A continuous demonotropic, devolatitizing, and defoaming device and process for polyacrylonitrile stock solution

Abstract

This invention provides a continuous demonomerization, devolatilization, and defoaming device and process for polyacrylonitrile (PA) stock solution. The device includes a feeding system, a screw extruder, a vacuum system, and a discharge system. The feeding system achieves main control of the weight loss flow rate and pipeline flow rate verification through a polymer stock buffer tank, a weighing sensor, a discharge regulating valve, and a pipeline flow meter. The screw extruder is equipped with a gradient reverse kneading block, and the vacuum port is located in the rear half of the reverse kneading block and inclined upstream towards the material flow direction. The inner wall of the devolatilization cylinder module is equipped with a diamond-shaped micro-groove array. This device can improve the stability of continuous removal of residual monomers, volatile components, and microbubbles, and reduce the risks of suction carryover, blockage, wall flow, and gumming.

Description

Technical Field

[0001] This invention belongs to the technical field of polymer material post-processing and chemical devolatilization equipment, specifically relating to a continuous demonotropic, devaporized, and defoamed device and process for polyacrylonitrile stock solution. Background Technology

[0002] Polyacrylonitrile-based carbon fiber precursor is typically produced from acrylonitrile monomers through solution polymerization, solution purification, spinning, and post-treatment. After the polymerization reaction, the polyacrylonitrile solution may still contain unreacted acrylonitrile monomers, volatile solvent components, and microbubbles entrained or formed during transport, stirring, and filtration. If these residual monomers, volatile components, and microbubbles are not effectively controlled before spinning, they can easily affect the uniformity and stability of the spinning solution and the continuity of the subsequent spinning process.

[0003] In existing post-treatment processes for polyacrylonitrile spinning solutions, common methods for monomer removal, devolatile matter removal, or defoaming include static vacuum defoaming, monomer removal kettles, umbrella-type or scraped-film monomer removal equipment, packed towers, plate towers, and dynamic monomer removal and defoaming devices. For example, patent document CN101856570B discloses a dynamic monomer removal and defoaming method and apparatus for carbon fiber spinning solutions, which achieves continuous dynamic monomer removal and defoaming through structures such as a monomer removal tower, a defoaming kettle, and an ultrasonic generator. Another example is patent document CN105037619A, which discloses a monomer removal method for polyacrylonitrile spinning solutions, primarily using solvent vapor in a packed tower to exchange gases with the polyacrylonitrile spinning solution to carry away residual volatile monomers. The above solutions can achieve desizing or defoaming of polyacrylonitrile spinning solution to a certain extent, but their equipment forms mostly rely on tower, kettle or packing gas-liquid contact structures. When processing high-viscosity polyacrylonitrile raw solution, there may still be engineering adaptation issues such as material distribution uniformity, film formation stability, wall flow, material hanging, cleaning and maintenance, and connection with previous and subsequent continuous processes.

[0004] Furthermore, in the field of polyacrylonitrile-based carbon fiber precursor preparation, there are already published literatures detailing the process of obtaining spinning dope through demonstration, degassing, and filtration after polymerization. For example, patent document CN103614800A discloses a technical route for obtaining spinning dope through filtration, demonstration, and degassing after polymerization under nitrogen protection, followed by dry-jet wet spinning. This type of disclosure indicates that demonstration and degassing are common treatment steps for polyacrylonitrile dope before it enters the spinning process. However, for high-viscosity polyacrylonitrile dope, simply setting up demonstration, degassing, or conventional vacuum devolatilization equipment is insufficient to solve the problem of fluctuating demonstration, devolatilization, and degassing effects caused by feed fluctuations, uneven liquid film thickness, material carryover during vacuum port suction, vacuum port blockage, wall flow inside the cylinder, and localized stagnation and gelation during continuous operation.

[0005] When using screw compressors for polymer devolatilization, the material typically needs to form an interface through the shearing, mixing, and conveying action of the screw, allowing volatile components to escape. The volatile components and bubbles are then extracted through a vacuum port. For ordinary low- or medium-viscosity polymers, conventional screw devolatilization equipment can achieve a certain devolatilization effect by setting up exhaust ports or vacuum ports. However, polyacrylonitrile (PAC) solutions are characterized by high viscosity, sensitivity to residence time and shear conditions, and a tendency to exhibit localized wall adhesion and gelation. If the feed flow rate fluctuates significantly, the material filling state and liquid film thickness within the screw will change, easily leading to unstable renewal of the devolatilization interface. If the vacuum port position and direction are not properly matched with the material film-forming area, material splashing, material carryover during vacuum suction, or blockage of the vacuum channel may occur. If the inner wall of the cylinder does not adequately spread and renew the high-viscosity PAC, wall flow, localized stagnation, or gelation may also occur, affecting the stability of continuous operation.

[0006] Therefore, for the continuous removal of monomers, volatile components, and microbubbles from high-viscosity polyacrylonitrile raw materials, it is necessary to propose a device and process that can achieve synergistic cooperation between closed and stable feeding, gradient film formation in the screw, fixed-point oblique vacuuming, and stable renewal of the liquid film on the inner wall of the cylinder, so as to improve the removal stability of residual monomers, volatile components, and microbubbles, and reduce the adverse effects of vacuum port extraction, blockage, wall flow, and gelation on continuous operation. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a continuous demonotropic, devolatilization, and defoaming device and process for polyacrylonitrile (PAC) stock solution, in order to solve the problems in existing PAC stock solution demonotropic, devolatilization, and defoaming treatments, such as the inability of batch, tower, or conventional screw devolatilization equipment to simultaneously meet the requirements of continuous and stable feeding, uniform film formation, and deep removal of high-viscosity stock solution; fluctuations in feed flow rate can easily lead to unstable material filling state and liquid film thickness in the screw; lack of targeted matching between conventional vacuum port and reverse kneading block film formation area can easily lead to suction carrying, material splashing, or vacuum port blockage; insufficient spreading and renewal effect of the inner wall of the cylinder on high-viscosity stock solution can easily lead to wall flow, local retention, or gelation; and the difficulty in continuously, stably, and synergistically removing residual monomers, volatile components, and microbubbles within a short residence time.

[0008] This invention does not simply involve feeding polyacrylonitrile (PA) stock into a screw extruder and then subjecting it to vacuum treatment. Instead, it addresses the interactions between high-viscosity PA stock during continuous conveying, screw shearing film formation, vacuum extraction, and the renewal of the liquid film on the inner wall of the extruder. It combines a dual-checked stable feeding structure based on loss-in-weight metering and pipeline flow rate, a segmented film-forming structure with gradient reverse kneading blocks, a vacuum extraction structure located in the latter half of the reverse kneading block and tilted upstream in the material flow direction, and a rhomboid micro-groove array structure to assist in liquid film adhesion and shearing renewal. Through the coordination of these structures, the stock flow rate entering the screw extruder, the liquid film formation state in the devolatilization section, the vacuum extraction position, and the liquid film renewal state on the inner wall of the extruder are mutually adapted, thereby improving the stability of the continuous demonotropic, devolatilization, and defoaming processes of the PA stock.

[0009] To achieve the above objectives, the technical solution of the present invention is implemented as follows: A continuous degassing, de-volatile, and defoaming device for polyacrylonitrile (PA) stock solution includes a feeding system, a screw extruder, a vacuum system, and a discharge system. The feeding system includes a polymerization liquid buffer tank, a weighing sensor, a nitrogen pressure delivery pipeline, a discharge regulating valve, a pipeline flow meter, and a control unit. The discharge port of the polymerization liquid buffer tank is connected to the feed port of the screw extruder through the discharge regulating valve and the pipeline flow meter. The weighing sensor is installed in the polymerization liquid buffer tank. The weighing sensor, the discharge regulating valve, and the pipeline flow meter are respectively connected to the control unit.

[0010] In the aforementioned feeding system, the polymerization liquid buffer tank receives the polyacrylonitrile raw material output from the upstream polymerization section and buffers fluctuations in the discharge pressure and instantaneous flow rate of the upstream polymerization reactor. The nitrogen pressure delivery pipeline continuously conveys the polyacrylonitrile raw material to the screw extruder under a closed, inert atmosphere, reducing the possibility of air entering the raw material system and generating new bubbles. A load cell detects the weight loss flow rate by monitoring changes in the weight of the polymerization liquid buffer tank, while a pipeline flow meter detects the flow rate entering the screw extruder. The control unit uses the weight loss flow rate as the primary control signal and the pipeline flow rate as a calibration signal to adjust the opening of the discharge regulating valve, thereby reducing measurement errors caused by zero-point drift, temperature drift, or pipe wall adhesion in a single metering method.

[0011] By employing the aforementioned dual-check stable feeding method, the material filling state in each devolatilization section of the screw extruder can be made more stable, reducing fluctuations in liquid film thickness, vacuum port splashing, material carryover during suction, and fluctuations in residual sheet removal caused by inconsistent feed amounts. This feeding system works in conjunction with the subsequent reverse kneading block film-forming structure and the fixed-point suction structure at the vacuum port, rather than existing as a separate conventional feeding accessory.

[0012] The screw extruder includes a modular barrel and a co-rotating twin screw disposed within the modular barrel. The modular barrel has multiple devouring barrel modules along the material flow direction. The co-rotating twin screw has multiple reverse kneading blocks within the devouring barrel modules. The multiple reverse kneading blocks form at least two gradient sections along the material flow direction. At least one of the staggered angle, number of pieces, and effective length of the reverse kneading blocks in different gradient sections is different.

[0013] In the above structure, the reverse kneading blocks are used to locally impede, shear, stretch, and renew the high-viscosity polyacrylonitrile stock solution within the corresponding devolatilization cylinder module, transforming the material from a relatively concentrated conveying state to a liquid film state suitable for the escape of volatile components and microbubbles. Multiple reverse kneading blocks form gradient sections along the material flow direction, which can be zoned and matched according to the gradual decrease in residual monomer and bubble content in the polyacrylonitrile stock solution, to the shear intensity, residence state, and liquid film renewal capacity of different devolatilization stages. This avoids the situation where each devolatilization stage uses the same reverse kneading structure, resulting in insufficient removal in the front stage, excessive shearing in the rear stage, or unstable liquid film renewal.

[0014] The vacuum system includes multiple vacuum ports, multiple vacuum branch pipes, and a vacuum distribution pipe. The multiple vacuum ports are respectively located in the devolatilization cylinder module where the corresponding reverse kneading block is located, and each vacuum port is connected to the vacuum distribution pipe through a corresponding vacuum branch pipe.

[0015] The vacuum port is located in the rear half of the region corresponding to the axial length of the reverse kneading block, and the central axis of the vacuum port is inclined to the upstream side of the material flow direction in the vertical section along the axis of the co-rotating twin screws. The inner inlet of the vacuum port is an unobstructed opening that is directly connected to the inner cavity of the modular cylinder.

[0016] In the first half of the reverse kneading block, the high-viscosity polyacrylonitrile stock solution mainly undergoes extrusion, accumulation, shearing, and initial spreading. In the second half of the reverse kneading block along its axial length, the material is further stretched and spread into a relatively continuous thin liquid film. Residual monomers, volatile solvent components, and microbubbles on the surface of the liquid film and near the liquid film rupture interface are more likely to escape. Therefore, positioning the vacuum port in the second half of the reverse kneading block helps to match the vacuum suction position with the actual film formation and interface renewal position of the material, thereby improving suction efficiency and reducing ineffective suction.

[0017] The vacuum inlet is angled upstream of the material flow direction, causing the suction direction to deviate from the main splashing and backlash directions of the material under the constraints of screw rotation and cylinder. Light gaseous components and broken bubbles can enter the vacuum system through the vacuum inlet, while high-viscosity polyacrylonitrile stock solution is less likely to directly enter the vacuum branch pipe through the vacuum inlet. Because the inlet inside the cylinder is an unobstructed passage, it avoids material accumulation dead zones behind the baffle plate or at the base of the baffle component, thus reducing material buildup, gelling, and the frequency of cleaning and maintenance.

[0018] At least part of the devolatilization cylinder module has a diamond-shaped micro-groove array on its inner wall.

[0019] The diamond-shaped microgroove array is used to form a shallow surface structure on the inner wall of the devolatilization cylinder module. This increases the adhesion and spreading ability of the high-viscosity polyacrylonitrile (PAC) stock solution on the inner wall of the cylinder, making it easier for the material to form a stable liquid film along the inner wall of the cylinder, rather than forming localized wall flow or large-area slippage. For high-viscosity PAC stock solutions, the diamond-shaped microgroove array is not used to form a deep cavity for material storage. Instead, through shallow grooves, rounded corners, and a flat bottom transition, the groove area is placed within the shear influence area formed by the periodic sweep of the outer edge of the helical ridge. When the outer edge of the helical ridge periodically sweeps across the groove opening, the material near the groove opening is subjected to shear disturbance and renewal, maintaining the exchange of liquid films inside and outside the groove, thereby reducing the risk of long-term material retention and localized gelation.

[0020] The diamond-shaped microgroove array works in conjunction with the reverse kneading block and the vacuum port: the reverse kneading block shears, stretches, and spreads the high-viscosity raw liquid into a liquid film; the diamond-shaped microgroove array improves the adhesion and uniformity of the liquid film on the inner wall of the cylinder; the vacuum port extracts volatile components and air bubbles at the point where the liquid film is fully spread in the latter half of the reverse kneading block. This reduces the volatility instability caused by discontinuous liquid film, localized wall flow, or material splashing.

[0021] The control unit uses the weight loss flow rate of the polymer buffer tank obtained by the weighing sensor as the main control signal, and uses the pipeline flow rate obtained by the pipeline flow meter as the verification signal to control the opening of the discharge regulating valve; the discharge system is connected to the discharge port of the screw extruder.

[0022] In one optional embodiment, the modular cylinder includes a first cylinder module to an eleventh cylinder module numbered sequentially along the material flow direction, wherein the first cylinder module is a feeding cylinder module, the second cylinder module is a preheating cylinder module, the third to ninth cylinder modules are respectively the first to seventh devolatilization cylinder modules, the tenth cylinder module is a homogenization cylinder module, the eleventh cylinder module is a discharge cylinder module, and multiple vacuum ports are respectively provided in the third to ninth cylinder modules.

[0023] The first cylindrical module receives the polyacrylonitrile stock solution from the feeding system and completes the initial conveying. The second cylindrical module preheats and adjusts the viscosity of the material, giving it flowability suitable for shear film formation and vacuum devolatilization before it enters the subsequent devolatilization modules. Cylindrical modules 3 through 9 serve as continuous devolatilization zones, used to form liquid films in stages and extract volatile components and bubbles. The 10th cylindrical module homogenizes the stock solution after demonotropic, devolatilization, and defoaming processes. The 11th cylindrical module stabilizes the discharge. This segmented arrangement allows for seamless integration of material conveying, preheating, devolatilization, homogenization, and discharge processes, reducing the difficulty of controlling temperature, pressure, and devolatilization status within a single long cylindrical module.

[0024] In one embodiment of the invention that optimizes the present invention, the plurality of reverse kneading blocks include a high-residue zone reverse kneading block, a medium-residue zone reverse kneading block, and a trace-effect zone reverse kneading block arranged sequentially along the material flow direction. The staggered angle of the high-residue zone reverse kneading block is greater than that of the medium-residue zone reverse kneading block, and the staggered angle of the medium-residue zone reverse kneading block is greater than that of the trace-effect zone reverse kneading block. The number of high-residue zone reverse kneading blocks is less than or equal to the number of medium-residue zone reverse kneading blocks, and the number of medium-residue zone reverse kneading blocks is less than or equal to the number of trace-effect zone reverse kneading blocks. The effective length of the high-residue zone reverse kneading block is greater than or equal to the effective length of the medium-residue zone reverse kneading block, and the effective length of the medium-residue zone reverse kneading block is greater than or equal to the effective length of the trace-effect zone reverse kneading block.

[0025] In the high residual monomer zone, where the content of residual monomers and bubbles in the material is relatively high, using reverse kneading blocks with larger stagger angles and longer effective lengths is beneficial for enhancing local hindrance, shearing, and interface renewal, allowing volatile components to escape more fully from the interface. In the medium residual monomer zone, where the content of residual monomers in the material decreases, a medium stagger angle and number of flakes configuration is used to maintain film renewal while reducing unnecessary shearing. In the trace zone, where the content of residual monomers and microbubbles is further reduced, using reverse kneading blocks with relatively smaller stagger angles, a larger number of flakes, and shorter effective lengths is beneficial for maintaining continuous renewal of the thin liquid film and reducing the impact of excessive shearing on the polyacrylonitrile molecular chains and the viscosity stability of the original solution.

[0026] Furthermore, the plurality of devolatilization cylinder modules include a first devolatilization cylinder module to a seventh devolatilization cylinder module arranged sequentially along the material flow direction. The high residual single-zone reverse kneading block is disposed within the first devolatilization cylinder module and the second devolatilization cylinder module, the medium residual single-zone reverse kneading block is disposed within the third devolatilization cylinder module to the fifth devolatilization cylinder module, and the trace zone reverse kneading block is disposed within the sixth devolatilization cylinder module and the seventh devolatilization cylinder module.

[0027] In one alternative embodiment, the center point of the vacuum port is located between 1 / 2 and 3 / 4 of the axial length of the corresponding reverse kneading block; the axial opening range of the vacuum port along the material flow direction at least covers the area between 1 / 2 and the end position of the corresponding reverse kneading block.

[0028] The center point of the vacuum port is positioned between 1 / 2 and 3 / 4 of the axial length of the corresponding reverse kneading block. This ensures the vacuum port avoids the high-pressure accumulation area when the material first enters the reverse kneading block and corresponds to the liquid film formation area after the material has been sheared, stretched, and spread. The axial opening range of the vacuum port covers the rear half of the reverse kneading block, which helps to expand the effective pumping range while avoiding excessively forward pumping of highly viscous material that has not yet formed a sufficient film.

[0029] In one embodiment of the invention that can be optimized, the central axis of the vacuum port is inclined upstream of the material flow direction relative to the radial direction of the top of the modular cylinder in a vertical section along the axis of the co-rotating twin screws, and forms an angle of 30° to 60° with the top radial line of the modular cylinder at the vacuum port.

[0030] The aforementioned angular relationships define the spatial orientation of the vacuum port relative to the material flow direction within the axial vertical cross-section. When the vacuum port is tilted upstream of the material flow direction, the vacuum suction direction forms a reverse component relative to the material's forward direction driven by the screw. This reduces the likelihood of high-viscosity raw liquid being carried into the vacuum channel in the forward direction, while simultaneously allowing the volatilized gaseous components to enter the vacuum system under the influence of pressure difference. An angle of 30° to 60° is a suitable range that balances pumping throughput, processing feasibility, and anti-slip material effect.

[0031] Furthermore, the vacuum port does not have a baffle plate at the inner inlet of the cylinder, the inner wall of the vacuum port is a smooth inner wall, and the transition between the vacuum port and the inner cavity of the modular cylinder adopts a rounded transition with a radius of R5mm to R10mm.

[0032] The absence of a baffle plate at the vacuum port prevents material stagnation at the base of the baffle plate. Smooth inner walls and rounded corners reduce gas flow resistance and decrease the likelihood of polyacrylonitrile solution adhering, accumulating, and gelling at sharp corners or steps. This structure is particularly suitable for devolatilization environments with high viscosity and easy wall adhesion of polyacrylonitrile solution.

[0033] In one alternative embodiment, the rhomboid microgroove array is disposed on the inner wall of the third to ninth cylindrical modules.

[0034] The third to ninth cylinder modules are the main vacuum devolatilization cylinder modules. The diamond-shaped microgroove array is set on the inner wall of this area, so that the microgroove structure corresponds to the vacuum devolatilization area and the reverse kneading block film-forming area, thereby improving the liquid film spreading and renewal ability at the actual location of devaporization and debubbling.

[0035] Furthermore, the rhomboid microgrooves in the rhomboid microgroove array have a rhomboid side length of 0.4mm to 0.6mm, an interior angle of 90° to 120°, a groove depth of 0.2mm to 0.4mm, and a spacing of 1.0mm to 2.0mm between adjacent rhomboid vertices. The interior corner radius of the rhomboid microgroove is R0.2mm to R0.3mm, and the edge corner radius is R0.1mm to R0.2mm. The bottom of the rhomboid microgroove is a flat bottom, and the flat bottom and the sidewall of the groove are transitioned by a rounded corner.

[0036] The aforementioned parameters for the rhomboid microgrooves ensure that the grooves maintain a shallow surface structure, preventing material accumulation in deep cavities. The rhomboid side length, spacing, and inner angles create continuously distributed liquid film adhesion points on the inner wall of the cylinder; the groove depth limits the renewal rate of material after entering the groove; and the rounded inner corners, rounded edges, and flat groove bottom reduce material stagnation at sharp corners and local dead zones. Through this structure, the microgrooves improve liquid film adhesion and spreading capabilities while reducing the risk of adhesive buildup caused by the groove structure itself.

[0037] Preferably, the center point of the vacuum port is located at 2 / 3 of the axial length of the corresponding reverse kneading block.

[0038] Preferably, the central axis of the vacuum port forms a 45° angle with the top radial line of the modular cylinder at the vacuum port.

[0039] Furthermore, the inner diameter of the vacuum port is 0.5 to 0.8 times the screw diameter of the co-rotating twin screws.

[0040] Preferably, the inner diameter of the vacuum port is 0.6 to 0.7 times the screw diameter of the co-rotating twin screws.

[0041] The inner diameter of the vacuum port is matched with the screw diameter of the co-rotating twin screw, so that the vacuum port can provide sufficient pumping cross-sectional area without weakening the local structural strength of the cylinder or increasing the risk of material being sucked up due to excessively large opening.

[0042] In one optional embodiment, the high residual single-zone reverse kneading block is a reverse kneading block with a staggered angle of 35° to 40°, 4 to 6 pieces, and an effective length of 1.8D to 2.2D; the medium residual single-zone reverse kneading block is a reverse kneading block with a staggered angle of 28° to 34°, 6 to 8 pieces, and an effective length of 1.6D to 2.0D; the trace area reverse kneading block is a reverse kneading block with a staggered angle of 20° to 27°, 8 to 10 pieces, and an effective length of 1.3D to 1.7D; wherein, D is the screw diameter of the co-rotating twin screw.

[0043] Preferably, the high-residue single-area reverse kneading block is a KB-R35° / 5 pieces / 2.0D long reverse kneading block, the medium-residue single-area reverse kneading block is a KB-R30° / 7 pieces / 1.8D long reverse kneading block, and the trace area reverse kneading block is a KB-R25° / 9 pieces / 1.5D long reverse kneading block.

[0044] The above-mentioned preferred structure is a specific implementation of a gradient reverse kneading block. In practical applications, the staggered angle, number of flakes, and effective length of each section can be adjusted within the above range according to the viscosity, solid content, initial residual monomer content, and target throughput of the polyacrylonitrile stock solution, as long as it can progressively adapt to the requirements of monomer removal, volatilization, and defoaming along the material flow direction.

[0045] In an embodiment of the invention that can be optimized, the depth of the rhomboid microgroove is less than or equal to the radial gap between the outer edge of the screw ridge of the co-rotating twin screw and the inner wall of the modular cylinder, and the groove of the rhomboid microgroove is located in the shear influence area periodically swept by the outer edge of the screw ridge.

[0046] This structure keeps the rhomboid microgrooves within the area that the outer edge of the screw ridge can periodically influence. When the outer edge of the screw ridge passes through the opening of the rhomboid microgroove, the material near the opening is subjected to periodic shearing, stretching, and renewal. The material within the groove is less likely to remain static for extended periods, thus reducing the possibility of the polyacrylonitrile solution gelling due to localized retention. It should be noted that the shear influence area periodically swept by the outer edge of the screw ridge does not require mechanical contact between the screw ridge and the bottom of the groove, but rather that the movement of the screw ridge can generate shear disturbances sufficient to renew the liquid film on the highly viscous material near the opening and within the shallow groove.

[0047] Furthermore, one diagonal direction of the rhomboid microgroove is arranged along the axial direction of the modular cylinder.

[0048] This arrangement allows the rhomboid microgrooves to guide material flow in the axial direction, while the staggered distribution of the rhomboid edges in the circumferential and axial directions promotes the lateral spreading of the liquid film and the renewal of local interfaces.

[0049] In one optional embodiment, the control unit is provided with a flow deviation judgment module. The flow deviation judgment module receives the weight loss flow signal from the weighing sensor and the pipeline flow signal from the pipeline flow meter, and outputs a normal operation signal, a warning signal, a load reduction signal or a shutdown protection signal based on the deviation between the weight loss flow signal and the pipeline flow signal.

[0050] Furthermore, when the deviation between the weightlessness flow signal and the pipeline flow signal is less than or equal to 1%, the control unit outputs a normal operation signal; when the deviation is greater than 1% and less than or equal to 3%, the control unit outputs a warning signal; when the deviation is greater than 3% and less than or equal to 5%, the control unit outputs a load reduction signal; and when the deviation is greater than 5%, the control unit outputs a shutdown protection signal.

[0051] Through the above-mentioned deviation classification processing, continuous production can be maintained when the metering signal fluctuates slightly, timely warnings or load reduction can be provided when the metering deviation increases, and shutdown protection can be triggered when the metering deviation exceeds the safety limit. This avoids abnormal feeding conditions from entering the screw extruder and causing vacuum port material extraction, abnormal discharge pressure, or loss of control over devolatilization.

[0052] In one alternative embodiment, the pipeline flow meter is an electromagnetic flow meter, a Coriolis mass flow meter, a gear-type volumetric flow meter, or an online flow detection device suitable for high-viscosity polymer liquids.

[0053] The aforementioned pipeline flowmeters, serving as calibration devices for weighing loss-in-weight measurements, can be selected in different types based on the conductivity, viscosity, full-pipe condition, and on-site installation conditions of the polyacrylonitrile stock solution. Using electromagnetic flowmeters can improve measurement reliability through full-pipe delivery and periodic calibration; employing Coriolis mass flowmeters or gear-type volumetric flowmeters can further adapt to certain high-viscosity or highly variable conductivity material conditions.

[0054] In one optional embodiment, the nitrogen pressurization pipeline is connected to the nitrogen inlet of the polymer buffer tank, and the nitrogen pressurization pipeline is equipped with a pressure regulating valve and a safety valve.

[0055] Furthermore, the normal operating pressure of the nitrogen pressure delivery pipeline is 0.2MPa to 0.3MPa, the pressure fluctuation range is ±0.02MPa, and the maximum safe pressure is 0.5MPa.

[0056] The pressure regulating valve is used to maintain a stable nitrogen delivery pressure, while the safety valve is used for pressure relief protection in case of abnormal overpressure. By using the pressure regulating valve and the safety valve in combination, the risk of overpressure in the buffer tank can be reduced while maintaining continuous delivery of polyacrylonitrile solution.

[0057] In one optional embodiment, the polymer buffer tank is a vertical pressure-bearing sealed tank, and the polymer buffer tank is equipped with a jacketed insulation structure and a slow-speed anchor stirrer.

[0058] Furthermore, the volume of the polymerization liquid buffer tank is 10m³ to 20m³, the pressure resistance rating is 0.6MPa, the working liquid level range is 20% to 80%, the insulation temperature of the jacket insulation structure is 60℃ to 65℃, and the rotation speed of the slow anchor stirrer is 5rpm to 10rpm.

[0059] The jacketed insulation structure helps maintain a relatively stable viscosity of the polyacrylonitrile stock solution before it enters the screw extruder, while the slow-speed anchor agitator reduces the possibility of localized stratification or uneven temperature distribution during prolonged storage. The slow agitation method helps avoid excessive shearing of the high-viscosity polyacrylonitrile stock solution.

[0060] In one alternative embodiment, there are four weighing sensors, which are arranged in a four-point support manner on the polymer buffer tank.

[0061] In one optional embodiment, the discharge regulating valve is a pneumatic diaphragm regulating valve, and the valve core of the pneumatic diaphragm regulating valve is an equal percentage characteristic valve core.

[0062] The four-point support method helps improve the stability and balance of the weight detection of the polymer buffer tank; the equal percentage characteristic valve core helps to obtain a more stable flow regulation effect in different opening ranges, adapting to the fine adjustment needs in the continuous pressure feeding process of high viscosity polyacrylonitrile raw material.

[0063] In one optional embodiment, the vacuum system further includes a condenser, a collection tank, a vacuum unit, and an exhaust gas treatment device, wherein the vacuum distribution pipe, the condenser, the collection tank, the vacuum unit, and the exhaust gas treatment device are connected in sequence.

[0064] Furthermore, the vacuum unit includes at least one of a liquid ring vacuum pump, a dry vacuum pump, and a vacuum unit formed by combining a Roots pump and a liquid ring vacuum pump.

[0065] Furthermore, the inlet side of the vacuum unit is equipped with a switching valve and a check valve, and the collection tank is equipped with a liquid level detector and a drain valve.

[0066] The condenser is used to condense the extracted acrylonitrile monomer, solvent vapor, or other condensable volatile components. The collection tank is used to collect the condensate and any entrained trace amounts of liquid. The tail gas treatment device is used for further treatment of the uncondensed gas. Switch valves and check valves reduce the possibility of condensate or gas-liquid mixtures being drawn back into the modular cylinder during shutdown or vacuum fluctuations. Level detectors and drain valves monitor the level and provide drain protection when the liquid level in the collection tank rises.

[0067] In an alternative safety control implementation, the vacuum system, nitrogen pressurization pipeline, or polymer liquid buffer tank may also be equipped with an oxygen content detector, nitrogen purging interface, explosion-proof electrical components, pressure interlocks, vacuum interlocks, or exhaust gas treatment interlocks. The aforementioned safety control structure can be selected and configured according to the management requirements of the production site for the protection of acrylonitrile monomer, solvent vapor, and inert gas, without altering the basic technical concept of this invention regarding stable feeding, gradient film formation, upstream inclined vacuuming, and diamond-shaped microgroove liquid film renewal.

[0068] In one optional embodiment, the discharge system includes a discharge pressure sensor, a discharge gear metering pump, and a raw material filter, wherein the discharge port of the screw extruder, the discharge pressure sensor, the discharge gear metering pump, and the raw material filter are arranged sequentially along the material flow direction.

[0069] Furthermore, the filtration accuracy of the raw liquid filter is 0.5μm to 5μm.

[0070] The discharge pressure sensor monitors the discharge status at the end of the screw extruder, the discharge gear metering pump stably supplies polyacrylonitrile (PAT) dopant to subsequent processes, and the dopant filter removes any residual gel particles or impurities. This discharge system, together with the upstream stable feeding system, forms a continuous dopant processing chain, ensuring that the PAT dopant after demonotropic, devolatile, and defoaming processes can stably enter the subsequent spinning stage.

[0071] In one optional embodiment, the screw diameter of the co-rotating twin screw is 50mm to 120mm, and the length-to-diameter ratio is 44:1 to 56:1.

[0072] Preferably, the screw diameter of the co-rotating twin screw is 80 mm and the length-to-diameter ratio is 52:1.

[0073] In one alternative embodiment, each of the first to eleventh cylinder modules is provided with an independent temperature control unit.

[0074] Independent temperature control units are used to separately adjust the temperatures of the feeding, preheating, devolatilization, homogenization, and discharging zones, ensuring that the polyacrylonitrile stock solution maintains suitable viscosity and volatile component diffusion conditions as it enters different functional stages. The segmented temperature control, combined with the gradient reverse kneading block, can improve the removal efficiency of residual monomers and bubbles while reducing prolonged high-temperature residence time.

[0075] This invention also provides a continuous process for removing monomers, volatilization, and defoaming from polyacrylonitrile (PA) stock solution, using the aforementioned continuous PA, volatilization, and defoaming device. The process includes the following steps: feeding the polymerized PA stock solution into a polymerization buffer tank under nitrogen pressure; obtaining the weight loss flow rate of the polymerization buffer tank using a weighing sensor, obtaining the pipeline flow rate entering the screw extruder using a pipeline flow meter, and adjusting the opening of the discharge regulating valve using the weight loss flow rate as the main control signal and the pipeline flow rate as a verification signal; continuously feeding the PA stock solution into the screw extruder, causing it to be sheared, stretched, and spread into a liquid film under the action of a reverse kneading block; extracting volatile components and bubbles from the PA stock solution through a vacuum port inclined towards the upstream side of the material flow direction in the latter half of the axial length direction corresponding to the reverse kneading block; allowing the PA stock solution to pass through the inner wall of a volatilization cylinder module equipped with a diamond-shaped microgroove array; and outputting the PA stock solution after removal of monomers, volatilization, and defoaming through a discharge system.

[0076] In this process, the weight loss flow control and pipeline flow verification first stabilize the amount of material entering the screw extruder. Then, the polyacrylonitrile dopant is sheared and stretched in the reverse kneading block area to form a liquid film. Volatile components and bubbles are then extracted by a vacuum port located in the latter half of the reverse kneading block and inclined upstream towards the material flow direction. Simultaneously, the diamond-shaped micro-groove array on the inner wall of the devolatilization cylinder module assists in liquid film adhesion and shear renewal. These steps are seamlessly connected, forming a continuous process chain of feed stability, liquid film formation, vacuum extraction, and cylinder inner wall renewal.

[0077] In one optional embodiment, the polyacrylonitrile stock solution has a solid content of 16% to 24%, a viscosity of 20,000 cP to 120,000 cP, and an initial residual monomer content of 0.5% to 2.0%.

[0078] Furthermore, the feed rate of the polyacrylonitrile stock solution is 50 kg / h to 700 kg / h, the rotation speed of the co-rotating twin screw is 20 rpm to 80 rpm, and the total material residence time is 3 min to 8 min.

[0079] In one optional embodiment, the screw extruder includes a feeding section, a preheating section, a devolatilization section, a homogenization section, and a discharge section; the temperature of the feeding section is 40℃~50℃, the temperature of the preheating section is 60℃~70℃, the temperature of the devolatilization section is 63℃~68℃, the temperature of the homogenization section is 60℃~65℃, and the temperature of the discharge section is 55℃~65℃.

[0080] In one optional embodiment, the absolute pressure at the vacuum port is 0.8 kPa to 20 kPa. Preferably, when the vacuum unit is a vacuum unit formed by combining a Roots pump and a liquid ring vacuum pump or a dry vacuum pump, the absolute pressure at the vacuum port is 0.8 kPa to 5 kPa. More preferably, the absolute pressure at the vacuum port is 0.8 kPa to 1.5 kPa.

[0081] In one alternative embodiment, the polyacrylonitrile stock solution forms an adhering liquid film with a thickness of 0.3 mm to 0.8 mm in the latter half of the reverse kneading block region.

[0082] The above process parameters are used to ensure that the polyacrylonitrile stock solution can be continuously transported, sheared into a film, and vacuum devolatilized within a short residence time. When the thickness of the attached liquid film formed in the latter half of the reverse kneading block is controlled within an appropriate range, it helps to shorten the migration path of residual monomers and microbubbles to the liquid film surface, thereby improving the escape efficiency of volatile components.

[0083] In one optional embodiment, the residual monomer content of the polyacrylonitrile stock solution after monomer removal, de-volatile removal, and de-foaming is less than or equal to 0.1%.

[0084] Preferably, the residual monomer content of the polyacrylonitrile stock solution after monomer removal, devolatification, and defoaming is less than or equal to 0.05%.

[0085] More preferably, the residual monomer content of the polyacrylonitrile stock solution after monomer removal, de-volatile removal, and de-foaming is less than or equal to 0.03%.

[0086] In one optional embodiment, the microbubble removal rate of the polyacrylonitrile stock solution after demonotropic and defoaming treatment is greater than or equal to 99.9%.

[0087] Preferably, the microbubble removal rate of the polyacrylonitrile stock solution after demonotropic and defoaming treatment is greater than or equal to 99.97%.

[0088] For different initial residual monomer content, original solution viscosity, and processing volume, the residual monomer content after monomer removal, devolatation, and defoaming can reach less than or equal to 0.1%; under optimal conditions, it can reach less than or equal to 0.05%; and under further optimized conditions, it can reach less than or equal to 0.03%. The above description of the graded effects is used to balance the feasibility under different conditions and the processing effect of the preferred embodiment.

[0089] In one alternative embodiment, the volatile components extracted by the vacuum system are condensed by a condenser and then enter a collection tank, while the uncondensed gas enters a tail gas treatment device.

[0090] In one alternative embodiment, when the discharge pressure of the screw extruder rises abnormally, the feed rate of polyacrylonitrile raw material and the rotational speed of the co-rotating twin screws are reduced; when the discharge pressure continues to rise, feeding is stopped and the machine is shut down.

[0091] In one alternative embodiment, the polymer buffer tank is purged with nitrogen before feeding and is kept in a nitrogen-sealed state during operation.

[0092] In one optional embodiment, the pipeline flow meter is an electromagnetic flow meter, the polyacrylonitrile raw liquid is kept in a full pipe for delivery, and the flow signal of the pipeline flow meter is used as a verification signal for the weight loss flow signal of the weighing sensor.

[0093] In one embodiment of the invention that can be optimized, the openings of the rhombic microgrooves in the rhombic microgroove array are located within the shear influence area periodically swept by the outer edge of the screw ridge of the co-rotating twin screw, and the polyacrylonitrile stock solution is periodically sheared and renewed at the openings of the rhombic microgrooves.

[0094] In one alternative embodiment, the polyacrylonitrile stock solution is directly fed into the spinning section after being output by the discharge system.

[0095] Compared with existing technologies, the continuous demonotropic, devolatilization, and defoaming device and process for polyacrylonitrile (PAC) stock solution described in this invention has at least the following beneficial effects: This invention establishes a stable feeding method combining weight loss flow control and pipeline flow verification through a polymerization liquid buffer tank, weighing sensor, discharge regulating valve, pipeline flow meter, and control unit. It also utilizes a nitrogen pressure delivery pipeline to achieve closed-loop continuous transport of the PAC stock solution, thereby reducing the impact of feed fluctuations on the material filling state and liquid film thickness within the screw. Furthermore, by setting reverse kneading blocks within the devolatilization cylinder module to form gradient sections along the material flow direction, the high residual monomer zone, medium residual monomer zone, and trace monomer zone are adapted to the shearing, stretching, and interface renewal requirements at different stages, which is beneficial for high viscosity... The polyacrylonitrile (PA) stock solution forms a liquid film suitable for the escape of volatile components and microbubbles. By setting the vacuum port in the rear half of the axial length of the corresponding reverse kneading block and tilting it upstream of the material flow direction, the vacuum suction position is matched with the liquid film formation area, reducing the risk of material splashing, suction carrying, and vacuum port blockage. By setting a diamond-shaped microgroove array on at least part of the inner wall of the devolatilization cylinder module, the adhesion, spreading, and shear renewal of the high-viscosity PA filtrate stock solution on the inner wall of the cylinder are promoted, reducing the possibility of wall flow, local retention, and gelation. At the same time, the vacuum system can condense, capture, and treat the extracted volatile components, and the discharge system can stably output the stock solution after devolatilization and degassing. Therefore, this invention can form a continuous processing link that combines stable feeding, gradient film formation, fixed-point upstream inclined vacuuming, inner wall liquid film renewal, and stable discharge, thereby improving the synergistic removal stability of residual monomers, volatile components, and microbubbles in polyacrylonitrile raw materials, and reducing the impact of feeding fluctuations, vacuum port blockage, wall flow gelling, and discharge fluctuations on the continuity of subsequent spinning. Attached Figure Description

[0096] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a schematic diagram of the overall process structure of a continuous polyacrylonitrile feedstock demonotropic, devolatile, and defoaming device according to an embodiment of the present invention. Figure 2 This is an axial cross-sectional view of the positional relationship between the vacuum port and the rear half of the reverse kneading block in one embodiment of the present invention. Figure 3 This is a schematic diagram showing the fit between the vacuum port and the co-rotating twin screws in the cross-section of the cylinder in one embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a co-rotating twin screw and a reverse kneading block in one embodiment of the present invention; Figure 5 This is a schematic diagram of the modular cylindrical end face structure in one embodiment of the present invention; Figure 6 for Figure 5 A magnified schematic diagram of the partial structure of the rhomboid micro-groove at point A; Figure 7 This is a schematic diagram of the axial engagement structure of the vacuum port, vacuum chamber, reverse kneading block and co-rotating twin screws in the devolatilization cylinder module in one embodiment of the present invention.

[0097] Explanation of reference numerals in the attached figures: 1. Polymerization reactor; 2. Polymerization liquid buffer tank; 3. Weighing sensor; 4. Discharge regulating valve; 5. Pipeline flow meter; 6. Screw extruder drive motor; 7. Screw extruder; 8. Vacuum distribution pipe; 9. Hand valve; 10. Vacuum sensor; 11. Vacuum unit; 12. Discharge pressure sensor; 13. Discharge gear metering pump; 14. Raw material filter; 15. Vacuum branch pipe; 16. Tail gas treatment device; 17. Condenser; 18. Collection tank; 61. Modular cylinder; 62. Vacuum chamber; 63. Vacuum port; 64. Co-rotating twin screws; 65. Reverse kneading block. Detailed Implementation

[0098] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0099] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0100] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0101] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0102] like Figures 1 to 7 As shown, this embodiment provides a continuous polyacrylonitrile (PA) stock solution demonotropic, devolatile, and defoaming device and process for continuously removing residual acrylonitrile monomers, solvent volatiles, and microbubbles from high-viscosity PA stock solutions after polymerization. The device includes a feeding system, a screw extruder 7, a vacuum system, and a discharge system. The polymerized PA stock solution is fed from the polymerization reactor 1 into the polymerization liquid buffer tank 2, and after stable metering by the feeding system, it enters the screw extruder 7. Inside the screw extruder 7, it sequentially undergoes preheating, shearing film formation, vacuum extraction, inner wall liquid film renewal, and homogenization before being discharged through the discharge system to the subsequent spinning stage. Example 1: Device structure example.

[0103] In this embodiment, the feeding system includes a polymerization liquid buffer tank 2, a weighing sensor 3, a nitrogen pressure delivery pipeline, a discharge regulating valve 4, a pipeline flow meter 5, and a control unit. The polymerization liquid buffer tank 2 is a vertical, pressure-bearing, sealed tank. Its inlet is connected to the upstream polymerization reactor 1, and its outlet is connected to the feed inlet of the screw extruder 7 through the discharge regulating valve 4 and the pipeline flow meter 5. The nitrogen pressure delivery pipeline is connected to the nitrogen inlet of the polymerization liquid buffer tank 2 and is used to stably pressurize the polyacrylonitrile raw material to the screw extruder 7 under nitrogen sealing conditions, thereby reducing the entry of air into the raw material system and reducing the possibility of secondary entrainment of air bubbles.

[0104] Weighing sensors 3 are installed on the support portion of the polymerization liquid buffer tank 2. In this embodiment, four weighing sensors 3 are installed in a four-point support configuration on the polymerization liquid buffer tank 2 to detect the weight change of the polymerization liquid buffer tank 2 in real time. The control unit reads the weight signal from the weighing sensors 3 according to a preset sampling period and calculates the weight loss flow rate of the polymerization liquid buffer tank 2 based on the weight decrease per unit time. A pipeline flow meter 5 is installed on the conveying pipeline downstream of the discharge regulating valve 4 to detect the pipeline flow rate entering the screw extruder 7. The control unit uses the weight loss flow rate as the main control signal and the pipeline flow rate as the verification signal, and controls the opening degree of the discharge regulating valve 4 according to the difference between the weight loss flow rate and the target feed flow rate; when the weight loss flow rate is greater than the target feed flow rate, the control unit controls the discharge regulating valve 4 to close slightly; when the weight loss flow rate is less than the target feed flow rate, the control unit controls the discharge regulating valve 4 to open wider.

[0105] To achieve the control method described in the claims, which uses "weight loss flow rate as the main control signal and pipeline flow rate as the verification signal," the control unit in this embodiment is equipped with a flow deviation judgment module. The flow deviation judgment module receives the weight loss flow rate signal from the weighing sensor 3 and the pipeline flow rate signal from the pipeline flow meter 5, and calculates the relative deviation between them. When the deviation is less than or equal to 1%, the control unit maintains normal operation; when the deviation is greater than 1% but less than or equal to 3%, the control unit outputs a warning signal and can correct the flow conversion coefficient; when the deviation is greater than 3% but less than or equal to 5%, the control unit outputs a load reduction signal and reduces the feed rate to 50%–80% of the rated feed rate; when the deviation is greater than 5%, the control unit outputs a shutdown protection signal, causing the feeding system and screw extruder 7 to enter a safe shutdown state. Through the above control method, the impact of single metering element drift, pipe wall adhesion, or abnormal full-pipe conditions on feed stability can be reduced.

[0106] In this embodiment, the nitrogen pressurization pipeline is equipped with a pressure regulating valve and a safety valve. The normal operating pressure is 0.2MPa~0.3MPa, the allowable pressure fluctuation range is ±0.02MPa, and the maximum safe pressure is 0.5MPa. The nitrogen purity is preferably not less than 99.95%. The polymerization liquid buffer tank 2 has a volume of 10m³~20m³, a pressure resistance rating of 0.6MPa, and a working liquid level range of 20%~80%. The polymerization liquid buffer tank 2 can also be equipped with a jacketed insulation structure and a slow-speed anchor agitator. The jacket insulation temperature is 60℃~65℃, and the speed of the slow-speed anchor agitator is 5rpm~10rpm to maintain the temperature uniformity and viscosity stability of the polyacrylonitrile stock solution before entering the screw extruder 7. The discharge regulating valve 4 can be a pneumatic diaphragm regulating valve with an equal percentage characteristic valve core. The diameter can be selected from DN50 to DN100 according to the production capacity, and the adjustment response cycle is preferably not greater than 1s.

[0107] The pipeline flow meter 5 can be an electromagnetic flow meter, a Coriolis mass flow meter, a gear volumetric flow meter, or other online flow detection devices suitable for high-viscosity polymer liquids. When using an electromagnetic flow meter, the polyacrylonitrile raw liquid is kept in a full pipe for transport, and the flow signal of the electromagnetic flow meter is used as a calibration signal for weighing loss-in-weight measurement. When the conductivity, viscosity, or on-site installation conditions of the raw liquid are not suitable for electromagnetic flow meters, a Coriolis mass flow meter or a gear volumetric flow meter can be used for online calibration.

[0108] In this embodiment, the screw extruder 7 includes a screw extruder drive motor 6, a modular barrel 61, and a co-rotating twin screw 64 disposed within the modular barrel 61. The co-rotating twin screw 64 is driven to rotate by the screw extruder drive motor 6. The modular barrel 61 includes barrel modules numbered sequentially along the material flow direction, namely, barrel module 1 is the feeding barrel module, barrel module 2 is the preheating barrel module, barrel modules 3 to 9 are respectively the first to seventh devolatilization barrel modules, barrel module 10 is the homogenization barrel module, and barrel module 11 is the discharge barrel module. Each of the barrel modules 1 to 11 is equipped with an independent temperature control unit to perform segmented temperature control of the feeding, preheating, devolatilization, homogenization, and discharge areas.

[0109] In one specific structure, the screw diameter of the co-rotating twin-screw 64 is 50mm to 120mm, and the length-to-diameter ratio is 44:1 to 56:1. As a preferred embodiment, the screw diameter of the co-rotating twin-screw 64 is 80mm, and the length-to-diameter ratio is 52:1. The feed cylinder module receives the polyacrylonitrile stock solution from the polymerization liquid buffer tank 2 and completes the initial conveying; the preheating cylinder module is used to bring the stock solution to a viscosity suitable for shear film formation and vacuum devolatilization; the first to seventh devolatilization cylinder modules are used for segmented shear film formation and vacuum extraction; the homogenization cylinder module is used to mix and homogenize the stock solution after demonotropic, devolatilization, and defoaming; and the discharge cylinder module is used to stably output the stock solution.

[0110] The co-rotating twin-screw extruder 64 has multiple reverse kneading blocks within the third to ninth cylinder modules. These cylinder modules correspond to the first to seventh devolatilization cylinder modules arranged sequentially along the material flow direction. The multiple reverse kneading blocks form three gradient zones along the material flow direction: a high residual volume zone, a medium residual volume zone, and a trace volume zone. Specifically, the high residual volume zone reverse kneading blocks are located within the first and second devolatilization cylinder modules; the medium residual volume zone reverse kneading blocks are located within the third to fifth devolatilization cylinder modules; and the trace volume zone reverse kneading blocks are located within the sixth and seventh devolatilization cylinder modules. The misalignment angle of the high-residue single-area reverse kneading block is greater than that of the medium-residue single-area reverse kneading block, and the misalignment angle of the medium-residue single-area reverse kneading block is greater than that of the trace-area reverse kneading block; the number of high-residue single-area reverse kneading blocks is less than or equal to the number of medium-residue single-area reverse kneading blocks, and the number of medium-residue single-area reverse kneading blocks is less than or equal to the number of trace-area reverse kneading blocks; the effective length of the high-residue single-area reverse kneading block is greater than or equal to the effective length of the medium-residue single-area reverse kneading block, and the effective length of the medium-residue single-area reverse kneading block is greater than or equal to the effective length of the trace-area reverse kneading block.

[0111] In one specific embodiment, the high-residue single-zone reverse kneading block is a reverse kneading block with a staggered angle of 35° to 40°, 4 to 6 pieces, and an effective length of 1.8D to 2.2D; the medium-residue single-zone reverse kneading block is a reverse kneading block with a staggered angle of 28° to 34°, 6 to 8 pieces, and an effective length of 1.6D to 2.0D; and the trace-area reverse kneading block is a reverse kneading block with a staggered angle of 20° to 27°, 8 to 10 pieces, and an effective length of 1.3D to 1.7D, where D is the screw diameter of the co-rotating twin screw 64. As a preferred embodiment, the high-residue single-zone reverse kneading block is a KB-R35° / 5 pieces / 2.0D length reverse kneading block, the medium-residue single-zone reverse kneading block is a KB-R30° / 7 pieces / 1.8D length reverse kneading block, and the trace-area reverse kneading block is a KB-R25° / 9 pieces / 1.5D length reverse kneading block. The outer surface of the reverse kneading block can be rounded with R0.2mm to R0.3mm to reduce the risk of local shearing and material adhesion of the high-viscosity polyacrylonitrile stock solution by sharp corners.

[0112] like Figure 7 As shown, the vacuum chamber 62 is located above the modular cylinder 61, the vacuum port 63 is connected to the vacuum chamber 62, the co-rotating twin screws 64 are located inside the modular cylinder 61, and the reverse kneading block 65 is located below the corresponding area of ​​the vacuum port 63, which is used to generate shearing, stretching and interface renewal effects on the polyacrylonitrile stock solution in the devolatilization cylinder module.

[0113] like Figure 2 and Figure 3 As shown, the vacuum system includes multiple vacuum ports 63, multiple vacuum branch pipes 15, and a vacuum distribution pipe 8. The multiple vacuum ports 63 are respectively located in the 3rd to 9th cylinder modules, and are respectively positioned at the locations of the reverse kneading blocks. Each vacuum port 63 is connected to the vacuum distribution pipe 8 via a corresponding vacuum branch pipe 15. The vacuum distribution pipe 8 is connected to the vacuum unit 11 and subsequent vacuum processing equipment via a manual valve 9 and a vacuum sensor 10.

[0114] Each vacuum port 63 is located in the rear half of the axial length of the corresponding reverse kneading block. Specifically, the center point of the vacuum port 63 is located between 1 / 2 and 3 / 4 of the axial length of the corresponding reverse kneading block, preferably at 2 / 3 of the axial length; the axial opening range of the vacuum port 63 along the material flow direction at least covers the area between 1 / 2 and the end of the axial length of the corresponding reverse kneading block. The front half of the reverse kneading block mainly subjectes the polyacrylonitrile stock solution to compression, accumulation, and initial shearing; the rear half of the reverse kneading block further stretches and spreads the polyacrylonitrile stock solution into an adhering liquid film, making it easier for residual monomers, volatile solvent components, and microbubbles to migrate to the surface of the liquid film or near the liquid film rupture interface. Therefore, positioning the vacuum port 63 in the rear half of the reverse kneading block allows the vacuum suction position to match the liquid film formation area.

[0115] The central axis of the vacuum port 63 is inclined upstream of the material flow direction in the vertical section along the axis of the co-rotating twin screws 64, relative to the radial direction of the top of the modular cylinder 61, and forms an angle of 30° to 60° with the top radial line of the modular cylinder 61 at the vacuum port 63; preferably, the angle is 45°. When the vacuum port 63 is inclined upstream of the material flow direction, the vacuum suction direction has an upstream component relative to the material forward direction, allowing volatile components and bubbles to enter the vacuum system under the action of pressure difference, while reducing the possibility of high-viscosity polyacrylonitrile raw liquid being carried into the vacuum channel in the forward direction of material flow. The inner inlet of the vacuum port 63 is an unobstructed opening that directly communicates with the inner cavity of the modular cylinder 61, that is, no baffle is provided at the inner inlet of the vacuum port 63. The inner wall of the vacuum port 63 is a smooth inner wall, and the transition between the vacuum port 63 and the inner cavity of the modular cylinder 61 adopts a rounded transition with a radius of R5mm to R10mm. The inner diameter of the vacuum port 63 can be 0.5 to 0.8 times the diameter of the screw of the co-rotating twin screw 64, preferably 0.6 to 0.7 times. For a structure with an 80mm screw diameter, the vacuum port 63 can be a DN50 specification.

[0116] In this embodiment, the inner walls of the 3rd to 9th cylindrical modules are provided with an array of rhomboid microgrooves. For example... Figure 6 As shown, the rhomboid microgrooves in the rhomboid microgroove array have a rhomboid side length of 0.4mm to 0.6mm, an interior angle of 90° to 120°, a groove depth of 0.2mm to 0.4mm, and a spacing between adjacent rhomboid vertices of 1.0mm to 2.0mm. The interior corner radius of the rhomboid microgrooves is R0.2mm to R0.3mm, and the edge corner radius is R0.1mm to R0.2mm. The bottom of the rhomboid microgrooves is a flat bottom, and a rounded transition is used between the flat bottom and the sidewall to avoid a pointed bottom structure. Preferably, one diagonal direction of the rhomboid microgrooves is arranged along the axial direction of the modular cylinder 61.

[0117] To demonstrate that the rhomboid microgroove array does not form long-term material accumulation dead zones, this embodiment further specifies that the groove opening of the rhomboid microgroove is located within the shear influence area periodically swept by the outer edge of the screw ridge of the co-rotating twin screw 64. When the co-rotating twin screw 64 rotates, the outer edge of the screw ridge periodically passes near the groove opening of the rhomboid microgroove, causing the polyacrylonitrile stock solution near the groove opening and in the shallow groove to undergo periodic shear disturbance and liquid film renewal. It should be noted that the shear influence area does not require mechanical contact between the outer edge of the screw ridge and the bottom of the rhomboid microgroove, but rather that the movement of the outer edge of the screw ridge can generate a shearing effect sufficient to renew the liquid film of the high-viscosity stock solution near the groove opening and in the shallow groove. Through the combination of shallow grooves, rounded corners, flat groove bottoms, and periodic shear renewal, the rhomboid microgroove array can promote the adhesion, spreading, and interface renewal of the polyacrylonitrile stock solution on the inner wall of the cylinder, while reducing the risk of local retention and gelation.

[0118] In this embodiment, the vacuum system also includes a condenser 17, a collection tank 18, a vacuum unit 11, and a tail gas treatment device 16. The vacuum distribution pipe 8, condenser 17, collection tank 18, vacuum unit 11, and tail gas treatment device 16 are connected sequentially. The vacuum unit 11 is preferably a combination of a Roots pump and a liquid ring vacuum pump; in other alternative embodiments, the vacuum unit 11 may also be a liquid ring vacuum pump or a dry vacuum pump. The condenser 17 is used to condense acrylonitrile monomer, solvent vapor, or other condensable volatile components extracted through the vacuum port 63; the collection tank 18 is used to collect condensate and any entrained trace amounts of liquid; the tail gas treatment device 16 is used to treat uncondensed gas. A switch valve and a check valve may be installed on the inlet side of the vacuum unit 11, and a level detector and a drain valve may be installed on the collection tank 18 to reduce the possibility of condensate or gas-liquid mixtures being drawn back into the modular cylinder 61 during shutdown, vacuum fluctuations, or when the liquid level in the collection tank 18 rises.

[0119] In this embodiment, the discharge system includes a discharge pressure sensor 12, a discharge gear metering pump 13, and a raw material filter 14. The discharge port of the screw extruder 7, the discharge pressure sensor 12, the discharge gear metering pump 13, and the raw material filter 14 are arranged sequentially along the material flow direction. The discharge pressure sensor 12 is used to monitor the discharge pressure at the end of the screw extruder 7; the discharge gear metering pump 13 is used to stably deliver the demonotropic, devolatile, and deaerated polyacrylonitrile raw material to subsequent processes; the raw material filter 14 is used to remove any residual gel particles or impurities in the raw material, and its filtration accuracy can be 0.5μm to 5μm, preferably 1μm. After being filtered by the raw material filter 14, the demonotropic, devolatile, and deaerated polyacrylonitrile raw material can directly enter the subsequent spinning stage. Example 2: Preferred process operation example.

[0120] The apparatus described in Example 1 is used for continuous demonotropic, devolatogenic, and defoaming treatment of polyacrylonitrile (PA) stock solution. Before treatment, the polymerization liquid buffer tank 2 and related conveying pipelines are purged with nitrogen to ensure that the polymerization liquid buffer tank 2 is under nitrogen protection and this nitrogen sealing is maintained during operation. The PA stock solution output from the polymerization reactor 1 is temporarily stored in the polymerization liquid buffer tank 2, and then enters the screw extruder 7 under nitrogen pressure conveying and dual-check metering control.

[0121] In this embodiment, the polyacrylonitrile stock solution has a solid content of 20%, a viscosity of 65000 cP, an initial residual monomer content of 1.8%, and a feed rate of 200 kg / h. The co-rotating twin-screw extruder 64 has a screw diameter of 80 mm, a length-to-diameter ratio of 52:1, a screw speed of 40 rpm, and a total material residence time of 5 min. The segmented temperatures of the modular cylinder 61 are as follows: feed section 45℃, preheating section 65℃, first to seventh devolatilization sections 65℃, homogenization section 63℃, and discharge section 60℃. The vacuum degree at each vacuum port 63 is 1.1 kPa absolute pressure.

[0122] During operation, the control unit controls the opening of the discharge regulating valve 4 based on the weight loss flow signal output by the weighing sensor 3, and verifies the flow rate based on the pipeline flow signal output by the pipeline flow meter 5, ensuring that the feed flow rate fluctuation is controlled within ±0.5% to ±1%. Stable feeding maintains a relatively constant material filling state within the screw extruder 7, forming an adhering liquid film with a thickness of 0.3mm to 0.8mm in the latter half of the reverse kneading block region. Residual monomers, solvent volatiles, and microbubbles escape from the surface of the adhering liquid film or near the liquid film rupture interface, and enter the vacuum system through the vacuum port 63, which is inclined upstream in the material flow direction. The volatile components condensed by the condenser 17 enter the collection tank 18, while the uncondensed gas enters the tail gas treatment device 16.

[0123] After the above treatment, the residual polyacrylonitrile content in the raw polyacrylonitrile solution is less than or equal to 0.03%, the solvent loss rate is less than or equal to 2.2%, and the microbubble removal rate is greater than or equal to 99.97%. No obvious blockage of the vacuum port occurred during continuous operation, and the output raw solution can stably enter the subsequent spinning section through the discharge gear metering pump 13 and the raw solution filter 14. Example 3: Applicable examples for different working conditions.

[0124] To illustrate the applicability of the device of the present invention to different polyacrylonitrile raw materials under different operating conditions, based on the device of Example 1, the screw diameter, length-to-diameter ratio, screw speed, residence time, barrel temperature and vacuum degree can be adjusted according to the solid content, viscosity, initial residual monomer content and throughput of the polyacrylonitrile raw material.

[0125] In one optional operating condition, the solid content of the polyacrylonitrile raw solution is 16%–24%, the viscosity is 20,000 cP–120,000 cP, the initial residual monomer content is 0.5%–2.0%, and the feed rate is 50 kg / h–700 kg / h. The screw diameter of the co-rotating twin-screw extruder 64 can be 50 mm–120 mm, the length-to-diameter ratio can be 44:1–56:1, the screw speed can be 20 rpm–80 rpm, and the total material residence time can be 3 min–8 min. The segmented temperatures of the modular cylinder 61 can be set as follows: feed section 40℃–50℃, preheating section 60℃–70℃, devolatilization section 63℃–68℃, homogenization section 60℃–65℃, and discharge section 55℃–65℃. The absolute pressure at each vacuum port 63 can be 0.8 kPa to 20 kPa; when the vacuum unit 11 adopts a vacuum unit formed by combining a Roots pump and a liquid ring vacuum pump or a dry vacuum pump, the absolute pressure at each vacuum port 63 can be 0.8 kPa to 5 kPa, preferably 0.8 kPa to 1.5 kPa.

[0126] Under the aforementioned different operating conditions, the control unit still uses the weight loss flow rate of the polymer buffer tank 2 as the main control signal and the pipeline flow rate obtained by the pipeline flow meter 5 as the verification signal; the co-rotating twin screws 64 still form a liquid film through gradient reverse kneading blocks; the vacuum port 63 is still located in the latter half of the reverse kneading block region and tilted towards the upstream side of the material flow direction; the inner walls of the 3rd to 9th cylinder modules are still provided with a diamond-shaped microgroove array to assist in liquid film adhesion and shear renewal. For operating conditions with different initial residual monomer content, raw liquid viscosity, and processing volume, the residual monomer content of the polyacrylonitrile raw liquid after monomer removal, devolatilization, and defoaming can be less than or equal to 0.1%; under optimal operating conditions, it can be less than or equal to 0.05%; under further optimized operating conditions, it can be less than or equal to 0.03%. The microbubble removal rate of the polyacrylonitrile raw liquid after monomer removal, devolatilization, and defoaming can be greater than or equal to 99.9%, preferably greater than or equal to 99.97%. Example 4: Abnormal operating conditions and safety control examples.

[0127] During continuous operation, the control unit receives detection signals from the vacuum sensor 10, the discharge pressure sensor 12, the weighing sensor 3, and the pipeline flow meter 5 in real time, and can perform corresponding control according to abnormal conditions.

[0128] When the vacuum level abnormally increases or decreases, the control unit can adjust the manual valve 9 or regulating valve on the vacuum pipeline to restore the vacuum level to the set range. When the vacuum level changes significantly and the discharge pressure sensor 12 detects a synchronous abnormality in the discharge pressure, the control unit can determine that there is a risk of material carrying or blockage at the vacuum port 63 and output an alarm signal. When the discharge pressure abnormally increases, the control unit reduces the feed rate of polyacrylonitrile raw material and the rotation speed of the co-rotating twin screw 64. When the discharge pressure continues to rise, the control unit stops feeding and shuts down the machine.

[0129] When the pressure in the polymerization liquid buffer tank 2 exceeds the safety threshold, the safety valve automatically releases pressure and simultaneously closes the nitrogen inlet valve or reduces the nitrogen delivery pressure. When the nitrogen pressure is insufficient, the system outputs an alarm signal and restricts feeding. When the pressure difference in the raw material filter 14 is too large, the control unit outputs an alarm signal, prompting the switch of the filter or shutdown for maintenance. When the liquid level in the collection tank 18 is too high, the liquid level detector outputs an alarm signal and drains the liquid through the drain valve. If the liquid level continues to rise, the vacuum unit 11 is shut down or the vacuum system enters a protection state. To further improve safety, the polymerization liquid buffer tank 2, the vacuum system, or the tail gas treatment device 16 can also be equipped with an oxygen content detector, pressure interlock, vacuum interlock, explosion-proof electrical components, and tail gas treatment interlock. The above safety structures can be selected and configured according to on-site management requirements without changing the basic technical concept of stable feeding, gradient film formation, upstream inclined vacuuming, and diamond-shaped microgroove liquid film renewal of this invention. Example 5: Comparative test case.

[0130] To illustrate that the technical effect of this invention does not originate from conventional twin-screw devolatilization equipment, but rather from the synergistic cooperation between stable feeding, gradient reverse kneading blocks, a vacuum port 63 inclined upstream in the material flow direction, a diamond-shaped micro-groove array, and an unobstructed through-hole structure, this embodiment uses an 80mm co-rotating twin-screw extruder of the same specifications for comparative testing. All tests used the same batch of polyacrylonitrile stock solution, with a solid content of 20%, a viscosity of 65000 cP, an initial residual monomer content of 1.3%, a screw speed of 40 rpm, a devolatilization zone temperature of 65°C, and a feed rate of 200 kg / h. Except for the differences described below, the other structures and process conditions of each comparative example are the same as those of this invention.

[0131] The present invention adopts the structure described in Embodiment 1, that is, a stable feeding method that combines the main control of the weight loss flow of the weighing sensor 3 with the pipeline flow verification of the pipeline flow meter 5. It adopts a gradient reverse kneading block with high residual single zone, medium residual single zone and trace zone. The vacuum port 63 is set in the rear half of the reverse kneading block and is inclined to the upstream side in the direction of material flow. No baffle is set at the inner side inlet of the vacuum port 63. A diamond-shaped micro-groove array is set on the inner wall of the 3rd cylinder module to the 9th cylinder module.

[0132] The difference between Comparative Example 1 and the present invention is that a common vertical vacuum port is used instead of the oblique vacuum port 63 in the present invention, which is inclined to the upstream side in the material flow direction and preferably forms a 45° angle with the radial line of the top of the modular cylinder 61.

[0133] The difference between Comparative Example 2 and the present invention is that the diamond-shaped micro-groove array is not provided, and the inner wall of the cylinder of the third to ninth cylinder modules is a normal smooth inner wall.

[0134] The difference between Comparative Example 3 and the present invention is that it does not use gradient reverse kneading blocks arranged in sections along the material flow direction, but instead uses reverse kneading blocks with the same staggered angle or the same effective length in all devouring sections.

[0135] The difference between Comparative Example 4 and the present invention is that it does not use the dual-verification feeding control method that combines the weight loss measurement of the weighing sensor 3 and the flow verification of the pipeline flow meter 5, but only uses ordinary pumping or single flow control method to feed material to the screw extruder 7.

[0136] The difference between Comparative Example 5 and the present invention is that it adopts a conventional vacuum port structure with a baffle plate, instead of the unobstructed through-hole structure in the present invention where the inner inlet of the vacuum port 63 is directly connected to the inner cavity of the modular cylinder 61.

[0137] Under the same test conditions described above, the present invention and comparative examples 1 to 5 were compared and tested, and the results are shown in Table 1 below.

[0138] Table 1. Comparison test results of the present invention with Comparative Examples 1 to 5. Residual order content (%) 0.05 0.12 0.09 0.11 0.08 0.07 Microbubble removal rate (%) 99.97 99.5 99.8 99.6 99.7 99.9 Solvent loss rate (%) 2.2 5.8 3.5 4.2 2.8 2.4 Vacuum port material carrying amount (%) 0.08 3.5 0.25 0.15 0.3 0.04 Vacuum port blockage cycle (days) No obvious blockage was observed. 5 28 35 25 48 Continuous operation days (days) 50 7 32 38 28 50 Discharge viscosity fluctuation (%) 0.8 3.2 1.5 2.1 2.5 0.9 Spinning breakage rate (times / ton of yarn) 2.1 12.5 4.8 6.3 5.2 2.3 Cleaning and maintenance frequency (times / month) 0.5 4 1 0.8 1.2 0.5 Energy consumption per unit of output (kWh / kg) 0.35 0.52 0.41 0.45 0.38 0.37 The residual content was determined by gas chromatography; the microbubble removal rate was calculated by the change in the number of microbubbles per unit volume of raw solution before and after treatment; the vacuum port material carrying amount was the proportion of the mass of raw solution entrained in the vacuum trapping system per unit time to the mass of feed material in the same period; the solvent loss rate was the proportion of the mass of condensed and trapped solvent per unit time to the mass of solvent in the feed material; the spinning breakage rate was statistically analyzed under the same spinneret, spinning temperature, metering pump speed and drawing conditions.

[0139] Table 1 shows that when a conventional vertical vacuum port is used in Comparative Example 1, the amount of material carried in the vacuum port and the risk of blockage increase significantly, indicating that the upward tilt of the vacuum port 63 towards the material flow direction helps reduce the risk of material carry-in and blockage. In Comparative Example 2, without the diamond-shaped microgroove array, the residual monomer content, microbubble removal rate, continuous operating days, and spinning breakage rate are all inferior to the scheme of this invention, indicating that the diamond-shaped microgroove array is beneficial for promoting the adhesion, spreading, and renewal of the liquid film of high-viscosity polyacrylonitrile stock solution on the inner wall of the cylinder. In Comparative Example 3, without the gradient reverse kneading block, the residual monomer content and spinning breakage rate increase, indicating that the partitioned reverse kneading block along the material flow direction is beneficial for adapting to the shearing, stretching, and liquid film renewal requirements of different devolatilization stages. In Comparative Example 4, without dual verification of loss-in-weight metering and flow meter, the discharge viscosity fluctuation and the risk of material carry-in at the vacuum port increase, indicating that stable feeding plays an important role in maintaining the material filling state and liquid film thickness inside the screw. While the baffle plate in Comparative Example 5 can reduce the amount of material carried in the short-term vacuum port, the baffle plate structure easily increases local material accumulation and cleaning and maintenance risks. Furthermore, the residual monomer content, solvent loss rate, and energy consumption per unit output are still inferior to the solution of this invention. Therefore, this invention improves the overall stability of continuous monomer removal, volatilization, and defoaming of polyacrylonitrile stock solution through the synergistic cooperation of dual-check stable feeding, gradient reverse kneading block, the inclined vacuum port 63 on the upstream side of the latter half of the reverse kneading block, the diamond-shaped micro-groove array, and the unobstructed through-hole structure.

[0140] It should be noted that the comparison results shown in Table 1 are a set of typical comparative test results obtained under the same batch of raw solution and the same test conditions, used to illustrate the influence of each key structure on the effects of single-wax removal, de-volatile matter removal, defoaming, vacuum port material carrying, continuous operation stability, and subsequent spinning stability; these test results should not be construed as limiting the scope of protection of this invention. Under different initial residual single-wax content, raw solution viscosity, throughput, and operating conditions, those skilled in the art can make adaptive adjustments based on the structure and process parameters disclosed in this invention.

[0141] The above comparison results show that when using a conventional vertical vacuum port, the amount of material carried in the vacuum port and the risk of blockage increase significantly, indicating that tilting the vacuum port upstream in the material flow direction helps reduce the risk of material carry-in and blockage. Without the diamond-shaped microgroove array, the residual monomer content, microbubble removal rate, continuous operation days, and spinning breakage rate are all inferior to the scheme of this invention, indicating that the diamond-shaped microgroove array is beneficial to promoting liquid film adhesion and renewal. Without the gradient reverse kneading block, the residual monomer content and spinning breakage rate increase, indicating that the partitioned reverse kneading block is beneficial to adapting to different devolatilization stages. Without the weight loss flow rate control and pipeline flow rate verification, the discharge viscosity fluctuation and the risk of material carry-in in the vacuum port increase, indicating that stable feeding plays an important role in maintaining the liquid film thickness and devolatilization stability inside the screw. Although setting a baffle can reduce the short-term material carry-in, the baffle structure increases local material accumulation and maintenance risks, and the overall residual monomer content, solvent loss rate, and energy consumption are still inferior to the scheme of this invention. Therefore, it can be seen that the present invention improves the overall stability of continuous demonotropic, devolatile, and defoaming of polyacrylonitrile feed solution through the synergistic cooperation between stable feeding, gradient film formation, upstream inclined vacuuming, and diamond-shaped microgroove liquid film renewal.

[0142] It should be noted that the specific values ​​in the above embodiments and comparative examples are used to illustrate the feasibility and technical effects of the technical solution of the present invention, and should not be construed as limiting the scope of protection of the present invention. Without departing from the technical concept of the present invention, those skilled in the art can make adaptive adjustments to the screw diameter, aspect ratio, reverse kneading block stagger angle, vacuum port size, vacuum degree, barrel temperature and flow control parameters according to the solid content, viscosity, initial residual monomer content, throughput and subsequent spinning requirements of the polyacrylonitrile stock solution.

[0143] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A continuous depolymerization, devolatilization and defoaming device for polyacrylonitrile dope, characterized by, Includes the feeding system, screw extruder (7), vacuum system and discharge system; The feeding system includes a polymer buffer tank (2), a weighing sensor (3), a nitrogen pressure delivery pipeline, a discharge regulating valve (4), a pipeline flow meter (5), and a control unit. The discharge port of the polymer buffer tank (2) is connected to the feed port of the screw extruder (7) through the discharge regulating valve (4) and the pipeline flow meter (5). The weighing sensor (3) is installed in the polymer buffer tank (2). The weighing sensor (3), the discharge regulating valve (4), and the pipeline flow meter (5) are respectively connected to the control unit. The screw extruder (7) includes a modular barrel (61) and a co-rotating twin screw (64) disposed within the modular barrel (61). The modular barrel (61) is provided with multiple devouring barrel modules along the material flow direction. The co-rotating twin screw (64) is provided with multiple reverse kneading blocks within the devouring barrel modules. The multiple reverse kneading blocks form at least two gradient sections along the material flow direction. At least one of the staggered angle, number of pieces, and effective length of the reverse kneading blocks in different gradient sections is different. The vacuum system includes multiple vacuum ports (63), multiple vacuum branch pipes (15) and a vacuum distribution pipe (8). The multiple vacuum ports (63) are respectively located in the devolatilization cylinder module where the corresponding reverse kneading block is located. Each vacuum port (63) is connected to the vacuum distribution pipe (8) through the corresponding vacuum branch pipe (15). The vacuum port (63) is located in the rear half of the region in the axial length direction of the corresponding reverse kneading block, and the central axis of the vacuum port (63) is inclined to the upstream side of the material flow direction in the vertical section along the axis of the co-rotating twin screw (64). The inner inlet of the vacuum port (63) is an unobstructed opening that is directly connected to the inner cavity of the modular cylinder (61). At least a portion of the inner wall of the devolatilization cylinder module is provided with an array of rhomboid microgrooves; The control unit uses the weight loss flow rate of the polymer buffer tank (2) obtained by the weighing sensor (3) as the main control signal, and uses the pipeline flow rate obtained by the pipeline flow meter (5) as the verification signal to control the opening degree of the discharge regulating valve (4); The discharge system is connected to the discharge port of the screw extruder (7).

2. The polyacrylonitrile dope continuous depolymerization, devolatilization and defoaming device according to claim 1, characterized in that, The modular cylinder (61) includes a first cylinder module to an eleventh cylinder module arranged sequentially along the material flow direction. The first cylinder module is a feeding cylinder module, the second cylinder module is a preheating cylinder module, the third to ninth cylinder modules are respectively the first to the seventh devolatilization cylinder modules, the tenth cylinder module is a homogenization cylinder module, and the eleventh cylinder module is a discharge cylinder module. The plurality of vacuum ports (63) are respectively arranged in the third to the ninth cylinder modules.

3. The polyacrylonitrile dope continuous single removal, devolatilization and defoaming device according to claim 1, characterized in that, The plurality of reverse kneading blocks include a high residual single-area reverse kneading block, a medium residual single-area reverse kneading block, and a trace amount reverse kneading block arranged sequentially along the material flow direction. The staggered angle of the high residual single-area reverse kneading block is greater than that of the medium residual single-area reverse kneading block, and the staggered angle of the medium residual single-area reverse kneading block is greater than that of the trace area reverse kneading block. The number of pieces of the high residual single-zone reverse kneading block is less than or equal to the number of pieces of the medium residual single-zone reverse kneading block, and the number of pieces of the medium residual single-zone reverse kneading block is less than or equal to the number of pieces of the trace area reverse kneading block. The effective length of the high residual single-zone reverse kneading block is greater than or equal to the effective length of the medium residual single-zone reverse kneading block, and the effective length of the medium residual single-zone reverse kneading block is greater than or equal to the effective length of the trace area reverse kneading block.

4. The polyacrylonitrile dope continuous single removal, devolatilization and defoaming device according to claim 3, characterized in that, The plurality of devouring cylinder modules include a first devouring cylinder module to a seventh devouring cylinder module arranged sequentially along the material flow direction; The high residual single-zone reverse kneading block is disposed in the first devolatilization cylinder module and the second devolatilization cylinder module, the medium residual single-zone reverse kneading block is disposed in the third to fifth devolatilization cylinder modules, and the trace zone reverse kneading block is disposed in the sixth devolatilization cylinder module and the seventh devolatilization cylinder module.

5. The polyacrylonitrile dope continuous single-elimination devolatilization and defoaming device according to claim 1, characterized in that, The center point of the vacuum port (63) is located between 1 / 2 and 3 / 4 of the axial length of the corresponding reverse kneading block; the axial projection of the vacuum port (63) along the material flow direction is located in the area between 1 / 2 and the end position of the corresponding reverse kneading block axial length.

6. The polyacrylonitrile dope continuous single-elimination devolatilization and defoaming device according to claim 1, characterized in that, The central axis of the vacuum port (63) is inclined upstream of the material flow direction in the vertical section along the axis of the co-rotating twin screws (64) in the radial direction relative to the top of the modular cylinder (61), and forms an angle of 30° to 60° with the top radial line of the modular cylinder (61) at the vacuum port (63).

7. The polyacrylonitrile dope continuous single-elimination devolatilization and defoaming device according to claim 1, characterized in that, The vacuum port (63) has no baffle plate at the inner entrance of the cylinder. The inner wall of the vacuum port (63) is a smooth inner wall. The transition between the vacuum port (63) and the inner cavity of the modular cylinder (61) adopts a rounded transition with a radius of R5mm to R10mm.

8. The continuous demonotropic, devolatitizing, and defoaming device for polyacrylonitrile stock solution according to claim 2, characterized in that, The rhomboid microgroove array is disposed on the inner wall of the 3rd to 9th cylindrical modules.

9. The continuous demonotropic, devolatitizing, and defoaming device for polyacrylonitrile stock solution according to claim 1, characterized in that, The rhomboid microgrooves in the array have rhomboid side lengths of 0.4mm to 0.6mm, rhomboid interior angles of 90° to 120°, groove depths of 0.2mm to 0.4mm, and spacing between adjacent rhomboid vertices of 1.0mm to 2.0mm. The interior corner radius of the rhomboid microgrooves is R0.2mm to R0.3mm, and the edge corner radius is R0.1mm to R0.2mm. The bottom of the rhomboid microgrooves is a flat bottom, and the flat bottom is transitioned to the sidewall of the groove with a rounded corner.

10. A continuous process for depolymerization, devolatilization and defoaming of polyacrylonitrile dope, characterized in that, The process is carried out using the continuous demonotropic, devolatitizing, and defoaming apparatus for polyacrylonitrile stock solution as described in any one of claims 1 to 9, and the process includes the following steps: The polymerized polyacrylonitrile stock solution was fed into the polymerization liquid buffer tank (2) under nitrogen pressure. The weight loss flow rate of the polymer buffer tank (2) is obtained by the weighing sensor (3), the pipeline flow rate entering the screw extruder (7) is obtained by the pipeline flow meter (5), and the opening degree of the discharge regulating valve (4) is adjusted by using the weight loss flow rate as the main control signal and the pipeline flow rate as the verification signal. The polyacrylonitrile stock solution is continuously fed into the screw extruder (7), so that the polyacrylonitrile stock solution is sheared, stretched and spread to form a liquid film under the action of the reverse kneading block. In the latter half of the region in the axial length direction of the corresponding reverse kneading block, volatile components and bubbles in the polyacrylonitrile stock solution are extracted through the vacuum port (63) that is inclined towards the upstream side of the material flow direction. The polyacrylonitrile stock solution is passed through the inner wall of the devolatilization cylinder module, which has a diamond-shaped microgroove array. The polyacrylonitrile raw material, after being de-monotropically and de-bubblyed, is output through the discharge system.

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