Sizing agent-coated carbon fiber bundle and method for producing same

Abstract

To provide a sizing agent-coated carbon fiber bundle that ensures proper resin impregnation in an aqueous slurry impregnation process and keeps its moldability or processability not impaired when processed into a prepreg.SOLUTION: A sizing agent-coated carbon fiber bundle is coated with at least a water-soluble compound (A) having an amino group and / or a compound (B) having a polyalkylene glycol. As measured by X-ray photoelectron spectroscopy (XPS), its surface oxygen level (O / C) is 0.28 or more and 0.45 or less and surface nitrogen level (N / C) is 0.05 or more and 0.20 or less. The sizing agent-coated carbon fiber bundle satisfies the following (i) and (ii): (i) after water washing for 50 seconds, the surface oxygen level (O / C) is 0.15 or more and 0.25 or less and the surface nitrogen level (N / C) is 0.15 or more and 0.30 or less; and (ii) the number of adhesion sites is 20 or less as evaluated by a water dispersion.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a sizing-agent-coated carbon fiber bundle that has high adhesion to thermoplastic resins represented by polyphenylene sulfide, polyaryl ether ketone, polyether sulfone, polyamide imide, and the like, is excellent in resin impregnation in an aqueous slurry impregnation process, and is unlikely to impair moldability or processability when processed into a prepreg, and a method for producing the same. [Background technology]

[0002] Carbon fibers are lightweight yet have excellent strength and elastic modulus, and therefore are used as composite materials in combination with various matrix resins in many fields such as aircraft parts, spacecraft parts, automobile parts, ship parts, civil engineering and construction materials, and sporting goods. Although the properties required for carbon fiber reinforced composite materials vary somewhat depending on the application, adhesion at the interface between the carbon fiber and the matrix resin is one of the most important basic properties, and much research and technological development has been carried out on the surface treatment of carbon fibers.

[0003] Conventionally, thermosetting resins such as epoxy resins have been widely used as matrix resins in carbon fiber composite materials. However, the molding and processing of carbon fiber reinforced composite materials using thermosetting resins as matrix resins has some problems in terms of molding and processing costs, such as the need for large equipment such as autoclaves and the need for a relatively long time to control the curing reaction. In recent years, attention has been paid to carbon fiber reinforced composite materials using thermoplastic resins as matrix resins, which can significantly reduce the molding and processing time because they do not require a curing reaction and do not necessarily require large equipment such as autoclaves.

[0004] For the above reasons, conventional technology development for surface treatment of carbon fiber has been mainly conducted for thermosetting resins. For example, in the case of epoxy resin, there are many reactive functional groups such as hydroxyl groups generated during the curing reaction, polar groups such as amines, which are curing agents, and glycidyl groups, so surface treatment of carbon fiber has often been carried out with consideration for the bonds and interactions with these. In contrast, thermoplastic resins differ greatly from thermosetting resins in terms of the types and amounts of functional groups present, and the temperature range during molding, so surface design tailored to thermoplastic resins is important.

[0005] As a surface treatment for thermoplastic resins, for example, Patent Document 1 proposes a method of improving adhesion to thermoplastic resins with few functional groups by applying polyethyleneimine as a sizing agent to carbon fiber bundles. Patent Document 2 proposes a method of applying a sizing agent in which polyethyleneimine is mixed with modified polyethylene glycol in order to improve adhesion to thermoplastic resins and further improve processability in advanced processing of carbon fiber bundles. Furthermore, Patent Documents 3 and 4 propose conditions for optimizing the openability of carbon fiber bundles in various advanced processing processes.

[0006] Now, in order to composite a thermoplastic resin with carbon fiber, a method different from that used for a thermosetting resin, which often has low viscosity and good handling in an uncured state, is used. For example, various processes are performed according to the type and purpose of the thermoplastic resin to be combined with the carbon fiber, such as a melt impregnation method in which the carbon fiber is impregnated with a molten thermosetting resin, a solution impregnation method in which the thermoplastic resin is impregnated with a solution in which the thermoplastic resin is dissolved in a solvent and the solvent is removed, and a slurry impregnation method in which the carbon fiber is impregnated by passing a slurry consisting of fine particles of the thermoplastic resin. Among these, the aqueous slurry impregnation method using water as a dispersion medium is superior in terms of economy, etc. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2013-166924 A [Patent Document 2] JP 2019-065441 A [Patent Document 3] JP 2019-210587 A [Patent Document 4] JP 2019-210586 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the above-mentioned conventional techniques have the following problems.

[0009] In Patent Document 1, polyethyleneimine is used as a sizing agent to improve adhesion to polypropylene, which is a matrix resin, but the focus is mainly on the melt impregnation process, and its suitability for an aqueous slurry impregnation process is unclear.

[0010] Patent Document 2 describes the idea of ​​combining polyethyleneimine with modified polyethylene glycol to achieve both adhesion to thermoplastic resins and processability in advanced processing, but its suitability for aqueous slurry impregnation processes is unclear.

[0011] Patent Documents 3 and 4 each have the idea of ​​optimizing mechanical openability and air openability, which are important for uniform impregnation, but it is not clear whether they are suitable for an aqueous slurry impregnation process.

[0012] Thus, in order to achieve both improved adhesion to thermoplastic resins and processability and fiber-spreading properties in specific advanced processing processes, a technique of using polyethyleneimine in combination with modified polyethylene glycol has been proposed; however, no attention has been paid to the aqueous slurry impregnation process, and there has been no suggestion regarding a sizing agent-coated carbon fiber bundle suitable for this specific process.

[0013] Therefore, an object of the present invention is to provide a sizing-agent-coated carbon fiber bundle that has a sizing agent coated thereon that has high adhesion to thermoplastic resins, excellent resin impregnation properties in an aqueous slurry impregnation process, and is unlikely to impair moldability or processability when processed into a prepreg, and a method for producing the same. [Means for solving the problem]

[0014] The present invention, which solves the above-mentioned problems, provides a sizing-agent-coated carbon fiber bundle that is coated with at least a water-soluble compound (A) having an amino group and / or a compound (B) containing a polyalkylene glycol, the sizing-agent-coated carbon fiber bundle having a surface oxygen concentration (O / C) of 0.28 or more and 0.45 or less and a surface nitrogen concentration (N / C) of 0.05 or more and 0.20 or less, both of which are measured by X-ray photoelectron spectroscopy (XPS), and which satisfies the following (i) and (ii): (i) After rinsing for 50 seconds with the water rinsing method described below, the surface oxygen concentration (O / C) is 0.15 or more and 0.25 or less, and the surface nitrogen concentration (N / C) is 0.15 or more and 0.30 or less. (ii) The number of adhesions evaluated by the water dispersion test described below is 20 or less.

[0015] The method for producing a sizing-agent-coated carbon fiber bundle of the present invention is characterized in that it includes a drying step of drying the carbon fiber bundle at 180 to 240°C after the step of applying the sizing agent to the carbon fiber bundle. Effect of the Invention

[0016] According to the present invention, it is possible to provide a sizing-agent-coated carbon fiber bundle that has been coated with a sizing agent that has high adhesion to thermoplastic resins typified by polyphenylene sulfide, polyaryl ether ketone, polyether sulfone, polyamide imide, and the like, is excellent in resin impregnation in an aqueous slurry impregnation process, and is unlikely to impair moldability or processability when processed into a prepreg. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a diagram showing a method for evaluating 50-second water washing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described.

[0019] The sizing-agent-coated carbon fiber bundle of the present invention is a sizing-agent-coated carbon fiber bundle that is coated with at least a water-soluble compound (A) having an amino group and / or a compound (B) containing a polyalkylene glycol, and has a surface oxygen concentration (O / C) of 0.28 or more and 0.45 or less and a surface nitrogen concentration (N / C) of 0.05 or more and 0.20 or less, both of which are measured by X-ray photoelectron spectroscopy (XPS), and satisfies the following (i) and (ii): (i) After rinsing for 50 seconds with the water rinsing method described below, the surface oxygen concentration (O / C) is 0.15 or more and 0.25 or less, and the surface nitrogen concentration (N / C) is 0.15 or more and 0.30 or less. (ii) The number of adhesions evaluated by the water dispersion test described below is 20 or less.

[0020] In the following, the surface oxygen concentration (O / C) may be simply referred to as O / C, and the surface nitrogen concentration may be simply referred to as N / C. A water-soluble compound having at least an amino group may be simply referred to as a water-soluble compound (A) having an amino group or as compound (A). Furthermore, a compound (B) containing a polyalkylene glycol may be simply referred to as compound (B).

[0021] The inventors' investigations revealed that when a sizing agent containing a water-soluble compound (A) having an amino group and / or a compound (B) containing a polyalkylene glycol is used for a carbon fiber bundle, the resin impregnation in the aqueous slurry impregnation process is likely to decrease, and the sizing agent remaining on the carbon fiber surface during prepreg production is likely to decompose thermally, resulting in a decrease in mechanical properties. In response to this problem, the inventors discovered that a sizing-agent-coated carbon fiber bundle that has high adhesion to thermoplastic resins, excellent resin impregnation in the aqueous slurry impregnation process, and is unlikely to impair moldability or processability when processed into a prepreg can be obtained by controlling the O / C and N / C of the carbon fiber bundle and the O / C and N / C after washing the carbon fiber bundle with water under specific conditions, and controlling the number of adhesions evaluated by an aqueous dispersion test to a certain value or less.

[0022] In the present invention, the sizing agent refers to a compound applied to the surface of the carbon fiber bundle in order to increase adhesion to the resin or improve the handleability of the carbon fiber bundle. In the present invention, the sizing agent is required to contain at least a water-soluble compound (A) having an amino group and / or a compound (B) containing a polyalkylene glycol, and a sizing agent other than the compound (A) and the compound (B) may also be contained.

[0023] The sizing-agent-coated carbon fiber bundle constituting the present invention must contain at least a water-soluble compound (A) having an amino group and / or a compound (B) containing polyalkylene glycol, and the sizing-agent-coated carbon fiber bundle coated with the sizing agent must satisfy specific conditions. In the present invention, either the water-soluble compound (A) having at least an amino group or the compound (B) containing polyalkylene glycol may be used, or both the water-soluble compound (A) having at least an amino group and the compound (B) containing polyalkylene glycol may be used.

[0024] Carbon fiber bundles coated with a sizing agent containing a water-soluble compound (A) having an amino group tend to exhibit excellent adhesion to thermoplastic resins. As a result, the mechanical properties of thermoplastic resin molded products using carbon fiber bundles coated with the sizing agent are often improved. Although the mechanism is not clear, it is believed that the amino group has high polarity and exhibits excellent adhesion by forming strong interactions such as hydrogen bonds with highly polar oxygen-containing structures such as carboxyl groups and hydroxyl groups on the carbon fiber bundle surface and in the resin.

[0025] Polyalkylene glycol is a compound in which multiple alkylene glycols are polymerized, and is a compound represented by the general formula HO-(CnHmO)sH, or the formula R1-O-(CnHmO)sH, or the formula R2-O-(CnHmO)s-R3 (wherein R1, R2, and R3 represent substituents having one or more carbon atoms). Compounds containing polyalkylene glycol exhibit appropriate lubricity, and carbon fiber bundles coated with a compound containing polyalkylene glycol have excellent handleability and can suppress the generation of fluff in the process of processing into a prepreg.

[0026] Whether or not a sizing agent-coated carbon fiber bundle contains a water-soluble compound having an amino group or a compound containing polyalkylene glycol can be determined by evaluating the sizing agent-coated carbon fiber bundle itself, or by extracting and evaluating the sizing agent from the sizing agent-coated carbon fiber bundle. For example, there is a method of measuring the sizing agent-coated carbon fiber bundle with time-of-flight secondary ion mass spectrometry (TOF-SIMS) to detect characteristic fragment ion species and identify the compound, or a method of combining structural evaluation from IR spectrum obtained by infrared spectroscopy after freeze-drying the sizing agent extracted with water, and proton NMR, carbon NMR, and mass spectrometry evaluation of the freeze-dried solid to identify the compound.

[0027] Furthermore, the sizing-agent-coated carbon fiber bundle of the present invention must have a surface oxygen concentration (O / C) of 0.28 to 0.45 and a surface nitrogen concentration (N / C) of 0.05 to 0.20, as measured by X-ray photoelectron spectroscopy (XPS). The sizing-agent-coated carbon fiber bundle with an O / C of 0.28 to 0.45 and an N / C of 0.05 to 0.20 can achieve high levels of both high handleability and high adhesion to the matrix resin. When the O / C is less than 0.28, the amount of the compound containing polyalkylene glycol applied to the carbon fiber bundle is small, and the handleability is reduced. When the O / C is greater than 0.45, the amount of the compound containing polyalkylene glycol becomes excessive, which tends to stabilize the properties such as thermal stability of the resulting thermoplastic resin molded body. When the N / C is less than 0.05, the water-soluble compound having an amino group is not sufficiently applied, and sufficient adhesion cannot be obtained. In addition, when N / C is larger than 0.20, the water-soluble compound having an amino group is present in a large amount on the outermost surface of the carbon fiber bundle, which deteriorates the handleability. It is preferable that O / C is 0.30 or more and 0.45 or less and N / C is 0.06 or more and 0.18 or less, and it is more preferable that O / C is 0.32 or more and 0.45 or less and N / C is 0.07 or more and 0.15 or less.

[0028] In addition, the sizing agent-coated carbon fiber bundle of the present invention must have an O / C of 0.15 to 0.25 and an N / C of 0.15 to 0.30 after the carbon fiber bundle is washed with water by the method described in the Examples. The fact that the O / C after washing with water under specific conditions is lower than that before washing with water indicates that compounds containing polyalkylene glycol have been removed by washing with water, and by controlling the O / C to 0.15 to 0.25 or less, it is possible to suppress a decrease in the thermal stability of the resin. In addition, the fact that the N / C after washing with water under specific conditions is higher than that before washing with water indicates that a water-soluble compound having an amino group is present on the outermost surface of the carbon fiber after washing with water, and by controlling the N / C to 0.15 to 0.30 or less, high adhesion can be obtained even after passing through an aqueous slurry impregnation process. After washing with water, O / C is preferably 0.16 to 0.23 and N / C is preferably 0.17 to 0.28, and more preferably O / C is 0.17 to 0.21 and N / C is preferably 0.19 to 0.26.

[0029] Furthermore, the sizing agent-coated carbon fiber bundle constituting the present invention preferably has an O / C of 0.15 to 0.25 and an N / C of 0.10 to 0.25 after heating in air at 300°C for 5 minutes. In the molding process of highly heat-resistant thermoplastic prepregs represented by polyphenylene sulfide, polyaryl ether ketone, polyether sulfone, polyamide imide, etc., it is common to heat and mold at 320°C or higher in order to allow the thermoplastic resin to fully penetrate into the fiber bundle and improve impregnation. In the process of molding such prepregs, a part of the sizing agent is decomposed by heating at a high temperature, generating decomposition products. In particular, the generation of decomposition products of the sizing agent at a high temperature of 320°C or higher, which is the same as the molding temperature, may affect the properties such as the thermal stability of the molded product. For this reason, the sizing agent is decomposed and removed at a temperature lower than the molding temperature, and the properties such as the thermal stability of the obtained thermoplastic resin molded product can be stabilized. Here, the fact that the O / C after heating at 300°C for 5 minutes is lower than that before the heat treatment indicates that the compound containing polyalkylene glycol is decomposed and removed during the heat treatment, and the decrease in the thermal stability of the resin can be suppressed by controlling the O / C after the heat treatment to be 0.15 to 0.25. In addition, the fact that the N / C after heating at 300°C for 5 minutes is higher than that before the heat treatment indicates that a water-soluble compound having an amino group is present on the outermost surface of the carbon fiber after the heat treatment, and high adhesion to the matrix resin can be obtained even at high molding temperatures by controlling the N / C to be 0.10 to 0.25. In air, the O / C after heating at 300°C for 5 minutes is preferably 0.16 to 0.24 and the N / C to be 0.11 to 0.24, and more preferably the O / C to be 0.17 to 0.23 and the N / C to be 0.12 to 0.23.

[0030] The O / C and N / C of the carbon fiber bundle can be determined by X-ray photoelectron spectroscopy according to the following procedure. First, the carbon fiber bundle from which dirt and the like adhering to the surface of the carbon fiber bundle has been removed is cut to 20 mm, spread and arranged on a copper sample support, and then AlKα1, 2 is used as the X-ray source, and the inside of the sample chamber is kept at 1×10-8 Torr. The binding energy value of the main peak (peak top) of C1s is adjusted to 284.6 eV as a correction value for the peak associated with charging during measurement. The C1s peak area is determined by drawing a straight baseline in the range of 282 to 296 eV. The O1s peak area is determined by drawing a straight baseline in the range of 528 to 540 eV, and the N1s peak area is determined by drawing a straight baseline in the range of 391 to 411 eV. Here, the surface oxygen concentration and the surface nitrogen concentration can be calculated as the atomic ratio from the ratio of the above-mentioned O1s or N1s peak area to the C1s peak area using the sensitivity correction value specific to the device.

[0031] In the present invention, the number of adhesions must be 20 or less, preferably 15 or less, and more preferably 12 or less. In the present invention, adhesion refers to a portion where the single fibers constituting the carbon fiber bundle are locally adhered to each other, and is evaluated by the water dispersion test described later. As a result of the investigation by the present inventors, it was found that the smaller the number of adhesions, the easier it is to improve the resin impregnation in the water-based slurry impregnation process described later, and the easier it is to obtain a high-quality prepreg. If the number of adhesions is 20 or less, the resin impregnation is likely to be high. The number of adhesions can be controlled by the composition of the sizing agent, the heat treatment temperature after application of the sizing agent, and the like.

[0032] The sizing agent-coated carbon fiber bundle constituting the present invention preferably has an absorbance of 0.01 or less at 600 nm and 0.10 or less at 300 nm of the sizing agent-coated carbon fiber bundle extract measured by the method described in the Examples. The absorbance at 600 nm represents the amount of elution of brittle oxides attached to the fiber surface caused by the oxidation treatment of the carbon fiber, and the absorbance at 300 nm represents the amount of elution of the sizing agent applied to the surface. By making the absorbance at 600 nm 0.01 or less, the sizing agent reacts sufficiently with the surface of the carbon fiber, and high adhesion to the matrix resin is obtained. In addition, by making the absorbance at 300 nm 0.10 or less, the adhesion of excess sizing agent is eliminated, and the properties such as thermal stability of the obtained thermoplastic resin molded body are easily stabilized. The absorbance at 600 nm is more preferably 0.008 or less, and even more preferably 0.006 or less. Furthermore, the absorbance at 300 nm is more preferably 0.08 or less, and even more preferably 0.06 or less.

[0033] The amount of the sizing agent in the sizing-coated carbon fiber bundle constituting the present invention is preferably 0.10% by mass or more and 0.50% by mass or less in 100% by mass of the sizing-coated carbon fiber bundle. In the present invention, the amount of the sizing agent is evaluated by the method described below. If the amount of the sizing agent is 0.10% by mass or more, the sizing agent uniformly attached to the surface can improve the abrasion resistance of the carbon fiber bundle, suppress the generation of fluff during production and processing, and improve the quality of the carbon fiber sheet with good fiber opening, such as smoothness. From the viewpoint of increasing the IFSS, that is, the adhesion to the thermoplastic resin, the amount of the sizing agent is more preferably 0.15% by mass or more, and even more preferably 0.20% by mass or more. On the other hand, if the amount of the sizing agent is 0.50% by mass or less, it is easy to stabilize the properties such as thermal stability in the obtained thermoplastic resin molded body. The amount of the sizing agent is more preferably 0.45% by mass or less, and even more preferably 0.40% by mass or less. The amount of the sizing agent can be controlled by the concentration of the sizing agent solution, etc.

[0034] The mass W of the water-soluble compound (A) having an amino group used in the present invention Aand the mass W of the compound (B) containing polyalkylene glycol B It is preferable that satisfies formula (a). 0.20≦W A / (W A +W B )≦0.50...Equation (a).

[0035] W A / (W A +W B When the ratio W satisfies the formula (a), the adhesiveness can be increased, and the properties such as the thermal stability of the resin can be easily stabilized when the resin is processed into a prepreg. A / (W A +W B If W is less than 0.20, the amount of water-soluble compound (A) having an amino group will be so small that sufficient adhesiveness may not be obtained. A / (W A +W B If the W is greater than 0.50, the adhesiveness is high, but the thermal stability of the resin when processed into a prepreg may decrease, resulting in a decrease in mechanical properties. A / (W A +W B ) is more preferably 0.25 or more and 0.45 or less, and further preferably 0.30 or more and 0.40 or less.

[0036] Specific examples of the water-soluble compound (A) having an amino group used in the present invention include aliphatic amine compounds, aromatic amine compounds, etc. Among them, aliphatic amine compounds are preferred from the viewpoint of showing high adhesion. The reason why aliphatic amine compounds have high adhesion is considered to be that they have a very high polarity compared to other compounds having an amino group.

[0037] Specific examples of the aliphatic amine compounds include polyalkyleneamines such as diethylenetriamine, triethylenetetramine, dicyandiamide, tetraethylenepentamine, dipropylenediamine, piperidine, N,N-dimethylpiperazine, triethylenediamine, polyamidoamine, polyethyleneimine, polypropyleneimine, polybutyleneimine, 1,1-dimethyl-2-methylethyleneimine, 1,1-dimethyl-2-propylethyleneimine, N-acetylpolyethyleneimine, N-propionylpolyethyleneimine, N-butyrylpolyethyleneimine, N-parylylpolyethyleneimine, N-hexanoylpolyethyleneimine, and N-stearoylpolyethyleneimine, as well as derivatives thereof and mixtures thereof.

[0038] Among aliphatic amine compounds, compounds having 3 or more functional groups in one molecule are preferably used because they tend to have high adhesiveness. In particular, polyalkyleneimines are preferably used because they tend to increase the amount of functional groups in one molecule and improve adhesiveness. The reason why compounds having 3 or more functional groups in one molecule tend to have high adhesiveness is thought to be that the polarity of the molecule tends to increase as the amount of functional groups increases.

[0039] Specific examples of the aromatic amine compounds include 1,2-phenylenediamine, 1,3-phenylenediamine, 1,4-phenylenediamine, benzidine, triaminophenol, triglycidylaminocresol, 2,4,6-triaminophenol, 1,2,3-triaminopropane, 1,2,3-triaminobenzene, 1,2,4-triaminobenzene, 1,3,5-triaminobenzene, derivatives thereof, and mixtures thereof.

[0040] The weight average molecular weight Mw of the compound (A) is preferably 2,500 or less. The weight average molecular weight Mw is measured by gel permeation chromatography (GPC) and is obtained using pullulan as a standard substance. The larger the Mw, the higher the viscosity of the sizing agent, so that a large force may be required to separate the carbon fibers that are adhered to each other via the sizing agent. By setting the Mw to 2,500 or less, the viscosity, which is an index of the ease of movement of the sizing agent, is reduced, and the force that binds the carbon fibers to each other is weakened, which makes it easier to improve the openability of the carbon fiber bundle. The Mw of the compound (A) is more preferably 2,000 or less, and even more preferably 1,500 or less. On the other hand, in terms of decomposition, the larger the Mw, the easier it is to control the volatilization and decomposition of the sizing agent at high temperatures. The Mw of the compound (A) is preferably 500 or more, and more preferably 650 or more.

[0041] The weight average molecular weight Mw of the compound (B) containing the polyalkylene glycol is preferably 500 to 1000, and the SP value is preferably 21 or more. When Mw is less than 500, the sizing agent is easily decomposed by heat during the drying process after application, which may make it difficult to stably apply it to carbon fibers. When Mw is greater than 1000, the sizing agent has high heat resistance and is less likely to decompose during the processing process of the prepreg, which may affect the properties of the obtained thermoplastic resin molded body, such as thermal stability. When the SP value is 21 or more, adhesion is easily suppressed, and the impregnation of the resin can be improved. Here, the SP value is a commonly known solubility parameter, and is widely used as an index of solubility and polarity. The SP value specified in the present invention is a value calculated from the molecular structure based on the Fedors method described in Polym. Eng. Sci., 14(2), 147-154 (1974). The SP value is more preferably 21.5 or more, and even more preferably 22 or more. There is no specific upper limit for the SP value, but in reality, a value of around 30 is considered a guideline.

[0042] The compound (B) containing the polyalkylene glycol is preferably a derivative of polypropylene glycol having no aromatic ring. Compounds having aromatic rings have high heat resistance and are less likely to decompose during the processing step of the prepreg, which may affect the properties of the obtained thermoplastic resin molded body, such as thermal stability. Since derivatives of polypropylene glycol have high thermal decomposition properties, it is possible to achieve both coating stability in the sizing coating step and removability during the processing step of the prepreg by adjusting the molecular weight. In the present invention, the derivative of polypropylene glycol is a general term for compounds in which a part of the structure of polypropylene glycol is replaced with another substituent or structure.

[0043] The number of terminals of the polyalkylene glycol-containing compound (B) is preferably 3 or more and 5 or less. When the number of terminals is 3 or more, adhesion can be effectively suppressed and resin impregnation can be improved. On the other hand, when the number of terminals is greater than 5, the heat resistance of the sizing agent is increased, making it difficult to decompose during the processing step of the prepreg, which may affect the properties such as the thermal stability of the obtained thermoplastic resin molded product.

[0044] Specific examples of the compound (B) containing polyalkylene glycol used in the present invention include polyethylene glycol, polypropylene glycol, polybutylene glycol, and copolymers thereof and derivatives thereof. Specific examples include polyethylene glycol derivatives such as polyethylene glycol fatty acid esters (C4 to C18), polyoxyethylene monoalkyl ethers (C4 to C18), polyoxyethylene dialkyl ethers (C4 to C18), bisphenol A ethylene oxide adducts, ethylenediamine polyoxyethylene adducts, triethanolamine polyoxyethylene adducts, aromatic diamine polyoxyethylene adducts, sucrose polyoxyethylene adducts, sorbitol polyoxyethylene adducts, sucrose polyoxyethylene adducts, trimethylolpropane polyoxyethylene adducts, pentaerythritol polyoxyethylene adducts, polyoxyethylene triol, glycerin polyoxyethylene adducts, diglycerin polyoxyethylene adducts, polyglycerin polyoxyethylene adducts, and diethylenetriamine polyoxyethylene adducts; polypropylene glycol derivatives such as polyoxyethylene triol, polyoxyethylene triol, polyoxyethylene triglycerides ... Ethylene glycol fatty acid esters (C4-C18), polyoxypropylene monoalkyl ethers (C4-C18), polyoxypropylene dialkyl ethers (C4-C18), bisphenol A propylene oxide adducts, ethylenediamine polyoxypropylene adducts, triethanolamine polyoxypropylene adducts, aromatic diamine polyoxypropylene adducts, sucrose polyoxypropylene adducts, sorbitol polyoxypropylene adducts, sucrose polyoxypropylene adducts, trimethylolpropane polyoxypropylene adducts , pentaerythritol polyoxypropylene adducts, polyoxypropylene triols, glycerin polyoxypropylene adducts, diglycerin polyoxypropylene adducts, polyglycerin polyoxypropylene adducts, polypropylene glycol derivatives such as diethylenetriamine polyoxypropylene, ethylenediamine polyether polyols, triethanolamine polyether polyols, aromatic diamine polyether polyols, sucrose polyether polyols, sorbitol polyether polyols, sucrose polyether polyols,Examples of the copolymer include derivatives of polyethylene glycol / polypropylene glycol copolymers such as trimethylolpropane polyether polyol, pentaerythritol polyether polyol, glycerin polyether polyol, diglycerin polyether polyol, polyglycerin polyether polyol, diethylenetriamine polyether polyol, and mixtures thereof.

[0045] The sizing agent in the sizing-agent-coated carbon fiber bundle constituting the present invention may contain a third component within a range that does not impair the effects of the present invention. For example, by adding a smoothing agent such as a nonionic surfactant, the wet FF friction coefficient of the surface layer of the single yarn in the carbon fiber bundle can be reduced, and the resin impregnation can be improved. The wet FF friction coefficient is the friction coefficient when sizing-agent-coated carbon fiber bundles are rubbed against each other in the longitudinal direction in a water-wet state, and can be determined by the method described in the examples. If the wet FF friction coefficient is 0.45 or less, the resin impregnation is likely to be high, and if it is 0.38 or less, the resin impregnation is likely to be even higher.

[0046] When a nonionic surfactant is added as the third component, specific examples thereof include polyoxyethylene alkyl ethers such as polyoxyethylene dodecyl ether, polyoxyethylene oleyl ether, and polyoxyethylene stearyl ether, polyoxyethylene polyoxypropylene glycol, and polyoxyethylene alkylphenyl ether; sorbitan fatty acid esters such as sorbitan monooleate, sorbitan monostearate, sorbitan sesquioleate, sorbitan coconut oil fatty acid, sorbitan monopalmitate, sorbitan tristearate, and sorbitan trioleate; polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan trioleate; polyoxyethylene glycerin fatty acid esters such as polyoxyethylene glyceryl monooleate; and polyoxyethylene sorbitol fatty acids such as polyoxyethylene sorbit tetraoleate. Examples of the polyethylene glycol fatty acid esters include acid esters, polyoxyethylene hydrogenated castor oil, polyglycerin fatty acid esters, sucrose fatty acid esters, PEG monocaprylate esters, PEG monoheptyl acid esters, PEG monopelargonate esters, PEG monocaprate esters, PEG monolaurate esters, PEG monomyristate esters, PEG monopentadecylate esters, PEG monopalmitate esters, PEG monolinoleate esters, PEG dilaurate esters, PEG monooleate esters, PEG dioleate esters, PEG monostearate esters, PEG distearate esters, PEG dicaprylate esters, PEG diheptyl acid esters, PEG dipelargonate esters, PEG dicaprate esters, PEG dilaurate esters, PEG dimyristate esters, PEG dipentadecylate esters, PEG dipalmitate esters, and PEG dilinoleate esters. In addition, "PEG" is an abbreviation for "polyethylene glycol". When a nonionic surfactant is added as the third component, the amount added is preferably 10% by mass or less relative to 100% by mass of the total amount of the sizing agent.

[0047] In the sizing-agent-coated carbon fiber bundle of the present invention, the sizing agent is preferably substantially free of a compound having an epoxy group. Here, "substantially free of a compound" means that such a compound is not present at all, or even if it is present in the form of an additive, it is 1 mass% or less in 100 mass% of the total amount of the sizing agent. Highly reactive epoxy groups react with amino groups of an amine compound to form a strong crosslinked structure. Therefore, by making the sizing agent substantially free of a compound having an epoxy group, the formation of a crosslinked structure between carbon fiber single yarns is suppressed, and the openability is easily improved.

[0048] The carbon fiber bundle used in the present invention is not particularly limited, but from the viewpoint of mechanical properties, polyacrylonitrile carbon fiber is preferably used. The polyacrylonitrile carbon fiber bundle used in the present invention is obtained by subjecting a carbon fiber precursor fiber made of a polyacrylonitrile polymer to flame retardation treatment in an oxidizing atmosphere at a maximum temperature of 200 to 300°C, then subjecting it to preliminary carbonization treatment in an inert atmosphere at a maximum temperature of 500 to 1,200°C, and then subjecting it to carbonization treatment in an inert atmosphere at a maximum temperature of 1,200 to 2,000°C.

[0049] In the present invention, in order to improve the adhesion between the carbon fiber bundle and the thermoplastic resin, it is preferable to introduce oxygen-containing functional groups onto the surface of the carbon fiber bundle by subjecting the carbon fiber bundle to an oxidation treatment. As the oxidation treatment method, gas phase oxidation, liquid phase oxidation, and liquid phase electrolytic oxidation are used, but from the viewpoints of high productivity and enabling uniform treatment, liquid phase electrolytic oxidation is preferably used.

[0050] In the present invention, examples of the electrolyte used in the liquid-phase electrolytic oxidation include acidic electrolytes and alkaline electrolytes. 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, and salts such as ammonium sulfate and ammonium hydrogen sulfate. Among them, sulfuric acid and nitric acid, which show strong acidity, are preferably used. Examples of the alkaline electrolyte include aqueous solutions of hydroxides such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, and barium hydroxide, aqueous solutions of carbonates such as sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, barium carbonate, and ammonium carbonate, aqueous solutions of bicarbonates such as sodium bicarbonate, potassium bicarbonate, magnesium bicarbonate, calcium bicarbonate, barium bicarbonate, and ammonium bicarbonate, aqueous solutions of ammonia, tetraalkylammonium hydroxide, and hydrazine, and the like.

[0051] In the present invention, the amount of oxygen-containing functional groups introduced into the carbon fiber bundle is preferably such that the surface oxygen concentration (O / C), which is the ratio of the number of oxygen (O) and carbon (C) atoms on the fiber surface measured by X-ray photoelectron spectroscopy, is within the range of 0.08 to 0.30. When the O / C is 0.08 or more, the number of carboxyl groups and hydroxyl groups on the carbon fiber surface increases, and the interaction with the sizing agent is strengthened, improving the adhesiveness. The O / C is more preferably 0.10 or more, and even more preferably 0.12 or more. On the other hand, in terms of the decrease in strength of the carbon fiber itself due to oxidation, the smaller the O / C, the better, and the O / C is preferably 0.30 or less. The O / C is more preferably 0.25 or less, and even more preferably 0.22 or less.

[0052] Next, the method for producing the sizing-agent-coated carbon fiber bundle of the present invention will be described. First, the means for applying (applying) the sizing agent to the carbon fiber bundle in the present invention will be described.

[0053] In the present invention, the sizing agent is preferably diluted with a solvent and used as a homogeneous solution. Examples of such solvents include water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, dimethylformamide, and dimethylacetamide, among which water is preferably used because it is easy to handle and has an advantage from the viewpoint of safety.

[0054] Examples of the application method include a method of immersing a carbon fiber bundle in a sizing agent solution via a roller, a method of contacting a carbon fiber bundle with a roller to which the sizing agent solution is attached, and a method of spraying the sizing agent solution in the form of a mist onto the carbon fiber bundle. In producing the sizing agent-coated carbon fiber bundle of the present invention, the method of immersing a carbon fiber bundle in a sizing agent solution via a roller is preferably used. The sizing agent may be applied by either a batch method or a continuous method, but the continuous method is preferably used because it has good productivity and small variation. Another preferred embodiment is to vibrate the carbon fiber bundle with ultrasonic waves when applying the sizing agent.

[0055] The concentration of the sizing agent solution used in the method of immersing the carbon fiber bundle in the sizing agent solution via a roller may be controlled so that the amount of sizing agent attached to the sizing-coated carbon fiber bundle is a desired value.

[0056] The method for producing a sizing-coated carbon fiber bundle in the present invention preferably includes a drying step of drying at 180 to 240° C. after the step of coating the carbon fiber bundle with a sizing agent.

[0057] In the present invention, after applying the sizing agent solution, it is preferable to obtain a sizing-agent-coated carbon fiber bundle by contact drying means, for example, by contacting the carbon fiber bundle with a heated roller. The carbon fiber bundle introduced into the heated roller is pressed against the heated roller by tension and rapidly dried, so that the flat shape of the carbon fiber bundle expanded by the heated roller is easily fixed by the sizing agent. The flattened carbon fiber bundle has a small contact area between the individual fibers, and therefore tends to have high openability.

[0058] In the present invention, after passing through a heated roller as a preliminary drying step, a further heat treatment may be added as a second drying step. Either a contact type or a non-contact type heating method may be adopted for the heat treatment as the second drying step. By carrying out the heat treatment, the dilution solvent remaining in the sizing agent can be further removed, and the friction characteristics of the sizing-agent-coated carbon fiber bundle can be stabilized. The heat treatment conditions are typically preferably set between 180 and 240°C, and may be appropriately adjusted so as to satisfy each of the requirements of the sizing-agent-coated carbon fiber bundle of the present invention described above. In general, the higher the heat treatment temperature, the lower the wet FF friction coefficient tends to be, and conversely, the higher the single yarn adhesion tends to be. With this general relationship in mind, the temperature may be appropriately adjusted. The heat treatment may also be carried out by microwave irradiation and / or infrared irradiation.

[0059] In the present invention, the sizing-agent-coated carbon fiber bundle is preferably compounded with a thermoplastic resin (D) to form a thermoplastic resin composition.

[0060] The thermoplastic resin (D) in the present invention is preferably at least one thermoplastic resin selected from the group consisting of polyketone resins, polyether ketone resins, polyether nitrile resins, polyimide resins, polyamide imide resins, polyether imide resins, polysulfone resins, polyether sulfone resins, polyarylene sulfide resins, polyether ether kentone resins, polyphenylene ether resins, polyoxymethylene resins, polyamide resins, polyester-based resins, polycarbonate resins, fluorine-based resins, styrene-based resins, and polyolefin-based resins.

[0061] The thermoplastic resin composition of the present invention can be preferably used in the form of a molding material such as a prepreg or a UD tape.

[0062] Next, a method for producing a molded article using the thermoplastic resin composition of the present invention will be described. The method for producing a molded article of the present invention preferably includes a step of heating to 300°C or higher when obtaining the thermoplastic resin composition using the sizing agent-coated carbon fiber bundle and the thermoplastic resin (D). By heating to 300°C or higher in the molding step, the thermoplastic resin is sufficiently permeated into the fiber bundle, improving the impregnation property, and the physical properties of the thermoplastic resin composition are also improved.

[0063] Specific examples of the molded article obtained by molding the thermoplastic resin composition of the present invention include not only the molded article as a final product, but also molding materials used to produce the molded article (e.g., pellets, stampable sheets, UD tapes, prepregs, etc., as exemplified below).

[0064] Specific examples of the molded article of the present invention include molding materials such as pellets, stampable sheets, UD tapes, and prepregs, as well as housings and trays, chassis, and other internal parts and cases for electric and electronic devices such as electronic appliances, mechanical parts, panels, and other building materials, motor parts, alternator terminals, alternator connectors, IC regulators, potentiometer bases for light dimmers, suspension parts, various valves such as exhaust gas valves, various pipes for fuel, exhaust systems, or intake systems, air intake nozzles, snorkels, intake manifolds, various arms, various frames, various hinges, various bearings, fuel pumps, gasoline tanks, CNG tanks, engine coolant joints, carburetor main bodies, carburetor spacers, exhaust gas sensors, coolant sensors, oil temperature sensors, brakes, etc. Pad wear sensors, throttle position sensors, crankshaft position sensors, air flow meters, brake butt wear sensors, thermostat bases for air conditioners, heating hot air flow control valves, brush holders for radiator motors, water pump impellers, turbine vanes, wiper motor related parts, distributors, starter switches, starter relays, transmission wire harnesses, windshield washer nozzles, air conditioner panel switch boards, fuel-related electromagnetic valve coils, fuse connectors, battery trays, AT brackets, headlamp supports, pedal housings, handles, door beams, protectors, chassis, frames, armrests, horn terminals, step motor rotors, lamp sockets, lamp reflectors, lamp housings, brake pistons, noise shields, radiator supports, spare tire covers, seat shells, solenoid bobbins, engine oil filters, ignition device cases, under covers, scuff plates, pillar trims, propeller shafts, wheels, fenders,Examples of the materials include automobile and motorcycle related parts, components and exterior panels such as fascias, bumpers, bumper beams, bonnets, aero parts, platforms, cowl louvers, roofs, instrument panels, spoilers and various modules, and aircraft related parts, components and exterior panels such as landing gear pods, winglets, spoilers, edges, ladders, elevators, failings and ribs, and molded parts such as wind turbine blades. In particular, the materials are preferably used for aircraft parts, wind turbine blades, automobile exterior panels, and housings, trays and chassis of electronic devices. EXAMPLES

[0065] The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples.

[0066] <Method for measuring the amount of sizing agent attached> 2.0±0.5 g of the sizing-coated carbon fiber bundle was weighed (W1) (unit: g, read to the fourth decimal place), and then placed in an electric furnace (capacity 120 cm) set to a temperature of 450°C in a nitrogen gas flow of 50 mL / min. 3 ) for 15 minutes to completely decompose the sizing agent. The carbon fiber bundle was then transferred to a container in a 20 L / min dry nitrogen gas flow and cooled for 15 minutes, after which it was weighed (W2) (unit: g, read to the fourth decimal place) and the heat loss ΔW was calculated by W1-W2. The heat loss ΔW was divided by the mass W1 of the sizing agent-coated carbon fiber bundle before the heat decomposition as shown in formula (b) and expressed as a percentage to be used as the amount of the sizing agent attached. The amount of the sizing agent attached was measured twice, the average value was calculated, and the value rounded off to the third decimal place was used as the amount of the sizing agent attached in the present invention. Amount of sizing agent applied (mass%) = ΔW / W1 × 100 (b).

[0067] <Method of measuring the coefficient of friction of wet FF> A bar made of stainless steel SUS304 with a diameter of 50 mm was fixed parallel to the ground and not rotated, and the sizing agent-coated carbon fiber bundle to be evaluated was wound on its surface. The sizing agent-coated carbon fiber bundle was wound so as to cover the surface of the bar over a width of 8 cm without any gaps. At this time, the bundles already wound and the bundles to be newly wound next to them were wound so that the ends of each bundle overlapped by about 1 mm. In addition, to prevent sagging, the beginning and end of the winding were fixed by attaching tape to the surface of the bar. Next, the same sizing agent-coated carbon fiber bundle was wound around the center of the 8 cm-wide range covered by the sizing agent-coated carbon fiber bundle, with both ends facing vertically downward for 1.5 turns, i.e., the contact angle was 3π (rad). At this time, the bundle was wound with a gap of typically 3 to 5 mm in the width direction so as not to overlap itself. The sizing agent-coated carbon fiber bundle wound 1.5 turns was uniformly wetted with 5 mL of clean water. At this time, a dropper was used to ensure that the entire circumference was thoroughly wetted. Next, a weight (T1 = 0.08 g / tex) was attached to one end of the sizing-coated carbon fiber bundle wound 1.5 times, and a spring scale was attached to the other end. The spring scale was pulled vertically downward at a speed of 1 m / min, and the force at which the sizing-coated carbon fiber bundle wound 1.5 times started to move was read, and the tension T2 (g / tex) was obtained by dividing it by the fineness of the sizing-coated carbon fiber bundle. The measurement was completed within 10 seconds from the start of wetting with water. The wet FF friction coefficient was calculated from the following formula. The measurement was performed twice, and the average value was taken as the wet FF friction coefficient. The measurement bobbin was used that had been placed under the measurement atmosphere temperature and humidity conditions (measurement conditions: 23 ± 3 ° C / 60 ± 5%) for more than 2 hours before the measurement.

[0068] Wet FF friction coefficient = ln(T2 / T1) / θ T2: Tension when the carbon fiber bundle starts to move T1: Weight mass (=0.25g / tex) θ: Contact angle (=3πrad).

[0069] <Method of measuring adhesion number> The evaluation was carried out by the water dispersion test described below. An anionic surfactant, sodium dioctyl sulfosuccinate (manufactured by Tokyo Chemical Industry Co., Ltd.), was dissolved in 100 g of water to a concentration of 0.05% by mass to prepare a dispersion medium. The carbon fiber bundle to be measured, cut to a length of 5 mm, was added to the dispersion medium that had been stirred with a magnetic stirrer at a rotation speed of 200 rpm. After stirring for 30 seconds, the mixture was filtered using a separable funnel with an inner diameter of 95 mm onto a quantitative filter paper (grade: 5C, manufactured by ADVANTEC Co., Ltd.) with a diameter of 110 mm. The filtration was performed by suction filtration using an aspirator, and the filter paper after filtration was left in a place not exposed to wind for 2 hours to air dry. The filter paper was sandwiched between laminate films and laminated by passing it through a laminator. The surface of the laminated filter paper was observed under a microscope under the conditions described below, and images of 16 fields of view were obtained. In order to obtain images of 16 fields of view without omissions or overlaps, 16 marks were made in advance with a marker in a grid pattern on the surface of the filter paper, and images of 16 fields of view were obtained so that the marks were near the center of the field of view. In the present invention, a mass in which multiple single yarns are gathered in parallel and in contact with each other without any gaps, and which looks like a single thick fiber, and which has a thickness of 40 μm or more, was defined as adhesion. When determining whether or not it was adhesion, those that clearly exceeded the standard were judged visually, and those that were difficult to judge visually, such as those with a thickness of around 40 μm, were judged by measuring the diameter using image processing software. The image processing software was the open source software “imageJ”, and the following procedure was used. First, the image to be analyzed was loaded into “imageJ”, and a line segment was drawn that passed through the position that divided the long axis of the single yarn mass whose diameter was to be measured in half and was perpendicular to the long axis, and the brightness profile along the line was obtained by selecting “Plot profile” from the “Analyze” command. The half-width of the profile was read and converted into actual size to be the "thickness" of the single yarn clump. If this was 40 μm or more, it was determined to be sticking. The thickness of each sticking differed, but this was not particularly distinguished in the present invention. The number of stickings in each of the acquired images of 16 fields of view was counted, and the total number of stickings was obtained by adding up the numbers for the 16 fields of view.The above procedure, starting with dispersion and filtration, was repeated twice, and the average of the two adhesion numbers was used as the adhesion number in the present invention. Microscope: Nikon SMZ1270 Camera: Nikon DS-Vi1 Monitor: Nikon DS-L3 Magnification: 1x Gain: 170 Exposure time: 100ms Image mode: Full Pixel resolution: 8μm / pixel Recording mode: 1,600 x 1,200 pixels (12.8 mm x 9.6 mm).

[0070] <How to determine absorbance of carbon fiber extract> The absorbance of the extract of carbon fiber coated with a sizing agent as defined in the present invention was determined by the following procedure. 1.0 mass part of a carbon fiber bundle was cut out, and a 20 cm 3 The carbon fiber bundle was placed in a glass container with a lid and 10.0 parts by mass of DMSO at 25°C was added. The sizing agent and surface oxides attached to the sizing agent-coated carbon fiber bundle were extracted by treating it for 15 minutes under ultrasonic irradiation with an oscillation frequency of 40 kHz. The solution extracted from the carbon fiber was placed in a quartz cell with an optical path length of 1.0 cm, and the absorbance at 200 to 900 nm was measured using a UV-Vis spectrophotometer with DMSO as the control liquid, and the absorbance at 300 nm and 600 nm was recorded. The ultraviolet-visible spectrophotometer used was a V-550 manufactured by JASCO Corporation.

[0071] <How to wash carbon fiber bundles> The sizing agent-coated carbon fiber bundle was washed in the following procedure. The sizing agent-coated carbon fiber bundle 1a installed in the unwinding process 11 shown in Fig. 1 was passed through water 1d in the water washing tank 18 via the free roller 15 before the water washing tank, the free roller 16 in the water washing tank, and the free roller 17 after the water washing tank in the water washing process 12, and then passed through water 1e in the water washing tank 22 via the same free roller 19 before the water washing tank, the free roller 20 in the water washing tank, and the free roller 21 after the water washing tank, and then passed continuously through the drying process 13 to dry the water and take up in the winding process 14. The unwinding tension from the creel was 800g, the process speed was 2.4m / min, the water temperature was 25±5°C, the diameter of the free roller in the water washing tank was 150mm, and the contact angle between the sizing agent-coated carbon fiber bundle and the free roller in the water washing tank was πrad. The liquid level was adjusted so that the time spent underwater in one water washing tank was 25 seconds, and the total time spent in the two water washing tanks was 50 seconds. The drying process was a non-contact drying process, and the sizing-coated carbon fiber bundle 1b after washing was dried at a drying temperature of 150°C for 1 minute to obtain the sizing-coated carbon fiber bundle 1c after washing and drying.

[0072] <Method of measuring interfacial shear strength (IFSS)> A single fiber was extracted from the carbon fiber bundle coated with the sizing agent, and a resin film having a thickness of 0.52 mm was placed on each side. A molded plate having a thickness of 0.50 mm was obtained with the carbon fiber single fiber embedded therein by a heat press. The heat press was performed under the conditions of a set temperature of 380°C and a pressure of 0.4 to 0.5 MPa. A dumbbell-shaped test piece for IFSS measurement was punched out from this molded plate, and the test piece was smoothed by polishing with 1200 grit sandpaper to avoid breakage from the new cross section generated by punching. Both ends of the dumbbell-shaped sample were clamped, and a tensile force was applied in the fiber axis direction (longitudinal direction), generating a strain of 12% at a speed of 2.0 mm / min. The test piece after the test was placed on a hot plate set at a temperature of 380°C to melt the crystals, and when it became transparent, it was immersed in water to quench and make it transparent. The fragmented fiber length inside the sample made transparent by heating was observed under a microscope. Furthermore, the critical fiber length lc was calculated from the average broken fiber length la by the formula lc (μm) = (4 / 3) × la (μm). The strand tensile strength σ and the diameter d of the carbon fiber single yarn were measured, and the interfacial shear strength (IFSS), which is an index of the adhesive strength at the carbon fiber / resin interface, was calculated by the following formula. The resin film used was D-1, which will be described later. IFSS(MPa)=σ(MPa)×d(μm) / (2×lc)(μm). In the examples, the test results were the average of five measurements (n=5), and were classified into the following four levels according to the IFSS value. S: IFSS is 38 (MPa) or more A: IFSS is 36 (MPa) or more and less than 38 (MPa) B: IFSS is 34 (MPa) or more and less than 36 (MPa) C: IFSS is less than 34 (MPa).

[0073] <Prepreg Formation and Evaluation of Resin Impregnation> The carbon fiber bundle to be evaluated was prepared as a unit with 12,000 filaments, and six units were arranged in the width direction and subjected to prepreg formation. In the prepreg formation, the carbon fiber bundle was pulled out from the bobbin, run in the air for 3 m, and passed through an aqueous slurry tank in which thermoplastic resin particles were dispersed in water to pick up the resin, and was continuously brought into contact with a hot plate set at a surface temperature of 120°C to volatilize the water, and passed through a melting chamber set at an atmospheric temperature of 380°C. The bundle was then taken up while being rubbed against the inner surface of a 30 mm wide pressure die set to a thickness of about 200 μm, thereby obtaining a resin-impregnated prepreg. The aqueous slurry was prepared by adding 2 to 4 parts by mass of thermoplastic resin particles and 0.5 parts by mass of Brij (registered trademark) S100 (manufactured by Sigma-Aldrich) as a surfactant to 100 parts by mass of water, and circulating and stirring the mixture using a circulation pump. The set temperature of the pressure die was 380°C. The amount of thermoplastic resin fine particles in the aqueous slurry was finely adjusted so that the resin content of the final prepreg was 34% by mass. The take-up speed was 0.5 m / min. The thermoplastic resin fine particles used were D-2 described later, powdered with an average particle size of 23 μm. The resin impregnation of the prepreg obtained was evaluated sensorily. Specifically, a prepreg with a width of about 30 mm was bent by hand in the direction in which the fiber axis of the carbon fiber is bent (0 degree direction) and in the thickness direction to be broken by bending. The end portion caused by the bending break was visually observed and classified into the following five stages according to the degree of fuzz. The bending evaluation was repeated 10 times, and the average score was adopted. In the present invention, in consideration of the fact that the evaluation is a sensory evaluation, the criteria for the score AA were set to Comparative Example 9, the criteria for the score C to Comparative Example 4, and the criteria for the score D to Comparative Examples 5 and 8, thereby preventing deviations by the evaluators. AA: No fluffing A: There is a small amount of fuzz, but it is all less than 1mm in length. B: There is fluff with a length of more than 1 mm, but it is small compared to C. C: Fuzz less than 1 mm wide and longer than 1 mm is present D: Fluff with a width of 1 mm or more is present The resin particles used were D-2, which will be described later.

[0074] <Evaluation of thermal stability of prepreg> Differential scanning calorimetry (DSC) was performed on the prepared prepreg specimen under the measurement conditions described below, and the temperature rise-lowering cycle was repeated twice. The peak top temperature of the crystallization peak during the temperature drop process of the second cycle was recorded as T1. In addition, DSC measurement was performed on the thermoplastic resin (D-2) using the same measurement method, and the peak top temperature (T0) of the crystallization peak during the temperature drop process of the first cycle was read, and it was found to be T0 = 275.0 ° C. The peak top change amount when processed into a prepreg from T0-T1 was calculated, and the thermal stability of the resin in the prepreg was evaluated. In addition, such measurements were performed three times, the average value was calculated, and the change amount of the peak top was classified into the following four stages according to the change amount of the peak top. S: Peak top change is less than 19.0℃ A: The change in the peak top is 19.0℃ or more and less than 20.0℃ B: The change in the peak top is 20.0°C or more and less than 21.0°C. C: Peak top change is 21.0°C or more DSC measurement conditions Sample size: 10.0mg (±0.5mg) Measurement atmosphere: Nitrogen (purity 99.999% or more by volume) Measurement conditions: 1. Hold at 50℃ for 1 minute 2. Heat up from 50℃ to 380℃ at 50℃ / min 3. Hold at 380℃ for 3 minutes 4. Decrease temperature from 380℃ to 50℃ at 10℃ / min 5. Hold at 50℃ for 1 minute 6. Heat from 50℃ to 380℃ at 50℃ / min 7. Hold at 380℃ for 30 minutes 8. Decrease temperature from 380℃ to 50℃ at 10℃ / min.

[0075] The compounds and thermoplastic resins used in each of the examples and comparative examples are as follows.

[0076] Compound (A) A-1: Polyethyleneimine (Mw=1,300, viscosity:6,800mPa·s) (BASF Japan Ltd. "Lupasol" (registered trademark) G20 Waterfree) Compound (B) B-1: Polyethylene glycol (Mw=600, SP value=21.7, number of ends=2) (PEG600 manufactured by Sanyo Chemical Industries, Ltd.) B-2: Polyethylene glycol diglyceryl ether (Mw=750, SP value=23.6, number of ends=4) ("SC-E750" manufactured by Sakamoto Pharmaceutical Co., Ltd.) B-3: Polypropylene glycol (Mw=600, SP value=20.2, number of ends=2) (SANNYX (registered trademark) PP600 manufactured by Sanyo Chemical Industries, Ltd.) B-4: Polypropylene glycol glyceryl ether (Mw=400, SP value=23.7, number of ends=3) (SANNYX (registered trademark) GP400 manufactured by Sanyo Chemical Industries, Ltd.) B-5: Polypropylene glycol glyceryl ether (Mw=1000, SP value=20.2, number of ends=3) (SANNYX (registered trademark) GP1000 manufactured by Sanyo Chemical Industries, Ltd.) B-6: Polypropylene glycol diglyceryl ether (Mw=750, SP value=22.7, number of ends=4) ("SC-P750" manufactured by Sakamoto Pharmaceutical Co., Ltd.) B-7: Polypropylene glycol diglyceryl ether (Mw=1000, SP value=21.2, number of ends=4) ("SC-P1000" manufactured by Sakamoto Pharmaceutical Co., Ltd.) B-8: Sorbitol polypropylene glycol ether (Mw=750, SP value=23.8, number of ends=6) (SANNYX (registered trademark) SP750 manufactured by Sanyo Chemical Industries, Ltd.) B-9: PEG monooleate ester (Mw=600, SP value=19.3, number of ends=2) (SANYO CHEMICAL INDUSTRIES, LTD. "IONET" (registered trademark) MO600) B-10: PEG distearate ester (Mw=4000, SP value=19.0, number of ends=2) ("IONET" (registered trademark) DS4000 manufactured by Sanyo Chemical Industries, Ltd.) thermoplastic resin D-1: Polyphenylene sulfide (glass transition temperature 89℃) ("Durafide" (registered trademark) PPS W-540, manufactured by Polyplastics Co., Ltd.) D-2: Polyether ketone ketone (Arkema "KEPSTAN (registered trademark)" 7002).

[0077] Example 1 This example comprises the following first to fifth steps.

[0078] - First process: Manufacturing the raw carbon fiber bundles The acrylonitrile copolymer was spun and sintered to obtain a carbon fiber bundle with a total filament count of 12,000, a total fineness of 800 tex, a strand tensile strength of 5.1 GPa, and a strand tensile modulus of elasticity of 240 GPa. The carbon fiber bundle was then electrolytically surface-treated with an aqueous solution of ammonium bicarbonate as the electrolyte and an electrical charge of 80 coulombs per gram of carbon fiber bundle. The carbon fiber bundle that had been electrolytically surface-treated was then washed with water and dried in heated air to obtain the carbon fiber bundle that would become the raw material. The carbon fiber bundle obtained after this process had an O / C of 0.20 and an N / C of 0.09.

[0079] The second step is to apply a sizing agent to the carbon fiber bundle. Using (A-1) as compound (A) and (B-1) as compound (B), 3 parts by mass of (A-1) and 7 parts by mass of (B-1) were weighed and dissolved in about 1,540 parts by mass of water, to obtain an aqueous solution of about 0.65% by mass in which the sizing agent was uniformly dissolved. This aqueous solution was used as an aqueous solution of a sizing agent, and the sizing agent was applied to a surface-treated carbon fiber bundle by a dipping method, and then the bundle was heat-treated for 15 seconds at a temperature of 120°C with a hot roller as a preliminary drying step, and then heat-treated for 60 seconds in heated air at a temperature of 200°C as a second drying step, to obtain a sizing-agent-coated carbon fiber bundle. The amount of the sizing agent attached was adjusted to 0.35% by mass with respect to the total amount of the surface-treated sizing-agent-coated carbon fiber bundle (100% by mass). The evaluation results are summarized in Table 1.

[0080] The third step is to wash the sizing-coated carbon fiber bundles with water. The sizing-agent-coated carbon fiber bundle obtained in the second step was washed with water as described in the above section <Method of washing carbon fiber bundle with water> to obtain a sizing-agent-coated carbon fiber bundle after washing with water for 50 seconds. The obtained carbon fiber bundle was evaluated by X-ray photoelectron spectroscopy (XPS).

[0081] The fourth step is to heat treat the sizing-coated carbon fiber bundles. Approximately 2.0 g of the sizing agent-coated carbon fiber bundle obtained in the second step was prepared and placed in an electric furnace (capacity 120 cm) set to a temperature of 450° C. in a nitrogen gas flow of 50 mL / min. 3 ) for 5 minutes to allow the sizing agent to pyrolyze. The carbon fiber bundles were then transferred to a container in a dry nitrogen gas flow of 20 liters / min and cooled for 15 minutes, after which they were evaluated by X-ray photoelectron spectroscopy (XPS).

[0082] The fifth step is to prepare the prepreg. A prepreg was produced using the sizing-coated carbon fiber bundle obtained in the second step by the method described above in <Prepreg Formation and Evaluation of Resin Impregnation>. The thermal stability of the prepreg was evaluated using the obtained prepreg by the method described above in <Evaluation of Thermal Stability of Prepreg>.

[0083] [Table 1]

[0084] [Table 2]

[0085] (Examples 2-10) The types and compounding ratios of the compounds (A) and (B) used in the sizing agent and the amount of the sizing agent applied were changed to the values ​​shown in Table 1, and sizing-agent-coated carbon fiber bundles were obtained in the same manner as in Example 1, and various evaluations were performed. The results are summarized in Table 1.

[0086] (Comparative Examples 1-9) The types and compounding ratios of the compounds (A) to (B) used in the sizing agent, the amount of the sizing agent attached, and the drying temperature were changed to the values ​​shown in Table 2, and a sizing-agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, and various evaluations were performed. The results are summarized in Table 2.

[0087] Comparative Example 10 A carbon fiber bundle was obtained in the same manner as in Example 1, except that no sizing agent was applied, and various evaluations were carried out. The results are summarized in Table 2. [Industrial Applicability]

[0088] According to the present invention, it is possible to provide a sizing-agent-coated carbon fiber bundle that has high adhesion to thermoplastic resins such as polyphenylene sulfide, polyaryl ether ketone, polyether sulfone, polyamide imide, etc., is excellent in resin impregnation in an aqueous slurry impregnation process, and is unlikely to impair moldability or processability when processed into a prepreg. The thermoplastic resin composite using the present invention is lightweight yet has excellent strength, and therefore can be suitably used in many fields such as aircraft members, spacecraft members, automobile members, ship members, civil engineering and construction materials, and sporting goods. [Explanation of symbols]

[0089] 11: Unwinding process 12:Washing process 13:Drying process 14: Winding process 15: Free roller in front of the washing tank 16: Free roller in the washing tank 17: Free roller after washing tank 18:Washing tank 19: Free roller in front of the washing tank 20: Free roller in the washing tank 21: Free roller after washing tank 22:Washing tank 1a: Carbon fiber bundle coated with sizing agent 1b: Carbon fiber bundle coated with sizing agent after washing with water 1c: Carbon fiber bundle coated with sizing agent after washing and drying 1d: Water 1e: Water

Claims

1. A sizing-agent-coated carbon fiber bundle is formed by coating a water-soluble compound (A) having at least an amino group and a compound (B) containing a polyalkylene glycol, the water-soluble compound (A) having at least an amino group contains polyethyleneimine, the compound (B) containing polyalkylene glycol has 3 or more and 5 or less terminals, the surface oxygen concentration (O / C) measured by X-ray photoelectron spectroscopy (XPS) is 0.28 or more and 0.45 or less, and the surface nitrogen concentration (N / C) is 0.05 or more and 0.20 or less, and the sizing-agent-coated carbon fiber bundle satisfies the following (i) and (ii): (i) After washing for 50 seconds with the water washing method described below, the surface oxygen concentration (O / C) is 0.15 or more and 0.25 or less, and the surface nitrogen concentration (N / C) is 0.15 or more and 0.30 or less. (ii) The number of adhesions evaluated by the water dispersion test described below is 20 or less. <Method of washing carbon fiber bundles> The sizing agent-coated carbon fiber bundle is washed in the following procedure. The sizing agent-coated carbon fiber bundle installed in the unwinding process is passed through the water in the washing tank via a free roller before the washing tank, a free roller in the washing tank, and a free roller after the washing tank in the washing process, and then passed through the water in the washing tank via the same free roller before the washing tank, a free roller in the washing tank, and a free roller after the washing tank, and then passed through the drying process continuously to dry the water and take up in the winding process. The unwinding tension from the creel is 800 g, the process speed is 2.4 m / min, the water temperature is 25±5° C., the diameter of the free roller in the washing tank is 150 mm, and the contact angle between the sizing agent-coated carbon fiber bundle and the free roller in the washing tank is πrad. In addition, the liquid level is adjusted so that the underwater passing time in one washing tank is 25 seconds, and the total time in the two washing tanks is 50 seconds. The drying step is a non-contact drying step, in which the washed, sizing-agent-coated carbon fiber bundle is dried at a drying temperature of 150° C. for 1 minute to obtain a washed and dried, sizing-agent-coated carbon fiber bundle. <Method for measuring adhesion number using water dispersion test> An anionic surfactant, sodium dioctyl sulfosuccinate (manufactured by Tokyo Chemical Industry Co., Ltd.), is dissolved in 100 g of water to a concentration of 0.05% by mass to form a dispersion medium. A carbon fiber bundle to be measured, which is a carbon fiber bundle with a total number of filaments of 12,000 cut to a length of 5 mm, is put into the dispersion medium that has been stirred with a magnetic stirrer at a rotation speed of 200 rpm. After stirring for 30 seconds, the mixture is filtered using a separable funnel with an inner diameter of 95 mm on a quantitative filter paper (grade: 5C, manufactured by ADVANTEC Co., Ltd.) with a diameter of 110 mm. Filtration is performed by suction filtration using an aspirator, and the filter paper after filtration is left to stand in a place away from the wind for 2 hours to air dry. The filter paper is sandwiched between laminate films and laminated by passing through a laminator. The laminated filter paper surface is observed under a microscope under the conditions described below, and images of 16 fields of view are obtained. In order to obtain images of 16 fields of view without omission or overlap, 16 marks are made in advance with a marker in a grid pattern on the surface of the filter paper, and images of 16 fields of view are obtained so that the marks are near the center of the field of view. A mass in which multiple single threads are gathered in parallel and in contact with each other without any gaps, which looks like a single thick fiber, and which has a thickness of 40 μm or more is defined as adhesion. When determining whether or not adhesion is present, those that clearly exceed the standard are judged visually, and those that are difficult to judge visually, such as those with a thickness of around 40 μm, are judged by measuring the diameter using image processing software. The image processing software is the open source software "imageJ" and is performed as follows. First, the image to be analyzed is loaded into "ImageJ", a line segment is drawn that passes through the position that bisects the long axis of the single yarn bundle whose diameter is to be measured and is perpendicular to the long axis, and a brightness profile along the line segment is obtained by selecting "Plot profile" from the "Analyze" command. The half-width of the profile is read and converted into actual size to be the "thickness" of the single yarn bundle, and if this is 40 μm or more, it is determined to be a sticking. The sticking varies in thickness, but no particular distinction is made. The number of stickings in each of the 16 acquired images is counted, and the total number of stickings is obtained by adding up the numbers for the 16 fields of view. The above procedure, starting with dispersion and filtration, is repeated twice, and the average of the two adhesion numbers is used as the adhesion number. Microscope: Nikon SMZ1270 Camera: Nikon DS-Vi1 Monitor: Nikon DS-L3 Magnification: 1x Gain: 170 Exposure time: 100 ms Image mode: Full Pixel resolution: 8 μm / pixel Recording mode: 1,600 x 1,200 pixels (12.8 mm x 9.6 mm)

2. 2. The sizing-agent-coated carbon fiber bundle according to claim 1, wherein the surface oxygen concentration (O / C) after heating at 300° C. for 5 minutes in air is 0.15 or more and 0.25 or less, and the surface nitrogen concentration (N / C) is 0.10 or more and 0.25 or less.

3. 3. The sizing-agent-coated carbon fiber bundle according to claim 1, wherein the extract obtained by the following extraction procedure has an absorbance at 600 nm of 0.01 or less and an absorbance at 300 nm of 0.10 or less. <Extraction operation> 1.0 mass part of the carbon fiber bundle was cut out and the volume was 20 cm ３ The sizing agent and surface oxides adhering to the sizing-agent-coated carbon fiber bundle are extracted by treating for 15 minutes under irradiation of ultrasonic waves with an oscillation frequency of 40 kHz.

4. The sizing-agent-coated carbon fiber bundle according to any one of claims 1 to 3, wherein the amount of the sizing agent attached is 0.10 mass% or more and 0.50 mass% or less based on 100 mass% of the sizing-agent-coated carbon fiber bundle.

5. The mass W of the water-soluble compound (A) having at least an amino group Ａ and the mass W of the compound (B) containing the polyalkylene glycol Ｂ The sizing-agent-coated carbon fiber bundle according to any one of claims 1 to 4, wherein the formula (a) is satisfied. 0.20 ≤ W Ａ / (W Ａ + W Ｂ ) ≤ 0.50... Equation (a)

6. The sizing agent-coated carbon fiber bundle according to any one of claims 1 to 5, wherein the weight average molecular weight Mw of the compound (B) containing polyalkylene glycol is 500 or more and 1000 or less, and the SP value is 21 or more.

7. 7. The sizing-agent-coated carbon fiber bundle according to claim 1, wherein the compound (B) containing polyalkylene glycol is a derivative of polypropylene glycol having no aromatic ring.

8. The method for producing a sizing-agent-coated carbon fiber bundle according to any one of claims 1 to 7, comprising a drying step of drying the carbon fiber bundle at 180 to 240°C after a step of applying the sizing agent to the carbon fiber bundle.

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