A process for the ammoniation of polyacrylonitrile powder
By ammoniation of polyacrylonitrile powder, the defect caused by the rapid coagulation and diffusion rate during spinning was solved, the hydrophilicity of the spinning solution was improved, the operation was simplified, and the carbon fiber performance was ensured, achieving a highly efficient and environmentally friendly ammoniation effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHANGCHUN UNIV OF TECH
- Filing Date
- 2025-01-20
- Publication Date
- 2026-05-12
AI Technical Summary
In the existing polyacrylonitrile spinning process, the fast solidification double diffusion rate leads to defects such as macropores, core-sheath structure, and irregular fiber structure, which affect the performance of carbon fibers. Existing ammoniation methods are inefficient or have a negative impact on the polymerization process.
Before spinning, the polyacrylonitrile powder after desizing is ammonified using ammonium salt as the ammonification reagent. The ammonification temperature and time are controlled to achieve efficient ammonification and improve the hydrophilicity of the spinning solution.
It effectively improves the hydrophilicity of polyacrylonitrile, simplifies operation, is environmentally friendly, avoids the toxicity and odor problems of gaseous ammonia and liquid amines, and ensures that the performance of carbon fibers is not affected.
Smart Images
Figure CN119841990B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of polyacrylonitrile-based carbon fiber technology, and more particularly to an ammoniation method for polyacrylonitrile powder. Background Technology
[0002] With the development of aerospace, wind turbine blades, electric vehicles, pressure vessels, and other fields, the need for lightweight, high-strength composite materials is becoming increasingly urgent. Carbon fiber is often combined with matrices such as plastics, metals, and ceramics to form fiber-reinforced composite materials for the preparation of high-strength structural materials. The carbon fiber preparation method involves first spinning the precursor into filaments, and then obtaining carbon fibers through pre-oxidation and carbonization. The precursors used for spinning mainly include polyacrylonitrile (PAN), viscose fiber, and pitch. Among these, polyacrylonitrile-based carbon fiber has the advantages of excellent finished product quality, simple processing, and excellent mechanical properties, making it the mainstream in carbon fiber production.
[0003] In the production of polyacrylonitrile precursor fibers, the solidification and formation of the spinning solution is achieved through the dual diffusion of solvent and precipitant, as well as the precipitation of polyacrylonitrile molecules. Currently, the most commonly used spinning method in industry is wet spinning. However, the solidification dual diffusion rate in wet spinning is relatively fast, which easily leads to defects in polyacrylonitrile fibers such as macropores, core-sheath structures, and irregular fiber structures. These defects will be inherited by polyacrylonitrile fibers and carbon fibers, severely weakening the performance and application areas of carbon fibers.
[0004] The coagulation and diffusion process is closely related to the hydrophilicity of the spinning solution. Increasing the hydrophilicity of the spinning solution can slow down the coagulation and formation rate, reducing defects such as macropores, core-sheath structures, and irregular fiber structures. Ammoniation of the spinning solution to improve its hydrophilicity is an effective way to avoid these problems. Currently, the mainstream ammoniation methods are divided into three types: adding ammonia before polymerization, adding ammonia before demonization after polymerization (referred to as adding ammonia after polymerization), and adding ammonia in the coagulation bath. All of these methods can improve the hydrophilicity of the spinning solution, but they also have some drawbacks, mainly as follows: 1. Adding ammonia before polymerization hinders the polymerization reaction and adversely affects mass and heat transfer during the polymerization process. 2. Adding ammonia before demonization after polymerization makes it difficult to control the degree of ammoniaization. 3. Adding ammonia in the coagulation bath makes it difficult for the ammonia in the coagulation bath to mix and react uniformly with the high-viscosity spinning solution, resulting in low ammoniaization efficiency. Summary of the Invention
[0005] In view of this, the present invention provides an ammoniation method for polyacrylonitrile powder. This invention starts from the source of the spinning solution, effectively ammoniating the de-isolated polyacrylonitrile powder before preparing the spinning solution, which can effectively improve the hydrophilicity of polyacrylonitrile, and is simple to operate and environmentally friendly.
[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:
[0007] An ammoniation method for polyacrylonitrile powder includes the following steps:
[0008] After removing the single components from the carboxyl-containing polyacrylonitrile liquid obtained by precipitation polymerization, it is first dried to obtain carboxyl-containing polyacrylonitrile powder.
[0009] The carboxyl-containing polyacrylonitrile powder is soaked in an aqueous solution of an ammoniation reagent for ammoniation; the ammoniation reagent is an ammonium salt.
[0010] Preferably, the ammonium salt includes one or more of ammonium carbonate, ammonium acetate, ammonium formate, and ammonium bicarbonate.
[0011] Preferably, the concentration of the amination reagent aqueous solution is 0.01 mol / L to 5 mol / L.
[0012] Preferably, the molar amount of amino groups in the ammonium salt of the amination reagent aqueous solution is greater than or equal to the molar amount of carboxyl groups in the amination-containing polyacrylonitrile powder.
[0013] Preferably, the molar ratio of the amino group in the ammonium salt to the carboxyl group in the carboxyl-containing polyacrylonitrile powder is 1 to 10:1; more preferably, it is 1 to 5:1.
[0014] Preferably, the comonomer used in the precipitation polymerization is a carboxyl-containing comonomer, which includes one or more of itaconic acid, acrylic acid, methacrylic acid, maleic acid, methylmaleic acid, and fumaric acid.
[0015] Preferably, the ammoniation temperature is 30–100°C and the ammoniation time is 0.5–48 h.
[0016] Preferably, the method for removing singletons is as follows: pour the carboxyl-containing polyacrylonitrile solution into deionized water, and then filter and rinse it.
[0017] Preferably, the temperature of the first drying is 40-80°C; more preferably, it is 50-70°C.
[0018] Preferably, after ammoniation, the process further includes washing the obtained ammoniation product and then subjecting it to a second drying; the temperature of the second drying is 40–80°C; more preferably 50–70°C.
[0019] This invention provides an ammoniation method for polyacrylonitrile powder, comprising the following steps: firstly drying the carboxyl-containing polyacrylonitrile solution obtained by precipitation polymerization to obtain carboxyl-containing polyacrylonitrile powder; and immersing the carboxyl-containing polyacrylonitrile powder in an aqueous solution of an ammoniation reagent for ammoniation; wherein the ammoniation reagent is one or more of ammonium carbonate, ammonium acetate, ammonium formate, and ammonium bicarbonate. This invention starts from the source of the spinning solution, performing efficient ammoniation on the polyacrylonitrile powder after desizing before preparing the spinning solution. The operation is simple, the ammoniation efficiency is high, and it can effectively improve the hydrophilicity of polyacrylonitrile. Furthermore, current ammoniation methods usually use liquid amines or ammonia gas as ammoniation reagents, which have strong odors and toxicity. However, the ammoniation reagent used in this invention is ammonium salt or carbamide, which overcomes the disadvantages of commonly used liquid amines and gaseous ammonia, such as strong odors and high toxicity. It also solves the problem that gaseous ammonia and most liquid amines are insoluble in spinning solution solvents. The ammoniation system is pure and environmentally friendly. In addition, the specific ammoniation reagent used in this invention will not introduce impurities other than carbon, hydrogen, oxygen, and nitrogen into the system, avoiding the generation of impurities during subsequent pre-oxidation and carbonization that affect the performance of the final carbon fiber. Attached Figure Description
[0020] Figure 1 The NMR spectrum of the carboxyl-containing polyacrylonitrile powder before amination in Example 1;
[0021] Figure 2 The NMR spectrum of the ammoniated polyacrylonitrile powder in Example 1;
[0022] Figure 3 The results are the water contact angle test results of the carboxyl-containing polyacrylonitrile powder before amination in Example 1;
[0023] Figure 4 The results are the water contact angle test results of the ammoniated polyacrylonitrile powder in Example 1;
[0024] Figure 5 The results are DSC test results of the polyacrylonitrile powder before and after amination in Example 1. Detailed Implementation
[0025] This invention provides a method for ammoniation of polyacrylonitrile powder, comprising the following steps:
[0026] After removing the single components from the carboxyl-containing polyacrylonitrile liquid obtained by precipitation polymerization, it is first dried to obtain carboxyl-containing polyacrylonitrile powder.
[0027] The carboxyl-containing polyacrylonitrile powder is soaked in an aqueous solution of an ammoniation reagent for ammoniation; the ammoniation reagent is an ammonium salt.
[0028] This invention involves first drying the carboxyl-containing polyacrylonitrile slurry obtained from precipitation polymerization to obtain carboxyl-containing polyacrylonitrile powder. In this invention, the carboxyl-containing polyacrylonitrile slurry is specifically a polymer slurry containing carboxyl-containing polyacrylonitrile; the precipitation polymerization specifically involves a precipitation polymerization reaction using acrylonitrile monomer and a comonomer. This invention does not have special requirements for the specific operation method of the precipitation polymerization; methods well-known to those skilled in the art can be used. In this invention, the comonomer preferably includes a carboxyl-containing comonomer; the carboxyl-containing comonomer preferably includes one or more of itaconic acid, acrylic acid, methacrylic acid, maleic acid, methylmaleic acid, and fumaric acid.
[0029] In this invention, the preferred method for removing unreacted monomers is to pour the carboxyl-containing polyacrylonitrile solution into deionized water, and then filter and rinse it; the amount of deionized water used is sufficient to terminate the precipitation polymerization reaction; this invention does not have special requirements on the number of filtrations and rinses, as long as the unreacted monomers are removed.
[0030] In this invention, the temperature of the first drying is preferably 40-80°C, more preferably 50-70°C; the first drying is preferably vacuum drying.
[0031] After obtaining carboxyl-containing polyacrylonitrile powder, the present invention soaks the carboxyl-containing polyacrylonitrile powder in an aqueous solution of an ammoniation reagent for ammoniation. In the present invention, the ammoniation reagent is an ammonium salt, preferably including one or more of ammonium carbonate, ammonium acetate, ammonium formate, and ammonium bicarbonate. The concentration of the aqueous solution of the ammoniation reagent is preferably 0.01 mol / L to 5 mol / L, more preferably 0.1 to 0.5 mol / L. The molar amount of amino groups in the ammonium salt in the aqueous solution of the ammoniation reagent is greater than or equal to the molar amount of carboxyl groups in the ammonized carboxyl-containing polyacrylonitrile powder. Specifically, the molar ratio of amino groups in the ammonium salt to carboxyl groups in the carboxyl-containing polyacrylonitrile powder is 1 to 10:1, more preferably 1 to 5:1; further preferably 1 to 2:1; the mass ratio of the aqueous solution of the ammoniation reagent to the carboxyl-containing polyacrylonitrile powder is preferably 1 to 50:1, specifically 10:1.
[0032] In this invention, the ammoniation temperature is preferably 30–100°C, specifically 40°C, 50°C, 55°C, 60°C, 65°C, 70°C, 80°C, or 90°C; the ammoniation time is preferably 0.5–48 h, specifically 1 h, 3 h, 5 h, 10 h, 15 h, 18 h, 24 h, 36 h, or 48 h; the ammoniation is preferably carried out under water bath heating conditions; by controlling the ammoniation temperature and time within the above ranges, this invention enables the ammoniation reagent and the carboxyl groups in the carboxyl-containing polyacrylonitrile powder to react fully, achieving efficient ammoniation.
[0033] In this invention, after ammoniation, the product is washed and then dried a second time; the washing is preferably done with deionized water, and this invention removes residual ammoniation reagent from the ammoniation product by washing; the temperature of the second drying is preferably 40-80°C, specifically 50°C, 55°C, 60°C, 65°C or 70°C; the second drying is preferably vacuum drying.
[0034] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0035] Example 1
[0036] The polymer slurry containing carboxyl-containing polyacrylonitrile obtained by precipitation polymerization was poured into excess deionized water to terminate the polymerization. After repeated rinsing and filtration to remove unreacted monomers, the product was dried in a vacuum oven at 60°C to constant weight, finally yielding a carboxyl-containing polyacrylonitrile powder with a copolymer composition of 2 mol% acrylic acid, 1 mol% itaconic acid, and 97 mol% acrylonitrile. 10 g of the obtained carboxyl-containing polyacrylonitrile powder was placed in 100 g of a 0.5 mol / L ammonium carbonate solution and reacted for 1 hour in a water bath at 50°C. After the reaction was stopped, the powder was filtered, and the ammoniated powder was rinsed repeatedly with deionized water to remove residual ammonium carbonate. The ammoniated polyacrylonitrile powder was then dried in a vacuum oven at 60°C.
[0037] Example 2
[0038] The polymer slurry containing carboxyl-containing polyacrylonitrile obtained by precipitation polymerization was poured into excess deionized water to terminate the polymerization. After repeated rinsing and filtration to remove unreacted monomers, the product was dried in a vacuum oven at 60°C to constant weight, finally yielding a carboxyl-containing polyacrylonitrile powder with a copolymer composition of 2 mol% acrylic acid, 1 mol% itaconic acid, and 97 mol% acrylonitrile. 10 g of the obtained carboxyl-containing polyacrylonitrile powder was placed in 100 g of a 0.5 mol / L ammonium bicarbonate solution and reacted for 1 hour at a water bath temperature of 50°C. After the reaction was stopped, the powder was filtered, and the ammoniated powder was rinsed repeatedly with deionized water to remove residual ammonium bicarbonate. The ammoniated polyacrylonitrile powder was then dried in a vacuum oven at 60°C.
[0039] Example 3
[0040] The polymer slurry containing carboxyl-containing polyacrylonitrile obtained by precipitation polymerization was poured into excess deionized water to terminate the polymerization. The mixture was then repeatedly washed and filtered to remove unreacted monomers. The product was then dried in a vacuum oven at 60°C to constant weight, finally yielding a carboxyl-containing polyacrylonitrile powder with a copolymer composition of 2 mol% acrylic acid, 1 mol% itaconic acid, and 97 mol% acrylonitrile. 10 g of the obtained carboxyl-containing polyacrylonitrile powder was placed in 100 g of a 0.5 mol / L ammonium acetate solution and reacted for 1 hour in a water bath at 50°C. After the reaction was stopped, the mixture was filtered, and the aminated powder was repeatedly washed with deionized water to remove residual ammonium acetate. The aminated polyacrylonitrile powder was then dried in a vacuum oven at 60°C.
[0041] Example 4
[0042] The polymer slurry containing carboxyl-containing polyacrylonitrile obtained by precipitation polymerization was poured into excess deionized water to terminate the polymerization. The mixture was then repeatedly washed and filtered to remove unreacted monomers. The product was then dried in a vacuum oven at 60°C to constant weight, finally yielding a carboxyl-containing polyacrylonitrile powder with a copolymer composition of 2 mol% acrylic acid, 1 mol% itaconic acid, and 97 mol% acrylonitrile. 10 g of the obtained carboxyl-containing polyacrylonitrile powder was placed in 100 g of a 1.5 mol / L ammonium carbonate solution and reacted for 1 hour at a water bath temperature of 50°C. After the reaction was stopped, the mixture was filtered, and the amination powder was repeatedly washed with deionized water to remove residual ammonium carbonate. The amination powder was then dried in a vacuum oven at 60°C to obtain the amination-treated polyacrylonitrile powder.
[0043] Example 5
[0044] The polymer slurry containing carboxyl-containing polyacrylonitrile obtained by precipitation polymerization was poured into excess deionized water to terminate the polymerization. The mixture was then repeatedly washed and filtered to remove unreacted monomers. The product was then dried in a vacuum oven at 60°C to constant weight, ultimately yielding a carboxyl-containing polyacrylonitrile powder with a copolymer composition of 2 mol% acrylic acid, 1 mol% itaconic acid, and 97 mol% acrylonitrile. 10 g of the obtained carboxyl-containing polyacrylonitrile powder was placed in 100 g of a 0.5 mol / L ammonium formate solution and reacted for 1 hour in a water bath at 50°C. After the reaction was stopped, the mixture was filtered, and the amination powder was repeatedly washed with deionized water to remove any remaining ammonium formate. The amination powder was then dried in a vacuum oven at 60°C to obtain the amination-treated polyacrylonitrile powder.
[0045] Example 6
[0046] The polymer slurry containing carboxyl-containing polyacrylonitrile obtained by precipitation polymerization was poured into excess deionized water to terminate the polymerization. The mixture was then repeatedly washed and filtered to remove unreacted monomers. The product was then dried in a vacuum oven at 60°C to constant weight, finally yielding a carboxyl-containing polyacrylonitrile powder with a copolymer composition of 1 mol% acrylic acid, 1 mol% itaconic acid, and 98 mol% acrylonitrile. 10 g of the obtained carboxyl-containing polyacrylonitrile powder was placed in 100 g of a 0.5 mol / L ammonium carbonate solution and reacted for 1 hour at a water bath temperature of 50°C. After the reaction was stopped, the mixture was filtered, and the amination powder was repeatedly washed with deionized water to remove residual ammonium carbonate. The amination powder was then dried in a vacuum oven at 60°C to obtain the amination-treated polyacrylonitrile powder.
[0047] Performance testing
[0048] Nuclear magnetic resonance (NMR) tests were performed on the polyacrylonitrile powders before and after amination in Example 1, and the results are as follows: Figure 1 and Figure 2 As shown. According to Figure 1 and Figure 2 It can be seen that the ammonium salt aqueous solution effectively aminated the carboxyl groups in polyacrylonitrile.
[0049] The polyacrylonitrile powders before and after amination in Example 1 were respectively laid into films and tested for water contact angle. The results are as follows: Figure 3 and Figure 4 As shown in the figure, the hydrophilicity of the amination-treated polyacrylonitrile is significantly improved.
[0050] DSC tests were performed on the polyacrylonitrile powders before and after amination in Example 1, and the results are as follows: Figure 5 As shown. According to Figure 5 It can be seen that the concentrated heat release during the thermal stabilization process of the ammoniated polyacrylonitrile powder is further alleviated, which is beneficial to the preparation of high-performance polyacrylonitrile carbon fibers.
[0051] The polyacrylonitrile powders before and after amination in Examples 2-6 were tested by NMR, water contact angle and DSC. The results showed that effective amination was achieved in all cases and the hydrophilicity of polyacrylonitrile was greatly improved.
[0052] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for ammoniation of polyacrylonitrile powder, characterized in that, Includes the following steps: After removing the single components from the carboxyl-containing polyacrylonitrile liquid obtained by precipitation polymerization, it is first dried to obtain carboxyl-containing polyacrylonitrile powder. The carboxyl-containing polyacrylonitrile powder is ammonified by immersing it in an aqueous solution of an ammonifying reagent; the ammonifying reagent is an ammonium salt; the concentration of the aqueous solution of the ammonifying reagent is 0.01 mol / L to 5 mol / L; the molar amount of amino groups in the ammonium salt in the aqueous solution of the ammonifying reagent is greater than or equal to the molar amount of carboxyl groups in the ammonified carboxyl-containing polyacrylonitrile powder; after ammonification, the resulting ammonification product is washed and then subjected to a second drying; the ammonium salt includes one or more of ammonium carbonate, ammonium acetate, ammonium formate, and ammonium bicarbonate.
2. The ammoniation method according to claim 1, characterized in that, The molar ratio of the amino group in the ammonium salt to the carboxyl group in the carboxyl-containing polyacrylonitrile powder is 1~10:
1.
3. The ammoniation method according to claim 1, characterized in that, The comonomer used in the precipitation polymerization is a carboxyl-containing comonomer; the carboxyl-containing comonomer includes one or more of itaconic acid, acrylic acid, methacrylic acid, maleic acid, methylmaleic acid and fumaric acid.
4. The ammoniation method according to claim 1, characterized in that, The ammoniation temperature is 30~100℃, and the ammoniation time is 0.5~48h.
5. The ammoniation method according to claim 1, characterized in that, The method for removing singletons is as follows: pour the carboxyl-containing polyacrylonitrile solution into deionized water, and then filter and rinse it.
6. The ammoniation method according to claim 1, characterized in that, The temperature for the first drying process is 40~80℃.
7. The ammoniation method according to claim 1, characterized in that, The second drying temperature is 40~80℃.