Sizing agent coated carbon fiber bundle

Abstract

To provide a sizing agent-coated carbon fiber bundle that does not impair moldability or processability in a prepreg having a carbon fiber impregnated with a crystalline thermoplastic resin represented by polyphenylene sulfide, polyaryletherketone, polyether sulfone, polyamide imide or the like even with good handleability of the agent-coated carbon fiber bundle.SOLUTION: A sizing agent-coated carbon fiber bundle has a sizing agent applied onto a sizing agent-coated carbon fiber bundle, the amount of the sizing agent being 0.15 pts.mass or more and 1.00 pts.mass or less relative to the sizing agent-coated carbon fiber bundle 100 pts.mass. 1 pt.mass of extract from a sizing agent-coated carbon fiber by extraction operation and 0.10 pt.mass of a polyether ketone ketone resin are mixed and the mixture is subjected to differential scanning calorimetry (DSC measurement) under specific conditions, so that the temperature difference between peak tops of a crystallization peak in a cooling process in the first cycle and a crystallization peak in the second cycle is 13°C or lower.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sizing-agent-coated carbon fiber bundle that exhibits bundling properties suitable for the handling of the sizing-agent-coated carbon fiber bundle and is coated with a sizing agent that is unlikely to impair the moldability and processability of the prepreg, in a prepreg in which element fibers are impregnated by a wet method with a crystalline thermoplastic resin typified by polyphenylene sulfide, polyaryl ether ketone, polyether sulfone, polyamide imide, etc. [Background technology]

[0002] Carbon fiber, being lightweight yet possessing excellent strength and elastic modulus, is used in a wide range of applications, including aircraft, spacecraft, automobile, ship, civil engineering, and sports equipment, as composite materials in combination with various matrix resins. A typical example of a carbon fiber composite is a molded product obtained by press-molding (a molding method in which preforms obtained by laminating prepregs are degassed and shaped under pressure). Prepregs are typically produced by impregnating a carbon fiber substrate, consisting of continuous carbon fiber bundles aligned in one direction, with resin. While composite materials using discontinuous carbon fibers (chopped, web, etc.) have been proposed, which offer excellent conformability to complex shapes and allow for rapid molding, prepregs offer superior practical performance as structural materials in terms of mechanical properties such as specific strength and specific rigidity, as well as the stability of their properties.

[0003] In recent years, carbon fiber composite materials have come to require molding materials with excellent moldability, ease of handling, and mechanical properties of the resulting molded products. This has led to the need for higher economic efficiency and productivity in the industrial sector. One answer to this demand is the development of prepregs using thermoplastic resins as the matrix resin. One example of a manufacturing method involves passing a carbon fiber tape containing powdered thermoplastic matrix resin through a thermoplastic resin slurry in which the powdered thermoplastic matrix resin is dispersed with a surfactant, and then impregnating the carbon fiber tape with the thermoplastic resin using heat and pressure.

[0004] To make the most of the excellent properties of carbon fibers after composite processing, it is important to ensure excellent handleability during carbon fiber processing and reduce winding of fuzz and breakage due to winding. Carbon fiber bundles that are not coated with a sizing agent lack bundling ability and generate a large amount of fuzz, which can accumulate during the prepreg production process and deteriorate the prepreg quality. Therefore, to improve the handleability of carbon fiber bundles, a method is usually used in which a sizing agent is applied to the carbon fiber bundle and an abrasion-resistant coating film is applied to the carbon fiber surface (see Patent Documents 1 and 2).

[0005] A method has also been proposed in which continuous fibers of carbon fiber bundles are cut and dispersed into single fibers for use in papermaking. The process of making paper from carbon fiber bundles is often an aqueous process. To utilize the excellent properties of carbon fiber bundles, it is important to achieve both bundling properties to maintain the shape of the carbon fiber bundles when handling them in the chopping process prior to the papermaking process, and excellent openability to quickly disperse them into single fibers when introduced into an aqueous medium in the papermaking process and suppress re-agglomeration. Therefore, a sizing agent that combines bundling properties and water dispersibility is applied. Generally, to improve the handleability of carbon fiber bundles, epoxy resins or the like are often attached as sizing agents (sizing agents). However, the sizing agents themselves have strong interactions or too strong interactions with the carbon fiber surfaces, which tend to result in poor openability in water when applied to aqueous processes. For this reason, for example, Patent Documents 3 to 5 propose methods of using surfactants or water-soluble polymers as sizing agents for carbon fiber bundles to improve handleability when cut into chopped carbon fibers and improve openability in water.

[0006] The excellent properties of carbon composite materials are significantly influenced by the properties of the interface between the carbon fiber and resin. Therefore, the properties of the sizing agent present at the interface between the carbon fiber and resin are important. For example, Patent Document 6 proposes a method in which a sizing agent is applied uniformly to carbon fiber bundles after applying a surfactant, thereby obtaining a carbon fiber composite material with excellent mechanical properties. Patent Document 7 also proposes a method in which a sizing agent with a controlled amount of thermal decomposition under specific conditions is applied to suppress voids during the production of thermoplastic resin molded products. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Patent No. 3,957,716 [Patent Document 2] Japanese Patent Application Publication No. 57-171767 [Patent Document 3] International Publication No. 2006 / 019139 [Patent Document 4] Japanese Patent Application Laid-Open No. 2000-54269 [Patent Document 5] Patent No. 6571892 [Patent Document 6] Japanese Patent Application Publication No. 2017-137603 [Patent Document 7] International Publication No. 2020 / 138139 Summary of the Invention [Problem to be solved by the invention]

[0008] On the other hand, when handling and interfacial properties are controlled by applying a sizing agent to carbon fiber bundles as described above, when combined with a crystalline thermoplastic matrix resin that requires high molding temperatures, depending on the components of the sizing agent, the gradual decomposition of the sizing agent remaining in the prepreg due to the high temperature and long heating times during the molding process of the carbon fiber reinforced composite material can change the crystallization behavior of the crystalline thermoplastic matrix resin, adversely affecting the moldability and processability of the composite. As a result, CFRP may not be able to demonstrate its full performance.

[0009] In other words, although studies have been conducted on suppressing fuzz generation from carbon fiber bundles by applying a sizing agent and on improving processability in aqueous processes, there has been no idea of ​​minimizing the effect of sizing-coated carbon fiber bundles on the crystallization behavior of crystalline thermoplastic matrix resins when processing carbon fibers in aqueous processes, and maintaining the moldability and processability of the composite.

[0010] The present invention has been made in view of the above, and has an object to provide a sizing-agent-coated carbon fiber bundle that is less likely to impair the moldability and processability of a composite obtained by compounding a crystalline thermoplastic resin, typified by polyphenylene sulfide, polyaryl ether ketone, polyether sulfone, polyamide imide, etc., through an aqueous process, even when the sizing-agent-coated carbon fiber bundle has excellent handleability. [Means for solving the problem]

[0011] The present invention for solving the above problems is a sized carbon fiber bundle in which the amount of sizing agent attached is 0.15 parts by mass or more and 1.00 parts by mass or less with respect to 100 parts by mass of the sized carbon fiber bundle. When a mixture of an extract extracted from 1 part by mass of the sized carbon fiber and 0.10 parts by mass of a polyether ketone ketone resin (KEPSTAN (registered trademark) 7002) is subjected to differential scanning calorimetry (DSC measurement) under the conditions shown below, it is a sized carbon fiber bundle in which the temperature difference between the crystallization peak in the cooling process of the first cycle and the peak top of the crystallization peak in the second cycle is 13°C or less.

[0012] <Extraction conditions> Immerse 1 part by mass of the sized carbon fiber bundle in 1,000 parts by mass of pure water at 25°C. After 60 seconds have elapsed, pull it up above the liquid surface and wait for 10 seconds in the air. Put the sized carbon fiber bundle into a new container, add 50 parts by mass of pure water at 25°C, and treat it for 15 minutes under ultrasonic irradiation with an oscillation frequency of 40 kHz to extract the sizing agent remaining in the sized carbon fiber bundle, and recover the solid content by concentrating the obtained extract solution.

[0013] <DSC measurement conditions> Sample amount: 3.0 mg (±0.5 mg) Measurement atmosphere: Nitrogen (purity 99.999 volume% or more) Measurement conditions: 1. Hold at 50°C for 1 minute 2. Heat up from 50°C to 380°C at 50°C / min 3. Hold at 380°C for 3 minutes 4. Cool down from 380°C to 50°C at 10°C / min 5. Hold at 50°C for 1 minute 6. Heat up from 50°C to 380°C at 50°C / min 7. Hold at 380°C for 30 minutes 8. Cool down from 380°C to 50°C at 10°C / min

Effects of the invention

[0014] According to the present invention, even when showing a bundling property suitable for the handling property of a sizing agent-coated carbon fiber bundle, in a composite material with a crystalline thermoplastic resin typified by super engineering plastics such as polyphenylene sulfide, polyaryl ether ketone, polyether sulfone, polyamideimide, etc., a sizing agent-coated carbon fiber bundle coated with a sizing agent that does not impair the moldability and processability of the composite can be obtained.

Embodiment for Carrying Out the Invention

[0015] Hereinafter, embodiments for carrying out the present invention will be described.

[0016] The sizing agent-coated carbon fiber bundle of the present invention is a sizing agent-coated carbon fiber bundle in which the sizing agent adhesion amount is 0.15 parts by mass or more and 1.00 parts by mass or less with respect to 100 parts by mass of the sizing agent-coated carbon fiber bundle. When a mixture of an extract extracted from 1 part by mass of the sizing agent-coated carbon fiber and 0.10 parts by mass of a polyether ketone ketone resin (KEPSTAN (registered trademark) 7002) is subjected to DSC measurement under the following conditions, it is a sizing agent-coated carbon fiber bundle in which the temperature difference between the crystallization peak in the cooling process of the first cycle and the peak top of the crystallization peak of the second cycle is 13°C or less.

[0017] <Extraction operation> Immerse 1 part by mass of the sizing agent-coated carbon fiber bundle in 1,000 parts by mass of pure water at 25°C, pull it up above the liquid surface after 60 seconds have elapsed, and wait in the air for 10 seconds. Put the sizing agent-coated carbon fiber bundle into a new container, add 50 parts by mass of pure water at 25°C, and treat it for 15 minutes under ultrasonic irradiation with an oscillation frequency of 40 kHz to extract the sizing agent remaining in the sizing agent-coated carbon fiber bundle, and concentrate the obtained extract solution to recover the solid content.

[0018] <DSC measurement conditions> Sample amount: 3.0 mg (±0.5 mg) Measurement atmosphere: Nitrogen (purity 99.999 volume% or more) Measurement conditions: Hold at 1.50°C for 1 minute 2. Heat 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°C for 1 minute 6. Heat from 50℃ to 380℃ at 50℃ / min 7. Hold at 380℃ for 30 minutes 8. Decrease temperature from 380°C to 50°C at 10°C / min.

[0019] The inventors' investigations revealed that when a sizing agent that improves handleability after application to carbon fiber bundles is used, the sizing agent is likely to remain in the composite after resin impregnation using an aqueous process, and this remaining sizing agent changes the crystallization behavior of the crystalline thermoplastic matrix, potentially reducing the processability and moldability of the prepreg. To address this issue, the inventors discovered that even when a compound that is easy to handle is used as the sizing agent, it is possible to achieve both excellent moldability and processability in a prepreg made of a crystalline thermoplastic resin by controlling the change in the DSC crystallization peak of the water extract of the sizing-agent-coated carbon fiber bundles and a specific crystalline thermoplastic resin.

[0020] The sizing-agent-coated carbon fiber bundle of the present invention needs to have a sizing agent adhesion amount of 0.15 parts by mass or more and 1.00 parts by mass or less per 100 parts by mass of the sizing-agent-coated carbon fiber bundle, and the sizing-agent-coated carbon fiber bundle obtained by coating the sizing agent on the carbon fiber bundle needs to satisfy specific conditions.

[0021] By setting the amount of sizing agent to 0.15 parts by mass or more, it is possible to reduce the frictional force between the single yarns in the carbon fiber bundle, improve the handleability of the sizing-coated carbon fiber bundle, and suppress the generation of fluff during production and processing. The amount of sizing agent is preferably 0.20 parts by mass or more, and more preferably 0.25 parts by mass or more. On the other hand, by setting the amount of sizing agent to 1.00 parts by mass or less, it is possible to reduce the remaining amount in a short period of time, thereby reducing the impact on the mechanical properties of the composite material. The amount of sizing agent is preferably 0.80 parts by mass or less, and more preferably 0.60 parts by mass or less.

[0022] The sizing-agent-coated carbon fiber bundle of the present invention is prepared by the extraction procedure described below. When a mixture of 1 part by mass of the extract extracted from the sizing-agent-coated carbon fiber and 0.10 parts by mass of polyether ketone ketone resin (KEPSTAN® 7002) is subjected to DSC measurement under the conditions described below, the temperature difference between the crystallization peak during the cooling process of the first cycle and the crystallization peak during the second cycle must be 13°C or less. During the resin impregnation step in the aqueous process, some of the sizing agent attached to the carbon fiber bundle easily dissolves into the slurry solution, but the sizing agent incorporated into the oxide film on the carbon fiber surface does not easily dissolve and is left behind in the prepreg. The sizing agent remaining in the prepreg gradually decomposes during heat treatment in the molding and processing steps, thereby changing the crystallization behavior of the crystalline thermoplastic matrix. By keeping the peak-top temperature difference at 13°C or less, the excellent molding speed characteristic of crystalline thermoplastic resins can be maintained. The peak-top temperature difference is more preferably 10°C or less, and even more preferably 5°C or less.

[0023] <Extraction operation> Immerse a sizing agent-coated carbon fiber bundle of 1 part by mass in 1,000 parts by mass of pure water at 25°C. After 60 seconds, pull it up above the liquid surface and wait in the air for 10 seconds to remove the excess sizing agent adhering to the carbon fiber surface. Put the sizing agent-coated carbon fiber bundle into a new container, add 50 parts by mass of pure water at 25°C, and treat it for 15 minutes under ultrasonic irradiation with an oscillation frequency of 40 kHz to extract the sizing agent remaining in the sizing agent-coated carbon fiber bundle, and recover the solid content by concentrating the obtained extract solution.

[0024] <DSC measurement conditions> Sample amount: 3.0 mg (±0.5 mg) Measurement atmosphere: Nitrogen (purity 99.999% by volume or more) Measurement conditions: 1. Hold at 50°C for 1 minute 2. Heat up from 50°C to 380°C at 50°C / min 3. Hold at 380°C for 3 minutes 4. Cool down from 380°C to 50°C at 10°C / min 5. Hold at 50°C for 1 minute 6. Heat up from 50°C to 380°C at 50°C / min 7. Hold at 380°C for 30 minutes 8. Cool down from 380°C to 50°C at 10°C / min.

[0025] The sizing agent-coated carbon fiber bundle of the present invention refers to the mass reduction rate W at 300°C obtained under the measurement conditions described in the examples for the sizing agent-coated carbon fiber bundle A and the sizing agent adhesion rate W B The ratio of (W A / W B ) is preferably 0.3 or more and 1.0 or less. When W A / W B is 0.3 or more, the thermal decomposition amount of the sizing agent in the temperature range below the melting temperature of the thermoplastic resin increases, so that the amount of the sizing agent remaining in the composite can be reduced, and the influence on the crystallization behavior of the thermoplastic resin can be reduced. W A / W B is more preferably 0.4 or more, and even more preferably 0.5 or more. On the other hand, W A / W BThere is no clear standard for the upper limit, but 1.0 is the theoretical upper limit.

[0026] The sizing agent constituting the sizing-agent-coated carbon fiber bundle of the present invention preferably has a number-average molecular weight Mn of 2,000 or less. The number-average molecular weight Mn is measured by gel permeation chromatography (hereinafter abbreviated as GPC) using polyethylene glycol as a standard substance. By setting Mn to 2,000 or less, the molecular chain becomes shorter and thermal decomposition improves, allowing for thermal decomposition at a lower temperature in a shorter time. 1,000 or less is more preferable, and 300 or less is even more preferable. On the other hand, from the viewpoint of application, a Mn of 120 or more is preferable because it can suppress the volatilization and thermal decomposition of the sizing agent when it is incorporated into untreated carbon fiber. 135 or more is more preferable.

[0027] The number average molecular weight Mn of the sizing agent constituting the sizing-agent-coated carbon fiber bundle can be confirmed by using the evaluation results or catalog value of the supplier, or if it is unknown, by extracting the sizing agent from the carbon fiber bundle containing the sizing agent with water and performing GPC analysis.

[0028] The sizing agent constituting the sizing-agent-coated carbon fiber bundle of the present invention preferably contains polyalkylene glycol and / or a surfactant. Because polyalkylene glycol and / or a surfactant have poor reactivity with the carbon fiber surface, the carbon fiber bundle coated with these improves the elution of the sizing agent when immersed in water. As a result, the amount of sizing agent remaining in the composite is reduced, making it possible to reduce the effect on the crystallization behavior of the thermoplastic resin.

[0029] Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, polybutylene glycol, etc. Among these, polyethylene glycol, which is highly water-soluble, is preferred.

[0030] Surfactants can be classified into nonionic surfactants and ionic surfactants.

[0031] Examples of nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene dodecyl ether, polyoxyethylene oleyl ether, and polyoxyethylene stearyl ether; polyoxyethylene polyoxypropylene glycol; polyoxyethylene alkylphenyl ethers; 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; polyoxyethylene sorbitol fatty acid esters such as polyoxyethylene sorbit tetraoleate; Oxyethylene hydrogenated castor oil; polyethylene glycol fatty acid esters such as polyglycerin fatty acid esters, sucrose fatty acid esters, PEG monocaprylate, PEG monoheptylate, PEG monopelargonate, PEG monocaprate, PEG monolaurate, PEG monomyristate, PEG monopentadecylate, PEG monopalmitate, PEG monolinoleate, PEG dilaurate, PEG monooleate, PEG dioleate, PEG monostearate, PEG distearate, PEG dicaprylate, PEG diheptylate, PEG dipelargonate, PEG dicaprate, PEG dilaurate, PEG dimyristate, PEG dipentadecylate, PEG dipalmitate, and PEG dilinoleate.

[0032] Ionic surfactants can be further divided into cationic surfactants, anionic surfactants, and amphoteric surfactants.

[0033] Specific examples of cationic surfactants include alkyltrimethylammonium salts, dialkyldimethylammonium salts, trialkylmonomethylammonium salts, alkylamine hydrochlorides, alkylamine bromates, alkylpyridinium salts, alkyl-4-methylpyridinium salts, alkylbenzyldimethylammonium salts, alkylamine ethylene oxide adducts, fatty acid ester amine salts, fatty acid amide amine salts, and 2-alkyl-1-hydroxyethylimidazoline salts.

[0034] Specific examples of anionic surfactants include soap, polyoxyethylene alkyl ether carboxylates, alkyl hydroxy ether carboxylates, alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkanoyl methyl taurides, dialkyl sulfosuccinates, alkyl sulfosuccinate di-salts, polyoxyethylene alkyl ether sulfosuccinate di-salts, higher alkyl sulfates, polyoxyethylene alkyl ether sulfates, sulfated oils, sulfated fatty acid esters, sulfated olefins, higher alkyl phosphates, polyoxyethylene alkyl ether phosphates, and dithiophosphates. The cations constituting the salt include alkali metal cations such as sodium and alkaline earth metal cations such as calcium, with alkali metal cations being preferred to increase water solubility. Furthermore, ammonium salts may be used instead of metal salts.

[0035] Specific examples of amphoteric surfactants include betaine surfactants such as fatty acid amidopropyl betaine, myristyl amidopropyl betaine, coconut oil fatty acid amidopropyl betaine, lauric acid amidopropyl betaine, cocamidopropyl betaine, fatty acid amidopropyl dimethylaminoacetic acid betaine, coconut fatty acid amidopropyl dimethylaminoacetic acid betaine, lauric acid amidopropyl dimethylaminoacetic acid betaine, stearyl dimethylaminoacetic acid betaine, lauryl dimethylaminoacetic acid betaine, lauryl dihydroxyethyl betaine, and 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine; sulfobetaine surfactants such as alkyl hydroxy sulfobetaine, cocamidopropyl hydroxy sulfobetaine, and lauramidopropyl hydroxy sulfobetaine; fatty acid amidopropyl dimethylaminoacetic acid betaine; and amine oxide surfactants such as lauryl amine oxide, lauric acid amidopropyl dimethylamine oxide, lauryl dimethylamine oxide, coconut oil alkyl dimethylamine oxide, dodecyl dimethylamine oxide, decyl dimethylamine oxide, and tetradecyl dimethylamine oxide; and amino acid surfactants such as N-lauroyl-N'-carboxymethyl-N'-hydroxyethyl ethylenediamine sodium, N-coconut oil fatty acid acyl-N'-carboxyethyl-N'-hydroxyethyl ethylenediamine sodium, sodium β-lauryl aminopropionate, sodium cocaminopropionate, alkyl carboxymethyl hydroxyethyl imidazolium betaine, lauryl dimethyl aminoacetic acid betaine, alkyl diaminoethyl glycine hydrochloride, and sodium lauryl aminodipropionate.

[0036] In the sizing agent constituting the present invention, the total amount of polyalkylene glycol and / or surfactant is preferably 70 parts by mass or more per 100 parts by mass of the total amount of the sizing agent.

[0037] By making the total amount of polyalkylene glycol and / or surfactant 70 parts by mass or more, the hydrophilic group in the surfactant improves elution, making it easier for the sizing agent to be eluted during washing with water, and the amount of sizing agent remaining on the carbon fiber bundle can be reduced, more preferably 85 parts by mass or more, and even more preferably 95 parts by mass or more.

[0038] The sizing agent of the present invention preferably does not contain an aromatic compound. When a compound having an aromatic structure is heated, the aromatic moiety, which has high heat resistance, remains on the surface of the carbon fiber bundle as char, and the remaining char changes the crystallization behavior of the crystalline thermoplastic prepreg.

[0039] In the sizing agent constituting the present invention, when the surfactant is a nonionic surfactant, it is preferable that the nonionic surfactant has a hydrophilic lipophilic balance (HLB) of 15 or more and 20 or less. The HLB specified in the present invention is a value calculated from the molecular structure based on Griffin's method described in "New Introduction to Surfactants," page 128, (1992). By adjusting the HLB of the nonionic surfactant to 15 or more and 20 or less, the hydrophilicity of the nonionic surfactant is improved, making it easier for the sizing agent to elute during washing with water, and reducing the amount of sizing agent remaining on the carbon fiber bundle.

[0040] Furthermore, when the surfactant is an anionic surfactant, the ratio of hydrophilic groups in the ions constituting the anionic surfactant is preferably 17% or more. By making the ratio of hydrophilic groups in the anions 17% or more, the elution of the ionic moieties into water is improved, making it easier for the sizing agent to be eluted during washing with water, and the amount of sizing agent remaining on the carbon fiber bundle can be reduced. A ratio of 20% or more is preferable, and 30% or more is even more preferable.

[0041] The hydrophilic group ratio is calculated from the molecular weight of the anionic surfactant. It can be calculated from the ratio of the molecular weight of the hydrophilic group part of the anionic surfactant to the molecular weight of the anionic surfactant. Here, the hydrophilic group is a sulfate ester group (SO4 - ), sulfonic acid group (SO3 - ), and carboxyl groups (COO- ), phosphate group (HPO3 - ), hydroxyl group (OH - In addition, if unreacted moieties remain during the production of the anionic moiety of the surfactant, the reaction rate is calculated from the total amount of the starting material and the reacted material (anion of the anionic surfactant) and the amount of the reacted material, and the hydrophilic group ratio of the anionic moiety of the present invention is calculated by multiplying the hydrophilic group ratio calculated from the molecular weight of the anionic moiety of the anionic surfactant by the reaction rate.

[0042] When the surfactant is a cationic surfactant or a zwitterionic surfactant, the average number of carbon atoms in the lipophilic alkyl group of the hydrophobic group constituting the surfactant is preferably 17 or less.

[0043] By setting the average carbon number of the alkyl group to 17 or less, the elution property of the surfactant into water is improved, making it easier for the sizing agent to be eluted during washing with water, and the amount of sizing agent remaining on the carbon fiber bundle can be reduced. The average carbon number of the alkyl group is more preferably 16.5 or less, and even more preferably 16 or less. Also, 8 or more is preferable. If the average carbon number is less than 8, the surface free energy of the sizing agent increases, which may increase the coefficient of friction and reduce handleability.

[0044] The average carbon number of the alkyl groups that make up a cationic or zwitterionic surfactant can be evaluated by extracting the sizing agent with water from a sizing-coated carbon fiber bundle and evaluating it. One method is to freeze-dry the extracted sizing agent and then evaluate its structure from the IR spectrum obtained by infrared spectroscopy, combining proton NMR, carbon NMR, and mass spectrometry analysis of the freeze-dried product.

[0045] Next, the components constituting the sizing agent-coated carbon fiber bundle used in the present invention will be described.

[0046] Although there are no particular limitations on the carbon fiber bundles used in the present invention, polyacrylonitrile-based carbon fibers are preferably used from the viewpoint of mechanical properties. Polyacrylonitrile-based carbon fiber bundles can be obtained by subjecting carbon fiber precursor fibers made of polyacrylonitrile-based polymers to flame retardation treatment in an oxidizing atmosphere at a maximum temperature of 200 to 300°C, followed by preliminary carbonization treatment in an inert atmosphere at a maximum temperature of 500 to 1,200°C, and then carbonization treatment in an inert atmosphere at a maximum temperature of 1,200 to 2,000°C.

[0047] The carbon fiber bundle of the present invention preferably has a strand strength of 4.0 GPa or more, more preferably 4.9 GPa or more. If the carbon fiber bundle has a strand strength of 4.0 GPa or more, the strand strength of the carbon fiber bundle after washing off the sizing agent with water is sufficiently high, and the effect of improving the mechanical properties of the composite material is likely to be obtained.

[0048] In the present invention, in order to improve the adhesion between the carbon fiber bundles and the matrix resin, it is preferable to introduce oxygen-containing functional groups onto the surfaces of the carbon fiber bundles by subjecting the carbon fiber bundles to an oxidation treatment. As the oxidation treatment method, gas phase oxidation, liquid phase oxidation, and liquid phase electrolytic oxidation are used, but liquid phase electrolytic oxidation is preferably used from the viewpoints of high productivity and enabling uniform treatment.

[0049] In the present invention, the electrolyte used in the liquid-phase electrolytic oxidation may be an acidic electrolyte or an alkaline electrolyte. Examples of acidic electrolytes 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 these, sulfuric acid and nitric acid, which exhibit strong acidity, are preferred. Examples of alkaline electrolytes 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; and aqueous solutions of ammonia, tetraalkylammonium hydroxide, and hydrazine.

[0050] The carbon fiber bundle in the present invention preferably has a surface oxygen concentration of 0.08 or more and 0.25 or less as measured by X-ray photoelectron spectroscopy.

[0051] The presence of functional groups on the carbon fiber surface creates affinity with the matrix resin, enabling high adhesive strength to be achieved. If the surface oxygen concentration (O / C) is less than 0.08, the affinity between the carbon fiber surface and the matrix resin may decrease, resulting in low adhesive strength. A surface oxygen concentration of 0.08 or higher is preferred. A concentration of 0.08 or higher is preferred because it increases the affinity between the carbon fiber surface and the matrix resin. Furthermore, an O / C of 0.25 or lower is more preferred. If the O / C exceeds 0.25, the number of functional groups increases, but the surface layer of the carbon fiber may peel off more easily, resulting in low adhesive strength.

[0052] Next, the method for producing the sizing agent-coated carbon fiber bundle of the present invention will be described.

[0053] First, the means for applying (applying) the sizing agent to the carbon fiber bundle constituting the present invention will be described.

[0054] In the present invention, the sizing agent is preferably diluted with a solvent to form a homogeneous solution, such as water, methanol, ethanol, 2-propanol, acetone, methyl ethyl ketone, dimethylformamide, and dimethylacetamide. Among these, water is preferred because of its ease of handling.

[0055] Examples of application methods include a method of immersing a carbon fiber bundle in a sizing agent solution via a roller, a method of bringing a carbon fiber bundle into contact with a roller to which the sizing agent solution is attached, and a method of spraying a mist of the sizing agent solution 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 preferred because it has good productivity and small variations. Another preferred embodiment is to ultrasonically vibrate the carbon fiber bundle when applying the sizing agent.

[0056] 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 bringing the carbon fiber bundle into contact 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 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 smaller contact area between individual fibers, which increases the contact area with water when immersed in water, making it more likely to have high elution properties. In addition, in the present invention, after passing the carbon fiber bundle through a heated roller as a preliminary drying step, a further heat treatment may be performed as a second drying step. For the heat treatment as the second drying step, a non-contact heating method is preferable, which makes it easy to perform heat treatment at a high temperature. By performing the heat treatment, the dilution solvent remaining in the sizing agent can be further removed, and the viscosity of the sizing agent can be stabilized, thereby stably increasing elution properties.

[0057] Furthermore, by carrying out this heat treatment, the surface free energy of the polyethylene glycol and / or nonionic surfactant on the carbon fiber can be controlled to reduce the coefficient of friction, thereby improving the handleability of the sizing-agent-coated carbon fiber bundle. The heat treatment temperature is preferably in the range of 120 to 260°C. At 120°C or higher, the viscosity due to the interaction of the polyethylene glycol and / or nonionic surfactant with water is reduced by removing the dilution solution, which tends to improve handleability. 150°C or higher is preferred, and 180°C or higher is more preferred. On the other hand, by setting the upper limit of the heat treatment temperature to 260°C or lower, thermal degradation of the polyethylene glycol and / or nonionic surfactant components can be suppressed, making it easier to maintain elution properties. 240°C or lower is preferred, and 220°C or lower is more preferred.

[0058] The heat treatment can also be carried out by microwave irradiation and / or infrared irradiation. [Example]

[0059] Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.

[0060] Mass loss rate W at <300℃ A Measurement conditions> 2.0±0.5 g of sizing agent-coated carbon fiber bundle was weighed (W A0 ) (read in grams to four decimal places), and then place in an electric furnace (capacity 120 cm) set to a temperature of 300°C in a nitrogen gas flow of 50 ml / min. 3 ) for 5 minutes to thermally decompose the sizing agent. Then, the carbon fiber bundle was transferred to a container in a dry nitrogen gas flow of 20 liters / minute, and after cooling for 15 minutes, the carbon fiber bundle was weighed (W A1 ) (read in g to four decimal places) and calculate the mass loss rate (W A The measurement was carried out twice, and the average value was calculated as the mass loss rate (W A ) was decided. Mass loss rate W at 300℃ A (mass%)=(WA0 -W A1 ) / W A0 ×100···(i).

[0061] <Sizing agent adhesion rate W B and measuring method for the amount of sizing agent attached> 2.0±0.5 g of sizing agent-coated carbon fiber bundle was weighed (W B0 ) (read in g to four decimal places), and then place 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 thermally decompose the sizing agent. Then, the carbon fiber bundle was transferred to a container in a dry nitrogen gas flow of 20 liters / minute, and after cooling for 15 minutes, the carbon fiber bundle was weighed (W B1 ) (read in g to four decimal places) and calculate the sizing agent adhesion rate (W B The measurement was carried out twice, and the average value was calculated as the mass loss rate (W B ) The sizing agent adhesion rate was converted into parts by mass relative to 100 parts by mass of the sizing agent-coated carbon fiber bundle (rounded to two decimal places), and the resulting value was taken as the amount of the sizing agent (parts by mass). Sizing agent adhesion rate W B (mass%)=(W B0 -W B1 ) / W B0 ×100···(i).

[0062] <W A / W B > W calculated as above A W B It was calculated by dividing by

[0063] <Method for determining the change in crystallization peak of a mixture of sizing agent extract and resin> A. Sizing agent extraction procedure One part by mass of a sizing-agent-coated carbon fiber bundle was submerged in 1,000 parts by mass of pure water at 25°C. After 60 seconds, the bundle was raised above the liquid surface and left in the air for 10 seconds to remove excess sizing agent from the carbon fiber surface. The sizing-agent-coated carbon fiber bundle was placed in a new container, 50 parts by mass of pure water at 25°C was added, and the bundle was treated for 15 minutes under ultrasonic irradiation at an oscillation frequency of 40 kHz to extract the sizing agent remaining in the sizing-agent-coated carbon fiber bundle. The resulting extract solution was concentrated to recover the solid content. For the ultrasonic treatment, a Bransonic (registered trademark) CPX5800-J tabletop ultrasonic cleaner manufactured by Yamato Scientific Co., Ltd. was used. B. Preparation of DSC measurement samples The sizing agent extract obtained by the above procedure was mixed with 0.10 parts by mass of polyether ketone ketone resin powder (KEPSTAN (registered trademark) 7002), and stirred until homogenous to prepare a sample for DSC measurement. C.DSC measurement conditions Measurement equipment: TA Instruments DSC Q2500 Aluminum pan for DSC measurement: TA Instruments Hermetic Aluminum Pan. Sample size: 3.0 mg (±0.5 mg). Measurement atmosphere: Nitrogen (purity 99.999% or more by volume) Nitrogen flow rate: 50 ml / min Measurement conditions: 1. Hold at 50°C for 1 minute 2. Heat 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°C 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 D. Evaluation Method Regarding the DSC measurement results, the peak top temperature of the crystallization peak during the cooling process in the first cycle was defined as T1, and the peak top temperature of the crystallization peak during the cooling process in the second cycle was defined as T2, and the peak top change was calculated from T1 - T2. The measurement was performed twice, and the average value was defined as the peak top change.

[0064] <How to determine the crystallization completion time of unidirectional prepreg> The unidirectional prepreg was cut into 1 mm pieces, and 10.0 mg (±0.5 mg) was weighed out and placed in an aluminum pan for DSC measurement, which was then pressed and sealed. Measurements were performed under the following measurement conditions. The time from the start of the temperature drop in the second cycle to the end of the crystallization heat generation in the temperature drop in the second cycle was taken as 0 minutes, and the time required for the crystallization heat generation in the temperature drop in the second cycle to be completely completed was taken as the crystallization completion time. The time when the crystallization was completely completed was determined by fitting the baseline to the data from 350°C to 210°C in the temperature drop process with a spline curve, and then calculating the difference between the baseline and the exothermic peak height as I. p As a result, the difference in height from the baseline to the low temperature side from the peak top is 0.02I. p The time when this happened was the point in time when this happened. A.DSC measurement conditions Measurement equipment: TA Instruments DSC Q2500 Aluminum pan for DSC measurements: TA Instruments Hermetic Aluminum Pan Sample amount: 10.0 mg (±0.5 mg) Measurement atmosphere: Nitrogen (purity 99.999% or more by volume) Nitrogen flow rate: 50 ml / min Measurement conditions: 1. Hold at 50°C for 1 minute 2. Heat from 50℃ to 380℃ at 50℃ / min 3.Hold at 380℃ for 30 minutes 4. Decrease temperature from 380°C to 50°C at 10°C / min. The measurement was carried out twice, and the average value was taken as the time to complete crystallization of the unidirectional prepreg. In the present invention, the preferable range of the crystallization completion time of the unidirectional prepreg was evaluated in three stages according to the following criteria, with ⊚ and ◯ representing pass and × representing fail. ◎: Crystallization completion time is less than 12.0 minutes ○: Crystallization completion time is 12.0 minutes or more and less than 15.0 minutes ×: Crystallization completion time is 15.0 minutes or more.

[0065] <CF Rubbing Fiber Measurement Method> Two metal bars with a diameter of 50 mm and a surface roughness Rmax of 0.3 μm (material: made of stainless steel SUS304) were arranged vertically at an interval of 150 mm, and the carbon fiber bundles passed while contacting the metal bars at a total angle of 0.785π (rad). Then, the carbon fiber bundles were passed over the metal bars, the unwinding tension from the package was set to 800 g, and the carbon fiber bundles were pulled at a speed of 6 m per minute by the driving roll to pass through the metal bars. After passing through the second metal bar, a laser beam was irradiated at a right angle from the side to the fiber yarn, and the number of fibers was detected and counted for 5 minutes by the fiber detector, and the number was recorded.

[0066] In the present invention, the preferable range of handleability was evaluated in two stages according to the following criteria, ○ was regarded as qualified, and × was regarded as unqualified. ○: Fiber less than 20 pieces / m ×: Fiber 20 pieces / m or more.

[0067] The materials and components used in each example and each comparative example are as follows.

[0068] (A) Component: Sizing agent A-1: Polyethylene glycol (PEG600 manufactured by Sanyo Chemical Industries, Ltd., HLB: 20, number average molecular weight: 600) A-2: PEG monooleate (“Ionnet (registered trademark)” MO600 manufactured by Sanyo Chemical Industries, Ltd., HLB: 13.8) A-3: PEG monostearate (“Ionnet (registered trademark)” MS1000 manufactured by Sanyo Chemical Industries, Ltd., HLB: The 15.7) A-4: PEG dioleate (Sanyo Chemical Industries, Ltd. "IONET (registered trademark)" DO600, HLB: 10.5) A-5: PEG dioleate ester (Sanyo Chemical Industries, Ltd. "IONET (registered trademark)" DO1000, HLB: 12.9) A-6: Bisphenol A ethylene oxide adduct ("Newpol (registered trademark)" BPE180, HLB: 16.2, manufactured by Sanyo Chemical Industries, Ltd.). A-7: Polyvinyl alcohol (PVA (degree of polymerization approximately 500) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). A-8: Cetyltrimethylammonium chloride (Kao Corporation's "Cotamin (registered trademark)" 60W). A-9: Dioctyl sodium sulfosuccinate ("Sunmorin (registered trademark)" OT-70 manufactured by Sanyo Chemical Industries, Ltd.) A-10: Triethylene glycol (Alfa Aesar Corporation, HLB: 20, number average molecular weight: 150).

[0069] (B): Thermoplastic resin B-1: Polyether ketone ketone (Arkema "KEPSTAN (registered trademark)" 7002).

[0070] (C): Resin dispersant C-1: Nonionic surfactant (Emulmin (registered trademark) NL-70 manufactured by Sanyo Chemical Industries, Ltd.).

[0071] This example comprises the following first to fifth steps.

[0072] First process: A process for producing carbon fiber bundles as raw materials An acrylonitrile copolymer was spun and calcined to obtain a carbon fiber bundle with a total filament count of 12,000 and a total fineness of 800 tex. The strand strength and strand modulus of this carbon fiber bundle were evaluated and found to be 5.1 GPa and 240 GPa, respectively. The carbon fiber bundle was then subjected to an electrolytic surface treatment using an aqueous ammonium bicarbonate solution as the electrolyte at an electrical charge of 80 coulombs per gram of carbon fiber bundle. The carbon fiber bundle subjected to this electrolytic surface treatment was then washed with water and dried in heated air to obtain the raw carbon fiber bundle.

[0073] Second step: A step of applying a sizing agent to the carbon fiber bundle Compound (A) (A-1) was used as the compound (A) with the composition shown in Table 1, and water was added to uniformly dissolve the compound to obtain an approximately 0.8% by mass aqueous solution. This aqueous solution was used as a sizing agent aqueous solution, and the sizing agent was applied to a surface-treated carbon fiber bundle by immersion. The bundle was then heat-treated with a hot roller at 120°C for 15 seconds as a preliminary drying step, and then heat-treated in heated air at 210°C for 60 seconds as a second drying step to obtain a sizing-agent-coated carbon fiber bundle. The amount of sizing agent attached was adjusted to 0.40 parts by mass relative to 100 parts by mass of the total amount of the surface-treated sizing-agent-coated carbon fiber bundle. Furthermore, when thermal decomposition was evaluated in this second step, W A / W B =0.51, which indicates that the thermal decomposition rate is sufficiently high.

[0074] Third step: Evaluating the handling properties of the sizing-coated carbon fiber bundles Using the sizing-coated carbon fiber bundle obtained in the second step, the handleability was evaluated based on the CF abrasion fluff measurement method. As a result, it was found that fluffing was unlikely to occur during the processing step in which the bar was present in the air and underwater, and the handleability was sufficiently good.

[0075] Fourth step: DSC evaluation Regarding the sizing agent-coated carbon fiber bundle obtained in the previous process, DSC evaluation of the mixture of the extract extracted from the carbon fiber bundle and the polyether ketone ketone resin was performed according to the <extraction conditions> and <DSC measurement conditions> described in the above columns, and the temperature difference of the crystallization peak was calculated. As a result, the temperature difference at the peak top was 11.0 °C, indicating that the influence on the crystallization behavior of the resin was sufficiently small.

[0076] ·The fifth step: The step of creating a unidirectional prepreg The sizing agent-coated carbon fiber bundle obtained in the second step was unwound from the bobbin and passed through a resin slurry in which polyether ketone ketone resin particles (KEPSTAN (registered trademark) 7002) were dispersed in a 0.50 mass% aqueous solution of a nonionic surfactant (C-1) for 1 minute to attach the resin particles. Then, it was placed in an electric furnace heated to 400 °C for 1 minute to melt the resin. Thereafter, it was sandwiched between polyimide films and pressurized at 1.0 MPa while heating at 350 °C for 2 minutes to obtain a unidirectional prepreg. The resin content of the unidirectional prepreg was 34 mass%. Using this unidirectional prepreg, according to the <method for determining the crystallization completion time of the unidirectional prepreg>, the time from the start of temperature drop to complete crystallization was measured. As a result, the crystallization completion time of the unidirectional prepreg was 13.2 minutes, indicating that the influence on the crystallization temperature of the resin was relatively small.

[0077] The above results were summarized in Tables 1 and 2.

[0078]

Table 1

[0079]

Table 2

[0080] (Example 2) A sizing-agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, except that A-2 was used as compound A in the second step, and various evaluations were carried out. The results are shown in Table 1, and it was found that the handleability was good and the effect on the crystallization temperature of the resin was relatively small.

[0081] Example 3 Except for using A-3 as compound A in the second step and changing the amount of sizing agent applied, a sizing-coated carbon fiber bundle was obtained in the same manner as in Example 1, and various evaluations were carried out. The results are shown in Table 1, and it was found that the handleability was good and the effect on the crystallization temperature of the resin was small.

[0082] Example 4 A sizing-agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, except that A-3 was used as compound A in the second step, and various evaluations were carried out. The results are shown in Table 1, and it was found that the handleability was good and the effect on the crystallization temperature of the resin was small.

[0083] Example 5 Except for using A-3 as compound A in the second step and changing the amount of sizing agent applied, a sizing-agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, and various evaluations were carried out. The results are shown in Table 1, and it was found that the handleability was good and the effect on the crystallization temperature of the resin was relatively small.

[0084] Example 6 A sizing-agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, except that A-4 was used as compound A in the second step, and various evaluations were carried out. The results are shown in Table 1, and it was found that the handleability was good and the effect on the crystallization temperature of the resin was relatively small.

[0085] Example 7 Except for using A-5 as compound A in the second step and changing the amount of sizing agent applied, a sizing-agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, and various evaluations were carried out. The results are shown in Table 1, and it was found that the handleability was good and the effect on the crystallization temperature of the resin was small.

[0086] Example 8 A sizing-agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, except that A-5 was used as compound A in the second step, and various evaluations were carried out. The results are shown in Table 1, and it was found that the handleability was good and the effect on the crystallization temperature of the resin was relatively small.

[0087] Example 9 A sizing-agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, except that A-6 was used as compound A in the second step, and various evaluations were carried out. The results are shown in Table 1, and it was found that the handleability was good and the effect on the crystallization temperature of the resin was relatively small.

[0088] Example 10 A sizing-agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, except that A-8 was used as compound A in the second step, and various evaluations were carried out. The results are shown in Table 1, and it was found that the handleability was good and the effect on the crystallization temperature of the resin was small.

[0089] Example 11 A sizing-agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, except that A-9 was used as compound A in the second step, and various evaluations were carried out. The results are shown in Table 1, and it was found that the handleability was good and the effect on the crystallization temperature of the resin was small.

[0090] Example 12 A sizing-agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, except that A-10 was used as compound A in the second step and the second drying step was not performed, and various evaluations were carried out. The results are shown in Table 1, and it was found that the handleability was good and the effect on the resin was extremely small.

[0091] (Comparative Example 1) Except for using A-3 as compound A in the second step and changing the amount of sizing agent applied, a sizing-agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, and various evaluations were carried out. The results are shown in Table 2, and it was found that the effect on the resin crystallization temperature was small, but the handleability was poor.

[0092] (Comparative Example 2) A sizing agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, except that A-3 was used as compound A in the second step and the amount of sizing agent applied was changed, and various evaluations were performed. The results are shown in Table 2, and it was found that the handleability was good, but the effect on the crystallization temperature of the resin was large.

[0093] (Comparative Example 3) Except for using A-5 as compound A in the second step and changing the amount of sizing agent applied, a sizing-agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, and various evaluations were carried out. The results are shown in Table 2, and it was found that the effect on the resin crystallization temperature was small, but the handleability was poor.

[0094] Comparative Example 4 A sizing-agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, except that A-5 was used as compound A in the second step and the amount of sizing agent applied was changed, and various evaluations were performed. The results are shown in Table 2, and it was found that the handleability was good, but the effect on the crystallization temperature of the resin was large.

[0095] (Comparative Example 5) A sizing-agent-coated carbon fiber bundle was obtained in the same manner as in Example 1, except that A-7 was used as compound A in the second step, and various evaluations were carried out. The results are shown in Table 2, and it was found that the handleability was good, but the effect on the crystallization temperature of the resin was large.

Claims

1. A sizing-agent-coated carbon fiber bundle having a sizing agent adhesion amount of 0.15 parts by mass or more and 1.00 parts by mass or less per 100 parts by mass of the sizing-agent-coated carbon fiber bundle, wherein when a mixture of an extract extracted from 1 part by mass of the sizing-agent-coated carbon fiber by the extraction operation described below and 0.10 parts by mass of a polyether ketone ketone resin (KEPSTAN (registered trademark 7002)) is subjected to differential scanning calorimetry (DSC measurement) under the conditions shown below, the sizing-agent-coated carbon fiber bundle has a temperature difference of 13°C or less between the peak tops of the crystallization peak in the cooling process of the first cycle and the crystallization peak in the second cycle. <Extraction operation> One part by mass of a carbon fiber bundle coated with a sizing agent is submerged in 1,000 parts by mass of pure water at 25° C., and after 60 seconds has passed, it is pulled up above the liquid surface and left to stand in the air for 10 seconds. The sizing-agent-coated carbon fiber bundle is placed in a new container, and 50 parts by mass of pure water at 25°C is added, followed by treatment for 15 minutes under ultrasonic irradiation at an oscillation frequency of 40 kHz to extract the sizing agent remaining in the sizing-agent-coated carbon fiber bundle, and the obtained extract solution is concentrated to recover the solid content. <DSC measurement conditions> Sample amount: 3.0 mg (±0.5 mg) Measurement atmosphere: nitrogen (purity 99.999% by volume or more) Measurement conditions:

1. Hold at 50°C for 1 minute 2. Heat from 50°C to 380°C at 50°C / min 3. Hold at 380°C for 3 minutes 4. Decrease temperature from 380°C to 50°C at 10°C / min 5. Hold at 50°C for 1 minute 6. Heat from 50°C to 380°C at 50°C / min 7. Hold at 380°C for 30 minutes 8. Decrease temperature from 380°C to 50°C at 10°C / min

2. The mass loss rate W at 300 ° C. obtained under the following measurement conditions is the sizing agent-coated carbon fiber bundle. Ａ and the sizing agent adhesion rate W Ｂ The ratio (W Ａ / W Ｂ 2. The sizing-agent-coated carbon fiber bundle according to claim 1, wherein the sizing agent-coated carbon fiber bundle has a sizing agent-coated bond strength of 0.3 or more and 1.0 or less. < Mass loss rate W at 300°C Ａ Measurement conditions> 2.0±0.5 g of the sizing agent-coated carbon fiber bundle was weighed (W Ａ０ ) (read to four decimal places), and then place in an electric furnace (capacity 120 cm) set to a temperature of 300°C in a nitrogen gas flow of 50 ml / min. ３ ) for 5 minutes to thermally decompose the sizing agent. Then, the carbon fiber bundle was transferred to a container in a dry nitrogen gas flow of 20 liters / minute, and cooled for 15 minutes, after which the carbon fiber bundle was weighed (W Ａ１ ) (read to four decimal places) and calculate the mass loss rate (W Ａ ) is calculated. Mass loss rate W at 300 ° C Ａ (mass%) = (W Ａ０ -W Ａ１ ) / W Ａ０ × 100 (i) <Sizing agent adhesion rate (W Ｂ ) Measurement method > 2.0±0.5 g of the sizing agent-coated carbon fiber bundle was weighed (W Ｂ０ ) (read to four decimal places), and then place 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 thermally decompose the sizing agent. Then, the carbon fiber bundle was transferred to a container in a dry nitrogen gas flow of 20 liters / minute, and after cooling for 15 minutes, the carbon fiber bundle was weighed (W Ｂ１ ) (read to four decimal places) and calculate the sizing agent adhesion rate (W Ｂ ) is calculated. Sizing agent adhesion rate W Ｂ (mass%) = (W Ｂ０ -W Ｂ１ ) / W Ｂ０ ×100...(ii)

3. The sizing agent-coated carbon fiber bundle according to claim 1 or 2, wherein the sizing agent contains polyalkylene glycol and / or a surfactant.

4. The sizing-agent-coated carbon fiber bundle according to claim 3, wherein the total amount of the polyalkylene glycol and / or surfactant is 70 parts by mass or more relative to 100 parts by mass of the total amount of the sizing agent.

5. 5. The sizing-agent-coated carbon fiber bundle according to claim 3, wherein the surfactant does not contain an aromatic compound.

6. The sizing agent-coated carbon fiber bundle according to any one of claims 3 to 5, wherein the surfactant satisfies any one of the following (iii) to (v): (iii) The surfactant is a nonionic surfactant and has an HLB of 15 or more and 20 or less. (iv) The surfactant is an anionic surfactant, and the ratio of hydrophilic groups in the ions constituting the anionic surfactant is 17% or more. (v) The surfactant is a cationic surfactant or an amphoteric surfactant, and the number of carbon atoms in the lipophilic alkyl group constituting the surfactant is 17 or less.

7. A sizing-agent-coated carbon fiber bundle having a sizing agent adhesion amount of 0.20 parts by mass or more and 0.80 parts by mass or less per 100 parts by mass of the sizing-agent-coated carbon fiber bundle, wherein when a mixture of an extract extracted from 1 part by mass of the sizing-agent-coated carbon fiber by the extraction operation described below and 0.10 parts by mass of a polyether ketone ketone resin (KEPSTAN (registered trademark 7002)) is subjected to differential scanning calorimetry (DSC measurement) under the conditions shown below, the sizing-agent-coated carbon fiber bundle has a temperature difference of 10°C or less between the peak top of the crystallization peak in the cooling process of the first cycle and the peak top of the crystallization peak in the second cycle. <Extraction operation> One part by mass of a carbon fiber bundle coated with a sizing agent is submerged in 1,000 parts by mass of pure water at 25° C., and after 60 seconds has passed, it is pulled up above the liquid surface and left to stand in the air for 10 seconds. The sizing-agent-coated carbon fiber bundle is placed in a new container, and 50 parts by mass of pure water at 25°C is added, followed by treatment for 15 minutes under ultrasonic irradiation at an oscillation frequency of 40 kHz to extract the sizing agent remaining in the sizing-agent-coated carbon fiber bundle, and the obtained extract solution is concentrated to recover the solid content. <DSC measurement conditions> Sample amount: 3.0 mg (±0.5 mg) Measurement atmosphere: nitrogen (purity 99.999% by volume or more) Measurement conditions:

1. Hold at 50°C for 1 minute 2. Heat from 50°C to 380°C at 50°C / min 3. Hold at 380°C for 3 minutes 4. Decrease temperature from 380°C to 50°C at 10°C / min 5. Hold at 50°C for 1 minute 6. Heat from 50°C to 380°C at 50°C / min 7. Hold at 380°C for 30 minutes 8. Decrease temperature from 380°C to 50°C at 10°C / min

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