Fiber-reinforced resin molded article

Abstract

To provide a fiber-reinforced resin molded article that exhibits superior processability.SOLUTION: A fiber-reinforced resin molded article is obtained by impregnating reinforcing fibers with a resin composition comprising an epoxy resin, an epoxy diluent, a curing agent, and a curing accelerator, followed by curing. The epoxy diluent contains a monofunctional epoxy resin, the curing accelerator contains a tertiary amine, and the resin composition has a glass transition temperature (Tg) of 110°C or lower.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a fiber-reinforced resin molding that can be used as a material for a wide range of applications. [Background technology]

[0002] Fiber-reinforced resin composites are lightweight, high-strength, and highly rigid, and therefore have a wide range of applications, from sports and leisure to industrial applications such as vehicles, aircraft, construction, civil engineering, etc. Molded articles of such fiber-reinforced resin composites (hereinafter also referred to as "fiber-reinforced resin molded articles") are molded using a mold.

[0003] When producing a fiber-reinforced resin molded product, an epoxy resin composition that has excellent impregnation ability into reinforcing fibers is generally used. As an example, Patent Document 1 describes an epoxy resin composition for fiber-reinforced composite materials that has excellent resin injection workability, excellent impregnation ability into reinforcing fibers, and can exhibit excellent heat resistance. Patent Document 1 also describes that by using this epoxy resin composition for fiber-reinforced composite materials, fiber-reinforced composite materials that have excellent heat resistance and mechanical strength can be produced. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-120127 Summary of the Invention [Problem to be solved by the invention]

[0005] Fiber-reinforced resin molded products are relatively lightweight yet have high strength, and therefore are widely used as alternatives to metal, wood, and other materials, for example, in building materials such as underlayment materials, interior materials, exterior materials, sheet materials, siding supports, sidings, ceiling boards, and braces; materials used in furniture such as shelves, desks, and chairs; materials used in housings for electrical or electronic devices; materials used in vehicles or vehicle components; and materials used in structural materials in the civil engineering field.

[0006] When manufacturing products using such metal, wood, and other materials, the materials are often fastened together by screwing or drilling holes. However, for example, fastening fiber-reinforced resin materials together, or fastening a fiber-reinforced resin material to a metal or wooden material by screwing, can cause cracks or burrs in the materials. Thus, fiber-reinforced resin materials have problems with the workability of screwing and drilling holes.

[0007] For example, the epoxy resin composition described in Patent Document 1 is prepared so that the fiber-reinforced composite material produced has particularly excellent heat resistance and strength. Therefore, when such a fiber-reinforced composite material is subjected to screwing or drilling, it is expected that problems with processability will arise.

[0008] Therefore, an object of the present invention is to provide a fiber-reinforced resin molding that has excellent processability. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention. That is, the present invention includes the following preferred embodiments.

[0010] A fiber-reinforced resin molding according to a first aspect of the present invention is a fiber-reinforced resin molding obtained by impregnating reinforcing fibers with a resin composition containing an epoxy resin, an epoxy diluent, a curing agent, and a curing accelerator, and curing the resin composition; the epoxy diluent comprises a monofunctional epoxy resin; The curing accelerator comprises a tertiary amine, and The resin composition has a glass transition temperature Tg of 110° C. or lower.

[0011] A fiber-reinforced resin molded product according to a second aspect of the present invention is the fiber-reinforced resin molded product of the first aspect, in which the curing agent contains an acid anhydride. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a fiber-reinforced resin molding having excellent processability. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present inventors have conducted extensive research into fiber-reinforced resin moldings with excellent processability, and have found that fiber-reinforced resin moldings with excellent processability can be obtained by incorporating a monofunctional epoxy resin as an epoxy diluent and a tertiary amine as a curing accelerator in a resin composition and adjusting the glass transition temperature (Tg) of the resin composition to 110°C or lower.

[0014] In this specification, "having excellent processability" means excellent processability in both screwing and drilling, as will be described in detail in the examples below.

[0015] Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present invention.

[0016] 1. Components of fiber-reinforced resin moldings The fiber-reinforced resin molded article of this embodiment is obtained by impregnating reinforcing fibers with a resin composition and curing the resin composition. First, the components of the fiber-reinforced resin molded article of this embodiment will be described.

[0017] <Resin composition> The resin composition contains an epoxy resin, an epoxy diluent, a curing agent, and a curing accelerator. The resin composition may also contain other optional additives. The components of the resin composition, a method for preparing the resin composition, and the physical properties of the resin composition are described in detail below.

[0018] (epoxy resin) The epoxy resin is a resin that serves as the main component of the resin composition. The type of epoxy resin is not particularly limited as long as it does not impair the processability of the fiber-reinforced resin molding of this embodiment. For example, the epoxy resin is preferably a resin selected from bisphenol A epoxy resins and bisphenol F epoxy resins. Furthermore, the epoxy resin is preferably a bisphenol A epoxy resin.

[0019] The epoxy resin is preferably contained in the resin composition in an amount of 30 to 88 parts by mass, based on 100 parts by mass of the total of the epoxy resin and epoxy diluent. When the epoxy resin is contained in an amount of 30 parts by mass or more, a fiber-reinforced resin molded article having good bending strength can be obtained. When the epoxy resin is contained in an amount of 88 parts by mass or less, a decrease in the toughness of the fiber-reinforced resin molded article due to an excessive increase in the viscosity or crosslink density of the resin composition can be prevented.

[0020] The epoxy resin is contained in an amount of preferably 40 parts by mass or more, even more preferably 45 parts by mass or more, and particularly preferably 50 parts by mass or more, per 100 parts by mass of the epoxy resin and epoxy diluent combined. The epoxy resin is contained in an amount of preferably 86 parts by mass or less, even more preferably 85 parts by mass or less, per 100 parts by mass of the epoxy resin and epoxy diluent combined.

[0021] (epoxy diluent) The epoxy diluent dilutes the epoxy resin, thereby providing the resin composition with an appropriate viscosity and reducing the crosslink density of the resin composition.

[0022] In the fiber-reinforced resin molding of this embodiment, the epoxy diluent contains a monofunctional epoxy resin. When a monofunctional epoxy resin is contained as the epoxy diluent and a tertiary amine is contained as a curing accelerator, as described below, the glass transition temperature Tg of the resin composition can be efficiently lowered. Specifically, by containing a combination of a monofunctional epoxy resin and a tertiary amine in the resin composition, a fiber-reinforced resin molding can be obtained that has excellent processability and is less susceptible to cracking and splinters.

[0023] Examples of monofunctional epoxy resins include glycidyl compounds such as glycidyl ether compounds and glycidyl ester compounds.

[0024] In this specification, the term "glycidyl compound" refers to all glycidyl compounds, including glycidyl compounds whose main chain is composed of C-C bonds, glycidyl compounds whose main chain is composed of C-O bonds, and glycidyl compounds whose main chain is composed of C-C bonds and C-O bonds.

[0025] Specifically, the monofunctional epoxy resin is not particularly limited, but examples thereof include butylphenyl glycidyl ether, n-butyl glycidyl ether, versatic acid glycidyl ester, styrene oxide, ethylhexyl glycidyl ether, phenyl glycidyl ether, and cresyl glycidyl ether. Of these, the monofunctional epoxy resin preferably contains butylphenyl glycidyl ether, from the viewpoint of more reliably obtaining a fiber-reinforced resin molding having excellent processability. Note that two or more types of monofunctional epoxy resins may be used in combination.

[0026] The monofunctional epoxy resin may be a commercially available product, such as p-tert-butylphenyl glycidyl ether "Denacol (registered trademark) EX-146" (manufactured by Nagase ChemteX Corporation), 2-ethylhexyl glycidyl ether "Denacol (registered trademark) EX-121" (manufactured by Nagase ChemteX Corporation), or phenyl glycidyl ether "Denacol (registered trademark) EX-141" (manufactured by Nagase ChemteX Corporation).

[0027] The monofunctional epoxy resin is preferably contained in the resin composition in an amount of 12 to 70 parts by mass, relative to 100 parts by mass of the total of the epoxy resin and epoxy diluent. When the monofunctional epoxy resin is contained in an amount of 12 parts by mass or more, the glass transition temperature Tg of the resin composition can be efficiently lowered. Furthermore, the crosslink density of the resin composition can be reduced, thereby increasing the toughness of the fiber-reinforced resin molded article. As a result, a fiber-reinforced resin molded article having excellent processability and being less susceptible to cracking and splinters can be more reliably obtained. When the monofunctional epoxy resin is contained in an amount of 70 parts by mass or less, a fiber-reinforced resin molded article having good flexural strength can be obtained.

[0028] The monofunctional epoxy resin is preferably contained in an amount of 14 parts by mass or more, and even more preferably 15 parts by mass or more, per 100 parts by mass of the epoxy resin and epoxy diluent combined together, and more preferably 60 parts by mass or less, and even more preferably 55 parts by mass or less, and particularly preferably 50 parts by mass or less, per 100 parts by mass of the epoxy resin and epoxy diluent combined together.

[0029] The epoxy diluent may contain one or more monofunctional epoxy resins and one or more other epoxy diluents other than the monofunctional epoxy resins, as long as this does not impair the processability effect of the fiber-reinforced resin molding of this embodiment.

[0030] The type of epoxy diluent other than the monofunctional epoxy resin is not particularly limited, and any epoxy diluent other than the monofunctional epoxy resin known to those skilled in the art can be used. For example, such an epoxy diluent may be a multifunctional glycidyl compound having two or more functional groups.

[0031] (hardening agent) The curing agent cures the epoxy resin and provides the fiber-reinforced resin molding with suitable moldability and bending properties.

[0032] The type of curing agent is not particularly limited as long as it does not impair the processability of the fiber-reinforced resin molded article of this embodiment, but it is preferable that the curing agent contains an acid anhydride. When an acid anhydride is contained as a curing agent, the glass transition temperature Tg of the resin composition can be more efficiently lowered. As a result, a fiber-reinforced resin molded article with excellent processability can be more reliably obtained.

[0033] Examples of acid anhydrides include phthalic anhydride compounds, maleic anhydride compounds, and nadic anhydride. Of these, the acid anhydride is preferably a phthalic anhydride compound from the viewpoint of viscosity. Furthermore, when a phthalic anhydride compound is included as the acid anhydride, a fiber-reinforced resin molding having favorable moldability can be obtained. The phthalic anhydride compound is not particularly limited, but examples include methyltetrahydrophthalic anhydride, tetrahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, and hexahydrophthalic anhydride. Of these, the phthalic anhydride compound is preferably liquid, low-viscosity methyltetrahydrophthalic anhydride, from the viewpoint of easily realizing a low viscosity of the resin composition. Note that two or more types of acid anhydrides may be used in combination.

[0034] The content of the acid anhydride is not particularly limited, but is preferably adjusted so that the ratio of the acid anhydride equivalent to the total epoxy equivalent of the epoxy resin and the epoxy diluent is 0.8 to 1.1. When the acid anhydride equivalent ratio is 0.8 or more, it is possible to avoid insufficient curing of the fiber-reinforced resin molded body and excessive increase in viscosity of the resin composition. Furthermore, when the acid anhydride equivalent ratio is 1.1 or less, it is possible to avoid defects such as cracks in the fiber-reinforced resin molded body.

[0035] The ratio of the acid anhydride equivalent to the total epoxy equivalent of the epoxy resin and the epoxy diluent is preferably 0.90 or more, and more preferably 0.95 or more, and more preferably 1.05 or less, and even more preferably 1.0 or less.

[0036] The curing agent may contain a curing agent other than an acid anhydride as long as the effect of processability in the fiber-reinforced resin molding of this embodiment is not impaired. Examples of the curing agent other than an acid anhydride include aromatic polyamines, phenolic resins, and aliphatic polyamines. Alternatively, the curing agent may contain a combination of one or more acid anhydrides and one or more other curing agents other than acid anhydrides.

[0037] (curing accelerator) The curing accelerator accelerates the curing of the epoxy resin. Specifically, by including the curing accelerator, it is possible to achieve a curing time suitable for pultrusion molding, which will be described later, for example, a curing time of about 2 minutes.

[0038] In the fiber-reinforced resin molding of this embodiment, the curing accelerator contains a tertiary amine. When a tertiary amine is contained as the curing accelerator and a monofunctional epoxy resin is contained as the epoxy diluent as described above, the glass transition temperature Tg of the resin composition can be efficiently lowered. Specifically, as described above, by containing a combination of a monofunctional epoxy resin and a tertiary amine in the resin composition, a fiber-reinforced resin molding with excellent processability and resistance to cracking and splinters can be obtained. Furthermore, when a tertiary amine is contained as the curing accelerator, the interfacial shear strength of the fiber-reinforced resin molding can be increased.

[0039] The tertiary amine is not particularly limited, but examples thereof include aliphatic tertiary amines such as triethylamine, triethyltetramine, tributylamine, diethylenetriamine, hexamethylenetetramine, and diethylaminopropylamine, and aromatic tertiary amines such as benzyldimethylamine, dimethylaminomethylphenol, and dimethylaniline. Of these, the tertiary amine preferably contains dimethylaminomethylphenol, from the viewpoint of more reliably obtaining a fiber-reinforced resin molding having excellent processability. Note that two or more types of tertiary amines may be used in combination.

[0040] The tertiary amine may be a commercially available product, such as tris-2,4,6-dimethylaminomethylphenol "Ancamine K54" (manufactured by Evonik Japan Co., Ltd.), diazabicycloundensine "DBU" (manufactured by San-Apro Co., Ltd.), or amine adduct curing agent "Amicure MY-24" (manufactured by Ajinomoto Fine-Techno Co., Ltd.).

[0041] The tertiary amine is preferably contained in the resin composition in an amount of 0.5 to 5 parts by mass, based on 100 parts by mass of the total of the epoxy resin and epoxy diluent. When the tertiary amine is contained in an amount of 0.5 parts by mass or more, the processability effect and the effect as a curing accelerator in this embodiment can be efficiently exhibited. Furthermore, the interfacial shear strength of the fiber-reinforced resin molding can be more reliably increased. When the tertiary amine is contained in an amount of 5 parts by mass or less, an increase in the viscosity of the resin composition in a short period of time can be suppressed.

[0042] The tertiary amine is preferably contained in an amount of 1.0 part by mass or more, and more preferably 1.5 parts by mass or more, per 100 parts by mass of the epoxy resin and epoxy diluent combined, and more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less, per 100 parts by mass of the epoxy resin and epoxy diluent combined.

[0043] The curing accelerator may contain one or more tertiary amines and one or more other curing accelerators other than tertiary amines, as long as the effect of processability in the fiber-reinforced resin molded body of this embodiment is not impaired.

[0044] Curing accelerators other than tertiary amines are not particularly limited, but examples include phosphorus compounds, Lewis acids, dimethylurea, etc. However, it is preferable that the curing accelerator is substantially free of imidazole derivatives. By substantially not including imidazole derivatives in the curing accelerator, an excessive decrease in the interfacial shear strength of the fiber-reinforced resin molding or an excessive increase in the glass transition temperature Tg of the resin composition can be prevented. Specifically, the content of the imidazole derivative per 100 parts by mass of the total of the epoxy resin and the epoxy diluent is preferably limited to 0.5 parts by mass or less, more preferably 0.3 parts by mass or less, even more preferably 0.1 parts by mass or less, particularly preferably 0.05 parts by mass or less, and most preferably 0 parts by mass.

[0045] (Other additives) The resin composition in this embodiment may contain, in addition to the epoxy resin, epoxy diluent, curing agent, and curing accelerator, other additives such as an internal mold release agent, a filler, a pigment, an ultraviolet absorber, and an antioxidant.

[0046] Among these additives, the resin composition preferably contains an internal mold release agent. The internal mold release agent is not particularly limited, but examples thereof include any internal mold release agent known to those skilled in the art, such as fatty acid amine-based mold release agents and fatty acid ester-based mold release agents. Two or more of these internal mold release agents may be contained. Furthermore, commercially available products may be used as the internal mold release agent. Examples of commercially available products include MoldWiz (registered trademark) "INT-1888LE" (manufactured by Accel Plastics Research Laboratories), MoldWiz (registered trademark) "INT-1846N2" ​​(manufactured by Accel Plastics Research Laboratories), and MoldWiz (registered trademark) "INT-1324B" (manufactured by Accel Plastics Research Laboratories).

[0047] The internal release agent is preferably contained in the resin composition in an amount of 0.1 to 15 parts by mass, based on 100 parts by mass of the total of the epoxy resin and the epoxy diluent. When the internal release agent is contained in an amount of 0.1 part by mass or more, the fiber-reinforced resin molded body can be easily pulled out from the mold. When the internal release agent is contained in an amount of 15 parts by mass or less, a decrease in the heat resistance and strength of the fiber-reinforced resin molded body can be suppressed.

[0048] The internal release agent is contained in an amount of preferably 1 part by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the epoxy resin and the epoxy diluent combined, and more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the epoxy resin and the epoxy diluent combined.

[0049] (Method for preparing resin composition) In the method for preparing the resin composition, first, the epoxy resin, epoxy diluent, curing agent, curing accelerator, and other optional additives are weighed out so as to obtain the preferred mass ratios described above, and then the weighed components are kneaded using any device known to those skilled in the art to obtain the resin composition.

[0050] (Physical properties of resin composition) In the fiber-reinforced resin molded article of this embodiment, the glass transition temperature Tg of the resin composition is 110° C. or lower. If the glass transition temperature Tg is 110° C. or lower, the fiber-reinforced resin molded article is likely to soften due to frictional heat during screwing or drilling. Therefore, it is possible to obtain a fiber-reinforced resin molded article with excellent processability that is less likely to crack or splinter when a drill screw is screwed into it.

[0051] In this specification, the "glass transition temperature Tg of a resin composition" means a glass transition temperature measured by a dynamic viscoelasticity test (torsion pendulum method) in accordance with JIS K7244-10:2005 using a thermal analyzer, as will be described in detail in the Examples below.

[0052] The glass transition temperature Tg of the resin composition is preferably 108° C. or lower, more preferably 106° C. or lower, and even more preferably 100° C. or lower. There are no particular restrictions on the lower limit of the glass transition temperature Tg of the resin composition, but from the viewpoint of the heat resistance of the fiber-reinforced resin molded product, the glass transition temperature Tg may be, for example, 60° C. or higher.

[0053] As described above, the glass transition temperature Tg of the resin composition can be adjusted to 110°C or less by incorporating a monofunctional epoxy resin as an epoxy diluent and a tertiary amine as a curing accelerator in combination in the resin composition and adjusting the contents of these to preferred values. Alternatively, a desired glass transition temperature Tg can be achieved by selecting a curing agent that is likely to lower the glass transition temperature Tg and further adjusting the content thereof.

[0054] In the fiber reinforced resin molding of this embodiment, the crosslink density of the resin composition is 1.0 mol / cm 3 The crosslink density of the resin composition is preferably 1.0 mol / cm or less. 3 If the thickness is less than this, the toughness increases, and the occurrence of cracks and burrs when a drill screw is screwed into the fiber-reinforced resin molded body can be more reliably prevented. In other words, a fiber-reinforced resin molded body with excellent processability can be more reliably obtained.

[0055] In this specification, the "crosslink density of the resin composition" means a crosslink density measured by performing a dynamic viscoelasticity test (torsion pendulum method) in accordance with JIS K7244-10:2005 using a thermal analyzer, as will be described in detail in the Examples below.

[0056] The crosslink density of the resin composition is 0.9 mol / cm 3 The lower limit of the crosslink density of the resin composition is not particularly limited, but from the viewpoint of maintaining the strength of the fiber-reinforced resin molding, the crosslink density of the resin composition is preferably 0.6 mol / cm or less, for example. 3 Anything above that is fine.

[0057] As described above, the crosslink density of the resin composition can be increased to 1.0 mol / cm by, for example, adding an appropriate type of epoxy diluent to the resin composition and adjusting the content thereof to a preferred value. 3 It can be adjusted as follows:

[0058] In the fiber-reinforced resin molding of this embodiment, the viscosity of the resin composition is preferably 1000 mPa·s or less. When the viscosity of the resin composition is 1000 mPa·s or less, the resin composition can be impregnated into the reinforcing fibers well, and a well-formed fiber-reinforced resin molding can be obtained after curing.

[0059] The viscosity of the resin composition is more preferably 900 mPa·s or less, even more preferably 800 mPa·s or less, and particularly preferably 700 mPa·s or less. There is no particular lower limit to the viscosity of the resin composition, but it may be, for example, 100 mPa·s or more.

[0060] In this specification, the "viscosity of a resin composition" refers to the initial viscosity of the resin composition. Specifically, the viscosity of a resin composition refers to the viscosity at 25°C measured immediately after the preparation of the resin composition.

[0061] <Reinforced fiber> The reinforcing fibers are used to improve the strength of the fiber-reinforced resin molded article. Specifically, the reinforcing fibers are impregnated with the above-mentioned resin composition, and after curing, the resin composition and the reinforcing fibers are integrated.

[0062] The type of reinforcing fiber is not particularly limited, as long as it is any fiber known to those skilled in the art as a reinforcing fiber for forming a fiber-reinforced resin molded article. Examples of reinforcing fibers include carbon fiber, glass fiber, boron fiber, alumina fiber, silicon nitride fiber, and basalt fiber. These reinforcing fibers may be used alone or in combination of two or more. Among these, from the viewpoints of specific strength and specific elasticity, it is preferable that the reinforcing fiber contains one or more of carbon fiber, glass fiber, boron fiber, alumina fiber, and silicon nitride fiber. Furthermore, since this can further improve the strength and corrosion resistance of the fiber-reinforced resin molded article, it is more preferable that the reinforcing fiber be carbon fiber. Examples of carbon fibers that can be used include PAN (polyacrylonitrile)-based carbon fiber and pitch-based carbon fiber. Of these, PAN-based carbon fiber is particularly preferable from the viewpoint of particularly high strength. When carbon fiber is used as the reinforcing fiber, the carbon fiber may be surface-treated with a metal.

[0063] In the fiber-reinforced resin molded body of this embodiment, the volume fraction Vf of the reinforcing fibers relative to the entire fiber-reinforced resin molded body is preferably 80% or less. If the volume fraction Vf of the reinforcing fibers is 80% or less, it is possible to avoid the occurrence of cracks due to an excessively low resin ratio in the fiber-reinforced resin molded body. The volume fraction Vf of the reinforcing fibers is more preferably 78% or less, and even more preferably 75% or less.

[0064] The lower limit of the volume fraction Vf of the reinforcing fibers is not particularly limited as long as the fiber-reinforced resin molding has sufficient strength, but it may be about 50%. If the volume fraction Vf of the reinforcing fibers is 50% or more, the fiber-reinforced resin molding is sufficiently reinforced by the reinforcing fibers, so that excessive reduction in strength such as bending strength of the fiber-reinforced resin molding can be avoided. The volume fraction Vf of the reinforcing fibers is preferably 53% or more, and more preferably 55% or more.

[0065] In this specification, the "volume content Vf of reinforcing fibers" is a value measured by a combustion method.

[0066] 2. Manufacturing method of fiber-reinforced resin molding The fiber-reinforced resin molded body of this embodiment can be produced by impregnating the reinforcing fibers with the resin composition described above and solidifying or curing the composition at a mold temperature of 100°C to 250°C for 1 minute to 10 minutes.

[0067] The method for impregnating the reinforcing fiber with the resin composition is not particularly limited, and any method known to those skilled in the art can be used. For example, the reinforcing fiber bundle may be immersed in a container containing the resin composition, or the resin composition may be applied to the reinforcing fiber bundle.

[0068] The mold used for curing is not particularly limited. For example, a mold such as a die having through holes into which the resin composition can be poured and through which the bundle of reinforcing fibers can pass, or an injection mold into which the reinforcing fibers and resin fibers can be poured, can be used.

[0069] More specifically, the fiber reinforced resin molded article of this embodiment can be manufactured by applying a pultrusion method, a VaRTM (Vacuum assisted Resin Transfer Molding) molding method, or the like.

[0070] In the pultrusion molding method, first, a mixture in which the resin composition is impregnated into the reinforcing fiber substrate is drawn into the interior of a mold, or the resin composition is impregnated into the reinforcing fiber in the mold. Next, the resin composition is heated and cured in the mold or at the location where it is removed from the mold, and the resulting cured product is pulled out of the mold. When the pultrusion molding method is applied to the production of the fiber-reinforced resin molded article of this embodiment, the mold temperature is preferably 100°C to 250°C. A mold temperature of 100°C or higher allows the resin composition to be rapidly cured within a moldable time. A mold temperature of 250°C or lower prevents deterioration of physical properties due to thermal decomposition of the resin. Furthermore, by applying the pultrusion molding method within this temperature range, curing can be completed in about 1 to 10 minutes.

[0071] The VaRTM molding method is a molding method that uses a mold to which a plastic film is attached. In the VaRTM molding method, first, stacked reinforcing fibers are sealed between the mold and the plastic film, and the air between them is removed using a vacuum pump. Next, a resin composition is injected into the space from which the air has been removed using negative pressure, and the reinforcing fibers are impregnated with the resin composition. Thereafter, the reinforcing fibers and resin composition are sandwiched between the mold and the plastic film and cured into the desired shape. When the VaRTM molding method is applied to the production of the fiber-reinforced resin molded article of this embodiment, the mold temperature (mold temperature) is preferably 100°C to 200°C. Furthermore, curing can be completed in about 1 minute to 15 minutes after the reinforcing fibers are impregnated with the resin composition.

[0072] 3. Physical properties of fiber-reinforced resin moldings In the fiber-reinforced resin molding of this embodiment, the interfacial shear strength is preferably 47 MPa or more. When the interfacial shear strength is 47 MPa or more, the cured resin and the reinforcing fibers are well adhered to each other, which prevents cracks from occurring during screwing or drilling. In other words, a fiber-reinforced resin molding with excellent processability can be more reliably obtained.

[0073] In this specification, the term "interfacial shear strength (of a fiber-reinforced resin molding)" refers to the interfacial shear strength measured by the microdroplet method using a composite interface property evaluation device, as will be described in detail in the examples below.

[0074] The interfacial shear strength of the fiber-reinforced resin molded body is more preferably 48 MPa or more, and even more preferably 49 MPa or more. The upper limit of the interfacial shear strength of the fiber-reinforced resin molded body is not particularly limited, but from the viewpoint of maintaining sufficient interlaminar shear strength, the interfacial shear strength may be, for example, 70 MPa or less.

[0075] As mentioned above, the interfacial shear strength of the fiber-reinforced resin molding can be efficiently increased by including mainly a tertiary amine as a curing accelerator, and by including as little imidazole derivative as possible.

[0076] The flexural strength of the fiber-reinforced resin molded body is preferably 1200 MPa or more. When the flexural strength is 1200 MPa or more, the fiber-reinforced resin molded body has sufficient flexural strength, and can be suitably used as a substitute for various materials.

[0077] In this specification, the "bending strength (of a fiber-reinforced resin molding)" means the bending strength measured by carrying out a three-point bending test in accordance with JIS K 7074:1988, as will be described in detail in the examples below.

[0078] The flexural modulus of the fiber-reinforced resin molded body is preferably 130 GPa or more. When the flexural modulus is 130 GPa or more, the fiber-reinforced resin molded body has a sufficient flexural modulus, and can be suitably used as a substitute for various materials.

[0079] In this specification, the "flexural modulus (of a fiber-reinforced resin molding)" refers to the flexural modulus measured by a three-point bending test in accordance with JIS K 7074:1988, as will be described in detail in the Examples below.

[0080] Thus, in the fiber-reinforced resin molded article of this embodiment, a monofunctional epoxy resin as an epoxy diluent and a tertiary amine as a curing accelerator are combined in the resin composition, and the glass transition temperature Tg of the resin composition is adjusted to 110°C or lower. As a result, the fiber-reinforced resin molded article has excellent processability. Specifically, even when fiber-reinforced resin molded articles are fastened to each other or to other materials with screws, or when holes are drilled in the fiber-reinforced resin molded article, cracks and burrs are unlikely to occur. Therefore, the fiber-reinforced resin molded article of this embodiment can be suitably used as a substitute for metal or wood materials in materials such as base materials, interior materials, exterior materials, sheet materials, building materials, materials used in furniture, materials used for housings of electrical or electronic devices, materials used in vehicles or vehicle components, and materials used in civil engineering structures. [Example]

[0081] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0082] In this example, various resin compositions were prepared by varying the types and amounts of epoxy resin, epoxy diluent, curing agent, and curing accelerator contained in the resin composition. Test pieces of various fiber-reinforced resin moldings were then prepared using the resin compositions. Furthermore, the physical properties (glass transition temperature Tg and crosslink density) of the various resin compositions were measured, and processability tests (screw-driving processability test and hole-drilling processability test) were conducted using the test pieces of the various fiber-reinforced resin moldings. Furthermore, although not related to the problem to be solved by the present invention, as reference tests, the interfacial shear strength and bending test were also conducted using the test pieces of the various fiber-reinforced resin moldings.

[0083] In this example, the glass transition temperature Tg (°C) and crosslink density (mol / cm 3 ) was measured by a dynamic viscoelasticity test (torsion pendulum method) in accordance with JIS K7244-10:2005 using a thermal analyzer ("EXSTAR6000", manufactured by Hitachi High-Tech Science Corporation). The size of the test piece was 25 mm (length) × 10 mm (width) × 1 mm (thickness). In this example, the volume content (%) of carbon fiber was measured by a combustion method.

[0084] First, the materials used to prepare test specimens of the fiber-reinforced resin moldings of the respective Examples and Comparative Examples and the methods for preparing the test specimens will be described in detail below.

[0085] <Materials for test specimens of fiber-reinforced resin moldings> The materials used in producing the test pieces of the fiber-reinforced resin moldings of the examples and comparative examples and shown in Table 1 are as follows. Bisphenol A epoxy resin: "EPICLON850" (registered trademark), manufactured by DIC Corporation (epoxy equivalent: 189 g / eq) Monofunctional epoxy resin: p-tert-butylphenyl glycidyl ether, "Denacol (registered trademark) EX-146", manufactured by Nagase ChemteX Corporation (epoxy equivalent: 225 g / eq) Bifunctional epoxy resin: Neopentyl glycol glycidyl ether, "ADEKA GLYCIROL ED-523T" manufactured by ADEKA Corporation (epoxy equivalent: 140g / eq) Hardener: Methyltetrahydrophthalic anhydride, "HN-2200", manufactured by Resonac Co., Ltd. (acid anhydride equivalent: 168g / eq) Tertiary amine: Tris-2,4,6-dimethylaminomethylphenol, "Ancamine K54," manufactured by Evonik Japan Co., Ltd. Imidazole compound: 1-cyanoethyl-2-ethyl-4-methylimidazole, Curezol (registered trademark) "2E4MZ-CN", manufactured by Shikoku Chemicals Corporation Internal release agent: Aliphatic amine-based release agent, MoldWiz (registered trademark) "INT-1888LE", manufactured by Axel Plastics Research Laboratories Carbon fiber: TORAYCA (registered trademark) "T700S-24K" (fiber diameter 7 μm, fineness: 1650 tex), manufactured by Toray Industries, Inc.

[0086] <Method for preparing test pieces of fiber-reinforced resin moldings> Test pieces of the fiber-reinforced resin moldings of each Example and Comparative Example were prepared by the following method. First, an epoxy resin, an epoxy diluent, a curing agent, a curing accelerator, and an internal mold release agent were mixed in the ratios shown in Table 1 below for each Example and Comparative Example to prepare a resin composition. After preparation, the glass transition temperature Tg (°C) and crosslink density (mol / cm) of the resin composition obtained for each Example and Comparative Example were measured. 3 ) was measured by the method described above. The measurement results are summarized in Table 1 below.

[0087] Carbon fibers were used as the reinforcing fibers. The resin compositions of each Example and Comparative Example prepared as described above were impregnated into reinforcing fibers, and the resin compositions and reinforcing fibers were filled into a mold and held for a predetermined time. The resin compositions were cured and then pulled out to obtain fiber-reinforced resin molded articles (pultrusion molding method). The mold temperature was 180°C, and the holding time in the mold was 2 minutes. The obtained rectangular fiber-reinforced resin molded articles were cut to prepare test pieces of the fiber-reinforced resin molded articles of each Example and Comparative Example (for example, test pieces with a size of 500 mm (length) × 30 mm (width) × 2 mm (thickness)) for use in the subsequent tests.

[0088] In all examples and comparative examples, the amount of reinforcing fiber impregnated with the resin composition was adjusted so that the volume fraction Vf of the reinforcing fiber was 70%.

[0089] The blending ratio of the resin composition, the physical properties of the resin composition, and the physical properties of the fiber-reinforced resin molded article in each example and comparative example are summarized in Table 1 below.

[0090] [Table 1]

[0091] Next, the processability test methods (screw driving processability test method and hole drilling processability test method) using test pieces of fiber-reinforced resin moldings, as well as the method for measuring interfacial shear strength and bending test method as reference evaluations, will be described in detail below.

[0092] <Processability test method> (Screw driving workability test method) The screw driving workability test was carried out by the following method. A drill screw was screwed into a test piece of a fiber-reinforced resin molding measuring 500 mm (length) × 30 mm (width) × 2 mm (thickness) produced in each of the above-mentioned Examples and Comparative Examples. The test piece was then observed around the protruding tip of the screw. If no cracks or burrs were found in the test piece, the test result was judged to be "good" (i.e., excellent screw driving workability). On the other hand, if cracks or burrs were found in the test piece, the test result was judged to be "poor" (i.e., poor screw driving workability).

[0093] (Drilling workability test method) The drilling workability test was carried out by the following method. A 3 mm diameter hole was drilled using a drill in a test piece of the fiber-reinforced resin molding having a size of 500 mm (length) × 30 mm (width) × 2 mm (thickness) produced in each of the above examples and comparative examples. The vicinity of the opening of the test piece was then observed. If no cracks or burrs occurred in the test piece, the test result was judged to be "good" (i.e., excellent drilling workability). On the other hand, if cracks or burrs occurred in the test piece, the test result was judged to be "poor" (i.e., poor drilling workability).

[0094] <Method for measuring interfacial shear strength> The interfacial shear strength (MPa) of the test pieces of the fiber-reinforced resin moldings used for reference evaluation was measured by the microdroplet method using a composite interfacial property evaluation device ("MODEL HM410", manufactured by Toei Sangyo Co., Ltd.) Note that the size of the test pieces used in each example and comparative example was a resin ball diameter of approximately 50 μm, and these test pieces were used as the evaluation subjects.

[0095] <Bending test method> A bending test of the test pieces of the fiber-reinforced resin moldings used for reference evaluation was carried out as follows: Using the test pieces of the fiber-reinforced resin moldings with dimensions of 100 mm (length) × 15 mm (width) × 2 mm (thickness) produced in each of the above-mentioned Examples and Comparative Examples, a three-point bending test was carried out in accordance with JIS K 7074:1988 to measure the bending strength and bending modulus of the test pieces of the fiber-reinforced resin moldings.

[0096] The evaluation or measurement results of the processability test, interfacial shear strength and bending test for the test pieces of the fiber-reinforced resin moldings of each Example and Comparative Example are summarized in Table 2 below.

[0097] [Table 2]

[0098] <Consideration> As shown in Table 2 above, the test pieces of the fiber-reinforced resin moldings of Examples 1 to 3 all had excellent processability (screw-driving processability and hole-drilling processability). Furthermore, the test pieces of the fiber-reinforced resin moldings of Examples 1 to 3 maintained sufficient values ​​for the interfacial shear strength, flexural strength, and flexural modulus of elasticity, which were used as reference evaluations.

[0099] On the other hand, as shown in Table 2 above, the test piece of the fiber-reinforced resin molding of Comparative Example 1 had poor workability in both screw driving and drilling. This is presumably because the resin composition containing only an imidazole compound and no tertiary amine as a curing accelerator had a high glass transition temperature Tg (°C) of the resin composition, and the interfacial shear strength of the test piece of the fiber-reinforced resin molding also decreased, ultimately leading to poor workability.

[0100] The test piece of the fiber-reinforced resin molding of Comparative Example 2 also had poor workability in both screwing and drilling. This is presumably because the resin composition containing only a difunctional epoxy resin and no monofunctional epoxy resin as an epoxy diluent has a high glass transition temperature Tg (°C), which ultimately leads to poor workability.

[0101] The test piece of the fiber-reinforced resin molding of Comparative Example 3 also had poor workability in both screwing and drilling. This is because the resin composition containing no epoxy diluent had a low glass transition temperature Tg (°C) and a low crosslink density (mol / cm 3 ) and ultimately lead to deterioration of workability.

[0102] The test piece of the fiber-reinforced resin molding of Comparative Example 4 also had poor workability in both screwing and drilling. This is because the resin composition containing only an excessively small amount of monofunctional epoxy resin as the epoxy diluent has a low glass transition temperature Tg (°C) and a low crosslink density (mol / cm 3 ) also maintained a high value, which is assumed to ultimately lead to a deterioration in workability.

Claims

1. A fiber-reinforced resin molding is obtained by impregnating reinforcing fibers with a resin composition containing an epoxy resin, an epoxy diluent, a curing agent, and a curing accelerator, and curing the impregnated fiber. the epoxy diluent comprises a monofunctional epoxy resin; The curing accelerator comprises a tertiary amine, and The resin composition has a glass transition temperature Tg of 110°C or less.

2. The fiber-reinforced resin molding according to claim 1 , wherein the curing agent includes an acid anhydride.

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