CN112522810A - Asphalt-based carbon fiber and preparation method thereof - Google Patents

Asphalt-based carbon fiber and preparation method thereof Download PDF

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Publication number
CN112522810A
CN112522810A CN202011419370.0A CN202011419370A CN112522810A CN 112522810 A CN112522810 A CN 112522810A CN 202011419370 A CN202011419370 A CN 202011419370A CN 112522810 A CN112522810 A CN 112522810A
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carbon fiber
asphalt
temperature
raw material
spinning
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叶崇
伍孝
余洋
陈坤
石奎
黄东
刘金水
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Hunan Dongying Special Carbon Asphalt Material Co ltd
Hunan Dongying Carbon Material Technology Co ltd
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Hunan Dongying Special Carbon Asphalt Material Co ltd
Hunan Dongying Carbon Material Technology Co ltd
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Priority to CN202011419370.0A priority Critical patent/CN112522810A/en
Publication of CN112522810A publication Critical patent/CN112522810A/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
    • D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
    • D01F8/18—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from other substances
    • 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
    • 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
    • D01F9/145—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from pitch or distillation residues

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  • Engineering & Computer Science (AREA)
  • Textile Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Inorganic Fibers (AREA)

Abstract

The invention provides an asphalt-based activated carbon fiber, which comprises a sheath-core structure; the core layer of the skin-core structure is anisotropic carbon; the skin layer of the skin-core structure is isotropic carbon; a mixed transition layer which is formed by transition from anisotropic carbon to isotropic carbon along the direction from the core layer to the skin layer is arranged between the core layer and the skin layer; the surface of the cortex is distributed with nanometer pores. The invention also provides a preparation method of the asphalt-based activated carbon fiber.

Description

Asphalt-based carbon fiber and preparation method thereof
Technical Field
The invention relates to the technical field of materials and preparation thereof, in particular to a high-strength asphalt-based activated carbon fiber and a preparation method thereof.
Background
The activated carbon fiber is used as a third-generation activated carbon material, has far better adsorption performance than the traditional powdery and granular activated carbon, has better mechanical property and forming processing advantages, and is widely applied to the fields of gas purification, solvent recovery, water treatment, toxic gas filtration and the like at present. But is affected by the surface pores of the activated carbon fibers, the strength of the activated carbon fibers is generally low, especially when the specific surface area exceeds 500m2After/g, the tensile strength is reduced to only 30-200 MPa.
In order to solve the problem of low strength of the activated carbon fiber, the existing solution is as follows:
the polyacrylonitrile-based carbon fiber is used for preparing the activated carbon fiber. The polyacrylonitrile-based carbon fiber has higher strength and is generally used for preparing high-strength activated carbon fiber. However, the polyacrylonitrile-based carbon fiber has high activation difficulty, is not easy to control and has high overall cost. Meanwhile, when the specific surface area of the polyacrylonitrile-based carbon fiber exceeds 1000m2At/g, the strength properties are likewise greatly reduced.
Thanks to the aromatic heterocyclic conjugated effect of polyimide, the patent CN201210334784.2 uses polyimide fiber as raw material, and obtains activated carbon fiber with better strength through carbonization and activation. However, polyamide fibers are relatively expensive and not suitable for large-scale industrialization.
The activated carbon fiber is prepared by adopting viscose-based activated carbon fiber. The viscose-based activated carbon fiber is easy to activate and low in cost, and is always commonly used for preparing activated carbon fiber. However, as the raw materials are adopted and the catalyst is needed to carry out catalytic curing on the raw materials, the production process has large environmental pollution and tends to be eliminated.
Patent CN201710834671.1 discloses a method for preparing activated carbon fiber from mesophase pitch (anisotropic pitch), which has relatively high strength, but difficult activation of anisotropic carbon, high modulus, and brittle and breakable fiber.
In view of the above, a new technical solution is needed to solve the above technical problems.
Disclosure of Invention
The first purpose of the invention is to provide a carbon fiber with high specific surface area and high tensile strength.
The second purpose of the invention is to provide a preparation method of the carbon fiber with high specific surface area and high tensile strength.
In order to achieve the purpose, the invention adopts the following technical means:
an asphalt-based carbon fiber, the asphalt-based carbon fiber comprising a sheath-core structure; the pitch-based carbon fiber comprises a sheath-core structure; the core layer of the skin-core structure is anisotropic carbon; the skin layer of the skin-core structure is isotropic carbon; a mixed transition layer which is formed by transition from anisotropic carbon to isotropic carbon along the direction from the core layer to the skin layer is arranged between the core layer and the skin layer; the surface of the cortex is distributed with nanometer pores.
Preferably, the diameter of the pitch-based carbon fiber is 5 to 18 μm.
Preferably, the thickness of the skin layer is 0.002 to 0.05 μm.
Preferably, the thickness of the mixed transition layer is 0.3 to 2.5 μm.
Preferably, the core layer has a diameter of 4 to 16 μm.
Preferably, the depth of the micropores is less than or equal to 0.05 μm.
A preparation method of pitch-based carbon fiber comprises the following steps:
melting and extruding the raw material A and the raw material B by a screw, spraying, spinning and collecting filaments to obtain asphalt fibers; oxidizing the asphalt fiber, performing first heat treatment at the temperature of 450-; the raw material A is isotropic oxidized asphalt, the raw material B is anisotropic asphalt, the softening temperature of the raw material A is lower than that of the raw material B, and the temperature difference between the softening temperatures of the raw material A and the raw material B is less than 5 ℃.
Preferably, the softening point of the isotropic oxidized asphalt is 250-280 ℃, the ash content is less than 80ppm, and the oxygen content is less than 1.5%;
preferably, the softening point of the anisotropic asphalt is 250-285 ℃, and the ash content is less than 30 ppm;
preferably, the weight ratio of the raw material A to the raw material B is 5: 95-25: 75;
preferably, the temperature of the screw melt extrusion is 280-320 ℃.
Preferably, the spinning temperature is 260-320 ℃, the spinning temperature is 280-340 ℃, and the spinneret plate temperature is lower than the spinning temperature by 20-40 ℃;
preferably, the spinning speed is 0.06-0.15g/min/H, wherein H is the number of spinneret holes of a spinneret plate used for spinning.
Preferably, the spinning pressure is 0.3-2MPa, and the yarn collecting speed is 500-1000 m/min; the temperature of the oxidation is 180-320 ℃, the time of the oxidation is 90-400min, and the atmosphere of the oxidation is air.
Preferably, the temperature of the activation is 550-1000 ℃, the time of the activation is 5-60min, and the atmosphere of the activation is water vapor or carbon dioxide.
Preferably, the spinneret plate comprises guide holes, counterbores and micropores. The guide hole, the reaming hole and the micropore are connected in sequence. The guide hole is of an inverted bell mouth structure, the height of the bell mouth structure is 1-3mm, the diameter of an upper opening is 2-3.5mm, and the diameter of a lower opening is 1.5-3 mm.
Preferably, the chambering is of an inverted bell mouth structure, the height of the bell mouth structure is 2-5mm, the diameter of an upper opening is 1.5-3mm, and the diameter of a lower opening is 0.15-0.3 mm.
Preferably, the diameter of the micropores is 0.15-0.3mm, and the length-diameter ratio of the micropores is 1:1-5: 1.
Compared with the prior art, the invention has the following beneficial effects:
1. the pitch-based carbon fiber provided by the invention has a sheath-core structure, the sheath-core structure is easy to activate, and the specific surface area of the pitch-based carbon fiber can reach 1350m2The core layer has high strength, and the tensile strength of the single filament of the pitch-based carbon fiber can reach 750 MPa.
2. The method improves the separation of isotropic components of the mixed asphalt in the fiber forming process of the asphalt filaments, forms the sheath-core structure fiber of the anisotropic asphalt core wrapped by the isotropic asphalt, and forms the sheath-core isotropic carbon through subsequent treatment, the pores are developed, the anisotropic carbon core layer has molecular orientation characteristics and high strength, and the existence of the mixed transition carbon layer enables the surface layer defects not to be easily diffused into the fiber, so that the high specific surface area is obtained, the high strength characteristic is still maintained, and the strength of the activated carbon fiber is improved.
3. The use of the isotropic pitch enables the prepared carbon fiber to be easily activated, the control of the pore structure to be simpler, and the activated carbon fiber with high specific surface area can be obtained without using a catalyst by adjusting the oxidation process.
4. The preparation method provided by the invention has the advantages of simple implementation means, mature process and low cost.
Drawings
FIG. 1 shows a photomicrograph of the pitch-based carbon fiber prepared in example 1.
Detailed Description
The invention provides an asphalt-based carbon fiber, which comprises a sheath-core structure; the core layer of the skin-core structure is made of anisotropic carbon, and the skin layer of the skin-core structure is made of isotropic carbon. The anisotropic carbon has high strength, and can be used as a core layer to improve the monofilament tensile strength of the pitch-based carbon fiber. The surface of the isotropic carbon skin layer with the nano-scale holes is distributed, so that the specific surface area of the asphalt-based carbon fiber can be improved. The mixed transition layer is formed naturally in the preparation process of the asphalt-based carbon fiber, no obvious limit exists among the core layer, the mixed transition layer and the skin layer, and the core layer, the mixed transition layer and the skin layer are tightly combined together.
In certain embodiments of the present invention, the pitch-based carbon fibers have a diameter of 5 to 18 μm. Preferably 10-16 μm. The smaller the diameter of the pitch-based carbon fiber is, the more rigorous the preparation process and parameters are, the high preparation cost is, and the strength of the pitch-based carbon fiber is reduced along with the reduction of the diameter of the pitch-based carbon fiber; the asphalt-based carbon fiber has too high diameter, so that the strength is reduced, and the specific surface area is reduced.
Specifically, the thickness of the skin layer is 0.002-0.05 μm. The thinner the thickness of the skin layer is, the higher the specific surface area of the pitch-based carbon fiber is. When the thickness of the skin layer is more than 0.05 μm, the surface of the skin layer has a decreased depth of micropores, and the specific surface area of the pitch-based carbon fiber tends to decrease.
Specifically, the thickness of the mixed transition layer is 0.3-2.5 μm. Preferably 0.3-1.5 μm. The thickness of the mixed transition layer below 0.3 μm may result in the surface of the pitch-based carbon fiber not being able to form a skin layer during the preparation process, and if the thickness of the mixed transition layer exceeds 1.5 μm, it may result in a decrease in the strength of the pitch-based carbon fiber.
Specifically, the diameter of the core layer is 4-16 μm. Preferably 6-14 μm. When the diameter of the core layer is less than 4 μm, the strength of the pitch-based carbon fiber may be reduced. When the diameter of the core layer is larger than 16 mu m, the strength of the pitch-based carbon fiber is also reduced, and meanwhile, the specific surface area is reduced.
Specifically, the depth of the micropores is less than or equal to 0.05 μm. If the depth of the micropores is too large, the structure of the core layer may be damaged, thereby reducing the strength of the pitch-based carbon fiber.
The invention also provides a preparation method of the pitch-based carbon fiber, which comprises the following steps: melting and extruding the raw material A and the raw material B by a screw, spraying, spinning and collecting filaments to obtain asphalt fibers; oxidizing the asphalt fiber, performing first heat treatment at the temperature of 450-; the raw material A is isotropic oxidized asphalt, the raw material B is anisotropic asphalt, the softening temperature of the raw material A is lower than that of the raw material B, and the temperature difference between the softening temperatures of the raw material A and the raw material B is less than 5 ℃. The raw material A and the raw material B are melted and mixed by a double-screw extruder to obtain a relatively uniform melt, and the melt is more uniform in temperature through a material dispersion cavity filled with metal sand. Because the viscosity of the asphalt is greatly influenced by temperature, when a melt is sprayed by a spinneret plate, low-viscosity isotropic asphalt is easily dispersed to the wall of a pore in a micropore, and high-viscosity anisotropic asphalt is easily gathered at the center of the micropore, so that the asphalt fiber with a skin-core structure is obtained.
Specifically, the softening point of the isotropic oxidized asphalt is 250-280 ℃, the ash content is less than 80ppm, and the oxygen content is less than 1.5%. The conventional isotropic spinning pitch has a softening point of 250-280 ℃. If the softening temperature is too low, the carbon residue of the asphalt is low, which can result in low carbon fiber yield and further influence the strength of the prepared carbon fiber; and if the softening temperature is too high, the requirement of the production process on equipment is increased, so that the production cost is increased. The ash content of the isotropic oxidized asphalt cannot exceed 100ppm, which affects the strength of the carbon fiber, and the lower the ash content of the isotropic oxidized asphalt, the higher the strength of the carbon fiber prepared. The oxygen content of the isotropic oxidized asphalt should be less than 1.5% to prevent the softening point of the isotropic oxidized asphalt from being too high.
Specifically, the softening point of the anisotropic asphalt is 250-285 ℃, and the ash content is less than 30 ppm; if the softening temperature is too low, the carbon residue of the asphalt is low, which can result in low carbon fiber yield and further influence the strength of the prepared carbon fiber; and if the softening temperature is too high, the requirement of the production process on equipment is increased, so that the production cost is increased. The ash content of the isotropic oxidized asphalt cannot exceed 50ppm, which affects the strength of the carbon fiber, and the lower the ash content of the isotropic oxidized asphalt, the higher the strength of the carbon fiber produced.
Specifically, the weight ratio of the raw material A to the raw material B is 5: 95-25: 75. if the specific gravity of the raw material a is too low, the sheath-core structure cannot be prepared, and if the specific gravity of the raw material a is too high, the strength of the prepared carbon fiber is reduced.
Specifically, the temperature of the screw for melt extrusion is 280-320 ℃. The viscosity of the molten asphalt extruded at this temperature is 50-10 pas, which makes it easier to achieve uniform mixing of the raw material A and the raw material B.
Specifically, the spinning temperature is 260-320 ℃, the spinning temperature is 280-340 ℃, and the spinneret plate temperature is lower than the spinning temperature by 20-40 ℃; the spinning temperature is pitch fiber design temperature, and the too high temperature of spouting can lead to the pitch silk to glue on the spinneret surface, and the temperature of spouting is crossed lowly and can lead to the increase of spinning pressure. The spinning temperature is 280-340 ℃, the viscosity of the spinning asphalt is 10-2.5 Pa.s, and the viscosity is easy to flow to the guide micropore wall by isotropic asphalt.
Specifically, the spinning speed is 0.06-0.15g/min/H, wherein H is the number of spinneret orifices of a spinneret plate used for spinning. The spinning speed is required to correspond to the spinning pressure and the diameter of the micropores of the spinneret plate.
Specifically, the spinning pressure is 0.3-2MPa, and the yarn collecting speed is 500-1000 m/min. Too high spinning pressure can cause decomposition gas generated by material decomposition to be dissolved in the material, and finally fiber defects are formed; the spinning pressure is too low to stabilize the spinning. Too high wire winding speed has high requirements on wire winding equipment, and too high rotating speed is not beneficial to dynamic balance of the equipment, so that the wire winding is unstable finally; too low a take-up rate can reduce efficiency.
Specifically, the temperature of the oxidation is 180-320 ℃, the time of the oxidation is 90-400min, and the atmosphere of the oxidation is air. Too high an oxidation temperature easily causes the fiber to melt and be oxidized excessively, and too low an oxidation temperature easily causes the fiber not to realize 'solidification setting', and also causes too long an oxidation time and increases the manufacturing cost. The oxygen content of the non-melting fiber obtained after oxidation is 11-18 percent, and then the solidification and the shaping are realized.
Preferably, the temperature of the second heat treatment (low-temperature carbonization) is 450-. The low-temperature carbonization temperature is too high, so that the fiber carbon structure is shaped easily, and the activation difficulty is increased; the low temperature carbonization temperature is too low, and water vapor or carbon dioxide is easy to etch, so that the strength of the fiber is low.
Specifically, the activation temperature is 550-1000 ℃, the activation time is 5-60min, and the activation atmosphere is water vapor or carbon dioxide. The activation temperature is too high, the requirement on equipment is too high, the activation temperature exceeds 1100 ℃, the service life of the equipment is greatly reduced, the activation temperature is too low, and the water vapor or carbon dioxide is not easy to etch, so that the specific surface area is low.
Specifically, the temperature of the second heat treatment (high temperature carbonization) is 1000-. When the high-temperature carbonization temperature is too high, micropores generated by activation collapse, so that the specific surface area is reduced, and when the high-temperature carbonization temperature is too low, the activation cannot be completed.
The present invention will be further described with reference to the following examples.
The spinning die head adopted in the spinning and spinning steps in the embodiment of the invention comprises a material dispersing cavity at the upper part and a spinneret plate, wherein metal sand or filter filler is filled in the material dispersing cavity; the upper part of the spinneret plate is provided with 200-mesh 3000-mesh filter screens, and the number of the spinneret plate holes is 100-mesh 1000-mesh filter screens. The material temperature of the metal sand or the filter filler can be uniform; the filter screen on the upper part of the spinneret plate is mainly used for filtering impurities possibly brought in materials and can also be used for homogenizing the pressure of the materials. The spinneret plate is also provided with guide holes, counterbores and micropores. The guide hole, the reaming hole and the micropore are connected in sequence. The guide hole is of an inverted bell mouth structure, the height of the bell mouth structure is 1-3mm, the diameter of an upper opening is 2-3.5mm, and the diameter of a lower opening is 1.5-3 mm. The chambering is of an inverted bell mouth structure, the height of the bell mouth structure is 2-5mm, the diameter of an upper opening is 1.5-3mm, and the diameter of a lower opening is 0.15-0.3 mm. The diameter of the micropores is 0.15-0.3mm, and the length-diameter ratio of the micropores is 1:1-5: 1.
Example 1
Filling 80-mesh metal sand in a material dispersing cavity of the spinning die head; 2000 meshes of filter screen are arranged at the upper part of the spinneret plate, and the number of holes of the spinneret plate is 500. The spinneret plate is special for the spinneret plate, the guide hole is of an inverted-bell-mouth structure, the height is 1mm, the diameter of an upper opening is 3.5mm, the diameter of a lower opening is 3mm, the hole expansion is of an inverted-bell-mouth structure, the height is 3mm, the diameter of the upper opening is 3mm, the diameter of the lower opening is 0.2mm, the diameter of a micropore is 0.2mm, and the length-diameter ratio of the micropore is 3: 1.
Taking ethylene tar-based isotropic oxidized asphalt with the softening point of 257 ℃, ash content of 50ppm and oxygen content of 1.2 percent as a raw material A; taking anisotropic asphalt with the softening point of 260 ℃ and the ash content of 30ppm as a raw material B; uniformly mixing the raw material A and the raw material B according to the mass ratio of 10:90, adding the mixture into an intermeshing double-screw extruder, heating the mixture to 290 ℃, and melting and uniformly mixing the mixture to obtain molten asphalt. The molten asphalt is extruded by a meshing twin-screw extruder and then conveyed to a metering pump, the molten asphalt is conveyed to a spinning die head by the metering pump at the speed of 0.1g/min/500, and the pressure of the spinning die head is controlled to be 1.2MPa by the metering pump. And heating the spinning die head to 300 ℃, heating the surface of the spinneret plate to 270 ℃, and then carrying out spinning on the molten asphalt and spinning. After spinning, the filaments are collected at a filament collecting speed of 600m/min to obtain pitch fibers with the diameter of 14 mu m; heating the asphalt fiber from 180 ℃ to 280 ℃ at a heating rate of 1 ℃/min, and then keeping the temperature for 180min to carry out air oxidation treatment, thereby obtaining an infusible fiber with the oxygen content of 13%; performing heat treatment on the infusible fiber at 600 ℃ for 15min in a nitrogen atmosphere to obtain low-temperature carbonized fiber; activating the low-temperature carbonized fiber at 890 ℃ for 15min in a water vapor atmosphere to obtain low-temperature activated carbon fiber; and (3) carrying out heat treatment on the low-temperature activated carbon fiber at 1000 ℃ for 2min under the nitrogen atmosphere to obtain the pitch-based carbon fiber.
The diameter of the pitch-based carbon fiber is 12 mu m, the pitch-based carbon fiber consists of an isotropic porous carbon skin layer with the thickness of 0.03 mu m, a mixed transition carbon layer with the thickness of 0.5 mu m and an anisotropic carbon core layer with the diameter of 11 mu m, nano-scale holes are distributed on the surface of the isotropic porous carbon skin layer, and the depth of the holes is<0.03 μm. Specific surface area of activated carbon fiber 1350m2The tensile strength of the monofilament is 530 MPa.
Example 2
Filling 80-mesh metal steel balls into a material dispersing cavity of the spinning die head; the upper part of the spinneret plate is provided with a 1000-mesh filter screen, the number of holes of the spinneret plate is 1000, and the spinneret plate is special for the spinneret plate, the guide hole is of an inverted bell-mouth structure, the height is 1mm, the diameter of an upper opening is 3.5mm, the diameter of a lower opening is 3mm, the hole expansion is of an inverted bell-mouth structure, the height is 5mm, the diameter of the upper opening is 3mm, the diameter of the lower opening is 0.3mm, the diameter of a micropore is 0.3mm, and.
Taking ethylene tar-based isotropic oxidized asphalt with the softening point of 270 ℃, ash content of 80ppm and oxygen content of 0.8 percent as a raw material A; taking anisotropic asphalt with the softening point of 275 ℃ and the ash content of 10ppm as a raw material B; uniformly mixing the raw material A and the raw material B according to the mass ratio of 20:80, adding the mixture into a meshing type double-screw extruder, heating to 295 ℃, melting and uniformly mixing to obtain the molten asphalt. The molten asphalt is extruded by a meshing type double-screw extruder and then is conveyed to a metering pump, the molten asphalt is conveyed to a spinning die head by the metering pump at the speed of 0.2g/min/1000, and the pressure of the spinning die head is controlled to be 0.9MPa by the metering pump. And heating the spinning die head to 310 ℃, heating the surface of the spinneret plate to 285 ℃, and then carrying out spinning on the molten asphalt and spinning. After spinning, the filaments are collected at a filament collecting speed of 500m/min to obtain the pitch fibers with the diameter of 16 mu m; heating the asphalt fiber from 180 to 280 ℃ at a heating rate of 0.5 ℃/min, and then keeping the temperature for 200min to perform air oxidation treatment, thereby obtaining an infusible fiber with an oxygen content of 13%; performing heat treatment on the infusible fiber at 500 ℃ for 30min in a nitrogen atmosphere to obtain low-temperature carbonized fiber; activating the low-temperature carbonized fiber at 800 ℃ for 20min in a water vapor atmosphere to obtain low-temperature activated carbon fiber; and (3) carrying out heat treatment on the low-temperature activated carbon fiber at 1000 ℃ for 5min under the nitrogen atmosphere to obtain the pitch-based carbon fiber.
The diameter of the pitch-based carbon fiber is 14 mu m, and the pitch-based carbon fiber consists of an isotropic porous carbon skin layer with the thickness of 0.03 mu m, a mixed transition carbon layer with the thickness of 0.4 mu m and an anisotropic carbon core layer with the diameter of 12.2 mu m, wherein the surface of the isotropic porous carbon skin layer is fully distributed with nano-scale holes, and the depth of the holes is<0.03 μm. The specific surface area of the activated carbon fiber is 1050m2G, tensile strength of the monofilament 670 MPa.
Example 3
Filling 60-mesh metal steel balls in a material dispersing cavity of the spinning die head; the upper part of the spinneret plate is provided with a 1000-mesh filter screen, the number of holes of the spinneret plate is 1000, and the spinneret plate is special for the spinneret plate, the guide hole is of an inverted bell-mouth structure, the height is 1mm, the diameter of an upper opening is 3.5mm, the diameter of a lower opening is 3mm, the hole expansion is of an inverted bell-mouth structure, the height is 5mm, the diameter of the upper opening is 3mm, the diameter of the lower opening is 0.3mm, the diameter of a micropore is 0.3mm, and.
Taking ethylene tar-based isotropic oxidized asphalt with the softening point of 270 ℃, ash content of 50ppm and oxygen content of 1.3 percent as a raw material A; taking anisotropic asphalt with the softening point of 274 ℃ and the ash content of 10ppm as a raw material B; uniformly mixing the raw material A and the raw material B according to the mass ratio of 15:85, adding the mixture into an intermeshing double-screw extruder, heating the mixture to 300 ℃, and melting and uniformly mixing the mixture to obtain molten asphalt. The molten asphalt is extruded by a meshing type double-screw extruder and then is conveyed to a metering pump, the molten asphalt is conveyed to a spinning die head by the metering pump at the speed of 0.09g/min/1000, and the pressure of the spinning die head is controlled to be 2MPa by the metering pump. And heating the spinning die head to 325 ℃, heating the surface of the spinneret plate to 290 ℃, and then carrying out spinning on the molten asphalt and spinning. After spinning, winding the filaments at a filament winding speed of 800m/min to obtain asphalt fibers with the diameter of 13 mu m; heating the asphalt fiber from 180 ℃ to 280 ℃ at a heating rate of 1 ℃/min, and then keeping the temperature for 120min to carry out air oxidation treatment, thereby obtaining non-melting fiber with the oxygen content of 11%; performing heat treatment on the infusible fiber at 700 ℃ for 10min in a nitrogen atmosphere to obtain low-temperature carbonized fiber; activating the low-temperature carbonized fiber at 900 ℃ for 5min in a steam atmosphere to obtain low-temperature activated carbon fiber; and (3) carrying out heat treatment on the low-temperature activated carbon fiber at 1400 ℃ for 5min under the nitrogen atmosphere to obtain the pitch-based carbon fiber.
The diameter of the pitch-based carbon fiber is 11.5 mu m, the pitch-based carbon fiber consists of an isotropic porous carbon skin layer with the thickness of 0.03 mu m, a mixed transition carbon layer with the thickness of 0.5 mu m and an anisotropic carbon core layer with the diameter of about 10.5 mu m, nano-scale holes are distributed on the surface of the isotropic porous carbon skin layer, and the depth of the holes is<0.03 μm. The specific surface area of the activated carbon fiber is 850m2G, monofilament tensile strength 750 MPa.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (10)

1. An asphalt-based activated carbon fiber characterized by:
the pitch-based activated carbon fiber comprises a sheath-core structure;
the core layer of the skin-core structure is anisotropic carbon;
the skin layer of the skin-core structure is isotropic carbon;
a mixed transition layer which is formed by transition from anisotropic carbon to isotropic carbon along the direction from the core layer to the skin layer is arranged between the core layer and the skin layer;
the surface of the cortex is distributed with nanometer pores.
2. An asphalt-based activated carbon fiber as defined in claim 1, wherein:
the diameter of the asphalt-based activated carbon fiber is 5-18 μm;
the thickness of the skin layer is 0.002-0.05 μm;
the thickness of the mixed transition layer is 0.3-2.5 μm;
the core layer has a diameter of 4-16 μm.
3. An asphalt-based activated carbon fiber as defined in claim 1, wherein:
the depth of the micropores is less than or equal to 0.05 μm.
4. A process for the preparation of pitch-based activated carbon fiber as in any of claims 1 to 3 comprising the steps of:
melting and extruding the raw material A and the raw material B by a screw, spraying, spinning and collecting filaments to obtain asphalt fibers;
oxidizing the asphalt fiber, performing first heat treatment at the temperature of 450-;
the raw material A is isotropic oxidized asphalt, the raw material B is anisotropic asphalt, the softening temperature of the raw material A is lower than that of the raw material B, and the temperature difference between the softening temperatures of the raw material A and the raw material B is less than 5 ℃.
5. A process for the preparation of pitch-based activated carbon fiber as claimed in claim 4, characterized in that:
the softening point of the isotropic oxidized asphalt is 250-280 ℃, the ash content is less than 80ppm, and the oxygen content is less than 1.5%;
the softening point of the anisotropic asphalt is 250 ℃ and 285 ℃, and the ash content is less than 30 ppm.
6. The method for producing pitch-based carbon fiber according to claim 4, wherein:
the weight ratio of the raw material A to the raw material B is 5: 95-25: 75;
the temperature of the screw for melt extrusion is 280-320 ℃.
7. The method for producing pitch-based carbon fiber according to claim 4, wherein:
the spinning temperature is 260-320 ℃, the spinning temperature is 280-340 ℃, and the spinneret plate temperature is lower than the spinning temperature by 20-40 ℃;
the spinning speed is 0.06-0.15g/min/H, wherein H is the number of spinneret orifices of a spinneret plate used for spinning.
8. The method for producing pitch-based carbon fiber according to claim 4, wherein:
the spinning pressure is 0.3-2MPa, and the yarn collecting speed is 500-1000 m/min.
9. The method for producing pitch-based carbon fiber according to claim 4, wherein:
the temperature of the oxidation is 180-320 ℃, the time of the oxidation is 90-400min, and the atmosphere of the oxidation is air.
10. The method for producing pitch-based carbon fiber according to claim 4, wherein:
the activation temperature is 550-1000 ℃, the activation time is 5-60min, and the activation atmosphere is water vapor or carbon dioxide.
CN202011419370.0A 2020-12-07 2020-12-07 Asphalt-based carbon fiber and preparation method thereof Pending CN112522810A (en)

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JPH02264018A (en) * 1988-12-02 1990-10-26 Petoka:Kk Activated carbon fiber and its production
JPH0382820A (en) * 1989-08-23 1991-04-08 Kawasaki Steel Corp Activated carbon fiber, its production and pitch fiber for activated carbon fiber
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JPH02264018A (en) * 1988-12-02 1990-10-26 Petoka:Kk Activated carbon fiber and its production
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