JP2011213991A - Carbon fiber-reinforced composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon fiber-reinforced composite material having both of excellent impact resistance and electrical conductivity.SOLUTION: The carbon fiber-reinforced composite material is produced by layering and curing two or more prepregs comprising at least carbon fibers [A], a thermosetting resin [B], thermoplastic resin particles [C], and conductive particles [D] with a particle diameter fluctuation factor of 5% or less; and between the layers of the carbon fibers [A] in the carbon fiber-reinforced composite material, 30% or more in number of the conductive particles [D] are brought into contact with each of the carbon fibers [A]. Alternatively, the carbon fiber-reinforced composite material comprises: at least carbon fibers [A]; a thermosetting resin [B]; thermoplastic resin particles [C]; and conductive particles [D] with a particle diameter fluctuation factor of 5% or less, and between the layers of the carbon fibers [A] in the carbon fiber-reinforced composite material, 30% or more in number of the conductive particles [D] are brought into contact with each of the carbon fibers [A].

Description

  The present invention relates to 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.

  The carbon fiber reinforced composite material has, as one aspect thereof, a non-uniform material formed by molding a prepreg having carbon fibers that are reinforcing fibers and a matrix resin as essential constituent elements. There will be a large difference in physical properties in other directions. 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 carbon fiber reinforced 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, these technologies give 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 layers, a method in which conductive particles such as metal particles and carbon particles (see Patent Document 3) are mixed in advance with a matrix resin, or a conductive film in a matrix resin (see Patent Document 4). ) Can be considered, but these methods do not sufficiently satisfy both of high conductivity and impact resistance, and the interlayer design is difficult.

  In addition, as a method for improving the adhesion between the matrix resin and the conductive particles, there is a method using a silane coupling agent (see Patent Document 5). This method is also sufficient to achieve both high conductivity and impact resistance. It was not satisfactory.

US Pat. No. 5,028,478 JP-A-3-26750 JP 2008-231395 A JP 2009-062473 A JP 2009-077405 A

  Accordingly, an object of the present invention is to provide a carbon fiber reinforced composite material that has excellent mechanical properties such as impact resistance and conductivity.

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

  That is, it includes at least [A] carbon fiber, [B] thermosetting resin, [C] thermoplastic resin particles, and [D] conductive particles, and [D] coefficient of variation of the particle diameter of the conductive particles. A carbon fiber reinforced composite material obtained by laminating and curing two or more prepregs of 5% or less, and [D] having a number of 30% or more between the [A] carbon fiber layers of the carbon fiber reinforced composite material. The carbon fiber reinforced composite material, wherein the conductive particles are in contact with the respective [A] carbon fibers.

  According to a preferred embodiment of the carbon fiber reinforced composite material of the present invention, [D] conductive particles are unevenly distributed on the surface side of the prepreg.

  Moreover, according to the preferable aspect of the carbon fiber reinforced composite material of this invention, [D] electroconductive particle is [B] thermosetting resin, [C] thermoplastic resin particle, and [D] electroconductive particle. 0.01 to 50% by mass with respect to the total of the above.

  According to a preferred embodiment of the carbon fiber reinforced composite material of the present invention, [D] conductive particles are carbon particles, particles in which the core or core of an inorganic material is coated with a conductive substance, and organic materials At least one selected from the group consisting of conductive particles in which the cores or cores are coated with a conductive substance.

  According to a preferred aspect of the carbon fiber reinforced composite material of the present invention, the conductive substance is platinum, gold, silver, copper, nickel, titanium, cobalt, palladium, tin, zinc, iron, chromium, aluminum, and It comprises at least one selected from the group consisting of carbon.

  According to another aspect of the carbon fiber reinforced composite material of the present invention, at least [A] carbon fiber, [B] thermosetting resin, [C] thermoplastic resin particles, and [D] conductive particles. A carbon fiber reinforced composite material comprising [D] conductive particles having a coefficient of variation of particle size of 5% or less and a number of [D] conductive particles of 30% or more. It is contacting with each [A] carbon fiber between the layers of [A] carbon fiber of material.

With such a carbon fiber reinforced composite material, a volume resistivity of 1.0 × 10 ³ Ωcm or less is realized while maintaining a compressive strength after impact of 280 MPa or more.

  In the present invention, the prepreg used contains conductive particles having a coefficient of variation of particle size of 5% or less, so that the carbon fiber reinforced composite material obtained by curing the conductive particles, or the carbon fiber reinforced composite material. By including conductive particles having a coefficient of variation of particle size of 5% or less, the carbon fiber reinforced composite material can have both excellent impact resistance and conductivity. In the present invention, since the coefficient of variation of the particle size of the conductive particles contained in the prepreg or carbon fiber reinforced composite material used is 5% or less, the number of conductive particles of 30% or more is reinforced with carbon fiber. It contacts each carbon fiber between the carbon fiber layers of the composite material, thereby exhibiting excellent conductivity. That is, in the prior art, if the impact resistance is high, the conductivity is low, and if the conductivity is high, only a carbon fiber reinforced composite material that is inferior in impact resistance can be obtained. And a carbon fiber reinforced composite material having both conductivity and conductivity.

  In addition, since the carbon fiber reinforced composite material of the present invention has both excellent impact resistance and conductivity, in addition to aircraft components, sports equipment such as tennis rackets and golf shafts, automobile bumpers and doors, etc. The present invention can be preferably applied to outer plate members, automobile structural members such as chassis and front side members, and blades of windmills.

  As a result of pursuing the conductive mechanism of the carbon fiber reinforced composite material composed of carbon fiber, thermosetting resin, thermoplastic resin particles, and conductive particles, the inventors have found that the coefficient of variation in particle size is 5% or less. At least 30% of the conductive particles are in contact with each carbon fiber between the carbon fiber layers of the carbon fiber reinforced composite material obtained by laminating and curing two or more prepregs containing certain conductive particles. It has been clarified that the carbon fiber reinforced composite material has excellent impact resistance and conductivity at a high level, and the present invention has been achieved. Hereinafter, the present invention will be described in detail.

  Each of the carbon fiber reinforced composite materials of the present invention includes [A] carbon fiber, [B] thermosetting resin, [C] thermoplastic resin particles, and [D] conductive particles.

  [A] The carbon fiber used in the present invention can be any type of carbon fiber depending on the application, but it exhibits higher conductivity, and therefore has a tensile elastic modulus of at least 280 GPa. It is preferable that 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. In addition, from the viewpoint of impact resistance, a carbon fiber reinforced composite material having excellent impact resistance and high rigidity and mechanical strength is obtained, so that the tensile strength is preferably 4.4 to 6.5 GPa, The tensile elongation is also an important factor, and is preferably a high-strength, high-strength carbon fiber of 1.7 to 2.3%. Therefore, from the point of achieving both high conductivity and impact resistance, the tensile elastic modulus is at least 280 GPa, the tensile strength is at least 4.4 GPa, and the tensile elongation is at least 1.7%. Carbon fiber 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 [A] 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 mass or more and a monomer copolymerizable with acrylonitrile is less than 10% by mass as a carbon fiber precursor. 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 of which are manufactured by Toray Industries, Inc.).

  The form and arrangement of the carbon fibers can be selected as appropriate from long fibers aligned in one direction, tows, woven fabrics, nonwoven 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.

  The [B] thermosetting resin used in the present invention is not particularly limited as long as it is a resin that undergoes a crosslinking reaction by heat and at least partially forms a three-dimensional crosslinked structure. Examples of such thermosetting resins include unsaturated polyester resins, vinyl ester resins, epoxy resins, benzoxazine resins, phenol resins, urea resins, melamine resins, and polyimide resins, and these modified products and two or more types thereof. A blended resin or the like can also be used. In addition, these thermosetting resins may be self-curing by heating, or may be blended with a curing agent or a curing accelerator.

  Among these thermosetting resins, an epoxy resin excellent in the balance of heat resistance, mechanical properties, and adhesiveness with carbon fibers is preferably used. In particular, an epoxy resin whose precursor is an amine, a phenol, or a compound having a carbon-carbon double bond is preferably used. Specifically, various isomers of tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol, and triglycidylaminocresol are exemplified as glycidylamine type epoxy resins having amines as precursors. Tetraglycidyldiaminodiphenylmethane is preferable as a resin for composite materials as an aircraft structural material because of its excellent heat resistance.

  A glycidyl ether type epoxy resin having phenol as a precursor is also preferably used as the thermosetting resin. 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, a bisphenol A type epoxy resin that is solid at room temperature (about 25 ° C.) gives a structure having a low crosslinking density in a cured resin compared to a bisphenol A type epoxy resin that is liquid at room temperature (about 25 ° C.). The cured resin is lower in heat resistance but higher in toughness, and is preferably used in combination with a glycidylamine type epoxy resin, a liquid bisphenol A type epoxy resin or a bisphenol F type epoxy resin. It is done.

  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 are preferably used because they give a cured resin having high fracture toughness and high elongation.

  These epoxy resins may be used alone or in combination as appropriate. It is preferable to mix and use at least a bifunctional epoxy resin and a trifunctional or higher functional epoxy resin since both the fluidity of the resin and the heat resistance after curing can be obtained. 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 an epoxy resin that is liquid at least at room temperature and an epoxy resin that is solid at room temperature is effective for making the tackiness and draping property of the prepreg appropriate.

  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.

  As a curing agent for the epoxy resin, any compound having an active group capable of reacting with an epoxy group can be used. As the curing agent, a compound having an amino group, an acid anhydride group and an azide group is suitable. 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. These curing agents may be used alone or in combination.

  By using aromatic diamine as a curing agent, a cured resin having good heat resistance can be obtained. In particular, various isomers of diaminodiphenylsulfone are most suitable for obtaining a cured resin having good heat resistance. It is preferable to add the aromatic diamine so that the amount of the curing agent is stoichiometrically equivalent. However, in some cases, for example, by using an equivalent ratio of about 0.7 to 0.8, a high elastic modulus is obtained. The cured resin is obtained.

  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 and water resistance can be obtained while curing at a relatively low temperature. It is done. Curing with an acid anhydride gives a cured resin having a lower water absorption than amine compound curing. In addition, the storage stability of the prepreg is improved by using a latent product of these hardeners, for example, a microencapsulated product. In particular, the tackiness and draping properties hardly change even when left at room temperature.

  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.

  It is also preferable to mix and dissolve a thermoplastic resin in the thermosetting resin. Such a thermoplastic resin is generally selected from a carbon-carbon bond, an amide bond, an imide bond, an ester bond, an ether bond, a carbonate bond, a urethane bond, a thioether bond, a sulfone bond, and a carbonyl bond in the main chain. Although it is preferably a thermoplastic resin having a bond, 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, 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 and dissolved in the thermosetting resin.

  In the present invention, since the particles of [C] thermoplastic resin are used as an essential component, the resulting carbon fiber reinforced composite material can achieve excellent impact resistance. As the material for the [C] thermoplastic resin particles used in the present invention, those similar to the various thermoplastic resins exemplified above as the thermoplastic resin mixed and dissolved in the thermosetting resin may be used. it can. Of these, polyamides that can greatly improve impact resistance due to excellent toughness are most preferable. Among polyamides, nylon 12, nylon 11 and nylon 6/12 copolymer have particularly good adhesive strength with [B] thermosetting resin, so the interlayer of the carbon fiber reinforced composite material at the time of falling weight impact. The peel strength is high, and the impact resistance improvement effect is high, which is preferable. [C] When particles made by mixing a thermosetting resin such as epoxy resin are used as thermoplastic resin particles, the adhesion to the matrix resin is improved and the impact resistance of the carbon fiber reinforced composite material is improved. More preferably.

  The shape of the thermoplastic resin particles may be spherical, non-spherical, porous, needle-shaped, whisker-shaped, or flake-shaped. However, since the spherical shape does not deteriorate the flow characteristics of the thermosetting resin, carbon fiber is used. Since the exfoliation property is excellent and the delamination caused by the local impact is reduced during the falling weight impact (or local impact) on the carbon fiber reinforced composite material, the carbon fiber reinforcement after the impact is reduced. When stress is applied to the composite material, a carbon fiber reinforced composite material exhibiting high impact resistance can be obtained with fewer delamination portions caused by the local impact that is the starting point of fracture due to stress concentration. Therefore, it is preferable.

[D] electroconductive particle used by this invention should just be a particle | grain which behaves as an electrically favorable conductor, and is not limited to what consists only of a conductor. Preferably, the particles have a volume resistivity of 10 to 10 ⁻⁹ Ωcm, more preferably 1 to 10 ⁻⁹ Ωcm, and still more preferably 10 ⁻¹ to 10 ⁻⁹ Ωcm. If the volume resistivity is too high, sufficient conductivity may not be obtained in the carbon fiber reinforced composite material. The conductive particles include, for example, carbon particles, metal particles, polyacetylene particles, polyaniline particles, polypyrrole particles, polythiophene particles, polyisothianaphthene particles, polyethylene polymer particles such as polyethylene dioxythiophene particles, and inorganic material nuclei. Alternatively, particles in which the core is coated with a conductive substance, or particles in which the core or core of an organic material is coated with a conductive substance can be used. Among these, since it exhibits high conductivity and stability, carbon particles, particles in which the core or core of an inorganic material is coated with a conductive substance, and the core or core of an organic material are coated with a conductive substance. Are particularly preferably used.

  The volume resistivity mentioned here is calculated from the sample thickness and resistance value measured by setting the sample in a cylindrical cell having four probe electrodes and applying a pressure of 60 MPa to the sample. It is set as the volume specific resistance.

  The carbon particles can be obtained, for example, by firing thermosetting resin particles or thermoplastic resin particles. The firing temperature is preferably 600 ° C to 3000 ° C, more preferably 800 ° C to 3000 ° C, and still more preferably 2000 ° C to 3000 ° C. When fired at a temperature of 2000 ° C. or higher, carbon particles having excellent conductivity can be obtained. Examples of the thermosetting resin particles include phenol resin particles, epoxy resin particles, and benzoxazine particles. Examples of thermoplastic resin particles include polyacrylonitrile particles, polyetherimide particles, polyamideimide particles, polyphenylene sulfide particles, polyamide particles, polyimide particles, polyether ketone particles, and polyethersulfone particles. Is used. Of these, phenol resin particles are particularly preferably used because the carbon particles obtained have high conductivity.

  Examples of the carbon particles include “Bellepearl (registered trademark)” C-600, C-800, C-2000 (manufactured by Air Water Co., Ltd.), “NICABEADS (registered trademark)” ICB, PC, MC (Nippon Carbon Co., Ltd.). Glassy carbon (manufactured by Tokai Carbon Co., Ltd.), high purity artificial graphite SG series, SGB series, SN series (manufactured by SEC Carbon Co., Ltd.), true spherical carbon (manufactured by Gunei Chemical Industry Co., Ltd.) ) And the like.

  The conductive substance used when the core or core of the inorganic material or the core or core of the organic material is coated to form conductive particles is sufficient if it contains a substance that is an electrically good conductor. For example, metals such as platinum, gold, silver, copper, nickel, titanium, cobalt, palladium, tin, zinc, iron, chromium, aluminum, polyacetylene, polyaniline, polypyrrole, polythiophene, polyisothianaphthene, polyethylenedioxythiophene, etc. Conductive polymers, carbon black such as channel black, thermal black, furnace black, ketjen black, and carbon such as carbon nanotubes, fullerene, graphene, and hollow carbon fiber can be used. Among these, metal and carbon are particularly preferably used because of high conductivity.

  When a metal is used as the conductive substance, any metal may be used, but the standard electrode potential is preferably −2.0 to 2.0 V, more preferably −1.8 to 1.8 V. If the standard electrode potential is too low, it may be unstable and unfavorable for safety, and if it is too high, workability and productivity may be reduced. Here, the standard electrode potential refers to the electrode potential when a metal is immersed in a solution containing the metal ions and the standard hydrogen electrode (platinum immersed in a 1N HCl solution in contact with hydrogen gas at 1 atm. Electrode) expressed as a difference from the potential. For example, Ti: -1.74V, Ni: -0.26V, Cu: 0.34V, Ag: 0.80V, Au: 1.52V.

  When using the said metal, it is preferable that it is the metal used by plating. As a preferable metal, platinum, gold, silver, copper, tin, nickel, titanium, cobalt, zinc, iron, chromium, aluminum, etc. are used because it can prevent corrosion of the metal due to a potential difference with the carbon fiber, and among these, Platinum, gold, silver, copper, tin, nickel, or titanium is particularly preferably used because the volume resistivity exhibits high conductivity and stability of 10 to 10 −9 Ωcm. In addition, these metals may be used independently and may be used as an alloy which has these metals as a main component.

  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, the method using electroless plating is preferably used because plating can be applied to nonconductors. It is done. As the dry plating, methods such as vacuum deposition, plasma CVD (chemical vapor deposition), photo CVD, ion plating, and sputtering can be adopted. However, since excellent adhesion can be obtained even at a low temperature, the sputtering method is used. 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.

  It is also preferable to use metal fine particles as the conductive substance constituting the conductive layer. In this case, the metal used as the metal fine particles is platinum, gold, silver, copper, tin, nickel, titanium, cobalt, zinc, iron, chromium, aluminum, or these because it prevents corrosion due to a potential difference with the carbon fiber. An alloy mainly containing tin, tin oxide, indium oxide, indium oxide / tin (ITO), or the like is preferably used. Among these, platinum, gold, silver, copper, tin, nickel, titanium, or an alloy containing these as a main component is particularly preferably used because of high conductivity and stability. Here, the fine particles refer to particles having an average particle size smaller than the average particle size of [D] conductive particles (usually, 0.1 times or less).

  A mechanochemical bonding method is preferably used as a method of coating the core or core with the 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 core or core of an inorganic material or organic material, and the core or core is covered with the metal microparticle.

  When the metal fine particles are coated on the core of an inorganic material or an organic material (including a thermoplastic resin), the particle size of the metal fine particle is preferably 1/1000 to 1/10 times the average particle diameter of the core, and more Preferably it is 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. Furthermore, when the metal fine particles are coated on the core of the inorganic or organic material, the particle size of the metal fine particles is preferably 1/1000 to 1/10 times the average particle size of the core, more preferably 1/500. It is about 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.

  When carbon is used as the conductive material, crystalline carbon and amorphous carbon are preferably used, and carbon black such as channel black, thermal black, furnace black, ketjen black, carbon nanotube, fullerene, graphene, hollow Carbon fiber or the like is preferably used. Among these, hollow carbon fibers are preferably used, and the outer shape thereof 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. In that case, the total number of the graphite layers to be formed is preferably 1 to 100 layers, more preferably 1 to 10 layers, still more preferably 1 to 4 layers, and particularly preferably 1 to 2 layers. belongs to.

  As the amorphous carbon, for example, “Bellpearl (registered trademark)” C-600, C-800, C-2000 (manufactured by Air Water Co., Ltd.), “NICABEADS (registered trademark)” ICB, PC, MC ( Nippon Carbon Co., Ltd.), Glassy Carbon (Tokai Carbon Co., Ltd.), High Purity Artificial Graphite SG Series, SGB Series, SN Series (SEC Carbon Co., Ltd.), True Spherical Carbon (Gunei Chemical Industry Co., Ltd.) ))) And the like.

  In particular, if a thermoplastic resin is used as the organic material, and the particles in which the core or core of the thermoplastic resin is coated with the conductive substance are employed, the resulting carbon fiber reinforced composite material has even better impact resistance. This is preferable because it can be realized.

  In the [D] conductive particles of a type coated with a conductive substance, the conductive particles are composed of an inorganic or organic material that is a core or core and a conductive layer made of a conductive substance, If necessary, an adhesive layer as described below may be provided between the core or core and the conductive layer.

  In the [D] conductive particles of a type coated with a conductive substance, examples of the inorganic material used as the core or core 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 carbon, crystalline carbon and amorphous carbon are preferably used. As the amorphous carbon, for example, “Bellpearl (registered trademark)” C-600, C-800, C-2000 (manufactured by Air Water Co., Ltd.), “NICABEADS (registered trademark)” ICB, PC, MC ( Nippon Carbon Co., Ltd.), Glassy Carbon (Tokai Carbon Co., Ltd.), High Purity Artificial Graphite SG Series, SGB Series, SN Series (SEC Carbon Co., Ltd.), True Spherical Carbon (Gunei Chemical Industry Co., Ltd.) ))) And the like.

  In the [D] conductive particles of the type coated with a conductive substance, when an organic material is used as the core or core, the organic material used as the core or core includes unsaturated polyester resin, vinyl ester resin, epoxy Thermosetting resins such as resin, benzoxazine resin, phenol resin, urea resin, melamine resin and polyimide resin, polyamide resin, phenol resin, amino resin, acrylic resin, ethylene-vinyl acetate resin, polyester resin, urea resin, melamine resin , Alkyd resins, polyimide resins, urethane resins, and thermoplastic resins such as divinylbenzene resins. 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.

  In the case of [D] conductive particles in which the core or core of the thermoplastic resin is coated with a conductive substance, [C] the carbon fiber reinforced composite material has high impact resistance without adding the thermoplastic resin particles. Since conductivity can be expressed, by using this together with [C] thermoplastic resin particles, higher impact resistance and conductivity can be expressed.

[D] The thermoplastic resin used as the core or core material of the conductive particles used in the present invention includes various thermoplastic resins exemplified above as thermoplastic resins used by mixing and dissolving in the thermosetting resin. Similar ones can be used. Among them, it is preferable to use a thermoplastic resin having a strain energy release rate (G _1c ) of 1500 to 50000 J / m ² as a core or core material. More preferably, 3000~40000J / ^{m 2,} more preferably 4000~30000J / ^{m 2.} If the strain energy release rate (G _1c ) is too small, the impact resistance of the carbon fiber reinforced composite material may be insufficient, and if it is too large, the rigidity of the carbon fiber reinforced composite material may decrease. As such a thermoplastic resin, for example, polyamide, polyamideimide, polyethersulfone, polyetherimide and the like are preferably used, and polyamide is particularly preferable. Among polyamides, nylon 12, nylon 11 and nylon 6/12 copolymer are preferably used. G _1c is evaluated by [D] a compact plate method or a double tension method defined in ASTM D 5045-96, using a resin plate formed by molding a thermoplastic resin that is a core or core material of conductive particles.

  In the [D] conductive particles of the type coated with a conductive substance, an adhesive layer may or may not exist between the core or core and the conductive layer, but the core or core and conductive layer may be present. If it is easy to peel off, it 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, etc. are preferable, among which vinyl acetate resin, acrylic resin, vinyl acetate - acrylic resins, vinyl acetate - vinyl chloride resins, ethylene - vinyl acetate resins, ethylene - vinyl acetate resins, ethylene - include acrylic resins and epoxy resins.

  In the type [D] conductive particles coated with a conductive substance, the conductive particles coated with the conductive substance are represented by [volume of core or core] / [volume of conductive layer]. The volume ratio is preferably 0.1 to 500, more preferably 1 to 300, and still more preferably 5 to 100. If the volume ratio is less than 0.1, not only the weight of the obtained carbon fiber reinforced composite material is increased, but also it may not be able to uniformly disperse during resin preparation. In some cases, sufficient conductivity cannot be obtained in the composite material.

  [D] The specific gravity of the conductive particles in which the core or core of the conductive particles used in the present invention is coated with a conductive substance is preferably at most 3.2. When the specific gravity of the conductive particles exceeds 3.2, not only does the weight of the obtained carbon fiber reinforced composite material increase, but there are cases where it cannot be uniformly dispersed during resin preparation. From this viewpoint, the specific gravity of the conductive particles is preferably 0.8 to 2.2. If the specific gravity of the conductive particles is less than 0.8, it may not be uniformly dispersed during resin preparation.

  [D] The shape of the conductive particles may be spherical, non-spherical, porous, needle-shaped, whisker-shaped, or flake-shaped. However, since the spherical shape does not deteriorate the flow characteristics of the thermosetting resin, carbon is used. Excellent impregnation into fibers. In addition, when falling weight impact (or local impact) on the carbon fiber reinforced composite material, delamination caused by the local impact is further reduced, so stress was applied to the carbon fiber reinforced composite material after such impact. In some cases, there are fewer delaminations caused by the local impact, which is the starting point of fracture due to stress concentration, and there is a high probability of contact with the carbon fibers in the laminated layer, making it easy to form a conductive path. Therefore, it is preferable in that a carbon fiber reinforced composite material that exhibits high impact resistance and conductivity is obtained.

  In the present invention, the mass ratio represented by [[C] the amount of thermoplastic resin particles (parts by mass)] / [[D] the amount of conductive particles (parts by mass)] is 1-1000, Preferably it is 10-500, More preferably, you may be 10-100. When the mass ratio is less than 1, sufficient impact resistance cannot be obtained in the obtained carbon fiber reinforced composite material, and when the mass ratio is greater than 1000, sufficient carbon fiber reinforced composite material is obtained. This is because conductivity cannot be obtained.

  In the present invention, [D] the average particle diameter of the conductive particles is the same as or larger than the average particle diameter of the [C] thermoplastic resin particles, and the average diameter is preferably at most 150 μm. [D] When the average particle diameter of the conductive particles is smaller than the average particle diameter of the [C] thermoplastic resin particles, the [D] conductive particles are added to the insulating [C] thermoplastic resin particles. It may be buried between layers, and a conductive path between the [A] carbon fiber and the [D] conductive particles in the layer may be difficult to form, and may not provide a sufficient conductivity improving effect.

  Here, the measurement method of an average particle diameter is demonstrated about the case where an object is a particle | grain.

  Regarding the average particle size of the particles, for example, the particles are magnified 1000 times or more with a microscope such as a scanning electron microscope, photographed, randomly selected particles, and the diameter of the circle circumscribing the particles as the particle size The average particle size (n = 50) can be obtained. When determining the volume ratio represented by [volume of core] / [volume of conductive layer] of conductive particles coated with a conductive substance, first, the average particle size of the core of conductive particles The diameter is measured by the above method, or the average particle diameter of the conductive particles is measured by the above method. Thereafter, the cross section of the conductive particles coated with the conductive substance was magnified 10,000 times with a scanning microscope, photographed, the thickness of the conductive layer was measured (n = 10), and the average Calculate the value. Such measurement is carried out on the above randomly selected conductive particles (n = 50). The average particle diameter of the conductive particles is obtained by adding the average particle diameter of the core of the conductive particles and twice the average value of the thickness of the conductive layer, or the average particle diameter of the conductive particles and the conductivity By subtracting twice the average value of the thickness of the conductive layer, the average particle diameter of the core of the conductive particles is obtained. Then, 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. .

  [D] It is 0.01-50 mass% with respect to the sum total of [D] electroconductive particle, [B] thermosetting resin, [C] thermoplastic resin particle, and [D] electroconductive particle, The obtained carbon fiber reinforced composite material is preferable because it exhibits excellent conductivity. More preferably, it is 0.05-10 mass%, More preferably, it is 0.1-5 mass%. [D] Obtained when the conductive particles are less than 0.01% by mass with respect to the sum of [B] thermosetting resin, [C] thermoplastic resin particles, and [D] conductive particles. In the carbon fiber reinforced composite material, it is difficult to form a conductive path and may not provide a sufficient conductivity improvement effect. When the amount exceeds 50% by mass, sufficient impact resistance cannot be obtained in the obtained carbon fiber reinforced composite material. There is.

  In the present invention, the coefficient of variation of the particle size of [D] conductive particles contained in the prepreg or carbon fiber reinforced composite material used is required to be 5% or less. When the coefficient of variation of the particle diameter of the conductive particles exceeds 5%, the probability that the conductive particles come into contact with each carbon fiber between the carbon fiber layers of the carbon fiber reinforced composite material is reduced, so that the carbon fiber obtained is obtained. The conductivity of the reinforced composite material is not sufficiently improved.

  The coefficient of variation of the particle size of the conductive particles is calculated by calculating the standard deviation from the measurement of the average particle size mentioned above, and from that, the coefficient of variation is calculated as (standard deviation / average particle size) × 100 (%). Can do. The standard deviation can be calculated with reference to, for example, page 44 of “Introduction to Statistical Methods for Quality Control of New Editions”. In addition, as a means for obtaining the average particle diameter of the conductive particles from the prepreg used in the present invention, after extracting the conductive particles from the prepreg, a means using a Coulter counter can be employed, A scanning electron microscope, a transmission electron microscope, or a laser microscope can be employed as a means for obtaining the average particle diameter of the conductive particles from the carbon fiber reinforced composite material.

  In obtaining the resin composition for carbon fiber reinforced composite material of the present invention, it is also preferable to use a masterbatch composed of thermosetting resin, thermoplastic resin particles, and conductive particles. That is, depending on the mixing method, the original mechanical properties and conductivity may not be exhibited due to the presence of aggregates of conductive particles. Mixing of aggregates is suppressed, and dispersibility in the resin composition is improved. By improving the dispersibility, the conductivity and mechanical properties of the carbon fiber reinforced composite material of the present invention are stabilized and variations are reduced. In addition, if the mass ratio of the thermosetting resin amount is too small, the dispersibility of the conductive particles may be deteriorated. Conversely, if the mass ratio of the thermosetting resin is larger than this range, the master batch method is used. Usefulness may be reduced.

  As an application method of the masterbatch, for example, the following procedure is given as an example. First, a thermosetting resin, thermoplastic resin particles, and conductive particles are kneaded with a stirrer, and conductive particles are dispersed to prepare a masterbatch so that the mass ratio of the designed matrix resin composition is obtained. The target epoxy resin composition for a carbon fiber composite material is obtained by adding the prepared master batch to a composition such as the remaining thermosetting resin, particles of thermoplastic resin, and a curing agent.

  In order to obtain the matrix resin composition for carbon fiber reinforced composite material of the present invention, the thermoplastic resin particles, the conductive particles and the constituents other than the curing agent are uniformly heated and kneaded at about 150 ° C., and the curing reaction proceeds. It is preferable to add thermoplastic resin particles, conductive particles, and a curing agent and knead after cooling to a difficult temperature, but the blending method of each component is not particularly limited to this method.

  In the present invention, [D] conductive particles may have low adhesion to [B] thermosetting resin, but if these are subjected to surface treatment, they are strong against thermosetting resin. Adhesion can be realized, and the impact resistance can be further improved. From this point of view, it is preferable to apply a material that has been subjected to at least one treatment selected from the group consisting of coupling treatment, oxidation treatment, ozone treatment, plasma treatment, corona treatment, and blast treatment. Among them, those that have been subjected to a surface treatment by a coupling treatment, oxidation treatment, or plasma treatment that can form a chemical bond or hydrogen bond with a thermosetting resin are more preferably used because strong adhesion to the thermosetting resin can be realized. .

  In the surface treatment, the surface treatment can be performed using heating and ultrasonic waves in order to help shorten the surface treatment time and to disperse [D] conductive particles. The heating temperature is at most 200 ° C, preferably 30 to 120 ° C. That is, if the temperature is too high, the odor becomes strong and the environment may deteriorate, or the operating cost may increase.

  The prepreg used in the present invention clearly shows a state in which the above-described particles (thermoplastic resin particles, conductive particles) are present locally when the layer rich in particles, that is, the cross section thereof is observed. It is preferable that the layer (hereinafter sometimes abbreviated as “particle layer”) that can be confirmed in the above is formed in the vicinity of the surface of the prepreg.

  In this way, by taking a structure in which the particles are unevenly distributed on the surface side, when the prepreg is laminated and the epoxy resin is cured to form a carbon fiber reinforced composite material, the prepreg layer, that is, the carbon fiber reinforced composite material layer A resin layer is easily formed between them, whereby the adhesion and adhesion between the carbon fiber reinforced composite material layers are enhanced, and the resulting carbon fiber reinforced composite material exhibits high impact resistance.

  From such a viewpoint, the particle layer is preferably 20% deep, more preferably 10% deep from the surface of the prepreg in the thickness direction starting from the surface with respect to 100% of the thickness of the prepreg. It is preferable that it exists in the range. When laminating two or more prepregs, when the particle layer of the prepreg is present only on one side, the prepreg is preferably laminated so that the surface on which the particle layer is present faces in the same direction. On the other hand, when the particle layer is present only on one side of the prepreg, the prepreg can be front and back, so care must be taken when laminating. That is, if the prepreg is placed so that there is an interlayer with and without particles, there is a possibility of becoming a carbon fiber reinforced composite material that is weak against impact. Therefore, in order to eliminate the distinction between the front and back and facilitate lamination, The particle layer should be present on both the front and back sides of the prepreg.

  Further, the ratio of the thermoplastic resin particles and the conductive particles present in the particle layer is preferably 90 to 100 with respect to 100% by mass of the total amount of the thermoplastic resin particles and the conductive particles in the prepreg. It is mass%, More preferably, it is 95-100 mass%.

  The abundance of the particles can be evaluated by, for example, the following method. That is, the prepreg is sandwiched between two smooth polytetrafluoroethylene resin plates with a smooth surface, and the temperature is gradually raised to the curing temperature over 7 days to gel and cure to cure the plate-like prepreg. Make a thing. 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 above line and the total area of the particles existing over the thickness of the prepreg are obtained. Calculate the abundance of particles present in the 20% depth range. Here, the total area of the particles is obtained by cutting out the particle portion from the cross-sectional photograph and converting it from the mass. 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 amount of conductive particles is preferably in the range of 20% by mass or less based on the prepreg. When it exceeds 20 mass% with respect to a prepreg, mixing of particle | grains and resin will become difficult, and the tack | tuck and drape property of a prepreg may fall. That is, in order to provide impact resistance due to the particles while maintaining the properties of the epoxy resin as the base resin, the amount of the conductive particles is preferably 20% by mass or less based on the prepreg, and more preferably. Is 15% by mass or less. In order to further improve the handling of the prepreg, the amount of conductive particles is preferably 10% by mass or less. The amount of the particles is preferably 1% by mass or more, more preferably 2% by mass or more with respect to 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, the prepreg of the present invention is a method in which thermoplastic resin particles and conductive particles are directly applied to the surface of a primary prepreg composed of an epoxy resin that is a carbon fiber and a matrix resin, and an epoxy resin that is a matrix resin. Prepare a mixture of these thermoplastic resin particles and conductive particles uniformly mixed, and in the process of impregnating this mixture into carbon fiber, the reinforcing fibers prevent the thermoplastic resin particles and conductive particles from entering. A method of localizing particles on the surface portion of the prepreg by blocking or heat that contains a high concentration of these particles on the surface of the primary prepreg by pre-impregnating carbon fiber with an epoxy resin in advance to produce a primary prepreg. It can be produced by a method of sticking a curable resin film. A prepreg for a carbon fiber composite material having both impact resistance and conductivity can be obtained by uniformly presenting the thermoplastic resin particles and the conductive particles within a depth range of 20% of the thickness of the prepreg. .

  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. By using a combination of thermoplastic resin particles and conductive particles, delamination caused by local impact is reduced during falling weight impact (or local impact) on carbon fiber reinforced composite material. In addition, when stress is applied to the carbon fiber reinforced composite material after the impact, there are few delamination portions caused by the local impact, which is a starting point of fracture due to stress concentration, or particles of conductive particles. Since the coefficient of variation in diameter is 5% or less, the contact probability with the carbon fiber in the laminated layer is high, and it is easy to form a conductive path. Therefore, a carbon fiber reinforced composite material that exhibits high impact resistance and conductivity. Is obtained.

  In the present invention, it is necessary that 30% or more of the [D] conductive particles are in contact with the respective [A] carbon fibers between the [A] carbon fiber layers of the carbon fiber reinforced composite material. When the conductive particles are not in contact with the respective carbon fibers between the carbon fiber layers of the carbon fiber reinforced composite material, or the number of conductive particles is less than 30% between the carbon fiber layers of the carbon fiber reinforced composite material. When the particles are in contact with the respective carbon fibers, it is difficult to form a conductive path, so that the conductivity of the carbon fiber reinforced composite material is not sufficiently improved. That is, in the size between the carbon fiber layers of the carbon fiber reinforced composite material and the size of the conductive particles, the value of [conductive particle size] / [size between carbon fiber layers of the carbon fiber reinforced composite material] is 0. 0.5-2, preferably 0.7-1.6, more preferably 0.8-1.2. [A] The ratio of the number of [D] conductive particles in contact with each [A] carbon fiber between the layers of [A] carbon fibers is preferably 30% or more in terms of forming a conductive path. Is 50% or more, more preferably 70% or more.

  Further, without impregnating the prepreg, the matrix resin composition of the present invention is directly impregnated into the reinforcing fiber, followed by heat curing, such as hand lay-up method, filament winding method, pultrusion method, resin injection, A carbon fiber reinforced composite material can also be produced by a molding method such as a molding method or a resin transfer molding method. In the present invention, the carbon fiber reinforced composite material layer formed by using these forming methods refers to a layer formed between the [A] carbon fiber layer and the [A] carbon fiber layer. Shall mean. Also in this case, [A] [D] conductive particles existing between carbon fiber layers have a coefficient of variation of particle size of 5% or less and the number of [D] conductive particles of 30% or more. Are in contact with the respective [A] carbon fibers between the [A] carbon fiber layers of the carbon fiber reinforced composite material.

Since the carbon fiber reinforced composite material obtained in this way is excellent in a conductive path, a volume resistivity of 1.0 × 10 ³ Ωcm or less is realized while maintaining a compressive strength after impact of 280 MPa or more. . Such a carbon fiber reinforced composite material includes: [A] carbon fiber, [B] thermosetting resin blending ratio, [C] thermoplastic resin particles, [D] average particle diameter of conductive particles, [D] conductive By appropriately adjusting the coefficient of variation of the conductive particles, it is possible to control the configuration and arrangement of the [D] conductive particles between the layers of the [A] carbon fiber in contact with the [D] conductive particles, The compressive strength after impact and the volume resistivity can each be preferably designed to be 280 MPa or more and 1.0 × 10 ³ Ωcm or less, more preferably 285 MPa or more and 5.0 × 10 ² Ωcm or less, respectively. When using thermoplastic resin particles with high toughness between carbon fiber layers, the balance between the toughness of the layers and the impact resistance and conductivity of the carbon fiber reinforced composite material is taken into account. For example, the compression strength after impact and the volume resistivity may be designed to be 415 MPa or less and 1.7 × 10 ⁻³ Ωcm or more.

  Since the carbon fiber reinforced composite material of the present invention has the above-described features, it is preferably used for computer applications such as aircraft structural members, windmill blades, automobile outer plates, and IC trays and notebook PC housings. .

  Hereinafter, the prepreg used in the present invention and the carbon fiber reinforced composite material of the present invention 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. Further, the present invention is not limited to these examples.

<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'-diaminodiphenyl sulfone (made by 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>
・ Nylon 12 particles SP-10 (manufactured by Toray Industries, Inc., shape: true sphere)
-Epoxy-modified nylon particles A obtained by the following production method
90 parts by mass of transparent polyamide (trade name “Grillamide (registered trademark)”-TR55, manufactured by Mzavelke), 7.5 parts by mass of epoxy resin (product name “jER (registered trademark)” 828, manufactured by Japan Epoxy Resin Co., Ltd.) And 2.5 parts by mass of a curing agent (trade name “Tomide (registered trademark)” # 296, manufactured by Fuji Kasei Kogyo Co., Ltd.) in a mixed solvent of 300 parts by mass of chloroform and 100 parts by mass 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 mass 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: 12.5 μm).

<Conductive particles>
“NICABEADS (registered trademark)” ICB-2020 (manufactured by Nippon Carbon Co., Ltd.) (average particle size: 26.69 μm, coefficient of variation: 4.87%)
The above particles were repeatedly classified and used after the coefficient of variation in particle size was reduced to 5% or less.
“NICABEADS (registered trademark)” MC-2020 (manufactured by Nippon Carbon Co., Ltd.) (average particle size: 24.35 μm, coefficient of variation: 2.12%)
The above particles were repeatedly classified and used after the coefficient of variation in particle size was reduced to 5% or less.
“NICABEADS (registered trademark)” PC-2020 (manufactured by Nippon Carbon Co., Ltd.) (average particle size: 25.05 μm, coefficient of variation: 3.87%)
The above particles were repeatedly classified and used after the coefficient of variation in particle size was reduced to 5% or less.
SGL-50 (manufactured by SEC Carbon Co., Ltd.) (average particle size: 26.73 μm, coefficient of variation: 4.72%)
The above particles were repeatedly classified and used after the coefficient of variation in particle size was reduced to 5% or less.
SGL-25 (manufactured by SEC Carbon Co., Ltd.) (average particle size: 24.91 μm, coefficient of variation: 3.27%)
The above particles were repeatedly classified and used after the coefficient of variation in particle size was reduced to 5% or less.
Glassy carbon (manufactured by Tokai Carbon Co., Ltd.) (average particle size: 25.57 μm, coefficient of variation: 3.83%)
The above particles were repeatedly classified and used after the coefficient of variation in particle size was reduced to 5% or less.
・ Spherical carbon (manufactured by Gunei Chemical Industry Co., Ltd.) (average particle size: 26.27 μm, coefficient of variation: 4.18%)
The above particles were repeatedly classified and used after the coefficient of variation in particle size was reduced to 5% or less.
Carbon particles A (average particle size: 25.02 μm, coefficient of variation: 3) obtained by firing phenol resin particles (Marilyn HF-050, manufactured by Gunei Chemical Industry Co., Ltd.) at 2000 ° C. and repeating the classification. .54%)
Carbon particles B (average particle diameter: 24.37 μm) obtained by firing phenol resin particles (“Bellpearl (registered trademark)” R-800, manufactured by Air Water Co., Ltd.) at 2000 ° C. and repeating classification. , Coefficient of variation: 4.87%)
Carbon particles C (average particle size: 26.12 μm) obtained by firing phenol resin particles (“Bellpearl (registered trademark)” S-870, manufactured by Air Water Co., Ltd.) at 2000 ° C. and repeating classification. , Coefficient of variation: 3.11%)
"Bellepearl (registered trademark)" C-800 (manufactured by Air Water Co., Ltd.) (average particle size: 15.05 µm, coefficient of variation: 4.05%)
The above particles were repeatedly classified and used after the coefficient of variation in particle size was reduced to 5% or less.
"Bellepearl (registered trademark)" C-2000 (manufactured by Air Water Co., Ltd.) (average particle size: 15.12 µm, coefficient of variation: 4.38%).

The above particles were repeatedly classified and used after the coefficient of variation in particle size was reduced to 5% or less.
UF-G30 (Showa Denko Co., Ltd.) (average particle size: 10.12 μm, coefficient of variation: 3.66%)
The above particles were repeatedly classified and used after the coefficient of variation in particle size was reduced to 5% or less.
-"Micropearl (registered trademark)" AU215 (manufactured by Sekisui Chemical Co., Ltd.) (average particle size: 15.5 μm, coefficient of variation: 4.1%) (Patent Document 3 (Japanese Patent Laid-Open No. 2008-232395)) The same conductive particles as those described in Example 1)
-"Micropearl (registered trademark)" CU215 (manufactured by Sekisui Chemical Co., Ltd.) (average particle size: 15.5 μm, coefficient of variation: 4.1%) (Patent Document 5 (Japanese Patent Laid-Open No. 2009-074075)) Conductive particles identical to the conductive particles described in Example 13).

<Coupling agent>
-Z-6011 (made by Toray Dow Corning Co., Ltd.): 3-aminopropyltriethoxysilane.

<Conductive film>
Conductive film described in Example 10 of conductive film B (thickness: 13.7 μm, volume resistivity: 3.8 × 10 ⁻⁵ Ωcm) (Patent Document 4 (Japanese Patent Laid-Open No. 2009-062473)) The same conductive film).

(1) Presence of particles existing in a 20% depth range of prepreg The prepreg is sandwiched between two smooth polytetrafluoroethylene resin plates on the surface and brought into close contact, and gradually over 7 days. The temperature was raised to 150 ° C. and gelled and cured to produce a plate-shaped resin cured product. After curing, the film was cut from the direction perpendicular to the contact surface, and the cross-section was polished, then magnified 200 times or more with an optical microscope, and photographed so that the upper and lower surfaces of the prepreg were within the visual field. By the same operation, the distance between the polytetrafluoroethylene resin plates was measured at five locations in the horizontal direction of the cross-sectional photograph, and the average value (n = 5) was taken as the thickness of the prepreg.

  On both sides of the prepreg, two lines parallel to the surface of the prepreg were 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. The total area of the fine particles was obtained by cutting out the particle portion from the cross-sectional photograph and converting from the mass. When it was difficult to discriminate the particles dispersed in the matrix resin after photography, a means for staining the particles was used.

(2) Measurement of compressive strength after impact of carbon fiber reinforced composite material [+ 45 ° / 0 ° / −45 ° / 90 °] A unidirectional prepreg is laminated in a pseudo-isotropic manner with 24 plies in a _3S configuration, and is autoclaved. 25 laminates were formed by molding at a temperature of 180 ° C. for 2 hours under a pressure of 0.59 MPa and 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 according to SACMA SRM 2R-94, and compression after impact was performed. The strength was determined.

(3) Conductivity measurement of carbon fiber reinforced composite material Each unidirectional prepreg is [+ 45 ° / 0 ° / −45 ° / 90 °] in a _2S configuration, and is quasi-isotropically laminated with 16 plies. 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. 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 to both sides was prepared. did. These samples were measured for resistance in the stacking direction by a four-terminal method using an R6581 digital multimeter manufactured by Advantest Corp. to determine volume resistivity.

(4) Determination of contact between conductive particles between carbon fiber layers and each carbon fiber Lamination direction so that carbon fiber layer and carbon fiber layer can observe carbon fiber reinforced composite material produced in (3) After cutting the cross section vertically and polishing the cross section, it is magnified 200 times or more with a laser microscope (KEYENCE VK-9510) so that two or more carbon fiber layers and two or more carbon fiber layers fit within the field of view. did. From the same operation, 100 locations where conductive particles exist were arbitrarily selected. Since conductive particles have a high probability of being cut at a cross section having a particle size smaller than the average particle size, the conductive particles are regarded as the average particle size, and the conductive particles of that size are each of the carbon fibers. When touching or intersecting with each other, the presence or absence of contact was determined as being in contact. As a criterion, among 100 conductive particles, the number of conductive particles in contact with both the upper surface carbon fiber and the lower surface carbon fiber between layers is 70 or more (70% or more). ○○, 69 to 50 (50% or more and less than 70%) ○○, 49 to 30 (30% or more and less than 50%) ○, 3 to 29 (3% or more and 30 Less than%), Δ was less than 2 (less than 3%).
Example 1
In a kneading apparatus, 50 parts by mass of “jER” 825 and 50 parts by mass of ELM 434 were mixed with 10 parts by mass of PES5003P, and the thermoplastic resin was dissolved in the epoxy resin. Thereafter, 20 parts by mass of epoxy-modified nylon particles A and 1.8 parts by mass of classified “NICABEADS” ICB-2020 are kneaded, and 40 parts by mass of 4,4′-diaminodiphenylsulfone as a curing agent is further kneaded. A matrix resin composition was prepared.

The prepared thermosetting resin composition was applied onto release paper using a knife coater to prepare ^two 52 g / m ² resin films. Next, on the carbon fibers (T800S-24K-10E) arranged in one direction in a sheet shape, the two resin films prepared as described above are stacked from both sides of the carbon fibers, and the resin is impregnated by heating and pressurization. A unidirectional prepreg having a basis weight of 190 g / m ² and a mass fraction of the matrix resin of 35.4% was produced.

  Using the obtained prepreg, (1) the abundance ratio of particles existing in the depth range of 20% of the thickness of the prepreg, (2) compression strength measurement after impact of the carbon fiber reinforced composite material, (3) carbon fiber Conducting as described in Conductivity Measurement of Reinforced Composite Material and (4) Judgment of Conductive Particles Between Carbon Fiber Layers and Contact with Respective Carbon Fibers to Obtain Carbon Fiber Reinforced Composite Material, After Impact Compressive strength and volume resistivity were measured. The results are shown in Table 1.

(Examples 2-18, Comparative Examples 1-13)
Except that the epoxy resin, curing agent, thermoplastic resin, thermoplastic resin particles, conductive particles, coupling agent, and the type and amount of the conductive film were changed as shown in Tables 1 and 2, A prepreg was produced in the same manner as in Example 1. Using the produced unidirectional prepreg, the abundance ratio of particles existing within a depth range of 20% of the thickness of the prepreg, the compressive strength and conductivity after impact of the carbon fiber reinforced composite material, and the conductive particles between the carbon fiber layers Was measured and contact with each carbon fiber was determined. The obtained results are summarized in Tables 1 and 2.

  By comparing Examples 1 to 18 with Comparative Examples 1 to 13, the carbon fiber reinforced composite material of the present invention has a coefficient of variation of the particle size of conductive particles of 5% or less and a number of 30% or more. The conductive particles are in contact with the carbon fibers between the carbon fiber layers of the carbon fiber reinforced composite material, so they have excellent conductive paths, achieve high compressive strength after impact and low volume resistivity, and high resistance. It can be seen that both impact and conductivity are compatible.

  According to the present invention, since a carbon fiber reinforced composite material having both excellent mechanical properties and conductivity can be obtained, such as an aircraft structural member, a windmill blade, an automobile outer plate, an IC tray, and a casing (housing) of a notebook computer. It can be widely used for computer applications and is useful.

Claims (7)

At least [A] carbon fiber, [B] thermosetting resin, [C] thermoplastic resin particles, [D] conductive particles, and [D] coefficient of variation of the particle size of the conductive particles is 5%. A carbon fiber reinforced composite material obtained by laminating and curing two or more of the following prepregs, wherein [D] conductivity is 30% or more between layers of [A] carbon fibers of the carbon fiber reinforced composite material. The carbon fiber reinforced composite material is characterized in that the particles of [A] are in contact with the respective [A] carbon fibers. [D] The carbon fiber reinforced composite material according to claim 1, wherein the conductive particles are unevenly distributed on the surface side of the prepreg. [D] Conductive particles are 0.01-50 mass% with respect to the sum total of [B] thermosetting resin, [C] thermoplastic resin particles, and [D] conductive particles. The carbon fiber reinforced composite material according to either 1 or 2. [D] Conductive particles are carbon particles, particles in which a core or core of an inorganic material is coated with a conductive material, and conductive particles in which a core or core of an organic material is coated with a conductive material. The carbon fiber reinforced composite material according to claim 1, which is at least one selected from the group consisting of particles. The conductive material comprises at least one selected from the group consisting of platinum, gold, silver, copper, nickel, titanium, cobalt, palladium, tin, zinc, iron, chromium, aluminum, and carbon. The carbon fiber reinforced composite material described in 1. A carbon fiber reinforced composite material including at least [A] carbon fiber, [B] thermosetting resin, [C] thermoplastic resin particles, and [D] conductive particles, wherein [D] conductive particles The coefficient of variation of the particle diameter is 5% or less, and 30% or more of the [D] conductive particles are bonded to each [A] carbon fiber between the [A] carbon fiber layers of the carbon fiber reinforced composite material. A carbon fiber reinforced composite material characterized by being in contact. The carbon fiber reinforced composite material according to any one of claims 1 to 6, which has a compressive strength after impact of 280 MPa or more and a volume resistivity of 1.0 x 10 ³ Ωcm or less.