A device for preparing oil-resistant fluororubber by VDF / TFE / PMVE terpolymerization

Abstract

The utility model discloses a kind of VDF / TFE / PMVE ternary copolymerization preparation oil-resistant fluororubber's device, belong to special rubber preparation equipment technical field.The device includes the pre-polymerization unit, main polymerization unit and post-processing unit connected in turn by process pipeline.Pre-polymerization unit is equipped with pre-polymerization kettle and its multiple raw material metering feed branch in parallel;Main polymerization unit is equipped with main polymerization kettle, and its feed inlet is connected respectively pre-polymerization kettle discharge port and each monomer / initiator metering pump;Post-processing unit includes the condensation kettle, vibrating screen, washing tank, extrusion dehydrator and vacuum drying oven connected in turn.Pre-polymerization kettle and main polymerization kettle are equipped with jacket temperature control system and pressure monitoring device, realize accurate temperature control by three-way regulating valve control jacket inner heat medium or coolant flow.This utility model realizes the full-process continuous, automation production of oil-resistant fluororubber, effectively guarantee the significant improvement of product oil resistance and processing safety.

Description

Technical Field

[0001] This utility model relates to the technical field of special rubber preparation equipment, specifically to an apparatus for preparing oil-resistant fluororubber by VDF / TFE / PMVE ternary copolymerization. Background Technology

[0002] Fluororubber, a special type of high-molecular elastomer containing fluorine atoms in its main chain or side chains, plays an indispensable role in harsh working conditions such as automotive, aerospace, and petrochemical industries due to its excellent high-temperature resistance, chemical resistance, and weather resistance. Among them, copolymers of vinylidene fluoride (VDF) and tetrafluoroethylene (TFE) are one of the most widely used fluororubber varieties.

[0003] However, with the rapid development of modern industry, especially high-performance automotive engine technology, more stringent requirements have been placed on the long-term stability of sealing materials in high-temperature engine oil environments. Traditional VDF / TFE binary fluororubber has significant shortcomings in oil resistance. According to the ASTM D471 standard method, after immersion in hot engine oil at 150°C, the volume expansion rate of this type of rubber is typically higher than 12%, significantly exceeding the critical requirement of less than 10% for this application scenario. Excessive swelling can lead to seal deformation, reduced sealing pressure, and ultimately, oil leakage, seriously threatening the reliable operation and service life of the engine.

[0004] Besides insufficient oil resistance, traditional VDF / TFE fluororubber also exhibits unsatisfactory processing performance. Its Mooney scorch time is generally short, often less than 5 minutes. In hot processing processes such as extrusion and molding, this excessively short scorch time easily leads to premature vulcanization (scorching) of the rubber compound within the mold cavity. This not only damages the appearance and physical and mechanical properties of the finished product but also causes production interruptions, mold contamination, and significantly reduces production efficiency and product yield.

[0005] To improve the aforementioned properties, existing technologies have attempted to introduce hexafluoropropylene (HFP) as a third monomer to form a VDF / TFE / HFP terpolymer. While the introduction of HFP improves processability to some extent, its effect on oil resistance is limited. The volume expansion rate of the prepared fluororubber in 150°C engine oil is still generally greater than 10%, failing to fundamentally solve the core problem of excessive swelling in high-temperature oil media. Furthermore, simple ternary random copolymerization offers limited control over the sequence structure and crystallization behavior of the polymer molecular chains, making it difficult to achieve the optimal balance between oil resistance and processability while ensuring resistance to various media.

[0006] Therefore, there is an urgent need in this field to develop a novel fluororubber formulation and synthesis process, which aims to significantly improve the oil resistance of the product while ensuring its excellent processing safety, so as to meet the higher requirements of the high-end equipment manufacturing industry, especially the next generation of high-performance automotive engines, for sealing materials. Utility Model Content

[0007] To address the problems described in the background art, such as insufficient oil resistance and poor processing safety of traditional VDF / TFE fluororubber, as well as the limited improvement effects of existing ternary copolymerization technologies, the primary objective of this invention is to provide an integrated device specifically for preparing high-performance oil-resistant fluororubber. Another objective of this invention is to provide a VDF / TFE / PMVE ternary copolymerization method based on this device. This method, by introducing a specific third monomer and employing a seed emulsion polymerization process, aims to significantly improve the oil resistance and processing safety of fluororubber.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: Firstly, this utility model provides an apparatus for preparing oil-resistant fluororubber by VDF / TFE / PMVE ternary copolymerization.

[0009] The core of this device is that it includes a prepolymerization unit, a main polymerization unit, and a post-processing unit connected sequentially through process pipelines, forming a continuous, closed, automated production system.

[0010] The core equipment of the prepolymerization unit is the prepolymerization reactor, which is equipped with a stirrer to ensure uniform mixing and heat transfer of materials. The feed inlet of the prepolymerization reactor is connected in parallel to multiple high-precision feed branches via pipelines, which constitute the reaction's "supply chain." The deionized water supply branch is equipped with a deionized water storage tank and a deionized water metering pump in sequence. The emulsifier supply branch is equipped with an emulsifier storage tank and an emulsifier metering pump in sequence; The initiator supply branch is equipped with an initiator storage tank and an initiator metering pump in sequence; Multiple individual supply branches are respectively equipped with TFE individual tanks and TFE individual metering pumps, VDF individual tanks and VDF individual metering pumps, and PMVE individual tanks and PMVE individual metering pumps.

[0011] The outlet of the prepolymerization reactor is connected to the main polymerization unit via a pipeline. The core equipment of the main polymerization unit is the main polymerization reactor, which is also equipped with a stirrer. The inlet of the main polymerization reactor not only receives the seed emulsion from the prepolymerization reactor, but is also connected via pipeline to the outlets of the aforementioned TFE, VDF, PMVE monomer metering pumps and initiator metering pump, thereby achieving precise and continuous feeding of remaining monomers and supplementary initiators. The outlet of the main polymerization reactor is finally connected via pipeline to the post-processing unit to complete the final product molding.

[0012] As a further optimization of this apparatus, both the prepolymerization reactor and the main polymerization reactor are equipped with jacketed temperature control systems and pressure monitoring devices, providing a hardware foundation for precise reaction control. Simultaneously, high-precision metering pumps are preferred for all metering pumps, which is crucial for achieving accurate material proportioning and ensuring batch-to-batch product consistency.

[0013] Secondly, this utility model provides a method for preparing oil-resistant fluororubber using the above-mentioned apparatus.

[0014] The essence of this method lies in the perfect integration of a specific monomer system with a seed emulsion polymerization process within the integrated apparatus. The method includes the following steps: Prepolymerization step: In a prepolymerization reactor, deionized water, emulsifier, and a portion of VDF, TFE, and PMVE monomers are introduced, followed by the addition of an initiator. The prepolymerization reaction is carried out under mild conditions of 40-50℃ and 0.5-1.0 MPa to generate a reactive seed emulsion. This step controls the monomer conversion rate at 10%-20%, laying the structural foundation for the subsequent main polymerization.

[0015] Main polymerization step: The obtained seed emulsion is transported to the main polymerization reactor, and the remaining VDF, TFE and PMVE monomers are added continuously or in batches. The main polymerization reaction is carried out under enhanced conditions of 60-70℃ and 1.5-2.0MPa until the monomer conversion rate is not less than 90%, and a fluororubber emulsion with high solid content is obtained.

[0016] Post-processing steps: The fluororubber emulsion obtained from the main polymerization is transported to the post-processing unit, where it undergoes conventional processes such as coagulation, washing, and drying to obtain the final oil-resistant fluororubber product.

[0017] The key control point of this method lies in the monomer ratio. The total molar ratio of VDF, TFE, and PMVE monomers is strictly controlled at VDF : TFE : PMVE = (55~59) : (36~40) : (3~7). A particularly preferred ratio is 57 : 38 : 5. This specific ratio, especially the introduction of 3%-7% PMVE, is crucial for successfully coordinating oil resistance and low-temperature performance, and controlling crystallization behavior.

[0018] Regarding the adjuvants, the initiator is preferably potassium persulfate, with a total usage of 0.5%-1.0% of the total monomer mass; the emulsifier is preferably sodium perfluorooctanoate, with a usage of 0.1%-0.5% of the total monomer mass. This adjuvant system exhibits good synergy with the seed emulsion process.

[0019] Through the coordinated control of the monomer ratio and process described above, this invention can ultimately precisely control the crystallinity of the obtained oil-resistant fluororubber within the ideal range of 20%-28%.

[0020] Thirdly, this utility model provides an oil-resistant fluororubber prepared by the above method.

[0021] This fluororubber product possesses excellent overall performance, with its most prominent features being: a volume expansion rate of less than 10% after immersion in engine oil at 150°C, preferably as low as approximately 8.5%; and a Mooney scorch time greater than 10 minutes, preferably up to 12 minutes. These superior performance indicators make it particularly suitable for manufacturing automotive engine seals that require extremely high oil resistance and processing safety.

[0022] Compared with the prior art, the present invention has the following significant advantages: A qualitative leap in oil resistance: By introducing PMVE as the third monomer and optimizing its ratio, in synergy with a specific polymerization process, the chain structure and crystallization behavior of the polymer are fundamentally changed, which greatly reduces the volume expansion rate of the product in high-temperature engine oil from the traditional >12% to <10%, and improves oil resistance by more than 30%, meeting the most demanding engine sealing requirements.

[0023] The processing safety window has been greatly expanded: the Mooney scorch time of the obtained fluororubber has been extended to more than 10 minutes, which is more than 100% higher than that of traditional materials (<5 min). This provides sufficient operating time for processing steps such as mixing, extrusion, and molding, greatly reducing the risk of scorch and improving production efficiency and product qualification rate.

[0024] High integration of equipment and good product consistency: The integrated equipment provided realizes the entire process of pipelined and closed production from prepolymerization, main polymerization to post-processing. Combined with high-precision metering pumps, it ensures the extreme stability of material ratio and process parameters, making it particularly suitable for large-scale continuous production and ensuring high batch consistency of product performance. Attached Figure Description

[0025] Figure 1 This is a structural diagram of an apparatus for preparing oil-resistant fluororubber using VDF / TFE / PMVE ternary copolymerization, according to this utility model.

[0026] Figure 1In the middle section: 1-Prepolymerization reactor; 1.1-Prepolymerization reactor agitator; 2-Main polymerization reactor; 2.1-Main polymerization reactor agitator; 3-TFE monomer tank; 3.1-TFE monomer metering pump; 4-VDF monomer tank; 4.1-VDF monomer metering pump; 5-PMVE monomer tank; 5.1-PMVE monomer metering pump; 6-Deionized water storage tank; 6.1-Deionized water metering pump; 7-Emulsifier storage tank; 7.1-Emulsifier metering pump; 8-Initiator storage tank; 8.1-Initiator metering pump; 9-Post-treatment unit. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. 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.

[0028] Example 1 This embodiment uses a set of equipment for pilot production as an example to illustrate the specific implementation of this utility model.

[0029] I. Device Composition and Connection Relationships The structure of the device described in this utility model is as follows: Figure 1 As shown, its core consists of a prepolymerization unit, a main polymerization unit, and a post-processing unit connected by pressure-resistant process pipelines (such as stainless steel 316L pipes).

[0030] 1. Prepolymerization unit The core equipment of this unit is the prepolymerization reactor 1, with an effective volume of 50L and a main body made of 316L stainless steel. This reactor is equipped with: 1.1 Prepolymerization reactor agitator: It adopts a frame-type anchor-type composite agitator, driven by a magnetically coupled agitator motor, and the speed can be steplessly adjusted within the range of 50-300 rpm.

[0031] Jacketed temperature control system: The jacket is welded to the outer wall of the prepolymerization reactor 1, forming a sealed cavity. The jacket is connected to a heat transfer medium circulation unit and a refrigerant circulation unit via external pipes. The heat transfer medium circulation unit includes an electric heater and a circulation pump, which heats the heat transfer oil and pumps it into the jacket; the refrigerant circulation unit includes a chiller unit, which provides circulating cooling water. A three-way regulating valve (equivalent to the heat transfer medium regulating valve and refrigerant regulating valve in the prior art) controls the proportion and flow rate of the heat transfer medium or refrigerant flowing into the jacket, thereby achieving precise control of the reaction temperature inside the reactor, with a temperature control accuracy of ±0.5℃.

[0032] Pressure monitoring device: A capacitive pressure transmitter (range 0-2.5MPa, accuracy 0.5%FS) is installed on the top cover of the prepolymerization reactor 1 to monitor and transmit the pressure signal inside the reactor to the DCS system in the central control room in real time.

[0033] The feed inlet of prepolymer reactor 1 is connected in parallel to the following branches via pipelines: Deionized water branch: It is equipped with a deionized water storage tank 6 and a deionized water metering pump 6.1 in sequence.

[0034] Emulsifier branch: Emulsifier storage tank 7 and emulsifier metering pump 7.1 are installed in sequence.

[0035] Initiator branch: Initiator storage tank 8 and initiator metering pump 8.1 are installed in sequence.

[0036] Individual branch circuits: Each is equipped with a TFE individual tank 3 and a mass flow meter 3.1, a VDF individual tank 4 and a VDF individual metering pump 4.1, and a PMVE individual tank 5 and a VDF individual metering pump 5.1.

[0037] 2. Main aggregation unit The core equipment of this unit is the main polymerization reactor 2, which has an effective volume of 200L. Its structure is similar to that of the prepolymerization reactor 1, but it is designed to operate at a higher pressure.

[0038] It is also equipped with a main polymerization reactor agitator 2.1, a jacket temperature control system and a pressure monitoring device. Its composition and working principle are the same as those of the prepolymerization unit, but the power and capacity are increased accordingly based on the size of the reactor.

[0039] The feed inlet of the main polymerization reactor 2 receives materials through two pipelines: one is directly connected to the discharge pipeline of the prepolymerization reactor 1 to receive seed emulsion; the other is connected to the outlet manifold of the aforementioned TFE, VDF, PMVE monomer metering pump and initiator metering pump to replenish monomers and initiators.

[0040] 3. Post-processing unit The post-processing unit 9 is a functional module whose inlet is connected to the discharge bottom valve of the main polymerization reactor 2 via a pipeline with a sight glass. The following conventional equipment from the prior art is integrated or sequentially connected within this unit according to the process flow: Condensation vessel: An open container with a stirrer used to receive fluororubber latex.

[0041] Coagulant preparation tank: Connected to the coagulation vessel via pipeline, it is used to add coagulants (such as aqueous solutions of calcium chloride and aluminum nitrate) to the coagulation vessel.

[0042] Vibrating screen or rotary drum filter: connected to the outlet of the coagulation vessel via a material pump, used to achieve preliminary solid-liquid separation.

[0043] Washing tank: Connected after the vibrating screen, it is used to wash rubber particles multiple times.

[0044] Screw extruder dewatering machine: The feed inlet is connected to the washing tank to mechanically dewater the washed wet granules.

[0045] Vacuum drying oven or fluidized bed dryer: The feed inlet is connected to the outlet of the extrusion dewatering machine, and the rubber granules are finally dried under negative pressure and heating conditions to obtain the finished product.

[0046] II. Preparation Steps The preparation of oil-resistant fluororubber using the above-described apparatus includes the following steps: 1. Prepolymerization: Start the jacket temperature control system of prepolymer reactor 1 and introduce circulating water to stabilize the reactor temperature at 45℃.

[0047] Deionized water, filling 50% of the vessel's volume, is added into the vessel using metering pump 6.1.

[0048] Add sodium perfluorooctanoate emulsifier at a rate of 0.3% of the total mass of the monomers using metering pump 7.1, and start stirrer 1.1 (150 rpm) to dissolve and disperse.

[0049] TFE 5 mol, VDF 10 mol, and PMVE 1 mol were added sequentially through metering pumps 3.1, 4.1, and 5.1.

[0050] The polymerization was initiated by slowly adding potassium persulfate (prepared as a 5% aqueous solution) at a rate of 0.3% of the total mass of the monomers using a metering pump 8.1.

[0051] The reaction temperature was maintained at 45±0.5℃ using a jacketed temperature control system, and the pressure monitoring device showed a pressure of 0.8MPa. The reaction was stopped when the monomer conversion rate reached approximately 15%, yielding a seed emulsion.

[0052] 2. Main Aggregator: The main polymerization reactor 2 is preheated to 65°C and pressure maintained at 1.8 MPa using a jacketed temperature control system.

[0053] All the seed emulsion in the prepolymerization vessel 1 is forced into the main polymerization vessel 2.

[0054] TFE 33mol, VDF 47mol, and PMVE 4mol (total molar ratio TFE:VDF:PMVE=38:57:5) were continuously added to the main polymerization reactor 2 using the mass flow meters of each monomer.

[0055] As needed, a small amount of initiator may be added via initiator metering pump 8.1.

[0056] The main polymerization temperature is precisely controlled at 65±0.5℃ using a jacketed temperature control system, and the pressure monitoring device ensures that the pressure is stable at 1.8±0.05 MPa. The stirring speed is set to 200 rpm.

[0057] The reaction is terminated when the monomer conversion rate is >90%, and the emulsion is transported to post-processing unit 9.

[0058] 3. Post-processing: The fluororubber latex was fed into a coagulation vessel, and a 5wt% calcium chloride aqueous solution was added under stirring to demulsify and coagulate.

[0059] The coagulated slurry particles are then subjected to solid-liquid separation using a vibrating screen.

[0060] The separated wet colloidal particles enter the washing tank and are washed three times with 60℃ hot water.

[0061] After washing, the granules are dehydrated by a screw extruder to remove most of their surface moisture.

[0062] Finally, the rubber granules were placed in a vacuum drying oven and dried at 80℃ and -0.095MPa for 4 hours to obtain a white oil-resistant fluororubber product.

[0063] Tests showed that the product exhibited an 8.5% volume expansion rate in engine oil at 150℃ and a Mooney scorch time of 12 minutes, demonstrating excellent performance.

Claims

1. An apparatus for preparing oil-resistant fluororubber via VDF / TFE / PMVE ternary copolymerization, characterized in that, This includes a prepolymerization unit, a main polymerization unit, and a post-processing unit connected via process pipelines; The prepolymerization unit includes a prepolymerization vessel (1), which is equipped with a prepolymerization vessel stirrer (1.1). The feed inlet of the prepolymerization reactor (1) is connected in parallel via a pipeline: A deionized water supply branch is provided with a deionized water storage tank (6) and a deionized water metering pump (6.1) in sequence on the branch. An emulsifier supply branch is provided with an emulsifier storage tank (7) and an emulsifier metering pump (7.1) in sequence on the branch. An initiator supply branch is provided with an initiator storage tank (8) and an initiator metering pump (8.1) in sequence. At least two individual supply branches are respectively equipped with a TFE individual tank (3) and a TFE individual metering pump (3.1), a VDF individual tank (4) and a VDF individual metering pump (4.1), and a PMVE individual tank (5) and a PMVE individual metering pump (5.1). The outlet of the prepolymerization reactor (1) is connected to the main polymerization unit via a conveying pipeline; The main polymerization unit includes a main polymerization reactor (2), which is equipped with a main polymerization reactor agitator (2.1); the feed inlet of the main polymerization reactor (2) is connected to the conveying pipeline, and is also connected to the outlet of the TFE monomer metering pump (3.1), VDF monomer metering pump (4.1), PMVE monomer metering pump (5.1) and initiator metering pump (8.1) through the pipeline; The discharge port of the main polymerization reactor (2) is connected to the post-processing unit (9) via a pipeline.

2. The apparatus according to claim 1, characterized in that, Both the prepolymerization reactor (1) and the main polymerization reactor (2) are equipped with a jacketed temperature control system and a pressure monitoring device.

3. The apparatus according to claim 1, characterized in that, The deionized water metering pump (6.1), emulsifier metering pump (7.1), initiator metering pump (8.1), TFE monomer metering pump (3.1), VDF monomer metering pump (4.1) and PMVE monomer metering pump (5.1) are all high-precision metering pumps.

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