens) used in the compression tests had dimensions of 10 mm×10 mm×4 mm, and were prepared by curing the target resin compositions at 130° C. for 1 hour.

[0089] <tg> The Tg(on-set) of the epoxy resin composition was measured by the DMA method (dynamic viscoelasticity measurement) in accordance with the test standard ASTM D7028-07.

[0090] <Elastic modulus in rubber-like plateau> The elastic modulus of the rubber-like plateau of the epoxy resin composition was determined as the storage elastic modulus value at the glass transition temperature + 50°C obtained by the DMA method (dynamic viscoelasticity measurement).

[0091] <Improved elongation> The improvement in elongation of the epoxy resin composition is shown in the following compression test: If the compression elongation was 52% or more, it was marked as "◎"; If the compression elongation was 50% or more but less than 52%, it was marked as "Good"; If the compression elongation was 48% or more but less than 50%, it was marked as "△"; If the compression elongation is less than 48%, it is marked as "X". It was evaluated as follows. <Fiber impregnation> The impregnation of the epoxy resin composition into the fiber is evaluated by determining whether the appearance of the carbon fiber in contact with the touch roll having the resin composition film attached thereto during the resin impregnation step in the towpreg manufacturing process is as follows: If it was evenly wet, we marked it with "◎"; If it is wet but has spots, mark it as "○"; If there are unevenly distributed non-wet areas, the rating is "△"; If there are always areas that are not wet, mark them as "X". It was evaluated as follows. <Resin life> The pot life of an epoxy resin composition is the period from when the resin composition is prepared to when it is left to stand at 25°C for a certain period of time until the resin loses its fluidity. If it is more than two weeks, mark it with "◎" If it is more than one week but less than two weeks, mark it as "〇"; If it was more than 3 days but less than 1 week, it was marked as "△"; If it was less than 3 days, mark it as "X". It was evaluated as follows. <tg> The Tg of the epoxy resin composition was measured by DMA. If Tg was 110℃ or higher, it was marked as "◎"; If Tg was 100°C or higher and less than 110°C, it was marked as "Good." If Tg was 90°C or higher but less than 100°C, it was marked as "△"; If the Tg was less than 90°C, it was marked as "X". It was evaluated as follows.

[0092] <<Materials>> In the examples and comparative examples, the following materials were used.

[0093] <Epoxy resin composition> (Difunctional or higher aromatic epoxy resin) Component A: Bisphenol A epoxy resin (Mitsubishi Chemical Corporation, JER828)

[0094] (Aliphatic monoepoxy compounds) Component B (B-1): Butyl glycidyl ether (manufactured by Yokkaichi Chemical Co., Ltd., product name DY-BP) Component B (B-2): 2-ethylhexyl glycidyl ether (manufactured by Yokkaichi Chemical Co., Ltd., product name Epogose 2EH) B component (B-3): Lauryl glycidyl ether (manufactured by Yokkaichi Chemical Co., Ltd., product name Epogoce LA)

[0095] (Aromatic monoepoxy compounds) B component (B-4): Styrene oxide (Tokyo Chemical Industry Co., Ltd., product number E0013) B component (B-5): Phenyl glycidyl ether (Tokyo Chemical Industry Co., Ltd., product number G0098)

[0096] (Amine-based curing agent that is solid at 25℃) Component C: DICY (dicyandiamide, Mitsubishi Chemical Corporation, Dicy7, active hydrogen equivalent 21 g / eq)

[0097] (Amine-based curing agent that is liquid at 25℃) D component: DETDA (diethyltoluenediamine, Kumiai Chemical Co., Ltd. Heartcure 10, active hydrogen equivalent 44.5 g / eq)

[0098] (Component E: Accelerator) TDU: 1,1'-(4-methyl-1,3-phenylene)bis(3,3-dimethylurea) (PTI Japan, Omicure 24)

[0099] <<Examples 1 to 12 and Comparative Examples 1 to 16>> In Examples 1 to 12 and Comparative Examples 1 to 16, epoxy resin compositions were produced and their physical properties were evaluated.

[0100] <Examples 1 to 5> In Examples 1 to 5, epoxy resin compositions were produced with various compositions shown in Table 1 below. Specifically, after mixing components A and B, components C and E were added and stirred until homogenous, and component D was added. The mixture was heated in an oven at 130°C for 1 hour to produce an epoxy resin composition. In Examples 1 to 5, butyl glycidyl ether was used as the monoepoxy compound.

[0101] The physical properties of the resulting epoxy resin composition were measured and evaluated as described above. The evaluation results are shown in Table 1 below.

[0102] <Examples 6 to 7> In Examples 6 and 7, epoxy resin compositions were produced and their physical properties were evaluated in the same manner as in Example 2, except that 2-ethylhexyl glycidyl ether was used as the monoepoxy compound. The results are shown in Table 1 below.

[0103] <Example 8> In Example 8, an epoxy resin composition was produced and its physical properties were evaluated in the same manner as in Example 2, except that lauryl glycidyl ether was used as the monoepoxy compound. The results are shown in Table 1 below.

[0104] <Example 9> In Example 9, an epoxy resin composition was produced and its physical properties were evaluated in the same manner as in Example 2, except that styrene oxide was used as the monoepoxy compound. The results are shown in Table 1 below.

[0105] <Examples 10 to 11> In Examples 10 and 11, epoxy resin compositions were produced and their physical properties were evaluated in the same manner as in Example 2, except that phenyl glycidyl ether was used as the monoepoxy compound. The results are shown in Table 1 below.

[0106] <Example 12> In Example 12, an epoxy resin composition was produced and its physical properties were evaluated in the same manner as in Example 5, except that the amount of component D was changed. The results are shown in Table 1 below.

[0107] [Table 1]

[0108] As shown in Table 1, the epoxy resin compositions according to Examples 1 to 12, which contain a bifunctional or higher aromatic epoxy resin (component A), a monoepoxy compound (component B), a first amine-based curing agent (component C) that is a solid by itself at 25°C, a second amine-based curing agent (component D) that is a liquid by itself at 25°C, and an accelerator (component E), and in which the ratio E2 / E1 of the total number E1 of epoxy groups derived from the bifunctional or higher aromatic epoxy resin (component A) to the total number E2 of epoxy groups derived from the monoepoxy compound (component B) is 0.053 to 0.169, have sufficient compressive strength, resin impregnation, and pot life, and also exhibit excellent compressive elongation. Such properties are particularly useful in applications under high pressure, particularly in applications where they are used for pressure vessels.

[0109] <Comparative Example 1> In Comparative Example 1, the production of an epoxy resin composition and the evaluation of its physical properties were carried out in the same manner as in Example 2, except that the content of butyl glycidyl ether as component B was changed. The results are shown in Table 2 below.

[0110] <Comparative Example 2> In Comparative Example 2, the epoxy resin composition was produced and its physical properties were evaluated in the same manner as in Example 2, except that the epoxy resin composition did not contain component B. The results are shown in Table 2 below.

[0111] <Comparative Example 3> In Comparative Example 3, except that the content of the curing agent was changed, the epoxy resin composition was produced and its physical properties were evaluated in the same manner as in Comparative Example 2. The results are shown in Table 2 below.

[0112] <Comparative Example 4> In Comparative Example 4, except that the contents of the curing agent and the accelerator were changed, the epoxy resin composition was produced and its physical properties were evaluated in the same manner as in Comparative Example 2. The results are shown in Table 2 below.

[0113] <Comparative Example 5> In Comparative Example 5, except that the contents of the curing agent and the accelerator were changed, the epoxy resin composition was produced and its physical properties were evaluated in the same manner as in Comparative Example 2. The results are shown in Table 2 below.

[0114] <Comparative Examples 6 to 7> In Comparative Examples 6 to 7, except that the curing agent DETDA (component D) was not used, the epoxy resin compositions were produced and their physical properties were evaluated in the same manner as in Comparative Examples 3 and 4. The results are shown in Table 2 below.

[0115] <Comparative Example 8> In Comparative Example 8, except that the curing agent DETDA (component D) was not used, the epoxy resin composition was produced and its physical properties were evaluated in the same manner as in Comparative Example 5. The results are shown in Table 2 below.

[0116] <Comparative Example 9> In Comparative Example 9, except that the amount of the accelerator was changed, the epoxy resin composition was produced and its physical properties were evaluated in the same manner as in Comparative Example 8. The results are shown in Table 2 below.

[0117] <Comparative Examples 10 to 11> In Comparative Examples 10 to 11, except that the amount of the curing agent DICY (component C) was changed, the epoxy resin compositions were produced and their physical properties were evaluated in the same manner as in Comparative Examples 8 to 9. The results are shown in Table 2 below.

[0118] <Comparative Example 12> In Comparative Example 12, except that the curing agent DETDA (component D) was not used, the epoxy resin composition was produced and its physical properties were evaluated in the same manner as in Example 3. The results are shown in Table 2 below.

[0119] <Comparative Example 13> In Comparative Example 13, except that the curing agent DETDA (component D) was not used, the production of an epoxy resin composition and the evaluation of its physical properties were carried out in the same manner as in Example 6. The results are shown in Table 2 below.

[0120] <Comparative Examples 14 to 15> In Comparative Examples 14 and 15, the epoxy resin compositions were produced and their properties evaluated in the same manner as in Example 3, except that the curing agent DICY (component C) and accelerator (component E) were not used and the content of the curing agent DETDA (component D) was changed. The results are shown in Table 2 below. In Comparative Example 15, in which the content of DETDA (component D) was 18.00 parts by weight, the curing reaction of the resin composition did not proceed sufficiently (poor curing), so a compression test could not be performed.

[0121] <Comparative Example 16> In Comparative Example 16, the epoxy resin composition was produced and its physical properties were evaluated in the same manner as in Comparative Example 14, except that the monoepoxy compound (component B) was not used and the amount of DETDA was changed. The results are shown in Table 2 below.

[0122] [Table 2]

[0123] The epoxy resin composition according to Comparative Example 1 contained components A to E, but had a relatively low ratio E2 / E1 of the total number E1 of epoxy groups derived from the difunctional or higher aromatic epoxy resin (component A) to the total number E2 of epoxy groups derived from the monoepoxy compound (component B), which was 0.029. The epoxy resin compositions according to Comparative Examples 2 to 16 lacked at least one of components A to E.

[0124] As seen in Table 2, Comparative Example 1, which contained a small amount of component B, Comparative Examples 2 to 5, which contained no component B, Comparative Examples 6 to 11, which contained no component B or curing agent component D, and Comparative Examples 12 to 13, which contained no curing agent component D, showed relatively low compressive elongation. Comparative Examples 5 to 13 also showed poor results in terms of impregnation.

[0125] In addition, Comparative Examples 14 to 15 lacking the C and E components, and Comparative Example 16 lacking the B, C and E components, showed relatively high compressive elongation, but were relatively poor in terms of pot life. The pot life (storage stability) of an epoxy resin composition can be an important performance when used in prepreg applications, for example. Comparative Examples 14 to 15 also showed poor results in terms of heat resistance (Tg). In Comparative Example 15, as described above, curing could not be performed well.< / tg> < / tg>

Claims

1. The following ingredients: (A) Difunctional or higher aromatic epoxy resin (B) Monoepoxy compound (C) a first amine-based curing agent that is a solid by itself at 25°C (D) A second amine-based curing agent that is liquid by itself at 25°C. (E) Accelerator An epoxy resin composition comprising: a ratio E2 / E1 of a total number E1 of epoxy groups derived from the difunctional or higher aromatic epoxy resin to a total number E2 of epoxy groups derived from the monoepoxy compound is 0.04 or more and 0.25 or less; Epoxy resin composition.

2. 2. The epoxy resin composition according to claim 1, wherein a ratio A2 / A1 of a total number A1 of active hydrogens derived from the first amine curing agent to a total number A2 of active hydrogens derived from the second amine curing agent is 0.20 or more and 1.50 or less.

3. 3. The epoxy resin composition according to claim 1, wherein the monoepoxy compound is an aliphatic monoepoxy compound and / or an aromatic monoepoxy compound.

4. The epoxy resin composition according to claim 3 , wherein the monoepoxy compound is an aliphatic monoepoxy compound.

5. 4. The epoxy resin composition according to claim 3, wherein the aliphatic monoepoxy compound is at least one selected from butyl glycidyl ether, 2-ethylhexyl glycidyl ether, and glycidyl lauryl ether.

6. 4. The epoxy resin composition according to claim 3, wherein the aromatic monoepoxy compound is at least one selected from styrene oxide and phenyl glycidyl ether.

7. 3. The epoxy resin composition according to claim 1, wherein the first amine-based curing agent is at least one selected from the group consisting of dicyandiamide and derivatives thereof.

8. 3. The epoxy resin composition according to claim 1, wherein the second amine-based curing agent is a compound having an aromatic ring.

9. 3. The epoxy resin composition according to claim 1, wherein the second amine-based curing agent is at least one selected from diethyltoluenediamine and its derivatives.

10. 3. The epoxy resin composition according to claim 1, wherein the accelerator is at least one selected from 1,1'-(4-methyl-1,3-phenylene)bis(3,3-dimethylurea) and its derivatives.

11. 3. The epoxy resin composition according to claim 1, wherein the di- or higher functional aromatic epoxy resin is a bisphenol A type epoxy resin.

12. A prepreg comprising reinforcing fibers and the epoxy resin composition according to claim 1 or 2 impregnated into the reinforcing fibers.

13. 13. The prepreg according to claim 12 for a pressure vessel.

14. The prepreg of claim 12, wherein the reinforcing fibers are carbon fibers.

15. 13. Winding the prepreg according to claim 12, which is a tow prepreg, around a substrate to form an intermediate body; and heat-curing the intermediate body; Including, A method for manufacturing a pressure vessel.

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