A modified polyfluoroethylene propylene, a method of making and a polyfluoroethylene propylene film

Abstract

The application belongs to the technical field of fluorinated industry, and particularly relates to a modified polyperfluoroethylene propylene, a preparation method and a polyperfluoroethylene propylene film. The modified polyperfluoroethylene propylene is a terpolymer of tetrafluoroethylene, hexafluoropropylene and perfluoroalkyl vinyl ether; the content of the hexafluoropropylene structural unit in the terpolymer is 15.9wt%-17wt%, and the content of the perfluoroalkyl vinyl ether structural unit is 3wt%-3.5wt%. The polydispersity index PDI of the modified polyperfluoroethylene propylene is 1.95-2.15, and the critical shear rate is 330-410s ﹣1 . The preparation method of the modified polyperfluoroethylene propylene is to change the temperature and pressure alternately in the reaction process, so that the polyperfluoroethylene propylene with uniform molecular weight distribution and high shear resistance is prepared. The polyperfluoroethylene propylene film is prepared by extruding the modified polyperfluoroethylene propylene into a casting film.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fluorinated chemicals, and particularly relates to a modified polyfluoroethylene propylene, a preparation method and a polyfluoroethylene propylene film. BACKGROUND

[0002] Polyfluoroethylene propylene (FEP) is a random copolymer of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP), which can be processed by melt extrusion, molding, spraying and other general thermoplastic processing methods. However, in the polymerization process of preparing polyfluoroethylene propylene, the reactivity of hexafluoropropylene is much lower than that of tetrafluoroethylene, so the content of hexafluoropropylene in the mixed gas at the beginning of the reaction is relatively high, and it is extremely difficult for the high component hexafluoropropylene to combine into the main chain of polyfluoroethylene propylene. It can be seen that it is difficult for hexafluoropropylene monomer to be uniformly distributed on the polyfluoroethylene propylene molecular chain, and it is easy to cause the self-polymerization of tetrafluoroethylene monomer, resulting in the problem of crystal point nodules in polyfluoroethylene propylene products. In addition, in order to improve the mechanical properties and bending resistance of polyfluoroethylene propylene, special monomers are added in the preparation of polyfluoroethylene propylene to increase the side chain length of polyfluoroethylene propylene molecular chain, thereby increasing the flexibility of the whole molecular chain. Since the special monomers are also distributed unevenly on the polyfluoroethylene propylene molecular chain, the critical shear rate of polyfluoroethylene propylene is relatively low, generally 200-300 s ﹣1 (adopting high-pressure capillary rheometer, tested at 372℃), when polyfluoroethylene propylene is processed into products, it is easy to cause melt fracture and resin fiberization, resulting in problems such as glue, nodules, breakdown, concave-convex and the like. In summary, there is an urgent need to solve the problems of crystal points, nodules and poor shear resistance of polyfluoroethylene propylene resin during use.

[0003] Patent US5703185A discloses a fluorine-containing polymer extrusion process, which uses perfluoroethyl vinyl ether as the third monomer of TFE / HFP copolymer, which delays the occurrence of melt fracture to some extent, and realizes high-speed coating about 1.5 times faster than the traditional extrusion rate. However, in the reaction process, in order to increase the amount of the third monomer, non-environmental chlorofluorocarbon or chlorofluorohydrocarbon solvents are used.

[0004] Patent JP7112013B1 discloses a fluorine-containing copolymer, which is copolymerized from tetrafluoroethylene monomer, hexafluoropropylene monomer and perfluoro vinyl ether monomer, wherein the content of hexafluoropropylene monomer is 9.6-10.5wt%, and the content of perfluoro vinyl ether monomer is 1.2-1.6wt%. Although the fluorine-containing copolymer has good deformation resistance, 120℃ tensile creep resistance and durability to repeated load, methanol is added as a cosolvent in the polymerization process, which brings great difficulty to subsequent water treatment, and the contained methanol will affect the color of the resin during extrusion.

[0005] CN110467699A discloses a kind of polyfluoroethylene-propylene resin and its preparation method, the process of polyfluoroethylene-propylene resin is prepared in emulsion polymerization method with tetrafluoroethylene and hexafluoropropylene as raw material, first, ammonium persulfate and potassium persulfate composite initiator are used to initiate polymerization reaction, then ammonium persulfate and peroxide succinic acid composite initiator are used to control chain growth in chain initiation period.The ammonium persulfate and peroxide succinic acid composite initiator used in the method are the composite of inorganic initiator and organic initiator, the half-life of the two initiators is different at the same temperature, one of the initiators is easily deactivated, while the other initiator is still in reaction, and the proportion of one of the initiators is extremely small, which can cause the molecular weight distribution to be extremely uneven, resulting in poor resin processing performance, and further affecting the performance of the product. SUMMARY

[0006] The purpose of the present application is to provide a modified polyfluoroethylene-propylene resin with uniform molecular weight distribution and high shear resistance, which solves the problem of crystal points and nodules caused by poor shear resistance and uneven molecular weight distribution of polyfluoroethylene-propylene resin in the prior art.

[0007] A modified polyfluoroethylene-propylene resin is a terpolymer of tetrafluoroethylene, hexafluoropropylene and perfluoroalkyl vinyl ether; the content of hexafluoropropylene structural unit in the terpolymer is 15.9wt%-17wt%, and the content of perfluoroalkyl vinyl ether structural unit is 3wt%-3.5wt%; the polydispersity index PDI of the modified polyfluoroethylene-propylene resin is 1.95-2.15, and the critical shear rate is 330-410s ﹣1 .

[0008] The content range of hexafluoropropylene structural unit in the modified polyfluoroethylene-propylene resin can make the elongation at break of polyfluoroethylene-propylene resin reach 330-360%, increasing the flexibility of polyfluoroethylene-propylene resin. The content range of perfluoroalkyl vinyl ether structural unit makes the tensile strength of the modified polyfluoroethylene-propylene resin reach 28-30MPa, and the bending resistance MIT number of 200μm film made of the modified polyfluoroethylene-propylene resin can reach 45000-60000 times.

[0009] The polydispersity index PDI of polyfluoroethylene-propylene resin in the prior art is generally 3.0-3.5; the polydispersity index PDI of the modified polyfluoroethylene-propylene resin is 1.95-2.15, and the molecular weight distribution is uniform, which is more beneficial to the processing of polyfluoroethylene-propylene resin. The critical shear rate of traditional polyfluoroethylene-propylene resin is generally 200-300s ﹣1 , the critical shear rate of the modified polyfluoroethylene-propylene resin can reach 330-410s﹣1 It can be seen that the modified polyfluoroethylene propylene has more excellent shear resistance and is more resistant to shear and less likely to melt rupture.

[0010] In the present application, the modified polyfluoroethylene propylene has a weight average molecular weight of 350,000-400,000 g / mol, a melt index of 8.0-10.5 g / 10 min, a melting point of 255-260℃, and a thermal decomposition temperature of 412-420℃. The thermal decomposition temperature of traditional polyfluoroethylene propylene is generally 390-410℃, while the thermal decomposition temperature of the modified polyfluoroethylene propylene in the present application can reach 412-420℃.

[0011] In the present application, the modified polyfluoroethylene propylene is extruded into a film with a thickness of 100 μm by a casting film extruder, and the number of crystal points in the film is measured by a flaw detector. The number of large crystal points with a diameter of >0.25 mm is 0-1 / m 2 , the number of medium crystal points with a diameter of 0.15-0.25 mm is 1-3 / m 2 , and the number of small crystal points with a diameter of <0.15 mm is 2-6 / m 2 . First, the modified polyfluoroethylene propylene is extruded into a film with a thickness of 100 μm by a single screw extruder at a speed of 0.3 m / min, and the number of crystal points in the film is measured by a flaw detector.

[0012] In combination with the polydispersity index PDI, critical shear rate, melt index, thermal decomposition temperature, and crystal point number of the modified polyfluoroethylene propylene described above, it can be seen that hexafluoropropylene and perfluoro ether are relatively uniformly distributed in the modified polyfluoroethylene propylene.

[0013] The present application also provides a preparation method of the modified polyfluoroethylene propylene described above, which is prepared by alternating changes in temperature and pressure during the reaction process to obtain polyfluoroethylene propylene with uniform molecular weight distribution and high shear resistance.

[0014] A preparation method of the modified polyfluoroethylene propylene, comprising the following steps:

[0015] (1) Deionized water and perfluoro ether dispersant are added to a polymerization reactor, stirring is started, and vacuum is drawn, and oxygen content is measured.

[0016] (2) After the oxygen content is ≤30 ppm, the initial mixed monomers composed of tetrafluoroethylene and hexafluoropropylene are introduced; the temperature in the reactor is raised to 50-70℃, which is recorded as T1; the mixed monomers are added to the reactor to a pressure of 4.0-5.0 MPa, which is recorded as P1; the initial organic initiator is added, and copolymerization is carried out; and the organic initiator is continuously added during the reaction. The added mixed monomers are also composed of tetrafluoroethylene and hexafluoropropylene.

[0017] (3) After 20-50 min of reaction, the reaction rate reaches 5-10 kg / h, and after the rate is stable, the temperature in the kettle is adjusted to 70-120℃, which is recorded as T2; the pressure in the kettle is adjusted to 3.0-4.0 MPa, which is recorded as P2. The special monomer perfluoroalkyl vinyl ether is added for the first time, and the reaction continues, and inorganic initiators are continuously added during the reaction. After the addition of the special monomer perfluoroalkyl vinyl ether, the reaction rate will decrease, and the decrease will be 2-5 kg / h; the organic initiators that may be left in step (2) have a certain half-life at the reaction temperature, and their activity decreases accordingly, so they basically do not bring any adverse effects to step (3).

[0018] (4) After 10-30 min of reaction, the reaction rate reaches 5-10 kg / h again, the temperature in the kettle is adjusted to T1 again, the mixed monomers are added to adjust the pressure in the kettle to P1 again, and the reaction continues, and the organic initiators are continuously added during the reaction.

[0019] (5) After 20-50 min of reaction, the temperature in the kettle is adjusted to T2 again, and the pressure in the kettle is adjusted to P2 again; the special monomer perfluoroalkyl vinyl ether is added for the second time, and the reaction continues, and inorganic initiators are continuously added during the reaction.

[0020] (6) After 10-30 min of reaction, the temperature in the kettle is adjusted to T1 again, the mixed monomers are added to adjust the pressure in the kettle to P1 again, and the reaction continues, and the organic initiators are continuously added during the reaction; steps (5) and (6) are taken as a circulating unit, and the circulation is repeated until the number of times of adding the special monomer perfluoroalkyl vinyl ether reaches the set N times, wherein N is an integer greater than or equal to 3.

[0021] (7) After the Nth addition of the special monomer perfluoroalkyl vinyl ether and 10-30 min of reaction, the temperature in the kettle is adjusted back to T1, the mixed monomers are added to adjust the pressure in the kettle back to P1, and the organic initiators are added to continue the reaction; the temperature in the kettle is maintained at T1, and the pressure in the kettle is maintained at P1; until the total amount of the mixed monomers added during the entire reaction process reaches the predetermined value, the addition of the mixed monomers and the organic initiators is stopped, the reaction is ended, and the polyfluoroethylene propylene emulsion is obtained.

[0022] (8) The polyfluoroethylene propylene emulsion obtained in step (7) is subjected to coagulation, washing, drying, and granulation to obtain polyfluoroethylene propylene.

[0023] In the present application, the mass ratio of tetrafluoroethylene to hexafluoropropylene in the initial mixed monomers in the preparation method of the modified polyfluoroethylene propylene is 10-50:50-90; the addition amount of the initial mixed monomers is 0.01-0.2 MPa.

[0024] Preferably, the mass ratio of tetrafluoroethylene: hexafluoropropylene in the initial mixed monomers is 20-40: 60-80.

[0025] In the present application, the mass ratio of tetrafluoroethylene: hexafluoropropylene in the additional mixed monomers in the preparation method of the modified polyfluoroethylene-propylene is 70-98: 2-30.

[0026] Preferably, the mass ratio of tetrafluoroethylene: hexafluoropropylene in the additional mixed monomers is 80-95: 5-20.

[0027] In the present application, the amount of perfluoroether dispersant in the preparation method of the modified polyfluoroethylene-propylene is 0.1%-0.5% of the mass of deionized water.

[0028] In the present application, the amount of initial organic initiator in the preparation method of the modified polyfluoroethylene-propylene is 0.001%-0.05% of the mass of deionized water.

[0029] In the present application, the total amount of additional organic initiator in the preparation method of the modified polyfluoroethylene-propylene is 0.02%-0.25% of the mass of deionized water. The total amount is the total amount of additional organic initiator during the entire reaction process.

[0030] In the present application, the organic initiator in the preparation method of the modified polyfluoroethylene-propylene is any one of diisopropyl peroxydicarbonate (IPP), di-n-propyl peroxydicarbonate (NPP), or perfluoroacyl peroxide.

[0031] Preferably, the perfluoroacyl peroxide is any one of perfluorobutyryl peroxide, perfluorohexanoyl peroxide, perfluoro(3-oxapentanoyl) peroxide, perfluoro(3,6-dioxaoctanoyl) peroxide, perfluoro(2-methyl-3-oxahexanoyl) peroxide, and perfluoro(2,5-dimethyl-3,6-dioxanonyl) peroxide. Such initiators can increase the stability of the end group, further improve the uniformity of the polyfluoroethylene-propylene molecular chain, and improve the thermal stability of the polyfluoroethylene-propylene.

[0032] In the present application, the special monomer perfluoroalkyl vinyl ether is any one of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, or perfluoropropyl vinyl ether. The total amount of the special monomer perfluoroalkyl vinyl ether is 0.2%-0.8% of the mass of deionized water.

[0033] In the present application, the inorganic initiator in the preparation method of the modified polyfluoroethylene-propylene is at least one of ammonium persulfate or potassium persulfate. The total amount of the inorganic initiator is 0.01%-0.1% of the mass of deionized water.

[0034] In the preparation method of the modified polyfluoroethylene propylene in the present application, the predetermined value of the total amount of the mixed monomers supplemented in step (8) is 0.1-0.5 MPa. That is, when the total amount of the supplemented mixed monomers reaches 0.1-0.5 MPa, the supplementation of the monomers and the organic initiator is stopped, and the polymerization reaction is ended.

[0035] A polyfluoroethylene propylene film is prepared by extruding a cast film using the modified polyfluoroethylene propylene or the modified polyfluoroethylene propylene prepared by the above preparation method; the thickness of the film is 20-500 μm; the elongation at break of the polyfluoroethylene propylene film is 355-385%, the tensile strength is 21-28 MPa, the MIT bending resistance is 12000-60000 times, and the breakdown voltage is 85-120 kV / mm. The film processing is carried out by a casting method, and the processing temperature is between 320-380°C.

[0036] The modified polyfluoroethylene propylene has the advantages of uniform molecular weight distribution and high shear resistance, which solves the problems of crystal points and nodules caused by poor shear resistance and uneven molecular weight distribution of the polyfluoroethylene propylene in the prior art. In the preparation method of the modified polyfluoroethylene propylene, the self-polymerization probability of tetrafluoroethylene monomers is greatly reduced by alternating between different temperatures and pressures of low temperature and high pressure and high temperature and low pressure during the polymerization reaction, which reduces the problems of crystal points and nodules of the product, effectively solves the problems of unstable polymerization and fluctuation of product quality in the pure water phase medium polymerization process, and improves the processing performance of the product. At the same time, the probability of the special monomer entering the molecular chain is increased, the uniformity of the addition of the special monomer is ensured by adding the special monomer in batches and stages, so that the prepared resin has a higher critical shear rate and better shear resistance.

[0037] In addition, the effective control of the polymerization reaction is realized by the synergistic cooperation of different reaction temperatures and different types of initiators. And no non-environmentally friendly cosolvent is added during the preparation process, the impurities are less, and the operation is simple. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 The nuclear magnetic resonance fluorine spectrum (F-NMR) spectrum of the modified polyfluoroethylene propylene described in Example 5. 19 F-NMR) spectrum of the modified polyfluoroethylene propylene described in Example 5.

[0039] Figure 2 The infrared spectrum of the modified polyfluoroethylene propylene described in Example 5. DETAILED DESCRIPTION

[0040] The technical solutions of the present application will be described in detail below. All raw materials used in the examples are commercially available unless otherwise specified.

[0041] 1. The melt index is tested according to GB / T 3682.1-2018.

[0042] 2. Melting point was tested by differential scanning calorimeter.

[0043] 3. The critical shear rate was tested by high pressure capillary rheometer.

[0044] 4. Thermal decomposition temperature (1% weight loss) was tested by thermogravimetric analyzer under nitrogen atmosphere.

[0045] 5. The molecular weight and polydispersity index were determined by torque rheometer.

[0046] 6. Copolymer composition: infrared and 19 F-NMR were combined to analyze the proportion of each structural unit. The infrared spectrum was an infrared transmission spectrum, which was tested by a model Nicolet iS 10 Fourier transform infrared spectrometer. Nuclear magnetic resonance 19 F-NMR was tested by a model Bruker Advance III 300MHz nuclear magnetic resonance spectrometer.

[0047] 7. Crystal point number determination (extruded film test): a flaw detector was used to determine the number of crystal points.

[0048] 8. The mechanical strength and elongation at break of the resin and film were tested according to the HGT 2904-1997 standard.

[0049] 9. The folding resistance MIT of the resin and film was determined according to the provisions in GB 457-2008.

[0050] Example 1

[0051] The preparation method of the modified polyperfluoroethylene propylene includes the following steps:

[0052] (1) 6L of deionized water and 35g of perfluoroether dispersant CF3-O-[-CF(OCF3)-CF2-O-]2-CF2-O-COONH4 aqueous solution with a concentration of 20wt% were added to a polymerization kettle, stirring was started, vacuum was drawn, and oxygen content was measured.

[0053] (2) When the oxygen content is less than or equal to 30 ppm, introduce an initial mixed monomer composed of tetrafluoroethylene and hexafluoropropylene into the reactor at 0.09 MPa, wherein the mass ratio of tetrafluoroethylene:hexafluoropropylene is 21:79; then start to increase the temperature, and increase the temperature in the polymerization reactor to 50°C (T1), at which time the pressure in the polymerization reactor is 2.0 MPa; rapidly inject 0.48 g of an initial organic initiator diisopropyl peroxydicarbonate (IPP) solution in perfluorocyclohexane with a concentration of 50 wt%; and supplement the mixed monomer to the pressure in the polymerization reactor to 4.0 MPa (P1) to start the reaction, wherein the mass ratio of tetrafluoroethylene:hexafluoropropylene in the supplemented mixed monomer is 85:15; during the reaction, uniformly supplement 0.96 g of an organic initiator diisopropyl peroxydicarbonate (IPP) solution in perfluorocyclohexane with a concentration of 50 wt%.

[0054] (3) After 25 min of reaction, when the reaction rate reaches 8 kg / h, after the rate is stable, adjust the temperature in the polymerization reactor to 75°C (T2) and the pressure to 3.0 MPa (P2); rapidly inject 3 g of a special monomer perfluoropropyl vinyl ether for the first time, after the special monomer is added, the reaction rate decreases to 4 kg / h; during the reaction, uniformly inject 12 g of an inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt%, and continue to react.

[0055] (4) After 10 min of reaction, when the reaction rate reaches 8 kg / h again, adjust the temperature in the polymerization reactor to 50°C (T1), supplement the mixed monomer to adjust the pressure in the polymerization reactor to 4.0 MPa (P1), and uniformly supplement 0.96 g of an organic initiator diisopropyl peroxydicarbonate (IPP) solution in perfluorocyclohexane with a concentration of 50 wt%, and continue to react.

[0056] (5) After 25 min of reaction, adjust the temperature in the polymerization reactor to 75°C (T2) and the pressure to 3.0 MPa (P2); rapidly inject 3 g of a special monomer perfluoropropyl vinyl ether for the second time; during the reaction, uniformly inject 12 g of an inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt%, and continue to react.

[0057] (6) After 10 min of reaction, adjust the temperature in the polymerization reactor to 50°C (T1), supplement the mixed monomer to adjust the pressure in the polymerization reactor to 4.0 MPa (P1), and uniformly supplement 0.96 g of an organic initiator diisopropyl peroxydicarbonate (IPP) solution in perfluorocyclohexane with a concentration of 50 wt%, and continue to react.

[0058] (7) After 25 min, the temperature in the polymerization reactor was adjusted to 75°C (T2), and the pressure to 3.0 MPa (P2); 3 g of the special monomer perfluoropropyl vinyl ether was rapidly injected for the third time; during the reaction, 12 g of the inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% was uniformly injected, and the reaction was continued.

[0059] (8) After 10 min, the temperature in the polymerization reactor was adjusted to 50°C (T1), the pressure in the polymerization reactor was adjusted to 4.0 MPa (P1) by adding the mixed monomers, and 0.96 g of the organic initiator dicumyl peroxide (IPP) solution in perfluorocyclohexane with a concentration of 50 wt% was uniformly added, and the reaction was continued.

[0060] (9) After 25 min, the temperature in the polymerization reactor was adjusted to 75°C (T2), and the pressure to 3.0 MPa (P2); 3 g of the special monomer perfluoropropyl vinyl ether was rapidly injected for the fourth time; during the reaction, 12 g of the inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% was uniformly injected, and the reaction was continued.

[0061] (10) After 10 min, the temperature in the polymerization reactor was adjusted to 50°C (T1), the pressure in the polymerization reactor was adjusted to 4.0 MPa (P1) by adding the mixed monomers, and 0.96 g of the organic initiator dicumyl peroxide (IPP) solution in perfluorocyclohexane with a concentration of 50 wt% was uniformly added, and the reaction was continued.

[0062] Until the amount of the mixed monomers added in the entire reaction process reached 0.2 MPa, the reaction was ended, and a polyfluoroethylene propylene emulsion was obtained. The obtained polyfluoroethylene propylene emulsion was subjected to conventional mechanical coagulation, washing, granulation, fluorination, removal of small molecule volatile substances at high temperature, and treatment of fluorinated end groups according to the conventional method in the prior art, to obtain the modified polyfluoroethylene propylene resin.

[0063] In the entire reaction process, the total amount of the special monomer perfluoropropyl vinyl ether added was 12 g, which was added in four times. During the reaction of each time of injecting the special monomer perfluoropropyl vinyl ether for 10 min, 12 g of the ammonium persulfate aqueous solution with a concentration of 2.5 wt% was uniformly injected, and a total of 48 g of the inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% was injected. In other reaction processes without the special monomer, dicumyl peroxide (IPP) dissolved in perfluorocyclohexane was uniformly added, and a total of 4.8 g of the organic initiator dicumyl peroxide (IPP) solution in perfluorocyclohexane with a concentration of 50 wt% was added.

[0064] Example 2

[0065] The preparation method of the modified polyfluoroethylene propylene includes the following steps:

[0066] (1) Add 6 L of deionized water and 80 g of perfluoroether dispersant CF3-0-[-CF(OCF3)-CF2-0-]2-CF2-0-COONH4 aqueous solution with a concentration of 20 wt% into a polymerization kettle, start stirring and vacuumize, and measure the oxygen content.

[0067] (2) When the oxygen content is ≤30 ppm, introduce an initial mixed monomer composed of tetrafluoroethylene and hexafluoropropylene into the kettle at 0.12 MPa, wherein the mass ratio of tetrafluoroethylene: hexafluoropropylene is 28:72; then start heating, and raise the temperature in the polymerization kettle to 60°C (T1), at which time the pressure in the polymerization kettle is 2.5 MPa; quickly inject 2.4 g of an initial organic initiator diisopropyl peroxydicarbonate (IPP) perfluorocyclohexane solution with a concentration of 50 wt%; and supplement the mixed monomer to the pressure in the polymerization kettle to 4.5 MPa (P1) to start the reaction, wherein the mass ratio of tetrafluoroethylene: hexafluoropropylene in the supplemented mixed monomer is 88:12; during the reaction, uniformly supplement 3.84 g of an organic initiator diisopropyl peroxydicarbonate (IPP) perfluorocyclohexane solution with a concentration of 50 wt%.

[0068] (3) After 35 min of reaction, when the reaction rate reaches 9 kg / h, after the rate is stable, adjust the temperature in the polymerization kettle to 90°C (T2) and the pressure to 3.5 MPa (P2); quickly inject 7 g of a special monomer perfluoropropyl vinyl ether for the first time, after the special monomer is added, the reaction rate decreases to 5 kg / h; during the reaction, uniformly inject 36 g of an inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt%, and continue the reaction.

[0069] (4) After 15 min of reaction, when the reaction rate reaches 9 kg / h again, adjust the temperature in the polymerization kettle to 60°C (T1), supplement the mixed monomer to adjust the pressure in the polymerization kettle to 4.5 MPa (P1), and uniformly supplement 3.84 g of an organic initiator diisopropyl peroxydicarbonate (IPP) perfluorocyclohexane solution with a concentration of 50 wt%, and continue the reaction.

[0070] The total amount of 28 g of special monomer perfluoropropyl vinyl ether is added in four times in the way of steps (3) and (4). The reaction is ended until the amount of the mixed monomer added reaches 0.4 MPa. The polyperfluoroalkyl ether emulsion is obtained. During the process of adding the special monomer perfluoropropyl vinyl ether for 15 min, 36 g of the aqueous solution of ammonium persulfate with a concentration of 2.5 wt% is added uniformly. A total of 144 g of the aqueous solution of inorganic initiator ammonium persulfate with a concentration of 2.5 wt% is added uniformly. During the process of the other reactions without the special monomer, the diisopropyl peroxydicarbonate (IPP) dissolved in perfluorocyclohexane is added uniformly. A total of 19.2 g of the organic initiator diisopropyl peroxydicarbonate (IPP) perfluorocyclohexane solution with a concentration of 50 wt% is added.

[0071] Example 3

[0072] The preparation method of the modified polyperfluoroalkyl ether includes the following steps:

[0073] (1) 6 L of deionized water and 140 g of the aqueous solution of perfluoroether dispersant CF3-O-[-CF(OCF3)-CF2-O-]2-CF2-O-COONH4 with a concentration of 20 wt% are added into a polymerization kettle. The stirring is started and the vacuum is extracted. The oxygen content is measured.

[0074] (2) When the oxygen content is less than or equal to 30 ppm, the initial mixed monomers composed of tetrafluoroethylene and hexafluoropropylene are introduced into the kettle at 0.2 MPa. The mass ratio of tetrafluoroethylene to hexafluoropropylene is 35:65. Then the temperature in the polymerization kettle is increased to 70°C (T1). At this time, the pressure in the polymerization kettle is 3.0 MPa. 4.8 g of the initial organic initiator diisopropyl peroxydicarbonate (IPP) perfluorocyclohexane solution with a concentration of 50 wt% is quickly added. The mixed monomers are added until the pressure in the polymerization kettle reaches 5.0 MPa (P1) to start the reaction. The mass ratio of tetrafluoroethylene to hexafluoropropylene in the added mixed monomers is 93:7. During the reaction process, 5.76 g of the organic initiator diisopropyl peroxydicarbonate (IPP) perfluorocyclohexane solution with a concentration of 50 wt% is added uniformly.

[0075] (3) After 45 min of the reaction, the reaction rate reaches 10 kg / h. After the rate is stable, the temperature in the polymerization kettle is adjusted to 110°C (T2) and the pressure is adjusted to 4.0 MPa (P2). 10 g of the special monomer perfluoropropyl vinyl ether is quickly added for the first time. After the special monomer is added, the reaction rate is reduced to 5 kg / h. During the reaction process, 48 g of the aqueous solution of inorganic initiator ammonium persulfate with a concentration of 2.5 wt% is added uniformly. The reaction is continued.

[0076] (4) After 25 min, when the reaction rate reached 10 kg / h again, the temperature in the polymerizer was adjusted to 70 °C (T1), the pressure in the polymerizer was adjusted to 5.0 MPa (P1) by adding the mixed monomers, and 5.76 g of the organic initiator diisopropyl peroxydicarbonate (IPP) solution with a concentration of 50 wt% in perfluorocyclohexane was added uniformly and the reaction was continued.

[0077] According to the modes of steps (3) and (4), the total amount of 40 g of the special monomer perfluoropropyl vinyl ether was added in four times. Until the amount of the added mixed monomers reached 0.4 MPa, the reaction was ended, and the polyperfluoroalkyl ethylene emulsion was obtained. During the process of adding the special monomer perfluoropropyl vinyl ether for 25 min each time, 48 g of the inorganic initiator ammonium persulfate solution with a concentration of 2.5 wt% was added uniformly, and a total of 192 g of the inorganic initiator ammonium persulfate solution with a concentration of 2.5 wt% was added. During the other reaction processes without adding the special monomer, diisopropyl peroxydicarbonate (IPP) dissolved in perfluorocyclohexane was added uniformly, and a total of 28.8 g of the organic initiator diisopropyl peroxydicarbonate (IPP) solution with a concentration of 50 wt% in perfluorocyclohexane was added.

[0078] Example 4

[0079] The preparation method of the modified polyperfluoroalkyl ethylene, comprising the following steps:

[0080] (1) 6 L of deionized water and 35 g of perfluoroether dispersant CF3-O-[-CF(OCF3)-CF2-O-]2-CF2-O-COONH4 aqueous solution with a concentration of 20 wt% were added to the polymerizer, the stirring was started, and the vacuum was extracted, and the oxygen content was measured.

[0081] (2) After the oxygen content was ≤30 ppm, the initial mixed monomers composed of tetrafluoroethylene and hexafluoropropylene were introduced into the polymerizer at 0.09 MPa, and the mass ratio of tetrafluoroethylene to hexafluoropropylene was 21:79; then the temperature in the polymerizer was increased to 50 °C (T1), and the pressure in the polymerizer was 2.0 MPa at this time; 0.48 g of the initial organic initiator perfluoromethyl crotonyl peroxide solution with a concentration of 50 wt% in perfluorocyclohexane was rapidly added; and the mixed monomers were added to the polymerizer to a pressure of 4.0 MPa (P1) to start the reaction, and the mass ratio of tetrafluoroethylene to hexafluoropropylene in the added mixed monomers was 85:15; during the reaction, 0.96 g of the organic initiator perfluoromethyl crotonyl peroxide solution with a concentration of 50 wt% in perfluorocyclohexane was added uniformly.

[0082] (3) After 25 min, the reaction rate reached 7 kg / h, and after the rate was stable, the temperature in the polymerization kettle was adjusted to 75°C (T2), and the pressure was adjusted to 3.0 MPa (P2); 3 g of a special monomer perfluoroethyl vinyl ether was quickly added for the first time, and after the special monomer was added, the reaction rate decreased to 4 kg / h; during the reaction, 12 g of inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% was uniformly added, and the reaction was continued.

[0083] (4) After 10 min, when the reaction rate reached 7 kg / h again, the temperature in the polymerization kettle was adjusted to 50°C (T1), the pressure in the polymerization kettle was adjusted to 4.0 MPa (P1) by adding mixed monomers, and 0.96 g of organic initiator perfluoromethylcyclohexane solution of perfluorohexanoyl peroxide with a concentration of 50 wt% was uniformly added, and the reaction was continued.

[0084] According to the modes of steps (3) and (4), the total amount of 12 g of special monomer perfluoroethyl vinyl ether is added in 4 times. Until the amount of mixed monomers added in the whole reaction process reaches 0.2 MPa, the reaction is ended, and a polyperfluoroethyl propylene emulsion is obtained. During the process of adding 10 min of special monomer perfluoroethyl vinyl ether each time, 12 g of ammonium persulfate aqueous solution with a concentration of 2.5 wt% is uniformly added, and a total of 48 g of inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% is added. In other reaction processes without adding special monomers, perfluorohexanoyl peroxide dissolved in perfluorocyclohexane is uniformly added, and a total of 4.8 g of organic initiator perfluorohexanoyl peroxide perfluorocyclohexane solution with a concentration of 50 wt% is added.

[0085] Example 5

[0086] The preparation method of the modified polyperfluoroethyl propylene, comprising the following steps:

[0087] (1) 6 L of deionized water and 80 g of perfluoroether dispersant CF3-O-[-CF(OCF3)-CF2-O-]2-CF2-O-COONH4 aqueous solution with a concentration of 20 wt% were added to the polymerization kettle, the stirring was started, and the vacuum was extracted, and the oxygen content was measured.

[0088] (2) When the oxygen content is less than or equal to 30 ppm, the initial mixed monomers composed of tetrafluoroethylene and hexafluoropropylene are introduced into the reactor at 0.12 MPa, wherein the mass ratio of tetrafluoroethylene to hexafluoropropylene is 28:72; then the temperature in the polymerization reactor is raised to 60°C (T1), and the pressure in the polymerization reactor is 2.5 MPa at this time; 2.4 g of the initial organic initiator perfluorocyclohexane solution of perfluoromethyl crotonyl peroxide with a concentration of 50 wt% is rapidly injected; and the mixed monomers are supplemented to the pressure in the polymerization reactor of 4.5 MPa (P1) to start the reaction, wherein the mass ratio of tetrafluoroethylene to hexafluoropropylene in the supplemented mixed monomers is 88:12; during the reaction, 3.84 g of the organic initiator perfluorocyclohexane solution of perfluoromethyl crotonyl peroxide with a concentration of 50 wt% is uniformly supplemented.

[0089] (3) After 35 min of reaction, the reaction rate reaches 8 kg / h, and after the rate is stable, the temperature in the polymerization reactor is adjusted to 90°C (T2), and the pressure is adjusted to 3.5 MPa (P2); 7 g of a special monomer perfluoroethyl vinyl ether is rapidly injected for the first time, and after the special monomer is added, the reaction rate decreases to 5 kg / h; during the reaction, 36 g of an inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% is uniformly injected, and the reaction continues.

[0090] (4) After 15 min of reaction, when the reaction rate reaches 8 kg / h again, the temperature in the polymerization reactor is adjusted to 60°C (T1), the mixed monomers are supplemented to adjust the pressure in the polymerization reactor to 4.5 MPa (P1), and 3.84 g of the organic initiator perfluorocyclohexane solution of perfluoromethyl crotonyl peroxide with a concentration of 50 wt% is uniformly supplemented, and the reaction continues.

[0091] According to the modes of steps (3) and (4), the total amount of 28 g of the special monomer perfluoroethyl vinyl ether is added in 4 times. Until the total amount of the supplemented mixed monomers reaches 0.4 MPa, the reaction is completed, and a polyfluoroethylene propylene emulsion is obtained. During the process of injecting 15 min of the special monomer perfluoroethyl vinyl ether each time, 36 g of an inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% is uniformly injected, and a total of 144 g of the inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% is injected. During the other reaction processes without the special monomer, the perfluoromethyl crotonyl peroxide dissolved in perfluorocyclohexane is uniformly supplemented, and a total of 19.2 g of the organic initiator perfluorocyclohexane solution of perfluoromethyl crotonyl peroxide with a concentration of 50 wt% is supplemented.

[0092] The nuclear magnetic resonance spectrum of the modified polyfluoroethylene propylene Figure 1 The corresponding group positions and areas in the nuclear magnetic resonance spectrum are shown in Table 1.

[0093] Table 1: Corresponding group positions and areas in the nuclear magnetic resonance spectrum

[0094]

[0095] The infrared spectrum of the modified polyfluoroethylene propylene Figure 2 The corresponding group position and area in the infrared spectrum are shown in Table 2.

[0096] Table 2: The corresponding group position and area in the infrared spectrum

[0097]

[0098] Example 6

[0099] The preparation method of the modified polyfluoroethylene propylene, comprising the following steps:

[0100] (1) 6 L of deionized water and 140 g of perfluoroether dispersant CF3-0-[-CF(OCF3)-CF2-0-]2-CF2-0-COONH4 aqueous solution with a concentration of 20 wt% are added into a polymerization kettle, stirring is started, vacuum is drawn, and oxygen content is measured.

[0101] (2) When the oxygen content is less than or equal to 30 ppm, the initial mixed monomers composed of tetrafluoroethylene and hexafluoropropylene are introduced into the kettle at 0.2 MPa, wherein the mass ratio of tetrafluoroethylene to hexafluoropropylene is 35:65; then the temperature in the polymerization kettle is raised to 70°C (T1), at this time the pressure in the polymerization kettle is 3.0 MPa; 4.8 g of the initial organic initiator perfluorocyclohexane solution of perfluorohexanoyl peroxide with a concentration of 50 wt% is quickly injected; and the mixed monomers are supplemented to make the pressure in the polymerization kettle 5.0 MPa (P1) to start the reaction, wherein the mass ratio of tetrafluoroethylene to hexafluoropropylene in the supplemented mixed monomers is 93:7; during the reaction, 5.76 g of the organic initiator perfluorocyclohexane solution of perfluorohexanoyl peroxide with a concentration of 50 wt% is uniformly supplemented.

[0102] (3) After 45 min of reaction, when the reaction rate reaches 10 kg / h, the temperature in the polymerization kettle is adjusted to 110°C (T2) and the pressure is adjusted to 4.0 MPa (P2) after the rate is stable; 10 g of the special monomer perfluoroethyl vinyl ether is quickly injected for the first time, and after the special monomer is added, the reaction rate is reduced to 4 kg / h; during the reaction, 48 g of the inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% is uniformly injected, and the reaction continues.

[0103] (4) After 25 min of reaction, when the reaction rate reaches 10 kg / h again, the temperature in the polymerization kettle is adjusted to 70°C (T1), the pressure in the polymerization kettle is adjusted to 5.0 MPa (P1) by supplementing the mixed monomers, and 5.76 g of the organic initiator perfluorocyclohexane solution of perfluorohexanoyl peroxide with a concentration of 50 wt% is uniformly supplemented, and the reaction continues.

[0104] The total amount of 40 g of special monomer perfluoroethyl vinyl ether is added in four times in the way of steps (3) and (4). The reaction is ended until the amount of the mixed monomers added reaches 0.5 MPa. The polyperfluoroalkylpropylene emulsion is obtained. During the process of 25 min for each time of adding the special monomer perfluoroethyl vinyl ether, 48 g of the aqueous solution of ammonium persulfate with a concentration of 2.5 wt% is added uniformly. A total of 192 g of the aqueous solution of inorganic initiator ammonium persulfate with a concentration of 2.5 wt% is added uniformly. During the other reaction processes without the special monomer, the perfluorohexanoyl peroxide dissolved in perfluorocyclohexane is added uniformly. A total of 28.8 g of the perfluorohexanoyl peroxide solution in perfluorocyclohexane with a concentration of 50 wt% is added.

[0105] Example 7

[0106] The preparation method of the modified polyperfluoroalkylpropylene includes the following steps:

[0107] (1) 6 L of deionized water and 80 g of the aqueous solution of perfluoroether dispersant CF3-O-[-CF(OCF3)-CF2-O-]2-CF2-O-COONH4 with a concentration of 20 wt% are added into a polymerization kettle. The stirring is started and the vacuum is extracted. The oxygen content is measured.

[0108] (2) When the oxygen content is less than or equal to 30 ppm, the initial mixed monomers composed of tetrafluoroethylene and hexafluoropropylene are introduced into the kettle at 0.12 MPa. The mass ratio of tetrafluoroethylene to hexafluoropropylene is 28:72. Then the temperature in the polymerization kettle is increased to 60°C (T1). At this time, the pressure in the polymerization kettle is 2.5 MPa. 2.4 g of the initial organic initiator di-n-propyl peroxide carbonate (NPP) solution in perfluorocyclohexane with a concentration of 50 wt% is quickly added. The mixed monomers are added until the pressure in the polymerization kettle reaches 4.5 MPa (P1) to start the reaction. The mass ratio of tetrafluoroethylene to hexafluoropropylene in the added mixed monomers is 88:12. During the reaction process, 3.84 g of the organic initiator di-n-propyl peroxide carbonate (NPP) solution in perfluorocyclohexane with a concentration of 50 wt% is added uniformly.

[0109] (3) After 35 min of the reaction, the reaction rate reaches 9 kg / h. After the rate is stable, the temperature in the polymerization kettle is adjusted to 90°C (T2) and the pressure is adjusted to 3.5 MPa (P2). 7 g of the special monomer perfluoropropyl vinyl ether is quickly added for the first time. After the special monomer is added, the reaction rate is reduced to 5 kg / h. During the reaction process, 36 g of the aqueous solution of inorganic initiator ammonium persulfate with a concentration of 2.5 wt% is added uniformly. The reaction is continued.

[0110] (4) After 15 min, when the reaction rate reached 9 kg / h again, the temperature in the polymerizer was adjusted to 60 °C (T1), the pressure in the polymerizer was adjusted to 4.5 MPa (P1) by adding the mixed monomers, and 3.84 g of organic initiator di-n-propyl peroxydicarbonate (NPP) solution with a concentration of 50 wt% in perfluorocyclohexane was added uniformly to continue the reaction.

[0111] According to the methods of steps (3) and (4), the total amount of 28 g of special monomer perfluoropropyl vinyl ether was added in four times. The reaction was completed until the total amount of the added mixed monomers reached 0.4 MPa. During the process of adding the special monomer perfluoropropyl vinyl ether for 15 min each time, 36 g of inorganic initiator ammonium persulfate solution with a concentration of 2.5 wt% was added uniformly, and a total of 144 g of inorganic initiator ammonium persulfate solution with a concentration of 2.5 wt% was added. During the other reaction processes without adding special monomers, di-n-propyl peroxydicarbonate (NPP) dissolved in perfluorocyclohexane was added uniformly, and a total of 19.2 g of organic initiator di-n-propyl peroxydicarbonate (NPP) solution with a concentration of 50 wt% in perfluorocyclohexane was added.

[0112] Example 8

[0113] The preparation method of the modified polyfluoroethylene propylene includes the following steps:

[0114] (1) 6 L of deionized water and 35 g of perfluoroether dispersant CF3-O-[-CF(OCF3)-CF2-O-]2-CF2-O-COONH4 aqueous solution with a concentration of 20 wt% were added to the polymerizer, the stirring was started, and the vacuum was extracted, and the oxygen content was measured.

[0115] (2) When the oxygen content was ≤30 ppm, the initial mixed monomers composed of tetrafluoroethylene and hexafluoropropylene were introduced into the polymerizer at 0.09 MPa, and the mass ratio of tetrafluoroethylene to hexafluoropropylene was 21:79. Then the temperature in the polymerizer was increased to 50 °C (T1), and the pressure in the polymerizer was 2.0 MPa at this time. 0.48 g of initial organic initiator perfluoro(3-oxapentanoyl) peroxide solution in perfluorocyclohexane with a concentration of 50 wt% was rapidly added. The pressure in the polymerizer was adjusted to 4.0 MPa (P1) by adding the mixed monomers, and the reaction was started, wherein the mass ratio of tetrafluoroethylene to hexafluoropropylene in the added mixed monomers was 85:15. During the reaction process, 0.96 g of organic initiator perfluoro(3-oxapentanoyl) peroxide solution in perfluorocyclohexane with a concentration of 50 wt% was added uniformly.

[0116] (3) After 25 min of reaction, the reaction rate reached 7 kg / h, and after the rate was stable, the temperature in the polymerization kettle was adjusted to 75°C (T2), and the pressure was adjusted to 3.0 MPa (P2); 3 g of a special monomer perfluoroethyl vinyl ether was quickly injected for the first time, and after the special monomer was added, the reaction rate decreased to 4 kg / h; during the reaction, 12 g of inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% was uniformly injected, and the reaction was continued.

[0117] (4) After 10 min of reaction, when the reaction rate reached 7 kg / h again, the temperature in the polymerization kettle was adjusted to 50°C (T1), the pressure in the polymerization kettle was adjusted to 4.0 MPa (P1) by adding mixed monomers, and 0.96 g of organic initiator perfluoro(3-oxapentanoyl) peroxide in perfluorocyclohexane solution with a concentration of 50 wt% was uniformly added, and the reaction was continued.

[0118] According to the modes of steps (3) and (4), the total amount of 12 g of special monomer perfluoroethyl vinyl ether is added in 4 times. Until the amount of mixed monomers added in the whole reaction process reaches 0.2 MPa, the reaction is ended, and a polyfluoroethylene propylene emulsion is obtained. During the process of injecting 10 min of special monomer perfluoroethyl vinyl ether each time, 12 g of ammonium persulfate aqueous solution with a concentration of 2.5 wt% is uniformly injected, and a total of 48 g of inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% is injected. In other reaction processes without adding special monomers, perfluoro(3-oxapentanoyl) peroxide dissolved in perfluorocyclohexane is uniformly added, and a total of 4.8 g of organic initiator perfluoro(3-oxapentanoyl) peroxide in perfluorocyclohexane solution with a concentration of 50 wt% is added.

[0119] Example 9

[0120] The preparation method of the modified polyfluoroethylene propylene includes the following steps:

[0121] (1) 6 L of deionized water and 80 g of perfluoroether dispersant CF3-O-[-CF(OCF3)-CF2-O-]2-CF2-O-COONH4 aqueous solution with a concentration of 20 wt% are added to the polymerization kettle, the stirring is started, and the vacuum is extracted, and the oxygen content is measured.

[0122] (2) When the oxygen content is less than or equal to 30 ppm, the initial mixed monomers composed of tetrafluoroethylene and hexafluoropropylene are introduced into the reactor at 0.12 MPa, wherein the mass ratio of tetrafluoroethylene to hexafluoropropylene is 28:72; then the temperature in the polymerization reactor is raised to 60°C (T1), and the pressure in the polymerization reactor is 2.5 MPa at this time; 2.4 g of the initial organic initiator perfluoro(2,5-dimethyl-3,6-dioxanonanoyl) peroxide with a concentration of 50 wt% in perfluorocyclohexane is rapidly injected; and the mixed monomers are supplemented to the pressure in the polymerization reactor of 4.5 MPa (P1) to start the reaction, wherein the mass ratio of tetrafluoroethylene to hexafluoropropylene in the supplemented mixed monomers is 88:12; during the reaction, 3.84 g of the organic initiator perfluoro(2,5-dimethyl-3,6-dioxanonanoyl) peroxide with a concentration of 50 wt% in perfluorocyclohexane is uniformly supplemented.

[0123] (3) After 35 min of reaction, the reaction rate reaches 8 kg / h, and after the rate is stable, the temperature in the polymerization reactor is adjusted to 90°C (T2), and the pressure is adjusted to 3.5 MPa (P2); 7 g of a special monomer perfluoroethyl vinyl ether is rapidly injected for the first time through an auxiliary pump, and after the special monomer is added, the reaction rate decreases to 5 kg / h; during the reaction, 36 g of an inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% is uniformly injected through a metering pump, and the reaction continues.

[0124] (4) After 15 min of reaction, when the reaction rate reaches 8 kg / h again, the temperature in the polymerization reactor is adjusted to 60°C (T1), the mixed monomers are supplemented to adjust the pressure in the polymerization reactor to 4.5 MPa (P1), and 3.84 g of the organic initiator perfluoro(2,5-dimethyl-3,6-dioxanonanoyl) peroxide with a concentration of 50 wt% in perfluorocyclohexane is uniformly supplemented, and the reaction continues.

[0125] In the manner of steps (3) and (4), the total amount of 28 g of the special monomer perfluoroethyl vinyl ether is added in four times. Until the total amount of the supplemented mixed monomers reaches 0.4 MPa, the reaction is completed, and a polyfluoroethylene propylene emulsion is obtained. During the process of injecting the special monomer perfluoroethyl vinyl ether for 15 min each time, 36 g of an ammonium persulfate aqueous solution with a concentration of 2.5 wt% is uniformly injected, and a total of 144 g of an inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% is injected. During the other reaction processes without the special monomer, perfluoro(2,5-dimethyl-3,6-dioxanonanoyl) peroxide dissolved in perfluorocyclohexane is uniformly supplemented, and a total of 19.2 g of the organic initiator perfluoro(2,5-dimethyl-3,6-dioxanonanoyl) peroxide with a concentration of 50 wt% in perfluorocyclohexane is supplemented.

[0126] Comparative Example 1

[0127] The preparation method of the polytetrafluoroethylene propylene described in this comparative example differs from that in Example 2 in that the temperature and pressure remain constant throughout the reaction process, maintained at 60°C and 4.5 MPa. Furthermore, the amounts of organic and inorganic initiators added are also different.

[0128] The specific operation steps are as follows: (1) Add 6L of deionized water and 80g of 20wt% perfluoroether dispersant CF3-O-[-CF(OCF3)-CF2-O-]2-CF2-O-COONH4 aqueous solution to the polymerization kettle, turn on the stirring to draw a vacuum, and measure the oxygen content.

[0129] (2) When the oxygen content is ≤30ppm, introduce 0.12MPa of the initial mixed monomer composed of tetrafluoroethylene and hexafluoropropylene into the reactor, wherein the mass ratio of tetrafluoroethylene to hexafluoropropylene is 28:72; then start heating to raise the temperature in the polymerization reactor to 60℃ (T1), at which time the pressure in the polymerization reactor is 2.5MPa; quickly inject 0.48g of a perfluorocyclohexane solution of diisopropyl peroxide (IPP) with a concentration of 50wt% as the initial organic initiator; and add mixed monomers until the pressure in the polymerization reactor is 4.5MPa (P1) to start the reaction, wherein the mass ratio of tetrafluoroethylene to hexafluoropropylene in the added mixed monomers is 88:12; during the reaction, uniformly add 0.96g of a perfluorocyclohexane solution of diisopropyl peroxide (IPP) with a concentration of 50wt% as the organic initiator.

[0130] (3) After the reaction has been going on for 35 minutes, the reaction rate reaches 9 kg / h. The temperature inside the polymerization reactor is maintained at 60℃ (T1) and the pressure is maintained at 4.5 MPa (P1). 7 g of special monomer perfluoropropyl vinyl ether is added quickly for the first time. After the special monomer is added, the reaction rate drops to 5 kg / h. During the reaction, 12 g of 2.5 wt% inorganic initiator ammonium persulfate aqueous solution is added evenly to continue the reaction.

[0131] (4) After the reaction has been going on for 15 minutes and the reaction rate has reached 9 kg / h again, the temperature inside the polymerization reactor is maintained at 60℃ (T1) and the pressure is maintained at 4.5 MPa (P1). 0.96 g of a 50 wt% solution of diisopropyl peroxide (IPP) organic initiator in perfluorocyclohexane is added evenly to continue the reaction.

[0132] The total amount of 28 g of special monomer perfluoropropyl vinyl ether was added in four times in the way of steps (3) and (4). The reaction was ended until the amount of mixed monomers added reached 0.4 MPa. The polyperfluoroalkyl alkyl vinyl ether emulsion was obtained. During the process of 15 min for each time of adding the special monomer perfluoropropyl vinyl ether, 12 g of 2.5 wt% ammonium persulfate aqueous solution was added uniformly. A total of 48 g of 2.5 wt% inorganic initiator ammonium persulfate aqueous solution was added. During the process of adding no special monomer, 4.8 g of 50 wt% diisopropyl peroxydicarbonate (IPP) in perfluorocyclohexane was added uniformly.

[0133] Comparative Example 2

[0134] The preparation method of the polyperfluoroalkyl alkyl vinyl ether in the comparative example was different from that in Example 6 in that the temperature and pressure in the whole reaction process were kept unchanged, and were maintained at 70℃ and 5.0 MPa.

[0135] The specific operation steps were as follows: (1) 6 L of deionized water and 140 g of 20 wt% perfluoroether dispersant CF3-O-[-CF(OCF3)-CF2-O-]2-CF2-O-COONH4 aqueous solution were added into the polymerization kettle, the stirring was started, and the vacuum was extracted, and the oxygen content was measured.

[0136] (2) When the oxygen content was ≤30 ppm, the initial mixed monomers composed of tetrafluoroethylene and hexafluoropropylene were introduced into the kettle at 0.2 MPa, and the mass ratio of tetrafluoroethylene to hexafluoropropylene was 35:65. Then the temperature in the polymerization kettle was increased to 70℃ (T1), and the pressure in the polymerization kettle was 3.0 MPa at this time. 4.8 g of 50 wt% initial organic initiator perfluoromethyl crotonyl peroxide in perfluorocyclohexane was quickly added. The mixed monomers were added until the pressure in the polymerization kettle reached 5.0 MPa (P1), and the reaction was started. The mass ratio of tetrafluoroethylene to hexafluoropropylene in the added mixed monomers was 93:7. During the reaction process, 5.76 g of 50 wt% organic initiator perfluoromethyl crotonyl peroxide in perfluorocyclohexane was added uniformly.

[0137] (3) After 45 min of reaction, the reaction rate reached 10 kg / h, and after the rate was stable, the temperature in the polymerization kettle was maintained at 70℃ (T1), and the pressure in the polymerization kettle was maintained at 5.0 MPa (P1). 10 g of special monomer perfluoroethyl vinyl ether was quickly added for the first time. After the addition of the special monomer, the reaction rate decreased to 4 kg / h. During the reaction process, 48 g of 2.5 wt% inorganic initiator ammonium persulfate aqueous solution was added uniformly, and the reaction was continued.

[0138] (4) After 25 min, when the reaction rate reached 10 kg / h again, the temperature in the polymerization kettle was maintained at 70 °C (T1), and the pressure was maintained at 5.0 MPa (P1), and 5.76 g of organic initiator perfluoromethyl crotonyl peroxide solution with a concentration of 50 wt% in perfluorocyclohexane was continuously added, and the reaction was continued.

[0139] According to the manner of steps (3) and (4), the total amount of 40 g of special monomer perfluoroethyl vinyl ether was added in 4 times. Until the total amount of the mixed monomers added during the whole reaction process reached 0.5 MPa, the reaction was stopped, and the polyperfluoroethyl propylene emulsion was obtained.

[0140] Comparative Example 3

[0141] The preparation method of the polyperfluoroethyl propylene in the comparative example is different from that of Example 2 in that the temperature and pressure during the whole reaction process are maintained at 60 °C and 4.5 MPa. In addition, inorganic initiators are used during the whole reaction process, and no organic initiators are used.

[0142] The specific operation steps are as follows: (1) 6 L of deionized water and 80 g of perfluoroether dispersant CF3-O-[-CF(OCF3)-CF2-O-]2-CF2-O-COONH4 aqueous solution with a concentration of 20 wt% are added to the polymerization kettle, stirring is started, vacuum is drawn, and the oxygen content is measured.

[0143] (2) After the oxygen content is ≤30 ppm, the initial mixed monomers composed of tetrafluoroethylene and hexafluoropropylene are introduced into the kettle at 0.12 MPa, and the mass ratio of tetrafluoroethylene to hexafluoropropylene is 28:72. Then the temperature in the polymerization kettle is raised to 60 °C (T1), and the pressure in the polymerization kettle is 2.5 MPa at this time. 12 g of initial inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% is quickly injected, and the mixed monomers are added to the polymerization kettle until the pressure reaches 4.5 MPa (P1) to start the reaction. During the reaction, the inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% is continuously added.

[0144] (3) After 35 min of reaction, when the reaction rate reaches 9 kg / h, the temperature in the polymerization kettle is maintained at 60 °C (T1), and the pressure is maintained at 4.5 MPa (P1) after the rate is stable. 7 g of special monomer perfluoropropyl vinyl ether is quickly injected for the first time. After the special monomer is added, the reaction rate decreases to 5 kg / h. During the reaction, the inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% is continuously added, and the reaction is continued.

[0145] (4) After 15 min, when the reaction rate reached 9 kg / h again, the temperature in the polymerization kettle was maintained at 60°C (T1), the pressure was maintained at 4.5 MPa (P1), and the concentration of 2.5 wt% inorganic initiator ammonium persulfate aqueous solution was continuously added, and the reaction was continued.

[0146] According to the manner of steps (3) and (4), the total amount of 28 g of special monomer perfluoropropyl vinyl ether was added in four times. Until the total amount of the mixed monomers added in the whole reaction process reached 0.4 MPa, the reaction was ended, and the polyperfluoroethyl propylene emulsion was obtained. During the whole reaction process, 400 g of inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% was continuously added into the polymerization kettle.

[0147] Comparative Example 4

[0148] The preparation method of the polyperfluoroethyl propylene in the comparative example is different from that of Example 2 in that the special monomer is added at one time, not in batches.

[0149] The specific operation steps are as follows: (1) 6 L of deionized water and 80 g of perfluoroether dispersant CF3-O-[-CF(OCF3)-CF2-O-]2-CF2-O-COONH4 aqueous solution with a concentration of 20 wt% are added into the polymerization kettle, the stirring is started, the vacuum is extracted, and the oxygen content is measured.

[0150] (2) After the oxygen content is less than or equal to 30 ppm, the initial mixed monomers composed of tetrafluoroethylene and hexafluoropropylene are introduced into the kettle at 0.12 MPa, and the mass ratio of tetrafluoroethylene to hexafluoropropylene is 28:72; then the temperature in the polymerization kettle is raised to 60°C (T1), and at this time the pressure in the polymerization kettle is 2.5 MPa; 2.4 g of the initial organic initiator diisopropyl peroxydicarbonate (IPP) perfluorocyclohexane solution with a concentration of 50 wt% is quickly injected; and the mixed monomers are added to the polymerization kettle until the pressure reaches 4.5 MPa (P1) to start the reaction, and the mass ratio of tetrafluoroethylene to hexafluoropropylene in the added mixed monomers is 88:12; during the reaction, 3.84 g of the organic initiator diisopropyl peroxydicarbonate (IPP) perfluorocyclohexane solution with a concentration of 50 wt% is uniformly added.

[0151] (3) After 35 min of reaction, when the reaction rate reaches 9 kg / h, the temperature in the polymerization kettle is adjusted to 90°C (T2) and the pressure is adjusted to 3.5 MPa (P2) after the rate is stable; 28 g of special monomer perfluoropropyl vinyl ether is quickly added into the polymerization kettle at one time, and after the special monomer is added, the reaction rate decreases to 5 kg / h; during the reaction, 144 g of inorganic initiator ammonium persulfate aqueous solution with a concentration of 2.5 wt% is uniformly injected, and the reaction is continued.

[0152] (4) After 15 min, when the reaction rate reaches 9 kg / h again, adjust the temperature in the polymerizer to 60°C (T1), add mixed monomers to adjust the pressure in the polymerizer to 4.5 MPa (P1), and continue the reaction.

[0153] Until the amount of mixed monomers added in the whole reaction process reaches 0.4 MPa, the reaction is ended, and a polyfluoroethylene propylene emulsion is obtained. The obtained polyfluoroethylene propylene emulsion is subjected to mechanical condensation, washing, granulation, and fluorination devolatilization to obtain the polyfluoroethylene propylene resin.

[0154] Table 3: Test results of the properties of the polyfluoroethylene propylene resins obtained in each example and the comparative example

[0155]

[0156] Table 4: Test results of the extruded film

[0157]

[0158] Table 5: Test results of the properties of the polyfluoroethylene propylene film obtained

[0159]

[0160] From the above data, it can be seen that the resin has a higher critical shear rate and better shear resistance.

Claims

1. A modified polyfluoroethylene propylene characterized in that, The modified polyfluoroethylene propylene is a terpolymer of tetrafluoroethylene, hexafluoropropylene and perfluoroalkyl vinyl ether; the content of hexafluoropropylene structural unit in the terpolymer is 15.9wt%-17wt%, and the content of perfluoroalkyl vinyl ether structural unit is 3wt%-3.5wt%; the polydispersity index PDI of the modified polyfluoroethylene propylene is 1.95-2.15; the critical shear rate of the modified polyfluoroethylene propylene is 330-410s ﹣1 at 372℃, measured by a high-pressure capillary rheometer.

2. The modified polyfluoroethylene propylene of claim 1, wherein, The modified polyfluoroethylene propylene has a weight average molecular weight of 350-400 kg / mol, a melt index of 8.0-10.5 g / 10 min, a melting point of 255-260 ℃, and a thermal decomposition temperature of 412-420 ℃.

3. The modified polyfluoroethylene propylene of claim 1, wherein, The modified polyfluoroethylene propylene is extruded into a film by a casting film to obtain a film with a thickness of 100 μm. The film has 0-1 big crystal points with a diameter > 0.25 mm / m 2 , 1-3 medium crystal points with a diameter in the range of 0.15-0.25 mm / m 2 , and 2-6 small crystal points with a diameter < 0.15 mm / m 2 .

4. A process for the preparation of the modified polyfluoroethylene propylene according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: (1) adding deionized water and perfluoro ether dispersant into a polymerization reactor, starting stirring and vacuumizing, and measuring oxygen content; (2) after the oxygen content is less than or equal to 30 ppm, the initial mixed monomers composed of tetrafluoroethylene and hexafluoropropylene are introduced, the temperature in the reactor is increased to 50-70 ℃, recorded as T1, the mixed monomers are added to the reactor until the pressure in the reactor is 4.0-5.0 MPa, recorded as P1, the initial organic initiator is added, and the copolymerization reaction is carried out; during the reaction, the organic initiator is continuously added; (3) after the reaction is carried out for 20-50 min, the temperature in the reactor is adjusted to 70-120 ℃, recorded as T2, the pressure in the reactor is adjusted to 3.0-4.0 MPa, recorded as P2, the special monomer perfluoroalkyl vinyl ether is added for the first time, and the reaction is continuously carried out, during which the inorganic initiator is continuously added; (4) after the reaction is carried out for 10-30 min, the temperature in the reactor is adjusted to T1 again, the mixed monomers are added to adjust the pressure in the reactor to P1 again, and the reaction is continuously carried out, during which the organic initiator is continuously added; (5) after the reaction is carried out for 20-50 min, the temperature in the reactor is adjusted to T2 again, the pressure in the reactor is adjusted to P2 again, the special monomer perfluoroalkyl vinyl ether is added for the second time, and the reaction is continuously carried out, during which the inorganic initiator is continuously added; (6) after the reaction is carried out for 10-30 min, the temperature in the reactor is adjusted to T1 again, the mixed monomers are added to adjust the pressure in the reactor to P1 again, and the reaction is continuously carried out, during which the organic initiator is continuously added; steps (5) and (6) are taken as a cyclic unit, and the cycle is repeated until the number of times of adding the special monomer perfluoroalkyl vinyl ether reaches a set N, wherein N is an integer greater than or equal to 3; (7) after the special monomer perfluoroalkyl vinyl ether is added for the Nth time and the reaction is carried out for 10-30 min, the temperature in the reactor is adjusted to T1 again, the mixed monomers are added to adjust the pressure in the reactor to P1 again, and the organic initiator is added to continuously carry out the reaction; the temperature in the reactor is maintained at T1, and the pressure in the reactor is maintained at P1; until the total amount of the mixed monomers added in the whole reaction process reaches a predetermined value, the addition of the mixed monomers and the organic initiator is stopped, the reaction is ended, and the polyfluoroethylene propylene emulsion is obtained; (8) the polyfluoroethylene propylene emulsion obtained in step (7) is subjected to coagulation, washing, drying and granulation to obtain the modified polyfluoroethylene propylene.

5. The method for preparing modified perfluoroethylene propylene according to claim 4, characterized in that, The amount of the perfluoro ether dispersant in step (1) is 0.1%-0.5% of the mass of the deionized water.

6. The method for preparing modified perfluoroethylene propylene according to claim 4, characterized in that, In the initial mixed monomers in step (2), the mass ratio of tetrafluoroethylene to hexafluoropropylene is 10-50:50-90; the amount of the initial mixed monomers added is 0.01-0.2 MPa; and the amount of the initial organic initiator in step (2) is 0.001%-0.05% of the mass of the deionized water.

7. The method for preparing modified perfluoroethylene propylene according to claim 4, characterized in that, In the added mixed monomers, the mass ratio of tetrafluoroethylene to hexafluoropropylene is 70-98:2-30.

8. The method for preparing modified perfluoroethylene propylene according to claim 4, characterized in that, The total amount of the supplement of the organic initiator is 0.02%-0.25% of the mass of the deionized water.

9. The method for preparing modified perfluoroethylene propylene according to claim 4, characterized in that, The organic initiator is any one of diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate or perfluoroacyl peroxide.

10. The method for preparing modified perfluoroethylene propylene according to claim 4, characterized in that, The special monomer perfluoroalkyl vinyl ether is any one of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether or perfluoropropyl vinyl ether; the total amount of the special monomer perfluoroalkyl vinyl ether is 0.2%-0.8% of the mass of the deionized water.

11. The method for preparing modified perfluoroethylene propylene according to claim 4, characterized in that, The inorganic initiator is at least one of ammonium persulfate or potassium persulfate; the total amount of the inorganic initiator is 0.01%-0.1% of the mass of the deionized water.

12. The method for preparing modified perfluoroethylene propylene according to claim 4, characterized in that, The predetermined value of the total amount of the supplement of the mixed monomer is 0.1-0.5MPa.

13. A polyfluoroethylene propylene film characterized by, The modified polyfluoroethylene propylene prepared by the method of any one of claims 1-3 or the method of any one of claims 4-12 is prepared by extrusion of a cast film; the thickness of the film is 20-500μm; the tensile strength of the polyfluoroethylene propylene film is 21-28MPa, the elongation at break is 355-385%, the MIT bending resistance is 12000-60000 times, and the breakdown voltage is 85-120kV / mm.

Images