Prepreg, carbon fiber reinforced plastic, and method for manufacturing prepreg

Abstract

Provided is a prepreg in which the toughness and elastic modulus of a cured product thereof are improved. In an embodiment of the prepreg according to the present invention, a matrix resin composition and carbon fibers are contained, the matrix resin composition containing an epoxy resin and a (meth)acrylate monomer represented by a specific structural formula.

Description

[Technical Field]

[0001] The present invention relates to a prepreg, a carbon fiber reinforced plastic, and a method for producing a prepreg. This application claims priority based on Japanese Patent Application No. 2022-017599 filed on February 8, 2022, and Japanese Patent Application No. 2022-029211 filed on February 28, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] Fiber-reinforced plastics are lightweight, strong, and rigid, making them widely used in a variety of applications, from sports and leisure to industrial applications such as automobiles and aircraft. One method for manufacturing fiber-reinforced plastics is to use an intermediate material, called a prepreg, in which a matrix resin is impregnated into a reinforcing material made of long fibers (continuous fibers) such as reinforcing fibers. This method makes it easy to control the reinforcing fiber content of fiber-reinforced plastics, and can increase the fiber content. Molded products can be obtained by stacking multiple prepregs and heat-curing them.

[0003] To meet the demand for lightweight construction, carbon fiber, which has excellent specific strength and specific modulus, is often used as the reinforcing fiber, while epoxy resin, which has excellent adhesion to the carbon fiber, is often used as the matrix resin. However, epoxy resins generally tend to be brittle and have low toughness when cured. Consequently, fiber-reinforced plastics using epoxy resins as the matrix resin also tend to have low fracture toughness and impact resistance. Therefore, improving the toughness of epoxy resins has long been a technical challenge. Previously, toughening was achieved by adding engineering plastics such as polyethersulfone or block copolymers as modifiers, utilizing the phase separation structure that occurs during the epoxy resin curing process. However, these methods tend to lower the glass transition temperature (Tg) and modulus of elasticity of the cured product, and a significant increase in viscosity due to the addition of polymers is unavoidable. Furthermore, the need to synthesize the polymer in advance has disadvantages such as increased process complexity and cost.

[0004] To address these issues, attempts have been made to polymerize the monomers that form the modifier polymer in situ, simultaneously generating the modifier polymer and curing the epoxy resin (Non-Patent Document 1). In situ polymerization avoids a significant increase in the viscosity of the matrix resin, and because it allows for the generation of any polymer depending on the monomer selected, it facilitates the design and compounding of a modifier polymer tailored to the matrix resin. In this attempt, a polymer generated by radical polymerization is used as the modifier. In the field of fiber-reinforced plastics, technological development is underway to manufacture intermediate materials using a combination of epoxy resin and radically polymerizable monomers (Patent Documents 1-3). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Toshiyuki Oyama, Network Polymers, 36, 211 (2015) [Patent documents]

[0006] [Patent Document 1] Japanese Patent No. 3669090 [Patent Document 2] Japanese Patent Application Publication No. 11-43547 [Patent Document 3] Japanese Patent No. 5424021 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a prepreg having improved toughness or modulus of elasticity after curing. [Means for solving the problem]

[0008] The present invention includes the following aspects.

[0009] [1] A prepreg comprising a matrix resin composition and carbon fibers, wherein the matrix resin composition comprises an epoxy resin and a (meth)acrylic monomer represented by the following structural formula (1):

[0010] [ka]

[0011] (In formula (1), R represents a hydrogen atom or a methyl group, X represents an aryl group which may have a substituent selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, and a halogen atom; an alicyclic structure; and a heterocyclic structure; and n represents an integer of 1 to 30.) [2] The prepreg of [1], wherein the matrix resin composition contains a curing agent. [3] The prepreg of [2], wherein the curing agent comprises at least one selected from the group consisting of dicyandiamide, aromatic amines, ureas, and imidazoles. [4] The prepreg according to any one of [1] to [3], wherein the matrix resin composition contains a thermal radical polymerization initiator. [5] The prepreg according to [4], containing 0.1 to 10 parts by mass of the thermal radical polymerization initiator relative to 100 parts by mass of the (meth)acrylic monomer. [6] The prepreg according to [4] or [5], wherein the thermal radical polymerization initiator contains an organic peroxide. [7] The prepreg of any one of [4] to [6], wherein the thermal radical polymerization initiator contains a compound having a 10-hour half-life temperature of 70°C or higher. [8] The prepreg according to any one of [1] to [7], wherein in the formula (1), X is a structure selected from the group consisting of an aryl group having a substituent selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, and a halogen atom; an alicyclic structure; and a heterocyclic structure. [9] In the formula (1), n ​​represents an integer of 2 to 30. A prepreg according to any one of [1] to [8].

[10] The prepreg according to any one of [1] to [9], wherein the glass transition temperature of the polymer of the (meth)acrylic monomer is equal to or lower than the glass transition temperature of the cured product of the epoxy resin.

[11] The prepreg according to any one of [1] to

[10] , wherein the (meth)acrylic monomer has an average double bond equivalent of 150 g / eq or more.

[12] The prepreg according to any one of [1] to

[11] , wherein the (meth)acrylic monomer is contained in an amount of 5 to 45 parts by mass per 100 parts by mass of the epoxy resin.

[13] The prepreg according to any one of [1] to

[12] , wherein the (meth)acrylic monomer contains a (meth)acrylic monomer having a molecular weight of 190 or more.

[14] The prepreg according to any one of [1] to

[13] , wherein the monofunctional (meth)acrylic monomer is contained in an amount of 70% by mass or more relative to the total mass of the (meth)acrylic monomer.

[15] A fiber-reinforced plastic obtained by curing any one of the prepregs according to [1] to

[14] .

[16] A prepreg comprising a matrix resin composition containing the following components [A] to [D] and carbon fibers, wherein the viscosity of the matrix resin composition at 70°C is 10 Pa s or more, and the average double bond equivalent of [B] is 160 g / eq or more. [A] Epoxy resin [B] (Meth)acrylic monomer [C] Hardener [D] Thermal radical polymerization initiator

[17] The prepreg of

[16] , wherein the matrix resin composition, when cured under the following curing conditions, produces a cured product having a sea-island phase-separated structure, in which the cured product of [A] constitutes a sea phase and the polymer of [B] constitutes an island phase. Curing conditions: The matrix resin composition is poured between two glass plates and formed into a 2 mm thick plate, which is heated to an oven ambient temperature of 130°C at a rate of 2°C / min and maintained at 130°C for 120 minutes.

[18] The prepreg according to

[16] or

[17] , containing 30 mass% or more of an epoxy resin having a molecular weight of 500 or more relative to the total mass of the epoxy resins.

[19] The prepreg of any one of

[16] to

[18] , wherein the weight average molecular weight of [A] is 1,500 or more.

[20] The prepreg according to any one of

[16] to

[19] , wherein the average epoxy equivalent of the prepreg [A] is 200 g / eq or more.

[21] The prepreg of any one of

[16] to

[20] , wherein the [A] contains an epoxy resin having an oxazolidone ring skeleton or a bisphenol F type epoxy resin.

[22] The prepreg of any one of

[16] to

[21] , containing 5 to 45 parts by mass of [B] per 100 parts by mass of [A].

[23] The prepreg according to any one of

[16] to

[22] , wherein the [B] contains a (meth)acrylic monomer having a molecular weight of 190 or more.

[24] The prepreg according to any one of

[16] to

[23] , wherein the prepreg contains a monofunctional (meth)acrylic monomer in an amount of 70% by mass or more relative to the total mass of [B].

[25] The prepreg according to any one of

[16] to

[24] , wherein the [B] contains a (meth)acrylic monomer having one or more oxyethylene groups in the molecule.

[26] The prepreg according to any one of

[16] to

[25] , wherein the [B] contains a (meth)acrylic monomer having one or more cyclic skeletons in the molecule.

[27] The prepreg of any one of

[16] to

[26] , wherein the glass transition temperature of the polymer [B] is equal to or lower than the glass transition temperature of the cured product of [A].

[28] The prepreg of any one of

[16] to

[27] , wherein the [C] contains at least one member selected from the group consisting of dicyandiamide, aromatic amines, ureas, and imidazoles.

[29] A prepreg according to any one of

[16] to

[28] , containing 50 mass % or more of [C1] a component having a melting point of 70°C or higher relative to the total mass of the [C].

[30] The prepreg of any one of

[16] to

[29] , containing 0.1 to 10 parts by mass of [D] relative to 100 parts by mass of [B].

[31] The prepreg of any one of

[16] to

[30] , wherein the [D] contains [D1] an organic peroxide.

[32] The prepreg of any one of

[16] to

[31] , wherein the [D] contains a compound having a 10-hour half-life temperature of 70°C or higher.

[33] The matrix resin composition has a plane strain fracture toughness K measured by ASTM D5045 of a cured product cured under the following curing conditions: Ic is 1.6 MPa m 1 / 2 Any of the prepregs

[16] to

[32] , which are as described above. Curing conditions: The matrix resin composition is poured between two glass plates and formed into a 2 mm thick plate, which is heated to an oven ambient temperature of 130°C at a rate of 2°C / min and maintained at 130°C for 120 minutes.

[34] The matrix resin composition has a strain energy release rate G measured by ASTM D5045 of a cured product cured under the following curing conditions: Ic is 0.7kJ / m 2 Any of the prepregs

[16] to

[33] above. Curing conditions: The matrix resin composition is poured between two glass plates and formed into a 2 mm thick plate, which is heated to an oven ambient temperature of 130°C at a rate of 2°C / min and maintained at 130°C for 120 minutes.

[35] A fiber-reinforced plastic obtained by curing any one of the prepregs

[16] to

[34] .

[36] A method for producing a prepreg by impregnating a carbon fiber substrate with a matrix resin composition containing the following components [A] to [D]: A method for producing a prepreg, comprising blending [B] such that the viscosity of the matrix resin composition at 70°C is 10 Pa s or more and the average double bond equivalent of [B] in the matrix resin composition is 160 g / eq or more. [A] Epoxy resin [B] (Meth)acrylic monomer [C] Hardener [D] Thermal radical polymerization initiator

[37] A fiber-reinforced plastic comprising carbon fiber, a cured epoxy resin, and a polymer derived from a (meth)acrylic monomer represented by the following structural formula (1):

[0012] [ka]

[0013] (In formula (1), R represents a hydrogen atom or a methyl group, X represents an aryl group which may have a substituent selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, and a halogen atom; an alicyclic structure; and a heterocyclic structure; and n represents an integer of 1 to 30.)

[38] The fiber-reinforced plastic according to

[37] , wherein in the formula (1), X is a structure selected from the group consisting of an aryl group having a substituent selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, and a halogen atom; an alicyclic structure; and a heterocyclic structure.

[39] The fiber-reinforced plastic according to

[37] or

[38] , wherein n represents an integer of 2 to 30 in the formula (1).

[40] A prepreg comprising a matrix resin composition and carbon fiber, wherein the matrix resin composition has a plane strain fracture toughness K measured by ASTM D5045 of a cured product cured under the following curing conditions: Ic is 1.6 MPa m 1 / 2 This is what prepreg is all about. Curing conditions: The matrix resin composition is poured between two glass plates and formed into a 2 mm thick plate, which is heated to an oven ambient temperature of 130°C at a rate of 2°C / min and maintained at 130°C for 120 minutes.

[41] The plane strain fracture toughness K Ic is 2.2 MPa m 1 / 2 The prepreg of

[40] is as above.

[42] The strain energy release rate G of the cured product cured under the above curing conditions, as measured by ASTM D5045 Ic is 0.7kJ / m 2 The prepreg of

[41] is as above.

[43] The strain energy release rate G of the cured product cured under the above curing conditions, as measured by ASTM D5045 Ic is 1.2kJ / m 2 Any of the prepregs

[40] to

[42] , which are as described above.

[44] The prepreg according to any one of

[40] to

[43] , wherein the matrix resin composition contains an epoxy resin.

[45] The prepreg according to any one of

[40] to

[44] , wherein the matrix resin composition contains a (meth)acrylic monomer.

[46] The prepreg according to any one of

[40] to

[45] , wherein the matrix resin composition contains a (meth)acrylic monomer represented by the following structural formula (1):

[0014] [ka]

[0015] (In formula (1), R represents a hydrogen atom or a methyl group, X represents an aryl group which may have a substituent selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, and a halogen atom; an alicyclic structure; and a heterocyclic structure; and n represents an integer of 1 to 30.)

[47] The prepreg according to

[46] , wherein in the formula (1), X is a structure selected from the group consisting of an aryl group having a substituent selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, and a halogen atom; an alicyclic structure; and a heterocyclic structure.

[48] ​​The prepreg according to

[46] or

[47] , wherein n represents an integer of 2 to 30 in the formula (1).

[49] The prepreg of any one of

[40] to

[48] , wherein the matrix resin composition contains at least one selected from the group consisting of dicyandiamide, aromatic amines, ureas, and imidazoles.

[0016] [1a] A prepreg that satisfies (a) or (b). (a) A prepreg comprising a matrix resin composition containing the following components [A] to [D] and carbon fibers, wherein the viscosity of the matrix resin composition at 70°C is 10 Pa s or more, and the average double bond equivalent of [B] is 150 g / eq or more. [A] Epoxy resin [B] (Meth)acrylic monomer [C] Hardener [D] Thermal radical polymerization initiator (b) A prepreg comprising a matrix resin composition containing the following components [A] to [D] and carbon fibers, wherein the viscosity of the matrix resin composition at 70°C is 10 Pa·s or more. [A] Epoxy resin [B] A (meth)acrylic monomer represented by the following structural formula (1): [C] Hardener [D] Thermal radical polymerization initiator

[0017] [ka]

[0018] (In formula (1), R represents a hydrogen atom or a methyl group, X represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, an aryl group which may have a halogen atom, an alicyclic structure, or a heterocyclic structure, and n represents an integer of 1 to 30.) [2a] The prepreg according to [1a], wherein a cured product of the matrix resin composition cured under the following curing conditions has a sea-island phase-separated structure, in which the cured product of [A] constitutes the sea phase and the polymer of [B] constitutes the island phase. [3a] The prepreg according to [1a] or [2a], wherein the component having a molecular weight of 500 or more among [A] is contained in an amount of 30 parts by mass or more out of 100 parts by mass of the total epoxy resin. [4a] The prepreg according to any one of [1a] to [3a], wherein [A] has a weight average molecular weight of 1,500 or more. [5a] The prepreg according to any one of [1a] to [4a], wherein the average epoxy equivalent of [A] is 200 g / eq or more. [6a] The prepreg according to any one of [1a] to [5a], wherein [A] contains an epoxy resin having an oxazolidone ring skeleton or a bisphenol F type epoxy resin. [7a] The prepreg according to any one of [1a] to [6a], containing 5 to 45 parts by mass of [B] per 100 parts by mass of [A]. [8a] The prepreg according to any one of [1a] to [7a], wherein [B] contains a (meth)acrylic monomer having a molecular weight of 190 or more. [9a] [B] The prepreg according to any one of [1a] to [8a], which contains 70% by mass or more of a monofunctional (meth)acrylic monomer relative to 100% by mass. [10a] The prepreg according to any one of [1a] to [9a], wherein [B] contains a (meth)acrylic monomer having one or more oxyethylene groups in the molecule. [11a] The prepreg according to any one of [1a] to [10a], wherein [B] contains a (meth)acrylic monomer having one or more cyclic skeletons in the molecule. [12a] The prepreg according to [2a], wherein the glass transition temperature of the polymer [B] is equal to or lower than the glass transition temperature of the cured product of [A]. [13a] The prepreg according to any one of [1a] to [12a], wherein [C] contains at least one member selected from the group consisting of dicyandiamide, aromatic amines, ureas, and imidazoles. [14a] The prepreg according to any one of [1a] to [13a], containing 50 mass % or more of [C1] a component having a melting point of 70° C. or higher relative to 100 mass % of [C]. [15a] The prepreg according to any one of [1a] to [14a], which contains 0.1 to 10 parts by mass of [D] per 100 parts by mass of [B]. [16a] The prepreg according to any one of [1a] to [15a], wherein [D] contains [D1] an organic peroxide. [17a] The prepreg according to any one of [1a] to [16a], wherein the 10-hour half-life temperature of [D] is 70°C or higher. [18a] The prepreg according to any one of [1a] to [17a], wherein the matrix resin composition further contains a thermoplastic resin [E]. [19a] The prepreg according to [18a], wherein [E] contains at least one thermoplastic resin selected from the group consisting of polyvinyl formal, polyvinyl butyral, polyether sulfone, and phenoxy resin. [20a] The plane strain fracture toughness K of the cured product of the matrix resin composition cured under the following curing conditions, as measured by ASTM D5045 Ic is 1.6 MPa m 1 / 2The prepreg according to any one of [1a] to [19a] above. Curing conditions; The matrix resin is poured between two glass plates to form a 2 mm thick plate, which is then heated to an oven ambient temperature of 130°C at a rate of 2°C / min and maintained at 130°C for 120 minutes. [21a] The matrix resin composition cured under the following curing conditions has a strain energy release rate GIc of 0.7 kJ / m as measured by ASTM D5045: 2 The prepreg according to any one of [1a] to [20a] above. Curing conditions; The matrix resin is poured between two glass plates to form a 2 mm thick plate, which is then heated to an oven ambient temperature of 130°C at a rate of 2°C / min and maintained at 130°C for 120 minutes. [22a] A fiber-reinforced plastic obtained by curing the prepreg according to any one of [1a] to [21a]. [23a] A method for producing a prepreg, which comprises impregnating a carbon fiber substrate with a matrix resin composition containing the following components [A] to [D], and blending [B] so that the viscosity of the matrix resin composition at 70°C is 10 Pa s or more and the average double bond equivalent of [B] in the matrix resin composition is 150 g / eq or more. [A] Epoxy resin [B] (Meth)acrylic monomer [C] Hardener [D] Thermal radical polymerization initiator [24a] A method for producing a prepreg, comprising overlaying a film made of a matrix resin composition containing the following components [A] to [D] on a carbon fiber substrate and impregnating the film. [A] Epoxy resin [B] A (meth)acrylic monomer represented by the following structural formula (1): [C] Hardener [D] Thermal radical polymerization initiator

[0019] [ka]

[0020] (In formula (1), R represents a hydrogen atom or a methyl group, X represents an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, an aryl group which may have a halogen atom, an alicyclic structure, or a heterocyclic structure, and n represents an integer of 1 to 30.) [25a] The method for producing a prepreg according to [23a] or [24a], wherein the film is impregnated into a carbon fiber substrate at 50 to 110°C. [Effects of the Invention]

[0021] According to a preferred embodiment of the present invention, a prepreg can be provided which has improved toughness or elastic modulus after curing. DETAILED DESCRIPTION OF THE INVENTION

[0022] <Prepreg> One embodiment of the present invention relates to a prepreg. One aspect of the prepreg (also referred to as the "first prepreg of the present invention") comprises a matrix resin composition containing the following components [A] to [D] and carbon fibers, wherein the viscosity of the matrix resin at 70°C is 10 Pa s or more and the average double bond equivalent of [B] is 160 g / eq or more. [A] Epoxy resin [B] (Meth)acrylic monomer [C] Hardener [D] Thermal radical polymerization initiator

[0023] Another embodiment of the prepreg (also referred to as the "second prepreg of the present invention") comprises a matrix resin composition and carbon fibers, where the matrix resin composition comprises an epoxy resin and a (meth)acrylic monomer represented by the following structural formula (1): The matrix resin in the second prepreg of the present invention preferably further contains a curing agent, a radical polymerization initiator, and more preferably a thermal radical polymerization initiator.

[0024] [ka]

[0025] (In formula (1), R represents a hydrogen atom or a methyl group, X represents an aryl group which may have a substituent selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, and a halogen atom; an alicyclic structure; and a heterocyclic structure; and n represents an integer of 1 to 30.)

[0026] When a prepreg contains [A] an epoxy resin, [B] a (meth)acrylic monomer, [C] a curing agent, and [D] a thermal radical polymerization initiator (e.g., the first prepreg of the present invention), or when the prepreg further contains a curing agent and a radical polymerization initiator in addition to the epoxy resin and (meth)acrylic monomer (e.g., the second prepreg of the present invention further contains a curing agent and a radical polymerization initiator), heating the prepreg simultaneously causes the curing reaction between the epoxy resin and the curing agent and radical polymerization of the (meth)acrylic monomer by the radical polymerization initiator or thermal radical polymerization initiator. In other words, the matrix of a molded product formed from such a prepreg is composed of a cured epoxy resin and a (meth)acrylic polymer. Prepregs can be produced, for example, by applying a matrix resin to the surface of a substrate such as release paper to form a film, then layering the film on both sides or one side of a reinforcing fiber substrate and applying heat and pressure to impregnate the reinforcing fiber substrate with the resin. In this specification, the first prepreg of the present invention and the second prepreg of the present invention may be collectively referred to as "the prepreg of the present invention."

[0027] <Resin viscosity> If the viscosity of the matrix resin composition at 70°C is 10 Pa·s or higher, resin repellency does not occur on the substrate surface during film production, allowing for the production of a uniform film. In addition, the shape of the produced prepreg can be maintained, thereby suppressing cracking, excessive resin flow during molding, and variations in fiber content. From the perspective of processability, such as prepreg tack and drape, the viscosity of the matrix resin composition at 70°C is preferably 20 Pa·s or higher, more preferably 30 Pa·s or higher. To suppress blurring during the film formation process and reduce unimpregnated areas during the impregnation process of the reinforcing fiber substrate, the viscosity is preferably 200 Pa·s or lower, more preferably 150 Pa·s or lower. The above upper and lower limits can be arbitrarily combined. For example, a viscosity of 10 to 200 Pa·s is preferred, a viscosity of 20 to 200 Pa·s is more preferred, and a viscosity of 30 to 150 Pa·s is even more preferred. The viscosity referred to here refers to the complex viscosity η* obtained by placing an uncured matrix resin on a plate and measuring the temperature dependency under the following measurement conditions. Apparatus: Rheometer (Thermo Fisher Scientific, "HAAKE MARS 40") Plate used: 25φ parallel plate Plate gap: 0.5 mm Measurement frequency: 10rad / sec Measurement temperature: 30~130℃ Stress: 300Pa

[0028] <Average double bond equivalent> By setting the average double bond equivalent of the (meth)acrylic monomer to 150 g / eq or more, the toughening effect of the (meth)acrylic monomer polymer is highly exhibited, improving the toughness and impact resistance of the matrix resin and further the fiber-reinforced plastic. From the viewpoint of improving the toughness of the cured product, the average double bond equivalent of the (meth)acrylic monomer may be 160 g / eq or more, preferably 190 g / eq or more, and more preferably 250 g / eq or more. In particular, in the first prepreg of the present invention, the average double bond equivalent of the (meth)acrylic monomer is 160 g / eq or more. From the viewpoint of compatibility with the epoxy resin, the average double bond equivalent of the (meth)acrylic monomer [B] is preferably 1500 g / eq or less, more preferably 1000 g / eq or less. The above upper and lower limits can be arbitrarily combined. For example, 160 to 1500 g / eq is preferred, 190 to 1500 g / eq is more preferred, and 250 to 1000 g / eq is even more preferred. In the second prepreg of the present invention, the lower limit may be 150 g / eq in combination with the above upper limit. For example, 150 to 1500 g / eq is preferred, 160 to 1500 g / eq is more preferred, 190 to 1500 g / eq is even more preferred, and 250 to 1000 g / eq is particularly preferred. Here, the double bond equivalent can be calculated by the following formula. Double bond equivalent = molecular weight of (meth)acrylic monomer / number of double bonds in molecule Furthermore, when multiple (meth)acrylic monomers are used in combination, the average double bond equivalent can be calculated as follows. For example, the calculation method will be explained using an example in which three types of (meth)acrylic monomers are used in combination. When W1 parts by mass of (meth)acrylic monomer 1 with a double bond equivalent of E1 (g / eq), W2 parts by mass of (meth)acrylic monomer 2 with a double bond equivalent of E2 (g / eq), and W3 parts by mass of (meth)acrylic monomer 3 with a double bond equivalent of E3 (g / eq) are blended, the average double bond equivalent can be calculated using the following formula. The structure and content of the (meth)acrylic monomers in the matrix resin composition can be determined by chemical analysis methods such as NMR, gas chromatography, and liquid chromatography. Average double bond equivalent E=(W1+W2+W3) / (W1 / E1+W2 / E2+W3 / E3)

[0029] <Sea-island phase separation structure> The cured product of the matrix resin composition preferably has a sea-island phase-separated structure, with the cured product of the epoxy resin constituting the sea phase and the polymer of the (meth)acrylic monomer constituting the island phase. During the thermal curing process of the prepreg, the polymerization of the (meth)acrylic monomer proceeds simultaneously with the curing reaction of the epoxy resin in the matrix resin composition. During this process, the compatibility of the components decreases as the curing reaction of the epoxy resin and the polymerization reaction of the (meth)acrylic monomer proceed. As a result, phase separation between the cured product of the epoxy resin and the polymer of the (meth)acrylic monomer proceeds, and the phase-separated structure is maintained by gelation or curing of the system. In other words, the matrix resin composition of the prepreg is in a homogeneous, compatible state before the curing reaction, but reaction-induced phase separation occurs when the prepreg is thermally cured. By setting the average double bond equivalent of the (meth)acrylic monomer within the above range, reaction-induced phase separation during the thermal curing process of the matrix resin composition is strongly promoted, making it easier to produce a cured product in which the cured epoxy resin and the (meth)acrylic monomer polymer are clearly phase-separated. Furthermore, a cured product in which the cured epoxy resin constitutes a sea phase and the (meth)acrylic monomer polymer constitutes an island phase and this clearly separated phase state exhibits high toughness. The phase-separated structure can also be designed so that one of the phases has improved adhesion to fibers. The phase separation state of the cured product of the matrix resin composition can be confirmed, for example, by injecting the matrix resin between two glass plates to form a 2 mm-thick plate, heating the oven ambient temperature to 130°C at a rate of 2°C / min, and holding the cured product at 130°C for 120 minutes, and then observing the cross-section of the cured product using a transmission electron microscope (TEM) or scanning electron microscope (SEM). If necessary, electronic staining may be applied. Staining can be performed using conventional stains such as RuO4 or OsO4. If there are two or more domains with different contrast in an electron microscope image, it can be determined that a phase separation structure of two or more phases exists. From the viewpoint of forming an island-sea structure in fiber-reinforced plastics and exhibiting toughness, the plane strain fracture toughness K measured by ASTM D5045 of the cured product obtained under the above conditions was Ic is 1.6 MPa m 1 / 2 It is preferable that the pressure is 1.8 MPa m or more. 1 / 2 The strain energy release rate G of the cured product obtained under the above conditions, as measured by ASTM D5045, is more preferably equal to or greater than 100%. Ic is 0.7kJ / m 2 It is preferable that the pressure is 0.9 MPa m or more. 1 / 2 More preferably, it is equal to or greater than this.

[0030] <Epoxy resin> Examples of epoxy resins contained in the prepreg include bisphenol A epoxy resins, bisphenol F epoxy resins, epoxy resins having an oxazolidone ring skeleton, novolac epoxy resins, glycidylamine epoxy resins, and naphthalene epoxy resins. The matrix resin composition preferably contains at least one epoxy resin selected from the group consisting of bisphenol A epoxy resins, bisphenol F epoxy resins, and epoxy resins having an oxazolidone ring skeleton, as this increases the molecular weight between crosslinks of the cured epoxy resin and provides relatively high toughness. It is particularly preferred that the matrix resin composition contain at least one of bisphenol F epoxy resins or epoxy resins having an oxazolidone ring skeleton. Epoxy resins may be used in combination; combining multiple epoxy resins can produce prepregs with excellent handleability and fiber-reinforced plastics with excellent mechanical properties and heat resistance. The epoxy resins may be used alone or in combination of two or more.

[0031] <Molecular weight of epoxy resin> Epoxy resins have various skeletons and molecular weight distributions depending on the type. Depending on the molecular weight, they exhibit different properties, such as being liquid or solid at 25°C. Melt viscosity also varies greatly. While affected by the skeleton of the epoxy resin, epoxy resins with a molecular weight of 500 or less are liquid at 25°C, while those with a molecular weight of 500 or more can be semi-solid or solid at 25°C.

[0032] Among the epoxy resins, components having a molecular weight of 500 or more are preferably blended in an amount of 30% by mass or more relative to the total mass of the epoxy resins. The lower limit of the blending amount of the epoxy resin having a molecular weight of 500 or more is more preferably 35% by mass or more, and even more preferably 40% by mass or more. The upper limit of the blending amount of the epoxy resin having a molecular weight of 500 or more is more preferably 70% by mass or less, and even more preferably 60% by mass or less. The above upper and lower limits can be arbitrarily combined. For example, 30 to 70% by mass is preferred, 35 to 70% by mass is more preferred, and 40 to 60% by mass is even more preferred. When the blending amount of the epoxy resin having a molecular weight of 500 or more in the epoxy resin is equal to or greater than the lower limit, the viscosity at room temperature increases, imparting appropriate tackiness, thereby obtaining a prepreg with excellent handleability and also resulting in a cured product with excellent toughness. On the other hand, when the blending amount of the epoxy resin having a molecular weight of 500 or more is equal to or less than the upper limit, a prepreg with excellent drapeability (mold shape conformability) and a void-free fiber-reinforced plastic can be obtained.

[0033] Among epoxy resins, components having a molecular weight of 500 or less primarily contribute to improving the solubility of the thermoplastic resin and improving the strength, elastic modulus, and heat resistance of the cured resin. The amount of epoxy resin having a molecular weight of 500 or less is preferably 20% by mass or more relative to the total mass of the epoxy resins. The lower limit of the amount of epoxy resin having a molecular weight of 500 or less is more preferably 25% by mass or more, and even more preferably 30% by mass or more. The upper limit of the amount of epoxy resin having a molecular weight of 500 or less is preferably 80% by mass or less, more preferably 75% by mass or less, even more preferably 70% by mass or less, and particularly preferably 50% by mass or less. The above upper and lower limits can be arbitrarily combined. For example, 20 to 80% by mass is preferred, 20 to 75% by mass is more preferred, 25 to 70% by mass is even more preferred, and 30 to 50% by mass is particularly preferred. If the amount of epoxy resin having a molecular weight of 500 or less in the epoxy resin is equal to or greater than the lower limit, the thermoplastic resin is easily dissolved, resulting in excellent processability, and a cured resin product having excellent strength, elastic modulus, and heat resistance can be obtained. On the other hand, if the content of epoxy resin having a molecular weight of 500 or less is equal to or less than the upper limit, a prepreg having appropriate tackiness and excellent handleability can be obtained, and the cured product will have excellent toughness.

[0034] The weight-average molecular weight of the entire epoxy resin contained in the prepreg is preferably 1500 or more. If the weight-average molecular weight is 1500 or more, a prepreg with excellent handleability can be obtained by imparting appropriate tackiness, and the cured product tends to have excellent toughness. The weight-average molecular weight is more preferably 2000 or more.

[0035] The molecular weight can be measured by gel permeation chromatography (GPC) under the following conditions, and calculated as a value converted into standard polystyrene. Equipment: Tosoh Corporation high-speed GPC equipment HLC-8320GPC model UV detector: Tosoh UV-8320 Flow rate: 0.35mL / min Inlet temperature: 40℃ Oven temperature: 40°C RI temperature: 40℃ UV wavelength: 254nm Sample injection volume: 10 μL Columns: Three columns connected in the order of (1) to (3). (1) Tosoh TSKgel superHZM-M (4.6mm ID x 15cm L) (2) Tosoh TSKgel superHZM-M (4.6mm ID x 15cm L) (3) Tosoh TSKgel HZ2000 (4.6mm ID x 15cm L) Guard column: Tosoh TSKguardcolumn SuperHZ-L (4.6 mm ID x 3.5 cm L) Solvent: THF (stabilizer: BHT) Sample concentration: Resin content adjusted to 0.05% by mass

[0036] <Average epoxy equivalent> The average epoxy equivalent of the entire epoxy resin contained in the prepreg is preferably 200 g / eq or more. If the average epoxy equivalent is 200 g / eq or more, the molecular weight between crosslink points of the cured resin product will be large, and the cured product will have excellent toughness. The average epoxy equivalent is more preferably 220 g / eq or more, and even more preferably 250 g / eq or more. When multiple epoxy resins are used in combination, the average epoxy equivalent can be calculated as follows. For example, the calculation method will be explained using an example where three types of epoxy resins are used in combination. When mixing W1 parts by mass of epoxy resin 1 with an epoxy equivalent of E1 (g / eq), W2 parts by mass of epoxy resin 2 with an epoxy equivalent of E2 (g / eq), and W3 parts by mass of epoxy resin 3 with an epoxy equivalent of E3 (g / eq), the average epoxy equivalent can be calculated using the following formula. Average epoxy equivalent weight = (W1 + W2 + W3) / (W1 / E1 + W2 / E2 + W3 / E3)

[0037] Commercially available bisphenol A epoxy resins having a main component with a molecular weight of 500 or less and being liquid at 25°C include jER827 and jER828 (both manufactured by Mitsubishi Chemical Corporation), YD-127 and YD-128 (both manufactured by Nippon Steel Chemical & Material Co., Ltd.), EPICLON840 and EPICLON850 (both manufactured by DIC Corporation), and DER331 and DER332 (both manufactured by The Dow Chemical Company). Commercially available bisphenol F epoxy resins having a main component with a molecular weight of 500 or less and being liquid at 25°C include jER806 and jER807 (manufactured by Mitsubishi Chemical Corporation), YDF-170 (manufactured by Nippon Steel Chemical & Material Co., Ltd.), EPICLON830 and EPICLON835 (manufactured by DIC Corporation), and DER354 (manufactured by The Dow Chemical Company). Commercially available glycidyl amine epoxy resins whose main component has a molecular weight of 500 or less and are liquid at 25°C include jER630 and jER604 (both manufactured by Mitsubishi Chemical Corporation), Sumiepoxy ELM-100 and ELM-434 (both manufactured by Sumitomo Chemical Co., Ltd.), YH-404, YH-513 and YH-514 (both manufactured by Nippon Steel Chemical & Material Co., Ltd.), and Araldite MY0500, MY0510, MY0600, MY0610, MY720 and MY721 (all manufactured by Huntsman Advanced Materials).

[0038] Commercially available bisphenol A epoxy resins having a main component with a molecular weight of 500 or more and which are semi-solid or solid at 25°C include jER1001, jER1002, jER1004, jER1007, and jER1009 (all manufactured by Mitsubishi Chemical Corporation), EPICLON2050, EPICLON3050, EPICLON4050, and EPICLON7050 (all manufactured by DIC Corporation), and YD-011, YD-012, YD-013, YD-014, YD-902, YD-903N, YD-904, YD-907, YD-7910, and YD-6020 (all manufactured by Nippon Steel Chemical & Material Co., Ltd.). Examples of bisphenol F epoxy resins having a main component with a molecular weight of 500 or more and being semi-solid or solid at 25°C include jER4004P, jER4005P, jER4007P, and jER4010P (all manufactured by Mitsubishi Chemical Corporation) and YDF-2001, YDF-2004, and YDF-2005RD (all manufactured by Nippon Steel Chemical & Material Co., Ltd.). Examples of epoxy resins having an oxazolidone ring skeleton whose main component has a molecular weight of 500 or more and is semi-solid or solid at 25°C include ACR1348 (manufactured by ADEKA CORPORATION), DER852, DER858 (all manufactured by The Dow Chemical Company), TSR-400 (manufactured by DIC Corporation), and YD-952 (manufactured by Nippon Steel Chemical & Material Co., Ltd.).

[0039] Other commercially available epoxy resins that can be contained in the prepreg include, for example, phenol novolac epoxy resins such as jER152 and jER154 (manufactured by Mitsubishi Chemical Corporation), EPICLON N-740, EPICLON N-770, and EPICLON N-775 (manufactured by DIC Corporation), and YDPN-638 (manufactured by Nippon Steel Chemical & Material Co., Ltd.); Cresol novolac epoxy resins such as EPICLON N-660, EPICLON N-670, EPICLON N-680, and EPICLON N-690 (all manufactured by DIC Corporation); bisphenol A novolac epoxy resins such as jER157S70 (manufactured by Mitsubishi Chemical Corporation), EPICLON N-865, and EPICLON N-885 (all manufactured by DIC Corporation); biphenylaralkyl epoxy resins such as NC-3000-L, NC-3000, and NC-3000-H (all manufactured by Nippon Kayaku Co., Ltd.); Naphthalene-type epoxy resins such as EPICLON HP-4700, EPICLON HP-4710, EPICLON HP-4770 (all manufactured by DIC Corporation), NC-7000L, NC-7300L (all manufactured by Nippon Kayaku Co., Ltd.) can be used. One of these may be used alone, or two or more may be used in combination.

[0040] <(Meth)acrylic monomer> The (meth)acrylic monomer contained in the prepreg contributes to improving the elastic modulus and toughness of the cured product. Examples of (meth)acrylic monomers include monofunctional (meth)acrylic monomers and difunctional or higher functional (meth)acrylic monomers (also called "polyfunctional (meth)acrylic monomers"). In order to achieve a balance between the elastic modulus and toughness of the cured product, one of these may be used alone, or two or more may be used in combination. As described above, the cured product of the matrix resin composition of the prepreg preferably has a sea-island phase-separated structure, with the cured epoxy resin constituting the sea phase and the polymer of the (meth)acrylic monomer constituting the island phase. To form the sea-island structure, the (meth)acrylic monomer is preferably contained in an amount of 5 parts by mass or more, more preferably 10 parts by mass or more, per 100 parts by mass of the total epoxy resin. The (meth)acrylic monomer is preferably contained in an amount of 45 parts by mass or less, more preferably 40 parts by mass or less, per 100 parts by mass of the total epoxy resin. The above upper and lower limits can be arbitrarily combined. For example, 5 to 45 parts by mass is preferred, and 10 to 40 parts by mass is more preferred. Having the (meth)acrylic monomer content within this range facilitates the formation of a sea-island structure in which the polymer of the (meth)acrylic monomer constitutes the island phase, resulting in a good balance of elastic modulus, toughness, and heat resistance. The content of the (meth)acrylic monomer in the case of a prepreg can be determined by a separation analysis method such as gas chromatography or liquid chromatography, and in the case of a cured product, it can be determined by pyrolysis gas chromatography.

[0041] <Molecular weight of (meth)acrylic monomer> From the viewpoint of ease of handling, it is preferable that a (meth)acrylic monomer having a molecular weight of 190 or more is contained. The molecular weight of the (meth)acrylic monomer is preferably 190 or more, more preferably 220 or more. If the molecular weight of the (meth)acrylic monomer is 190 or more, volatilization of the (meth)acrylic monomer can be suppressed, and the preparation temperature when preparing the resin composition and the impregnation temperature when producing the prepreg can be sufficiently increased, thereby enabling products of consistent quality to be obtained. From the viewpoint of uniform dispersion in the resin composition, the molecular weight is preferably 1500 or less, more preferably 1000 or less. The above upper and lower limits can be arbitrarily combined. For example, 190 to 1500 is preferable, and 220 to 1000 is more preferable.

[0042] <Monofunctional (meth)acrylic monomer content> The prepreg may contain 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more of the monofunctional (meth)acrylic monomer relative to the total mass of the (meth)acrylic monomers contained in the prepreg. The prepreg preferably contains 70% by mass or more of the monofunctional (meth)acrylic monomer relative to the total mass of the (meth)acrylic monomers contained in the prepreg. When the content of the monofunctional (meth)acrylic monomer is within this range, phase separation between the cured epoxy resin and the polymer of the (meth)acrylic monomer proceeds strongly, tending to facilitate the formation of a distinct sea-island phase-separated structure. The reason for this is thought to be as follows: During the thermal curing process of the prepreg, as the curing reaction of the epoxy resin and the polymerization reaction of the (meth)acrylic monomer proceed, their mutual compatibility decreases. During this process, the polymer of the monofunctional (meth)acrylic monomer does not form a crosslinked structure and has high mobility, so phase separation between the cured epoxy resin and the polymer of the (meth)acrylic monomer proceeds quickly, and curing is thought to be complete after sufficient phase separation has progressed. If the sea-island phase separation structure is clear, the island phases composed of polymers of (meth)acrylic monomers tend to exert a strong toughness-imparting effect. To obtain a clear sea-island phase separation structure, the monofunctional (meth)acrylic monomer is contained in an amount of more than 75 mass%, and particularly preferably 80 mass% or more, based on the total mass of (meth)acrylic monomers. The monofunctional (meth)acrylic monomer may be contained in an amount of 99 mass% or less, or even 95 mass% or less, based on the total mass of (meth)acrylic monomers. 100 mass% may be monofunctional (meth)acrylic monomers.

[0043] <Types of (meth)acrylic monomers> As the (meth)acrylic monomer, a (meth)acrylic monomer represented by the following structural formula (1) is preferred from the viewpoint of the elastic modulus and toughness of the cured product. In particular, the (meth)acrylic monomer in the matrix resin composition contained in the second prepreg of the present invention is a (meth)acrylic monomer represented by the following structural formula (1).

[0044] [ka]

[0045] (In formula (1), R represents a hydrogen atom or a methyl group, X represents an aryl group which may have a substituent selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, and a halogen atom; an alicyclic structure; and a heterocyclic structure; and n represents an integer of 1 to 30.)

[0046] The (meth)acrylic monomer represented by formula (1) has an ethylene glycol moiety and a cyclic structure as X in its molecular structure, and thus the cured product has a good balance between elastic modulus and toughness. In the matrix resin composition contained in the first prepreg of the present invention, the (meth)acrylic monomer [B] is preferably a (meth)acrylic monomer having one or more oxyethylene groups in the molecule, as this can reduce the volatility of the monomer and improve the toughness of the cured resin. Furthermore, in the matrix resin composition contained in the first prepreg of the present invention, the (meth)acrylic monomer [B] preferably has one or more cyclic skeletons in the molecule, as this can reduce the volatility of the monomer and improve the toughness of the cured resin. Specifically, in the matrix resin composition contained in the first prepreg of the present invention, the (meth)acrylic monomer [B] preferably includes a (meth)acrylic monomer represented by formula (1), and more preferably is a (meth)acrylic monomer represented by formula (1).

[0047] From the viewpoint of achieving both elastic modulus and toughness of the cured product, in formula (1), it is preferable that R is a hydrogen atom, X is an aryl group which may have an aliphatic hydrocarbon group having 1 to 10 carbon atoms or an alicyclic structure, and n is an integer of 1 to 10; more preferably, R is a hydrogen atom, X is a phenyl group which may have an aliphatic hydrocarbon group having 1 to 10 carbon atoms, and n is an integer of 1 to 10. The aryl group for X in formula (1) which may have a substituent selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, and a halogen atom is preferably an aryl group which has a substituent selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, and a halogen atom. In formula (1), n ​​is preferably 2 to 30, more preferably 2 to 20, and even more preferably 2 to 10. In another embodiment, n in formula (1) is preferably 1 to 10.

[0048] Examples of the aryl group include a phenyl group, a naphthyl group, an acenaphthylene group, an acenaphthene group, an anthracene group, a phenanthrene group, a tetracene group, a fluorene group, a fluoranthene group, a pyrene group, a benzo(a)anthracene group, and a chrysene group. From the viewpoints of solubility in epoxy resins and availability, a phenyl group and a naphthyl group are preferred, and a phenyl group is more preferred.

[0049] Examples of alicyclic structures include monocyclic cycloalkanes such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, cycloundecane, and cyclododecane, and derivatives thereof (including those substituted with one or more groups selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, a halogen atom, and an aryl group, as described below; if applicable, those in which some or all of the unsaturated bonds have been saturated; and, if applicable, those in which the heteroatom has been oxidized). Hereinafter, this In the preceding paragraphs, "derivatives" have the same meaning; monocyclic cycloalkenes and derivatives thereof, such as cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, and cyclooctene; bicyclic cycloalkanes and derivatives thereof, such as norbornane, bicycloundecane, and decahydronaphthalene; bicyclic cycloalkenes and derivatives thereof, such as norbornene, norbornadiene, and azulene; and polycyclic alicyclic structures and derivatives thereof, such as cubane, basketane, hausane, adamantane, tricyclodecane, and dicyclopentadiene. From the viewpoint of achieving a high elastic modulus and low moisture absorption rate in the cured product of the matrix resin composition, polycyclic alicyclic structures and derivatives thereof are preferred, dicyclopentadiene and derivatives thereof are more preferred, and dicyclopentadiene and tetrahydrodicyclopentadiene are even more preferred.

[0050] Examples of heterocyclic structures include monocyclic nitrogen-containing heterocyclic structures such as pyrrolidine, pyrrole, piperidine, piperazine, pyridine, hexaethyleneimine, azatropylidene, imidazole, pyrazole, imidazoline, triazole, tetrazole, pyridazine, pyrimidine, pyridazine, pyrazine, and triazine; bicyclic nitrogen-containing heterocyclic structures such as indole, isoindole, benzimidazole, purine, benzotriazole, quinoline, isoquinoline, quinazoline, quinoxaline, cinnoline, and pteridine; and carbazole, acridine, naphthazine, phenazine, benzo-C-cinnoline, porphyrin, and chlorine. Examples of heterocyclic structures include polycyclic nitrogen-containing heterocyclic structures such as oxirane, oxetane, tetrahydrofuran, furan, furanone, pyrrolidone, tetrahydropyran, pyran, oxazole, isoxazole, cyclohexane oxide, dioxane, morpholine, oxazine, oxazolidone, caprolactone, and caprolactam; bicyclic oxygen-containing heterocyclic structures such as coumarin, chromone, benzofuran, chromene, and isochromene; and monocyclic sulfur-containing heterocyclic structures such as tetrahydrothiophene, thiophene, tetrahydrothiopyran, thiopyran, thiazole, and isothiazole. Oxygen-containing heterocyclic structures are preferred because they have excellent solubility with epoxy resins and do not react with epoxy resins, resulting in matrix resin compositions with excellent pot life, and oxirane, oxetane, tetrahydrofuran, and dioxane are more preferred. The heterocyclic structure may be substituted with one or more groups selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, a halogen atom, and an aryl group.

[0051] Examples of the aliphatic hydrocarbon group having 1 to 10 carbon atoms include straight-chain aliphatic hydrocarbon groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, and decyl; and branched-chain aliphatic hydrocarbon groups such as isopropyl, isobutyl, sec-butyl, tert-butyl, isopentyl, neopentyl, tert-pentyl, and isohexyl. Nonyl and octyl groups are preferred, with nonyl being more preferred, as these facilitate phase separation of the polymer from the cured epoxy resin.

[0052] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine. From the viewpoint of stability of the (meth)acrylic monomer, fluorine and chlorine are preferred, and fluorine is more preferred.

[0053] Examples of the (meth)acrylic monomer represented by formula (1) include phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, nonylphenoxypolyethylene glycol (meth)acrylate, cyclopentyloxyethyl (meth)acrylate, cyclohexyloxyethyl (meth)acrylate, 2-cyclohexen-1-yloxyethyl (meth)acrylate, 1-cyclohexen-1-yloxyethyl (meth)acrylate, tetrahydro-2-furan ... oxyethyl (meth)acrylate, 2-tetrahydropyranyloxyethyl (meth)acrylate, 1,4-dioxan-2-yloxyethyl (meth)acrylate, 1,3-dioxan-2-yloxyethyl (meth)acrylate, 2-naphthoxyethyl (meth)acrylate, 1-naphthoxyethyl (meth)acrylate, 9-anthracenyloxyethyl (meth)acrylate, 1H-imidazol-1-yloxyethyl (meth)acrylate, 4-pyridazinyloxyethyl (meth)acrylate, 1-pyrenyloxyethyl (meth)acrylate, and compounds having an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, or a halogen atom added to the terminal of these. In particular, the (meth)acrylic monomer in the matrix resin contained in the second prepreg of the present invention may contain (meth)acrylic monomers having other structures in addition to the (meth)acrylic monomer represented by formula (1).

[0054] Examples of monofunctional (meth)acrylic monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 4-hydroxybenzyl (meth)acrylate, 4-hydroxyphenyl (meth)acrylate, cyclohexanedimethanol mono(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, phenoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate, 2-(meth)acryloyloxymethyl-2-methylbicycloheptane, adamantyl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, tetracyclododecanyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, icosyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, methoxytriethylene glycol (meth)acrylate, butoxyethyl (meth)acrylate, methoxydipropylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, polyethylene glycol monomethyl ether (meth)acrylate, polypropylene glycol monomethyl (meth)acrylate, 4-acryloyloxymethyl-2-methyl-2-ethyl-1,3-dioxolane, 4-acryloyloxymethyl-2-methyl-2-isobutyl-1,(Meth)acrylic acid esters such as 3-dioxolane, o-phenylphenol (meth)acrylate, ethoxylated o-phenylphenol (meth)acrylate, N-(meth)acryloyloxyethyl hexahydrophthalimide, para-cumylphenol (meth)acrylate, ethoxylated para-cumylphenol (meth)acrylate, and trimethylolpropane formal (meth)acrylate; and (meth)acrylamides such as acrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N-methylolacrylamide, N-methoxymethylacrylamide, N-butoxymethylacrylamide, Nt-butylacrylamide, N-benzyl(meth)acrylamide, N-phenyl(meth)acrylamide, N-(4-hydroxybenzyl)(meth)acrylamide, N-(4-hydroxyphenyl)(meth)acrylamide, acryloylmorpholine, hydroxyethylacrylamide, and methylenebisacrylamide. Monofunctional (meth)acrylic monomers having one or more oxyethylene groups in the molecule or monofunctional (meth)acrylic monomers having one or more cyclic skeletons in the molecule are preferred, as they can reduce the volatility of the monomer and improve the toughness of the cured resin. Monofunctional (meth)acrylic monomers having one or more oxyethylene groups and one or more cyclic skeletons in the molecule are more preferred.

[0055] Examples of bifunctional (meth)acrylic monomers include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, 1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 2-methyl Examples of suitable diols include 1,8-octanediol, 1,10-decanediol, neopentyl glycol hydroxypivalate, tricyclodecane dimethanol, cyclohexane dimethanol, bisphenol A, hydrogenated bisphenol A, bisphenol F, dioxane glycol, and bisphenoxyfluorene ethanol, as well as di(meth)acrylates obtained by esterifying diols obtained by adding ethylene oxide, propylene oxide, or caprolactone to these diols with (meth)acrylic acid. Bifunctional (meth)acrylic monomers having one or more oxyethylene groups in the molecule or bifunctional (meth)acrylic monomers having one or more cyclic skeletons in the molecule are preferred, as they can achieve a high balance of elastic modulus, strength, and toughness in the cured resin. Bifunctional (meth)acrylic monomers having one or more oxyethylene groups and one or more cyclic skeletons in the molecule are more preferred.

[0056] Examples of trifunctional (meth)acrylic monomers include triols and tetraols such as trimethylolpropane, tris(2-hydroxyethyl)isocyanurate, glycerol, and pentaerythritol, as well as tri(meth)acrylates obtained by esterifying triols or tetraols obtained by adding ethylene oxide, propylene oxide, caprolactone, or the like to these triols or tetraols with (meth)acrylic acid. Because they can achieve a high balance between the elastic modulus, strength, and toughness of the cured resin, trifunctional (meth)acrylic monomers having one or more oxyethylene groups in the molecule or trifunctional (meth)acrylic monomers having one or more cyclic skeletons in the molecule are preferred, and trifunctional (meth)acrylic monomers having one or more oxyethylene groups and one or more cyclic skeletons in the molecule are more preferred.

[0057] Examples of tetrafunctional or higher (meth)acrylic monomers include tetrafunctional or higher polyols such as ditrimethylolpropane, pentaerythritol, dipentaerythritol, and tripentaerythritol, as well as poly(meth)acrylates obtained by esterifying polyols obtained by adding ethylene oxide, propylene oxide, or caprolactone to these polyols with (meth)acrylic acid. Because they can achieve a high balance of elastic modulus, strength, and toughness in the cured resin, tetrafunctional or higher (meth)acrylic monomers having one or more oxyethylene groups in the molecule or tetrafunctional or higher (meth)acrylic monomers having one or more cyclic skeletons in the molecule are preferred, and tetrafunctional or higher (meth)acrylic monomers having one or more oxyethylene groups and one or more cyclic skeletons in the molecule are more preferred.

[0058] The matrix resin composition contained in the prepreg may contain an oligomer or prepolymer having a radically polymerizable double bond. Specific examples include macromonomers, acrylic acrylates, epoxy acrylates, urethane acrylates, and polyester acrylates. These may be used alone or in combination of two or more.

[0059] The glass transition temperature (TgA) of the polymer of the (meth)acrylic monomer contained in the matrix resin composition of the prepreg is preferably equal to or lower than the glass transition temperature (TgE) of the cured epoxy resin contained in the matrix resin composition of the prepreg, as this enhances its toughness. The TgA can be set to 25°C or lower. The formation of a sea-island phase-separated structure, consisting of a sea phase made of the cured epoxy resin with a high glass transition temperature and an island phase made of the polymer of the (meth)acrylic monomer with a low glass transition temperature, enables both high elastic modulus and high toughness. The improved toughness of the sea-island phase-separated structure is achieved when a crack reaches the dispersed island phases through (a) cavitation due to stress concentration in the island phases, (b) release of strain constraints and relaxation of stress concentration due to cavitation, (c) induction of shear deformation of the resin due to cavitation, (d) energy absorption due to deformation of the island phases themselves, and (e) crack growth inhibition by the island phases. These effects are efficiently exhibited by the island phase having a lower glass transition temperature than the sea phase and a lower strength.

[0060] <Curing agent> The first prepreg of the present invention contains a curing agent, and the second prepreg of the present invention may contain a curing agent. As the curing agent contained in the prepreg, for example, in addition to amine-based curing agents such as dicyandiamide, aliphatic amines, alicyclic amines, aromatic amines, ureas, and imidazoles, acid anhydrides, phenols, and boron chloride amine complexes are preferred, and dicyandiamide, aromatic amines, ureas, and imidazoles are more preferred. These curing agents may be used alone or in combination of two or more.

[0061] When the prepreg contains a curing agent, the total content of the curing agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more, per 100 parts by mass of all epoxy resins contained in the matrix resin, in order to sufficiently promote curing of the epoxy resin. From the viewpoint of storage stability of the resin composition, the content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, per 100 parts by mass of all epoxy resins. The above upper and lower limits can be arbitrarily combined. For example, 1 to 60 parts by mass is preferred, and 2 to 50 parts by mass is more preferred.

[0062] Dicyandiamide has a melting point of approximately 210°C, so it is not compatible with epoxy resins at low temperatures, and when used as a curing agent, it provides a resin composition with an excellent pot life. Commercially available dicyandiamide products include, for example, DICY7 and DICY15 (both manufactured by Mitsubishi Chemical Corporation) and DICYANEX1400F (manufactured by Evonik Japan Co., Ltd.). When the prepreg contains a curing agent, and dicyandiamide is used as the curing agent, the content of dicyandiamide is preferably 1 to 15 parts by mass, and more preferably 2 to 10 parts by mass, per 100 parts by mass of all epoxy resins contained in the matrix resin composition. Since the heat resistance and mechanical properties of the cured resin tend to be better, the number of moles of active hydrogen in dicyandiamide is preferably 0.4 to 1 times, and more preferably 0.5 to 0.8 times, the total number of moles of epoxy groups in the epoxy resins contained in the matrix resin composition.

[0063] Examples of aromatic amines include 3,3'-diisopropyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-4,4'-diaminodiphenylmethane, 3,3'-diethyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-diisopropyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetraethyl-4,4'-diaminodiphenylmethane, 3,3'-diisopropyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, 3,3'-di-t- Examples of suitable cured products include butyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetraisopropyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-diisopropyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetra-t-butyl-4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 4,4'-methylene-bis[2-isopropyl-6-methylaniline], m-phenylenediamine, m-xylylenediamine, and diethyltoluenediamine. 4,4'-Diaminodiphenylsulfone and 3,3'-diaminodiphenylsulfone are preferred because they provide cured products with excellent heat resistance and mechanical properties, and exhibit little decrease in heat resistance due to linear expansion coefficient and moisture absorption. 4,4'-Diaminodiphenyl sulfone is preferred because it can maintain the tack life of the prepreg for a long period of time. 3,3'-Diaminodiphenyl sulfone is preferred because it can increase the elastic modulus and toughness of the cured product. 4,4'-Diaminodiphenyl sulfone and 3,3'-Diaminodiphenyl sulfone may be blended together.

[0064] When the prepreg contains a curing agent, and the curing agent is an aromatic amine, the content of the aromatic amine is preferably 1 to 60 parts by mass, more preferably 2 to 50 parts by mass, per 100 parts by mass of the total epoxy resin contained in the matrix resin composition. When the content of the aromatic amine is 1 part by mass or more, the heat resistance and elastic modulus tend to be excellent. When the content of the aromatic amine is 60 parts by mass or less, the toughness tends to be excellent. The active hydrogen equivalent number of the amino group is preferably 0.5 to 1.5 times, more preferably 0.6 to 1.4 times, the epoxy equivalent number of the total epoxy resin contained in the matrix resin composition. By blending these epoxy resin curing agents so that the active hydrogen equivalent number of the amino group is 0.5 to 1.5 times the epoxy equivalent number of the total epoxy resin, the elastic modulus, toughness, and heat resistance of the cured resin tend to be within good ranges.

[0065] Among aromatic amines, commercially available products of 4,4'-diaminodiphenyl sulfone include, for example, Seikacure S (active hydrogen equivalent 62 g / eq, manufactured by Wakayama Seika Kogyo Co., Ltd.) and Sumicure S (active hydrogen equivalent 62 g / eq, manufactured by Sumitomo Chemical Co., Ltd.). Commercially available products of 3,3'-diaminodiphenyl sulfone include, for example, 3,3'-DAS (active hydrogen equivalent 62 g / eq, manufactured by Mitsui Fine Chemicals, Inc.). Other aromatic amines include, for example, MDA-220 (active hydrogen equivalent 50 g / eq, manufactured by Mitsui Chemicals, Inc.), jER Cure W (active hydrogen equivalent 45 g / eq, manufactured by Mitsubishi Chemical Corporation), Lonzacure M-DEA (active hydrogen equivalent 78 g / eq), Lonzacure M-DIPA (active hydrogen equivalent 92 g / eq), Lonzacure M-MIPA (active hydrogen equivalent 78 g / eq), and Lonzacure DETDA 80 (active hydrogen equivalent 45 g / eq) (all manufactured by Lonza Corporation).

[0066] Ureas have a dimethylureido group in the molecule, and when heated at high temperatures, they produce an isocyanate group and dimethylamine, activating the epoxy group. Examples of ureas include aromatic dimethylurea, in which the dimethylureido group is bonded to an aromatic ring, and aliphatic dimethylurea, in which the dimethylureido group is bonded to an aliphatic compound. Aromatic dimethylurea is preferred because it tends to increase the heat resistance and bending strength of the cured product.

[0067] When the prepreg contains a curing agent, and the curing agent contains ureas, the content of the ureas is preferably 1 to 15 parts by mass, more preferably 1 to 10 parts by mass, per 100 parts by mass of the total epoxy resin contained in the matrix resin composition. If the content of the ureas is 1 part by mass or more, the curing of the epoxy resin contained in the matrix resin composition is promoted, and the mechanical properties and heat resistance of the cured product tend to be improved. If the content of the ureas is 15 parts by mass or less, the heat resistance and toughness of the cured resin tend to be maintained at a high level.

[0068] Suitable examples of aromatic dimethylureas include phenyldimethylurea, methylenebis(phenyldimethylurea), and tolylenebis(dimethylurea), such as 4,4'-methylenebis(phenyldimethylurea) (MBPDMU), 3-phenyl-1,1-dimethylurea (PDMU), 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 3-(3-chloro-4-methylphenyl)-1,1-dimethylurea, 2,4-bis(3,3-dimethylureido)toluene (TBDMU), and dimethylurea obtained from m-xylylene diisocyanate and dimethylamine. MBPDMU, PDMU, DCMU, and TBDMU are more preferred in terms of their ability to accelerate curing and impart heat resistance to the cured resin. Examples of the aliphatic dimethylurea include dimethylurea obtained from isophorone diisocyanate and dimethylamine, and dimethylurea obtained from hexamethylene diisocyanate and dimethylamine.

[0069] Commercially available ureas include, for example, DCMU, DCMU-99 (manufactured by Hodogaya Chemical Co., Ltd.); MBPDMU, Technicure MDU-11 (manufactured by A&C Catalysts) and Omicure 52 (manufactured by PTI Japan); PDMU, Omicure 94 (manufactured by PTI Japan); TBDMU, Omicure 24 (manufactured by PTI Japan) and U-CAT 3512T (manufactured by San-Apro Co., Ltd.); and aliphatic dimethylurea, U-CAT 3513N (manufactured by San-Apro Co., Ltd.).

[0070] Imidazoles have a nitrogen atom with an unshared electron pair in their structure, which can activate the epoxy group and promote curing. Examples of imidazoles that can be used include imidazole, imidazole adduct, clathrate imidazole, microencapsulated imidazole, and imidazole compounds coordinated with a stabilizer.

[0071] When the prepreg contains a curing agent, and the curing agent is an imidazole, the content of the imidazole is preferably 1 to 15 parts by mass, more preferably 1 to 10 parts by mass, per 100 parts by mass of the total epoxy resin contained in the matrix resin composition. When the content of the imidazole is 1 part by mass or more, the curing and curing acceleration action of the epoxy resin contained in the matrix resin composition and heat resistance tend to be sufficient. When the content of the imidazole is 15 parts by mass or less, a cured resin with better mechanical properties tends to be obtained.

[0072] Examples of imidazoles include 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazolium trimellitate, 1-cyanoethyl-2-undecylimidazole, and 1-cyanoethyl-2-phenylimidazolium trimellitate. Tate, 2,4-diamino-6-(2'-methylimidazolyl-(1'))-ethyl-s-triazine, 2,4-diamino-6-(2'-undecylimidazolyl-(1'))-ethyl-s-triazine, 2,4-diamino-6-(2'-ethyl-4-methylimidazolyl-(1'))-ethyl-s-triazine, 2,4-diamino-6-(2'-methylimidazolyl-(1'))-ethyl Examples include ethyl-s-triazine-isocyanuric acid adduct, 2-phenylimidazole-isocyanuric acid adduct, 2-methylimidazole-isocyanuric acid adduct, 1-cyanoethyl-2-phenyl-4,5-di(2-cyanoethoxy)methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole. Imidazoles that have been modified by adducting, encapsulating, microencapsulating, or incorporating stabilizers are examples of imidazoles that have been modified. Modification reduces activity, allowing for accelerated cure at low temperatures while maintaining excellent pot life.

[0073] Commercially available imidazole products include, for example, 2E4MZ, 2P4MZ, 2PZ-CN, C11Z-CNS, C11Z-A, 2MZA-PW, 2MAOK-PW, 2P4MHZ-PW, and 2PHZ-PW (all manufactured by Shikoku Chemicals Corporation). Commercially available imidazole adducts include, for example, PN-50, PN-50J, PN-40, PN-40J, PN-31, PN-23, and PN-H (all manufactured by Ajinomoto Fine-Techno Co., Ltd.), which have a structure in which an imidazole compound is added to the epoxy group of an epoxy resin by ring-opening addition. Commercially available clathrate imidazole products include, for example, TIC-188, KM-188, HIPA-2P4MHZ, NIPA-2P4MHZ, TEP-2E4MZ, HIPA-2E4MZ, and NIPA-2E4MZ (all manufactured by Nippon Soda Co., Ltd.). Commercially available microcapsule-type imidazole products include, for example, Novacure HX3721, Novacure HX3722, Novacure HX3742, and Novacure HX3748 (all manufactured by Asahi Kasei E-Materials Corporation); and LC-80 (manufactured by A&C Catalysts). An imidazole compound coordinated with a stabilizer can be prepared, for example, by combining Cureduct P-0505 (bisphenol A diglycidyl ether / 2-ethyl-4-methylimidazole adduct), an imidazole adduct manufactured by Shikoku Chemical Industry Co., Ltd., with L-07N (epoxy-phenol-boric acid ester blend), a stabilizer manufactured by Shikoku Chemical Industry Co., Ltd. Similar effects can be obtained by using an imidazole compound such as any of the above-mentioned imidazoles or imidazole adducts instead of Cureduct P-0505.

[0074] Examples of acid anhydrides include hydrogenated methylnadic anhydride and methylhexahydrophthalic anhydride.

[0075] <Melting point of hardener> When the prepreg contains a curing agent, the curing agent preferably contains a component having a melting point of 70°C or higher (hereinafter also referred to as "curing agent C1"). When curing agent C1 is contained as the curing agent, the curing agent C1 is preferably contained in an amount of 50 mass% or more, and more preferably 70 mass% or more, based on the total mass of the curing agent. By ensuring that the melting point of curing agent C1 is within this range, or by ensuring that the content of curing agent C1 is within this range, it is possible to prevent the epoxy resin and the curing agent from becoming miscible with each other at low temperatures and to prevent the epoxy resin and the curing agent from reacting immediately with each other, thereby enabling a matrix resin composition with a long pot life to be obtained, and a prepreg with a long usable life to be obtained.

[0076] Examples of the curing agent C1 include dicyandiamide (melting point 208°C), 4,4'-diaminodiphenyl sulfone (melting point 175°C), 3,3'-diaminodiphenyl sulfone (melting point 170°C), 4,4'-methylene-bis[2-isopropyl-6-methylaniline] (melting point 72°C), 4,4'-methylenebis(phenyldimethylurea) (melting point 216°C), 3-phenyl-1,1-dimethylurea (melting point 126°C), 3-(3,4-dichlorophenyl)-1,1-dimethylurea (melting point 159°C), 2,4-bis(3,3-dimethylurea) 2,4-Diamino-6-(2'-ethyl-4-methylimidazolyl-(1'))-ethyl-s-triazine (melting point 248°C), 2,4-Diamino-6-(2'-methylimidazolyl-(1'))-ethyl-s-triazine·isocyanuric acid adduct (melting point 260°C or higher), 2-phenyl-4,5-dihydroxymethylimidazole (melting point 230°C or higher), 2-phenyl-4-methyl-5-hydroxymethylimidazole (melting point 191°C).

[0077] <Radical polymerization initiator> The first prepreg of the present invention contains a thermal radical polymerization initiator. The second prepreg of the present invention may contain a radical polymerization initiator, preferably a thermal radical polymerization initiator. Radical polymerization initiators include thermal radical polymerization initiators that are activated by heat and photoradical polymerization initiators that are activated by light irradiation. It is preferable to use a thermal radical polymerization initiator because it can generate radicals simultaneously with the thermal curing of the epoxy resin. By blending a thermal radical polymerization initiator into the matrix resin composition contained in the prepreg, the polymerization of the (meth)acrylic monomer can proceed simultaneously with the thermal curing of the epoxy resin.

[0078] When the prepreg contains a radical polymerization initiator or a thermal radical polymerization initiator, the content of the radical polymerization initiator or the thermal radical polymerization initiator is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, per 100 parts by mass of (meth)acrylic monomer to ensure sufficient polymerization of the (meth)acrylic monomer. From the viewpoint of storage stability of the prepreg, the content of the radical polymerization initiator or the thermal radical polymerization initiator is preferably 10 parts by mass or less, more preferably 9 parts by mass or less, per 100 parts by mass of (meth)acrylic monomer. The above upper and lower limits can be arbitrarily combined. For example, the content of the radical polymerization initiator or the thermal radical polymerization initiator is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 9 parts by mass, per 100 parts by mass of (meth)acrylic monomer.

[0079] From the viewpoint of storage stability of the prepreg, the thermal radical polymerization initiator preferably contains a compound having a 10-hour half-life temperature of 70°C or higher, and more preferably contains a compound having a 10-hour half-life temperature of 100°C or higher. That is, the 10-hour half-life temperature of the thermal radical polymerization initiator is preferably 70°C or higher, and more preferably 100°C or higher. In order to allow the polymerization of the (meth)acrylic monomer to proceed sufficiently during the curing process of the epoxy resin, the 10-hour half-life temperature of the thermal radical polymerization initiator is preferably 150°C or lower. For example, a temperature of 70 to 150°C is preferred, and 100 to 150°C is more preferred.

[0080] <Organic peroxides> Examples of the thermal radical polymerization initiator include azo compounds and organic peroxides. It is preferable to use an organic peroxide (hereinafter also referred to as "organic peroxide D1") as the thermal radical polymerization initiator because it does not generate gas during thermal decomposition. When the prepreg contains organic peroxides D1 as a thermal radical polymerization initiator, the content of organic peroxides D1 is preferably 80 mass % or more, and more preferably 90 mass % or more, relative to the total mass of the radical polymerization initiator or thermal radical polymerization initiator, in order to obtain a high-quality fiber reinforced plastic without voids. When the prepreg contains organic peroxides D1 as a thermal radical polymerization initiator, the content of organic peroxides D1 is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, per 100 parts by mass of (meth)acrylic monomer, in order to sufficiently promote the polymerization of the (meth)acrylic monomer. From the viewpoint of the storage stability of the prepreg, the content of organic peroxides D1 is preferably 10 parts by mass or less, more preferably 9 parts by mass or less, per 100 parts by mass of (meth)acrylic monomer. The above upper and lower limits can be arbitrarily combined. For example, 0.1 to 10 parts by mass is preferred, and 0.2 to 9 parts by mass is more preferred.

[0081] As the organic peroxides D1, for example, peroxide compounds such as diacyl peroxide, alkyl peroxy ester, peroxydicarbonate, peroxyketal, dialkyl peroxide, and hydroperoxide are preferred.

[0082] Examples of organic peroxides D1 include ketone peroxides such as methyl ethyl ketone peroxide (110°C) and acetylacetone peroxide (130°C); 1,1-di(t-butylperoxy)3,3,5-trimethylcyclohexane (95°C), 1,1-di(t-hexylperoxy)cyclohexane (87.1°C), 1,1-di(t-butylperoxy)cyclohexane (90.7°C), 2,2-di(t-butylperoxy)butane (103.1°C), and n-butyl 4,4-di(t-butylperoxy)valerate (104. peroxyketals such as 2,2-di(4,4-di-t-butylperoxycyclohexyl)propane (94.7°C), 1,1-di(t-hexylperoxy)3,3,5-trimethylcyclohexane (86.7°C), and 1,1-di(t-butylperoxy)cyclododecane (95°C); p-menthane hydroperoxide (128°C), diisopropylbenzene hydroperoxide (145.1°C), 1,1,3,3-tetramethylbutyl hydroperoxide (152.9°C), and cumene hydroperoxide (157.9°C). Hydroperoxides such as di(2-t-butylperoxyisopropyl)benzene (119.2°C), dicumyl peroxide (116.4°C), 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (117.9°C), t-butylcumyl peroxide (119.5°C), di-t-hexyl peroxide (116.4°C), di-t-butyl peroxide (123.7°C), 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3 (128. dialkyl peroxides such as diisobutyryl peroxide (32.7°C), di(3,5,5-trimethylhexanoyl) peroxide (59.4°C), lauroyl peroxide (61.6°C), disuccinic acid peroxide (65.9°C), m-toluoyl peroxide (73.1°C), dibenzoyl peroxide (73.6°C), dioctanoyl peroxide (63°C); di-n-propyl peroxydicarbonate (40.3°C), diisopropyl peroxydicarbonate (40.peroxydicarbonates such as di(4-t-butylcyclohexyl) peroxydicarbonate (40.8°C), di(2-ethylhexyl) peroxydicarbonate (43.6°C), di-sec-butyl peroxydicarbonate (40.5°C), and di(3-methoxybutyl) peroxydicarbonate (43°C); cumyl peroxyneodecanoate (36.5°C), 1,1,3,3-tetramethylbutylperoxyneodecanoate ester (40.7°C), t-hexyl peroxyneodecanoate (44.5°C), t-butyl peroxyneodecanoate (46.4°C), t-hexyl peroxypivalate (53.2°C), t-butyl peroxypivalate (54.6°C), 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (65.3°C), 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane (66.2°C), t- Hexylperoxy-2-ethylhexanoate (69.9°C), t-butylperoxy-2-ethylhexanoate (72.1°C), t-hexylperoxyisopropyl monocarbonate (95°C), t-butylperoxy-3,5,5-trimethylhexanoate (97.1°C), t-butylperoxylaurate (98.3°C), t-butylperoxyisopropyl monocarbonate (98.7°C), t-butylperoxy-2-ethylhexanoate Examples include peroxyesters such as t-hexyl monocarbonate (99°C), t-hexyl peroxybenzoate (99.4°C), 2,5-dimethyl-2,5-di(benzoylperoxy)hexane (99.7°C), t-butyl peroxyacetate (101.9°C), t-butyl peroxybenzoate (104.3°C), t-butyl peroxymaleic acid (96.1°C), and t-butyl peroxyisobutyrate (75°C). The values ​​in parentheses indicate the 10-hour half-life temperature of each compound. The organic peroxides D1 can be used alone or in combination of two or more.

[0083] <Thermoplastic resin> The matrix resin composition contained in the prepreg can contain a thermoplastic resin (hereinafter also referred to as "thermoplastic resin E" or "thermoplastic resin [E]"). Examples of thermoplastic resins include polyamide, polyester, polycarbonate, polyethersulfone, polyphenylene ether, polyphenylene sulfide, polyetheretherketone, polyetherketone, polyimide, polytetrafluoroethylene, polyether, polyolefin, liquid crystal polymer, polyarylate, polysulfone, polyacrylonitrilestyrene, polystyrene, polyacrylonitrile, polymethyl methacrylate, ABS (acrylonitrile-butadiene-styrene copolymer), AES (acrylonitrile-ethylene-propylene rubber-styrene copolymer), ASA (acrylonitrile-acrylic rubber-styrene copolymer), polyvinyl chloride, polyvinyl formal, polyvinyl butyral, phenoxy resin, and block copolymer. Polyvinyl formal, polyvinyl butyral, polyethersulfone, and phenoxy resin are more preferred due to their excellent solubility in epoxy resins and resin flow controllability. Polyvinyl formal is even more preferred due to its excellent resin flow controllability even in small amounts. The thermoplastic resin may be used alone or in combination of two or more kinds.

[0084] When the prepreg contains a thermoplastic resin, the content of the thermoplastic resin is preferably 1 part by mass or more and 30 parts by mass or less, more preferably 2 parts by mass or more and 10 parts by mass or less, and even more preferably 3 parts by mass or more and 6 parts by mass or less, relative to 100 parts by mass of all epoxy resins contained in the matrix resin composition. When the content of the thermoplastic resin is 1 part by mass or more, resin flow controllability tends to be exhibited well. When the content of the thermoplastic resin is 30 parts by mass or less, the increase in viscosity of the matrix resin composition is small.

[0085] <Other additives> The matrix resin composition may contain additives. Examples of additives include curing accelerators for epoxy resins, inorganic fillers, internal mold release agents, organic pigments, and inorganic pigments. Examples of additives include phosphorus-based flame retardants (phosphorus-containing epoxy resins, red phosphorus, phosphazene compounds, phosphates, phosphate esters, etc.); inorganic flame retardants such as hydrated metal compounds (aluminum hydroxide, magnesium hydroxide, etc.), inorganic oxides and other additives (antimony compounds, zinc borate, zinc stannate, Mo compounds, ZrO, zinc sulfide, zeolite, titanium oxide nanofillers, etc.); release agents such as silicone oil, wetting and dispersing agents, antifoaming agents, defoaming agents, natural waxes, synthetic waxes, metal salts of straight-chain fatty acids, acid amides, esters, and paraffins; inorganic fillers such as powders and glass fibers, including crystalline silica, fused silica, calcium silicate, alumina, calcium carbonate, talc, and barium sulfate; colorants such as carbon black and red iron oxide; and silane coupling agents. These may be used alone or in combination of two or more.

[0086] <Method of manufacturing matrix resin composition> The matrix resin composition can be obtained by mixing the above-described components under heat. Examples of the method for mixing the components include a method using a mixer such as a three-roll mill, a planetary mixer, a kneader, a homogenizer, or a homodisper. The matrix resin composition improves the toughness of fiber reinforced plastics, and the plane strain fracture toughness K measured by ASTM D5045 of the cured product cured under the following curing conditions is Ic is 1.6 MPa m 1 / 2 It is preferable that the resistance is 2.1 MPa m or more. 1 / 2 More preferably, it is 2.2 MPa m 1 / 2 It is more preferable that the plane strain fracture toughness K Ic is 5.0 MPa m 1 / 2 For example, it may be 1.6 to 5.0 MPa m 1 / 2 , 2.1 to 5.0 MPa m 1 / 2 , 2.2 to 5.0 MPa m 1 / 2It can be said that: The matrix resin composition improves the toughness of fiber reinforced plastics, and the strain energy release rate G measured by ASTM D5045 of the cured product cured under the following curing conditions is Ic is 0.7kJ / m 2 It is preferable that the value is 1.2 kJ / m or more. 2 More preferably, it is 1.5 kJ / m or more. 2 It is more preferable that the strain energy release rate G Ic is 3.0 kJ / m 2 For example, it may be 0.7 to 3.0 kJ / m 2 , 1.2~3.0kJ / m 2 , 1.5~3.0kJ / m 2 It can be said that: Curing conditions: The matrix resin composition is poured between two glass plates and formed into a 2 mm thick plate, which is heated to an oven ambient temperature of 130°C at a rate of 2°C / min and maintained at 130°C for 120 minutes.

[0087] <Reinforced fiber> The reinforcing fibers can be present in the prepreg as a reinforcing fiber substrate (an aggregate of reinforcing fibers; in the case of carbon fibers, a carbon fiber substrate), and are preferably in the form of a sheet. The orientation of the fibers in the reinforcing fiber substrate may be such that the reinforcing fibers are aligned in a single direction, or may be such that the reinforcing fibers are aligned in a random direction. Examples of the form of the reinforcing fiber substrate include woven fabrics of reinforcing fibers, nonwoven fabrics of reinforcing fibers, and sheets in which long reinforcing fibers are aligned in one direction. In order to be able to mold fiber-reinforced plastics with high specific strength and specific modulus, it is preferable to use a sheet made of a bundle of reinforcing fibers in which continuous fibers are aligned in one direction for the prepreg, and from the viewpoint of ease of handling, it is preferable to use a woven fabric of reinforcing fibers for the prepreg. The weight per unit area of ​​the reinforcing fiber substrate is 10 g / m 2 More than 4000g / m 2 It can be as follows:

[0088] Examples of the material for the reinforcing fiber include glass fiber, carbon fiber, aramid fiber, boron fiber, etc. From the viewpoint of the mechanical properties and weight reduction of the obtained fiber-reinforced plastic, carbon fiber is preferred as the reinforcing fiber.

[0089] The fiber diameter of the carbon fiber is preferably 3 to 12 μm. The number of carbon fibers in the carbon fiber bundle is preferably 1,000 to 70,000. A sheet-like reinforcing fiber substrate may be formed by using a plurality of carbon fiber bundles and aligning the fibers in one direction, or a sheet-like reinforcing fiber substrate may be formed by scattering chopped carbon fiber bundles obtained by chopping carbon fiber bundles. From the viewpoint of the rigidity of the obtained fiber-reinforced plastic, the strand tensile strength of the carbon fiber is preferably 1.5 to 9 GPa, and the strand tensile modulus of the carbon fiber is preferably 150 to 400 GPa. Here, the strand tensile strength and strand tensile modulus of the carbon fiber are values ​​measured in accordance with JIS R7601:1986.

[0090] <Prepreg manufacturing method> The prepreg is obtained by impregnating a reinforcing fiber substrate with a matrix resin composition. One embodiment of the prepreg manufacturing method of the present invention is a method for manufacturing a prepreg by impregnating a carbon fiber substrate with a matrix resin composition containing the following components [A] to [D], and includes blending [B] so that the viscosity of the matrix resin composition at 70°C is 10 Pa s or more and the average double bond equivalent of [B] in the matrix resin composition is 160 g / eq or more. Here, [A] is an epoxy resin, [B] is a (meth)acrylic monomer, [C] is a curing agent, and [D] is a thermal radical polymerization initiator. The epoxy resin, (meth)acrylic monomer, curing agent, thermal radical polymerization initiator, matrix resin, carbon fiber substrate, and prepreg in this embodiment can each be exemplified by the above-mentioned embodiments as preferred embodiments.

[0091] Methods for impregnating a reinforcing fiber substrate with a matrix resin composition include, for example, a wet method in which a matrix resin composition is dissolved in a solvent such as methyl ethyl ketone or methanol to reduce its viscosity and then impregnated into the reinforcing fiber substrate, and a hot melt method (dry method) in which a matrix resin composition is heated to reduce its viscosity and then impregnated into the reinforcing fiber substrate. The impregnation temperature is set according to the viscosity of the matrix resin composition, but is preferably 40 to 120°C, more preferably 50 to 110°C, from the viewpoint of preventing the initiation of a curing reaction of the matrix resin composition and ensuring that the matrix resin composition is sufficiently impregnated into the reinforcing fibers.

[0092] The wet method is a method in which a reinforcing fiber substrate is immersed in a solution of a matrix resin composition, then pulled out, and the solvent is evaporated using an oven or the like. Hot melt methods include a method in which a matrix resin composition whose viscosity has been reduced by heating is directly impregnated into a reinforcing fiber substrate, and a method in which a film in which the matrix resin composition is applied to the surface of a substrate such as release paper is placed on one or both sides of the reinforcing fiber substrate, and the resin is impregnated into the reinforcing fiber substrate by heating and pressurizing. The coating layer obtained by applying the composition to the surface of a substrate such as release paper may be used in the hot melt method in an uncured state, or may be used in the hot melt method after being cured. In the hot melt method, substantially no solvent remains in the prepreg.

[0093] The content of the matrix resin composition in the prepreg (hereinafter also referred to as "resin content") is preferably 15 to 50 mass %, more preferably 15 to 45 mass %, and even more preferably 15 to 40 mass %, relative to the total mass of the prepreg. If the resin content is equal to or greater than the above lower limit, sufficient adhesion between the reinforcing fibers and the matrix resin can be ensured, and if it is equal to or less than the above upper limit, the mechanical properties of the fiber-reinforced plastic are further improved. The content of reinforcing fibers in the prepreg (hereinafter also referred to as "fiber content") is preferably 40 to 80% by volume, more preferably 45 to 80% by volume, and even more preferably 50 to 80% by volume, relative to the total volume of the prepreg. If the fiber content is equal to or greater than the above lower limit, the mechanical properties of the fiber-reinforced plastic are improved, and if it is equal to or less than the above upper limit, sufficient adhesion between the reinforcing fibers and the matrix resin can be ensured.

[0094] The total content of the matrix resin composition and reinforcing fibers in the prepreg may be 70% by mass or more, 80% by mass or more, 90% by mass or more, or may be 100% by mass, based on the total mass of the prepreg.

[0095] <Fiber reinforced plastic> One embodiment of the fiber-reinforced plastic of the present invention is obtained by curing the above-mentioned prepreg. Another embodiment of the fiber-reinforced plastic of the present invention comprises carbon fiber, a cured epoxy resin, and a polymer derived from the (meth)acrylic monomer represented by the aforementioned formula (1). The carbon fiber, the epoxy resin before curing of the cured epoxy resin product, and the (meth)acrylic monomer represented by formula (1) in this embodiment can be exemplified by the aforementioned embodiments as preferred embodiments. Fiber-reinforced plastics are obtained by curing prepregs, and thus contain reinforcing fibers and a cured product of a matrix resin composition contained in the prepregs. A fiber-reinforced plastic is obtained by curing a laminate of one prepreg or two or more prepregs. For example, two or more of the above-described prepregs are laminated together, and then the resulting laminate is molded by a method such as heat curing while applying pressure to obtain a molded product made of fiber-reinforced plastic. A prepreg made of a thermoplastic resin composition and reinforcing fibers other than the prepregs described above, or a prepreg made of an epoxy resin composition and reinforcing fibers, may be laminated onto the above-described prepreg.

[0096] Examples of molding methods include press molding, autoclave molding, bagging molding, wrapping tape molding, internal pressure molding, sheet wrap molding, as well as RTM (Resin Transfer Molding), VaRTM (Vacuum assisted Resin Transfer Molding), filament winding, and RFI (Resin Film Infusion), which impregnate a reinforcing fiber filament or preform with a matrix resin composition and harden it to obtain a molded product. Autoclave molding is preferred from the viewpoint of easily obtaining a high-quality fiber-reinforced plastic, and press molding is preferred from the viewpoint of obtaining high productivity.

[0097] When fiber-reinforced plastics are produced by press molding, it is preferable to clamp a prepreg or a preform produced by laminating prepregs in a mold adjusted to a curing temperature in advance and heat and pressurize the prepreg or preform to cure it. Known conditions can be applied for press molding. The temperature inside the mold during press molding is preferably 100 to 180°C. The pressure during press molding is preferably 1 to 15 MPa. The heating and pressurizing time during press molding is preferably 1 to 20 minutes. [Example]

[0098] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. The raw materials used in the examples and comparative examples are shown below.

[0099] <Ingredients used> [A] Epoxy resin jER 807: Liquid bisphenol F epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name "jER 807") jER 4007P: Solid bisphenol F epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name "jER 4007P") TSR-400: Solid epoxy resin with an oxazolidone ring structure (manufactured by DIC Corporation, product name "EPICLON TSR-400") [B] (Meth)acrylic monomer FA-310AH: Phenoxyethyl acrylate (molecular weight 192, monofunctional, double bond equivalent weight 192 g / eq, manufactured by Showa Denko Materials Co., Ltd., product name "Fancryl FA-310AH") AMP-20GY: Phenoxydiethylene glycol acrylate (molecular weight 236, monofunctional, double bond equivalent weight 236 g / eq, manufactured by Shin-Nakamura Chemical Co., Ltd., product name "NK Ester AMP-20GY") FA-314A: Nonylphenoxy polyethylene glycol acrylate (molecular weight 452, monofunctional, double bond equivalent weight 452 g / eq, manufactured by Showa Denko Materials Co., Ltd., product name "Fancryl FA-314A") FA-318A: Nonylphenoxy polyethylene glycol acrylate (molecular weight 626, monofunctional, double bond equivalent weight 626 g / eq, manufactured by Showa Denko Materials Co., Ltd., product name "Fancryl FA-318A") FA-512AS: Dicyclopentenyloxyethyl acrylate (molecular weight 248, monofunctional, double bond equivalent weight 248 g / eq, manufactured by Showa Denko Materials Co., Ltd., product name "Fancryl FA-512AS") PE-4A: Pentaerythritol tetraacrylate (molecular weight 352, tetrafunctional, double bond equivalent 88 g / eq, manufactured by Kyoeisha Chemical Co., Ltd., product name "Light Acrylate PE-4A") [C] Hardener (epoxy resin hardener) DICYANEX 1400F: Dicyandiamide (active hydrogen equivalent: 21 g / eq, manufactured by Evonik Japan Co., Ltd., product name: DICYANEX 1400F) DCMU-99: 3-(3,4-dichlorophenyl)-1,1-dimethylurea (manufactured by Hodogaya Chemical Co., Ltd., product name "DCMU-99") [D] Polymerization initiator PERCUMYL D: Dicumyl peroxide (thermal radical polymerization initiator, 10-hour half-life temperature 116.4°C, NOF Corporation, product name "Percumyl D") [E] Thermoplastic resin VINYLEC E: Polyvinyl formal resin (manufactured by JNC Corporation, product name "VINYLEC E")

[0100] <Method for preparing matrix resin composition> (Experimental Examples 1 to 10) Resin compositions were prepared as follows using jER 807, jER4007P, and TSR-400 as epoxy resins, FA-310AH, AMP-20GY, FA-314A, FA-318A, FA-512AS, and PE-4A as (meth)acrylic monomers, DICYANEX 1400F and DCMU-99 as curing agents, PECUMYL D as a polymerization initiator, and VINYLEC E as a thermoplastic resin. According to the composition shown in Table 1, the curing agent (solid) and the liquid component of the epoxy resin were weighed into a container and mixed by stirring so that the mass ratio of the solid component to the liquid component was 1:1. This was further mixed finely in a three-roll mill to obtain a master batch containing the curing agent. Next, the epoxy resins and thermoplastic resins other than those used in the curing agent-containing masterbatch from the compositions listed in Table 1 were weighed into a flask and heated and stirred at 150°C using an oil bath to dissolve and mix the thermoplastic resin. After cooling to 80°C, a (meth)acrylic monomer was added and stirred to obtain a uniform viscous liquid. After cooling to approximately 65°C, the curing agent-containing masterbatch and thermal radical polymerization initiator were added and stirred to obtain an uncured matrix resin composition. (Experimental Example 11) As shown in the formulation in Table 1, uncured matrix resin compositions were obtained in the same manner as in Experimental Examples 1 to 10, except that no (meth)acrylic monomer was used.

[0101] <Preparation of cured matrix resin composition> The uncured matrix resin compositions obtained in Experimental Examples 1 to 11 were degassed in a vacuum at 60 to 70°C, then poured between two glass plates to form them into plates. The temperature was raised at a rate of 2°C / min, and the mixture was heated and cured by holding it in an oven at an ambient temperature of 130°C for 120 minutes, producing cured products with thicknesses of 2 mm and 3.2 mm.

[0102] The matrix resin compositions and their cured products were subjected to various measurements and evaluations according to the evaluation methods described below. The results are shown in Table 1.

[0103] <Resin viscosity at 70°C> The uncured epoxy resin composition was placed on a plate, and the temperature dependency of the complex viscosity η* was measured under the following measurement conditions to obtain the resin viscosity at 70°C. Apparatus: Rheometer (Thermo Fisher Scientific, "HAAKE MARS 40") Plate used: 25φ parallel plate Plate gap: 0.5 mm Measurement frequency: 10rad / sec Measurement temperature: 30~130℃ Stress: 300Pa

[0104] <Plane strain fracture toughness K of cured matrix resin Ic , strain energy release rate G Ic Measurement of The 3.2 mm thick cured product obtained in the above <Preparation of cured product of matrix resin composition> was processed into a test specimen with a length of 31 mm and a width of 7 mm. This test specimen was subjected to a test at a crosshead speed of 10 mm / min and deformation mode I (open-type) using a universal testing machine (INSTRON, "INSTRON5965") equipped with a three-point bending jig (indenter R = 5 mm, support R = 5 mm, distance between supports (L) = 28 mm) under an environment of 23°C and 50% RH. The load at break was obtained, and the plane strain fracture toughness K was measured according to ASTM D5045 (2014). Ic and strain energy release rate G Ic The initial pre-crack was introduced into the test piece by sliding a razor blade over the test piece.

[0105] <Observation of phase separation structure> The 2 mm thick cured product obtained in the above <Preparation of a cured product of a matrix resin composition> was subjected to electron staining by exposure to OsO vapor for approximately 16 hours, and then ultrathin sections with a thickness of 70 nm were cut out. The phase-separated structure was observed by observing the obtained sections using a transmission electron microscope (TEM). TEM equipment: JEM-1400Flash (manufactured by JEOL Ltd.) Conditions: Accelerating voltage 80 kV Observation magnification: 10,000x The phase-separated structure observed under the above conditions was classified into the following three types. A: The cured epoxy resin is the sea phase, and the (meth)acrylic monomer polymer is the island phase, with a clear sea-island phase separation. B: The cured epoxy resin is the sea phase, and the (meth)acrylic monomer polymer is the island phase, with an unclear sea-island phase separation C: The cured epoxy resin is the sea phase and the (meth)acrylic monomer polymer is the island phase. No sea-island phase separation.

[0106] [Table 1]

[0107] In Experimental Examples 1 to 9, compared with Experimental Example 11, which did not contain any (meth)acrylic monomer, and Experimental Example 10, which used only pentaerythritol tetraacrylate as the (meth)acrylic monomer, a phase-separated structure was observed in the obtained cured products, and in general, a large K Ic and G Ic The results confirmed a significant improvement in the toughness of the cured product. The cured product had a sea phase of cured epoxy resin and an island phase of polymerized (meth)acrylic monomer, with a clear boundary between them forming a sea-island phase separation (State A), which is thought to be due to the significant toughening effect of the polymerized (meth)acrylic monomer. In a bending test of the cured product, it was confirmed that Experimental Examples 1, 6, and 8 had improved elastic moduli compared to Experimental Example 11.

[0108] <Prepreg production> Using a hot melt coater (manufactured by Hirano Tecseed Co., Ltd., "R-HC"), the uncured matrix resin compositions obtained in Experimental Examples 4 and 6 were applied to release paper in a resin basis weight of 27 g / m. 2 A resin film was prepared by coating the following carbon fiber on the resin film at a fiber basis weight of 100 g / m. 2 The carbon fiber sheet was then wound on a drum winding device to form a sheet of 154 g / m2. Another resin film was then attached to the carbon fiber sheet on the drum winding device. The carbon fiber sheet sandwiched between the two resin films was passed through a fusing press (manufactured by Asahi Textile Machinery Co., Ltd., "JR-600LTSW") under conditions of a temperature of 100°C, a pressure of 0.4 MPa, and a feed rate of 2 m / min, and the carbon fiber sheet was impregnated with the uncured matrix resin composition, resulting in a prepreg basis weight of 154 g / m2. 2 A unidirectional prepreg with a resin content of 35% by mass was obtained. [Carbon fiber] TR50S: Manufactured by Mitsubishi Chemical Corporation, product name "PYROFIL TR 50S15L", tensile modulus: 235 GPa, tensile strength: 4.9 GPa.

[0109] <Production of carbon fiber reinforced plastic> The prepreg obtained in "Preparation of Prepreg" was cut into 300mm x 300mm pieces, and 20 sheets were stacked with the carbon fibers aligned in the same direction to obtain a laminate. This laminate was heated to 130°C at 2°C / min under a pressure of 0.7 MPa in an autoclave, and then heat-cured at 130°C for 120 minutes to obtain a 2mm-thick carbon fiber-reinforced plastic panel.

[0110] <Measurement of Charpy impact strength of carbon fiber reinforced plastics> A test piece measuring 80 mm in length and 10 mm in width was cut out from the 2 mm thick panel obtained in "Preparation of carbon fiber reinforced plastic." The test piece was cut out so that the longitudinal axis direction of the test piece was parallel to the orientation direction of the carbon fibers. The Charpy impact strength of this test piece was measured using a Charpy impact tester (manufactured by Yasuda Seiki Seisakusho Co., Ltd.) in accordance with ISO 179-1 under the conditions of a hammer weight of 7.5 J and flatwise impact. The Charpy impact strength is the value obtained by dividing the obtained absorbed energy by the cross-sectional area of ​​the test piece. The Charpy impact strength of the carbon fiber reinforced plastic using the matrix resin composition obtained in Experimental Example 4 was 93 kJ / m 2 The Charpy impact strength of the carbon fiber reinforced plastic using the matrix resin composition obtained in Experimental Example 6 was 99 kJ / m 2 It was.

[0111] When the matrix resin composition in the prepreg contains the (meth)acrylic monomer represented by structural formula (1) or when the average double bond equivalent of the (meth)acrylic monomer [B] is 160 g / eq or more, the resulting carbon fiber reinforced plastic exhibits impact resistance sufficient for practical use. In particular, the effect of the matrix is ​​more readily reflected in impacts in the non-fiber reinforced direction, so a greater improvement in impact resistance can be expected. The impact strength in the non-fiber reinforced direction can be measured in the "Measurement of the Charpy impact strength of carbon fiber reinforced plastics" by using a test specimen cut so that the long axis of the test specimen is perpendicular to the carbon fiber orientation direction. [Industrial Applicability]

[0112] According to a preferred embodiment of the present invention, a prepreg can be provided which has improved toughness or elastic modulus after curing.

Claims

1. A prepreg comprising a matrix resin composition and carbon fibers, wherein the matrix resin composition comprises an epoxy resin and a (meth)acrylic monomer represented by the following structural formula (1): 【Chemistry 1】 (In formula (1), R represents a hydrogen atom or a methyl group, X represents a structure selected from the group consisting of an aryl group which may have a substituent selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, and a halogen atom; an alicyclic structure; and a heterocyclic structure, and n represents an integer of 2 to 30.)

2. The prepreg of claim 1 , wherein the matrix resin composition includes a curing agent.

3. 3. The prepreg according to claim 2, wherein the curing agent comprises at least one selected from the group consisting of dicyandiamide, aromatic amines, ureas, and imidazoles.

4. The prepreg according to claim 1 , wherein the matrix resin composition includes a thermal radical polymerization initiator.

5. The prepreg according to claim 4, wherein the thermal radical polymerization initiator is contained in an amount of 0.1 to 10 parts by mass relative to 100 parts by mass of the (meth)acrylic monomer.

6. The prepreg according to claim 4 , wherein the thermal radical polymerization initiator comprises an organic peroxide.

7. The prepreg according to claim 4 , wherein the thermal radical polymerization initiator comprises a compound having a 10-hour half-life temperature of 70° C. or higher.

8. 2. The prepreg according to claim 1, wherein the glass transition temperature of the polymer of the (meth)acrylic monomer is equal to or lower than the glass transition temperature of a cured product of the epoxy resin.

9. 2. The prepreg according to claim 1, wherein the (meth)acrylic monomer has an average double bond equivalent of 150 g / eq or more.

10. The prepreg according to claim 1, wherein the (meth)acrylic monomer is contained in an amount of 5 to 45 parts by mass relative to 100 parts by mass of the epoxy resin.

11. The prepreg according to claim 1 , wherein the (meth)acrylic monomer comprises a (meth)acrylic monomer having a molecular weight of 190 or more.

12. The prepreg according to claim 1, comprising 70% by mass or more of a monofunctional (meth)acrylic monomer relative to the total mass of the (meth)acrylic monomers.

13. A fiber-reinforced plastic obtained by curing the prepreg according to any one of claims 1 to 12.

14. 2. The prepreg according to claim 1, comprising a matrix resin composition containing the following components [A] to [D] and carbon fibers, wherein the viscosity of the matrix resin composition at 70°C is 10 Pa s or more, and the average double bond equivalent of [B] is 160 g / eq or more. [A] Epoxy resin [B] (Meth)acrylic monomer [C] Curing agent [D] Thermal radical polymerization initiator

15. The prepreg according to claim 14, wherein the matrix resin composition, when cured under the following curing conditions, produces a cured product having a sea-island phase-separated structure, in which the cured product of [A] constitutes a sea phase and the polymer of [B] constitutes an island phase. Curing conditions: The matrix resin composition is poured between two glass plates and formed into a plate having a thickness of 2 mm, and the oven temperature is raised to 130°C at a rate of 2°C / min, and maintained at 130°C for 120 minutes.

16. 15. The prepreg according to claim 14, comprising 30% by mass or more of an epoxy resin having a molecular weight of 500 or more relative to the total mass of the epoxy resins.

17. The prepreg according to claim 14, wherein the weight average molecular weight of [A] is 1,500 or more.

18. The prepreg according to claim 14, wherein the average epoxy equivalent of the [A] is 200 g / eq or more.

19. The prepreg according to claim 14, wherein the component [A] contains an epoxy resin having an oxazolidone ring skeleton or a bisphenol F type epoxy resin.

20. The prepreg according to claim 14, wherein the [B] is contained in an amount of 5 to 45 parts by mass relative to 100 parts by mass of the [A].

21. The prepreg according to claim 14, wherein the component [B] contains a (meth)acrylic monomer having a molecular weight of 190 or more.

22. The prepreg according to claim 14, wherein the prepreg contains 70 mass% or more of a monofunctional (meth)acrylic monomer relative to the total mass of [B].

23. The prepreg according to claim 14, wherein the component [B] contains a (meth)acrylic monomer having one or more oxyethylene groups in the molecule.

24. The prepreg according to claim 14, wherein the component [B] contains a (meth)acrylic monomer having one or more cyclic skeletons in the molecule.

25. The prepreg according to claim 14, wherein the glass transition temperature of the polymer [B] is equal to or lower than the glass transition temperature of the cured product of the polymer [A].

26. The prepreg according to claim 14, wherein the compound [C] includes at least one selected from the group consisting of dicyandiamide, aromatic amines, ureas, and imidazoles.

27. The prepreg according to claim 14, comprising 50 mass% or more of a component [C1] having a melting point of 70°C or higher relative to the total mass of the [C].

28. The prepreg according to claim 14, wherein the [D] is contained in an amount of 0.1 to 10 parts by mass relative to 100 parts by mass of the [B].

29. The prepreg according to claim 14, wherein the [D] comprises [D1] an organic peroxide.

30. The prepreg according to claim 14, wherein the [D] contains a compound having a 10-hour half-life temperature of 70°C or higher.

31. The matrix resin composition has a plane strain fracture toughness K of a cured product measured according to ASTM D5045 under the following curing conditions. Ｉｃ is 1.6 MPa m １／２ The prepreg according to claim 14, wherein the prepreg is as described above. Curing conditions: The matrix resin composition is poured between two glass plates and formed into a plate having a thickness of 2 mm, and the oven temperature is raised to 130°C at a rate of 2°C / min, and maintained at 130°C for 120 minutes.

32. The matrix resin composition has a strain energy release rate G of 100% or less, as measured by ASTM D5045, of a cured product cured under the following curing conditions: Ｉｃ is 0.7 kJ / m ２ The prepreg according to claim 14, wherein the prepreg is as described above. Curing conditions: The matrix resin composition is poured between two glass plates and formed into a plate having a thickness of 2 mm, and the oven temperature is raised to 130°C at a rate of 2°C / min, and maintained at 130°C for 120 minutes.

33. A fiber reinforced plastic obtained by curing the prepreg according to any one of claims 14 to 32.

34. A method for producing a prepreg according to claim 1, in which a matrix resin composition containing the following components [A] to [D] is impregnated into a carbon fiber substrate, 2. The method for producing a prepreg according to claim 1, comprising blending [B] such that the viscosity of the matrix resin composition at 70°C is 10 Pa s or more and the average double bond equivalent of [B] in the matrix resin composition is 160 g / eq or more. [A] Epoxy resin [B] (Meth)acrylic monomer [C] Curing agent [D] Thermal radical polymerization initiator

35. A fiber-reinforced plastic comprising carbon fibers, a cured epoxy resin, and a polymer derived from a (meth)acrylic monomer represented by the following structural formula (1): 【Chemistry 2】 (In formula (1), R represents a hydrogen atom or a methyl group, X represents a structure selected from the group consisting of an aryl group which may have a substituent selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a hydroxyl group, and a halogen atom; an alicyclic structure; and a heterocyclic structure, and n represents an integer of 2 to 30.)

36. A prepreg comprising a matrix resin composition and carbon fibers, wherein the matrix resin composition has a plane strain fracture toughness K measured by ASTM D5045 of a cured product cured under the following curing conditions: Ｉｃ is 1.6 MPa m １／２ The prepreg according to claim 1, wherein the prepreg is as described above. Curing conditions: The matrix resin composition is poured between two glass plates and formed into a plate having a thickness of 2 mm, and the oven temperature is raised to 130°C at a rate of 2°C / min, and maintained at 130°C for 120 minutes.

37. The plane strain fracture toughness K Ｉｃ is 2.2 MPa m １／２ The prepreg according to claim 36, wherein

38. The strain energy release rate G of the cured product cured under the above curing conditions as measured by ASTM D5045 Ｉｃ is 0.7 kJ / m ２ The prepreg according to claim 37, wherein

39. The strain energy release rate G of the cured product cured under the above curing conditions as measured by ASTM D5045 Ｉｃ is 1.2 kJ / m ２ The prepreg according to claim 36 or 37, wherein

40. 38. The prepreg of claim 36 or 37, wherein the matrix resin composition comprises an epoxy resin.

41. 38. The prepreg according to claim 36 or 37, wherein the matrix resin composition comprises a (meth)acrylic monomer.

42. 38. The prepreg according to claim 36 or 37, wherein the matrix resin composition comprises at least one selected from the group consisting of dicyandiamide, aromatic amines, ureas, and imidazoles.

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