Tetrafluoroethylene-based melt-processable perfluorinated copolymer and preparation method thereof

Abstract

The invention belongs to the technical field of fluorine-containing high-molecular polymers, and particularly relates to a tetrafluoroethylene-based melt-processable perfluorinated copolymer and a preparation method thereof. The perfluorinated copolymer is formed by carrying out ternary polymerization on tetrafluoroethylene, perfluorinated cycloolefin and perfluorinated vinyl ether; wherein the perfluorinated vinyl ether is perfluorinated alkyl vinyl ether or perfluorinated cyclic vinyl ether; the mass percent of the tetrafluoroethylene monomer is 10%-90%, the mass percent of the perfluorocycloolefin monomer is 5%-40%, and the mass percent of the perfluorovinyl ether monomer is 5%-85%. Through selection of functional monomers with different structures and components, the tetrafluoroethylene-based perfluorinated copolymer has the advantages of melt processing, high-speed extrusion, high transparency, low refraction, high product yield and the like on the basis of ensuring the excellent performance of polytetrafluoroethylene, and is wide in application field; the fiber can be widely used in the fields of optical fiber cables, biomedical treatment, electronics, 5G communication and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fluorine-containing high molecular polymers, and particularly relates to a tetrafluoroethylene-based melt-processable perfluorinated copolymer and a preparation method thereof. BACKGROUND

[0002] Polytetrafluoroethylene (PTFE) has excellent high and low temperature resistance, corrosion resistance, electrical properties, self-lubricating properties, etc., but its viscous flow temperature is higher than its decomposition temperature, and it cannot be melt-processed like general thermoplastic plastics. It can only be processed by molding-sintering-machining, and cannot be used to make parts with complex structures. The processing efficiency is low, the energy consumption is high, the material utilization rate is low, and the processing cost is high, which limits the use of polytetrafluoroethylene.

[0003] In order to realize the melt-processability of PTFE, people have carried out copolymerization research of tetrafluoroethylene and other monomers, and synthesized tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-ethylene copolymer (ETFE), tetrafluoroethylene-perfluoropropyl vinyl ether copolymer (PFA), tetrafluoroethylene-chlorotrifluoroethylene copolymer (PCTFE), etc. However, the modified polytetrafluoroethylene obtained in the prior art has low modified monomer content, poor cracking resistance, and is prone to cracking, which affects the mechanical properties of the product. At the same time, the modification of short side chains is not enough to make the polymer meet the ever-changing needs of high-end application fields, such as high transparency, low refractive index, low dielectricity, and high-speed extrusion performance. Therefore, the polymer structure needs to be further developed on this basis.

[0004] The polymerization process of the modified polytetrafluoroethylene generally uses high temperature and high pressure, which is complicated and difficult to operate. The amount of dispersant used in the polymerization process is large, and the dispersion effect is not good. The reactivity of the modified monomer is low. The particle size of the polymer emulsion is uncontrollable. Over-polymerization is prone to occur.

[0005] The method for preparing a perfluoro vinyl ether modified polytetrafluoroethylene resin disclosed in patent CN113736003A first has a high polymerization pressure of 1.8-2.3 MPa. Secondly, the emulsifying effect is increased by using a part of the co-emulsifier obtained by Michael addition to replace the perfluorooctanoic acid emulsifier. However, the Michael addition reaction has a 1,2-addition competition reaction, which needs to be purified. In addition, the method selects an anionic surfactant as the dispersant, and adds hydrochloric acid for activation. The fluorine-containing anionic surfactant tends to exist in a molecular form under acidic conditions, and cannot form anions. Therefore, it cannot play the role of mutual non-contact due to charge repulsion of the anionic end micelles, and is prone to micelle collision and instability. This is not conducive to the hydrolysis of the dispersant, and will increase the amount of dispersant, so that the co-emulsifier cannot achieve the desired effect.

[0006] Patent IN202117021972A mentions that when performing emulsion polymerization of fluorine-containing monomers, non-fluorinated surfactants are used to solve the ecological system and biological accumulation problems of fluorine-containing hydrocarbon emulsifiers. During polymerization, the micelles formed by the dispersant provide a polymerization site. However, the dispersing effect of non-fluorinated dispersants on fluorine-containing monomers is not good, which leads to a large amount of use, a large amount of washing wastewater, and a large amount of residual dispersant affecting product quality. At the same time, at a high polymerization temperature of 85°C or higher, the rearrangement of the comonomer is prone to occur, which leads to abnormal chain termination, and thus the comonomer is ineffective, the amount is large, the distribution is uneven, the molecular weight distribution is wide, and the product quality is affected. SUMMARY

[0007] One of the purposes of the present application is to provide a tetrafluoroethylene-based melt-processable perfluorocopolymer with wider applicability and excellent performance. The tetrafluoroethylene-based perfluorocopolymer is selected by different structural functional monomers and components, so that the material has the advantages of melt processability, high-speed extrusion, high transparency, low refractive index, high product yield, etc. on the basis of ensuring the excellent performance of polytetrafluoroethylene, and has a wide application field and can be widely used in optical fiber cables, biomedical, electronics, 5G communication and other fields.

[0008] The specific technical solutions are as follows: A tetrafluoroethylene-based melt-processable perfluorocopolymer is prepared by terpolymerization of tetrafluoroethylene, perfluorocycloalkene and perfluoro vinyl ether; wherein the perfluoro vinyl ether is perfluoroalkyl vinyl ether or perfluoro cyclic vinyl ether.

[0009] The mass percentage of the tetrafluoroethylene monomer is 10%-90%, the mass percentage of the perfluorocycloalkene monomer is 5%-40%, and the mass percentage of the perfluoro vinyl ether monomer is 5%-85%.

[0010] The structural formula of the above perfluorocopolymer is as follows: ; In the formula, Rf1 is perfluoro vinyl ether, wherein when Rf1 is perfluoroalkyl vinyl ether, the double bond is in a straight chain, and the end side substituent is a straight chain or a branched chain; when Rf1 is perfluoro cyclic vinyl ether, the double bond is in a ring. Rf2 is perfluorocycloalkene, and the double bond is in a ring.

[0011] In the formula, n, m, k are the number of structural units. n is 4-40, m is 1-25, and k is 1-10.

[0012] The total content of the modified monomer in the tetrafluoroethylene-based copolymer in the prior art is generally 4%-10%, and the molecular chain is mainly tetrafluoroethylene, and such tetrafluoroethylene copolymer cannot have high transparency and low dielectric. The perfluoro copolymer described in the application can have a high proportion of modified monomers, has the characteristics of being meltable and soluble, can be coated on chips, electrical appliances, optical fibers and the like with high technical content in micron level, the processing mode is flexible, and the polymer has high added value.

[0013] In the application, the monomer perfluorocycloalkene in the tetrafluoroethylene-based melt-processable perfluoro copolymer is one or more of perfluorocyclopentene, perfluorocyclobutene or perfluorocyclohexene. Perfluorocyclohexene has a CAS number of 335-75-9 and a molecular weight of 262.0482, and can be purchased from Balingwei Technology Co., Ltd.

[0014] In the application, the monomer perfluoroalkyl vinyl ether in the tetrafluoroethylene-based melt-processable perfluoro copolymer is one or more of perfluoromethyl vinyl ether (CF3-O-CF=CF2), perfluoroethyl vinyl ether (CF3-CF2-O-CF=CF2) or perfluoro-n-propyl vinyl ether (CF3-CF2-CF2-O-CF=CF2). The monomer perfluoro cyclic vinyl ether is 5-trifluoromethoxy-2,2,4-trifluoro-1,3-dioxole.

[0015] In the application, the tetrafluoroethylene-based melt-processable perfluoro copolymer has a weight average molecular weight of 100,000-500,000 g / mol; and the perfluoro copolymer has a PDI of 1.3-1.6.

[0016] In the application, the tetrafluoroethylene-based melt-processable perfluoro copolymer has a tensile strength of >32 MPa; a melt index of 2-50 g / 10 min; a relative dielectric constant of 1.95-2.15 and a dielectric loss of 0.0002-0.0008 measured at a frequency of 2.5 GHz; a thermal decomposition temperature of above 360℃; a light transmittance of >85% from near ultraviolet to infrared; a refractive index of 1.30-1.39; and a water contact angle of >105°. From the data range of the dielectric loss of the perfluoro copolymer, the high light transmittance in the 190 nm-900 nm wave band and the tensile strength, it can be seen that the modified monomers (perfluorocycloalkene and perfluoro vinyl ether) in the copolymer are uniformly distributed.

[0017] In the present application, when the perfluorinated copolymer is prepared by terpolymerization of 10-30% of tetrafluoroethylene monomer, 5%-20% of perfluorocycloalkene monomer, and 50%-85% of perfluorocyclic vinyl ether monomer by mass percentage, the perfluorinated copolymer is non-crystalline, has no melting point, has a glass transition temperature of 130°C or higher, has excellent light transmittance in the ultraviolet to infrared wave band, the light transmittance is >94%, and has a relatively low refractive index, the refractive index is 1.29-1.32; it can be seen that the synergistic cooperation of the three monomers in this range can improve the high transparency of the perfluorinated copolymer.

[0018] When the perfluorinated copolymer is prepared by terpolymerization of 50%-85% of tetrafluoroethylene monomer, 10%-40% of perfluorocycloalkene monomer, and 5%-10% of perfluoroalkyl vinyl ether monomer by mass percentage, the melting point of the perfluorinated copolymer is 260-310°C, the dielectric constant is 1.95-2.1, the dielectric loss is 2×10 -4 -4×10 -4 ; it can be seen that the synergistic cooperation of the three monomers in this range can improve the low dielectric property of the perfluorinated copolymer.

[0019] When the perfluorinated copolymer is prepared by terpolymerization of 75%-90% of tetrafluoroethylene monomer, 5%-10% of perfluorocycloalkene monomer, and 5%-15% of perfluoroalkyl vinyl ether monomer by mass percentage, the melting point of the perfluorinated copolymer is 290-310°C, the melt index is 20-50 g / 10 min, and the critical shear rate is 120-300 s -1 ; it can be seen that the synergistic cooperation of the three monomers in this range can improve the high-speed extrusion property of the perfluorinated copolymer. The range of the amount of the comonomer, the amount of the initiator and the chain transfer agent, and the polymerization process ensure that the copolymer has the high-speed extrusion property.

[0020] In the copolymerization system of the three selected monomers, adjusting in the range of the amount can make the melt-processable perfluorinated copolymer focus on different performance directions, greatly expand the application range of the obtained copolymer, and obtain a large number of types, which can be used in different applications, such as high transparency, low dielectric, high-speed extrusion property, and special applications in high-tech fields.

[0021] The perfluorinated copolymer is used in communication transmission, electronics, medical treatment, and automobiles. Because it can be melt-processed, the low dielectric loss of the product can be used as an electronic circuit substrate, an integrated circuit, and an electronic device; the high-speed extrusion property can be used for manufacturing wire and cable sheaths; the high-transparency property can be used as optical materials, lenses, reactor and processing equipment windows, etc.; because the perfluorinated copolymer has the properties of strength, weather resistance, corrosion resistance, and high mechanical strength, it can be used for manufacturing automobile parts, interior decoration, and housing.

[0022] An emulsion of the above perfluorinated copolymer, comprising the following raw materials in parts by weight: tetrafluoroethylene 10-90 parts, perfluorocycloalkene 5-40 parts, perfluorovinyl ether 5-85 parts, fluorine-containing solubilizer 5-20 parts, initiator 0.1-2 parts, dispersant 3-10 parts, reducing agent 0.07-5 parts, pH adjuster 0.3-3 parts, chain transfer agent 0.08-1.3 parts, and termination agent 0.008-0.1 parts.

[0023] In the prior art, the weight ratio of the reducing agent to the initiator is generally 1:1, while the present application selects a high proportion of the reducing agent for feeding, maximizes the efficiency advantage of the initiator, and makes it possible to ensure the weak alkaline in the kettle to help reduce the dispersant dosage. In addition to improving the utilization rate of the initiator, it can also consume oxygen generated by the thermal decomposition of the peroxide system, and strictly control the oxygen content of the system.

[0024] In the present application, the fluorine-containing solubilizer in the perfluorinated copolymer emulsion is one or more of hexafluorobenzene, perfluorobutane, perfluorohexane, perfluoropentane or perfluoroheptane.

[0025] The initiator is any one of potassium persulfate, ammonium persulfate, succinic acid peroxide, dibenzoyl peroxide, diisopropyl carbonate peroxide or azobis isobutyronitrile.

[0026] The dispersant is one or more of perfluoropolyether sulfonate, perfluoropolyether carboxylate, perfluoropolyether sulfate or perfluorohexanoate. The dispersant is an anionic surfactant.

[0027] Preferably, the dispersant is one or more of ammonium perfluorohexanoate, ammonium perfluoropolyether carboxylate, ammonium perfluoropolyether sulfonate or ammonium perfluoropolyether sulfate.

[0028] The reducing agent is one or more of bisulfite, mercaptan or ferrous salt.

[0029] Preferably, the reducing agent is one or more of sodium bisulfite, potassium bisulfite, primary dodecane mercaptan, ferrous chloride or ammonium sulfite.

[0030] The pH adjuster is one or more of sodium carbonate, ammonia, sodium bicarbonate, ammonium carbonate or potassium carbonate.

[0031] The chain transfer agent is one or more of alkane, halogenated hydrocarbon or alcohol.

[0032] Preferably, the chain transfer agent is one or more of methane, ethane, isopentane, n-hexane and cyclohexane, etc. alkane; carbon tetrachloride, chloroform, dichloromethane, monochlorodifluoroethane, monofluorodichloroethane, perfluoroalkyl iodide (perfluorohexyl iodine alkane), etc. halogenated hydrocarbon; methanol, isopropyl alcohol, etc.

[0033] The termination agent is one or more of quinone, nitro salt, aromatic polyhydroxy compound or terpinene.

[0034] Preferably, the termination agent is one or more of p-phenylphenol, sodium dimethyl dithiocarbamate, sodium polysulfide, sodium nitrite or dipentene. The addition of the termination agent effectively inhibits the gel phenomenon caused by post-reaction of the emulsion after the reaction is completed, thereby ensuring the stability of the emulsion.

[0035] In the present application, the emulsion of the perfluorinated copolymer has a particle size of 170-220 nm and a solid content of 20-30 wt%. The emulsion can be stably stored for more than 3 months when left to stand, and can be stably stirred for more than 3 h at a rotation speed of 800 rpm. It can be seen that the emulsion of the perfluorinated copolymer according to the present application is a stable liquid with micro-nano particle size.

[0036] Another object of the present application is to provide a preparation method of the perfluorinated copolymer emulsion, which uses an environmentally friendly dispersant, innovative polymerization conditions and treatment methods on the basis of introducing a comonomer into a polymerization main chain of tetrafluoroethylene, to obtain a stable emulsion with uniform copolymer comonomer distribution and micro-nano particle size.

[0037] A preparation method of the perfluorinated copolymer emulsion, which uses an oxidation-reduction system for polymerization, specifically includes the following steps: (1) Pre-treated deionized water, a reducing agent, a dispersant, a pH adjuster and a fluorine-containing solubilizer are added to a reaction kettle, and oxygen is removed by vacuum replacement. The initial amount of the dispersant is 2 / 3 of the total amount of the dispersant; and the pH adjuster is used to control the pH value of the system before the reaction to be 7-9.

[0038] (2) After the oxygen content in the reaction kettle is less than 10 ppm, the reaction kettle is filled with perfluorocycloalkene, perfluorovinyl ether, tetrafluoroethylene (TFE) monomer and initiator, and the polymerization reaction is started. The polymerization reaction temperature is 20-60℃, and the polymerization reaction pressure is 0.2-1.0 MPa. When the polymerization reaction temperature is 20-40℃, the polymerization reaction pressure is 0.4-1.0 MPa; and when the polymerization reaction temperature is 40-60℃, the polymerization reaction pressure is 0.2-0.4 MPa. During the reaction, tetrafluoroethylene monomer is continuously supplemented to maintain the constant pressure in the kettle; only part of the TFE monomer is initially added, and the reaction is started when the pressure in the reaction kettle is 0.2-1.0 MPa, and then the TFE monomer is continuously supplemented to the reaction pressure.

[0039] (3) When the amount of tetrafluoroethylene fed is 1 / 3-1 / 2 of the planned total amount of tetrafluoroethylene, the dispersant is added, and the amount of the added dispersant is 1 / 3 of the total amount of the dispersant. When the amount of tetrafluoroethylene fed is 1 / 2-2 / 3 of the planned total amount of tetrafluoroethylene, 500-5000 ppm of a chain transfer agent is added. According to the amount of tetrafluoroethylene fed and the respective planned total amounts of perfluorocycloalkene and perfluorovinyl ether, the perfluorocycloalkene and perfluorovinyl ether are added. The dispersant is added at 1 / 3-1 / 2 to stabilize the existing emulsion micelles containing macromolecular chains and ensure stable growth of the molecular chains.

[0040] The perfluorocycloalkene and perfluorovinyl ether monomers are indirectly added according to the polymerization process, and the respective amounts of the perfluorocycloalkene and perfluorovinyl ether monomers added are basically consistent with the overall polymerization concentration. For example, if 8 kg of perfluorocycloalkene monomer is planned to be fed with 100 kg of tetrafluoroethylene, then 0.08 kg of perfluorocycloalkene monomer is added for every 1 kg of tetrafluoroethylene reacted at a certain reaction rate, so as to ensure that the monomer concentration in the reactor is within a certain range.

[0041] The timely addition of the chain transfer agent ensures the quality of the emulsion and the minimum amount of the dispersant. The prior art generally adds the chain transfer agent before the reaction starts, but the present application adds the chain transfer agent in the later stage, which can avoid the termination of short molecular chains caused by the addition of the chain transfer agent in the early stage and can effectively control the molecular weight after the molecular chains grow to a certain amount.

[0042] The polymerization uniformity can be determined according to the polymerization reaction rate. If the reaction rate rapidly increases within a certain time, the copolymerization modifier monomer needs to be supplemented, and the overall polymerization concentration is kept consistent, that is, the proportion of the overall monomer concentration is controlled within a certain range. For example, if 0.06 kg of copolymerization monomer is supplemented for every 1 kg of TFE consumed at a certain stable polymerization rate, the addition amount is 6%.

[0043] (4) When the amount of tetrafluoroethylene fed reaches the planned total amount of tetrafluoroethylene, 50-400 ppm of a terminator is added, and the unreacted monomers and fluorine-containing solvents are recovered. The obtained polymer is subjected to a post-treatment process to obtain a target perfluoropolymer. The end of the reaction is indicated by reaching the set monomer value of tetrafluoroethylene. The post-treatment process is a common process for fluorine-containing polymer emulsion polymerization, including steps such as demulsification, washing, drying, granulation, and fluorination.

[0044] In the present application, the method for pretreating the deionized water in step (1) of the preparation method is to heat the deionized water to above 70°C, reduce the dissolved oxygen in the water, and then seal the deionized water with nitrogen and cool it for standby use. Under the conditions of 20°C and 100 KPa, the dissolved oxygen in pure water is about 9 mg / L. After pretreatment, the oxygen content in the deionized water under the same conditions can be reduced by more than 80%.

[0045] The polymerization process of the adopted redox system in the application has a low temperature and more importantly a low pressure, which reduces the concentration of tetrafluoroethylene monomer in the polymerization kettle, is beneficial to the participation of the modified monomer in the copolymerization with tetrafluoroethylene, and improves the reactivity ratio of the comonomer. Compared with the decomposition of pure initiator, the redox reaction system has a low activation energy required for the reaction, and can easily decompose into free radicals at a low temperature of 20-60 DEG C, and can generate free radical initiation polymerization at normal temperature, and the reaction temperature is related to the speed of generating free radicals.

[0046] The application has the following beneficial effects: the application adopts a redox system, the temperature range is 20-60 DEG C, and the reaction pressure is between 0.2-1.0 MPa, wherein, the addition of the fluorine-containing solubilizer improves the instantaneous effective concentration of the modified monomer when participating in the copolymerization, the addition of the terminator effectively inhibits the gel phenomenon caused by the post-reaction of the emulsion after the reaction, the introduction of the unsaturated fluorine-containing modified monomer with different structures changes the composition and space structure of polytetrafluoroethylene, and the perfluoropolymer with flexible processing mode and unique performance is obtained. The perfluoropolymer has high transparency, low dielectric constant, low dielectric loss, the existence of large free volume, unique gas permeability and selection characteristics.

[0047] The application provides a preparation method of a tetrafluoroethylene-based meltable perfluorocopolymer, which is initiated by using a redox system, is safe and effective, and through pretreatment, component selection and optimization, the oxygen content in the polymerization process is strictly controlled to be not more than 10 ppm, the addition of a terminator controls the free radical activity after the polymerization is completed, a stable emulsion with uniform micro-nano particle size is obtained, and through a post-treatment procedure, the perfluorocopolymer with uniform polymerization monomer distribution and flexible processing mode can be obtained.

[0048] In the application, the perfluorocopolymer has a tensile strength of 32 MPa or more, a melt index of 2-50 g / 10 min, a relative dielectric constant of 1.95-2.15 measured at a frequency of 2.5 GHz, a dielectric loss of 0.0002-0.0008, a thermal decomposition temperature of more than 360 DEG C, a light transmittance of more than 85 % in the near ultraviolet to infrared range, and a weight average molecular weight of 100,000-500,000 g / mol, and a water contact angle of more than 105 DEG. It can be seen that the obtained perfluorocopolymer has excellent low dielectric, high transparency, high temperature resistance, high weather resistance and other characteristics, and widens new applications of the product in the fields of communication transmission, electronics and electrical appliances, medical treatment, automobiles and the like. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 It is an infrared spectrum of the perfluorocopolymer.

[0050] 1236 cm -1 It is a characteristic absorption peak of the cyclic fluorine-containing monomer; 1200 cm -1 It is a characteristic absorption peak of -CF2; 1139 cm -1 It is a C-F bond absorption peak; 983 cm-1 The -CF2 structural feature absorption peak is that of a perfluoroolefin. DETAILED DESCRIPTION

[0051] The application is further described in detail below in conjunction with examples.

[0052] 1. Infrared spectrum: Nicolet iS10 Fourier transform infrared spectrometer.

[0053] 2. Tensile strength: adjust according to the standard environment specified in GB / T 2918, and the adjustment time is at least 4 h.

[0054] 3. Melt index: according to the provisions of GB / T 3682.

[0055] 4. Dielectric constant and dielectric loss: according to the method specified in 6.2 of GB / T 1409-2006, and the measurement frequency is 1 MHz.

[0056] 5. Light transmittance and refractive index: B method specified in 7.2 of GB / T 2410-2008.

[0057] 6. Water contact angle: A method specified in GB / T 39691-2020.

[0058] Example 1 The tetrafluoroethylene-based melt-processable perfluorocopolymer is copolymerized from the following monomers: tetrafluoroethylene 160 g (87.9%), perfluorocyclopentene 10 g (5.5%), and perfluoro-n-propyl vinyl ether 12 g (6.6%). The weight average molecular weight of the obtained perfluorocopolymer is 160,000 g / mol.

[0059] The preparation method of the tetrafluoroethylene-based melt-processable perfluorocopolymer emulsion, and the specific steps are as follows: (1) 600 ml of pretreated deionized water, 0.9 g of reducing agent ammonium sulfite, 2.4 g of dispersant perfluoropolyether carboxylate ammonium, 0.6 g of pH regulator sodium carbonate, and 16 g of solubilizer perfluoroheptane are sucked into a clean and sealed 1 L vacuum polymerization kettle, and the reaction kettle is evacuated and replaced with nitrogen for more than three times.

[0060] (2) After the oxygen content is qualified (<10 ppm), perfluorocyclopentene 5 g and perfluoro-n-propyl vinyl ether 6 g are added to the reaction kettle under the condition of ensuring the vacuum in the kettle, the temperature is raised to the reaction temperature 30℃, at this time, due to the low boiling point of the modified monomer, part of the pressure in the kettle has been volatilized, tetrafluoroethylene (TFE) monomer is supplemented to make the pressure in the kettle to 0.6 MPa, then 0.9 g of initiator ammonium persulfate is added to the reaction kettle, and the reaction is started. TFE monomer is continuously supplemented to maintain the constant pressure in the kettle during the reaction.

[0061] (3) When the TFE monomer feed amount reached 70 g, 1.2 g of dispersant was supplemented.

[0062] When the TFE monomer cumulative feed amount reached 80 g, 5 g of perfluorocyclopentene and 6 g of perfluoro-n-propyl vinyl ether were supplemented.

[0063] When the TFE monomer cumulative feed amount reached 100 g, 0.5 g of chain transfer agent perfluoro-hexyl iodide was added.

[0064] (4) When the TFE cumulative feed amount reached 160, 0.03 g of terminator dipentene was added into the kettle through a special pipeline to end the reaction, stop stirring, recover the monomer in the kettle and vent, and discharge after nitrogen replacement to obtain a blue transparent stable emulsion with a particle size of 175 nm and a solid content of 24 wt%. The emulsion was still flowable after long-term storage and was not demulsified after being stored for more than 3 months under stirring at 800 rpm.

[0065] The post-treatment section included: demulsification at 1600 rpm or with alkali metal salt at 1000 rpm; pure water washing until the conductivity was <3 μS / cm; drying at 120°C for more than 8 h; granulation at 360°C with a cutter speed of 20 rpm; and esterification at 200°C for 8 h.

[0066] The final product had a tensile strength of 34 MPa, a dielectric constant of 2.12, a dielectric loss of 4.355 x 10 -4 , and a melting point of 304°C. The melt index was 26 g / 10 min and the critical shear rate was 200 s -1 under a load of 5 kg at 372°C, indicating that the product was a high-speed extrudable resin.

[0067] The initiator used in the example had a half-life of more than 10 h at the above-mentioned temperature, and the polymerization rate was ensured not to be greatly attenuated during the entire polymerization. The modified monomer used in the example was condensed and recovered before venting at the end of the reaction. After the polymerization was completed, the stirring was stopped, the pressure in the kettle was removed, and the water vapor possibly carried was removed by a self-made dryer, and then the kettle was slowly discharged into a pre-cooled condenser tube at -10°C. The modified monomer was collected from the bottom, and the non-condensed gas was discharged from the top. A small part of the modified monomer was tested for purity, and was immediately stored at low temperature. On the basis of ensuring safety and environmental protection, the cost was greatly reduced.

[0068] Example 2 The tetrafluoroethylene-based melt-processable perfluorocopolymer was copolymerized from the following monomers: tetrafluoroethylene 130 g (74.3%), perfluorocyclohexene 30 g (17.1%), and perfluoro-methyl vinyl ether 15 g (8.6%). The weight average molecular weight of the obtained perfluorocopolymer was 230,000 g / mol.

[0069] The preparation method of the tetrafluoroethylene-based melt-processable perfluorocopolymer emulsion is specifically as follows: (1) A clean and sealed 1L vacuum polymerization kettle is used to suck in pretreated 550ml deionized water, 0.7g reducing agent potassium bisulfite, 2.5g dispersant ammonium perfluoropolyether carboxylate, 0.8g pH regulator sodium bicarbonate, and 15g solubilizer perfluorocycloether, and the reaction kettle is evacuated and replaced with nitrogen for more than three times.

[0070] (2) After the oxygen content is qualified, 15g of perfluorocyclohexene and 8g of perfluoromethyl vinyl ether are added to the reaction kettle under the condition of ensuring the vacuum in the kettle, the temperature is raised to the reaction temperature of 55℃, the TFE monomer is supplemented to make the pressure in the kettle to 0.3MPa, then 0.32g of initiator potassium persulfate is added to the reaction kettle, and the reaction is started. The monomer is continuously supplemented to maintain the constant pressure in the kettle during the reaction.

[0071] (3) When the TFE monomer feeding amount reaches 60g, 7g of perfluoromethyl vinyl ether, 15g of perfluorocyclohexene, and 1.25g of dispersant are supplemented, and the initiator can be selectively added at one time or in batches; the addition of another monomer is determined according to the previous input proportion.

[0072] When the cumulative TFE feeding amount reaches 80g, 0.2g of chain transfer agent methane is added.

[0073] (4) When the cumulative TFE monomer feeding amount reaches 130g, 0.4g of 5% sodium nitrite aqueous solution is added to the kettle through a special pipeline to terminate the reaction, stop stirring, recover the monomer in the kettle and empty it, and after nitrogen replacement, the product is discharged to obtain a blue-white emulsion with an emulsion particle size of 197nm, an emulsion solid content of 25wt%, and no obvious change after one week.

[0074] The final product has a tensile strength of 34.7MPa, a light transmittance of 89% at a wavelength of 550nm, a dielectric constant of 1.97, and a dielectric loss of 3.1x10 -4 , a melt index of 5g / 10min at 360℃ under a 5kg weight condition, a melting point of 305℃, a thermal decomposition temperature of 440℃, and a low dielectric resin product.

[0075] The reaction pressure in the embodiment is 0.3MPa, which can ensure a lower concentration of tetrafluoroethylene in the kettle, balance the reactivity difference between tetrafluoroethylene and the comonomer, make the frequency of alkene ether structure on the polytetrafluoroethylene main chain more uniform, improve the flowability of the polymer melt state, and have excellent properties such as high heat distortion temperature and high product surface finish, thereby further expanding the application possibilities of the polymer in the communication and electronic circuit fields. The surface roughness Ra max of the product is 0.15μm.

[0076] The present embodiment uses a reaction temperature of 55°C to ensure the active free radical concentration of the initiator in the polymerization system and to ensure normal molecular chain growth when the comonomer participates in polymerization under low pressure polymerization conditions.

[0077] The polymerization process used in the present embodiment in combination with the temperature and pressure makes the polymerization more inclined to the modified monomer. The fluorine content of the copolymer is 76.2%, which reflects the increased participation of the modified monomer in copolymerization and the increased conversion rate, and the performance of the polymer is maximally changed and optimized under the feeding ratio.

[0078] Example 3 The tetrafluoroethylene-based melt-processable perfluorocopolymer is copolymerized from the following monomers: tetrafluoroethylene 50 g (19.2%), perfluorocyclopentene 40 g (15.4%), and 5-trifluoromethoxy-2,2,4-trifluoro-1,3-dioxole (TTD) 170 g (65.4%). The number average molecular weight of the obtained perfluorocopolymer is 290,000 g / mol.

[0079] The preparation method of the tetrafluoroethylene-based melt-processable perfluorocopolymer emulsion is as follows: (1) A clean and sealed 2L vacuum polymerization kettle is filled with pretreated 800ml deionized water, 0.6g reducing agent ferrous chloride, 1.5g pH regulator sodium carbonate, and 15g dispersant ammonium perfluorohexanoate aqueous solution (20wt%), and the reaction kettle is evacuated and replaced with nitrogen for more than three times.

[0080] (2) After the oxygen content is qualified, the perfluorocyclopentene 20g, the perfluorocyclic vinyl ether TTD 60g, and the solubilizing agent perfluorocyclic ether 16g are added to the reaction kettle under the condition of ensuring the vacuum in the kettle, the temperature is raised to the reaction temperature 42°C, the TFE monomer is supplemented to make the pressure in the kettle to 0.28MPa, then the initiator ammonium persulfate 0.5g is added to the reaction kettle, and the reaction is started. The TFE monomer is continuously supplemented to maintain the constant pressure in the kettle during the reaction.

[0081] (3) When the TFE monomer feeding amount reaches 20g, 10g of perfluorocyclopentene, 60g of TTD, and 10g of dispersant ammonium perfluorohexanoate aqueous solution (15wt%) are supplemented.

[0082] When the cumulative TFE monomer feeding amount reaches 30g, the chain transfer agent perfluorohexyl iodide 0.2g is added.

[0083] When the cumulative TFE monomer feeding amount reaches 35g, 10g of perfluorocyclopentene and 50g of TTD are supplemented.

[0084] (4) When the cumulative amount of TFE monomer reaches 50 g, 0.05 g of the terminator sodium nitrite is added into the kettle through a special pipeline to end the reaction, stop stirring, recover the monomer in the kettle and vent, and discharge after nitrogen replacement to obtain a blue-white emulsion with an emulsion particle size of 220 nm and a solid content of 24 wt%.

[0085] The final product is an amorphous perfluoropolymer with a glass transition temperature of 163°C, good thermal stability, a thermal decomposition temperature of more than 385°C, a light transmittance of 96% from near ultraviolet to infrared, a refractive index of 1.3, good weather resistance, excellent hydrophobicity with a water contact angle of more than 110°, and dielectric wetting properties, which can be applied to gene detection chips in the field of biological medicine. It meets the requirements of high light transmittance, low refractive index, acid and alkali resistance, and non-fluorescence, and can be used as optical fiber cable coating, anti-reflection film for optical lenses, etc.

[0086] Example 4 The tetrafluoroethylene-based melt-processable perfluorocopolymer is copolymerized from the following monomers: tetrafluoroethylene 150 g (87.2%), perfluorocyclobutene 10 g (5.8%), and perfluoro-n-propyl vinyl ether 12 g (7.0%). The weight average molecular weight of the obtained perfluorocopolymer is 130,000 g / mol.

[0087] The preparation method of the tetrafluoroethylene-based melt-processable perfluorocopolymer emulsion includes the following specific steps: (1) A clean and sealed 1 L vacuum polymerization kettle is filled with pretreated 530 ml of deionized water, 0.8 g of reducing agent ammonium sulfite, 2.8 g of dispersant perfluoropolyether carboxylate ammonium, 0.79 g of pH regulator sodium carbonate, and 17 g of solubilizer perfluoroheptane, and the reaction kettle is evacuated and replaced with nitrogen three times or more.

[0088] (2) After the oxygen content is less than 10 ppm, the reaction kettle is added with perfluorocyclobutene 5 g and perfluoro-n-propyl vinyl ether 6 g, heated to a reaction temperature of 38°C, supplemented with TFE monomer to make the pressure in the kettle 0.55 MPa, and then added with 0.8 g of initiator ammonium persulfate to start the reaction. The monomer is constantly supplemented to maintain the constant pressure in the kettle during the reaction.

[0089] (3) When the amount of TFE monomer reaches 70 g, 1.4 g of dispersant is supplemented, and perfluorocyclobutene 5 g and perfluoro-n-propyl vinyl ether 6 g are added.

[0090] When the cumulative amount of TFE monomer reaches 90 g, 0.5 g of chain transfer agent perfluoro-hexyl iodocane is added.

[0091] (4) When the cumulative amount of TFE reaches 150 g, 0.025 g of the terminating agent dipentene is added into the reactor through a special pipeline to end the reaction, stop stirring, recover the monomers in the reactor and vent, and discharge the material after nitrogen replacement. The blue transparent emulsion with an average particle size of 180 nm is obtained, and the emulsion has a solid content of 24.5 wt%, and is not stratified and has no insoluble particles after being stored for more than 3 months.

[0092] The final product has a tensile strength of 32.5 MPa, a dielectric constant of 2.12, a dielectric loss of 3.950 x 10 -4 , a melting point of 293 ℃, a melt index of 35 g / 10 min under the condition of 372 ℃ and 5 kg, and a critical shear rate of 230 s -1 , and is a high-speed extrudable resin product.

[0093] Comparative Example 1 The preparation method of the tetrafluoroethylene-based melt-processable perfluorocopolymer emulsion in the present comparative example is as follows: (1) 550 ml of pretreated deionized water, 0.8 g of reducing agent ammonium sulfite, 2.5 g of dispersant perfluoropolyether carboxylate ammonium, 0.6 g of pH regulator sodium carbonate, and 0.3 g of chain transfer agent perfluorohexyl iodide are sucked into a clean and sealed 1 L vacuum polymerization reactor, and the reaction kettle is evacuated and replaced with nitrogen three times or more.

[0094] (2) After the oxygen content is qualified, perfluorocyclobutene 12 g and perfluoromethyl vinyl ether (PMVE) 10 g are added to the reaction kettle under the condition of maintaining the vacuum in the kettle, the temperature is raised to the reaction temperature of 40 ℃, TFE monomer is supplemented to make the pressure in the kettle reach 0.6 MPa, and then 0.8 g of initiator ammonium persulfate is added to the reaction kettle to start the reaction. The TFE monomer is continuously supplemented to maintain the constant pressure in the kettle during the reaction.

[0095] (3) When the amount of TFE monomer reaches 80 g, 2 g of dispersant perfluoropolyether carboxylate ammonium is supplemented. (4) When the amount of TFE monomer reaches 150 g, 0.03 g of the terminating agent dipentene is added into the reactor through a special pipeline to end the reaction, stop stirring, recover the monomers in the reactor and vent, and discharge the material after nitrogen replacement. The blue transparent emulsion with an average particle size of 180 nm is obtained, and the emulsion has a solid content of 24.5 wt%, and is not stratified and has no insoluble particles after being stored for more than 3 months.

[0096] The final product has a tensile strength of 32.5 MPa, a dielectric constant of 2.12, a dielectric loss of 3.950 x 10 -1 , a melting point of 293 ℃, a melt index of 35 g / 10 min under the condition of 372 ℃ and 5 kg, and a critical shear rate of 230 s -1 , and is a high-speed extrudable resin product.

[0097] The comparative example once inputs the modified monomer, but from the test results of the tensile and melting point tests, the actual amount of the modified monomer participating in the copolymerization is less, the polymeric rate of the ether monomer is low, the modified polytetrafluoroethylene does not play an obvious role, resulting in a higher melting point and lower tensile strength of the product, causing waste of high-value modified monomers and increasing the cost of the product. The comparative example does not use a fluorine-containing solubilizer, and the use of the fluorine-containing solubilizer is beneficial to the gas-liquid transfer of the modified monomer and the participation of the modified monomer in the copolymerization, so as to play the maximum modification role under a certain feeding ratio and ensure the polymeric rate of the modified monomer. The chain transfer agent used in the comparative example is added in the early stage of polymerization, and it can be seen from the 0.5% thermal decomposition temperature of the polymer that the chain transfer agent plays a role in the early stage of polymerization, which is not conducive to the high-temperature resistance of the polymer. The dispersant used in the comparative example is not added in time, and is added after the cumulative amount of tetrafluoroethylene exceeds 1 / 2 of the total planned amount, even if the addition amount is increased, the effect on stabilizing the polymerization emulsion is not as expected, resulting in a slight powder after the emulsion is discharged, which affects the stability of the emulsion.

[0098] Comparative Example 2 The preparation method of the tetrafluoroethylene-based melt-processable perfluorocopolymer emulsion in the comparative example is as follows: (1) 480 ml of pretreated deionized water, 1.5 g of reducing agent sodium bisulfite, 3.5 g of dispersant potassium perfluoropolyether carboxylate, 2.5 g of pH regulator sodium carbonate, and 13 g of solubilizer perfluoroheptane were sucked into a clean and sealed 1 L vacuum polymerization kettle, and the reaction kettle was evacuated and replaced with nitrogen for more than three times.

[0099] (2) After the oxygen content is qualified, the reaction kettle is added with 6 g of perfluoromethyl vinyl ether under the condition of ensuring the vacuum in the kettle, the temperature is raised to the reaction temperature of 45°C, the TFE monomer is supplemented to make the pressure in the kettle to 0.35 MPa, then 0.45 g of initiator ammonium persulfate is added into the reaction kettle, and the reaction is started. The TFE monomer is continuously supplemented to maintain the constant pressure in the kettle during the reaction.

[0100] (3) When the amount of TFE monomer reaches 50 g, 6 g of perfluoroethyl vinyl ether is added, and 1.75 g of dispersant potassium perfluoropolyether carboxylate is added.

[0101] When the amount of TFE monomer reaches 70 g, 0.5 g of chain transfer agent methanol is added.

[0102] (4) When the amount of TFE monomer reaches 110 g, 0.03 g of terminator p-phenylphenol is added into the kettle through a special pipeline, the reaction is ended, the stirring is stopped, the monomer in the kettle is recovered and discharged, and the product is obtained after nitrogen replacement and discharge. The average particle size of the slightly emulsified blue emulsion is 320 nm.

[0103] The final product has a tensile strength of 28 MPa, a melting point of 312°C, a melt index of 6.5 g / 10 min, a dielectric constant of 2.15, a dielectric loss of 8 x 10 -4 , a critical shear rate of 55 s -1 , and a translucent resin product with a thermal decomposition temperature of 330°C.

[0104] The product obtained in this comparative example has a melting point of more than 310°C and cannot be extruded at high speed, and the resin has a light transmittance of less than 70%. The use of an excessive amount of reducing agent results in a strong alkalinity of the system (pH = 11) and a high electrolyte concentration, which is not conducive to the formation of uniform particle sizes in the emulsion and can reduce the stability of the emulsion.

[0105] Comparative Example 3 The preparation method of the tetrafluoroethylene-based melt-processable perfluorinated copolymer emulsion in this comparative example is as follows: (1) A clean and sealed 1L vacuum polymerization kettle was used to suck in 580ml of pretreated deionized water, 3.5g of dispersant sodium perfluoropolyether carboxylate, 0.27g of reducing agent sodium bisulfite, 0.6g of pH regulator sodium carbonate, and 10g of solubilizer perfluorocycloether. The reaction kettle was evacuated and replaced with nitrogen three times or more.

[0106] (2) After the oxygen content is qualified, 6g of perfluorocyclobutene and 6g of perfluoro-n-propyl vinyl ether (PPVE) are added to the reaction kettle under the condition of maintaining the vacuum in the kettle. The temperature is raised to 35°C, and TFE monomer is supplemented to maintain the pressure in the kettle to 0.7MPa. Then, 0.6g of initiator potassium persulfate is added to the reaction kettle to start the reaction. The monomer is continuously supplemented to maintain the constant pressure in the kettle during the reaction.

[0107] (3) When the amount of TFE monomer reaches 90g, 5g of perfluorocyclobutene, 5g of PPVE, and 1.75g of perfluoropolyether carboxylic acid are supplemented.

[0108] When the amount of TFE monomer reaches 100g, 0.5g of chain transfer agent n-hexane is added.

[0109] (4) When the amount of TFE monomer reaches 180g, 0.05g of terminating agent sodium nitrite is added to the kettle through a special pipeline to end the reaction, stop stirring, recover the monomer in the kettle, and vent. After nitrogen replacement, the material is discharged.

[0110] In this comparative example, the molar ratio of reducing agent to initiator is 1:1. Compared with the normal reaction speed, the polymerization speed decreases, the polymerization time is prolonged to more than 8h, which is 3-5h longer than the normal reaction speed, and the production efficiency is reduced. It is shown that increasing the proportion of reducing agent at a low temperature of 35°C is beneficial to maximizing the initiation efficiency of the initiator, and the appropriate amount also reduces the problem of excessive use of initiator.

[0111] Testing revealed that the polymer product had a weight-average molecular weight of 125,000 g / mol, a PDI of 3.35, a tensile strength of 23 MPa, a melt index of 15 g / 10 min at 372℃ with a 5 kg weight, and a 0.5% thermal decomposition temperature of 250℃. The wide PDI molecular weight distribution of the polymer obtained in this comparative example indicates that a slow reaction rate negatively impacts the polymer's molecular weight distribution, resulting in more undesirable termination of active end groups in the polymer chains, which is detrimental to the overall product performance.

[0112] Comparative Example 4 The preparation method of the perfluoropolymer emulsion with melt-processable tetrafluoroethylene described in this comparative example includes the following specific steps: (1) Inhale 540ml of pretreated deionized water, 3.7g of dispersant sodium perfluoropolyether carboxylate, 0.75g of pH adjuster sodium carbonate, and 11g of solubilizer perfluorocyclic ether into a clean, sealed 1L vacuum polymerization reactor. Evacuate the reactor and replace it with nitrogen three times or more.

[0113] (2) After the oxygen content is qualified, under the condition of ensuring the vacuum inside the reactor, add 7g of perfluorocyclobutene and 7g of perfluoropropyl vinyl ether (PPVE) to the reactor, raise the temperature to the reaction temperature of 70°C, add TFE monomer to make the pressure in the reactor reach 0.7MPa, and then add 0.5g of potassium persulfate initiator to the reactor to start the reaction. During the reaction, monomer is continuously added to maintain a constant pressure inside the reactor.

[0114] (3) When the amount of TFE monomer feed reaches 80g, add 6g of perfluorocyclobutene monomer, 6g of PPVE, and 1.85g of perfluoropolyether carboxylic acid.

[0115] When the TFE monomer feed amount reaches 100g, add 0.45g of chain transfer agent ethane.

[0116] (4) When the amount of TFE monomer fed reaches 170g, 0.04g of the terminator sodium nitrite is added into the reactor through a special pipeline to end the reaction, stop stirring, recover the monomer in the reactor and vent it, and then release the material after nitrogen replacement.

[0117] The obtained polymer product was tested and found to have a weight-average molecular weight of 55,000 g / mol, a tensile strength of 13 MPa, a melt index of 360°C without added weights, and a 0.5% thermal decomposition temperature of 210°C.

[0118] The polymerization temperature and pressure in this comparative system are relatively high. The high-temperature environment results in a high number of active free radicals in the initiator, which easily leads to random collisions of molecular chains of different lengths. This is not conducive to the uniform participation of modified monomers (cyclic monomers, perfluoroolefin ethers) in polymerization, affecting the molecular weight and uniform molecular weight distribution, thus affecting the thermal stability of the product and resulting in a low thermal decomposition temperature.

[0119] Comparative Example 5 The preparation method of the tetrafluoroethylene-based melt-processable perfluorocopolymer emulsion in this comparative example is as follows: (1) A clean and sealed 1L vacuum polymerization kettle was filled with pretreated 550ml deionized water, 3.5g dispersant perfluoropolyether ammonium carboxylate, 1.1g pH regulator potassium carbonate, and 15g hexafluorobenzene. The reaction kettle was evacuated and replaced with nitrogen for more than three times.

[0120] (2) After the oxygen content was qualified, the reaction kettle was filled with perfluoropropyl vinyl ether 5g and PPD 10g under the condition of ensuring the vacuum in the kettle. Then the temperature was raised to the reaction temperature of 42℃, and TFE monomer was supplemented to make the pressure in the kettle reach 0.35MPa. Then 0.3g initiator potassium persulfate was added to the reaction kettle to start the reaction. The monomer was continuously supplemented to maintain the constant pressure in the kettle during the reaction.

[0121] (3) After adding the initiator, 4g of PPD, 10g of monomer PPD, 0.4g of chain transfer agent, and 1g of perfluorohexanoic acid ammonium were supplemented after 1h. After 2h of cumulative reaction, 3g of modified monomer perfluorocyclohexene, 3g of PPVE, and 1g of dispersant perfluorohexanoic acid ammonium were supplemented.

[0122] (4) After 3h of cumulative reaction, 2g of terminating agent dipentene was added to the kettle through a special pipeline to end the reaction, stop stirring, recover the monomer in the kettle and empty it, and then discharge the material after nitrogen replacement. The solid content of the liquid was 5%.

[0123] The obtained polymer product was yellowish after drying, with coarse particles and low yield, which was unqualified product.

[0124] As can be seen in this comparative example, even at the polymerization temperature and pressure described in the present application, it is difficult to initiate without a reducing agent, that is, the initiator thermal decomposition system is not suitable. The initiator thermal decomposition has a slow initiation rate at low temperature, resulting in low yield. And without a reducing agent, the trace oxygen produced in the polymerization process or the decomposition of the initiator is not controlled, which affects the color, particle size and practical value of the product.

[0125] Comparative Example 6 The preparation method of the tetrafluoroethylene-based melt-processable perfluorocopolymer emulsion in this comparative example is as follows: (1) A clean and sealed 1L vacuum polymerization kettle was filled with pretreated 550ml deionized water, 3.5g dispersant perfluoropolyether ammonium carboxylate, 1.1g pH regulator potassium carbonate, and 15g hexafluorobenzene. The reaction kettle was evacuated and replaced with nitrogen for more than three times.

[0126] (2) After the oxygen content is qualified, under the condition of ensuring the vacuum in the reactor, 6 g of perfluoropropyl vinyl ether, 10 g of TTD, and 6 g of perfluorocyclohexene are added into the reactor, then the temperature is increased to 50°C, TFE monomer is supplemented to make the pressure in the reactor reach 0.35 MPa, then 0.6 g of initiator potassium persulfate is added into the reactor, and the reaction is started. The monomer is continuously supplemented to maintain the constant pressure in the reactor during the reaction.

[0127] (3) When the amount of TFE monomer reaches 50 g, 6 g of perfluoropropyl vinyl ether monomer, 10 g of TTD, and 3 g of dispersant ammonium perfluorohexanoate are supplemented.

[0128] When the amount of TFE monomer reaches 100 g, 6 g of perfluorocyclohexene and 10 g of TTD are supplemented, and 0.2 g of chain transfer agent is added. (4) When the amount of TFE monomer reaches 150 g, the reaction is ended, the stirring is stopped, the monomer in the reactor is recovered and discharged after being replaced by nitrogen, and the emulsion has a solid content of 23%. However, after being placed overnight, the emulsion shows a gel phenomenon and has no flow state.

[0129] It can be seen from the comparative example that the absence of a terminator in the redox system described in the application is not conducive to the long-term stable storage of the emulsion, and a gel is formed.

[0130] Comparative Example 7 The preparation method of the tetrafluoroethylene-based melt-processable perfluorocopolymer emulsion in the present comparative example is as follows: (1) 500 ml of pretreated deionized water, 3.5 g of dispersant sodium perfluoropolyether carboxylate, and 0.7 g of pH regulator sodium carbonate are sucked into a clean and sealed 1 L vacuum polymerization reactor, 30 g of solubilizer perfluorocyclohexene is added, and the reactor is evacuated and replaced by nitrogen for more than three times.

[0131] (2) After the oxygen content is qualified, under the condition of ensuring the vacuum in the reactor, 6 g of perfluorocyclopentene and 7 g of PPVE are added into the reactor, the temperature is increased to 38°C, TFE monomer is supplemented to make the pressure in the reactor reach 0.5 MPa, then 0.6 g of initiator potassium persulfate is added into the reactor, and the reaction is started. The monomer is continuously supplemented to maintain the constant pressure in the reactor during the reaction.

[0132] (3) When the amount of TFE monomer reaches 60 g, 1.75 g of dispersant perfluoropolyether carboxylic acid is supplemented.

[0133] When the amount of TFE monomer reaches 80 g, 5 g of perfluorocyclopentene monomer and 6 g of PPVE are supplemented, and 0.3 g of chain transfer agent ethane is added.

[0134] (4) When the amount of TFE monomer fed reaches 150g, 0.05g of the terminator sodium nitrite is added into the reactor through a special pipeline to end the reaction, stop stirring, recover the monomer in the reactor and vent it, and then release the material after nitrogen replacement.

[0135] The obtained polymer product was tested and found to have a weight-average molecular weight of 70,000 g / mol, a tensile strength of 16.5 MPa, and a melt index that allowed it to flow directly at 372°C without the addition of weights. The results from the comparative polymerization products show that if the amount of solubilizer used in emulsion polymerization exceeds a certain range, it not only leads to a slower polymerization rate but also directly affects the length of the formed polymer chains, resulting in a lower molecular weight.

[0136] Comparative Example 8 The preparation method of the perfluoropolymer emulsion with melt-processable tetrafluoroethylene described in this comparative example includes the following specific steps: (1) Inhale 580ml of pretreated deionized water, 0.9g of reducing agent ammonium sulfite, 2.4g of dispersant perfluoropolyether ammonium carboxylate, 0.6g of pH adjuster sodium carbonate, and 16g of solubilizer perfluoroheptane into a clean, sealed 1L vacuum polymerization reactor. Evacuate the reactor and replace it with nitrogen more than three times.

[0137] (2) After the oxygen content is qualified to be <10ppm, under the condition of ensuring vacuum inside the reactor, add 5g of modified monomer hexafluoropropylene and 6g of perfluoropropyl vinyl ether to the reactor, and then raise the temperature to the reaction temperature of 30℃. At this time, due to the low boiling point of the modified monomer, some pressure has been generated in the reactor due to volatilization. Add TFE monomer to make the pressure in the reactor reach 0.6MPa, and then add 0.9g of initiator ammonium persulfate to the reactor to start the reaction. During the reaction, monomer is continuously added to maintain a constant pressure inside the reactor.

[0138] (3) When the amount of TFE monomer fed reaches 70g, add 1.2g of dispersant.

[0139] When the cumulative amount of TFE monomers fed reaches 80g, add 5g of hexafluoropropylene and 6g of perfluoropropyl vinyl ether.

[0140] When the cumulative amount of TFE monomer fed reaches 100g, add 0.5g of chain transfer agent perfluorohexyl iodide.

[0141] (4) When the cumulative amount of TFE feed reaches 160, 0.03g of the terminator dipentene is added to the reactor through a special pipeline to end the reaction, stop stirring, recover the monomer in the reactor and vent it, and discharge the material after nitrogen replacement to obtain a blue transparent emulsion.

[0142] The final product has a tensile strength of 29.4 MPa, a dielectric constant of 2.15, and a dielectric loss of 8.51 × 10⁻⁶. -4, melting point 310℃, at 372℃, 5kg under the condition, test melt index is 8g / 10min, light transmittance 73%, critical shear rate is 40s -1 If the modified monomer is not perfluorocycloalkene but hexafluoropropene, it cannot have high transparency and low dielectric properties.

[0143] Comparative Example 9 The preparation method of the tetrafluoroethylene-based melt-processable perfluorocopolymer emulsion in this comparative example is as follows: (1) Into a clean and sealed 1L vacuum polymerization kettle, 510ml of pretreated deionized water, 2.05g of reducing agent sodium bisulfite, 3g of dispersant perfluoropolyether ammonium carboxylate, 0.6g of pH regulator sodium carbonate, and 16g of solubilizer perfluoroheptane were sucked in, and the reaction kettle was evacuated and replaced with nitrogen for more than three times.

[0144] (2) After the oxygen content was qualified (<10ppm), the modified monomers perfluorocyclohexene 5g and perfluoromethyl vinyl ether 6g were added to the reaction kettle under the condition of maintaining the vacuum in the kettle, the temperature was raised to the reaction temperature 35℃, the TFE monomer was supplemented to make the pressure in the kettle to 0.6MPa, then 0.45g of initiator ammonium persulfate was added to the reaction kettle, and the reaction was started. The monomer was continuously supplemented to maintain the constant pressure in the kettle during the reaction.

[0145] (3) When the TFE monomer dosage reached 70g, 1.5g of dispersant was supplemented, and 5g of perfluorocyclohexene and 6g of perfluoromethyl vinyl ether were added.

[0146] When the cumulative TFE monomer dosage reached 100g, 0.43g of chain transfer agent perfluoroheptyl iodide was added.

[0147] (4) When the cumulative TFE dosage reached 155g, 0.03g of terminator dipentene was added to the kettle through a special pipeline, the reaction was stopped, the stirring was stopped, the monomer in the kettle was recovered and vented, and after nitrogen replacement, the material was discharged. The normal emulsion was not discharged, and the demulsification phenomenon occurred in the kettle.

[0148] In this comparative example, the molar ratio of reducing agent to initiator is as high as 9.98:1, and the excessive increase of the amount of reducing agent can cause serious demulsification of the emulsion. In the comparative example, the dispersant is an anionic surfactant, and the addition of excessive electrolyte in the system can cause the double electric layer of micelles to be thin and weaken its stability, affecting the product quality and production efficiency.

[0149] Comparative Example 10 The preparation method of the tetrafluoroethylene-based melt-processable perfluorocopolymer emulsion in this comparative example is as follows: (1) Into a clean, sealed 2L vacuum polymerization reactor, 800ml of pretreated deionized water, 0.6g of reducing agent sodium bisulfite, 1.5g of pH regulator sodium carbonate, and 15g of dispersant ammonium perfluorohexanoate (20%) aqueous solution were sucked in. The reactor was evacuated and replaced with nitrogen for more than three times.

[0150] (2) After the oxygen content was qualified, 20g of perfluorocyclopentene, 60g of perfluorocyclic vinyl ether TTD, and 16g of perfluorosolubilizer fluorine ring ether were added to the reactor while maintaining the vacuum in the reactor. The temperature was raised to the reaction temperature of 48°C, and TFE monomer was supplemented to maintain the pressure in the reactor to 0.78MPa. Then, 0.5g of over-initiator ammonium sulfate was added to start the reaction. During the reaction, TFE monomer was continuously supplemented to maintain the constant pressure in the reactor.

[0151] (3) When the amount of TFE monomer reached 20g, 10g of perfluorocyclopentene, 60g of TTD, and 10g of dispersant ammonium perfluorohexanoate (15%) aqueous solution were supplemented.

[0152] When the cumulative amount of TFE monomer reached 35g, 10g of perfluorocyclopentene, 50g of TTD, and 0.2g of chain transfer agent perfluorohexyl iodine were supplemented.

[0153] (4) When the cumulative amount of TFE monomer reached 50g, 0.05g of terminator sodium nitrite was added to the reactor through a special pipeline to end the reaction, stop stirring, recover the monomer in the reactor, and empty the reactor. After nitrogen replacement, the product was discharged to obtain a blue-white emulsion with an emulsion particle size of 200nm and a solid content of 24wt%.

[0154] The final perfluoropolymer had a glass transition temperature of 133°C and a melting point of 232°C. The light transmittance from near ultraviolet to infrared was about 80%, and the refractive index was 1.35. Compared with Example 3, the polymerization temperature and pressure were changed, resulting in uneven monomer polymerization, tetrafluoroethylene homopolymerization, and crystallization, which resulted in a melting point. The copolymer under this condition lost the properties of high transparency and low refractive index, and did not have the characteristics of biological medical and optical applications, losing high added value.

[0155] Comparative Example 11 The preparation method of the tetrafluoroethylene-based melt-processable perfluorocopolymer emulsion was as follows: (1) Into a clean, sealed 2L vacuum polymerization reactor, 800ml of pretreated deionized water, 0.6g of reducing agent sodium bisulfite, 1.5g of pH regulator sodium carbonate, and 20g of dispersant ammonium perfluorohexanoate aqueous solution (20%) were sucked in. The reactor was evacuated and replaced with nitrogen for more than three times.

[0156] (2) After the oxygen content is qualified, 60 g of perfluorocyclic vinyl ether TTD and 16 g of solubilizing agent perfluorocyclic ether are added to the reaction kettle under the condition of ensuring the vacuum in the kettle, the temperature is raised to the reaction temperature of 48°C, TFE monomer is supplemented to make the pressure in the kettle to 0.35 MPa, then 0.5 g of initiator ammonium persulfate is added to the reaction kettle to start the reaction. TFE monomer is continuously supplemented to maintain the constant pressure in the kettle during the reaction.

[0157] (3) When the TFE monomer feeding amount reaches 30 g, 60 g of TTD is supplemented, and 10 g of dispersant ammonium perfluorohexanoate aqueous solution (20%) is supplemented.

[0158] When the cumulative TFE monomer feeding amount reaches 50 g, 50 g of TTD is supplemented, and 0.2 g of chain transfer agent perfluorohexyl iodine is added.

[0159] (4) When the cumulative TFE monomer feeding amount reaches 65 g, 0.05 g of terminator sodium nitrite is added to the kettle through a special pipeline to end the reaction, the stirring is stopped, the monomer in the kettle is recovered and vented, and the product is discharged after nitrogen replacement to obtain a blue-white emulsion with an emulsion particle size of 195 nm and a solid content of 22%.

[0160] The perfluoropolymer obtained has a glass transition temperature of 125°C and a melting point of 261°C. Due to the partial crystallization of the copolymer, the light transmittance from near ultraviolet to infrared is 86%, and the refractive index is 1.35.

[0161] Compared with Example 3, the present comparative example does not use perfluorocyclic olefin monomer, even if the feeding ratio is increased to 28% TFE and 72% perfluorocyclic vinyl ether, it is difficult to obtain an amorphous fluororesin, and it is unable to play the role of adding a large proportion of modifying monomer to give the product high performance and high added value. It can be seen that within the scope of the present patent, the perfluorocyclic olefin monomer cannot be replaced.

[0162] Comparative Example 12 The preparation method of the tetrafluoroethylene-based melt-processable perfluorocopolymer emulsion in the present comparative example is as follows: (1) 530 ml of pretreated deionized water, 0.55 g of reducing agent sodium bisulfite, 2.5 g of dispersant perfluoropolyether carboxylic acid ammonium, and 0.7 g of pH regulator sodium bicarbonate are sucked into a clean and sealed 1 L vacuum polymerization kettle, and the reaction kettle is evacuated and replaced with nitrogen for more than three times.

[0163] (2) After the oxygen content is qualified, 7 g of perfluorocyclohexene and 7 g of perfluoromethyl vinyl ether are added to the reaction kettle under the condition of ensuring the vacuum in the kettle, the temperature is raised to the reaction temperature of 55°C, TFE monomer is supplemented to make the pressure in the kettle to 0.3 MPa, then 0.4 g of initiator potassium persulfate is added to the reaction kettle to start the reaction. TFE monomer is continuously supplemented to maintain the constant pressure in the kettle during the reaction.

[0164] (3) When the TFE monomer charge reaches 60 g, supplement perfluoromethyl vinyl ether 7 g, perfluorocyclohexene 7 g, and supplement dispersant 1.25 g at the same time.

[0165] When the TFE cumulative charge reaches 80 g, supplement chain transfer agent methane 0.2 g.

[0166] (4) When the TFE monomer cumulative charge reaches 130 g, 0.4 g of the terminator 5% sodium nitrite aqueous solution is added into the kettle through a special pipeline, the reaction is ended, the stirring is stopped, the monomer in the kettle is recovered and vented, and the product is discharged after nitrogen replacement, to obtain a blue emulsion with an emulsion particle size of 210 nm, an emulsion solid content of 23 wt%, and no obvious change in state after one week of storage.

[0167] The final product has a tensile strength of 32 MPa, a light transmittance of 84% at a wavelength of 550 nm, a dielectric constant of 2.17, and a dielectric loss of 7.1 x 10 -4 The resin has a melt index of 3.5 g / 10 min, a melting point of 309 ℃, and a thermal decomposition temperature of 420 ℃ under the condition of 5 kg weight at 372 ℃.

[0168] Compared with Example 2, the charge ratio of perfluorocyclohexene in the present comparative example is 8.86%, which does not reach the limited ratio, and the obtained resin does not have excellent low dielectric and low dielectric loss properties, indicating that the perfluorocyclic monomer plays an important role in the low dielectric properties of the present terpolymer fluororesin, and a sufficient amount is required.

Claims

1. A perfluoropolymer that is melt-processable on tetrafluoroethylene, characterized in that, The perfluoro copolymer is a terpolymer composed of tetrafluoroethylene, perfluorocyclic olefin and perfluorovinyl ether; wherein the perfluorovinyl ether is a perfluoroalkyl vinyl ether or a perfluorocyclic vinyl ether. The mass percentage of the tetrafluoroethylene monomer is 10%-90%, the mass percentage of the perfluorocyclic olefin monomer is 5%-40%, and the mass percentage of the perfluorovinyl ether monomer is 5%-85%.

2. The perfluoropolymer of tetrafluoroethylene that is melt-processable according to claim 1, characterized in that, The perfluorocycloolefin is one or more of perfluorocyclopentene, perfluorocyclobutene, or perfluorocyclohexene.

3. The perfluoropolymer of tetrafluoroethylene that is melt-processable according to claim 1, characterized in that, The perfluoroalkyl vinyl ether is one or more of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether or perfluoron-propyl vinyl ether; The perfluorocyclic vinyl ether is 5-trifluoromethoxy-2,2,4-trifluoro-1,3-m-dioxacyclopentene.

4. The perfluoropolymer of tetrafluoroethylene that is melt-processable according to claim 1, characterized in that, The weight-average molecular weight of the perfluorinated copolymer is 100,000-500,000 g / mol; the PDI of the perfluorinated copolymer is 1.3-1.

6.

5. The perfluoropolymer of tetrafluoroethylene that is melt-processable according to claim 1, characterized in that, The perfluorinated copolymer has a tensile strength >32MPa; a melt index of 2-50g / 10min; a relative permittivity of 1.95-2.15 and a dielectric loss of 0.0002-0.0008 measured at 2.5GHz; a thermal decomposition temperature above 360℃; a near-ultraviolet to infrared transmittance >85% and a refractive index of 1.29-1.39; and a water contact angle above 105°.

6. The perfluoropolymer of tetrafluoroethylene that is melt-processable according to claim 1, characterized in that, When the perfluorinated copolymer is formed by ternary copolymerization of 10%-30% tetrafluoroethylene monomer, 5%-20% perfluorinated cyclic olefin monomer, and 50%-85% perfluorinated cyclic vinyl ether monomer by mass percentage, the glass transition temperature of the perfluorinated copolymer is above 130°C; the transmittance in the ultraviolet to infrared band is >94%, and the refractive index is 1.29-1.32; When the perfluorinated copolymer is composed of 50%-85% by mass of tetrafluoroethylene monomer, 10%-40% by mass of perfluorocyclic olefin monomer, and 5%-10% by mass of perfluoroalkyl vinyl ether monomer, the perfluorinated copolymer has a melting point of 260-310℃, a dielectric constant of 1.95-2.1, and a dielectric loss of 2×10⁻⁶. -4 -4×10 -4 ; When the perfluorinated copolymer is composed of 75%-90% by mass of tetrafluoroethylene monomer, 5%-10% by mass of perfluorocyclic olefin monomer, and 5%-15% by mass of perfluoroalkyl vinyl ether monomer, the perfluorinated copolymer has a melting point of 290-310℃, a melt index of 20-50 g / 10 min, and a critical shear rate of 120-300 s. -1 .

7. The application of the perfluorovinyl tetrafluoroethylene melt-processable perfluoropolymer as described in any one of claims 1-6 in 5G communication transmission, electronics, biomedicine, optical fiber cables, and automobiles.

8. An emulsion of a perfluoropolymer of tetrafluoroethylene vinyl that is melt-processable according to any one of claims 1-6, characterized in that, The raw materials include the following parts by weight: 10-90 parts tetrafluoroethylene, 5-40 parts perfluorocycloolefin, 5-85 parts perfluorovinyl ether, 5-20 parts fluorinated solubilizer, 0.1-2 parts initiator, 3-10 parts dispersant, 0.07-5 parts reducing agent, 0.3-3 parts pH adjuster, 0.08-1.3 parts chain transfer agent, and 0.008-0.1 parts terminator.

9. The perfluoropolymer emulsion of tetrafluoroethylene vinyl that can be melt-processed according to claim 8, characterized in that, The fluorinated solubilizer is one or more of hexafluorobenzene, perfluorobutane, perfluorohexane, perfluoropentane or perfluoroheptane; The initiator is any one of potassium persulfate, ammonium persulfate, succinic acid peroxide, benzoyl peroxide, diisopropyl peroxide, or azobisisobutyronitrile. The dispersant is one or more of perfluoropolyether sulfonates, perfluoropolyether carboxylates, perfluoropolyether sulfates, or perfluorohexanoates. The reducing agent is one or more of bisulfite, thiol or ferrous salt; The pH adjuster is one or more of sodium carbonate, ammonia, sodium bicarbonate, ammonium carbonate, or potassium carbonate; The chain transfer agent is one or more of alkanes, halogenated hydrocarbons, or alcohols; The terminator is one or more of quinone, nitrate, aromatic polyhydroxy compound or terpinene.

10. The perfluoropolymer emulsion of tetrafluoroethylene vinyl that can be melt-processed according to claim 8, characterized in that, The emulsion has a particle size of 170-220 nm and a solid content of 20-30 wt%. After standing for more than 3 months, the emulsion is uniform without stratification and no insoluble powder breaks out. The emulsion remains stable for more than 3 hours when stirred at 800 rpm.

11. The method for preparing the perfluoropolymer emulsion of tetrafluoroethylene vinyl that is melt-processable as described in claim 8, characterized in that, Includes the following steps: (1) Add pretreated deionized water, reducing agent, dispersant, pH adjuster and fluorine-containing solubilizer to the reactor, and remove oxygen by evacuation and replacement; The initial amount of dispersant added is 2 / 3 of the total amount of dispersant; the pH adjuster controls the pH value of the system to be 7-9 before the reaction. (2) After the oxygen content in the reactor is less than 10 ppm, the perfluorocyclic olefin, perfluorovinyl ether, tetrafluoroethylene monomer and initiator are introduced into the reactor to start the polymerization reaction. The polymerization reaction temperature is 20-60℃ and the polymerization reaction pressure is 0.2-1.0 MPa. Specifically, when the polymerization temperature is 20-40℃, the polymerization pressure is 0.4-1.0 MPa; when the polymerization temperature is 40-60℃, the polymerization pressure is 0.2-0.4 MPa. During the reaction, tetrafluoroethylene monomer is continuously added to maintain a constant pressure inside the reactor; (3) When the amount of tetrafluoroethylene fed to the target amount is 1 / 3 to 1 / 2 of the total planned amount of tetrafluoroethylene, add dispersant, and the amount added is 1 / 3 of the total amount of dispersant; When the amount of tetrafluoroethylene fed to the feed reaches 1 / 2 to 2 / 3 of the planned total amount of tetrafluoroethylene, add 500-5000 ppm of chain transfer agent; Based on the amount of tetrafluoroethylene fed and the planned total amounts of perfluorocyclic olefins and perfluorovinyl ethers, supplement the perfluorocyclic olefins and perfluorovinyl ethers. (4) When the amount of tetrafluoroethylene fed to the total amount of tetrafluoroethylene planned, add a terminator with a content of 50-400 ppm, recover the unreacted monomers and the fluorinated solvents, and the resulting polymer is processed to obtain the target perfluoropolymer.

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