Perfluororesin and preparation method thereof

Abstract

In order to solve the problems of high production cost and low yield caused by the fact that the existing amorphous fluororesin uses a fluorine-containing solvent for polymerization reaction, the invention provides perfluororesin and a preparation method thereof, and the preparation method of the perfluororesin comprises the following steps: in a protective gas atmosphere, mixing a solvent, an emulsifier and a pH regulator to obtain a mixed solution; adding a monomer and an initiator into the mixed solution to carry out emulsion polymerization reaction to obtain an emulsion, and carrying out post-treatment on the emulsion to obtain the perfluororesin, the monomers are tetrafluoroethylene, perfluoroalkyl vinyl ether and perfluoro (2, 2-dimethyl)-1, 3-dioxole; the solvent is deionized water. According to the preparation method of the perfluororesin provided by the invention, the perfluororesin with an extremely low dielectric constant can be prepared; deionized water is used as a solvent, a fluorine-containing solvent is not used, meanwhile, an emulsifier is added for emulsion polymerization, reaction conditions are relatively mild, the production cost is low, the production efficiency is high, and the yield is high.

Description

Technical Field

[0001] The present invention relates to the technical field of perfluororesin, in particular to a perfluororesin and a preparation method thereof. Background Art

[0002] Fluoroplastics have the advantages of chemical resistance, heat resistance, cold resistance and good insulation, and are widely used in many fields such as chemical industry, electronic appliances, and aerospace. In order to meet the needs of different applications, polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polyvinylidene fluoride (PVDF) and other fluorinated polymers have been developed and produced. PTFE, FEP, PFA, and PVDF are homopolymers or polymers containing a small amount of comonomers. They are easy to crystallize and are non-transparent polymers. Amorphous transparent perfluoropolymers were developed in the late 20th century. They not only have the advantages of heat resistance and chemical resistance similar to other fluoroplastics, but also have the characteristics of high light transmittance, low refractive index, low dielectric constant, good solubility and high gas permeability. They have good application prospects in optical fibers, separation membranes, analytical instruments, medical and military equipment, etc. At present, amorphous fluorinated polymers are mainly perfluoroolefin ether homopolymers, perfluoroolefin ether and tetrafluoroethylene (TFE) copolymers and other types. The existing amorphous fluorinated polymer product brands on the market include Cytop, Hyflon AD and the like.

[0003] Cytop is obtained by Asahi Glass Company using the intramolecular cyclopolymerization of the monomer perfluoro-4-vinyloxy-1-butene (PBVE). The reaction uses diisopropyl peroxydicarbonate (IPP) as an initiator, and the polymerization reaction is completed in a fluorocarbon solvent FC-77 or F113 under conditions below standard atmospheric pressure; the corresponding patent is US4910276A, which uses a fluorinated solvent as a polymerization medium and prepares a five-membered cyclic amorphous polymer through PBVE homopolymerization.

[0004] Hyflon AD is an amorphous fluororesin obtained by Oshimont Company through copolymerization of tetrafluoroethylene and special monomer 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole (TTD). Due to the P-π conjugation effect of trifluoromethoxy and olefin in TTD monomer, its stability is better; the corresponding patent is US 5883177A, which uses TTD to polymerize in a fluorinated solvent to obtain a coating solution.

[0005] The above polymers are all amorphous fluororesins with excellent light transmittance and low dielectric constant properties, but require the use of fluorine-containing solvents for polymerization reactions. When amorphous fluororesins are prepared in industrial production, the production cost is high and the yield is low. Summary of the invention

[0006] In view of the problem that the existing amorphous fluororesin uses fluorinated solvents for polymerization reaction, has high production cost and low yield, the present application provides a perfluororesin and a preparation method thereof.

[0007] In a first aspect, the present invention provides a method for preparing a perfluororesin, comprising the following steps: In a protective gas atmosphere, a solvent, an emulsifier, and a pH adjuster are mixed to obtain a mixed solution, a monomer and an initiator are added to the mixed solution to carry out an emulsion polymerization reaction to obtain an emulsion, and the emulsion is post-treated to obtain the perfluororesin; The monomers are tetrafluoroethylene, perfluoroalkyl vinyl ether and perfluoro(2,2-dimethyl)-1,3-dioxole; The solvent is deionized water.

[0008] Preferably, adding monomers and initiators to the mixed solution to carry out emulsion polymerization to obtain an emulsion comprises the following steps: Adding the monomer and the initiator to the mixed solution to carry out emulsion polymerization to generate an emulsion containing a perfluororesin, and continuously adding the monomer during the reaction to maintain a constant reaction pressure; In the monomers, the molar ratio of tetrafluoroethylene, perfluoroalkyl vinyl ether and perfluoro(2,2-dimethyl)-1,3-dioxole is (60-80):(0.5-10):(10-39.5).

[0009] Preferably, the perfluoroalkyl vinyl ether includes a compound represented by Formula 1, CF2=CFOR, Formula 1 Wherein, R is selected from a C1~C3 perfluoroalkyl group.

[0010] Preferably, the perfluoroalkyl vinyl ether includes perfluoropropyl vinyl ether, perfluoroethyl vinyl ether, and perfluoromethyl vinyl ether.

[0011] Preferably, the resistivity of the deionized water is ≥18 MΩ·m; And / or, the amount of the solvent added is 40% to 60% of the volume of the reaction container.

[0012] Preferably, the emulsifier comprises a perfluoropolyether carboxylate; The perfluoropolyether carboxylates include CF3CF2CF2OCF(CF3)COONH4, CF3CF2OCF(CF3)CF2OCF(CF3)COONH4, CF3O(CF2O) n One or more of CF2COONH4, where n is 1 to 3; And / or, the mass ratio of the emulsifier to the solvent is (0.03~0.3):100.

[0013] Preferably, the pH regulator includes one or more of ammonium carbonate, ammonium bicarbonate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, and disodium hydrogen phosphate; And / or, the mass ratio of the pH regulator to the solvent is (0.01-0.5):100.

[0014] Preferably, the emulsion polymerization reaction temperature is 30-95°C, and the emulsion polymerization reaction pressure is 0.8-3.0MPa; And / or, the solid content of the emulsion is 20% to 35%; The post-treatment of the emulsion to obtain the perfluororesin comprises the following steps: The emulsion is sequentially subjected to coagulation, washing and drying to obtain the perfluororesin; The drying temperature is 95-105°C.

[0015] Preferably, The initiator includes persulfate, and the mass ratio of the initiator to the solvent is (0.0002-0.3):100.

[0016] In a first aspect, the present invention provides a perfluororesin, which is prepared by the above-mentioned method for preparing a perfluororesin. In the frequency range of 1 to 40 GHz, the dielectric constant of the perfluororesin is 1.8 to 2.0.

[0017] The preparation method of perfluororesin provided in the present application adopts tetrafluoroethylene, perfluoroalkyl vinyl ether and perfluoro (2,2-dimethyl) -1,3-dioxole for copolymerization, and can prepare perfluororesin with extremely low dielectric constant, and the dielectric constant of perfluororesin obtained in the frequency range of 1 to 40 GHz is as low as 1.8. Deionized water is used as solvent, and no fluorinated solvent is used. At the same time, an emulsifier is added for emulsion polymerization, and the reaction conditions are relatively mild, the production cost is low, and the production efficiency is high. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0019] In order to illustrate the technical solution of the present invention, specific embodiments are provided below for illustration.

[0020] In a first aspect, the present application provides a method for preparing a perfluororesin, comprising the following steps: Mixing a solvent, an emulsifier, and a pH adjuster to obtain a mixed solution, adding a monomer and an initiator to the mixed solution to perform an emulsion polymerization reaction to obtain an emulsion, and post-treating the emulsion to obtain the perfluororesin; The monomers are tetrafluoroethylene, perfluoroalkyl vinyl ether and perfluoro(2,2-dimethyl)-1,3-dioxole; The solvent is deionized water.

[0021] The preparation method provided in the present application uses deionized water as a solvent instead of a fluorinated solvent, thereby reducing the cost of raw materials, and the reaction is easy to control, and is suitable for continuous production. At the same time, a fluorinated emulsifier is added for emulsion polymerization, and the reaction conditions are relatively mild, and emulsion polymerization can occur without the need for a high reaction pressure or reaction temperature, further reducing the production cost. In addition, the fluorinated emulsifier has good solubility in aqueous media, and no metal ion components will remain as impurities in the final product.

[0022] The monomer is a mixed monomer of tetrafluoroethylene, perfluoroalkyl vinyl ether and perfluoro (2,2-dimethyl) -1,3-dioxole. Under the action of initiator and emulsifier, the three monomers are emulsion polymerized to obtain a perfluoro resin with a low dielectric constant. Specifically, in the monomer, tetrafluoroethylene (TFE) provides a fluorocarbon skeleton for the perfluoro resin; perfluoro (2,2-dimethyl) -1,3-dioxole (PDD) has a five-membered ring structure, and the introduction of perfluoroalkyl vinyl ether for reaction can ensure that the resulting copolymer has an extremely low dielectric constant.

[0023] The preparation method of perfluororesin provided in the present application adopts tetrafluoroethylene, perfluoroalkyl vinyl ether and perfluoro (2,2-dimethyl) -1,3-dioxole for copolymerization, and can prepare perfluororesin with extremely low dielectric constant, and the dielectric constant of perfluororesin obtained in the frequency range of 1 to 40 GHz is as low as 1.8. Deionized water is used as solvent, and no fluorinated solvent is used. At the same time, an emulsifier is added for emulsion polymerization, and the reaction conditions are relatively mild, the production cost is low, and the production efficiency is high.

[0024] In some embodiments, under a protective gas atmosphere, mixing a solvent, an emulsifier, and a pH adjuster to obtain a mixed solution comprises the following steps: The reaction container is cleaned, vacuumed and filled with protective gas for replacement, a solvent, an emulsifier and a pH adjuster are added, and the protective gas is replaced by vacuum until the oxygen content is ≤20ppm, and then stirred and mixed to obtain a mixed solution.

[0025] Specifically, before the reaction, the air in the reaction container is replaced with a protective gas to limit the oxygen content in the reaction container to ≤20ppm, thereby preventing the monomer from undergoing an oxidation reaction with oxygen, preventing oxygen from undergoing a side reaction during the emulsion polymerization process, and reducing by-products.

[0026] The protective gas includes at least one of nitrogen and a rare gas.

[0027] The protective gas is preferably nitrogen.

[0028] In some embodiments, adding monomers and initiators to the mixed solution to perform emulsion polymerization to obtain an emulsion comprises the following steps: Adding the monomer and the initiator to the mixed solution to carry out emulsion polymerization to generate an emulsion containing a perfluororesin, and continuously adding the monomer during the reaction to maintain a constant reaction pressure; In the monomers, the molar ratio of tetrafluoroethylene, perfluoroalkyl vinyl ether and perfluoro(2,2-dimethyl)-1,3-dioxole is (60-80):(0.5-10):(10-39.5).

[0029] Specifically, a portion of monomers and initiators are first added to the mixed solution to carry out emulsion polymerization reaction. To maintain a constant reaction pressure, another portion of monomers is continuously added during the reaction to ensure that the reaction proceeds continuously and stably.

[0030] The molar ratio of tetrafluoroethylene, perfluoroalkyl vinyl ether and perfluoro(2,2-dimethyl)-1,3-dioxole in the monomer is (60~80):(0.5~10):(10~39.5), which can be understood as dividing the total amount of monomer added into two parts, one part of monomer and the other part of monomer. One part of monomer is added first for reaction. As the reaction proceeds, the pressure in the reaction container will decrease. In order to maintain a constant pressure, another part of monomer is continuously added during the reaction to maintain a constant pressure in the reaction container.

[0031] The molar ratio of tetrafluoroethylene, perfluoroalkyl vinyl ether and perfluoro(2,2-dimethyl)-1,3-dioxole is (60-80):(0.5-10):(10-39.5), which is conducive to the production of perfluororesin with a low dielectric constant.

[0032] In some embodiments, the perfluoroalkyl vinyl ether includes a compound represented by Formula 1, CF2=CFOR, Formula 1 Wherein, R is selected from a C1~C3 perfluoroalkyl group.

[0033] Specifically, R is selected from perfluoroalkyl groups having 1 to 3 carbon atoms, including perfluoro C1 to C3 straight-chain alkyl groups and perfluoro C1 to C3 branched alkyl groups. For example, R can be perfluoromethyl, perfluoroethyl, and the like.

[0034] The perfluoroalkyl vinyl ether is selected from the compounds shown in Formula 1, which is conducive to reacting with perfluoro(2,2-dimethyl)-1,3-dioxole (PDD) to ensure that the generated copolymer has an extremely low dielectric constant.

[0035] In some embodiments, the perfluoroalkyl vinyl ether includes perfluoropropyl vinyl ether (PPVE), perfluoroethyl vinyl ether (PEVE), and perfluoromethyl vinyl ether (PMVE).

[0036] In some preferred embodiments, the perfluoroalkyl vinyl ether is perfluoromethyl vinyl ether (PMVE).

[0037] In some embodiments, the resistivity of the deionized water is ≥18 MΩ·m.

[0038] Specifically, the solvent used is deionized water, and the resistivity of the deionized water is limited to ≥18 MΩ·m. The ion impurity content in the deionized water is extremely low, which prevents the impurities in the deionized water from affecting the emulsion polymerization reaction and avoids the introduction of impurities into the generated polymer.

[0039] In some embodiments, the amount of solvent added is 40% to 60% of the volume of the reaction container.

[0040] Specifically, the volume of deionized water added to the reaction container is 40% to 60% of the volume of the reaction container. For example, the volume of deionized water added to the reaction container can be 40%, 42%, 45%, 48%, 50%, 55%, 60%, etc. of the volume of the reaction container.

[0041] In some embodiments, the emulsifier comprises a perfluoropolyether carboxylate.

[0042] Specifically, the emulsifier includes perfluoropolyether carboxylates, which can reduce the surface tension between the aqueous phase of deionized water and the oil phase of the monomer, so that the monomers of tetrafluoroethylene, perfluoroalkyl vinyl ether and perfluoro (2,2-dimethyl) -1,3-dioxole can be better dispersed in the aqueous phase to form a stable emulsion system, thereby ensuring the smooth progress of the polymerization reaction.

[0043] In some embodiments, the perfluoropolyether carboxylate includes CF3CF2CF2OCF(CF3)COONH4, CF3CF2OCF(CF3)CF2OCF(CF3)COONH4, CF3O(CF2O) n One or more of CF2COONH4, n is 1~3.

[0044] Specifically, the structure of CF3CF2CF2OCF(CF3)COONH4 contains a branched perfluoromethyl group, the structure of CF3CF2OCF(CF3)CF2OCF(CF3)COONH4 also contains a branched perfluoromethyl group, and CF3O(CF2O) n The structure of CF2COONH4 contains (CF2O) n The groups can greatly reduce the oil-water interfacial tension, allowing the oily monomer to be better dispersed in the water phase and form an emulsion.

[0045] CF3CF2OCF(CF3)CF2OCF(CF3)COONH4, CF3O(CF2O) n CF2COONH4 also has the function of stabilizing the emulsion and preventing the emulsion from agglomerating, and solubilizing the monomer.

[0046] In some embodiments, the mass ratio of the emulsifier to the solvent is (0.03-0.3):100.

[0047] Specifically, the mass ratio of the emulsifier to the solvent deionized water is (0.03~0.3):100. The added emulsifier helps to greatly reduce the oil-water interfacial tension, and the oily monomer is better dispersed in the water phase to form a stable emulsion, which is beneficial to the polymerization reaction.

[0048] If the amount of emulsifier added is too low, the oily monomer cannot be better dispersed in the water phase, affecting the polymerization reaction; if the amount of emulsifier added is too high, it will affect demulsification, increase the difficulty of separation and purification steps, and increase the impurity residues of perfluororesin.

[0049] Specifically, the mass ratio of the emulsifier to the solvent deionized water can be 0.03:100, 0.05:100, 0.07:100, 0.08:100, 0.09:100, 0.1:100, 0.15:100, 0.2:100, 0.25:100, 0.3:100, etc., as long as the mass ratio of the emulsifier to the solvent is in the range of (0.03~0.3):100.

[0050] In some preferred embodiments, the mass ratio of the emulsifier to the solvent is (0.05-0.1):100.

[0051] Specifically, the mass ratio of the emulsifier to the solvent is in the range of (0.05-0.1):100. Adding less emulsifier can also make the oily monomer better dispersed in the water phase to form a stable emulsion, which is beneficial to the polymerization reaction and has low production costs.

[0052] In some embodiments, the pH adjuster includes one or more of ammonium carbonate, ammonium bicarbonate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, and disodium hydrogen phosphate.

[0053] Specifically, the pH adjuster mainly plays the role of adjusting the pH value of the solution.

[0054] In some embodiments, the mass ratio of the pH adjuster to the solvent is (0.01-0.5):100.

[0055] Specifically, the mass ratio of the pH adjuster to the solvent is in the range of (0.01-0.5):100, which is beneficial to adjusting the pH value of the mixed solution formed by water, emulsifier and pH adjuster, and also to adjusting the pH value of the solution during the emulsion polymerization reaction. Adjusting the pH value to within the range of 3-7 is beneficial to the polymerization reaction.

[0056] The mass ratio of the pH adjuster to the solvent can be 0.01:100, 0.05:100, 0.07:100, 0.08:100, 0.09:100, 0.1:100, 0.2:100, 0.3:100, 0.4:100, 0.5:100, etc., as long as the mass ratio is within the range of (0.01~0.5):100.

[0057] In some preferred embodiments, the mass ratio of the pH regulator to the solvent is (0.05-0.1):100.

[0058] In some embodiments, the emulsion polymerization reaction temperature is 30-95° C., and the emulsion polymerization reaction pressure is 0.8-3.0 MPa.

[0059] Specifically, the preparation method provided in the present application uses deionized water as a solvent and adds an emulsifier to carry out an emulsion polymerization reaction. The reaction temperature is 30~95°C and the reaction pressure is in the range of 0.8~3.0MPa. The reaction temperature and reaction pressure are both low, the reaction conditions are relatively mild, and the production cost is reduced.

[0060] Specifically, the emulsion polymerization temperature can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 80°C, 90°C, etc., as long as the emulsion polymerization temperature is within the range of 30-95°C. The emulsion polymerization pressure can be 0.8MPa, 1.0MPa, 1.2MPa, 1.5MPa, 1.7MPa, 2.0MPa, 2.4MPa, 2.5MPa, 3.0MPa, etc., as long as the emulsion polymerization pressure is within the range of 0.8-3.0MPa.

[0061] In some preferred embodiments, the emulsion polymerization reaction temperature is 50-80°C.

[0062] The reaction temperature of emulsion polymerization is preferably in the range of 50-80°C, which is beneficial to improving the reaction rate and production efficiency.

[0063] In some preferred embodiments, the emulsion polymerization reaction pressure is 1.0-1.5 MPa.

[0064] The reaction pressure of emulsion polymerization is preferably in the range of 1.0 to 1.5 MPa. The lower the reaction pressure, the higher the reaction rate and the lower the production cost.

[0065] In some embodiments, the solid content of the emulsion is 20% to 35%.

[0066] Specifically, monomers and initiators are added to carry out emulsion polymerization to obtain an emulsion. After the reaction, the solid content of the emulsion obtained is 20% to 35%. The amount of monomers to be added can be calculated according to the solid content range of the emulsion, so as to carry out the emulsion polymerization reaction. The solidification amount of the emulsion can be 20%, 22%, 23%, 25%, 26%, 27%, 28%, 29%, 30%, etc., as long as the solid content of the emulsion is within the range of 20% to 35%.

[0067] In some preferred embodiments, the solid content of the emulsion is 25%.

[0068] In some embodiments, post-processing the emulsion to obtain the perfluororesin comprises the following steps: The emulsion is sequentially subjected to coagulation, washing and drying to obtain the perfluororesin; The drying temperature is 95-105°C.

[0069] Specifically, the content of the monomer to be included is calculated based on the solid content of the emulsion. When the feeding is stopped, the reaction is completed and cooled to room temperature (25±5°C), the monomer is recovered, and the emulsion obtained after the reaction is discharged. The emulsion is sequentially condensed, washed, and dried to obtain the perfluororesin.

[0070] Drying removes deionized water on the surface of perfluororesin to improve purity. The specific drying temperature can be 95°C, 96°C, 98°C, 100°C, 101°C, 102°C, 103°C, 105°C, etc., as long as the drying temperature is within the range of 95°C~105°C.

[0071] The drying time can be limited according to the specific situation, such as 5 to 20 hours of drying time.

[0072] In some embodiments, the coagulation method is to coagulate the latex with an aqueous nitric acid solution.

[0073] Specifically, using nitric acid aqueous solution to coagulate the latex is beneficial to separating the perfluororesin from the emulsion system, while reducing the residual impurities such as emulsifiers, thereby facilitating the subsequent processing steps of the perfluororesin.

[0074] In some embodiments, deionized water is used for washing to remove water-soluble impurities, such as emulsifiers, pH adjusters and other impurities.

[0075] In some preferred embodiments, the drying method is vacuum drying.

[0076] More preferably, the drying temperature is 100°C.

[0077] In some embodiments, the initiator comprises a persulfate.

[0078] In some embodiments, the persulfate includes one or more of ammonium persulfate, potassium persulfate, and sodium persulfate.

[0079] In some preferred embodiments, the initiator is ammonium persulfate.

[0080] The initiator initiates the polymerization of the monomers.

[0081] In some embodiments, the mass ratio of the initiator to the solvent is (0.0002-0.3):100.

[0082] Specifically, the mass ratio of the initiator to the solvent being within the above range is conducive to initiating the emulsion polymerization reaction of the monomers to generate a perfluororesin with a low dielectric constant.

[0083] Specifically, the mass ratio of the initiator to the solvent can be in the following ranges: (0.0002-0.01):100, (0.01-0.05):100, (0.05-0.09):100, (0.09-0.15):100 or (0.15-0.3):100.

[0084] In some preferred embodiments, the mass ratio of the initiator to the solvent is (0.01-0.09):100.

[0085] Specifically, the mass ratio of the initiator to the solvent is in the range of (0.01-0.09):100, which ensures that the initiator can initiate the monomer to undergo emulsion polymerization while using less initiator and reducing costs.

[0086] The reaction container may be a container such as a reaction kettle, which is not limited in this application.

[0087] In a second aspect, the present application provides a perfluororesin, which is prepared by the above-mentioned method for preparing a perfluororesin, and has a dielectric constant of 1.8 to 2.0 within a frequency range of 1 to 40 GHz.

[0088] Specifically, the perfluororesin prepared by the preparation method of the perfluororesin provided in the present application has a dielectric constant of 1.8 to 2.0 in the frequency range of 1 to 40 GHz, and the dielectric constant of the perfluororesin is low, and has low dielectric loss. When the perfluororesin with a low dielectric constant is used as an insulating material, it can reduce the delay of the signal during transmission, increase the transmission rate of the signal, and have a better insulation effect.

[0089] The perfluororesin provided in the present application is prepared by the above-mentioned perfluororesin preparation method. The perfluororesin has excellent light transmittance, low dielectric constant, high tensile strength, good toughness, chemical corrosion resistance, and high temperature resistance. In the frequency range of 1 to 40 GHz, the dielectric constant of the perfluororesin can be as low as 1.8. When used as an insulating material, it can increase signal transmission speed, reduce signal loss, and improve insulation performance.

[0090] In some preferred embodiments, the dielectric constant of the perfluororesin is 1.8.

[0091] The perfluororesin prepared by the preparation method of the perfluororesin provided in the present application has a minimum dielectric constant of 1.8, and the extremely low dielectric constant makes the perfluororesin have better insulation performance.

[0092] The perfluororesin provided in this application is a type of plastic, namely Teflon AF. The perfluororesin provided in this application is used in the fields of semiconductors, electronics and electrical, machinery manufacturing, medical equipment, construction, etc., and can be used in electronic components, optical fiber modification, separation membranes, etc.

[0093] The present invention is further described below by way of examples.

[0094] Example 1 Material preparation: The emulsifier is CF3CF2CF2OCF(CF3)COONH4, the pH adjuster is ammonium bicarbonate, the initiator is ammonium persulfate, and the monomers are TFE, PMVE and PDD.

[0095] S1: After cleaning and drying the stainless steel high-pressure reactor, evacuate and fill with nitrogen three times, add 40L of deionized water, 40g of CF3CF2CF2OCF(CF3)COONH4, and 20g of ammonium bicarbonate into the reactor, evacuate and replace until the oxygen content is ≤20ppm, mix and stir evenly to obtain a mixed solution, heat to 45°C, add monomers with a composition of 60 mol% TFE, 5 mol% PMVE, and 35 mol% PDD into the mixed solution in the reactor, increase the pressure to 1MPa, add 4g of ammonium persulfate to initiate the reaction, and continuously introduce monomers with a composition of 60 mol% TFE, 5 mol% PMVE, and 35 mol% PDD during the reaction. When the comonomer feed amount is 10.5kg, stop the reaction, cool to room temperature, recover the monomers and discharge the material. The solid content of the emulsion is 21%.

[0096] Before the monomers are introduced, the pH value of the solution in the reactor is in the range of 3 to 7 during the reaction.

[0097] S2: The emulsion obtained by the reaction was coagulated with an aqueous nitric acid solution, washed with deionized water, and dried in a vacuum oven at 100° C. and -0.09 MPa for 10 hours to obtain the final product, perfluororesin.

[0098] Example 2 Material preparation: The emulsifier is CF3CF2CF2OCF(CF3)COONH4, the pH regulator is potassium dihydrogen phosphate, the initiator is potassium persulfate, and the monomers are TFE, PMVE and PDD.

[0099] S1: After cleaning and drying the stainless steel high-pressure reactor, evacuate and fill with nitrogen three times, add 40L of deionized water, 20g of CF3CF2CF2OCF(CF3)COONH4, and 20g of potassium dihydrogen phosphate into the reactor, evacuate and replace until the oxygen content is ≤20ppm, mix and stir evenly to obtain a mixed solution, heat to 55°C, add monomers with a composition of 60 mol% TFE, 10 mol% PMVE, and 30 mol% PDD into the mixed solution in the reactor, increase the pressure to 1MPa, add 8g of potassium persulfate to initiate the reaction, and continuously introduce monomers with a composition of 60 mol% TFE, 10 mol% PMVE, and 30 mol% PDD during the reaction. When the comonomer feed amount is 12kg, stop the reaction, cool to room temperature, recover the monomers and discharge the material, and the solid content of the emulsion is 24%.

[0100] Before the monomers are introduced, the pH value of the solution in the reactor is in the range of 3 to 7 during the reaction.

[0101] S2: The emulsion obtained by the reaction was coagulated with an aqueous nitric acid solution, washed with deionized water, and dried in a vacuum oven at 100° C. and -0.09 MPa for 10 hours to obtain the final product, perfluororesin.

[0102] Example 3 Material preparation: The emulsifier is CF3CF2CF2OCF(CF3)COONH4, the pH regulator is ammonium bicarbonate, the initiator is sodium persulfate, and the monomers are TFE, PMVE and PDD.

[0103] S1: After cleaning and drying the stainless steel high-pressure reactor, evacuate and fill with nitrogen three times, add 50L of deionized water, 50g of CF3CF2CF2OCF(CF3)COONH4, and 25g of ammonium carbonate into the reactor, evacuate and replace until the oxygen content is ≤20ppm, mix and stir evenly to obtain a mixed solution, heat to 60°C, add monomers with a composition of 70 mol% TFE, 10 mol% PMVE, and 20 mol% PDD into the mixed solution in the reactor, increase the pressure to 1.5MPa, add 25g of sodium persulfate to initiate the reaction, and continuously introduce monomers with a composition of 70 mol% TFE, 10 mol% PMVE, and 20 mol% PDD during the reaction. When the comonomer feed amount is 20kg, stop the reaction, cool to room temperature, recover the monomers and discharge the material, and the solid content of the emulsion is 29%.

[0104] Before the monomers are introduced, the pH value of the solution in the reactor is in the range of 3 to 7 during the reaction.

[0105] S2: The emulsion obtained by the reaction was coagulated with an aqueous nitric acid solution, washed with deionized water, and dried in a vacuum oven at 100° C. and -0.09 MPa for 10 hours to obtain the final product, perfluororesin.

[0106] Example 4 Most of the steps in this embodiment are the same as those in Embodiment 1, except that the emulsifier in this embodiment is CF3CF2OCF(CF3)CF2OCF(CF3)COONH4, and the rest is the same as in Embodiment 1.

[0107] Example 5 Most of the steps of this embodiment are the same as those of embodiment 1, except that the emulsifier in this embodiment is CF3O(CF2O)3CF2COONH4, and the rest is the same as embodiment 1.

[0108] Example 6 Most of the steps of this embodiment are the same as those of embodiment 1, except that the monomers of this embodiment are TFE, PPVE and PDD, and the composition of the monomers is 60 mol% TFE, 5 mol% PPVE, and 35 mol% PDD.

[0109] Example 7 Most of the steps of this embodiment are the same as those of embodiment 1, except that the amount of the emulsifier added in this embodiment is 120 g, the amount of the pH adjuster ammonium bicarbonate added is 40 g, and the rest is the same as that of embodiment 1.

[0110] Example 8 Most of the steps in this embodiment are the same as those in Embodiment 7, except that the amount of emulsifier added in this embodiment is 150 g, and the rest is the same as in Embodiment 7.

[0111] Example 9 Most of the steps in this embodiment are the same as those in Example 7, except that the amount of emulsifier added in this embodiment is 8 g, and the rest is the same as in Example 7.

[0112] Example 10 Most of the steps of this embodiment are the same as those of embodiment 1, except that the monomer composition of this embodiment is 80 mol % TFE, 10 mol % PMVE, and 10 mol % PDD.

[0113] Embodiment 11 Most of the steps of this embodiment are the same as those of embodiment 1, except that the monomer composition of this embodiment is 90 mol % TFE, 2 mol % PMVE, and 8 mol % PDD.

[0114] Example 12 Most of the steps of this embodiment are the same as those of embodiment 1, except that the reaction temperature of this embodiment is 90°C and the reaction pressure is 3.0 MPa.

[0115] Comparative Example 1 Most of the steps of this comparative example are the same as those of Example 1, except that the monomers used in this comparative example are TFE and PMVE, and the composition of the monomers is 60 mol% TFE and 40 mol% PMVE.

[0116] Comparative Example 2 Most of the steps of this comparative example are the same as those of Example 1, except that the monomers used in this comparative example are TFE and PDD, and the composition of the monomers is 60 mol % TFE and 40 mol % PDD.

[0117] It should be noted that the reactors used in the above embodiments and comparative examples are all 100L stainless steel high-pressure reactors, and are equipped with a thermometer, pressure gauge, heater, stirring paddle, internal cooling water pipe, liquid metering pump, feed pipe and valve, discharge pipe and valve and mass flow meter, etc.

[0118] Performance Testing The above-mentioned embodiments and comparative examples were subjected to the following performance tests.

[0119] Dielectric Constant: The dielectric constant of the perfluororesin products prepared in the above-mentioned embodiments and comparative examples was tested under the condition of 1-40 GHz according to the ASTM D150 test method.

[0120] Refractive Index: The refractive index of the perfluororesin products prepared in the above-mentioned embodiments and comparative examples was tested according to the ASTM 542 test method.

[0121] Tensile Strength: The tensile strength of the perfluororesin products prepared in the above examples and comparative examples was tested according to the ASTM D638 test method.

[0122] Elongation at break: The perfluororesin products prepared in the above-mentioned embodiments and comparative examples were tested for elongation at break according to the ASTM D638 test method.

[0123] Light transmittance: The light transmittance of the perfluororesin products prepared in the above-mentioned embodiments and comparative examples was tested according to the ASTM D1003 test method.

[0124] Table 1 It can be seen from Table 1 that, by comparing Example 1 with Comparative Examples 1 and 2, the monomers used in Comparative Example 1 are TFE and PMVE, and the perfluororesin prepared has a high dielectric constant and low transmittance; Comparative Example 2 uses monomers TFE and PDD, and although the transmittance of the perfluororesin obtained is improved, the dielectric constant tested in the frequency range of 1 to 40 GHz is still relatively high, indicating that the perfluoroether resin obtained by emulsion polymerization using tetrafluoroethylene, perfluoroalkyl vinyl ether and perfluoro (2,2-dimethyl) -1,3-dioxole as monomers and using deionized water, an emulsifier, etc. has a high transmittance and a low dielectric constant.

[0125] By comparing Examples 1, 6, 10 and 11, it can be seen that among the added monomers, if the molar amount of the added PDD monomer is small, although the tensile strength of the obtained resin increases, the dielectric constant is relatively high and the transmittance is reduced, indicating that in the monomers added when preparing the perfluororesin, the molar ratio of tetrafluoroethylene, perfluoroalkyl vinyl ether and perfluoro(2,2-dimethyl)-1,3-dioxole is in the range of (60~80):(0.5~10):(10~39.5), which is conducive to the production of a perfluororesin with high transmittance and low dielectric constant.

[0126] Comparison of Examples 1, 4, and 5, changing the type of emulsifier, as long as the emulsifier is selected from CF3CF2CF2OCF(CF3)COONH4, CF3CF2OCF(CF3)CF2OCF(CF3)COONH4, CF3O(CF2O) n One or more of CF2COONH4, where n is 1 to 3, have the same effect and can greatly reduce the oil-water interfacial tension, allowing the oily monomer to be better dispersed in the water phase and form an emulsion, which is beneficial to the occurrence of emulsion polymerization.

[0127] Comparing Examples 1 and 7 with Examples 8 and 9, the amount of emulsifier added in Example 8 is too much, while the amount of emulsifier added in Example 9 is less, and the obtained perfluororesin has a reduced elongation at break, a large rigidity of the resin, and is easily deformed under the action of external force; this indicates that when the mass ratio of the emulsifier to the solvent is in the range of (0.03-0.3):100, the obtained perfluororesin has a high elongation at break, a low dielectric constant, a high tensile strength, a high refractive index, and a high light transmittance.

[0128] From the comparison of Examples 1 to 3 and 9, it can be seen that by changing the polymerization reaction temperature within the range of 30 to 95° C. and the reaction pressure within the range of 0.8 to 3.0 MPa, the reaction temperature is low, the reaction pressure is low, the reaction conditions are relatively mild, the production cost is low, and the production efficiency is high.

[0129] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, it should be understood by those skilled in the art that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should be included in the protection scope of the present invention.

Claims

1. A method for preparing a perfluororesin, characterized in that: The following steps are involved: In a protective gas atmosphere, a solvent, an emulsifier, and a pH adjuster are mixed to obtain a mixed solution, a monomer and an initiator are added to the mixed solution to carry out an emulsion polymerization reaction to obtain an emulsion, and the emulsion is post-treated to obtain the perfluororesin; The monomers are tetrafluoroethylene, perfluoroalkyl vinyl ether and perfluoro(2,2-dimethyl)-1,3-dioxole; The solvent is deionized water.

2. The method for preparing perfluororesin according to claim 1, characterized in that: Adding monomers and initiators to the mixed solution to carry out emulsion polymerization to obtain an emulsion comprises the following steps: Adding the monomer and the initiator to the mixed solution to carry out emulsion polymerization to generate an emulsion containing a perfluororesin, and continuously adding the monomer during the reaction to maintain a constant reaction pressure; In the monomers, the molar ratio of tetrafluoroethylene, perfluoroalkyl vinyl ether and perfluoro(2,2-dimethyl)-1,3-dioxole is (60-80):(0.5-10):(10-39.5).

3. The method for preparing perfluororesin according to claim 1, characterized in that: The perfluoroalkyl vinyl ether includes a compound represented by Formula 1, CF2=CFOR, Formula 1 Wherein, R is selected from a C1~C3 perfluoroalkyl group.

4. The method for preparing a perfluororesin according to claim 1 or 3, characterized in that: The perfluoroalkyl vinyl ether includes perfluoropropyl vinyl ether, perfluoroethyl vinyl ether and perfluoromethyl vinyl ether.

5. The method for preparing perfluororesin according to claim 1, characterized in that: The resistivity of the deionized water is ≥18MΩ·m; And / or, the amount of the solvent added is 40% to 60% of the volume of the reaction container.

6. The method for preparing perfluororesin according to claim 1, characterized in that: The emulsifier includes a perfluoropolyether carboxylate; The perfluoropolyether carboxylates include CF3CF2CF2OCF(CF3)COONH4, CF3CF2OCF(CF3)CF2OCF(CF3)COONH4, CF3O(CF2O) n One or more of CF2COONH4, where n is 1 to 3; And / or, the mass ratio of the emulsifier to the solvent is (0.03~0.3):

100.

7. The method for preparing perfluororesin according to claim 1, characterized in that: The pH regulator includes one or more of ammonium carbonate, ammonium bicarbonate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, and disodium hydrogen phosphate; And / or, the mass ratio of the pH regulator to the solvent is (0.01-0.5):

100.

8. The method for preparing perfluororesin according to claim 1, characterized in that: The emulsion polymerization reaction temperature is 30~95℃, and the emulsion polymerization reaction pressure is 0.8~3.0MPa; And / or, the solid content of the emulsion is 20% to 35%; The post-treatment of the emulsion to obtain the perfluororesin comprises the following steps: The emulsion is sequentially subjected to coagulation, washing and drying to obtain the perfluororesin; The drying temperature is 95-105°C.

9. The method for preparing perfluororesin according to claim 1, characterized in that: The initiator includes persulfate, and the mass ratio of the initiator to the solvent is (0.0002-0.3):

100.

10. A perfluororesin, characterized in that: The perfluororesin is prepared by the method for preparing a perfluororesin according to any one of claims 1 to 9, and has a dielectric constant of 1.8 to 2.0 within a frequency range of 1 to 40 GHz.

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