JP2014159564A - Prepreg and sizing agent-coated carbon fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a prepreg for producing a carbon fiber composite material which exhibits excellent tensile modulus of elasticity and tensile strength of a perforated plate, and to provide a sizing agent-coated carbon fiber which is a raw material thereof.SOLUTION: A prepreg contains a carbon fiber (I) and a thermosetting resin (II). In the carbon fiber (I), when a single fiber apparent stress is 15.3 GPa in a fragmentation method of a single fiber composite, the number of fiber breaks is 2.0 pieces/mm or more, and when the single fiber apparent stress is 12.2 GPa, the number of fiber breaks is 1.7 pieces/mm or less. The thermosetting resin (II) contains an epoxy compound (A) and an aromatic amine curing agent (B).

Description

  The present invention relates to a carbon fiber coated with a sizing agent (hereinafter referred to as sizing agent-coated carbon fiber) and a prepreg. More specifically, the present invention relates to carbon having a specific single fiber strength distribution from which a carbon fiber reinforced composite material having good physical properties, particularly high perforated plate tensile strength (hereinafter sometimes abbreviated as OHT) is obtained. The present invention relates to a sizing agent-coated carbon fiber excellent in adhesiveness to a matrix resin using fibers, and a prepreg using such carbon fiber or sizing agent-coated carbon fiber.

  Carbon fiber has contributed to weight reduction of aircraft by being used for aircraft applications as a reinforcing fiber of fiber reinforced composite material due to its high specific strength and specific modulus. The flow of is being accelerated. For reducing the weight of aircraft, it is most effective to improve the tensile modulus of carbon fiber that governs the rigidity of the carbon fiber reinforced composite material. Therefore, it is required to have a wide balance of physical properties such as further improvement of mechanical properties of carbon fiber, and further improvement of tensile / compressive strength and perforated plate tensile / compressive strength as a carbon fiber reinforced composite material. In particular, when carbon fiber reinforced composite materials are used for aircraft applications, it is often the case that perforated plates are used rather than the tensile strength of unidirectional carbon fiber reinforced composite materials because they are often used with fasteners by drilling pseudo isotropic materials. Tensile strength is important. Since many factors affect the perforated plate tensile strength, the mechanism of its strength development is often unclear, and the influence of carbon fiber on the perforated plate tensile strength is generally It was known to be proportional to strength.

Strand strength is used as a simple method for examining the strength potential of carbon fiber, which is a reinforcing fiber. Tensile strength of a simple unidirectional carbon fiber reinforced composite material obtained by impregnating a specific epoxy resin. (Hereinafter referred to as unidirectional composite material strength). The unidirectional composite material strength is generally strongly related to the single fiber strength distribution, and the predicted value σ _c ^* of the unidirectional composite material strength generally agrees with the actually measured value when predicted by the following formula shown in Non-Patent Document 1. It has been known.

Here, σ ₀ , m, L ₀ , and τ represent the Weibull shape factor, Weibull scale factor, test length, and interfacial shear strength in the single fiber strength test, respectively, and the strand strength that is a kind of unidirectional carbon fiber reinforced composite material In the case of the test, the interfacial shear strength is 7 MPa.

  The single fiber strength test is widely studied as a method for examining fiber strength more precisely than the strand strength test (Non-patent Documents 2 and 3, Patent Documents 1 and 2). As shown in these documents, the behavior of the apparent strength distribution changes by shortening the sample length (specifically, the Weibull shape factor of the single fiber strength distribution increases as the sample length decreases). Has disclosed various behaviors, and there was no unified view of these behaviors. In order to cope with such a problem, there is a method of evaluating the single fiber strength distribution from a fragmentation test of a single fiber composite in which the stress distribution in the longitudinal direction of the single fiber is interpreted in detail (Non-Patent Documents 4 and 5). ). However, compared with the generally used single fiber strength test, the fragmentation test of the single fiber composite is immature as an evaluation method of the single fiber strength distribution, and there are not many examination examples. For this reason, there has been no discussion of precise intensity distribution in the short sample length region.

  There are examples of investigating the characteristics of carbon fibers for the purpose of improving the tensile strength of the perforated plate of carbon fiber reinforced composite materials (Patent Documents 3 and 4). In Patent Document 3, it is an attempt to improve the perforated plate tensile strength of the carbon fiber reinforced composite material by changing the surface morphology of the carbon fiber and the surface treatment conditions for the carbon fiber. It was not something to control. Patent Document 4 discloses a concept of increasing the perforated plate tensile strength of the carbon fiber reinforced composite material by controlling the spreadability of the carbon fiber and the wettability of the surface thereof. It was a low level.

  In recent years, in order to improve the tensile elastic modulus of carbon fibers irrespective of the control of the maximum temperature of the carbonization process, several techniques for stably performing firing at a high stretching tension have been proposed (Patent Document 5, 6 and 7). In Patent Document 5, although having a specific molecular weight distribution, the strand strength / elastic modulus level is high in a normal condition range, but the single fiber strength distribution in the short test length region of the carbon fiber is not controlled. Patent Documents 6 and 7 focus on the tensile modulus of carbon fiber, and the single fiber strength of the carbon fiber cannot be controlled.

JP 2010-013772 A JP 2009-256833 A JP 2010-047865 A JP 2010-111957 A JP 2008-248219 A JP 2008-308776 A JP 2008-308777 A

“Journal of American Ceramics Society” (USA), 1991, 74, 11, p. 2837-2845. “Composites: Part A” (Netherlands), 1999, 30, p. 1017-1021. “Journal of Materials Science” (Switzerland) 26 (1985), p. 3260-3270. “Composites: Part A” (Netherlands), 2002, 33, p. 1327-1335. “Composites Science and Technology” (Netherlands), 1995, 55, p. 33-39.

  In combination with a specific matrix resin that expresses extremely high perforated plate tensile strength in carbon fibers having an excellent tensile modulus, the present inventors have developed a carbon fiber reinforced composite material even if the strand strength of the carbon fibers is increased. The perforated plate tensile strength is not improved, so that the perforated plate tensile strength is not satisfactory (in other words, the order of the carbon fiber strand strength and the order of the perforated plate tensile strength of the carbon fiber reinforced composite material are The effect of carbon fiber reinforced composite materials on the perforated plate tensile strength due to changes in the surface condition of carbon fibers is small, and therefore the single fiber strength distribution in the short test length region of carbon fibers I came to pay attention. Then, this invention aims at providing the prepreg for producing the carbon fiber reinforced composite material which expresses the outstanding tensile elasticity modulus and perforated board tensile strength, and the carbon fiber thru | or sizing agent application | coating carbon fiber used therefor. .

  As a result of various studies such as matrix resin, interface, and fiber morphology of carbon fiber reinforced composite materials, the present inventors have found that the high strength (short sample length) region of carbon fiber that has not been clearly measured in the past. The inventors have found that by controlling the fiber strength distribution, the perforated plate tensile strength of the carbon fiber reinforced composite material can be improved, and the present invention has been achieved.

The present invention has the following configuration. That is, it is a prepreg containing carbon fiber (I) and thermosetting resin (II) shown below.
(I) When the single fiber apparent stress is 15.3 GPa by the fragmentation method of the single fiber composite, the number of fiber breaks is 2.0 pieces / mm or more, and the fiber when the single fiber apparent stress is 12.2 GPa. Carbon fibers having a number of breaks of 1.7 pieces / mm or less,
(II) A thermosetting resin containing an epoxy compound (A) and an aromatic amine curing agent (B).

  The sizing agent-coated carbon fiber of the present invention is characterized in that a sizing agent containing an aliphatic epoxy compound (C) and an aromatic epoxy compound (D) is applied to the carbon fiber. When the single fiber apparent stress is 15.3 GPa by the fragmentation method of the fiber composite, the fiber break number is 2.0 pieces / mm or more, and when the single fiber apparent stress is 12.2 GPa, the fiber break number is 1. 7 pieces / mm or less.

  The sizing agent-coated carbon fiber of the present invention is preferably (a) CHx, C- of the C1s inner shell spectrum measured on the surface of the sizing agent coated on the carbon fiber at a photoelectron escape angle of 15 ° by X-ray photoelectron spectroscopy. The height (cps) of the component of the bond energy (284.6 eV) attributed to C, C = C, and the height (cps) of the component of the bond energy (286.1 eV) attributed to (B) C—O. ) Ratio (a) / (b) is 0.50 to 0.90.

  The sizing agent-coated carbon fiber of the present invention preferably has an average tearable distance of 300 mm to 710 mm and is substantially untwisted.

  Moreover, the prepreg of the present invention is characterized by comprising the above-described sizing agent-coated carbon fiber and a thermosetting resin (II) containing an epoxy compound (A) and an aromatic amine curing agent (B).

  ADVANTAGE OF THE INVENTION According to this invention, the prepreg for producing the carbon fiber reinforced composite material which expresses the outstanding tensile elasticity modulus and perforated board tensile strength, and the carbon fiber thru | or sizing agent application | coating carbon fiber used for it are obtained. And, when the prepreg of the present invention is used, the carbon fiber composite material obtained by curing it has high physical properties such as tensile elastic modulus and perforated plate tensile strength in a well-balanced manner. The fuel consumption rate can be improved.

FIG. 1 is a diagram illustrating a method of measuring a tearable distance. FIG. 2 is a diagram showing an example of a fragmentation test result of a single fiber composite using the sizing agent-coated carbon fiber according to the embodiment of the present invention.

  The prepreg of the present invention contains the following carbon fiber (I) and thermosetting resin (II). First, carbon fiber (I) is demonstrated.

  In the present invention, the carbon fiber (I) has a fiber breakage number of 1.7 pieces / mm or less when the single fiber apparent stress by a fragmentation method of a single fiber composite (specific method will be described later) is 12.2 GPa. Preferably, it is 1.5 pieces / mm or less, More preferably, it is 1.0 piece / mm or less. Fragmentation method of single fiber composite is to count the number of fiber breaks at each strain while giving strain to the composite (single fiber composite) in which carbon fiber (I) single fiber is embedded in resin. The single fiber strength distribution can be investigated. In order to convert the single fiber composite strain when the fiber is broken into the single fiber strength, it is necessary to consider the difference between the single fiber composite strain and the fiber strain and the elastic modulus at each fiber strain. In addition, the description regarding the single fiber strength will be described later. Here, the single fiber apparent stress indicates a product of single fiber composite strain and single fiber elastic modulus of carbon fiber. When fiber breakage occurs, there is a difference between single fiber composite strain and fiber strain to show the behavior that fiber stress recovers as the distance from the fiber breakage portion increases. Considering the behavior, the maximum fiber stress may hardly increase even if the single fiber composite strain is increased. However, the difference between the single fiber apparent stress and the maximum fiber stress is often very small up to 1.0 fiber breaks / mm, and the difference increases as the number of fiber breaks further increases. Since there is a correlation between the apparent stress and the maximum fiber stress, it is easy to use the single fiber apparent stress. It should be noted here that the elastic modulus of the carbon fiber has an elastic modulus nonlinearity that increases as the strain increases, and that the correct fiber stress cannot be obtained by a simple calculation. When the number of such fiber breaks exceeds 1.7 pieces / mm, the OHT decreases due to insufficient single fiber strength of the carbon fiber, and the smaller the number of such fiber breaks, the higher the single fiber strength. The number is preferably 1.7 pieces / mm or less. Normally, the strength of a unidirectional carbon fiber reinforced composite material is 6 or 7 GPa or less even when divided by the fiber cross-sectional area under the assumption that the load applied to the entire composite material is borne by the fiber alone. However, the relationship between the carbon fiber rupture probability exceeding the strength and the strength of the carbon fiber reinforced composite material has not been discussed in the past. It was clarified that the carbon fiber breakage probability in the high-strength region has a strong influence on the OHT.

  The single fiber strength test is generally used as a method for evaluating the single fiber strength distribution of carbon fibers. In the single fiber strength test, the chuck is embedded with a single fiber using a cyanate or epoxy adhesive in the chuck. As a result, stress is applied to the fibers in the adhesive and the fibers may break in the adhesive. That is, the present inventors pay attention to the fact that the single fiber strength test is a single fiber pull-out test from the adhesive, and in the single fiber strength test, stress is applied to several mm of fibers in the resin. It was revealed that it was loaded. In other words, the inventors of the present invention have a longer substantial test length even when the distance between chucks is less than 5 mm. In particular, the shorter the distance between chucks, the greater the difference between the actual test length and the distance between chucks. It can be said that it was made clear that the single fiber strength distribution in the long region could not be evaluated. In order to deal with such a problem, the present inventors decided to evaluate the single fiber strength distribution from the fragmentation test of the single fiber composite. The results of the single fiber strength distribution calculated from the fragmentation test of the single fiber composite and the single fiber strength test with a test length of 25 mm agreed well with each other by the present inventors. It became clear that it was excellent as an evaluation method of intensity distribution. Furthermore, if the matrix resin used for the single fiber composite is appropriately selected and the bond strength at the single fiber-matrix resin interface is set to a certain level, the strength distribution can be evaluated with high accuracy up to a short test length of about 1 mm. Became clear. Heretofore, there has been no example in which precise intensity distribution in such a high strength (short sample length) region has been discussed.

  In the present invention, the carbon fiber (I) has a fiber breakage number of 2.0 pieces / mm or more when the single fiber apparent stress by the fragmentation method of the single fiber composite is 15.3 GPa, preferably 3.0 pieces / mm. mm or more. When the number of fiber breaks is less than 2.0 pieces / mm, when the number of fiber breaks increases due to a decrease in the interfacial adhesion between the carbon fiber and the matrix resin, the fibers cannot bear stress and the OHT is lowered. Stress is transmitted to the fiber between the break points from the break point where the stress load is 0 by interfacial shear with the resin. Especially when the number of breaks increases in this way, the fiber stress is difficult to increase, so the number of fiber breaks Becomes saturated. Therefore, it should be mentioned here that the actual fiber stress is smaller than the single fiber apparent stress. If the single fiber elastic modulus of the carbon fiber is low, the single fiber composite may break before loading the single fiber apparent stress to 15.3 GPa, but if the fiber breakage is saturated, that breakage is substituted. can do. Here, saturation means that the number of fiber breaks is Δ0.2 / mm when the change in strain of the single fiber composite is Δ1%.

  In the present invention, the carbon fiber (I) preferably has a fiber breakage number of 0.3 / mm or less, more preferably when the single fiber apparent stress by the fragmentation method of the single fiber composite is 6.8 GPa. Is 0.2 piece / mm or less, more preferably 0.1 piece / mm or less. If the fiber stress at which the number of fiber breaks is around 0.3 / mm is too low, stress concentration on the adjacent fibers of the broken fiber in the carbon fiber reinforced composite material is likely to be induced. Therefore, a high OHT can be maintained by setting the number of fiber breaks to 0.3 pieces / mm or less.

  In the present invention, the carbon fiber (I) preferably has a fiber breakage number of 1.7 pieces / mm or less when the single fiber composite strain by the fragmentation method of the single fiber composite is 3.6%, more preferably It is 1.5 pieces / mm or less, More preferably, it is 1.0 piece / mm or less. When the number of fiber breaks exceeds 1.7 pieces / mm, OHT is decreased due to insufficient single fiber strength of the carbon fiber, and the smaller the number of fiber breaks, the higher the single fiber strength of the carbon fiber, which is preferable. . Usually, since the rupture elongation of a unidirectional carbon fiber reinforced composite material is 2% or less, there has never been discussed the relationship between the carbon fiber rupture probability exceeding the elongation and the composite material strength. The inventors have also clarified that the probability of carbon fiber breakage in the high elongation region strongly affects OHT in combination with a specific resin when trying to increase OHT.

  In the present invention, the carbon fiber (I) preferably has a fiber breakage number of 2.0 pieces / mm or more when the single fiber composite strain by the fragmentation method of the single fiber composite is 4.5%, more preferably It is 3.0 pieces / mm or more. The fragmentation method is frequently used by examining the interfacial shear strength at the fiber / resin interface in addition to examining the single fiber strength of the carbon fiber. At that time, a simple Kelly-Tyson model that is not accurate is often used, and it is said that the higher the number of saturated fiber breaks in the fragmentation method, the higher the interfacial shear strength. Basically, the higher the interfacial shear strength, the higher the strength of the unidirectional carbon fiber reinforced composite material, so the OHT can be increased. Even when the single fiber composite strain is 4.5%, the number of fiber breaks is often not saturated, but if the number of fiber breaks at that strain is substantially evaluated, it is sufficient to evaluate the height of interfacial adhesion. . When the number of fiber breaks is 2.0 pieces / mm or more, when the number of breaks increases due to a decrease in interfacial adhesion, the fibers in the vicinity of the breaks easily bear fiber stress, and a high OHT can be maintained.

  Furthermore, in the present invention, the carbon fiber (I) preferably has a fiber breakage number of 0.1 / mm or less when the single fiber composite strain by the fragmentation method of the single fiber composite is 2.0%. Preferably it is 0.08 piece / mm or less, More preferably, it is 0.06 piece / mm or less. If the fiber stress at which the number of fiber breaks is near 0.1 pieces / mm is too low, stress concentration on the adjacent fibers of the broken fibers in the composite material is likely to be induced. By setting it as below, high OHT can be maintained.

  In the present invention, the strand strength of the carbon fiber (I) is preferably 6.4 GPa or more, more preferably 6.8 GPa or more, and further preferably 7.0 GPa or more. Moreover, it is preferable that the strand elastic modulus of carbon fiber (I) is 320 GPa or more, More preferably, it is 340 GPa or more, More preferably, it is 350 GPa or more. When the carbon fiber strain in the fragmentation method is converted into fiber stress, a strand elastic modulus is necessary. Essentially, it is important that the fiber breakage is small even at high fiber stress. Therefore, OHT may decrease when the strand elastic modulus is less than 320 GPa. In the present invention, the strand tensile strength and elastic modulus of the carbon fiber (I) can be determined according to the following procedure in accordance with the resin impregnated strand test method of JIS-R-7608 (2004). That is, as a resin prescription, “Celoxide (registered trademark)” 2021P (manufactured by Daicel Chemical Industries) / 3 boron fluoride monoethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) / Acetone = 100/3/4 (parts by mass) As a curing condition, normal pressure, 130 ° C., and 30 minutes are used. Ten strands of the carbon fiber bundle are measured, and the average value is defined as the strand tensile strength and the strand elastic modulus. The strain range when measuring the strand elastic modulus is 0.45 to 0.85%.

  In this invention, it is preferable that the single fiber elastic modulus of carbon fiber is 320 GPa, More preferably, it is 340 GPa or more, More preferably, it is 350 GPa or more. In the fragmentation method, in order to evaluate the single fiber strength, it is important that the fiber breakage is small even at a high fiber stress rather than the fiber breakage at a high single fiber composite strain. Convert to fiber stress. In order to convert the carbon fiber strain into the fiber stress in the fragmentation method, the strand elastic modulus or single fiber elastic modulus of the carbon fiber is necessary. Here, the single fiber elastic modulus is used. The higher the single fiber elastic modulus, the higher the fiber stress is applied even if the composite fiber single fiber composite strain is low, and the OHT decreases when the single fiber elastic modulus is less than 320 GPa due to the relationship with the matrix resin properties. Sometimes. In this invention, the single fiber elastic modulus of carbon fiber (I) can be calculated | required based on JIS-R-7606 (2000). That is, in the single fiber tensile test, the slip occurs between the carbon fiber and the adhesive of the chuck part in the chuck, so it is not possible to accurately measure the single fiber elastic modulus. However, the longer the gauge length, the smaller the error. Therefore, the gauge length is 50 mm. The strain range when measuring the single fiber modulus is the entire range from 0% strain to breakage.

  In the present invention, the total fineness of the carbon fiber (I) is preferably 400 to 3000 tex. The number of filaments of carbon fiber is preferably 10,000 to 30,000.

  In the present invention, the single fiber diameter of the carbon fiber (I) is preferably 4.5 to 6.0 μm. Since carbon fibers contain surface defects, the smaller the single fiber diameter, the lower the probability of surface defects and the higher the strand strength, but the fracture behavior in the high strength region in the fragmentation test is the same as the single fiber diameter. On the other hand, the larger the single fiber diameter, the easier the matrix resin is impregnated between the single fibers and, as a result, the OHT can be increased. Therefore, it is preferable to select an appropriate single fiber diameter.

  Furthermore, the thermosetting resin (II) contained in the prepreg of the present invention contains an epoxy compound (A) and an aromatic amine curing agent (B). Carbon fiber (I) expresses high OHT by the combination of epoxy compound (A) and thermosetting resin (II) containing aromatic amine curing agent (B).

  The epoxy compound (A) used for the epoxy resin is not particularly limited, and is a bisphenol type epoxy compound, an amine type epoxy compound, a phenol novolak type epoxy compound, a cresol novolak type epoxy compound, a resorcinol type epoxy compound, a glycidyl aniline type. Among epoxy compounds, phenol aralkyl type 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. One or more types can be selected and used.

  Here, the bisphenol type epoxy compound is obtained by glycidylation of two phenolic hydroxyl groups of a bisphenol compound. 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, MY725 (manufactured by Huntsman Advanced Materials Co., Ltd.). Commercially available products of triglycidylaminophenol or triglycidylaminocresol include “SUMI Epoxy (registered trademark)” ELM100, ELM120 (manufactured by Sumitomo Chemical Co., Ltd.), “Araldide (registered trademark)” MY0500, MY0510, MY0600, MY0610. (The above is manufactured by 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, “Epicron (registered trademark)” HP7200, “Epicron (registered trademark)” HP7200H, “Epicron (registered trademark)” HP7200HH (above, Dai Nippon Ink Chemical Co., Ltd.), XD-1000-L, XD-1000-2L (above, Nippon Kayaku Co., Ltd.), “Tactix (registered trademark)” 556 (Huntsman Advanced Materials) Etc.).

  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.

  Particularly preferred is an epoxy resin containing at least a polyfunctional glycidylamine type epoxy compound as the epoxy compound (A). It is preferable to use in combination with the sizing agent-coated carbon fiber of the present invention because the OHT of the carbon fiber reinforced composite material can be improved. The reason is not necessarily clear, but it is considered that when the epoxy compound is used, the strength distribution in the high strength region of the carbon fiber has a strong influence on the OHT.

  Examples of the polyfunctional glycidylamine type epoxy compound 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. 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.

  As commercial products of tetraglycidyldiaminodiphenylmethane, for example, “Sumiepoxy (registered trademark)” ELM434 (manufactured by Sumitomo Chemical Co., Ltd.), YH434L (manufactured by Tohto Kasei Co., Ltd.), “Araldite (registered trademark)” MY720, MY721, MY725 (Manufactured by Huntsman Advanced Materials Co., Ltd.), “jER (registered trademark)” 604 (manufactured by Mitsubishi Chemical Corporation), and the like can be used. Examples of triglycidylaminophenol and triglycidylaminocresol include, for example, “Sumiepoxy (registered trademark)” ELM100 (manufactured by Sumitomo Chemical Co., Ltd.), “Araldite (registered trademark)” MY500, MY0510, “Araldite (registered trademark)” MY0600. MY610 (manufactured by Huntsman Advanced Materials Co., Ltd.), “jER (registered trademark)” 630 (manufactured by Mitsubishi Chemical Corporation), and the like can be used.

  The polyfunctional glycidylamine type epoxy compound is preferably an aromatic epoxy compound (A1) having at least one glycidylamine skeleton and having a trifunctional or higher functional epoxy group.

  The proportion of the polyfunctional glycidylamine type aromatic epoxy compound (A1) is preferably 30 to 100% by mass in the epoxy compound (A), and more preferably 50% by mass or more. Since the ratio of a glycidyl amine type epoxy compound is 30 mass% or more and OHT of a carbon fiber reinforced composite material is improved, it is preferable.

  The aromatic amine curing agent (B) of the present invention is not particularly limited as long as it is an aromatic amine used as an epoxy resin curing agent. Specifically, 3,3′-diaminodiphenyl sulfone is used. (3,3′-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- (dimethylamino Methyl) phenol (DMP-10), 2,4,6-tris (dimethylaminomethyl) phenol (DMP-30) , It can be used 2,4,6-tris (dimethylaminomethyl) 2-ethylhexanoic acid ester of phenol. These may be used alone or in admixture of two or more.

  As a combination of the sizing agent applied to the sizing-coated carbon fiber of the present invention and the aromatic amine curing agent (B), the following combinations are preferable. The sizing agent and aromatic amine curing agent (B) are mixed at a temperature of amine equivalent / epoxy equivalent of 0.9, which is the ratio of amine equivalent to epoxy equivalent of the sizing agent and aromatic amine curing agent (B) to be applied, and the temperature. It is preferable that the glass transition point rise when stored for 20 days in an environment of 25 ° C. and 60% humidity is 25 ° C. or less. When the temperature is 25 ° C. or lower, the reaction in the sizing agent outer layer and the matrix resin is suppressed when the prepreg is formed, and the decrease in OHT of the carbon fiber reinforced composite material after storing the prepreg for a long time is preferable. Moreover, it is more preferable that the increase in the glass transition point is 15 ° C. or less. More preferably, it is 10 ° C. or lower. The glass transition point can be determined by differential scanning calorimetry (DSC).

  Moreover, it is preferable that the total amount of aromatic amine hardening | curing agent (B) 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. Preferably, the amount is in the range of 0.7 to 0.9 equivalent. 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 OHT of the carbon 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.

  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. The thermoplastic resin is preferably contained in the epoxy resin that constitutes the prepreg. Furthermore, as the thermoplastic resin, a thermoplastic resin soluble in an 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) 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)", "RADE" (Registered trademark) "(or, Solvay Advanced Polymers Co., Ltd.), as a polyvinylpyrrolidone," Luviskol (registered trademark) "can be exemplified (BASF Japan 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 OHT can be increased and the characteristics of the sizing agent-coated carbon fiber of the present invention can be maximized. Polyethersulfones include “Sumika Excel” (registered trademark) 3600P, “Sumika Excel” (registered trademark) 5003P, “Sumika Excel” (registered trademark) 5200P, “Sumika Excel” (registered trademark, Sumitomo Chemical Co., Ltd.) 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 Corporation), polyetherimide includes “Ultem” (registered trademark) 1000, “Ultem” (registered trademark) 1010, “Ultem” (registered trademark) 1040 (above, SABIC Innovative Plastics Japan) Etc.) It is possible to use.

  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.

  Moreover, 6-40 mass parts is preferable with respect to 100 mass parts of epoxy resins, when mixing | blending the amount of this thermoplastic resin in an epoxy resin composition, More preferably, it is 6-25 mass parts. On the other hand, when used in a dispersed state, the amount is preferably 10 to 40 parts by mass, more preferably 15 to 30 parts by mass with respect to 100 parts by mass of the epoxy resin. Even if the thermoplastic resin is less than or exceeds the blending amount, OHT may be lowered.

  Next, the manufacturing method suitable for the prepreg of the present invention will be described.

  The prepreg of the present invention is obtained by impregnating the above-described carbon fiber (I) (sizing agent-coated carbon fiber) coated with a sizing agent with 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 the reinforced carbon fiber bundle is 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.

  Also, in the hot melt method, a method of directly impregnating sizing agent-coated carbon fibers 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 produced, and then sizing is performed. A prepreg can be produced by a method in which the film is overlapped from both sides or one side of the agent-coated carbon fiber and heated and pressed to impregnate the sizing agent-coated carbon fiber with the matrix resin. 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. The prepreg of the present invention thus obtained is suitably used for sports applications such as golf shafts and fishing rods and other general industrial applications, including aircraft members, spacecraft members, automobile members, and ship members.

  Next, the manufacturing method of the above-mentioned sizing agent-coated carbon fiber will be described.

  In the present invention, the polyacrylonitrile polymer suitably used in the production of sizing agent-coated carbon fibers preferably has a weight average molecular weight of 500,000 to 900,000, more preferably 700,000 to 900,000. In the case of a polyacrylonitrile-based polymer having a weight average molecular weight that is generally used for carbon fibers, the weight average molecular weight of which is less than 500,000, since the connection between molecules in the fiber axis direction is reduced, the polymer chain end is highly affected. The strength of the single fiber of the carbon fiber is likely to decrease in the strength region. Further, the weight average molecular weight is preferably higher, but a polyacrylonitrile polymer having a high molecular weight exceeding 900,000 needs to have a low polymer concentration when spinning as a polymer solution. Voids are formed in the carbon fiber, and the single fiber strength of the carbon fiber is easily lowered in a high strength region. The weight average molecular weight of the polyacrylonitrile-based polymer can be controlled by changing the amounts of monomers, initiators, chain transfer agents and the like during polymerization. Specifically, the weight average molecular weight can be increased by increasing the monomer concentration at the start of polymerization, decreasing the initiator concentration, and decreasing the chain transfer agent concentration. In the present invention, the polyacrylonitrile-based polymer means that at least acrylonitrile is the main constituent of the polymer skeleton, and the main constituent usually occupies 90 to 100 mol% of the polymer skeleton. Say.

  The polydispersity Mz / Mw of the polyacrylonitrile polymer suitable for the present invention is 1.4 to 2.4. The larger Mz / Mw means that components having different molecular weights are included on the high molecular weight side, and even if Mz / Mw is less than 1.4 or Mz / Mw exceeds 2.4, a single unit of carbon fiber in a high strength region. A decrease in fiber strength is likely to occur.

  In the present invention, the polyacrylonitrile-based polymer suitably used in the production of the sizing agent-coated carbon fiber contains a copolymer component from the viewpoint of improving the yarn production and efficiently performing the flameproofing treatment. Generally, when the amount of the copolymer component is small, the flameproofing reaction becomes non-uniform, and when the amount of the copolymer component is large, the site itself may be thermally decomposed and recognized as a carbon fiber defect. A preferable amount of the copolymer component is 0.1 to 0.8% by mass. Preferred examples of the copolymer component include those having one or more carboxyl groups or amide groups from the above viewpoint. In order to prevent a decrease in heat resistance, it is preferable to use a small amount of a monomer having a high flame resistance promoting effect, and it is preferable to use a copolymer component having a carboxyl group rather than an amide group. Further, the number of amide groups and carboxyl groups contained is more preferably two or more than one, and from this viewpoint, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, citraconic acid, ethacrylic acid Maleic acid and mesaconic acid are preferred, itaconic acid, maleic acid and mesaconic acid are more preferred, and itaconic acid is most preferred.

  As a polymerization method for producing the polyacrylonitrile polymer suitably used in the present invention, a known polymerization method can be selected. The spinning solution suitably used in the production of the sizing agent-coated carbon fiber of the present invention is obtained by dissolving the polyacrylonitrile polymer in a solvent in which a polyacrylonitrile polymer such as dimethyl sulfoxide, dimethylformamide and dimethylacetamide is soluble. It is a thing. The polyacrylonitrile polymer used in the present invention is preferably a spinning solution having a concentration of 10 to 18% by mass. When the concentration of the spinning solution is less than 10% by mass, voids are formed in the carbon fiber, and the single fiber strength of the carbon fiber is easily lowered in the high strength region, and the concentration of the spinning solution is 18% by mass. If it exceeds%, the weight average molecular weight of the polymer may have to be lowered for spinnability.

  The method for producing a polyacrylonitrile-based precursor fiber suitably used in the production of the sizing agent-coated carbon fiber of the present invention includes a spinning process in which spinning is performed by discharging from a spinneret by a dry and wet spinning method, and the fiber obtained in the spinning process. A water-washing process for washing in a water bath, a water-bath drawing process for drawing the fibers obtained in the water-washing process in a water bath, and a drying heat-treatment process for drying and heat-treating the fibers obtained in the water-bath drawing process. Accordingly, the process includes a steam stretching step of steam stretching the fiber obtained in the drying heat treatment step.

  In the present invention, the coagulation bath preferably contains a solvent such as dimethyl sulfoxide, dimethylformamide and dimethylacetamide used as a solvent for the spinning solution and a so-called coagulation promoting component. As the coagulation accelerating component, a component that does not dissolve the polyacrylonitrile polymer and is compatible with the solvent used in the spinning solution can be used. Specifically, it is preferable to use water as a coagulation promoting component.

  The water bath temperature in the water washing step is preferably washed using a water bath having a plurality of stages of 20 to 90 ° C. Moreover, it is preferable that the draw ratio in a water bath extending process is 1.3-5 times, More preferably, it is 2-4 times. After the water bath stretching step, it is preferable to apply an oil agent made of silicone or the like to the yarn for the purpose of preventing adhesion between single fibers. As such a silicone oil agent, it is preferable to use a modified silicone, and it is preferable to use one containing an amino-modified silicone having high heat resistance.

  After the water washing step, the water bath stretching step, the oil agent applying step, and the drying heat treatment step performed by a known method, by performing steam stretching as necessary, the poly used suitably in the production of sizing agent-coated carbon fibers. Acrylonitrile-based precursor fibers are obtained. In the present invention, the steam stretching is preferably performed at least 3 times, more preferably 4 times or more, and still more preferably 5 times or more in the pressurized steam.

  In the method for suitably producing the sizing agent-coated carbon fiber of the present invention, the above-mentioned polyacrylonitrile-based precursor fiber is flame-resistant, pre-carbonized, and carbonized to obtain a carbon fiber.

  In the present invention, the flame resistance of the polyacrylonitrile-based precursor fiber is preferably performed at as high a temperature as possible without causing a runaway reaction. Specifically, it is preferably performed in air at 200 to 300 ° C. In the present invention, the flameproofing treatment time can be suitably selected within a range of 10 to 100 minutes, but for the purpose of improving the mechanical properties of the obtained carbon fiber, the specific gravity of the obtained flameproof fiber. Is preferably set in a range of 1.3 to 1.4.

Subsequent to the flame resistance, preliminary carbonization is performed. In the preliminary carbonization step, it is preferable that the obtained flame-resistant fiber is heat-treated in an inert atmosphere at a maximum temperature of 500 to 1200 ° C. until the specific gravity is 1.5 to 1.8 g / cm ³ .

Subsequent to the preliminary carbonization, carbonization is performed. In the present invention, in the carbonization step, the pre-carbonized fiber bundle obtained is carbonized in an inert atmosphere at a maximum temperature of 1200 to 2000 ° C. so that the carbonization tension satisfies the formula (2). And it is preferable that it is a manufacturing method of the carbon fiber whose average tearable distance of a pre-carbonized fiber bundle is 500-700 mm.
4.9 ≦ carbonization tension (mN / dtex) ≦ −0.0225 × (average tearable distance of pre-carbonized fiber bundle (mm)) + 23.5 (2).

  The temperature of the carbonization step is preferably higher from the viewpoint of increasing the strand elastic modulus of the carbon fiber to be obtained, but if it is too high, the strength of the high strength region may decrease, and it is set in consideration of both. Is good. A more preferable temperature range is 1200 to 1800 ° C, and a more preferable temperature range is 1200 to 1600 ° C.

  The tension (carbonization tension) in the carbonization step is represented by a value obtained by dividing the tension (mN) measured on the outlet side of the carbonization furnace by the fineness (dtex) of the polyacrylonitrile-based precursor fiber when it is completely dried. When the tension is lower than 4.9 mN / dtex, the crystallite orientation of the carbon fiber cannot be increased, and a high strand elastic modulus is not exhibited. Further, the tension is preferably higher from the viewpoint of increasing the strand elastic modulus of the carbon fiber to be obtained, but if it is too high, the process passability and the quality may be lowered, and in a range satisfying the formula (2). It is preferable to set. The meaning of the first-order coefficient −0.0225 on the right-hand side of Equation (2) is a tension gradient that can be set with an increase in the average tearable distance, and the constant term 23.5 is used to reduce the average tearable distance to the limit. This tension can be set when the length is shortened.

  The tearable distance of the pre-carbonized fiber bundle in the carbonization step is an index that represents the entangled state of the fiber bundle, and is determined as follows. First, the fiber bundle is cut to a length of 1160 mm, and one end thereof is fixed on a horizontal base so as not to move with an adhesive tape (this point is referred to as a fixing point A). One end of the fiber bundle that is not fixed is divided into two with fingers, and one of the ends is tensioned and fixed on the table so as not to move with an adhesive tape (this point is referred to as a fixing point B). Move the other of the two halves along the table so that the fixed point A becomes a fulcrum and does not come loose, rest at a position where the linear distance from the fixed point B is 500 mm, and fix it on the table so that it does not move with adhesive tape. (This point is called a fixed point C). The area surrounded by the fixed points A, B, and C is visually observed, the entanglement point farthest from the fixed point A is found, and the distance projected on the straight line connecting the fixed point A and the fixed point B is 1 mm at the minimum scale. Read with the ruler of, and make the tearable distance. The arithmetic average value of 30 measurements of the above operation is defined as the average tearable distance. A method of measuring the tearable distance is shown in FIG. In this measurement method, the entanglement point farthest from the fixed point A is the point where the linear distance from the fixed point A is the longest and three or more single fibers having no slack are entangled.

  Conventionally, the hook drop method has been generally used as a method for evaluating the entangled state. As defined in JIS L1013 (2010), the degree of entanglement of the fiber bundle by the hook drop method is fixed to the upper part of the drooping device, the weight is suspended at the lower end of the fiber bundle, and the sample is placed vertically. After that, a hook with a weight of 10 g with a smooth surface of 0.6 mm in diameter is inserted so as to divide the fiber bundle into two parts 1 cm below the upper fixed end of the sample, and the descent distance is measured. .

  In the present invention, as the degree of entanglement of the pre-carbonized fiber bundle in the carbonization process, not by the conventional hook drop method, but by making the average tearable distance within a specific range, while avoiding the strength reduction of the carbon fiber high strength region High stretch tension in the carbonization process can be expressed. In order to apply a high drawing tension in the carbonization process, it is necessary to create a fiber bundle state in which the stress transmission ability between single fibers is high. For that purpose, it is important to form a fine entanglement network between single fibers. The conventional hook drop method is an evaluation at a “point” using a hook, whereas the tearable distance is an evaluation at a “surface” that looks at the entire bundle. Due to this difference, in the carbonization process, It is considered that a state for expressing a high stretching tension can be appropriately defined.

  In the present invention, the shorter the tearable distance of the pre-carbonized fiber bundle in the carbonization process, the higher the degree of entanglement, the higher the stress transmission ability between single fibers, and the higher the stretching tension in the carbonization process. When the distance is less than 500 mm, the single fiber strength of the carbon fiber in the high strength region tends to decrease. If the entangling process with a tearable distance exceeding 700 mm is not performed or weak, the stress of the single fiber that breaks with a certain probability, which is the carbonization process, is borne by the other single fiber that has not broken. It induces structural variation between fibers and accompanying strength variation.

  As the means for achieving the average tearable distance of the preliminary carbonized fiber, any method can be adopted as long as the numerical range described above can be achieved. In the present invention, as a method for controlling the average tearable distance, The entanglement process by the fluid to the fiber bundle is preferably used. Among them, it is preferable to perform the fluid entanglement process in any of the manufacturing process and the flameproofing process of the polyacrylonitrile-based precursor fiber, that is, in a place where a fiber bundle having a fiber elongation of 5% or more is processed. In other steps, OHT may be lowered.

  As the fluid used for the fluid entanglement treatment, both gas and liquid can be used, but air or nitrogen is preferable because it is inexpensive. In the fluid entanglement process, the fluid is preferably sprayed onto the fiber bundle using a nozzle, and the shape of the nozzle that sprays the fluid is not particularly limited, but it is preferable to use one having 2 to 8 ejection holes. The arrangement of the ejection ports is not particularly limited, but an even number of ejection holes are arranged so as to surround the fiber bundle so that the angle formed by the fiber bundle longitudinal direction and the fluid blowing direction is in the range of 88 ° to 90 °. It is preferable to arrange the jet holes at positions facing each other so as to form a pair of two holes. Other conditions such as fiber bundle tension and fluid discharge pressure during the fluid entanglement process may be examined so as to adjust the tearable distance appropriately.

  In the carbonization step, the fiber bundle is preferably substantially untwisted. Here, “substantially untwisted” means that it is 1 turn or less per 1 m of fiber bundle even if twist is present.

  The carbon fiber of the present invention preferably has an average tearable distance of 300 to 710 mm. When the distance is less than 300 mm, the matrix resin is less likely to be impregnated between the single fibers, and may reduce OHT. When the distance is 710 mm or more, thread cracking during widening is induced in prepreg processing, It may not be suitable for producing a thin prepreg with a low basis weight. Furthermore, when a carbon fiber reinforced composite material is used, stress transmission in the carbon fiber reinforced composite material also becomes non-uniform, which may reduce OHT.

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

  In the present invention, examples of the electrolytic solution used in the liquid phase electrolytic oxidation include an acidic electrolytic solution and an alkaline electrolytic solution. From the viewpoint of adhesion, a liquid phase electrolytic oxidation is performed in an alkaline electrolytic solution, and then a sizing agent is applied. 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 / liter, more preferably in the range of 0.1 to 1 mol / liter. When the concentration of the electrolytic solution is 0.01 mol / liter or more, the electrolytic treatment voltage is lowered, which is advantageous for the operating cost. On the other hand, when the concentration of the electrolytic solution is 5 mol / liter or less, it is advantageous from the viewpoint of safety.

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

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

In the present invention, the current density in the liquid phase electrolytic oxidation is preferably in the range of 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 in} 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 for the operating cost. On the other hand, when the current density is 1000 amperes / m ² or less, it is advantageous from the viewpoint of safety.

  In the present invention, the total amount of electrolytic electricity employed in the electrolytic treatment is preferably 3 to 300 coulomb / g per gram of carbon fiber. If the total amount of electrolytic electricity is less than 3 coulombs / g, functional groups may not be sufficiently imparted to the carbon fiber surface, and the number of fiber breaks when the single fiber apparent stress by the fragmentation method of the single fiber composite is 15.3 GPa. May be less than 2.0 pieces / mm. On the other hand, when the total amount of electrolytic electricity exceeds 300 coulombs / g, defects on the surface of the carbon fiber single fiber are enlarged, and the number of fiber breaks when the single fiber apparent stress is 12.2 GPa by the fragmentation method of the single fiber composite is 1. May exceed 7 / mm.

  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 and a spray method can be used. Especially, it is preferable to use a dip method from a viewpoint that washing | cleaning is easy, Furthermore, it is a preferable aspect to use a dip method, vibrating a carbon fiber with an ultrasonic wave. 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.

The present invention is a sizing agent-coated carbon fiber that is a carbon fiber coated with a sizing agent containing at least an aliphatic epoxy compound (C) and an aromatic epoxy compound (D). Preferably, the sizing agent surface has a bond energy (284) attributed to (a) CHx, C—C, C = C in the C _1s core spectrum measured by X-ray photoelectron spectroscopy at a photoelectron escape angle of 15 °. The ratio (a) / (b) of the height (cps) of the component (.6 eV) and the height (cps) of the component (286.1 eV) attributed to C—O is 0.50. A sizing agent-coated carbon fiber characterized by a value of ˜0.90.

  In the present invention, it is necessary to use an aliphatic epoxy compound (C) and an aromatic epoxy compound (D) in combination.

  According to the knowledge of the present inventors, such a range is excellent in the interfacial adhesion between the carbon fiber and the matrix resin, and also when the sizing agent-coated carbon fiber is used for the prepreg when the prepreg is stored for a long period of time. The change over time is small, and it is suitable for sizing agent-coated carbon fibers for carbon fiber reinforced composite materials. Therefore, by using such a sizing agent, the sizing agent-coated carbon fiber of the present invention has a fiber breakage number of 2.0 pieces / mm or more when the single fiber apparent stress is 15.3 GPa according to the fragmentation method of the single fiber composite. Can be controlled.

  Carbon fiber consisting of only aromatic epoxy compound (D) as epoxy compound and coated with sizing agent that does not contain aliphatic epoxy compound (C) has low reactivity between sizing agent and matrix resin, and preserves prepreg for a long time. There is an advantage that the change in physical properties is small. There is also an advantage that a rigid interface layer can be formed. However, the aromatic epoxy compound (D) is derived from the rigidity of the compound, and it has been confirmed that the adhesion between the carbon fiber and the matrix resin is slightly inferior to the aliphatic epoxy compound (A). .

  In addition, it has been confirmed that carbon fibers coated with a sizing agent composed only of an aliphatic epoxy compound (C) as an epoxy compound have high adhesiveness with a matrix resin. Although the mechanism is not certain, the aliphatic epoxy compound (C) is derived from a flexible skeleton and a structure having a high degree of freedom, and the functional group of the carboxyl group and hydroxyl group on the surface of the carbon fiber and the aliphatic epoxy compound are strongly interacting with each other. It is considered possible to form an action. However, the aliphatic epoxy compound (C) exhibits high adhesiveness due to the interaction with the carbon fiber surface, while having high reactivity with the compound having a functional group represented by the curing agent in the matrix resin, When stored for a long time in this state, it has been confirmed that the structure of the interface layer changes due to the interaction between the matrix resin and the sizing agent, and the physical properties of the carbon fiber reinforced composite material obtained from the prepreg deteriorate.

  In the present invention, when the aliphatic epoxy compound (C) and the aromatic epoxy compound (D) are mixed, the aliphatic epoxy compound (C) having higher polarity is unevenly distributed on the carbon fiber side, and is opposite to the carbon fiber. There is a phenomenon that the aromatic epoxy compound (D) having a low polarity tends to be unevenly distributed in the outermost layer of the sizing layer. As a result of the inclined structure of the sizing layer, the aliphatic epoxy compound (C) has a strong interaction with the carbon fiber in the vicinity of the carbon fiber, thereby improving the adhesion between the carbon fiber and the matrix resin. In addition, the aromatic epoxy compound (D) present in a large amount in the outer layer plays a role of blocking the aliphatic epoxy compound (C) from the matrix resin when the sizing agent-coated carbon fiber is used as a prepreg. As a result, the reaction between the aliphatic epoxy compound (C) and the highly reactive component in the matrix resin is suppressed, so that stability during long-term storage is exhibited. When the aliphatic epoxy compound (C) is almost completely covered with the aromatic epoxy compound (D), the interaction between the sizing agent and the matrix resin is reduced and the adhesiveness is lowered. The ratio of the aliphatic epoxy compound (C) and the aromatic epoxy compound (D) is important.

  In this invention, it is preferable that the epoxy equivalent of the sizing agent apply | coated to carbon fiber is 350-550 g / mol. It is preferable for it to be 550 g / mol or less because the adhesion between the carbon fiber coated with the sizing agent and the matrix resin is improved. Moreover, since it is 350 g / mol or more, when this sizing agent application | coating carbon fiber is used for a prepreg, since the reaction with the resin component and sizing agent which are used for a prepreg can be suppressed, prepreg is stored for a long time This is also preferable because the physical properties of the obtained carbon fiber reinforced composite material are improved. The epoxy equivalent of the carbon fiber coated with the sizing agent in the present invention is that the sizing agent-coated fiber is immersed in a solvent typified by N, N-dimethylformamide, and is eluted from the fiber by ultrasonic cleaning. It can be obtained by acid-base titration by opening the epoxy group with hydrochloric acid. Epoxy equivalent is preferably 360 g / mol or more, and more preferably 380 g / mol or more. Moreover, 530 g / mol or less is preferable and 500 g / mol or less is more preferable. In addition, the epoxy equivalent of the sizing agent applied to the carbon fiber can be controlled by the epoxy equivalent of the sizing agent used for application and the heat history in drying after application.

  In this invention, it is preferable that the aliphatic epoxy compound (C) eluted from a sizing agent application | coating fiber is 0.3 mass part or less with respect to 100 mass parts of sizing agent application | coating carbon fibers. By setting the elution amount to 0.3 parts by mass or less, when the sizing agent-coated carbon fiber of the present invention is used as a prepreg together with a thermosetting resin, the reaction between the resin component of the thermosetting resin and the sizing agent is performed. Since it can suppress, the physical property of the carbon fiber reinforced composite material obtained also when the prepreg is stored for a long period of time is preferable. 0.1 mass part or less is more preferable, and 0.05 mass part or less is still more preferable. In this invention, the elution amount of the aliphatic epoxy compound (C) eluted from a sizing agent application | coating fiber is calculated | required in the following procedures.

  After immersing 0.1g of carbon fiber coated with sizing agent in 10ml of a mixture of acetonitrile and chloroform at a volume ratio of 9: 1, ultrasonic cleaning is performed for 20 minutes to elute the sizing agent from the fiber, and then 5ml of the sample solution. The sample is collected, the solvent is distilled off in nitrogen, and the above-mentioned mixed solution of acetonitrile and chloroform is added to a constant volume until the volume becomes 0.2 ml, and a 25-fold concentrated solution is prepared. The solution is separated from the other peaks of the aliphatic epoxy compound (C) by liquid chromatography using a mixture of water and acetonitrile as a mobile phase and detected by an evaporative light scattering detector (ELSD). . Then, by creating a calibration curve using the peak area of the solution of the aliphatic epoxy compound (C) whose concentration is known in advance, and quantifying the concentration of the aliphatic epoxy compound (C) based on the calibration curve, The elution amount of the aliphatic epoxy compound (C) with respect to 100 parts by mass of the sizing agent-coated carbon fiber is determined.

The present invention relates to (a) CHx, C-C, C = C binding energy (284.C) of the C _1s core spectrum measured on the sizing agent surface by X-ray photoelectron spectroscopy at a photoelectron escape angle of 15 °. The ratio (a) / (b) between the height (cps) of the component of 6 eV) and the height (cps) of the component of (b) binding energy (286.1 eV) attributed to C—O is 0.50 0.90. Preferably, it is 0.55 or more, more preferably 0.57 or more. Moreover, Preferably it is 0.80 or less, More preferably, it is 0.74 or less. That (a) / (b) is large indicates that there are many compounds derived from aromatics on the surface and few compounds derived from aliphatic esters. The present invention has been made by finding that when this (a) / (b) falls within a specific range, it has excellent adhesion to the matrix resin and has little deterioration in physical properties when stored for a long time in the state of a prepreg. It is a thing.

  X-ray photoelectron spectroscopy measurement method is an analysis method that irradiates a sample carbon fiber with X-rays in an ultra-high vacuum and measures the kinetic energy of photoelectrons emitted from the surface of the carbon fiber with an apparatus called an energy analyzer. That is. By examining the kinetic energy of the photoelectrons emitted from the carbon fiber surface of the sample, the binding energy converted from the energy value of the X-rays incident on the carbon fiber of the sample is uniquely determined. From the binding energy and the photoelectron intensity The type and concentration of elements present on the outermost surface (˜nm) of the sample and the chemical state thereof can be analyzed.

In the present invention, the peak ratio of (a) and (b) on the sizing agent surface of the sizing agent-coated fiber is determined by X-ray photoelectron spectroscopy according to the following procedure. Cut the sizing agent-coated carbon fiber to 20 mm, spread and arrange it on a copper sample support, and then use AlKα _1,2 as the X-ray source and keep the sample chamber at 1 × 10 ⁻⁸ Torr for measurement. Is called. As correction of the peak accompanying charging during measurement, first, the binding energy value of the main peak of C _1s is adjusted to 286.1 eV. At this time, the peak area of C _1s is obtained by drawing a straight baseline in the range of 282 to 296 eV. Further, a linear base line of 282 to 296 eV obtained by calculating the area at the C _1s peak is defined as the origin (zero point) of the photoelectron intensity, and (b) the peak of the binding energy 286.1 eV attributed to the CO component is obtained. The height (cps: photoelectron intensity per unit time) and the height (cps) of the component having a binding energy of 284.6 eV attributed to (a) CHx, C—C, C = C are obtained, and (a) / ( b) is calculated.

(A) Component of binding energy (284.6 eV) belonging to (a) CHx, C—C, C = C of the C _1s inner-shell spectrum measured by X-ray photoelectron spectroscopy with a photoelectron escape angle of 15 ° in the inner layer of sizing The ratio (a) / (b) of the height (cps) of the component (b) and the height (cps) of the component of the binding energy (286.1 eV) attributed to C—O is 0.45 to 1.0. Preferably there is. The inner layer of the sizing agent was obtained by ultrasonically washing the sizing-coated carbon fiber with an acetone solvent for 1 to 10 minutes and then washing away with distilled water, and the remaining sizing agent adhering to the carbon fiber was 0.10 ± 0.05% by mass After controlling to a range, a measurement is performed by the method mentioned above.

  In the present invention, the sizing agent contains at least an aliphatic epoxy compound (C) and an aromatic epoxy compound (D). The aliphatic epoxy compound (C) is preferably contained in an amount of 35 to 65% by mass based on the total amount of the applied sizing agent. Adhesiveness improves by being applied 35 mass% or more. Moreover, by being 65 mass% or less, components other than aliphatic epoxy can be used as the sizing agent, and the prepreg produced using the obtained sizing agent-coated fiber is also obtained when stored for a long time. The physical properties of the fiber reinforced composite material are improved. 38 mass% or more is more preferable, and 40 mass% or more is further more preferable. Moreover, 60 mass% or less is more preferable, and 55 mass% or more is further more preferable.

  It is preferable that 35-60 mass% of aromatic epoxy compounds (D) are contained. By containing 35% by mass or more of the aromatic epoxy compound (D), the composition of the aromatic compound in the outer layer of the sizing agent can be maintained high, so that the aliphatic epoxy compound and the matrix are highly reactive during long-term storage of the prepreg. Reduction in physical properties due to reaction with the reactive compound in the resin is suppressed. The amount of 60% by mass or less is preferable because the above-described inclined structure in the sizing agent can be expressed and the adhesiveness can be maintained. 37 mass% or more is more preferable, and 39 mass% or more is further more preferable. Moreover, 55 mass% or less is more preferable, and 45 mass% or more is further more preferable.

  As an epoxy component in the sizing agent in this invention, an aliphatic epoxy compound (C) and an aromatic epoxy compound (D) are contained. The mass ratio (C) / (D) of the aliphatic epoxy compound (C) and the aromatic epoxy compound (D) is preferably 52/48 to 80/20. When (C) / (D) is 52/48 or more, the ratio of the aliphatic epoxy compound (A) present on the carbon fiber surface is increased, and the adhesion between the carbon fiber and the matrix resin is improved. As a result, the composite properties such as tensile strength of the obtained carbon fiber reinforced resin are preferably increased. Moreover, 80/20 or less is preferable because the amount of the highly reactive aliphatic epoxy compound present on the surface of the carbon fiber is reduced and the reactivity with the matrix resin can be suppressed. The mass ratio of (C) / (D) is more preferably 55/45 or more, and further preferably 60/40 or more. Moreover, 75/35 or less is more preferable, and 73/37 or less is further more preferable.

  In this invention, it is preferable that the adhesion amount of a sizing agent is the range of 0.1-3.0 mass parts with respect to 100 mass parts of carbon fibers, More preferably, it is 0.2-3.0 mass parts. It is a range. When the amount of the sizing agent is within such a range, high OHT can be expressed.

  The method for measuring the amount of sizing agent attached is that 2 ± 0.5g of sizing coated carbon fiber is sampled and the amount of mass change before and after the heat treatment when heat treatment is performed at 450 ° C. for 15 minutes in a nitrogen atmosphere. It is the mass% of the value divided by the previous mass.

  In this invention, it is preferable that the adhesion amount of an aliphatic epoxy compound (C) is the range of 0.05-2.0 mass parts with respect to 100 mass parts of carbon fibers, More preferably, it is 0.2-2. The range is 0.0 parts by mass. More preferably, it is 0.3-1.0 mass part. An adhesion amount of the aliphatic epoxy compound (C) of 0.05 parts by mass or more is preferable because the adhesion between the sizing agent-coated carbon fiber and the matrix resin is improved by the aliphatic epoxy compound (C) on the carbon fiber surface.

  The aliphatic epoxy compound (C) 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 adhesiveness of the sizing agent-coated carbon fiber is improved, which is preferable.

  In the present invention, the aliphatic epoxy compound (C) has one or more epoxy groups in the molecule. As a result, a strong bond between the carbon fiber and the epoxy group in the sizing agent can be formed. The number of epoxy groups in the molecule is preferably 2 or more, and more preferably 3 or more. In the case of an epoxy compound having two or more epoxy groups in the molecule, even if one epoxy group forms a covalent bond with the oxygen-containing functional group on the surface of the carbon fiber, the remaining epoxy group is covalently bonded to the matrix resin. Alternatively, it is preferable because a hydrogen bond can be formed and adhesion can be further improved. There is no particular upper limit on the number of epoxy groups, but 10 is sufficient from the viewpoint of adhesion.

  In the present invention, the aliphatic epoxy compound (C) is preferably an epoxy compound having 3 or more functional groups of 2 or more, more preferably an epoxy compound having 4 or more of 2 or more functional groups. . The functional group possessed by the epoxy compound is preferably selected from a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, or a sulfo group in addition to the epoxy group. In the case of an epoxy compound having three or more epoxy groups or other functional groups in the molecule, even if one epoxy group forms a covalent bond with an oxygen-containing functional group on the carbon fiber surface, the remaining two or more The epoxy group or other functional group can form a covalent bond or a hydrogen bond with the matrix resin, and the adhesion is further improved. There is no particular upper limit on the number of functional groups containing an epoxy group, but 10 is sufficient from the viewpoint of adhesiveness.

  In this invention, it is preferable that the epoxy equivalent of an aliphatic epoxy compound (C) is less than 360 g / mol, More preferably, it is less than 270 g / mol, More preferably, it is less than 180 g / mol. When the epoxy equivalent is less than 360 g / mol, an interaction with the carbon fiber is formed at a high density, and the adhesion between the carbon fiber and the matrix resin is further improved. There is no particular lower limit of the epoxy equivalent, but 90 g / mol or more is sufficient from the viewpoint of adhesiveness.

  In the present invention, specific examples of the aliphatic epoxy compound (C) 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.

  Examples of the glycidyl ether type epoxy compound include a glycidyl ether type epoxy compound obtained by a reaction with epichlorohydrin. Further, as glycidyl ether type epoxy compounds, 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, pen Erythritol, sorbitol, and the arabitol, glycidyl ether type epoxy compound obtained by reaction of epichlorohydrin are also exemplified. 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 (C) used in the present invention include epoxy compounds such as triglycidyl isocyanurate in addition to these epoxy compounds.

  In the present invention, the aliphatic epoxy compound (C) is at least one selected from one or more epoxy groups and a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, a carboxyl group, an ester group and a sulfo group. It is preferable to have one or more functional groups. Specific examples of the epoxy compound include, for example, a compound having an epoxy group and a hydroxyl group, a compound having an epoxy group and an amide group, a compound having an epoxy group and an imide group, a compound having an epoxy group and a urethane group, and an epoxy group and a urea group. Compounds having an epoxy group and a sulfonyl group, and compounds having an epoxy group and a sulfo group.

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

  Examples of the compound having an 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 compound 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. 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 compound having a urea group in addition to the epoxy group include a urea-modified epoxy compound. A urea-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 urea.

  The aliphatic epoxy compound (C) used in the present invention is ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, tetra from the viewpoint of high adhesion among the above. Propylene glycol, polypropylene glycol, trimethylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, polybutylene glycol, 1,5-pentanediol, neo Pentyl glycol, 1,6-hexanediol, glycerol, diglycerol, polyglycerol, trimethylolpropane, pentaerythritol, sorbitol, and arabitol , Glycidyl ether type epoxy compound obtained by reaction of epichlorohydrin is more preferable.

  Among these, the aliphatic epoxy compound (C) in the present invention is preferably a polyether type polyepoxy compound and / or a polyol type polyepoxy compound having two or more epoxy groups in the molecule from the viewpoint of high adhesiveness.

  In addition, the aliphatic epoxy compound (C) is 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, glycerol, diglycerol, polyglycerol, trimethylolpropane, pentaerythritol, sorbitol, and arabitol, and epi More preferably glycidyl ether type epoxy compound obtained by reaction with Rorohidorin.

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

  In the present invention, the aromatic epoxy compound (D) has one or more aromatic rings in the molecule. The aromatic ring may be an aromatic ring hydrocarbon composed 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 fiber-reinforced composite material composed of sizing agent-coated carbon fibers and a matrix resin, a so-called interface layer in the vicinity of the carbon fibers may be affected by the carbon fibers or the sizing agent and have different characteristics from the matrix resin. When the epoxy compound has one or more aromatic rings, a rigid interface layer is formed, the stress transmission ability between the carbon fiber and the matrix resin is improved, and the mechanical properties such as 0 ° tensile strength of the fiber reinforced composite material are improved. improves. Further, the hydrophobicity is improved by the aromatic ring, so that the interaction with the carbon fiber is weaker than that of the aliphatic epoxy compound, and the aliphatic epoxy compound can be covered and exist in the outer layer of the sizing layer. Thus, when the sizing agent-coated carbon fiber is used for a prepreg, it is preferable because a change with time when stored for a long period of time can be suppressed. Having two or more aromatic rings is preferable because long-term stability due to the aromatic rings is improved. There is no particular upper limit on the number of aromatic rings, but 10 is sufficient from the viewpoint of suppressing the reaction with the mechanical properties and the matrix resin.

  In the present invention, the aromatic epoxy compound (D) has at least one kind in the molecule having one or more epoxy groups and one or more aromatic rings in the molecule. The functional group other than the epoxy group is preferably selected from a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, a carboxyl group, an ester group or a sulfo group, and two or more types are included in one molecule. Also good. In addition to the aromatic epoxy compound (D), an aromatic ester compound and an aromatic urethane compound are preferably used in order to improve the stability and high-order processability of the compound.

  In the present invention, the number of epoxy groups of the aromatic epoxy compound (D) is preferably 2 or more, and more preferably 3 or more. Moreover, it is preferable that it is 10 or less.

  In the present invention, the aromatic epoxy compound (D) is preferably an epoxy compound having 3 or more functional groups of 2 or more, more preferably an epoxy compound having 4 or more of 2 or more functional groups. . The functional group possessed by the epoxy compound is preferably selected from a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, or a sulfo group in addition to the epoxy group. In the case of an epoxy compound having three or more epoxy groups or other functional groups in the molecule, even if one epoxy group forms a covalent bond with an oxygen-containing functional group on the carbon fiber surface, the remaining two or more The epoxy group or other functional group can form a covalent bond or a hydrogen bond with the matrix resin, and the adhesion is further improved. There is no particular upper limit on the number of functional groups containing an epoxy group, but 10 is sufficient from the viewpoint of adhesiveness.

  In the present invention, the epoxy equivalent of the aromatic epoxy compound (D) is preferably less than 360 g / mol, more preferably less than 270 g / mol, and even more preferably less than 180 g / mol. When the epoxy equivalent is less than 360 g / mol, covalent bonds are formed at a high density, and the adhesion between the carbon fiber and the matrix resin is further improved. There is no particular lower limit of the epoxy equivalent, but 90 g / mol or more is sufficient from the viewpoint of adhesiveness.

  In the present invention, specific examples of the aromatic epoxy compound (D) include, for example, a glycidyl ether type epoxy compound derived from a polyol, a glycidyl amine type epoxy compound derived from an amine having multiple 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.

  Examples of the glycidyl ether type epoxy compound include bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetrabromobisphenol A, phenol novolac, cresol novolac, hydroquinone, resorcinol, 4,4′-dihydroxy-3,3 ′, 5. , 5′-tetramethylbiphenyl, 1,6-dihydroxynaphthalene, 9,9-bis (4-hydroxyphenyl) fluorene, tris (p-hydroxyphenyl) methane, and tetrakis (p-hydroxyphenyl) ethane. Examples of the glycidyl ether type epoxy include a compound and a glycidyl ether type epoxy compound having a biphenyl aralkyl skeleton.

  Examples of the glycidylamine type epoxy compound include N, N-diglycidylaniline, N, N-diglycidyl-o-toluidine, m-xylylenediamine, m-phenylenediamine, 4,4′-diaminodiphenylmethane and 9,9. -Bis (4-aminophenyl) fluorene.

  Further, for example, as a glycidylamine type epoxy compound, both the hydroxyl group and amino group of aminophenols of m-aminophenol, p-aminophenol, and 4-amino-3-methylphenol are reacted with epichlorohydrin. And an epoxy compound obtained.

  Examples of the glycidyl ester type epoxy compound include glycidyl ester type epoxy compounds obtained by reacting phthalic acid, terephthalic acid, and hexahydrophthalic acid with epichlorohydrin.

  As the aromatic epoxy compound (D) used in the present invention, in addition to these epoxy compounds, epoxy compounds synthesized from the above-mentioned epoxy compounds, for example, oxazolidone from bisphenol A diglycidyl ether and tolylene diisocyanate An epoxy compound synthesized by a ring formation reaction is exemplified.

  In the present invention, in addition to one or more epoxy groups, at least one functional group selected from a hydroxyl group, an amide group, an imide group, a urethane group, a urea group, a sulfonyl group, a carboxyl group, an ester group, and a sulfo group. Preferably used. For example, compounds having epoxy group and hydroxyl group, compounds having epoxy group and amide group, compounds having epoxy group and imide group, compounds having epoxy group and urethane group, compounds having epoxy group and urea group, epoxy group and sulfonyl Examples thereof include compounds having a group and compounds having an epoxy group and a sulfo group.

  Examples of the compound having an amide group in addition to the epoxy group include glycidyl benzamide and an amide-modified epoxy compound. The amide-modified epoxy can be obtained by reacting an epoxy group of an epoxy compound having two or more epoxy groups with a carboxyl group of a dicarboxylic acid amide containing an aromatic ring.

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

  As a compound having a urethane group in addition to an epoxy group, the terminal hydroxyl group of polyethylene oxide monoalkyl ether is reacted with a polyvalent isocyanate containing an aromatic ring having a reaction equivalent to the amount of the hydroxyl group, and then the reaction product obtained It can be obtained by reacting an isocyanate residue with a hydroxyl group in a polyvalent epoxy compound. Here, examples of the polyvalent isocyanate used include 2,4-tolylene diisocyanate, metaphenylene diisocyanate, paraphenylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, and biphenyl-2,4,4′-triisocyanate. It is done.

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

  Examples of the compound having a sulfonyl group in addition to the epoxy group include bisphenol S-type epoxy.

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

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

  In the present invention, when the prepreg is stored for a long time, the aromatic epoxy compound (D) is a phenol novolak type epoxy compound, a cresol novolak type epoxy compound, a tetraglycidyl diaminodiphenylmethane, a bisphenol A type epoxy compound or a bisphenol F type epoxy compound. From the viewpoint of stability and adhesiveness, it is preferably a bisphenol A type epoxy compound or a bisphenol F type epoxy compound.

  Furthermore, the sizing agent used in the present invention may contain one or more components other than the aliphatic epoxy compound (C) and the aromatic epoxy compound (D). Accelerator that enhances adhesion between carbon fiber and sizing agent. Convergence or flexibility is imparted to carbon fiber coated with sizing agent to improve handling, scratch resistance and fluff resistance, and improve matrix resin impregnation. In order to improve the long-term stability of the prepreg in the present invention, compounds other than (C) and (D) can be contained. For the purpose of stabilizing the sizing agent, auxiliary components such as a dispersant and a surfactant may be added.

  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. In addition, since the surface oxygen concentration (O / C) is 0.50 or less, the decrease in the single fiber strength of the carbon fiber itself due to oxidation is suppressed, that is, the single fiber apparent stress by the fragmentation method of the single fiber composite is reduced. The number of fiber breaks at 12.2 GPa can be controlled to 1.7 pieces / mm or less.

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 into 20 mm, spread and arranged on a copper sample support base, and then AlKα ₁ and ₂ were used as X-ray sources. The inside of the chamber was measured at 1 × 10 ⁻⁸ Torr. 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 sizing agent-coated carbon fiber of the present invention is obtained by trial and error by paying attention to the points of the above preferred production method and according to the conventional means of those skilled in the art so that the fragmentation fracture behavior matches the scope of the present invention. be able to.

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

(A) X-ray photoelectron spectroscopy of sizing agent-coated carbon fiber sizing agent surface In the present invention, the peak ratio of (a) and (b) on the sizing agent-coated fiber sizing agent surface is determined by X-ray photoelectron spectroscopy. It was determined according to the following procedure. 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. As correction of the peak accompanying charging during measurement, first, the binding energy value of the main peak of C _1s was adjusted to 286.1 eV. At this time, the peak area of C _1s was obtained by drawing a straight baseline in the range of 282 to 296 eV. Further, a linear base line of 282 to 296 eV obtained by calculating the area at the C _1s peak is defined as the origin (zero point) of the photoelectron intensity, and (b) the peak of the binding energy 286.1 eV attributed to the CO component is obtained. The height (cps: photoelectron intensity per unit time) and the height (cps) of the component having a binding energy of 284.6 eV attributed to (a) CHx, C—C, C = C are obtained, and (a) / ( b) was calculated.

Incidentally, when the peak of from (a) is large _(b), when combined binding energy of the main peak of _{C 1s} to _286.1, the peak of _{C 1s} does not fall within the scope of 282～296EV. In that case, after adjusting the binding energy value of the C _1s main peak to 284.6 eV, (a) / (b) was calculated by the above method.

(B) Strand tensile strength and strand elastic modulus of carbon fiber bundle The strand tensile strength and strand elastic modulus of the carbon fiber bundle are determined according to the following procedure in accordance with the resin-impregnated strand test method of JIS-R-7608 (2004). It was. 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.

(C) Surface oxygen concentration of carbon fiber (O / C)
The surface oxygen concentration (O / C) of the carbon fiber was determined by X-ray photoelectron spectroscopy according to the following procedure. First, the carbon fiber from which the dirt adhering to the surface with a solvent is removed is cut to about 20 mm and spread on a copper sample support. Next, the sample support was set in the sample chamber, and the inside of the sample chamber was kept at 1 × 10 ⁻⁸ Torr. Subsequently, AlKα ₁ and ₂ were used as the X-ray source, and the photoelectron escape angle was 90 °. The bond energy value of the C _1s main peak (peak top) was adjusted to 286.1 eV as a peak correction value associated with charging during measurement. The C _1s peak area was determined by drawing a straight base line in the range of 282 to 296 eV. The O _1s peak area was determined by drawing a straight base line in the range of 528 to 540 eV. Here, the surface oxygen concentration is calculated as an atomic ratio by using a sensitivity correction value unique to the apparatus from the ratio of the O _1s peak area to the C _1s peak area. As the X-ray photoelectron spectroscopy apparatus, ESCA-1600 manufactured by ULVAC-PHI Co., Ltd. was used, and the sensitivity correction value unique to the apparatus was 2.33.

(D) Fragmentation method The measurement of the number of fiber breaks by the fragmentation method was performed by the following procedures (a) to (e).

(A) Preparation of resin 190 parts by mass of bisphenol A type epoxy resin compound “Epototo YD-128” (manufactured by Nippon Steel Chemical Co., Ltd.) and 20.7 parts by mass of diethylenetriamine (manufactured by Wako Pure Chemical Industries, Ltd.) The mixture was stirred with a spatula and defoamed using an automatic vacuum defoamer.

(B) Sampling of carbon fiber single fiber and fixing to mold A carbon fiber bundle having a length of about 20 cm was divided into approximately four equal parts, and single fibers were sampled in order from the four bundles. At this time, the entire bundle was sampled as evenly as possible. Next, double-sided tape was applied to both ends of the perforated mount, and the single fibers were fixed to the perforated mount in a state where a constant tension was applied to the sampled single fibers. Next, a glass plate on which a polyester film “Lumirror” (registered trademark) (manufactured by Toray Industries, Inc.) was attached was prepared, and a 2 mm thick spacer for adjusting the thickness of the test piece was fixed on the film. . A perforated mount with single fibers fixed thereon was placed on the spacer, and a glass plate on which a film was similarly attached was further set on the spacer with the surface on which the film was attached facing downward. At this time, in order to control the fiber embedding depth, a tape having a thickness of about 70 μm was attached to both ends of the film.

(C) From resin casting to curing The resin prepared in the procedure (a) was poured into the mold (the space surrounded by the spacer and the film) in the procedure (b). The mold into which the resin was poured was heated for 5 hours using an oven preliminarily heated to 50 ° C., and then cooled to a temperature of 30 ° C. at a temperature lowering rate of 2.5 ° C./min. Thereafter, the mold was removed and cut to obtain a test piece of 2 cm × 7.5 cm × 0.2 cm. At this time, the test piece was cut so that the single fiber was located within the center 0.5 cm width of the test piece width.

(D) Fiber Embedding Depth Measurement Fiber embedding depth for the test piece obtained by the procedure (c) above using a laser Raman spectrophotometer (JASCO NRS-3000) laser and a 532 nm notch filter. Measurements were made. First, a laser is applied to the surface of the single fiber, the stage height is adjusted so that the beam diameter of the laser becomes the smallest, and the height at that time is defined as A (μm). Next, a laser is applied to the surface of the test piece, the stage height is adjusted so that the beam diameter of the laser becomes the smallest, and the height at that time is defined as B (μm). The fiber embedding depth d (μm) was calculated by the following formula using the refractive index of the resin 1.732 measured using the above laser.

(E) Four-point bending test Tensile strain was applied to the test piece obtained in the above procedure (c) by four-point bending using a jig having an outer indenter interval of 50 mm and an inner indenter interval of 20 mm. Stepwise was strained every 0.1%, the specimen was observed with a polarizing microscope, and the number of breaks at the central portion 10 mm in the longitudinal direction of the specimen was measured. A value obtained by dividing the measured number of breaks by 10 was defined as the number of fiber breaks (pieces / mm). Further, the strain ε (%) was measured using a strain gauge attached at a position about 5 mm away from the center of the test piece in the width direction. The strain ε _c of the final single fiber composite is as follows in consideration of the gauge factor κ of the strain gauge, the fiber embedding depth d (μm) measured by the above procedure (d), and the residual strain of 0.14 (%). It was calculated by the following formula.

The n number in the test was 30.

(E) Single fiber elastic modulus of carbon fiber The single fiber elastic modulus of carbon fiber is calculated | required as follows based on JISR7606 (2000). That is, first, a bundle of carbon fibers of about 20 cm is divided into approximately four equal parts, and single yarns are sampled in order from the four bundles, and the whole bundle is sampled as evenly as possible. The sampled single yarn is fixed to the perforated mount using an adhesive. A base sheet on which a single yarn is fixed is attached to a tensile tester, and a tensile test is performed with a gauge length of 50 mm, a strain rate of 2 mm / min, and 20 samples. The elastic modulus is defined by the following formula.
Elastic modulus = (obtained strength) / (cross-sectional area of single fiber × obtained elongation)
The cross-sectional area of the single fiber is obtained by dividing the mass per unit length (g / m) by the density (g / m ³ ) and further dividing by the number of filaments for the fiber bundle to be measured. The density was measured by the Archimedes method using a specific gravity solution as o-dichloroethylene.

(F) Perforated plate tensile strength It was performed in accordance with ASTM D5766 (Open-hole Tensile Strength of Polymer Matrix Composite Laminates).
a. Test condition and room temperature (RTD): 69 ° F (20.6 ° C) ± 5 ° F
Low temperature condition (LTD): -75 ° F (-59.4 ° C) ± 5 ° F
b. Laminated structure 16ply (45/90 / -45 / 0) _2s
c. After cutting the molding condition prepreg to a predetermined size and laminating it so as to have the configuration of b described above, a vacuum bag is formed, and the temperature is raised to 180 ° C. at a heating rate of 1.5 ° C./min using an autoclave. And cured at a pressure of 6 atm for 2 hours to obtain a pseudo isotropic reinforcing material (carbon fiber composite material).
d. Sample size Dimensions: length 308mm x width 38.1mm x thickness 4.5mm
The materials and components used in each example and each comparative example are as follows.
-Component (C): C-1 to C-3
C-1: “Denacol (registered trademark)” EX-810 (manufactured by Nagase ChemteX Corporation)
Diglycidyl ether of ethylene glycol Epoxy equivalent: 113 g / mol, Number of epoxy groups: 2
C-2: “Denacol (registered trademark)” EX-611 (manufactured by Nagase ChemteX Corporation)
Sorbitol polyglycidyl ether epoxy equivalent: 167 g / mol, number of epoxy groups: 4
Number of hydroxyl groups: 2
C-3: “Denacol (registered trademark)” EX-521 (manufactured by Nagase ChemteX Corporation)
Polyglycerin polyglycidyl ether Epoxy equivalent: 183 g / mol, number of epoxy groups: 3 or more.
-(D) component: D-1-D-3
D-1: “jER (registered trademark)” 828 (manufactured by Mitsubishi Chemical Corporation)
Diglycidyl ether of bisphenol A Epoxy equivalent: 189 g / mol, Number of epoxy groups: 2
D-2: “jER (registered trademark)” 1001 (manufactured by Mitsubishi Chemical Corporation)
Diglycidyl ether of bisphenol A Epoxy equivalent: 475 g / mol, Number of epoxy groups: 2
D-3: “jER (registered trademark)” 807 (manufactured by Mitsubishi Chemical Corporation)
Diglycidyl ether of bisphenol F Epoxy equivalent: 167 g / mol, number of epoxy groups: 2.
-(A) component: A-1 to A-3
A-1: “Sumiepoxy (registered trademark)” ELM434 (manufactured by Sumitomo Chemical Co., Ltd.)
Tetraglycidyldiaminodiphenylmethane Epoxy equivalent: 120 g / mol
A-2: “jER (registered trademark)” 828 (manufactured by Mitsubishi Chemical Corporation)
Diglycidyl ether of bisphenol A Epoxy equivalent: 189 g / mol
A-3: GAN (manufactured by Nippon Kayaku Co., Ltd.)
N-diglycidylaniline (B) component:
“Seika Cure (registered trademark)” S (4,4′-diaminodiphenyl sulfone, manufactured by Wakayama Seika Co., Ltd.)
・ Thermoplastic resin "Sumika Excel (registered trademark)" 5003P (manufactured by Sumitomo Chemical Co., Ltd.)
Polyethersulfone.

(Examples 1-16, Comparative Examples 1-26)
In this example, the following first step: a step of producing a carbon fiber as a raw material, second step: a step of performing a surface treatment of the carbon fiber, third step: a step of attaching a sizing agent to the carbon fiber And Step IV: It consists of preparation of a prepreg.
-Step I A copolymer consisting of 99.5 mol% acrylonitrile and 0.5 mol% itaconic acid is polymerized by solution polymerization using dimethyl sulfoxide as a solvent and 2,2'-azobisisobutyronitrile as an initiator. Thus, a polyacrylonitrile copolymer having a weight average molecular weight of 700,000 and Mz / Mw of 1.8 was produced. Ammonia gas was blown into the manufactured polyacrylonitrile-based polymer until the pH reached 8.5, and the polymer concentration was adjusted to 15% by mass to obtain a spinning solution. The obtained spinning solution was discharged into the air once at 40 ° C. using a spinneret having a diameter of 0.15 mm and a hole number of 6,000, passed through a space of about 4 mm, and then controlled at 3 ° C. 35 A coagulated yarn was obtained by a dry and wet spinning method introduced into a coagulation bath comprising an aqueous solution of% dimethyl sulfoxide. The coagulated yarn was washed with water by a conventional method, and then stretched 3.5 times in two warm water baths. Subsequently, an amino-modified silicone-based silicone oil agent is applied to the fiber bundle after stretching in the water bath, a drying densification treatment is performed using a heating roller at 160 ° C., two yarns are combined, and a single fiber After the number of yarns is 12,000, the yarn is stretched 3.7 times in pressurized steam, the yarn drawing total draw ratio is 13 times, and then the entanglement process is performed to obtain a single fiber fineness of 0.7 dtex and a single fiber number of 12,000 polyacrylonitrile. A system precursor fiber was obtained. Here, the entanglement treatment means that the angle formed by the fiber bundle longitudinal direction and the fluid blowing direction is 90 °, and eight ejection holes are arranged so as to surround the fiber bundle, and each ejection hole is composed of two holes. Using fluid spray nozzles arranged at opposing positions so as to form a set, the tension of the fiber bundle was adjusted to 3 mN / dtex, and the fluid discharge pressure was set to 0.35 MPa. Next, in the air of 240-260 degreeC, it flame-proofed, extending | stretching by the draw ratio 1, and obtained the flame-resistant fiber bundle of specific gravity 1.35-1.36. The obtained flame-resistant fiber bundle was subjected to a preliminary carbonization treatment while being stretched at a stretch ratio of 1.15 in a nitrogen atmosphere at a temperature of 300 to 800 ° C. to obtain a preliminary carbonized fiber bundle. The obtained pre-carbonized fiber bundle was carbonized at a maximum temperature of 1500 ° C. and a tension of 5.5 mN / dtex in a nitrogen atmosphere. This was designated as carbon fiber A.

  A carbon fiber was obtained in the same manner as the carbon fiber A except that the entanglement treatment was not performed. This was designated as carbon fiber B.

  A carbon fiber except that a spinning solution having a weight average molecular weight of 400,000, Mz / Mw of 3.5, and a polymer concentration of 19% was obtained by adjusting the amount of initiator and the charging timing during solution polymerization. Carbon fiber was obtained in the same manner as A. This was designated as carbon fiber C.

  A carbon fiber was obtained in the same manner as the carbon fiber C except that the entanglement treatment was not performed. This was designated as carbon fiber D.

Other than that, “TORAYCA (registered trademark)” T800S-24k-10E, “TORAYCA (registered trademark)” T700S-24k-50E (manufactured by Toray Industries, Inc.), “Hexow (registered trademark)” IM-10 The analysis was also performed using (Hexcel) IM-9 (manufactured by Hexcel) and "TENAX (trademark)" IM600 (manufactured by Toho Tenax).
Step II The obtained carbon fiber was subjected to electrolytic surface treatment with an aqueous ammonium hydrogen carbonate solution 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. This surface treatment was designated as surface treatment A. At this time, the surface oxygen concentration O / C was 0.15.

  The obtained 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 charge of 500 coulomb per 1 g 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. This surface treatment was designated as surface treatment B. At this time, the surface oxygen concentration O / C was 0.22.

  The obtained carbon fiber was subjected to electrolytic surface treatment using an aqueous sulfuric acid solution having a concentration of 0.1 mol / l as an electrolytic solution and an electric quantity of 80 coulomb per 1 g 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. This surface treatment was designated as surface treatment C. At this time, the surface oxygen concentration O / C was 0.20.

  The obtained carbon fiber was subjected to electrolytic surface treatment with an aqueous solution of nitric acid having a concentration of 0.1 mol / l as an electrolyte and an electric quantity of 80 coulomb per 1 g 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. This surface treatment was designated as surface treatment D. At this time, the surface oxygen concentration O / C was 0.14.

When the obtained carbon fiber is not surface-treated, it is referred to as surface treatment E for convenience. At this time, the surface oxygen concentration O / C was 0.02.
-Step III (D) 10 parts by weight of D-1 and 10 parts by weight of D-2 as components, 2 moles of EO2 mole adduct of bisphenol A, 1.5 moles of maleic acid, 0.5 moles of sebacic acid After preparing an aqueous dispersion emulsion comprising 20 parts by mass of the condensate and 10 parts by mass of polyoxyethylene (70 mol) styrenated (5 mol) cumylphenol as an emulsifier, 50 parts by mass of C-3 as component (C) Partially mixed to prepare a sizing solution. After this sizing agent was applied to the carbon fiber surface-treated by the dipping method, heat treatment was performed at a temperature of 210 ° C. for 75 seconds to obtain a sizing agent-coated carbon fiber bundle. The adhesion amount of the sizing agent was adjusted to be 1.0 part by mass with respect to 100 parts by mass of the surface-treated carbon fiber. This was designated as sizing agent A. Component of binding energy (284.6 eV) attributed to (a) CHx, C—C, C = C of C _1s inner shell spectrum measured by X-ray photoelectron spectroscopy on the sizing agent surface at a photoelectron escape angle of 15 ° The ratio (a) / (b) between the height (cps) of (b) and the height (cps) of the component of the binding energy (286.1 eV) attributed to C—O was 0.67.

  It was performed in the same manner as the sizing agent A, except that the amount of the sizing agent adhered was adjusted to 0.2 parts by mass with respect to 100 parts by mass of the surface-treated carbon fiber. This was designated as sizing agent B. The ratio (a) / (b) was 0.67.

  The sizing agent was deposited in the same manner as the sizing agent A, except that the amount of sizing agent was adjusted to 2.0 parts by mass with respect to 100 parts by mass of the surface-treated carbon fiber. This was designated as Sizing Agent C. The ratio (a) / (b) was 0.67.

  For the sake of convenience, the one without the sizing agent applied is referred to as sizing agent D.

  D-1 and D-2 components, bisphenol A EO 2 mol adduct 2 mol, maleic acid 1.5 mol, sebacic acid 0.5 mol condensate, C-3 component 10: 10: 20: 50 to 22 .5: 22.5: Performed in the same manner as Sizing Agent A except that the ratio was changed to 45: 0. This was designated as Sizing Agent E. The ratio (a) / (b) was 0.99.

  D-1 component, D-2 component, 2 mol of EO2 mol adduct of bisphenol A, 1.5 mol of maleic acid, 0.5 mol of sebacic acid, condensate C-1, component C-3, and emulsifier 10 : 10: 20: 0: 50: 10 to 0: 0: 0: 50: 50: 0. This was designated as Sizing Agent F. The ratio (a) / (b) was 0.26.

  It carried out similarly to sizing agent A except having changed D-2 component into D-3 component. This was designated as sizing agent G. The ratio (a) / (b) was 0.63.

  D-1 component, D-2 component, bisphenol A EO 2 mol adduct 2 mol, maleic acid 1.5 mol, sebacic acid 0.5 mol condensate, C-1 component, C-3 component, emulsifier 0 : 0: 0: 50: 50: 0 Performed in the same manner as the sizing agent E except that it was changed from 20: 0: 20: 25: 25: 10. This was designated as sizing agent H. The ratio (a) / (b) was 0.60.

  The procedure was the same as that for the sizing agent H except that the C-1 component was changed to the C-2 component. This was designated as Sizing Agent I. The ratio (a) / (b) was 0.62.

Subsequently, a strand strength test and a single fiber elastic modulus test of sizing agent-coated carbon fibers were performed. In addition, as an accelerated test assuming use conditions, the sizing agent-coated carbon fiber was stored at a temperature of 70 ° C. and a humidity of 95% for 3 days, and then a sizing agent-coated carbon fiber fragmentation test was performed. The results are summarized in Table 1.
-Step IV In the kneading apparatus, as component (A), 35 parts by mass of (A-1), 35 parts by mass of (A-2), 30 parts by mass of (A-3), and 14 parts by mass of Sumika After mixing and dissolving Excel 5003P, 40 parts by mass of 4,4′-diaminodiphenyl sulfone as component (B) was kneaded to prepare an epoxy resin composition for a carbon fiber reinforced composite material. This was designated as Resin Composition A.

  A resin composition was obtained in the same manner as the resin composition A, except that the amount of Sumika Excel 5003P was changed from 10 parts by mass to 5 parts by mass. This was designated as Resin Composition B.

  (A-1): (A-2): (A-3): (B) = 50: 50: 0: A resin composition was obtained in the same manner as the resin composition A except that the composition ratio was changed. . This was designated as Resin Composition C.

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. Assuming actual use conditions, the prepreg was stored at a temperature of 25 ° C. and a humidity of 60% for 20 days, and then the composite material was molded and subjected to an OHT test. The results are shown in Table 2.

  In Steps I to III, the evaluation results of the sizing agent-coated carbon fibers produced in combination as shown in Table 1 are shown in Table 1, Example 1 (Carbon fiber A), Comparative Example 2 (Carbon fiber C), and Comparative Example 3. FIG. 2 shows the fragmentation test results of (Carbon fiber D). Table 2 shows the evaluation results of the prepregs produced by combining the sizing agent-coated carbon fibers shown in Table 1 and the matrix resin. Judging from Tables 1 and 2, the higher the strand strength, the smaller the number of fiber breaks when the single fiber apparent stress is 6.8 GPa, and the lower the number of fiber breaks when the single fiber apparent stress is 12.2 GPa, the lower the temperature. It was found that the OHT in the test tended to be high. “Hexply (registered trademark)” IM-10 / M91 having the largest catalog value of OHT (room temperature conditions) among commercially available prepregs is about 600 MPa (= 88 ksi), and is used in “ Considering from the result of fragmentation test of Hexto (registered trademark) “IM-10”, it is a reasonable OHT.

1: Fiber bundle 2: Fixed point A
3: Fixed point B
4: Fixed point C
5: Entanglement point 6: Tearable distance

  When the prepreg of the present invention is used, the carbon fiber composite material obtained by curing it has high physical properties such as tensile elastic modulus and perforated plate tensile strength. Therefore, it can greatly contribute to the weight reduction of the aircraft and improve the fuel consumption rate of the aircraft.

The present invention has the following configuration. That is, it is a prepreg containing the sizing agent-coated carbon fiber (I) and the thermosetting resin (II) shown below.
(I) A sizing agent-coated carbon fiber in which a sizing agent is applied to carbon fiber, and the number of fiber breaks is 2.0 when the single fiber apparent stress is 15.3 GPa according to the fragmentation method of the single fiber composite of carbon fiber. Sizing agent-coated carbon fiber having a fiber breakage number of 1.7 pieces / mm or less when the single fiber apparent stress is 12.2 GPa,
(II) A thermosetting resin containing an epoxy compound (A) and an aromatic amine curing agent (B).

Claims (5)

A prepreg containing carbon fiber (I) and thermosetting resin (II) shown below.
(I) When the single fiber apparent stress is 15.3 GPa by the fragmentation method of the single fiber composite, the number of fiber breaks is 2.0 pieces / mm or more, and the fiber when the single fiber apparent stress is 12.2 GPa. Thermosetting resin containing carbon fiber (II) epoxy compound (A) and aromatic amine curing agent (B) having a number of breaks of 1.7 pieces / mm or less A sizing agent-coated carbon fiber obtained by coating a carbon fiber with a sizing agent containing an aliphatic epoxy compound (C) and an aromatic epoxy compound (D), wherein the carbon fiber is a single fiber appearance by a fragmentation method of a single fiber composite. A sizing in which the number of fiber breaks is 2.0 pieces / mm or more when the stress is 15.3 GPa and the number of fiber breaks is 1.7 pieces / mm or less when the single fiber apparent stress is 12.2 GPa. Agent coated carbon fiber. The binding energy attributed to (a) CHx, C—C, C = C of the C _1s inner shell spectrum measured on the surface of the sizing agent applied to the carbon fiber at a photoelectron escape angle of 15 ° by X-ray photoelectron spectroscopy. Ratio (a) / (b) between the height (cps) of the component (284.6 eV) and the height (cps) of the component (286.1 eV) attributed to C—O (b) Sizing agent application | coating carbon fiber of Claim 2 whose is 0.50-0.90. Sizing agent application | coating carbon fiber of Claim 3 whose average tearable distance is 300 mm-710 mm, and is substantially untwisted. A prepreg comprising a sizing agent-coated carbon fiber according to any one of claims 2 to 4, and a thermosetting resin (II) containing an epoxy compound (A) and an aromatic amine curing agent (B).

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