Synthesis process of chain flexible fluorinated ethylene propylene resin

Abstract

The invention discloses a synthesis process of chain flexible fluorinated ethylene propylene resin, and relates to the technical field of fluorine-containing polymer synthesis. The process comprises the following steps of: deoxidizing and preparing a water phase, introducing an emulsifying system, adding an initial monomer, adding an initiator and a chain transfer agent, monitoring a gas phase, controlling a supplemented monomer, terminating polymerization, treating an emulsion and the like. Particularly, a chain flexibility modifier is introduced in the polymerization process, so that the flexibility of a polymer chain segment is improved, and the flowability and the stability of a melt are improved. By precisely controlling the synergistic effect of the gas phase composition and the chain flexibility modifier, the melt index fluctuation is remarkably reduced, and the processing defects such as bubbles and wiredrawing phenomena are reduced. Compared with the prior art, the preparation method has the advantages that the melting uniformity of the resin is improved, the elongation at break and the processing stability are improved, and the preparation method is suitable for preparing the high-performance FEP resin.

Description

Technical Field

[0001] This invention relates to the field of fluoropolymer synthesis technology, and in particular to a synthesis process for a chain-flexible perfluoroethylene propylene resin. Background Technology

[0002] Perfluoroethylene propylene (FEP) is a fluoropolymer prepared by free radical emulsion copolymerization of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP). It has good chemical resistance, low coefficient of friction, high temperature resistance, and melt processability (e.g., by injection molding or screw extrusion). FEP typically contains about 5%-20% (mol%) of HFP to compensate for the relatively poor polymerization properties of HFP and to regulate the polymer's melting point and mechanical properties.

[0003] Existing methods for preparing FEP (Fluoroethylene Polypropylene) mostly employ emulsion polymerization, such as using a persulfate initiator and a perfluoropolyether ammonium carboxylate (PFOS) emulsifier system to carry out a TFE / HFP copolymerization reaction in an aqueous phase. This type of technology is documented in published patents. For example, patent document US7125941B2 proposes polymerizing fluorinated monomers in an aqueous emulsion and stabilizing the system with an emulsifier to form a polymer. Patent CN107880202A uses an emulsion polymerization method with an inorganic initiator to prepare a poly(fluoroethylene propylene) resin emulsion, which is then coagulated, washed, and sintered to obtain the final product. CN105504133B uses tetrafluoroethylene, hexafluoropropylene, and perfluoroalkyl vinyl ether as comonomers. A pH buffer, chelating agent, and emulsifier are added to pure water, followed by a fluorocarbon solvent and an initial monomer mixture. The polymerization reaction is initiated under specific temperature and pressure, with additional monomer mixture added during the reaction to ultimately obtain modified poly(fluoroethylene propylene). The polytetrafluoroethylene propylene resin prepared by the above method exhibits large batch-to-batch fluctuations in its properties, poor melt uniformity and stability, and may produce defects during processing.

[0004] In actual industrial preparation processes, fluctuations in the molar ratio of HFP to TFE in the gas phase can cause uneven monomer distribution during polymerization. This unevenness usually leads to problems such as poor melt uniformity of the final FEP, unstable melt flow, wide molecular weight distribution, and inconsistent melt distribution in areas of overheating during processing. Consequently, defects such as bubbles, stringing, and surface blemishes are prone to occur during extrusion or injection molding.

[0005] Furthermore, existing technologies rarely address the addition of additives to the polymerization system to improve chain flexibility and further enhance melt processing performance. Current methods mostly focus on molecular structure and terminal group design, but exploration of post-polymerization additive introduction and chain flexibility improvement is insufficient. Summary of the Invention

[0006] Based on the problems raised in the background art, the present invention proposes a synthesis process for chain-flexible perfluoroethylene propylene resin.

[0007] The technical solution is as follows: A synthesis process for a chain-flexible perfluoroethylene propylene resin, comprising the following steps by weight: Step 1: Deoxygenation and Aqueous Phase Preparation Add 25-35 parts of deionized water to the reactor and vacuum treat it until the oxygen content is ≤30ppm; Step 2: Introduction of the emulsion system Add 0.03-0.05 parts of perfluoropolyether ammonium carboxylate emulsifier to the reactor; Step 3: Initial monomer addition and pressurization Heat to 45-60℃; add the initial mixed monomers of tetrafluoroethylene and hexafluoropropylene until the pressure in the reactor reaches 3.0-4.0 MPa. Step 4: Addition of initiator and chain transfer agent When the pressure reaches the required level, add 0.01-0.1 parts of initiator, 0.02-0.08 parts of chain transfer agent, and chain flexibility modifier to initiate emulsion polymerization; Step 5: Gas phase monitoring and monomer replenishment control Depending on the pressure of the reactor, tetrafluoroethylene and hexafluoropropylene are dynamically added as a mixed monomer to maintain the pressure fluctuation of the reactor not exceeding 50 kPa. Step 6: Polymerization Termination and Emulsion Treatment When the solid content of the emulsion reaches 30-40 wt%, the reaction is terminated; unreacted monomers are recovered. Step 7: Mixing, Coagulation and Drying The emulsion was added to a MgCl2 coagulation system for coagulation, followed by vacuum drying to obtain FEP resin containing a chain flexibility modifier.

[0008] Preferably, the perfluoropolyether carboxylic acid ammonium emulsifier is selected from one of perfluorooctanoic acid ammonium, perfluorooctanoic acid potassium, and perfluorooctanoic acid sodium.

[0009] Preferably, the initial molar ratio of the tetrafluoroethylene to the hexafluoropropylene monomers is (25-55):(45-75).

[0010] Preferably, the initiator is selected from potassium persulfate or ammonium persulfate.

[0011] Preferably, the chain transfer agent is selected from diethyl malonate, methanol, methyl formate, and cyclohexane.

[0012] Preferably, the amount of the chain flexibility modifier added is 0.3-0.6 wt% of the total amount of the initial mixed monomers of tetrafluoroethylene and hexafluoropropylene.

[0013] Preferably, the method for preparing the chain flexibility modifier is as follows: Add 1200-2400 parts of solvent toluene to the reaction vessel, followed by 50-100 parts of 1,1,3,3-tetramethyldisiloxane, 60-120 parts of allyl glycidyl ether and 50-100 parts of allyl cyclodextrin. Subsequently, 0.05-0.1 parts of the catalyst chloroplatinic acid-vinylsiloxane complex were added, and the reaction was carried out at 75-85°C for 110-140 minutes. The chain flexibility modifier was obtained by removing toluene by atmospheric distillation at 110-120°C.

[0014] Preferably, the molar ratio of the tetrafluoroethylene to the hexafluoropropylene added mixed monomer is (5-15):(85-95).

[0015] Reaction mechanism The Si-H bonds of 1,1,3,3-tetramethyldisiloxane undergo hydrosilylation with the allyl groups of allyl glycidyl ether and allyl cyclodextrin, respectively. Toluene, as a solvent, can dissolve the raw materials and improve the reaction contact efficiency. The cavity structure of cyclodextrin can encapsulate fluorinated monomers, increasing the solubility of monomers in the system. At the same time, the silicon-oxygen segments regulate the flexibility of the copolymer molecular chain.

[0016] Compared with the prior art, the present invention has the following advantages: 1) Solid chain flexible additives participate in the copolymerization process, inserting or connecting between polymer chains to improve the flexibility and fluidity of the entire melt system, thereby improving melt uniformity and stability and increasing the elongation at break of the resin.

[0017] 2) Thanks to the synergistic effect of precise gas phase control and chain flexibility improvement additives, the batch-to-batch melt index (MFR) fluctuation is small.

[0018] 3) Defect rates such as bubble rate and stringing phenomenon in extrusion molding have been effectively improved. Detailed Implementation

[0019] The features of the present invention are further illustrated below through embodiments, but the scope of protection of this patent is not limited to the embodiments. Example 1

[0020] Raw materials and parameters: Deionized water: 25 kg Perfluoropolyether ammonium carboxylate emulsifier (ammonium perfluorooctanoate): 0.03 kg Initiator (potassium persulfate): 0.01 kg Chain transfer agent (diethyl malonate): 0.02 kg Chain flexibility modifier: 0.3 wt% of total monomers Emulsion solids content: 30wt% Synthesis steps: Deoxygenation and aqueous phase preparation (step 1): Add 25 kg of deionized water to the reactor and treat it under vacuum until the oxygen content is ≤30 ppm.

[0021] Emulsion system introduction (step 2): Add 0.03 kg of ammonium perfluorooctanoate to the reaction system.

[0022] Initial monomer addition and pressurization (step 3): Heat to 45°C, add the initial mixed monomers with a TFE:HFP molar ratio of 25:75, until the pressure in the reactor reaches 3.0 MPa.

[0023] Initiator and chain transfer agent addition (step 4): After the pressure stabilizes, add 0.01 kg potassium persulfate, 0.02 kg diethyl malonate, and 0.3 wt% of chain flexibility modifier to initiate emulsion polymerization.

[0024] Gas phase monitoring and monomer replenishment control (step 5): Based on pressure changes, dynamically replenish the mixed monomers with a TFE:HFP molar ratio of 5:95 to maintain pressure fluctuations ≤50kPa.

[0025] Polymerization termination and emulsion treatment (step 6): When the solid content of the emulsion reaches 30 wt%, the reaction is terminated and unreacted monomers are recovered.

[0026] Mixing, coagulation and drying (step 7): The emulsion was added to the MgCl2 coagulation system for coagulation, and then vacuum dried at 80°C for 8 hours to obtain the chain flexible FEP resin.

[0027] Preparation of chain flexibility modifier: 1200 g of toluene was added to the reaction vessel, followed by 50 g of 1,1,3,3-tetramethyldisiloxane, 60 g of allyl glycidyl ether, and 50 g of allyl cyclodextrin.

[0028] Add 0.05 g of chloroplatinic acid-vinylsiloxane complex and react at 75°C for 110 minutes.

[0029] Toluene was removed by distillation at 110℃ and atmospheric pressure to obtain a chain flexibility modifier. Example 2

[0030] Raw materials and parameters: Deionized water: 28 kg Perfluoropolyether ammonium carboxylate emulsifier (potassium perfluorooctanoate): 0.04 kg Initiator (ammonium persulfate): 0.03 kg Chain transfer agent (methanol): 0.04 kg Chain flexibility modifier: 0.4 wt% of total monomers Emulsion solids content: 33wt% Synthesis steps: Deoxygenation and aqueous phase preparation (step 1): Add 28 kg of deionized water to the reactor and vacuum process until the oxygen content is ≤30 ppm.

[0031] Emulsion system introduction (step 2): Add 0.04 kg of potassium perfluorooctanoate.

[0032] Initial monomer addition and pressurization (step 3): Heat to 50°C, add the initial mixed monomers with a TFE:HFP molar ratio of 35:65, and pressurize to 3.3 MPa.

[0033] Initiator and chain transfer agent addition (step 4): Add 0.03 kg ammonium persulfate, 0.04 kg methanol, and 0.4 wt% of chain flexibility modifier (total monomer amount).

[0034] Gas phase monitoring and monomer replenishment control (step 5): Replenish with a mixed monomer with a TFE:HFP molar ratio of 8:92 to maintain pressure stability.

[0035] Polymerization termination and emulsion treatment (step 6): The reaction is terminated when the solid content reaches 33 wt%, and the monomer is recovered.

[0036] Mixing, coagulation and drying (step 7): After coagulation with MgCl2, the product is dried under vacuum at 85°C for 7 hours to obtain the product.

[0037] Preparation of chain flexibility modifier: Add 70 g of 1,1,3,3-tetramethyldisiloxane, 80 g of allyl glycidyl ether, and 70 g of allyl cyclodextrin to 1500 g of toluene.

[0038] Add 0.06 g of chloroplatinic acid-vinylsiloxane complex, react at 78°C for 120 minutes, and remove toluene by distillation at 112°C. Example 3

[0039] Raw materials and parameters: Deionized water: 32 kg Perfluoropolyether ammonium carboxylate emulsifier (sodium perfluorooctanoate): 0.045 kg Initiator (ammonium persulfate): 0.06 kg Chain transfer agent (methyl formate): 0.06 kg Chain flexibility modifier: 0.5 wt% of total monomers Emulsion solids content: 37wt% Synthesis steps: Deoxygenation and aqueous phase preparation (step 1): 32 kg of deionized water is vacuum deoxygenated to ≤30 ppm.

[0040] Emulsion system introduction (step 2): Add 0.045 kg of sodium perfluorooctanoate.

[0041] Initial monomer addition and pressurization (step 3): Heat to 55°C, add initial monomer with a TFE:HFP molar ratio of 45:55, and increase the pressure to 3.7 MPa.

[0042] Initiator and chain transfer agent addition (step 4): Add 0.06 kg ammonium persulfate, 0.06 kg methyl formate, and 0.5 wt% modifier of total monomers.

[0043] Gas phase monitoring and monomer replenishment control (step 5): Replenish monomers with a TFE:HFP molar ratio of 12:88 to maintain pressure stability.

[0044] Polymerization termination and emulsion treatment (step 6): The reaction was terminated when the solid content was 37 wt%.

[0045] Mixing, coagulation and drying (step 7): After coagulation, vacuum dry at 90°C for 6 hours to obtain the product.

[0046] Preparation of chain flexibility modifier: Add 85 g of 1,1,3,3-tetramethyldisiloxane, 100 g of allyl glycidyl ether, and 85 g of allyl cyclodextrin to 2000 g of toluene.

[0047] Add 0.08 g of chloroplatinic acid-vinylsiloxane complex, react at 82°C for 130 minutes, and remove toluene by distillation at 115°C. Example 4

[0048] Raw materials and parameters: Deionized water: 35 kg Perfluoropolyether ammonium carboxylate emulsifier (ammonium perfluorooctanoate): 0.05 kg Initiator (potassium persulfate): 0.1 kg Chain transfer agent (cyclohexane): 0.08 kg Chain flexibility modifier: 0.6 wt% of total monomers Emulsion solids content: 40wt% Synthesis steps: Deoxygenation and aqueous phase preparation (step 1): 35 kg of deionized water is vacuum deoxygenated to ≤30 ppm.

[0049] Emulsion system introduction (step 2): Add 0.05 kg of ammonium perfluorooctanoate.

[0050] Initial monomer addition and pressurization (step 3): Heat to 60°C, add initial monomer with a TFE:HFP molar ratio of 55:45, and pressurize to 4.0 MPa.

[0051] Initiator and chain transfer agent addition (step 4): Add 0.1 kg potassium persulfate, 0.08 kg cyclohexane, and 0.6 wt% modifier of total monomer.

[0052] Gas phase monitoring and monomer replenishment control (step 5): Replenish monomers with a TFE:HFP molar ratio of 15:85 to maintain pressure fluctuation ≤50kPa.

[0053] Polymerization termination and emulsion treatment (step 6): The reaction is terminated when the solid content is 40 wt%, and the monomer is recovered.

[0054] Mixing, coagulation and drying (step 7): After coagulation, vacuum dry at 95°C for 5 hours to obtain chain flexible FEP resin.

[0055] Preparation of chain flexibility modifier: Add 100 g of 1,1,3,3-tetramethyldisiloxane, 120 g of allyl glycidyl ether, and 100 g of allyl cyclodextrin to 2400 g of toluene.

[0056] Add 0.1 g of chloroplatinic acid-vinylsiloxane complex, react at 85°C for 140 minutes, and remove toluene by distillation at 120°C.

[0057] Comparative Example 1 Raw materials and parameters: Deionized water: 25 kg Perfluoropolyether ammonium carboxylate emulsifier (ammonium perfluorooctanoate): 0.03 kg Initiator (potassium persulfate): 0.01 kg Chain transfer agent (diethyl malonate): 0.02 kg Chain flexibility modifier: 0.3 wt% of total monomers Emulsion solids content: 30wt% Synthesis steps: Deoxygenation and aqueous phase preparation (step 1): Add 25 kg of deionized water to the reactor and treat it under vacuum until the oxygen content is ≤30 ppm.

[0058] Emulsion system introduction (step 2): Add 0.03 kg of ammonium perfluorooctanoate to the reaction system.

[0059] Initial monomer addition and pressurization (step 3): Heat to 45°C, add the initial mixed monomers with a TFE:HFP molar ratio of 25:75, until the pressure in the reactor reaches 3.0 MPa.

[0060] Initiator and chain transfer agent addition (step 4): After the pressure stabilizes, add 0.01 kg potassium persulfate and 0.02 kg diethyl malonate to initiate emulsion polymerization.

[0061] Gas phase monitoring and monomer replenishment control (step 5): Based on pressure changes, dynamically replenish the mixed monomers with a TFE:HFP molar ratio of 5:95 to maintain pressure fluctuations ≤50kPa.

[0062] Polymerization termination and emulsion treatment (step 6): When the solid content of the emulsion reaches 30 wt%, the reaction is terminated and unreacted monomers are recovered.

[0063] Mixing, coagulation and drying (step 7): The emulsion was added to the MgCl2 coagulation system for coagulation, and then vacuum dried at 80°C for 8 hours to obtain the chain flexible FEP resin.

[0064] Comparative Example 2 Raw materials and parameters: Deionized water: 25 kg Perfluoropolyether ammonium carboxylate emulsifier (ammonium perfluorooctanoate): 0.03 kg Initiator (potassium persulfate): 0.01 kg Chain transfer agent (diethyl malonate): 0.02 kg Chain flexibility modifier: 0.3 wt% of total monomers Emulsion solids content: 30wt% Synthesis steps: Deoxygenation and aqueous phase preparation (step 1): Add 25 kg of deionized water to the reactor and treat it under vacuum until the oxygen content is ≤30 ppm.

[0065] Emulsion system introduction (step 2): Add 0.03 kg of ammonium perfluorooctanoate to the reaction system.

[0066] Initial monomer addition and pressurization (step 3): Heat to 45°C, add the initial mixed monomers with a TFE:HFP molar ratio of 25:75, until the pressure in the reactor reaches 3.0 MPa.

[0067] Initiator and chain transfer agent addition (step 4): After the pressure stabilizes, add 0.01 kg potassium persulfate, 0.02 kg diethyl malonate, and 0.3 wt% of chain flexibility modifier to initiate emulsion polymerization.

[0068] Gas phase monitoring and monomer replenishment control (step 5): Based on pressure changes, dynamically replenish the mixed monomers with a TFE:HFP molar ratio of 5:95 to maintain pressure fluctuations ≤50kPa.

[0069] Polymerization termination and emulsion treatment (step 6): When the solid content of the emulsion reaches 30 wt%, the reaction is terminated and unreacted monomers are recovered.

[0070] Mixing, coagulation and drying (step 7): The emulsion was added to the MgCl2 coagulation system for coagulation, and then vacuum dried at 80°C for 8 hours to obtain the chain flexible FEP resin.

[0071] Preparation of chain flexibility modifier: 1200 g of toluene was added to the reaction vessel, followed by 60 g of allyl glycidyl ether and 50 g of allyl cyclodextrin.

[0072] Add 0.05 g of chloroplatinic acid-vinylsiloxane complex and react at 75°C for 110 minutes.

[0073] Toluene was removed by distillation at 110℃ and atmospheric pressure to obtain a chain flexibility modifier.

[0074] Comparative Example 3 Raw materials and parameters: Deionized water: 25 kg Perfluoropolyether ammonium carboxylate emulsifier (ammonium perfluorooctanoate): 0.03 kg Initiator (potassium persulfate): 0.01 kg Chain transfer agent (diethyl malonate): 0.02 kg Chain flexibility modifier: 0.3 wt% of total monomers Emulsion solids content: 30wt% Synthesis steps: Deoxygenation and aqueous phase preparation (step 1): Add 25 kg of deionized water to the reactor and treat it under vacuum until the oxygen content is ≤30 ppm.

[0075] Emulsion system introduction (step 2): Add 0.03 kg of ammonium perfluorooctanoate to the reaction system.

[0076] Initial monomer addition and pressurization (step 3): Heat to 45°C, add the initial mixed monomers with a TFE:HFP molar ratio of 25:75, until the pressure in the reactor reaches 3.0 MPa.

[0077] Initiator and chain transfer agent addition (step 4): After the pressure stabilizes, add 0.01 kg potassium persulfate, 0.02 kg diethyl malonate, and 0.3 wt% of chain flexibility modifier to initiate emulsion polymerization.

[0078] Gas phase monitoring and monomer replenishment control (step 5): Based on pressure changes, dynamically replenish the mixed monomers with a TFE:HFP molar ratio of 5:95 to maintain pressure fluctuations ≤50kPa.

[0079] Polymerization termination and emulsion treatment (step 6): When the solid content of the emulsion reaches 30 wt%, the reaction is terminated and unreacted monomers are recovered.

[0080] Mixing, coagulation and drying (step 7): The emulsion was added to the MgCl2 coagulation system for coagulation, and then vacuum dried at 80°C for 8 hours to obtain the chain flexible FEP resin.

[0081] Preparation of chain flexibility modifier: 1200 g of toluene was added to the reaction vessel, followed by 50 g of 1,1,3,3-tetramethyldisiloxane and 60 g of allyl glycidyl ether.

[0082] Add 0.05 g of chloroplatinic acid-vinylsiloxane complex and react at 75°C for 110 minutes.

[0083] Toluene was removed by distillation at 110℃ and atmospheric pressure to obtain a chain flexibility modifier.

[0084] Test method: 1. Melt Flow Index (MFR) Test Test standards and methods: The test was conducted according to ASTM D1238, with the temperature controlled at 260°C, a load of 5 kg, and the melt flow rate (g / 10 min) measured after heating and pre-stabilizing for 5 minutes. Each embodiment was repeated three times, and the three samples were measured. The average value was taken and the standard deviation was calculated.

[0085] 2. Differential Scanning Calorimetry (DSC) Test standards and methods: The melt peak width and thermal profile of FEP resin were tested according to ASTM D4591-07, and the thermal behavior and crystallization consistency of the material were evaluated against the reference temperature. 3. Elongation at break: ASTM D638-22 standard was adopted. Specimen type: Type I (thickness ≤ 3.2 mm). Tensile speed: 50 mm / min, selected according to material hardness. Test results: MFR (g / 10min) MFR fluctuation range (±%) Half-width at half maximum (ΔT_m) of the melting peak Elongation at break % Example 1 12.4 ±3.5 3.2 366 Example 2 13.0 ±3.2 3.0 375 Example 3 13.6 ±3.0 2.9 382 Example 4 14.2 ±2.9 2.7 390 Comparative Example 1 12.6 ±4.6 4.0 348 Comparative Example 2 12.3 ±4.0 3.5 356 Comparative Example 3 12.4 ±3.8 3.4 359 The above examples and comparative examples effectively demonstrate that this method improves melt uniformity and stability, increases resin elongation at break, and exhibits small batch-to-batch melt index (MFR) fluctuations.

[0086] The above are merely specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent substitutions, or modifications made based on the present invention to solve essentially the same technical problems and achieve essentially the same technical effects are all covered within the protection scope of the present invention.

Claims

1. A process for the synthesis of a chain flexible polyfluoroethylene propylene resin, characterized in that, According to the quality parts, including the following steps: Step 1: oxygen removal and water phase preparation Into the reactor, 25-35 parts of deionized water was added and vacuum treated to oxygen content ≤30ppm; Step 2: emulsion system introduction Into the reactor, 0.03-0.05 parts of ammonium perfluoropolyether carboxylate emulsifier was added; Step 3: initial monomer addition and pressurization Heated to 45-60℃; added initial mixed monomers of tetrafluoroethylene and hexafluoropropylene, until the pressure of the reactor was 3.0-4.0MPa, Step 4: initiator and chain transfer agent addition When the pressure reached the requirement, 0.01-0.1 parts of initiator, 0.02-0.08 parts of chain transfer agent and chain flexibility modifier were added, and the emulsion polymerization was initiated; Step 5: gas phase monitoring and monomer addition control According to the pressure of the reactor, the additional mixed monomers of tetrafluoroethylene and hexafluoropropylene were dynamically added to maintain the pressure fluctuation of the reactor within 50kPa; Step 6: polymerization termination and emulsion treatment When the solid content of the emulsion reached 30-40wt%, the reaction was terminated; the unreacted monomers were recovered; Step 7: mixing, coagulation and drying The emulsion was added into the MgCl2 coagulation system for coagulation, and then vacuum dried to obtain FEP resin containing chain flexibility modifier; The chain flexibility modifier was prepared by reaction of 1,1,3,3-tetramethyldisiloxane, allyl glycidyl ether, allyl-cyclodextrin and catalyst chloroplatinic acid-vinylsiloxane complex.

2. The process for the synthesis of chain flexible poly perfluoroalkyl vinyl ether resin as claimed in claim 1, wherein: The ammonium perfluoropolyether carboxylate emulsifier is selected from one of ammonium perfluorooctanoate, potassium perfluorooctanoate and sodium perfluorooctanoate.

3. The process for synthesis of chain flexible poly perfluoroalkyl vinyl ether resin as claimed in claim 1, wherein: The molar ratio of the initial mixed monomers of tetrafluoroethylene and hexafluoropropylene is (25-55):(45-75).

4. The process for synthesis of chain flexible poly perfluoroalkyl vinyl ether resin as claimed in claim 1, wherein: The initiator is selected from potassium persulfate or ammonium persulfate.

5. The process for synthesis of chain flexible poly perfluoroalkyl vinyl ether resin as claimed in claim 1, wherein: The chain transfer agent is selected from one of malonic acid diethyl ester, methanol, methyl formate and cyclohexane.

6. The process for synthesis of chain flexible poly perfluoroalkyl vinyl ether resin as claimed in claim 1, wherein: The addition amount of the chain flexibility modifier is 0.3-0.6wt% of the total amount of the initial mixed monomers of tetrafluoroethylene and hexafluoropropylene.

7. The process for synthesis of chain flexible poly perfluoroalkyl vinyl ether resin as claimed in claim 1, wherein: The preparation method of the chain flexibility modifier: Into the reaction vessel, 1200-2400 parts of solvent toluene was added, followed by addition of 50-100 parts of 1,1,3,3-tetramethyldisiloxane, 60-120 parts of allyl glycidyl ether and 50-100 parts of allyl-cyclodextrin; Then 0.05-0.1 parts of catalyst chloroplatinic acid-vinylsiloxane complex was added, and the reaction was carried out at 75-85℃ for 110-140 minutes, and the chain flexibility modifier was obtained after toluene was distilled out at normal pressure at 110-120℃.

8. The process for synthesis of chain flexible poly perfluoroalkyl vinyl ether resin as claimed in claim 1, wherein: The molar ratio of the additional mixed monomers of tetrafluoroethylene and hexafluoropropylene is (5-15):(85-95).