A continuous polymerization method and system for aramid III

Abstract

The present invention provides a continuous polymerization method and system of aramid III, belonging to the technical field of chemical fiber preparation. On the one hand, a continuous polymerization method of aramid III is provided, including monomer dissolution, prepolymerization reaction, polymerization reaction and spinning, and finally, aramid III is obtained; on the other hand, a continuous polymerization system of aramid III is provided, including an amine reactor, an acyl chloride reactor, a micro-tube reactor and a screw reactor, to ensure the continuity of the polymerization process of aramid III. The preparation process of aramid III has the advantages of low labor intensity, stable product quality, easy to realize automatic control and adjustment, and more suitable for large-scale mass production.

Description

Technical Field

[0001] The invention relates to a method for preparing aramid III, in particular to a continuous polymerization method and a system for aramid III, belonging to the technical field of chemical fiber preparation. Background Art

[0002] Aramid, the full name of which is "aromatic polyamide fiber", is defined as: at least 85% of the amide chains (-CONH-) are directly connected to two benzene rings. Among them, para-aramid refers to an aromatic polyamide fiber in which the amide chain (-CONH-) in the fiber molecular chain is directly connected to the para position of the benzene ring to form a polymer structure. Para-aramid mainly includes two types: aramid II and aramid III. Aramid II, also known as aramid 1414, is made by polymerization of terephthaloyl chloride and p-phenylenediamine and dry-wet spinning technology; aramid III is copolymerized by terephthaloyl chloride, p-phenylenediamine and 5(6)-amino-2-(4-aminophenyl)benzimidazole.

[0003] Aramid III is a high-performance fiber obtained by introducing an aromatic heterocyclic structural unit into the molecular chain of Aramid II. The comprehensive mechanical properties of Aramid III are more than 30% higher than those of Aramid II, and it has better wear resistance and UV protection. Among them, domestic Aramid III is a heterocyclic aromatic polyamide fiber similar to Russian APMOC fiber.

[0004] Preparation of aramid III polymer, in the prior art "02133701.2, a process method and production device for preparing high-viscosity aramid III resin mother liquor", the process provided is composed of the steps of preparing prepolymer mother liquor and preparing aramid III resin mother liquor. In the former step, p-phenylenediamine and M3 monomer react with part of terephthaloyl chloride in N,N-dimethylacetamide dissolved with lithium chloride, and the temperature is controlled at -5℃-20℃ to generate a prepolymer mother liquor with a viscosity of 50-100Pa•S; in the latter step, the prepolymer mother liquor reacts with the remaining terephthaloyl chloride added, and the temperature is controlled at 10℃-45℃ to generate qualified aramid III resin. The device for implementing this process is a two-stage forced external circulation system composed of a prepolymerization reactor and a polymerization reactor through a delivery pump and a pipeline, which can fully mix the materials and effectively control the reaction temperature of the system. As for "201010108545.6, a high-performance heterocyclic aromatic fiber and its preparation and application method", p-phenylenediamine and 5(6)-amino-2-(4-aminophenyl)benzimidazole are added to a reaction kettle filled with a composite solvent, stirred at room temperature for 50-150 minutes under nitrogen protection, and then the temperature in the kettle is reduced to -5°C-10°C, and terephthaloyl chloride is added in 3-6 batches, with an interval of 10-100 minutes between each batch, and finally a polymer solution with a polymer solid content of 2-10% and a dynamic viscosity of 40,000-300,000 centipoise is obtained.

[0005] The above-mentioned prior arts all use kettle reactors to produce polymers by intermittent polymerization. 02133701.2 uses two reactors to respectively carry out the prepolymerization and polymerization steps; 201010108545.6 combines the prepolymerization and polymerization into one reactor to produce polymers. The defects of these two technical methods are mainly manifested in:

[0006] 1. During the polymerization reaction stage, terephthaloyl chloride needs to be added to the reaction system several times until the dynamic viscosity index of the polymerization liquid meets the requirements, and the production operation is relatively complicated;

[0007] Second, intermittent reactors are used, and inevitably there are batch quality differences between materials in a single reactor, which causes certain quality fluctuations in fiber products;

[0008] Third, the production efficiency of polymer manufacturing is low and is not suitable for use in large-scale expansion processes.

[0009] However, as the market application of aramid III becomes wider and wider and the demand for products becomes greater and greater, it is necessary to improve the production efficiency of its polymers and develop continuous polymerization technology for aramid III polymers.

[0010] In addition, "201310103261.1 A method for preparing poly(p-phenylene terephthalamide) resin" adopts a mixer and a pre-reactor, which can effectively distribute the heat generated by the entire reaction to the mixer, the pre-reactor and the twin-screw reactor, solve the heat transfer problem, and control the polymerization process; and "200310109431.3 A method for semi-continuous preparation of poly(p-phenylene terephthalamide) resin" discloses: p-phenylenediamine is first pre-condensed with part of terephthaloyl chloride in a solvent system of a solvent and a co-solvent, and the pre-condensate and the remaining terephthaloyl chloride powder are added to a twin-screw extruder, and dry liquid ammonia is passed to neutralize the hydrogen chloride gas generated by the reaction; and a polymer additive polyvinyl pyrrolidone is added to the twin-screw extruder to obtain a polymer. The above-mentioned prior art all adopts twin-screw reactor to realize continuous polymerization reaction. Patents 201310103261.1 and 200310109431.3 are two methods for manufacturing aramid II (aramid 1414). The two methods adopt the same reactor and realize the manufacturing of aramid II products through different process technologies, and have independent technical characteristics. However, aramid II and aramid III have different monomers and have different essential differences in molecular chain structure.

[0011] Furthermore, in "202110184079.8 A method for continuous polymerization of heterocyclic aramid", p-phenylenediamine, 2-(4-aminophenyl)-5-aminobenzimidazole and terephthaloyl chloride are used as monomers, N-methylpyrrolidone / calcium chloride composite system is used as solvent, and twin-screw extruder is used as continuous polymerization reactor. The design of twin-screw extruder is used to realize continuous and stable polymerization of heterocyclic aramid; extractant is used to accelerate the solvent removal process in the polymerization system, accelerate the solidification rate of the polymer, and cooperate with high-speed shear to achieve uniform crushing of the polymer, and finally continuous washing and continuous drying are used to obtain pure heterocyclic aramid polymer solid powder with uniform particle size. It is a method for continuous polymerization of heterocyclic aramid formed with reference to the aramid II process. Except for the different polymerization reaction monomers, its process technology route is similar to that of aramid II. This method obtains heterocyclic aramid polymer solid powder through polymerization reaction and separation technology. However, the defects of this technology are mainly manifested in:

[0012] 1. Adding terephthaloyl chloride to the twin-screw reactor in a molten state at once is not conducive to the control of the polymerization reaction. First, the temperature of terephthaloyl chloride in a molten state is very high, and the polymerization reaction itself is a violent exothermic reaction. The combination of the two increases the heat exchange load of the reaction. In addition, adding terephthaloyl chloride to the twin-screw reactor at a time is not conducive to controlling the molecular weight of the polymer. This operation is very difficult to control in engineering and can easily lead to unstable product quality during industrial production.

[0013] Second, the product obtained by this technology is a polymer solid powder, and the obtained polymer needs to be further dissolved in an appropriate solvent before spinning to produce fibers. This technology has the disadvantages of long process route, large equipment investment, and complex production control. Summary of the invention

[0014] The present invention aims to solve the problems of the prior art and proposes a continuous polymerization method and system for aramid III. In this technical solution, based on the method of connecting a micro-tube reactor in series with a twin-screw reactor, a kettle reactor is replaced to allow the polymerization monomer to react continuously in the reactor, thereby realizing the continuous production of aramid III.

[0015] The continuous polymerization method is easy to realize automatic control, and the prepared polymer has stable performance, which effectively avoids the problem of amplification effect caused by continuous amplification of a batch reactor, and also solves the problems of low production efficiency and high labor cost of intermittent batch reactors.

[0016] In order to achieve the above technical objectives, the following technical solutions are proposed:

[0017] A continuous polymerization method for aramid III comprises the following steps:

[0018] A. Monomer Dissolution

[0019] Preparation of amine solution: Add polymerization solvent into an amine reaction kettle, then add monomer 5(6)-amino-2-(4-aminophenyl)benzimidazole and monomer p-phenylenediamine respectively, stir until completely dissolved, and obtain amine solution;

[0020] Preparation of acyl chloride solution: Add polymerization solvent to the acyl chloride reaction kettle, then add monomer terephthaloyl chloride, stir until completely dissolved, to obtain acyl chloride solution;

[0021] Wherein, the polymerization solvent is a homogeneous mixed solution including amide and chloride;

[0022] B. Prepolymerization

[0023] The amine solution and part of the acyl chloride solution are introduced into a micro-tube reactor, the temperature is controlled at 15-25°C, and the prepolymerization reaction is carried out for 5-10 minutes to obtain an aramid III prepolymer solution. The prepolymerization reaction is a violently exothermic process. Compared with the kettle reactor in the prior art, the heat exchange area of ​​the micro-tube reactor increases exponentially, and has a strong heat exchange capacity, so that the pre-polymerization reaction temperature can be controlled, thereby ensuring the effectiveness of the pre-polymerization reaction. Among them, the pre-polymerization reaction time is further limited. If the material residence time is too long, the number of micro-tube reactor modules increases, the equipment cost increases, and the production cost increases. The reaction time is limited to 5-10 minutes. Under the premise of ensuring the quality and efficiency of the pre-polymerization reaction, the cost is solved to ensure the continuity of the preparation process;

[0024] The molar flow rate of terephthaloyl chloride involved in the partial acyl chloride solution accounts for 92-97% of the total molar flow rate of terephthaloyl chloride;

[0025] C. Polymerization

[0026] The aramid III prepolymer solution and the remaining acyl chloride solution are introduced into a screw reactor, the temperature is controlled at 35-45°C, and the polymerization reaction is carried out for 6-12 minutes to obtain an aramid III polymer solution. The polymerization reaction in the screw reactor is an exothermic reaction, and the screw reactor is equipped with a cooling and heat exchange system to prevent the reaction system temperature from being too high to produce side reactions. Among them, the polymerization reaction time is further limited. If the reaction time is too short, the polymerization reaction will be incomplete, and the molecular weight distribution of the generated polymer will be wide and the quality will be low; if the reaction time is too long, the production efficiency will be low and waste will be generated. The reaction time is limited to 6-12 minutes. On the premise of ensuring the quality and efficiency of the polymerization reaction, the cost is solved and the continuity of this preparation process is guaranteed;

[0027] The molar flow rate of terephthaloyl chloride involved in the remaining part of the acyl chloride solution accounts for 3-8% of the total molar flow rate of terephthaloyl chloride;

[0028] D. Spinning

[0029] The obtained aramid III polymer solution is spun by using the existing technology, washed with water and dried to obtain aramid III.

[0030] Preferably, in step A, the amide is any one of N-methylpyrrolidone, N,N-dimethylacetamide or N-methylformamide; the chloride is any one of lithium chloride solution, calcium chloride solution or magnesium chloride solution. The amide is an organic solvent for dissolving aramid III prepolymer and polymer; the chloride is an inorganic salt cosolvent for increasing the solubility of aramid III prepolymer and polymer in amide solvents.

[0031] Preferably, the solubility concentration of the chloride in the amide solvent is 1-10%, and the solubility concentration of the chloride in the amide solvent is closely related to the solubility of the aramid III prepolymer and the polymer in the polymerization solvent.

[0032] Preferably, in steps B and C, the ratio of the sum of the molar flow rates of the amine monomers 5(6)-amino-2-(4-aminophenyl)benzimidazole and p-phenylenediamine participating in the prepolymerization reaction to the sum of the molar flow rates of terephthaloyl chloride participating in the prepolymerization reaction and the polymerization reaction is 1:0.95-1.05.

[0033] Among them, the dynamic viscosity of the aramid III prepolymer solution is 1000-10000 cP, and the corresponding prepolymer intrinsic viscosity is 1-3 dL / g; the dynamic viscosity of the aramid III polymer solution is 10000-100000 cP, and the corresponding polymer intrinsic viscosity is 5-7 dL / g.

[0034] A continuous polymerization system for aramid III, comprising an amine reactor, an acyl chloride reactor, a micro-tube reactor and a screw reactor, wherein the amine reactor is connected with a polymerization solvent feed pipe, a 5(6)-amino-2-(4-aminophenyl)benzimidazole feed pipe and a p-phenylenediamine feed pipe, and the acyl chloride reactor is connected with a polymerization solvent feed pipe and a terephthaloyl chloride feed pipe;

[0035] The amine reactor is arranged at the front section of the micro-tube reactor, and the amine reactor is connected to the micro-tube reactor through the amine solution delivery pipe; the acyl chloride reactor is arranged at the front section of the micro-tube reactor, and the acyl chloride reactor is connected to the micro-tube reactor through the acyl chloride solution delivery pipe I; the screw reactor is arranged at the back section of the micro-tube reactor, and the micro-tube reactor is connected to the screw reactor through the prepolymer solution delivery pipe; the acyl chloride reactor is connected to the screw reactor through the acyl chloride solution delivery pipe II.

[0036] Preferably, the micro-tube reactor and the screw reactor are both connected to a cooling and heat exchange system to control the temperature of the reaction system and prevent the reaction system temperature from being too high to cause side reactions.

[0037] Preferably, the front stage of the micro-tube reactor is further provided with a mixer I, and the amine solution delivery pipe and the acyl chloride solution delivery pipe are both connected to the mixer I, and the amine solution and the acyl chloride solution are pre-mixed before prepolymerization to improve the quality of subsequent prepolymerization reaction.

[0038] Preferably, the front section of the screw reactor is further provided with a mixer II, and the prepolymer solution delivery pipe and the acyl chloride solution delivery pipe II are both connected to the mixer II, so that the prepolymer solution and the acyl chloride solution are premixed before polymerization to improve the quality of subsequent polymerization reaction.

[0039] Preferably, the screw reactor is connected to a polymer solution delivery pipe, and both the prepolymer solution delivery pipe and the polymer solution delivery pipe are provided with an online dynamic viscometer to monitor the viscosity of the aramid III prepolymer solution and the aramid III polymer solution, which is then used to adjust the feed amount of the acyl chloride solution.

[0040] Preferably, the micro-tube reactor is provided with an upper heat transfer layer, a material layer for placing the prepolymer solution and a lower heat transfer layer, the material layer is arranged between the heat transfer layer and the lower heat transfer layer, the amine solution and the acyl chloride solution enter the middle material layer at the same time, and are pushed forward under pressure, continuously mixed and reacted, and finally an aramid III prepolymer solution is generated.

[0041] Preferably, the screw reactor is a twin-screw reactor.

[0042] Preferably, the screw reactor has at least two stages, and the screw reactors are connected in series. The number of series stages of the screw reactor is determined by the reaction time of the material in the screw reactor. The multi-stage screw reactor is conducive to increasing the residence reaction time of the material in the screw reactor, thereby ensuring the quality and efficiency of the continuous polymerization process.

[0043] In this technical solution, the screw reactor involved is a screw reactor in the existing mature technology, which can be directly customized and purchased on the market. The screw reactor consists of a transmission system, a barrel, a screw and a heat exchange system. The screw is the core component of the screw reactor, which consists of a screw core shaft and a screw element; the screw element consists of a thread block and a kneading block. The thread block mainly plays a conveying role in the polymerization reaction, and the kneading block is mainly used for mixing and shearing in the polymerization reaction. The heat exchange system is a cooling system. The polymerization reaction is an exothermic reaction, and the heat generated by the reaction needs to be continuously removed to control the reaction temperature.

[0044] In the present technical solution, according to actual needs, metering pumps and flow meters are provided on the amine solution delivery pipe, acyl chloride solution delivery pipe I and acyl chloride solution delivery pipe II; regulating valves are provided under the amine reactor and the acyl chloride reactor.

[0045] The positional relationships involved in this technical solution, such as "front-end process", "back-end process", "inside" and "between", are defined according to the conditions under actual use. They are conventional terms in this technical field and are also conventional terms used by technical personnel in this field in actual use.

[0046] The beneficial technical effects brought about by adopting this technical solution are:

[0047] 1) In the present invention, the engineering bottleneck problem of prepolymerization reaction and polymerization reaction in the continuous production process of aramid III is solved through the combination of a micro-tube reactor and a screw reactor.

[0048] The prepolymerization reaction of aramid III is a violent exothermic reaction. The dynamic viscosity of the generated prepolymer solution gradually increases, and the mixing difficulty of the reaction system increases. The microtube reactor can solve the heat and mass transfer problems of the reaction process very well, so that the reaction temperature can be stably controlled at 15-25°C. Compared with the twin-screw reactor, the heat exchange efficiency of the prepolymer reaction using a microtube reactor is higher, and the molecular weight distribution of the obtained prepolymer is more uniform, which is more conducive to obtaining fiber products with higher performance; in the aramid III polymerization stage, the dynamic viscosity of the reaction system continues to increase, exceeding 10,000 cP, which doubles the microtube fluid resistance in the screw reactor. The microtube reactor can no longer meet the reaction requirements. Therefore, in the aramid III polymerization stage, a screw reactor is used to realize the forced transportation and mixing of high-viscosity materials, and further condensation polymerization reaction is carried out in the screw reactor to generate aramid III polymer;

[0049] 2) In the present invention, the industrial production of the continuous polymerization process of aramid III polymer is realized.

[0050] At present, the polymerization reaction of aramid III adopts intermittent polymerization reaction technology, and the reactors used are all stirred tank reactors. Intermittent tank reactors have the inherent disadvantages of complex operation and high labor costs. Microtube reactors and screw reactors can be combined with automatic control technology to successfully solve this problem. By upgrading reactor devices and technologies, cumbersome manual repetitive labor processes are eliminated, the difficulty of operation is reduced, the probability of production misoperation is greatly reduced, and long-term continuous and stable production of fiber polymers is achieved. At the same time, this technology also liberates human resources, freeing workers from long-term repetitive simple work, and is more conducive to giving full play to their intelligence and creativity;

[0051] 3) In the present invention, continuous production is carried out by connecting a micro-tube reactor in series with a twin-screw reactor, and the product quality is more stable.

[0052] The stirred tank reactor in the prior art adopts an intermittent feeding, reaction, and discharging operation process. Although the production control technology has been improving and the production stability of intermittent reactors has been continuously improving, the inherent characteristic of this type of reactor is that its production is a non-steady-state process, and product quality inevitably fluctuates between batches. For intermittent reactors, what engineers can do is to control the fluctuation range of product quality as much as possible, but they cannot eliminate such fluctuations. The micro-tube reactor in series with the screw reactor is a steady-state production process. Compared with the stirred tank reactor, the control parameters of the series reactor, such as the feed state, reaction temperature, reaction pressure, reaction time, etc., are stable, and the quality of the obtained product is also stable;

[0053] 4) In the present invention, continuous production is carried out by connecting a micro-tube reactor in series with a screw reactor, and the product production capacity is large, which is more suitable for large-scale production.

[0054] The intermittent reactors in the prior art have high labor intensity, unstable product quality, are not easy to automatically control and adjust, have low production capacity, and are more suitable for the production of multiple varieties and small batches of products. Correspondingly, the micro-tube reactor in series with the screw reactor has low labor intensity, stable product quality, easy to achieve automatic control and adjustment, and is more suitable for large-scale mass production of products. The production capacity of the micro-tube reactor can be achieved by adding or reducing the reaction unit modules; the production capacity of the screw reactor can be controlled by adjusting the diameter and length of the twin-screw equipment. This series arrangement has well solved the problem of large-scale manufacturing of high-quality aramid III polymers and achieved continuous, stable and efficient production of polymers. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is a logical connection diagram of the continuous polymerization system in the present invention;

[0056] In the figure, 1, amine reactor, 2, acyl chloride reactor, 3, metering pump, 4, flow meter, 5, mixer I, 6, microtube reactor, 61, upper heat transfer layer, 62, material layer, 63, lower heat transfer layer, 7, screw reactor, 8, polymerization solvent feed pipe, 9, 5 (6) -amino-2-(4-aminophenyl) benzimidazole feed pipe, 10, p-phenylenediamine feed pipe, 11, terephthaloyl chloride feed pipe, 12, amine solution delivery pipe, 13, acyl chloride solution delivery pipe I, 14, prepolymer solution delivery pipe, 15, acyl chloride solution delivery pipe II, 16, mixer II, 17, polymer solution delivery pipe. DETAILED DESCRIPTION

[0057] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] Example 1

[0059] This embodiment provides a continuous polymerization method of aramid III, which specifically includes the following steps:

[0060] A. Monomer Dissolution

[0061] Preparation of amine solution: Add polymerization solvent into amine reaction kettle 1, then add monomer 5(6)-amino-2-(4-aminophenyl)benzimidazole and monomer p-phenylenediamine respectively, stir until completely dissolved, and obtain amine solution;

[0062] Preparation of acyl chloride solution: Add polymerization solvent to acyl chloride reaction kettle 2, then add monomer terephthaloyl chloride, stir until completely dissolved, and obtain acyl chloride solution;

[0063] Wherein, the polymerization solvent is a homogeneous mixed solution including amide and chloride. The amide is any one of N-methylpyrrolidone, N,N-dimethylacetamide or N-methylformamide; the chloride is any one of lithium chloride solution, calcium chloride solution or magnesium chloride solution. The amide is an organic solvent used to dissolve aramid III prepolymer and polymer; the chloride is an inorganic salt cosolvent used to increase the solubility of aramid III prepolymer and polymer in amide solvents;

[0064] The solubility concentration of chloride in amide solvent is 1-10%, and the solubility concentration of chloride in amide solvent is closely related to the solubility of aramid III prepolymer and polymer in the solvent.

[0065] B. Prepolymerization

[0066] The amine solution and part of the acyl chloride solution (wherein the molar flow of terephthaloyl chloride involved accounts for 92-97% of the total molar flow of terephthaloyl chloride) are introduced into the micro-tube reactor 6, the temperature is controlled at 15-25°C, and the prepolymerization reaction is carried out for 5-10 minutes to obtain an aramid III prepolymer solution. The prepolymerization reaction is a violently exothermic process. Compared with the kettle reactor in the prior art, the heat exchange area of ​​the micro-tube reactor 6 increases exponentially and has a strong heat exchange capacity, so that the prepolymerization reaction temperature can be controlled, thereby ensuring the effectiveness of the prepolymerization reaction. Among them, the prepolymerization reaction time is further limited. If the material residence time is too long, the number of modules of the micro-tube reactor 6 increases, the equipment cost increases, and the production cost increases. The reaction time is limited to 5-10 minutes. On the premise of ensuring the quality and efficiency of the prepolymerization reaction, the cost is solved to ensure the continuity of this preparation process;

[0067] C. Polymerization

[0068] The aramid III prepolymer solution and the remaining part of the acyl chloride solution (wherein the molar flow of terephthaloyl chloride involved accounts for 3-8% of the total molar flow of terephthaloyl chloride) are introduced into the screw reactor 7, the temperature is controlled at 35-45°C, and the polymerization reaction is carried out for 6-12 minutes to obtain the aramid III polymer solution. The polymerization reaction in the screw reactor 7 is an exothermic reaction. The screw reactor 7 is equipped with a cooling and heat exchange system to prevent the reaction system temperature from being too high to produce side reactions. Among them, the polymerization reaction time is further limited. If the reaction time is too short, the polymerization reaction is incomplete, and the molecular weight distribution of the generated polymer is wide and the quality is low; if the reaction time is too long, the production efficiency is low and waste is generated. The reaction time is limited to 6-12 minutes. On the premise of ensuring the quality and efficiency of the polymerization reaction, the cost is solved and the continuity of this preparation process is guaranteed;

[0069] The ratio of the sum of the molar flow rates of the amine monomers 5(6)-amino-2-(4-aminophenyl)benzimidazole and p-phenylenediamine involved in the prepolymerization reaction to the sum of the molar flow rates of terephthaloyl chloride involved in the prepolymerization reaction and the polymerization reaction is 1:0.95-1.05;

[0070] D. Spinning

[0071] The obtained aramid III polymer solution is spun by using the existing technology, washed with water and dried to obtain aramid III.

[0072] Among them, the dynamic viscosity of the aramid III prepolymer solution is 1000-10000 cP, and the corresponding prepolymer intrinsic viscosity is 1-3 dL / g; the dynamic viscosity of the aramid III polymer solution is 10000-100000 cP, and the corresponding polymer intrinsic viscosity is 5-7 dL / g.

[0073] Example 2

[0074] This embodiment provides a continuous polymerization system that cooperates with the continuous polymerization method in Embodiment 1.

[0075] like Figure 1 As shown: a continuous polymerization system of aramid III, comprising an amine reactor 1, an acyl chloride reactor 2, a micro-tube reactor 6 and a screw reactor 7, wherein the amine reactor 1 is connected with a polymerization solvent feed pipe 8, a 5(6)-amino-2-(4-aminophenyl)benzimidazole feed pipe and a p-phenylenediamine feed pipe 10, and the acyl chloride reactor 2 is connected with a polymerization solvent feed pipe 8 and a terephthaloyl chloride feed pipe 11;

[0076] The amine reactor 1 is arranged in the front section of the micro-tube reactor 6, and the amine reactor 1 is connected to the micro-tube reactor 6 through the amine solution delivery pipe 12; the acyl chloride reactor 2 is arranged in the front section of the micro-tube reactor 6, and the acyl chloride reactor 2 is connected to the micro-tube reactor 6 through the acyl chloride solution delivery pipe Ⅰ13; the screw reactor 7 is arranged in the rear section of the micro-tube reactor 6, and the micro-tube reactor 6 is connected to the screw reactor 7 through the prepolymer solution delivery pipe 14; the acyl chloride reactor 2 is connected to the screw reactor 7 through the acyl chloride solution delivery pipe Ⅱ15.

[0077] The micro-tube reactor 6 and the screw reactor 7 are both connected to a cooling and heat exchange system to control the temperature of the reaction system and prevent the reaction system temperature from being too high to cause side reactions.

[0078] The front section of the micro-tube reactor 6 is also provided with a mixer I, and the amine solution delivery pipe 12 and the acyl chloride solution delivery pipe are both connected to the mixer I, and the amine solution and the acyl chloride solution are pre-mixed before prepolymerization to improve the quality of the subsequent prepolymerization reaction.

[0079] The front section of the screw reactor 7 is also provided with a mixer II 16, and the prepolymer solution delivery pipe 14 and the acyl chloride solution delivery pipe II 15 are both connected to the mixer II 16, so that the prepolymer solution and the acyl chloride solution are premixed before polymerization to improve the quality of subsequent polymerization reaction.

[0080] The screw reactor 7 is connected to a polymer solution delivery pipe 17. Both the prepolymer solution delivery pipe 14 and the polymer solution delivery pipe 17 are provided with an online dynamic viscometer to monitor the viscosity of the aramid III prepolymer solution and the aramid III polymer solution, and then used to adjust the feed amount of the acyl chloride solution.

[0081] The micro-tube reactor 6 is provided with an upper heat transfer layer 61, a material layer 62 for placing a prepolymer solution, and a lower heat transfer layer 63. The material layer 62 is arranged between the heat transfer layer 61 and the lower heat transfer layer 63. The amine solution and the acyl chloride solution enter the middle material layer 62 at the same time and are pushed forward under pressure, continuously mixed and reacted, and finally an aramid III prepolymer solution is generated.

[0082] The screw reactor 7 is a twin-screw reactor, and the screw reactor 7 can be one-stage or two-stage or more. When the screw reactor 7 is two-stage or more, the screw reactors 7 are connected in series. The number of series stages of the screw reactor 7 is determined by the reaction time of the material in the screw reactor 7. The multi-stage screw reactor 7 is conducive to increasing the residence reaction time of the material in the screw reactor 7, thereby ensuring the quality and efficiency of the continuous polymerization process.

[0083] Example 3

[0084] A continuous polymerization method for aramid III, the method comprising the following steps:

[0085] A monomer dissolution

[0086] Preparation of amine solution: Add polymerization solvent (composed of N-methylpyrrolidone and lithium chloride, the concentration of lithium chloride in N-methylpyrrolidone is 10%) into amine reaction kettle 1, then add monomer 5(6)-amino-2-(4-aminophenyl)benzimidazole and monomer p-phenylenediamine respectively, stir until completely dissolved, and obtain amine solution;

[0087] Preparation of acyl chloride solution: Add polymerization solvent (composed of N-methylpyrrolidone and lithium chloride, the concentration of lithium chloride in N-methylpyrrolidone is 10%) into acyl chloride reaction kettle 2, then add monomer terephthaloyl chloride, stir until completely dissolved, and obtain acyl chloride solution;

[0088] B Prepolymerization

[0089] The amine solution in the amine reaction kettle 1 and part of the acyl chloride solution in the acyl chloride reaction kettle 2 are simultaneously transported to the micro-tube reactor 6 by the metering pump 3, and the two parts of the solution are pre-condensed and polymerized in the micro-tube reactor 6 to generate an aramid III prepolymer solution;

[0090] The molar flow rate of terephthaloyl chloride entering the micro-tube reactor 6 accounts for 92% of its total flow rate, the prepolymerization temperature is 25° C., and the residence time of the material in the micro-tube reactor 6 for prepolymerization is 5 min.

[0091] C polymerization

[0092] The aramid III prepolymer solution and the remaining acyl chloride solution in the acyl chloride reaction kettle 2 are respectively transported into the twin-screw reactor 7 by the metering pump 3, and the two parts of the solution are further subjected to condensation polymerization reaction in the twin-screw reactor 7 to generate an aramid III polymer solution;

[0093] The remaining molar flow rate of terephthaloyl chloride entering the twin-screw reactor 7 accounts for 8% of the total flow rate, the reaction temperature of the polymerization reaction is 35° C., and the residence time of the material in the twin-screw reactor 7 for the polymerization reaction is 12 minutes;

[0094] D. Spinning

[0095] The obtained aramid III polymer solution is spun by using the existing technology, washed with water and dried to obtain aramid III.

[0096] In the above prepolymerization and polymerization reaction, the ratio of the total molar flow rate of terephthaloyl chloride to the sum of the molar flow rates of 5(6)-amino-2-(4-aminophenyl)benzimidazole and p-phenylenediamine was 0.96.

[0097] The microtube diameter of the microtube reactor 6 involved is 2 mm, and the system involves two stages of twin-screw reactors connected in series.

[0098] Example 4

[0099] This embodiment is improved on the basis of embodiment 3. The polymerization solvent used in this embodiment is composed of N,N-dimethylacetamide and calcium chloride, wherein the concentration of calcium chloride in N,N-dimethylacetamide is 5%;

[0100] In the prepolymerization reaction, the molar flow rate of terephthaloyl chloride entering the micro-tube reactor 6 accounts for 95% of its total flow rate, the prepolymerization reaction temperature is 15° C., and the residence time of the material in the micro-tube reactor 6 for the prepolymerization reaction is 10 min;

[0101] During the polymerization reaction, the molar flow rate of terephthaloyl chloride entering the twin-screw reactor 7 accounted for 5% of its total flow rate, the reaction temperature of the polymerization reaction was 45° C., and the residence time of the material in the twin-screw reactor 7 for the stepwise polymerization reaction was 6 minutes.

[0102] The microtube diameter of the microtube reactor 6 involved is 2 mm, and there is a first-stage twin-screw reactor in the system involved.

[0103] Example 5

[0104] This embodiment is improved on the basis of embodiment 3. The polymerization solvent used in this embodiment is composed of N-methylformamide and magnesium chloride, wherein the concentration of calcium chloride in N,N-dimethylacetamide is 1%;

[0105] In the prepolymerization reaction, the molar flow rate of terephthaloyl chloride entering the micro-tube reactor 6 accounts for 97% of its total flow rate, the prepolymerization reaction temperature is 20° C., and the residence time of the material in the micro-tube reactor 6 for the prepolymerization reaction is 7 minutes;

[0106] During the polymerization reaction, the molar flow rate of terephthaloyl chloride entering the twin-screw reactor 7 accounted for 3% of its total flow rate, the reaction temperature of the polymerization reaction was 40° C., and the residence time of the material in the twin-screw reactor 7 for the stepwise polymerization reaction was 8 minutes.

[0107] The microtube diameter of the microtube reactor 6 involved is 3 mm, and there is a first-stage twin-screw reactor in the system involved.

[0108] Example 6

[0109] This embodiment is improved on the basis of embodiment 3. The polymerization solvent used in this embodiment is composed of N-methylpyrrolidone and magnesium chloride, wherein the concentration of calcium chloride in N,N-dimethylacetamide is 3.5%;

[0110] In the prepolymerization reaction, the molar flow rate of terephthaloyl chloride entering the micro-tube reactor 6 accounts for 96% of its total flow rate, the prepolymerization reaction temperature is 18° C., and the residence time of the material in the micro-tube reactor 6 for the prepolymerization reaction is 8 minutes;

[0111] During the polymerization reaction, the molar flow rate of terephthaloyl chloride entering the twin-screw reactor 7 accounted for 4% of its total flow rate, the reaction temperature of the polymerization reaction was 42° C., and the residence time of the material in the twin-screw reactor 7 for the stepwise polymerization reaction was 11 minutes.

[0112] The microtube diameter of the microtube reactor 6 involved is 3 mm, and there is a two-stage twin-screw reactor in the system involved.

[0113] Example 7

[0114] This embodiment is improved on the basis of embodiment 3. The polymerization solvent used in this embodiment is composed of N,N-dimethylacetamide and lithium chloride, wherein the concentration of calcium chloride in N,N-dimethylacetamide is 4.5%;

[0115] In the prepolymerization reaction, the molar flow rate of terephthaloyl chloride entering the micro-tube reactor 6 accounted for 96% of its total flow rate, the prepolymerization reaction temperature was 23° C., and the residence time of the material in the micro-tube reactor 6 for the prepolymerization reaction was 9 minutes;

[0116] During the polymerization reaction, the molar flow rate of terephthaloyl chloride entering the twin-screw reactor 7 accounted for 4% of its total flow rate, the reaction temperature of the polymerization reaction was 38° C., and the residence time of the material in the twin-screw reactor 7 for the stepwise polymerization reaction was 10 min.

[0117] The microtube diameter of the microtube reactor 6 involved is 4 mm, and there is a two-stage twin-screw reactor in the system involved.

[0118] Example 8

[0119] This embodiment is improved on the basis of embodiment 3. The polymerization solvent used in this embodiment is composed of N-methylpyrrolidone and calcium chloride, wherein the concentration of calcium chloride in N,N-dimethylacetamide is 5.5%;

[0120] In the prepolymerization reaction, the molar flow rate of terephthaloyl chloride entering the micro-tube reactor 6 accounted for 96.5% of its total flow rate, the prepolymerization reaction temperature was 17° C., and the residence time of the material in the micro-tube reactor 6 for the prepolymerization reaction was 10 min;

[0121] During the polymerization reaction, the molar flow rate of terephthaloyl chloride entering the twin-screw reactor 7 accounted for 3.5% of its total flow rate, the reaction temperature of the polymerization reaction was 38° C., and the residence time of the material in the twin-screw reactor 7 for the stepwise polymerization reaction was 10 min.

[0122] The microtube diameter of the microtube reactor 6 involved is 5 mm, and there is a two-stage twin-screw reactor in the system involved.

[0123] Based on the above-mentioned Examples 3-8, the prepared aramid III polymer solution was used to prepare fibers using the same spinning process, and the obtained fiber performance data is shown in Table 1 below.

[0124]

[0125] Comparative Examples 1-6

[0126] In order to better illustrate the present invention, the present invention has carried out a series of comparative studies based on Example 8.

[0127] 1. Effect of prepolymerization reactor (micro-tube reactor) and terephthaloyl chloride feeding times on fiber properties

[0128] The present invention has made comparative examples 1 and 2 on the basis of embodiment 8. Compared with embodiment 8, comparative example 1 does not use a microtube reactor, and only performs prepolymerization and polymerization in a twin-screw reactor; comparative example 2 still does not use a microtube reactor, and cancels the prepolymerization reaction, and directly combines the terephthaloyl chloride solution from two feedings into one feeding in a twin-screw reactor for polymerization. The above two aramid III polymer solutions are spun under the same conditions, and the properties of the obtained fibers are shown in Table 2 below.

[0129]

[0130] Comparative Example 1 shows that the fiber performance obtained by using only a twin-screw reactor is not high. This is because the polymerization reaction of aramid III monomer is special. Compared with aramid II, the reaction temperature has a greater impact on the molecular weight distribution of the prepolymer. There are defects in using a twin-screw reactor for prepolymerization, and the use of a micro-tube reactor with higher heat exchange efficiency can solve this problem well.

[0131] Comparative Example 2 shows that if the prepolymerization step is eliminated and the monomer terephthaloyl chloride is added to the reaction system once to directly perform the polymerization reaction, and the obtained polymer is used to prepare fibers, the obtained fiber properties are very poor. This is because the reaction ratio of the acyl chloride and diamine monomers cannot be strictly controlled by using the one-time addition method, and the molecular weight distribution of the obtained polymer is wide, which cannot meet the fiber preparation requirements.

[0132] 2. Effect of prepolymerization temperature on fiber properties

[0133] The present invention made comparative examples 3 and 4 based on Example 8. Compared with Example 8, the prepolymerization reaction temperature of Comparative Example 3 is 10°C, and other reaction conditions are the same; the prepolymerization reaction temperature of Comparative Example 4 is 29°C, and other reaction conditions are the same. The above two aramid III polymer solutions were spun under the same conditions, and the fiber properties obtained are shown in Table 3 below.

[0134]

[0135] Comparative Example 3 shows that when the prepolymerization temperature is reduced to 10° C., the properties of the prepared fiber are reduced. As the temperature is reduced, the prepolymerization speed slows down and the reaction is incomplete, resulting in a broadened molecular weight distribution of the polymer obtained in the subsequent polymerization reaction.

[0136] Comparative Example 4 shows that when the prepolymerization temperature is increased to 29° C., the prepared fiber performance is lower. This is because as the temperature increases, side reactions occur during the prepolymerization of the aramid III monomer, and the polymers obtained by the side reactions become impurities in the fiber.

[0137] Similarly, in the polymerization step, the reason for controlling the temperature is similar to that for controlling the temperature in the prepolymerization step.

[0138] 3. Effect of prepolymerization time on fiber properties

[0139] The present invention made comparative examples 5 and 6 based on Example 8. Compared with Example 8, the prepolymerization reaction time of Comparative Example 5 is 3 minutes, and other reaction conditions are the same; the prepolymerization reaction time of Comparative Example 6 is 12 minutes, and other reaction conditions are the same. The above two aramid III polymer solutions were spun under the same conditions, and the fiber properties obtained are shown in Table 4 below.

[0140]

[0141] Comparative Example 5 shows that when the prepolymerization reaction time is reduced to 3 minutes, the properties of the prepared fiber are reduced. Because the reaction time is reduced, the prepolymerization reaction is incomplete, resulting in a wider molecular weight distribution of the polymer obtained in the subsequent polymerization reaction and poorer quality.

[0142] Comparative Example 6 shows that when the prepolymerization reaction time is increased to 12 minutes, the properties of the prepared fibers are basically the same. However, increasing the reaction time requires increasing the length of the reactor equipment, which increases the industrial investment and is not conducive to controlling production costs.

[0143] Similarly, in the polymerization step, the reasons for controlling the reaction time are similar to those for controlling the reaction time in the prepolymerization reaction.

[0144] 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 continuous polymerization method for aramid III, characterized in that: The steps include: A. Monomer Dissolution Preparation of amine solution: Add a polymerization solvent into an amine reaction kettle (1), then add monomer 5-amino-2-(4-aminophenyl)benzimidazole and monomer p-phenylenediamine respectively, and stir until completely dissolved to obtain an amine solution; Alternatively, the amine solution is prepared by adding a polymerization solvent to an amine reaction kettle (1), and then adding a monomer 6-amino-2-(4-aminophenyl)benzimidazole and a monomer p-phenylenediamine, respectively, and stirring until they are completely dissolved to obtain an amine solution; Preparation of acyl chloride solution: Add polymerization solvent to acyl chloride reaction kettle (2), then add monomer terephthaloyl chloride, stir until completely dissolved, to obtain acyl chloride solution; Wherein, the polymerization solvent is a homogeneous mixed solution including amide and chloride; B. Prepolymerization The amine solution and part of the acyl chloride solution are introduced into the micro-tube reactor (6), the temperature is controlled at 15-25° C., and the prepolymerization reaction is carried out for 5-10 minutes to obtain an aramid III prepolymer solution; The molar flow rate of terephthaloyl chloride involved in the partial acyl chloride solution accounts for 92-97% of the total molar flow rate of terephthaloyl chloride; C. Polymerization The aramid III prepolymer solution and the remaining acyl chloride solution are introduced into a screw reactor (7), the temperature is controlled at 35-45° C., and a polymerization reaction is carried out for 6-12 minutes to obtain an aramid III polymer solution; The molar flow rate of terephthaloyl chloride involved in the remaining part of the acyl chloride solution accounts for 3-8% of the total molar flow rate of terephthaloyl chloride; D. Spinning The obtained aramid III polymer solution is spun, washed with water and dried to obtain aramid III; The continuous polymerization method of aramid III adopts a continuous polymerization device, which comprises an amine reactor (1), an acyl chloride reactor (2), a micro-tube reactor (6) and a screw reactor (7); the amine reactor (1) is connected to a polymerization solvent feed pipe (8), a 5-amino-2-(4-aminophenyl)benzimidazole feed pipe or a 6-amino-2-(4-aminophenyl)benzimidazole feed pipe and a p-phenylenediamine feed pipe (10); and the acyl chloride reactor (2) is connected to a polymerization solvent feed pipe (8) and a terephthaloyl chloride feed pipe (11); The amine reaction kettle (1) is arranged at the front section of the micro-tube reactor (6), and the amine reaction kettle (1) is connected to the micro-tube reactor (6) through an amine solution delivery pipe (12); the acyl chloride reaction kettle (2) is arranged at the front section of the micro-tube reactor (6), and the acyl chloride reaction kettle (2) is connected to the micro-tube reactor (6) through an acyl chloride solution delivery pipe I (13); the screw reactor (7) is arranged at the back section of the micro-tube reactor (6), and the micro-tube reactor (6) is connected to the screw reactor (7) through a prepolymer solution delivery pipe (14); the acyl chloride reaction kettle (2) is connected to the screw reactor (7) through an acyl chloride solution delivery pipe II (15).

2. The continuous polymerization method of aramid III according to claim 1, characterized in that: In step A, the amide is any one of N-methylpyrrolidone, N,N-dimethylacetamide or N-methylformamide; the chloride is any one of lithium chloride solution, calcium chloride solution or magnesium chloride solution.

3. The continuous polymerization method of aramid III according to claim 1 or 2, characterized in that: The chloride is dissolved in the amide solvent at a concentration of 1-10%.

4. The continuous polymerization method of aramid III according to claim 1, characterized in that: In steps B and C, the ratio of the sum of the molar flows of the amine monomers 5-amino-2-(4-aminophenyl)benzimidazole or 6-amino-2-(4-aminophenyl)benzimidazole and p-phenylenediamine involved in the prepolymerization reaction to the sum of the molar flows of terephthaloyl chloride involved in the prepolymerization reaction and the polymerization reaction is 1:0.95-1.

05.

5. The continuous polymerization method of aramid III according to claim 1, characterized in that: The micro-tube reactor (6) and the screw reactor (7) are both connected to a cooling and heat exchange system.

6. The continuous polymerization method of aramid III according to claim 1, characterized in that: The micro-tube reactor (6) is provided with a mixer I in the front section, and the amine solution delivery pipe (12) and the acyl chloride solution delivery pipe are both connected to the mixer I; the screw reactor (7) is provided with a mixer II (16) in the front section, and the prepolymer solution delivery pipe (14) and the acyl chloride solution delivery pipe II (15) are both connected to the mixer II (16); The screw reactor (7) is connected to a polymer solution delivery pipe (17); The prepolymer solution delivery pipe (14) and the polymer solution delivery pipe (17) are both provided with an online dynamic viscometer.

7. The continuous polymerization method of aramid III according to claim 1, characterized in that: An upper heat transfer layer (61), a material layer (62) for placing a prepolymer solution, and a lower heat transfer layer (63) are arranged in the micro-tube reactor (6), and the material layer (62) is arranged between the heat transfer layer (61) and the lower heat transfer layer (63).

8. The continuous polymerization method of aramid III according to claim 1, characterized in that: The screw reactor (7) has at least two stages, and the screw reactors (7) are connected in series.

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