Modified etfe and method of making

Abstract

The application provides a modified ETFE and a preparation method, and belongs to the technical field of fluorine-containing polymer materials. The modified ETFE is obtained by polymerization of tetrafluoroethylene, ethylene and methacryloyloxyethyl phosphate in a fluorine-containing solvent. The modified ETFE combines the excellent performance of fluorine resins and the reaction characteristics of functional groups, has excellent chemical resistance and heat resistance of ETFE itself, obviously improves the adhesion, flame retardance and processability of the material, reduces the crystallinity of the modified ETFE, and is widely applied in the fields of high-performance coatings, metal corrosion prevention, cable insulation, composite materials and adhesives.

Description

Technical Field

[0001] This invention belongs to the field of fluorine-containing polymer materials technology, and relates to a modified ETFE and its preparation method. Background Technology

[0002] ETFE (ethylene-tetrafluoroethylene copolymer) is a high-performance fluoropolymer that combines the excellent chemical stability and weather resistance of polytetrafluoroethylene (PTFE) with the good processability of polyethylene. It can be processed through extrusion, compression molding, and injection molding. ETFE is widely used in chemical corrosion protection, aerospace, nuclear power cables, and building films.

[0003] Traditional ETFE exhibits poor adhesion to metals and inorganic materials, limiting its application in coatings and composites. Furthermore, the lack of reactive functional groups in ETFE makes further chemical modification difficult. Therefore, to improve the performance of ETFE, researchers have attempted to introduce a third monomer for copolymerization modification. For example, CN109721675A discloses an ETFE copolymer using glycidyl fluoride methacrylate as the third monomer, which improves adhesion and leveling properties. CN101508753A uses perfluoropropyl vinyl ether or nonafluorohexene as the third monomer, improving the resin's processing performance and resistance to high-temperature cracking.

[0004] However, there is no existing technology for modifying ETFE by introducing methacryloyloxyethyl phosphate as a third monomer. Summary of the Invention

[0005] Based on the above objectives, the present invention provides a modified ETFE and a preparation method thereof.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This application provides a modified ETFE obtained by polymerizing tetrafluoroethylene, ethylene, and methacryloyloxyethyl phosphate in a fluorinated solvent.

[0008] In addition, this application also provides a method for preparing modified ETFE, the method comprising: adding tetrafluoroethylene, ethylene, methacryloxyethyl phosphate and chain transfer agent to a fluorinated solvent under a nitrogen atmosphere; when the temperature is stable at 0-100℃ and the pressure is stable at 0.1-8MPa, adding an initiator to carry out a polymerization reaction to obtain modified ETFE; wherein, tetrafluoroethylene, ethylene and methacryloxyethyl phosphate are added during the polymerization reaction.

[0009] The present invention has the following beneficial effects:

[0010] (1) Acryloyl groups are introduced into the molecular chain of modified ETFE to provide sites for its cross-linking reaction, and then a three-dimensional network structure is formed by UV curing or thermal curing to improve the performance of the material.

[0011] (2) Phosphate groups are introduced into the molecular chain of modified ETFE. They have a certain polarity and good molecular chain flexibility, which can disrupt the regularity of the ETFE molecular chain, reduce the crystallinity of modified ETFE, and thus process at a lower temperature, broaden the processing window, and reduce energy consumption and equipment requirements.

[0012] (3) Methacryloxyethyl phosphate can build a molecular bridge between the copolymer and various polar and non-polar substrates, greatly improving the interfacial strength of the copolymer to composite materials such as metals, ceramics, glass fibers, and engineering plastics, solving the problem of poor adhesion of traditional ETFE, especially for metal anti-corrosion coatings that require excellent adhesion.

[0013] (4) Methacryloxyethyl phosphate is a highly efficient flame retardant that can make modified ETFE have better flame retardancy. It does not require the addition of traditional flame retardants and avoids the performance reduction or even deterioration caused by the migration and precipitation of small molecule flame retardants.

[0014] (5) The proportions of monomers and the chain structure design in the modified ETFE make the copolymer have suitable melt flowability, which can be processed by extrusion, injection molding, spraying and other methods.

[0015] (6) The modified ETFE has an adhesion of 70 N / cm and a limiting oxygen index of 60%.

[0016] (7) This modified ETFE combines the excellent properties of fluoropolymers with the reactive characteristics of functional groups. In addition to the excellent chemical resistance and heat resistance of ETFE itself, it also significantly improves the adhesion and processability of the material. It is widely used in high-performance coatings, metal corrosion protection, cable insulation, composite materials and adhesives. Detailed Implementation

[0017] This application provides a modified ETFE, which is obtained by polymerizing tetrafluoroethene (TFE), ethylene (E), and 2-Hydroxyethyl methacrylate phosphate (MEPA) in a fluorinated solvent.

[0018] Methacryloxyethyl phosphate is a multifunctional monomer, CAS number 52628-03-2. Methacryloxyethyl phosphate contains both acryloyl and phosphate groups, providing crosslinking reaction sites, excellent adhesion, and good flame retardancy. This application introduces methacryloxyethyl phosphate as a third monomer into the ETFE molecular chain, thereby improving the adhesion and processability of traditional ETFE products through specific functional groups and endowing them with superior flame retardant properties, thus expanding their application range.

[0019] Specifically, the introduction of methacryloxyethyl phosphate gives the modified ETFE the following functions:

[0020] (1) Acryloyl groups are introduced into the molecular chain of modified ETFE to provide sites for its cross-linking reaction, and then a three-dimensional network structure is formed by UV curing or thermal curing to improve the performance of the material.

[0021] (2) Phosphate groups are introduced into the molecular chain of modified ETFE. They have a certain polarity and good molecular chain flexibility, which can disrupt the regularity of the ETFE molecular chain, reduce the crystallinity of modified ETFE, and thus process at a lower temperature, broaden the processing window, and reduce energy consumption and equipment requirements.

[0022] (3) Methacryloxyethyl phosphate can build a molecular bridge between the copolymer and various polar and non-polar substrates, greatly improving the interfacial strength of the copolymer to composite materials such as metals, ceramics, glass fibers, and engineering plastics, solving the problem of poor adhesion of traditional ETFE, especially for metal anti-corrosion coatings that require excellent adhesion.

[0023] (4) Methacryloxyethyl phosphate is a highly efficient flame retardant that can make modified ETFE have better flame retardancy. It does not require the addition of traditional flame retardants and avoids the performance reduction or even deterioration caused by the migration and precipitation of small molecule flame retardants.

[0024] (5) The proportions of monomers and the chain structure design in the modified ETFE make the copolymer have suitable melt flowability, which can be processed by extrusion, injection molding, spraying and other methods.

[0025] In this application, the method for preparing modified ETFE includes:

[0026] The air in the reaction vessel was purged with nitrogen to reduce the O2 content to below 10 ppm, and the vessel was kept under a nitrogen atmosphere. Tetrafluoroethylene, ethylene, methacryloxyethyl phosphate, and a chain transfer agent were added to a fluorinated solvent. Once the temperature stabilized at 0-100℃ and the pressure stabilized at 0.1-8 MPa, an initiator was added, and the polymerization reaction was carried out for 1-25 hours. During polymerization, tetrafluoroethylene, ethylene, and methacryloxyethyl phosphate were added continuously. The polymerization reaction was stopped when the total mass of added tetrafluoroethylene and ethylene reached 260 kg. The reaction product was cooled with circulating water, monomer recovered, solvent evaporated, dried, and pulverized to obtain modified ETFE.

[0027] In the modified ETFE of this application, the molar percentage of tetrafluoroethylene and ethylene is 45-60 mol%: 40-55 mol%, and the molar percentage of methacryloxyethyl phosphate in the modified ETFE is 0.1-4 mol%. More preferably, the molar percentage of tetrafluoroethylene and ethylene is 48-55 mol%: 43-50 mol%, and the molar percentage of methacryloxyethyl phosphate in the modified ETFE is 0.1-2 mol.

[0028] During the polymerization process, the added tetrafluoroethylene and ethylene have a tetrafluoroethylene molar percentage of 53 mol%. This specific ratio stems from the difference in the reactivity of the ethylene and tetrafluoroethylene monomers. Tetrafluoroethylene is more reactive and is preferentially consumed during polymerization, leading to a continuous decrease in its concentration in the reaction system. Without replenishment, the tetrafluoroethylene content in the subsequently generated ETFE polymer chains will gradually decrease, causing compositional drift and sequence inhomogeneity in the ETFE copolymer, ultimately deteriorating the material's properties. Therefore, by continuously replenishing monomers at a fixed ratio, the stability of the reaction system composition can be maintained, ensuring that the final product has a uniform molecular structure and excellent overall performance. Through extensive experimental optimization, this replenishment ratio has yielded a modified ETFE that achieves the optimal balance between heat resistance, chemical resistance, strength, toughness, and processability.

[0029] In addition, different amounts of methacryloyloxyethyl phosphate are added due to factors such as polymerization ratio, temperature, and pressure. To ensure the modification of tetrafluoroethylene and ethylene polymerization by methacryloyloxyethyl phosphate, the molar ratio of methacryloyloxyethyl phosphate is controlled between 0.1 and 4 mol during copolymerization.

[0030] In this application, the polymerization reaction can employ known polymerization methods such as emulsion polymerization, suspension polymerization, and solution polymerization. Among these, solution polymerization has excellent heat dissipation and temperature control capabilities, good reactivity, and produces clean polymers without residues. It can safely and stably produce modified ETFE with uniform molecular weight. Therefore, solution polymerization is preferred in this application.

[0031] In this application, the fluorinated solvent is selected from one or more of hydrochlorofluoroethers, chlorofluorocarbons, hydrofluorocarbons, and perfluorinated carbons, such as 1,3-dichloropentafluoropropane, 1,1-dichloro-1-fluoroethane, dichlorofluoromethane, trichlorofluoromethane, trichlorotrifluoroethane, difluoromethane, tetrafluoroethane, tetrafluorocarbon, tetrafluoroethylene, perfluoron-butane, tetrafluoroethyl ether, perfluoromethylcyclohexane, etc., which can increase the solubility of the monomer, reduce the reaction pressure, and at the same time have a relatively high reaction rate.

[0032] In this application, chain transfer agents include alcohols such as methanol, ethanol, n-propanol, isopropanol, and tert-butanol, and alkanes such as methane, ethane, and cyclohexane. Different molecular weights of modified ETFE are obtained by adjusting the amount added, thus balancing processing and performance. From the perspective of convenient formulation and easy removal by simple water washing, methanol and ethanol are preferred as chain transfer agents in this application, which also allows for convenient adjustment of the molecular weight of the modified ETFE.

[0033] In this application, oil-soluble initiators are selected, including organic peroxide initiators and azo compound initiators. Among them, organic peroxide initiators are preferably free radical initiators with a half-life of 10 hours and a temperature range of 10-80°C, such as perfluorocycloalkylformyl peroxide, tert-butyl peroxypentanoate, and bis(2-ethylhexyl) percarbonate. Azo initiators include azobisisovalerate and azobisisobutyronitrile.

[0034] Preferred polymerization temperatures are 55-80℃, polymerization pressure is 1.4-2.0MPa, and polymerization time is 2-18h.

[0035] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0036] Example 1

[0037] This application provides a modified ETFE, the preparation method of which includes:

[0038] A 500L vertical stainless steel polymerization reactor was purged with nitrogen until the O2 content in the reactor decreased to below 10 ppm, and the reactor was placed under a nitrogen atmosphere. 400 kg of 1,3-dichloropentafluoropropane, 25 kg of methanol, and 42 kg of methacryloxyethyl phosphate were added to the reactor, and stirring was started. Tetrafluoroethylene and ethylene were then introduced into the reactor at a molar ratio of 90:10 until the pressure reached 1.5 MPa, and the temperature was raised to 60°C. Once the temperature and pressure stabilized, 200 g of bis(2-ethylhexyl) peroxide dicarbonate was added to the reactor to initiate the polymerization reaction. After the polymerization reaction began, a mixture of tetrafluoroethylene and ethylene gas with a tetrafluoroethylene content of 53 mol% and 30 kg of methacryloxyethyl phosphate were added to the reactor. The polymerization reaction was stopped when the total mass of the added tetrafluoroethylene and ethylene reached 260 kg. The reaction product was cooled by circulating water, the monomer was recovered, the solvent was evaporated, dried, and pulverized to obtain modified ETFE1.

[0039] Example 2

[0040] This application provides a modified ETFE, the preparation method of which includes:

[0041] A 500L vertical stainless steel polymerization reactor was purged with nitrogen until the O2 content in the reactor decreased to below 10 ppm, and the reactor was kept under a nitrogen atmosphere. 400 kg of perfluorobutane, 20 kg of ethyl acetate, and 20 kg of methacryloxyethyl phosphate were added to the reactor, and stirring was started. Tetrafluoroethylene and ethylene (80:20 molar ratio) were then introduced into the reactor until the pressure reached 1.8 MPa, and the temperature was raised to 70°C. Once the temperature and pressure stabilized, 300 g of dicyclohexyl peroxide was added to the reactor to initiate the polymerization reaction. After the polymerization reaction began, a mixture of tetrafluoroethylene and ethylene (53 mol% tetrafluoroethylene content) and 8.5 kg of methacryloxyethyl phosphate were added to the reactor. The polymerization reaction was stopped when the total mass of added tetrafluoroethylene and ethylene reached 260 kg. The reaction product was cooled with circulating water, monomer recovered, solvent evaporated, dried, and pulverized to obtain modified ETFE2.

[0042] Example 3

[0043] This application provides a modified ETFE, the preparation method of which includes:

[0044] A 500L vertical stainless steel polymerization reactor was purged with nitrogen until the O2 content in the reactor decreased to below 10 ppm, and the reactor was kept under a nitrogen atmosphere. 400 kg of tetrafluoroethyl ether, 22 kg of ethanol, and 27 kg of methacryloxyethyl phosphate were added to the reactor, and stirring was started. Tetrafluoroethylene and ethylene (85:15 molar ratio) were then introduced into the reactor until the pressure reached 1.6 MPa, and the temperature was raised to 65°C. Once the temperature and pressure stabilized, 230 g of tert-butyl peroxypentanoate was added to the reactor to initiate the polymerization reaction. After the polymerization reaction began, a mixture of tetrafluoroethylene and ethylene (53 mol% tetrafluoroethylene content) and 16 kg of methacryloxyethyl phosphate were added to the reactor. The polymerization reaction was stopped when the total mass of added tetrafluoroethylene and ethylene reached 260 kg. The reaction product was cooled with circulating water, monomer recovered, solvent evaporated, dried, and pulverized to obtain modified ETFE3.

[0045] Example 4

[0046] This application provides a modified ETFE, the preparation method of which includes:

[0047] A 500L vertical stainless steel polymerization reactor was purged with nitrogen until the O2 content in the reactor decreased to below 10 ppm, and the reactor was kept under a nitrogen atmosphere. 400 kg of perfluoromethylcyclohexane, 13 kg of cyclohexane, and 28 kg of methacryloxyethyl phosphate were added to the reactor, and stirring was started. Tetrafluoroethylene and ethylene (83:17 molar ratio) were then introduced into the reactor until the pressure reached 1.5 MPa, and the temperature was raised to 65°C. Once the temperature and pressure stabilized, 200 g of diisopropyl peroxide dicarbonate was added to the reactor to initiate the polymerization reaction. After the polymerization reaction began, a mixture of tetrafluoroethylene and ethylene (53 mol% tetrafluoroethylene content) and 20 kg of methacryloxyethyl phosphate were added to the reactor. The polymerization reaction was stopped when the total mass of the added tetrafluoroethylene and ethylene reached 260 kg. The reaction product was cooled with circulating water, the monomer was recovered, the solvent was evaporated, dried, and pulverized to obtain modified ETFE4.

[0048] Example 5

[0049] This application provides a modified ETFE, the preparation method of which includes:

[0050] A 500L vertical stainless steel polymerization reactor was purged with nitrogen until the O2 content in the reactor decreased to below 10 ppm, and the reactor was placed under a nitrogen atmosphere. 400 kg of 1,3-dichloropentafluoropropane, 15 kg of methanol, and 35 kg of methacryloxyethyl phosphate were added to the reactor, and stirring was started. Tetrafluoroethylene and ethylene with a molar ratio of 84:16 were added to the reactor until the pressure reached 1.5 MPa, and the temperature was raised to 80°C. Once the temperature and pressure stabilized, 230 g of tert-butyl peroxypentanoate was added to the reactor to begin the polymerization reaction. After the polymerization reaction started, a mixture of tetrafluoroethylene and ethylene with a tetrafluoroethylene content of 53 mol% and 27 kg of methacryloxyethyl phosphate were added to the reactor. The polymerization reaction was stopped when the total mass of added tetrafluoroethylene and ethylene reached 260 kg. The reaction product was cooled with circulating water, monomer recovered, solvent evaporated, dried, and pulverized to obtain modified ETFE5.

[0051] Comparative Example 1

[0052] This application provides a modified ETFE as a comparative example, the preparation method of which includes:

[0053] A 500L vertical stainless steel polymerization reactor was evacuated with nitrogen until the O2 content in the reactor decreased to below 10 ppm, and the reactor was kept under a nitrogen atmosphere. 400 kg of perfluoromethylcyclohexane and 16 kg of cyclohexane were added to the reactor, and stirring was started. Tetrafluoroethylene and ethylene with a molar ratio of 70:30 were then introduced into the reactor until the pressure reached 1.3 MPa, and the temperature was raised to 58°C. Once the temperature and pressure stabilized, 200 g of diisopropyl peroxide dicarbonate was added to the reactor to begin the polymerization reaction. After the polymerization reaction started, a mixture of tetrafluoroethylene and ethylene with a tetrafluoroethylene content of 51 mol% was added to the reactor. The polymerization reaction was stopped when the total mass of the added tetrafluoroethylene and ethylene reached 260 kg. The reaction product was cooled by circulating water, the monomer was recovered, the solvent was evaporated, dried, and pulverized to obtain ETFE1.

[0054] Comparative Example 2

[0055] This application provides a modified ETFE as a comparative example, the preparation method of which includes:

[0056] A 500L vertical stainless steel polymerization reactor was purged with nitrogen until the O2 content in the reactor decreased to below 10 ppm, and the reactor was kept under a nitrogen atmosphere. 400 kg of tetrafluoroethyl ether, 23 kg of methanol, and 26 kg of methacryloxyethyl phosphate were added to the reactor, and stirring was started. Tetrafluoroethylene and ethylene with a molar ratio of 75:25 were then introduced into the reactor until the pressure reached 1.4 MPa, and the temperature was raised to 55°C. Once the temperature and pressure stabilized, 220 g of bis(2-ethylhexyl) peroxide dicarbonate was added to the reactor to begin the polymerization reaction. After the polymerization reaction started, a mixture of tetrafluoroethylene and ethylene with a tetrafluoroethylene content of 43 mol% and 19 kg of methacryloxyethyl phosphate were added to the reactor. The polymerization reaction was stopped when the total mass of the added tetrafluoroethylene and ethylene reached 260 kg. The reaction product was cooled by circulating water, the monomer was recovered, the solvent was evaporated, dried, and pulverized to obtain modified ETFE6.

[0057] Comparative Example 3

[0058] This application provides a modified ETFE as a comparative example, the preparation method of which includes:

[0059] A 500L vertical stainless steel polymerization reactor was purged with nitrogen until the O2 content in the reactor decreased to below 10 ppm, and the reactor was placed under a nitrogen atmosphere. 400 kg of 1,3-dichloropentafluoropropane, 27 kg of ethanol, and 25 kg of methacryloxyethyl phosphate were added to the reactor, and stirring was started. Tetrafluoroethylene and ethylene (92:8 molar ratio) were then introduced into the reactor until the pressure reached 1.0 MPa, and the temperature was raised to 50°C. Once the temperature and pressure stabilized, 180 g of perfluorocycloalkylformyl peroxide was added to the reactor to initiate the polymerization reaction. After the polymerization reaction began, a mixture of tetrafluoroethylene and ethylene (46 mol% tetrafluoroethylene content) and 12 kg of methacryloxyethyl phosphate were added to the reactor. The polymerization reaction was stopped when the total mass of added tetrafluoroethylene and ethylene reached 260 kg. The reaction product was cooled with circulating water, monomer recovered, solvent evaporated, dried, and pulverized to obtain modified ETFE7.

[0060] The ETFE prepared in Examples 1-5 and Comparative Examples 1-3 were tested for melt flow rate, melting point, composition, adhesion strength, limiting oxygen index, and thermal stability, and the results are shown in Table 1. The specific procedures for each test are as follows:

[0061] Melt flow rate test: ETFE prepared in Examples 1-5 and Comparative Examples 1-3 were tested according to the international standard ASTM-3159. The test load was 5 kg and the temperature was 297 °C.

[0062] Melting point determination: Differential scanning calorimetry was used for determination. The temperature was increased to 300℃ at a rate of 10℃ / min and held for 5min; then decreased to 150℃ at a rate of -10℃ / min and held for 5min; finally, the temperature was increased to 300℃ at a rate of 10℃ / min, and the second melting peak temperature was taken as the melting point.

[0063] Composition analysis: determined by fusion F-NMR nuclear magnetic resonance and fluorine content analysis.

[0064] Adhesion strength testing: The adhesion strength of ETFE prepared in Examples 1-5 and Comparative Examples 1-3 was tested according to ISO 4624-2016. Specifically, 50×150×2mm SS400 steel was pretreated, and a coating with a thickness of 200±20μm was sprayed onto the sample plate using an electrostatic spraying process to obtain the test sample. An HD-5000N coating adhesion strength tester was used, with the peel conditions set to a tensile speed of 50mm / min and an angle of 90 degrees between the test metal substrate and the coating. The maximum load was taken as the peel strength, i.e., the adhesion force. The greater the peel strength, the higher the adhesion between the coating and the test metal substrate.

[0065] Limiting Oxygen Index (LOI) Testing: The ETFE prepared in Examples 1-5 and Comparative Examples 1-3 were tested according to ASTM D2863 / ISO 4589-2. Specifically, the ETFE prepared in Examples 1-5 and Comparative Examples 1-3 were prepared into identical specimens with a length of 80-150 mm, a width of 6.5-10 mm, and a thickness ≤10.5 mm. The specimens were vertically mounted on a fixture and inserted into the combustion chamber from the top. The oxygen and nitrogen flow rates were adjusted, and the gas flow was allowed to continue for at least 30 seconds to flush the combustion chamber and stabilize the concentration. The top of the specimen was ignited with an igniter, and the combustion time or combustion length was observed. Based on the results, the oxygen concentration was continuously increased or decreased to preliminarily determine the oxygen concentration. The formal test was conducted using the rise and fall method. Starting from the preliminarily estimated concentration, the oxygen concentration step was fixed at 0.5%, and 15 valid specimens were tested repeatedly. The oxygen concentration values ​​of the last combustion reaction and the non-combustion reaction were recorded. The limiting oxygen index was calculated according to the formula LOI = [O2] / ([O2]+[N2])×100%.

[0066] Thermal stability test: The thermal stability of the polymer was evaluated by heating 3 mg of the copolymer from room temperature to 500°C at a rate of 10°C / min using a thermogravimetric analyzer in air. The temperature at which the weight loss was 1 wt% was recorded.

[0067] Table 1: Performance testing of ETFE prepared in Examples 1-5 and Comparative Examples 1-3

[0068]

[0069] As can be seen from Table 1:

[0070] (1) Comparing Example 1 and Comparative Example 1, the polymer prepared in Comparative Example 1 has higher crystallinity and therefore a higher melting point, but its adhesion is significantly weaker and its limiting oxygen index is 32%. In contrast, the polymer prepared in Example 1 has lower crystallinity and therefore a lower melting point, but its adhesion is significantly higher than that of Comparative Example 1, and its limiting oxygen index reaches 60%. This indicates that ETFE prepared by modifying tetrafluoroethylene and ethylene with methacryloyloxyethyl phosphate can reduce the crystallinity and melting point of the modified ETFE, while increasing its adhesion and limiting oxygen index. This is because the third monomer, methacryloyloxyethyl phosphate, can disrupt the regularity of the ETFE molecular chain, reducing its crystallinity and melting point, and this effect becomes more significant with increasing dosage. At the same time, the increase in the overall fluorine content of the copolymer helps to enhance its heat resistance.

[0071] (2) Compared with Examples 1, 4, 5 and Comparative Example 2, the amount of methacryloyloxyethyl phosphate added in Comparative Example 2 was relatively low, resulting in a lower content of it in the final copolymer. In addition, although the copolymer had a higher fluorine content and retained some heat resistance, the insufficient amount of methacryloyloxyethyl phosphate had a limited effect on improving adhesion and limiting oxygen index, resulting in only a slight improvement in these two properties, which failed to reach the level of Examples 1, 4, and 5.

[0072] (3) Comparing Example 2 and Comparative Example 3, compared with Example 2, the amount of methacryloyloxyethyl phosphate added in Comparative Example 3 was increased. However, due to the lower polymerization pressure and temperature, the actual copolymerization efficiency of methacryloyloxyethyl phosphate was limited under the influence of the reactivity ratio, resulting in no significant increase in its content in the final composition. Therefore, the melting point of Comparative Example 3 was only slightly lower than that of Example 2, while the adhesion and limiting oxygen index remained at a good level. This further illustrates that the content of methacryloyloxyethyl phosphate plays a dominant role in these two properties, but is also subject to the adjustment of polymerization process conditions.

[0073] (4) Comparing Examples 2 and 4, the amount of chain transfer agent added in Example 2 is higher than that in Example 4, and the melt flow rate of Example 2 is higher than that of Example 4. This is because the chain transfer agent regulates the molecular weight by terminating the growth of molecular chains. The increase in its amount will lead to a decrease in the average molecular weight of the polymer, which is reflected in a significant increase in the melt flow rate, thereby improving the processing fluidity.

[0074] As can be seen from the above, the special functional groups contained in the third monomer, methacryloxyethyl phosphate, are key to the excellent adhesion and flame retardancy of ETFE. It not only improves the interfacial adhesion between the copolymer and the substrate, but also significantly enhances the limiting oxygen index through a gas-phase flame retardant mechanism. Therefore, the content of the third monomer, methacryloxyethyl phosphate, has a decisive influence on the adhesion and flame retardancy of ETFE. However, the final incorporation amount of the third monomer, methacryloxyethyl phosphate, and the copolymerization effect are the result of the synergistic effect of multiple process parameters such as the feed ratio, polymerization pressure, and temperature.

[0075] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing modified ETFE, characterized in that, include: Under a nitrogen atmosphere, tetrafluoroethylene, ethylene, methacryloxyethyl phosphate and a chain transfer agent are added to a fluorinated solvent. When the temperature is stable at 55-100℃ and the pressure is stable at 1.5-8MPa, an initiator is added to carry out a polymerization reaction to obtain modified ETFE. In the polymerization reaction, tetrafluoroethylene, ethylene and methacryloxyethyl phosphate are added. In the modified ETFE, the molar percentage of tetrafluoroethylene and ethylene is 45-60 mol%: 40-55 mol%, and the molar percentage of methacryloxyethyl phosphate in the modified ETFE is 0.1-4 mol.

2. The method for preparing modified ETFE according to claim 1, characterized in that, Of the added tetrafluoroethylene and ethylene, the molar percentage of tetrafluoroethylene is 53 mol.

3. The method for preparing modified ETFE according to claim 1, characterized in that, In the modified ETFE, the molar percentage of tetrafluoroethylene and ethylene is 48-55 mol%: 43-50 mol%, and the molar percentage of methacryloxyethyl phosphate in the modified ETFE is 0.1-2 mol.

4. The method for preparing modified ETFE according to claim 1, characterized in that, The fluorinated solvent includes one or more of hydrochlorofluoroethers, chlorofluorocarbons, hydrofluorocarbons, and perfluorocarbons.

5. The method for preparing modified ETFE according to claim 1, characterized in that, The chain transfer agent includes one or more of methanol, ethanol, n-propanol, isopropanol, tert-butanol, methane, ethane, and cyclohexane.

6. The method for preparing modified ETFE according to claim 1, characterized in that, The initiators include organic peroxide initiators and azo compound initiators.

7. The method for preparing modified ETFE according to claim 1, characterized in that, The polymerization temperature is 55-80℃ and the polymerization pressure is 1.4-2.0MPa.

8. A modified ETFE, characterized in that, The modified ETFE is prepared according to any one of claims 1-7.

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