CN110685041B - Preparation method of polyacrylonitrile-based carbon fiber - Google Patents
Preparation method of polyacrylonitrile-based carbon fiber Download PDFInfo
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- CN110685041B CN110685041B CN201810733834.1A CN201810733834A CN110685041B CN 110685041 B CN110685041 B CN 110685041B CN 201810733834 A CN201810733834 A CN 201810733834A CN 110685041 B CN110685041 B CN 110685041B
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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
Abstract
The invention relates to a preparation method of polyacrylonitrile-based carbon fibers, which mainly solves the problems of large coke discharge amount of a low-carbon furnace and large residual quantity of silicon dioxide in the prior art. The invention adopts a preparation method of polyacrylonitrile-based carbon fiber, which comprises at least two steps of oiling and drying densification; wherein, the polyacrylonitrile precursor after accomplishing first oiling and dry densification is soaked through the water bath, and the moisture content of control precursor is 5% ~ 20%, carries out the second again and oils and dry densification's technical scheme, has solved this problem betterly, can be used to in the production of preparation high performance carbon fiber.
Description
Technical Field
The invention relates to a preparation method of polyacrylonitrile-based carbon fibers, and belongs to the technical field of preparation of polyacrylonitrile carbon fibers.
Background
From the last 50 century, developed countries are in urgent need of new structural materials and corrosion-resistant materials for developing large rockets and artificial satellites and improving the performance of airplanes in a comprehensive manner, so that carbon fibers reappear on a stage made of the new materials, and three raw material systems of PAN-based carbon fibers, viscose-based carbon fibers and asphalt-based carbon fibers are gradually formed. Compared with other methods, the PAN-based carbon fiber precursor production process is simple, and the product has good mechanical properties, so that the PAN-based carbon fiber precursor production process is rapidly developed and becomes the mainstream of the current carbon fiber precursor production.
Oiling is a key step in the preparation process of the carbon fiber precursor. The oiling is that the surface of the polyacrylonitrile protofilament is uniformly coated with an oiling agent film, the oiling agent can permeate into the protofilament, but most of the oiling agent still stays on the surface of the protofilament, the protofilament can be protected by the oiling agent from being scratched, the bunching property and the antistatic property of the protofilament can be improved, and the occurrence of doubling and filament breakage in the further post-treatment process of the protofilament is avoided. The oiling amount of the protofilament needs to be proper, and the oiling amount is too much, so that silicon pollution is caused; too little oil causes the adhesion between filaments or doubling.
For polyacrylonitrile-based carbon fiber precursor, a two-stage oiling method is generally adopted. The first oiling is uniformly coated on the surface of the protofilament, so that the cluster shape and the antistatic property of the protofilament are improved, the existing surface is protected, and the subsequent spinnability is improved; the second oiling process mainly aims at the moisture and heat resistance of the protofilament to avoid melting in the subsequent high-temperature treatment.
The thermal stabilization of polyacrylonitrile is to convert a linear macromolecular chain of a polyacrylonitrile precursor into a heat-resistant ladder-type polymer structure, so that the polyacrylonitrile is not melted and is not combusted in the subsequent carbonization process, and a thermodynamic stable state is maintained, thereby being a key step for preparing high-performance carbon fibers.
The polyacrylonitrile precursor mainly generates cyclization reaction and oxidation reaction in the thermal stabilization process, and the cyclization degree and the oxidation degree of the polyacrylonitrile precursor have obvious influence on the performance of the final carbon fiber. If the thermal stabilization temperature is too low or the time is too short, a sufficient heat-resistant structure cannot be formed in the polyacrylonitrile fiber, which may cause breakage of excessive molecular chains in subsequent high-temperature treatment, thereby generating defects affecting the properties of the final carbon fiber; if the heat stabilization temperature is too high or the time is too long, excessive oxygen-containing structures may be formed in the fibers, with CO or CO in subsequent high temperature heat treatment2The carbon in the skeleton is taken away by the escaping form of the carbon fiber, a plurality of holes are left, the structural defects in the fiber are caused, and the carbonization yield and the mechanical property of the final carbon fiber are seriously reduced.
The domestic patent CN101876096A is a production method of a precursor oiling agent used in the production process of carbon fibers, and the precursor oiling agent has reasonable process and simple operation. The oiling agent has the advantages of fast penetration and good lubricity during use, can improve the strand integrity, can form a film on the surface of a monofilament, is high-temperature resistant, does not stick a roller in the process of drying a densification roller, can well protect the protofilament in the whole pre-oxidation process and the initial stage of low-temperature carbonization, greatly reduces the phenomena of monofilament adhesion and doubling, reduces the surface defects of the protofilament and improves the performance of the protofilament.
Disclosure of Invention
The invention aims to solve the technical problems of large coke discharging amount and large residual quantity of silicon dioxide of a low-carbon furnace in the prior art, and provides a preparation method of polyacrylonitrile-based carbon fiber.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a preparation method of polyacrylonitrile-based carbon fiber comprises at least two steps of oiling, drying and densification; wherein, the polyacrylonitrile precursor after finishing the first oiling and the dry densification is soaked by water bath, the water content of the polyacrylonitrile precursor is controlled to be 5% -20%, and then the second oiling and the dry densification are carried out.
In the above technical solution, the preparation method preferably specifically comprises the following steps:
(1) oiling:
a) the polyacrylonitrile protofilament after washing enters a first oiling and extrusion roller for extrusion, and then enters a first drying densification step;
b) soaking the polyacrylonitrile protofilament obtained in the step a) in a water bath, extruding the polyacrylonitrile protofilament by using an extrusion roller, and controlling the water content of the protofilament to be 5-20%;
c) performing second oiling on the polyacrylonitrile precursor obtained in the step b), extruding the polyacrylonitrile precursor leaving the second oiling, and performing second drying densification to finish the oiling process of the polyacrylonitrile-based carbon fiber precursor;
or d) repeating the steps b) and c) or repeating the step c), finishing the oiling process of the polyacrylonitrile-based carbon fiber precursor,
(2) performing steam drafting and heat setting on the oiled polyacrylonitrile precursor to obtain a polyacrylonitrile copolymer precursor;
(3) performing thermal stabilization treatment on a polyacrylonitrile precursor at the temperature of 180-280 ℃ for 30-60 min, wherein the total draft is 0-6%, and obtaining a thermal stabilization fiber;
(4) and carbonizing the thermal stabilization fiber at the temperature of 300-1500 ℃ for 2-10 min under the inert gas condition, wherein the total draft is-4-5%, and thus obtaining the polyacrylonitrile-based carbon fiber.
In the technical scheme, the temperature of the first drying densification in the step (1) is between 70 and 100 ℃, and the duration of the first drying densification is between 20 and 60 seconds. The temperature of the second drying densification in the step (1) is between 100 and 140 ℃, and the time of the second drying densification is between 20 and 60 seconds. Soaking in water bath in the step (1), wherein pure water is used as a medium, and the conductivity of the pure water is 0.1-10 us/cm at 25 ℃; the dipping temperature is between 20 ℃ and 60 ℃, and the dipping time is not less than 5 s. And (2) soaking in water bath in the step (1), and controlling the water content of the polyacrylonitrile-based carbon fiber precursor soaked in the water bath to be between 5 and 10 percent.
In the technical scheme, the polyacrylonitrile copolymer precursor is binary or ternary copolymer, wherein the mass fraction of the propenyl monomer is not less than 92%, and the comonomer comprises acids, esters and amides. The polyacrylonitrile copolymer precursor is 3-48K. The polyacrylonitrile copolymer precursor is prepared by wet method or dry-jet wet spinning.
In the above technical solution, the preferable solution is: the thermal stabilization temperature in the step (2) is 180-270 ℃, and the temperature is divided into 4-6 temperature zones. The thermal stabilization time is 40-55 min. The carbonization treatment in the step (3) comprises two processes of low-temperature carbonization and high-temperature carbonization; the low-temperature carbonization temperature is 300-700 ℃, the heat treatment time is 2-6 min, and the drafting is 0-6%; the high-temperature carbonization temperature is 1000-1500 ℃, the heat treatment time is 1-4 min, and the drafting is-4 to-1 percent.
According to the invention, the method that the water bath is added between two oiling steps to soak and control the water content of the polyacrylonitrile protofilament is adopted, so that the oiling rate and the oiling uniformity of the protofilament are improved, and the high-performance carbon fiber is prepared through thermal stabilization and low and high temperature carbonization treatment, so that the coke discharge amount of a low-carbon furnace and the residue of silica are greatly reduced, and the tensile strength and the tensile modulus of the carbon fiber are obviously improved.
By adopting the technical scheme of the invention, the tensile strength of the prepared carbon fiber is higher than 4800MPa, the tensile modulus is higher than 240GPa, the low carbon coke discharge amount is less, the generation amount of silicon dioxide is less, the cleaning period exceeds 6 months, and a better technical effect is obtained.
The embodiment proves that the carbon fiber is prepared by adding the water bath between two oiling processes for soaking and controlling the water content, and further through thermal stabilization and low and high temperature carbonization treatment, the mechanical property of the final carbon fiber can be controlled, the service life of the low carbon furnace is prolonged, the operation cycle of the low carbon furnace is greatly prolonged, and the application prospect is good.
The present invention will be further illustrated by the following specific examples.
Detailed Description
[ example 1 ]
The copolymerization components of the precursor are respectively 95.5 percent of acrylonitrile, 3.5 percent of methyl acrylate and 1 percent of itaconic acid. The polyacrylonitrile protofilament from the washed polyacrylonitrile enters a first oiling step and an extrusion roller for extrusion, and then enters a first drying step for densification, wherein the temperature is 70 ℃ and the time is 20 s; after water bath soaking and extrusion by an extrusion roller, controlling the water content of the precursor to be 5% by adjusting the pressure between the extrusion roller and an oiling separation bath roller, oiling in a second step, extruding the polyacrylonitrile precursor which leaves the second oiling step, and performing drying densification in the second step at the temperature of 100 ℃ for 20 s; finally, steam drafting and heat setting are carried out, the steam pressure of the steam drafting is 3 kilograms, and the drafting multiple is 2.5; the steam pressure of the heat setting is 1 kilogram, the drafting multiple is 0.96, and the polyacrylonitrile protofilament is obtained. Performing thermal stabilization treatment on the polyacrylonitrile precursor at the temperature of 180-280 ℃ by 5 air atmosphere heating furnaces, wherein the temperature is 180 ℃, 220 ℃, 235 ℃, 255 ℃ and 275 ℃; the total heating time was 60min, and the total draft was 2%, yielding a thermostabilized fiber. The obtained heat-stabilized fiber is carbonized at low temperature and carbonized at high temperature in nitrogen. The low-temperature carbonization temperature is 300-700 ℃, the heat treatment time is 4min, and the drafting is 3%; the high-temperature carbonization temperature is 1000-1500 ℃, the heat treatment time is 2min, and the drafting is-3%. The carbon fiber is low in carbon coke discharge amount and low in silicon dioxide generation amount, is cleaned once every 7 months, and is subjected to mechanical property test according to the national standard GB-T3362-2005.
[ example 2 ]
The copolymerization components of the precursor are respectively 96.0 percent of acrylonitrile, 3.5 percent of methyl acrylate and 0.5 percent of acrylamide. The polyacrylonitrile protofilament from the washed polyacrylonitrile enters a first oiling step and an extrusion roller for extrusion, and then enters a first drying step for densification, wherein the temperature is 100 ℃ and the time is 60 seconds; after water bath soaking and extrusion by an extrusion roller, controlling the water content of the precursor to be 10% by adjusting the pressure between the extrusion roller and an oiling separation bath roller, oiling in a second step, extruding the polyacrylonitrile precursor which leaves the second oiling step, and performing drying densification in a second step at the temperature of 140 ℃ for 60 s; finally, steam drafting and heat setting are carried out, the steam pressure of the steam drafting is 2.5 kilograms, and the drafting multiple is 2.2; the steam pressure of the heat setting is 1.2 kg, the drafting multiple is 0.95, and the polyacrylonitrile protofilament is obtained. Performing thermal stabilization treatment on the polyacrylonitrile precursor at the temperature of 180-280 ℃ by 5 air atmosphere heating furnaces, wherein the temperature is 180 ℃, 220 ℃, 235 ℃, 250 ℃ and 265 ℃; the total heating time was 60min, and the total draft was 2%, yielding a thermostabilized fiber. The obtained heat-stabilized fiber is carbonized at low temperature and carbonized at high temperature in nitrogen. The low-temperature carbonization temperature is 300-700 ℃, the heat treatment time is 4min, and the drafting is 3%; the high-temperature carbonization temperature is 1000-1500 ℃, the heat treatment time is 2min, and the drafting is-3%. The carbon fiber is low in carbon coke discharge amount and low in silicon dioxide generation amount, is cleaned once every 8 months, and is subjected to mechanical property test according to the national standard GB-T3362-2005.
[ example 3 ]
The copolymerization components of the precursor are respectively 97.0 percent of acrylonitrile and 3.0 percent of acrylamide. The polyacrylonitrile protofilament from the washed polyacrylonitrile enters a first oiling step and an extrusion roller for extrusion, and then enters a first drying step for densification, wherein the temperature is 100 ℃ and the time is 60 seconds; after water bath soaking and extrusion by an extrusion roller, controlling the water content of the precursor to be 20% by adjusting the pressure between the extrusion roller and an oiling separation bath roller, oiling in a second step, extruding the polyacrylonitrile precursor which leaves the second oiling step, and performing drying densification in a second step at the temperature of 140 ℃ for 60 s; finally, steam drafting and heat setting are carried out, the steam pressure of the steam drafting is 3.5 kilograms, and the drafting multiple is 2.7; the steam pressure of the heat setting is 1 kilogram, the drafting multiple is 0.97, and the polyacrylonitrile protofilament is obtained. Performing thermal stabilization treatment on the polyacrylonitrile precursor at the temperature of 180-280 ℃ by using 5 air atmosphere heating furnaces, wherein the temperature is 205 ℃, 220 ℃, 235 ℃, 250 ℃ and 255 ℃; the total heating time was 60min, and the total draft was 2%, yielding a thermostabilized fiber. The obtained heat-stabilized fiber is carbonized at low temperature and carbonized at high temperature in nitrogen. The low-temperature carbonization temperature is 300-700 ℃, the heat treatment time is 4min, and the drafting is 3%; the high-temperature carbonization temperature is 1000-1500 ℃, the heat treatment time is 2min, and the drafting is-3%. The carbon fiber is low in carbon coke discharge amount and low in silicon dioxide generation amount, is cleaned once every 9 months, and is subjected to mechanical property test according to the national standard GB-T3362-2005.
[ example 4 ]
The copolymerization components of the precursor are respectively 96.0 percent of acrylonitrile, 3.0 percent of methacrylic acid and 1.0 percent of itaconic acid. The polyacrylonitrile protofilament from the washed polyacrylonitrile enters a first oiling step and an extrusion roller for extrusion, and then enters a first drying step for densification, wherein the temperature is 100 ℃ and the time is 60 seconds; after water bath soaking and extrusion by an extrusion roller, controlling the water content of the precursor to be 10% by adjusting the pressure between the extrusion roller and an oiling separation bath roller, oiling in a second step, extruding the polyacrylonitrile precursor which leaves the second oiling step, and performing drying densification in a second step at the temperature of 140 ℃ for 60 s; finally, steam drafting and heat setting are carried out, the steam pressure of the steam drafting is 3 kilograms, and the drafting multiple is 2.2; the steam pressure of the heat setting is 1 kilogram, the drafting multiple is 0.96, and the polyacrylonitrile protofilament is obtained. Performing thermal stabilization treatment on the polyacrylonitrile precursor at the temperature of 180-280 ℃ by using 5 air atmosphere heating furnaces, wherein the temperature is 220 ℃, 230 ℃, 240 ℃, 250 ℃ and 255 ℃; the total heating time was 60min, and the total draft was 2%, yielding a thermostabilized fiber. The obtained heat-stabilized fiber is carbonized at low temperature and carbonized at high temperature in nitrogen. The low-temperature carbonization temperature is 300-700 ℃, the heat treatment time is 4min, and the drafting is 3%; the high-temperature carbonization temperature is 1000-1500 ℃, the heat treatment time is 2min, and the drafting is-3%. The carbon fiber is low in carbon coke discharge amount and low in silicon dioxide generation amount, is cleaned once every 6 months, and is subjected to mechanical property test according to the national standard GB-T3362-2005.
[ example 5 ]
The copolymerization components of the precursor are respectively 96.0 percent of acrylonitrile, 2.5 percent of methyl methacrylate and 1.5 percent of itaconic acid. The polyacrylonitrile protofilament from the washed polyacrylonitrile enters a first oiling step and an extrusion roller for extrusion, and then enters a first drying step for densification, wherein the temperature is 100 ℃ and the time is 60 seconds; after water bath soaking and extrusion by an extrusion roller, controlling the water content of the precursor to be 10% by adjusting the pressure between the extrusion roller and an oiling separation bath roller, oiling in a second step, extruding the polyacrylonitrile precursor which leaves the second oiling step, and performing drying densification in a second step at the temperature of 140 ℃ for 60 s; finally, steam drafting and heat setting are carried out, the steam pressure of the steam drafting is 3.5 kilograms, and the drafting multiple is 2.5; the steam pressure of the heat setting is 1 kg, the drafting multiple is 0.95, and the polyacrylonitrile protofilament is obtained. Performing thermal stabilization treatment on the polyacrylonitrile precursor at the temperature of 180-280 ℃ by using 5 air atmosphere heating furnaces, wherein the temperature is 220 ℃, 230 ℃, 240 ℃, 250 ℃ and 255 ℃; the total heating time was 60min, and the total draft was 2%, yielding a thermostabilized fiber. The obtained heat-stabilized fiber is carbonized at low temperature and carbonized at high temperature in nitrogen. The low-temperature carbonization temperature is 300-700 ℃, the heat treatment time is 4min, and the drafting is 3%; the high-temperature carbonization temperature is 1000-1500 ℃, the heat treatment time is 2min, and the drafting is-3%. The carbon fiber is low in carbon coke discharge amount and low in silicon dioxide generation amount, is cleaned once every 7 months, and is subjected to mechanical property test according to the national standard GB-T3362-2005.
[ example 6 ]
The copolymerization components of the precursor are respectively 98.0 percent of acrylonitrile and 2.0 percent of acrylamide. The polyacrylonitrile protofilament from the washed polyacrylonitrile enters a first oiling step and an extrusion roller for extrusion, and then enters a first drying step for densification, wherein the temperature is 100 ℃ and the time is 60 seconds; after water bath soaking and extrusion by an extrusion roller, controlling the water content of the precursor to be 10% by adjusting the pressure between the extrusion roller and an oiling separation bath roller, oiling in a second step, extruding the polyacrylonitrile precursor which leaves the second oiling step, and performing drying densification in a second step at the temperature of 140 ℃ for 60 s; finally, steam drafting and heat setting are carried out, the steam pressure of the steam drafting is 3.5 kilograms, and the drafting multiple is 2.5; the steam pressure of the heat setting is 1 kilogram, the drafting multiple is 0.95, and the polyacrylonitrile protofilament is obtained. Performing thermal stabilization treatment on the polyacrylonitrile precursor at the temperature of 180-280 ℃ by using 5 air atmosphere heating furnaces, wherein the temperature is 220 ℃, 230 ℃, 240 ℃, 250 ℃ and 255 ℃; the total heating time was 45min, and the total draft was 2%, yielding a thermostabilized fiber. The obtained heat-stabilized fiber is carbonized at low temperature and carbonized at high temperature in nitrogen. The low-temperature carbonization temperature is 300-700 ℃, the heat treatment time is 4min, and the drafting is 3%; the high-temperature carbonization temperature is 1000-1500 ℃, the heat treatment time is 2min, and the drafting is-3%. The carbon fiber is low in carbon coke discharge amount and low in silicon dioxide generation amount, is cleaned once every 8 months, and is subjected to mechanical property test according to the national standard GB-T3362-2005.
[ example 7 ]
The copolymerization components of the precursor are respectively 97.5 percent of acrylonitrile and 2.5 percent of itaconic acid. The polyacrylonitrile protofilament from the washed polyacrylonitrile enters a first oiling step and an extrusion roller for extrusion, and then enters a first drying step for densification, wherein the temperature is 100 ℃ and the time is 60 seconds; after water bath soaking and extrusion by an extrusion roller, controlling the water content of the precursor to be 10% by adjusting the pressure between the extrusion roller and an oiling separation bath roller, oiling in a second step, extruding the polyacrylonitrile precursor which leaves the second oiling step, and performing drying densification in a second step at the temperature of 140 ℃ for 60 s; finally, steam drafting and heat setting are carried out, the steam pressure of the steam drafting is 3.5 kilograms, and the drafting multiple is 2.5; the steam pressure of the heat setting is 1 kilogram, the drafting multiple is 0.95, and the polyacrylonitrile protofilament is obtained. Performing thermal stabilization treatment on the polyacrylonitrile precursor at the temperature of 180-280 ℃ by using 5 air atmosphere heating furnaces, wherein the temperature is 220 ℃, 230 ℃, 240 ℃, 250 ℃ and 255 ℃; the total heating time was 45min, and the total draft was 4.5%, yielding a thermostabilized fiber. The obtained heat-stabilized fiber is carbonized at low temperature and carbonized at high temperature in nitrogen. The low-temperature carbonization temperature is 300-700 ℃, the heat treatment time is 4min, and the drafting is 3%; the high-temperature carbonization temperature is 1000-1500 ℃, the heat treatment time is 2min, and the drafting is-3%. The carbon fiber is low in carbon coke discharge amount and low in silicon dioxide generation amount, is cleaned once every 9 months, and is subjected to mechanical property test according to the national standard GB-T3362-2005.
[ COMPARATIVE EXAMPLE 1 ]
The copolymerization components of the precursor are respectively 95.5 percent of acrylonitrile, 3.5 percent of methyl acrylate and 1 percent of itaconic acid. The polyacrylonitrile protofilament from the washed polyacrylonitrile enters a first oiling step and an extrusion roller for extrusion, and then enters a first drying step for densification, wherein the temperature is 70 ℃ and the time is 20 s; performing second oiling, extruding the polyacrylonitrile protofilament which leaves the second oiling, and performing second drying densification at the temperature of 100 ℃ for 20 s; finally, steam drafting and heat setting are carried out, the steam pressure of the steam drafting is 3 kilograms, and the drafting multiple is 2.5; the steam pressure of the heat setting is 1 kilogram, the drafting multiple is 0.96, and the polyacrylonitrile protofilament is obtained. Performing thermal stabilization treatment on the precursor fiber at the temperature of 180-280 ℃ by 5 air atmosphere heating furnaces, wherein the temperature is 180 ℃, 220 ℃, 235 ℃, 255 ℃ and 275 ℃; the total heating time was 60min, and the total draft was 2%, yielding a thermostabilized fiber. The obtained heat-stabilized fiber is carbonized at low temperature and carbonized at high temperature in nitrogen. The low-temperature carbonization temperature is 300-700 ℃, the heat treatment time is 4min, and the drafting is 3%; the high-temperature carbonization temperature is 1000-1500 ℃, the heat treatment time is 2min, and the drafting is-3%. The coke discharging amount of low carbon is large, the production amount of silicon dioxide is large, and the cleaning is carried out once every 1 month. And testing the mechanical property of the carbon fiber according to the national standard GB-T3362-2005.
It can be seen from comparative example 1 and example 1 that the tensile strength and tensile modulus of the carbon fiber can be significantly increased by adopting the scheme of the invention; the coke discharging amount of the low-carbon furnace and the residue of the silicon dioxide are reduced, and the cleaning period of the coke and the silicon dioxide in the low-carbon furnace is prolonged to more than 6 months.
TABLE 1
Claims (9)
1. A preparation method of polyacrylonitrile-based carbon fibers comprises at least two steps of oiling, drying and densification, and steps of thermal stabilization and carbonization; soaking the polyacrylonitrile protofilament subjected to the first oiling and drying densification in a water bath, controlling the water content of the protofilament to be 5-20%, and then performing the second oiling and drying densification; soaking in water bath, wherein pure water is used as a medium, and the conductivity of the pure water is 0.1-10 us/cm at 25 ℃; the dipping temperature is between 20 ℃ and 60 ℃, and the dipping time is not less than 5 s.
2. The method for preparing polyacrylonitrile-based carbon fiber according to claim 1, characterized by comprising the following steps:
(1) oiling:
a) the polyacrylonitrile protofilament after washing enters a first oiling and extrusion roller for extrusion, and then enters a first drying densification step;
b) soaking the polyacrylonitrile protofilament obtained in the step a) in a water bath, extruding the polyacrylonitrile protofilament by using an extrusion roller, and controlling the water content of the protofilament to be 5-20%;
c) performing second oiling on the polyacrylonitrile precursor obtained in the step b), extruding the polyacrylonitrile precursor leaving the second oiling, and performing second drying densification to finish the oiling process of the polyacrylonitrile precursor;
or d) repeating the steps b) and c) or repeating the step c), finishing the oiling process of the polyacrylonitrile protofilament,
(2) steam drafting and heat setting the oiled polyacrylonitrile protofilament to obtain a polyacrylonitrile copolymer precursor;
(3) performing thermal stabilization treatment on a polyacrylonitrile precursor at the temperature of 180-280 ℃ for 30-60 min, wherein the total draft is 0-6%, and obtaining a thermal stabilization fiber;
(4) and carbonizing the thermal stabilization fiber at the temperature of 300-1500 ℃ for 2-10 min under the inert gas condition, wherein the total draft is-4-5%, and thus obtaining the polyacrylonitrile-based carbon fiber.
3. The method for preparing polyacrylonitrile-based carbon fiber according to claim 1, characterized in that the temperature of the first dry densification is between 70 ℃ and 100 ℃, and the duration of the first dry densification is between 20s and 60 s; the temperature of the second drying densification is between 100 and 140 ℃, and the time of the second drying densification is between 20 and 60 seconds.
4. The method for preparing polyacrylonitrile-based carbon fiber according to claim 1, characterized in that the water content of the polyacrylonitrile-based carbon fiber after being soaked in water bath is controlled between 5% and 10% by adjusting the pressure between the extrusion roller and the upper separation bath roller.
5. The method for producing polyacrylonitrile-based carbon fibers according to claim 1, wherein the polyacrylonitrile filaments are made of a binary or ternary polyacrylonitrile copolymer, wherein the mass fraction of the acrylonitrile-based unit of the polyacrylonitrile copolymer is not less than 92%.
6. The method for preparing polyacrylonitrile-based carbon fibers according to claim 1, characterized in that the number of the monofilaments in the polyacrylonitrile precursor filament tow is 3-48K; the polyacrylonitrile filaments are preferably prepared by wet or dry-jet wet spinning.
7. The preparation method of polyacrylonitrile-based carbon fiber according to claim 2, characterized in that the thermal stabilization temperature in the step (3) is 180-270 ℃, and is divided into 4-6 temperature zones.
8. The method for producing polyacrylonitrile-based carbon fibers according to claim 7, characterized in that the thermal stabilization temperature is 200 to 260 ℃; the thermal stabilization time is 40-55 min.
9. The method for preparing polyacrylonitrile-based carbon fiber according to claim 1, characterized in that the carbonization treatment in the step (4) includes two processes of low-temperature carbonization and high-temperature carbonization; the low-temperature carbonization temperature is 300-700 ℃, the heat treatment time is 2-6 min, and the drafting is 0-6%; the high-temperature carbonization temperature is 1000-1500 ℃, the heat treatment time is 1-4 min, and the drafting is-4 to-1 percent.
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| JP2001355120A (en) * | 2000-06-12 | 2001-12-26 | Toho Tenax Co Ltd | Large tow precursor, method for producing the same and method for producing carbon fiber |
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