Method for manufacturing and uses of stretched polytetrafluoroethylene film

Abstract

The present invention provides a method for producing a modified polytetrafluoroethylene stretched film and its use. The method for producing the modified polytetrafluoroethylene stretched film includes the steps of: (1) uniformly mixing a modified polytetrafluoroethylene emulsion with a lubricant, extruding and rolling the mixture; (2) stretching the mixture in the longitudinal direction at high temperature, then stretching the mixture in the transverse direction, and sintering and solidifying the mixture at high temperature for 5-15 minutes after stretching, so that the product is a modified polytetrafluoroethylene stretched film. In this method, the modified polytetrafluoroethylene stretched film produced by adding a polymeric AOI modified monomer is softer, has good stretching performance, has small pore size, high porosity, and uniform pore size distribution; and uses an ammonium salt polymer dispersant as a production raw material, so that the product is clean and clean, does not cause environmental pollution, and is not involved in the metabolism of the human body. Compared with the currently widely used perfluoroacid and its salt as a production auxiliary, the present invention is a very environmentally friendly and healthy technical solution, and has good future application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of filter materials, and specifically relates to a manufacturing method and uses of a modified polytetrafluoroethylene stretched film.

Background Art

[0002] Polytetrafluoroethylene (Teflon or PTFE) is usually called the "king of plastics". It is a polymer compound obtained by polymerizing tetrafluoroethylene. Due to its special molecular structure, it has extremely excellent chemical stability and a very wide temperature resistance performance. It can be used for a long time within the temperature range of -180°C to 260°C, which is difficult to achieve with other polymer materials. Moreover, it has even more excellent corrosion resistance, sealing performance, high lubricity, high adhesion resistance, high electrical insulation, and good anti-aging properties, and is called the "king of plastics" in the industry. Since Dr. Planket invented polytetrafluoroethylene in 1938, it has brought revolutionary changes to the plastic industry.

[0003] Film technology has achieved remarkable development in the past 50 to 60 years and is widely used in people's lives, industrial fields, and scientific research fields. Microporous films mainly made of various organic polymer materials such as cellulose acetate, polyamide, polysulfone, nylon 66, polyethersulfone, polyvinylidene fluoride, polyethylene, and polypropylene have been developed. Except for polyethylene and polypropylene manufacturing microporous films by the stretching method, most of the others are obtained by the phase inversion method of manufacturing cellulose esters composed of polymer materials, a certain solvent, and additives. The common drawback of these polymer materials above is that the use temperature is limited and they have no resistance to acids, alkalis, and chemicals.

[0004] Developed in the 1970s, expanded polytetrafluoroethylene (known as ePTFE outside of China) overcomes the shortcomings of conventional film materials and has become an ideal method for manufacturing high-performance microporous films, and is widely used in various harsh environments. PTFE expanded microporous film was initially developed independently by Gore Corporation in the United States. By mechanically stretching PTFE fine powder through extrusion, rolling, and stretching operations, the crystals are transformed from powder particles into fibers and woven into a mesh structure. This film has 9 billion micropores per square centimeter, small pore size, uniform pore size distribution, low relative density, high film strength, and a smooth surface.

[0005] Polytetrafluoroethylene (PTE) microporous films are manufactured by mechanically stretching PTE under special conditions without any additives, and their original properties remain completely unchanged. As such, PTE still possesses a wide operating temperature range, chemical resistance, a small film material coefficient, biocompatibility, and hydrophobicity. They are widely used in fields such as dust removal, sterilization, product purification and material recovery in the air in the pharmaceutical industry, waterproof and breathable textiles, water treatment, food health, biopharmaceuticals, and filtration separation. In particular, their advantages as filter materials are unparalleled. Accordingly, research on the base and applications of PTE is relatively widespread, and obtaining novel PTE with high overall performance and multifunctionality by selecting different filler materials and appropriate modification methods has become a focus of research for a wide range of scientific researchers.

[0006] Patent CN112108008A provides a polytetrafluoroethylene biaxially oriented film, a method for producing the same, and its applications. The PTFE stretched film, produced by co-extruding and stretching at least two layers of film substrates, followed by solidification and molding at high temperature, has small pore diameters and high porosity, but the problem of environmental pollution is not solved. Patent CN104448637B provides a method for producing a polytetrafluoroethylene film for air filtration. The produced polytetrafluoroethylene film has a high porosity, a uniform pore diameter distribution, and is thin, but its stretching performance needs to be further improved. Conventional polytetrafluoroethylene films have difficulty simultaneously meeting the demands for small pore diameters, uniform distribution, and high mechanical strength.

[0007] Therefore, in order to better meet the needs of real life, it is necessary to provide modified polytetrafluoroethylene stretched films that have small pore sizes, high porosity, a uniform pore size distribution, are clean, environmentally friendly, safe, and have excellent stretchability. [Overview of the project] [Problems that the invention aims to solve]

[0008] In response to the problems of the prior art, the objective of the present invention is to provide a modified polytetrafluoroethylene stretched film that has small pore size, high porosity, a uniform pore size distribution, and is clean, environmentally friendly, safe, and has excellent stretchability, in order to meet the demands of actual production and application.

[0009] To achieve this objective, the technical proposal of the present invention is as follows. [Means for solving the problem]

[0010] The present invention provides a method for producing a modified polytetrafluoroethylene stretched film, and the method for producing the modified polytetrafluoroethylene stretched film is as follows: Step (1) involves uniformly mixing a modified polytetrafluoroethylene emulsion with a lubricant and then extruding and rolling it, The process includes step (2), which involves stretching the material longitudinally at a high temperature, then stretching it transversely, and then sintering and solidifying it at a high temperature for 5-15 minutes after stretching, wherein the product is a modified polytetrafluoroethylene stretched film.

[0011] In the method for producing a modified polytetrafluoroethylene stretched film of the present invention, the lubricant described in step (1) is selected from Kryptox EG2000 or Kryptox EG3000.

[0012] In the method for producing a modified polytetrafluoroethylene stretched film of the present invention, the amount of lubricant used in step (1) is 10-15% of the mass of the modified polytetrafluoroethylene emulsion (for example, 10%, 10.1%, 10.2%, 10.3%, 10.4%, 10.5%, 10.6%, 10.7%, 10.8%, 10.9%, 11%, 11.1%, 11.2%, 11.3%, 11.4%, 11.5%, 11.6%, 11.7%, 11.8%, 11. 9%, 12%, 12.1%, 12.2%, 12.3%, 12.4%, 12.5%, 12.6%, 12.7%, 12.8%, 12.9%, 13%, 13.1%, 13.2%, 13.3%, 13.4%, 13.5%, 13.6%, 13.7%, 13.8%, 13.9%, 14%, 14.1%, 14.2%, 14.3%, 14.4%, 14.5%, 14.6%, 14.7%, 14.8%, 14.9%, 15%, or any of these values).

[0013] In the method for producing a modified polytetrafluoroethylene stretched film of the present invention, the stretching temperature described in step (2) is 210-230°C (for example, 210°C, 211°C, 212°C, 213°C, 214°C, 215°C, 216°C, 217°C, 218°C, 219°C, 220°C, 221°C, 222°C, 223°C, 224°C, 225°C, 226°C, 227°C, 228°C, 229°C, 230°C or so The sintering solidification temperature is 350-370°C (for example, 350°C, 351°C, 352°C, 353°C, 354°C, 355°C, 356°C, 357°C, 358°C, 359°C, 360°C, 361°C, 362°C, 363°C, 364°C, 365°C, 366°C, 367°C, 368°C, 369°C, 370°C, or any of these temperature values).

[0014] In some embodiments of the present invention, the modified polytetrafluoroethylene emulsion comprises 0.5-2 parts of an ammonium salt polymer dispersant, 0.2-1 part of an emulsifier, 1-1.5 parts of an AOI-modified monomer (AOI being an abbreviation for ethyl isocyanate acrylate), 0.5-3 parts of an initiator, 40-60 parts of a tetrafluoroethylene monomer, and 30-60 parts of water.

[0015] In some embodiments of the present invention, the structure of the ammonium salt polymer dispersant is shown below. [ka] However, x is an integer between 2 and 5, y is an integer between 5 and 8, and * represents the bonding site of a chemical bond.

[0016] In some embodiments of the present invention, the method for producing the ammonium salt polymer dispersant is as follows: Step (1) involves adding a solvent to the reactor, heating it to raise the temperature, and then adding perfluorohexanol acrylate, acrylic acid, and an initiator dropwise to the reactor and allowing the reaction to proceed while maintaining the temperature for 2-4 hours. The process comprises step (2), in which diethanolamine is added to the product obtained in step (1) and reacted, and after the reaction is complete, the solvent is removed and the resulting product is an ammonium salt polymer dispersant.

[0017] In the method for producing the ammonium salt polymer dispersant according to the present invention, the molar ratio of perfluorohexanol acrylate, acrylic acid, and diethanolamine is 1-4:1:1 (for example, 1:1:1, 2:1:1, 3:1:1, 4:1:1, or any of these values).

[0018] In the method for producing an ammonium salt polymer dispersant according to the present invention, the reaction temperature described in step (1) is 60-70°C (for example, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, or any of these temperature values), the solvent is one or more combinations selected from perfluorohexane, perfluoroheptane, perfluorooctane, and monobromododecafluorohexane, the initiator is one or a combination thereof selected from perfluorobutyryl peroxide and perfluorohexanoyl peroxide, and the amount of initiator used is 1%-2% of the total mass of perfluorohexanol acrylate and acrylic acid (for example, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or any of these values).

[0019] In some embodiments of the present invention, the emulsifier is one or more combinations selected from Kryptox EG2000, Kryptox EG3000, Kryptox 143, and Kryptox 280.

[0020] In some embodiments of the present invention, the initiator is one of perfluorobutyryl peroxide and perfluorohexanoyl peroxide, or a combination thereof.

[0021] In some embodiments of the present invention, the structure of the AOI-modified monomer is shown below: [Chemical formula] However, m is an integer from Ⅰ to Ⅱ, n is an integer from 10 to 20, and * is the bonding site of the chemical bond.

[0022] In some embodiments of the present invention, the method for producing the AOI-modified monomer is as follows: Step (1): Add a solvent to the reactor, heat it to raise the temperature, and then drop perfluorohexanol acrylate, hydroxyethyl acrylate, and an initiator into the reactor. After the dropping is completed, keep the temperature for 2 - 4 hours. Step (2): Add AOI to the product obtained in Step (1) and react. After the reaction is completed, remove the solvent. The resulting product is the AOI-modified monomer.

[0023] In the method for producing the AOI-modified monomer in the present invention, the molar ratio of the perfluorohexanol acrylate, hydroxyethyl acrylate, and AOI is 10 - 20:1:1 (for example, 10:1:1, 11:1:1, 12:1:1, 13:1:1, 14:1:1, 15:1:1, 16:1:1, 17:1:1, 18:1:1, 19:1:1, 20:1:1 or any value among them may be used).

[0024] Please note that the values of "Ⅰ" and "Ⅱ" in the translation of item need to be filled with the correct content according to the actual situation. Since the original text has some unclear or incomplete information, this is a translation based on the overall understanding. If there are specific values or more detailed information, the translation can be adjusted accordingly.In the method for producing AOI-modified monomers according to the present invention, the reaction temperature described in step (1) is 60-70°C (for example, 60°C, 61°C, 62°C, 63°C, 64°C, 65°C, 66°C, 67°C, 68°C, 69°C, 70°C, or any of these temperature values), the solvent is one or more combinations selected from perfluorohexane, perfluoroheptane, perfluorooctane, and monobromododecafluorohexane, the initiator is one or a combination thereof selected from perfluorobutyryl peroxide and perfluorohexanoyl peroxide, and the amount of initiator used is 1%-2% of the total mass of perfluorohexanol acrylate and acrylic acid (for example, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or any of these values).

[0025] In some embodiments of the present invention, the method for producing the modified polytetrafluoroethylene emulsion is as follows: Step (1) involves adding a dispersant, emulsifier, and deionized water to a high-pressure emulsification reactor after stirring, stirring, raising the temperature to 40-60°C, and raising the system pressure to 3-4 MPa. The process comprises step (2) adding tetrafluoroethylene monomer, AOI-modified monomer, and initiator to a high-pressure emulsification reactor, raising the temperature, and reacting for 2-4 hours, wherein the product after the reaction is a modified polytetrafluoroethylene emulsion. [Effects of the Invention]

[0026] Compared to the prior art, the present invention has the following beneficial effects.

[0027] (1) The modified polytetrafluoroethylene stretched film according to the present invention is modified by adding an AOI-modified monomer to affect the overall structure of the modified polytetrafluoroethylene stretched film, thereby reducing the crystallinity of the system. The resulting modified polytetrafluoroethylene stretched film is softer, has good stretching performance, has a relatively small pore size, a relatively high porosity, and a uniform pore size distribution.

[0028] (2) The method for producing a modified polytetrafluoroethylene stretched film according to the present invention uses an ammonium salt polymer dispersant as a raw material, provides good stability to the product, and the resulting product is clean and pure, does not cause environmental pollution, and does not participate in human metabolism. Compared to methods currently on the market that use perfluoro acid and its salts as production aids, the present invention is a very environmentally friendly and healthy technology. [Brief explanation of the drawing]

[0029] [Figure 1] This is a schematic diagram of the structure of the modified polytetrafluoroethylene stretched film produced in Example 1. [Figure 2] This is a schematic diagram of the structure of a conventional modified polytetrafluoroethylene stretched film. [Modes for carrying out the invention]

[0030] The present invention will be described below with reference to specific examples. The following examples are merely illustrations of the present invention and are used solely for illustrative purposes; they do not limit the present invention. Other combinations and various modifications are possible within the scope of the spirit of the present invention without departing from its essence or scope.

[0031] The compounds and related reagents used in the following examples are all commercially available, and the AOI was purchased from Showa Denko Corporation.

[0032] (Manufacturing of ammonium salt polymer dispersant I) The manufacturing method is as follows: (1) Add 100 g of perfluoroheptane to the reactor, raise the temperature to 70°C, and add 1 mol of perfluorohexanol acrylate, 1 mol of acrylic acid, and 1 g of perfluorobutyryl peroxide dropwise to the reactor at a constant rate using a peristaltic pump. After the addition is complete, keep the temperature at 4 hours to allow the reaction to proceed. (2) Add 1 mol of diethanolamine to the reactor and allow the reaction to proceed while maintaining a temperature of 70°C. After the reaction is complete, remove the perfluoroheptane and the product is ammonium salt polymer dispersant I.

[0033] (Manufacturing of Ammonium Salt Polymer Dispersant II) The manufacturing method is as follows: (1) Add 100 g of perfluoroheptane to the reactor, raise the temperature to 70°C, and add 4 mol of perfluorohexanol acrylate, 1 mol of acrylic acid droplets, and 1 g of perfluorobutyryl peroxide dropwise to the reactor at a constant rate using a peristaltic pump. After the addition is complete, keep the temperature at 4 hours to allow the reaction to proceed. (2) Add 1 mol of diethanolamine to the reactor and allow the reaction to proceed while maintaining a temperature of 70°C. After the reaction is complete, remove the perfluoroheptane and the product is ammonium salt polymer dispersant I.

[0034] (Production of AOI-modified monomer I) The manufacturing method is as follows: (1) Add 100 g of perfluoroheptane to the reactor, raise the temperature to 70°C, and add 1 mol of perfluorohexanol acrylate, 0.1 mol of hydroxyethyl acrylate, and 1 g of perfluorobutyryl peroxide dropwise to the reactor at a constant rate using a peristaltic pump. After the addition is complete, keep the temperature at 4 hours to allow the reaction to proceed. (2) Add 0.1 mol of AOI to the product obtained in step (1) and react with it. After the reaction is complete, remove the perfluoroheptane and the resulting product is AOI-modified monomer I.

[0035] (Production of AOI-modified monomer II) The manufacturing method is as follows: (1) Add 100 g of perfluoroheptane to the reactor, raise the temperature to 70°C, and add 2 mol of perfluorohexanol acrylate, 0.1 mol of hydroxyethyl acrylate, and 1 g of perfluorobutyryl peroxide dropwise to the reactor at a constant rate using a peristaltic pump. After the addition is complete, keep the temperature at 4 hours to allow the reaction to proceed. (2) Add 0.1 mol of AOI to the product obtained in step (1) and react with it. After the reaction is complete, remove the perfluoroheptane and the resulting product is II, which is an AOI-modified monomer.

[0036] (Modified polytetrafluoroethylene emulsion I) A modified polytetrafluoroethylene emulsion comprising 2 parts by weight of ammonium salt polymer dispersant II, 1 part by weight of Kryptox EG2000, 1.5 parts by weight of AOI-modified monomer II, 3 parts by weight of perfluorobutyryl peroxide, 60 parts by weight of tetrafluoroethylene monomer, and 30 parts by weight of deionized water. The manufacturing method is as follows: (1) Ammonium salt polymer dispersant II, Kryptox EG2000 and deionized water are stirred and added to the high-pressure emulsification reactor, stirred, and the temperature is raised to 60°C, nitrogen gas is added and the system pressure is raised to 4 MPa, (2) Tetrafluoroethylene monomer, AOI-modified monomer II, and perfluorobutyryl peroxide are each added to a high-pressure emulsification reactor, the temperature is raised and the reaction is carried out for 3 hours, and after the reaction is complete the product is modified polytetrafluoroethylene emulsion I.

[0037] (Modified polytetrafluoroethylene emulsion II) A modified polytetrafluoroethylene emulsion comprising 0.5 parts by weight of ammonium salt polymer dispersant II, 1 part by weight of Kryptox EG2000, 1.5 parts by weight of AOI-modified monomer II, 3 parts by weight of perfluorobutyryl peroxide, 60 parts by weight of tetrafluoroethylene monomer, and 30 parts by weight of deionized water. The manufacturing method is the same as that for modified polytetrafluoroethylene emulsion I.

[0038] (Modified polytetrafluoroethylene emulsion III) A modified polytetrafluoroethylene emulsion comprising 0.5 parts by weight of ammonium salt polymer dispersant II, 1 part by weight of Kryptox EG2000, 1 part by weight of AOI modified monomer II, 3 parts by weight of perfluorobutyryl peroxide, 60 parts by weight of tetrafluoroethylene monomer, and 30 parts by weight of deionized water. The manufacturing method is the same as that for modified polytetrafluoroethylene emulsion I.

[0039] (Modified polytetrafluoroethylene emulsion IV) A modified polytetrafluoroethylene emulsion comprising 0.5 parts by weight of ammonium salt polymer dispersant I, 1 part by weight of Kryptox EG2000, 1 part by weight of AOI-modified monomer II, 3 parts by weight of perfluorobutyryl peroxide, 60 parts by weight of tetrafluoroethylene monomer, and 30 parts by weight of deionized water. The manufacturing method is the same as that for modified polytetrafluoroethylene emulsion I.

[0040] (Modified polytetrafluoroethylene emulsion V) A modified polytetrafluoroethylene emulsion comprising 0.5 parts by weight of ammonium salt polymer dispersant I, 1 part by weight of Kryptox EG2000, 1 part by weight of AOI-modified monomer I, 3 parts by weight of perfluorobutyryl peroxide, 60 parts by weight of tetrafluoroethylene monomer, and 30 parts by weight of deionized water. The manufacturing method is the same as that for modified polytetrafluoroethylene emulsion I.

[0041] (Modified polytetrafluoroethylene emulsion VI) A modified polytetrafluoroethylene emulsion comprising 0.5 parts by weight of ammonium salt polymer dispersant I, 1 part by weight of Kryptox EG2000, 1 part by weight of AOI-modified monomer I, 3 parts by weight of perfluorobutyryl peroxide, 40 parts by weight of tetrafluoroethylene monomer, and 30 parts by weight of deionized water. The manufacturing method is the same as that for modified polytetrafluoroethylene emulsion I.

[0042] (Modified polytetrafluoroethylene emulsion VII) A modified polytetrafluoroethylene emulsion comprising 0.5 parts by weight of ammonium salt polymer dispersant I, 0.2 parts by weight of Kryptox EG2000, 1 part by weight of AOI-modified monomer I, 3 parts by weight of perfluorobutyryl peroxide, 40 parts by weight of tetrafluoroethylene monomer, and 30 parts by weight of deionized water. The manufacturing method includes the same as that for modified polytetrafluoroethylene emulsion I.

[0043] (Modified polytetrafluoroethylene emulsion VIII) A modified polytetrafluoroethylene emulsion comprising 0.5 parts by weight of ammonium salt polymer dispersant I, 0.2 parts by weight of Kryptox EG2000, 1 part by weight of AOI-modified monomer I, 1 part by weight of perfluorobutyryl peroxide, 40 parts by weight of tetrafluoroethylene monomer, and 30 parts by weight of deionized water. The manufacturing method is the same as that for modified polytetrafluoroethylene emulsion I.

[0044] (Modified polytetrafluoroethylene emulsion IX) A modified polytetrafluoroethylene emulsion comprising 0.5 parts by weight of ammonium salt polymer dispersant I, 0.2 parts by weight of Kryptox EG2000, 1 part by weight of AOI-modified monomer I, 1 part by weight of perfluorobutyryl peroxide, 40 parts by weight of tetrafluoroethylene monomer, and 60 parts by weight of deionized water. The manufacturing method is the same as that for modified polytetrafluoroethylene emulsion I. [Examples]

[0045] A modified polytetrafluoroethylene stretched film, wherein the modified polytetrafluoroethylene stretched film is manufactured by the following method: (1) Mix 100g of modified polytetrafluoroethylene emulsion I and 15g of Kryptox EG2000 uniformly, and extrude and roll the mixture. (2) The material is stretched longitudinally at 220°C, then transversely, and after stretching, it is sintered and solidified at 360°C for 10 minutes, and the product is a modified polytetrafluoroethylene stretched film. A schematic diagram of its structure is shown in Figure 1. [Examples]

[0046] A modified polytetrafluoroethylene stretched film, wherein the modified polytetrafluoroethylene stretched film is manufactured by the following method: (1) Mix 100g of modified polytetrafluoroethylene emulsion II and 15g of Kryptox EG2000 uniformly, and extrude and roll the mixture. (2) The material was stretched longitudinally at 220°C, then transversely, and after stretching, it was sintered and solidified at 360°C for 10 minutes, and the product was a modified polytetrafluoroethylene stretched film. [Examples]

[0047] A modified polytetrafluoroethylene stretched film, wherein the modified polytetrafluoroethylene stretched film is manufactured by the following method: (1) Mix 100g of modified polytetrafluoroethylene emulsion III and 15g of Kryptox EG2000 uniformly, and extrude and roll the mixture. (2) The material was stretched longitudinally at 220°C, then transversely, and after stretching, it was sintered and solidified at 360°C for 10 minutes, and the product was a modified polytetrafluoroethylene stretched film. [Examples]

[0048] A modified polytetrafluoroethylene stretched film, wherein the modified polytetrafluoroethylene stretched film is manufactured by the following method: (1) Mix 100g of modified polytetrafluoroethylene emulsion IV and 15g of Kryptox EG2000 uniformly, and extrude and roll the mixture. (2) The material was stretched longitudinally at 220°C, then transversely, and after stretching, it was sintered and solidified at 360°C for 10 minutes, and the product was a modified polytetrafluoroethylene stretched film. [Examples]

[0049] A modified polytetrafluoroethylene stretched film, wherein the modified polytetrafluoroethylene stretched film is manufactured by the following method: (1) Mix 100g of modified polytetrafluoroethylene emulsion V and 15g of Kryptox EG2000 uniformly, and extrude and roll the mixture. (2) The material was stretched longitudinally at 220°C, then transversely, and after stretching, it was sintered and solidified at 360°C for 10 minutes, and the product was a modified polytetrafluoroethylene stretched film. [Examples]

[0050] A modified polytetrafluoroethylene stretched film, wherein the modified polytetrafluoroethylene stretched film is manufactured by the following method: (1) Mix 100g of modified polytetrafluoroethylene emulsion VI and 15g of Kryptox EG2000 uniformly, and extrude and roll the mixture. (2) The material was stretched longitudinally at 220°C, then transversely, and after stretching, it was sintered and solidified at 360°C for 10 minutes, and the product was a modified polytetrafluoroethylene stretched film. [Examples]

[0051] A modified polytetrafluoroethylene stretched film, wherein the modified polytetrafluoroethylene stretched film is manufactured by the following method: (1) Mix 100g of modified polytetrafluoroethylene emulsion VII and 15g of Kryptox EG2000 uniformly, and extrude and roll the mixture. (2) The material was stretched longitudinally at 220°C, then transversely, and after stretching, it was sintered and solidified at 360°C for 10 minutes, and the product was a modified polytetrafluoroethylene stretched film. [Examples]

[0052] A modified polytetrafluoroethylene stretched film, wherein the modified polytetrafluoroethylene stretched film is manufactured by the following method: (1) Mix 100g of modified polytetrafluoroethylene emulsion VIII and 15g of Kryptox EG2000 uniformly, and extrude and roll the mixture. (2) The material was stretched longitudinally at 220°C, then transversely, and after stretching, it was sintered and solidified at 360°C for 10 minutes, and the product was a modified polytetrafluoroethylene stretched film. [Examples]

[0053] A modified polytetrafluoroethylene stretched film, wherein the modified polytetrafluoroethylene stretched film is manufactured by the following method: (1) Mix 100g of modified polytetrafluoroethylene emulsion IX and 15g of Kryptox EG2000 uniformly, and extrude and roll the mixture. (2) The material was stretched longitudinally at 220°C, then transversely, and after stretching, it was sintered and solidified at 360°C for 10 minutes, and the product was a modified polytetrafluoroethylene stretched film. [Examples]

[0054] A modified polytetrafluoroethylene stretched film, wherein the modified polytetrafluoroethylene stretched film is manufactured by the following method: (1) Mix 100g of modified polytetrafluoroethylene emulsion IX and 10g of Kryptox EG2000 uniformly, and extrude and roll the mixture. (2) The material was stretched longitudinally at 220°C, then transversely, and after stretching, it was sintered and solidified at 360°C for 10 minutes, and the product was a modified polytetrafluoroethylene stretched film.

[0055] (Comparative Example 1) The difference from Example 1 was that the modified polytetrafluoroethylene emulsion raw material used in the production of the modified polytetrafluoroethylene stretched film did not contain AOI-modified monomers.

[0056] (Comparative Example 2) The difference from Example 1 was that in the production of the modified polytetrafluoroethylene stretched film, 3g of the lubricant Kryptox EG2000 was used.

[0057] Performance tests were conducted on the modified polytetrafluoroethylene stretched films produced in the above examples and comparative examples. Tensile strength and elongation at break were tested according to the requirements of GB / T1040.3-2006. Porosity was measured using a porosity tester, and pore size and pore size distribution were measured using a scanning electron microscope (SEM). The measurement results are shown in Table 1.

[0058] [Table 1]

[0059] As can be seen by comparing the test results of Comparative Example 1 and Example 1, the modified polytetrafluoroethylene stretched film produced in Example 1 effectively increases its tensile strength and elongation at break by adding a polymer AOI-modified monomer, resulting in a modified polytetrafluoroethylene stretched film with good stretching performance, relatively small pore size, relatively high porosity, and a uniform pore size distribution. As can be seen by comparing Comparative Example 2 and Example 1, the modified polytetrafluoroethylene stretched film produced in Example 1 can enhance its stretching performance when used as a filter cotton for a moisture-proof mask by adding an appropriate amount of lubricant. As can be seen by comprehensively comparing the comparative examples and examples, the modified polytetrafluoroethylene stretched film according to the present invention, by adding a polymer AOI-modified monomer, affects the overall structure of the modified polytetrafluoroethylene stretched film, reducing the crystallinity of the system, and the resulting modified polytetrafluoroethylene stretched film is softer, has good stretching performance, relatively small pore size, relatively high porosity, and a uniform pore size distribution. Furthermore, by using an ammonium salt polymer dispersant as a manufacturing raw material, the resulting product is clean and pure, does not cause environmental pollution, and does not participate in human metabolism. Compared to methods currently on the market that use perfluoro acid and its salts as production aids, the manufacturing method of the present invention is a very environmentally friendly and healthy technology.

[0060] The embodiments described above are merely for illustrating the technical concept and features of the present invention, and their purpose is to enable those familiar with this art to understand and implement the present invention. They do not limit the scope of protection of the present invention, and all substantially equivalent changes or modifications made in accordance with the spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for producing a modified polytetrafluoroethylene stretched film, Step (1) involves uniformly mixing a modified polytetrafluoroethylene emulsion in a weight ratio of 100:10 to 15 with a lubricant called Krytox (registered trademark) EG2000 and extruding and rolling it, Step (2) involves stretching the material longitudinally at 210-230°C, then transversely, and after stretching, sintering and solidifying it at 350-370°C for 5-15 minutes, with the product being a modified polytetrafluoroethylene stretched film. Includes, The modified polytetrafluoroethylene emulsion contains an ammonium salt polymer dispersant, Krytox® EG2000, AOI-modified monomer, perfluorobutyryl peroxide, tetrafluoroethylene monomer, and water in a weight ratio of 0.5-2:0.2-1:1-1.5:1-3:40-60:30-60, and the method for producing the modified polytetrafluoroethylene emulsion is as follows: Step (1) involves adding a dispersant, emulsifier, and deionized water to a high-pressure emulsification reactor after stirring, stirring, raising the temperature to 40-60°C, and raising the system pressure to 3-4 MPa. Step (2) involves adding tetrafluoroethylene monomer, AOI-modified monomer, and initiator to a high-pressure emulsification reactor, raising the temperature, and reacting for 2-4 hours, and after the reaction is complete, the product being a modified polytetrafluoroethylene emulsion. The structure of the ammonium salt polymer dispersant is, Here, x is an integer between 2 and 5, y is an integer between 5 and 8, and * is the bonding site of the chemical bond. The structure of the AOI-modified monomer is shown below. A method for producing a modified polytetrafluoroethylene stretched film, characterized in that, m is an integer between 1 and 2, n is an integer between 10 and 20, and * is a chemical bond site.

2. The method for producing the ammonium salt polymer dispersant is: Step (1) involves adding a solvent to the reactor, heating it to raise the temperature, and then adding perfluorohexanol acrylate, acrylic acid, and an initiator dropwise to the reactor and allowing the reaction to proceed while maintaining the temperature for 2-4 hours. A method for producing a modified polytetrafluoroethylene stretched film according to claim 1, comprising step (2) in which diethanolamine is added to the product obtained in step (1) and reacted, the solvent is removed after the reaction is complete, and the resulting product is an ammonium salt polymer dispersant.

3. The method for producing a modified polytetrafluoroethylene stretched film according to claim 2, characterized in that the molar ratio of perfluorohexanol acrylate, acrylic acid, and diethanolamine is 1-4:1:1, the reaction temperature in step (1) is 60-70°C, the solvent is one or more combinations selected from perfluorohexane, perfluoroheptane, perfluorooctane, and monobromododecafluorohexane, the initiator is one or a combination thereof selected from perfluorobutyryl peroxide and perfluorohexanoyl peroxide, and the amount of initiator used is 1%-2% of the total mass of perfluorohexanol acrylate and acrylic acid.

4. The method for producing the AOI-modified monomer is: Step (1) involves adding a solvent to the reactor, heating it to raise the temperature, and then adding perfluorohexanol acrylate, hydroxyethyl acrylate, and an initiator dropwise to the reactor, and maintaining the temperature for 2-4 hours after the dropwise addition is complete. A method for producing a modified polytetrafluoroethylene stretched film according to claim 1, comprising step (2) adding AOI to the product obtained in step (1) and reacting it, removing the solvent after the reaction is complete, and the resulting product being an AOI-modified monomer.

5. The method for producing a modified polytetrafluoroethylene stretched film according to claim 4, characterized in that the molar ratio of perfluorohexanol acrylate, hydroxyethyl acrylate, and AOI is 10-20:1:1, the reaction temperature in step (1) is 60-70°C, the solvent is one or more combinations selected from perfluorohexane, perfluoroheptane, perfluorooctane, and monobromododecafluorohexane, the initiator is one or a combination thereof selected from perfluorobutyryl peroxide and perfluorohexanoyl peroxide, and the amount of initiator used is 1%-2% of the total mass of perfluorohexanol acrylate and acrylic acid.

Images