Preparation method of PTFE porous non-woven fiber membrane and PTFE porous non-woven fiber membrane
By using salt particles as a fiberizing agent and pore-forming agent, the high cost and low performance problems in the preparation of PTFE fiber membranes were solved, realizing the preparation of efficient and low-cost porous nonwoven PTFE fiber membranes, improving the mechanical properties of the membrane material and the simplicity of the preparation process.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HIGH ENERGY DIGITAL MFG (XIAN) TECH CO LTD
- Filing Date
- 2026-04-08
- Publication Date
- 2026-05-12
AI Technical Summary
Existing methods for preparing PTFE fiber membranes suffer from problems such as high preparation costs, low degree of fiberization, and poor mechanical properties, making it difficult to meet the requirements.
Salt particles were used as a fiberization aid and pore-forming agent. A PTFE-salt particle composite self-supporting membrane was prepared through fibrillation treatment and fiber network reinforcement treatment. The properties of the salt particles were then used for separation to obtain a PTFE porous nonwoven fiber membrane.
The efficient fiberization of PTFE porous nonwoven fiber membranes has been achieved. The preparation process is simple and low-cost, the membrane material has excellent performance and improved mechanical properties, and it can also achieve stable preparation of ultrathin films.
Smart Images
Figure CN122006498A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of organic membrane manufacturing technology, and particularly relates to a method for preparing a PTFE porous nonwoven fiber membrane and the PTFE porous nonwoven fiber membrane. Background Technology
[0002] Polytetrafluoroethylene (PTFE) is a core substrate for preparing high-performance porous membrane materials due to its excellent chemical stability, resistance to high and low temperatures, hydrophobic and oleophobic properties, low dielectric constant, and good physiological inertness. PTFE is widely used in many fields such as air and water filtration, waterproofing and breathability, seawater desalination, lithium battery separators, and chemical separation.
[0003] The insoluble and infusible nature of PTFE makes the fabrication process of its fibrous membranes extremely complex. Currently, commonly used methods for preparing PTFE fiber membranes include electrospinning, membrane splitting, and template methods. Among these, PTFE fiber membranes prepared by electrospinning have insufficient mechanical properties; those prepared by membrane splitting have limited thickness, making it difficult to prepare fiber membrane materials with a thickness less than 5 μm; and when using the template method to prepare porous PTFE fiber membranes, the template is difficult to remove completely.
[0004] Therefore, existing methods for preparing PTFE fiber membranes suffer from problems such as high production costs, low degree of fiberization, and poor mechanical properties. The preparation processes are complex, and the resulting PTFE fiber membranes often fail to meet requirements. Therefore, a fiber membrane preparation process that can solve these manufacturing problems is urgently needed. Summary of the Invention
[0005] This application provides a method for preparing a PTFE porous nonwoven fiber membrane and the PTFE porous nonwoven fiber membrane. Salt particles can be used as a fiberizing aid and pore-forming agent to achieve efficient fiberization of PTFE and prepare a PTFE porous nonwoven fiber membrane with high performance.
[0006] In a first aspect, embodiments of this application provide a method for preparing a PTFE porous nonwoven fiber membrane. The method includes: uniformly mixing PTFE raw materials with salt particles, and performing fibrillation treatment on the mixture to obtain a fibrillated mixture; performing fiber network reinforcement treatment on the fibrillated mixture and calendering to obtain a PTFE-salt particle composite self-supporting membrane; and removing the salt particles from the PTFE-salt particle composite self-supporting membrane according to the type of salt using a separation method corresponding to the salt particles to obtain the PTFE porous nonwoven fiber membrane.
[0007] In this embodiment, PTFE raw materials and salt particles are first subjected to fibrillation treatment to obtain a fibrillated mixture. Then, the fibrillated mixture is subjected to fiber network reinforcement treatment to obtain a PTFE-salt particle composite self-supporting membrane. Finally, based on the properties of the salt particles, a corresponding separation method is used to remove the salt particles from the PTFE-salt particle composite self-supporting membrane, thus obtaining the prepared PTFE porous nonwoven fiber membrane. During the fibrillation process, the salt particles not only act as a shear force transmission medium (i.e., as a fibrillation aid) but also as a pore-forming agent to prevent premature entanglement of PTFE fibers, achieving efficient PTFE fibrillation. The PTFE-salt particle composite self-supporting membrane obtained in this way has a skeletal structure formed by fiber interweaving and automatically shrinks and thins during the removal of salt particles, while still maintaining its self-supporting structure after thinning. This provides a method for preparing a PTFE porous nonwoven fiber membrane that is simple in preparation process, low in preparation cost, and produces a PTFE porous nonwoven fiber membrane with high performance.
[0008] In some embodiments, the mass ratio of PTFE to the salt particles ranges from 0.1% to 30%.
[0009] In some embodiments, the salts include readily soluble salts or readily decomposable salts; the readily soluble salts include: sodium chloride, sodium sulfate, lithium bromide, lithium chloride, lithium sulfate, lithium ethoxide, sodium ethoxide, sodium acetate, or sodium methanesulfonate; the readily thermally decomposable salts include: ammonium chloride, ammonium bromide, ammonium iodide, ammonium bicarbonate, ammonium carbonate, ammonium nitrate, ammonium acetate, ammonium benzoate, tetraethylammonium tetrafluoroborate, or triethanolamine.
[0010] In some embodiments, the step of performing fiber network reinforcement treatment on the fibrillated mixture and calendering it to obtain a PTFE-salt particle composite self-supporting film includes: performing a kneading treatment on the fibrillated mixture for a preset time at a first preset temperature to obtain a kneaded fibrillated mixture; and continuously rolling the kneaded fibrillated mixture at a second preset temperature to calender the kneaded fibrillated mixture to a preset thickness to obtain the PTFE-salt particle composite self-supporting film.
[0011] In some embodiments, the first preset temperature and the second preset temperature range from 25°C to 400°C; the preset duration ranges from 0.5 minutes to 10 minutes; and the preset thickness ranges from 1 μm to 2000 μm.
[0012] In some embodiments, after removing the salt particles from the PTFE-salt particle composite self-supporting membrane, the thickness of the resulting PTFE porous nonwoven fiber membrane is less than or equal to 5 μm.
[0013] In some embodiments, the step of removing the salt particles from the PTFE-salt particle composite self-supporting membrane using a separation method corresponding to the salt particles, based on the type of salt, to obtain the PTFE porous nonwoven fiber membrane, includes: when the salt is a type easily soluble in a solvent, the separation method includes: washing the PTFE-salt particle composite self-supporting membrane with a solvent capable of dissolving the salt particles to remove the salt particles from the PTFE-salt particle composite self-supporting membrane, thereby obtaining the PTFE porous nonwoven fiber membrane; when the salt is a type easily decomposed by heat, the separation method includes: heating the PTFE-salt particle composite self-supporting membrane to thermally decompose the salt particles, thereby removing the salt particles from the PTFE-salt particle composite self-supporting membrane, thereby obtaining the PTFE porous nonwoven fiber membrane.
[0014] In some embodiments, washing the PTFE-salt particle composite self-supporting membrane with a solvent capable of dissolving the salt particles to remove the salt particles and obtain the PTFE porous nonwoven fiber membrane includes: washing the PTFE-salt particle composite self-supporting membrane multiple times with a solvent capable of dissolving the salt particles to remove the salt particles and obtain a PTFE self-supporting membrane gel; and evaporating the PTFE self-supporting membrane gel to obtain the PTFE porous nonwoven fiber membrane.
[0015] In some embodiments, after obtaining the PTFE porous nonwoven fiber membrane, the method further includes: extruding and thinning the PTFE porous nonwoven fiber membrane, and / or sintering the PTFE self-supporting membrane under preset conditions to obtain a reinforced PTFE porous nonwoven fiber membrane.
[0016] Secondly, embodiments of this application provide a PTFE porous nonwoven fiber membrane, which is prepared by the PTFE porous nonwoven fiber membrane preparation method described in any one of the first aspects. The PTFE porous nonwoven fiber membrane is a self-supporting membrane. The PTFE porous nonwoven fiber membrane has a three-dimensional porous network structure formed by interwoven PTFE continuous fibers. The continuous fibers are formed by fibrillation treatment and stretching of PTFE material. The diameter of the PTFE continuous fibers is 200nm~800nm. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 A flowchart illustrating a method for preparing a PTFE porous nonwoven fiber membrane according to an embodiment of this application; Figure 2 A scanning electron microscope image of the PTFE-salt particle composite self-supporting membrane in Example 1 provided as an embodiment of this application; Figure 3 A scanning electron microscope image of the PTFE porous nonwoven fiber membrane in Example 1 provided as an embodiment of this application; Figure 4 Scanning electron microscope image of the PTFE porous nonwoven fiber membrane in Example 2 provided in one embodiment of this application; Figure 5 The diagram shows the mechanical property test results of Embodiment 1, Embodiment 2, and the comparative example provided as an embodiment of this application. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the accompanying drawings in the present invention are for illustrative and descriptive purposes only and are not intended to limit the scope of protection of the present invention. Furthermore, it should be understood that the schematic drawings are not drawn to scale. The flowcharts used in this invention illustrate operations implemented according to some embodiments of the present invention. It should be understood that the operations in the flowcharts may not be implemented in sequence, and steps without logical contextual relationships may be reversed or implemented simultaneously. In addition, those skilled in the art, guided by the content of this invention, may add one or more other operations to the flowcharts, or remove one or more operations from the flowcharts.
[0020] Furthermore, the embodiments described herein are merely some, not all, of the embodiments of the invention. The components of the embodiments of the invention described and illustrated herein can typically be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.
[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.
[0022] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.
[0023] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.
[0024] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0025] Figure 1 This is a flowchart illustrating a method for preparing a PTFE porous nonwoven fiber membrane according to an embodiment of this application.
[0026] Reference Figure 1 The preparation method of PTFE porous nonwoven fiber membrane includes: S110: PTFE raw material is uniformly mixed with salt particles, and the mixture is subjected to fibrillation treatment to obtain fibrillated mixture.
[0027] In some embodiments, the PTFE raw material comprises PTFE particles of various morphologies and PTFE emulsions. When the PTFE raw material is a PTFE emulsion, the water in the emulsion needs to be evaporated before it is uniformly mixed with the salt particles, or the water in the mixture is evaporated after uniform mixing with the salt particles. The mass ratio of PTFE to salt particles ranges from 0.1% to 30%.
[0028] In some embodiments, the salts include readily soluble or readily decomposable salts. The readily soluble salts include: sodium chloride, sodium sulfate, lithium bromide, lithium chloride, lithium sulfate, lithium ethoxide, sodium ethoxide, sodium acetate, or sodium methanesulfonate. The readily thermally decomposable salts include: ammonium chloride, ammonium bromide, ammonium iodide, ammonium bicarbonate, ammonium carbonate, ammonium nitrate, ammonium acetate, ammonium benzoate, tetraethylammonium tetrafluoroborate, or triethanolamine.
[0029] In some embodiments, when the mixture of PTFE raw material and salt particles is subjected to fibrillation treatment, the fibrillation temperature can be set to 25°C to 400°C, preferably room temperature or 300°C.
[0030] S120: The fibrillated mixture is subjected to fiber network reinforcement treatment and calendered to obtain a PTFE-salt particle composite self-supporting membrane.
[0031] In some embodiments, the fibrillated mixture is subjected to fiber network strengthening treatment and calendered to obtain a PTFE-salt particle composite self-supporting membrane, including: kneading the fibrillated mixture for a preset time at a first preset temperature to obtain a kneaded fibrillated mixture; and continuously rolling the kneaded fibrillated mixture at a second preset temperature to calender the fibrillated mixture to a preset thickness to obtain a PTFE-salt particle composite self-supporting membrane.
[0032] The first and second preset temperatures range from 25℃ to 400℃, with a preferred temperature of 100℃. The preset duration ranges from 0.5 minutes to 10 minutes, with a preferred duration of 5 minutes. The preset thickness ranges from 1μm to 2000μm.
[0033] In some implementations, the preset thickness can be set to around 100 μm, such as 75 μm to 150 μm. In this case, the fabrication process difficulty is greatly reduced, and after removing salt particles, the shrinkage characteristics of PTFE fibers can be utilized to achieve a thickness of less than 5 μm for the PTFE porous nonwoven fiber membrane, thus enabling the ultrathin fabrication of PTFE porous nonwoven fiber membranes with lower process difficulty.
[0034] S130: Depending on the type of salt, the salt particles in the PTFE-salt particle composite self-supporting membrane are removed using a separation method corresponding to the salt particles, resulting in a PTFE porous nonwoven fiber membrane.
[0035] In some embodiments, when the salt is of a type that is readily soluble in a solvent, the separation method includes: washing the PTFE-salt particle composite self-supporting membrane with a solvent that can dissolve the salt particles to remove the salt particles from the PTFE-salt particle composite self-supporting membrane, thereby obtaining a PTFE porous nonwoven fiber membrane.
[0036] As an example, assuming the salt particles are lithium bromide, the PTFE-salt particle composite self-supporting membrane prepared according to steps S110 and S120 is a PTFE-lithium bromide composite self-supporting membrane.
[0037] In this case, since lithium bromide is an easily soluble salt and readily soluble in alcohol solvents, ethanol solution can be used as a solvent to wash the PTFE-lithium bromide composite self-supporting membrane to remove lithium bromide.
[0038] When washing the PTFE-lithium bromide composite self-supporting membrane, it can be immersed in an ethanol solution, with the ethanol solution replaced 3-4 times to completely dissolve and remove the lithium bromide. The remaining PTFE self-supporting membrane is then evaporated to dryness, yielding a PTFE porous nonwoven fiber membrane. The pores in the PTFE porous nonwoven fiber membrane are formed after the lithium bromide dissolves.
[0039] In some embodiments, during the removal of salt particles and evaporation, the PTFE fibers automatically shrink, reducing the thickness of the PTFE self-supporting membrane and consequently reducing the thickness of the prepared PTFE porous nonwoven fiber membrane. Referring to the example in S120, when the preset thickness range is 75μm to 150μm, washing the PTFE-salt particle composite self-supporting membrane with a thickness of 75μm to 150μm removes the salt particles, resulting in a PTFE porous nonwoven fiber membrane with a thickness less than or equal to 5μm.
[0040] In some implementations, for cost-saving and environmental protection purposes, after obtaining the PTFE porous nonwoven fiber membrane, the solvent containing the dissolved salt particles can be evaporated to dryness, and the crystalline salt particles can be recovered.
[0041] In some embodiments, when the salt is a type that is easily thermally decomposed, the separation method includes: heating the PTFE-salt particle composite self-supporting membrane to thermally decompose the salt particles, thereby removing the salt particles from the PTFE-salt particle composite self-supporting membrane and obtaining a PTFE porous nonwoven fiber membrane.
[0042] As an example, suppose the salt particles are ammonium chloride. Then, the PTFE-salt particle composite self-supporting membrane prepared according to steps S110 and S120 is a PTFE-ammonium chloride composite self-supporting membrane.
[0043] In this case, since lithium bromide is a thermally decomposable salt, when removing salt particles from the PTFE-ammonium chloride composite self-supporting membrane, the membrane can be transferred to a tube furnace under argon protection. The furnace should be heated above the thermal decomposition temperature of ammonium chloride (337.8℃) to completely remove the ammonium chloride, resulting in a self-supporting PTFE porous nonwoven fiber membrane. The pores in the PTFE porous nonwoven fiber membrane are formed after the ammonium chloride is decomposed and removed.
[0044] In some embodiments, after obtaining the PTFE porous nonwoven fiber membrane, the method further includes: extruding and thinning the PTFE porous nonwoven fiber membrane, and / or sintering the PTFE self-supporting membrane under preset conditions to obtain a reinforced PTFE porous nonwoven fiber membrane.
[0045] As an example, the temperature for extruding and thinning the PTFE self-supporting membrane can be set to 50℃~200℃, the roller pressing line pressure to be 5N / cm~120N / cm, and the roller differential speed ratio to be 1.0~1.8. Multi-pass step-by-step roller pressing can be used, with a single-pass compression ratio ≤30%, and a PTFE porous nonwoven fiber membrane with a thickness of 1~6μm can be obtained after processing.
[0046] Preferably, the temperature for extruding and thinning the PTFE self-supporting membrane is 80℃~150℃, the roller pressing line pressure is 10N / cm~80N / cm, the roller differential speed ratio is 1.05~1.3, and the single-pass compression ratio is 10%~20%.
[0047] As an example, the preset conditions can be sintering in an inert gas environment, with a sintering strengthening treatment temperature of 300℃~400℃ and a holding time of 5min~120min. Preferably, the PTFE self-supporting membrane can be sintered in an inert gas environment at 350℃ for 15min.
[0048] This application also provides a PTFE porous nonwoven fiber membrane. This PTFE porous nonwoven fiber membrane is prepared using the aforementioned method for preparing PTFE porous nonwoven fiber membranes. This PTFE porous nonwoven fiber membrane is a self-supporting membrane with a three-dimensional porous network structure formed by interwoven continuous PTFE fibers. The continuous fibers are formed by fibrillating and stretching PTFE material through a fibrillation treatment, and their microstructure consists of continuous stretched filaments or ribbons, avoiding the defects of PTFE particle overlap and sintering neck connections commonly found in electrospinning and sintering methods. In some embodiments, the diameter of the PTFE continuous fibers is 200 nm to 800 nm.
[0049] In this application, salt particles are used as a fiberization aid, shear force transmission medium, fiber isolation and dispersant, and pore-forming agent. During the fibrillation process, the salt particles can uniformly transmit shear force, which promotes the PTFE raw material to fully undergo in-situ rupture and stretching to form continuous fibers, while avoiding premature entanglement and agglomeration of PTFE fibers, thus achieving efficient and uniform fiberization of PTFE.
[0050] The resulting PTFE fibers have a continuous long fiber structure and do not have the weak points formed by the overlap of PTFE particles in the electrospinning process, thus improving the mechanical properties and structural stability of the membrane material from the structural source.
[0051] This invention uses a dry fibrillation process combined with a salt-induced pore process. First, a mixture of PTFE and salt particles is fibrillated and then rolled to form a thick PTFE-salt particle composite self-supporting membrane. When removing the salt particles, relying on the uniform spontaneous shrinkage effect of the continuous PTFE fiber interwoven skeleton, a self-supporting PTFE porous nonwoven fiber membrane with a thickness of less than 10 μm can be directly obtained. Through process optimization, the membrane thickness can be further controlled to 5 μm and below.
[0052] This approach overcomes the limitations of traditional stretching methods in preparing ultrathin self-supporting membranes and the inability of electrospinning to balance self-support and mechanical properties in ultrathin films. Because the entire preparation process can achieve stable and continuous preparation of ultrathin films (thickness of 5 μm and below) even under non-ultrathin processing conditions, the core steps of the overall preparation process only include mixed fibrillation, fiber network reinforcement, roll forming, and desalination. The process flow is simple, requires minimal equipment, and has a high tolerance for production errors. The PTFE porous nonwoven fiber membrane preparation process is compatible with the already industrially applied dry solid electrolyte preparation process. The equipment is reusable, and large-scale continuous production can be achieved without significant modifications to existing dry production lines, greatly reducing the equipment, labor, and material costs of PTFE porous nonwoven fiber membranes.
[0053] Meanwhile, the preparation method of PTFE porous nonwoven fiber membrane has a large adjustment space. By adjusting the process parameters of fibrillation treatment, fiber network strengthening treatment conditions, and roll forming process, the degree of fibrillation of PTFE, fiber interlacing density and membrane pore structure can be flexibly controlled to adapt to the customized requirements of membrane performance for different application scenarios.
[0054] Furthermore, the membrane thickness can be further precisely controlled through subsequent extrusion thinning processes, and the bonding force of fiber interlacing nodes can be strengthened through sintering processes, thereby further improving the mechanical properties and structural stability of the membrane.
[0055] Meanwhile, the solvent containing dissolved salt generated during the washing process can be separated, recovered, and reused through simple evaporation and condensation. This enables the reuse of salt materials, reduces the amount of waste generated during production, further lowers production costs, and meets the requirements of green industrial production.
[0056] The following describes the preparation method of PTFE porous nonwoven fiber membrane in conjunction with the above configuration, providing three embodiments and one comparative example.
[0057] Example 1: Figure 2 A scanning electron microscope image of the PTFE-salt particle composite self-supporting membrane in Example 1 provided as an embodiment of this application. Figure 3 A scanning electron microscope image of the PTFE porous nonwoven fiber membrane in Example 1 provided as an embodiment of this application.
[0058] In Example 1, the PTFE raw material is PTFE particles, and the salt particles are lithium bromide.
[0059] First, 100g of lithium bromide and 3g of PTFE particles are premixed at 1500rpm for 3min in a fiberization device.
[0060] Then, at room temperature, the mixture was fiberized at 8000 rpm for 3 minutes to obtain a fibrillated mixture.
[0061] Next, the obtained fibrillated mixture was kneaded for 5 minutes to form a clay-like structure. The kneaded mixture was then progressively thinned using a differential speed roller press, ultimately forming a PTFE-salt particle composite self-supporting membrane of approximately 130 μm. The structure of the PTFE-salt particle composite self-supporting membrane is as follows: Figure 2 As shown.
[0062] Finally, the PTFE-salt particle composite self-supporting membrane was fixed on aluminum foil and transferred to anhydrous ethanol for three washes to remove lithium bromide, yielding a PTFE porous fiber gel. The PTFE porous fiber gel was then evaporated at 80°C to remove the anhydrous ethanol, resulting in a PTFE porous nonwoven fiber membrane. In Example 1, the thickness of the obtained PTFE porous fiber membrane was approximately 16 μm. The microstructure of the PTFE porous fiber membrane is as follows. Figure 3 As shown. Reference Figure 3 Under scanning electron microscopy (SEM), the PTFE porous fiber membrane exhibits a structure in which fibers and pores are interwoven in a uniform manner. Most of the PTFE fibers have a diameter between 300 nm and 700 nm, and the interwoven fibers form a large number of through-pore structures.
[0063] Example 2: Figure 4A scanning electron microscope image of the PTFE porous nonwoven fiber membrane in Example 2 provided as an embodiment of this application.
[0064] In Example 2, the PTFE raw material was PTFE particles, and the salt particles were lithium bromide. The preliminary steps in Example 2 were the same as in Example 1. After preparing the PTFE porous fiber membrane shown in Example 1, the PTFE porous fiber membrane can be further thinned to approximately 6 μm by hot rolling at a constant speed of 100°C along the calendering direction. The microstructure of the PTFE porous nonwoven fiber membrane after roll thinning is as follows... Figure 4 As shown in the figure. SEM results indicate that hot rolling of PTFE porous nonwoven fiber membranes can significantly improve the interweaving degree of PTFE fibers, resulting in smaller pores and a denser structure.
[0065] Comparative Example The comparative example is a commercially available PTFE porous fiber membrane product prepared by the stretching method, with a thickness of 25 μm.
[0066] The PTFE porous nonwoven fiber membranes prepared in the comparative example, Example 1 and Example 2 were cut into samples with a length of 3.3 cm and a width of 2 cm, and their mechanical properties were tested on a tensile testing machine.
[0067] Table 1 is a comparison table of the mechanical properties of Example 1, Example 2 and the comparative example. Figure 5 The diagram shows the mechanical property test results of Embodiment 1, Embodiment 2, and the comparative example provided as an embodiment of this application.
[0068] Table 1
[0069] Refer to Table 1 and Figure 5 The mechanical property test results shown indicate that the PTFE porous fiber membrane prepared in Example 2, after being thinned by hot rolling, can achieve a mechanical strength of 21 MPa and an elastic modulus of 112 MPa. The PTFE strength of Example 1 is close to the mechanical strength of the PTFE fiber membrane in the comparative example, while the mechanical properties of the PTFE fiber membrane in Example 2 are more than three times the mechanical strength of the PTFE fiber membrane in the comparative example.
[0070] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0071] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for preparing a PTFE porous nonwoven fiber membrane, characterized in that, The method includes: The PTFE raw material is uniformly mixed with salt particles, and the mixture is then subjected to fibrillation treatment to obtain a fibrillated mixture. The fibrillated mixture was subjected to fiber network reinforcement treatment and calendered to obtain a PTFE-salt particle composite self-supporting membrane. Depending on the type of salt, the salt particles in the PTFE-salt particle composite self-supporting membrane are removed using a separation method corresponding to the salt particles, thereby obtaining the PTFE porous nonwoven fiber membrane.
2. The method according to claim 1, characterized in that, The mass ratio of PTFE to salt particles ranges from 0.1% to 30%.
3. The method according to claim 1, characterized in that, The types of salts include easily soluble salts or easily decomposed salts; The readily soluble salts include: sodium chloride, sodium sulfate, lithium bromide, lithium chloride, lithium sulfate, lithium ethoxide, sodium ethoxide, sodium acetate, or sodium methanesulfonate. The thermally decomposable salts include: ammonium chloride, ammonium bromide, ammonium iodide, ammonium bicarbonate, ammonium carbonate, ammonium nitrate, ammonium acetate, ammonium benzoate, tetraethylammonium tetrafluoroborate, or triethanolamine.
4. The method according to claim 1, characterized in that, The step of performing fiber network reinforcement treatment on the fibrillated mixture and calendering to obtain a PTFE-salt particle composite self-supporting membrane includes: The fibrillated mixture is kneaded for a preset time at a first preset temperature to obtain a kneaded fibrillated mixture; The kneaded fibrillated mixture is continuously rolled at a second preset temperature to calender it to a preset thickness, thereby obtaining the PTFE-salt particle composite self-supporting membrane.
5. The method according to claim 4, characterized in that, The range of the first preset temperature and the second preset temperature is 25℃~400℃; The preset duration ranges from 0.5 minutes to 10 minutes; The preset thickness ranges from 1μm to 2000μm.
6. The method according to claim 5, characterized in that, After removing the salt particles from the PTFE-salt particle composite self-supporting membrane, the thickness of the resulting PTFE porous nonwoven fiber membrane is less than or equal to 5 μm.
7. The method according to any one of claims 1 to 6, characterized in that, The step of removing the salt particles from the PTFE-salt particle composite self-supporting membrane using a separation method corresponding to the salt particles, based on the type of salt, to obtain the PTFE porous nonwoven fiber membrane, includes: When the salt is of a type that is easily soluble in a solvent, the separation method includes: washing the PTFE-salt particle composite self-supporting membrane with a solvent that can dissolve the salt particles to remove the salt particles from the PTFE-salt particle composite self-supporting membrane, thereby obtaining the PTFE porous nonwoven fiber membrane. When the salt is a type that is easily decomposed by heat, the separation method includes: heating the PTFE-salt particle composite self-supporting membrane to thermally decompose the salt particles, thereby removing the salt particles from the PTFE-salt particle composite self-supporting membrane and obtaining the PTFE porous nonwoven fiber membrane.
8. The method according to claim 7, characterized in that, The step of washing the PTFE-salt particle composite self-supporting membrane with a solvent capable of dissolving the salt particles to remove the salt particles from the PTFE-salt particle composite self-supporting membrane, thereby obtaining the PTFE porous nonwoven fiber membrane, includes: The PTFE-salt particle composite self-supporting membrane is washed multiple times using a solvent that can dissolve the salt particles to remove the salt particles from the PTFE-salt particle composite self-supporting membrane, thereby obtaining a PTFE self-supporting membrane gel. The PTFE self-supporting membrane gel was evaporated to obtain the PTFE porous nonwoven fiber membrane.
9. The method according to claim 7, characterized in that, After obtaining the PTFE porous nonwoven fiber membrane, the method further includes: The PTFE porous nonwoven fiber membrane is thinned by extrusion, and / or the PTFE self-supporting membrane is sintered under preset conditions to obtain a reinforced PTFE porous nonwoven fiber membrane.
10. A PTFE porous nonwoven fiber membrane, characterized in that, The PTFE porous nonwoven fiber membrane is prepared by the PTFE porous nonwoven fiber membrane preparation method according to any one of claims 1 to 9, and the PTFE porous nonwoven fiber membrane is a self-supporting membrane. The PTFE porous nonwoven fiber membrane has a three-dimensional porous network structure formed by interwoven PTFE continuous fibers. The continuous fibers are formed by fibrillation treatment and stretching of PTFE material. The continuous fibers are continuous stretched filaments or strips, and the diameter of the PTFE continuous fibers is 200nm~800nm.