Method for producing fiber-reinforced resin molded article

Abstract

To produce a fiber-reinforced resin molded article having strong bonding strength in high-temperature high-humidity environments with good appearance quality while maintaining productivity.SOLUTION: There is provided a method for producing a fiber-reinforced resin molded article having a thermoplastic resin [p] which is a crystalline resin having a glass transition temperature (°C) of 100 (°C) or more on a surface layer and a fiber-reinforced resin molded article having a thermoplastic resin [p] which is an amorphous resin having a glass transition temperature (°C) of 180 (°C) or more on a surface layer, which comprises: a shaping step of shaping a reinforced fiber substrate [A] having the thermoplastic resin [p] on a surface layer at a predetermined temperature state defined in relation to the glass transition temperature of the thermoplastic resin [p]; an impregnation step of impregnating a preheated thermosetting resin [B] with the shaped reinforced fiber substrate [A], followed by curing; and a demolding step of demolding the thermoplastic resin [p] in a state of less than the glass transition temperature (°C).SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for producing a fiber-reinforced resin molded product by so-called resin transfer molding (RTM), in which a reinforcing fiber substrate is impregnated with an uncured thermosetting resin and cured. [Background technology]

[0002] Fiber-reinforced plastic molded products are materials with excellent mechanical properties and light weight, and are widely used as structural components in aircraft, automobiles, industrial equipment, etc. A typical manufacturing method for fiber-reinforced plastic molded products is to laminate and cure fiber-reinforced prepregs, which are continuous reinforcing fibers impregnated with uncured resin, but this method is not suitable for easily mass-producing molded products with complex shapes.

[0003] Another manufacturing method is resin transfer molding (RTM), in which a reinforcing fiber substrate is placed in a mold, and uncured resin is injected into the mold to impregnate the reinforcing fiber substrate, and then cured. This molding method is capable of molding parts with relatively complex shapes.

[0004] However, in order to produce components with more complex shapes, a technology is needed to integrally bond them to other molded products, etc. Patent Document 1 describes a method for producing a fiber-reinforced resin molded product in which a thermoplastic substrate is placed on the surface of a continuous reinforcing fiber substrate such as a carbon fiber fabric in a mold, and a thermosetting resin is injected into the substrate and cured. In the fiber-reinforced resin molded product produced in this way, the thermoplastic resin functions as an adhesive layer to bond to other components. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4774839 specification Summary of the Invention [Problem to be solved by the invention]

[0006] Fiber-reinforced resin molded articles produced by the method of Patent Document 1 can be joined to other molded articles by thermal welding via a thermoplastic resin layer. However, the manufacturing method described in Patent Document 1 involves impregnating the reinforcing fiber substrate with a thermoplastic resin inside a mold. Therefore, when using a highly heat-resistant thermoplastic resin intended for use in a high-temperature, high-humidity environment, there is a productivity issue in that it takes time to cool the mold from the melting temperature of the thermoplastic resin to the curing temperature of the thermosetting resin. Furthermore, the straightness of the reinforcing fibers can be disrupted during impregnation with the thermoplastic resin, which can lead to a deterioration in appearance quality.

[0007] An object of the present invention is to improve productivity in RTM of a fiber-reinforced resin molded article having a highly heat-resistant thermoplastic resin layer on the surface. [Means for solving the problem]

[0008] The present invention, which solves the above-mentioned problems, employs the following means. (1) A method for producing a fiber-reinforced resin molded product having a surface layer of a thermoplastic resin [p] that is a crystalline resin having a glass transition temperature (°C) of 100 (°C) or higher, comprising: a shaping step of shaping the reinforcing fiber substrate [A] having the thermoplastic resin [p] on the surface layer in a state where the thermoplastic resin [p] is at a glass transition temperature (°C) or higher and lower than a melting point (°C); an impregnation step of impregnating the shaped reinforcing fiber substrate [A] with a preheated thermosetting resin [B] and curing the resin; a demolding step in which the thermoplastic resin [p] is demolded at a temperature lower than the glass transition temperature (°C); A method for producing a fiber-reinforced resin molded product having the above items in this order. (2) A method for producing a fiber-reinforced resin molded product having a surface layer of a thermoplastic resin [p] that is an amorphous resin having a glass transition temperature (°C) of 180 (°C) or higher, comprising: a shaping step of shaping the reinforcing fiber substrate [A] having the thermoplastic resin [p] on the surface layer in a state where the thermoplastic resin [p] is at a glass transition temperature (°C) -30 (°C) or higher and at a glass transition temperature (°C) or lower; an impregnation step of impregnating the shaped reinforcing fiber substrate [A] with a preheated thermosetting resin [B] and curing the resin; a demolding step in which the thermoplastic resin [p] is demolded at a temperature lower than the glass transition temperature (°C); A method for producing a fiber-reinforced resin molded product having the above items in this order. [Effects of the Invention]

[0009] According to the present invention, a fiber-reinforced resin molded article having a highly heat-resistant thermoplastic resin layer on the surface thereof can be produced with high productivity by RTM. [Brief explanation of the drawings]

[0010] [Figure 1] Schematic cross-sectional view of a reinforcing fiber substrate [A] with a thermoplastic resin [p] on the surface [Figure 2] Schematic cross-sectional view showing how to measure the thickness of the surface thermoplastic resin [p] [Figure 3] Schematic diagram for explaining an embodiment using a molding die in the manufacturing method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The manufacturing method of the present invention will be described in detail below along with preferred embodiments.

[0012] [Fiber reinforced plastic molded products] The present invention is a method for producing a fiber-reinforced plastic molded article having a surface layer of a highly heat-resistant thermoplastic resin [p], i.e., a crystalline resin having a glass transition temperature (°C) of 100°C or higher or an amorphous resin having a glass transition temperature (°C) of 180°C or higher. That is, the finished fiber-reinforced plastic molded article has a highly heat-resistant thermoplastic resin [p] layer on the surface.

[0013] Examples of crystalline resins with a glass transition temperature (Tg) of 100°C or higher as the thermoplastic resin [p] include polyarylene ether ketones such as polyketones, polyether ketones, and polyether ketone ketones, alicyclic polyamides, semi-aromatic polyamides, and modified polyphenylene sulfides. Examples of amorphous resins with a Tg of 180°C or higher include polyetherimides, polyethersulfones, polysulfones, modified polysulfones, and polyamideimides. The thermoplastic resin [p] may be a copolymer or modified product of these resins, or a blend of two or more of these resins. It may also contain an elastomer or rubber component to improve impact resistance. Furthermore, other fillers or additives may be added depending on the application.

[0014] For details about the reinforcing fibers and thermosetting resin [B] contained in the fiber-reinforced resin molded product, please refer to the description of the reinforcing fiber base material [A] in the explanation of the shaping process and the description of the thermosetting resin [B] in the explanation of the impregnation process.

[0015] [Formation process] In order to mold such a fiber-reinforced resin molded product, in the present invention, a reinforcing fiber substrate [A] having a thermoplastic resin [p] on the surface layer is used. In this specification, the term "reinforcing fiber substrate [A]" is used as a term that represents a concept including the thermoplastic resin [p]. Typically, in the shaping process, the thermoplastic resin [p] is present only on the surface layer of the reinforcing fiber substrate [A], and the other parts of the reinforcing fiber substrate [A] are not impregnated with the resin.

[0016] The form of the reinforcing fibers constituting the reinforcing fiber substrate [A] is not particularly limited, but from the viewpoint of productivity, it is preferable that they are made of continuous fibers. Here, in this specification, continuous fibers mean fibers having a length of 10 mm or more. As long as they have this length, they do not necessarily have to be continuous throughout the entire reinforcing fiber substrate [A], and they may be interrupted along the way. Examples of the form of continuous fibers include the form of a woven fabric woven with fiber bundles, and the form of filaments, braids, filament bundles, spun yarns, etc., aligned in one direction. Two or more of these reinforcing fiber forms may be combined. Among these, from the viewpoint of achieving both light weight and strength / rigidity in the molded product, the form of a unidirectional reinforcing fiber bundle in which the reinforcing fibers are aligned in one direction is more preferable.

[0017] The reinforcing fibers constituting the reinforcing fiber substrate [A] are not particularly limited, and examples thereof include glass fibers, polyacrylonitrile-based, rayon-based, lignin-based, and pitch-based carbon fibers (including graphite fibers), potassium titanate whiskers, zinc oxide whiskers, calcium carbonate whiskers, wollastonite whiskers, aluminum borate whiskers, aramid fibers, alumina fibers, silicon carbide fibers, ceramic fibers, asbestos fibers, gypsum fibers, and metal fibers. Among these, glass fibers, polyacrylonitrile-based, and pitch-based carbon fibers are preferred, and polyacrylonitrile-based or pitch-based carbon fibers are more preferred from the viewpoints of lightness and mechanical properties, with polyacrylonitrile-based carbon fibers being particularly preferred.

[0018] The Gurley number of the reinforcing fiber substrate [A] is preferably 10,000 s or more. Within this range, the thermoplastic resin [p] adequately covers the surface of the fiber-reinforced resin molded article, preventing the thermosetting resin injected during molding from seeping out to the surface, resulting in a molded article with strong bonding strength. Here, the Gurley number of seconds is defined as the time required for 10 ml of air to pass through the surface of a 250 mm diameter fiber-reinforced fiber substrate using a Gurley densometer (Type B) under conditions of a pressure of 6.0 kPa (600 mmH2O) and a temperature of 23°C.

[0019] The reinforcing fiber substrate [A] preferably has an impregnation coefficient of 25% by mass or more, more preferably 50% by mass or more, as measured by the Water Pick-Up method. By setting the impregnation coefficient within this range, the injected thermosetting resin [B] is easily impregnated in the in-plane direction, suppressing the occurrence of unimpregnated areas and enabling the production of a fiber-reinforced resin molded product with excellent mechanical properties. The Water Pick-Up method is a method for evaluating the impregnation of a reinforcing fiber substrate using capillary action. The mass W1 of a reinforcing fiber substrate cut into a 100 mm x 100 mm piece with two sides at 0° and 90° to the reinforcing fiber direction is measured in advance. A 5 mm area (i.e., 100 mm x 5 mm) from the end of one side of the reinforcing fiber substrate (in the case of a unidirectional fiber-reinforced substrate, the fiber direction is arranged vertically) is immersed in water for 5 minutes, and the moisture adhering to the surface of the obtained reinforcing fiber substrate is wiped off with a rag or the like to determine the mass W2. The moisture increase calculated from (W2 - W1) is divided by W1 and expressed as a percentage.

[0020] FIG. 1 is a cross-sectional schematic diagram showing the configuration of a reinforcing fiber substrate [A] having a thermoplastic resin [p] on the surface layer. In the configuration of FIG. 1a, the fiber bundles on the outermost surface of the reinforcing fiber substrate 1 are in contact with the thermoplastic resin [p]. From the viewpoint of improving the bonding strength, it is preferable that at least a part of the thermoplastic resin [p] is impregnated into the fiber bundles in the reinforcing fiber substrate [A], as in the configuration of FIG. 1b. In other words, it is preferable that the thermoplastic resin [p] is present inside the fiber bundles on the surface layer of the reinforcing fiber substrate.

[0021] The thickness of the thermoplastic resin [p] on the surface layer of the reinforcing fiber substrate [A] is preferably 30 μm to 300 μm. From the viewpoint of achieving both formability and bonding strength of the substrate, 100 μm to 200 μm is more preferable. The thickness of the thermoplastic resin [p] here refers to the average value of the distance t between the surface of the thermoplastic resin [p] layer 2 and the closest reinforcing fiber 11 completely embedded in the thermoplastic resin [p] in the cross section of the reinforcing fiber substrate [A], as shown in FIG. 2. The distance is measured at any 10 points, and the average value of the obtained measurements is defined as the thickness.

[0022] The method for producing the reinforcing fiber substrate [A] having a thermoplastic resin [p] layer is not particularly limited, but for example, a method in which a film made of thermoplastic resin [p] is placed on one side of a sheet made of reinforcing fibers and heated and pressurized can be mentioned. In particular, from the viewpoint of productivity and fiber straightness, a method in which a thermoplastic resin film is placed on one side of the reinforcing fiber sheet while the sheet made of reinforcing fibers is running, heated and melted with an IR heater or the like, and then pressed with a roller or the like to continuously produce the reinforcing fiber substrate [A] is preferred.

[0023] In the manufacturing method of the present invention, RTM can also be performed by laminating reinforcing fiber substrates other than the reinforcing fiber substrate [A]. That is, before the impregnation step, a lamination step may be performed in which the reinforcing fiber substrate [A] is arranged so that the thermoplastic resin [p] is on the outermost surface, and a predetermined number of other reinforcing fiber sheets are arranged on the side opposite the thermoplastic resin [p]. In this case, the lamination step is preferably performed before the shaping step. At this time, in order to improve the handleability of the resulting molded article and to impart toughness to the molded article, a nonwoven fabric or particles mainly composed of a thermoplastic resin may be further arranged between the layers of the laminated reinforcing fiber substrates.

[0024] From the viewpoint of further improving the impregnation of the thermosetting resin [B], it is preferable to laminate a reinforcing fiber substrate [A] with a Gurley number of 100 to 5000 s on the side of the reinforcing fiber substrate [A] that contacts the resin injection port. This allows the thermosetting resin [B] injected from the resin injection port to first spread in the in-plane direction in the outermost layer, thereby suppressing the occurrence of unimpregnated areas at the end of the reinforcing fiber substrate [A].

[0025] In the molding process, if the thermoplastic resin [p] is a crystalline resin, the reinforcing fiber substrate [A] having the thermoplastic resin [p] on the surface is molded when the thermoplastic resin [p] is at or above its glass transition temperature (°C) but below its melting point (°C). If the thermoplastic resin [p] is an amorphous resin, the thermoplastic resin [p] is molded when the thermoplastic resin [p] is at or above its glass transition temperature (°C) - 30°C but below its glass transition temperature (°C). The glass transition temperature (°C) and melting point (°C) are values measured using a differential scanning calorimeter (DSC) in accordance with JIS K7121 (2012). By keeping the temperature of the thermoplastic resin [p] within the above range during the molding process, a decrease in production efficiency due to the heating and cooling time of the molding mold can be suppressed. Furthermore, the substrate itself exhibits flexibility, resulting in good moldability and conformability to the molding mold, especially when the molding mold has a complex, uneven, or curved shape.

[0026] The method for heating the reinforcing fiber substrate [A] having the thermoplastic resin [p] on the surface layer is not particularly limited, and examples thereof include a method of heating the substrate as a whole using a heating furnace or an IR heater, a method of placing the substrate in a preheated mold and heating it directly, or a method of heating the thermoplastic resin [p] using a hot plate.

[0027] The shape of the reinforcing fiber substrate [A] is not particularly limited, and it can be shaped into a desired shape according to the shape of the target part, such as a flat surface, a curved surface, or an uneven surface.

[0028] In the shaping step, it is preferable to apply a pressure of 1 MPa to 5 MPa in the thickness direction of the reinforcing fiber substrate [A]. The pressure can be applied by temporarily closing the molding die, for example. In particular, by applying a pressure within the above range using upper and lower molding dies, even if a highly heat-resistant thermoplastic resin [p] is present, the substrate can conform to the curved uneven shape and adhere closely to the molding die.

[0029] [Impregnation process] The impregnation process is a process in which a preheated thermosetting resin [B] is impregnated into a shaped reinforcing fiber substrate [A] and cured, as shown in Figure 3. Note that it is also possible to use a vacuum-assisted resin transfer molding (VaRTM) method, which is a type of RTM method, to impregnate the substrate under reduced pressure, or a high-pressure resin transfer molding (HP-RTM) method, which injects the thermosetting resin under high pressure to impregnate the substrate.

[0030] The thermosetting resin [B] is not particularly limited, but examples include unsaturated polyester, vinyl ester, epoxy, phenol (resol type), urea-melamine, polyimide, urethane, copolymers and modified products thereof, etc. From the viewpoint of mechanical properties, epoxy resin is particularly preferable. Furthermore, in consideration of the mechanical strength of the integrally molded product under high temperature and high humidity conditions, a thermosetting resin with a glass transition temperature (°C) of 130°C or higher at a degree of cure of 90% or higher is more preferable, and 150°C or higher is even more preferable.

[0031] In the impregnation process, after the reinforcing fiber substrate [A] is shaped, preheated thermosetting resin [B] is injected through a resin injection port located on the side opposite to the surface containing the thermoplastic resin [p], and the thermosetting resin [B] is impregnated into the reinforcing fiber substrate [A] and cured. The resin injection port is preferably arranged so as to contact the reinforcing fiber bundle surface of the reinforcing fiber substrate [A]. Furthermore, when the molded product has a three-dimensional structure with multiple uneven portions, it is preferable to have multiple resin injection ports from the perspective of impregnation. In addition, in order to promote resin impregnation and suck out unnecessary resin, it is also preferable that the resin suction port is arranged so as to contact the reinforcing fiber bundle surface of the reinforcing fiber substrate [A].

[0032] [Demolding process] The demolding step after the thermosetting resin [B] has hardened is carried out when the thermoplastic resin [p] is at a temperature below its glass transition temperature (°C). By keeping the temperature within the above range, deformation of the thermoplastic resin layer is suppressed, and a strong bond can be achieved without voids at the bonded surface with other components.

[0033] Furthermore, when a crystalline thermoplastic resin [p] is used, the degree of crystallinity of the thermoplastic resin [p] in the molded article that has returned to room temperature after demolding is preferably 60% or less. By keeping the crystallinity within the above range, the amount of heat required to melt the thermoplastic resin when joining it to other members is small, allowing for efficient welding and joining. [Example]

[0034] The present invention will be explained in more detail below by showing examples, but the present invention is not limited to the descriptions of the examples in any way.

[0035] [Evaluation and measurement methods] (1) Glass transition temperature and melting point of thermoplastic resin Measurements were performed using a differential scanning calorimeter (DSC) based on JIS K7121 (2012).

[0036] (2) Gurley seconds Using a Gurley Densometer (Type B), the time required for 10 ml of air to pass through the surface of a fiber-reinforced substrate with a diameter of 2.5 cm under conditions of a pressure of 600 mmH2O and a temperature of 23°C was measured in Gurley seconds.

[0037] (3) Water Pick-Up A sample W1 of the reinforcing fiber substrate was cut into a 100 mm x 100 mm piece with two sides at 0° and 90° to the direction of the reinforcing fibers, and was measured in advance. A 5 mm area (i.e., 100 mm x 5 mm) from the end of one side of the reinforcing fiber substrate (in the case of a unidirectional fiber-reinforced substrate, the fiber direction is oriented vertically) was immersed in water for 5 minutes, and the water adhering to the surface of the obtained reinforcing fiber substrate was wiped off with a cloth or the like, after which the mass W2 was determined, and the increase in water content calculated from (W2 - W1) was divided by W1 to calculate the mass, which was expressed as a percentage.

[0038] (4) Thickness of the thermoplastic resin layer The cross section of the reinforcing fiber substrate was observed with an optical microscope, and the distance between the thermoplastic resin surface and the reinforcing fiber buried in the thermoplastic resin closest to the surface was measured in the thickness direction of the thermoplastic resin present on the surface layer of the reinforcing fiber substrate. The average value of the measurements at any 10 points was taken as the thickness of the thermoplastic resin layer.

[0039] (5) Appearance of molded product The molded product was evaluated on the following three levels based on the position of the fiber straightness as viewed from the thermoplastic resin surface and the presence or absence of gaps within or between the fiber bundles. A: Maintains straight fiber direction and is good with no gaps (gaps) within or between fiber bundles. B: Either straight fibers or fine grain is poor C: Both fiber straightness and weave are poor.

[0040] (6) Productivity Five consecutive moldings were carried out, and the quantity that could be produced per unit time was comprehensively judged and relatively evaluated on the following three levels. A: Good B: Normal C: Inferior (7)Join strength The molded products obtained by the manufacturing method of the present invention were cut to a predetermined size, and the molded products were heat-welded together at a temperature 20°C higher than the melting point of the thermoplastic resin by applying a pressure of 3 MPa for 1 minute to obtain test pieces, and (a) the bond strength at 23°C, (b) the bond strength at 80°C after water absorption, and (c) the fatigue bond strength were evaluated. Bond strength at 23°C The obtained test pieces were subjected to a tensile shear test at an ambient temperature of 23°C based on JIS K6850 (1994), and the test results were evaluated as follows. A:25MPa or more B: 20MPa or more and less than 25MPa C: Less than 20 MPa (fail) - Bond strength at 80℃ after water absorption The obtained test pieces were immersed in warm water at 70°C for two weeks, and then subjected to a tensile shear test at an ambient temperature of 80°C according to JIS K6850 (1994). The test results were evaluated as follows. A:15MPa or more B: 10 MPa or more and less than 15 MPa C: Less than 10 MPa (fail) Fatigue joint strength The obtained test specimen was attached to a fatigue testing machine, and the test was carried out at an ambient temperature of 23°C with a sinusoidal stress waveform, stress ratio R = 0.1, and frequency of 10 Hz, in accordance with JASO M353 (1998). 5 The maximum stress of the stress waveform at which the specimen broke in 1000 times was taken as the fatigue joint strength, and the test results were evaluated as follows: A:13MPa or more B: 9 MPa or more and less than 13 MPa C: Less than 9 MPa (fail) [Materials used] Reinforced fiber base material [A] CF-UD: Carbon fiber ("Torayca (registered trademark)" T700S-24K, manufactured by Toray Industries, Inc.) with a basis weight of 200 g / m 2 A reinforcing fiber substrate in which a reinforcing fiber sheet aligned in one direction is run on one side of the reinforcing fiber sheet, and the following thermoplastic resin film is placed on the reinforcing fiber sheet, and heated and melted by an IR heater to adhere to one side. CF-Fabric: Carbon fiber fabric "TORAYCA (registered trademark)" CO6343 manufactured by Toray Industries, Inc., basis weight (W) 200 g / m 2 A reinforcing fiber substrate in which the following thermoplastic resin [p] is layered on the surface and attached to one side by hot pressing.

[0041] Thermoplastic resin [p] PEKK: Polyether ketone ketone (KEPSTAN® 7002, manufactured by Arkema, crystalline) with a basis weight of 10 g or 120 g / m 2 Film PEI: Polyetherimide (ULTEM® 1010, manufactured by SABIC, amorphous) with a basis weight of 120 g / m 2 Film PA6: Polyamide 6 ("Amilan (registered trademark)" CM1007, manufactured by Toray Industries, Inc., crystalline) with a basis weight of 120 g / m 2 Film Thermosetting resin [B] EP1: A resin mixture of 90 parts by weight of "Epikote (registered trademark)" 828 (manufactured by Japan Epoxy Resins Co., Ltd.), 10 parts by weight of "ERISYS (registered trademark)" GE-20 (manufactured by CVC), and 32 parts by weight of "Ancamin (registered trademark)" 2049 (manufactured by PTI Japan Co., Ltd.) EP2: A resin obtained by mixing 60 parts by mass of "Araldite (registered trademark)" MY721 (manufactured by Huntsman Advanced Materials), 40 parts by mass of "jER (registered trademark)" 825 (manufactured by Mitsubishi Chemical Corporation), 10 parts by mass of "Sumikaexcel (registered trademark)" PES5003P (manufactured by Sumitomo Chemical Co., Ltd.), and 45 parts by mass of Seikacure S (manufactured by Wakayama Seika Kogyo Co., Ltd.) [Production of molded products] Seven reinforcing fiber sheets consisting of the same type of reinforcing fiber and basis weight were laminated on the side of the reinforcing fiber substrate [A] that was not coated with the thermoplastic resin [p], and the edges were temporarily secured. The thermoplastic resin [p] was then heated to a predetermined temperature using an IR heater. The heated substrate was then placed in a mold heated to a predetermined temperature based on the curing temperature of the thermosetting resin [B], with the thermoplastic resin [p] surface in contact with the mold. The upper mold was then closed and a pressure of 1 MPa was applied. The thermosetting resin [B], preheated to a predetermined temperature, was then injected into the mold at an injection pressure of 0.2 MPa using a resin injection device, and the reinforcing fiber substrate was impregnated while vacuuming through the resin suction port. After impregnation, the material was held at the predetermined temperature for 2 hours, cooled to 30°C, and demolded to obtain a fiber-reinforced composite material. The resulting fiber-reinforced composite material had a thickness of approximately 1.5 mm.

[0042] (Examples 1 and 2) As shown in Table 1, molding at a specified temperature using a unidirectional reinforcing fiber substrate with a surface layer of PEKK resin or PEI resulted in molded products with excellent appearance, productivity, and bond strength. In particular, the bond strength and fatigue bond strength in an 80°C environment after water absorption showed excellent results.

[0043] (Comparative Example 1) As shown in Table 1, CF-UD was impregnated with thermosetting resin and molded at a specified temperature, but it was difficult to mold the unsealed CF-UD, which resulted in misalignment of the substrate and fiber flow, resulting in poor appearance. Also, since there was no thermoplastic resin layer on the surface, it was impossible to evaluate the bonding.

[0044] (Comparative Example 2) As shown in Table 1, when molding was performed at a specified temperature using a unidirectional reinforcing fiber substrate with a PA6 resin surface layer, a molded product with a good appearance was obtained, but the bonding strength and fatigue bonding strength in an 80°C environment after water absorption were low.

[0045] (Comparative Example 3) As shown in Table 1, when molding was performed at a temperature lower than the glass transition temperature (°C) using a unidirectional reinforcing fiber substrate with a PEKK resin surface layer, the thermoplastic resin layer was hard and difficult to shape, and the reinforcing fiber substrate shifted after placement, resulting in a molding with a poor appearance.

[0046] Example 3 As shown in Table 1, when a reinforcing fiber substrate with a shorter Gurley seconds was used compared to Example 1, a small amount of thermosetting resin leaked out from the thermoplastic resin on the surface layer, which affected the decrease in bonding strength.

[0047] Example 4 As shown in Table 1, when a reinforcing fiber substrate with a smaller WPU was used compared to Example 1, pinholes like voids were observed on the thermosetting resin surface, resulting in a poor appearance. Furthermore, the bonding strength and fatigue bonding strength in an 80°C environment after water absorption were poor, presumably due to the influence of unimpregnated material inside.

[0048] Example 5 As shown in Table 1, when a thin reinforcing fiber substrate of the thermoplastic resin [p] was used, the bonding strength was inferior to that of Example 1.

[0049] Example 6 As shown in Table 1, when a reinforcing fiber substrate in which part of the thermoplastic resin [p] did not penetrate into the reinforcing fiber substrate but was in close contact with the surface of the reinforcing fiber was used, the bonding strength was inferior to that of Example 1.

[0050] Example 7 As shown in Table 1, results equivalent to those in Example 1 were obtained when a CF-fabric substrate was used.

[0051] Example 8 As shown in Table 1, when a thermosetting resin [B] having a higher glass transition temperature (°C) than that of Example 1 was used, the bonding strength and fatigue strength in an 80°C environment after water absorption were good.

[0052] [Table 1] [Industrial Applicability]

[0053] The molded articles obtained by the manufacturing method of the present invention can be used in fields where lightweight and mechanical properties are required, and are particularly suitable for aircraft structural members, automobile exterior panels, wind turbine blades, etc. [Explanation of symbols]

[0054] 1 Reinforced fiber base material [A] 11 Reinforced Fiber 2 Thermoplastic resin [p] layer 3 Molding mold (top) 4 Molding mold (bottom) 5 Resin injection port 6 Resin suction port t Thickness of the surface thermoplastic resin [p]

Claims

1. A method for producing a fiber-reinforced resin molded product having a surface layer of a thermoplastic resin [p] that is a crystalline resin having a glass transition temperature (°C) of 100 (°C) or higher, the method comprising: A shaping step of shaping the reinforcing fiber substrate [A] having the thermoplastic resin [p] on the surface layer in a state where the thermoplastic resin [p] is at a glass transition temperature (°C) or higher and lower than a melting point (°C); an impregnation step of impregnating the shaped reinforcing fiber substrate [A] with a preheated thermosetting resin [B] and curing it; a demolding step in which the thermoplastic resin [p] is demolded at a temperature lower than the glass transition temperature (°C); A method for producing a fiber-reinforced resin molded product having the above items in this order.

2. A method for producing a fiber-reinforced resin molded product having a surface layer of a thermoplastic resin [p] that is an amorphous resin having a glass transition temperature (°C) of 180 (°C) or higher, comprising: A shaping step of shaping the reinforcing fiber substrate [A] having the thermoplastic resin [p] on the surface layer in a state where the thermoplastic resin [p] is at a glass transition temperature (°C) -30 (°C) or higher and a glass transition temperature (°C) or lower; an impregnation step of impregnating the shaped reinforcing fiber substrate [A] with a preheated thermosetting resin [B] and curing it; a demolding step in which the thermoplastic resin [p] is demolded at a temperature lower than the glass transition temperature (°C); A method for producing a fiber-reinforced resin molded product having the above items in this order.

3. The method for producing a fiber-reinforced resin molded product according to claim 1 or 2, wherein the Gurley number of the reinforcing fiber base material [A] is 10,000 s or more.

4. The method for producing a fiber-reinforced resin molded product according to claim 1 or 2, wherein the impregnation ability of the reinforcing fiber base material [A] by the Water Pick-Up method is 25% by mass or more.

5. The method for producing a fiber-reinforced resin molded product according to claim 1 or 2, wherein a pressure of 1 MPa to 5 MPa is applied in the thickness direction of the reinforcing fiber base material [A] in the shaping step.

6. The method for producing a fiber-reinforced resin molded product according to claim 1 or 2, wherein the thickness of the thermoplastic resin [p] on the surface layer of the reinforcing fiber base material [A] is 30 μm to 300 μm.

7. The method for producing a fiber-reinforced resin molded product according to claim 1 or 2, wherein at least a part of the thermoplastic resin [p] is impregnated into the fiber bundles in the reinforcing fiber substrate [A].

8. The method for producing a fiber-reinforced resin molded product according to claim 1, wherein the crystallinity of the thermoplastic resin [p] when returned to room temperature after demolding is 60% or less.

9. The method for producing a fiber-reinforced resin molded product according to claim 1 or 2, wherein the reinforcing fiber substrate [A] is a unidirectional reinforcing bundle.

10. 3. The method for producing a fiber-reinforced resin molded product according to claim 1, further comprising a lamination step of arranging the reinforcing fiber substrate [A] so that the thermoplastic resin [p] is the outermost surface before the impregnation step, and arranging a predetermined number of other reinforcing fiber sheets on the surface opposite the thermoplastic resin [p].

11. 11. The method for producing a fiber-reinforced resin molded product according to claim 10, wherein in the lamination step, a reinforcing fiber base material having a Gurley second number of 100 to 5000 s is laminated on the side of the reinforcing fiber base material [A] in contact with the resin injection port.

12. 3. The method for producing a fiber-reinforced resin molded product according to claim 1, wherein the thermosetting resin [B] has a glass transition temperature (°C) of 130 (°C) or higher at a degree of cure of 90% or higher.

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