FRP molded articles and methods for manufacturing the same, FRP products and methods for manufacturing the same

Abstract

The primary objective of this invention is to provide an FRP molded article in which surface irregularities caused by reinforcing fibers in the in-mold coating are reduced, and a method for manufacturing the same. [Solution] The FRP molded body 4 has a fiber-reinforced resin base material 3C containing reinforcing fibers and matrix resin, and an in-mold coating film 2C fixed to the surface of the fiber-reinforced resin base material 3C, wherein the in-mold coating film 2C contains inorganic fillers and the thickness of the in-mold coating film 2C is greater than 200 μm.

Description

[Technical Field]

[0001] This invention relates to FRP molded articles, methods for manufacturing the same, FRP products, and methods for manufacturing the same. [Background technology]

[0002] Fiber-reinforced plastic (FRP) has high specific strength and specific stiffness, and its superior mechanical properties have led to its use in lightweighting FRP products such as automotive exterior panels. Demand is increasing due to its effects on improving vehicle driving performance and fuel efficiency. FRP products may have multiple layers of coating, including colored and primer coatings, formed through multi-layer painting.

[0003] In the manufacture of multi-layer coated FRP products, intermediate FRP molded products are useful. For example, Patent Document 1 discloses an FRP molded product having an in-mold coating film formed simultaneously with the molding of the prepreg by an in-mold coating method. In-mold painting is also known as in-mold coating. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2007-331369 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the surface of the in-mold coating on the FRP molded body described in Patent Document 1 often exhibits irregularities caused by reinforcing fibers that are visible to the naked eye. These defects occur along the fiber direction of the prepreg, and once they appear, they are difficult to conceal even with paint. In particular, in typical automobile body painting, which involves baking at temperatures above 80°C, the irregularities can even become more noticeable.

[0006] The primary objective of this invention is to provide an FRP molded article in which surface irregularities caused by reinforcing fibers in the in-mold coating are reduced, and a method for manufacturing the same. [Means for solving the problem]

[0007] According to one aspect of the present invention, an FRP molded article is provided, comprising a fiber-reinforced resin substrate containing reinforcing fibers and a matrix resin, and an in-mold coating film fixed to the surface of the fiber-reinforced resin substrate, wherein the in-mold coating film contains an inorganic filler and the thickness of the in-mold coating film is greater than 200 μm. [Effects of the Invention]

[0008] The present invention provides an FRP molded article in which surface irregularities caused by reinforcing fibers in the in-mold coating are reduced, and a method for manufacturing the same. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram showing a press machine. [Figure 2] Figure 2 is a cross-sectional view of the molding die. [Figure 3] Figure 3 is a cross-sectional view of the mold. [Figure 4] Figure 4 is a cross-sectional view of the molding die. [Figure 5] Figure 5 is a cross-sectional view illustrating the manufacturing process of an FRP molded product. [Figure 6] Figure 6 is a cross-sectional view illustrating the manufacturing process of an FRP molded product. [Figure 7] Figure 7 is a cross-sectional view illustrating the manufacturing process of an FRP molded product. [Figure 8] Figure 8 is a cross-sectional view illustrating the manufacturing process of an FRP molded product. [Figure 9] Figure 9 is a cross-sectional view illustrating the manufacturing process of an FRP molded product. [Figure 10] Figure 10 is a cross-sectional view of an FRP molded product. [Figure 11]FIG. 11 is a cross-sectional view of the molding die used in the experiment. DETAILED DESCRIPTION OF EMBODIMENTS

[0010] 1. Press molding apparatus The FRP molded article according to the embodiment can preferably be produced using a press molding apparatus. FIG. 1 is a schematic diagram showing the configuration of a typical press molding apparatus. Referring to FIG. 1, the press molding apparatus 1 includes a press machine 10, a molding die 20, and a vacuum pump 30. The press machine 10 is composed of a main frame 11, a bolster 12 fixed to the lower part of the main frame 11, a slide 13 capable of moving up and down in the vertical direction above the bolster 12, and an elevator 14 for moving the slide 13 up and down. The molding die 20 is composed of a lower die 20L fixed to the upper surface of the bolster 12, and an upper die 20U fixed to the lower surface of the slide 13.

[0011] As shown in FIG. 2, the lower die 20L has a convex portion 21 having a vertical outer peripheral surface, and further has an annular convex portion 22 arranged along the outer periphery of the convex portion 21 and sharing the outer peripheral surface with the convex portion 21. The convex portion 21 is provided with a seal ring 23 that goes around its outer peripheral surface. The upper die 20U has a concave portion 24 that can be fitted with the convex portion 21 of the lower die 20L via the seal ring 23, and further has an annular concave portion 25 arranged along the outer periphery of the concave portion 24 and sharing the outer peripheral surface with the concave portion 24. The annular convex portion 22 of the lower die 20L and the annular concave portion 25 of the upper die 20U can be fitted to each other.

[0012] When the slide 13 is lowered to fit the convex portion 21 of the lower die 20L and the concave portion 24 of the upper die 20U, a closed space 26 is formed between the upper die 20U and the lower die 20L as shown in FIG. 3. Since the closed space 26 is made airtight by the action of the seal ring 23, vacuum degassing can be performed by operating the vacuum pump 30 connected to the closed space 26 through a hole provided in the upper die 20U.

[0013] When the slide 13 is lowered further to engage the annular projection 22 and the annular recess 25, a molded cavity 27 is formed, as shown in Figure 4. The molded cavity 27 has a shear edge 31 formed between the inner wall surface of the annular projection 22 and the inner wall surface of the annular recess 25. In the lower mold 20L and the upper mold 20U, the surfaces exposed inside the molding cavity 27 are the molding surface 28L and the molding surface 28U, respectively.

[0014] Each of the upper mold 20U and the lower mold 20L is equipped with a heater (not shown), which may be, for example, a steam heater, an oil heater, or an electric heater, and is capable of maintaining the temperature of the mold 20 at any temperature within a temperature range (e.g., 120 to 180°C) suitable for curing the thermosetting prepreg.

[0015] 2. Method for manufacturing FRP molded articles A method for manufacturing an FRP molded article according to a preferred embodiment includes the following steps. The first step is to prepare a mold consisting of an upper mold and a lower mold, with a molding surface provided. The second step is to maintain the mold at the molding temperature. A third step: forming a layer of thermosetting powder coating on at least a portion of the molding surface of the mold, which is maintained at the molding temperature. The fourth step is to place a thermosetting prepreg in a closed space formed by closing the mold. A fifth step involves degassing the gas between the prepreg and the layer of the thermosetting powder coating while vacuum degassing the closed space. The sixth step involves bringing the upper mold and the lower mold closer together and pressurizing the prepreg placed in the enclosed space together with the layer of thermosetting powder coating.

[0016] The method according to the above preferred embodiment will be explained as follows, using the press forming apparatus shown in Figures 1-4 as an example.

[0017] (1) First step An example of a mold prepared in the first step is shown in Figure 4. The mold 20 consists of an upper mold 20U and a lower mold 20L. The molding surfaces 28U and 28L may be mirror-finished or non-mirror-finished, respectively.

[0018] (2) Second step In the second step, the mold 20 is maintained at the molding temperature. The second step is usually started before the third step and onward, and continues until the curing of the thermosetting prepreg is complete, at least until the sixth step. In other words, before the third step and onward, the mold 20 is heated to the molding temperature, and the mold 20 is maintained at the molding temperature until at least the sixth step is completed.

[0019] The molding temperature is set to a temperature that allows the thermosetting prepreg to cure within the desired time. The higher the molding temperature, the shorter the time required to sufficiently cure the thermosetting prepreg, thus shortening the molding cycle in continuous molding. However, in order to prevent deformation of the cured product (FRP molded body) during demolding, it is preferable that the molding temperature be lower than the glass transition temperature of the matrix resin after the prepreg has cured. The molding temperature should typically be set within the range of 120 to 180°C, taking the above factors into consideration.

[0020] (3) Third step In the third step, as shown in Figure 5, a layer 2 of thermosetting powder coating is formed on the molding surface 28U of the mold 20. However, the layer 2 of thermosetting powder coating may be formed on only one side of the molding surface 28U and the molding surface 28L, or on both sides. The layer 2 of thermosetting powder coating may be formed on at least a portion of the molding surface as needed.

[0021] Powder coatings contain inorganic fillers in thermosetting resins such as epoxy resin, epoxy polyester resin, polyester resin, acrylic resin, and polyurethane resin. Because inorganic fillers are incorporated into the powder coating, thermal shrinkage of the powder coating layer 2 during molding is reduced, thereby reducing surface irregularities on the molded product.

[0022] Examples of inorganic fillers include, but are not limited to, titanium dioxide, iron oxide, aluminum hydroxide, alumina, mica, quartz, feldspar, and zeolite. One type of inorganic filler may be used alone, or two or more types may be used in combination.

[0023] The inorganic filler content is preferably 20% by mass or more of the total amount of powder coating, more preferably 30-60% by mass, and even more preferably 40-50% by mass. If the inorganic filler content is above the lower limit of the above numerical range, it is easier to further reduce the thermal shrinkage of layer 2 of the powder coating during molding. If the inorganic filler content is below the upper limit of the above numerical range, the thermosetting properties of the powder coating are sufficient.

[0024] A preferred thermosetting powder coating is a powder coating for PIMC (Powder In Mold Coating). The powder coating for PIMC may further contain thickeners, reactive diluents, low-shrinkage agents, defoaming agents, colorants, pigments, etc. For details on the components of the powder coating for PIMC, see, for example, Japanese Patent Publication No. 59-91157 and Japanese Patent Publication No. 1-158080.

[0025] The density of powder coatings is 1.37 to 1.61 g / cm³. 3 The particle size of powder coatings is often within the range of 20 to 150 μm in the longitudinal direction. Commercially available powder coatings for PIMC can be obtained, for example, from Tiger Coatings GmbH & Co. KG.

[0026] As shown in the example in Figure 5, when forming a layer 2 of powder coating on the molding surface 28U of the upper mold, electrostatic powder coating is preferably used. This method is also preferable from the viewpoint of uniform coating. In other examples, when forming a layer of thermosetting powder coating on the molding surface of the lower mold, electrostatic powder coating can also be preferably used. In some cases, layers of powder coating may be formed on both the molding surfaces of the upper and lower molds.

[0027] Layer 2 of the powder coating is applied to a thickness of more than 200 μm. A thickness of more than 200 μm in layer 2 of the powder coating makes it easier to conceal irregularities caused by the reinforcing fibers of the prepreg. Considering its contribution to the weight reduction of FRP products, the upper limit of the thickness of layer 2 of the powder coating may be 700 μm, 1,000 μm, 2,000 μm, etc.

[0028] To apply a powder coating containing thermosetting resin and inorganic fillers to a desired thickness using an electrostatic spray coating system, parameters such as voltage, current, and discharge flow rate should be appropriately set. It is then useful to maintain a constant distance between the spray nozzle and the surface being coated, using a manual or robotic arm, while moving the spray nozzle at a constant speed. After coating, the film thickness may be measured and checked using an ultrasonic film thickness gauge.

[0029] Because a grounded mold carries a negative charge, powder coatings that have been given a positive charge by electrostatic spraying can adhere strongly to the mold surface due to electrostatic force. Therefore, even if there are vertical surfaces or undercuts on the mold surface, the powder coating will not fall off under its own weight, and a consistent thickness can be maintained.

[0030] The method for forming a layer of thermosetting powder coating on a molded surface is not limited to electrostatic powder coating. In other examples, when forming this layer on the molded surface of a lower mold, a method of manually sprinkling the powder coating onto the molded surface using a sieve may also be employed.

[0031] After applying the powder coating to the molded surface, a certain period of time may be applied to melt and thicken the powder coating. This thickening can suppress excessive flow. The preferred time is 30 to 1,200 seconds, and more preferably 120 to 720 seconds. If the thickening time is above the lower limit of the above numerical range, the powder coating layer 2 will be sufficiently thickened. If the thickening time is below the upper limit of the above numerical range, cracking due to thermal degradation can be prevented.

[0032] After a certain period of time, the heat from the mold thickens the powder coating, causing it to adhere to the mold. Therefore, even when press pressure is applied when layering with the prepreg, the thickness of the in-mold coating remains relatively unchanged compared to before pressing.

[0033] (4) Fourth step In the fourth step, as shown in Figures 6 and 7, the thermosetting prepreg 3 is placed in the closed space 26 formed by closing the mold 20. As shown in Figure 6, the thermosetting prepreg 3 can be placed on the molding surface opposite to the layer 2 of thermosetting powder coating. More specifically, the thermosetting prepreg 3 is placed on the molding surface 28L of the lower mold 20L with the mold 20 open, and then the mold 20 is closed to form a closed space 26. Alternatively, as shown in Figure 7, the prepreg 3 may be placed on top of the layer 2 of thermosetting powder coating. The thermosetting prepreg 3 may be preformed into the net shape or approximate net shape.

[0034] Thermosetting prepreg 3 is an intermediate material used in the manufacture of FRP molded products, and is made by impregnating a fiber-reinforced material consisting of reinforcing fibers with a thermosetting resin matrix. The thermosetting prepreg 3 may be a continuous fiber prepreg. A continuous fiber prepreg is a sheet made of bundles of reinforcing fibers in which continuous fibers are aligned in a single direction, impregnated with a thermosetting resin matrix. Examples of thermosetting prepregs 3 include UD (unidirectional) prepregs, woven prepregs, tow prepregs, and sheet molding compounds (SMCs).

[0035] The fiber reinforcement material for UD prepregs is a UD sheet. Examples of fabric structures used as fiber reinforcement materials for woven prepregs include plain weave, twill weave, and satin weave. The fiber reinforcement material for woven prepregs may also be a non-crimped fabric. SMC's fiber reinforcement material is a random mat formed by scattering chopped fiber bundles.

[0036] Examples of reinforcing fibers include carbon fibers, glass fibers, aramid fibers, high-strength polyester fibers, boron fibers, alumina fibers, silicon nitride fibers, and nylon fibers. Carbon fibers are preferred because they improve specific strength and specific elasticity. The reinforcing fiber may be used alone or in combination of two or more types.

[0037] The thermosetting resin matrix contained in thermosetting prepreg 3 is a composition comprising a thermosetting resin and a curing agent, and various additives may be added in addition to the curing agent as needed. Examples of such additives include, but are not limited to, thickeners, reactive diluents, low shrinkage agents, flame retardants, defoamers, defoaming agents, mold release agents, particulate fillers, colorants, and silane coupling agents.

[0038] Examples of thermosetting resins include, but are not limited to, epoxy resins, vinyl ester resins, (meth)acrylate resins, unsaturated polyester resins, urea resins, polyurethane resins, and phenolic resins. It is also possible to use a mixture of two or more thermosetting resins. Vinyl ester resins are sometimes called epoxy (meth)acrylate resins.

[0039] The thermosetting prepreg 3 may be a prepreg assembly containing multiple prepregs. In this case, the prepreg assembly may contain only prepregs of the same type, or it may contain two or more types of carbon prepregs.

[0040] The thermosetting prepreg 3 may include a laminate of the same or different types of prepregs. When laminating multiple UD prepregs, cross-ply or angle-ply may be used as required. When the thermosetting prepreg 3 includes a laminate having multiple prepregs, it is desirable to degas it by vacuum bagging before placing it in the closed space 26.

[0041] The prepreg 3 or prepreg laminate may be kept warm for a certain period of time in a temperature-controlled space such as an oven. In particular, if the prepreg 3 or prepreg laminate is at a low temperature before molding, problems such as reduced resin flow may occur. Because the behavior during molding becomes unstable in this way, it is useful to control the temperature to 20-60°C. In addition, if prepreg 3 or the prepreg laminate contains volatile components, it is possible to remove these volatile components beforehand by applying a thermal history.

[0042] The charge ratio is the ratio of the area of ​​the prepreg 3 to the area of ​​the molded surface. Generally, the higher the charge ratio, the less the prepreg flows during molding, which helps to suppress defects such as cracking of the powder coating layer due to flow. On the other hand, the higher the charge ratio, the more likely gas in the prepreg is to remain as voids in the FRP molded body, which can worsen the appearance. For this reason, the charge ratio in typical press molding is 30-99%. In this embodiment, by degassing the gas between the prepreg 3 and the thermosetting powder coating layer 2 while vacuum degassing the closed space 26, void formation can be suppressed even if the prepreg charge rate is typically 50% or more.

[0043] Based on the inventors' experimental results, a suitable range for the charge rate of prepreg 3 on the molded surface has been found depending on the type of prepreg. When the thermosetting prepreg 3 is SMC, the charge rate is preferably 30% or more, more preferably 40% or more, and even more preferably 49% or more. The upper limit of the charge rate when the thermosetting prepreg 3 is SMC is not particularly limited, but may be, for example, 80%, 90%, 99%, etc.

[0044] When the thermosetting prepreg 3 is a continuous fiber prepreg, the charge rate is preferably 90% or higher, more preferably 95% or higher, and even more preferably 96% or higher. The upper limit of the charge rate when the thermosetting prepreg 3 is a continuous fiber prepreg is not particularly limited, but may be, for example, 97%, 98%, 99%, etc.

[0045] (5) Fifth step In the fifth step, the enclosed space 26 is degassed under vacuum, and the gas between the prepreg 3 and the thermosetting powder coating layer 2 is removed. When prepreg 3 overlaps with layer 2 of thermosetting powder coating, gas may get trapped between prepreg 3 and layer 2 of thermosetting powder coating. Gas may also get trapped within layer 2 of thermosetting powder coating. If the prepreg and thermosetting powder coating are pressurized and cured while gas is present, the compressed gas remains inside the FRP molded body. Afterward, when the mold is opened and the pressurized state is removed, the compressed gas remaining inside the FRP molded body expands, causing holes or bulges in the FRP molded body, degrading its appearance.

[0046] The larger the area of ​​the prepreg, the easier it is for gas to enter between the prepreg and the layer of thermosetting powder coating. In the manufacturing method of the FRP molded article of this embodiment, the area of ​​the prepreg 3 is 1,500 cm². 2 It is even more useful when the above conditions are met. The area of ​​the prepreg 3 is preferably 1,600 cm². 2 More preferably 1,800 cm 2 That's all.

[0047] As shown in Figure 3, the vacuum degassing method involves starting the vacuum degassing process when a closed space 26 is formed between the upper mold 20U and the lower mold 20L by the sealing ring 23. To prevent powder coating from entering the vacuum pump 30, a filter or the like may be installed between the mold 20 and the vacuum pump 30.

[0048] As shown in Figure 4, when the upper mold 20U and the lower mold 20L approach each other and the annular protrusion 22 of the lower mold 20L and the annular recess 25 of the upper mold 20U engage, a molding cavity 27 having a shear edge 31 is formed. Due to the large pressure loss at the shear edge 31, the degassing efficiency of the molding cavity 27 is low. However, while the degassing efficiency is reduced, the shear edge can suppress excessive leakage of the resin of prepreg 3 or the prepreg laminate, which has low viscosity during molding, or heated powder coating, to the outside of the molded surface, which is effective in stabilizing the thickness of the FRP molded product and improving the surface quality.

[0049] Therefore, preferably, the downward speed of the upper mold 20U may be reduced so that the closed space 26 is sufficiently vacuum-degassed before the shear edge 31 is formed, or, instead or in addition to that, the downward movement of the upper mold 20U can be temporarily stopped before the shear edge 31 is formed to vacuum-degas the closed space 26. These considerations are unnecessary when using a type of mold that does not form a shear edge.

[0050] The vacuum pressure in the closed space 26 when vacuum degassing is complete is preferably -0.1 MPa or less. The mold closing speed of the upper mold 20U is preferably 3 mm / second or less, more preferably 2 mm / second or less, and even more preferably 1 mm / second or less, in order to allow for a longer vacuum degassing time.

[0051] The degree of vacuum achieved by the vacuum degassing device varies depending on the specified vacuum level of the device. The vacuum time from the moment the space becomes closed until pressurization of the prepreg and thermosetting powder coating is started is preferably 7 seconds or more, more preferably 15 seconds or more, and even more preferably 20 seconds or more. The vacuum degassing time is preferably the time required from the time the device reaches the specified vacuum level until the shear edge is formed.

[0052] (6) Sixth step In the sixth step, as shown in Figure 8, the upper mold 20U and the lower mold 20L are brought closer together while the enclosed space in which the thermosetting prepreg is placed is degassed under vacuum, and the prepreg 3 is pressurized together with the powder coating layer 3.

[0053] As shown in Figure 6, when the upper mold 20U and the lower mold 20L are separated, the pressure is 0 MPa. As shown in Figure 8, when the upper mold 20U begins to press the prepreg 3 through the powder coating layer 2, the pressure suddenly rises and instantly increases to the molding pressure. It is preferable to vacuum degass the material while pressurizing it. This is because it allows for the removal of gases generated by heating and compression, as well as gases extruded from the prepreg or powder coating layers.

[0054] The thermosetting prepreg 3 is cured by being pressurized within a mold 20 held at the molding temperature. The pressurizing time is set to a sufficient amount of time for curing to be completed. The temperature of the mold is maintained at the molding temperature while pressurizing is continued.

[0055] The molding pressure in the sixth step is preferably in the range of 3 to 11 MPa. The molding pressure is defined as the value obtained by dividing the pressing force of the press by the vertical projected area of ​​the molding cavity.

[0056] After the completion of the sixth step, the mold 20 is opened as shown in Figure 9, and the FRP molded body 4 with the in-mold coating 2C is removed. There is no need to change the temperature of the mold 20 when removing the FRP molded body 4. Normally, the temperature of the mold 20 is maintained at the molding temperature until the next molding cycle is started.

[0057] By gradually returning the removed FRP molded body 4 to room temperature, surface cracking and other issues can be suppressed. For example, by quickly placing the removed FRP molded body 4 into an oven preheated to 40-70°C, a step-by-step process can be considered to return it from the molding temperature to room temperature.

[0058] The FRP molded body 4 is an intermediate product used in the manufacture of multi-layer coated FRP products. As shown in an enlarged view in Figure 10, the FRP molded body 4 has a fiber-reinforced resin substrate 3C formed from a cured thermosetting prepreg 3, and an in-mold coating 2C fixed to the surface of the fiber-reinforced resin substrate 3C. The fiber-reinforced resin substrate 3C contains reinforcing fibers and matrix resin. The in-mold coating 2C contains inorganic fillers and is formed by the curing of a layer 2 of thermosetting powder coating through gelation.

[0059] The inorganic filler content is preferably 20% by mass or more of the total amount of the in-mold coating 2C, more preferably 30-60% by mass, and even more preferably 40-50% by mass. If the inorganic filler content is above the lower limit of the above numerical range, it is easier to further reduce the unevenness of the in-mold coating 2C. If the inorganic filler content is below the upper limit of the above numerical range, the adhesion between the in-mold coating 2C and the fiber-reinforced resin substrate 3C is sufficient.

[0060] The thickness of the in-mold coating 2C is greater than 200 μm. A thickness of more than 200 μm of the in-mold coating 2C can conceal the irregularities caused by the reinforcing fibers of the prepreg 3. The thickness of the in-mold coating 2C is preferably 201 μm or more, more preferably 210 μm or more, and even more preferably 250 μm or more. Considering the contribution to weight reduction of the FRP product, the upper limit of the thickness of the in-mold coating 2C of the FRP molded body 4 may be 700 μm, 1,000 μm, 2,000 μm, etc.

[0061] Based on the inventors' experimental results, a suitable range has been found for the thickness and weight of the in-mold coating 2C, depending on the type of prepreg. When the prepreg 3 is a continuous fiber prepreg, the thickness of the in-mold coating 2C is preferably 10-40% of the thickness of the fiber-reinforced resin substrate 3C, more preferably 11-20%, and even more preferably 11-15%. If the thickness of the in-mold coating 2C is above the lower limit of the above numerical range, it is easier to conceal the irregularities caused by the reinforcing fibers of the continuous fiber prepreg. If the thickness of the in-mold coating 2C is below the upper limit of the above numerical range, it can be expected to contribute to weight reduction of the FRP product.

[0062] When the prepreg 3 is a continuous fiber prepreg, the weight of the in-mold coating 2C is preferably 40% or less of the weight of the fiber-reinforced resin substrate 3C, more preferably 30% or less, and even more preferably 20% or less. If the weight of the in-mold coating 2C is below the above upper limit, it can be expected to contribute to the weight reduction of the FRP product. The lower limit of the weight of the in-mold coating 2C is not particularly limited, but may be, for example, 5%, 9%, 10%, etc., of the weight of the fiber-reinforced resin substrate 3C.

[0063] When the prepreg 3 is SMC, the thickness of the in-mold coating 2C is preferably 20-50% of the thickness of the fiber-reinforced resin substrate 3C, more preferably 21-40%, and even more preferably 21-30%. If the thickness of the in-mold coating 2C is above the lower limit of the above numerical range, it is easier to conceal the irregularities caused by the reinforcing fibers of the SMC. If the thickness of the in-mold coating 2C is below the upper limit of the above numerical range, it can be expected to contribute to weight reduction of the FRP product.

[0064] When the prepreg 3 is SMC, the weight of the in-mold coating 2C is preferably 50% or less of the weight of the fiber-reinforced resin substrate 3C, more preferably 40% or less, and even more preferably 30% or less. If the weight of the in-mold coating 2C is below the above upper limit, it can be expected to contribute to the weight reduction of the FRP product. The lower limit of the weight of the in-mold coating 2C is not particularly limited, but may be, for example, 7%, 11%, 12%, etc., of the weight of the fiber-reinforced resin substrate 3C.

[0065] The area of ​​the in-mold coating 2C is not particularly limited, but 900 cm² 21,500 cm or more 2 1,800 cm or more 2 or the like. The upper limit of the area of the in-mold coating film 2C is not particularly limited, and may be 300 cm 2 , 500 cm 2 , 600 cm 2 or the like.

[0066] The thermosetting powder coating material is preferably a primer coating material. Therefore, the FRP molded article according to the embodiment is preferably an FRP molded article having a primer coating film.

[0067] 3. Top coating The FRP molded article 4 having the in-mold coating film 2C is an intermediate product in the production of a multi-layer coated FRP product, and is further subjected to top coating to become a finished FRP product. Such an FRP product includes the FRP molded article 4 and a top coating film provided on the surface of the in-mold coating film 2C.

[0068] When the FRP molded article 4 having the in-mold coating film 2C is produced by the production method according to the embodiment, usually, before proceeding to top coating, the in-mold coating film 2C may be polished to flatten the surface. In top coating, at least one coating film including a colored coating film is formed on the in-mold coating film 2C.

[0069] The coating film formed by top coating is preferably a bake coating film, and is formed by drying the applied coating material at a temperature of 80°C or higher, typically 100°C or higher. The coating film formed by top coating may include a colored coating film and a clear coating film formed on the colored coating film. The clear coating film may be formed as a top coat.

[0070] The coating film formed by top coating may include a colored coating film and a base coating film formed thereunder. When a plurality of coating films are formed in layers by top coating, preferably, a plurality of coating materials are applied in layers wet-on-wet and then baked simultaneously in one step.

[0071] Examples of FRP products include, but are not limited to, automobile bodies, automobile roofs, and automobile side panels. FRP products may also have curved shapes.

[0072] 4. Experimental Results The results of the experiments conducted by the inventors are described below.

[0073] The materials used in each experiment are as follows: • Release agent: A commercially available water-based external release agent containing fluorine compounds and wax for CFRP molding (NEOS Co., Ltd.'s Free Release 65) • Powder coating: Tiger Drylac 261 / 10013 PIMC Epoxy Primer (a powder coating containing thermosetting resin and inorganic fillers) from Tiger Coatings GmbH & Co. KG. • SMC1: STR120 (thermosetting, 2.0mm thickness) from Mitsubishi Chemical Corporation. Twill weave prepreg 1: TR3524 362GMP (thermosetting, 0.22mm thickness) product of Mitsubishi Chemical Corporation. Twill weave prepreg 2: TRK501 362GMP (thermosetting, 0.44mm thickness) from Mitsubishi Chemical Corporation.

[0074] In each experiment, the mold 40 shown in Figure 11 was mounted on a hydraulic press to prepare the press molding apparatus. The mold 40 has a lower mold 40L and an upper mold 40U that can be mated together via a seal ring 43. The lower mold 40L is provided with a seal ring 43 that encircles its outer surface. The lower mold 40L is provided with an annular projection 42 along its outer circumference, and the upper mold 40U is provided with an annular recess 45 that can be mated together with the annular projection 42.

[0075] When the lower mold 40L and the upper mold 40U are fitted together, a closed space is formed. A hole is provided in the annular recess 45 to allow vacuum degassing of this closed space, and it is connected to a vacuum pump 50. When the annular protrusion 42 of the lower mold 40L and the annular recess 45 of the upper mold 40U are fitted together, a plate-shaped molding cavity with a shear edge is formed. The shear edge is formed between the inner wall surface of the annular protrusion 42 and the inner wall surface of the annular recess 45, and the gap is 0.05 to 0.1 mm. The surface area of ​​the molding surface 48U and molding surface 48L of the molding cavity is 900 cm². 2 The height of the molding cavity is variable between 1 mm and 3 mm. The material of the molding die 40 is carbon steel S45C, and the molding surfaces 48U and 48L are mirror-finished with hard chrome plating.

[0076] 4.1 Experiment 1-1 Follow the procedure below to project an area of ​​900 cm². 2 A square FRP substrate with sides of 30 cm was obtained. The mold 40 shown in Figure 11 was heated, and it was confirmed that its temperature stabilized within the range of 140 ± 6°C. Next, a release agent was applied to the molding surface 48L of the lower mold 40L and the molding surface 48U of the upper mold 40U. Then, a twill weave prepreg laminate was placed on the molding surface 48L of the lower mold 40L. After that, the mold 40 was closed and press molding was performed.

[0077] The twill weave prepreg laminate was fabricated using the following procedure. First, twill weave prepreg 1 and twill weave prepreg 2 were cut so that they were 1 mm away from the shear edge of the molding surface 48L all around. Then, the three cut pieces of twill weave prepreg 1 and the three cut pieces of twill weave prepreg 2 were laminated together. During press molding of the twill weave prepreg laminate, twill weave prepreg 1 came into contact with the powder coating layer. The thickness of the twill weave prepreg laminate is approximately 2 mm, and the surface area is 888 cm². 2 (The charge level is approximately 99%), and the mass is approximately 266g.

[0078] The molding pressure during press forming was 4 MPa, and the pressurizing time was 900 seconds. Vacuum degassing of the enclosed space formed by closing the mold during molding was initiated before the shear edge was formed. With a mold closing speed of 1.0 mm / second, the vacuum pressure in the enclosed space reached -0.1 MPa before the shear edge was formed. The vacuum pump was kept running until the molding pressure reached 4 MPa. The vacuum time from the formation of the enclosed space to the start of vacuum degassing and pressurization was 25 seconds or more.

[0079] The thickness of the FRP substrate obtained using the above procedure was measured at five arbitrary points using a micrometer. The average value of the five points was calculated to be 2,042 μm.

[0080] A test piece measuring 200mm x 200mm was cut from the center of the FRP substrate obtained using the above procedure. A topcoat coating was applied to this test piece using the following procedure. (i) The entire topcoat surface of the test specimen was sanded with #600 sandpaper. Then, the sanding residue was removed by wiping with a cloth soaked in isopropyl alcohol. (ii) Following (i), polyurethane primer paint, polyurethane black paint, and polyurethane clear paint were applied to the topcoat surface of the test specimen in that order using a spray gun. The specimens were then dried in a 100°C oven for 1 hour. At this time, the thickness of the topcoat was approximately 109 μm.

[0081] The LongWave (LW) value of the surface of the topcoat film formed by the above procedure was measured using a BYK MicroWaveScan4824. The method for measuring the LW value of the surface of the topcoat film is as follows: Three locations were randomly selected from the surface of the topcoat film. One location was measured parallel to the warp direction of the prepreg, one location was measured parallel to the weft direction of the prepreg, and one location was measured at a 45-degree angle to the warp direction of the prepreg. The measurement length for all locations was 10 cm. The average value of the three measured points was calculated to evaluate the surface irregularity. The output LW value has no units; a larger LW value indicates greater surface irregularity and a poorer surface appearance. A smaller LW value indicates less surface irregularity and a better surface appearance.

[0082] 4.2 Experiment 1-2 The following procedure for in-mold painting will result in a projected area of ​​900 cm². 2 A square FRP molded body with sides of 30 cm was obtained.

[0083] The mold 40 shown in Figure 11 was heated, and it was confirmed that its temperature stabilized within the range of 140 ± 6°C. Next, the outer wall surface of the annular protrusion 45 of the upper mold 40U, specifically the part that forms the shear edge during molding, was masked with heat-resistant tape. In addition, an enclosure was provided around the mold 40 to prevent powder scattering. Subsequently, a release agent was applied to the molding surface 48L of the lower mold 40L and the molding surface 48U of the upper mold 40U. Then, 25g of powder coating was uniformly applied to the mirror-finish molding surface 48U of the upper mold 40U from the spray nozzle of an electrostatic powder coating apparatus. Immediately after the application of the powder coating was completed, the enclosure to prevent powder scattering was removed, and all of the heat-resistant tape masking applied to the annular protrusion 45 of the upper mold 40U was peeled off. A preheating time of 120 seconds was allowed for the applied powder coating. Next, a twill weave prepreg laminate was placed on the molding surface 48L of the lower mold 40L. Then, the mold 40 was closed and press molding was performed.

[0084] The twill weave prepreg laminate was created by cutting twill weave prepreg 1 and twill weave prepreg 2 so that they were 1 mm away from the shear edge of the molding surface 48L all around. Then, the three cut pieces of twill weave prepreg 1 and the three cut pieces of twill weave prepreg 2 were laminated together. During press molding of the twill weave prepreg laminate, twill weave prepreg 1 comes into contact with the powder coating layer. The thickness of the twill weave prepreg laminate is approximately 2 mm, and the surface area is 888 cm². 2 (The charge level is approximately 99%), and the mass is approximately 266g.

[0085] The molding pressure during press forming was 4 MPa, and the pressurizing time was 900 seconds. Vacuum degassing of the enclosed space formed by closing the mold was initiated before the shear edge was formed. With a mold closing speed of 1.0 mm / second, the vacuum pressure in the enclosed space reached -0.1 MPa before the shear edge was formed. The vacuum pump was kept running until the molding pressure reached 4 MPa. The vacuum time from the formation of the enclosed space to the start of vacuum degassing and pressurization was 25 seconds or more.

[0086] The thickness of the FRP molded body obtained using the above procedure was measured at five arbitrary points using a micrometer. The average value of the five points was calculated to be the thickness of the FRP molded body, which was 2,245 μm. Since the thickness of the FRP substrate obtained in Experiment 1-1 was 2,042 μm, the thickness of the in-mold coating was calculated to be 203 μm from the difference between the thickness of the FRP substrate and the FRP molded body.

[0087] A test piece measuring 200mm x 200mm was cut from the center of the molded FRP body. The in-mold coated side of this test piece was then coated with a topcoat using the following procedure. (i) The entire in-mold coating surface of the test specimen was polished by rubbing it with #600 sandpaper. Then, the polishing residue was removed by wiping it with a cloth soaked in isopropyl alcohol. (ii) Following (i), polyurethane primer paint, polyurethane black paint, and polyurethane clear paint were applied in that order to the in-mold coating surface of the test specimen using a spray gun. The specimens were then dried in a 100°C oven for 1 hour. At this time, the thickness of the topcoat was approximately 109 μm. The LW value of the surface of the topcoat formed by the above procedure was measured using the same method as in Experiment 1-1.

[0088] 4.3 Experiments 1-3 An FRP molded body was obtained under the same conditions as in Experiment 1-2, except that 50g of powder coating was applied to the mirror-finish molding surface 48U of the upper mold 40U using an electrostatic powder coating apparatus. The thickness of the in-mold coating on the FRP molded body obtained in Experiment 1-3 was 411 μm. Subsequently, a topcoat was applied to the in-mold coating surface of the FRP molded body under the same conditions as in Experiment 1-2. Then, the LW value of the surface of the topcoat coating was measured using the same method as in Experiment 1-1.

[0089] 4.4 Experiment 1-4 An FRP molded body was obtained under the same conditions as in Experiment 1-2, except that 75g of powder coating was applied to the mirror-finish molding surface 48U of the upper mold 40U using an electrostatic powder coating apparatus. The thickness of the in-mold coating on the FRP molded body obtained in Experiment 1-4 was 678 μm. Subsequently, a topcoat was applied to the in-mold coating surface of the FRP molded body under the same conditions as in Experiment 1-2. Then, the LW value of the surface of the topcoat coating was measured using the same method as in Experiment 1-1.

[0090] 4.5 Experiment 2-1 The following procedure will create a projection area of ​​441 cm². 2 A square FRP base material with sides of 21 cm was obtained. The mold 40 shown in Figure 11 was heated, and it was confirmed that its temperature stabilized within the range of 140 ± 6°C. Next, a release agent was applied to the molding surface 48L of the lower mold 40L and the molding surface 48U of the upper mold 40U. Then, the SMC laminate was placed on the molding surface 48L of the lower mold 40L. After that, the mold 40 was closed and press molding was performed.

[0091] The SMC laminate is constructed by cutting SMC1 so that it is 45mm away from the shear edge of the molding surface 48L all around, and then laminating two of the cut SMC1 pieces. The thickness of the SMC laminate is 4mm, and the surface area of ​​the SMC laminate is 440cm². 2 (The charge rate is approximately 49%), and the mass of the SMC laminate is 258g.

[0092] The molding pressure during press forming was 11 MPa, and the pressurizing time was 900 seconds. Vacuum degassing of the enclosed space formed by closing the mold was initiated before the shear edge was formed. With a mold closing speed of 1.0 mm / second, the vacuum pressure in the enclosed space reached -0.1 MPa before the shear edge was formed. The vacuum pump was kept running until the molding pressure reached 11 MPa. The vacuum time from the formation of the enclosed space to the start of vacuum degassing and pressurization was 25 seconds or more.

[0093] The thickness of the FRP substrate obtained using the above procedure was measured at five arbitrary points using a micrometer. The average value of the five points was calculated to be 2,141 μm.

[0094] 4.6 Experiment 2-2 An FRP molded body was obtained by in-mold painting according to the procedure described below. The mold 40 shown in Figure 11 was heated, and it was confirmed that its temperature stabilized within the range of 140 ± 6°C. Next, the outer wall surface of the annular protrusion 45 of the upper mold 40U, specifically the part that forms the shear edge during molding, was masked with heat-resistant tape. In addition, an enclosure was provided around the mold 40 to prevent powder scattering. Subsequently, a release agent was applied to the molding surface 48L of the lower mold 40L and the molding surface 48U of the upper mold 40U. Then, 25g of powder coating was uniformly applied to the mirror-finish molding surface 48U of the upper mold 40U using an electrostatic powder coating apparatus. Immediately after the application of the powder coating was completed, the enclosure to prevent powder scattering was removed, and all of the heat-resistant tape masking applied to the annular protrusion 45 of the upper mold 40U was peeled off. A preheating time of 120 seconds was allowed for the applied powder coating. Next, the SMC laminate was placed on the molding surface 48L of the lower mold 40L. Then, the mold 40 was closed and press molding was performed.

[0095] The SMC laminate is constructed by cutting SMC1 so that it is 45 mm away from the shear edge of the molding surface 48L all around, and then laminating two of the cut SMC1 pieces. The thickness of the SMC laminate is 4 mm, and the surface area of ​​the SMC laminate is 441 cm². 2 (The charge rate is approximately 49%), and the mass of the SMC laminate is 258g.

[0096] The molding pressure during press forming was 11 MPa, and the pressurizing time was 900 seconds. Vacuum degassing of the enclosed space formed by closing the mold was initiated before the shear edge was formed. With a mold closing speed of 1.0 mm / second, the vacuum pressure in the enclosed space reached -0.1 MPa before the shear edge was formed. The vacuum pump was kept running until the molding pressure reached 11 MPa. The vacuum time from the formation of the enclosed space to the start of vacuum degassing and pressurization was 25 seconds or more.

[0097] The thickness of the FRP molded body obtained using the above procedure was measured at five arbitrary points using a micrometer. The average value of the five points was calculated to be the thickness of the FRP molded body, which was 2,355 μm. Since the thickness of the FRP substrate obtained in Experiment 2-1 was 2,141 μm, the thickness of the in-mold coating was calculated to be 214 μm from the difference between the thickness of the FRP substrate and the FRP molded body.

[0098] Next, a topcoat was applied to the in-mold coating surface of the FRP molded body under the same conditions as in Experiment 1-2. Subsequently, the LW value of the surface of the topcoat was measured using the same method as in Experiment 1-1.

[0099] 4.7 Experiment 2-3 An FRP molded body was obtained under the same conditions as in Experiment 2-2, except that 50g of powder coating was applied to the mirror-finish molding surface 48U of the upper mold 40U using an electrostatic powder coating apparatus. The thickness of the in-mold coating on the FRP molded body obtained in Experiment 2-3 was 400 μm. Subsequently, a topcoat was applied to the in-mold coating surface of the FRP molded body under the same conditions as in Experiment 1-2. Then, the LW value of the surface of the topcoat coating was measured using the same method as in Experiment 1-1.

[0100] 4.8 Experiment 2-4 An FRP molded body was obtained under the same conditions as in Experiment 2-2, except that 75g of powder coating was applied to the mirror-finish molding surface 48U of the upper mold 40U using an electrostatic powder coating apparatus. The thickness of the in-mold coating on the FRP molded body obtained in Experiment 2-4 was 696 μm. Subsequently, a topcoat was applied to the in-mold coating surface of the FRP molded body under the same conditions as in Experiment 1-2. Then, the LW value of the surface of the topcoat coating was measured using the same method as in Experiment 1-1.

[0101] 4.9 Experimental Results The results of each experiment described above, along with the experimental conditions, are shown in Table 1.

[0102] [Table 1]

[0103] The surface roughness of topcoat painted products can be evaluated using the LongWave measurement value (LW value). A lower LW value indicates less surface roughness. While the LW value of the FRP substrate obtained in Experiment 1-1 was 6.5, for example, the LW value of the FRP molded body obtained in Experiment 1-2 was 1.6, a reduction to approximately 1 / 4 of the original value. The LW values ​​of the FRP molded bodies obtained in Experiments 1-2 and 1-3 were also lower than those of Experiment 1-1. From these results, it was confirmed that the roughness of the topcoat film was reduced.

[0104] The LW values ​​of the FRP molded bodies obtained in Experiments 2-2, 2-3, and 2-4 were also lower than those in Experiment 2-1. From these results, it was confirmed that the unevenness of the topcoat film was reduced.

[0105] Table 1's "Weight Increase Rate" is calculated as the percentage of the weight of the powder coating relative to the weight of the twill weave prepreg or SMC. For example, in Experiment 1-2, the amount of powder coating added was 25g compared to the total material input of 266g, resulting in a weight increase of approximately 9.4% (25 / 266 × 100 ≈ 9.4). From the perspective of reducing the weight of FRP products, a lower weight increase rate is preferable.

[0106] 5. Summary of Embodiments Preferred embodiments of the present invention include, but are not limited to, the following. [Embodiment 1] An FRP molded article comprising a fiber-reinforced resin substrate containing reinforcing fibers and a matrix resin, and an in-mold coating film fixed to the surface of the fiber-reinforced resin substrate, wherein the in-mold coating film contains inorganic fillers and the thickness of the in-mold coating film is greater than 200 μm. [Embodiment 2] The FRP molded article according to Embodiment 1, wherein the matrix resin contains a cured product of a thermosetting resin, and the thermosetting resin may be an epoxy resin. [Embodiment 3] The FRP molded article according to Embodiment 1 or 2, wherein the in-mold coating contains a cured product of a thermosetting resin, and the thermosetting resin may be an epoxy resin. [Embodiment 4] The FRP molded article according to any one of Embodiments 1 to 3, wherein the reinforcing fiber is carbon fiber. [Embodiment 5] The FRP molded article according to any one of Embodiments 1 to 4, wherein the fiber-reinforced resin substrate is a cured product of a prepreg or a laminate having a plurality of prepregs. [Embodiment 6] The FRP molded article according to Embodiment 5, wherein the prepreg is a continuous fiber prepreg, and the thickness of the in-mold coating is 10 to 40% of the thickness of the fiber-reinforced resin substrate. [Embodiment 7] The FRP molded article according to Embodiment 6, wherein the weight of the in-mold coating is 40% or less of the weight of the fiber-reinforced resin substrate. [Embodiment 8] The FRP molded article according to Embodiment 5, wherein the prepreg is a sheet molding compound and the thickness of the in-mold coating is 20 to 50% of the thickness of the fiber-reinforced resin substrate. [Embodiment 9] The FRP molded article according to Embodiment 8, wherein the weight of the in-mold coating is 50% or less of the weight of the fiber-reinforced resin substrate. [Embodiment 10] The area of ​​the in-mold coating is 900 cm² 2 The above describes the FRP molded article according to any one of Embodiments 1 to 9. [Embodiment 11] The FRP molded article according to any one of Embodiments 1 to 10, wherein the in-mold coating is a primer coating. [Embodiment 12] The FRP molded article according to any one of Embodiments 1 to 11, wherein the inorganic filler is at least one selected from the group consisting of titanium oxide, aluminum hydroxide, and mica. [Embodiment 13] The FRP molded article according to any one of Embodiments 1 to 12, wherein the content of the inorganic filler is 20% by mass or more of the total amount of the in-mold coating film. [Embodiment 14] A method for manufacturing an FRP molded article according to any one of Embodiments 1 to 13, comprising applying pressure to a layer of thermosetting powder coating formed on at least a portion of the molding surface of a mold having an upper mold and a lower mold, and to a thermosetting prepreg placed in a closed space formed by closing the mold, thereby forming the in-mold coating on the surface of the fiber-reinforced resin substrate. [Embodiment 15] The manufacturing method according to Embodiment 14, further comprising polishing the surface of the in-mold coating film. [Embodiment 16] The density of the powder coating is 1.37 to 1.61 g / cm³ 3 The manufacturing method according to Embodiment 14 or 15. [Embodiment 17] The manufacturing method according to any one of Embodiments 14 to 16, wherein the prepreg is a sheet molding compound, and the charge rate of the sheet molding compound to the molding surface is 30% or more. [Embodiment 18] An FRP product comprising an FRP molded body according to any one of Embodiments 1 to 13 and a topcoat coating provided on the surface of the in-mold coating. [Embodiment 19] An FRP product according to Embodiment 18, which is an automobile body. [Embodiment 20] An FRP product according to Embodiment 18, which is an automobile roof. [Embodiment 21] An FRP product according to Embodiment 18, which is an automobile side panel. [Embodiment 22] An FRP product according to any one of embodiments 18 to 21, having a curved portion. [Embodiment 23] A method for manufacturing an FRP product, comprising applying a topcoat to the surface of the in-mold coating of the FRP molded body described in any of Embodiments 1 to 13. [Embodiment 24] The manufacturing method according to Embodiment 23, wherein the topcoat coating includes baked coating. [Embodiment 25] The manufacturing method according to Embodiment 24, wherein in the baking coating, the applied paint is dried at a temperature of 80°C or higher.

[0107] Although the present invention has been described above with reference to specific embodiments, each embodiment is presented as an example and does not limit the scope of the present invention. Each embodiment described herein can be modified in various ways within the scope in which the effects of the invention are achieved, and can be combined with features described in other embodiments to the extent that is feasible. [Industrial applicability]

[0108] Applying a topcoat to FRP molded bodies with an in-mold coating is useful for efficiently manufacturing FRP products. [Explanation of Symbols]

[0109] 1. Press forming machine 2. Layer of thermosetting powder coating 2C In-Mold Coating 3 Prepreg 3C Fiber-reinforced resin substrate 4 FRP molded body 10 Press machine 11 Mainframe 12 bolster 13 slides 20 mold 20L lower mold 20U upper mold 21 Convex part 22 Annular protrusion 23 Seal ring 24 recesses 25 Annular recess 26 Closed space 27 Molded Cavities 28L, 28U molding surface 30 Vacuum pumps 31 Shear Edge 40 mold 40L lower mold 40U upper type 42 Annular protrusion 43 Seal ring 45 Annular recess 48L, 48U molding surface 50 Vacuum pump

Claims

1. A fiber-reinforced resin substrate containing reinforcing fibers and matrix resin, An in-mold coating film fixed to the surface of the fiber-reinforced resin substrate, It has, The in-mold coating contains an inorganic filler, An FRP molded article having an in-mold coating thickness of more than 200 μm.

2. The FRP molded article according to claim 1, wherein the matrix resin contains a cured product of a thermosetting resin, and the thermosetting resin may be an epoxy resin.

3. The FRP molded article according to claim 1, wherein the in-mold coating contains a cured product of a thermosetting resin, and the thermosetting resin may be an epoxy resin.

4. The FRP molded article according to claim 1, wherein the reinforcing fiber is carbon fiber.

5. The FRP molded article according to claim 1, wherein the fiber-reinforced resin substrate is a cured product of a prepreg or a laminate having a plurality of prepregs.

6. The aforementioned prepreg is a continuous fiber prepreg. The FRP molded article according to claim 5, wherein the thickness of the in-mold coating is 10 to 40% of the thickness of the fiber-reinforced resin substrate.

7. The FRP molded article according to claim 6, wherein the weight of the in-mold coating is 40% or less of the weight of the fiber-reinforced resin substrate.

8. The aforementioned prepreg is a sheet molding compound, The FRP molded article according to claim 5, wherein the thickness of the in-mold coating is 20 to 50% of the thickness of the fiber-reinforced resin substrate.

9. The FRP molded article according to claim 8, wherein the weight of the in-mold coating is 50% or less of the weight of the fiber-reinforced resin substrate.

10. The area of ​​the in-mold coating is 900 cm². ２ The above is the FRP molded article according to claim 1.

11. The FRP molded article according to claim 1, wherein the in-mold coating is a primer coating.

12. The FRP molded article according to claim 1, wherein the inorganic filler is at least one selected from the group consisting of titanium oxide, aluminum hydroxide, and mica.

13. The FRP molded article according to claim 1, wherein the content of the inorganic filler is 20% by mass or more of the total amount of the in-mold coating film.

14. A method for manufacturing an FRP molded article according to any one of claims 1 to 13, A manufacturing method comprising forming an in-mold coating on the surface of a fiber-reinforced resin substrate by applying pressure to a layer of thermosetting powder coating formed on at least a portion of the molding surface of a mold having an upper mold and a lower mold, and to a thermosetting prepreg placed in a closed space formed by closing the mold.

15. The manufacturing method according to claim 14, further comprising polishing the surface of the in-mold coating film.

16. The density of the aforementioned powder coating is 1.37 to 1.61 g / cm³. ３ The manufacturing method according to claim 14.

17. The aforementioned prepreg is a sheet molding compound, The manufacturing method according to claim 14, wherein the charge rate of the sheet molding compound on the molded surface is 30% or more.

18. An FRP molded article according to any one of claims 1 to 13, A topcoat coating provided on the surface of the in-mold coating, FRP products that have [the specified feature].

19. An FRP product according to claim 18, which is an automobile body.

20. The FRP product according to claim 18, which is an automobile roof.

21. The FRP product according to claim 18, which is an automobile side panel.

22. The FRP product according to claim 18, having a curved portion.

23. A method for manufacturing an FRP product, comprising applying a topcoat to the surface of the in-mold coating of an FRP molded product according to any one of claims 1 to 13.

24. The manufacturing method according to claim 23, wherein the topcoat coating includes baked coating.

25. The manufacturing method according to claim 24, wherein in the aforementioned baking coating, the applied paint is dried at a temperature of 80°C or higher.

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