Polytetrafluoroethylene dispersion resin as well as preparation method and application thereof

Abstract

The invention provides polytetrafluoroethylene dispersion resin and a preparation method thereof, and the preparation method comprises the following steps: adding deionized water, a stabilizer, a dispersant, an anti-sticking agent and an initiator into a reaction container, sealing the reaction container, carrying out deoxygenization operation until the oxygen content in the container is qualified, adding a modifier and gas-phase tetrafluoroethylene, and carrying out heat preservation for 2-4 hours; and carrying out a polymerization reaction under the conditions that the pressure in the container is 1.8-3.2 MPa and the temperature is 60-90 DEG C, collecting a polytetrafluoroethylene polymerization dispersion liquid after the reaction is finished, and carrying out agglutination, washing and drying to obtain the polytetrafluoroethylene dispersion resin. The preparation method disclosed by the invention is simple in steps and strong in operability, the SSG of the prepared polytetrafluoroethylene dispersion resin is 2.130-2.150 g / ml, and a polytetrafluoroethylene membrane prepared from the dispersion resin has the advantages of uniform appearance, high strength, small pore diameter and the like, and can be applied to multiple fields such as a precise filtering membrane, a clothing membrane, a medical bacteria filtering membrane, a proton exchange membrane and the like.

Description

Technical Field

[0001] The present invention relates to the field of polymers, and in particular to a polytetrafluoroethylene dispersion resin, a preparation method and application thereof. Background Art

[0002] Polytetrafluoroethylene is a high molecular polymer made from tetrafluoroethylene monomers, commonly known as "plastic king" or "Teflon". Polytetrafluoroethylene has excellent chemical stability, corrosion resistance, sealing, high lubricity and non-stickiness, electrical insulation and good anti-aging resistance, making it widely used in many fields such as anti-corrosion, electronic and electrical, medical and construction.

[0003] Polytetrafluoroethylene can be produced by a variety of conventional polymerization methods. The main polymerization methods used in industry include suspension polymerization and dispersion polymerization. The polytetrafluoroethylene obtained by dispersion polymerization has a high molecular weight and a narrow molecular weight distribution. In addition, since the nano-scale particles generated during the polymerization process are evenly distributed, the mechanical properties and thermal stability of the product are also good, and it can be used to prepare microporous membranes for various purposes.

[0004] CN101421319A discloses a method for preparing a tetrafluoroethylene polymer and its aqueous dispersion, which is characterized in that paraffin wax and ammonium perfluorooctanoate are added to the aqueous phase, the temperature is raised to 70°C, tetrafluoroethylene monomer is introduced, the reaction pressure is kept at 0.80MPa, ammonium persulfate is added, the polymerization reaction begins, the reaction temperature is 70±2°C, after a certain tetrafluoroethylene consumption is reached, a hydroquinone aqueous solution is added, and a polytetrafluoroethylene aqueous dispersion is obtained by polymerization, and polytetrafluoroethylene fine powder is obtained by condensation and drying, and a film product is obtained by stretching after extrusion molding. The standard relative density (SSG) of the dispersed resin obtained by this method is between 2.140 and 2.165, and the film product has a uniform appearance. The patent application does not introduce its use and product performance.

[0005] CN103665240B discloses a method for preparing a polytetrafluoroethylene dispersion resin, which includes adding deionized water, an initiator, a pH regulator, perfluorobutylethylene, a dispersant and a stabilizer into a reactor, introducing nitrogen to remove oxygen, controlling the pressure of the reactor to 1.5-3.0 MPa and the temperature to 70-105°C, adding gaseous tetrafluoroethylene monomer for polymerization, collecting the polytetrafluoroethylene polymer dispersion, and obtaining the polytetrafluoroethylene dispersion resin through agglomeration, washing and drying. The resin has an SSG of 2.16-2.17, and has the characteristics of uniform film appearance and good air permeability, but the film strength is slightly low. Summary of the invention

[0006] In view of the above-mentioned problems in the prior art, the present invention aims to provide a method for preparing a polytetrafluoroethylene dispersion resin, a polytetrafluoroethylene dispersion resin prepared by the method, and a polytetrafluoroethylene film prepared by the polytetrafluoroethylene dispersion resin, so as to effectively solve or at least alleviate one or more problems existing in the prior art.

[0007] Therefore, according to one aspect of the present invention, a method for preparing a polytetrafluoroethylene dispersion resin is provided, comprising the following steps: 1) adding deionized water, a stabilizer, an anti-sticking agent and a first initiator into a reaction container, sealing the reaction container and performing a deoxygenation operation until the oxygen content in the container reaches a qualified level; 2) adding a modifier and adding a gaseous tetrafluoroethylene monomer into a reaction vessel, maintaining the pressure in the vessel at 1.8 to 3.2 MPa and the temperature at 60 to 90° C. to carry out a polymerization reaction, and during the reaction, adding a second initiator into the vessel; and 3) When the solid content of the reaction solution reaches 25-40%, the reaction is terminated, and the polytetrafluoroethylene polymer dispersion is collected, and the polytetrafluoroethylene dispersion resin is obtained by coagulation, washing, and drying; wherein the dispersant is added in one go in step 1) or in batches in steps 1) and 2); wherein the first initiator and the second initiator are selected from an oxidative initiator and a reductive initiator, and the first initiator and the second initiator are not initiators of the same type; wherein the modifier is selected from the group consisting of perfluoropropylethylene, perfluorobutylethylene, perfluoropentylethylene, perfluorohexylethylene, perfluoroheptylethylene, perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, perfluoro-n-propyl vinyl ether, hexafluoropropylene, chlorotrifluoroethylene, trifluoroethylene, ethylene, and mixtures thereof; and The dosage of the modifier is 0.022-0.15% of the weight of deionized water.

[0008] According to another aspect of the present invention, a polytetrafluoroethylene dispersion resin prepared by the above method is provided.

[0009] According to still another aspect of the present invention, there is provided a polytetrafluoroethylene film prepared from the polytetrafluoroethylene dispersion resin.

[0010] The present invention obtains a polytetrafluoroethylene dispersion resin with an SSG of 2.130 to 2.150 g / ml by emulsion polymerization of tetrafluoroethylene monomer under a redox initiation system and under the action of a modifier of a specific type and amount. The prepared resin can be further made into a high-strength, small-pore membrane, which can be used as a precision filtration membrane, a clothing membrane, a medical bacteria filtration membrane, a proton exchange membrane, etc. DETAILED DESCRIPTION

[0011] In order to make those skilled in the art further understand the present invention, the specific embodiments of the present invention are described in detail below. However, it should be understood that the embodiments of the present invention described are merely exemplary and the present invention is not limited to these embodiments.

[0012] According to one aspect of the present invention, there is provided a method for preparing a polytetrafluoroethylene dispersion resin, comprising the following steps: 1) adding deionized water, a stabilizer, an anti-sticking agent and a first initiator into a reaction container, sealing the reaction container and performing a deoxygenation operation until the oxygen content in the container reaches a qualified level; 2) adding a modifier and adding a gaseous tetrafluoroethylene monomer into a reaction vessel, maintaining the pressure in the vessel at 1.8 to 3.2 MPa and the temperature at 60 to 90° C. to carry out a polymerization reaction, and during the reaction, adding a second initiator into the vessel; and 3) When the solid content of the reaction solution reaches 25-40%, the reaction is terminated, and the polytetrafluoroethylene polymer dispersion is collected, and the polytetrafluoroethylene dispersion resin is obtained by coagulation, washing, and drying; wherein the dispersant is added in one go in step 1) or in batches in steps 1) and 2); wherein the first initiator and the second initiator are selected from an oxidative initiator and a reductive initiator, and the first initiator and the second initiator are not initiators of the same type; wherein the modifier is selected from the group consisting of perfluoropropylethylene, perfluorobutylethylene, perfluoropentylethylene, perfluorohexylethylene, perfluoroheptylethylene, perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, perfluoro-n-propyl vinyl ether, hexafluoropropylene, chlorotrifluoroethylene, trifluoroethylene, ethylene, and mixtures thereof; and The dosage of the modifier is 0.022-0.15% of the weight of deionized water.

[0013] In step 1), in order to prevent oxygen from interfering with the polymerization reaction, oxygen in the reaction vessel filled with deionized water needs to be removed before the polymerization reaction occurs until the oxygen content is qualified. In the present invention, the term "qualified oxygen content" means that the volume content of oxygen in the gas phase of the reaction vessel filled with deionized water after the deoxygenation operation is less than 30 ppm, preferably less than 20 ppm.

[0014] The deoxygenation operation applicable to the method of the present invention is not particularly limited and can be a conventional measure known in the art. In some embodiments, the deoxygenation operation is selected from inert gas purging, vacuuming, and combinations thereof. The applicable inert gas is not particularly limited and can be any inert gas known in the art, such as nitrogen, argon, helium or a mixture of two or more thereof, preferably nitrogen.

[0015] In some embodiments, the amount of deionized water is 60-80% of the volume of the reaction container, preferably 65-75%.

[0016] In some embodiments, the stabilizer is selected from saturated hydrocarbons having 12 or more carbon atoms which are inert in the polymerization reaction and are liquid under the polymerization reaction conditions, wherein solid paraffin is preferred. In addition, as dispersion stabilizers other than saturated hydrocarbons, fluorinated oils, fluorinated solvents, silicone oils, etc. can be cited.

[0017] Furthermore, the amount of the stabilizer is 2.0-6.0% by weight of the deionized water, preferably 3.0-5.0%.

[0018] In the method for producing the polytetrafluoroethylene dispersion resin of the present invention, in order to reduce the amount of coagulants generated during polymerization, an anti-adhesive is added to the polymerization system. In some embodiments, the anti-adhesive is selected from malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, and mixtures thereof, preferably succinic acid.

[0019] Furthermore, the amount of the anti-sticking agent is 0.005-0.05% by weight of the deionized water, preferably 0.02-0.03%.

[0020] The initiator used in the method of the present invention is a redox initiation system. Therefore, in step 1), any one of an oxidative initiator and a reductive initiator can be selected as the first initiator, and the other can be added as the second initiator in the subsequent polymerization step.

[0021] The oxidative initiator includes, but is not limited to, persulfates of alkali metals or alkaline earth metals, such as potassium persulfate, ammonium persulfate, potassium permanganate, potassium bromate, potassium chlorate, and mixtures thereof, preferably potassium permanganate. The reductive initiator includes, but is not limited to, sulfites, bisulfites, ferrous oxide, oxalic acid, and mixtures thereof, preferably oxalic acid.

[0022] Furthermore, the amount of the oxidizing initiator is 0.0001-0.001% by weight of deionized water, preferably 0.00015-0.0005% by weight, and the amount of the reducing initiator is 0.0005-0.006% by weight of deionized water, preferably 0.001-0.005%.

[0023] In some embodiments, the dispersant is added in step 1) at one time.

[0024] In some embodiments, the dispersant is selected from perfluoro / fluorinated polyether carboxylates, perfluoro / fluorinated alkyl carboxylates, and mixtures thereof, preferably perfluoro carboxylates, such as ammonium perfluorooctanoate. Below the critical micelle concentration, the addition of the dispersant can prevent the primary particles of the polymerized polytetrafluoroethylene from aggregating into coarse particles, thereby forming a temporarily stable dispersion system.

[0025] Furthermore, the amount of the dispersant used is 0.02-0.5% by weight of deionized water, preferably 0.15-0.35%.

[0026] In step 2), after adding the modifier and tetrafluoroethylene monomer, a polymerization reaction is carried out, and during the polymerization process, the pressure in the reaction container is maintained at 1.8-3.2 MPa and the temperature is maintained at 60-90° C. Since the pressure in the reaction container decreases due to the continuous consumption of the monomer during the polymerization reaction, tetrafluoroethylene monomer needs to be added during the reaction to maintain the pressure within the above range.

[0027] In step 2), preferably, the modifier is selected from perfluoropropylethylene, perfluorobutylethylene, perfluoropentylethylene, perfluorohexylethylene, perfluoroheptylethylene, and mixtures thereof. More preferably, the modifier comprises perfluorohexylethylene, for example, the modifier can be selected from a mixture of perfluorohexylethylene and perfluorobutylethylene, and the weight ratio of the two is preferably 1:1 to 10:1. Most preferably, the modifier is perfluorohexylethylene.

[0028] Preferably, the amount of the modifier used is 0.025-0.15% by weight of deionized water.

[0029] In step 2), preferably, the second initiator can be added dropwise continuously after the gas-phase tetrafluoroethylene monomer is first added into the reaction container.

[0030] In some embodiments, the dispersant is added in batches in step 1) and step 2). In this case, the total amount of the dispersant is still within the range defined above, and the weight ratio of the first part of the dispersant added in step 1) to the second part of the dispersant added in step 2) is preferably 1:4 to 4:1.

[0031] Preferably, the dispersant is added in batches in step 1) and step 2).

[0032] The polymerization reaction in step 2) can be carried out under stirring, and the preferred stirring speed is 50 to 250 rpm. At this stirring speed, it is not easy to generate high shear force to destroy the micelles of the dispersant, and the micelle morphology is maintained, and the dissolution rate of the tetrafluoroethylene monomer and the micronization and uniform distribution of bubbles can be increased, thereby reducing the amount of initiator used.

[0033] In step 3), coagulation can be performed by adding a coagulant and stirring the dispersion, but preferably, the aqueous dispersion is stirred at high speed without adding a coagulant. Examples of the coagulant include water-soluble organic compounds such as methanol and acetone; inorganic salts such as potassium nitrate and ammonium carbonate; inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and ammonium carbonate is more preferred.

[0034] The drying temperature in step 3) is not particularly limited, but is preferably dried at a temperature of 120 to 220°C, more preferably 150 to 200°C.

[0035] According to another aspect of the present invention, a polytetrafluoroethylene dispersion resin prepared by the above method is provided.

[0036] In some embodiments, the polytetrafluoroethylene dispersion resin prepared by the above method has an SSG of 2.130 to 2.150 g / ml.

[0037] As is well known to those skilled in the art, SSG is a standard concept of ASTM, which indirectly characterizes the molecular weight of polytetrafluoroethylene. The larger the SSG value, the lower the molecular weight; the smaller the SSG value, the higher the molecular weight. For polytetrafluoroethylene with an SSG of less than 2.150, the stretch ratio of its extruded product exceeds 3000%, which is suitable for stretch molding.

[0038] In some embodiments, the polytetrafluoroethylene dispersion resin prepared by the above method has a secondary particle size of 350 to 650 μm.

[0039] According to still another aspect of the present invention, there is provided a polytetrafluoroethylene film prepared from the polytetrafluoroethylene dispersion resin.

[0040] The polytetrafluoroethylene membrane can be, for example, a high-strength, small-pore precision filtration membrane, a clothing membrane, a medical bacteria filtration membrane, a proton exchange membrane, and the like.

[0041] Preferably, the prepared polytetrafluoroethylene membrane has a tensile strength of 40 to 100 MPa, preferably 45 to 75 MPa, and an average pore size of 25 to 150 nm, preferably 50 to 100 nm.

[0042] The present invention provides a method for preparing polytetrafluoroethylene, and obtains a polytetrafluoroethylene dispersion resin with an SSG of 2.130 to 2.150 g / ml, which is further used to prepare a polytetrafluoroethylene membrane having the characteristics of uniform appearance, high strength, small pore size, etc., so that the membrane can be applied to multiple fields such as precision filtration membrane, clothing membrane, medical bacteria filtration membrane, proton exchange membrane, etc. The method of the present invention has simple steps, strong operability, and can realize large-scale production. Example

[0043] The present invention will be further described below in conjunction with the embodiments so that those skilled in the art can fully understand the purpose, features and effects of the present invention. However, the protection scope of the present invention is not limited by the following embodiments.

[0044] Description of the main performance parameter testing methods and equipment in the embodiments: 1. Resin particle size The test was conducted using the Mastersizer 3000E laser particle size analyzer: about 2 g of sample was weighed and placed in the sample tray of the laser particle size analyzer. The air pressure was set to 4 Bar, the injection speed was 50%, and the system was flushed twice with air flow before the test.

[0045] 2. SSG The measurement was performed based on ASTM D 4895.

[0046] 3. Membrane appearance, membrane thickness, and average pore size (1) Membrane preparation The polytetrafluoroethylene and oil are mixed in proportion; the mixed materials are pressed into a cylindrical blank on a blanking machine, and then calendered into a polytetrafluoroethylene-based film at 160°C-200°C by a calender; the polytetrafluoroethylene-based film is longitudinally stretched at a ratio of 5-25; the longitudinally stretched base band is placed in a transverse expansion device, and the transverse expansion speed is changed by adjusting the film running speed; the film after transverse expansion at a ratio of 10-50 is heat-set at 300°C-380°C, air-quenched at room temperature, and finally rolled into a polytetrafluoroethylene biaxially stretched film.

[0047] (2) Film appearance: visual observation; Film thickness: measured using Filmetrics-F20 multi-function film thickness tester; Membrane pore size: The bubble pressure method was used at 22°C using a BSD-PB membrane pore size analyzer and BSD16 infiltration solution was used to infiltrate a polytetrafluoroethylene biaxially stretched membrane at normal pressure for measurement.

[0048] 4. Membrane tensile strength The test was carried out using an Instron-6800 universal material tensile testing machine.

[0049] Example 1 Add 20L of deionized water, 1g of oxalic acid, 4g of succinic acid, 10g of ammonium perfluorooctanoate and 0.8kg of paraffin to a clean 30L stainless steel reaction container, seal the container, evacuate and replace with nitrogen, analyze the oxygen content, and it is qualified when the oxygen content is ≤20ppm. Add 5g of perfluorobutylethylene, heat the reaction container to 80±1℃, introduce gaseous monomer tetrafluoroethylene until the pressure in the container is 2.8MPa, continue to add potassium permanganate solution (30mg of potassium permanganate as dry matter), and maintain the pressure in the container at 2.8MPa and the temperature at 80-88℃ during the reaction. When the tetrafluoroethylene feed reaches 2kg, continuously add the remaining 20g of ammonium perfluorooctanoate to the polymerization system. When the tetrafluoroethylene feed reaches 9kg (solid content of about 31%), the reaction is completed, the gaseous monomer is recovered, the material is discharged at a reduced temperature, and the paraffin is separated to obtain a polytetrafluoroethylene polymerization dispersion. After post-treatment, coagulation, washing and drying, polytetrafluoroethylene dispersed resin is obtained.

[0050] Example 2 Add 20L of ionized water, 1g of oxalic acid, 4g of succinic acid, 10g of ammonium perfluorooctanoate and 0.8kg of paraffin to a clean 30L stainless steel reaction container, seal the container, evacuate and replace with nitrogen, analyze the oxygen content, and it is qualified when the oxygen content is ≤20ppm. Add 2.5g of perfluorobutylethylene and 2.5g of perfluorohexylethylene, heat the reaction container to 80±1℃, introduce gaseous monomer tetrafluoroethylene until the pressure in the container is 3.0MPa, continue to add potassium permanganate solution (30mg of potassium permanganate as dry matter), and maintain the pressure in the container at 3.0MPa and the temperature at 80-88℃ during the reaction. When the tetrafluoroethylene feed reaches 2kg, continuously add the remaining 20g of ammonium perfluorooctanoate to the polymerization system. When the tetrafluoroethylene feed reaches 9kg (solid content of about 31%), the reaction is completed, the gaseous monomer is recovered, the temperature is lowered and the material is discharged, and the paraffin is separated to obtain a polytetrafluoroethylene polymerization dispersion. After post-treatment, coagulation, washing and drying, polytetrafluoroethylene dispersed resin is obtained.

[0051] Example 3 Add 20L of ionized water, 1g of oxalic acid, 4g of succinic acid, 10g of ammonium perfluorooctanoate and 0.8kg of paraffin to a clean 30L stainless steel reaction container, seal the container, evacuate and replace with nitrogen, analyze the oxygen content, and it is qualified when the oxygen content is ≤20ppm. Add 5.0g of perfluorohexylethylene, heat the reaction container to 80±1℃, introduce gaseous monomer tetrafluoroethylene until the pressure in the container is 3.2MPa, continue to add potassium permanganate solution (30mg of potassium permanganate as dry matter), maintain the pressure in the container at 3.2MPa and the temperature at 80-88℃ during the reaction. When the tetrafluoroethylene feed reaches 2kg, continuously add the remaining 20g of ammonium perfluorooctanoate to the polymerization system. When the tetrafluoroethylene feed reaches 9kg (solid content of about 31%), the reaction is completed, the gaseous monomer is recovered, the temperature is lowered and the material is discharged, and the paraffin is separated to obtain a polytetrafluoroethylene polymerization dispersion. After post-treatment, coagulation, washing and drying, polytetrafluoroethylene dispersed resin is obtained.

[0052] Comparative Example 1 The preparation was carried out according to the method of Example 1, except that the amount of perfluorobutylethylene added as the modifier was 4.0 g.

[0053] Comparative Example 2 The preparation was carried out according to the method of Example 1, except that no modifier was added.

[0054] The properties of the polytetrafluoroethylene dispersion resins prepared in Examples 1 to 3 and Comparative Examples 1 to 2 and the polytetrafluoroethylene films prepared from the dispersion resins were characterized as described above, and the results are summarized in the following Table 1: Table 1 Conclusion: Compared with Comparative Examples 1 and 2, the membrane pore size obtained by the polytetrafluoroethylene dispersion resin obtained by the method of the present invention is reduced, and the membrane tensile strength is significantly increased. In particular, when the modifier contains perfluorohexylethylene, the membrane pore size and tensile strength are further improved.

[0055] The terms “including” and “comprising” used in the present invention include both the case of being composed of the included elements and the case of including other elements in addition to the included elements.

[0056] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the substantial technical content of the present invention. The substantial technical content of the present invention is broadly defined in the scope of the claims of this application. Any technical entity or method completed by others, if it is exactly the same as that defined in the scope of the claims of this application, or is an equivalent variation, will be deemed to be included in the scope of the claims of this application.

Claims

1. A method for preparing a polytetrafluoroethylene dispersion resin, comprising the following steps: 1) adding deionized water, a stabilizer, an anti-sticking agent and a first initiator into a reaction container, sealing the reaction container and performing a deoxygenation operation until the oxygen content in the container reaches a qualified level; 2) adding a modifier and adding a gaseous tetrafluoroethylene monomer into a reaction vessel, maintaining the pressure in the vessel at 1.8 to 3.2 MPa and the temperature at 60 to 90° C. to carry out a polymerization reaction, and during the reaction, adding a second initiator into the vessel; and 3) When the solid content of the reaction solution reaches 25-40%, the reaction is terminated, and the polytetrafluoroethylene polymer dispersion is collected, and the polytetrafluoroethylene dispersion resin is obtained by coagulation, washing, and drying; wherein the dispersant is added in one go in step 1) or in batches in steps 1) and 2); wherein the first initiator and the second initiator are selected from an oxidative initiator and a reductive initiator, and the first initiator and the second initiator are not initiators of the same type; wherein the modifier is selected from the group consisting of perfluoropropylethylene, perfluorobutylethylene, perfluoropentylethylene, perfluorohexylethylene, perfluoroheptylethylene, perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, perfluoro-n-propyl vinyl ether, hexafluoropropylene, chlorotrifluoroethylene, trifluoroethylene, ethylene, and mixtures thereof; and The dosage of the modifier is 0.022-0.15% of the weight of deionized water.

2. The method according to claim 1, characterized in that The stabilizer is selected from solid paraffin, fluorine oil, fluorine solvent and silicone oil. Preferably, the amount of the stabilizer is 2.0-6.0% by weight of deionized water.

3. The method according to claim 1 or 2, characterized in that: The anti-sticking agent is selected from malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, and mixtures thereof. Preferably, the amount of the anti-sticking agent is 0.005-0.05% by weight of deionized water.

4. The method according to any one of claims 1 to 3, characterized in that The dispersant is selected from perfluoro / fluorinated polyether carboxylates, perfluoro / fluorinated alkyl carboxylates, and mixtures thereof. Preferably, the amount of the dispersant is 0.02-0.5% by weight of deionized water.

5. The method according to any one of claims 1 to 4, characterized in that The oxidative initiator is selected from persulfates of alkali metals or alkaline earth metals, potassium permanganate, potassium bromate, potassium chlorate, and mixtures thereof. Preferably, the oxidative initiator is used in an amount of 0.0001 to 0.001% by weight of deionized water.

6. The method according to any one of claims 1 to 5, characterized in that The reducing initiator is selected from sulfite, bisulfite, ferrous oxide, oxalic acid, and mixtures thereof. Preferably, the reducing initiator is used in an amount of 0.0005-0.006% by weight of deionized water.

7. The method according to any one of claims 1 to 6, characterized in that The modifier is selected from the group consisting of perfluoropropylethylene, perfluorobutylethylene, perfluoropentylethylene, perfluorohexylethylene, perfluoroheptylethylene, and mixtures thereof. Preferably, the modifier comprises perfluorohexylethylene.

8. The method according to any one of claims 1 to 7, characterized in that In step 2), the reaction pressure is 1.8-3.2 MPa, and the reaction temperature is 60-90°C.

9. A polytetrafluoroethylene dispersion resin prepared by the method according to any one of claims 1 to 8.

10. A polytetrafluoroethylene film prepared from the polytetrafluoroethylene dispersion resin according to claim 9.

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