CN110863270A - Method for reducing ash content of high-strength polyacrylonitrile-based carbon fiber and application thereof - Google Patents
Method for reducing ash content of high-strength polyacrylonitrile-based carbon fiber and application thereof Download PDFInfo
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- 229920000049 Carbon (fiber) Polymers 0.000 title claims abstract description 89
- 239000004917 carbon fiber Substances 0.000 title claims abstract description 89
- 229920002239 polyacrylonitrile Polymers 0.000 title claims abstract description 72
- 238000000034 method Methods 0.000 title claims abstract description 46
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims description 80
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 22
- 230000003647 oxidation Effects 0.000 claims abstract description 19
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 72
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 claims description 32
- 238000001035 drying Methods 0.000 claims description 23
- 239000002243 precursor Substances 0.000 claims description 20
- 238000010306 acid treatment Methods 0.000 claims description 15
- 238000007598 dipping method Methods 0.000 claims description 15
- 238000007654 immersion Methods 0.000 claims description 12
- 239000003960 organic solvent Substances 0.000 claims description 12
- 238000010000 carbonizing Methods 0.000 claims description 9
- 238000005406 washing Methods 0.000 claims description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- 238000002791 soaking Methods 0.000 claims description 8
- 238000009987 spinning Methods 0.000 claims description 8
- 238000002166 wet spinning Methods 0.000 claims description 8
- 238000004513 sizing Methods 0.000 claims description 7
- 238000004381 surface treatment Methods 0.000 claims description 7
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 6
- 230000001590 oxidative effect Effects 0.000 claims description 6
- 239000007921 spray Substances 0.000 claims description 2
- 238000005470 impregnation Methods 0.000 claims 1
- 238000003763 carbonization Methods 0.000 abstract description 29
- 230000008569 process Effects 0.000 abstract description 9
- 239000003795 chemical substances by application Substances 0.000 abstract description 7
- 230000009286 beneficial effect Effects 0.000 abstract description 5
- 238000006243 chemical reaction Methods 0.000 abstract description 5
- 238000000265 homogenisation Methods 0.000 abstract description 4
- 239000000835 fiber Substances 0.000 description 31
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 16
- 238000010438 heat treatment Methods 0.000 description 11
- 239000003921 oil Substances 0.000 description 11
- 229910052757 nitrogen Inorganic materials 0.000 description 8
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 6
- 238000007363 ring formation reaction Methods 0.000 description 6
- 229910052710 silicon Inorganic materials 0.000 description 6
- 239000010703 silicon Substances 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 230000006872 improvement Effects 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 238000005096 rolling process Methods 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 125000003118 aryl group Chemical group 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000007792 addition Methods 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 238000006356 dehydrogenation reaction Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 125000003010 ionic group Chemical group 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- -1 polysiloxane Polymers 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 238000012805 post-processing Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000011112 process operation Methods 0.000 description 1
- 239000013079 quasicrystal Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- FVBUAEGBCNSCDD-UHFFFAOYSA-N silicide(4-) Chemical group [Si-4] FVBUAEGBCNSCDD-UHFFFAOYSA-N 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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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
- D01F11/00—Chemical after-treatment of artificial filaments or the like during manufacture
- D01F11/10—Chemical after-treatment of artificial filaments or the like during manufacture of carbon
- D01F11/12—Chemical after-treatment of artificial filaments or the like during manufacture of carbon with inorganic substances ; Intercalation
- D01F11/121—Halogen, halogenic acids or their salts
-
- 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
- D01F11/00—Chemical after-treatment of artificial filaments or the like during manufacture
- D01F11/10—Chemical after-treatment of artificial filaments or the like during manufacture of carbon
- D01F11/14—Chemical after-treatment of artificial filaments or the like during manufacture of carbon with organic compounds, e.g. macromolecular compounds
-
- 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
Abstract
The invention provides a method for reducing ash content of high-strength polyacrylonitrile-based carbon fibers and application thereof, which can effectively remove ash content in the polyacrylonitrile-based carbon fibers, simultaneously does not reduce the heat resistance of an oil agent, is beneficial to homogenization reaction of the carbon fibers in the pre-oxidation carbonization process, and keeps the body performance of the carbon fibers.
Description
Technical Field
The invention belongs to the technical field of carbon fiber preparation, and particularly relates to a method for reducing ash content of high-strength polyacrylonitrile-based carbon fibers and application of the method to production of the high-strength polyacrylonitrile-based carbon fibers.
Background
Polyacrylonitrile (PAN) based carbon fiber has the characteristics of light weight, high strength, high modulus, high heat conductivity, high electric conductivity, good dimensional stability, good fatigue performance and the like, and is widely applied to the fields of wind power blades, aerospace, sports and leisure, automobile industry and the like.
The spinning oil is an important auxiliary agent essential for preparing the carbon fiber, and is one of key technologies for ensuring the smooth progress of the carbon fiber manufacturing process (such as spinning, pre-oxidation and carbonization processes), greatly reducing or eliminating burrs, doubling and breaking, and improving the quality of the carbon fiber due to the surface defects and the internal defects of the carbon fiber. The spinning oil agent adopted in the industry at present generally takes functional group modified polysiloxane as a main component, and because the spinning oil agent has the characteristic of high heat resistance, the surface of high-strength polyacrylonitrile-based carbon fiber (generally the carbonization treatment temperature is below 1500 ℃) contains trace silicide residues, which are called ash. The ash content affects not only the bulk properties of the carbon fiber but also the interfacial properties with the matrix resin.
In the prior art, for example, chinese patents CN20131090060.x and CN201711050156.0 all reduce carbon fiber ash by reducing silicon content in oil or using a silicon-free oil, but the reduction of silicon content in oil causes the heat resistance of oil itself to be reduced, which is not favorable for homogenization reaction of carbon fiber in the pre-oxidation carbonization process, resulting in the reduction of bulk performance of carbon fiber.
Disclosure of Invention
In view of the above, the present invention is directed to a method for reducing ash content of high-strength polyacrylonitrile-based carbon fibers while maintaining bulk properties of the carbon fibers. The method comprises the following steps:
and (3) carrying out organic solvent dipping treatment and hydrofluoric acid treatment on the polyacrylonitrile-based carbon fiber.
In one embodiment, the organic solvent comprises one or a combination of several of n-hexane, acetone and ethanol, the dipping treatment temperature of the organic solvent is 25 +/-3 ℃, and the treatment time is 15-60 s.
In one embodiment, the hydrofluoric acid treatment temperature is 25 +/-3 ℃, the treatment time is 20-60 s, and the pH value of the hydrofluoric acid is 3-4.
In one embodiment, the method specifically includes:
and (3) carrying out normal hexane dipping treatment on the polyacrylonitrile-based carbon fiber, drying, and then carrying out hydrofluoric acid treatment.
The invention also provides a production method of the high-strength polyacrylonitrile-based carbon fiber, which comprises the following steps:
pre-oxidizing and carbonizing polyacrylonitrile precursor to obtain carbon fiber preform;
carrying out normal hexane dipping treatment and hydrofluoric acid treatment on the carbon fiber preform to remove ash;
and (3) carrying out post-treatment on the carbon fiber preform without ash content to obtain the high-strength polyacrylonitrile-based carbon fiber.
In one embodiment, the method specifically includes:
preparing polyacrylonitrile protofilament by adopting dry-method spray wet spinning or wet-method spinning;
pre-oxidizing the polyacrylonitrile precursor at 190-280 ℃ for 45-90 min, carbonizing at 300-900 ℃ for 2 +/-0.5 min, and carbonizing at 1000-1500 ℃ for 2.5 +/-0.5 min to obtain the carbon fiber preform.
In one embodiment, the method specifically includes:
and (3) soaking the carbon fiber preform by using normal hexane, drying, and then treating by using hydrofluoric acid to remove ash.
In one embodiment, the method specifically includes:
and (3) carrying out anodic oxidation surface treatment, water washing, drying, sizing and drying on the carbon fiber preform without ash content to obtain the high-strength polyacrylonitrile-based carbon fiber.
In one embodiment, the temperature of the n-hexane dipping treatment is 25 +/-3 ℃, and the treatment time is 15-60 s; and/or the hydrofluoric acid treatment temperature is 25 +/-3 ℃, the treatment time is 20-60 s, and the pH value of the hydrofluoric acid is 3.
The invention also provides the high-strength polyacrylonitrile-based carbon fiber prepared by the method, wherein the diameter of the polyacrylonitrile-based carbon fiber is 4.0-8.0 mu m, the tensile strength is 3.5-5.5 GPa, the tensile modulus is 200-260 GPa, the ash content is 0.1-0.2%, and the interlaminar shear strength is more than 115 MPa.
The invention has the following beneficial effects: through the steps of dipping the polyacrylonitrile-based carbon fiber in an organic solvent and treating the polyacrylonitrile-based carbon fiber with hydrofluoric acid, ash in the polyacrylonitrile-based carbon fiber can be effectively removed in a post-treatment mode without depending on the improvement of a spinning oil agent, and meanwhile, the heat resistance of the oil agent is not reduced, so that the homogenization reaction of the carbon fiber in the pre-oxidation carbonization process is facilitated, and the performance of the carbon fiber body is kept; meanwhile, the treatment steps can be beneficial to surface improvement while the surface of the carbon fiber is cleaned, so that the interface performance of the carbon fiber is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a flow chart of an embodiment of the method for producing high-strength polyacrylonitrile-based carbon fiber according to the present application.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, a method of reducing ash content of high strength polyacrylonitrile-based carbon fiber according to an embodiment of the present invention will be described. In the present embodiment, the method includes the steps of subjecting the polyacrylonitrile-based carbon fiber to an organic solvent immersion treatment and a hydrofluoric acid treatment.
Specifically, the method comprises the steps of dipping polyacrylonitrile-based carbon fiber in an organic solvent, drying, and treating with hydrofluoric acid. The dipping treatment temperature of an organic solvent such as n-hexane is 25 +/-3 ℃, and the treatment time is 15-60 s; the temperature of the hydrofluoric acid treatment is 25 +/-3 ℃, the treatment time is 20-60 s, and the pH value of the hydrofluoric acid is 3-4. Of course, the organic solvent can be one or a combination of n-hexane, acetone and ethanol.
The invention also provides a production method of the high-strength polyacrylonitrile-based carbon fiber, which comprises the following steps:
and S11, pre-oxidizing and carbonizing polyacrylonitrile protofilament to obtain a carbon fiber preform.
The polyacrylonitrile protofilament can be prepared by dry-jet wet spinning or wet spinning, and the diameter, orientation degree, specification and the like of the protofilament can be selected according to requirements. Specifically, the carbon fiber preform is obtained by pre-oxidizing polyacrylonitrile precursor at 190-280 ℃ for 45-90 min, carbonizing polyacrylonitrile precursor at 300-900 ℃ for 2 +/-0.5 min, and carbonizing polyacrylonitrile precursor at 1000-1500 ℃ for 2.5 +/-0.5 min.
The pre-oxidation of the polyacrylonitrile-based protofilament is usually realized by adopting a multi-stage heating method, and adopting a mode of 4 temperature zones, 6 temperature zones or 10 temperature zones and the like within a certain temperature range. In the pre-oxidation stage, the orientation of the quasicrystal region is removed from the physical change angle, so that the molecular chain conformation of the protofilament fiber is changed; from the perspective of chemical structure change, cyclization, oxidation and dehydrogenation reactions cause structural changes, so that molecular chains shrink. The cyclization reaction mechanism mainly comprises homopolymerized PAN precursor cyclization reaction initiated by free radicals and copolymerized PAN precursor cyclization reaction initiated by ionic groups. The cyclization reaction is the basis of an oxidation reaction, in the pre-oxidation process, except oxygen elements carried by comonomers, oxygen is combined into the precursor fibers in the air atmosphere for oxidation reaction, and the oxygen elements are added, so that oxygen-containing aromatic rings are combined in the heat-resistant trapezoidal structure formed by cyclization to generate.
The low-temperature carbonization stage is mainly characterized in that the heat-resistant trapezoidal structure in the pre-oxidized fiber is subjected to a cross-linking reaction at high temperature to form a prototype-aromatic ring plane of the carbon network structure.
In the high-temperature carbonization stage, the aromatic ring plane formed by low-temperature carbonization is further dehydrogenated, and the aromatic ring structure is rearranged to form a carbon network structure, namely a disordered-layer graphite structure, so that the carbon fiber is endowed with higher mechanical properties.
And S12, performing normal hexane dipping treatment and hydrofluoric acid treatment on the carbon fiber preform to remove ash.
Specifically, the temperature of normal hexane dipping treatment is 25 +/-3 ℃, and the treatment time is 15-60 s; and/or the temperature of hydrofluoric acid treatment is 25 +/-3 ℃, the treatment time is 20-60 s, and the pH value of the hydrofluoric acid is 3. The normal hexane dipping treatment and the hydrofluoric acid treatment can obviously reduce the ash content in the carbon fiber and improve the interlaminar shear strength of the carbon fiber.
And S13, performing post-treatment on the carbon fiber preform without ash to obtain the high-strength polyacrylonitrile-based carbon fiber.
The post-processing herein specifically includes: and (3) carrying out anodic oxidation surface treatment, water washing, drying, sizing and drying on the carbon fiber preform without ash content to obtain the high-strength polyacrylonitrile-based carbon fiber.
The invention also provides the high-strength polyacrylonitrile-based carbon fiber prepared by the method, wherein the diameter of the polyacrylonitrile-based carbon fiber is 4.0-8.0 mu m, the tensile strength is 3.5-5.5 GPa, the tensile modulus is 200-260 GPa, the ash content is 0.1-0.2%, and the interlaminar shear strength is more than 115 MPa.
Specific examples and comparative examples are provided below to better explain the technical solution of the present invention.
Example 1:
(1) pre-oxidation of Polyacrylonitrile (PAN) precursor
Selecting 24K PAN precursor produced by Wehai expanded fiber Limited company through wet spinning, and in an air medium, adopting a 6-section gradient heating mode, wherein the pre-oxidation starting temperature is 200 ℃, the termination temperature is 270 ℃, the retention time is 70min, and the obtained density is 1.35g/cm3The pre-oxidized fiber of (1).
(2) Low temperature carbonization
And carrying out low-temperature carbonization on the obtained pre-oxidized fiber at the temperature of 400-750 ℃ for 1.5min under the protection of nitrogen, and applying + 1% drafting.
(3) High temperature carbonization
And (3) under the protection of nitrogen, treating the obtained low-temperature carbonized fiber for 1.5min by adopting a 7-section gradient temperature rise mode, wherein the initial temperature of high-temperature carbonization is 1000 ℃, and the maximum temperature is 1300 ℃, and applying-3.0% drafting.
(4) N-hexane immersion treatment and hydrofluoric acid immersion treatment
Soaking the obtained high-temperature carbonized fiber at 25 +/-3 ℃ for 40s by using normal hexane, then carrying out heat treatment at 100 +/-3 ℃ for 20s, drying, treating the obtained fiber at 25 +/-3 ℃ for 40s by using a pH (potential of Hydrogen) 3 hydrofluoric acid solution, and then washing for 20s to remove organic matters such as tar and the like and silicon elements on the surface of the carbon fiber.
(5) Post-treatment
The obtained fiber is subjected to surface treatment, water washing, drying, sizing, drying and rolling treatment to obtain the 24K PAN-based high-strength carbon fiber, the diameter of which is 7.1 mu m, the tensile strength of which is 4.2GPa, the tensile modulus of which is 240GPa, the ash content of which is 0.13 percent and the interlaminar shear strength of which is 120 MPa.
Example 2:
(1) PAN precursor preoxidation
Selecting 12K PAN precursor produced by Wehai expanded fiber Limited company through wet spinning, and in an air medium, adopting a 6-section gradient heating mode, wherein the pre-oxidation starting temperature is 200 ℃, the termination temperature is 260 ℃, the retention time is 80min, and the obtained density is 1.35g/cm3The pre-oxidized fiber of (1).
(2) Low temperature carbonization
And carrying out low-temperature carbonization on the obtained pre-oxidized fiber at the temperature of 400-750 ℃ for 2.0min under the protection of nitrogen, and applying + 3% drafting.
(3) High temperature carbonization
And (3) treating the obtained low-temperature carbonized fiber for 2.0min by adopting a 7-section gradient heating mode under the protection of nitrogen, wherein the initial temperature of high-temperature carbonization is 1000 ℃, the maximum temperature is 1400 ℃, and a drafting of-3.0% is applied.
(4) N-hexane immersion treatment and hydrofluoric acid immersion treatment
Soaking the obtained high-temperature carbonized fiber at 25 +/-3 ℃ for 30s by using normal hexane, and then carrying out heat treatment at 100 +/-3 ℃ for 20s for drying; the obtained fiber is treated by hydrofluoric acid solution with pH value of 3 at 25 +/-3 ℃ for 30s and then washed by water for 20s, so that organic matters such as tar on the surface of the carbon fiber and silicon elements are removed.
(5) Post-treatment
The obtained fiber is subjected to surface treatment, water washing, drying, sizing, drying and rolling treatment to obtain the 12K PAN-based high-strength carbon fiber, the diameter of which is 7.0 mu m, the tensile strength of which is 5.1GPa, the tensile modulus of which is 255GPa, the ash content of which is 0.15 percent and the interlaminar shear strength of which is 123 MPa.
Example 3
(1) Pre-oxidation of Polyacrylonitrile (PAN) precursor
Selecting 24K PAN precursor produced by Wehai expanded fiber Limited company through wet spinning, and in an air medium, adopting a 6-section gradient heating mode, wherein the pre-oxidation starting temperature is 200 ℃, the termination temperature is 270 ℃, the retention time is 70min, and the obtained density is 1.35g/cm3The pre-oxidized fiber of (1).
(2) Low temperature carbonization
And carrying out low-temperature carbonization on the obtained pre-oxidized fiber at the temperature of 400-750 ℃ for 1.5min under the protection of nitrogen, and applying + 1% drafting.
(3) High temperature carbonization
And (3) under the protection of nitrogen, treating the obtained low-temperature carbonized fiber for 1.5min by adopting a 7-section gradient temperature rise mode, wherein the initial temperature of high-temperature carbonization is 1000 ℃, and the maximum temperature is 1300 ℃, and applying-3.0% drafting.
(4) N-hexane immersion treatment and hydrofluoric acid immersion treatment
Soaking the obtained high-temperature carbonized fiber at 25 +/-3 ℃ for 20s by using normal hexane, then carrying out heat treatment at 100 +/-3 ℃ for 20s, drying, treating the obtained fiber at 25 +/-3 ℃ for 20s by using a pH (potential of Hydrogen) 3 hydrofluoric acid solution, and then washing for 20s, so as to remove organic matters such as tar and the like and silicon elements on the surface of the carbon fiber.
(5) Post-treatment
The obtained fiber is subjected to surface treatment, water washing, drying, sizing, drying and rolling treatment to obtain the 24K PAN-based high-strength carbon fiber, the diameter of which is 7.1 mu m, the tensile strength of which is 4.0GPa, the tensile modulus of which is 240GPa, the ash content of which is 0.18 percent and the interlaminar shear strength of which is 116 MPa.
Example 4
(1) PAN precursor preoxidation
Selecting 12K PAN precursor produced by Wehai expanded fiber Limited company through wet spinning, and in an air medium, adopting a 6-section gradient heating mode, wherein the pre-oxidation starting temperature is 200 ℃, the termination temperature is 260 ℃, the retention time is 80min, and the obtained density is 1.35g/cm3The pre-oxidized fiber of (1).
(2) Low temperature carbonization
And carrying out low-temperature carbonization on the obtained pre-oxidized fiber at the temperature of 400-750 ℃ for 2.0min under the protection of nitrogen, and applying + 3% drafting.
(3) High temperature carbonization
And (3) treating the obtained low-temperature carbonized fiber for 2.0min by adopting a 7-section gradient heating mode under the protection of nitrogen, wherein the initial temperature of high-temperature carbonization is 1000 ℃, the maximum temperature is 1400 ℃, and a drafting of-3.0% is applied.
(4) N-hexane immersion treatment and hydrofluoric acid immersion treatment
Soaking the obtained high-temperature carbonized fiber at 25 +/-3 ℃ for 60s by using normal hexane, and then carrying out heat treatment at 100 +/-3 ℃ for 20s for drying; the obtained fiber is treated by hydrofluoric acid solution with pH value of 3 at 25 +/-3 ℃ for 50s and then washed by water for 20s, so that organic matters such as tar on the surface of the carbon fiber and silicon elements are removed.
(5) Post-treatment
The obtained fiber is subjected to surface treatment, water washing, drying, sizing, drying and rolling treatment to obtain the 12K PAN-based high-strength carbon fiber, the diameter of which is 7.0 mu m, the tensile strength of which is 5.2GPa, the tensile modulus of which is 258GPa, the ash content of which is 0.10 percent and the interlaminar shear strength of which is 125 MPa.
Comparative example 1:
(1) the procedures of PAN precursor pre-oxidation, (2) low-temperature carbonization, (3) high-temperature carbonization, and (5) post-treatment were the same as in example 1.
The 24K PAN-based high-strength carbon fiber is prepared without (4) n-hexane soaking treatment and hydrofluoric acid soaking treatment, and has the diameter of 7.1 mu m, the tensile strength of 4.2GPa, the tensile modulus of 240GPa, the ash content of 0.33 percent and the interlaminar shear strength of 116 MPa.
Comparative example 2:
(1) the procedures of PAN precursor pre-oxidation, (2) low-temperature carbonization, (3) high-temperature carbonization, and (5) post-treatment were the same as in example 2.
The 12K PAN-based high-strength carbon fiber is prepared without the steps of (4) normal hexane immersion treatment and hydrofluoric acid immersion treatment, and has the diameter of 7.0 mu m, the tensile strength of 5.1GPa, the tensile modulus of 255GPa, the ash content of 0.29 percent and the interlaminar shear strength of 114 MPa.
The invention has the following beneficial effects: through the steps of dipping the polyacrylonitrile-based carbon fiber in an organic solvent and treating the polyacrylonitrile-based carbon fiber with hydrofluoric acid, ash in the polyacrylonitrile-based carbon fiber can be effectively removed in a post-treatment mode without depending on the improvement of a spinning oil agent, and meanwhile, the heat resistance of the oil agent is not reduced, so that the homogenization reaction of the carbon fiber in the pre-oxidation carbonization process is facilitated, and the performance of the carbon fiber body is kept; meanwhile, the treatment steps can be beneficial to surface improvement while the surface of the carbon fiber is cleaned, so that the interface performance of the carbon fiber is improved.
The aspects, embodiments, features and examples of the present invention should be considered as illustrative in all respects and not intended to be limiting of the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.
The use of headings and chapters in this disclosure is not meant to limit the disclosure; each section may apply to any aspect, embodiment, or feature of the disclosure.
Throughout this specification, where a composition is described as having, containing, or comprising specific components or where a process is described as having, containing, or comprising specific process steps, it is contemplated that the composition of the present teachings also consist essentially of, or consist of, the recited components, and the process of the present teachings also consist essentially of, or consist of, the recited process steps.
Unless specifically stated otherwise, use of the terms "comprising", "having", and "has" are generally to be construed as open-ended and not limiting.
The use of the singular herein includes the plural (and vice versa) unless specifically stated otherwise. Furthermore, the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. In addition, where the term "about" is used before a quantity, the present teachings also include the particular quantity itself unless specifically stated otherwise.
It should be understood that the order of steps or the order in which particular actions are performed is not critical, so long as the teachings of the invention remain operable. Further, two or more steps or actions may be performed simultaneously.
In addition, the inventors of the present invention have also made experiments with other materials, process operations, and process conditions described in the present specification with reference to the above examples, and have obtained preferable results.
While the invention has been described with reference to illustrative embodiments, it will be understood by those skilled in the art that various other changes, omissions and/or additions may be made and substantial equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated any use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.
Claims (10)
1. The method for reducing the ash content of the high-strength polyacrylonitrile-based carbon fiber is characterized by comprising the steps of carrying out organic solvent dipping treatment and hydrofluoric acid treatment on the polyacrylonitrile-based carbon fiber.
2. The method according to claim 1, wherein the organic solvent comprises one or more of n-hexane, acetone and ethanol, the temperature of the impregnation treatment of the organic solvent is 25 +/-3 ℃, and the treatment time is 15-60 s.
3. The method according to claim 1, wherein the hydrofluoric acid treatment temperature is 25 ± 3 ℃, the treatment time is 20-60 s, and the pH value of the hydrofluoric acid is 3-4.
4. The method according to claim 1, characterized in that it comprises in particular:
and (3) carrying out normal hexane dipping treatment on the polyacrylonitrile-based carbon fiber, drying, and then carrying out hydrofluoric acid treatment.
5. A production method of high-strength polyacrylonitrile-based carbon fibers is characterized by comprising the following steps:
pre-oxidizing and carbonizing polyacrylonitrile precursor to obtain carbon fiber preform;
carrying out normal hexane dipping treatment and hydrofluoric acid treatment on the carbon fiber preform to remove ash;
and (3) carrying out post-treatment on the carbon fiber preform without ash content to obtain the high-strength polyacrylonitrile-based carbon fiber.
6. The method according to claim 5, characterized in that the method comprises in particular:
preparing polyacrylonitrile protofilament by adopting dry-method spray wet spinning or wet-method spinning;
pre-oxidizing the polyacrylonitrile precursor at 190-280 ℃ for 45-90 min, carbonizing at 300-900 ℃ for 2 +/-0.5 min, and carbonizing at 1000-1500 ℃ for 2.5 +/-0.5 min to obtain the carbon fiber preform.
7. The method according to claim 5, characterized in that the method comprises in particular:
and (3) soaking the carbon fiber preform by using normal hexane, drying, and then treating by using hydrofluoric acid to remove ash.
8. The method according to claim 5, characterized in that the method comprises in particular:
and (3) carrying out anodic oxidation surface treatment, water washing, drying, sizing and drying on the carbon fiber preform without ash content to obtain the high-strength polyacrylonitrile-based carbon fiber.
9. The method according to claim 5, wherein the temperature of the n-hexane immersion treatment is 25 +/-3 ℃, and the treatment time is 15-60 s; and/or the hydrofluoric acid treatment temperature is 25 +/-3 ℃, the treatment time is 20-60 s, and the pH value of the hydrofluoric acid is 3.
10. The high-strength polyacrylonitrile-based carbon fiber prepared by the method is characterized in that the diameter of the polyacrylonitrile-based carbon fiber is 4.0-8.0 μm, the tensile strength is 3.5-5.5 GPa, the tensile modulus is 200-260 GPa, the ash content is 0.1-0.2%, and the interlaminar shear strength is more than 115 MPa.
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