Manufacturing method for FRP molded bodies, manufacturing method for FRP products

Abstract

The primary objective of this invention is to provide a method for manufacturing FRP molded articles that can prevent appearance defects caused by cracking of the plain mold coating. [Solution] The present invention provides a method for manufacturing an FRP molded article, which includes preheating a layer 2 of thermosetting paint before pressurizing the prepreg 3, and starting to pressurize the prepreg 3 when the paint torque is 5.5 [N·m] or more, or when the paint torque is 7.6% or more of the maximum torque.

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing FRP molded articles and a method for manufacturing FRP products. [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, in conventional in-mold painting methods, the plain mold coating, which contains paint heated on the surface of the mold held at the molding temperature, can tear during pressing, damaging the appearance of the FRP product.

[0006] The primary objective of this invention is to provide a method for manufacturing FRP molded articles that can prevent appearance defects caused by cracking of the plain mold coating. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a method for producing an FRP molded article having a fiber-reinforced resin base material containing reinforcing fibers and a matrix resin, and an in-mold coating film fixed to at least a part of the surface of the fiber-reinforced resin base material, the method comprising: holding a molding die having an upper die and a lower die and provided with a molding surface at a molding temperature; forming a layer of a thermosetting coating material on at least a part of the molding surface of the molding die held at the molding temperature; preheating the layer of the thermosetting coating material; placing a thermosetting prepreg in a closed space formed by closing the molding die; and bringing the upper die and the lower die close to each other to pressurize the prepreg placed in the closed space together with the layer of the thermosetting coating material, wherein pressurization of the prepreg is started when the torque of the coating material is 5.5 [N·m] or more.

[0008] According to another aspect of the present invention, there is provided a method for producing an FRP molded article having a fiber-reinforced resin base material containing reinforcing fibers and a matrix resin, and an in-mold coating film fixed to at least a part of the surface of the fiber-reinforced resin base material, the method comprising: holding a molding die having an upper die and a lower die and provided with a molding surface at a molding temperature; forming a layer of a thermosetting coating material on at least a part of the molding surface of the molding die held at the molding temperature; preheating the layer of the thermosetting coating material; placing a thermosetting prepreg in a closed space formed by closing the molding die; and bringing the upper die and the lower die close to each other to pressurize the prepreg placed in the closed space together with the layer of the thermosetting coating material, wherein pressurization of the prepreg is started when the torque of the coating material is 7.6% or more of the maximum torque of the coating material. Effects of the Invention

[0009] There is provided a method for producing an FRP molded article, which can prevent appearance defects caused by breakage of the in-mold coating film. Brief Description of the Drawings

[0010] [Figure 1] Figure 1 is a schematic diagram showing a pressing apparatus. [Figure 2] Figure 2 is a cross-sectional view of a molding die. [Figure 3] Figure 3 is a cross-sectional view of a molding die. [Figure 4] Figure 4 is a cross-sectional view of a molding die. [Figure 5] Figure 5 is a cross-sectional view for explaining the production process of an FRP molded body. [Figure 6] Figure 6 is a cross-sectional view for explaining the production process of an FRP molded body. [Figure 7] Figure 7 is a cross-sectional view for explaining the production process of an FRP molded body. [Figure 8] Figure 8 is a cross-sectional view for explaining the production process of an FRP molded body. [Figure 9] Figure 9 is a cross-sectional view for explaining the production process of an FRP molded body. [Figure 10] Figure 10 is a cross-sectional view of an FRP molded body. [Figure 11] Figure 11 is a cross-sectional view of a molding die used in an experiment. [Figure 12] Figure 12 shows a cylindrical stamping die and a piston used in the experiment. [Figure 13] Figure 13 is a torque curve acquired in the experiment. [Figure 14] Figure 14 shows an FRP molded product in the shape of an automobile body produced in the experiment. [Figure 15] Figure 15 shows a top view of the SMC laminate produced in the experiment. [Figure 16] Figure 16 is a top view for explaining the coating method of a paint in the experiment. [Mode for Carrying Out the Invention]

[0011] 1. Press molding apparatus The FRP molded body according to the embodiment can preferably be produced using a press molding apparatus. Figure 1 is a schematic diagram showing the configuration of a typical press forming apparatus. Referring to Figure 1, the press forming apparatus 1 includes a press machine 10, a mold 20, and a vacuum pump 30. The press machine 10 consists of a main frame 11, a bolster 12 fixed to the lower part of the main frame 11, a slide 13 that can move up and down vertically above the bolster 12, and a lifting mechanism 14 that moves the slide 13 up and down. The molding die 20 consists 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.

[0012] As shown in Figure 2, the lower mold 20L has a protrusion 21 having a vertical outer surface, and further has an annular protrusion 22 arranged along the outer surface of the protrusion 21 and sharing its outer surface with the protrusion 21. The protrusion 21 is provided with a seal ring 23 that encircles its outer surface. The upper mold 20U has a recess 24 that can be fitted into the protrusion 21 of the lower mold 20L via the seal ring 23, and further has an annular recess 25 arranged along the outer surface of the recess 24 and sharing its outer surface with the recess 24. The annular protrusion 22 of the lower mold 20L and the annular recess 25 of the upper mold 20U can be fitted into each other.

[0013] When the slide 13 is lowered to engage the convex portion 21 of the lower mold 20L with the concave portion 24 of the upper mold 20U, a closed space 26 is formed between the upper mold 20U and the lower mold 20L, as shown in Figure 3. Since the enclosed space 26 becomes airtight due to the action of the seal ring 23, vacuum degassing can be performed by operating the vacuum pump 30 connected to the enclosed space 26 through a hole provided in the upper mold 20U.

[0014] 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.

[0015] 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.

[0016] 2. Method for manufacturing FRP molded articles A method for manufacturing an FRP molded article according to a preferred embodiment includes, but is not limited to, the following steps. The first step is to prepare a mold having 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 paint on at least a portion of the molding surface of the mold, which is maintained at the molding temperature. A fourth step involves preheating the layer of the aforementioned thermosetting paint. A fifth step is to place a thermosetting prepreg in a closed space formed by closing the mold. A sixth step involves degassing the gas between the prepreg and the layer of the thermosetting paint while vacuum degassing the closed space. The seventh 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 paint.

[0017] 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.

[0018] (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.

[0019] (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 by the seventh 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 seventh step is completed.

[0020] 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 generally be set within the range of 120 to 180°C, taking the above considerations into account. The molding temperature may also be 130 to 170°C, 130 to 160°C, or 135 to 150°C, and is not particularly limited.

[0021] (3) Third step In the third step, as shown in Figure 5, a layer 2 of thermosetting paint is formed on the molding surface 28U of the mold 20. However, the layer 2 of thermosetting paint may be formed on only one side of the molding surface 28U and the molding surface 28L, or on both sides. The paint may be either a powder coating or a liquid coating, but a powder coating is preferred over a liquid coating because dripping is undesirable.

[0022] Powder coatings contain inorganic fillers in addition to thermosetting resins such as epoxy resin, epoxy polyester resin, polyester resin, acrylic resin, and polyurethane resin. Because inorganic fillers are added to the powder coating, thermal shrinkage of the thermosetting powder coating layer 2 during molding is reduced.

[0023] 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.

[0024] The inorganic filler content is preferably 20% by mass or more of the total amount of powder coating, more preferably 20-60% by mass, and even more preferably 45-55% 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] It is preferable to apply the thermosetting paint layer 2 such that its thickness immediately after formation exceeds 200 μm. A thickness of more than 200 μm in the thermosetting paint layer 2 makes it easier to conceal irregularities caused by the reinforcing fibers of the prepreg. Considering its contribution to weight reduction of FRP products, the upper limit of the thickness of the thermosetting paint layer 2 may be 700 μm, 1,000 μm, 2,000 μm, etc.

[0029] 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 either a human 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.

[0030] 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.

[0031] 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.

[0032] (4) Fourth step In the fourth step, layer 2 of the thermosetting paint is preheated before molding the prepreg. Preheating causes the paint to thicken due to the heat of the mold, and the plain mold coating adheres to the mold 20, thus suppressing excessive flow during press molding. As already mentioned, the mold 20 is kept at the molding temperature until at least the seventh step is completed. Since the mold is kept at the molding temperature when the formation of the paint layer 2 begins, the preheating of the thermosetting paint layer 2 begins immediately after its formation and ends with the start of pressurization of the prepreg.

[0033] The shape of layer 2 of the thermosetting paint in plan view is not particularly limited, but the contact time between the paint and the mold differs between the start point and the end point of paint application by the amount of the powder application time t0. Therefore, in layer 2 of the thermosetting paint, there is a time difference in the thermal history by the amount of the powder application time t0. For example, the paint at the start point of application has the longest contact time with the mold among the layers 2 of the paint, so the influence of the thermal history tends to be greater. On the other hand, the paint at the end point of application has the shortest contact time with the mold among the layers 2 of the paint, so the influence of the thermal history tends to be less. Therefore, the inventors came up with the idea of ​​using the torque change of the thermosetting paint to control the thermal history of the plain mold coating film.

[0034] The torque of a paint exhibits a correlation with the heating time, and this correlation can be pre-measured and confirmed using a curing characteristics tester (e.g., a Curustometer available from ENEOS Material Trading Co., Ltd.). Using a curing characteristics tester, a torque curve showing the correlation between the heating time and torque of a paint under constant temperature conditions can be obtained. For typical paints, the viscosity increases with heating time, and then remains almost constant. Therefore, in the torque curve, the torque value rises to the maximum torque with increasing heating time, and thereafter remains almost unchanged from the maximum torque (see, for example, Figure 13). The torque at the start of pressurization of the prepreg is calculated from the torque curve and the time until the start of paint pressurization. The temperature at which the torque curve is obtained is the same as the molding temperature.

[0035] In some cases, during preheating, a holding time is provided from the completion of the formation of the thermosetting paint layer 2 until the start of pressurization of the prepreg, until the paint torque of the paint layer reaches 7.6% or more of the maximum torque. Alternatively, a holding time is provided until the paint torque of the paint layer reaches preferably 10% or more of the maximum torque, and more preferably 15% or more. Or, a holding time is provided from the completion of the formation of the thermosetting paint layer 2 until the start of pressurization of the prepreg until the paint torque of the paint layer reaches 0.63 [N·m] or more. In the thermosetting paint layer 2, the influence of thermal history tends to decrease and the torque tends to decrease from the coating application start point toward the coating application end point. The starting point of the holding time here is the time point when the formation of the thermosetting paint layer 2 is completed, and the torque of the portion least affected by the thermal history among the thermosetting paint layers in which gelation is progressing can be monitored.

[0036] The maximum torque output by the curing property tester is T MAX , the elapsed time t required for the torque of the paint at the molding temperature to reach 0.076×T MAX , and the elapsed time t required for the torque of the paint at the molding temperature to reach 0.63 [N·m] 1A can be read from the torque curve. 1B According to the studies by the present inventors, after the formation of the thermosetting paint layer 2 on the molding surface 28U is completed, that is, after the spraying of the electrostatic coating spray is stopped at the coating application end point, if a holding time of t 1A or more, or t 1B or more has elapsed, it can be considered that all the paint in the thermosetting paint layer 2 has sufficiently increased in viscosity. Therefore, by providing a holding time of t 1A or more, or t 1B or more, tearing of the pre-molded coating film can be prevented, and tearing of the in-mold coating film can also be prevented.

[0037] As described above, the preheating of the thermosetting paint layer 2 starts immediately after the start of its formation, and ends when the pressurization of the prepreg starts. In some examples, it is preferable to start the pressurization of the prepreg before the torque of at least a part of the paint in the thermosetting paint layer 2 reaches 84.5% of the maximum torque. Alternatively, it is preferable to start the pressurization of the prepreg before the torque of at least a part of the paint in the thermosetting paint layer 2 reaches 7.0 [N·m]. Therefore, the torque of the thermosetting paint layer 2 during preheating is preferably 84.5% or less of the maximum torque, or 7.0 [N·m] or less. ​In layer 2 of the thermosetting paint, the influence of thermal history increases and the torque tends to increase as the application process moves backward from the end point to the start point. The starting point for time management here is the start of the formation of layer 2 of the thermosetting paint, and the torque is monitored in the part of the thermosetting paint layer where the influence of thermal history is greatest as gelation progresses.

[0038] The maximum torque output by the curing characteristics tester is T MAX In this case, the torque of the paint at the molding temperature is 0.845 × T MAX The elapsed time t required to reach this point 2A The elapsed time t required for the paint torque at the molding temperature to reach 7.0 [N·m] 2B This can be read from the torque curve. From the start of forming the layer 2 of thermosetting paint on the molded surface 28U, that is, from the start of spraying the electrostatic paint at the paint application starting point, t 2A or t 2B The preheating is completed and the prepreg pressurization is started before the specified time has elapsed. According to the inventor's research, from the start of the formation of the thermosetting paint layer 2 to t 2A or t 2B If preheating is completed before the specified time has elapsed, the plain mold coating does not need to be heated to a certain degree, making it easier to prevent cracking of the in-mold coating.

[0039] The preheating time t3 from the start of forming layer 2 of the thermosetting paint to the start of molding the prepreg is t 2A or t 2B While there are no particular limitations on the length of the preheating time, it may be 11 minutes or longer, 12 minutes or longer, or 15 minutes or longer. There are also no particular limitations on the upper limit of the preheating time t3, but it may be 30 minutes or less, or 20 minutes or less.

[0040] (5) Fifth step In the fifth 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 paint. 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 paint. The thermosetting prepreg 3 may be preformed into the net shape or approximate net shape.

[0041] 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 prepregs, woven prepregs, tow prepregs, and sheet molding compounds (SMCs).

[0042] 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.

[0043] When prepreg 3 is SMC, material flow occurs during press molding, making it particularly prone to tearing of the plain mold coating and in-mold coating. Therefore, the usefulness of the manufacturing method according to the embodiment is further enhanced. The area of ​​SMC may be 99% or less, 95% or less, or 49% or less of the projected area of ​​the FRP molded body, and is not particularly limited. The flow distance during press molding of SMC may be 20 cm or more, 25 cm or more, or 30 cm or more, and is not particularly limited.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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 paint 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 between 30% and 99%. In this embodiment, by vacuum degassing the closed space 26 while degassing the gas between the prepreg 3 and the thermosetting paint layer 2, void formation can be suppressed even if the prepreg charge rate is typically 50% or more.

[0051] As a result of the inventors' research, 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 49% or higher, more preferably 40% or higher, and even more preferably 49% or higher. 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.

[0052] 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.

[0053] (6) Sixth step In the sixth step, the enclosed space 26 is degassed under vacuum, and the gas between the prepreg 3 and the thermosetting paint layer 2 is removed. When prepreg 3 overlaps with layer 2 of thermosetting paint, gas may get trapped between prepreg 3 and layer 2 of thermosetting paint. Gas may also get trapped within layer 2 of thermosetting paint. If the prepreg and thermosetting paint are cured under pressure while gas is present, the gas remains compressed within the FRP molded body. Afterward, when the mold is opened and the pressure is removed, the compressed gas remaining within the FRP molded body expands, causing holes or bulges in the FRP molded body, degrading its appearance.

[0054] The larger the area of ​​the prepreg, the easier it is for gas to enter between the prepreg and the layer of thermosetting paint. 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.

[0055] 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 paint from entering the vacuum pump 30, a filter or the like may be installed between the mold 20 and the vacuum pump 30.

[0056] 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 or heated paint from the prepreg 3 or prepreg laminate, which have low viscosity during molding, to the outside of the molded surface, thus stabilizing the thickness of the FRP molded product and improving the surface quality.

[0057] 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.

[0058] The vacuum pressure in the closed space 26 when vacuum degassing is complete is preferably -0.1 MPa or less. The die closing speed of the upper die 20U during press molding of the prepreg is preferably 1.0 to 5.0 mm / second, more preferably 1.0 to 2.0 mm / second, and even more preferably 1.0 to 1.5 mm / second. If the die closing speed is above the lower limit of the above numerical range, the prepreg will spread to every corner of the mold during molding, making it less likely for unfilled areas to occur. If the die closing speed is below the upper limit of the above numerical range, it is possible to prevent damage to the mold by preventing the upper and lower dies from coming into contact before the prepreg has spread sufficiently within the mold during molding.

[0059] 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 paint 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.

[0060] (7) Step Seven In the seventh step, as shown in Figure 8, the upper mold 20U and the lower mold 20L are brought closer together while the enclosed space containing the thermosetting prepreg is degassed under vacuum, and the prepreg 3 is pressurized together with the paint layer 3. In some examples, pressurization of the prepreg 3 is started when the torque of the preheated paint is 7.6% or more of the maximum torque of the paint. Alternatively, in some other examples, pressurization of the prepreg 3 is started when the torque of the preheated paint is 5.5 [N·m] or more.

[0061] 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 paint layer 2, the pressure suddenly rises and instantly increases to the molding pressure. It is preferable to perform vacuum degassing even while pressurizing. This is because it allows for the removal of gases generated by heating and compression, as well as gases pushed out from the prepreg and paint layers.

[0062] 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.

[0063] The molding pressure in the seventh step is preferably in the range of 3 to 10 MPa. The molding pressure is defined as the value obtained by dividing the pressing force of the press machine by the vertical projected area of ​​the molding cavity.

[0064] After the completion of the seventh 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.

[0065] 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.

[0066] 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 at least a portion of 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 paint through gelation.

[0067] 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 45-55% 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.

[0068] The thickness of the in-mold coating 2C is preferably more 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. A thickness of 210 μm or more is more preferable, and 250 μm or more is even more preferable. 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] The area of ​​the in-mold coating 2C is not particularly limited, but 10,000 cm² is not recommended. 2More than 20,000cm 2 More than 35,000cm 2 The above may be the case. There is no particular upper limit on the area of ​​the in-mold coating 2C, but 5,000 cm² is acceptable. 2 , 10,000cm 2 , 17,500cm 2 It may be something like this.

[0074] The thermosetting paint is preferably a primer paint. Therefore, the FRP molded article according to the embodiment is preferably an FRP molded article having a primer coating.

[0075] 3. Top coat painting The FRP molded body 4 having an in-mold coating 2C is an intermediate product in the manufacture of multi-layer coated FRP products, and becomes a finished FRP product by further topcoating. Such an FRP product has the FRP molded body 4 and a topcoat coating applied to the surface of the in-mold coating 2C.

[0076] When manufacturing an FRP molded body 4 having an in-mold coating 2C using the manufacturing method according to the embodiment, the in-mold coating 2C is usually polished to flatten the surface before proceeding to topcoat painting. In topcoat painting, at least one coating film, including a colored coating film, is formed on the in-mold coating 2C.

[0077] The coating film formed by the topcoat is preferably a baked coating film, which is formed by drying the applied paint at a temperature of 80°C or higher, typically 100°C or higher. The coating formed by the topcoat may include a colored coating and a clear coating formed on top of the colored coating. The clear coating may be formed as a topcoat.

[0078] The coating formed by the topcoat may include a colored coating and an undercoat formed beneath it. When multiple coatings are layered in the topcoat, preferably, the multiple paints are applied wet-on-wet and then baked simultaneously in a single step.

[0079] 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.

[0080] 4. Experimental Results The results of the experiments conducted by the inventors are described below.

[0081] 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) • Paint: A powder coating was used, which consisted of epoxy resin blended with 45-55% by mass of inorganic fillers that suppress thermal shrinkage, such as aluminum hydroxide and pigments. The density was 1.6 g / cm³. 3 That is the case. • SMC1: STR120 (thermosetting, 2.0mm thickness) from Mitsubishi Chemical Corporation.

[0082] 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.

[0083] 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 projected area of ​​the molded cavity is 34,600 cm². 2The height of the molding cavity is variable between 1 mm and 3 mm. The material of the mold 40 is aluminum for FRP molding, and the molding surfaces 48U and 48L are smoothed by sanding with sandpaper of grit #1000 or higher.

[0084] The same powder coating was used in all of the experiments described below. The torque curve and maximum torque of the powder coating when heated to 140°C were obtained using the procedure described below. In this experiment, torque was measured using a curing properties tester (Curlastometer 7Type P, hereinafter referred to as "Curlastometer") available from ENEOS Material Trading Co., Ltd. In order to measure torque with the Curlastometer, the powder coating needs to be molded into a predetermined shape. Therefore, a mold 60 having a cylindrical part and a piston 62 were prepared as shown in Figure 12. The piston 62 is used to press the powder coating into a cylindrical recess 61 with a diameter of 25 mm and a depth of 50 mm formed on the upper surface of the cylindrical part of the mold 60.

[0085] The molding procedure for powder coating using the mold 60 and piston 62 is as follows. First, the mold 60 and piston 62 were heated to 60-70°C. A release agent was applied to the parts of the heated mold 60 and piston 62 that would come into contact with the powder coating. Then, 7.9g of powder coating was placed into the recess 61 of the mold 60. The piston 62 was inserted into the recess 61 of the mold 60, and approximately 1 ton of pressure was applied to the powder coating using a hand press, compressing the powder coating through the piston 62. After compression, the piston 62 was withdrawn, and the cylindrically formed powder coating was removed. Through these steps, the powder coating was formed into a cylindrical shape with a diameter of 25mm and a height of 10mm ± 1mm.

[0086] A cylindrical powder coating was placed in a torque meter. The measurement temperature was set to the molding temperature and the measurement time to 60 minutes, and the torque curve of the powder coating at its molding temperature was obtained. In each of the following experiments, the molding temperature was 140°C, so the measurement temperature was set to 140°C. The obtained torque curve is shown in Figure 13. In Figure 13, the elapsed time is plotted on the X axis and the torque is plotted on the Y axis to display the torque curve.

[0087] From the acquired torque curve and the measurement item "MH" of the device, a maximum torque of 8.3 [N·m] was obtained. The value of 7.6% of the maximum torque is 8.3 [N·m] × 7.6 / 100 ≈ 0.63 [N·m]. The elapsed time t when the torque reaches 7.6% of the maximum torque, i.e., 0.63 [N·m] is... 1A Reading from Figure 13, the answer is 5 minutes and 30 seconds. Similarly, the value of 84.5% of the maximum torque is 8.3 [N·m] × 84.5 / 100 ≈ 7.01 [N·m]. The elapsed time t when the torque is 84.5% of the maximum torque, i.e., 7.01 [N·m]. 2A Reading from Figure 13, the answer is 12 minutes and 3 seconds.

[0088] 4.1 Experiment 1-1 An FRP molded part of an automobile body with the shape shown in Figure 14 was obtained by following the procedure described below. As shown in Figure 14, the projected dimensions of the FRP molded part produced in the experiment are 2500 mm in the longitudinal direction of the vehicle body and 1500 mm in the width direction of the vehicle body. Curved sections with a variable radius of 150 mm with a minimum radius R are provided at the four corners of the outer circumference. The dimension in the height direction of the vehicle body is 200 mm. The thickness of the FRP molded part is a uniform thickness of 2.5 mm, including the in-mold coating and the FRP base material. The projected area of ​​the molding cavity side on which the in-mold coating was applied is 34,630 cm². 2 That is the case.

[0089] To obtain an FRP molded product of an automobile body with the shape shown in Figure 14, an SMC laminate 70 shown in Figure 15 was prepared. The SMC laminate 70 has one first cut pattern 71 and four second cut patterns 72 that are superimposed on both ends of the first cut pattern 71.

[0090] The dimensions of the first cut pattern 71 are a rectangle with a length of 2,200 mm in the front-to-rear direction of the vehicle body and a width of 1,000 mm in the vehicle body direction. SMC1 was cut to the dimensions of the first cut pattern 71, and one piece of the first cut pattern 71 was prepared. The dimensions of the four second cut patterns 72 are all rectangles with a length of 350 mm in the front-to-rear direction of the vehicle body and a width of 1,200 mm in the vehicle body direction. SMC1 was cut to the dimensions of the second cut pattern 72, and four pieces of the second cut pattern 72 were prepared.

[0091] Two sets of stacked second cut patterns 72 were prepared, with the four sides of each rectangle aligned. These stacks of second cut patterns 72 were stacked at each end of the first cut pattern 71, as shown in Figure 15, so as to coincide with both ends. At both ends of the SMC stack 70, stacks consisting of two second cut patterns are placed on top of the first cut pattern 71, and a total of three SMC1s are stacked at each end in the front-rear direction of the vehicle body. The thickness at both ends of the SMC stack 70 is 6.0 mm. The mass of the SMC stack 70 is approximately 11.3 kg, and its projected area is 23,400 cm². 2 Therefore, the charge rate is calculated as the projected area of ​​the SMC laminate 70 divided by the projected area of ​​the molded cavity, which is 23,400 cm². 2 / 34,600cm 2 ×100 ≈ approximately 68%.

[0092] The FRP molded automobile body with the shape shown in Figure 14 was manufactured as follows. First, the mold 40 shown in Figure 11 was heated, and it was confirmed that its temperature stabilized within the range of 140 ± 5°C. Next, the outer wall surface of the annular protrusion 45 of the upper mold 40U, 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. After that, 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. Next, 3,120 g of powder coating was applied to the mirror-finish molding surface 48U of the upper mold 40U from the spray nozzle of an electrostatic powder coating apparatus. When applying the powder coating, as shown in Figure 16, application was started from one point on the molding surface 48U, and a layer 2 of powder coating was formed by drawing a circle in the direction of the arrow. The powder coating time t0 from the start to the end of application was 5 minutes and 55 seconds. Furthermore, measurements were taken at five or more random locations using a DeFelsko PosiTector6000 electromagnetic / eddy current film thickness gauge to confirm that the coating thickness was within the range of 500 ± 50 μm.

[0093] 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. At the same time, a holding time t1 of 3 minutes and 25 seconds was provided between the end of powder coating application and the start of molding. When the heating time was 3 minutes and 25 seconds, the torque T1 of the powder coating was read from Figure 13 to be 0.0310 [N·m], which was 0.37% of the maximum torque (8.3 [N·m]).

[0094] The preheating time t3 from the start of powder coating to the start of molding was 9 minutes and 20 seconds, which is the sum of the powder coating time of 5 minutes and 55 seconds and the holding time of 3 minutes and 25 seconds. When the heating time was 9 minutes and 22 seconds, the torque T3 of the powder coating read from Figure 13 was 5.271 [N·m], which was 63.5% of the maximum torque (8.3 [N·m]).

[0095] Next, the SMC laminate 70 shown in Figure 15 was placed on the molding surface 48L of the lower die 40L, with a maximum distance of 27 mm from the shear edge. Then, the mold 40 was closed and press molding was performed. The molding pressure during press molding was 10 MPa and the pressurizing time was 900 seconds.

[0096] Vacuum degassing of the closed space formed by closing the mold during molding was initiated before the shear edge was formed. When the mold closing speed was set to 1.0–5.0 mm / second, the vacuum pressure in the closed space reached -0.1 MPa before the shear edge was formed. The vacuum pump was kept running until the molding pressure reached 10 MPa. The vacuum time from the formation of the closed space to the start of vacuum degassing and pressurization was 37 seconds or more.

[0097] The mold 40 was opened, and an FRP molded automobile body with the shape shown in Figure 14 was removed. Visual inspection of the surface of the in-mold coating revealed a visible tear in the in-mold coating, exposing the black fiber-reinforced resin substrate beneath the coating.

[0098] 4.2 Experiment 1-2 Except for changing the holding time t1 from the end of powder coating application to the start of molding as shown in Table 1, an FRP molded body of the same shape was obtained under the same conditions as in Experiment 1-1.

[0099] 4.3 Experiments 1-3 Except for changing the powder coating time t0 required for applying the powder coating and the holding time t1 from the end of powder coating application to the start of molding, as shown in Table 1, an FRP molded body of the same shape was obtained under the same conditions as in Experiment 1-1.

[0100] 4.4 Experiment 2-1 Except for changing the powder coating time t0 required for applying the powder coating and the holding time t1 from the end of powder coating application to the start of molding, as shown in Table 1, an FRP molded body of the same shape was obtained under the same conditions as in Experiment 1-1.

[0101] 4.5 Experiment 2-2 Except for changing the powder coating time t0 required for applying the powder coating and the holding time t1 from the end of powder coating application to the start of molding, as shown in Table 1, an FRP molded body of the same shape was obtained under the same conditions as in Experiment 1-1.

[0102] 4.6 Experiment 2-3 Except for changing the powder coating time t0 required for applying the powder coating and the holding time t1 from the end of powder coating application to the start of molding, as shown in Table 1, an FRP molded body of the same shape was obtained under the same conditions as in Experiment 1-1.

[0103] 4.7 Experimental Results The results of each experiment described above, along with the experimental conditions, are shown in Table 1. Table 1 also shows the preheating time t3, from the start of powder coating application to the start of prepreg molding.

[0104] [Table 1]

[0105] In Table 1, “T t1 " is the torque value when the powder coating at the molding temperature of 140°C is heated for the same amount of time as the holding time t1. t1 / T MAX " is T MAX T for t1 This shows the ratio and is equivalent to the degree of hardening at the time of holding time t1. "T t2 " is the torque value when the powder coating at the molding temperature of 140°C is heated for the same amount of time as the preheating time t3. t2 / T MAX " is T MAX T for t2 This indicates the ratio and is equivalent to the degree of hardening at the end of preheating.

[0106] In experiments 1-1, 1-2, and 1-3, the holding time t1 from the end of powder coating application to the start of molding was short. Reading the torque of the powder coating when heated for the same amount of time as the holding time t1 from Figure 13, it was less than 7.6% of the maximum torque (8.3 [N·m]) in all cases. As a result, rupture of the in-mold coating was confirmed in all three experiments: 1-1, 1-2, and 1-3.

[0107] In contrast, in experiments 2-1, 2-2, and 2-3, a sufficient holding time t1 was provided between the end of powder coating application and the start of molding. Reading the torque of the powder coating after heating for the same duration as the holding time t1 from Figure 13, it was consistently 7.6% or more of the maximum torque (8.3 [N·m]). As a result, no rupture of the in-mold coating was observed in experiments 2-1, 2-2, and 2-3.

[0108] 5. Summary of Embodiments Preferred embodiments of the present invention include, but are not limited to, the following. [Embodiment 1] A method for manufacturing an FRP molded article having a fiber-reinforced resin substrate containing reinforcing fibers and a matrix resin, and an in-mold coating film fixed to at least a portion of the surface of the fiber-reinforced resin substrate, comprising: holding a mold having an upper mold and a lower mold and a molding surface at a molding temperature; forming a layer of thermosetting paint on at least a portion of the molding surface of the mold held at the molding temperature; preheating the layer of thermosetting paint; placing a thermosetting prepreg in a closed space formed by closing the mold; and bringing the upper mold and the lower mold closer together to pressurize the prepreg placed in the closed space together with the layer of thermosetting paint, wherein pressurizing the prepreg is started when the torque of the paint is 5.5 [N·m] or more. [Embodiment 2] The manufacturing method according to Embodiment 1, wherein after forming the layer of thermosetting paint, a holding time is provided until the torque of the paint reaches 5.5 [N·m] or more. [Embodiment 3] The manufacturing method according to Embodiment 1 or 2, wherein pressurization of the prepreg is started before the torque of at least a portion of the layer of the thermosetting paint reaches 7.0 [N·m]. [Embodiment 4] A method for manufacturing an FRP molded article having a fiber-reinforced resin substrate containing reinforcing fibers and a matrix resin, and an in-mold coating film fixed to at least a portion of the surface of the fiber-reinforced resin substrate, comprising: holding a mold having an upper mold and a lower mold and a molding surface at a molding temperature; forming a layer of thermosetting paint on at least a portion of the molding surface of the mold held at the molding temperature; preheating the layer of thermosetting paint; placing a thermosetting prepreg in a closed space formed by closing the mold; and bringing the upper mold and the lower mold closer together to pressurize the prepreg placed in the closed space together with the layer of thermosetting paint, wherein pressurizing the prepreg is started when the torque of the paint is 7.6% or more of the maximum torque of the paint. [Embodiment 5] The manufacturing method according to Embodiment 4, wherein after forming the layer of thermosetting paint, a holding time is provided until the torque of the paint reaches 7.6% or more of the maximum torque of the paint. [Embodiment 6] The manufacturing method according to Embodiment 4 or 5, wherein pressurization of the prepreg is started before the torque of at least a portion of the layer of the thermosetting paint reaches 84.5% of the maximum torque of the paint. [Embodiment 7] The manufacturing method according to any one of Embodiments 1 to 6, wherein the coating is a powder coating. [Embodiment 8] The manufacturing method according to any one of Embodiments 1 to 7, wherein the molding temperature is 120 to 180°C. [Embodiment 9] The manufacturing method according to any one of Embodiments 1 to 8, wherein the preheating time from the completion of the formation of the thermosetting paint layer to the start of pressurizing the prepreg is 10 minutes or more. [Embodiment 10] The manufacturing method according to any one of Embodiments 1 to 9, wherein the paint contains a thermosetting resin and an inorganic filler. [Embodiment 11] The manufacturing method according to Embodiment 10, wherein the inorganic filler is at least one selected from the group consisting of titanium oxide, aluminum hydroxide, and mica. [Embodiment 12] The manufacturing method according to Embodiment 10 or 11, wherein the content of the inorganic filler is 40% by mass or more of the total amount of the paint. [Embodiment 13] The manufacturing method according to any one of Embodiments 1 to 12, wherein the thickness of the thermosetting paint layer immediately after formation is greater than 200 μm. [Embodiment 14] The manufacturing method according to any one of Embodiments 1 to 13, wherein the layer of thermosetting paint is a layer applied using an electrostatic spray coating. [Embodiment 15] The manufacturing method according to any one of Embodiments 1 to 14, wherein the die closing speed of the molding die during press molding of the prepreg is 1.0 to 5.0 mm / second. [Embodiment 16] The manufacturing method according to any one of Embodiments 1 to 15, wherein the prepreg is a sheet molding compound. [Embodiment 17] The manufacturing method according to Embodiment 16, wherein the area of ​​the sheet molding compound is 99% or less of the projected area of ​​the FRP molded body, and material flow occurs during press molding. [Embodiment 18] The manufacturing method according to Embodiment 17, wherein the flow distance of the sheet molding compound during press molding is 20 cm or more. [Embodiment 19] The area of ​​the in-mold coating is 10,000 cm² 2 The manufacturing method described in any of Embodiments 1 to 18. [Embodiment 20] The manufacturing method according to any one of Embodiments 1 to 19, further comprising degassing the gas between the prepreg and the layer of the thermosetting paint while vacuum degassing the closed space. [Embodiment 21] A method for manufacturing an FRP product, comprising: manufacturing an FRP molded body using the manufacturing method described in any of Embodiments 1 to 20; and applying a topcoat to the surface of the in-mold coating of the FRP molded body. [Embodiment 22] The manufacturing method according to Embodiment 21, wherein the topcoat coating includes baked coating. [Embodiment 23] The manufacturing method according to Embodiment 22, wherein in the baking coating, the applied paint is dried at a temperature of 80°C or higher. [Embodiment 24] The manufacturing method according to any one of Embodiments 21 to 23, wherein the FRP product is an automobile body. [Embodiment 25] The manufacturing method according to any one of Embodiments 21 to 23, wherein the FRP product is an automobile roof. [Embodiment 26] The manufacturing method according to any one of Embodiments 21 to 23, wherein the FRP product is an automobile side panel. [Embodiment 27] The manufacturing method according to any one of Embodiments 21 to 23, wherein the FRP product has a curved portion.

[0109] 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]

[0110] Applying a topcoat to FRP molded bodies with an in-mold coating is useful for efficiently manufacturing FRP products. [Explanation of symbols]

[0111] 1. Press forming machine 2. Layer of thermosetting paint 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 type 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 method for manufacturing an FRP molded article having a fiber-reinforced resin substrate containing reinforcing fibers and a matrix resin, and an in-mold coating film fixed to at least a portion of the surface of the fiber-reinforced resin substrate, The molding die, which has an upper mold and a lower mold and is provided with a molding surface, is maintained at a molding temperature. Forming a layer of thermosetting paint on at least a portion of the molding surface of the mold held at the molding temperature, Preheating the aforementioned thermosetting paint layer, The thermosetting prepreg is placed in a closed space formed by closing the mold, The upper mold and the lower mold are brought close together, and the prepreg placed in the enclosed space is pressurized together with the layer of thermosetting paint. Includes, A manufacturing method comprising: starting to pressurize the prepreg when the torque of the paint is 5.5 [N・m] or more.

2. The manufacturing method according to claim 1, wherein after forming the layer of the thermosetting paint, a holding time is provided until the torque of the paint reaches 5.5 [N・m] or more.

3. The manufacturing method according to claim 1, wherein the pressurization of the prepreg is started before the torque of at least a portion of the layer of the thermosetting paint reaches 7.0 [N·m].

4. A method for manufacturing an FRP molded article having a fiber-reinforced resin substrate containing reinforcing fibers and a matrix resin, and an in-mold coating film fixed to at least a portion of the surface of the fiber-reinforced resin substrate, The molding die, which has an upper mold and a lower mold and is provided with a molding surface, is maintained at a molding temperature. Forming a layer of thermosetting paint on at least a portion of the molding surface of the mold held at the molding temperature, Preheating the aforementioned thermosetting paint layer, The thermosetting prepreg is placed in a closed space formed by closing the mold, The upper mold and the lower mold are brought close together, and the prepreg placed in the enclosed space is pressurized together with the layer of thermosetting paint. Includes, A manufacturing method comprising: starting to pressurize the prepreg when the torque of the paint is 7.6% or more of the maximum torque of the paint.

5. The manufacturing method according to claim 4, wherein after forming the layer of the thermosetting paint, a holding time is provided until the torque of the paint reaches 7.6% or more of the maximum torque of the paint.

6. The manufacturing method according to claim 4, wherein pressurization of the prepreg is started before the torque of at least a portion of the layer of the thermosetting paint reaches 84.5% of the maximum torque of the paint.

7. The manufacturing method according to claim 1 or 4, wherein the coating is a powder coating.

8. The manufacturing method according to claim 1 or 4, wherein the molding temperature is 120 to 180°C.

9. The manufacturing method according to claim 1 or 4, wherein the preheating time from the completion of the formation of the thermosetting paint layer to the start of pressurizing the prepreg is 10 minutes or more.

10. The manufacturing method according to claim 1 or 4, wherein the paint contains a thermosetting resin and an inorganic filler.

11. The manufacturing method according to claim 10, wherein the inorganic filler is at least one selected from the group consisting of titanium oxide, aluminum hydroxide, and mica.

12. The manufacturing method according to claim 10, wherein the content of the inorganic filler is 40% by mass or more of the total amount of the paint.

13. The manufacturing method according to claim 1 or 4, wherein the thickness of the thermosetting paint layer immediately after formation is greater than 200 μm.

14. The manufacturing method according to claim 1 or 4, wherein the layer of thermosetting paint is a layer applied using an electrostatic spray coating.

15. The manufacturing method according to claim 1 or 4, wherein the die closing speed of the molding die during press molding of the prepreg is 1.0 to 5.0 mm / second.

16. The manufacturing method according to claim 1 or 4, wherein the prepreg is a sheet molding compound.

17. The manufacturing method according to claim 16, wherein the area of ​​the sheet molding compound is 99% or less of the projected area of ​​the FRP molded body, and material flow occurs during press molding.

18. The manufacturing method according to claim 17, wherein the flow distance of the sheet molding compound during press molding is 20 cm or more.

19. The area of ​​the in-mold coating is 10,000 cm². ２ The manufacturing method according to claim 1 or 4.

20. The manufacturing method according to claim 1 or 4, further comprising degassing the gas between the prepreg and the layer of the thermosetting paint while vacuum degassing the closed space.

21. A method for manufacturing an FRP molded article using the manufacturing method described in claim 1 or 4, The process involves applying a topcoat to the surface of the in-mold coating of the FRP molded body, A method for manufacturing FRP products, including [the specified element].

22. The manufacturing method according to claim 21, wherein the topcoat coating includes baked coating.

23. The manufacturing method according to claim 22, wherein in the aforementioned baking coating, the applied paint is dried at a temperature of 80°C or higher.

24. The manufacturing method according to claim 21, wherein the FRP product is an automobile body.

25. The manufacturing method according to claim 21, wherein the FRP product is an automobile roof.

26. The manufacturing method according to claim 21, wherein the FRP product is an automobile side panel.

27. The manufacturing method according to claim 21, wherein the FRP product has a curved portion.

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