Epoxy resin composition, cured product thereof, and fiber-reinforced composite material

Abstract

The present invention relates to: an epoxy resin composition containing (A) an epoxy resin having an alicyclic structure and (B) an epoxy resin curing agent containing bis (aminomethyl) cyclohexane; a cured product thereof; and a fiber-reinforced composite material containing the cured product and reinforcing fibers.

Description

[0001] This application is a divisional application of the Chinese patent application "Epoxy resin composition and its cured product, and fiber-reinforced composite material" with an international application date of February 14, 2020 and application number 202080008623.7 (international application number PCT / JP2020 / 005792). Technical Field

[0002] The present invention relates to an epoxy resin composition and a cured product thereof, and a fiber-reinforced composite material comprising the cured product of the epoxy resin composition and reinforcing fibers. Background Art

[0003] Among fiber-reinforced composite materials (hereinafter referred to as "FRP"), carbon fiber-reinforced plastics (CFRP) have attracted considerable attention as a metal replacement due to their exceptionally high elastic modulus and strength, combined with their lightweight nature. Demand for CFRP is expected to accelerate, particularly in automotive structural applications, wind turbine blades, pressure vessels, and aerospace applications. Demand for the carbon fibers and matrix resins, such as epoxy resins, used in CFRP has also been increasing in recent years.

[0004] The molding methods for FRP vary depending on the application, such as automotive structural materials, wind turbine blades, pressure vessels, and aerospace applications. Therefore, the required properties of the matrix resin for FRP also vary depending on the application.

[0005] For example, wind turbine blades are already produced using infusion molding, Vacuum-Assisted Resin Transfer Molding (Vacuum-Assisted Resin Transfer Molding), or Light-RTM. In these methods, reinforcing fibers are pre-placed in a mold consisting of an upper mold and a lower mold made of film or FRP. The mold is then evacuated, and an epoxy resin composition serving as a matrix resin is filled under normal pressure to impregnate the reinforcing fibers. The epoxy resin is then cured to form the blade.

[0006] Infusion molding, Va-RTM, and Light-RTM molding methods typically require several tens of minutes to fill the mold with an epoxy resin composition containing a mixture of epoxy resin and epoxy resin curing agent due to the characteristics of these molding methods. Therefore, epoxy resin compositions used in these molding methods are required to have low viscosity and a long pot life. Epoxy resin curing agents such as isophorone diamine and polyamine compounds with a polyether backbone are used.

[0007] In addition, in FRP for pressure vessel applications, a filament winding method is used. The filament winding method is a method in which a matrix resin such as an epoxy resin composition is impregnated into reinforcing fiber filaments and covered on the outer surface of the liner, and then the matrix resin is cured. If the epoxy resin composition used in this method has a short pot life and cures quickly, the epoxy resin will cure in the stage before molding. Therefore, the fast-curing epoxy resin composition cannot be applied to the filament winding method.

[0008] In contrast, FRP used in automotive structural materials is molded using the high-cycle RTM method, which is an improvement on the existing RTM method.

[0009] The conventional RTM method is a closed-type molding method using a pair of upper and lower molds. A fiber-reinforced preform is placed within the mold, clamped and sealed, and then a resin, such as an epoxy resin composition, is injected through an injection port into the mold to impregnate the fiber-reinforced preform. The resin is then cured and demolded. However, the conventional RTM method requires several hours of molding time (preform placement, resin impregnation, resin curing, and demolding). Therefore, the more productive high-cycle RTM method has been adopted for the production of FRP for automotive structural materials.

[0010] The molding technology based on the high-cycle RTM method significantly shortens the configuration time of the fiber-reinforced preform, the resin impregnation time, the resin curing time, and the demolding time. In the high-cycle RTM method, in the process from resin impregnation to curing, for example, in the high-pressure RTM method, which is a type of high-cycle RTM method, reinforcing fibers are arranged in a pair of upper and lower molds and sealed, and the mold is decompressed. Then, the epoxy resin curing agent and the epoxy resin as the main agent of the epoxy resin composition are pressure-fed in a mist form from their respective tanks to the mixing head, and after collision mixing, they are quickly injected into the mold and impregnated into the reinforcing fibers to cure the epoxy resin. In order to increase the filling speed into the mold and the impregnation speed into the reinforcing fibers, the epoxy resin composition after collision mixing is injected at high pressure from multiple injection holes.

[0011] In the high-cycle RTM method, since the epoxy resin and epoxy resin curing agent are mixed and then quickly injected into the mold, the pot life of the epoxy resin composition, the mixture of epoxy resin and epoxy resin curing agent, is not as important. On the other hand, from the perspective of productivity, high impregnation into the reinforcing fibers, high filling speed into the mold, and fast curing are required. Therefore, the epoxy resin composition used in the high-cycle RTM method is required to have low viscosity and fast curing.

[0012] Polyamines are known to be useful as epoxy resin curing agents. For example, Patent Documents 1 to 3 disclose low-viscosity, fast-curing epoxy resin curing agents containing bis(aminomethyl)cyclohexane.

[0013] Patent Document 4 discloses a method for producing a fiber-reinforced composite using a resin composition comprising: (b1) a liquid epoxy resin, (b2) a curing agent comprising 1,3-bis(aminomethyl)cyclohexane, and (b3) an accelerator comprising at least one compound selected from the group consisting of sulfonic acid and sulfonic acid imidazolium salts.

[0014] Prior art literature

[0015] Patent Literature

[0016] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-163955

[0017] Patent Document 2: Japanese Patent Application Laid-Open No. 2011-6499

[0018] Patent Document 3: Japanese Patent Application Laid-Open No. 2015-93948

[0019] Patent Document 4: Japanese Patent Application No. 2017-509781 Summary of the Invention

[0020] Problems to be solved by the invention

[0021] Design has always been a priority for FRP, a structural material used in luxury vehicles. In particular, there is a desire for materials that exhibit minimal yellowing of the cured product and high weather resistance, even after prolonged exposure to ultraviolet radiation. However, cured products of existing epoxy resin compositions for FRP do not always meet these requirements in terms of weather resistance.

[0022] The present invention aims to provide an epoxy resin composition having low viscosity, rapid curing, and the ability to form a cured product that exhibits minimal yellowing and excellent weather resistance even when exposed to ultraviolet radiation for a long period of time, as well as a cured product thereof, and a fiber-reinforced composite material comprising the cured product and reinforcing fibers.

[0023] Solutions for solving problems

[0024] The present inventors have discovered that an epoxy resin composition containing a main component epoxy resin having a predetermined structure and an epoxy resin curing agent containing bis(aminomethyl)cyclohexane can solve the above-mentioned problems.

[0025] That is, the present invention relates to the following.

[0026] [1] An epoxy resin composition comprising: an epoxy resin (A) having an alicyclic structure; and an epoxy resin curing agent (B) containing bis(aminomethyl)cyclohexane.

[0027] [2] The epoxy resin composition according to [1], wherein the component (A) is an epoxy resin represented by the following general formula (1).

[0028]

[0029] (In formula (1), R 1 ~R 4 Each independently represents an alkyl group having 1 to 6 carbon atoms, and each independently represents an integer from 0 to 4. 1 , multiple R 2 , multiple R 3 and multiple R 4 All of them are optionally the same or different from each other. 1 and Y 2 Each is independently a single bond, -CH2-, -CH(CH3)- or -C(CH3)2-. 5 is -CH2CH(OH)- or -CH(OH)CH2-. m represents the average number of repeating units and is a number from 0 to 2.

[0030] [3] The epoxy resin composition according to [1] or [2], wherein the content of bis(aminomethyl)cyclohexane in the component (B) is 30% by mass or more.

[0031] [4] The epoxy resin composition according to any one of [1] to [3], wherein the content of the sulfonic acid-based curing accelerator is less than 0.5% by mass.

[0032] [5] A cured product, which is a cured product of the epoxy resin composition according to any one of [1] to [4].

[0033] [6] A fiber-reinforced composite material comprising: a cured product of the epoxy resin composition according to any one of [1] to [4]; and reinforcing fibers.

[0034] [7] The fiber-reinforced composite material according to [6], wherein the reinforcing fibers are carbon fibers.

[0035] Effects of the Invention

[0036] The epoxy resin composition of the present invention can be used to produce FRP for automotive structural materials, building materials, and the like with high productivity using a high-cycle RTM method. Furthermore, it can provide a cured product and FRP that exhibits minimal yellowing and high weather resistance even when exposed to ultraviolet radiation for extended periods. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Graph showing the results of weather resistance tests on the cured products obtained in Example 1, Comparative Example 1, and Comparative Example 2. DETAILED DESCRIPTION

[0038] [Epoxy resin composition]

[0039] The epoxy resin composition of the present invention contains an epoxy resin (A) having an alicyclic structure (hereinafter also referred to as "component (A)") and an epoxy resin curing agent (B) containing bis(aminomethyl)cyclohexane (hereinafter also referred to as "component (B)").

[0040] An epoxy resin composition containing component (A) as a main agent and component (B) as a curing agent containing bis(aminomethyl)cyclohexane has low viscosity and cures quickly. Furthermore, it can form a cured product that exhibits minimal yellowing and excellent weather resistance even when exposed to ultraviolet radiation for extended periods.

[0041] <Epoxy resin (A)>

[0042] The epoxy resin composition of the present invention contains an epoxy resin (A) having an alicyclic structure as a main component.

[0043] Component (A) may be any resin having at least one alicyclic structure and at least two epoxy groups. From the viewpoint of obtaining a low-viscosity epoxy resin composition, a liquid epoxy resin that is liquid at room temperature (25° C.) is preferred.

[0044] The number of ring carbon atoms in the alicyclic structure of component (A) is preferably 5 to 20, more preferably 5 to 12, further preferably 5 to 10, further preferably 5 to 8, and further preferably 6. The alicyclic structure may be saturated or unsaturated, and may be monocyclic or polycyclic. From the viewpoint of weather resistance, the alicyclic structure is preferably a saturated alicyclic structure having no unsaturated bond. In addition, the alicyclic structure may have a substituent. Examples of the substituent include an alkyl group having 1 to 8 carbon atoms, a hydroxyl group, and an alkoxy group having 1 to 8 carbon atoms.

[0045] Examples of the alicyclic structure include, but are not limited to, cycloalkane rings, cycloolefin rings, bicycloalkane rings, bicycloolefin rings, and tricycloalkane rings. Among these, cycloalkane rings are preferred, cycloalkane rings having 5 to 8 carbon atoms are more preferred, and cyclohexane rings are still more preferred.

[0046] From the perspective of weather resistance of the cured product, component (A) is preferably an epoxy resin containing an alicyclic structure and no aromatic ring. If component (A) is an epoxy resin containing no aromatic ring, a cured product with minimal yellowing and excellent weather resistance can be obtained even when exposed to ultraviolet radiation for a long time.

[0047] Preferred examples of component (A) include epoxy resins obtained by reacting epichlorohydrin with at least one selected from the group consisting of polyols having an alicyclic structure, polyamines having an alicyclic structure, and compounds having an alicyclic structure and having a hydroxyl group and an amino group.

[0048] Examples of the polyol having an alicyclic structure include dihydroxycyclohexane, biscyclohexanediol, 2,2-bis(4-hydroxycyclohexyl)propane, and bis(4-hydroxycyclohexyl)methane.

[0049] Examples of the polyamine having an alicyclic structure include bis(aminomethyl)cyclohexane and diaminodicyclohexylmethane. Examples of the compound having an alicyclic structure and having a hydroxyl group and an amino group include aminocyclohexanol.

[0050] Preferred examples of component (A) include hydrogenated epoxy resins obtained by hydrogenating epoxy resins having aromatic rings, such as biphenol epoxy resins, bisphenol A epoxy resins, bisphenol F epoxy resins, and phenol novolac epoxy resins.

[0051] Among the above, from the viewpoints of low viscosity of the epoxy resin composition, rapid curing, mechanical strength and weather resistance of the cured product, and availability, the epoxy resin represented by the following general formula (1) is more preferred as component (A).

[0052]

[0053] (In formula (1), R 1 ~R 4 Each independently represents an alkyl group having 1 to 6 carbon atoms, and each independently represents an integer from 0 to 4. 1 , multiple R 2 , multiple R 3 and multiple R 4 All of them are optionally the same or different from each other. 1 and Y 2 Each is independently a single bond, -CH2-, -CH(CH3)- or -C(CH3)2-. 5 is -CH2CH(OH)- or -CH(OH)CH2-. m represents the average number of repeating units and is a number from 0 to 2.

[0054] R 1~R 4 An alkyl group having 1 to 4 carbon atoms is preferred, and at least one selected from the group consisting of a methyl group, an ethyl group, an isopropyl group, and a tert-butyl group is more preferred.

[0055] p, q, r, and s are preferably all integers of 0 to 2, more preferably 0 or 1, and even more preferably all 0.

[0056] Y 1 and Y 2 Preferred is -CH2- or -C(CH3)2-, more preferably -C(CH3)2-.

[0057] From the viewpoint of ensuring low viscosity and mechanical strength of the cured product, m is preferably 0 to 1, more preferably 0 to 0.5, and even more preferably 0 to 0.2.

[0058] The epoxy resin represented by the general formula (1) may be obtained by reacting a compound represented by the following general formula (2) with epichlorohydrin, or may be a hydrogenated epoxy resin obtained by hydrogenating an epoxy resin represented by the following general formula (3).

[0059]

[0060] (In formula (2), R 1 、R 2 , p, q, and Y 1 Same as above.)

[0061]

[0062] (In formula (3), R 1 ~R 5 ,p,q,r,s,Y 1 and Y 2 , and m are the same as above.)

[0063] The hydrogenation rate of the hydrogenated epoxy resin is preferably close to 100% from the viewpoint of obtaining a cured product with excellent weather resistance, but may be 50% or more, preferably 70 to 100%, more preferably 80 to 100%, further preferably 90 to 100%, and even more preferably 95 to 100%.

[0064] From the viewpoint of achieving both low viscosity and rapid curing of the epoxy resin composition, the epoxy equivalent of component (A) is preferably 400 g / equivalent or less, more preferably 300 g / equivalent or less, further preferably 250 g / equivalent or less, and even more preferably 220 g / equivalent or less.

[0065] <Epoxy resin curing agent (B)>

[0066] The epoxy resin composition of the present invention contains an epoxy resin curing agent (B) comprising bis(aminomethyl)cyclohexane. Using component (B) as the curing agent results in a low-viscosity epoxy resin composition that cures quickly. The cured product exhibits minimal yellowing and excellent weather resistance even when exposed to ultraviolet radiation for extended periods.

[0067] Examples of bis(aminomethyl)cyclohexane include 1,2-bis(aminomethyl)cyclohexane, 1,3-bis(aminomethyl)cyclohexane, and 1,4-bis(aminomethyl)cyclohexane, and these may be used alone or in combination. 1,3-bis(aminomethyl)cyclohexane is preferred from the viewpoints of low viscosity and rapid curing.

[0068] Bis(aminomethyl)cyclohexane contains both cis and trans isomers. The ratio of the cis and trans isomers is arbitrary, but when both are contained, the freezing point is lowered, allowing handling in a liquid form even in low-temperature environments such as winter. Therefore, the cis / trans ratio is preferably 99 / 1 to 1 / 99, more preferably 95 / 5 to 30 / 70, even more preferably 90 / 10 to 50 / 50, and even more preferably 85 / 15 to 60 / 40.

[0069] Component (B) may contain a curing agent component other than bis(aminomethyl)cyclohexane, but from the perspective of the weather resistance of the cured product, component (B) is preferably composed solely of an epoxy resin curing agent that does not contain an aromatic ring. When component (B) is composed solely of an epoxy resin curing agent that does not contain an aromatic ring, a cured product can be obtained that exhibits minimal yellowing and excellent weather resistance, even when exposed to ultraviolet radiation for extended periods.

[0070] Preferred curing agent components other than bis(aminomethyl)cyclohexane include menthanediamine, isophoronediamine (IPDA), diaminodicyclohexylmethane, bis(4-amino-3-methylcyclohexyl)methane, N-aminomethylpiperazine, N-aminoethylpiperazine, bis(aminomethyl)tricyclodecane, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, polyoxyalkylenediamine, and polyoxyalkylenetriamine. These may be used alone or in combination of two or more.

[0071] From the viewpoints of low viscosity and rapid curing of the epoxy resin composition, and weather resistance of the cured product, the content of bis(aminomethyl)cyclohexane in component (B) is preferably 30% by mass or greater, more preferably 50% by mass or greater, further preferably 70% by mass or greater, even further preferably 80% by mass or greater, and even further preferably 90% by mass or greater. The upper limit is 100% by mass.

[0072] The epoxy resin composition of the present invention may further contain other components such as epoxy resins other than component (A), fillers, modifying components such as plasticizers, flow control components such as thixotropic agents, pigments, leveling agents, tackifiers, and elastomer fine particles, depending on the application.

[0073] From the perspective of achieving the effects of the present invention, the total amount of component (A) and component (B) in the epoxy resin composition is preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and even more preferably 90% by mass or more. The upper limit is 100% by mass.

[0074] The epoxy resin composition of the present invention does not exclude the inclusion of a known curing accelerator as an optional component, but even without containing a curing accelerator, sufficiently rapid curing can be achieved.

[0075] From the perspective of avoiding corrosion of production lines and molds, the occurrence of voids and defects caused by gas leakage during the molding process, and deterioration of the appearance of the cured product, when used in high-cycle RTM methods, etc., it is preferred that the content of a curing accelerator such as p-toluenesulfonic acid and its salts be low. For example, in the epoxy resin composition of the present invention, the content of the sulfonic acid-based curing accelerator is preferably less than 0.5% by mass, more preferably 0.3% by mass or less, even more preferably 0.1% by mass or less, and even more preferably 0% by mass.

[0076] The content ratio of component (A) and component (B) in the epoxy resin composition of the present invention is as follows: the ratio of the number of active amine hydrogens in component (B) to the number of epoxy groups in component (A) (number of active amine hydrogens in component (B) / number of epoxy groups in component (A)) is preferably 1 / 0.5 to 1 / 2, more preferably 1 / 0.75 to 1 / 1.5, and even more preferably 1 / 0.8 to 1 / 1.2.

[0077] The epoxy resin composition of the present invention preferably has a viscosity of 500 mPa·s or less at 80°C, more preferably 200 mPa·s or less, even more preferably 100 mPa·s or less, and even more preferably 50 mPa·s or less. An epoxy resin composition with a viscosity of 500 mPa·s or less at 80°C improves productivity when used in FRP applications. While there is no particular lower limit for the viscosity of the epoxy resin composition at 80°C, it is preferably 5 mPa·s or greater to suppress turbulence within the mold and disruption of the reinforcing fibers due to an increase in the Reynolds number during FRP molding.

[0078] The epoxy resin composition of the present invention preferably has an initial viscosity within the above range after 2 minutes and 30 seconds at 80°C after mixing component (A) and component (B). The above viscosity can be measured using an E-type viscometer, specifically, by the method described in the Examples.

[0079] The epoxy resin composition of the present invention preferably has a gelation time of 40 minutes or less, more preferably 35 minutes or less, at a temperature of 80°C from the viewpoint of rapid curing. From the viewpoint of workability, it is preferably 0.5 minutes or more, more preferably 1.0 minutes or more. Furthermore, the gelation time at a temperature of 130°C is preferably 10 minutes or less, more preferably 7 minutes or less. From the viewpoint of workability, it is preferably 0.5 minutes or more, more preferably 1.0 minutes or more.

[0080] The gelation time can be measured using a rheometer using the method described in the Examples. Specifically, the storage modulus G' and loss modulus G" of the epoxy resin composition are measured using a rheometer at 80°C or 130°C, a frequency of 1 Hz, and a plate spacing of 0.5 mm. The gelation time is defined as the point where G' and G" intersect.

[0081] The method for producing the epoxy resin composition of the present invention is not particularly limited, and the composition can be produced by mixing the component (A), the component (B), and other components as needed using a known method and apparatus.

[0082] The epoxy resin composition of the present invention is preferably used for fiber-reinforced composite materials, particularly preferably for carbon fiber-reinforced composite materials, due to its low viscosity and rapid curing.

[0083] [cured material]

[0084] The cured product of the epoxy resin composition of the present invention (hereinafter also referred to as the "cured product of the present invention") is obtained by curing the epoxy resin composition of the present invention described above by a known method. The curing conditions of the epoxy resin composition are appropriately selected depending on the application and form and are not particularly limited.

[0085] The form of the cured product of the present invention is not particularly limited and can be selected according to the intended use.

[0086] [Fiber-reinforced composite materials]

[0087] The fiber-reinforced composite material (FRP) of the present invention comprises a cured product of the epoxy resin composition and reinforcing fibers, and can be obtained by impregnating the reinforcing fibers with the epoxy resin composition and then curing the composition.

[0088] As reinforcing fiber, for example, glass fiber, carbon fiber, boron fiber and metal fiber etc. can be enumerated. Reinforcing fiber can be used alone or in combination of two or more. Among them, from the viewpoint of the intensity and lightness of the composite material obtained, preferably carbon fiber. That is, the fiber reinforced composite material of the present invention is preferably a carbon fiber reinforced composite material (CFRP) comprising a cured product of the aforementioned epoxy resin composition and carbon fiber.

[0089] The carbon fibers used in CFRP can be manufactured using raw materials such as rayon and polyacrylonitrile (PAN), or by spinning asphalt such as petroleum and coal. Furthermore, recycled carbon fibers obtained by recycling carbon fiber ends or by removing the resin from CFRP can also be used. Carbon fibers can be formed in various forms, such as those obtained by simply arranging monofilaments or multifilaments in a unidirectional or alternating manner, or in the form of fabrics such as woven fabrics, nonwoven fabrics, or mats. Among these, monofilaments, fabrics, nonwoven fabrics, or mats are preferred, and fabrics are more preferred.

[0090] The average fiber diameter of the carbon fibers is preferably 1 to 100 μm, more preferably 3 to 50 μm, and even more preferably 4 to 20 μm. When the average fiber diameter is within this range, processing is facilitated, and the resulting CFRP exhibits excellent elastic modulus and strength. The average fiber diameter can be measured by observation using a scanning electron microscope (SEM), for example. By randomly selecting 50 or more fibers and measuring their lengths, the number-average average fiber diameter can be calculated.

[0091] The fineness of the carbon fibers is preferably 20 to 4500 tex, more preferably 50 to 4000 tex. A fineness within this range facilitates impregnation with the epoxy resin composition, resulting in excellent elastic modulus and strength of the resulting composite material. It should be noted that the fineness can be calculated by calculating the weight of long fibers of any length per 1000 m. Generally, carbon fibers with a filament count of approximately 500 to 60,000 are preferably used.

[0092] In addition to the cured epoxy resin composition and reinforcing fibers, FRP may also include a foaming material. The foaming material is not particularly limited, and examples thereof include foaming materials composed of resin materials such as polyvinyl chloride resin, polyurethane resin, polystyrene resin, polyolefin resin, acrylic resin, phenolic resin, polymethacrylimide resin, and epoxy resin.

[0093] <Method for producing fiber-reinforced composite materials>

[0094] There is no particular limitation on the method for producing the fiber-reinforced composite material of the present invention. The epoxy resin composition of the present invention cures rapidly, and therefore, it is preferred that component (A) and component (B) be mixed immediately before molding, and then rapidly impregnated into the reinforcing fibers and cured.

[0095] From the perspective of impregnating the reinforcing fibers with the epoxy resin composition and curing it in a shorter time, the method for producing a fiber-reinforced composite material of the present invention preferably includes a molding step using the following methods: low-pressure RTM, medium-pressure RTM, high-pressure RTM, compression RTM, liquid compression molding, liquid deposition, spray deposition, surface RTM, prepreg compression molding, or liquid casting. Of these molding methods, low-pressure RTM, medium-pressure RTM, or high-pressure RTM are preferred from the perspective of use in high-cycle RTM, with medium-pressure RTM or high-pressure RTM being more preferred. From the perspective of molding speed, high-pressure RTM is even more preferred.

[0096] In this specification, the term "low pressure" in the low-pressure RTM method refers to a pressure of less than 0.5 MPa when the epoxy resin, the main component of the epoxy resin composition, and the epoxy resin curing agent are pressure-fed and mixed. Similarly, the term "medium pressure" in the medium-pressure RTM method refers to a pressure of 0.5 MPa to less than 7 MPa, and the term "high pressure" in the high-pressure RTM method refers to a pressure of 7 MPa to 20 MPa.

[0097] In the above molding method, the component (A) and component (B) used in the epoxy resin composition of the present invention can be mixed and used immediately before molding. Therefore, the pot life of the epoxy resin composition is not so necessary. In addition, the epoxy resin composition has low viscosity and cures quickly. Therefore, filling into the mold and impregnation into the reinforcing fibers are fast, and curing is rapid, thus significantly shortening the molding time. Therefore, the epoxy resin composition of the present invention is particularly suitable for the above molding method. In addition, by using the above molding method, the epoxy resin composition of the present invention can be applied to manufacture medium or large FRPs such as automotive structural materials and building materials with good productivity.

[0098] In the high-pressure RTM method, for the device for mixing the component (A) as the main agent of the epoxy resin composition with the component (B) as the epoxy resin curing agent, it is preferred to use a collision mixer. For example, a reinforcing fiber is configured and sealed in a pair of upper and lower molds, and the mold is decompressed. Then, component (A) and component (B) are filled into each tank, respectively discharged at high speed from a very small hole (orifice), and collision mixed in the mixing chamber of the collision mixer. The epoxy resin composition prepared in this way is injected into the mold at high pressure so that it is impregnated with reinforcing fibers, and then, the epoxy resin is cured.

[0099] In low-pressure RTM method, for the device that the component (A) as the main agent of epoxy resin composition is mixed with the component (B) as epoxy resin curing agent, preferably use dynamic mixer.Dynamic mixer possesses the high-speed rotating body that surface has concavoconvex cylindrical.For example, component (A) and component (B) are filled into each tank, liquid is sent to dynamic mixer respectively, utilize aforementioned rotating body by 2 liquid mixing.The epoxy resin composition prepared in this way is injected into mould, is impregnated with reinforcing fiber, then, epoxy resin is solidified.Low-pressure RTM method is favourable in the case that the compounding ratio of component (A) and component (B) is significantly different, device cost, the viewpoint of the space-saving of device.

[0100] In the medium pressure RTM method, for the device for mixing the component (A) as the main agent of the epoxy resin composition with the component (B) as the epoxy resin curing agent, a static mixer is preferably used. A static mixer is a tubular mixer equipped with one or more static mixers, wherein the static mixer is composed of a plurality of mixing units. For example, component (A) and component (B) are filled into each tank and liquid is fed to the static mixer respectively. The 2 liquids of component (A) and component (B) are introduced into the twisted unit of the static mixer, thereby utilizing the effects of segmentation / conversion / inversion to mix the 2 liquids. The epoxy resin composition thus prepared is injected into a mold so that it is impregnated with reinforcing fibers, and then, the epoxy resin is cured. The medium pressure RTM method is advantageous in that the epoxy resin composition can be pressurized into the mold and the cost of the device is low.

[0101] When the FRP contains a foaming material in addition to the cured epoxy resin composition and the reinforcing fibers, the reinforcing fibers and the foaming material are placed in the mold, and the FRP can be produced in the same manner as described above.

[0102] The epoxy resin curing agent and epoxy resin composition of the present invention can also be suitably used in liquid compression molding (LCM) and liquid deposition methods. In LCM and liquid deposition methods, the epoxy resin composition is cast onto reinforcing fibers (or, if the FRP also includes a foaming material, onto both the reinforcing fibers and the foaming material) and then heated and compressed to cure the epoxy resin.

[0103] In the molding of FRP, the temperature when the epoxy resin composition is injected into the mold or impregnated into the reinforcing fiber is preferably 30 to 120°C, more preferably 50 to 100°C. When component (A) and component (B) are supplied from separate tanks and mixed immediately before molding, the temperature during mixing can also be set separately. The temperature when mixing component (A) can be appropriately adjusted according to the viscosity of the epoxy resin, preferably 30 to 120°C, more preferably 50 to 100°C. From the viewpoint of suppressing the increase in viscosity, the temperature when mixing component (B) is preferably 5 to 30°C, more preferably 10 to 25°C.

[0104] From the viewpoint of moldability and productivity, the impregnation time of the epoxy resin composition into the reinforcing fibers is preferably 0.1 to 15 minutes, more preferably 0.2 to 10 minutes, and even more preferably 0.5 to 5 minutes.

[0105] The curing temperature of the epoxy resin composition is preferably 50-200°C, more preferably 80-150°C, and even more preferably 100-150°C. When the curing temperature is 50°C or higher, the epoxy resin cures sufficiently, resulting in excellent mechanical properties of the resulting FRP. Furthermore, when the curing temperature is 200°C or lower, the cost of adjusting the mold temperature can be reduced. The curing time of the epoxy resin composition can be appropriately selected based on factors such as the curing temperature. From the perspective of moldability and productivity, it is preferably 0.1-15 minutes, more preferably 0.2-10 minutes, and even more preferably 0.5-5 minutes.

[0106] The epoxy resin composition of the present invention can be used to produce FRP with good productivity by the above-mentioned molding method. The fiber-reinforced composite material of the present invention is preferably a carbon fiber-reinforced composite material, preferably an automotive structural material, a building material, and particularly an automotive structural material. Examples of automotive structural materials include bumpers, spoilers, fairings, front grilles, decorative parts, engine hoods, trunk lids, fenders, door panels, roof panels, instrument panels, door trims, side panel trims, roof linings, pillar trims, floor panel side trims, tone panels, rear storage panels, instrument panels, console boxes, skirting boards, switch housings, seat backs, seat frames, armrests, sun visors, intake manifolds, engine bonnets, engine undercaps, and oil filter housings.

[0107] Example

[0108] The present invention will be described in detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. It should be noted that various measurements and evaluations of the epoxy resin composition were performed according to the following methods.

[0109] (Viscosity)

[0110] The viscosity of the epoxy resin composition was measured at 80°C using an E-type viscometer "TVE-22H Cone-Plate Viscometer" (manufactured by Toki Sangyo Co., Ltd.). The viscosity measurement at 80°C was started immediately after the epoxy resin and epoxy resin curing agent were mixed to prepare the epoxy resin composition, and the measured value was read every 2 minutes and 30 seconds.

[0111] (Gelation time)

[0112] Evaluations were performed using the ARES-G2 rheometer (TA Instruments) at 80°C and 130°C. The epoxy resin composition was placed between aluminum plates heated to 80°C or 130°C. The storage modulus G' and loss modulus G" were measured at 80°C or 130°C, a frequency of 1 Hz, and a distance of 0.5 mm between the plates. The point where G' and G" intersected was defined as the gelation time. A shorter gelation time indicates faster curing.

[0113] (Glass transition temperature (Tg))

[0114] The Tg of a cured epoxy resin composition is determined by performing differential scanning calorimetry analysis from 30°C to 250°C at a heating rate of 5°C / min on an epoxy resin composition that has been cured by heating at 130°C for 30 minutes using a differential scanning calorimeter "DSC 6200" (manufactured by Seiko Instruments Inc.).

[0115] (Weather resistance test)

[0116] Weather resistance test was conducted according to ISO4982 Part 3 Method A.

[0117] The epoxy resin composition obtained in each example was cured at 130°C for 30 minutes in a mold of 20 mm x 20 mm x 2 mm thick to prepare a test piece. The test piece was placed in a UV tester "Suntest XXL+" (manufactured by Toyo Seiki Co., Ltd.) and the test piece was placed in a UV tester "Suntest XXL+" (manufactured by Toyo Seiki Co., Ltd.) using a xenon lamp at an illumination of 60 W / m 2 The film was irradiated with ultraviolet rays having a wavelength of 300 to 400 nm at an intensity of 1000 nm, while repeating a cycle of setting a dry condition (humidity 50%) at a temperature of 38° C. for 102 minutes and then setting a water spray condition for 18 minutes.

[0118] Reach the specified UV exposure (kJ / m 2 ) Afterwards, the test piece was removed and the YI value was measured using a colorimeter ("ZE2000" manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7373:2006. A smaller increase in the YI value indicates better weather resistance of the cured product. In particular, a YI value of 2.0 or less is preferred, as the cured product exhibits less yellowish tinge upon visual observation.

[0119] Example 1 (Production and Evaluation of Epoxy Resin Composition)

[0120] As the main agent, a hydrogenated bisphenol A type liquid epoxy resin ("YX8000" manufactured by Mitsubishi Chemical Corporation, hydrogenated bisphenol A diglycidyl ether, epoxy equivalent 205 g / equivalent) as an epoxy resin (A) having an alicyclic structure was used, and as the epoxy resin curing agent (B), 1,3-bis(aminomethyl)cyclohexane (1,3-BAC, manufactured by Mitsubishi Gas Chemical Corporation, cis / trans ratio = 77 / 23) was used.

[0121] The epoxy resin and epoxy resin curing agent are blended so that the number of epoxy groups in the epoxy resin as the main agent and the number of active amine hydrogens in the epoxy resin curing agent are 1 / 1.05 (the number of active amine hydrogens in the epoxy resin curing agent / the number of epoxy groups in the epoxy resin is 1 / 0.95) and mixed to produce an epoxy resin composition.

[0122] The obtained epoxy resin composition was evaluated by the above-mentioned method. The results of the composition viscosity, gelation time, and glass transition temperature (Tg) of the cured product are shown in Table 1, and the results of the weather resistance test are shown in Table 2.

[0123] Comparative Example 1

[0124] Epoxy resin compositions were prepared in the same manner as in Example 1 except that isophorone diamine (IPDA, manufactured by EVONIK) was used instead of 1,3-bis(aminomethyl)cyclohexane as the epoxy resin curing agent, and evaluated by the aforementioned method. The results are shown in Tables 1 and 2.

[0125] Comparative Example 2

[0126] In Example 1, except that 4,4'-methylenebis(cyclohexylamine) (PACM, manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of 1,3-bis(aminomethyl)cyclohexane as the epoxy resin curing agent, an epoxy resin composition was produced in the same manner as in Example 1 and evaluated by the aforementioned method. The results are shown in Tables 1 and 2.

[0127] [Table 1]

[0128] Table 1

[0129]

[0130] [Table 2]

[0131] Table 2

[0132]

[0133] It should be noted that the results of Table 2 are also shown in Figure 1 . Figure 1This is a graph showing the results of weather resistance tests on the cured products obtained in Example 1 and Comparative Examples 1 and 2. The horizontal axis is plotted as UV irradiation dose (kJ / m 2 ), the vertical axis is plotted as the YI value of the cured product.

[0134] According to Table 1, the epoxy resin composition of the present invention (Example 1) has a lower initial viscosity and a shorter gelation time than the epoxy resin compositions of Comparative Examples 1 and 2, and cures quickly. Therefore, the epoxy resin composition containing the curing agent is suitable for manufacturing various molded bodies using molding methods such as high-cycle RTM method. Moreover, according to Table 2 and Figure 1 It can be seen that the cured product of the epoxy resin composition of the present invention (Example 1) has a higher initial (UV irradiation dose 0 kJ / m 2 ) is high, but the increase in the YI value after the weathering test is suppressed, indicating good weathering resistance. Furthermore, as compared with Comparative Example 2, the cured product of Example 1 also has a low initial YI value, and the increase in the YI value after the weathering test is also suppressed.

[0135] Example 2 (Manufacturing of CFRP)

[0136] The epoxy resin composition obtained in Example 1 was impregnated into a carbon fiber fabric (Toray Industries, Inc. "CO6343", T300 plain weave, 3K, 198 g / m 2 , 0.25mm thick, 4ply) to produce a CFRP substrate. The CFRP substrate was then placed in aluminum upper and lower molds preheated to 120°C in an oven. The molds were quickly sealed and heated for 3 minutes to cure the epoxy resin composition, producing the CFRP. The resulting CFRP could be easily released from the aluminum upper and lower molds, confirming that the epoxy resin composition cured quickly. Furthermore, there were no defects associated with poor impregnation of the epoxy resin composition into the carbon fibers, resulting in a good appearance.

[0137] Industrial applicability

[0138] The epoxy resin composition of the present invention can be used to produce FRPs such as automotive structural materials and building materials with high productivity using high-cycle RTM methods. Furthermore, it can provide cured products and FRPs that exhibit minimal yellowing and high weather resistance even when exposed to ultraviolet radiation for extended periods.

Claims

1. A fiber-reinforced composite material comprising: a cured product of an epoxy resin composition; and reinforcing fibers, wherein the epoxy resin composition comprises: an epoxy resin (A) having an alicyclic structure; and an epoxy resin curing agent (B) comprising bis(aminomethyl)cyclohexane. The component (A) comprises only the epoxy resin represented by the following general formula (1), In formula (1), R 1 ~R 4 Each independently represents an alkyl group having 1 to 6 carbon atoms, p, q, r and s each independently represent an integer from 0 to 4, and multiple R 1 , multiple R 2 , multiple R 3 and multiple R 4 All of them are the same or different from each other, Y 1 and Y 2 Each independently represents a single bond, -CH2-, -CH(CH3)- or -C(CH3)2-, R 5 is -CH2CH(OH)-, or -CH(OH)CH2-, m represents the average number of repeating units, which is a number from 0 to 2, The component (B) comprises only bis(aminomethyl)cyclohexane, The total amount of component (A) and component (B) in the epoxy resin composition is 70% by mass or more, The content ratio of component (A) to component (B) in the epoxy resin composition is such that the ratio of the number of active amine hydrogen atoms in component (B) to the number of epoxy groups in component (A), i.e., the number of active amine hydrogen atoms in component (B) / the number of epoxy groups in component (A), is 1 / 0.5 to 1 / 2. The reinforcing fibers are in the form of monofilaments, cloth, non-woven fabric or mat.

2. The fiber-reinforced composite material according to claim 1, wherein: The content of the sulfonic acid-based curing accelerator is less than 0.5% by mass.

3. The fiber-reinforced composite material according to claim 1 or 2, wherein: The reinforcing fibers are carbon fibers.

4. The fiber-reinforced composite material according to claim 1 or 2, wherein: The content ratio of the cis-isomer / trans-isomer of the bis(aminomethyl)cyclohexane is 95 / 5 to 30 / 70.

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