Towpreg

Abstract

To provide a towpreg excellent in balance of heat resistance and 0° tensile strength availability and capable of improving explosion strength of a pressure container.SOLUTION: A towpreg formed by impregnating an epoxy resin composition that satisfies the conditions (I) and (II), including all of the following components [A] to [C], into a reinforced fiber. [A] bifunctional epoxy resin that is liquid at 25°C, [B] at least one epoxy resin selected from the group consisting of a biphenyl epoxy resin, a biphenyl aralkyl epoxy resin, a dicyclopentadiene epoxy resin and an oxazolidone epoxy resin, [C] dicyandiamide, (I) among total epoxy resin 100 pts.mass, the component [B] is contained by 5 to 40 pts.mass, (II) viscosity at 25°C of the epoxy resin composition is 1 to 150 Pa s.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention particularly relates to a tow prepreg suitably used for manufacturing a hollow container or cylinder made of a fiber-reinforced composite material. More specifically, the present invention relates to a tow prepreg capable of obtaining a fiber-reinforced composite material having an excellent balance between heat resistance and 0° tensile strength utilization rate and capable of improving the bursting strength of a pressure vessel.

Background Art

[0002] Fiber-reinforced composite materials using reinforcing fibers such as carbon fibers and glass fibers are applied to many fields such as aviation, aerospace, automobiles, railway vehicles, ships, civil engineering, and sports equipment because of their excellent light weight. In particular, in applications that require high performance, fiber-reinforced composite materials using continuous reinforcing fibers are used. As the reinforcing fiber, carbon fiber having excellent specific strength and specific modulus is used, and as the thermosetting resin, epoxy resin having excellent adhesiveness to carbon fiber is often used.

[0003] In recent years, with the expansion of the use of carbon fibers, the molding methods have also been expanding. Among these, filament winding is a method suitably used for manufacturing a hollow container or cylinder such as a pressure vessel. From the viewpoints of productivity and quality, in addition to the conventional wet method, a method using a narrow intermediate base material (hereinafter referred to as a tow prepreg) such as a tow prepreg, yarn prepreg, or strand prepreg in which a thermosetting resin is impregnated in advance in a reinforcing fiber bundle has attracted attention.

[0004] A tow prepreg is usually supplied in a bobbin shape in which several hundred to several thousand meters are wound around a paper tube, unwound at high speed in the molding process of a fiber-reinforced composite material, and used for filament winding molding. Therefore, during the manufacturing, storage, and use periods of the tow prepreg, it is required that the viscosity of the impregnated epoxy resin composition hardly increases with time and the unwinding property at high speed hardly decreases.

[0005] In the application of pressure vessels where tow pregs are preferably used, the demand for further weight reduction of components is increasing, and there is a need for a technology to reduce the amount of reinforcing fibers used by improving the burst strength. To improve the burst strength, it is useful to increase the tensile strength in the fiber axis direction (0° tensile strength) of the fiber-reinforced composite material, which can be achieved by increasing the tensile strength of the reinforcing fibers or by increasing the 0° tensile strength utilization rate. The 0° tensile strength utilization rate is an index of how effectively the fiber-reinforced composite material utilizes the strength of the reinforcing fibers. When using the same type and amount of reinforcing fibers, a higher 0° tensile strength utilization rate results in a higher 0° tensile strength.

[0006] In addition, pressure vessels are also required to have sufficient heat resistance against the temperature rise that occurs during rapid filling of high-pressure gas, and to have little performance degradation due to repeated use over a long period of time or use in high-temperature and high-humidity environments. To meet these required performances, it is useful to improve the elongation and toughness of the matrix resin, improve the heat resistance (glass transition temperature), and reduce the hygroscopicity.

[0007] Patent Document 1 discloses an epoxy resin composition for wet filament winding molding that uses a liquid amine as a curing agent and has an excellent balance between heat resistance and 0° tensile strength utilization rate. In such an epoxy resin composition, the fiber-reinforced composite material can obtain a high 0° tensile strength utilization rate, but the viscosity stability over time (pot life) is insufficient for use as a tow preg.

[0008] Patent Document 2 discloses a tow preg that contains dicyandiamide as a curing agent and a large amount of core-shell rubber particles, and can produce a pressure vessel with excellent drapability, tackiness, and unwindability and a high bursting pressure. However, such a tow preg is insufficient from the perspective of achieving both heat resistance and strength utilization rate.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

[0010] In view of such a background, an object of the present invention is to provide a tow preform capable of obtaining a fiber-reinforced composite material excellent in the balance between heat resistance and 0° tensile strength utilization rate. [Means for Solving the Problems]

[0011] The present invention adopts the following means to solve such problems. That is, the tow preform of the present invention is a tow preform obtained by impregnating reinforcing fibers with an epoxy resin composition containing all of the following components [A] to [C] and satisfying conditions (I) and (II). [A] A bifunctional epoxy resin that is liquid at 25°C [B] An epoxy resin selected from the group consisting of a biphenyl type epoxy resin, a biphenyl aralkyl type epoxy resin, a dicyclopentadiene type epoxy resin, and an oxazolidone type epoxy resin [C] Dicyandiamide (I) Among 100 parts by mass of all epoxy resins, 5 to 40 parts by mass of component [B] is contained (II) The viscosity of the epoxy resin composition at 25°C is 1 to 150 Pa·s [Advantages of the Invention]

[0012] The fiber-reinforced composite material obtained by molding and curing the tow preform of the present invention is excellent in the balance between heat resistance and 0° tensile strength utilization rate, so that a pressure vessel having excellent heat resistance and burst strength can be obtained. [Modes for Carrying Out the Invention]

[0013] The present invention has the following configuration: The towpreg of the present invention is a towpreg obtained by impregnating reinforcing fibers with an epoxy resin composition that contains all of the following components [A] to [C] and satisfies conditions (I) and (II): [A] Bifunctional epoxy resin that is liquid at 25°C [B] At least one epoxy resin selected from the group consisting of biphenyl-type epoxy resins, biphenylaralkyl-type epoxy resins, dicyclopentadiene-type epoxy resins, and oxazolidone-type epoxy resins. [C] Dicyandiamide (I) Contains 5 to 40 parts by mass of component [B] out of 100 parts by mass of the total epoxy resin (II) The viscosity of the epoxy resin composition at 25°C is 1 to 150 Pa·s.

[0014] (Regarding ingredient [A]) Component [A] in the present invention is a bifunctional epoxy resin that is liquid at 25°C. Component [A] is necessary to adjust the viscosity of the epoxy resin composition to a level suitable for towpreg production without impairing the good balance between heat resistance and 0° tensile strength utilization. Here, bifunctional means having two epoxy groups per molecule. Examples of such epoxy resins include bisphenol-type epoxy resins such as bisphenol A and bisphenol F, glycidylamine-type epoxy resins such as glycidylaniline, and aliphatic epoxy resins such as polyethylene glycol, polypropylene glycol, butanediol, neopentyl glycol, hexanediol, and cyclohexanedimethanol. These epoxy resins may be used alone or in appropriate mixtures.

[0015] Examples of commercially available bisphenol type epoxy resins include "jER (registered trademark)" 825, "jER (registered trademark)" 828 (both are bisphenol A type epoxy resins, manufactured by Mitsubishi Chemical Corporation), "EPICLON (registered trademark)" 830, "EPICLON (registered trademark)" 807 (both are bisphenol F type epoxy resins, manufactured by DIC Corporation), "jER (registered trademark)" 806 (bisphenol F type epoxy resin, manufactured by Mitsubishi Chemical Corporation), and the like.

[0016] Examples of commercially available glycidylamine type epoxy resins include GAN (N,N-diglycidylaniline, manufactured by Nippon Kayaku Co., Ltd.), GOT (N,N-diglycidyl-o-toluidine, manufactured by Nippon Kayaku Co., Ltd.), and the like.

[0017] Commercially available aliphatic epoxy resins include "Denacol (registered trademark)" EX-821, "Denacol (registered trademark)" EX-850 (polyethylene glycol type epoxy resins, manufactured by Nagase ChemteX Corporation), "Denacol (registered trademark)" EX-920, "Denacol (registered trademark)" EX-941 (polypropylene glycol type epoxy resins, manufactured by Nagase ChemteX Corporation), "Denacol (registered trademark)" EX-214 (1,4-butanediol type epoxy resin, manufactured by Nagase ChemteX Corporation), "Araldite (registered trademark)" DY-026 (1,4-butanediol type epoxy resin, manufactured by Huntsman Japan Co., Ltd.), and "Denacol (registered trademark)" EX-212 (1,6 Examples of epoxy resins that can be used include 1,6-hexanediol-type epoxy resin, manufactured by Nagase ChemteX Corporation), ADEKA Resin (registered trademark) ED-503 (1,6-hexanediol-type epoxy resin, manufactured by ADEKA Corporation), Denacol (registered trademark) EX-211 (neopentyl glycol-type epoxy resin, manufactured by Nagase ChemteX Corporation), ADEKA Resin (registered trademark) ED-523 (neopentyl glycol-type epoxy resin, manufactured by ADEKA Corporation), Denacol (registered trademark) EX-216 (cyclohexanedimethanol-type epoxy resin, manufactured by Nagase ChemteX Corporation), and Rikaresin (registered trademark) DME-100 (cyclohexanedimethanol-type epoxy resin, manufactured by New Japan Chemical Co., Ltd.).

[0018] In the present invention, as component [A], it is preferable to contain 3 to 20 parts by mass of an aliphatic epoxy resin [A1] in 100 parts by mass of the total epoxy resin component. By containing component [A1] within such a range, without impairing the favorable balance between heat resistance and the utilization rate of the tensile strength at 0°, the viscosity of the epoxy resin composition can be effectively reduced, and in addition to being able to adjust it to a range suitable for the production of tow pregs, when used in combination with component [D1] and component [D2] described later, compared with the case where each component is used alone or when two components are used in combination, an effect of improving the specific tensile elongation at break and toughness value can be obtained. Although the reason for obtaining such an effect is not clear, it is presumed that this is because the different tensile elongation at break and toughness value improvement mechanisms possessed by component [A1], component [D1], and component [D2] work in concert. Examples of such component [A1] include polyethylene glycol type epoxy resin, polypropylene glycol type epoxy resin, butanediol type epoxy resin, neopentyl glycol type epoxy resin, hexanediol type epoxy resin, cyclohexanedimethanol type epoxy resin, and the like.

[0019] Furthermore, among component [A1], since it is possible to suppress the hygroscopicity of the cured matrix resin, it is more preferable to contain a bifunctional epoxy resin having an alkylene skeleton with 4 to 10 carbon atoms. Examples of such a bifunctional epoxy resin having an alkylene skeleton with 4 to 10 carbon atoms include butanediol type epoxy resin (number of carbon atoms in the alkylene skeleton: 4), neopentyl glycol type epoxy resin (number of carbon atoms in the alkylene skeleton: 5), hexanediol type epoxy resin (number of carbon atoms in the alkylene skeleton: 6), cyclohexanedimethanol type epoxy resin (number of carbon atoms in the alkylene skeleton: 8), and the like.

[0020] (Regarding component [B]) Component [B] in the present invention is an epoxy resin that is at least one selected from the group consisting of a biphenyl type epoxy resin, a biphenyl aralkyl type epoxy resin, a dicyclopentadiene type epoxy resin, and an oxazolidone type epoxy resin.

[0021] Examples of commercially available products of the biphenyl type epoxy resin which is Component [B] include "jER (registered trademark)" YX4000, "jER (registered trademark)" YX4000H, "jER (registered trademark)" YL6121H (all manufactured by Mitsubishi Chemical Corporation), and the like.

[0022] Examples of commercially available products of the biphenyl aralkyl type epoxy resin which is one type of Component [B] include NC-3000-L, NC-3000, NC-3100 (all manufactured by Nippon Kayaku Co., Ltd.), and the like.

[0023] Examples of commercially available products of the dicyclopentadiene type epoxy resin which is one type of Component [B] include "EPICLON (registered trademark)" HP-7200L, "EPICLON (registered trademark)" HP-7200, "EPICLON (registered trademark)" HP-7200H (all manufactured by DIC Corporation), XD-1000-2L, XD-1000, XD-1000H (all manufactured by Nippon Kayaku Co., Ltd.), and the like.

[0024] Examples of commercially available products of the oxazolidone type epoxy resin which is one type of Component [B] include "D.E.R. (registered trademark)" 858 (manufactured by Olin Corporation), and the like.

[0025] Among Components [B], since the balance between heat resistance and the 0° tensile strength utilization rate is the best, it is more preferable to contain the dicyclopentadiene type epoxy resin [B1]. It is further preferable that Component [B1] is a bifunctional type having two epoxy groups in one molecule. Examples of commercially available products of such bifunctional Component [B1] include "EPICLON (registered trademark)" HP-7200L (manufactured by DIC Corporation), and the like.

[0026] In the present invention, it is necessary to contain 5 to 40 parts by mass of Component [B] out of 100 parts by mass of the total epoxy resin, and it is preferable to contain 5 to 30 parts by mass. By setting the content of Component [B] within such a range, the balance between heat resistance and the 0° tensile strength utilization rate can be maintained well, and the viscosity of the epoxy resin composition can be adjusted to a viscosity suitable for the production of prepreg.

[0027] (Other epoxy resins) Epoxy resins other than components [A] and [B] may be contained within the range that does not impair the effects of the present invention. Examples of such epoxy resins include, but are not limited to, solid bisphenol-type epoxy resins such as solid bisphenol A, solid bisphenol F, and solid bisphenol S; glycidylamine-type epoxy resins such as diaminodiphenylmethane, diaminodiphenylsulfone, aminophenol, metaxylenediamine, and 1,3-bisaminomethylcyclohexane; and isocyanurate, hydantoin, phenol novolac, orthocresol novolac, bisnaphthalene, trishydroxyphenylmethane, and tetraphenylolethane epoxy resins. These epoxy resins may be used alone or in appropriate mixtures.

[0028] (About ingredient [C]) Component [C] of the present invention is dicyandiamide. Dicyandiamide is a heat-activated latent curing agent. That is, it is in a low-activity state below a certain temperature, but when subjected to a certain thermal history, it undergoes a phase change, chemical change, or the like, and becomes highly active. Component [C] is a necessary component for imparting stability to the epoxy resin composition, preventing thickening of the epoxy resin composition during the epoxy resin composition preparation process, the towpreg production process, and the towpreg storage period, while also promoting rapid curing reaction under heated conditions.

[0029] Commercially available dicyandiamide products include "jER Cure (registered trademark)" DICY7 and "jER Cure (registered trademark)" DICY15 (both manufactured by Mitsubishi Chemical Corporation).

[0030] The content of dicyandiamide is preferably such that the number of moles of active hydrogen in dicyandiamide is 0.3 to 1.2 equivalents, more preferably 0.4 to 0.9 equivalents, relative to the number of moles of epoxy groups in all epoxy resin components contained in the epoxy resin composition. That is, in the epoxy resin composition used in the towpreg of the present invention, the content of component [C] is preferably 2.5 to 20 parts by mass, more preferably 3.5 to 15 parts by mass, relative to 100 parts by mass of all epoxy resin components including component [A]. By keeping the content of component [C] within this range, deterioration in heat resistance and mechanical properties due to insufficient curing or excessive reaction heat generation can be prevented, and a good cured product can be obtained. Here, in the present invention, one molecule of dicyandiamide is interpreted as reacting with four epoxy groups, and the active hydrogen equivalent is treated as 21 g / eq.

[0031] (Regarding ingredient [D]) The epoxy resin composition used in the towpreg of the present invention preferably contains a rubber component as component [D]. Here, the rubber component refers to a liquid or solid rubber component commonly used to enhance the toughness of cured epoxy resins. The inclusion of component [D] enhances the toughness of the cured resin, resulting in a pressure vessel with minimal performance degradation with repeated use. Examples of such component [D] include rubber microparticles such as acrylic rubber microparticles, butadiene rubber microparticles, butadiene-styrene rubber microparticles, and silicone rubber microparticles; core-shell rubber microparticles with a core-shell structure in which rubber microparticles are coated with a different polymer; liquid butadiene nitrile rubber, CTBN (carboxyl-terminated butadiene nitrile rubber), ATBN (amino-terminated butadiene nitrile rubber), and butadiene nitrile rubber modified with carboxy groups in the main chain. These rubber components may be used alone or in appropriate mixtures.

[0032] Examples of commercially available products of such rubber components include “Kaneka (registered trademark)” MX-125, “Kaneka (registered trademark)” MX-150, “Kaneka (registered trademark)” MX-154, “Kaneka (registered trademark)” MX-257, “Kaneka (registered trademark)” MX-267, “Kaneka (registered trademark)” MX-416, “Kaneka (registered trademark)” MX-451, “Kaneka (registered trademark)” MX-EXP(HM5) (all manufactured by Kaneka Corporation), “PARALOID (registered trademark)” EXL-2655, “PARALOID (registered trademark)” EXL-2668 (both manufactured by Dow Chemical Company), “Hypro (registered trademark)” 1300X31, “Hypro (registered trademark)” 1300X13, “Hypro (registered trademark)” 1300X13NA, “Hypro (registered trademark)” 1300X8 (all manufactured by CVC Thermoset Specialties), etc.

[0033] In the present invention, since a particularly excellent toughness improvement effect is obtained as compared with the case where each of the components [D] is used alone, it is more preferable to contain both the core-shell rubber particles [D1] and the carboxyl group-terminated butadiene nitrile rubber [D2].

[0034] Examples of commercially available products of the component [D1] include “Kaneka (registered trademark)” MX-125, “Kaneka (registered trademark)” MX-150, “Kaneka (registered trademark)” MX-154, “Kaneka (registered trademark)” MX-257, “Kaneka (registered trademark)” MX-267, “Kaneka (registered trademark)” MX-416, “Kaneka (registered trademark)” MX-451, “Kaneka (registered trademark)” MX-EXP(HM5) (all manufactured by Kaneka Corporation), “PARALOID (registered trademark)” EXL-2655, “PARALOID (registered trademark)” EXL-2668 (both manufactured by Dow Chemical Company), etc.

[0035] Examples of commercially available products of component [D2] include "Hypro®" 1300X31, "Hypro®" 1300X13, "Hypro®" 1300X13NA, "Hypro®" 1300X8 (manufactured by CVC Thermoset Specialties, etc.).

[0036] In the present invention, since it is possible to achieve both an excellent toughness improvement effect and heat resistance, when both core-shell rubber particles [D1] and carboxyl group-terminated butadiene nitrile rubber [D2] are included, the sum of the content of component [D1] and the content of component [D2] is preferably 5 to 45 parts by mass, more preferably 9 to 35 parts by mass, and even more preferably 9 to 20 parts by mass with respect to 100 parts by mass of the total epoxy resin component. Also, the content of component [D2] is preferably 0.5 to 15 parts by mass, more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass of the total epoxy resin component.

[0037] Furthermore, in the present invention, the mass ratio (mass of component [D2] / mass of component [D1]) obtained by dividing the mass of component [D2] by the mass of component [D1] is preferably 0.1 to 0.8. By setting the content of component [D2] with respect to component [D1] within such a range, specifically excellent toughness can be effectively obtained and heat resistance can be achieved at the same time.

[0038] (Regarding component [E]) The epoxy resin composition used in the towpreg of the present invention preferably contains an aromatic urea as component [E]. Using component [E] in combination with component [C] can achieve a good balance between the viscosity stability over time and the curing rate of the epoxy resin composition. Here, aromatic urea refers to a compound having a structure in which a urea group is bonded to an aromatic ring. Specific examples include 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 3-(4-chlorophenyl)-1,1-dimethylurea, phenyldimethylurea (PDMU), and 2,4-toluenebis(3,3-dimethylurea) (TBDMU). These compounds may be used alone or in appropriate mixtures.

[0039] Commercially available products of such component [E] include DCMU99 (DCMU, manufactured by Hodogaya Chemical Co., Ltd.), "Omicure (registered trademark)" 24 (TBDMU, manufactured by Chori GLEX Co., Ltd.), and "Dyhard (registered trademark)" UR505 (4,4'-methylenebis(phenyldimethylurea), manufactured by AlzChem).

[0040] Among the components [E], it is preferable to use TBDMU, since it can give a cured resin product with excellent heat resistance.

[0041] The content of component [E] is preferably 1.0 to 10 parts by mass, and more preferably 1.1 to 5.0 parts by mass, per 100 parts by mass of all epoxy resin components including component [A].

[0042] Furthermore, in the present invention, the molar ratio obtained by dividing the total number of moles of epoxy groups by the number of moles of urea groups (total number of moles of epoxy groups / number of moles of urea groups) is more preferably 15 to 55. By setting the molar ratio of total epoxy groups to urea groups within this range, a good balance between rapid curing properties and heat resistance can be achieved.

[0043] (Other additives) The epoxy resin composition used in the tow prepeg of the present invention can contain various additives such as viscosity modifiers such as thermoplastic resins and thixotropic agents, defoaming agents, stabilizers, flame retardants, and pigments within the range that does not lose the effects of the present invention. As the thermoplastic resin, it is preferably a thermoplastic resin soluble in the epoxy resin. Examples of the thermoplastic resin soluble in the epoxy resin include polyvinyl acetal resins such as polyvinyl formal and polyvinyl butyral, polyvinyl alcohol, phenoxy resin, polyamide, polyimide, polyvinyl pyrrolidone, polysulfone, and the like. Examples of the thixotropic agent include organic ones such as amide wax and hydrogenated castor oil, and inorganic ones such as silica, alumina, mixed oxides of aluminum and silicon, titanium oxide, light calcium carbonate, smectite-based clay minerals (montmorillonite, beidellite, bentonite, hectorite, saponite, etc.), sepiolite, and carbon black. Examples of the defoaming agent include non-silicon polymer-based defoaming agents and silicon-based defoaming agents.

[0044] The epoxy resin composition to be impregnated into the tow prepeg of the present invention needs to have a viscosity at 25°C of 1 to 150 Pa·s, preferably 1 to 110 Pa·s, and more preferably 1 to 50 Pa·s. By setting the viscosity within such a range, the liquid delivery property of the epoxy resin composition during tow prepeg production, the impregnation property into the reinforcing fibers, and the unwindability of the tow prepeg can be improved.

[0045] In the present invention, the glass transition temperature of the resin cured product is preferably 110 to 160°C, and more preferably 120 to 150°C. By setting the glass transition temperature of the resin cured product within such a range, the heat resistance and toughness of the resin cured product can be balanced well. Here, the resin cured product refers to the one obtained by curing the epoxy resin composition of the present invention under heating conditions. The curing conditions of the epoxy resin composition are not particularly limited. For example, after raising the temperature at a rate of 1 to 20°C / min, the curing reaction can be completed by heat treatment at 110 to 160°C for 0.5 to 8 hours.

[0046] For the preparation of the epoxy resin composition used in the tow prepreg of the present invention, various known methods can be used. For example, kneading may be carried out using machines such as a kneader, a planetary mixer, a mechanical stirrer, a dissolver, and a three-roll mill, or it may be mixed by hand using a beaker and a spatula, etc.

[0047] The tow prepreg of the present invention is obtained by impregnating a reinforcing fiber bundle with the epoxy resin composition used in the tow prepreg of the present invention. Here, as the reinforcing fiber bundle, a reinforcing fiber bundle composed of 1,000 to 70,000 filaments with a diameter of 3 to 100 μm is usually used.

[0048] Examples of the reinforcing fiber bundle used in the tow prepreg of the present invention include fiber bundles composed of glass fiber, carbon fiber, aramid fiber, boron fiber, alumina fiber, silicon carbide fiber, etc. Two or more of these fiber bundles may be mixed and used. Among these, it is preferable to use a carbon fiber bundle that can obtain a lightweight and high-rigidity fiber-reinforced composite material. Specific examples of such a carbon fiber bundle include carbon fiber bundles such as acrylic-based, pitch-based, and rayon-based, and in particular, an acrylic-based carbon fiber bundle having a high tensile strength is preferably used.

[0049] The mass content ratio (Rc) of the epoxy resin composition in the tow prepreg of the present invention can be set without particular limitation according to the purpose, but is preferably 20 to 40%, more preferably 20 to 30%, and most preferably 22 to 28%. If the mass content ratio of the epoxy resin composition and the reinforcing fiber bundle is 20% or more, the occurrence of defects such as unimpregnated portions and voids inside the obtained fiber-reinforced composite material can be suppressed. Also, if it is 40% or less, the volume content ratio of the reinforcing fiber bundle can be increased, so that the mechanical properties of the fiber-reinforced composite material can be effectively exhibited and weight reduction can be contributed to.

[0050] The prepreg of the present invention can be manufactured by various known methods. That is, the epoxy resin composition used for the prepreg of the present invention is made to have a lower viscosity by heating without using an organic solvent, and is impregnated while immersing a reinforcing fiber bundle, or the epoxy resin composition made to have a lower viscosity by heating is formed into a coating film on a rotating roll or release paper, and then transferred to one side or both sides of the reinforcing fiber bundle, and then pressurized and impregnated by passing through a bending roll or a pressure roll. Since a high-quality prepreg can be manufactured, the manufacturing method of the prepreg of the present invention preferably includes a step of bringing a rotating roll coated with an epoxy resin composition into contact with at least one side of a reinforcing fiber bundle. The prepreg is usually supplied in a bobbin shape in which several hundred to several thousand meters are wound around a paper tube.

[0051] The fiber-reinforced composite material of the present invention can be obtained by heat-curing the prepreg of the present invention. The prepreg of the present invention can be used in many fields such as aerospace, automobiles, railway vehicles, ships, civil engineering and sports goods, and in particular, can be suitably used for manufacturing hollow containers such as pressure vessels and cylinders.

Examples

[0052] Hereinafter, the present invention will be described in detail with reference to examples. However, the scope of the present invention is not limited to these examples. The unit "part" of the composition ratio means parts by mass unless otherwise noted. In addition, the measurement of various properties (physical properties) was carried out under an environment of a temperature of 23°C and a relative humidity of 50% unless otherwise noted.

[0053] <Materials used in Examples and Comparative Examples> (1) Reinforcing fiber bundle · "Torayca (registered trademark)" T720SC-36K (tensile strength 5,880 MPa, number of filaments 36,000, total fineness 1,650 tex, density 1.8 g / cm 3 , manufactured by Toray Industries, Inc.).

[0054] (2) Component [A] (other than component [A1]): A bifunctional epoxy resin that is liquid at 25°C · "jER (Registered Trademark)" 828 (Liquid Bisphenol A-Type Epoxy Resin, manufactured by Mitsubishi Chemical Corporation) · "jER (Registered Trademark)" 806 (Liquid Bisphenol F-Type Epoxy Resin, manufactured by Mitsubishi Chemical Corporation) · GAN (N,N-Diglycidylaniline, manufactured by Nippon Kayaku Co., Ltd.).

[0055] (3) Component [A1]: Aliphatic Epoxy Resin · "Denacol (Registered Trademark)" EX-821 (Polyethylene Glycol-Type Epoxy Resin, manufactured by Nagase ChemteX Corporation) · "Denacol (Registered Trademark)" EX-211 (Neopentyl Glycol-Type Epoxy Resin, carbon number of alkylene skeleton: 5, manufactured by Nagase ChemteX Corporation) · "Denacol (Registered Trademark)" EX-212 (1,6-Hexanediol-Type Epoxy Resin, carbon number of alkylene skeleton: 6, manufactured by Nagase ChemteX Corporation) · "Denacol (Registered Trademark)" EX-216 (Cyclohexanedimethanol-Type Epoxy Resin, carbon number of alkylene skeleton: 8, manufactured by Nagase ChemteX Corporation).

[0056] (4) Component [B]: An epoxy resin which is at least one selected from the group consisting of biphenyl-type epoxy resin, biphenyl aralkyl-type epoxy resin, dicyclopentadiene-type epoxy resin, and oxazolidone-type epoxy resin · "jER (Registered Trademark)" YX4000 (Biphenyl-Type Epoxy Resin, manufactured by Mitsubishi Chemical Corporation) · NC-3000-L (Biphenyl Aralkyl-Type Epoxy Resin, manufactured by Nippon Kayaku Co., Ltd.) · "EPICLON (Registered Trademark)" HP-7200L (Dicyclopentadiene-Type Epoxy Resin, manufactured by DIC Corporation) · "D.E.R. (Registered Trademark)" 858 (Oxazolidone-Type Epoxy Resin, manufactured by Olin Corporation).

[0057] (5) Other Epoxy Resins "Sumiepoxy (registered trademark)" ELM-434 (tetraglycidyldiaminodiphenylmethane, manufactured by Sumitomo Chemical Co., Ltd.).

[0058] (6) Component [C]: Dicyandiamide "jER Cure (registered trademark)" DICY7 (epoxy resin curing agent, dicyandiamide, manufactured by Mitsubishi Chemical Corporation).

[0059] (7) Other hardeners "Seikacure (registered trademark)" S (epoxy resin curing agent, 4,4'-diaminodiphenyl sulfone, manufactured by Seika Corporation).

[0060] (8) Component [D1]: Core-shell rubber particles Kane Ace (registered trademark) MX-150 (liquid bisphenol A epoxy resin masterbatch containing 40% polybutadiene rubber core-shell rubber particles, manufactured by Kaneka Corporation) "Kane Ace (registered trademark)" MX-257 (liquid bisphenol A type epoxy resin masterbatch containing 37% polybutadiene rubber type core-shell rubber particles, manufactured by Kaneka Corporation).

[0061] (9) Component [D2]: Carboxyl-terminated butadiene nitrile rubber "Hypro(R)" 1300X13NA (carboxyl-terminated butadiene nitrile rubber, manufactured by CVC Thermoset Specialties).

[0062] (10) Component [E]: Aromatic urea "Omicure" (registered trademark) 24 (TBDMU, manufactured by Chori GLEX Co., Ltd.).

[0063] (11) Other additives BYK® 1790 (defoaming agent, manufactured by BYK Japan Co., Ltd.).

[0064] <Method for preparing epoxy resin composition> All components except for component [C] and component [E] were added to a beaker, which was then heated to 100°C and stirred until homogeneous. The resin temperature was then lowered to 25-60°C, after which component [C] and component [E] were added and stirred until homogeneous, yielding an epoxy resin composition. Whether component [B] was compatible with component [A] and homogeneous was determined visually. The component content ratios for the examples and comparative examples are shown in Tables 1-3.

[0065] <Method for measuring viscosity of epoxy resin composition at 25°C> In accordance with JIS Z8803 (2011) "Viscosity measurement method using a cone-plate rotational viscometer," measurements were taken using an E-type viscometer (TVE-30H, manufactured by Toki Sangyo Co., Ltd.) equipped with a standard cone rotor (1°34' x R24) at a rotation speed of 5 to 20 rpm. The temperature inside the sample cup was adjusted to the measurement temperature (25°C), and the epoxy resin composition was poured into the cup. The value was read once the displayed value had stabilized after at least one minute had passed.

[0066] <Method for evaluating gelation initiation time of epoxy resin composition> Using a Cure Monitor LT-451 (manufactured by Lambient Technologies), the change in ionic viscosity of an epoxy resin composition at 150°C was measured over time. The ionic viscosity of an epoxy resin composition reaches a minimum at the start of curing, increases as the curing reaction progresses, and then saturates upon completion. In the present invention, the percentage of the ionic viscosity value at a certain point in time relative to the ionic viscosity at the completion of the curing reaction (the highest value obtained by measurement) was calculated as the cure index (Cd), and the time required for Cd to reach 20% was defined as the gelation initiation time.

[0067] <How to make a cured resin board> The epoxy resin composition was degassed in a vacuum and then poured into a mold set to a thickness of 2 mm or 6 mm using Teflon (registered trademark) spacers. The composition was then heated from room temperature to 150°C in a hot air oven at a rate of 2.5°C per minute, and then held at that temperature for 1 hour to cure the epoxy resin composition. The composition was then cooled to room temperature and demolded to produce a cured resin plate.

[0068] <Method for measuring glass transition temperature> A test piece with a width of 12.7 mm and a length of 45 mm was cut out from a 2-mm-thick resin cured plate, and DMA measurement was performed in the temperature range of 30 to 250 °C under the conditions of a torsional vibration frequency of 1.0 Hz and a heating rate of 5.0 °C / min using a viscoelasticity measuring device (ARES, manufactured by TA Instruments). The glass transition temperature (Tg) was defined as the temperature at the intersection of the tangent line in the glass state and the tangent line in the transition state in the storage modulus G’ curve.

[0069] <Method for measuring tensile fracture elongation of epoxy resin cured product> A dumbbell-shaped test piece of type 1BA conforming to JIS K7161 (1994) was cut out from a 2-mm-thick resin cured plate, and then a tensile test was carried out at a test speed of 1 mm / min with the distance between chucks set to 58 mm using an Instron universal testing machine (manufactured by Instron) to measure the tensile fracture elongation.

[0070] <Method for measuring fracture toughness of resin cured product> The test was carried out in accordance with the SENB (Single Edge Noched Bend) test method conforming to ASTM D5045. A test piece with a length of 60 mm and a width of 12.7 mm was cut out from a 6-mm-thick resin cured plate, and then a pre-crack was introduced. Thereafter, using an Instron universal testing machine (manufactured by Instron), with the distance between supports set to 50.8 mm, the crosshead speed set to 10 mm / min, and the number of samples n = 6, the fracture toughness value (K IC ) was measured.

[0071] <Method for measuring water absorption rate of resin cured product> A resin cured plate processed to a size of 2 mm in thickness, 60 mm in length, and 10 mm in width was vacuum dried at 60 °C for 24 hours and then left standing for 7 days under the hygrothermal conditions of a temperature of 85 °C and a humidity of 95% RH. The percentage of the mass change after exposure to the hygrothermal conditions with respect to the dry mass of the test piece was taken as the water absorption rate.

[0072] <Method for producing top prepeg> Using a towprep manufacturing apparatus equipped with a creel, kiss roll, nip roll, and winder, an epoxy resin composition adjusted to a temperature of 20 to 60°C was applied to one side of carbon fiber "Toreca (registered trademark)" T720SC-36K, and then passed through a nip roll to impregnate the epoxy resin composition into the inside of the reinforcing fiber bundle, obtaining a towprep with a resin content of 25%. The bobbin of the towprep was wound with 2300 m on a paper tube so as to have a cylindrical shape with an initial tension of 600 to 1000 gf, a winding ratio of 6 to 10, and a winding width of 230 to 260 mm.

[0073] <Method for Measuring Utilization Rate of 0° Tensile Strength of Fiber Reinforced Composite Material> The towprep was sandwiched between metal plates with a release film attached, and while applying a constant tension to the tow, the temperature was raised from room temperature to 150°C at a rate of 2.5°C per minute in a hot air oven, and then held at 150°C for 1 hour to cure the towprep. Glass fiber reinforced plastic tabs with a width of 14 mm and a length of 50 mm were adhered to both ends of the cured towprep so that the distance between the tabs was 150 mm to prepare test pieces. For this test piece, a tensile test was performed using an Instron universal testing machine (manufactured by Instron Corporation) at a crosshead speed of 3.0 mm / min to obtain the breaking load per cross-sectional area in the fiber longitudinal direction (0° direction). The cross-sectional area of the test piece was obtained by dividing the mass per unit length of the reinforcing fiber by the density. Also, the 0° tensile strength utilization rate was calculated using the average value of the tensile strengths of 10 test pieces. The 0° tensile strength utilization rate (%) was calculated by 0° tensile strength of the towprep cured product / strand strength of the reinforcing fiber × 100.

[0074] <Method for Measuring Strand Strength of Reinforcing Fiber> The strand strength of the reinforcing fiber was determined according to the following procedure in accordance with JIS R7608:2007 "Test Method for Resin-Impregnated Strand". The resin-impregnated strand of the carbon fiber bundle to be measured was prepared by impregnating carbon fiber or graphitized fiber with a composition consisting of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexyl carboxylate (100 parts by mass), boron trifluoride monoethylamine (3 parts by mass), and acetone (4 parts by mass), and curing at a temperature of 125°C for 30 minutes. The number of specimens for measuring the resin-impregnated strand of carbon fiber was six, and the average value of each measurement result was taken as the strand strength. The measurement elongation range for the tensile modulus was set to a range of elongation from 0.3% to 0.7%. In this example, "Celloxide (registered trademark)" 2021P manufactured by Daicel Chemical Industries, Ltd. was used as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexyl carboxylate.

[0075] (Example 1) 80 parts by mass of "jER (registered trademark)" 828 was used as component [A], 20 parts by mass of "jER (registered trademark)" YX-4000 was used as component [B], 6.3 parts by mass of "jER Cure (registered trademark)" DICY7 was used as component [C], 1.7 parts by mass of "Omicure (registered trademark)" 24 was used as component [E], and 0.5 parts by mass of "BYK (registered trademark)" 1790 was used as other additives. An epoxy resin composition was prepared according to the above <Method for Preparing Epoxy Resin Composition>. The viscosity of this epoxy resin composition at 25°C was 22 Pa·s, and the gelation time at 150°C was 3.5 minutes. The glass transition temperature of the resin cured product was 140°C, the tensile fracture elongation was 5.5%, and the fracture toughness value (K IC ) was 0.8 MPa·m 0.5 , and the water absorption rate was 5.4%.

[0076] Next, using this epoxy resin composition, a towpreg was obtained according to the above <Method for Producing Towpreg>. The 0° tensile strength utilization rate obtained using this towpreg was 91%.

[0077] As described above, good results were obtained in all the tests.

[0078] (Example 2) As shown in Table 1, an epoxy resin composition and a prepreg were prepared and evaluated in the same manner as in Example 1, except that 20 parts by mass of NC-3000-L was included as component [B]. The evaluation results were good in all of the viscosity of the resin composition at 25°C, the gelation time at 150°C, the glass transition temperature of the resin cured product, the tensile elongation at break, the fracture toughness value (K IC ), the water absorption rate, and the 0° tensile strength utilization rate of the fiber reinforced composite material.

[0079] (Example 3) As shown in Table 1, an epoxy resin composition and a prepreg were prepared and evaluated in the same manner as in Example 1, except that 20 parts by mass of "EPICLON (registered trademark)" 7200-L was included as component [B]. The evaluation results were good in all of the viscosity of the resin composition at 25°C, the gelation time at 150°C, the glass transition temperature of the resin cured product, the tensile elongation at break, the fracture toughness value (K IC ), the water absorption rate, and the 0° tensile strength utilization rate of the fiber reinforced composite material.

[0080] (Example 4) As shown in Table 1, an epoxy resin composition and a prepreg were prepared and evaluated in the same manner as in Example 1, except that 20 parts by mass of "D.E.R. (registered trademark)" 858 was included as component [B]. The evaluation results were good in all of the viscosity of the resin composition at 25°C, the gelation time at 150°C, the glass transition temperature of the resin cured product, the tensile elongation at break, the fracture toughness value (K IC ), the water absorption rate, and the 0° tensile strength utilization rate of the fiber reinforced composite material.

[0081] (Examples 5 and 6) As shown in Table 1, the resin composition was changed, and "hypro (registered trademark)" CTBN1300X13NA was used as component [D]. As a result of preparing and evaluating an epoxy resin composition and a prepreg in the same manner as in Example 1, the viscosity of the resin composition at 25°C, the gelation time at 150°C, the glass transition temperature of the resin cured product, the tensile elongation at break, the fracture toughness value (K IC ), the water absorption rate, and the 0° tensile strength utilization rate of the fiber reinforced composite material were all good. Especially for KIC showed excellent values with component [D].

[0082] (Examples 7 - 9) As shown in Table 1, the resin composition was changed, and "Kaneka (registered trademark)" MX - 257 was used as component [D]. In the same manner as in Example 1, an epoxy resin composition and a prepreg were prepared and evaluated. As a result, for the viscosity of the resin composition at 25°C, the gelation time at 150°C, the glass transition temperature of the resin cured product, the tensile fracture elongation, the fracture toughness value (K IC ), water absorption rate, and the 0° tensile strength utilization rate of the fiber - reinforced composite material, good results were obtained. In particular, K IC showed excellent values with component [D].

[0083] (Examples 10 - 13) As shown in Table 1 and Table 2, the resin composition was changed, and "Kaneka (registered trademark)" MX - 150 was used as component [D1], and "hypro (registered trademark)" CTBN1300X13NA was used as component [D2]. In the same manner as in Example 1, an epoxy resin composition and a prepreg were prepared and evaluated. As a result, for the viscosity of the resin composition at 25°C, the gelation time at 150°C, the glass transition temperature of the resin cured product, the tensile fracture elongation, the fracture toughness value (K IC ), water absorption rate, and the 0° tensile strength utilization rate of the fiber - reinforced composite material, good results were obtained. In particular, K IC showed particularly excellent values with the combined use of component [D1] and component [D2]. Among them, Examples 10 - 12 where the mass of component [D2] / the mass of component [D1] was 0.1 - 0.8 showed particularly excellent K IC improvement effects and heat resistance.

[0084] (Examples 14 - 19) As shown in Table 2, the resin composition was changed, and component [A1] was used. In the same manner as in Example 1, an epoxy resin composition and a prepreg were prepared and evaluated. As a result, for the viscosity of the resin composition at 25°C, the gelation time at 150°C, the glass transition temperature of the resin cured product, the tensile fracture elongation, the fracture toughness value (K IC) Good results were obtained in all of water absorption and the utilization rate of the 0° tensile strength of the fiber-reinforced composite material. By the component [A1], without impairing the good balance between heat resistance and the utilization rate of the 0° tensile strength, the viscosity of the epoxy resin composition can be effectively reduced. Moreover, by using it in combination with the component [D1] and the component [D2], as compared with the case where each component is used alone or the case where two components are used in combination, the effects of improving specific tensile elongation at break and toughness value were obtained. Further, in Examples 15 to 19 using a bifunctional epoxy resin having an alkylene skeleton with 4 to 10 carbon atoms as the component [A1], the moisture absorption of the resin cured product could be suppressed as compared with Example 14.

[0085] (Comparative Example 1) As shown in Table 3, the resin composition was changed, and instead of using the component [B], 20 parts by mass of "Sumiepoxy (registered trademark)" ELM-434 was used as another epoxy resin. In the same manner as in Example 1, an epoxy resin composition and a prepreg were prepared and evaluated. As a result, the glass transition temperature of the resin cured product was good at 144 °C, but the utilization rate of the 0° tensile strength of the fiber-reinforced composite material was insufficient at 84%.

[0086] (Comparative Example 2) As shown in Table 3, the resin composition was changed, the component [B] was not used, and as the component [A], 80 parts by mass of "jER (registered trademark)" 806 and 20 parts by mass of GAN were used. In the same manner as in Example 1, an epoxy resin composition and a prepreg were prepared and evaluated. As a result, the utilization rate of the 0° tensile strength of the fiber-reinforced composite material was good at 93%, but the glass transition temperature of the resin cured product was insufficient at 95 °C.

[0087] (Comparative Examples 3 and 4) As shown in Table 3, the resin composition was changed, the component [B] was 3 parts by mass, and the content was made less than 5 parts by mass. In the same manner as in Example 1, an epoxy resin composition and a prepreg were prepared and evaluated. As a result, the glass transition temperature of the resin cured product was good, but the utilization rate of the 0° tensile strength of the fiber-reinforced composite material was insufficient, and the effect of the component [B] was not sufficiently obtained.

[0088] (Comparative Example 5) As shown in Table 3, the resin composition was changed, and an epoxy resin composition and a prepreg were prepared and evaluated in the same manner as in Example 1. As a result, since the viscosity of the resin composition at 25°C was as high as 171 Pa·s, equipment for high-temperature heating conditions was required for feeding the epoxy resin composition in the manufacturing apparatus used, and the manufacturing efficiency of the prepreg was insufficient.

[0089] (Comparative Example 6) As shown in Table 3, the resin composition was changed, and instead of using Component [A], 80 parts by mass of "Sumiepoxy (registered trademark)" ELM-434 was used as another epoxy resin. As a result of preparing and evaluating an epoxy resin composition and a prepreg in the same manner as in Example 1, the glass transition temperature of the cured resin was as good as 196°C, but the 0° tensile strength utilization rate of the fiber-reinforced composite material was insufficient at 77%.

[0090] (Comparative Example 7) As shown in Table 3, the resin composition was changed, and instead of using Component [C], "Seikacure (registered trademark)" S was used as another curing agent. As a result of preparing and evaluating an epoxy resin composition in the same manner as in Example 1, it did not cure under the conditions of the above <Method for Producing Resin Cured Plate>, and the curing rate was insufficient.

[0091]

Table 1

[0092]

Table 2

[0093]

Table 3

Claims

1. A prepreg obtained by impregnating a reinforcing fiber with an epoxy resin composition containing all of the following components [A], [B1], [C], [D1] and [D2] and satisfying conditions (I) and (II). [A] A bifunctional epoxy resin that is liquid at 25°C [B1] A dicyclopentadiene-type epoxy resin [C] Dicyandiamide [D1] Core-shell rubber particles [D2] Carboxyl-terminated butadiene-nitrile rubber (I) Among 100 parts by mass of the total epoxy resin, 5 to 40 parts by mass of component [B1] is contained (II) The viscosity of the epoxy resin composition at 25°C is 1 to 150 Pa·s

2. The prepreg according to Claim 1, wherein the epoxy resin composition satisfies condition (III). (III) Mass of component [D2] / Mass of component [D1] = 0.1 to 0.8

3. The prepreg according to Claim 1 or 2, wherein the epoxy resin composition satisfies the following condition (IV). (IV) Glass transition temperature is 110 to 160°C

4. The prepreg according to any one of Claims 1 to 3, wherein the epoxy resin composition contains 3 to 20 parts by mass of the following component [A1] as component [A] in 100 parts by mass of the total epoxy resin component. [A1] An aliphatic epoxy resin

5. The prepreg according to Claim 4, wherein the epoxy resin composition contains a bifunctional epoxy resin having an alkylene skeleton with 4 to 10 carbon atoms as component [A1].

6. A fiber-reinforced composite material obtained by curing the prepreg according to any one of Claims 1 to 5.

Images