JP2017155372A - Sizing agent applied carbon fiber, manufacturing method of sizing agent applied carbon fiber, prepreg and carbon fiber reinforced composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sizing agent applied carbon fiber excellent in physical properties when made as a carbon fiber reinforced composite material and a manufacturing method of the sizing agent applied carbon fiber, a prepreg and a carbon fiber reinforced composite material excellent in physical properties using the sizing agent applied carbon fiber.SOLUTION: There is provided a sizing agent applied carbon fiber made by applying a sizing agent containing at least following (A) and (B) of 0.1 pts.mass to 5 pts.mass based on 100 pts.mass of the sizing agent applied carbon fiber. (A) an aliphatic epoxy compound and (B) a rubbery copolymer having no epoxy group formed by polymerizing a vinyl compound having at least an aromatic skeleton as a copolymer component.SELECTED DRAWING: None

Description

  The present invention relates to a sizing agent-coated carbon fiber that constitutes a carbon fiber-reinforced composite material having excellent adhesiveness with a matrix resin and having high mechanical strength, a method for producing a sizing agent-coated carbon fiber, a prepreg, and a carbon fiber-reinforced composite material. Is.

  Because it is lightweight and has excellent strength, rigidity, dimensional stability, etc., fiber-reinforced composite materials are widely used in general industrial fields such as office equipment, computer applications (IC trays, notebook PC cases, etc.), and automobile applications. The demand is increasing year by year. These reinforcing fibers include metal fibers such as aluminum fibers and stainless fibers, organic fibers such as aramid fibers and PBO fibers, inorganic fibers such as silicon carbide fibers, and carbon fibers. Carbon fibers are preferred from the viewpoint of the balance between rigidity and lightness, and among them, polyacrylonitrile-based carbon fibers are suitably used.

However, the fiber reinforced composite material is a heterogeneous material having reinforced fibers and a matrix resin as essential components, and therefore there is a large difference between the physical properties in the arrangement direction of the reinforced fibers and the physical properties in other directions. For example, it is known that the impact resistance indicated by resistance to falling weight impact is governed by delamination strength, that is, interlayer toughness such as G _Ic (opening mode) and G _IIc (in-plane shear mode). 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 the property of being easily destroyed by stresses from other than the direction of the carbon fibers that are reinforcing fibers. Yes.

  Therefore, in order to solve such problems, that is, the affinity between the reinforcing fiber and the matrix resin is increased, and in addition to the improvement in tensile strength and compressive strength in the fiber direction, the stress from other than the arrangement direction of the reinforcing fiber is dealt with. There is a constant need for improved composite material properties.

  As a sizing agent imparted to such carbon fibers, unsaturated polyester resins and epoxy resins are preferably used. Generally, in a carbon fiber reinforced composite material molded article using a matrix resin, high interfacial adhesion is required between the carbon fiber and the matrix resin in order to develop high tensile strength and compressive strength in the fiber direction. Therefore, as a sizing agent to be imparted to the carbon fiber, an epoxy resin is particularly preferably used for the purpose of providing such a carbon fiber reinforced composite material having enhanced interfacial adhesion and high mechanical strength. For example, a method of applying diglycidyl ether of bisphenol A as a sizing agent to carbon fibers has been proposed (Patent Documents 1 and 2). Further, a method of applying an epoxy adduct of polyalkylene glycol as a sizing agent to carbon fibers has been proposed (Patent Documents 3, 4, and 5).

  Furthermore, in order to solve the above-mentioned problems, a sizing agent for improving the strength against stress from other than the fiber arrangement direction has been studied in addition to the improvement in tensile strength and compressive strength in the fiber direction. For example, a method of obtaining a carbon fiber reinforced composite material method having excellent interlaminar shear strength by using a sizing agent containing, as an essential component, an epoxy resin that is incompatible with the flexible epoxy resin and the flexible epoxy resin Has been proposed (Patent Document 6).

  On the other hand, in order to improve impact resistance, a method of using a sizing agent composed of an elastomer and an organic compound for a fiber-reinforced composite material (Patent Document 7) has been proposed.

US Pat. No. 3,957,716 JP-A-57-171767 JP-A-57-128266 U.S. Pat. No. 4,555,446 JP-A-62-33872 International Publication No. 07/060833 JP 2009-121013 A

  However, the above method is not necessarily sufficient in consideration of the demand for further weight reduction and high interlaminar toughness of the carbon fiber reinforced composite material, which will increase further in the future. That is, it is desired to develop a sizing agent that can increase the toughness and strength of the matrix resin and increase the interlayer toughness of the carbon fiber reinforced composite material.

  Accordingly, an object of the present invention is to provide a sizing agent-coated carbon fiber and a sizing agent that are excellent in interfacial adhesion between the carbon fiber and the matrix resin, and that exhibit high toughness in the carbon fiber reinforced composite material, in view of the above-described problems in the prior art. An object of the present invention is to provide a method for producing a coated carbon fiber, a prepreg, and a carbon fiber reinforced composite material having excellent mechanical properties using the carbon fiber.

  The present inventors apply a sizing agent, which is a combination of a plurality of specific compounds, to a carbon fiber and make it exist at the interface between the carbon fiber and the matrix resin, whereby a prepreg and carbon fiber reinforced using the carbon fiber are formed. The present inventors have found that the toughness of the composite material can be improved and have arrived at the present invention.

That is, the present invention is a sizing agent-coated carbon in which a sizing agent containing at least the following (A) and (B) is applied in an amount of 0.1 to 5 parts by mass with respect to 100 parts by mass of the sizing agent-coated carbon fiber. Fiber.
(A) Aliphatic epoxy compound (B) A rubbery copolymer having no epoxy group (hereinafter simply referred to as “rubbery copolymer (B ) ").

  In the sizing agent-coated carbon fiber of the present invention, in the above invention, the sizing agent preferably contains 5 to 80% by mass of the rubbery copolymer (B).

  In the sizing agent-coated carbon fiber of the present invention, in the above invention, the vinyl compound is preferably styrene.

  In the sizing agent-coated carbon fiber of the present invention, in the above invention, the rubbery copolymer (B) in the sizing agent is preferably a styrene butadiene copolymer.

  In the sizing agent-coated carbon fiber of the present invention, in the above invention, the rubbery copolymer (B) in the sizing agent preferably has a glass transition temperature of more than 25 ° C. and 100 ° C. or less.

  The sizing agent-coated carbon fiber of the present invention is the above-described invention, wherein the aliphatic epoxy compound (A) in the sizing agent has a polyether type polyepoxy compound or a polyol type polyepoxy compound having two or more epoxy groups in the molecule. It is preferable that

  In the sizing agent-coated carbon fiber of the present invention, in the above invention, the aliphatic epoxy compound (A) in the sizing agent is selected from glycerin, diglycerin, polyglycerin, trimethylolpropane, pentaerythritol, sorbitol, and arabitol. It is preferable that it is a glycidyl ether type | mold epoxy compound obtained by reaction with 1 type | mold and epichlorohydrin.

Moreover, the manufacturing method of the sizing agent application | coating carbon fiber of this invention apply | coats the sizing agent characterized by performing heat processing, after apply | coating the sizing agent containing at least following (A) and (B) to carbon fiber, In the step, the amount of the sizing agent attached is 0.1 to 5 parts by mass with respect to 100 parts by mass of the sizing agent-coated carbon fiber, and the heat treatment conditions are 160 to 260 in the heat treatment step. It includes a method for producing a sizing agent-coated carbon fiber having a temperature range of 0 ° C. for 30 to 600 seconds.
(A) Aliphatic epoxy compound (B) A rubbery copolymer having no epoxy group, which is polymerized using at least a vinyl compound having an aromatic skeleton as a copolymerization component. The prepreg of the present invention is the sizing agent described above. It consists of the carbon fiber which apply | coated and thermosetting resin.

  In the prepreg of the present invention, the thermosetting resin of the present invention is preferably an epoxy resin.

  The carbon fiber reinforced composite material of the present invention is characterized by curing the above prepreg.

  The carbon fiber reinforced composite material of the present invention is characterized by comprising the above sizing agent-coated carbon fiber and a thermosetting resin.

  In the carbon fiber reinforced composite material of the present invention, the thermosetting resin of the present invention is preferably an epoxy resin.

  According to the present invention, a carbon fiber reinforced composite material having high interlayer toughness can be obtained by forming a high-strength, high-toughness interface between carbon fibers and a matrix resin.

  Hereinafter, preferred embodiments of the present invention will be described.

The present invention is a sizing agent-coated carbon fiber in which a sizing agent containing at least the following (A) and (B) is applied in an amount of 0.1 to 5 parts by mass with respect to 100 parts by mass of the sizing agent-coated carbon fiber. .
(A) Aliphatic epoxy compound (B) A rubbery copolymer having no epoxy group, which is polymerized using a vinyl compound having at least an aromatic skeleton as a copolymerization component First, the sizing agent used in the present invention will be described. .

The sizing agent of the present invention contains at least the following (A) and (B).
(A) Aliphatic epoxy compound (B) Rubber-like copolymer having no epoxy group, polymerized using at least a vinyl compound having an aromatic skeleton as a copolymerization component Aliphatic epoxy compound (A) and rubber-like copolymer When the sizing agent containing the coalescence (B) is applied to the carbon fiber, the presence of the aliphatic epoxy compound (A) causes the carbon fiber and the aliphatic epoxy compound (A) to interact strongly, and the carbon fiber and the matrix The adhesiveness with the resin is enhanced, and the presence of the rubbery copolymer (B) makes it possible to maintain characteristics such as high elongation and high toughness at the interface between the carbon fiber and the matrix resin. Thereby, it is possible to provide a carbon fiber reinforced composite material having high strength fracture toughness at the time of interlaminar fracture of the carbon fiber reinforced composite material.

  When the sizing agent is composed only of the aliphatic epoxy compound (A) and does not contain the rubbery copolymer (B), it is confirmed that the carbon fiber coated with the sizing agent has high adhesion to the matrix resin. Yes. Although the mechanism is not clear, since the aliphatic epoxy compound (A) is highly polar and easily wetted to the surface-treated carbon fiber, a functional group such as a carboxyl group and a hydroxyl group on the surface of the carbon fiber and an aliphatic epoxy compound ( It is believed that A) can form a strong interaction. However, since the aliphatic epoxy compound (A) is firmly bonded to the carbon fiber or the matrix resin, it has poor mobility and locally bears external stress at the carbon fiber interface, resulting in high brittleness.

  In addition, when the sizing agent is composed only of the rubber-like copolymer (B) and does not contain the aliphatic epoxy compound (A), the carbon fiber composite material is subjected to external stress due to the flexibility of the rubber-like copolymer. Can be uniformly dispersed. However, since the rubber-like copolymer (B) has few terminal functional groups and a small interaction with the carbon fiber, the adhesion between the carbon fiber and the matrix resin is not sufficient.

  The sizing agent-coated carbon fiber of the present invention is 0.1 part by mass of a sizing agent containing at least an aliphatic epoxy compound (A) and a rubbery copolymer (B) with respect to 100 parts by mass of the sizing agent-coated carbon fiber. It is applied in an amount of 5 parts by mass or less. Preferably it is the range of 0.3 mass part or more and 3 mass parts or less. When the adhesion amount of the sizing agent is 0.1 parts by mass or more, the sizing agent-coated carbon fibers are sufficiently bonded to the matrix resin. Furthermore, when the adhesion amount of the sizing agent is 5 parts by mass or less, since the matrix resin is impregnated into the carbon fiber bundle, voids in the obtained composite material are reduced, and the mechanical properties are excellent.

  The aliphatic epoxy compound (A) used in the present invention is an epoxy compound that does not contain an aromatic ring in the molecule, and has one or more epoxy groups in the molecule. As a result, a strong bond between the carbon fiber and the epoxy group in the sizing agent can be formed. An epoxy compound having a plurality of epoxy groups in the molecule and having a flexible aliphatic main chain interacts with the surface functional group of the carbon fiber and adheres firmly to the surface of the carbon fiber. And the physical properties of the carbon fiber reinforced composite material are improved.

  An aliphatic epoxy compound (A) can be used individually or in combination of 2 or more types. Aliphatic epoxy compounds (A) include glycidyl ether type epoxy compounds derived from alcohols, glycidyl amine type epoxy compounds derived from amines having multiple active hydrogens, glycidyl ester type epoxy compounds derived from carboxylic acids, and Examples thereof include an epoxy compound obtained by oxidizing a compound having a plurality of double bonds in the molecule.

  Examples of the glycidyl ether type epoxy compound include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol, trimethylene glycol, and polybutylene. Glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1, 4-cyclohexanedimethanol, hydrogenated bisphenol A, hydrogenated bisphenol F, glycerol, diglycerol, polyglycerol, trimethylolpropane, Pentaerythritol, sorbitol, and the arabitol, glycidyl ether type epoxy compound obtained by the reaction of epichlorohydrin. Examples of the epoxy compound include a glycidyl ether type epoxy compound having a dicyclopentadiene skeleton and a glycidyl ether type epoxy compound having a biphenylaralkyl skeleton.

  Examples of the glycidyl ester type epoxy compound include a glycidyl ester type epoxy compound obtained by reacting dimer acid with epichlorohydrin.

  Examples of the epoxy compound obtained by oxidizing a compound having a plurality of double bonds in the molecule include an epoxy compound having an epoxycyclohexane ring in the molecule. Furthermore, the epoxy compound includes epoxidized soybean oil.

  In addition to these epoxy compounds, epoxy compounds such as triglycidyl isocyanurate can be mentioned.

  Further, as the epoxy compound, an epoxy compound having at least one functional group selected from one or more epoxy groups and an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, and a sulfo group is used. You can also.

  Examples of the compound having an epoxy group and an amide group include an amide-modified epoxy compound. The amide-modified epoxy can be obtained by reacting an epoxy group of an epoxy compound having two or more epoxy groups with a carboxyl group of a dicarboxylic acid amide.

  Examples of the compound having an epoxy group and an imide group include glycidyl phthalimide. Specifically, “Denacol (registered trademark)” EX-731 (manufactured by Nagase ChemteX Corporation) and the like can be mentioned.

  Examples of the compound having an epoxy group and a urethane group include a urethane-modified epoxy compound.

  Examples of the compound having an epoxy group and a urea group include a urea-modified epoxy compound. The urea-modified epoxy can be obtained by reacting the epoxy group of an epoxy compound having two or more epoxy groups with the carboxyl group of the dicarboxylic acid urea.

  Among the above, the aliphatic epoxy compound (A) used in the present invention is a compound having two or more epoxy groups in the molecule from the viewpoint of high adhesion, and is a polyether type polyepoxy compound and / or A polyol type polyepoxy compound is preferred. As the number of epoxy groups increases, the adhesion is further strengthened by increasing the interaction with the functional groups on the carbon fiber surface. Furthermore, since the interaction with the functional group on the surface of the carbon fiber is strengthened by having a hydroxyl group or an ether bond in the molecule, the physical properties of the fiber-reinforced composite material are improved. There is no upper limit to the number of epoxy groups, but 10 is sufficient from the viewpoint of adhesiveness.

  The aliphatic epoxy compound (A) used in the present invention is glycidyl obtained by reacting one kind selected from glycerin, diglycerin, polyglycerin, trimethylolpropane, pentaerythritol, sorbitol, and arabitol with epichlorohydrin. More preferably, it is an ether type epoxy compound. Since these compounds have flexible molecular chains, the interaction with the functional group on the carbon fiber surface is further increased, and the physical properties of the fiber-reinforced composite material are further improved.

  The epoxy value of the aliphatic epoxy compound (A) used in the present invention is preferably 2.0 meq / g or more. When the epoxy value of the aliphatic epoxy compound (A) is 2.0 meq / g or more, an interaction with the carbon fiber is formed at a high density, and the adhesion between the carbon fiber and the matrix resin is further improved. The upper limit of the epoxy value is not particularly limited, but 8.0 meq / g is sufficient from the viewpoint of adhesiveness because the interaction with the carbon fiber is strengthened. The epoxy value of the aliphatic epoxy compound (A) is more preferably 3.0 to 7.0 meq / g.

  Specific examples of products of these compounds include polyglycerin polyglycidyl ether (for example, “Denacol (registered trademark)” EX-512, EX-521 manufactured by Nagase ChemteX Corporation), trimethylolpropane polyglycidyl ether (for example, "Denacol (registered trademark) EX-321" manufactured by Nagase ChemteX Corporation, glycerol polyglycidyl ether (for example, "Denacol (registered trademark)" EX-313, EX-314 manufactured by Nagase ChemteX Corporation) ), Sorbitol polyglycidyl ether (for example, “Denacol (registered trademark)” EX-611, EX-612, EX-614, EX-614B, EX-622 manufactured by Nagase ChemteX Corporation), pentaerythritol polyglycidyl ether (For example, Nagase ChemteX Corporation) And the like of "Denacol (registered trademark)" EX-411). These compounds can be used alone or in combination of two or more.

  Further, the aliphatic epoxy compound (A) in the sizing agent is preferably contained in an amount of 20% by mass or more, more preferably 50% by mass or more, and further preferably 60% by mass or more based on the total amount of the sizing agent. Moreover, it is preferable that the compound which has an epoxy group in a sizing agent is contained in the ratio of 95 mass% or less with respect to the sizing agent whole quantity, More preferably, it is 90 mass% or less, More preferably, it is 85 mass% or less. .

  The rubber-like copolymer (B) used in the present invention has an elastic modulus of 1 to 10 MPa at a temperature not lower than the glass transition temperature and not higher than the melting point, and exhibits a high elongation of 100 to 800% under stress. It is a copolymer having the property of returning to its original state when loaded. Rubber elasticity in a polymer is derived from the fact that a long-chain polymer is cross-linked and reversibly deforms without breaking in a low stress state due to the expansion and contraction of the molecular chain between the cross-linking points.

  The rubbery copolymer (B) used in the present invention is a rubbery copolymer having no epoxy group, which is polymerized using at least a vinyl compound having an aromatic skeleton as a copolymerization component. By having an aromatic skeleton as a copolymerization component, the aliphatic epoxy compound (A) is attached to the surface of the carbon fiber due to the difference in polarity with the aliphatic epoxy compound (A) used together. Adhesiveness can be increased by attaching the rubber-like copolymer (B) to the outer layer of the carbon fiber, and high elongation and toughness can be imparted to the interface between the carbon fiber and the matrix resin. . Further, since the rubbery copolymer (B) does not have an epoxy group, the aliphatic epoxy compound (A) and the rubbery copolymer (B) form an independent structure and are attached to the carbon fiber. be able to. This makes it possible to achieve both the advantages of the aliphatic epoxy compound (A) and the rubbery copolymer (B) listed above.

  Examples of the vinyl compound having at least an aromatic skeleton in the rubbery copolymer (B) include styrene, alkyl styrene, aryl styrene, halogenated styrene, alkoxy styrene, vinyl benzoate, and divinyl benzene.

  Specific examples of the alkyl styrene include o-methyl styrene, m-methyl styrene, p-methyl styrene, o-ethyl styrene, m-ethyl styrene, p-ethyl styrene, on-propyl styrene, mn-propyl. Styrene, pn-propyl styrene, o-isopropyl styrene, m-isopropyl styrene, p-isopropyl styrene, mn-butyl styrene, pn-butyl styrene, p-tert-butyl styrene, 4-butenyl styrene 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,5-dimethylstyrene, mesitylstyrene and the like.

  Specific examples of the aryl styrene include p-phenyl styrene.

  Specific examples of the halogenated styrene include o-fluorostyrene, m-fluorostyrene, p-fluorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, o-bromostyrene, m-bromostyrene, p -Bromostyrene, o-methyl-p-fluorostyrene and the like.

  Specific examples of alkoxystyrene include o-methoxystyrene, m-methoxystyrene, p-methoxystyrene and the like. The said vinyl compound may be used individually by 1 type, and may be used in combination of 2 or more type.

  In the rubbery copolymer (B), the lower limit of the copolymerization ratio of the vinyl compound having at least an aromatic skeleton is preferably 1 part by mass or more, preferably 10 parts by mass or more, out of 100 parts by mass of the rubbery copolymer. More preferred is 15 parts by mass or more. When it is 1 part by mass or more, sufficient elasticity can be imparted to the interface between the carbon fiber and the matrix resin. In the rubbery copolymer (B), the upper limit of the copolymerization ratio of the vinyl compound having at least an aromatic skeleton is preferably 95 parts by mass or less, out of 100 parts by mass of the rubbery copolymer, and 90 parts by mass. Part or less is more preferable. When the amount is 95 parts by mass or less, sufficient elongation and toughness can be imparted to the interface between the carbon fiber and the matrix resin.

  Examples of the compound that can be copolymerized with a vinyl compound having an aromatic skeleton include compounds having an unsaturated group. Specific examples thereof include butadiene, isoprene, chloroprene, vinylpyridine, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene and 4-phenyl. -1-butene, 6-phenyl-1-hexene, 3-methyl-1-butene, 4-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 3-methyl-1 -Hexene, 4-methyl-1-hexene, 5-methyl-1-hexene, 3,3-dimethyl-1-pentene, 3,4-dimethyl-1-pentene, 4,4-dimethyl-1-pentene, vinyl Cyclohexane, hexafluoropropene, tetrafluoroethylene, 2-fluoropropene, fluoroethylene, 1,1-difluoroethylene, 3-fluoro Ropen, trifluoroethylene, 3,4-dichloro-1-butene, dicyclopentadiene, acrylonitrile, acrylic acid, acrylic esters, methacrylic acid esters, vinyl acetate, norbornene, acetylene and the like. The said compound which has an unsaturated group may be used individually by 1 type, and may be used in combination of 2 or more type.

  Specific examples of the rubbery copolymer (B) include copolymers of styrene-butadiene-butene, styrene-ethylene-propylene, styrene-butadiene, vinylpyridine-styrene-butadiene, and styrene-isoprene-butadiene. it can.

  The rubbery copolymer (B) in the sizing agent of the present invention is preferably contained in a ratio of 5% by mass or more, more preferably 10% by mass or more, with respect to the total amount of the sizing agent. When the ratio of the rubber-like copolymer (B) is higher than 5% by mass, the high-strength and high-toughness properties of the rubber-like copolymer (B) are effectively expressed when the carbon fiber reinforced composite material is obtained. . Moreover, it is preferable that (B) rubber-like copolymer in a sizing agent is contained in the ratio of 80 mass% or less with respect to the sizing agent whole quantity, More preferably, it is 50 mass% or less. When the ratio of the rubber-like copolymer (B) is lower than 80% by mass, the elongation and toughness of the rubber-like copolymer (B) act appropriately on the matrix resin, and the carbon fiber reinforced composite material has excellent mechanical properties. Can be obtained.

  In the present invention, the vinyl compound having an aromatic skeleton which is a copolymer component of the rubber-like copolymer (B) in the sizing agent is preferably styrene. When the vinyl compound having an aromatic skeleton that is a copolymer component of the rubber-like copolymer (B) is styrene, the rubber-like copolymer (B) has an appropriate elastic modulus, and the sizing agent coating of the present invention is applied. Excellent mechanical properties when carbon fiber is a carbon fiber reinforced composite material.

  In the present invention, the rubbery copolymer (B) in the sizing agent is preferably a styrene butadiene copolymer. The styrene-butadiene copolymer is obtained by copolymerizing styrene and butadiene. The glass transition temperature can be controlled by blocking the styrene and butadiene components, vulcanizing, and the ratio of the styrene components. When the rubbery copolymer (B) is a styrene butadiene copolymer, the styrene component is incompatible with the aliphatic epoxy compound (A), and the butadiene component is sufficient for the carbon fiber and matrix resin interface. Elongation and toughness can be imparted, and the physical properties of the carbon fiber reinforced composite material can be improved.

  When the rubbery copolymer (B) in the sizing agent is applied to the carbon fiber, it can be used after being dispersed in a solvent. Examples of such a solvent include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, dimethylformamide, and dimethylacetamide. Among them, handling is easy and advantageous from the viewpoint of safety. For this reason, water is preferably used. Specific examples of aqueous dispersion products containing a styrene butadiene copolymer as the rubbery copolymer (B) include, for example, SB (styrene butadiene) latex 0695, 0696, 0561, 0589, 0602, manufactured by JSR Corporation. 2108, 0533, 0545, 0548, 0568, 0568V, 0573, 0597C, 0640, “Nipol (registered trademark)” LX110, LX112, LX430, LX433C, LX435, 2507H, manufactured by Asahi Kasei Co., Ltd. L-1638, L-7708, L-2301, L-5702, A-3255, L-3200, A-7090, DL-612, L-7063, L-5930, L-7431, A-7688, L7850, etc. Can be mentioned. These compounds can be used alone or in combination of two or more.

  In this invention, it is preferable that the glass transition temperature of the rubber-like copolymer (B) in a sizing agent is more than 25 degreeC and 100 degrees C or less. Since the rubbery copolymer (B) has a sufficient elastic modulus when the glass transition temperature is higher than 25 ° C., the load can be sufficiently transmitted from the matrix resin to the carbon fiber when used as a composite material. Is possible. If the glass transition temperature of the rubber-like copolymer (B) is 100 ° C. or less, it has a certain degree of elongation, so that the stress load at the interface between the carbon fiber and the matrix resin can be made uniform, and the toughness is improved. To do.

  In the present invention, when a sizing agent containing at least the aliphatic epoxy compound (A) and the rubbery copolymer (B) is applied to the carbon fiber, it can be dispersed in a solvent and used. Examples of such a solvent include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, dimethylformamide, and dimethylacetamide. Among them, handling is easy and advantageous from the viewpoint of safety. For this reason, water is preferably used.

  Further, the sizing agent used in the present invention may contain components other than those described above. For example, an adhesion promoting component that enhances the adhesion between the sizing component and the oxygen-containing functional group and / or matrix resin contained on the carbon fiber surface, and auxiliary agents such as a dispersant and a surfactant for the purpose of stability of the sizing component Ingredients can be added.

  Examples of the adhesion promoting component include triisopropylamine, dibutylethanolamine, diethylethanolamine, triisopropanolamine, diisopropylethylamine, N-benzylimidazole, 1,8-diazabicyclo [5,4,0] -7-undecene (DBU). ), 1,5-diazabicyclo [4,3,0] -5-nonene (DBN), 1,4-diazabicyclo [2.2.2] octane, 5,6-dibutylamino-1,8-diaza-bicyclo Tertiary amine compounds such as [5,4,0] undecene-7 (DBA) and salts thereof, phosphine compounds such as tributylphosphine and triphenylphosphine, and quaternary phosphonium salts such as salts thereof. These compounds are preferably added in an amount of 1 to 25% by mass, more preferably 2 to 8% by mass, based on the total amount of the sizing agent used in the present invention.

  Examples of the dispersant and the surfactant include nonionic surfactants, cationic surfactants, and anionic surfactants, but it is preferable to use a nonionic surfactant from the viewpoint of solution stability when a water emulsion solution is used. . More specifically, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene fatty acid amide ether, polyhydric alcohol fatty acid ester, polyoxyethylene polyhydric alcohol fatty acid ester, fatty acid sucrose Examples thereof include esters, alkylolamides, and polyoxyalkylene block copolymers. Furthermore, you may add a polyester compound, an unsaturated polyester compound, etc. suitably in the range which does not affect the effect of this invention.

  Furthermore, as long as the effect of the present invention is not affected, a component that imparts convergence or flexibility to the sizing agent-coated carbon fiber may be appropriately added. Thereby, the handleability, scratch resistance, and fluff resistance of the sizing agent-coated carbon fiber can be improved, and the impregnation property of the matrix resin can be improved.

  Next, the manufacturing method of polyacrylonitrile-type carbon fiber is demonstrated.

  As a spinning method for obtaining a carbon fiber precursor fiber, spinning methods such as wet, dry, and dry-wet can be used. From the viewpoint of easily obtaining high-strength carbon fibers, it is preferable to use a wet or dry wet spinning method.

  The total fineness of the carbon fibers used in the present invention is preferably 400 to 3000 tex. Moreover, the number of filaments of carbon fiber is preferably 1000 to 100,000, and more preferably 3000 to 50000. In order to further improve the adhesion between the carbon fibers and the matrix resin, it is preferable to apply the above sizing agent to carbon fibers having a surface roughness (Ra) of 6.0 to 100 nm, and the surface roughness (Ra) is In order to obtain 6.0 to 100 nm carbon fiber, it is preferable to spin the precursor fiber by a wet spinning method.

  In the wet spinning method, a solution obtained by dissolving a polyacrylonitrile homopolymer or copolymer in a solvent can be used as the spinning dope. As the solvent, an organic solvent such as dimethyl sulfoxide, dimethylformamide, or dimethylacetamide, or an aqueous solution of an inorganic compound such as nitric acid, sodium rhodanate, zinc chloride, or sodium thiocyanate is used. Dimethyl sulfoxide and dimethylacetamide are suitable as the solvent.

  The above spinning solution is spun through a die and discharged into a spinning bath to be solidified. As the spinning bath, an aqueous solution of a solvent used as a solvent for the spinning dope can be used. It is preferable to use a spinning solution containing the same solvent as the spinning solution, and a dimethyl sulfoxide aqueous solution and a dimethylacetamide aqueous solution are preferable. The fiber solidified in the spinning bath is washed with water and drawn to obtain a precursor fiber. The obtained precursor fiber is subjected to flameproofing treatment and carbonization treatment, and further subjected to graphitization treatment as necessary to obtain carbon fiber. As conditions for the carbonization treatment and graphitization treatment, the maximum heat treatment temperature is preferably 1100 ° C. or higher, more preferably 1300 to 3000 ° C.

  Furthermore, fine carbon fibers are preferably used from the viewpoint of obtaining carbon fibers having high strength and elastic modulus. Specifically, the single fiber diameter of the carbon fiber is preferably 7.5 μm or less, more preferably 6 μm or less, and further preferably 5.5 μm or less. The lower limit of the single fiber diameter is not particularly limited, but by making it 4.5 μm or more, the single fiber is hardly cut in the process, and the productivity is improved.

  The carbon fiber is usually subjected to an oxidation treatment in order to improve adhesion with the matrix resin, and oxygen-containing functional groups are introduced to the surface. As the oxidation treatment method, vapor phase oxidation, liquid phase oxidation, and liquid phase electrolytic oxidation are used. From the viewpoint of high productivity and uniform treatment, liquid phase electrolytic oxidation is preferably used.

  In the present invention, examples of the electrolytic solution used in the liquid phase electrolytic oxidation include an acidic electrolytic solution and an alkaline electrolytic solution. Examples of the acidic electrolyte include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, boric acid, and carbonic acid, organic acids such as acetic acid, butyric acid, oxalic acid, acrylic acid, and maleic acid, or ammonium sulfate and ammonium hydrogen sulfate. And the like. Of these, sulfuric acid and nitric acid exhibiting strong acidity are preferably used. Specific examples of the alkaline electrolyte include aqueous solutions of hydroxides such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide and barium hydroxide, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, Aqueous solutions of carbonates such as barium carbonate and ammonium carbonate, aqueous solutions of bicarbonates such as sodium bicarbonate, potassium bicarbonate, magnesium bicarbonate, calcium bicarbonate, barium bicarbonate and ammonium bicarbonate, ammonia, tetraalkylammonium hydroxide And an aqueous solution of hydrazine. Among these, from the viewpoint of not containing an alkali metal that causes curing inhibition of the matrix resin, an aqueous solution of ammonium carbonate and ammonium hydrogen carbonate or an aqueous solution of tetraalkylammonium hydroxide exhibiting strong alkalinity is preferably used.

  In the present invention, from the viewpoint that the covalent bond formation between the sizing agent component and the oxygen-containing functional group on the surface of the carbon fiber is promoted, and the adhesiveness is further improved, the carbon fiber is subjected to an electrolytic treatment with an alkaline electrolyte or an acidic aqueous solution. It is preferable to apply a sizing agent after electrolytic treatment in the substrate, followed by washing with an alkaline aqueous solution. When electrolytic treatment is performed, the excessively oxidized portion on the carbon fiber surface becomes a fragile layer and exists at the interface, which may be the starting point of destruction when made into a composite material. It is considered that formation of a covalent bond is promoted by dissolution and removal with an aqueous solution.

  In the present invention, the pH of the alkaline aqueous solution used for washing is preferably in the range of 7 to 14, more preferably in the range of 10 to 14. Specific examples of alkaline aqueous solutions include aqueous solutions of hydroxides such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide and barium hydroxide, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, and barium carbonate. And aqueous solutions of carbonates such as ammonium carbonate, aqueous solutions of bicarbonates such as sodium bicarbonate, potassium bicarbonate, magnesium bicarbonate, calcium bicarbonate, barium bicarbonate and ammonium bicarbonate, ammonia, tetraalkylammonium hydroxide and hydrazine An aqueous solution of Among these, from the viewpoint of not containing an alkali metal that causes curing inhibition of the matrix resin, an aqueous solution of ammonium carbonate or ammonium hydrogen carbonate, or an aqueous solution of tetraalkylammonium hydroxide exhibiting strong alkalinity is preferably used. As a method for washing the carbon fiber with an alkaline aqueous solution, for example, a dip method and a spray method can be used. Especially, it is preferable to use a dip method from a viewpoint that washing | cleaning is easy, Furthermore, it is a preferable aspect to use a dip method, vibrating a carbon fiber with an ultrasonic wave.

  The concentration of the electrolytic solution used in the present invention is preferably in the range of 0.01 to 5 mol / liter, more preferably in the range of 0.1 to 1 mol / liter. When the concentration of the electrolytic solution is 0.01 mol / liter or more, the electrolytic treatment voltage is lowered, which is advantageous in terms of operating cost. On the other hand, when the concentration of the electrolytic solution is 5 mol / liter or less, it is advantageous from the viewpoint of safety.

  The temperature of the electrolytic solution used in the present invention is preferably in the range of 10 to 100 ° C, more preferably in the range of 10 to 40 ° C. When the temperature of the electrolytic solution is 10 ° C. or higher, the efficiency of the electrolytic treatment is improved, which is advantageous in terms of operating cost. On the other hand, when the temperature of the electrolytic solution is 100 ° C. or lower, it is advantageous from the viewpoint of safety.

In the present invention, the current density in the liquid phase electrolytic oxidation is preferably in the range of 1.5 to 1000 amperes / m ² per 1 m ² of the surface area of the carbon fiber in the electrolytic treatment solution, more preferably 3 to 500 amperes / m. it is within the range of m ^2. When the current density is 1.5 amperes / m ² or more, the efficiency of the electrolytic treatment is improved, which is advantageous in terms of operating cost. On the other hand, when the current density is 1000 amperes / m ² or less, it is advantageous from the viewpoint of safety.

  In the present invention, the amount of electricity in the liquid phase electrolytic oxidation is preferably optimized in accordance with the carbonization degree of the carbon fiber, and a larger amount of electricity is required when processing the carbon fiber having a high elastic modulus.

  In the present invention, the carbon fiber has a surface oxygen concentration (O / C), which is a ratio of the number of atoms of oxygen (O) and carbon (C) on the fiber surface measured by X-ray photoelectron spectroscopy. The thing within the range of 05-0.50 is preferable, More preferably, it is a thing within the range of 0.07-0.30, More preferably, it is a thing within the range of 0.10-0.30. When the surface oxygen concentration (O / C) is 0.05 or more, an oxygen-containing functional group on the surface of the carbon fiber can be secured and strong adhesion with the matrix resin can be obtained. Moreover, when the surface oxygen concentration (O / C) is 0.5 or less, a decrease in strength of the carbon fiber itself due to oxidation can be suppressed.

The surface oxygen concentration of the carbon fiber can be determined by X-ray photoelectron spectroscopy according to the following procedure. First, carbon fibers from which dirt and the like adhering to the carbon fiber surface were removed with a solvent were cut into 20 mm, spread and arranged on a copper sample support base, and then AlKα ₁ and ₂ were used as X-ray sources. The chamber is kept at 1 × 10 ⁻⁸ Torr. As a correction value for the peak accompanying charging during measurement, the binding energy value of the main peak (peak top) of C _1s is adjusted to 284.6 eV. The C _1s peak area is obtained by drawing a straight base line in the range of 282 to 296 eV. The O _1s peak area is obtained by drawing a straight base line in the range of 528 to 540 eV. Here, the surface oxygen concentration can be calculated as an atomic ratio by using a sensitivity correction value unique to the apparatus from the ratio of the O _1s peak area to the C _1s peak area.

  In the present invention, it is preferable that the carbon fiber is washed with an electrolytic treatment or an alkaline aqueous solution, then washed with water and dried. In this case, if the drying temperature is too high, the functional groups present on the outermost surface of the carbon fiber are likely to disappear due to thermal decomposition. Therefore, it is desirable to dry at the lowest possible temperature. Specifically, the drying temperature is preferably 250 ° C. Hereinafter, drying at 210 ° C. or lower is more preferable. On the other hand, considering the efficiency of drying, the drying temperature is preferably 110 ° C. or higher, and more preferably 140 ° C. or higher.

  As shown above, the carbon fiber preferably used in the present invention can be obtained.

  The strand strength of the carbon fiber used in the present invention is preferably 3.5 GPa or more, more preferably 4 GPa or more, and further preferably 5 GPa or more. Moreover, it is preferable that the strand elastic modulus of the carbon fiber used by this invention is 220 GPa or more, More preferably, it is 240 GPa or more, More preferably, it is 280 GPa or more. In addition, the strand tensile strength and strand elastic modulus of a carbon fiber bundle can be calculated | required by the resin impregnation strand test method of JIS-R-7608 (2004).

  Next, a method for producing the sizing coated carbon fiber of the present invention will be described.

  In the present invention, a sizing agent containing at least the aliphatic epoxy compound (A) and the rubbery copolymer (B) can be diluted with a solvent. Examples of such a solvent include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, dimethylformamide, and dimethylacetamide. Among them, handling is easy and advantageous from the viewpoint of safety. For this reason, water is preferably used.

  Next, means for applying (applying) the sizing agent used in the present invention to the carbon fiber will be described. As a coating method, a sizing agent-containing liquid in which the aliphatic epoxy compound (A) and the rubbery copolymer (B) component of the sizing agent used in the present invention and other sizing agent components are simultaneously dissolved or dispersed is used. A method of applying once or a method of applying a plurality of times using a sizing agent-containing liquid in which each component is arbitrarily selected and individually dissolved or dispersed are preferably used. In this case, the aliphatic epoxy compound (A) and the rubbery copolymer (B) component and other components can be applied in any order. Hereinafter, the application means in the case where the above sizing agent dispersion liquid simultaneously contains the aliphatic epoxy compound (A) and the rubbery copolymer (B) component and other components will be described. It can be similarly performed when each of the sizing agent-containing liquid containing (A) and the rubbery copolymer (B) and the sizing agent-containing liquid containing other components are separately applied.

  Examples of the application means include, for example, a method of immersing carbon fiber in a sizing agent-containing liquid via a roller, a method of contacting carbon fiber to a roller to which the sizing agent-containing liquid is attached, There is a method of spraying. Further, the sizing agent applying means may be either a batch type or a continuous type, but a continuous type capable of improving productivity and reducing variation is preferably used. At this time, it is preferable to control the concentration and temperature of the sizing agent-containing liquid, the yarn tension, and the like so that the amount of the sizing agent active component attached to the carbon fiber is uniformly attached within an appropriate range. Moreover, it is also a preferable aspect that the carbon fiber is vibrated with ultrasonic waves when the sizing agent is applied.

  In the present invention, the thickness of the sizing agent layer applied to the carbon fiber and dried is preferably within a range of 2.0 to 20 nm, and the maximum value of the thickness does not exceed twice the minimum value. By such a uniform sizing agent layer, a large effect of improving adhesiveness can be obtained stably, and furthermore, excellent high-order workability can be obtained.

  In the present invention, the carbon fiber is produced by applying a sizing agent-containing liquid, followed by heat treatment, and removing and drying the solvent contained in the sizing agent-containing liquid. The heat treatment is considered to have an effect of promoting the formation of a covalent bond between the sizing agent component and the functional group on the surface of the carbon fiber and enhancing the adhesion between the carbon fiber and the matrix resin. As heat treatment conditions, a temperature range of 130 ° C. to 260 ° C., more preferably a temperature range of 160 ° C. to 260 ° C., and preferably 30 to 600 seconds. In the case of 130 ° C. or higher or 30 seconds or longer, water and organic solvent in which the sizing agent component is dissolved and dispersed can be sufficiently removed. In the case of 260 degrees C or less or 600 seconds or less, it is particularly excellent in terms of operating cost and / or safety.

  The heat treatment can also be performed by microwave irradiation and / or infrared irradiation. When the carbon fiber is heat-treated by microwave irradiation and / or infrared irradiation, the carbon fiber that is an object to be heated can be heated to a desired temperature in a short time. In addition, since the inside of the carbon fiber can be quickly heated by microwave irradiation and / or infrared irradiation, the temperature difference between the inside and outside of the carbon fiber bundle can be reduced, and the adhesion unevenness of the sizing agent can be reduced. It becomes possible to do.

  Furthermore, as another means for imparting to the carbon fiber used in the present invention, the aliphatic epoxy compound (A) and the rubbery copolymer (B) are added to the electrolytic solution, and the surface of the carbon fiber simultaneously with the electrolytic treatment. The aliphatic epoxy compound (A) and the rubber-like copolymer (B) may be added in the washing step after the electrolytic treatment and the method of imparting to the carbon fiber surface at the same time as washing with water. In these cases, the amount of the sizing agent component attached can be controlled by controlling the concentration, temperature, yarn tension and the like of the electrolytic treatment solution.

  The sizing coated carbon fiber of the present invention is used in the form of, for example, tow, woven fabric, knitted fabric, braid, web, mat, and chopped. In particular, for applications that require high specific strength and high specific modulus, a tow in which carbon fibers are aligned in one direction is most suitable, and a prepreg impregnated with a matrix resin is preferably used.

  Next, the prepreg and fiber reinforced composite material in the present invention will be described.

  The sizing coated carbon fiber in the present invention can be used as a prepreg and a fiber reinforced composite material in combination with a matrix resin.

  A thermosetting resin is preferably used as the matrix resin of the prepreg and fiber-reinforced composite material of the present invention. Examples of the thermosetting resins include unsaturated polyester resins, vinyl ester resins, epoxy resins, phenol resins, melamine resins, urea resins, thermosetting polyimide resins, cyanate ester resins, and bismaleimide resins, and their modifications. Body, and a resin obtained by blending two or more of these. Among them, it is preferable to use an epoxy resin because it has an advantage of excellent balance of mechanical properties and small curing shrinkage.

  The epoxy compound used for the epoxy resin is not particularly limited, and is a bisphenol type epoxy compound, an amine type epoxy compound, a phenol novolac type epoxy compound, a cresol novolac type epoxy compound, a resorcinol type epoxy compound, a phenol aralkyl type epoxy compound, One or more selected from naphthol aralkyl type epoxy compounds, dicyclopentadiene type epoxy compounds, epoxy compounds having a biphenyl skeleton, isocyanate-modified epoxy compounds, tetraphenylethane type epoxy compounds, triphenylmethane type epoxy compounds and the like are used. be able to.

  The curing agent is not particularly limited, and examples thereof include an aromatic amine curing agent, dicyanamide or a derivative thereof. Further, amines such as alicyclic amines, phenol compounds, acid anhydrides, polyamideamino, organic acid hydrazides, and isocyanates can be used in combination with aromatic amine curing agents.

  Among these, it is preferable to use an epoxy resin containing a polyfunctional glycidylamine type epoxy resin and an aromatic diamine curing agent. In general, a matrix resin containing a polyfunctional glycidylamine type epoxy resin and an aromatic diamine curing agent has a high crosslinking density, and can improve the heat resistance and compressive strength of the fiber-reinforced composite material.

  As the polyfunctional glycidylamine type epoxy resin, for example, tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, triglycidylaminocresol and the like can be preferably used. The polyfunctional glycidylamine type epoxy resin has an effect of improving heat resistance, and the proportion thereof is preferably 30 to 100% by mass in 100% by mass of all epoxy resins. When the ratio of the glycidylamine type epoxy resin is 30% by mass or more, the compressive strength of the fiber reinforced composite material is improved and the heat resistance is excellent.

  The aromatic diamine curing agent is not particularly limited as long as it is an aromatic amine used as an epoxy resin curing agent. Specifically, 3,3′-diaminodiphenylsulfone (3,3′- DDS), 4,4′-diaminodiphenylsulfone (4,4′-DDS), diaminodiphenylmethane (DDM), diaminodiphenyl ether (DADPE), bisaniline, benzyldimethylaniline, 2- (dimethylaminomethyl) phenol (DMP-10) ), 2,4,6-tris (dimethylaminomethyl) phenol (DMP-30), tri-2-ethylhexylate of DMP-30, and the isomers and derivatives thereof can be preferably used. These may be used alone or in combination of two or more.

  The aromatic diamine curing agent is preferably contained in a stoichiometric amount of 50 to 120% by mass, more preferably 60 to 120% by mass, and even more preferably 70 to 90% by mass with respect to the total epoxy resin. . The heat resistance of the cured resin obtained when the aromatic amine curing agent is 50% by mass or more of the stoichiometric amount with respect to the total epoxy resin is improved. Moreover, when an aromatic amine hardening | curing agent is 120 mass% or less, the toughness of the resin cured material obtained improves.

  Moreover, an effect promoter can also be mix | blended for the purpose of promoting hardening of an epoxy resin. Examples of the curing accelerator include urea compounds, tertiary amines and salts thereof, imidazoles and salts thereof, triphenylphosphine or derivatives thereof, carboxylic acid metal salts and Lewis acids, Bronsted acids and salts thereof, and the like.

  A thermoplastic resin can be blended with the matrix resin of the fiber-reinforced composite material of the present invention in order to improve physical properties such as toughness of the obtained cured resin. Examples of such thermoplastic resins include carbon-carbon bonds, amide bonds, imide bonds (polyetherimide, etc.), ester bonds, ether bonds, siloxane bonds, carbonate bonds, urethane bonds, urea bonds, thioether bonds, A thermoplastic resin having a bond selected from the group consisting of a sulfone bond, an imidazole bond, and a carbonyl bond can be used. For example, those having both heat resistance and toughness such as polysulfone, polyethersulfone, polyetherimide, polyimide, polyamide, polyamideimide, polyphenylene ether, phenoxy resin, and vinyl polymer can be preferably used.

  In particular, polyethersulfone and polyetherimide are preferable because these effects can be exhibited without substantially impairing heat resistance.

  Moreover, when it dissolves in an epoxy resin composition, 1-40 mass parts is preferable with respect to 100 mass parts of epoxy resins, More preferably, the compounding quantity of said thermoplastic resin is 1-25 mass parts. . On the other hand, when used in a dispersed state, the amount is preferably 10 to 40 parts by mass, more preferably 15 to 30 parts by mass with respect to 100 parts by mass of the epoxy resin. When the blending amount of the thermoplastic resin is satisfied, the toughness improving effect is further improved. Further, when the thermoplastic resin does not exceed the above range, the impregnation property, tack drape, and heat resistance are improved.

  It is preferable that the thermoplastic resin is uniformly dissolved in the epoxy resin composition or finely dispersed in the form of particles so as not to hinder the prepreg manufacturing process centering on impregnation.

  Further, in order to modify the matrix resin used in combination with the sizing agent-coated carbon fiber of the present invention, a thermosetting resin other than the thermosetting resin used for the matrix resin, elastomer, filler, rubber particles, thermoplastic resin particles Inorganic particles and other additives can also be blended.

  As said thermoplastic resin particle, the thing similar to the various thermoplastic resins illustrated previously can be used. Of these, polyamide particles and polyimide particles are preferably used. Among polyamides, nylon 12, nylon 6, nylon 11, nylon 6/12 copolymer, and epoxy compound described in Example 1 of JP-A-01-104624 are used. Since semi-IPN (polymer interpenetrating network structure) nylon (semi-IPN nylon) can give particularly good adhesive strength with thermosetting resin, it is a carbon fiber reinforced composite material during impact from falling weight It is preferable because of its high delamination strength and high impact resistance improvement effect.

  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 there is no origin of stress concentration. This is a preferred embodiment in terms of giving high impact resistance.

  As the rubber particles, cross-linked rubber particles, and core-shell rubber particles obtained by graft polymerization of a different polymer on the surface of the cross-linked rubber particles are preferably used from the viewpoint of handleability and the like.

  In addition, the matrix resin used in the present invention is blended with inorganic particles such as silica, alumina, smectite, and synthetic mica in order to adjust the fluidity such as thickening of the matrix resin within a range that does not impair the effects of the present invention. You can also.

  The prepreg of the present invention is produced by a wet method in which the above matrix resin is dissolved in a solvent such as methyl ethyl ketone or methanol to lower the viscosity and impregnated, and a hot melt method (dry method) in which the viscosity is lowered by heating and impregnated. be able to.

  The wet method is a method in which carbon fibers coated with a sizing agent are immersed in a matrix resin solution, and then the solvent is evaporated using an oven or the like. The hot melt method is a method in which a matrix resin whose viscosity is reduced by heating is used. A method of directly impregnating carbon fiber, or a coating film prepared from a matrix resin is once placed on a release paper or the like, and then the film is stacked from both sides or one side of the sizing agent-coated carbon fiber and heated and pressed. Thus, a sizing agent-coated carbon fiber is impregnated with a matrix resin. The hot melt method is a preferable method because substantially no solvent remains in the prepreg.

  The fiber-reinforced composite material of the present invention can be produced by, for example, a method in which the obtained prepreg is laminated and then the matrix resin is heated and cured while applying pressure to the laminate. As a method for applying heat and pressure, a press molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, an internal pressure molding method, a vacuum pressure molding method, and the like are employed. The fiber reinforced composite material does not go through a prepreg, and includes, for example, a filament winding method, a hand layup method, a resin injection molding method, “SCRIMP (registered trademark)”, a resin film infusion method, and a resin transfer method. It can also be produced by a molding method such as a molding method.

  The fiber reinforced composite material of the present invention is, for example, a personal computer, a display, an OA device, a mobile phone, a portable information terminal, a facsimile, a compact disc, a portable MD, a portable radio cassette, a PDA (a portable information terminal such as an electronic notebook), a video. Cameras, digital still cameras, optical equipment, audio equipment, air conditioners, lighting equipment, recreational goods, toy products, and other electrical and electronic equipment casings and internal parts such as trays and chassis, cases, mechanism parts, and panels Applications such as building materials, motor parts, alternator terminals, alternator connectors, IC regulators, light meter potentiometer bases, suspension parts, various valves such as exhaust gas valves, fuel related, exhaust system or various intake system pipes, air intake nozzles Snorkel, intake manifold, various arms, various frames, various hinges, various bearings, fuel pump, gasoline tank, CNG tank, engine coolant joint, carburetor main body, carburetor spacer, exhaust gas sensor, coolant sensor, oil temperature sensor, Brake pad wear sensor, throttle position sensor, crankshaft position sensor, air flow meter, brake butt wear sensor, thermostat base for air conditioner, heating hot air flow control valve, brush holder for radiator motor, water pump impeller, turbine vane, wiper Motor-related parts, distributors, starter switches, starter relays, transmission wire hubs , Window washer nozzle, air conditioner panel switch board, coil for fuel related electromagnetic valve, connector for fuse, battery tray, AT bracket, headlamp support, pedal housing, handle, door beam, protector, chassis, frame, armrest, horn terminal, Step motor rotor, lamp socket, lamp reflector, lamp housing, brake piston, noise shield, radiator support, spare tire cover, seat shell, solenoid bobbin, engine oil filter, ignition device case, under cover, scuff plate, pillar trim, propeller shaft, Wheel, fender, fascia, bumper, bumper beam, bonnet, aero parts, platform Cars, cowl louvers, roofs, instrument panels, spoilers and various modules, automobile-related parts, parts and skins, landing gear pods, winglets, spoilers, edges, ladders, elevators, fairings, ribs, etc. Aircraft related parts, members and skins, windmill blades and the like. In particular, it is preferably used for aircraft members, windmill blades, automobile outer plates, casings of electronic devices, trays, chassis, and the like.

  Hereinafter, the carbon fiber coated with the sizing agent of the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

  The materials and components used as sizing agent components in each Example and each Comparative Example are as follows.

Aliphatic epoxy compound (A): (A-1 to A-3)
(A-1) “Denacol (registered trademark)” EX-521 (manufactured by Nagase ChemteX Corporation: polyglycerin polyglycidyl ether)
(A-2) “Denacol (registered trademark)” EX-411 (manufactured by Nagase ChemteX Corporation: pentaerythritol polyglycidyl ether)
(A-3) “Denacol (registered trademark)” EX-614B (manufactured by Nagase ChemteX Corporation: sorbitol polyglycidyl ether).

Aromatic epoxy compound “jER (registered trademark)” 828 (manufactured by Mitsubishi Chemical Corporation: bisphenol A type glycidyl ether).

・ Rubber copolymer (B): (B-1 to B-3)
(B-1) 0548 (manufactured by JSR Corporation: aqueous dispersion of styrene-butadiene copolymer): glass transition temperature -49 ° C
(B-2) 0597 (manufactured by JSR Corporation: aqueous dispersion of styrene-butadiene copolymer): glass transition temperature 28 ° C.
(B-3) 0640 (manufactured by JSR Corporation: aqueous dispersion of styrene-butadiene copolymer): Glass transition temperature 55 ° C.

Epoxy-modified nitrile-butadiene rubber “ADEKA RESIN (registered trademark)” EPR-1039 (manufactured by ADEKA Corporation)
Urethane rubber VONDIC 8510 (manufactured by DIC Corporation: aqueous dispersion of a copolymer of aliphatic isocyanate and aliphatic ester).

Example 1
In this example, carbon fiber was used as the reinforcing fiber. This example comprises the following I step, II step and III step.

Step I: Step of producing carbon fiber A copolymer composed of 99 mol% acrylonitrile and 1 mol% itaconic acid was spun and fired, the total number of filaments was 12,000, the specific gravity was 1.8, the strand tensile strength was 6 A carbon fiber having a tensile modulus of 320 GPa and a tensile modulus of 8 GPa was obtained. Next, the carbon fiber was subjected to an electrolytic surface treatment using an aqueous solution of ammonium hydrogen carbonate having a concentration of 0.1 mol / liter as an electrolytic solution. The carbon fiber subjected to the electrolytic surface treatment was subsequently washed with water and dried in heated air at a temperature of 150 ° C. to obtain a carbon fiber as a raw material.

Step II: Step of producing sizing agent-coated carbon fiber and evaluation 70 parts by mass of (A-1) as a compound having an epoxy group in the molecule, and (B-2) as a rubbery copolymer having a solid content of A sizing agent solution was prepared using water as a solvent so as to be 30 parts by mass. This sizing agent solution was applied to the surface-treated carbon fiber obtained as described above using an immersion method, and then heat treated at a temperature of 210 ° C. for 180 seconds to obtain a sizing agent-coated carbon fiber bundle. The adhesion amount of the sizing agent was measured by the method described below and adjusted so as to be 0.5 part by mass with respect to 100 parts by mass of the sizing agent-coated carbon fiber.

<Measurement of sizing agent adhesion>
About 2 g of a sizing agent-coated carbon fiber bundle was weighed (W1) (reading to the fourth decimal place), then placed in an electric furnace (capacity 120 cm ³ ) set at a temperature of 450 ° C. in a nitrogen stream of 50 ml / min. The sizing agent was completely pyrolyzed for a minute. Then, the carbon fiber bundle is transferred to a container in a dry nitrogen stream at 20 liters / minute and cooled for 15 minutes. It was.
Sizing agent adhesion amount (% by mass) = [W1 (g) −W2 (g)] / [W1 (g)] × 100
The amount of the sizing agent attached to 100 parts by mass of the sizing agent-coated carbon fiber bundle was defined as the mass part of the attached sizing agent. In this example, the measurement was performed twice, and the average value was defined as the mass part of the sizing agent.

  Subsequently, the interfacial shear strength (IFSS) of the sizing agent-coated carbon fiber was measured by the method described below. As a result, it was found that the adhesion of the carbon fiber coated with the sizing agent was sufficiently high.

<Measurement of interfacial shear strength (IFSS)>
Interfacial shear strength (IFSS) was measured by the following procedures (a) to (d).

(A) Preparation of resin 100 parts by mass of bisphenol A type epoxy resin compound “jER (registered trademark)” 828 (manufactured by Mitsubishi Chemical Corporation) and 14.5 parts by mass of metaphenylenediamine (manufactured by Sigma-Aldrich Japan Co., Ltd.) , Each in a container. Thereafter, in order to reduce the viscosity of jER828 and to dissolve metaphenylenediamine, the mixture was heated at a temperature of 75 ° C. for 15 minutes, then mixed well and vacuum degassed at a temperature of 80 ° C. for about 15 minutes.

(B) Fixing the carbon fiber single yarn to the dedicated mold The single fiber was extracted from the carbon fiber bundle, and both ends were fixed with an adhesive in a state where a constant tension was applied to the single fiber in the longitudinal direction of the dumbbell mold. Then, in order to remove the water | moisture content adhering to carbon fiber and a mold, it vacuum-dried for 30 minutes or more at the temperature of 80 degreeC. The dumbbell mold is made of silicone rubber, and the shape of the casting part is a central part width of 5 mm, a length of 25 mm, a both end part width of 10 mm, and an overall length of 150 mm.

(C) Resin casting / curing Pour the resin prepared in the above procedure (b) into the mold after vacuum drying in the above step (b), and use an oven to raise the temperature at a rate of 1.5 ° C./min. The temperature was raised to 75 ° C. and held for 2 hours, then the temperature was raised to 125 ° C. at a heating rate of 1.5 minutes, held for 2 hours, and then lowered to a temperature of 30 ° C. at a cooling rate of 2.5 ° C./min. . Then, it demolded and the test piece was obtained.

(D) Interfacial shear strength (IFSS) measurement Tensile force was applied to the test piece obtained in the above procedure (c) in the fiber axis direction (longitudinal direction) to cause 12% distortion, and then the test piece was examined with a polarizing microscope. The fiber breakage number N (pieces) in the range of 22 mm at the center was measured. Next, the average broken fiber length la is calculated by the formula of la (μm) = 22 × 1000 (μm) / N (pieces), and the critical fiber length lc is further calculated from the average broken fiber length la by lc (μm) = Calculation was performed using the formula (4/3) × la (μm). The strand tensile strength σ and the diameter d of the carbon fiber single yarn were measured, and the interfacial shear strength IFSS, which is an index of the bond strength between the carbon fiber and the resin interface, was calculated by the following equation. In the examples, the average of the number of measurements n = 5 was used as the test result.
Interfacial shear strength IFSS (MPa) = σ (MPa) × d (μm) / (2 × lc) (μm)
In addition, the strand tensile strength was calculated | required according to the following procedure based on the resin impregnation strand test method of JIS-R-7608 (2004). As the resin formulation, “Celoxide (registered trademark)” 2021P (manufactured by Daicel Chemical Industries) / boron trifluoride monoethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) / Acetone = 100/3/4 (parts by mass) is used. The curing conditions were normal pressure, temperature 125 ° C., and curing time 30 minutes. Ten strands of the carbon fiber bundle were measured, and the average value was defined as the strand tensile strength.

  The interfacial shear strength IFSS is an index of the adhesive strength between the carbon fiber and the matrix resin. In the present invention, 30 MPa or more is a preferable range.

Step III: Preparation of prepreg, molding and evaluation of carbon fiber reinforced composite laminate <Preparation of prepreg>
First, bisphenol A type epoxy resin, “jER (registered trademark)” 828 (manufactured by Mitsubishi Chemical Corporation) 60 parts by mass, tetraglycidyldiaminodiphenylmethane, ELM434 (manufactured by Sumitomo Chemical Co., Ltd.) 40 parts by mass, 4, 4 ′ -40 parts by mass of diaminodiphenylsulfone, “Seika Cure (registered trademark)” S (manufactured by Wakayama Seika Co., Ltd.) and 10 parts by mass of polyethersulfone “Sumika Excel (registered trademark)” PES5003P (manufactured by Sumitomo Chemical Co., Ltd.) A kneaded epoxy resin composition was prepared, and this was coated on a release paper with a resin basis weight of 30 g / m ² using a knife coater to produce a primary resin film. Sizing agent-coated carbon fibers impregnated with sizing agent-coated carbon fibers are superposed on both sides of a sizing agent-coated carbon fiber (weight per unit area 190 g / m ² ) aligned in one direction while heating and pressing using a heat roll. By doing so, a primary prepreg was produced. Next, a resin composition was prepared by further kneading 80 parts by mass of the above-mentioned epoxy resin composition with “Trepearl (registered trademark)” TN (manufactured by Toray Industries, Inc., average particle size: 13.0 μm). A secondary resin film was prepared by coating the release paper with a resin basis weight of 20 g / m ² using a coater. This secondary resin film was superposed on both sides of the primary prepreg and impregnated with the epoxy resin composition to produce the desired prepreg.

<Formation of Carbon Fiber Reinforced Composite Material and Measurement of Mode I Interlaminar Fracture Toughness (G _Ic )>
The prepreg produced as described above was cut and unidirectionally laminated, and then heat-cured using an autoclave to produce a unidirectional reinforcing material (carbon fiber reinforced composite material). The mode I interlaminar fracture toughness (G _Ic ) at the initial stage of crack growth was determined according to the double-sided beam test described in JIS K7086 (1993). The results are shown in Table 1. In the present invention, the mode I interlaminar fracture toughness (G _Ic ) is preferably 700 J / m ² or more. In Table 1, the value of the mode I interlaminar fracture toughness _{(G Ic)} are marked 950J / ^{m 2} or more of A, less than 700 J / ^{m 2} or more 950J / ^{m 2} B, less than 700 J / ^{m 2} at C ing.

As a result of evaluating the mechanical properties by the above method, Mode I interlaminar fracture toughness (G _Ic ) showed a high value. This indicates that the adhesion between the carbon fiber and the matrix resin is good and the interlaminar fracture toughness is enhanced.

(Examples 2 to 4)
Step I: Step of producing carbon fiber as raw material The same procedure as in Example 1 was performed.

Step II: Step of producing sizing agent-coated carbon fiber and evaluation (A-1), (A-2), the ratio of (A-3) and (B-2) are as shown in Table 1. A sizing agent-coated carbon fiber was obtained in the same manner as in Example 1 except that. Subsequently, when the interfacial shear strength (IFSS) was measured using the obtained sizing agent-coated carbon fiber, it was found that the adhesiveness was sufficiently high. The results are shown in Table 1.

Step III: Preparation of prepreg, molding of carbon fiber reinforced composite material laminate and evaluation In the same manner as in Example 1, a unidirectional reinforcing material (carbon fiber reinforced composite material) was prepared and evaluated for mechanical properties. The I interlaminar fracture toughness (G _Ic ) showed a sufficiently high value. The results are shown in Table 1.

(Examples 5 to 8)
Step I: Process for producing carbon fiber Same as Example 1.

Step II: Step of producing sizing agent-coated carbon fiber and evaluation The same procedure as in Example 1 except that the ratio of (A-1) and (B-2) in the sizing agent solution is as shown in Table 1. Sizing agent coated carbon fiber was obtained by this method. Subsequently, when the interfacial shear strength (IFSS) was measured using the obtained sizing agent-coated carbon fiber, it was found that the adhesiveness was sufficiently high. The results are shown in Table 1.

Step III: Preparation of prepreg, molding of carbon fiber reinforced composite material laminate and evaluation In the same manner as in Example 1, a unidirectional reinforcing material (carbon fiber reinforced composite material) was prepared and evaluated for mechanical properties. The I interlaminar fracture toughness (G _Ic ) showed a high value. The results are shown in Table 1.

(Examples 9 to 13)
Step I: Step of producing carbon fiber The same procedure as in Example 1 was performed.

Step II: Step and evaluation for producing sizing agent-coated carbon fiber Except that the sizing agent solution concentration was adjusted so that the amount of sizing agent adhesion was as shown in Table 1 with respect to 100 parts by mass of sizing agent-coated carbon fiber, this was carried out. Sizing agent-coated carbon fibers were obtained in the same manner as in Example 1. Subsequently, when the interfacial shear strength (IFSS) was measured using the obtained sizing agent-coated carbon fiber, it was found that the adhesiveness was sufficiently high. The results are shown in Table 1.

Step III: Preparation of prepreg, molding of carbon fiber reinforced composite material laminate and evaluation In the same manner as in Example 1, a unidirectional reinforcing material (carbon fiber reinforced composite material) was prepared and evaluated for mechanical properties. The I interlaminar fracture toughness (G _Ic ) showed a sufficiently high value. The results are shown in Table 1.

(Examples 14 and 15)
Step I: Step of producing carbon fiber The same procedure as in Example 1 was performed.

Step II: Step and evaluation for producing sizing agent-coated carbon fiber The sizing agent-coated carbon fiber was prepared in the same manner as in Example 1 except that the component (B) in the sizing agent solution was changed to Table 1. Obtained. Subsequently, when the interfacial shear strength (IFSS) was measured using the obtained sizing agent-coated carbon fiber, it was found that the adhesiveness was sufficiently high. The results are shown in Table 1.

Step III: Preparation of prepreg, molding of carbon fiber reinforced composite material laminate and evaluation In the same manner as in Example 1, a unidirectional reinforcing material (carbon fiber reinforced composite material) was prepared and evaluated for mechanical properties. The I interlaminar fracture toughness (G _Ic ) showed a sufficiently high value. The results are shown in Table 1.

(Comparative Example 1)
Step I: Step of producing carbon fiber The same procedure as in Example 1 was performed.

Step II: Step of producing sizing agent-coated carbon fiber and evaluation A sizing agent-coated carbon fiber was obtained in the same manner as in Example 1 except that the sizing agent solution was prepared using only the component (A-2). . Subsequently, when the interfacial shear strength (IFSS) was measured using the obtained sizing agent-coated carbon fiber, it was found that the adhesiveness was sufficiently high. The results are shown in Table 2.

Step III: Preparation of prepreg, molding of carbon fiber reinforced composite material laminate and evaluation In the same manner as in Example 1, a unidirectional reinforcing material (carbon fiber reinforced composite material) was prepared and evaluated for mechanical properties. The interlaminar fracture toughness (G _Ic ) showed a low value. The results are shown in Table 2.

(Comparative Example 2)
Step I: Step of producing carbon fiber The same procedure as in Example 1 was performed.

Step II: Step of producing sizing agent-coated carbon fiber and evaluation Sizing agent-coated carbon fiber in the same manner as in Example 1 except that the sizing agent solution was formulated with an aromatic epoxy compound and (B-2). Got. Subsequently, when the interfacial shear strength (IFSS) was measured using the obtained sizing agent-coated carbon fiber, it was found that the adhesiveness was low. The results are shown in Table 2.

Step III: Preparation of prepreg, molding of carbon fiber reinforced composite material laminate and evaluation In the same manner as in Example 1, a unidirectional reinforcing material (carbon fiber reinforced composite material) was prepared and evaluated for mechanical properties. The interlaminar fracture toughness (G _Ic ) showed a low value. The results are shown in Table 2.

(Comparative Example 3)
Step I: Step of producing carbon fiber The same procedure as in Example 1 was performed.

Step II: Step for producing sizing agent-coated carbon fiber and evaluation Sizing agent-coated carbon fiber was obtained in the same manner as in Example 1 except that the sizing agent solution was prepared only by (B-2). Subsequently, when the interfacial shear strength (IFSS) was measured using the obtained sizing agent-coated carbon fiber, it was found that the adhesiveness was low. The results are shown in Table 2.

Step III: Preparation of prepreg, molding of carbon fiber reinforced composite material laminate and evaluation In the same manner as in Example 1, a unidirectional reinforcing material (carbon fiber reinforced composite material) was prepared and evaluated for mechanical properties. The interlaminar fracture toughness (G _Ic ) showed a low value. The results are shown in Table 2.

(Comparative Example 4)
Step I: Step of producing carbon fiber The same procedure as in Example 1 was performed.

Step II: Steps for producing sizing agent-coated carbon fibers and evaluations The procedure was carried out except that the sizing agent solution concentration was adjusted so that the amount of sizing agent adhesion was as shown in Table 2 with respect to 100 parts by mass of sizing agent-coated carbon fibers. Sizing agent-coated carbon fibers were obtained in the same manner as in Example 1. Subsequently, when the interfacial shear strength (IFSS) was measured using the obtained sizing agent-coated carbon fiber, it was found that the adhesiveness was low. The results are shown in Table 2.

Step III: Preparation of prepreg, molding of carbon fiber reinforced composite material laminate and evaluation In the same manner as in Example 1, a unidirectional reinforcing material (carbon fiber reinforced composite material) was prepared and evaluated for mechanical properties. The interlaminar fracture toughness (G _Ic ) showed a low value. The results are shown in Table 2.

(Comparative Example 5)
Step I: Step of producing carbon fiber The same procedure as in Example 1 was performed.

Step II: Steps for producing sizing agent-coated carbon fibers and evaluations The procedure was carried out except that the sizing agent solution concentration was adjusted so that the amount of sizing agent adhesion was as shown in Table 2 with respect to 100 parts by mass of sizing agent-coated carbon fibers. Sizing agent-coated carbon fibers were obtained in the same manner as in Example 1. Subsequently, when the interfacial shear strength (IFSS) was measured using the obtained sizing agent-coated carbon fiber, it was found that the adhesiveness was sufficiently high. The results are shown in Table 2.

Step III: Preparation of prepreg, molding of carbon fiber reinforced composite material laminate and evaluation In the same manner as in Example 1, an attempt was made to prepare a unidirectional reinforcing material (carbon fiber reinforced composite material), but the carbon fiber bundle was hard. Could not mold.
(Comparative Example 6)
Step I: Step of producing carbon fiber The same procedure as in Example 1 was performed.

Step II: Step of producing sizing agent-coated carbon fiber and evaluation Sizing agent application in the same manner as in Example 1 except that the sizing agent solution was formulated with (A-1) and epoxy-modified nitrile-butadiene rubber. Carbon fiber was obtained. Subsequently, when the interfacial shear strength (IFSS) was measured using the obtained sizing agent-coated carbon fiber, it was found that the adhesiveness was high. The results are shown in Table 2.

Step III: Preparation of prepreg, molding of carbon fiber reinforced composite material laminate and evaluation In the same manner as in Example 1, a unidirectional reinforcing material (carbon fiber reinforced composite material) was prepared and evaluated for mechanical properties. The interlaminar fracture toughness (G _Ic ) showed a low value. The results are shown in Table 2.
(Comparative Example 7)
Step I: Step of producing carbon fiber The same procedure as in Example 1 was performed.

Step II: Step of producing sizing agent-coated carbon fiber and evaluation A sizing agent-coated carbon fiber was obtained in the same manner as in Example 1 except that the sizing agent solution was formulated with (A-1) and urethane rubber. It was. Subsequently, when the interfacial shear strength (IFSS) was measured using the obtained sizing agent-coated carbon fiber, it was found that the adhesiveness was high. The results are shown in Table 2.

Step III: Preparation of prepreg, molding of carbon fiber reinforced composite material laminate and evaluation In the same manner as in Example 1, a unidirectional reinforcing material (carbon fiber reinforced composite material) was prepared and evaluated for mechanical properties. The interlaminar fracture toughness (G _Ic ) showed a low value. The results are shown in Table 2.

Claims (13)

A sizing agent-coated carbon fiber in which a sizing agent containing at least the following (A) and (B) is applied by 0.1 to 5 parts by mass with respect to 100 parts by mass of the sizing agent-coated carbon fiber.
(A) Aliphatic epoxy compound (B) A rubbery copolymer having no epoxy group, which is polymerized using a vinyl compound having at least an aromatic skeleton as a copolymerization component Sizing agent application | coating carbon fiber of Claim 1 in which the said sizing agent contains 5-80 mass% of rubber-like copolymers (B). Sizing agent application | coating carbon fiber in any one of Claim 1 or 2 whose said vinyl compound is styrene. Sizing agent application | coating carbon fiber in any one of Claims 1-3 whose rubber-like copolymer (B) is a styrene butadiene copolymer. Sizing agent application | coating carbon fiber in any one of Claims 1-4 whose glass transition temperature of a rubber-like copolymer (B) is larger than 25 degreeC, and is 100 degrees C or less. The sizing according to any one of claims 1 to 5, wherein the aliphatic epoxy compound (A) is a compound having two or more epoxy groups in a molecule, and is a polyether type polyepoxy compound or a polyol type polyepoxy compound. Agent coated carbon fiber. Glycidyl obtained by reacting an aliphatic epoxy compound (A) with one or more compounds selected from glycerin, diglycerin, polyglycerin, trimethylolpropane, pentaerythritol, sorbitol, and arabitol, and epichlorohydrin Sizing agent application | coating carbon fiber in any one of Claims 1-6 which is an ether type epoxy compound. A method for producing a sizing agent-coated carbon fiber by applying heat treatment after applying a sizing agent containing at least the following (A) and (B), and in the step of applying the sizing agent, the adhesion amount of the sizing agent is The sizing agent-applied carbon fiber is 100 parts by mass to be 0.1 parts by mass or more and 5 parts by mass or less, and the conditions for the heat treatment are 160 to 260 ° C. for 30 to 600 seconds, The manufacturing method of the sizing agent application | coating carbon fiber in any one of Claims 1-7.
(A) Aliphatic epoxy compound (B) A rubbery copolymer having no epoxy group, which is polymerized using a vinyl compound having at least an aromatic skeleton as a copolymerization component A prepreg comprising the sizing agent-coated strong carbon fiber according to claim 1 and a thermosetting resin. The prepreg according to claim 9, wherein the thermosetting resin is an epoxy resin. A carbon fiber reinforced composite material obtained by curing the prepreg according to claim 9 or 10. A carbon fiber reinforced composite material comprising a sizing agent-coated carbon fiber according to any one of claims 1 to 7 and a cured product of a thermosetting resin. The carbon fiber reinforced composite material according to claim 12, wherein the thermosetting resin is an epoxy resin.