A waterproof breathable membrane and its preparation method

Abstract

The present application relates to the technical field of waterproof breathable membranes, and in particular to a waterproof breathable membrane and a preparation method thereof. A waterproof breathable membrane comprises a non-woven fabric and an expanded polytetrafluoroethylene membrane provided on the non-woven fabric, wherein the non-woven fabric and the expanded polytetrafluoroethylene membrane are hot-pressed and bonded at a high temperature of 140-150°C and a pressure of 0.5-1.1 MPa, and the expanded polytetrafluoroethylene membrane comprises the following raw materials in parts by weight: 25-35 parts of expanded polytetrafluoroethylene, 1520 parts of polystyrene, 10-15 parts of polyvinylpyrrolidone, 3040 parts of 2-hydroxy N, N-dimethylamide, 0.2-0.6 parts of coupling agent, 4-6 parts of filler, 14 parts of sodium hexametaphosphate, 13 parts of sodium methylene dinaphthalene sulfonate, and 35 parts of pore-forming agent. The waterproof breathable membrane of the present application has the advantages of strong air permeability, heat dissipation performance, corrosion resistance and good mechanical properties, and is widely used in the fields of electronics industry, automobile, battery, smart home, etc.

Description

Technical Field

[0001] The present application relates to the technical field of waterproof breathable membranes, and in particular to a waterproof breathable membrane and a preparation method thereof. Background Art

[0002] Polytetrafluoroethylene (PTFE) is used as a raw material for waterproof and breathable membranes due to its excellent waterproof, corrosion-resistant, chemical-resistant, high and low temperature resistant, and aging-resistant properties. Expanded polytetrafluoroethylene (ePTFE) is made from polytetrafluoroethylene resin through a stretching process to form a porous film material. This makes it waterproof and dustproof while also being breathable and sound-permeable. It is widely used in the electronics industry, automobiles, chemical packaging, smart homes, and other fields. During use in these fields, the film material is used to protect electronic product components from harsh external environments, ensuring the normal operation of electronic products; to balance the internal and external pressure differences of automotive sensors, ECUs, and outdoor lighting to prevent condensation and fogging; and to discharge gases and heat generated during battery use to prevent moisture and corrosion, thereby ensuring battery safety.

[0003] At present, waterproof breathable membranes have problems such as poor mechanical properties, low air permeability and poor heat dissipation performance. Therefore, it is necessary to further improve the existing waterproof breathable membranes to enhance their comprehensive performance and better meet market needs. Summary of the Invention

[0004] The purpose of this application is to provide a waterproof breathable membrane and a preparation method thereof to address the deficiencies of current technology.

[0005] This application provides a waterproof and breathable membrane, which adopts the following technical solutions:

[0006] A waterproof and breathable membrane comprises a non-woven fabric and an expanded polytetrafluoroethylene membrane arranged on the non-woven fabric. The non-woven fabric and the expanded polytetrafluoroethylene membrane are hot-pressed and bonded at a high temperature of 140-150°C and a pressure of 0.5-1.1 MPa. The expanded polytetrafluoroethylene membrane comprises the following raw materials in parts by weight: 25-35 parts of expanded polytetrafluoroethylene, 15-20 parts of polystyrene, 10-15 parts of polyvinyl pyrrolidone, 30-40 parts of 2-hydroxy-N,N-dimethylamide, 0.2-0.6 parts of a coupling agent, 4-6 parts of a filler, 1-4 parts of sodium hexametaphosphate, 1-3 parts of sodium methylene dinaphthalene sulfonate, and 3-5 parts of a pore-forming agent.

[0007] By adopting the above technical solution, expanded polytetrafluoroethylene (ePTFE) serves as the primary waterproof and breathable layer. Its small pore size effectively blocks moisture penetration, while its high air permeability allows for the escape of water vapor, thereby maintaining a dry and breathable interior. Non-woven fabric serves as a support layer, providing mechanical strength and enhancing the abrasion resistance and tensile properties of the entire membrane, while also making the material more durable. Polystyrene acts as an additive to improve the physical properties of ePTFE, enhancing its strength and durability. Polyvinylpyrrolidone acts as an additive to increase its flexibility and ductility, improving its bending and impact resistance. 2-Hydroxy-N,N-dimethylamide acts as an additive to enhance the material's film-forming properties, improving its air permeability and waterproofing. Coupling agent acts as an additive to strengthen the bond between ePTFE and other components, enhancing the stability of the overall structure. Filler is used to adjust the density and porosity of the ePTFE material and plays a significant role in its air permeability and mechanical properties. Sodium hexametaphosphate acts as an additive to provide a flame retardant, enhancing the material's fire resistance. Sodium methylene dinaphthalene sulfonate: As an additive, it improves the material's antistatic and antimicrobial properties. Pore-forming agents: Used to create a pore structure, increase the material's air permeability, and improve its moisture-wicking properties. Therefore, by combining the appropriate composition, this waterproof and breathable membrane can simultaneously possess multiple excellent properties, including waterproofing, air permeability, corrosion resistance, and excellent mechanical properties.

[0008] Preferably, the non-woven fabric is one of PP non-woven fabric, PE non-woven fabric, and PE-PP non-woven fabric, and the gram weight of the non-woven fabric is 30-40 g / m2.

[0009] Preferably, the method for preparing expanded polytetrafluoroethylene comprises the following steps:

[0010] S31, 21g of expanded microspheres, 500g of polytetrafluoroethylene resin and 68g of extrusion aid were added into a mixer and mixed uniformly for 30-40min to obtain a mixture;

[0011] S32, sealing the mixture and placing it in a 45°C oven for aging for 20 hours, then molding it under a pressure of 3 MPa for 2-3 minutes, and then extruding it under a pressure of 12 MPa to obtain an extrudate;

[0012] S33. The extrudate is rolled into a sheet with a thickness of 0.06 mm at a speed of 30 m / s, and then the extrusion aid is removed in a 200°C oven for 3-6 minutes. Then, the sheet is stretched to 2.5 times in a 280°C stretching box, and the expanded microspheres are expanded at the same time. Finally, the sheet is sintered and shaped in a 280°C sintering box for 1-2 minutes to obtain expanded polytetrafluoroethylene material.

[0013] Preferably, in step S31, the expanded microspheres are Akzo Nobel expanded microspheres, with a particle size of 10-30 μm and a true density of 1000-1200 kg / m 3 The extrusion aid is Isopar C type extrusion aid from ExxonMobil.

[0014] By adopting the above technical solution, in this preparation method, the preparation process of expanded polytetrafluoroethylene is as follows: S31: The expanded microspheres, polytetrafluoroethylene resin and extrusion aid are mixed evenly. Expanded microspheres are a kind of filler. By adding expanded microspheres, the expanded polytetrafluoroethylene material can have the characteristics of high compression resilience, multi-directional expansion and low density. S32: The mixture is matured and pressure-molded, and then an extrudate is obtained through an extrusion process. This process enables the mixture to form a certain structure and excludes air. S33: The extrudate is calendered into a sheet, and the extrusion aid is removed in an oven. Then, it is stretched in a stretching box, which causes the expanded microspheres to expand to form a pore structure in the material and improve the air permeability of the material. Finally, it is sintered and shaped in a sintering box to ensure the stability of the expanded polytetrafluoroethylene material. By adding expanded microspheres, the expanded polytetrafluoroethylene material has the characteristics of high compression resilience, multi-directional expansion and low density.

[0015] Preferably, the coupling agent is a composition of propyltrimethoxysilane, vinyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane in a mass ratio of 1:(2-4):(4-6).

[0016] By adopting the above technical solution, coupling agents play a vital role in the preparation of waterproof and breathable membranes, synergizing with other raw materials. Specifically, propyltrimethoxysilane promotes compatibility and adhesion between the various components in the membrane material, enhancing the material's mechanical strength and durability. Propyltrimethoxysilane interacts with other components to optimize the material's structure and improve its corrosion resistance. Vinyltriethoxysilane: This silane coupling agent imparts excellent high-temperature resistance to the expanded polytetrafluoroethylene (ePTFE) membrane, increasing its thermal stability. It also strengthens the bond between the polymer matrix and the nonwoven fabric, enhancing the mechanical properties of the ePTFE membrane. γ-Glycidoxypropyltrimethoxysilane: This silane coupling agent acts primarily as a compatibilizer, improving the pore structure and pore size distribution of the ePTFE membrane and enhancing its breathability. Furthermore, it interacts with other raw materials in the ePTFE membrane, enhancing the material's mechanical strength and durability. Through the synergistic effect of the above three coupling agents, the expanded polytetrafluoroethylene membrane can have better air permeability, heat dissipation, corrosion resistance and mechanical properties. When combined with the non-woven fabric, it can play a role in supporting and improving the mechanical strength, so that the waterproof and breathable membrane has excellent performance and service life.

[0017] Preferably, the filler is one or more of diatomaceous earth, montmorillonite, talc, and calcium carbonate, and the particle size of the diatomaceous earth, montmorillonite, talc, and calcium carbonate is 50-120 nanometers.

[0018] Preferably, the pore-forming agent is one or more of ammonium bicarbonate, ammonium oxalate and ammonium nitrate.

[0019] Preferably, the pore-forming agent is a composition of ammonium bicarbonate, ammonium oxalate and ammonium nitrate in a mass ratio of 5:(1-3):(2-4).

[0020] By adopting the above technical solution, the pore-forming agent plays a key role in the production of waterproof and breathable membranes, synergizing with other raw materials. Specifically, the following functions are involved: Ammonium bicarbonate: When decomposed by heat, ammonium bicarbonate produces carbon dioxide gas, which is released from the casting solution to form pores. The addition of ammonium bicarbonate can create a porous structure in the expanded polytetrafluoroethylene (ePTFE) membrane. Furthermore, ammonium bicarbonate increases the viscosity of the casting solution, helping to control the size and distribution of pores. Ammonium oxalate: When decomposed by heat, ammonium oxalate also produces gas, creating pores that are released from the casting solution. Ammonium oxalate improves the uniformity of pore distribution, resulting in a more uniform pore size distribution in the polytetrafluoroethylene membrane and enhancing breathability. Ammonium nitrate also produces gas, forming pores and improving breathability. When combined with ammonium oxalate and ammonium bicarbonate, ammonium nitrate improves the uniform distribution of fillers, achieving a uniform pore distribution and increasing the porosity of the ePTFE membrane. By adding a pore-forming agent, specifically a combination of ammonium bicarbonate, ammonium oxalate, and ammonium nitrate, the expanded polytetrafluoroethylene membrane possesses excellent air permeability, heat dissipation, corrosion resistance, and good mechanical properties. Furthermore, the pore-forming agent, combined with sodium hexametaphosphate and sodium methylene dinaphthalene sulfonate, improves the uniformity of pore distribution and evenly distributes the filler in the casting solution, ultimately achieving a uniform pore size distribution and high air permeability for the waterproof and breathable membrane.

[0021] Preferably, the method for preparing the expanded polytetrafluoroethylene membrane comprises the following steps:

[0022] S91. Add expanded polytetrafluoroethylene, polystyrene, polyvinyl pyrrolidone, and 2-hydroxy-N,N-dimethylamide to a stirring kettle according to their weight proportions, and stir at a temperature of 65-75° C. for 4-6 hours to obtain a casting solution A.

[0023] S92. Add a coupling agent, a filler, sodium hexametaphosphate, and sodium methylene dinaphthalene sulfonate to the casting solution A according to their weight proportions, stir at 60-70° C. for 3-4 hours, then add a pore-forming agent and continue stirring for 6 minutes to obtain a paste.

[0024] S93, forming the obtained paste into a film by multiple roll forming;

[0025] S94. Heat the film at 250-280° C. for 3-4 hours. After cooling, soak the film in clean water for 8-10 hours. Then, take out the film and dry it to obtain an expanded polytetrafluoroethylene film.

[0026] Preferably, in step S93, the thickness of the film is 20-30 μm.

[0027] In summary, the beneficial technical effects of this application are:

[0028] 1. Strong breathability: Expanded polytetrafluoroethylene membrane has small pore size and large porosity, with an average pore size of 0.4-0.6μm and a porosity greater than 80%, which makes the expanded polytetrafluoroethylene membrane have excellent breathability, able to block moisture while maintaining air circulation.

[0029] 2. Heat dissipation performance: The air permeability of expanded polytetrafluoroethylene membrane gives it good heat dissipation performance, which can effectively remove the heat generated in the body and improve the safety performance of electronic and battery components.

[0030] 3. Corrosion resistance: Polytetrafluoroethylene has excellent corrosion resistance, which makes the waterproof breathable membrane less susceptible to corrosion and damage in a humid environment and has a longer service life.

[0031] 4. Good mechanical properties: Non-woven fabric as a supporting layer can provide support and enhance the mechanical strength of the membrane, so that the waterproof and breathable membrane has good strength and wear resistance and is not easily damaged.

[0032] 5. Expanded polytetrafluoroethylene material has the characteristics of high compression resilience, multi-directional expansion and low density. By adding expanding microspheres, the resilience and expansion of the material are further increased, and the performance of the expanded polytetrafluoroethylene membrane is improved.

[0033] 6. The pore-forming agent decomposes upon heating, generating gas and bubbles, which create a porous structure within the waterproof, breathable membrane. The combination of sodium hexametaphosphate and sodium methylene dinaphthalene sulfonate makes the pores more uniform and evenly distributes the filler within the casting solution, achieving uniform pore size distribution and high breathability within the PTFE membrane. DETAILED DESCRIPTION

[0034] The embodiments of the present application will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0035] Example 1

[0036] A waterproof and breathable membrane comprises a non-woven fabric and an expanded polytetrafluoroethylene membrane arranged on the non-woven fabric. The non-woven fabric and the expanded polytetrafluoroethylene membrane are hot-pressed and bonded at a high temperature of 140°C and a pressure of 0.5 MPa. The expanded polytetrafluoroethylene membrane comprises the following raw materials in parts by mass: 25 parts of expanded polytetrafluoroethylene, 15 parts of polystyrene, 10 parts of polyvinyl pyrrolidone, 30 parts of 2-hydroxy-N,N-dimethylamide, 0.2 parts of a coupling agent, 4 parts of diatomaceous earth, 1 part of sodium hexametaphosphate, 1 part of sodium methylene dinaphthalene sulfonate, and 3 parts of ammonium bicarbonate. The non-woven fabric is a PP non-woven fabric with a gram weight of 30 g / m2. The coupling agent is a composition of propyltrimethoxysilane, vinyltriethoxysilane, and γ-glycidyloxypropyltrimethoxysilane in a mass ratio of 1:2:4. The particle size of the diatomaceous earth is 100-120 nanometers.

[0037] The preparation method of expanded polytetrafluoroethylene comprises the following steps:

[0038] S31, 21g expanded microspheres, 500g polytetrafluoroethylene resin and 68g extrusion aid were added into a mixer and mixed evenly for 30min to obtain a mixture. The expanded microspheres were Akzo Nobel expanded microspheres with a particle size of 10μm and a true density of 1200kg / m 3 , the extrusion aid is Isopar C type extrusion aid from ExxonMobil;

[0039] S32, sealing the mixture and placing it in a 45°C oven for aging for 20 hours, then molding it under a pressure of 3 MPa for 2 minutes, and then extruding it under a pressure of 12 MPa to obtain an extrudate;

[0040] S33. The extrudate is rolled into a sheet with a thickness of 0.06 mm at a speed of 30 m / s, and then the extrusion aid is removed in a 200°C oven for 3 minutes. Then, the sheet is stretched 2.5 times in a 280°C stretching box, and the expanded microspheres are expanded at the same time. Finally, the sheet is sintered and shaped in a 280°C sintering box for 1 minute to obtain expanded polytetrafluoroethylene material.

[0041] The method for preparing an expanded polytetrafluoroethylene membrane comprises the following steps:

[0042] S91. Add expanded polytetrafluoroethylene, polystyrene, polyvinyl pyrrolidone, and 2-hydroxy-N,N-dimethylamide into a stirring kettle according to their weight proportions, and stir at 65° C. for 6 hours to obtain a casting solution A.

[0043] S92. Add a coupling agent, diatomaceous earth, sodium hexametaphosphate, and sodium methylene dinaphthalene sulfonate to the casting solution A in parts by mass, stir at 60° C. for 4 hours, then add ammonium bicarbonate and continue stirring for 6 minutes to obtain a paste;

[0044] S93, forming the obtained paste into a film with a thickness of 20 μm by multiple roll forming;

[0045] S94. Heat the film at 250° C. for 4 hours. After cooling, soak the film in clean water for 8 hours. Then take out the film and dry it to obtain an expanded polytetrafluoroethylene film.

[0046] Example 2

[0047] A waterproof and breathable membrane comprises a non-woven fabric and an expanded polytetrafluoroethylene membrane arranged on the non-woven fabric. The non-woven fabric and the expanded polytetrafluoroethylene membrane are hot-pressed and bonded at a high temperature of 150°C and a pressure of 1.1 MPa. The expanded polytetrafluoroethylene membrane comprises the following raw materials in parts by mass: 35 parts of expanded polytetrafluoroethylene, 20 parts of polystyrene, 15 parts of polyvinyl pyrrolidone, 40 parts of 2-hydroxy-N,N-dimethylamide, 0.6 parts of a coupling agent, 6 parts of montmorillonite, 4 parts of sodium hexametaphosphate, 3 parts of sodium methylene dinaphthalene sulfonate, and 5 parts of ammonium oxalate. The non-woven fabric is a PE non-woven fabric with a gram weight of 40g / m2. The coupling agent is a composition of propyltrimethoxysilane, vinyltriethoxysilane, and γ-glycidyloxypropyltrimethoxysilane in a mass ratio of 1:4:6. The particle size of the montmorillonite is 100-120 nanometers.

[0048] The preparation method of expanded polytetrafluoroethylene comprises the following steps:

[0049] S31, 21g expanded microspheres, 500g polytetrafluoroethylene resin and 68g extrusion aid were added into a mixer and mixed evenly for 40min to obtain a mixture. The expanded microspheres were Akzo Nobel expanded microspheres with a particle size of 30μm and a true density of 1000kg / m 3 , the extrusion aid is Isopar C type extrusion aid from ExxonMobil;

[0050] S32, sealing the mixture and placing it in a 45°C oven for aging for 20 hours, then molding it at a pressure of 3 MPa for 3 minutes, and then extruding it at a pressure of 12 MPa to obtain an extrudate;

[0051] S33. The extrudate is rolled into a sheet with a thickness of 0.06 mm at a speed of 30 m / s, and then the extrusion aid is removed in a 200°C oven for 6 minutes, and then stretched to 2.5 times in a 280°C stretching box, and the expanded microspheres are expanded at the same time, and finally sintered and shaped in a 280°C sintering box for 2 minutes to obtain expanded polytetrafluoroethylene material.

[0052] The method for preparing an expanded polytetrafluoroethylene membrane comprises the following steps:

[0053] S91. Add expanded polytetrafluoroethylene, polystyrene, polyvinyl pyrrolidone, and 2-hydroxy-N,N-dimethylamide into a stirring kettle according to their weight proportions, and stir at 75° C. for 4 hours to obtain a casting solution A.

[0054] S92. Add a coupling agent, montmorillonite, sodium hexametaphosphate, and sodium methylene dinaphthalene sulfonate to the casting solution A in parts by mass, stir at 70° C. for 3 hours, then add ammonium oxalate and continue stirring for 6 minutes to obtain a paste;

[0055] S93, forming the obtained paste into a film with a thickness of 30 μm by multiple roll forming;

[0056] S94. Heat the film at 280° C. for 3 hours. After cooling, soak the film in clean water for 10 hours. Then, take out the film and dry it to obtain an expanded polytetrafluoroethylene membrane.

[0057] Example 3

[0058] A waterproof and breathable membrane comprises a non-woven fabric and an expanded polytetrafluoroethylene membrane arranged on the non-woven fabric. The non-woven fabric and the expanded polytetrafluoroethylene membrane are hot-pressed and bonded at a high temperature of 145°C and a pressure of 0.7 MPa. The expanded polytetrafluoroethylene membrane comprises the following raw materials in parts by mass: 30 parts of expanded polytetrafluoroethylene, 18 parts of polystyrene, 12 parts of polyvinyl pyrrolidone, 35 parts of 2-hydroxy-N,N-dimethylamide, 0.3 parts of a coupling agent, 5 parts of talc, 2 parts of sodium hexametaphosphate, 2 parts of sodium methylene dinaphthalene sulfonate, and 4 parts of ammonium nitrate. The non-woven fabric is a PE-PP non-woven fabric with a PP content of 45% and a gram weight of 35 g / m2. The coupling agent is a composition of propyltrimethoxysilane, vinyltriethoxysilane, and γ-glycidyloxypropyltrimethoxysilane in a mass ratio of 1:3:5. The particle size of the talc is 50-70 nanometers.

[0059] The preparation method of expanded polytetrafluoroethylene comprises the following steps:

[0060] S31, 21g expanded microspheres, 500g polytetrafluoroethylene resin and 68g extrusion aid were added into a mixer and mixed evenly for 35min to obtain a mixture. The expanded microspheres were Akzo Nobel expanded microspheres with a particle size of 20μm and a true density of 1150kg / m 3 , the extrusion aid is Isopar C type extrusion aid from ExxonMobil;

[0061] S32, sealing the mixture and placing it in a 45°C oven for aging for 20 hours, then molding it under a pressure of 3 MPa for 2.5 minutes, and then extruding it under a pressure of 12 MPa to obtain an extrudate;

[0062] S33. The extrudate is rolled into a sheet with a thickness of 0.06 mm at a speed of 30 m / s, and then the extrusion aid is removed in a 200°C oven for 5 minutes, and then stretched to 2.5 times in a 280°C stretching box, and the expanded microspheres are expanded at the same time, and finally sintered and shaped in a 280°C sintering box for 1.5 minutes to obtain expanded polytetrafluoroethylene material.

[0063] The method for preparing an expanded polytetrafluoroethylene membrane comprises the following steps:

[0064] S91. Add expanded polytetrafluoroethylene, polystyrene, polyvinyl pyrrolidone, and 2-hydroxy-N,N-dimethylamide into a stirring kettle according to their weight proportions, and stir at 70° C. for 5 hours to obtain a casting solution A.

[0065] S92. Add a coupling agent, talc, sodium hexametaphosphate, and sodium methylene dinaphthalene sulfonate to the casting solution A in parts by mass, stir at 65° C. for 3.5 hours, then add ammonium nitrate and continue stirring for 6 minutes to obtain a paste;

[0066] S93, the obtained paste is subjected to multiple roll forming processes to form a film having a thickness of 0.25 μm;

[0067] S94. Heat the film at 270° C. for 3.5 hours. After cooling, soak the film in clean water for 9 hours. Then, take out the film and dry it to obtain an expanded polytetrafluoroethylene film.

[0068] Example 4

[0069] A waterproof breathable membrane, comprising a non-woven fabric and an expanded polytetrafluoroethylene membrane arranged on the non-woven fabric, wherein the non-woven fabric and the expanded polytetrafluoroethylene membrane are heat-pressed and bonded at a high temperature of 145°C and a pressure of 0.8 MPa, and the expanded polytetrafluoroethylene membrane comprises the following raw materials in parts by mass: 30 parts of expanded polytetrafluoroethylene, 18 parts of polystyrene, 13 parts of polyvinyl pyrrolidone, 35 parts of 2-hydroxy-N, N-dimethylamide, 0.4 parts of coupling agent, and carbonic acid. 5 parts of calcium, 2 parts of sodium hexametaphosphate, 2 parts of sodium methylene dinaphthalene sulfonate, 4 parts of pore-forming agent, the non-woven fabric is PP non-woven fabric with a gram weight of 30-40g / ㎡, the coupling agent is a composition of propyltrimethoxysilane, vinyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane in a mass ratio of 1:3:5, the particle size of calcium carbonate is 60-80 nanometers, and the pore-forming agent is a composition of ammonium bicarbonate, ammonium oxalate and ammonium nitrate in a mass ratio of 5:1:2.

[0070] The preparation method of expanded polytetrafluoroethylene comprises the following steps:

[0071] S31, 21g expanded microspheres, 500g polytetrafluoroethylene resin and 68g extrusion aid were added into a mixer and mixed evenly for 35min to obtain a mixture. The expanded microspheres were Akzo Nobel expanded microspheres with a particle size of 20μm and a true density of 1150kg / m 3 , the extrusion aid is Isopar C type extrusion aid from ExxonMobil;

[0072] S32, sealing the mixture and placing it in a 45°C oven for aging for 20 hours, then molding it at a pressure of 3 MPa for 3 minutes, and then extruding it at a pressure of 12 MPa to obtain an extrudate;

[0073] S33. The extrudate is rolled into a sheet with a thickness of 0.06 mm at a speed of 30 m / s, and then the extrusion aid is removed in a 200°C oven for 4 minutes. Then, the sheet is stretched 2.5 times in a 280°C stretching box, and the expanded microspheres are expanded at the same time. Finally, the sheet is sintered and shaped in a 280°C sintering box for 1 minute to obtain expanded polytetrafluoroethylene material.

[0074] The method for preparing an expanded polytetrafluoroethylene membrane comprises the following steps:

[0075] S91. Add expanded polytetrafluoroethylene, polystyrene, polyvinyl pyrrolidone, and 2-hydroxy-N,N-dimethylamide into a stirring kettle according to their weight proportions, and stir at 75° C. for 4 hours to obtain a casting solution A.

[0076] S92. Add a coupling agent, calcium carbonate, sodium hexametaphosphate, and sodium methylene dinaphthalene sulfonate to the casting solution A in parts by mass, stir at 70° C. for 3 hours, then add a pore-forming agent and continue stirring for 6 minutes to obtain a paste;

[0077] S93, the obtained paste is subjected to multiple roll forming processes to form a film having a thickness of 0.25 μm;

[0078] S94. Heat the film at 270° C. for 3 hours. After cooling, soak the film in clean water for 8 hours. Then take out the film and dry it to obtain an expanded polytetrafluoroethylene membrane.

[0079] Example 5

[0080] The same as Example 4, except that equal amounts of pore-forming agents, namely, ammonium bicarbonate, ammonium oxalate, and ammonium nitrate, are used in a mass ratio of 5:3:4.

[0081] Example 6

[0082] The same as Example 4, except that equal amounts of pore-forming agents, namely, ammonium bicarbonate, ammonium oxalate, and ammonium nitrate, are used in a mass ratio of 5:2:3.

[0083] Comparative Example 1

[0084] The same as Example 4, except that an equal amount of polytetrafluoroethylene is used instead of the expanded polytetrafluoroethylene prepared in this application.

[0085] Comparative Example 2

[0086] The same as Example 4, except that an equal amount of propyltrimethoxysilane is used instead of the coupling agent, which is a composition of propyltrimethoxysilane, vinyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane in a mass ratio of 1:3:5.

[0087] Comparative Example 3

[0088] The same as Example 4, except that an equal amount of vinyltriethoxysilane is used instead of the coupling agent, which is a composition of propyltrimethoxysilane, vinyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane in a mass ratio of 1:3:5.

[0089] Comparative Example 4

[0090] The same as Example 4, except that an equal amount of γ-glycidyloxypropyltrimethoxysilane is used instead of the coupling agent, which is a composition of propyltrimethoxysilane, vinyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane in a mass ratio of 1:3:5.

[0091] Performance Testing

[0092] The waterproof breathable membranes prepared in Examples 1-6 and Comparative Examples 1-4 were subjected to performance tests, and the results are shown in Table 1.

[0093] Tensile strength: tested in accordance with ASTM D461-87;

[0094] Pore ​​size: The average pore size of the waterproof and breathable membrane is measured according to the particle method specified in GB / T 38949-202, Determination of Pore Size of Porous Membranes. Porosity: The porosity of the waterproof and breathable membrane is tested using the immersion medium method.

[0095] Air permeability: According to JISL 1096, in a closed space, with a fixed air pressure of 7kPa, the gas flow rate through the waterproof breathable membrane is measured and the air permeability per unit area is calculated in ml / min / cm 2 ;

[0096] Water pressure resistance: According to GB / T 4744-1997, measure the waterproof breathable membrane with a fixed aperture, apply a fixed pressure, maintain it for 1 hour, and observe whether the waterproof membrane surface seeps water. 10kPa is equivalent to 1m of water pressure.

[0097] Table 1

[0098]

[0099] As can be seen from Table 1, the waterproof breathable membranes prepared in Examples 1-6 all performed well in terms of mechanical properties, air permeability, average pore size, porosity, water pressure resistance, etc. The waterproof and breathable membrane of the present application has the advantages of strong air permeability, heat dissipation performance, corrosion resistance, and good mechanical properties. The non-woven fabric supports and enhances the mechanical strength. The prepared expanded polytetrafluoroethylene membrane has a small pore size and large air permeability. Its average pore size is 0.4-0.6μm and the porosity is greater than 80%; the pore-forming agent will generate gas after thermal decomposition, and the gas will form bubbles in the casting liquid, and eventually flush out of the casting liquid, so that a porous structure is formed in the casting liquid. The combination of sodium hexametaphosphate and sodium methylene dinaphthalene sulfonate can make the pore distribution more uniform, and the combination of sodium hexametaphosphate and sodium methylene dinaphthalene sulfonate can make the filler evenly distributed in the casting liquid. Obtaining a uniform pore distribution can make the pore size distribution of the polyvinylidene fluoride membrane uniform, and at the same time, the porosity is high, which is conducive to improving the air permeability and is widely used in the electronics industry, automobiles, batteries, smart homes and other fields.

[0100] As can be seen from Table 1, the performance comparison analysis of the waterproof breathable membranes prepared in Examples 4-6 and Examples 1-3 shows that the pore-forming agent is a composition of ammonium bicarbonate, ammonium oxalate and ammonium nitrate in a mass ratio of 5:3:4, a composition of 5:1:2, or a composition of 5:2:3, and the synergistic effect between ammonium bicarbonate, ammonium oxalate and ammonium nitrate is utilized to improve the air permeability and water pressure resistance of the waterproof breathable membrane.

[0101] As can be seen from Table 1, the performance comparison analysis of the waterproof breathable membranes prepared in Example 4 and Comparative Example 1 shows that the waterproof breathable membrane finally prepared from the expanded polytetrafluoroethylene prepared in the present application has better air permeability and water pressure resistance.

[0102] As can be seen from Table 1, the performance comparison analysis of the waterproof breathable membranes prepared in Example 4 and Comparative Examples 2-4 shows that a coupling agent is used in which a composition of propyltrimethoxysilane, vinyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane is used in a mass ratio of 1:3:5, and the synergistic effect between propyltrimethoxysilane, vinyltriethoxysilane and γ-glycidyloxypropyltrimethoxysilane is utilized to improve the comprehensive performance of the waterproof breathable membrane.

[0103] The above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit the present application. Although the above embodiments provide a detailed description of the present application, relevant technical personnel should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modifications and equivalent replacements that do not depart from the spirit and scope of the present application should be included in the scope of protection of the present application.

Claims

1. A waterproof breathable membrane, characterized in that: The invention comprises a non-woven fabric and an expanded polytetrafluoroethylene film arranged on the non-woven fabric, wherein the non-woven fabric and the expanded polytetrafluoroethylene film are hot-pressed and bonded at a high temperature of 140-150°C and a pressure of 0.5-1.1 MPa. The expanded polytetrafluoroethylene film comprises the following raw materials in parts by weight: 25-35 parts of expanded polytetrafluoroethylene, 15-20 parts of polystyrene, 10-15 parts of polyvinyl pyrrolidone, 30-40 parts of 2-hydroxy-N, N-dimethylamide, and a coupling agent. 0.2-0.6 parts, 4-6 parts of filler, 1-4 parts of sodium hexametaphosphate, 1-3 parts of sodium methylene dinaphthalene sulfonate, and 3-5 parts of a pore-forming agent; wherein the coupling agent is a composition of propyltrimethoxysilane, vinyltriethoxysilane, and γ-glycidyloxypropyltrimethoxysilane in a mass ratio of 1:(2-4):(4-6); and the pore-forming agent is a composition of ammonium bicarbonate, ammonium oxalate, and ammonium nitrate in a mass ratio of 5:(1-3):(2-4); The method for preparing expanded polytetrafluoroethylene comprises the following steps: S31, add 21g expanded microspheres, 500g polytetrafluoroethylene resin and 68g extrusion aid into a mixer and mix them evenly for 30-40min to obtain a mixture; the expanded microspheres are Akzo Nobel expanded microspheres with a particle size of 10-30μm and a true density of 1000-1200kg / m 3 ; S32, sealing the mixture and placing it in a 45°C oven for aging for 20 hours, then molding it under a pressure of 3 MPa for 2-3 minutes, and then extruding it under a pressure of 12 MPa to obtain an extrudate; S33, rolling the extrudate into a sheet with a thickness of 0.06 mm at a speed of 30 m / s, then removing the extrusion aid in a 200° C. oven for 3-6 minutes, then stretching it to 2.5 times in a 280° C. stretching oven to simultaneously expand the microspheres, and finally sintering and shaping it in a 280° C. sintering oven for 1-2 minutes to obtain expanded polytetrafluoroethylene, wherein the extrusion aid is Isopar C extrusion aid from ExxonMobil; The method for preparing the expanded polytetrafluoroethylene membrane comprises the following steps: S91. Add expanded polytetrafluoroethylene, polystyrene, polyvinyl pyrrolidone, and 2-hydroxy-N,N-dimethylamide to a stirring kettle according to their weight proportions, and stir at a temperature of 65-75° C. for 4-6 hours to obtain a casting solution A. S92. Add a coupling agent, a filler, sodium hexametaphosphate, and sodium methylene dinaphthalene sulfonate to the casting solution A according to their weight proportions, stir at 60-70° C. for 3-4 hours, then add a pore-forming agent and continue stirring for 6 minutes to obtain a paste. S93, forming the obtained paste into a film with a thickness of 20-30 μm by multiple roll forming; S94. Heat the film at 250-280° C. for 3-4 hours. After cooling, soak the film in clean water for 8-10 hours. Then, take out the film and dry it to obtain an expanded polytetrafluoroethylene film.

2. A waterproof breathable membrane according to claim 1, characterized in that: The non-woven fabric is one of PP non-woven fabric, PE non-woven fabric, and PE-PP non-woven fabric, and the gram weight of the non-woven fabric is 30-40g / ㎡.

3. The waterproof breathable membrane according to claim 1, characterized in that: The filler is one or more of diatomaceous earth, montmorillonite, talc, and calcium carbonate, and the particle size of the diatomaceous earth, montmorillonite, talc, and calcium carbonate is 50-120 nanometers.

Images