High-efficiency preparation technology for step-by-step polymerization of tetrafluoroethylene-hexafluoropropylene copolymer

Abstract

The invention discloses a step-by-step polymerization efficient preparation technology of fluorinated ethylene propylene, and relates to the technical field of fluorine-containing polymers. The method is realized through two-step emulsion polymerization. In the first step, an initial emulsion is prepared, in the second step, the initial emulsion is used for expansion polymerization, and finally the high-purity FEP emulsion is obtained. The method has the advantages of simplicity and convenience in operation, easiness in control of reaction conditions, high polymerization efficiency and the like, and can be widely applied to preparation of high-performance fluorine materials.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorine-containing polymers, in particular to a high-efficiency preparation technology of polyperfluoroethylene propylene by step polymerization. Background Art

[0002] Fluorinated ethylene propylene (FEP) is a partially fluorinated copolymer made from tetrafluoroethylene (TFE) and hexafluoropropylene (HFP). FEP exhibits numerous excellent properties, including a very low coefficient of friction, exceptional chemical and high-temperature stability, and superior electrical insulation. It is widely used in cable sheathing, chemical equipment linings, anti-corrosion coatings, and high-frequency electronic components.

[0003] Traditional FEP preparation methods are mainly suspension polymerization and emulsion polymerization, but the following problems still exist:

[0004] Limitations of Suspension Polymerization

[0005] During suspension polymerization, tetrafluoroethylene (TFE) and hexafluoropropylene (HFP) struggle to maintain a stable copolymerization ratio due to gas-liquid equilibrium issues. This results in large fluctuations in the copolymer composition and a wide molecular weight distribution. Furthermore, suspension polymerization processes struggle to control particle size and uniformity, making them unsuitable for certain high-precision applications.

[0006] Disadvantages of traditional emulsion polymerization

[0007] In emulsion polymerization, although the reaction stability can be improved by introducing emulsifiers, the following deficiencies still exist in actual operation:

[0008] Low monomer conversion rate: Especially in the later stages, the concentration of reaction monomers decreases and the polymerization rate decreases significantly, resulting in insufficient monomer utilization.

[0009] Poor emulsion stability: Some systems are prone to emulsion separation or polymer precipitation problems under high temperature and high pressure.

[0010] Uneven molecular structure: Due to fluctuations in copolymerization reaction conditions, HFP is unevenly distributed in the polymer, affecting the melting properties and mechanical properties of FEP.

[0011] Economic issues

[0012] Ternary FEP is a widely used industrial product made from the copolymerization of tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and perfluoroalkyl vinyl ether. Its synthesis requires the simultaneous presence of all three monomers. However, this often results in excessive addition of the expensive perfluoroalkyl vinyl ether monomer, resulting in unnecessary waste and driving up production costs. Summary of the Invention

[0013] The present invention provides a high-efficiency preparation technology of polyperfluoroethylene propylene by step-by-step polymerization. Through the process innovation of step-by-step emulsion polymerization, the waste of perfluoroalkyl vinyl ether is effectively reduced, while also improving the monomer conversion rate and the consistency of product performance.

[0014] The specific plan is as follows:

[0015] A highly efficient preparation technology of polyperfluoroethylene propylene by step-by-step polymerization, the operating steps of which are as follows:

[0016] Step 1:

[0017] Add 400-500 parts of high-purity water to a reactor with a stirring speed of 20-50 rpm; add 2-10 parts of a surfactant; add 0.5-5 parts of a perfluoroalkyl vinyl ether monomer; and 0.05-0.5 parts of a fourth monomer; adjust the polymerization reactor to a reaction temperature of 1; add 10-20 parts of tetrafluoroethylene monomer to the reactor, and control the pressure in the reactor to a reaction pressure of 1; add 0.5-2 parts of an initiator solution to initiate a copolymerization reaction, and continuously add 1-5 parts of tetrafluoroethylene monomer and 1-3 parts of an initiator solution during the reaction; and after completion, recover unreacted monomer to obtain an initial emulsion;

[0018] Step 2:

[0019] Add 300-500 parts of the initial emulsion to the reactor, stirring at a speed of 10-30 rpm; add 2-10 parts of a surfactant; add 10-30 parts of a hexafluoropropylene monomer; add 3-10 parts of a tetrafluoroethylene monomer; adjust the polymerization kettle to a reaction temperature of 2; add 10-30 parts of a mixed gas of tetrafluoroethylene monomer and hexafluoropropylene monomer to the reactor, control the pressure in the reactor to a reaction pressure of 2; add 0.5-2 parts of an initiator solution to initiate a copolymerization reaction;

[0020] Step 3:

[0021] After the polymerization reaction starts, the initiator solution is continuously added into the reactor at a constant speed, and at the same time, the mixed monomer gas of tetrafluoroethylene and hexafluoropropylene is continuously added into the reactor, and the reaction pressure of the reactor is maintained at 3 and the reaction temperature is maintained at 3; when the total amount of the mixed monomer added reaches 50-150 parts, the monomer and initiator are stopped to terminate the copolymerization reaction; and the unreacted monomer is recovered to obtain a polyperfluoroethylene propylene resin emulsion.

[0022] Preferably, the surfactant is selected from one or a combination of ammonium perfluorooctanoate, perfluorohexyl sulfonate, and ammonium perfluorooctane sulfonate, and is an aqueous solution with a concentration of 10-60%.

[0023] Preferably, the perfluoroalkyl vinyl ether is one or a combination of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, and perfluoro-n-propyl vinyl ether.

[0024] Preferably, the preparation method of the fourth monomer is:

[0025] In a dry reaction vessel, 18-36 parts by weight of 2-phenylthiophenol, 35-70 parts of 3,3,4,4,5,5,6,6,7,7,8,8-dodecafluoro-1,9-decadiene, 0.06-0.4 parts of vinylferrocene, and 3-5 parts of triethylamine are added; 169-320 parts of tetrahydrofuran is used as a solvent, and the reactants are fully dissolved to form a uniform solution; the reaction temperature is 50-60° C., the reaction time is 100-130 minutes, and after the reaction is completed, the solvent tetrahydrofuran is removed by reduced pressure distillation to obtain a fourth monomer.

[0026] Preferably, the initiator solution is selected from one of aqueous solutions of ammonium persulfate (APS), potassium persulfate (KPS), or sodium persulfate (SPS), and the concentration of the solution is 2-10 wt%.

[0027] Preferably, the particle size of the initial emulsion is 20-50 nm, and the solid content of the initial emulsion is 1-8%.

[0028] Preferably, the molar ratio of tetrafluoroethylene to hexafluoropropylene in the mixed monomer is 8-18:1.

[0029] Preferably, in step 1, the reaction temperature 1 is 50-70° C., and the reaction pressure 1 is 1.0-1.5 MPa;

[0030] In step 2: the reaction temperature 2 is 70-90° C., and the reaction pressure 2 is 2.0-3.0 MPa;

[0031] In step 3: the reaction temperature 3 is 80-90° C., and the reaction pressure 3 is 2.0-2.8 MPa.

[0032] Technical effect:

[0033] 1) Introduction of Functional Groups: Through a thiol-olefin click chemistry addition reaction, biphenyl and dodecafluoro groups were successfully introduced into the fourth monomer's molecular structure. The biphenyl group's large conjugated system imparts excellent rigidity and heat resistance to the fourth monomer; the dodecafluoro group provides excellent chemical stability, low surface energy, and hydrophobicity. The addition of ferrocene reduces the polymer's melt viscosity and improves its processing properties, making it easier to process through extrusion, injection molding, and other processing operations, facilitating the preparation of various shapes.

[0034] 2) Impact on the FEP Stepwise Polymerization Process: Improving Copolymerization Performance: The unique molecular structure of the fourth monomer in the FEP stepwise polymerization process allows for better interaction with the FEP monomer, enhancing copolymerization activity and selectivity. The rigid structure of the biphenyl group increases interchain interactions, promoting copolymerization. The chemical stability of the dodecafluoro group reduces side reactions, improving polymerization efficiency and product purity.

[0035] 3) Improved Copolymer Performance: The introduction of the fourth monomer significantly improves the performance of the FEP copolymer. The presence of biphenyl and dodecafluoro functional groups in the fourth monomer enhances the copolymer's heat resistance, mechanical properties, chemical stability, and surface properties. The copolymer exhibits increased heat distortion temperature, tensile strength, and hardness, enhanced chemical tolerance, and improved surface hydrophobicity and antifouling properties.

[0036] 4) Expanding Applications: Fluorinated ethylene propylene copolymers, with their unique properties, can meet the needs of a wider range of applications. For example, in the electronics and electrical sectors, they can be used to manufacture high-temperature and corrosion-resistant insulation materials; in the aerospace sector, they can be used to prepare high-performance sealing materials and protective coatings; and in the chemical industry, they can be used to manufacture corrosion-resistant pipes and containers. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0038] Example 1

[0039] Step 1:

[0040] Add 450 kg of high-purity water to the reactor and set the stirring speed to 30 rpm. Then add 6 kg of surfactant (an aqueous solution of ammonium perfluorooctanoate, with a concentration of 40%), and then add 3 kg of perfluoroethyl vinyl ether monomer and 0.3 kg of the fourth monomer. Adjust the polymerization kettle to a reaction temperature of 60°C, and add 15 kg of tetrafluoroethylene monomer. After controlling the pressure in the kettle to 1.2 MPa, add 1 kg of an aqueous solution of ammonium persulfate (APS) (with a concentration of 5 wt%) as an initiator to initiate the copolymerization reaction. During the reaction, continue to add 2 kg of tetrafluoroethylene monomer and continuously add 1.5 kg of an aqueous solution of ammonium persulfate (APS) at the same time. After the reaction is completed, recover the unreacted monomer to obtain an initial emulsion (with a solid content of 5%).

[0041] Preparation method of the fourth monomer: In a dry reaction vessel, accurately weigh 27kg of 2-phenylthiophenol, 50kg of 3,3,4,4,5,5,6,6,7,7,8,8-twelve fluoro-1,9-decadiene, 0.2kg of vinyl ferrocene, and 4kg of triethylamine. Subsequently, 240kg of tetrahydrofuran was added as a solvent to ensure that all reactants were fully dissolved to form a uniform solution. The temperature of the reaction system was maintained at 55°C and the reaction was continued for 120 minutes. After the reaction was completed, the solvent tetrahydrofuran was completely removed by reduced pressure distillation to finally obtain the desired fourth monomer.

[0042] Step 2:

[0043] Add 400 kg of the initial emulsion to the reactor and adjust the stirring speed to 20 rpm. Next, add 8 kg of a surfactant (a 30% aqueous solution of perfluorohexanesulfonate), followed by 20 kg of hexafluoropropylene monomer and 5 kg of tetrafluoroethylene monomer. Adjust the reactor temperature to 80°C and add 20 kg of a mixture of tetrafluoroethylene and hexafluoropropylene monomers (at a molar ratio of 12:1). After controlling the pressure in the reactor to 2.5 MPa, add 1 kg of a 7 wt% aqueous solution of potassium persulfate (KPS) as an initiator to initiate the copolymerization reaction.

[0044] Step 3:

[0045] After the polymerization reaction began, a potassium persulfate (KPS) aqueous solution (7 wt% concentration) was continuously added to the reactor at a constant rate. Simultaneously, a mixed monomer gas of tetrafluoroethylene and hexafluoropropylene (molar ratio of 12:1) was added. The reaction pressure in the reactor was maintained at 2.4 MPa and the reaction temperature at 85°C. When the total amount of mixed monomers added reached 100 kg, the addition of monomers and initiator was stopped, terminating the copolymerization reaction. Unreacted monomers were recovered to obtain a poly(perfluoroethylene-propylene) resin emulsion.

[0046] Example 2

[0047] Step 1:

[0048] Add 420 kg of high-purity water to the reactor and set the stirring speed to 25 rpm. Add 4 kg of surfactant (50% concentration of ammonium perfluorooctane sulfonate aqueous solution), then add 1 kg of perfluoromethyl vinyl ether monomer and 0.1 kg of the fourth monomer. Adjust the polymerization kettle to a reaction temperature of 55°C and add 12 kg of tetrafluoroethylene monomer. After controlling the pressure in the kettle to 1.1 MPa, add 0.8 kg of sodium persulfate (SPS) aqueous solution (concentration of 4 wt%) as an initiator to initiate the copolymerization reaction. During the reaction, continue to add 3 kg of tetrafluoroethylene monomer and continuously add 1 kg of sodium persulfate (SPS) aqueous solution at the same time. After the reaction is completed, recover the unreacted monomer to obtain an initial emulsion (solid content of 6%).

[0049] The fourth monomer is prepared by adding 18 kg of 2-phenylthiophenol, 35 kg of 3,3,4,4,5,5,6,6,7,7,8,8-dodecafluoro-1,9-decadiene, 0.06 kg of vinylferrocene, and 3 kg of triethylamine to a dry reaction vessel. Then, 169 kg of tetrahydrofuran is added as a solvent to dissolve all substances to form a uniform solution. The reaction is allowed to proceed at a reaction temperature of 50°C for 100 minutes. After completion of the reaction, the tetrahydrofuran solvent is removed by vacuum distillation to obtain a pure fourth monomer.

[0050] Step 2:

[0051] Add 350 kg of the initial emulsion to the reactor and adjust the stirring speed to 15 rpm. Add 6 kg of surfactant (a mixed aqueous solution of ammonium perfluorooctanoate and perfluorohexyl sulfonate, each at a concentration of 25%, for a total of 6 kg), followed by 15 kg of hexafluoropropylene monomer and 8 kg of tetrafluoroethylene monomer. Adjust the reactor temperature to 75°C and add 15 kg of a mixture of tetrafluoroethylene and hexafluoropropylene monomers (at a molar ratio of 10:1). After controlling the reactor pressure to 2.2 MPa, add 1.2 kg of an aqueous solution of ammonium persulfate (APS) (at a concentration of 3 wt%) as an initiator to initiate the copolymerization reaction.

[0052] Step 3:

[0053] After the polymerization reaction began, an aqueous solution of ammonium persulfate (APS) (3 wt% concentration) was continuously added to the reactor at a constant rate. Simultaneously, a mixed monomer gas of tetrafluoroethylene and hexafluoropropylene (10:1 molar ratio) was added, maintaining the reactor pressure at 2.1 MPa and the reaction temperature at 82°C. When the total amount of mixed monomers added reached 80 kg, the addition of monomers and initiator was stopped, terminating the copolymerization reaction. Unreacted monomers were recovered to produce a poly(perfluoroethylene-propylene) resin emulsion.

[0054] Example 3

[0055] Step 1:

[0056] Add 500 kg of high-purity water to the reactor and set the stirring speed to 45 rpm. Add 10 kg of surfactant (an aqueous solution of ammonium perfluorooctanoate, with a concentration of 60%), and then add 2 kg of perfluoro-n-propyl vinyl ether monomer and 0.4 kg of the fourth monomer. Adjust the polymerization kettle to a reaction temperature of 70°C and add 20 kg of tetrafluoroethylene monomer thereto. After controlling the pressure in the kettle to 1.5 MPa, add 2 kg of potassium persulfate (KPS) aqueous solution (with a concentration of 10 wt%) as an initiator to initiate the copolymerization reaction. During the reaction, continue to add 5 kg of tetrafluoroethylene monomer and continuously add 3 kg of potassium persulfate (KPS) aqueous solution at the same time. After the reaction is completed, recover the unreacted monomer to obtain an initial emulsion (with a solid content of 2%).

[0057] Preparation method of the fourth monomer: In a pre-dried reaction vessel, weigh 36kg of 2-phenylthiophenol, 70kg of 3,3,4,4,5,5,6,6,7,7,8,8-dodecafluoro-1,9-decadiene, 0.4kg of vinylferrocene, and 5kg of triethylamine. Subsequently, 320kg of tetrahydrofuran solvent is added thereto to ensure that the reactants are completely dissolved to form a uniform solution system. The reaction temperature is set at 60°C and the reaction is allowed to continue for 130 minutes. After the reaction is completed, the solvent tetrahydrofuran is removed by vacuum distillation to obtain the target product, the fourth monomer.

[0058] Step 2:

[0059] Add 500 kg of the initial emulsion to the reactor and adjust the stirring speed to 30 rpm. Add 2 kg of a surfactant (a 10% aqueous solution of ammonium perfluorooctanesulfonate), followed by 30 kg of hexafluoropropylene monomer and 3 kg of tetrafluoroethylene monomer. Adjust the reactor temperature to 90°C and add 30 kg of a mixture of tetrafluoroethylene and hexafluoropropylene monomers (at a molar ratio of 18:1). After controlling the pressure in the reactor to 3.0 MPa, add 0.5 kg of a 2 wt% aqueous solution of sodium persulfate (SPS) as an initiator to initiate the copolymerization reaction.

[0060] Step 3:

[0061] After the polymerization reaction began, a sodium persulfate (SPS) aqueous solution (2 wt% concentration) was continuously added to the reactor at a constant rate. Simultaneously, a mixed monomer gas of tetrafluoroethylene and hexafluoropropylene (molar ratio of 18:1) was added. The reactor pressure was maintained at 2.8 MPa and the reaction temperature at 90°C. When the total amount of mixed monomers added reached 150 kg, the monomer and initiator additions were stopped, terminating the copolymerization reaction. Unreacted monomers were recovered to produce a fluoroethylene-propylene resin emulsion.

[0062] Example 4

[0063] Step 1:

[0064] Add 480 kg of high-purity water to the reactor and set the stirring speed to 20 rpm. Add 7 kg of surfactant (a mixed aqueous solution of perfluorohexane sulfonate and ammonium perfluorooctane sulfonate, each with a concentration of 35%, a total of 7 kg), and then add 0.5 kg of perfluoromethyl vinyl ether monomer and 0.05 kg of the fourth monomer. Adjust the polymerization kettle to a reaction temperature of 50°C and add 10 kg of tetrafluoroethylene monomer. After controlling the pressure in the kettle to 1.0 MPa, add 1.5 kg of ammonium persulfate (APS) aqueous solution (concentration of 8 wt%) as an initiator to initiate the copolymerization reaction. During the reaction, continue to add 1 kg of tetrafluoroethylene monomer and continuously add 2 kg of ammonium persulfate (APS) aqueous solution at the same time. After the reaction is completed, recover the unreacted monomer to obtain an initial emulsion (solid content of 8%).

[0065] Preparation of the fourth monomer: In a dry reaction vessel, accurately weigh 24 kg of 2-phenylthiophenol, 60 kg of 3,3,4,4,5,5,6,6,7,7,8,8-dodecafluoro-1,9-decadiene, 0.3 kg of vinylferrocene, and 4.5 kg of triethylamine. Then, add 280 kg of tetrahydrofuran as a solvent to fully dissolve and mix the reactants. Maintain the reaction temperature at 57°C and allow the reaction to proceed for 115 minutes. After completion of the reaction, remove the tetrahydrofuran solvent by vacuum distillation to obtain a pure fourth monomer product.

[0066] Step 2:

[0067] Add 300 kg of the initial emulsion to the reactor and adjust the stirring speed to 10 rpm. Add 4 kg of a surfactant (30% aqueous solution of ammonium perfluorooctanoate), followed by 10 kg of hexafluoropropylene monomer and 10 kg of tetrafluoroethylene monomer. Adjust the reactor temperature to 70°C and add 10 kg of a mixture of tetrafluoroethylene and hexafluoropropylene monomers (at a molar ratio of 8:1). After controlling the pressure in the reactor to 2.0 MPa, add 2 kg of a 6 wt% aqueous solution of potassium persulfate (KPS) as an initiator to initiate the copolymerization reaction.

[0068] Step 3:

[0069] After the polymerization reaction began, a potassium persulfate (KPS) aqueous solution (6 wt% concentration) was continuously added to the reactor at a constant rate. Simultaneously, a mixed monomer gas of tetrafluoroethylene and hexafluoropropylene (in a molar ratio of 8:1) was added. The reactor pressure was maintained at 2.0 MPa and the reaction temperature at 80°C. When the total amount of mixed monomers added reached 50 kg, the monomer and initiator additions were stopped, terminating the copolymerization reaction. Unreacted monomers were recovered to produce a fluoroethylene-propylene resin emulsion.

[0070] Comparative Example 1

[0071] The only difference between this example and Example 1 is that the fourth monomer is not added in step 1.

[0072] Comparative Example 2

[0073] The only difference between this example and Example 1 is that 2-phenylthiophenol is not added during the preparation of the fourth monomer in step 1.

[0074] Comparative Example 3

[0075] The only difference between this example and Example 1 is that 3,3,4,4,5,5,6,6,7,7,8,8-dodecafluoro-1,9-decadiene is not added during the preparation of the fourth monomer in step 1.

[0076] The test results of the above specific implementation plan are as follows:

[0077]

[0078] The applicant declares that the above-described embodiments are used to further illustrate the present invention, but the present invention is not limited to these embodiments. This does not mean that the present invention must rely on these embodiments in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for raw materials in the present invention, additions of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A high-efficiency preparation technology of polyperfluoroethylene propylene by step-by-step polymerization, the operation steps of which are as follows: Step 1: Add 400-500 parts by mass of high-purity water to a reactor with a stirring speed of 20-50 rpm; add 2-10 parts of a surfactant; add 0.5-5 parts of a perfluoroalkyl vinyl ether monomer; and 0.05-0.5 parts of a fourth monomer; adjust the polymerization reactor to a reaction temperature of 1; add 10-20 parts of tetrafluoroethylene monomer to the reactor, and control the pressure in the reactor to a reaction pressure of 1; add 0.5-2 parts of an initiator solution to initiate a copolymerization reaction, and continuously add 1-5 parts of tetrafluoroethylene monomer and 1-3 parts of an initiator solution during the reaction; and after completion, recover unreacted monomer to obtain an initial emulsion; Step 2: Add 300-500 parts of the initial emulsion to the reactor, stirring at a speed of 10-30 rpm; add 2-10 parts of a surfactant; add 10-30 parts of a hexafluoropropylene monomer; add 3-10 parts of a tetrafluoroethylene monomer; adjust the polymerization kettle to a reaction temperature of 2; add 10-30 parts of a mixed gas of tetrafluoroethylene monomer and hexafluoropropylene monomer to the reactor, control the pressure in the reactor to a reaction pressure of 2; add 0.5-2 parts of an initiator solution to initiate a copolymerization reaction; Step 3: After the polymerization reaction begins, the initiator solution is continuously added to the reactor at a constant rate, and at the same time, a mixed monomer gas of tetrafluoroethylene and hexafluoropropylene is continuously added to the reactor, and the reaction pressure and reaction temperature of the reactor are maintained at 3; when the total amount of the mixed monomer added reaches 50-150 parts, the monomer and initiator are stopped to terminate the copolymerization reaction; and the unreacted monomer is recovered to obtain a polyperfluoroethylene propylene resin emulsion; The fourth monomer is prepared by reacting 2-phenylthiophenol, 3,3,4,4,5,5,6,6,7,7,8,8-dodecafluoro-1,9-decadiene and vinylferrocene.

2. The high-efficiency preparation technology of polyperfluoroethylene-propylene by step-by-step polymerization according to claim 1, characterized in that: The surfactant is selected from one or a combination of ammonium perfluorooctanoate, perfluorohexyl sulfonate, and ammonium perfluorooctane sulfonate, and is in the form of an aqueous solution with a concentration of 10-60%.

3. The high-efficiency preparation technology of polyperfluoroethylene-propylene by step-by-step polymerization according to claim 1, characterized in that: The perfluoroalkyl vinyl ether is one or a combination of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, and perfluoro-n-propyl vinyl ether.

4. The high-efficiency preparation technology of polyperfluoroethylene-propylene by step-by-step polymerization according to claim 1, characterized in that: The preparation method of the fourth monomer is: In a dry reaction vessel, 18-36 parts by weight of 2-phenylthiophenol, 35-70 parts of 3,3,4,4,5,5,6,6,7,7,8,8-dodecafluoro-1,9-decadiene, 0.06-0.4 parts of vinylferrocene, and 3-5 parts of triethylamine are added; 169-320 parts of tetrahydrofuran is used as a solvent, and the reactants are fully dissolved to form a uniform solution; the reaction temperature is 50-60° C., the reaction time is 100-130 minutes, and after the reaction is completed, the solvent tetrahydrofuran is removed by reduced pressure distillation to obtain a fourth monomer.

5. The high-efficiency preparation technology of polyperfluoroethylene propylene by step-by-step polymerization according to claim 1, characterized in that: The initiator solution is selected from an aqueous solution of ammonium persulfate, potassium persulfate, or sodium persulfate, and the concentration of the solution is 2-10 wt%.

6. The high-efficiency preparation technology of polyperfluoroethylene-propylene by step-by-step polymerization according to claim 1, characterized in that: The particle size of the initial emulsion is 20-50 nm, and the solid content of the initial emulsion is 1-8%.

7. The high-efficiency preparation technology of polyperfluoroethylene-propylene by step-by-step polymerization according to claim 1, characterized in that: The molar ratio of tetrafluoroethylene to hexafluoropropylene in the mixed monomer is 8-18:

1.

8. The high-efficiency preparation technology of polyperfluoroethylene-propylene by step-by-step polymerization according to claim 1, characterized in that: In the step 1: the reaction temperature 1 is 50-70° C., and the reaction pressure 1 is 1.0-1.5 MPa; In step 2: the reaction temperature 2 is 70-90° C., and the reaction pressure 2 is 2.0-3.0 MPa; In step 3: the reaction temperature 3 is 80-90° C., and the reaction pressure 3 is 2.0-2.8 MPa.

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