CN115142148A - A kind of high-performance binary polyacrylonitrile-based carbon fiber precursor and preparation method thereof - Google Patents

Abstract

The invention discloses a high-performance binary polyacrylonitrile-based carbon fiber precursor and a preparation method thereof, belonging to the field of preparation of carbon fiber precursors and comprising the following steps: under the condition of nitrogen protection, dissolving acrylonitrile in N, N-dimethylformamide, adding an initiator azo iso-butylcyano formamide, reacting a second comonomer N-vinylpyridine amide in a continuous dropwise manner to obtain an acrylonitrile polymer, and then filtering, vacuum-demonomerizing and defoaming to obtain a spinning solution; and (3) carrying out dry-jet wet spinning, washing, drafting, heat setting and other processes on the spinning solution to obtain the carbon fiber precursor. According to the invention, N-vinylpyridine amide is used as a comonomer, and amide groups can increase the compactness of protofilaments; meanwhile, the amino in the amide can promote the cyclization reaction, reduce the pre-oxidation temperature and reduce the production cost; the pyridine group and the N atom in the initiator azo isobutyl cyano formamide are favorable for crosslinking reaction, promote the conversion of the pre-oxidized fiber ring-shaped aromatic structure to a two-dimensional aromatic condensed ring layer structure and improve the carbon yield.

Description

A kind of high-performance binary polyacrylonitrile-based carbon fiber precursor and preparation method thereof

technical field

The invention belongs to the field of preparation of carbon fiber precursors, in particular to a high-performance binary polyacrylonitrile-based carbon fiber precursor and a preparation method thereof.

Background technique

As a representative of high-performance fibers, carbon fiber has a variety of excellent properties, such as high strength and high modulus, electrical conductivity, good heat resistance and corrosion resistance, etc., and is widely used in aerospace, sports and leisure, industry and other fields.

According to the types of raw silk, carbon fibers mainly include polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, and viscose-based carbon fibers. Among them, polyacrylonitrile-based carbon fibers occupy more than 90% of the market share due to their simple production process and excellent comprehensive performance. They are all hotspots in carbon fiber research and industrialization. At present, Japan and the United States are in a leading position in the global carbon fiber industry. They have developed high-performance products earlier and formed industry norms. Representative companies include Japan's Toray and the United States. Hexcel has achieved polyacrylonitrile-based carbon fiber. "Standardization, Serialization, Generalization and Practicalization". Although the research on carbon fiber in my country started early, due to the weak process foundation and backward equipment technology, the quality of carbon fiber is low, the performance stability is poor, and the localization technology of polyacrylonitrile-based carbon fiber has been hovering at a low level for a long time. After entering the 21st century, my country's carbon fiber industry has developed rapidly, and a number of outstanding enterprises have emerged, achieving technological breakthroughs. At present, mass production of T300, T700, T800 and other levels has been achieved, and the technical process of T1000 level has also been achieved. progress.

The quality of polyacrylonitrile-based carbon fibers mainly depends on the quality of polyacrylonitrile precursors, and high-quality precursors are very important for the preparation of high-performance polyacrylonitrile-based carbon fibers. In the process of preparing carbon fiber precursors, a second monomer or a third monomer is usually introduced to improve the shortcomings of poor solubility of acrylonitrile homopolymer, difficulty in spinning, and concentrated heat release. Usually, there are three main types of comonomers added. : Carboxylic acids, carboxylic acid esters, amides, carboxylic acid comonomers mainly include itaconic acid, acrylic acid, methacrylic acid; carboxylic acid ester comonomers mainly include methyl acrylate, methyl methacrylate; Amide comonomers mainly include acrylamide and the like.

The ultimate goal of polyacrylonitrile precursor fiber is to obtain carbon fiber through carbonization, and the pre-oxidation temperature and carbon yield are important indicators to measure the quality of polyacrylonitrile-based carbon fiber precursor fiber. Every 5°C decrease in pre-oxidation temperature and every 1% increase in carbon yield can greatly reduce the cost of industrialized production of carbon fiber, which is of great significance to the production of carbon fiber. Therefore, how to further reduce the pre-oxidation temperature and improve the carbon yield has become a problem that needs to be further studied.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a high-performance binary polyacrylonitrile-based carbon fiber precursor based on these shortcomings in the prior art, which can further reduce the pre-oxidation temperature and improve the carbon yield.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

A high-performance binary polyacrylonitrile-based carbon fiber precursor, comprising the following raw materials in parts by weight: 97-99 parts of a first comonomer, 1-3 parts of a second comonomer, and 0.4-1 part of an initiator; One comonomer is acrylonitrile and the second comonomer is N-vinylpyridine amide.

Preferably, the mass ratio of the first comonomer to the second comonomer is 97.5-98.5:1.5-2.5, and the total concentration of the monomers is 18-26 wt %, more preferably 20-24 wt %. The initiator accounts for 0.4 to 1.0 wt % of the total monomer mass, more preferably 0.4 to 0.7 wt %.

Preferably, the mass ratio of the first comonomer to the second comonomer is 98:2.

Preferably, the initiator includes azoisobutylcyanoformamide.

Preferably, the N-vinyl pyridine amide includes one or more of N-vinyl-2-pyridine amide, N-vinyl-3-pyridine amide, and N-vinyl-4-pyridine amide.

The general structural formula of the second comonomer N-vinylpyridine amide is:

其中R为

where R is

Preferably, the raw material further includes a solvent, and the solvent includes N,N-dimethylformamide, and the amount thereof is 284-455 parts.

Preferably, the diameter of the carbon fiber precursor is 11-13um, the strength is 8.9-12.1cN/dtex, and the carbon yield is greater than 54%.

In order to improve the heat resistance and carbon yield of polyacrylonitrile fibers, the present invention uses N-vinylpyridine amide as a comonomer and azoisobutyl cyanoformamide as an initiator, and adopts the method of solution polymerization to prepare spinning Precursor, the amide group can improve the hydrophilicity of the polymer, promote the double diffusion of fiber forming, increase the compactness of the precursor, and obtain high-quality precursor; the amino group in the amide group can promote the cyclization reaction and further reduce the pre-oxidation temperature. , reducing the production cost; at the same time, the N atom in the pyridine group is conducive to the cross-linking reaction, promoting the transformation of the cyclic aromatic structure of the pre-oxygen fiber to the two-dimensional aromatic condensed ring layer structure, and improving the carbon yield.

A preparation method of the above-mentioned high-performance binary polyacrylonitrile-based carbon fiber precursor is characterized in that, comprising the following steps:

A: The first comonomer and the initiator are dissolved in a solvent in proportion, the second comonomer is continuously added dropwise, and a polymerization reaction is carried out under a certain temperature condition to obtain an acrylonitrile polymer, Then through filtration, de-single and defoaming to obtain spinning dope;

B: The carbon fiber precursor is obtained by subjecting the spinning dope through secondary filtration, spinning, water washing, hot water drawing, oiling, drying and densification, and high-pressure steam drawing.

The continuous dripping method ensures that the second comonomer is evenly distributed on each segment of the precursor, and ensures the improvement of the overall performance of the carbon fiber precursor. If all the second comonomer is added to the reaction kettle at the beginning, due to the relatively high activity of the second comonomer, as the reaction proceeds, the concentration of the second comonomer gradually decreases, resulting in polymer molecules The chain structure changes, and the raw silk performance is unstable.

Preferably, it includes the following steps:

A: Under nitrogen protection conditions, the first comonomer and the initiator are dissolved in the solvent in proportion by mechanical stirring, the second comonomer is continuously added dropwise, and the temperature is raised to the reaction temperature for the first 30 minutes 60-70 ℃, more preferably 62-67 ℃, then keep at this temperature to carry out the polymerization reaction for 12-20 hours, more preferably 14-18 hours, and finally raise the temperature to 80 ℃ for 2 hours to obtain the Acrylonitrile polymer, then through primary filtration, vacuum de-singling and degassing to obtain the spinning dope;

B: secondary filtration of the spinning dope, followed by the following steps:

B1: Dry-jet wet spinning is adopted. The process parameters are: the distance of the air section is 1-5 mm, the temperature of the air section is 30°C, the relative humidity is 65%, and the content of the solvent in the first coagulation bath is 50-65wt% , more preferably 55-60 wt%, the temperature of the first coagulation bath is 0-10 ℃, more preferably 3-8 ℃, the content of the solvent in the second coagulation bath is 40-50 wt%, more preferably 44-47 wt% , the temperature of the second coagulation bath is 30～40℃;

B2: multi-stage washing, the washing temperature is 50 ~ 70 ℃;

B3: carry out two-stage hot water drafting, the temperature of the first-stage hot water is 60-80°C, more preferably 68-76°C, and the drafting ratio is 1.1-1.4 times; the temperature of the second-stage hot water is 90-100°C , more preferably at 94 to 98 ° C, and the draft ratio is 1.4 to 1.8 times;

B4: Perform oiling, using amino-modified silicone oil, and the oiling rate is 0.5-1.2 wt%, more preferably 0.7-1.0 wt%.

B5: performing drying and densification, the temperature of the drying and densification is 140-160° C., more preferably 145-155° C., and the time is 0.5-2 min, preferably 0.8-1.4 min;

B5: carry out two-stage high-pressure steam drafting, the first-stage pressure is 0.1-0.3MPa, more preferably 0.2-0.25MPa, the second-stage pressure is 0.3-0.5MPa, more preferably 0.3-0.4MPa, and the total two-stage drafting pressure is 0.3-0.5MPa. The multiple is 2 to 4 times, more preferably 2.2 to 3.4 times, and the carbon fiber precursor is obtained.

Preferably, in step A, the operation of adding the second comonomer specifically includes: adding 30% of the total mass of the second comonomer to the system before the temperature rise of the polymerization reaction, and heating up to the polymerization reaction The remaining second comonomer was continuously added dropwise at the beginning of the reaction temperature, and the dropwise addition was completed within 4 hours.

Preferably, in step A, the viscosity-average molecular weight of the acrylonitrile polymer is 1.2×10 ⁵ to 2.1×10 ⁵ g/mol, more preferably 1.6×10 ⁵ to 1.8×10 ⁵ g/mol. The weight content of the acrylonitrile polymer in the silk stock solution is 16-24 wt%, more preferably 18-22 wt%; in step A, the primary filtration is carried out in a candle-wick filter with a filtration accuracy of 5um; step B In step B2, the multi-stage washing is three-stage washing, the temperature of the first-stage washing is 50-60°C, and the temperature of the second-stage washing is 50-60°C. The temperature of the third-stage washing is 60-70°C.

Compared with the prior art, implementing the present invention has the following beneficial effects:

1) The present invention adopts the amide comonomer N-vinylpyridine amide, and the hydrophilicity of the amide group can improve the hydrophilicity of the polymer, promote the double diffusion of fiber forming, increase the compactness of the precursor, and help improve the final carbon fiber. performance.

2) The amino group in the amide group can promote the cyclization reaction, further reduce the pre-oxidation temperature, and reduce the production cost.

3) The amide group and the N atom in the pyridine group left at the end of the molecular chain after the initiation of the initiator azoisobutylcyanoformamide is conducive to the cross-linking reaction and promotes the cyclic aromatic structure of the pre-oxygen fiber to the two-dimensional aromatic structure. The transformation of the fused ring layer structure improves the carbon yield.

Description of drawings

1 is a comparison diagram of the DSC curves of the acrylonitrile polymers obtained in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 of the present invention, respectively.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

Example 1

Under nitrogen protection, 9.8kg of acrylonitrile and 60g of N-vinyl-4-pyridine amide were dissolved in 31.66kg of N,N-dimethylformamide by mechanical stirring, and then 50g of azoisobutylcyanoformamide was added. , the temperature was gradually raised from 30 °C to 60 °C within 30 min, and then the remaining 140g of the second monomer N-vinyl-4-pyridine amide was continuously added dropwise. The dropwise addition was completed within 4 hours, and the reaction was maintained at 60 °C for a total of 16 hours. Raised to 80°C and kept for 2 hours to obtain acrylonitrile polymer, followed by primary filtration (candle core filter, filtration precision 5um), vacuum de-monolysis, and degassing to obtain spinning stock solution, the molecular weight of the prepared polyacrylonitrile was 1.8 ×10 ⁵ g/mol, molecular weight distribution was 2.52.

The spinning stock solution obtained above was subjected to secondary filtration (laminated filter, filtration accuracy 1um), dry spray wet spinning (the distance of the air section was 5 mm, the temperature of the air section was 30 ° C, and the relative humidity was 65%, The content of N,N-dimethylformamide in the first coagulation bath is 50-65wt%, the temperature of the first coagulation bath is 5°C, and the content of N,N-dimethylformamide in the second coagulation bath is 40% ～50wt%, the temperature of the second coagulation bath is 40 ℃ ) drafting (1.2 times), secondary hot water (95°C) drafting (1.6 times), oiling, drying and densification (temperature 150°C, time 1min), steam (0.3MPa) drafting (2.5 times) The carbon fiber precursor was obtained, and the carbon fiber precursor was prepared, with a diameter of 11.2um and a strength of 12.0cN/dtex.

Example 2

Under nitrogen protection, 9.9kg of acrylonitrile and 30g of N-vinyl-2-pyridine amide were dissolved in 31.66kg of N,N-dimethylformamide by mechanical stirring, and then 100g of azoisobutylcyanoformamide was added. , the temperature was gradually raised from 30 °C to 60 °C within 30 min, and then the remaining 70g of the second monomer N-vinyl-2-pyridine amide was continuously added dropwise. The addition was completed within 4 hours, and the reaction was maintained at 60 °C for a total of 20 hours. Raised to 80°C for 2 hours to obtain acrylonitrile polymer, then first-stage filtration (candle core filter, filtration accuracy 5um), vacuum de-monolysis, and defoaming to obtain spinning stock solution, the molecular weight of the prepared polyacrylonitrile is 1.2 ×10 ⁵ g/mol, molecular weight distribution was 2.43.

The spinning stock solution obtained above was subjected to secondary filtration (laminated filter, filtration accuracy 1um), dry spray wet spinning (the distance of the air section was 5 mm, the temperature of the air section was 30 ° C, and the relative humidity was 65%, The content of N,N-dimethylformamide in the first coagulation bath is 50-65wt%, the temperature of the first coagulation bath is 0°C, and the content of N,N-dimethylformamide in the second coagulation bath is 40 ~50wt%, the temperature of the second coagulation bath is 40°C.), three-stage washing (the first-stage washing temperature is 60°C, the second-stage washing temperature is 65°C, and the third-stage washing temperature is 70°C), the first-stage hot water (80°C) ) drafting (1.4 times), secondary hot water (100℃) drafting (1.8 times), oiling, drying and densification (temperature 160℃, time 0.5min), steam (0.3MPa) drafting (2.5 times) The carbon fiber precursor was obtained, with a diameter of 12.1um and a strength of 10.87cN/dtex.

Example 3

Under nitrogen protection, 9.7kg of acrylonitrile and 100g of N-vinyl-3-pyridine amide were dissolved in 33.48kg of N,N-dimethylformamide by mechanical stirring, and then 40g of azoisobutylcyanoformamide was added. , the temperature was gradually increased from 30 °C to 70 °C within 30 min, and then the remaining 200g of the second monomer N-vinyl-3-pyridine amide was continuously added dropwise. The addition was completed within 4 hours, and the reaction was maintained at 70 °C for a total of 12 hours. Raised to 80°C for 2 hours to obtain acrylonitrile polymer, then first-stage filtration (candle filter, filtration precision 5um), vacuum de-monolysis and defoaming to obtain spinning stock solution, the molecular weight of the prepared polyacrylonitrile is 1.4 ×10 ⁵ g/mol, molecular weight distribution was 2.42.

The spinning stock solution obtained above was subjected to secondary filtration (laminated filter, filtration accuracy 1um), dry spray wet spinning (the distance of the air section was 1 mm, the temperature of the air section was 30 ° C, and the relative humidity was 65%, The content of N,N-dimethylformamide in the first coagulation bath is 50-65wt%, the temperature of the first coagulation bath is 10°C, and the content of N,N-dimethylformamide in the second coagulation bath is 40% ~50wt%, the temperature of the second coagulation bath is 30°C.), three-stage washing (the first-stage washing temperature is 50°C, the second-stage washing temperature is 55°C, and the third-stage washing temperature is 60°C), the first-stage hot water (60°C) ) drafting (1.1 times), secondary hot water (90℃) drafting (1.4 times), oiling, drying and densification (temperature 140℃, time 2min), steam (0.3MPa) drafting (2.5 times) The carbon fiber precursor was obtained, with a diameter of 12.2um and a strength of 10.21cN/dtex.

Comparative Example 1

Under nitrogen protection, 9.8kg of acrylonitrile was dissolved in 33.48kg of N,N-dimethylformamide by mechanical stirring, then 50g of azobisisobutyronitrile was added, and the temperature was gradually increased from 30°C to 60°C within 30 min. The reaction was kept at 60 °C for a total of 16 hours, and finally raised to 80 °C for 2 hours to obtain acrylonitrile homopolymer, and then first-stage filtration (candle-wick filter, filtration accuracy 5um), vacuum de-singling and defoaming to obtain spinning. The molecular weight of the prepared polyacrylonitrile solution was 1.9×10 ⁵ g/mol, and the molecular weight distribution was 2.51.

The spinning stock solution obtained above was subjected to secondary filtration (laminated filter, filtration accuracy 1um), dry spray wet spinning (the distance of the air section was 5 mm, the temperature of the air section was 30 ° C, and the relative humidity was 65%, The content of N,N-dimethylformamide in the first coagulation bath is 50-65wt%, the temperature of the first coagulation bath is 5°C, and the content of N,N-dimethylformamide in the second coagulation bath is 40% ～50wt%, the temperature of the second coagulation bath is 40 ℃ ) drafting (1.2 times), secondary hot water (95°C) drafting (1.6 times), oiling, drying and densification (temperature 150°C, time 1min), steam (0.3MPa) drafting (2.5 times) The carbon fiber precursor was obtained, and the carbon fiber precursor was prepared, the diameter was 12.4um, the strength was 9.67cN/dtex, and the carbon yield after carbonization was 45.2%.

Comparative Example 2

Under nitrogen protection, 10kg of acrylonitrile, 207g of acrylic acid and 247g of methyl acrylate were dissolved in 33.28kg of N,N-dimethylformamide by mechanical stirring, and then 84g of azoisobutylcyanoformamide was added. The temperature was gradually raised from 30°C to 60°C, kept at 60°C for a total of 16 hours, and finally raised to 80°C for 2 hours to obtain acrylonitrile polymer. The spinning stock solution was obtained by single and degassing. The molecular weight of the prepared polyacrylonitrile was 1.2×10 ⁵ g/mol, and the molecular weight distribution was 2.62.

The spinning stock solution obtained above was subjected to secondary filtration (laminated filter, filtration accuracy 1um), dry spray wet spinning (the distance of the air section was 5 mm, the temperature of the air section was 30 ° C, and the relative humidity was 65%, The content of N,N-dimethylformamide in the first coagulation bath is 50-65wt%, the temperature of the first coagulation bath is 5°C, and the content of N,N-dimethylformamide in the second coagulation bath is 40% ～50wt%, the temperature of the second coagulation bath is 40 ℃ ) drafting (1.2 times), secondary hot water (95℃) drafting (1.5 times), oiling, drying and densification (temperature 150℃, time 1min), steam (0.3MPa) drafting (2.2 times) The carbon fiber precursor was obtained, the diameter was 12.9um, the strength was 8.31cN/dtex, and the carbon yield after carbonization was 48.7%.

Comparative Example 3

Under nitrogen protection, 9.8kg of acrylonitrile and 60g of 3-amide-3-butenoic acid methyl ester were dissolved in 31.66kg of N,N-dimethylformamide by mechanical stirring, and then 50g of azoisobutyl cyano was added. Formamide, gradually heat up from 30°C to 60°C within 30min, then start to continuously add the remaining 140g of the second monomer itaconic acid amide monomethyl ester dropwise, complete the dropwise addition within 4 hours, keep the reaction at 60°C for a total of 16 hours, and finally add Raised to 80°C and kept for 2 hours to obtain acrylonitrile polymer, followed by primary filtration (candle core filter, filtration precision 5um), vacuum de-monolysis and defoaming to obtain spinning stock solution, the molecular weight of the prepared polyacrylonitrile was 1.7 ×10 ⁵ g/mol, molecular weight distribution was 2.62.

The spinning stock solution obtained above was subjected to secondary filtration (laminated filter, filtration accuracy 1um), dry spray wet spinning (the distance of the air section was 5 mm, the temperature of the air section was 30 ° C, and the relative humidity was 65%, The content of N,N-dimethylformamide in the first coagulation bath is 50-65wt%, the temperature of the first coagulation bath is 5°C, and the content of N,N-dimethylformamide in the second coagulation bath is 40% ～50wt%, the temperature of the second coagulation bath is 40 ℃ ) drafting (1.2 times), secondary hot water (95°C) drafting (1.6 times), oiling, drying and densification (temperature 150°C, time 1min), steam (0.3MPa) drafting (2.5 times) The carbon fiber precursor was obtained, and the carbon fiber precursor was prepared, with a diameter of 12.9um and a strength of 8.31cN/dtex.

Effect example 1

The DSC curves of the acrylonitrile polymers obtained in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 were drawn respectively and compared, and the results are shown in Figure 1 .

It can be seen from Fig. 1 that the pre-oxidation temperature of the acrylonitrile polymer obtained by the present invention is effectively lowered, and the production cost is reduced.

Effect example 2

Using conventional carbonization methods, under the same conditions, carbon fiber precursors obtained in Examples 1 to 3 and Comparative Examples 1 to 3 were carbonized to obtain corresponding carbon fibers, and the carbon yield was counted. The results are shown in Table 1. .

Table 1

raw silk Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 carbon yield 55.23% 54.52% 54.41% 45.25% 48.70% 49.77%

As can be seen from Table 1, Comparative Examples 1 to 2 are carbon fiber precursors commonly used in the present, and their carbon yields are less than 50%. The monomers of Comparative Example 3 are acrylonitrile and methyl 3-amide-3-butenoate, and N atoms are also introduced, but the carbon yield of Comparative Example 3 is still less than 50%. However, after the carbon fiber precursors of Examples 1 to 3 obtained by the present invention are carbonized, the carbon yield is steadily increased to more than 54%, which is significantly improved. Especially in Example 1, the carbon yield reached 55.23%, which is of great significance for the industrial production of carbon fibers.

The above disclosures are only preferred embodiments of the present invention, and of course, the scope of the rights of the present invention cannot be limited by this. Therefore, the equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims (10)

1. A high-performance binary polyacrylonitrile-based carbon fiber precursor is characterized by comprising the following raw materials in parts by weight: 97-99 parts of first comonomer, 1-3 parts of second comonomer and 0.4-1 part of initiator; the first comonomer is acrylonitrile and the second comonomer is N-vinylpyridine amide.

2. The high-performance binary polyacrylonitrile-based carbon fiber strand as claimed in claim 1, wherein the mass ratio of the first comonomer to the second comonomer is 98.

3. The high performance binary polyacrylonitrile-based carbon fiber strand as claimed in claim 1, wherein said initiator comprises azoisobutyrylcyanocarboxamide.

4. The high performance binary polyacrylonitrile-based carbon fiber strand as claimed in claim 1, wherein the N-vinylpyridine amide includes one or more of N-vinyl-2-pyridine amide, N-vinyl-3-pyridine amide and N-vinyl-4-pyridine amide.

5. The high-performance binary polyacrylonitrile-based carbon fiber precursor as claimed in claim 1, wherein the raw material further comprises a solvent, and the solvent comprises N, N-dimethylformamide in an amount of 284-455 parts.

6. The high-performance binary polyacrylonitrile-based carbon fiber precursor as claimed in claim 1, wherein the diameter of said carbon fiber precursor is 11-13 um, the strength is 8.9-12.1 cN/dtex, and the carbon yield is more than 54%.

7. The preparation method of the high-performance binary polyacrylonitrile-based carbon fiber precursor as claimed in claim 1, characterized by comprising the following steps:

a: dissolving the first comonomer and the initiator in a solvent according to a proportion, carrying out polymerization reaction on the second comonomer in a continuous dropwise adding mode under a certain temperature condition to obtain an acrylonitrile polymer, and then filtering, demonomerizing and defoaming to obtain a spinning solution;

b: and (3) performing secondary filtration, spinning, washing, hot water stretching, oiling, drying densification and high-pressure steam drafting on the spinning stock solution to obtain the carbon fiber precursor.

8. The method of claim 7, comprising the steps of:

a: under the condition of nitrogen protection, dissolving the first comonomer and the initiator in a solvent according to a proportion by mechanical stirring, continuously dropwise adding the second comonomer, heating to a reaction temperature of 60-70 ℃ for 30min, keeping the temperature for carrying out the polymerization reaction for 12-20 hours, heating to 80 ℃ for 2 hours to obtain an acrylonitrile polymer, and then carrying out primary filtration, vacuum demonomerization and defoaming to obtain the spinning stock solution;

b: the spinning solution is subjected to secondary filtration and then the following steps:

b1: spinning by adopting a dry-jet wet method, and the process parameters are as follows: the distance of the air section is 1-5 mm, the temperature of the air section is 30 ℃, the relative humidity is 65%, the content of the solvent in the first coagulating bath is 50-65wt%, the temperature of the first coagulating bath is 0-10 ℃, the content of the solvent in the second coagulating bath is 40-50 wt%, and the temperature of the second coagulating bath is 30-40 ℃;

b2: carrying out multi-stage water washing at 50-70 ℃;

b3: two-stage hot water drafting is carried out, the temperature of the first-stage hot water is 60-80 ℃, the drafting multiple is 1.1-1.4 times, the temperature of the second-stage hot water is 90-100 ℃, and the drafting multiple is 1.4-1.8 times;

b4: oiling is carried out, and the oiling rate is 0.5-1.2 wt% by adopting amino modified silicone oil.

B5: drying densification is carried out, the temperature of the drying densification is 140-160 ℃, and the time is 0.5-2 min;

b5: and (3) carrying out two-stage high-pressure steam drafting, wherein the first-stage pressure is 0.1-0.3 MPa, the second-stage pressure is 0.3-0.5 MPa, and the total multiple of the two-stage drafting is 2-4 times, so as to prepare the carbon fiber precursor.

9. The method of claim 7, wherein the step a, the adding of the second comonomer specifically comprises: and adding 30% of the total mass of the second comonomer into the system before the temperature of the polymerization reaction is raised, continuously dropwise adding the rest of the second comonomer when the temperature is raised to the reaction temperature of the polymerization reaction, and completing dropwise adding within 4 hours.

10. The process according to claim 8, wherein in the step A, the viscosity average molecular weight of the acrylonitrile polymer is 1.2X 10 ⁵ ～2.1×10 ⁵ g/mol, wherein the weight content of the acrylonitrile polymer in the spinning solution is 16-24 wt%; in the step A, the first-stage filtration is carried out in a candle core type filter, and the filtration precision is 5um; in the step B, the secondary filtration is carried out in a laminated filter, and the filtration precision is 1um; in the step B2, the multistage washing is three-stage washing, the temperature of the first-stage washing is 50-60 ℃, the temperature of the second-stage washing is 55-65 ℃, and the temperature of the third-stage washing is 60-70 ℃.

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