WO2024128171A1 - Sizing agent-attached carbon short fiber - Google Patents

Sizing agent-attached carbon short fiber Download PDF

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WO2024128171A1
WO2024128171A1 PCT/JP2023/044154 JP2023044154W WO2024128171A1 WO 2024128171 A1 WO2024128171 A1 WO 2024128171A1 JP 2023044154 W JP2023044154 W JP 2023044154W WO 2024128171 A1 WO2024128171 A1 WO 2024128171A1
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carbon fiber
sizing agent
attached
short fibers
fiber short
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PCT/JP2023/044154
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French (fr)
Japanese (ja)
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裕貴 鈴木
秀和 吉川
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帝人株式会社
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  • the present invention relates to carbon fiber short fibers with a sizing agent attached thereto and a method for producing the same.
  • the present invention relates to carbon fiber short fibers with a sizing agent attached thereto for use in compounds and a method for producing the same.
  • Carbon fiber has excellent specific strength and specific modulus of elasticity, and is lightweight, so it is used as a reinforcing fiber for thermosetting and thermoplastic resins in a wide range of applications, including aircraft, sports and leisure, and general industry. As its applications expand, even higher performance is required of carbon fiber reinforced composite materials (CFRP, hereafter also referred to as composites).
  • CFRP carbon fiber reinforced composite materials
  • a compound having a resin and carbon fibers dispersed in the resin can be used.
  • a carbon fiber reinforced composite material can be manufactured by melting a pellet-shaped compound (pellets) and injection molding it.
  • the carbon fiber reinforced composite material formed from the compound has a structure in which the carbon fibers are dispersed in the resin, unlike a material that is made by impregnating a sheet of carbon fibers aligned in one direction with resin.
  • Such pellets can be produced, for example, by kneading short carbon fibers with resin and extruding the mixture.
  • a sizing agent is applied to the carbon fiber for the purposes of improving the processability of the carbon fiber and improving the affinity between the carbon fiber and the matrix resin in the composite material.
  • Patent Document 1 describes a sizing agent for inorganic fibers that contains an ester of a specific carboxylic acid component and a specific alcohol component.
  • Patent Document 2 describes a sizing agent that contains at least a polyoxyalkylene group and an epoxy group.
  • Patent document 3 describes a sizing agent for carbon fiber bundles that contains an aliphatic epoxy resin.
  • Patent Document 4 describes a carbon fiber bundle having a sizing agent attached thereto, and describes that the sizing agent contains an aromatic thermoplastic resin having a softening point in the range of 80 to 200° C. and an aromatic diester.
  • Patent Document 5 describes a sizing agent that contains an amine adduct, which is a reaction product of an epoxy compound and an amine compound, and polyurethane.
  • Patent document 6 discloses a carbon fiber bundle having a specific range of friction coefficient, amount of oxygen-containing functional groups on the carbon fiber surface, and tensile strength and elastic modulus of the strand. This document describes the purpose of the invention as improving the composite properties of carbon fibers.
  • Patent document 7 describes carbon fibers that exhibit specific ranges of average single fiber tensile strength, resin-impregnated strand tensile strength, fiber friction coefficient, and amount of pyrolyzable organic matter. This document describes the object of the invention as being to provide carbon fibers that exhibit ultra-high strength composite properties.
  • composites can be manufactured using short carbon fibers.
  • a sizing agent can be applied to the short carbon fibers to form short carbon fibers with a sizing agent attached.
  • Composites manufactured using conventional carbon fiber short fibers with sizing agents applied may not be able to obtain sufficient mechanical properties such as strength, and in particular, carbon fiber reinforced composite materials formed from compounds with a relatively high carbon fiber content may not be able to obtain sufficient mechanical properties.
  • the present disclosure aims to provide a sizing-adhered carbon fiber short fiber that provides improved composite strength.
  • the present disclosure aims to provide a sizing-adhered carbon fiber short fiber that can achieve improved strength in a carbon fiber reinforced composite material formed from a compound and having a relatively high fiber content.
  • a sizing-agent-attached carbon fiber short fiber having a carbon fiber short fiber and a sizing agent attached to the carbon fiber short fiber In the elastic modulus distribution measured by a scanning probe microscope on the surface of the sizing agent-attached carbon fiber short fibers, the proportion of a portion showing an elastic modulus of 30 MPa or more is 90% or more, and the proportion of a portion showing an elastic modulus of 5000 MPa or less is 90% or more. Carbon fiber short fibers with sizing agent attached.
  • ⁇ Aspect 6> The carbon fiber short fibers having a sizing agent attached thereto according to any one of aspects 1 to 5, wherein the amount of thermal decomposition when heat-treated at 400° C. in air for 20 minutes is 0.50% or less based on the total weight of the carbon fiber short fibers having a sizing agent attached thereto.
  • ⁇ Aspect 7> The sizing-agent-attached carbon fiber short fibers according to any one of aspects 1 to 6, wherein the average length of the sizing-agent-attached carbon fiber short fibers is 1 mm to 25 mm.
  • ⁇ Aspect 8> The sizing agent-attached carbon fiber short fiber according to any one of aspects 1 to 7, wherein the single fiber diameter of the carbon fiber short fiber is 4 to 8 ⁇ m.
  • ⁇ Aspect 9> The carbon fiber short fibers having a sizing agent attached thereto according to any one of aspects 1 to 8, wherein the carbon fiber short fibers are formed from carbon fibers exhibiting a tensile modulus of elasticity of 245 GPa or more.
  • ⁇ Aspect 10> A carbon fiber short fiber having a sizing agent attached thereto according to any one of aspects 1 to 9, for use in a carbon fiber reinforced composite material.
  • ⁇ Aspect 11> The sizing agent-attached carbon fiber short fiber according to aspect 10, wherein the fiber volume content of the carbon fiber in the carbon fiber reinforced composite material is 20 volume% to 55 volume%.
  • ⁇ Aspect 12> Providing a carbon fiber short fiber; and Applying a sizing agent composition to the surface of the carbon fiber short fibers; A method for producing carbon fiber short fibers with a sizing agent, comprising: The O/C ratio of the surface of the carbon fiber short fiber is 15% to 30%, and The sizing agent composition contains a water-soluble resin or a granular resin having an average particle size of 0.3 ⁇ m or less. Method.
  • ⁇ Aspect 13> The method of claim 12, wherein the sizing composition comprises a water-soluble resin.
  • ⁇ Aspect 14> Providing a sizing agent-attached carbon fiber short fiber according to any one of aspects 1 to 11; and kneading and extruding the sizing agent-attached carbon fiber short fibers and a resin to form a compound; A method for producing a compound comprising: ⁇ Aspect 15> 15. The method of claim 14, wherein the compound is in pellet form.
  • ⁇ Aspect 16> Producing a compound by the method of claim 14 or 15; and molding the compound to form a carbon fiber reinforced composite material.
  • a method for producing a carbon fiber reinforced composite material comprising:
  • the present invention provides carbon fiber short fibers with a sizing agent attached thereto, which can provide improved composite strength.
  • the present invention provides carbon fiber short fibers with a sizing agent attached thereto, which can achieve improved strength in carbon fiber reinforced composite materials formed from compounds and having a relatively high fiber content.
  • FIG. 1 is an image showing the elastic modulus distribution on the surface of the carbon fiber short fibers to which a sizing agent was applied according to Example 8, obtained by measurement using a scanning probe microscope.
  • 2 is a graph showing the distribution of elastic modulus on the surface of the sizing-agent-attached carbon fiber short fibers according to Example 8, obtained by measurement using a scanning probe microscope.
  • the vertical axis shows the frequency
  • the horizontal axis shows the elastic modulus (GPa).
  • the carbon fiber short fibers having a sizing agent attached thereto have carbon fiber short fibers and a sizing agent attached to the carbon fiber short fibers, and in the elastic modulus distribution measured by a scanning probe microscope on the surface of the carbon fiber short fibers having a sizing agent attached thereto, the proportion of portions exhibiting an elastic modulus of 30 MPa or more is 90% or more, and the proportion of portions exhibiting an elastic modulus of 5000 MPa or less is 90% or more.
  • the inventors have discovered that by optimizing the distribution of elastic modulus on the surface of sizing-agent-attached carbon fiber short fibers, it is possible to provide sizing-agent-attached carbon fiber short fibers that can result in carbon fiber reinforced composite materials with improved tensile strength.
  • carbon fiber raw material such as chopped fiber
  • a resin composition such as acrylic resin
  • pelletized such as chopped fiber
  • the carbon fiber short fiber raw material may break, and as a result, the desired physical properties such as tensile strength of the composite material may not be obtained.
  • TS tensile strength
  • the proportion of the portion showing an elastic modulus of 5000 MPa or less is 90% or more in the elastic modulus distribution when measured by a scanning probe microscope on the surface of the carbon fiber short fiber with a sizing agent attached.
  • the distribution of the sizing agent on the carbon fiber surface is relatively uniform, which is believed to result in the carbon fiber surface being sufficiently coated and resulting in a large portion of the surface being relatively elastic. Because a relatively wide area of the carbon fiber surface is covered with the sizing agent and is highly elastic, it is believed that fiber breakage caused by contact between carbon fibers during the compounding process is suppressed.
  • the residual fiber length of the carbon fibers in the carbon fiber reinforced composite material becomes relatively large, which in turn makes it possible to obtain a carbon fiber reinforced composite material with a relatively high aspect ratio and, as a result, to obtain a carbon fiber reinforced composite material with improved strength.
  • the proportion of the portion showing an elastic modulus of 30 MPa or more is 90% or more in the elastic modulus distribution when measured by a scanning probe microscope on the surface of the carbon fiber short fiber with the sizing agent attached thereto.
  • the proportion of the portion showing an elastic modulus of 30 MPa or more being 90% or more, good heat resistance of the carbon fiber short fiber with the sizing agent attached thereto can be ensured.
  • the elasticity of the carbon fiber surface can be improved by increasing the amount of sizing agent attached thereto, but if the amount of sizing agent is too large, it is thought that there is an increased risk of generation of decomposition gas due to the sizing agent during the manufacturing process of the compound and/or composite.
  • the surface portion with a relatively low elastic modulus is reduced, which is thought to reflect the reduction in the surface portion to which the sizing agent is excessively attached.
  • the carbon fiber short fibers with sizing agent according to the present invention are believed to be particularly useful for producing carbon fiber reinforced composite materials with a relatively high fiber content (particularly a fiber volume content of 20 to 55% by volume).
  • a relatively high fiber content particularly a fiber volume content of 20 to 55% by volume.
  • the fibers according to the present invention even in such cases, fiber breakage can be suppressed and relatively long fibers can remain, resulting in excellent composite strength.
  • the sizing agent-adhered carbon fiber short fibers according to the present disclosure are preferably sizing agent-adhered carbon fiber short fibers for use in carbon fiber reinforced composite materials having a fiber volume content of the carbon fibers of 20 volume % to 55 volume %, 25 volume % to 50 volume %, or even 30 volume % to 40 volume %.
  • the elastic modulus of the surface of the sizing agent-attached short carbon fibers can be measured by a scanning probe microscope (SPM).
  • FIG. 2 is a graph (histogram) showing the elastic modulus distribution on the surface of the carbon fiber short fiber with a sizing agent attached according to Example 8, obtained by measurement using a scanning probe microscope.
  • the vertical axis shows the frequency
  • the horizontal axis shows the elastic modulus (GPa).
  • the proportion of the parts showing an elastic modulus of 30 MPa or more is 92% or more, 94% or more, 96% or more, or even 98% or more, and/or the proportion of the parts showing an elastic modulus of 5000 MPa or less (preferably 4000 MPa or less, more preferably 3000 MPa or less, even more preferably 2000 MPa or less, and particularly preferably 1000 MPa or less) is 92% or more, 94% or more, 96% or more, or even 98% or more.
  • the elastic modulus of the surface of the carbon fiber not coated with a sizing agent is generally 10,000 to 30,000 MPa or more.
  • the average elastic modulus (number average value) on the surface of the carbon fiber short fibers with a sizing agent attached thereto is in the range of 30 MPa to 3,000 MPa, more preferably in the range of 100 MPa to 2,000 MPa, and even more preferably in the range of 400 MPa to 1,000 MPa, when measured by a scanning probe microscope.
  • This average elastic modulus can be obtained by averaging the elastic moduli measured at 10,000 or more locations using a scanning probe microscope.
  • the carbon fiber short fibers with a sizing agent according to the present invention have a carbon fiber short fiber and a sizing agent attached to the carbon fiber short fiber.
  • the carbon fiber short fibers with a sizing agent according to the present invention are composed of a carbon fiber short fiber and a sizing agent attached to the carbon fiber short fiber.
  • the sizing agent is usually attached to the surface of the carbon fiber short fiber.
  • the average length of the carbon fiber short fibers with sizing agent attached may be 0.5 mm to 30 mm. This average length is preferably 1 mm to 25 mm, and more preferably 2 mm to 15 mm.
  • the average length of the carbon fiber short fibers with a sizing agent attached can be determined by measuring the lengths of 30 or more carbon fiber short fibers with a sizing agent attached using a vernier caliper and/or an optical microscope and calculating the average value from these measurements.
  • sizing agent means components that remain on the carbon fibers after the sizing agent composition is applied to the carbon fibers and dried, and these may be solid or liquid.
  • the ratio of the sizing agent to the carbon fiber short fibers is 0.6% by mass to 5.0% by mass, preferably 0.7% by mass to 4.0% by mass, more preferably 0.8% by mass to 3.3% by mass.
  • the surface elasticity of the carbon fiber to which the sizing agent is attached can be improved, and the coverage and uniformity of the elastic layer (layer formed by the sizing agent) on the surface of the carbon fiber to which the sizing agent is attached can also be improved.
  • resins with relatively high melting points e.g., PEEK
  • PEEK resins with relatively high melting points
  • gas may be generated due to the sizing agent as a result of exposure to high temperatures (e.g., 320°C or higher, or even 360°C or higher, or 400°C or higher) during the production process of the pellets and/or molded products. This may, for example, contaminate the mold used in injection molding.
  • the generated gas may decompose the resin into smaller molecules.
  • the sizing agent is made of polyimide resin, and the ratio of polyimide resin to the carbon fiber short fibers is 0.6% by mass to 5.0% by mass. This ratio is preferably 0.7% by mass to 4.0% by mass, and more preferably 0.8% by mass to 3.3% by mass.
  • the mass of sizing agent attached to short carbon fiber can be measured according to JIS R7604 method (Method B).
  • the amount of thermal decomposition when the sizing-agent-attached carbon fiber short fibers are heat-treated at 400° C. in air for 20 minutes is 0.50% or less based on the total weight of the sizing-agent-attached carbon fiber short fibers.
  • gas generation is suppressed when the carbon fiber short fibers with sizing agent attached are subjected to high-temperature treatment (for example, high-temperature treatment at 300°C or higher or 350°C or higher), so a composite material with particularly good quality is obtained.
  • high-temperature treatment for example, high-temperature treatment at 300°C or higher or 350°C or higher
  • This 400°C decomposition amount range can be achieved, for example, by reducing the amount of sizing agent attached to the carbon fiber short fibers.
  • This 400°C decomposition amount can be measured using a muffle furnace. Specifically, the 400°C decomposition amount is the weight loss rate when 1 g of carbon fiber short fibers with sizing agent attached is heat-treated for 20 minutes in a muffle furnace (in air) set at 400°C.
  • This 400°C decomposition amount is more preferably 0.40% or less, 0.30% or less, 0.20% or less, or even 0.10% or less, based on the total weight of the carbon fiber short fibers with the sizing agent attached.
  • the lower limit of this 400°C decomposition amount is not particularly limited, but may be, for example, 0.01% or more, 0.05% or more, or 0.08% or more.
  • the average thickness of the sizing layer (average thickness of the sizing agent) of the carbon fiber short fibers to which a sizing agent is attached may be 5 to 100 nm.
  • the average thickness of the sizing layer is preferably 10 to 60 nm, more preferably 12 to 40 nm, and even more preferably 14 to 30 nm.
  • This average thickness of the sizing agent attached to the carbon fiber short fibers with sizing agent attached can be obtained by averaging the values measured for 30 or more carbon fibers using cross-sectional images perpendicular to the fiber axis direction of the carbon fibers obtained using a transmission electron microscope (TEM).
  • TEM transmission electron microscope
  • the sizing agent includes a water-soluble resin and/or a granular resin having an average particle size of 0.3 ⁇ m or less.
  • the sizing agent includes a water-soluble resin.
  • the sizing agent includes the water-soluble resin and/or the granular resin having an average particle size of 0.3 ⁇ m or less in a proportion of 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more, particularly 100% by mass, based on the total mass of the sizing agent.
  • the sizing agent contains polyimide or blocked isocyanate (particularly polyimide) in a proportion of 70 mass% or more, 80 mass% or more, 90 mass% or more, 95 mass% or more, or 99 mass% or more, and particularly 100 mass% of the polyimide or blocked isocyanate, based on the total mass of the sizing agent.
  • the sizing agent can be attached to the carbon fibers, for example, by applying a liquid sizing agent composition to the carbon fibers (e.g., by dipping). In this case, if a sizing agent composition with a relatively high viscosity is used, there is a risk that the amount of sizing agent attached to the carbon fibers will be excessively large.
  • the sizing agent is a water-soluble resin and/or a granular resin with an average particle size of 0.3 ⁇ m or less
  • the viscosity of the aqueous solution or aqueous dispersion as the sizing agent composition used to attach the sizing agent can be relatively suppressed, and it is therefore believed that the amount of sizing agent attached to the carbon fibers can be suppressed.
  • Water-soluble resins include, but are not limited to, polyimide precursors and polyester resins. These resins can be applied to carbon fiber short fibers in the form of an aqueous solution, for example.
  • Resins constituting granular resins having an average particle size of 0.3 ⁇ m or less include, but are not limited to, polyurethane resins, epoxy resins, blocked isocyanates, etc. These resins can be applied to carbon fiber short fibers, for example, in the form of an emulsion.
  • the lower limit of this average particle size is not particularly limited, but may be, for example, 0.01 ⁇ m or more, 0.05 ⁇ m or more, or 0.1 ⁇ m or more.
  • the average particle size of the granular resin can be determined as the D50 particle size using a particle size distribution analyzer.
  • the sizing agent preferably contains a polyimide resin, and in particular consists of a polyimide resin.
  • Polyimide resins are polymers containing repeating units with imide bonds. Polyimide resins are particularly aromatic polyimide resins. Polyimide resins can be obtained, for example, by a method including polycondensation of tetracarboxylic dianhydrides and diamines in a solvent.
  • the polyimide resin according to the present disclosure is preferably a polyimide (particularly an aromatic polyimide) that does not have a melting point and has a thermal decomposition temperature of 400°C or higher (particularly 450°C or higher).
  • the melting point of a resin such as a polyimide can be measured as the temperature at the apex of the melting peak when the temperature is increased at 10°C/min in a nitrogen atmosphere by DSC (differential scanning calorimetry) according to JIS K7121.
  • the thermal decomposition temperature can be measured in a nitrogen atmosphere at a temperature increase rate of 10°C/min by TG (thermogravimetry) according to JIS K7120.
  • the polyimide resin may be obtained by applying an aqueous solution containing a polyimide precursor compound (or a mixture thereof) to carbon fibers, followed by imidization by drying at a predetermined temperature.
  • Carbon fiber short fiber examples include chopped carbon fibers and milled fibers.
  • Chopped carbon fibers can be obtained, for example, by cutting carbon fiber tows.
  • Milled fibers can be obtained, for example, by grinding chopped carbon fibers with a grinder. Milled fibers often have an average length of 0.2 mm or less.
  • the carbon fiber short fibers are particularly chopped carbon fibers.
  • Chopped carbon fibers can be obtained, for example, by cutting a bundle of continuously produced carbon fibers to a certain length. The cutting may be performed by a known method.
  • the O/C ratio (ratio of O atoms to C atoms) on the surface of the carbon fiber short fibers is preferably 15% to 30% (which may also be expressed as 0.15 to 0.30). This O/C ratio is more preferably 18% to 29%, further preferably 20% to 28%, and most preferably 21% to 27%. In this case, the adhesion of the sizing agent to the carbon fibers is optimized.
  • a water-soluble resin or a granular resin having an average particle size of 0.3 ⁇ m or less is used as the sizing agent, uniform distribution of the sizing agent on the carbon fiber surface can be ensured. That is, when a sizing agent is applied to carbon fibers, if an aqueous solution or dispersion of a water-soluble resin or a granular resin having an average particle size of 0.3 ⁇ m or less is used as the sizing agent composition, it may not be easy to uniformly apply the sizing agent to the carbon fiber surface due to relatively low viscosity.
  • the O/C ratio of the surface of the carbon fiber short fiber is within the above range, the wettability of the sizing agent to the carbon fiber surface is improved, so it is considered that uniform distribution of the sizing agent on the carbon fiber surface can be achieved even if an aqueous solution or dispersion of a water-soluble resin or a granular resin having an average particle size of 0.3 ⁇ m or less is used as the sizing agent composition.
  • the O/C ratio of the surface of the carbon fiber short fiber is 15% to 30%
  • the sizing agent includes a water-soluble resin or includes a granular resin having an average particle size of 0.3 ⁇ m or less, and in particular, the sizing agent includes a water-soluble resin.
  • the O/C ratio on the surface of short carbon fiber can be determined by X-ray photoelectron spectroscopy (XPS) on the surface of carbon fiber from which the sizing agent has been removed using an appropriate solvent, etc.
  • XPS X-ray photoelectron spectroscopy
  • the carbon fiber short fibers preferably exhibit a tensile modulus (strand modulus) of 230 GPa or more.
  • This strand modulus is more preferably 240 GPa or more, or even 245 GPa or more, and even more preferably 260 GPa or more, 270 GPa or more, or even 280 GPa or more.
  • the upper limit of this tensile modulus may be, for example, 400 GPa or less, 350 GPa or less, or 300 GPa or less.
  • This tensile modulus (strand modulus) can be measured in accordance with JIS R 7608.
  • the short carbon fibers may have a single fiber diameter of 3 to 10 ⁇ m.
  • the carbon fiber short fibers preferably have a single fiber diameter of 4 ⁇ m to 8 ⁇ m, and more preferably 4.5 to 6.5 ⁇ m.
  • a composite material with particularly good physical properties can be obtained.
  • the aspect ratio of the carbon fibers in the composite material can be made relatively large, and as a result, it is believed that a composite material exhibiting particularly good tensile strength can be obtained.
  • the single fiber diameter of carbon fibers can be obtained by averaging the diameters of 30 or more carbon fibers measured using images obtained using an electron microscope, etc.
  • the carbon fiber is not particularly limited, and may be any carbon fiber such as pitch-based, rayon-based, polyacrylonitrile (PAN)-based, etc., but acrylonitrile-based carbon fiber is preferred in terms of operability, processability, mechanical strength, etc.
  • PAN polyacrylonitrile
  • the fineness, strength, and other properties of the carbon fiber are also not particularly limited, and any known carbon fiber can be used without limitation.
  • the form of the carbon fiber is not particularly limited, but may be in the form of a carbon fiber bundle composed of multiple single threads (filaments).
  • the number of filaments constituting the carbon fiber bundle is preferably 1,000 to 80,000, and more preferably in the range of 3,000 to 50,000.
  • the tensile strength of the carbon fiber is 4,000 to 10,000 MPa when measured according to JIS R 7608.
  • PAN-based carbon fibers can be produced, for example, by the following method.
  • the acrylic precursor fiber is produced by spinning a spinning solution containing 90% by mass or more, more preferably 95% by mass or more, of acrylonitrile and 10% by mass or less of other monomers, which is either homopolymerized or copolymerized.
  • other monomers include itaconic acid and (meth)acrylic acid esters.
  • the precursor fiber can be obtained by washing, drying, stretching, and oiling the raw fiber after spinning. In terms of production efficiency, the number of filaments of the precursor fiber is preferably 1,000 or more, more preferably 3,000 or more.
  • the precursor fiber is heated in heated air at 200 to 300° C. for 10 to 100 minutes for flame retardation treatment.
  • the fiber is preferably stretched at a stretch ratio in the range of 0.90 to 1.20.
  • the flame-retardant treated precursor fiber is carbonized at 300 to 2000° C. in an inert atmosphere to obtain carbon fiber.
  • a graphitization treatment may be further carried out at a high temperature of 2000 to 3000° C.
  • the carbon fiber obtained above is preferably subjected to a surface oxidation treatment in order to improve wettability with a sizing agent and/or a matrix resin.
  • the surface oxidation treatment can be performed by any conventionally known method, but electrolytic oxidation is generally used industrially because the apparatus is simple and the process is easy to control.
  • the amount of electricity used in the surface oxidation treatment is preferably in the range of 10 to 150 coulombs per gram of carbon fiber. By adjusting the amount of electricity within this range, it is possible to obtain carbon fiber that has excellent mechanical properties as a fiber and improved adhesion to resin.
  • electrolyte examples include nitric acid, sulfuric acid, ammonium sulfate, and sodium bicarbonate.
  • the electrolyte concentration of the electrolyte is preferably 0.1N or more, and more preferably 0.1 to 1N.
  • the sizing agent-attached carbon fiber short fibers satisfying the surface elastic modulus characteristics according to the present invention can be obtained, for example, by optimizing the type of sizing agent, the form of the sizing agent composition when the sizing agent is applied (aqueous solution, dispersion, etc.), and/or the surface properties (particularly the O/C ratio) of the carbon fibers to which the sizing agent is applied.
  • the method for producing the sizing agent-attached carbon fiber short fibers according to the present disclosure is not particularly limited, but it is preferable to produce them according to the following production method according to the present disclosure.
  • the sizing agent composition contains a water-soluble resin or a granular resin having an average particle size of 0.3 ⁇ m or less, and in particular, the sizing agent composition contains a water-soluble resin.
  • the manufacturing method according to the present disclosure includes providing carbon fiber short fibers (fiber providing step, step a).
  • carbon fiber short fibers (particularly chopped carbon fibers) are provided.
  • the carbon fiber short fibers preferably have an average length of 0.5 mm to 30 mm, more preferably 1 mm to 25 mm, and even more preferably 2 mm to 15 mm.
  • chopped carbon fibers can be obtained as short carbon fiber fibers by cutting the continuously produced carbon fiber bundles with a cutter or the like.
  • the short carbon fiber fibers provided in this process may form an aggregate, for example, a chip-shaped aggregate.
  • the carbon fiber short fibers may be bonded to each other via a sizing agent or the like applied during the carbon fiber manufacturing process.
  • the aggregate of carbon fiber short fibers can be opened at will to separate the carbon fiber short fibers from each other.
  • the sizing agent according to the present disclosure can be applied to the carbon fiber short fibers thus opened.
  • the method of opening is not particularly limited, and a known method can be used.
  • the carbon fiber short fibers used in the manufacturing method of the present disclosure are characterized in that the O/C ratio of their surface is 15% to 30%.
  • the O/C ratio of their surface is 15% to 30%.
  • the manufacturing method according to the present disclosure includes applying a sizing agent composition to the surface of the carbon fiber short fibers (a sizing agent applying step, step b).
  • a sizing agent applying step for example, the sizing agent can be applied by contacting the carbon fiber short fibers with a sizing agent composition containing the sizing agent.
  • Specific examples include an immersion method in which the carbon fibers are directly immersed in the sizing agent composition, and a spray method in which the sizing agent composition is sprayed onto the carbon fibers.
  • drying treatment After the sizing agent application step, a drying treatment can be further carried out to remove the solvent and the dispersion medium contained in the sizing agent composition. This drying treatment can be carried out by a known method.
  • the sizing agent composition includes a sizing agent and a dispersion medium or a solvent.
  • the method for preparing the sizing agent composition is not particularly limited, and a known preparation method can be used.
  • the above description of the carbon fiber short fiber with the sizing agent according to the present disclosure can be referred to.
  • the dispersion medium or solvent for the sizing agent composition includes water and organic solvents (e.g., alcohols such as methanol, acetone, etc.).
  • organic solvents e.g., alcohols such as methanol, acetone, etc.
  • the sizing agent composition may be an aqueous sizing agent dispersion (emulsion) prepared by emulsifying using a surfactant.
  • the concentration of the sizing agent in the solution or dispersion may be 0.5 to 20% by mass.
  • the surfactant is not particularly limited, and anionic, cationic, or nonionic surfactants can be used. Among them, nonionic surfactants are preferred from the viewpoint of emulsification performance and stability of the dispersion liquid.
  • Nonionic surfactants include polyethylene glycol type (higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, fatty acid ethylene oxide adducts, polypropylene glycol ethylene oxide adducts, etc.) and polyhydric alcohol type (glycerin fatty acid esters, sorbitol fatty acid esters, fatty acid alkanolamides, etc.), but it is particularly preferable to use polyoxyethylene polyoxypropylene block polymers, which can reduce the frictional resistance between the carbon fiber surface and metal.
  • Emulsification methods include using a batch equipped with an agitator, using a ball mill, using a shaker, and using a high-shear emulsifier such as a Gaulin homogenizer.
  • surfactant there are no particular limitations on the surfactant as long as it can emulsify the sizing agent, but it is usually sufficient to add about 0.1 to 30% by weight.
  • the sizing agent composition used in the manufacturing method according to the present disclosure is characterized in that it contains a water-soluble resin or a granular resin having an average particle size of 0.3 ⁇ m or less.
  • a water-soluble resin or a granular resin having an average particle size of 0.3 ⁇ m or less for details of this characteristic, please refer to the above description regarding the sizing agent-attached carbon fiber short fiber according to the present disclosure.
  • a sizing agent composition containing a water-soluble resin or a granular resin having an average particle size of 0.3 ⁇ m or less is used, and short carbon fiber fibers having a surface O/C ratio of 15% to 30% are used.
  • the viscosity of the aqueous solution or dispersion as the sizing agent composition can be made relatively low, so that the amount of sizing agent attached to the carbon fiber can be reduced, and the wettability of the sizing agent to the carbon fiber is improved due to the relatively high O/C ratio, so that the sizing agent can be applied uniformly to the carbon fiber surface.
  • the present disclosure includes a compound formed using the carbon fiber short fibers having a sizing agent attached thereto according to the present disclosure.
  • the compound may be in the form of pellets (pellet-shaped compound).
  • the compound contains carbon fiber (short carbon fiber) derived from the sizing agent-attached carbon fiber short fiber according to the present disclosure, and resin.
  • carbon fiber short carbon fiber
  • resin for the carbon fiber (short carbon fiber) contained in the compound, the above description regarding the sizing agent-attached carbon fiber short fiber according to the present disclosure may be referenced.
  • the resin contained in the compound may be a thermosetting resin or a thermoplastic resin.
  • thermosetting resins include epoxy resins, unsaturated polyester resins, phenolic resins, vinyl ester resins, cyanate ester resins, urethane acrylate resins, phenoxy resins, alkyd resins, urethane resins, prepolymerized resins of maleimide resins and cyanate ester resins, bismaleimide resins, polyimide resins and polyisoimide resins having acetylene ends, and polyimide resins having Nadic acid ends. These can be used alone or as a mixture of two or more. Among these, epoxy resins and vinyl ester resins, which have excellent heat resistance, elastic modulus, and chemical resistance, are preferred. These thermosetting resins may contain commonly used colorants and various additives in addition to curing agents and curing accelerators.
  • thermoplastic resins include polypropylene (PP) resin, polysulfone (PS) resin, polyethersulfone (PES) resin, polyetherketone resin, polyetheretherketone (PEEK) resin, polyamide (PA) resin, aromatic polyamide resin, polyester (PE) resin, aromatic polyester resin, polycarbonate (PC) resin, aromatic polycarbonate resin, polyetherimide (PEI) resin, polyarylene oxide resin, thermoplastic polyimide resin, polyamideimide resin, polyacetal resin, polyphenylene oxide resin, polyphenylene sulfide resin, polyarylate resin, polyacrylonitrile resin, polyaramid resin, polybenzimidazole resin, etc. These can be used alone or as a mixture of two or more kinds.
  • a preferred thermoplastic resin is polyetheretherketone (PEEK) resin. These thermoplastic resins may contain colorants and various additives.
  • the carbon fiber content (fiber volume content Vf) in the compound (particularly the pellet-shaped compound) according to the present disclosure may be 18 volume% or more, 20 volume% or more, 23 volume% or more, 25 volume% or more, or 30 volume% or more, and/or 60 volume% or less, 55 volume% or less, or 50 volume% or less, preferably 20 to 55 volume%.
  • the compound (particularly the pellet-shaped compound) according to the present disclosure comprises a resin and carbon fibers dispersed in the resin, and the fiber volume fraction Vf of the carbon fibers is 18 vol.% or more, 20 vol.% or more, 23 vol.% or more, 25 vol.% or more, or 30 vol.% or more, and/or 60 vol.% or less, 55 vol.% or less, or 50 vol.% or less, and particularly 20 to 55 vol.%.
  • the compound (particularly the pellet-shaped compound) can be produced from the sizing agent-attached carbon fiber short fibers according to the present disclosure and resin.
  • the specific aspects of the compound production method are not particularly limited, and known methods can be referred to.
  • the compound (particularly the pellet-shaped compound) can be produced by supplying the sizing agent-attached carbon fiber short fibers according to the present disclosure and resin to a twin-screw extruder, optionally heating, kneading, and extruding.
  • the invention according to the present disclosure includes a carbon fiber reinforced composite material (composite) formed using the carbon fiber short fibers to which the sizing agent according to the present disclosure is attached.
  • the carbon fiber reinforced composite material contains carbon fiber (short carbon fiber) derived from the short carbon fiber with a sizing agent attached according to the present disclosure, and a resin.
  • the carbon fiber reinforced composite material according to the present disclosure comprises a resin and carbon fibers dispersed in the resin, and the fiber volume fraction Vf of the carbon fibers is 18 vol.% or more, 20 vol.% or more, 23 vol.% or more, 25 vol.% or more, or 30 vol.% or more, and/or 60 vol.% or less, 55 vol.% or less, or 50 vol.% or less, and in particular 20 to 55 vol.%.
  • the above description regarding the sizing agent-attached short carbon fiber fibers of this disclosure may be referenced.
  • the above description regarding the compound (particularly the pellet-shaped compound) may be referenced.
  • the method for producing the carbon fiber reinforced composite material according to the present disclosure is not particularly limited, but may be, for example, produced by the following method: A compound (particularly a pellet-shaped compound) formed from the sizing agent-attached carbon fiber short fibers according to the present disclosure and a resin is molded to form a carbon fiber reinforced composite material.
  • the method for forming a carbon fiber reinforced composite material by molding a compound (especially a pellet-shaped compound) is not particularly limited, and any known method can be used.
  • the compound (especially a pellet-shaped compound) can be molded, for example, by injection molding.
  • ⁇ O/C ratio The ratio of oxygen atoms to carbon atoms (O/C ratio) on the surface of the carbon fiber was determined by X-ray photoelectron spectroscopy (XPS) on the carbon fiber before the sizing agent was attached.
  • XPS X-ray photoelectron spectroscopy
  • the fibers are cut and spread out on a stainless steel sample support, and then the photoelectron escape angle is set to 90 degrees, MgK ⁇ is used as the X-ray source, and the inside of the sample chamber is kept at a vacuum of 1 ⁇ 10 ⁇ 6 [Pa].
  • the binding energy value B.E. of the main peak of C1s is first adjusted to 284.6 [eV].
  • the O1s peak area is obtained by drawing a straight baseline in the range of 527 to 540 [eV].
  • the C1s peak area is also obtained by drawing a straight baseline in the range of 281 to 297 [eV].
  • 2.6865 is used as the sensitivity correction coefficient of the O1s peak relative to the C1s peak.
  • the ratio of the O1s peak area to the C1s peak area was calculated to obtain the surface oxygen concentration ratio of the carbon fiber.
  • ⁇ Surface elastic modulus> The elastic modulus (MPa) of the surface of the carbon fiber short fibers with the sizing agent attached was measured under the following measurement conditions using a scanning probe microscope (SPM) (Oxford Instruments Jupiter XR). Measurement mode: First-force mapping Probe: Oxford Instruments FS-1500 Scan size: 3.5 ⁇ m x 3.5 ⁇ m Pixel size: 13.7 nm Image size: 256 pixels x 128 pixels Z rate: 200 Hz Set point: 200 nN Force distance: 300 nm
  • the amount (mass %) of the sizing agent is a value relative to the carbon fiber short fibers, which was calculated based on the difference in mass before and after chemical decomposition of the carbon fiber short fibers with the sizing agent attached thereto using a mixture of sulfuric acid and hydrogen peroxide in accordance with JIS R 7604.
  • the layer thickness (nm) of the sizing agent was calculated from the density and specific gravity of the main component of the sizing agent, the specific gravity of the carbon fiber, the single fiber diameter, the number of filaments, and the amount of sizing agent attached to the carbon fiber short fibers.
  • ⁇ Amount decomposed at 400°C> The amount of decomposition at 400° C. (wt %) was measured using short carbon fibers with a sizing agent attached thereto, under conditions of 400° C., 20 minutes, and in an air atmosphere, with a thermogravimetric differential calorimeter (TG-DTA).
  • TG-DTA thermogravimetric differential calorimeter
  • ⁇ Strand Elastic Modulus> The strand modulus (tensile modulus) of the carbon fiber was measured in accordance with JIS R 7608.
  • ⁇ Particle size of sizing agent The particle size ( ⁇ m) of the granular resin used as a sizing agent was measured as the D50 particle size using a particle size distribution meter (MT3000II manufactured by Microtrac Bell Co., Ltd.).
  • the composites (carbon fiber reinforced composite materials) used in the examples and comparative examples were produced as follows:
  • the sizing agent-attached carbon fiber short fibers according to the examples or comparative examples and a resin (PEEK resin, manufactured by Victrex plc., product name VICTREX PEEK 150P) were supplied to a twin-screw extruder (manufactured by Japan Steel Works, Ltd., product name TEX30X) at a fiber volume content (Vf) of the carbon fiber of 33 volume %, and were kneaded and extruded at 380°C to produce a pellet-shaped compound.
  • the pellets were injection molded using an injection molding machine (manufactured by Japan Steel Works, Ltd., product name J-110AD-180H) at a cylinder temperature of 400°C and a mold temperature of 200°C to produce ISO 20753 A1 type test specimens.
  • an injection molding machine manufactured by Japan Steel Works, Ltd., product name J-110AD-180H
  • ⁇ Remaining fiber length (composite)> The remaining fiber length in the composite was determined by observing carbon fibers isolated by baking at 585° C. for 2 hours under a microscope and measuring the weight average fiber length of approximately 500 fibers.
  • ⁇ Cracked gas> The decomposition gases generated during the extrusion process in producing the compound and during the molding process in producing the composite were evaluated according to the following criteria: A: The amount of decomposition gas measured after heat treatment at 400° C. for 20 minutes in an air atmosphere was less than 0.5%. ⁇ : The amount of decomposition gas measured after heat treatment at 400° C. for 20 minutes in an air atmosphere was 0.5% or more.
  • Examples 1 to 5 and Comparative Examples 1 to 3 >>
  • carbon fiber short fibers having a single fiber diameter of 7 ⁇ m were used as a raw material to produce carbon fiber short fibers having a sizing agent attached thereto, and the properties thereof were evaluated.
  • Example 1 (Production of carbon fiber short fibers with sizing agent) Carbon fiber material A (tensile strength: 4300 MPa, tensile modulus (strand modulus): 240 GPa, single fiber diameter: 7 ⁇ m, number of filaments: 24000) was used as the carbon fiber material. The O/C ratio on the fiber surface of carbon fiber material A was 23% (0.23).
  • the carbon fibers were cut to an average length of 6 mm to obtain chopped carbon fibers.
  • a sizing agent composition in the form of an aqueous solution having the following composition was applied to the chopped carbon fibers by immersion, and the solvent was removed by drying to produce the sizing agent-attached carbon fiber short fibers according to Example 1.
  • the sizing agent composition used in Example 1 was an aqueous solution composed of the following: Polyimide (PI) precursor (MICHELMAN HP-1632) ⁇ water
  • Example 2 Except for increasing the amount of the sizing agent applied, the carbon fiber short fibers applied with the sizing agent according to Example 2 were produced and evaluated in the same manner as in Example 1. The materials used and the evaluation results are shown in Table 1 below.
  • Example 3 Except for increasing the amount of the sizing agent applied, the carbon fiber short fibers applied with the sizing agent according to Example 3 were produced and evaluated in the same manner as in Example 1. The materials used and the evaluation results are shown in Table 1 below.
  • Example 4 Except for increasing the amount of the sizing agent applied, the carbon fiber short fibers applied with the sizing agent according to Example 4 were produced and evaluated in the same manner as in Example 1. The materials used and the evaluation results are shown in Table 1 below.
  • Example 5 The carbon fiber short fibers with a sizing agent attached thereto according to Example 5 were produced and evaluated in the same manner as in Example 1, except that a blocked isocyanate (BI) emulsion (TP-11, manufactured by Meisei Chemical Industry Co., Ltd.) was used as the sizing agent composition instead of an aqueous solution of polyimide (PI). The materials used and the evaluation results are shown in Table 1 below.
  • BI blocked isocyanate
  • TP-11 manufactured by Meisei Chemical Industry Co., Ltd.
  • Comparative Example 3 The carbon fiber short fibers with a sizing agent attached thereto according to Comparative Example 3 were produced and evaluated in the same manner as in Example 1, except that a suspension of polyamide (PA) (Sepolsion PA150, manufactured by Sumitomo Seika Chemicals Co., Ltd.) was used instead of an aqueous solution of polyimide (PI) as the sizing agent composition.
  • PA polyamide
  • PI polyimide
  • the carbon fiber short fibers with sizing agent applied according to Examples 1 to 5 had an elastic modulus distribution measured on their surfaces using a scanning probe microscope in which the proportion of areas showing an elastic modulus of 30 MPa or more was 90% or more, and the proportion of areas showing an elastic modulus of 5000 MPa or less was 90% or more, demonstrating excellent composite properties (relatively high tensile strength).
  • the carbon fiber short fibers with sizing agent attached according to Examples 1 to 5 showed a relatively long remaining fiber length in the composite. Without intending to be limited by theory, it is believed that the carbon fiber short fibers with sizing agent attached according to Examples 1 to 5 have a uniform distribution of the sizing agent attached to the fiber surface, and therefore the carbon fibers are well protected by the elasticity caused by the sizing agent, and as a result, fiber breakage during the manufacturing process of the pellets and/or composites (particularly the kneading process) is suppressed. The larger the aspect ratio of the reinforcing fibers in the composite, the better the composite properties.
  • the sizing-applied carbon fiber short fibers of Comparative Example 1 showed a 60% proportion of areas exhibiting an elastic modulus of 5000 MPa or less in the elastic modulus distribution measured on the surface by a scanning probe microscope, indicating relatively poor composite properties.
  • the amount of sizing agent applied was insufficient, so that the sizing agent was not applied uniformly to the fiber surfaces, and as a result, the fiber surfaces were not sufficiently coated.
  • the fibers were not protected by the elasticity of the sizing agent, it is believed that relatively many fiber breaks occurred during the manufacturing process of the pellets and/or composites (particularly the kneading process).
  • Examples 6 to 10 and Comparative Example 4 >> In each of Examples 6 to 10 and Comparative Example 4, carbon fiber short fibers having a single fiber diameter of 5.7 ⁇ m were used as the raw material to produce carbon fiber short fibers having a sizing agent attached thereto, and the properties thereof were evaluated.
  • Example 6 The sizing-adhered carbon fiber short fibers of Example 6 were produced and evaluated in the same manner as in Example 1, except that carbon fiber material B (tensile strength: 5000 MPa, tensile modulus (strand modulus): 285 GPa, single fiber diameter: 5.7 ⁇ m, number of filaments: 36,000) was used as the carbon fiber material.
  • the O/C ratio on the fiber surface of carbon fiber material B was 25% (0.25).
  • the materials used and the evaluation results are shown in Table 2 below.
  • Example 7 The carbon fiber short fibers with a sizing agent attached thereto according to Example 7 were produced and evaluated in the same manner as in Example 6, except that the amount of the sizing agent attached was increased.
  • the materials used and the evaluation results are shown in Table 2 below.
  • Example 8 The carbon fiber short fibers with a sizing agent attached thereto according to Example 8 were produced and evaluated in the same manner as in Example 6, except that the amount of the sizing agent attached was increased.
  • the materials used and the evaluation results are shown in Table 2 below.
  • Example 9 The carbon fiber short fibers with a sizing agent attached thereto according to Example 9 were produced and evaluated in the same manner as in Example 6, except that the amount of the sizing agent attached was increased. The materials used and the evaluation results are shown in Table 2 below.
  • Example 10 A sizing agent-attached carbon fiber short fiber according to Example 10 was produced and evaluated in the same manner as in Example 6, except that a blocked isocyanate (BI) emulsion (TP-11) was used as the sizing agent composition. The materials used and the evaluation results are shown in Table 2 below.
  • BI blocked isocyanate
  • Comparative Example 4 A sizing-adhered carbon fiber short fiber according to Comparative Example 4 was produced and evaluated in the same manner as in Example 6, except that a carbon fiber material having an O/C ratio of 14% (0.14) on the carbon fiber surface was used. The materials used and the evaluation results are shown in Table 2 below.
  • the carbon fiber short fibers with sizing agent according to Examples 6 to 10 had an elastic modulus distribution measured on their surfaces by a scanning probe microscope in which the proportion of areas showing an elastic modulus of 30 MPa or more was 90% or more, and the proportion of areas showing an elastic modulus of 5000 MPa or less was 90% or more, demonstrating excellent composite properties (relatively high tensile strength).
  • the carbon fiber short fibers with sizing agent attached according to Examples 6 to 10 showed a relatively long remaining fiber length in the composite. Without intending to be limited by theory, it is believed that the carbon fiber short fibers with sizing agent attached according to Examples 6 to 10 have a uniform distribution of sizing agent attached to the fiber surface, and therefore the carbon fibers are well protected by the elasticity caused by the sizing agent, and as a result, fiber breakage during the manufacturing process of the pellets and/or composites (particularly the kneading process) is suppressed.
  • the sizing-applied carbon fiber short fibers of Comparative Example 4 showed a relatively low composite property, with 50% of the surface showing an elastic modulus of 5000 MPa or less in the elastic modulus distribution measured by a scanning probe microscope.
  • the remaining fiber length and composite property were reduced, even though the amount of sizing agent applied was the same as in Example 6.
  • the O/C ratio on the carbon fiber surface was relatively low at 14%, so that the sizing agent was not well retained on the carbon fiber surface, resulting in an uneven distribution of the sizing agent on the carbon fiber surface.
  • the coating on at least a portion of the carbon fiber surface was insufficient, and relatively many fiber breaks occurred during the manufacturing process of the pellets and/or composites (especially the kneading process).

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Abstract

The present disclosure relates to the provision of a sizing agent-attached carbon short fiber that provides improved composite strength. The sizing agent-attached carbon short fiber comprises a carbon short fiber and a sizing agent attached to the carbon short fiber. In the elastic modulus distribution as measured on the surface of the sizing agent-attached carbon short fiber by means of a scanning probe microscope, the proportion of a part that exhibits an elastic modulus of at least 30 Mpa is at least 90%, and the proportion of a part that exhibits an elastic modulus of at most 5000 MPa is at most 90%.

Description

サイジング剤付着炭素繊維ショートファイバーCarbon fiber short fiber with sizing agent
　本発明は、サイジング剤付着炭素繊維ショートファイバー及びその製造方法に関する。特に、本発明は、コンパウンドで用いるためのサイジング剤付着炭素繊維ショートファイバー及びその製造方法に関する。 The present invention relates to carbon fiber short fibers with a sizing agent attached thereto and a method for producing the same. In particular, the present invention relates to carbon fiber short fibers with a sizing agent attached thereto for use in compounds and a method for producing the same.
　炭素繊維は、比強度・比弾性率に優れ、軽量であるため、熱硬化性樹脂及び熱可塑性樹脂の強化繊維として、航空機、スポーツ・レジャー、一般産業など幅広い用途に利用される。利用用途が拡大されるにつれ、炭素繊維強化複合材料（ＣＦＲＰ、以下コンポジットとも言う）には、さらに高い性能が求められている。 Carbon fiber has excellent specific strength and specific modulus of elasticity, and is lightweight, so it is used as a reinforcing fiber for thermosetting and thermoplastic resins in a wide range of applications, including aircraft, sports and leisure, and general industry. As its applications expand, even higher performance is required of carbon fiber reinforced composite materials (CFRP, hereafter also referred to as composites).
　炭素繊維強化複合材料を製造するために、樹脂と樹脂中に分散した炭素繊維とを有するコンパウンドを用いることができる。具体的には、例えば、ペレット状のコンパウンド（ペレット）を溶融させて射出成形することによって、炭素繊維強化複合材料を製造することができる。コンパウンドから形成される炭素繊維強化複合材料は、一方向に引き揃えられた炭素繊維からなるシートに樹脂を含浸させる場合などとは異なり、炭素繊維が樹脂中に分散した構造を有する。 To manufacture carbon fiber reinforced composite materials, a compound having a resin and carbon fibers dispersed in the resin can be used. Specifically, for example, a carbon fiber reinforced composite material can be manufactured by melting a pellet-shaped compound (pellets) and injection molding it. The carbon fiber reinforced composite material formed from the compound has a structure in which the carbon fibers are dispersed in the resin, unlike a material that is made by impregnating a sheet of carbon fibers aligned in one direction with resin.
　このようなペレットは、例えば、炭素繊維のショートファイバーと樹脂とを混練し押出成形することによって製造することができる。 Such pellets can be produced, for example, by kneading short carbon fibers with resin and extruding the mixture.
　ここで、炭素繊維の製造過程では、炭素繊維の工程通過性の向上、及び、複合材料における炭素繊維とマトリックス樹脂との親和性の向上などの目的のために、炭素繊維にサイジング剤が付与される。 In the carbon fiber manufacturing process, a sizing agent is applied to the carbon fiber for the purposes of improving the processability of the carbon fiber and improving the affinity between the carbon fiber and the matrix resin in the composite material.
　特許文献１は、特定のカルボン酸成分と特定のアルコール成分とのエステルを含有する無機繊維用集束剤について記載している。 Patent Document 1 describes a sizing agent for inorganic fibers that contains an ester of a specific carboxylic acid component and a specific alcohol component.
　特許文献２は、成分中に少なくともポリオキシアルキレン基とエポキシ基を含有するサイジング剤について記載している。 Patent Document 2 describes a sizing agent that contains at least a polyoxyalkylene group and an epoxy group.
　特許文献３は、脂肪族系エポキシ樹脂を含む、炭素繊維束用のサイジング剤について記載している。 Patent document 3 describes a sizing agent for carbon fiber bundles that contains an aliphatic epoxy resin.
　特許文献４は、サイジング剤が付着している炭素繊維束について記載しており、サイジング剤が、軟化点８０～２００℃の範囲内の芳香族系熱可塑性樹脂と芳香族ジエステルと
を含むことを記載している。 Patent Document 4 describes a carbon fiber bundle having a sizing agent attached thereto, and describes that the sizing agent contains an aromatic thermoplastic resin having a softening point in the range of 80 to 200° C. and an aromatic diester.
　特許文献５は、エポキシ化合物とアミン化合物の反応物であるアミンアダクトとポリウレタンとを含有するサイジング剤について記載している。 Patent Document 5 describes a sizing agent that contains an amine adduct, which is a reaction product of an epoxy compound and an amine compound, and polyurethane.
　また、従来、コンポジットの物性を向上させるために、炭素繊維に対して種々の改良が検討されてきた。 Also, various improvements to carbon fibers have been considered in the past to improve the physical properties of composites.
　特許文献６は、摩擦係数、炭素繊維表面の酸素含有官能基量、並びにストランドの引張強度及び弾性率が特定範囲である炭素繊維束を開示している。この文献は、発明の目的として、炭素繊維のコンポジット物性を向上させることを記載している。 Patent document 6 discloses a carbon fiber bundle having a specific range of friction coefficient, amount of oxygen-containing functional groups on the carbon fiber surface, and tensile strength and elastic modulus of the strand. This document describes the purpose of the invention as improving the composite properties of carbon fibers.
　特許文献７は、特定範囲の平均単繊維引張強度、樹脂含浸ストランド引張強度、繊維摩擦係数、及び熱分解性有機物量を示す炭素繊維を記載している。この文献は、発明の目的として、超高強度コンポジット物性を示す炭素繊維を提供することを記載している。 Patent document 7 describes carbon fibers that exhibit specific ranges of average single fiber tensile strength, resin-impregnated strand tensile strength, fiber friction coefficient, and amount of pyrolyzable organic matter. This document describes the object of the invention as being to provide carbon fibers that exhibit ultra-high strength composite properties.
特開２００２－３３９２４６号公報JP 2002-339246 A 特開２００３－３３７６号公報JP 2003-3376 A 特開２００５－２６４３８３号公報JP 2005-264383 A 特開２００５－２８１９５５号公報JP 2005-281955 A 特開２０１６－３４１２号公報JP 2016-3412 A 特開昭６０－２３９５２１号公報Japanese Patent Application Laid-Open No. 60-239521 特開昭６１－２９６１２３号公報Japanese Patent Application Laid-Open No. 61-296123
　上述のとおり、炭素繊維のショートファイバーを用いてコンポジットを製造することができる。また、取扱い性、成形性及びコンポジット特性等を向上させるために、炭素繊維ショートファイバーにサイジング剤を付与し、サイジング剤付着炭素繊維ショートファイバーを形成することができる。 As described above, composites can be manufactured using short carbon fibers. In addition, in order to improve the handling, moldability, and composite properties, a sizing agent can be applied to the short carbon fibers to form short carbon fibers with a sizing agent attached.
　従来のサイジング剤付着炭素繊維ショートファイバーを用いて製造されたコンポジットは、強度などの機械特性の点で十分な特性を得られない場合があり、特に、炭素繊維の繊維含有率が比較的高いコンパウンドから形成される炭素繊維強化複合材料において、十分な機械特性を得ることができない場合があった。 Composites manufactured using conventional carbon fiber short fibers with sizing agents applied may not be able to obtain sufficient mechanical properties such as strength, and in particular, carbon fiber reinforced composite materials formed from compounds with a relatively high carbon fiber content may not be able to obtain sufficient mechanical properties.
　本開示は、向上したコンポジット強度をもたらすサイジング剤付着炭素繊維ショートファイバーを提供することを目的とする。特に、本開示は、コンパウンドから形成される炭素繊維強化複合材料であって比較的高い繊維含有率を有する炭素繊維強化複合材料において、向上した強度を達成することができるサイジング剤付着炭素繊維ショートファイバーを提供することを目的とする。 The present disclosure aims to provide a sizing-adhered carbon fiber short fiber that provides improved composite strength. In particular, the present disclosure aims to provide a sizing-adhered carbon fiber short fiber that can achieve improved strength in a carbon fiber reinforced composite material formed from a compound and having a relatively high fiber content.
　上記の課題は、本発明に係る下記の態様によって、解決することができる。
＜態様１＞
　炭素繊維ショートファイバー及びこの炭素繊維ショートファイバーに付着しているサイジング剤を有しているサイジング剤付着炭素繊維ショートファイバーであって、
　前記サイジング剤付着炭素繊維ショートファイバーの表面で走査型プローブ顕微鏡によって測定したときの弾性率分布において、３０ＭＰａ以上の弾性率を示す部分の割合が９０％以上であり、かつ５０００ＭＰａ以下の弾性率を示す部分の割合が９０％以上である、
サイジング剤付着炭素繊維ショートファイバー。
＜態様２＞
　前記炭素繊維ショートファイバーの表面のＯ／Ｃ比が、１５％～３０％であり、かつ、
　前記サイジング剤が、水溶性樹脂を含み、又は、０．３μｍ以下の平均粒子径を有する粒状樹脂を含む、
態様１に記載のサイジング剤付着炭素繊維ショートファイバー。
＜態様３＞
　前記サイジング剤が、水溶性樹脂を含む、態様１又は２に記載のサイジング剤付着炭素繊維ショートファイバー。
＜態様４＞
　前記サイジング剤が、ポリイミド樹脂を含む、態様１又は２に記載のサイジング剤付着炭素繊維ショートファイバー。
＜態様５＞
　前記炭素繊維ショートファイバーに付着している前記サイジング剤が、前記炭素繊維ショートファイバーに対して、０．８質量％～３．３質量％である、態様１～４のいずれかに記載のサイジング剤付着炭素繊維ショートファイバー。
＜態様６＞
　空気中で２０分にわたって４００℃で加熱処理したときの熱分解量が、サイジング剤付着炭素繊維ショートファイバーの総重量に対して０．５０％以下である、態様１～５のいずれかに記載のサイジング剤付着炭素繊維ショートファイバー。
＜態様７＞
　前記サイジング剤付着炭素繊維ショートファイバーの平均長さが、１ｍｍ～２５ｍｍである、態様１～６のいずれかに記載のサイジング剤付着炭素繊維ショートファイバー。
＜態様８＞
　前記炭素繊維ショートファイバーの単繊維径が、４～８μｍである、態様１～７のいずれかに記載のサイジング剤付着炭素繊維ショートファイバー。
＜態様９＞
　前記炭素繊維ショートファイバーが、２４５ＧＰａ以上の引張弾性率を示す炭素繊維から形成されている、態様１～８のいずれかに記載のサイジング剤付着炭素繊維ショートファイバー。
＜態様１０＞
　炭素繊維強化複合材料のための、態様１～９のいずれかに記載のサイジング剤付着炭素繊維ショートファイバー。
＜態様１１＞
　前記炭素繊維強化複合材料における炭素繊維の繊維体積含有率が２０体積％～５５体積％である、態様１０に記載のサイジング剤付着炭素繊維ショートファイバー。
＜態様１２＞
　炭素繊維ショートファイバーを提供すること、及び、
　前記炭素繊維ショートファイバーの表面に、サイジング剤組成物を適用すること、
を含む、サイジング剤付着炭素繊維ショートファイバーの製造方法であって、
　前記炭素繊維ショートファイバーの表面のＯ／Ｃ比が、１５％～３０％であり、かつ、
　前記サイジング剤組成物が、水溶性樹脂を含み、又は、０．３μｍ以下の平均粒子径を有する粒状樹脂を含む、
方法。
＜態様１３＞
　前記サイジング剤組成物が、水溶性樹脂を含む、態様１２に記載の方法。
＜態様１４＞
　態様１～１１のいずれかに係るサイジング剤付着炭素繊維ショートファイバーを提供すること、及び、
　前記サイジング剤付着炭素繊維ショートファイバーと樹脂とを混練かつ押出して、コンパウンドを形成すること、
を含む、コンパウンドの製造方法。
＜態様１５＞
　前記コンパウンドがペレット状である、態様１４に記載の方法。
＜態様１６＞
　態様１４又は１５に記載の方法によってコンパウンドを製造すること、及び
　前記コンパウンドを成形して、炭素繊維強化複合材料を形成すること、
を含む、炭素繊維強化複合材料の製造方法。 The above problems can be solved by the following aspects of the present invention.
<Aspect 1>
A sizing-agent-attached carbon fiber short fiber having a carbon fiber short fiber and a sizing agent attached to the carbon fiber short fiber,
In the elastic modulus distribution measured by a scanning probe microscope on the surface of the sizing agent-attached carbon fiber short fibers, the proportion of a portion showing an elastic modulus of 30 MPa or more is 90% or more, and the proportion of a portion showing an elastic modulus of 5000 MPa or less is 90% or more.
Carbon fiber short fibers with sizing agent attached.
<Aspect 2>
The O/C ratio of the surface of the carbon fiber short fiber is 15% to 30%, and
The sizing agent contains a water-soluble resin or a granular resin having an average particle size of 0.3 μm or less.
The carbon fiber short fiber according to claim 1, wherein the sizing agent is attached to the carbon fiber short fiber.
<Aspect 3>
The carbon fiber short fibers according to claim 1 or 2, wherein the sizing agent comprises a water-soluble resin.
<Aspect 4>
The carbon fiber short fibers according to claim 1 or 2, wherein the sizing agent comprises a polyimide resin.
<Aspect 5>
The sizing agent adhered to the carbon fiber short fibers is 0.8% by mass to 3.3% by mass relative to the carbon fiber short fibers.
<Aspect 6>
The carbon fiber short fibers having a sizing agent attached thereto according to any one of aspects 1 to 5, wherein the amount of thermal decomposition when heat-treated at 400° C. in air for 20 minutes is 0.50% or less based on the total weight of the carbon fiber short fibers having a sizing agent attached thereto.
<Aspect 7>
The sizing-agent-attached carbon fiber short fibers according to any one of aspects 1 to 6, wherein the average length of the sizing-agent-attached carbon fiber short fibers is 1 mm to 25 mm.
<Aspect 8>
The sizing agent-attached carbon fiber short fiber according to any one of aspects 1 to 7, wherein the single fiber diameter of the carbon fiber short fiber is 4 to 8 μm.
<Aspect 9>
The carbon fiber short fibers having a sizing agent attached thereto according to any one of aspects 1 to 8, wherein the carbon fiber short fibers are formed from carbon fibers exhibiting a tensile modulus of elasticity of 245 GPa or more.
<Aspect 10>
A carbon fiber short fiber having a sizing agent attached thereto according to any one of aspects 1 to 9, for use in a carbon fiber reinforced composite material.
<Aspect 11>
The sizing agent-attached carbon fiber short fiber according to aspect 10, wherein the fiber volume content of the carbon fiber in the carbon fiber reinforced composite material is 20 volume% to 55 volume%.
<Aspect 12>
Providing a carbon fiber short fiber; and
Applying a sizing agent composition to the surface of the carbon fiber short fibers;
A method for producing carbon fiber short fibers with a sizing agent, comprising:
The O/C ratio of the surface of the carbon fiber short fiber is 15% to 30%, and
The sizing agent composition contains a water-soluble resin or a granular resin having an average particle size of 0.3 μm or less.
Method.
<Aspect 13>
The method of claim 12, wherein the sizing composition comprises a water-soluble resin.
<Aspect 14>
Providing a sizing agent-attached carbon fiber short fiber according to any one of aspects 1 to 11; and
kneading and extruding the sizing agent-attached carbon fiber short fibers and a resin to form a compound;
A method for producing a compound comprising:
<Aspect 15>
15. The method of claim 14, wherein the compound is in pellet form.
<Aspect 16>
Producing a compound by the method of claim 14 or 15; and molding the compound to form a carbon fiber reinforced composite material.
A method for producing a carbon fiber reinforced composite material, comprising:
　本発明によれば、向上したコンポジット強度をもたらすことができるサイジング剤付着炭素繊維ショートファイバーを提供できる。特に、本発明によれば、コンパウンドから形成される炭素繊維強化複合材料であって比較的高い繊維含有率を有する炭素繊維強化複合材料において、向上した強度を達成することができるサイジング剤付着炭素繊維ショートファイバーを提供できる。 The present invention provides carbon fiber short fibers with a sizing agent attached thereto, which can provide improved composite strength. In particular, the present invention provides carbon fiber short fibers with a sizing agent attached thereto, which can achieve improved strength in carbon fiber reinforced composite materials formed from compounds and having a relatively high fiber content.
図１は、走査型プローブ顕微鏡を用いた測定で得られた、実施例８に係るサイジング剤付着炭素繊維ショートファイバーの表面における弾性率分布を示す画像である。FIG. 1 is an image showing the elastic modulus distribution on the surface of the carbon fiber short fibers to which a sizing agent was applied according to Example 8, obtained by measurement using a scanning probe microscope. 図２は、走査型プローブ顕微鏡を用いた測定で得られた、実施例８に係るサイジング剤付着炭素繊維ショートファイバーの表面における弾性率分布を示すグラフである。縦軸は頻度を示し、横軸は弾性率（ＧＰａ）を示す。2 is a graph showing the distribution of elastic modulus on the surface of the sizing-agent-attached carbon fiber short fibers according to Example 8, obtained by measurement using a scanning probe microscope. The vertical axis shows the frequency, and the horizontal axis shows the elastic modulus (GPa).
≪サイジング剤付着炭素繊維ショートファイバー≫
　本発明に係るサイジング剤付着炭素繊維ショートファイバーは、炭素繊維ショートファイバー、及びこの炭素繊維ショートファイバーに付着しているサイジング剤を有しており、サイジング剤付着炭素繊維ショートファイバーの表面で走査型プローブ顕微鏡によって測定したときの弾性率分布において、３０ＭＰａ以上の弾性率を示す部分の割合が９０％以上であり、かつ５０００ＭＰａ以下の弾性率を示す部分の割合が９０％以上である。 <Carbon short fiber with sizing agent>
The carbon fiber short fibers having a sizing agent attached thereto according to the present invention have carbon fiber short fibers and a sizing agent attached to the carbon fiber short fibers, and in the elastic modulus distribution measured by a scanning probe microscope on the surface of the carbon fiber short fibers having a sizing agent attached thereto, the proportion of portions exhibiting an elastic modulus of 30 MPa or more is 90% or more, and the proportion of portions exhibiting an elastic modulus of 5000 MPa or less is 90% or more.
　本件発明者は、サイジング剤付着炭素繊維ショートファイバー表面の弾性率の分布を最適化することによって、向上した引張強度を有する炭素繊維強化複合材料をもたらすことができるサイジング剤付着炭素繊維ショートファイバーを提供できることを見出した。 The inventors have discovered that by optimizing the distribution of elastic modulus on the surface of sizing-agent-attached carbon fiber short fibers, it is possible to provide sizing-agent-attached carbon fiber short fibers that can result in carbon fiber reinforced composite materials with improved tensile strength.
　炭素繊維強化複合材料の製造過程では、例えば、炭素繊維ショートファイバーを含む炭素繊維原料（チョップドファイバーなど）を樹脂組成物と混錬してペレット化し、このペレットを射出成形して成形品を製造する。この製造過程で、特にペレット化の過程（コンパウンド化工程）において、炭素繊維原料である炭素繊維ショートファイバーが折れて、その結果として、複合材料の引張強度などに関して所望の物性が得られない場合があった。繊維強化複合材料では、含有される強化繊維のアスペクト比（長さ／直径）が大きいほど、繊維強化複合材料の引張強度（ＴＳ）が大きくなると考えられる。 In the manufacturing process of carbon fiber reinforced composite materials, for example, carbon fiber raw material (such as chopped fiber) containing short carbon fiber fibers is kneaded with a resin composition and pelletized, and these pellets are injection molded to produce molded products. During this manufacturing process, particularly in the pelletization process (compounding step), the carbon fiber short fiber raw material may break, and as a result, the desired physical properties such as tensile strength of the composite material may not be obtained. In fiber reinforced composite materials, it is believed that the greater the aspect ratio (length/diameter) of the reinforcing fibers contained, the greater the tensile strength (TS) of the fiber reinforced composite material.
　これに対して、本発明では、サイジング剤付着炭素繊維ショートファイバーの表面で走査型プローブ顕微鏡によって測定したときの弾性率分布において、５０００ＭＰａ以下の弾性率を示す部分の割合が９０％以上である。理論によって限定する意図はないが、この場合には、炭素繊維表面にサイジング剤が均一に分布しているため、コンパウンド化工程などの際に外力に対して炭素繊維が良好に保護されると考えられる。 In contrast, in the present invention, the proportion of the portion showing an elastic modulus of 5000 MPa or less is 90% or more in the elastic modulus distribution when measured by a scanning probe microscope on the surface of the carbon fiber short fiber with a sizing agent attached. Although there is no intention to be limited by theory, it is believed that in this case, since the sizing agent is uniformly distributed on the carbon fiber surface, the carbon fiber is well protected against external forces during the compounding process, etc.
　すなわち、本発明では、炭素繊維表面におけるサイジング剤の分布が比較的均一になっており、それによって、炭素繊維表面が十分に被覆され、比較的弾性に富んだ表面部分が多くなっていると考えられる。炭素繊維の表面の比較的広い範囲がサイジング剤で覆われて弾性に富んでいることによって、コンパウンド化工程の間に炭素繊維同士が接触することによる繊維の折れなどが抑制されると考えられる。 In other words, in the present invention, the distribution of the sizing agent on the carbon fiber surface is relatively uniform, which is believed to result in the carbon fiber surface being sufficiently coated and resulting in a large portion of the surface being relatively elastic. Because a relatively wide area of the carbon fiber surface is covered with the sizing agent and is highly elastic, it is believed that fiber breakage caused by contact between carbon fibers during the compounding process is suppressed.
　したがって、本発明によれば、炭素繊維強化複合材料中の炭素繊維の残存繊維長が比較的大きくなることによって、炭素繊維のアスペクト比が比較的高くなり、その結果、向上した強度を有する炭素繊維強化複合材料を得ることができると考えられる。 According to the present invention, the residual fiber length of the carbon fibers in the carbon fiber reinforced composite material becomes relatively large, which in turn makes it possible to obtain a carbon fiber reinforced composite material with a relatively high aspect ratio and, as a result, to obtain a carbon fiber reinforced composite material with improved strength.
　さらに、本発明では、サイジング剤付着炭素繊維ショートファイバーの表面で走査型プローブ顕微鏡によって測定したときの弾性率分布において、３０ＭＰａ以上の弾性率を示す部分の割合が９０％以上である。３０ＭＰａ以上の弾性率を示す部分の割合が９０％以上であることによって、サイジング剤付着炭素繊維ショートファイバーの良好な耐熱性を確保することができる。なお、一般に、付着させるサイジング剤の量を多くすることによって炭素繊維表面の弾性を向上させることができるが、サイジング剤の量が多すぎると、コンパウンド及び／又はコンポジットの製造過程でサイジング剤に起因する分解ガスの発生などのおそれが高まると考えらえる。理論によって限定する意図はないが、本発明では、弾性率が比較的低い表面部分が低減されており、これは、サイジング剤が過剰に付着した表面部分が低減されていることを反映していると考えられる。 Furthermore, in the present invention, the proportion of the portion showing an elastic modulus of 30 MPa or more is 90% or more in the elastic modulus distribution when measured by a scanning probe microscope on the surface of the carbon fiber short fiber with the sizing agent attached thereto. By having the proportion of the portion showing an elastic modulus of 30 MPa or more being 90% or more, good heat resistance of the carbon fiber short fiber with the sizing agent attached thereto can be ensured. In general, the elasticity of the carbon fiber surface can be improved by increasing the amount of sizing agent attached thereto, but if the amount of sizing agent is too large, it is thought that there is an increased risk of generation of decomposition gas due to the sizing agent during the manufacturing process of the compound and/or composite. Although there is no intention to be limited by theory, in the present invention, the surface portion with a relatively low elastic modulus is reduced, which is thought to reflect the reduction in the surface portion to which the sizing agent is excessively attached.
　本発明に係るサイジング剤付着炭素繊維ショートファイバーは、比較的高い繊維含有率（特には繊維体積含有率２０～５５体積％）を有する炭素繊維強化複合材料を製造するために、特に有用であると考えられる。すなわち、比較的高い繊維含有率を有するコンポジットを製造する場合には、繊維同士の相互作用によって繊維が折れやすくなっていると考えられる。本発明に係る繊維によれば、このような場合であっても繊維折れを抑制して比較的長い繊維を残存させることができるので、優れたコンポジット強度を得ることができる。 The carbon fiber short fibers with sizing agent according to the present invention are believed to be particularly useful for producing carbon fiber reinforced composite materials with a relatively high fiber content (particularly a fiber volume content of 20 to 55% by volume). In other words, when producing a composite with a relatively high fiber content, it is believed that the fibers are more likely to break due to the interaction between the fibers. With the fibers according to the present invention, even in such cases, fiber breakage can be suppressed and relatively long fibers can remain, resulting in excellent composite strength.
　本開示に係るサイジング剤付着炭素繊維ショートファイバーは、好ましくは、炭素繊維の繊維体積含有率が２０体積％～５５体積％、２５体積％～５０体積％、又はさらには３０体積％～４０体積％の炭素繊維強化複合材料のための、サイジング剤付着炭素繊維ショートファイバーである。 The sizing agent-adhered carbon fiber short fibers according to the present disclosure are preferably sizing agent-adhered carbon fiber short fibers for use in carbon fiber reinforced composite materials having a fiber volume content of the carbon fibers of 20 volume % to 55 volume %, 25 volume % to 50 volume %, or even 30 volume % to 40 volume %.
＜弾性率分布＞
　サイジング剤付着炭素繊維ショートファイバーの表面の弾性率は、走査型プローブ顕微鏡（ＳＰＭ）によって測定できる。 <Elasticity distribution>
The elastic modulus of the surface of the sizing agent-attached short carbon fibers can be measured by a scanning probe microscope (SPM).
　すなわち、走査型プローブ顕微鏡を用いて、サイジング剤付着炭素繊維ショートファイバーの表面のうちランダムに選択される１万箇所以上における弾性率をそれぞれ計測することによって、弾性率分布を得ることができ、この弾性率分布に基づいて、３０ＭＰａ以上の弾性率を示す部分の割合、及び、５０００ＭＰａ以下の弾性率を示す部分の割合を決定することができる。図２は、走査型プローブ顕微鏡を用いた測定で得られた、実施例８に係るサイジング剤付着炭素繊維ショートファイバーの表面における弾性率分布を示すグラフ（ヒストグラム）である。縦軸は頻度を示し、横軸は弾性率（ＧＰａ）を示す。図２に示すこのようなヒストグラムを用いて、３０ＭＰａ以上の弾性率を示す部分の割合、及び、５０００ＭＰａ以下の弾性率を示す部分の割合を決定することができる。 In other words, by using a scanning probe microscope to measure the elastic modulus at more than 10,000 randomly selected locations on the surface of the carbon fiber short fiber with a sizing agent attached, a distribution of elastic modulus can be obtained, and based on this distribution of elastic modulus, the proportion of the portion showing an elastic modulus of 30 MPa or more and the proportion of the portion showing an elastic modulus of 5000 MPa or less can be determined. Figure 2 is a graph (histogram) showing the elastic modulus distribution on the surface of the carbon fiber short fiber with a sizing agent attached according to Example 8, obtained by measurement using a scanning probe microscope. The vertical axis shows the frequency, and the horizontal axis shows the elastic modulus (GPa). Using such a histogram shown in Figure 2, the proportion of the portion showing an elastic modulus of 30 MPa or more and the proportion of the portion showing an elastic modulus of 5000 MPa or less can be determined.
　好ましくは、サイジング剤付着炭素繊維ショートファイバーの表面で走査型プローブ顕微鏡によって測定したときの弾性率分布において、３０ＭＰａ以上（好ましくは４０ＭＰａ以上、より好ましくは５０ＭＰａ以上、更に好ましくは７５ＭＰａ以上、最も好ましくは１００ＭＰａ以上）の弾性率を示す部分の割合が、９２％以上、９４％以上、９６％以上、若しくはさらには９８％以上であり、かつ／又は、５０００ＭＰａ以下（好ましくは４０００ＭＰａ以下、より好ましくは３０００ＭＰａ以下、さらに好ましくは２０００ＭＰａ以下、特に好ましくは１０００ＭＰａ以下）の弾性率を示す部分の割合が、９２％以上、９４％以上、９６％以上、若しくはさらには９８％以上である。なお、サイジング剤で被覆されていない炭素繊維の表面の弾性率は、一般に１００００～３００００ＭＰａ以上である。 Preferably, in the elastic modulus distribution measured by a scanning probe microscope on the surface of the carbon fiber short fibers with a sizing agent attached, the proportion of the parts showing an elastic modulus of 30 MPa or more (preferably 40 MPa or more, more preferably 50 MPa or more, even more preferably 75 MPa or more, and most preferably 100 MPa or more) is 92% or more, 94% or more, 96% or more, or even 98% or more, and/or the proportion of the parts showing an elastic modulus of 5000 MPa or less (preferably 4000 MPa or less, more preferably 3000 MPa or less, even more preferably 2000 MPa or less, and particularly preferably 1000 MPa or less) is 92% or more, 94% or more, 96% or more, or even 98% or more. The elastic modulus of the surface of the carbon fiber not coated with a sizing agent is generally 10,000 to 30,000 MPa or more.
　本開示に係る好ましい実施態様では、サイジング剤付着炭素繊維ショートファイバーの表面において、走査型プローブ顕微鏡によって測定したときに、弾性率の平均値（数平均値）が、３０ＭＰａ～３０００ＭＰａの範囲にあり、より好ましくは、１００ＭＰａ～２０００ＭＰａの範囲にあり、更に好ましくは４００ＭＰａ～１０００ＭＰａの範囲にある。この弾性率の平均値は、走査型プローブ顕微鏡を用いて１万箇所以上で計測した弾性率を平均して得ることができる。 In a preferred embodiment of the present disclosure, the average elastic modulus (number average value) on the surface of the carbon fiber short fibers with a sizing agent attached thereto is in the range of 30 MPa to 3,000 MPa, more preferably in the range of 100 MPa to 2,000 MPa, and even more preferably in the range of 400 MPa to 1,000 MPa, when measured by a scanning probe microscope. This average elastic modulus can be obtained by averaging the elastic moduli measured at 10,000 or more locations using a scanning probe microscope.
＜サイジング剤付着炭素繊維ショートファイバー＞
　本発明に係るサイジング剤付着炭素繊維ショートファイバーは、炭素繊維ショートファイバー、及びこの炭素繊維ショートファイバーに付着しているサイジング剤を有する。好ましくは、本発明に係るサイジング剤付着炭素繊維ショートファイバーは、炭素繊維ショートファイバー、及び、炭素繊維ショートファイバーに付着しているサイジング剤から構成される。サイジング剤は、通常、炭素繊維ショートファイバーの表面に付着している。 <Short carbon fiber with sizing agent>
The carbon fiber short fibers with a sizing agent according to the present invention have a carbon fiber short fiber and a sizing agent attached to the carbon fiber short fiber. Preferably, the carbon fiber short fibers with a sizing agent according to the present invention are composed of a carbon fiber short fiber and a sizing agent attached to the carbon fiber short fiber. The sizing agent is usually attached to the surface of the carbon fiber short fiber.
　サイジング剤付着炭素繊維ショートファイバーの平均長さは、０．５ｍｍ～３０ｍｍであってよい。この平均長さは、好ましくは１ｍｍ～２５ｍｍ、より好ましくは２ｍｍ～１５ｍｍである。 The average length of the carbon fiber short fibers with sizing agent attached may be 0.5 mm to 30 mm. This average length is preferably 1 mm to 25 mm, and more preferably 2 mm to 15 mm.
　サイジング剤付着炭素繊維ショートファイバーの平均長さは、ノギス及び／又は光学顕微鏡を用いて３０本以上のサイジング剤付着炭素繊維ショートファイバーの長さを計測し、この計測値から平均値を算出することによって決定することができる。 The average length of the carbon fiber short fibers with a sizing agent attached can be determined by measuring the lengths of 30 or more carbon fiber short fibers with a sizing agent attached using a vernier caliper and/or an optical microscope and calculating the average value from these measurements.
（サイジング剤）
　本開示において、「サイジング剤」は、サイジング剤組成物を炭素繊維に付与し、乾燥した後で、炭素繊維上に残留している成分を意味し、これらは、固体であっても液体であってもよい。 (Sizing agent)
In this disclosure, "sizing agent" means components that remain on the carbon fibers after the sizing agent composition is applied to the carbon fibers and dried, and these may be solid or liquid.
（サイジング剤の量）
　本発明の１つの実施態様では、炭素繊維ショートファイバーに対して、サイジング剤の割合が、０．６質量％～５．０質量％である。この割合は、好ましくは０．７質量％～４．０質量％、より好ましくは０．８質量％～３．３質量％である。 (Amount of sizing agent)
In one embodiment of the present invention, the ratio of the sizing agent to the carbon fiber short fibers is 0.6% by mass to 5.0% by mass, preferably 0.7% by mass to 4.0% by mass, more preferably 0.8% by mass to 3.3% by mass.
　一般的には、サイジング剤の量を比較的多くすることによって、サイジング剤が付着した炭素繊維の表面弾性を向上させることができ、また、サイジング剤が付着した炭素繊維の表面における弾性層（サイジング剤によって構成される層）の被覆率及び均一性も向上すると考えられる。 In general, it is believed that by using a relatively large amount of sizing agent, the surface elasticity of the carbon fiber to which the sizing agent is attached can be improved, and the coverage and uniformity of the elastic layer (layer formed by the sizing agent) on the surface of the carbon fiber to which the sizing agent is attached can also be improved.
　しかしながら、例えば耐熱性用途では、比較的高い融点を有する樹脂（例えばＰＥＥＫ）を用いるので、サイジング剤の量が多すぎる場合には、ペレット及び／又は成形品の製造過程で高温（例えば３２０℃以上、又はさらには３６０℃以上、若しくは４００℃以上）にさらされる結果として、サイジング剤に起因してガスが発生することがある。これは、例えば、射出成形で用いられる金型を汚染するおそれがある。さらに、炭素繊維強化複合材料の物性に悪影響を及ぼすおそれがあり、例えば、発生したガスによって樹脂が分解されて低分子化されてしまうことがある。 However, for example, in heat-resistant applications, resins with relatively high melting points (e.g., PEEK) are used, so if the amount of sizing agent is too large, gas may be generated due to the sizing agent as a result of exposure to high temperatures (e.g., 320°C or higher, or even 360°C or higher, or 400°C or higher) during the production process of the pellets and/or molded products. This may, for example, contaminate the mold used in injection molding. Furthermore, it may have an adverse effect on the physical properties of the carbon fiber reinforced composite material, for example, the generated gas may decompose the resin into smaller molecules.
　これに対して、炭素繊維ショートファイバーに対するサイジング剤の量が上記の範囲である場合には、高温処理の過程におけるサイジング剤に由来する分解ガスの発生が抑制されるので、特に良好な品質を有する複合材料が得られる。 In contrast, when the amount of sizing agent relative to the carbon fiber short fibers is within the above range, the generation of decomposition gases derived from the sizing agent during high-temperature treatment is suppressed, resulting in a composite material of particularly good quality.
　本発明の特に好ましい１つの実施態様では、サイジング剤がポリイミド樹脂からなり、炭素繊維ショートファイバーに対して、ポリイミド樹脂の割合が、０．６質量％～５．０質量％である。この割合は、好ましくは０．７質量％～４．０質量％、より好ましくは０．８質量％～３．３質量％である。 In one particularly preferred embodiment of the present invention, the sizing agent is made of polyimide resin, and the ratio of polyimide resin to the carbon fiber short fibers is 0.6% by mass to 5.0% by mass. This ratio is preferably 0.7% by mass to 4.0% by mass, and more preferably 0.8% by mass to 3.3% by mass.
　炭素繊維ショートファイバーに付着したサイジング剤の質量は、ＪＩＳ　Ｒ７６０４法（Ｂ法）に従って測定できる。 The mass of sizing agent attached to short carbon fiber can be measured according to JIS R7604 method (Method B).
（４００℃分解量）
　本開示に係る好ましい１つの実施態様では、サイジング剤付着炭素繊維ショートファイバーを空気中で２０分にわたって４００℃で加熱処理したときの熱分解量が、サイジング剤付着炭素繊維ショートファイバーの総重量に対して、０．５０％以下である。 (Amount decomposed at 400°C)
In one preferred embodiment of the present disclosure, the amount of thermal decomposition when the sizing-agent-attached carbon fiber short fibers are heat-treated at 400° C. in air for 20 minutes is 0.50% or less based on the total weight of the sizing-agent-attached carbon fiber short fibers.
　この場合、サイジング剤付着炭素繊維ショートファイバーを高温処理（例えば３００℃以上又は３５０℃以上の高温処理）する場合のガス発生が抑制されるので、特に良好な品質を有する複合材料が得られる。この４００℃分解量の範囲は、例えば、炭素繊維ショートファイバーに付着したサイジング剤の量を低減することによって、達成できる。 In this case, gas generation is suppressed when the carbon fiber short fibers with sizing agent attached are subjected to high-temperature treatment (for example, high-temperature treatment at 300°C or higher or 350°C or higher), so a composite material with particularly good quality is obtained. This 400°C decomposition amount range can be achieved, for example, by reducing the amount of sizing agent attached to the carbon fiber short fibers.
　この４００℃分解量は、マッフル炉を用いて計測できる。具体的には、４００℃分解量は、サイジング剤付着炭素繊維ショートファイバー１ｇを４００℃に設定したマッフル炉（空気中）で２０分間加熱処理したときの重量減少率のことである。 This 400°C decomposition amount can be measured using a muffle furnace. Specifically, the 400°C decomposition amount is the weight loss rate when 1 g of carbon fiber short fibers with sizing agent attached is heat-treated for 20 minutes in a muffle furnace (in air) set at 400°C.
　この４００℃分解量は、より好ましくは、サイジング剤付着炭素繊維ショートファイバーの総重量に対して、０．４０％以下、０．３０％以下、０．２０％以下、又はさらには０．１０％以下である。この４００℃分解量の下限は特に限定されないが、例えば、０．０１％以上、０．０５％以上、又は０．０８％以上であってよい。 This 400°C decomposition amount is more preferably 0.40% or less, 0.30% or less, 0.20% or less, or even 0.10% or less, based on the total weight of the carbon fiber short fibers with the sizing agent attached. The lower limit of this 400°C decomposition amount is not particularly limited, but may be, for example, 0.01% or more, 0.05% or more, or 0.08% or more.
（サイジング層の平均層厚）
　本開示に係る好ましい１つの実施態様では、サイジング剤付着炭素繊維ショートファイバーに関して、サイジング層の平均層厚（サイジング剤の平均厚み）が、５～１００ｎｍであってよい。このサイジング層の平均層厚は、好ましくは１０～６０ｎｍ、より好ましくは１２～４０ｎｍ、さらに好ましくは１４～３０ｎｍである。 (Average thickness of sizing layer)
In a preferred embodiment of the present disclosure, the average thickness of the sizing layer (average thickness of the sizing agent) of the carbon fiber short fibers to which a sizing agent is attached may be 5 to 100 nm. The average thickness of the sizing layer is preferably 10 to 60 nm, more preferably 12 to 40 nm, and even more preferably 14 to 30 nm.
　サイジング剤付着炭素繊維ショートファイバーに付着したサイジング剤のこの平均厚みは、透過電子顕微鏡（ＴＥＭ）を用いて取得した炭素繊維の繊維軸方向に対して垂直な断面の画像を用いて、３０以上の炭素繊維で計測した値を平均することによって得ることができる。 This average thickness of the sizing agent attached to the carbon fiber short fibers with sizing agent attached can be obtained by averaging the values measured for 30 or more carbon fibers using cross-sectional images perpendicular to the fiber axis direction of the carbon fibers obtained using a transmission electron microscope (TEM).
（サイジング剤の種類）
　本発明の１つの実施態様では、サイジング剤が、水溶性樹脂、及び／又は０．３μｍ以下の平均粒子径を有する粒状樹脂を含む。特には、サイジング剤が、水溶性樹脂を含む。　好ましくは、サイジング剤は、水溶性樹脂、及び／又は０．３μｍ以下の平均粒子径を有する粒状樹脂を、サイジング剤の合計質量に対して、７０質量％以上、８０質量％以上、９０質量％以上、９５質量％以上、若しくは９９質量％以上の割合で含み、特には１００質量％で含む。
　特に好ましくは、サイジング剤は、ポリイミド又はブロックイソシアネート（特にはポリイミド）を、サイジング剤の合計質量に対して、７０質量％以上、８０質量％以上、９０質量％以上、９５質量％以上、若しくは９９質量％以上の割合で含み、特には１００質量％で含む。 (Type of sizing agent)
In one embodiment of the present invention, the sizing agent includes a water-soluble resin and/or a granular resin having an average particle size of 0.3 μm or less. In particular, the sizing agent includes a water-soluble resin. Preferably, the sizing agent includes the water-soluble resin and/or the granular resin having an average particle size of 0.3 μm or less in a proportion of 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more, particularly 100% by mass, based on the total mass of the sizing agent.
Particularly preferably, the sizing agent contains polyimide or blocked isocyanate (particularly polyimide) in a proportion of 70 mass% or more, 80 mass% or more, 90 mass% or more, 95 mass% or more, or 99 mass% or more, and particularly 100 mass% of the polyimide or blocked isocyanate, based on the total mass of the sizing agent.
　サイジング剤は、例えば、液状のサイジング剤組成物を炭素繊維に適用（例えば浸漬法で適用）することによって、炭素繊維に付着させることができる。この際に、比較的粘度の高いサイジング剤組成物を用いた場合には、炭素繊維へのサイジング剤の付着量が過度に大きくなるおそれがある。これに対して、サイジング剤が水溶性樹脂及び／又は０．３μｍ以下の平均粒子径を有する粒状樹脂である場合には、サイジング剤を付着する際に用いるサイジング剤組成物としての水溶液又は水分散液の粘度を比較的抑制できるので、炭素繊維へのサイジング剤の付着量を抑制できると考えられる。 The sizing agent can be attached to the carbon fibers, for example, by applying a liquid sizing agent composition to the carbon fibers (e.g., by dipping). In this case, if a sizing agent composition with a relatively high viscosity is used, there is a risk that the amount of sizing agent attached to the carbon fibers will be excessively large. In contrast, if the sizing agent is a water-soluble resin and/or a granular resin with an average particle size of 0.3 μm or less, the viscosity of the aqueous solution or aqueous dispersion as the sizing agent composition used to attach the sizing agent can be relatively suppressed, and it is therefore believed that the amount of sizing agent attached to the carbon fibers can be suppressed.
　また、０．３μｍ超の平均粒子径を有する粒状樹脂の場合には、炭素繊維に均一に付着させることが容易ではなく、均一な付着のためには付着量を比較的多くする必要がある。これに対して、０．３μｍ以下の平均粒子径を有する粒状樹脂を用いることによって、付着量を抑制しつつ、炭素繊維表面への均一な付着を容易に達成することができると考えられる。 Furthermore, in the case of granular resin with an average particle size of more than 0.3 μm, it is not easy to adhere uniformly to the carbon fiber, and a relatively large amount of adhesion is required to achieve uniform adhesion. In contrast, by using granular resin with an average particle size of 0.3 μm or less, it is believed that uniform adhesion to the carbon fiber surface can be easily achieved while suppressing the amount of adhesion.
　水溶性樹脂としては、ポリイミド前駆体やポリエステル樹脂等が挙げられるが、これに限定されない。これらの樹脂は、例えば、水溶液の形態で炭素繊維ショートファイバーに適用できる。 Water-soluble resins include, but are not limited to, polyimide precursors and polyester resins. These resins can be applied to carbon fiber short fibers in the form of an aqueous solution, for example.
　０．３μｍ以下の平均粒子径を有する粒状樹脂を構成する樹脂としては、ポリウレタン樹脂、エポキシ樹脂、ブロックイソシアネート等が挙げられるが、これに限定されない。これらの樹脂は、例えば、乳化物の形態で炭素繊維ショートファイバーに適用できる。なお、この平均粒子径の下限は特に限定されないが、例えば、０．０１μｍ以上、０．０５μｍ以上、又は０．１μｍ以上であってよい。 Resins constituting granular resins having an average particle size of 0.3 μm or less include, but are not limited to, polyurethane resins, epoxy resins, blocked isocyanates, etc. These resins can be applied to carbon fiber short fibers, for example, in the form of an emulsion. The lower limit of this average particle size is not particularly limited, but may be, for example, 0.01 μm or more, 0.05 μm or more, or 0.1 μm or more.
　粒状樹脂の平均粒子径は、粒度分布計を用いて、Ｄ５０粒径として決定できる。 The average particle size of the granular resin can be determined as the D50 particle size using a particle size distribution analyzer.
（ポリイミド）
　サイジング剤は、好ましくはポリイミド樹脂を含み、特にはポリイミド樹脂からなる。 (Polyimide)
The sizing agent preferably contains a polyimide resin, and in particular consists of a polyimide resin.
　ポリイミド樹脂は、イミド結合を有する繰り返し単位を含むポリマーである。ポリイミド樹脂は、特には芳香族ポリイミド樹脂である。ポリイミド樹脂は、例えば、テトラカルボン酸二無水物とジアミンとを溶媒中で重縮合することを含む方法によって得ることができる。 Polyimide resins are polymers containing repeating units with imide bonds. Polyimide resins are particularly aromatic polyimide resins. Polyimide resins can be obtained, for example, by a method including polycondensation of tetracarboxylic dianhydrides and diamines in a solvent.
　本開示に係るポリイミド樹脂は、好ましくは、融点を有さず、かつ４００℃以上（特には４５０℃以上）の熱分解温度を有するポリイミド（特には芳香族ポリイミド）である。ポリイミドなどの樹脂の融点は、ＪＩＳ　Ｋ７１２１に従ってＤＳＣ（示差走査熱量測定）法によって窒素雰囲気中１０℃／ｍｉｎで昇温したときの融解ピークの頂点の温度として計測することができる。また、熱分解温度は、ＪＩＳ　Ｋ７１２０に従って、ＴＧ（熱重量測定）法によって、窒素雰囲気中１０℃／ｍｉｎの昇温条件で計測することができる。 The polyimide resin according to the present disclosure is preferably a polyimide (particularly an aromatic polyimide) that does not have a melting point and has a thermal decomposition temperature of 400°C or higher (particularly 450°C or higher). The melting point of a resin such as a polyimide can be measured as the temperature at the apex of the melting peak when the temperature is increased at 10°C/min in a nitrogen atmosphere by DSC (differential scanning calorimetry) according to JIS K7121. The thermal decomposition temperature can be measured in a nitrogen atmosphere at a temperature increase rate of 10°C/min by TG (thermogravimetry) according to JIS K7120.
　ポリイミド樹脂は、ポリイミドの前駆体化合物（又はその混合体）を含有する水溶液を炭素繊維に付着させた後で、所定温度での乾燥処理によってイミド化することによって得られたものであってもよい。 The polyimide resin may be obtained by applying an aqueous solution containing a polyimide precursor compound (or a mixture thereof) to carbon fibers, followed by imidization by drying at a predetermined temperature.
（炭素繊維ショートファイバー）
炭素繊維ショートファイバーとしては、チョップド炭素繊維、及びミルドファイバーが挙げられる。チョップド炭素繊維は、例えば、炭素繊維束（ｃａｒｂｏｎ　ｆｉｂｅｒ　ｔｏｗ）を切断処理することによって得ることができる。ミルドファイバーは、例えば、チョップド炭素繊維を粉砕機ですり潰すことによって得ることができる。ミルドファイバーは、多くの場合、０．２ｍｍ以下の平均長さを有する。炭素繊維ショートファイバーは、特には、チョップド炭素繊維である。チョップド炭素繊維は、例えば、連続的に製造される炭素繊維の束を一定の長さにカットすることによって得ることができる。カットは、公知の方法で行ってよい。 (Carbon fiber short fiber)
Examples of the carbon fiber short fibers include chopped carbon fibers and milled fibers. Chopped carbon fibers can be obtained, for example, by cutting carbon fiber tows. Milled fibers can be obtained, for example, by grinding chopped carbon fibers with a grinder. Milled fibers often have an average length of 0.2 mm or less. The carbon fiber short fibers are particularly chopped carbon fibers. Chopped carbon fibers can be obtained, for example, by cutting a bundle of continuously produced carbon fibers to a certain length. The cutting may be performed by a known method.
（炭素繊維表面のＯ／Ｃ比）
　炭素繊維ショートファイバーの表面のＯ／Ｃ比（Ｏ原子のＣ原子に対する割合）は、好ましくは、１５％～３０％（０．１５～０．３０とも表記されうる）である。このＯ／Ｃ比は、より好ましくは１８％～２９％、さらに好ましくは２０％～２８％、最も好ましくは２１％～２７％である。この場合には、炭素繊維に対するサイジング剤の付着性が最適化される。 (O/C ratio of carbon fiber surface)
The O/C ratio (ratio of O atoms to C atoms) on the surface of the carbon fiber short fibers is preferably 15% to 30% (which may also be expressed as 0.15 to 0.30). This O/C ratio is more preferably 18% to 29%, further preferably 20% to 28%, and most preferably 21% to 27%. In this case, the adhesion of the sizing agent to the carbon fibers is optimized.
　また、この場合には、サイジング剤として水溶性樹脂又は０．３μｍ以下の平均粒子径を有する粒状樹脂を用いた場合であっても、炭素繊維表面におけるサイジング剤の均一な分布を確保できる。すなわち、サイジング剤を炭素繊維に付着させる際に、サイジング剤組成物として水溶性樹脂又は０．３μｍ以下の平均粒子径を有する粒状樹脂の水溶液又は分散液を用いる場合、粘性が比較的低いことなどから、炭素繊維の表面にサイジング剤を均一に付着させることが容易でない場合がある。これに対して、炭素繊維ショートファイバーの表面のＯ／Ｃ比が上記の範囲である場合には、炭素繊維表面へのサイジング剤の濡れ性が向上するので、サイジング剤組成物として水溶性樹脂又は０．３μｍ以下の平均粒子径を有する粒状樹脂の水溶液又は分散液を用いた場合であっても、炭素繊維表面におけるサイジング剤の均一な分布を実現できると考えられる。 In this case, even if a water-soluble resin or a granular resin having an average particle size of 0.3 μm or less is used as the sizing agent, uniform distribution of the sizing agent on the carbon fiber surface can be ensured. That is, when a sizing agent is applied to carbon fibers, if an aqueous solution or dispersion of a water-soluble resin or a granular resin having an average particle size of 0.3 μm or less is used as the sizing agent composition, it may not be easy to uniformly apply the sizing agent to the carbon fiber surface due to relatively low viscosity. In contrast, when the O/C ratio of the surface of the carbon fiber short fiber is within the above range, the wettability of the sizing agent to the carbon fiber surface is improved, so it is considered that uniform distribution of the sizing agent on the carbon fiber surface can be achieved even if an aqueous solution or dispersion of a water-soluble resin or a granular resin having an average particle size of 0.3 μm or less is used as the sizing agent composition.
　本発明に係るより好ましい実施態様では、
　炭素繊維ショートファイバーの表面のＯ／Ｃ比が、１５％～３０％であり、かつ、
　サイジング剤が、水溶性樹脂を含み、又は、０．３μｍ以下の平均粒子径を有する粒状樹脂を含み、特には、サイジング剤が、水溶性樹脂を含む。 In a more preferred embodiment of the present invention,
The O/C ratio of the surface of the carbon fiber short fiber is 15% to 30%, and
The sizing agent includes a water-soluble resin or includes a granular resin having an average particle size of 0.3 μm or less, and in particular, the sizing agent includes a water-soluble resin.
　炭素繊維ショートファイバーの表面のＯ／Ｃ比は、適切な溶剤などを用いてサイジング剤を除去した炭素繊維の表面において、Ｘ線光電子分光法（ＸＰＳ）によって決定できる。 The O/C ratio on the surface of short carbon fiber can be determined by X-ray photoelectron spectroscopy (XPS) on the surface of carbon fiber from which the sizing agent has been removed using an appropriate solvent, etc.
（引張弾性率）
　炭素繊維ショートファイバーは、好ましくは、２３０ＧＰａ以上の引張弾性率（ストランド弾性率）を示す。このストランド弾性率は、より好ましくは、２４０ＧＰａ以上、又はさらには２４５ＧＰａ以上であり、さらに好ましくは、２６０ＧＰａ以上、２７０ＧＰａ以上、又はさらには２８０ＧＰａ以上である。この引張弾性率の上限は、例えば、４００ＧＰａ以下、３５０ＧＰａ以下、又は３００ＧＰａ以下であってよい。 (Tensile Modulus)
The carbon fiber short fibers preferably exhibit a tensile modulus (strand modulus) of 230 GPa or more. This strand modulus is more preferably 240 GPa or more, or even 245 GPa or more, and even more preferably 260 GPa or more, 270 GPa or more, or even 280 GPa or more. The upper limit of this tensile modulus may be, for example, 400 GPa or less, 350 GPa or less, or 300 GPa or less.
　この引張弾性率（ストランド弾性率）は、ＪＩＳ　Ｒ　７６０８に従って計測できる。 This tensile modulus (strand modulus) can be measured in accordance with JIS R 7608.
（炭素繊維ショートファイバーの単繊維径）
　炭素繊維ショートファイバーは、３～１０μｍの単繊維径を有してよい。 (single fiber diameter of short carbon fiber)
The short carbon fibers may have a single fiber diameter of 3 to 10 μm.
　炭素繊維ショートファイバーは、好ましくは４μｍ～８μｍ、さらに好ましくは４．５～６．５μｍの単繊維径を有する。この場合には、本発明に係るサイジング剤付着炭素繊維ショートファイバーを用いて複合材料を製造したときに、特に良好な物性を有する複合材料を得ることができる。理論によって限定する意図はないが。本発明によれば、比較的細い炭素繊維ショートファイバーを用いた場合であっても、コンパウンド化工程などで繊維折れが抑制され、複合材料中で比較的長い残存繊維長を確保できる。したがって、炭素繊維ショートファイバーとして単繊維径４～８μｍ（又はさらには４．５～６．５μｍ）のものを用いた場合には、複合材料中の炭素繊維のアスペクト比を比較的大きくでき、その結果として、特に良好な引張強度を示す複合材料が得られると考えられる。 The carbon fiber short fibers preferably have a single fiber diameter of 4 μm to 8 μm, and more preferably 4.5 to 6.5 μm. In this case, when a composite material is produced using the carbon fiber short fibers with a sizing agent according to the present invention, a composite material with particularly good physical properties can be obtained. Although there is no intention to be limited by theory, according to the present invention, even when relatively thin carbon fiber short fibers are used, fiber breakage is suppressed during the compounding process, etc., and a relatively long remaining fiber length can be ensured in the composite material. Therefore, when carbon fiber short fibers with a single fiber diameter of 4 to 8 μm (or even 4.5 to 6.5 μm) are used, the aspect ratio of the carbon fibers in the composite material can be made relatively large, and as a result, it is believed that a composite material exhibiting particularly good tensile strength can be obtained.
　炭素繊維の単繊維径は、電子顕微鏡等を用いて取得した画像を用いて計測した３０以上の炭素繊維の直径を平均することによって得ることができる。 The single fiber diameter of carbon fibers can be obtained by averaging the diameters of 30 or more carbon fibers measured using images obtained using an electron microscope, etc.
（炭素繊維）
　炭素繊維は、特に制限が無く、ピッチ系、レーヨン系、ポリアクリロニトリル（ＰＡＮ）系など、いずれの炭素繊維であってもよいが、操作性、工程通過性、及び機械強度等を鑑みると、アクリロニトリル系の炭素繊維が好ましい。炭素繊維の繊度、強度等の特性も特に制限が無く、公知のいずれの炭素繊維も制限無く使用できる。 (Carbon fiber)
The carbon fiber is not particularly limited, and may be any carbon fiber such as pitch-based, rayon-based, polyacrylonitrile (PAN)-based, etc., but acrylonitrile-based carbon fiber is preferred in terms of operability, processability, mechanical strength, etc. The fineness, strength, and other properties of the carbon fiber are also not particularly limited, and any known carbon fiber can be used without limitation.
　炭素繊維の形態は、特に制限されないが、複数の単糸（フィラメント）から構成される炭素繊維束の形態であってよい。炭素繊維束を構成するフィラメントの構成本数は、生産性の観点などから１，０００本～８０，０００本であることが好ましく、さらには３，０００本～５０，０００本の範囲であることが好ましい。好ましくは、ＪＩＳ　Ｒ　７６０８に従って計測したときに、炭素繊維の引張強度が４０００～１００００ＭＰａである。 The form of the carbon fiber is not particularly limited, but may be in the form of a carbon fiber bundle composed of multiple single threads (filaments). From the viewpoint of productivity, the number of filaments constituting the carbon fiber bundle is preferably 1,000 to 80,000, and more preferably in the range of 3,000 to 50,000. Preferably, the tensile strength of the carbon fiber is 4,000 to 10,000 MPa when measured according to JIS R 7608.
　ＰＡＮ系炭素繊維は、例えば、以下の方法により製造することができる。 PAN-based carbon fibers can be produced, for example, by the following method.
　（前駆体繊維）
　アクリル系前駆体繊維は、好ましくは、アクリロニトリルを９０質量％以上、より好ましくは９５質量％以上含有し、その他の単量体を１０質量％以下含有する単量体を単独又は共重合した紡糸溶液を紡糸して製造される。その他の単量体としてはイタコン酸、（メタ）アクリル酸エステル等が例示される。紡糸後の原料繊維を、水洗、乾燥、延伸、オイリング処理することにより、前駆体繊維を得ることができる。前駆体繊維のフィラメント数は、製造効率の面では１，０００本以上が好ましく、３，０００本以上がより好ましい。 (Precursor Fiber)
The acrylic precursor fiber is produced by spinning a spinning solution containing 90% by mass or more, more preferably 95% by mass or more, of acrylonitrile and 10% by mass or less of other monomers, which is either homopolymerized or copolymerized. Examples of other monomers include itaconic acid and (meth)acrylic acid esters. The precursor fiber can be obtained by washing, drying, stretching, and oiling the raw fiber after spinning. In terms of production efficiency, the number of filaments of the precursor fiber is preferably 1,000 or more, more preferably 3,000 or more.
　（耐炎化処理）
　前駆体繊維を、加熱空気中２００～３００℃で１０～１００分間加熱し、耐炎化処理する。耐炎化処理では、延伸倍率０．９０～１．２０の範囲で繊維を延伸処理することが好ましい。 (Flameproofing treatment)
The precursor fiber is heated in heated air at 200 to 300° C. for 10 to 100 minutes for flame retardation treatment. In the flame retardation treatment, the fiber is preferably stretched at a stretch ratio in the range of 0.90 to 1.20.
　（炭素化処理）
　耐炎化処理した前駆体繊維を、不活性雰囲気下において３００～２０００℃で炭素化して、炭素繊維を得る。より引張強度の高い緻密な内部構造をもつ炭素繊維束を得るためには、３００℃～１０００℃で低温炭素化した後、１０００～２０００℃で高温炭素化する二段階の炭素化工程を経て、炭素化処理を行うことが好ましい。より高い弾性率が求められる場合は、さらに、２０００～３０００℃の高温で黒鉛化処理を行ってもよい。 (Carbonization treatment)
The flame-retardant treated precursor fiber is carbonized at 300 to 2000° C. in an inert atmosphere to obtain carbon fiber. In order to obtain a carbon fiber bundle having a dense internal structure with higher tensile strength, it is preferable to carry out the carbonization treatment through a two-stage carbonization process in which low-temperature carbonization at 300 to 1000° C. is followed by high-temperature carbonization at 1000 to 2000° C. When a higher elastic modulus is required, a graphitization treatment may be further carried out at a high temperature of 2000 to 3000° C.
（表面酸化処理）
　上記で得られた炭素繊維は、サイジング剤及び／又はマトリックス樹脂との濡れ性を改善するために、表面酸化処理を行うことが好ましい。表面酸化処理は、従来公知のいずれの方法でも行うことができるが、装置が簡便であり工程での管理が容易であることから、工業的には電解酸化を用いることが一般的である。 (Surface oxidation treatment)
The carbon fiber obtained above is preferably subjected to a surface oxidation treatment in order to improve wettability with a sizing agent and/or a matrix resin. The surface oxidation treatment can be performed by any conventionally known method, but electrolytic oxidation is generally used industrially because the apparatus is simple and the process is easy to control.
　表面酸化処理の電気量は、炭素繊維１ｇに対して１０～１５０クーロンになる範囲とすることが好ましい。電気量をこの範囲で調節すると、繊維としての力学的特性に優れ、かつ、樹脂との接着性の向上した炭素繊維を得ることができる。 The amount of electricity used in the surface oxidation treatment is preferably in the range of 10 to 150 coulombs per gram of carbon fiber. By adjusting the amount of electricity within this range, it is possible to obtain carbon fiber that has excellent mechanical properties as a fiber and improved adhesion to resin.
　電解液としては、例えば、硝酸、硫酸、硫酸アンモニウムや炭酸水素ナトリウムなどが挙げられる。電解液の電解質濃度は０．１規定以上が好ましく、０．１～１規定がより好ましい。 Examples of the electrolyte include nitric acid, sulfuric acid, ammonium sulfate, and sodium bicarbonate. The electrolyte concentration of the electrolyte is preferably 0.1N or more, and more preferably 0.1 to 1N.
＜＜サイジング剤付着炭素繊維ショートファイバーの製造方法＞＞
　本発明に係る表面弾性率の特性を満たすサイジング剤付着炭素繊維ショートファイバーは、例えば、サイジング剤の種類、サイジング剤を付与する際のサイジング剤組成物の態様（水溶液、分散体等）、及び／又は、サイジング剤が付与される炭素繊維の表面物性（特にはＯ／Ｃ比）などを最適化することによって得ることができる。 <<Method of manufacturing carbon fiber short fibers with sizing agent>>
The sizing agent-attached carbon fiber short fibers satisfying the surface elastic modulus characteristics according to the present invention can be obtained, for example, by optimizing the type of sizing agent, the form of the sizing agent composition when the sizing agent is applied (aqueous solution, dispersion, etc.), and/or the surface properties (particularly the O/C ratio) of the carbon fibers to which the sizing agent is applied.
　本開示に係るサイジング剤付着炭素繊維ショートファイバーの製造方法は、特に限定されないが、好ましくは、下記の本開示に係る製造方法によって製造することができる。 　The method for producing the sizing agent-attached carbon fiber short fibers according to the present disclosure is not particularly limited, but it is preferable to produce them according to the following production method according to the present disclosure.
　すなわち：
　（ａ）炭素繊維ショートファイバーを提供すること、及び、
（ｂ）炭素繊維ショートファイバーの表面に、サイジング剤組成物を適用すること、
を含み、
　炭素繊維ショートファイバーの表面のＯ／Ｃ比が、１５％～３０％であり、かつ、
　サイジング剤組成物が、水溶性樹脂を含み、又は、０．３μｍ以下の平均粒子径を有する粒状樹脂を含み、特には、サイジング剤組成物が、水溶性樹脂を含む、
サイジング剤付着炭素繊維ショートファイバーの製造方法。 Namely:
(a) providing carbon fiber short fibers; and
(b) applying a sizing agent composition to the surface of the carbon fiber short fibers;
Including,
The O/C ratio of the surface of the carbon fiber short fiber is 15% to 30%, and
The sizing agent composition contains a water-soluble resin or a granular resin having an average particle size of 0.3 μm or less, and in particular, the sizing agent composition contains a water-soluble resin.
A method for producing carbon fiber short fibers with sizing agent attached.
　この製造方法における構成要素（炭素繊維ショートファイバーなど）の詳細については、本開示に係るサイジング剤付着炭素繊維ショートファイバーに関する上記の記載を参照できる。 For details about the components (such as short carbon fiber) in this manufacturing method, please refer to the above description of the sizing agent-attached short carbon fiber disclosed herein.
＜繊維提供工程＞
　本開示に係る製造方法は、炭素繊維ショートファイバーを提供すること（繊維提供工程、工程ａ）を含む。この繊維提供工程では、炭素繊維ショートファイバー（特にはチョップド炭素繊維）を提供する。炭素繊維ショートファイバーは、好ましくは０．５ｍｍ～３０ｍｍ、より好ましくは１ｍｍ～２５ｍｍ、さらに好ましくは２ｍｍ～１５ｍｍの平均長さを有する。 <Fiber provision process>
The manufacturing method according to the present disclosure includes providing carbon fiber short fibers (fiber providing step, step a). In this fiber providing step, carbon fiber short fibers (particularly chopped carbon fibers) are provided. The carbon fiber short fibers preferably have an average length of 0.5 mm to 30 mm, more preferably 1 mm to 25 mm, and even more preferably 2 mm to 15 mm.
　この工程では、例えば、連続的に製造された炭素繊維束をカッター等で切断することによって、炭素繊維ショートファイバーとしてのチョップド炭素繊維を得ることができる。この工程で提供される炭素繊維ショートファイバーは、集合体を形成していてよく、例えばチップ状の集合体であってよい。 In this process, for example, chopped carbon fibers can be obtained as short carbon fiber fibers by cutting the continuously produced carbon fiber bundles with a cutter or the like. The short carbon fiber fibers provided in this process may form an aggregate, for example, a chip-shaped aggregate.
（開繊）
　炭素繊維ショートファイバーの集合体では、炭素繊維の製造過程で付与されるサイジング剤などを介して、炭素繊維ショートファイバー同士が互いに接着していることがある。この場合、炭素繊維ショートファイバーの集合体を随意に開繊して、炭素繊維ショートファイバーを互いに分離することができる。そして、このようにして開繊処理された炭素繊維ショートファイバーに対して、本開示に係るサイジング剤を適用することができる。開繊の方法は特に限定されず、公知の方法を用いることができる。 (Opening)
In an aggregate of carbon fiber short fibers, the carbon fiber short fibers may be bonded to each other via a sizing agent or the like applied during the carbon fiber manufacturing process. In this case, the aggregate of carbon fiber short fibers can be opened at will to separate the carbon fiber short fibers from each other. Then, the sizing agent according to the present disclosure can be applied to the carbon fiber short fibers thus opened. The method of opening is not particularly limited, and a known method can be used.
　本開示に係る製造方法で用いる炭素繊維ショートファイバーは、その表面のＯ／Ｃ比が１５％～３０％であるという特徴を有する。この特徴の詳細については、本開示に係るサイジング剤付着炭素繊維ショートファイバーに関する上記の記載を参照できる。 The carbon fiber short fibers used in the manufacturing method of the present disclosure are characterized in that the O/C ratio of their surface is 15% to 30%. For details of this characteristic, please refer to the above description of the carbon fiber short fibers with sizing agent attached thereto according to the present disclosure.
＜サイジング剤適用工程＞
　本開示に係る製造方法は、炭素繊維ショートファイバーの表面に、サイジング剤組成物を適用すること（サイジング剤適用工程、工程ｂ）を含む。このサイジング剤適用工程では、例えば、サイジング剤を含有するサイジング剤組成物に炭素繊維ショートファイバーを接触させることによって、サイジング剤を適用できる。具体的な例としては、炭素繊維を直接サイジング剤組成物に浸漬させる浸漬方式、及び、サイジング剤組成物を炭素繊維にスプレーで吹き付けるスプレー法などが挙げられる。 <Sizing agent application process>
The manufacturing method according to the present disclosure includes applying a sizing agent composition to the surface of the carbon fiber short fibers (a sizing agent applying step, step b). In this sizing agent applying step, for example, the sizing agent can be applied by contacting the carbon fiber short fibers with a sizing agent composition containing the sizing agent. Specific examples include an immersion method in which the carbon fibers are directly immersed in the sizing agent composition, and a spray method in which the sizing agent composition is sprayed onto the carbon fibers.
（乾燥処理）
　サイジング剤適用工程の後に、サイジング剤組成物に含まれていた溶媒、分散媒を除去するための乾燥処理をさらに行うことができる。この乾燥処理は、公知の方法で行うことができる。 (Drying treatment)
After the sizing agent application step, a drying treatment can be further carried out to remove the solvent and the dispersion medium contained in the sizing agent composition. This drying treatment can be carried out by a known method.
（サイジング剤組成物）
　サイジング剤組成物は、サイジング剤、及び分散媒又は溶媒を含む。サイジング剤組成物を調製する方法は特に限定されず、公知の調製方法を用いることができる。サイジング剤の詳細については、本開示に係るサイジング剤付着炭素繊維ショートファイバーに関する上記の記載を参照できる。 (Sizing agent composition)
The sizing agent composition includes a sizing agent and a dispersion medium or a solvent. The method for preparing the sizing agent composition is not particularly limited, and a known preparation method can be used. For details of the sizing agent, the above description of the carbon fiber short fiber with the sizing agent according to the present disclosure can be referred to.
　サイジング剤組成物の分散媒又は溶媒としては、水、及び有機溶剤（例えば、メタノールなどのアルコール類や、アセトンなど）が挙げられる。 The dispersion medium or solvent for the sizing agent composition includes water and organic solvents (e.g., alcohols such as methanol, acetone, etc.).
　サイジング剤組成物は、界面活性剤を用いて乳化させることによって調製されるサイジング剤水分散液（エマルジョン）であってもよい。 The sizing agent composition may be an aqueous sizing agent dispersion (emulsion) prepared by emulsifying using a surfactant.
　サイジング剤組成物がサイジング剤溶液又はサイジング剤分散液である場合、溶液又は分散液中におけるサイジング剤の濃度は、０．５～２０％質量％であってよい。 When the sizing agent composition is a sizing agent solution or sizing agent dispersion, the concentration of the sizing agent in the solution or dispersion may be 0.5 to 20% by mass.
　界面活性剤は、特に制限されず、アニオン系、カチオン系、ノニオン系界面活性剤等を用いることができる。中でもノニオン系界面活性剤が、乳化性能および分散液の安定性の観点から好ましい。 The surfactant is not particularly limited, and anionic, cationic, or nonionic surfactants can be used. Among them, nonionic surfactants are preferred from the viewpoint of emulsification performance and stability of the dispersion liquid.
　ノニオン系界面活性剤としては、ポリエチレングリコール型（高級アルコールエチレンオキサイド付加物、アルキルフェノールエチレンオキサイド付加物、脂肪酸エチレンオキサイド付加物、ポリプロピレングリコールエチレンオキサイド付加物等）、多価アルコール型（グリセリンの脂肪酸エステル、ソルビトール脂肪酸エステル、脂肪酸アルカノールアミド等）等の界面活性剤が挙げられるが、炭素繊維表面と金属との間の摩擦抵抗を低減することができる、ポリオキシエチレンポリオキシプロピレンブロックポリマーを用いることが特に好ましい。 Nonionic surfactants include polyethylene glycol type (higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, fatty acid ethylene oxide adducts, polypropylene glycol ethylene oxide adducts, etc.) and polyhydric alcohol type (glycerin fatty acid esters, sorbitol fatty acid esters, fatty acid alkanolamides, etc.), but it is particularly preferable to use polyoxyethylene polyoxypropylene block polymers, which can reduce the frictional resistance between the carbon fiber surface and metal.
　乳化方法としては、撹拌翼を具備したバッチを用いる方法、ボールミルを用いる方法、振とう器を用いる方法、ガウリンホモジナイザ等の高せん断乳化機を用いる方法等が挙げられる。 Emulsification methods include using a batch equipped with an agitator, using a ball mill, using a shaker, and using a high-shear emulsifier such as a Gaulin homogenizer.
　界面活性剤は、サイジング剤を乳化できれば特に制限はないが、通常０．１～３０質量％程度添加すればよい。 There are no particular limitations on the surfactant as long as it can emulsify the sizing agent, but it is usually sufficient to add about 0.1 to 30% by weight.
　本開示に係る製造方法で用いるサイジング剤組成物は、水溶性樹脂を含み、又は、０．３μｍ以下の平均粒子径を有する粒状樹脂を含むという特徴を有する。この特徴の詳細については、本開示に係るサイジング剤付着炭素繊維ショートファイバーに関する上記の記載を参照できる。 The sizing agent composition used in the manufacturing method according to the present disclosure is characterized in that it contains a water-soluble resin or a granular resin having an average particle size of 0.3 μm or less. For details of this characteristic, please refer to the above description regarding the sizing agent-attached carbon fiber short fiber according to the present disclosure.
　本開示に係る製造方法では、水溶性樹脂又は０．３μｍ以下の平均粒子径を有する粒状樹脂を含むサイジング剤組成物に用いるとともに、表面のＯ／Ｃ比が１５％～３０％である炭素繊維ショートファイバーを用いる。この場合には、サイジング剤組成物としての水溶液又は分散液の粘度を比較的低くできることなどから、炭素繊維に付着されるサイジング剤の量を低減できるとともに、比較的高いＯ／Ｃ比に起因して炭素繊維に対するサイジング剤の濡れ性が向上しているので、炭素繊維表面上にサイジング剤を均一に適用できると考えられる。 In the manufacturing method disclosed herein, a sizing agent composition containing a water-soluble resin or a granular resin having an average particle size of 0.3 μm or less is used, and short carbon fiber fibers having a surface O/C ratio of 15% to 30% are used. In this case, the viscosity of the aqueous solution or dispersion as the sizing agent composition can be made relatively low, so that the amount of sizing agent attached to the carbon fiber can be reduced, and the wettability of the sizing agent to the carbon fiber is improved due to the relatively high O/C ratio, so that the sizing agent can be applied uniformly to the carbon fiber surface.
＜＜コンパウンド＞＞
　本開示は、本開示に係るサイジング剤付着炭素繊維ショートファイバーを用いて形成されるコンパウンドを含む。コンパウンドは、ペレット状（ペレット状のコンパウンド）であってよい。 ＜＜Compound＞＞
The present disclosure includes a compound formed using the carbon fiber short fibers having a sizing agent attached thereto according to the present disclosure. The compound may be in the form of pellets (pellet-shaped compound).
　コンパウンドは、本開示に係るサイジング剤付着炭素繊維ショートファイバーに由来する炭素繊維（炭素繊維ショートファイバー）、及び樹脂を含有する。コンパウンドに含まれる炭素繊維（炭素繊維ショートファイバー）については、本開示に係るサイジング剤付着炭素繊維ショートファイバーに関する上記の記載を参照することができる。 The compound contains carbon fiber (short carbon fiber) derived from the sizing agent-attached carbon fiber short fiber according to the present disclosure, and resin. For the carbon fiber (short carbon fiber) contained in the compound, the above description regarding the sizing agent-attached carbon fiber short fiber according to the present disclosure may be referenced.
　コンパウンド（特にはペレット状のコンパウンド）に含有される樹脂としては、熱硬化性樹脂又は熱可塑性樹脂が挙げられる。 The resin contained in the compound (especially the pellet-shaped compound) may be a thermosetting resin or a thermoplastic resin.
　熱硬化性樹脂の具体例として、エポキシ樹脂、不飽和ポリエステル樹脂、フェノール樹脂、ビニルエステル樹脂、シアン酸エステル樹脂、ウレタンアクリレート樹脂、フェノキシ樹脂、アルキド樹脂、ウレタン樹脂、マレイミド樹脂とシアン酸エステル樹脂の予備重合樹脂、ビスマレイミド樹脂、アセチレン末端を有するポリイミド樹脂及びポリイソイミド樹脂、ナジック酸末端を有するポリイミド樹脂等を挙げることができる。これらは１種又は２種以上の混合物として用いることもできる。中でも、耐熱性、弾性率、耐薬品性に優れたエポキシ樹脂やビニルエステル樹脂が好ましい。これらの熱硬化性樹脂には、硬化剤、硬化促進剤以外に、通常用いられる着色剤や各種添加剤等が含まれていてもよい。 Specific examples of thermosetting resins include epoxy resins, unsaturated polyester resins, phenolic resins, vinyl ester resins, cyanate ester resins, urethane acrylate resins, phenoxy resins, alkyd resins, urethane resins, prepolymerized resins of maleimide resins and cyanate ester resins, bismaleimide resins, polyimide resins and polyisoimide resins having acetylene ends, and polyimide resins having Nadic acid ends. These can be used alone or as a mixture of two or more. Among these, epoxy resins and vinyl ester resins, which have excellent heat resistance, elastic modulus, and chemical resistance, are preferred. These thermosetting resins may contain commonly used colorants and various additives in addition to curing agents and curing accelerators.
　熱可塑性樹脂としては、例えば、ポリプロピレン（ＰＰ）樹脂、ポリスルホン（ＰＳ）樹脂、ポリエーテルスルホン（ＰＥＳ）樹脂、ポリエーテルケトン樹脂、ポリエーテルエーテルケトン（ＰＥＥＫ）樹脂、ポリアミド（ＰＡ）樹脂、芳香族ポリアミド樹脂、ポリエステル（ＰＥ）樹脂、芳香族ポリエステル樹脂、ポリカーボネート（ＰＣ）樹脂、芳香族ポリカーボネート樹脂、ポリエーテルイミド（ＰＥＩ）樹脂、ポリアリーレンオキシド樹脂、熱可塑性ポリイミド樹脂、ポリアミドイミド樹脂、ポリアセタール樹脂、ポリフェニレンオキシド樹脂、ポリフェニレンスルフィド樹脂、ポリアリレート樹脂、ポリアクリロニトリル樹脂、ポリアラミド樹脂、ポリベンズイミダゾール樹脂等が挙げられる。これらは１種又は２種以上の混合物として用いることもできる。好ましい熱可塑性樹脂は、ポリエーテルエーテルケトン（ＰＥＥＫ）樹脂である。これらの熱可塑性樹脂には、着色剤や各種添加剤等が含まれていてもよい。 Examples of thermoplastic resins include polypropylene (PP) resin, polysulfone (PS) resin, polyethersulfone (PES) resin, polyetherketone resin, polyetheretherketone (PEEK) resin, polyamide (PA) resin, aromatic polyamide resin, polyester (PE) resin, aromatic polyester resin, polycarbonate (PC) resin, aromatic polycarbonate resin, polyetherimide (PEI) resin, polyarylene oxide resin, thermoplastic polyimide resin, polyamideimide resin, polyacetal resin, polyphenylene oxide resin, polyphenylene sulfide resin, polyarylate resin, polyacrylonitrile resin, polyaramid resin, polybenzimidazole resin, etc. These can be used alone or as a mixture of two or more kinds. A preferred thermoplastic resin is polyetheretherketone (PEEK) resin. These thermoplastic resins may contain colorants and various additives.
　本開示に係るコンパウンド（特にはペレット状のコンパウンド）における炭素繊維の含有率（繊維体積含有率Ｖｆ）は、１８体積％以上、２０体積％以上、２３体積％以上、２５体積％以上、若しくは３０体積％以上であってよく、かつ／又は、６０体積％以下、５５体積％以下、若しくは５０体積％以下であってよく、好ましくは２０～５５体積％である。 The carbon fiber content (fiber volume content Vf) in the compound (particularly the pellet-shaped compound) according to the present disclosure may be 18 volume% or more, 20 volume% or more, 23 volume% or more, 25 volume% or more, or 30 volume% or more, and/or 60 volume% or less, 55 volume% or less, or 50 volume% or less, preferably 20 to 55 volume%.
　好ましい１つの実施態様では、本開示に係るコンパウンド（特にはペレット状のコンパウンド）は、樹脂と、樹脂中に分散した炭素繊維とを含み、炭素繊維の繊維体積含有率Ｖｆが、１８体積％以上、２０体積％以上、２３体積％以上、２５体積％以上、若しくは３０体積％以上であり、かつ／又は、６０体積％以下、５５体積％以下、若しくは５０体積％以下であり、特には２０～５５体積％である。 In a preferred embodiment, the compound (particularly the pellet-shaped compound) according to the present disclosure comprises a resin and carbon fibers dispersed in the resin, and the fiber volume fraction Vf of the carbon fibers is 18 vol.% or more, 20 vol.% or more, 23 vol.% or more, 25 vol.% or more, or 30 vol.% or more, and/or 60 vol.% or less, 55 vol.% or less, or 50 vol.% or less, and particularly 20 to 55 vol.%.
　コンパウンド（特にはペレット状のコンパウンド）は、本開示に係るサイジング剤付着炭素繊維ショートファイバー及び樹脂から製造できる。コンパウンドの製造方法の具体的な態様は、特に限定されず、公知の方法を参照することができる。例えば、二軸押出機に本開示に係るサイジング剤付着炭素繊維ショートファイバーと樹脂とを供給し、随意に加熱して混練・押出することによって、コンパウンド（特にはペレット状のコンパウンド）を製造できる。 The compound (particularly the pellet-shaped compound) can be produced from the sizing agent-attached carbon fiber short fibers according to the present disclosure and resin. The specific aspects of the compound production method are not particularly limited, and known methods can be referred to. For example, the compound (particularly the pellet-shaped compound) can be produced by supplying the sizing agent-attached carbon fiber short fibers according to the present disclosure and resin to a twin-screw extruder, optionally heating, kneading, and extruding.
＜＜炭素繊維強化複合材料＞＞
　本開示に係る発明は、本開示に係るサイジング剤付着炭素繊維ショートファイバーを用いて形成される炭素繊維強化複合材料（コンポジット）を含む。 <<Carbon fiber reinforced composite materials>>
The invention according to the present disclosure includes a carbon fiber reinforced composite material (composite) formed using the carbon fiber short fibers to which the sizing agent according to the present disclosure is attached.
　炭素繊維強化複合材料は、本開示に係るサイジング剤付着炭素繊維ショートファイバーに由来する炭素繊維（炭素繊維ショートファイバー）、及び樹脂を含有する。 The carbon fiber reinforced composite material contains carbon fiber (short carbon fiber) derived from the short carbon fiber with a sizing agent attached according to the present disclosure, and a resin.
　好ましい１つの実施態様では、本開示に係る炭素繊維強化複合材料は、樹脂と、樹脂中に分散した炭素繊維とを含み、炭素繊維の繊維体積含有率Ｖｆが、１８体積％以上、２０体積％以上、２３体積％以上、２５体積％以上、若しくは３０体積％以上であり、かつ／又は、６０体積％以下、５５体積％以下、若しくは５０体積％以下であり、特には２０～５５体積％である。 In a preferred embodiment, the carbon fiber reinforced composite material according to the present disclosure comprises a resin and carbon fibers dispersed in the resin, and the fiber volume fraction Vf of the carbon fibers is 18 vol.% or more, 20 vol.% or more, 23 vol.% or more, 25 vol.% or more, or 30 vol.% or more, and/or 60 vol.% or less, 55 vol.% or less, or 50 vol.% or less, and in particular 20 to 55 vol.%.
　炭素繊維強化複合材料に含まれる炭素繊維（炭素繊維ショートファイバー）については、本開示に係るサイジング剤付着炭素繊維ショートファイバーに関する上記の記載を参照することができる。また、炭素繊維強化複合材料に含まれる樹脂については、コンパウンド（特にはペレット状のコンパウンド）に関する上記の記載を参照することができる。 For the carbon fibers (short carbon fiber fibers) contained in the carbon fiber reinforced composite material, the above description regarding the sizing agent-attached short carbon fiber fibers of this disclosure may be referenced. Also, for the resin contained in the carbon fiber reinforced composite material, the above description regarding the compound (particularly the pellet-shaped compound) may be referenced.
　本開示に係る炭素繊維強化複合材料の製造方法は、特には限定されないが、例えば下記を含む方法によって製造することができる：
　本開示に係るサイジング剤付着炭素繊維ショートファイバーと樹脂とから形成されたコンパウンド（特にはペレット状のコンパウンド）を成形して、炭素繊維強化複合材料を形成すること。 The method for producing the carbon fiber reinforced composite material according to the present disclosure is not particularly limited, but may be, for example, produced by the following method:
A compound (particularly a pellet-shaped compound) formed from the sizing agent-attached carbon fiber short fibers according to the present disclosure and a resin is molded to form a carbon fiber reinforced composite material.
　本開示に係るサイジング剤付着炭素繊維ショートファイバーと樹脂とからコンパウンド（特にはペレット状のコンパウンド）を形成する方法については、上記の記載を参照することができる。 　For the method of forming a compound (particularly a pellet-shaped compound) from the sizing agent-attached carbon fiber short fibers and resin according to the present disclosure, please refer to the above description.
　コンパウンド（特にはペレット状のコンパウンド）を成形して炭素繊維強化複合材料を形成する方法は、特に限定されず、公知の方法を用いることができる。コンパウンド（特にはペレット状のコンパウンド）は、例えば、射出成型法によって成形することができる。 The method for forming a carbon fiber reinforced composite material by molding a compound (especially a pellet-shaped compound) is not particularly limited, and any known method can be used. The compound (especially a pellet-shaped compound) can be molded, for example, by injection molding.
　以下、実施例を参照して本発明をより詳細に説明する。本発明は実施例の記載によって限定されない。 The present invention will be described in more detail below with reference to examples. The present invention is not limited to the description of the examples.
＜＜評価方法＞＞
　下記の実施例及び比較例では、それぞれ、サイジング剤付着炭素繊維ショートファイバーを製造し、その特性を評価した。評価方法は、下記のとおりである。 <<Evaluation method>>
In the following Examples and Comparative Examples, short carbon fibers having a sizing agent attached thereto were produced and their properties were evaluated by the following methods.
＜単繊維径＞
　サイジング剤付着炭素繊維ショートファイバーを構成する炭素繊維ショートファイバーの単繊維径（μｍ）は、用いた炭素繊維材料の比重、フィラメント数及び繊度から計算によって得た。 <Single fiber diameter>
The single fiber diameter (μm) of the short carbon fibers constituting the sizing agent-attached short carbon fibers was calculated from the specific gravity, number of filaments and fineness of the carbon fiber material used.
＜Ｏ／Ｃ比＞
　炭素繊維の表面における酸素原子と炭素原子との比（Ｏ／Ｃ比）は、サイジング剤を付着させる前の炭素繊維において、Ｘ線光電子分光法（ＸＰＳ）によって決定した。 <O/C ratio>
The ratio of oxygen atoms to carbon atoms (O/C ratio) on the surface of the carbon fiber was determined by X-ray photoelectron spectroscopy (XPS) on the carbon fiber before the sizing agent was attached.
　より具体的には、繊維をカットしてステンレス製の試料支持台上に拡げて並べた後、光電子脱出角度を９０度に設定し、Ｘ線源としてＭｇＫαを用い、試料チャンバー内を１×１０－６［Ｐａ］の真空度に保つ。測定時の帯電に伴うピークの補正として、まずＣ１ｓの主ピークの結合エネルギ値Ｂ．Ｅ．を２８４．６［ｅＶ］に合わせる。Ｏ１ｓピーク面積を、５２７～５４０［ｅＶ］の範囲で直線のベースラインを引くことにより求める。また、Ｃ１ｓピーク面積を、２８１～２９７［ｅＶ］の範囲で直線のベースラインを引くことにより求める。Ｃ１ｓピークに対するＯ１ｓピークの感度補正係数として２．６８６５を用いる。上記のＯ１ｓピーク面積とＣ１ｓピーク面積の比を計算することによって、炭素繊維の表面酸素濃度の比を求めた。 More specifically, the fibers are cut and spread out on a stainless steel sample support, and then the photoelectron escape angle is set to 90 degrees, MgKα is used as the X-ray source, and the inside of the sample chamber is kept at a vacuum of 1×10 −6 [Pa]. To correct the peak associated with charging during measurement, the binding energy value B.E. of the main peak of C1s is first adjusted to 284.6 [eV]. The O1s peak area is obtained by drawing a straight baseline in the range of 527 to 540 [eV]. The C1s peak area is also obtained by drawing a straight baseline in the range of 281 to 297 [eV]. 2.6865 is used as the sensitivity correction coefficient of the O1s peak relative to the C1s peak. The ratio of the O1s peak area to the C1s peak area was calculated to obtain the surface oxygen concentration ratio of the carbon fiber.
＜表面の弾性率＞
　サイジング剤付着炭素繊維ショートファイバーの表面の弾性率（ＭＰａ）は、走査型プローブ顕微鏡（ＳＰＭ）（Ｏｘｆｏｒｄ　Ｉｎｓｔｒｕｍｅｎｔｓ社製Ｊｕｐｉｔｅｒ　ＸＲ）によって以下の測定条件で計測した。
　測定モード：ファースト・フォース・マッピング
　プローブ：Ｏｘｆｏｒｄ　Ｉｎｓｔｒｕｍｅｎｔｓ社製ＦＳ－１５００
　スキャンサイズ：３．５μｍ×３．５μｍ
　ピクセルサイズ：１３．７ｎｍ
　画像サイズ：２５６ピクセル×１２８ピクセル
　Ｚレート：２００Ｈｚ
　セットポイント：２００ｎＮ
　フォースディスタンス：３００ｎｍ <Surface elastic modulus>
The elastic modulus (MPa) of the surface of the carbon fiber short fibers with the sizing agent attached was measured under the following measurement conditions using a scanning probe microscope (SPM) (Oxford Instruments Jupiter XR).
Measurement mode: First-force mapping Probe: Oxford Instruments FS-1500
Scan size: 3.5 μm x 3.5 μm
Pixel size: 13.7 nm
Image size: 256 pixels x 128 pixels Z rate: 200 Hz
Set point: 200 nN
Force distance: 300 nm
　そして、得られた弾性率の分布に関するデータから、「弾性率が５０００ＭＰａ以下である表面部位の割合（％）」、及び、「弾性率が３０ＭＰａ以上である表面部位の割合（％）」を、それぞれ算出した。さらに、この弾性率分布データに基づいて、サイジング剤付着炭素繊維ショートファイバーの表面における弾性率の平均値（数平均）も算出した。なお、ＢＲＵＫＥＲ社製ＳＰＭを用いる場合、ピークフォースタッピングモードで測定可能である。実施例８のサイジング剤付着炭素繊維ショートファイバーに対して行った測定結果を図１及び図２に示す。図１は、弾性率分布を示す画像であり、図２は、弾性率分布を示すグラフである。 Then, from the data on the distribution of the elastic modulus obtained, the "percentage (%) of surface areas with an elastic modulus of 5000 MPa or less" and the "percentage (%) of surface areas with an elastic modulus of 30 MPa or more" were calculated. Furthermore, based on this elastic modulus distribution data, the average value (number average) of the elastic modulus on the surface of the carbon fiber short fiber with the sizing agent applied was also calculated. When using a BRUKER SPM, it can be measured in peak force tapping mode. The measurement results performed on the carbon fiber short fiber with the sizing agent applied in Example 8 are shown in Figures 1 and 2. Figure 1 is an image showing the elastic modulus distribution, and Figure 2 is a graph showing the elastic modulus distribution.
＜サイジング剤付着量＞
　サイジング剤の付着量（質量％）は、炭素繊維ショートファイバーに対する値である。これは、ＪＩＳ　Ｒ　７６０４に従って、サイジング剤付着炭素繊維ショートファイバーを硫酸と過酸化水素の混合物によって化学分解した前後の質量差に基づいて算出した。 <Amount of sizing agent attached>
The amount (mass %) of the sizing agent is a value relative to the carbon fiber short fibers, which was calculated based on the difference in mass before and after chemical decomposition of the carbon fiber short fibers with the sizing agent attached thereto using a mixture of sulfuric acid and hydrogen peroxide in accordance with JIS R 7604.
＜サイジング層の平均層厚（サイジング剤の平均厚み）＞
　サイジング剤の層厚（ｎｍ）は、サイジング剤付着炭素繊維ショートファイバーにおいて、サイジング剤主成分の密度比重、炭素繊維比重、単繊維径、フィラメント数及びサイジング剤付着量から計算して得た。 <Average thickness of sizing layer (average thickness of sizing agent)>
The layer thickness (nm) of the sizing agent was calculated from the density and specific gravity of the main component of the sizing agent, the specific gravity of the carbon fiber, the single fiber diameter, the number of filaments, and the amount of sizing agent attached to the carbon fiber short fibers.
＜４００℃分解量＞
　４００℃分解量（重量％）は、サイジング剤付着炭素繊維ショートファイバーを用いて、熱重量示差熱測定装置（ＴＧ－ＤＴＡ）によって、４００℃、２０分、空気雰囲気の条件で、計測した。
＜ストランド弾性率＞
　炭素繊維のストランド弾性率（引張弾性率）は、ＪＩＳ　Ｒ　７６０８に従って計測した。 <Amount decomposed at 400°C>
The amount of decomposition at 400° C. (wt %) was measured using short carbon fibers with a sizing agent attached thereto, under conditions of 400° C., 20 minutes, and in an air atmosphere, with a thermogravimetric differential calorimeter (TG-DTA).
<Strand Elastic Modulus>
The strand modulus (tensile modulus) of the carbon fiber was measured in accordance with JIS R 7608.
＜サイジング剤の粒子径＞
　サイジング剤として用いた粒状樹脂の粒子径（μｍ）は、粒度分布計（マイクロトラック・ベル株式会社製ＭＴ３０００II）を用いて、Ｄ５０粒子径として計測した。 <Particle size of sizing agent>
The particle size (μm) of the granular resin used as a sizing agent was measured as the D50 particle size using a particle size distribution meter (MT3000II manufactured by Microtrac Bell Co., Ltd.).
＜コンポジットの製造＞
　実施例及び比較例で用いたコンポジット（炭素繊維強化複合材料）は、下記のとおりにして製造した：
　実施例又は比較例に係るサイジング剤付着炭素繊維ショートファイバーと、樹脂（ＰＥＥＫ樹脂、Ｖｉｃｔｒｅｘ　ｐｌｃ．社製、製品名ＶＩＣＴＲＥＸ　ＰＥＥＫ　１５０Ｐ）とを、炭素繊維の繊維体積含有率（Ｖｆ）３３体積％で、二軸押出機（日本製鋼所社製、製品名ＴＥＸ３０Ｘ）に供給し、３８０℃で混練・押出することによって、ペレット状のコンパウンドを製造した。 <Composite manufacturing>
The composites (carbon fiber reinforced composite materials) used in the examples and comparative examples were produced as follows:
The sizing agent-attached carbon fiber short fibers according to the examples or comparative examples and a resin (PEEK resin, manufactured by Victrex plc., product name VICTREX PEEK 150P) were supplied to a twin-screw extruder (manufactured by Japan Steel Works, Ltd., product name TEX30X) at a fiber volume content (Vf) of the carbon fiber of 33 volume %, and were kneaded and extruded at 380°C to produce a pellet-shaped compound.
　そして、射出成形機（日本製鋼所社製、製品名Ｊ－１１０ＡＤ－１８０Ｈ）を用いてシリンダー温度４００℃、金型温度２００℃で上記ペレットを射出成形することによって、ＩＳＯ　２０７５３　Ａ１型試験片を製造した。 Then, the pellets were injection molded using an injection molding machine (manufactured by Japan Steel Works, Ltd., product name J-110AD-180H) at a cylinder temperature of 400°C and a mold temperature of 200°C to produce ISO 20753 A1 type test specimens.
＜コンポジットの特性＞
　コンポジットの引張強度（ＭＰａ）及び引張弾性率（ＧＰａ）は、それぞれ、ＪＩＳ　Ｋ　　７１６１に従って計測した。 <Composite properties>
The tensile strength (MPa) and tensile modulus (GPa) of the composite were measured according to JIS K 7161, respectively.
＜残存繊維長（コンポジット）＞
　コンポジット中における残存繊維長は、５８５℃で２時間の焼成処理によって単離した炭素繊維をマイクロスコープで観察し、約５００本の重量平均繊維長を計測した。 <Remaining fiber length (composite)>
The remaining fiber length in the composite was determined by observing carbon fibers isolated by baking at 585° C. for 2 hours under a microscope and measuring the weight average fiber length of approximately 500 fibers.
＜アスペクト比（コンポジット）＞
　アスペクト比（コンポジット）は、コンポジット中における残存繊維長、及び単繊維径から算出した。 <Aspect ratio (composite)>
The aspect ratio (composite) was calculated from the remaining fiber length in the composite and the single fiber diameter.
＜分解ガス＞
　コンパウンドを製造する際の押出工程、及び、コンポジットを製造する際の成形工程で発生した分解ガスについて、下記の基準に従って評価した：
　〇：空気雰囲気下における４００℃での２０分にわたる熱処理で計測される分解ガスの量が、０．５％未満であった。
　△：空気雰囲気下における４００℃での２０分にわたる熱処理で計測される分解ガスの量が、０．５％以上であった。 <Cracked gas>
The decomposition gases generated during the extrusion process in producing the compound and during the molding process in producing the composite were evaluated according to the following criteria:
A: The amount of decomposition gas measured after heat treatment at 400° C. for 20 minutes in an air atmosphere was less than 0.5%.
Δ: The amount of decomposition gas measured after heat treatment at 400° C. for 20 minutes in an air atmosphere was 0.5% or more.
＜＜実施例１～５及び比較例１～３＞＞
　実施例１～５及び比較例１～３では、それぞれ、単繊維径７μｍの炭素繊維ショートファイバーを原料としてサイジング剤付着炭素繊維ショートファイバーを製造し、その特性を評価した。 <<Examples 1 to 5 and Comparative Examples 1 to 3>>
In each of Examples 1 to 5 and Comparative Examples 1 to 3, carbon fiber short fibers having a single fiber diameter of 7 μm were used as a raw material to produce carbon fiber short fibers having a sizing agent attached thereto, and the properties thereof were evaluated.
＜実施例１＞
（サイジング剤付着炭素繊維ショートファイバーの製造）
　炭素繊維材料として炭素繊維材料Ａ（引張強度：４３００ＭＰａ、引張弾性率（ストランド弾性率）：２４０ＧＰａ、単繊維径：７μｍ、フィラメント数：２４０００本）を用いた。炭素繊維材料Ａの繊維表面におけるＯ／Ｃ比は、２３％（０．２３）であった。 Example 1
(Production of carbon fiber short fibers with sizing agent)
Carbon fiber material A (tensile strength: 4300 MPa, tensile modulus (strand modulus): 240 GPa, single fiber diameter: 7 μm, number of filaments: 24000) was used as the carbon fiber material. The O/C ratio on the fiber surface of carbon fiber material A was 23% (0.23).
　この炭素繊維を６ｍｍの平均長さに切断して、チョップド炭素繊維を得た。 The carbon fibers were cut to an average length of 6 mm to obtain chopped carbon fibers.
　このチョップド炭素繊維に、浸漬法によって、下記の組成を有する水溶液の形態のサイジング剤組成物を適用し、乾燥によって溶媒を除去して、実施例１に係るサイジング剤付着炭素繊維ショートファイバーを製造した。 A sizing agent composition in the form of an aqueous solution having the following composition was applied to the chopped carbon fibers by immersion, and the solvent was removed by drying to produce the sizing agent-attached carbon fiber short fibers according to Example 1.
　実施例１で用いたサイジング剤組成物の組成は、下記から構成される水溶液であった：
　・ポリイミド（ＰＩ）前駆体（ＭＩＣＨＥＬＭＡＮ社製、ＨＰ－１６３２）
　・水 The sizing agent composition used in Example 1 was an aqueous solution composed of the following:
Polyimide (PI) precursor (MICHELMAN HP-1632)
·water
　実施例１に係るサイジング剤付着炭素繊維ショートファイバーについて、上述した評価方法に従って評価を行った。結果を下記の表１に示す。 The carbon fiber short fibers with sizing agent attached according to Example 1 were evaluated according to the evaluation method described above. The results are shown in Table 1 below.
　＜実施例２＞
　サイジング剤の付着量を増加したこと以外は、実施例１と同様にして、実施例２に係るサイジング剤付着炭素繊維ショートファイバーの製造及び評価を行った。用いた材料及び評価結果を下記の表１に示す。 Example 2
Except for increasing the amount of the sizing agent applied, the carbon fiber short fibers applied with the sizing agent according to Example 2 were produced and evaluated in the same manner as in Example 1. The materials used and the evaluation results are shown in Table 1 below.
　＜実施例３＞
　サイジング剤の付着量を増加したこと以外は、実施例１と同様にして、実施例３に係るサイジング剤付着炭素繊維ショートファイバーの製造及び評価を行った。用いた材料及び評価結果を下記の表１に示す。 Example 3
Except for increasing the amount of the sizing agent applied, the carbon fiber short fibers applied with the sizing agent according to Example 3 were produced and evaluated in the same manner as in Example 1. The materials used and the evaluation results are shown in Table 1 below.
　＜実施例４＞
　サイジング剤の付着量を増加したこと以外は、実施例１と同様にして、実施例４に係るサイジング剤付着炭素繊維ショートファイバーの製造及び評価を行った。用いた材料及び評価結果を下記の表１に示す。
　＜実施例５＞
　サイジング剤組成物として、ポリイミド（ＰＩ）の水溶液の代わりにブロックイソシアネート（ＢＩ）乳化物（明成化学工業社製、ＴＰ－１１）を用いたこと以外は、実施例１と同様にして、実施例５に係るサイジング剤付着炭素繊維ショートファイバーの製造及び評価を行った。用いた材料及び評価結果を下記の表１に示す。 Example 4
Except for increasing the amount of the sizing agent applied, the carbon fiber short fibers applied with the sizing agent according to Example 4 were produced and evaluated in the same manner as in Example 1. The materials used and the evaluation results are shown in Table 1 below.
Example 5
The carbon fiber short fibers with a sizing agent attached thereto according to Example 5 were produced and evaluated in the same manner as in Example 1, except that a blocked isocyanate (BI) emulsion (TP-11, manufactured by Meisei Chemical Industry Co., Ltd.) was used as the sizing agent composition instead of an aqueous solution of polyimide (PI). The materials used and the evaluation results are shown in Table 1 below.
　＜比較例１＞
　サイジング剤の付着量を低減したこと以外は、実施例１と同様にして、比較例１に係るサイジング剤付着炭素繊維ショートファイバーの製造及び評価を行った。用いた材料及び評価結果を下記の表１に示す。 <Comparative Example 1>
Except for reducing the amount of sizing agent applied, the carbon fiber short fibers applied with a sizing agent according to Comparative Example 1 were produced and evaluated in the same manner as in Example 1. The materials used and the evaluation results are shown in Table 1 below.
　＜比較例２＞
　サイジング剤の付着量を増加したこと、及び、１１％のＯ／Ｃ比を有する炭素繊維材料を用いたこと以外は、実施例１と同様にして、比較例２に係るサイジング剤付着炭素繊維ショートファイバーの製造及び評価を行った。用いた材料及び評価結果を下記の表１に示す。 <Comparative Example 2>
Except for increasing the amount of the sizing agent attached and using a carbon fiber material having an O/C ratio of 11%, the carbon fiber short fibers attached with the sizing agent according to Comparative Example 2 were produced and evaluated in the same manner as in Example 1. The materials used and the evaluation results are shown in Table 1 below.
　＜比較例３＞
　サイジング剤組成物として、ポリイミド（ＰＩ）の水溶液の代わりにポリアミド（ＰＡ）（住友精化社製、セポルジョンＰＡ１５０）のサスペンジョンを用いたこと以外は、実施例１と同様にして、比較例３に係るサイジング剤付着炭素繊維ショートファイバーの製造及び評価を行った。用いた材料及び評価結果を下記の表１に示す。 <Comparative Example 3>
The carbon fiber short fibers with a sizing agent attached thereto according to Comparative Example 3 were produced and evaluated in the same manner as in Example 1, except that a suspension of polyamide (PA) (Sepolsion PA150, manufactured by Sumitomo Seika Chemicals Co., Ltd.) was used instead of an aqueous solution of polyimide (PI) as the sizing agent composition. The materials used and the evaluation results are shown in Table 1 below.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１で見られるとおり、実施例１～５に係るサイジング剤付着炭素繊維ショートファイバーは、それらの表面で走査型プローブ顕微鏡によって測定したときの弾性率分布において、３０ＭＰａ以上の弾性率を示す部分の割合が９０％以上であり、かつ５０００ＭＰａ以下の弾性率を示す部分の割合が９０％以上であり、優れたコンポジット特性（比較的高い引張強度）を示した。 As can be seen from Table 1, the carbon fiber short fibers with sizing agent applied according to Examples 1 to 5 had an elastic modulus distribution measured on their surfaces using a scanning probe microscope in which the proportion of areas showing an elastic modulus of 30 MPa or more was 90% or more, and the proportion of areas showing an elastic modulus of 5000 MPa or less was 90% or more, demonstrating excellent composite properties (relatively high tensile strength).
　また、表１で見られるとおり、実施例１～５に係るサイジング剤付着炭素繊維ショートファイバーは、コンポジット中において、比較的長い残存繊維長を示した。理論によって限定する意図はないが、実施例１～５に係るサイジング剤付着炭素繊維ショートファイバーは、繊維表面に付着したサイジング剤の分布が均一であるため、サイジング剤に起因する弾性によって炭素繊維が良好に保護され、その結果として、ペレット及び／又はコンポジットの製造過程（特には混練処理）の間の繊維の折れが抑制されると考えられる。コンポジット中における強化繊維のアスペクト比が大きいほど、コンポジット特性が向上する。 Also, as can be seen from Table 1, the carbon fiber short fibers with sizing agent attached according to Examples 1 to 5 showed a relatively long remaining fiber length in the composite. Without intending to be limited by theory, it is believed that the carbon fiber short fibers with sizing agent attached according to Examples 1 to 5 have a uniform distribution of the sizing agent attached to the fiber surface, and therefore the carbon fibers are well protected by the elasticity caused by the sizing agent, and as a result, fiber breakage during the manufacturing process of the pellets and/or composites (particularly the kneading process) is suppressed. The larger the aspect ratio of the reinforcing fibers in the composite, the better the composite properties.
　これに対して、比較例１に係るサイジング剤付着炭素繊維ショートファイバーは、その表面で走査型プローブ顕微鏡によって測定したときの弾性率分布において、５０００ＭＰａ以下の弾性率を示す部分の割合が６０％であり、比較的低いコンポジット特性を示した。理論によって限定する意図はないが、比較例１では、適用されるサイジング剤の量が不十分であったため、繊維表面に均一にサイジング剤が適用されず、その結果として、繊維表面が十分に被覆されていなかったと考えられる。この場合には、繊維がサイジング剤の弾性によって保護されないので、ペレット及び／又はコンポジットの製造過程（特には混練処理）で、繊維折れが比較的多く発生したと考えられる。 In contrast, the sizing-applied carbon fiber short fibers of Comparative Example 1 showed a 60% proportion of areas exhibiting an elastic modulus of 5000 MPa or less in the elastic modulus distribution measured on the surface by a scanning probe microscope, indicating relatively poor composite properties. Without intending to be limited by theory, it is believed that in Comparative Example 1, the amount of sizing agent applied was insufficient, so that the sizing agent was not applied uniformly to the fiber surfaces, and as a result, the fiber surfaces were not sufficiently coated. In this case, since the fibers were not protected by the elasticity of the sizing agent, it is believed that relatively many fiber breaks occurred during the manufacturing process of the pellets and/or composites (particularly the kneading process).
　比較例２に係るサイジング剤付着炭素繊維ショートファイバーは、その表面で走査型プローブ顕微鏡によって測定したときの弾性率分布において、５０００ＭＰａ以下の弾性率を示す部分の割合が５０％であり、比較的低いコンポジット特性を示した。比較例２では、適用されたサイジング剤の量が実施例１よりも多かったにもかかわらず、残存繊維長及びコンポジット特性が低下していた。理論によって限定する意図はないが、比較例２では、炭素繊維の表面におけるＯ／Ｃ比が比較的低く１１％であったため、サイジング剤が炭素繊維表面に良好に保持されず、その結果として、炭素繊維表面におけるサイジング剤の分布が不均一になり、繊維表面が十分に被覆されていなかっと考えられる。この場合には、繊維がサイジング剤の弾性によって十分に保護されないので、ペレット及び／又はコンポジットの製造過程（特には混練処理）で、繊維折れが比較的多く発生したと考えられる。 In the elastic modulus distribution of the carbon fiber short fibers with sizing agent attached in Comparative Example 2, the proportion of the portion showing an elastic modulus of 5000 MPa or less was 50% in the surface measured by a scanning probe microscope, and the composite properties were relatively low. In Comparative Example 2, the amount of sizing agent applied was greater than in Example 1, but the remaining fiber length and composite properties were reduced. Although there is no intention to be limited by theory, it is believed that in Comparative Example 2, the O/C ratio on the carbon fiber surface was relatively low at 11%, so that the sizing agent was not well retained on the carbon fiber surface, and as a result, the distribution of the sizing agent on the carbon fiber surface was uneven, and the fiber surface was not sufficiently covered. In this case, it is believed that the fibers were not sufficiently protected by the elasticity of the sizing agent, and therefore relatively many fiber breaks occurred during the manufacturing process of the pellets and/or composites (especially the kneading process).
　比較例３に係るサイジング剤付着炭素繊維ショートファイバーは、サイジング剤付着炭素繊維ショートファイバーの表面で走査型プローブ顕微鏡によって測定したときの弾性率分布において、３０ＭＰａ以上の弾性率を示す部分の割合が７０％であり、かつ５０００ＭＰａ以下の弾性率を示す部分の割合が７０％であり、比較的低いコンポジット特性を示した。比較例３では、適用されたサイジング剤の量が実施例１とほぼ同等であったにもかかわらず、残存繊維長及びコンポジット特性が低下していた。理論によって限定する意図はないが、比較例３では、サイジング剤として、比較的粒径の大きいＰＡ樹脂粒子のサスペンジョンを用いたため、ＰＩの水溶液を用いた実施例１などと比較して、炭素繊維表面におけるサイジング剤の均一性が低下したと考えられる。 In the case of the carbon fiber short fibers with a sizing agent attached in Comparative Example 3, the elastic modulus distribution measured by a scanning probe microscope on the surface of the carbon fiber short fibers with a sizing agent attached showed that 70% of the portions showed an elastic modulus of 30 MPa or more and 70% of the portions showed an elastic modulus of 5000 MPa or less, and showed relatively low composite properties. In Comparative Example 3, the amount of sizing agent applied was almost the same as in Example 1, but the remaining fiber length and composite properties were reduced. Although there is no intention to be limited by theory, it is believed that the uniformity of the sizing agent on the carbon fiber surface was reduced in Comparative Example 3 compared to Example 1, in which an aqueous solution of PI was used, because a suspension of PA resin particles with a relatively large particle size was used as the sizing agent.
＜＜実施例６～１０及び比較例４＞＞
　実施例６～１０及び比較例４では、それぞれ、単繊維径５．７μｍの炭素繊維ショートファイバーを原料としてサイジング剤付着炭素繊維ショートファイバーを製造し、その特性を評価した。 <<Examples 6 to 10 and Comparative Example 4>>
In each of Examples 6 to 10 and Comparative Example 4, carbon fiber short fibers having a single fiber diameter of 5.7 μm were used as the raw material to produce carbon fiber short fibers having a sizing agent attached thereto, and the properties thereof were evaluated.
＜実施例６＞
　炭素繊維材料として、炭素繊維材料Ｂ（引張強度：５０００ＭＰａ、引張弾性率（ストランド弾性率）：２８５ＧＰａ、単繊維径：５．７μｍ、フィラメント数：３６０００本）を用いたこと以外は、実施例１と同様にして、実施例６に係るサイジング剤付着炭素繊維ショートファイバーを製造し、評価を行った。炭素繊維材料Ｂの繊維表面におけるＯ／Ｃ比は、２５％（０．２５）であった。用いた材料及び評価結果を下記の表２に示す。 Example 6
The sizing-adhered carbon fiber short fibers of Example 6 were produced and evaluated in the same manner as in Example 1, except that carbon fiber material B (tensile strength: 5000 MPa, tensile modulus (strand modulus): 285 GPa, single fiber diameter: 5.7 μm, number of filaments: 36,000) was used as the carbon fiber material. The O/C ratio on the fiber surface of carbon fiber material B was 25% (0.25). The materials used and the evaluation results are shown in Table 2 below.
＜実施例７＞
　サイジング剤の付着量を増加したこと以外は実施例６と同様にして、実施例７に係るサイジング剤付着炭素繊維ショートファイバーを製造し、評価を行った。用いた材料及び評価結果を下記の表２に示す。 Example 7
The carbon fiber short fibers with a sizing agent attached thereto according to Example 7 were produced and evaluated in the same manner as in Example 6, except that the amount of the sizing agent attached was increased. The materials used and the evaluation results are shown in Table 2 below.
＜実施例８＞
　サイジング剤の付着量を増加したこと以外は実施例６と同様にして、実施例８に係るサイジング剤付着炭素繊維ショートファイバーを製造し、評価を行った。用いた材料及び評価結果を下記の表２に示す。 Example 8
The carbon fiber short fibers with a sizing agent attached thereto according to Example 8 were produced and evaluated in the same manner as in Example 6, except that the amount of the sizing agent attached was increased. The materials used and the evaluation results are shown in Table 2 below.
＜実施例９＞
　サイジング剤の付着量を増加したこと以外は実施例６と同様にして、実施例９に係るサイジング剤付着炭素繊維ショートファイバーを製造し、評価を行った。用いた材料及び評価結果を下記の表２に示す。
＜実施例１０＞
　サイジング剤組成物としてブロックイソシアネート（ＢＩ）乳化物（ＴＰ－１１）を用いた以外には実施例６と同様にして、実施例１０に係るサイジング剤付着炭素繊維ショートファイバーを製造し、評価を行った。用いた材料及び評価結果を下記の表２に示す。 <Example 9>
The carbon fiber short fibers with a sizing agent attached thereto according to Example 9 were produced and evaluated in the same manner as in Example 6, except that the amount of the sizing agent attached was increased. The materials used and the evaluation results are shown in Table 2 below.
Example 10
A sizing agent-attached carbon fiber short fiber according to Example 10 was produced and evaluated in the same manner as in Example 6, except that a blocked isocyanate (BI) emulsion (TP-11) was used as the sizing agent composition. The materials used and the evaluation results are shown in Table 2 below.
＜比較例４＞
　炭素繊維表面のＯ／Ｃ比が１４％（０．１４）の炭素繊維材料を用いたこと以外は、実施例６と同様にして、比較例４に係るサイジング剤付着炭素繊維ショートファイバーを製造し、評価を行った。用いた材料及び評価結果を下記の表２に示す。 <Comparative Example 4>
A sizing-adhered carbon fiber short fiber according to Comparative Example 4 was produced and evaluated in the same manner as in Example 6, except that a carbon fiber material having an O/C ratio of 14% (0.14) on the carbon fiber surface was used. The materials used and the evaluation results are shown in Table 2 below.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表２で見られるとおり、実施例６～１０に係るサイジング剤付着炭素繊維ショートファイバーは、それらの表面で走査型プローブ顕微鏡によって測定したときの弾性率分布において、３０ＭＰａ以上の弾性率を示す部分の割合が９０％以上であり、かつ５０００ＭＰａ以下の弾性率を示す部分の割合が９０％以上であり、優れたコンポジット特性（比較的高い引張強度）を示した。 As can be seen from Table 2, the carbon fiber short fibers with sizing agent according to Examples 6 to 10 had an elastic modulus distribution measured on their surfaces by a scanning probe microscope in which the proportion of areas showing an elastic modulus of 30 MPa or more was 90% or more, and the proportion of areas showing an elastic modulus of 5000 MPa or less was 90% or more, demonstrating excellent composite properties (relatively high tensile strength).
　また、表２で見られるとおり、実施例６～１０に係るサイジング剤付着炭素繊維ショートファイバーは、コンポジット中において、比較的長い残存繊維長を示した。理論によって限定する意図はないが、実施例６～１０に係るサイジング剤付着炭素繊維ショートファイバーは、繊維表面に付着したサイジング剤の分布が均一であるため、サイジング剤に起因する弾性によって炭素繊維が良好に保護され、その結果として、ペレット及び／又はコンポジットの製造過程（特には混練処理）の間の繊維の折れが抑制されると考えられる。 Also, as can be seen from Table 2, the carbon fiber short fibers with sizing agent attached according to Examples 6 to 10 showed a relatively long remaining fiber length in the composite. Without intending to be limited by theory, it is believed that the carbon fiber short fibers with sizing agent attached according to Examples 6 to 10 have a uniform distribution of sizing agent attached to the fiber surface, and therefore the carbon fibers are well protected by the elasticity caused by the sizing agent, and as a result, fiber breakage during the manufacturing process of the pellets and/or composites (particularly the kneading process) is suppressed.
　これに対して、比較例４に係るサイジング剤付着炭素繊維ショートファイバーは、その表面で走査型プローブ顕微鏡によって測定したときの弾性率分布において、５０００ＭＰａ以下の弾性率を示す部分の割合が５０％であり、比較的低いコンポジット特性を示した。比較例４では、適用されたサイジング剤の量が実施例６と同じであったにもかかわらず、残存繊維長及びコンポジット特性が低下していた。理論によって限定する意図はないが、比較例４では、炭素繊維の表面におけるＯ／Ｃ比が比較的低く１４％であったため、サイジング剤が炭素繊維表面に良好に保持されず、その結果として、炭素繊維表面におけるサイジング剤の分布が不均一になったと考えられる。この場合には、少なくとも一部の炭素繊維表面における被覆が不十分となり、ペレット及び／又はコンポジットの製造過程（特には混練処理）で、繊維折れが比較的多く発生したと考えられる。 In contrast, the sizing-applied carbon fiber short fibers of Comparative Example 4 showed a relatively low composite property, with 50% of the surface showing an elastic modulus of 5000 MPa or less in the elastic modulus distribution measured by a scanning probe microscope. In Comparative Example 4, the remaining fiber length and composite property were reduced, even though the amount of sizing agent applied was the same as in Example 6. Although there is no intention to be limited by theory, it is believed that in Comparative Example 4, the O/C ratio on the carbon fiber surface was relatively low at 14%, so that the sizing agent was not well retained on the carbon fiber surface, resulting in an uneven distribution of the sizing agent on the carbon fiber surface. In this case, it is believed that the coating on at least a portion of the carbon fiber surface was insufficient, and relatively many fiber breaks occurred during the manufacturing process of the pellets and/or composites (especially the kneading process).

Claims (16)

  1. 　炭素繊維ショートファイバー及びこの炭素繊維ショートファイバーに付着しているサイジング剤を有しているサイジング剤付着炭素繊維ショートファイバーであって、
    　前記サイジング剤付着炭素繊維ショートファイバーの表面で走査型プローブ顕微鏡によって測定したときの弾性率分布において、３０ＭＰａ以上の弾性率を示す部分の割合が９０％以上であり、かつ５０００ＭＰａ以下の弾性率を示す部分の割合が９０％以上である、
    サイジング剤付着炭素繊維ショートファイバー。     A sizing-agent-attached carbon fiber short fiber having a carbon fiber short fiber and a sizing agent attached to the carbon fiber short fiber,
    In the elastic modulus distribution measured by a scanning probe microscope on the surface of the sizing agent-attached carbon fiber short fibers, the proportion of a portion showing an elastic modulus of 30 MPa or more is 90% or more, and the proportion of a portion showing an elastic modulus of 5000 MPa or less is 90% or more.
    Carbon fiber short fibers with sizing agent attached.
  2. 　前記炭素繊維ショートファイバーの表面のＯ／Ｃ比が、１５％～３０％であり、かつ、
    　前記サイジング剤が、水溶性樹脂を含み、又は、０．３μｍ以下の平均粒子径を有する粒状樹脂を含む、
    請求項１に記載のサイジング剤付着炭素繊維ショートファイバー。     The O/C ratio of the surface of the carbon fiber short fiber is 15% to 30%, and
    The sizing agent contains a water-soluble resin or a granular resin having an average particle size of 0.3 μm or less.
    The carbon fiber short fibers having a sizing agent attached thereto according to claim 1 .
  3. 　前記サイジング剤が、水溶性樹脂を含む、請求項１又は２に記載のサイジング剤付着炭素繊維ショートファイバー。 The carbon fiber short fiber with a sizing agent attached thereto according to claim 1 or 2, wherein the sizing agent contains a water-soluble resin.
  4. 　前記サイジング剤が、ポリイミド樹脂を含む、請求項１又は２に記載のサイジング剤付着炭素繊維ショートファイバー。 The carbon fiber short fiber with a sizing agent attached thereto according to claim 1 or 2, wherein the sizing agent contains a polyimide resin.
  5. 　前記炭素繊維ショートファイバーに付着している前記サイジング剤が、前記炭素繊維ショートファイバーに対して、０．８質量％～３．３質量％である、請求項１又は２に記載のサイジング剤付着炭素繊維ショートファイバー。 The carbon fiber short fibers with a sizing agent attached thereto according to claim 1 or 2, wherein the sizing agent attached to the carbon fiber short fibers is 0.8% by mass to 3.3% by mass relative to the carbon fiber short fibers.
  6. 　空気中で２０分にわたって４００℃で加熱処理したときの熱分解量が、サイジング剤付着炭素繊維ショートファイバーの総重量に対して０．５０％以下である、請求項１又は２に記載のサイジング剤付着炭素繊維ショートファイバー。 The carbon fiber short fibers with a sizing agent attached according to claim 1 or 2, in which the amount of thermal decomposition when heat-treated in air at 400°C for 20 minutes is 0.50% or less of the total weight of the carbon fiber short fibers with a sizing agent attached.
  7. 　前記サイジング剤付着炭素繊維ショートファイバーの平均長さが、１ｍｍ～２５ｍｍである、請求項１又は２に記載のサイジング剤付着炭素繊維ショートファイバー。 The carbon fiber short fibers with a sizing agent attached thereto according to claim 1 or 2, wherein the average length of the carbon fiber short fibers with a sizing agent attached thereto is 1 mm to 25 mm.
  8. 　前記炭素繊維ショートファイバーの単繊維径が、４～８μｍである、請求項１又は２に記載のサイジング剤付着炭素繊維ショートファイバー。 The carbon fiber short fiber with a sizing agent applied thereto according to claim 1 or 2, wherein the single fiber diameter of the carbon fiber short fiber is 4 to 8 μm.
  9. 　前記炭素繊維ショートファイバーが、２４５ＧＰａ以上の引張弾性率を示す炭素繊維から形成されている、請求項１又は２に記載のサイジング剤付着炭素繊維ショートファイバー。 The carbon fiber short fiber with a sizing agent applied thereto according to claim 1 or 2, wherein the carbon fiber short fiber is formed from carbon fiber exhibiting a tensile modulus of elasticity of 245 GPa or more.
  10. 　炭素繊維強化複合材料のための、請求項１又は２に記載のサイジング剤付着炭素繊維ショートファイバー。 Carbon fiber short fibers with a sizing agent according to claim 1 or 2 for use in carbon fiber reinforced composite materials.
  11. 　前記炭素繊維強化複合材料における炭素繊維の繊維体積含有率が２０体積％～５５体積％である、請求項１０に記載のサイジング剤付着炭素繊維ショートファイバー。 The carbon fiber short fiber with a sizing agent according to claim 10, wherein the fiber volume content of the carbon fiber in the carbon fiber reinforced composite material is 20 volume % to 55 volume %.
  12. 　炭素繊維ショートファイバーを提供すること、及び、
    　前記炭素繊維ショートファイバーの表面に、サイジング剤組成物を適用すること、
    を含む、サイジング剤付着炭素繊維ショートファイバーの製造方法であって、
    　前記炭素繊維ショートファイバーの表面のＯ／Ｃ比が、１５％～３０％であり、かつ、
    　前記サイジング剤組成物が、水溶性樹脂を含み、又は、０．３μｍ以下の平均粒子径を有する粒状樹脂を含む、
    方法。     Providing a carbon fiber short fiber; and
    Applying a sizing agent composition to the surface of the carbon fiber short fibers;
    A method for producing carbon fiber short fibers with a sizing agent, comprising:
    The O/C ratio of the surface of the carbon fiber short fiber is 15% to 30%, and
    The sizing agent composition contains a water-soluble resin or a granular resin having an average particle size of 0.3 μm or less.
    Method.
  13. 　前記サイジング剤組成物が、水溶性樹脂を含む、請求項１２に記載の方法。 The method of claim 12, wherein the sizing composition comprises a water-soluble resin.
  14. 　請求項１又は２に係るサイジング剤付着炭素繊維ショートファイバーを提供すること、及び、
    　前記サイジング剤付着炭素繊維ショートファイバーと樹脂とを混練かつ押出して、コンパウンドを形成すること、
    を含む、コンパウンドの製造方法。     Providing a sizing agent-attached carbon fiber short fiber according to claim 1 or 2; and
    kneading and extruding the sizing agent-attached carbon fiber short fibers and a resin to form a compound;
    A method for producing a compound comprising:
  15. 　前記コンパウンドがペレット状である、請求項１４に記載の方法。 The method of claim 14, wherein the compound is in pellet form.
  16. 　請求項１４に記載の方法によってコンパウンドを製造すること、及び
    　前記コンパウンドを成形して、炭素繊維強化複合材料を形成すること、
    を含む、炭素繊維強化複合材料の製造方法。     Producing a compound by the method of claim 14; and molding the compound to form a carbon fiber reinforced composite material.
    A method for producing a carbon fiber reinforced composite material, comprising:
PCT/JP2023/044154 2022-12-16 2023-12-11 Sizing agent-attached carbon short fiber WO2024128171A1 (en)

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Publication number Priority date Publication date Assignee Title
JP2003181833A (en) * 2001-12-14 2003-07-02 Toho Tenax Co Ltd Carbon fiber chopped fiber
JP2004241132A (en) * 2003-02-03 2004-08-26 Aica Kogyo Co Ltd Conductive particulate, conductive resin emulsion and its manufacturing method as well as conductive paint composition and conductive sheet member
JP2004244531A (en) * 2003-02-14 2004-09-02 Toho Tenax Co Ltd Carbon fiber chopped strand for thermoplastic resin and fiber reinforced composite material
JP2013216997A (en) * 2012-04-10 2013-10-24 Toho Tenax Co Ltd Carbon fiber chopped strand and method for producing the same
JP2023141277A (en) * 2022-03-23 2023-10-05 帝人株式会社 Sizing agent adhered carbon fiber short fiber

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003181833A (en) * 2001-12-14 2003-07-02 Toho Tenax Co Ltd Carbon fiber chopped fiber
JP2004241132A (en) * 2003-02-03 2004-08-26 Aica Kogyo Co Ltd Conductive particulate, conductive resin emulsion and its manufacturing method as well as conductive paint composition and conductive sheet member
JP2004244531A (en) * 2003-02-14 2004-09-02 Toho Tenax Co Ltd Carbon fiber chopped strand for thermoplastic resin and fiber reinforced composite material
JP2013216997A (en) * 2012-04-10 2013-10-24 Toho Tenax Co Ltd Carbon fiber chopped strand and method for producing the same
JP2023141277A (en) * 2022-03-23 2023-10-05 帝人株式会社 Sizing agent adhered carbon fiber short fiber

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