Regulation and control method of molecular weight of polymerization liquid and preparation method of carbon fiber spinning liquid

Abstract

The invention relates to a method for regulating and controlling the molecular weight of a polymer solution and a method for preparing a carbon fiber spinning solution, belongs to the field of fiber materials, and solves at least one of the problems of insufficient accuracy of molecular weight regulation, wider molecular weight distribution, poorer operability, limited industrial applicability and the like in the existing method for regulating and controlling the molecular weight of the polymer solution. The method for regulating and controlling the molecular weight of the polymer liquid comprises the following steps: adding a material containing a reaction monomer into a polymerization device; raising the temperature to a polymerization temperature, and adding part of the initiator; and monitoring the viscosity of the material in real time, and determining the time for adding the residual initiator according to the viscosity change of the material. The regulation and control precision of the molecular weight of the polymer is remarkably improved, the molecular weight distribution is narrower, and the operability and the industrial applicability are good.

Description

Technical Field

[0001] The present invention relates to the field of fiber materials, and particularly to a method for regulating the molecular weight of a polymerization solution and a method for preparing a carbon fiber spinning solution. Background Art

[0002] There are various methods for regulating the molecular weight of a polymerization solution, but existing methods still have problems such as insufficient precision, complex operation, and limited applicability. For example, in the preparation of carbon fibers, the control of the molecular weight of the polymerization solution is a key step because the molecular weight directly affects the microscopic structure and macroscopic properties of the fibers, such as modulus and strength.

[0003] However, existing methods for regulating the molecular weight of a polymerization solution have many limitations in practical applications, especially in the field of carbon fiber preparation. For example, the method of adding initiator batchwise based on temperature or reaction time indicators can regulate the molecular weight, but it is difficult to achieve the dual goals of high molecular weight and narrow molecular weight distribution simultaneously. The method of adding initiator batchwise based on conversion rate indicators is theoretically feasible, but in actual operation, it is difficult to accurately grasp the optimal addition timing of the initiator, resulting in difficult-to-precisely regulate the molecular weight and its distribution, and poor operability. In addition, although adding a molecular weight regulator (such as a chain transfer agent) to the polymerization solution can regulate the molecular weight, the chain transfer reaction may cause branching of the polymer chain, thereby affecting the uniformity of the molecular weight distribution and possibly reducing the rate and efficiency of the polymerization reaction.

[0004] Although new technologies such as photoinduced polymerization provide new ideas for molecular weight regulation, these methods are usually complex in operation, require precise control of light conditions and reaction time, and often need to make major modifications to existing equipment in practical applications, increasing the difficulty and cost of industrial application. Therefore, existing methods still have significant limitations in meeting the high requirements for regulating the molecular weight of a polymerization solution, and there is an urgent need to develop a more efficient, precise, and industrialization-friendly regulation strategy. Summary of the Invention

[0005] In view of the above analysis, the present invention aims to provide a method for regulating the molecular weight of a polymerization solution and a method for preparing a carbon fiber spinning solution, so as to solve at least one of the problems existing in existing methods for regulating the molecular weight of a polymerization solution, such as insufficient precision in molecular weight regulation, wide molecular weight distribution, poor operability, and limited industrial applicability.

[0006] The object of the present invention is achieved by the following technical solutions:

[0007] The present invention provides a method for regulating the molecular weight of a polymerization solution, comprising:

[0008] Adding a material containing reaction monomers to a polymerization device;

[0009] Heating to a polymerization temperature and adding a part of the initiator;

[0010] Monitor the viscosity of the material in real time, and determine the timing of adding the remaining initiator according to the change in the viscosity of the material:

[0011] Control the molecular weight of the polymer by controlling the viscosity threshold, the material temperature, and the proportion of the remaining initiator in the total initiator amount.

[0012] Furthermore, the step of monitoring the viscosity of the material in real time includes: setting up a material return pipeline, monitoring the pressure of the material at a fixed position in the return pipeline in real time, and obtaining the viscosity of the material monitored in real time according to the real-time viscosity value converted from the pressure value.

[0013] Furthermore, lead the material out of the polymerization device, make the material flow through the return pipeline at a constant temperature and a constant flow rate, and finally converge back to the polymerization device; by monitoring the pressure of the material at a fixed position in the return pipeline in real time, and combining with the pressure-viscosity relationship formula, convert the pressure value into a real-time viscosity value.

[0014] Furthermore, the method for determining the pressure-viscosity relationship formula includes: by setting multiple data acquisition times, at each data acquisition time, record the pressure value at the fixed position of the return pipeline and the viscosity value obtained by the experimental method, perform mathematical fitting on the pressure value and the viscosity value, and establish the pressure-viscosity relationship formula.

[0015] Furthermore, making the material flow through the return pipeline at a constant temperature and a constant flow rate includes: placing the return pipeline in a constant temperature circulating water system, and setting a constant speed gear pump on the return pipeline.

[0016] Furthermore, the polymerization liquid is an acrylonitrile-based polymerization liquid; the pressure-viscosity relationship formula is:

[0017] y = -0.045x 2 +13.78x - 106.8

[0018] wherein, y is the viscosity measured by the falling ball method, with the unit of P; x is the pressure, with the unit of Kpa.

[0019] Furthermore, the constant temperature is 40 - 50 °C; and / or, the constant flow rate is 1 - 2 L / h.

[0020] Furthermore, the position where the material is led out of the polymerization device is set 10 - 20 cm below the lower end of the stirring device in the polymerization device.

[0021] Furthermore, the viscosity threshold includes the viscosity threshold for adding the remaining initiator and the viscosity threshold for terminating the reaction; and / or,

[0022] the material temperature includes the polymerization temperature and the target temperature to which the material is heated before adding the remaining initiator.

[0023] The present invention provides a method for preparing a carbon fiber spinning solution, comprising:

[0024] Adding a material containing acrylonitrile, comonomer and solvent into a polymerization device, and regulating the molecular weight of the acrylonitrile-based polymerization solution according to the above-mentioned regulation method;

[0025] Performing a degassing treatment on the acrylonitrile-based polymerization solution that meets the target molecular weight;

[0026] Performing an ammoniation treatment on the degassed acrylonitrile-based polymerization solution.

[0027] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0028] (1) In the present invention, the initiator is added in batches during the preparation of the polymerization solution, and the viscosity change of the material is monitored in real time. Based on the viscosity change, the optimal addition time of the remaining initiator after the polymerization starts is quickly judged, and through the coordinated control of the material temperature and the proportion of the remaining initiator in the total initiator amount, the molecular weight of the polymer is effectively regulated to the target level. Compared with the existing methods (such as traditional indicators such as temperature or reaction time, molecular weight regulators), the change in the viscosity of the material can more accurately reflect the actual progress of the polymerization reaction, so as to more accurately grasp the appropriate time to add the initiator, significantly improve the regulation accuracy of the polymer molecular weight, and make the molecular weight distribution narrower. The polydispersity index PDI of the acrylonitrile-based polymerization solution prepared by the regulation method provided in the embodiment of the present invention is 2.0 - 3.0.

[0029] (2) Although traditional indicators such as conversion rate can be used as one of the evaluation indicators of the reaction degree, the determination process is too cumbersome and time-consuming. Obtaining each conversion rate requires sampling and drying the material in the reaction process for several hours to obtain a solid, and then calculating the conversion rate, which is difficult to be efficiently applied in industrial production.

[0030] Compared with the existing methods (such as conversion rate or other new technologies such as photoinduced polymerization), the viscosity index adopted by the present invention has stronger operability and good industrial applicability while ensuring the regulation accuracy of the molecular weight and its narrow distribution. In practical applications, the optimal time to add the initiator can be conveniently grasped, thereby significantly improving the stability of the viscosity and molecular weight of different batches of polymerization solutions, and making the molecular weight distribution narrower. Through the method of the present invention, the requirements for the polymer molecular weight in different application scenarios are better met, providing a more stable and uniform polymerization solution for the preparation of subsequent products.

[0031] (3) In some preferred embodiments, by setting up a reflux pipeline, measuring the material pressure at a fixed position in the pipeline under constant temperature and constant flow rate, and controlling the material temperature and flow rate in the reflux pipeline, etc., the accuracy of regulating the molecular weight of the polymerization solution can be further improved, and a narrow molecular weight distribution can be achieved.

[0032] (4) In some preferred embodiments, for different reaction systems, such as acrylonitrile-based polymerization solutions, by obtaining and setting a suitable pressure-viscosity relationship in a scientific manner, the viscosity change of the acrylonitrile-based polymerization solution can be monitored in real time, so as to accurately grasp the progress of the polymerization reaction. This method not only avoids the problem of broadened molecular weight distribution caused by temperature fluctuations or cumbersome conversion rate determination in traditional methods, but also can more conveniently determine the optimal addition timing of the initiator in actual operation, significantly improving the molecular weight stability and distribution uniformity of different batches of polymerization solutions, which is particularly important for the subsequent preparation of carbon fibers, because the molecular weight, its distribution, and viscosity of the polymerization solution directly affect the properties and processing performance of the fibers. The weight average molecular weight M of the acrylonitrile-based polymerization solution prepared by using the regulation method provided in the embodiments of the present invention W is 210,000 - 250,000, the polydispersity index PDI is 2.1 - 2.6, and the falling ball method viscosity at 40 - 50 °C is 620 - 910 P; the residual monomer content of the carbon fiber spinning solution prepared by using the carbon fiber spinning solution preparation method provided in the embodiments of the present invention is ≤ 350 ppm, preferably, the residual monomer content is less than 100 ppm, more preferably, the residual monomer content is less than 50 ppm, and further, the residual monomer content is less than 30 ppm. The pH of the carbon fiber spinning solution prepared by using the carbon fiber spinning solution preparation method provided in the embodiments of the present invention is 8.4 - 9.5, preferably, the pH is 8.9 - 9.5.

[0033] In the present invention, the above technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can be made obvious from the description, or understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the content specifically pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings are only for the purpose of showing specific embodiments, and are not considered as limiting the present invention. Throughout the drawings, the same reference signs represent the same components.

[0035] Figure 1 is a schematic flow chart of the method for regulating the molecular weight of the polymerization solution provided by the embodiments of the present invention;

[0036] Figure 2 is a schematic structural diagram of the monomer removal device provided by the embodiments of the present invention;

[0037] Figure 3 Schematic structural diagram of the ammoniation device provided by an embodiment of the present invention;

[0038] Figure 4 Schematic structural diagram of the polymerization device provided by an embodiment of the present invention;

[0039] Reference numerals:

[0040] 100 - Depolymerization device; A - Tank body; B - Solvent vaporizer; C - Real - time viscosity monitoring device; 11 - Perforated partition; 12 - Polymerization liquid inlet; 13 - Distribution plate; 14 - Solvent inlet; 15 - Coiled pipe; 15a - Coiled pipe inlet; 15b - Coiled pipe outlet; 16 - Solvent vapor; 17 - Vacuum extraction port; 18 - Polymerization liquid discharge port; 200 - Ammoniation device; 21 - Inclined paddle stirrer; 21a - Stirring paddle; 21b - Rotating shaft; 22 - Ammonia gas inlet; 23 - Polymerization liquid inlet; 24 - Polymerization liquid outlet; 25 - First motor; 300 - Polymerization device; 31 - Stirring device; 32 - Inert gas inlet; 33 - Inert gas outlet; 34 - Second motor; 35 - On - line pressure - viscosity converter; 36 - Constant - speed gear pump; 37 - Circulating water inlet; 38 - Circulating water outlet. Detailed implementation manners

[0041] The following will specifically describe the preferred embodiments of the present invention with reference to the accompanying drawings. The accompanying drawings form a part of this application and are used together with the embodiments of the present invention to explain the principle of the present invention, rather than to limit the scope of the present invention.

[0042] In a first aspect, the present invention provides a method for regulating the molecular weight of a polymerization liquid, including:

[0043] Adding a material containing reaction monomers into a polymerization device;

[0044] Heating to a polymerization temperature and adding a part of initiator;

[0045] Real - time monitoring the viscosity of the material, and determining the timing of adding the remaining initiator according to the viscosity change of the material:

[0046] Controlling through a viscosity threshold, the material temperature, and the proportion of the remaining initiator in the total amount of initiator to achieve the regulation of the molecular weight of the polymer.

[0047] In some preferred embodiments, the step of real - time monitoring the viscosity of the material includes: setting a material reflux pipeline, real - time monitoring the pressure at a fixed position of the material in the reflux pipeline, and obtaining the real - time monitored viscosity of the material according to the real - time viscosity value converted from the pressure value.

[0048] Specifically, the material is led out from the polymerization device, and the material flows through the reflux pipeline at a constant temperature and a constant flow rate, and finally converges back to the polymerization device; by real-time monitoring the pressure of the material at a fixed position of the reflux pipeline and combining with the pressure-viscosity relationship formula, the pressure value is converted into a real-time viscosity value.

[0049] To ensure the reliability and consistency of the pressure measurement results, the step of making the material flow through the reflux pipeline at a constant temperature and a constant flow rate includes: placing the reflux pipeline in a constant temperature circulating water system, and setting a constant speed gear pump on the reflux pipeline. By the constant temperature circulating water system, it is ensured that the temperature of the material remains constant during the flowing process, and by controlling the rotation speed of the gear pump, it can be ensured that the material flows through the pipeline at a constant flow rate.

[0050] It can be understood that under the conditions of constant flow rate, constant temperature and a fixed-length pipeline (constant pipeline resistance), by measuring the pressure generated when the polymerization liquid flows through a fixed position of the reflux pipeline and combining with the pressure-viscosity relationship formula, the viscosity of the material can be obtained. Preferably, the above real-time monitoring of the material viscosity is applicable to materials with a viscosity of 0-1000P.

[0051] Preferably, the constant temperature is 40-50 °C; and / or, the constant flow rate is 1-2 L / h.

[0052] Preferably, the position where the material is led out from the polymerization device is set 10-20 cm below the lower end of the stirring device in the polymerization device, and this position belongs to the position with the best fluidity of the polymerization liquid, which is convenient for timely and accurately monitoring the real-time viscosity of the polymerization liquid in the polymerization kettle.

[0053] Preferably, the length of the reflux pipeline is 0.5-1.5 meters, and the pipe diameter is 5-20 mm. Exemplarily, the length of the reflux pipeline is 1.0 meter, and the pipe diameter is 10 mm.

[0054] In some embodiments, the step of real-time monitoring the pressure of the material at a fixed position of the reflux pipeline and combining with the pressure-viscosity relationship formula to convert the pressure value into a real-time viscosity value includes: setting an on-line pressure-viscosity converter at a fixed position of the reflux pipeline, and the on-line pressure-viscosity converter includes a pressure detector and a processor;

[0055] The pressure detector is used to collect the pressure signal of the polymerization liquid in the reflux pipeline in real time, and transmit the pressure signal to the processor through a line;

[0056] The processor converts the pressure signal into a viscosity value according to the preset pressure-viscosity relationship formula, and transmits the viscosity value result to a display device arranged outside the polymerization device through a line for real-time display.

[0057] In some embodiments, the method for determining the pressure-viscosity relationship includes: by setting multiple data acquisition times, at each data acquisition time, recording the pressure value at a fixed position of the reflux pipeline and the viscosity value obtained by an experimental method, performing mathematical fitting on the pressure value and the viscosity value, and establishing a pressure-viscosity relationship.

[0058] Specifically, the steps for obtaining the viscosity value by the experimental method include: sampling from the polymerization device and measuring the viscosity of the sample using a viscosity measuring instrument. Preferably, the sampling position is adjacent to the position where the material is led out of the polymerization device. Exemplarily, the viscosity measuring instrument includes a falling ball viscometer, a rotational viscometer, a capillary viscometer, a rheometer, a vibrating viscometer, and an ultrasonic viscometer.

[0059] In some embodiments, the polymerization liquid is an acrylonitrile-based polymerization liquid; the pressure-viscosity relationship is:

[0060] y = -0.045x 2 +13.78x - 106.8

[0061] where y is the viscosity measured by the falling ball method, with the unit of P; x is the pressure, with the unit of Kpa.

[0062] Exemplarily, the viscosity y is the viscosity measured by the falling ball method at 40 - 50 °C. For example, within the ±Δ time range near each data acquisition time t, preferably Δ ≤ 10 min, the pressure values at a fixed position of the reflux pipeline are recorded N times, and samples are taken from the polymerization device N times at the same time points as the recorded pressure values. N temperature points are selected within 40 - 50 °C for viscosity measurement. Through data fitting software (such as EXCEL, Matlab, or Python), the viscosity y and the pressure x are fitted, and the fitting criterion is: the coefficient of determination R 2 ≥ 95%, preferably R 2 ≥ 98%, to obtain a pressure-viscosity relationship. The model types of the pressure-viscosity relationship include at least one of exponential, linear, logarithmic, polynomial (second order and above), and power. For example, N is 3, and the test conditions are 40 °C, 45 °C, and 50 °C respectively. For example, Δ = 8 min, 5 min, 2 min, 1 min.

[0063] Exemplarily, the viscosity thresholds include the viscosity threshold for adding the remaining initiator and the viscosity threshold for terminating the reaction. Since the remaining initiator can be added in multiple times, multiple viscosity thresholds can be set.

[0064] Exemplarily, the material temperature includes the polymerization temperature and the target temperature to which the material is heated before adding the remaining initiator. Among them, before adding the initiator again when the viscosity reaches a certain threshold, the material needs to be heated to the target temperature again.

[0065] In some embodiments, determining the timing of adding the remaining initiator according to the viscosity change of the material includes: when the viscosity of the material reaches the first viscosity threshold, adding the remaining initiator, and when the viscosity of the material reaches the second viscosity threshold, terminating the reaction to obtain an acrylonitrile-based polymerization solution with a target molecular weight; the first viscosity threshold < the second viscosity threshold.

[0066] Preferably, the first viscosity threshold is 200P - 400P; and / or, the second viscosity threshold is 600P - 1000P.

[0067] Preferably, the polymerization temperature is 50 - 60°C. When the viscosity of the material reaches the first viscosity threshold, the temperature of the material is raised to the target temperature of 60 - 70°C.

[0068] Preferably, the proportion of the remaining initiator in the total initiator is 20 - 40%.

[0069] Through the control of the above-mentioned appropriate viscosity thresholds, material temperature (polymerization temperature and the target temperature to which it is raised when reaching the threshold), and the proportion of the remaining initiator in the total initiator, it is beneficial to obtain an acrylonitrile-based polymerization solution with high molecular weight and narrow distribution while increasing the polymerization reaction rate.

[0070] Exemplarily, the polymerization temperature is 52°C, 54°C, 56°C, 58°C. Preferably, the polymerization temperature is 55 - 60°C.

[0071] Exemplarily, the target temperature is 62°C, 64°C, 67°C, 69°C. Preferably, the target temperature is 66 - 68°C.

[0072] Exemplarily, the first viscosity threshold is 250P, 280P, 330P, 350P, 380P. More preferably, the first viscosity threshold is 300P - 400P.

[0073] Exemplarily, the second viscosity threshold is 650P, 700P, 750P, 800P, 850P, 900P, 950P. Preferably, the second viscosity threshold is 750P - 950P.

[0074] Exemplarily, the proportion of the remaining initiator in the total initiator is 23%, 25%, 27%, 30%, 33%, 35%, 37%. Preferably, the proportion of the remaining initiator in the total initiator is 30 - 40%. It should be noted that by finely controlling the viscosity threshold, material temperature (polymerization temperature and the target temperature to which it is raised when reaching the viscosity threshold), and the proportion of the remaining initiator in the total initiator, while obtaining a polymerization solution with high molecular weight and narrow distribution, the micro-regulation of the molecular weight of the polymerization solution can be achieved.

[0075] In some embodiments, the polymerization solution is an acrylonitrile-based polymerization solution, the polymerization temperature is 50 - 52 °C, the first viscosity threshold is 200P - 250P. When the viscosity of the material reaches the first viscosity threshold, the target temperature to which it is heated is 68 - 70 °C, and the proportion of the remaining initiator in the total amount of the initiator is 35 - 40%; the second viscosity threshold is 620 - 650P; the molecular weight (M W ) of the obtained acrylonitrile-based polymerization solution is 200,000 - 220,000, and the polydispersity index (PDI) is 2.5 - 3.0.

[0076] In some embodiments, the polymerization solution is an acrylonitrile-based polymerization solution, the polymerization temperature is 54 - 56 °C, the first viscosity threshold is 250P - 300P. When the viscosity of the material reaches the first viscosity threshold, the target temperature to which it is heated is 64 - 66 °C, and the proportion of the remaining initiator in the total amount of the initiator is 35 - 40%; the second viscosity threshold is 700 - 750P; the molecular weight (M W ) of the obtained acrylonitrile-based polymerization solution is 210,000 - 230,000, and the polydispersity index (PDI) is 2.2 - 2.7.

[0077] In some embodiments, the polymerization solution is an acrylonitrile-based polymerization solution, the polymerization temperature is 58 - 60 °C, the first viscosity threshold is 250P - 300P. When the viscosity of the material reaches the first viscosity threshold, the target temperature to which it is heated is 60 - 62 °C, and the proportion of the remaining initiator in the total amount of the initiator is 35 - 40%; the second viscosity threshold is 700 - 750P; the molecular weight (M W ) of the obtained acrylonitrile-based polymerization solution is 220,000 - 240,000, and the polydispersity index (PDI) is 2.2 - 2.7.

[0078] In some embodiments, the polymerization solution is an acrylonitrile-based polymerization solution, the polymerization temperature is 54 - 56 °C, the first viscosity threshold is 300P - 350P. When the viscosity of the material reaches the first viscosity threshold, the target temperature to which it is heated is 64 - 66 °C, and the proportion of the remaining initiator in the total amount of the initiator is 30 - 35%; the second viscosity threshold is 800 - 850P; the molecular weight (M W ) of the obtained acrylonitrile-based polymerization solution is 230,000 - 250,000, and the polydispersity index (PDI) is 2.0 - 2.5.

[0079] In some embodiments, the polymerization solution is an acrylonitrile-based polymerization solution, the polymerization temperature is 54 - 56 °C, the first viscosity threshold is 350P - 400P. When the viscosity of the material reaches the first viscosity threshold, the target temperature to which it is heated is 64 - 66 °C, and the proportion of the remaining initiator in the total amount of the initiator is 30 - 35%; the second viscosity threshold is 900 - 950P; the molecular weight (M W) is 230,000 - 250,000, and the polydispersity index (PDI) is 2.0 - 2.5.

[0080] In a second aspect, the present invention provides a method for preparing a carbon fiber spinning solution, comprising the following steps:

[0081] Adding a material containing acrylonitrile, comonomer, and solvent into a polymerization device, and regulating the molecular weight of the acrylonitrile-based polymerization solution according to the regulation method described in the first aspect;

[0082] Performing a degassing treatment on the acrylonitrile-based polymerization solution that meets the target molecular weight;

[0083] Performing an ammoniation treatment on the degassed acrylonitrile-based polymerization solution.

[0084] Specifically, in terms of the ratio of the total amount of the material and the initiator, by weight, acrylonitrile is 20 - 24 parts, comonomer is 1 - 2 parts, solvent is 73.65 - 78.85 parts, and the total amount of initiator is 0.15 - 0.35 parts. Preferably, the total amount of initiator is 0.2 - 0.3 parts.

[0085] Optionally, the comonomer is one or a combination of itaconic acid, acrylic acid, methyl acrylate, methyl methacrylate, ethyl methacrylate, isobutyl acrylic acid, β-butyl itaconate, acrylamide, acrylamide oxime, hydroxyethyl acrylonitrile, α-chloropropionitrile, or diacetone acrylamide. Exemplarily, the comonomer is itaconic acid.

[0086] Optionally, the initiator is at least one of azobisisobutyronitrile, azobisisoheptonitrile, and dimethyl azobisisobutyrate. Exemplarily, the initiator is azobisisobutyronitrile (AIBN).

[0087] Optionally, the solvent is at least one of dimethyl sulfoxide, sodium thiocyanate, and N,N-dimethylformamide. Exemplarily, the solvent is dimethyl sulfoxide.

[0088] In some embodiments, the material further includes a molecular weight regulator; Exemplarily, the molecular weight regulator is isopropanol; Taking acrylonitrile and comonomer as copolymerization components, the addition amount of the molecular weight regulator is 0.002 - 0.005% of the total mass of the copolymerization components.

[0089] Specifically, after adding the material into the polymerization device, before the polymerization starts, the material is stirred by a stirring device to make it uniformly mixed. The stirring device is located in the middle of the inner liquid in the polymerization kettle and stirs in the same direction.

[0090] Preferably, the stirring device includes a helical ribbon agitator and a scraping wall agitator.

[0091] Preferably, before the polymerization starts, the rotational speed of the stirring is 20 - 80 rpm, and the stirring time is 30 - 60 min. Exemplarily, the rotational speed of the stirring is 30 rpm, 40 rpm, 50 rpm, 60 rpm, 70 rpm. The stirring time is 35 min, 40 min, 45 min, 50 min, 55 min.

[0092] (a) For the ribbon agitator, it satisfies: S 1 =(50 - 70%)S 2 , S 1 =Π×(1 / 2D 1 ), 2 , D 1 is the outer diameter of the ribbon, and S 2 is the internal cross-sectional area of the polymerization kettle. Exemplarily, S 1 / S 2 =55%, 60%, 65%.

[0093] (b) For the scraping wall agitator, it satisfies: L ≤ 10 mm, where L represents the gap between the scraping wall component (such as a scraper or a knife) of the scraping wall agitator and the inner wall of the polymerization kettle. As the polymerization reaction proceeds, the viscosity of the internal liquid in the polymerization kettle continuously increases and becomes a highly viscous liquid. By using the scraping wall agitator and controlling L, it effectively avoids the adhesion of the highly viscous liquid on the inner wall of the polymerization kettle to form agglomerated rubber blocks on the wall.

[0094] During the stirring process, the proportion of the liquid level height h of the internal liquid in the polymerization kettle to the total height H of the polymerization kettle is 10% - 90%. Exemplarily, h / H = 20%, 30%, 40%, 50%, 60%, 70%, 80%. Preferably, h / H = 80 - 90%.

[0095] By selecting the above preferred stirring device and stirring parameters, etc., it can efficiently ensure that the materials are evenly mixed before the polymerization starts.

[0096] Preferably, by weight, acrylonitrile is 22 - 24 parts, the comonomer is 1 - 2 parts, the solvent is 73.7 - 76.8 parts, the stirring rotational speed is 40 - 60 rpm, and the stirring time is 30 - 45 min.

[0097] Preferably, by weight, acrylonitrile is 20 - 22 parts, the comonomer is 1 - 2 parts, the solvent is 74.7 - 77.8 parts, the stirring rotational speed is 50 - 70 rpm, and the stirring time is 45 - 55 min.

[0098] Exemplarily, the evenness of the material mixing is judged by the uniformity of the temperature of the internal liquid in the polymerization kettle. Specifically, during the stirring process, when the temperature difference of the internal liquid in the polymerization kettle ≤ 1°C, this is used as the judgment basis for the mixing to be uniform.

[0099] Specifically, the polymerization reaction is carried out under the protection of an inert gas. The flow rate of the inert gas is 50 - 100 L / h; the pressure of the inert gas ≤ 0.1 Mpa. Oxygen in the air has an inhibiting effect on polymerization. The inert gas can isolate oxygen. Using an inert gas with an appropriate flow rate and pressure is helpful for the polymerization reaction.

[0100] Preferably, the inert gas enters the polymerization kettle from one side at the top of the polymerization kettle and flows out of the polymerization kettle from the other side at the top of the polymerization kettle, so that the original air in the polymerization kettle can be better replaced. The inert gas is selected from at least one of nitrogen, argon or helium.

[0101] Exemplarily, the flow rate of the inert gas is 60 L / h, 70 L / h, 75 L / h, 85 L / h.

[0102] Exemplarily, the pressure of the inert gas is 0.07 Mpa, 0.05 Mpa, 0.04 Mpa, 0.02 Mpa, 0.01 Mpa.

[0103] Preferably, the flow rate of the inert gas is 80 - 90 L / h; the pressure of the inert gas is 0.06 - 0.08 Mpa. By precisely controlling the flow rate and pressure of the inert gas, it is beneficial to polymerize to obtain a polymer solution with high molecular weight and narrow distribution.

[0104] Preferably, the initiator is pre-dissolved in a solvent and then added to the polymerization device in batches, which helps to ensure that the initiator reaches a uniform distribution more quickly in the whole reaction system, improves the uniformity of the polymerization reaction rate at different positions in the polymerization device, and is beneficial to obtaining a polymer solution with high molecular weight and narrow distribution. Preferably, for the case where the initiator is 0.15 - 0.35 parts, the solvent used to dissolve the initiator is 5 - 10 parts.

[0105] Specifically, after the polymerization is started, the materials in the polymerization kettle are continuously stirred, and the stirring speed is 30 - 80 rpm. Exemplarily, after the polymerization is started, the stirring speed is 35 rpm, 40 rpm, 45 rpm, 50 rpm, 55 rpm, 60 rpm, 65 rpm, 70 rpm, 75 rpm.

[0106] Preferably, after the polymerization is started and before adding the remaining initiator, the stirring speed is 30 - 60 rpm, more preferably 40 - 60 rpm. After adding the remaining initiator, the stirring speed is 50 - 80 rpm, more preferably 50 - 70 rpm.

[0107] Preferably, in the de - monomerization process, the polymerization liquid undergoes gas - liquid exchange with the counter - flowing solvent vapor through multiple perforated partitions. At each perforated partition, the polymerization liquid is divided into two parts: one part of the polymerization liquid spreads on the perforated partition to form a thin liquid layer and flows downward through the holes on the perforated partition, and the other part of the polymerization liquid flows downward from the suspended end on the side of the perforated partition.

[0108] Adopting this optimized de - monomerization method can significantly improve the de - monomerization effect and efficiency, effectively avoid caking or coking inside the de - monomerization device, and reduce the formation of gels in the polymerization liquid during the de - monomerization process. After the polymerization liquid is introduced into the de - monomerization device, it is evenly distributed on the first - layer perforated partition through porous distribution to form a uniform thin liquid layer; the polymerization liquid mainly flows through the holes on the partition to the next - layer partition and continues to spread on the lower - layer partition to form a thin liquid layer, thereby ensuring that the thin liquid layer of the polymerization liquid on each partition can undergo efficient gas - liquid exchange with the solvent vapor. At the same time, the excess high - viscosity material can smoothly flow to the next - layer partition through the channel between the suspended end of the partition and the inner wall of the tank; this flow path not only ensures the de - monomerization effect but also effectively avoids caking and coking on the inner wall of the device, reduces the formation of gels in the polymerization liquid, and guarantees the efficient progress of production. Compared with traditional de - monomerization methods such as falling - film towers and high - gravity rotating beds, the de - monomerization process of the present invention significantly reduces the stringent requirements for process parameters and equipment processing precision. Especially when treating acrylonitrile - based polymerization liquids with higher viscosities and higher molecular weights, the present invention shows better adaptability and stability, effectively avoiding the common coking and caking problems in traditional methods, and significantly reducing the formation of gels in the polymerization liquid during de - monomerization.

[0109] More preferably, one part of the polymerization liquid flows through the holes on the perforated partition to the next - layer perforated partition or the polymerization liquid collection area, and the positions of the holes where the polymerization liquid flows out of the adjacent - layer perforated partitions are different. The other part of the polymerization liquid flows from the suspended end on the side of the perforated partition to the next - layer perforated partition or the polymerization liquid collection area. In the de - monomerization process, by optimizing the flow path of the polymerization liquid as described above, the contact time between the polymerization liquid and the solvent vapor is extended, ensuring that unreacted monomers (such as acrylonitrile) are more fully removed, meeting the de - monomerization requirements of high - viscosity polymerization liquids.

[0110] In some embodiments, in the de - monomerization process, the polymerization liquid enters the de - monomerization device from the top or upper part of the de - monomerization device. After porous distribution, it is distributed on the first - layer perforated partition, enabling the polymerization liquid to be evenly distributed on the first - layer perforated partition, thereby improving the de - monomerization effect and efficiency.

[0111] It can be understood that the process of the devolatilization treatment includes: the polymer solution enters the devolatilization device and flows through multiple perforated partitions from top to bottom in sequence, forming a continuous liquid film flow; at the same time, the solvent vapor enters the devolatilization device and passes through multiple perforated partitions from bottom to top in sequence, fully contacting the flowing-down polymer solution and performing gas-liquid exchange. The solvent vapor carries the residual volatile monomers in the polymer solution and is discharged from the devolatilization device; the polymer solution after the devolatilization treatment is discharged from the devolatilization device, completing the devolatilization process.

[0112] Exemplarily, the devolatilization treatment is carried out under negative pressure. The vacuum degree of the negative pressure is 100 - 5000 Pa. Exemplarily, the vacuum degrees are 200 Pa, 500 Pa, 800 Pa, 1000 Pa, 2000 Pa, 3000 Pa, 4000 Pa. Preferably, the vacuum degree is 500 - 2000 Pa.

[0113] Preferably, in the devolatilization treatment, the inlet temperature of the polymer solution is 50 - 70 °C, preferably 65 - 70 °C. Exemplarily, the inlet temperatures of the polymer solution are 54 °C, 58 °C, 62 °C, 66 °C.

[0114] Preferably, in the devolatilization treatment, the inlet flow rate of the polymer solution is 3 - 5 m 3 / h, preferably 3 - 4 m 3 / h. In the devolatilization treatment, the temperature of the devolatilization system is controlled at 50 - 70 °C. More preferably, the temperature of the devolatilization system gradually increases from top to bottom. Exemplarily, the inlet flow rates of the polymer solution are 3.3 m 3 / h, 3.6 m 3 / h, 3.9 m 3 / h, 4.2 m 3 / h, 4.5 m 3 / h, 4.8 m 3 / h.

[0115] Preferably, in the devolatilization treatment, the inlet temperature of the solvent vapor is 80 - 100 °C; more preferably 90 - 100 °C. Exemplarily, the inlet temperatures of the solvent vapor are 84 °C, 88 °C, 92 °C, 96 °C.

[0116] Preferably, in the devolatilization treatment, the inlet pressure of the solvent vapor is 0.01 - 0.5 Mpa; more preferably 0.2 - 0.3 Mpa. Exemplarily, the inlet pressures of the solvent vapor are 0.05 Mpa, 0.1 Mpa, 0.15 Mpa, 0.25 Mpa, 0.35 Mpa, 0.40 Mpa, 0.45 Mpa.

[0117] In some embodiments, in the devolatilization treatment, the inlet viscosity of the acrylonitrile-based polymer solution is 600 - 1000 P, and the weight-average molecular weight is 200,000 - 250,000.

[0118] The inventors found that in the said single-removing treatment, when the liquid inlet flow rate of the polymerization liquid and the gas inlet flow rate of the solvent vapor satisfy a specific relationship, a better single-removing effect can be obtained. Specifically, the liquid inlet flow rate Q of the polymerization liquid 1 and the gas inlet flow rate Q of the solvent vapor 2 satisfy the following relational expression:

[0119] Q 2 ≥k×Q 1 ×m×α×1000

[0120] wherein, the unit of Q 1 is m 3 / h, the unit of Q 2 is L / h, m is the mass percentage of the residual monomer in the polymerization liquid; α is the flow coefficient of the solvent vapor, and the value range of α is 1.0 - 1.2; k is the proportionality coefficient, and the value range of k is 1.5 - 1.9.

[0121] Exemplarily, k = 1.60, 1.65, 1.70, 1.72, 1.74, 1.75, 1.80, 1.85. For example, k = 1.737.

[0122] Preferably, Q 1 is 3 - 5 m 3 / h.

[0123] When 3.0 m 3 / h ≤ Q 1 <3.7 m 3 / h, preferably, the value of k is 1.8 - 1.9.

[0124] When 3.7 m 3 / h ≤ Q 1 <4.4 m 3 / h, preferably, the value of k is 1.7 - 1.8.

[0125] When 4.4 m 3 / h ≤ Q 1 ≤5.0 m 3 / h, preferably, the value of k is 1.6 - 1.7.

[0126] In one embodiment, Q 1 = 3 m 3 / h, m = 10%, α = 1.0, k = 1.9, then when Q 2 ≥570 L / h, after testing, the acrylonitrile (AN) residual monomer in the polymerization liquid after single-removing is less than 100 ppm.

[0127] In one embodiment, Q 1 = 4 m 3 / h, m = 10%, α = 1.1, k = 1.73, then when Q 2 ≥ 760 L / h, after testing, the residual acrylonitrile (AN) in the polymerized liquid after removing monomers is less than 100 ppm.

[0128] In one embodiment, Q 1 = 5 m 3 / h, m = 9%, α = 1.2, k = 1.60, then when Q 2 ≥ 860 L / h, after testing, the residual acrylonitrile (AN) in the polymerized liquid after removing monomers is less than 100 ppm.

[0129] The above embodiments fully verify the reliability of the relational expression Q 2 ≥ k × Q 1 × m × α × 1000.

[0130] In the above embodiments, by precisely controlling the process parameters of monomer removal, such as the inlet flow rate of the polymerized liquid, the inlet flow rate of the solvent vapor, the inlet temperature of the polymerized liquid, the inlet temperature / pressure of the solvent vapor, etc., it is beneficial to improve the monomer removal efficiency and effect, avoid skinning or coking of the monomer removal equipment, and significantly reduce the formation of gels in the polymerized liquid. In some embodiments, the monomer removal effect is remarkable, the residual monomer content after monomer removal is lower than 100 ppm, and the monomer removal process is efficient and continuous. The polymerized liquid can continuously enter and flow out of the monomer removal device according to the working conditions. In addition, the phenomenon of skinning or coking of the equipment is significantly reduced. Through the viewing window on the monomer removal device, there is no obvious discoloration on the inner wall of the device. In the traditional monomer removal device, due to uneven heat absorption during the flow of the polymerized liquid, local gels are generated, and even coking occurs on the inner wall of the device, resulting in a filter replacement cycle for removing gels from the polymerized liquid after monomer removal of only 1 - 2 months, or even shorter. However, with the monomer removal treatment of the present invention, the formation of gels in the polymerized liquid is significantly reduced, so that the filter replacement cycle is extended to more than 3 months, improving the operation efficiency and service life of the equipment. The above replacement cycle is based on the condition that the pressure increase reaches half of the filter pressure resistance rating for filter replacement.

[0131] Exemplarily, in the monomer removal treatment, the solvent vapor is at least one of dimethyl sulfoxide, sodium thiocyanate, and N,N - dimethylformamide. The selected solvent vapor is the same as the solvent in the polymerized liquid.

[0132] In the ammoniation treatment, in the storage tank of the ammoniation device, the polymerized liquid remains flowing and the temperature is controlled at 60 - 65 °C, which is the optimal temperature range for ammoniation of the acrylonitrile - based polymerized liquid. Specifically, the polymerized liquid flows in from the upper part of the storage tank of the ammoniation device and flows out from the lower part of the storage tank.

[0133] In order to ensure that groups such as carboxyl groups on the molecular chain in the polymerized liquid are effectively converted into hydrophilic groups such as carboxyl amines through ammoniation, preferably, in the ammoniation treatment, according to the flow rate Q of the polymerized liquid3 Combined with the following relationship: M = Q 3 ×n, determine the mass M of ammonia gas to be introduced per 1 kg of the polymerization solution; where the unit of M is mg, and Q 3 has the unit of m 3 / h, and the value range of n is 1.25 - 3.0.

[0134] In the ammoniation treatment, the appropriate range of ammonia gas introduction amount is set according to the flow rate of the polymerization solution and combined with the quantitative relationship, so as to accurately control the ammonia gas introduction amount, thereby ensuring the ammoniation effect, improving the ammoniation uniformity, enhancing the hydrophilicity of polyacrylonitrile, stabilizing the ammoniation degree, prolonging the service life of the spinning solution, and further improving the properties of carbon fiber.

[0135] Exemplarily, n = 1.5, 1.8, 2.1, 2.4, 2.7.

[0136] Preferably, the value range of Q 3 is 3 - 5 m 3 / h.

[0137] When 3.0 m 3 / h ≤ Q 3 <3.5 m 3 / h, preferably, the value range of n is 2.0 - 2.7.

[0138] When 3.5 m 3 / h ≤ Q 3 <4.3 m 3 / h, preferably, the value range of n is 1.25 - 1.75.

[0139] When 4.3 m 3 / h ≤ Q 3 ≤5.0 m 3 / h, preferably, the value range of n is 1.6 - 2.0.

[0140] In one embodiment, Q 3 = 3 m 3 / h, then when M satisfies 6 - 8 mg, after testing, the pH of the ammoniated spinning solution is 8 - 10, and the ammoniation effect is good.

[0141] In one embodiment, Q 3 = 4 m 3 / h, then when M satisfies 5 - 7 mg, after testing, the pH of the ammoniated spinning solution is 8 - 10, and the ammoniation effect is good.

[0142] In one embodiment, Q 3 = 5 m 3 / h, then when M satisfies 8 - 10 mg, after testing, the pH of the ammoniated spinning solution is 8 - 10, and the ammoniation effect is good.

[0143] Preferably, the ammonia introduction time is controlled within 5 - 8 hours.

[0144] Preferably, in the ammoniation treatment, a diagonal blade agitator is used to stir the polymerization solution. The diagonal blade agitator includes a plurality of diagonal stirring blades. The inclination angle of the diagonal stirring blades is 40 - 50°, and the diagonal stirring blades are rectangular blades with a length of L satisfying πL 2 =(50 - 70%)S 4 , S 4 is the cross-sectional area of the storage tank in the ammoniation device. During the ammoniation treatment, the stirring speed is controlled within 30 - 50 r / min. Exemplarily, during ammoniation, the stirring speed is controlled at 35 r / min, 40 r / min, 45 r / min.

[0145] By using a diagonal blade agitator to lift the polymerization solution upward, strong axial flow can be generated, causing the polymerization solution to form an up-and-down circulating flow during stirring. This flow pattern helps ammonia to disperse better in the polymerization solution, improving the mass transfer efficiency and ammoniation effect. By precisely controlling the structural parameters of the diagonal blade agitator, the up-and-down circulating flow can be better promoted, further improving the mass transfer efficiency and ammoniation effect.

[0146] Preferably, the ammoniation treatment is carried out under a slightly positive pressure, enabling ammonia to diffuse more effectively and come into full contact with the polymerization solution, while ensuring the safety of the system. Specifically, during the ammoniation process, a pressure slightly higher than the external atmospheric pressure, i.e., a slightly positive pressure, is applied inside the storage tank. The slightly positive pressure is 0 - 2000 Pa, that is, the pressure inside the storage tank is 0 - 2000 Pa higher than the external atmospheric pressure. More preferably, the slightly positive pressure is 100 - 1000 Pa. Exemplarily, the slightly positive pressure is 50 Pa, 200 Pa, 500 Pa, 800 Pa, 1300 Pa, 1500 Pa, 1800 Pa.

[0147] Using the ammoniation treatment provided in the above embodiments of the present invention can ensure that the pH of the obtained carbon fiber spinning solution is within 8 - 10, further within 8.4 - 9.8, and preferably the pH is 8.9 - 9.5.

[0148] In a third aspect, the present invention provides a carbon fiber spinning solution, which is prepared by the preparation method described in the second aspect.

[0149] Specifically, the molecular weight M of the acrylonitrile-based polymerization solution obtained by polymerization Wis 200,000 - 250,000, the polydispersity index PDI is 2.0 - 3.0, the falling ball viscosity at 40 - 50 °C is 600 - 1000 P, the solid content in the polymerization solution is 19.0 - 21.0%, the polymerization conversion rate ≥ 90%, and the residual monomer content of the acrylonitrile-based polymerization solution obtained by polymerization is ≤ 10%. After the monomer removal treatment, the residual monomer content of the acrylonitrile-based polymerization solution is ≤ 350 ppm. After the ammoniation treatment, the pH of the obtained carbon fiber spinning solution is 8 - 10.

[0150] In some embodiments, the molecular weight M of the acrylonitrile-based polymerization solution obtained by polymerization W is 210,000 - 250,000, the polydispersity index PDI is 2.1 - 2.6, the falling ball viscosity at 40 - 50 °C is 620 - 910 P, the solid content in the polymerization solution is 19.2 - 20.6%, the polymerization conversion rate is 92 - 95%, and the residual monomer content of the acrylonitrile-based polymerization solution obtained by polymerization is ≤ 3%, further, the residual monomer content of the acrylonitrile-based polymerization solution obtained by polymerization is ≤ 2%, further, the residual monomer content of the acrylonitrile-based polymerization solution obtained by polymerization is ≤ 1%. After the monomer removal treatment, the residual monomer content of the acrylonitrile-based polymerization solution is < 100 ppm, more preferably, the residual monomer content after monomer removal is less than 50 ppm, further, the residual monomer content after monomer removal is less than 30 ppm. After the ammoniation treatment, the pH of the obtained carbon fiber spinning solution is 8.4 - 9.8, preferably the pH is 8.9 - 9.5.

[0151] Fourthly, the present invention provides a production device for a carbon fiber spinning solution, and the production device is used for the carbon fiber spinning solution obtained by the preparation method as described in the second aspect or the production and preparation of the carbon fiber spinning solution as described in the third aspect.

[0152] Specifically, the production device includes a monomer removal device, an ammoniation device, and a polymerization device.

[0153] (1) Monomer removal device:

[0154] The monomer removal device 100 includes a tank body A and a multi-layer perforated partition plate 11 arranged in the tank body. The multi-layer perforated partition plates are arranged in layers from top to bottom along the axial direction of the tank body, and each layer of perforated partition plate is perpendicular to the axial direction of the tank body. Each layer of perforated partition plate includes a fixed end on one side and a suspended end on the other side. The fixed end is conformally fixed to the inner wall of the tank body, and the other suspended end extends freely. The suspended end of the upper layer of perforated partition plate is located on one side of the axial direction of the tank body, and the suspended end of the lower layer of perforated partition plate adjacent to the upper layer of perforated partition plate is located on the other side of the axial direction of the tank body. The suspended ends of the multi-layer perforated partition plates form an alternating staggered layout in space.

[0155] Compared with the prior art, the present invention provides a multi-layered perforated partition in the monomer removal device. The polymerization liquid forms a thin liquid layer on each partition, and the overhanging ends of adjacent partitions are arranged staggeredly to ensure the smooth flow of the polymerization liquid. This structural design optimizes the flow path of the polymerization liquid in the tank. On the one hand, the specific surface area of the material is increased through the thin liquid layer, and on the other hand, the residence time of the liquid in the device is extended, providing more opportunities for the solvent vapor to contact the residual monomers, thus significantly improving the monomer removal effect.

[0156] The monomer removal device of the present invention designs a channel between the overhanging end of each perforated partition and the inner wall of the tank to ensure that the polymerization liquid can flow smoothly to the next layer after forming a thin liquid layer. This structure not only realizes the uniform distribution and effective guidance of high molecular weight and high viscosity polymerization liquid materials on the partition, but also significantly reduces problems such as coking, crusting, or gel formation in the polymerization liquid that are prone to occur in traditional devices when processing such materials. In addition, it effectively avoids blockage inside the monomer removal device, improves operation stability, reduces the equipment cleaning and maintenance costs, and enhances production efficiency.

[0157] Preferably, the area of each perforated partition accounts for 80%-90% of the cross-sectional area of the tank at that layer position, and the remaining 10-20% serves as a smooth channel for the flow of the polymerization liquid.

[0158] Preferably, the holes in adjacent layers of perforated partitions are arranged in a staggered layer pattern, and the hole positions on each perforated partition are offset relative to the hole positions of its directly adjacent perforated partition. This staggered hole distribution can further increase the contact area and time between the solvent vapor and the polymerization liquid, thereby improving the gas-liquid exchange efficiency, helping the solvent vapor to more effectively remove the residual monomers in the polymerization liquid. In addition, the staggered holes can optimize the flow path, make the polymerization liquid flow more uniformly, reduce local overheating or overcooling, reduce the risk of coking and crusting, and reduce gel formation in the polymerization liquid.

[0159] Preferably, the multi-layered perforated partitions are distributed parallel and equidistantly from top to bottom along the axial direction of the tank. Adopting the above preferred partition distribution method helps to achieve uniform flow of the polymerization liquid in the tank, reduce flow dead zones, reduce the risk of coking and crusting, reduce gel formation in the polymerization liquid, and ensure sufficient contact between the solvent vapor and the polymerization liquid, improving the monomer removal effect and efficiency.

[0160] Preferably, inside the tank, the distance between the first perforated partition and the last perforated partition accounts for 1 / 2 to 4 / 5 of the total height of the tank, preferably 60%-70%, such as 2 / 3. This can make more efficient use of the tank space, increase the contact time and area between the polymerization liquid and the solvent vapor, improve the monomer removal effect and efficiency. By leaving appropriate spaces above and below, it helps the heat transfer and mass transfer processes to proceed, ensuring the uniform distribution of heat and substances throughout the tank, reducing the dead zones of the polymerization liquid in the tank, avoiding local overheating or overcooling, and being beneficial to reducing the risk of coking and crusting and the formation of gels in the polymerization liquid.

[0161] Furthermore, a polymerization liquid inlet 12 is provided at the top or upper part of the tank. A perforated distribution plate 13 is provided between the polymerization liquid inlet 12 and the adjacent first perforated partition, and the distribution plate 13 is arranged parallel to the first perforated partition.

[0162] Preferably, the area ratio of the distribution plate 13 to the first perforated partition is 40%-60%, more preferably 45%-55%.

[0163] Preferably, the ratio of the distance between the upper surface of the distribution plate 13 and the lower end of the polymerization liquid inlet 12 to the distance between the lower end of the polymerization liquid inlet 12 and the upper surface of the first perforated partition is 15%-40%; more preferably 20%-30%.

[0164] The main function of the distribution plate is to evenly distribute the polymerization liquid entering from the inlet after porous distribution onto the first perforated partition, so as to form a uniform thin layer of polymerization liquid on the perforated partition. By controlling the spatial layout of the distribution plate in the tank and the area ratio with the adjacent perforated partition, it is beneficial to form a more uniform thin layer of polymerization liquid, increase the contact area and time between the polymerization liquid and the solvent vapor, and improve the monomer removal effect and efficiency.

[0165] By optimizing the structural parameters of multiple perforated partitions, distribution plates, etc. in the monomer removal device, a better monomer removal effect can be obtained, while avoiding local overheating or overcooling, further reducing the risk of coking and crusting, and reducing the formation of gels in the polymerization liquid. Using the monomer removal device provided by the present invention to perform monomer removal treatment on the polymerization liquid can ensure that the content of residual monomers in the polymerization liquid after monomer removal is reduced to below 100 ppm.

[0166] Specifically, the perforated partition has at least one of the following characteristics:

[0167] (a) The number of layers of the perforated partition is 4-8 layers;

[0168] (b) The pore size of each layer of the perforated partition is 0.5-2 mm, and the pore spacing is 10-40 mm; for example, the pore size is 1 mm, 1.5 mm; the pore spacing is 20 mm, 30 mm.

[0169] (c) The arrangement of the multiple holes on each layer of the perforated partition is preferably a circular array; further, the multiple holes cover the entire perforated partition.

[0170] (d) The spacing between two adjacent layers of perforated partitions is 300-800 mm; preferably 400-600 mm, for example 500 mm;

[0171] (e) The thickness of each layer of perforated partition is 6-12 mm;

[0172] (f) The holes of adjacent perforated partitions are arranged in staggered layers, and the offset distance between the centers of the corresponding holes in adjacent layers is 10-30 mm; preferably, they are arranged in an alternating staggered manner: the odd-numbered layers and the even-numbered layers are kept consistent, but the odd-numbered layers are staggered a certain distance from the even-numbered layers.

[0173] (g) In order to make the polymer solution spread into a thin film on the perforated partition plate to improve the single removal effect, preferably, the material of the perforated partition plate is selected from 316L stainless steel, 1Cr18NiMo3 stainless steel, and AL-1100 aluminum alloy. The above materials are all commercially available alloy grades.

[0174] Furthermore, a solvent vapor inlet is provided at the lower part of the tank body, and the desolventizing device also includes a solvent vaporizer B. The upper part of the solvent vaporizer B is connected to the solvent vapor inlet through a pipeline, and a solvent inlet 14 is provided at the bottom of the solvent vaporizer B. A coil 15 is provided inside the solvent vaporizer B, and one end of the coil 15 is connected to a coil inlet 15a provided at the upper part of the solvent vaporizer B, and the other end of the coil 15 is connected to a coil outlet 15b provided at the lower part of the solvent vaporizer B.

[0175] It can be understood that, during operation, the solvent enters the solvent vaporizer B from the solvent inlet 14, the water vapor enters the coil from the coil inlet 15a, flows along the coil, and finally flows out from the coil outlet 15b. During the process of flowing in the coil, the water vapor transfers heat to the solvent outside the coil, causing it to vaporize into solvent vapor 16, and the solvent vapor 16 flows into the tank body A through the solvent vapor inlet.

[0176] Exemplarily, the solvent vapor inlet is arranged below the last layer of perforated partitions and above the liquid level of the polymer liquid after de-monomerization and the liquefied solvent mixture collected at the bottom of the tank body A.

[0177] Specifically, a vacuum port 17 is provided on the upper part or top of the tank body A; the monomer removal device further includes a liquid ring vacuum jet device, which is connected to the vacuum port 17 through a pipeline, so as to provide a stable negative pressure inside the tank body A in the monomer removal device and discharge the solvent vapor carrying the monomer. Specifically, a heating jacket is provided on the outer wall of the tank body A so that the polymerization liquid inside the tank body A reaches the required monomer removal temperature.

[0178] Specifically, a polymerized liquid discharge port 18 is provided at the lower part or bottom of the tank body A.

[0179] (2) Ammoniation device:

[0180] The ammoniation device 200 includes a storage tank and an inclined blade agitator 21 arranged inside the storage tank; the inclined blade agitator 21 includes a plurality of agitator paddles 21a arranged in layers along the axial direction of the storage tank, and the plurality of agitator paddles are commonly connected to the same rotating shaft 21b. Preferably, the plurality of agitator paddles are evenly distributed along the axial direction of the storage tank.

[0181] Each agitator paddle includes a plurality of inclined agitator blades. Preferably, the inclination angle of the inclined agitator blades is 40 - 50°, and the inclined agitator blades are rectangular blades with a length of L and satisfying πL 2 =(50 - 70%)S 4 , S 4 is the cross-sectional area of the storage tank. Preferably, πL 2 =(50 - 55%)S 4 .

[0182] Exemplarily, the inclined blade agitator includes 2, 3 or 4 agitator paddles, and each agitator paddle includes at least two inclined agitator blades. For example, each agitator paddle includes 3 or 4 inclined agitator blades.

[0183] Preferably, the ammonia gas inlet 22 is arranged within the height range of 1 / 5 to 2 / 5 of the lower part of the storage tank, that is, in the area between 1 / 5 height and 2 / 5 height upward from the bottom of the storage tank.

[0184] A polymerized liquid inlet 23 is provided at the upper part or top of the storage tank, and a polymerized liquid outlet 24 is provided at the lower part or bottom of the storage tank; the top end of the rotating shaft 21b of the inclined blade agitator is driven by a first motor 25.

[0185] (3) Polymerization device:

[0186] The polymerization device 300 includes a polymerization kettle and a stirring device 31 arranged inside the polymerization kettle, and the stirring device 31 is selected from a helical ribbon agitator and a scraping wall agitator.

[0187] For the helical ribbon agitator, it satisfies: S 1 =(50 - 70%)S 2 , S 1 =Π×(1 / 2D 1 ) 2 , D 1 is the outer diameter of the helical ribbon, and S 2 is the inner cross-sectional area of the polymerization kettle. Exemplarily, S 1 / S 2= 55%, 60%, 65%.

[0188] For the scraping wall type stirrer, it satisfies: L ≤ 10 mm, where L represents the gap between the scraping wall component (such as a scraper or a spatula) of the scraping wall type stirrer and the inner wall of the polymerization kettle.

[0189] On one side of the top of the polymerization device 300, there is an inert gas inlet 32, and on the other side, there is an inert gas outlet 33. Preferably, both the inert gas inlet 32 and the inert gas outlet 33 are located within the height range of 1 / 10 to 1 / 5 from the top of the polymerization device downwards. The stirring device 31 is driven by a second motor 34.

[0190] In some embodiments, the polymerization device further includes a real-time viscosity monitoring device C, which includes a reflux pipeline. Both ends of the reflux pipeline are communicated with the inside of the polymerization kettle. An on-line pressure-viscosity converter 35 is arranged on the reflux pipeline. The on-line pressure-viscosity converter includes a pressure detector and a processor. The pressure detector is arranged at a fixed position of the reflux pipeline for real-time collection of the pressure signal of the polymerization liquid in the pipeline. The pressure detector is connected to the processor through a line. The processor is used to convert the collected pressure signal into a viscosity value. Figure 4 Among them, T represents the temperature monitoring component, and P represents the pressure monitoring component.

[0191] Furthermore, the processor of the real-time viscosity monitoring device C is connected to a display arranged outside the polymerization device through a line. After the processor converts the collected pressure signal into a viscosity value, it transmits the data to the display through the line, so as to display the viscosity of the polymerization liquid in real time.

[0192] Preferably, a constant-speed gear pump 36 is arranged on the reflux pipeline, and a circulating water system is arranged outside the reflux pipeline. For example, the circulating water system is a water tank. The constant-temperature circulating water enters from one side of the water tank and flows out from the other side. Exemplarily, the constant-temperature circulating water enters the water tank from the circulating water inlet 37 at the bottom of the water tank and flows out of the water tank from the circulating water outlet 38 at the top of the water tank. The constant-speed gear pump and the circulating water system can ensure the constant temperature and flow rate of the polymerization liquid in the reflux pipeline.

[0193] In the method for preparing the carbon fiber spinning solution provided by the embodiment of the present invention, preferably, a material containing acrylonitrile, a comonomer, and a solvent is added to the above-mentioned polymerization device 300. The deodorization treatment is carried out by using the above-mentioned deodorization device 100. The ammoniation treatment is carried out by using the above-mentioned ammoniation device 200.

[0194] It can be understood that the acrylonitrile-based polymerization liquid refers to a polymer solution mainly composed of acrylonitrile monomers formed through a polymerization reaction (such as free radical polymerization).

[0195] The technical solution of the present invention will be further described in detail below in conjunction with specific examples and comparative examples.

[0196] Example 1-1:

[0197] This example provides a method for regulating the molecular weight of an acrylonitrile-based polymerization solution, including:

[0198] Material preparation: By weight, 20 parts of acrylonitrile, 1 part of itaconic acid, 0.2 part of azobisisobutyronitrile (AIBN), and 73.7 parts of dimethyl sulfoxide; 0.2 part of AIBN is pre-dissolved in 8 parts of dimethyl sulfoxide as the initiator for free radical polymerization;

[0199] Add acrylonitrile, itaconic acid, and dimethyl sulfoxide into the polymerization device, and stir the materials in the polymerization device through a scraping wall stirrer, L = 10 mm, the stirring speed is 20 rpm, and the stirring time is 60 min; the proportion of the liquid level height h of the internal liquid in the polymerization device to the total height H of the polymerization device is 80%;

[0200] When the temperature difference of the materials ≤ 1 °C, heat up to the polymerization temperature of 54 °C, and first add part of the initiator, and the proportion of the part of the initiator in the total amount of the initiator is 60%;

[0201] Monitor the material viscosity in real time. When the material viscosity reaches the first threshold of 250 P, heat the material to the target temperature of 64 °C and add the remaining 40% of the initiator;

[0202] When the material viscosity reaches the second threshold of 620 P, terminate the reaction;

[0203] The polymerization is carried out under nitrogen protection, the nitrogen flow rate is 50 L / h, the pressure is 0.1 Mpa, and during the polymerization, the stirring speed is 30 rpm; the molecular weight and PDI of the acrylonitrile-based polymerization solution obtained after polymerization are shown in Table 1, and it meets the target molecular weight.

[0204] Example 2-1:

[0205] The difference between this example and Example 1-1 is that when the temperature difference of the materials ≤ 1 °C, heat up to the polymerization temperature of 58 °C, and first add part of the initiator, and the proportion of the part of the initiator in the total amount of the initiator is 65%;

[0206] Monitor the material viscosity in real time. When the material viscosity reaches the first threshold of 300 P, heat the material to the target temperature of 62 °C and add the remaining 35% of the initiator;

[0207] When the material viscosity reaches the second threshold of 710 P, terminate the reaction; the remaining steps and parameters are similar to those of Example 1-1.

[0208] Example 3-1:

[0209] The difference between this example and Example 1-1 is that when the temperature difference of the material ≤ 1°C and the temperature is raised to the polymerization temperature of 54°C, part of the initiator is added first, and the proportion of the part of the initiator in the total amount of the initiator is 70%;

[0210] The viscosity of the material is monitored in real time. When the viscosity of the material reaches the first threshold of 350 P, the material is heated to the target temperature of 66°C, and the remaining 30% of the initiator is added;

[0211] When the viscosity of the material reaches the second threshold of 760 P, the reaction is terminated; the remaining steps and parameters are similar to those of Example 1-1.

[0212] Example 4-1:

[0213] The difference between this example and Example 1-1 is that when the temperature difference of the material ≤ 1°C and the temperature is raised to the polymerization temperature of 55°C, part of the initiator is added first, and the proportion of the part of the initiator in the total amount of the initiator is 68%;

[0214] The viscosity of the material is monitored in real time. When the viscosity of the material reaches the first threshold of 320 P, the material is heated to the target temperature of 65°C, and the remaining 32% of the initiator is added;

[0215] When the viscosity of the material reaches the second threshold of 840 P, the reaction is terminated; the remaining steps and parameters are similar to those of Example 1-1.

[0216] Example 5-1:

[0217] The difference between this example and Example 1-1 is that when the temperature difference of the material ≤ 1°C and the temperature is raised to the polymerization temperature of 56°C, part of the initiator is added first, and the proportion of the part of the initiator in the total amount of the initiator is 65%;

[0218] The viscosity of the material is monitored in real time. When the viscosity of the material reaches the first threshold of 300 P, the material is heated to the target temperature of 64°C, and the remaining 35% of the initiator is added;

[0219] When the viscosity of the material reaches the second threshold of 810 P, the reaction is terminated; the remaining steps and parameters are similar to those of Example 1-1.

[0220] Example 6-1:

[0221] The difference between this example and Example 1-1 is that when the temperature difference of the material ≤ 1°C and the temperature is raised to the polymerization temperature of 54°C, part of the initiator is added first, and the proportion of the part of the initiator in the total amount of the initiator is 75%;

[0222] The viscosity of the material is monitored in real time. When the viscosity of the material reaches the first threshold of 350 P, the material is heated to the target temperature of 64°C, and the remaining 25% of the initiator is added;

[0223] When the material viscosity reaches the second threshold of 910 P, the reaction is terminated; the remaining steps and parameters are similar to those in Example 1-1.

[0224] Example 7-1:

[0225] The difference between this example and Example 1-1 is that when the temperature difference of the material ≤ 1 °C and the temperature is raised to the polymerization temperature of 57 °C, part of the initiator is added first, and the proportion of the part of the initiator in the total amount of the initiator is 70%;

[0226] The material viscosity is monitored in real time. When the material viscosity reaches the first threshold of 350 P, the material is heated to the target temperature of 67 °C, and the remaining 30% of the initiator is added;

[0227] When the material viscosity reaches the second threshold of 620 P, the reaction is terminated; the remaining steps and parameters are similar to those in Example 1-1.

[0228] Example 8:

[0229] This example provides a device 100 for removing monomers from a carbon fiber polymerization solution. The device 100 for removing monomers includes a tank A and a plurality of perforated partitions 11 arranged horizontally (i.e., perpendicular to the axial direction of the tank) in the tank A. The plurality of perforated partitions are arranged in parallel and equally spaced layers from top to bottom along the axial direction of the tank. Each perforated partition includes a fixed end on one side and a suspended end on the other side. The fixed end is conformally fixed to the inner wall of the tank, and the other suspended end extends freely. The suspended end of one perforated partition is located on one side of the axial direction of the tank, and the suspended ends of adjacent perforated partitions are located on the other side of the axial direction of the tank. The suspended ends of the plurality of perforated partitions form an alternating staggered layout in space.

[0230] The area of each perforated partition accounts for 75% of the cross-sectional area of the tank at that layer position, and the remaining 25% serves as a smooth channel for the flow of the polymerization solution; the holes of adjacent perforated partitions are arranged in an alternating staggered layer distribution, and the misalignment distance between the centers of the corresponding holes of adjacent layers is 10 mm; the aperture size of the holes on each perforated partition is 1.0 mm, the hole pitch is 20 mm, and the holes are arranged in a circular array; the thickness of each perforated partition is 6 mm.

[0231] Inside the tank A, the distance between the first perforated partition and the last perforated partition accounts for 1 / 2 of the total height of the tank; a polymerization solution inlet 12 is provided at the top of the tank A, and a perforated distribution plate 13 is provided between the polymerization solution inlet 12 and the adjacent first perforated partition, and the distribution plate 13 is arranged parallel to the first perforated partition; the area ratio of the distribution plate 13 to the first perforated partition is 30%, and the ratio of the distance between the upper surface of the distribution plate 13 and the lower end of the polymerization solution inlet 12 to the distance between the lower end of the polymerization solution inlet 12 and the upper surface of the first perforated partition is 50%.

[0232] A solvent vapor inlet is provided at the lower part of the tank body A. The monomer removal device further includes a solvent vaporizer B. The top of the solvent vaporizer B is connected to the solvent vapor inlet through a pipeline. A solvent inlet 14 is provided at the bottom of the solvent vaporizer B. A coil 15 is provided inside the solvent vaporizer B. One end of the coil 15 is connected to a coil inlet 15a provided at the upper part of the solvent vaporizer, and the other end of the coil 15 is connected to a coil outlet 15b provided at the lower part of the solvent vaporizer. A polymerized liquid discharge port 18 is provided at the bottom of the tank body A. The solvent is vaporized into solvent vapor 16 by heating through the solvent vaporizer B and enters the storage tank from the solvent vapor inlet. A vacuum extraction port 17 is provided at the upper part of the tank body A. The monomer removal device further includes a liquid ring type vacuum jet device, which is connected to the vacuum extraction port 17 through a pipeline, so as to provide a stable negative pressure inside the tank body A in the monomer removal device and discharge the solvent vapor carrying monomers.

[0233] Example 9:

[0234] The difference between this example and Example 8 is that the area of each layer of perforated baffle accounts for 85% of the cross-sectional area of the tank body at this layer position, and the remaining 15% serves as a smooth channel for the flow of the polymerized liquid. The dislocation distance between the corresponding hole centers of adjacent layers is 20 mm. Inside the tank body A, the distance between the first layer of perforated baffle and the last layer of perforated baffle accounts for 70% of the total height of the tank body. The area ratio of the distribution plate 13 to the first layer of perforated baffle is 50%. The ratio of the distance between the upper surface of the distribution plate 13 and the lower end of the polymerized liquid feed port 12 to the distance between the lower end of the polymerized liquid feed port 12 and the upper surface of the first layer of perforated baffle is 30%.

[0235] Examples 1-2

[0236] This example provides a method for preparing a carbon fiber spinning solution, including:

[0237] S1: According to the regulation method described in Examples 1-1, prepare an acrylonitrile-based polymerized liquid that meets the target molecular weight;

[0238] S2: Perform monomer removal treatment on the acrylonitrile-based polymerized liquid that meets the target molecular weight. In the monomer removal treatment, the polymerized liquid enters from the top of the monomer removal device in Example 8 and is evenly distributed on the first layer of perforated baffle through porous distribution, and successively passes through the second to fifth layers of perforated baffles arranged alternately to perform gas-liquid exchange with the solvent vapor flowing countercurrently. At each layer of perforated baffle, the polymerized liquid is divided into two parts: one part of the polymerized liquid flows through the holes on the perforated baffle to the next layer of perforated baffle or the polymerized liquid collection area, and the positions where the polymerized liquid flows out of the holes on the adjacent layer of perforated baffle are different. The other part of the polymerized liquid flows from the suspended end on the side of the baffle to the next layer of perforated baffle or the polymerized liquid collection area. Among them, the monomer removal treatment is carried out at 500 Pa, the inlet temperature of the polymerized liquid is 50 °C, and the inlet flow rate Q of the polymerized liquid 1 is 3 m3 / h; the inlet temperature of the solvent vapor is 80°C. The inlet flow rate of the solvent vapor is 80L / h, and the pressure of the solvent vapor is 0.5Mpa;

[0239] S3: Ammonia bubbling method is used to introduce ammonia into the polymer solution after the removal of singles for ammoniation treatment; specifically, the temperature of the polymer solution placed in the storage tank is adjusted to 60°C, and then ammonia is introduced from the lower 1 / 5 of the storage tank. During the ammoniation process, the temperature is controlled at 60°C, the micro-positive pressure is 100 Pa, and an inclined blade stirrer is used for stirring at a stirring speed of 55 r / min; the inclined blade stirrer includes 3 stirring paddles, each of which includes 3 rectangular inclined stirring paddles with an inclination angle of 35°, and the length is L and satisfies πL 2 =70%×S 4 , S 4 is the cross-sectional area of ​​the tank; the flow rate of the polymer solution Q 3 =3m3 / h, the required amount of ammonia is calculated based on the introduction of 4.0mg of ammonia into every 1kg of polymerization liquid.

[0240] Example 2-2:

[0241] This embodiment provides a method for preparing a carbon fiber spinning solution, comprising:

[0242] S1: According to the control method described in Example 2-1, an acrylonitrile-based polymer solution meeting the target molecular weight is prepared;

[0243] The difference between steps S2 and S3 of this embodiment and embodiment 1-2 is that in step S2, the air intake flow rate of the solvent vapor is 100 L / h; in step S3, the required amount of ammonia is calculated based on 6 mg of ammonia introduced into every 1 kg of polymerization liquid; the remaining steps and parameters are similar to those of embodiment 1-2.

[0244] Example 3-2:

[0245] This embodiment provides a method for preparing a carbon fiber spinning solution, comprising:

[0246] S1: According to the control method described in Example 3-1, an acrylonitrile-based polymer solution meeting the target molecular weight is prepared;

[0247] The difference between steps S2 and S3 of this embodiment and those of embodiment 1-2 is that in step S2, the stripping device of embodiment 9 is used for stripping, and the inlet flow rate of the solvent vapor is 100 L / h; in step S3, each stirring paddle includes 3 rectangular oblique stirring blades with an inclination angle of 35°, whose length is L and satisfies πL 2 =50%×S 4 , S 4is the cross-sectional area of the storage tank, and the amount of ammonia required is calculated by introducing 5 mg of ammonia into every 1 kg of the polymerization solution; the remaining steps and parameters are similar to those in Examples 1-2.

[0248] Example 4-2:

[0249] This example provides a method for preparing a carbon fiber spinning solution, including:

[0250] S1: According to the regulation method described in Example 4-1, prepare an acrylonitrile-based polymerization solution that meets the target molecular weight;

[0251] The differences between steps S2 and S3 in this example and those in Examples 1-2 are as follows: in step S2, the degassing device of Example 9 is used for degassing treatment, and the inlet flow rate of the solvent vapor is 80 L / h; in step S3, each stirring paddle includes 3 rectangular inclined stirring paddle blades with an inclination angle of 45°, and its length is L and satisfies πL 2 = 60% × S4, where S4 is the cross-sectional area of the storage tank, and the amount of ammonia required is calculated by introducing 5 mg of ammonia into every 1 kg of the polymerization solution; the remaining steps and parameters are similar to those in Examples 1-2.

[0252] Example 5-2:

[0253] This example provides a method for preparing a carbon fiber spinning solution, including:

[0254] S1: According to the regulation method described in Example 5-1, prepare an acrylonitrile-based polymerization solution that meets the target molecular weight;

[0255] The differences between steps S2 and S3 in this example and those in Examples 1-2 are as follows: in step S2, the degassing device of Example 9 is used for degassing treatment, and the inlet flow rate Q 1 of the polymerization solution is 4 m 3 / h, and the inlet flow rate of the solvent vapor is 170 L / h; in step S3, the flow rate Q 3 of the polymerization solution is 4 m3 / h, and the amount of ammonia required is calculated by introducing 6.0 mg of ammonia into every 1 kg of the polymerization solution; the remaining steps and parameters are similar to those in Examples 1-2.

[0256] Example 6-2:

[0257] This example provides a method for preparing a carbon fiber spinning solution, including:

[0258] S1: According to the regulation method described in Example 6-1, prepare an acrylonitrile-based polymerization solution that meets the target molecular weight;

[0259] The differences between steps S2 and S3 in this example and those in Examples 1-2 are as follows: in step S2, the degassing device of Example 9 is used for degassing treatment, and the inlet flow rate Q1 5m 3 / h, the inlet flow rate of the solvent vapor is 250L / h; in step S3, the flow rate of the polymer solution is Q 3 =5m3 / h, the amount of ammonia required is calculated based on the introduction of 12.0mg of ammonia into every 1kg of polymerization liquid; the remaining steps and parameters are similar to those of Example 1-2.

[0260] Example 7-2:

[0261] This embodiment provides a method for preparing a carbon fiber spinning solution, comprising:

[0262] S1: According to the control method described in Example 7-1, an acrylonitrile-based polymer solution meeting the target molecular weight is prepared;

[0263] The difference between steps S2 and S3 of this embodiment and those of embodiment 1-2 is that in step S2, the single-dip removal device of embodiment 9 is used for single-dip removal treatment, the inlet temperature of the polymerization liquid is 67°C, and the inlet flow rate Q of the polymerization liquid is 1 5m 3 / h; the inlet temperature of the solvent vapor is 95°C. The inlet flow rate of the solvent vapor is 100L / h, and the pressure of the solvent vapor is 0.3Mpa; in step S3, the flow rate of the polymer solution Q 3 =5m3 / h, the amount of ammonia required is calculated based on the introduction of 10.0mg of ammonia into every 1kg of polymerization liquid; the remaining steps and parameters are similar to those of Example 1-2.

[0264] Comparative Example 1:

[0265] The difference between this comparative example and Example 1-1 is that: when the temperature difference of the material is ≤1°C, when the temperature is raised to 70°C, a portion of the initiator is added, and the portion of the initiator accounts for 55% of the total amount of the initiator, and the material viscosity is monitored in real time. When the material viscosity reaches the first threshold value of 150P, the remaining 45% of the initiator is added; when the material viscosity reaches the second threshold value of 630P, the reaction is terminated. The remaining steps and parameters are similar to Example 1-1.

[0266] Comparative Example 2:

[0267] The difference between this comparative example and Example 1-1 is that: when the temperature difference of the material is ≤1°C, when the temperature is raised to 50°C, a portion of the initiator is added, and the portion of the initiator accounts for 85% of the total amount of the initiator, and the material viscosity is monitored in real time. When the material viscosity reaches the first threshold value of 450P, the material is heated to the target temperature of 55°C, and the remaining 15% of the initiator is added; when the material viscosity reaches the second threshold value of 630P, the reaction is terminated. The remaining steps and parameters are similar to Example 1-1.

[0268] Comparative Example 3:

[0269] The difference between this comparative example and Example 1-1 is as follows: when the temperature difference of the material ≤ 1°C and the temperature is raised to 65°C, part of the initiator is added, and the proportion of this part of the initiator in the total amount of the initiator is 90%. The viscosity of the material is monitored in real time. When the viscosity of the material reaches the first threshold of 450 P, the remaining 10% of the initiator is added; when the viscosity of the material reaches the second threshold of 560 P, the reaction is terminated. The remaining steps and parameters are similar to those in Example 1-1.

[0270] Comparative Example 4:

[0271] The difference between this comparative example and Example 1-2 is as follows: in step S3, the amount of ammonia required is calculated according to 2.0 mg of ammonia introduced into every 1 kg of the polymerization solution; the remaining steps and parameters are similar to those in Example 1-2.

[0272] Comparative Example 5:

[0273] The difference between this comparative example and Example 1-2 is as follows: in step S3, the amount of ammonia required is calculated according to 14.0 mg of ammonia introduced into every 1 kg of the polymerization solution; the remaining steps and parameters are similar to those in Example 1-2.

[0274] Comparative Example 6:

[0275] The difference between this comparative example and Example 1-2 lies in that the difference between the de-single device adopted and that in Example 8 is as follows: the area of the perforated partition plate along the horizontal direction on each layer (referred to as the horizontal perforated partition plate) accounts for 50-79% of the cross-sectional area of the tank body at the position of this layer, and an inclined baffle is arranged on each layer of the horizontal perforated partition plate. The included angle between the inclined baffle and the horizontal perforated partition plate is 10°-60°. The holes on the horizontal perforated partition plate are within the vertical projection range of the inclined baffle, and the connection line between the inclined baffle and the horizontal perforated partition plate is parallel to the chord corresponding to the two end points of the arc on the horizontal perforated partition plate; the remaining steps and parameters are similar to those in Example 1-2.

[0276] Table 1 Test Results of Examples and Comparative Examples

[0277]

[0278] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for regulating the molecular weight of a polymer solution, characterized in that: include: Adding a material containing reactive monomers into a polymerization device; Raise the temperature to the polymerization temperature and add part of the initiator; Monitor the material viscosity in real time and determine the timing of adding the remaining initiator based on the viscosity change of the material: The molecular weight of the polymer can be regulated by controlling the viscosity threshold, material temperature and the proportion of the remaining initiator in the total amount of initiator.

2. The control method according to claim 1, characterized in that: The step of real-time monitoring of material viscosity includes: setting a material reflux pipeline, real-time monitoring of the pressure of the material at a fixed position of the reflux pipeline, and obtaining the real-time monitored material viscosity according to a real-time viscosity value converted from a pressure value.

3. The control method according to claim 2, characterized in that: The material is led out from the polymerization device, and the material is made to flow through the reflux pipeline at a constant temperature and a constant flow rate, and finally converged back to the polymerization device; by real-time monitoring of the pressure of the material at a fixed position of the reflux pipeline, and combining the pressure-viscosity relationship, the pressure value is converted into a real-time viscosity value.

4. The control method according to claim 3, characterized in that: The method for determining the pressure-viscosity relationship includes: setting multiple data collection moments, recording the pressure value at a fixed position of the return pipeline and the viscosity value obtained by an experimental method at each data collection moment, performing mathematical fitting of the pressure value and the viscosity value, and establishing the pressure-viscosity relationship.

5. The control method according to claim 3, characterized in that: The method of making the material flow through the reflux pipeline at a constant temperature and a constant flow rate includes: placing the reflux pipeline in a constant temperature circulating water system, and arranging a constant speed gear pump on the reflux pipeline.

6. The control method according to claim 3, characterized in that: The polymerization liquid is an acrylonitrile-based polymerization liquid; the pressure-viscosity relationship is: y=-0.045x 2 +13.78x-106.8 Wherein, y is the viscosity measured by the falling ball method, the unit is P; x is the pressure, the unit is KPa.

7. The control method according to claim 6, characterized in that: The constant temperature is 40-50° C.; and / or the constant flow rate is 1-2 L / h.

8. The control method according to claim 3, characterized in that: The position for leading the materials out of the polymerization device is set at 10 to 20 cm below the lower end of the stirring device in the polymerization device.

9. The control method according to claim 1, characterized in that: The viscosity threshold includes a viscosity threshold for adding residual initiator and a viscosity threshold for terminating the reaction; and / or, The material temperature includes the polymerization temperature, the target temperature to which the material is heated before adding the remaining initiator.

10. A method for preparing a carbon fiber spinning solution, characterized in that: include: Adding materials including acrylonitrile, comonomers and solvents into a polymerization device, and regulating the molecular weight of the acrylonitrile-based polymer solution according to the regulation method according to any one of claims 1 to 9; Performing a single-removal treatment on acrylonitrile-based polymer solution meeting the target molecular weight; The acrylonitrile-based polymer solution after the monomer removal treatment is subjected to an ammoniation treatment.

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