Fiber-reinforced plastic, integral molded product, and prepreg

Abstract

The present invention relates to a fiber-reinforced plastic comprising: a reinforcing fiber group comprising reinforcing fibers, a thermosetting resin layer containing a first thermosetting resin, and a thermoplastic resin layer, wherein a surface layer of the fiber-reinforced plastic has the thermoplastic resin layer, an interface of the thermoplastic resin layer with the thermosetting resin layer is located inside the reinforcing fiber group, and the thermoplastic resin layer contains a dispersed phase of a second thermosetting resin.

Description

Technical Field

[0001] This invention relates to fiber-reinforced plastics, integrally molded articles, and prepreg preforms. Background Technology

[0002] Fiber-reinforced plastics, which use thermosetting resins as the matrix resin and combine them with reinforcing fibers such as carbon fiber and glass fiber, are lightweight and have excellent mechanical properties such as strength and rigidity, as well as heat resistance and corrosion resistance. Therefore, they are used in many fields such as aerospace, automobiles, railway vehicles, ships, civil engineering and sports equipment.

[0003] However, fiber-reinforced plastics are not suitable for manufacturing components or molded bodies with complex shapes using a single molding process. In the above-mentioned applications, it is necessary to prepare components formed from fiber-reinforced plastics and then join or bond them with other components to achieve integration.

[0004] For example, as a method to integrate fiber-reinforced plastics with components of the same or different types, mechanical joining methods such as bolts, rivets, and screws, as well as joining methods involving adhesives, can be used. Mechanical joining methods suffer from the problem of reduced strength around the holes due to the creation of openings in the fiber-reinforced plastic and other components. When adhesives are involved, there is a problem of poor bonding or adhesion at the boundary between the fiber-reinforced plastic molded body and other components due to peeling or other defects. Furthermore, the above-mentioned joining methods require pre-processing of the joining parts, such as opening processes and adhesive coating processes, which reduces processability.

[0005] Therefore, as a method for bonding without opening pores in the fiber-reinforced plastic or joining it with other components without the presence of adhesives, fiber-reinforced plastics with thermoplastic resin on their surface have been proposed.

[0006] Patent Document 1 discloses a laminate formed by integrally integrating a thermoplastic resin layer disposed on a surface with a thermosetting resin layer, which is a matrix resin of a fiber-reinforced plastic, and the laminate itself. By integrally integrating the thermoplastic resin layer and the thermosetting resin layer with an uneven shape, they are firmly bonded together. Furthermore, by disposing the thermoplastic resin layer on the surface, it is possible to melt the thermoplastic resin layer to achieve bonding of other adherends to the fiber-reinforced plastic.

[0007] Patent document 2 discloses a laminated molded article impregnated with a thermosetting resin material and a method for manufacturing the same, which has fine gaps between the fiber reinforcing layers. Because a thermoplastic resin material is inserted between the fiber reinforcing layers, the interlayer toughness of the molded article is improved.

[0008] Patent document 3 discloses a resin molded body formed by welding a thermoplastic resin molded body and a thermosetting resin molded body having a thermoplastic resin portion partially exposed on its surface. Since the thermoplastic resin portion allows for integration by welding, the thermoplastic resin molded body and the thermosetting resin molded body can be joined without the use of adhesives, rivets, or other connecting components.

[0009] Patent document 4 discloses a first molded body with exposed reinforcing fibers, a joint body integrally formed with a second molded body, and a method for manufacturing the same. Since the second molded body is complexed with the exposed reinforcing fibers formed on the surface of the first molded body, the bonding strength is improved.

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: International Publication No. 2004 / 060658

[0013] Patent Document 2: International Publication No. 2008 / 020628

[0014] Patent Document 3: Japanese Patent Application Publication No. 2016-175397

[0015] Patent Document 4: Japanese Patent Application Publication No. 2017-39234 Summary of the Invention

[0016] The problem that the invention aims to solve

[0017] The laminate described in Patent Document 1 requires no openings or adhesives, effectively utilizing the strength and rigidity of the fiber-reinforced resin. The bonding process is simple, resulting in high processability. However, to expand the product's applicability, further improvements in bonding quality are needed. For example, because the thermoplastic resin layer flows during welding, there are sometimes concerns about accompanying thickness variations and disordered arrangement of reinforcing fibers.

[0018] Patent Document 2 describes a laminated article with an emphasis on the characteristics of the layers. However, if the surface is provided with a thermoplastic resin material, the thermoplastic resin material can be considered as the bonding layer during welding. However, in the laminated article, the thermoplastic resin material is impregnated with thermosetting resin, making it difficult to sufficiently ensure the bonding area during welding. In other words, it is unsuitable for bonding processes with other adhered materials, which is the subject of this study.

[0019] The joint described in Patent Document 3 is composed of a thermoplastic resin component embedded in a thermosetting resin component, which can form a bonding layer during welding. Therefore, the thermoplastic resin component is prone to flow out during welding, making it difficult to control the thickness of the bonding layer. Furthermore, no reinforcing structure is disclosed regarding the boundary between the thermosetting and thermoplastic resin components, which may result in insufficient bonding strength.

[0020] In the bond described in Patent Document 4, a high-strength bond is attempted to be formed by sanding and flame-treating the surface of SMC (Sheet Molding Compound) with a thermosetting resin as the base resin to expose the fibers, and then fusing CFRP (Chemical Fiber Reinforced Polymer) with a thermoplastic resin as the base resin to that surface. However, methods such as sanding and flame-treating can cause significant damage to the molded body, which cannot meet the color quality requirements and can also damage the exposed fibers. Therefore, the fiber-based reinforcement effect is also limited.

[0021] Therefore, the objective of this invention is to provide a fiber-reinforced plastic and an integrally molded article capable of suppressing resin outflow and fiber misalignment during integration, thereby exhibiting excellent bonding strength, as well as a prepreg preform with high processability that can be formed from the fiber-reinforced plastic.

[0022] Methods for solving problems

[0023] The inventors of this application conducted repeated and careful research, and as a result found a solution to the above-mentioned problems, thus completing this invention. That is, this invention is as follows.

[0024] [1] A fiber-reinforced plastic, comprising: a group of reinforcing fibers including reinforcing fibers, a thermosetting resin layer containing a first thermosetting resin, and a thermoplastic resin layer.

[0025] in,

[0026] The surface layer of the fiber-reinforced plastic has the thermoplastic resin layer.

[0027] The interface between the thermoplastic resin layer and the thermosetting resin layer is located inside the reinforcing fiber assembly.

[0028] The thermoplastic resin layer comprises a dispersed phase of a second thermosetting resin.

[0029] [2] The fiber-reinforced plastic as described in [1], wherein,

[0030] The reinforcing fibers contained in the thermoplastic resin layer are in contact with the dispersed phase of the second thermosetting resin.

[0031] [3] Fiber-reinforced plastics as described in [1] or [2], wherein,

[0032] The reinforcing fibers contained in the thermoplastic resin layer are bonded together using the second thermosetting resin.

[0033] [4] The fiber-reinforced plastic as described in any one of [1] to [3], wherein the length of the long axis of the dispersed phase of the second thermosetting resin is 50 nm or more.

[0034] [5] The fiber-reinforced plastic as described in [4], wherein the length of the long axis of the dispersed phase of the second thermosetting resin is 1 μm or more.

[0035] [6] The fiber-reinforced plastic as described in any one of [1] to [5], wherein,

[0036] In the thickness direction section, the volume proportion of the dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer is 10% or more, relative to 100% by volume of the thermoplastic resin layer within the reinforcing fiber group.

[0037] [7] The fiber-reinforced plastic as described in any one of [1] to [5], wherein, in the thickness direction section, the volume percentage of the dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer is 3% to 50% to 100% by volume of the reinforcing fibers contained in the thermoplastic resin layer.

[0038] [8] The fiber-reinforced plastic as described in any one of [1] to [5], wherein, with respect to 100% by volume of a region 50 μm from the interface between the thermoplastic resin layer and the thermosetting resin layer in the thickness direction section toward the surface of the thermoplastic resin layer, the sum of the volume ratios of the reinforcing fibers and the second thermosetting resin contained in the thermoplastic resin layer is 10% by volume or more.

[0039] [9] The fiber-reinforced plastic as described in any one of [1] to [8], wherein the second thermosetting resin is a resin of the same kind as the first thermosetting resin.

[0040]

[10] The fiber-reinforced plastic as described in any one of [1] to [9], wherein the glass transition temperature of the second thermosetting resin is 150°C or higher.

[0041]

[11] A monolithic article wherein the second component is bonded to the first component formed of the fiber-reinforced plastic of any one of [1] to

[10] via the thermoplastic resin layer of the fiber-reinforced plastic.

[0042]

[12] The integrally molded article as described in

[11] , wherein the distance t between the thermosetting resin layer and the second component is 10 μm or more.

[0043]

[13] A prepreg preform comprising: a reinforcing fiber bundle containing reinforcing fibers, a thermosetting resin layer containing a first thermosetting resin, and a thermoplastic resin layer.

[0044] in,

[0045] The prepreg blank has the thermoplastic resin layer on its surface.

[0046] The interface between the thermoplastic resin layer and the thermosetting resin layer is located inside the reinforcing fiber assembly.

[0047] The thermoplastic resin layer comprises a dispersed phase of a second thermosetting resin bonded to the reinforcing fibers.

[0048]

[14] The prepreg blank as described in

[13] , wherein the length of the long axis of the dispersed phase of the second thermosetting resin is 1 μm or more.

[0049]

[15] The prepreg blank as described in

[13] or

[14] , wherein,

[0050] With respect to 100% by volume of a region 50 μm from the interface between the thermoplastic resin layer and the thermosetting resin layer in the thickness direction section toward the surface of the thermoplastic resin layer, the sum of the volume ratios of the reinforcing fibers and the second thermosetting resin contained in the thermoplastic resin layer is 10% by volume or more.

[0051]

[16] The prepreg blank as described in any one of

[13] to

[15] , wherein the second thermosetting resin is a resin of the same kind as the first thermosetting resin.

[0052]

[17] The fiber-reinforced plastic as described in any one of [1] to

[10] , the integrally molded article as described in

[11] or

[12] , or the prepreg preform as described in any one of

[13] to

[16] , having a surface free energy of 10 to 50 mJ / m as determined by the Wilhelmy method. 2 The reinforcing fiber is used as the reinforcing fiber.

[0053] Invention Effects

[0054] According to the present invention, it is possible to obtain fiber-reinforced plastics and integrally molded articles that can suppress resin outflow and fiber arrangement disorder at high temperatures for welding with a second component, thereby exhibiting excellent bonding strength and color quality, as well as prepreg blanks with high processability that can form the fiber-reinforced plastics. Attached Figure Description

[0055] [ Figure 1 ] Figure 1This is a schematic diagram illustrating one embodiment of the prepreg or fiber-reinforced plastic of the present invention.

[0056] [ Figure 2 ] Figure 2 This is a diagram illustrating a cross-sectional view of a prepreg or fiber-reinforced plastic according to an embodiment of the present invention.

[0057] [ Figure 3 ] Figure 3 This is a schematic diagram of a cross-section perpendicular to the plane of the prepreg or the plane of the fiber-reinforced plastic in this invention. It is a diagram that helps to illustrate how the average boundary line of the boundary surface between the thermosetting resin layer and the thermoplastic resin layer is obtained. Detailed Implementation

[0058] The present invention will now be described with appropriate reference to the accompanying drawings, which are provided for easy understanding of the invention and are not intended to limit the invention.

[0059] <Prepreg blank>

[0060] The prepreg blank of the present invention comprises: a reinforcing fiber bundle containing reinforcing fibers, a thermosetting resin layer containing a first thermosetting resin, and a thermoplastic resin layer.

[0061] in,

[0062] The prepreg blank has at least one surface layer containing the thermoplastic resin layer.

[0063] The interface between the thermoplastic resin layer and the thermosetting resin layer is located inside the reinforcing fiber assembly.

[0064] The thermoplastic resin layer comprises a dispersed phase (hereinafter sometimes simply referred to as the dispersed phase) of a second thermosetting resin in contact with the reinforcing fibers.

[0065] Figure 1 This is a schematic diagram of a cross-section perpendicular to the plane of the prepreg blank according to an embodiment of the present invention.

[0066] like Figure 1 As shown, the prepreg blank according to the embodiments of the present invention includes: a reinforcing fiber group 12 comprising reinforcing fibers 1 and 14, a thermosetting resin layer 2 containing a first thermosetting resin, and a thermoplastic resin layer 3, wherein the surface layer of the prepreg blank is the thermoplastic resin layer 3, the interface between the thermoplastic resin layer 3 and the thermosetting resin layer 2 is located inside the reinforcing fiber group 12, and the thermoplastic resin layer 3 includes a dispersed phase 4 of a second thermosetting resin in contact with the reinforcing fibers 14. It should be noted that... Figure 1 In the embodiment shown, the thermoplastic resin layer 3 forms the entire surface of the prepreg blank, but as described later, the thermoplastic resin layer 3 may only form a portion of the surface of the prepreg blank.

[0067] In the prepreg blanks according to embodiments of the present invention, the so-called dispersed phase 4 of the second thermosetting resin refers to a region in the thermoplastic resin layer observed in a cross section perpendicular to the plane of the prepreg blank, which is mainly composed of a partially independent thermosetting resin. For example, the dispersed phase 4 of the second thermosetting resin in contact with the reinforcing fiber 14 exists partially independently as a discontinuous region within a continuous region mainly composed of thermoplastic resin.

[0068] Furthermore, using an island structure analogy, the thermoplastic resin layer is the marine phase, and the dispersed phase of the second thermosetting resin bonded to the reinforcing fibers is equivalent to the island phase. That is, it can be said that the thermoplastic resin layer 3 has an island structure in which the island phase, mainly composed of thermosetting resin, is dispersed within a marine phase, mainly composed of thermoplastic resin.

[0069] In addition, in the thermoplastic resin layer 3 containing the dispersed phase 4 and the reinforcing fibers 14, the second thermosetting resin is connected to the multiple reinforcing fibers 14 and forms the dispersed phase 4 of the second thermosetting resin.

[0070] That is, the prepreg blank involved in this embodiment can be regarded as having multiple reinforcing fibers contained in the thermoplastic resin layer connected to the dispersed phase of the second thermosetting resin, thereby partially bonding the multiple reinforcing fibers together. When molding into a molded article and welding the obtained molded article, even if the thermoplastic resin layer becomes fluid due to high temperature conditions, it can suppress the disorder and movement of the reinforcing fibers, prevent excessive flow of the thermoplastic resin layer, and ensure the thickness of the thermoplastic resin layer as the bonding layer, which helps to improve the color quality.

[0071] The shape of the dispersed phase of the second thermosetting resin is not particularly limited, as long as it forms independent regions. For example, in a cross-section perpendicular to the plane of the prepreg blank, the dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer can be fibrous, round, elliptical, rectangular, or have a complex shape with unevenness.

[0072] Here, the length of the long axis of the dispersed phase of the second thermosetting resin is preferably 50 nm or more, more preferably 100 nm or more, even more preferably 300 nm or more, and even more preferably 1 μm or more. By setting the length of the long axis of the dispersed phase of the second thermosetting resin within this range, the flow of the thermoplastic resin layer under high-temperature conditions during molding and welding can be effectively suppressed, thus ensuring higher color quality.

[0073] To determine the length of the long axis of the dispersed phase of the second thermosetting resin, known methods can be used, such as observing a cross-section of the prepreg orthogonal to the fiber direction. Examples include methods using cross-sectional images obtained by X-ray CT, methods using elemental analysis distribution images obtained by energy-dispersive X-ray spectrophotometry (EDS), and methods using cross-sectional observation images obtained by optical microscopy, scanning electron microscopy (SEM), or transmission electron microscopy (TEM). It should be noted that the long axis of the dispersed phase of the second thermosetting resin is defined as the average length of a line segment passing through the interior of the dispersed phase of the second thermosetting resin as confirmed by the aforementioned cross-sectional observation images, passing through the two furthest points on the outer periphery of the dispersed phase, measured on at least 20 randomly selected dispersed phases.

[0074] For the prepreg blank according to the embodiments of the present invention, as long as the volume ratio of the dispersed phase of the thermosetting resin contained in the thermoplastic resin layer is 1% or more in the cross section in the thickness direction relative to 100% by volume of the thermoplastic resin layer in the reinforcing fiber group, it is preferable to be 10% or more by volume, and more preferably 15% or more by volume. From the viewpoint of further effectively suppressing the flow of the thermoplastic resin layer under high temperature conditions during molding and welding, it is preferable to be 10% or more by volume.

[0075] The aforementioned volume percentage (volume %) can be determined using known methods of observing a cross-section of the prepreg orthogonal to the fiber direction. Examples include methods of determination using cross-sectional images obtained by X-ray CT, methods of determination using elemental distribution images obtained by energy-dispersive X-ray spectrometer (EDS), or methods of determination using cross-sectional observation images obtained by optical microscope, scanning electron microscope (SEM), or transmission electron microscope (TEM).

[0076] Regarding the dispersed phase of the second thermosetting resin, from the viewpoint of being able to perform welding with the second component with higher color quality, it is more preferable for the thermoplastic resin layer to be dispersed near the interface between the thermosetting resin layer and the thermoplastic resin layer than for it to be uniformly dispersed in the thermoplastic resin layer.

[0077] Specifically, in the cross-section along the thickness direction of the prepreg, when the region extending 50 μm from the interface between the thermoplastic resin layer and the thermosetting resin layer toward the surface of the thermoplastic resin layer is defined as 100% by volume, the sum of the volume ratios of the reinforcing fibers and the second thermosetting resin contained in the thermoplastic resin layer is preferably 10% by volume or more, more preferably 10% by volume or more and 90% by volume or less, and even more preferably 20% by volume or more and 70% by volume or less. By setting this to a more preferred range, the flow of the thermoplastic resin layer under high-temperature conditions during molding and welding can be more effectively suppressed.

[0078] (Interface between thermosetting resin layer and thermoplastic resin layer)

[0079] In the prepreg blank according to the embodiments of the present invention, the interface between the thermosetting resin layer and the thermoplastic resin layer is located inside the reinforcing fiber group.

[0080] From the viewpoint of further improving mechanical bonding, a concave-convex shape is preferred for the shape of this interface. There are no particular limitations on the means of confirming the concave-convex shape of the interface; it can be confirmed by observing a cross-section of the prepreg preform orthogonal to the fiber direction. Furthermore, further preferred interface shapes are described below. Figure 2 The cross-sectional observation surface of the prepreg blank is described.

[0081] For example, such as Figure 2 As shown, the cross-sectional observation surface 8 is a cross-section obtained by cutting perpendicular to the plane of the prepreg (in the thickness direction of the prepreg) from a direction that is 90 degrees different from the fiber direction 6 of the reinforcing fiber group 12 contained in the thermosetting resin layer and thermoplastic resin layer in the prepreg blank 5.

[0082] Here, known methods can be used to determine the cross-sectional curve. Examples include methods such as determining the cross-sectional curve using X-ray CT after the prepreg has cured, methods using elemental analysis distribution images obtained with energy-dispersive X-ray spectrophotometer (EDS), and methods using cross-sectional observation images obtained with optical microscopes, scanning electron microscopes (SEM), or transmission electron microscopes (TEM). During observation, the thermosetting resin layer and / or thermoplastic resin layer may also be stained to adjust contrast. Figure 3 An example of a method for determining a cross-sectional curve is shown.

[0083] exist Figure 3 In the observation image 9 shown, the thermosetting resin layer 2 and the thermoplastic resin layer 3 are tightly bonded, and this is illustrated as interface 10 in observation image 9. Furthermore, interface 10 is in contact with multiple reinforcing fibers. Using the surface 100 on the thermoplastic resin layer 3 side of observation image 9 as a reference line, vertical baselines 120 are drawn from the thermoplastic resin layer 3 towards the thermosetting resin layer 2 at 10 μm intervals. The point where the vertical baseline drawn from the reference line first intersects with the thermosetting resin layer 2 is plotted, and the line connecting the plotted points is taken as the cross-sectional curve 130. It can be confirmed that the cross-sectional curve 130 has a concave-convex shape relative to the reference line.

[0084] The average thickness of the prepreg blank is not particularly limited, but from the viewpoint of productivity, it is preferably 50 μm or more and 400 μm or less. In addition, when the average thickness of the prepreg blank is set to 100%, from the viewpoint of the prepreg blank's drape and workability, the average thickness ratio of the thermoplastic resin layer is preferably 2% or more and 60% or less, more preferably 5% or more and 30% or less.

[0085] As an example of a method for determining the average thickness of the prepreg blank as a whole and the average thickness of the thermoplastic resin layer, the following method can be used: observe the cross-section of the prepreg blank with an optical microscope, determine the measurement positions of 10 randomly selected images at equal intervals in each image, and take the average value of the measurement data of a total of 100 points as the average thickness of the prepreg blank as a whole and the average thickness of the thermoplastic resin layer.

[0086] In the prepreg blanks according to embodiments of the present invention, the impregnation rate of thermosetting resin and thermoplastic resin (hereinafter, sometimes collectively referred to as resin) in the reinforcing fiber group is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more.

[0087] The impregnation rate here refers to the proportion of resin impregnated in the reinforcing fiber group constituting the prepreg preform. The impregnation rate can be determined by measuring the proportion of unimpregnated areas using a specific method. A higher impregnation rate means smaller voids in the prepreg preform, and a high impregnation rate is preferred from the viewpoint of further improving the surface appearance and mechanical properties of the resulting molded article.

[0088] As a method for determining impregnation rate, the following method can be used: In the observation of the cross section of the prepreg orthogonal to the fiber direction, the total cross-sectional area of ​​the prepreg including the voids in the prepreg is set as A0, and the cross-sectional area of ​​the voids is set as A1, and the impregnation rate is calculated by the following formula (1).

[0089] Impregnation rate (%) = (A0-A1) × 100 / A0···(1)

[0090] The details of the elements constituting the prepreg blank of the present invention are described below.

[0091] <Reinforcing Fiber Group>

[0092] The reinforcing fiber bundle is an aggregate (fiber bundle) of reinforcing fibers, which can be either continuous or discontinuous fibers, and can be appropriately selected from unidirectional arrangement, layering, or fabric configurations. From the viewpoint of obtaining lightweight and more durable fiber-reinforced plastics, continuous fibers or fabrics in which the reinforcing fibers are arranged in a unidirectional direction are preferred.

[0093] The fiber bundle can be composed of the same reinforcing fibers or different reinforcing fibers. The number of fibers constituting the reinforcing fiber bundle is not particularly limited, but can be exemplified as 300 to 60,000 fibers. From a productivity point of view, it is preferable to have 300 to 48,000 fibers, and more preferably 1,000 to 24,000 fibers.

[0094] There are no particular restrictions on the types of reinforcing fibers that make up the reinforcing fiber group. 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. One type of fiber or two or more types of fibers can be used together.

[0095] From the perspective of high specific strength, specific stiffness, and lightweight effect, PAN (Polyacrylonitrile), pitch-based, and synthetic fiber carbon fibers are preferred. Furthermore, from the perspective of improving the economy of the obtained prepreg blank, glass fiber is preferred, especially from the perspective of balancing mechanical properties and economy, a combination of carbon fiber and glass fiber is preferred. Moreover, from the perspective of improving the impact absorption and shapeability of the obtained prepreg blank, aramid fiber is preferred, especially from the perspective of balancing mechanical properties and impact absorption, a combination of carbon fiber and aramid fiber is preferred. Additionally, from the perspective of improving the electrical conductivity of the obtained prepreg blank, reinforcing fibers coated with metals such as nickel, copper, and ytterbium, as well as pitch-based carbon fibers, can also be used.

[0096] From the perspective of improving mechanical properties, it is preferable that the reinforcing fibers constituting the reinforcing fiber group have undergone surface treatment with a sizing agent. Examples of sizing agents include multifunctional epoxy resins, urethane resins, acrylic polymers, polyols, polyethyleneimine, and ethylene oxide adducts of aliphatic alcohols. Specifically, examples include polyglycidyl ethers of aliphatic polyols such as glycerol triglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, araitol polyglycidyl ether, trimethylolpropane triglycidyl ether, and pentaerythritol polyglycidyl ether, as well as polyacrylic acid, acrylic acid, and methyl methacrylate. The following are suitable materials: copolymers of acrylic acid, copolymers of acrylic acid and maleic acid, or mixtures of two or more of the above, polyvinyl alcohol, glycerol, diglycerol, polyglycerol, sorbitol, araitol, trimethylolpropane, pentaerythritol, polyethyleneimine containing a large number of amino groups in one molecule, polyoxyethylene oil ether, etc. Among the above, glycerol triglycidyl ether, diglycerol polyglycidyl ether, and polyglycerol polyglycidyl ether are preferred because they contain a large number of highly reactive epoxy groups in one molecule, and are highly water-soluble and easy to coat.

[0097] In addition, as reinforcing fibers, it is preferable to use fibers with a surface free energy of 10–50 mJ / m as measured by the Wilhelmy method.2 The reinforcing fibers are controlled within this range. High affinity with both the thermosetting and thermoplastic resin layers is achieved, inhibiting fiber aggregation and improving intralayer dispersion. Consequently, a more stable dispersed phase of the second thermosetting resin is formed within the thermoplastic resin layer. Furthermore, the reinforcing fibers exhibit high affinity with both the thermosetting and thermoplastic resin layers, resulting in high bonding strength at the interface between the thermosetting and thermoplastic resins that the reinforcing fibers cross. The surface free energy of the reinforcing fibers is preferably 15–40 mJ / m². 2 More preferably 18–35 mJ / m 2 .

[0098] Methods for controlling the surface free energy of reinforcing fibers include surface oxidation treatment to adjust the amount of oxygen-containing functional groups such as carboxyl and hydroxyl groups; and the attachment of one or more compounds to the surface. When attaching multiple compounds to the surface, compounds with high and low surface free energy can be mixed. The method for calculating the surface free energy of reinforcing fibers is described below. The surface free energy can be calculated using the following method: the contact angles between the reinforcing fiber and three solvents (purified water, ethylene glycol, and tricresyl phosphate) are measured respectively, and then the surface free energy is calculated using the Owens approximation. The steps are shown below, but the measuring equipment and detailed methods are not necessarily limited to the following.

[0099] Using a DataPhysics DCAT11, first, a single fiber is taken from the reinforcing fiber bundle and cut into eight fibers of 12 ± 2 mm in length. These fibers are then bonded parallel to each other, spaced 2–3 mm apart, on a dedicated retainer FH12 (a flat plate coated with adhesive). Next, the tips of the individual fibers are trimmed and placed within the DCAT11 retainer. During the measurement, a cell containing each solvent is brought close to the lower ends of the eight fibers at a speed of 0.2 mm / s, immersing them until 5 mm from the tip of each fiber. Then, the fibers are lifted at a speed of 0.2 mm / s. This operation is repeated at least four times. The force F acting on the individual fiber while immersed in the liquid is measured using an electronic balance. This value is used to calculate the contact angle θ using the following formula.

[0100] COSθ = (Force F (mN) on 8 single fibers) / (8 (number of single fibers) × circumference of single fiber (m) × surface tension of solvent (mJ / m)) 2 ))

[0101] It should be noted that the measurements were performed on individual fibers extracted from different locations within three reinforcing fiber bundles. That is, for a single reinforcing fiber bundle, the average contact angle of a total of 24 individual fibers was calculated.

[0102] Surface free energy γ of reinforcing fiber f With the polar component γ of surface free energy p f and the nonpolar component of surface free energy γ d f Calculate it in the form of the sum.

[0103] Regarding the polar component γ of surface free energy p f In this case, the surface tension composition and contact angle of each liquid are substituted into the Owens approximation (a formula consisting of the polar and non-polar components of the inherent surface tension of each solvent and the contact angle θ), and plotted on X and Y. The surface free energy is then obtained by taking the square of the slope 'a' when performing a linear approximation using the least squares method. The non-polar component γ of the surface free energy is... d f The surface free energy γ of the reinforcing fiber is obtained from the square of the intercept b. f It is the sum of the square of the slope a and the square of the intercept b.

[0104] Y = a·X + b

[0105]

[0106]

[0107] The polar component γ of the surface free energy of reinforcing fibers p f =a 2

[0108] The nonpolar component γ of the surface free energy of the reinforcing fiber d f =b 2

[0109] Total surface free energy γ f =a 2 +b 2 .

[0110] The polar and non-polar components of the surface tension of each solvent are shown below.

[0111] Purified water

[0112] Surface tension 72.8 mJ / m 2 Polar component 51.0 mJ / m 2 Nonpolar component 21.8 (mJ / m 2 )

[0113] · Ethylene glycol

[0114] Surface tension 48.0 mJ / m2 Polar component 19.0 mJ / m 2 Nonpolar component 29.0 (mJ / m 2 )

[0115] Trimethylbenzene Phosphate

[0116] Surface tension 40.9 mJ / m 2 Polar component 1.7 mJ / m 2 Nonpolar component 39.2 (mJ / m 2 ).

[0117] Furthermore, regarding the reinforcing fiber bundles, if the tensile strength of the fiber bundle, as determined by the resin impregnation fiber bundle test method according to JIS R7608 (2007), is 3.5 GPa or higher, a prepreg blank with excellent bonding strength in addition to tensile strength can be obtained. Therefore, it is preferable if the tensile strength of the fiber bundle is 4.0 GPa or higher, which is even more preferable. The bonding strength mentioned here refers to the tensile shear bonding strength determined according to ISO 4587 (1995).

[0118] From the viewpoint of operability and economy when stacking, the prepreg blanks according to the embodiments of the present invention preferably have a reinforcing fiber content of 30 to 2,000 g / m² per unit area. 2 More preferably 50–300 g / m 2 the following.

[0119] The mass content of reinforcing fibers constituting the reinforcing fiber group in the prepreg blank is preferably 30-90% by mass, more preferably 35-85% by mass, and even more preferably 40-80% by mass. If the mass content of reinforcing fibers is within the preferred range, it is easy to obtain molded articles with better specific strength and specific modulus of elasticity.

[0120] <Thermosetting resin layer>

[0121] The thermosetting resin layer is formed by curing a thermosetting resin composition with the first thermosetting resin as the main component. The first thermosetting resin may contain additives, etc., as needed.

[0122] There are no particular limitations on the type of the first thermosetting resin, and examples include: unsaturated polyester resin, vinyl ester resin, epoxy resin, phenolic resin, urea resin, melamine resin, polyimide resin, cyanate ester resin, bismaleimide resin, benzoxazine resin, or copolymers of the above resins, modified versions, and resins obtained by blending at least two of the above. To improve impact resistance, an elastomer or rubber component may be added to the first thermosetting resin composition.

[0123] Among them, epoxy resin is preferred due to its excellent mechanical properties, heat resistance, and bonding properties with reinforcing fibers.

[0124] Examples of epoxy resin main agents 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 with a biphenyl backbone; epoxy resins with a naphthalene backbone; epoxy resins with a dicyclopentadiene backbone; Novolac-type epoxy resins such as phenol Novolac type epoxy resin and cresol Novolac type epoxy resin; and N,N,O-triglycidyl m-aminophenol. Glycidyl amine type epoxy resins such as hydroglycerol-based p-aminophenol, N,N,O-triglycidyl-4-amino-3-methylphenol, N,N,N',N'-tetraglycidyl-4,4'-methylenediphenylamine, N,N,N',N'-tetraglycidyl-2,2'-diethyl-4,4'-methylenediphenylamine, N,N,N',N'-tetraglycidyl-m-phenylenediamine, N,N-diglycidyl-aniline, and N,N-diglycidyl-o-toluidine, resorcinol diglycidyl ether, and triglycidyl isocyanurate, etc.

[0125] The first thermosetting resin composition may also include a curing agent. Examples of curing agents in the first thermosetting resin composition include dicyandiamide, aromatic amine compounds, phenol Novolac resin, cresol Novolac resin, polyphenol compounds, imidazole derivatives, tetramethylguanidine, thiourea addition amine, carboxylic acid hydrazide, formamide, polythiols, etc.

[0126] In addition, these curing agents are preferably 0.8 to 1.2 equivalents of the number of reactive functional groups of the first thermosetting resin.

[0127] In addition, depending on its application, the first thermosetting resin composition may contain fillers such as mica, talc, kaolin, hydrotalcite, sericite, bentonite, calcium silicate, sepiolite, montmorillonite, wollastonite, silica, calcium carbonate, glass beads, glass sheets, glass microspheres, clay, molybdenum disulfide, titanium dioxide, zinc oxide, antimony oxide, calcium polyphosphate, graphite, barium sulfate, magnesium sulfate, zinc borate, calcium borate, aluminum borate whiskers, potassium titanate whiskers, and polymer compounds; conductive materials such as metal-based and metal oxide-based compounds; halogen-based flame retardants such as brominated resins; antimony-based flame retardants such as antimony trioxide and antimony pentaoxide; phosphorus-based flame retardants such as ammonium polyphosphate, aromatic phosphates, and red phosphorus; organic acid metal salt flame retardants such as organoborate metal salts, carboxylic acid metal salts, and aromatic sulfonamide metal salts; zinc borate, zinc, zinc oxide, and... Inorganic flame retardants such as zirconium compounds, nitrogen-based flame retardants such as cyanuric acid, isocyanuric acid, melamine, melamine cyanurate, melamine phosphate, and guanidine nitride, fluorine-based flame retardants such as PTFE, organosilicon-based flame retardants such as polyorganosiloxanes, metal hydroxide-based flame retardants such as aluminum hydroxide and magnesium hydroxide, and other flame retardants, flame retardant additives such as cadmium oxide, zinc oxide, cuprous oxide, copper oxide, ferrous oxide, ferric oxide, cobalt oxide, manganese oxide, molybdenum oxide, tin oxide, and titanium dioxide, pigments, dyes, lubricants, release agents, compatibilizers, dispersants, crystal nucleating agents such as mica, talc, and kaolin, plasticizers such as phosphate esters, heat stabilizers, antioxidants, anti-coloring agents, ultraviolet absorbers, flow modifiers, foaming agents, antibacterial agents, vibration damping agents, deodorizers, sliding modifiers, and antistatic agents such as polyether ester amides, etc. Especially when used in electrical and electronic equipment, automobiles, aircraft, etc., flame retardancy is sometimes required, and it is preferable to add phosphorus-based flame retardants, nitrogen-based flame retardants, or inorganic flame retardants.

[0128] Regarding the aforementioned flame retardant, in order to exhibit a flame retardant effect while maintaining a good balance with the mechanical properties of the resin used and the resin flowability during molding, the flame retardant is preferably set to 1 to 20 parts by weight, more preferably 1 to 15 parts by weight, relative to 100 parts by weight of the first thermosetting resin composition.

[0129] From the viewpoint of the balance between the mechanical properties of the obtained molded article and the weldability with the second component, the volume of the reinforcing fiber contained in the thermosetting resin layer is preferably 50 to 99% of the total volume of the reinforcing fiber contained in the prepreg blank, more preferably 75 to 95%.

[0130] Methods for determining the amount of reinforcing fibers in a thermosetting resin layer can be exemplified by the following: using an X-ray CT image of a small piece of fiber-reinforced plastic obtained by curing a prepreg blank, performing a detailed analysis, and determining the percentage by dividing the volume of reinforcing fibers present in the thermosetting resin layer by the total volume of reinforcing fibers contained in the small piece; or, based on a cross-sectional photograph of the small piece obtained using an optical microscope, scanning electron microscope (SEM), or transmission electron microscope (TEM), determining the percentage by dividing the area of ​​reinforcing fibers present in the thermosetting resin layer by the area of ​​reinforcing fibers contained in the small piece as a whole. During observation, the thermosetting resin layer and / or thermoplastic resin layer may also be stained to adjust contrast.

[0131] <Thermoplastic resin layer>

[0132] The thermoplastic resin layer is not particularly limited except for containing a dispersed phase of a second thermosetting resin, and can be formed using a thermoplastic resin composition with thermoplastic resin as the main component. The thermoplastic resin composition may also contain additives as needed.

[0133] There are no particular restrictions on the types of thermoplastic resins that serve as the main component of the thermoplastic resin layer. Examples include: polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polypropylene terephthalate (PTT), polyethylene naphthalate (PEN), liquid crystal polyester, polyethylene (PE), polypropylene (PP), polybutene, polyoxymethylene (POM), polyamide (PA), polyphenylene sulfide (PPS), polyarylene sulfides, polyketone (PK), polyetherketone (PEK), polyetheretherketone (PEEK), polyarylene etherketone (PAEK), polyetherketone ketone (PEKK), and polyethernitrile (PEN). Crystalline resins such as "fluoropolymers such as polytetrafluoroethylene", amorphous resins such as "styrene resins and polycarbonate (PC), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyphenylene ether (PPE), polyimide (PI), polyamide-imide (PAI), polyether-imide (PEI), polysulfone (PSU), polyethersulfone, polyarylate (PAR)", and thermoplastic resins selected from phenolic resins, phenoxy resins, and thermoplastic elastomers such as polystyrene, polyolefin, polyurethane, polyester, polyamide, polybutadiene, polyisoprene, fluoropolymers, and acrylonitrile, as well as their copolymers and modified products.

[0134] From the viewpoint of the lightweight nature of the obtained prepreg blank, polyolefins are preferred. From the viewpoint of strength, polyamides are preferred. Furthermore, from the viewpoint of heat resistance, polyarylene sulfides such as polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyarylene etherketone (PAEK), and polyetherketoneketone (PEKK) are preferred.

[0135] In addition, depending on the application, the thermoplastic resin composition may also contain fillers such as mica, talc, kaolin, hydrotalcite, sericite, bentonite, calcium silicate, sepiolite, montmorillonite, wollastonite, silica, calcium carbonate, glass beads, glass sheets, glass microspheres, clay, molybdenum disulfide, titanium dioxide, zinc oxide, antimony oxide, calcium polyphosphate, graphite, barium sulfate, magnesium sulfate, zinc borate, calcium borate, aluminum borate whiskers, potassium titanate whiskers, and polymer compounds; conductive materials such as metal-based and metal oxide-based compounds; halogen-based flame retardants such as brominated resins; antimony-based flame retardants such as antimony trioxide and antimony pentaoxide; phosphorus-based flame retardants such as ammonium polyphosphate, aromatic phosphates, and red phosphorus; organic acid metal salt flame retardants such as organoborate metal salts, carboxylic acid metal salts, and aromatic sulfonylimide metal salts; zinc borate, zinc, zinc oxide, and... Inorganic flame retardants such as zirconium compounds, nitrogen-based flame retardants such as cyanuric acid, isocyanuric acid, melamine, melamine cyanurate, melamine phosphate, and guanidine nitride, fluorine-based flame retardants such as PTFE, organosilicon-based flame retardants such as polyorganosiloxanes, metal hydroxide-based flame retardants such as aluminum hydroxide and magnesium hydroxide, and other flame retardants, flame retardant additives such as cadmium oxide, zinc oxide, cuprous oxide, copper oxide, ferrous oxide, ferric oxide, cobalt oxide, manganese oxide, molybdenum oxide, tin oxide, and titanium dioxide, pigments, dyes, lubricants, release agents, compatibilizers, dispersants, crystal nucleating agents such as mica, talc, and kaolin, plasticizers such as phosphate esters, heat stabilizers, antioxidants, anti-coloring agents, ultraviolet absorbers, flow modifiers, foaming agents, antibacterial agents, vibration damping agents, deodorizers, sliding modifiers, and antistatic agents such as polyether ester amides, etc. Especially when used in electrical and electronic equipment, automobiles, aircraft, etc., flame retardancy is sometimes required, and it is preferable to add phosphorus-based flame retardants, nitrogen-based flame retardants, or inorganic flame retardants.

[0136] Regarding the aforementioned flame retardant, in order to exhibit a flame-retardant effect while maintaining good balance with the mechanical properties of the resin used and the resin flowability during molding, the flame retardant is preferably set at 1 to 20 parts by weight relative to 100 parts by weight of the thermoplastic resin composition. More preferably, it is 1 to 15 parts by weight.

[0137] From the viewpoint of ensuring a suitable amount of resin for welding with the second component and improving color quality, the unit area weight of the thermoplastic resin layer in the prepreg blank is preferably 10 g / m². 2 Above 500g / m 2The following is more preferably 20g / m 2 Above 200g / m 2 the following.

[0138] Here, the weight per unit area refers to the weight per 1m². 2 The mass (g) of the thermoplastic resin layer contained in the prepreg blank.

[0139] Alternatively, the thermoplastic resin layer can also exist as part of the surface layer of the fiber-reinforced plastic. The thermoplastic resin layer present on the surface of the prepreg also forms a thermoplastic resin layer in the molded article obtained by molding the prepreg, enabling integration with the second component through welding via this thermoplastic resin layer. In this method, the area of ​​the thermoplastic resin layer can be minimized, thereby improving the productivity of both the prepreg and the fiber-reinforced plastic.

[0140] <Second thermosetting resin>

[0141] The second thermosetting resin is insoluble in the thermoplastic resin to form a dispersed phase, and is mainly composed of a thermosetting resin capable of bonding with the reinforcing fibers. Furthermore, to improve the bond strength without compromising the toughness of the thermoplastic resin layer, a thermosetting resin with high toughness is preferred. Additionally, depending on the application of the fiber-reinforced plastic, additives may also be included.

[0142] Specifically, the same resin as the first thermosetting resin can be exemplified.

[0143] The second thermosetting resin is of the same type as the first thermosetting resin, but from the viewpoint of ease of setting conditions in the molding of the prepreg and the welding of the molded article, it is more preferable to use the same resin. It should be noted that, in this invention, "of the same type" means that the main components are the same except for additives, etc.

[0144] Similarly, the cured product of the second thermosetting resin is preferably of the same type as the cured product of the first thermosetting resin composition that forms the thermosetting resin layer, and more preferably the same.

[0145] Regarding the curing agents and additives that may be included in the second thermosetting resin, specific examples can be given that are the same as those that may be included in the first thermosetting resin layer, and the preferred examples are also the same.

[0146] <Prepreg Manufacturing Method>

[0147] As a method for producing the prepreg blank of the present invention, a method for manufacturing a prepreg blank comprising the following steps can be exemplified: impregnating one side of a reinforcing fiber sheet constituting a group of reinforcing fibers with a precursor of a second thermosetting resin, and then impregnating the reinforcing fiber sheet with a precursor of a thermoplastic resin layer to form a dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer; and impregnating the other side of the reinforcing fiber sheet with a precursor of a thermosetting resin layer to form a thermosetting resin layer.

[0148] Alternatively, a method for manufacturing a prepreg blank comprising the following steps can be illustrated: impregnating a thermoplastic resin precursor onto one side of a reinforcing fiber sheet constituting a reinforcing fiber group, and then, while impregnating a thermosetting resin layer precursor onto the reinforcing fiber sheet, heating and pressurizing the interface region between the thermoplastic resin and the thermosetting resin to incorporate a portion of the thermosetting resin into the thermoplastic resin layer, thereby forming a dispersed phase of a second thermosetting resin.

[0149] Additionally, a method for manufacturing a prepreg blank comprising the following steps can be illustrated: a step of impregnating both sides of a reinforcing fiber sheet constituting a reinforcing fiber group with a precursor of a thermosetting resin layer to form a thermosetting resin layer; and a step of softening or melting a precursor of a thermoplastic resin layer on at least one side of the thermosetting resin layer and applying pressure to mix the precursor of the thermosetting resin layer with the precursor of the thermoplastic resin layer to form a dispersed phase of a second thermosetting resin contained in the thermoplastic resin layer.

[0150] Furthermore, it can be illustrated that in the above-described process, pressure is applied to vibrate the precursor of the thermosetting resin layer and the precursor of the thermoplastic resin layer during mixing, thereby applying shear force. This facilitates the mixing of the thermoplastic resin layer and the thermosetting resin layer, promoting the formation of the dispersed phase of the thermosetting resin. Additionally, by complicating the interface formed by the thermoplastic resin layer and the thermosetting resin layer, the weldability of the fiber-reinforced plastic can be improved in addition to the effects of the present invention; from this viewpoint, this method is preferred. The vibration method is not particularly limited as long as it can apply shear force to any of the thermoplastic resin layer, the thermosetting resin layer, and the reinforcing fibers. Examples of mechanisms for implementing this include ultrasonic vibrators, reciprocating stationary rods, and other devices that perform periodic motion.

[0151] As the temperature at which the precursor of the thermoplastic resin layer melts, if the thermoplastic resin, which is the main component of the precursor of the thermoplastic resin layer, is crystalline, it is preferable to heat and press mold at a temperature above its melting point +30°C; if it is amorphous, it is preferable to heat and press mold at a temperature above its glass transition temperature +30°C.

[0152] As a method for forming the dispersed phase of the second thermosetting resin, which is attached to the reinforcing fibers and included in the thermoplastic resin layer of the prepreg, examples include methods using any of the following (i) to (v). These steps can be combined in multiple ways, and are not limited to these methods.

[0153] (i) The process of including the precursor of the dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer in the precursor of the thermoplastic resin layer.

[0154] (ii) A process of further impregnating a precursor of a thermoplastic resin layer with a dispersed phase of a second thermosetting resin contained in a thermoplastic resin layer onto a prepreg intermediate obtained by impregnating a precursor of a thermosetting resin layer into a reinforcing fiber sheet constituting a reinforcing fiber group.

[0155] (iii) A process of coating a prepreg intermediate containing a dispersion phase of a second thermosetting resin contained in a thermoplastic resin layer onto a prepreg intermediate obtained by impregnating a precursor of a thermoplastic resin layer with a reinforcing fiber group, and then containing the dispersion phase in the thermoplastic resin layer.

[0156] (iv) A process in which a precursor of a thermosetting resin is impregnated in a prepreg intermediate obtained by impregnating a reinforcing fiber sheet constituting a reinforcing fiber group, a precursor of a thermoplastic resin layer is impregnated in the intermediate, and pressure is applied to the thermoplastic resin to contain the thermosetting resin in the thermoplastic resin layer, thereby forming a dispersed phase.

[0157] (v) A process of applying shear force based on a vibration device or the like to a prepreg intermediate obtained by impregnating a thermoplastic resin layer precursor with a prepreg group containing a thermosetting resin layer precursor, thereby forming a dispersed phase of thermosetting resin contained in the thermoplastic resin layer.

[0158] <Precursors for thermosetting resin layers>

[0159] The precursor of the thermosetting resin layer is a composition impregnated with a reinforcing fiber group to form a thermosetting resin layer. There are no particular limitations on the method of impregnating the precursor of the thermosetting resin layer with the reinforcing fiber group; for example, a method of using a hot roller to heat and pressurize the fiber group to soften or melt it for impregnation can be cited.

[0160] There are no restrictions on the form of the precursor of the thermosetting resin layer, such as liquid, sheet, non-woven fabric, and particle. However, from the viewpoint that it can be uniformly impregnated into the reinforcing fiber group, sheet is preferred.

[0161] <Precursor for thermoplastic resin layer>

[0162] The precursor of the thermoplastic resin layer is a composition (thermoplastic resin composition) impregnated with a reinforcing fiber group to form a thermoplastic resin layer. There are no particular limitations on the method of impregnating the precursor of the thermoplastic resin layer with the reinforcing fiber group; for example, a method of impregnation by melting it with a hot roller and heating and pressurizing it can be cited.

[0163] There are no restrictions on the form of the precursor of the thermoplastic resin layer, such as liquid, sheet, non-woven fabric, and particle. From the viewpoint that it can be uniformly impregnated into the reinforcing fiber group, sheet or non-woven fabric is preferred.

[0164] From the viewpoint of ensuring stable heat-welding properties, the precursor of the thermoplastic resin layer can be disposed in a portion of the surface layer of the prepreg blank. That is, when the prepreg blank is molded into a molded article, the thermoplastic resin layer only needs to be disposed in the portion that becomes the bonding surface with the second component. From the viewpoint of obtaining a bonding surface margin, it is more preferable that the thermoplastic resin layer is disposed in 50% or more of the surface area, and more preferably 80% or more.

[0165] <Precursor of the dispersed phase of the second thermosetting resin>

[0166] The precursor of the dispersed phase of the second thermosetting resin can be used in the form of liquid, sheet, non-woven fabric, particles, etc. From the viewpoint of forming a dispersed phase in the thermoplastic resin layer, particles are preferred.

[0167] When the precursor of the dispersed phase of the second thermosetting resin is included in the precursor of the thermoplastic resin layer in advance, that is, when the above-described step (i) is performed, from the viewpoint of the process stability of the prepreg blank, the precursor of the dispersed phase of the second thermosetting resin is preferably in the range of 10 to 40 parts by mass relative to 100 parts by mass of the precursor of the thermoplastic resin layer, more preferably in the range of 15 to 40 parts by mass, and even more preferably in the range of 25 to 40 parts by mass.

[0168] <Fiber-reinforced plastics>

[0169] As another aspect of the present invention, the fiber-reinforced plastic comprises: a reinforcing fiber bundle containing reinforcing fibers, a thermosetting resin layer containing a first thermosetting resin, and a thermoplastic resin layer.

[0170] The surface layer of the fiber-reinforced plastic includes the thermoplastic resin layer.

[0171] The interface between the thermoplastic resin layer and the thermosetting resin layer is located inside the reinforcing fiber assembly.

[0172] The thermoplastic resin layer comprises a dispersed phase of a second thermosetting resin.

[0173] As an embodiment of the fiber-reinforced plastic of the present invention, an example is a molded body obtained by molding the prepreg blank of the present invention, that is, a body formed by curing the first and second thermosetting resins constituting the prepreg blank.

[0174] Furthermore, fiber-reinforced plastics can be molded individually, or multiple sheets can be stacked together, or they can be stacked with other materials. Regarding the configuration of the stack, there are no particular limitations except that the prepreg of the present invention is placed on any of the outermost stack units corresponding to the surface of the molded article; prepregs, films, sheets, nonwoven fabrics, porous materials, metals, etc., can be stacked depending on the application.

[0175] Figure 1 This is a schematic diagram of a cross-section perpendicular to a plane, showing a portion of the surface of the fiber-reinforced plastic according to an embodiment of the present invention. That is, the present invention can be shown by observing at least one cross-section of the fiber-reinforced plastic.

[0176] The surface of the fiber-reinforced plastic according to the embodiments of the present invention can be used in the same way as the prepreg blank according to the embodiments of the present invention described above. Figure 1 The following description is provided. Specifically, it includes: a reinforcing fiber assembly 12 comprising reinforcing fibers 1 and 14, a thermosetting resin layer 2 containing a first thermosetting resin, and a thermoplastic resin layer 3, wherein the surface layer of the fiber-reinforced plastic is the thermoplastic resin layer 3, the interface between the thermoplastic resin layer 3 and the thermosetting resin layer 2 is located inside the reinforcing fiber assembly 12, and the thermoplastic resin layer 3 contains a dispersed phase 4 of a second thermosetting resin.

[0177] The dispersed phase 4 of the fiber-reinforced plastic in the embodiments of the present invention refers to a region of partially independent cured thermosetting resin in the thermoplastic resin layer observed in a cross-section perpendicular to the plane of the fiber-reinforced plastic, similar to the prepreg blank of the present invention described above. That is, in the molding of the prepreg blank of the present invention, since the dispersed phase 4 is incorporating reinforcing fibers, the flow of the thermoplastic resin layer is suppressed, and only the curing reaction of the thermosetting resin is promoted. Therefore, the reinforcing fibers, thermoplastic resin layer, thermosetting resin layer, and second thermosetting resin layer described in the prepreg blank description can also be maintained.

[0178] Therefore, the fiber-reinforced plastic according to the embodiments of the present invention can be regarded as having multiple reinforcing fibers contained in the thermoplastic resin layer connected to the dispersed phase of the second thermosetting resin, thereby partially combining the multiple reinforcing fibers with each other. When the molded article is welded, even if the thermoplastic resin layer becomes fluid due to high temperature conditions, it can suppress the disorder and movement of the reinforcing fibers, prevent the excessive flow of the thermoplastic resin layer, help improve the color quality, and ensure the thickness of the thermoplastic resin layer as the bonding layer.

[0179] Similarly, the shape of the dispersed phase of the second thermosetting resin is not particularly limited, as long as it forms independent regions. For example, in cross-sectional observation of the dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer in a cross-section perpendicular to the plane, it can be fibrous, round, elliptical, rectangular, or have a complex shape with unevenness.

[0180] The length of the long axis of the dispersed phase of the second thermosetting resin is also preferably 50 nm or more, more preferably 100 nm or more, further preferably 300 nm or more, and even more preferably 1 μm or more. By setting the length of the long axis of the dispersed phase of the second thermosetting resin within this range, the flow of the thermoplastic resin layer under high-temperature conditions during welding can be effectively suppressed, ensuring higher color quality.

[0181] Similarly, in the case of the fiber-reinforced plastic according to the embodiments of the present invention, in the cross section in the thickness direction, the volume ratio of the dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer is only 1% or more, preferably 10% or more, and more preferably 15% or more, relative to 100% by volume of the thermoplastic resin layer in the reinforcing fiber group.

[0182] From the viewpoint of both suppressing the flow of thermoplastic resin during welding and maintaining the balance of the high toughness of thermoplastic resin, the volume ratio of the dispersed phase of the second thermosetting resin relative to 100% by volume of the reinforcing fibers contained within the thermoplastic resin layer is preferably 3% by volume or more and 50% by volume or less.

[0183] Similarly, regarding the dispersed phase of the second thermosetting resin, it is more preferable for the thermoplastic resin layer to be dispersed near the interface between the thermosetting resin layer and the thermoplastic resin layer than for it to be uniformly dispersed in the thermosetting resin layer.

[0184] Specifically, in the cross-section along the thickness direction of the fiber-reinforced plastic, when the region extending 50 μm from the interface between the thermoplastic resin layer and the thermosetting resin layer towards the surface of the thermoplastic resin layer is defined as 100% by volume, the sum of the volume ratios of the reinforcing fibers and the second thermosetting resin contained in the thermoplastic resin layer is preferably 10% by volume or more, more preferably 30% by volume or more. Furthermore, when this sum of volume ratios is preferably 90% by volume or less, more preferably 70% by volume or less, it is preferable to consider it as such.

[0185] (Interface between thermosetting resin layer and thermoplastic resin layer)

[0186] Similarly, in the fiber-reinforced plastics according to embodiments of the present invention, the interface between the thermosetting resin layer and the thermoplastic resin layer is located inside the reinforcing fiber group.

[0187] The elements constituting the fiber-reinforced plastics according to the embodiments of the present invention—namely, the reinforcing fibers or groups of reinforcing fibers, the thermoplastic resin, the thermosetting resin, and the second thermosetting resin—are within the same scope as those described in the prepreg blanks of the present invention, and the preferred scope is also the same. Furthermore, the various observation methods and analytical methods are also the same as those described in the specific examples of the prepreg blanks of the present invention.

[0188] Here, in the fiber-reinforced plastic according to the embodiments of the present invention, from the viewpoint of maintaining the bonding of multiple fibers in the thermoplastic resin layer under high-temperature conditions during welding with the second member, a glass transition temperature of 150°C or higher is preferred, and more preferably 180°C or higher. As analytical methods for the second thermosetting resin and the first thermosetting resin contained in the thermosetting resin layer, the following methods can be exemplified: analysis using the glass transition temperature obtained by differential scanning calorimetry (DSC), analysis using elemental distribution images obtained by energy dispersive X-ray spectrometer (EDS), and analysis using the elastic modulus obtained by nanoindentation.

[0189] The fiber-reinforced plastics involved in the embodiments of the present invention are not limited to examples of prepreg molding as one embodiment of the present invention. Any embodiment of the present invention can be obtained by processes such as autoclave molding, compression molding, pultrusion molding, resin transfer molding (RTM) molding, and resin injection molding (RI) of the prepreg.

[0190] The fiber-reinforced plastic structures involved in the embodiments of the present invention are not particularly limited, and various structures can be selected according to the application, such as flat sheets, curved sheets, concave-convex structures, hollow structures, and sandwich structures. Generally, when a flat sheet structure requires high mechanical properties, a prepreg preform is preferred, and when a complex three-dimensional structure is required, RTM molding is preferred.

[0191] <One-piece molded products>

[0192] The integrally molded article according to the embodiments of the present invention is an integrally molded article obtained by bonding a first component formed of fiber-reinforced plastic according to the embodiments of the present invention and a second component formed of other structural components through a thermoplastic resin layer disposed on the surface of the fiber-reinforced plastic.

[0193] In the integrally molded article according to the embodiments of the present invention, the distance t between the fiber-reinforced plastic thermosetting resin layer and the second member is greater than the length of the long axis of the dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer. From the viewpoint of ensuring the quality stability of the weld strength based on the weld, it is preferably 10 μm or more and 200 μm or less, and more preferably 30 μm or more and 100 μm or less.

[0194] There are no restrictions on the joining method between the first component and the second component. Examples include hot plate welding, vibration welding, ultrasonic welding, laser welding, resistance welding, induction welding, insert injection molding, and substrate injection molding.

[0195] The fiber-reinforced plastics and integrally molded articles of the present invention are preferably used in computer applications such as aircraft structural components, windmill blades, automobile outer panels and IC trays, and laptop casings, as well as in sports applications such as golf clubs and tennis rackets.

[0196] Example

[0197] The present invention will now be described in further detail using examples. However, the scope of the present invention is not limited to these examples. Furthermore, unless otherwise specified, all measurements of various properties are performed at an environment of 23°C and 50% relative humidity.

[0198] <Reinforcing fiber bundles>

[0199] • Reinforcing fiber bundle 1

[0200] A reinforcing fiber bundle 1, consisting of 24,000 continuous carbon fibers in total, is obtained by spinning, sintering, and surface oxidation of a copolymer mainly composed of polyacrylonitrile. This bundle is used to form a reinforcing fiber assembly. The characteristics of this reinforcing fiber bundle 1 are as follows.

[0201] Single fiber diameter: 7μm

[0202] Density: 1.8 g / cm³ 3

[0203] Tensile strength: 4.2 GPa

[0204] Tensile modulus of elasticity: 230 GPa

[0205] Surface free energy: 15 mJ / m 2

[0206] • Reinforcing fiber bundles 2

[0207] Using reinforcing fiber 1 as a base, various sizing agent compounds were mixed with acetone to obtain a solution containing approximately 1% by mass of the compounds homogeneously. After coating the aforementioned carbon fiber bundles with each compound using an impregnation method, a heat treatment was performed at 210°C for 90 seconds, adjusting the amount of each compound adhered to 0.5 parts by mass relative to 100 parts by mass of the carbon fibers with the adhered compound. The sizing agent compounds used in each carbon fiber and the surface free energy after sizing agent coating are as follows.

[0208] • Reinforcing fiber bundles 2-1

[0209] Bisphenol A diglycidyl ether (“jER” (registered trademark) 828, manufactured by Mitsubishi Chemical Co., Ltd.) Surface free energy: 9 mJ / m 2

[0210] • Reinforcing fiber bundles 2-2

[0211] Polyethylene glycol diglycidyl ether (“Denacol” (registered trademark) EX-841, manufactured by Nagase ChemteX Co., Ltd.)

[0212] Surface free energy: 20 mJ / m 2

[0213] • Reinforce fiber bundles 2-3

[0214] Sorbitol polyglycidyl ether (“Denacol” (registered trademark) EX-614B, manufactured by Nagase ChemteX Co., Ltd.)

[0215] Surface free energy: 32 mJ / m 2

[0216] <Thermosetting Resin Composition>

[0217] Thermosetting resin composition 1

[0218] 50 parts by weight of epoxy resin main agent (Araldite MY721 (Huntsman Advanced Materials), 50 parts by weight of jER 825 (Mitsubishi Chemical), and 7 parts by weight of Sumikaexcel PES5003P (Sumitomo Chemical)) were added to a mixing apparatus and heated and mixed at 150°C until the components were compatible. Then, while continuing to mix, the temperature was lowered to 80°C, and 45.1 parts by weight of curing agent (Seikacure S (Wakayama Seika Kogyo Co., Ltd.)) were added. The mixture was then mixed at 80°C for 30 minutes to obtain thermosetting resin composition 1.

[0219] Thermosetting resin composition 2

[0220] 50 parts by weight of epoxy resin main agent (jER (registered trademark) 825 (manufactured by Mitsubishi Chemical Co., Ltd.)), 50 parts by weight of (jER (registered trademark) 154 (manufactured by Mitsubishi Chemical Co., Ltd.)), and 7 parts by weight of (Sumikaexcel (registered trademark) PES5003P (manufactured by Sumitomo Chemical Co., Ltd.)) were added to a mixing apparatus and heated and mixed at 150°C until the components were compatible. Then, while continuing to mix, the temperature was lowered to 80°C, and 6.8 parts by weight of solidifying agent (DICY7 (manufactured by Mitsubishi Chemical Co., Ltd.)) was added, and the mixture was mixed at 60°C for 30 minutes to obtain thermosetting resin composition 2.

[0221] <Method for Determining the Glass Transition Temperature of Thermosetting Resin Cured Products>

[0222] The thermosetting resin composition prepared by the above method was injected into a mold, and heated in a hot air dryer from 30°C to the temperature recorded in Table 1 at a rate of 1.5°C / min. After curing for the time recorded in Table 1, the temperature was cooled to 30°C at a rate of 2.5°C / min to produce a 2mm thick plate-shaped cured resin product. Test pieces with a width of 12.7mm and a length of 45mm were cut from the prepared plate-shaped cured resin product. The test pieces were dried in a vacuum oven at 60°C for 24 hours. The storage modulus curve was obtained using dynamic viscoelasticity testing according to JISK 7244-7 (2007). In this storage modulus curve, the temperature value at the intersection of the tangent in the glass state and the tangent in the transition state was taken as the glass transition temperature. Here, the temperature was measured at a heating rate of 5°C / min and a frequency of 1Hz.

[0223] <Thermoplastic Resin Composition>

[0224] Thermoplastic resin composition 1

[0225] Low melting point polyamide (Amilan (registered trademark) CM4000 (manufactured by Toray Co., Ltd.), ternary copolymer polyamide resin, melting point 155℃)

[0226] Thermoplastic resin composition 2

[0227] Polyamide 6 (Amilan (registered trademark) CM1007 (manufactured by Toray Co., Ltd.), melting point 225°C)

[0228] Thermoplastic resin composition 3

[0229] Polyphenylene sulfide (Torelina (registered trademark) A670T05 (manufactured by Toray Co., Ltd.), melting point 278°C)

[0230] Thermoplastic resin composition 4

[0231] Polyetherketoneketone (Kepstan 7002 (manufactured by Arkema Corporation), melting point 332℃)

[0232] <Evaluation Methods for Thermoplastic Resins>

[0233] The melting point of thermoplastic resins was determined using a differential scanning calorimeter (DSC) based on JIS K7121 (2012). In cases where multiple melting points were observed in mixtures, the highest melting point was taken as the melting point of the thermoplastic resin.

[0234] <Cross-section observation of prepreg or fiber-reinforced plastic>

[0235] In a prepreg or fiber-reinforced plastic, an image at 1000x magnification is taken using an optical microscope of a cross-section obtained by cutting along the thickness direction at an angle orthogonal to the direction of the outermost fiber layer. For the prepreg, images are also obtained in the same manner from a cross-section obtained by cutting a material cured under no-load conditions.

[0236] (1) Obtaining the cross-sectional curve

[0237] like Figure 3 As shown, within any 300 μm square observation area in the obtained image, the cross-sectional curve is obtained using the following method. Using the end 100 of the thermoplastic resin layer 3 side of the rectangular observation image 9 as a reference line, vertical baselines 120 are drawn from the thermoplastic resin layer 3 towards the thermosetting resin layer 2 at 5 μm intervals. The point where the vertical baseline drawn from the reference line first intersects with the thermosetting resin layer 2 is plotted, and the line connecting the plotted points is taken as the cross-sectional curve 130.

[0238] (2) Analysis of thermoplastic resin layer 1

[0239] Within any 300 μm square observation area in the obtained image, the dispersed phase of the second thermosetting resin in contact with the reinforcing fibers contained in the thermoplastic resin layer was extracted, and its size was measured.

[0240] The dimension is set as the value of the major axis of the dispersed phase of the second thermosetting resin. It should be noted that the major axis of the dispersed phase of the second thermosetting resin refers to the line segment passing through the interior of the dispersed phase of the second thermosetting resin as confirmed by the above cross-sectional view, passing through the two farthest points on the outer periphery of the dispersed phase of the second thermosetting resin. When there are 20 or fewer dispersed phases of the second thermosetting resin, the length is represented by the average value of the lengths obtained by measuring all the dispersed phases. When there are 20 or more dispersed phases, the length is represented by the average value of the lengths obtained by measuring 20 randomly selected dispersed phases.

[0241] (3) Analysis of thermoplastic resin layer 2

[0242] Within any 300 μm square observation area in the obtained image, the area S0 of the thermoplastic resin layer within the reinforcing fiber group and the area S1 of the dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer are calculated respectively. Here, the end of the thermoplastic resin layer side is used as the reference line, and vertical baselines are drawn from the thermoplastic resin layer toward the thermosetting resin layer at 10 μm intervals, dividing the image into segments. In each segment, the reinforcing fiber closest to the reference line is drawn, and the line connecting the drawn points is used as the boundary line of the reinforcing fiber group, defining the area of ​​the thermoplastic resin layer within the reinforcing fiber group. By dividing the obtained S1 by S0, the volume ratio A (volume %) of the dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer relative to the thermoplastic resin layer within the reinforcing fiber group is obtained.

[0243] (4) Analysis of thermoplastic resin layer 3

[0244] Within any 300 μm square observation area in the obtained image, the area S2 of the reinforcing fibers contained in the thermoplastic resin layer and the area S3 of the dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer are calculated respectively. By dividing the obtained S3 by S2, the volume ratio B (volume %) of the dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer relative to the reinforcing fibers contained in the thermoplastic resin layer is obtained.

[0245] (5) Analysis of thermoplastic resin layer 4

[0246] Within any 300 μm square observation area in the obtained image, a 50 μm region is obtained from the cross-sectional curve toward the surface of the thermoplastic resin layer, and its area S4 is calculated. The area S5 of the dispersed phase of the reinforcing fiber and the second thermosetting resin contained in the aforementioned 50 μm region is calculated.

[0247] By dividing the obtained S5 by S4, the sum of the volume percentages (volume %) of the reinforcing fibers and the second thermosetting resin contained in the thermoplastic resin layer near the cross-sectional curve is obtained relative to the thermoplastic resin layer near the cross-sectional curve.

[0248] <Evaluation of the weldability of fiber-reinforced plastics>

[0249] Fiber-reinforced plastic was cut into 100mm wide and 100mm long pieces along the length of the test piece, with an angle of 0° relative to the fiber direction of the reinforcing fibers. The pieces were then dried in a vacuum oven for 24 hours. Next, the cut fiber-reinforced plastic was placed on a heat-resistant glass plate and pressurized at 3MPa for 1 minute at a temperature 20°C higher than the melting point of the thermoplastic resin composition, thereby obtaining a component tightly bonded to the heat-resistant glass plate. The area S6 of the thermoplastic resin composition was calculated by observing the fiber-reinforced plastic from the heat-resistant glass plate side. The rate of change P of the projected area of ​​the thermoplastic resin composition was obtained by dividing the obtained S6 by the area of ​​the fiber-reinforced plastic, and the results were evaluated as follows.

[0250] Less than 1.2: A

[0251] 1.2 or higher but less than 1.5: B

[0252] 1.5 and above: C

[0253] <Determination of the thickness of the bonding layer in a one-piece molded article>

[0254] The fiber-reinforced plastic was cut into 100mm wide and 100mm long pieces with an angle of 0° relative to the length direction of the reinforcing fibers. The pieces were then dried in a vacuum oven for 24 hours. The cut fiber-reinforced plastic was placed in contact with an aluminum alloy component and pressurized at 3MPa for 1 minute at a temperature 20° higher than the melting point of the thermoplastic resin composition, thereby obtaining a monolithic article. A 1000x image was taken using an optical microscope of the cross-section obtained from the joint of the monolithic article. A cross-sectional curve was obtained within any 300μm square observation area in the obtained image using the same method as described in <(1) Obtaining the Cross-Section Curve>. A perpendicular line was drawn from the fiber-reinforced plastic side surface of the aluminum alloy component towards the fiber-reinforced plastic side, and the distance until it intersects the cross-sectional curve was calculated. The average value obtained by repeating the above process a total of 20 times was evaluated as the joint layer thickness of the monolithic article.

[0255] (Example 1)

[0256] On one side, a reinforced fiber sheet (with a unit area weight of 193 g / m²) is formed by arranging the reinforcing fiber bundles 1 in one direction, opening them into fibers, and forming a continuous state of reinforcing fiber groups. 2 Proceeding in one direction, while forming a thermoplastic resin composition 2, which serves as a precursor for the thermoplastic resin layer, with a unit area weight of 120 g / m². 2A nonwoven resin sheet is disposed on a reinforcing fiber sheet. The thermoplastic resin composition 2 is heated by an IR heater to partially melt it and attach it to one side of the reinforcing fiber sheet. The composition is then pressed by a clamping roller whose surface temperature is kept below the melting point of the thermoplastic resin composition 2 to impregnate it into the reinforcing fiber sheet. The resulting object is then cooled to obtain a prepreg intermediate.

[0257] Using a doctor blade coater, the thermosetting resin composition 1, which serves as a precursor for the thermosetting resin layer, is applied at a resin unit area weight of 100 g / m². 2 After coating the release paper to form a thermosetting resin film, the thermosetting resin film is laminated onto the other side of the thermoplastic resin composition 2 impregnated in the intermediate. The thermosetting resin composition 1 is impregnated in the intermediate while being heated and pressurized using a hot roller, and simultaneously the thermoplastic resin composition 2 is completely melted, resulting in a prepreg blank 1. At this point, the thermosetting resin enters the unmelted nonwoven fabric portion to form a thermoplastic resin layer; therefore, the characteristics of the prepreg blank 1 are shown in Table 2.

[0258] (Example 2)

[0259] Except for the use of thermosetting resin composition 2 and thermoplastic resin composition 1, prepreg blank 2 was obtained using the same method as in Example 1. The properties of prepreg blank 2 are shown in Table 2.

[0260] (Example 3)

[0261] On one side, a reinforced fiber sheet (with a unit area weight of 193 g / m²) is formed by arranging, opening, and forming a continuous group of reinforcing fiber bundles 1 in one direction. 2 While moving in one direction, the thermosetting resin composition 1 is cryogenically pulverized and the resulting particles are dispersed on one side of the reinforcing fiber sheet as a precursor of the dispersed phase of the second thermosetting resin. The particles formed by the thermosetting resin composition 1 are then heated with an IR heater to impregnate the surface of the reinforcing fiber sheet.

[0262] Furthermore, the thermoplastic resin composition 2, which serves as a precursor for the thermoplastic resin layer, has a unit area weight of 120 g / m². 2 A film-like resin sheet is disposed on the same surface as the surface where the above-mentioned particles are dispersed in the reinforcing fiber sheet. The thermoplastic resin composition 2 is melted by heating with an IR heater and adhered to the entire surface of one side of the reinforcing fiber sheet. The surface temperature is kept below the melting point of the thermoplastic resin composition 2 by a clamping roller to impregnate it into the reinforcing fiber sheet. The resulting object is cooled to obtain a prepreg intermediate.

[0263] Using a doctor blade coater, the thermosetting resin composition 1, which serves as a precursor for the thermosetting resin layer, is applied at a resin unit area weight of 100 g / m². 2 After coating the release paper to form a thermosetting resin film, the thermosetting resin film is laminated onto the surface of the intermediate opposite to the surface of the impregnated thermoplastic resin composition 1. The thermosetting resin composition 1 is impregnated into the intermediate by heating and pressing with a hot roller to obtain a prepreg blank 3. The characteristics of the prepreg blank 3 are shown in Table 2.

[0264] (Example 4)

[0265] Except for the use of thermoplastic resin composition 3, prepreg blank 4 was obtained using the same method as in Example 3. The properties of prepreg blank 4 are shown in Table 2.

[0266] (Example 5)

[0267] Except for the use of thermosetting resin composition 2 and thermoplastic resin composition 3, prepreg blank 5 was obtained using the same method as in Example 3. The properties of prepreg blank 5 are shown in Table 2.

[0268] (Example 6)

[0269] On one side, a reinforced fiber sheet (with a unit area weight of 193 g / m²) is formed by arranging the reinforcing fiber bundles 1 in one direction, opening the fibers, and forming a continuous reinforcing fiber group. 2 While moving in one direction, the thermosetting resin composition 2 is cryogenically pulverized and the resulting particles are dispersed on one side of the reinforcing fiber sheet as a precursor of the dispersed phase of the second thermosetting resin. The particles formed by heating the thermosetting resin composition 2 are impregnated near the surface of the reinforcing fiber sheet using an IR heater.

[0270] Furthermore, the thermoplastic resin composition 2, which serves as a precursor for the thermoplastic resin layer, has a unit area weight of 120 g / m². 2 A film-like resin sheet is disposed on the same surface as the surface where the above-mentioned particles are dispersed in the reinforcing fiber sheet. The thermoplastic resin composition 2 is melted by heating with an IR heater and adhered to the entire surface of one side of the reinforcing fiber sheet. The surface temperature is kept below the melting point of the thermoplastic resin composition 2 by a clamping roller to impregnate it into the reinforcing fiber sheet. The resulting object is cooled to obtain a prepreg intermediate.

[0271] Using a doctor blade coater, the thermosetting resin composition 1, which serves as a precursor for the thermosetting resin layer, is applied at a resin unit area weight of 100 g / m². 2After coating the release paper to form a thermosetting resin film, the thermosetting resin film is laminated onto the surface of the intermediate opposite to the surface of the impregnated thermoplastic resin composition 1. The thermosetting resin composition 1 is impregnated into the intermediate while being heated and pressurized using a hot roller to obtain a prepreg blank 6. The characteristics of the prepreg blank 6 are shown in Table 2.

[0272] (Comparative Example 1)

[0273] In addition to using a unit area weight of 120 g / m² formed from thermoplastic resin composition 3. 2 Apart from using a film-like resin sheet as a precursor for the thermoplastic resin layer, prepreg blank 7 was obtained using the same method as in Example 1. The characteristics of prepreg blank 7 are shown in Table 2.

[0274] (Refer to Example 1)

[0275] Thermosetting resin composition 1 was applied using a doctor blade coater at a resin unit area weight of 50 g / m². 2 The resin film is coated onto release paper. This resin film is then laminated onto a reinforcing fiber sheet (193 g / m²) formed from reinforcing fiber bundles 1 twisted in one direction. 2 On both sides of the prepreg, a hot roller is used to heat and pressurize the thermosetting resin composition while impregnating the reinforcing fiber bundle to obtain the prepreg blank 8.

[0276] (See Example 2 for reference)

[0277] Except for using thermosetting resin composition 2, the prepreg blank 9 was obtained by the same method as in Reference Example 1.

[0278] (Example 7)

[0279] The prepreg blank 1 prepared in Example 1 and the prepreg blank 8 prepared in Reference Example 1 are cut into the specified size, and 2 prepreg blanks 1 and 6 prepreg blanks 8 are prepared.

[0280] The fiber direction of the reinforcing fiber is set to 0°, and the direction orthogonal to the fiber direction is defined as 90°, with [0° / 90°] as the reference. 2s (The symbol 's' indicates mirror symmetry) A preform is prepared by lamination. At this time, the two outermost sheets on each side are laminated as prepreg blanks 1, and the two surface layers of the preform are configured as thermoplastic resin layers containing thermoplastic resin. The preform is placed in a compression molding die, and clamps and spacers are used as needed. A pressure of 0.6 MPa is applied using a press while maintaining the shape, and the mixture is heated at 180°C for 2 hours, thereby obtaining fiber-reinforced plastic 1. The properties of fiber-reinforced plastic 1 are shown in Table 3.

[0281] (Example 8)

[0282] The prepreg blanks 2 and 9 prepared in Example 2 were cut to the specified size, preparing 2 prepreg blanks 2 and 6 prepreg blanks 9. The fiber direction of the reinforcing fiber was set to 0°, and the direction orthogonal to the fiber direction was defined as 90°, with [0° / 90°] as the reference. 2s (The symbol 's' indicates mirror symmetry) A preform is prepared by lamination. At this time, the two outermost sheets on each side are laminated as prepreg blanks 2, and the two surface layers of the preform are configured as thermoplastic resin layers containing thermoplastic resin. The preform is placed in a compression molding die, and clamps and spacers are used as needed. A pressure of 0.6 MPa is applied using a press while maintaining the shape, and the mixture is heated at 135°C for 2 hours, thereby obtaining fiber-reinforced plastic 2. The properties of fiber-reinforced plastic 2 are shown in Table 3.

[0283] (Example 9)

[0284] The prepreg blank 3 prepared in Example 3 and the prepreg blank 8 prepared in Reference Example 1 are cut into the specified size, and 2 prepreg blanks 3 and 6 prepreg blanks 8 are prepared.

[0285] The fiber direction of the reinforcing fiber is set to 0°, and the direction orthogonal to the fiber direction is defined as 90°, with [0° / 90°] as the reference. 2s (The symbol 's' indicates mirror symmetry) A preform is prepared by lamination. In this case, the two outermost sheets on each side are laminated as prepreg blanks 3, and the two surface layers of the preform are configured as thermoplastic resin layers containing thermoplastic resin. The preform is placed in a compression molding die, and clamps and spacers are used as needed. A pressure of 0.6 MPa is applied using a press while maintaining the shape, and the mixture is heated at 180°C for 2 hours, thereby obtaining fiber-reinforced plastic 3. The properties of fiber-reinforced plastic 3 are shown in Table 3.

[0286] (Example 10)

[0287] The prepreg blank 4 prepared in Example 4 and the prepreg blank 8 prepared in Reference Example 1 are cut into the specified size, and 2 prepreg blanks 4 and 6 prepreg blanks 8 are prepared.

[0288] The fiber direction of the reinforcing fiber is set to 0°, and the direction orthogonal to the fiber direction is defined as 90°, with [0° / 90°] as the reference. 2s(The symbol 's' indicates mirror symmetry) A preform is prepared by lamination. At this time, the two outermost sheets on each side are laminated as prepreg blanks 4, and the two surface layers of the preform are configured as thermoplastic resin layers containing thermoplastic resin. The preform is placed in a compression molding die, and clamps and spacers are used as needed. A pressure of 0.6 MPa is applied using a press while maintaining the shape, and the mixture is heated at 180°C for 2 hours, thereby obtaining fiber-reinforced plastic 4. The properties of fiber-reinforced plastic 4 are shown in Table 3.

[0289] (Example 11)

[0290] The prepreg blank 5 prepared in Example 5 and the prepreg blank 9 prepared in Reference Example 2 are cut into the specified size, and 2 prepreg blanks 5 and 6 prepreg blanks 9 are prepared.

[0291] The fiber direction of the reinforcing fiber is set to 0°, and the direction orthogonal to the fiber direction is defined as 90°, with [0° / 90°] as the reference. 2s (The symbol 's' indicates mirror symmetry) A preform is prepared by lamination. At this time, the two outermost sheets on each side are laminated as prepreg blanks 5, and the two surface layers of the preform are configured as thermoplastic resin layers containing thermoplastic resin. The preform is placed in a compression molding die, and clamps and spacers are used as needed. A pressure of 0.6 MPa is applied using a press while maintaining the shape, and the mixture is heated at 135°C for 2 hours, thereby obtaining fiber-reinforced plastic 5. The properties of fiber-reinforced plastic 5 are shown in Table 3.

[0292] (Example 12)

[0293] Cut the prepreg blank 6 prepared in Example 6 and the prepreg blank 8 prepared in Reference Example 1 into specified sizes, and prepare 2 prepreg blanks 6 and 6 prepreg blanks 8.

[0294] The fiber direction of the reinforcing fiber is set to 0°, and the direction orthogonal to the fiber direction is defined as 90°, with [0° / 90°] as the reference. 2s (The symbol 's' indicates mirror symmetry) A preform is prepared by lamination. In this case, the two outermost sheets on each side are laminated as prepreg blanks 6, and the two surface layers of the preform are configured as thermoplastic resin layers containing thermoplastic resin. The preform is placed in a compression molding die, and clamps and spacers are used as needed. While maintaining the shape, a pressure of 0.6 MPa is applied using a press, and the mixture is heated at 180°C for 2 hours, thereby obtaining fiber-reinforced plastic 6. The properties of fiber-reinforced plastic 6 are shown in Table 3.

[0295] (Comparative Example 2)

[0296] The prepreg blanks 7 and 9 prepared in Comparative Example 1 and Reference Example 2 were cut into specified sizes, and 2 prepreg blanks 7 and 6 prepreg blanks 9 were prepared.

[0297] The fiber direction of the reinforcing fiber is set to 0°, and the direction orthogonal to the fiber direction is defined as 90°, with [0° / 90°] as the reference. 2s (The symbol 's' indicates mirror symmetry) A preform is prepared by lamination. In this case, the two outermost sheets on each side are laminated as prepreg blanks 7, and the two surface layers of the preform are configured as thermoplastic resin layers containing thermoplastic resin. The preform is placed in a compression molding die, and clamps and spacers are used as needed. A pressure of 0.6 MPa is applied using a press while maintaining the shape, and the mixture is heated at 135°C for 2 hours, thereby obtaining fiber-reinforced plastic 7. The properties of fiber-reinforced plastic 7 are shown in Table 3.

[0298] (Example 13)

[0299] On one side, a reinforced fiber sheet (with a unit area weight of 193 g / m²) is formed by arranging, opening, and forming a continuous group of reinforcing fiber bundles 1 in one direction. 2 Proceeding in one direction, while forming a thermoplastic resin composition 2, which serves as a precursor for the thermoplastic resin layer, with a unit area weight of 120 g / m². 2 A film-like resin sheet is disposed on the surface of a reinforcing fiber sheet. The thermoplastic resin composition 2 is heated by an IR heater to melt it and make it adhere to the entire surface of one side of the reinforcing fiber sheet. The surface temperature is kept below the melting point of the thermoplastic resin composition 2 by a clamping roller to impregnate it into the reinforcing fiber sheet. The resulting object is cooled to obtain a prepreg blank intermediate.

[0300] Using a doctor blade coater, the thermosetting resin composition 1, which serves as a precursor for the thermosetting resin layer, is applied at a resin unit area weight of 100 g / m². 2 After coating the release paper to form a thermosetting resin film, the thermosetting resin film is laminated onto the surface of the intermediate opposite to the surface containing the impregnated thermoplastic resin composition 2. The film is then heated and pressurized using a hot roller and immediately passed through an ultrasonic generator, thereby dispersing the precursor of the thermoplastic resin layer within the reinforcing fiber sheet. At this time, the frequency of the ultrasonic generator is set to 20 kHz, the amplitude to 100%, and the pressure to 1.0 MPa. Furthermore, the distance between the speaker of the ultrasonic generator and the prepreg intermediate is approximately 25 mm, and the duration of ultrasonic vibration is approximately 1.0 second. Thus, while applying shear force to the intermediate, the thermosetting resin composition 1 is impregnated within it, forming a dispersed phase of the thermosetting resin, resulting in a prepreg 13. The characteristics of the prepreg 13 are shown in Table 4.

[0301] (Example 14)

[0302] Except for the use of reinforcing fiber bundles 2-1 in Example 13, the prepreg blank 14 was obtained in the same manner as in Example 13. The characteristics of the prepreg blank 14 are shown in Table 4.

[0303] (Example 15)

[0304] Except for the use of reinforcing fiber bundles 2-2 in Example 13, the prepreg blank 15 was obtained in the same manner as in Example 13. The characteristics of the prepreg blank 15 are shown in Table 4.

[0305] (Example 16)

[0306] Except for the use of reinforcing fiber bundles 2-3 in Example 13, the prepreg blank 16 was obtained in the same manner as in Example 13. The characteristics of the prepreg blank 16 are shown in Table 4.

[0307] (Example 17)

[0308] The prepreg blanks 13 and 8 prepared in Example 1 are cut into specified sizes to prepare 2 prepreg blanks 13 and 6 prepreg blanks 8.

[0309] The fiber direction of the reinforcing fiber is set to 0°, and the direction orthogonal to the fiber direction is defined as 90°, with [0° / 90°] as the reference. 2s (The symbol 's' indicates mirror symmetry) A preform is prepared by lamination. At this time, the two outermost sheets on each side are laminated as prepreg blanks 13, and the two surface layers of the preform are configured as thermoplastic resin layers containing thermoplastic resin. The preform is placed in a compression molding die, and clamps and spacers are used as needed. A pressure of 0.6 MPa is applied using a press while maintaining the shape, and the mixture is heated at 180°C for 2 hours, thereby obtaining fiber-reinforced plastic 13. The properties of fiber-reinforced plastic 13 are shown in Table 5.

[0310] (Example 18)

[0311] Except that the prepreg blank 14 prepared in Example 14 was used in Example 17, the fiber-reinforced plastic 14 was obtained in the same manner as in Example 17. The properties of the fiber-reinforced plastic 14 are shown in Table 5.

[0312] (Example 19)

[0313] Except that the prepreg blank 15 prepared in Example 15 was used in Example 17, fiber-reinforced plastic 15 was obtained in the same manner as in Example 17. The properties of fiber-reinforced plastic 15 are shown in Table 5.

[0314] (Example 20)

[0315] Except that the prepreg blank 16 prepared in Example 16 was used in Example 17, the fiber-reinforced plastic 16 was obtained in the same manner as in Example 17. The properties of the fiber-reinforced plastic 16 are shown in Table 5.

[0316] (Example 21)

[0317] On one side, a reinforced fiber sheet (with a unit area weight of 193 g / m²) is formed by arranging, opening, and forming a continuous group of reinforcing fiber bundles 1 in one direction. 2 Proceeding in one direction, while forming a thermoplastic resin composition 3, which serves as a precursor for the thermoplastic resin layer, with a unit area weight of 120 g / m². 2 A film-like resin sheet is disposed on the surface of a reinforcing fiber sheet. The thermoplastic resin composition 3 is melted by heating with an IR heater, so that it adheres to the entire surface of one side of the reinforcing fiber sheet. The surface temperature is kept below the melting point of the thermoplastic resin composition 3 by a clamping roller, so that it is impregnated in the reinforcing fiber sheet. The resulting object is cooled to obtain a prepreg blank intermediate.

[0318] Using a doctor blade coater, the thermosetting resin composition 1, which serves as a precursor for the thermosetting resin layer, is applied at a resin unit area weight of 100 g / m². 2 After coating the release paper to make a thermosetting resin film, the thermosetting resin film is stacked on the surface of the intermediate opposite to the surface of the impregnated thermoplastic resin composition 3. After heating and pressurizing with a hot roller, it is immediately passed through an ultrasonic generator, thereby applying shear force to the intermediate while impregnating the thermosetting resin composition 1 into the intermediate to form a dispersed phase of thermosetting resin, thus obtaining a prepreg blank 21.

[0319] At this point, the frequency of the ultrasonic generator is set to 20kHz, the amplitude to 100%, and the pressure to 1.0MPa. Additionally, the distance between the speaker of the ultrasonic generator and the intermediate prepreg blank is approximately 25mm, and the duration of ultrasonic vibration is approximately 0.7 seconds.

[0320] The characteristics of the prepreg blank 21 are shown in Table 4.

[0321] (Example 22)

[0322] On one side, a reinforced fiber sheet (with a unit area weight of 193 g / m²) is formed by arranging, opening, and forming a continuous group of reinforcing fiber bundles 1 in one direction. 2 Proceeding in one direction, while forming a thermoplastic resin composition 4, which serves as a precursor for the thermoplastic resin layer, with a unit area weight of 120 g / m². 2A film-like resin sheet is disposed on the surface of a reinforcing fiber sheet. The thermoplastic resin composition 4 is heated by an IR heater to melt it and make it adhere to the entire surface of one side of the reinforcing fiber sheet. The surface temperature is maintained below the melting point of the thermoplastic resin composition 4 by a clamping roller to impregnate it into the reinforcing fiber sheet. The resulting object is cooled to obtain a prepreg blank intermediate.

[0323] Using a doctor blade coater, the thermosetting resin composition 1, which serves as a precursor for the thermosetting resin layer, is applied at a resin unit area weight of 100 g / m². 2 After coating the release paper to make a thermosetting resin film, the thermosetting resin film is stacked on the surface of the intermediate opposite to the surface of the impregnated thermoplastic resin composition 4. After being heated and pressurized by a hot roller, it is immediately passed through an ultrasonic generator, thereby applying shear force to the intermediate while impregnating the thermosetting resin composition 1 into the intermediate to form a dispersed phase of thermosetting resin, thus obtaining a prepreg blank 22.

[0324] At this point, the frequency of the ultrasonic generator is set to 20kHz, the amplitude to 100%, and the pressure to 1.0MPa. Additionally, the distance between the speaker of the ultrasonic generator and the intermediate prepreg blank is approximately 25mm, and the duration of ultrasonic vibration is approximately 0.8 seconds.

[0325] The characteristics of the prepreg blank 22 are shown in Table 4.

[0326] (Example 23)

[0327] The prepreg blanks 21 prepared in Example 21 and 8 prepared in Reference Example 1 are cut into specified sizes to prepare 2 prepreg blanks 21 and 6 prepreg blanks 8.

[0328] The fiber direction of the reinforcing fiber is set to 0°, and the direction orthogonal to the fiber direction is defined as 90°, with [0° / 90°] as the reference. 2s (The symbol 's' indicates mirror symmetry) A preform is prepared by lamination. At this time, the two outermost sheets on each side are laminated as prepreg blanks 21, and the two surface layers of the preform are configured as thermoplastic resin layers containing thermoplastic resin. The preform is placed in a compression molding die, and clamps and spacers are used as needed. A pressure of 0.6 MPa is applied using a press while maintaining the shape, and the mixture is heated at 180°C for 2 hours, thereby obtaining fiber-reinforced plastic 23. The properties of fiber-reinforced plastic 23 are shown in Table 5.

[0329] (Example 24)

[0330] Cut the prepreg blank 22 prepared in Example 22 and the prepreg blank 8 prepared in Reference Example 1 into specified sizes, and prepare 2 prepreg blanks 22 and 6 prepreg blanks 8.

[0331] The fiber direction of the reinforcing fiber is set to 0°, and the direction orthogonal to the fiber direction is defined as 90°, with [0° / 90°] as the reference. 2s (The symbol 's' indicates mirror symmetry) A preform is prepared by lamination. At this time, the two outermost sheets on each side are laminated as prepreg blanks 22, and the two surface layers of the preform are configured as thermoplastic resin layers containing thermoplastic resin. The preform is placed in a compression molding die, and clamps and spacers are used as needed. A pressure of 0.6 MPa is applied using a press while maintaining the shape, and the mixture is heated at 180°C for 2 hours, thereby obtaining fiber-reinforced plastic 24. The properties of fiber-reinforced plastic 24 are shown in Table 5.

[0332] <Discussion>

[0333] A comparison of Examples 1-6 and Comparative Example 1 shows that a dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer and reinforcing fibers contained in the thermoplastic resin layer are formed. A comparison of Examples 1-2 and Examples 3-6 shows that by imparting a dispersed phase of the second thermosetting resin to the reinforcing fiber sheet pre-formed with the reinforcing fiber group, the size of the dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer and bonded to the reinforcing fibers of the thermoplastic resin layer can be controlled.

[0334] Based on the comparison of Examples 7-12 and Comparative Example 2, it is shown that by having a dispersed phase of a second thermosetting resin contained in the thermoplastic resin layer and reinforcing fibers contained in the thermoplastic resin layer, flow-out of the thermoplastic resin layer can be suppressed during the fusion welding to form an integral molded article, resulting in a molded article with high bonding quality. Furthermore, based on the comparison of Examples 7 and 12, and Examples 10 and 11, it is shown that by having the second thermosetting resin contained in the thermoplastic resin layer have a high glass transition temperature, the amount of heat-induced deformation during the fusion welding to form an integral molded article is reduced, flow-out of the thermoplastic resin layer can be suppressed, resulting in a molded article with high bonding quality.

[0335] A comparison of Examples 1 and 13 shows that by vibrating the interface between the thermoplastic resin layer and the thermosetting resin layer, the dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer can be densely formed. Furthermore, a comparison of Examples 13-16 shows that by using reinforcing fibers with high surface free energy, the flowability of the resin is improved, and the volume proportion of the dispersed phase of the second thermosetting resin relative to the thermoplastic resin contained in the thermoplastic resin layer increases.

[0336] Based on the comparison of Examples 21-22 and Comparative Example 1, it was confirmed that by vibrating the interface between the thermoplastic resin layer and the thermosetting resin layer, a dispersed phase of the second thermosetting resin contained in the thermoplastic resin layer can be formed.

[0337] Any of Examples 17-20 and Examples 23-24 demonstrates that by having a dispersed phase of a second thermosetting resin contained in a thermoplastic resin layer and reinforcing fibers contained in a thermoplastic resin layer, it is possible to suppress the outflow of the thermoplastic resin layer during the fusion welding process to form an integral molded article, thereby producing a molded article with high bonding quality.

[0338] [Table 1]

[0339]

[0340] [Table 2]

[0341]

[0342] [Table 3]

[0343]

[0344] [Table 4]

[0345]

[0346] [Table 5]

[0347]

[0348] The present invention has been described in detail and with reference to specific embodiments, but those skilled in the art will understand that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2020-096947, filed on June 3, 2020, the contents of which are incorporated herein by reference.

[0349] Explanation of reference numerals in the attached figures

[0350] 1.14 Reinforcing Fibers

[0351] 2. Thermosetting resin layer

[0352] 3. Thermoplastic resin layer

[0353] 4. Dispersed phase of the second thermosetting resin

[0354] 5. Fiber-reinforced plastic or prepreg preform

[0355] 6. Fiber orientation

[0356] 8. Cross-sectional observation plane

[0357] 9. Observe the image

[0358] 10 Interfaces

[0359] 12 Reinforcing Fiber Group

[0360] 100 end

[0361] 120 vertical baseline

[0362] 130 cross-sectional curve

Claims

1. A prepreg preform comprising: a reinforcing fiber bundle containing reinforcing fibers, a thermosetting resin layer containing a first thermosetting resin, and a thermoplastic resin layer. in, The prepreg blank has the thermoplastic resin layer on its surface. The interface between the thermoplastic resin layer and the thermosetting resin layer is located inside the reinforcing fiber assembly. The thermoplastic resin layer comprises a dispersed phase of a second thermosetting resin bonded to the reinforcing fibers. In a cross-section along the thickness direction of the prepreg, if a region extending 50 μm from the interface between the thermoplastic resin layer and the thermosetting resin layer toward the surface of the thermoplastic resin layer is defined as 100% by volume, then the sum of the volume ratios of the reinforcing fibers and the second thermosetting resin contained in the thermoplastic resin layer is 20% to 70% by volume. The average thickness of the prepreg blank is between 50 μm and 400 μm. When the average thickness of the prepreg blank is set to 100%, the average thickness ratio of the thermoplastic resin layer is between 5% and 30%.

2. The prepreg blank as described in claim 1, wherein, The length of the long axis of the dispersed phase of the second thermosetting resin is 1 μm or more.

3. The prepreg blank as described in claim 1 or 2, wherein, The second thermosetting resin is a resin of the same type as the first thermosetting resin.

4. The prepreg blank as described in claim 1 or 2, wherein its surface free energy, as determined by the Wilhelmy method, is 10–50 mJ / m. 2 The reinforcing fiber is used as the reinforcing fiber.

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