Method for manufacturing epoxy resin compositions, prepregs, and pressure vessels

Abstract

The purpose of this disclosure is to provide an epoxy resin composition that exhibits sufficient tensile strength and improved storage stability. [Solution] The epoxy resin composition of the present disclosure comprises the following components: (A) a bifunctional or more aromatic epoxy resin, (B) a monoepoxy compound, (C) a first amine-based curing agent that is solid on its own at 25°C, (D) a second amine-based curing agent that is liquid on its own at 25°C, and (E) an accelerator, wherein the second amine-based curing agent is a compound represented by the following formula (1): JPEG2026139484000025.jpg2190In formula, R is hydrogen, chlorine, bromine, an alkyl group having 1 to 4 carbon atoms, and / or an alkylsulfanyl group having 1 to 4 carbon atoms. One or more of the Rs are alkyl groups having 1 to 4 carbon atoms, and One or more of the R groups are chlorine, bromine, and / or alkylsulfanil groups having 1 to 4 carbon atoms.

Description

[Technical Field]

[0001] This disclosure relates to epoxy resin compositions, prepregs, and methods for manufacturing pressure vessels. [Background technology]

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

[0003] A pressure vessel is a container designed to store gases or liquids 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 purposes such as on-board use and hydrogen refueling stations has been progressing.

[0004] A pressure vessel may have, for example, an inner frame (liner) made of metal or resin, and an outer layer made of carbon fiber reinforced polymer (CFRP).

[0005] Methods for manufacturing such pressure vessels include, in addition to wrapping carbon fibers around a liner while attaching resin to them, wrapping carbon fibers (especially tow prepreg) with resin already attached around a liner and then performing a heat-curing treatment.

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

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

[0008] Patent Document 3 discloses a tow prepreg obtained by impregnating a reinforcing fiber bundle with a specific epoxy resin composition. This epoxy resin composition comprises an epoxy resin that does not have a hydroxyl group in the chemical structure of its main component, a liquid aromatic amine, and a toughening agent. This tow prepreg is said to be suitably used in the manufacture of hollow containers and cylinders made of fiber-reinforced composite materials.

[0009] The invention described in Patent Document 4 aims to provide a method for curing an epoxy resin composition for fiber-reinforced composite materials, particularly suitable for the filament winding method. This document describes a fiber-reinforced composite material comprising an epoxy resin composition comprising 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 and the like, and states that the elastic modulus of the rubber state in the dynamic viscoelastic evaluation of the cured product obtained by curing this epoxy resin composition is 10 MPa or less. It also describes adding a specific phenylglycidyl ether to the epoxy resin composition, and states that this results in a fiber-reinforced composite material with an appropriate curing speed and excellent tensile strength utilization rate. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] International Publication No. 2020 / 250957 [Patent Document 2] Japanese Patent Publication No. 2021-161242 [Patent Document 3] Japanese Patent Publication No. 2021-116403 [Patent Document 4] Japanese Patent Publication No. 2021-161239 [Patent Document 5] Japanese Patent Publication No. 2017-119861 [Overview of the project] [Problems that the invention aims to solve]

[0012] As mentioned above, the requirements for pressure vessels have become more stringent in recent years, with demands for larger sizes and further improvements in pressure resistance.

[0013] In pressure vessels, the tensile strength of the fiber-reinforced composite material (e.g., carbon fiber-reinforced composite material) used in the pressure vessel is important from the perspective of withstanding the pressure (expansion pressure) applied from inside the vessel. Improving the tensile strength of the fiber-reinforced composite material makes it possible to store more gas in the pressure vessel and also reduces the amount of composite material required to store a certain amount of gas.

[0014] Fiber-reinforced composite materials manufactured using conventional prepregs (particularly tow prepregs) sometimes lacked sufficient mechanical properties (especially pressure resistance). In particular, when fiber-reinforced composite materials manufactured from conventional tow prepregs were used in pressure vessels, they sometimes failed to meet the high requirements for pressure vessels (especially for larger sizes and improved pressure resistance).

[0015] Here, it is considered that the resin constituting the fiber-reinforced composite material needs to have relatively high strength in order to prevent fracture even under high stress, and also needs to have high fracture strain (elongation) in order to suppress the expansion of fracture due to localized stress concentration.

[0016] Accordingly, various studies have been conducted on conventional epoxy resin compositions to achieve sufficient strength along with excellent fracture strain (elongation), but it has been difficult to provide an epoxy resin composition that has excellent fracture strength and good storage stability. Specifically, conventional epoxy resin compositions have high resin reactivity, and their viscosity and strength may change when used over a long period of time.

[0017] Accordingly, an object of the present disclosure is to provide an epoxy resin composition that exhibits sufficient fracture strength and improved storage stability.

Means for Solving the Problem

[0018] The present disclosure achieves the above object by the following means. (Aspect 1) The following components: (A) an aromatic epoxy resin having two or more functional groups, (B) a monoepoxy compound, (C) a first amine-based curing agent that is solid alone at 25°C, (D) a second amine-based curing agent that is liquid alone at 25°C, and (E) an accelerator An epoxy resin composition comprising, the second amine-based curing agent is a compound represented by the following formula (1):

Chemical Formula

[0019] The epoxy resin composition of this disclosure provides an epoxy resin composition that exhibits sufficient tensile strength and improved storage stability. [Modes for carrying out the invention]

[0020] The embodiments of this disclosure will be described in detail below. However, this disclosure is not limited to the embodiments described below, and can be implemented in various ways within the scope of the gist of this disclosure. Furthermore, in the description of the drawings, the same elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0021] ≪Epoxy resin composition≫ The epoxy resin composition disclosed herein comprises the following components: (A) Aromatic epoxy resins with two or more functionalities, (B) Monoepoxy compounds, (C) A first amine-based curing agent that is solid in its elemental form at 25°C. (D) A second amine-based curing agent that is liquid on its own at 25°C, and (E) Accelerator An epoxy resin composition comprising, The second amine-based curing agent is the compound shown in formula (1) below: [ka] During the ceremony, R is hydrogen, chlorine, bromine, an alkyl group having 1 to 4 carbon atoms, and / or an alkylsulfanyl group having 1 to 4 carbon atoms. One or more of the Rs are alkyl groups having 1 to 4 carbon atoms, and One or more of the R groups are chlorine, bromine, and / or alkylsulfanil groups having 1 to 4 carbon atoms.

[0022] The above epoxy resin composition provides an epoxy resin composition that exhibits sufficient breaking strength and improved storage stability.

[0023] According to this disclosure, the second amine-based curing agent contains chlorine, bromine, and / or an alkylsulfanil group having 1 to 4 carbon atoms in its structure. The curing agent contains chlorine, bromine, and / or sulfur, which can improve the storage stability of the resin.

[0024] (Component A: Bifunctional or higher aromatic epoxy resin) The epoxy resin composition of this disclosure comprises a bifunctional or more aromatic epoxy resin. The bifunctional or more aromatic epoxy resin is, in particular, a bifunctional aromatic epoxy resin.

[0025] Examples of bifunctional epoxy resins include bisphenol-type epoxy resins (e.g., bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, bisphenol S-type epoxy resin), ethylene glycol diglycidyl ether-type epoxy resin, neopentyl glycol diglycidyl ether-type epoxy resin, 1,4-butanediol diglycidyl ether-type epoxy resin, 1,6-hexanediol diglycidyl ether-type epoxy resin, 1,7-heptanediol diglycidyl ether-type epoxy resin, 1,8-octanediol diglycidyl ether-type epoxy resin, cyclohexanedimethanol diglycidyl ether, polyethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether. These may be used individually or in combination of two or more types.

[0026] Examples of aromatic epoxy resins with three or more functionalities include N,N,N',N'-tetraglycidyldiaminodiphenylmethane, N,N,N',N'-tetraglycidyl-m-xylenediamine, N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-m-aminophenol, N,N,O-triglycidyl-3-methyl-4-aminophenol, triglycidylaminocresol, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether type epoxy resin, diglycerol polyglycidyl ether, pentaerythritol tetraglycidyl ether type epoxy resin, sorbitol polyglycidyl ether, and polyglycerol polyglycidyl ether. These may be used individually or in combination of two or more.

[0027] The bifunctional or more aromatic epoxy resin (component A) is particularly preferably a bisphenol A type epoxy resin.

[0028] The content of bifunctional or more aromatic epoxy resins is preferably 60 to 95% by mass, more preferably 70 to 90% by mass, and particularly preferably 75 to 85% by mass, based on the total mass of the epoxy resin composition.

[0029] (Component B: Monoepoxy compound) The epoxy resin composition of this disclosure comprises a monoepoxy compound.

[0030] Examples of monoepoxy compounds include aliphatic monoepoxy compounds and aromatic monoepoxy compounds.

[0031] The aliphatic monoepoxy compound is preferably at least one selected from butyl glycidyl ether, 2-ethylhexyl glycidyl ether, and glycidyl lauryl ether.

[0032] Aromatic monoepoxy compounds include styrene oxide, phenyl glycidyl ether, and combinations thereof.

[0033] Aliphatic monoepoxy compounds and aromatic monoepoxy compounds may be combined or used separately as appropriate to suit the desired physical properties. In one preferred embodiment, the monoepoxy compound is an aliphatic monoepoxy compound. Aliphatic monoepoxy compounds are considered more advantageous than aromatic monoepoxy compounds in terms of elongation and impregnation. In particular, advantages of aliphatic monoepoxy compounds include low viscosity and low surface energy, which can provide more favorable effects than aromatic compounds in terms of impregnation into fibrous substrates.

[0034] In another embodiment relating to this 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, etc.

[0035] The content of the monoepoxy compound is preferably 1 to 20% by mass, more preferably 1.5 to 15% by mass, and particularly preferably 2 to 10% by mass, based on the total mass of the epoxy resin composition.

[0036] (Component C: First amine-based curing agent) The epoxy resin composition of this disclosure comprises a first amine-based curing agent. The first amine-based curing agent is solid in its elemental form at 25°C.

[0037] Examples of first amine-based curing agents that are solid in their elemental form at 25°C include dicyandiamide and its derivatives, as well as imidazole derivatives and diaminodiphenyl sulfone.

[0038] The first amine-based curing agent is preferably at least one selected from dicyandiamide and its derivatives.

[0039] The content of the first amine-based curing agent is preferably 0.5 to 12% by mass, more preferably 1 to 8% by mass, and particularly preferably 2 to 7% by mass, based on the total mass of the epoxy resin composition.

[0040] (Component D: Second amine-based curing agent) The epoxy resin composition of this disclosure comprises a second amine-based curing agent. The second amine-based curing agent of this disclosure is a liquid on its own at 25°C and is a compound represented by the following formula (1): [ka] During the ceremony, R is hydrogen, chlorine, bromine, an alkyl group having 1 to 4 carbon atoms, and / or an alkylsulfanyl group having 1 to 4 carbon atoms. One or more of the Rs are alkyl groups having 1 to 4 carbon atoms, and One or more of the R groups are chlorine, bromine, and / or alkylsulfanil groups having 1 to 4 carbon atoms.

[0041] The second amine-based curing agent may be a compound represented by the following formula (2): [ka] During the ceremony, R′ is hydrogen, an alkyl group having 1 to 4 carbon atoms, and / or an alkylsulfanyl group having 1 to 4 carbon atoms. One or more of the R′ are alkyl groups having 1 to 4 carbon atoms, and One or more of the R′ groups are alkylsulfanil groups having 1 to 4 carbon atoms.

[0042] In this disclosure, the alkyl group having 1 to 4 carbon atoms is not particularly limited, but examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, an ethylene group, and the like.

[0043] In this disclosure, an alkylsulfanil group (also called an alkylthio group) having 1 to 4 carbon atoms refers to a functional group in which sulfur is directly bonded to an aromatic compound, and this sulfur is further bonded to an alkyl chain having 1 to 4 carbon atoms. In this disclosure, the alkyl chain included in the alkylsulfanil group having 1 to 4 carbon atoms is not particularly limited, but may be linear or branched.

[0044] When the second amine-based curing agent is a compound represented by formula (2) above, examples of the second amine-based curing agent include the compound represented by formula (2A) or formula (2B) below (Dimethyl thiotolene diamine (DMTDA)). [ka] [ka]

[0045] The second amine-based curing agent may be a compound represented by the following formula (3): [ka] During the ceremony, X is chlorine or bromine. R'' is hydrogen and / or an alkyl group having 1 to 4 carbon atoms, and One or more of the R'' are alkyl groups with 1 to 4 carbon atoms.

[0046] When the second amine-based curing agent is a compound represented by formula (3) above, examples of the second amine-based curing agent include the compound represented by formula (3A) or formula (3B) below (Chloro diethyl toluene diamine (CDETDA)). [ka] [ka]

[0047] The content of the second amine-based curing agent is preferably 2 to 20% by mass, more preferably 3 to 15% by mass, and particularly preferably 4 to 10% by mass, based on the total mass of the epoxy resin composition.

[0048] (Component E: Accelerator) The epoxy resin compositions of this disclosure may contain accelerators (curing accelerators).

[0049] Examples of curing accelerators include urea compounds, particularly aromatic urea compounds (aromatic urea compounds). Specific examples 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, methylene-bis(p-N',N'-dimethylureidophenyl), and others. Of 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 individually or in combination of two or more.

[0050] The accelerator is particularly preferably at least one selected from 1,1'-(4-methyl-1,3-phenylene)bis(3,3-dimethylurea) and its derivatives.

[0051] The amount of accelerator in the epoxy resin composition is preferably 0.5 to 5% by mass, more preferably 1 to 4% by mass, and particularly preferably 1.5 to 3% by mass, based on the total mass of the epoxy resin composition.

[0052] (Other ingredients) The epoxy resin compositions of this disclosure may contain other components such as rubbery particulate compounds, thermoplastic resins, defoamers, leveling agents, flame retardants, flame retardant aids, and pigments, to the extent that they do not impair the effects of this disclosure. The other components are preferably present in an amount of 15% by mass or less, 10% by mass or less, or even more preferably 5% by mass or less, relative to the epoxy resin composition. Examples of rubbery particulate compounds include silicone rubber, butadiene rubber, styrene-butadiene rubber, methyl methacrylate-butadiene-styrene rubber, butadiene nitrile rubber and its modifications, and core-shell rubber (CSR). The rubbery particulate compounds may be used individually or in combination of two or more. The above-mentioned rubbery particulate compounds may also be included as tougheners for forming the crosslinked structure of the epoxy resin composition.

[0053] (ratio E2 / E1) In the epoxy resin composition of this disclosure, the ratio E2 / E1 of the total number of epoxy groups E1 derived from the bifunctional or more aromatic epoxy resin to the total number of epoxy groups E2 derived from the monoepoxy compound may be 0.04 or more and 0.25 or less. Although there is no intention to limit it by theory, it is believed that having the ratio E2 / E1 of the bifunctional or more aromatic epoxy resin to the monoepoxy compound in the epoxy resin composition within this range makes it possible to achieve both compressive elongation and compressive strength at a high level.

[0054] The above ratio E2 / E1 may be 0.05 or greater, 0.06 or greater, or 0.07 or greater, and / or 0.24 or less, 0.22 or less, 0.20 or less, or 0.18 or less.

[0055] The total number of epoxy groups is calculated as the sum of the epoxy groups of all epoxy components contained in the resin composition. The number of epoxy groups Ni for each epoxy resin can be calculated from the epoxy equivalent Eq (g / eq) of a specific epoxy component contained in the epoxy resin composition and the mass Wi (g) of that specific epoxy component in the epoxy resin composition (Ni = Wi / Eq). The epoxy equivalent is a value measured in accordance with JIS K7236.

[0056] (ratio A2 / A1) In the epoxy resin composition of this disclosure, the ratio A2 / A1 of the total number of active hydrogens A1 derived from the first amine-based curing agent to the total number of active hydrogens A2 derived from the second amine-based curing agent may be 0.20 or more and 1.50 or less.

[0057] The ratio A2 / A1 is more preferably 0.25 or greater, 0.30 or greater, 0.35 or greater, 0.40 or greater, 0.45 or greater, or 0.50 or greater, and / or 1.40 or less, 1.30 or less, or 1.20 or less.

[0058] By keeping the ratio A2 / A1 within the above range, an optimal balance between handling and storage properties can be achieved.

[0059] A smaller A2 / A1 ratio can result in a composition with better storage stability. In one embodiment of the present disclosure, the A2 / A1 ratio is 0.20-0.90, 0.25-0.70, 0.25-0.50, or even 0.30-0.40.

[0060] Furthermore, a larger ratio of A2 / A1 can result in a composition with superior impregnation properties. In another embodiment of this disclosure, the ratio of A2 / A1 is 0.40 to 1.50, or even 0.60 to 1.30.

[0061] While there is no intention to limit the theory, the first amine-based curing agent (corresponding to A1), which is solid at room temperature, has latent properties, so a composition with a high concentration of this component is thought to have higher storage stability. On the other hand, adding the second amine-based curing agent (corresponding to A2), which is liquid, is thought to reduce the viscosity of the resin and improve its impregnation into fibers.

[0062] (H T / E T ) In an epoxy resin composition, the total number of epoxy groups derived from a bifunctional or more aromatic epoxy resin and a monoepoxy compound (E T ) and the total number of active hydrogens (H) derived from the first and second amine-based curing agents. Tratio with )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. In one embodiment according to the present disclosure, the ratio H T / E T is 0.65 to 0.85, or further 0.70 to 0.80. In this case, particularly good physical properties (especially strength) may be obtained. When the value of the ratio H T / E T is relatively high, the physical properties (especially strength) of a cured product obtained from the epoxy resin composition can be improved.

[0063] (Content of Each Component) In one aspect according to the present disclosure, components A to E are contained in the following content ranges, relative to the total mass of the epoxy resin composition: (A) 60 to 95% by mass of an aromatic epoxy resin having two or more functional groups, (B) 1 to 20% by mass of a monoepoxy compound, (C) 0.5 to 12% by mass of a first amine-based curing agent, (D) 2 to 20% by mass of a second amine-based curing agent, and (E) 0.5 to 5% by mass of an accelerator.

[0064] In a preferred aspect according to the present disclosure, components A to E are contained in the following content ranges, relative to the total mass of the epoxy resin composition: (A) 70 to 90% by mass of an aromatic epoxy resin having two or more functional groups, (B) 1.5 to 15% by mass of a monoepoxy compound, (C) 1 to 8% by mass of a first amine-based curing agent, (D) 3 to 15% by mass of a second amine-based curing agent, and (E) 1 to 4% by mass of an accelerator.

[0065] In a more preferred aspect according to the present disclosure, components A to E are contained in the following content ranges, relative to the total mass of the epoxy resin composition: (A) 75 to 85% by mass of an aromatic epoxy resin having two or more functional groups, (B) 2-10% by mass of monoepoxy compound, (C) 2-7% by mass of a first amine-based curing agent, (D) 4-10% by mass of a second amine-based curing agent, and (E) 1.5 to 3% by mass of an accelerator.

[0066] (Manufacturing of epoxy resin compositions) The method for producing the epoxy resin composition is not particularly limited, and the epoxy resin composition of this disclosure can be produced by known methods. The epoxy resin composition can be obtained, for example, by uniformly kneading the above components A to E and other components as needed in predetermined amounts.

[0067] For mixing, equipment such as planetary mixers, three-roll mixers, universal agitators, homogenizers, homodispensers, ball mills, bead mills, extruders, heated roll mixers, kneaders, roller mixers, and Banbury mixers can be used.

[0068] (Compressive strength and compressive elongation) Preferably, the epoxy resin composition according to this 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 10 mm × 10 mm × 4 mm pieces and measured according to JIS 7181.

[0069] Prepreg This disclosure also includes prepregs. The prepregs of this disclosure include reinforcing fibers and the epoxy resin composition according to this disclosure. In particular, the prepregs of this disclosure include reinforcing fibers and the epoxy resin composition according to this disclosure impregnated in the reinforcing fibers. The prepregs are, in particular, prepregs for pressure vessels, and in particular, tow prepregs.

[0070] The prepregs of this disclosure may be for use in pressure vessels.

[0071] The method for producing a prepreg (especially a tow prepreg) is not particularly limited. For example, a prepreg (especially a tow prepreg) can be produced by impregnating reinforcing fibers with an epoxy resin composition having the properties of the present disclosure.

[0072] One aspect of the method for manufacturing the prepreg relating to this disclosure is: To provide reinforcing fibers and epoxy resin compositions according to this disclosure, Impregnating the reinforcing fibers with the epoxy resin composition according to this disclosure Includes.

[0073] The method for impregnating reinforcing fibers with an epoxy resin composition is not particularly limited. For example, methods include immersing reinforcing fibers in a solution containing an epoxy resin composition and then removing the solvent, impregnating reinforcing fibers with an epoxy resin composition whose viscosity has been reduced by heating, and impregnating reinforcing fibers by layering a film-like epoxy resin composition onto layers of reinforcing fibers and then heating and pressurizing it.

[0074] The fiber volume content of reinforcing fibers in the prepreg may be 45 to 80 volume% of the total prepreg. 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.

[0075] <Touplipreg> The tow prepreg may include a reinforcing fiber bundle and an epoxy resin composition. The reinforcing fiber bundle may have a form in which reinforcing fiber filaments are aligned in one direction. The tow prepreg may be manufactured by known methods.

[0076] <Reinforced Fiber> The form of the reinforcing fibers that can be used in the prepreg (especially tow prepreg) and its manufacturing method is not particularly limited, but may be in the form of bundles of reinforcing fiber filaments (so-called "tow"), or in the form of a sheet, and in particular may be in the form of a sheet in which the reinforcing fiber bundles are aligned in one direction. The reinforcing fibers may also be in the form of a woven fabric, such as plain weave, twill weave, satin weave, etc.

[0077] Examples of reinforcing fibers include glass fibers, aramid fibers, carbon fibers, boron fibers, alumina fibers, and silicon carbide fibers.

[0078] The reinforcing fibers are, in particular, carbon fibers. Examples of carbon fibers include polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, and rayon-based carbon fibers.

[0079] (Carbon fiber) To obtain high composite material properties, the carbon fibers preferably have 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 count of 6000 to 75000. A more preferable range is 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 count of 12000 to 60000. By setting the modulus of elasticity 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 non-fiber direction of the composite material can be well maintained. From this viewpoint, the carbon fibers are preferably polyacrylonitrile-based.

[0080] The diameter of a single reinforcing 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 acquired with an electron microscope or the like.

[0081] ≪Method of manufacturing a pressure vessel≫ The method for manufacturing a pressure vessel as disclosed herein is The tow prepreg described in this disclosure, which is a prepreg, is wrapped around a substrate to form an intermediate, and The above intermediate is subjected to heat curing treatment. Includes.

[0082] For example, a pressure vessel can be manufactured by forming an intermediate by winding the tow prepreg according to this disclosure onto a substrate, and then thermosetting this intermediate. This pressure vessel has a structure in which, for example, the inner shell liner is covered with a layer of fiber-reinforced composite material.

[0083] The base material may be made of metal or resin. Preferably, the base material is a liner (or core material) made of metal or resin.

[0084] The temperature for the heat curing treatment is preferably 80°C to 250°C, more preferably 110°C to 200°C, and even more preferably 120°C to 150°C. The duration of the heat curing treatment may be 30 minutes to 30 hours, and even more preferably 10 to 20 hours.

[0085] The fiber volume content of reinforcing fibers in fiber-reinforced composite materials may be 45 to 80 volume percent of the total fiber-reinforced composite material. This volume content may be 50 volume percent or more, 55 volume percent or more, 60 volume percent or more, or 65 volume percent or more, and / or 75 volume percent or less, or 70 volume percent or less.

[0086] The present disclosure will be further described with reference to the following embodiments, but the scope of the present disclosure is not limited to these embodiments. [Examples]

[0087] ≪Measurement Methods and Evaluation Methods≫ In the examples and comparative examples, the physical properties were measured and evaluated as follows.

[0088] <Upper yield point, compressive strength, and compressive elongation> With respect to the epoxy resin composition, the upper yield point, compressive strength, and compressive elongation are values ​​measured by performing a compression test in accordance with the test standard JIS7181.

[0089] The test specimens (resin test specimens) used in the compression test had dimensions of 10 mm × 10 mm × 4 mm and were prepared by curing the target resin composition at 130°C for 1 hour.

[0090] <Viscosity> Regarding the epoxy resin composition, viscosity was measured using a NETCH Kinexus lab+ rheometer within 1 minute of preparation. For viscosity evaluation, the resin thickness between parallel plates with a diameter of 25 mm was set to 0.5 mm, and viscosity measurements were performed up to 150°C at a heating rate of 2°C / min under conditions of an angular velocity of 10 radians / second, obtaining the viscosity at 30°C and 50°C.

[0091] With respect to the epoxy resin composition of this disclosure, if the viscosity at 30°C is excessively high, it becomes difficult to remove the tow preg obtained by impregnating it with the epoxy resin composition from its wound state. If the viscosity at 30°C is excessively low, the tow preg may deform during use. Furthermore, with respect to the epoxy resin composition of this disclosure, if the viscosity at 50°C is excessively high, it is undesirable because it reduces the impregnation of the resin in the prepreg manufacturing process.

[0092] <Thickening ratio> Regarding epoxy resin compositions, the viscosity increase was measured when the epoxy resin composition, prepared within 1 minute, was subjected to viscosity measurement for 5 hours under isothermal holding conditions at 50°C. Viscosity measurements were performed using a NETCH Kinexus lab+ rheometer, with a resin thickness of 0.5 mm between parallel plates with a diameter of 25 mm, and an angular velocity of 10 radians / second. The viscosity increase ratio was calculated as the ratio of the viscosity of the epoxy resin composition after 5 hours at 50°C to the minimum viscosity obtained from the start of the measurement.

[0093] <Curing time> The curing time of the epoxy resin was measured using a NETCH DSC3500 Sirius. A 5 mg sample was sealed in a sealed aluminum pan, heated to 130°C at a rate of 100°C / min, and the time from the rise to the end of the exothermic peak while the pan was held isothermally was measured.

[0094] <Tension during the release of toupreg> The tension required to remove the tow preg wrapped around the container was evaluated as the tow preg unwinding tension. The tow preg unwinding tension was measured immediately after manufacturing, one week after manufacturing, and four weeks after manufacturing.

[0095] <Productivity of Toupreg> The productivity of Toupreg is determined by the viscosity increase of the resin after 5 hours at 50°C. If the value is 1.5 times or less, mark it as "〇". A multiplier of 1.5 to 2.0 is indicated by "△". If the value is greater than 2.0 times, mark it with "×". It was evaluated as such.

[0096] <Storage stability of Toupreg> Regarding the storage stability of toupreg, the release tension of toupreg is If the value four weeks after manufacturing is 6.0N or less, it is marked with "〇". If the value after one week from manufacturing is 6.0N or less, and the value after four weeks exceeds 6.0N, it is marked with "△". If the value one week after manufacturing exceeds 6.0N, mark it as "×". It was evaluated as such.

[0097] <Relief during filament winding (FW)> Regarding the release tension during fairway wood play, when the release tension of the toe preg immediately after manufacturing was measured using the above method, If the release tension is 4.5N or less, mark it as "〇". If the release tension is greater than 4.5N and less than or equal to 6.0N, it is marked with "△". If the release tension is greater than 6.0N, mark it with "×". It was evaluated as such.

[0098] <Process contamination in filament winding> Regarding process contamination in filament winding, when filament winding was performed using a tow prepreg, resin adhesion to rollers during the process was rated "○" when there was almost none, rated "△" when there was a slight amount of adhesion, and rated "×" when a large amount of adhesion was observed. Evaluation was performed according to the above criteria.

[0099] <Shape stability of tow prepreg> Regarding the shape stability of the tow prepreg, when filament winding was performed using the tow prepreg, the case where there was almost no twisting of the tow or width fluctuation was rated "○", the case where a slight amount of tow twisting and width fluctuation was observed was rated "△", and the case where a large amount of tow twisting and width fluctuation was observed was rated "×". Evaluation was performed according to the above criteria.

[0100] <Impregnability into fibers> The impregnability of the epoxy resin composition into fibers was evaluated based on the appearance of carbon fibers that came into contact with a touch roll to which a resin composition film had adhered, in the resin impregnation step of the tow prepreg manufacturing process, the case where the fibers were uniformly wetted was rated "◎", the case where the fibers were wetted but spots were present was rated "○", the case where non-wetted portions were unevenly distributed was rated "△", and the case where non-wetted portions were always present was rated "×". Evaluation was performed according to the above criteria.

[0101] <Curing time> The curing time of the epoxy resin composition was evaluated as follows: the case where the curing time was 1 hour or less was rated "○", the case where the curing time was 1 hour or more and 4 hours or less was rated "△", and the case where the curing time was 4 hours or more or curing did not occur was rated "×" Evaluation was performed according to the above criteria.

[0102] <<Materials>> The following materials were used in the examples and comparative examples.

[0103] <Epoxy resin composition> (Bifunctional or higher aromatic epoxy resin) Component A (A-1): Bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, JER828) Component A (A-2): Bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, JER834)

[0104] (Aliphatic monoepoxy compounds) Component B (B-1): Butyl glycidyl ether (manufactured by Yokkaichi Synthetic Co., Ltd., product name DYBP) Component B (B-2): 2-ethylhexyl glycidyl ether (manufactured by Yokkaichi Synthetic Co., Ltd., product name: Epogose 2EH)

[0105] (Aromatic monoepoxy compounds) Component B (B-3): Phenylglycidyl ether (manufactured by Tokyo Chemical Industry Co., Ltd., product number G0098)

[0106] (An amine-based curing agent that is solid in its elemental form at 25°C) Component C: DICY (dicyandiamide, manufactured by Mitsubishi Chemical Corporation, Dicy7, active hydrogen equivalent 21 g / eq)

[0107] (An amine-based curing agent that is liquid on its own at 25°C) Component D (D-1): DETDA (Diethyltoluenediamine, manufactured by Kumiai Chemical Co., Ltd., HeartCure 10, active hydrogen equivalent 44.5 g / eq) Component D (D-2): CDETDA (chlorodiethyltoluenediamine, manufactured by Arxada, P-25i) Component D (D-3): DMTDA (Dimethylthiotoluenediamine, manufactured by Kumiai Chemical Co., Ltd., HeartCure 30)

[0108] (Promoting agent) E component: TDU (1,1'-(4-methyl-1,3-phenylene)bis(3,3-dimethylurea), manufactured by PTI Japan Co., Ltd., Omicure 24)

[0109] (Tuffner (rubber-like particles)) CSR (Core-shell type rubber particles, manufactured by Kaneka Corporation, KaneAce® MX-154)

[0110] Examples 1-4 and Comparative Examples 1-5 In Examples 1-4 and Comparative Examples 1-5, epoxy resin compositions were prepared and their physical properties were evaluated.

[0111] <Examples 1-4> In Examples 1 to 4, epoxy resin compositions were prepared with various compositions shown in Table 1 below. Specifically, after mixing components A, B, and Tuffer, components C and E were added and stirred until homogeneous, and then component D was added and mixed. The mixture was then heated in an oven at 130°C for 1 hour to produce the epoxy resin composition.

[0112] The physical properties of the obtained epoxy resin composition were measured and evaluated as described above. The evaluation results are shown in Table 1 below.

[0113] [Table 1]

[0114] <Comparative Examples 1-5> In Comparative Examples 1 to 5, epoxy resin compositions were prepared using various compositions shown in Table 2 below. Specifically, after mixing components A, B, and Tuffer, components C and E were added and stirred until homogeneous, and then component D was added and mixed. The mixture was then heated in an oven at 130°C for 1 hour to produce the epoxy resin composition.

[0115] The physical properties of the obtained epoxy resin composition were measured and evaluated as described above. The evaluation results are shown in Table 2 below.

[0116] [Table 2]

[0117] Compared to Comparative Examples 1-5, which used D-1 as component D, Examples 1-4, which used D-2 or D-3 as component D, showed improved productivity and storage stability of the toupreg obtained using them. Furthermore, Examples 1-4 also showed improved, lower values ​​in terms of the change in toupreg tension at 4 weeks after manufacturing compared to the toupreg tension at thawing immediately after manufacturing. From this, it was possible to improve the storage stability of toupreg while maintaining its high strength by using CDETDA or DMTDA as the second amine-based curing agent.

Claims

1. The following ingredients: (A) Aromatic epoxy resin with two or more functions, (B) Monoepoxy compounds, (C) A first amine-based curing agent that is solid in its elemental form at 25°C. (D) A second amine-based curing agent that is liquid on its own at 25°C, and (E) Accelerator An epoxy resin composition comprising, The second amine-based curing agent is the compound shown in formula (1) below: 【Chemistry 1】 During the ceremony, R is hydrogen, chlorine, bromine, an alkyl group having 1 to 4 carbon atoms, and / or an alkylsulfanyl group having 1 to 4 carbon atoms. One or more of the Rs are alkyl groups having 1 to 4 carbon atoms, and One or more of R are chlorine, bromine, and / or alkylsulfanil groups having 1 to 4 carbon atoms. Epoxy resin composition.

2. The epoxy resin composition according to claim 1, wherein the second amine-based curing agent is a compound represented by the following formula (2): 【Chemistry 2】 During the ceremony, R' is hydrogen, an alkyl group having 1 to 4 carbon atoms, and / or an alkylsulfanil group having 1 to 4 carbon atoms. One or more of R' are alkyl groups having 1 to 4 carbon atoms, and One or more of the R' groups are alkylsulfanil groups having 1 to 4 carbon atoms.

3. The epoxy resin composition according to claim 2, wherein the second amine-based curing agent is a compound represented by the following formula (2A) or formula (2B). 【Transformation 3】 【Chemistry 4】

4. The epoxy resin composition according to claim 1, wherein the second amine-based curing agent is a compound represented by the following formula (3): 【Transformation 5】 During the ceremony, X is chlorine or bromine, R'' is hydrogen and / or an alkyl group having 1 to 4 carbon atoms, and One or more of the R'' are alkyl groups having 1 to 4 carbon atoms.

5. The epoxy resin composition according to claim 4, wherein the second amine-based curing agent is a compound represented by the following formula (3A) or formula (3B). 【Transformation 6】 【Transformation 7】

6. The epoxy resin composition according to any one of claims 1 to 5, wherein the ratio E2 / E1 of the total number of epoxy groups E1 derived from the bifunctional or more aromatic epoxy resin to the total number of epoxy groups E2 derived from the monoepoxy compound is 0.04 or more and 0.25 or less.

7. The epoxy resin composition according to any one of claims 1 to 5, wherein the ratio A2 / A1 of the total number of active hydrogens A1 derived from the first amine-based curing agent to the total number of active hydrogens A2 derived from the second amine-based curing agent is 0.20 or more and 1.50 or less.

8. The epoxy resin composition according to any one of claims 1 to 5, wherein the monoepoxy compound is an aliphatic monoepoxy compound and / or an aromatic monoepoxy compound.

9. The epoxy resin composition according to any one of claims 1 to 5, wherein the first amine-based curing agent is at least one selected from dicyandiamide and its derivatives.

10. The epoxy resin composition according to any one of claims 1 to 5, wherein the accelerator is a urea compound.

11. The epoxy resin composition according to any one of claims 1 to 5, wherein the aforementioned bifunctional or more aromatic epoxy resin is a bisphenol A type epoxy resin.

12. A prepreg comprising reinforcing fibers and an epoxy resin composition according to any one of claims 1 to 5 impregnated into the reinforcing fibers.

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

14. The prepreg according to claim 12, wherein the reinforcing fiber is carbon fiber.

15. The prepreg described in claim 12, which is a tow prepreg, is wrapped around a substrate to form an intermediate, and The intermediate is subjected to a heat-curing treatment. including, A method for manufacturing a pressure vessel.

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