WO2011102400A1 - Production method for precursor fibre for obtaining high-strength and high elastic modulus carbon fibre - Google Patents

Production method for precursor fibre for obtaining high-strength and high elastic modulus carbon fibre Download PDF

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Publication number
WO2011102400A1
WO2011102400A1 PCT/JP2011/053317 JP2011053317W WO2011102400A1 WO 2011102400 A1 WO2011102400 A1 WO 2011102400A1 JP 2011053317 W JP2011053317 W JP 2011053317W WO 2011102400 A1 WO2011102400 A1 WO 2011102400A1
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Prior art keywords
carbon
carbon nanotubes
spinning
spinning dope
fiber
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PCT/JP2011/053317
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French (fr)
Japanese (ja)
Inventor
浩和 西村
公一 平尾
信輔 山口
卓也 赤石
義弘 渡辺
文志 古月
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東洋紡績株式会社
日本エクスラン工業株式会社
国立大学法人北海道大学
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Priority to JP2012500633A priority Critical patent/JPWO2011102400A1/en
Publication of WO2011102400A1 publication Critical patent/WO2011102400A1/en

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    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
    • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
    • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
    • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
    • D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
    • D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/168—After-treatment
    • C01B32/174—Derivatisation; Solubilisation; Dispersion in solvents
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/71—Ceramic products containing macroscopic reinforcing agents
    • C04B35/78—Ceramic products containing macroscopic reinforcing agents containing non-metallic materials
    • C04B35/80—Fibres, filaments, whiskers, platelets, or the like
    • C04B35/83—Carbon fibres in a carbon matrix
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F1/00—General methods for the manufacture of artificial filaments or the like
    • D01F1/02—Addition of substances to the spinning solution or to the melt
    • D01F1/10—Other agents for modifying properties
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/50—Constituents or additives of the starting mixture chosen for their shape or used because of their shape or their physical appearance
    • C04B2235/52—Constituents or additives characterised by their shapes
    • C04B2235/5284—Hollow fibers, e.g. nanotubes
    • C04B2235/5288—Carbon nanotubes

Definitions

  • the present invention relates to a method for producing a precursor fiber for obtaining a carbon fiber having high strength and high elastic modulus.
  • the present invention also relates to a precursor fiber obtained by such a production method and a high-strength and high-modulus carbon fiber obtained from such a precursor fiber. Furthermore, the present invention relates to a spinning dope used for the production of such precursor fibers.
  • carbon fiber Since carbon fiber has extremely excellent physical properties such as light weight, high strength, and high elastic modulus, it forms exercise equipment such as fishing rods, golf clubs and skis, CNG tanks, flywheels, wind turbines for wind power generation, turbine blades, etc. It is used as a reinforcing material for structures such as materials, roads and piers, as well as aircraft and space materials, and its uses are expanding.
  • Carbon fibers are roughly classified into PAN-based carbon fibers made from polyacrylonitrile and pitch-based carbon fibers made from coal-derived coal tar, petroleum-derived decant oil, ethylene bottom, and the like. Any carbon fiber is manufactured by first producing a precursor fiber from these raw materials and heating the precursor fiber at a high temperature to make it flame resistant, pre-carbonized, and carbonized.
  • PAN-based carbon fibers can achieve a very high tensile strength of about 6 GPa at the maximum, but it is difficult to develop a tensile elastic modulus and remains at a maximum of about 300 GPa.
  • pitch-based carbon fibers that are currently available on the market can achieve a very high tensile elastic modulus of about 800 GPa at the maximum, but the tensile strength is difficult to develop and remains at about 3 GPa at the maximum.
  • a carbon fiber having a high tensile strength and a high tensile modulus is desirable, but there is no carbon fiber currently proposed that satisfies this requirement.
  • precursor fibers carbon nanotube-containing PAN precursor fibers obtained by adding carbon nanotubes to a polyacrylonitrile-based polymer and spinning them are higher than conventional PAN-based precursor fibers. It is disclosed to exhibit a tensile modulus.
  • the precursor fiber obtained by the method of Patent Document 1 is excellent in terms of tensile elastic modulus, since the cross-sectional shape is not circular but is distorted greatly, the carbon fiber obtained from this precursor fiber is a conventional PAN-based carbon. Does not show high tensile strength like fibers. Therefore, after all, a carbon fiber having both the high tensile strength and the high tensile elastic modulus has not been obtained yet.
  • the present invention has been created in view of the current state of the prior art, and its purpose is to provide precursor fibers capable of producing carbon fibers having high tensile strength and high tensile modulus, and industrially advantageous production thereof. It is to provide a method.
  • the present inventor has intensively studied the improvement of the method of Patent Document 1, and as a result, in the case of a carbon nanotube-containing PAN precursor fiber obtained by the method of Patent Document 1, Since dimethylformamide (DMF) is used, carbon nanotubes easily aggregate and precipitate instantly when the carbon nanotube dispersion is added to the spinning dope. Also, the carbon nanotubes are added to the DMF using ultrasonic waves in advance. Even if it is dispersed, the stability of the dispersed state is low, and agglomeration / precipitation occurs during the preparation of the spinning stock solution.
  • DMF dimethylformamide
  • the present inventors further provide a method for suppressing the precipitation of carbon nanotubes in the spinning stock solution while using dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or dimethylacetamide (DMAc) as a solvent for the spinning stock solution.
  • DMF dimethylformamide
  • DMSO dimethyl sulfoxide
  • DMAc dimethylacetamide
  • amphoteric molecules contained in the spinning dope are extracted into the coagulation bath during spinning and hardly remain in the yarn, so that it is found that the effect of improving the physical properties of the yarn by adding carbon nanotubes is high, thereby completing the present invention. It came.
  • a method for producing a carbon fiber precursor fiber which comprises the following steps: (1) a step of preparing a solution of amphoteric molecules of dimethylformamide, dimethylsulfoxide, or dimethylacetamide; (2) adding carbon nanotubes to this amphoteric molecule solution, dispersing the carbon nanotubes, and preparing a carbon nanotube dispersion; (3) A step of mixing the carbon nanotube dispersion and the polyacrylonitrile polymer to prepare a spinning dope; (4) A step of obtaining a coagulated yarn from the spinning dope by a wet or dry wet spinning method; and (5) a step of drawing the coagulated yarn to obtain a carbon fiber precursor fiber.
  • the spinning dope prepared in step (3) contains 5 to 35% by weight of polyacrylonitrile-based polymer, and further 0.01 to 5% by weight with respect to the polyacrylonitrile-based polymer. Carbon nanotubes and 0.01-5.0 wt% amphoteric molecules.
  • the wetting treatment is performed before the carbon nanotubes are dispersed in the step (2), and the carbon nanotube dispersion is further stabilized.
  • a carbon fiber precursor fiber produced by the above method wherein the carbon fiber precursor fiber has a substantially circular cross section and includes carbon nanotubes.
  • a carbon fiber produced by flame-proofing, pre-carbonizing and carbonizing the precursor fiber characterized by having a high tensile strength and a high tensile elastic modulus. Fiber is provided.
  • a spinning dope comprising a solution of dimethylformamide, dimethyl sulfoxide, or dimethylacetamide containing a polyacrylonitrile-based polymer, carbon nanotubes, and amphoteric molecules, and the carbon nanotubes are dispersed by the action of the amphoteric molecules.
  • a spinning dope is provided that is dispersed in a solution.
  • amphoteric molecules suppress aggregation and precipitation of carbon nanotubes from the spinning dope as a dispersant, and the amphoteric molecules are extracted into a coagulation bath during spinning.
  • the obtained yarn does not contain a lump of aggregates and precipitates, and can be sufficiently stretched to orient the polymer chains and the carbon nanotubes. Therefore, carbon fibers obtained from such precursor fibers have a high tensile elastic modulus in addition to the high tensile strength that is characteristic of PAN-based carbon fibers due to the inclusion of appropriately oriented carbon nanotubes and the orientation of polymer chains. Indicates.
  • the spinning dope used in the production method of the present invention is different from the spinning dope using a dispersing agent usually used for dispersion of carbon nanotubes, and it is necessary to perform ultrasonic irradiation and centrifugation during dispersion of the carbon nanotubes. Therefore, the production method of the present invention is very suitable for industrial production.
  • step (1) a solution of amphoteric molecule DMF, DMSO, or DMAc is prepared (step (1)).
  • the amphoteric molecule used in the present invention is a molecule having a positive charge group and a negative charge group in one molecule, and each group forms a salt with a counter ion.
  • amphoteric molecules can be used alone or in admixture of two or more, and can also be used in combination with a cationic surfactant, an anionic surfactant or a neutral surfactant. .
  • Preparation of amphoteric molecule DMF, DMSO, or DMAc solution can be easily performed by adding amphoteric molecule to DMF, DMSO, or DMAc and stirring at room temperature.
  • DMF, DMSO, or DMAc may be used singly or as a mixture thereof.
  • the concentration of the amphoteric molecule is preferably 0.01 to 5.0% by weight, more preferably 0.1 to 2.0% by weight. If the amount is less than the above lower limit, the effect of the carbon nanotube as a dispersant may not be sufficiently exhibited. On the other hand, if the above upper limit is exceeded, there is a possibility that the effect of the carbon nanotube as a dispersant will not be sufficiently exhibited.
  • carbon nanotubes are added to the DMF, DMSO, or DMAc solution of the amphoteric molecule to disperse the carbon nanotubes, thereby preparing a carbon nanotube dispersion (step (2)).
  • the carbon nanotube used in the present invention may be a single-walled carbon nanotube, a double-walled carbon nanotube, a multi-walled carbon nanotube, or a mixture thereof.
  • the ends of various carbon nanotubes may be closed or perforated.
  • the diameter of the carbon nanotube is preferably 0.4 nm or more and 100 nm or less, and more preferably 0.8 nm or more and 80 nm or less.
  • the length of the carbon nanotube is not limited, and an arbitrary length can be used, but it is preferably 0.6 ⁇ m or more and 200 ⁇ m or less.
  • the purity of the carbon nanotubes used in the present invention is preferably 80% or more as carbon purity, more preferably 90% or more, and still more preferably 95% or more. Carbon purity is determined by differential thermal analysis.
  • Examples of carbon nanotube impurities include amorphous carbon components and catalytic metals.
  • the amorphous carbon component can be removed by heating in air at 200 ° C. or higher or by washing with hydrogen peroxide.
  • the catalyst metal during the production of carbon nanotubes such as iron can be removed by washing with water.
  • the amount of carbon nanotube added is preferably 0.01 to 5% by weight, more preferably 0.1 to 3% by weight, based on the amount of polyacrylonitrile-based polymer to be mixed in the next step (3). preferable. If it is less than the said minimum, there exists a possibility that the amount of carbon nanotubes in the precursor fiber obtained may decrease and a sufficiently high tensile elastic modulus cannot be achieved. On the other hand, if the above upper limit is exceeded, the spinning dope loses spinnability, and spinning may be difficult.
  • Dispersion of carbon nanotubes is necessary in order to loosen the bundled carbon nanotubes.
  • amphoteric molecules When amphoteric molecules are used, they are dispersed if gently stirred, but they are also industrially efficient and evenly dispersed. It is better to disperse by applying physical force.
  • the dispersion method include a ball mill, a bead mill, and dispersion using a plurality of three or more rolls. If the dispersion becomes black and transparent visually, the carbon nanotubes are sufficiently dispersed.
  • the wetting treatment refers to a treatment for creating a trigger for the dispersion of the carbon nanotubes by allowing the amphoteric molecules as a dispersant to penetrate between the bundled carbon nanotubes.
  • the amphoteric molecules are used, carbon nanotubes are gradually dispersed by electrostatic force only by applying gentle stirring.
  • the amphoteric molecules are infiltrated between the carbon nanotubes by a physical method, and the dispersion is completed in a short time without unevenness.
  • a temperature is applied to a system in which carbon nanotubes exist in an autoclave to swell the bundle of carbon nanotubes, and then a pressure is applied.
  • the temperature range at this time is 50 to 150 ° C., more preferably 80 to 150 ° C., and the pressure range is 1.1 to 2.0 atm.
  • the stabilization treatment is a treatment for preventing the dispersed carbon nanotubes from reaggregating, and has an effect of preventing a change with time when the carbon nanotube dispersion liquid is not used immediately.
  • Stabilizers include polyhydric alcohols such as polyhydric alcohols such as glycerol and ethylene glycol, polyvinyl alcohol, polyoxyethylenes such as polyoxyethylenated fatty acids and ester derivatives thereof, polysaccharides, For example, water-soluble cellulose, water-soluble starch, water-soluble glycogen, derivatives thereof such as cellulose acetate, amylopectin, and amines such as alkylamine are exemplified. These stabilizers may be used alone or in combination of two or more. The amount of the stabilizer added is preferably 0.006 to 3% by weight, more preferably 0.06 to 1.2% by weight, based on the amount of the carbon nanotube dispersion.
  • step (3) the carbon nanotube dispersion and the polyacrylonitrile polymer are mixed to prepare a spinning dope.
  • a polyacrylonitrile-based polymer may be added to the carbon nanotube dispersion, or a polymer solution obtained by dissolving a polyacrylonitrile-based polymer in DMF, DMSO, or DMAc and a carbon nanotube dispersion are mixed. Also good. Further, a polymer solution in which a small amount of polyacrylonitrile-based polymer is dissolved in the carbon nanotube dispersion liquid and a polymer solution in which only the polyacrylonitrile-based polymer is dissolved in DMF, DMSO, or DMAc may be mixed. Mixing does not have to be performed at once, and may be performed separately.
  • polyacrylonitrile-based polymer used in the present invention polyacrylonitrile and a copolymer composed of a vinyl monomer copolymerizable with acrylonitrile can be used.
  • the copolymer include acrylonitrile-methacrylic acid copolymer, acrylonitrile-methyl methacrylate copolymer, acrylonitrile-acrylic acid copolymer, acrylonitrile-itaconic acid copolymer, acrylonitrile Examples include methacrylic acid-itaconic acid copolymer, acrylonitrile-methyl methacrylate-itaconic acid copolymer, and acrylonitrile-acrylic acid-itaconic acid copolymer.
  • the acrylonitrile component should be 85 mol% or more. Is preferred.
  • These polymers may form a salt with alkali metal or ammonia. These polymers can be used alone or as a mixture of two or more.
  • the amount of polyacrylonitrile-based polymer added is preferably such that it is 5 to 35% by weight, more preferably 10 to 25% by weight in the spinning dope. If it is less than the above lower limit, the spinning tension cannot be applied, and the orientation of the carbon itself and the carbon nanotubes in the yarn is insufficient, which may cause insufficient strength. On the other hand, if the above lower limit is exceeded, there is a risk of increasing the back pressure during spinning.
  • the spinning dope obtained by the above step (3) consists of a solution of DMF, DMSO, or DMAc containing polyacrylonitrile-based polymer, carbon nanotubes, and amphoteric molecules.
  • the carbon nanotubes are stably dispersed in DMF, DMSO, or DMAc due to the dispersing action of amphoteric molecules, and are difficult to precipitate even if any impact is applied.
  • the viscosity of the spinning dope of the present invention is usually 30 ° C., preferably 2 to 20 Pa ⁇ sec for wet spinning, and preferably 100 to 500 Pa ⁇ sec for dry and wet spinning.
  • the range is below the above range, there is a possibility that the spinning solution may adhere to the nozzle surface at the time of spinning, or there is a problem of cutting of the discharged yarn or quality unevenness. This may cause problems in spinning operability, such as inability to perform stable spinning.
  • a coagulated yarn is obtained from this spinning dope by a wet or dry wet spinning method (step (4)).
  • the hole diameter of the spinneret is usually preferably from 0.03 to 0.1 mm for wet spinning, and preferably from 0.1 to 0.3 mm for dry and wet spinning.
  • the draft ratio may decrease during spinning and the productivity may be significantly impaired, and there is a problem of cutting of the discharged yarn and quality unevenness.
  • the discharge linear velocity of the spinning dope becomes low. Therefore, there is a possibility that problems may occur in the operability of spinning, such as an increase in yarn tension in the coagulation bath.
  • the coagulation bath it is preferable to use a mixture of DMF, DMSO, or DMAc and a so-called coagulation promoting component.
  • a component that does not dissolve the polyacrylonitrile-based polymer and is compatible with the solvent (DMF, DMSO, or DMAc) used in the polymer solution is preferable. Specifically, water may be used. preferable.
  • the coagulation bath used in dry-wet spinning has a high concentration of DMF, DMSO, or DMAc within a range in which the cross-section of the single fiber constituting the coagulated yarn is a perfect circle and the side surface of the fiber is smooth. It is preferable to set the temperature low.
  • the temperature of the coagulation bath is preferably 5 ° C. to 20 ° C., for example. If it is less than 5 ° C., the rate of solidification is slow and the take-off rate is lowered. If it exceeds 20 ° C., the yarns are liable to be fused, which is not preferable.
  • the coagulation water washing step may be performed in a single step, but is preferably performed in a multi-step process while gradually reducing the concentration.
  • a precursor fiber having a substantially circular cross section can be obtained, and the tensile strength can be further increased.
  • the second and subsequent water washing steps may be performed during or after the stretching step described later.
  • the first stage coagulation bath is preferably washed with water in a concentration range of 70% by weight or more and less than 90% by weight of DMF, DMSO, or DMAc. If the concentration of DMF, DMSO, or DMAc is less than 70% by weight, only the surface layer of the fiber may solidify first, and the fiber cross section may become distorted. Further, if the concentration of DMF, DMSO, or DMAc is 90% by weight or more, a careful water washing step may be required.
  • the second stage coagulation bath is preferably washed with water in a concentration range of 5% by weight or more and less than 30% by weight of DMF, DMSO, or DMAc.
  • the concentration of DMF, DMSO, or DMAc is less than 5% by weight, DMF, DMSO, or DMAc in the fiber cannot be removed in a short time, and a more careful washing step may be required later. Further, when the concentration of DMF, DMSO, or DMAc is 30% by weight or more, there is no change in the concentration of DMF, DMSO, or DMAc in the fiber after water washing, and there is a possibility that water washing is not substantially performed. In the case where the water washing step is performed in three or more stages, it is preferable to further solidify by lowering the concentration of DMF, DMSO, or DMAc.
  • the take-up speed during spinning is preferably in the range of 3 to 20 m / min. If it is less than 3 m / min, the productivity may be extremely low. On the other hand, if it exceeds 20 m / min, yarn breakage frequently occurs in the vicinity of the spinneret and the operability may be significantly impaired.
  • the coagulated yarn obtained in the step (4) is drawn to obtain a carbon fiber precursor fiber (step (5)).
  • a carbon fiber excellent in mechanical properties can be obtained by increasing the orientation of molecular chains in the fiber.
  • the stretching is preferably performed so that the total stretching ratio is 4 to 12 times, and more preferably, the total stretching ratio is 5 to 7 times. If the total draw ratio is less than the above lower limit, the orientation of the carbon nanotubes in the yarn is insufficient, and there is a possibility that a carbon fiber precursor in which the polyacrylonitrile-based polymer is densely oriented cannot be obtained. Further, when the total draw ratio exceeds the above upper limit, yarn breakage frequently occurs during drawing and there is a possibility that the drawing stability may be lacking.
  • the stretching operation may be any of cold stretching, stretching in hot water, and stretching in steam. Moreover, even if it extends
  • the precursor fibers obtained by the above steps (1) to (5) have a substantially circular cross section necessary for exhibiting high tensile strength, and carbon nanotubes that provide high tensile elastic modulus in an appropriate orientation. Including. Therefore, if this precursor fiber is flame-resistant, pre-carbonized, and carbonized, a carbon fiber having extremely high tensile strength and tensile elastic modulus can be obtained.
  • the flame resistance, pre-carbonization, and carbonization of the precursor fiber may be performed according to conventional methods.
  • the precursor fiber is first stretched in air at a stretch ratio of 0.8 to 2.5. Flame resistance at 200 to 300 ° C., and then pre-carbonized by heating to 300 to 800 ° C. while stretching in an inert gas at a stretch ratio of 0.9 to 1.5, and further stretching in an inert gas
  • Carbon fibers can be obtained by heating to 1000 to 2000 ° C. at a ratio of 0.9 to 1.1 for carbonization.
  • Examples of the inert gas used during the preliminary carbonization treatment and the carbonization treatment include nitrogen, argon, xenon, and carbon dioxide. Nitrogen is preferably used from an economical viewpoint.
  • the maximum temperature achieved during the carbonization treatment is set between 1200 ° C. and 3000 ° C. depending on the desired mechanical properties of the carbon fiber. Generally, the higher the maximum temperature reached in the carbonization treatment, the higher the tensile modulus of the carbon fiber obtained. On the other hand, the tensile strength reaches a maximum at 1500 ° C.
  • the carbonization treatment is performed at 1000 to 2000 ° C., more preferably at 1200 to 1700 ° C., and even more preferably at 1300 to 1600 ° C., so that the two mechanical properties of tensile modulus and tensile strength can be maximized. It is possible.
  • the tensile strength and tensile modulus of the carbon fiber obtained in this example were measured using a tensile tester “TG200NB” manufactured by NMB in accordance with JIS R7606 (2000) “Testing Method for Tensile Properties of Carbon Fiber-Single Fiber”. It was measured.
  • Example 1A Preparation of stock solution for spinning: 5 g of amphoteric molecule 3- (N, N-dimethylmyristylammonio) propanesulfonate was added to 1000 g of DMF and stirred at room temperature for 5 minutes. To this was added 5 g of double-walled carbon nanotubes (Unimid's XO grade), and then wet treatment was performed at 130 ° C. and 1.5 atm for about 2 hours using an autoclave (manufactured by Hirayama, HICLAB HG-50).
  • the carbon nanotubes were dispersed in the amphoteric molecule solution for about 90 minutes while stirring at 40 Hz using a bead mill (Dyno-mill, manufactured by Switzerland, zirconium beads, diameter 0.65 mm). Further, 3 g of polyoxyethylene alkyl lauryl ether sulfonate was added and the mixture was gently stirred for about 5 minutes to perform a stabilization treatment, thereby obtaining a carbon nanotube dispersion. 46 g of the carbon nanotube dispersion, 23 g of AN94-MAA6 copolymer, and 31 g of DMF were mixed and stirred for 1 hour at room temperature to obtain a spinning dope. The composition of the obtained spinning dope is shown in Table 1.
  • Spinning The above spinning solution is extruded from a spinneret having a pore diameter of 0.15 mm and a number of holes of 10 at 80 ° C., and a coagulation bath (1%) of 77 wt% DMF controlled to a temperature of 15 ° C. through an air gap length of 5 mm. Spinning was performed by a dry and wet spinning method introduced into the stage) to obtain a coagulated yarn. Thereafter, it was washed with a 10% by weight DMF aqueous solution (second stage), then stretched twice in air at room temperature, and further washed with water (third stage). Thereafter, the yarn was further stretched 3 times in boiling water, an amino-modified silicone oil agent was applied, and the yarn was dried at 150 ° C. for 5 minutes to obtain a precursor fiber having a single yarn fineness of 1.3 dTex. When the cross-sectional shape of the obtained precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section.
  • Flameproofing treatment The above precursor fibers were heated in air at a constant length for 1 hour at the first stage 220 ° C, the second stage 230 ° C, the third stage 240 ° C, and the fourth stage 250 ° C, respectively. A 1.38 flameproof yarn was obtained.
  • Precarbonization treatment The flameproofing yarn was heated at 700 ° C. for 2 minutes in a nitrogen stream at a constant length to obtain a precarbonized yarn.
  • Carbonization treatment The precarbonized yarn was heated at 1300 ° C. for 2 minutes in a nitrogen stream at a constant length to obtain carbon fibers. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber.
  • Example 2A A spinning dope was obtained in the same manner as in Example 1A using single-walled carbon nanotubes (Hipco manufactured by CNI) instead of double-walled carbon nanotubes.
  • the composition of the obtained spinning dope is shown in Table 1. This was further stirred for 3 hours with a rotation / revolution mixer to obtain the final spinning dope. Spinning, preliminary carbonization treatment, and carbonization treatment were carried out in the same manner as in Example 1A to obtain carbon fibers.
  • Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber.
  • the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
  • Example 3A A spinning dope was obtained in the same manner as in Example 1A, except that multi-walled carbon nanotubes (Baytubes manufactured by Bayer) were used instead of double-walled carbon nanotubes in Example 1A.
  • the composition of the obtained spinning dope is shown in Table 1.
  • carbon fibers were obtained in the same manner as in Example 1A.
  • Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber.
  • the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
  • Example 4A A spinning dope was obtained in the same manner as in Example 1A, except that AN95-MA5 copolymer was used instead of AN94-MAA6 copolymer in Example 1A.
  • the composition of the obtained spinning dope is shown in Table 1.
  • carbon fibers were obtained in the same manner as in Example 1A.
  • Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber.
  • the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
  • Example 5A A spinning dope was obtained in the same manner as in Example 3A, except that AN95-MAA4-IA1 copolymer was used instead of AN94-MAA6 copolymer in Example 3A.
  • the composition of the obtained spinning dope is shown in Table 1.
  • carbon fibers were obtained in the same manner as in Example 3A.
  • Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber.
  • the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
  • Example 6A A spinning dope was obtained in the same manner as in Example 1A, except that PAN was used instead of the AN94-MAA6 copolymer in Example 1A.
  • the composition of the obtained spinning dope is shown in Table 1.
  • carbon fibers were obtained in the same manner as in Example 1A.
  • Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber.
  • the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
  • Example 7A In Example 6A, single-walled carbon nanotubes were used instead of double-walled carbon nanotubes, and a spinning dope was produced by stirring for 3 hours with a rotation / revolution mixer in the same manner as in Example 2A. A spinning dope was obtained. The composition of the obtained spinning dope is shown in Table 1. Using this spinning dope, carbon fibers were obtained in the same manner as in Example 6A. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber. In addition, when the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
  • Example 8A A spinning dope was obtained in the same manner as in Example 4A, except that multi-walled carbon nanotubes were used instead of double-walled carbon nanotubes in Example 4A.
  • the composition of the obtained spinning dope is shown in Table 1.
  • carbon fibers were obtained in the same manner as in Example 4A.
  • Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber.
  • the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
  • Example 9A A spinning dope was obtained in the same manner as in Example 1A, except that 1.0 g of double-walled carbon nanotubes was used in Example 1A.
  • the composition of the obtained spinning dope is shown in Table 1.
  • carbon fibers were obtained in the same manner as in Example 1A.
  • Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber.
  • the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
  • Example 10A A stock solution for spinning was obtained in the same manner as in Example 3A, except that 5 g of 3- (N, N-dimethylstearylammonio) propanesulfonate was used as the amphoteric molecule in Example 3A.
  • the composition of the obtained spinning dope is shown in Table 1.
  • carbon fibers were obtained in the same manner as in Example 3A.
  • Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber.
  • the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
  • Example 11A A stock spinning solution was obtained in the same manner as in Example 1A, except that 5 g of 3-[(3-cholamidopropyl) dimethylammonio] -1-propanesulfonate was used as the amphoteric molecule in Example 1A.
  • the composition of the obtained spinning dope is shown in Table 1.
  • carbon fibers were obtained in the same manner as in Example 1A.
  • Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber.
  • the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
  • Comparative Example 1A DMF77g and AN94-MAA6 copolymer 23g were stirred at room temperature for 1 hour to obtain a spinning dope. Using this spinning dope, carbon fibers were obtained in the same manner as in Example 1A. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber. In addition, when the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
  • the above spinning solution is extruded from a spinneret having a hole diameter of 0.15 mm and a hole number of 1 at 80 ° C., introduced into a coagulation bath consisting of 15 l of methanol cooled to ⁇ 60 ° C. through an air gap length of 40 mm, and the yarn is wound I took it. After dipping the yarn for one day in methanol at -60 ° C, it is stretched 9 times, applied with an amino-modified silicone oil, and dried at 150 ° C for 5 minutes to give a precursor fiber having a single yarn fineness of 1.8 dTex. Got. When the cross-sectional shape of the obtained precursor fiber was confirmed with an electron microscope, it was not a substantially circular cross-section but a distorted shape.
  • Example 1A shows the tensile strength and tensile modulus of the obtained carbon fiber.
  • the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A. In Reference Example 1A, it took about three times longer to disperse the carbon nanotubes than in Examples 1A to 11A.
  • carbon nanotubes are dispersed in an amphoteric molecule solution for about 90 minutes with stirring at 40 Hz. Got. No stabilization treatment was performed on any of them.
  • these dispersions were allowed to stand for 2 weeks, the carbon nanotubes aggregated with each other, and a black solid appeared at the bottom of the container.
  • the carbon nanotube dispersion prepared by performing the stabilization treatment as in Examples 1A to 11A, 1B to 11B, or 1C to 11C does not show aggregation of the carbon nanotubes even after standing for 2 weeks. It was.
  • Examples 1B to 11B, Comparative Examples 1B to 2B, Reference Example 1B A spinning dope was prepared in the same manner as in Examples 1A to 11A, Comparative Examples 1A to 2A, and Reference Example 1A, except that DMSO was used instead of DMF, to obtain carbon fibers.
  • Table 3 shows the cross-sectional shape of the precursor fiber and the physical properties of the carbon fiber.
  • Examples 1C to 11C, Comparative Examples 1C to 2C, Reference Example 1C A spinning dope was prepared in the same manner as in Examples 1A to 11A, Comparative Examples 1A to 2A, and Reference Example 1A, except that DMAc was used instead of DMF, to obtain carbon fibers.
  • Table 4 shows the cross-sectional shape of the precursor fiber and the physical properties of the carbon fiber.
  • Examples 1A to 11A, 1B to 11B, 1C to 11C and Reference Examples 1A to 1C in which carbon nanotubes were added and amphoteric molecules were used as a dispersant, all had high tensile strength and While carbon fibers having a tensile modulus were obtained, Comparative Examples 1A to 1C (conventional general PAN carbon fibers) that did not use carbon nanotubes and did not use amphoteric molecules had a tensile strength of Although it was high, the tensile elastic modulus was inferior. Further, Comparative Examples 2A to 2C, which used carbon nanotubes but did not use amphoteric molecules, had higher tensile elastic modulus than Comparative Examples 1A to 1C, but were inferior in tensile strength.
  • carbon fiber having both high tensile strength and high tensile elastic modulus can be obtained.
  • Such carbon fibers are extremely useful as aircraft materials and spacecraft materials.

Abstract

Disclosed is a production method for a precursor fibre which enables the production of a carbon fibre having high strength and high elastic modulus. The disclosed production method includes: a step for preparing a solution of amphoteric molecule dimethylformamide, dimethyl sulfoxide or dimethyl acetamide; a step for preparing a carbon nanotube dispersion liquid by adding carbon nanotubes to the amphoteric molecule acetamide solution, and dispersing the carbon nanotubes; a step for preparing a spinning dope by mixing the carbon nanotube dispersion liquid and a polyacrylonitrile polymer; a step for obtaining a coagulated yarn from the spinning dope by means of a wet or dry spinning method; and a step for obtaining a precursor fibre for a carbon fibre by drawing out the coagulated yarn.

Description

高強度かつ高弾性率の炭素繊維を得るための前駆体繊維の製造方法Method for producing precursor fiber for obtaining high strength and high modulus carbon fiber
　本発明は、高強度かつ高弾性率の炭素繊維を得るための前駆体繊維の製造方法に関する。また、本発明は、かかる製造方法によって得られる前駆体繊維、及びかかる前駆体繊維から得られる高強度かつ高弾性率の炭素繊維に関する。さらに、本発明は、かかる前駆体繊維の製造に使用する紡糸原液に関する。 The present invention relates to a method for producing a precursor fiber for obtaining a carbon fiber having high strength and high elastic modulus. The present invention also relates to a precursor fiber obtained by such a production method and a high-strength and high-modulus carbon fiber obtained from such a precursor fiber. Furthermore, the present invention relates to a spinning dope used for the production of such precursor fibers.
　炭素繊維は、軽量かつ高強度、高弾性率という極めて優れた物性を有することから、釣竿、ゴルフクラブやスキー板等の運動用具やＣＮＧタンク、フライホイール、風力発電用風車、タービンブレード等の形成材料、道路、橋脚等の構造物の補強材、さらには、航空機、宇宙用素材として使われ、さらにその用途は広がりつつある。 Since carbon fiber has extremely excellent physical properties such as light weight, high strength, and high elastic modulus, it forms exercise equipment such as fishing rods, golf clubs and skis, CNG tanks, flywheels, wind turbines for wind power generation, turbine blades, etc. It is used as a reinforcing material for structures such as materials, roads and piers, as well as aircraft and space materials, and its uses are expanding.
　このような炭素繊維の用途の拡大につれて、より高強度、高弾性率を有する炭素繊維の開発が望まれるようになってきている。 As the use of such carbon fibers expands, development of carbon fibers having higher strength and higher elastic modulus has been desired.
　炭素繊維は、ポリアクリロニトリルを原料とするＰＡＮ系炭素繊維と、石炭由来のコールタール、石油由来のデカントオイルやエチレンボトムなどを出発原料とするピッチ系炭素繊維に大別される。いずれの炭素繊維も、まずこれらの原料から前駆体繊維を製造し、この前駆体繊維を高温で加熱して耐炎化、予備炭素化、及び炭素化することによって製造される。 Carbon fibers are roughly classified into PAN-based carbon fibers made from polyacrylonitrile and pitch-based carbon fibers made from coal-derived coal tar, petroleum-derived decant oil, ethylene bottom, and the like. Any carbon fiber is manufactured by first producing a precursor fiber from these raw materials and heating the precursor fiber at a high temperature to make it flame resistant, pre-carbonized, and carbonized.
　物性の点から見ると、現在市販されているＰＡＮ系炭素繊維は、最大６ＧＰａ程度という極めて高い引張強度を達成することができるが、引張弾性率が発現しにくく、最大でも３００ＧＰａ程度に留まっている。一方、現在市販されているピッチ系炭素繊維は、最大８００ＧＰａ程度という極めて高い引張弾性率を達成することができるが、引張強度が発現しにくく、最大でも３ＧＰａ程度に留まっている。航空機や宇宙用素材として使用するためには、高引張強度かつ高引張弾性率の炭素繊維が望ましいが、このように、現在提案されている炭素繊維の中にこの要件を満たすものは存在しない。 From the viewpoint of physical properties, currently available PAN-based carbon fibers can achieve a very high tensile strength of about 6 GPa at the maximum, but it is difficult to develop a tensile elastic modulus and remains at a maximum of about 300 GPa. . On the other hand, pitch-based carbon fibers that are currently available on the market can achieve a very high tensile elastic modulus of about 800 GPa at the maximum, but the tensile strength is difficult to develop and remains at about 3 GPa at the maximum. For use as an aircraft or space material, a carbon fiber having a high tensile strength and a high tensile modulus is desirable, but there is no carbon fiber currently proposed that satisfies this requirement.
　一方、特許文献１には、ポリアクリロニトリル系ポリマーにカーボンナノチューブを添加して紡糸することによって得られた前駆体繊維（カーボンナノチューブ含有ＰＡＮ系前駆体繊維）が、従来のＰＡＮ系前駆体繊維より高い引張弾性率を示すことが開示されている。 On the other hand, in Patent Document 1, precursor fibers (carbon nanotube-containing PAN precursor fibers) obtained by adding carbon nanotubes to a polyacrylonitrile-based polymer and spinning them are higher than conventional PAN-based precursor fibers. It is disclosed to exhibit a tensile modulus.
　特許文献１の方法で得られた前駆体繊維は、引張弾性率の点では優れるが、断面形状が円形ではなく大きく歪んでいるため、この前駆体繊維から得られる炭素繊維は従来のＰＡＮ系炭素繊維のような高い引張強度を示さない。従って結局、高引張強度及び高引張弾性率という二つの特性を両立させた炭素繊維は未だ得られていない。 Although the precursor fiber obtained by the method of Patent Document 1 is excellent in terms of tensile elastic modulus, since the cross-sectional shape is not circular but is distorted greatly, the carbon fiber obtained from this precursor fiber is a conventional PAN-based carbon. Does not show high tensile strength like fibers. Therefore, after all, a carbon fiber having both the high tensile strength and the high tensile elastic modulus has not been obtained yet.
米国特許第６８５２４１０号US Pat. No. 6,852,410
　本発明は、かかる従来技術の現状に鑑み創案されたものであり、その目的は、高引張強度かつ高引張弾性率の炭素繊維を製造することができる前駆体繊維及びその工業的に有利な製造方法を提供することにある。 The present invention has been created in view of the current state of the prior art, and its purpose is to provide precursor fibers capable of producing carbon fibers having high tensile strength and high tensile modulus, and industrially advantageous production thereof. It is to provide a method.
　本発明者は、上記目的を達成するために、特許文献１の方法の改良について鋭意検討した結果、特許文献１の方法で得られるカーボンナノチューブ含有ＰＡＮ系前駆体繊維の場合、紡糸原液の溶剤としてジメチルホルムアミド（ＤＭＦ）を使用しているため、紡糸原液にカーボンナノチューブ分散液を添加した際に瞬時にカーボンナノチューブが凝集・析出しやすく、また、事前に超音波などを用いて、ＤＭＦにカーボンナノチューブを分散させておいたとしても、分散状態の安定性が低く、紡糸原液作成中に凝集・析出すること、このため、得られた凝固糸中に凝集・析出物の塊が散在し、延伸時にこの塊を起点に糸切れを生じやすく、十分な延伸を行うことができないこと、このため前駆体繊維中のポリマー鎖及びカーボンナノチューブの配向が不十分になり、カーボンナノチューブの添加により本来期待されるべき高い引張強度および引張弾性率を発現することができないことが判明した。また、カーボンナノチューブが紡糸原液中で多量に凝集・析出すると、紡糸原液の曵糸性がなくなったり、紡糸口金のフィルター詰まりを起こし、紡糸不可能になることが判明した。これらの現象は、溶剤としてＤＭＦの代わりにジメチルスルホキシド（ＤＭＳＯ）又はジメチルアセトアミド（ＤＭＡｃ）を使用した場合でも同じであった。そこで、本発明者らは、ジメチルホルムアミド（ＤＭＦ）、ジメチルスルホキシド（ＤＭＳＯ）、又はジメチルアセトアミド（ＤＭＡｃ）を紡糸原液の溶剤として使用しつつも紡糸原液中のカーボンナノチューブの析出を抑制する方法についてさらに検討したところ、カーボンナノチューブを添加する際に両性分子を分散剤として併用すると、カーボンナノチューブが安定に溶剤中に分散されて凝集・析出しにくくなることを見出した。また、紡糸原液に含まれる両性分子は、紡糸時に凝固浴中へ抽出されてしまい、糸中にほとんど残らないため、カーボンナノチューブの添加による糸物性改善効果が高いことを見出し、本発明の完成に至った。 In order to achieve the above object, the present inventor has intensively studied the improvement of the method of Patent Document 1, and as a result, in the case of a carbon nanotube-containing PAN precursor fiber obtained by the method of Patent Document 1, Since dimethylformamide (DMF) is used, carbon nanotubes easily aggregate and precipitate instantly when the carbon nanotube dispersion is added to the spinning dope. Also, the carbon nanotubes are added to the DMF using ultrasonic waves in advance. Even if it is dispersed, the stability of the dispersed state is low, and agglomeration / precipitation occurs during the preparation of the spinning stock solution. For this reason, clumps of agglomeration / precipitate are scattered in the obtained coagulated yarn, and during stretching, Starting from this lump, thread breakage tends to occur, and sufficient stretching cannot be performed. For this reason, polymer chains and carbon nanochus in the precursor fiber Orientation becomes insufficient, it can not express high tensile strength and tensile modulus they should be originally expected has been found by the addition of carbon nanotubes. It was also found that if carbon nanotubes agglomerate and precipitate in a large amount in the spinning dope, the spinning dope loses spinnability or the spinneret filter becomes clogged, making spinning impossible. These phenomena were the same even when dimethyl sulfoxide (DMSO) or dimethylacetamide (DMAc) was used as a solvent instead of DMF. Therefore, the present inventors further provide a method for suppressing the precipitation of carbon nanotubes in the spinning stock solution while using dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or dimethylacetamide (DMAc) as a solvent for the spinning stock solution. As a result of the investigation, it has been found that when an amphoteric molecule is used in combination as a dispersant when carbon nanotubes are added, the carbon nanotubes are stably dispersed in a solvent and are less likely to aggregate and precipitate. In addition, the amphoteric molecules contained in the spinning dope are extracted into the coagulation bath during spinning and hardly remain in the yarn, so that it is found that the effect of improving the physical properties of the yarn by adding carbon nanotubes is high, thereby completing the present invention. It came.
　即ち、本発明によれば、以下の工程を含むことを特徴とする、炭素繊維の前駆体繊維の製造方法が提供される：
（１）両性分子のジメチルホルムアミド、ジメチルスルホキシド、又はジメチルアセトアミドの溶液を調製する工程；
（２）この両性分子の溶液にカーボンナノチューブを添加し、カーボンナノチューブを分散させ、カーボンナノチューブ分散液を調製する工程；
（３）このカーボンナノチューブ分散液とポリアクリロニトリル系ポリマーを混合し、紡糸原液を調製する工程；
（４）この紡糸原液から、湿式又は乾湿式紡糸法によって凝固糸を得る工程；そして
（５）この凝固糸を延伸して炭素繊維の前駆体繊維を得る工程。 That is, according to the present invention, there is provided a method for producing a carbon fiber precursor fiber, which comprises the following steps:
(1) a step of preparing a solution of amphoteric molecules of dimethylformamide, dimethylsulfoxide, or dimethylacetamide;
(2) adding carbon nanotubes to this amphoteric molecule solution, dispersing the carbon nanotubes, and preparing a carbon nanotube dispersion;
(3) A step of mixing the carbon nanotube dispersion and the polyacrylonitrile polymer to prepare a spinning dope;
(4) A step of obtaining a coagulated yarn from the spinning dope by a wet or dry wet spinning method; and (5) a step of drawing the coagulated yarn to obtain a carbon fiber precursor fiber.
　本発明の製造方法の好ましい態様では、工程（３）で調製される紡糸原液が、５～３５重量％のポリアクリロニトリル系ポリマーを含み、さらにポリアクリロニトリル系ポリマーに対して０．０１～５重量％のカーボンナノチューブ及び０．０１～５．０重量％の両性分子を含む。 In a preferred embodiment of the production method of the present invention, the spinning dope prepared in step (3) contains 5 to 35% by weight of polyacrylonitrile-based polymer, and further 0.01 to 5% by weight with respect to the polyacrylonitrile-based polymer. Carbon nanotubes and 0.01-5.0 wt% amphoteric molecules.
　本発明の製造方法の好ましい態様では、工程（２）においてカーボンナノチューブを分散させる前に濡れ処理を行い、さらにカーボンナノチューブ分散液に安定化処理を行う。 In a preferred embodiment of the production method of the present invention, the wetting treatment is performed before the carbon nanotubes are dispersed in the step (2), and the carbon nanotube dispersion is further stabilized.
　また、本発明によれば、上記方法によって製造される、炭素繊維の前駆体繊維であって、略円形断面を有しかつカーボンナノチューブを含むことを特徴とする炭素繊維の前駆体繊維が提供される。 In addition, according to the present invention, there is provided a carbon fiber precursor fiber produced by the above method, wherein the carbon fiber precursor fiber has a substantially circular cross section and includes carbon nanotubes. The
　さらに、本発明によれば、上記前駆体繊維を耐炎化、予備炭素化及び炭素化することによって製造される炭素繊維であって、高い引張強度及び高い引張弾性率を有することを特徴とする炭素繊維が提供される。 Furthermore, according to the present invention, a carbon fiber produced by flame-proofing, pre-carbonizing and carbonizing the precursor fiber, characterized by having a high tensile strength and a high tensile elastic modulus. Fiber is provided.
　さらに、本発明によれば、ポリアクリロニトリル系ポリマー、カーボンナノチューブ、及び両性分子を含む、ジメチルホルムアミド、ジメチルスルホキシド、又はジメチルアセトアミドの溶液からなる紡糸原液であって、両性分子の分散作用によりカーボンナノチューブが溶液中に分散していることを特徴とする紡糸原液が提供される。 Furthermore, according to the present invention, there is provided a spinning dope comprising a solution of dimethylformamide, dimethyl sulfoxide, or dimethylacetamide containing a polyacrylonitrile-based polymer, carbon nanotubes, and amphoteric molecules, and the carbon nanotubes are dispersed by the action of the amphoteric molecules. A spinning dope is provided that is dispersed in a solution.
　本発明のカーボンナノチューブ含有ＰＡＮ系前駆体繊維の製造方法では、両性分子が分散剤として紡糸原液からのカーボンナノチューブの凝集・析出を抑制しており、しかも両性分子が紡糸中に凝固浴中に抽出されて糸中に残らないため、得られた糸は、凝集・析出物の塊を含まず、十分に延伸させてポリマー鎖及びカーボンナノチューブを配向させることができる。従って、かかる前駆体繊維から得られる炭素繊維は、適切に配向されたカーボンナノチューブの含有および高分子鎖の配向に起因するＰＡＮ系炭素繊維の特徴である高い引張強度に加えて、高い引張弾性率を示す。さらに、本発明の製造方法で使用する紡糸原液は、カーボンナノチューブの分散に通常使われている分散剤を使用した紡糸原液とは異なり、カーボンナノチューブの分散時に超音波照射や遠心分離を行う必要がないため、本発明の製造方法は、工業生産に極めて適している。 In the method for producing a carbon nanotube-containing PAN precursor fiber according to the present invention, amphoteric molecules suppress aggregation and precipitation of carbon nanotubes from the spinning dope as a dispersant, and the amphoteric molecules are extracted into a coagulation bath during spinning. Thus, since the yarn does not remain in the yarn, the obtained yarn does not contain a lump of aggregates and precipitates, and can be sufficiently stretched to orient the polymer chains and the carbon nanotubes. Therefore, carbon fibers obtained from such precursor fibers have a high tensile elastic modulus in addition to the high tensile strength that is characteristic of PAN-based carbon fibers due to the inclusion of appropriately oriented carbon nanotubes and the orientation of polymer chains. Indicates. Furthermore, the spinning dope used in the production method of the present invention is different from the spinning dope using a dispersing agent usually used for dispersion of carbon nanotubes, and it is necessary to perform ultrasonic irradiation and centrifugation during dispersion of the carbon nanotubes. Therefore, the production method of the present invention is very suitable for industrial production.
　以下、本発明のカーボンナノチューブ含有ＰＡＮ系炭素繊維の前駆体繊維の製造方法について詳述する。 Hereinafter, the method for producing the precursor fiber of the carbon nanotube-containing PAN-based carbon fiber of the present invention will be described in detail.
　本発明の製造方法ではまず、両性分子のＤＭＦ、ＤＭＳＯ、又はＤＭＡｃの溶液を調製する（工程（１））。 In the production method of the present invention, first, a solution of amphoteric molecule DMF, DMSO, or DMAc is prepared (step (1)).
　本発明で使用する両性分子とは、１分子中に正電荷からなる基と負電荷からなる基を有する分子であって、それぞれの基が対イオンとの塩を形成しているものである。具体的には、３－（Ｎ，Ｎ－ジメチルステアリルアンモニオ）プロパンスルホネート、３－（Ｎ，Ｎ－ジメチルミリスチルアンモニオ）プロパンスルホネート、３－［（３－コールアミドプロピル）ジメチルアンモニオ］－１－プロパンスルホネート、３－［（３－コールアミドプロピル）ジメチルアンモニオ］－２－ヒドロキシプロパンスルホネート、ｎ－ドデシルーＮ，Ｎ’－ジメチル－３－アンモニオ－１－プロパンスルホネート、ｎ－ヘキサデシル－Ｎ，Ｎ’－ジメチル－３－アンモニオ－１－プロパンスルホネート、ｎ－オクチルホスホコリン、ｎ－ドデシルホスホコリン、ｎ－テトラデシルホスホコリン、ｎ－ヘキサデシルホスホコリン、ジメチルアルキルベタイン、パーフルオロアルキルベタイン、レシチン、２－メタクリロイルオキシエチルホスホリルコリンのポリマーおよびポリペプチド等が挙げられる。両性分子は、これらを単独又は２種類以上混合して使用することができ、さらに、陽イオン性界面活性剤、陰イオン性界面活性剤又は中性界面活性剤と併用して使用することもできる。 The amphoteric molecule used in the present invention is a molecule having a positive charge group and a negative charge group in one molecule, and each group forms a salt with a counter ion. Specifically, 3- (N, N-dimethylstearylammonio) propanesulfonate, 3- (N, N-dimethylmyristylammonio) propanesulfonate, 3-[(3-cholamidopropyl) dimethylammonio]- 1-propanesulfonate, 3-[(3-cholamidopropyl) dimethylammonio] -2-hydroxypropanesulfonate, n-dodecyl-N, N′-dimethyl-3-ammonio-1-propanesulfonate, n-hexadecyl-N , N′-dimethyl-3-ammonio-1-propanesulfonate, n-octylphosphocholine, n-dodecylphosphocholine, n-tetradecylphosphocholine, n-hexadecylphosphocholine, dimethylalkylbetaine, perfluoroalkylbetaine, Lecithin, 2-methacrylo Polymers and polypeptides etc. oxyethyl phosphoryl choline. These amphoteric molecules can be used alone or in admixture of two or more, and can also be used in combination with a cationic surfactant, an anionic surfactant or a neutral surfactant. .
　両性分子のＤＭＦ、ＤＭＳＯ、又はＤＭＡｃの溶液の調製は、ＤＭＦ、ＤＭＳＯ、又はＤＭＡｃに両性分子を添加して室温で攪拌することによって容易に行うことができる。ＤＭＦ、ＤＭＳＯ、又はＤＭＡｃは、それぞれ単独で用いてもよいし、それらを混合して用いてもよい。両性分子の濃度は、０．０１～５．０重量％であることが好ましく、０．１～２．０重量％であることがさらに好ましい。上記下限未満では、カーボンナノチューブの分散剤としての効果を十分発揮できないおそれがある。また、上記上限を越えると、やはりカーボンナノチューブの分散剤としての効果を十分に発揮しなくなるおそれがある。 Preparation of amphoteric molecule DMF, DMSO, or DMAc solution can be easily performed by adding amphoteric molecule to DMF, DMSO, or DMAc and stirring at room temperature. DMF, DMSO, or DMAc may be used singly or as a mixture thereof. The concentration of the amphoteric molecule is preferably 0.01 to 5.0% by weight, more preferably 0.1 to 2.0% by weight. If the amount is less than the above lower limit, the effect of the carbon nanotube as a dispersant may not be sufficiently exhibited. On the other hand, if the above upper limit is exceeded, there is a possibility that the effect of the carbon nanotube as a dispersant will not be sufficiently exhibited.
　次に、この両性分子のＤＭＦ、ＤＭＳＯ、又はＤＭＡｃの溶液にカーボンナノチューブを添加し、カーボンナノチューブを分散させ、カーボンナノチューブ分散液を調製する（工程（２））。 Next, carbon nanotubes are added to the DMF, DMSO, or DMAc solution of the amphoteric molecule to disperse the carbon nanotubes, thereby preparing a carbon nanotube dispersion (step (2)).
　本発明で使用するカーボンナノチューブは、単層カーボンナノチューブ、二層カーボンナノチューブ、多層カーボンナノチューブのいずれであっても良く、これらの混合物であっても良い。各種カーボンナノチューブの末端は、閉じていても良いし、穴が開いていても良い。カーボンナノチューブの直径は、好ましくは０．４ｎｍ以上１００ｎｍ以下であり、より好ましくは０．８ｎｍ以上８０ｎｍ以下である。カーボンナノチューブの長さは、制限されるものではなく、任意の長さのものを用いることができるが、好ましくは０．６μｍ以上２００μｍ以下である。 The carbon nanotube used in the present invention may be a single-walled carbon nanotube, a double-walled carbon nanotube, a multi-walled carbon nanotube, or a mixture thereof. The ends of various carbon nanotubes may be closed or perforated. The diameter of the carbon nanotube is preferably 0.4 nm or more and 100 nm or less, and more preferably 0.8 nm or more and 80 nm or less. The length of the carbon nanotube is not limited, and an arbitrary length can be used, but it is preferably 0.6 μm or more and 200 μm or less.
　本発明で使用するカーボンナノチューブの純度は、炭素純度として８０％以上であることが好ましく、より好ましくは９０％以上、さらに好ましくは９５％以上である。炭素純度は、示差熱分析により決定される。カーボンナノチューブの不純物としては、非晶炭素成分や触媒金属が挙げられる。空気中での２００℃以上での加熱、または、過酸化水素水で洗浄することにより、非晶炭素成分を除くことができる。さらに、塩酸、硝酸、硫酸等の鉱酸で洗浄後、水洗することにより鉄等のカーボンナノチューブ製造時の触媒金属を除去することができる。本発明では、これらの精製操作を組み合わせることにより、種々の不純物を除去し、炭素純度を高めたカーボンナノチューブを使用することが好ましい。 The purity of the carbon nanotubes used in the present invention is preferably 80% or more as carbon purity, more preferably 90% or more, and still more preferably 95% or more. Carbon purity is determined by differential thermal analysis. Examples of carbon nanotube impurities include amorphous carbon components and catalytic metals. The amorphous carbon component can be removed by heating in air at 200 ° C. or higher or by washing with hydrogen peroxide. Furthermore, after washing with a mineral acid such as hydrochloric acid, nitric acid, sulfuric acid, etc., the catalyst metal during the production of carbon nanotubes such as iron can be removed by washing with water. In the present invention, it is preferable to use carbon nanotubes in which various impurities are removed and carbon purity is increased by combining these purification operations.
　カーボンナノチューブの添加量は、次の工程（３）で混合するポリアクリロニトリル系ポリマーの量に対して０．０１～５重量％であることが好ましく、０．１～３重量％であることがさらに好ましい。上記下限未満では、得られる前駆体繊維中のカーボンナノチューブ量が少なくなり、十分高い引張弾性率を達成できないおそれがある。また、上記上限を越えると、紡糸原液に曵糸性がなくなり、紡糸が困難になるおそれがある。 The amount of carbon nanotube added is preferably 0.01 to 5% by weight, more preferably 0.1 to 3% by weight, based on the amount of polyacrylonitrile-based polymer to be mixed in the next step (3). preferable. If it is less than the said minimum, there exists a possibility that the amount of carbon nanotubes in the precursor fiber obtained may decrease and a sufficiently high tensile elastic modulus cannot be achieved. On the other hand, if the above upper limit is exceeded, the spinning dope loses spinnability, and spinning may be difficult.
　カーボンナノチューブの分散は、バンドルしたカーボンナノチューブをほぐすために必要であり、両性分子を用いた場合、緩やかに撹拌をしておけば分散するが、やはり、工業的に効率良くむら無く分散処理するためには物理的な力を加えて分散するのが良い。分散の方法として、ボールミル、ビーズミル、３本以上の複数本のロールによる分散等が挙げられる。分散液が目視で黒色透明になれば、カーボンナノチューブは充分分散している。 Dispersion of carbon nanotubes is necessary in order to loosen the bundled carbon nanotubes. When amphoteric molecules are used, they are dispersed if gently stirred, but they are also industrially efficient and evenly dispersed. It is better to disperse by applying physical force. Examples of the dispersion method include a ball mill, a bead mill, and dispersion using a plurality of three or more rolls. If the dispersion becomes black and transparent visually, the carbon nanotubes are sufficiently dispersed.
　カーボンナノチューブの分散を短時間に効率的に行うためには、分散前に濡れ処理を行うことが好ましい。ここで、濡れ処理とは、バンドルしたカーボンナノチューブの間に分散剤である両性分子を滲入させてカーボンナノチューブの分散のきっかけを作る処理を言う。通常、両性分子を用いる場合、緩やかな撹拌を与えるだけで静電気力により徐々にカーボンナノチューブが分散していく。しかし、工業的に大きなスケールで短時間で分散させようとする場合、物理的な方法で、両性分子をカーボンナノチューブ間に滲入させることにより、むら無く、短時間で分散が完了する。この物理的な方法としては、オートクレーブ中でカーボンナノチューブが存在する系に温度を掛けてカーボンナノチューブのバンドルを膨潤させたのち、圧力を掛ける方法が挙げられる。このときの温度範囲は５０～１５０℃、より好ましくは、８０～１５０℃であり、圧力範囲は１．１～２．０気圧である。 In order to efficiently disperse the carbon nanotubes in a short time, it is preferable to perform a wetting treatment before the dispersion. Here, the wetting treatment refers to a treatment for creating a trigger for the dispersion of the carbon nanotubes by allowing the amphoteric molecules as a dispersant to penetrate between the bundled carbon nanotubes. Usually, when amphoteric molecules are used, carbon nanotubes are gradually dispersed by electrostatic force only by applying gentle stirring. However, when trying to disperse in an industrially large scale in a short time, the amphoteric molecules are infiltrated between the carbon nanotubes by a physical method, and the dispersion is completed in a short time without unevenness. As this physical method, there is a method in which a temperature is applied to a system in which carbon nanotubes exist in an autoclave to swell the bundle of carbon nanotubes, and then a pressure is applied. The temperature range at this time is 50 to 150 ° C., more preferably 80 to 150 ° C., and the pressure range is 1.1 to 2.0 atm.
　カーボンナノチューブ分散液の調製後、分散液の安定性を上げるために分散液に安定化剤を添加する安定化処理を行うことが好ましい。安定化処理は、分散したカーボンナノチューブが再凝集するのを防ぐための処理であり、カーボンナノチューブ分散液をすぐに使用しない場合の経時変化を防ぐ効果がある。安定化剤としては、多級アルコール類、例えば、グリセロール、エチレングリコール等の多級アルコール、ポリビニルアルコール、また、ポリオキシエチレン類、例えば、ポリオキシエチレン化脂肪酸やそのエステル誘導体、また、多糖類、例えば、水溶性セルロース、水溶性デンプン、水溶性グリコーゲン、それらの誘導体、例えば、酢酸セルロース、アミロペクチン、また、アミン類、例えば、アルキルアミン等が挙げられる。これらの安定化剤は単独でも２種類以上用いても良い。安定化剤の添加量はカーボンナノチューブ分散液の量に対して、０．００６～３重量％であることが好ましく、さらに好ましくは０．０６～１．２重量％である。 After the preparation of the carbon nanotube dispersion, it is preferable to perform a stabilization treatment by adding a stabilizer to the dispersion in order to increase the stability of the dispersion. The stabilization treatment is a treatment for preventing the dispersed carbon nanotubes from reaggregating, and has an effect of preventing a change with time when the carbon nanotube dispersion liquid is not used immediately. Stabilizers include polyhydric alcohols such as polyhydric alcohols such as glycerol and ethylene glycol, polyvinyl alcohol, polyoxyethylenes such as polyoxyethylenated fatty acids and ester derivatives thereof, polysaccharides, For example, water-soluble cellulose, water-soluble starch, water-soluble glycogen, derivatives thereof such as cellulose acetate, amylopectin, and amines such as alkylamine are exemplified. These stabilizers may be used alone or in combination of two or more. The amount of the stabilizer added is preferably 0.006 to 3% by weight, more preferably 0.06 to 1.2% by weight, based on the amount of the carbon nanotube dispersion.
　次に、このカーボンナノチューブ分散液とポリアクリロニトリル系ポリマーを混合し、紡糸原液を調製する（工程（３））。 Next, the carbon nanotube dispersion and the polyacrylonitrile polymer are mixed to prepare a spinning dope (step (3)).
　この混合においては、カーボンナノチューブ分散液にポリアクリロニトリル系ポリマーを添加してもよいし、また、ポリアクリロニトリル系ポリマーをＤＭＦ、ＤＭＳＯ、又はＤＭＡｃに溶解させたポリマー溶液とカーボンナノチューブ分散液を混合してもよい。また、カーボンナノチューブ分散液に少量のポリアクリロニトリル系ポリマーを溶解させたポリマー溶液と、ポリアクリロニトリル系ポリマーのみをＤＭＦ、ＤＭＳＯ、又はＤＭＡｃに溶解させたポリマー溶液を混合してもよい。混合は一度に行う必要はなく、分けて行ってもよい。 In this mixing, a polyacrylonitrile-based polymer may be added to the carbon nanotube dispersion, or a polymer solution obtained by dissolving a polyacrylonitrile-based polymer in DMF, DMSO, or DMAc and a carbon nanotube dispersion are mixed. Also good. Further, a polymer solution in which a small amount of polyacrylonitrile-based polymer is dissolved in the carbon nanotube dispersion liquid and a polymer solution in which only the polyacrylonitrile-based polymer is dissolved in DMF, DMSO, or DMAc may be mixed. Mixing does not have to be performed at once, and may be performed separately.
　本発明で使用するポリアクリロニトリル系ポリマーとしては、ポリアクリロニトリル、および、アクリロニトリルと共重合可能なビニル単量体からなる共重合体を使うことができる。共重合体としては、耐炎化反応に有効な作用を有するアクリロニトリル－メタクリル酸共重合体、アクリロニトリル－メタクリル酸メチル共重合体、アクリロニトリル－アクリル酸共重合体、アクリロニトリル－イタコン酸共重合体、アクリロニトリル－メタクリル酸－イタコン酸共重合体、アクリロニトリル－メタクリル酸メチル－イタコン酸共重合体、アクリロニトリル－アクリル酸－イタコン酸共重合体等が挙げられ、いずれの場合もアクリロニトリル成分が８５モル％以上であることが好ましい。これらのポリマーは、アルカリ金属またはアンモニアとの塩を形成していても良い。また、これらのポリマーは単独または２種以上の混合物としても使用できる。 As the polyacrylonitrile-based polymer used in the present invention, polyacrylonitrile and a copolymer composed of a vinyl monomer copolymerizable with acrylonitrile can be used. Examples of the copolymer include acrylonitrile-methacrylic acid copolymer, acrylonitrile-methyl methacrylate copolymer, acrylonitrile-acrylic acid copolymer, acrylonitrile-itaconic acid copolymer, acrylonitrile Examples include methacrylic acid-itaconic acid copolymer, acrylonitrile-methyl methacrylate-itaconic acid copolymer, and acrylonitrile-acrylic acid-itaconic acid copolymer. In any case, the acrylonitrile component should be 85 mol% or more. Is preferred. These polymers may form a salt with alkali metal or ammonia. These polymers can be used alone or as a mixture of two or more.
　ポリアクリロニトリル系ポリマーの添加量は、紡糸原液中、５～３５重量％になるような量であることが好ましく、さらに好ましくは１０～２５重量％になるような量である。上記下限未満では、紡糸張力をかけることができず、繊維自身および糸中のカーボンナノチューブの配向が不足し、強度不足の原因となるおそれがある。また、上記下限を越えると紡糸時に背圧上昇の原因となるおそれがある。 The amount of polyacrylonitrile-based polymer added is preferably such that it is 5 to 35% by weight, more preferably 10 to 25% by weight in the spinning dope. If it is less than the above lower limit, the spinning tension cannot be applied, and the orientation of the carbon itself and the carbon nanotubes in the yarn is insufficient, which may cause insufficient strength. On the other hand, if the above lower limit is exceeded, there is a risk of increasing the back pressure during spinning.
　以上の工程（３）によって得られた紡糸原液は、ポリアクリロニトリル系ポリマー、カーボンナノチューブ、及び両性分子を含むＤＭＦ、ＤＭＳＯ、又はＤＭＡｃの溶液からなる。これらの溶液中では、両性分子の分散作用によりカーボンナノチューブがＤＭＦ、ＤＭＳＯ、又はＤＭＡｃ中に安定に分散しており、何らかの衝撃が加えられても析出しにくくなっている。 The spinning dope obtained by the above step (3) consists of a solution of DMF, DMSO, or DMAc containing polyacrylonitrile-based polymer, carbon nanotubes, and amphoteric molecules. In these solutions, the carbon nanotubes are stably dispersed in DMF, DMSO, or DMAc due to the dispersing action of amphoteric molecules, and are difficult to precipitate even if any impact is applied.
　本発明の紡糸原液の粘度は、通常３０℃で、湿式紡糸では、２～２０Ｐａ・ｓｅｃであることが好ましく、乾湿式紡糸では１００～５００Ｐａ・ｓｅｃであることが好ましい。それぞれの紡糸方法において、上記範囲を下回ると、紡糸時にノズル面に紡糸原液が付着してしまう恐れがあったり、吐出糸条の切断や品質斑の問題があり、上記範囲を上回ると、メルトフラクチャーが生じて安定に紡糸を行うことができなくなるなど、紡糸の操業性に問題が生じるおそれがある。 The viscosity of the spinning dope of the present invention is usually 30 ° C., preferably 2 to 20 Pa · sec for wet spinning, and preferably 100 to 500 Pa · sec for dry and wet spinning. In each spinning method, if the range is below the above range, there is a possibility that the spinning solution may adhere to the nozzle surface at the time of spinning, or there is a problem of cutting of the discharged yarn or quality unevenness. This may cause problems in spinning operability, such as inability to perform stable spinning.
　次に、この紡糸原液から、湿式又は乾湿式紡糸法によって凝固糸を得る（工程（４））。 Next, a coagulated yarn is obtained from this spinning dope by a wet or dry wet spinning method (step (4)).
　紡糸口金の孔径は、湿式紡糸では、通常、０．０３～０．１ｍｍであることが好ましく、乾湿式紡糸では０．１～０．３ｍｍであることが好ましい。上記範囲を下回ると、紡糸時にドラフト比が小さくなり生産性を著しく損なうおそれがあったり、吐出糸条の切断や品質斑の問題があり、上記範囲を上回ると、紡糸原液の吐出線速度が小さくなり凝固浴内での糸の張力が大きくなるなど、紡糸の操業性に問題が生じるおそれがある。 The hole diameter of the spinneret is usually preferably from 0.03 to 0.1 mm for wet spinning, and preferably from 0.1 to 0.3 mm for dry and wet spinning. Below the above range, the draft ratio may decrease during spinning and the productivity may be significantly impaired, and there is a problem of cutting of the discharged yarn and quality unevenness. When the above range is exceeded, the discharge linear velocity of the spinning dope becomes low. Therefore, there is a possibility that problems may occur in the operability of spinning, such as an increase in yarn tension in the coagulation bath.
　凝固浴としては、ＤＭＦ、ＤＭＳＯ、又はＤＭＡｃと、いわゆる凝固促進成分の混合物を用いることが好ましい。凝固促進成分としては、ポリアクリロニトリル系ポリマーを溶解せず、かつポリマー溶液に用いた溶媒（ＤＭＦ、ＤＭＳＯ、又はＤＭＡｃ）と相溶性があるものが好ましく、具体的には、水を使用することが好ましい。乾湿式紡糸で用いられる凝固浴は、凝固糸を構成する単繊維の横断面が真円状で、かつ繊維側面が平滑となる範囲でＤＭＦ、ＤＭＳＯ、又はＤＭＡｃの濃度を高くし、凝固浴の温度を低く設定することが好ましい。凝固浴の温度としては、例えば５℃～２０℃が好ましい。５℃未満であると凝固の速度が遅く引き取り速度が低下する。２０℃を超えると糸同士が融着しやすくなり好ましくない。 As the coagulation bath, it is preferable to use a mixture of DMF, DMSO, or DMAc and a so-called coagulation promoting component. As the coagulation accelerating component, a component that does not dissolve the polyacrylonitrile-based polymer and is compatible with the solvent (DMF, DMSO, or DMAc) used in the polymer solution is preferable. Specifically, water may be used. preferable. The coagulation bath used in dry-wet spinning has a high concentration of DMF, DMSO, or DMAc within a range in which the cross-section of the single fiber constituting the coagulated yarn is a perfect circle and the side surface of the fiber is smooth. It is preferable to set the temperature low. The temperature of the coagulation bath is preferably 5 ° C. to 20 ° C., for example. If it is less than 5 ° C., the rate of solidification is slow and the take-off rate is lowered. If it exceeds 20 ° C., the yarns are liable to be fused, which is not preferable.
　凝固水洗工程は、一段工程で実施してもよいが、徐々に濃度を下げながら多段工程で実施することが好ましい。多段工程で凝固水洗を行うことにより、略円形断面の前駆体繊維を得ることができ、引張強度を一層高くすることができる。但し、あまりに多くの工程を通過することは、コスト上好ましくない。また、２段目以降の水洗工程は、後述する延伸工程中又は延伸工程後に行ってもかまわない。 The coagulation water washing step may be performed in a single step, but is preferably performed in a multi-step process while gradually reducing the concentration. By performing coagulation water washing in a multistage process, a precursor fiber having a substantially circular cross section can be obtained, and the tensile strength can be further increased. However, it is not preferable in terms of cost to pass through too many steps. Further, the second and subsequent water washing steps may be performed during or after the stretching step described later.
　１段目の凝固浴は、７０重量％以上９０重量％未満のＤＭＦ、ＤＭＳＯ、又はＤＭＡｃの濃度範囲で水洗を行うことが好ましい。ＤＭＦ、ＤＭＳＯ、又はＤＭＡｃの濃度が７０重量％未満では、繊維の表層のみが先に凝固し、繊維断面がいびつになるおそれがある。また、ＤＭＦ、ＤＭＳＯ、又はＤＭＡｃの濃度が９０重量％以上では、入念な水洗工程が必要となるおそれがある。
　２段目の凝固浴は、５重量％以上３０重量％未満のＤＭＦ、ＤＭＳＯ、又はＤＭＡｃの濃度範囲で水洗を行うことが好ましい。ＤＭＦ、ＤＭＳＯ、又はＤＭＡｃの濃度が５重量％未満では、繊維中のＤＭＦ、ＤＭＳＯ、又はＤＭＡｃを短時間で除去できず、後にさらに入念な水洗工程が必要となるおそれがある。また、ＤＭＦ、ＤＭＳＯ、又はＤＭＡｃの濃度が３０重量％以上では、水洗後の繊維中のＤＭＦ、ＤＭＳＯ、又はＤＭＡｃの濃度に変化がなく、実質的に水洗にならないおそれがある。３段以上水洗工程を行う場合には、さらにＤＭＦ、ＤＭＳＯ、又はＤＭＡｃの濃度を低くして凝固を行うことが好ましい。 The first stage coagulation bath is preferably washed with water in a concentration range of 70% by weight or more and less than 90% by weight of DMF, DMSO, or DMAc. If the concentration of DMF, DMSO, or DMAc is less than 70% by weight, only the surface layer of the fiber may solidify first, and the fiber cross section may become distorted. Further, if the concentration of DMF, DMSO, or DMAc is 90% by weight or more, a careful water washing step may be required.
The second stage coagulation bath is preferably washed with water in a concentration range of 5% by weight or more and less than 30% by weight of DMF, DMSO, or DMAc. If the concentration of DMF, DMSO, or DMAc is less than 5% by weight, DMF, DMSO, or DMAc in the fiber cannot be removed in a short time, and a more careful washing step may be required later. Further, when the concentration of DMF, DMSO, or DMAc is 30% by weight or more, there is no change in the concentration of DMF, DMSO, or DMAc in the fiber after water washing, and there is a possibility that water washing is not substantially performed. In the case where the water washing step is performed in three or more stages, it is preferable to further solidify by lowering the concentration of DMF, DMSO, or DMAc.
　紡糸時の引き取り速度は、３～２０ｍ／分の範囲にあることが好ましい。３ｍ／分未満では、生産性が極めて低くなるおそれがある。一方、２０ｍ／分を越えると、紡糸口金近傍での糸切れが多発し、操業性を著しく損なうおそれがある。 The take-up speed during spinning is preferably in the range of 3 to 20 m / min. If it is less than 3 m / min, the productivity may be extremely low. On the other hand, if it exceeds 20 m / min, yarn breakage frequently occurs in the vicinity of the spinneret and the operability may be significantly impaired.
　次に、工程（４）で得られた凝固糸を延伸して炭素繊維の前駆体繊維を得る（工程（５））。延伸することによって、繊維中の分子鎖の配向性を高めて力学物性に優れた炭素繊維を得ることができる。延伸は、トータルの延伸倍率が４～１２倍になるように行うことが好ましく、より好ましくは、トータルの延伸倍率が５～７倍になるように行う。トータルの延伸倍率が上記下限未満では、糸中のカーボンナノチューブの配向が不充分で、ポリアクリロニトリル系高分子が緻密に配向した炭素繊維前駆体を得ることができないおそれがある。また、トータルの延伸倍率が上記上限を越える場合は、延伸時に糸切れが頻発し、延伸安定性に欠けるおそれがある。延伸操作は、冷延伸、熱水中での延伸、蒸気中での延伸のいずれの方法でも良い。また、１度に延伸しても、多段で延伸しても良い。 Next, the coagulated yarn obtained in the step (4) is drawn to obtain a carbon fiber precursor fiber (step (5)). By stretching, a carbon fiber excellent in mechanical properties can be obtained by increasing the orientation of molecular chains in the fiber. The stretching is preferably performed so that the total stretching ratio is 4 to 12 times, and more preferably, the total stretching ratio is 5 to 7 times. If the total draw ratio is less than the above lower limit, the orientation of the carbon nanotubes in the yarn is insufficient, and there is a possibility that a carbon fiber precursor in which the polyacrylonitrile-based polymer is densely oriented cannot be obtained. Further, when the total draw ratio exceeds the above upper limit, yarn breakage frequently occurs during drawing and there is a possibility that the drawing stability may be lacking. The stretching operation may be any of cold stretching, stretching in hot water, and stretching in steam. Moreover, even if it extends | stretches at once, you may extend | stretch in multiple steps.
　以上の工程（１）～（５）によって得られた前駆体繊維は、高引張強度を発揮するのに必要な略円形断面を有し、しかも高引張弾性率をもたらすカーボンナノチューブを適切な配向で含む。従って、この前駆体繊維を耐炎化、予備炭素化、及び炭素化すれば、極めて高い引張強度及び引張弾性率を有する炭素繊維を得ることができる。 The precursor fibers obtained by the above steps (1) to (5) have a substantially circular cross section necessary for exhibiting high tensile strength, and carbon nanotubes that provide high tensile elastic modulus in an appropriate orientation. Including. Therefore, if this precursor fiber is flame-resistant, pre-carbonized, and carbonized, a carbon fiber having extremely high tensile strength and tensile elastic modulus can be obtained.
　本発明では、前駆体繊維の耐炎化、予備炭素化、及び炭素化は、常法に従って行えばよく、例えば、前駆体繊維をまず、空気中で延伸比０．８～２．５で延伸しながら２００～３００℃で耐炎化し、次に、不活性気体中で延伸比０．９～１．５で延伸しながら３００～８００℃に加熱して予備炭素化し、さらに、不活性気体中で延伸比０．９～１．１で１０００～２０００℃に加熱して炭素化することによって炭素繊維を得ることができる。 In the present invention, the flame resistance, pre-carbonization, and carbonization of the precursor fiber may be performed according to conventional methods. For example, the precursor fiber is first stretched in air at a stretch ratio of 0.8 to 2.5. Flame resistance at 200 to 300 ° C., and then pre-carbonized by heating to 300 to 800 ° C. while stretching in an inert gas at a stretch ratio of 0.9 to 1.5, and further stretching in an inert gas Carbon fibers can be obtained by heating to 1000 to 2000 ° C. at a ratio of 0.9 to 1.1 for carbonization.
　予備炭素化処理および炭素化処理時に用いられる不活性気体としては、窒素、アルゴン、キセノン、および二酸化炭素等が挙げられる。経済的な観点からは窒素が好ましく用いられる。炭素化処理時の最高到達温度は所望の炭素繊維の力学物性に応じて１２００～３０００℃の間で設定される。一般的に炭素化処理の最高到達温度が高い程、得られる炭素繊維の引張弾性率が大きくなる。一方、引張強度は１５００℃で極大となる。本発明では、炭素化処理を１０００～２０００℃、より好ましくは１２００～１７００℃、さらに好ましくは１３００～１６００℃で行うことにより、引張弾性率と引張強度の２つの力学物性を最大限に発現させることが可能である。 Examples of the inert gas used during the preliminary carbonization treatment and the carbonization treatment include nitrogen, argon, xenon, and carbon dioxide. Nitrogen is preferably used from an economical viewpoint. The maximum temperature achieved during the carbonization treatment is set between 1200 ° C. and 3000 ° C. depending on the desired mechanical properties of the carbon fiber. Generally, the higher the maximum temperature reached in the carbonization treatment, the higher the tensile modulus of the carbon fiber obtained. On the other hand, the tensile strength reaches a maximum at 1500 ° C. In the present invention, the carbonization treatment is performed at 1000 to 2000 ° C., more preferably at 1200 to 1700 ° C., and even more preferably at 1300 to 1600 ° C., so that the two mechanical properties of tensile modulus and tensile strength can be maximized. It is possible.
　以下、実施例で本発明をさらに具体的に説明するが、本発明はこれらの実施例により限定されるものではない。 Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
　なお、本実施例で得た炭素繊維の引張強度および引張弾性率は、ＪＩＳ　Ｒ７６０６（２０００）「炭素繊維－単繊維の引張特性の試験方法」に従ってＮＭＢ社製引張試験機「ＴＧ２００ＮＢ」を用いて測定した。 The tensile strength and tensile modulus of the carbon fiber obtained in this example were measured using a tensile tester “TG200NB” manufactured by NMB in accordance with JIS R7606 (2000) “Testing Method for Tensile Properties of Carbon Fiber-Single Fiber”. It was measured.
実施例１Ａ
　紡糸原液の調製：ＤＭＦ１０００ｇに両性分子３－（Ｎ，Ｎ－ジメチルミリスチルアンモニオ）プロパンスルホネート５ｇを添加し、室温で５分間撹拌した。これに二層カーボンナノチューブ（Ｕｎｉｄｙｍ社製ＸＯグレード）５ｇを添加した後、オートクレーブ（Ｈｉｒａｙａｍａ製、ＨＩＣＬＡＶＥ　ＨＧ－５０）を用い、１３０℃、１．５気圧で約２時間濡れ処理をした。室温まで冷却した後、ビーズミル（Ｄｙｎｏ－ｍｉｌｌ，スイス製、ジルコニウムビーズ、直径０．６５ｍｍ）を用い、４０Ｈｚで撹拌しながら約９０分間、カーボンナノチューブを両性分子溶液に分散した。さらに、ポリオキシエチレンアルキルラウリルエーテルスルホネート３ｇを加えて、約５分間緩やかに撹拌することにより安定化処理を行い、カーボンナノチューブ分散液を得た。上記カーボンナノチューブ分散液４６ｇとＡＮ９４－ＭＡＡ６共重合体２３ｇ、ＤＭＦ　３１ｇを混合し、室温で１時間攪拌した後、紡糸原液を得た。得られた紡糸原液の組成を表１に示す。 Example 1A
Preparation of stock solution for spinning: 5 g of amphoteric molecule 3- (N, N-dimethylmyristylammonio) propanesulfonate was added to 1000 g of DMF and stirred at room temperature for 5 minutes. To this was added 5 g of double-walled carbon nanotubes (Unimid's XO grade), and then wet treatment was performed at 130 ° C. and 1.5 atm for about 2 hours using an autoclave (manufactured by Hirayama, HICLAB HG-50). After cooling to room temperature, the carbon nanotubes were dispersed in the amphoteric molecule solution for about 90 minutes while stirring at 40 Hz using a bead mill (Dyno-mill, manufactured by Switzerland, zirconium beads, diameter 0.65 mm). Further, 3 g of polyoxyethylene alkyl lauryl ether sulfonate was added and the mixture was gently stirred for about 5 minutes to perform a stabilization treatment, thereby obtaining a carbon nanotube dispersion. 46 g of the carbon nanotube dispersion, 23 g of AN94-MAA6 copolymer, and 31 g of DMF were mixed and stirred for 1 hour at room temperature to obtain a spinning dope. The composition of the obtained spinning dope is shown in Table 1.
　紡糸：上記紡糸原液を８０℃にて孔径０．１５ｍｍ、孔数１０の紡糸口金から押し出し、エアギャップ長５ｍｍを経て、１５℃の温度にコントロールした７７重量％ＤＭＦの水溶液からなる凝固浴（１段目）に導入する乾湿式紡糸法により紡糸し、凝固糸とした。その後、１０重量％のＤＭＦ水溶液（２段目）により水洗した後、常温空気中で２倍に延伸し、水（３段目）でさらに水洗した。この後、さらにこの糸を沸騰水中で３倍に延伸し、アミノ変性シリコーン油剤を付与して、１５０℃、５分間乾燥することにより、単糸繊度１．３ｄＴｅｘの前駆体繊維を得た。得られた前駆体繊維の断面形状を電子顕微鏡で確認したところ、略円形断面であった。 Spinning: The above spinning solution is extruded from a spinneret having a pore diameter of 0.15 mm and a number of holes of 10 at 80 ° C., and a coagulation bath (1%) of 77 wt% DMF controlled to a temperature of 15 ° C. through an air gap length of 5 mm. Spinning was performed by a dry and wet spinning method introduced into the stage) to obtain a coagulated yarn. Thereafter, it was washed with a 10% by weight DMF aqueous solution (second stage), then stretched twice in air at room temperature, and further washed with water (third stage). Thereafter, the yarn was further stretched 3 times in boiling water, an amino-modified silicone oil agent was applied, and the yarn was dried at 150 ° C. for 5 minutes to obtain a precursor fiber having a single yarn fineness of 1.3 dTex. When the cross-sectional shape of the obtained precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section.
　耐炎化処理：上記の前駆体繊維を空気中で一定長にて、１段目２２０℃、２段目２３０℃、３段目２４０℃、４段目２５０℃でそれぞれ１時間加熱して、比重１．３８の耐炎化処理糸を得た。
　予備炭素化処理：上記耐炎化処理糸を窒素気流中で一定長にて、７００℃で２分間加熱して予備炭素化処理糸を得た。
　炭素化処理：上記予備炭素化処理糸を窒素気流中で一定長にて、１３００℃で２分間加熱して炭素繊維を得た。得られた炭素繊維の引張強度及び引張弾性率を表２に示す。 Flameproofing treatment: The above precursor fibers were heated in air at a constant length for 1 hour at the first stage 220 ° C, the second stage 230 ° C, the third stage 240 ° C, and the fourth stage 250 ° C, respectively. A 1.38 flameproof yarn was obtained.
Precarbonization treatment: The flameproofing yarn was heated at 700 ° C. for 2 minutes in a nitrogen stream at a constant length to obtain a precarbonized yarn.
Carbonization treatment: The precarbonized yarn was heated at 1300 ° C. for 2 minutes in a nitrogen stream at a constant length to obtain carbon fibers. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber.
実施例２Ａ
　二層カーボンナノチューブの代わりに単層カーボンナノチューブ（ＣＮＩ社製Ｈｉｐｃｏ）を使用して実施例１Ａと同様にして紡糸原液を得た。得られた紡糸原液の組成を表１に示す。これをさらに自転公転型ミキサーで３時間撹拌して最終の紡糸原液とした。実施例１Ａと同様にして紡糸、予備炭素化処理、および炭素化処理をして、炭素繊維を得た。得られた炭素繊維の引張強度及び引張弾性率を表２に示す。なお、前駆体繊維の断面形状を電子顕微鏡で確認したところ、実施例１Ａと同様に略円形断面であった。 Example 2A
A spinning dope was obtained in the same manner as in Example 1A using single-walled carbon nanotubes (Hipco manufactured by CNI) instead of double-walled carbon nanotubes. The composition of the obtained spinning dope is shown in Table 1. This was further stirred for 3 hours with a rotation / revolution mixer to obtain the final spinning dope. Spinning, preliminary carbonization treatment, and carbonization treatment were carried out in the same manner as in Example 1A to obtain carbon fibers. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber. In addition, when the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
実施例３Ａ
　実施例１Ａにおいて二層カーボンナノチューブの代わりに多層カーボンナノチューブ（Ｂａｙｅｒ社製Ｂａｙｔｕｂｅｓ）を使用した以外は、実施例１Ａと同様にして紡糸原液を得た。得られた紡糸原液の組成を表１に示す。この紡糸原液を用いて実施例１Ａと同様にして炭素繊維を得た。得られた炭素繊維の引張強度及び引張弾性率を表２に示す。なお、前駆体繊維の断面形状を電子顕微鏡で確認したところ、実施例１Ａと同様に略円形断面であった。 Example 3A
A spinning dope was obtained in the same manner as in Example 1A, except that multi-walled carbon nanotubes (Baytubes manufactured by Bayer) were used instead of double-walled carbon nanotubes in Example 1A. The composition of the obtained spinning dope is shown in Table 1. Using this spinning dope, carbon fibers were obtained in the same manner as in Example 1A. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber. In addition, when the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
実施例４Ａ
　実施例１ＡにおいてＡＮ９４－ＭＡＡ６共重合体の代わりにＡＮ９５－ＭＡ５共重合体を使用した以外は、実施例１Ａと同様にして紡糸原液を得た。得られた紡糸原液の組成を表１に示す。この紡糸原液を用いて実施例１Ａと同様にして炭素繊維を得た。得られた炭素繊維の引張強度及び引張弾性率を表２に示す。なお、前駆体繊維の断面形状を電子顕微鏡で確認したところ、実施例１Ａと同様に略円形断面であった。 Example 4A
A spinning dope was obtained in the same manner as in Example 1A, except that AN95-MA5 copolymer was used instead of AN94-MAA6 copolymer in Example 1A. The composition of the obtained spinning dope is shown in Table 1. Using this spinning dope, carbon fibers were obtained in the same manner as in Example 1A. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber. In addition, when the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
実施例５Ａ
　実施例３ＡにおいてＡＮ９４－ＭＡＡ６共重合体の代わりにＡＮ９５－ＭＡＡ４－ＩＡ１共重合体を使用した以外は、実施例３Ａと同様にして紡糸原液を得た。得られた紡糸原液の組成を表１に示す。この紡糸原液を用いて実施例３Ａと同様にして炭素繊維を得た。得られた炭素繊維の引張強度及び引張弾性率を表２に示す。なお、前駆体繊維の断面形状を電子顕微鏡で確認したところ、実施例１Ａと同様に略円形断面であった。 Example 5A
A spinning dope was obtained in the same manner as in Example 3A, except that AN95-MAA4-IA1 copolymer was used instead of AN94-MAA6 copolymer in Example 3A. The composition of the obtained spinning dope is shown in Table 1. Using this spinning dope, carbon fibers were obtained in the same manner as in Example 3A. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber. In addition, when the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
実施例６Ａ
　実施例１ＡにおいてＡＮ９４－ＭＡＡ６共重合体の代わりにＰＡＮを使用した以外は、実施例１Ａと同様にして紡糸原液を得た。得られた紡糸原液の組成を表１に示す。この紡糸原液を用いて実施例１Ａと同様にして炭素繊維を得た。得られた炭素繊維の引張強度及び引張弾性率を表２に示す。なお、前駆体繊維の断面形状を電子顕微鏡で確認したところ、実施例１Ａと同様に略円形断面であった。 Example 6A
A spinning dope was obtained in the same manner as in Example 1A, except that PAN was used instead of the AN94-MAA6 copolymer in Example 1A. The composition of the obtained spinning dope is shown in Table 1. Using this spinning dope, carbon fibers were obtained in the same manner as in Example 1A. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber. In addition, when the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
実施例７Ａ
　実施例６Ａにおいて二層カーボンナノチューブの代わりに単層カーボンナノチューブを使用し、実施例２Ａと同様に自転公転型ミキサーで３時間撹拌して紡糸ドープを製造した以外は、実施例６Ａと同様にして紡糸原液を得た。得られた紡糸原液の組成を表１に示す。この紡糸原液を用いて実施例６Ａと同様にして炭素繊維を得た。得られた炭素繊維の引張強度及び引張弾性率を表２に示す。なお、前駆体繊維の断面形状を電子顕微鏡で確認したところ、実施例１Ａと同様に略円形断面であった。 Example 7A
In Example 6A, single-walled carbon nanotubes were used instead of double-walled carbon nanotubes, and a spinning dope was produced by stirring for 3 hours with a rotation / revolution mixer in the same manner as in Example 2A. A spinning dope was obtained. The composition of the obtained spinning dope is shown in Table 1. Using this spinning dope, carbon fibers were obtained in the same manner as in Example 6A. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber. In addition, when the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
実施例８Ａ
　実施例４Ａにおいて二層カーボンナノチューブの代わりに多層カーボンナノチューブを使用した以外は、実施例４Ａと同様にして紡糸原液を得た。得られた紡糸原液の組成を表１に示す。この紡糸原液を用いて実施例４Ａと同様にして炭素繊維を得た。得られた炭素繊維の引張強度及び引張り弾性率を表２に示す。なお、前駆体繊維の断面形状を電子顕微鏡で確認したところ、実施例１Ａと同様に略円形断面であった。 Example 8A
A spinning dope was obtained in the same manner as in Example 4A, except that multi-walled carbon nanotubes were used instead of double-walled carbon nanotubes in Example 4A. The composition of the obtained spinning dope is shown in Table 1. Using this spinning dope, carbon fibers were obtained in the same manner as in Example 4A. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber. In addition, when the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
実施例９Ａ
　実施例１Ａにおいて二層カーボンナノチューブ１．０ｇを使用した以外は、実施例１Ａと同様にして紡糸原液を得た。得られた紡糸原液の組成を表１に示す。この紡糸原液を用いて実施例１Ａと同様にして炭素繊維を得た。得られた炭素繊維の引張強度及び引張り弾性率を表２に示す。なお、前駆体繊維の断面形状を電子顕微鏡で確認したところ、実施例１Ａと同様に略円形断面であった。 Example 9A
A spinning dope was obtained in the same manner as in Example 1A, except that 1.0 g of double-walled carbon nanotubes was used in Example 1A. The composition of the obtained spinning dope is shown in Table 1. Using this spinning dope, carbon fibers were obtained in the same manner as in Example 1A. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber. In addition, when the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
実施例１０Ａ
　実施例３Ａにおいて両性分子として３－（Ｎ，Ｎ－ジメチルステアリルアンモニオ）プロパンスルホネート５ｇを使用した以外は、実施例３Ａと同様にして紡糸原液を得た。得られた紡糸原液の組成を表１に示す。この紡糸原液を用いて実施例３Ａと同様にして炭素繊維を得た。得られた炭素繊維の引張強度及び引張り弾性率を表２に示す。なお、前駆体繊維の断面形状を電子顕微鏡で確認したところ、実施例１Ａと同様に略円形断面であった。 Example 10A
A stock solution for spinning was obtained in the same manner as in Example 3A, except that 5 g of 3- (N, N-dimethylstearylammonio) propanesulfonate was used as the amphoteric molecule in Example 3A. The composition of the obtained spinning dope is shown in Table 1. Using this spinning dope, carbon fibers were obtained in the same manner as in Example 3A. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber. In addition, when the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
実施例１１Ａ
　実施例１Ａにおいて両性分子として３－［（３－コールアミドプロピル）ジメチルアンモニオ］－１－プロパンスルホネート５ｇを使用した以外は、実施例１Ａと同様にして紡糸原液を得た。得られた紡糸原液の組成を表１に示す。この紡糸原液を用いて実施例１Ａと同様にして炭素繊維を得た。得られた炭素繊維の引張強度及び引張り弾性率を表２に示す。なお、前駆体繊維の断面形状を電子顕微鏡で確認したところ、実施例１Ａと同様に略円形断面であった。 Example 11A
A stock spinning solution was obtained in the same manner as in Example 1A, except that 5 g of 3-[(3-cholamidopropyl) dimethylammonio] -1-propanesulfonate was used as the amphoteric molecule in Example 1A. The composition of the obtained spinning dope is shown in Table 1. Using this spinning dope, carbon fibers were obtained in the same manner as in Example 1A. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber. In addition, when the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
比較例１Ａ
　ＤＭＦ７７ｇとＡＮ９４－ＭＡＡ６共重合体２３ｇを、室温で１時間撹拌した後、紡糸原液を得た。この紡糸原液を用いて実施例１Ａと同様にして炭素繊維を得た。得られた炭素繊維の引張強度及び引張弾性率を表２に示す。なお、前駆体繊維の断面形状を電子顕微鏡で確認したところ、実施例１Ａと同様に略円形断面であった。 Comparative Example 1A
DMF77g and AN94-MAA6 copolymer 23g were stirred at room temperature for 1 hour to obtain a spinning dope. Using this spinning dope, carbon fibers were obtained in the same manner as in Example 1A. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber. In addition, when the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A.
比較例２Ａ
　紡糸原液の調製：ＤＭＦ６００ｍｌに二層カーボンナノチューブ（Ｕｎｉｄｙｍ社製ＸＯグレード）０．０２５ｇを添加し、超音波装置（ＢＲＡＮＳＯＮ　３５１０Ｒ　ＭＴ）で４２ｋＨｚ，１００Ｗの超音波を３６時間照射した。この分散液を合計６本調製した。５００ｍｌ三口フラスコ中でＤＭＦ１００ｍｌを撹拌しながら乾燥したＡＮ９４－ＭＡＡ６共重合体１５ｇを３０分間かけて添加した。７０℃で１５分間加熱して均一な溶液にした。室温まで放冷後、上記のカーボンナノチューブ分散液を１５０ｍｌずつ添加してＤＭＦ３６００ｍｌを留去して紡糸原液とした。 Comparative Example 2A
Preparation of spinning stock solution: 0.025 g of double-walled carbon nanotubes (Xy grade manufactured by Unidym) was added to 600 ml of DMF, and ultrasonic waves of 42 kHz and 100 W were irradiated for 36 hours with an ultrasonic device (BRANSON 3510R MT). A total of 6 dispersions were prepared. While stirring 100 ml of DMF in a 500 ml three-necked flask, 15 g of dried AN94-MAA6 copolymer was added over 30 minutes. Heat to 70 ° C. for 15 minutes to make a uniform solution. After allowing to cool to room temperature, 150 ml of the above carbon nanotube dispersion was added and 3600 ml of DMF was distilled off to obtain a spinning dope.
　紡糸：上記紡糸原液を８０℃にて孔径０．１５ｍｍ、孔数１の紡糸口金から押し出し、エアギャップ長４０ｍｍを経て－６０℃に冷却したメタノール１５ｌからなる凝固浴中へ導入し、糸を巻き取った。－６０℃のメタノール中に１昼夜糸を漬けた後、９倍延伸を行い、アミノ変性シリコーン油剤を付与して、１５０℃、５分間乾燥することにより、単糸繊度１．８ｄＴｅｘの前駆体繊維を得た。得られた前駆体繊維の断面形状を電子顕微鏡で確認したところ、略円形断面ではなく、歪な形状をしていた。 Spinning: The above spinning solution is extruded from a spinneret having a hole diameter of 0.15 mm and a hole number of 1 at 80 ° C., introduced into a coagulation bath consisting of 15 l of methanol cooled to −60 ° C. through an air gap length of 40 mm, and the yarn is wound I took it. After dipping the yarn for one day in methanol at -60 ° C, it is stretched 9 times, applied with an amino-modified silicone oil, and dried at 150 ° C for 5 minutes to give a precursor fiber having a single yarn fineness of 1.8 dTex. Got. When the cross-sectional shape of the obtained precursor fiber was confirmed with an electron microscope, it was not a substantially circular cross-section but a distorted shape.
参考例１Ａ　濡れ処理なしの例
　ＤＭＦ１０００ｇに両性分子３－（Ｎ，Ｎ－ジメチルミリスチルアンモニオ）プロパンスルホネート５ｇを添加し、室温で５分間撹拌した。これに二層カーボンナノチューブ（Ｕｎｉｄｙｍ社製ＸＯグレード）５ｇを添加した後、ビーズミル（Ｄｙｎｏ－ｍｉｌｌ，スイス製、ジルコニウムビーズ、直径０．６５ｍｍ）を用い、４０Ｈｚで撹拌しながら約２７０分間、カーボンナノチューブを両性分子溶液に分散した。さらに、ポリオキシエチレンアルキルラウリルエーテルスルホネート３ｇを加えて、約５分間緩やかに撹拌することにより安定化処理を行い、カーボンナノチューブ分散液を得た。上記カーボンナノチューブ分散液３０ｇとＡＮ９４－ＭＡＡ６共重合体１５ｇ、およびジメチルアセトアミド５５ｇを添加し、紡糸原液を得た。これを用いて実施例１Ａと同様にして炭素繊維を得た。得られた炭素繊維の引張強度及び引張り弾性率を表２に示す。なお、前駆体繊維の断面形状を電子顕微鏡で確認したところ、実施例１Ａと同様に略円形断面であった。参考例１Ａでは、実施例１Ａ～１１Ａと比較してカーボンナノチューブの分散に約３倍の時間を要した。 Reference Example 1A Example without Wetting Treatment 5 g of amphoteric molecule 3- (N, N-dimethylmyristylammonio) propanesulfonate was added to 1000 g of DMF and stirred at room temperature for 5 minutes. After adding 5 g of double-walled carbon nanotubes (Unimym XO grade) to this, using a bead mill (Dyno-mill, Switzerland, zirconium beads, diameter 0.65 mm), carbon nanotubes were stirred for about 270 minutes while stirring at 40 Hz. Was dispersed in an amphoteric molecule solution. Further, 3 g of polyoxyethylene alkyl lauryl ether sulfonate was added and the mixture was gently stirred for about 5 minutes to perform a stabilization treatment, thereby obtaining a carbon nanotube dispersion. 30 g of the carbon nanotube dispersion, 15 g of AN94-MAA6 copolymer, and 55 g of dimethylacetamide were added to obtain a spinning dope. Using this, a carbon fiber was obtained in the same manner as in Example 1A. Table 2 shows the tensile strength and tensile modulus of the obtained carbon fiber. In addition, when the cross-sectional shape of the precursor fiber was confirmed with an electron microscope, it was a substantially circular cross-section as in Example 1A. In Reference Example 1A, it took about three times longer to disperse the carbon nanotubes than in Examples 1A to 11A.
参考例２　安定化処理なしの例
　ＤＭＦ、ＤＭＳＯ、又はＤＭＡｃ１０００ｇのそれぞれに両性分子３－（Ｎ，Ｎ－ジメチルミリスチルアンモニオ）プロパンスルホネート５ｇを添加し、室温で５分間撹拌した。これらに二層カーボンナノチューブ（Ｕｎｉｄｙｍ社製ＸＯグレード）５ｇを添加した後、オートクレーブ（Ｈｉｒａｙａｍａ製、ＨＩＣＬＡＶＥ　ＨＧ－５０）を使い、１３０℃、１．５気圧で約２時間濡れ処理をした。室温まで冷却した後、ビーズミル（Ｄｙｎｏ－ｍｉｌｌ，スイス製、ジルコニウムビーズ、直径０．６５ｍｍ）を用い、４０Ｈｚで撹拌しながら約９０分間、カーボンナノチューブを両性分子溶液に分散し、各カーボンナノチューブ分散液を得た。いずれのものにも安定化処理は行わなかった。これらの分散液を２週間静置しておいたところ、いずれもカーボンナノチューブ同士の凝集が起こり、容器の底に黒色固体が出現した。なお、実施例１Ａ～１１Ａ、１Ｂ～１１Ｂ、又は１Ｃ～１１Ｃのように安定化処理を行って調製したカーボンナノチューブ分散液は、２週間静置しておいてもカーボンナノチューブの凝集は認められなかった。 Reference Example 2 Example without stabilization treatment 5 g of amphoteric molecule 3- (N, N-dimethylmyristylammonio) propanesulfonate was added to 1000 g of DMF, DMSO, or DMAc, respectively, and stirred at room temperature for 5 minutes. After adding 5 g of double-walled carbon nanotubes (Uniym's XO grade) to these, an autoclave (manufactured by Hirayama, HICLAVE HG-50) was used for wet treatment at 130 ° C. and 1.5 atm for about 2 hours. After cooling to room temperature, using a bead mill (Dyno-mill, manufactured by Switzerland, zirconium beads, diameter 0.65 mm), carbon nanotubes are dispersed in an amphoteric molecule solution for about 90 minutes with stirring at 40 Hz. Got. No stabilization treatment was performed on any of them. When these dispersions were allowed to stand for 2 weeks, the carbon nanotubes aggregated with each other, and a black solid appeared at the bottom of the container. In addition, the carbon nanotube dispersion prepared by performing the stabilization treatment as in Examples 1A to 11A, 1B to 11B, or 1C to 11C does not show aggregation of the carbon nanotubes even after standing for 2 weeks. It was.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　実施例１Ｂ～１１Ｂ、比較例１Ｂ～２Ｂ、参考例１Ｂ
　ＤＭＦの代わりにＤＭＳＯを使用する以外は、それぞれ実施例１Ａ～１１Ａ、比較例１Ａ～２Ａ、参考例１Ａと同様にして紡糸原液を作成し、炭素繊維を得た。前駆体繊維の断面形状と炭素繊維の物性を表３に示す。 Examples 1B to 11B, Comparative Examples 1B to 2B, Reference Example 1B
A spinning dope was prepared in the same manner as in Examples 1A to 11A, Comparative Examples 1A to 2A, and Reference Example 1A, except that DMSO was used instead of DMF, to obtain carbon fibers. Table 3 shows the cross-sectional shape of the precursor fiber and the physical properties of the carbon fiber.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　実施例１Ｃ～１１Ｃ、比較例１Ｃ～２Ｃ、参考例１Ｃ
　ＤＭＦの代わりにＤＭＡｃを使用する以外は、それぞれ実施例１Ａ～１１Ａ、比較例１Ａ～２Ａ、参考例１Ａと同様にして紡糸原液を作成し、炭素繊維を得た。前駆体繊維の断面形状と炭素繊維の物性を表４に示す。 Examples 1C to 11C, Comparative Examples 1C to 2C, Reference Example 1C
A spinning dope was prepared in the same manner as in Examples 1A to 11A, Comparative Examples 1A to 2A, and Reference Example 1A, except that DMAc was used instead of DMF, to obtain carbon fibers. Table 4 shows the cross-sectional shape of the precursor fiber and the physical properties of the carbon fiber.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　表２～４からわかるように、カーボンナノチューブを添加し、分散剤として両性分子を使用した実施例１Ａ～１１Ａ，１Ｂ～１１Ｂ，１Ｃ～１１Ｃ及び参考例１Ａ～１Ｃはいずれも、高い引張強度及び引張弾性率の炭素繊維が得られているのに対し、カーボンナノチューブを使用せず、両性分子を使用しなかった比較例１Ａ～１Ｃ（従来の一般的なＰＡＮ系炭素繊維）は、引張強度は高いが引張弾性率が劣っていた。また、カーボンナノチューブは使用したが、両性分子を使用しなかった比較例２Ａ～２Ｃは、引張弾性率が比較例１Ａ～１Ｃより高いが引張強度が劣っていた。 As can be seen from Tables 2 to 4, Examples 1A to 11A, 1B to 11B, 1C to 11C and Reference Examples 1A to 1C, in which carbon nanotubes were added and amphoteric molecules were used as a dispersant, all had high tensile strength and While carbon fibers having a tensile modulus were obtained, Comparative Examples 1A to 1C (conventional general PAN carbon fibers) that did not use carbon nanotubes and did not use amphoteric molecules had a tensile strength of Although it was high, the tensile elastic modulus was inferior. Further, Comparative Examples 2A to 2C, which used carbon nanotubes but did not use amphoteric molecules, had higher tensile elastic modulus than Comparative Examples 1A to 1C, but were inferior in tensile strength.
　本発明の製造方法によって得られた前駆体繊維を使用すれば、高い引張強度と高い引張弾性率を兼ね備えた炭素繊維を得ることができる。かかる炭素繊維は、航空機材料や宇宙船材料として極めて有用である。 If the precursor fiber obtained by the production method of the present invention is used, carbon fiber having both high tensile strength and high tensile elastic modulus can be obtained. Such carbon fibers are extremely useful as aircraft materials and spacecraft materials.

Claims (7)

  1. 　以下の工程を含むことを特徴とする、炭素繊維の前駆体繊維の製造方法：
    （１）両性分子のジメチルホルムアミド、ジメチルスルホキシド、又はジメチルアセトアミドの溶液を調製する工程；
    （２）この両性分子の溶液にカーボンナノチューブを添加し、カーボンナノチューブを分散させ、カーボンナノチューブ分散液を調製する工程；
    （３）このカーボンナノチューブ分散液とポリアクリロニトリル系ポリマーを混合し、紡糸原液を調製する工程；
    （４）この紡糸原液から、湿式又は乾湿式紡糸法によって凝固糸を得る工程；そして
    （５）この凝固糸を延伸して炭素繊維の前駆体繊維を得る工程。     A method for producing a carbon fiber precursor fiber, comprising the following steps:
    (1) a step of preparing a solution of amphoteric molecules of dimethylformamide, dimethylsulfoxide, or dimethylacetamide;
    (2) adding carbon nanotubes to this amphoteric molecule solution, dispersing the carbon nanotubes, and preparing a carbon nanotube dispersion;
    (3) A step of mixing the carbon nanotube dispersion and the polyacrylonitrile polymer to prepare a spinning dope;
    (4) A step of obtaining a coagulated yarn from the spinning dope by a wet or dry wet spinning method; and (5) a step of drawing the coagulated yarn to obtain a carbon fiber precursor fiber.
  2. 　工程（３）で調製される紡糸原液が、５～３５重量％のポリアクリロニトリル系ポリマーを含み、さらにポリアクリロニトリル系ポリマーに対して０．０１～５重量％のカーボンナノチューブ及び０．０１～５．０重量％の両性分子を含むことを特徴とする請求項１に記載の方法。 The spinning dope prepared in the step (3) contains 5 to 35% by weight of a polyacrylonitrile-based polymer, and further 0.01 to 5% by weight of carbon nanotubes and 0.01 to 5.5% of the polyacrylonitrile-based polymer. 2. A method according to claim 1 comprising 0% by weight of amphoteric molecules.
  3. 　工程（２）においてカーボンナノチューブを分散させる前に濡れ処理を行うことを特徴とする請求項１又は２に記載の方法。 The method according to claim 1 or 2, wherein a wet treatment is performed before the carbon nanotubes are dispersed in the step (2).
  4. 　工程（２）においてカーボンナノチューブ分散液に安定化処理を行うことを特徴とする請求項１～３のいずれかに記載の方法。 The method according to any one of claims 1 to 3, wherein the carbon nanotube dispersion is subjected to stabilization treatment in the step (2).
  5. 　請求項１～４のいずれかに記載の方法によって製造される、炭素繊維の前駆体繊維であって、略円形断面を有しかつカーボンナノチューブを含むことを特徴とする炭素繊維の前駆体繊維。 A carbon fiber precursor fiber produced by the method according to any one of claims 1 to 4, having a substantially circular cross section and containing carbon nanotubes.
  6. 　請求項５に記載の炭素繊維の前駆体繊維を耐炎化、予備炭素化、及び炭素化することによって製造されることを特徴とする炭素繊維。 A carbon fiber produced by subjecting the carbon fiber precursor fiber according to claim 5 to flame resistance, pre-carbonization, and carbonization.
  7. 　ポリアクリロニトリル系ポリマー、カーボンナノチューブ、及び両性分子を含む、ジメチルホルムアミド、ジメチルスルホキシド、又はジメチルアセトアミドの溶液からなる紡糸原液であって、両性分子の分散作用によりカーボンナノチューブが溶液中に分散していることを特徴とする紡糸原液。 A spinning dope comprising a solution of dimethylformamide, dimethylsulfoxide, or dimethylacetamide containing polyacrylonitrile-based polymer, carbon nanotubes, and amphoteric molecules, and the carbon nanotubes are dispersed in the solution by the dispersing action of the amphoteric molecules. Spinning stock solution characterized by
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