Modified aramid based on polyamide solution containing heterocyclic monomer and preparation method thereof
By introducing 2-imidazolium-p-phenylenediamine heterocyclic monomers, the polymerization and spinning processes of aramid were optimized, and a tightly oriented polyamide backbone was constructed. This solved the problems of insufficient flexibility and complex modification processes in traditional aramid, and improved high-temperature stability and flexibility.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHONGZHOU TIMES CO LTD
- Filing Date
- 2025-12-26
- Publication Date
- 2026-06-05
AI Technical Summary
Traditional aramid fibers lack flexibility and have complex modification processes, making them prone to brittle fracture in extreme environments and exhibiting poor compatibility.
By introducing 2-imidazolyl-p-phenylenediamine heterocyclic monomers and optimizing the polymerization and spinning processes, a polyamide solution containing heterocyclic monomers is formed. The condensation reaction of the solution with p-phenylenediamine and terephthaloyl chloride is used to construct a tightly oriented polyamide backbone, and the intermolecular forces are enhanced through the heterocyclic conjugation effect.
It improves the overall performance of aramid fibers, enhances their flexibility and high-temperature stability, while maintaining their basic mechanical properties, and solves the problem of embrittlement of traditional aramid fibers in extreme environments.
Smart Images
Figure CN121451313B_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of high-performance fiber materials technology, specifically relating to a modified aramid based on a polyamide solution containing heterocyclic monomers and its preparation method. Background Technology
[0002] Aramid, as a high-performance synthetic fiber, possesses excellent properties such as high strength, high modulus, and high temperature resistance, and is widely used in aerospace, defense, and special protection fields. Traditional aramid is prepared through the polycondensation reaction of p-phenylenediamine and terephthaloyl chloride. While its molecular chain structure is regular, it lacks flexibility and is prone to embrittlement and breakage under extreme environments.
[0003] Existing modification methods mostly improve performance by introducing flexible segments or nanofillers, but these methods suffer from poor compatibility and complex processes. Therefore, developing a method for preparing modified aramid fibers from polyamide solutions containing heterocyclic monomers is of great significance for expanding the application range of aramid fibers. Summary of the Invention
[0004] To address the issues of insufficient flexibility and complex modification processes in existing aramid fibers, this application provides a modified aramid fiber based on a polyamide solution containing heterocyclic monomers and its preparation method. By introducing a 2-imidazolium-p-phenylenediamine heterocyclic monomer, the polymerization and spinning processes are optimized to improve the overall performance of the aramid fiber.
[0005] To achieve the above objectives, this application provides the following technical solution:
[0006] In a first aspect, this application provides a modified aramid based on a polyamide solution containing heterocyclic monomers, wherein the modified aramid is prepared by spinning a polyamide solution containing heterocyclic monomers; the polyamide solution containing heterocyclic monomers includes p-phenylenediamine, terephthaloyl chloride, 2-imidazolyl-p-phenylenediamine, N-methylpyrrolidone, and triethylamine. Specifically, p-phenylenediamine and 2-imidazolyl-p-phenylenediamine provide amino groups, and terephthaloyl chloride provides acyl chloride groups; the amino groups and acyl chloride groups undergo a condensation reaction to form the polyamide backbone.
[0007] The amino groups in p-phenylenediamine and 2-imidazolyl-p-phenylenediamine ( The HCl group (-COCl) attacks the acyl chloride group (-COCl) in terephthaloyl chloride, undergoing a nucleophilic substitution reaction, removing HCl and forming an amide bond (-CONH-), ultimately constructing a repeating unit including " "and" The polyamide backbone consists of Ar, a benzene ring, and Ar', a benzene ring containing an imidazole group. This repeating unit structure allows for tight and directional packing of molecular chains, reducing gaps caused by structural bending and branching between chains. It ensures uniform and stable intermolecular forces and avoids mechanical weaknesses caused by disordered chain structures, such as branch breakage and stress concentration at chain entanglements. This provides structural support for fundamental mechanical properties such as tensile strength and elastic modulus. The p-phenylenediamine molecule has a symmetrical structure, with no significant steric hindrance in the spatial arrangement of its para-amino groups, ensuring uniform reaction with the acyl chloride group. This provides a regular linear structure for the polyamide backbone, unlike other polyamides such as m-phenylenediamine and o-phenylenediamine. The meta-amino group of m-phenylenediamine, which is difficult to achieve with phenylenediamine derivatives, tends to lead to disordered molecular chain arrangement, while ortho-substituted o-phenylenediamine will cause steric hindrance to polymerization. The 2-imidazolium group enhances intermolecular forces through heterocyclic conjugation. The nitrogen atom in the 2-imidazolium group is highly electronegative and can form intermolecular hydrogen bonds (-NH…N-) with the amide bonds of adjacent molecular chains. Simultaneously, the conjugated structure of the imidazolium ring enhances interchain bonding through π-π stacking, inhibiting molecular chain movement and slippage at high temperatures, thereby improving the fiber's elongation at break and thermal stability. Triethylamine combines with the HCl produced in the reaction to form triethylamine hydrochloride, promoting the forward reaction.
[0008] Furthermore, the mass ratio of p-phenylenediamine, terephthaloyl chloride, 2-imidazolyl p-phenylenediamine, N-methylpyrrolidone, and triethylamine is (2-4):(15-17):(18-20):(41-49):(16-18).
[0009] Secondly, this application provides a method for preparing modified aramid based on a polyamide solution containing heterocyclic monomers, comprising the following steps:
[0010] S1. Under nitrogen protection, p-phenylenediamine and 2-imidazolyl-p-phenylenediamine are added to N-methylpyrrolidone and stirred until homogeneous to obtain a mixed amine solution;
[0011] S2. Control the reaction temperature at 5-10℃, add terephthaloyl chloride to the mixed amine solution in batches, with a total feeding time of 30-40 min, and stir at a speed of 350-400 r / min for 0.5-1 h to form a polyamide prepolymer solution;
[0012] S3. Add triethylamine to the polyamide prepolymer solution, heat to 25-30℃ and continue stirring for 60-70 min to complete the polymerization reaction and obtain reaction solution A;
[0013] S4. Filter the reaction solution A through a filter membrane, and then degas it under vacuum at 35-40℃ for 20-30 minutes to obtain the polyamide spinning solution.
[0014] S5. Mix the polyamide spinning solution with the first acid solution, control the mixing temperature at 10-15℃ and the mixing time at 5-8 min, to obtain the preheated spinning solution;
[0015] S6. The preheated spinning solution is delivered to the spinneret through a metering pump, and the spinneret is spun into filaments. The orifice diameter of the spinneret is 0.05-0.08 mm, and the pressure is 0.3-0.5 MPa, thus obtaining the filaments formed by the spinneret.
[0016] S7. Introduce the filament formed by spinning into the second acid solution for curing. The temperature is controlled at 20-25℃, and the residence time of the filament in the second acid solution is 30-40s to obtain the cured filament.
[0017] S8. The cured filaments are sent into the cleaning tank and cleaned using a three-stage water washing process to obtain the cleaned filaments.
[0018] S9. The cleaned filaments are oiled in an oil bath. The oil used in the oil bath includes any one of isooctyl stearate and polyethylene glycol monooleate. The oil bath temperature is 40-45℃ and the oiling time is 5-8s to obtain the oiled filaments.
[0019] S10. Introduce the oiled filament into the winding device, control the winding speed to 800-1000 m / min, and wind the filament into a cylinder to obtain modified aramid based on a polyamide solution containing heterocyclic monomers.
[0020] Furthermore, the p-phenylenediamine and 2-imidazolyl-p-phenylenediamine described in S1 are stirred at 0-5°C for 30-45 min.
[0021] Furthermore, phthaloyl chloride in S2 is added to the mixed amine solution in 3-5 batches.
[0022] Adding materials in batches and controlling the stirring rate can avoid uneven molecular chain distribution caused by excessively high local concentrations, which is conducive to the formation of prepolymers with uniform molecular weight distribution.
[0023] Adding triethylamine to S3 as an acid-binding agent can neutralize the hydrogen chloride generated in the reaction and promote the forward polycondensation reaction; raising the temperature to 25-30℃ can increase the reaction rate and ensure that the monomers react fully to form high molecular weight polyamide.
[0024] Furthermore, the filter membrane in S4 is a composite filter membrane modified with a silane coupling agent, wherein the composite filter membrane includes any one of polytetrafluoroethylene, polyethersulfone, polypropylene, and cellulose acetate.
[0025] Further, the silane coupling agent includes any one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, or γ-methacryloxypropyltrimethoxysilane; the modification method is as follows: the composite filter membrane is immersed in a 2-5% (w / w) silane coupling agent ethanol solution, ultrasonically treated for 20-30 min, and then dried at 60-80℃.
[0026] Modification with silane coupling agents can improve the hydrophilicity of the filter membrane surface and enhance its adsorption capacity for minute impurities in polar polyamide solutions; certain types of composite filter membranes have solvent resistance and suitable pore structure, which can reduce solution loss while effectively filtering; ultrasonic treatment can promote the uniform grafting of silane coupling agents on the filter membrane surface, while drying can achieve the curing and cross-linking of the coupling agents.
[0027] Furthermore, under vacuum conditions, degassing at 35°C for 20 minutes yields a polyamide spinning solution. Filtration removes mechanical impurities and gel particles from the solution, preventing clogging of the spinneret orifices during spinning. Vacuum degassing eliminates air bubbles in the solution, preventing fiber defects caused by bubble rupture during spinning.
[0028] Furthermore, in S5, the first acid solution is a sulfuric acid solution with a mass fraction of 10%-15%, and the volume ratio of the polyamide spinning solution to the first acid solution is (1:3)-(1:5).
[0029] Sulfuric acid, as a pretreatment agent, can break hydrogen bonds in the spinning solution through protonation, reduce solution viscosity, and provide an acidic environment for subsequent curing steps.
[0030] Furthermore, the second acid solution in S7 is a sulfuric acid solution with a mass fraction of 25%-30%.
[0031] Through solvent exchange, N-methylpyrrolidone in the spinning solution diffuses into the sulfuric acid solution, causing the polyamide molecular chains to precipitate and solidify due to decreased solubility.
[0032] Furthermore, the S8 process involves a three-stage washing process: the first stage uses water at 30-35℃ for 5-8 minutes; the second stage uses water at 40-45℃ with a 0.5%-1% sodium carbonate solution for 10-12 minutes; and the third stage uses water at 50-55℃ with pure water to a pH of 6.5-7.5 for 8-10 minutes. This three-stage washing process improves cleaning efficiency through gradual temperature increases, the sodium carbonate solution neutralizes residual acid to prevent fiber degradation under acidic conditions, and the final wash to neutral pH ensures stable fiber properties.
[0033] Beneficial technical effects:
[0034] In the molecular structure design of this modified aramid based on a polyamide solution containing heterocyclic monomers, p-phenylenediamine and 2-imidazolyl p-phenylenediamine are used in combination as amino donors to react with terephthaloyl chloride, resulting in covalent bonding. The p-phenylenediamine molecule has a symmetrical structure, and the electron cloud density and spatial environment of the two amino groups are completely identical, exhibiting no difference in activity or spatial priority in their reaction with terephthaloyl chloride. The resulting polyamide backbone includes… "and" The regular linear structure of aramid allows for tight and directional packing of molecular chains, reducing gaps caused by structural bending and branching between chains. This results in uniform and stable intermolecular forces, providing aramid with stable basic mechanical properties. The introduction of 2-imidazolium p-phenylenediamine, through the unique conjugation effect and polar interaction of heterocycles, allows for two main benefits. First, the nitrogen atom in the imidazolium ring is highly electronegative, forming intermolecular hydrogen bonds with the amide bonds of adjacent molecular chains. Second, the conjugated structure of the imidazolium ring enhances the interchain bonding force through π-π packing. These two effects work together to improve intermolecular forces, effectively addressing the lack of flexibility caused by the excessive rigidity of a single p-phenylenediamine chain segment. The enhanced interchain bonding force also inhibits molecular chain movement and slippage at high temperatures, further optimizing the heat resistance of aramid. This allows aramid to maintain its basic mechanical properties while possessing superior flexibility and structural stability at high temperatures. Attached Figure Description
[0035] Figure 1 This is a photograph of the modified aramid fiber based on a polyamide solution containing heterocyclic monomers prepared in Example 1.
[0036] Figure 2 This is a flowchart illustrating the preparation process of a modified aramid based on a polyamide solution containing heterocyclic monomers. Detailed Implementation
[0037] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application will be provided below.
[0038] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.
[0039] Example 1
[0040] like Figure 2 As shown, this embodiment provides a method for preparing modified aramid based on a polyamide solution containing heterocyclic monomers, specifically including the following steps:
[0041] S1. Under nitrogen protection, add 2 parts of p-phenylenediamine and 18 parts of 2-imidazolyl-p-phenylenediamine to 41 parts of N-methylpyrrolidone, control the temperature at 0-5℃, stir for 30 min to obtain a mixed amine solution.
[0042] S2. Control the reaction temperature at 5℃, add 15 parts of terephthaloyl chloride to the mixed amine solution in 3 batches, with a total feeding time of 30 min, and stir at 350 r / min for 0.5 h to form a polyamide prepolymer solution;
[0043] S3. Add 16 parts of triethylamine to the polyamide prepolymer solution, heat to 25°C and continue stirring for 60 min to complete the polymerization reaction and obtain reaction solution A.
[0044] S4. Immerse the polytetrafluoroethylene composite filter membrane in a 2% (w / w) γ-aminopropyltriethoxysilane ethanol solution, sonicate for 20 min, and then dry the filter membrane at 60°C to obtain a modified polytetrafluoroethylene composite filter membrane. Filter reaction solution A through the modified polytetrafluoroethylene composite filter membrane, and then degas under vacuum at 35°C for 20 min to obtain a polyamide spinning solution.
[0045] S5. Mix the polyamide spinning solution obtained in step S4 with a 10% sulfuric acid solution at a volume ratio of 1:3, control the mixing temperature at 10°C and the mixing time at 5 min to obtain the preheated spinning solution.
[0046] S6. The preheated spinning solution is delivered to the spinneret through a metering pump. The spinneret has an orifice diameter of 0.05 mm and a pressure of 0.3 MPa to obtain the filament formed by spinning.
[0047] S7. Introduce the filament formed by spinning into a 25% sulfuric acid solution, control the temperature at 20℃, and let the filament stay in the sulfuric acid solution for 30 seconds to obtain the cured filament.
[0048] S8. The cured filaments are subjected to a three-stage water washing process: the first stage is at a water temperature of 30℃ and a rinsing time of 5 minutes; the second stage is at a water temperature of 40℃ and is rinsed with a 0.5% sodium carbonate solution for 10 minutes; the third stage is at a water temperature of 50℃ and is rinsed with pure water until the pH value is 6.5-7.5 for 8 minutes to obtain the cleaned filaments.
[0049] S9. The cleaned filaments are oiled in an oil bath. The oil used isooctyl stearate oil is used. The oil bath temperature is 40℃ and the oiling time is 5s to obtain the oiled filaments.
[0050] S10. Introduce the oiled filament into a winding device, control the winding speed at 800 m / min, and wind the filament into a cylinder to obtain modified aramid based on a polyamide solution containing heterocyclic monomers. The actual product is as follows: Figure 1 As shown.
[0051] Example 2
[0052] like Figure 2 As shown, this embodiment provides a method for preparing modified aramid based on a polyamide solution containing heterocyclic monomers, specifically including the following steps:
[0053] S1. Under nitrogen protection, add 3 parts of p-phenylenediamine and 19 parts of 2-imidazolyl p-phenylenediamine to 45 parts of N-methylpyrrolidone, control the temperature at 0-5℃, and stir for 35 min to obtain a mixed amine solution.
[0054] S2. Control the reaction temperature at 8℃, add 16 parts of terephthaloyl chloride to the mixed amine solution in 4 batches, with a total feeding time of 35 min, and stir at 380 r / min for 1 h to form a polyamide prepolymer solution.
[0055] S3. Add 17 parts of triethylamine to the polyamide prepolymer solution, heat to 28°C and continue stirring for 65 min to complete the polymerization reaction and obtain reaction solution A.
[0056] S4. Immerse the polyethersulfone composite filter membrane in a 3% (w / w) solution of γ-glycidyl etheroxypropyltrimethoxysilane in ethanol, sonicate for 25 min, and then dry the filter membrane at 70°C to obtain the modified polyethersulfone composite filter membrane. Filter reaction solution A through the modified polyethersulfone composite filter membrane, and then degas under vacuum at 35°C for 30 min to obtain the polyamide spinning solution.
[0057] S5. Mix the polyamide spinning solution obtained in step S4 with a 12% sulfuric acid solution at a volume ratio of 1:4, control the mixing temperature at 12°C and the mixing time at 6 min to obtain the preheated spinning solution.
[0058] S6. The preheated spinning solution is delivered to the spinneret through a metering pump. The spinneret has an orifice diameter of 0.06 mm and a pressure of 0.4 MPa to obtain the filament formed by spinning.
[0059] S7. Introduce the filament formed by spinning into a 28% sulfuric acid solution, control the temperature at 22℃, and let the filament stay in the sulfuric acid solution for 35 seconds to obtain the cured filament.
[0060] S8. The cured filaments are subjected to a three-stage water washing process: the first stage water temperature is 32℃ and the rinsing time is 6min; the second stage water temperature is 42℃ and the rinsing time is 11min with a sodium carbonate solution of 0.8% by mass; the third stage water temperature is 52℃ and the rinsing time is 9min with pure water until the pH value is 6.5-7.5, to obtain the cleaned filaments.
[0061] S9. The cleaned filaments are oiled in an oil bath using polyethylene glycol monooleate as the oil agent. The oil bath temperature is 42℃ and the oiling time is 6s to obtain the oiled filaments.
[0062] S10. Introduce the oiled filament into the winding device, control the winding speed to 900m / min, and wind the filament into a cylinder to obtain modified aramid based on a polyamide solution containing heterocyclic monomers.
[0063] Example 3
[0064] like Figure 2 As shown, this embodiment provides a method for preparing modified aramid based on a polyamide solution containing heterocyclic monomers, specifically including the following steps:
[0065] S1. Under nitrogen protection, add 4 parts of p-phenylenediamine and 20 parts of 2-imidazolyl p-phenylenediamine to 49 parts of N-methylpyrrolidone, control the temperature at 0-5℃, stir for 40 min to obtain a mixed amine solution.
[0066] S2. Control the reaction temperature at 10℃, add 17 parts of terephthaloyl chloride to the mixed amine solution in 5 batches, with a total feeding time of 40 min, and stir at a speed of 400 r / min for 0.5 h to form a polyamide prepolymer solution;
[0067] S3. Add 18 parts of triethylamine to the polyamide prepolymer solution, heat to 30°C and continue stirring for 70 min to complete the polymerization reaction and obtain reaction solution A.
[0068] S4. A polypropylene composite filter membrane was immersed in a 4% (w / w) γ-methacryloxypropyltrimethoxysilane ethanol solution, ultrasonically treated for 30 min, and then dried at 80℃ to obtain a modified polypropylene composite filter membrane. The reaction solution A was filtered through the modified polypropylene composite filter membrane, and then degassed at 38℃ for 20 min under vacuum to obtain a polyamide spinning solution.
[0069] S5. Mix the polyamide spinning solution obtained in step S4 with a 15% sulfuric acid solution at a volume ratio of 1:5, control the mixing temperature at 15℃ and the mixing time at 8min to obtain the preheated spinning solution.
[0070] S6. The preheated spinning solution is delivered to the spinneret through a metering pump. The spinneret has an orifice diameter of 0.08 mm and a pressure of 0.5 MPa to obtain the filament formed by spinning.
[0071] S7. Introduce the filaments formed by spinning into a 30% sulfuric acid solution, control the temperature at 25℃, and allow the filaments to remain in the sulfuric acid solution for 40 seconds to obtain the cured filaments.
[0072] S8. The cured filaments are subjected to a three-stage water washing process: the first stage water temperature is 35℃ and the rinsing time is 8min; the second stage water temperature is 45℃ and the rinsing time is 1% sodium carbonate solution for 12min; the third stage water temperature is 55℃ and the rinsing time is 10min with pure water until the pH value is 6.5-7.5, to obtain the cleaned filaments.
[0073] S9. The cleaned filaments are oiled in an oil bath. The oil used isooctyl stearate oil is used. The oil bath temperature is 45℃ and the oiling time is 8s to obtain the oiled filaments.
[0074] S10. Introduce the oiled filament into the winding device, control the winding speed to 1000m / min, and wind the filament into a cylinder to obtain modified aramid based on a polyamide solution containing heterocyclic monomers.
[0075] Example 4
[0076] like Figure 2 As shown, this embodiment provides a method for preparing modified aramid based on a polyamide solution containing heterocyclic monomers, specifically including the following steps:
[0077] S1. Under nitrogen protection, 3.5 parts of p-phenylenediamine and 18.5 parts of 2-imidazolyl p-phenylenediamine were added to 47 parts of N-methylpyrrolidone. The temperature was controlled at 0-5℃ and the mixture was stirred for 45 minutes to obtain a mixed amine solution.
[0078] S2. Control the reaction temperature at 7℃, add 16.5 parts of terephthaloyl chloride to the mixed amine solution in 4 batches, with a total feeding time of 38 min, and stir at a speed of 375 r / min for 0.75 h to form a polyamide prepolymer solution;
[0079] S3. Add 16.5 parts of triethylamine to the polyamide prepolymer solution, heat to 27°C and continue stirring for 68 minutes to complete the polymerization reaction and obtain reaction solution A;
[0080] S4. Immerse the cellulose acetate composite filter membrane in a 5% (w / w) γ-aminopropyltriethoxysilane mixed ethanol solution, sonicate for 28 min, and then dry the filter membrane at 75°C to obtain a modified cellulose acetate composite filter membrane. Filter reaction solution A through the modified cellulose acetate composite filter membrane, and then degas under vacuum at 35°C for 30 min to obtain a polyamide spinning solution.
[0081] S5. Mix the polyamide spinning solution obtained in step S4 with a 13% sulfuric acid solution at a volume ratio of 1:4, control the mixing temperature at 13℃ and the mixing time at 7 min to obtain the preheated spinning solution.
[0082] S6. The preheated spinning solution is delivered to the spinneret through a metering pump. The spinneret has an orifice diameter of 0.07 mm and a pressure of 0.4 MPa to obtain the filament formed by spinning.
[0083] S7. Introduce the filament formed by spinning into a 27% sulfuric acid solution, control the temperature at 23℃, and let the filament stay in the sulfuric acid solution for 38 seconds to obtain the cured filament.
[0084] S8. The cured filaments are subjected to a three-stage water washing process: the first stage water temperature is 33℃ and the rinsing time is 7min; the second stage water temperature is 43℃ and the rinsing time is 11min with a 0.7% sodium carbonate solution; the third stage water temperature is 53℃ and the rinsing time is 9min with pure water until the pH value is 6.5-7.5, to obtain the cleaned filaments.
[0085] S9. The cleaned filaments are oiled in an oil bath. The oil is polyethylene glycol monooleate oil, the oil bath temperature is 43℃, and the oiling time is 7s to obtain the oiled filaments.
[0086] S10. Introduce the oiled filament into the winding device, control the winding speed to 900m / min, and wind the filament into a cylinder to obtain modified aramid based on a polyamide solution containing heterocyclic monomers.
[0087] Comparative Example 1
[0088] Comparative Example 1 provides a method for preparing modified aramid based on a polyamide solution containing heterocyclic monomers. The difference from Example 1 is that 2-imidazolyl-p-phenylenediamine is not added in S1, while the other steps and parameters are the same as in Example 1.
[0089] Comparative Example 2
[0090] Comparative Example 2 provides a method for preparing modified aramid based on a polyamide solution containing heterocyclic monomers. The difference from Example 1 is that terephthaloyl chloride is added in S2 in one step, while the other steps and parameters are the same as in Example 1.
[0091] Mechanical tests were conducted on the modified aramid fibers based on polyamide solutions containing heterocyclic monomers prepared in Examples 1-4 and Comparative Examples 1-2. The specific test results are shown in Table 1.
[0092] Table 1. Mechanical property test results of aramid fibers modified with heterocyclic monomer-containing polyamide solutions obtained in Examples 1-4 and Comparative Examples 1-2.
[0093]
[0094] Thermal tests were performed on the aramid fibers based on polyamide solutions containing heterocyclic monomers prepared in Examples 1-4 and Comparative Examples 1-2. The specific test results are shown in Table 2.
[0095] Table 2. Thermal property test results of aramid fibers modified with heterocyclic monomer-containing polyamide solutions prepared in Examples 1-4 and Comparative Examples 1-2.
[0096]
[0097] As shown in Tables 1 and 2, Examples 1-4 and Comparative Examples 1-2 focused on the preparation method and performance of modified aramid fibers based on polyamide solutions containing heterocyclic monomers. The core principle was to achieve performance control through molecular structure design and process parameter optimization. Examples 1-4 obtained modified aramid fibers with different structures by adjusting the batch and increment of terephthaloyl chloride addition, reaction temperature, stirring rate, sulfuric acid concentration, spinning parameters, and washing conditions in the spinning process. The introduction of 2-imidazolium-based p-phenylenediamine enhances the rigidity of the molecular chain through the conjugation effect of the heterocyclic structure, while the polar effect of the imidazolium group enhances intermolecular forces, thereby improving the mechanical strength and thermal stability of the fiber. The incremental addition of terephthaloyl chloride in batches avoids uneven polymerization caused by excessively high local concentrations, ensuring a uniform distribution of molecular chain length and thus improving the stability of fiber performance.
[0098] In contrast, Comparative Example 1, lacking the addition of 2-imidazolyl-p-phenylenediamine, relies solely on the rigid structure formed by p-phenylenediamine and terephthaloyl chloride. Lacking the heterocyclic conjugation effect and the reinforcing effect of polar groups, intermolecular forces are weakened, resulting in a significant decrease in mechanical properties. The elastic modulus may drop to around 120 GPa, the tensile strength to approximately 3.8 GPa, and the elongation at break is also reduced. In terms of thermal properties, due to the single heat-resistant structure of the molecular chain, the glass transition temperature and pyrolysis temperature are likely lower than in the example, and the limiting oxygen index (LOI) may drop to 38%, making its overall performance far inferior to the example. Comparative Example 2, by adding terephthaloyl chloride all at once, deviating from the requirement of adding it in 3-5 batches, resulted in intense local polymerization reactions, uneven molecular chain length distribution, and the formation of low-molecular-weight fragments in some areas due to excessively rapid reactions. This weakened the overall structural integrity of the fiber, and its performance was also inferior to the example. Its tensile strength was approximately 4.8 GPa, the elastic modulus approximately 135 GPa, and its thermal properties, such as pyrolysis temperature and auto-ignition temperature, were also slightly lower than in the example, failing to achieve the superior performance level of the example.
[0099] Therefore, this application has achieved the improvement of aramid performance from both the molecular structure and preparation process levels by introducing 2-imidazolium-p-phenylenediamine to enhance intermolecular interactions and increasing the feed in batches to ensure polymerization uniformity. The modified aramid based on polyamide solution containing heterocyclic monomers obtained is significantly better than the comparative scheme with missing raw materials or unreasonable process in terms of mechanical and thermal properties. Moreover, the preparation process has a certain degree of controllability and stability, and has good application prospects and promotion value.
[0100] It should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application, and all such modifications and substitutions should be covered within the scope of the claims of this application.
Claims
1. A modified aramid fiber based on a polyamide solution containing heterocyclic monomers, characterized in that, The modified aramid is prepared by spinning a polyamide solution containing heterocyclic monomers; The polyamide solution containing heterocyclic monomers includes p-phenylenediamine, terephthaloyl chloride, 2-imidazolyl-p-phenylenediamine, N-methylpyrrolidone, and triethylamine; A method for preparing modified aramid fibers based on polyamide solutions containing heterocyclic monomers: S1. Under nitrogen protection, p-phenylenediamine and 2-imidazolyl-p-phenylenediamine are added to N-methylpyrrolidone and stirred until homogeneous to obtain a mixed amine solution; S2. Control the reaction temperature at 5-10℃, add terephthaloyl chloride to the mixed amine solution in batches, with a total feeding time of 30-40 min, and stir at a speed of 350-400 r / min for 0.5-1 h to form a polyamide prepolymer solution; S3. Add triethylamine to the polyamide prepolymer solution, heat to 25-30℃ and continue stirring for 60-70 min to complete the polymerization reaction and obtain reaction solution A; S4. Filter the reaction solution A through a filter membrane, and then degas it under vacuum at 35-40℃ for 20-30 minutes to obtain the polyamide spinning solution. S5. Mix the polyamide spinning solution with the first acid solution, control the mixing temperature at 10-15℃ and the mixing time at 5-8 min, to obtain the preheated spinning solution. S6. The preheated spinning solution is delivered to the spinneret through a metering pump, and the spinneret is spun into filaments. The orifice diameter of the spinneret is 0.05-0.08 mm and the pressure is 0.3-0.5 MPa, thus obtaining the filaments formed by spinning. S7. Introduce the filament formed by spinning into the second acid solution for curing. The temperature is controlled at 20-25℃, and the residence time of the filament in the second acid solution is 30-40s to obtain the cured filament. S8. The cured filaments are sent into the cleaning tank and cleaned using a three-stage water washing process to obtain the cleaned filaments. S9. The cleaned filaments are oiled in an oil bath. The oil used in the oil bath includes any one of isooctyl stearate and polyethylene glycol monooleate. The oil bath temperature is 40-45℃ and the oiling time is 5-8s to obtain the oiled filaments. S10. Introduce the oiled filament into the winding device, control the winding speed to 800-1000 m / min, and wind the filament into a cylinder to obtain modified aramid based on a polyamide solution containing heterocyclic monomers.
2. The modified aramid fiber based on a polyamide solution containing heterocyclic monomers according to claim 1, characterized in that, The mass ratio of p-phenylenediamine, terephthaloyl chloride, 2-imidazolyl p-phenylenediamine, N-methylpyrrolidone and triethylamine is (2-4):(15-17):(18-20):(41-49):(16-18).
3. The method for preparing modified aramid based on a polyamide solution containing heterocyclic monomers according to claim 1, characterized in that, The p-phenylenediamine and 2-imidazolyp-phenylenediamine described in S1 are stirred at 0~5℃ for 30~45 min.
4. The method for preparing modified aramid based on a polyamide solution containing heterocyclic monomers according to claim 1, characterized in that, S2 phthaloyl chloride was added to the mixed amine solution in 3 to 5 batches.
5. The method for preparing modified aramid based on a polyamide solution containing heterocyclic monomers according to claim 1, characterized in that, The filter membrane in S4 is a composite filter membrane modified with a silane coupling agent, and the composite filter membrane includes any one of polytetrafluoroethylene, polyethersulfone, polypropylene and cellulose acetate.
6. The method for preparing modified aramid based on a polyamide solution containing heterocyclic monomers according to claim 5, characterized in that, Silane coupling agents include any one of γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, or γ-methacryloyloxypropyltrimethoxysilane; The modification method is as follows: the composite filter membrane is immersed in a 2-5% (w / w) silane coupling agent ethanol solution, ultrasonically treated for 20-30 min, and then dried at 60-80℃.
7. The method for preparing modified aramid based on a polyamide solution containing heterocyclic monomers according to claim 1, characterized in that, In S5, the first acid solution is a sulfuric acid solution with a mass fraction of 10%-15%, and the volume ratio of the polyamide spinning solution to the first acid solution is (1:3)-(1:5).
8. The method for preparing modified aramid based on a polyamide solution containing heterocyclic monomers according to claim 1, characterized in that, The second acid solution in S7 is a sulfuric acid solution with a mass fraction of 25%-30%.
9. The method for preparing modified aramid based on a polyamide solution containing heterocyclic monomers according to claim 1, characterized in that, The S8 three-stage water washing process is as follows: the first stage water temperature is 30-35℃, and the rinsing time is 5-8 minutes; the second stage water temperature is 40-45℃, and the rinsing time is 10-12 minutes with a sodium carbonate solution of 0.5%-1% by mass; the third stage water temperature is 50-55℃, and the rinsing time is 8-10 minutes with pure water until the pH value reaches 6.5-7.5.