JP2010059225A - Epoxy resin composition for carbon fiber-reinforced composite material, prepreg, and carbon fiber-reinforced composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epoxy resin composition for a carbon fiber-reinforced composite material, a prepreg and a carbon fiber-reinforced composite material having both of excellent shock resistance and mechanical characteristics at low temperature. <P>SOLUTION: The epoxy resin composition for a carbon fiber-reinforced composite material contains a monofunctional epoxy resin in an amount of 3 to 40 wt.% with respect to the whole epoxy resin amount and an epoxy resin having three or more functional groups in an amount of 40 to 80 wt.%, and further contains thermoplastic resin particles having an average particle diameter of 1 to 150 μm. A prepreg and a carbon fiber-reinforced composite material are provided using the composition. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a prepreg excellent in impact resistance and low-temperature strength when a carbon fiber reinforced composite material is used, and an epoxy resin composition for carbon fiber reinforced composite material used for such a prepreg. .

  Since carbon fiber reinforced composite materials are excellent in strength and rigidity, they are widely used in computer applications such as aircraft structural members, windmill blades, automobile outer plates, IC trays, and notebook PC housings. The demand is increasing year by year. In recent years, as the number of use cases increases, the required characteristics for this carbon fiber reinforced composite material have become stricter. In particular, as applied to structural materials such as aircraft members and automobile members, carbon fiber reinforced composite materials are required to have high strength in more severe use environments such as high temperature and high humidity and low temperature.

  In order to increase the strength of the carbon fiber reinforced composite material, it is necessary to increase the strength of the reinforcing fibers and to increase the fiber volume fraction (higher Vf). Conventionally, a method for obtaining a high-strength reinforcing fiber has been proposed (see Patent Document 1). However, in this proposal, there is no mention of strength that is developed when the reinforcing fiber is a fiber-reinforced composite material. Generally, the higher the strength of a reinforcing fiber, the more difficult it is to use the original strength of the fiber when a fiber-reinforced composite material is obtained. For example, even if the strand strength of the reinforcing fiber is improved, the tensile strength cannot be sufficiently utilized, and the tensile strength utilization rate (tensile strength of fiber reinforced composite material / (strand strength of reinforcing fiber × volume fiber content)) × 100) tends to decrease. Therefore, even if such a high-strength carbon fiber can be obtained, it is necessary to further solve technical problems in order to develop the strength as a fiber-reinforced composite material.

  Further, when the reinforcing fiber is made to have a high Vf, the tensile strength utilization rate tends to decrease. Furthermore, the impact resistance tends to decrease, and it becomes difficult to achieve a balance with the tensile strength.

  Furthermore, it is known that even if the reinforcing fibers have the same strength, the tensile strength utilization rate varies greatly depending on the matrix resin to be combined and the molding conditions. In particular, when the curing temperature condition of the matrix resin is 180 ° C. or higher, there is a problem that high strength is difficult to develop due to thermal stress strain remaining in the fiber-reinforced composite material during the curing. For this reason, studies have been made on the modification of the matrix resin so that sufficient tensile strength can be obtained even at a temperature of 180 ° C.

  It is known that when the tensile elongation at break of the matrix resin is increased, the tensile strength utilization rate of the fiber reinforced composite material is improved. In order to improve the tensile elongation at break of the matrix resin, it is effective to lower the crosslink density of the matrix resin. However, the heat resistance of the fiber reinforced composite material may decrease due to the decrease of the crosslink density, and the effective blending is limited. There is a problem that is. In order to solve this, it has been shown that a high tensile strength utilization factor can be obtained by satisfying a specific relationship between the tensile elongation at break and the fracture toughness KIc (see Patent Document 2). However, in order to improve the fracture toughness KIc, when a large amount of a thermoplastic resin or a rubber component is added to the matrix resin, the viscosity generally increases, and the processability and handleability of prepreg production may be impaired.

  Impact resistance is an important characteristic for such a structural material, and more specifically, compressive strength after receiving an impact force is important. For example, the fiber reinforced composite material may receive impact force due to the fall of tools or impact of pebbles, etc., and peeling may occur between the layers of the fiber reinforced composite material, reducing the compressive strength and making it unusable as a structural material . Further, when the fiber reinforced composite material is thinned with weight reduction, the impact resistance may be lowered. For this reason, the demand for impact resistance of fiber reinforced composite materials is also increasing.

In order to improve the impact resistance of the carbon fiber reinforced composite material, a method of blending a rubber component with a matrix resin (see Patent Document 3), a method of blending a thermoplastic resin (see Patent Document 4), and called interleaf. A method of inserting a kind of adhesive layer or shock absorbing layer between layers (see Patent Document 5) and a method of strengthening the interlayer with particles (see Patent Document 6) have been proposed. However, these approaches are not only inefficient but also have their own drawbacks. When the rubber component is used, the heat resistance is lowered when the content of the rubber component is increased, and the effect of improving the interlayer strength is very small when the content of the elastomer is small. Further, when a thermoplastic resin is used, if the content of the thermoplastic resin is increased, the toughness of the matrix resin is improved and the impact resistance of the carbon fiber reinforced composite material is improved, but the viscosity of the matrix resin is increased. The impregnation property of the prepreg may be impaired. In Interleaf, both the heat resistance and impact resistance improvement effects can be achieved by using a thermoplastic resin film with good heat resistance, but the reinforcing fiber content cannot be increased and the tackiness is lost. Problems such as poor handling of the prepreg may occur. Furthermore, interlaminar strengthening by particles is a technology that selectively increases the toughness of the laminate where the stress is concentrated most under impact by the addition of a thermoplastic resin, and there is no solution to the tensile strength improvement technology at low temperatures. Not. In addition, the blending of the particles tends to decrease the fiber volume fraction (Vf) and decrease the strength in the fiber direction, and there is still a technical problem to make it compatible with impact resistance.
Japanese Patent Laid-Open No. 11-241230 Japanese Patent Laid-Open No. 9-235397 Japanese Patent Laid-Open No. 13-13962 JP-A-7-278212 Japanese Patent Laid-Open No. 60-231738 Japanese Examined Patent Publication No. 6-94515

  Accordingly, an object of the present invention is to provide a prepreg excellent in impact resistance and strength at low temperatures when a carbon fiber reinforced composite material is used, and an epoxy resin composition for a carbon fiber reinforced composite material used for such a prepreg. It is to provide.

  In order to achieve the above object, the present invention has any one of the following configurations.

  That is, the epoxy resin composition for a carbon fiber reinforced composite material of the present invention includes 3 to 40% by weight of a monofunctional epoxy resin and 40 to 80% by weight of a trifunctional or higher functional epoxy resin based on the total amount of the epoxy resin. And the epoxy resin composition for carbon fiber reinforced composite materials characterized by including the thermoplastic resin particle whose average particle diameter is 1-150 micrometers.

  According to a preferred embodiment of the epoxy resin composition for carbon fiber reinforced composite material of the present invention, the monofunctional epoxy resin has a cyclic chemical structure, and more preferably a monofunctional epoxy having an aromatic ring. Resin.

  According to a preferred aspect of the epoxy resin composition for carbon fiber reinforced composite material of the present invention, the thermoplastic resin particles are resin particles that do not dissolve in the epoxy resin, and the blending amount of the thermoplastic resin particles is carbon fiber reinforced. It is 5-30 weight% with respect to the epoxy resin composition total amount for composite materials.

  According to a preferred embodiment of the epoxy resin composition for carbon fiber reinforced composite material of the present invention, the epoxy resin contains a soluble thermoplastic resin.

  Moreover, the prepreg of the present invention is a prepreg formed by impregnating carbon fibers with the above epoxy resin composition for carbon fiber reinforced composite material.

  Furthermore, the carbon fiber reinforced composite material of the present invention is a carbon fiber reinforced composite material obtained by curing a prepreg impregnated with the above epoxy resin composition for carbon fiber reinforced composite material.

  ADVANTAGE OF THE INVENTION According to this invention, the epoxy resin composition for carbon fiber reinforced composite materials excellent in heat resistance and the process property at the time of obtaining a prepreg can be obtained. A prepreg can be obtained by combining this epoxy resin composition for carbon fiber reinforced composite material and carbon fiber, and by curing this, a carbon fiber reinforced composite material excellent in impact resistance and low-temperature strength can be obtained. be able to. In general, the tensile strength of the carbon fiber composite material is greatly reduced at a low temperature compared to a room temperature. In the conventional technology, if the tensile strength at low temperature is expressed at the same level as at room temperature, the impact resistance is impaired, and it is very difficult to achieve both the impact resistance and the tensile strength at low temperature. . With the epoxy resin composition for carbon fiber reinforced composite material of the present invention, a carbon fiber reinforced composite material having both impact resistance and strength at low temperature can be obtained at a level that could not be achieved so far.

  Carbon fiber reinforced composite materials obtained from this epoxy resin composition for carbon fiber reinforced composite materials are used in aerospace applications such as primary wing, tail and floor beam aircraft primary structural materials, flaps, ailerons, cowls, fairings and interiors. It is suitably used for secondary structural materials such as materials, rocket motor cases and satellite structural materials. Among these aerospace applications, especially for fuselage skins and wing skins, which are primary aircraft structural material applications that require tensile strength at low temperatures because they need impact resistance and are exposed to low temperatures during altitude flight. Preferably used. Further, in sports applications, it is suitably used for golf shafts, fishing rods, tennis, badminton, squash and other racket applications, hockey and other stick applications, and ski pole applications. In addition, in general industrial applications, structural materials for moving bodies such as automobiles, ships and railway vehicles, drive shafts, leaf springs, windmill blades, pressure vessels, flywheels, paper rollers, roofing materials, cables, reinforcement bars, and repair reinforcement It is suitably used for civil engineering and building material applications such as materials.

  Hereinafter, the epoxy resin composition for carbon fiber composite material, prepreg and carbon fiber reinforced composite material of the present invention will be described in detail.

  The epoxy resin composition for a carbon fiber reinforced composite material of the present invention is an epoxy resin composition containing a monofunctional epoxy resin, a trifunctional or higher functional epoxy resin, and thermoplastic resin particles.

  First, in the present invention, a monofunctional epoxy resin is an essential component in order to achieve both high impact resistance and tensile strength.

  The monofunctional epoxy resin used in the present invention is a compound having one epoxy group in one molecule. If the blending amount of the monofunctional epoxy resin is small, there is almost no effect of improving the strength of the carbon fiber reinforced composite material. If the blending amount is too large, the heat resistance is remarkably impaired. The blending amount of the monofunctional epoxy resin is preferably 3 to 40% by weight, more preferably 5 to 30% by weight, based on the total amount of the epoxy resin blended.

  As the monofunctional epoxy resin used in the present invention, various epoxy resins can be used. From the viewpoint of heat resistance, it is preferable that the chemical structure has a ring structure such as cyclohexane. An epoxy resin having an aromatic ring such as a benzene ring is preferably used.

  Commercially available monofunctional epoxy resins include “Denacol” (registered trademark) Ex-731 (manufactured by Nagase ChemteX Corp.), OPP-G (o-phenylphenylglycidyl ether, Sanko Co., Ltd.), “Denacol” "(Registered trademark) Ex-141 (phenyl glycidyl ether, manufactured by Nagase ChemteX Corporation)" "Denacol" (registered trademark) Ex-146 (p-tert-butylphenyl glycidyl ether, manufactured by Nagase ChemteX Corporation) And “Denacol” (registered trademark) Ex-147 (dibromophenyl glycidyl ether, manufactured by Nagase ChemteX Corporation).

  In the present invention, a trifunctional or higher functional epoxy resin is an essential component in order to achieve both high heat resistance and impact resistance.

  The trifunctional or higher functional epoxy resin used in the present invention is a compound having three or more epoxy groups in one molecule. Examples of the trifunctional or higher functional epoxy resin include a glycidylamine type epoxy resin and a glycidyl ether type epoxy resin.

  Examples of the tri- or higher functional glycidyl ether type epoxy resin include epoxy resins such as phenol novolac type, orthocresol novolak type, trishydroxyphenylmethane type, and tetraphenylolethane type.

  Examples of the tri- or more functional glycidylamino epoxy resin include diaminodiphenylmethane type, diaminodiphenylsulfone type, aminophenol type, metaxylenediamine type, 1,3-bisaminomethylcyclohexane type, isocyanurate type, and hydantoin type. An epoxy resin is mentioned.

  If the amount of the trifunctional or higher functional epoxy resin is too small, the heat resistance is impaired, and if it is too large, the material becomes brittle and the impact resistance and strength of the carbon fiber reinforced composite material are impaired. The compounding amount of the tri- or higher functional epoxy resin is 40 to 80% by weight, more preferably 50 to 70% by weight, based on the total amount of the epoxy resin compounded.

  The trifunctional or higher functional epoxy resin used in the present invention includes a single epoxy resin having three or more epoxy groups in one molecule, a trifunctional or higher functional epoxy resin, and two or more epoxy groups in one molecule. A blend of a bifunctional epoxy resin, a copolymer of an epoxy resin and a thermosetting resin, a modified product thereof and a tri- or higher functional epoxy resin, a bifunctional epoxy resin, an epoxy resin and a thermosetting resin Copolymers and compounds obtained by blending two or more of these modified products can also be used.

  Examples of the thermosetting resin used by copolymerizing with an epoxy resin include unsaturated polyester resins, vinyl ester resins, epoxy resins, benzoxazine resins, phenol resins, urea resins, melamine resins, and polyimides. .

  These compounds may be used alone or in combination as appropriate. By blending at least a bifunctional epoxy resin and a trifunctional or higher functional epoxy resin, the fluidity of the resin and the heat resistance after curing are combined. In particular, the combination of a glycidylamine type epoxy resin and a glycidyl ether type epoxy resin makes it possible to achieve both heat resistance, water resistance and processability. In addition, blending at least one epoxy resin that is liquid at room temperature and at least one epoxy resin that is solid at room temperature makes the prepreg tack and drape suitable.

  In the present invention, among epoxy resins, in particular, epoxy resins having amines, phenols and a compound having a carbon-carbon double bond as a precursor are preferably used. Specifically, various isomers of tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol, and triglycidylaminocresol are exemplified as glycidylamine type epoxy resins having amines as precursors. Since tetraglycidyldiaminodiphenylmethane is excellent in heat resistance, it is preferably used as a component of an epoxy resin composition for carbon fiber composite materials used for aircraft structural materials and the like.

  A glycidyl ether type epoxy resin having phenol as a precursor is also preferably used. Examples of such epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, and resorcinol type epoxy resins.

  Since the liquid bisphenol A type epoxy resin, bisphenol F type epoxy resin and resorcinol type epoxy resin have low viscosity, it is preferable to use them in combination with other epoxy resins.

  In addition, the solid bisphenol A type epoxy resin gives a structure having a lower crosslink density compared to the liquid bisphenol A type epoxy resin, so that the heat resistance is low, but a tougher structure is obtained, so that a glycidylamine type epoxy resin is obtained. Or liquid bisphenol A type epoxy resin or bisphenol F type epoxy resin.

  An epoxy resin having a naphthalene skeleton provides a cured resin having a low water absorption and high heat resistance. Biphenyl type epoxy resins, dicyclopentadiene type epoxy resins, phenol aralkyl type epoxy resins and diphenylfluorene type epoxy resins are also preferably used because they give a cured resin having a low water absorption rate. Urethane-modified epoxy resins and isocyanate-modified epoxy resins give cured resins having high fracture toughness and high elongation.

  Phenol novolac type epoxy resins and cresol novolac type epoxy resins have high heat resistance and low water absorption, and thus give a cured resin having high heat resistance and water resistance. By using these phenol novolac-type epoxy resins and cresol novolac-type epoxy resins, the tackiness and draping properties of the prepreg can be adjusted while improving the heat and water resistance.

  Commercially available products of bisphenol A type epoxy resins include “Epon” (registered trademark) 825 (manufactured by Japan Epoxy Resin Co., Ltd.), “Epiclon” (registered trademark) 850 (manufactured by Dainippon Ink and Chemicals, Inc.), “ Epototo ”(registered trademark) YD-128 (manufactured by Toto Kasei Co., Ltd.), DER-331, and DER-332 (above, manufactured by Dow Chemical Co., Ltd.).

  Commercial products of bisphenol F type epoxy resin include “jER” (registered trademark) 806, “jER” (registered trademark) 807, “jER” (registered trademark) 1750 (above Japan Epoxy Resin Co., Ltd.), “Epiclon” 830 (manufactured by Dainippon Ink & Chemicals, Inc.) and “Epototo” (registered trademark) YD-170 (manufactured by Toto Kasei Co., Ltd.).

  Examples of commercially available resorcinol-type epoxy resins include “Deconal” (registered trademark) EX-201 (manufactured by Nagase ChemteX Corporation).

  Commercially available diaminodiphenylmethane type epoxy resins include ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), “Araldite” (registered trademark) MY720, “Araldite” (registered trademark) MY721, “Araldite” (registered trademark) MY9512, “Araldite” "(Registered trademark) MY9663 (manufactured by Huntsman Advanced Materials, Inc.)" and "Epototo" (registered trademark) YH-434 (manufactured by Toto Kasei Co., Ltd.).

  Examples of commercially available metaxylenediamine type epoxy resins include TETRAD-X (manufactured by Mitsubishi Gas Chemical Company).

  Examples of commercially available 1,3-bisaminomethylcyclohexane type epoxy resins include TETRAD-C (manufactured by Mitsubishi Gas Chemical Company).

  Examples of commercially available isocyanurate-type epoxy resins include TEPIC-P (manufactured by Nissan Chemical Co., Ltd.).

  Examples of commercially available trishydroxyphenylmethane type epoxy resins include Tactix 742 (manufactured by Huntsman Advanced Materials).

  Examples of commercially available tetraphenylolethane type epoxy resins include “jER” (registered trademark) 1031S (manufactured by Japan Epoxy Resin Co., Ltd.).

  Commercial products of aminophenol type epoxy resins include ELM120, ELM100 (manufactured by Sumitomo Chemical Co., Ltd.), “jER” (registered trademark) 630 (manufactured by Japan Epoxy Resin Co., Ltd.), and “Araldite” (registered trademark). Examples thereof include MY0510 (manufactured by Vantico).

  Examples of commercially available glycidyl aniline type epoxy resins include GAN and GOT (manufactured by Nippon Kayaku Co., Ltd.).

  Examples of commercially available biphenyl type epoxy resins include NC-3000 (manufactured by Nippon Kayaku Co., Ltd.).

  Examples of commercially available dicyclopentadiene type epoxy resins include HP7200 (manufactured by Dainippon Ink & Chemicals, Inc.).

  Examples of commercially available urethane-modified epoxy resins include AER4152 (manufactured by Asahi Kasei Epoxy Corporation).

  Examples of commercially available phenol novolac type epoxy resins include DEN431, DEN438 (manufactured by Dow Chemical Co., Ltd.), “jER” 152 (registered trademark) (manufactured by Japan Epoxy Resins Co., Ltd.), and the like.

  Examples of commercially available products of ortho-cresol novolak type epoxy resin include EOCN-1020 (manufactured by Nippon Kayaku Co., Ltd.) and “Epiclon” N-660 (manufactured by Dainippon Ink & Chemicals, Inc.).

  Examples of hydantoin-type epoxy resin commercial products include AY238 (manufactured by Huntsman Advanced Materials).

  From the balance between adhesion to carbon fibers and mechanical properties, it is preferable that 30 to 70% by weight of glycidylamine type epoxy is blended in the total epoxy resin composition, and more preferably 40 to 60%.

  A curing agent can be blended in the epoxy resin composition for carbon fiber reinforced composite material of the present invention.

  In the present invention, the curing agent is a curing agent for an epoxy resin, and is a compound having an active group capable of reacting with an epoxy group. Specific examples of the curing agent include dicyandiamide, aromatic polyamine, aminobenzoic acid esters, various acid anhydrides, phenol novolac resin, cresol novolac resin, polyphenol compound, imidazole derivative, aliphatic amine, tetramethylguanidine. Thiourea addition amine, carboxylic acid anhydride such as methylhexahydrophthalic anhydride, carboxylic acid hydrazide, carboxylic acid amide, polymercaptan and Lewis acid complex such as boron trifluoride ethylamine complex.

  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, various isomers of diaminodiphenylsulfone 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 preferably added so as to be stoichiometrically equivalent, but by using an equivalent ratio of about 0.7 to 0.9, a higher elastic modulus resin than when used in an equivalent amount. Is also a preferred embodiment. These curing agents may be used alone or in combination.

  Commercially available aromatic polyamine curing agents include “SumiCure” (registered trademark) S (manufactured by Sumitomo Chemical Co., Ltd.), MDA-220 (manufactured by Mitsui Chemicals, Inc.), “jER Cure” (registered trademark) W ( Japan Epoxy Resin Co., Ltd.) and 3,3′-DAS (Mitsui Chemicals Co., Ltd.).

  Moreover, the thing which made these epoxy resin and hardening | curing agent, or some of them pre-react can be mix | blended in a composition. This method may be effective for viscosity adjustment and storage stability improvement.

  In the present invention, it is also a preferred embodiment that a thermoplastic resin is mixed or dissolved in the above epoxy resin. Such thermoplastic resins are generally selected from the group consisting of carbon-carbon bonds, amide bonds, imide bonds, ester bonds, ether bonds, carbonate bonds, urethane bonds, thioether bonds, sulfone bonds and carbonyl bonds in the main chain. A thermoplastic resin having a selected bond is preferred. Further, this thermoplastic resin may have a partially crosslinked structure, and may be crystalline or amorphous. In particular, polyamide, polycarbonate, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyarylate, polyester, polyamideimide, polyimide, polyetherimide, polyimide having phenyltrimethylindane structure, polysulfone, polyethersulfone, polyetherketone, polyetherether It is preferable that at least one resin selected from the group consisting of ketone, polyaramid, polyether nitrile, and polybenzimidazole is mixed or dissolved in the epoxy resin.

  As these thermoplastic resins, commercially available polymers may be used, or so-called oligomers having a molecular weight lower than that of commercially available polymers may be used. As the oligomer, an oligomer having a functional group capable of reacting with an epoxy resin at a terminal or in a molecular chain is preferable.

  Mixtures of epoxy resins and thermoplastic resins give better results than using them alone. The brittleness of the epoxy resin is covered with the toughness of the thermoplastic resin, and the molding difficulty of the thermoplastic resin is covered with the epoxy resin, thereby providing a balanced base resin. The use ratio (parts by weight) of the epoxy resin and the thermoplastic resin is preferably in the range of 2 to 50 parts by weight of the thermoplastic resin with respect to a total of 100 parts by weight of the blended epoxy resin in terms of balance. More preferably, it is the range of 5-35 weight part.

  In the present invention, the thermoplastic resin particles are an essential component in order to realize excellent impact resistance. This thermoplastic resin particle is a different component from the thermoplastic resin contained in said epoxy resin.

  In the present invention, since thermoplastic resin particles are used as an essential component, excellent impact resistance can be realized. As the raw material of the thermoplastic resin particles used in the present invention, the same thermoplastic resins as exemplified above can be used as the thermoplastic resin that can be used by mixing or dissolving in the epoxy resin. Of these, polyamide is most preferable, and among polyamides, nylon 12, nylon 11 and nylon 6/12 copolymer give particularly good adhesive strength with a thermosetting resin.

  The shape of the thermoplastic resin particles may be spherical particles, non-spherical particles, or porous particles, but the spherical shape is superior in viscoelasticity because it does not deteriorate the flow characteristics of the resin, and the starting point of stress concentration. This is a preferred embodiment in that it provides high impact resistance.

  The amount of the thermoplastic resin particles is preferably in the range of 5 to 30% by weight, more preferably 5 to 20% by weight, based on the total amount of the epoxy resin composition for carbon fiber reinforced composite material. When the amount of the thermoplastic resin particles exceeds 30% by weight, the tackability and the drapeability are lowered when a prepreg is obtained, so that the handleability is deteriorated. Similarly, if the amount of the thermoplastic resin particles is less than 5% by weight, it is difficult to obtain a sufficient effect.

  The average particle diameter of the thermoplastic particles used in the present invention may be 150 μm or less, preferably 1 to 150 μm, more preferably 2 to 50 μm. In the case where the average particle diameter of the thermoplastic resin particles exceeds 150 μm, the spacing between fiber bundles and the interlayer in the carbon fiber reinforced composite material obtained by disturbing the arrangement of the reinforcing fibers or molding are made thicker than necessary. Therefore, the physical properties of the carbon fiber reinforced composite material may be reduced. However, even thermoplastic resin particles having an average particle size exceeding 150 μm are particles of a material that partially dissolves in the epoxy resin during molding and becomes smaller, or between filaments and carbon fiber composite materials by deformation by heating during molding There is also a material that narrows the interlayer between before forming, and in that case, it can be used as a suitable material. In addition, when the average particle diameter of the thermoplastic resin particles is less than 1 μm, the thermoplastic resin particles easily enter the gaps between the filaments of the reinforcing fibers, and the amount of particles localized on the surface of the prepreg is reduced. There is a possibility that the impact improvement effect cannot be obtained.

  In order to obtain the epoxy resin composition for carbon fiber reinforced composite material of the present invention, components other than the thermoplastic resin particles and the curing agent were uniformly heated and kneaded at a temperature of about 150 ° C. and cooled to a temperature of about 80 ° C. It is preferable to add and knead the thermoplastic resin particles and the curing agent later, but the blending method of each component is not particularly limited to this method.

  The epoxy resin composition for carbon fiber reinforced composite material of the present invention includes a coupling agent, a thermosetting resin particle, a thermoplastic resin soluble in an epoxy resin, silica gel, and carbon black, as long as the effects of the present invention are not hindered. Inorganic fillers such as clay, carbon nanotubes and metal powder can be blended.

  As the carbon fiber used in the present invention, a carbon fiber having a strand strength of 4400 MPa to 9500 MPa and an elastic modulus of 230 GPa to 400 GPa in a strand tensile test is preferably used.

  Here, the strand tensile test refers to a test performed based on JIS R7601 (1986) after impregnating a bundle of carbon fibers with a resin having the following composition and curing the resin at a temperature of 130 ° C. for 35 minutes.

[* Resin composition]
3,4-epoxycyclohexylmethyl-3,4-epoxy-cyclohexyl-carboxylate (for example, ERL-4221, manufactured by Union Carbide): 100 parts by weight- boron trifluoride monoethylamine (for example, manufactured by Stella Chemifa Corporation) ): 3 parts by weight Acetone (for example, manufactured by Wako Pure Chemical Industries, Ltd.): 4 parts by weight The carbon fiber used in the present invention varies depending on the application, but from the viewpoint of impact resistance, a tensile elastic modulus of 400 GPa at the highest. It is preferable that the carbon fiber has. From the viewpoint of strength, a composite material having high rigidity and mechanical strength can be obtained. The carbon fiber is preferably 4 to 6.5 GPa. Furthermore, tensile elongation is also an important factor. It is preferably 7 to 2.3% high strength and high elongation carbon fiber. Therefore, from the viewpoint of achieving both high impact resistance and tensile strength, the tensile modulus is at least 230 GPa and the tensile strength is at least 4. 4 GPa and a tensile elongation of at least 1. Carbon fiber having the characteristic of 7% is most suitable.

  Examples of commercially available carbon fibers include “Torayca” (registered trademark) T800S-24K, “Torayca” (registered trademark) T700G-24K (manufactured by Toray Industries, Inc.), and the like.

  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 preferable to be in the form of continuous fibers (filaments) such as long fibers or woven fabrics aligned in one direction.

  The carbon fiber used in the present invention is preferably used in the form of a carbon fiber bundle composed of a plurality of filaments.

  The carbon fiber bundle used in the present invention preferably has a single fiber fineness of 0.2 to 2.0 dtex, and more preferably a single fiber fineness of 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. . On the other hand, if 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 cause a decrease in strength. On the other hand, when the number of filaments exceeds 50,000, it is difficult to impregnate the resin during prepreg production or molding. The number of filaments is more preferably in the range of 2800 to 25000.

  The prepreg according to the present invention is obtained by impregnating carbon fibers with the above epoxy resin composition for carbon fiber reinforced composite materials. The carbon fiber weight fraction of the prepreg is preferably 40 to 90% by weight, more preferably 50 to 80% by weight. If the carbon fiber weight fraction is too low, the weight of the resulting composite material becomes excessive, and the advantages of the fiber-reinforced composite material having excellent specific strength and specific elastic modulus may be impaired. On the other hand, if the carbon fiber weight fraction is too high, poor impregnation of the resin composition occurs, and the resulting carbon 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 (hereinafter referred to as particles) in which the state in which all the thermoplastic resin particles described above are present locally can be clearly observed when the cross section thereof is observed. Is sometimes abbreviated as a layer.) Is preferably a structure formed in the vicinity of the surface of the prepreg.

  By taking such a structure, when the prepreg is laminated and the epoxy resin is cured to form a carbon fiber reinforced composite material, a resin layer is easily formed between the prepreg layers, that is, the composite material layer, Adhesiveness and adhesion between the composite material layers are improved, and the resulting carbon fiber reinforced composite material exhibits high impact resistance.

  From such a viewpoint, the particle layer has a depth of preferably up to 20%, more preferably up to 10% from the surface of the prepreg, starting from the surface, in the thickness direction, with respect to the thickness of the prepreg of 100%. It is preferable that it exists in the range of the depth of this.

  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 layers of the prepreg are mistaken and there is an interlayer having thermoplastic resin particles and an interlayer having no thermoplastic resin particles, a composite material that is weak against impact 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 thermoplastic resin particles present in the particle layer is preferably 90 to 100% by weight, more preferably 95 to 100% by weight with respect to 100% by weight of the total amount of the thermoplastic resin particles in the prepreg. It is.

  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. Two lines parallel to the surface of the prepreg are drawn on both surfaces of the prepreg cured product from the surface of the prepreg cured product at a depth of 20% of the thickness. 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 weight. When it is difficult to discriminate the particles dispersed in the resin after photography, 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 is a method of applying thermoplastic resin particles in the form of particles on the surface of a primary prepreg composed of carbon fiber and an epoxy resin that is a matrix resin, and in an epoxy resin that is a matrix resin. A mixture in which these thermoplastic resin particles are uniformly mixed is prepared, and in the process of impregnating the mixture into carbon fiber, the penetration of these thermoplastic resin particles is blocked by reinforcing fibers, and the thermoplastic resin is applied to the surface portion of the prepreg. A method of localizing particles, or pre-impregnating a carbon fiber with an epoxy resin to prepare a primary prepreg, and sticking a thermosetting resin film containing a high concentration of these thermoplastic resin particles on the surface of the primary prepreg It can manufacture by the method to do.

  When the thermoplastic resin particles are uniformly present in a depth range of 20% of the thickness of the prepreg, a prepreg for a carbon fiber composite material having high impact resistance can be obtained.

  The carbon fiber reinforced composite material of the present invention can be produced by taking, as an example, a method of laminating the above-described prepreg of the present invention in a predetermined form and curing the resin by pressurization and heating.

  The carbon fiber reinforced composite material of the present invention is preferably used for computer applications such as aircraft structural members, windmill blades, automobile outer plates, IC trays, and housings (housings) of notebook computers.

  Hereinafter, the epoxy resin composition for carbon fiber reinforced composite material of the present invention, and the prepreg and carbon fiber reinforced composite material using the same will be described more specifically with reference to examples. The carbon fiber, the resin raw material, the preparation method of the prepreg and the carbon fiber reinforced composite material, the evaluation method of the post-impact compressive strength, and the tensile strength evaluation method 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>
"Torayca" (registered trademark) T800G-24K-31E (24,000 filaments, tensile strength 5.9 GPa, tensile elastic modulus 290 GPa, tensile elongation 2.0% carbon fiber, total fineness 1.03 g / m , Manufactured by Toray Industries, Inc.)
<Epoxy resin>
"Denacol" (registered trademark) Ex-731 (N-glycidylphthalimide, manufactured by Nagase ChemteX Corporation)
・ OPP-G (o-phenylphenyl glycidyl ether, manufactured by Sanko Co., Ltd.)
"Denacol" (registered trademark) Ex-141 (phenylglycidyl ether, manufactured by Nagase ChemteX Corporation)
"Denacol" (registered trademark) Ex-146 (p-tert-butylphenylglycidyl ether, manufactured by Nagase ChemteX Corporation)

"Epon" (registered trademark) 825 (bisphenol A type epoxy resin, manufactured by Japan Epoxy Resin Co., Ltd.)
・ ELM434 (Tetraglycidyldiaminodiphenylmethane, manufactured by Sumitomo Chemical Co., Ltd.)
"JER" (registered trademark) 630 (triglycidyl-p-aminophenol, Japan Epoxy Resin Co., Ltd.)
・ TETRAD-C (Tetraglycidyl-1,3-bisaminomethylcyclohexane, manufactured by Mitsubishi Gas Chemical Co., Ltd.)
<Curing agent>
"Seika Cure" (registered trademark) -S (4,4'-diaminodiphenyl sulfone, manufactured by Wakayama Seika Co., Ltd.)
<Thermoplastic resin>
"Sumika Excel" (registered trademark) PES5003P (polyethersulfone, manufactured by Sumitomo Chemical Co., Ltd.)
<Thermoplastic resin particles>
-Epoxy-modified nylon particles A obtained by the following production method
90 parts by weight of transparent polyamide (trade name “Grillamide” (registered trademark) -TR55, manufactured by Mzavelke), epoxy resin (trade name “jER” (registered trademark) 828, manufactured by Japan Epoxy Resin Co., Ltd.) 7.5 parts by weight And 2.5 parts by weight of a curing agent (trade name “Tomide” (registered trademark) # 296, manufactured by Fuji Kasei Kogyo Co., Ltd.) are added to a mixed solvent of 300 parts by weight of chloroform and 100 parts by weight of methanol, A homogeneous solution was obtained. Next, the obtained uniform solution was atomized using a spray gun for coating, well stirred, and sprayed toward the liquid surface of 3000 parts by weight of n-hexane to precipitate a solute. The precipitated solid was separated by filtration and washed well with n-hexane, and then vacuum-dried at a temperature of 100 ° C. for 24 hours to obtain epoxy-modified nylon particles A (average particle size: 12 μm).
“Sumika Excel” (registered trademark) PES5003P (polyethersulfone, manufactured by Sumitomo Chemical Co., Ltd.) was freeze-pulverized, and the particle size was adjusted by classification to obtain polyethersulfone particles B (average particle size: 141 μm).
Nylon resin particle C (nylon fine particle SP-500, manufactured by Toray Industries, Inc., average particle size: 5.9 μm)
Polyimide particles D (polyimide particles UBE-R, manufactured by Ube Industries, average particle size: 12.3 μm)
-“Sumika Excel” (registered trademark) PES5003P (polyethersulfone, manufactured by Sumitomo Chemical Co., Ltd.) was freeze-pulverized and the particle size was adjusted by classification to obtain polyethersulfone particles E (average particle size: 206 μm).
(1) Definition of 0 ° of carbon fiber reinforced composite material As described in JIS K7017 (1999), the fiber direction of the unidirectional fiber reinforced composite material is defined as the axial direction, and the axial direction is defined as the 0 ° axis. The direction perpendicular to the axis is defined as 90 °.

(2) Presence of particles existing in the range of 20% depth of prepreg The prepreg is sandwiched and adhered between two smooth polytetrafluoroethylene resin plates on the surface, and gradually over 7 days. Then, the temperature is raised to 150 ° C. to gel and cure to produce a plate-shaped resin cured product. After curing, cut from the direction perpendicular to the contact surface, polish the cross-section, enlarge it 200 times or more with an optical microscope, and take a picture so that the upper and lower surfaces of the prepreg are within the field of view. 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 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. The abundance of particles present in the 20% depth range was calculated. Here, the total area of the fine particles was obtained by cutting out the particle portion from the cross-sectional photograph and converting from the weight.

(3) Measurement of average particle diameter of thermoplastic resin particles Regarding the average particle diameter of the thermoplastic resin particles, the thermoplastic resin particles were magnified 1000 times or more with a microscope such as a scanning electron microscope and photographed, and the thermoplastic resin was randomly selected. Particles were selected, and the diameter of the circumscribed circle of the thermoplastic resin particles was defined as the particle diameter, and the average value of the particle diameters (n = 50) was obtained.

(4) Measurement of post-impact compressive strength of carbon fiber reinforced composite material [+ 45 ° / 0 ° / −45 ° / 90 °] A quasi-isotropic 24-ply laminate in a _{3 s} configuration, in an autoclave 25 laminates were produced by molding at a temperature of 180 ° C. for 2 hours under a pressure of 0.59 MPa and at a heating rate of 1.5 ° C./min. A sample 150 mm long × 100 mm wide (thickness 4.5 mm) was cut out from each of these laminates, and a falling weight impact of 6.7 J / mm was applied to the center of the sample in accordance with SACMA SRM 2R-94. The strength was determined.

(5) Measurement of 0 ° tensile strength of carbon fiber reinforced composite material Cut unidirectional prepreg into a predetermined size, laminate 6 sheets in one direction, perform vacuum bag, use autoclave, temperature 180 ° C, pressure cured at 6 kg / ^cm 2, 4 hours to obtain unidirectional reinforcing material (carbon fiber reinforced composite material). This unidirectional reinforcing material was cut to a width of 12.7 mm and a length of 230 mm, and a glass fiber reinforced plastic tab having a length of 1.2 mm and a length of 50 mm was bonded to both ends to obtain a test piece. The test piece was subjected to a tensile test using an Instron at a crosshead speed of 1.27 mm / min and a measurement temperature of −60 ° C.

Example 1
In a kneading apparatus, 3 parts by weight of “Denacol” (registered trademark) Ex-731, 60 parts by weight of ELM 434, and 37 parts by weight of “EPON” 825 were kneaded, and then a curing agent 4,4′- 40 parts by weight of diaminodiphenylsulfone was kneaded to prepare an epoxy resin composition (base resin composition).

For the epoxy resin composition for carbon fiber reinforced composite materials shown in Table 1 (in the table, the numbers represent parts by weight), the base resin composition excluding the thermoplastic resin particles prepared as described above was used as a knife coater. It was coated on release paper with a resin basis weight of 25 g / m ² to prepare a resin film. This resin film is superposed on both sides of carbon fibers (weight per unit area 190 g / m ² ) aligned in one direction, using a heat roll, and an epoxy resin composition (base resin) while heating and pressing at a temperature of 100 ° C. and 1 atm. Composition) was impregnated into carbon fiber to obtain a primary prepreg. Next, an epoxy resin composition for carbon fiber reinforced composite material prepared by adding thermoplastic resin particles so that the final epoxy resin composition of the prepreg for carbon fiber reinforced composite material has the blending amount shown in Table 1 is used as a knife. A release film was coated with a coater at a resin basis weight of 25 g / m ² to prepare a resin film. This resin film is overlapped on both sides of the primary prepreg, using a heat roll, and impregnating the primary prepreg with the epoxy resin composition for carbon fiber reinforced composite material while heating and pressing at a temperature of 100 ° C. and 1 atm. A prepreg was obtained. The obtained prepreg was used as described in (3) Measurement of post-impact compressive strength of carbon fiber reinforced composite material and (4) Measurement of 0 ° tensile strength of carbon fiber reinforced composite material. A material was obtained and the compressive strength after impact and the 0 ° tensile strength at low temperature were measured. The results are shown in Table 1.

(Examples 2-16, 20-24, Comparative Examples 1-6)
A prepreg was prepared in the same manner as in Example 1 except that the type and blending amount of the epoxy resin and the like were changed as shown in Tables 1 to 3, 5 and 6, and evaluated in the same manner as in Example 1. The results are shown in Tables 1-3, 5 and 6.

(Examples 17 to 19)
Each epoxy resin of the type and blending amount shown in Table 4 and the thermoplastic resin PES5003P are blended and dissolved, and then the curing agent 4,4′-diaminodiphenylsulfone is kneaded to obtain an epoxy resin composition (base Resin composition) was prepared. A prepreg was produced in the same manner as in Example 1 and evaluated in the same manner as in Example 1. The results are shown in Table 4.

(Comparative Example 7)
A prepreg was produced in the same manner as in Example 1 except that the type and blending amount of the epoxy resin and the like were changed as shown in Table 6. The obtained prepreg was used as described in (3) Measurement of post-impact compressive strength of carbon fiber reinforced composite material and (4) Measurement of 0 ° tensile strength of carbon fiber reinforced composite material. When trying to obtain the material, cracks occurred on the surface of the carbon fiber composite material.

(Comparative Example 8)
Preparation of a prepreg was attempted in the same manner as in Example 1 except that the type and blending amount of the epoxy resin and the like were changed as shown in Table 6. However, when the resin film was produced, a lot of streaks occurred, and the target prepreg could not be obtained.

By comparison with Examples 1-24 and Comparative Examples 1-8, the carbon fiber reinforced composite material using the epoxy resin composition for a carbon fiber reinforced composite material of the present invention has high compressive strength after impact and tensile strength at low temperatures. It can be seen that it achieves strength and achieves both high impact resistance and mechanical properties at low temperatures. Moreover, by contrast with Examples 1-9 and Comparative Examples 1-7, the scope of claim 1 in the present invention can achieve specifically high impact resistance and mechanical properties at low temperatures, It can be seen that the high impact resistance and the mechanical properties at low temperatures are compatible.

Claims (8)

  3 to 40% by weight of monofunctional epoxy resin with respect to the total amount of epoxy resin, and 40 to 80% by weight of trifunctional or higher epoxy resin and thermoplastic resin particles having an average particle diameter of 1 to 150 μm An epoxy resin composition for a carbon fiber reinforced composite material.   The epoxy resin composition for a carbon fiber reinforced composite material according to claim 1, wherein the monofunctional epoxy resin is a resin having a cyclic chemical structure.   The epoxy resin composition for a carbon fiber reinforced composite material according to claim 1 or 2, wherein the monofunctional epoxy resin is a resin having an aromatic ring in a chemical structure.   The epoxy resin composition for a carbon fiber-reinforced composite material according to any one of claims 1 to 3, wherein the thermoplastic resin particles are resin particles that do not dissolve in the epoxy resin.   The carbon fiber reinforced composite according to any one of claims 1 to 4, wherein the amount of the thermoplastic resin particles is 5 to 30% by weight based on the total amount of the epoxy resin composition for carbon fiber reinforced composite material. Epoxy resin composition for materials.   Furthermore, the epoxy resin composition for carbon fiber reinforced composite materials in any one of Claims 1-5 containing the thermoplastic resin which can be melt | dissolved in an epoxy resin.   A prepreg obtained by impregnating carbon fiber with the epoxy resin composition for carbon fiber-reinforced composite material according to claim 1. A carbon fiber reinforced composite material obtained by curing the prepreg according to claim 7.