JP5359125B2 - Prepreg and carbon fiber reinforced composites - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an epoxy resin composition for a carbon fiber-reinforced composite material having excellent impact resistance and conductivity, a prepreg, and a carbon fiber reinforced composite material having excellent impact resistance and conductivity. <P>SOLUTION: The epoxy resin composition for a carbon fiber-reinforced composite material is either a resin composition (A) containing at least an epoxy resin, a curing agent, a coupling agent, thermoplastic resin particles and conductive particles, or a resin composition (B) containing an epoxy resin, a curing agent, a coupling agent, and conductive particles formed by covering cores of a thermoplastic resin with a conductive material. The amount of the coupling agent added is 0.001 to 0.5 wt.% for the entire resin composition. A prepreg and a carbon fiber-reinforced composite material using it are also disclosed. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

The present invention relates to a prepreg and a carbon fiber reinforced composite material having both excellent mechanical properties and conductivity.

  Carbon fiber reinforced composite materials are useful because they are excellent in strength, rigidity, electrical conductivity, etc., and are useful for computers such as aircraft structural members, windmill blades, automobile skins, and IC trays and notebook computer housings (housings). Widely used in applications, 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, the impact resistance shown by the resistance to falling weight impact is governed by the delamination strength determined by the plate edge delamination strength between the layers of the carbon fiber reinforced composite material, so it only improves the strength of the reinforcing fibers. Then, it is known that it does not lead to drastic improvement. 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, various techniques have been proposed for the purpose of improving the physical properties of the composite material that can cope with stresses from other than the direction in which the reinforcing fibers are arranged.

  As one of them, a prepreg in which resin fine particles are dispersed in a surface portion has been proposed. For example, a technique for providing a high-toughness composite material with good heat resistance using a prepreg in which resin fine particles made of a thermoplastic resin such as nylon are dispersed on a partial surface has been proposed (see Patent Document 1). In addition, a technique has been proposed in which a high degree of toughness is expressed in a carbon fiber reinforced composite material by combining a matrix resin whose toughness has been improved by adding a polysulfone oligomer and resin fine particles made of a thermosetting resin (Patent Document 2). reference.). However, such a technique provides a resin layer that becomes an insulating layer between layers while providing high impact resistance. Therefore, among the conductivity that is one of the characteristics of the carbon fiber reinforced composite material, there is a disadvantage that the conductivity in the thickness direction is extremely inferior, and the carbon fiber reinforced composite material has both excellent impact resistance and conductivity. It was difficult.

  Therefore, as a method for improving the conductivity between the layers, there can be considered a method in which conductive particles such as metal particles (see Patent Document 3) and carbon particles (see Patent Document 4) are mixed in advance in the matrix resin. In this document, there is no mention of coexistence of high conductivity and impact resistance, and the impact resistance is sufficiently satisfied due to the low adhesion between the fine particles and the matrix resin and the low toughness of the fine particles themselves. It is not a thing.

In addition, as a method for improving the adhesion to the matrix resin, there is a method using carbon particles using a silane coupling agent (see Patent Document 5). In this patent document as well, high impact resistance and electrical conductivity are used. There is no mention of coexistence with.
US Pat. No. 5,028,478 JP-A-3-26750 JP-A-6-344519 Japanese Patent Laid-Open No. 8-34864 JP-A-8-157620

It is an object of the present invention, it aims to provide excellent mechanical properties and having both a conductive, prepreg and excellent carbon fiber reinforced composite material having both mechanical properties and conductivity such as impact resistance was is there.

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

That is, in the prepreg of the present invention, carbon fiber is impregnated with at least a resin composition containing an epoxy resin mixed with or dissolved in a thermoplastic resin, a curing agent, a coupling agent, thermoplastic resin particles, and conductive particles. The thermoplastic resin mixed or dissolved in the epoxy resin is polyethersulfone having a hydroxyl group at the terminal, and the ratio (part by weight) is epoxy resin: thermoplastic resin = 100: 2. To 100: 50, the coupling agent is 0.005 to 0.1% by weight based on the total resin composition , and the thermoplastic resin particles are 1 to 10% by weight in 100% by weight of the prepreg. The particles are contained in an amount of 0.01 to 20% by weight based on the total resin composition, and both the thermoplastic resin particles and the conductive particles are 90 to 100% by weight. But with respect to 100% the thickness of the prepreg from the surface of the prepreg, a prepreg, characterized in that it is localized in the range of 20% of the depth in the thickness direction starting from the surface.

According to a preferred embodiment of the epoxy resin composition used in the present invention (hereinafter, this epoxy resin composition may be referred to as “the epoxy resin composition for carbon fiber-reinforced composite material of the present invention ”). The coupling agent is a silane coupling agent, and more preferably a silane coupling agent having an epoxy group or an amino group.

  According to a preferred embodiment of the epoxy resin composition for carbon fiber reinforced composite material of the present invention, the average particle size of the conductive particles is equal to or larger than the average particle size of the thermoplastic resin particles, and The specific gravity of the conductive particles is at most 3.2.

  According to a preferred aspect of the epoxy resin composition for a carbon fiber reinforced composite material of the present invention, the conductive particles are formed by coating carbon particles, inorganic material nuclei and organic material nuclei with a conductive substance. At least one selected from the group consisting of conductive particles, and the conductive substance comprises at least one selected from the group consisting of platinum, gold, silver, copper, nickel, titanium and carbon It is.

Furthermore, carbon fiber reinforced composite material of the present invention is formed by curing the prepreg.

  In the present invention, a carbon fiber reinforced composite material that has strong impact resistance and conductivity in a molded body obtained by hardening the epoxy resin as a matrix resin and conductive particles and curing it. Can be obtained. In the prior art, if the impact resistance is high, the conductivity is low, and the one having a high conductivity is only a carbon fiber reinforced composite material inferior in impact resistance. It has become possible to provide a carbon fiber reinforced composite material that satisfies the above requirements.

Further, in the present invention, the carbon fiber reinforced composite material satisfying the impact resistance and conductivity of the same time uses a prepreg that carbon fiber reinforced composite material for epoxy resin composition having the specific composition is impregnated in the carbon fibers It is obtained by this. By using this embodiment, adhesion and dispersion with the epoxy resin composition of the conductive particles is improved.

  As a result of pursuing the conductive mechanism of the carbon fiber reinforced composite material composed of carbon fiber, epoxy resin, curing agent and thermoplastic resin particles, the present inventors have mixed carbon containing conductive particles and a certain amount of coupling agent. Surprisingly, the epoxy resin composition for fiber-reinforced composite materials has a strong bond between the conductive particles and the epoxy resin, which is a matrix resin, and has high impact resistance and conductivity at a high level. It was found that a fiber reinforced composite material can be obtained. Furthermore, the carbon fiber reinforced composite epoxy resin composition containing conductive particles in which the core of the thermoplastic resin is coated with a conductive material instead of the thermoplastic resin particles has excellent impact resistance and conductivity. It has been found that a carbon fiber reinforced composite material having a high degree of carbon can be obtained, and the present invention has been achieved.

Prepreg and carbon fiber reinforced composite material of the present invention are all epoxy resin, curing agent, coupling agent, contains a thermoplastic resin particles and conductive particles. Both the prepreg and the carbon fiber reinforced composite material contain carbon fibers.

  The carbon fiber used in the present invention can be any type of carbon fiber depending on the application, but it is a carbon fiber having a tensile modulus of at least 280 GPa because it exhibits higher conductivity. Is preferred. Moreover, it is preferable that it is a carbon fiber which has a tensile elasticity modulus of 440 GPa at the maximum from the point of coexistence with impact resistance. Further, from the viewpoint of impact resistance, a composite material having excellent impact resistance and high rigidity and mechanical strength can be obtained. 4 to 6.5 GPa, while 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 conductivity and impact resistance, the tensile modulus is at least 280 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. The tensile modulus, tensile strength and tensile elongation can be measured by a strand tensile test described in JIS R7601-1986.

  The carbon fiber used in the present invention can be produced as follows. First, in the case of an acrylic carbon fiber, a precursor made of a polyacrylonitrile copolymer having a constitution in which acrylonitrile is 90% by weight or more and a monomer copolymerizable with acrylonitrile is less than 10% by weight. It is preferable to use fiber bundles. Examples of the copolymerizable monomer include acrylic acid, methacrylic acid, itaconic acid or their methyl ester, propyl ester, butyl ester, alkali metal salt, ammonium salt, allyl sulfonic acid, methallyl sulfonic acid, and styrene. At least one selected from the group consisting of sulfonic acids and alkali metal salts thereof can be used.

  The polyacrylonitrile-based precursor fiber bundle preferably has a single fiber fineness of 1.0 to 2.0 dtex, more preferably 1.1 to 1.7 dtex, and still more preferably 1.2 to 1.5 dtex. It is. If the single fiber fineness is less than 1.0 dtex, the elastic modulus and strength of the carbon fiber bundle are too high, and the productivity tends to be inferior. Moreover, when the single fiber fineness exceeds 2.0 dtex, it becomes easy to produce spots in the carbonization step, which may reduce the overall strength. The polyacrylonitrile-based precursor fiber bundle is heated and flame-resistant in an oxidizing atmosphere such as air, preferably in a temperature range of 200 ° C. to 300 ° C., to produce flame-resistant fibers.

  Next, before the carbonization treatment of the next step, the flameproof fiber is preliminarily carbonized in an inert atmosphere such as nitrogen, preferably within a temperature range of 300 ° C to 1000 ° C. Thus, after pre-carbonizing the flameproofed fiber, the maximum temperature is preferably 1000 to 1400 ° C, more preferably 1000 to 1300 ° C, and even more preferably 1100 to 1250 ° C in an inert atmosphere such as nitrogen. A carbon fiber bundle can be manufactured by carbonizing in the temperature range of. When the maximum carbonization temperature exceeds 1400 ° C., the elastic modulus of the carbon fiber bundle becomes too high, and when it is less than 1000 ° C., the crystal size of the carbon fiber becomes small and the growth of the carbon crystals is insufficient. When the fiber bundle has a high moisture content and the fiber-reinforced composite material is molded, the matrix resin may not be sufficiently cured, and the tensile strength of the fiber-reinforced composite material may not be sufficiently developed.

  Examples of commercially available carbon fibers include “Torayca” (registered trademark) T800SC-24K-10E and “Torayca” (registered trademark) T700SC-24K-50C (all manufactured by Toray Industries, Inc.).

  The form and arrangement of carbon fibers can be selected as appropriate from long fibers aligned in one direction, tows, woven fabrics, non-woven fabrics, mats, knits, braids, rovings, choppeds, etc., but they are lighter and more durable. In order to obtain a carbon fiber reinforced composite material, the carbon fibers are preferably in the form of continuous fibers such as long fibers, woven fabrics, tows and rovings aligned in one direction.

  The carbon fiber bundle used in the present invention needs to have a single fiber fineness of 0.2 to 2.0 dtex, preferably 0.4 to 1.8 dtex. If it is less than 0.2 dtex, the carbon fiber bundle may be easily damaged by the contact with the guide roller during twisting, and the same damage may also occur in the impregnation treatment step of the resin composition. If it exceeds 2.0 dtex, the resin composition may not be sufficiently impregnated into the carbon fiber bundle, and as a result, the fatigue resistance may be lowered.

  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, 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.

  Moreover, a preform can be applied as a form of carbon fiber. Here, the preform is usually a laminated fabric base fabric made of carbon fibers of long fibers, a fabric base fabric stitched and integrated with stitch yarns, or a fiber structure such as a three-dimensional fabric or a braided fabric. Means a thing.

  As the epoxy resin used in the present invention, an epoxy resin alone, a copolymer of an epoxy resin and a thermosetting resin, a modified body, a resin blended with two or more kinds, and the like can 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. .

  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 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.

  These epoxy resins may be used alone or in combination as appropriate. The blending of at least a bifunctional epoxy resin and a trifunctional or higher functional epoxy resin has both the fluidity of the resin and the heat resistance after curing. In particular, the combination of glycidylamine type epoxy and glycidyl ether type epoxy makes it possible to achieve both heat resistance and 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.

  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 resin include “jER” (registered trademark) 825 and “jER” (registered trademark) 834 (all of which are manufactured by Japan Epoxy Resins Co., Ltd.), “Epicron” (registered trademark) 850 ( Dainippon Ink Chemical Co., Ltd.), “Epototo” (registered trademark) YD-128 (manufactured by Toto Kasei Co., Ltd.), DER-331 and DER-332 (all of which are manufactured by Dow Chemical Co., Ltd.). .

  As commercial products of bisphenol F type epoxy resin, “jER” (registered trademark) 806, “jER” (registered trademark) 807, and “jER” (registered trademark) 1750 (all are manufactured by Japan Epoxy Resins Co., Ltd.), “Epiclon” 830 (manufactured by Dainippon Ink & Chemicals, Inc.), “Epototo” (registered trademark) YD-170 (manufactured by Toto Kasei Co., Ltd.), and the like.

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

  Commercially available epoxy resins of the tetraglycidyldiaminodiphenylmethane type include ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), “Araldite” (registered trademark) MY720, “Araldite” (registered trademark) MY721, “Araldite” (registered trademark) MY9512 and “Araldite” (registered trademark) MY9663 (all manufactured by Vantico), “Epototo” (registered trademark) YH-434 (manufactured by Toto Kasei Co., Ltd.), and the like.

  As commercial products of aminophenol type epoxy resins, ELM120 and ELM100 (all of which are manufactured by Sumitomo Chemical Co., Ltd.), “Epicoat” (registered trademark) 630 (manufactured by Japan Epoxy Resin Co., Ltd.), and “Araldite” (registered) Trademark) MY0510 (manufactured by Vantico) and the like.

  Examples of commercially available glycidyl aniline type epoxy resins include GAN and GOT (all of which are 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 and DEN438 (all of which are manufactured by Dow Chemical Co., Ltd.) and “Epicoat” (registered trademark) (manufactured by Japan Epoxy Resins Co., Ltd.).

  From the balance between adhesiveness with conductive particles and mechanical properties, the glycidylamine type epoxy is preferably blended in an amount of 30 to 70% by weight, more preferably 40 to 60%, in the total epoxy resin composition.

  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. More specifically, examples of the curing agent include dicyandiamide, various isomers of diaminodiphenylmethane and diaminodiphenylsulfone, aminobenzoic acid esters, various acid anhydrides, phenol novolac resins, cresol novolac resins, polyphenol compounds, imidazole derivatives. Lewis such as aliphatic amine, tetramethylguanidine, thiourea addition amine, carboxylic acid anhydride such as methylhexahydrophthalic anhydride, carboxylic acid hydrazide, carboxylic acid amide, polymercaptan and boron trifluoride ethylamine complex Examples include acid complexes.

  By using aromatic diamine as a curing agent, an epoxy resin cured product having good heat resistance can be obtained. In particular, various isomers of diaminodiphenylsulfone are most suitable 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 amount added depends on the type of epoxy resin and curing agent. For example, in the case of an aromatic amine curing agent, it is preferable to add it so as to be stoichiometrically equivalent, but by using an equivalent ratio of about 0.7 to 0.8, 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.

  Examples of commercially available aromatic amine curing agents include "SumiCure" (registered trademark) S (manufactured by Sumitomo Chemical Co., Ltd.), MDA-220 (manufactured by Mitsui Chemicals Fine Co., Ltd.), and "Epicure" (registered trademark). W (manufactured by Japan Epoxy Resin Co., Ltd.), 3,3′-DAS (manufactured by Mitsui Chemicals, Inc.), and the like.

  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.

The present invention, in the epoxy resin, used by mixing or dissolving the thermoplastic 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 preferable, but it may have a partially crosslinked structure. Further, it may be crystalline or amorphous. In particular, polyamide, polycarbonate, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyarylate, polyester, polyamideimide, polyimide, polyetherimide, phenyltrimethylindane structure polyimide, 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. In the present invention, polyethersulfone having a terminal hydroxyl group is used as the thermoplastic resin.

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. In the present invention, the epoxy resin, the thermoplastic resin, and the use ratio (parts by weight) are in the range of 100: 2 to 100: 50 , preferably in the range of 100: 5 to 100: 35, taking such balance into consideration. is there.

  In the first aspect of the present invention, since the 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 greatly improves the peel strength of the honeycomb core / skin panel. Among polyamides, nylon 12, nylon 11 and nylon 6/12 copolymer give particularly good adhesive strength with thermosetting resins.

  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 in the range of 1 to 10% by weight in 100% by weight of the prepreg . When the amount of the thermoplastic resin particles exceeds 10% by weight with respect to the prepreg, the tackability and draping properties of the prepreg are lowered, and the handleability tends to be deteriorated. The amount of the thermoplastic resin particles, in order to obtain a high impact resistance is a prepreg to-1 wt% or more, preferably 2 wt% or more.

  In the present invention, a coupling agent is an essential component in order to strengthen the adhesion between the epoxy resin that is a matrix resin and the conductive particles described later. Furthermore, the coupling agent has the effect of improving the adhesion with the carbon fiber and reducing the surface energy of the conductive particles, and significantly improving the dispersibility of the conductive particles in the matrix resin.

  As the coupling agent used in the present invention, silane-based, titanium-based, aluminum-based, and triazine thiol-based coupling agents are preferably used, and these coupling agents may be used alone or in combination. . If the coupling agent is not appropriate, the adhesion between the conductive particles and the matrix resin becomes insufficient, the impact resistance may be lowered, and the dispersibility of the conductive particles in the epoxy resin that is the matrix resin is deteriorated. Processability may be reduced. In order to avoid such a problem, it is preferable to use a coupling agent that has an affinity with the epoxy resin and is compatible, or a coupling agent that can react with the epoxy resin and realize strong adhesion. As such a coupling agent, for example, a coupling agent having at least one epoxy group, phenolic hydroxyl group, carboxyl group, mercapto group, amino group or monosubstituted amino group is preferably used.

  As the coupling agent, a silane coupling agent is particularly preferably used because coupling agents having various functional groups are easily available. Specific examples of the silane coupling agent include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3- (2-aminoethyl) aminopropyltrimethoxysilane, 3- (phenylamino). ) Propyltrimethoxysilane and 3- (2-aminoethyl) aminopropylmethyldimethoxysilane, and the epoxy silane includes 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3- Examples thereof include glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane. Examples of vinylsilane include vinyltrichlorosilane and vinyltrimethoxy. Run, vinyl triethoxysilane, vinyltris (2-methoxyethoxy) silane and vinyl triacetoxy silane.

  In particular, a silane coupling agent having an epoxy group, an amino group or a monosubstituted amino group in the molecule is particularly preferably used because it can be applied to a wide range of resins and has high reactivity.

  The compounding amount of the coupling agent is such that the entire resin composition consisting of epoxy resin / curing agent / thermoplastic particles / coupling agent / conductive particles or the core of epoxy resin / curing agent / coupling agent / thermoplastic resin is conductive. Preferably, the content is 0.001 to 0.5% by weight, more preferably 0.05 to 0.2% by weight, based on the total resin composition made of conductive particles coated with a conductive substance. If the amount of the coupling agent is too small, the adhesion between the epoxy resin and the conductive particles may not be sufficiently exhibited, or the dispersibility of the conductive particles in the epoxy resin may be deteriorated. Conversely, if the amount of coupling agent is too large, the mechanical properties of the cured product may be reduced.

  Commercially available coupling agents include, for example, Z-6040 (3-glycidoxypropyltrimethoxysilane), Z-6011 (3-aminopropyltriethoxysilane) and Z-6300 (vinyltrimethoxysilane (all above) And Toray Dow Corning Co., Ltd.)).

The conductive particles used in the present invention may be particles that are electrically good conductors, such as carbon particles, particles in which the core of an inorganic material is coated with a conductive material, organic materials such as thermoplastic resins, and the like. Conductive polymer particles such as polyacetylene particles and polyaniline particles, polypyrrole particles, polythiophene particles, polyisothianaphthene particles, and polyethylenedioxythiophene particles can be used in addition to particles in which the core of the material is coated with a conductive substance. I can .

  Conductive particles in which the core of an inorganic material or organic material is coated with a conductive substance are composed of an inorganic material or organic material that is a core and a conductive layer made of a conductive substance. An adhesive layer may be placed between the core and the conductive layer.

  Examples of inorganic materials that can be used as the core of conductive particles coated with a conductive substance include inorganic oxides, inorganic-organic composites, and carbon.

  Examples of inorganic oxides include single inorganic oxides such as silica, alumina, zirconia, titania, silica / alumina, silica / zirconia, and two or more composite inorganic oxides. Examples of the inorganic organic composite include polyorganosiloxane obtained by hydrolyzing metal alkoxide and / or metal alkyl alkoxide. As the carbon, glassy carbon is preferably used. For example, “Bellepearl” (registered trademark) C-600, C-800, C-2000 (manufactured by Air Water Co., Ltd.), “NICABEADS” (registered trademark). ) ICB, PC, MC (manufactured by Nippon Carbon Co., Ltd.) and the like are specifically mentioned.

  Organic materials include polyamide resin, phenol resin, amino resin, acrylic resin, ethylene-vinyl acetate resin, polyester resin, urea resin, melamine resin, alkyd resin, polyimide resin, urethane resin, divinylbenzene resin, epoxy resin, etc. These thermoplastic resins, thermosetting resins, organic-inorganic hybrid copolymers, and the like. Further, two or more kinds of the materials mentioned here may be used in combination. Among these, acrylic resins and divinylbenzene resins having excellent heat resistance and polyamide resins having excellent impact resistance are preferably used. When using a thermoplastic resin in such an organic material, the same thing as the above-mentioned thermoplastic resin particle can also be used as a nucleus of a thermoplastic resin. Among these, it is preferable to use a polyamide resin having excellent impact resistance as a nucleus.

  Examples of the conductive substance used in the present invention include metal and carbon. In the conductive particles coated with a conductive material, a conductive layer is formed of the conductive material. However, the conductive layer may be a continuous film of metal or carbon, or a conductive layer. It may be a collection of fibrous or particulate materials such as conductive fibers, carbon black and metal fine particles.

  As the conductive fiber, a conductive fiber made of carbon is preferable. A more preferable conductive fiber is a hollow carbon fiber. The outer diameter of the hollow carbon fiber is preferably 0.1 to 1000 nm, more preferably 1 to 100 nm. Even if the outer diameter of the hollow carbon fiber is too small or too large, it is often difficult to produce such a hollow carbon fiber.

  The hollow carbon fiber may have a graphite layer formed on the surface. At that time, the total number of the graphite layers constituting is preferably 1 to 100 layers, more preferably 1 to 10 layers, still more preferably 1 to 4 layers, and particularly preferably 1 layer or 2 layers. Is of layer.

  Carbon black such as channel black, thermal black and furnace black made of carbon is also preferably used as a material constituting the conductive layer.

  The metal as the conductive material is preferably a metal used by plating. As a preferable metal, platinum, gold, silver, copper, tin, nickel, titanium, cobalt, zinc, iron, chromium, aluminum, magnesium, and the like are used in order to prevent corrosion due to a potential difference with the carbon fiber. In view of high conductivity and stability, platinum, gold, silver, copper, tin, nickel and titanium are particularly preferably used. These metals may be used alone or as an alloy containing these metals as main components.

  As a method of performing metal plating using the above metal, wet plating and dry plating are preferably used. As the wet plating, methods such as electroless plating, displacement plating, and electroplating can be employed. Among them, a method using electroless plating is preferably used because it is possible to apply plating to nonconductors. . Moreover, as dry plating, methods such as vacuum deposition, plasma CVD (chemical vapor deposition), photo CVD, ion plating, and sputtering can be adopted, but excellent adhesion can be obtained even at low temperatures. A method by sputtering is preferably used.

  The metal plating may be a single metal film or a multi-layer film made of a plurality of metals. When metal plating is performed, it is preferable that a plating film having an outermost layer made of gold, nickel, copper, or titanium is formed. By using the above-mentioned metal as the outermost surface, the connection resistance value can be reduced and the surface can be stabilized. For example, when forming a gold layer, a method of forming a nickel layer by electroless nickel plating and then forming a gold layer by displacement gold plating is preferably used.

  In the conductive particles in which the core used in the present invention is coated with a conductive substance, an adhesive layer may or may not exist between the core and the conductive layer, but the core and the conductive layer are peeled off. If easy, an adhesive layer may be present. The main components of the adhesive layer in this case are vinyl acetate resin, acrylic resin, vinyl acetate-acrylic resin, vinyl acetate-vinyl chloride resin, ethylene-vinyl acetate resin, ethylene-vinyl acetate resin, ethylene-acrylic resin, polyamide. , Polyvinyl acetal, polyvinyl alcohol, polyester, polyurethane, urea resin, melamine resin, phenol resin, resorcinol resin, epoxy resin, polyimide, natural rubber, chloroprene rubber, nitrile rubber, urethane rubber, SBR, recycled rubber, butyl rubber, aqueous vinyl urethane , Α-olefin, cyanoacrylate, modified acrylic resin, epoxy resin, epoxy-phenol, butyral-phenol, nitrile-phenol, and the like are preferable. Acid vinyl resins, acrylic resins, vinyl acetate - acrylic resin, vinyl acetate - vinyl chloride resins, ethylene - vinyl acetate resins, ethylene - vinyl acetate resins, ethylene - include acrylic resins and epoxy resins.

  In addition, when metal fine particles are used as the conductive material constituting the conductive layer, the metal used as the metal fine particles prevents corrosion due to a potential difference from the carbon fiber, so platinum, gold, silver, copper, tin, nickel , Titanium, cobalt, zinc, iron, chromium, aluminum and magnesium, or an alloy containing these as a main component, or tin oxide, indium oxide, indium oxide / tin (ITO), or the like is preferably used. Among these, platinum, gold, silver, copper, tin, nickel, titanium, and alloys containing these as the main components are particularly preferably used because they exhibit high conductivity and stability.

  A mechanochemical bonding method is preferably used as a method for coating the nucleus with the above-mentioned metal fine particles. Mechanochemical bonding is a method of creating composite fine particles by adding mechanical energy to mechanically bond multiple different material particles at the molecular level, creating strong nanobonds at the interface, In the present invention, metal fine particles are bonded to the nuclei of an inorganic material or an organic material, and the nuclei are covered with the metal fine particles. The particle size of the metal fine particles is preferably 1/1000 to 1/10 times the average particle size of the nucleus, more preferably 1/500 to 1/100 times. In some cases, it is difficult to produce fine metal particles having a particle size that is too small. Conversely, if the particle size of the fine metal particles is too large, uneven coating may occur.

  As the conductive particles in which the core is coated with the conductive material, the volume ratio represented by [volume of core] / [volume of conductive layer] is preferably 0.1 to 500, more preferably. The electroconductive particle which is 1-300, More preferably, is 5-100 is used. If the volume ratio is too small, not only will the weight of the resulting carbon fiber reinforced composite material increase, but it may not evenly disperse during resin preparation, and conversely, if the volume ratio is too large, the resulting carbon fiber reinforced composite material is sufficient. Conductivity may not be obtained.

  The specific gravity of the conductive particles used in the present invention is preferably at most 3.2. If the specific gravity of the conductive particles is too large, not only will the weight of the resulting carbon fiber reinforced composite material increase, but it may not evenly disperse during the preparation of the epoxy resin composition. The specific gravity of the conductive particles is preferably 1 to 2.2. If the specific gravity of the conductive particles is too small, it may not be uniformly dispersed during the preparation of the epoxy resin composition.

  The shape of the conductive 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 there is no origin of stress concentration, which is high. This is a preferred embodiment in terms of imparting impact resistance.

  In the prepreg of the present invention, in the case of the first embodiment in which the thermoplastic resin particles and the conductive particles are used in combination, it is preferable that the average particle size of the conductive particles is the same as or larger than the average particle size of the thermoplastic resin particles. When the average particle diameter of the conductive particles is smaller than the average particle diameter of the thermoplastic resin particles, the conductive particles may be buried between layers, and a sufficient conductivity improvement effect may not be brought about.

  In the present invention, the average particle size of the thermoplastic resin particles and the conductive particles is preferably at most 150 μm. If the average particle size is too large, the arrangement of the carbon fibers may be disturbed, or if the particle layer is formed in the vicinity of the surface of the prepreg as will be described later, the layer of the resulting composite material is made thicker than necessary. When formed into a composite material, its physical properties may be reduced. The average particle size is preferably 1 to 150 μm, more preferably 3 to 60 μm, and particularly preferably 5 to 30 μm. If the average particle size is too small, the particles will sink between the fibers of the carbon fiber, will not be localized in the interlayer part of the prepreg laminate, the effect of the presence of the particles will not be sufficiently obtained, and the impact resistance tends to be low. is there.

  In addition, the conductive particles in which the core is covered with the conductive material of the second aspect are also preferably at most 150 μm. If the average particle size is too large, the arrangement of the carbon fibers may be disturbed, or if the particle layer is formed in the vicinity of the surface of the prepreg as will be described later, the layer of the resulting composite material is made thicker than necessary. When formed into a composite material, its physical properties may be reduced. The average particle size is preferably 1 to 150 μm, more preferably 3 to 60 μm, and particularly preferably 5 to 30 μm. If the average particle size is too small, the particles will sink between the fibers of the carbon fiber, will not be localized in the interlayer part of the prepreg laminate, the effect of the presence of the particles will not be sufficiently obtained, and the impact resistance tends to be low. is there.

  The average particle size used here is a photograph such as a scanning electron microscope and magnified particles more than 1000 times, photographed randomly, select the particles, the diameter of the circle circumscribing the particles as the particle size, The average value of the particle diameter (n = 50) is defined as the average particle diameter of the particles. When determining the volume ratio represented by [nuclear volume] / [conductive layer volume] of conductive particles in which the core is coated with a conductive substance, first, the average particle diameter of the core of the conductive particles Is measured by the above method. Thereafter, a cross-sectional photograph of the conductive particles coated with the conductive material is magnified 10,000 times with a scanning microscope and observed, and the average thickness (n = 5) of the conductive layer is measured. Conductive particles are selected at random, the thickness of the conductive layer is measured by the above-described method, and the average value (n = 10) of the thickness of the conductive layer is measured. The average particle diameter of the conductive particles is obtained by adding the average particle diameter of the core of the conductive particles and the average value of the thickness of the conductive layer. The volume ratio represented by [volume of nucleus] / [volume of conductive layer] can be calculated using the average particle diameter of the core of the conductive particles and the average particle diameter of the conductive particles.

The amount of the conductive particles is 0.01 to 20% by weight relative to the total resin composition of the, preferably 0.05 to 10 wt%. If the addition amount of the conductive particles is small, sufficient conductivity cannot be obtained, and if the addition amount is too large, the impact resistance may be lowered.

  In the present invention, when the thermoplastic resin particles and the conductive particles are used in combination, it is represented by [amount of thermoplastic resin particles (parts by weight)] / [amount of conductive particles (parts by weight)]. The weight ratio is preferably 1 to 1000, more preferably 5 to 200, and particularly preferably 10 to 100. If the weight ratio is less than 1, sufficient impact resistance may not be obtained, and if the weight ratio is greater than 1000, sufficient conductivity may not be obtained.

  In the present invention, it is also preferable to use a master batch comprising an epoxy resin, conductive particles, and a coupling agent. That is, depending on the mixing method, the original mechanical properties and conductivity may not be exhibited due to the aggregation of the conductive particles, whereas the master batch can be incorporated into the resin composition. By suppressing the mixing of coarse aggregates and using a coupling agent, the dispersibility in the resin composition is further improved. By improving the dispersibility, the bending elongation of a cured resin obtained by curing the epoxy resin composition for a carbon fiber reinforced composite material of the present invention is improved. The mixing ratio of the coupling agent and the conductive particles in the master batch is preferably a ratio of 1/200 to 1/10 by weight, and preferably contains 20 to 95% by weight of epoxy resin. If the amount of the coupling agent is too small, the adhesion between the epoxy resin and the conductive particles may not be sufficiently exhibited, and the dispersibility of the conductive particles in the epoxy resin may be deteriorated. Conversely, if the amount of coupling agent is too large, the mechanical properties of the cured product may be reduced. Further, if the weight ratio of the epoxy resin is too small, the dispersibility of the conductive particles may be deteriorated. Conversely, if the weight ratio of the epoxy resin is larger than this range, the usefulness of using the master batch method is lowered. There is a case.

  As an application method of the masterbatch, for example, the following procedure is given as an example. First, knead the epoxy resin, conductive particles and coupling agent with a stirrer, disperse the conductive particles to prepare a master batch, and the remaining epoxy resin so as to have a weight ratio of the designed epoxy resin composition, The target epoxy resin composition for carbon fiber composite material is obtained by adding the prepared master batch to a compound such as thermoplastic resin, thermoplastic resin particles, and curing agent.

  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 are uniformly heated and kneaded at about 150 ° C. and cooled to a temperature at which the curing reaction does not proceed easily. Although it is preferable to add and knead the thermoplastic resin particles and the curing agent, the blending method of each component is not particularly limited to this method.

  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 may be excessive, which may impair the advantages of the fiber-reinforced composite material having excellent specific strength and specific elastic modulus, and the carbon fiber weight fraction may be high. If it is too high, resin impregnation failure occurs, and the resulting 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 abbreviated as a particle layer) in which it is possible to clearly confirm the state in which all the above-mentioned particles are localized when the cross section is observed. 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 20% in the thickness direction from the surface of the prepreg to the thickness of the prepreg of 100% , preferably a depth of 10%. it is that they exist within. 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 and there are layers with and without particles, a composite material that is vulnerable to impacts will result. 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 existing ratio of the thermoplastic resin particles and conductive particles present in the particle layer, the prepreg is 90 to 100% by weight relative to the total amount 100% by weight of the thermoplastic resin particles and conductive particles, preferably 95 to 100% by weight.

  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. If it is difficult to discriminate the particles dispersed in the resin after photography, a means for dyeing the particles can also be employed.

In the present invention, the total amount of the thermoplastic resin particles and the conductive particles is preferably in the range of 20% by weight or less based on the prepreg. If it exceeds 20% by weight based on the prepreg, mixing of the particles and the resin becomes difficult, and the tack and drape properties of the prepreg may deteriorate. That is, the amount of the sum of the thermoplastic resin particles and the conductive particles is 20% by weight or less with respect to the prepreg in order to impart impact resistance by the particles while maintaining the characteristics of the epoxy resin as the base resin. More preferably, it is 15 weight% or less. In order to further improve the handling of the prepreg, the total amount of the thermoplastic resin particles and the conductive particles is preferably 10% by weight or less. The amount of the particles is preferably 1% by weight or more, more preferably 2% by weight or more based on the prepreg in order to obtain high impact resistance and conductivity .

  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, in the prepreg of the present invention, the surface of a primary prepreg composed of an epoxy resin that is a carbon fiber and a matrix resin is coated with a thermoplastic resin particle and a conductive particle, or a core of the thermoplastic resin with a conductive substance. The conductive particles are applied in the form of particles, a mixture in which these particles are uniformly mixed in an epoxy resin as a matrix resin is prepared, and these fibers are reinforced with reinforcing fibers in the process of impregnating the mixture into carbon fibers. A method of blocking the invasion of the particles to localize the particles on the surface portion of the prepreg, or by pre-impregnating carbon fiber with an epoxy resin in advance to prepare a primary prepreg, and the concentration of these particles on the primary prepreg surface is high. It can manufacture by the method of sticking the film of the thermosetting resin contained in. The thermoplastic resin particles, the conductive particles, and the conductive particles obtained by coating the core of the thermoplastic resin with a conductive material are uniformly present in a depth range of 20% of the thickness of the prepreg. A prepreg for a carbon fiber composite material having both conductivity and conductivity is 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. When the plastic resin particles and the conductive particles are used in combination, delamination caused by local impact is reduced during falling weight impact (or local impact) on the carbon fiber reinforced composite material. When stress is applied to the carbon fiber reinforced composite material after impact, there are few delamination parts caused by the local impact that becomes the starting point of fracture due to stress concentration, and conductive particles are in the laminated layer. Since the probability of contact with the carbon fiber is high and a conductive path is easily formed, a carbon fiber reinforced composite material that exhibits high impact resistance and conductivity can be obtained.

  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, the prepreg using the same, and the carbon fiber reinforced composite material will be described more specifically with reference to examples. The resin raw materials, prepregs and carbon fiber reinforced composite materials used in the examples, and methods for evaluating post-impact compressive strength 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) T800S-24K-10E (24,000 fibers, 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>
・ Bisphenol A type epoxy resin, "jER" (registered trademark) 825 (manufactured by Japan Epoxy Resin Co., Ltd.)
・ Tetraglycidyldiaminodiphenylmethane, ELM434 (manufactured by Sumitomo Chemical Co., Ltd.)
<Curing agent>
・ 4,4'-Diaminodiphenylsulfone (Mitsui Chemicals Fine Co., Ltd.)
<Thermoplastic resin>
・ Polyethersulfone having a hydroxyl group at the terminal "SUMICA EXCEL" (registered trademark) PES5003P (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, followed by vacuum drying at 100 ° C. for 24 hours to obtain epoxy-modified nylon particles A. (Average particle size: 12 μm).

<Coupling agent>
Z-6040 (Toray Dow Corning Co., Ltd.): 3-glycidoxypropyltrimethoxysilane Z-6011 (Toray Dow Corning Co., Ltd.): 3-aminopropyltriethoxysilane Z-6300 (Toray Dow Corning Co., Ltd.): Vinyltrimethoxysilane “Disnet” (registered trademark) DB (Sankyo Chemical Co., Ltd.): 2-dibutylamino-4,6 dimercapto-s-triazine “Plenact” "(Registered trademark) AL-M (manufactured by Ajinomoto Fine Techno Co., Ltd.): acetoalkoxyaluminum diisopropylate triethanolamine titanate (manufactured by Mitsubishi Gas Chemical Co., Ltd.): diisopropoxy bis (triethanolaminate) Titanium “Orgatics” (registered trademark) TPHS (manufactured by Matsumoto Fine Chemical Co., Ltd.): Polyhi B alkoxy titanium stearate <conductive particles>
Particle “Micropearl” (registered trademark) CU215 (manufactured by Sekisui Chemical Co., Ltd., specific gravity: 1.43 g / cm ³ , plated with nickel on divinylbenzene polymer particles and further plated with copper) Thickness: 156 nm, [volume of nucleus] / [volume of conductive layer]: 23.31)
Particles obtained by plating nickel on divinylbenzene polymer particles “Micropearl” (registered trademark) NI215 (manufactured by Sekisui Chemical Co., Ltd., specific gravity: 1.58 g / cm ³ , conductive layer thickness: 261 nm, [volume of core] ] / [Volume of conductive layer]: 10.73).
Glassy carbon particle “Bellepearl” (registered trademark) C-2000 (Air Water Co., Ltd., specific gravity: 1.5 g / cm ³ )
-Conductive particles B obtained by the following production method
100 g of epoxy-modified nylon particles A are added to 1000 ml of electroless nickel plating solution NLT-PLA (manufactured by Nikko Metal Plating Co., Ltd.), and then plated at a temperature of 50 ° C. for 60 minutes to obtain conductive particles B. Produced. The specific gravity of the conductive particles B was 1.4 g / cm ³ , the thickness of the conductive layer was 180 nm, and [volume of nucleus] / [volume of conductive layer] was 24.9.

(1) Measurement of the average particle size of the particles and the volume ratio represented by [volume of the core] / [volume of the conductive layer] of the conductive particles. The particles are randomly selected, the diameter of the circle circumscribing the particles is defined as the particle size, and the average value of the particle sizes (n = 50) is defined as the average particle size of the particles. When determining the volume ratio represented by [volume of core] / [volume of conductive layer] of conductive particles in which nuclei are coated with a conductive material, first, the average particle diameter of the nuclei of the conductive particles Is measured by the above method. Thereafter, a cross-sectional photograph of the conductive particles coated with the conductive substance is observed with a scanning microscope at a magnification of 10,000 times, and the average thickness (n = 5) of the conductive layer is measured. Conductive particles are selected at random, the thickness of the conductive layer is measured by the above-described method, and the average value (n = 10) of the thickness of the conductive layer is measured. The average particle diameter of the conductive particles is obtained by adding the average particle diameter of the core of the conductive particles and the average value of the thickness of the conductive layer. Then, using the average particle diameter of the nuclei of the conductive particles and the average particle diameter of the conductive particles, a volume ratio represented by [volume of nuclei] / [volume of the conductive layer] is calculated. In the examples, S-4000 manufactured by Hitachi, Ltd. was used as a scanning electron microscope.

  The average particle diameter measurement results of the thermoplastic resin particles and the conductive particles were as follows.

<Thermoplastic resin particles>
・ Epoxy-modified nylon particles A ... (average particle size) 12.5μm
<Conductive particles>
・ "Micropearl" CU215 (average particle size) 15.5μm
・ "Micropearl" NI215 (average particle size) 15.4μm
・ "Belpearl" C-2000 ... (average particle size) 15.3 [mu] m
-Conductive particle B (average particle size) 13.8 μm.

(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 intervals between the polytetrafluoroethylene resin plates are measured at five locations in the horizontal direction of the cross-sectional photograph, and the average value (n = 5) is 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. Calculate the abundance of particles present in the 20% depth range. Here, the total area of the fine 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 matrix resin after photography, a means for dyeing the particles can also be employed.

(3) Compressive strength measurement after impact of fiber reinforced composite material [+ 45 ° / 0 ° / −45 ° / 90 °] A unidirectional prepreg was laminated in a pseudo-isotropic manner with _{3 ps} in a _{3 s} configuration. 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.

(4) Conductivity measurement of fiber reinforced composite material Unidirectional prepregs were each laminated at a [0 °] ₈ configuration in a pseudo-isotropic 24-ply manner, and autoclaved at 180 ° C for 2 hours at 0.59 MPa. The laminate was molded at a temperature elevation rate of 1.5 ° C./min under the pressure of 25 to produce 25 laminates. From each of these laminates, a sample having a length of 50 mm × width 50 mm (thickness 3 mm) was cut out, and a sample in which a conductive paste “Dotite” (registered trademark) D-550 (manufactured by Fujikura Kasei Co., Ltd.) was applied on both sides was prepared. did. For these samples, the resistance in the stacking direction was measured by a four-terminal method using an R6581 digital multimeter manufactured by Advantest Corp., and the volume resistivity was determined.

(5) Measurement of bending elongation of cured epoxy resin The bending elongation was measured as follows. First, the uncured epoxy resin composition was degassed in a vacuum, and then cured for 2 hours at a temperature of 180 ° C. in a mold set to a thickness of 2 mm by a 2 mm thick “Teflon (registered trademark)” spacer. A cured resin product having a thickness of 2 mm was obtained, and this cured resin product was cut into a width of 10 ± 0.1 mm and a length of 60 ± 1 mm to prepare a test piece. Using an Instron universal testing machine (Instron), three-point bending was measured at a crosshead speed of 1.0 mm / min, an indenter diameter of 10 mm, a support diameter of 4 mm, and a span of 32 mm. Asked. The number of measurements was n = 5, and the average value was obtained.

Example 1
In a kneader, 49 parts by weight of “jER” 825 and 50 parts by weight of ELM 434 were mixed with 10 parts by weight of PES5003P, and then mixed with “jER” 825 and Z-6040 (95% of “jER” 825). 5 parts by weight of Z-6040 was mixed with 1.5 parts by weight of the parts by weight. Thereafter, 0.01 parts by weight of “Micropearl” CU215 is kneaded, and further 40 parts by weight of 4,4′-diaminodiphenylsulfone as a curing agent is kneaded to produce an epoxy resin composition for carbon fiber reinforced composite material. did.

For the epoxy resin composition for carbon fiber reinforced composite materials shown in Table 1 (in the table, the numbers represent parts by weight), a base resin excluding thermoplastic resin particles was prepared, and the basis weight of the resin was 31 g / m using a knife coater. ² was coated on the release paper to prepare a resin film. An epoxy resin composition for a carbon fiber reinforced composite material is obtained by superimposing the resin film on both sides of a carbon fiber (weight per unit area 190 g / m ² ) aligned in one direction and using a heat roll while heating and pressing at 100 ° C. and 1 atm. Was impregnated to obtain a primary prepreg. Next, an epoxy resin composition prepared by adding thermoplastic particles so that the final epoxy resin composition of the carbon fiber reinforced composite material prepreg has the blending amount shown in Table 1, and using a knife coater, the resin weight is 21 g. Coating was performed on the release paper at / m ² to prepare a resin film. This resin film was superimposed on both sides of the primary prepreg, and a heat roll was used to impregnate the epoxy resin composition for carbon fiber reinforced composite material while heating and pressing at 100 ° C. and 1 atm to obtain the desired prepreg. The obtained prepreg was used as described in (3) Measurement of post-impact compressive strength of fiber reinforced composite material and (4) Measurement of conductivity of fiber reinforced composite material to obtain a fiber reinforced composite material. Post compression strength and volume resistivity were measured. The results are shown in Table 1.

(Example 2-18 and Comparative Example 1-4)
A prepreg was produced in the same manner as in Example 1 except that the type and blending amount of the coupling agent or conductive particles were changed as shown in Tables 1 to 5. Using the produced unidirectional prepreg, the abundance of particles existing in the range of 20% depth of the prepreg, the compressive strength after impact of the fiber-reinforced composite material, and the conductivity were measured. The obtained results are summarized in Tables 1 to 5.

( Reference Example 1 )
20 parts by weight of “Micropearl” NI215 and 0.1 part by weight of Z-6040 were blended into 80 parts by weight of ELM434 and then kneaded to prepare a masterbatch. In a kneader, 50 parts by weight of “jER” 825 and 44 parts by weight of ELM 434 were mixed with 10 parts by weight of PES5003P, and then 7.5 parts by weight of the master batch was kneaded. Thereafter, 40 parts by weight of 4,4′-diaminodiphenylsulfone as a curing agent was kneaded to prepare an epoxy resin composition for carbon fiber reinforced composite material. The obtained epoxy resin composition was carried out as described in (5) Measurement of bending elongation of cured epoxy resin, and the bending elongation was measured. The results obtained are shown in Table 6.

( Reference Example 2 )
20 parts by weight of “Micropearl” NI215 and 0.4 parts by weight of Z-6040 were blended into 80 parts by weight of ELM434 and then kneaded to prepare a masterbatch.

  In a kneader, 50 parts by weight of “jER” 825 and 44 parts by weight of ELM 434 were mixed with 10 parts by weight of PES5003P, and then 7.5 parts by weight of the master batch was kneaded. Thereafter, 40 parts by weight of 4,4'-diaminodiphenyl sulfone as a curing agent was kneaded to prepare an epoxy resin composition for carbon fiber reinforced composite material. The obtained epoxy resin composition was carried out as described in (5) Measurement of bending elongation of cured epoxy resin, and the bending elongation was measured. The results obtained are shown in Table 6.

( Reference Example 3 )
20 parts by weight of “Micropearl” NI215 and 2 parts by weight of Z-6040 were blended into 80 parts by weight of ELM434 and then kneaded to prepare a masterbatch.

  In a kneader, 50 parts by weight of “jER” 825 and 44 parts by weight of ELM 434 were mixed with 10 parts by weight of PES5003P, and then 7.5 parts by weight of the master batch was kneaded. Thereafter, 40 parts by weight of 4,4'-diaminodiphenyl sulfone as a curing agent was kneaded to prepare an epoxy resin composition for carbon fiber reinforced composite material. The obtained epoxy resin composition was carried out as described in (5) Measurement of bending elongation of cured epoxy resin, and the bending elongation was measured. The results obtained are shown in Table 6.

( Reference Example 4 )
In a kneader, 49 parts by weight of “jER” 825 and 50 parts by weight of ELM434 were mixed with 10 parts by weight of PES5003P and dissolved, and then a mixture of “jER” 825 and Z-6040 (“jER” 825 with 97 1 part by weight of 3 parts by weight of Z-6040 to 1 part by weight was kneaded. Thereafter, 1 part by weight of “Micropearl” NI215 was kneaded and 40 parts by weight of 4,4′-diaminodiphenylsulfone as a curing agent was further kneaded to prepare an epoxy resin composition for carbon fiber reinforced composite material. The obtained epoxy resin composition was carried out as described in (5) Measurement of bending elongation of cured epoxy resin, and the bending elongation was measured. The results obtained are shown in Table 6.

( Reference Examples 5 and 6 )
An epoxy resin composition for carbon fiber reinforced composite material was produced in the same manner as in Reference Example 4 except that the amount of coupling agent was changed as shown in Table 6. The obtained epoxy resin composition was carried out as described in (5) Measurement of bending elongation of cured epoxy resin, and the bending elongation was measured. The results obtained are summarized in Table 6.

By comparing Examples 1 to 18 and Comparative Examples 1 to 4, the carbon fiber reinforced composite material using the epoxy resin composition for carbon fiber reinforced composite material of the present invention is composed of conductive particles and an epoxy resin which is a matrix resin. It can be seen that it has a strong adhesive strength, achieves high post-impact compressive strength and low volume resistivity, and achieves both high impact resistance and conductivity. Further, in Example 7-9, in comparison with Comparative Example 1 or Comparative Example 4, the present invention can achieve specific low volume resistivity and high compression strength after impact, conductivity and impact resistance It turns out that it is the range which can be compatible. Furthermore, as shown in Examples 13 to 18, even if various coupling agents are used, the adhesion between the conductive particles and the epoxy resin is made strong, and both high impact resistance and conductivity are achieved. It can be seen that the effect is particularly high in the composition of Z-6040 (manufactured by Toray Dow Corning Co., Ltd.).

  Further, in Example 12, since the conductive particles B in which the core of the thermoplastic resin is coated with the conductive material are used, a low volume resistivity and a high compressive strength after impact can be achieved. It can be seen that both impact resistance and impact resistance are compatible.

Furthermore, it can be seen from Reference Examples 1 to 6 that the use of the master batch improves the dispersibility of the conductive particles and improves the resin bending elongation.

  According to the present invention, an epoxy resin composition for a carbon fiber reinforced composite material having excellent mechanical properties and conductivity, a prepreg, and a carbon fiber reinforced composite material can be obtained. In addition, it can be widely used in computer applications such as IC trays and casings (housings) of notebook computers, and is useful.

Claims (8)

A prepreg formed by impregnating carbon fiber with a resin composition containing at least an epoxy resin in which a thermoplastic resin is mixed or dissolved , a curing agent, a coupling agent, thermoplastic resin particles, and conductive particles , The thermoplastic resin mixed or dissolved in the epoxy resin is a polyethersulfone having a hydroxyl group at the terminal, and the ratio (part by weight) is epoxy resin: thermoplastic resin = 100: 2 to 100: 50, The coupling agent is 0.005 to 0.1% by weight based on the total resin composition , the thermoplastic resin particles are 1 to 10% by weight in 100% by weight of the prepreg, and the conductive particles are based on the total resin composition. 0.01 to 20% by weight, and 90 to 100% by weight of both the thermoplastic resin particles and the conductive particles are based on the prepreg thickness of 100%. The prepreg is characterized by being localized within a depth range of 20% in the thickness direction starting from the surface of the prepreg. The prepreg according to claim 1, wherein the coupling agent is a silane coupling agent. The prepreg according to claim 2 , wherein the coupling agent is a silane coupling agent having an epoxy group or an amino group. The prepreg according to any one of claims 1 to 3 , wherein the average particle diameter of the conductive particles is the same as or larger than the average particle diameter of the thermoplastic resin particles and is 1 to 150 µm. The prepreg in any one of Claims 1-4 whose specific gravity of electroconductive particle is 0.8-3.2. Conductive particles is at least one selected from the group consisting of carbon particles, nuclei and conductive particles, each formed by coating a conductive material nuclear organic material of the inorganic material, one of the claims 1 to 5 The prepreg according to crab. It is obtained by using a masterbatch containing a coupling agent and conductive particles in a weight ratio of 1/200 to 1/10 and a total amount of epoxy resin of 20 to 95% by weight. The prepreg according to any one of 1 to 6 . Carbon fiber reinforced composite material formed by curing a prepreg according to any one of claims 1 to 7.