JP2014145003A - Prepreg and fiber reinforced composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber reinforced composite material expressing stable shock resistance and interlaminar toughness, and also having moisture thermal time compression strength, to provide a prepreg for obtaining the same, and a fiber reinforced composite material using the same.SOLUTION: There is provided a prepreg consisting of [A] to [D] and a reinforced fiber, and 90 mass% or more of total amount of [C] and [D] exist in a depth range of 20% of depth of the prepreg from a prepreg surface. [A] an epoxy resin. [B] an epoxy resin curing agent. [C] a polymer particle insoluble in the epoxy resin, satisfying following (c-i) to (c-iii). (c-i) A sphericity of the particle is 90 to 100. (c-ii) The glass transition temperature is in a range of 80 to 180°C. (c-iii) The average particle diameter is in the range of 10 to 30 μm. [D] a polymer particle insoluble in the epoxy resin, satisfying following (d-i) and (d-ii). (d-i) The glass transition temperature is in the range of 80 to 155°C. (d-ii) The average particle diameter is in the range more than 1/1000 and less than 1/10 of [C].

Description

  The present invention relates to a prepreg from which a fiber reinforced composite material having excellent interlaminar toughness and compressive strength under wet heat can be obtained, and a fiber reinforced composite material using the prepreg.

  Fiber reinforced composite materials, especially carbon fiber reinforced composite materials, are useful because they are excellent in specific strength and specific rigidity, and are useful for aircraft structural members, windmill blades, automobile outer plates, IC trays, and notebook PC housings (housings). ) And other computer applications, and the demand is increasing year by year.

  Carbon fiber reinforced composite material is a heterogeneous material formed by molding a prepreg composed of carbon fibers, which are reinforcing fibers, and a matrix resin as essential components. Therefore, the physical properties of the reinforcing fibers in the alignment direction and the physical properties in other directions There is a big difference. For example, it is known that interlayer toughness, which indicates the difficulty of progressing interlaminar fracture of reinforcing fibers, does not lead to drastic improvement only by improving the strength of the reinforcing fibers. In particular, a carbon fiber reinforced composite material using a thermosetting resin as a matrix resin reflects the low toughness of the matrix resin, and has a property of being easily broken by stress from other than the direction in which the reinforcing fibers are arranged. Therefore, while maintaining the compressive strength in the fiber direction under the high-temperature and high-humidity environment required for aircraft structural materials, the composite material properties that can cope with stresses from other than the array direction of reinforcing fibers including interlayer toughness Various techniques have been proposed for the purpose of improvement.

  Furthermore, in recent years, the application site of fiber reinforced composite materials for aircraft structural materials has expanded, and the application of fiber reinforced composite materials to wind turbine blades and various turbines aimed at improving power generation efficiency and energy conversion efficiency is also progressing. Studies are being made on application to thick members having a large number of laminated prepregs and members having a three-dimensional curved shape. When tensile stress or compressive stress is applied to such a thick member or curved member, an out-of-plane tearing stress occurs between the fiber layers, and cracks due to the opening mode occur between the layers. Due to the progress, the strength and rigidity of the entire member may decrease, leading to total destruction. In order to counter this stress, interlaminar toughness in the open mode, i.e. mode I, is required.

  In addition, when such a large structural material is molded, it is inevitable that a difference in thermal history occurs between the parts. Accordingly, such fiber reinforced composite materials are also required to have the same form and characteristics even when the temperature-time profile during molding varies to some extent.

  On the other hand, a technology has been proposed in which a particulate material using a high toughness polyamide or the like is arranged in the fiber interlayer region to increase the mode II interlayer toughness and suppress damage to the falling weight impact on the member surface (patent) Reference 1). However, even when this technique is used, a sufficient effect is not obtained with respect to the mode I interlayer toughness.

  On the other hand, a material having high interlaminar fracture toughness in addition to impact resistance is disclosed by using a matrix resin containing high melting point thermoplastic particles and low melting point thermoplastic particles (see Patent Document 2). However, even when this technology is used, it is difficult to achieve both mode I interlaminar toughness and compressive strength in the fiber direction during wet heat, and depending on the molding conditions of the fiber reinforced composite material, the interlaminar morphology varies due to melting and deformation of the interlaminar particles The stable interlayer toughness could not be expressed. Furthermore, a material capable of improving impact resistance and interlaminar toughness while maintaining heat resistance by combining two types of particles having different glass transition temperatures (Tg) is disclosed. True spherical polyamide particles having different Tg and particle sizes The example which combined these is disclosed (refer patent document 3). However, even when this technique is used, the form of the interlayer varies due to the melting and deformation of the interlayer particles depending on the molding conditions of the fiber-reinforced composite material, and stable interlayer toughness cannot be expressed. Moreover, the crack which progresses between layers transitions in a reinforcement fiber layer, and the problem that a toughness value fluctuates was also seen.

US Pat. No. 5,028,478 Special table 2010-525101 JP 7-41576 A

  An object of the present invention is to provide a prepreg from which a fiber-reinforced composite material that stably exhibits interlaminar toughness and also has compressive strength during wet heat is obtained, and a fiber-reinforced composite material using the prepreg.

In order to achieve the above object, the present invention has any one of the following configurations. That is, it is a prepreg composed of the following [A] to [D] and reinforcing fibers, and 90% by mass or more of the total amount of [C] and [D] is 20% of the thickness of the prepreg from the prepreg surface. It is a prepreg characterized by existing in a range.
[A] epoxy resin [B] epoxy resin curing agent [C] sphericity of polymer particles (ci) particles insoluble in epoxy resin that satisfy the following conditions (ci) to (c-iii) (C-ii) the glass transition temperature is in the range of 80 to 180 ° C. (c-iii) the average particle diameter is in the range of 10 to 30 μm [D] the following (di) and Polymer particles insoluble in epoxy resin satisfying the condition of (d-ii) (d-i) Glass transition temperature is in the range of 80 to 155 ° C. (d-ii) Average particle diameter is 1/1000 of [C]. In the range below 1/10.

  According to a preferred embodiment of the prepreg of the present invention, [C] has a particle size distribution index in the range of 1.0 to 1.8.

  According to a preferred embodiment of the prepreg of the present invention, [C] is polymer particles insoluble in an epoxy resin made of crystalline polyamide.

  According to the preferable aspect of the prepreg of this invention, the mass content rate of [D] with respect to the total amount of [C] and [D] exists in the range of 5-30 mass%.

  According to a preferred embodiment of the prepreg of the present invention, the sphericity of [D] is 90-100.

  According to a preferred embodiment of the prepreg of the present invention, [C] is a polyamide particle containing a chemical structure of the general formula (1).

(Wherein R ₁ and R ₂ represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a halogen element, and may be the same or different. R ₃ is a methylene having 1 to 20 carbon atoms) Represents a group)
According to a preferred embodiment of the prepreg of the present invention, the epoxy resin [A] includes a polyfunctional amine type epoxy resin.

  According to a preferred embodiment of the prepreg of the present invention, the epoxy resin curing agent [B] is an aromatic amine, and diaminodiphenylsulfone or a derivative or isomer thereof is used alone or with other aromatic amine. You may use it in combination.

  Moreover, in this invention, the said prepreg can be hardened and it can be set as a fiber reinforced composite material.

  ADVANTAGE OF THE INVENTION According to this invention, the fiber reinforced composite material which expresses interlayer toughness stably and has compressive strength at the time of wet heat, and the prepreg for obtaining this are obtained.

  Hereinafter, the prepreg and fiber-reinforced composite material of the present invention will be described in detail.

  The epoxy resin [A] in the present invention means a compound having two or more epoxy groups in one molecule.

  Specific examples of the epoxy resin [A] in the present invention include an aromatic glycidyl ether obtained from a phenol having a plurality of hydroxyl groups, an aliphatic glycidyl ether obtained from an alcohol having a plurality of hydroxyl groups, a glycidyl amine obtained from an amine, and a carboxyl group. Examples thereof include glycidyl esters obtained from a plurality of carboxylic acids and epoxy resins having an oxirane ring.

  Among them, a glycidylamine type epoxy resin can be suitably used because of its low viscosity, excellent impregnation into reinforcing fibers, and excellent mechanical properties such as heat resistance and elastic modulus when used as a fiber reinforced composite material. Such glycidylamine type epoxy resins can be broadly classified into polyfunctional amine type epoxy resins and bifunctional amine type epoxy resins.

  Such a polyfunctional amine type epoxy resin refers to a glycidyl amine type epoxy resin containing three or more epoxy groups in one molecule of the epoxy resin. Examples of such polyfunctional amine type epoxy resins include tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, tetraglycidylxylylenediamine, halogen substituted products thereof, alkyl substituted products, aralkyl substituted products, allyl substituted products, and alkoxy substituted products. Aralkoxy-substituted products, allyloxy-substituted products, hydrogenated products, and the like can be used.

  Such a polyfunctional amine type epoxy resin is not particularly limited, but tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, tetraglycidylxylylenediamine, a substituted product thereof, a hydrogenated product, and the like are preferably used.

  Examples of the tetraglycidyldiaminodiphenylmethane include “Sumiepoxy (registered trademark)” ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), YH434L (manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.), and “jER (registered trademark)” 604 (Mitsubishi Chemical Corporation). ), “Araldide (registered trademark)” MY720, MY721 (manufactured by Huntsman Advanced Materials), etc. can be used. Examples of triglycidylaminophenol and alkyl substitution products thereof include “Sumiepoxy (registered trademark)” ELM100, ELM120 (manufactured by Sumitomo Chemical Co., Ltd.), “Araldide (registered trademark)” MY0500, MY0510, MY0600 (Huntsman Advanced Material). And “jER (registered trademark)” 630 (manufactured by Mitsubishi Chemical Corporation), etc. can be used. As tetraglycidylxylylenediamine and hydrogenated products thereof, “TETRAD (registered trademark)”-X, “TETRAD (registered trademark)”-C (manufactured by Mitsubishi Gas Chemical Co., Inc.) and the like can be used.

  The polyfunctional amine type epoxy resin is preferably used as the epoxy resin [A] in the present invention because it is excellent in the balance between the heat resistance of the obtained cured resin and the mechanical properties such as the elastic modulus. The polyfunctional amine type epoxy resin is desirably contained in an amount of 40 to 70% by mass in the total epoxy resin.

  The epoxy resin [A] in the present invention may contain an epoxy resin other than glycidylamine, a copolymer of an epoxy resin and a thermosetting resin, or the like. Examples of the thermosetting resin used by being copolymerized with an epoxy resin include unsaturated polyester resin, vinyl ester resin, epoxy resin, benzoxazine resin, phenol resin, urea resin, melamine resin, and polyimide resin. It is done. These resin compositions and compounds may be used alone or in combination as appropriate.

  Of the epoxy resins used as epoxy resins other than glycidylamine, a glycidyl ether type epoxy resin having phenol as a precursor is preferably used as the bifunctional epoxy resin. Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, naphthalene type epoxy resins, biphenyl type epoxy resins, urethane-modified epoxy resins, hydantoin type and resorcinol type epoxy resins. It is done.

The polymer particle [C] insoluble in the epoxy resin in the present invention needs to satisfy the following conditions (ci) to (c-iii).
(Ci) The sphericity of the particles is 90-100.
(C-ii) The glass transition temperature is in the range of 80 to 180 ° C.
(C-iii) The average particle diameter is in the range of 10 to 30 μm.

  Here, insoluble in an epoxy resin means that the polymer particles are not substantially dissolved in the epoxy resin when the epoxy resin in which the polymer particles are dispersed is heated and cured. This means that the particles can be observed with a clear interface between the particles and the matrix resin without substantially reducing the original size in the cured epoxy resin using a microscope.

  The polymer particles [C] in the present invention are required to have a sphericity of 90 to 100, and preferably 96 to 100. By setting such high sphericity, the viscosity of the epoxy resin composition in which the polymer particles are dispersed can be kept low, and the amount of the polymer particles can be increased accordingly, and [D ], The particle filling rate can be increased. When the sphericity is less than 90, the blending amount of the polymer particles is limited due to an increase in the viscosity of the epoxy resin composition, and the particle filling effect when combined with [D] is small.

  The sphericity is calculated according to the following numerical conversion formula from the average of 30 particles selected by observing particles with a scanning electron microscope, measuring the short diameter and the long diameter, and randomly selecting particles.

  Note that n is 30 measurements.

  The polymer particles [C] in the present invention are required to have a glass transition temperature in the range of 80 to 180 ° C, preferably in the range of 130 to 155 ° C, and in the range of 130 to 150 ° C. It is more preferable. By setting such a relatively high glass transition temperature, deformation of the polymer particles does not occur when the prepreg of the present invention is laminated and heat-cured, and mainly the reinforcing fibers described below, the epoxy resin [A], and the epoxy resin A layer composed of polymer particles and a resin composition (hereinafter referred to as an interlayer or interlayer resin layer, or interlayer region) between a fiber layer composed of a curing agent [B] (hereinafter sometimes referred to as a fiber layer) and the fiber layer. It is possible to obtain a fiber-reinforced composite material that can be stably formed, has excellent interlaminar toughness, and can stably secure compressive strength during wet heat. When such a glass transition temperature is less than 80 ° C., a fiber-reinforced composite material having an insufficient balance between interlayer toughness and wet compressive strength is obtained. On the other hand, when the glass transition temperature is higher than 180 ° C., the toughness of the polymer particles themselves tends to be insufficient, the interfacial adhesion between the polymer particles and the matrix resin is insufficient, and the fiber reinforced composite material has insufficient interlayer toughness. It becomes.

  Such a glass transition temperature is measured by using a differential scanning calorimetry (DSC method) from 30 ° C. to a temperature higher than the predicted glass transition temperature by 30 ° C. or higher under a temperature rising condition of 20 ° C./min. Glass transition observed when the temperature is raised and held for 1 minute, then cooled to 0 ° C. under a temperature drop condition of 20 ° C./minute, held for 1 minute, and then measured again under a temperature rise condition of 20 ° C./minute. It is the temperature (Tg).

  The polymer particles [C] in the present invention are required to have an average particle diameter in the range of 10 to 30 μm. The average particle diameter refers to the number average particle diameter. In the fiber reinforced composite material obtained by laminating an epoxy resin composition in which such polymer particles are dispersed and a prepreg in combination with a reinforcing fiber and heat-curing, the average particle diameter is in such a range. Can be obtained, and as a result, the interlayer toughness becomes stable and high.

  Moreover, it is preferable that the polymer particle [C] insoluble in the epoxy resin in the present invention has a particle size distribution index of 1.0 to 1.8 ((c-iv)), and 1.1 to 1.5. It is more preferable that In the fiber reinforced composite material obtained by laminating a prepreg in which the epoxy resin composition in which the polymer particles are dispersed and the reinforcing fiber are combined and heat-curing by setting such a relatively narrow particle size distribution, [D] In combination, the particle filling rate in the interlayer region tends to be effectively increased. In addition, there is a tendency that a fiber-reinforced composite material having a uniform interlayer thickness can be obtained without the occurrence of a region having an excessive interlayer thickness due to the presence of some coarse particles. When such a particle size distribution index exceeds 1.8, when combined with [D], it is difficult to improve the particle filling rate in the interlayer region, and due to the occurrence of unevenness in the interlayer thickness, It tends to be a material with large variations.

  The particle size distribution index is determined based on the following numerical conversion formula for the value of the particle diameter obtained by the method described later.

  Here, Di: particle size of each particle, n: number of measurement 100, Dn: number average particle size, Dv: volume average particle size, PDI: particle size distribution index.

  The polymer particle [C] in the present invention is not limited to a resin type, and any of a thermoplastic resin and a thermosetting resin having a glass transition temperature in the range of 80 to 180 ° C. is applicable.

  Specific examples of the thermoplastic resin include vinyl polymer, polyester, polyamide, polyarylene ether, polyarylene sulfide, polyethersulfone, polysulfone, polyetherketone, polyetheretherketone, polyurethane, polycarbonate, polyamideimide, Examples thereof include polyimide, polyetherimide, polyacetal, silicone, and copolymers thereof.

  Specific examples of thermosetting resins include epoxy resins, benzoxazine resins, vinyl ester resins, unsaturated polyester resins, urethane resins, phenol resins, melamine resins, maleimide resins, cyanate ester resins, and urea resins. It is done.

  One or more of the above-described resins can be used.

  Among these, polyamide, which is a thermoplastic resin, is preferably used because of its high elongation, toughness, and adhesiveness with the matrix resin. Examples of the polyamide include polyamides obtained by polycondensation of a lactam having three or more members, a polymerizable aminocarboxylic acid, a dibasic acid and a diamine or a salt thereof, or a mixture thereof.

  Examples of polyamides having a glass transition temperature in the range of 80 ° C. to 180 ° C. include polyhexamethylene terephthalamide (nylon 6T), polynonane terephthalamide (nylon 9T), poly-m-xylene adipamide (nylon MXD) 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane, a copolymer of dodecadioic acid and isophthalic acid (for example, “Grillamide (registered trademark)” TR55, manufactured by Mzavelke), 3,3 Copolymer of '-dimethyl-4,4'-diaminodicyclohexylmethane and dodecadioic acid (for example, “Grillamide (registered trademark)” TR90, manufactured by Mzavelke), 4,4′-diaminodicyclohexylmethane and dodeca Copolymers of diacids (for example, “Trogamide®” CX7323, Gusa Co., Ltd.) and the like.

  Especially, it is preferable that the polymer particle [C] in this invention is a polyamide ((cv)) which has crystallinity. Since it has crystallinity, it is possible to obtain a fiber-reinforced composite material having a stable interlayer thickness and interlayer toughness that can suppress deformation of particles when a fiber-reinforced composite material is used.

  Examples of polyamides that exhibit crystallinity include polyhexamethylene terephthalamide (nylon 6T), polynonane terephthalamide (nylon 9T), poly-m-xylene adipamide (nylon MXD), 4,4'-diaminodicyclohexylmethane. And a copolymer of dodecadioic acid (for example, “Trogamide (registered trademark)” CX7323, manufactured by Degussa).

  In addition, in addition to the interlaminar toughness of the fiber reinforced composite material, a fiber reinforced composite material excellent in moisture and heat resistance and solvent resistance can be obtained. It is preferable that it is a polyamide containing the chemical structure of 1).

(Wherein R ₁ and R ₂ represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a halogen element, and may be the same or different. R ₃ is a methylene having 1 to 20 carbon atoms) Represents a group).

  As such a polyamide, a copolymer of 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane and dodecadioic acid (for example, “Grillamide (registered trademark)” TR90, manufactured by Mzavelke), A copolymer of 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane, isophthalic acid and 12-aminododecanoic acid, and a copolymer of 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane and dodecanedioic acid A mixture with a polymer (for example, “Grillamide (registered trademark)” TR70LX, manufactured by Mzavelke), a copolymer of 4,4′-diaminodicyclohexylmethane and dodecadioic acid (for example, “trogamide ( Registered trademark) "CX7233, manufactured by Degussa).

The polymer particle [D] in the present invention must satisfy the following conditions (d-i) and (d-ii).
(D-i) The glass transition temperature is in the range of 80 to 155 ° C. (d-ii) The average particle diameter is in the range of more than 1/1000 of [C] and less than 1/10.

  The polymer particles [D] in the present invention must have a glass transition temperature in the range of 80 to 155 ° C, preferably in the range of 130 to 155 ° C, and more preferably in the range of 130 to 150 ° C. . By setting such a relatively high glass transition temperature, deformation of the polymer particles does not occur during heat curing, a stable interlayer thickness is formed, excellent interlaminar toughness, and stable compressive strength when wet heat is ensured. It is possible to obtain a fiber-reinforced composite material that can be obtained. When such a glass transition temperature is less than 80 ° C., a fiber-reinforced composite material having an insufficient balance between interlayer toughness and wet compressive strength is obtained. On the other hand, when such a glass transition temperature exceeds 155 ° C., the toughness of the polymer particles themselves tends to be insufficient, and the interfacial adhesion between the polymer particles and the matrix resin becomes insufficient, and the fiber reinforced composite material has insufficient interlayer toughness. It becomes.

  The polymer particle [D] in the present invention needs to have an average particle diameter in a range larger than 1/1000 of [C] and smaller than 1/10, and in a range larger than 1/100 and smaller than 1/10. It is preferable. When the average particle diameter is within this range, the polymer particles [D] are distributed at the interface between the fiber layer and the interlayer resin layer, and the toughness of the interface is improved to prevent cracks in the fiber layer. Stablely improves interlayer toughness. When the average particle diameter exceeds 1/10, the particles cannot be distributed at the interface, and the interface toughness improving effect is reduced. When the average particle size is less than 1/1000, the particles cannot stay at the interface with the interlayer resin layer and do not contribute to the toughness of the interface by entering the fiber layer deeply, or increase in viscosity due to the incorporation of small particle size This deteriorates the prepreg manufacturing process.

  In addition, the polymer particles [D] in the present invention preferably have a mass content of [D] in the range of 5 to 30% by mass with respect to the total amount of [C] and [D]. When the mass content of [D] is within such a range, the increase in the viscosity of the resin composition is suppressed as much as possible, and the particle filling rate at the interlayer region and the interface between the fiber layer and the interlayer resin layer is effectively increased. Can do. When the mass content is less than 5% by mass, the effect of filling the small particle size particles near the interface between the fiber layer and the interlayer resin layer is reduced, so the change in the interlaminar fracture mode of the fiber reinforced composite material or the interlayer toughening The improvement effect becomes smaller. On the other hand, when this mass content rate exceeds 30 mass%, the manufacturing process of a prepreg deteriorates by the viscosity raise of a resin composition.

  The polymer particles [D] in the present invention are not limited to polymer species, and may be the same polymer species as [C] or non-identical polymer species.

  The polymer particles [D] in the present invention preferably have a sphericity of 90 to 100 ((d-iii)), and more preferably 96 to 100. By setting such high sphericity, the viscosity of the epoxy resin composition in which such polymer particles are dispersed can be kept low, and the amount of polymer particles can be increased accordingly, and [C ], The particle filling rate can be increased. When the sphericity is less than 90, the blending amount of the polymer particles is limited due to the increase in viscosity of the epoxy resin composition, and the filling effect at the interface is small.

  The prepreg of the present invention is used by blending an epoxy resin curing agent [B]. Such an epoxy resin curing agent is a compound having an active group capable of reacting with an epoxy group. Specifically, for example, dicyandiamide, aromatic polyamine, aminobenzoic acid esters, various acid anhydrides, phenol novolac resin, cresol novolac resin, polyphenol compound, imidazole derivative, aliphatic amine, tetramethylguanidine, thiourea-added amine Carboxylic acid anhydrides such as methylhexahydrophthalic anhydride, carboxylic acid hydrazides, carboxylic acid amides, polymercaptans, and Lewis acid complexes such as boron trifluoride ethylamine complexes.

  By using an aromatic polyamine as a curing agent, an epoxy resin cured product having good heat resistance can be obtained. In particular, among aromatic polyamines, diaminodiphenyl sulfone or a derivative thereof, or various isomers thereof are the most suitable curing agents for obtaining a cured epoxy resin having good heat resistance.

  Further, by using a combination of dicyandiamide and a urea compound such as 3,4-dichlorophenyl-1,1-dimethylurea or imidazoles as a curing agent, high heat resistance and water resistance can be obtained while curing at a relatively low temperature. . Curing the epoxy resin with an acid anhydride gives a cured product having a lower water absorption than the amine compound curing. In addition, by using a latent product of these curing agents, for example, a microencapsulated product, the storage stability of the prepreg, in particular, tackiness and draping properties hardly change even when left at room temperature.

  The optimum value of the addition amount of the curing agent varies depending on the type of the epoxy resin and the curing agent. For example, in the case of an aromatic amine curing agent, it is preferable to add the stoichiometric equivalent, but the ratio of the active hydrogen amount of the aromatic amine curing agent to the epoxy group amount of the epoxy resin is 0.7 to 0. By setting the ratio to about .9, a high elastic modulus resin may be obtained as compared with the case where it is used in an equivalent amount, which is also a preferable embodiment. These curing agents may be used alone or in combination.

  Commercially available aromatic polyamine curing agents include Seika Cure S (manufactured by Wakayama Seika Kogyo Co., Ltd.), MDA-220 (manufactured by Mitsui Chemicals), “jER Cure (registered trademark)” W (Mitsubishi Chemical Corporation) )), And 3,3′-DAS (manufactured by Mitsui Chemicals), Lonzacure (registered trademark) M-DEA (manufactured by Lonza Corp.), Lonzacure (registered trademark) M-DIPA (manufactured by Lonza Corp.) ), Lonzacure (registered trademark) M-MIPA (manufactured by Lonza Corporation), Lonzacure (registered trademark) DETDA 80 (manufactured by Lonza Corporation), and the like.

  Moreover, the epoxy resin [A] and the epoxy resin curing agent [B], or a product obtained by pre-reacting a part thereof can be blended in the composition. This method may be effective for viscosity adjustment and storage stability improvement.

  The prepreg of the present invention is a coupling agent, a thermosetting polymer particle, a thermoplastic resin that can be dissolved in an epoxy resin, or silica gel, carbon black, clay, carbon nanotube, metal powder, as long as the effects of the present invention are not hindered. An inorganic filler such as a body can be blended.

  The prepreg of the present invention comprises an epoxy resin composition comprising an epoxy resin [A], an epoxy resin curing agent [B], polymer particles [C], and polymer particles [D]. 90% by mass or more of the total amount is impregnated into the reinforcing fiber in a form in which the total amount is within a range of 20% of the thickness of the prepreg from the prepreg surface. As the reinforcing fiber used in the prepreg of the present invention, carbon fiber, glass fiber, aramid fiber, boron fiber, PBO fiber, high strength polyethylene fiber, alumina fiber, silicon carbide fiber, and the like can be used. Two or more kinds of these fibers may be mixed and used. The form and arrangement of the reinforcing fibers are not limited, and for example, fiber structures such as long fibers arranged in one direction, a single tow, a woven fabric, a knit, a non-woven fabric, a mat and a braid are used.

  In particular, in applications where there is a high demand for weight reduction and high strength of materials, carbon fibers can be suitably used because of their excellent specific modulus and specific strength.

  The carbon fiber preferably used in the present invention may be any type of carbon fiber depending on the application, but is a carbon fiber having a tensile elastic modulus of 400 GPa at the highest in terms of interlayer toughness and impact resistance. It is preferable. From the viewpoint of strength, a carbon fiber having a tensile strength of preferably 4.4 to 6.5 GPa is preferably used because a composite material having high rigidity and mechanical strength can be obtained. Further, the tensile elongation is also an important factor, and it is preferably a high-strength, high-stretch carbon fiber of 1.7 to 2.3%. Therefore, carbon fibers having the characteristics that the tensile modulus is at least 230 GPa, the tensile strength is at least 4.4 GPa, and the tensile elongation is at least 1.7% are most suitable.

  Commercially available carbon fibers include “Torayca (registered trademark)” T800G-24K, “Torayca (registered trademark)” T800S-24K, “Torayca (registered trademark)” T700G-24K, and “Torayca (registered trademark)” T300- 3K, and “Torayca (registered trademark)” T700S-12K (manufactured by Toray Industries, Inc.).

  The form and arrangement of the carbon fibers can be appropriately selected from long fibers and woven fabrics arranged in one direction. However, in order to obtain a carbon fiber reinforced composite material that is lighter and more durable, It is preferably in the form of continuous fibers such as long fibers (fiber bundles) or woven fabrics arranged in one direction.

  The carbon fiber bundle used in the present invention preferably has a single fiber fineness of 0.2 to 2.0 dtex, more preferably 0.4 to 1.8 dtex. If the single fiber fineness is less than 0.2 dtex, damage to the carbon fiber bundle due to contact with the guide roller may easily occur during twisting, and similar damage may also occur in the impregnation treatment step of the resin composition. . When the single fiber fineness exceeds 2.0 dtex, the carbon fiber bundle may not be sufficiently impregnated with the resin composition, and as a result, fatigue resistance may be reduced.

  In the carbon fiber bundle used in the present invention, the number of filaments in one fiber bundle is preferably in the range of 2500 to 50000. When the number of filaments is less than 2500, the fiber arrangement tends to meander and easily cause a decrease in strength. If the number of filaments exceeds 50,000, resin impregnation may be difficult during prepreg production or molding. The number of filaments is more preferably in the range of 2800 to 40000.

  The prepreg of the present invention is obtained by impregnating a reinforcing fiber with a resin composition having an epoxy resin [A], an epoxy resin curing agent [B], polymer particles [C], and polymer particles [D]. Preferably, the fiber mass fraction of the prepreg is preferably 40 to 90% by mass, more preferably 50 to 80% by mass. If the fiber mass fraction is too low, the resulting fiber reinforced composite material may have an excessive mass, which may impair the advantages of the fiber reinforced composite material having excellent specific strength and specific elastic modulus. If it is too high, poor impregnation of the resin composition occurs, and the resulting fiber-reinforced composite material tends to have a lot of voids, and its mechanical properties may be greatly deteriorated.

  The prepreg of the present invention is a layer rich in particles, that is, a layer in which at least the polymer particles [C] and the polymer particles [D] can be clearly identified when the cross section is observed ( Hereinafter, it may be abbreviated as a particle layer.) May be a structure formed in the vicinity of the surface of the prepreg.

  By adopting such a structure, when a prepreg is laminated and an epoxy resin is cured to form a fiber-reinforced composite material, the polymer layer [C] and the polymer particle [D] are provided between the fiber layer and the fiber layer. An interlayer resin layer is easily formed, and a high degree of interlayer toughness and impact resistance are expressed in the resulting fiber-reinforced composite material.

  From such a viewpoint, the particle layer comprising the polymer particles [C] and the polymer particles [D] is preferably in the thickness direction from the surface of the prepreg with respect to the thickness of the prepreg of 100%. Is preferably in the range of 20% deep, more preferably 10% deep. Further, the particle layer may be present only on one side, but care must be taken because the prepreg can be front and back. If the prepreg stacking is mistaken to form layers with and without particles, a composite material with low interlayer toughness is obtained. In order to eliminate the distinction between front and back and facilitate lamination, the particle layer should be present on both the front and back sides of the prepreg.

  Furthermore, the abundance ratio of the polymer particles [C] and the polymer particles [D] existing in the particle layer is 90 to 100% by mass with respect to the total amount of the polymer particles [C] and [D] in the prepreg. , Preferably it is 95-100 mass%.

  The abundance of the particles can be evaluated by, for example, the following method. That is, the prepreg is sandwiched between two smooth polytetrafluoroethylene resin plates with a smooth surface, and the temperature is gradually raised to the curing temperature over 7 days to gel and cure to cure the plate-like prepreg. Make a thing. A micrograph of the cross section of the obtained cured product is taken. In the case of a prepreg in which the particle layer is arranged on both sides using this cross-sectional photograph, a line parallel to the surface of the prepreg is formed on both sides of the prepreg cured product at a position 20% deep from the surface of the prepreg cured product. Draw a total of two each. Next, the total area of the particles existing between the surface of the prepreg and the line and the total area of the particles existing over the thickness of the prepreg are obtained, and from the surface of the prepreg with respect to 100% of the thickness of the prepreg. Calculate the abundance of particles present in the 20% depth range. Here, the total area of the particles is obtained by cutting out the particle portion from the cross-sectional photograph and converting it from the mass. It is also possible to measure using commonly used image processing software. If it is difficult to identify the particles dispersed in the resin in the cross-sectional photograph, a means for dyeing the particles can also be employed.

  The prepreg of the present invention can be produced by applying a method as disclosed in JP-A-1-26651, JP-A-63-170427 or JP-A-63-170428. Specifically, the prepreg of the present invention has polymer particles [C] and [C] on the surface of a primary prepreg composed of a resin composition having reinforcing fibers, an epoxy resin [A], and an epoxy resin curing agent [B]. D] is applied in the form of particles, and in the process of preparing a mixture in which these particles are uniformly mixed in a matrix resin and impregnating the mixture into the reinforcing fibers, the reinforcing fibers block the penetration of these particles. The method of localizing particles on the surface portion of the prepreg, or preparing a primary prepreg by impregnating the resin composition in advance with a reinforcing fiber, and containing the particles at a high concentration on the surface of the primary prepreg It can manufacture by the method of sticking the resin film which consists of resin compositions. When the polymer particles [C] and the polymer particles [D] are uniformly present within a depth range of 20% of the prepreg thickness, a prepreg for a fiber composite material having high interlayer toughness can be obtained.

  The prepreg of the present invention is a wet method in which a resin composition comprising an epoxy resin [A] and an epoxy resin curing agent [B] is dissolved in a solvent such as methyl ethyl ketone or methanol to lower the viscosity and impregnate the reinforcing fibers. And it can manufacture suitably by the hot-melt method etc. which make an epoxy resin composition low-viscosity by heating, and make a reinforced fiber impregnate.

  In the wet method, the reinforced fiber is dipped in a solution of a resin composition having an epoxy resin [A] and an epoxy resin curing agent [B], then pulled up, and the solvent is evaporated using an oven or the like to obtain a prepreg. Is the method.

  The hot melt method is a method in which a reinforcing fiber is impregnated directly with a resin composition having an epoxy resin [A] and an epoxy resin curing agent [B] whose viscosity is reduced by heating, or the resin composition is released from release paper or the like. This is a method of preparing a prepreg by preparing a resin film coated on the upper side of the reinforced fiber, and then superposing the resin film from both sides or one side of the reinforcing fiber and transferring and impregnating the resin composition by heating and pressing. This hot melt method is a preferred embodiment because substantially no solvent remains in the prepreg.

  In addition, the fiber reinforced composite material of the present invention is obtained by laminating a plurality of prepregs produced by such a method, and then applying an epoxy resin [A] and an epoxy resin curing agent while applying heat and pressure to the obtained laminate. The resin composition comprising [B] can be produced by a method of heat curing.

  As a method for applying heat and pressure, a press molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, an internal pressure molding method, and the like are used. In particular, a wrapping tape method and an internal pressure molding method are preferably used for molding sports equipment.

  The wrapping tape method is a method in which a prepreg is wound around a mandrel or the like and a tubular body made of a fiber reinforced composite material is formed, and is a suitable method for producing a rod-like body such as a golf shaft or a fishing rod. . More specifically, the prepreg is wound around a mandrel, and a wrapping tape made of a thermoplastic resin film is wound outside the prepreg to fix the prepreg and apply pressure, and the epoxy resin [A] and the epoxy resin are cured in an oven. In this method, the resin composition having the agent [B] is heat-cured, and then the cored bar is removed to obtain a tubular body.

  In addition, the internal pressure molding method is to set a preform in which a prepreg is wound on an internal pressure applying body such as a tube made of a thermoplastic resin in a mold, and then apply high pressure gas to the internal pressure applying body to apply pressure. At the same time, the mold is heated to form a tubular body. This internal pressure molding method is particularly preferably used when molding a complicated shape such as a golf shaft, a bat, and a racket such as tennis or badminton.

  The fiber-reinforced composite material of the present invention is a resin composition comprising the above-described prepreg of the present invention laminated in a predetermined form, and pressurizing and heating to have an epoxy resin [A] and an epoxy resin curing agent [B]. As an example, a method of curing can be produced.

The fiber-reinforced composite material of the present invention is a polymer particle insoluble in an epoxy resin [A] that simultaneously satisfies the conditions (ci) to (c-iii) and (di) to (d-ii). By using C] and polymer particles [D], the degree of filling of the polymer particles in the fiber interlayer region becomes high. Therefore, even when placing the same amount of polymer particles in the interlayer, fiber interlayer thickness is especially small fiber-reinforced composite material was obtained, as a result, becomes sufficiently high interlayer toughness G _IC. The interlayer thickness is preferably in the range of 10 to 30 μm. Such interlayer thickness can be measured, for example, by the following procedure. The fiber reinforced composite material is cut from the direction orthogonal to the reinforcing fibers, and the cross section is polished, and then magnified 200 times or more with an optical microscope and photographed. For a randomly selected fiber interlayer region on the photo, the reinforcing fiber volume content is 50%, and the line drawn parallel to the fiber layer is 100 μm in length as the boundary line between the fiber layer region and the fiber interlayer region. The average boundary line is drawn over the distance, and the distance between them is defined as the interlayer thickness.

  In the present invention, both polymer particles [C] and [D] are localized in an interlayer region sandwiched between reinforcing fiber layers, and [D] having a small particle diameter is between [C] having a large particle diameter. When distributed in a filling form, these particles are closely packed in the interlayer region, and even when the same amount of polymer particles is arranged between the layers, a fiber-reinforced composite material having a small interlayer thickness is obtained.

  In the fiber reinforced composite material of the present invention, the sphericity of the polymer particles [C] observed with an optical microscope is preferably in the range of 90 to 100, and more preferably in the range of 96 to 100, in the cross section. preferable. In particular, [C] having a large particle diameter maintains a high sphericity even after molding, so that the sphericity is maintained as a whole of the polymer particles, thereby obtaining a stable interlayer thickness regardless of molding conditions. Mechanical properties such as toughness are stably expressed. Such sphericity can be measured, for example, by the following procedure. The fiber reinforced composite material is cut from a direction orthogonal to the carbon fiber, and the cross section is polished, and then magnified 200 times or more with an optical microscope and photographed. The short diameter and long diameter of [C] particles are measured from this photograph, and calculated from the average of 30 randomly selected particles according to the following numerical conversion formula.

  Note that n is 30 measurements.

  Hereinafter, the prepreg and the fiber-reinforced composite material of the present invention will be described more specifically with reference to examples. The production methods and evaluation methods of the resin raw materials, prepregs and fiber reinforced composite materials used in the examples are shown below. The production environment and evaluation of the prepregs of the examples are performed in an atmosphere at a temperature of 25 ° C. ± 2 ° C. and a relative humidity of 50% unless otherwise specified.

<Carbon fiber (reinforced fiber)>
"Torayca (registered trademark)" T800G-24K-31E (carbon fiber with 24,000 filaments, tensile strength 5.9 GPa, tensile elastic modulus 294 GPa, tensile elongation 2.0%, manufactured by Toray Industries, Inc.).

<Epoxy resin [A]>
"Sumiepoxy (registered trademark)" ELM434 (tetraglycidyldiaminodiphenylmethane, manufactured by Sumitomo Chemical Co., Ltd.)
"Araldite (registered trademark)" MY0600 (m-aminophenol type epoxy resin, epoxy equivalent 118, manufactured by Huntsman Advanced Materials Co., Ltd.)
"Epiclon (registered trademark)" 830 (bisphenol F type epoxy resin, manufactured by DIC Corporation)
<Epoxy resin curing agent [B]>
3,3′-DAS (3,3′-diaminodiphenylsulfone, manufactured by Mitsui Chemicals Fine Co., Ltd.).

<Other ingredients>
"Sumika Excel (registered trademark)" PES5003P (polyethersulfone, manufactured by Sumitomo Chemical Co., Ltd.).

<Polymer particles [C]>
Particle 1 (particles having an average particle diameter of 18 μm, a particle diameter distribution of 1.2, a sphericity of 98, and a Tg of 137 ° C., produced from “Trogamide (registered trademark)” CX7323 as a raw material)
In a 1000 ml pressure-resistant glass autoclave (Pressure Glass Industry Co., Ltd., Hyperglaster TEM-V1000N), 37 g of polyamide (weight average molecular weight 17,000, “Trogamide (registered trademark)” CX7323) manufactured by Degussa as an organic polymer, organic 285 g of N-methyl-2-pyrrolidone as a solvent, 28 g of polyvinyl alcohol as polymer B (“GOHSENOL (registered trademark)” GM-14 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) Weight average molecular weight 29,000, sodium acetate content 0.23 mass% , SP value 32.8 (J / cm ³ ) ^1/2 ) was added, and after replacing with 99% by volume or more of nitrogen, the mixture was heated to 180 ° C. and stirred for 2 hours until the polymer was dissolved. Thereafter, 350 g of ion-exchanged water as a poor solvent was dropped at a speed of 2.92 g / min via a liquid feed pump. When about 200 g of ion exchange water was added, the system turned white. After the entire amount of water has been added, the temperature is lowered while stirring, and the resulting suspension is filtered, washed with 700 g of ion-exchanged water, reslurried, and filtered, and vacuum-dried at 80 ° C. for 10 hours. This gave 36 g of a gray colored solid. When the obtained powder was observed with a scanning electron microscope, it was a polyamide fine particle having a true spherical fine particle shape, an average particle size of 18 μm, and a particle size distribution index of 1.2.

・ Particle 2 (particles having an average particle diameter of 13 μm, a particle diameter distribution of 1.2, a sphericity of 97, and a Tg of 137 ° C., produced from “Trogamide (registered trademark)” CX7323 as a raw material)
In a 1000 ml pressure-resistant glass autoclave (Pressure Glass Industry Co., Ltd., Hyperglaster TEM-V1000N), 35 g of polyamide (weight average molecular weight 17,000, “Trogamide (registered trademark)” CX7323) manufactured by Degussa as an organic polymer, organic 287 g of N-methyl-2-pyrrolidone as a solvent, 28 g of polyvinyl alcohol as polymer B (“GOHSENOL (registered trademark)” GM-14, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), weight average molecular weight 29,000, sodium acetate content 0.23 mass% , SP value 32.8 (J / cm ³ ) ^1/2 ) was added, and after replacing with 99% by volume or more of nitrogen, the mixture was heated to 180 ° C. and stirred for 2 hours until the polymer was dissolved. Thereafter, 350 g of ion-exchanged water as a poor solvent was dropped at a speed of 2.92 g / min via a liquid feed pump. When about 200 g of ion exchange water was added, the system turned white. After the entire amount of water has been added, the temperature is lowered while stirring, and the resulting suspension is filtered, washed with 700 g of ion-exchanged water, reslurried, and filtered, and vacuum-dried at 80 ° C. for 10 hours. And 34 g of a gray colored solid were obtained. When the obtained powder was observed with a scanning electron microscope, it was a polyamide fine particle having a true spherical particle shape, an average particle size of 13 μm, and a particle size distribution index of 1.2.

  -Particle 3 ("Trepearl (registered trademark)" TN, manufactured by Toray Industries, Inc., average particle size 13.0 μm, particle size distribution 2.10, sphericity 96, Tg 167 ° C.).

<Polymer particle [D]>
-Particles 4 (particles having an average particle size of 1.1 μm, a particle size distribution of 1.2, a sphericity of 92, and a Tg of 137 ° C. prepared from “Trogamide (registered trademark)” CX7323 as a raw material)
(Method for producing particle 4)
In a 2000 mL flask, polyamide (weight average molecular weight 17,000, “Trogamide (registered trademark)” CX7233 manufactured by Degusa) was dissolved in formic acid to a concentration of 5 mass%. 450 g of ethanol was added to 300 g of this polyamide-formic acid mixed solution and stirred. Then, the polyamide-formic acid-ethanol mixed solution was poured into 1875 g of ethanol cooled to 18 ° C. with stirring. Stirring was continued for about 10 minutes until the particles were completely precipitated, followed by centrifugation (15 ° C., 9500 rpm, 10 minutes) to remove the supernatant, and the resulting particles were reslurried with ethanol. The obtained suspension was centrifuged again (15 ° C., 9500 rpm, 10 minutes), and then the particles were recovered and freeze-dried to obtain particles 4 as a white solid.

-Particle 5 (SSX-101, manufactured by Sekisui Plastics Co., Ltd., average particle size 1.5 μm, true spherical particles made of crosslinked polymethyl methacrylate, Tg 120 ° C.)
<Other particles>
-Particle 6 (particles having an average particle diameter of 4 μm, a particle diameter distribution of 1.2, a sphericity of 98, and a Tg of 137 ° C., produced from “Trogamide (registered trademark)” CX7323 as a raw material)
20 g of polyamide (weight average molecular weight 17,000, “Trogamide (registered trademark)” CX7323) manufactured by Degussa as a polymer A in a 1000 ml pressure-resistant glass autoclave (pressure-resistant glass industry, Hyper Glaster TEM-V1000N), organic 295 g of N-methyl-2-pyrrolidone as a solvent, 35 g of polyvinyl alcohol as polymer B (“GOHSENOL (registered trademark)” GM-14, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), weight average molecular weight 29,000, sodium acetate content 0.23 mass% , SP value 32.8 (J / cm ³ ) ^1/2 ) was added, and after replacing with 99% by volume or more of nitrogen, the mixture was heated to 180 ° C. and stirred for 2 hours until the polymer was dissolved. Thereafter, 350 g of ion-exchanged water as a poor solvent was dropped at a speed of 2.92 g / min via a liquid feed pump. When about 200 g of ion exchange water was added, the system turned white. After the entire amount of water has been added, the temperature is lowered while stirring, and the resulting suspension is filtered, washed with 700 g of ion-exchanged water, reslurried, and filtered, and vacuum-dried at 80 ° C. for 10 hours. This yielded 26 g of a gray colored solid. When the obtained powder was observed with a scanning electron microscope, it was a polyamide fine particle having a true spherical fine particle shape, an average particle size of 4 μm, and a particle size distribution index of 1.2.

  -Particle 7 (SP-500, manufactured by Toray Industries, Inc., average particle size: 5 μm, particle size distribution: 1.1, sphericity: 96, Tg: 55 ° C.).

Particle 8 (“Kane Ace (registered trademark)” MX-416, manufactured by Kaneka Corporation, core-shell rubber particles made of styrene-butadiene-methyl methacrylate, average particle size: 0.1 μm, Tg: −100 ° C.)
This is a masterbatch having a concentration of 25% by mass based on tetraglycidyldiaminodiphenylmethane. In the composition tables of Examples and Comparative Examples in Table 1, the number of blended parts as rubber particles is shown.

Particle 9 (SO-C5, manufactured by Admatechs Co., Ltd., true spherical silica particles, average particle size: 1.6 μm)
(1) Measurement of average particle diameter, particle diameter distribution index, and sphericity of polymer particles [C] and [D] The individual particle diameters of polymer particles [C] and [D] were measured with a scanning electron microscope (JEOL). With a scanning electron microscope (JSM-6301NF) manufactured by Co., Ltd., the particles were observed at 1000 times and measured. When the particles were not perfect circles, the major axis was measured as the particle diameter.

  The average particle diameter was calculated by measuring the diameter of 100 particles randomly selected from the photograph and calculating the arithmetic average thereof. The average particle diameter here refers to the number average particle diameter. The particle size distribution index indicating the particle size distribution was calculated based on the following numerical conversion formula for the individual particle diameter values obtained above.

  Di: particle diameter of each particle, n: number of measurement 100, Dn: number average particle diameter, Dv: volume average particle diameter, PDI: particle diameter distribution index.

  The sphericity is calculated according to the following formula from the average of 30 short diameters and long diameters of particles randomly selected from a photograph.

  Note that n is 30 measurements.

(2) Measurement of glass transition temperature (Tg) of polymer particles [C] and [D] The polymer particles were measured at 30 ° C. from the predicted glass transition temperature by using a differential scanning calorimetry method (DSC method). After raising the temperature at a temperature rising rate of 20 ° C./min for 1 minute, holding it for 1 minute, cooling it to 0 ° C. at a temperature lowering condition of 20 ° C./min, holding it for 1 minute, It refers to the glass transition temperature (Tg) observed when measured again at a temperature rising condition of 20 ° C./min.

  Specifically, in the portion showing the step change of the obtained DSC curve, the straight line equidistant from the extended straight line of each baseline in the vertical axis direction and the curve of the step change portion of the glass transition intersect. The temperature at the point was taken as the glass transition temperature. A differential scanning calorimeter 2910 manufactured by TA Instruments was used as a measuring device.

(3) Preparation of Epoxy Resin Composition In the kneader, 50 parts by mass of “Sumiepoxy (registered trademark)” ELM434, 20 parts by mass of “Araldite (registered trademark)” MY0600, “Epiclon (registered trademark)” 30 parts by mass of 830 and 15 parts by mass of “SUMICA EXCEL (registered trademark)” 5003P were added, the temperature was raised to 160 ° C. while kneading, and the mixture was kneaded at 160 ° C. for 1 hour to obtain a transparent viscous liquid. Obtained. After the temperature was lowered to 80 ° C. while kneading, 40 parts by mass of 3,3′-DAS and the particle components (polymer particles [C], [D] and other particles) in the composition shown in Table 1 totaled 74 parts by mass. The resulting mixture was further kneaded to obtain an epoxy resin composition. The particles 8 were charged in the state of a masterbatch, and tetraglycidyldiaminodiphenylmethane contained in the masterbatch was charged in a calculation included in the above-mentioned “Sumiepoxy (registered trademark)” ELM434 (50 parts by mass).

(4) Preparation of prepreg The epoxy resin composition was applied onto release paper using a knife coater to prepare a resin film. Next, two resin films are stacked on both sides of the carbon fiber on a carbon fiber “Treca (registered trademark)” T800G-24K-31E manufactured by Toray Industries, Ltd., which is arranged in one direction in a sheet shape, and heated and pressurized. The resin was impregnated with carbon fiber to obtain a unidirectional prepreg having a carbon fiber basis weight of 190 g / m ² and a matrix resin mass fraction of 35.5%. At that time, the following two-stage impregnation method was applied to prepare a prepreg in which polymer particles [C] and [D] were highly localized on the surface layer.

In order to produce a resin film for primary prepreg, an epoxy resin composition having the same composition as that described in (3) other than the particle component and containing no particle component was prepared by the procedure of (3). This epoxy resin composition was applied onto release paper using a knife coater to prepare a 30 g / m ² resin film having a normal weight per unit area of 60% by mass. Next, two resin films are superposed on both sides of the carbon fiber on a carbon fiber “Torayca (registered trademark)” T800G-24K-31E manufactured by Toray Industries, Ltd., which is arranged in one direction in a sheet shape, and a heat roll is applied. The carbon fiber was impregnated with the resin while heating and pressurizing at a temperature of 100 ° C. and a pressure of 1 atmosphere to obtain a primary prepreg.

Furthermore, in order to produce a resin film for two-stage impregnation, the epoxy resin composition containing the particle component prepared in (3) was applied onto a release paper using a knife coater, and a normal 40 mass% basis weight was obtained. A 20 g / m ² resin film was produced. This was overlapped from both sides of the primary prepreg and heated and pressurized at a temperature of 80 ° C. and an atmospheric pressure of 1 atm using a heat roll to obtain a prepreg in which resin particles were highly localized on the surface layer. By using such a two-stage impregnation method, a prepreg in which resin particles are highly localized on the surface layer can be obtained.

(5) Presence of polymer particles [C] and [D] existing in a depth range of 20% of the prepreg thickness (4) The unidirectional prepreg produced in (4) is smooth polytetrafluoride on two surfaces. It is sandwiched between the ethylene resin plates and brought into close contact, and the temperature is gradually raised to 150 ° C. over 7 days for gelation and curing to produce a plate-like resin cured product. After curing, the film was cut from the direction perpendicular to the contact surface, and the cross-section was polished, then magnified 200 times or more with an optical microscope, and photographed so that the upper and lower surfaces of the prepreg were within the visual field. By the same operation, the distance between the polytetrafluoroethylene resin plates was measured at five locations in the horizontal direction of the cross-sectional photograph, and the average value (n = 5) was taken as the thickness of the prepreg. With respect to both sides of the prepreg, two lines parallel to the surface of the prepreg are drawn from the surface of the prepreg at a depth of 20% of the thickness. Next, the total area of the polymer particles [C] and [D] existing between the surface of the prepreg and the above line, and the total area of the polymer particles [C] and [D] existing over the thickness of the prepreg The surface layer abundance ratio of the polymer particles [C] and [D] existing in the range of 20% depth from the surface of the prepreg was calculated with respect to the prepreg thickness of 100%. Here, the total area of the polymer particles [C] and [D] was obtained by cutting out the particle portion from the cross-sectional photograph and converting from the mass.

(6) Preparation of composite plate for mode I interlaminar toughness (G _IC ) test and G _IC measurement In accordance with JIS K7086 (1993), a composite plate for G _IC test is performed by the following operations (a) to (e). Was made.
(A) The unidirectional prepreg produced in (4) was laminated in 20 ply with the fiber direction aligned. However, a fluororesin film having a width of 40 mm and a thickness of 12.5 μm was sandwiched between the laminated central planes (between the 10th and 11th plys) perpendicular to the fiber arrangement direction.
(B) The laminated prepreg is covered with a nylon film so that there is no gap, and is molded in an autoclave at a temperature of 180 ° C. for 2 hours under a pressure of 0.59 MPa at a heating rate of 1.5 ° C./min. Directional fiber reinforced composite material was molded.
(C) The unidirectional fiber reinforced composite material obtained in (b) was cut into a width of 20 mm and a length of 195 mm. The fiber direction was cut so as to be parallel to the length side of the sample.
(D) According to JIS K7086 (1993), a pin load block (length: 25 mm, made of aluminum) was bonded to the end of the test piece (the side where the film was sandwiched).
(E) A white paint was applied to both sides of the test piece in order to make it easier to observe the crack growth.

Using the composite material-made flat plate prepared by the following procedure was performed G _IC measurement.

In accordance with JIS K7086 (1993) Annex 1, a test was performed using an Instron universal testing machine (Instron). The crosshead speed was 0.5 mm / min until the crack growth reached 20 mm, and 1 mm / min after reaching 20 mm. According to JIS K7086 (1993), the mode I interlaminar fracture toughness value (G _{IC in the} initial stage of crack growth) and the mode I interlaminar fracture in the crack growth process are determined from the load, displacement, and crack length. The toughness value was calculated. Crack growth early _{G IC} and crack propagation than 10mm measured value of 5 or more in 60mm from an average of six or more points of measurements were compared as _{G IC.}

The failure mode of the G _IC, was determined by the following procedure. The specimen after the G _IC test was completely peeled off along the crack. The fracture surface was observed with the naked eye, and a white area where cracks propagated in the interlayer region including the particles and a black area where cracks propagated in the fiber layer were observed with the naked eye. When the ratio of the white region in the range of crack propagation from 10 mm to 60 mm was 90% or more, it was a normal interlaminar fracture mode and was determined as “◯”. On the other hand, when it is 80% or more and less than 90%, it is determined as “Δ” which is generally a normal interlaminar fracture mode, and when it is less than 80%, it is an abnormal fracture mode in which cracks propagate in the fiber layer. Was determined.

(7) Measurement of compressive strength during wet heat of fiber reinforced composite material 12-ply of the unidirectional prepreg prepared in (4) is laminated with the fiber direction aligned with the compression direction, and the laminated prepreg is made of nylon film so that there are no gaps. And laminated in an autoclave at a temperature of 180 ° C. for 2 hours under a pressure of 0.59 MPa at a heating rate of 1.5 ° C./min. A test piece with a tab having a thickness of 2 mm, a width of 15 mm, and a length of 78 mm was prepared from this laminate, and immersed in warm water at 71 ° C. for 14 days. This test piece was measured for 0 ° compressive strength at 82 ° C. according to JIS K7076 (1991) using a universal testing machine with a thermostatic bath. The number of samples was n = 5.

(8) Measurement of interlayer thickness of fiber reinforced composite material The unidirectional prepreg produced in (4) was laminated in 20 ply with the fiber direction aligned. The laminated prepreg is covered with a nylon film so that there is no gap, and is molded in an autoclave at a temperature of 180 ° C. for 2 hours under a pressure of 0.59 MPa at a heating rate of 1.5 ° C./min to produce a laminate. did. This was cut from a direction orthogonal to the carbon fiber, and the cross section was polished, then magnified 200 times or more with an optical microscope and photographed. For a randomly selected fiber interlayer region on the photo, the carbon fiber volume content is 50%, and the line drawn parallel to the carbon fiber layer is 100 μm long as the boundary line between the fiber layer region and the fiber interlayer region. The average boundary line was drawn, and the distance between them was defined as the interlayer thickness. The same operation was arbitrarily performed on five fiber interlayer regions, and the average value was adopted.

Example 1
Using a kneader, an epoxy resin composition was prepared by the procedure (3), and a prepreg in which the polymer particles [C] and [D] were highly localized on the surface layer was obtained by the procedure (4). Using the obtained prepreg, (5) Presence of polymer particles [C] and [D] existing in a depth range of 20% of the thickness of the prepreg, (6) Mode I interlayer toughness (G _IC ) test creating and G _IC measurement use composite material plates (7) moist heat during compression strength measurements of the fiber-reinforced composite material were performed interlayer thickness measurements (8) fiber-reinforced composite material. The results are shown in Table 1.

There is no problem in the impregnation state and surface quality of the prepreg, and the abundance ratio of the particles [C] and [D] existing at a depth range of 20% from the prepreg surface is 97%, and the polymer particles [C] and [D A prepreg localized in the surface layer was obtained. As a result, G _IC and the fiber-reinforced composite material is a good level, failure mode was normal. The compressive strength at the time of wet heat was also a level with no problem.

(Example 2)
A prepreg was produced in the same manner as in Example 1 except that the blending ratio of the polymer particles [D] was increased. Interlayer thickness of the fiber-reinforced composite material becomes narrower, as a result of the particles are more densely packed in layers, G _IC and its failure mode of the fiber-reinforced composite material, wet heat during compression strength, was excellent in any.

(Examples 3 and 4)
A prepreg was produced in the same manner as in Example 2 except that the blending ratio of the polymer particles [D] was further increased. The interlayer thickness of the fiber reinforced composite material was slightly increased and the particle packing between the layers was slightly roughened. As a result, the G _IC of the fiber reinforced composite material and the compressive strength during wet heat were slightly decreased, but they were at a sufficient level.

(Example 5)
A prepreg was prepared in the same manner as in Example 1 except that the particle diameter of the polymer particle [C] was 18 μm, and the polymer particle [D] was changed to a true spherical particle made of crosslinked polymethyl methacrylate having a particle diameter of 1.5 μm. did. Although the compressive strength was reduced during wet heat, it was at an acceptable level.

(Example 6)
A prepreg was produced in the same manner as in Example 2 except that the polymer particles [C] were changed to polyamide particles having a Tg of 167 ° C. Failure mode G _IC test was generally successful, G _IC value of the fiber-reinforced composite material was also an acceptable level.

(Comparative Example 1)
An epoxy resin composition was prepared in the same manner as in Example 1 except that the polymer particles [C] were not included. The viscosity was so high that a prepreg could not be prepared.

(Comparative Example 2)
An epoxy resin composition and a prepreg were produced in the same manner as in Example 1 except that the polymer particles [D] were not included. Interlayer thickness of the fiber-reinforced composite material is thick, results particles filling of the interlayer becomes rough, G _IC of the fiber-reinforced composite material is insufficient, were those failure mode is also abnormal.

(Comparative Example 3)
Since the average particle diameter exceeds 1/10 of [C], an epoxy resin composition and a prepreg were produced in the same manner as in Example 1 except that particles 6 not corresponding to [D] were included. As a result, as a wide interlayer thickness of the fiber-reinforced composite material, G _IC is insufficient, were those failure mode is also abnormal.

(Comparative Example 4)
The glass transition temperature is 80 ° C. or lower, and since the average particle diameter exceeds 1/10 of the polymer particles [C], the same procedure as in Example 1 is performed except that the particles 7 not corresponding to [D] are included. An epoxy resin composition and a prepreg were prepared. As a result, G _IC and its failure mode of the fiber-reinforced composite material, became insufficient with moist heat during compression strength.

(Comparative Example 5)
Since the glass transition temperature was 80 ° C. or lower, an epoxy resin composition and a prepreg were prepared in the same manner as in Example 1 except that the particles 8 not corresponding to [D] were included. As a result, G _IC and its failure mode of the fiber-reinforced composite material, became insufficient with moist heat during compression strength.

(Comparative Example 6)
Since it is not a polymer particle, an epoxy resin composition and a prepreg were prepared in the same manner as in Example 5 except that the particle 9 not corresponding to [D] was included. As a result, G _IC of the fiber-reinforced composite material becomes insufficient.

  According to the present invention, a fiber-reinforced composite material having high levels of interlaminar toughness and compressive strength during wet heat can be obtained regardless of molding conditions, and is particularly suitable for structural materials. For example, for aerospace applications, primary aircraft structural materials such as main wings, tail wings and floor beams, secondary structural materials such as flaps, ailerons, cowls, fairings and interior materials, rocket motor cases and satellite structural materials Preferably used. In general industrial applications, structural materials for moving objects such as automobiles, ships, and railway vehicles, drive shafts, leaf springs, windmill blades, various turbines, pressure vessels, flywheels, paper rollers, roofing materials, cables, reinforcing bars, It is also suitable for civil engineering and building material applications such as repair and reinforcement materials. Furthermore, in sports applications, it is suitably used for golf shafts, fishing rods, tennis, badminton and squash rackets, hockey sticks, and ski pole applications.

Claims (11)

A prepreg comprising the following [A] to [D] and reinforcing fibers, wherein 90% by mass or more of the total amount of [C] and [D] is within a range of a depth of 20% of the prepreg thickness from the prepreg surface A prepreg characterized by being present in
[A] epoxy resin [B] epoxy resin curing agent [C] sphericity of polymer particles (ci) particles insoluble in epoxy resin that satisfy the following conditions (ci) to (c-iii) (C-ii) the glass transition temperature is in the range of 80 to 180 ° C. (c-iii) the average particle diameter is in the range of 10 to 30 μm [D] the following (di) and Polymer particles insoluble in epoxy resin satisfying the condition of (d-ii) (d-i) Glass transition temperature is in the range of 80 to 155 ° C. (d-ii) Average particle diameter is 1/1000 of [C]. Above and below 1/10 The prepreg according to claim 1, wherein [C] is a polymer particle insoluble in an epoxy resin that further satisfies the following condition (c-iv).
(C-iv) The particle size distribution index is in the range of 1.0 to 1.8. The prepreg according to claim 1 or 2, wherein [C] is a polymer particle insoluble in an epoxy resin that further satisfies the following condition (c-v).
(Cv) It consists of polyamide which has crystallinity. The prepreg according to any one of claims 1 to 3, wherein the mass content of [D] with respect to the total amount of [C] and [D] is in the range of 5 to 30 mass%. The prepreg according to any one of claims 1 to 4, wherein [D] is a polymer particle insoluble in an epoxy resin that further satisfies the following condition (d-iii).
(D-iii) The sphericity of the particles is 90-100 The prepreg according to any one of claims 1 to 5, wherein [C] is a polyamide particle containing a chemical structure of the general formula (1).

(Wherein R ₁ and R ₂ represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a halogen element, and may be the same or different. R ₃ is a methylene having 1 to 20 carbon atoms) Represents a group) The prepreg according to any one of claims 1 to 6, wherein [A] contains a polyfunctional amine-type epoxy resin. The prepreg according to any one of claims 1 to 7, wherein [B] is an aromatic polyamine. The prepreg according to any one of claims 1 to 8, wherein [B] is diaminodiphenylsulfone or a derivative or isomer thereof. A fiber-reinforced composite material obtained by curing the prepreg according to claim 1. The fiber-reinforced composite material according to claim 10, wherein the reinforcing fibers are carbon fibers.