CN111088558B - Preparation method of polyacrylonitrile-based carbon fiber - Google Patents
Preparation method of polyacrylonitrile-based carbon fiber Download PDFInfo
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- 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
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Abstract
The invention relates to a preparation method of polyacrylonitrile-based carbon fibers, which mainly solves the problems of more carbon fiber broken filaments, poor mechanical property and large coke discharge amount of a low-carbon furnace in the prior art. The invention adopts a preparation method of polyacrylonitrile-based carbon fiber, which comprises the steps of oiling, drying densification, steam drafting, heat setting, heat stabilization and carbonization; the method is characterized in that oiling and drying densification are carried out at least twice, at least one step is carried out before the steps of steam drafting and heat setting, and at least one step is carried out after the steps of steam drafting and heat setting, so that the problem is well solved, and the method can be used for producing high-performance carbon fibers.
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 can not melt and combust in the subsequent carbonization process and keep a thermodynamic stable state, and is 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 treatment 2 The 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 protofilament oiling agent used in the production process of carbon fibers, and the protofilament 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 more carbon fiber broken filaments, poor mechanical property and large coke discharge amount 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 the steps of oiling, drying densification, steam drafting, heat setting, heat stabilization and carbonization; wherein the oiling and dry densification is performed at least two times, at least one time is performed before the steam drawing and heat setting step, and at least one time is performed after the steam drawing and heat setting step.
In the technical scheme, the oiling and drying densification preferably has n steps, and the method specifically comprises the following steps:
a) Feeding the polyacrylonitrile precursor from the washed polyacrylonitrile precursor into a first oiling step, extruding by an extrusion roller, and performing first drying densification;
b) Oiling and drying densification are carried out on the obtained polyacrylonitrile protofilament for the second to the x-th channels;
c) Carrying out steam drafting and heat setting on the obtained polyacrylonitrile protofilament;
d) Oiling and drying densification are carried out on the obtained polyacrylonitrile protofilament from the (x + 1) th path to the nth path, so that the oiling process is completed, and a polyacrylonitrile precursor is obtained;
wherein n is 3 or more, and x is 2 or more and (n-1) or less;
e) Performing thermal stabilization treatment on a polyacrylonitrile precursor at the temperature of between 180 and 280 ℃ for 30 to 60min, wherein the total draft is 0 to 6 percent, and obtaining thermal stabilization fibers;
f) 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 above-described aspect, as another preferable aspect: the oiling and drying densification preferably has n channels, and specifically comprises the following steps:
a) The polyacrylonitrile protofilament from washing enters into first oiling and extrusion roller to be extruded, and then enters into first drying densification;
b) Carrying out steam drafting and heat setting on the obtained polyacrylonitrile protofilament;
c) Performing second-nth oiling and drying densification on the obtained polyacrylonitrile precursor to finish the oiling process to obtain a polyacrylonitrile precursor;
wherein n is equal to or greater than 3.
Finishing the oiling process of the polyacrylonitrile protofilament by adopting the step (1) or the step (2) to obtain a polyacrylonitrile copolymer precursor;
d) Performing thermal stabilization treatment on a polyacrylonitrile precursor at the temperature of between 180 and 280 ℃ for 30 to 60min, wherein the total draft is 0 to 6 percent, and obtaining thermal stabilization fibers;
e) 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 above technical solution, the temperature of the first drying densification is preferably 70-100 ℃, and the duration of the first drying densification is preferably 20-60 s. The temperature of the second drying densification is preferably between 100 and 140 ℃, and the time of the second drying densification is between 20 and 60 seconds. The temperature of the third drying densification is between 70 and 100 ℃, and the time of the third drying densification is between 5 and 20 seconds. The preparation of the oiling agent adopts pure water with the conductivity of 0.1-10 mu s/cm at 25 ℃. The mass concentration of the oil agent applied on the first oil is between 1.5 and 3 percent; the mass concentration of the oil agent applied in the second oiling process is 2-4%; the mass concentration of the oil agent applied in the third oil is between 0.5 and 1.5 percent.
In the technical scheme, the polyacrylonitrile precursor is preferably prepared from a polyacrylonitrile copolymerization precursor, the polyacrylonitrile copolymerization precursor is preferably binary or ternary copolymerization, wherein the mass fraction of the allyl monomer is not less than 92%, and the comonomer comprises acids, esters and amides. More preferably, the number of the monofilaments in the polyacrylonitrile precursor filament tow is preferably 3 to 48K. The polyacrylonitrile filaments are preferably prepared by wet or dry-jet wet spinning.
In the above technical solution, the preferable solution is: the thermal stabilization temperature is 180-270 ℃, and the temperature is divided into 4-6 temperature zones. The thermal stabilization time is 40-55 min. The carbonization treatment 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, on the basis of the traditional oiling route, oiling is added after steam drafting and heat setting, and then the oiling rate and the oiling uniformity of the precursor are improved by a drying densification method, the spinning stability is improved, the adhesion of a drying densification roller to an oiling agent is reduced, and the high-performance carbon fiber is prepared by heat stabilization and low and high temperature carbonization treatment, so that the coke discharge amount of a low-carbon furnace and the residue of silicon dioxide are greatly reduced, carbon fiber broken filaments are 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 prepared carbon fiber has the tensile strength higher than 4800MPa, the tensile modulus higher than 240GPa, less carbon coke discharge, less silicon dioxide generation, less carbon fiber broken filaments and a cleaning period longer than 6 months, thereby obtaining better technical effects.
The embodiment proves that the carbon fiber is prepared by adding oiling after steam drafting and heat setting on the basis of the traditional oiling route and further by thermal stabilization and low and high temperature carbonization through a drying densification method, the mechanical property of the final carbon fiber can be controlled, the service life of a low carbon furnace is prolonged, carbon fiber broken filaments are reduced, 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 ] A method for producing a polycarbonate
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. Feeding the polyacrylonitrile precursor from the washed polyacrylonitrile precursor into a first oiling step and an extrusion roller for extrusion, wherein the mass concentration of an oiling agent for the first oiling step is 2%, and the polyacrylonitrile precursor is subjected to first drying densification at the temperature of 70 ℃ for 20s; performing second oiling, wherein the mass concentration of the oiling agent on the second oiling is 3%, extruding the polyacrylonitrile protofilament which leaves the second oiling, and performing second drying densification at the temperature of 100 ℃ for 20s; finally, steam drafting and heat setting are carried out, the steam pressure of the steam drafting is 0.3MPa, and the drafting multiple is 2.5; steam pressure of the heat setting is 0.1MPa, the drawing multiple is 0.96, the obtained protofilament is subjected to steam heat setting, then the third oiling is carried out, the mass concentration of an oiling agent on the third oiling is 1%, the protofilament leaving the third oiling is subjected to extrusion, the third drying densification is carried out, the temperature is 100 ℃, the time for the third oiling is 10s, and finally the high-performance 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 has less broken filaments, low carbon coke discharge amount and less 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 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. Feeding the polyacrylonitrile precursor from the washed polyacrylonitrile precursor into a first oiling step and an extrusion roller for extrusion, wherein the mass concentration of an oiling agent for the first oiling step is 1.5%, and the polyacrylonitrile precursor is subjected to first drying densification at the temperature of 100 ℃ for 60s; the obtained protofilament is subjected to steam drafting and heat setting, the steam pressure of the steam drafting is 0.25MPa, and the drafting multiple is 2.2; steam pressure of heat setting is 0.12MPa, drafting multiple is 0.95, then second oiling is carried out, mass concentration of oiling agent on the second oiling is 1%, the protofilament leaving the second oiling is extruded, second drying densification is carried out, temperature is 100 ℃, oiling time on the second oiling is 10s, and finally filament winding is carried out to obtain the high-performance polyacrylonitrile protofilament. 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 is 60min, the total draft is 2%, and the thermostabilization fiber is obtained. 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 has less broken filaments, less low-carbon coke discharge and less 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 3 ] A method for producing a polycarbonate
The copolymerization components of the precursor are respectively 97.0 percent of acrylonitrile and 3.0 percent of acrylamide. Feeding the polyacrylonitrile precursor from the washed polyacrylonitrile precursor into a first oiling step and an extrusion roller for extrusion, wherein the mass concentration of an oiling agent for the first oiling step is 2.5%, and the polyacrylonitrile precursor is subjected to first drying densification at the temperature of 100 ℃ for 60s; then, second oiling is carried out, the mass concentration of an oiling agent on the second oiling is 3%, the polyacrylonitrile protofilament leaving the second oiling enters second drying densification after being extruded, the temperature is 140 ℃, and the time is 60s; finally, steam drafting and heat setting are carried out, the steam pressure of the steam drafting is 0.35MPa, and the drafting multiple is 2.7; steam pressure of the heat setting is 0.1MPa, the drawing multiple is 0.97, the obtained protofilament is subjected to steam heat setting, then the third oiling is carried out, the mass concentration of an oiling agent on the third oiling is 0.8%, the protofilament leaving the third oiling is extruded, the third drying densification is carried out, the temperature is 75 ℃, the time of the third oiling is 20s, and finally the high-performance polyacrylonitrile protofilament is obtained. Performing thermal stabilization treatment on the polyacrylonitrile precursor at the temperature of between 180 and 280 ℃ by using 5 air atmosphere heating furnaces, wherein the temperature is respectively 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 has less broken filaments, less low-carbon coke discharge and less 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 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. Feeding the polyacrylonitrile precursor fiber from the washed polyacrylonitrile precursor fiber into a first oiling step and an extrusion roller for extrusion, wherein the mass concentration of an oiling agent for the first oiling step is 2%, the polyacrylonitrile precursor fiber is subjected to first drying densification at the temperature of 90 ℃ for 55s, and the obtained precursor fiber is subjected to steam drafting, wherein the steam pressure of the steam drafting is 0.3MPa, and the drafting multiple is 2.2; steam pressure of heat setting is 0.1MPa, drafting multiple is 0.96, then second oiling is carried out, mass concentration of oiling agent on the second oiling is 1.2%, the protofilament leaving the second oiling is extruded, second drying densification is carried out, temperature is 90 ℃, oiling time on the second oiling is 15s, and finally filament winding is carried out to obtain high-performance polyacrylonitrile protofilament. Obtaining the polyacrylonitrile protofilament. Performing thermal stabilization treatment on the polyacrylonitrile precursor at the temperature of 180-280 ℃ by 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 ] A method for producing a polycarbonate
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. Feeding the polyacrylonitrile precursor from the washed polyacrylonitrile precursor into a first oiling step and an extrusion roller for extrusion, wherein the mass concentration of an oiling agent for the first oiling step is 1.5%, and the polyacrylonitrile precursor is subjected to first drying densification at the temperature of 80 ℃ for 50s; performing second oiling, wherein the mass concentration of the oiling agent on the second oiling is 2.5%, extruding the polyacrylonitrile protofilament which leaves the second oiling, and performing second drying densification at the temperature of 120 ℃ for 50s; finally, performing steam drafting and heat setting, wherein the steam pressure of the steam drafting is 0.25MPa, and the drafting multiple is 2.5; steam pressure of heat setting is 0.1MPa, the drafting multiple is 0.95, steam heat setting is carried out on the obtained protofilament, then third oiling is carried out, the mass concentration of oiling agent on the third oiling is 1.2%, the protofilament leaving the third oiling is extruded, third drying densification is carried out, the temperature is 95 ℃, the time of the third oiling is 10s, and finally the high-performance polyacrylonitrile protofilament is obtained. Performing thermal stabilization treatment on the polyacrylonitrile precursor at the temperature of between 180 and 280 ℃ by using 5 air atmosphere heating furnaces, wherein the temperature is respectively 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 6 ]
The copolymerization components of the precursor are respectively 98.0 percent of acrylonitrile and 2.0 percent of acrylamide. Feeding the polyacrylonitrile precursor from the washed polyacrylonitrile precursor into a first oiling step and an extrusion roller for extrusion, wherein the mass concentration of an oiling agent for the first oiling step is 2%, and the polyacrylonitrile precursor is subjected to first drying densification at the temperature of 85 ℃ for 40s; carrying out steam drafting and heat setting on the obtained protofilament, wherein the steam pressure of the steam drafting is 0.3MPa, and the drafting multiple is 2.5; steam pressure of heat setting is 0.1MPa, the drafting multiple is 0.95, then the second oiling is carried out, the mass concentration of oiling agent on the second oiling is 1.3%, the protofilament leaving the second oiling is extruded, the second drying densification is carried out, the temperature is 95 ℃, the time for oiling on the second oiling is 10s, and finally the high-performance polyacrylonitrile protofilament is obtained after filament winding. Performing thermal stabilization treatment on the polyacrylonitrile precursor at the temperature of 180-280 ℃ by 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 6 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. And (3) feeding the polyacrylonitrile protofilament subjected to washing into a first oiling process and extruding by an extruding roller, wherein the mass concentration of an oiling agent for the first oiling process is 2%. Performing first drying densification at 100 ℃ for 60s; performing second oiling, wherein the mass concentration of the oiling agent on the second oiling is 3.5%, extruding the polyacrylonitrile protofilament which leaves the second oiling, and performing second drying densification at the temperature of 140 ℃ for 60s; finally, steam drafting and heat setting are carried out, the steam pressure of the steam drafting is 0.35MPa, and the drafting multiple is 2.5; steam pressure of heat setting is 0.1MPa, the drafting multiple is 0.95, the obtained protofilament is subjected to steam heat setting, then the third oiling is carried out, the mass concentration of an oiling agent on the third oiling is 1.2%, the protofilament leaving the third oiling is extruded, the third drying densification is carried out, the temperature is 90 ℃, the time of the third oiling is 15s, and finally the high-performance 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 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 6 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. Feeding the polyacrylonitrile precursor from the washed polyacrylonitrile precursor into a first oiling step and an extrusion roller for extrusion, wherein the mass concentration of an oiling agent for the first oiling step is 2%, and the polyacrylonitrile precursor is subjected to first drying densification at the temperature of 70 ℃ for 20s; then, second oiling is carried out, the mass concentration of an oiling agent on the second oiling is 3%, the polyacrylonitrile protofilament leaving the second oiling enters second drying densification after being extruded, the temperature is 100 ℃, and the time is 20s; finally, steam drafting and heat setting are carried out, the steam pressure of the steam drafting is 0.3MPa, and the drafting multiple is 2.5; the steam pressure of the heat setting is 0.1MPa, 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 carbon fiber has more broken filaments, more low-carbon coke discharging amount and more silicon dioxide generation amount, is cleaned once every 1 month, and is subjected to mechanical property test according to the national standard GB-T3362-2005.
[ COMPARATIVE EXAMPLE 2 ]
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. Feeding the polyacrylonitrile precursor from the washed polyacrylonitrile precursor into a first oiling step and an extrusion roller for extrusion, wherein the mass concentration of an oiling agent for the first oiling step is 2%, and the polyacrylonitrile precursor is subjected to first drying densification at the temperature of 70 ℃ for 20s; finally, performing steam drafting and heat setting, wherein the steam pressure of the steam drafting is 0.3MPa, and the drafting multiple is 2.5; the steam pressure of the heat setting is 0.1MPa, 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 is 60min, the total draft is 2%, and the thermostabilization fiber is obtained. 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 has more broken filaments, more low-carbon coke discharging amount and more silicon dioxide generation amount, is cleaned once every 20 days, and is subjected to mechanical property test according to the national standard GB-T3362-2005.
As can be seen from the embodiment 1, the comparative example 1 and the comparative example 2, the scheme of the invention can inhibit the formation of carbon fiber broken filaments, reduce the generation of low-carbon coke discharging and silicon dioxide, improve the tensile strength and the tensile modulus of the carbon fiber and improve the cleaning period of tar and silicon dioxide in a low-carbon furnace to more than 6 months.
TABLE 1
Claims (11)
1. A preparation method of polyacrylonitrile-based carbon fibers comprises the steps of oiling, drying densification, steam drafting, heat setting, heat stabilization and carbonization; the method is characterized in that the oiling and drying densification is carried out by n times, wherein n is more than or equal to 3, at least one time is carried out before the steam drawing and heat setting step, and at least one time is carried out after the steam drawing and heat setting step; wherein the temperature of the first drying densification is between 70 and 100 ℃, and the time length of the first drying densification is between 20 and 60s; the temperature of the second drying densification is between 100 ℃ and 140 ℃, and the time duration of the second drying densification is between 20s and 60s; the temperature of the third drying densification is between 70 and 100 ℃, and the time of the third drying densification is between 5 and 20s.
2. The method for preparing polyacrylonitrile-based carbon fibers according to claim 1, wherein the oiling and dry densification has n passes, specifically comprising the steps of:
a) The polyacrylonitrile protofilament from washing enters into first oiling and extrusion roller to be extruded, and then enters into first drying densification;
b) Performing second-path oiling to the obtained polyacrylonitrile protofilament, performing the x-path oiling, drying and densifying;
c) Carrying out steam drafting and heat setting on the obtained polyacrylonitrile protofilament;
d) Oiling the obtained polyacrylonitrile protofilament in the (x + 1) th to nth processes, drying and densifying to finish the oiling process;
wherein n is 3 or more, and x is 2 or more and (n-1) or less;
e) Performing thermal stabilization treatment on a polyacrylonitrile precursor at the temperature of between 180 and 280 ℃ for 30 to 60min, wherein the total draft is 0 to 6 percent, and obtaining thermal stabilization fibers;
f) 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, wherein the oiling and dry densification has n passes, specifically comprising the steps of:
a) Feeding the polyacrylonitrile precursor from the washed polyacrylonitrile precursor into a first oiling step, extruding by an extrusion roller, and performing first drying densification;
b) Carrying out steam drafting and heat setting on the obtained polyacrylonitrile protofilament;
c) Performing second-nth oiling and drying densification on the obtained polyacrylonitrile protofilament to finish the oiling process;
wherein n is greater than or equal to 3;
d) Performing thermal stabilization treatment on a polyacrylonitrile precursor at the temperature of between 180 and 280 ℃ for 30 to 60min, wherein the total draft is 0 to 6 percent, and obtaining thermal stabilization fibers;
e) 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.
4. The method for preparing polyacrylonitrile-based carbon fiber according to any one of claims 1 to 3, characterized in that pure water with an electric conductivity of 0.1 to 10 μ s/cm at 25 ℃ is adopted in the preparation of the oil agent in the oiling.
5. The preparation method of the polyacrylonitrile-based carbon fiber according to any one of claims 1 to 3, wherein the mass concentration of the oil agent applied to the first oiling process is 1.5-3%; the mass concentration of the oiling agent applied in the second oil is 2-4%; the mass concentration of the oiling agent applied in the third step is 0.5-1.5%.
6. The method for preparing polyacrylonitrile-based carbon fibers according to claim 1, wherein the polyacrylonitrile filaments are prepared from a binary or ternary polyacrylonitrile copolymer, wherein the mass fraction of the acrylonitrile unit of the polyacrylonitrile copolymer is not less than 92%.
7. The method for preparing polyacrylonitrile-based carbon fiber according to claim 1, characterized in that the number of the monofilaments in the polyacrylonitrile precursor filament tow is 3 to 48K.
8. The method for preparing polyacrylonitrile-based carbon fiber according to claim 7, characterized in that the polyacrylonitrile precursor is prepared by a wet method or a dry-jet wet spinning method.
9. The method according to claim 2 or 3, wherein the thermal stabilization temperature is 180-270 ℃ and is divided into 4-6 temperature zones.
10. The method for preparing polyacrylonitrile-based carbon fibers according to claim 9, characterized in that the heat stabilization temperature is 200-260 ℃; the thermal stabilization time is 40-55 min.
11. The method for producing polyacrylonitrile-based carbon fibers according to claim 1, characterized in that the carbonization treatment 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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| CN1417393A (en) * | 2002-12-16 | 2003-05-14 | 中国科学院山西煤炭化学研究所 | Prepn of polyacrylonitrile-base high-performance raw carbon fiber |
| CN101724922A (en) * | 2009-11-26 | 2010-06-09 | 中复神鹰碳纤维有限责任公司 | Method for preparing high-strength polyacrylonitrile-based precursor for carbon fiber |
| CN102766989A (en) * | 2012-07-25 | 2012-11-07 | 北京化工大学 | Middle-modulus high-strength polyacrylonitrile-based carbon fiber, and preparation method thereof |
| CN106592019A (en) * | 2015-10-19 | 2017-04-26 | 中国石油化工股份有限公司 | Polyacrylonitrile-based high-performance carbon fiber preparation method |
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| CN101724922A (en) * | 2009-11-26 | 2010-06-09 | 中复神鹰碳纤维有限责任公司 | Method for preparing high-strength polyacrylonitrile-based precursor for carbon fiber |
| CN102766989A (en) * | 2012-07-25 | 2012-11-07 | 北京化工大学 | Middle-modulus high-strength polyacrylonitrile-based carbon fiber, and preparation method thereof |
| CN106592019A (en) * | 2015-10-19 | 2017-04-26 | 中国石油化工股份有限公司 | Polyacrylonitrile-based high-performance carbon fiber preparation method |
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