JP6051987B2 - Method for producing carbon fiber coated with sizing agent - Google Patents

Description

  The present invention relates to a sizing agent-coated carbon fiber suitable for use in aircraft members, spacecraft members, automobile members, marine members, sports applications such as golf shafts and fishing rods, and other general industrial applications, and the sizing agent-coated carbon fibers. The present invention relates to a manufacturing method, a prepreg and a carbon fiber reinforced composite material. More specifically, the present invention is excellent in mechanical properties under severe environments such as low temperatures, and is suitable as a structural material. When an epoxy resin is used as a matrix resin, the matrix resin and the carbon fiber are used. The present invention relates to a sizing agent-coated carbon fiber that has excellent adhesiveness and suppresses deterioration of physical properties when the prepreg is stored for a long period of time, and a method for producing the sizing agent-coated carbon fiber, a prepreg, and a carbon fiber reinforced composite material. .

  Since carbon fiber is lightweight and has excellent strength and elastic modulus, many composite materials combined with various matrix resins are used for aircraft members, spacecraft members, automobile members, ship members, civil engineering and building materials, and sporting goods. Used in the field. In a composite material using carbon fibers, in order to make use of the excellent characteristics 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 of improving the interlaminar shear strength, which is an index of adhesiveness, by subjecting carbon fibers to electrolytic treatment has been proposed (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 proposed (refer patent document 2 and 3).

  For example, an aliphatic type epoxy compound having a plurality of epoxy groups has been proposed as a sizing agent (see Patent Documents 4, 5, and 6). Further, a method of applying an epoxy adduct of polyalkylene glycol as a sizing agent to carbon fibers has been proposed (see Patent Documents 7, 8 and 9). In addition, a method of applying diglycidyl ether of bisphenol A to carbon fibers as an aromatic sizing agent has been proposed (see Patent Documents 2 and 3). Moreover, the method of apply | coating what added the epoxy group to the polyalkylene oxide adduct as a sizing agent to carbon fiber is proposed (refer patent documents 10 and 11).

  Focusing on the functional groups contained in the sizing agent, proposals have been made that achieve high adhesion by having hydroxyl groups (see Patent Documents 12 and 13). Patent Document 12 describes the combined use of an epoxy compound and an ammonium salt having an epoxy compound and a functional group such as a hydroxyl group in one molecule. In Patent Document 13, there is a proposal regarding the combined use of an epoxy compound, a hydroxyl group and / or a carboxyl group, and a compound having an amino group, and a sizing agent coating having high adhesiveness by regulation of the hydroxyl value, the carboxyl group value, and the epoxy value. Carbon fiber has been proposed. Although it focuses on hydrogen bonding by hydroxyl groups formed by the reaction of amino groups and epoxy groups and hydroxyl groups on carbon fibers, it defines the functional groups of the sizing agent before it is applied to carbon fibers and is applied to carbon fibers. There is no point of focus on controlling the ratio of the functional group after being formed. Moreover, all contain the hardening | curing agent component which accelerates | stimulates reaction of epoxy, such as an amino group and ammonium salt.

  Further, a proposal has been made focusing on the functional group ratio of the sizing agent after being applied and dried on carbon fibers (see Patent Document 14). Patent Document 15 discloses a production method in which drying / heat treatment is performed after drying / heat treatment of carbon fiber strands to which a sizing agent is attached until the epoxy equivalent of the sizing agent before drying / heat treatment is 2.0 to 4.0 times. Proposed. There is no description about water at the time of heat treatment, and it is not intended for hydrolysis of epoxy groups.

  In addition, as an example of introducing a functional group other than a hydroxyl group and an epoxy group, one containing a halogen has been proposed (see Patent Document 15). However, there is no focus on controlling the amount and ratio of functional groups including hydroxyl groups and halogens.

  The idea of simultaneously realizing long-term stability, high adhesion, and high processability of the prepreg by controlling the functional group of the sizing agent applied to the sizing agent-coated carbon fiber instead of the epoxy compound applied to the sizing agent There was no.

Japanese Patent Laid-Open No. 04-361619 US Pat. No. 3,957,716 JP-A-57-171767 Japanese Examined Patent Publication No. 63-14114 JP-A-7-279040 JP-A-8-113876 JP-A-57-128266 U.S. Pat. No. 4,555,446 JP 62-033872 A JP 61-028074 A Japanese Patent Laid-Open No. 01-272867 JP 2012-052279 A JP 2011-214209 A JP 2011-47063 A JP-A-8-188968

The present invention has been made in view of the above, and is a carbon fiber reinforced composite material that is excellent in adhesiveness and storage stability and excellent in heat resistance and mechanical strength in severe use environments such as under low temperature. It is an object of the present invention to provide a sizing agent-coated carbon fiber, a sizing agent-coated carbon fiber production method, a prepreg, and a production method from which a carbon fiber reinforced composite material can be obtained .

  The present inventors have found that the above-described object can be achieved by setting the functional group of the sizing agent component eluted from the sizing agent-coated carbon fiber to a specific range by performing a specific treatment. That is, in the present invention, the epoxy compound itself used for the sizing agent can be selected from known epoxy compounds, but the selection of the epoxy compound used for the sizing agent, the sizing agent or / and the sizing agent-coated carbon fiber in the presence of water or It can be said that it is important as a sizing agent technique to provide a functional range of the sizing agent within a specific range by giving a thermal history under wet conditions.

In order to solve the above-described problems and achieve the object, the sizing agent-coated carbon fiber obtained in the present invention (hereinafter sometimes referred to as the sizing agent-coated carbon fiber of the present invention) is a molecule of carbon fiber. A sizing agent-coated carbon fiber coated with a sizing agent containing an epoxy compound (A) having a hydroxyl group and an epoxy group as a main component, wherein the sizing agent has a nitrogen or phosphorus content of 1.3% by mass or less. And the hydroxyl value (a) meq. Of the sizing agent eluted by immersing the sizing agent-coated carbon fiber in an N, N-dimethylformamide solvent and sonicating. / G and epoxy value (b) meq. / G satisfies the following (I) to (III).
(I) 8 ≦ (a) + (b) ≦ 16
(II) (a) / (b) ≧ 2
(III) (b) ≧ 0.5
In the sizing agent-coated carbon fiber of the present invention, in the above invention, the epoxy compound (A) contains halogen in the molecule, and the surface of the sizing agent-coated carbon fiber is measured by X-ray photoelectron spectroscopy. It is essential that the carbon is 0.005 to 0.030.
Moreover, the sizing agent application | coating carbon fiber of this invention makes it essential that the weight average molecular weights of the said eluted sizing agent are 1000-5000 in the said invention.

Moreover, the sizing agent-coated carbon fiber of the present invention is the above-described invention, wherein the hydroxyl value (a) meq. / G satisfies the following (IV).
(IV) (a) ≧ 9
Moreover, the sizing agent application | coating carbon fiber of this invention makes it essential that the said epoxy compound (A) is an aliphatic epoxy compound (A1) in the said invention.

  The sizing agent-coated carbon fiber of the present invention is the above-described invention, wherein the aliphatic epoxy compound (A1) is selected from glycerol, diglycerol, polyglycerol, trimethylolpropane, pentaerythritol, sorbitol, and arabitol. And a glycidyl ether type epoxy compound obtained by reaction with epichlorohydrin.

The method for producing a sizing agent-coated carbon fiber of the present invention must be a method including a step satisfying the following (V) or / and (VI).
(V) The process of apply | coating to the carbon fiber the sizing agent containing liquid which has heat-processed at 20-150 degreeC for 0.5 to 20000 hours in the presence of water and which has the said epoxy compound (A) as a main component.
(VI) wherein the epoxy compound sizing agent-containing liquid consisting mainly of (A) after coating and drying the carbon fibers, further 20 to 150 ° C., the step of heat treatment at humid humidity 50-90% 20-20000 hours.

Moreover, the manufacturing method of the sizing agent application | coating carbon fiber of this invention WHEREIN: The epoxy value (b2) after heat processing and the epoxy value (b2) after heat processing shown in said (V), and the said (V) The epoxy value (b3) before the heat treatment shown in VI) and the epoxy value (b4) after the heat treatment satisfy the following (VII).
(VII) 1.5 ≦ [(b1) / (b2)] × [(b3) / (b4)] ≦ 10.

  Further, the prepreg of the present invention is a sizing agent-coated carbon fiber according to any one of the above, or a sizing agent-coated carbon fiber produced by the method for producing a sizing agent-coated carbon fiber according to any one of the above. And a thermosetting resin.

  The prepreg of the present invention is characterized in that, in the above invention, the thermosetting resin contains an epoxy compound and a latent curing agent (B).

  The prepreg of the present invention is characterized in that, in the above invention, the latent curing agent (B) is an aromatic amine curing agent (B1) containing a diphenylsulfone skeleton.

  The prepreg of the present invention is characterized in that, in the above invention, the latent curing agent (B) is dicyandiamide or a derivative (B2) thereof.

  Moreover, the carbon fiber reinforced composite material of the present invention is formed by molding the prepreg according to any one of the above.

  Moreover, the carbon fiber reinforced composite material of the present invention is a sizing agent-coated carbon fiber according to any one of the above, or a sizing agent-coated fiber manufactured by the method according to any one of the above and a thermosetting resin. A cured product is included.

  According to the present invention, it is possible to obtain a sizing agent-coated carbon fiber having excellent adhesion with a matrix resin. Further, by applying the sizing agent-coated carbon fiber, it is possible to obtain a prepreg for obtaining a carbon fiber reinforced composite material having a small change with time even during long-term storage and having excellent physical properties.

  Hereinafter, the form for implementing the manufacturing method of the sizing agent application | coating carbon fiber and sizing agent application | coating carbon fiber of this invention in more detail is demonstrated.

The sizing agent-coated carbon fiber according to the present invention is a sizing agent-coated carbon fiber obtained by coating a carbon fiber with a sizing agent containing, as a main component, an epoxy compound (A) having a hydroxyl group and an epoxy group in the molecule. The agent contains a curing agent having a nitrogen or phosphorus content of 1.3% by mass or less, and the sizing agent-coated carbon fiber is immersed in an N, N-dimethylformamide solvent and subjected to ultrasonic treatment. The hydroxyl value of the eluted sizing agent (a) meq. / G and epoxy value (b) meq. / G satisfies the following (I) to (III).
(I) 8 ≦ (a) + (b) ≦ 16
(II) (a) / (b) ≧ 2
(III) (b) ≧ 0.5.

  According to the knowledge of the present inventors, those satisfying all such ranges are excellent in interfacial adhesion between the carbon fiber and the matrix resin, and even when the sizing agent-coated carbon fiber is used for the prepreg, the prepreg is used for a long time. There is little decrease in physical properties when stored, and it is suitable for carbon fibers for composite materials.

  First, each component of the sizing agent-coated carbon fiber used in the present invention and the sizing agent used therefor will be described.

  The epoxy compound (A) of the present invention is a compound having a hydroxyl group and an epoxy group in the molecule. It is preferable that the epoxy compound (A) contains an epoxy group and a hydroxyl group because a strong bond between the epoxy group and the hydroxyl group in the carbon fiber and the sizing agent can be formed and the adhesiveness is improved. It has been confirmed that the epoxy group has a strong bond particularly with the carbon fiber, and when the sizing agent containing the epoxy group is used, the adhesion between the carbon fiber and the matrix resin is high. On the other hand, the reactivity with the compound having a functional group represented by the curing agent in the matrix resin is high, and when the sizing agent-coated carbon fiber is used for the prepreg, the matrix resin and the sizing agent are stored in the prepreg state for a long time. It has been confirmed that there is a problem that the structure of the interface layer is changed by the interaction of the above, and the physical properties of the carbon fiber reinforced composite material obtained from the prepreg are lowered.

  In addition, the hydroxyl group improves the adhesion to the carbon fiber, and when the sizing agent-coated carbon fiber of the present invention is used for the prepreg, the reactivity with the matrix resin is low, and the change in physical properties when the prepreg is stored for a long time is small. There is an advantage. However, it has been confirmed that when a sizing agent containing only a hydroxyl group is used, the adhesion between the carbon fiber and the matrix resin is slightly inferior. In the present invention, the fact that the epoxy compound (A) has a hydroxyl group and an epoxy group in the molecule does not need to have one or more functional groups in one molecule, and it is sufficient if it has an average. .

Therefore, in the present invention, the ratio of the hydroxyl group and the epoxy group of the sizing agent containing the epoxy compound (A) applied to the carbon fiber as a main component is important, and this can be expressed well. It can be said that the ratio of the hydroxyl group and the epoxy group contained in the eluted component is important. In the present invention, the hydroxyl value (a) meq. Of the sizing agent eluted by immersing the sizing agent-coated carbon fiber in an N, N-dimethylformamide solvent and subjecting it to ultrasonic treatment. / G and epoxy value (b) meq. It is important that / g satisfies the following (I) to (III).
(I) 8 ≦ (a) + (b) ≦ 16
(II) (a) / (b) ≧ 2
(III) (b) ≧ 0.5.

  The ratio of hydroxyl groups and epoxy groups of the eluted sizing agent is determined by immersing the sizing agent-coated carbon fiber of the present invention in an N, N-dimethylform solvent and performing ultrasonic cleaning for 30 minutes three times each. It can be determined by analyzing the eluted sizing agent solution. The sizing agent remaining in the carbon fiber when the sizing agent is eluted from the sizing agent-coated carbon fiber is preferably 0.20% by mass or less.

  The amount of sizing agent attached was measured by measuring the change in mass before and after the heat treatment when 2 ± 0.5 g of sizing agent-coated carbon fiber was sampled and heat-treated at 450 ° C. for 15 minutes in a nitrogen atmosphere. The amount of change is divided by the mass before heat treatment (mass%).

  The hydroxyl value (a) and epoxy value (b) of the sizing agent of the present invention can be controlled by heat treatment of the sizing agent and sizing agent-coated carbon fiber described below, in addition to the type of sizing agent used for coating. is there. Due to the thermal history, the epoxy compound applied to the carbon fiber can be controlled by hydrolysis by self-condensation or reaction with water. In the present invention, hydrolysis by reaction with water is preferably used from the viewpoint of increasing hydroxyl groups.

  Accordingly, in the present invention, the kind of sizing agent to be used itself may be any known one, and by controlling the sizing agent applied to the sizing agent-coated carbon fiber within the above range, processability, composite physical properties, prepreg storage It is important to suppress changes over time.

  In the present invention, the hydroxyl value (a) meq. / G and epoxy value (b) meq. / G total ((a) + (b)) is 8-16 meq. / G. 8 meq. By being / g or more, the functional group of the sizing agent becomes sufficient, and the adhesiveness becomes higher. A preferred range is 9 meq. / G or more, more preferably 11 meq. / G or more. Further, (a) + (b) is 16 meq. By being below / g, the flexibility becomes high and the spreadability becomes good.

  In the present invention, the hydroxyl value (a) meq. / G and epoxy value (b) meq. (A) / (b) which is the ratio of / g is 2 or more. That it is 2 or more has shown that there is much quantity of a hydroxyl group with respect to an epoxy group, and can suppress the reactivity with matrix resin, improving the interaction with the carbon fiber surface. Further, (a) / (b) is more preferably 4 or more.

  The epoxy value (b) of the eluted sizing agent in the present invention is 0.5 meq. / G or more. The epoxy group has a stronger interaction with the surface of the carbon fiber than the hydroxyl group, and 0.5 meq. At / g or more, the adhesion between the sizing agent and the carbon fiber is further improved, and the physical properties of the composite are improved when the sizing agent-coated carbon fiber is used in a carbon fiber reinforced composite material. The epoxy value (b) is 1 meq. / G or more is preferable. On the other hand, since epoxy groups are highly reactive, when sizing agent-coated carbon fibers are used in the prepreg, the epoxy groups in the sizing agent react with the matrix resin, resulting in deterioration of physical properties when the prepreg is stored for a long period of time. I know that. The epoxy value is 4 meq. / G or less is preferable because a decrease in physical properties when the prepreg is stored for a long period of time is reduced. The epoxy value (b) was 3 meq. / G or less is more preferable, and 2 meq. / G or less is more preferable.

  The epoxy value can be determined by acid-base titration using a solution in which the above sizing agent is eluted, opening the epoxy group with hydrochloric acid.

  Moreover, the hydroxyl value (a) of the eluted sizing agent in the present invention is 9 meq. / G or more is preferable. The hydroxyl value (a) is 9 meq. Since the wettability between the sizing agent and the carbon fiber is improved even when the epoxy value is small, it is preferable because the sizing agent adheres uniformly and the adhesiveness is improved. The hydroxyl value (a) is 10 meq. / G or more, more preferably 11 meq. / G or more is more preferable. From the viewpoint of suppressing the thickening of the sizing agent due to hydrogen bonding by the hydroxyl group, 15 meq. / G or less is preferable.

  The hydroxyl value of the sizing agent can be determined by acetylating the hydroxyl group with acetic anhydride using a solvent eluting the sizing agent and titrating the produced acetic acid with a potassium hydroxide solution. Since the epoxy group is also titrated, it is corrected with the above epoxy value.

Moreover, it is essential that the weight average molecular weight of the eluted sizing agent in the present invention is 1000 to 5000 . It is preferable for the weight average molecular weight to be 1000 or more because breakage of single yarn due to adhesion at the time of releasing the sizing agent-coated carbon fiber can be suppressed. When the weight average molecular weight is 5000 or less, the functional group can be increased and the adhesiveness is improved . The weight average molecular weight is preferably 1500 or more, and preferably 3000 or less.

  The weight average molecular weight can be determined by gel permeation chromatography (GPC) using the eluted sizing agent as a monodisperse polystyrene standard and dimethylformamide (with 0.01 N-lithium bromide) as a solvent.

  The sizing agent-coated carbon fiber of the present invention contains the epoxy compound (A) as a main component. The main component means that it is 50% by mass or more based on the total amount of the sizing agent excluding the solvent before coating. Moreover, it is preferable that it is 80 mass% or more, it is preferable that it is 90 mass% or more, and it is preferable that it is 95 mass% or more. One kind of epoxy compound (A) may be used, or two or more kinds may be used.

  The sizing agent of the sizing agent-coated carbon fiber of the present invention includes a curing agent that has a nitrogen or phosphorus content of 1.3% by mass or less. The curing agent in the present invention is a substance having a function of curing the resin by adding it to a thermosetting resin and reacting it to form a three-dimensional network structure. It includes both those that become molecular skeleton components of the cured resin and those that have a catalyst that promotes the curing reaction. Even when storing the prepreg using the sizing agent-coated carbon fiber of the present invention for a long period of time by setting the content in the sizing agent of the curing agent to 1.3 mass% or less in nitrogen or phosphorus content, Since the change of the interface layer due to the reaction of the epoxy compound can be suppressed, the composite physical properties are favorable, which is preferable. The content of the curing agent in the sizing agent is preferably 0.025% by mass or less, more preferably 0.005% by mass or less in terms of nitrogen or phosphorus content, and most preferably no curing agent is contained in the sizing agent. Examples of the curing agent include a compound having a primary amino group, a secondary amino group, a tertiary amine compound, a tertiary amine salt, and a quaternary ammonium salt. In addition to amine compounds, compounds having active hydrogen such as phosphonium salts are also exemplified. Both aromatic and aliphatic are included. Further, both monofunctional and polyfunctional have an effect of promoting curing.

The epoxy compound (A) can contain a halogen, a carboxyl group, a urea group, a sulfonyl group, and a sulfo group in addition to the epoxy group and the hydroxyl group. When the epoxy compound (A) is an epoxy compound having another functional group, even when the epoxy group forms a covalent bond or a hydrogen bond with the oxygen-containing functional group on the surface of the carbon fiber, the other functional group is not bonded to the matrix resin. A covalent bond or a hydrogen bond can be formed, which is preferable because adhesion is further improved. In the present invention, it is essential that the epoxy compound (A) contains a halogen in the molecule.

  In particular, the inclusion of halogen is preferable because the polarity is increased and the adhesiveness is improved. The halogen is preferably bromine, chlorine or fluorine. In producing an epoxy compound, a method of causing epichlorohydrin to act on a compound having a hydroxyl group is preferably used. At this time, from the viewpoint of processability that the amount of remaining chlorine can be controlled within the preferred range of the present invention, the halogen is more preferably chlorine.

It is essential that the halogen / carbon, which is the ratio of the number of atoms of halogen and carbon, measured by X-ray photoelectron spectroscopy on the surface of the sizing agent-coated carbon fiber of the present invention is 0.005 to 0.030 . By allowing the ratio of the halogen and the number of atoms of carbon is 0.005 or more, reasons are not clear, you improve adhesion. From the viewpoint of corrosion resistance and the like, it is preferably 0.030 or less . 0.010 or more is preferable and 0.020 or less is preferable.

The halogen concentration on the surface of the sizing agent was determined by X-ray photoelectron spectroscopy according to the following procedure. The case where the halogen is chlorine will be described as an example. First, the sizing agent-coated carbon fibers of the present invention were cut into 20 mm, spread and arranged on a copper sample support, and then Alα ₁ and ₂ were used as an X-ray source, and the inside of the sample chamber was 1 × 10 ⁻⁸ torr. Keep it in a measurement. Measured with a photoelectron escape angle of 45 °. As a correction value for the peak accompanying charging during measurement, the binding energy value of the C _1s main peak (peak top) 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, and the Cl _2p peak area is obtained by drawing a straight base line in the range of 195 to 205 eV. The surface oxygen concentration (Cl / C) is expressed as an atomic ratio calculated by dividing the ratio of the Cl _2p peak area by the sensitivity correction value unique to the apparatus. When ESCA-1600 manufactured by ULVAC-PHI Co., Ltd. is used as the X-ray photoelectron spectroscopy apparatus, the sensitivity correction value unique to the apparatus is 3.04.

When the halogen compound is fluorine, the F _1s peak area is obtained by drawing a straight base line in the range of 681 to 691 eV, and 3.18 is used as the sensitivity correction value unique to the apparatus. When the halogen compound is bromine, the Br _3d peak area is obtained by drawing a straight base line in the range of 65 to 75 eV, and 3.66 is used as the sensitivity correction value unique to the apparatus.

Examples of the epoxy compound (A) used as the main component of the sizing agent-coated carbon fiber of the present invention include an aliphatic epoxy compound (A1) and an aromatic epoxy compound (A2) . In the present invention, the epoxy compound (A) It is essential to use the aliphatic epoxy compound (A1).

  The aliphatic epoxy compound (A1) preferably used in the present invention is an epoxy compound containing no aromatic ring. Since it has a flexible skeleton with a high degree of freedom, it can have a strong interaction with carbon fibers. As a result, the adhesion between the carbon fiber coated with the sizing agent and the matrix resin is improved.

  Moreover, the aromatic epoxy compound (A2) preferably used in the present invention is an epoxy compound having one or more aromatic rings in the molecule. The aromatic ring may be an aromatic ring hydrocarbon consisting only of carbon, or a heteroaromatic ring such as furan, thiophene, pyrrole or imidazole containing a heteroatom such as nitrogen or oxygen. The aromatic ring may be a polycyclic aromatic ring such as naphthalene or anthracene. In a carbon fiber reinforced composite material composed of a carbon fiber coated with a sizing agent and a matrix resin, a so-called interface layer in the vicinity of the carbon fiber is affected by the carbon fiber or the sizing agent and may have different characteristics from the matrix resin. . When the sizing agent contains an aromatic epoxy compound (A2) having one or more aromatic rings, a rigid interface layer is formed, and the stress transmission capability between the carbon fiber and the matrix resin is improved, which is preferable.

  In the present invention, the aliphatic epoxy compound (A1) is particularly preferable from the viewpoint of adhesiveness.

  In the present invention, specific examples of the aliphatic epoxy compound (A1) include, for example, a glycidyl ether type epoxy compound derived from a polyol, a glycidyl amine type epoxy compound derived from an amine having a plurality of active hydrogens, and a polycarboxylic acid. Examples thereof include an induced glycidyl ester type epoxy compound and an epoxy compound obtained by oxidizing a compound having a plurality of double bonds in the molecule. From the viewpoint of suppressing deterioration of physical properties when the prepreg is stored for a long time, a glycidyl ether type epoxy compound and a glycidyl ester type epoxy compound are preferable.

  Examples of the glycidyl ether type epoxy compound include a glycidyl ether type epoxy compound obtained by a reaction between a polyol and epichlorohydrin. For example, as a glycidyl ether type epoxy compound, 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, trimethylolpropane, Pentaerythritol, sorbitol, and one and selected from arabitol, glycidyl ether type epoxy compound obtained by reaction with epichlorohydrin. Examples of the glycidyl ether type epoxy compound include a glycidyl ether type epoxy compound having a dicyclopentadiene skeleton.

  Examples of the glycidylamine type epoxy compound include 1,3-bis (aminomethyl) cyclohexane.

  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.

  Examples of the aliphatic epoxy compound (A1) used in the present invention include epoxy compounds such as triglycidyl isocyanurate in addition to these epoxy compounds.

  Examples of the aliphatic epoxy compound (A1) 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 aliphatic epoxy compound (A1) having an amide group in addition to the epoxy 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 an aliphatic dicarboxylic acid amide.

  Examples of the aliphatic epoxy compound (A1) having a urethane group in addition to the epoxy group include a urethane-modified epoxy compound. Specifically, “Adeka Resin (registered trademark)” EPU-78-13S, EPU-6, EPU-11, EPU-15, EPU-16A, EPU-16N, EPU-17T-6, EPU-1348, EPU-1395 (manufactured by ADEKA Corporation) and the like can be mentioned. 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 compound. Can be obtained. Here, examples of the polyvalent isocyanate used include hexamethylene diisocyanate, isophorone diisocyanate, and norbornane diisocyanate.

  Examples of the aliphatic epoxy compound (A1) having a urea group in addition to the epoxy group include a urea-modified epoxy compound. The urea-modified epoxy compound can be obtained by reacting the epoxy group of an epoxy compound having two or more epoxy groups with the carboxyl group of the aliphatic dicarboxylic acid urea.

  The aliphatic epoxy compound (A1) used in the present invention is one selected from glycerol, diglycerol, polyglycerol, trimethylolpropane, pentaerythritol, sorbitol, and arabitol from the viewpoint of high adhesion among the above, A glycidyl ether type epoxy compound obtained by reaction with chlorohydrin is more preferred.

  In the present invention, the aliphatic epoxy compound (A1) is more preferably polyglycerol polyglycidyl ether.

  The epoxy value of the aliphatic epoxy compound (A1) used in the present invention is preferably 3 meq./g or more. 3 meq. / G or more is preferable because many hydroxyl groups can be contained when heat-treated in the presence of water. The aliphatic epoxy compound (A1) has an epoxy value of 4 meq. / G or more is more preferable. From the viewpoint of controlling the number of functional groups contained in the sizing agent applied to the carbon fiber, 15 meq. / G or less is preferable, and 10 meq. / G or less is more preferable. 8 meq. / G or less is more preferable.

  Furthermore, components other than the epoxy compound (A) can be contained in the sizing agent applied to the sizing agent-coated carbon fiber of the present invention, depending on the purpose. By blending the sizing agent-coated carbon fiber with a material that imparts convergence or flexibility, the handling property, scratch resistance and fluff resistance can be improved, and the impregnation property of the matrix resin can be improved. A general sizing agent such as polyester or polyurethane can be used. For the purpose of stabilizing the sizing agent, auxiliary components such as a dispersant and a surfactant may be added.

  In the present invention, as additives such as surfactants, for example, polyalkylene oxides such as polyethylene oxide and polypropylene oxide, higher alcohols, polyhydric alcohols, alkylphenols, styrenated phenols and the like, polyalkylene oxides such as polyethylene oxide and polypropylene oxide, etc. Nonionic surfactants such as a compound to which is added and a block copolymer of ethylene oxide and propylene oxide are preferably used. Moreover, you may add a polyester resin, an unsaturated polyester compound, etc. suitably in the range which does not affect the effect of this invention.

  In this invention, it is preferable that the adhesion amount to the carbon fiber of a sizing agent is the range of 0.05-5.0 mass% with respect to sizing agent application | coating carbon fiber, More preferably, it is 0.05-0. The range is 95% by mass. When the sizing agent adhesion amount is 0.05% by mass or more, when the sizing agent-coated carbon fiber is prepreg and woven, it can withstand friction caused by a metal guide that passes therethrough, and generation of fluff is suppressed. Excellent quality such as smoothness of fiber sheet. On the other hand, if the amount of sizing agent deposited is 5.0% by mass or less, the matrix resin is impregnated inside the carbon fiber without being hindered by the sizing agent film around the sizing agent-coated carbon fiber. The generation of voids is suppressed, the quality of the composite material is excellent, and at the same time the mechanical properties are excellent. The adhesion amount of the sizing agent is determined by the method described above.

  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. With such a uniform sizing agent layer, a large effect of improving adhesiveness can be obtained stably, and further, stable high-order workability can be obtained.

  Next, the carbon fiber used in the present invention will be described. Examples of the carbon fiber used in the present invention 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.

  In the carbon fiber according to the present invention, the strand strength of the obtained carbon fiber bundle 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 obtained 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 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 trifluoride monoethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) / Acetone = 100/3/4 (part by mass) is used. As curing conditions, normal pressure, 130 ° C., and 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.

  The carbon fiber used in the present invention preferably has a surface roughness (Ra) of 6.0 to 100 nm. More preferably, it is 15-80 nm, and 30-60 nm is suitable. Carbon fiber with a surface roughness (Ra) of 6.0 to 60 nm has a highly active edge portion on the surface, so the reactivity with the epoxy group of the sizing agent described above is improved and the interfacial adhesion is improved. This is preferable. Moreover, since the carbon fiber whose surface roughness (Ra) is 6.0-100 nm has an unevenness | corrugation on the surface, it can improve interface adhesiveness by the anchor effect of a sizing agent, and is preferable.

The average roughness (Ra) of the carbon fiber surface can be measured by using an atomic force microscope (AFM). For example, a carbon fiber cut to several millimeters in length is prepared, fixed on a substrate (silicon wafer) using a silver paste, and 3 atomic fibers at the center of each single fiber by an atomic force microscope (AFM). What is necessary is just to observe the image of a three-dimensional surface shape. As an atomic force microscope, a Dimension 3000 stage system or the like can be used in NanoScope IIIa manufactured by Digital Instruments and can be observed under the following observation conditions.
・ Scanning mode: Tapping mode ・ Probe: Silicon cantilever ・ Scanning range: 0.6μm × 0.6μm
・ Scanning speed: 0.3Hz
-Number of pixels: 512 × 512
・ Measurement environment: Room temperature, in air.

  In addition, for each sample, an image obtained by observing one single fiber from one point at a time approximates the roundness of the fiber cross section with a cubic surface, and the average roughness (Ra) for the entire image obtained. It is preferable to calculate the average roughness (Ra) and evaluate the average value for five single fibers.

  In the present invention, the total fineness of the carbon fibers 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 the present invention, the single fiber diameter of the carbon fiber is preferably 4.5 to 7.5 μm. Since it is 7.5 micrometers or less, since a carbon fiber with high intensity | strength and elastic modulus can be obtained, it is used preferably. More preferably, it is 6 μm or less, and further preferably 5.5 μm or less. When the thickness is 4.5 μm or more, it is difficult to cause single fiber cutting in the process, and productivity is hardly lowered.

  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 0.07-0.25. 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 0.50 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, carbon fibers from which dirt and the like adhering to the carbon fiber surface were removed with a solvent were cut to 20 mm, spread and arranged on a copper sample support base, and then AlKα ₁ and ₂ were used as an X-ray source. The inside of the chamber was measured at 1 × 10 ⁻⁸ Torr. Measurement was performed at a photoelectron escape angle of 90 °. As a correction value for the peak accompanying charging during measurement, the binding energy value of the C _1s main peak (peak top) 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, and the O _1s peak area is obtained by drawing a straight base line in the range of 528 to 540 eV. The surface oxygen concentration (O / C) is represented by an atomic ratio calculated by dividing the ratio of the O _1s peak area by the sensitivity correction value unique to the apparatus. When ESCA-1600 manufactured by ULVAC-PHI Co., Ltd. is used as the X-ray photoelectron spectroscopy apparatus, the sensitivity correction value unique to the apparatus is 2.33.

  The carbon fiber used in the present invention has a surface carboxyl group concentration (COOH / C) represented by the ratio of the number of carbon group (COOH) and carbon (C) atoms measured by chemical modification X-ray photoelectron spectroscopy. ) Is preferably in the range of 0.003 to 0.015. A more preferable range of the carboxyl group concentration (COOH / C) on the carbon fiber surface is 0.004 to 0.010. The carbon fiber used in the present invention has a surface hydroxyl group concentration (COH / C) expressed by the ratio of the number of hydroxyl groups (OH) and carbon (C) on the surface of the carbon fiber measured by chemical modification X-ray photoelectron spectroscopy. ) Is preferably in the range of 0.001 to 0.050. The surface hydroxyl group concentration (COH / C) on the carbon fiber surface is more preferably in the range of 0.010 to 0.040.

  The surface carboxyl group concentration (COOH / C) and hydroxyl group concentration (COH / C) of the carbon fiber are determined by X-ray photoelectron spectroscopy according to the following procedure.

The surface hydroxyl group concentration (COH / C) is determined by chemical modification X-ray photoelectron spectroscopy according to the following procedure. First, carbon fiber bundles from which the sizing agent and the like have been removed with a solvent are cut, spread and arranged on a platinum sample support, and placed in dry nitrogen gas containing 0.04 mol / liter of anhydrous trifluoride acetic acid gas. After 10 minutes of exposure at room temperature and chemical modification treatment, it was mounted on an X-ray photoelectron spectrometer with a photoelectron escape angle of 35 °, AlKα ₁ , ₂ was used as the X-ray source, and the inside of the sample chamber was 1 × 10 ⁻⁸ Torr. Keep the degree of vacuum. As correction of the peak accompanying charging during measurement, first, the binding energy value of the main peak of C _1s is adjusted to 284.6 eV. The C _1s peak area [C _1s ] is obtained by drawing a straight base line in the range of 282 to 296 eV, and the F _1s peak area [F _1s ] is obtained by drawing a straight base line in the range of 682 to 695 eV. Desired. Moreover, reaction rate r is calculated | required from _C1s peak division _| segmentation of the polyvinyl alcohol chemically modified simultaneously.

  The surface hydroxyl group concentration (COH / C) is represented by a value calculated by the following equation.

COH / C = {[F _1s ] / (3k [C _1s ] −2 [F _1s ]) r} × 100 (%)
Note that k is the sensitivity correction value of the F _1s peak area with respect to the C _1s peak area unique to the apparatus, and when using the model SSX-100-206 manufactured by SSI of the United States, the sensitivity correction value specific to the apparatus is 3.919. .

The surface carboxyl group concentration (COOH / C) is determined by chemical modification X-ray photoelectron spectroscopy according to the following procedure. First, carbon fiber bundles from which the sizing agent and the like have been removed with a solvent are cut and spread and arranged on a platinum sample support, and 0.02 mol / liter of trifluorinated ethanol gas, 0.001 mol / liter of dicyclohexyl. After exposure to air containing carbodiimide gas and 0.04 mol / liter pyridine gas at 60 ° C. for 8 hours and chemical modification treatment, it was mounted on an X-ray photoelectron spectrometer with a photoelectron escape angle of 35 ° as an X-ray source. Using AlKα ₁ and ₂ , the inside of the sample chamber is kept at a vacuum of 1 × 10 ⁻⁸ Torr. As correction of the peak accompanying charging during measurement, first, the binding energy value of the main peak of C _1s is adjusted to 284.6 eV. The C _1s peak area [C _1s ] is obtained by drawing a straight base line in the range of 282 to 296 eV, and the F _1s peak area [F _1s ] is obtained by drawing a straight base line in the range of 682 to 695 eV. Desired. Simultaneously, the reaction rate r is determined from the C _1s peak splitting of the polyacrylic acid chemically modified, and the residual rate m of the dicyclohexylcarbodiimide derivative is determined from the O _1s peak splitting.

  The surface carboxyl group concentration COOH / C was represented by the value calculated by the following formula.

COOH / C = {[F _1s ] / (3k [C _1s ] − (2 + 13 m) [F _1s ]) r} × 100 (%)
Note that k is the sensitivity correction value of the F _1s peak area with respect to the C _1s peak area unique to the apparatus, and the sensitivity correction value specific to the apparatus when using the model SSX-100-206 manufactured by SSI of the United States is 3.919. is there.

  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. From the viewpoint of easily obtaining high-strength carbon fibers, it is preferable to use a wet or dry wet spinning method. In particular, the use of a dry and wet spinning method is more preferable because carbon fibers having high strength can be obtained.

  In order to further improve the adhesion between the carbon fiber and the matrix resin, a carbon fiber having a surface roughness (Ra) of 6.0 to 100 nm is preferable. In order to obtain a carbon fiber having the surface roughness, a wet spinning method is used. Preferably, the precursor fiber is spun by.

  As the spinning dope, a solution obtained by dissolving a homopolymer or copolymer of polyacrylonitrile in a solvent can be used. 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, discharged in a spinning bath or in the air, and then coagulated in the spinning bath. 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 if necessary, further subjected to graphitization treatment to obtain carbon fiber. As conditions for carbonization treatment and graphitization treatment, the maximum heat treatment temperature is preferably 1100 ° C. or higher, more preferably 1400 to 3000 ° C.

  The obtained carbon fiber is usually subjected to an oxidation treatment in order to improve the adhesiveness with the matrix resin, whereby oxygen-containing functional groups are introduced. 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. From the viewpoint of adhesion, a liquid phase electrolytic oxidation is performed in an alkaline electrolytic solution, and then a sizing agent is applied. It is more preferable.

  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.

  The concentration of the electrolytic solution used in the present invention is preferably in the range of 0.01 to 5 mol / L, more preferably in the range of 0.1 to 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.

  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 less than 100 ° C., 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 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 ² within the range. 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, it is preferable to wash and dry the carbon fiber after the electrolytic treatment. As a cleaning method, for example, a dip 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 a dip method, vibrating a carbon fiber with an ultrasonic wave. Also, 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, drying is performed at 210 ° C. or lower. 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.

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

It is preferable that the manufacturing method of the sizing agent application | coating carbon fiber of this invention includes the process of satisfy | filling the following (V) or / and (VI).
(V) The process of apply | coating to the carbon fiber the sizing agent containing liquid which has as a main component the epoxy compound (A) heat-processed at 20-150 degreeC for 0.5 to 20000 hours in presence of water.
(VI) A step of applying a sizing agent-containing liquid containing the epoxy compound (A) as a main component to carbon fibers and drying, followed by heat treatment for 20 to 20000 hours under wet conditions of 20 to 150 ° C. and humidity of 50 to 90%.

  By the above method, a sizing agent-coated carbon fiber having a hydroxyl group and an epoxy group at a specific ratio can be suitably obtained.

The method for producing sizing agent-coated carbon fibers of the present invention includes the epoxy value (b1) before the heat treatment shown in (V), the epoxy value (b2) after the heat treatment, and the above (VI). It is preferable that the epoxy value (b3) before the heat treatment and the epoxy value (b4) after the heat treatment satisfy (VII).
(VII) 1.5 ≦ [(b1) / (b2)] × [(b3) / (b4)] ≦ 10
By satisfy | filling the said range, the ratio of an epoxy group and a hydroxyl group can enter into a preferable range by hydrolysis. [[B1) / (b2)] × [(b3) / (b4)] is more preferably 2 or more, and more preferably 5 or less.

  In the present invention, a method of heat-treating the epoxy compound (A) in the presence of water before applying a sizing agent to carbon fibers is preferably used.

  By heating in the presence of water, hydrolysis of the epoxy group is promoted, and the proportion of the hydroxyl group can be increased. In addition, after heating in presence of water, when storing an epoxy compound (A) for a long term, or when using other than water as a solution of a sizing agent containing liquid, it is preferable to distill water off. It is preferable to store the water content at 200 ppm or less. Moreover, it is more preferable that it is 100 ppm or less. By setting the water content to 200 ppm or less, it is possible to suppress a decrease in the epoxy value during long-term storage. When water is used as the solvent as the sizing agent-containing liquid, the water used when the epoxy compound (A) is heat-treated may be used as it is as the sizing agent-containing liquid without distilling off the water.

  When the heat treatment is performed in the presence of water, the concentration of the epoxy compound (A) in the aqueous solution is preferably 0.2% by mass or more. It is preferably 0.2% by mass or more because it is not necessary to remove and concentrate water when used as a sizing agent-containing liquid. The upper limit is not limited as long as water is present, but the epoxy compound (A) is preferably 95% by mass or less from the viewpoint of uniformly heat-treating by improving the stirrability.

  The heat treatment temperature is preferably 20 ° C. or higher and 150 ° C. or lower. The reaction is promoted at 20 ° C. or higher, and deterioration of physical properties at 150 ° C. or lower is suppressed. It is preferable because it can be treated at normal pressure by setting it to 98 ° C. or lower. 50 degreeC or more and 90 degrees C or less are preferable.

  The time is appropriately determined depending on the heat treatment temperature and the reactivity of the compound, but from the viewpoint of reaction uniformity and productivity, 0.5 hours or more and 20000 hours or less are preferably used. From the viewpoint of productivity, 2 hours or more and 30 hours or less are more preferable.

  In addition to the above heating in the presence of water, the heating can be performed in the absence of water. Epoxy groups and hydroxyl groups can react between molecules to reduce functional groups and increase molecular weight.

  The heating temperature is preferably 130 ° C. or higher and 300 ° C. or lower. Reaction is accelerated | stimulated because it is 130 degreeC or more, and decomposition | disassembly of an epoxy compound (A) is suppressed at 300 degrees C or less. 180 degreeC or more and 260 degrees C or less are preferable. The time is appropriately determined depending on the temperature and the reactivity of the compound, but from the viewpoint of reaction uniformity and productivity, 1 minute or more and 10,000 minutes or less are preferably used. 5 minutes or more and 1000 minutes or less are more preferable.

  For the heat treatment, the aqueous solution or the epoxy compound (A) may be heated in an oven, or may be transferred to a reaction vessel typified by a flask and heated with stirring. You may make it react under pressure in a pressurized container. In the present invention, when the heat treatment is performed, components other than the epoxy compound (A) may be contained within a range not inhibiting the control of the reaction. In order to accelerate the reaction, a reaction accelerator such as an alkali or an acid may be added. However, it remains in the sizing agent, so that it should not be used from the viewpoint of suppressing deterioration in physical properties of the prepreg during long-term storage. preferable.

  In the present invention, as a method of applying the sizing agent to the carbon fiber, a method of applying the sizing agent-containing liquid in which the epoxy compound (A) and other components are simultaneously dissolved or dispersed in a solvent, and a method of applying the sizing agent to the carbon fiber, A method of applying to carbon fiber in a plurality of times is preferably used. In the present invention, it is preferable to adopt a one-step application in which a sizing agent-containing liquid containing all the components of the sizing agent is applied to the carbon fiber at a time from the viewpoint of the effect and ease of processing.

  The sizing agent according to the present invention can be used as a sizing agent-containing liquid obtained by diluting a sizing agent component with a solvent. Examples of such a solvent include water, methanol, ethanol, isopropanol, acetone, methyl ethyl ketone, dimethylformamide, and dimethylacetamide. Among them, handling is easy and advantageous from the viewpoint of safety. Therefore, an aqueous dispersion or aqueous solution emulsified with a surfactant is preferably used.

  The concentration of the sizing agent in the sizing agent-containing liquid is usually preferably in the range of 0.2 to 20% by mass. The sizing agent-containing liquid may be diluted by mixing the epoxy compound (A) with a solvent at one time. Moreover, after diluting an epoxy compound (A) with a solvent and obtaining a sizing agent containing liquid with a high density | concentration, it can also dilute in multiple times, such as further diluting with a solvent.

  Examples of means for applying (coating) the sizing agent to the carbon fiber include a method of immersing the carbon fiber in a sizing agent-containing liquid via a roller, a method of contacting the carbon fiber with a roller to which the sizing agent-containing liquid is attached, and a sizing agent. There is a method of spraying the liquid on the carbon fiber in the form of a mist. 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 of the sizing agent-containing liquid, the temperature, 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.

  The liquid temperature of the sizing agent-containing liquid when the sizing liquid is applied to the carbon fiber is preferably in the range of 10 to 50 ° C. in order to suppress fluctuations in the concentration of the sizing agent due to solvent evaporation. In addition, after applying the sizing agent-containing liquid, the amount of sizing agent adhered can be adjusted and uniformly applied to the carbon fiber by adjusting the amount of squeezing out the excess sizing agent-containing liquid.

  In the present invention, as a method of giving a thermal history after applying a sizing agent-containing liquid mainly composed of an epoxy compound (A) to carbon fibers, heat treatment after applying the sizing agent-containing liquid to carbon fibers, and a sizing agent A method of heat-treating the bobbin on which the coated carbon fiber is wound is mentioned.

In the method for producing the sizing agent-coated carbon fiber, a method of drying is generally employed for the purpose of removing the solvent contained in the sizing agent-coated carbon fiber after applying the sizing agent-containing liquid. In this invention, after apply | coating a sizing agent containing liquid to carbon fiber, processability becomes favorable by giving the heat processing of specific temperature and time, and is preferable. By extending the heat treatment time or raising the heat treatment temperature, the intermolecular reaction of epoxy groups and hydroxyl groups can be promoted, the epoxy value and hydroxyl value can be lowered, and the molecular weight can be increased. Moreover, the point which can control a functional group and molecular weight in a short time is preferable. The heat treatment under drying may be the same as the drying process or may be performed separately.
The heat treatment is preferably performed in a temperature range of 160 to 300 ° C. for 30 to 900 seconds. The heat treatment conditions are preferably in the temperature range of 200 to 250 ° C. for 60 to 500 seconds, and more preferably in the temperature range of 210 to 240 ° C. for 90 to 300 seconds. It is preferable that the heat treatment conditions are 160 ° C. or higher and 30 seconds or longer because the molecular weight increases and yarn breakage due to adhesion or the like when the carbon fiber is unwound from the bobbin can be suppressed. On the other hand, when the heat treatment conditions are 300 ° C. or less and 900 seconds or less, decomposition and volatilization of the sizing agent can be suppressed, and thus the interaction with the carbon fibers is promoted, and the adhesion between the carbon fibers and the matrix resin is sufficient.

  Moreover, it is preferable to heat-treat the sizing agent-coated carbon fiber under moisture. As a method of heat-treating the sizing agent-coated carbon fibers under wet conditions, the bobbin shape around which the sizing agent-coated carbon fibers are wound may be heat treated. In the case of continuous processing, it is preferable because the processing is performed uniformly, and the processing time can be increased by performing the bobbin state processing, which is preferable in terms of process. In the case of continuous processing, it is possible to pass through a tube through steam and to pass through a box having a constant humidity. In the treatment in the bobbin state, it can be stored in a constant temperature and humidity chamber. The temperature and humidity may be constant during the heat treatment, but may be changed during the heat treatment. By controlling the humidity, not only the intermolecular reaction between the epoxy group and the hydroxyl group, but also the hydrolysis of the epoxy group can be controlled. Moreover, reaction can be accelerated | stimulated by raising temperature. Preferable heat treatment conditions are 20 to 20000 hours under a humidity of 20 to 150 ° C. and a humidity range of 50 to 90%. From the point of uniformity, it is preferable to perform heat treatment at 20 to 40 ° C. and a humidity of 50 to 70% for 10,000 to 20,000 hours. Moreover, it is preferable from the point of productivity to perform the heat processing for 20 to 500 hours at 60-98 degreeC and 70-90% of humidity.

  The heat treatment can also be performed by microwave irradiation and / or infrared irradiation. When the sizing agent-coated carbon fiber is heat-treated by microwave irradiation and / or infrared irradiation, the microwave penetrates into the carbon fiber and is absorbed, so that the carbon fiber which is the object to be heated can be heated to a desired temperature in a short time. Can be heated. 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.

  The sizing agent-coated carbon fiber of the present invention is suitably used in the form of, for example, tow, woven fabric, knitted fabric, braided string, web, mat, and chopped.

  The sizing agent-coated carbon fiber of the present invention can be used as a carbon fiber reinforced composite material in combination with a matrix resin. As the matrix resin, a thermosetting resin and a thermoplastic resin (the resin described here may be a resin composition) are used.

  Next, a carbon fiber reinforced thermosetting resin composite material using a thermosetting resin as the matrix resin will be described.

  In particular, for applications that require a high specific strength and specific elastic modulus, a tow in which carbon fibers are aligned in one direction is most suitable, and a method using a prepreg impregnated with a matrix resin is preferably used. .

  The sizing agent-coated carbon fiber of the present invention can be used for a prepreg and a carbon fiber reinforced composite material in combination with a thermosetting resin. In the present invention, the prepreg includes the sizing agent-coated carbon fibers described above or the sizing agent-coated carbon fibers produced by the method described above and a matrix resin.

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

  Among these thermosetting resins, it is preferable to use an epoxy resin containing at least an epoxy compound (C) because it has an advantage of excellent balance of mechanical properties and small curing shrinkage.

  The epoxy compound (C) 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 novolak type epoxy compound, a resorcinol type epoxy compound, a phenol aralkyl type. Select one or more of epoxy compounds, 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, etc. Can be used.

  Here, the bisphenol type epoxy compound is obtained by glycidylation of two phenolic hydroxyl groups of a bisphenol compound. The bisphenol A type, the bisphenol F type, the bisphenol AD type, the bisphenol S type, or the halogen or alkyl of these bisphenols. Examples include substituted products and hydrogenated products. Moreover, not only a monomer but the high molecular weight body which has several repeating units can also be used conveniently.

  Commercially available bisphenol A type epoxy compounds include “jER (registered trademark)” 825, 828, 834, 1001, 1002, 1003, 1003F, 1004, 1004AF, 1005F, 1006FS, 1007, 1009, 1010 (and above, Mitsubishi Chemical) Etc.). Examples of the brominated bisphenol A type epoxy compound include “jER (registered trademark)” 505, 5050, 5051, 5054, 5057 (manufactured by Mitsubishi Chemical Corporation). Examples of commercially available hydrogenated bisphenol A type epoxy compounds include ST5080, ST4000D, ST4100D, and ST5100 (manufactured by Nippon Steel Chemical Co., Ltd.).

  Commercially available bisphenol F type epoxy compounds include “jER (registered trademark)” 806, 807, 4002P, 4004P, 4007P, 4009P, 4010P (above, manufactured by Mitsubishi Chemical Corporation), “Epiclon (registered trademark)” 830. 835 (above, manufactured by DIC Corporation), “Epototo (registered trademark)” YDF2001, YDF2004 (above, manufactured by Nippon Steel Chemical Co., Ltd.), and the like. Examples of the tetramethylbisphenol F type epoxy compound include YSLV-80XY (manufactured by Nippon Steel Chemical Co., Ltd.).

  Examples of the bisphenol S-type epoxy compound include “Epiclon (registered trademark)” EXA-154 (manufactured by DIC Corporation).

  Examples of the amine-type epoxy compound include tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol, triglycidylaminocresol, tetraglycidylxylylenediamine, halogens thereof, alkynol-substituted products, and hydrogenated products.

  Commercially available products of tetraglycidyldiaminodiphenylmethane include “Sumiepoxy (registered trademark)” ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), YH434L (manufactured by Nippon Steel Chemical Co., Ltd.), and “jER (registered trademark)” 604 (Mitsubishi Chemical). (Manufactured by Co., Ltd.), “Araldide (registered trademark)” MY720, MY721 (manufactured by Huntsman Advanced Materials Co., Ltd.), and the like. Commercially available products of triglycidylaminophenol or triglycidylaminocresol include “Sumiepoxy (registered trademark)” ELM100, ELM120 (manufactured by Sumitomo Chemical Co., Ltd.), “Araldide (registered trademark)” MY0500, MY0510, MY0600 (and above) , Huntsman Advanced Materials Co., Ltd.), “jER (registered trademark)” 630 (manufactured by Mitsubishi Chemical Corporation), and the like. Examples of commercially available tetraglycidylxylylenediamine and hydrogenated products thereof include TETRAD-X and TETRAD-C (manufactured by Mitsubishi Gas Chemical Co., Ltd.).

  Commercially available products of phenol novolac type epoxy compounds are “jER (registered trademark)” 152, 154 (manufactured by Mitsubishi Chemical Corporation), “Epicron (registered trademark)” N-740, N-770, N-775 ( As mentioned above, DIC Corporation) etc. are mentioned.

  As a commercial item of a cresol novolac type epoxy compound, “Epiclon (registered trademark)” N-660, N-665, N-670, N-673, N-695 (above, manufactured by DIC Corporation), EOCN-1020 , EOCN-102S, EOCN-104S (manufactured by Nippon Kayaku Co., Ltd.), and the like.

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

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

  Examples of commercially available epoxy compounds having a biphenyl skeleton include “jER (registered trademark)” YX4000H, YX4000, YL6616 (manufactured by Mitsubishi Chemical Corporation), NC-3000 (manufactured by Nippon Kayaku Co., Ltd.), and the like. It is done.

  Commercially available dicyclopentadiene type epoxy compounds include “Epicron (registered trademark)” HP7200L (epoxy equivalents 245 to 250, softening point 54 to 58), “Epicron (registered trademark)” HP7200 (epoxy equivalents 255 to 260, softening) 59-63), "Epiclon (registered trademark)" HP7200H (epoxy equivalents 275-280, softening point 80-85), "Epiclon (registered trademark)" HP7200HH (epoxy equivalents 275-280, softening point 87-92) ( As described above, manufactured by Dainippon Ink & Chemicals, Inc.), XD-1000-L (epoxy equivalents 240 to 255, softening point 60 to 70), XD-1000-2L (epoxy equivalents 235 to 250, softening point 53 to 63) (Nippon Kayaku Co., Ltd.), “Tactix (registered trademark)” 556 (epoxy equivalent 2 5-235, a softening point of 79 ° C.) (Vantico Inc Co., Ltd.) and the like.

  Examples of commercially available isocyanate-modified epoxy compounds include XAC4151, AER4152 (produced by Asahi Kasei Epoxy Co., Ltd.) and ACR1348 (produced by ADEKA Co., Ltd.) having an oxazolidone ring.

  Examples of commercially available tetraphenylethane type epoxy compounds include “jER (registered trademark)” 1031 (manufactured by Mitsubishi Chemical Corporation), which is a tetrakis (glycidyloxyphenyl) ethane type epoxy compound.

  As a commercial item of a triphenylmethane type epoxy compound, “Tactics (registered trademark)” 742 (manufactured by Huntsman Advanced Materials Co., Ltd.) and the like can be mentioned.

  In particular, an epoxy resin containing at least a glycidylamine type epoxy compound having a plurality of functional groups as the epoxy compound (C) is preferable. An epoxy resin containing at least a glycidylamine type epoxy compound having a plurality of functional groups is preferable because it has a high multi-crosslinking density and can improve the heat resistance and compressive strength of the carbon fiber reinforced composite material.

  Examples of the glycidylamine-type epoxy compound having a plurality of functional groups include tetraglycidyldiaminodiphenylmethane, triglycidylaminophenol and triglycidylaminocresol, N, N-diglycidylaniline, N, N-diglycidyl-o-toluidine, N , N-diglycidyl-4-phenoxyaniline, N, N-diglycidyl-4- (4-methylphenoxy) aniline, N, N-diglycidyl-4- (4-tert-butylphenoxy) aniline and N, N-diglycidyl- 4- (4-phenoxyphenoxy) aniline and the like can be mentioned. In many cases, these compounds are obtained by adding epichlorohydrin to a phenoxyaniline derivative and cyclizing with an alkali compound. Since the viscosity increases as the molecular weight increases, N, N-diglycidyl-4-phenoxyaniline is particularly preferably used from the viewpoint of handleability.

  Specific examples of the phenoxyaniline derivative include 4-phenoxyaniline, 4- (4-methylphenoxy) aniline, 4- (3-methylphenoxy) aniline, 4- (2-methylphenoxy) aniline, 4- (4 -Ethylphenoxy) aniline, 4- (3-ethylphenoxy) aniline, 4- (2-ethylphenoxy) aniline, 4- (4-propylphenoxy) aniline, 4- (4-tert-butylphenoxy) aniline, 4- (4-cyclohexylphenoxy) aniline, 4- (3-cyclohexylphenoxy) aniline, 4- (2-cyclohexylphenoxy) aniline, 4- (4-methoxyphenoxy) aniline, 4- (3-methoxyphenoxy) aniline, 4- (2-methoxyphenoxy) aniline, 4- (3-phenoxyf) Noxy) aniline, 4- (4-phenoxyphenoxy) aniline, 4- [4- (trifluoromethyl) phenoxy] aniline, 4- [3- (trifluoromethyl) phenoxy] aniline, 4- [2- (trifluoro) Methyl) phenoxy] aniline, 4- (2-naphthyloxyphenoxy) aniline, 4- (1-naphthyloxyphenoxy) aniline, 4-[(1,1′-biphenyl-4-yl) oxy] aniline, 4- ( 4-nitrophenoxy) aniline, 4- (3-nitrophenoxy) aniline, 4- (2-nitrophenoxy) aniline, 3-nitro-4-aminophenyl phenyl ether, 2-nitro-4- (4-nitrophenoxy) Aniline, 4- (2,4-dinitrophenoxy) aniline, 3-nitro-4-phenoxyaniline, -(2-chlorophenoxy) aniline, 4- (3-chlorophenoxy) aniline, 4- (4-chlorophenoxy) aniline, 4- (2,4-dichlorophenoxy) aniline, 3-chloro-4- (4- Chlorophenoxy) aniline, 4- (4-chloro-3-tolyloxy) aniline, and the like.

  Examples of commercially available products of tetraglycidyldiaminodiphenylmethane include “Sumiepoxy (registered trademark)” ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), YH434L (manufactured by Tohto Kasei Co., Ltd.), “Araldite (registered trademark)” MY720 (Huntsman Advanced -Materials Co., Ltd.), "jER (registered trademark) 604" (Mitsubishi Chemical Co., Ltd.), etc. can be used. Examples of triglycidylaminophenol and triglycidylaminocresol include, for example, “Sumiepoxy (registered trademark)” ELM100 (manufactured by Sumitomo Chemical Co., Ltd.), “Araldite (registered trademark)” MY0510, “Araldite (registered trademark)” MY0600 (and above) , Huntsman Advanced Materials Co., Ltd.), “jER (registered trademark)” 630 (Mitsubishi Chemical Co., Ltd.), and the like can be used.

  Among the above-mentioned glycidylamine type epoxy compounds having a plurality of functional groups, an aromatic epoxy compound (C1) having at least one glycidylamine skeleton and having 3 or more epoxy groups is preferable.

  The epoxy resin containing the glycidylamine type aromatic epoxy compound (C1) having 3 or more epoxy groups has an effect of improving heat resistance, and the ratio is preferably 30 to 100% by mass in the epoxy resin. A more desirable ratio is 50% by mass or more. The ratio of the glycidylamine type aromatic epoxy compound is preferably 30% by mass or more, since the compressive strength of the carbon fiber reinforced composite material is improved and the heat resistance is improved.

  When using these epoxy compounds (C), you may add catalysts and hardening | curing agents, such as an acid and a base, as needed. For example, for curing epoxy resins, Lewis acids such as boron halide complexes and p-toluenesulfonate, and polyamine curing agents such as diaminodiphenylsulfone, diaminodiphenylmethane and their derivatives and isomers are preferably used.

  In the prepreg of the present invention, the latent curing agent (B) is preferably used as the curing agent. The latent curing agent described here is a curing agent for the thermosetting resin of the present invention, which is a curing agent that is activated by applying a temperature and reacts with a reactive group such as an epoxy group, and is 70 ° C. or higher. It is preferable that the reaction is activated. Here, activation at 70 ° C. means that the reaction start temperature is in the range of 70 ° C. Such reaction start temperature (hereinafter referred to as activation temperature) can be determined by, for example, differential scanning calorimetry (DSC). Specifically, for an epoxy resin composition in which 10 parts by mass of the curing agent to be evaluated is added to 100 parts by mass of the bisphenol A type epoxy compound having an epoxy equivalent of about 184 to 194, the inflection of the exothermic curve obtained by differential scanning calorimetry analysis It is obtained from the intersection of the point tangent and the baseline tangent.

  The latent curing agent (B) is preferably an aromatic amine curing agent (B1), or dicyandiamide or a derivative thereof (B2). The aromatic amine curing agent (B1) 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) is used. 3'-DDS), 4,4'-diaminodiphenylsulfone (4,4'-DDS), diaminodiphenylmethane (DDM), 3,3'-diisopropyl-4,4'-diaminodiphenylmethane, 3,3'-di -T-butyl-4,4'-diaminodiphenylmethane, 3,3'-diethyl-5,5'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-diisopropyl-5,5'-dimethyl-4 , 4′-diaminodiphenylmethane, 3,3′-di-t-butyl-5,5′-dimethyl-4,4′-diaminodiphenylmethane, 3,3 ′, 5,5 ′ -Tetraethyl-4,4'-diaminodiphenylmethane, 3,3'-diisopropyl-5,5'-diethyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-diethyl -4,4'-diaminodiphenylmethane, 3,3 ', 5,5'-tetraisopropyl-4,4'-diaminodiphenylmethane, 3,3'-di-t-butyl-5,5'-diisopropyl-4, 4'-diaminodiphenylmethane, 3,3 ', 5,5'-tetra-t-butyl-4,4'-diaminodiphenylmethane, diaminodiphenyl ether (DADPE), bisaniline, benzyldimethylaniline, 2- (dimethylaminomethyl) phenol (DMP-10), 2,4,6-tris (dimethylaminomethyl) phenol (DMP-30), 2 4,6-tris (dimethylaminomethyl) 2-ethylhexanoic acid ester of a phenol or the like can be used. These may be used alone or in admixture of two or more.

  Commercially available aromatic amine curing agents (B1) include Seika Cure S (manufactured by Wakayama Seika Kogyo Co., Ltd.), MDA-220 (manufactured by Mitsui Chemicals), “jER Cure (registered trademark)” W (Japan) Epoxy Resin Co., Ltd.), and 3,3′-DAS (Mitsui Chemicals Co., Ltd.), Lonzacure® M-DEA (Lonza Co., Ltd.), “Lonzacure®” M-DIPA (Lonza Co., Ltd.), “Lonzacure (registered trademark)” M-MIPA (Lonza Co., Ltd.), “Lonzacure (registered trademark)” DETDA 80 (Lonza Co., Ltd.), and the like.

  The dicyandiamide derivative or its derivative (B2) is a compound reacted with at least one of an amino group, an imino group and a cyano group. For example, o-tolylbiguanide, diphenylbiguanide, dicyandiamide amino group, imino A group or a cyano group is pre-reacted with an epoxy group of an epoxy compound used in an epoxy resin composition.

  As a commercial item of dicyandiamide or its derivative (B2), DICY-7, DICY-15 (above, Japan Epoxy Resin Co., Ltd. product) etc. are mentioned.

  Curing agents other than aromatic amine curing agent (B1), dicyandiamide or its derivative (B2) include amines such as alicyclic amines, phenolic compounds, acid anhydrides, polyaminoamides, organic acid hydrazides, and isocyanates as aromatic diamines. You may use together with a hardening | curing agent.

  Moreover, it is preferable that the total amount of a hardening | curing agent contains the quantity from which an active hydrogen group becomes the range of 0.6-1.2 equivalent with respect to 1 equivalent of epoxy groups of all the epoxy resin components, More preferably, 0.7- Including an amount in the range of 0.9 equivalents. Here, the active hydrogen group means a functional group that can react with the epoxy group of the curing agent component, and when the active hydrogen group is less than 0.6 equivalent, the reaction rate, heat resistance, and elastic modulus of the cured product. In some cases, the glass transition temperature and strength of the fiber reinforced composite material may be insufficient. If the active hydrogen group exceeds 1.2 equivalents, the reaction rate, glass transition temperature, and elastic modulus of the cured product are sufficient, but the plastic deformation ability is insufficient, so the impact resistance of the carbon fiber reinforced composite material May be insufficient.

  Moreover, when a thermosetting resin is an epoxy resin, a hardening accelerator (D) can also be mix | blended in order to accelerate hardening.

  Examples of the curing accelerator (D) include urea compounds, tertiary amines and salts thereof, imidazoles and salts thereof, triphenylphosphine or derivatives thereof, carboxylic acid metal salts, Lewis acids, Bronsted acids and salts thereof, and the like. It is done. Of these, the urea compound (D1) is preferably used from the balance between storage stability and catalytic ability.

  In particular, when the urea compound (D1) is used as the curing accelerator (D), it is preferable that the latent curing agent (B) is used in combination with dicyandiamide or a derivative (D2) thereof.

  Examples of the urea compound (D1) include N, N-dimethyl-N ′-(3,4-dichlorophenyl) urea, toluenebis (dimethylurea), 4,4′-methylenebis (phenyldimethylurea), and 3-phenyl. -1,1-dimethylurea and the like can be used. Examples of commercially available urea compounds include DCMU99 (manufactured by Hodogaya Chemical Co., Ltd.), “Omicure (registered trademark)” 24, 52, 94 (manufactured by Emerald Performance Materials, LLC).

  It is preferable that the compounding quantity of a urea compound (D1) shall be 1-4 mass parts with respect to 100 mass parts of all the epoxy resin components. When the compounding quantity of this urea compound (D1) is less than 1 mass part, reaction may not fully advance and the elasticity modulus and heat resistance of hardened | cured material may be insufficient. Moreover, when the compounding quantity of this urea compound exceeds 4 mass parts, since the self-polymerization reaction of an epoxy compound inhibits reaction with an epoxy compound and a hardening | curing agent, the toughness of hardened | cured material is insufficient, and an elasticity modulus May decrease.

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

  The prepreg of the present invention preferably contains a thermoplastic resin in order to adjust toughness and fluidity. From the viewpoint of heat resistance, polysulfone, polyethersulfone, polyetherimide, polyimide, polyamide, polyamide More preferably, it contains at least one selected from imide, polyphenylene ether, phenoxy resin, and polyolefin. Moreover, the oligomer of a thermoplastic resin can be included. Moreover, an elastomer, a filler, and another additive can also be mix | blended. Note that the thermoplastic resin is preferably contained in the thermosetting resin constituting the prepreg. Furthermore, when an epoxy resin is used as the thermosetting resin, as the thermoplastic resin, a thermoplastic resin soluble in the epoxy resin, organic particles such as rubber particles and thermoplastic resin particles, and the like can be blended. As the thermoplastic resin soluble in the epoxy resin, a thermoplastic resin having a hydrogen bonding functional group that can be expected to improve the adhesion between the resin and the carbon fiber is preferably used.

  As the thermoplastic resin soluble in epoxy resin and having a hydrogen bonding functional group, a thermoplastic resin having an alcoholic hydroxyl group, a thermoplastic resin having an amide bond, or a thermoplastic resin having a sulfonyl group can be used.

  Examples of the thermoplastic resin having an alcoholic hydroxyl group include polyvinyl acetal resins such as polyvinyl formal and polyvinyl butyral, polyvinyl alcohol, and phenoxy resins. Examples of the thermoplastic resin having an amide bond include polyamide, polyimide, Polyvinyl pyrrolidone can be mentioned, and as a thermoplastic resin having a sulfonyl group, polysulfone can be mentioned. Polyamide, polyimide and polysulfone may have a functional group such as an ether bond and a carbonyl group in the main chain. The polyamide may have a substituent on the nitrogen atom of the amide group.

  Examples of commercially available thermoplastic resins that are soluble in epoxy resins and have hydrogen-bonding functional groups include, as polyvinyl acetal resins, Denkabutyral (manufactured by Denki Kagaku Kogyo Co., Ltd.), “Vinylec (registered trademark)” (Chisso ( Manufactured by Co., Ltd.), “UCAR (registered trademark)” PKHP (made by Union Carbide Co., Ltd.) as a phenoxy resin, “Macromelt (registered trademark)” (produced by Henkel Hakusui Co., Ltd.), “Amilan (registered) as a polyamide resin Trademark) ”(manufactured by Toray Industries, Inc.),“ Ultem (registered trademark) ”(manufactured by SABIC Innovative Plastics Japan LLC),“ Matrimid (registered trademark) ”5218 (manufactured by Ciba), and“ polysulfone ” "Sumika Excel (registered trademark)" (manufactured by Sumitomo Chemical Co., Ltd.), "UDEL (registered trademark)", RADEL Registered trademark) "(or, Solvay Advanced Polymers Co., Ltd.), as a polyvinylpyrrolidone," Luviskol (registered trademark) "(BASF Japan Ltd. can be exemplified, Ltd.).

  In addition, the acrylic resin has high compatibility with the epoxy resin, and is suitably used for fluidity adjustment such as thickening. Examples of commercially available acrylic resins include “Dianal (registered trademark)” BR series (manufactured by Mitsubishi Rayon Co., Ltd.), “Matsumoto Microsphere (registered trademark)” M, M100, M500 (Matsumoto Yushi Seiyaku Co., Ltd.) And “Nanostrength (registered trademark)” E40F, M22N, M52N (manufactured by Arkema Co., Ltd.), and the like.

  In particular, polyethersulfone and polyetherimide are preferable because these effects can be exhibited without substantially impairing heat resistance. Polyethersulfone includes "Sumika Excel" (registered trademark) 3600P, "Sumika Excel" (registered trademark) 5003P, "Sumika Excel" (registered trademark) 5200P, "Sumika Excel" 2 (registered trademark, above, Sumitomo Chemical Industries) 7200P, “VIrantage” (registered trademark) PESU VW-10200, “VIrantage” (registered trademark) PESU VW-10700 (registered trademark, manufactured by Solvay Advance Polymers, Inc.), “Ultrason” (registered) Trademark) 2020SR (manufactured by BASF Corp.), polyetherimide includes “Ultem” (registered trademark) 1000, “Ultem” (registered trademark) 1010, “Ultem” (registered trademark) 1040 (above, SABIC Innovative Plastics) (Made by Japan GK) It can be used.

  The thermoplastic resin is preferably 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.

  In addition, the amount of the thermoplastic resin to be dissolved in the epoxy resin composition is preferably 1 to 40 parts by mass, more preferably 1 to 25 parts by mass with respect to 100 parts by mass of the epoxy resin. 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. If the thermoplastic resin is less than this blending amount, the effect of improving toughness may be insufficient. Moreover, when a thermoplastic resin exceeds the said range, impregnation property, tack drape, and heat resistance may fall.

  Furthermore, in order to modify the matrix resin of the present invention, in addition to the thermoplastic resin described above, a thermosetting resin other than an epoxy resin, an elastomer, a filler, rubber particles, thermoplastic resin particles, inorganic particles, and other additives are added. It can also be blended.

  Rubber particles can also be blended with the epoxy resin preferably used in the present invention. As such 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.

  As commercial products of crosslinked rubber particles, FX501P (manufactured by JSR Co., Ltd.) composed of a crosslinked product of carboxyl-modified butadiene-acrylonitrile copolymer, CX-MN series (manufactured by Nippon Shokubai Co., Ltd.) composed of acrylic rubber fine particles, YR-500 series (manufactured by Nippon Steel Chemical Co., Ltd.) and the like can be used.

  Commercially available core-shell rubber particles include, for example, “Paraloid (registered trademark)” EXL-2655 (manufactured by Kureha Chemical Co., Ltd.), acrylic ester / methacrylic ester, composed of a butadiene / alkyl methacrylate / styrene copolymer. "STAPHYLOID (registered trademark)" AC-3355 made of a copolymer, TR-2122 (above, manufactured by Takeda Pharmaceutical Co., Ltd.), "PARARAID (registered trademark)" made of a copolymer of butyl acrylate and methyl methacrylate “EXL-2611, EXL-3387 (manufactured by Rohm & Haas)”, “Kane Ace (registered trademark)” MX (manufactured by Kaneka Corporation), and the like can be used.

  As the thermoplastic resin particles, those similar to the various thermoplastic resins exemplified above 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 nylon modified with an epoxy compound (epoxy modified nylon) are particularly good. Since the adhesive strength with the thermosetting resin can be given, the delamination strength of the carbon fiber reinforced composite material at the time of falling weight impact is high, and the impact resistance improvement effect is high, which is preferable. As commercial products of polyamide particles, SP-500, SP-10 (manufactured by Toray Industries, Inc.), “Orgasol (registered trademark)” (manufactured by Arkema Co., Ltd.) and the like can be used.

  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. In the present invention, inorganic particles such as silica, alumina, smectite, and synthetic mica are blended in the epoxy resin composition in order to adjust fluidity such as thickening of the epoxy resin composition within a range that does not impair the effects of the present invention. be able to.

  The prepreg of the present invention is also preferably used by mixing conductive fillers for the purpose of increasing the contact probability between carbon fibers and improving the conductivity of the carbon fiber reinforced composite material. Examples of such conductive fillers include carbon black, carbon nanotube, vapor grown carbon fiber (VGCF), fullerene, metal nanoparticles, carbon particles, metal-plated thermoplastic resin particles, and metal-plated metals. The thermosetting resin particle | grains etc. which were illustrated previously are mentioned, It may be used independently or may be used together. Of these, carbon black and carbon particles that are inexpensive and highly effective are preferably used. For example, furnace black, acetylene black, thermal black, channel black, ketjen black, and the like can be used. Carbon black blended in two or more types is also preferably used. Further, as such carbon particles, “Bell Pearl (registered trademark)” C-600, C-800, C-2000 (manufactured by Kanebo Co., Ltd.), “NICABEADS (registered trademark)” ICB, PC, MC (Nippon Carbon Co., Ltd.) And the like). Specific examples of the metal-plated thermosetting resin particles include “Micropearl (registered trademark)” AU215, in which divinylbenzene polymer particles are plated with nickel and then gold is plated thereon.

  Next, the manufacturing method of the prepreg of this invention is demonstrated.

  The prepreg of the present invention is obtained by impregnating a sizing agent-coated carbon fiber bundle with a thermosetting resin composition that is a matrix resin. The prepreg can be produced by, for example, a wet method in which a matrix resin is dissolved in a solvent such as methyl ethyl ketone or methanol to lower the viscosity and impregnated, or a hot melt method in which the viscosity is lowered by heating and impregnated.

  In the wet method, after sizing agent-coated carbon fiber bundles are immersed in a liquid containing a matrix resin, the prepreg can be obtained by pulling up and evaporating the solvent using an oven or the like.

  In addition, in the hot melt method, a method of directly impregnating a carbon resin bundle coated with a sizing agent with a matrix resin whose viscosity has been reduced by heating, or a film in which a matrix resin composition is once coated on release paper or the like is first prepared. A prepreg can be produced by a method in which the film is laminated from both sides or one side of the sizing agent-coated carbon fiber bundle and heated and pressed to impregnate the sizing agent-coated carbon fiber bundle into the sizing agent-coated carbon fiber bundle. The hot melt method is a preferable means because there is no solvent remaining in the prepreg.

  In order to form a carbon fiber reinforced composite material using the prepreg of the present invention, a method of heat-curing a matrix resin while applying pressure to the laminate after laminating the prepreg can be used.

  Examples of methods for applying heat and pressure include a press molding method, an autoclave molding method, a bagging molding method, a wrapping tape method, and an internal pressure molding method. Especially for sporting goods, the wrapping tape method and the internal pressure molding method are preferably employed. The For aircraft applications where higher quality and higher performance laminated composite materials are required, the autoclave molding method is preferably employed. A press molding method is preferably used for various vehicle exteriors.

  The carbon fiber mass fraction of the prepreg of the present invention is preferably 40 to 90 mass%, more preferably 50 to 80 mass%. If the carbon fiber mass fraction is too low, the mass of the resulting composite material may be excessive, which may impair the advantages of the fiber-reinforced composite material having excellent specific strength and specific elastic modulus, and the carbon fiber mass fraction may be high. If the amount is too high, poor impregnation of the matrix resin composition occurs, and the resulting composite material tends to have a lot of voids, and the mechanical properties thereof may be greatly deteriorated.

  As the sizing agent-coated carbon fiber in the present invention, a carbon fiber reinforced composite material can be obtained by an arbitrary molding method such as an open mold type, pressure molding, continuous molding, matched die molding, and the like according to the intended use.

  In addition, as a method for obtaining a carbon fiber reinforced composite material in the present invention, in addition to autoclave molding using the above prepreg, hand lay-up, RTM, “SCRIMP (registered trademark)”, filament winding, pultrusion and SMC press molding. A molding method such as reaction injection molding or resin film infusion can be selected and applied according to the purpose. By applying any of these molding methods, a fiber-reinforced composite material containing the above-described sizing agent-coated carbon fiber and a cured product of the thermosetting resin composition can be obtained.

  The carbon fiber reinforced composite material of the present invention is used for computer structures such as aircraft structural members, windmill blades, automobile outer plates, IC trays and notebook PC housings, and golf shafts, bats, badminton, tennis rackets, etc. It is preferably used for sports applications.

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

(1) X-ray photoelectron spectroscopy (halogen / carbon) on the sizing agent-coated carbon fiber surface
In the present invention, the halogen / carbon ratio on the sizing agent surface of the sizing agent-coated carbon fiber was determined by X-ray photoelectron spectroscopy using AlKα _1,2 as the X-ray source according to the following procedure. The case where the halogen is chlorine is shown.

Cut the sizing agent-coated carbon fiber to 20 mm, and spread and arrange it on a copper sample support. Then, use AlKα _1,2 as the X-ray source and keep the sample chamber at 1 × 10 ⁻⁸ Torr for measurement. It was. The photoelectron escape angle was 15 °. The binding energy value of the C _1s main peak (peak top) was adjusted to 284.6 eV as a peak correction value associated with charging during measurement. At this time, the C _1s peak area was obtained by drawing a straight base line in the range of 282 to 296 eV, and the Cl _2p peak area was obtained by drawing a straight base line in the range of 195 to 205 eV. The surface oxygen concentration (Cl / C) is expressed as an atomic ratio calculated by dividing the ratio of the Cl _2p peak area by the sensitivity correction value unique to the apparatus. ESCA-1600 manufactured by ULVAC-PHI Co., Ltd. was used as the X-ray photoelectron spectroscopy apparatus, and 3.04 was used as the sensitivity correction value unique to the apparatus.

When the halogen compound is fluorine, the F _1s peak area was obtained by drawing a straight base line in the range of 681 to 691 eV, and 3.18 was used as the device-specific sensitivity correction value. When the halogen compound is bromine, the Br _3d peak area was obtained by drawing a straight base line in the range of 65 to 75 eV, and the sensitivity correction value unique to the apparatus was 3.66.

(2) Elution of sizing agent of sizing agent-coated carbon fiber 30 g of sizing agent-coated carbon fiber was immersed in 150 ml of N, N-dimethylformamide and subjected to ultrasonic cleaning.

(3) Epoxy value (b) (b3) (b4)
Using the sizing agent solution eluted in (2), the epoxy group was ring-opened with hydrochloric acid and obtained by acid-base titration.

(4) Epoxy value (b1) (b2) and epoxy value of epoxy compound (A) or epoxy compound (C) used for thermosetting resin The epoxy value of the epoxy compound is obtained by converting the epoxy compound to N, N-dimethylformamide. It melt | dissolved, the epoxy group was opened with hydrochloric acid, and it calculated | required by acid-base titration. In (b1) and (b2), the epoxy value was calculated for the components excluding the solvent.

(5) Hydroxyl value (a)
Using the sizing agent solution eluted in (2), the hydroxyl group was acetylated using acetic anhydride, and the generated acetic acid was titrated with a potassium hydroxide solution. Since the epoxy group was also titrated, it was corrected with the value of the epoxy value measured in (3).

(6) Weight average molecular weight of eluted sizing agent The weight average molecular weight was determined by GPC using dimethylformamide (0.01N-lithium bromide added) as a solvent. In addition, the measurement sample was adjusted so that it might become 2 mg of epoxy compounds with respect to 1 ml of solvent using the sizing liquid eluted in (2). TSK-gelα3000 (manufactured by Tosoh Corporation) was used as a column, and calculation was performed using monodisperse polystyrene as a standard. A differential refractive index detector was used as the detector.

(7) Processability Judging from the releasability when drawing the sizing agent-coated carbon fiber from the bobbin when creating a prepreg, and the point of fluff on the roller. When the release property was good and fluff was not seen, it was rated as “Good”. Moreover, when releasing or when there was much fuzz on a roller, it was set as x. In the present invention, ◯ is a preferred range.

(8) Strand tensile strength and elastic modulus of carbon fiber bundles Strand tensile strength and strand elastic modulus of carbon fiber bundles 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.

(9) Method of measuring sizing adhesion amount Electricity set to a temperature of 450 ° C. in a nitrogen stream of 50 ml / min after weighing about 2 g of sizing adhesion carbon fiber bundle (W1) (reading to the fourth decimal place) Leave in a furnace (capacity 120 cm ³ ) for 15 minutes to completely pyrolyze the sizing agent. 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.

(10) Measurement of interfacial shear strength (IFSS) The interfacial shear strength (IFSS) was measured by the following procedures (a) to (d).
(A) Preparation of resin 100 parts by mass of a bisphenol A type epoxy 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 was placed in a container. Thereafter, the mixture was heated at a temperature of 75 ° C. for 15 minutes in order to reduce the viscosity of the jER828 and dissolve the metaphenylenediamine. Then, both were mixed well and vacuum defoaming was performed 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 was made of silicone rubber, and the shape of the cast part was a central part width of 5 mm, a length of 25 mm, both end part widths 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 held for 2 hours, then rises to a temperature of 125 ° C at a heating rate of 1.5 ° C / min, held for 2 hours, and then reaches a temperature of 30 ° C at a cooling rate of 2.5 ° C / min. The temperature dropped. Then, it demolded and the test piece was obtained.
(D) Measurement of interfacial shear strength (IFSS) Tensile force was applied to the test piece obtained in the above procedure (c) in the fiber axis direction (longitudinal direction), and a tensile test was performed at a strain rate of 0.3% / second. For each 1% tension, the number of fiber breaks in the range of 22 mm in the center of the specimen is measured with a polarizing microscope, and the number of fiber breaks when the fiber breakage is saturated and no single fiber breakage occurs is N (pieces). It was. Using the number of fiber breaks, an average break fiber length la (μm) = 22 × 1000 (μm) / N (pieces) was calculated. Further, the critical fiber length lc (μm) = (4/3) × la (μm) was calculated from the average breaking fiber length la. In the present invention, the interfacial shear strength (IFSS), which is an index of the adhesive strength between the carbon fiber and the resin interface, was calculated by the following equation. σ is the strand tensile strength determined in (8), and d is the diameter of the carbon fiber single yarn.
Interfacial shear strength IFSS (MPa) = σ (MPa) × d (μm) / (2 × lc) (μm)
When the IFSS value is 30 MPa or more, ◯, 20 MPa or more and less than 30 MPa is Δ, and less than 20 MPa is ×. ○ Δ is a preferred range in the present invention.

(11) Definition of 0 ° of fiber reinforced composite material As described in JIS K7017 (1999), the fiber direction of a unidirectional fiber reinforced composite material is defined as the axial direction, and the axial direction is defined as the 0 ° axis. The direction was defined as 90 °.

(12) Measurement of 0 ° tensile strength of fiber reinforced composite material Cut unidirectional prepreg within 24 hours after preparation into a predetermined size, and stack 6 sheets in one direction, then vacuum bag and autoclave It was cured at a temperature of 180 ° C. and a pressure of 6 kg / cm ² for 2 hours to obtain a unidirectional reinforcing material (carbon fiber reinforced composite material). The unidirectional reinforcing material was cut into a width of 12.7 mm and a length of 230 mm, and a glass fiber reinforced plastic tab having a length of 1.2 mm and a length of 50 mm was bonded to both ends to obtain a test piece. The test piece thus obtained was subjected to a tensile test at a crosshead speed of 1.27 mm / min using an Instron universal testing machine.

In the present invention, the value obtained by dividing the value of the 0 ° tensile strength (MPa) by the value of the strand strength obtained in (8) was obtained as the strength utilization rate (%) by the following formula.
Strength utilization rate = tensile strength / ((CF basis weight / 190) × Vf / 100 × strand strength) × 100
CF basis weight = 190 g / m ²
Vf = 56%
When the strength utilization rate was 80% or more, ◯ was given, and less than 80% was taken as x. ○ is a preferred range in the present invention.

(13) 0 ° tensile strength after storage of prepreg After storing the prepreg at a temperature of 25 ° C and a humidity of 60% for 20 days, the 0 ° tensile strength MPa was measured in the same manner as in (12). Relationship between 0 degree tensile strength (c) MPa when cured within 24 hours after prepreg production measured in (12) and 0 degree tensile strength (d) MPa when cured after prepreg storage, that is, tensile strength The decrease rate was calculated from the following formula (1).

((C)-(d)) / (c) (%) (1)
When the tensile strength reduction rate was less than 5%, O, 5% or more and less than 8%, and Δ or 8% or more, respectively. ○ is a preferred range in the present invention.

The materials and components used in each example and each comparative example are as follows.
Epoxy compound (A): “Denacol (registered trademark)” EX-512 (manufactured by Nagase ChemteX Corporation) corresponding to the aliphatic epoxy compound (A1)
Polyglycerin polyglycidyl ether Epoxy value: 6.0 meq. / G, hydroxyl value 2.6 meq. / G, halogen (Cl): 6.5% by mass.
-Latent curing agent (B) component: B-1 corresponds to an aromatic amine curing agent (B1).
B-1: “Seika Cure (registered trademark)” S (4,4′-diaminodiphenyl sulfone, manufactured by Wakayama Seika Co., Ltd.)
-Epoxy compound (C) component: C-1 to C-2.
C-1: Tetraglycidyldiaminodiphenylmethane, “Sumiepoxy (registered trademark)” ELM434 (manufactured by Sumitomo Chemical Co., Ltd.)
Epoxy value: 8.3 meq. / G
C-2: “jER (registered trademark)” 828 (manufactured by Mitsubishi Chemical Corporation)
Diglycidyl ether of bisphenol A Epoxy value: 5.3 meq. / G.
-Thermoplastic resin "Sumika Excel (registered trademark)" 5003P (polyethersulfone, manufactured by Sumitomo Chemical Co., Ltd.).

(Reference Example 1)
As the epoxy compound (A), an epoxy value of 6.0 meq. / G polyglycerin polyglycidyl ether 15 mass% aqueous solution was heated and stirred to obtain A-1 to A-6 shown in Table 1.

(Reference Example 2)
The carbon fiber used as a raw material was manufactured as follows.

  A copolymer composed of 99 mol% of acrylonitrile and 1 mol% of itaconic acid is dried and wet-spun, fired, total number of filaments 24,000, total fineness 1,000 tex, specific gravity 1.8, strand tensile strength 5.9 GPa A carbon fiber having a strand tensile elastic modulus of 295 GPa was obtained. Next, the carbon fiber was subjected to electrolytic surface treatment with an aqueous solution of ammonium hydrogen carbonate having a concentration of 0.1 mol / l as an electrolytic solution at an electric quantity of 80 coulomb per gram of 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 0.15, the surface carboxyl group concentration COOH / C was 0.005, and the surface hydroxyl group concentration COH / C was 0.018. The surface roughness (Ra) of the carbon fiber at this time was 3.0 nm.

(Reference Example 3)
The prepreg was produced as follows.

  In a kneading apparatus, 80 parts by mass of Sumiepoxy ELM434, 20 parts by mass of jER828 and 10 parts by mass of Sumika Excel 5003P were mixed and dissolved, and then Seikacure S (4,4′-diaminodiphenylsulfone) was used as a curing agent. 40 mass parts knead | mixing and produced the epoxy resin composition for carbon fiber reinforced composite materials.

The obtained epoxy resin composition was coated on a release paper with a resin basis weight of 52 g / m ² using a knife coater to prepare a resin film. This resin film is superposed on both sides of a sizing agent-coated carbon fiber (weight per unit area 190 g / m ² ) aligned in one direction, and a heat roll is used to heat and press at 100 ° C. and 1 atm. Was impregnated into carbon fiber coated with a sizing agent to obtain a prepreg.

(Examples 1-4, Comparative Examples 1 and 2)
After applying the sizing agent (A-1 to 6) obtained in Reference Example 1 to the carbon fiber obtained in Reference Example 2 by a dipping method, heat treatment was performed at a temperature of 210 ° C. for 75 seconds to apply the sizing agent. A carbon fiber bundle was obtained. The adhesion amount of the sizing agent was adjusted to 0.6% by mass with respect to the sizing agent-coated carbon fiber. No heat treatment was performed on the bobbins wound up under wet conditions.

  Subsequently, X-ray photoelectron spectroscopy measurement on the surface of the sizing agent, interfacial shear strength (IFSS) of the carbon fiber coated with the sizing agent, hydroxyl value (a) of the sizing agent eluted from the carbon fiber coated with the sizing agent, and epoxy value (b) ((B) is the same value as (b3) and (b4)), and the weight average molecular weight was measured. The results are summarized in Table 1.

  Then, the initial stage of the prepreg obtained by the method of Reference Example 3 and a tensile test after storing the prepreg for a long time were performed. The results are shown in Table 2.

(Examples 5 and 6, Comparative Examples 3 and 4)
After applying the sizing agent (A-1) obtained in Reference Example 1 to the carbon fiber obtained in Reference Example 2 by a dipping method, heat treatment was performed at a temperature of 210 ° C. for 75 seconds to obtain a sizing agent-coated carbon fiber. Got a bunch. The adhesion amount of the sizing agent was adjusted to 0.6% by mass with respect to the sizing agent-coated carbon fiber. The epoxy value (b3) of this sizing agent-coated carbon fiber bundle was 4.6 meq. / G. Subsequently, heat treatment was performed under wet conditions until the epoxy value (b) ((b) was the same value as (b4)) reached the values shown in Table 3.

  Subsequently, X-ray photoelectron spectroscopy measurement on the surface of the sizing agent, interfacial shear strength (IFSS) of the carbon fiber coated with the sizing agent, hydroxyl value (a) of the sizing agent eluted from the carbon fiber coated with the sizing agent, and epoxy value (b) The weight average molecular weight was measured. The results are summarized in Table 3.

  Then, the initial stage of the prepreg obtained by the method of Reference Example 3 and a tensile test after storing the prepreg for a long time were performed. The results are shown in Table 3.

(Comparative Example 5)
After applying the sizing agent (A-1) obtained in Reference Example 1 to the carbon fiber obtained in Reference Example 2 by a dipping method, heat treatment was performed at a temperature of 210 ° C. for 75 seconds to obtain a sizing agent-coated carbon fiber. Got. The adhesion amount of the sizing agent was adjusted to 0.6% by mass with respect to the sizing agent-coated carbon fiber. The epoxy value (b3) of this sizing agent-coated carbon fiber bundle was 4.6 meq. / G. Subsequently, heat treatment was performed at 260 ° C. until the epoxy value (b) reached the value shown in Table 3. Note that (b3) / (b4) is 1.0 because no treatment is performed under wet conditions.

  Subsequently, X-ray photoelectron spectroscopy measurement on the surface of the sizing agent, interfacial shear strength (IFSS) of the carbon fiber coated with the sizing agent, hydroxyl value (a) of the sizing agent eluted from the carbon fiber coated with the sizing agent, and epoxy value (b) The results of the weight average molecular weight are summarized in Table 3.

  Then, the initial stage of the prepreg obtained by the method of Reference Example 3 and a tensile test after storing the prepreg for a long time were performed. The results are shown in Table 3.

  The sizing agent-coated carbon fiber and the method for producing the sizing agent-coated carbon fiber of the present invention are suitable for processing into woven fabrics and prepregs because of excellent adhesion, long-term stability when made into a prepreg and high-order processability. . Further, since the prepreg and carbon fiber reinforced composite material of the present invention are lightweight and have excellent strength and elastic modulus, they are used in many fields such as aircraft members, spacecraft members, automobile members, ship members, civil engineering and building materials, and sporting goods. Can be suitably used.

Claims (4)

A method for producing a sizing agent-coated carbon fiber satisfying the following (X), comprising a step of satisfying the following (V) or / and (VI).
(V) The process of apply | coating to carbon fiber the sizing agent containing liquid which heat-processed at 20-150 degreeC for 0.5 to 20000 hours in the presence of water and which has the following epoxy compound (A) as a main component.
(VI) A step of applying a sizing agent-containing liquid containing the following epoxy compound (A) as a main component to carbon fiber and drying, followed by heat treatment at 20 to 150 ° C. and a humidity of 50 to 90% for 20 to 20000 hours.
Sizing agent coated carbon fiber (X): carbon fiber, seen containing the following epoxy compound having a hydroxyl group and an epoxy group in the molecule (A) as the main component, and a 1.3 mass% or less in a nitrogen or phosphorus content A sizing agent containing a curing agent is applied, and the hydroxyl value (a) meq. Of the sizing agent eluted by immersing in an N, N-dimethylformamide solvent and sonicating. / G and epoxy value (b) meq. / G, together with satisfying the following (I) to (III), the weight average molecular weight of the eluted sizing agent is 1,000 to 5,000, and a halogen / carbon surface as measured by X-ray photoelectron spectroscopy 0 0.005 to 0.030 (I) 8 ≦ (a) + (b) ≦ 16
(II) (a) / (b) ≧ 2
(III) (b) ≧ 0.5
Epoxy compound (A): aliphatic epoxy compound containing halogen in the molecule (A1) Hydroxyl value of the eluted sizing agent (a) meq. The method for producing sizing agent-coated carbon fiber according to claim 1, wherein / g satisfies the following (IV).
(IV) (a) ≧ 9 Glycidyl ether type epoxy obtained by reacting the aliphatic epoxy compound (A1) with one selected from glycerol, diglycerol, polyglycerol, trimethylolpropane, pentaerythritol, sorbitol, and arabitol, and epichlorohydrin The manufacturing method of the sizing agent application | coating carbon fiber of Claim 1 or 2 which is a compound. After heat treatment with epoxy value (b2) before heat treatment shown in (V) and epoxy value (b2) after heat treatment and epoxy value (b3) before heat treatment shown in (VI) The manufacturing method of the carbon fiber for sizing agent application | coating in any one of Claims 1-3 with which epoxy value (b4) of following satisfy | fills following (VII).