Fiber reinforced plastic and its manufacturing method

Abstract

The present invention relates to a fiber-reinforced plastic that includes a reinforcing fiber group, a thermosetting resin layer, and a thermoplastic resin containing a first thermoplastic resin, wherein the fiber-reinforced plastic has the thermoplastic resin layer as the surface layer of the fiber-reinforced plastic, the interface between the thermoplastic resin layer and the thermosetting resin layer is located inside the reinforcing fiber group, and the thermosetting resin layer has a sea-island structure in which an island phase having a second thermoplastic resin or a rubbery polymer as the main component is dispersed in a sea phase having a thermosetting resin as the main component.

Description

[Technical Field]

[0001] The present invention relates to a fiber-reinforced plastic and a method for producing the same. [Background technology]

[0002] Fiber-reinforced plastics, which use thermosetting resins as a matrix resin and combine them with reinforcing fibers such as carbon fiber and glass fiber, are lightweight yet have excellent mechanical properties such as strength and rigidity, as well as heat resistance and corrosion resistance, and are therefore used in a wide range of fields, including aerospace, automobiles, railway vehicles, ships, civil engineering and construction, and sporting goods.

[0003] However, these fiber-reinforced plastics are not suitable for producing parts or molded bodies having complex shapes in a single molding process, and for the above-mentioned applications, it is necessary to produce a member made of fiber-reinforced plastic and then integrate it with another member by joining, fastening, or the like.

[0004] For example, methods for integrating fiber-reinforced plastics with similar or dissimilar components include mechanical joining methods using bolts, rivets, and screws, as well as joining methods using adhesives. Mechanical joining methods involve drilling holes in the fiber-reinforced plastic and the other component, which reduces the strength of the holes. When adhesives are used, there is the issue of poor bonding and adhesion due to peeling at the interface between the fiber-reinforced plastic molded body and the other component. Furthermore, these joining methods require pre-processing of the joining area, such as drilling holes and applying adhesive, which reduces processability.

[0005] Therefore, as a method for joining fiber-reinforced plastic to another member without drilling holes in the fiber-reinforced plastic or using an adhesive, fiber-reinforced plastic with a thermoplastic resin on the surface has been proposed.

[0006] Patent Document 1 discloses a laminate in which a thermoplastic resin layer disposed on the surface and a thermosetting resin layer, which is the matrix resin of the fiber-reinforced plastic, are integrated with each other to form an uneven surface, and a method for manufacturing the same. The thermoplastic resin layer and the thermosetting resin layer are integrated with each other to form an uneven surface, thereby firmly bonding them together. Furthermore, by disposing a thermoplastic resin layer on the surface, it is possible to melt the thermoplastic resin layer and bond the fiber-reinforced plastic to another adherend.

[0007] Patent Document 2 discloses a laminate having an adhesive resin layer containing a thermosetting resin and a thermoplastic resin present as a continuous phase between an adherend layer and a thermosetting resin layer, which is the matrix resin of a fiber-reinforced plastic, and a method for manufacturing the laminate. The thermoplastic resin present as a continuous phase in the adhesive resin layer acts as an anchor, firmly bonding the thermoplastic resin and thermosetting resin in the adhesive resin layer. Furthermore, it is said that melting the thermoplastic resin contained in the adhesive resin layer can improve the bonding strength between the adherend and the fiber-reinforced plastic. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2004 / 060658 [Patent Document 2] Japanese Patent Publication No. 2006-198784 Summary of the Invention [Problem to be solved by the invention]

[0009] The laminates in Patent Documents 1 and 2 do not require drilling or adhesives, can effectively utilize the strength, rigidity, and other properties of fiber-reinforced plastics, and have high processability due to the simplified joining process. However, to expand the range of applications as products, it is necessary not only to further improve the bond strength with the adherend, but also to increase the reliability of the joined structure. In Patent Document 1, the composite structure of reinforcing fibers and thermoplastic resin exhibits high toughness, but there are concerns about cracking due to stress concentration in the thermosetting resin, which has poor toughness. In Patent Document 2, the thermoplastic resin exists as a continuous phase in the thermosetting resin, which has poor toughness, but there are concerns about delamination due to stress concentration at the interface between the two resins. An object of the present invention is to provide a fiber-reinforced plastic that can not only be bonded to other adherends with excellent bonding strength, but also can achieve high reliability in the bonded structure. [Means for solving the problem]

[0010] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved, and have completed the present invention. [1] A fiber reinforced plastic including a group of reinforcing fibers, a thermosetting resin layer, and a thermoplastic resin layer containing a first thermoplastic resin, The thermoplastic resin layer is a surface layer of the fiber reinforced plastic, The interface between the thermoplastic resin layer and the thermosetting resin layer is located inside the reinforcing fiber group, The thermosetting resin layer is a fiber-reinforced plastic having a sea-island structure in which island phases mainly composed of a second thermoplastic resin or a rubbery polymer are dispersed in a sea phase mainly composed of a thermosetting resin. [2] The fiber-reinforced plastic according to [1], wherein the second thermoplastic resin is the same type of resin as the first thermoplastic resin. [3] The fiber-reinforced plastic according to [2], wherein the second thermoplastic resin is the same resin as the first thermoplastic resin. [4] The fiber-reinforced plastic according to [1] or [2], wherein the melting points of the second thermoplastic resin and the rubbery polymer are higher than the melting point of the first thermoplastic resin. [5] The fiber-reinforced plastic according to any one of [1] to [4], wherein the island phase contains a component of the thermosetting resin of the sea phase. [6] The fiber-reinforced plastic according to any one of [1] to [5], wherein the island phases are unevenly distributed in the vicinity of the interface between the thermosetting resin layer and the thermoplastic resin layer. [7] The fiber-reinforced plastic according to any one of [1] to [6], wherein in a range of 100 μm in the thickness direction from the outermost fiber toward the thermosetting resin layer side in the thickness direction cross section, the volume fraction of the island phase is 1 vol % or more with respect to said range (100 vol %). [8] The fiber-reinforced plastic according to any one of [1] to [7], wherein the average particle size of the island phases in a cross section in the thickness direction is 0.1 μm or more and 10 μm or less. [9] The fiber-reinforced plastic according to any one of [1] to [8], wherein the length of the major axis of the island phase is 3 μm or more and 30 μm or less.

[10] The fiber-reinforced plastic according to any one of [1] to [9], wherein the elastic modulus of the island phase is lower than the elastic modulus of the sea phase.

[11] The fiber-reinforced plastic according to any one of [1] to

[10] , wherein the glass transition temperature of the island phase is lower than the glass transition temperature of the sea phase.

[12] The reinforcing fibers have a surface free energy of 10 to 50 mJ / m as measured by the Wilhelmy method. 2 The fiber-reinforced plastic according to any one of [1] to

[11] , wherein the reinforcing fiber is:

[13] [1] to

[12] A method for producing a fiber-reinforced plastic according to any one of the above [1] to

[12] , a step of impregnating both surfaces of a reinforcing fiber sheet constituting the reinforcing fiber groups with a precursor of the island phase and a precursor of the thermosetting resin layer to form the island phase and the thermosetting resin layer; A method for producing a fiber-reinforced plastic, comprising: a step of softening or melting a precursor of the island phases and a precursor of the thermoplastic resin layer and arranging them on at least one surface of the reinforcing fiber sheet on which the island phases and the thermosetting resin layer have been formed, thereby forming the island phases and the thermoplastic resin layer into an intermediate; and a step of molding the obtained intermediate.

[14] [1] to

[12] A method for producing a fiber-reinforced plastic according to any one of the above [1] to

[12] , a step of impregnating both surfaces of a reinforcing fiber sheet constituting the reinforcing fiber groups with a precursor of the island phase and a precursor of the thermosetting resin layer to form the island phase and the thermosetting resin layer; A method for producing a fiber-reinforced plastic, comprising: a step of softening or melting a precursor of the thermoplastic resin layer and arranging it on at least one surface of the reinforcing fiber sheet on which the island phases and the thermosetting resin layer have been formed, thereby forming the thermoplastic resin layer and obtaining an intermediate; and a step of molding the obtained intermediate.

[15] [1] to

[12] A method for producing a fiber-reinforced plastic according to any one of the above [1] to

[12] , A step of impregnating both surfaces of a reinforcing fiber sheet constituting the reinforcing fiber group with a precursor of the thermosetting resin layer to form the thermosetting resin layer; A method for producing a fiber-reinforced plastic, comprising: a step of softening or melting a precursor of the island phases and a precursor of the thermoplastic resin layer and arranging them on at least one surface of the reinforcing fiber sheet on which the thermosetting resin layer has been formed, thereby forming the island phases and the thermoplastic resin layer to form an intermediate; and a step of molding the obtained intermediate.

[16] [1] to

[12] A method for producing a fiber-reinforced plastic according to any one of the above [1] to

[12] , A step of impregnating one side of a reinforcing fiber sheet constituting the reinforcing fiber group with a precursor of the thermoplastic resin layer, forming the thermoplastic resin layer, and then vibrating the thermoplastic resin layer to disperse the precursor of the thermoplastic resin layer in the reinforcing fiber sheet; A method for producing a fiber-reinforced plastic, comprising the steps of: impregnating the other surface of the reinforcing fiber sheet with a precursor of the thermosetting resin layer to form an intermediate; and molding the obtained intermediate. [Effects of the Invention]

[0011] According to the present invention, it is possible to obtain a fiber-reinforced plastic that can not only be bonded to another adherend with excellent bonding strength, but also can achieve a highly reliable bonded structure. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing one embodiment of a fiber-reinforced plastic of the present invention. [Figure 2] FIG. 2 is a schematic diagram of a cross section perpendicular to the plane of a fiber-reinforced plastic in the present invention, and helps to explain the measurement of the volume fraction of island phases in the fiber-reinforced plastic. DETAILED DESCRIPTION OF THE INVENTION

[0013] The present invention will be described below with reference to the drawings as appropriate. However, the drawings are used to facilitate understanding of the present invention and are not intended to limit the present invention in any way.

[0014] <Fiber reinforced plastic> [Configuration of fiber reinforced plastic] A fiber reinforced plastic according to an embodiment of the present invention is a fiber reinforced plastic including a reinforcing fiber group, a thermosetting resin layer, and a thermoplastic resin layer containing a first thermoplastic resin, The thermoplastic resin layer is a surface layer of the fiber reinforced plastic, The interface between the thermoplastic resin layer and the thermosetting resin layer is located inside the reinforcing fiber group, The thermosetting resin layer has a sea-island structure in which island phases mainly composed of the second thermoplastic resin or rubber polymer are dispersed in a sea phase mainly composed of the thermosetting resin. When joining the fiber reinforced plastic according to the embodiment of the present invention to a component of the same or a different type, it is possible to form an integrally molded product having excellent joining strength by heat welding, which has high processability, without drilling holes in the fiber reinforced plastic to fasten the components or without using an adhesive.

[0015] As shown in FIG. 1 , a fiber-reinforced plastic 5 according to an embodiment of the present invention includes a group of reinforcing fibers including reinforcing fibers 1, a thermosetting resin layer 3, and a thermoplastic resin layer 4, the surface layer of the fiber-reinforced plastic being the thermoplastic resin layer 4, an interface 6 between the thermoplastic resin layer 4 and the thermosetting resin layer 3 being located inside the group of reinforcing fibers, and the thermosetting resin layer 3 having a sea-island structure in which island phases 7 mainly composed of a thermoplastic resin or a rubbery polymer are dispersed in a sea phase 8 mainly composed of a thermosetting resin.

[0016] The thermosetting resin layer 3 has a sea-island structure in which island phases 7, mainly composed of a thermoplastic resin or rubber polymer, are dispersed in a sea phase 8, mainly composed of a thermosetting resin. This increases the toughness of the thermosetting resin layer 3, thereby not only improving the bonding strength but also enhancing the reliability of the bonding structure in terms of suppressing the occurrence and propagation of cracks.

[0017] In addition, in the embodiment of the present invention, the interface between the thermoplastic resin layer 4 and the thermosetting resin layer 3 needs to be located inside the reinforcing fiber group. This allows the thermosetting resin layer 3 and the thermoplastic resin layer 4 to be firmly bonded together, and from the viewpoint of suppressing peeling between the two layers, it is possible to enhance the reliability of the bonded structure. Furthermore, from the viewpoint of more firmly bonding the thermosetting resin layer 3 and the thermoplastic resin layer 4, it is preferable that a part of the reinforcing fiber group be chemically and / or physically bonded to both the thermosetting resin layer 3 and the thermoplastic resin layer 4 at the interface 6 between the thermosetting resin layer 3 and the thermoplastic resin layer 4.

[0018] In an embodiment of the present invention, it is preferable that the island phases 7 are unevenly distributed in the vicinity of the interface 6 between the thermosetting resin layer 3 and the thermoplastic resin layer 4, from the viewpoint of efficiently increasing the toughness of the thermosetting resin in the vicinity of the thermoplastic resin layer where stress is concentrated, without significantly impairing the properties of the thermosetting resin layer. Specifically, the distance between the interface 6 and the island phase 7 is preferably 100 μm or less, more preferably 70 μm or less, and even more preferably 50 μm or less. Here, the distance between the interface 6 between the thermosetting resin layer 3 and the thermoplastic resin layer 4 and the island phase 7 is the average value of 10 measurements of the shortest distance between the interface 6 between the thermosetting resin layer 3 and the thermoplastic resin layer 4 and the outer periphery of a cross section of a randomly selected island phase 7. The shortest distance can be measured, for example, by using a known method of observing a cross section perpendicular to the fiber direction of a fiber-reinforced plastic. Examples of such methods include a method of measuring from a cross-sectional image acquired using X-ray CT, a method of measuring from an elemental analysis mapping image obtained by an energy dispersive X-ray spectrometer (EDS), or a method of measuring from a cross-sectional observation image obtained by an optical microscope, a scanning electron microscope (SEM), or a transmission electron microscope (TEM).

[0019] The island phases mainly composed of the second thermoplastic resin or rubber polymer may be present in both the thermosetting resin layer and the thermoplastic resin layer, or may be present only in the thermosetting resin layer. From the viewpoint of improving the bonding strength of the fiber-reinforced plastic, the island phases mainly composed of the second thermoplastic resin or rubber polymer are preferably present in both the thermosetting resin layer and the thermoplastic resin layer near the interface between the thermosetting resin layer and the thermoplastic resin layer, and from the viewpoint of processability, they are preferably present only in the thermosetting resin layer.

[0020] Here, the second thermoplastic resin is preferably the same type of resin as the first thermoplastic resin, and more preferably the same thermoplastic resin, from the viewpoint of being able to be processed at an equivalent process temperature. In the present invention, "being of the same kind" means that the main components, excluding additives, etc., are the same. Furthermore, "having the same main components" means that the main skeleton is the same, and includes those in which the number of repeating units or terminal treatments are different. Examples of methods for analyzing the island phases primarily composed of a thermoplastic resin or the island phases primarily composed of a rubbery polymer and the thermoplastic resin layer include a method of analyzing the glass transition temperature using a differential scanning calorimeter (DSC), a method of analyzing elemental analysis mapping images using an energy dispersive X-ray spectrometer (EDS), and a method of analyzing the elastic modulus using a nanoindentation method.

[0021] Alternatively, the second thermoplastic resin or the rubbery polymer preferably has a melting point higher than that of the first thermoplastic resin, from the viewpoint of suppressing structural changes at process temperatures. The melting points of the second thermoplastic resin and the rubbery polymer are preferably higher than that of the first thermoplastic resin.

[0022] Here, from the viewpoint of suppressing disturbance of the alignment of the reinforcing fibers, the average particle size of the island phases is preferably 0.1 μm or more and 10 μm or less, more preferably 0.3 μm or more and 5 μm or less, and even more preferably 0.5 μm or more and 3 μm or less. In particular, when high quality is required, it is desirable to align the reinforcing fibers uniformly.

[0023] The length of the major axis of the island phases mainly composed of the second thermoplastic resin or rubber polymer is preferably 3 μm or more and 30 μm or less, more preferably 5 μm or more and 25 μm or less, and even more preferably 5 μm or more and 20 μm or less, from the viewpoint of enhancing the toughness of the thermosetting resin. The major axis of the island phases is preferably located along the reinforcing fibers, since this may prevent the alignment of the reinforcing fibers from being disturbed. The average particle size and major axis length of the island phases can be confirmed, for example, by observing a cross section perpendicular to the fiber direction of the fiber-reinforced plastic using an optical microscope. The average particle size can be calculated from the diameter of a circle that roughly represents the outer shape of at least 20 randomly selected island phases observed on an orthogonal cross section of the reinforcing fibers. The maximum length of the island phase in the observed cross section can be used as the major axis length of the island phase. The major axis of the island phase is calculated from the line segment that passes through the two most distant points on the periphery of the island phase among the straight lines passing through the interior of the island phase observed in the cross-sectional observation image.

[0024] In a thickness direction cross section of the fiber reinforced plastic, within a range of 100 μm from the outermost fiber toward the thermosetting resin layer, the volume fraction of the island phases may be 0.1 vol% or more relative to the 100 vol% range, and from the viewpoint of further increasing the toughness of the thermosetting resin, it is preferably 1 vol% or more, more preferably 10 vol% or more. The upper limit may be within a range that does not significantly impair the mechanical properties of the thermosetting resin, and is preferably 95 vol% or less, more preferably 80 vol% or less. To help explain the measurement of the volume fraction of the island phases, a schematic diagram of a cross section perpendicular to the plane of the fiber-reinforced plastic is shown in Figure 2. In a cross section perpendicular to the fiber direction of the fiber-reinforced plastic, the fiber closest to the surface 9 of the fiber-reinforced plastic is defined as the outermost fiber 10, and the volume percentage of the island phases 7 is calculated in a measurement range 12 of 100 μm in the thickness direction toward the thermosetting resin layer 3 from a reference line 11 that passes through the center of the outermost fiber 10 and is horizontal to the surface of the fiber-reinforced plastic.

[0025] [Interface between thermosetting resin layer and thermoplastic resin layer] In fiber reinforced plastics, the interface between the thermosetting resin layer and the thermoplastic resin layer is located inside the group of reinforcing fibers.

[0026] The shape of the interface is preferably uneven from the viewpoint of further enhancing the mechanical bonding strength. As a result, the integrally molded product in which the fiber-reinforced plastic according to the embodiment of the present invention and another structural member are bonded via a thermoplastic resin layer has excellent bonding strength. The means for confirming the uneven shape of the interface is not particularly limited, but it can be confirmed by observing a cross section perpendicular to the fiber direction of the fiber-reinforced plastic. Here, the uneven shape of the interface can be confirmed by known methods. For example, it can be confirmed from a cross-sectional image acquired using X-ray CT, from an elemental analysis mapping image obtained using an energy dispersive X-ray spectrometer (EDS), or from a cross-sectional observation image obtained using an optical microscope, a scanning electron microscope (SEM), or a transmission electron microscope (TEM). During observation, the thermosetting resin layer and / or the thermoplastic resin layer may be dyed to adjust the contrast.

[0027] In the fiber reinforced plastic according to the embodiment of the present invention, the impregnation rate of the thermosetting resin and thermoplastic resin (hereinafter, the thermosetting resin and thermoplastic resin may be collectively referred to simply as resin) into the reinforcing fibers is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The impregnation rate here refers to the proportion of the reinforcing fibers that make up the fiber-reinforced plastic that are impregnated with resin. The impregnation rate can be determined by measuring the proportion of areas that are not impregnated with resin using a specific method. A higher impregnation rate means that there are fewer voids in the fiber-reinforced plastic, and a high impregnation rate is preferable from the perspective of further improving the surface appearance and mechanical properties. One method for measuring the impregnation rate is to observe a cross section perpendicular to the fiber direction of the fiber-reinforced plastic, and calculate the rate using the following formula (1) where the total cross-sectional area of ​​the fiber-reinforced plastic including voids in the fiber-reinforced plastic is A0 and the cross-sectional area of ​​the voids is A1.

[0028] Impregnation rate (%) = (A0 - A1) × 100 / A0 (1)

[0029] Hereinafter, each element constituting the fiber-reinforced plastic of the present invention will be described in detail.

[0030] [Thermosetting resin layer] The thermosetting resin layer has a sea-island structure in which island phases mainly composed of a second thermoplastic resin or a rubbery polymer are dispersed in a sea phase mainly composed of a thermosetting resin, and the interface between the thermoplastic resin layer and the thermosetting resin layer is located inside the group of reinforcing fibers. The thermosetting resin layer can be formed from a group of reinforcing fibers and a thermosetting resin. The reinforcing fiber group and the thermosetting resin composition will be described in detail below.

[0031] (Reinforced fiber group) The reinforcing fiber group refers to an aggregate of reinforcing fibers (fiber bundles), and may be either continuous fibers or discontinuous fibers, and may be appropriately selected from a form in which the reinforcing fibers are arranged in one direction, a laminated form thereof, a woven form, etc. From the viewpoint of obtaining a fiber-reinforced plastic that is lightweight and has a higher level of durability, it is preferable that the reinforcing fibers are continuous fibers or a woven form in which the reinforcing fibers are arranged in one direction. Such fiber bundles may be composed of the same reinforcing fibers or different reinforcing fibers. The number of fibers constituting the reinforcing fiber bundle is not particularly limited, and may be, for example, 300 to 60,000 fibers, and from the viewpoint of productivity, it is preferably 300 to 48,000 fibers, and more preferably 1,000 to 24,000 fibers.

[0032] The type of reinforcing fiber constituting the reinforcing fiber group is not particularly limited. For example, carbon fiber, glass fiber, aramid fiber, alumina fiber, silicon carbide fiber, boron fiber, metal fiber, natural fiber, mineral fiber, etc. can be used, and these can be used alone or in combination of two or more. Among these, PAN (Polyacrylonitrile), pitch, rayon, and other carbon fibers are preferred from the viewpoints of high specific strength and specific rigidity and lightweight effect. Furthermore, glass fiber is preferred from the viewpoint of improving the economic efficiency of the resulting fiber-reinforced plastic, and it is particularly preferable to use a combination of carbon fiber and glass fiber from the viewpoint of balancing mechanical properties and economic efficiency. Furthermore, aramid fiber is preferred from the viewpoint of improving the impact absorption and formability of the resulting fiber-reinforced plastic, and it is particularly preferable to use a combination of carbon fiber and aramid fiber from the viewpoint of balancing mechanical properties and impact absorption. Furthermore, reinforcing fibers coated with metals such as nickel, copper, and ytterbium, and pitch-based carbon fibers can also be used from the viewpoint of improving the electrical conductivity of the resulting fiber-reinforced plastic.

[0033] From the viewpoint of improving mechanical properties, it is preferable that the reinforcing fibers constituting the reinforcing fiber group are surface-treated with a sizing agent. Examples of the sizing agent include polyfunctional epoxy resins, urethane resins, acrylic acid polymers, polyhydric alcohols, polyethyleneimine, and ethylene oxide adducts of aliphatic alcohols, and specifically, polyglycidyl ethers of aliphatic polyhydric alcohols such as glycerol triglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, arabitol polyglycidyl ether, trimethylolpropane triglycidyl ether, and pentaerythritol polyglycidyl ether, polyacrylic acid, and copolymers of acrylic acid and methacrylic acid. Examples of the polymer include copolymers of acrylic acid and maleic acid, copolymers of acrylic acid and maleic acid, or mixtures of two or more of these, polyvinyl alcohol, glycerol, diglycerol, polyglycerol, sorbitol, arabitol, trimethylolpropane, pentaerythritol, polyethyleneimine containing a large number of amino groups per molecule, polyoxyethylene oleyl ether, and the like. Among these, glycerol triglycidyl ether, diglycerol polyglycidyl ether, and polyglycerol polyglycidyl ether are preferably used because they contain a large number of highly reactive epoxy groups per molecule, are highly water-soluble, and are easy to apply.

[0034] In addition, the reinforcing fiber should have a surface free energy of 10 to 50 mJ / m as measured by the Wilhelmy method. 2 It is preferable to use a fiber having a surface free energy of 15 to 40 mJ / m. By controlling the surface free energy within this range, the affinity with the thermosetting resin layer and the thermoplastic resin layer is increased, and the aggregation of the reinforcing fibers is suppressed, resulting in a good dispersion state within each layer. As a result, the resin flow within the layer is promoted, and the formation of a dispersed phase of the thermoplastic resin in the thermosetting resin is promoted. In addition, the reinforcing fibers exhibit high affinity with the thermosetting resin layer and the thermoplastic resin layer, and high bonding strength is exhibited at the interface between the thermosetting resin and the thermoplastic resin where the reinforcing fibers are present across. The surface free energy of the reinforcing fibers is preferably 15 to 40 mJ / m. 2 , more preferably 18 to 35 mJ / m2 is.

[0035] Methods for controlling the surface free energy of reinforcing fibers include oxidizing the surface and adjusting the amount of oxygen-containing functional groups such as carboxyl groups and hydroxyl groups, or attaching a single compound or multiple compounds to the surface. When attaching multiple compounds to the surface, compounds with high and low surface free energy can be mixed and attached. Below, we will explain how to calculate the surface free energy of reinforcing fibers. The surface free energy can be calculated by measuring the contact angles of the reinforcing fibers with three types of solvents (purified water, ethylene glycol, and tricresyl phosphate) and then calculating the surface free energy using Owens' approximation formula. The procedure is shown below, but the measuring equipment and detailed method are not necessarily limited to those shown below.

[0036] Using a DataPhysics DCAT11, first, one single fiber is removed from the reinforcing fiber bundle and cut into eight pieces with a length of 12±2 mm. Then, the fibers are attached parallel to a dedicated holder FH12 (a flat plate with a surface coated with an adhesive substance) with 2-3 mm between each fiber. The tips of the single fibers are then trimmed and placed in the DCAT11 holder. For measurement, a cell containing each solvent is brought close to the bottom ends of the eight single fibers at a speed of 0.2 mm / s, immersing the fibers up to 5 mm from their tips. The single fibers are then pulled up at a speed of 0.2 mm / s. This procedure is repeated four or more times. The force F acting on the single fibers while immersed in the liquid is measured using an electronic balance. This value is used to calculate the contact angle θ using the following equation: COSθ = (force F (mN) acting on eight single fibers) / (8 (number of single fibers) × circumference of single fiber (m) × surface tension of solvent (mJ / m 2 )) The measurement is carried out on single fibers extracted from three different locations of the reinforcing fiber bundle, i.e., the average contact angle is calculated for a total of 24 single fibers for one reinforcing fiber bundle.

[0037] Surface free energy γ of reinforcing fiber f is the polar component of the surface free energy γ pf , and the non-polar component of the surface free energy γ d f It is calculated as the sum of Polar component of surface free energy γ p f The non-polar component of the surface free energy γ is calculated by substituting the surface tension components and contact angle of each liquid into the Owens approximation formula shown below (a formula composed of the polar and non-polar components of the surface tension specific to each solvent, and the contact angle θ), plotting it on X and Y, and then approximating it linearly using the least squares method. d f is calculated by squaring the intercept b. The surface free energy of the reinforcing fiber γ f 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 the surface tension of the solvent (mJ / m 2 )) / √(non-polar component of the solvent surface tension (mJ / m 2 ) Y = (1 + COSθ) (polar component of the surface tension of the solvent (mJ / m 2 )) / 2√(non-polar component of the solvent surface tension (mJ / m 2 ) The polar component of the surface free energy of the reinforcing fiber, γ p f =a 2 The non-polar component of the surface free energy of the reinforcing fiber, γ d f =b 2 Total surface free energy γ f =a 2 +b 2 . The polar and non-polar components of the surface tension of each solvent are as follows: ·Purified water Surface tension 72.8mJ / m 2 , polar component 51.0mJ / m 2 , non-polar component 21.8 (mJ / m 2 ) Ethylene glycol Surface tension 48.0mJ / m 2 , polar component 19.0mJ / m2 , non-polar component 29.0 (mJ / m 2 ) Tricresol phosphate Surface tension 40.9mJ / m 2 , polar component 1.7mJ / m 2 , nonpolar component 39.2 (mJ / m 2 ).

[0038] Furthermore, the reinforcing fiber bundle preferably has a strand tensile strength of 3.5 GPa or more, measured in accordance with the resin-impregnated strand test method of JIS R7608 (2007), because a reinforced plastic having excellent bonding strength in addition to tensile strength can be obtained, and more preferably 4.0 GPa or more. The bonding strength referred to here refers to the tensile shear adhesive strength determined in accordance with ISO4587 (1995).

[0039] The mass content of the reinforcing fibers constituting the reinforcing fiber group in the fiber reinforced plastic is preferably 30 to 90 mass%, more preferably 35 to 85 mass%, and even more preferably 40 to 80 mass%. When the mass content of the reinforcing fibers is within the preferred range, a fiber reinforced plastic having better specific strength and specific modulus can be obtained.

[0040] Furthermore, from the viewpoint of the balance between the mechanical properties of the fiber-reinforced plastic and the weldability with the second component, the volume of the reinforcing fibers contained in the thermosetting resin layer is preferably 50 to 99% of the total volume of the reinforcing fibers contained in the entire fiber-reinforced plastic, and more preferably 75 to 95%.

[0041] The amount of reinforcing fibers in the thermosetting resin layer can be measured, for example, by performing segmentation analysis using an X-ray CT image of a small piece of fiber-reinforced plastic and dividing the volume of the reinforcing fibers in the thermosetting resin layer by the total volume of the reinforcing fibers in the small piece to determine the percentage [%]; or by dividing the area of ​​the reinforcing fibers in the thermosetting resin layer by the area of ​​the reinforcing fibers in the entire small piece from a cross-sectional observation photograph of the small piece obtained using an optical microscope, scanning electron microscope (SEM), or transmission electron microscope (TEM). During observation, the thermosetting resin layer and / or thermoplastic resin layer may be dyed to adjust the contrast.

[0042] (Thermosetting resin composition) The thermosetting resin composition contains a thermosetting resin, and may further contain additives depending on the application of the fiber reinforced plastic.

[0043] The type of thermosetting resin contained in the thermosetting resin composition is not particularly limited, and examples thereof include unsaturated polyester resins, vinyl ester resins, epoxy resins, phenolic resins, urea resins, melamine resins, polyimide resins, cyanate ester resins, bismaleimide resins, benzoxazine resins, copolymers or modified products thereof, and resins obtained by blending at least two of these. To improve impact resistance, an elastomer or rubber component may be added to the thermosetting resin. Among these, epoxy resins are preferred due to their excellent mechanical properties, heat resistance, and adhesion to reinforcing fibers.

[0044] Examples of the base resin of the epoxy resin include bisphenol type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD ​​type epoxy resin, and bisphenol S type epoxy resin; brominated epoxy resins such as tetrabromobisphenol A diglycidyl ether; epoxy resins having a biphenyl skeleton, epoxy resins having a naphthalene skeleton, epoxy resins having a dicyclopentadiene skeleton; novolac type epoxy resins such as phenol novolac type epoxy resin and cresol novolac type epoxy resin; Examples of epoxy resins include glycidyl amine type epoxy resins such as phenol, N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-4-amino-3-methylphenol, N,N,N',N'-tetraglycidyl-4,4'-methylenedianiline, N,N,N',N'-tetraglycidyl-2,2'-diethyl-4,4'-methylenedianiline, N,N,N',N'-tetraglycidyl-m-xylylenediamine, N,N-diglycidylaniline, and N,N-diglycidyl-o-toluidine; resorcinol diglycidyl ether; and triglycidyl isocyanurate.

[0045] The thermosetting resin composition may contain a curing agent, such as dicyandiamide, an aromatic amine compound, a phenol novolac resin, a cresol novolac resin, a polyphenol compound, an imidazole derivative, tetramethylguanidine, a thiourea-added amine, a carboxylic acid hydrazide, a carboxylic acid amide, or a polymercaptan. The amount of these curing agents is preferably 0.8 to 1.2 equivalents of the number of reactive functional groups in the thermosetting resin.

[0046] Further, the thermosetting resin composition may contain, depending on the application of the fiber-reinforced plastic, fillers such as mica, talc, kaolin, hydrotalcite, sericite, bentonite, xonotlite, sepiolite, smectite, montmorillonite, wollastonite, silica, calcium carbonate, glass beads, glass flakes, glass microballoons, clay, molybdenum disulfide, titanium oxide, zinc oxide, antimony oxide, calcium polyphosphate, graphite, barium sulfate, magnesium sulfate, zinc borate, calcium borate, aluminum borate whisker, potassium titanate whisker, and polymer compounds; conductivity imparting agents such as metals, metal oxides, carbon black, and graphite powder; halogen-based flame retardants such as brominated resins; antimony-based flame retardants such as antimony trioxide and antimony pentoxide; phosphorus-based flame retardants such as ammonium polyphosphate, aromatic phosphate, and red phosphorus; metal borates, metal carboxylates, and aromatic sulfonates. Organic acid metal salt flame retardants such as metal oxide salts, inorganic flame retardants such as zinc borate, zinc, zinc oxide and zirconium compounds, nitrogen-based flame retardants such as cyanuric acid, isocyanuric acid, melamine, melamine cyanurate, melamine phosphate and nitrogenated guanidine, fluorine-based flame retardants such as PTFE, silicone-based flame retardants such as polyorganosiloxane, metal hydroxide-based flame retardants such as aluminum hydroxide and magnesium hydroxide, and other flame retardants, cadmium oxide, zinc oxide, acid Flame retardant aids such as cuprous oxide, cupric oxide, ferrous oxide, ferric oxide, cobalt oxide, manganese oxide, molybdenum oxide, tin oxide, and titanium oxide, pigments, dyes, lubricants, mold release agents, compatibilizers, dispersants, crystal nucleating agents such as mica, talc, and kaolin, plasticizers such as phosphate esters, heat stabilizers, antioxidants, color inhibitors, UV absorbers, flow modifiers, foaming agents, antibacterial agents, vibration dampers, deodorizers, sliding property modifiers, and antistatic agents such as polyether ester amides may also be added. In particular, flame retardancy may be required when the application is for electrical and electronic devices, automobiles, aircraft, etc., and phosphorus-based flame retardants, nitrogen-based flame retardants, and inorganic flame retardants are preferably added. In order to achieve a flame retardant effect while maintaining a good balance of properties such as the mechanical properties of the resin used and the resin fluidity during molding, the amount of the flame retardant is preferably 1 to 20 parts by mass, more preferably 1 to 15 parts by mass, per 100 parts by mass of resin.

[0047] (Second thermoplastic resin) The second thermoplastic resin is not particularly limited except that it contains a thermoplastic resin as a main component, and a resin with high toughness is preferably used to improve the toughness of the thermosetting resin layer. The island phases can be formed using a thermoplastic resin composition containing a thermoplastic resin as a main component. The thermoplastic resin composition may contain additives depending on the application of the fiber-reinforced plastic.

[0048] The type of second thermoplastic resin that can be contained as a main component in the island phase is not particularly limited, and examples thereof include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), and liquid crystal polyester; polyolefins such as polyethylene (PE), polypropylene (PP), and polybutylene; polyarylene sulfides such as polyoxymethylene (POM), polyamide (PA), and polyphenylene sulfide (PPS); polyketone (PK), polyether ketone (PEK), polyether ether ketone (PEEK), polyaryl ether ketone (PAEK), polyether ketone ketone (PEKK), polyether nitrile (PEN), and poly Examples of the resin include crystalline resins such as fluororesins such as tetrafluoroethylene, amorphous resins such as styrene resins, polycarbonate (PC), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyphenylene ether (PPE), polyimide (PI), polyamideimide (PAI), polyetherimide (PEI), polysulfone (PSU), polyethersulfone, and polyarylate (PAR), as well as phenolic resins, phenoxy resins, and thermoplastic elastomers such as polystyrenes, polyolefins, polyurethanes, polyesters, polyamides, polybutadiene, polyisoprene, fluorine resins, and acrylonitriles, as well as copolymers and modified products thereof.

[0049] Among these, polyolefins are preferred from the viewpoint of the light weight of the resulting fiber-reinforced plastics, and polyarylene sulfides such as polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyaryl ether ketone (PAEK), and polyether ketone ketone (PEKK) are preferred from the viewpoint of heat resistance.

[0050] From the viewpoint of bonding strength, the second thermoplastic resin preferably contains, as a main component, one or more resins selected from the group consisting of polyamide, polyarylate, polyamideimide, polyimide, polyetherimide, polysulfone, and polyethersulfone. Among these, polyamide and polyimide are more preferred, and polyamide is most preferred because it has excellent toughness and can significantly improve impact resistance.

[0051] From the viewpoint of adhesion with the thermosetting resin layer, the island phase preferably contains a thermosetting resin, more preferably a component of the thermosetting resin of the sea phase. The second thermoplastic resin preferably contains a thermosetting resin, more preferably a component of the thermosetting resin of the sea phase. Here, the "thermosetting resin component of the sea phase" refers to the same resin component as the thermosetting resin contained in the sea phase. For example, a semi-IPN structure (polymer interpenetrating network structure) is preferably formed by combining the second thermoplastic resin with a thermosetting resin, since this can prevent peeling between the island phase and the sea phase. Examples of combinations that form a semi-IPN structure include a polyamide selected from polyamide 12, polyamide 6, polyamide 11, and polyamide 6 / 12 copolymer, and an epoxy compound. The ratio (mass %) of the second thermoplastic resin to the thermosetting resin can be in the range of 95:5 to 70:30, more preferably 90:10 to 80:20. Here, the thermosetting resin is not limited to epoxy compounds, but may be selected from unsaturated polyesters, vinyl ester resins, benzoxazine resins, phenolic resins, urea resins, melamine resins, and polyimide resins. It is more preferable that the thermosetting resin is the same thermosetting resin component as the sea phase.

[0052] Further, the second thermoplastic resin may contain, depending on its application, fillers such as mica, talc, kaolin, hydrotalcite, sericite, bentonite, xonotlite, sepiolite, smectite, montmorillonite, wollastonite, silica, calcium carbonate, glass beads, glass flakes, glass microballoons, clay, molybdenum disulfide, titanium oxide, zinc oxide, antimony oxide, calcium polyphosphate, graphite, barium sulfate, magnesium sulfate, zinc borate, calcium borate, aluminum borate whisker, potassium titanate whisker, and polymer compounds; conductive materials such as metal-based, metal oxide-based, carbon black, and graphite powder; halogen-based flame retardants such as brominated resins; antimony-based flame retardants such as antimony trioxide and antimony pentoxide; phosphorus-based flame retardants such as ammonium polyphosphate, aromatic phosphate, and red phosphorus; metal salts of borates; metal salts of carboxylates; and metal salts of aromatic sulfonimides. inorganic flame retardants such as zinc borate, zinc, zinc oxide and zirconium compounds; nitrogen-based flame retardants such as cyanuric acid, isocyanuric acid, melamine, melamine cyanurate, melamine phosphate and nitrogenated guanidine; fluorine-based flame retardants such as PTFE; silicone-based flame retardants such as polyorganosiloxane; metal hydroxide-based flame retardants such as aluminum hydroxide and magnesium hydroxide; other flame retardants; cadmium oxide, zinc oxide, iodine oxide Flame retardant aids such as copper, cupric oxide, ferrous oxide, ferric oxide, cobalt oxide, manganese oxide, molybdenum oxide, tin oxide, and titanium oxide, pigments, dyes, lubricants, mold release agents, compatibilizers, dispersants, crystal nucleating agents such as mica, talc, and kaolin, plasticizers such as phosphate esters, heat stabilizers, antioxidants, color inhibitors, UV absorbers, flow modifiers, foaming agents, antibacterial agents, vibration dampers, deodorizers, sliding property modifiers, and antistatic agents such as polyether ester amides may also be added. In particular, flame retardancy may be required when the application is for electrical and electronic devices, automobiles, aircraft, etc., and phosphorus-based flame retardants, nitrogen-based flame retardants, and inorganic flame retardants are preferably added.

[0053] In order to achieve a flame retardant effect while maintaining a good balance of properties such as the mechanical properties of the resin used and the resin fluidity during molding, the flame retardant is preferably used in an amount of 1 to 20 parts by mass, more preferably 1 to 15 parts by mass, per 100 parts by mass of the second thermoplastic resin.

[0054] (Shape of island phases mainly composed of second thermoplastic resin) The shape of the island phases mainly composed of the second thermoplastic resin is not particularly limited, as long as they have a sea-island structure dispersed in a sea phase mainly composed of a thermosetting resin. The shape of the island phases may be, for example, fibrous or particulate, and is preferably spherical from the viewpoint of suppressing disturbance of the alignment of the reinforcing fibers. For example, it is more preferable that the cross-sectional shape of the island phases mainly composed of the second thermoplastic resin observed in a cross section perpendicular to the plane of the fiber-reinforced plastic is circular, elliptical, or approximately circular with irregularities. Among these, circular shapes are even more preferable because they have fewer starting points for stress concentration.

[0055] From the viewpoint of improving the toughness of the thermosetting resin, the elastic modulus of the island phase mainly composed of the second thermoplastic resin is preferably lower than the elastic modulus of the sea phase mainly composed of the thermosetting resin, more preferably 70% or less, and even more preferably 50% or less, of the elastic modulus of the sea phase mainly composed of the thermosetting resin. An example of measuring the elastic modulus of the island phases mainly composed of the second thermoplastic resin and the sea phase mainly composed of the thermosetting resin is a method in which the island phases mainly composed of the second thermoplastic resin and the sea phase mainly composed of the thermosetting resin in a cross section cut out from the fiber-reinforced plastic are evaluated by nanoindentation.

[0056] The glass transition temperature of the island phase mainly composed of the second thermoplastic resin is preferably lower than that of the sea phase mainly composed of the thermosetting resin, which can further improve the toughness of the thermosetting resin layer. One example of a method for measuring the glass transition temperatures of the island phases mainly composed of the second thermoplastic resin and the sea phase mainly composed of the thermosetting resin is to extract each of the island phases mainly composed of the second thermoplastic resin and the sea phase mainly composed of the thermosetting resin from a cross section cut out from a fiber-reinforced plastic, and evaluate them using a differential scanning calorimeter (DSC).

[0057] (rubber polymer) The rubbery polymer preferably contains a rubber polymer as a main component, but is not otherwise particularly limited and may contain additives, etc., depending on the application. The rubber polymer is a polymer containing a polymer whose glass transition temperature is lower than room temperature, and in which some of the intermolecular molecules are bound to each other by covalent bonds, ionic bonds, van der Waals forces, entanglement, etc. Examples of rubber polymers include olefin resins, acrylic rubbers, silicone rubbers, fluorine rubbers, nitrile rubbers, vinyl rubbers, urethane rubbers, polyamide elastomers, polyester elastomers, and ionomers.

[0058] The additives that can be contained in the rubbery polymer include the additives that can be contained in the second thermoplastic resin described above, and preferred examples are also the same.

[0059] (Shape of rubbery polymer islands) The shape of the island phases containing a rubber polymer as the main component may be the same as that of the island phases containing the second thermoplastic resin as the main component, and preferred examples are also the same.

[0060] Furthermore, the elastic modulus of the island phases mainly composed of the rubber polymer is preferably lower than the elastic modulus of the sea phase mainly composed of the thermosetting resin, similar to the elastic modulus of the island phases mainly composed of the second thermoplastic resin, and the preferred ranges are also the same.

[0061] The island phases mainly composed of rubber polymers preferably form a semi-IPN structure, similar to the island phases mainly composed of thermoplastic resins, and the preferred range is the same as that of the thermoplastic resins.

[0062] [Thermoplastic resin layer] The thermoplastic resin layer is not particularly limited except that it contains the first thermoplastic resin, and preferably contains the first thermoplastic resin as a main component, and may further contain additives etc. depending on the application of the fiber reinforced plastic.

[0063] Examples of the first thermoplastic resin contained in the thermoplastic resin layer include the resins exemplified above as the second thermoplastic resin, and preferred examples are also the same.

[0064] Examples of additives that can be contained in the first thermoplastic resin layer include the additives that can be contained in the second thermoplastic resin described above, and preferred examples are also the same.

[0065] The weight of the thermoplastic resin layer in the fiber reinforced plastic is set to 10 g / m2 in order to ensure an amount of resin suitable for welding with the second component and improve quality. 2 More than 500g / m 2 It is preferable that the content is 20 g / m or less, and more preferably 20 g / m 2 More than 200g / m 2 The following is the result. Here, the basis weight is the weight of 1 m of fiber reinforced plastic. 2 This refers to the mass (g) of the thermoplastic resin layer contained per unit area.

[0066] In an embodiment of the present invention, the thermoplastic resin layer may be present as a part of the surface layer of the fiber-reinforced plastic. The thermoplastic resin layer present on the surface layer of the fiber-reinforced plastic can be integrated with another member by welding, and in a preferred embodiment, the area of ​​the thermoplastic resin layer can be minimized, thereby improving the efficiency of the fiber-reinforced plastic, which has excellent mechanical properties.

[0067] <Manufacturing method> There are no particular limitations on the method for producing the fiber reinforced plastic according to the embodiment of the present invention, and examples thereof include the following production methods (I) to (IV).

[0068] Manufacturing method (I) In the manufacturing method (I), both surfaces of a reinforcing fiber sheet constituting a reinforcing fiber group are impregnated with a precursor of an island phase and a precursor of a thermosetting resin layer; forming an island phase and a thermosetting resin layer; The method for producing fiber-reinforced plastic includes the steps of softening or melting and arranging a precursor of the island phases and a precursor of the thermoplastic resin layer on at least one surface of a reinforcing fiber sheet on which an island phase and a thermosetting resin layer have been formed, thereby forming the island phases and the thermoplastic resin layer to form an intermediate, and molding the obtained intermediate.

[0069] Manufacturing method (II) The manufacturing method (II) includes a step of impregnating both surfaces of a reinforcing fiber sheet constituting a reinforcing fiber group with a precursor of an island phase and a precursor of a thermosetting resin layer to form the island phase and the thermosetting resin layer; The method for producing fiber-reinforced plastic includes a step of softening or melting a precursor of a thermoplastic resin layer and arranging it on at least one surface of a reinforcing fiber sheet on which an island phase and a thermosetting resin layer have been formed, thereby forming a thermoplastic resin layer and forming an intermediate, and a step of molding the obtained intermediate.

[0070] Manufacturing method (III) The manufacturing method (III) includes a step of impregnating both surfaces of a reinforcing fiber sheet constituting a reinforcing fiber group with a precursor of a thermosetting resin layer to form a thermosetting resin layer; The method for producing fiber-reinforced plastic includes the steps of softening or melting and arranging a precursor of an island phase and a precursor of a thermoplastic resin layer on at least one surface of a reinforcing fiber sheet on which a thermosetting resin layer has been formed, thereby forming the island phase and the thermoplastic resin layer to form an intermediate, and molding the obtained intermediate.

[0071] Manufacturing method (IV) The manufacturing method (IV) includes a step of impregnating one side of a reinforcing fiber sheet constituting a reinforcing fiber group with a precursor of a thermoplastic resin layer, forming a thermoplastic resin layer, and then vibrating the thermoplastic resin layer to disperse the precursor of the thermoplastic resin layer in the reinforcing fiber sheet; The method for producing fiber-reinforced plastic includes a step of impregnating the other surface of the reinforcing fiber sheet with a precursor of a thermosetting resin layer to form an intermediate, and a step of molding the obtained intermediate.

[0072] In the embodiments of the present invention, the method for forming the thermosetting resin layer into a layer having a sea-island structure in which island phases mainly composed of a second thermoplastic resin or a rubbery polymer are dispersed in a sea phase mainly composed of a thermosetting resin is not particularly limited, and examples thereof include using any of the following methods (i) to (vii) in the method for producing a fiber-reinforced plastic. Furthermore, a plurality of these methods may be combined. (i) A step of incorporating a precursor of the island phase into a precursor of the thermoplastic resin layer. (ii) A step of incorporating a precursor of the island phase into a precursor of the thermosetting resin layer. (iii) A step of incorporating a precursor of the island phase into both the precursor of the thermosetting resin layer and the precursor of the thermoplastic resin layer. (iv) A step of applying a precursor for the island phase to at least one surface of the intermediate body obtained by impregnating the reinforcing fibers with the precursor for the thermosetting resin layer, and further impregnating the intermediate body with the precursor for the thermoplastic resin layer. (v) A step of applying a precursor of the island phase to an intermediate body in which the precursor of the thermoplastic resin layer is impregnated into the reinforcing fibers. (vi) A step of applying the island phase precursor to one surface of the thermoplastic resin layer precursor, and further impregnating the surface with the thermoplastic resin layer precursor. (vii) A step of vibrating the intermediate body in which the reinforcing fibers are impregnated with the thermoplastic resin precursor using a vibrating bar or the like to disperse the thermoplastic resin precursor in the reinforcing fibers.

[0073] [Precursor of thermosetting resin layer] The precursor of the thermosetting resin layer is a composition that is impregnated into the reinforcing fibers to form the thermosetting resin layer. There are no particular limitations on the method for impregnating the precursor of the thermosetting resin layer into the reinforcing fibers, but examples include a method in which the precursor is softened or melted by heating and pressurizing with a heat roller and then impregnated. The form of the precursor of the thermosetting resin layer is not limited as long as it is impregnated into the reinforcing fibers to form a thermosetting resin layer, and examples thereof include liquid, sheet, nonwoven fabric, particles, etc. However, from the viewpoint of being able to uniformly impregnate the reinforcing fibers, the precursor of the thermosetting resin layer is preferably in the form of a sheet.

[0074] [Thermoplastic resin layer precursor] The precursor of the thermoplastic resin layer is a composition that is impregnated into the reinforcing fiber group to form the thermoplastic resin layer. The method for impregnating the precursor of the thermoplastic resin layer into the reinforcing fiber group is not particularly limited, but for example, a method of heating and pressurizing with a heat roller, melting, and impregnating the precursor can be mentioned. The precursor of the thermoplastic resin layer is not limited in form as long as it is impregnated into the reinforcing fiber group to become a thermoplastic resin layer, and examples thereof include liquid, sheet, nonwoven fabric, particulate, etc. However, from the viewpoint of being able to uniformly impregnate the reinforcing fiber group, the precursor of the thermoplastic resin layer is preferably in sheet form. In order to simultaneously form the thermoplastic resin layer and the island phase from the same precursor, the precursor of the island phase and / or the precursor of the thermoplastic resin layer is preferably in powder form. By making the precursor in powder form, part of it can be impregnated into the thermosetting resin layer, and the remaining part can be melted on the surface of the fiber-reinforced plastic to form the thermoplastic resin layer.

[0075] The temperature at which the precursor of the thermoplastic resin layer is melted is preferably a temperature of at least 30°C above the melting point of the first thermoplastic resin, which is the main component of the precursor of the thermoplastic resin layer, if the first thermoplastic resin is crystalline, or at least 30°C above the glass transition temperature of the first thermoplastic resin if the first thermoplastic resin is amorphous.

[0076] Furthermore, the thermoplastic resin layer only needs to be placed on at least the portion that will be the joint surface with another component, but in order to ensure stable thermal welding, a certain margin of the joint surface may be required. From this perspective, it is preferable that the thermoplastic resin layer be present on at least 50% of the surface area of ​​the fiber-reinforced plastic, and more preferably at least 80%.

[0077] [Precursor of island phase] The island phase precursor is not particularly limited as long as it becomes an island phase present in the thermosetting resin layer in the fiber-reinforced plastic. Examples of the shape of the island phase precursor include a liquid, a sheet, a nonwoven fabric, and particles. However, from the viewpoint of being able to be uniformly present at the interface between the thermosetting resin layer and the thermoplastic resin layer, the island phase precursor is preferably in a particle form, and more preferably in a powder form.

[0078] When the island phase precursor is previously incorporated into the precursor of the thermosetting resin layer, the amount of the island phase precursor is preferably in the range of 10 to 40 parts by mass, more preferably 15 to 40 parts by mass, and even more preferably 25 to 40 parts by mass, per 100 parts by mass of the precursor of the thermosetting resin layer. By setting the amount of the island phase in this range, it is possible to achieve a balance between the adhesiveness between the fiber-reinforced plastic intermediates and the fiber-reinforced plastic bonding strength.

[0079] Similarly, when the island phase precursor is previously incorporated into the thermoplastic resin layer precursor, the island phase precursor is preferably contained in a range of 10 to 40 parts by mass, more preferably 15 to 40 parts by mass, and even more preferably 25 to 40 parts by mass, per 100 parts by mass of the thermoplastic resin layer precursor. By setting the island phase content within this range, it is possible to achieve a balance between the adhesiveness between the fiber-reinforced plastic intermediates and the bonding strength with the fiber-reinforced plastic.

[0080] A preferred embodiment of the fiber-reinforced plastic according to the present invention is a molding method using an intermediate such as a prepreg having a high impregnation rate or a semipreg having a low impregnation rate, as defined above. In this molding process, the fiber-reinforced plastic is shaped into a desired structure, and the curing reaction of the thermosetting resin is accelerated.

[0081] From the viewpoint of use as a structure, the glass transition temperature of the thermosetting resin is preferably 120° C. or higher, more preferably 150° C. or higher, and even more preferably 180° C. or higher. Through this molding process, the glass transition temperature of the thermosetting resin can be controlled to be higher than the glass transition temperature of the thermoplastic resin or rubber polymer of the island phase.

[0082] The fiber-reinforced plastic according to the embodiment of the present invention may be molded by using the intermediate alone, or by laminating a plurality of intermediates, or by laminating them with other materials. There are no particular limitations on the lamination configuration, except that the intermediate is placed on one of the outermost lamination units that corresponds to the surface of the molded body. Prepregs, films, sheets, nonwoven fabrics, porous bodies, metals, etc. can be laminated depending on the application.

[0083] The fiber reinforced plastic according to the embodiment of the present invention is not limited to the example of molding an intermediate, but can be suitably selected as long as it is formed into an embodiment of the present invention through the process of autoclave molding, press molding, pultrusion molding of prepreg, resin transfer molding (RTM), or resin infusion (RI) molding.

[0084] There are no particular limitations on the structure of the fiber-reinforced plastic of the present invention, and various structures can be selected depending on the application, such as a flat plate, a curved plate, a concave-convex structure, a hollow structure, or a sandwich structure.

[0085] The fiber-reinforced plastic of the present invention can be welded to another member via a thermoplastic resin layer arranged on the surface to form an integrally molded product. There are no limitations on the joining method, but examples include hot plate welding, vibration welding, ultrasonic welding, laser welding, resistance welding, induction welding, insert injection molding, and outsert injection molding.

[0086] The fiber reinforced plastic of the present invention is preferably used for aircraft structural members, wind turbine blades, automobile outer panels, computer applications such as IC trays and notebook computer housings, and sports applications such as golf shafts and tennis rackets. [Example]

[0087] The present invention will be described in more detail below with reference to examples, although the scope of the present invention is not limited to these examples.

[0088] <Reinforced fiber bundle> A-1 A polymer mainly composed of polyacrylonitrile was spun, calcined, and surface-oxidized to obtain a reinforcing fiber bundle A-1 consisting of 24,000 continuous carbon fibers in total. The properties of this carbon fiber bundle A-1 were as follows: Single fiber diameter: 7 μm Density: 1.8g / cm 3 Tensile strength: 4.2GPa Tensile modulus: 230GPa Surface free energy: 15 mJ / m 2

[0089] Using A-1 as a base, various sizing compounds were mixed with acetone to obtain a solution of approximately 1% by mass in which the compounds were uniformly dissolved. Each compound was applied to the carbon fiber bundle by immersion, and then heat-treated at 210°C for 90 seconds. The amount of each compound attached was adjusted to 0.5 parts by mass per 100 parts by mass of the carbon fiber to which the compound was attached. The sizing compounds used for each carbon fiber and the surface free energy after application of the sizing agent are as follows: A-2 Sorbitol polyglycidyl ether (Denacol® EX-614B, manufactured by Nagase ChemteX Corporation) Surface free energy: 32 mJ / m 2 A-3 Bisphenol A diglycidyl ether ("jER" (registered trademark) 828, manufactured by Mitsubishi Chemical Corporation) Surface free energy: 9 mJ / m 2 A-4 Polyethylene glycol diglycidyl ether (Denacol (registered trademark) EX-841, manufactured by Nagase ChemteX Corporation) Surface free energy: 20 mJ / m 2

[0090] <Precursor of the island phase> D-1 A homogeneous solution was obtained by adding 90 parts by weight of transparent polyamide (Grilamid® TR55, manufactured by M-Chemie Japan Co., Ltd.), 7.5 parts by weight of epoxy resin (jER® 828, manufactured by Mitsubishi Chemical Corporation), and 2.5 parts by weight of curing agent (Tomide® #296, manufactured by T&K Toka Co., Ltd.) to a mixed solvent of 300 parts by weight of chloroform and 100 parts by weight of methanol. The resulting homogeneous solution was then sprayed onto the surface of 3,000 parts by weight of n-hexane using a spray gun to precipitate the solute. The precipitated solid was filtered, thoroughly washed with n-hexane, and vacuum dried at 100°C for 24 hours to obtain spherical epoxy-modified polyamide particles with a semi-IPN structure, which were the precursor D-1 of the island phase, primarily composed of a second thermoplastic resin. The resulting island phase precursor D-1, which was mainly composed of the second thermoplastic resin, had an average particle size of 13 μm and a melting point of 250°C.

[0091] D-2 Polyurethane particles (Dymic Beads (registered trademark) UCN-5150D, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) were used as precursor D-2 of the island phase mainly composed of a rubbery polymer. The precursor D-2 of the island phase mainly composed of a rubbery polymer had an average particle size of 15 μm and a glass transition temperature of −27°C.

[0092] D-3 A low-melting-point polyamide (Amilan (registered trademark) CM4000 (manufactured by Toray Industries, Inc.), a terpolymer polyamide resin, melting point 155°C) was powdered to prepare precursor D-3 for the island phase mainly composed of a thermoplastic resin. The average particle size of precursor D-3 for the island phase mainly composed of a thermoplastic resin was 25 μm.

[0093] D-4 Polyamide 12 fine particles (SP-500 (manufactured by Toray Industries, Inc.), average particle size 5 μm, spherical shape) were used as precursor D-4.

[0094] <Precursor of the thermosetting resin layer> B-1 Epoxy resin base materials (jER (registered trademark) 828 (manufactured by Mitsubishi Chemical Corporation)), (jER (registered trademark) 1001 (manufactured by Mitsubishi Chemical Corporation)), (jER (registered trademark) 154 (manufactured by Mitsubishi Chemical Corporation)) were added in amounts of 30 parts by mass, 40 parts by mass, and 30 parts by mass, respectively, to a kneading device, and the mixture was heated and kneaded at 150 ° C. until the components were compatible. Next, while continuing the kneading, the temperature was lowered to 80 ° C., and then 26 parts by mass of a curing agent (3,3'DAS (3,3'-diaminodiphenyl sulfone, manufactured by Mitsubishi Chemical Fine Corporation)) was added, and the mixture was kneaded at 80 ° C. for 30 minutes to obtain a precursor B-1 of the thermosetting resin layer.

[0095] B-2 30 parts by mass, 40 parts by mass, and 30 parts by mass of epoxy resin base materials (jER® 828 (Mitsubishi Chemical Corporation)), jER® 1001 (Mitsubishi Chemical Corporation)), and jER® 154 (Mitsubishi Chemical Corporation)) were added to a kneading machine and heated to 150°C until the components were compatible. Then, 30 parts by mass of island phase precursor D-1, primarily composed of a thermoplastic resin, was added and kneaded until D-1 was dispersed. Next, while continuing kneading, the temperature was lowered to 80°C, and 26 parts by mass of a curing agent (3,3'DAS (3,3'-diaminodiphenyl sulfone, Mitsubishi Chemical Fine Chemical Corporation)) was added. The mixture was kneaded at 80°C for 30 minutes to obtain a precursor B-2 of the thermosetting resin layer containing D-1.

[0096] B-3 30 parts by mass, 40 parts by mass, and 30 parts by mass of epoxy resin base materials (jER® 828 (Mitsubishi Chemical Corporation)), jER® 1001 (Mitsubishi Chemical Corporation)), and jER® 154 (Mitsubishi Chemical Corporation)) were added to a kneading machine and heated to 150°C until the components were compatible. The mixture was then cooled to 80°C, and 30 parts by mass of a precursor D-2 for the island phase, primarily composed of a thermoplastic resin, was added and kneaded until D-2 was dispersed. Next, while continuing the kneading, 26 parts by mass of a curing agent (3,3'DAS (3,3'-diaminodiphenyl sulfone, Mitsubishi Chemical Fine Chemical Corporation)) was added and kneaded for 30 minutes at 80°C to obtain a precursor B-3 for the thermosetting resin layer containing D-2.

[0097] B-4 Epoxy resin base materials (Araldite® MY721 (Huntsman Advanced Materials)), jER® 825 (Mitsubishi Chemical Corporation)), and Sumikaexcel® PES5003P (Sumitomo Chemical Co., Ltd.)) were added to a kneading machine in amounts of 50 parts by mass, 50 parts by mass, and 7 parts by mass, respectively, and mixed at 150°C until the components were compatible. The mixture was then cooled to 80°C while still mixing, and 45.1 parts by mass of a curing agent (Seikacure S (Wakayama Seika Kogyo Co., Ltd.)) was added. The mixture was then mixed at 80°C for 30 minutes to obtain a thermosetting resin precursor B-4.

[0098] <Precursor of Thermoplastic Resin Layer> C-1 A low melting point polyamide (Amilan (registered trademark) CM4000 (manufactured by Toray Industries, Inc.), a terpolymer polyamide resin, melting point 155° C.) was formed into a sheet to obtain a precursor C-1 of the thermoplastic resin layer.

[0099] C-2 100 parts by mass of low-melting-point polyamide (Amilan (registered trademark) CM4000 (manufactured by Toray Industries, Inc.), terpolymer polyamide resin, melting point 155°C) and 30 parts by mass of thermoplastic resin domain precursor D-1 were placed in a twin-screw extruder and heated and kneaded at 180°C. The resulting kneaded product was formed into a sheet to obtain thermoplastic resin layer precursor C-2.

[0100] C-3 A low-melting-point polyamide (Amilan (registered trademark) CM4000 (manufactured by Toray Industries, Inc.), a terpolymer polyamide resin, melting point 155°C) was made into a powder form and used as precursor C-3 of the thermoplastic resin layer. The average particle size of precursor C-3 of the thermoplastic resin layer was 25 μm.

[0101] C-4 Polyamide 12 (Lilusamide (registered trademark) AMNO TLD (manufactured by Arkema), melting point 175°C) was formed into a sheet to obtain a precursor C-4 of the thermoplastic resin layer.

[0102] C-5 Polyphenylene sulfide (TORELINA (registered trademark) A670T05 (manufactured by Toray Industries, Inc.), melting point 278°C) was formed into a sheet to obtain a precursor C-5 of the thermoplastic resin layer.

[0103] C-6 Polyether ketone ketone (Kepstan (registered trademark) 7002 (manufactured by Arkema), melting point 332°C) was formed into a sheet to obtain a precursor C-6 of the thermoplastic resin layer.

[0104] <Prepreg manufacturing method> P-1 The reinforcing fiber bundles were aligned in one direction and spread to form a reinforcing fiber sheet with a continuous reinforcing fiber group. The weight of the reinforcing fiber sheet was 200 g / m 2The precursor of the thermosetting resin layer was coated on release paper using a knife coater to prepare a precursor film of the thermosetting resin layer, which was then superimposed on both sides of the reinforcing fiber sheet, and a prepreg intermediate was obtained in which the precursor of the thermosetting resin layer was impregnated into the reinforcing fiber sheet while heating and pressurizing using a heat roll at 80°C and 0.5 MPa. The basis weight of the precursor film of the thermosetting resin layer thus prepared was 50 g / m 2 It was decided. Next, a precursor of the thermoplastic resin layer was placed on one surface of the prepreg intermediate, and pressed at 0.5 MPa using a heat roll maintained at a temperature 30°C above the melting point of the precursor of the thermoplastic resin layer, to obtain a prepreg in which the interface between the thermosetting resin layer and the thermoplastic resin layer was located inside the reinforcing fiber group. The precursor of the thermoplastic resin layer had a basis weight of 50 g / m 2 The prepreg intermediate was placed on one surface of the prepreg intermediate so that the

[0105] P-2 The reinforcing fiber bundles were aligned in one direction and spread to form a reinforcing fiber sheet with a continuous reinforcing fiber group. The weight of the reinforcing fiber sheet was 200 g / m 2 The precursor of the thermosetting resin layer was coated on release paper using a knife coater to prepare a precursor film of the thermosetting resin layer, which was then superimposed on both sides of the reinforcing fiber sheet, and a prepreg intermediate was obtained in which the precursor of the thermosetting resin layer was impregnated into the reinforcing fiber sheet while heating and pressurizing using a heat roll at 80°C and 0.5 MPa. The basis weight of the precursor film of the thermosetting resin layer thus prepared was 50 g / m 2 It was decided. Next, a precursor of the island phase, mainly composed of a second thermoplastic resin, was sprayed onto one surface of the prepreg intermediate using a feeder. The spray amount was 11.5 g / m 2 It was dispersed so that Then, a precursor for the thermoplastic resin layer was placed on the surface of the prepreg intermediate body on which the precursor for the island phase mainly composed of the second thermoplastic resin had been sprayed. 2The prepreg intermediate was placed on one surface so that the interface between the thermosetting resin layer and the thermoplastic resin layer was positioned inside the reinforcing fiber group, and a prepreg was obtained in which the island phase, mainly composed of the second thermoplastic resin, was dispersed in the sea phase, mainly composed of the thermosetting resin, and was present near the interface.

[0106] P-3 The reinforcing fiber bundles were aligned in one direction and spread to form a reinforcing fiber sheet with a continuous reinforcing fiber group. The weight of the reinforcing fiber sheet was 200 g / m 2 The precursor of the thermosetting resin layer was coated on release paper using a knife coater to prepare a precursor film of the thermosetting resin layer, which was then superimposed on both sides of the reinforcing fiber sheet and heated and pressurized at 80°C and 0.5 MPa using a heat roll to obtain a prepreg in which only the precursor of the thermosetting resin layer was impregnated into the reinforcing fiber sheet. B-1 was used as the precursor of the thermosetting resin layer.

[0107] P-4 A prepreg in which only the precursor of the thermosetting resin layer was impregnated into a reinforcing fiber sheet was obtained in the same manner as in P-3, except that B-3 was used as the precursor of the thermosetting resin layer.

[0108] P-5 The reinforcing fiber bundles were aligned in one direction and spread to form a reinforcing fiber sheet with a continuous reinforcing fiber group. The weight of the reinforcing fiber sheet was 200 g / m 2 The precursor of the thermoplastic resin layer was placed on one surface of the fiber-reinforced sheet, and pressed at 0.5 MPa using a heat roll maintained at a temperature equal to or higher than the melting point of the precursor of the thermoplastic resin layer + 30°C, thereby obtaining a prepreg intermediate in which the precursor of the thermoplastic resin layer was impregnated into the reinforcing fiber sheet. The precursor of the thermoplastic resin layer had a basis weight of 50 g / m 2 The prepreg intermediate was placed on one surface of the prepreg intermediate so that the Immediately after heating and pressurizing using the heat roll, the sheet was passed through an ultrasonic generator that generates periodic vibrations to disperse the precursor of the thermoplastic resin phase into the reinforcing fiber sheet. The ultrasonic generator had a frequency of 20 kHz, an amplitude of 100%, and a pressure of 1.0 MPa. The contact distance between the ultrasonic generator horn and the prepreg intermediate was approximately 25 mm, and the ultrasonic vibration was applied for approximately 1.0 second. Next, the precursor of the thermosetting resin layer was coated on release paper using a knife coater to prepare a precursor film of the thermosetting resin layer, which was then placed on the opposite side of the reinforcing fiber sheet to the side on which the precursor of the thermoplastic resin layer was placed. Using a heat roll, the precursor of the thermosetting resin layer was impregnated into the reinforcing fiber sheet while being heated and pressurized at 80°C and 0.5 MPa to obtain a prepreg intermediate. The basis weight of the precursor film of the thermosetting resin layer thus prepared was 50 g / m 2 It was decided.

[0109] <Evaluation method> (1) Measurement of the volume fraction of island phases in fiber-reinforced plastics In a cross section perpendicular to the fiber direction of the outermost layer of the fiber-reinforced plastic, the fiber closest to the surface of the fiber-reinforced plastic was defined as the outermost fiber, and the volume fraction (vol %) of the island phase was determined within a measurement range of 100 μm in the thickness direction toward the thermosetting resin layer from a reference line that passes through the center of the outermost fiber and is horizontal to the surface of the fiber-reinforced plastic.

[0110] (2) Measurement method for bond strength of fiber-reinforced plastics The prepared prepregs were cut to a predetermined size, and two sheets of one type of prepreg prepared by the method P-1, P-2 or P-5, and six sheets of prepregs prepared by the method P-3 or P-4 were prepared. The fiber direction of the reinforcing fiber is defined as 0°, and the direction perpendicular to the fiber direction is defined as 90°, [0° / 90°] 2s(The symbol s indicates mirror symmetry) to produce a prepreg laminate. The two outermost layers on each side were prepregs produced by the methods P-1, P-2, or P-5, and the surface layer of the laminate was arranged to be a thermoplastic resin layer. This laminate was set in a press mold, and, while maintaining this shape using jigs or spacers as necessary, a pressure of 0.6 MPa was applied in a press and heated at 180°C for 2 hours to produce a fiber-reinforced plastic.

[0111] The resulting fiber-reinforced plastic was cut into two panels, 250 mm wide and 100 mm long, with the length of the test piece aligned at an angle of 0° relative to the fiber direction of the reinforcing fibers. The panels were dried in a vacuum oven for 24 hours, then stacked to a 12.5 mm overlapping length. The panels were then welded together at a temperature 20°C higher than the melting point of the thermoplastic resin layer under a pressure of 3 MPa for 1 minute to obtain a bonded assembly. A tab was attached to the resulting bonded assembly in accordance with ISO 4587:1995 (JIS K6850(1994)), and the resulting assembly was cut to a width of 25 mm to obtain a test piece. The obtained test pieces were dried in a vacuum oven for 24 hours, and the bonding strength (MPa) was evaluated at an environmental temperature of 23°C based on ISO4587:1995 (JIS K6850 (1994)).

[0112] Example 1 A prepreg was produced by the method described in P-2 above using A-1 as the reinforcing fiber bundle, B-2 as the precursor for the thermosetting resin layer, C-1 as the precursor for the thermoplastic resin layer, and D-1 as the precursor for the island phase. Test pieces for various evaluations were produced using the produced prepreg, and evaluations were performed. The interface between the thermosetting resin layer and the thermoplastic resin layer of the obtained prepreg was located inside the reinforcing fiber group formed by the carbon fiber bundles A-1, and the thermosetting resin layer had a sea-island structure in which island phases mainly composed of the second thermoplastic resin were dispersed in a sea phase mainly composed of the thermosetting resin. In addition, the thermoplastic resin-based island phase was contained near the interface between the thermoplastic resin layer and the thermosetting resin layer. When the reinforcing fiber sheet was impregnated with the precursor of the thermosetting resin layer, island phases composed mainly of the thermoplastic resin contained in the precursor B-2 of the thermosetting resin layer were unevenly distributed on the surface of the reinforcing fiber sheet, resulting in excellent bonding strength.

[0113] Example 2 A prepreg was produced by the method described in P-2 above using A-1 as the reinforcing fiber bundle, B-2 as the precursor for the thermosetting resin layer, C-2 as the precursor for the thermoplastic resin layer, and D-1 as the precursor for the island phase. Test pieces for various evaluations were produced using the produced prepreg, and evaluations were performed. The interface between the thermosetting resin layer and the thermoplastic resin layer of the obtained prepreg was located inside the reinforcing fiber group formed by the carbon fiber bundles A-1, and the thermosetting resin layer had a sea-island structure in which island phases mainly composed of the second thermoplastic resin were dispersed in a sea phase mainly composed of the thermosetting resin. Also, an island phase mainly composed of the thermoplastic resin was contained near the interface between the thermosetting resin layer and the thermoplastic resin layer. When the reinforcing fiber sheet is impregnated with the precursor of the thermosetting resin layer, island phases mainly composed of the second thermoplastic resin contained in the precursor of the thermosetting resin layer are unevenly distributed on the surface of the reinforcing fiber sheet, and further, island phases mainly composed of the second thermoplastic resin are also present in the thermoplastic resin layer, resulting in excellent bonding strength.

[0114] Example 3 A prepreg was produced by the method described in P-2 above using A-1 as the reinforcing fiber bundle, B-3 as the precursor for the thermosetting resin layer, C-1 as the precursor for the thermoplastic resin layer, and D-2 as the precursor for the island phase. Test pieces for various evaluations were produced using the produced prepreg, and evaluations were performed. The interface between the thermosetting resin layer and the thermoplastic resin layer of the obtained prepreg was located inside the reinforcing fiber group formed by the carbon fiber bundle A-1, and the thermosetting resin layer had a sea-island structure in which island phases mainly composed of a rubber polymer were dispersed in a sea phase mainly composed of a thermosetting resin. In addition, island phases mainly composed of a rubber polymer were contained near the interface between the thermoplastic resin layer and the thermoplastic resin layer. When the reinforcing fiber sheet was impregnated with the precursor of the thermosetting resin layer, island phases composed mainly of the rubber polymer contained in the precursor B-3 of the thermosetting resin layer were unevenly distributed on the surface of the reinforcing fiber sheet, resulting in excellent bonding strength.

[0115] Example 4 A prepreg was produced by the method described in P-2 above using A-1 as the reinforcing fiber bundle, B-1 as the precursor for the thermosetting resin layer, C-3 as the precursor for the thermoplastic resin layer, and D-3 as the precursor for the island phase mainly composed of thermoplastic resin. Test pieces for various evaluations were made using the produced prepreg and evaluated. The interface between the thermosetting resin layer and the thermoplastic resin layer of the obtained prepreg was located inside the reinforcing fiber group formed by the carbon fiber bundles A-1, and the thermosetting resin layer had a sea-island structure in which island phases mainly composed of the second thermoplastic resin were dispersed in a sea phase mainly composed of the thermosetting resin. Also, an island phase mainly composed of the thermoplastic resin was contained near the interface between the thermosetting resin layer and the thermoplastic resin layer. When the reinforcing fiber sheet is impregnated with the precursor of the thermoplastic resin layer, since the precursor of the thermoplastic resin layer is in powder form, part of it penetrates into the thermosetting resin layer, forming an island phase mainly composed of thermoplastic resin that is unevenly distributed near the interface between the thermosetting resin layer and the thermoplastic resin layer, resulting in excellent bonding strength.

[0116] Example 5 A prepreg was produced by the method described in P-2 above using A-1 as the reinforcing fiber bundle, B-1 as the precursor for the thermosetting resin layer, C-1 as the precursor for the thermoplastic resin layer, and D-1 as the precursor for the island phase mainly composed of a thermoplastic resin. Test pieces for various evaluations were produced using the produced prepreg, and evaluations were performed. The interface between the thermosetting resin layer and the thermoplastic resin layer of the obtained prepreg was located inside the reinforcing fiber group formed by the carbon fiber bundles A-1, and the thermosetting resin layer had a sea-island structure in which island phases mainly composed of the second thermoplastic resin were dispersed in a sea phase mainly composed of the thermosetting resin. Also, an island phase mainly composed of the thermoplastic resin was contained near the interface between the thermosetting resin layer and the thermoplastic resin layer. When the reinforcing fiber sheet is impregnated with the precursor of the thermosetting resin layer, island phases mainly composed of the second thermoplastic resin contained in the precursor of the thermosetting resin layer are unevenly distributed on the surface of the reinforcing fiber sheet, and further, island phases mainly composed of the second thermoplastic resin are also present in the thermoplastic resin layer, resulting in excellent bonding strength.

[0117] Example 6 A prepreg was produced by the method described in P-2 above using A-1 as the reinforcing fiber bundle, B-1 as the precursor for the thermosetting resin layer, C-1 as the precursor for the thermoplastic resin layer, and D-2 as the precursor for the island phase mainly composed of a rubber polymer. Test specimens for various evaluations were prepared using the produced prepreg and evaluated. The interface between the thermosetting resin layer and the thermoplastic resin layer of the obtained prepreg was located inside the reinforcing fiber group formed by the carbon fiber bundle A-1, and the thermosetting resin layer had a sea-island structure in which island phases mainly composed of a rubber polymer were dispersed in a sea phase mainly composed of a thermosetting resin. Furthermore, island phases mainly composed of a rubber polymer were contained near the interface in both the thermosetting resin layer and the thermoplastic resin layer. The island phases mainly composed of a rubber polymer were unevenly distributed near the interface between the thermosetting resin layer and the thermoplastic resin layer, and the island phases were present in both the thermosetting resin layer and the thermoplastic resin layer, resulting in excellent bonding strength.

[0118] Example 7 A prepreg was produced in the same manner as in Example 4, except that A-3 was used as the reinforcing fiber, C-1 was used as the precursor of the thermoplastic resin layer, and D-1 was used as the precursor of the island phase, and subjected to various evaluations. The interface between the thermosetting resin layer and the thermoplastic resin layer of the obtained prepreg was located inside the reinforcing fiber group formed by carbon fiber bundle A-3, and had a sea-island structure in which island phases were dispersed in a sea phase mainly composed of thermosetting resin. In addition, island phases mainly composed of thermoplastic resin were contained near the interface between the thermosetting resin layer and the thermoplastic resin layer. When the reinforcing fiber sheet is impregnated with the precursor of the thermoplastic resin layer, since the precursor of the thermoplastic resin layer is in powder form, part of it penetrates into the thermosetting resin layer, forming an island phase mainly composed of thermoplastic resin that is unevenly distributed near the interface between the thermosetting resin layer and the thermoplastic resin layer, resulting in excellent bonding strength.

[0119] Example 8 A prepreg was produced in the same manner as in Example 4, except that A-2 was used as the reinforcing fiber, C-4 was used as the precursor of the thermoplastic resin phase, and D-4 was used as the precursor of the island phase, and various evaluations were performed. The interface between the thermosetting resin layer and the thermoplastic resin layer of the obtained prepreg was located inside the reinforcing fiber group formed by the carbon fiber bundle A-2, and had a sea-island structure in which island phases were dispersed in a sea phase mainly composed of thermosetting resin. Furthermore, an island phase mainly composed of thermoplastic resin was contained near the interface between the thermosetting resin layer and the thermoplastic resin layer. It is believed that the use of carbon fiber A-2, which has a high affinity with thermosetting resin and thermoplastic resin, ensured the dispersibility of the carbon fiber, improved resin fluidity, and promoted the formation of island phases. When the reinforcing fiber sheet is impregnated with the precursor of the thermoplastic resin layer, since the precursor of the thermoplastic resin layer is in powder form, part of it penetrates into the thermosetting resin layer, forming an island phase mainly composed of thermoplastic resin that is unevenly distributed near the interface between the thermosetting resin layer and the thermoplastic resin layer, resulting in excellent bonding strength.

[0120] Example 9 A prepreg was produced by the method described in P-5 above using A-4 as the reinforcing fiber bundle, B-3 as the precursor of the thermosetting resin layer, and C-5 as the precursor of the thermoplastic resin layer. Test pieces for various evaluations were produced using the produced prepreg, and evaluations were performed. The interface between the thermosetting resin layer and the thermoplastic resin layer of the obtained prepreg was located inside the reinforcing fiber group formed by carbon fiber bundle A-3, and had a sea-island structure in which island phases were dispersed in a sea phase mainly composed of thermosetting resin. In addition, island phases mainly composed of thermoplastic resin were contained near the interface between the thermosetting resin layer and the thermoplastic resin layer. When the precursor of the thermoplastic resin layer was impregnated into the reinforcing fiber sheet, some of the precursor dispersed in the reinforcing fiber sheet due to vibration, forming an island phase consisting mainly of thermoplastic resin that was unevenly distributed near the interface between the thermosetting resin layer and the thermoplastic resin layer, resulting in excellent bonding strength.

[0121] Example 10 A prepreg was produced in the same manner as in Example 9, except that C-6 was used as the precursor of the thermoplastic resin phase, and subjected to various evaluations. The interface between the thermosetting resin layer and the thermoplastic resin layer of the obtained prepreg was located inside the reinforcing fiber group formed by the carbon fiber bundle A-4, and had a sea-island structure in which island phases were dispersed in a sea phase mainly composed of thermosetting resin. In addition, island phases mainly composed of thermoplastic resin were contained near the interface between the thermosetting resin layer and the thermoplastic resin layer. When the precursor of the thermoplastic resin layer was impregnated into the reinforcing fiber sheet, some of the precursor dispersed in the reinforcing fiber sheet due to vibration, forming an island phase consisting mainly of thermoplastic resin that was unevenly distributed near the interface between the thermosetting resin layer and the thermoplastic resin layer, resulting in excellent bonding strength.

[0122] (Comparative Example 1) A prepreg was produced by the method described in P-1 above using A-1 as the reinforcing fiber bundle, B-1 as the precursor of the thermosetting resin layer, and C-1 as the precursor of the thermoplastic resin layer. Test pieces for various evaluations were produced using the produced prepreg, and evaluations were performed. The resulting prepreg and test piece did not contain any island phases and therefore had low bonding strength.

[0123] (Comparative Examples 2 to 4) Prepregs were prepared and various evaluations were carried out using them as shown in Table 1. The interface between the thermosetting resin layer and the thermoplastic resin layer of the obtained prepreg was located inside the reinforcing fiber group formed by the carbon fiber bundles, and did not contain any island phases other than the thermoplastic resin layer and the thermosetting resin layer.

[0124] [Table 1]

[0125] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2020-096946) filed on June 3, 2020, the contents of which are incorporated herein by reference. [Explanation of symbols]

[0126] 1. Reinforced fiber 3.Thermosetting resin layer 4.Thermoplastic resin layer 5. Fiber-reinforced plastics 6. Interface 7. Island Phase 8. Thermosetting resin-based marine phase 9. Fiber-reinforced plastic surface 10.Outermost fiber 11. Reference Line 12. Measurement range

Claims

1. A fiber reinforced plastic including a group of reinforcing fibers, a thermosetting resin layer, and a thermoplastic resin layer containing a first thermoplastic resin, The thermoplastic resin layer is a surface layer of the fiber reinforced plastic, The interface between the thermoplastic resin layer and the thermosetting resin layer is located inside the reinforcing fiber group, the thermosetting resin layer has a sea-island structure in which island phases mainly composed of a second thermoplastic resin or a rubbery polymer are dispersed in a sea phase mainly composed of a thermosetting resin; the melting points of the second thermoplastic resin and the rubbery polymer are higher than the melting point of the first thermoplastic resin; A fiber-reinforced plastic in which the distance between the interface between the thermosetting resin layer and the thermoplastic resin layer and the island phase is 100 μm or less.

2. The fiber-reinforced plastic according to claim 1 , wherein the second thermoplastic resin is the same type of resin as the first thermoplastic resin.

3. The fiber-reinforced plastic according to claim 2 , wherein the second thermoplastic resin is the same resin as the first thermoplastic resin.

4. The fiber-reinforced plastic according to any one of claims 1 to 3, wherein the island phase contains a component of the thermosetting resin of the sea phase.

5. 5. The fiber-reinforced plastic according to claim 1, wherein in a range of 100 μm in the thickness direction from an outermost fiber toward the thermosetting resin layer side in a thickness direction cross section, the volume ratio of the island phase is 1 vol % or more with respect to said range 100 vol %.

6. The fiber-reinforced plastic according to any one of claims 1 to 5, wherein the average particle size of the island phases in the thickness direction cross section is 0.1 µm or more and 10 µm or less.

7. The fiber-reinforced plastic according to any one of claims 1 to 6, wherein the length of the major axis of the island phase is 3 µm or more and 30 µm or less.

8. The fiber-reinforced plastic according to any one of claims 1 to 7, wherein the elastic modulus of the island phase is lower than the elastic modulus of the sea phase.

9. The fiber-reinforced plastic according to any one of claims 1 to 8, wherein the glass transition temperature of the island phase is lower than the glass transition temperature of the sea phase.

10. The reinforcing fibers have a surface free energy measured by the Wilhelmy method of 10 to 50 mJ / m ２ The fiber-reinforced plastic according to any one of claims 1 to 9, wherein a reinforcing fiber is used.

11. A method for producing a fiber-reinforced plastic according to any one of claims 1 to 10, a step of impregnating both surfaces of a reinforcing fiber sheet constituting the reinforcing fiber groups with a precursor of the island phase and a precursor of the thermosetting resin layer to form the island phase and the thermosetting resin layer; a step of softening or melting a precursor of the island phases and a precursor of the thermoplastic resin layer and disposing them on at least one surface of the reinforcing fiber sheet on which the island phases and the thermosetting resin layer have been formed, thereby forming the island phases and the thermoplastic resin layer to form an intermediate; and a step of molding the obtained intermediate.

12. A method for producing a fiber-reinforced plastic according to any one of claims 1 to 10, a step of impregnating both surfaces of a reinforcing fiber sheet constituting the reinforcing fiber groups with a precursor of the island phase and a precursor of the thermosetting resin layer to form the island phase and the thermosetting resin layer; A step of softening or melting a precursor of the thermoplastic resin layer and disposing it on at least one surface of the reinforcing fiber sheet on which the island phase and the thermosetting resin layer are formed, thereby forming the thermoplastic resin layer to obtain an intermediate; and a step of molding the obtained intermediate.

13. A method for producing a fiber-reinforced plastic according to any one of claims 1 to 10, A step of impregnating both surfaces of a reinforcing fiber sheet constituting the reinforcing fiber group with a precursor of the thermosetting resin layer to form the thermosetting resin layer; a step of softening or melting a precursor of the island phase and a precursor of the thermoplastic resin layer and disposing them on at least one surface of the reinforcing fiber sheet on which the thermosetting resin layer has been formed, to form the island phase and the thermoplastic resin layer to form an intermediate; and a step of molding the obtained intermediate.

14. A method for producing a fiber-reinforced plastic according to any one of claims 1 to 10, A step of impregnating one side of a reinforcing fiber sheet constituting the reinforcing fiber group with a precursor of the thermoplastic resin layer, forming the thermoplastic resin layer, and then vibrating the thermoplastic resin layer to disperse the precursor of the thermoplastic resin layer in the reinforcing fiber sheet; a step of impregnating the other surface of the reinforcing fiber sheet with a precursor of the thermosetting resin layer to form an intermediate; and a step of molding the obtained intermediate.

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