Fiber-reinforced resins and integral molded products

Abstract

The present invention aims to provide a fiber-reinforced resin that allows for welding with other components via thermoplastic resin, and is less prone to damage even during high-temperature welding. The present invention is a fiber-reinforced resin comprising reinforcing fibers, and having an epoxy resin cured region and a thermoplastic resin region formed on its surface, wherein the aromatic ring content of the epoxy resin cured region constituting the aforementioned epoxy resin cured region is 50% to 90%.

Description

Technical Field

[0001] This invention relates to fiber-reinforced resin and integrally molded articles formed by fusing fiber-reinforced resin with other components. Prior Technology

[0002] Fiber-reinforced resins, which use thermosetting resins such as epoxy resin as a matrix and combine them with reinforcing fibers such as carbon fiber or glass fiber, are lightweight and possess excellent mechanical properties such as strength, rigidity, heat resistance, and corrosion resistance. Therefore, they have long been used in numerous fields such as aerospace, automotive, railway vehicles, shipbuilding, civil engineering, sporting goods, and electronic components. On the other hand, fiber-reinforced resins using thermosetting resins are not suitable for molding complex shapes. In order to manufacture parts or structures with complex shapes, it is necessary to mold fiber-reinforced resin components with relatively simple shapes and then integrate the fiber-reinforced resin with other components (hereinafter referred to as "other components") made of the same or different materials.

[0003] As a method of integrating fiber-reinforced resin with other components, mechanical joining methods such as bolts, rivets, and screws are used; or adhesive joining methods are used. However, mechanical joining methods require pre-processing steps such as drilling holes to prepare the joint, which leads to problems related to longer processing times, increased manufacturing costs, and reduced material strength due to processing. Adhesive joining methods require adhesive preparation, application, and curing steps, which also leads to longer processing times and difficulties in achieving sufficiently reliable bond strength.

[0004] As a solution to this problem, a fiber-reinforced resin has been developed in recent years, which involves forming a thermoplastic resin layer on the surface of a fiber-reinforced resin that uses a thermosetting resin (Patent Document 1). This fiber-reinforced resin can be easily bonded to other components by fusing the thermoplastic resin layer. [Previous Technical Documents] [Patent Literature]

[0005] Patent Document 1: International Publication No. 2004 / 060658 Summary of the Invention

[0006] [The problem the invention aims to solve]

[0007] In applications requiring special heat resistance, when using high-melting-point resins such as super engineering plastics as the thermoplastic resin layer of a fiber-reinforced resin, temperatures exceeding 300°C are necessary for welding with other components. At this temperature, the surrounding epoxy resin is also exposed to temperatures above 300°C. Since epoxy resin tends to decompose rapidly around 300°C, there are concerns about damage caused by epoxy resin decomposition when welding is performed at temperatures near 300°C.

[0008] The present invention aims to provide a fiber-reinforced resin that is possible to be welded to other components by means of a thermoplastic resin, and is not prone to damage even when welding is performed at such high temperatures. [Methods used to solve problems]

[0009] In order to solve the problem, the fiber-reinforced resin of the present invention is a fiber-reinforced resin that includes reinforcing fibers and has an epoxy resin curing region and a thermoplastic resin region formed on the surface, wherein the proportion of aromatic rings in the epoxy resin curing region constituting the aforementioned epoxy resin curing region is more than 50% and less than 90%. [Effects of the Invention]

[0010] By using the fiber-reinforced resin of the present invention, damage is less likely to occur when the thermoplastic resin area is fused with other components, and it is possible to produce integral molded articles with excellent tensile shear bond strength. Simple Explanation of the Diagram

[0011] Figure 1 is a schematic diagram of a cross-section of the fiber-reinforced resin of the present invention perpendicular to the surface, which serves as an illustration of the method for determining the average roughness length RSm and the average roughness height Rc described later. Implementation

[0012] [The form in which the invention is carried out]

[0013] In this specification, "~" is considered to represent a range of values ​​including both ends of it.

[0014] The fiber-reinforced resin of the present invention is a fiber-reinforced resin that includes reinforcing fibers and has an epoxy resin curing region and a thermoplastic resin region formed on the surface. The epoxy resin curing region constituting the epoxy resin curing region has an aromatic ring ratio of 50% to 90% in all its molecules.

[0015] The fiber-reinforced resin of this invention has thermoplastic resin regions formed on its surface, thereby enabling other components to be fused to these thermoplastic resin regions to create an integrally molded article. Furthermore, "other components" is not particularly limited and may include components comprising thermoplastic resin, components made of metal materials, or the fiber-reinforced resin of this invention. Additionally, sometimes the other components fused to the thermoplastic resin regions on the surface of the fiber-reinforced resin of this invention to form an integrally molded article are referred to as bonded materials. The thermoplastic resins contained in this thermoplastic resin region are not particularly limited, and examples include polyester resins (polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, polyethylene naphthalate, liquid crystal polyester, etc.), or polyolefin resins (polyethylene, polypropylene, polybutene, etc.), styrene resins, and urethane resins. Other examples include polyoxymethylene, polyamide resins (aliphatic polyamides such as polyamide 6 and polyamide 66, semi-aromatic polyamides, alicyclic polyamides, etc.), polycarbonate, polymethyl methacrylate, polyvinyl chloride, polyphenylene sulfide, and polyphenylene ether. The thermoplastic resins include polyether, modified polyphenylene ether, polyimide, polyamide-imide, polyether-imide, polysulfide, modified polysulfide, polyether-sulfide, and polyketone, polyarylene ether ketone (polyether ketone, polyether ether ketone, polyether ketone ketone, etc.), polyarylate, polyether nitrile, phenolic resins, phenoxy resins, etc. Furthermore, these thermoplastic resins can also be copolymers or modifiers of the above resins, and / or resins made by blending two or more types. Among these, fiber-reinforced resins with excellent heat resistance are particularly preferred, including polyketone, polyether ketone, polyether ether ketone, polyether ketone ketone, polyarylene ether ketone, alicyclic polyamide, semi-aromatic polyamide, polyphenylene sulfide, polyether-imide, polyether-sulfide, polysulfide, modified polysulfide, and polyamide-imide.

[0016] In particular, in the fiber-reinforced resin of the present invention, it is preferable that the epoxy resin cured region and the surface thermoplastic resin region are respectively layered and adjacent. Layered and adjacent means, for example, as shown in FIG. 1, in a cross-section obtained by cutting perpendicularly to the plane direction of the prepreg, that the continuous thermoplastic resin region 2 and the epoxy resin cured region 3 in the surface direction form a boundary surface 5 and are closely connected. When the thermoplastic resin is not layered and continuous, but exists in a particulate, fibrous, or non-woven form, the proportion of epoxy resin exposed on the surface increases, and the coverage of the thermoplastic resin on the outermost surface decreases, tending to reduce weldability.

[0017] A surface area mass of 10 g / m² or higher for the thermoplastic resin region results in excellent bonding strength with the bonded material, and is therefore preferred. A surface area mass of 20 g / m² is more preferable. While no upper limit is specifically defined, since the amount of thermoplastic resin will not become excessive compared to reinforcing fibers, and fiber-reinforced resins with excellent specific strength and specific modulus of elasticity can be obtained, a surface area mass of 500 g / m² or less for the thermoplastic resin region is preferred. Here, the surface area mass of the thermoplastic resin region refers to the mass (g) of thermoplastic resin constituting the thermoplastic resin region contained in 1 m² of fiber-reinforced resin.

[0018] Regarding the reinforcing fibers contained in the fiber-reinforcing resin of the present invention, the following can be used: glass fiber, carbon fiber, metal fiber, aromatic polyamide fiber, polyarylamide fiber, alumina fiber, silicon carbide fiber, boron fiber, basalt fiber, etc. These can be used alone or in combination of two or more.

[0019] For reinforcing fibers, carbon fiber with low specific gravity, high strength, and high modulus of elasticity is preferred. Commercially available carbon fiber products include: "TORAYCA (registered trademark)" T800G-24K, "TORAYCA (registered trademark)" T800S-24K, "TORAYCA (registered trademark)" T700G-24K, "TORAYCA (registered trademark)" T700S-24K, "TORAYCA (registered trademark)" T300-3K, "TORAYCA (registered trademark)" T1100G-24K, "TORAYCA (registered trademark)" M30S-18K, "TORAYCA (registered trademark)" M40J-12K, and "TORAYCA (registered trademark)" M60J-6K (all manufactured by Toray Industries, Inc.).

[0020] The thermal conductivity of the reinforcing fiber used in the fiber-reinforced resin of this invention is preferably 100 W / (m·K) or less. If the thermal conductivity of the reinforcing fiber is 100 W / (m·K) or less, the heat transferred to the epoxy resin curing material in the fiber-reinforced resin is suppressed when heat is applied to the fiber-reinforced resin during welding, and the thermal decomposition of the epoxy resin is suppressed, thus becoming a preferred state. The reinforcing fiber having the above-mentioned thermal conductivity is more preferably carbon fiber. The above-mentioned thermal conductivity is more preferably 50 W / (m·K) or less, and more preferably 30 W / (m·K) or less. The lower limit for the thermal conductivity of the reinforcing fiber is not particularly limited; if it is ordinary carbon fiber, the lower limit is 3 W / (m·K).

[0021] Furthermore, the reinforcing fibers used in the fiber-reinforced resin of the present invention, whose tensile strength is measured according to the resin impregnation strand test method of JIS R7608 (2007) is 5.5 GPa or higher, can obtain a fiber-reinforced resin with excellent bonding strength in addition to tensile strength, and is therefore preferred. It is further preferred if the tensile strength of the strand is 5.8 GPa or higher. The bonding strength referred to herein refers to the bonding strength when joined to other components by fusion through the thermoplastic resin area of ​​the surface, and is the tensile shear bond strength obtained according to ISO 4587:1995 (JIS K6850 (1994)).

[0022] These reinforcing fibers can also be surface-treated. Surface treatments include: bonding treatment with metals, treatment using coupling agents, treatment using sizing agents, and adhesion treatment with additives.

[0023] Specifically, for reinforcing fibers, it is preferable to use fibers with a surface free energy of 10 mJ / m² to 50 mJ / m² as measured by the Wilhelmy method. By controlling this range, the aforementioned reinforcing fibers exhibit high affinity with the aforementioned epoxy resin and thermoplastic resin, and demonstrate excellent tensile shear bond strength when joined to other components by fusion welding through the thermoplastic resin region of the surface. Furthermore, by suppressing the aggregation of the aforementioned reinforcing fibers, the dispersion of the reinforcing fibers in the molded article becomes better, and the deviation (coefficient of variation) of the tensile shear bond strength is reduced. The surface free energy of the aforementioned reinforcing fibers is preferably 15 mJ / m² to 40 mJ / m², more preferably 18 mJ / m² to 35 mJ / m². Regarding methods for controlling the surface free energy of the aforementioned reinforcing fibers, there are: methods that control the surface by oxidizing it and adjusting the amount of oxygen-containing functional groups such as carboxyl and hydroxyl groups; and methods that control the surface by attaching monomers or multiple compounds to the surface. When multiple compounds are attached to the surface, compounds with high and low surface free energies can be mixed for attachment. The surface free energy can be calculated by measuring the contact angles of the reinforcing fiber with three types of solvents (purified water, ethylene glycol, and trimethylol phosphate), and then calculating the surface free energy using Owens' approximation. The procedure is shown below, but the measuring equipment and detailed methods are not necessarily limited to the following.

[0024] Using the DCAT11 manufactured by DataPhysics, firstly, a single fiber was taken from the reinforcing fiber bundle and cut into eight pieces with a length of 12±2 mm. These single fibers were then attached parallel to each other, spaced 2-3 mm apart, to a dedicated clamping fixture FH12 (a flat plate coated with an adhesive material). Next, the tips of the single fibers were trimmed and placed on the DCAT11 clamping fixture. The measurement was performed by bringing a tank containing various solvents close to the lower ends of the eight single fibers at a speed of 0.2 mm / s, immersing them to 5 mm from the tip of each fiber. Then, the single fiber was lifted at a speed of 0.2 mm / s. This operation was repeated at least four times. The force F experienced by the single fiber during immersion in the liquid was measured using an electronic balance. Using this value, the contact angle θ was calculated using the following formula. COSθ = (Force F (mN) on 8 single fibers) / (8 (number of single fibers) × circumference of single fiber (m) × surface tension of solvent (mJ / m²)) Furthermore, the measurements were performed on individual fibers extracted from three different locations within the reinforcing fiber bundle. That is, the average contact angle for a total of 24 individual fibers was calculated for each reinforcing fiber bundle.

[0025] The surface free energy γf of the reinforcing fiber is calculated as the sum of the polar component γpf and the nonpolar component γdf of the surface free energy. The polar component γpf is obtained by substituting the surface tension components and contact angles of each liquid into Owens' approximation (formulated by the polar and nonpolar components of the inherent surface tension of each solvent, and the contact angle θ), plotted on X and Y, and then obtaining the square of the slope a when performing a linear approximation using the least squares method. The nonpolar component γdf of the surface free energy is obtained by the square of the intercept b. Therefore, the surface free energy γf of the reinforcing fiber is the sum of the square of the slope a and the square of the intercept b. Y = a·X + b X = √(polar component of solvent surface tension (mJ / m²)) / √(non-polar component of solvent surface tension (mJ / m²)) Y = (1 + COSθ)·(polar component of solvent surface tension (mJ / m²)) / 2√(non-polar component of solvent surface tension (mJ / m²)) The polar component of the surface free energy of the reinforcing fiber is γpf = a². The nonpolar component of the surface free energy of the reinforcing fiber is γdf = b2. The total surface free energy γf = a² + b².

[0026] The polar and non-polar components of the surface tension of each solvent are as follows. Purified water Surface tension: 72.8 mJ / m², polar component: 51.0 mJ / m², nonpolar component: 21.8 mJ / m² · Ethylene glycol Surface tension: 48.0 mJ / m², polar component: 19.0 mJ / m², nonpolar component: 29.0 mJ / m² Tricresol phosphate The surface tension is 40.9 mJ / m², with a polar component of 1.7 mJ / m² and a nonpolar component of 39.2 mJ / m².

[0027] Regarding the morphology and arrangement of the reinforcing fibers, suitable options include reinforcing fibers arranged in one direction, laminates of such fibers, woven fabrics, knitted fabrics, nonwoven fabrics, felts, and braided tapes. However, to obtain fiber-reinforcing resins with higher levels of lightweight and durability, it is preferable to use long fibers (fiber bundles) or continuous fibers such as woven fabrics in each preimpregnated material, where the reinforcing fibers are arranged in one direction. Furthermore, from the viewpoint of shapeability and shape conformability during molding, the use of nonwoven fabrics or felts with discontinuous reinforcing fibers is also preferable.

[0028] The mass content of reinforcing fibers in the fiber-reinforced resin of the present invention is preferably 30% by mass or more and 90% by mass or less, more preferably 35% by mass or more and 85% by mass or less, and even more preferably 40% by mass or more and 80% by mass or less. If the mass content of reinforcing fibers is 30% by mass or more, the amount of resin will not become excessive compared to the amount of fibers, making it easier to obtain a fiber-reinforced resin with excellent specific strength and specific modulus of elasticity. Furthermore, if the mass content of reinforcing fibers is 90% by mass or less, poor resin impregnation is less likely to occur, and the resulting fiber-reinforced resin will have fewer voids.

[0029] The epoxy resin cured material constituting the fiber-reinforcing resin of the present invention has an aromatic ring content of 50% to 90%. If the aromatic ring content is less than 50%, the epoxy resin cured material is prone to thermal decomposition at high temperatures, resulting in a significant reduction in mechanical properties such as compressive strength as a fiber-reinforcing resin, and tensile shear bond strength when fused with other components. If the aromatic ring content is 90% or more, the mechanical properties as a fiber-reinforcing resin are reduced due to compromised flexibility. The aromatic ring content of the epoxy resin cured material is preferably 55% to 80%.

[0030] In this specification, the aromatic ring ratio of the epoxy resin cured product refers to the mass ratio of aromatic rings constituting the chemical structure of the epoxy resin cured product, calculated by dividing the total mass of all aromatic rings in the entire chemical structural formula by the total mass of all molecules in the entire chemical structural formula. Furthermore, when the aromatic ring contains substituents such as methyl groups, the mass of the aromatic ring does not include the mass of the substituents. For example, the aromatic ring mass of benzene is set to 78.1 g / mol, and the aromatic ring mass of toluene is set to 77.1 g / mol for calculation.

[0031] When the chemical structures of each compound in the epoxy resin composition before curing are known, the aromatic ring ratio of the epoxy resin curing product can be calculated from its chemical structure. Furthermore, when the chemical structure is unknown, it can be calculated by identifying the chemical structure of the epoxy resin curing product using thermal decomposition gas chromatography-mass spectrometry. For example, when the epoxy resin curing product is composed of the chemical structures of formulas (1) and (2), and the molecular proportions are 70% and 30% of the total, respectively, the aromatic ring ratio of the epoxy resin curing product becomes... (76.1×4×0.70+(126.2+76.1×2)×0.3) / (676.9×0.7+522.6 ×0.3)=47.1%.

[0032]

[0033]

[0034] In this invention, the epoxy resin cured product, in terms of improving resistance to thermal decomposition at high temperatures, is preferably a cured product comprising an epoxy resin composition having a polycyclic aromatic hydrocarbon backbone or a biphenyl backbone.

[0035] Epoxy resins with a polycyclic aromatic hydrocarbon backbone include: epoxy resins with a naphthalene backbone, epoxy resins with anthracene backbone, epoxy resins with a phenanthrene backbone, epoxy resins with a pyrene backbone, and epoxy resins with a condensed tetraphenyl backbone. Examples include: naphthylene ether type epoxy resins, naphthalene glycol type epoxy resins, methyleneenedinaphthol type epoxy resins, dinaphthol type epoxy resins, naphthol phenylaryl type epoxy resins, naphthol biphenylaryl type epoxy resins, and anthracene glycol type epoxy resins. Epoxy resins with a biphenyl backbone include: biphenol diglycidyl ether and phenol biphenylaryl type epoxy resins.

[0036] Furthermore, in the epoxy resin cured product of the present invention, the epoxy resin composition with an average epoxy equivalent of 160 g / eq. to 255 g / eq. is preferred for improving resistance to thermal decomposition at high temperatures and exhibiting excellent glass transition temperature. More preferably, the average epoxy equivalent is 180 g / eq. to 255 g / eq. Here, as an example, when the product contains two components, epoxy resin 1 and epoxy resin 2, the average epoxy equivalent is calculated as follows. In addition, in this specification, epoxy equivalent refers to the value obtained by the method described in JIS K7236 (2009). Average epoxy equivalent (g / eq.) = (mass parts of epoxy resin 1 × epoxy equivalent of epoxy resin 1 + mass parts of epoxy resin 2 × epoxy equivalent of epoxy resin 2) / (mass parts of epoxy resin 1 + mass parts of epoxy resin 2) Furthermore, the same calculation method applies when the epoxy resin contains 3 or more components. When there are N epoxy resin components, from epoxy resin 1 to epoxy resin N, the calculation is as follows. Average epoxy equivalent (g / eq.) = (mass parts of epoxy resin 1 × epoxy equivalent of epoxy resin 1 + mass parts of epoxy resin 2 × epoxy equivalent of epoxy resin 2 + ... + mass parts of epoxy resin N × epoxy equivalent of epoxy resin N) / (mass parts of epoxy resin 1 + mass parts of epoxy resin 2 + ... + mass parts of epoxy resin N) The epoxy resin cured product of this invention comprises an epoxy resin composition containing a polyamine compound with an average active hydrogen equivalent of 55 g / eq. to 100 g / eq., which improves resistance to thermal decomposition at high temperatures, thus being preferable. In this specification, "polyamine compound" refers to a general term for compounds having two or more amine groups, such as dicyandiamide, aliphatic amine compounds, aromatic amine compounds, tetramethylguanidine, thiourea addition amines, and carboxylic acid hydrazide. Furthermore, in this specification, the active hydrogen equivalent of the polyamine compound refers to the active hydrogen equivalent calculated by liquid chromatography-mass spectrometry (LC / MS) to identify its chemical structure and proportions. Here, as an example, when the product contains two components, polyamine compound 1 and polyamine compound 2, the average active hydrogen equivalent is calculated as follows. Average active hydrogen equivalent (g / eq.) = (mass parts of polyamine compound 1 × active hydrogen equivalent of polyamine compound + mass parts of polyamine compound 2 × active hydrogen equivalent of polyamine compound 2) / (mass parts of polyamine compound 1 + mass parts of polyamine compound 2) When the compound contains 3 or more polyamine compounds, the calculation can be performed in the same way as for epoxy resins.

[0037] When the epoxy resin includes epoxy resins other than those with a polycyclic aromatic hydrocarbon backbone or a biphenyl backbone, examples of such epoxy resins include: bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD ​​type epoxy resin, bisphenol S type epoxy resin, and other bisphenol-type epoxy resins; brominated epoxy resins such as tetrabromobisphenol A diglycidyl ether; epoxy resins with a dicyclopentadiene backbone; phenolic varnish type epoxy resins such as phenolic varnish type epoxy resins and cresol phenolic varnish type epoxy resins; N,N,O-triglycidyl-m-aminophenol; N,N,O-triglycidyl-p-aminophenol; N,N,O-triglycidyl-4-amino-3-methylphenol; and others. Glycidylamine type epoxy resins such as phenyl phenol, N,N,N',N'-tetraglycidyl-4,4'-methylenediphenylamine, N,N,N',N'-tetraglycidyl-2,2'-diethyl-4,4'-methylenediphenylamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine, N,N-diglycidyl aniline, and N,N-diglycidyl-o-toluidine, as well as resorcinol diglycidyl ether and triglycidyl triisocyanate, etc.

[0038] By using aromatic amine compounds having two or more amino groups as polyamine compounds, good reactivity and excellent mechanical properties and heat resistance as hardened substances can be obtained, thus making them superior. Examples of aromatic amine compounds having two or more amino groups include diaminodiphenylamine, diaminobenzylaniline, diaminobenzophenone, and diaminodiphenylmethane, and their isomers, as well as adducts of aliphatic hydrocarbons or halogen groups, can be listed.

[0039] The epoxy resin cured product in the fiber-reinforced resin of the present invention is preferably a cured product of an epoxy resin composition whose heat loss rate is less than 1.0% when the cured product obtained by heating at 180°C for 120 minutes is held at 300°C for 2 minutes. More preferably, it is a cured product of an epoxy resin composition with a glass transition temperature of 180°C to 350°C. Because the cured product possesses such characteristics, when it is fused to other components through the thermoplastic resin layer on the surface of the fiber-reinforced resin, damage during fusion can be suppressed. A more preferred heat loss rate when held at 300°C for 2 minutes is less than 0.7%, and even more preferably less than 0.5%. The thermal mass reduction rate of epoxy resin cured products can be obtained based on JIS K7120 (1987). Furthermore, the glass transition temperature can be obtained based on JIS K7244-7 (2007).

[0040] In the fiber-reinforced resin of the present invention, it is preferable that the average roughness length RSm of the boundary surface between the aforementioned epoxy resin cured region and the aforementioned thermoplastic resin region is 100 μm or less, and the average roughness height Rc is 3.5 μm or more. Here, the average roughness length RSm and the average roughness height Rc of the boundary surface between the aforementioned epoxy resin cured region and the aforementioned thermoplastic resin region are defined as the average roughness length RSm and the average roughness height Rc of the cross-sectional curve formed by the boundary surface of the two resin regions in a cross-section obtained by cutting perpendicularly to the plane direction of the fiber-reinforced resin, as defined in JIS B0601 (2001). If the average roughness length RSm of the cross-sectional curve is 100 μm or less, then not only the chemical and / or physical bonding force, but also the mechanical bonding force such as entanglement, makes it more difficult for the epoxy resin cured region and the resin region containing the thermoplastic resin to peel off. The lower limit of RSm is not specifically limited, but from the viewpoint of avoiding a decrease in mechanical bonding strength due to stress concentration, it is preferable to be 15 μm or more. Furthermore, an average height Rc of the cross-sectional profile of 3.5 μm or more not only reflects the mechanical bonding strength due to entanglement, but also allows the reinforcing fibers present on the boundary surface to chemically and / or physically bond with the epoxy and thermoplastic resins, thus increasing the adhesion between the epoxy resin cured area and the resin area containing the thermoplastic resin, which is therefore preferable. A more favorable range for the average height Rc of the cross-sectional profile is 10 μm or more, where the reinforcing fibers easily bond with the two resin areas and the adhesion strength is further improved, and preferably 20 μm or more. While the upper limit of Rc is not specifically limited, from the viewpoint of avoiding a decrease in mechanical bonding strength due to stress concentration, it is preferable to be 100 μm or less.

[0041] Here, regarding the determination of the average height Rc and average length RSm of the cross-sectional curve, known methods can be used. Examples include: methods using cross-sectional images obtained from X-ray CT, methods using elemental analysis mapping images obtained from an energy dispersive X-ray spectrometer (EDS), and methods using cross-sectional observation images obtained from an optical microscope, scanning electron microscope (SEM), or transmission electron microscope (TEM). During observation, epoxy resin and / or thermoplastic resin may be stained to adjust contrast. In images obtained using any of the above methods, the average height Rc and average length RSm of the cross-sectional curve are determined within a 500 μm square area.

[0042] Figure 1 shows an example of a method for determining the average height Rc and average length RSm of a cross-sectional curve (Method 1 for determining cross-sectional curve elements). The end 6 of the epoxy resin cured area side of the rectangular observation image 4 is set as the baseline, and a vertical baseline 7 is drawn from the epoxy resin cured area 3 toward the thermoplastic resin area 2 at 5 μm intervals. The point where the vertical baseline drawn from the baseline first intersects with the thermoplastic resin area 2 is marked, and the line connecting the marked points is designated as the cross-sectional curve 8. The obtained cross-sectional curve 8 is subjected to filtering based on JIS B0601 (2001), and the average height Rc and average length RSm of the cross-sectional curve 8 are calculated.

[0043] Furthermore, the fiber-reinforced resin of the present invention preferably contains reinforcing fibers that cross the boundary between the aforementioned epoxy resin cured region and the aforementioned thermoplastic resin region and are in contact with both resin regions. The presence of such reinforcing fibers can be confirmed by observing a cross-section obtained by cutting perpendicularly in the planar direction. For example, in the cross-sectional observation image 4 shown in FIG1, a plurality of reinforcing fibers 1 are present on the boundary 5 between the thermoplastic resin region 2 and the epoxy resin cured region 3. The reinforcing fibers 1 on the boundary 5 are in contact with both the thermoplastic resin region 2 and the epoxy resin cured region 3. This state in which the thermoplastic resin and epoxy resin are in contact with the surrounding reinforcing fibers can be described as a state in which the reinforcing fibers "cross the boundary and are in contact with both resin regions".

[0044] By employing reinforcing fibers that cross the boundary between the epoxy resin cured region and the thermoplastic resin region and connect with both resin regions, the strength of the thermoplastic resin region is enhanced, as is the bond strength. Furthermore, the reinforcing fibers crossing the boundary region chemically and / or physically bond with the heat-cured epoxy resin and thermoplastic resin, thereby further enhancing the adhesion between the heat-cured epoxy resin region and the thermoplastic resin region, and ultimately improving the bond strength.

[0045] To improve impact resistance, elastomers or rubber components may be added to the fiber-reinforced resin of the present invention, either to the epoxy resin curing material or the thermoplastic resin. Furthermore, without compromising the purpose of the present invention, the epoxy resin curing material or the thermoplastic resin may also contain other fillers or additives depending on the application. Examples of such fillers include: inorganic fillers, flame retardants, conductivity-improving agents, crystallizing nucleating agents, ultraviolet absorbers, antioxidants, vibration damping agents, antibacterial agents, insect repellents, deodorizing agents, anti-coloring agents, heat stabilizers, mold release agents, antistatic agents, plasticizers, slip agents, colorants, pigments, dyes, foaming agents, foam inhibitors, coupling agents, etc.

[0046] One example of the method for manufacturing the fiber-reinforced resin of the present invention is by pressing and heating a preform to harden it. This preform system uses a prepreg comprising an epoxy resin composition before curing and reinforcing fibers, and has thermoplastic resin regions on its surface, and is laminated together with other prepregs as needed. The pressing and heating method can be, for example, compression molding, autoclave molding, bagging molding, wrapping tape molding, internal pressure molding, and hand lay-up. Other examples of methods for manufacturing the fiber-reinforced resin of the present invention include filament winding, pultrusion, resin injection molding, and resin transfer molding.

[0047] Furthermore, one integrally molded article of the present invention is formed by fusing the fiber-reinforced resin of the present invention with other components through the aforementioned thermoplastic resin region. Because it is formed by fusing with other components through the thermoplastic resin region, the bonding portion between the fiber-reinforced resin portion and other components has excellent tensile shear bond strength. [Example]

[0048] The present invention will now be described in detail with reference to examples. However, the scope of the present invention is not limited to these examples. Furthermore, unless otherwise specified, the unit "parts" for composition ratios refers to parts by mass. Also, unless otherwise specified, all measurements were performed at a temperature of 23°C and a relative humidity of 50%.

[0049] <Materials used in the embodiments and comparative examples> [Epoxy Resin] • Naphthalene ether type epoxy resin ("EPICLON" (registered trademark) HP-6000, manufactured by DIC (stock), epoxy equivalent: 250g / eq.) • Biphenyl aryl epoxy resin (NC-3000, manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent: 275 g / eq.) Tetraglycidyl diaminodiphenylmethane (SUMI-EPOXY (registered trademark) ELM434, manufactured by Sumitomo Chemical Co., Ltd., epoxy equivalent: 120 g / eq.) • Bisphenol F type epoxy resin (“EPICLON” (registered trademark) 830, manufactured by DIC (shareholding company), epoxy equivalent: 172 (g / eq.)) • Naphthol phenyl aralkyl type epoxy resin (NC-7000L, manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent: 230g / eq.).

[0050] [Polyamine compounds] ·4,4'-Diaminodiphenyl sulfonium (SEIKACURE-S, manufactured by Wakayama Seika Kogyo Co., Ltd., active hydrogen equivalent: 62 g / eq.).

[0051] [Viscosity modifier (thermoplastic resin soluble in epoxy resin)] • Polyether ion (“SUMIKAEXCEL” (registered trademark) PES5003P manufactured by Sumitomo Chemical Co., Ltd.).

[0052] [Reinforced Fibers] Referring to Japanese Patent Application Publication No. 2010-255168, carbon fibers 1-4 with different thermal conductivity were obtained by spinning and firing a copolymer of acrylonitrile with isocrine acid (before coating with sizing agent). A 1% by mass solution of sizing agent compound 1 was prepared by mixing and dissolving it in acetone. Each compound was then applied to the carbon fibers 1-4 by impregnation, followed by heat treatment at 210°C for 90 seconds. The amount of each compound attached was adjusted to 0.5 parts by mass relative to 100 parts by mass of carbon fibers with the attached compound, thereby obtaining carbon fibers 1-4 with a surface free energy coefficient of 20 mJ / m². The properties of each carbon fiber are as follows. • Carbon fiber 1: Tensile strength of strand 5.9 GPa, tensile modulus of elasticity of strand 294 GPa, thermal conductivity 10 W / (m·K) • Carbon fiber 2: Tensile strength of strand 5.5 GPa, tensile modulus of elasticity of strand 294 GPa, thermal conductivity 22 W / (m·K) • Carbon fiber 3: Tensile strength of strand 4.4 GPa, tensile modulus of elasticity of strand 377 GPa, thermal conductivity 69 W / (m·K) • Carbon fiber 4: Tensile strength of strand 4.1 GPa, tensile modulus of elasticity of strand 475 GPa, thermal conductivity 105 W / (m·K) Furthermore, for carbon fiber 1 (before coating with sizing agent), the sizing agent is applied with compounds 2 to 6 in the same manner as described above to obtain carbon fibers with different surface free energies. The compounds used in the sizing agents for each carbon fiber, and the surface free energy system after the sizing agent is applied, are as follows. • Compound 1 for sizing agents: Polyethylene glycol diglycidyl ether ("Denacol" (registered trademark) EX-841, manufactured by Nagase ChemteX Co., Ltd.), surface free energy: 20 mJ / m² • Compound 2 for sizing agents: Bisphenol A type diglycidyl ether ("jER" (registered trademark) 828, manufactured by Mitsubishi Chemical Corporation), surface free energy: 9 mJ / m² • Compound 3 for sizing agents: Sorbitol polyglycidyl ether ("Denacol" (registered trademark) EX-614B, manufactured by Nagase ChemteX Co., Ltd.), surface free energy: 32 mJ / m² • Sizing agent compound 4: Bisphenol A propylene oxide 24 molar adduct, surface free energy: 18 mJ / m² • Compound 5 for sizing agent: Polyallylamine (PAA-01, manufactured by Nippon Shokubai Co., Ltd.), surface free energy: 32 mJ / m² • Compound 6 for sizing agents: Polyethylene imide (SP-012, manufactured by Nippon Shokubai Co., Ltd.), surface free energy: 33 mJ / m² [Thermoplastic resin] • PPS: A thin film with a unit area mass of 120 g / m² made of polyphenylene sulfide (Torelina A900 (manufactured by Toray Industries, Inc., melting point 278°C, glass transition temperature 92°C)). • PEEK: A thin film with a unit area mass of 120 g / m² made of polyetheretherketone (PEEK 450G (manufactured by Victrex, melting point 343℃, glass transition temperature 143℃)). • PEKK: A thin film with a unit area mass of 120 g / m² composed of polyetherketoneketone (“KEPSTAN” (registered trademark) 6002 (manufactured by ARKEMA, melting point 300℃, glass transition temperature 160℃)). • PEI: A thin film with a unit area mass of 120 g / m² composed of polyetherimide ("ULTEM" (registered trademark) 1010, manufactured by SABIC Corporation, glass transition temperature 217°C). Semi-aromatic PA: A thin film with a unit area mass of 120 g / m² made of polyamide 6T (melting point 320℃, glass transition temperature 125℃).

[0053] Furthermore, the melting point of the thermoplastic resin was determined using a differential scanning calorimeter (DSC) based on JIS K7121 (2012). In cases where multiple melting points were observed in mixtures, the highest melting point was used as the melting point of the thermoplastic resin.

[0054] <Evaluation Methods> Properties of Cured Epoxy Resins The epoxy resin composition prepared in the following reference examples was injected into a mold and heated in a hot air dryer from 30°C to 180°C at a rate of 1.5°C / min for 120 minutes to harden. Then, it was cooled to 30°C at a rate of 2.5°C / min to produce a plate-shaped epoxy resin hardened material with a thickness of 2 mm.

[0055] From the resin-cured plate prepared by the above method, test pieces with a width of 12.7 mm and a length of 45 mm were cut out and dried in a vacuum oven at 60°C for 24 hours. The storage modulus curve was obtained by dynamic viscoelasticity test according to JIS K7244-7 (2007). The temperature value of the intersection of the tangent in the glass state and the tangent in the transition state in such storage modulus curve was set as the glass transition temperature.

[0056] Furthermore, approximately 10 mg of the plate-shaped resin hardened material prepared by the above method was crushed for evaluation. The rate of decrease in thermal mass was determined using a differential gravimetric analyzer according to JIS K7120 (1987). In all measurements, air was used as the influent gas. The evaluation of the rate of decrease in thermal mass when heated from room temperature to 300°C and from room temperature to 350°C was conducted at a heating rate of 50°C / min and a measurement temperature range of 25°C to 400°C, measuring the rate of decrease in mass at 300°C or 350°C. In isothermal measurements, the temperature was increased from 200°C to 300°C, held at 300°C for 2 minutes, and the rate of decrease in thermal mass was measured.

[0057] [Structural Observation of Fiber-Reinforced Resins] In the observation section obtained by cutting the fiber-reinforced resin perpendicularly to the plane, an image at 1000x magnification is captured using an optical microscope. In the obtained image, if the reinforcing fiber exists at the boundary between the thermoplastic resin region and the epoxy resin cured region, and the reinforcing fiber is in contact with both the thermoplastic resin region and the epoxy resin cured region, it is considered to exist as a "reinforcing fiber that crosses the boundary and is in contact with both resin regions". In any 500μm square observation range in the obtained image, the average length RSm and average height Rc of the cross-sectional curve elements obtained by the aforementioned method 1 for measuring cross-sectional curve elements are measured as defined in JIS B0601 (2001).

[0058] [Compressive strength of fiber-reinforced resin] Following SACMA-SRM 1R-94, after attaching the tabs to the fiber-reinforced resin, the direction of the reinforcing fiber axis was set as the length direction of the test piece, and rectangular test pieces with a length of 80 mm and a width of 15 mm were cut out. After drying the obtained test pieces in a vacuum oven at 60°C for 24 hours, the compressive strength was measured under the following three test conditions using a universal testing machine (Instron Japan, Inc., "Instron" (registered trademark) 5565 model P8564) according to SACMA-SRM 1R-94. 1) The test specimens were untreated, and their compressive strength was measured at 23°C. (Untreated condition) 2) After high-temperature exposure treatment in which the test piece is clamped between a hot plate at 300°C for 2 minutes, the compressive strength is measured at 23°C. 3) After immersion in hot water at 71℃ for 14 days for water absorption treatment, the compressive strength was measured at a high temperature of 120℃. Based on the measurement results in 2) above, the following evaluation is conducted. The results are shown in Tables 2-6. 1.4GPa and above:A Above 1.2 GPa but below 1.4 GPa: B Above 1.0 GPa but below 1.2 GPa: C Below 1.0 GPa: D (Unacceptable) Furthermore, based on the measurement results of 3) above, the evaluation is carried out as follows. The results are shown in Tables 2-6. Above 1.2 GPa: A Above 1.0 GPa but below 1.2 GPa: B Above 0.8 GPa but below 1.0 GPa: C Below 0.8 GPa: D (Unacceptable) [Tensile shear bond strength of one-piece molded articles] According to ISO 4587:1995 (JIS K6850 (1994)), the winglets are attached to the integrally formed article and cut with a width of 25 mm to obtain the target test piece.

[0059] The obtained test pieces were dried in a vacuum oven for 24 hours. Tensile shear bond strength was determined at an ambient temperature of 23°C based on ISO 4587:1995 (JIS K6850 (1994)). The results were evaluated as follows. The coefficient of variation was calculated by dividing the standard deviation by the mean of five tensile shear bond strength measurements. The results are shown in Tables 2-6. Above 28MPa: A 25MPa or higher but less than 28MPa: B 20MPa or higher but less than 25MPa: C Below 20MPa: D (Unqualified).

[0060] <Reference Examples 1-7: Adjustment of Epoxy Resin Composition> The epoxy resin, polyamine compound, and viscosity modifier listed in Table 1 were added to a mixing apparatus and heated for mixing to dissolve the viscosity modifier. Furthermore, the figures in Table 1 indicate that all epoxy resin is defined as 100 parts by mass. Next, while continuing to mix, the mixture was cooled to a temperature below 100°C, and the polyamine compound listed in Table 1 and other suitable hardeners were added and stirred to obtain the epoxy resin compositions used in Reference Examples 1-7.

[0061] [Table 1] Reference Example 1 See Example 2 See Example 3 See Example 4 See Example 5 See Example 6 See Example 7 Epoxy resin composition Epoxy resin / epoxy equivalent (g / eq) EPICLON HP-6000 / 250 50 35 100 20 NC-3000 / 275 50 ELM434 / 120 50 50 65 50 50 80 EPICLON 830 / 172 50 NC-7000L / 230 50 Polyamine compounds 4,4'-Diaminodiphenyl sulfonate 38 37 42 25 39 44 46 viscosity modifier PES5003P 10 10 10 10 10 10 10 Aromatic ring ratio (wt%) 54 55 51 64 51 49 48 Average epoxy equivalent (g / eq.) 185 198 166 250 175 146 146 Average active hydrogen equivalent (g / eq.) 62 62 62 62 62 62 62 Properties of epoxy resin cured products Glass transfer temperature (°C) 214 197 220 199 191 209 228 Reduction of thermal mass from room temperature to 300℃ (%) 0.68 0.89 0.93 0.37 0.90 1.30 1.25 Reduction of thermal mass from room temperature to 350℃ (%) 1.14 1.57 1.65 0.50 1.62 2.30 2.27 The rate of decrease in thermal mass after holding at 300℃ for 2 minutes (%) 0.38 0.53 0.77 0.07 0.71 1.16 1.14

[0062] <Fabrication of Fiber-Reinforced Resin One-Piece Molded Products> [Examples 1-5, Comparative Examples 1 and 2: Effect of Aromatic Ring Ratio on Cured Epoxy Resin Products] An epoxy resin film was prepared by coating the epoxy resin composition of Reference Examples 1-7 onto release paper using a blade coater at a resin area mass of 100 g / m². A reinforcing fiber sheet (with a unit area mass of 193 g / m²) formed by parallel arrangement of carbon fibers 1 (with sizing agent compound 1 already coated) was pulled out. While the sheet was being moved in one direction, a resin sheet composed of thermoplastic resin (PPS) at a unit area mass of 120 g / m² was placed on the reinforcing fiber sheet. The thermoplastic resin was melted by heating with an IR heater and adhered to one side of the reinforcing fiber sheet. Then, pressure was applied by a clamping roller whose surface temperature was maintained 100°C below the melting point of the thermoplastic resin to impregnate the reinforcing fiber sheet. The sheet was then cooled to obtain an intermediate. Next, the epoxy resin film is superimposed on the opposite surface of the intermediate impregnated with thermoplastic resin, and the epoxy resin composition is impregnated in the intermediate by heating and pressurizing with a hot roller to obtain a prepreg [I].

[0063] Using a blade coater, epoxy resin compositions from Reference Examples 1-7 were coated onto release paper at a resin unit area mass of 50 g / m² to prepare epoxy resin films. These epoxy resin films were then stacked on both sides of a reinforcing fiber sheet (unit area mass 193 g / m²) formed by aligning carbon fibers 1 in one direction. The epoxy resin composition was impregnated into the reinforcing fibers while being heated and pressed using a hot roller to obtain a prepreg [II].

[0064] The prepregs [I] and [II] prepared as described above are cut into specified sizes to obtain 2 pieces of prepreg [I] and 4 pieces of prepreg [II]. The outermost 2 pieces on each side are prepreg [I], and prepreg [II] is sandwiched in the middle. A total of 6 pieces are laminated with all of them having the same reinforcing fiber direction to form a preform. At this time, the outermost 2 pieces on each side of the preform are prepreg [I], and the surface layers on both sides of the preform are thermoplastic resin (PPS) layers. That is, 2 pieces of prepreg [I] sandwich 4 pieces of prepreg [II], and the PPS-impregnated side of the prepreg [I] is arranged as the outer side. The preform is placed in a compression molding die, and clamps or separators are used as needed to apply a pressure of 0.6 MPa with a press while maintaining this shape, and then heated at 180°C for 120 minutes to obtain fiber-reinforced resin for compressive strength evaluation and cross-sectional observation.

[0065] The prepregs [I] and [II] prepared as described above are cut into specified sizes to obtain 2 pieces of prepreg [I] and 6 pieces of prepreg [II]. The axial direction of the reinforcing fiber is defined as 0°, and the orthogonal direction of the axis is defined as 90°. The preform is fabricated by laminating at [0° / 90°] 2s (the notation s represents mirror symmetry). At this time, the two outermost pieces on each side of the preform are used as prepregs [I], and the surface layers on both sides of the preform are thermoplastic resin (PPS) layers. That is, the 6 pieces of prepreg [II] are sandwiched between the 2 pieces of prepreg [I], and the PPS-impregnated side of the prepreg [I] is the outermost side. The preform is placed in a compression molding die, and a clamp or separator is used as needed. While maintaining this shape, a pressure of 0.6 MPa is applied by a press, and the mixture is heated at 180°C for 120 minutes to obtain a fiber-reinforced resin for evaluating tensile shear bond strength.

[0066] Furthermore, with the 0° direction set along the length of the test piece, the fiber-reinforced resin obtained for evaluating tensile shear bond strength was cut into two pieces, each 250 mm wide and 92.5 mm long, and dried in a vacuum oven for 24 hours. Then, the two pieces, each 250 mm wide and 92.5 mm long, were overlapped with the 0° direction set along the length to form a width of 250 mm × length of 12.5 mm. A pressure of 3 MPa was applied at 300°C and held for 2 minutes to fuse the overlapping surfaces, resulting in a one-piece molded product for evaluating tensile shear bond strength.

[0067] Table 2 shows the evaluation results of the physical properties of fiber-reinforced resin and integrally molded articles.

[0068] [Table 2] Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Epoxy resin composition Reference Example Number Reference Example 1 See Example 2 See Example 3 See Example 4 See Example 5 See Example 6 See Example 7 Aromatic ring ratio (%) 54 55 51 64 51 49 48 thermoplastic resin PPS Reinforced Fibers Carbon fiber 1 Fiber-reinforced resin Reinforcing fibers that cross the boundary and connect with the two resin regions exist The average roughness length of the boundary surface, RSm (μm). 48 49 48 46 47 45 46 The average height of the boundary surface, Rc (μm). twenty one twenty two twenty two twenty two twenty two twenty four 26 Fiber-reinforced resin 1) Compressive strength (untreated condition) (GPa) 1.62 1.58 1.64 1.60 1.58 1.56 1.65 120℃ 9.1 9.1 2) Compressive strength (GPa) after exposure to 300℃ A A A A A D D 1.58 1.51 1.50 1.60 1.47 0.55 0.60 Compressive strength after exposure to 300℃ / Untreated compressive strength (%) 98 96 91 100 93 35 36 3) Compressive strength (GPa) at 120℃ after water absorption A B A A B B B 1.22 1.15 1.20 1.28 1.13 1.16 1.15 One-piece molded products Tensile shear bond strength (MPa) B B B B B D D 27.1 26.9 26.7 27.3 26.2 18.6 19.2 Coefficient of variation (CV) (%) of tensile shear bond strength 4.7 4.9 4.9 4.7 5.2 5.2 5.4

[0069] [Examples 6-8: The Influence of Thermal Conductivity on Reinforcing Fibers] Except for using the epoxy resin composition of Reference Example 1 and changing the type of carbon fiber constituting the reinforcing fiber sheet as described in Table 3, the process was carried out in the same manner as in Example 1 to obtain the fiber-reinforced resin and the integrally molded article.

[0070] The evaluation results of the physical properties of the fiber-reinforced resin and the integrally molded article are shown together with the evaluation results of Example 1 in Table 3.

[0071] [Table 3] Example 1 Example 6 Example 7 Example 8 Epoxy resin composition Reference Example 1 thermoplastic resin PPS Reinforced Fibers Reinforced Fibers Carbon fiber 1 Carbon fiber 2 Carbon fiber 3 Carbon fiber 4 Thermal conductivity (mJ / m²) 10 twenty two 69 105 Fiber-reinforced resin 1) Compressive strength (untreated condition) (GPa) 1.62 1.44 1.32 1.18 120℃ 9.1 9.1 9.1 2) Compressive strength (GPa) after exposure to 300℃ A B C C 1.58 1.35 1.18 1.02 Compressive strength after exposure to 300℃ / Untreated compressive strength (%) 98 94 89 86 3) Compressive strength (GPa) at 120℃ after water absorption A B B C 1.22 1.10 1.03 0.85 One-piece molded products Tensile shear bond strength (MPa) B B B C 27.1 26.4 25.3 23.8 Coefficient of variation (CV) (%) of tensile shear bond strength 4.7 5.1 5.5 5.8

[0072] [Examples 9-12, Comparative Examples 3 and 4: Effect of Thermoplastic Resin Type] Using the epoxy resin compositions of Reference Examples 1, 6, and 7, and changing the type of thermoplastic resin as described in Table 4, the welding temperature at which the integrally molded article is obtained is also changed as described in Table 4. Otherwise, the process is the same as in Example 1, and fiber-reinforced resin and integrally molded article are obtained.

[0073] The evaluation results of the physical properties of the fiber-reinforced resin and the integrally molded article are shown in Table 4 together with the evaluation results of Example 1.

[0074] [Table 4] Example 1 Example 9 Example 10 Example 11 Example 12 Comparative Example 3 Comparative Example 4 Epoxy resin composition Reference Example 1 See Example 6 See Example 7 thermoplastic resin PPS PEEK PEKK PEI Semi-aromatic PA PEEK PEKK Reinforced Fibers Carbon fiber 1 Fiber-reinforced resin Reinforcing fibers that cross the boundary and connect with the two resin regions exist The average roughness length of the boundary surface, RSm (μm). 50 47 42 47 44 44 48 The average height of the boundary surface, Rc (μm). twenty two twenty one twenty three twenty two twenty two twenty three twenty three Fiber-reinforced resin 1) Compressive strength (untreated condition) (GPa) 1.62 1.63 1.63 1.62 1.61 1.58 1.65 2) Compressive strength (GPa) after exposure to 300℃ A A A A A D D 1.58 1.60 1.60 1.59 1.58 0.57 0.59 Compressive strength after exposure to 300℃ / Untreated compressive strength (%) 98 98 98 98 98 36 36 3) Compressive strength (GPa) at 120℃ after water absorption A A A A A B B 1.22 1.23 1.23 1.22 1.21 1.18 1.18 One-piece molded products Welding temperature (°C) 300 360 320 300 320 360 320 Tensile shear bond strength (MPa) B A A A A D D 27.1 30.4 30.1 29.1 30.1 15.2 16.3 Coefficient of variation (CV) (%) of tensile shear bond strength 4.7 4.8 4.7 4.7 4.7 5.0 5.3

[0075] [Example 13: The effect of reinforcing fibers across the epoxy resin cured region and the thermoplastic resin region] The fiber-reinforced resin of Example 13, which does not have reinforcing fibers crossing the boundary and connecting with the two resin regions, was prepared by the following method. Using the epoxy resin composition of Reference Example 1, a prepreg [II] prepared in the same way as in Example 1 was cut into a specified size, and six sheets were laminated in such a way that all the reinforcing fibers were in the same direction. A film with a unit area mass of 120 g / m² of PPS was then attached to both surfaces to form a preform. Then, in the same manner as in Example 1, the resin was heated and pressed using a press to obtain the fiber-reinforced resin for evaluating compressive strength and observing cross-sections.

[0076] The prepreg [II] obtained above was cut into specified sizes, and the axial direction of the reinforcing fibers was defined as 0°, and the orthogonal direction of the axes was defined as 90°. After lamination at [0° / 90°] 2s (the notation s indicates mirror symmetry), a film of PPS with a unit area mass of 120 g / m2 was attached to both surfaces to form a preform. Then, in the same manner as in Example 1, the process was carried out by heating and pressing with a press to obtain fiber-reinforcing resin for evaluating tensile shear bond strength. Finally, the product was fused together in the same way as in Example 1 to obtain an integrally molded product.

[0077] The evaluation results of the physical properties of the fiber-reinforced resin and the integrally molded article are shown together with the evaluation results of Example 1 in Table 5.

[0078] [Table 5] Example 1 Example 13 Epoxy resin composition Reference Example 1 thermoplastic resin PPS Reinforced Fibers Carbon fiber 1 Fiber-reinforced resin Reinforcing fibers that cross the boundary and connect with the two resin regions exist none The average roughness length of the boundary surface, RSm (μm). 46 181 The average height of the boundary surface, Rc (μm). twenty four 2 One-piece molded products Welding temperature (°C) 300 Holding time (minutes) 2 Tensile shear bond strength (MPa) B C 27.1 21.2 Coefficient of variation (CV) (%) of tensile shear bond strength 4.7 4.8

[0079] [Examples 14-18: The Influence of Surface Free Energy on Reinforcing Fibers] Except for using the epoxy resin composition of Reference Example 1 and changing the type of carbon fiber constituting the reinforcing fiber sheet as described in Table 6, the process was carried out in the same manner as in Example 1 to obtain the fiber-reinforced resin and the integrally molded article.

[0080] The evaluation results of the physical properties of the fiber-reinforced resin and the integrally molded article are shown together with the evaluation results of Example 1 in Table 6.

[0081] [Table 6] Example 1 Example 14 Example 15 Example 16 Example 17 Example 18 Epoxy resin composition Reference Example 1 thermoplastic resin PPS Reinforced Fibers Carbon fiber 1 Sizing agent compounds Sizing 1 Sizing 2 3-step sizing Sizing 4 Sizing 5 Sizing 6 Surface free energy (mJ / m²) 20 9 32 18 32 33 Fiber-reinforced resin 1) Compressive strength (untreated condition) (GPa) 1.62 1.61 1.63 1.61 1.62 1.62 120℃ 9.1 9.1 9.1 9.1 9.1 2) Compressive strength (GPa) after exposure to 300℃ A A A A A A 1.58 1.57 1.59 1.57 1.58 1.58 Compressive strength after exposure to 300℃ / Untreated compressive strength (%) 98 98 98 98 98 98 3) Compressive strength (GPa) at 120℃ after water absorption A A A A A A 1.22 1.21 1.23 1.21 1.22 1.22 One-piece molded products Tensile shear bond strength (MPa) B C A B A A 27.1 23.5 31.2 25.8 29.8 30.5 Coefficient of variation (CV) (%) of tensile shear bond strength 4.7 9.3 4.5 7.2 5.1 5.4

[0082] 1: Reinforced Fibers 2: Thermoplastic Resin Area 3: Epoxy resin hardened area 4: Observe the images 5: Boundary surface 6: Baseline 7: Vertical baseline 8: Cross-sectional curve

Claims

1. A fiber-reinforced resin comprising reinforcing fibers and having an epoxy resin curing region and a thermoplastic resin region formed on its surface, wherein the epoxy resin curing region comprising the epoxy resin curing material has an aromatic ring ratio of 50% to 90% in all its molecules, and the epoxy resin curing material is a curing material of an epoxy resin composition having a heat loss rate of 1.0% or less when a curing material obtained by heating at 180°C for 120 minutes is held at 300°C for 2 minutes, and a glass transition temperature of 180°C to 350°C or higher.

2. The fiber-reinforced resin of claim 1, wherein the epoxy resin hardened region and the thermoplastic resin region are respectively formed in layers and adjacent to each other.

3. The fiber-reinforced resin of claim 1 or 2, wherein the thermal conductivity of the reinforcing fiber is 3 W / (m‧K) or more and 100 W / (m‧K) or less.

4. The fiber-reinforced resin of claim 3, wherein the thermal conductivity of the reinforcing fiber is 3 W / (m‧K) or more and 50 W / (m‧K) or less.

5. The fiber-reinforced resin of claim 1 or 2 uses reinforcing fibers with a surface free energy coefficient of 10 mJ / m2 or more and 50 mJ / m2 or less as determined by the Wilhelmy method.

6. The fiber-reinforced resin of claim 1 or 2, wherein the epoxy resin curing compound is a curing compound comprising an epoxy resin composition having a polycyclic aromatic hydrocarbon backbone or a biphenyl backbone.

7. The fiber-reinforced resin of claim 1 or 2, wherein the epoxy resin curing material is a curing material of an epoxy resin composition in which the average epoxy equivalent of all epoxy resins is 160 g / eq. or more and 255 g / eq. or less.

8. The fiber-reinforced resin of claim 1 or 2, wherein the epoxy resin curing compound is a curing compound comprising an epoxy resin composition of a polyamine compound having an average active hydrogen equivalent of 55 g / eq. to 100 g / eq.

9. The fiber-reinforced resin of claim 1 or 2, wherein the reinforcing fiber is present across the boundary between the thermoplastic resin region and the epoxy resin hardened region and is in contact with both resin regions.

10. The fiber-reinforced resin of claim 1 or 2, wherein the average roughness length RSm of the boundary surface between the epoxy resin hardened region and the thermoplastic resin region is less than 100 μm and the average roughness height Rc is more than 3.5 μm.

11. A monolithic article formed by fusing a fiber-reinforced resin, as claimed in any one of claims 1 to 10, with other components through the thermoplastic resin region.

Images