A polytetrafluoroethylene sterilization film, a preparation method and use thereof

Abstract

The application discloses a polytetrafluoroethylene bacteria-removing membrane and a preparation method and application thereof. The bacteria-removing membrane comprises a main body, the main body has non-directional winding channels, one side surface of the main body is a first outer surface, the other side surface is a second outer surface, the first outer surface and the second outer surface are substantially symmetrical, the main body comprises original nodes and support fibers, and part of adjacent nodes are connected by the support fibers. The IPA bubble point of the bacteria-removing membrane is 0.14-0.28 MPa, the density of the bacteria-removing membrane is greater than 400 kg / m 3 , the LRV of the bacteria-removing membrane to Pseudomonas Defectiva is greater than 7, and the Gurley value of the bacteria-removing membrane is 25-50 s·1inch ‑2 ·100ml ‑1 . The bacteria-removing membrane has large membrane holes, high density and relatively winding channels, and can not only ensure efficient interception of bacteria, but also has high flux, and is particularly suitable for liquid sterilization and / or gas sterilization. In addition, the application further provides a preparation method of the bacteria-removing membrane, and the preparation method is convenient, rapid, effective, simple to operate, green and environment-friendly, and suitable for large-scale promotion.

Description

Technical Field

[0001] This invention relates to the field of membrane materials technology, and more specifically to a polytetrafluoroethylene antibacterial membrane, its preparation method, and its uses. Background Technology

[0002] In the biopharmaceutical and food industries, sterilization is often necessary at specific stages to prevent harmful bacteria from affecting product quality. One of the most common sterilization methods is membrane filtration, ensuring the product is virtually bacteria-free. In the 1960s, membrane filters with a pore size of 0.45 μm were considered "sterilization-grade" liquid filters and were successfully applied to the sterilization filtration of injectable drugs. However, Dr. Frances Bowman later observed that certain microorganisms could... 4 ~10 6 cfu / cm 2 When the bacteria reach a high level of filtration, they can penetrate a 0.45μm filter, causing contamination of the culture medium after "sterilization" filtration. Therefore, there is an urgent need in industries such as pharmaceuticals for a membrane with higher filtration precision that can completely trap these bacteria.

[0003] In the early 1980s, based on the ASTM F838 standard method for bacterial retention, Millipore, an American company, pioneered the first truly sterile-grade filter. It was based on a polyvinylidene fluoride (PVDF) membrane. Because the bubble point of this membrane was approximately twice that of the traditional 0.45μm "sterile-grade" membrane, Millipore divided 0.45 by 2, naming it a 0.22μm membrane. Today, the industry consensus is that filter membranes that pass the ASTM F838 test are labeled as 0.22μm or 0.2μm. Here, 0.22μm does not actually measure the pore size of the membrane, but rather indicates that the membrane can effectively retain various bacteria (such as *Pseudomonas degenerates*). Subsequently, various PVDF sterile membranes have been developed. For example, Chinese patent application number CN201110124786.4 discloses a high-strength asymmetric polyvinylidene fluoride microporous membrane, which has… It has strong mechanical strength and retention efficiency; Chinese patent application number 2020113819488 also discloses a polyvinylidene fluoride filter membrane, which has a large flow rate and high tensile strength; however, these membranes also have certain drawbacks, because these sterilization membranes are all made of PVDF material. This type of sterilization membrane cannot withstand strong acids, has relatively poor stability, is not compatible with many liquids, and often cannot meet the requirements of air sterilization (for air sterilization, it is often desirable for the filter membrane to have strong hydrophobicity); this limits the development of sterilization membranes to some extent.

[0004] Compared to PVDF, polytetrafluoroethylene (PTFE) exhibits superior thermal stability, chemical corrosion resistance, and resistance to strong acids and alkalis, playing a crucial role in fields such as biopharmaceuticals, with significant demand gaps both domestically and internationally. Currently, PTFE filter membranes are typically prepared using the methods disclosed in US patents US3953566 and US4187390. This preparation method mainly includes the following steps: mixing PTFE dispersion resin with kerosene as a lubricant, extruding the mixture into a paste, and removing the lubricant; then performing unidirectional or bidirectional stretching below the melting point of PTFE to obtain the PTFE filter membrane.

[0005] For example, Chinese Patent Application No. 2020115812924 discloses a polytetrafluoroethylene (PTFE) porous membrane. The outer surface of this porous membrane includes nodes and fibers, with adjacent nodes connected by fibers. The nodes extend in the same direction. Along a 100μm length along the fiber direction, there are 5-20 nodes with a width of 0.5-10μm; along a 50μm length along the node direction, there are 15-60 fibers with a width of 0.05-1μm. This node and fiber density gives the porous membrane not only high tensile strength and good mechanical properties, but also low pressure loss. Simultaneously, the average pore size of this PTFE porous membrane is 1-20μm, with a porosity of 60-90%, resulting in high flux and high air permeability. It is suitable for filtering stripping and etching solutions in semiconductor manufacturing processes, as well as for use as a breathable membrane in electronic and medical devices.

[0006] However, such porous PTFE membranes cannot be used as sterilization membranes because their pores are relatively large, making it impossible to guarantee efficient bacterial retention. To ensure efficient bacterial retention, researchers generally employ various methods to reduce the pore size of PTFE membranes. However, when the overall pore size of the membrane decreases, the overall flux of the membrane drops significantly (for example, if the pore size is reduced to half its original size, the flux may become one-quarter or even lower). Furthermore, small-pore membranes are particularly prone to clogging, making it difficult to filter fluids for extended periods and resulting in a shorter lifespan. Therefore, such PTFE membranes cannot meet the needs of practical applications, meaning they still cannot be used as sterilization membranes. These problems significantly limit the development of sterilization membranes. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a polytetrafluoroethylene (PTFE) sterilization membrane, its preparation method, and its applications. This sterilization membrane has a high bacterial retention efficiency and a high throughput, making it particularly suitable for liquid sterilization and / or gas sterilization.

[0008] To achieve the above objectives, the present invention provides the following technical solution: a polytetrafluoroethylene (PTFE) antibacterial membrane, comprising a main body having non-directional tortuous pathways within the main body, one side surface of the main body being a first outer surface, and the other side surface of the main body being a second outer surface, the first outer surface and the second outer surface being substantially symmetrical; the main body includes primary nodes and supporting fibers, with some adjacent nodes connected by the supporting fibers; the IPA bubble point of the antibacterial membrane is 0.14-0.28 MPa; the density of the antibacterial membrane is greater than 400 kg / m³. 3 The sterilization membrane has an LRV greater than 7 against defective Pseudomonas aeruginosa.

[0009] The sterilization membrane has a Gurley value of 25-50 s·1 inch. -2 100ml -1 .

[0010] In the main structure of the polytetrafluoroethylene sterilizing membrane provided by this invention, it can be found that there is no skin structure (dense structure). Each outer surface has a certain fiber structure, and these fibers intertwine to form pores of a certain size. Further research shows that the two outer surfaces of the main body (the first outer surface and the second outer surface) are basically symmetrical. In this invention, symmetry means that the fiber structure and membrane pore size of the two outer surfaces of the main body are basically the same (on the outer surface of the membrane, the relatively coarser fiber entities are called surface nodes, and the relatively finer fiber entities are called surface fibers). Therefore, any one of the outer surfaces of this invention can be used as the liquid inlet surface without special requirements. When processing the sterilizing membrane, the process is more convenient, and there is no situation of "reversed liquid inlet and outlet surfaces".

[0011] Through extensive research, the researchers of this invention discovered that, in addition to the conventional view that only by reducing the size of the membrane pores or increasing the membrane thickness can the retention efficiency of bacteria be improved, when the overall pore size of the membrane is controlled within a certain range (it does not require very small pores; the pore size is relatively large), and under the synergistic effect of the high-density membrane structure, it can also have a high retention efficiency of bacteria (i.e., to ensure retention efficiency, one can only reduce the size of the membrane pores or increase the membrane thickness, which is a "technical bias"). Furthermore, due to the relatively large pore size, it also has a high flux, meeting the needs of practical applications. This is likely because the main structure of this invention is similar to a sponge structure, with non-directional tortuous pathways within the main body. These non-directional tortuous pathways refer to irregularly oriented groove structures and / or discretely distributed pore structures (i.e., the original nodes and supporting fibers interweave to form these tortuous pathways), and each non-directional tortuous pathway is interconnected. Such a membrane structure helps to improve the membrane's fluid retention efficiency.

[0012] Furthermore, since the tortuous pathways are formed through the combined action of the original nodes and supporting fibers, and both the original nodes and supporting fibers are solid parts within the membrane body, an increase in membrane density means a greater number and density of original nodes and supporting fibers within the membrane body, leading to the formation of more and more tortuous pathways. This unexpectedly improves the bacterial retention efficiency. Moreover, once the membrane pore size is adjusted to a suitable size (in this invention, the IPA bubble point is used to characterize the overall membrane pore size; a larger bubble point indicates a smaller overall membrane pore size, and vice versa), specifically when the IPA bubble point is 0.14-0.28 MPa, and the membrane as a whole has a high density (greater than 400 kg / m³),... 3 The synergistic effect of the dense primary nodes and supporting fibers inside the membrane, with various pathways intertwined and tortuous, ensures that the membrane has a high retention efficiency for bacteria and also has a good flux. However, such synergistic effect is not suitable for retaining impurities with very small particle sizes (less than 100 nm) or impurities with very large particle sizes (greater than 1 μm).

[0013] Meanwhile, higher-density sterilization membranes also possess good mechanical strength, enabling industrial processing such as folding the filter membrane, which is convenient and effective. In this invention, density refers to a measure of mass within a specific volume; density equals the mass of an object divided by its volume (or can be obtained by dividing weight by membrane thickness), and its unit can be g / m³. 3 or kg / m 3In this invention, the bubble point is used to characterize the overall pore size of the membrane (rather than the pore size of a single membrane pore on its surface; the two are fundamentally different). Generally, the larger the overall pore size of the membrane, the lower the bubble point; the smaller the overall pore size, the higher the bubble point. The bubble point is an important performance characteristic of polymer filter membranes, and it includes the bubble initiation point and the point at which bubbles fully emerge. When continuous bubbling begins in the middle of the filter membrane, the pressure at this point is recorded as the bubble initiation point; when all bubbles have emerged from the filter membrane, the pressure at this point is recorded as the point at which bubbles fully emerge. The methods for testing the bubble point are well known in the art. For example, the procedures for these tests are explained in detail in ASTM F316-70 and ANS / ASTM F316-70 (re-approved in 1976), which are incorporated herein by reference. The test solution used in this invention is IPA (isopropanol). The bubble pressure of the filter membrane in this invention is 0.14-0.28 MPa. Its relatively low bubble pressure indicates that the overall pore size of the polytetrafluoroethylene sterilizing membrane is relatively large, which is beneficial for the high flux of the sterilizing membrane. In addition, because the membrane pores of this invention are relatively large, they are not easily clogged. When sterilizing and filtering various fluids, the fluid can pass through the filter membrane quickly and stably. Furthermore, due to the inherent characteristics of the PTFE membrane and its low dissolution (no additives are added during the preparation process), it is ensured that the effective substances of the drug solution are not significantly affected after passing through the filter membrane.

[0014] In the bacterial retention challenge experiment of the sterilization membrane of the present invention, Pseudomonas aeruginosa (ATCC 19146) with a bacterial diameter of 0.3-0.4 μm was used and tested according to the standard of ASTM F838-2015ae1. The test results showed that the sterilization membrane had an LRV greater than 7 for Pseudomonas aeruginosa, which can effectively capture bacteria and meet the needs of practical applications.

[0015] Compared to liquid sterilization, the flux of the sterilizing membrane is more important in gaseous sterilization. Therefore, in this invention, the flux of the sterilizing membrane was tested using a Gurley permeability tester. The test results showed that the Gurley value of the sterilizing membrane of this invention is 25-50 s·1 inch. -2 100ml -1 This demonstrates that the sterilization membrane has a high flux, fast filtration speed, and can filter a large amount of fluid in a certain period of time, resulting in high economic efficiency per unit time. It is suitable for liquid and gas sterilization, and is particularly suitable for air and liquid filtration in the pharmaceutical industry.

[0016] As a further improvement of the present invention, the IPA foaming point of the sterilizing membrane is 0.16-0.24 MPa; the density of the sterilizing membrane is 430-800 kg / m³. 3 .

[0017] Research has shown that when the density of the sterilization membrane is too high, on the one hand, the membrane manufacturing process becomes extremely complex, making industrialization difficult and resulting in low economic efficiency; on the other hand, excessively high density also means that the pathways formed by the original nodes and supporting fibers are too tortuous, which reduces the filter membrane flux, preventing fluid from passing through the membrane quickly enough to complete sterilization filtration. Therefore, the preferred density of the sterilization membrane in this invention is 430-800 kg / m³. 3 At this density, it is easy to ensure sufficient retention of bacteria in the fluid, while also ensuring that the filter membrane has high tensile strength and compressive strength. With the synergistic effect of IPA bubble point of 0.16-0.24MPa (relatively large overall pore size of the membrane), it also ensures that the membrane has a large flux and dirt holding capacity, and a long service life.

[0018] As a further improvement of the present invention, the original nodes are granular structures with an average SEM diameter of 150-650 nm, and the cross-sectional density of the original nodes is not less than 40 nodes / 100 μm. 2 Preferably, the SEM average diameter of the protonodes is 200-600 nm, and the cross-sectional density of the protonodes is 50-150 per 100 μm. 2 .

[0019] In the main cross-sectional structure of the sterilization membrane of this invention, we found several granular structures, which we call primary nodes. These primary nodes are connected by supporting fibers, and there are gaps between adjacent supporting fibers, which form pathways to facilitate fluid passage. Compared to the supporting fibers, these primary nodes are relatively coarse, with an average SEM diameter of 150-650 nm. This coarseness of the primary nodes contributes to the high mechanical strength of the sterilization membrane as a whole. Furthermore, the number of these primary nodes is relatively large, with a cross-sectional density of not less than 40 per 100 μm. 2Adjacent primary nodes are connected by supporting fibers. The combined effect of these numerous primary nodes and supporting fibers creates many tortuous pathways. This variety in the number and size of primary nodes ensures the stability of each pathway, preventing collapse or shrinkage during filtration. This allows for long-term, efficient bacterial retention, ensuring sufficient bacterial capture while maintaining high flux and low pressure loss in the filter membrane. However, if the primary nodes are too fine, the overall mechanical strength of the membrane will be low, and the stability of each pathway cannot be effectively guaranteed. This can lead to partial pore collapse within the pathways, compromising efficient bacterial retention and causing leakage. Conversely, if the primary nodes are too coarse, these... The presence of primary nodes can actually hinder fluid flow, reducing fluid velocity and resulting in lower membrane filtration speed and higher pressure loss. Conversely, if the cross-sectional density of primary nodes is too low (meaning there are not enough nodes), the membrane's tortuous flow rate will be insufficient, impacting retention efficiency and overall mechanical strength. However, if the cross-sectional density of primary nodes is too high (meaning there are too many nodes), the flow path will be overly tortuous, reducing membrane flux and increasing pressure loss and energy consumption. Therefore, the synergistic effect of appropriate SEM average diameter and cross-sectional density of primary nodes further ensures that the membrane has high flux, high retention efficiency, high strength, and low pressure loss.

[0020] In this invention, the SEM average diameter of the original nodes represents the thickness of the original nodes; while the cross-sectional density of the original nodes represents the number of original nodes within a certain area (the specific area depends on the situation) of the cross-section of the sterilization membrane, thus indicating the number of original nodes on the cross-section. In this invention, the SEM average diameter and cross-sectional density of the original nodes (the cross-section refers to a section cut along the fiber length direction of the membrane surface, which is the direction of membrane movement and longitudinal stretching) can be obtained by characterizing the morphology of the membrane cross-section structure using a scanning electron microscope, and then measuring the diameter and number of the original nodes using computer software (such as Matlab, NIS-Elements, etc.) or manually, thereby further calculating the corresponding SEM average diameter and cross-sectional density. Of course, it is understood that those skilled in the art can also obtain the above parameters through other measurement methods.

[0021] As a further improvement of the present invention, the ratio of the average SEM diameter of the original node to the film thickness is 0.004-0.016; preferably, the ratio is 0.008-0.012.

[0022] As is well known, the fluid filtration process is mainly completed in the thickness direction of the membrane. The fluid passes through the membrane from one surface and exits from the other surface. The primary nodes can be regarded as relatively dense blocky regions with low porosity within the membrane cross-section, while the supporting fibers are regions with higher porosity within the membrane cross-section. When the size of the primary nodes is too large, it will cause considerable resistance to the fluid flow and affect the fluid flow velocity within the membrane, resulting in lower membrane flux and greater pressure loss. Conversely, when the primary nodes are too small, the mechanical strength of the sterilization membrane is too low. Through research, when the ratio of the average SEM diameter of the primary nodes to the membrane thickness is 0.004-0.016, there is a suitable ratio between the two, and the primary nodes are relatively small, which can ensure both membrane strength and high flux.

[0023] As a further improvement of the present invention, the average SEM length of the supporting fiber is 500-2500 nm, and the average SEM diameter of the supporting fiber is 60-300 nm.

[0024] Preferably, the SEM average length of the supporting fibers is 800-2000 nm; the SEM average diameter of the supporting fibers is 90-260 nm; adjacent nodes are connected by supporting fibers, and there are certain gaps between the supporting fibers for fluid to pass through; therefore, the length and width of the supporting fibers affect the overall mechanical strength, retention efficiency, and dirt holding capacity of the sterilization membrane; when the supporting fibers are too short, there will be too many nodes on the membrane cross-section, resulting in greater resistance, pressure loss, and energy consumption when the fluid passes through the sterilization membrane; it will also lead to fewer pores in the membrane (lower porosity), thereby reducing the membrane's dirt holding capacity and flux. The following issues exist: When the supporting fibers are too long, the number of nodes on the overall membrane cross-section is too small, resulting in a low overall membrane density and affecting retention efficiency. Conversely, when the supporting fibers are too thin, the overall mechanical strength of the membrane is insufficient, and the supporting fibers are prone to breakage and pore collapse during fluid flow, making long-term stable filtration impossible. Furthermore, when the supporting fibers are too thick, the fluid flow velocity within the membrane is too low, significantly impacting membrane throughput. Therefore, this invention ensures a high overall membrane density by using supporting fibers of appropriate length and thickness. Simultaneously, this, combined with the size and number of nodes, further guarantees flux, retention efficiency, and mechanical strength.

[0025] The present invention measures the SEM average length and SEM average diameter of the supporting fibers by characterizing the membrane cross-section using a scanning electron microscope, followed by measurement and calculation using computer software (such as Matlab, NIS-Elements, etc.) or manually. The overall SEM average length and average diameter of the cross-section are reflected by measuring the SEM average length and average diameter of the corresponding area. In actual measurement, the membrane cross-section can be characterized first using an electron microscope to obtain the corresponding SEM image, and a certain area, such as 1 μm, can be selected. 2 (1μm x 1μm) or 25μm 2 (5μm x 5μm), the specific area size depends on the actual situation. Then, the SEM length and SEM diameter of the supporting fibers on this area are measured by appropriate computer software or manually. Then, the average SEM length and average SEM diameter of the supporting fibers in this area are calculated to obtain the average SEM length and average SEM diameter of the supporting fibers on the membrane cross section. Of course, those skilled in the art can also obtain the above parameters by other measurement methods. The above measurement methods are for reference only.

[0026] As a further improvement of the present invention, the ratio of the average SEM length to the average SEM diameter of the supporting fiber is 2-20; the ratio of the average SEM length of the supporting fiber to the average SEM diameter of the original node is 1.5-10. Preferably, the ratio of the average SEM length to the average SEM diameter of the supporting fiber is 4-15; the ratio of the average SEM length of the supporting fiber to the average SEM diameter of the original node is 2-8.

[0027] By controlling the support fibers to have a suitable aspect ratio, and simultaneously controlling the ratio of the average SEM length of the support fibers to the average SEM diameter of the original nodes within a suitable range, the overall retention efficiency and mechanical strength of the membrane can be further improved, while also having a high flow rate; and during long-term filtration, it can stably and efficiently retain bacteria, with slow flux decay and a long service life.

[0028] As a further improvement of the present invention, a plurality of the original nodes are stacked on each other to form an original node aggregate, wherein the SEM diameter of the original node aggregate is not less than 0.3 μm.

[0029] Further observation of the membrane cross-section revealed that some primary nodes accumulate together. These accumulated primary nodes are referred to as primary node aggregates. They are relatively coarse, and measurements show that the SEM diameter of the primary node aggregates is no less than 0.3 μm. This further enhances the mechanical properties of the membrane. Furthermore, since the sterilization membrane of this invention is high-density and high-porosity, the presence of primary node aggregates ensures the stability of the tortuous pathways. Even under special circumstances (such as a sudden increase in pressure or a sudden increase in instantaneous fluid flux), the membrane pore structure inside the membrane body is not prone to collapse, further improving the service life of the sterilization membrane.

[0030] As a further improvement of the present invention, the SEM average diameter of the original nodal aggregate is 0.5-1.4 μm, and the cross-sectional density of the original nodal aggregate is 2-18 aggregates / 100 μm. 2 Preferably, the cross-sectional density of the original nodal aggregates is 4-12 aggregates / 100μm. 2 .

[0031] In cross-section, the presence of primary nodal aggregates is beneficial to improving the mechanical strength of the membrane and maintaining the stability of membrane flux. When the diameter of the primary nodal aggregates is too large and / or the number is too large, on the one hand, it will reduce the overall porosity of the membrane and the initial membrane flux will be too low; on the other hand, it will also increase the resistance of the fluid passing through the filter membrane and the pressure loss will be greater. In this invention, the primary nodal aggregates have a suitable diameter and a relatively small number, so that while ensuring the mechanical strength of the membrane, the membrane flux is basically unaffected and remains large.

[0032] In this invention, the SEM average diameter and cross-sectional density of the original nodal aggregates can be obtained by characterizing the morphology of the membrane cross-section structure using a scanning electron microscope, and then by measuring the diameter and number of the original nodal aggregates using computer software (such as Matlab, NIS-Elements, etc.) or manually, thereby further calculating the corresponding SEM average diameter and cross-sectional density; of course, it is understood that those skilled in the art can also obtain the above parameters through other measurement methods.

[0033] As a further improvement of the present invention, both the first outer surface and the second outer surface include surface fibers and surface nodes; adjacent surface nodes are connected by the surface fibers, the SEM average length of the surface fibers is 800-2200 nm, and the aspect ratio of the surface fibers is 4-16. Preferably, the SEM average length of the surface fibers is 1000-2000 nm, and the aspect ratio of the surface fibers is 5-15.

[0034] On the outer surface of this invention, relatively coarse fiber entities are called surface nodes, and relatively fine fiber entities are called surface fibers. Due to basic symmetry, the characteristics (length and thickness) of the corresponding surface fibers and surface nodes on both outer surfaces are basically the same. Research has shown that the length of the surface fibers is an important factor affecting the pore size, tensile strength, and other characteristic properties of the sterilization membrane. The length of the surface fibers is essentially the distance between two adjacent surface nodes. Generally, the longer the surface fibers, the larger the pore size on the surface of the sterilization membrane. The longest surface fibers tend to form the largest pores, while the shortest surface fibers tend to form the smallest pores. When the length of the surface fibers is too large, the overall pore size of the membrane becomes too large, resulting in low sterilization efficiency and low mechanical strength. Conversely, when the length of the surface fibers is too small, the membrane flux becomes too low, and the pressure loss becomes too large. Therefore, a suitable surface fiber is required.

[0035] Research has found that for sterilization membranes, the average SEM length of the surface fibers is 800-2200 nm. This length is relatively suitable, ensuring both the overall flux of the membrane and its efficient retention of bacteria. Besides the length of the surface fibers, the aspect ratio (the ratio of the fiber's length to its width) also needs to be considered. An excessively large aspect ratio can cause the surface fibers to break during fluid filtration, thus affecting retention efficiency. This is especially true for the outer surface, the inlet surface, where the breakage rate of the surface fibers increases significantly when fluid passes through it instantaneously. Furthermore, in practical applications, sterilization membranes typically require... When folded for use, the folded areas of the sterilizing membrane are more prone to breakage and bacterial leakage compared to the non-folded areas. Therefore, it is even more important for the surface fibers to have a suitable aspect ratio to ensure a longer service life of the sterilizing membrane during filtration. At the same time, the aspect ratio of the surface fibers cannot be too small, as this would make the surface fibers too coarse, greatly increasing the resistance of fluid passing through the filter membrane. Meanwhile, with surface fibers of suitable length and thickness on the membrane surface, the lower layer fibers in the membrane structure are interlaced with the upper layer fibers, which is more conducive to improving the retention efficiency. This further ensures that the sterilizing membrane still has high retention efficiency even when the membrane pores are relatively large.

[0036] The measurement of various surface morphology parameters of the filter membrane (such as the average SEM length of surface fibers and the average SEM length of surface nodes) can be performed by characterizing the membrane structure using a scanning electron microscope, followed by measurement using computer software (such as Matlab, NIS-Elements, etc.) or manually, and then performing corresponding calculations. During the membrane fabrication process, in the direction perpendicular to the membrane thickness (if the membrane is a flat sheet, this direction is planar; if the membrane is a hollow fiber membrane, this direction is perpendicular to the radius), its various characteristics, such as pore size distribution, are roughly uniform and consistent. Therefore, the average pore size of the entire plane can be reflected by measuring the average pore size of a portion of the corresponding plane. In actual measurement, the membrane surface can be characterized first using an electron microscope to obtain the corresponding SEM image, and a certain area, such as 1 μm, can be selected. 2 (1μm x 1μm) or 25μm 2 (5μm x 5μm), the specific area size depends on the actual situation. Then, the length and width of the surface fibers and the length and width of the surface nodes on this area are measured by appropriate computer software or manually. Then, calculations are performed to obtain the SEM average length and aspect ratio of the surface fibers and the SEM average length and aspect ratio of the surface nodes in this area. This value can be used as the corresponding characteristic value on the outer surface. Of course, those skilled in the art can also obtain the above parameters by other measurement methods. The above measurement methods are for reference only.

[0037] As a further improvement of the present invention, the SEM average length of the surface nodes is 600-2600 nm, and the aspect ratio of the surface nodes is 1.5-6. Preferably, the SEM average length of the surface nodes is 800-2400 nm, and the aspect ratio of the surface nodes is 2-5.

[0038] On the outer surface of the membrane, relatively coarse fibers are called surface nodes. The length of the surface nodes has a certain influence on the pore area ratio and pore size of the membrane surface, which in turn affects the overall mechanical strength and flux of the membrane. Compared with the existing nodes that are very long (often greater than 20 μm), the surface nodes in this invention are relatively short, with an average SEM length of 600-2600 nm. With this length, large pores are not formed, and the pore size is relatively suitable, which is conducive to ensuring sufficient retention of bacteria. Furthermore, the aspect ratio of the surface nodes is 1.5-6. With the surface nodes of this length and aspect ratio, the membrane surface can obtain a high porosity, which further makes the membrane as a whole have high porosity. That is, the sterilization membrane has high porosity and high density, thereby ensuring that the sterilization membrane of this invention has high retention efficiency and high flux.

[0039] As a further improvement of the present invention, the average density S of the membrane bulk is 45%-85%, and the average density S is calculated by the following formula: S = D 实 / D×100%;

[0040] In the above formula, D 实 D is the sum of the thicknesses of all entities along the thickness direction of the membrane body, where each entity includes the original node and the supporting fiber, and D is the thickness of the membrane body.

[0041] To better demonstrate that the sterilizing membrane of this invention is a high-density filter membrane, this invention uses the characteristic of average density S. Average density refers to the ratio of the sum of the thicknesses of all solid parts in the thickness direction of the membrane body to the membrane thickness. The magnitude of this ratio reflects the area occupied by solid parts in the thickness direction of the membrane body; the larger the ratio, the higher the density of the membrane, the fewer the pores, and thus the higher the density of the membrane. In this invention, the average density S of the membrane body is 45%-85% (preferably, the average density S is 50%-80%), thereby further demonstrating that the sterilizing membrane has a high density. The original nodes and supporting fibers are basically tightly packed together, forming a relatively tortuous path, thus ensuring that the membrane has greater mechanical strength and higher retention efficiency. However, the average density S will not be too high, and a certain gap must exist to ensure that the membrane flux is large and the filtration resistance is not too high.

[0042] The average compactness of the sterilization filter membrane in this application can be measured by characterizing the membrane structure using a scanning electron microscope, followed by measurement using computer software (such as Matlab, NIS-Elements, etc.) or manually, and then performing corresponding calculations. In actual measurement, the membrane cross-section can be characterized first using an electron microscope to obtain the corresponding SEM image. Multiple sites (at least 3) can be selected, and then a straight line parallel to the thickness direction can be drawn along the site. The length of the solid part (support point and support fiber) on the line can be measured, and then divided by the overall membrane thickness to obtain the compactness of that site. The average value can then be taken to obtain the average compactness Q of the membrane. In addition, it should be noted that the fibers in the pore part are not included in the solid part, because the fibers in the pore part are not actually the fibers at the cross-section, but the fibers near the cross-section, and therefore are not counted.

[0043] As a further improvement of the present invention, the thickness of the sterilization membrane is 20-90 μm, the porosity is 55%-85%, and the tensile strength of the sterilization membrane is 10-40 MPa.

[0044] The membrane thickness can be determined by characterizing the membrane structure using a scanning electron microscope, followed by calculation using computer software (such as Matlab, NIS-Elements, etc.) or manual measurement. When the membrane thickness is too small, its mechanical strength will be low; simultaneously, the filtration time will be too short, resulting in ineffective filtration. Conversely, when the membrane thickness is too large, the filtration time will be too long, leading to excessive time costs. The antibacterial membrane of this invention has a thickness of 20-90 μm (preferably 35-75 μm), ensuring that it not only possesses high mechanical strength but also achieves effective filtration with high efficiency, short filtration time, and low time costs.

[0045] Generally, as the overall density of the membrane increases, the porosity of the membrane will be lower. However, in this invention, due to the relatively large pore size of the membrane and its ideal porous structure, the sterilization membrane still maintains a high porosity (i.e., the sterilization membrane of this invention is high-density and high-porosity). Testing shows that the porosity of this sterilization membrane is 55%-85% (preferably 60%-80%), resulting in a high dirt-holding capacity, the ability to trap more impurity particles, and a long service life. Furthermore, the combination of large pore size and high porosity ensures that the sterilization membrane has a large flux and low pressure loss, thus meeting the needs of practical applications. Commonly used porosity testing methods include mercury intrusion porosimetry, density method, and wet-dry membrane weighing method. This application uses the wet-dry membrane weighing method for measurement. Of course, those skilled in the art can obtain the above parameters through other measurement methods; the above measurement methods are for reference only.

[0046] Tensile strength is a crucial indicator for evaluating the mechanical strength of a filter membrane. Under certain conditions, a higher tensile strength indicates better mechanical strength. Tensile strength refers to the membrane's ability to withstand parallel tensile forces. During testing, the membrane sample is subjected to a tensile load until failure. The tensile strength can be calculated based on the maximum tensile load at failure and the change in the membrane sample's dimensions (length). Tensile strength can be measured using a universal tensile testing machine. The testing methods for tensile strength are well-known in the field; for example, ASTM D790 or ISO 178 details the procedures for tensile strength testing. The tensile strength of the polytetrafluoroethylene (PTFE) antibacterial membrane in this invention is 10-40 MPa, indicating that the antibacterial membrane of this invention has high tensile strength, good mechanical properties, high industrial practical value, and fully meets market demands.

[0047] In addition, the present invention also provides a method for preparing a polytetrafluoroethylene antibacterial membrane, comprising the following steps:

[0048] A. Mixing: Mix and stir the polytetrafluoroethylene dispersion resin and lubricant until a paste is obtained;

[0049] B. Blank making: The above paste is pre-pressed into a cylindrical blank;

[0050] C. Extrusion: The preform obtained in step B is extruded to form a flat strip-shaped matrix;

[0051] D. Calendering: Calendering the strip matrix so that the thickness of the calendered strip matrix is ​​15-40% of the thickness of the strip matrix before calendering;

[0052] E. Drying: The strip-shaped substrate is dried to allow the lubricant to evaporate;

[0053] F. Longitudinal stretching: The dried strip matrix is ​​stretched longitudinally at a temperature of 200-320℃ and a stretching ratio of 2-10 times to obtain the first strip matrix.

[0054] G. Lateral stretching: The first strip matrix is ​​laterally stretched at a temperature of 100-300℃ and a stretching ratio of 18-40 times to obtain the second matrix.

[0055] H. First heat setting: The second substrate is placed in an environment with a temperature of 330-390℃ for the first heat setting. During the first heat setting, the longitudinal shrinkage rate and transverse shrinkage rate of the second substrate are not greater than 15%, and the heat setting time is 0.2-3 minutes to obtain the sterilization film semi-finished product.

[0056] I. Second heat setting: The sterile film semi-finished product is placed in an environment with a temperature of 330-390℃ for a second heat setting. During the second heat setting, the longitudinal shrinkage rate and transverse shrinkage rate of the sterile film semi-finished product are not greater than 10%. The second heat setting time is 5-20 minutes to obtain the sterile film.

[0057] As a further improvement of the present invention, the number average molecular weight of the polytetrafluoroethylene dispersion resin is 4 million to 12 million; the lubricant is at least one of lubricating oil, palm oil, naphthenic oil, white oil, aviation kerosene, defatted kerosene, and paraffin wax.

[0058] As a further improvement of the present invention, step A, mixing, specifically refers to mixing and stirring polytetrafluoroethylene dispersion resin and lubricant according to a weight ratio of 1:0.1-1:0.3, and then placing them in an environment with a temperature of 35-50°C for 8-24 hours to obtain a paste.

[0059] The temperature of the second heat setting is at least 10°C higher than that of the first heat setting; the time of the second heat setting is at least 4 minutes longer than that of the first heat setting.

[0060] As a further improvement of the present invention, the thickness of the strip matrix after calendering in step D is 0.8-1.5 mm; the longitudinal stretching rate in step F is 8%-75% / s; and the transverse stretching rate in step G is 25-70% / s.

[0061] In preparing the polytetrafluoroethylene (PTFE) antibacterial membrane of the present invention, the raw material PTFE dispersion resin and lubricant are first mixed and stirred. The number average molecular weight of the PTFE dispersion resin is 4 million to 12 million. Since the filter membrane prepared by the present invention is used for sterilization, its pore size will not be large. When the number average molecular weight is too small, the mechanical strength of the filter membrane will be too low. When the number average molecular weight is too large, it is not easy to form a filter membrane with high porosity, which will lead to a low flux of the filter membrane. By selecting a PTFE dispersion resin with a certain number average molecular weight, the prepared PTFE antibacterial membrane has sufficient mechanical strength and flux.

[0062] The lubricant is at least one of lubricating oil, palm oil, naphthenic oil, white oil, aviation kerosene, degreased kerosene, and paraffin wax. The lubricant can be a single substance or a mixture of several of the above substances. By selecting a suitable lubricant, the polytetrafluoroethylene (PTFE) dispersion resin can be easily processed to obtain the desired antibacterial membrane structure. Preferably, the weight ratio of PTFE dispersion resin to lubricant in this invention is 1:0.1-1:0.3. This weight ratio further ensures uniform mixing of the lubricant and PTFE, facilitating subsequent processing. Excessive lubricant can lead to residues even after drying and other processes; furthermore, it can result in insufficient fiberization and low mechanical strength of the film during film formation, failing to meet the requirements of practical applications.

[0063] After the polytetrafluoroethylene (PTFE) dispersion resin and lubricant are mixed evenly, they are placed in an oven at a temperature of 35-50℃ for 8-24 hours to obtain a paste. The purpose of maturation is to ensure that the PTFE dispersion resin and lubricant are mixed more evenly, and that the lubricant is evenly dispersed in the PTFE dispersion resin, which facilitates subsequent preform extrusion. Next, the paste is pre-pressed into a cylindrical preform. Then, the preform is extruded by placing it into an extruder to form a flat strip matrix.

[0064] Next, calendering is performed: the strip matrix is ​​calendered so that the thickness of the calendered strip matrix is ​​15%-40% of the thickness of the strip matrix before calendering. In this invention, by calendering the extruded strip matrix, the thickness of the strip matrix after calendering is 15%-40% of the thickness of the strip matrix before calendering. The thickness of the strip matrix is ​​greatly reduced, which is conducive to the generation of a certain force between the resin particles and to the full fusion of fibers in the thickness direction (if the change in film thickness before and after calendering is small or even non-existent, it will not be conducive to subsequent fusion and will not form ideal fibers). The structure), and in conjunction with the subsequent first and second heat setting, can form a high-density polytetrafluoroethylene (PTFE) antibacterial membrane, which has an ideal membrane pore and fiber structure; preferably, the thickness of the calendered strip substrate in step D is 0.8-1.5 mm. Strip substrates of this thickness can easily obtain antibacterial membranes with suitable pore size, porosity and thickness after subsequent longitudinal and transverse stretching steps; then drying: the calendered strip substrate is placed in an oven to dry so that the lubricant evaporates, wherein the drying temperature is 100-250℃;

[0065] Then, longitudinal stretching is performed. The dried strip matrix is ​​longitudinally stretched on a film stretching machine at a temperature of 200-320℃ and a stretching ratio of 2-10 times to obtain the first strip matrix. Preferably, the longitudinal stretching rate is 8%-75% / s, and the stretching rate (including longitudinal and transverse stretching rates) is specifically achieved by the distance between the rollers and the speed difference between the rollers. During the longitudinal stretching process, nodes and fibers begin to split. Because the activation energy for fiber formation of PTFE resin is very low, a higher stretching temperature is required. It is easy to form an ideal fiber structure, which, in conjunction with subsequent transverse stretching, forms a suitable membrane pore size to facilitate bacterial retention. The longitudinal stretching temperature is preferably 200-320℃. If the longitudinal stretching temperature exceeds 320℃, the stretching temperature will be above the melting point of polytetrafluoroethylene, and the stretching and sintering processes will occur simultaneously. The stretching and sintering will randomly occur in different areas of the membrane, resulting in very poor uniformity of the stretched membrane. If the longitudinal stretching temperature is below 200℃, the degree of fiberization of the membrane will be insufficient, and a high-density, high-porosity sterilization membrane cannot be formed, resulting in a low final flux and high pressure drop.

[0066] After longitudinal stretching, transverse stretching is performed directly without any heat setting. Heat setting at this stage would lock the structure, resulting in elongated, nearly parallel, and coarse surface nodes. Direct transverse stretching, however, allows for the formation of shorter (and less coarse) nodes on the membrane surface, preventing excessively large pores and maintaining high porosity. The transverse stretching temperature is 100-300℃, with a stretching ratio of 18-40 times. High stretching ratios at these temperatures facilitate achieving ideal pore sizes. Preferably, the transverse stretching rate is 25-70% / s, avoiding excessive speed. This stretching rate and ratio promote fiber separation, increasing porosity and flux. It also facilitates the formation of numerous small primary nodes (with moderate diameters of both the primary nodes and their aggregates), thus increasing the overall membrane density.

[0067] The second substrate, after being stretched laterally, undergoes a first heat setting, which can also be considered a preliminary setting. The preliminary setting time should not be too long, mainly serving the purpose of initial fusion and setting. During the first heat setting process, the membrane should also be stretched to a certain extent to relax stress (eliminate internal stress caused by the incoordination of material microstructure deformation), so that the film has high mechanical strength. On the other hand, the surface shrinkage rate of the second substrate during the first heat setting process should be reduced (both longitudinal and transverse shrinkage rates should not exceed 15%), and it is desirable for it to shrink to a certain extent in the thickness direction, thereby causing fiber fusion (fiber bonding), which is conducive to the formation of a high-density antibacterial membrane. If the first heat setting time is too long, it is easy to cause excessive fusion of fibers, excessively large original nodes and original node aggregates, resulting in uneven membrane pore size and fiber inhomogeneity.

[0068] Finally, a second heat setting is performed. This second heat setting requires a longer time and necessitates keeping the semi-finished sterile membrane taut, essentially maintaining a taut state throughout. By limiting longitudinal and transverse shrinkage (the longitudinal and transverse shrinkage rates of the semi-finished sterile membrane during the second heat setting are both no greater than 10%), shrinkage primarily occurs in the thickness direction. Through this extended second heat setting, recrystallization occurs, and the fibers in the membrane thickness direction fuse (co-filament), resulting in a high-density sterile membrane with suitable pore sizes. Preferably, the temperature of the second heat setting is at least 10°C higher than that of the first heat setting, and the second heat setting time is at least 4 minutes longer than that of the first heat setting. Through the combined effect of the first and second heat setting, the membrane is fully set, resulting in a sterile membrane with good dimensional stability and high strength. This membrane also exhibits high bacterial retention efficiency and high throughput, making it suitable for a wide range of applications.

[0069] As a further improvement of the present invention, the polytetrafluoroethylene sterilization membrane is used for liquid sterilization and / or gas sterilization.

[0070] The beneficial effects of this invention are as follows: The polytetrafluoroethylene (PTFE) antibacterial membrane provided by this invention comprises a main body with non-directional tortuous pathways within it. One side surface of the main body is a first outer surface, and the other side surface is a second outer surface. The first and second outer surfaces are substantially symmetrical. The main body includes primary nodes and supporting fibers, with some adjacent nodes connected by the supporting fibers. The antibacterial membrane has an IPA (increase pressure) of 0.14-0.28 MPa and relatively large pore size. The density of the antibacterial membrane is greater than 400 kg / m³. 3 The high-density, relatively large-pore sterilization membrane ensures sufficient retention of bacteria, with an LRV greater than 7 for defective Pseudomonas, and also has a large flux, with a Gurley value of 25-50 s·1 inch. -2 100ml -1 The sterilization membrane is used for liquid sterilization and / or gas sterilization, and has a wide range of applications. In addition, the present invention also provides a method for preparing the sterilization membrane, which is convenient, fast and effective, simple to operate, green and environmentally friendly, and suitable for large-scale promotion. Attached Figure Description

[0071] Figure 1 The image shows a scanning electron microscope (SEM) image of the longitudinal section of the polytetrafluoroethylene antibacterial membrane prepared in Example 1, with a magnification of 1000×.

[0072] Figure 2 The image shown is a further magnified scanning electron microscope (SEM) image of the longitudinal section of the polytetrafluoroethylene antibacterial membrane prepared in Example 1, with a magnification of 5000×.

[0073] Figure 3 The image shows a scanning electron microscope (SEM) image of the liquid inlet surface of the polytetrafluoroethylene antibacterial membrane prepared in Example 1, with a magnification of 500×.

[0074] Figure 4 The image shown is a further magnified scanning electron microscope (SEM) image of the liquid inlet surface of the polytetrafluoroethylene antibacterial membrane prepared in Example 1, with a magnification of 2000×.

[0075] Figure 5 The image shows a scanning electron microscope (SEM) image of the liquid outlet surface of the polytetrafluoroethylene antibacterial membrane prepared in Example 1, with a magnification of 500×.

[0076] Figure 6 The image shown is a further magnified scanning electron microscope (SEM) image of the liquid outlet surface of the polytetrafluoroethylene sterilization membrane prepared in Example 1, with a magnification of 2000×. Detailed Implementation

[0077] To more clearly illustrate the overall concept of this application, a detailed description is provided below by way of embodiments. Numerous specific details are set forth in the following description to provide a more thorough understanding of this application. However, it will be apparent to those skilled in the art that this application can be implemented without one or more of these details. In other instances, to avoid confusion with this application, some technical features well-known in the art have not been described.

[0078] Unless otherwise specified, the raw materials and equipment used in the preparation of the polytetrafluoroethylene (PTFE) antibacterial membrane in the following embodiments are commercially available. The structural morphology of the PTFE antibacterial membrane was characterized using a Hitachi S-5500 scanning electron microscope.

[0079] Example 1: A method for preparing a polytetrafluoroethylene (PTFE) antibacterial membrane, comprising the following steps:

[0080] A. Mixing: Polytetrafluoroethylene dispersion resin and lubricant are mixed and stirred at a weight ratio of 1:0.2, and then placed in an environment at a temperature of 40°C for 16 hours to mature, thereby obtaining a paste; the number average molecular weight of the polytetrafluoroethylene dispersion resin is 8 million; the lubricant is lubricating oil.

[0081] B. Blank making: The above paste is pre-pressed into a cylindrical blank;

[0082] C. Extrusion: The preform obtained in step B is extruded to form a flat strip-shaped matrix;

[0083] D. Calendering: The strip substrate is calendered so that the thickness of the calendered strip substrate is 30% of the thickness of the strip substrate before calendering; the thickness of the calendered strip substrate in step D is 1.1 mm;

[0084] E. Drying: The strip-shaped substrate is dried to allow the lubricant to evaporate;

[0085] F. Longitudinal stretching: The dried strip matrix is ​​longitudinally stretched at a temperature of 260℃ and a stretching ratio of 6 times to obtain the first strip matrix; the longitudinal stretching rate is 50% / s.

[0086] G. Lateral stretching: The first strip matrix is ​​laterally stretched at a temperature of 220°C and a stretching ratio of 30 times to obtain the second matrix; wherein the lateral stretching rate is 55% / s.

[0087] H. First heat setting: The second substrate is placed in an environment with a temperature of 355℃ for the first heat setting. During the first heat setting, the longitudinal shrinkage rate and the transverse shrinkage rate of the second substrate are both no more than 15%, and the heat setting time is 2 minutes to obtain the sterilization film semi-finished product.

[0088] I. Second heat setting: The sterile film semi-finished product is placed in an environment with a temperature of 370℃ for a second heat setting. During the second heat setting, the longitudinal shrinkage rate and transverse shrinkage rate of the sterile film semi-finished product are both no more than 10%. The second heat setting time is 14 minutes to obtain the sterile film.

[0089] Example 2: A method for preparing a polytetrafluoroethylene antibacterial membrane, comprising the following steps:

[0090] A. Mixing: Polytetrafluoroethylene dispersion resin and lubricant are mixed and stirred at a weight ratio of 1:0.2, and then placed in an environment at a temperature of 45°C for 13 hours to mature, thereby obtaining a paste; the number average molecular weight of the polytetrafluoroethylene dispersion resin is 9 million; the lubricant is palm oil.

[0091] B. Blank making: The above paste is pre-pressed into a cylindrical blank;

[0092] C. Extrusion: The preform obtained in step B is extruded to form a flat strip-shaped matrix;

[0093] D. Calendering: The strip substrate is calendered so that the thickness of the calendered strip substrate is 25% of the thickness of the strip substrate before calendering; the thickness of the calendered strip substrate in step D is 1.2 mm;

[0094] E. Drying: The strip-shaped substrate is dried to allow the lubricant to evaporate;

[0095] F. Longitudinal stretching: The dried strip matrix is ​​longitudinally stretched at a temperature of 250℃ and a stretching ratio of 5 times to obtain the first strip matrix; the longitudinal stretching rate is 40% / s.

[0096] G. Lateral stretching: The first strip matrix is ​​laterally stretched at a temperature of 200°C and a stretching ratio of 28 times to obtain the second matrix; wherein the lateral stretching rate is 50% / s.

[0097] H. First heat setting: The second substrate is placed in an environment with a temperature of 350℃ for the first heat setting. During the first heat setting, the longitudinal shrinkage rate and the transverse shrinkage rate of the second substrate are both no more than 15%, and the heat setting time is 1.5 minutes, to obtain the sterilization film semi-finished product.

[0098] I. Second heat setting: The sterile film semi-finished product is placed in an environment with a temperature of 365℃ for a second heat setting. During the second heat setting, the longitudinal shrinkage rate and transverse shrinkage rate of the sterile film semi-finished product are both no more than 10%. The second heat setting time is 12 minutes to obtain the sterile film.

[0099] Example 3: A method for preparing a polytetrafluoroethylene (PTFE) antibacterial membrane, comprising the following steps:

[0100] A. Mixing: Polytetrafluoroethylene dispersion resin and lubricant are mixed and stirred at a weight ratio of 1:0.15, and then placed in an environment at a temperature of 40°C for 10 hours to obtain a paste; the number average molecular weight of the polytetrafluoroethylene dispersion resin is 5 million; the lubricant is naphthenic oil.

[0101] B. Blank making: The above paste is pre-pressed into a cylindrical blank;

[0102] C. Extrusion: The preform obtained in step B is extruded to form a flat strip-shaped matrix;

[0103] D. Calendering: The strip substrate is calendered so that the thickness of the calendered strip substrate is 34% of the thickness of the strip substrate before calendering; the thickness of the calendered strip substrate in step D is 1.4 mm;

[0104] E. Drying: The strip-shaped substrate is dried to allow the lubricant to evaporate;

[0105] F. Longitudinal stretching: The dried strip matrix is ​​longitudinally stretched at a temperature of 300℃ and a stretching ratio of 8 times to obtain the first strip matrix; the longitudinal stretching rate is 70% / s.

[0106] G. Lateral stretching: The first strip matrix is ​​laterally stretched at a temperature of 270°C and a stretching ratio of 36 times to obtain the second matrix; wherein the lateral stretching rate is 65% / s.

[0107] H. First heat setting: The second substrate is placed in an environment with a temperature of 370℃ for the first heat setting. During the first heat setting, the longitudinal shrinkage rate and the transverse shrinkage rate of the second substrate are both no more than 15%, and the heat setting time is 3 minutes to obtain the sterilization film semi-finished product.

[0108] I. Second heat setting: The sterile film semi-finished product is placed in an environment with a temperature of 390℃ for a second heat setting. During the second heat setting, the longitudinal shrinkage rate and transverse shrinkage rate of the sterile film semi-finished product are both no more than 10%. The second heat setting time is 17 minutes to obtain the sterile film.

[0109] Example 4: A method for preparing a polytetrafluoroethylene (PTFE) antibacterial membrane, comprising the following steps:

[0110] A. Mixing: Polytetrafluoroethylene dispersion resin and lubricant are mixed and stirred at a weight ratio of 1:0.15, and then placed in an environment at a temperature of 36°C for 12 hours to obtain a paste; the number average molecular weight of the polytetrafluoroethylene dispersion resin is 6.5 million; the lubricant is white oil.

[0111] B. Blank making: The above paste is pre-pressed into a cylindrical blank;

[0112] C. Extrusion: The preform obtained in step B is extruded to form a flat strip-shaped matrix;

[0113] D. Calendering: The strip matrix is ​​calendered so that the thickness of the calendered strip matrix is ​​36% of the thickness of the strip matrix before calendering; the thickness of the calendered strip matrix in step D is 1.3 mm;

[0114] E. Drying: The strip-shaped substrate is dried to allow the lubricant to evaporate;

[0115] F. Longitudinal stretching: The dried strip matrix is ​​longitudinally stretched at a temperature of 280℃ and a stretching ratio of 7 times to obtain the first strip matrix; the longitudinal stretching rate is 60% / s.

[0116] G. Lateral stretching: The first strip matrix is ​​laterally stretched at a temperature of 250°C and a stretching ratio of 34 times to obtain the second matrix; the lateral stretching rate in step G is 60% / s.

[0117] H. First heat setting: The second substrate is placed in an environment with a temperature of 365℃ for the first heat setting. During the first heat setting, the longitudinal shrinkage rate and the transverse shrinkage rate of the second substrate are both no more than 15%, and the heat setting time is 2.5 minutes, to obtain the sterilization film semi-finished product.

[0118] I. Second heat setting: The sterile film semi-finished product is placed in an environment with a temperature of 385℃ for a second heat setting. During the second heat setting, the longitudinal shrinkage rate and transverse shrinkage rate of the sterile film semi-finished product are both no more than 10%. The second heat setting time is 16 minutes to obtain the sterile film.

[0119] Example 5: A method for preparing a polytetrafluoroethylene (PTFE) antibacterial membrane, comprising the following steps:

[0120] A. Mixing: Polytetrafluoroethylene dispersion resin and lubricant are mixed and stirred at a weight ratio of 1:0.25, and then placed in an environment at 45°C for 18 hours to mature, thereby obtaining a paste; the number average molecular weight of the polytetrafluoroethylene dispersion resin is 10 million; the lubricant is aviation kerosene.

[0121] B. Blank making: The above paste is pre-pressed into a cylindrical blank;

[0122] C. Extrusion: The preform obtained in step B is extruded to form a flat strip-shaped matrix;

[0123] D. Calendering: The strip substrate is calendered so that the thickness of the calendered strip substrate is 21% of the thickness of the strip substrate before calendering; the thickness of the calendered strip substrate in step D is 1.0 mm;

[0124] E. Drying: The strip-shaped substrate is dried to allow the lubricant to evaporate;

[0125] F. Longitudinal stretching: The dried strip matrix is ​​longitudinally stretched at a temperature of 240℃ and a stretching ratio of 4 times to obtain the first strip matrix; the longitudinal stretching rate is 30% / s.

[0126] G. Lateral stretching: The first strip matrix is ​​laterally stretched at a temperature of 180°C and a stretching ratio of 24 times to obtain the second matrix; wherein the lateral stretching rate is 40% / s.

[0127] H. First heat setting: The second substrate is placed in an environment with a temperature of 340℃ for the first heat setting. During the first heat setting, the longitudinal shrinkage rate and the transverse shrinkage rate of the second substrate are both no more than 15%, and the heat setting time is 1 minute, to obtain the sterilization film semi-finished product.

[0128] I. Second heat setting: The sterile film semi-finished product is placed in an environment with a temperature of 350℃ for a second heat setting. During the second heat setting, the longitudinal shrinkage rate and transverse shrinkage rate of the sterile film semi-finished product are both no more than 10%. The second heat setting time is 10 minutes to obtain the sterile film.

[0129] Example 6: A method for preparing a polytetrafluoroethylene (PTFE) antibacterial membrane, comprising the following steps:

[0130] A. Mixing: Mix the polytetrafluoroethylene dispersion resin and lubricant at a weight ratio of 1:0.25, then place them in an environment at 48°C for 24 hours to mature, thereby obtaining a paste.

[0131] The polytetrafluoroethylene dispersion resin has a number average molecular weight of 11 million; the lubricant is degreased kerosene.

[0132] B. Blank making: The above paste is pre-pressed into a cylindrical blank;

[0133] C. Extrusion: The preform obtained in step B is extruded to form a flat strip-shaped matrix;

[0134] D. Calendering: The strip substrate is calendered so that the thickness of the calendered strip substrate is 20% of the thickness of the strip substrate before calendering; the thickness of the calendered strip substrate in step D is 0.9 mm;

[0135] E. Drying: The strip-shaped substrate is dried to allow the lubricant to evaporate;

[0136] F. Longitudinal stretching: The dried strip matrix is ​​longitudinally stretched at a temperature of 220℃ and a stretching ratio of 3 times to obtain the first strip matrix; the longitudinal stretching rate is 20% / s.

[0137] G. Lateral stretching: The first strip matrix is ​​laterally stretched at a temperature of 150°C and a stretching ratio of 22 times to obtain the second matrix; wherein the lateral stretching rate is 30% / s.

[0138] H. First heat setting: The second substrate is placed in an environment with a temperature of 335℃ for the first heat setting. During the first heat setting, the longitudinal shrinkage rate and the transverse shrinkage rate of the second substrate are both no more than 15%, and the heat setting time is 0.5 minutes, to obtain the sterilization film semi-finished product.

[0139] I. Second heat setting: The sterile film semi-finished product is placed in an environment with a temperature of 345℃ for a second heat setting. During the second heat setting, the longitudinal shrinkage rate and transverse shrinkage rate of the sterile film semi-finished product are both no more than 10%. The second heat setting time is 8 minutes to obtain the sterile film.

[0140] Example 7: A method for preparing a polytetrafluoroethylene (PTFE) antibacterial membrane, comprising the following steps:

[0141] Based on Example 1, the longitudinal stretching rate in step F was set to 5% / s, the transverse stretching rate in step G was set to 20% / s, and all other preparation conditions remained unchanged, to obtain the corresponding sterilization membrane.

[0142] Example 8: A method for preparing a polytetrafluoroethylene (PTFE) antibacterial membrane, comprising the following steps:

[0143] Based on Example 1, the longitudinal stretching rate in step F was set to 90% / s, the transverse stretching rate in step G was set to 80% / s, and all other preparation conditions remained unchanged, to obtain the corresponding sterilization membrane.

[0144] Example 9: A method for preparing a polytetrafluoroethylene (PTFE) antibacterial membrane, comprising the following steps:

[0145] Based on Example 1, the number average molecular weight of the polytetrafluoroethylene dispersion resin in step A was set to 3 million; the temperature of the second heat setting in step I was set to 360°C (5°C higher than the first heat setting temperature), and the second heat setting time was set to 5 min (3 min longer than the first heat setting time), with all other conditions remaining unchanged, to obtain a sterile film.

[0146] Comparative Example 1: A method for preparing a polytetrafluoroethylene antibacterial membrane, comprising the following steps:

[0147] Based on Example 1, without calendering, the flat strip substrate formed by extrusion is directly dried; at the same time, during the first heat setting, the longitudinal shrinkage rate and transverse shrinkage rate of the second substrate are not controlled, and during the second heat setting, the longitudinal shrinkage rate and transverse shrinkage rate of the sterilization film semi-finished product are not controlled; with other conditions unchanged, the corresponding sterilization film is obtained.

[0148] Comparative Example 2: A method for preparing a polytetrafluoroethylene antibacterial membrane, comprising the following steps:

[0149] A. Mixing: Polytetrafluoroethylene dispersion resin and lubricant are mixed and stirred at a weight ratio of 1:0.2, and then placed in an environment at a temperature of 40°C for 16 hours to mature, thereby obtaining a paste; the number average molecular weight of the polytetrafluoroethylene dispersion resin is 8 million; the lubricant is lubricating oil.

[0150] B. Blank making: The above paste is pre-pressed into a cylindrical blank;

[0151] C. Extrusion: The preform obtained in step B is extruded to form a flat strip-shaped matrix;

[0152] D. Drying: The strip-shaped substrate is dried to allow the lubricant to evaporate;

[0153] E. Longitudinal stretching: The dried strip matrix is ​​longitudinally stretched at a temperature of 260℃ and a stretching ratio of 2 times to obtain the first strip matrix; the longitudinal stretching rate is 50% / s.

[0154] F. Lateral stretching: The first strip matrix is ​​laterally stretched at a temperature of 220°C and a stretching ratio of 16 times to obtain the second matrix; wherein the lateral stretching rate is 55% / s.

[0155] G. First heat setting: The second substrate is placed in an environment with a temperature of 355℃ for the first heat setting, and the heat setting time is 2 minutes to obtain the sterilization film semi-finished product.

[0156] H. Second heat setting: The sterile film semi-finished product is placed in an environment with a temperature of 370℃ for a second heat setting for 14 minutes to obtain the sterile film.

[0157] Various tests were conducted on the antibacterial membranes prepared in Examples 1-9 and Comparative Examples 1 and 2 to obtain parameters such as IPA bubble point, density, LRV against defective Pseudomonas, gas flux (Gurley value), porosity, and tensile strength.

[0158] Table 1

[0159] Sample IPA foaming point / MPa <![CDATA[Density kg / m 3 > LRV <![CDATA[Gurley value / s·1 inch -2 ·100 ml -1 > Example 1 0.19 600 Greater than 7 35 Example 2 0.21 650 Greater than 7 40 Example 3 0.16 500 Greater than 7 28 Example 4 0.17 550 Greater than 7 30 Example 5 0.23 700 Greater than 7 42 Example 6 0.25 760 Greater than 7 48 Example 7 0.20 680 Greater than 7 41 Example 8 0.18 530 Greater than 7 34 Example 9 0.20 570 Greater than 7 38 Comparative Example 1 0.10 300 3.6 30 Comparative Example 2 0.36 350 Greater than 7 160

[0160] Table 2

[0161] Sample Thickness / μm Porosity / % Tensile strength / MPa Average density S / % Example 1 50 70 26 65 Example 2 45 65 30 70 Example 3 70 76 35 51 Example 4 60 74 32 55 Example 5 40 62 21 73 Example 6 30 60 23 78 Example 7 48 67 27 67 Example 8 52 72 18 58 Example 9 49 68 22 61 Comparative Example 1 160 60 12 30 Comparative Example 2 40 30 8 39

[0162] As shown in Tables 1 and 2, the sterilization membranes prepared in Examples 1 to 9 have relatively large pores and high density, which makes them not only highly efficient at retaining bacteria but also have high throughput, good tensile strength, and high mechanical strength, making them suitable for various processing and with a wide range of applications. In contrast, the sterilization membrane prepared in Comparative Example 1 has relatively large pores, so even if the membrane is made thicker, its bacterial retention efficiency is still poor. The sterilization membrane in Comparative Example 2 maintains retention efficiency by making the pores smaller, but its throughput is significantly reduced, which cannot meet the needs of practical applications.

[0163] Structural characterization: The morphology of the polytetrafluoroethylene antibacterial membranes obtained in each embodiment was characterized using scanning electron microscopy to obtain the required data.

[0164] Table 3: Corresponding characteristics of original nodes and original node aggregates

[0165]

[0166] Comparative Examples 1 and 2 did not employ a calendering process during the preparation of the sterilization membrane, nor did they control the shrinkage of the membrane surface during the second heat setting. This resulted in insufficient fusion of the cross-sectional fibers in the thickness direction of the corresponding sterilization membranes, leading to excessively small diameters and a small number of original nodes and clusters of original nodes, further resulting in excessively low density of the sterilization membranes. In contrast, Example 7, compared with Example 1, showed that due to excessively slow transverse and longitudinal stretching rates, the original nodes formed were excessively large in diameter and numerous, resulting in a significant decrease in the flux of the sterilization membrane in Example 7 compared to that in Example 1.

[0167] However, the diameter of the sterilization film in Example 8 was too small and the number of films was too few, which resulted in a significant decrease in the mechanical strength of the sterilization film in Example 8 compared to that in Example 1.

[0168] Table 4: Corresponding characteristics of supporting fibers

[0169]

[0170]

[0171] Table 5: Corresponding characteristics of surface fibers and surface nodes

[0172]

[0173] As can be seen from the tables above, the polytetrachloroethylene antibacterial membranes prepared in Examples 1-9 of the present invention all have ideal fiber structures, which are beneficial to the polytetrachloroethylene antibacterial membranes having high tensile strength, high throughput and sufficient retention of bacteria.

[0174] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A polytetrafluoroethylene antibacterial membrane, characterized in that: The device includes a main body with a non-directional tortuous path inside. One side surface of the main body is a first outer surface, and the other side surface of the main body is a second outer surface. The first outer surface and the second outer surface are substantially symmetrical. The main body includes original nodes and supporting fibers, and some adjacent nodes are connected by supporting fibers; The IPA bubble point of the sterilization membrane is 0.14-0.28 MPa; The density of the sterilization membrane is 400 kg / m³. 3 -800kg / m 3 ; The sterilization membrane has an LRV greater than 7 against defective Pseudomonas aeruginosa. The sterilization membrane has a Gurley value of 25-50 s·1 inch. -2 100ml -1 .

2. The polytetrafluoroethylene antibacterial membrane according to claim 1, characterized in that: The IPA bubble point of the sterilization membrane is 0.16-0.24 MPa; The density of the sterilizing membrane is 430-800 kg / m³. 3 .

3. The polytetrafluoroethylene antibacterial membrane according to claim 1, characterized in that: The protonodes have a granular structure with an average SEM diameter of 150-650 nm and a cross-sectional density of no less than 40 per 100 μm. 2 .

4. The polytetrafluoroethylene antibacterial membrane according to claim 1, characterized in that: The ratio of the average SEM diameter of the original node to the film thickness is 0.004-0.

016.

5. The polytetrafluoroethylene antibacterial membrane according to claim 4, characterized in that: The ratio of the average SEM diameter of the original node to the film thickness is 0.008-0.

012.

6. The polytetrafluoroethylene antibacterial membrane according to claim 1, characterized in that: The average SEM length of the supporting fiber is 500-2500 nm, and the average SEM diameter of the supporting fiber is 60-300 nm.

7. The polytetrafluoroethylene antibacterial membrane according to claim 1, characterized in that: The ratio of the average SEM length to the average SEM diameter of the supporting fiber is 2-20. The ratio of the average SEM length of the supporting fiber to the average SEM diameter of the original node is 1.5-10.

8. The polytetrafluoroethylene antibacterial membrane according to claim 1, characterized in that: Several of the original nodes are stacked on top of each other to form an original node aggregate, and the SEM diameter of the original node aggregate is not less than 0.3 μm.

9. The polytetrafluoroethylene antibacterial membrane according to claim 8, characterized in that: The average SEM diameter of the original nodal aggregates was 0.5-1.4 μm. The cross-sectional density of the original nodal aggregates is 2-18 aggregates / 100μm. 2 .

10. The polytetrafluoroethylene antibacterial membrane according to claim 1, characterized in that: Both the first outer surface and the second outer surface include surface fibers and surface nodes; adjacent surface nodes are connected by the surface fibers, the SEM average length of the surface fibers is 800-2200 nm, and the aspect ratio of the surface fibers is 4-16.

11. The polytetrafluoroethylene antibacterial membrane according to claim 10, characterized in that: The average SEM length of the surface nodes is 600-2600 nm, and the aspect ratio of the surface nodes is 1.5-6.

12. The polytetrafluoroethylene antibacterial membrane according to claim 10, characterized in that: The average density S of the membrane bulk is 45%-85%, and the average density S is calculated by the following formula: S=D 实 / D×100%; In the above formula, D 实 D is the sum of the areas of all entities within a certain region along the thickness direction of the membrane body, where the entities include the original nodes and the supporting fibers.

13. The polytetrafluoroethylene antibacterial membrane according to claim 1, characterized in that: The sterilization membrane has a thickness of 20-90 μm and a porosity of 55%-85%; the tensile strength of the sterilization membrane is 10-40 MPa.

14. A method for preparing a polytetrafluoroethylene antibacterial membrane according to any one of claims 1 to 13, characterized in that: Includes the following steps: A. Mixing: Mix and stir the polytetrafluoroethylene dispersion resin and lubricant until a paste is obtained; B. Blank making: The above paste is pre-pressed into a cylindrical blank; C. Extrusion: The preform obtained in step B is extruded to form a flat strip-shaped matrix; D. Calendering: The strip matrix is ​​calendered so that the thickness of the calendered strip matrix is ​​15-40% of the thickness of the strip matrix before calendering; E. Drying: The strip-shaped substrate is dried to allow the lubricant to evaporate; F. Longitudinal stretching: The dried strip matrix is ​​stretched longitudinally at a temperature of 200-320℃ and a stretching ratio of 2-10 times to obtain the first strip matrix. G. Lateral stretching: The first strip matrix is ​​laterally stretched at a temperature of 100-300℃ and a stretching ratio of 18-40 times to obtain the second matrix. H. First heat setting: The second substrate is placed in an environment with a temperature of 330-390℃ for the first heat setting. During the first heat setting, the longitudinal shrinkage rate and transverse shrinkage rate of the second substrate are not greater than 15%, and the heat setting time is 0.2-3 minutes to obtain the sterilization film semi-finished product. I. Second heat setting: The sterile film semi-finished product is placed in an environment with a temperature of 330-390℃ for a second heat setting. During the second heat setting, the longitudinal shrinkage rate and transverse shrinkage rate of the sterile film semi-finished product are not greater than 10%. The second heat setting time is 5-20 minutes to obtain the sterile film.

15. The method for preparing a polytetrafluoroethylene antibacterial membrane according to claim 14, characterized in that: The number average molecular weight of the polytetrafluoroethylene dispersion resin is 4 million to 12 million. The lubricant is at least one of the following: lubricating oil, palm oil, naphthenic oil, white oil, aviation kerosene, degreased kerosene, and paraffin wax.

16. The method for preparing a polytetrafluoroethylene antibacterial membrane according to claim 14, characterized in that: Step A, mixing, specifically refers to mixing and stirring polytetrafluoroethylene dispersion resin and lubricant at a weight ratio of 1:0.1-1:0.3, then placing it in an environment at a temperature of 35-50℃ for 8-24 hours to obtain a paste. The temperature of the second heat setting is at least 10°C higher than that of the first heat setting; the time of the second heat setting is at least 4 minutes longer than that of the first heat setting.

17. The method for preparing a polytetrafluoroethylene antibacterial membrane according to claim 14, characterized in that: The thickness of the strip matrix after calendering in step D is 0.8-1.5 mm; In step F, the longitudinal stretching rate is 8%-75% / s, and in step G, the transverse stretching rate is 25-70% / s.

18. The use of a polytetrafluoroethylene antibacterial membrane as described in any one of claims 1-13, characterized in that: The polytetrafluoroethylene sterilization membrane is used for liquid sterilization and / or gas sterilization.

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