JP4924768B2 - Method for producing carbon fiber coated with sizing agent - Google Patents

Description

  The present invention relates to a method for producing carbon fiber that is suitably used for aircraft members, spacecraft members, automobile members, ship members, and the like. More specifically, the present invention relates to a method for producing a sizing agent-coated carbon fiber that is excellent in adhesion to a matrix resin and excellent in high-order processability.

  Since carbon fiber is lightweight but excellent in strength and elastic modulus, composite materials combining this with various matrix resins are aircraft members, spacecraft members, automobile members, ship members, civil engineering and building materials, and sporting goods. It is used in many fields. In a composite material using carbon fibers, in order to make use of the excellent properties of carbon fibers, it is important that the adhesion between the carbon fibers and the matrix resin is excellent.

  In order to improve the adhesion between the carbon fiber and the matrix resin, a method of introducing an oxygen-containing functional group on the surface of the carbon fiber is usually performed by subjecting the carbon fiber to oxidation treatment such as gas phase oxidation or liquid phase oxidation. . For example, a method has been proposed in which the interlaminar shear strength, which is an index of adhesion, is improved by subjecting carbon fibers to electrolytic treatment (see Patent Document 1). However, in recent years, as the level of required properties for composite materials has improved, the adhesion that can be achieved by such oxidation treatment alone is becoming insufficient.

  On the other hand, since carbon fiber is brittle and has poor convergence and friction resistance, fluff and yarn breakage are likely to occur in the high-order processing step. For this reason, the method of apply | coating a sizing agent to carbon fiber is performed normally.

  For example, a method of applying diglycidyl ether of bisphenol A as a sizing agent to carbon fibers has been proposed (see Patent Documents 2 and 3). In addition, a method of applying a polyalkylene oxide adduct of bisphenol A as a sizing agent to carbon fibers has been proposed (see Patent Documents 4 and 5). Moreover, the method of apply | coating what added the epoxy group to the polyalkylene oxide addition product of bisphenol A as a sizing agent to carbon fiber is proposed (refer patent document 6 and 7). Furthermore, a method of applying an epoxy adduct of polyalkylene glycol as a sizing agent to carbon fibers has been proposed (see Patent Documents 8, 9 and 10).

  According to these methods, it is known that the converging property and friction resistance of the carbon fiber are improved. However, these conventional proposals do not have a technical idea of positively improving the adhesion between the carbon fiber and the matrix resin by using a sizing agent, and actually greatly improve the adhesion between the carbon fiber and the matrix resin. I couldn't make it.

  Separately, a method of applying a urethane compound having an epoxy group and a quaternary ammonium salt as a sizing agent to carbon fibers has been proposed (see Patent Document 11). Even with this proposed method, the convergence and friction resistance are improved, but the adhesion between the carbon fiber and the matrix resin cannot be improved.

  As described above, the sizing agent is conventionally used as a so-called paste agent for the purpose of improving the high-order workability, and the sizing agent has hardly been studied to improve the adhesion between the carbon fiber and the matrix resin. . Further, even in the case where the adhesiveness is studied, the effect of improving the adhesiveness is insufficient, or the effect is expressed only when combined with a special carbon fiber.

  For example, a method of applying N, N, N ′, N′-tetraglycidylmetaxylylenediamine as a sizing agent to carbon fibers has been proposed (see Patent Document 12). However, this proposed method has been shown to improve the interlaminar shear strength, which is an index of adhesion, compared to the case of using diglycidyl ether of bisphenol, but the effect of improving adhesion is still insufficient. Met. In addition, N, N, N ′, N′-tetraglycidylmetaxylylenediamine used in this proposal contains an aliphatic tertiary amine in the skeleton and has nucleophilicity. In particular, there is a problem that the carbon fiber bundle becomes hard and the high-order workability is lowered.

  Further, carbon fibers having surface oxygen concentration O / C, surface hydroxyl group concentration and carboxyl group concentration within specific ranges are used, and an aliphatic compound having a plurality of epoxy groups is applied to the carbon fiber as a sizing agent. Has been proposed (see Patent Document 13). However, this proposed method shows that EDS, which is an index of adhesion, is improved. However, the effect of improving the adhesion between the carbon fiber and the matrix resin is still insufficient, and the adhesion is not improved. The improvement effect was limited to be manifested only when combined with special carbon fibers.

Japanese Patent Laid-Open No. 04-361619 Japanese Patent Laid-Open No. 50-059589 JP-A-57-171767 JP 07-009444 A JP 2000-336577 A JP 61-028074 A Japanese Patent Laid-Open No. 01-272867 JP-A-57-128266 JP 59-009273 A JP 62-033872 A JP 58-013781 A JP 52-059794 A Japanese Patent Laid-Open No. 07-279040

  Accordingly, an object of the present invention is to provide a method for producing a sizing agent-coated carbon fiber that is excellent in adhesion between the carbon fiber and the matrix resin and excellent in high-order workability in view of the problems in the above-described conventional technology. is there.

  The present inventors have a bifunctional or higher functional epoxy compound and / or a monofunctional or higher functional epoxy group as a sizing agent, a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, and a sulfo group. When a sizing agent containing an epoxy compound having at least one functional group and a specific quaternary ammonium salt in a specific ratio is applied to the carbon fiber and heat-treated at a specific temperature and time, the carbon fiber and the matrix The present inventors have found that the adhesiveness with a resin can be improved and have arrived at the present invention.

  That is, the present invention has a bifunctional or higher functional epoxy compound (A1) and / or a monofunctional or higher functional epoxy group as the component (A), a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group. And at least the following general formula (I) or (II) as component (B) with respect to 100 parts by mass of the epoxy compound (A2) having at least one functional group selected from a group and a sulfo group

(In the above formula, R _{1 to} R ₅ represent a hydrocarbon group having 1 to 22 carbon atoms, a group having 1 to 22 carbon atoms and an ether structure, a hydrocarbon having 1 to 22 carbon atoms and an ester structure, respectively. Or a group containing a hydrocarbon having 1 to 22 carbon atoms and a hydroxyl group, and R ₆ and R ₇ are each a hydrogen atom, a hydrocarbon group having 1 to 8 carbon atoms, or a carbon atom having 1 to 8 carbon atoms. (B) a sizing containing a quaternary ammonium salt having a cation moiety represented by any one of a group containing hydrogen and an ether structure, or a group containing a hydrocarbon having 1 to 8 carbon atoms and an ester structure. A sizing agent-coated carbon fiber is produced by applying a sizing agent containing 0.1 to 25 parts by mass of an agent to carbon fiber and heat-treating it in a temperature range of 160 to 260 ° C. for 30 to 600 seconds.

According to a preferred aspect of the manufacturing method of sizing agent coated carbon fiber of the present invention, R ₁ and R ₂ of the general formula (I) are each a hydrocarbon group having 1 to 22 carbon atoms, 1 to 22 carbon atoms It represents either a group containing a hydrocarbon and an ether structure, or a group containing a hydrocarbon having 1 to 22 carbon atoms and an ester structure, and R ₃ and R ₄ are each a hydrocarbon group having 2 to 22 carbon atoms and a carbon number. Represents a group containing 2 to 22 hydrocarbons and an ether structure, a group containing 2 to 22 carbon atoms and an ester structure, or a group containing 2 to 22 carbon atoms and a hydroxyl group, R _{5 in the} general formula (II) is a hydrocarbon group having 1 to 22 carbon atoms, a group containing a hydrocarbon having 1 to 22 carbon atoms and an ether structure, a group containing a hydrocarbon having 1 to 22 carbon atoms and an ester structure, Or containing a hydrocarbon having 1 to 22 carbon atoms and a hydroxyl group It represents either, R ₆ and R ₇ are each hydrogen, a hydrocarbon group having 1 to 8 carbon atoms, a group containing a hydrocarbon and an ether structure having 1 to 8 carbon atoms or a hydrocarbon of 1 to 8 carbon atoms, And a group containing an ester structure.

  According to a preferred embodiment of the method for producing a sizing agent-coated carbon fiber of the present invention, the carbon fiber is subjected to an electrolytic treatment in an alkaline aqueous solution, or the carbon fiber is subjected to an electrolytic treatment in an acidic aqueous solution, followed by an alkaline aqueous solution. After cleaning, a sizing agent is applied.

  According to a preferred embodiment of the method for producing a sizing agent-coated carbon fiber of the present invention, the (A) epoxy compound is a trifunctional or higher functional epoxy resin containing three or more epoxy groups in the molecule.

  According to the preferable aspect of the manufacturing method of the sizing agent application | coating carbon fiber of this invention, the said (A) epoxy compound is that an aromatic ring is included in a molecule | numerator.

  According to the preferable aspect of the manufacturing method of the sizing agent application | coating carbon fiber of this invention, the said (A) epoxy compound is either a phenol novolak-type epoxy resin, a cresol novolak-type epoxy resin, or tetraglycidyl diamino diphenylmethane. is there.

  According to the preferable aspect of the manufacturing method of the sizing agent application | coating carbon fiber of this invention, the surface oxygen concentration O / C measured by the X ray electron spectroscopy of the said carbon fiber is 0.05-0.30.

  According to the present invention, a bifunctional or higher functional epoxy compound and / or a monofunctional or higher functional epoxy group is selected from a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, and a sulfo group. In the sizing agent mainly composed of an epoxy compound having at least one functional group, a specific amount of a specific quaternary ammonium salt is blended, and only when the heat treatment is performed under specific conditions, the epoxy compound and The formation of a covalent bond is promoted between the carboxyl group and the oxygen-containing functional group such as a hydroxyl group originally contained in the carbon fiber surface or introduced by oxidation treatment. Thereby, when a specific quaternary ammonium salt is not blended, even if a specific quaternary ammonium salt is blended, if the blending amount is out of a specific range, even if a specific quaternary ammonium salt is blended, from a specific heat treatment condition Compared with the case where it comes off, it is possible to obtain sizing agent-coated carbon fibers that have significantly improved adhesion to the matrix resin. In addition, the sizing agent-coated carbon fiber obtained by the production method of the present invention has excellent bundling properties and scratch resistance, and therefore has excellent workability to fabrics and prepregs. Since the carbon fiber reinforced composite material obtained from the sizing agent-coated carbon fiber and the matrix resin is lightweight and excellent in strength and elastic modulus, the aircraft member, spacecraft member, automobile member, ship member, civil engineering building material, and It can be suitably used in many fields such as sports equipment.

  Next, the form for implementing the manufacturing method of the sizing agent application | coating carbon fiber of this invention is demonstrated.

  The present invention has a bifunctional or higher functional epoxy compound (A1) and / or a monofunctional or higher functional epoxy group as the component (A), a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, And at least one of the following general formula (I) or (II) with respect to 100 parts by mass of the epoxy compound (A2) having at least one functional group selected from sulfo groups

(In the above formula, R _{1 to} R ₅ represent a hydrocarbon group having 1 to 22 carbon atoms, a group having 1 to 22 carbon atoms and an ether structure, a hydrocarbon having 1 to 22 carbon atoms and an ester structure, respectively. Or a group containing a hydrocarbon having 1 to 22 carbon atoms and a hydroxyl group, and R ₆ and R ₇ are each a hydrogen atom, a hydrocarbon group having 1 to 8 carbon atoms, or a carbon atom having 1 to 8 carbon atoms. (B) a quaternary ammonium salt having a cation moiety represented by any one of a group containing hydrogen and an ether structure or a group containing a hydrocarbon having 1 to 8 carbon atoms and an ester structure) A sizing agent-coated carbon fiber is produced by applying a sizing agent containing 25 parts by mass to carbon fiber and heat-treating it at a temperature range of 160 to 260 ° C. for 30 to 600 seconds.

  (A1) used in the present invention is a compound having two or more epoxy groups in the molecule.

  (A2) used in the present invention has at least one functional epoxy group, and is selected from a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, and a sulfo group. It is an epoxy compound having a functional group.

  The mechanism by which the adhesion is improved by applying a sizing agent containing a specific amount of (A) and (B) to carbon fiber and heat-treating it under specific conditions is not certain, but first, the fourth grade of component (B) After the ammonium salt extracts and anionizes the hydrogen ion of the oxygen-containing functional group such as the carboxyl group and hydroxyl group of the carbon fiber used in the present invention, the anionized functional group and the epoxy group contained in the component (A) are nucleophilic. It is thought to react. Thereby, the strong coupling | bonding of the carbon fiber and epoxy which are used by this invention is formed. On the other hand, in relation to the matrix resin, each of (A1) and (A2) will be described as follows.

  In the case of (A1), it is considered that the remaining epoxy groups not participating in the covalent bond with the carbon fiber used in the present invention react with the matrix resin-containing functional group to form a covalent bond, or form a hydrogen bond. It is done. In particular, when the matrix resin is an epoxy resin, it is considered that a strong interface can be formed by the reaction between the epoxy group of (A1) and the epoxy group of the matrix resin, or the reaction via the amine curing agent contained in the epoxy resin. . The structure (A1) preferably contains one or more unsaturated groups. When the matrix resin is a radical polymerization resin such as an unsaturated polyester resin or vinyl ester resin, the unsaturation of (A1) It is possible for the unsaturated group of the group and the matrix resin to undergo a radical reaction to form a strong interface.

  In the case of (A2), the epoxy group of (A2) forms a covalent bond with an oxygen-containing functional group such as a carboxyl group and a hydroxyl group of the carbon fiber used in the present invention, but the remaining hydroxyl group, amide group, imide group, urethane A group, a urea group, a sulfonyl group, or a sulfo group is considered to form an interaction such as a covalent bond or a hydrogen bond depending on the matrix resin. If the matrix resin is an epoxy resin, the hydroxyl group, amide group, imide group, urethane group, urea group, sulfonyl group, or sulfo group of (A2) reacts with the epoxy group of the matrix resin or the amine curing agent and the epoxy group. It is considered that a strong interface can be formed by the interaction with the hydroxyl group thus formed. Further, if the matrix resin is a thermoplastic resin typified by polyamide, polyester and acid-modified polyolefin, (A2) hydroxyl group, amide group, imide group, urethane group, urea group, sulfonyl group, or sulfo group It is considered that a strong interface can be formed by the interaction with amide groups, ester groups, acid anhydride groups, carboxyl groups such as terminals, hydroxyl groups, and amino groups contained in these matrix resins.

  That is, in the case of (A1), the remaining epoxy group not involved in the covalent bond with the carbon fiber is the hydroxyl group, amide group, imide group, urethane group, urea group, sulfonyl group, or sulfo group in the case of (A2). It is considered to have a function corresponding to the group.

  In the present invention, the (A) epoxy compound is preferably a trifunctional or higher functional epoxy compound, and more preferably a tetrafunctional or higher functional epoxy compound. (A) When the epoxy compound is a tri- or higher functional epoxy epoxy having three or more epoxy groups in the molecule, even when one epoxy group forms a covalent bond with an oxygen-containing functional group on the carbon fiber surface The remaining two or more epoxy groups can form a covalent bond with the matrix resin, and the adhesion is further improved. As for the upper limit of the number of epoxy groups, the adhesiveness may be saturated with 10 or more.

  In the present invention, the epoxy equivalent of the (A) epoxy compound is preferably less than 360 g / mol, more preferably less than 270 g / mol, and even more preferably less than 180 g / mol. When the epoxy equivalent is less than 360 g / mol, covalent bonds are formed at a high density, and the adhesion between the carbon fiber and the matrix resin is further improved. About the lower limit of an epoxy equivalent, adhesiveness may be saturated at less than 90 g / mol.

  In the present invention, the (A) epoxy compound preferably has one or more aromatic rings, and more preferably has two or more aromatic rings. In a fiber-reinforced composite material composed of carbon fibers and a matrix resin, a so-called interface layer in the vicinity of the carbon fibers may be affected by the carbon fibers or the sizing agent and have different characteristics from the matrix resin. (A) When the epoxy compound has one or more aromatic rings, a rigid boundary layer is formed, the stress transmission ability between the carbon fiber and the matrix resin is improved, and the fiber reinforced composite material has a 0 ° tensile strength, etc. Mechanical properties are improved. With respect to the upper limit of the number of aromatic rings, the mechanical characteristics may be saturated when the number is 10 or more.

  In the present invention, the (A) epoxy compound is preferably a phenol novolac type epoxy resin, a cresol novolac type epoxy resin, or tetraglycidyl diaminodiphenylmethane. These epoxy resins have a large number of epoxy groups, a small epoxy equivalent, and have two or more aromatic rings. In addition to improving the adhesion between carbon fiber and matrix resin, fiber reinforced composite materials Improve mechanical properties such as 0 ° tensile strength. More preferred are phenol novolac epoxy resins and cresol novolac epoxy resins.

  In the present invention, specific examples of the (A1) bifunctional or higher functional epoxy compound include, for example, a glycidyl ether type epoxy resin derived from a polyol, a glycidyl amine type epoxy resin derived from an amine having a plurality of active hydrogens, and a polycarboxylic acid. Examples thereof include a glycidyl ester type epoxy resin derived from an acid and an epoxy resin obtained by oxidizing a compound having a plurality of double bonds in the molecule.

  Examples of the glycidyl ether type epoxy resin include bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetrabromobisphenol A, phenol novolac, cresol novolac, hydroquinone, resorcinol, 4,4′-dihydroxy-3,3 ′, 5. , 5′-tetramethylbiphenyl, 1,6-dihydroxynaphthalene, 9,9-bis (4-hydroxyphenyl) fluorene, tris (p-hydroxyphenyl) methane, and tetrakis (p-hydroxyphenyl) ethane with epichlorohydrin Examples thereof include glycidyl ether type epoxy resins obtained by the reaction.

  Furthermore, as the glycidyl ether type epoxy resin, for example, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, polypropylene glycol, trimethylene glycol, 1 , 2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, polybutylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1 , 4-cyclohexanedimethanol, hydrogenated bisphenol A, hydrogenated bisphenol F, glycerol, diglycerol, polyglycerol, trimethylol propylene , Pentaerythritol, sorbitol, and arabitol and include glycidyl ether type epoxy resins obtained by reaction of epichlorohydrin. Moreover, the glycidyl ether type epoxy resin which has a dicyclopentadiene frame | skeleton, and the glycidyl ether type epoxy resin which has a biphenyl aralkyl frame | skeleton are mentioned.

  Examples of the glycidylamine type epoxy resin include N, N-diglycidylaniline, N, N-diglycidyl-o-toluidine, 1,3-bis (aminomethyl) cyclohexane, m-xylylenediamine, m-phenylenediamine, 4,4′-diaminodiphenylmethane, and 9,9-bis (4-aminophenyl) fluorene.

  Furthermore, as a glycidylamine type epoxy resin, for example, both the hydroxyl group and amino group of aminophenols of m-aminophenol, p-aminophenol, and 4-amino-3-methylphenol are reacted with epichlorohydrin. The obtained epoxy resin is mentioned.

  Examples of the glycidyl ester type epoxy resin include glycidyl ester type epoxy resins obtained by reacting phthalic acid, terephthalic acid, hexahydrophthalic acid, dimer acid and the like with epichlorohydrin.

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

  In addition to these epoxy resins, epoxy resins such as triglycidyl isocyanurate can be mentioned. Furthermore, the epoxy resin synthesize | combined from the epoxy resin mentioned above as a raw material, for example, the epoxy resin synthesize | combined by the oxazolidone ring formation reaction from bisphenol A diglycidyl ether and tolylene diisocyanate is mentioned.

  In the present invention, (A2) has at least one functional epoxy group, and has at least one functional group selected from a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, and a sulfo group. Specific examples of the epoxy compound include, for example, a compound having an epoxy group and a hydroxyl group, a compound having an epoxy group and an amide group, an epoxy group and an imide group, a compound having an epoxy group and a urethane group, a compound having an epoxy group and a urea group, Examples thereof include compounds having an epoxy group and a sulfonyl group, and compounds having an epoxy group and a sulfo group.

  Examples of the compound having an epoxy group and a hydroxyl group include sorbitol-type polyglycidyl ether and glycerol-type polyglycidyl ether. Specifically, Denacol (registered trademark) EX-611, EX-612, EX-614, EX -614B, EX-622, EX-512, EX-521, EX-421, EX-313, EX-314 and EX-321 (manufactured by Nagase ChemteX Corporation).

  Examples of the compound having an epoxy group and an amide group include glycamide and amide-modified epoxy resins. An amide-modified epoxy can be obtained by reacting an epoxy group of a bifunctional or higher epoxy resin 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 (trademark registration) EX-731 (made by Nagase ChemteX Corporation) etc. are mentioned.

  Examples of the compound having an epoxy group and a urethane group include a urethane-modified epoxy resin. Specifically, Adeka Resin (registered trademark) EPU-78-13S, EPU-6, EPU-11, EPU-15, EPU- 16A, EPU-16N, EPU-16A, EPU-17T-6, EPU-1348, EPU-1395 (manufactured by ADEKA Corporation) and the like. Alternatively, by reacting the terminal hydroxyl group of the polyethylene oxide monoalkyl ether with a polyvalent isocyanate equivalent to the amount of the hydroxyl group, and then reacting the isocyanate residue of the obtained reaction product with the hydroxyl group in the polyvalent epoxy resin. Obtainable. Here, as the polyvalent isocyanate used, 2,4-tolylene diisocyanate, metaphenylene diisocyanate, paraphenylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, norbornane diisocyanate, triphenylmethane triisocyanate and biphenyl-2, Examples include 4,4′-triisocyanate.

  Examples of the compound having an epoxy group and a urea group include a urea-modified epoxy resin. The amide-modified epoxy can be obtained by reacting the epoxy group of the bifunctional or higher epoxy resin with the carboxyl group of the dicarboxylic acid urea.

  Examples of the compound having an epoxy group and a sulfonyl group include bisphenol S-type epoxy.

  Examples of the compound having an epoxy group and a sulfo group include glycidyl p-toluenesulfonate and glycidyl 3-nitrobenzenesulfonate.

  The quaternary ammonium salt (B) having a cation moiety used in the present invention has the following general formula (I) or (II):

(In the above formula, R _{1 to} R ₅ represent a hydrocarbon group having 1 to 22 carbon atoms, a group having 1 to 22 carbon atoms and an ether structure, a hydrocarbon having 1 to 22 carbon atoms and an ester structure, respectively. Or a group containing a hydrocarbon having 1 to 22 carbon atoms and a hydroxyl group, and R ₆ and R ₇ are each a hydrogen atom, a hydrocarbon group having 1 to 8 carbon atoms, or a carbon atom having 1 to 8 carbon atoms. It represents a quaternary ammonium salt having a cation moiety represented by any one of a group containing hydrogen and an ether structure, or a group containing a hydrocarbon having 1 to 8 carbon atoms and an ester structure. is there.

  The present inventors have a bifunctional or higher functional epoxy compound and / or a monofunctional or higher functional epoxy group, and are selected from a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, and a sulfo group. In the sizing agent mainly composed of an epoxy compound having at least one functional group, the cation moiety (B) represented by any one of the above general formulas (I) and (II) with respect to 100 parts by mass of the epoxy compound The epoxy compound and the carbon fiber are used only when the sizing agent containing 0.1 to 25 parts by mass of the quaternary ammonium salt having the above is applied to the carbon fiber and heat-treated under specific conditions. Facilitates the formation of covalent bonds between carboxyl groups, hydroxyl groups and other oxygen-containing functional groups originally contained on the surface or introduced by oxidation treatment The result, it was found that the adhesion to the matrix resin can be greatly improved.

In the present invention, the mechanism by which covalent bond formation is promoted by the incorporation of a quaternary ammonium salt is not clear, but such an effect can be obtained only with a quaternary ammonium salt having a specific structure. Therefore, R _{1 to} R ₅ in the above general formula (I) or (II) are each a hydrocarbon group having 1 to 22 carbon atoms, a group having 1 to 22 carbon atoms and an ether structure, It must be either a group containing an ester structure of 22 or a group containing a hydrocarbon having 1 to 22 carbon atoms and a hydroxyl group. When the carbon number is 23 or more, the reason is not clear, but the adhesiveness is insufficient.

  Here, a C1-C22 hydrocarbon group is a group which consists only of a carbon atom and a hydrogen atom, and any of a saturated hydrocarbon group and an unsaturated hydrocarbon group may be included, even if it contains a ring structure. Also good. As the hydrocarbon group, for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, cyclohexyl group, octyl group, decyl group, dodecyl group, tetradecyl group, hexadecyl group, octadecyl group, oleyl group, A docosyl group, a benzyl group, a phenyl group, etc. are mentioned.

  Examples of the group containing a hydrocarbon having 1 to 22 carbon atoms and an ether structure include a methoxymethyl group, an ethoxymethyl group, a propoxymethyl group, a butoxymethyl group, a phenoxymethyl group, a methoxyethyl group, an ethoxyethyl group, and a propoxy group. Examples thereof include polyether groups such as ethyl group, butoxyethyl group, phenoxyethyl group, methoxyethoxymethyl group, methoxyethoxyethyl group, polyethylene glycol group, and polypropylene glycol group.

  Examples of the group containing a hydrocarbon having 1 to 22 carbon atoms and an ester structure include an acetoxymethyl group, an acetoxyethyl group, an acetoxypropyl group, an acetoxybutyl group, a methacryloyloxyethyl group, and a benzoyloxyethyl group. It is done.

  Examples of the group containing a hydrocarbon having 1 to 22 carbon atoms and a hydroxyl group include a hydroxymethyl group, a hydroxyethyl group, a hydroxypropyl group, a hydroxybutyl group, a hydroxypentyl group, a hydroxyhexyl group, a hydroxycyclohexyl group, and a hydroxyoctyl group. Group, hydroxydecyl group, hydroxydodecyl group, hydroxytetradecyl group, hydroxyhexadecyl group, hydroxyoctadecyl group, hydroxyoleyl group, hydroxydocosyl group and the like.

Especially, it is preferable that the carbon number of R < ₁ > -R < ₅ > of the quaternary ammonium salt which has a cation part (B) exists in the range of 1-14, More preferably, it exists in the range of 1-8. When the carbon number is less than 14, when the quaternary ammonium salt acts as a reaction accelerator, the steric hindrance is moderately small and the reaction promoting effect is enhanced, and the adhesion is further improved.

In the present invention, the number of carbon atoms of R ₃ and R ₄ of the quaternary ammonium salt having a cation moiety (B) represented by the general formula (I) is preferably 2 or more, more preferably 3 or more. More preferably, it is 4 or more. When the carbon number is 2 or more, homopolymerization of the epoxy resin due to the quaternary ammonium salt acting as an initiator is suppressed, and the adhesiveness is further improved.

In the present invention, R ₆ and R ₇ of the quaternary ammonium salt (B) having a cation moiety represented by the above general formula (II) are each hydrogen, a hydrocarbon group having 1 to 8 carbon atoms, or 1 carbon atom. It is preferably any one of a group containing ˜8 hydrocarbon and an ether structure, or a group containing a hydrocarbon having 1 to 8 carbon atoms and an ester structure. When hydrogen or the number of carbon atoms is less than 8, the ratio of active sites in the molecule is high, and a large adhesion improvement effect can be obtained even with a small amount.

  In the present invention, the molecular weight of the cation moiety of the (B) quaternary ammonium salt having a cation moiety is preferably in the range of 100 to 400 g / mol, more preferably in the range of 100 to 300 g / mol. More preferably, it is in the range of 100 to 200 g / mol. When the molecular weight of the cation moiety is 100 g / mol or more, volatilization is suppressed even during the heat treatment, and a large adhesive improvement effect can be obtained even with a small amount. On the other hand, when the molecular weight of the cation moiety is 400 g / mol or less, the ratio of the active moiety in the molecule is high, and a large adhesion improvement effect can be obtained even with a small amount.

  In the present invention, examples of the cation moiety of the quaternary ammonium salt represented by the general formula (I) include tetramethylammonium, ethyltrimethylammonium, trimethylpropylammonium, butyltrimethylammonium, trimethylpentylammonium, hexyltrimethylammonium, Cyclohexyltrimethylammonium, trimethyloctylammonium, decyltrimethylammonium, dodecyltrimethylammonium, tetradecyltrimethylammonium, hexadecyltrimethylammonium, trimethyloctadecylammonium, trimethyloleylammonium, docosyltrimethylammonium, benzyltrimethylammonium, trimethylphenylammonium, diethyldimethylammonium Dimethyl, dimethyldipropylammonium, dibutyldimethylammonium, dimethyldipentylammonium, dihexyldimethylammonium, dicyclohexyldimethylammonium, dimethyldioctylammonium, didecyldimethylammonium, ethyldecyldimethylammonium, didodecyldimethylammonium, ethyldodecyldimethylammonium, ditetradecyl Dimethyl ammonium, ethyl tetradecyl dimethyl ammonium, dihexadecyl dimethyl ammonium, ethyl hexadecyl dimethyl ammonium, dimethyl dioctadecyl ammonium, ethyl octadecyl dimethyl ammonium, dimethyl dioleyl ammonium, ethyl dimethyl oleyl ammonium, didocosyl dimethyl ammonium, Silethyldimethylammonium, dibenzyldimethylammonium, benzylethyldimethylammonium, benzyldimethylpropylammonium, benzylbutyldimethylammonium, benzyldecyldimethylammonium, benzyldodecyldimethylammonium, benzyltetradecyldimethylammonium, benzylhexadecyldimethylammonium, benzyloctadecyldimethyl Ammonium, benzyldimethyloleylammonium, dimethyldiphenylammonium, ethyldimethylphenylammonium, dimethylpropylphenylammonium, butyldimethylphenylammonium, decyldimethylphenylammonium, dodecyldimethylphenylammonium, tetradecyldimethylphenylammonium , Hexadecyldimethylphenylammonium, dimethyloctadecylphenylammonium, dimethyloleylphenylammonium, tetraethylammonium, triethylmethylammonium, triethylpropylammonium, butyltriethylammonium, triethylpentylammonium, triethylhexylammonium, triethylcyclohexylammonium, triethyloctylammonium, decyl Triethylammonium, dodecyltriethylammonium, tetradecyltriethylammonium, hexadecyltriethylammonium, triethyloctadecylammonium, triethyloleylammonium, benzyltriethylammonium, triethylphenylammonium, diethyldipropylan Ni, dibutyl diethyl ammonium, diethyl dipentyl ammonium, diethyl dihexyl ammonium, diethyl dicyclohexyl ammonium, diethyl dioctyl ammonium, didecyl diethyl ammonium, didodecyl diethyl ammonium, ditetradecyl diethyl ammonium, diethyl dihexadecyl ammonium, diethyl dioctadecyl ammonium, diethyl Dioleylammonium, dibenzyldiethylammonium, diethyldiphenylammonium, tetrapropylammonium, methyltripropylammonium, ethyltripropylammonium, butyltripropylammonium, benzyltripropylammonium, phenyltripropylammonium, tetrabutylammonium, tributy Methylammonium, tributylethylammonium, tributylpropylammonium, benzyltributylammonium, tributylphenylammonium, tetrapentylammonium, tetrahexylammonium, tetraheptylammonium, tetraoctylammonium, methyltrioctylammonium, ethyltrioctylammonium, trioctylpropylammonium, Butyl trioctyl ammonium, dimethyl dioctyl ammonium, diethyl dioctyl ammonium, dioctyl dipropyl ammonium, dibutyl dioctyl ammonium, tetradecyl ammonium, tetradodecyl ammonium, 2-hydroxyethyl trimethyl ammonium, 2-hydroxyethyl triethyl ammonium, 2-hy Droxyethyltripropylammonium, 2-hydroxyethyltributylammonium, polyoxyethylenetrimethylammonium, polyoxyethylenetriethylammonium, polyoxyethylenetripropylammonium, polyoxyethylenetributylammonium, bis (2-hydroxyethyl) dimethylammonium, bis (2-hydroxyethyl) diethylammonium, bis (2-hydroxyethyl) dipropylammonium, bis (2-hydroxyethyl) dibutylammonium, bis (polyoxyethylene) dimethylammonium, bis (polyoxyethylene) diethylammonium, bis ( Polyoxyethylene) dipropylammonium, bis (polyoxyethylene) dibutylammonium, tris (2-hydride) Xylethyl) methylammonium, tris (2-hydroxyethyl) ethylammonium, tris (2-hydroxyethyl) propylammonium, tris (2-hydroxyethyl) butylammonium, tris (polyoxyethylene) methylammonium, tris (polyoxyethylene) Examples include ethylammonium, tris (polyoxyethylene) propylammonium, and tris (polyoxyethylene) butylammonium.

  Examples of the cation moiety of the quaternary ammonium salt represented by the general formula (II) include 1-methylpyridinium, 1-ethylpyridinium, 1-ethyl-2-methylpyridinium, and 1-ethyl-4-methylpyridinium. 1-ethyl-2,4-dimethylpyridinium, 1-ethyl-2,4,6-trimethylpyridinium, 1-propylpyridinium, 1-butylpyridinium, 1-butyl-2-methylpyridinium, 1-butyl-4- Methylpyridinium, 1-butyl-2,4-dimethylpyridinium, 1-butyl-2,4,6-trimethylpyridinium, 1-pentylpyridinium, 1-hexylpyridinium, 1-cyclohexylpyridinium, 1-octylpyridinium, 1-decyl Pyridinium, 1-dodecylpyridinium, - tetradecyl pyridinium, 1-hexadecyl pyridinium, 1-octadecyl pyridinium, 1-oleyl pyridinium, and 1-docosyl pyridinium, and 1-benzyl pyridinium and the like.

  In the present invention, examples of the anion moiety of the (B) quaternary ammonium salt having a cation moiety include halogen ions of fluoride anion, chloride anion, bromide anion and iodide anion. Examples thereof include a hydroxide anion, an acetate anion, an oxalate anion, a sulfate anion, a benzenesulfonate anion, and a toluenesulfonate anion.

  Especially, as a counter ion, it is preferable that it is a halogen ion from a viewpoint that the size is small and it does not inhibit the reaction promotion effect of a quaternary ammonium salt.

  In the present invention, these quaternary ammonium salts may be used alone or in combination.

  In the present invention, (B) quaternary ammonium salts having a cation moiety include, for example, trimethyloctadecylammonium chloride, trimethyloctadecylammonium bromide, trimethyloctadecylammonium hydroxide, trimethyloctadecylammonium acetate, trimethyloctadecylammonium benzoate, trimethyl Octadecylammonium-p-toluenesulfonate, trimethyloctadecylammonium hydrochloride, trimethyloctadecylammonium tetrachloroiodate, trimethyloctadecylammonium hydrogensulfate, trimethyloctadecylammonium methylsulfate, benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, benzyltrimethyl Ammonium hydroxide, benzyltrimethylammonium acetate, benzyltrimethylammonium benzoate, benzyltrimethylammonium-p-toluenesulfonate, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium hydroxide, tetrabutylammonium acetate, tetra Butylammonium benzoate, tetrabutylammonium-p-toluenesulfonate, (2-methoxyethoxymethyl) triethylammonium chloride, (2-methoxyethoxymethyl) triethylammonium bromide, (2-methoxyethoxymethyl) triethylammonium hydroxide, (2-Methoxyethoxymethyl) triethylammonium-p-toluenesulfonate (2-acetoxyethyl) trimethylammonium chloride, (2-acetoxyethyl) trimethylammonium bromide, (2-acetoxyethyl) trimethylammonium hydroxide, (2-acetoxyethyl) trimethylammonium-p-toluenesulfonate, (2-hydroxy Ethyl) trimethylammonium chloride, (2-hydroxyethyl) trimethylammonium bromide, (2-hydroxyethyl) trimethylammonium hydroxide, (2-hydroxyethyl) trimethylammonium-p-toluenesulfonate, bis (polyoxyethylene) dimethylammonium Chloride, bis (polyoxyethylene) dimethylammonium bromide, bis (polyoxyethylene) dimethylammonium hydroxide, (Polyoxyethylene) dimethylammonium-p-toluenesulfonate, 1-hexadecylpyridinium chloride, 1-hexadecylpyridinium bromide, 1-hexadecylpyridinium hydroxide, 1-hexadecylpyridinium-p-toluenesulfonate, etc. Is mentioned.

  In the sizing agent used in the present invention, (A) a quaternary ammonium salt having a cation moiety represented by any one of the above general formulas (I) and (II) with respect to 100 parts by mass of the epoxy compound. It is necessary to mix 0.1 to 25 parts by mass, and (B) the amount of the quaternary ammonium salt having a cation moiety is preferably 0.1 to 10 parts by mass, more preferably 0.1 to 10 parts by mass. 8 parts by mass. (B) When the amount of the quaternary ammonium salt having a cation moiety is less than 0.1 parts by mass, (A) covalent bond formation between the epoxy compound and the oxygen-containing functional group on the carbon fiber surface is not promoted, and carbon Adhesion between the fiber and the matrix resin becomes insufficient. On the other hand, if the blending amount of (B) quaternary ammonium salt having a cation moiety exceeds 25 parts by mass, (B) the quaternary ammonium salt having a cation moiety covers the carbon fiber surface and the formation of a covalent bond is inhibited. Adhesion between the fiber and the matrix resin becomes insufficient.

  The sizing agent used in the present invention comprises (A) an epoxy compound and other components other than the quaternary ammonium salt having a cation moiety (B) represented by any one of the above general formulas (I) and (II). One or more types may be included.

  Examples of such other components include polyalkylene oxides such as polyethylene oxide and polypropylene oxide, polyalkylene oxides such as polyethylene oxide and polypropylene oxide added to higher alcohols, polyhydric alcohols, alkylphenols, and styrenated phenols. Nonionic surfactants such as compounds and block copolymers of ethylene oxide and propylene oxide are preferably used. Moreover, you may add a polyester resin, an unsaturated polyester resin, etc. suitably in the range which does not affect the effect of this invention.

  In the present invention, the sizing agent can be diluted with a solvent. Examples of such a solvent include water, methanol, ethanol, isopropanol, acetone, methyl ethyl ketone, dimethylformamide, dimethylacetamide, and the like. Among these, water is preferably used because it is easy to handle and advantageous from the viewpoint of safety.

  In this invention, it is preferable that the adhesion amount of the sizing agent to carbon fiber is the range of 0.1-10 mass parts with respect to 100 mass parts of carbon fibers, More preferably, it is 0.2-3 mass parts. It is a range. When the sizing agent is attached in an amount of 0.1 part by mass or more, when carbon fiber is prepreg and weaved, it can withstand friction caused by a metal guide that passes therethrough, and generation of fluff can be suppressed. Excellent quality such as smoothness. On the other hand, when the adhesion amount of the sizing agent is 10 parts by mass or less, a matrix resin such as an epoxy resin can be impregnated inside the carbon fiber bundle without being inhibited by the sizing agent film around the carbon fiber bundle. The generation of voids is suppressed, the quality of the composite material is excellent, and at the same time the mechanical properties are excellent.

  In the present invention, the thickness of the sizing agent layer applied to the carbon fiber and dried is preferably in the range of 2 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 further, high-order processability is stable.

  In the present invention, examples of the carbon fiber to which the sizing agent is applied include polyacrylonitrile (PAN) -based, rayon-based, and pitch-based carbon fibers. Of these, PAN-based carbon fibers having an excellent balance between strength and elastic modulus are preferably used.

  Next, a method for producing a PAN-based carbon fiber will be described.

  As a spinning method for obtaining a carbon fiber precursor fiber, spinning methods such as wet, dry, and dry-wet can be used. Among these, it is preferable to use a wet or dry wet spinning method from the viewpoint that a high-strength carbon fiber is easily obtained. As the spinning dope, a polyacrylonitrile homopolymer or copolymer solution or suspension can be used.

  Spinning, coagulating, washing and drawing the above spinning stock solution through a die to form a precursor fiber. The obtained precursor fiber is subjected to a flameproofing treatment and carbonization treatment, and if necessary, carbonized by further graphitization treatment. Get fiber. As heat treatment conditions for carbonization and graphitization, the maximum heat treatment temperature is preferably 1100 ° C. or higher, more preferably 1400 ° C. or higher.

  In the present invention, fine carbon fibers are preferably used from the viewpoint that carbon fibers having high strength and elastic modulus can be obtained. Specifically, the single fiber diameter of the carbon fiber is preferably 7.5 μm or less, the single fiber diameter is more preferably 6 μm or less, and even more preferably 5.5 μm or less. The lower limit value of the single fiber diameter is about 4.5 μm from the viewpoint of productivity, and if it is less than 4.5 μm, the single fiber is likely to be cut in the production process, and the productivity may be lowered.

  The obtained carbon fiber is usually subjected to an oxidation treatment to introduce an oxygen-containing functional group in order to improve adhesion with the matrix resin. 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 aqueous solutions of inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, boric acid and carbonic acid, aqueous solutions of organic acids such as acetic acid, butyric acid, oxalic acid, acrylic acid and maleic acid, or ammonium sulfate and sulfuric acid. An aqueous solution of a salt such as ammonium hydrogen may be mentioned. Of these, an aqueous solution of sulfuric acid and nitric acid exhibiting strong acidity is preferably used.

  Specific examples of the alkaline electrolyte include an aqueous solution of hydroxide such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide and barium hydroxide, inorganic water such as ammonia water, sodium carbonate and sodium bicarbonate. Aqueous solutions of salts, aqueous solutions of organic salts such as sodium acetate and sodium benzoate, as well as potassium, magnesium, calcium, barium, other metal and ammonium salts of these inorganic and organic salts, and And aqueous solutions of organic compounds such as hydrazine. Among these, from the viewpoint of not containing an alkali metal that causes curing inhibition of the matrix resin, an aqueous solution of an inorganic salt such as ammonium carbonate or ammonium hydrogen carbonate, or an aqueous solution of a tetraalkylammonium hydroxide salt exhibiting strong alkalinity is preferably used. .

  In the present invention, from the viewpoint that (A) the covalent bond formation between the epoxy compound and the oxygen-containing functional group on the surface of the carbon fiber is promoted and the adhesion is further improved, the carbon fiber is subjected to liquid phase electrolysis treatment in an alkaline electrolyte. It is preferable to apply a sizing agent after the treatment, or after performing liquid phase electrolytic oxidation in an acidic electrolyte followed by washing with an alkaline aqueous solution. When liquid phase electrolytic oxidation is performed, excessively oxidized parts on the carbon fiber surface exist at the interface as fragile layers, and may be the starting point of destruction when made into a composite material. It is considered that the covalent bond formation is promoted by dissolving and removing the solution with an alkaline aqueous solution.

  In this invention, it is preferable that the density | concentration of the electrolyte solution used by liquid phase electrolytic oxidation exists in the range of 0.01-5 mol / L, More preferably, it exists in the range of 0.1-1 mol / L. When the concentration of the electrolytic solution is 0.01 mol / L 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 / L or less, it is advantageous from the viewpoint of safety.

  In this invention, it is preferable that the temperature of the electrolyte solution used by liquid phase electrolytic oxidation exists in the range of 10-100 degreeC, More preferably, it exists in the range of 10-40 degreeC. When the temperature of the electrolytic solution is 10 ° C. or higher, the efficiency of liquid phase electrolytic oxidation 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 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 current density in the liquid phase electrolytic oxidation is preferably in the range of surface area 1 m ² per 1.5~1000A / m ² of carbon fiber in the electrolyte solution, more preferably 3~500A / m ² Is within the range. When the current density is 1.5 A / m ² or more, the efficiency of liquid phase electrolytic oxidation is improved, which is advantageous in terms of operating cost. On the other hand, when the current density is 1000 A / m ² or less, it is advantageous from the viewpoint of safety.

  In the present invention, from the viewpoint that (A) the covalent bond formation between the epoxy compound and the oxygen-containing functional group on the surface of the carbon fiber is promoted and the adhesion is further improved, the carbon fiber is treated with an alkaline water solution after liquid phase electrolytic oxidation. It is preferable to wash with the property. Among these, it is preferable to perform liquid phase electrolytic oxidation with an acidic electrolytic solution and then wash with an alkaline 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. Examples of the alkaline aqueous solution include aqueous solutions of hydroxides such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide and barium hydroxide, aqueous solutions of inorganic salts such as aqueous ammonia, sodium carbonate and sodium bicarbonate, Aqueous solutions of organic salts such as sodium acetate and sodium benzoate, and potassium, magnesium, calcium, barium, other metal and ammonium salts of these inorganic and organic salts, and hydrazine Examples include an aqueous solution of an organic compound. Among these, from the viewpoint of not containing an alkali metal that causes curing inhibition of the matrix resin, an aqueous solution of an inorganic salt such as ammonium carbonate or ammonium hydrogen carbonate, or an aqueous solution of a tetraalkylammonium hydroxide salt exhibiting strong alkalinity is preferably used. .

  In the present invention, as a method for washing carbon fibers with an alkaline aqueous solution, for example, a dipping method or 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 the dip method while vibrating the carbon fiber with ultrasonic waves.

  In the present invention, the carbon fiber is preferably washed with water and dried after being washed with liquid phase electrolytic oxidation or an alkaline aqueous solution. 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, so it is desirable to dry at the lowest possible temperature. Specifically, the drying temperature is preferably 250 ° C. or lower. More preferably, it is 210 ° C. or lower.

  Examples of means for applying (coating) the sizing agent to the carbon fiber include, for example, a method of immersing the carbon fiber in a sizing liquid through a roller, a method of contacting the carbon fiber with a roller to which the sizing liquid is attached, and a sizing liquid in a mist form There is a method of spraying on carbon fiber. 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 variations is preferably used. At this time, it is preferable to control the sizing solution concentration, temperature, yarn tension, and the like so that the amount of the sizing agent active ingredient attached to the carbon fiber is uniformly attached within an appropriate range. Moreover, carbon fiber can be vibrated with an ultrasonic wave at the time of sizing agent provision.

  In this invention, after apply | coating a sizing agent to carbon fiber, it is required to heat-process for 30 to 600 second in the temperature range of 160-260 degreeC. The heat treatment conditions are preferably in a temperature range of 170 to 250 ° C. for 30 to 500 seconds, and more preferably in a temperature range of 180 to 240 ° C. for 30 to 300 seconds. If the heat treatment condition is less than 160 ° C. and / or less than 30 seconds, the covalent bond formation between the epoxy resin of the sizing agent and the oxygen-containing functional group on the surface of the carbon fiber is not promoted, and the carbon fiber and the matrix resin Adhesiveness is insufficient. On the other hand, if the heat treatment condition exceeds 260 ° C. and / or exceeds 600 seconds, volatilization of the quaternary ammonium salt occurs, the covalent bond formation is not promoted, and the adhesion between the carbon fiber and the matrix resin is insufficient. Become.

  In the present invention, the strand strength of the obtained sizing agent-coated carbon fiber bundle is preferably 3.5 GPa or more, more preferably 4 GPa or more, and further preferably 5 GPa. Moreover, it is preferable that the strand elastic modulus of the obtained sizing agent application | coating carbon fiber bundle is 220 GPa or more, More preferably, it is 240 GPa or more, More preferably, it is 280 GPa or more.

  In the present invention, the strand tensile strength and elastic modulus of the sizing agent-coated carbon fiber bundle can be determined according to the following procedure in accordance with the resin impregnated strand test method of JIS-R-7608 (2004). As the resin formulation, “Celoxide” (registered trademark) 2021P (manufactured by Daicel Chemical Industries) / 3 boron fluoride monoethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) / Acetone = 100/3/4 (parts by mass) is used. As curing conditions, a normal pressure, a temperature of 130 ° C., and a time of 30 minutes are used. Ten strands of the carbon fiber bundle were measured, and the average value was defined as the strand tensile strength and the strand 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 0.06-0.30, More preferably, it is a thing within the range of 0.07-0.20. 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 is determined by X-ray photoelectron spectroscopy according to the following procedure. First, after cutting the carbon fiber from which the sizing agent and the like adhering to the carbon fiber surface with a solvent was cut to 20 mm, and spreading and arranging on a copper sample support base, using AlKα ₁ and ₂ as the X-ray source, The sample chamber is kept at 1 × 10 ⁻⁸ Torr. The kinetic energy value (KE) of the main peak of C _1s is set to 1202 eV as a peak correction value associated with charging during measurement. C _1s peak area, _K.P. E. Is obtained by drawing a straight base line in the range of 1191 to 1205 eV. O _1s peak area, E. Is obtained by drawing a straight base line in the range of 947 to 959 eV.

Here, the surface oxygen concentration is 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. As the X-ray photoelectron spectroscopy apparatus, ESCA-1600 manufactured by ULVAC-PHI Co., Ltd. was used, and the sensitivity correction value unique to the apparatus was 2.33.

  As the matrix resin, a thermosetting resin and a thermoplastic resin are used.

  Examples of the thermosetting resin include unsaturated polyester resins, vinyl ester resins, epoxy resins, phenol resins, melamine resins, urea resins, cyanate ester resins, and bismaleimide resins. 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. For the purpose of improving toughness and the like, the thermosetting resin can contain a thermoplastic resin described later or an oligomer thereof.

  Examples of the thermoplastic resin include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), and polyester such as liquid crystal polyester, polyethylene (PE), polypropylene ( In addition to polyolefins such as PP) and polybutylene, styrene resins, polyoxymethylene (POM), polyamide (PA), polycarbonate (PC), polymethylene methacrylate (PMMA), polyvinyl chloride (PVC), polyphenylene sulfide ( PPS), polyphenylene ether (PPE), modified PPE, polyimide (PI), polyamideimide (PAI), polyetherimide (PEI), polysulfone (PSU), modified PSU Polyethersulfone, polyketone (PK), polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyarylate (PAR), polyethernitrile (PEN), phenolic resin, phenoxy Resin and fluorine-based resins such as polytetrafluoroethylene, thermoplastic elastomers such as polystyrene, polyolefin, polyurethane, polyester, polyamide, polybutadiene, polyisoprene and fluorine, and copolymers thereof , Modified products, and resins blended in two or more types.

  Next, the composite material when the matrix resin is a thermosetting resin will be described.

  The sizing agent-coated carbon fiber obtained by the method for producing a sizing agent-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 specific elastic modulus, tows in which carbon fibers are aligned in one direction are most suitable, and prepregs in which carbon fibers are impregnated with a matrix resin are preferably used. .

  The prepreg is prepared by dissolving the matrix resin in a solvent such as methyl ethyl ketone or methanol to lower the viscosity and impregnating the carbon fiber, and the hot melt method (lowering method) of decreasing the viscosity by heating and impregnating the carbon fiber. Can be produced.

  The wet method is a method in which carbon fibers are immersed in a matrix resin solution, and then lifted and the solvent is evaporated by using an oven or the like. The hot melt method directly impregnates reinforcing fibers with a matrix resin whose viscosity has been reduced by heating. Or a method in which a matrix resin is once coated with a matrix resin on a release paper, and the carbon fiber is impregnated with matrix resin by heating and pressurizing the film from both sides or one side of the carbon fiber. is there. The hot melt method is preferably used because there is substantially no solvent remaining in the prepreg.

  After laminating the obtained prepreg, a composite material is produced by a method of heating and curing the matrix resin while applying pressure to the laminate. As a method for applying heat and pressure, a press molding method, an autoclave molding method, a packing molding method, a wrapping tape method, an internal pressure molding method, and the like are employed. The composite material is a method in which a matrix resin is directly impregnated with a carbon fiber without using a prepreg, followed by heat curing, such as a hand lay-up method, a resin injection molding method, and a resin transfer molding method. It can also be produced by a molding method. In these methods, it is preferable to prepare a resin by mixing two liquids of a matrix resin main component and a curing agent immediately before use.

  Next, the composite material when the matrix resin is a thermoplastic resin will be described.

  Thermoplastic composite materials are molded by molding methods such as injection molding (injection compression molding, gas assist injection molding, insert molding, etc.), blow molding, rotational molding, extrusion molding, press molding, transfer molding, and filament winding molding. However, injection molding is preferably used from the viewpoint of productivity. As the form of the molding material used for such molding, pellets, stampable sheets, prepregs and the like can be used, but the most preferable molding material is a pellet used for injection molding. The pellet generally refers to a pellet obtained by kneading a thermoplastic resin and chopped fiber or continuous fiber in an extruder, extruding and pelletizing. In the above-mentioned pellet, the fiber length in the pellet is shorter than the length in the pellet longitudinal direction, and the pellet includes a long fiber pellet. The long fiber pellet is one in which fibers are arranged substantially parallel to the longitudinal direction of the pellet as shown in Japanese Patent Publication No. 63-37694, and the fiber length in the pellet is equal to or longer than the pellet length. Point to. In this case, the thermoplastic resin may be impregnated or coated in the fiber bundle. In particular, in the case of long fiber pellets coated with a thermoplastic resin, the fiber bundle is pre-impregnated with a resin having the same viscosity as that of the coated fiber or a lower viscosity (or lower molecular weight) than the coated thermoplastic resin. Also good. In order for the composite material to have excellent electrical conductivity and mechanical properties (particularly strength and impact resistance), it is effective to increase the fiber length in the molded product. Among these, it is preferable to mold using long fiber pellets.

  Examples of uses of the sizing agent-coated carbon fiber obtained by the method for producing a sizing agent-coated carbon fiber of the present invention and a molded body made of a thermosetting resin and / or a thermoplastic resin include, for example, a personal computer, a display, an OA device, and a mobile phone. Telephone, personal digital assistant, facsimile, compact disc, portable MD, portable radio cassette, PDA (personal digital assistant such as electronic notebook), video camera, digital still camera, optical equipment, audio, air conditioner, lighting equipment, entertainment equipment, Electrical materials such as toy products, other household appliances, internal components such as casings and trays and chassis of chassis, mechanical parts, panels and other building materials, motor parts, alternator terminals, alternator connectors, IC regulators, light diodes Potentiometer , Suspension parts, various valves such as exhaust gas valves, fuel-related, exhaust or intake system pipes, air intake nozzle 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 Inn, wiper motor related parts, distributor, starter switch, starter relay, transmission wire harness, 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 tri Cars, propeller shafts, wheels, fenders, fascias, bumpers, bumper beams, bonnets, aero parts, platforms, cowl louvers, roofs, instrument panels, spoilers and various modules, automobile related parts, parts and skins Examples include landing gear pods, winglets, spoilers, edges, ladders, elevators, failings, ribs and other 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.

  EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not restrict | limited by these Examples.

<Strand tensile strength and elastic modulus of carbon fiber bundle>
The strand tensile strength and strand elastic modulus of the carbon fiber bundle were determined according to the following procedure in accordance with the resin impregnated strand test method of JIS-R-7608 (2004). As the resin formulation, “Celoxide” (registered trademark) 2021P (manufactured by Daicel Chemical Industries) / 3 boron trifluoride monoethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) / Acetone = 100/3/4 (part by mass) is used. As curing conditions, normal pressure, temperature of 125 ° C., and time of 30 minutes were used. Ten strands of the carbon fiber bundle were measured, and the average value was defined as the strand tensile strength and the strand elastic modulus.

<Surface oxygen concentration of carbon fiber (O / C)>
The surface oxygen concentration (O / C) of the carbon fiber was determined by X-ray photoelectron spectroscopy according to the following procedure. First, the carbon fiber from which the dirt adhering to the surface with a solvent is removed is cut to about 20 mm and spread on a copper sample support. Next, the sample support is set in the sample chamber, and the inside of the sample chamber is kept at 1 × 10 ⁻⁸ Torr. Subsequently, AlKα ₁ and ₂ were used as an X-ray source, and measurement was performed with a photoelectron escape angle of 90 °. In addition, the kinetic energy value (KE) of the main peak of C _1s was adjusted to 1202 eV as a peak correction value associated with charging during measurement. C _1s peak area, _K.P. E. As a linear base line in the range of 1191 to 1205 eV. In addition, the O _1s peak area is _{expressed as K.I.} E. As a linear base line in the range of 947 to 959 eV. Here, the surface oxygen concentration is 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. As the X-ray photoelectron spectroscopy apparatus, ESCA-1600 manufactured by ULVAC-PHI Co., Ltd. was used, and the sensitivity correction value unique to the apparatus was 2.33.

<Measurement method of sizing adhesion amount>
About 2 g of sizing-attached carbon fiber bundle was weighed (W1) (reading to the fourth decimal place) and then left in an electric furnace (capacity 120 cm3) set at a temperature of 450 ° C. in a nitrogen stream of 50 ml / min for 15 minutes. The sizing agent is completely pyrolyzed. Then, the carbon fiber bundle is transferred to a container in a dry nitrogen stream of 20 liters / minute and cooled for 15 minutes, and the carbon fiber bundle is weighed (W2) (reads up to the fourth decimal place), and the sizing adhesion amount is obtained by W1-W2. . A value obtained by converting this sizing adhesion amount into an amount with respect to 100 parts by mass of the carbon fiber bundle (rounded off to the third decimal place) was defined as a mass part of the adhering sizing agent. The measurement was performed twice, and the average value was defined as the mass part of the sizing agent.

<Measurement of interfacial shear strength (IFSS)>
Interfacial shear strength (IFSS) is 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.) , Put each in a container. Thereafter, heating is performed at a temperature of 75 ° C. for 15 minutes in order to reduce the viscosity of the jER828 and dissolve the metaphenylenediamine. Then, both are mixed well and vacuum defoaming is performed at a temperature of 80 ° C. for about 15 minutes.
(B) Fixing the carbon fiber single yarn to the special mold Pull out the single fiber from the carbon fiber bundle, and fix both ends with an adhesive in a state where a constant tension is 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-drys 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) From resin casting to curing The resin adjusted in the above procedure (b) is poured into the mold after the vacuum drying in the above step (b), and the temperature rising rate is 1.5 ° C. / The temperature rises to 75 ° C in minutes and is maintained for 2 hours, then the temperature rises to 125 ° C at a temperature increase rate of 1.5 minutes, and is maintained for 2 hours. . Then, it demolds and a test piece is obtained.
(D) Measurement of interfacial shear strength (IFSS) A tensile force was applied to the test piece obtained in the above procedure (c) in the fiber axis direction (longitudinal direction) to cause a strain of 12%, and then the test piece was tested with a polarizing microscope. The number of fiber breaks N (pieces) in the range of 22 mm at the center of each piece is measured. Next, the average broken fiber length la is calculated by the formula of la (μm) = 22 × 1000 (μm) / N (pieces). Next, the critical fiber length lc is calculated from the average broken fiber length la by the following formula: lc (μm) = (4/3) × la (μm). The strand tensile strength σ and the diameter d of the carbon fiber single yarn are measured, and the interface shear strength IFSS, which is an index of the bond strength between the carbon fiber and the resin interface, is 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).

  The materials and components used in each example and each comparative example are as follows.

-(A1) component: A-1 to A-4
A-1: “jER” (registered trademark) 828 (manufactured by Mitsubishi Chemical Corporation)
Diglycidyl ether of bisphenol A Epoxy equivalent: 189 g / mol, Number of epoxy groups: 2
A-2: “jER” (registered trademark) 152 (manufactured by Mitsubishi Chemical Corporation)
Phenol novolac glycidyl ether epoxy equivalent: 175 g / mol, epoxy group number: 3
A-3: “Araldite” (registered trademark) MY721 (manufactured by Huntsman Advanced Materials)
N, N, N ′, N′-tetraglycidyl-4,4′-diaminodiphenylmethane Epoxy equivalent: 113 g / mol, number of epoxy groups: 4
A-4: TETRAD-X (Mitsubishi Gas Chemical Co., Ltd.)
Tetraglycidyl metaxylenediamine Epoxy equivalent: 100 g / mol, Number of epoxy groups: 4.

-Corresponds to both (A1) component and (A2) component: A-5
A-5: “Denacol” (registered trademark) EX-611 (manufactured by Nagase ChemteX Corporation)
Sorbitol polyglycidyl ether epoxy equivalent: 167 g / mol, number of epoxy groups: 4
Number of hydroxyl groups: 2.

-(A2) component: A-6, A-7
A-6: “Denacol” (registered trademark) EX-731 (manufactured by Nagase ChemteX Corporation)
N-glycidyl phthalimide epoxy equivalent: 216 g / mol, number of epoxy groups: 1
Number of imide groups: 1
A-7: “ADEKA RESIN” (registered trademark) EPU-6 (manufactured by ADEKA Corporation)
Urethane-modified epoxy Epoxy equivalent: 250 g / mol, number of epoxy groups: 1 or more Urethane group: 1 or more.

-(B) component: B-1 to B-7
B-1: Benzyltrimethylammonium bromide (R ₁ has 7 carbon atoms, R _{2 to} R ₄ each have 1 carbon atom, anion site is bromide anion, manufactured by Tokyo Chemical Industry Co., Ltd.)
B-2: Tetrabutylammonium bromide (R _{1 to} R ₄ each have 4 carbon atoms, the anion portion is a bromide anion, manufactured by Tokyo Chemical Industry Co., Ltd.)
B-3: Trimethyloctadecyl ammonium bromide (R ₁ has 18 carbon atoms, R _{2 to} R ₄ each have 1 carbon atom, anion sites are bromide anions, manufactured by Tokyo Chemical Industry Co., Ltd.)
B-4: (2-methoxyethoxymethyl) triethylammonium chloride (R ₁ has 4 carbon atoms, R _{2 to} R ₄ each have 2 carbon atoms, anion sites are chloride anions, manufactured by Tokyo Chemical Industry Co., Ltd.)
B-5: (2-acetoxyethyl) trimethylammonium chloride (R ₁ has 4 carbon atoms, R _{2 to} R ₄ each have 1 carbon atom, anion sites are chloride anions, manufactured by Tokyo Chemical Industry Co., Ltd.)
B-6: (2-hydroxyethyl) trimethylammonium bromide (R ₁ has 2 carbon atoms, R _{2 to} R ₄ each have 1 carbon atom, anion sites are bromide anions, manufactured by Tokyo Chemical Industry Co., Ltd.)
B-7: 1-hexadecylpyridinium chloride (R ₅ has 16 carbon atoms, R ₆ and R ₇ are each a hydrogen atom, anion sites are chloride anions, manufactured by Tokyo Chemical Industry Co., Ltd.).

Example 1
The present example includes the following first step and second step.
Step I: Process for producing carbon fiber as a raw material A copolymer composed of 99 mol% of allylonitrile and 1 mol% of itaconic acid is spun and fired, the total number of filaments is 24,000, and the total fineness is 800. A carbon fiber having a tex, a specific gravity of 1.8, a strand tensile strength of 6.2 GPa, and a strand tensile modulus of 300 GPa was obtained. Subsequently, 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 / l as an electrolytic solution at an electric charge of 100 coulomb per 1 g of the carbon fiber. 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. At this time, the surface oxygen concentration O / C was 0.20. This was designated as carbon fiber A.
Step II: A step of attaching a sizing agent to carbon fibers The above (A-1) and (B-1) are mixed at a mass ratio of 100: 3, and acetone is further mixed, so that the sizing agent is uniform. An acetone solution of about 1% by mass dissolved in was obtained. Using an acetone solution of this sizing agent, the sizing agent was applied to the surface-treated carbon fiber by an immersion method, and then heat treated at a temperature of 210 ° C. for 90 seconds to obtain a sizing agent-coated carbon fiber bundle. The adhesion amount of the sizing agent was adjusted to 1 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. Subsequently, interfacial shear strength (IFSS) was measured using the obtained sizing agent-coated carbon fibers. The results are summarized in Table 1. As a result, it was found that IFSS was 35 MPa, and adhesion was sufficiently high.

(Examples 2 to 6)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
-Step II: Step of attaching sizing agent to carbon fiber In Step II of Example 1, (A-1) is changed to (A-2), and (A-2) and (B-1). As shown in Table 1, sizing agent-coated carbon fibers were obtained in the same manner as in Example 1 except that the mass ratio was changed in the range of 100: 1 to 100: 20. The adhesion amount of the sizing agent was 1 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. As a result of measuring the interfacial shear strength (IFSS) using the obtained sizing agent-coated carbon fiber, it was found that IFSS was 36 to 42 MPa, and all had sufficiently high adhesion. Especially, when the mass ratio of (A-2) and (B-1) is 100: 3 and 100: 5, the adhesiveness was extremely excellent. The results are shown in Table 1.

(Example 7)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
-Step II: Step of attaching sizing agent to carbon fiber The same method as in Example 1 except that (A-1) was changed to (A-3) in Step II of Example 1. The sizing agent coated carbon fiber was obtained. The adhesion amount of the sizing agent was 1 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. As a result of measuring the interfacial shear strength (IFSS) using the obtained sizing agent-coated carbon fiber, it was found that IFSS was 42 MPa, and all had sufficiently high adhesion. The results are shown in Table 1.

(Examples 8 to 13)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
-Step II: Step of attaching sizing agent to carbon fiber In Step II of Example 1, (A-1) is changed to (A-2), and (B-1) is changed to (B-2). Sizing agent-coated carbon fibers were obtained in the same manner as in Example 1 except that the carbon fibers were changed to (B-7). The adhesion amount of the sizing agent was 1 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. As a result of measuring the interfacial shear strength (IFSS) using the obtained sizing agent-coated carbon fiber, it was found that IFSS was 36 to 41 MPa, and all had sufficiently high adhesion. The results are shown in Table 2.

(Examples 14 to 18)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
-Step II: Step of attaching sizing agent to carbon fiber In Step II of Example 1, (A-1) was changed to (A-2), and the heat treatment temperature was changed as shown in Table 3. Sizing agent-coated carbon fibers were obtained in the same manner as in Example 1 except that the temperature was changed to the range of 180 to 240 ° C. and the heat treatment time was changed to the range of 30 to 480 seconds. The adhesion amount of the sizing agent was 1 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. As a result of measuring the interfacial shear strength (IFSS) using the obtained sizing agent-coated carbon fiber, it was found that IFSS was 36 to 42 MPa, and all had sufficiently high adhesion. In particular, when the heat treatment temperature was 210 ° C. and the heat treatment time was 300 seconds, the adhesiveness was extremely excellent. The results are shown in Table 3.

(Example 19)
-Step I: Step of producing carbon fiber as raw material Implemented except that sulfuric acid aqueous solution having a concentration of 0.05 mol / l was used as the electrolytic solution, and the amount of electricity was subjected to electrolytic surface treatment at 20 coulomb per gram of carbon fiber. Same as Example 1. At this time, the surface oxygen concentration O / C was 0.20. This was designated as carbon fiber B.
-Step II: Step of attaching sizing agent to carbon fiber Sizing agent-coated carbon fiber was obtained in the same manner as in Example 1. The adhesion amount of the sizing agent was 1 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. As a result of measuring the interfacial shear strength (IFSS) using the obtained sizing agent-coated carbon fiber, it was found that IFSS was 33 MPa and the adhesiveness was sufficiently high. The results are shown in Table 3.

(Example 20)
Process I: Process for producing carbon fiber as raw material The same as in Example 19.
-Step II: Step of attaching sizing agent to carbon fiber Sizing agent-coated carbon fiber was obtained in the same manner as in Example 3. The adhesion amount of the sizing agent was 1 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. As a result of measuring the interfacial shear strength (IFSS) using the obtained sizing agent-coated carbon fiber, it was found that IFSS was 36 MPa and the adhesiveness was sufficiently high. The results are shown in Table 3.

(Comparative Examples 1-3)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
-Step II: Step of attaching sizing agent to carbon fiber In Step II of Example 1, only one of (A-1), (A-2), and (A-4) was used. Except for the above, a sizing agent-coated carbon fiber was obtained in the same manner as in Example 1. The adhesion amount of the sizing agent was 1 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. As a result of measuring the interfacial shear strength (IFSS) using the obtained sizing agent-coated carbon fiber, it was found that IFSS was 23 to 29 MPa and adhesion was insufficient. The results are shown in Table 4.

(Comparative Example 4)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
Step II: A step of attaching a sizing agent to carbon fiber The above (A-2) and (B-1) are mixed at a mass ratio of 100: 30, and acetone is further mixed, so that the sizing agent is uniform. An acetone solution of about 1% by mass dissolved in was obtained. Using an acetone solution of this sizing agent, the sizing agent was applied to the surface-treated carbon fiber by an immersion method, and then heat treated at a temperature of 210 ° C. for 90 seconds to obtain a sizing agent-coated carbon fiber bundle. The adhesion amount of the sizing agent was adjusted to 1 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. Subsequently, interfacial shear strength (IFSS) was measured using the obtained sizing agent-coated carbon fibers. As a result, it was found that IFSS was 23 MPa and adhesion was insufficient. The results are shown in Table 4.

(Comparative Examples 5 to 8)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
Step II: Step of attaching sizing agent to carbon fiber In Step II of Example 1, (A-1) was changed to (A-2), and as shown in Table 4, the heat treatment temperature and Sizing agent-coated carbon fibers were obtained in the same manner as in Example 1 except that the heat treatment time was changed to 210 ° C. × 10 seconds, 210 ° C. × 720 seconds, 140 ° C. × 90 seconds, 280 ° C. × 90 seconds. . The adhesion amount of the sizing agent was 1 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. As a result of measuring the interfacial shear strength (IFSS) using the obtained sizing agent-coated carbon fiber, it was found that IFSS was 25 to 29 MPa, and all had sufficiently high adhesion. In particular, it was found that the adhesiveness was insufficient when the heat treatment temperature was 140 ° C. and the heat treatment time was 90 seconds. The results are shown in Table 4.

(Examples 21 to 23)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
-Step II: Step of attaching sizing agent to carbon fiber (A-5) and (B-1), (A-6) and (B-1), (A-7) and (B-1) Were mixed at a mass ratio of 100: 3, and acetone was further mixed to obtain an acetone solution of about 1% by mass in which the sizing agent was uniformly dissolved. Using this acetone solution of the sizing agent, the sizing agent was applied to the surface-treated carbon fiber by a dipping method, followed by heat treatment at a temperature of 210 ° C. for 90 seconds to obtain a sizing agent-coated carbon fiber. The adhesion amount of the sizing agent was adjusted to 1 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. Subsequently, as a result of measuring the interfacial shear strength (IFSS) using the obtained sizing agent-coated carbon fibers, it was found that IFSS was 33 and 34 MPa, and both had sufficiently high adhesiveness. The results are shown in Table 5.

(Comparative Examples 9-11)
-Step I: Step of producing carbon fiber as a raw material The same as in Example 1.
-Step II: Step of attaching sizing agent to carbon fiber In Examples 21 to 23, sizing agent-coated carbon fibers were obtained in the same manner as in Examples 21 to 23 except that (B-1) was not included. . The adhesion amount of the sizing agent was adjusted to 1 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. Then, as a result of measuring interface shear strength (IFSS) using the obtained sizing agent application | coating carbon fiber, IFSS was 24-29 Mpa, and it turned out that all are inadequate. The results are shown in Table 5.

Claims (8)

(A) As a component, it has a bifunctional or higher functional epoxy compound (A1) and / or a monofunctional or higher functional epoxy group, and is composed of a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, and a sulfo group. With respect to 100 parts by mass of the selected epoxy compound (A2) having at least one functional group, as component (B), at least the following general formula (I) or (II)

(In the above formula, R _{1 to} R ₅ represent a hydrocarbon group having 1 to 22 carbon atoms, a group having 1 to 22 carbon atoms and an ether structure, a hydrocarbon having 1 to 22 carbon atoms and an ester structure, respectively. Or a group containing a hydrocarbon having 1 to 22 carbon atoms and a hydroxyl group, and R ₆ and R ₇ are each a hydrogen atom, a hydrocarbon group having 1 to 8 carbon atoms, or a carbon atom having 1 to 8 carbon atoms. (B) a quaternary ammonium salt having a cation moiety represented by any one of a group containing hydrogen and an ether structure, or a group containing a hydrocarbon having 1 to 8 carbon atoms and an ester structure) A method for producing sizing agent-coated carbon fiber, in which a sizing agent containing ˜25 parts by mass is applied to carbon fiber and heat-treated at a temperature range of 160 to 260 ° C. for 30 to 600 seconds. R ₁ and R _{2 in} the general formula (I) are a hydrocarbon group having 1 to 22 carbon atoms, a group containing a hydrocarbon having 1 to 22 carbon atoms and an ether structure, a hydrocarbon having 1 to 22 carbon atoms and an ester structure. Or a group containing a hydrocarbon having 1 to 22 carbon atoms and a hydroxyl group, wherein R ₃ and R ₄ are hydrocarbon groups having 2 to 22 carbon atoms, hydrocarbons having 2 to 22 carbon atoms and an ether structure Represents a group containing a hydrocarbon group having 2 to 22 carbon atoms and an ester structure, or a group containing a hydrocarbon group having 2 to 22 carbon atoms and a hydroxyl group, and R _{5 in the} general formula (II) represents 1 to 22 carbon atoms. A hydrocarbon group having 1 to 22 carbon atoms and an ether structure, a hydrocarbon group having 1 to 22 carbon atoms and an ester structure, or a group having 1 to 22 carbon atoms and a hydroxyl group. Any one of R ₆ and R ₇ is hydrogen, carbon atom number 1 to 8 The sizing agent-coated carbon fiber according to claim 1, which represents any one of a hydrogen group, a group containing a hydrocarbon having 1 to 8 carbon atoms and an ether structure, or a group containing a hydrocarbon having 1 to 8 carbon atoms and an ester structure. Method. The sizing agent according to claim 1 or 2, wherein the sizing agent is applied after liquid phase electrolytic oxidation of the carbon fiber in an alkaline electrolytic solution, or after liquid phase electrolytic oxidation in an acidic electrolytic solution and subsequent washing with an alkaline aqueous solution. Manufacturing method of coated carbon fiber. (A) The manufacturing method of the sizing agent application | coating carbon fiber in any one of Claims 1-3 whose epoxy compound is a trifunctional or more than trifunctional epoxy compound containing 3 or more epoxy groups in a molecule | numerator. (A) The manufacturing method of the sizing agent application | coating carbon fiber in any one of Claims 1-4 whose epoxy compound contains an aromatic ring in a molecule | numerator. (A) The manufacturing method of the sizing agent application | coating carbon fiber in any one of Claims 1-5 whose epoxy compound is either a phenol novolak-type epoxy resin, a cresol novolak-type epoxy resin, or tetraglycidyl diamino diphenylmethane. (B) The manufacturing method of the sizing agent application | coating carbon fiber in any one of Claims 1-6 whose anion site | part of the quaternary ammonium salt which has a cation site | part is a halogen ion. The sizing agent-coated carbon fiber according to any one of claims 1 to 7, wherein the surface oxygen concentration O / C measured by X-ray electron spectroscopy of the carbon fiber is within a range of 0.05 to 0.50. Production method.