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.SOLUTION: There is provided a method for producing a fiber-reinforced resin molded article having a thermoplastic resin [p] on a surface layer and a thermosetting resin [B] having a glass transition temperature (°C) at a curing degree of 90% or more of 130°C or more as a matrix resin, which comprises: a shaping step of shaping a reinforced fiber substrate [A] having the thermoplastic resin [p] on a surface layer; an impregnation step of impregnating the preheated thermosetting resin [B] with the reinforced fiber substrate [A] while maintaining the reinforced fiber substrate [A] at less than the melting point when the thermoplastic resin [p] is a crystalline resin and at the glass transition temperature (°C)+10(°C) or less when the thermoplastic resin [p] is an amorphous resin; and a curing step of curing the thermosetting resin [B] in this order.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 the thermoplastic resin layer. However, in the manufacturing method described in Patent Document 1, the melting of the thermoplastic resin and the injection and curing reaction of the thermosetting resin are carried out in the same process. Therefore, when a highly heat-resistant thermosetting resin with a relatively high flow viscosity is used, the straightness of the fibers in the thermoplastic resin layer is easily disturbed, which can easily result in poor appearance. This has led to the problem of difficulty in producing molded articles that have excellent heat resistance and high appearance quality.

[0007] An object of the present invention is to improve the appearance quality of a fiber-reinforced resin molded article produced by RTM, which has a thermoplastic resin surface layer and a highly heat-resistant thermosetting resin as the matrix resin. [Means for solving the problem]

[0008] The present invention, which solves the above-mentioned problems, employs the following means.

[0009] A method for producing a fiber-reinforced resin molded product having a thermoplastic resin [p] on a surface layer and a thermosetting resin [B] having a glass transition temperature (°C) of 130°C or higher at a degree of cure of 90% or higher as a matrix resin, comprising: a shaping step of shaping the reinforcing fiber substrate [A] having the thermoplastic resin [p] on a surface layer; an impregnation step of impregnating the reinforcing fiber substrate [A] with the preheated thermosetting resin [B] in a state in which the reinforcing fiber substrate [A] is in a state of being lower than the melting point (°C) of the thermoplastic resin [p] when the thermoplastic resin [p] is a crystalline resin, or in a state in which the reinforcing fiber substrate [A] is in a state of being lower than the glass transition temperature (°C) + 10 (°C) of the thermoplastic resin [p] when the thermoplastic resin [p] is an amorphous resin; a curing step of curing the thermosetting resin [B]; A method for producing a fiber-reinforced resin molded product having the above items in this order. [Effects of the Invention]

[0010] According to the present invention, a fiber-reinforced plastic molded article having a highly heat-resistant thermosetting resin as a matrix resin and a thermoplastic resin as a surface layer can be produced by RTM with high appearance quality. [Brief explanation of the drawings]

[0011] [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

[0012] The manufacturing method of the present invention will be described in detail below along with preferred embodiments.

[0013] [Fiber reinforced plastic molded products] The present invention is a method for producing a fiber-reinforced plastic molded article having a thermoplastic resin [p] on the surface layer and a highly heat-resistant thermosetting resin [B] as the matrix resin.

[0014] The thermoplastic resin [p] is not particularly limited, and examples thereof include polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), and liquid crystal polyester; polyolefins such as polyethylene (PE), polypropylene (PP), and polybutylene; styrene-based resins; polyoxymethylene (POM), polyamide (PA), polycarbonate (PC), polymethylene methacrylate (PMMA), polyvinyl chloride (PVC), polyphenylene sulfide (PPS), polyphenylene ether (PPE), modified PPE, polyimide (PI), and polyamide-imide (PAI). Examples of suitable resins include polyetherimide (PEI), polysulfone (PSU), modified PSU, polyethersulfone (PES), polyketone (PK), polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyarylate (PAR), polyethernitrile (PEN), phenolic resins, phenoxy resins, and fluorine-based resins such as polytetrafluoroethylene. These include thermoplastic elastomers such as polystyrene, polyolefin, polyurethane, polyester, polyamide, polybutadiene, polyisoprene, and fluorine-based elastomers, as well as copolymers, modified products, and blends of at least two of these. Thermoplastic resins may contain elastomers or rubber components to improve impact resistance. Furthermore, other fillers and additives may be added depending on the application. In particular, from the viewpoint of heat resistance, crystalline resins with a glass transition temperature of 100°C or higher or amorphous resins with a glass transition temperature of 180°C or higher are preferred, such as PPS, PEEK, and PEKK. Here, the glass transition temperatures (°C) and melting points (°C) are values measured by a differential scanning calorimeter (DSC) based on JIS K7121 (2012).

[0015] 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.

[0016] [Formation process] In order to form 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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 sample 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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].

[0026] In the shaping process, when the thermoplastic resin [p] is a crystalline resin, it is preferable to shape the reinforcing fiber substrate [A] having the thermoplastic resin [p] on the surface layer when the thermoplastic resin [p] is at or above its glass transition temperature (°C) but below its melting point (°C). Furthermore, when the thermoplastic resin [p] is an amorphous resin, it is preferable to shape the thermoplastic resin [p] when the thermoplastic resin [p] is at or above its glass transition temperature (°C) - 30°C but below its glass transition temperature (°C). Here, the glass transition temperature (°C) and melting point (°C) are values measured using a differential scanning calorimeter (DSC) based on JIS K7121 (2012). By keeping the temperature of the thermoplastic resin [p] within the above range during the shaping process, it is possible to suppress a decrease in production efficiency due to the heating and cooling time of the molding die. Furthermore, because the substrate itself exhibits flexibility, it exhibits good shaping and conformability to the molding die, especially when the molding die has a complex, uneven or curved shape.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] [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. It is also possible to use a vacuum-assisted resin transfer molding (VaRTM) method, which is a type of RTM process, to impregnate the substrate under reduced pressure, or a high-pressure resin transfer molding (HP-RTM) method, which injects and impregnates the thermosetting resin under high pressure. In particular, the use of HP-RTM in the manufacturing method of the present invention can achieve both high appearance quality and impregnation performance.

[0031] The thermosetting resin [B] used has a glass transition temperature (°C) of 130°C or higher at a degree of cure of 90% or higher. From the viewpoint of heat resistance, the thermosetting resin [B] is preferably a thermosetting resin having a glass transition temperature (°C) of 150°C or higher, more preferably 180°C or higher. Here, the crystallinity is a value measured by a differential scanning calorimeter (DSC) based on JIS K7148-1 (2015), and the glass transition temperature (°C) is a value measured by a differential scanning calorimeter (DSC) based on JIS K7121 (2012). Examples of such thermosetting resin [B] include unsaturated polyester resins, vinyl ester resins, epoxy resins, phenolic resins, urea resins, melamine resins, polyimide resins, cyanate ester resins, bismaleimide resins, benzoxazine resins, copolymers or modified products thereof, and resins obtained by blending at least two of these.

[0032] From the viewpoint of flame resistance, the thermosetting resin [B] preferably contains at least one component selected from the group consisting of a cyanate ester resin having an average cyanate equivalent of 220 or less, a bismaleimide resin having an average maleimide equivalent of 210 or less, and a benzoxazine resin having an average oxazine equivalent of 300 or less. The term "major component" here refers to a component that accounts for 60% by mass or more of the thermosetting resin. The average cyanate equivalent is the value obtained by dividing the average molecular weight of the cyanate ester resin by the average number of cyanate groups. Specifically, the chemical structure and its proportion are identified by liquid chromatography-mass spectrometry (LC / MS), and the average cyanate equivalent is calculated from the average molecular weight and average number of cyanate groups of the cyanate ester resin. The term "average molecular weight" here refers to the number-average molecular weight. Like the average cyanate equivalent, the average bismaleimide equivalent and the average oxazine equivalent are calculated by dividing the average molecular weight of a bismaleimide resin by the average number of maleimide groups, or the average molecular weight of a benzoxazine resin by the average number of benzoxazine rings. Because these resins have a high crosslink density, there are many locations where molecular chains break during combustion, requiring more energy for combustion. In other words, they exhibit high resistance to combustion.

[0033] In the impregnation process, for example, after shaping the reinforcing fiber substrate [A], preheated thermosetting resin [B] is injected through a resin injection port located on the opposite side to the surface containing the thermoplastic resin [p], and the thermosetting resin [B] is impregnated into the reinforcing fiber substrate [A]. 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].

[0034] In the present invention, the reinforcing fiber substrate [A] is set to a temperature below the melting point (°C) of the thermoplastic resin [p] if it is a crystalline resin, or below the glass transition temperature (°C) + 10 (°C) if it is an amorphous resin, and in this state, the preheated thermosetting resin [B] is impregnated into the reinforcing fiber substrate [A]. When the thermoplastic resin [p] contained in the reinforcing fiber substrate [A] is set to such a temperature, the reinforcing fibers are fixed to a certain extent by the thermoplastic resin [p]. By impregnating the thermosetting resin [B] in this state, the straightness of the reinforcing fibers is maintained, and the appearance quality of the surface containing the thermoplastic resin [p] can be maintained.

[0035] [Curing process] After the impregnation process, the thermosetting resin [B] is cured to produce a molded product. From the perspective of appearance quality, the thermosetting resin [B] is preferably cured at a temperature below the melting point (°C) of the thermoplastic resin [p] if it is a crystalline resin, or at a temperature below the glass transition temperature (°C) + 10 (°C) if it is an amorphous resin. Curing the thermosetting resin [B] within the above range allows the reinforcing fibers on the surface of the reinforcing fiber substrate [A] to remain fixed by the thermoplastic resin [p], maintaining appearance quality. However, if the degree of cure of the thermosetting resin [B] is 60% or higher, the thermoplastic resin [p] may be heated at a temperature exceeding the above range. From the perspective of the mechanical properties of the molded product, the final degree of cure of the thermosetting resin [B] is 90% or higher. Furthermore, when using a thermosetting resin [B] that generates a large amount of heat during the curing reaction, it is preferable to control the temperature conditions of the curing process in two or more stages, taking into account the effect of heat generation on the temperature of the thermoplastic resin [p].

[0036] [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.

[0037] 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]

[0038] 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.

[0039] [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).

[0040] (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.

[0041] (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.

[0042] (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.

[0043] (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.

[0044] (6)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 (failure) [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.

[0045] 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 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 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.) EP2: a resin obtained by mixing 100 parts by mass of "jER (registered trademark)" 828 (manufactured by Mitsubishi Chemical Corporation), 7.7 parts by mass of "jER Cure (registered trademark)" DICY7 (manufactured by Mitsubishi Chemical Corporation), 2.4 parts by mass of DCMU99 (manufactured by Hodogaya Chemical Co., Ltd.), and 15.7 parts by mass of DABPA (manufactured by Daiwa Chemical Industry Co., Ltd.) CE: 100 parts by weight of bisphenol A cyanate ester resin (CYTESTER (registered trademark) TA, manufactured by Mitsubishi Gas Chemical Company, Inc., cyanate equivalent: 139) [Production of molded products] Seven reinforcing fiber sheets consisting of the same reinforcing fibers 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 the 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 a vacuum was drawn 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.

[0046] (Examples 1 and 2) As shown in Table 1, when a unidirectional reinforced fiber substrate with a PEKK resin surface layer was impregnated with EP1 resin or CE resin and molded at a specified temperature, molded products with excellent appearance and bond strength were obtained. In particular, the bond strength and fatigue bond strength in an 80°C environment after water absorption were excellent.

[0047] (Comparative Example 1) As shown in Table 1, CF-UD was impregnated with CE resin and molded at the 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. In addition, since there was no thermoplastic resin layer on the surface, it was impossible to evaluate the bonding.

[0048] (Comparative Example 2) As shown in Table 1, a unidirectional reinforced fiber substrate with a surface layer of PEKK resin was impregnated with EP2 resin, which has a lower glass transition temperature than EP1 resin, and molded at a specified temperature. As a result, a molded product with a good appearance was obtained, but the bond strength and fatigue bond strength in an 80°C environment after water absorption were low.

[0049] (Comparative Example 3) As shown in Table 1, when a unidirectional reinforcing fiber substrate with a surface layer of PA6 resin, which has a lower glass transition temperature than PEKK resin, was impregnated with CE resin and molded at a specified temperature, the straightness of the fibers was lost and a molded product with a poor appearance was obtained. This was thought to be due to the PA6 resin softening or melting at the impregnation and curing temperature of the CE resin.

[0050] Example 3 As shown in Table 1, when a reinforcing fiber substrate with a shorter Gurley seconds was used compared to Example 2, a small amount of thermosetting resin leaked out from the thermoplastic resin on the surface layer, which affected the decrease in bonding strength.

[0051] Example 4 As shown in Table 1, when a reinforcing fiber substrate with a smaller WPU was used compared to Example 2, 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.

[0052] 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 2.

[0053] 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 2.

[0054] Example 7 As shown in Table 1, results equivalent to those in Example 2 were obtained when a CF-fabric substrate was used.

[0055] Example 8 As shown in Table 1, when a thermoplastic resin [p] having a lower glass transition temperature (°C) was used compared to Example 1, the bonding strength and fatigue strength in an 80°C environment after water absorption were inferior to those of Example 1.

[0056] [Table 1] [Industrial Applicability]

[0057] 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]

[0058] 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 plastic molded product having a thermoplastic resin [p] on a surface layer and a thermosetting resin [B] having a glass transition temperature (°C) of 130°C or higher at a degree of cure of 90% or higher as a matrix resin, comprising: a shaping step of shaping the reinforcing fiber substrate [A] having the thermoplastic resin [p] on the surface layer; An impregnation step in which the reinforcing fiber substrate [A] is impregnated with the preheated thermosetting resin [B] in a state in which the reinforcing fiber substrate [A] is in a state of less than the melting point (°C) of the thermoplastic resin [p] when the thermoplastic resin [p] is a crystalline resin, or in a state in which the thermoplastic resin [p] is in a state of less than the glass transition temperature (°C) + 10 (°C) when the thermoplastic resin [p] is an amorphous resin; a curing step of curing the thermosetting resin [B]; A method for producing a fiber-reinforced resin molded product having the above items in this order.

2. 2. The method for producing a molded article according to claim 1, wherein the thermosetting resin [B] is a resin containing, as a main component, at least one selected from the group consisting of a cyanate ester resin having an average cyanate equivalent of 220 or less, a bismaleimide resin having an average maleimide equivalent of 210 or less, and a benzoxazine resin having an average oxazine equivalent of 300 or less.

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 or 2, 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 to 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. The thermoplastic resin [p] is a crystalline resin having a glass transition temperature of 100 (°C) or higher, or an amorphous resin having a glass transition temperature of 180 (°C) or higher. The method for producing a fiber-reinforced resin molded product according to claim 1 or 2.

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