Prepreg, epoxy resin composition, and method for producing prepreg

Abstract

To provide a prepreg that improves the elastic modulus and strength of FRP, an epoxy resin composition, and a method for producing a prepreg.SOLUTION: A prepreg comprises an epoxy resin composition comprising an epoxy resin and a polycarbonate diol having an isosorbide residue, and a fiber reinforcement. Alternatively, a prepreg comprises an epoxy resin composition comprising at least one curing agent selected from the group consisting of a bisphenol type epoxy resin, a dicyandiamide, an imidazole, a urea compound, and an amine, and a polycarbonate diol, and a fiber reinforcement, the content of the component (A) being 30 pts.mass or more relative to 100 pts.mass of the epoxy resin component in the epoxy resin composition.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention mainly relates to prepregs, epoxy resin compositions, and methods for producing prepregs.

Background Art

[0002] Carbon fiber reinforced composite materials (hereinafter also referred to as "CFRP") composed of carbon fibers and matrix resins are widely used in aircraft, automobiles, and industrial applications due to their excellent mechanical properties and the like. In recent years, as the usage track record has accumulated, the application range of CFRP has been expanding more and more. As the matrix resin of CFRP, conventionally, resin compositions containing thermosetting resins are often used because they are excellent in impregnation properties to carbon fibers and physical property expression after curing. In particular, epoxy resins and the like are used. The matrix resin composition of CFRP is required to have excellent performance in elastic modulus and toughness, but generally, the elastic modulus and toughness are in a trade-off relationship. It is described that by blending polycarbonate polyol into an epoxy resin composition and performing a specific purification treatment, the problem of coloring of the curable resin composition can be solved. (Patent Document 1). By using a curable resin composition in which a polycarbonate polyol having 2.5 or more hydroxyl groups in the molecule is blended with an alicyclic epoxy compound, it is described that a cured product having excellent heat and humidity resistance and mechanical properties while maintaining heat resistance and the like can be formed (Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] One of the objectives of the present invention is to provide a prepreg, an epoxy resin composition, and a method for producing a prepreg that improve the elastic modulus and strength of FRP. [Means for solving the problem]

[0005] The present invention includes the following embodiments [1] to

[18] . [1] A prepreg comprising an epoxy resin composition containing the following components (A) to (C) and a fiber reinforcing material, wherein component (A) is blended in an amount of 30 parts by mass or more per 100 parts by mass of epoxy resin component in the epoxy resin composition. Component (A): Bisphenol-type epoxy resin Component (B): At least one curing agent selected from the group consisting of dicyandiamide, imidazoles, urea compounds, and amines. Ingredients (C): Polycarbonate diol [2] A prepreg comprising an epoxy resin composition containing the following components (A) to (C) and a fiber reinforcing material, wherein the content of alicyclic epoxy resin is 70 parts by mass or less per 100 parts by mass of epoxy resin components in the epoxy resin composition. Component (A): Bisphenol-type epoxy resin Component (B): At least one curing agent selected from the group consisting of dicyandiamide, imidazoles, urea compounds, and amines. Ingredients (C): Polycarbonate diol [3] The prepreg according to [1] and [2], wherein the component (C) is a polycarbonate diol having a number average molecular weight of 300 or more and 5000 or less. [4] A prepreg according to any one of [1] to [3], wherein the component (C) is a polycarbonate diol having a 1,4-butanediol residue, a 1,5-pentanediol residue, a 3-methyl-1,5-pentanediol residue, or a 1,6-hexanediol residue. [5] A prepreg according to any one of [1] to [4], wherein the component (C) is a polycarbonate diol having an isosorbide residue, a neopentyl glycol residue, a cyclohexanediol residue, or a cyclohexanedimethanol residue. [6] A prepreg according to any one of [1] to [5], wherein the component (C) is a polycarbonate diol having a hydroxyl group equivalent of 150 to 2000. [7] The prepreg according to any one of [1] to [6], wherein component (C) is blended in an amount of 3 parts by mass or more and 25 parts by mass or less per 100 parts by mass of component (A). [8] The prepreg according to any one of [1] to [7], wherein component (B) is blended in an amount of 3 to 40 parts by mass per 100 parts by mass of component (A). [9] A prepreg according to any one of [1] to [8], wherein bisphenol A type epoxy resin is blended in 3 parts by mass or more per 100 parts by mass of component (A) of the component (A).

[10] A prepreg according to any one of [1] to [9], wherein the component (B) is an imidazole.

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

[10] , wherein the component (B) is dicyandiamide and a urea compound.

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

[11] , wherein the mass ratio of the epoxy resin composition to the fiber reinforcement ([mass of epoxy resin composition] / [mass of fiber reinforcement]) is 0.25 to 9.

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

[12] , wherein the fiber reinforcement material comprises continuous carbon fibers.

[14] A prepreg according to any of the items [1] to

[13] , wherein the prepreg is a UD prepreg.

[15] An epoxy resin composition comprising the following components (A) to (C), wherein component (A) is present in an amount of 30 parts by mass or more per 100 parts by mass of the epoxy resin composition. Component (A): Bisphenol-type epoxy resin Component (B): At least one curing agent selected from the group consisting of dicyandiamide, imidazoles, urea compounds, and amines. Ingredients (C): Polycarbonate diol

[16] The epoxy resin composition according to

[15] , wherein the component (C) is a polycarbonate diol having an isosorbide residue.

[17] The epoxy resin composition according to

[15] or

[16] , wherein when the epoxy resin composition is cured at 140°C, the flexural modulus measured in accordance with JIS K6911 is 3000 MPa or more.

[18] The epoxy resin composition according to any one of

[15] to

[17] , wherein when the epoxy resin composition is cured at 140°C, the bending strength measured in accordance with JIS K6911 is 120 MPa or more.

[19] A method for producing a prepreg, comprising impregnating a fiber reinforcing material with an epoxy resin composition described in any of

[15] to

[18] .

[20] A prepreg comprising a carbon fiber reinforcement and an epoxy resin composition according to any one of

[15] to

[19] .

[21] A prepreg comprising an epoxy resin composition containing at least one curing agent (component (B)) selected from the group consisting of epoxy resin, dicyandiamide, imidazoles, urea compounds, and amines, and a polycarbonate diol (component (C)), and a fiber reinforcing material, wherein the content of alicyclic epoxy resin is 70 parts by mass or less per 100 parts by mass of epoxy resin component in the epoxy resin composition.

[22] The prepreg according to

[21] , wherein the fiber reinforcement material comprises carbon fiber.

[23] A prepreg comprising an epoxy resin composition containing an epoxy resin and a polycarbonate diol having an isosorbide residue, and a fiber reinforcing material.

[24] The prepreg according to

[23] , wherein the epoxy resin composition is blended with imidazoles.

[25] The prepreg according to

[23] or

[24] , wherein the epoxy resin mixture is blended with an epoxy resin having an epoxy equivalent of 180 or less.

[26] The prepreg according to any one of

[23] to

[25] , which is blended with a polycarbonate diol having a number average molecular weight of 300 or more and 5000 or less.

[27] The prepreg according to any one of

[23] to

[26] , wherein the polycarbonate diol has a 1,4-butanediol residue, a 1,5-pentanediol residue, a 3-methyl-1,5-pentanediol residue, a neopentyl glycol residue or a 1,6-hexanediol residue.

[28] The prepreg according to any one of

[23] to

[27] , wherein the hydroxyl equivalent of the polycarbonate diol is 150 to 2500.

[29] The prepreg according to any one of

[23] to

[28] , wherein the polycarbonate diol is blended in an amount of 3 parts by mass or more and 25 parts by mass or less based on 100 parts by mass of the epoxy resin component. [Advantages of the Invention]

[0006] According to the present invention, it is possible to provide a prepreg, an epoxy resin composition, and a method for producing a prepreg in which the elastic modulus and strength of FRP are improved. [Modes for Carrying Out the Invention]

[0007] [Prepreg] One embodiment of the present invention relates to a prepreg. The prepreg according to the embodiment is composed of an epoxy resin composition in which an epoxy resin and a polycarbonate diol having an isosorbide residue are blended, and a fiber reinforcing material. The molded product obtained by curing the prepreg of this form has a balanced strength, elastic modulus, and heat resistance. The prepreg according to another embodiment is composed of an epoxy resin composition in which the following components (A) to (C) are blended and a fiber reinforcing material, and the component (A) is blended in an amount of 30 parts by mass or more with respect to 100 parts by mass of the epoxy resin component in the epoxy resin composition. Another aspect of the prepreg is composed of an epoxy resin composition in which the following components (A) to (C) are blended, or an epoxy resin, the following component (B), and an epoxy resin composition in which (C) is blended and a fiber reinforcing material, and the content of the alicyclic epoxy resin is 70 parts by mass or less with respect to 100 parts by mass of the epoxy resin component in the epoxy resin composition. The prepreg of this form can improve the strength and elastic modulus of the molded product obtained by curing. Component (A): Bisphenol type epoxy resin Component (B): At least one curing agent selected from the group consisting of dicyandiamide, imidazoles, urea compounds, and amines Component (C): Polycarbonate diol

[0008] The prepreg can be manufactured, for example, by the following procedure. First, an epoxy resin composition in which components (A) to (C) are blended is applied to one surface of a carrier film (first carrier film). Similarly, prepare another carrier film (second carrier film) having the epoxy resin composition applied to one surface. Next, a laminate is formed by sandwiching the fiber reinforcing material and the epoxy resin composition between the first carrier film and the second carrier film such that the surfaces of the first carrier film and the second carrier film to which the epoxy resin composition is applied face the fiber reinforcing material side. The obtained laminate is pressurized to impregnate the fiber reinforcing material with the epoxy resin composition, thereby obtaining a prepreg.

[0009] [Epoxy resin composition] One embodiment of the epoxy resin composition is a blend of an epoxy resin and a polycarbonate diol having an isosorbide residue. Another embodiment of the epoxy resin composition is a blend of components (A) to (C), with component (A) being blended in an amount of 30 parts by mass or more per 100 parts by mass of the epoxy resin component in the epoxy resin composition. Yet another embodiment of the epoxy resin composition is a blend of components (A) to (C), with component (A) being blended in an amount of 25 parts by mass or more per 100 parts by mass of the epoxy resin composition. The epoxy resin composition may also contain an epoxy resin other than a bisphenol-type epoxy resin.

[0010] The epoxy resin composition according to the embodiment may be liquid or semi-solid at room temperature, depending on the form of the prepreg. In the case of a prepreg impregnated at room temperature, it is preferable that the composition be liquid at room temperature. The viscosity at room temperature may be 50 Pa·s or less, 40 Pa·s or less, 30 Pa·s or less, 25 Pa·s or less, 20 Pa·s or less, 15 Pa·s or less, etc. Room temperature viscosity refers to the viscosity at 25°C. In the so-called hot melt method, in which the resin is heated and impregnated, the upper limit of the viscosity at room temperature may be 100,000 Pa·s or less, 70,000 Pa·s or less, 50,000 Pa·s or less, 30,000 Pa·s or less, 10,000 Pa·s or less, 7,000 Pa·s or less, 5,000 Pa·s or less, etc. The lower limit of viscosity at room temperature can be 1,000 Pa·s or higher, 3,000 Pa·s or higher, 5,000 Pa·s or higher, 7,000 Pa·s or higher, 10,000 or higher, etc.

[0011] The flexural strength of the cured epoxy resin composition according to the embodiment, when cured at 140°C, is preferably 120 MPa or higher, more preferably 140 MPa or higher, and particularly preferably 160 MPa or higher. If the flexural strength of the cured epoxy resin composition is equal to or higher than the above values, it is easier to obtain a prepreg that has high strength and high toughness when molded into a product.

[0012] The flexural modulus of the cured epoxy resin composition according to the embodiment, when cured at 140°C, is preferably 3.0 GPa (3000 MPa) or higher, more preferably 3.5 GPa (3500 MPa) or higher, and particularly preferably 3.9 GPa (3900 MPa) or higher. If the flexural modulus of the cured epoxy resin composition is equal to or higher than the above value, a prepreg with excellent compression properties is easily obtained when molded into a product.

[0013] Bending strength and bending modulus can be measured by the following method. Six test pieces, each 8 mm wide and 60 mm long, were cut from the cured material. Using a universal testing machine (Instron 5965, manufactured by Instron), bending strength, bending modulus, bending elongation at fracture, and bending yield elongation were measured under the following conditions, and the average value of the six pieces was calculated. Crosshead speed: 2 mm / min, span distance: The thickness of the cured resin plate was measured and set to (thickness × 16) mm.

[0014] Examples of epoxy resins include bisphenol-type epoxy resins, novolac-type epoxy resins, amine-type epoxy resins, and alicyclic epoxy resins. From the viewpoint of improving heat resistance, it is preferable that the epoxy resin composition contains an epoxy resin with an epoxy equivalent of 170 or less. From the viewpoint of manufacturing stability, storage stability, and curability during molding, the epoxy equivalent can be 80 or more, 90 or more, or 100 or more, and from the viewpoint of heat resistance, it can be 160 or less, or 150 or less. (Component (A)) Component (A) is a bisphenol-type epoxy resin. Examples of bisphenol-type epoxy resins include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol E type epoxy resin, bisphenol S type epoxy resin, bisphenol AF type epoxy resin, and bisphenol BP type epoxy resin. Bisphenol A type epoxy resin and bisphenol F type epoxy resin are preferred because they allow for easy adjustment of mechanical properties (strength and toughness) suitable for FRP to the desired range.

[0015] Regarding the amount of component (A), from the viewpoint of heat resistance, strength, and elastic modulus of the cured product, it is preferable to have 30 parts by mass or more, more preferably 40 parts by mass or more, and particularly preferable to have 60 parts by mass or more, per 100 parts by mass of epoxy resin components in the epoxy resin composition. It can be 100 parts by mass or less per 100 parts by mass of the total epoxy resin components. From the viewpoint of heat resistance, strength, and elastic modulus of the cured product, it is preferable to have 25 parts by mass or more, and particularly preferable to have 50 parts by mass or more, per 100 parts by mass of the epoxy resin composition. It can be 95 parts by mass or less per 100 parts by mass of the epoxy resin composition. Bisphenol A type epoxy resin can be blended in 60 parts by mass or more per 100 parts by mass of bisphenol type epoxy resin.

[0016] As amine-type epoxy resins, polyfunctional epoxy resins such as tetraglycidyldiaminodiphenylmethane-type epoxy resin, triglycidyl-p-aminophenol, and triglycidyl-m-aminophenol can be used. As novolac-type epoxy resins, phenol novolac-type epoxy resins produced from aromatic polyhydric phenols and epihalohydrins, cresol novolac-type epoxy resins, and bisphenol A novolac-type epoxy resins can be used. As alicyclic epoxy resins, epoxy resins such as 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, ε-caprolactone-modified 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, and 1,2-epoxy-4-vinylcyclohexane can be used.

[0017] The epoxy resin other than bisphenol-type epoxy resin is 70 parts by mass or less, preferably 60 parts by mass or less, and particularly preferably 40 parts by mass or less, per 100 parts by mass of the epoxy resin component. If an epoxy resin other than bisphenol-type epoxy resin is included, it can be 5 parts by mass or more per 100 parts by mass of the epoxy resin component. Within the above range, there is a tendency to improve the heat resistance and elastic modulus of the cured epoxy resin composition. If the amount exceeds the above range, there is a tendency for curing shrinkage to increase, and there is also a tendency for a large amount of unreacted epoxy resin to remain. In particular, alicyclic epoxy resin has low reactivity with component (B), so it is 70 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 15 parts by mass or less, and particularly preferably not included, per 100 parts by mass of the epoxy resin component.

[0018] (Component (B)) Component (B) is at least one curing agent selected from the group consisting of dicyandiamide, imidazoles, urea compounds, and amines. One or more curing agents may be incorporated into the epoxy resin composition according to the embodiment.

[0019] Urea compounds can be incorporated as curing accelerators for dicyandiamides and imidazoles, shortening the curing time of resin compositions and enabling curing at low temperatures. Furthermore, urea compounds can enhance the toughness of cured products. Examples of urea compounds, though not limited to these, include 3-(3,4-dichlorophenyl)-1,1-dimethylurea (sometimes abbreviated as DCMU), 3-(4-chlorophenyl)-1,1-dimethylurea, phenyldimethylurea (sometimes abbreviated as PDMU), and toluenebisdimethylurea (sometimes abbreviated as TBDMU). Furthermore, commercially available aromatic ureas include DCMU99 (manufactured by Hodogaya Chemical Co., Ltd.), “Omicure®” 24 (manufactured by PTI Japan Co., Ltd.), and “Dyhard®” UR505 (4,4'-methylenebis(phenyldimethylurea, manufactured by CVC). Toluenebisdimethylurea is preferred because it hardens quickly and exhibits high heat resistance in the cured product.

[0020] The curing time and curing temperature can be adjusted using amines. Examples of amines, though not limited to them, include aliphatic polyamines such as isophorone diamine (IPDA) and diethylenetriamine (DTA), and aromatic amines such as diaminodiphenylsulfone (DDS) and diaminodiphenylmethane (DDM). They may also be amines in which a part of the compound has been modified. Diaminodiphenylsulfone is preferred from the viewpoint of the heat resistance of the cured product.

[0021] Some imidazoles and dicyandiamides are typical examples of latent curing agents that initiate the curing of epoxy resins when heat is triggered. Imidazoles are compounds that have an imidazole ring, and include not only substituted imidazoles in which the hydrogen atoms of imidazole are replaced by substituents, but also imidazolium salts and imidazole complexes. Examples of imidazoles that act as latent curing agents include, but are not limited to, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2-phenyl-4-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4-benzyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-paratoluyl-4-methyl-5-hydroxymethylimidazole, 2-paratoluyl-4,5-dihydroxymethylimidazole, 2-metatoluyl-4-methyl-5-hydroxymethylimidazole, 2-metatoluyl-4,5-dihydroxymethylimidazole, 1-cyanoethyl-2-phenylimidazole, and 1-cyanoethyl-2-phenylimidazolium trimellitate.

[0022] Regarding the amount of component (B), since it allows the resin to harden in a short time, it is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and particularly preferably 8 parts by mass or more, per 100 parts by mass of the total epoxy resin component. Furthermore, since it has excellent storage stability, it is preferably 40 parts by mass or less, more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less, per 100 parts by mass of the total epoxy resin component. It is preferably 2 parts by mass or more, more preferably 4 parts by mass or more, per 100 parts by mass of the epoxy resin composition. It is preferably 35 parts by mass or less, more preferably 25 parts by mass or less, and particularly preferably 15 parts by mass or less, per 100 parts by mass of the epoxy resin composition. As a curing agent different from component (B), acid anhydrides and the like can be used, and the total amount of curing agent can be 3 parts by mass or more and 40 parts by mass or 5 parts by mass or 15 parts by mass or more, per 100 parts by mass of the epoxy resin component. When using dicyandiamide, it is preferable to use it in combination with a urea compound, and the amount can be 40 to 90 parts by mass of dicyandiamide and 10 to 60 parts by mass of the urea compound per 100 parts by mass of the total curing agent. When using imidazoles, the amount can be 100 parts by mass of imidazoles per 100 parts by mass of the total curing agent, and when used in combination with a urea compound, the amount can be 30 to 90 parts by mass of imidazoles and 10 to 70 parts by mass of the urea compound per 100 parts by mass of the total curing agent.

[0023] (Component (C)) Component (C) is polycarbonate diol. In the epoxy resin composition according to the embodiment, the number average molecular weight of component (C) polycarbonate diol is not limited, but may be, for example, 300 to 5000, 500 to 800, 800 to 1000, 1000 to 2000, 2000 to 2500, 2500 to 5000, etc. Within the above range, it tends to be easier to design the epoxy resin composition to have high strength.

[0024] In the epoxy resin composition according to the embodiment, the hydroxyl group equivalent of component (C) polycarbonate diol is not limited, but may be, for example, 150 to 2500, 250 to 400, 400 to 500, 500 to 2000, 1000 to 1250, or 1250 to 2500. Within the above range, it tends to be easier to design the epoxy resin composition to have high strength.

[0025] There are no particular limitations on the polycarbonate diols incorporated into the epoxy resin composition according to the embodiment. One or more arbitrary polycarbonate diols can be incorporated into the epoxy resin composition according to the embodiment as a polycarbonate diol component. Preferred examples of polycarbonate diols include polycarbonate diols having isosorbide residues, neopentyl glycol residues, cyclohexanediol residues, or cyclohexanedimethanol residues, and polycarbonate diols having 1,4-butanediol residues, 1,5-pentanediol residues, 3-methyl-1,5-pentanediol residues, or 1,6-hexanediol residues. The polycarbonate diols having the isosorbide residue, neopentyl glycol residue, cyclohexanediol residue, or cyclohexanedimethanol residue exemplified above may also have a 1,4-butanediol residue, a 1,5-pentanediol residue, a 3-methyl-1,5-pentanediol residue, or a 1,6-hexanediol residue, along with a diol residue selected from these four types of diol residues.

[0026] At least a portion of the polycarbonate diol component incorporated into the epoxy resin composition according to the embodiment may be a polycarbonate diol introduced into the structure by transesterification reaction, comprising at least one of the first repeating units and the second repeating units defined below. The first repeating unit and the second repeating unit are represented by the following general formulas (A) and (B), respectively.

[0027] [ka] The diol residue-OR of the first repeating unit 1 -O- represents an aliphatic diol HO-R that does not contain an alicyclic structure. 1 - Derived from OH The diol residue -OR of the second repeating unit 2 -O- represents an aliphatic diol containing an alicyclic structure, HO-R 2 - Derived from OH Aliphatic diols that do not contain alicyclic structures HO-R 1 Examples of -OH groups include 1,3-propanediol, 2-methyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, 1,18-octadecanediol, and 1,20-eicosanediol.

[0028] Aliphatic diols containing alicyclic structures HO-R 2Examples of -OH include 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, pentacyclopentadecanedimethanol, 2,6-decalingimethanol, 1,5-decalingimethanol, 2,3-decalingimethanol, 2,3-norbornanedimethanol, 2,5-norbornanedimethanol, 1,3-adamantanedimethanol, isosorbide, isomannide, and Soydet, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro(5.5)undecane (common name: spiroglycol), 3,9-bis(1,1-diethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro(5.5)undecane, 3,9-bis(1,1-dipropyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro(5.5)undecane, and dioxaneglycol.

[0029] Regarding the amount of component (C), it is preferable to add 1 part by mass or more, more preferably 5 parts by mass or more, and particularly preferable 8 parts by mass or more, per 100 parts by mass of the total epoxy resin component, as this can improve the strength of the FRP. From the viewpoint of heat resistance, it is preferable to add 40 parts by mass or less, more preferably 35 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferable 15 parts by mass or less, per 100 parts by mass of the total epoxy resin component. It is preferable to add 0.5 parts by mass or more, more preferably 3 parts by mass or more, per 100 parts by mass of the epoxy resin composition. It is preferable to add 35 parts by mass or less, more preferably 30 parts by mass or less, and particularly preferable 20 parts by mass or less, per 100 parts by mass of the epoxy resin composition.

[0030] Other known components can be added to the invention in an amount that does not impair its effects. Examples include flame retardants, inorganic fillers, internal mold release agents, and desiccants.

[0031] (Fiber reinforcement material) Examples of reinforcing fibers used in fiber reinforcement materials include carbon fibers, aramid fibers, silicon carbide fibers, alumina fibers, boron fibers, tungsten carbide fibers, and glass fibers. From the viewpoint of the mechanical properties of fiber-reinforced composite materials, carbon fibers and glass fibers are preferred, and carbon fibers are particularly preferred. The reinforcing fibers may be long fibers (continuous fibers), or short fibers of, for example, 0.01 to 30 cm. Examples of fiber reinforcement materials include UD sheets (unidirectional sheets) in which multiple long fibers are aligned in one direction, cloths (woven fabrics) made from long fibers, sheets of chopped reinforcement fibers, and nonwoven fabrics made of short fibers. Examples of weaving methods for cloths include plain weave, twill weave, satin weave, and triaxial weave. The basis weight of the fiber reinforcement material is 10 g / m². 2 More than 4000g / m 2 The following is possible:

[0032] Reinforcement fibers can be used as reinforcement fiber bundles consisting of single fibers ranging from 1,000 to 60,000. In the prepreg, the reinforcement fiber bundles may exist while maintaining their shape, or they may be separated into bundles consisting of fewer fibers.

[0033] (molded product) The molded article is obtained by curing a prepreg. For example, it can be a cured product of a laminate in which two or more prepregs are laminated. The molded article contains a cured epoxy resin composition contained in the prepreg and a fiber reinforcement. The molded article is obtained, for example, by laminating two or more of the aforementioned prepregs, and then molding it by applying pressure to the resulting laminate while heating and curing the epoxy resin composition.

[0034] Molding methods include press molding, autoclave molding, bagging molding, wrapping tape molding, internal pressure molding, sheet wrap molding, and RTM, VaRTM, filament winding, and RFI, which involve impregnating reinforcing fiber filaments or preforms with an epoxy resin composition and curing to obtain molded products.

[0035] When manufacturing molded products by press molding, prepregs, or preforms made by laminating prepregs, can be cured by placing them in a mold pre-set to a curing temperature and then heating and pressurizing them. The temperature inside the mold during press molding is preferably 100 to 160°C. Furthermore, the prepregs can be cured for 1 to 20 minutes under conditions of 1 to 15 MPa.

[0036] (Experimental Examples 1-14, Comparative Examples 1-4) First, according to the compositions listed in Tables 2-4, jER827 and the curing agent were weighed into a container so that the mass ratio of solid components to liquid components was 1:2, and then stirred and mixed. This was further finely mixed in a three-roll mill (Inoue Seisakusho Co., Ltd.) to obtain a curing agent masterbatch. Next, the components other than the curing agent masterbatch from the compositions listed in Tables 2-4 were weighed into a container, the container was heated to 50°C, stirred and mixed. After that, it was slowly cooled to room temperature, and the curing agent masterbatch was added and mixed in a mixer (Kurashiki Spinning Co., Ltd.) to obtain an epoxy resin composition.

[0037] (Method for manufacturing resin sheets) The epoxy resin composition, immediately after preparation, was degassed under vacuum and then injected into a 2mm thick gap formed between two 4mm thick glass plates using a spacer. Next, the epoxy resin composition sandwiched between the two glass plates was placed in a hot air circulating constant temperature bath preheated to 70°C, and the temperature inside the bath was increased at a rate of 10°C / min from 70°C to 140°C. Subsequently, the inside of the bath was heated for another 30 minutes to maintain the surface temperature at 140°C, thereby curing the epoxy resin composition and obtaining a 2mm thick resin plate.

[0038] (Resin bending test) Six test pieces, each 8 mm wide and 60 mm long, were cut from a resin sheet. Using a universal testing machine (Instron 5965, manufactured by Instron Corporation), the bending strength and bending modulus were measured under the following conditions, and the average value of the six pieces was calculated. Crosshead speed: 2 mm / min, span distance: The thickness of the cured resin plate was measured and set to (thickness × 16) mm.

[0039] (raw materials)

[0040] [Table 1]

[0041] The starting material used for diol A is a polycarbonate diol with a number average molecular weight of approximately 800, synthesized by reacting 1,4-butanediol, isosorbide, and diester carbonate in the presence of a transesterification catalyst. For details of the synthesis method, please refer to, for example, International Publication WO2011 / 129377. The starting material used for diol B is a polycarbonate diol with a number average molecular weight of approximately 800, synthesized by reacting 1,6-hexanediol, isosorbide, and diester carbonate in the presence of a transesterification catalyst. For details of the synthesis method, please refer to, for example, International Publication WO2011 / 129377. The raw material used as diol C is a polycarbonate diol with a number average molecular weight of approximately 2000, synthesized by reacting 1,4-butanediol, neopentyl glycol, and diester carbonate in the presence of a transesterification catalyst.

[0042] [Table 1]

[0043] Experimental Examples 1-5 contain various polycarbonate diols, and it can be confirmed that their flexural strength and elastic modulus are significantly improved compared to Comparative Example 1, which does not contain polycarbonate diols.

[0044] [Table 2]

[0045] Experimental Example 6 shows a significant improvement in elastic modulus and increased strength compared to Comparative Example 2. Experimental Example 7 shows a significant improvement in elastic modulus and increased strength compared to Comparative Example 3.

[0046] [Table 3]

[0047] Table 4 shows that when the amount of diol B added is 10 parts by mass and 20 parts by mass per 100 parts by mass of epoxy resin component, the elastic modulus and strength of the cured epoxy resin composition are particularly improved.

[0048] [Table 4]

[0049] In Comparative Example 4, the resin composition did not harden, and no resin plate was obtained. Based on the test results using the resin plates shown in Tables 1 to 4, it is estimated that the molded product obtained by curing a prepreg impregnated with carbon fibers in the epoxy resin composition of the experimental example has improved elastic modulus and strength compared to the molded product obtained by curing a prepreg impregnated with carbon fibers in the epoxy resin composition of the comparative example. [Industrial applicability]

[0050] Prepregs containing this epoxy resin composition can be used in a variety of structural materials, including the bodies or parts of transportation equipment (including automobiles, motorcycles, and bicycles), sporting goods, leisure goods, home appliance parts, agricultural machinery parts, and building materials.

Claims

1. A prepreg comprising an epoxy resin composition and a fiber reinforcing material, wherein the bisphenol-type epoxy resin is blended with a polycarbonate diol having isosorbide residues and at least one curing agent selected from the group consisting of dicyandiamide, imidazoles, urea compounds, and amines, and the bisphenol-type epoxy resin is blended in an amount of 30 parts by mass or more per 100 parts by mass of epoxy resin components in the epoxy resin composition.

2. The prepreg according to claim 1, wherein the epoxy resin composition is blended with imidazoles.

3. The prepreg according to claim 1 or 2, wherein the epoxy resin composition is blended with an epoxy resin having an epoxy equivalent of 170 or less.

4. The prepreg according to claim 1 or 2, comprising a polycarbonate diol having a number average molecular weight of 300 or more and 5000 or less.

5. The prepreg according to claim 1 or 2, wherein the polycarbonate diol has a 1,4-butanediol residue, a 1,5-pentanediol residue, a 3-methyl-1,5-pentanediol residue, a neopentyl glycol residue, or a 1,6-hexanediol residue.

6. The prepreg according to claim 1 or 2, wherein the hydroxyl group equivalent of the polycarbonate diol is 150 to 2500.

7. The prepreg according to claim 1 or 2, wherein the polycarbonate diol is blended in an amount of 3 to 25 parts by mass per 100 parts by mass of the epoxy resin component.

8. A prepreg comprising an epoxy resin composition containing the following components (A) to (C) and a fiber reinforcing material, wherein component (A) is blended in an amount of 30 parts by mass or more per 100 parts by mass of epoxy resin components in the epoxy resin composition, and the content of component (C) is 10 / 118 parts by mass or more per 100 parts by mass of epoxy resin composition. Component (A): Bisphenol-type epoxy resin Component (B): At least one curing agent selected from the group consisting of dicyandiamide, imidazoles, urea compounds, and amines. Ingredient (C): Polycarbonate diol

9. The prepreg according to claim 8, wherein the aforementioned component (C) is a polycarbonate diol having a number average molecular weight of 300 or more and 5000 or less.

10. The prepreg according to claim 8 or 9, wherein the component (C) is a polycarbonate diol having a 1,4-butanediol residue, a 1,5-pentanediol residue, a 3-methyl-1,5-pentanediol residue, or a 1,6-hexanediol residue.

11. The prepreg according to claim 8 or 9, wherein the component (C) is a polycarbonate diol having an isosorbide residue, a neopentyl glycol residue, a cyclohexanediol residue, or a cyclohexanedimethanol residue.

12. The prepreg according to claim 8 or 9, wherein the aforementioned component (C) is a polycarbonate diol having a hydroxyl group equivalent of 150 to 2000.

13. The prepreg according to claim 8 or 9, wherein the component (C) is blended in an amount of 3 to 25 parts by mass per 100 parts by mass of the epoxy resin component.

14. The prepreg according to claim 8 or 9, wherein the component (B) is blended in an amount of 3 to 40 parts by mass per 100 parts by mass of the epoxy resin component.

15. The prepreg according to claim 8 or 9, wherein, of the components (A), bisphenol A type epoxy resin is blended in an amount of 3 parts by mass or more per 100 parts by mass of component (A).

16. The prepreg according to claim 8 or 9, wherein the component (B) is an imidazole.

17. The prepreg according to claim 8 or 9, wherein the component (B) comprises dicyandiamide and a urea compound.

18. The prepreg according to claim 8 or 9, wherein the mass ratio of the epoxy resin composition to the fiber reinforcement ([mass of epoxy resin composition] / [mass of fiber reinforcement]) is 0.25 to 9.

19. The prepreg according to claim 8 or 9, wherein the fiber reinforcement includes continuous carbon fibers.

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