Ethylene-tetrafluoroethylene tetrapolymer and method for producing the same

Abstract

The present application relates to the technical field of fluoropolymers, and discloses an ethylene-tetrafluoroethylene tetrapolymer and a preparation method thereof.The method for preparing the ethylene-tetrafluoroethylene tetrapolymer comprises the following steps: mixing an organic solvent, perfluoroalkyl ethylene, fluoroalkyl acrylate and a molecular weight regulator under vacuum and in a water-free condition; adding tetrafluoroethylene, ethylene and an initiator into the obtained mixture to perform a polymerization reaction; and continuously adding tetrafluoroethylene, ethylene, perfluoroalkyl ethylene and fluoroalkyl acrylate after the polymerization reaction starts.According to the method, the composition of the polymer is controlled by adding fluoroalkyl acrylate, and a tetrapolymer resin with controllable composition and uniform distribution is prepared.The resin has low Young's modulus, high flexibility and heat resistance while maintaining good tensile strength.

Description

Technical Field

[0001] This invention relates to the field of fluoropolymer technology, specifically to an ethylene-tetrafluoroethylene tetrapolymer and its preparation method. Background Technology

[0002] Ethylene-tetrafluoroethylene copolymer (ETFE), also known as fluoroplastic-40, is a type of tetrafluoroethylene copolymer developed after FEP. ETFE is a semi-crystalline, semi-transparent polymer copolymerized from ethylene and tetrafluoroethylene. ETFE is a strong and tough material; while maintaining the good heat resistance, chemical resistance, and electrical insulation properties of PTFE, its radiation resistance and mechanical properties are greatly improved. However, with the widespread adoption of ETFE products, its high Young's modulus has become a limiting factor for its application in certain fields, such as flexible films or cables.

[0003] Patent application CN102471414A discloses an ETFE containing repeating units (A) based on TFE and repeating units (B) based on ethylene, with a molar ratio of repeating units (A) / repeating units (B) of 66 / 34-75 / 25. Relative to the total molar number of the repeating units (A) based on tetrafluoroethylene and the repeating units (B) based on ethylene, it contains 0-1 mol% of a component based on CH2=CX(CF2). n Y represents the repeating unit (C) of the monomer, where X and Y are independently hydrogen or fluorine atoms, and n is an integer from 2 to 8. Although this ETFE has good flexibility and meets the heat resistance requirements, its tensile strength is significantly reduced, failing to meet application needs.

[0004] Therefore, there is an urgent need to develop an ETFE that maintains good tensile strength while also possessing high flexibility and a high melting point. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem that existing ethylene-tetrafluoroethylene copolymers cannot simultaneously maintain good tensile strength, high flexibility, and high melting point. This invention provides an ethylene-tetrafluoroethylene quaternary copolymer and its preparation method. By strictly controlling the proportion of each monomer in the composition through quaternary copolymerization, the prepared ethylene-tetrafluoroethylene quaternary copolymer maintains good tensile strength while significantly reducing the Young's modulus of the resin. It also has both flexibility and heat resistance, and can be used in flexible films or cables.

[0006] To achieve the above objectives, a first aspect of the present invention provides a method for producing an ethylene-tetrafluoroethylene tetrapolymer, the method comprising: mixing an organic solvent, perfluoroalkylethylene, fluoroalkyl acrylate, and a molecular weight regulator under vacuum and anhydrous conditions; adding tetrafluoroethylene, ethylene, and an initiator to the resulting mixture to initiate a polymerization reaction; and continuing to add tetrafluoroethylene, ethylene, perfluoroalkylethylene, and fluoroalkyl acrylate after the polymerization reaction has started; wherein the perfluoroalkylethylene has the general structural formula CH2=CX(CF2). n Y, where X and Y are independently hydrogen atoms or fluorine atoms, n is an integer from 2 to 8, and the fluoroalkyl acrylate is at least one of perfluoroalkyl methacrylate, perfluoroalkyl methacrylate containing sulfur heteroatoms, perfluoroalkyl methacrylate containing nitrogen, and perfluorosulfonamide methacrylate.

[0007] Preferably, the perfluoroalkyl ethylene is at least one of CH2=CF(CF2)2F, CH2=CF(CF2)4F, CH2=CF(CF2)4H, CH2=CH(CF2)4F, CH2=CH(CF2)6F and CH2=CH(CF2)8H.

[0008] Preferably, the fluoroalkyl acrylate is a perfluoroalkyl methacrylate, and the general structural formula of the perfluoroalkyl methacrylate is Rf(CH2). m OC(O)C(CH3)=CH2, where Rf represents a fluoroalkyl group and m is an integer from 0 to 4.

[0009] Preferably, the perfluoroalkyl ethylene added after the start of the polymerization reaction accounts for 40-50 wt% of the total perfluoroalkyl ethylene content, and the fluoroalkyl acrylate added after the start of the polymerization reaction accounts for 20-50 wt% of the total fluoroalkyl acrylate content.

[0010] Preferably, the amounts of tetrafluoroethylene, ethylene, perfluoroalkylethylene, and fluoroalkyl acrylate are such that in the prepared ethylene-tetrafluoroethylene tetrapolymer, the content of repeating units provided by ethylene is 35-60 mol%, the content of repeating units provided by tetrafluoroethylene is 35-60 mol%, the content of repeating units provided by perfluoroalkylethylene is 0.5-10 mol%, and the content of repeating units provided by fluoroalkyl acrylate is 0.01-3 mol%.

[0011] Preferably, the amounts of tetrafluoroethylene and ethylene are such that the molar ratio of repeating units provided by ethylene to repeating units provided by tetrafluoroethylene in the prepared ethylene-tetrafluoroethylene tetrapolymer is 40 / 60-60 / 40.

[0012] Preferably, the amounts of perfluoroalkylethylene and fluoroalkyl acrylate are such that the molar ratio of repeating units provided by perfluoroalkylethylene to repeating units provided by fluoroalkyl acrylate in the prepared ethylene-tetrafluoroethylene tetrapolymer is 50 / 1 to 1 / 1.

[0013] Preferably, the organic solvent is at least one selected from chlorofluorocarbons, fluorinated hydrocarbons, hydrofluoroethers, chlorinated hydrocarbons, alcoholic organic solvents, and hydrocarbon organic solvents.

[0014] Preferably, the molecular weight regulator is at least one selected from methanol, ethanol, acetone, pentane, hexane, cyclohexane, and dichloropentafluoropropane.

[0015] Preferably, the initiator is at least one selected from tert-butyl peroxypentanoate, tert-butyl peroxyisobutyrate, diisopropyl peroxydicarbonate, and di-n-propyl peroxydicarbonate.

[0016] Preferably, the conditions for the polymerization reaction include: a temperature of 10-100℃, a pressure of 0.1-5MPa, and a time of 1-10h.

[0017] A second aspect of the present invention provides the preparation of an ethylene-tetrafluoroethylene tetrapolymer by the method described above.

[0018] Preferably, the melt index of the ethylene-tetrafluoroethylene tetrapolymer is in the range of 5-40 g / 10 min.

[0019] Preferably, the parameters of the ethylene-tetrafluoroethylene tetrapolymer include: melting point of 240-270℃, Young's modulus of less than 400MPa, tensile strength of more than 40MPa, and elongation of more than 300%.

[0020] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0021] (1) According to the ethylene-tetrafluoroethylene tetrapolymer of the present invention, on the basis of the original ternary copolymer, the polymer composition is controlled by the repeating units provided by fluoroalkyl acrylate to obtain a tetrapolymer resin with controllable composition and uniform distribution.

[0022] (2) According to the preparation method of ethylene-tetrafluoroethylene tetrapolymer of the present invention, by controlling the process formula and polymerization process, an ETFE resin with good tensile strength, low Young's modulus and high melting point is obtained.

[0023] (3) The ethylene-tetrafluoroethylene tetrapolymer described in this invention has both flexibility and heat resistance, and can be used in flexible films or cables. Attached Figure Description

[0024] Figure 1This is the infrared spectrum of the ethylene-tetrafluoroethylene tetrapolymer described in this invention. Detailed Implementation

[0025] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0026] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0027] The preparation method of the ethylene-tetrafluoroethylene tetrapolymer of the present invention includes:

[0028] Under vacuum and anhydrous conditions, an organic solvent, perfluoroalkylethylene, fluoroalkyl acrylate, and a molecular weight regulator are mixed. Tetrafluoroethylene, ethylene, and an initiator are then added to the resulting mixture to initiate a polymerization reaction. After the polymerization reaction begins, tetrafluoroethylene, ethylene, perfluoroalkylethylene, and fluoroalkyl acrylate are continuously added. According to the method described in this invention, the polymer composition is controlled by adding fluoroalkyl acrylate, resulting in a quaternary copolymer resin with controllable composition and uniform distribution. This resin exhibits good tensile strength, low Young's modulus, and high melting point, and also possesses flexibility and heat resistance, making it suitable for use in flexible films or cables.

[0029] The general structural formula of the perfluoroalkylethylene can be CH2=CX(CF2). n Y, where X and Y are independently hydrogen atoms or fluorine atoms, n is an integer from 2 to 8, and the fluoroalkyl acrylate is at least one of perfluoroalkyl methacrylate, perfluoroalkyl methacrylate containing sulfur heteroatoms, perfluoroalkyl methacrylate containing nitrogen, and perfluorosulfonamide methacrylate.

[0030] In the method described in this invention, the perfluoroalkylethylene can be at least one of CH2=CF(CF2)2F, CH2=CF(CF2)4F, CH2=CF(CF2)4H, CH2=CH(CF2)4F, CH2=CH(CF2)6F, and CH2=CH(CF2)8H. To ensure that the ethylene-tetrafluoroethylene tetrapolymer possesses both the reactivity of the monomer and the comprehensive properties of the copolymer, the perfluoroalkylethylene has the general structural formula CH2=CX(CF2). n In Y, n is preferably an integer between 2 and 4, and the perfluoroalkyl ethylene is more preferably CH2=CH(CF2)4F.

[0031] In the method described in this invention, the fluoroalkyl acrylate may be a perfluoroalkyl methacrylate, and the general structural formula of the perfluoroalkyl methacrylate may be Rf(CH2). m OC(O)C(CH3)=CH2, where Rf represents a fluoroalkyl group and m is an integer from 0 to 4. To ensure the heat resistance and chemical stability of the ethylene-tetrafluoroethylene tetrapolymer, the perfluoroalkyl methacrylate is preferably at least one of CF3(CH2)2OC(O)C(CH3)=CH2, F(CF2)2(CH2)2OC(O)C(CH3)=CH2, F(CF2)2OC(O)C(CH3)=CH2, and F(CF2)4OC(O)C(CH3)=CH2, more preferably F(CF2)2OC(O)C(CH3)=CH2 (perfluoroalkyl ethyl methacrylate).

[0032] In the method described in this invention, the organic solvent can be at least one selected from chlorofluorocarbons, fluorinated hydrocarbons, hydrofluoroethers, chlorinated hydrocarbons, alcoholic organic solvents, and hydrocarbon organic solvents. The chlorofluorocarbon can be, for example, trifluorotrichloroethane; the fluorinated hydrocarbon can be, for example, perfluorohexane; the hydrofluoroether can be, for example, tetrafluoroethyltrifluoroethyl ether; the chlorinated hydrocarbon can be, for example, pentachloroethane; the alcoholic organic solvent can be, for example, propanol; and the hydrocarbon organic solvent can be, for example, acetone. To ensure the chain transfer effect of the organic solvent, the solubility of the monomer, and environmental requirements, the organic solvent is preferably a fluorinated hydrocarbon and / or a hydrofluoroether. More preferably, the organic solvent is perfluorohexane, specifically 1H perfluorohexane.

[0033] In the method described in this invention, the molecular weight regulator can be at least one selected from methanol, ethanol, acetone, pentane, hexane, cyclohexane, and dichloropentafluoropropane. To ensure the mechanical and processing properties of the ethylene-tetrafluoroethylene tetrapolymer, methanol is preferably selected as the molecular weight regulator.

[0034] In the method described in this invention, the initiator can be a free radical initiator, preferably an initiator with a half-life of 10 hours and a temperature of 10-100°C, specifically, it can be at least one of tert-butyl peroxypentanoate, tert-butyl peroxyisobutyrate, diisopropyl peroxydicarbonate, and di-n-propyl peroxydicarbonate, preferably tert-butyl peroxypentanoate.

[0035] In the method described in this invention, the conditions for the polymerization reaction include: a temperature of 10-100°C, preferably 60-80°C; a pressure of 0.1-5 MPa, preferably 1-3 MPa; and a time of 1-10 h, preferably 2-8 h. In this document, the pressure is gauge pressure.

[0036] In the method described in this invention, the vacuum and anhydrous conditions allow for the dehydration and deoxygenation of the polymerization reactor. The vacuum can be achieved by purging the polymerization reactor with nitrogen. The polymerization reactor can be a vertical stainless steel polymerization reactor containing a stirring device. The stirring speed of the stirring device can be 500-700 rpm, preferably 550-650 rpm.

[0037] In the method described in this invention, the process of adding tetrafluoroethylene, ethylene and an initiator to the obtained mixture for polymerization includes: raising the temperature of the polymerization reactor to 10-100°C, preferably 60-80°C; adding a mixed gas of the tetrafluoroethylene and the ethylene to the obtained mixture until the pressure is 0.1-5 MPa, preferably 1-3 MPa; and then adding the initiator to the obtained mixture using an additive pump.

[0038] In the method described in this invention, the molar ratio of the organic solvent, the perfluoroalkyl ethylene, the fluoroalkyl acrylate, and the molecular weight regulator can be (40-80):(0.5-1.5):(0.02-0.15):1, preferably (45-78):(0.6-1):(0.05-0.12):1. The molar ratio of the ethylene and the tetrafluoroethylene can be 1:(3-6), preferably 1:(4-5.5). The ratio of the initiator and the molecular weight regulator can be (0.01-0.03):1, preferably (0.013-0.023):1.

[0039] In the method described in this invention, the process of continuously adding tetrafluoroethylene, ethylene, perfluoroalkylethylene, and fluoroalkyl acrylate after the polymerization reaction begins includes: after the polymerization reaction begins, continuously adding a mixed gas of the tetrafluoroethylene and the ethylene until the pressure is stable, and continuously adding the perfluoroalkylethylene and the fluoroalkyl acrylate using a metering pump. To ensure the compositional stability of the ethylene-tetrafluoroethylene quaternary copolymer, the concentration of reactants is maintained by continuously adding tetrafluoroethylene, ethylene, perfluoroalkylethylene, and fluoroalkyl acrylate after the polymerization reaction begins until the reaction ends.

[0040] In the method described in this invention, the perfluoroalkyl ethylene added after the start of the polymerization reaction accounts for 40-50 wt% of the total amount of perfluoroalkyl ethylene, preferably 42-45 wt%; the fluoroalkyl acrylate added after the start of the polymerization reaction accounts for 20-50 wt% of the total amount of fluoroalkyl acrylate, preferably 25-50 wt%.

[0041] In the method described in this invention, during the continued addition of tetrafluoroethylene, ethylene, perfluoroalkyl ethylene, and fluoroalkyl acrylate, the content of tetrafluoroethylene in the mixed gas of tetrafluoroethylene and ethylene can be 50-60 mol%, preferably 52-57 mol%; the content of ethylene in the mixed gas of tetrafluoroethylene and ethylene can be 40-50 mol%, preferably 43-48 mol%; and the molar ratio of perfluoroalkyl ethylene to fluoroalkyl acrylate can be (5-30):1, preferably (6.5-12):1.

[0042] In the method described in this invention, the amounts of tetrafluoroethylene, ethylene, perfluoroalkylethylene, and fluoroalkyl acrylate are such that in the prepared ethylene-tetrafluoroethylene tetrapolymer, the content of repeating units provided by ethylene can be 35-60 mol%, preferably 35-50 mol%; the content of repeating units provided by tetrafluoroethylene can be 35-60 mol%, preferably 50-60 mol%; and the content of repeating units provided by perfluoroalkylethylene can be 0.5-10 mol%, specifically, for example, 0.5 mol%, 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, etc. The content of repeating units provided by fluoroalkyl acrylates can be 0.01-3 mol%, specifically, for example, 0.01 mol%, 0.05 mol%, 0.1 mol%, 0.5 mol%, 1 mol%, 1.5 mol%, 2 mol%, 2.5 mol%, or 3 mol%, and is preferably 0.05-1.5 mol%, more preferably 0.05-0.5 mol%, to ensure the mechanical and heat resistance properties of the ethylene-tetrafluoroethylene tetrafluoroethylene copolymer.

[0043] In the method described in this invention, the amount of tetrafluoroethylene and ethylene used is such that the molar ratio of repeating units provided by ethylene to repeating units provided by tetrafluoroethylene in the prepared ethylene-tetrafluoroethylene tetrapolymer can be 40 / 60-60 / 40, specifically, for example, 40 / 60, 45 / 60, 50 / 60, 50 / 50, 55 / 50, 60 / 50, or 60 / 40. To ensure the mechanical and heat resistance properties of the ethylene-tetrafluoroethylene tetrapolymer, the molar ratio of repeating units provided by ethylene to repeating units provided by tetrafluoroethylene is preferably 40 / 60-50 / 50.

[0044] In the method described in this invention, the amounts of perfluoroalkylethylene and fluoroalkyl acrylate are such that the molar ratio of repeating units provided by perfluoroalkylethylene to repeating units provided by fluoroalkyl acrylate in the prepared ethylene-tetrafluoroethylene tetrapolymer can be 50 / 1 to 1 / 1, specifically, for example, 45 / 1, 40 / 1, 35 / 1, 30 / 1, 25 / 1, 20 / 1, 15 / 1, 10 / 1, 5 / 1, or 1 / 1. To ensure the mechanical and heat resistance properties of the ethylene-tetrafluoroethylene tetrapolymer, the molar ratio of repeating units provided by perfluoroalkylethylene to repeating units provided by fluoroalkyl acrylate is preferably 30 / 1 to 5 / 1, more preferably 20 / 1 to 5 / 1.

[0045] In the method described in this invention, the method may further include: stopping the reaction, recovering the unreacted tetrafluoroethylene and ethylene, and washing and drying the resulting product. The washing may be performed using an organic solvent, such as trifluorotrichloroethane, perfluorohexane, acetone, or propanol, preferably perfluorohexane, specifically 1H perfluorohexane. The drying conditions include: a temperature of 100-140°C, preferably 110-130°C; and a time of 6-10 hours, preferably 7-9 hours.

[0046] In some embodiments, the preparation method of the ethylene-tetrafluoroethylene tetrapolymer of the present invention includes the following steps:

[0047] (1) The polymerization reactor is vacuum dehydrated and deoxygenated. Organic solvent, perfluoroalkyl ethylene, fluoroalkyl acrylate and molecular weight regulator are added to the polymerization reactor and mixed at a stirring speed of 500-700 rpm. The molar ratio of the organic solvent, perfluoroalkyl ethylene, fluoroalkyl acrylate and molecular weight regulator is (40-80):(0.5-1.5):(0.02-0.15):1. The temperature of the polymerization reactor is raised to 10-100℃. A mixed gas of tetrafluoroethylene and ethylene with a molar ratio of ethylene and tetrafluoroethylene of 1:(3-6) is added to the obtained mixture until the pressure is 0.1-5 MPa. Then, the initiator is added to the obtained mixture using an additive pump to carry out the polymerization reaction. The ratio of the initiator and the molecular weight regulator is (0.01-0.03):1.

[0048] (2) After the polymerization reaction begins, continue to add the mixed gas of the tetrafluoroethylene and the ethylene until the pressure is stable. The content of the tetrafluoroethylene in the mixed gas of the tetrafluoroethylene and the ethylene is 50-60 mol%. The perfluoroalkyl ethylene (of which the perfluoroalkyl ethylene added after the polymerization reaction begins accounts for 40-50 wt% of the total amount of perfluoroalkyl ethylene) and the fluoroalkyl acrylate (of which the fluoroalkyl acrylate added after the polymerization reaction begins accounts for 20-50 wt% of the total amount of fluoroalkyl acrylate) are continuously added using a metering pump. The molar ratio of the perfluoroalkyl ethylene to the fluoroalkyl acrylate is (5-30):1. After 1-10 hours, the reaction is stopped, the unreacted tetrafluoroethylene and the ethylene are recovered, and the resulting product is washed and dried.

[0049] The general structural formula of the perfluoroalkylethylene is CH2=CX(CF2). n Y, where X and Y are independently hydrogen atoms or fluorine atoms, n is an integer from 2 to 8, the fluoroalkyl acrylate is at least one of perfluoroalkyl methacrylate, perfluoroalkyl methacrylate containing sulfur heteroatoms, perfluoroalkyl methacrylate containing nitrogen, and perfluorosulfonamide methacrylate, the organic solvent is at least one of chlorofluorocarbons, fluorinated hydrocarbons, hydrofluoroethers, chlorinated hydrocarbons, alcohol organic solvents, and hydrocarbon organic solvents, the molecular weight regulator is at least one of methanol, ethanol, acetone, pentane, hexane, cyclohexane, and dichloropentafluoropropane, and the initiator is a free radical initiator.

[0050] In other embodiments, the method for preparing the ethylene-tetrafluoroethylene tetrapolymer of the present invention includes the following steps:

[0051] (1) The polymerization reactor is vacuum dehydrated and deoxygenated. Organic solvent, perfluoroalkyl ethylene, fluoroalkyl acrylate and molecular weight regulator are added to the polymerization reactor and mixed at a stirring speed of 550-650 rpm. The molar ratio of the organic solvent, perfluoroalkyl ethylene, fluoroalkyl acrylate and molecular weight regulator is (45-78):(0.6-1):(0.05-0.12):1. The temperature of the polymerization reactor is raised to 60-80℃. A mixed gas of tetrafluoroethylene and ethylene with a molar ratio of ethylene and tetrafluoroethylene of 1:(4-5.5) is added to the obtained mixture until the pressure is 1-3 MPa. Then, the initiator is added to the obtained mixture using an additive pump to carry out the polymerization reaction. The ratio of the initiator and the molecular weight regulator is (0.013-0.023):1.

[0052] (2) After the polymerization reaction begins, continue to add the mixed gas of the tetrafluoroethylene and the ethylene until the pressure is stable. The content of the tetrafluoroethylene in the mixed gas of the tetrafluoroethylene and the ethylene is 52-57 mol%. The perfluoroalkyl ethylene (of which the perfluoroalkyl ethylene added after the polymerization reaction begins accounts for 42-45 wt% of the total amount of perfluoroalkyl ethylene) and the fluoroalkyl acrylate (of which the fluoroalkyl acrylate added after the polymerization reaction begins accounts for 25-50 wt% of the total amount of fluoroalkyl acrylate) are continuously added using a metering pump. The molar ratio of the perfluoroalkyl ethylene to the fluoroalkyl acrylate is (6.5-12):1. After 2-8 hours, the reaction is stopped, the unreacted tetrafluoroethylene and the ethylene are recovered, and the resulting product is washed and dried.

[0053] The general structural formula of the perfluoroalkylethylene is CH2=CX(CF2). n Y, where X and Y are independently hydrogen atoms or fluorine atoms, n is an integer from 2 to 8, the fluoroalkyl acrylate is at least one of perfluoroalkyl methacrylate, perfluoroalkyl methacrylate containing sulfur heteroatoms, perfluoroalkyl methacrylate containing nitrogen, and perfluorosulfonamide methacrylate, the organic solvent is at least one of chlorofluorocarbons, fluorinated hydrocarbons, hydrofluoroethers, chlorinated hydrocarbons, alcohol organic solvents, and hydrocarbon organic solvents, the molecular weight regulator is at least one of methanol, ethanol, acetone, pentane, hexane, cyclohexane, and dichloropentafluoropropane, and the initiator is a free radical initiator.

[0054] The present invention also provides an ethylene-tetrafluoroethylene tetrapolymer prepared by the above method, wherein the ethylene-tetrafluoroethylene tetrapolymer contains repeating units based on ethylene, repeating units based on tetrafluoroethylene, repeating units based on perfluoroalkylethylene, and repeating units based on fluoroalkyl acrylate, wherein the general structural formula of the perfluoroalkylethylene is CH2=CX(CF2). n Y, where X and Y are independently hydrogen or fluorine atoms, and n is an integer from 2 to 8. The fluoroalkyl acrylate is at least one of perfluoroalkyl methacrylate, perfluoroalkyl methacrylate containing sulfur heteroatoms, perfluoroalkyl methacrylate containing nitrogen, and perfluorosulfonamide methacrylate. The ethylene-tetrafluoroethylene tetrapolymer according to this invention has the characteristics of controllable composition and uniform distribution, thus maintaining good tensile strength while also possessing low Young's modulus, high flexibility, and high melting point, making it suitable for use in flexible films or cables.

[0055] In the ethylene-tetrafluoroethylene tetrapolymer of this invention, the perfluoroalkyl ethylene can be at least one of CH2=CF(CF2)2F, CH2=CF(CF2)4F, CH2=CF(CF2)4H, CH2=CH(CF2)4F, CH2=CH(CF2)6F, and CH2=CH(CF2)8H. To ensure that the ethylene-tetrafluoroethylene tetrapolymer possesses both the reactivity of the monomer and the comprehensive properties of the copolymer, the perfluoroalkyl ethylene has the general structural formula CH2=CX(CF2). n In Y, n is preferably an integer between 2 and 4, and the perfluoroalkyl ethylene is more preferably CH2=CH(CF2)4F.

[0056] In the ethylene-tetrafluoroethylene tetrapolymer described in this invention, the fluoroalkyl acrylate can be a perfluoroalkyl methacrylate, and the general structural formula of the perfluoroalkyl methacrylate can be Rf(CH2). m OC(O)C(CH3)=CH2, where Rf represents a fluoroalkyl group and m is an integer from 0 to 4. To ensure the heat resistance and chemical stability of the ethylene-tetrafluoroethylene tetrapolymer, the perfluoroalkyl methacrylate is preferably at least one of CF3(CH2)2OC(O)C(CH3)=CH2, F(CF2)2(CH2)2OC(O)C(CH3)=CH2, F(CF2)2OC(O)C(CH3)=CH2, and F(CF2)4OC(O)C(CH3)=CH2, more preferably F(CF2)2OC(O)C(CH3)=CH2 (perfluoroalkyl ethyl methacrylate).

[0057] In the ethylene-tetrafluoroethylene tetrapolymer of this invention, the molecular weight of the ethylene-tetrafluoroethylene tetrapolymer can be expressed by its melt index. The melt index range of the ethylene-tetrafluoroethylene tetrapolymer can be 5-40 g / 10 min, specifically, for example, 5 g / 10 min, 10 g / 10 min, 15 g / 10 min, 20 g / 10 min, 25 g / 10 min, 30 g / 10 min, 35 g / 10 min, or 40 g / 10 min. To ensure the mechanical and processing properties of the ethylene-tetrafluoroethylene tetrapolymer, the melt index range of the ethylene-tetrafluoroethylene tetrapolymer is preferably 10-25 g / 10 min. In this invention, the melt index of the ethylene-tetrafluoroethylene tetrapolymer is tested by a melt indexer. The testing conditions may include: a temperature of 297°C and a load of 5 kg.

[0058] In the ethylene-tetrafluoroethylene tetrapolymer of this invention, the parameters of the ethylene-tetrafluoroethylene tetrapolymer may include: a melting point of 240-270°C, a Young's modulus of less than 400 MPa, a tensile strength of more than 40 MPa, and an elongation of more than 300%. The ethylene-tetrafluoroethylene tetrapolymer of this invention maintains good tensile strength while exhibiting a significant decrease in Young's modulus, combining flexibility and heat resistance, and can be applied to flexible films or cables.

[0059] In some embodiments, the ethylene-tetrafluoroethylene tetrapolymer contains repeating units based on ethylene, repeating units based on tetrafluoroethylene, repeating units based on perfluoroalkylethylene, and repeating units based on fluoroalkyl acrylates, wherein the perfluoroalkylethylene has the general structural formula CH2=CX(CF2). n Y, where X and Y are independently hydrogen atoms or fluorine atoms, n is an integer from 2 to 8, the fluoroalkyl acrylate is at least one of perfluoroalkyl methacrylate, sulfur-containing heteroatom perfluoroalkyl methacrylate, perfluoronitrogen-containing fluoroalkyl methacrylate, and perfluorosulfonamide methacrylate, in the ethylene-tetrafluoroethylene quaternary copolymer, based on the ethylene-tetrafluoroethylene quaternary copolymer, the content of repeating units provided by ethylene is 35-60 mol%, the content of repeating units provided by tetrafluoroethylene is 35-60 mol%, the content of repeating units provided by perfluoroalkyl ethylene is 0.5-10 mol%, the content of repeating units provided by fluoroalkyl acrylate is 0.01-3 mol%, the molar ratio of repeating units provided by ethylene to repeating units provided by tetrafluoroethylene is 40 / 60-60 / 40, the molar ratio of repeating units provided by perfluoroalkyl ethylene to repeating units provided by fluoroalkyl acrylate is 50 / 1-1 / 1, and the melt index range of the ethylene-tetrafluoroethylene quaternary copolymer is 5-40 g / 10 min.

[0060] In other embodiments, the ethylene-tetrafluoroethylene tetrapolymer contains repeating units based on ethylene, repeating units based on tetrafluoroethylene, repeating units based on perfluoroalkylethylene, and repeating units based on fluoroalkyl acrylates, wherein the perfluoroalkylethylene is at least one selected from CH2=CF(CF2)2F, CH2=CF(CF2)4F, CH2=CF(CF2)4H, CH2=CH(CF2)4F, CH2=CH(CF2)6F, and CH2=CH(CF2)8H, and the fluoroalkyl acrylate is a perfluoroalkyl methacrylate with the general structural formula Rf(CH2). mOC(O)C(CH3)=CH2, where Rf represents fluoroalkyl, m is an integer from 0 to 4. In the ethylene-tetrafluoroethylene quaternary copolymer, based on the ethylene-tetrafluoroethylene quaternary copolymer, the content of repeating units provided by ethylene is 35-50 mol%, the content of repeating units provided by tetrafluoroethylene is 50-60 mol%, the content of repeating units provided by perfluoroalkyl ethylene is 1.1-2.5 mol%, the content of repeating units provided by fluoroalkyl acrylate is 0.05-0.5 mol%, the molar ratio of repeating units provided by ethylene to repeating units provided by tetrafluoroethylene is 40 / 60-60 / 40, the molar ratio of repeating units provided by perfluoroalkyl ethylene to repeating units provided by fluoroalkyl acrylate is 50 / 1-1 / 1, and the melt index range of the ethylene-tetrafluoroethylene quaternary copolymer is 10-25 g / 10 min.

[0061] The following examples further illustrate the ethylene-tetrafluoroethylene tetrapolymer and its preparation method according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0062] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0063] Example 1

[0064] Preparation of ethylene-tetrafluoroethylene tetrapolymer:

[0065] (1) Fill a 5L vertical stainless steel polymerization reactor containing a stirring device with nitrogen and evacuate it. Add 3300g of 1H perfluorohexane, 18g of perfluorobutylethylene, 3g of perfluoroalkyl methyl methacrylate and 4g of methanol and mix them at a stirring speed of 600rpm. Raise the temperature of the polymerization reactor to 66℃. Add a mixture of ethylene and tetrafluoroethylene (molar percentage is 20:80) to the mixture until the pressure is 1.7MPa. Then add 0.5g of tert-butyl peroxypentanoate to the mixture using an additive pump to carry out the polymerization reaction.

[0066] (2) After the polymerization reaction begins, a mixture of tetrafluoroethylene and ethylene gas is added continuously (the content of tetrafluoroethylene in the mixture of tetrafluoroethylene and ethylene gas is 52 mol%) to maintain a stable polymerization pressure. Perfluoroalkyl ethylene and fluoroalkyl acrylate are continuously added using a metering pump. When the amount of tetrafluoroethylene and ethylene gas added reaches 500g, the amount of perfluorobutylethylene added is 14g and the amount of perfluoroalkyl ethyl methacrylate is 1.8g. The reaction is stopped after 5h, the unreacted ethylene and tetrafluoroethylene are recovered by cooling, and the product is discharged through the discharge valve of the reactor. The obtained product is washed with 1H perfluorohexane and dried at 120℃ for 8h to obtain 437g of resin product.

[0067] Example 2

[0068] Preparation of ethylene-tetrafluoroethylene tetrapolymer:

[0069] (1) Fill a 5L vertical stainless steel polymerization reactor containing a stirring device with nitrogen and evacuate it. Add 3300g of 1H perfluorohexane, 22g of perfluorobutylethylene, 3.3g of perfluoroalkyl methyl methacrylate, and 5g of methanol and mix them at a stirring speed of 550rpm. Raise the temperature of the polymerization reactor to 60℃. Add a mixture of ethylene and tetrafluoroethylene (molar percentage is 15:85) to the mixture until the pressure is 1MPa. Then add 0.5g of tert-butyl peroxypentanoate to the mixture using an additive pump to carry out the polymerization reaction.

[0070] (2) After the polymerization reaction begins, a mixture of tetrafluoroethylene and ethylene gas (in which the content of tetrafluoroethylene in the mixture of tetrafluoroethylene and ethylene gas is 57 mol%) is added to maintain the polymerization pressure. Perfluoroalkyl ethylene and fluoroalkyl acrylate are continuously added using a metering pump. When the amount of tetrafluoroethylene and ethylene gas added reaches 455 g, the amount of perfluorobutylethylene added is 17 g and the amount of perfluoroalkyl ethyl methacrylate is 1.2 g. The reaction is stopped after 1 h, the unreacted ethylene and tetrafluoroethylene are cooled and recovered, and the product is discharged through the discharge valve of the reactor. The obtained product is washed with 1H perfluorohexane and dried at 100 °C for 6 h to obtain 417 g of resin product.

[0071] Example 3

[0072] Preparation of ethylene-tetrafluoroethylene tetrapolymer:

[0073] (1) Fill a 5L vertical stainless steel polymerization reactor containing a stirring device with nitrogen and evacuate it. Add 3300g of 1H perfluorohexane, 40g of perfluorobutylethylene, 2g of perfluoroalkyl methyl methacrylate and 7g of methanol and mix them at a stirring speed of 650rpm. Raise the temperature of the polymerization reactor to 80℃. Add a mixture of ethylene and tetrafluoroethylene (molar percentage is 20:80) to the mixture until the pressure is 1.7MPa. Then add 0.5g of tert-butyl peroxypentanoate to the mixture using an additive pump to carry out the polymerization reaction.

[0074] (2) After the polymerization reaction begins, a mixture of tetrafluoroethylene and ethylene gas is added continuously (the content of tetrafluoroethylene in the mixture of tetrafluoroethylene and ethylene gas is 56 mol%) to maintain a stable polymerization pressure. Perfluoroalkyl ethylene and fluoroalkyl acrylate are continuously added using a metering pump. When the amount of tetrafluoroethylene and ethylene gas added reaches 497 g, the amount of perfluorobutylethylene added is 30 g and the amount of perfluoroalkyl ethyl methacrylate is 2 g. After 10 h, the reaction is stopped, the unreacted ethylene and tetrafluoroethylene are cooled and recovered, and the product is discharged through the discharge valve of the reactor. The obtained product is washed with 1H perfluorohexane and dried at 140 °C for 12 h to obtain 480 g of resin product.

[0075] Example 4

[0076] Preparation of ethylene-tetrafluoroethylene tetrapolymer:

[0077] (1) Fill a 5L vertical stainless steel polymerization reactor containing a stirring device with nitrogen and evacuate it. Add 3300g of 1H perfluorohexane, 39g of perfluorobutylethylene, 4g of perfluoroalkyl methyl methacrylate, and 5g of methanol and mix them at a stirring speed of 600rpm. Raise the temperature of the polymerization reactor to 66℃. Add a mixture of ethylene and tetrafluoroethylene (molar percentage is 20:80) to the mixture until the pressure is 1.7MPa. Then add 0.5g of tert-butyl peroxypentanoate to the mixture using an additive pump to carry out the polymerization reaction.

[0078] (2) After the polymerization reaction begins, a mixture of tetrafluoroethylene and ethylene gas is added continuously (the content of tetrafluoroethylene in the mixture of tetrafluoroethylene and ethylene gas is 56 mol%) to maintain a stable polymerization pressure. Perfluoroalkyl ethylene and fluoroalkyl acrylate are continuously added using a metering pump. When the amount of tetrafluoroethylene and ethylene gas added reaches 472 g, the amount of perfluorobutylethylene added is 27 g and the amount of perfluoroalkyl ethyl methacrylate is 2.3 g. The reaction is stopped after 5 h, the unreacted ethylene and tetrafluoroethylene are cooled and recovered, and the product is discharged through the discharge valve of the reactor. The obtained product is washed with 1H perfluorohexane and dried at 140 °C for 12 h to obtain 479 g of resin product.

[0079] Comparative Example 1

[0080] Preparation of ethylene-tetrafluoroethylene binary copolymer:

[0081] (1) Fill a 5L vertical stainless steel polymerization reactor containing a stirring device with nitrogen and evacuate it. Add 3300g of 1H perfluorohexane and 4g of methanol and mix them at a stirring speed of 600rpm. Raise the temperature of the polymerization reactor to 66℃. Add a mixture of ethylene and tetrafluoroethylene (molar percentage of 20:80) to the mixture until the pressure is 1.7MPa. Then add 0.5g of tert-butyl peroxypentanoate to the mixture using an additive pump to carry out the polymerization reaction.

[0082] (2) After the polymerization reaction begins, a mixture of tetrafluoroethylene and ethylene gas is added (the content of tetrafluoroethylene in the mixture of tetrafluoroethylene and ethylene gas is 56 mol%) to maintain a stable polymerization pressure. When the amount of added tetrafluoroethylene and ethylene gas reaches 400 g, the reaction is stopped, the unreacted ethylene and tetrafluoroethylene are recovered by cooling, and the product is discharged through the discharge valve of the reactor. The obtained product is washed with 1H perfluorohexane and dried at 120°C for 8 h to obtain 410 g of resin product.

[0083] Comparative Example 2

[0084] Preparation of ethylene-tetrafluoroethylene terpolymer:

[0085] (1) Fill a 5L vertical stainless steel polymerization reactor containing a stirring device with nitrogen and evacuate it. Add 3300g of 1H perfluorohexane, 40g of perfluorobutylethylene and 5g of methanol and mix them at a stirring speed of 600rpm. Raise the temperature of the polymerization reactor to 66℃. Add a mixture of ethylene and tetrafluoroethylene (molar percentage is 20:80) to the mixture until the pressure is 1.7MPa. Then add 0.5g of tert-butyl peroxypentanoate to the mixture using an additive pump to carry out the polymerization reaction.

[0086] (2) After the polymerization reaction begins, a mixture of tetrafluoroethylene and ethylene gas (in which the content of tetrafluoroethylene in the mixture of tetrafluoroethylene and ethylene is 56 mol%) is added to maintain the polymerization pressure. The perfluoroalkyl ethylene is continuously added using a metering pump. When the amount of the added tetrafluoroethylene and ethylene gas mixture reaches 449 g, the amount of added perfluorobutylethylene is 30 g. The reaction is stopped after 5 h, the unreacted ethylene and tetrafluoroethylene are cooled and recovered, and the product is discharged through the discharge valve of the reactor. The obtained product is washed with 1H perfluorohexane and dried at 120 °C for 8 h to obtain 447 g of resin product.

[0087] Comparative Example 3

[0088] Preparation of ethylene-tetrafluoroethylene terpolymer:

[0089] (1) Fill a 5L vertical stainless steel polymerization reactor containing a stirring device with nitrogen and evacuate it. Add 3300g of 1H perfluorohexane, 50g of perfluorobutylethylene and 5g of methanol and mix them at a stirring speed of 600rpm. Raise the temperature of the polymerization reactor to 66℃. Add a mixture of ethylene and tetrafluoroethylene (molar percentage is 20:80) to the mixture until the pressure is 1.7MPa. Then add 0.5g of tert-butyl peroxypentanoate to the mixture using an additive pump to carry out the polymerization reaction.

[0090] (2) After the polymerization reaction begins, a mixture of tetrafluoroethylene and ethylene gas is added (the content of tetrafluoroethylene in the mixture of tetrafluoroethylene and ethylene gas is 56 mol%) to maintain the polymerization pressure. Perfluoroalkyl ethylene is continuously added using a metering pump. When the amount of tetrafluoroethylene and ethylene gas added reaches 480 g, the amount of perfluorobutylethylene added is 47 g. The reaction is stopped after 5 h. The unreacted ethylene and tetrafluoroethylene are cooled and recovered. The product is discharged through the discharge valve of the reactor and washed with 1H perfluorohexane. It is then dried at 120 °C for 8 h to obtain 447 g of resin product.

[0091] Test examples: The following tests were performed on the resin products obtained in Examples 1-4 and Comparative Examples 1-3:

[0092] (1) The tensile test specimens were prepared by compression molding technology; the tensile properties were tested in accordance with GB / T1040.1-2006.

[0093] (2) The melt index of the resin was tested using a melt indexer. The test conditions were: temperature 297℃, load 5kg.

[0094] (3) The melting point of the resin was determined by differential scanning calorimetry (DSC) by raising the sample from room temperature to 300°C at a rate of 10°C / min.

[0095] (4) The composition of the copolymer is obtained by measuring the intensity ratio of specific groups using infrared spectroscopy, wherein A is a repeating unit provided by tetrafluoroethylene, B is a repeating unit provided by perfluoroalkyl ethylene, and C is a repeating unit provided by fluoroalkyl acrylate.

[0096] The composition, melting point, melt index, tensile strength, elongation and Young's modulus of the copolymer are recorded in Table 1.

[0097] Table 1

[0098]

[0099] As can be seen from the results in Table 1, the examples using the ethylene-tetrafluoroethylene tetrapolymer of the present invention, while maintaining good tensile strength, also exhibit low Young's modulus, high flexibility, and high melting point. In contrast, the ethylene-tetrafluoroethylene binary copolymer has a lower elongation and a higher Young's modulus, while the ethylene-tetrafluoroethylene terpolymer cannot simultaneously maintain both good tensile strength and a low Young's modulus.

[0100] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing an ethylene-tetrafluoroethylene tetrapolymer, characterized in that, The method includes: Under vacuum and anhydrous conditions, an organic solvent, perfluoroalkyl ethylene, fluoroalkyl acrylate and a molecular weight regulator are mixed. Tetrafluoroethylene, ethylene and an initiator are added to the resulting mixture to carry out a polymerization reaction. After the polymerization reaction starts, tetrafluoroethylene, ethylene, perfluoroalkyl ethylene and fluoroalkyl acrylate are added continuously. The general structural formula of the perfluoroalkylethylene is CH2=CX(CF2). n Y, where X and Y are independently hydrogen or fluorine atoms, and n is an integer from 2 to 8. The fluoroalkyl acrylate is a perfluoroalkyl methacrylate, and the general structural formula of the perfluoroalkyl methacrylate is Rf(CH2). m OC(O)C(CH3)=CH2, where Rf represents a fluoroalkyl group and m is an integer from 0 to 4; The amounts of tetrafluoroethylene, ethylene, perfluoroalkylethylene, and fluoroalkyl acrylate used in the preparation of the ethylene-tetrafluoroethylene tetrapolymer are such that the content of repeating units provided by ethylene is 35-60 mol%, the content of repeating units provided by tetrafluoroethylene is 35-60 mol%, the content of repeating units provided by perfluoroalkylethylene is 0.5-10 mol%, and the content of repeating units provided by fluoroalkyl acrylate is 0.01-3 mol.

2. The method according to claim 1, characterized in that, The perfluoroalkyl ethylene is at least one of CH2=CF(CF2)2F, CH2=CF(CF2)4F, CH2=CF(CF2)4H, CH2=CH(CF2)4F, CH2=CH(CF2)6F and CH2=CH(CF2)8H.

3. The method according to claim 1 or 2, characterized in that, The perfluoroalkyl ethylene added after the start of the polymerization reaction accounts for 40-50 wt% of the total perfluoroalkyl ethylene content, and the fluoroalkyl acrylate added after the start of the polymerization reaction accounts for 20-50 wt% of the total fluoroalkyl acrylate content.

4. The method according to claim 1, characterized in that, The amounts of tetrafluoroethylene and ethylene used result in a molar ratio of repeating units provided by ethylene to repeating units provided by tetrafluoroethylene of 40 / 60-60 / 40 in the prepared ethylene-tetrafluoroethylene tetrapolymer.

5. The method according to claim 1 or 4, characterized in that, The amounts of perfluoroalkyl ethylene and fluoroalkyl acrylate are such that the molar ratio of repeating units provided by perfluoroalkyl ethylene to repeating units provided by fluoroalkyl acrylate in the prepared ethylene-tetrafluoroethylene tetrapolymer is 50 / 1 to 1 / 1.

6. The method according to claim 1, characterized in that, The organic solvent is at least one of chlorofluorocarbons, fluorinated hydrocarbons, hydrofluoroethers, chlorinated hydrocarbons, alcohol organic solvents, and hydrocarbon organic solvents.

7. The method according to claim 1, characterized in that, The molecular weight regulator is at least one of methanol, ethanol, acetone, pentane, hexane, cyclohexane, and dichloropentafluoropropane.

8. The method according to claim 1, characterized in that, The initiator is at least one of tert-butyl peroxypentanoate, tert-butyl peroxyisobutyrate, diisopropyl peroxydicarbonate, and di-n-propyl peroxydicarbonate.

9. The method according to claim 1, characterized in that, The conditions for the polymerization reaction include: temperature of 10-100℃, pressure of 0.1-5MPa, and time of 1-10h.

10. An ethylene-tetrafluoroethylene tetrapolymer prepared by the method according to any one of claims 1-9.

11. The ethylene-tetrafluoroethylene tetrapolymer according to claim 10, characterized in that, The melt index of the ethylene-tetrafluoroethylene tetrapolymer ranges from 5 to 40 g / 10 min.

12. The ethylene-tetrafluoroethylene tetrapolymer according to claim 10, characterized in that, The parameters of the ethylene-tetrafluoroethylene tetrapolymer include: melting point of 240-270℃, Young's modulus of less than 400MPa, tensile strength of more than 40MPa, and elongation of more than 300%.

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