An apparatus for preparing fluororubber by VDF suspension polymerization in supercritical CO2 medium

Abstract

The utility model discloses a kind of device for preparing fluororubber by VDF suspension polymerization in supercritical CO2 medium, belong to fluororubber production equipment technical field.The device includes feed module, polymerization reaction module, product separation module and CO2 recovery circulation module connected in sequence by high-pressure resistant pipeline.The feed module includes the three feed branches of supercritical CO2, VDF monomer and dispersant, which are arranged in parallel, and the outlets of each branch converge to a static mixer.The polymerization kettle of the polymerization reaction module is provided with an independent anti-sticking kettle agent inlet and a terminator inlet.The product separation module uses a cyclone separator to achieve gas-solid separation.The CO2 recovery circulation module liquefies and recovers CO2 through a cryogenic refrigerator.The utility model effectively solves the problem of kettle sticking in supercritical polymerization process through modular design and the innovative structure of an independent anti-sticking kettle agent dosing system, and improves the production continuity and medium recovery efficiency.

Description

Technical Field

[0001] This invention belongs to the field of fluororubber preparation technology, specifically relating to an apparatus for preparing fluororubber by VDF suspension polymerization in supercritical CO2 medium. Background Technology

[0002] Fluororubber plays an irreplaceable role in high-end fields such as aerospace, automotive, and chemical industries due to its excellent high-temperature resistance, oil resistance, and chemical resistance. Currently, industrial production of fluororubber mainly relies on traditional aqueous suspension polymerization or emulsion polymerization processes. However, these processes generate large amounts of difficult-to-treat fluoride-containing wastewater in the later stages of production, with chemical oxygen demand (COD) typically exceeding 8000 mg / L, posing serious environmental challenges and incurring high costs for waste treatment.

[0003] To address this environmental bottleneck, green polymerization technology using supercritical carbon dioxide (scCO2) as the medium has emerged. scCO2 possesses unique properties such as low viscosity, high diffusion coefficient, and easy recyclability, theoretically enabling zero emissions of the reaction medium. However, this technology faces two major obstacles in its industrialization: First, severe "clinging" occurs, with polymers adhering extensively to the reactor wall, leading to decreased heat transfer efficiency, product agglomeration, and requiring up to 2 hours of cleaning per batch, severely compromising production continuity. Second, due to the complex dissolution and dispersion behavior of monomers, initiators, and polymers in scCO2, conventional dispersion systems are inefficient, resulting in polymerization conversion rates generally below 85%, and the molecular weight distribution is difficult to control precisely, affecting the uniformity of product performance.

[0004] Although existing technologies attempt to improve the dispersant by using perfluoropolyether glycols and other similar agents, the sticking rate remains above 5%, failing to fundamentally solve the problem. Furthermore, existing solutions often fail to systematically address the synergistic issues between initiator efficiency, molecular weight control, and dispersion / anti-sticking in the unique scCO2 medium.

[0005] Therefore, there is an urgent need in this field to develop a novel green synthesis method and dedicated equipment for fluororubber that can achieve high conversion rate, low residue sticking rate and precise control of product molecular weight in scCO2 medium. Utility Model Content

[0006] To address the shortcomings in the aforementioned background technology, the present invention aims to provide a dedicated apparatus for the preparation of fluororubber by VDF suspension polymerization in supercritical CO2 medium. This apparatus can ensure efficient mixing of materials in scCO2 medium, precise control of the reaction, and efficient recovery of the medium.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A device for preparing fluororubber by VDF suspension polymerization in supercritical CO2 medium, the core of which is a feeding module, a polymerization reaction module, a product separation module and a CO2 recovery and circulation module connected in sequence through high-pressure resistant pipelines, forming a complete closed production system.

[0008] The feeding module includes parallel supercritical CO2 feeding branches, VDF monomer feeding branches, and dispersant feeding branches. Each branch is equipped with a storage tank and a metering pump in sequence, achieving high-precision independent metering and stable delivery of the three main materials. The outlets of all branches converge and connect to the inlet of a mixer, ensuring that the materials are fully premixed before entering the reactor.

[0009] The core equipment of the polymerization reaction module is the polymerization reactor. The inlet of the polymerization reactor is connected to the outlet of the mixer. Its innovative design lies in the fact that, in addition to the main inlet, the polymerization reactor also has a specially designed: The inlet of the anti-sticking agent is connected to an anti-sticking agent metering pump via a pipeline; The terminator inlet is connected to a terminator metering pump via a pipeline.

[0010] This structure allows auxiliary materials such as anti-sticking agents to be directly added to the core reaction area via an independent path, avoiding potential losses and uneven distribution that may occur with a premixer, thus more effectively utilizing their anti-sticking function. The polymerization reactor is equipped with a stirrer, a jacketed temperature control system, and temperature and pressure sensors to provide a stable and controllable environment for the reaction.

[0011] The product separation module includes a cyclone separator, whose inlet is connected to the outlet of the polymerization reactor. It uses centrifugal force to achieve rapid and efficient separation of solid fluororubber products and gaseous CO2. The separated solid products enter the finished product silo.

[0012] The CO2 recovery and circulation module includes a cryostat and a CO2 recovery tank. The gas outlet of the cyclone separator is connected to the inlet of the cryostat. The cryostat liquefies the CO2 gas using chilled brine and collects it in the CO2 recovery tank for easy recycling, significantly improving the utilization rate and economy of the medium.

[0013] As a further optimization of this utility model, the device is also equipped with a PLC controller. This controller is connected to the agitator, temperature sensor, and heat medium regulating valve of the polymerization reactor, as well as the temperature sensor and chilled brine regulating valve of the cryogenic reactor, forming a basic automated monitoring system, which improves the stability and controllability of the entire device operation.

[0014] Compared with the prior art, the device provided by this utility model has the following significant advantages: 1. Effectively solves the problem of sticking to the reactor: By setting up an independent inlet for the anti-sticking agent and working in conjunction with a high-efficiency static mixer and agitator, the uniform distribution and efficient function of the anti-sticking component in the reaction system are ensured, which can significantly reduce the risk of sticking to the reactor from a structural perspective and ensure production continuity.

[0015] 2. Uniform material mixing and high reaction efficiency: The design of "parallel metering feeding + static premixing" ensures that each component is accurately proportioned and uniformly mixed before entering the reactor, laying the foundation for obtaining high conversion rate and uniform product quality.

[0016] 3. High separation and recovery efficiency, environmental protection and energy saving: The integration of cyclone separation and cryogenic recovery technology realizes rapid and efficient separation of products and media, with a CO2 recovery rate of over 90%, realizing closed-loop circulation of reaction media, which meets the requirements of green chemical industry.

[0017] 4. Modular integration and easy operation and control: The entire process is divided into four functionally distinct modules, and key parameters are centrally monitored and automatically adjusted through a PLC controller. The system has a high degree of integration, which facilitates operation, maintenance and large-scale scaling. Attached Figure Description

[0018] Figure 1 This is a simplified structural diagram of the device described in this utility model.

[0019] Figure 1 In the middle section: 1-Supercritical CO2 storage tank; 1.1-High pressure pump; 2-VDF storage tank; 2.1-VDF metering pump; 3-Dispersant storage tank; 3.1-Dispersant metering pump; 4-Mixer; 5-Polymerization kettle; 5.1-Agitator; 5.2-Jacket; 5.3-First temperature sensor; 5.4-Hot water regulating valve; 6-Anti-sticking agent storage tank; 6.1-Anti-sticking agent metering pump; 7-Terminator storage tank; 7.1-Terminator metering pump; 8-PLC controller; 9-Cyclone separator; 10-Finished product silo; 11-Cryogenic cooler; 11.1-Refrigerated brine regulating valve; 11.2-Second temperature sensor; 12-CO2 recovery tank. Detailed Implementation

[0020] The present invention will now be described in further detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Example

[0021] The structure of the device described in this utility model is as follows: Figure 1 As shown, its core consists of a feeding module, a polymerization reaction module, a product separation module, and a CO2 recovery and circulation module, which are connected by high-pressure resistant stainless steel pipelines (such as 316L material, designed pressure 30MPa) to form a complete closed system.

[0022] 1. Feeding module This module enables high-precision metering and premixing of three main materials, including three parallel feed branches: Supercritical CO2 feed branch: Contains a supercritical CO2 storage tank 1 and a high-pressure pump 1.1 in sequence. The supercritical CO2 storage tank 1 has a volume of 100L, a design pressure of 15MPa, and is equipped with a cooling coil to maintain an internal temperature of 5℃ and a pressure of 6MPa. The high-pressure pump 1.1 has a maximum outlet pressure of 30MPa and a flow rate accuracy of ±0.5%.

[0023] The VDF unit feed branch is equipped with a VDF storage tank 2 and a VDF metering pump 2.1 in sequence. The VDF storage tank 2 has a volume of 50L and a design pressure of 3MPa. The VDF metering pump 2.1 is a high-pressure plunger pump with a flow accuracy of ±0.5%.

[0024] Dispersant feed branch: A dispersant storage tank 3 and a dispersant metering pump 3.1 are installed in sequence. The dispersant storage tank 3 is made of 316L stainless steel and lined with polytetrafluoroethylene. It has a volume of 20L and is equipped with a magnetic stirrer (not shown in the figure) inside, which continuously stirs at a speed of 300rpm to ensure that the perfluoroalkyl betaine dispersant solution is uniform.

[0025] The outlets of the three branch lines are converged via a tee fitting and connected to the inlet of a mixer 4. This mixer 4 is a Sulzer SMX type static mixer, with an internal mixing element having a specific surface area of ​​approximately 500 m². 2 / m 3 This ensures that CO2, VDF, and dispersant are fully mixed before entering the polymerization reactor.

[0026] 2. Polymerization Reaction Module This module is the core of this utility model, and its core equipment is the polymerization reactor 5.

[0027] Reactor structure: The polymerization reactor 5 has an effective volume of 50L, is made of Hastelloy C-276, has a design pressure of 25MPa, and a design temperature of 150℃. Multiple inlets are located on the reactor lid, connected via high-pressure pipelines to the outlet of the mixer 4, the anti-sticking agent metering pump 6.1, and the terminator metering pump 7.1.

[0028] Stirring system: The vessel is equipped with a stirrer 5.1, which is a double-layer inclined blade turbine type, driven by a magnetically coupled leak-free stirring motor, and the speed can be steplessly adjusted within the range of 0-800 rpm.

[0029] Temperature control system: The polymerization reactor 5 is equipped with a jacket 5.2, which is connected to a heat transfer medium circulation unit (not shown in the figure, but as an equivalent in the prior art) via an external pipe. By adjusting the opening of the heat transfer medium regulating valve 5.4, the flow rate of heat transfer oil flowing into the jacket can be controlled, thereby achieving precise control of the reaction temperature inside the reactor.

[0030] Monitoring and Control: The polymerization reactor 5 integrates a first temperature sensor 5.3 (PT100 platinum resistance thermometer, accuracy ±0.2℃) and a pressure sensor (not shown in the figure, capacitive, range 0-25MPa). In addition, the polymerization reaction module also has two independent auxiliary feeding systems: Anti-sticking agent system: includes anti-sticking agent storage tank 6 and anti-sticking agent metering pump 6.1. Anti-sticking agent storage tank 6 is a 10L container with a heat insulation layer and an external ultrasonic dispersion device (not shown in the figure) to maintain the stability of the nano-silica suspension.

[0031] Terminator system: including terminator storage tank 7 and terminator metering pump 7.1.

[0032] 3. Product separation module The core equipment of this module is the cyclone separator 9. Its inlet is connected to the discharge valve at the bottom of the polymerization reactor 5 via an insulated, pressure-resistant pipeline. The shell of the cyclone separator 9 is made of 316L stainless steel, and its design pressure is the same as that of the polymerization reactor. Its bottom solid discharge port is connected to the finished product silo 10 via a pneumatic butterfly valve for collecting the generated fluororubber particles.

[0033] 4. CO2 recovery and recycling module This module enables the liquefaction and circulation of the reaction medium, with the core equipment being the cryogenic cooler 11 and the CO2 recovery tank 12.

[0034] Cryogenic cooler 11: This is a shell-and-tube heat exchanger. The shell side is supplied with -25°C chilled brine controlled by a chilled brine regulating valve 11.1. The tube side inlet is connected to the gas outlet at the top of the cyclone separator 9, and the outlet is connected to the CO2 recovery tank 12. A second temperature sensor 11.2 is installed on the cryogenic cooler 11 to monitor the CO2 outlet temperature.

[0035] CO2 recovery tank 12: It is a 100L pressure-resistant storage tank with a design pressure of 8MPa. It is used to store liquefied CO2. Its outlet can be connected to the inlet of supercritical CO2 storage tank 1 or high-pressure pump 1.1 through a pipeline (the return path is not shown in the figure) to achieve recycling.

[0036] 5. Control System This invention features a centralized PLC controller 8. The PLC controller 8 is connected via signal cables (shown as dashed lines in the figure) to the stirrer 5.1, the first temperature sensor 5.3, the heat medium regulating valve 5.4, the second temperature sensor 11.2, and the chilled brine regulating valve 11.1, forming a basic automated monitoring system to maintain the stability of the reaction and recovery process.

[0037] The workflow of this utility model is briefly described as follows: Supercritical CO2, VDF monomer, and dispersant solutions are precisely metered in their respective branches and initially mixed in mixer 4 before entering polymerization reactor 5. Simultaneously, nano-silica anti-sticking agent and subsequent initiators are added directly to the reactor via independent pipelines. Under the monitoring of PLC controller 8, polymerization reactor 5 undergoes the reaction at the set temperature, pressure, and stirring speed. After the reaction, the material enters cyclone separator 9, where the solid fluororubber product is collected, and the gaseous CO2 is liquefied in cryogenic cooler 11 and recovered to CO2 recovery tank 12 for reuse.

[0038] The above description is merely a preferred embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in this utility model, based on the technical solution and inventive concept of this utility model, should be included within the protection scope of this utility model.

Claims

1. An apparatus for preparing fluororubber by VDF suspension polymerization in supercritical CO2 medium, characterized in that, It includes a feeding module, a polymerization reaction module, a product separation module, and a CO2 recovery and recycling module, which are connected sequentially via high-pressure resistant pipelines. The feeding modules include those configured in parallel: The supercritical CO2 feed branch is equipped with a supercritical CO2 storage tank (1) and a high-pressure pump (1.1) in sequence. The VDF unit feed branch is equipped with a VDF storage tank (2) and a VDF metering pump (2.1) in sequence. The dispersant feed branch is equipped with a dispersant storage tank (3) and a dispersant metering pump (3.1) in sequence. The outlets of each feed branch converge and connect to the inlet of a mixer (4); The polymerization reaction module includes a polymerization reactor (5), whose inlet is connected to the outlet of the mixer (4); the polymerization reactor (5) is equipped with a stirrer (5.1), a jacket (5.2), a first temperature sensor (5.3), and a heat medium regulating valve (5.4) connected to the jacket; the polymerization reactor (5) is also provided with: The terminator inlet is connected to a terminator metering pump (7.1) via a pipeline, and a terminator storage tank (7) is connected to the terminator metering pump (7.1). The inlet of the anti-sticking agent is connected to an anti-sticking agent metering pump (6.1) via a pipeline. The anti-sticking agent metering pump (6.1) is connected to an anti-sticking agent storage tank (6). The product separation module includes a cyclone separator (9), whose inlet is connected to the outlet of the polymerization reactor (5) via a pipeline, and whose solid outlet is connected to the finished product silo (10). The CO2 recovery and circulation module includes a cryostat (11) and a CO2 recovery tank (12); the gas outlet of the cyclone separator (9) is connected to the inlet of the cryostat (11) via a pipeline, and the outlet of the cryostat (11) is connected to the inlet of the CO2 recovery tank (12); the cryostat (11) is equipped with a chilled brine regulating valve (11.1) and a temperature sensor (11.2).

2. The apparatus according to claim 1, characterized in that, The device also includes a PLC controller (8), which is connected to the stirrer (5.1), the first temperature sensor (5.3), the heat medium regulating valve (5.4), the second temperature sensor (11.2), and the chilled brine regulating valve (11.1) respectively.

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