Prepreg and fiber-reinforced plastic

Abstract

Provided is a prepreg capable of suppressing deterioration in mechanical characteristics and chemical resistance of a fiber-reinforced plastic, and suppressing voids.　A prepreg (10) obtained by impregnating a fiber (20) with a resin composition (30), wherein the resin composition (30) contains the following components (A) to (C): (A) a resin having a urethane skeleton; (B) an ether and / or ester compound having an unsaturated hydrocarbon group; and (C) a thermal polymerization initiator which is a peroxide.

Description

Prepreg and Fiber Reinforced Plastic 【0001】 The present invention relates to a prepreg in which fibers are impregnated with a resin, and a fiber reinforced plastic using the prepreg. 【0002】 Conventionally, fibers such as carbon fibers are impregnated with a resin having a urethane skeleton to form a sheet-like prepreg, and this prepreg is laminated and cured to obtain a fiber reinforced plastic (FRP) (see Patent Document 1). The prepreg before use (during storage) usually has carrier films (release films) laminated on both sides. When in use, the prepreg with the carrier film is cut into an arbitrary size, the carrier film is peeled off, and then the prepregs are laminated and the resin is cured by heating to form a desired shape, thereby obtaining a fiber reinforced plastic (FRP). 【0003】 Such fiber reinforced plastics are used, for example, in notebook computers, tablets, smartphone displays, sports goods, reinforcing members for automotive and electronic parts, tanks (containers) for storing liquids, etc. In displays, sports goods, reinforcing members for automotive and electronic parts, etc., particularly high mechanical properties (physical properties) such as strength and toughness are required, and in tanks (containers) for storing liquids, etc., chemical resistance is particularly required. 【0004】 When using a resin having a urethane skeleton as the resin for the prepreg as in Patent Document 1, when manufacturing a fiber reinforced plastic, the resin is cured (crosslinked, thermoset) using a radical reaction in a heated state. However, the radical polymerization reaction is inhibited by contact with oxygen in the environment (oxygen exposure). When the curing of the resin is inhibited, the amount of uncured resin increases, leading to a decrease in the mechanical properties and chemical resistance of the fiber reinforced plastic. 【0005】 As a method of avoiding contact between oxygen and the resin, methods such as curing the resin under a nitrogen atmosphere or vacuum conditions, or covering the resin with a film or the like to block oxygen can be considered. However, using these methods increases costs and processes and is not economically viable. 【0006】On the other hand, for example, adding thiol compounds has been proposed as a method to accelerate the radical polymerization reaction (curing reaction) of resins (see Patent Document 2). However, when thiol compounds are added, the reaction starts at a low temperature, which may cause the viscosity of the prepreg resin to not decrease sufficiently, potentially leading to the formation of voids in the fiber-reinforced plastic. 【0007】 Furthermore, methods have been proposed to reduce uncured resin by adding, for example, an oxygen absorber (see Patent Document 3). However, when manufacturing fiber-reinforced plastics by thermosetting, the curing time is relatively long, and therefore the resin is exposed to oxygen for a long time, making it unavoidable that curing inhibition of the resin will occur, and there is a risk that uncured resin will remain. 【0008】 Japanese Patent Publication No. 2023-158535 Japanese Patent Publication No. 2004-277660 Japanese Patent Publication No. 7200130 【0009】 In view of the above circumstances, the present invention aims to provide a prepreg that can suppress the deterioration of the mechanical properties and chemical resistance of fiber-reinforced plastics and suppress voids, and a fiber-reinforced plastic using said prepreg. 【0010】 The characteristic configuration of the prepreg according to the present invention for solving the above problems is a prepreg in which fibers are impregnated with a resin composition, wherein the resin composition contains the following components (A) to (C): (A) a resin having a urethane skeleton, (B) an ether and / or ester compound having an unsaturated hydrocarbon group, and (C) a thermal polymerization initiator which is a peroxide. 【0011】With this prepreg configuration, by containing components (A) and (C), when the prepreg is heated, a radical polymerization reaction (hereinafter also referred to as "curing") of component (A) is initiated. Here, by containing component (B) in the prepreg, components (A), (B), and (C) work together in this radical polymerization reaction to suppress curing inhibition by oxygen in the environment and promote the radical polymerization reaction of component (A). As a result, even if the radical polymerization reaction due to curing takes a relatively long time, the remaining uncured component (A) is suppressed, thereby suppressing a decrease in the mechanical properties and chemical resistance of the fiber-reinforced plastic produced from the prepreg, and also suppressing voids. 【0012】 In the prepreg of this configuration, component (A) is preferably urethane (meth)acrylate and / or urethane-modified vinyl ester. 【0013】 With this prepreg configuration, by selecting the above compound as component (A), the mechanical properties and chemical resistance of the fiber-reinforced plastic produced from the prepreg can be further enhanced, and voids can be suppressed. 【0014】 In the prepreg of this configuration, component (B) is preferably diprenyl glycerin ether and / or isoprenyl methacrylate. 【0015】 With this prepreg configuration, by selecting the above compound as component (B), the inhibition of curing by oxygen during the radical polymerization reaction of component (A) can be further suppressed. As a result, the mechanical properties and chemical resistance of the fiber-reinforced plastic produced from the prepreg can be improved, and voids can be suppressed. 【0016】 In the prepreg of this configuration, component (C) is preferably a peroxyketal and / or peroxyester. 【0017】 With this prepreg configuration, by selecting the above compound as component (C), the radical polymerization reaction of component (A) can be further promoted. 【0018】 In the prepreg with this configuration, it is preferable that component (A) is urethane (meth)acrylate and component (C) is peroxyketal. 【0019】 According to this prepreg configuration, by selecting the above compounds as component (A) and component (C), it is possible to obtain an excellent fiber-reinforced plastic that suppresses mass loss and is less prone to void formation. 【0020】 In the prepreg with this configuration, the content of component (B) is preferably 4 to 6 parts by mass per 100 parts by mass of component (A). 【0021】 With this prepreg configuration, by setting the content of component (B) as described above, it is possible to obtain a very excellent fiber-reinforced plastic that is less prone to void formation while further suppressing mass loss. 【0022】 In the prepreg with this configuration, the fibers are preferably carbon fibers. 【0023】 With this prepreg configuration, the use of carbon fibers, which have excellent strength, as the fibers can enhance the mechanical properties of fiber-reinforced plastics. 【0024】 Another characteristic feature of the fiber-reinforced plastic according to the present invention, which solves the above problems, is that it is a cured product obtained by laminating and curing the prepreg. 【0025】 In this fiber-reinforced plastic configuration, the prepreg is laminated and cured to produce a cured product, which enhances the mechanical properties and chemical resistance of the fiber-reinforced plastic and suppresses voids. 【0026】 In the fiber-reinforced plastic of this configuration, it is preferable that the mass loss rate (MRm) when immersed in methanol with a purity of 99% or higher is 1.2% or less. 【0027】With this fiber-reinforced plastic configuration, the uncured portion of component (A) can be further suppressed by setting the mass loss rate (MRm) within the above range. As a result, the fiber-reinforced plastic exhibits improved mechanical properties and chemical resistance. 【0028】 In the fiber-reinforced plastic of this configuration, it is preferable that the Vickers hardness (HV) at a test load of 0.1 kgf (0.9807 N) is 25 or higher, in accordance with JIS Z 2244:2024. 【0029】 With this fiber-reinforced plastic configuration, the mechanical properties are enhanced by setting the Vickers hardness (HV) within the above range. 【0030】 In the fiber-reinforced plastic of this configuration, it is preferable that the void ratio is 6% or less. 【0031】 With this fiber-reinforced plastic configuration, the mechanical properties are enhanced by setting the void ratio within the above range. 【0032】 Figure 1 is a schematic perspective view showing a prepreg according to one embodiment of the present invention. Figure 2 is a schematic cross-sectional view showing a fiber-reinforced plastic according to one embodiment of the present invention. 【0033】 The prepreg and fiber-reinforced plastic of the present invention will be described with reference to the drawings. However, the layer structure shown in the drawings has been exaggerated or simplified as appropriate for the sake of clarity, and the relative thicknesses and scales of each layer do not necessarily accurately reflect the actual prepreg and fiber-reinforced plastic. 【0034】 [Prepreg] Figure 1 is a schematic perspective view showing a prepreg according to one embodiment of the present invention. The prepreg 10 is made by impregnating fibers 20 with a resin composition 30. The prepreg 10 is a thermosetting (for thermosetting) prepreg. 【0035】<Fibers> Examples of fibers 20 include carbon fibers, glass fibers, aramid fibers, alumina fibers, silicon carbide fibers, boron fibers, metal fibers, natural fibers, mineral fibers, synthetic fibers, and chemical fibers. Of these, carbon fibers are preferred. The fibers 20 can be used in the prepreg 10 in a state where they are aligned in one direction, or in a woven state. Examples of woven fabrics include plain weave, twill weave, and satin weave. 【0036】 Examples of carbon fibers include polyacrylonitrile (PAN) carbon fibers and pitch carbon fibers. By selecting carbon fibers as the fiber 20, the mechanical properties of the fiber-reinforced plastic 1 (see Figure 2) manufactured from the prepreg 10 can be further enhanced. The fiber 20 can be used alone, but it can also be used as a composite fiber or blended yarn of two or more types. 【0037】 Multiple fibers 20 are bundled together to form a fiber bundle. The fiber bundle of fiber 20 preferably contains 1,000 to 30,000 fibers, and more preferably 3,000 to 24,000 fibers. By setting the fiber bundle of fiber 20 within the above range, the tensile strength of fiber 20 can be made appropriate. 【0038】 The fineness (mass in grams per 1000 meters) of the fiber 20 is preferably 66 to 1800 tex, and more preferably 200 to 1650 tex. By setting the fineness of the fiber 20 within the above range, the tensile strength of the fiber 20 can be made appropriate. 【0039】 <Resin Composition> Resin composition 30 is a resin composition for prepregs. Resin composition 30 contains the following components (A) to (C): (A) a resin having a urethane skeleton (B) an ether or ester compound having an unsaturated hydrocarbon group (C) a thermal polymerization initiator which is a peroxide. 【0040】 The content (RC) of the resin composition 30 in the prepreg 10 is not particularly limited, but is preferably 20 to 60% by mass, and more preferably 20 to 40% by mass. By setting the content (RC) of the resin composition 30 within the above range, the mechanical properties of the fiber-reinforced plastic 1 produced from the prepreg 10 can be further improved. 【0041】 (Component (A): Resin having a urethane skeleton) The resin having a urethane skeleton, which is component (A), is not particularly limited as long as it has a urethane skeleton (-O-C(=O)-NH-) and is capable of radical polymerization by heating (thermosetting resin). Examples of component (A) include urethane (meth)acrylate and urethane-modified vinyl ester. Here, urethane (meth)acrylate means urethane acrylate and / or urethane methacrylate. Of these, urethane acrylate and / or urethane-modified vinyl ester are preferred as component (A). By selecting the above compound as component (A), the mechanical properties and chemical resistance of the fiber-reinforced plastic 1 produced from the prepreg 10 can be further improved, and voids can be suppressed. Component (A) can be used alone, but it can also be used as a mixture of two or more types. 【0042】 The content of component (A) in the resin composition 30 is preferably 50 to 97% by mass. By setting the content of component (A) within the above range, the mechanical properties and chemical resistance of the fiber-reinforced plastic 1 manufactured from the prepreg 10 can be further improved. 【0043】 (Component (B): Ether and / or ester compound having an unsaturated hydrocarbon group) Component (B), which is an ether and / or ester compound having an unsaturated hydrocarbon group, is an ether compound having an unsaturated hydrocarbon group and an ether structure, and / or an ester compound having an unsaturated hydrocarbon group and an ester structure. 【0044】Among component (B), as the ether compound having an unsaturated hydrocarbon group, for example, an allyl ether compound is preferable, and diprenyl glycerin ether (DPNG) represented by the following chemical formula (1) is more preferable. Among component (B), as the ester compound having an unsaturated hydrocarbon group, an ester compound having an isoprenyl group and a methacryloyl group is preferable, and isoprenyl methacrylate (IPEMA) represented by the following chemical formula (2) is more preferable. By selecting the above compounds as component (B), during the radical polymerization reaction of component (A), the inhibition of curing by oxygen can be more suppressed. As a result, the mechanical properties and chemical resistance of the fiber reinforced plastic 1 produced from the prepreg 10 can be enhanced, and voids can also be suppressed. Component (B) can be used alone as one kind, or can also be used as a mixture of two or more kinds. 【0045】 【0046】 【0047】 During the radical polymerization reaction of component (A), radicals are generated in the molecule of DPNG, and then oxygen is captured by reacting with oxygen. The generated peroxide radicals extract the hydrogen of other DPNGs to generate DPNG radicals, and by repeating these, oxygen is absorbed. As a result, it is considered that the radical polymerization reaction of component (A) is promoted without being inhibited by oxygen. IPEMA is considered to promote the radical polymerization reaction of component (A) without being inhibited by oxygen due to having an isoprenyl group and a methacryloyl group in the same molecule. 【0048】 The content of component (B) in the resin composition 30 is preferably 1 to 6% by mass. The content of component (B) is preferably 2 to 6 parts by mass with respect to 100 parts by mass of component (A). By setting the content of component (B) to be not less than the above lower limit, the uncuring of component (A) can be more suppressed. By setting the content of component (B) to be not more than the above upper limit, while sufficiently curing component (A), it is possible to suppress component (B) from becoming an impurity. 【0049】(Component (C): Thermal polymerization initiator) The thermal polymerization initiator, which is component (C), is a peroxide. Examples of component (C) include peroxyketal, ketone peroxide, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxyester, peroxydicarbonate, and peroxycarbonate. Of these, peroxyketal and peroxyester are preferred for component (C). By selecting the above compound as component (C), the radical polymerization reaction of component (A) can be further promoted. Component (C) can be used alone, but it can also be used as a mixture of two or more. 【0050】 The content of component (C) in the resin composition 30 is preferably 1 to 6% by mass. The content of component (C) is preferably 2 to 6 parts by mass per 100 parts by mass of component (A). By setting the content of component (C) above the lower limit, the uncuring of component (A) can be further suppressed. By limiting the content of component (C) to below the upper limit, voids can be suppressed while sufficiently curing component (A), and the formation of impurities by component (C) can be suppressed. 【0051】 (Component (D): Other components) In addition to components (A), (B), and (C), the resin composition 30 may appropriately contain other components (D), such as conventionally known additives, as long as they do not hinder the effects of the present invention. Other components (D) may include, for example, resins other than the above-mentioned component (A), such as unsaturated polyester acrylate monomers and methacrylate monomers, polymerization inhibitors (such as piperidine derivatives), curing accelerators (such as thiol compounds), inorganic fine particles such as finely powdered silica, pigments, elastomers, flame retardants (such as aluminum hydroxide, brominated compounds, and phosphorus compounds), and defoaming agents in appropriate amounts. 【0052】 The resin composition 30 can be manufactured by mixing and stirring components (A), (B), (C), and any other component (D) using a conventionally known stirring device, and heating as necessary. 【0053】The prepreg 10 is made by impregnating fibers 20 with a resin composition 30. Methods for impregnating the fibers 20 with the resin composition 30 include applying an uncured resin composition 30 to a release sheet (not shown) in advance, placing the fibers 20 aligned in one direction on the applied uncured resin composition 30, and passing them between a pair of rollers (not shown) to impregnate them; or applying the uncured resin composition 30 to the fibers 20 aligned in one direction, and then passing them between a pair of rollers to impregnate them. In these cases, the thickness of the prepreg 10 can be adjusted by adjusting the nip pressure of the pair of rollers. Alternatively, the pair of rollers may be heated to reduce the viscosity of the resin composition 30 while impregnation is performed. 【0054】 [Fiber-reinforced plastic] Figure 2 is a schematic cross-sectional view showing a fiber-reinforced plastic according to one embodiment of the present invention. The fiber-reinforced plastic 1 of this embodiment is a cured product obtained by laminating and curing a plurality of prepregs 10, and more specifically, a heat-cured product. 【0055】 According to the fiber-reinforced plastic 1 of this embodiment, since it is a cured product obtained by laminating and curing the prepreg 10 described above, the mechanical properties and chemical resistance of the fiber-reinforced plastic 1 are enhanced, and voids are suppressed. 【0056】 <Characteristics of Fiber-Reinforced Plastics> The fiber-reinforced plastic 1 preferably has a mass loss rate (MRm) of 1.2% or less, and more preferably 0.8% or less, when immersed in methanol with a purity of 99% or higher. By setting the mass loss rate (MRm) within the above range, the uncuring of component (A) is further suppressed. As a result, the mechanical properties and chemical resistance of the fiber-reinforced plastic 1 are improved. The lower limit of the mass loss rate (MRm) is not particularly limited, but for example, it can be 0.01% or more. The mass loss rate (MRm) can be determined by the measurement method described later. The mass loss rate (MRm) can be adjusted by appropriately setting the types and contents of components (A), (B), and (C) in the prepreg 10. 【0057】<Vickers Hardness (HV)> The fiber-reinforced plastic 1 preferably has a Vickers hardness (HV) of 25 or higher at a test load of 0.1 kgf (0.9807 N) in accordance with JIS Z 2244:2024 (i.e., Vickers hardness (HV) 0.1). By setting the Vickers hardness (HV) within the above range, the mechanical properties of the fiber-reinforced plastic 1 are enhanced. The upper limit of the Vickers hardness (HV) is not particularly limited, but for example, it can be 70 or less. The Vickers hardness (HV) can be determined by the measurement method described later. The Vickers hardness (HV) can be adjusted by appropriately setting the types and contents of components (A), (B), and (C) in the prepreg 10. 【0058】 <Void Content> The fiber-reinforced plastic 1 preferably has a void content of 6% or less. By setting the void content within the above range, the mechanical properties of the fiber-reinforced plastic 1 are enhanced. The lower limit of the void content is not particularly limited, but for example, it can be 0.01% or more. The void content can be determined by the measurement method described later. The void content can be adjusted by appropriately setting the types and contents of components (A), (B), and (C) in the prepreg 10. 【0059】 The fiber-reinforced plastic 1 can be manufactured by stacking multiple prepregs 10 and then applying heat pressing (heating and pressure). The pressure in the heat pressing is preferably set to 1 to 5 MPa, the heating temperature is preferably set to 110 to 150°C, and the holding temperature (the time for which the pressurized and heated states are maintained) is preferably set to 100 to 140 minutes. Figure 2 shows, as an example, a three-layer fiber-reinforced plastic 1 with three prepregs 10 stacked on top of each other, but the number of prepregs 10 stacked in the fiber-reinforced plastic 1 is not particularly limited and can be set appropriately depending on the application, etc. Carbon fiber reinforced plastic (CFRP) is preferred as the fiber-reinforced plastic 1. By using carbon fiber reinforced plastic for the fiber-reinforced plastic 1, its mechanical properties can be enhanced. 【0060】 The fiber-reinforced plastic laminate of the present invention will be described in more detail below with reference to examples. 【0061】 [Materials Used] <Fibers> ・Carbon fiber product name: T700SC-24K, manufactured by Toray Industries, Inc. Fiber bundle: 24,000 strands Specific gravity (D): 1.80 ・Carbon fiber woven product name: TR3110M, manufactured by Mitsubishi Chemical Corporation Density: Warp 12.5 strands / inch (strands / 2.54 cm) Weft 12.5 strands / inch (strands / 2.54 cm) Specific gravity (D): 1.80 ・Glass fiber product name: RS240PE-535, manufactured by Nitto Boseki Co., Ltd. Yarn count: 2400 g / 1000 m Specific gravity (D): 2.54 【0062】 <Component A: Resin with a urethane skeleton> ・Urethane (meth)acrylate Product name: EBECRYL8409 (aliphatic urethane acrylate, bifunctional), manufactured by Daicel Ornex Co., Ltd. Specific gravity (E): 1.2 ・Urethane-modified vinyl ester The urethane-modified vinyl ester obtained by adding 43g of the following diisocyanate to 100g of the following epoxy ester and stirring, and reacting them was used. ・Epoxy ester Product name: Epoxy ester 3000MK (bisphenol A diglycidyl ether methacrylic acid adduct), manufactured by Kyoeisha Chemical Co., Ltd. Specific gravity (E): 1.2 ・Diisocyanate Product name: Millionate NM (diphenylmethane diisocyanate, MDI), manufactured by Tosoh Corporation Specific gravity (E): 1.2 NCO content: 33.5% 【0063】 <Component B: Ether and / or ester compounds having unsaturated hydrocarbon groups> • Unsaturated hydrocarbon ether compound product name: DPNG (diprenyl glycerin ether), manufactured by Kuraray Co., Ltd. Specific gravity (E): 0.95 • Unsaturated hydrocarbon ester compound product name: IPEMA (isoprenyl methacrylate), manufactured by Kuraray Co., Ltd. Specific gravity (E): 0.92 【0064】<Component C: Peroxide-based thermal polymerization initiator> • Peroxyketal product name: Luperox® 531M80, manufactured by Sigma-Aldrich Japan G. K. Specific gravity (E): 0.90 • Peroxyester product name: Kaya Ester TMPO-70, manufactured by Kayaku Akzo Co., Ltd. Specific gravity (E): 0.86 【0065】 <Component D: Other components> - Curing accelerator (thiol compound) Product name: TMMP-LV, manufactured by SC Organic Chemicals Co., Ltd. Specific gravity (E): 1.2 【0066】 [Examples 1-19, Comparative Examples 1-5] Components (A), (B), (C), and (D) were appropriately mixed according to the formulations shown in Tables 1-4 below to obtain the prepreg resin compositions of Examples 1-19 and Comparative Examples 1-5. 【0067】 The obtained prepreg resin compositions were measured for mass loss rate, Vickers hardness (HV), and void ratio using the measurement method described below, and evaluated according to the criteria shown below. The results are shown in Tables 1 to 4. 【0068】 <Mass Loss Rate> The prepreg resin compositions of Examples 1 to 19 and Comparative Examples 1 to 5, which were previously uncured, were applied to a release sheet (carrier film). Fibers aligned in one direction were placed on the applied uncured prepreg resin composition and impregnated by passing them between a pair of rollers, thereby obtaining a rectangular prepreg measuring 300 mm × 200 mm × 0.2 mm. Next, the prepreg was cut into 200 mm × 200 mm squares, and 10 pieces of prepreg were stacked (laminated) so that they all faced the same direction. Using an autoclave, the material was molded under the following molding conditions to obtain a 2 mm thick plate-shaped fiber-reinforced plastic (FRP, in this case carbon fiber reinforced plastic (CFRP)). (Molding Conditions) ・Heating rate: 10°C / min ・Pressure: 0.5 MPa ・No vacuum ・Holding temperature: 150°C ・Holding time: 1 hour ・Cooling rate: 10°C / min 【0069】Next, fiber-reinforced plastic was cut into 45 mm x 45 mm x 2 mm squares to form test specimens, and the mass (M0) of each specimen was measured. The specimens were immersed in methanol (purity 99% or higher) for 1 hour, and then dried at 60°C for 1 hour. After drying, the mass (M1) of the specimens was measured again, and the mass loss (M3) was calculated by subtracting the mass of the specimen after immersion and drying (M1) from the mass of the specimen before immersion (M0) (M3 = M0 - M1). The mass loss rate (MR), which is the ratio (percentage) of the mass loss (M3) to the mass M0 before immersion, was calculated (MR = M3 / M0 × 100). This was done for three specimens (n=3), and the average mass loss rate (MRm) was obtained by averaging the results. The mass loss rate (MRm) was then evaluated according to the following criteria. Furthermore, a larger mass loss rate (MRm) indicates a greater impact on the mechanical properties and chemical resistance of the test specimen, while a smaller mass loss rate indicates a smaller impact on these properties. (Judgment Criteria) Excellent: Mass loss rate (MRm) of 0.8% or less (no impact on mechanical properties or chemical resistance) Good: Mass loss rate (MRm) greater than 0.8% and 1.2% or less (impacts mechanical properties and chemical resistance, but within acceptable limits) Poor: Mass loss rate (MRm) greater than 1.2% (decreased mechanical properties and chemical resistance) 【0070】 <Vickers Hardness (HV)> Using the test specimens (45 mm × 45 mm × 2 mm) of Examples 1 to 19 and Comparative Examples 1 to 5 obtained in the measurement of the "mass loss rate" described above, the Vickers hardness (HV) (HV0.1) was measured for three test specimens each at a test load of 0.1 kgf (0.9807 N) using the following formula (I), in accordance with JIS Z 2244:2024, and the average value was obtained (n=3). The average Vickers hardness (HV) was evaluated according to the following criteria. Vickers hardness (HV) = constant × (test force / indentation surface area) ... (I) Constant = 0.102 = 1 kgf / 9.807 N (criteria) Good: HV is 25 or higher (sufficient hardening) Poor: HV is less than 25 (insufficient hardening) 【0071】<Void Ratio> A prepreg was obtained in the same manner as described above for "mass loss rate". Test specimens were prepared by cutting the prepreg into 100 mm x 100 mm squares, and their mass (A) was measured. After measuring the mass, the test specimens were immersed in acetone (purity 99% or higher) for 10 minutes and then removed. This immersion in acetone and removal was repeated three times to dissolve the resin composition in acetone. Next, the fibers remaining after dissolution were dried at 60°C for 1 hour, and the mass (B) after drying was measured. Using masses (A) and (B), the resin content (C) [mass %], which is the content of the resin composition in the prepreg, was calculated according to the following formula (II). Resin content (C) = (A - B) / A × 100 ... (II) Next, using the specific gravity of the fibers (D) and the specific gravity of the (meth)acrylate resin (E), the fiber volume ratio (F) [volume %], which is the volume ratio of the fibers in the prepreg, was calculated according to the following formula (III). Fiber volume ratio (F) = {(100 - C) / D)} / [{(100 - C) / D} + (C / E)] × 100 ... (III) Next, using the fiber volume ratio (F), the resin volume ratio (G) [volume %], which is the volume ratio of the (meth)acrylate resin in the prepreg, was calculated according to the following formula (IV). Resin volume fraction (G) = 100 - F ... (IV) Next, using the specific gravity of the fibers (D), the specific gravity of the (meth)acrylate resin (E), the fiber volume fraction (F), and the resin volume fraction (G), the theoretical specific gravity (H) assuming a void ratio of 0% was calculated according to the following formula (V): Theoretical specific gravity (H) = D × F / 100 + E × G / 100 ... (V) Next, a 2 mm thick plate-shaped fiber-reinforced plastic (FRP, in this case carbon fiber reinforced plastic (CFRP)) was obtained in the same manner as the "mass loss rate" described above. The specific gravity (I) of the fiber-reinforced plastic was measured using a hydrometer (product name: MDS300, manufactured by Alpha Mirage Co., Ltd.) in accordance with JIS K 7112:1999 (underwater test method). Then, using the theoretical specific gravity (H) and the specific gravity of the fiber-reinforced plastic (I), the void fraction (J) was calculated according to the following formula (VI): Void fraction (J) = {1 - (I / H)} × 100 ... (VI) 【0072】(Judgment Criteria) Excellent: 3.5% or less (good appearance, no internal voids) Good: over 3.5% and 6% or less (good appearance, some minute internal voids) Poor: over 6% (poor appearance and internal voids) 【0073】 【0074】 【0075】 【0076】 【0077】 As shown in Tables 1 to 3, the fiber-reinforced plastics formed from the prepreg resin compositions of Examples 1 to 19, containing components (A), (B), and (C), exhibited superior mass loss rate, Vickers hardness (HV), and void ratio, demonstrating that a decrease in mechanical properties and chemical resistance was suppressed, and void formation was inhibited. In contrast, as shown in Table 4, the fiber-reinforced plastics formed from the prepreg resin compositions of Comparative Examples 1 to 5 were found to be inferior in at least one of the mass loss rate, Vickers hardness (HV), and void ratio. 【0078】 The prepreg and fiber-reinforced plastic of the present invention can be suitably used, for example, as displays for laptops, tablets, and smartphones; sports equipment; reinforcing members for automobiles and electronic components; and tanks (containers) for holding liquids. 【0079】 1 Fiber-reinforced plastic 10 Prepreg 20 Fiber 30 Resin composition

Claims

1. A prepreg in which fibers are impregnated with a resin composition, wherein the resin composition contains the following components (A) to (C): (A) a resin having a urethane skeleton; (B) an ether and / or ester compound having an unsaturated hydrocarbon group; and (C) a thermal polymerization initiator which is a peroxide.

2. The prepreg according to claim 1, wherein component (A) is urethane (meth)acrylate and / or urethane-modified vinyl ester.

3. The prepreg according to claim 1, wherein component (B) is diprenyl glycerin ether and / or isoprenyl methacrylate.

4. The prepreg according to claim 1, wherein component (C) is a peroxyketal and / or a peroxyester.

5. The prepreg according to claim 3, wherein component (A) is urethane (meth)acrylate and component (C) is peroxyketal.

6. The prepreg according to claim 5, wherein the content of component (B) is 4 to 6 parts by mass per 100 parts by mass of component (A).

7. The prepreg according to claim 1, wherein the fiber is a carbon fiber.

8. A fiber-reinforced plastic that is a cured product obtained by laminating and curing prepregs according to any one of claims 1 to 7.

9. The fiber-reinforced plastic according to claim 8, wherein the mass loss rate (MRm) when immersed in methanol with a purity of 99% or more is 1.2% or less.

10. The fiber-reinforced plastic according to claim 8, wherein the Vickers hardness (HV) at a test load of 0.1 kgf (0.9807 N) is 25 or greater, in accordance with JIS Z 2244:2024.

11. The fiber-reinforced plastic according to claim 8, wherein the void ratio is 6% or less.

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