Process method for preparing multi-component aramid copolymer through continuous polymerization

Abstract

The invention discloses a process method for preparing a multi-component aramid copolymer through continuous polymerization, and relates to the technical field of high polymer material preparation, and the process method comprises the following steps: S1, preparing a premix: weighing one or more aromatic diamine monomers according to a certain mass ratio, dissolving the aromatic diamine monomers in an amide solvent or a solvent compounded by amides and hydrotropy salt, and stirring to obtain the premix; uniformly stirring and dissolving in a reaction kettle under the protection of a nitrogen environment to form a premix; s2, low-temperature pre-polycondensation reaction; s3, low-temperature polycondensation reaction; s4, post-treatment: neutralizing, washing and drying the multi-element aramid polymer powder obtained in S3, and removing the solvent and the hydrotropy salt to obtain pure and uniform-particle brown yellow powder; or the obtained polymerization stock solution is neutralized, defoamed and filtered to obtain a spinning stock solution, the intrinsic viscosity of the processed brown yellow powder or spinning stock solution is larger than 4.5 dL / g, the polymer powder / polymerization solution can be used for preparing the multi-element aramid fiber through spinning, and the method effectively reduces the industrial production cost of the multi-element cyclic aramid fiber and improves the production efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material preparation, and in particular to a process for preparing polyaramid copolymers by continuous polymerization. Background Art

[0002] Aramid is a synthetic fiber made by spinning aromatic polyamide resin. It was first successfully developed by DuPont in the United States in 1972. Subsequently, Russia, the Netherlands, Japan and my country have developed high-performance aramid fibers with anti-bullet properties. Domestic aramid fibers are divided into aramid I (polyparaphenylene terephthalamide fiber), aramid II (polyparaphenylene terephthalamide fiber), and aramid III (heterocyclic aromatic polyamide fiber). Among them, aramid III, as a high-performance organic fiber, is a heterocyclic polyamide fiber made by copolymerizing aromatics containing benzimidazole structure as the third monomer on the basis of para-aramid through a special spinning process. Its performance is better than that of traditional aramid II fibers, and it is mainly used in high-end aerospace, electronics and electrical, and national defense and military fields, such as the production of aircraft components, airborne / satellite / shipborne radar covers, corrugated structural parts, satellite components, composite high-pressure vessels, aircraft structural materials, bulletproof armor materials, solid rocket engine casings and other fields.

[0003] At present, the polymerization of ternary (China's Aramid III, Russia's Armos, Japan's Technora) or multi-aramid fibers all adopts low-temperature solution intermittent batch polymerization. This method has the following problems: the molecular weight of the polymer varies from batch to batch, which affects the stability of fiber quality, and the production efficiency is low and the production cost is too high. Due to the above reasons, Aramid III cannot be produced on a large scale at present, which seriously restricts the application of high-performance multi-aramid fibers.

[0004] For example, the invention patent application with the publication number "CN101921395A" published on December 22, 2010 discloses a high-performance heterocyclic aramid fiber and its preparation and application. In this scheme, a heterocyclic ring is introduced into the polymer main chain through a ternary co-condensation reaction and a heterocyclic third monomer is used to participate in the co-condensation, thereby reducing the regularity of the polymer chain and the crystallinity, and forming a very strong intermolecular hydrogen bond, so that it has high strength and high modulus and high elongation at break. The production process of the heterocyclic aramid fiber is solution polymerization and wet spinning, which has achieved industrial production. However, this method is limited by the low spinning speed and has the problems of low efficiency and high cost.

[0005] For another example, the invention patent application with the publication number "CN112961342A" published on June 15, 2021 discloses a method for continuous polymerization of heterocyclic aramid. In this solution, p-phenylenediamine, 2-(4-aminophenyl)-5-aminobenzimidazole, and terephthaloyl chloride are used as monomers, an N-methylpyrrolidone / calcium chloride composite system is used as the solvent, and a twin-screw extruder is used as the continuous polymerization reactor, which has the advantage of continuously polymerizing heterocyclic aramid polymers. However, the extraction agent added in this method, such as chloroform, is environmentally harmful, and the addition amount is large, the treatment process is complex, and impurities are likely to remain, affecting the quality of the polymer. Summary of the Invention

[0006] The present invention provides a process for continuously polymerizing and preparing a polyarylene aramid copolymer. One or more aromatic diamines are selected and adapted to a solvent system to form a premix. A low-temperature continuous polycondensation process is adopted, and a continuous mixer or a continuous microtubular reactor is combined with a high-speed shearing device, a twin-screw or a coaxial main reactor, to realize the continuous preparation of a polyarylene aramid copolymer, and obtain a polyarylene aramid polymer powder or polymerization liquid with stable performance. The intrinsic viscosity of the yellowish-brown powder or spinning dope is greater than 4.5 dL / g. The polymer powder / polymerization liquid can be further used to prepare polyarylene aramid by wet spinning, dry spinning or wet-dry spinning. This process effectively reduces the industrial production cost of polycyclic aramid and improves the production efficiency.

[0007] The present invention is realized through the following technical solutions: A process for continuously polymerizing and preparing a polyarylene aramid copolymer, comprising the following steps: S1. Prepare a premix Weigh one or more aromatic diamine monomers according to a certain mass ratio, dissolve them in an amide solvent or a solvent prepared by mixing an amide and a co-solvent salt, and stir and dissolve them evenly in a reaction kettle under the protection of nitrogen environment to form a premix; S2. Low-temperature pre-polycondensation reaction The uniformly dissolved diamine monomer solution and terephthaloyl chloride are subjected to high-speed stirring and mixing polycondensation in a continuous mixer or a continuous microtubular reactor under the low-temperature condition of -10 to 0 °C to form a prepolymer mixture; S3. Low-temperature polycondensation reaction Then, add the remaining mass ratio of terephthaloyl chloride to the prepolymer mixture, and carry out polycondensation reaction after high-speed shearing by a twin-screw or a coaxial reactor at a low temperature of -10 to 0 °C, and a polyarylene aramid polymer powder or polymerization stock solution with stable batches can be continuously obtained; S4. Post-treatment The polyarylene aramid polymer powder obtained in S3 is subjected to neutralization, washing, and drying treatments to remove the solvent and solubilizing salts, resulting in a pure, uniformly granulated yellowish-brown powder; or the obtained polymerization stock solution is subjected to neutralization, degassing, and filtration treatments to obtain a spinning dope, and the intrinsic viscosity of the obtained yellowish-brown powder or spinning dope is greater than 4.5 dL / g.

[0008] Further, in step S1, the aromatic diamine monomer includes a heterocyclic-containing aromatic diamine monomer and / or a non-heterocyclic-containing aromatic diamine monomer.

[0009] Further, the heterocyclic-containing aromatic diamine monomer is an aromatic diamine having a substituted or unsubstituted phenylbenzimidazole or diphenyl ether type, including 5(6)-amino-2-(4-aminophenyl)benzimidazole, 3,4-diaminodiphenyl ether, 3,3'-dichloro-4,4'-diaminodiphenylmethane.

[0010] Further, the non-heterocyclic-containing aromatic diamine monomer includes a para-type aromatic diamine, and the para-type aromatic diamine includes p-phenylenediamine, p-benzidine, and 2-chloro-p-phenylenediamine.

[0011] Further, in step S1, the amide solvent includes one of N-methylpyrrolidone, N-acetylpyrrolidone, N,N-dimethylacetamide, N,N-diethylacetamide, tetramethylurea, and N,N-dimethylimidazolinone.

[0012] Further, in step S1, the water content of the amide solvent is less than 500 ppm. In this solution, considering that water affects the reaction activity of the acyl chloride group, too high a water content will reduce the reaction activity of the acyl chloride group. Therefore, it is appropriate to control the water content of the amide solvent to be less than 500 ppm.

[0013] Further, in step S1, the solubilizing salt is one of calcium chloride, lithium chloride, aluminum chloride, and magnesium chloride or a double salt system of two of them, and the content of the solubilizing salt in the solvent system is 0-8% of the amide solvent.

[0014] Further, in steps S2 and S3, the molar ratio of the total amount of the monomer aromatic diamine to terephthaloyl chloride is 0.995:1 to 1.005, wherein the mass ratio of the terephthaloyl chloride added in step S2 is 0-100%, and the remaining terephthaloyl chloride is added in step S3.

[0015] Further, in step S1, when adding the solvent, the temperature is controlled at 10-20°C. If the dissolution temperature is too high, the solution is prone to oxidation and discoloration; if the temperature is too low, it will affect the dissolution rate of the aromatic diamine monomer.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects: I. In the present invention, a process for continuously polymerizing to prepare a polyarylene aramid copolymer is proposed. One or more aromatic diamines are selected and adapted to a solvent system to form a premix. A low-temperature (-10~0°C) continuous polycondensation process is adopted, and a high-shear device such as a continuous mixer or a continuous microtubular device is combined with a twin-screw main reactor to realize the continuous preparation of the polyarylene aramid copolymer, and obtain polyarylene aramid polymer powder or polymerization liquid with high batch stability. Moreover, the intrinsic viscosity of the obtained polyarylene aramid polymer powder or polymerization liquid is greater than 4.5 dL / g. Then, the polymer powder / polymerization liquid is used to prepare polyarylene aramid by wet spinning, dry spinning or wet-dry spinning. This process method can be carried out continuously, can shorten the production cycle of polyarylene aramid, and helps to improve production efficiency and reduce the industrial production cost of polyarylene aramid.

[0017] II. In the present invention, first, the diamine monomer solution and terephthaloyl chloride are subjected to a low-temperature pre-polycondensation reaction in a continuous mixer or a continuous microtubular device, and then the material is sent to a twin-screw reactor to complete the main reaction. The whole production process is controlled for segmented polymerization to make the reaction process stable and controllable. The obtained polymerization liquid or polymer resin powder is uniform and pure, and the product performance and index parameters are stable and controllable. In addition, the production equipment used is simple and the product process flow is short.

[0018] III. In the present invention, the method for continuously polymerizing to prepare a polyarylene aramid copolymer realizes the continuous and stable preparation of polyarylene aramid resin powder, and the high-viscosity polyarylene aramid resin provides a raw material basis for breaking through the technology of preparing polyarylene aramid fiber by high-speed wet-dry spinning.

[0019] IV. In the present invention, in step S2, a continuous mixer such as a T-shaped mixer or a continuous microtubular device is used for the low-temperature pre-polycondensation reaction, which is convenient for the uniform dispersion and full mixing of the materials to achieve the purpose of the low-temperature pre-polycondensation reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a process flow chart related to the present invention.

[0021] Figure 2 It is a photo of the spinning dope obtained in the first group of Example 1.

[0022] Figure 3 It is a photo of the yellow resin powder obtained in the fifth group of Example 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The present invention will be further described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto.

[0024] To facilitate the public's understanding of the present invention, the following embodiments take the preparation of different polyarylene aramid copolymers by combining multiple monomers as an example to further illustrate the present solution. At the same time, the effects of the monomers, solvent systems, process conditions, etc. used on the products and the production process are investigated.

[0025] Example 1 This embodiment is a process method for continuously polymerizing to prepare a polyarylene aramid copolymer, belonging to the technical field of polymer material preparation, and includes the following steps: S1. Prepare a premix Weigh one or more aromatic diamine monomers according to a certain mass ratio, dissolve them in an amide solvent or a solvent prepared by mixing an amide with a co-solvent salt, and stir and dissolve them evenly in a reaction kettle under the protection of nitrogen environment to form a premix.

[0026] In this embodiment, the aromatic diamine monomers are p-phenylenediamine and 3,4'-diaminodiphenyl ether. The raw materials are weighed according to a molar ratio of 1:1. Under the protection of nitrogen, they are added to a dissolution kettle with N,N-dimethylacetamide as the solvent, and the water content of the solvent is 400 ppm. In this embodiment, the water content of the solvent is controlled within a range lower than 500 ppm.

[0027] In this step, the temperature is controlled at 20°C. If the dissolution temperature is too high, the solution is prone to oxidation and discoloration. If the temperature is too low, it will affect the dissolution rate of the aromatic diamine monomers. The co-solvent salt in this solvent system is lithium chloride, and the solution is reserved after being dissolved evenly.

[0028] S2. Low-temperature pre-polycondensation reaction The p-phenylenediamine and 3,4'-diaminodiphenyl ether monomer solutions dissolved evenly and a part of terephthaloyl chloride are mixed at a low temperature of -8°C through a high-speed stirrer to form a prepolymer.

[0029] S3. Low-temperature polycondensation reaction The prepolymer is transported through a pipeline to a twin-screw mixer, and the remaining part of terephthaloyl chloride is added. The temperature of the front section of the twin-screw mixer is controlled at -5°C to transport the materials, and the temperature of the rear section is set at 50°C for efficient kneading and mixing to carry out a polycondensation reaction to obtain a polymerization solution.

[0030] Using the above preparation process, then adjust the process conditions according to Table 1 below to prepare different groups of polyarylene aramid polymerization solutions.

[0031] Table 1 S4. Post-treatment The polymerization stock solution obtained in S3 is subjected to neutralization, defoaming, and filtration treatments to obtain a spinning stock solution. Refer to Figure 2 , Figure 2 is a photo of the spinning stock solution obtained in the first group.

[0032] The obtained polyaramid spinning dope of each group was then subjected to a dynamic viscosity test at 50 °C. Samples were taken for film preparation by scraping, washed to neutrality, and the solid substance obtained after drying was used to test its inherent viscosity by an Ubbelohde viscometer. The powdered polymer was washed with water to neutrality, and the logarithmic specific viscosity of the dried powder was measured by an Ubbelohde viscometer. The test results are shown in Table 2.

[0033] Table 2 As can be seen from the above experiments, for Groups 1, 2, and 3, after step S4, a uniform polymerization dope was obtained, which was then transported through a pipeline to a neutralization reactor, and alkaline substances calcium oxide or calcium hydroxide were added. Stirring and neutralization were carried out at 40 °C for 1.5 h, and then it was transported through a pipeline to a vacuum degassing kettle. The vacuum degree was controlled at -0.1 MPa, and the degassing time was 45 min to obtain a spinning dope. This dope can be subsequently used for wet or dry-wet spinning to prepare the ternary aramid. Compared with the para-aramid obtained by binary monomer polymerization, it has higher fiber strength and toughness.

[0034] For the polymerization dope obtained in Comparative Group 1, the test result of the inherent viscosity was only 2.4 dL / g, the viscosity was low, and the properties of the ternary aramid obtained by wet spinning were low.

[0035] Example 2 The difference between this example and Example 1 lies in that: In step S1, the aromatic diamine monomers were p-phenylenediamine and 5-amino-2-(4-aminophenyl)benzimidazole, with a molar ratio of 3:7. Under nitrogen protection, they were added to a dissolution kettle with N-methylpyrrolidone as the solvent. The water content of the solvent was 300 ppm, and the temperature was controlled at 15 °C. The dissolution temperature should not be too high, otherwise the solution is prone to oxidation, and if the temperature is too low, it will affect the dissolution rate of the aromatic diamine monomers. The cosolvent salt in this solvent system was calcium chloride, and the solution was uniformly dissolved and then reserved.

[0036] In step S2, the temperature of the premixed solution was lowered to -8 °C, and part of the terephthaloyl chloride monomer was first added, and a prepolymer was formed by high-speed stirring through a continuous micro-tubular reactor.

[0037] In step S3, the prepolymer was transported through a pipeline to a twin-screw reactor, and the remaining part of the terephthaloyl chloride was added. The temperature of the front section of the screw machine was controlled at -5 °C to transport the material, and the temperature of the rear section was 50 °C for efficient kneading and mixing, and a polycondensation reaction occurred to obtain a yellow powdered polymer.

[0038] Using the above preparation process, and then adjusting each process condition according to Table 3 below, various polyaramid polymerization resins were prepared.

[0039] Table 3 In step S4, the polyarylene amide polymer powder obtained in step S3 is washed with water multiple times until neutral, ground evenly, and then dried at a drying temperature of 105-120°C for 2-3 hours to obtain yellow resin powder with uniform particles. Refer to Figure 3 , Figure 3 This is a photo of the yellow resin powder obtained in the 5th group.

[0040] Then, the obtained resin powder is subjected to an intrinsic viscosity test. The reduced specific viscosity is measured using an Ubbelohde viscometer. The average value of the reduced specific viscosity of the powder in the experimental group is 5.03. The test results are shown in Table 4 for reference.

[0041] Table 4 As can be seen from Table 4, the intrinsic viscosity of the powder resin prepared by the method of this embodiment is greater than 4.5 dL / g, and the sulfuric acid liquid crystal dry-wet spinning method can be used for spinning. Compared with wet spinning, the dry-wet method combines the advantages of dry spinning and wet spinning. Using dry spinning to extrude in the air layer, the spinning speed is fast, and the wet spinning has a fast forming speed and easy structure control. While obtaining high strength and high toughness performance, the spinning speed can be effectively increased, and the production cost of ternary aramid can be reduced.

[0042] As can be seen from Comparative Groups 2 and 3, when the molar ratio of aromatic diamine to terephthaloyl chloride is not within the range of 1:0.995-1.005, the polycondensation reaction is incomplete, and thus a powdery polymer with uniform texture is not obtained.

[0043] Example 3 In the process method for continuously polymerizing and preparing a polyarylene amide copolymer in this embodiment, three aromatic diamine monomers, namely p-phenylenediamine, 5-amino-2-(4-aminophenyl)benzimidazole monomer, and o-chloro-p-phenylenediamine monomer, are selected to prepare a quaternary aramid. The specific preparation method is as follows: The difference between this embodiment and Example 2 is only that: In step S1, p-phenylenediamine, 5-amino-2-(4-aminophenyl)benzimidazole monomer, and o-chloro-p-phenylenediamine monomer are weighed respectively at a molar ratio of 1:3:1. Under nitrogen protection, they are dissolved in a dissolution kettle containing N-methylpyrrolidone as the solvent, and the temperature is controlled at 20°C. The cosolvent salt in this solvent system is calcium chloride, and after the solution is dissolved evenly, it is reserved for use.

[0044] Using the above preparation process, then adjust each process condition according to Table 5 below to prepare each group of polyarylene amide polymerization liquid or polymer powder.

[0045] Table 5 In this step S4, the polyarylene polymer powder obtained in step S3 is washed with water multiple times until neutral, ground evenly, and then dried at a temperature of 105-120 °C for 2-3 hours to obtain yellow resin powder with uniform particles.

[0046] The finally obtained yellow powder-state polymer in groups 7-9 is tested for its inherent viscosity by an Ubbelohde viscometer. The test results are shown in Table 6.

[0047] Table 6 As can be seen from Table 6, the intrinsic viscosity of the powder resin prepared by the method of this embodiment is greater than 4.5 dL / g. The dried powder resin can be spun into quaternary aramid fibers by the sulfuric acid liquid crystal method, and the fibers have the characteristics of high strength and high toughness.

[0048] From groups 7-9 and comparative group 4, it can be seen that too high a content of solubilizing salt will affect the polymer morphology. Through analysis, it is known that the polymer has a relatively high molecular weight, is not easy to precipitate from the solution, and the agglomerated particles are relatively large, thus affecting the obtained polymer morphology.

[0049] Comparative Example 1 This comparative example uses the preparation method of the prior art "CN101921395A", in which the raw materials are p-phenylenediamine, 5-amino-2-(4-aminophenyl)benzimidazole, and terephthaloyl chloride to prepare a polymerized liquid ternary aramid product. The characteristics of the product are 80-130 Pa•s. Using the wet spinning process, it is limited by a low spinning speed of 10-20 m / min, and the spinning preparation process takes a long time and has a high production cost. If continuous powder polymerization-sulfuric acid dry-wet high-speed spinning is used to prepare ternary aramid, the spinning speed can be greater than 100 m / min, effectively increasing the production capacity by 5-10 times and reducing the unit production cost.

[0050] Comparative Example 2 The difference between this comparative example and group 5 in Example 2 is only that Step S2 is cancelled, and the premix in step S1 is directly sent to the twin-screw mixer.

[0051] Finally, large agglomerated solid particles are obtained. Through research, it is found that the main reason is that: the monomers of the polycondensation reaction have high activity, the contact time of the materials is short, the reaction is violent, a large amount of heat is released and cannot be effectively transferred out, the materials are not evenly mixed, part of the reaction degree is high and forms gel solids, and part of the materials do not fully contact and the reaction degree is low, resulting in non-uniform products.

[0052] It can be seen that in the low-temperature pre-condensation reaction of step S2, the activity of the reactants is controlled under low-temperature conditions to ensure that the aromatic diamine monomer and the aromatic acyl chloride monomer are fully mixed, and a pre-condensation reaction occurs, so that the degree of reaction can be controlled to ensure that the prepolymer and the aromatic acyl chloride monomer continue to condense and polymerize in step S3, and chain growth reaction continues to occur, so as to obtain a uniform powder polymer.

[0053] It can be seen that the product prepared by this scheme and the product prepared by traditional technology have controllable product morphology, covering the polymerization liquid and powder polymer, and the obtained polymerization liquid and powder polymer have a characteristic viscosity greater than 4.5dL / g. Compared with traditional products, this product has a higher characteristic viscosity and can be adapted to wet or dry-wet spinning processes. It can be used in high-end aerospace, electronic and electrical, and national defense and military fields. However, the process of this scheme has the advantages of continuous production conditions, high production efficiency, and reduced production costs, which is conducive to expanding production.

[0054] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A process for preparing polyaramid copolymer by continuous polymerization, characterized in that: The following steps are involved: S1. Preparation of premix One or more aromatic diamine monomers are weighed according to a certain mass ratio, dissolved in an amide solvent or a solvent prepared by mixing amides with a solubilizing salt, and stirred and dissolved uniformly in a reaction kettle under nitrogen environment protection to form a premix; S2. Low temperature pre-condensation reaction The uniformly dissolved diamine monomer solution and terephthaloyl chloride are mixed and condensed at a low temperature of -10 to 0°C in a continuous mixer or a continuous micro-tube device at a high speed to form a prepolymer mixture; S3, low temperature polycondensation reaction Then, terephthaloyl chloride is added to the prepolymer mixture in an amount of the remaining mass percentage, and a polycondensation reaction is carried out after high-speed shearing in a twin-screw or twin-shaft reactor at a low temperature of -10 to 0°C to obtain a polyaramid polymer powder or a polymer stock solution; S4. Post-processing The polyaramid polymer powder obtained in S3 is neutralized, washed, and dried to remove the solvent and solubilizing salt to obtain a pure, uniformly granulated brown-yellow powder; or the obtained polymer stock solution is neutralized, degassed, and filtered to obtain a spinning stock solution, and the characteristic viscosity of the brown-yellow powder or spinning stock solution obtained after treatment is greater than 4.5dL / g.

2. The process for preparing polyaramid copolymer by continuous polymerization according to claim 1, characterized in that: In step S1, the aromatic diamine monomer includes a heterocyclic aromatic diamine monomer and / or a non-heterocyclic aromatic diamine monomer.

3. The process for preparing polyaramid copolymer by continuous polymerization according to claim 2, characterized in that: The heterocyclic aromatic diamine monomer is an aromatic diamine having substituted or unsubstituted phenylbenzimidazoles or diphenyl ethers, including 5(6)-amino-2-(4-aminophenyl)benzimidazole, 3,4-diaminodiphenyl ether, and 3,3'-dichloro-4,4'-diaminodiphenylmethane.

4. The process for preparing polyaramid copolymer by continuous polymerization according to claim 2, characterized in that: The heterocyclic-free aromatic diamine monomer includes para-type aromatic diamines, and the para-type aromatic diamines include p-phenylenediamine, p-biphenylenediamine and 2-chloro-p-phenylenediamine.

5. The process for preparing poly-aramid copolymer by continuous polymerization according to claim 1, characterized in that: In step S1, the amide solvent includes one of N-methylpyrrolidone, N-acetylpyrrolidone, N,N-dimethylacetamide, N,N-diethylacetamide, tetramethylurea, and N,N-dimethylimidazolidinone.

6. The process for preparing poly-aramid copolymer by continuous polymerization according to claim 1, characterized in that: In step S1, the water content of the amide solvent is lower than 500 ppm.

7. The process for preparing poly-aramid copolymer by continuous polymerization according to claim 1, characterized in that: In step S1, the dissolution-aiding salt is one or two complex salt systems selected from calcium chloride, lithium chloride, aluminum chloride, and magnesium chloride, and the content of the dissolution-aiding salt in the solvent system is 0-8% of the amide solvent.

8. The method for preparing a poly-aramid copolymer by continuous polymerization according to claim 1, characterized in that: In step S2 and step S3, the molar ratio of the total amount of the monomer aromatic diamine to the terephthaloyl chloride is 0.995:1-1.005, wherein the mass proportion of the terephthaloyl chloride added in step S2 is 0-100%, and the remaining terephthaloyl chloride is added in step S3.

9. The method for preparing a poly-aramid copolymer by continuous polymerization according to claim 1, characterized in that: In step S1, when adding the solvent, the temperature is controlled to be 10-20°C.

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