High-altitude ETFE copolymer and its controllable polymerization method and application

Abstract

This invention relates to the field of polymer synthesis technology. This invention provides a controlled polymerization method for a high-alternation-degree ETFE copolymer, comprising the following steps: (1) adding a solvent to a high-pressure reactor, replacing the air, and then filling it with an initial monomer mixture to a total pressure of 1.5-2.5 MPa, wherein the monomer mixture is a mixture of tetrafluoroethylene and ethylene; (2) heating to 60-85°C, adding an initiator to initiate the polymerization reaction; (3) simultaneously adding the monomer mixture continuously or semi-continuously during the polymerization reaction; (4) adding a chain transfer agent, and discharging the product after the reaction, i.e., the high-alternation-degree ETFE copolymer. This invention also provides a controlled polymerization method for a high-alternation-degree ETFE copolymer. This invention also provides an application of the high-alternation-degree ETFE copolymer in new energy, aerospace, high-end equipment manufacturing, and photovoltaic fields. The high-alternation-degree ETFE copolymer of this invention has high alternation degree (>92%), high thermal stability, and excellent mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of polymer material synthesis technology, specifically to a high-alternation-degree ETFE copolymer and its controlled polymerization method and applications. Background Technology

[0002] Ethylene-tetrafluoroethylene copolymer (ETFE), as one of the fluoropolymers with the best overall performance, plays an irreplaceable role in new energy, aerospace, and high-end equipment manufacturing. Especially in the photovoltaic industry, with the rapid development of flexible modules and building-integrated photovoltaics (BIPV), extreme demands are placed on the lightweight, flexibility, and long-term weather resistance of encapsulation materials. ETFE film, due to its excellent light transmittance, strong resistance to UV aging, wide operating temperature range, and outstanding mechanical strength, is considered an ideal prospective material.

[0003] However, the ultimate performance of ETFE materials is highly dependent on the microstructure of its molecular chains. Ideally, high-performance ETFE should exhibit a highly ordered alternation between ethylene (E) and tetrafluoroethylene (TFE) units. This alternating structure endows the molecular chains with extremely high rigidity and regularity, resulting in high crystallinity, high melting point, excellent creep resistance, and cut resistance. However, in actual free radical copolymerization reactions, due to the significant difference in the polymerization rates of TFE and ethylene monomers, and the influence of multiple factors such as reaction medium, temperature, and pressure, achieving and maintaining this ideal high degree of alternation is extremely difficult. Currently, even commercially available ETFE products with a TFE-ethylene molar ratio close to 50:50 typically struggle to achieve an actual alternation rate exceeding 90%. This means that approximately 10% of the molecular chains inevitably contain structural defects, such as continuous TFE-TFE sequences or ethylene-ethylene sequences. These defects, like dislocations in a crystal, significantly reduce the degree of crystallinity perfection of the material, leading to a decrease in melting point, insufficient high-temperature strength, and deterioration in long-term environmental stress cracking resistance. For photovoltaic modules designed to have a lifespan of over 25 years, even the slightest performance degradation of the encapsulation material can lead to the failure of the entire system. Therefore, optimizing the basic resin structure is the cornerstone of improving product reliability.

[0004] Furthermore, the industrial polymerization process of ETFE itself presents a high technological barrier. Tetrafluoroethylene monomers carry an unpredictable risk of explosive decomposition under high pressure, requiring extremely high precision in reaction control. Traditional polymerization processes, such as single-feed methods, struggle to maintain stable monomer concentrations in the reaction system. In the initial stages of the reaction, more reactive monomers are consumed more rapidly, leading to an imbalance in the monomer ratio in the later stages, resulting in polymer chain structures that differ from those in the earlier stages. This inhomogeneity in molecular chain structure directly manifests as a wide molecular weight distribution and large batch-to-batch performance fluctuations, causing significant challenges to downstream melt processing (such as extrusion and casting), severely impacting the thickness uniformity, surface quality, and mechanical consistency of film products. How to achieve precise and flexible control of molecular weight and its distribution without sacrificing structural regularity (i.e., high alternation) has always been a core technical challenge for researchers and engineers.

[0005] Therefore, developing an innovative polymerization method that can stably produce ETFE copolymers with high alternation, narrow molecular weight distribution, and controllable molecular weight is of great strategic significance for breaking through the performance bottleneck of high-end photovoltaic encapsulation film materials and promoting the upgrading of the new energy industry. Summary of the Invention

[0006] This invention aims to address the shortcomings of existing technologies by providing a high-alternation-degree ETFE copolymer, its controllable polymerization method, and its applications. The first objective of this invention is to provide an ETFE copolymer with high alternation degree (>92%), high thermal stability, and excellent mechanical properties. The second objective of this invention is to provide a method for the industrial production of the above copolymer, which effectively balances high reaction rate and high alternation degree, and allows for precise control of the product molecular weight.

[0007] To address the above problems, the present invention provides the following technical solution:

[0008] A controlled polymerization method for a high degree of alternation of ETFE copolymers includes the following steps:

[0009] (1) Add solvent to the high-pressure reactor, replace the air, and then fill it with the initial monomer mixture until the total pressure is 1.5-2.5 MPa. The monomer mixture is a mixture of tetrafluoroethylene and ethylene.

[0010] (2) Heat to 60-85℃, add initiator to initiate polymerization reaction;

[0011] (3) During the polymerization reaction, the monomer mixture is added continuously or semi-continuously.

[0012] (4) Add chain transfer agent, react for 2-6 hours and discharge to obtain white powder, i.e., high degree of alternation ETFE copolymer.

[0013] In the controlled polymerization method of the high-alternation ETFE copolymer described above, in step (1), the molar ratio of tetrafluoroethylene to ethylene in the monomer mixture is (70~80):(20~30).

[0014] In the controlled polymerization method for the high-alternation-degree ETFE copolymer described above, in step (1), the solvent is any one or a mixture of any two of 1,1,2-trichloro-1,2,2-trifluoroethane, hydrofluoroether, perfluorocarbon solvent, chlorinated solvent, isopropanol, or water. In this invention, 1,1,2-trichloro-1,2,2-trifluoroethane is abbreviated as "R113 solvent".

[0015] In the controlled polymerization method of the high-alternation ETFE copolymer described above, in step (2), the initiator is any one of organic peroxide or azo initiator.

[0016] In the controlled polymerization method of the high-alternation ETFE copolymer described above, in step (3), the monomer mixture is added continuously at a flow rate of 0.01-0.1 MPa / min.

[0017] In the controlled polymerization method of the high-alternation ETFE copolymer described above, in step (3), the molar ratio of tetrafluoroethylene to ethylene in the monomer mixture is (45~55):(45~55).

[0018] In the controlled polymerization method of the high-alternation ETFE copolymer described above, in step (4), the chain transfer agent is any one of hydrogen, ethane, and CHClCF2.

[0019] In the controlled polymerization method of the high-alternation ETFE copolymer described above, in step (3), a third monomer of 0.5%-3% of the mass of tetrafluoroethylene is added during the polymerization reaction. The third monomer is perfluoropropyl vinyl ether or alkyl vinyl ether.

[0020] Based on the same inventive concept, the present invention also provides a high degree of alternation ETFE copolymer, which is prepared by the controlled polymerization method described above.

[0021] Based on the same inventive concept, the present invention also provides the application of the high-alternation ETFE copolymer prepared by the controlled polymerization method as described above, or the application of the high-alternation ETFE copolymer as described above, which is used in the fields of new energy, aerospace, high-end equipment manufacturing, and photovoltaics.

[0022] Compared with existing technologies, the effects and advantages of this invention are:

[0023] 1. The present invention provides a controllable polymerization method for ETFE copolymers with high alternation degree. By adopting a dynamic feeding strategy of "maintaining the rate with high initial TFE concentration and maintaining alternation with equimolar addition", the present invention successfully solves the contradiction between the polymerization reaction rate and the alternation degree of the product. The alternation degree of the ETFE copolymer prepared by the present invention is stable at more than 92%, and its melting point, tensile strength and creep resistance are significantly improved.

[0024] 2. This invention provides a controlled polymerization method for high-alternation-degree ETFE copolymers, producing ETFE copolymers with regular molecular chain structures and narrow compositional distributions. Through precise control of the gas-phase chain regulator, the molecular weight can be flexibly adjusted within a wide range, such as an MFR of 0.5-50 g / 10 min (300℃, 5 kg), to meet the needs of different processing techniques.

[0025] 3. The present invention provides a controlled polymerization method for high-alternation ETFE copolymers. The continuous addition process keeps the monomer concentration in the reaction system relatively stable, and the resulting polymer has a uniform structure and excellent batch-to-batch quality stability, providing a reliable raw material guarantee for downstream manufacturing. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the core dynamic feeding process for preparing high-alternation ETFE copolymers according to the present invention, wherein (a) is Example 1 and (b) is Comparative Example 1;

[0027] Figure 2 This is a comparison chart of the DSC melt curves of the highly alternating ETFE polymerized in Example 1 of the present invention and the conventional ETFE polymerized in Comparative Example 1.

[0028] Figure 3 The high-alternation-degree ETFE copolymer polymerized in Example 1 of this invention 19 F NMR spectrum. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0032] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0033] The core principle of this invention is to achieve a high degree of alternation copolymerization of ethylene (E) and tetrafluoroethylene (TFE) by controlling the monomer ratio, initiator type, chain transfer agent, and monomer addition method. The properties of ETFE copolymers are highly dependent on the monomer sequence distribution; a high degree of alternation (i.e., E-TFE-E-TFE... sequence) endows the material with excellent heat resistance, chemical corrosion resistance, mechanical strength, and electrical insulation. This invention achieves controlled polymerization through the following mechanism:

[0034] The initial monomer ratio is controlled by using a tetrafluoroethylene-rich initial monomer mixture in which the molar ratio of tetrafluoroethylene to ethylene is (70~80):(20~30). This promotes the formation of TFE-rich segments at the beginning of the reaction, laying the foundation for the alternating structure.

[0035] Monomers are continuously added, with the monomer mixture added at a near 1:1 ratio during the reaction process to maintain the dynamic balance of monomer concentration in the reaction system, avoid local concentration fluctuations, and ensure that alternating copolymerization continues.

[0036] By using chain transfer agents, especially hydrogen, the molecular weight of the polymer can be adjusted by controlling the termination of molecular chain growth, thus avoiding excessively high molecular weights that would lead to processing difficulties.

[0037] Choosing appropriate solvents and initiators ensures that the reaction takes place in a homogeneous system with a moderate initiation rate, achieving stable and controllable polymerization kinetics.

[0038] This integrated control strategy effectively promotes the alternating insertion of monomers, improves the alternation degree of copolymers, and thus optimizes the performance of the final product.

[0039] A controlled polymerization method for a high degree of alternation of ETFE copolymers includes the following steps:

[0040] (1) Add solvent to the high-pressure reactor, replace the air, and then fill it with the initial monomer mixture until the total pressure is 1.5-2.5 MPa. The monomer mixture is a mixture of tetrafluoroethylene and ethylene.

[0041] (2) Heat to 60-85℃, add initiator to initiate polymerization reaction;

[0042] (3) During the polymerization reaction, the monomer mixture is added continuously or semi-continuously.

[0043] (4) Add chain transfer agent, react for 2-6 hours and discharge to obtain white powder, i.e., high degree of alternation ETFE copolymer.

[0044] Preferably, in step (1), the molar ratio of tetrafluoroethylene to ethylene in the monomer mixture is (70~80):(20~30). Most preferably, in step (1), the molar ratio of tetrafluoroethylene to ethylene in the monomer mixture is 75:25. Adding the initial monomer mixture can produce the following effects: promote alternating structure, which is beneficial for TFE monomers to preferentially participate in chain initiation, but due to the difference in the reactivity of ethylene, it can still drive alternating copolymerization and avoid the formation of ethylene homopolymer; optimize reaction stability, a higher TFE ratio can reduce the explosion risk of the reaction system (because TFE is easily decomposed under high pressure), while maintaining sufficient ethylene participation to ensure a smooth start of the copolymerization reaction; improve polymer performance, a high initial TFE ratio helps to introduce more fluorine atoms at the polymer chain ends, enhance the fluorination properties of the material, such as hydrophobicity and chemical resistance, and provide a basis for subsequent alternating structure.

[0045] Preferably, in step (1), the solvent is any one or a mixture of any two of 1,1,2-trichloro-1,2,2-trifluoroethane, hydrofluoroether (HFE), perfluorocarbon solvent, chlorinated solvent, isopropanol, or water. Preferably, the solvent is R113. R113 is preferred because it has good solubility for the monomer, can form a homogeneous reaction system to promote alternating copolymerization; its chemical inertness ensures no interference with the reaction, and its boiling point matches the reaction temperature, facilitating process control and recovery.

[0046] Preferably, in step (2), the initiator is any one of an organic peroxide or an azo initiator. Most preferably, in step (2), the initiator is an azo initiator, azobisisobutyronitrile (AIBN).

[0047] Preferably, in step (3), the monomer mixture is added continuously at a flow rate of 0.01-0.1 MPa / min. Most preferably, the flow rate is 0.05 MPa / min. The key advantage of controlling the monomer addition rate at 0.05 MPa / min is that it can dynamically match the polymerization consumption rate, thereby maintaining the stability of the monomer concentration in the reaction system. This avoids pressure fluctuations and homopolymerization risks caused by excessively fast flow rates, and also prevents monomer depletion and decreased alternation caused by excessively slow flow rates. Therefore, this optimized flow rate is key to achieving a stable and safe reaction and obtaining copolymers with high homogeneity and high alternation.

[0048] Preferably, in step (3), the molar ratio of tetrafluoroethylene to ethylene in the monomer mixture is (45~55):(45~55). Most preferably, in step (3), the molar ratio of tetrafluoroethylene to ethylene in the monomer mixture is 50:50. Under these conditions, it can synergize with the initial tetrafluoroethylene-rich feed, dynamically maintaining the optimal monomer ratio in the reaction system. Under these conditions, the microenvironment required for ideal alternating copolymerization is directly created, maximizing the alternating insertion of ethylene and tetrafluoroethylene monomers, thereby significantly improving the regularity and uniformity of the copolymer chain structure, and ultimately achieving simultaneous optimization of its key properties such as thermal stability and mechanical strength.

[0049] Preferably, in step (4), the chain transfer agent is any one of hydrogen, ethane, and CHClCF2. Preferably, the chain transfer agent is hydrogen, and the partial pressure of hydrogen in the reaction system is 0.01 MPa to 0.15 MPa. Most preferably, in step (4), the partial pressure of hydrogen in the reaction system is 0.05 MPa. Under these conditions, hydrogen, as a highly efficient chain transfer agent, can precisely control the polymer molecular weight and narrow its distribution, thereby achieving the best balance between avoiding processing difficulties due to excessively high molecular weight and affecting mechanical properties due to excessively low molecular weight. Simultaneously, this operation can also suppress chain branching side reactions, reduce structural defects, and ultimately synergistically improve the processing fluidity, alternation, and overall performance of the copolymer.

[0050] Preferably, in step (3), a third monomer accounting for 0.5%-3% of the mass of tetrafluoroethylene is added during the polymerization reaction, wherein the third monomer is perfluoropropyl vinyl ether or alkyl vinyl ether. Most preferably, in step (3), a third monomer accounting for 1.5% of the mass of tetrafluoroethylene is added during the polymerization reaction, wherein the third monomer is perfluoropropyl vinyl ether.

[0051] Based on the same inventive concept, the present invention also provides a high degree of alternation ETFE copolymer, which is prepared by the controlled polymerization method described above.

[0052] Based on the same inventive concept, the present invention also provides the application of the high-alternation ETFE copolymer prepared by the controlled polymerization method as described above, or the application of the high-alternation ETFE copolymer as described above, which is used in the fields of new energy, aerospace, high-end equipment manufacturing, and photovoltaics.

[0053] Example 1:

[0054] 2.5 L of R113 solvent was added to a 5 L high-pressure reactor. After purging the air, an initial monomer mixture of tetrafluoroethylene (TEFE) and ethylene was introduced until the total pressure reached 2.0 MPa. The molar ratio of TFE to ethylene in the initial monomer mixture was 75:25. The temperature was raised to 70 °C, and 0.5 g of azobisisobutyronitrile (AIBN) was added as an initiator. The reaction was started, and the monomer mixture was simultaneously added at a rate of 0.05 MPa / min. The molar ratio of TFE to ethylene in the added monomer mixture was 50:50, and the total pressure was kept constant. During the reaction, the partial pressure of hydrogen was maintained at 0.05 MPa as a chain transfer agent. After 4 hours of reaction, the product was discharged as a white powder. The experimental results showed that the TFE molar fraction was 50.2%, the MFR was 12.0 g / 10 min (300 °C, 5 kg), and the melting peak temperature measured by DSC was 272 °C. 19 F NMR calculations showed its alternation to be 93.5%.

[0055] Example 2:

[0056] The experimental steps in this embodiment are the same as in Example 1, except that the molar ratio of tetrafluoroethylene to ethylene in the initial monomer mixture is 70:30. The testing method is the same as in Example 1. The experimental results are as follows: TFE molar fraction is 51.0%, MFR is 10.5 g / 10min (300℃, 5kg), melting peak temperature is 270℃, and alternation degree is 92.8%.

[0057] Example 3:

[0058] The experimental steps in this embodiment are the same as in Example 1, except that the molar ratio of tetrafluoroethylene to ethylene in the added monomer mixture is 55:45. The testing method is the same as in Example 1. The experimental results are as follows: TFE molar fraction is 52.5%, MFR is 14.2 g / 10min (300℃, 5kg), melting peak temperature is 268℃, and alternation degree is 92.1%.

[0059] Example 4:

[0060] The experimental steps in this embodiment are the same as in Example 1, except that a mixture of water and isopropanol is used as the reaction solvent, with a water-to-isopropanol volume ratio of 7:3. In the initial monomer mixture, the molar ratio of tetrafluoroethylene to ethylene is 80:20, and in the supplementary monomer mixture, the molar ratio of tetrafluoroethylene to ethylene is 50:50. The testing method is the same as in Example 1. The experimental results are as follows: TFE molar fraction is 49.8%, MFR is 8.5 g / 10min (300℃, 5kg), melting peak temperature is 274℃, and alternation degree is 94.1%.

[0061] Example 5:

[0062] The experimental steps in this embodiment are the same as in Example 1, except that the chain transfer agent is replaced with ethane, and the partial pressure is maintained at 0.08 MPa. The experimental results show that the TFE molar fraction is 50.5%, the MFR is as high as 35.0 g / 10min (300℃, 5kg), the melting peak temperature is 266℃, and the alternation degree is 92.5%.

[0063] Example 6:

[0064] The experimental steps in this embodiment are the same as in Example 1, except that the chain transfer agent is changed to CHClCF2, and the amount added is 0.5% of the total monomer mass. The experimental results are as follows: TFE molar fraction is 49.9%, MFR is 0.8 g / 10min (300℃, 5kg, low flow), melting peak temperature is 275℃, and alternation degree is 93.8%.

[0065] Example 7:

[0066] The experimental procedures in this embodiment are the same as in Example 1, except that 1.5% (by mass of TFE) of perfluoropropyl vinyl ether (PPVE) was added to the monomer mixture. The experimental results showed that a terpolymer was obtained with a TFE molar fraction of 50.1%, an MFR of 15.5 g / 10 min (300°C, 5 kg), a melting peak temperature reduced to 255°C, and a degree of alternation of 92.0%. Its elongation at break remained above 600% even at 150°C.

[0067] Example 8:

[0068] The experimental steps in this embodiment are the same as in Example 1, except that the polymerization temperature is increased to 85℃. The experimental results show that the reaction rate is accelerated, the TFE molar fraction is 49.5%, the MFR is 18.0 g / 10min (300℃, 5kg), the melting peak temperature is 269℃, and the alternation degree is 92.2%.

[0069] Comparative Example 1:

[0070] The experimental procedure for this comparative example is the same as that in Example 1, except that a supplementary addition strategy is not used; the monomer mixture is added all at once. In the monomer mixture, the molar ratio of tetrafluoroethylene to ethylene is 50:50. The experimental results show that the TFE molar fraction is 50.0%, the MFR is 11.5 g / 10min (300℃, 5kg), the melting peak temperature is 268℃, and the alternation degree is only 88.5%.

[0071] Comparative Example 2:

[0072] The experimental procedures for this comparative example are the same as in Example 1, except that no chain transfer agent is added. The experimental results show that the MFR is extremely low (MFR < 0.1 g / 10min (300℃, 5kg), the molecular weight is too high, making processing difficult, the melting peak temperature is 276℃, and the alternation degree is 93.0%.

[0073] Figure 1 This is a schematic diagram illustrating the core dynamic feeding process for preparing high-alternation ETFE copolymers according to the present invention, where (a) is Example 1 and (b) is Comparative Example 1. From... Figure 1 As can be seen, this invention constructs a precision feeding system comprising an initial feeding unit, a replenishment control unit, and an intelligent closed-loop control unit. The process begins with the addition of an initial monomer mixture of tetrafluoroethylene (TEFE) and ethylene at a molar ratio of 75:25 to the polymerization reactor to rapidly initiate and establish a high reaction rate. Subsequently, the system activates its core closed-loop control: continuously monitoring the monomer composition in the gaseous phase within the reactor using real-time analytical instruments such as online infrared spectroscopy or gas chromatography, and feeding this signal back to the central controller. The controller compares the real-time data with a preset 50:50 ideal ratio and, based on a built-in material balance and kinetic model, dynamically and precisely adjusts the feed valve of the replenishment monomer storage tank using a PID algorithm to control the replenishment rate of the 50:50 TEFE / ethylene mixture. This allows the actual monomer composition within the system to smoothly transition and stabilize near the ideal stoichiometric ratio, thereby successfully producing high-quality ETFE with an alternation rate greater than 92%. In contrast, the traditional one-time feeding method in Comparative Example 1, due to its inability to maintain a constant monomer ratio, resulted in large compositional fluctuations, low product alternation rate (only about 88%), and poor batch consistency. This invention cleverly balances the requirements of reaction kinetics and product structural regularity. Through the closed-loop dynamic control strategy of online monitoring and feedback adjustment, it achieves efficient and precise control of the polymerization process. The obtained ETFE product has a higher melting point, better mechanical properties and thermal stability, demonstrating significant technical advantages.

[0074] The above-mentioned online infrared spectroscopy, gas chromatography, central controller, PID algorithm, and feed valve regulation are mature technologies and common knowledge in this field for monitoring gas phase composition.

[0075] The control basis points out that the controller not only compares the set value with the measured value, but also performs calculations based on the "built-in material balance and dynamics model", which improves the accuracy and intelligence of the control and goes beyond simple set value control.

[0076] Figure 2 This is a comparison of the DSC melt curves of the highly alternating ETFE polymerized in Example 1 of the present invention and the conventional ETFE polymerized in Comparative Example 1. From... Figure 2 It can be seen that the ETFE samples prepared in Example 1 of this invention are compared with those prepared in the conventional Comparative Example 1 by differential scanning calorimetry (DSC). Figure 2 As shown, the high alternation degree ETFE of Embodiment 1 of the present invention exhibits a higher and sharper melting peak, with a peak temperature (T0) of [missing information]. m The melting peak temperature of the ETFE prepared by the conventional method in Comparative Example 1 was 272.0℃. In contrast, the melting peak temperature of the ETFE prepared by the conventional method in Comparative Example 1 was 268.0℃, and the peak shape was slightly wider. The increase in melting temperature and the sharpening of the peak shape are direct evidence of improved regularity of copolymer molecular chains and more complete crystallization, indicating that the present invention has successfully synthesized a high-performance ETFE resin with higher alternation degree.

[0077] Figure 3 The high-alternation-degree ETFE copolymer polymerized in Example 1 of this invention 19 F NMR spectrum. From Figure 3 As can be seen from the above, the ETFE copolymer prepared in Example 1 of this invention showed good performance at high temperatures. 19 The FNMR spectrum was obtained using diisobutyl adipic acid as solvent at a temperature of 290°C. The main characteristic peak at chemical shift δ = -119.0 ppm belongs to a highly alternating sequence structure (-ECF2CF2E-), while the shoulder peak at δ = -111.9 ppm corresponds to the (-ECF2E-) sequence. The sharp morphology of each characteristic peak and the high signal-to-noise ratio indicate that the product possesses excellent molecular chain structure regularity. Integral calculations of the characteristic peak areas determined that the alternation degree of this copolymer is as high as 93.5%, significantly better than the comparative sample (88.5%).

[0078] It should be noted that the specific embodiments are merely representative examples of the present invention, and the technical solution of the present invention is obviously not limited to the above embodiments, and there can be many variations. Those skilled in the art who obtain the present invention based on its explicit disclosure or without objection from the written description should consider it to be within the scope of protection of this patent.

Claims

1. A controlled polymerization method for a high degree of alternation of ETFE copolymers, characterized in that, Includes the following steps: (1) Add solvent to the high-pressure reactor, replace the air, and then fill it with the initial monomer mixture until the total pressure is 1.5-2.5 MPa. The monomer mixture is a mixture of tetrafluoroethylene and ethylene. The solvent is any one or a mixture of any two of 1,1,2-trichloro-1,2,2-trifluoroethane, hydrofluoroether, perfluorocarbon solvent, chlorinated solvent, isopropanol, or water. (2) Heat to 60-85℃, add initiator to initiate polymerization reaction; (3) During the polymerization reaction, a monomer mixture is added continuously or semi-continuously; the monomer mixture is added continuously at a flow rate of 0.01-0.1 MPa / min; the molar ratio of tetrafluoroethylene to ethylene in the monomer mixture is 50:

50. (4) Add chain transfer agent, react for 2-6 hours and discharge to obtain white powder, i.e., high degree of alternation ETFE copolymer; the chain transfer agent is any one of hydrogen, ethane, and CHClCF2.

2. The controlled polymerization method for the high-alternation-degree ETFE copolymer according to claim 1, characterized in that, In step (1), the molar ratio of tetrafluoroethylene to ethylene in the monomer mixture is (70~80):(20~30).

3. The controlled polymerization method for the high-alternation-degree ETFE copolymer according to claim 1, characterized in that, In step (2), the initiator is any one of organic peroxide or azo initiator.

4. The controlled polymerization method for the high-alternation-degree ETFE copolymer according to claim 1, characterized in that, In step (3), a third monomer, accounting for 0.5%-3% of the mass of tetrafluoroethylene, is added during the polymerization reaction. The third monomer is perfluoropropyl vinyl ether or alkyl vinyl ether.

5. A high degree of alternation ETFE copolymer, characterized in that, Prepared by the controlled polymerization method according to any one of claims 1-4.

6. The application of the high-alternation ETFE copolymer prepared by the controlled polymerization method according to any one of claims 1-4, or the high-alternation ETFE copolymer according to claim 5, characterized in that, The applications are used in new energy, aerospace, high-end equipment manufacturing, and photovoltaic fields.

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