A cold reaction kettle for polyimide synthesis and a polyimide synthesis method

Abstract

This application provides a cold reactor for polyimide synthesis and a method for polyimide synthesis. The cold reactor includes a reactor body and a stirring system disposed on the reactor body. The stirring system includes a drive motor, a main stirring shaft, a high-speed stirring assembly, a high-viscosity stirring assembly, and a coupling mechanism. The upper end of the main stirring shaft is connected to the output end of the drive motor. The high-speed stirring assembly is fixedly disposed on the main stirring shaft. The high-viscosity stirring assembly is decoupled and coaxially sleeved on the main stirring shaft. The coupling mechanism is disposed between the drive motor and the main stirring shaft and is used to adjust whether the high-viscosity stirring assembly is decoupled from or coupled to the main stirring shaft. Therefore, in the initial stage of polyimide synthesis, the cold reactor can decouple the high-viscosity stirring assembly from the main stirring shaft through the coupling mechanism, while in the later stage of the reaction, it can couple the high-viscosity stirring assembly to the main stirring shaft through the coupling mechanism, thereby solving the problems of the prior art.

Description

Technical Field

[0001] This application relates to the field of polyimide synthesis technology, and in particular to a cold reaction vessel for polyimide synthesis and a method for polyimide synthesis. Background Technology

[0002] A reaction vessel is a container used for physical or chemical reactions, and its structural design must meet the heating, cooling, mixing, and reaction requirements of a specific process. In the field of polymer synthesis, reaction vessels can be mainly divided into two categories based on the reaction-driving and temperature-controlling methods: hot reaction vessels and cold reaction vessels. Hot reaction vessels typically rely on external heating devices (such as jackets, coils, and the introduction of heat transfer oil or steam) to provide initial or continuous energy to the reaction system, thereby promoting monomer dissolution and initiating the reaction. Cold reaction vessels, on the other hand, primarily utilize the heat released after the reactants are mixed to drive the reaction, and use a jacket cooling medium (such as cold water) to remove the heat, thus controlling the reaction temperature and progress. Therefore, cold reaction vessels are generally more suitable for the synthesis of high-performance polymers that are highly exothermic and temperature-sensitive. In the solution condensation polymerization of polyimide, due to the large exothermic reaction and extreme temperature sensitivity, cold reaction vessels are currently widely used as reaction vessels to achieve precise control of the polymerization reaction.

[0003] However, in the synthesis of polyimide using cold reactors, there is a mismatch between the current equipment structure of the cold reactor and the physical properties of the specific raw materials, leading to severe challenges in the synthesis process. Specifically, firstly, from the perspective of equipment structure, current cold reactors have inherent limitations. For example, in order to adapt to the rapidly increasing viscosity of the system in the later stages of the polymerization reaction (reaching hundreds of thousands of centipoises) and ensure that high-viscosity materials can be uniformly mixed to prevent local overheating or uneven polymerization, current cold reactors generally use a double-ribbon agitator. The core design of this agitator is to optimize the axial circulation and overall exchange capacity under the high-viscosity fluid in the later stages of the reaction, resulting in a large blade area and thus huge stirring resistance. Therefore, in order to match the load of the drive motor, the double-ribbon agitator in current cold reactors can usually only operate at a low speed, thus sacrificing the mixing capacity in the early stages of the reaction.

[0004] Secondly, considering the raw material characteristics of polyimide, the key monomers for polyimide have extremely high requirements for mixing performance in the initial stage of the reaction. In practical applications, the synthesis of polyimide typically involves two key monomers: a diamine monomer containing an imidazole group (hereinafter referred to as diamine monomer) and a dianhydride monomer containing a biphenyl group (hereinafter referred to as dianhydride monomer). The diamine monomer, upon contact with common solvents (such as N-methylpyrrolidone, NMP), does not completely dissolve but rapidly forms a viscous "porridge-like substance." If a very strong shear force is not applied at the moment of contact between the diamine monomer and the solvent to rapidly disperse it, this porridge-like substance easily agglomerates and clumps together. The dianhydride monomer, on the other hand, has even lower solubility at room temperature than the diamine monomer and is generally insoluble in common solvents. Therefore, during the reaction process in a cold reactor, the dianhydride monomer can only achieve physical suspension and dispersion in the solvent through mechanical stirring by a twin-ribbon impeller.

[0005] Therefore, when the aforementioned equipment limitations are combined with the characteristics of the raw materials, they constitute the key technical bottleneck in the current cold reactor synthesis of polyimide. Specifically, in the initial stage of the reaction, high-speed stirring is required to instantly disperse the diamine monomer to prevent agglomeration and to suspend the dianhydride monomer to prevent rapid sedimentation. However, the low rotation speed of the dual-ribbon agitator in the current cold reactor cannot provide this high-speed stirring. Consequently, in the initial stage of the reaction, diamine monomers easily form clumps and settle at the bottom of the reactor. Furthermore, the dianhydride monomers, due to poor dispersion, also settle and adhere to the surface of the diamine clumps, undergoing a rapid localized reaction to form a dense polymer shell. Ultimately, this forms an unresolved "dead material" at the bottom of the reactor, the presence of which negatively impacts the performance of the product. Summary of the Invention

[0006] The purpose of this application is to provide a cold reactor and a method for synthesizing polyimide, in order to solve the problems in the prior art.

[0007] To address the aforementioned technical problems, this application provides a cold reactor for polyimide synthesis, comprising a reactor body and a stirring system disposed within the reactor body. The stirring system includes: a drive motor, a main stirring shaft, a high-speed stirring assembly, a high-viscosity stirring assembly, and a coupling connection mechanism, wherein:

[0008] The upper end of the main stirring shaft is connected to the output end of the drive motor.

[0009] The high-speed stirring assembly is fixedly mounted on the main stirring shaft;

[0010] The high-viscosity stirring assembly is decoupled and coaxially sleeved on the main stirring shaft; and...

[0011] The coupling connection mechanism is disposed between the drive motor and the main stirring shaft, and is used to adjust the high viscosity stirring assembly to be decoupled from or coupled to the main stirring shaft.

[0012] Preferably, the stirring system further includes bottom-anchored stirring blades, wherein the bottom-anchored stirring blades are fixedly disposed at the lower end of the main stirring shaft.

[0013] Preferably, the high-viscosity stirring assembly is specifically one or more sets of large ribbon-type stirring blades.

[0014] Preferably, the high-speed stirring component is specifically one or more sets of propulsion stirring blades.

[0015] Preferably, the coupling connection mechanism includes a magnetically controlled coupler and a state switching controller, wherein: the state switching controller is used to control the magnetically controlled coupler to switch the working state so that the high viscosity stirring assembly is decoupled from or coupled to the main stirring shaft.

[0016] Preferably, the state switching controller has a manual control mode and / or an automatic control mode. In the manual control mode, the working state of the magnetic coupler is switched manually. In the automatic control mode, the working state of the magnetic coupler is switched automatically based on the acquired control signal related to the viscosity of the reaction system in the cold reactor.

[0017] Preferably, the stirring system is further provided with a signal detection unit, which is used to detect viscosity-related parameters of the reaction system in the cold reactor under the automatic control mode, and generate the control signal.

[0018] Preferably, the cold reaction vessel further includes a sealed agitator mounting base, wherein:

[0019] The sealed stirring paddle mounting base is disposed on the upper cover of the reactor body and is sealed and fitted at the position where the main stirring shaft and the high viscosity stirring assembly protrude from the upper cover.

[0020] Preferably, the cold reactor further includes a motor and gearbox mounting bracket, wherein:

[0021] The motor and gearbox mounting bracket is sleeved around the main stirring shaft and the coupling connection mechanism;

[0022] The drive motor is disposed on the upper end face of the motor and transmission mounting bracket; and the lower end face of the motor and transmission mounting bracket abuts against the sealed stirring paddle mounting base.

[0023] This application also provides a method for synthesizing polyimide based on the cold reactor provided in this application, the method comprising:

[0024] Solvent and diamine monomer are added to the cold reaction vessel;

[0025] The coupling connection mechanism is controlled to decouple the high viscosity stirring component from the main stirring shaft, and the drive motor is started to drive the high speed stirring component to run at a first speed to stir and disperse the material in the reactor at high speed.

[0026] Add dianhydride monomer to the cold reaction vessel;

[0027] The coupling connection mechanism is controlled to couple the high-viscosity stirring component to the main stirring shaft, and the drive motor is controlled to drive the high-speed stirring component and the high-viscosity stirring component to run at a second speed lower than the first speed, so as to stir the reaction system at a low speed, so that the diamine monomer and the dianhydride monomer can undergo a polymerization reaction to generate polyimide.

[0028] The cold reactor for polyimide synthesis provided in this application includes a reactor body and a stirring system disposed on the reactor body. The stirring system includes a drive motor, a main stirring shaft, a high-speed stirring assembly, a high-viscosity stirring assembly, and a coupling connection mechanism. The upper end of the main stirring shaft is drivenly connected to the output end of the drive motor. The high-speed stirring assembly is fixedly disposed on the main stirring shaft. The high-viscosity stirring assembly is decoupled and coaxially sleeved on the main stirring shaft. The coupling connection mechanism is disposed between the drive motor and the main stirring shaft and is used to adjust the high-viscosity stirring assembly to be decoupled from or coupled to the main stirring shaft. Therefore, in the process of synthesizing polyimide using this cold reactor, in the initial stage of the reaction, considering the characteristics of the key raw material monomers, the high-viscosity stirring component can be decoupled from the main stirring shaft through a coupling connection mechanism, thereby driving the high-speed stirring component to rotate at high speed through the main stirring shaft. In the later stage of the reaction, the high-viscosity stirring component can be coupled to the main stirring shaft through the coupling connection mechanism, thereby driving the high-viscosity stirring component to rotate at a relatively low speed through the main stirring shaft. Thus, through this structural design, it is possible to adapt to the raw material characteristics of polyimide in the initial and later stages of the reaction, solving the problems of existing technologies. Attached Figure Description

[0029] To more clearly illustrate the solutions in this application, the accompanying drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1This is a schematic diagram of the structure of a cold reactor for polyimide synthesis provided in the embodiments of this application;

[0031] Figure 2 This is a schematic diagram of the internal structure of the cold reactor provided in the embodiments of this application;

[0032] Figure 3 This is a schematic diagram of the specific process of polyimide synthesis provided in the embodiments of this application.

[0033] In the above view: 10-Reaction vessel body; 11-Top cover; 20-Stirring system; 21-Drive motor; 22-Main stirring shaft; 23-High-speed stirring assembly; 24-High-viscosity stirring assembly; 25-Coupling connection mechanism; 30-Bottom anchor-type stirring blade; 40-Sealed stirring blade mounting base; 50-Motor and gearbox mounting bracket; 60-Media jacket; 70-Bottom discharge port. Detailed Implementation

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application, are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0035] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0036] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0037] In view of the problems of the prior art pointed out in the background section above, this application provides a cold reactor and a method for synthesizing polyimide, which can solve the problems in the prior art. Figures 1-2The diagram shows the specific structure of the cold reactor. The cold reactor includes a reactor body 10 and a stirring system 20 disposed on the reactor body 10. The stirring system 20 includes: a drive motor 21, a main stirring shaft 22, a high-speed stirring component 23, a high-viscosity stirring component 24, and a coupling connection mechanism 25.

[0038] In this embodiment, the drive motor 21 can refer to the power source that provides rotational power to the entire stirring system 20. It can be an AC asynchronous motor, a permanent magnet synchronous motor, or other types of industrial motors. The specific model, power, and installation method can be set according to the capacity of the reactor and the stirring torque required by the process. This embodiment does not impose any special limitations on this. The output end of the drive motor 21 is connected to the upper end of the main stirring shaft 22, together forming the power input source of the entire stirring system 20.

[0039] The main stirring shaft 22 can refer to the core transmission component that runs through the interior of the reactor and carries various stirring components (including high-speed stirring component 23 and high-viscosity stirring component 24, etc.). Its material can be stainless steel, alloy steel, or other corrosion-resistant and high-strength metal materials, and its diameter and length can be set according to the actual situation such as the size of the reactor body 10 and the stirring depth. In the embodiment of this application, the upper end of the main stirring shaft 22 is connected to the output end of the drive motor 21, and the lower end can extend to near the bottom of the reverse cooling reactor.

[0040] The high-speed stirring assembly 23 in this application is fixedly mounted on the main stirring shaft 22. It is capable of high-speed stirring, thereby serving as a stirring unit for rapidly dispersing low-viscosity materials in the initial stage of the reaction. In practical applications, the high-speed stirring assembly 23 can be in the form of a propeller blade, a turbine blade, or a combination thereof. For example, it can be one or more sets of propeller blades, or other impeller structures capable of generating strong axial or radial flow fields. This application does not impose any special limitations on this. Furthermore, the high-speed stirring assembly 23 is fixedly mounted on the main stirring shaft 22, meaning that as long as the main stirring shaft 22 rotates (including rapid or slow rotation), the high-speed stirring assembly 23 will inevitably rotate as well. Thus, the cooperation between the high-speed stirring assembly 23 and the main stirring shaft 22 constitutes a basic stirring circuit. Regardless of the coupling state of the high-viscosity stirring assembly 24, this circuit can always be in a working state when the main stirring shaft 22 rotates. Thus, in the application embodiment, at the initial stage of polyimide synthesis, the viscosity of the reaction system is low, and the high-speed stirring component 23 can provide a high rotation speed, strong shear force and circulation flow rate to quickly disperse the poorly soluble diamine monomer and form a uniform porridge-like mixture with the solvent, preventing agglomeration and settling.

[0041] Furthermore, the high-speed stirring assembly 23 mentioned above can be structured as one or more sets of propeller-type stirring blades. These propeller-type stirring blades can be small (compared to the high-viscosity stirring assembly 24) with a helical shape. Their working principle is similar to that of a ship's propeller, generating strong axial thrust during rotation to drive the fluid inside the vessel to flow axially up and down, thereby forming a large-flow overall circulation. The propeller-type stirring blades can be positioned near or below the center of the main stirring shaft 22. For example, multiple sets of propeller-type stirring blades can be arranged near or below the center of the main stirring shaft 22. Each set of propeller-type stirring blades can be positioned inside the high-viscosity stirring assembly 24 or staggered with it.

[0042] In this embodiment, the high-viscosity stirring assembly 24 can be coaxially sleeved around the main stirring shaft 22, serving as a stirring unit for the overall mixing of high-viscosity materials in the later stages of the reaction. The specific form of the high-viscosity stirring assembly 24 can be a variation of a ribbon-type stirring impeller, a frame-type stirring impeller, or an anchor-type stirring impeller. For example, it can be one or more sets of ribbon-type stirring impellers with large diameter and large pitch (with a larger area compared to propeller-type stirring impellers), or other stirring forms suitable for the vertical exchange of high-viscosity fluids. This embodiment does not impose any special limitations on this.

[0043] The arrangement of the high-viscosity stirring component 24 within the main stirring shaft 22 differs from that of the high-speed stirring component 23. While the high-speed stirring component 23 is fixedly mounted on the main stirring shaft 22, the high-viscosity stirring component 24 is not rigidly fixed to the main stirring shaft 22. Instead, it is coaxially fitted in a decoupled manner, meaning the high-viscosity stirring component 24 is fitted outside the main stirring shaft 22, and there is a degree of freedom of relative movement between the two. This is only possible through coupling via the coupling connection mechanism 25 (which locks the high-viscosity stirring component 24 to the main stirring shaft 22, allowing both to rotate simultaneously). The coupling connection mechanism 25 will be described later.

[0044] Therefore, the high-viscosity stirring component 24 is designed to intervene after the viscosity of the reaction system increases. Utilizing its large surface area and special geometry, it propels the high-viscosity material through macroscopic vertical convection within the reactor, performing low-speed, high-torque stirring to eliminate mixing dead zones. In the initial stage of the reaction, the high-viscosity stirring component 24 can be decoupled from the main stirring shaft 22 (i.e., the lock between the high-viscosity stirring component 24 and the main stirring shaft 22 is released, allowing them to rotate freely relative to each other). At this point, the main stirring shaft 22 only needs to drive the high-speed stirring component 23 to rotate at high speed, while the high-viscosity stirring component 24 remains stationary relative to the main stirring shaft 22 or drifts slightly with the fluid, consuming no additional power and without increasing starting resistance.

[0045] It is important to note that the coupling connection mechanism 25 provided in this embodiment can refer to a mechanism disposed between the drive motor 21 and the main stirring shaft 22. Its function is to adjust the high-viscosity stirring component 24 to be decoupled from or coupled to the main stirring shaft 22. For example, the coupling connection mechanism 25 can be used to adjust the high-viscosity stirring component 24 to be coupled to the main stirring shaft 22, so that the two can rotate at the same or substantially the same speed (e.g., at a low speed in the later stage of the reaction). Alternatively, the coupling connection mechanism 25 can be used to adjust the high-viscosity stirring component 24 to be decoupled from the main stirring shaft 22, that is, to decouple the two, so that the two can rotate freely. For example, in the early stage of the reaction, the main stirring shaft 22 rotates rapidly, at which time the high-viscosity stirring component 24 can remain stationary or drift slightly with the fluid after decoupling.

[0046] The cold reactor for polyimide synthesis provided in this application includes a reactor body 10 and a stirring system 20 disposed on the reactor body 10. The stirring system 20 includes a drive motor 21, a main stirring shaft 22, a high-speed stirring component 23, a high-viscosity stirring component 24, and a coupling connection mechanism 25. The upper end of the main stirring shaft 22 is connected to the output end of the drive motor 21. The high-speed stirring component 23 is fixedly disposed on the main stirring shaft 22. The high-viscosity stirring component 24 is decoupled and coaxially sleeved on the main stirring shaft 22. The coupling connection mechanism 25 is disposed between the drive motor 21 and the main stirring shaft 22 and is used to adjust the high-viscosity stirring component 24 to be decoupled from or coupled to the main stirring shaft 22. Therefore, in the process of synthesizing polyimide using this cold reactor, in the initial stage of the reaction, considering the characteristics of the key raw material monomer, the high-viscosity stirring component 24 can be decoupled from the main stirring shaft 22 through the coupling connection mechanism 25, so that the main stirring shaft 22 drives the high-speed stirring component 23 to rotate at high speed. In the later stage of the reaction, the high-viscosity stirring component 24 can be coupled to the main stirring shaft 22 through the coupling connection mechanism 25, so that the main stirring shaft 22 drives the high-viscosity stirring component 24 to rotate at a relatively low speed. Therefore, through this structural design, it is possible to adapt to the raw material characteristics of polyimide in the initial and later stages of the reaction, thus solving the problems of the prior art.

[0047] It should be further explained that, considering that during the synthesis of polyimide, the dianhydride monomer can only be physically suspended and dispersed in the solvent by mechanical stirring in the cold reaction vessel (the dianhydride monomer is difficult to dissolve in the solvent), in order to avoid the dianhydride monomer from taking advantage of the bottom of the vessel, the stirring system provided in this application embodiment may also include a bottom anchor stirring blade 30, which is fixedly disposed at the lower end of the main stirring shaft 22.

[0048] The bottom-anchored stirring blade 30 is a stirring component located at the end of the main stirring shaft 22, with a shape adapted to the bottom contour of the reactor. Its outer edge maintains a small gap with the inner wall and bottom of the reactor body 10. In the technical solution of this application, the main function of the bottom-anchored stirring blade 30 is to solve the problem of easily settling materials such as dianhydride monomers accumulating at the bottom of the reactor. Thus, when the drive motor 21 drives the main stirring shaft 22 to rotate, the bottom-anchored stirring blade 30, fixedly located at the lower end of the main stirring shaft 22, also rotates. Its movement trajectory is close to the bottom and lower side wall of the reactor, effectively scraping up the material deposited at the bottom of the reactor and pushing it into the mainstream mixing zone in the center of the reactor. This improves the circulation of materials within the reactor across the entire height range, avoids excessively high local concentrations or residues of unreacted materials, and thus improves the uniformity of the initial mixing. The specific shape of the bottom anchor-type stirring blade 30 can be set according to the actual situation. For example, it can be a semi-circular shovel-shaped structure or an arc-shaped plate structure that fits the conical bottom of the vessel. This application embodiment does not make any special limitation on this.

[0049] In addition, to improve sealing, the cold reactor of this application may also include a sealed agitator mounting base 40. The sealed agitator mounting base 40 is disposed on the upper cover 11 of the reactor body 10 and is sealed around the position where the main agitator shaft 22 and the high-viscosity agitator assembly 24 protrude from the upper cover 11. In this way, the sealed agitator mounting base 40, by tightly fitting around the outer peripheral surface of the main agitator shaft 22 and the outer peripheral surface (or its extended shaft section) of the high-viscosity agitator assembly 24, constructs a barrier between the main agitator shaft 22, the high-viscosity agitator assembly 24 and the stationary reactor body 10. This barrier can effectively prevent solvent evaporation, leakage of inert protective gas (such as nitrogen) inside the reactor, and intrusion of moisture or impurities from the external environment into the reactor, thereby ensuring the stability and safety of the polymerization reaction system.

[0050] Specifically, the sealed agitator mounting base 40 can refer to a dedicated sealing integrated component located at the top cover 11 of the reactor body 10. Its function is to provide a centralized and reliable dynamic sealing interface for rotating components passing through the reactor cover. In practical applications, the sealed agitator mounting base 40 is fixedly connected to the top cover 11 of the reactor body 10 (for example, it can be an integrated design or a bolted connection), forming part of the top closed structure of the reaction vessel. Structurally, the sealed agitator mounting base 40 can have channels or cavities adapted to the outer contours of the main stirring shaft 22 and the high-viscosity stirring assembly 24, and sealing elements are integrated within these channels. These sealing elements can be one or more combinations of mechanical seals, packing seals, or lip seals; this embodiment does not impose any special limitations on this.

[0051] The cold reaction vessel may also include a motor and gearbox mounting bracket 50, which is sleeved around the main stirring shaft 22 and the coupling connection mechanism 25, and the drive motor 21 is disposed on the upper end face of the motor and gearbox mounting bracket 50; and the lower end face of the motor and gearbox mounting bracket 50 abuts against the sealed stirring paddle mounting base 40.

[0052] The motor and transmission mounting bracket 50 can refer to a support frame or housing structure used to support the drive motor 21 and the coupling connection mechanism 25. Its function is to provide a stable mounting base for the drive motor 21 and the coupling connection mechanism 25, and to effectively transfer the torque reaction force generated by the motor operation and its own gravity load to the sealing structure below. The specific shape, size and material of the motor and transmission mounting bracket 50 can be set according to the actual situation. For example, it can be a metal frame structure with sufficient rigidity, or it can be a cast box structure. This application embodiment does not make any special limitations on this.

[0053] In addition, through the contact between the lower end face of the motor and gearbox mounting bracket 50 and the sealing agitator mounting base 40, the motor and gearbox mounting bracket 50 and the sealing agitator mounting base 40 together form a continuous rigid support chain from the motor output end to the stirring shaft inside the vessel, which ensures the coaxiality stability of the main stirring shaft 22 during high-speed rotation or heavy-load stirring, and reduces the risk of seal failure caused by vibration or off-center load.

[0054] Considering the coupling connection mechanism 25 in this application, which is used to adjust the high-viscosity stirring assembly 24 to be decoupled from or coupled to the main stirring shaft 22 to adapt to different viscosity conditions, the coupling connection mechanism 25 can be further described here. The coupling connection mechanism 25 may include a magnetically controlled coupler and a state switching controller, wherein the state switching controller is used to control the magnetically controlled coupler to switch its operating state, thereby decoupling or coupling the high-viscosity stirring assembly 24 to or coupling it to the main stirring shaft 22.

[0055] The magnetically controlled coupler can refer to a mechanical-electric composite component that utilizes the principle of magnetic field induction to achieve torque transmission and non-contact power connection. In the technical solution of this application, the magnetically controlled coupler is disposed between the drive motor 21 and the main stirring shaft 22, or on the transmission path between the main stirring shaft 22 and the high-viscosity stirring component 24. The function of the magnetically controlled coupler is to act as a switch or clutch for power transmission, controlling whether the rotational power output by the drive motor 21 is transmitted to the high-viscosity stirring component 24 by the establishment and disappearance of the magnetic field.

[0056] For example, when the magnetically controlled coupler is in the coupled working state, a closed magnetic circuit is formed between its internal rotors, generating sufficient magnetic attraction or induced current, thereby driving the high-viscosity stirring component 24 to rotate synchronously with the main stirring shaft 22; when it is in the decoupled working state, the magnetic circuit is broken or the magnetic force is weakened to the point of being insufficient to transmit torque, and the high-viscosity stirring component 24 is stationary or freely floating relative to the main stirring shaft 22, thereby achieving separation between the two. In practical applications, the specific implementation of this magnetically controlled coupler can be set according to the actual situation. For example, it can be an energized electromagnetic clutch, which adjusts the magnetic force by controlling the on and off of the coil current; it can also be a permanent magnet magnetic powder clutch, which adjusts the transmitted torque by changing the magnetization state of the magnetic powder; or it can be an eddy current magnetic coupling, which uses the eddy current effect generated by the movement of a conductor in a magnetic field to transmit power. This application does not impose any special limitations on this, as long as non-contact power engagement and disengagement can be achieved.

[0057] The state switching controller can refer to an electronic control unit or logic circuit module used to send control commands to the magnetic coupler to change its operating state. In this application, the state switching controller is electrically connected to the magnetic coupler. Its function is to output corresponding electrical signals (such as voltage, current, or pulse signals) to the magnetic coupler according to preset logic, manual commands, or sensor feedback signals, thereby triggering the magnetic coupler to switch between coupling and decoupling states. Therefore, in this embodiment, the state switching controller and the magnetic coupler work together to form the core control part of the coupling connection mechanism 25, ensuring that the high-viscosity stirring component 24 can be accurately connected to or disconnected from the stirring system 20 according to the needs of the reaction process.

[0058] The state switching controller can be implemented as a standalone PLC controller, an embedded microprocessor, or a control logic module integrated into a frequency converter or motor driver. The source of its control signals can be set according to actual conditions; for example, it can originate from manual button input by the operator, or from feedback signals automatically generated after real-time monitoring of parameters such as temperature, torque, current, or viscosity within the reactor. This application does not impose any special limitations on this aspect.

[0059] In the initial stage of the polyimide synthesis reaction, the viscosity of the reaction system is low. At this time, the state switching controller controls the magnetic coupler to be in a decoupled state, and the power of the drive motor 21 is only transmitted to the high-speed stirring component 24, so that it runs at a high speed to achieve rapid dispersion and mixing of monomer and solvent. Meanwhile, the high-viscosity stirring component 24 remains stationary to avoid excessive resistance or splashing. As the reaction proceeds, the viscosity of the system gradually increases. When the preset threshold is reached or a switching command is received, the state switching controller sends a signal to activate the magnetic coupler, so that it enters the coupled state. At this time, the power of the drive motor 21 is transmitted to both the high-speed stirring component 23 and the high-viscosity stirring component 24. The two work together to tumble and mix the high-viscosity material at a lower speed to prevent local overheating or uneven mixing.

[0060] In addition, in this embodiment of the application, the state switching controller is provided with a manual control mode and / or an automatic control mode. In the manual control mode, the working state can be switched by manually controlling the magnetic coupler. In the automatic control mode, the working state of the magnetic coupler can be switched automatically according to the control signal related to the viscosity of the reaction system in the cold reactor.

[0061] This manual control mode refers to a working method where the operator directly intervenes to trigger the state switching. Therefore, in this manual control mode, the state switching controller receives operation commands from external manual input (such as signals emitted through physical buttons, knobs, or touch screen interfaces) and converts the commands into drive signals, which are then sent to the magnetic coupler. The magnetic coupler responds to the drive signal by performing mechanical actions (such as the engagement or release of an electromagnet, which in turn drives the engagement or disengagement of a mechanical locking mechanism), thereby achieving the coupling connection or decoupling separation between the high-viscosity stirring assembly 24 and the main stirring shaft 22.

[0062] Automatic control mode refers to a working mode in which the state switching is performed autonomously based on preset logic or real-time feedback signals. Therefore, in automatic control mode, the state switching controller is configured to continuously or periodically receive control signals related to the viscosity of the reaction system in the cold reactor. These control signals can be directly derived from reaction system parameters (such as stirring motor current, torque value, online viscometer reading, etc.) collected in real time by the signal detection unit, or they can be virtual signals based on time series or process formula presets.

[0063] When the state switching controller determines that the received control signal meets the preset switching conditions (such as the viscosity threshold reaching a specific value, the reaction time reaching a set point, or the motor load exceeding the limit range), it automatically outputs a drive signal to the magnetic coupler to drive the magnetic coupler to move, so that the high viscosity stirring component 24 is automatically coupled to or decoupled from the main stirring shaft 22. This automated control mode can eliminate human operation errors and ensure the high repeatability and stability of the process in large-scale industrial production.

[0064] To achieve automated control in the automatic control mode, the stirring system 20 may also be equipped with a signal detection unit. This signal detection unit is used to detect viscosity-related parameters of the reaction system in the cold reactor of this application in the automatic control mode and generate the aforementioned control signal.

[0065] Furthermore, the cold reactor provided in this embodiment may further include a bottom outlet 70, which is located at the bottom of the reactor body 10. When discharge is required, the valve of the bottom outlet 70 can be opened to allow the material inside the reactor to flow out through the outlet. Of course, to better control the temperature inside the cold reactor, the cold reactor may further include a media jacket 60, which can be fitted around the reactor body 10. This media jacket 60 can then be used to heat or cool the reactor body 10, thereby controlling the temperature inside the reactor.

[0066] The above is a detailed description of the structure of the cold reactor provided in the embodiments of this application. Based on the cold reactor provided in the embodiments of this application, the embodiments of this application can also provide a method for synthesizing polyimide, such as... Figure 3 The diagram shown illustrates the specific process flow of this polyimide synthesis method, which includes the following steps:

[0067] Step S61: Add solvent and diamine monomer to the cold reaction vessel.

[0068] The solvent can refer to an organic solvent capable of dissolving or dispersing the polyimide precursor, specifically including but not limited to polar aprotic solvents such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAc), or dimethylformamide (DMF). Its moisture content is typically controlled at extremely low levels (e.g., below 300 ppm) to prevent monomer hydrolysis. The diamine monomer can refer to an aromatic compound containing an imidazole group, used for polycondensation reactions with dianhydride monomers. In practical applications, the diamine monomer can be, for example, 5(6)-amino-2-(4'-aminophenyl)benzimidazole, p-phenylenediamine, or mixtures thereof.

[0069] In step S61, the ratio of diamine monomer to solvent is set according to the solid content of the target polymer, and can typically be as high as 10% to 15% or more. At this stage, the reaction system is in a low viscosity state, but the diamine monomer may not be completely dissolved in the solvent, and a homogeneous porridge-like suspension needs to be formed.

[0070] Step S62: Control the coupling connection mechanism to decouple the high viscosity stirring component from the main stirring shaft, and start the drive motor to drive the high speed stirring component to run at the first speed, so as to stir and disperse the material in the vessel at high speed.

[0071] In step S62, the coupling connection mechanism can be controlled to decouple the high viscosity stirring component from the main stirring shaft. At this time, since the high viscosity stirring component is decoupled from the main stirring shaft, the high viscosity stirring component remains stationary or independently suspended under the action of gravity and does not rotate with the main stirring shaft.

[0072] Since the high-speed stirring assembly is fixedly mounted on the main stirring shaft, and the high-speed stirring assembly is usually composed of one or more sets of propeller-type stirring blades, it has low fluid resistance and high shear efficiency. Therefore, the drive motor can be started to drive the high-speed stirring assembly to run at a first speed, and the material in the vessel can be stirred and dispersed at high speed. Here, the first speed can refer to a high speed range suitable for dispersing low viscosity systems, such as 800 rpm to 1200 rpm. In this way, the output torque of the drive motor mainly acts on the relatively light high-speed stirring assembly, enabling it to rotate rapidly and generate strong axial and radial flow fields.

[0073] Therefore, when the drive motor runs at its initial speed, the high-speed blades of the propeller-type agitator cut through the fluid, rapidly breaking up the added diamine monomer clumps and mixing them thoroughly with the solvent. This quickly and evenly suspends the resulting porridge-like substance, preventing it from settling and agglomerating into dense clumps. Because the high-viscosity stirring component is in a decoupled, stationary state, its enormous moment of inertia and resistance do not slow down the motor speed, thus ensuring the high shear force required for initial dispersion. This also avoids material splashing or dead zones of unreacted raw materials caused by low-speed agitation of the large blades.

[0074] Step S63: Add dianhydride monomer to the cold reaction vessel.

[0075] The dianhydride monomer can refer to a dianhydride monomer containing a biphenyl group, which is usually an aromatic compound. As another key raw material in polyimide synthesis, it can specifically be biphenyl dianhydride (BPDA), pyromellitic dianhydride (PMDA), or their derivatives. In practical applications, this dianhydride monomer is usually added in batches or continuously as a solid powder to the diamine monomer-solvent porridge mixture that has undergone high-speed dispersion, after rigorous drying. Because a uniform porridge-like dispersion system has been formed in the previous step S62, the settling rate of the dianhydride monomer after entering the reactor is significantly reduced compared to the pure solvent environment, and it is less likely to form an isolation layer at the bottom. Therefore, this feeding sequence and medium state can also suppress the phenomenon of dianhydride monomer directly settling and accumulating at the bottom, avoiding gelation or encapsulation of unreacted monomers due to excessively rapid local reactions, and ensuring that the polymerization reaction proceeds synchronously throughout the entire reactor volume.

[0076] Step S64: Control the coupling connection mechanism to couple the high viscosity stirring component to the main stirring shaft, and control the drive motor to drive the high speed stirring component and the high viscosity stirring component to run at a second speed lower than the first speed, so as to stir the reaction system at a low speed.

[0077] Of course, this low-speed stirring can eventually promote the polymerization reaction between the diamine monomer and the dianhydride monomer to produce polyimide.

[0078] For example, in step S64, the coupling connection mechanism can be controlled manually or automatically to couple the high-viscosity stirring component to the main stirring shaft, and the drive motor can be controlled to drive the high-speed stirring component and the high-viscosity stirring component to run at a second speed lower than the first speed. The second speed can refer to a low speed range suitable for mixing high-viscosity systems, such as 50 rpm to 200 rpm, which is significantly lower than the first speed.

[0079] At this point, because the high-viscosity stirring component is coupled to the main stirring shaft, the drive motor can simultaneously drive the high-speed stirring component (propeller blades) and the high-viscosity stirring component (ribbon blades) to work together. For example, when the dynamic viscosity of the reaction system rises to several thousand to tens of thousands of centipoises, a single high-speed stirring component can no longer effectively circulate the material, while the intervention of the high-viscosity stirring component can force macroscopic mixing of the entire batch of materials, eliminating the mixing dead zone caused by the viscosity gradient. In this way, by driving the high-speed stirring component and the high-viscosity stirring component to operate at a low speed with a second rotation speed, the rheological characteristics of the high-viscosity fluid in the later stage of polymerization are adapted, ensuring uniform dissipation of reaction heat energy and allowing the remaining trace amounts of unreacted monomers to fully contact and complete the polymerization.

[0080] The polyimide synthesis method provided in this application is based on the cold reactor provided in this application. Since the cold reactor can solve the problems in the prior art, this method can also solve the problems in the prior art. This will not be elaborated further here.

[0081] The above is a detailed description of the structure of the cold reactor provided in the embodiments of this application, and the polyimide synthesis method based on the cold reactor. Further relevant test data can be added here to illustrate the technical effects.

[0082] Example 1

[0083] In this Example 1, 800L of N-methylpyrrolidone (NMP) with a moisture content of 196ppm can be added to the cold reaction vessel as a solvent. Then, according to the requirement of a polymer solid content of 13%, a diamine monomer containing an imidazole group, specifically 5(6)-amino-2-(4'-aminophenyl)benzimidazole (R3), weighing 44.866kg, can be added to the vessel (of course, other related raw materials can also be added).

[0084] The control coupling connection mechanism decouples the high-viscosity stirring component from the main stirring shaft and starts the drive motor to drive the high-speed stirring component at 1000 rpm to stir and disperse the material in the vessel at high speed. The high-speed stirring and dispersion time is 1 hour.

[0085] Following the reaction material ratio, biphenyl dianhydride (BPDA), a dianhydride monomer containing biphenyl groups, was added to the reactor in a prepolymerization reaction at a mass of 78.122 kg. After stirring at 1000 rpm for 1 hour, the coupling mechanism was controlled to couple the high-viscosity stirring component to the main stirring shaft. The drive motor was further controlled to operate both the high-speed and high-viscosity stirring components at 150 rpm, thus performing low-speed stirring of the reaction system. After the reaction was completed, the product of Example 1 was analyzed.

[0086] Comparative Example 1

[0087] The difference between Comparative Example 1 and Example 1 above is that Comparative Example 1 uses a current cold reactor, and the stirring speed of the cold reactor is set to 150 rpm during the reaction. After the reaction is complete, the product of Comparative Example 1 is analyzed.

[0088] Table 1 below shows the sampling analysis data of the product of Example 1 and the sampling analysis data of the product of Comparative Example 1.

[0089] Table 1

[0090] Serial Number Dynamic viscosity (Pa·s) intrinsic viscosity dL / g Elongation at break % Fracture strength cN / dtex Elastic modulus cN / dtex Example 1 98230 8.02 2.6 29.21 926.32 Comparative Example 1 295421 8.12 3.2 26.55 809.51

[0091] As can be seen from Table 1, the elongation at break of the product of Example 1 is lower than that of Comparative Example 1, and the fracture strength and elastic modulus are higher than those of Comparative Example 1. Therefore, by using the cold reactor provided in this application embodiment, since it can control the coupling connection mechanism at different stages of the reaction to decouple or couple the high viscosity stirring component to the main stirring shaft, and thus carry out stirring at different speeds to adapt to the characteristics of the key raw materials, the possibility of forming "dead material" can be reduced and the performance of the product can be improved.

[0092] Obviously, the embodiments described above are only some embodiments of this application, not all embodiments. The accompanying drawings show preferred embodiments of this application, but do not limit the patent scope of this application. This application can be implemented in many different forms; rather, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this application's specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the scope of patent protection of this application.

Claims

1. A cold reaction vessel for the synthesis of polyimide, comprising a reaction vessel body and a stirring system disposed on the reaction vessel body, characterized in that, The stirring system includes: a drive motor, a main stirring shaft, a high-speed stirring assembly, a high-viscosity stirring assembly, and a coupling connection mechanism, wherein: The upper end of the main stirring shaft is connected to the output end of the drive motor. The high-speed stirring assembly is fixedly mounted on the main stirring shaft; The high-viscosity stirring assembly is decoupled and coaxially sleeved on the main stirring shaft; and... The coupling connection mechanism is disposed between the drive motor and the main stirring shaft, and is used to adjust the high viscosity stirring assembly to be decoupled from or coupled to the main stirring shaft.

2. The cold reaction vessel according to claim 1, characterized in that, The stirring system also includes bottom anchor-type stirring blades, wherein the bottom anchor-type stirring blades are fixedly installed at the lower end of the main stirring shaft.

3. The cold reaction vessel according to claim 1, characterized in that, The high-viscosity stirring assembly specifically comprises one or more sets of large ribbon-type stirring blades.

4. The cold reaction vessel according to claim 1, characterized in that, The high-speed stirring component specifically comprises one or more sets of propulsive stirring blades.

5. The cold reaction vessel according to claim 1, characterized in that, The coupling connection mechanism includes a magnetically controlled coupler and a state switching controller, wherein: the state switching controller is used to control the magnetically controlled coupler to switch the working state so that the high viscosity stirring assembly is decoupled from or coupled to the main stirring shaft.

6. The cold reaction vessel according to claim 5, characterized in that, The state switching controller has a manual control mode and / or an automatic control mode. In the manual control mode, the working state of the magnetic coupler is switched manually. In the automatic control mode, the working state of the magnetic coupler is switched automatically based on the acquired control signal related to the viscosity of the reaction system in the cold reactor.

7. The cold reaction vessel according to claim 6, characterized in that, The stirring system is also equipped with a signal detection unit, which is used to detect viscosity-related parameters of the reaction system in the cold reactor under the automatic control mode and generate the control signal.

8. The cold reaction vessel according to claim 1, characterized in that, The cold reaction vessel also includes a sealed stirring paddle mounting base, wherein: The sealed stirring paddle mounting base is disposed on the upper cover of the reactor body and is sealed and fitted at the position where the main stirring shaft and the high viscosity stirring assembly protrude from the upper cover.

9. The cold reaction vessel according to claim 8, characterized in that, The cold reaction vessel also includes a motor and gearbox mounting bracket, wherein: The motor and gearbox mounting bracket is sleeved around the main stirring shaft and the coupling connection mechanism; The drive motor is disposed on the upper end face of the motor and transmission mounting bracket; and the lower end face of the motor and transmission mounting bracket abuts against the sealed stirring paddle mounting base.

10. A method for synthesizing polyimide using a cold reactor according to any one of claims 1 to 9, characterized in that, The method includes: Solvent and diamine monomer are added to the cold reaction vessel; The coupling connection mechanism is controlled to decouple the high viscosity stirring component from the main stirring shaft, and the drive motor is started to drive the high speed stirring component to run at a first speed to stir and disperse the material in the reactor at high speed. Add dianhydride monomer to the cold reaction vessel; The coupling connection mechanism is controlled to couple the high-viscosity stirring component to the main stirring shaft, and the drive motor is controlled to drive the high-speed stirring component and the high-viscosity stirring component to run at a second speed lower than the first speed, so as to stir the reaction system at a low speed, so that the diamine monomer and the dianhydride monomer can undergo a polymerization reaction to generate polyimide.

Images