US20160326672A1 - Pan-based carbon fiber and production method therefor - Google Patents

Pan-based carbon fiber and production method therefor Download PDF

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US20160326672A1
US20160326672A1 US15/110,336 US201415110336A US2016326672A1 US 20160326672 A1 US20160326672 A1 US 20160326672A1 US 201415110336 A US201415110336 A US 201415110336A US 2016326672 A1 US2016326672 A1 US 2016326672A1
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fiber
pan
carbon fiber
spinning
sheath
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Tetsunori Higuchi
Mami SAKAGUCHI
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Tokyo (5%), University of
University of Tokyo NUC
Toray Industries Inc
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University of Tokyo NUC
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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
    • 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
    • D01F9/225—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 from stabilised polyacrylonitriles
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/06—Wet spinning methods
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/28—Formation of filaments, threads, or the like while mixing different spinning solutions or melts during the spinning operation; Spinnerette packs therefor
    • D01D5/30—Conjugate filaments; Spinnerette packs therefor
    • D01D5/34—Core-skin structure; Spinnerette packs therefor
    • 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
    • D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
    • D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
    • D01F8/08—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one polyacrylonitrile as constituent
    • 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
    • D01F9/32—Apparatus therefor
    • D01F9/328—Apparatus therefor for manufacturing filaments from polyaddition, polycondensation, or polymerisation products

Definitions

  • PAN polyacrylonitrile
  • Carbon fiber is broadly used in various uses, for example, for aerospace materials for airplanes, rockets and the like, and for sport articles such as tennis rackets and golf shafts and, further, is also used for transportation and mechanical fields such as ships and vehicles, from its properties such as mechanical and chemical properties and lightness in weight. Further, in recent years, from high conductivity or high radiation property of carbon fiber, application to uses for parts for electronic equipment such as housings of portable telephones or personal computers, or for electrodes of fuel cells, is strongly required. In particular, PAN-based carbon fiber, because of its high specific strength, is used in particular for aerospace materials for airplanes, space satellites and the like, for members for vehicles and the like and, recently, application to vehicle members is being remarkably increased. Therefore, it is desired to improve the productivity of carbon fiber.
  • the PAN-based carbon fiber can be obtained by inducing a polymer solution dissolved with mainly PAN into a solvent to a PAN-based fiber by spinning, and burning it at a high temperature under a condition of an inert atmosphere.
  • the PAN-based fiber is made into a carbon fiber
  • the PAN-based fiber is passed through a process of air stabilization (cyclization reaction and oxidation reaction of PAN) which heats the PAN-based fiber in air at a high temperature such as 200 to 300° C. It is general to obtain a carbon fiber by further treating it in a carbonization furnace at 2,000° C. to 3,000° C. for several minutes.
  • the known stabilization process is a rate-limiting factor, and it cannot be said to be a sufficiently efficient process.
  • a carbon fiber is excellent in specific strength and specific elastic modulus, it has a defect of a very low degree of elongation.
  • An increase of degree of elongation of carbon fiber is strongly desired accompanying with an increase of demand for carbon fiber. So far, to increase the degree of elongation of carbon fiber, although a fiber spun with a raw material composition, the main component of which is a polymer compound compounded with an aromatic sulfonic group or a salt thereof via a methylene-type bond, is disclosed (JP 6-173122 A), there is a defect in that the cost of the main raw material is too high.
  • the respective phases are layered.
  • this PAN-based carbon fiber has a sheath-core structure having three or more layers, and satisfies conditions A to D:
  • A in a sectional area in a direction perpendicular to a fiber axis, an area occupied by a core occupies 10 to 70% of the whole of the sectional area
  • B a thickness of a sheath is in a range of 100 nm to 10,000 nm
  • C a thickness of an intermediate layer is more than 0 nm and 5,000 nm or less
  • D a diameter in the direction perpendicular to the fiber axis is 2 ⁇ m or more.
  • the above-described PAN-based carbon fiber has a sheath-core structure having three or more layers, and satisfies conditions E to H:
  • a crystal size of a core is referred to as Lc1
  • a crystal size of a sheath is referred to as Lc2
  • a crystal size of an intermediate layer is referred to as Lc3.
  • an orientation degree f of a crystal of a core is 0.7 or less.
  • the PAN-based carbon fiber is obtained by carbonizing a fiber spun from a single kind of polymer solution for spinning.
  • the PAN-based carbon fiber is obtained by spinning a fiber from a polymer solution for spinning satisfying points A and B and carbonizing the spun fiber:
  • A a polymer in the polymer solution for spinning is a polymer prepared by modifying PAN with an amine-based compound and oxidizing it with a nitro compound
  • B the nitro compound is not contained in the polymer solution for spinning.
  • the PAN-based carbon fiber is obtained using a polymer solution for spinning having a divergent structure in which a gradient a is 0.1 or more and 0.3 or less as the result determined by GPC (Gel Permeation Chromatography).
  • [ ⁇ ] is an intrinsic viscosity
  • K is a constant inherent for a material
  • Mw is a weight average molecular weight
  • a method of producing a PAN-based carbon fiber comprises the steps of: spinning the above-described polymer solution for spinning; performing stabilization in air at 280° C. or higher and 400° C. or lower for 10 seconds or more and 15 minutes or less; and thereafter, performing carbonization.
  • the stabilization is performed using an infrared heater (for example, a ceramic heater) and a hot air drier (for example, a hot air circulation drier) together.
  • the time for stabilization can be greatly shortened and productivity can be improved, and a PAN-based carbon fiber capable of exhibiting a high degree of elongation while maintaining a sufficiently high strength can be obtained.
  • FIG. 1 shows a schematic sectional view in a direction perpendicular to a fiber axis showing an example of a sheath-core structure having three layers, and a partially enlarged view thereof.
  • FIG. 2 shows diagrams exemplifying electron diffractions of TEM (Transmission Electron Microscope) in a core, an intermediate layer and a sheath of a sheath-core structure.
  • TEM Transmission Electron Microscope
  • FIG. 3 is a characteristic diagram showing distribution curves converted from the light and shade of the electron diffraction diagrams depicted in FIG. 2 .
  • FIG. 4 is a schematic vertical sectional view showing an example of a hot air circulation furnace equipped with an infrared heater which is used for stabilization.
  • a carbon fiber means a fiber composed of 90% or more with C (carbon) component. It is possible to determine the content of C component by elemental analysis.
  • the PAN-based carbon fiber comprises three or more phases different in crystal size. By forming three or more phases, high functions can be provided to the carbon fiber. Further, the carbon fiber is preferably a carbon fiber in which the above-described respective phases are layered. By the layered structure, it tends that the strength of the carbon fiber is maintained and the carbon fiber has a high degree of elongation.
  • the carbon fiber preferably forms a sheath-core structure having three or more layers to exhibit the desired properties.
  • the sheath-core structure 1 having three or more layers is a structure having an intermediate layer 3 (for example, a plurality of intermediate layers) between a core 2 and a sheath 4 , which is a structure formed in three or more layers as a whole, and in particular, it is preferred to be a structure of three layers.
  • a crystal size of the core Lc1, a crystal size of the sheath Lc2, and a crystal size of the intermediate layer Lc3 have relationships of Lc1/Lc3 ⁇ 1.05, Lc1/Lc2 ⁇ 1.05, and 1.5 ⁇ Lc1 ⁇ 7.0 nm. More preferably, the relationships are Lc1/Lc3 ⁇ 1.10 and Lc1/Lc2 ⁇ 1.08. Further preferably, the relationships are Lc1/Lc3 ⁇ 1.15 and Lc1/Lc2 ⁇ 1.1. Lc referred here indicates an overlap thickness of graphite moment in a direction of fiber axis.
  • the crystal size Lc of each layer can be determined by converting from the light and shade of the electron diffraction diagrams of TEM (Transmission Electron Microscope) exemplified in FIG. 2 to the distribution curves as shown in FIG. 3 , and calculating Lc using a half-value width of each peak.
  • a crystal size can be calculated as a relative value of the known Lc of T300 (carbon fiber supplied by Toray Industries, Inc.).
  • a portion appearing in a rod-like form is a shade of a measuring device.
  • an orientation degree f of the core is preferably 0.7 or less, and more preferably 0.6 or less.
  • a high degree of elongation of a carbon fiber can be achieved.
  • the reason of a high degree of elongation is supposed in that, by forming an intermediate layer as a hard layer, relatively soft sheath and core take charge of impact caused when the intermediate layer is broken, and the carbon fiber elongates without reaching breakage.
  • a high degree of elongation of a carbon fiber means one in a range of 1.1% or more and 2.5% or less, more preferably in a range of 1.2 to 2.5%, and particularly preferably in a range of 1.3 to 2.5%.
  • a low degree of elongation means one of 1.0% or less. The higher the degree of elongation, the better molding processing property becomes, thereby suppressing occurrences of fluff in the process of obtaining a final product.
  • the core occupies 10 to 70% relative to the cross-sectional area of the fiber
  • the thickness of the sheath is 100 nm to 10,000 nm in a direction perpendicular to the fiber axis so as to cover the core
  • the thickness of the intermediate layer is more than 0 nm and 5,000 nm or less. More preferably, the thickness of the intermediate layer is 100 nm to 5,000 nm.
  • the core occupies 30 to 50% relative to the cross-sectional area of the fiber.
  • a flame resistant fiber is liable to be flattened in section at an initial stage of carbonization, and tends to become a fiber bundle intermingled with flat yarns.
  • the cross-sectional shape of a fiber can be observed by a laser microscope.
  • the rate of interminglement of flat yarns was determined by counting the numbers of non-circular ones and circular ones, respectively, in a photograph taken at 1,000 times in magnification of a section of a fiber bundle using a laser microscope.
  • Counting was performed by referring a single yarn with a ratio of a minor axis to a major axis of 1 to 0.8 as a circular one, and a single yarn with a ratio of a minor axis to a major axis of 0.1 or more and less than 0.8 as a flat yarn.
  • the carbon fiber because it is possible to obtain a carbonized yarn having a sheath-core structure with three or more layers by wet spinning a single kind of polymer and burning it, there is merit in that it is not necessary to perform compounding, coating or the like, after spinning. Further, because the respective layers are strongly combined by performing spinning and burning and forming three or more layers from a single kind of polymer, achieved is a structure in which it is possible to supplement poor points of the layers each other, as aforementioned.
  • the polymer solution for spinning is preferred to be a polymer prepared by modifying PAN with an amine-based compound and oxidizing it with a nitro compound.
  • a nitro compound in the fiber When a nitro compound is left in the polymer solution for spinning, it is supposed that the nitro compound in the fiber operates as an oxidant even in the process of stabilization, and it is believed that this oxidation during formation of a structure of a fiber is a cause of becoming a carbon fiber with a two-layer structure.
  • a method of controlling an amount of the nitro compound left in a polymer solution for spinning to 0% there are two kinds of methods of a method of removing it by washing with ethanol after PAN is modified with an amine-based compound and a nitro compound, and a method of making a nitro compound easily react by increasing the amount of amine-based compound. Since washing takes time and incurs cost and there is a possibility of being left in the polymer, more preferred is the latter method of controlling the amount of the residual nitro compound to 0% in the reaction system. Concrete explanation of such a method will be described later.
  • a state “modified with an amine-based compound” referred here exemplified is a state where an amine-based compound is chemically reacted with PAN as a raw material, or a state where an amine-based compound is incorporated into a polymer by hydrogen bonding or an interaction such as van der Waals force.
  • a section originating from an amine-based compound used as a modifier is added as a new spectrum in a spectrum of a polymer for spinning modified with the amine-based compound, relative to a spectrum of PAN as a raw material.
  • the mass of a polymer for spinning modified with an amine-based compound increases by 1.1 times or more, preferably 1.2 times or more, particularly preferably 1.3 times or more, relative to PAN as a raw material. Further, in an increase, the upper limit is preferably 3 times or less, more preferably 2.6 times or less, and further preferably 2.2 times or less. If the change in mass is smaller or greater than such a range, there is a possibility that the spinning property is damaged and the strength or the degree of elongation of a carbon fiber is reduced.
  • polyethylene polyamines such as ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine and N-aminoethyl piperazine, and ortho, meta and para phenylene diamines can be exemplified.
  • a functional group having an element of oxygen, nitrogen, sulfur or the like such as a hydroxyl group except an amino group
  • ethanol amine group such as monoethanol amine, diethanol amine, triethanol amine and N-aminoethyl ethanol amine can be exemplified.
  • monoethanol amine is more preferred.
  • the nitro compound is an oxidant and oxidizes PAN. Therefore, the fiber spun using PAN modified with an amine and oxidized by a nitro compound tends to be able to be finished with stabilization in a very short period of time of 10 seconds or more and 15 minutes or less.
  • an oxidant of nitro-based, nitroxide-based or the like can be exemplified.
  • aromatic nitro compounds such as nitrobenzene, o, m, p-nitrotoluene, nitroxylene, o, m, p-nitrophenol and o, m, p-nitrobenzoic acid can be exemplified.
  • nitrobenzene having a simple structure is most preferably used, since it is little in risk, and a quick oxidation is possible because of less steric hindrance.
  • the amount to be added of these oxidants is not particularly restricted so that PAN is sufficiently oxidized, it is preferred to use a nitro compound at 10 wt % or more relative to PAN, more preferably 15 wt % or more. Further, as the amount to be added of a nitro compound, to control the remaining rate of the nitro compound in the aforementioned polymer solution for spinning at 0%, it is preferred to use 1 to 50 parts by mass relative to 100 parts by mass of an amine-based compound to be employed. It is more preferred to use 20 to 45 parts by mass. At that time, the reaction temperature is preferably 130 to 300° C., and more preferably 130 to 250° C.
  • the reaction time is preferably 4 hours or more and 10 hours or less, and more preferably 5 hours or more and 8 hours or less. If heated for a time more than 10 hours, a polymer is too damaged, and finally the strength of a carbon fiber is reduced. In a time less than 4 hours, the nitro compound is liable to be left in the system, the structure of a carbon fiber finally obtained does not become three layers, and the degree of elongation tends to be reduced.
  • the amine-based compound and the polar organic solvent and an oxidant may be mixed before addition of PAN and may be simultaneously with addition of PAN. It is preferred that first PAN, an amine-based compound and a polar organic solvent are mixed, and after dissolution by heating, a polymer for spinning is prepared by adding an oxidant, from the viewpoint of less insoluble substances. Of course, it is not obstructed to mix a component other than PAN, an oxidant, an amine-based compound and a polar organic solvent with such a solution.
  • inorganic particles such as alumina or zeolite, a pigment such as carbon black, an antifoaming agent such as silicone, stabilizer•flame retardant such as a phosphorus compound, various kinds of surfactants, and other additives may be contained.
  • an inorganic compound such as lithium chloride or calcium chloride can be contained. These may be added before expediting the reaction, and may be added after expediting the reaction.
  • the molecular weight and the shape of a polymer for spinning are determined by GPC, and it is preferred that the value of the gradient a (hereinafter, referred to as “a”) is 0.1 to 0.3.
  • the “a” determined by GPC means “a” represented by Mark Houwink-Sakurada equation (1).
  • [ ⁇ ] is an intrinsic viscosity
  • K is a constant inherent for a material
  • Mw is a weight average molecular weight
  • the “a” of a polymer for spinning is 0.1 to 0.3, and it is understood that the polymer for spinning becomes a divergent structure much closer in shape to a spherical shape than to a rod-like shape.
  • a divergent structure molecules are more intertwined with each other as compared to employing a straight-chain structure. Accordingly, when stabilization of a spun fiber is performed, molecules of the polymer are easily combined with each other, and the time for the stabilization of the fiber tends to be able to be shortened.
  • the stabilization becomes insufficient, there is a tendency to be decomposed in a carbonization process and a tendency that the differences between the “Lc”s and between the orientation degree “f”s of three layers of a carbon fiber are smallened and the degree of elongation is reduced. Further, when the “a” becomes less than 0.1, because the molecular weight itself is being greatly decreased, spinning becomes difficult. Further, even if spinning can be carried out, the strength of the fiber tends to be fairly reduced.
  • PAN may be a homo PAN and may be a copolymerized PAN.
  • the structural unit originating from acrylonitrile (hereinafter, referred to as AN) is preferably 85 mol % or more, more preferably 90 mol % or more, and further preferably 92 mol % or more.
  • allyl sulfonic acid metal salt, methallyl sulfonic acid metal salt, acrylic ester, methacrylic ester, acrylic amide and the like can be also copolymerized.
  • components for accelerating stabilization components containing a vinyl group, concretely, acrylic acid, methacrylic acid, itaconic acid and the like, can also be copolymerized, and a part or the whole amount thereof may be neutralized with an alkali component such as ammonia.
  • the “a” determined by GPC is 0.4 or more and 0.7 or less.
  • the shape and form of the PAN may be any of powder, flake and fiber, and polymer waste, yarn waste and the like generated during polymerization or at the time of spinning can also be used as recycled raw material.
  • the polymer solution for spinning can be made by dissolving a polymer for spinning in an organic solvent.
  • concentration of the polymer solution for spinning when the concentration is low, productivity at the time of spinning tends to be low although the effect due to our method itself is not damaged, and when the concentration is high, flowability is poor and it tends to be hard to be spun. In consideration of being served to spinning, it is preferably 8 to 30 mass %.
  • concentration of the polymer for spinning can be determined by the following method.
  • the polymer solution for spinning is weighed, the solution of about 4 g is put into distilled water of 500 ml and boiled. A solid material is once taken out, it is again put into distilled water of 500 ml and boiled. A residual solid component is placed on an aluminum pan, dried for one day by an oven heated at a temperature of 120° C., and a polymer for spinning is isolated. The isolated solid component is weighed, and the concentration is determined by calculating a ratio with the mass of the original polymer solution for spinning.
  • the polymer for spinning tends to be easily made into a solution when employing, in particular, a polar organic solvent as the solvent among organic solvents. This is because the polymer for spinning modified with an amine-based compound is high in polarity and the polymer is well dissolved by a polar organic solvent.
  • the polar organic solvent means a solvent having an amino group, an amide group, a sulfonyl group, a sulfone group and the like and further having a good compatibility with water
  • ethylene glycol, diethylene glycol, triethylene glycol, a polyethylene glycol having a molecular weight of about 200 to 1,000, dimethyl sulfoxide (hereinafter, also abbreviated as DMSO), dimethyl formamide, dimethyl acetamide, N-methyl pyrrolidone and the like can be used. These may be used solely, and may be used as a mixture of two or more kinds. In particular, DMSO is preferably used because of its high dissolvability relative to PAN.
  • the viscosity of the polymer solution for spinning can be set in respective preferable ranges depending upon a forming method or a molding method using the polymer, a molding temperature, a kind of a die or a mold and the like. Generally, it can be 1 to 1,000 Pa ⁇ s in the measurement at 50° C. More preferably, it is 10 to 100 Pa ⁇ s, and further preferably, it is 20 to 600 Pa ⁇ s.
  • Such a viscosity can be measured by various viscosity measuring devices, for example, a rotary-type viscometer, a rheometer, a B-type viscometer or the like. The viscosity determined by any one method may be controlled in the above-described range. Further, even if out of such a range, by heating or cooling at the time of spinning, it can be used as an appropriate viscosity.
  • A. A method of modifying PAN with an amine and oxidizing with a nitro compound in a solution as described above.
  • B. A method of isolating PAN modified with an amine and oxidized with a nitro compound, and directly dissolving it in a solvent.
  • the dissolution may be performed under an atmospheric pressure, and as the case may be, it may be performed under a pressurized or pressure-reduced condition.
  • a mixer such as an extruder or a kneader can be used solely or at a form of combination thereof.
  • the dissolution is preferably performed using an amine-based compound and a polar organic solvent at the sum thereof of 100 to 1,900 parts by mass, preferably 150 to 1,500 parts by mass, relative to 100 parts by mass of an acrylic-based polymer.
  • non-reacted substances, insoluble substances, gel and the like are not contained in the polymer solution for spinning obtained by the above-described method, there is a possibility that they are left at a fine amount. It is preferred to filtrate or disperse non-reacted substances or insoluble substances using a sintered filter or the like before formation into fibers.
  • a wet spinning or a dry/wet spinning is employed to improve productivity of the process.
  • a wet spinning is used.
  • the spinning can be performed by preparing the aforementioned polymer solution for spinning as a polymer solution for spinning, elevating the pressure through a pipe by a booster pump or the like, extruding with metering by a gear pump or the like, and discharging from a die.
  • a booster pump or the like As the material of the die, SUS (stainless), gold, platinum and the like can be appropriately used.
  • the polymer solution for spinning before the polymer solution for spinning flows into holes of the die, the polymer solution for spinning is filtrated or dispersed using a sintered filter of inorganic fibers or using a woven fabric, a knitted fabric, a nonwoven fabric or the like comprising synthetic fibers such as polyester or polyamide as a filter, from the viewpoint that the fluctuation of the cross-sectional areas of single fibers in a fiber aggregate to be obtained can be reduced.
  • the hole diameter of the die an arbitrary range of 0.01 to 0.5 mm ⁇ can be employed, and as the hole length, an arbitrary range of 0.01 to 1 mm can be employed. Further, as the number of the holes of the die, an arbitrary range of 10 to 1,000,000 can be employed.
  • the hole arrangement an arbitrary one such as a staggered arrangement can be employed, and the holes may be divided in advance so as to realize easy yarn dividing.
  • Coagulated yarns are obtained by discharging the polymer solution for spinning from the die directly or indirectly into a coagulation bath. It is preferred that the liquid for the coagulation bath is formed from a solvent used for the polymer solution for spinning and a coagulation acceleration component, from the viewpoint of convenience, and it is more preferred to use water as the coagulation acceleration component.
  • the degree of swelling of the coagulated yarn obtained is preferably controlled to 50 to 1,000 mass %, more preferably 200 to 900 mass %, and further preferably 300 to 800 mass %.
  • the degree of swelling of the coagulated yarn controlled in such a range greatly relates to the toughness and easiness in deformation of the coagulated yarn and affects the spinnability.
  • the degree of swelling is decided from the viewpoint of spinnability, and affects a stretching property in bath at a later process, and if in such a range, the coefficient of variation of the cross-sectional areas of single fibers can be made small in the carbon fibers to be obtained.
  • the degree of swelling of the coagulated yarn can be controlled by the affinity between the polymer for spinning forming the coagulated yarn and the coagulation bath and the temperature or the concentration of the coagulation bath, and a degree of swelling in the above-described range can be achieved by controlling the temperature of the coagulation bath or the concentration of the coagulation bath in the aforementioned range relative to a specified polymer for spinning.
  • the coagulated yarn is stretched in a stretching bath or washed in a water washing bath.
  • it may be stretched in a stretching bath as well as washed in a water washing bath.
  • the draw ratio for the stretching is preferably 1.05 to 5 times, more preferably 1.1 to 3 times, and further preferably 1.15 to 2.5 times.
  • hot water or solvent/water is used, and the concentration of solvent/water for the stretching bath can be set at an arbitrary concentration of 0/100 to 80/20.
  • the temperature of both the stretching bath and the water washing bath is preferably 30 to 100° C., more preferably 50 to 95° C., and particularly preferably 65 to 95° C.
  • the fiber completed with coagulation is dried, and as needed, stretched to become a carbon fiber through stabilization and carbonization.
  • a drying method of bringing the fiber into direct contact with a plurality of dried and heated rollers a drying method of sending hot air or water vapor, a drying method of irradiating infrared rays or electromagnetic rays with a high frequency, a drying method of making a pressure reduced condition or the like can be appropriately selected and combined.
  • hot air is sent in a direction parallel or perpendicular to the running direction of the fiber.
  • far infrared rays, mid infrared rays or near infrared rays can be employed, and radiation of microwaves can also be employed.
  • the temperature for the drying can be employed arbitrarily at approximately 50 to 250° C., generally, the drying takes a long time at a low temperature and a short time at a high temperature.
  • the specific gravity of the fiber after drying is usually 1.15 to 1.5, preferably 1.2 to 1.4, and more preferably 1.2 to 1.35.
  • the coefficient of variation of the cross-sectional areas of single fibers in the fiber aggregate after drying is preferably 5 to 30%, more preferably 7 to 28%, and further preferably 10 to 25%.
  • elongation of the single fiber in the fiber aggregate after drying is preferably 0.5 to 20%.
  • oxidation calorific value (J/g) determined by differential scanning calorimetry (DSC) is preferably 50 to 4,000 J/g. As the case may be, not a continuous drying but a batch drying can be carried out.
  • a fiber is plasticized with moisture
  • a method of heating the fiber at a condition of containing water in the fiber such as a bath stretching using warm water or hot water, a stretching using steam (water vapor), or a heat stretching by a dryer or rolls after providing water to the fiber in advance, and heating/stretching by steam stretching is particularly preferred.
  • the stretching is carried out at a temperature of, preferably 70° C. or higher, more preferably 80° C. or higher, and further preferably 90° C. or higher.
  • a temperature of, preferably 70° C. or higher, more preferably 80° C. or higher, and further preferably 90° C. or higher At this stage, the fiber structure is already densified even if the temperature is elevated, there is no fear of generating micro voids, and a stretching at a temperature as high as possible is preferred because a high effect due to molecular orientation can be obtained.
  • the stretching property may be further enhanced by adding a solvent or other additives.
  • a higher stretching temperature in a bath stretching, basically 100° C. becomes the upper limit. Accordingly, a stretching using steam is employed more preferably.
  • the temperature of the stretching is preferred to be higher, when a saturated vapor is used, because the internal pressure of the apparatus is high, there is a possibility that the fiber is damaged by blowing vapor.
  • a saturated vapor with a temperature of 100° C. or higher and 150° C. or lower may be used. If the temperature exceeds 150° C., the effect due to the plasticization gradually gets to the top, and damage of the fiber due to blowing vapor becomes greater than the effect due to the plasticization.
  • an apparatus devising to pressurize the inside of the treatment apparatus by providing a plurality of apertures at the fiber inlet and outlet is preferably used.
  • the draw ratio for the bath stretching and the draw ratio for the stretching by steam are preferably 1.5 times or more, and more preferably 2.0 times or more.
  • the draw ratio for the stretching is preferred to be higher, and an upper limit thereof is not particularly present. However, from restriction on stability of spinning, it is frequently difficult to exceed about 6 times.
  • the means thereof is not restricted to the bath stretching or the steam stretching.
  • heat stretching by a drying furnace or a hot roller or the like after providing moisture may be possible.
  • a non-contact type stretching machine using a drying furnace further, a contact type stretching machine using a contact plate, a hot roller or the like, can also be used.
  • a contact type stretching machine evaporation of moisture is fast and, further, there is a high possibility that a fiber is mechanically scratched at a point occurred with stretching.
  • a required temperature becomes 250° C. or higher, and as the case may be, thermal decomposition of the polymer starts.
  • the effect due to stretching is low, and it is more difficult to obtain a carbon fiber with a high orientation than the stretching method using moisture. From these reasons, it is more preferred to use a bath stretching or a steam stretching.
  • the stretched yarn thus stretched is preferably dried again, as needed.
  • the moisture percentage of the fiber is preferably 10% or less, and more preferably 5% or less.
  • This drying method bringing the fiber into contact directly with a plurality of dried and heated rollers or hot plates, sending hot air or water vapor, irradiating infrared rays or electromagnetic rays with a high frequency, making a pressure reduced condition and the like can be appropriately selected and combined. It is preferred to employ drying due to rollers to perform an efficient drying.
  • the number of the rollers is not restricted.
  • the temperature of the rollers is preferably 100° C. or higher and 250° C. or lower, and more preferably 150° C. or higher and 200° C. or lower. If the drying at this process is insufficient, there is a possibility to cause a fiber breakage when a tension is applied to the fiber at a heat treatment process carried out later.
  • an oil component can be appropriately provided depending upon the necessity of a higher-order processing.
  • concentration of the oil is set at 0.01 to 20 mass %.
  • the oil comprises, for example, a main oil component such as silicone and a diluent component for diluting it.
  • concentration of oil means a content of the main oil component relative to the whole of the oil.
  • the kind of the oil component is not particularly restricted, polyether-based one, polyester surfactant, silicone, amino-modified silicone, epoxy-modified silicone or polyether-modified silicone can be provided solely or at a mixture thereof, and other oil components may be provided.
  • the adhesion amount of such an oil component is determined as a rate relative to the dried mass of the fiber included with the oil component, and it is preferably 0.05 to 5 mass %, more preferably 0.1 to 3 mass %, and further preferably 0.1 to 2 mass %. If the adhesion amount of an oil component is too little, there is a possibility that fusion of single fibers to each other occurs and the tensile strength of an obtained carbon fiber is reduced and, if too much, there is a possibility that it becomes difficult to obtain the desired effect.
  • the fiber obtained by the above-described process is transferred to a process for stabilization.
  • the fiber before being transferred to the stabilization process is preferably in a dried condition.
  • the method of stabilization in particular, it is preferred to use a dry-heating apparatus to control chemical reaction and suppress unevenness in fiber structure, and concrete equipment thereof will be described later.
  • the temperature and the treatment length are appropriately selected depending upon the oxidation degree of the used polymer for spinning, the fiber orientation degree and the required properties for a final product.
  • the treatment temperature for the stabilization is preferably 280° C. or higher and 400° C. or lower. More preferably, it is 300° C. or higher and 360° C. or lower, and particularly preferably, it is 300° C. to 330° C.
  • the treatment time of the stabilization is preferably 10 seconds or longer to prevent decomposition in a carbonization process. Further, when the treatment time of the stabilization exceeds 15 minutes, because the merit of shortening the time for stabilization becomes small and besides the fiber is fuzzed to cause reduction of strength and degree of elongation, it is preferred that the treatment time of the stabilization is 15 minutes or shorter. From the viewpoint of suppressing occurrences of fluff, more preferably it is 5 minutes or shorter.
  • the draw ratio for this stretching is preferably 1.05 to 4 times.
  • the draw ratio is set from required strength and fineness of the flame resistant fiber, process passing-through property and the temperature of the heat treatment. Concretely, the draw ratio for the stretching is 1.1 to 4 times, preferably 1.2 to 3 times, and more preferably 1.3 to 2.5 times.
  • an infrared heater and a hot air drier it is preferred to use an infrared heater and a hot air drier together.
  • the treatment time for stabilization tends to be shortened.
  • To use an infrared heater and a hot air drier together includes to treat separately from each other, and it is particularly preferred to provide an infrared heater in a hot air circulation drier and perform simultaneous treatment of emission (radiation) and heat transfer by the integrated hot air circulation drier equipped with the infrared heater.
  • an infrared heater in a hot air circulation drier and perform simultaneous treatment of emission (radiation) and heat transfer by the integrated hot air circulation drier equipped with the infrared heater.
  • high temperature-elevation•short-time treatment due to the infrared heater and uniform treatment of single fibers due to hot air can be achieved simultaneously.
  • a metal, a ceramic or the like can be used as the material of the infrared heater, it is preferred to be made from a ceramic from its high heat radiation rate and high thermal stability.
  • a schematic structure of a hot air circulation drier equipped with an infrared heater is exemplified in FIG. 4 , and as shown in the figure, it can be manufactured, for example, by providing two or more openings 15 a , 15 b to a forced-type hot air circulation drier 11 sold on the market so as to be able to treat a fiber continuously and, further, attaching an electric ceramic heater 16 sold on the market (for example, a ceramic plate heater “PLC-323”, supplied by NORITAKE CO., LTD.) inside the drier.
  • an electric ceramic heater 16 sold on the market (for example, a ceramic plate heater “PLC-323”, supplied by NORITAKE CO., LTD.) inside the drier.
  • two or more ceramic heaters are installed and, further, it is particularly preferred that they are installed to be able to irradiate the infrared rays to the fiber from both directions of upper and lower sides or left and right sides to irradiate the infrared rays to the fiber uniformly.
  • a non-treated fiber 12 (fiber before treatment) is introduced into hot air circulation drier 11 from opening 15 a while being guided by a roller 14 a , it is irradiated with the infrared rays from both directions of upper and lower sides by ceramic heaters 16 attached to, for example, punching metals 17 for attaching ceramic heaters, and at the same time, heat transfer treatment due to hot air (the flow of the hot air is shown by arrows 18 ) is performed, and a stabilized fiber 13 (fiber after treatment) is sent out from opening 15 b while being guided by a roller 14 b.
  • both a down flow system and an up flow system can be applied.
  • a fan to control the circulation amount of hot air although a propeller fan and a sirocco fan can be used, it is preferred to use a sirocco fan from the viewpoint of its good wind resistance. It is preferred to rotate this fan by a motor after conversion to a direct current by an inverter.
  • an inverter As a concrete inverter, “FR-E720-0.2K” supplied by Mitsubishi Electric Corporation can be exemplified, and as an induction motor, “5IK60A-SF” supplied by ORIENTAL MOTOR Co., Ltd. can be exemplified.
  • the rotational speed of the fan it is preferably 500 to 1,500 rpm, and to shorten the treatment time within a range which does not cause to fuzz, particularly preferably it is 800 to 1,200 rpm.
  • the fibers having been spun are in a bundle form comprising a plurality of single fibers, the number of single fibers included in a single bundle can be appropriately selected depending upon the purpose of use and, to control the aforementioned preferred number, it can be adjusted by the number of holes of a die, and a plurality of spun fibers may be doubled.
  • control the fineness of the single fiber in the aforementioned preferable range it can be controlled by selecting the hole diameter of a die or appropriately deciding the discharge amount from a die.
  • cross-sectional shape of a single fiber can be controlled by the shape of a discharge hole of a die such as a circular hole, an oval hole or a slit and the condition at the time of removing a solvent.
  • a carbon fiber is obtained by heat treating the flame resistant fiber at a high temperature in an inert atmosphere, so-called carbonizing.
  • a carbon fiber can be obtained by treating the aforementioned flame resistant fiber at a highest temperature in an inert atmosphere of 1,000° C. or higher and lower than 2,000° C. More preferably, as the lower side of the highest temperature, 1,000° C. or higher, 1,200° C. or higher and 1,300° C. or higher are preferred in order, and as the upper side of the highest temperature, 1,800° C. or lower can also be employed. Further, by further heating such a carbon fiber in an inert atmosphere at a temperature of 2,000 to 3,000° C., a carbon fiber developing in graphite structure can also be obtained.
  • the density is preferably 1.6 to 1.9 g/cm 3 , and more preferably 1.7 to 1.9 g/cm 3 . If such a density is too small, there is a possibility that many pores are present in a single fiber and the fiber strength is reduced, and on the contrary, if too great, there is a possibility that the denseness becomes too high and the degree of elongation is reduced. Such a density can be determined utilizing immersion method or sink-float method based on JIS R 7603(1999).
  • the single fibers of the carbon fibers are gathered to form an aggregate such as a fiber bundle.
  • the number of single fibers per one bundle is appropriately decided depending on the purpose of use, from the viewpoint of higher-order processing property, it is preferably 50 to 100,000/bundle, more preferably 100 to 80,000/bundle, and further preferably 200 to 60,000/bundle.
  • the tensile strength of a single fiber is preferably 1.0 to 10.0 GPa, more preferably 1.5 to 7.0 GPa, and further preferably 2.0 to 7.0 GPa.
  • a tensile strength can be determined based on JIS R7606(2000) using a universal tensile testing machine (for example, small-sized desk-top tester EZ-S, supplied by Shimadzu Corporation).
  • the diameter of the single fiber is 2 ⁇ m or more, in particular, 2 ⁇ m to 70 ⁇ m, preferably 2 to 50 ⁇ m, and more preferably 3 to 20 ⁇ m. If such a diameter of the single fiber is less than 2 ⁇ m, there is a possibility that the fiber is liable to be broken, and if more than 70 ⁇ m, a defect rather tends to be caused.
  • the single fiber of the carbon fiber may be one having a hollow portion. In this case, the hollow portion may be either continuous or discontinuous.
  • the carbon fiber tends to have a peak nearly at 26° in X-ray diffraction (XRD) similarly in a general PAN-based carbon fiber.
  • XRD X-ray diffraction
  • thermometer a cooler, an agitator and a nitrogen introducing tube were attached to a three neck flask having a sufficient capacity.
  • PAN was dissolved in DMSO at the rate described in Table 1, an amine-based compound and a nitro compound were added, and while stirring by a stirring blade at 300 rpm, heating was carried out in an oil bath at 150° C. for the time described in Table 1 to perform a reaction.
  • PAN and DMSO were put into a polyethylene bottle of 2 L, and they were stirred at 80° C. for the time described in Table 1 to dissolve PAN.
  • the obtained polymer solution for spinning was washed with ethanol or hot water, and the precipitate was dried to obtain a polymer for spinning.
  • the obtained polymer solution for spinning was served to a wet spinning apparatus as it was, thereby forming fibers.
  • the dried fiber was 1 denier.
  • a calibration curve of an added nitro compound was made.
  • the method of determining a sample is as follows.
  • the treatment was carried out under a condition of air at predetermined temperature and temperature elevation speed, using one furnace of a hot air circulation drier incorporated with an infrared heater as shown in FIG. 4 .
  • the hot air circulation drier was a down flow-system one, a sirocco fan having a diameter of 200 mm was controlled by an inverter (FR-E720-0.2K) supplied by Mitsubishi Electric Corporation and, further, it was rotated by an induction motor (5IK60A-SF) supplied by ORIENTAL MOTOR Co., Ltd.
  • the wind direction of the hot air was a cross flow, and the rotational speed of the fan was 1,200 rpm.
  • the infrared heater in the hot air circulation drier and six electric ceramic plate heaters (PLC-323) supplied by NORITAKE CO., LTD. were installed at each of the upper side and the lower side relative to a yarn path, respectively.
  • the temperature of the hot air in the furnace and the temperature of the infrared heater were set at an identical temperature.
  • the treatment was carried out under a nitrogen atmosphere at a predetermined temperature and at a tensile condition.
  • the carbonization was carried out by two furnaces. In the first furnace, the treatment was carried out at a temperature of 700 to 800° C., and in the second furnace, the treatment was carried out at a temperature of 1,300° C.
  • the temperature elevation speed was 50 to 200° C.
  • the mass of a sample cut out by 1 m from 12,000 carbon fibers was measured, and it was determined as the areal weight.
  • the unit of the areal weight is g/m.
  • Equation (1) An average value calculated from the above-described density of fiber and areal weight of fiber bundle by the following equation Equation (1) was calculated as a diameter of a cross section of a single fiber.
  • Equation (1) represented are 1: diameter of single fiber ( ⁇ m), Mf: areal weight of 12,000 carbon fibers (g/m), and ⁇ : density (g/cm 3 ).
  • the strength and degree of elongation of a single fiber were determined under the following conditions based on JIS R7606 (2000). Further, the strength was calculated by dividing a maximum load in an S-S curve with the cross section calculated from the density and the areal weight. Further, the degree of elongation was calculated from a displacement. The number of n was set at 5 or more.
  • This specimen was chipped in a fiber axis direction by the following method to prepare a thin-film test piece having a thickness of several-hundred ⁇ m. Further, it was chipped in parallel to the fiber axis direction to be able to pick up a center of a fiber, thereby preparing a thin-film test piece having a thickness of several-hundred ⁇ m. If hitting a void present in a fiber when a thin film for TEM is prepared, a sample is prepared at another position with no voids.
  • Intensity distribution graph was made from shades of colors by image analysis of TEM image. Further, from the intensity distribution graph, a crystal size Lc was calculated from a half-value width of a peak corresponding to (002) plane by the following equation Equation (2), and an orientation degree of a crystal was calculated from a total width of a half-value of the intensity distribution in each orientation direction by the following equation Equation (3).
  • Equation (2) ⁇ h: high angle side of (002) plane, and ⁇ l: low angle side of (002) plane.
  • FWHM is a total width of a half-value of intensity distribution in each orientation direction.
  • Measurement was carried out with n number of 2, and an average value of these two values was determined as the measured value. However, when a difference between the two values (the respective elemental rates of C, H and N) was more than ⁇ 0.4%, the measurement was repeated until it became ⁇ 0.4% or less.
  • the conditions for the measurement are as follows.
  • Polymer solution for spinning (a) was wet spun at a number of filaments of 12,000 to obtain fibers through a drying process.
  • the obtained fibers were served to stabilization at conditions of 300° C. and 5 minutes, and carbonization was carried out at a carbonization temperature of 1,300° C.
  • the obtained carbon fiber had a 3-layer sheath-core structure.
  • Lc it was 1.6 nm at the sheath, 1.8 nm at the intermediate layer and 2.1 nm at the core.
  • orientation degree f the sheath was oriented at 0.86, the intermediate layer was oriented at 0.89 and the core was oriented at 0.6 or less.
  • the tensile strength was 2.1 GPa, the degree of elongation was 1.7%, and they were good results.
  • Polymer solution for spinning (a) was treated in a manner similar to that in Example 1 to obtain fibers.
  • the obtained fibers were served to stabilization.
  • the stabilization was carried out at conditions of 320° C. and 5 minutes, and carbonization was carried out at a carbonization temperature of 1,300° C.
  • the obtained carbon fiber had a 3-layer sheath-core structure.
  • Lc it was 1.6 nm at the sheath, 1.8 nm at the intermediate layer and 2.1 nm at the core.
  • orientation degree f the sheath was oriented at 0.86, the intermediate layer was oriented at 0.89 and the core was oriented at 0.6 or less.
  • the tensile strength was 2.1 GPa, the degree of elongation was 1.6%, and they were good results.
  • Polymer solution for spinning (a) was treated in a manner similar to that in Example 1 to obtain fibers.
  • the obtained fibers were served to stabilization.
  • the stabilization was carried out at conditions of 340° C. and 5 minutes, and carbonization was carried out at a carbonization temperature of 1,300° C.
  • the obtained carbon fiber had a 3-layer sheath-core structure.
  • Lc it was 1.6 nm at the sheath, 1.8 nm at the intermediate layer and 2.1 nm at the core.
  • orientation degree f the sheath was oriented at 0.86, the intermediate layer was oriented at 0.89 and the core was oriented at 0.6 or less.
  • the tensile strength was 2.2 GPa, the degree of elongation was 1.5%, and they were good results.
  • Polymer solution for spinning (a) was treated in a manner similar to that in Example 1 to obtain fibers.
  • the obtained fibers were served to stabilization.
  • the stabilization was carried out at conditions of 360° C. and 5 minutes, and carbonization was carried out at a carbonization temperature of 1,300° C.
  • the obtained carbon fiber had a 3-layer sheath-core structure.
  • Lc it was 1.6 nm at the sheath, 1.8 nm at the intermediate layer and 2.1 nm at the core.
  • orientation degree f the sheath was oriented at 0.86, the intermediate layer was oriented at 0.89 and the core was oriented at 0.6 or less.
  • the tensile strength was 2.2 GPa, the degree of elongation was 1.5%, and they were good results.
  • Polymer solution for spinning (a) was treated in a manner similar to that in Example 1 to obtain fibers.
  • the obtained fibers were served to stabilization.
  • the stabilization was carried out at conditions of 300° C. and 10 minutes, and carbonization was carried out at a carbonization temperature of 1,300° C.
  • the obtained carbon fiber had a 3-layer sheath-core structure.
  • Lc it was 1.6 nm at the sheath, 1.8 nm at the intermediate layer and 2.1 nm at the core.
  • orientation degree f the sheath was oriented at 0.86, the intermediate layer was oriented at 0.89 and the core was oriented at 0.6 or less.
  • the tensile strength was 2.2 GPa, the degree of elongation was 1.6%, and they were good results.
  • Polymer solution for spinning (a) was treated in a manner similar to that in Example 1 to obtain fibers.
  • the obtained fibers were served to stabilization.
  • the stabilization was carried out at conditions of 360° C. and 10 minutes, and carbonization was carried out at a carbonization temperature of 1,300° C.
  • the obtained carbon fiber had a 3-layer sheath-core structure.
  • Lc it was 1.6 nm at the sheath, 1.8 nm at the intermediate layer and 2.1 nm at the core.
  • orientation degree f the sheath was oriented at 0.86, the intermediate layer was oriented at 0.89 and the core was oriented at 0.6 or less.
  • the tensile strength was 2.4 GPa, the degree of elongation was 1.6%, and they were good results.
  • Polymer solution for spinning (a) was treated in a manner similar to that in Example 1 to obtain fibers.
  • the obtained fibers were served to stabilization.
  • the stabilization was carried out at conditions of 300° C. and 15 minutes, and carbonization was carried out at a carbonization temperature of 1,300° C.
  • the obtained carbon fiber had a 3-layer sheath-core structure.
  • Lc it was 1.6 nm at the sheath, 1.8 nm at the intermediate layer and 2.0 nm at the core.
  • orientation degree f the sheath was oriented at 0.86, the intermediate layer was oriented at 0.89 and the core was oriented at 0.6 or less.
  • the tensile strength was 2.3 GPa, the degree of elongation was 1.6%, and they were good results.
  • Polymer solution for spinning (a) was treated in a manner similar to that in Example 1 to obtain fibers.
  • the obtained fibers were served to stabilization.
  • the stabilization was carried out at conditions of 360° C. and 15 minutes, and carbonization was carried out at a carbonization temperature of 1,300° C.
  • the obtained carbon fiber had a 3-layer sheath-core structure.
  • Lc it was 1.6 nm at the sheath, 1.8 nm at the intermediate layer and 2.1 nm at the core.
  • orientation degree f the sheath was oriented at 0.85, the intermediate layer was oriented at 0.88 and the core was oriented at 0.6 or less.
  • the tensile strength was 2.4 GPa, the degree of elongation was 1.6%, and they were good results.
  • Polymer solution for spinning (d) was treated in a manner similar to that in Example 1 to obtain fibers.
  • the obtained fibers were served to stabilization.
  • the stabilization was carried out at conditions of 360° C. and 15 minutes, and carbonization was carried out at a carbonization temperature of 1,300° C.
  • the obtained carbon fiber had a 3-layer sheath-core structure.
  • Lc it was 1.4 nm at the sheath, 1.6 nm at the intermediate layer and 1.8 nm at the core.
  • orientation degree f the sheath was oriented at 0.82, the intermediate layer was oriented at 0.84 and the core was oriented at 0.6 or less.
  • the tensile strength was 2.0 GPa, the degree of elongation was 1.3%, and they were good results.
  • Polymer solution for spinning (e) was treated in a manner similar to that in Example 1 to obtain fibers.
  • the obtained fibers were served to stabilization.
  • the stabilization was carried out at conditions of 360° C. and 15 minutes, and carbonization was carried out at a carbonization temperature of 1,300° C.
  • the obtained carbon fiber had a 3-layer sheath-core structure.
  • Lc it was 1.4 nm at the sheath, 1.6 nm at the intermediate layer and 1.8 nm at the core.
  • orientation degree f the sheath was oriented at 0.82, the intermediate layer was oriented at 0.84 and the core was oriented at 0.6 or less.
  • the tensile strength was 1.6 GPa, the degree of elongation was 1.6%, and they were good results.
  • Polymer solution for spinning (a) was treated in a manner similar to that in Example 1 to obtain fibers.
  • the obtained fibers were served to stabilization.
  • the stabilization was carried out at conditions of 360° C. and 30 minutes, and carbonization was carried out at a carbonization temperature of 1,300° C.
  • the obtained carbon fiber had a 3-layer sheath-core structure.
  • Lc it was 1.6 nm at the sheath, 1.8 nm at the intermediate layer and 2.0 nm at the core.
  • orientation degree f the sheath was oriented at 0.79, the intermediate layer was oriented at 0.81 and the core was oriented at 0.6 or less.
  • the fiber was fuzzed and the thickness thereof became small and, therefore, the tensile strength was reduced to 1.7 GPa, the degree of elongation was reduced to 1.5%, but they were good results.
  • Polymer solution for spinning (a) was wet spun in a manner similar to that in Example 1 to obtain fibers through a drying process.
  • the obtained fibers were served to stabilization at conditions of 240° C. and 15 minutes.
  • the stabilized fiber was tried to be carried out with carbonization at a carbonization temperature of 1,300° C., the fiber was burned and broken immediately after being introduced into a furnace, and could not be carbonized as a carbon fiber.
  • Polymer solution for spinning (a) was wet spun in a manner similar to that in Example 1 to obtain fibers through a drying process.
  • the obtained fibers were served to stabilization at conditions of 260° C. and 15 minutes.
  • the stabilized fiber was tried to be carried out with carbonization at a carbonization temperature of 1,300° C., the fiber was burned and broken immediately after being introduced into a furnace, and could not be carbonized as a carbon fiber.
  • Polymer solution for spinning (b) was wet spun in a manner similar to that in Example 1 to obtain fibers through a drying process.
  • the obtained fibers were served to stabilization at conditions of 240° C. and 15 minutes.
  • the stabilized fiber was tried to be carried out with carbonization at a carbonization temperature of 1,300° C., the fiber was burned and broken immediately after being introduced into a furnace, and could not be carbonized as a carbon fiber.
  • Polymer solution for spinning (b) was wet spun in a manner similar to that in Example 1 to obtain fibers through a drying process.
  • the obtained fibers were served to stabilization.
  • the fiber was stabilized at conditions of 280° C. and 15 minutes. Although a fusion happened at the stage of the stabilization, the fiber was carbonized as it was. Although the stabilized fibers were tried to be carried out with carbonization at a carbonization temperature of 1,300° C., most of the fibers were burned and broken in a furnace.
  • the tensile strength was reduced to 1.3 GPa, the degree of elongation was 1.0%, and they were very low tensile strength and degree of elongation to cause poor results.
  • Polymer solution for spinning (b) was wet spun in a manner similar to that in Example 1 to obtain fibers through a drying process. Although the obtained fibers were tried to be carried out with stabilization at conditions of 300° C. and 15 minutes, they were burned and broken in a furnace for stabilization.
  • Polymer solution for spinning (b) was wet spun in a manner similar to that in Example 1 to obtain fibers through a drying process. Although the obtained fibers were tried to be carried out with stabilization at conditions of 360° C. and 15 minutes, they were burned and broken in a furnace for stabilization.
  • Polymer solution for spinning (c) was treated in a manner similar to that in Example 1 to obtain fibers.
  • the obtained fibers were served to burning at conditions similar to those in Example 7 to obtain carbon fibers.
  • the obtained carbon fiber had a 2-layer sheath-core structure.
  • Lc it was 1.7 nm at the sheath and 1.5 nm at the core.
  • orientation degree f the sheath was oriented at 0.86, and the core was oriented at 0.83 or less.
  • the tensile strength was 1.9 GPa, and the degree of elongation was 0.8%. In particular, the degree of elongation was greatly reduced as compared with Example 8, and it was a poor result.
  • Polymer solution for spinning (a) was wet spun at a number of filaments of 12,000 to obtain fibers through a drying process, in a manner similar to that in Example 1.
  • the obtained fibers were served to stabilization at conditions of 300° C. and 5 minutes similar to those in Example 1, using a hot air circulation drier equipped with no infrared heater, and carbonization was carried out at a carbonization temperature of 1,300° C.
  • the obtained carbon fiber had substantially a 2-layer sheath-core structure.
  • Lc With respect to Lc, it was 1.6 nm at the sheath and 2.2 nm at the core.
  • orientation degree f With respect to orientation degree f, the sheath was oriented at 0.80, and the core was oriented at 0.6 or less.
  • the tensile strength was 1.8 GPa, and the degree of elongation was 1.0% and much lower than that in Example 1, and occurrences of fluff was also high.
  • Polymer solution for spinning (a) was wet spun at a number of filaments of 12,000 to obtain fibers through a drying process, in a manner similar to that in Example 1.
  • the obtained fibers were served to stabilization at conditions of 300° C. and 5 minutes similar to those in Example 1, using only an infrared heater (without hot air circulation), and carbonization was carried out at a carbonization temperature of 1,300° C., but yarn breakage happened because of unevenness of treatment.
  • the PAN-based carbon fiber and the production method therefor can be applied to production of any PAN-based carbon fiber required with shortening of time for stabilization and a high degree of elongation.

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US11535958B2 (en) 2019-08-09 2022-12-27 Raytheon Technologies Corporation Fiber having integral weak interface coating, method of making and composite incorporating the fiber
US12030820B2 (en) * 2019-08-09 2024-07-09 Rtx Corporation High temperature fiber, method of making and high temperature fiber composites

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CN105874112A (zh) 2016-08-17
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KR20160106044A (ko) 2016-09-09
WO2015105019A1 (ja) 2015-07-16
CN105874112B (zh) 2018-03-30
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