CN116585906A - Polytetrafluoroethylene sterilizing film and preparation method and application thereof - Google Patents
Polytetrafluoroethylene sterilizing film and preparation method and application thereof Download PDFInfo
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- CN116585906A CN116585906A CN202310522966.0A CN202310522966A CN116585906A CN 116585906 A CN116585906 A CN 116585906A CN 202310522966 A CN202310522966 A CN 202310522966A CN 116585906 A CN116585906 A CN 116585906A
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- 239000004810 polytetrafluoroethylene Substances 0.000 title claims abstract description 99
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- -1 Polytetrafluoroethylene Polymers 0.000 title claims abstract description 97
- 238000002360 preparation method Methods 0.000 title abstract description 16
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- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/30—Polyalkenyl halides
- B01D71/32—Polyalkenyl halides containing fluorine atoms
- B01D71/36—Polytetrafluoroethene
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
- B01D53/228—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion characterised by specific membranes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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Abstract
The invention discloses a polytetrafluoroethylene sterilization film and a preparation method and application thereof, wherein the sterilization film comprises a main body, a non-directional tortuous path is arranged in the main body, one side surface of the main body is a first outer surface, the other side surface is a second outer surface, and the first outer surface and the second outer surface are basically symmetrical; the main body comprises original nodes and supporting fibers, and part of adjacent nodes are connected through the supporting fibers; the IPA bubble point of the sterilizing film is 0.14-0.28MPa; the density of the degerming film is more than 400kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the The LRV of the degerming film against the defect pseudomonas is more than 7; the Gurley value of the degerming film is 25-50s·1inch ‑2 ·100ml ‑1 The method comprises the steps of carrying out a first treatment on the surface of the The degerming membrane has larger membrane holes, higher density and relatively tortuous passages, ensures high-efficiency interception of bacteria, has high flux and is particularly suitable for liquid degerming and/or gas degerming; in addition, the invention also provides a preparation method of the degerming film, which is convenient, quick and effective, simple to operate, environment-friendly and suitable for large-scale popularization.
Description
Technical Field
The invention relates to the technical field of membrane materials, in particular to a polytetrafluoroethylene sterilization membrane and a preparation method and application thereof.
Background
In the fields of biopharmaceutical, food and the like, in order to preventVarious harmful bacteria affect the quality of products, and sterilization is often required in corresponding links; one of the most common ways of sterilization at present is to sterilize the corresponding product through a filter membrane, so as to ensure that the product almost contains no bacteria; in the 60 s of the 20 th century, a 0.45 μm pore size membrane filter was considered to be a "sterilization grade" liquid filter and was successfully applied to sterilization filtration of injections. However, it was later observed by Francis Bowman doctor in the United states that a certain microorganism was present at 10 4 ～10 6 cfu/cm 2 Can penetrate 0.45 μm filters, resulting in contamination of the "sterilized" filtered media; thus, there is an urgent need in the pharmaceutical industry for a membrane with improved filtration accuracy that can completely retain such bacteria.
At the beginning of the 80 s, based on ASTM F838 bacteria entrapment standard method, the first truly sterilizing grade filter was introduced by Millipore corporation, usa, which was based on polyvinylidene fluoride (PVDF) filtration membranes, and since the bubble point value of such membranes was about twice that of conventional 0.45 μm "sterilizing grade" membranes, millipore was divided by 0.45 by 2 and named 0.22 μm membranes. Today, a common consensus within the industry is: the pore size of the filter membrane which can be tested by the ASTMF838 is nominally 0.22 μm or 0.2 μm, wherein the 0.22 μm does not truly measure the pore size of the filter membrane, but rather indicates that the membrane can effectively retain various bacteria (such as pseudomonas defectives for example); various PVDF sterilizing membranes have been developed subsequently, for example, china patent with the application number CN201110124786.4 discloses a high-strength asymmetric polyvinylidene fluoride microporous membrane which has strong mechanical strength and interception efficiency; chinese patent application No. 2020113819488 also discloses a polyvinylidene fluoride filtration membrane having a greater flow rate and a higher tensile strength; however, these membranes also have certain drawbacks, because they are made of PVDF materials, and they are not strong acid resistant, relatively weak in stability, and not compatible with many liquids, nor are they often satisfactory for air sterilization (strong hydrophobicity is often desired for the membranes); this limits to some extent the development of the sterilizing film.
Compared with PVDF materials, polytetrafluoroethylene materials have the characteristics of excellent thermal stability, chemical corrosion resistance, strong acid and alkali resistance and the like, play a very important role in the fields of biopharmaceuticals and the like, and have larger demand gaps at home and abroad; currently, polytetrafluoroethylene filters are generally prepared using the preparation methods disclosed in U.S. Pat. nos. US3953566 and US4187390, which mainly comprise the steps of: mixing polytetrafluoroethylene dispersion resin with lubricant kerosene, extruding in a paste state, and removing the lubricant; and then stretching unidirectionally or bidirectionally below the melting point of the polytetrafluoroethylene to obtain the polytetrafluoroethylene filtering membrane.
For example, china patent with application number 2020115812924 discloses a polytetrafluoroethylene porous membrane, wherein the outer surface of the porous membrane comprises nodes and fibers, the adjacent nodes are connected through the fibers, the extending directions of the nodes are consistent, and 5-20 nodes with the width of 0.5-10 μm are arranged along the length of 100 μm in the direction of the fibers; 15-60 fibers with a width of 0.05-1 μm along the length of 50 μm in the direction of the node; the porous membrane has larger tensile strength, good mechanical property and smaller pressure loss due to the node density and the fiber density; meanwhile, the polytetrafluoroethylene porous membrane has an average pore diameter of 1-20 mu m, a porosity of 60-90%, a large flux and a large ventilation amount, and is suitable for filtering stripping liquid and etching liquid in a semiconductor process and serving as a ventilation membrane in electronic equipment and medical equipment.
However, such polytetrafluoroethylene porous membrane cannot be used as a sterilizing membrane because the membrane pores are relatively large, and high-efficiency interception of bacteria cannot be ensured; in order to ensure efficient interception of bacteria, the existing research personnel generally adopt various modes to make membrane holes of a polytetrafluoroethylene membrane small, but when the aperture of the whole membrane is reduced, the flux of the whole membrane is greatly reduced (for example, the membrane holes become smaller to be half of the original flux, and the flux may become one fourth of the original flux or even lower), in addition, a small-hole filter membrane is particularly easy to block, corresponding fluid cannot be filtered for a long time, and the service life is short; then, the polytetrafluoroethylene film cannot meet the practical application requirements, that is, the polytetrafluoroethylene film still cannot be used as a sterilization film, and the development of the sterilization film is greatly limited due to the problems.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention aims to provide a polytetrafluoroethylene sterilization film, a preparation method and application thereof, wherein the sterilization film has high interception efficiency on bacteria, and meanwhile, the sterilization film has high flux, and is particularly suitable for liquid sterilization and/or gas sterilization.
In order to achieve the above purpose, the present invention provides the following technical solutions: a polytetrafluoroethylene sterilization membrane comprising a main body, wherein a non-directional tortuous path is arranged in the main body, one side surface of the main body is a first outer surface, the other side surface of the main body is a second outer surface, and the first outer surface and the second outer surface are basically symmetrical; the main body comprises original nodes and supporting fibers, and part of adjacent nodes are connected through the supporting fibers; the IPA bubble point of the sterilizing film is 0.14-0.28MPa; the density of the degerming film is more than 400kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the The LRV of the degerming film against the pseudomonas defectives is greater than 7;
the Gurley value of the degerming film is 25-50s.1inch -2 ·100ml -1 。
In the main structure of the polytetrafluoroethylene sterilizing membrane provided by the invention, the invention does not have any cortex structure (compact structure), and each outer surface has a certain fiber structure, and the fibers mutually encircle and stagger to form holes with certain aperture; further research shows that the two outer surfaces (the first outer surface and the second outer surface) of the main body are basically symmetrical, and the symmetry refers to that the characteristics of the fiber structures, the membrane pore sizes and the like of the two outer surfaces of the main body are basically the same (on the outer surface of the membrane, a relatively thick fiber entity is called a surface node, and a relatively thin fiber entity is called a surface fiber), so that any outer surface of the main body can be used as a liquid inlet surface, no special requirement exists, and the process is more convenient when the degerming membrane is subjected to various processing treatments, and the situation of 'liquid inlet and outlet surface opposite' does not exist;
The researchers of the invention find that, in addition to the conventional thinking that only the membrane hole is made small or the membrane thickness is increased to improve the interception efficiency of bacteria, when the whole pore diameter of the membrane hole is controlled in a certain range (no hole with small pore diameter is needed, the pore diameter of the membrane hole is bigger), under the synergistic effect of the high-density structure of the membrane, the membrane hole has very high interception efficiency on bacteria (namely, the interception efficiency is ensured, only the membrane hole is made small or the membrane thickness is increased, which belongs to 'technical prejudice'), and meanwhile, the membrane hole is relatively bigger, and has very high flux, so that the requirements of practical application are met; this is probably because the main body structure of the present invention is a sponge-like structure, and has a non-directional tortuous path in the main body, wherein the non-directional tortuous path refers to a randomly oriented grooved structure and/or a discretely distributed hole structure (i.e., the tortuous path is formed by interlacing the primary nodes and the supporting fibers), and the non-directional tortuous paths are mutually communicated; such a membrane structure helps to increase the efficiency of the membrane in retaining fluid;
furthermore, as the corresponding tortuous paths are formed under the combined action of the original nodes and the supporting fibers, and the original nodes and the supporting fibers are solid parts in the film main body, when the density of the film is increased, the more and more dense the original nodes and the supporting fibers in the film main body are, and then more tortuous paths are formed, so that the interception efficiency of bacteria is unexpectedly improved; with the pore diameter of the membrane being adjusted to a proper size (the membrane is characterized by the IPA bubble point, the larger the bubble point is, the smaller the membrane is, the smaller the bubble point is, the larger the membrane is, namely when the IPA bubble point is 0.14-0.28MPa, the membrane is further provided with higher density with the whole membrane, and the density is more than 400kg/m 3 (the original points and the supporting fibers in the membrane body are very dense, and various passages are staggered and bent), so that the membrane can have high interception efficiency on bacteria and good flux; however, such synergy is not suitable for trapping very small particle size impurities (less than 100 nm) nor for trapping very large particle size impurities (greater than 1 um);
at the same time, compared withThe high-density sterilization film has good mechanical strength, can be subjected to industrial treatment, such as operation of folding the filter film, and is convenient and effective to operate; density in the context of the present invention means a measure of the mass within a specified volume, the density being equal to the mass of the object divided by the volume (which can also be obtained by dividing the grammage by the film thickness) in g/m 3 Or kg/m 3 The method comprises the steps of carrying out a first treatment on the surface of the In the invention, the bubble point is used for representing the size of the pore diameter of the integral pore of the membrane (instead of the pore diameter of the membrane pores on a single surface, which are essentially different), and generally, the larger the pore diameter of the integral pore of the membrane is, the lower the bubble point is; the smaller the pore diameter of the integral pore of the membrane is, the higher the bubble point is; bubble point is an important performance feature of polymeric filters, including bubble point and complete out-bubble point; when continuous bubble emergence is started in the middle of the filter membrane, reading the pressure at the moment, and taking the pressure as a bubble point; when the filter membrane is completely foamed, reading the pressure at the moment to be used as a complete foaming point; bubble point testing methods are well known in the art. The procedure for these tests is explained in detail, for example, in ASTM F316-70 and ANS/ASTM F316-70 (re-approval 1976), which are incorporated herein by reference. The test liquid used in the invention is IPA (isopropyl alcohol), and the bubble pressure of the IPA bubble point of the filter membrane in the invention is 0.14-0.28MPa; the bubble point bubble pressure is relatively small, which indicates that the pore diameter of the whole hole of the polytetrafluoroethylene sterilization film is relatively large, thus being beneficial to the high flux of the sterilization film; in addition, as the membrane holes are relatively large and are not easy to block, when various fluids are subjected to sterilization and filtration, the fluids can rapidly and stably pass through the filter membrane; due to the self characteristics of the PTFE membrane, the PTFE membrane has low dissolution (various additives are not added in the preparation process), so that the effective substances of the PTFE membrane are not influenced basically after the liquid medicine passes through the filter membrane;
When the bacteria interception challenge experiment is carried out on the degerming film, the degerming film adopts the defect pseudomonas (ATCC 19146) with the bacterial diameter of 0.3-0.4 mu m, and tests are carried out according to the standards of ASTM F838-2015ae1, and the degerming film is found to have the LRV of more than 7 on the defect pseudomonas, so that the bacteria can be sufficiently caught, and the requirements of practical application are met;
in the case of gas, compared with liquid sterilizationIn sterilization, the flux of the sterilization film is more important, so that the sterilization film is subjected to flux test by using a Gurley air permeability tester, and the Gurley air permeability tester shows that the Gurley air permeability of the sterilization film is 25-50 s.1inch -2 ·100ml -1 Therefore, the degerming membrane has higher flux, high filtering speed, capability of filtering more fluid in a certain time, high economic benefit in unit time, suitability for liquid degerming and gas degerming, and particular suitability for air and liquid filtering in the pharmaceutical industry.
As a further improvement of the present invention, the IPA bubble point of the aseptic film is 0.16-0.24MPa; the density of the degerming film is 430-800kg/m 3 。
According to research, when the density of the degerming membrane is too high, on one hand, the membrane manufacturing process is very complex, the industrialization difficulty is very high, and the economic benefit is low, and on the other hand, the too high density also means that a passage formed by an original node and supporting fibers is too tortuous to a certain extent, so that the flux of the filter membrane can be reduced, and fluid cannot pass through the filter membrane in a short time, so that degerming filtration is completed; therefore, the density of the sterilizing film of the present invention is preferably 430 to 800kg/m 3 Under the density, the bacteria in the fluid can be easily trapped fully, and the filter membrane has higher tensile strength and compressive strength; under the synergistic effect of IPA bubble point of 0.16-0.24MPa (the pore diameter of the whole pore of the membrane is relatively large), the membrane is ensured to have larger flux and sewage receiving capacity, and the service life is longer.
As a further improvement of the present invention, the primary nodes are of a granular structure, the SEM average diameter of which is 150-650nm, and the cross-sectional density of the primary nodes is not less than 40/100 μm 2 . Preferably, the SEM average diameter of the origin is 200-600nm, and the cross-sectional density of the origin is 50-150/100 μm 2 。
In the main body section structure of the sterilizing film of the present invention, we find that there are a plurality of objects of granular structure, which are called as primary nodes, which are connected by a supporting fiber, and a certain gap exists between adjacent supporting fibers, and the gaps areA passage is formed to facilitate the passage of fluid; compared with the support fiber, the original nodes are relatively thicker, the SEM average diameter is 150-650nm, and the original nodes with the thickness are favorable for leading the whole degerming film to have higher mechanical strength; on the other hand, the number of these sites is relatively large, and the cross-sectional density is not less than 40 sites per 100 μm 2 The adjacent original nodes are connected through the supporting fibers, so that a plurality of tortuous paths are formed under the combined action of the original nodes and the supporting fibers, the thickness of the tortuous paths is high, the original nodes can ensure the stability of each path, so that the paths are not easy to collapse or shrink in the filtering process, bacteria can be effectively trapped for a long time, the sufficient capture of the bacteria is ensured, and meanwhile, the filter membrane is ensured to have higher flux and lower pressure loss; however, when the original points are too thin, on one hand, the integral mechanical strength of the membrane is not high, on the other hand, the stability of each passage cannot be effectively ensured, and the phenomena of collapse and the like of part of membrane holes in the passages are easy to occur, so that the efficient interception of bacteria cannot be ensured, and the bacteria leak; however, when the original points are too thick, the existence of the original points can affect the passing of the fluid, so that the flow rate of the fluid is reduced, namely, the filtration speed of the membrane is lower, and meanwhile, the pressure loss is higher; when the section density of the original nodes is too small, namely the number of the original nodes is insufficient, the tortuous flux of the membrane main body is easily caused to be insufficient, the interception efficiency has a certain influence, and the mechanical strength of the whole membrane has a certain influence; however, when the section density of the original nodes is too large, namely the number of the original nodes is too large, the passages are easy to be too tortuous, the flux of the filter membrane is reduced, the pressure loss of the sterilizing membrane is also increased, and the energy consumption is too large; namely, under the synergistic effect of the proper SEM average diameter and proper cross-section density of the original nodes, the filter membrane is further ensured to have high flux, high interception efficiency, high strength and low pressure loss.
The SEM average diameter of the original node is the thickness of the original node; the section density of the original nodes is the number of the original nodes in a certain section area (the specific area is determined according to the situation) of the sterilizing film, so that the number of the original nodes on the section is expressed; the SEM average diameter and the section density of the original node (the section is the section cut along the length direction of the surface fiber and the length direction of the surface fiber is the direction of film running and the longitudinal stretching direction) can be obtained by using a scanning electron microscope to perform morphology characterization on the film section structure and then using computer software (such as Matlab, NIS-Elements and the like) or manually to measure the diameter size and the number of the original node, so that the corresponding SEM average diameter and section density can be further calculated; it will of course be appreciated that the above parameters may also be obtained by other measurement means by a person skilled in the art.
As a further improvement of the present invention, the ratio of SEM average diameter to film thickness of the original nodes is 0.004-0.016; preferably, the ratio is 0.008 to 0.012.
As is known, the fluid filtration process is mainly performed in the thickness direction of the membrane, and the fluid penetrates through the thickness of the membrane from one surface of the membrane and comes out from the other surface of the membrane; the original node can be regarded as a block-shaped area with relatively compact porosity in the membrane section, the supporting fiber is an area with relatively large porosity in the membrane section, when the size of the original node is too large, the original node can cause no small resistance to the flow of fluid, and the flow speed of the fluid in the membrane is affected, so that the flux of the filter membrane is relatively low, and the pressure loss is increased; when the original point is too small, the mechanical strength of the degerming film is too low; through researches, when the ratio of the SEM average diameter of the original node to the film thickness is 0.004-0.016, the proper ratio is provided between the original node and the film thickness, and the original node is relatively smaller, so that the strength of the film is ensured, and the film is ensured to have higher flux.
As a further improvement of the present invention, the SEM average length of the support fiber is 500-2500nm, and the SEM average diameter of the support fiber is 60-300nm.
Preferably, the support fibers have an SEM average length of 800-2000nm; the SEM average diameter of the support fiber is 90-260nm; the adjacent nodes are connected through supporting fibers, and a certain gap is reserved between the supporting fibers for fluid to pass through; therefore, the length and the width of the support fiber can influence the characteristics of the whole mechanical strength, the interception efficiency, the sewage receiving amount and the like of the sterilizing film; when the support fiber is too short, the original points on the section of the membrane are too many, the resistance of the fluid passing through the degerming membrane is large, the pressure loss is large, and the energy consumption is too large; also results in less porosity (lower porosity) of the membrane as a whole, which in turn results in lower fouling capacity and flux of the membrane; when the support fiber is too long, the number of original nodes on the whole section of the membrane is too small, the whole density of the membrane is low, and the interception efficiency is affected; when the support fiber is too thin, the mechanical strength of the whole membrane is not high enough, and meanwhile, when fluid flows in the membrane body, the support fiber is easy to break, membrane holes collapse and the like, and the membrane cannot be stably filtered for a long time; when the support fiber is too thick, the flow velocity of the fluid in the membrane is too low, so that the passing of the membrane is greatly influenced; therefore, the invention further ensures that the whole membrane has higher high density by the support fiber with proper length and coarse fiber; meanwhile, the flux, the interception efficiency and the mechanical strength can be further ensured under the synergistic effect of the characteristics of the size, the number and the like of the nodes.
The method for measuring the SEM average length and the SEM average diameter of the support fiber can be used for carrying out morphology characterization on the film section structure by using a scanning electron microscope, then measuring by using computer software (such as Matlab, NIS-Elements and the like) or manually, and carrying out corresponding calculation; the SEM average length and the SEM average diameter of the corresponding area are measured to reflect the whole SEM average length and the whole SEM average diameter on the section; in actual measurement, the membrane section can be characterized by electron microscope to obtain corresponding SEM image, and a certain area, such as 1 μm 2 (1 μm by 1 μm) or 25 μm 2 (5 μm by 5 μm), measuring the SEM length and SEM diameter of the support fiber on the specific area according to the actual situation by using corresponding computer software or manually, and calculating to obtain the SEM average length and SEM average diameter of the support fiber in the area, namely the SEM average length and SEM average diameter of the support fiber on the membrane section; of course, the person skilled in the art can also obtain the above parameters by other measuring means, which are only used as reference.
As a further improvement of the present invention, the ratio of the SEM average length to the SEM average diameter of the support fiber is 2 to 20; the ratio of the SEM average length of the support fibers to the SEM average diameter of the origin is 1.5-10. Preferably, the support fibers have a ratio of SEM average length to SEM average diameter of 4 to 15; the ratio of the SEM average length of the support fibers to the SEM average diameter of the origin is 2-8.
When the support fiber has a proper length-diameter ratio, the ratio of the SEM average length of the support fiber to the SEM average diameter of the original node is controlled within a proper range, so that the whole interception efficiency and mechanical strength of the membrane can be further improved, and the membrane has higher flow rate; in addition, bacteria can be stably and efficiently trapped in the long-time filtering process, the flux attenuation is slower, and the service life is longer.
As a further improvement of the present invention, a plurality of the origin sites are stacked on each other to form an origin site aggregate, and the SEM diameter of the origin site aggregate is not less than 0.3 μm.
By further observing the cross section of the main body of the membrane, part of the primary nodes are mutually piled up, the primary nodes piled up together are called primary node aggregates, are relatively thick, and the SEM diameter of the primary node aggregates is not less than 0.3 mu m after measurement, so that the mechanical property of the membrane can be further improved; and because the degerming membrane is high in density and high in porosity, the existence of the original node aggregate can ensure the stability of a tortuous path, even under special conditions (such as sudden increase of pressure and sudden increase of fluid instantaneous flux), the membrane pore structure in the membrane body is not easy to collapse, and the service life of the degerming membrane is further prolonged.
As a further improvement of the present invention, the SEM average diameter of the agglomerate of sites is 0.5-1.4 μm, and the cross-sectional density of the agglomerate of sites is 2-18/100. Mu.m 2 . Preferably, the cross-sectional density of the primary node aggregates is 4-12/100 μm 2 。
On the section, the existence of the original node aggregate is beneficial to improving the mechanical strength of the membrane and maintaining the stability of the membrane flux; when the diameter of the original node aggregate is too large and/or the number of the original node aggregate is too large, on one hand, the porosity of the whole membrane can be reduced, and the initial flux of the membrane is too low; on the other hand, the resistance of the fluid passing through the filter membrane is increased, and the pressure loss is increased; the invention has proper diameter of the node aggregate and relatively small number, thus ensuring the mechanical strength of the membrane, and simultaneously ensuring that the flux of the membrane is basically not influenced and still is larger.
The SEM average diameter and the section density of the original node aggregate can be obtained by using a scanning electron microscope to perform morphology characterization on the membrane section structure and then using computer software (such as Matlab, NIS-Elements and the like) or manually measuring the membrane section structure to obtain the diameter size and the number of the original node aggregate, so that the corresponding SEM average diameter and section density can be further calculated; it will of course be appreciated that the above parameters may also be obtained by other measurement means by a person skilled in the art.
As a further improvement of the invention, the first outer surface and the second outer surface each comprise surface fibers and surface nodes; the adjacent surface nodes are connected through the surface fibers, the SEM average length of the surface fibers is 800-2200nm, and the length-diameter ratio of the surface fibers is 4-16. Preferably, the SEM average length of the surface fiber is 1000-2000nm, and the length-diameter ratio of the surface fiber is 5-15;
on the outer surface of the present invention, relatively coarse fiber entities are referred to as surface nodes and relatively fine fiber entities are referred to as surface fibers; because of the substantial symmetry, the characteristics (length and thickness) of the corresponding surface fibers and the characteristics (length and thickness) of the surface nodes are substantially the same on both outer surfaces; the length of the surface fiber is an important factor influencing the characteristic properties of the degerming membrane such as the pore size, the tensile strength and the like, and the length of the surface fiber is actually the distance between two adjacent surface nodes; in general, the longer the surface fiber is, the larger the pore diameter of the surface of the sterilizing film is, the longest surface fiber is easy to form the pore with the largest surface pore diameter, and the shortest surface fiber is easy to form the pore with the smallest surface pore diameter; when the length of the surface fiber is too large, the whole holes of the membrane are too large, the sterilization efficiency of the sterilization membrane is too low, the mechanical strength is too small, and when the length of the surface fiber is too small, the flux of the membrane is too low, and meanwhile, the pressure loss is too large, so that a proper surface fiber is needed;
According to the research, for the degerming membrane, the SEM average length of the surface fiber is 800-2200nm, and the length is relatively suitable, so that the integral flux of the membrane can be ensured, and the high-efficiency interception of bacteria by the filter membrane can be ensured; in addition to the length of the surface fibers, the aspect ratio of the surface fibers (the ratio of the length to the width of the surface fibers) needs to be considered, because when the aspect ratio is too large, the surface fibers are broken in the fluid filtration process, and the interception efficiency is affected; particularly the outer surface which is the liquid inlet surface, the breaking rate of the surface fiber increases greatly when the fluid passes through the surface instantaneously; furthermore, in actual use, the sterilizing film is usually folded for use, and compared with the non-crease position of the sterilizing film, the crease position of the sterilizing film is broken, so that the probability of bacterial leakage is relatively high, and the surface fiber is required to have a proper length-diameter ratio, so that the sterilizing film has a longer service life in the filtering process; meanwhile, the length-diameter ratio of the surface fibers cannot be too small, so that the surface fibers are too thick, and the resistance of fluid passing through the filter membrane is greatly increased; meanwhile, the surface of the membrane is provided with surface fibers with proper length and proper thickness, and fibers at the lower layer and fibers at the upper layer in the main structure of the membrane are mutually staggered and stacked, so that the interception efficiency is improved; further ensuring that the sterilizing membrane still has high interception efficiency when the membrane holes are relatively large.
The measurement mode of various surface morphology parameters (such as SEM average length of surface fibers, SEM average length of surface nodes and the like) of the filter membrane can be realized by using a scanning electron microscope to perform morphology characterization on the membrane structure, then computer software (such as Matlab, NIS-Elements and the like) or manual measurement is utilized, and corresponding calculation is performed; in the film preparation process, in the direction perpendicular to the film thickness (if the film is in the form of a flat plate filmThe direction is a planar direction; if the membrane is hollow fiber membrane shaped, the direction is perpendicular to the radial direction), its various characteristics such as pore size distribution are substantially uniform, and substantially consistent; the average pore size of the whole on the plane can be reflected by measuring the average pore size of a partial region on the corresponding plane. In practice, the surface of the film can be characterized by electron microscopy to obtain corresponding SEM image, and selecting a certain area, such as 1 μm 2 (1 μm by 1 μm) or 25 μm 2 (5 μm by 5 μm), measuring the length and width of the surface fiber on the specific area according to the actual situation, measuring the length and width of the surface node on the specific area by corresponding computer software or manually, and calculating to obtain the SEM average length and length-diameter ratio of the surface fiber in the area, and the SEM average length and length-diameter ratio of the surface node, wherein the value can be used as the corresponding characteristic value on the outer surface; of course, the person skilled in the art can also obtain the above parameters by other measuring means, which are only used as reference.
As a further improvement of the invention, the SEM average length of the surface nodes is 600-2600nm, and the length-diameter ratio of the surface nodes is 1.5-6. Preferably, the SEM average length of the surface nodes is 800-2400nm, and the aspect ratio of the surface nodes is 2-5.
On the outer surface of the membrane, relatively coarse fibers are called surface nodes, and the length of the surface nodes has a certain influence on the hole area rate and the membrane hole size of the surface of the membrane, so that the integral mechanical strength and flux of the membrane are influenced; compared with the existing nodes with large length (often more than 20 um), the length of the surface nodes in the invention is relatively short, and the SEM average length is 600-2600nm; under the action of the length, large membrane holes are not formed, and the membrane holes are relatively suitable, so that the bacteria can be fully trapped; further, the length-diameter ratio of the surface nodes is 1.5-6, and under the action of the surface nodes with the length and the length-diameter ratio, the surface of the membrane is facilitated to obtain higher porosity, and the whole membrane is further enabled to have high porosity; the degerming membrane has high porosity and high density, so that the degerming membrane has high interception efficiency and high flux.
As a further improvement of the invention, the average density S of the film body is 45% -85%, the average density S being calculated by the following formula: s=d Real world /D×100％；
In the above, D Real world The thickness of the film body is the sum of the thicknesses of all entities in the thickness direction of the film body, the entities comprise the original nodes and the supporting fibers, and D is the thickness of the film body.
In order to better embody the invention, the sterilizing membrane is a high-density filter membrane, the invention is embodied by using the characteristic of average density S, the average density refers to the ratio of the sum of the thicknesses of all the solid parts to the membrane thickness in the thickness direction of the membrane main body, and the size of the ratio reflects the area occupied by the solid parts in the thickness direction of the membrane main body; the greater the ratio, the higher the film density can be demonstrated, the fewer the relative voids, and in turn the higher the film density; the average density S of the membrane main body is 45% -85% (preferably, the average density S is 50% -80%), so that the sterilization membrane is further embodied to have higher density, the original nodes and the support fibers are basically tightly close together, and the formed passage is relatively tortuous, so that the membrane is ensured to have higher mechanical strength and higher interception efficiency; but the average density S is not too high, a certain gap is necessarily required to exist, the flux of the membrane is ensured to be large, and the filtration resistance is not too high;
The average compactness of the sterilization filter membrane can be measured by using computer software (such as Matlab, NIS-Elements and the like) or manually after the morphology of the membrane structure is characterized by using a scanning electron microscope, and corresponding calculation is performed; during actual measurement, the cross section of the membrane can be characterized by an electron microscope to obtain a corresponding SEM image, a plurality of sites (at least 3 sites) are selected, then a straight line parallel to the thickness direction is drawn along the sites, the length value of a solid part (a supporting point and supporting fibers) on the straight line is measured, the whole thickness of the membrane is divided to obtain the compactness of the sites, and then the average compactness Q of the membrane can be obtained by taking an average value; it should also be noted that the fibers in the void fraction are not counted as solid fractions, because the fibers in the void fraction are not substantially fibers at the cross-section, but are close to fibers near the cross-section, and therefore not counted.
As a further improvement of the application, the thickness of the degerming film is 20-90 mu m, and the porosity is 55% -85%; the tensile strength of the degerming film is 10-40MPa.
The thickness of the film can be calculated and measured by using computer software (such as Matlab, NIS-Elements and the like) or manually after the appearance of the film structure is characterized by using a scanning electron microscope; when the thickness of the film is too small, the mechanical strength of the film is low; meanwhile, as the filtering time is too short, effective filtering cannot be performed; when the thickness of the filter membrane is too large, the filtering time is too long, and the time cost is too high. The thickness of the degerming film is 20-90 mu m (preferably, the film thickness is 35-75 mu m), so that the degerming film not only has higher mechanical strength, but also can be used for effective filtration, and has higher filtration efficiency, shorter filtration time and lower time cost;
In general, as the overall density of the membrane increases, the porosity of the membrane will be lower; when the whole pore diameter of the membrane is relatively large, the membrane also has an ideal porous structure, so that the degerming membrane still has large porosity (namely, the degerming membrane is high-density and high-porosity); through tests, the porosity of the degerming membrane is 55% -85% (preferably, the porosity is 60% -80%), so that the filter membrane has higher dirt receiving capacity, can intercept more impurity particles, has longer service life, and in addition, the combination of larger aperture and high porosity ensures that the degerming membrane has larger flux and lower pressure loss, thereby meeting the requirements of practical application; common porosity testing methods include mercury intrusion, density, dry-wet film weighing, etc.; the application adopts a dry-wet film weighing method to measure, and of course, the person skilled in the art can also obtain the parameters through other measuring means, and the measuring means only serve as reference;
an important index for evaluating the mechanical strength of the filter membrane is the tensile strength of the filter membrane; under certain conditions, the greater the tensile strength of the film, the better the mechanical strength of the film is also demonstrated; tensile strength refers to the ability of a film to withstand parallel stretching; when the film sample is tested under certain conditions, the film sample is subjected to the action of tensile load until the film sample is broken, and the tensile strength of the film can be calculated according to the maximum tensile load corresponding to the film sample during the breaking, the change of the size (length) of the film sample and the like; tensile strength may be measured by a universal tensile tester, methods of testing tensile strength are well known in the art, for example, procedures for testing tensile strength are explained in detail in ASTM D790 or ISO 178; the tensile strength of the polytetrafluoroethylene antibacterial film is 10-40MPa; the application has the advantages of high tensile strength, good mechanical property and high industrial practical value, and can completely meet the market demand.
In addition, the invention also provides a preparation method of the polytetrafluoroethylene sterilization film, which comprises the following steps:
A. mixing: mixing and stirring polytetrafluoroethylene dispersion resin and a lubricant uniformly to obtain paste;
B. blank manufacturing: prepressing the paste into a cylindrical blank body;
C. extrusion: extruding the blank obtained in the step B to form a flat strip-shaped matrix;
D. calendering: calendering the strip-shaped matrix to ensure that the thickness of the strip-shaped matrix after calendering is 15-40% of the thickness of the strip-shaped matrix before calendering;
E. and (3) drying: drying the strip-shaped matrix to volatilize the lubricant;
F. stretching in the longitudinal direction: longitudinally stretching the dried strip-shaped matrix at 200-320 ℃ with a longitudinal stretching multiple of 2-10 times to obtain a first strip-shaped matrix;
G. and (3) transversely stretching: transversely stretching the first strip-shaped matrix at 100-300 ℃ with a transverse stretching multiple of 18-40 times to obtain a second matrix;
H. and (3) performing primary heat setting: placing the second matrix in an environment with the temperature of 330-390 ℃ for primary heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the second matrix are not more than 15% during the primary heat setting, and the heat setting time is 0.2-3 minutes, so as to obtain a semi-finished product of the degerming film;
I. And (5) performing secondary heat setting: and (3) placing the semi-finished product of the degerming film in an environment with the temperature of 330-390 ℃ for secondary heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the semi-finished product of the degerming film are not more than 10% during the secondary heat setting, and the secondary heat setting time is 5-20 minutes, so that the degerming film is obtained.
As a further improvement of the present invention, the number average molecular weight of the polytetrafluoroethylene dispersion resin is 400 to 1200 tens of thousands; the lubricant is at least one of lubricating oil, palm oil, naphthenic oil, white oil, aviation kerosene, degreasing kerosene and paraffin.
As a further improvement of the invention, the step A of mixing specifically means that polytetrafluoroethylene dispersion resin and lubricant are mixed and stirred according to the weight ratio of 1:0.1-1:0.3, and then are put into an environment with the temperature of 35-50 ℃ for curing for 8-24 hours, so as to obtain paste;
the temperature of the second heat setting is at least 10 ℃ higher than that of the first heat setting; the second heat setting is at least 4 minutes longer than the first heat setting.
As a further improvement of the invention, the thickness of the rolled strip-shaped matrix after repressing in the step D is 0.8-1.5mm; the longitudinal stretching rate in the step F is 8% -75%/s, and the transverse stretching rate in the step G is 25% -70%/s.
When the polytetrafluoroethylene sterilization film is prepared, firstly, raw materials of polytetrafluoroethylene dispersion resin and lubricant are mixed and stirred, wherein the number average molecular weight of the polytetrafluoroethylene dispersion resin is 400-1200 ten thousand, and as the prepared filter film is used for sterilization, the film holes are not larger, and when the number average molecular weight is too small, the mechanical strength of the formed filter film is too low; when the number average molecular weight is too large, a high-porosity filter membrane is not easy to form, and the flux of the filter membrane is too low; the polytetrafluoroethylene dispersion resin with a certain number average molecular weight is selected so that the prepared polytetrafluoroethylene sterilization film has enough mechanical strength and flux;
the lubricant is at least one of lubricating oil, palm oil, naphthenic oil, white oil, aviation kerosene, degreasing kerosene and paraffin; the lubricant can be one substance only or a mixture of the substances, and by selecting a proper lubricant, the polytetrafluoroethylene dispersion resin can be processed conveniently to obtain the degerming film with a required film structure; preferably, the weight ratio of the polytetrafluoroethylene dispersion resin to the lubricant is 1:0.1-1:0.3, and the weight ratio further ensures that the lubricating oil and the polytetrafluoroethylene are uniformly mixed, so that the subsequent processing treatment of each item is facilitated; if the lubricating oil is excessive, the lubricating oil is easy to remain to a certain extent even if the lubricating oil is subjected to process treatment such as drying; on the other hand, the degree of fibrosis is too low in the film forming process, and the film forming mechanical strength is too low to meet the requirements of practical application;
Uniformly mixing polytetrafluoroethylene dispersion resin and a lubricant, then placing the mixture into an oven at the temperature of 35-50 ℃ for curing for 8-24 hours to obtain paste, wherein the curing aim is to ensure that the polytetrafluoroethylene dispersion resin and the lubricant are uniformly mixed, and the lubricant can be uniformly dispersed in the polytetrafluoroethylene dispersion resin so as to facilitate the subsequent blank making extrusion; then, blank making is carried out, and the paste is pre-pressed into a cylindrical blank body; extruding, namely putting the blank into a pushing machine for extrusion to form a flat strip-shaped matrix;
then rolling: calendering the strip-shaped matrix to ensure that the thickness of the strip-shaped matrix after calendering is 15-40% of the thickness of the strip-shaped matrix before calendering; according to the invention, the extruded strip-shaped matrix is rolled, the thickness of the strip-shaped matrix is 15% -40% of the thickness of the strip-shaped matrix before rolling, and the thickness of the strip-shaped matrix is greatly reduced, so that certain acting force is generated between resin particles, the fibers in the thickness direction are fully fused (if the film thickness is small or even unchanged before rolling, the subsequent fusion is not facilitated, an ideal fiber structure is not formed), and a high-density polytetrafluoroethylene sterilization film can be formed under the synergistic effect of the subsequent first heat setting and the second heat setting, and the sterilization film has ideal film holes and fiber structures; preferably, the thickness of the tape-shaped substrate after the casting in the step D is 0.8-1.5mm, and the tape-shaped substrate with the thickness is easy to obtain a degerming film with proper pore diameter, porosity and thickness after the subsequent steps of longitudinal drawing, transverse drawing and the like; and drying: drying the rolled strip-shaped matrix in an oven to volatilize the lubricant, wherein the drying temperature is 100-250 ℃;
Then longitudinal stretching treatment is carried out, the dried strip-shaped matrix is longitudinally stretched on a film drawing machine, the longitudinal stretching temperature is 200-320 ℃, and the longitudinal stretching multiple is 2-10 times, so that a first strip-shaped matrix is obtained; preferably, the longitudinal stretching rate is 8% -75%/s in the longitudinal direction, and the stretching rate (including the longitudinal stretching rate and the transverse stretching rate) is specifically realized through the distance between rollers and the rotating speed difference between the rollers; the nodes and the fibers start to split in the longitudinal stretching process, and because the activation energy of PTFE resin fiber formation is low, an ideal fiber structure is easy to form at a higher stretching temperature, and the fiber structure is matched with the subsequent transverse stretching to form a proper membrane hole size so as to conveniently entrap bacteria; the longitudinal stretching temperature is preferably 200-320 ℃, if the longitudinal stretching temperature exceeds 320 ℃, the stretching temperature is above the melting point of polytetrafluoroethylene, the stretching and sintering processes are carried out simultaneously, stretching and sintering can randomly occur in different regions of the film, and the uniformity of the film after stretching is poor; if the longitudinal stretching temperature is lower than 200 ℃, the fiber forming degree of the film is insufficient, a high-density and high-pore sterilizing film cannot be formed, the final flux of the film is too low, and the pressure loss is large;
After the longitudinal stretching is finished, the transverse stretching is directly carried out, and any heat setting is not carried out, because if the heat setting is carried out at this time, the structure locking effect is realized, the final surface forming nodes are in a strip shape, and the surface nodes are almost parallel (the surface nodes are thick and long); the transverse stretching is directly carried out, so that relatively short nodes (which are not too thick) are formed on the surface of the membrane, and the membrane holes of the degerming membrane are not too large and have high porosity; the transverse stretching temperature is 100-300 ℃, the transverse stretching multiple is 18-40 times, and the transverse stretching of higher multiple is carried out at the temperature, so that the ideal film pore size is obtained; preferably, the transverse stretching rate is 25-70%/s, and the stretching rate is not too fast; under the action of the speed and the multiple of the transverse stretching, the fibers are separated from each other, the porosity is improved, and the flux is improved; meanwhile, small and more original nodes are formed (the diameters of the original nodes and the diameters of original node aggregates are not too large), so that the overall density of the film is improved;
the second matrix after transverse stretching is subjected to primary heat setting, and can be regarded as primary setting, the primary setting time cannot be too long, and the primary fusion setting function is mainly achieved; in the first heat setting process, the film is also strained to a certain extent, and the stress is relaxed (the internal stress caused by uncooled deformation of the microstructure of the material is eliminated), so that the film has high mechanical strength; on the other hand, the surface shrinkage rate (both the longitudinal shrinkage rate and the transverse shrinkage rate are not more than 15%) of the second matrix in the first heat setting process is reduced, and certain shrinkage is expected to be carried out in the thickness direction, so that fusion (doubling) of fibers occurs, and the high-density sterilization film is formed; if the first heat setting is too long, excessive fusion of the fibers is easily caused, and the primary nodes and primary node aggregates are too large, so that the membrane pore size is uneven and the fibers are uneven;
Finally, performing secondary heat setting, wherein the time of the secondary heat setting is longer, and the semi-finished product of the degerming film is more required to be tensioned, so that the semi-finished product of the degerming film is basically in a tensioned state all the time, and basically only generates shrinkage in the thickness direction by limiting the longitudinal shrinkage and the transverse shrinkage (the longitudinal shrinkage and the transverse shrinkage of the semi-finished product of the degerming film are not more than 10 percent during the secondary heat setting); through the second heat setting for an ultra-long time, recrystallization is carried out, and fibers in the film thickness direction are fused (combined), so that a high-density degerming film with proper film holes is obtained; preferably, the temperature of the second heat setting is at least 10 ℃ higher than the temperature 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, and the membrane is completely set under the combined action of the first heat setting and the second heat setting, so that the degerming membrane with good dimensional stability and high strength is obtained, and has high interception efficiency and high flux on bacteria and wide application range.
As a further improvement of the present invention, the polytetrafluoroethylene sterilization film is used for liquid sterilization and/or gas sterilization.
The invention has the beneficial effects that: the polytetrafluoroethylene sterilization film comprises a main body, wherein a non-directional tortuous path is arranged in the main body, one side surface of the main body is a first outer surface, the other side surface of the main body is a second outer surface, and the first outer surface and the second outer surface are basically symmetrical; the main body comprises original nodes and supporting fibers, and part of adjacent nodes are connected through the supporting fibers; the IPA bubble point of the sterilizing film is 0.14-0.28MPa, and the film holes are relatively large; the density of the degerming film is more than 400kg/m 3 The degerming membrane with relatively high density and relatively large membrane holes ensures the sufficient interception of bacteria, has the LRV of more than 7 on the defect pseudomonas and has larger flux, and the Gurley value is 25-50 s.1 inch -2 ·100ml -1 The method comprises the steps of carrying out a first treatment on the surface of the The degerming film is used for liquid degerming and/or gas degerming, and has wide application range; in addition, the invention also provides a preparation method of the degerming film, which is convenient, quick and effective, simple to operate, environment-friendly and suitable for large-scale popularization.
Drawings
FIG. 1 is a Scanning Electron Microscope (SEM) image of a longitudinal section of a polytetrafluoroethylene sterilization film obtained by the preparation of example 1, wherein the magnification is 1000X;
FIG. 2 is a Scanning Electron Microscope (SEM) image of a longitudinal section of the polytetrafluoroethylene sterilization film obtained in example 1 at a magnification of 5000;
FIG. 3 is a Scanning Electron Microscope (SEM) image of the inlet surface of the polytetrafluoroethylene antibacterial film prepared in example 1, wherein the magnification is 500×;
FIG. 4 is a Scanning Electron Microscope (SEM) image of the polytetrafluoroethylene sterilization film prepared in example 1 at a magnification of 2000;
FIG. 5 is a Scanning Electron Microscope (SEM) image of the liquid surface of the polytetrafluoroethylene antibacterial film prepared in example 1, wherein the magnification is 500×;
FIG. 6 is a Scanning Electron Microscope (SEM) image of the liquid surface of the polytetrafluoroethylene sterilization film obtained in example 1 at a magnification of 2000.
Detailed Description
In order to more clearly illustrate the general concept of the present application, the following detailed description is given by way of example. In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present application. It will be apparent, however, to one skilled in the art that the application may be practiced without one or more of these details. In other instances, well-known features have not been described in detail in order to avoid obscuring the application.
In the following examples, raw materials and equipment for preparing the polytetrafluoroethylene antibacterial film are commercially available, unless otherwise specified. The structural morphology of the polytetrafluoroethylene sterilization film is characterized by adopting a scanning electron microscope with the model of S-5500 provided by Hitachi.
Example 1 a method for preparing a polytetrafluoroethylene sterilization film comprising the steps of:
A. mixing: mixing polytetrafluoroethylene dispersion resin and a lubricant according to a weight ratio of 1:0.2, and then placing the mixture into an environment with a temperature of 40 ℃ for curing for 16 hours to obtain paste; the number average molecular weight of the polytetrafluoroethylene dispersion resin is 800 ten thousand; the lubricant is lubricating oil;
B. Blank manufacturing: prepressing the paste into a cylindrical blank body;
C. extrusion: extruding the blank obtained in the step B to form a flat strip-shaped matrix;
D. calendering: calendering the strip-shaped matrix so that the thickness of the strip-shaped matrix after calendering is 30% of the thickness of the strip-shaped matrix before calendering; the thickness of the strip-shaped matrix after the casting in the step D is 1.1mm;
E. and (3) drying: drying the strip-shaped matrix to volatilize the lubricant;
F. stretching in the longitudinal direction: longitudinally stretching the dried strip-shaped matrix at 260 ℃ with a longitudinal stretching multiple of 6 times to obtain a first strip-shaped matrix; wherein the machine direction stretch rate is 50%/s;
G. and (3) transversely stretching: transversely stretching the first strip-shaped matrix at 220 ℃ with a transverse stretching multiple of 30 times to obtain a second matrix; wherein the transverse stretching rate is 55%/s;
H. and (3) performing primary heat setting: and (3) placing the second matrix in an environment with the temperature of 355 ℃ for primary heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the second matrix are not more than 15% during primary heat setting, and the heat setting time is 2 minutes, so that the semi-finished product of the degerming film is obtained.
I. And (5) performing secondary heat setting: and (3) placing the semi-finished product of the degerming film in an environment with the temperature of 370 ℃ for secondary heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the semi-finished product of the degerming film are not more than 10% during the secondary heat setting, and the secondary heat setting time is 14 minutes, so that the degerming film is obtained.
Example 2 a method for preparing a polytetrafluoroethylene antibacterial film comprising the steps of:
A. mixing: mixing polytetrafluoroethylene dispersion resin and a lubricant according to a weight ratio of 1:0.2, and then placing the mixture into an environment with a temperature of 45 ℃ for curing for 13 hours to obtain paste; the number average molecular weight of the polytetrafluoroethylene dispersion resin is 900 ten thousand; the lubricant is palm oil;
B. blank manufacturing: prepressing the paste into a cylindrical blank body;
C. extrusion: extruding the blank obtained in the step B to form a flat strip-shaped matrix;
D. calendering: calendering the strip-shaped substrate so that the thickness of the strip-shaped substrate after calendering is 25% of the thickness of the strip-shaped substrate before calendering; the thickness of the strip-shaped matrix after the casting in the step D is 1.2mm;
E. and (3) drying: drying the strip-shaped matrix to volatilize the lubricant;
F. stretching in the longitudinal direction: longitudinally stretching the dried strip-shaped matrix at the longitudinal stretching temperature of 250 ℃ and the longitudinal stretching multiple of 5 times to obtain a first strip-shaped matrix; wherein the machine direction stretch rate is 40%/s;
G. and (3) transversely stretching: transversely stretching the first strip-shaped matrix at the temperature of 200 ℃ and the transverse stretching multiple of 28 times to obtain a second matrix; wherein the transverse stretching rate is 50%/s;
H. And (3) performing primary heat setting: and (3) placing the second matrix in an environment with the temperature of 350 ℃ for primary heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the second matrix are not more than 15% during primary heat setting, and the heat setting time is 1.5 minutes, so that the semi-finished product of the degerming film is obtained.
I. And (5) performing secondary heat setting: and (3) placing the semi-finished product of the degerming film in an environment with the temperature of 365 ℃ for carrying out second heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the semi-finished product of the degerming film are not more than 10% during the second heat setting, and the second heat setting time is 12 minutes, so that the degerming film is obtained.
Example 3 a method for preparing a polytetrafluoroethylene sterilization film comprising the steps of:
A. mixing: mixing polytetrafluoroethylene dispersion resin and a lubricant according to a weight ratio of 1:0.15, and then placing the mixture into an environment with a temperature of 40 ℃ for curing for 10 hours to obtain paste; the number average molecular weight of the polytetrafluoroethylene dispersion resin is 500 ten thousand; the lubricant is naphthenic oil;
B. blank manufacturing: prepressing the paste into a cylindrical blank body;
C. extrusion: extruding the blank obtained in the step B to form a flat strip-shaped matrix;
D. Calendering: calendering the strip-shaped substrate so that the thickness of the strip-shaped substrate after calendering is 34% of the thickness of the strip-shaped substrate before calendering; the thickness of the strip-shaped matrix after the casting in the step D is 1.4mm;
E. and (3) drying: drying the strip-shaped matrix to volatilize the lubricant;
F. stretching in the longitudinal direction: longitudinally stretching the dried strip-shaped matrix at 300 ℃ with a longitudinal stretching multiple of 8 times to obtain a first strip-shaped matrix; wherein the machine direction stretch rate is 70%/s;
G. and (3) transversely stretching: transversely stretching the first strip-shaped matrix at 270 ℃ with a transverse stretching multiple of 36 times to obtain a second matrix; wherein the transverse stretching rate is 65%/s;
H. and (3) performing primary heat setting: and (3) placing the second matrix in an environment with the temperature of 370 ℃ for primary heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the second matrix are not more than 15% during primary heat setting, and the heat setting time is 3 minutes, so that the semi-finished product of the degerming film is obtained.
I. And (5) performing secondary heat setting: and (3) placing the semi-finished product of the degerming film in an environment with the temperature of 390 ℃ for secondary heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the semi-finished product of the degerming film are not more than 10% during the secondary heat setting, and the secondary heat setting time is 17 minutes, so that the degerming film is obtained.
Example 4 a method for preparing a polytetrafluoroethylene antibacterial film comprising the steps of:
A. mixing: mixing polytetrafluoroethylene dispersion resin and a lubricant according to a weight ratio of 1:0.15, and then placing the mixture into an environment with a temperature of 36 ℃ for curing for 12 hours to obtain paste; the number average molecular weight of the polytetrafluoroethylene dispersion resin is 650 ten thousand; the lubricant is white oil;
B. blank manufacturing: prepressing the paste into a cylindrical blank body;
C. extrusion: extruding the blank obtained in the step B to form a flat strip-shaped matrix;
D. calendering: calendering the strip-shaped matrix so that the thickness of the strip-shaped matrix after calendering is 36% of the thickness of the strip-shaped matrix before calendering; the thickness of the strip-shaped matrix after the casting in the step D is 1.3mm;
E. and (3) drying: drying the strip-shaped matrix to volatilize the lubricant;
F. stretching in the longitudinal direction: longitudinally stretching the dried strip-shaped matrix at the longitudinal stretching temperature of 280 ℃ and the longitudinal stretching multiple of 7 times to obtain a first strip-shaped matrix; wherein the machine direction stretch rate is 60%/s;
G. and (3) transversely stretching: transversely stretching the first strip-shaped matrix at the temperature of 250 ℃ and the transverse stretching multiple of 34 times to obtain a second matrix; the transverse stretching rate in the step G is 60%/s;
H. And (3) performing primary heat setting: and placing the second matrix in an environment with the temperature of 365 ℃ for primary heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the second matrix are not more than 15% during primary heat setting, and the heat setting time is 2.5 minutes, so that the semi-finished product of the degerming film is obtained.
I. And (5) performing secondary heat setting: and (3) placing the semi-finished product of the degerming film in an environment with the temperature of 385 ℃ for secondary heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the semi-finished product of the degerming film are not more than 10% during the secondary heat setting, and the secondary heat setting time is 16 minutes, so that the degerming film is obtained.
Example 5 a method for preparing a polytetrafluoroethylene sterilization film comprising the steps of:
A. mixing: mixing polytetrafluoroethylene dispersion resin and a lubricant according to a weight ratio of 1:0.25, and then placing the mixture into an environment with a temperature of 45 ℃ for curing for 18 hours to obtain a paste; the number average molecular weight of the polytetrafluoroethylene dispersion resin is 1000 ten thousand; the lubricant is aviation kerosene;
B. blank manufacturing: prepressing the paste into a cylindrical blank body;
C. extrusion: extruding the blank obtained in the step B to form a flat strip-shaped matrix;
D. Calendering: calendering the strip-shaped substrate so that the thickness of the strip-shaped substrate after calendering is 21% of the thickness of the strip-shaped substrate before calendering; the thickness of the strip-shaped matrix after the casting in the step D is 1.0mm;
E. and (3) drying: drying the strip-shaped matrix to volatilize the lubricant;
F. stretching in the longitudinal direction: longitudinally stretching the dried strip-shaped matrix at 240 ℃ with a longitudinal stretching multiple of 4 times to obtain a first strip-shaped matrix; wherein the machine direction stretch rate is 30%/s;
G. and (3) transversely stretching: transversely stretching the first strip-shaped matrix at 180 ℃ with a transverse stretching multiple of 24 times to obtain a second matrix; wherein the transverse stretching rate is 40%/s;
H. and (3) performing primary heat setting: and (3) placing the second matrix in an environment with the temperature of 340 ℃ for primary heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the second matrix are not more than 15% during primary heat setting, and the heat setting time is 1 minute, so as to obtain the semi-finished product of the degerming film.
I. And (5) performing secondary heat setting: and (3) placing the semi-finished product of the degerming film in an environment with the temperature of 350 ℃ for secondary heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the semi-finished product of the degerming film are not more than 10% during the secondary heat setting, and the secondary heat setting time is 10 minutes, so that the degerming film is obtained.
Example 6 a method for preparing a polytetrafluoroethylene sterilization film comprising the steps of:
A. mixing: mixing polytetrafluoroethylene dispersion resin and a lubricant according to a weight ratio of 1:0.25, and then placing the mixture into an environment with a temperature of 48 ℃ for curing for 24 hours to obtain a paste;
the number average molecular weight of the polytetrafluoroethylene dispersion resin is 1100 ten thousand; the lubricant is defatted kerosene;
B. blank manufacturing: prepressing the paste into a cylindrical blank body;
C. extrusion: extruding the blank obtained in the step B to form a flat strip-shaped matrix;
D. calendering: calendering the strip-shaped matrix so that the thickness of the strip-shaped matrix after calendering is 20% of the thickness of the strip-shaped matrix before calendering; the thickness of the strip-shaped matrix after the casting in the step D is 0.9mm;
E. and (3) drying: drying the strip-shaped matrix to volatilize the lubricant;
F. stretching in the longitudinal direction: longitudinally stretching the dried strip-shaped matrix at 220 ℃ with a longitudinal stretching multiple of 3 times to obtain a first strip-shaped matrix; wherein the machine direction stretch rate is 20%/s;
G. and (3) transversely stretching: transversely stretching the first strip-shaped matrix at the transverse stretching temperature of 150 ℃ and the transverse stretching multiple of 22 times to obtain a second matrix; wherein the transverse stretching rate is 30%/s;
H. And (3) performing primary heat setting: and (3) placing the second matrix in an environment with the temperature of 335 ℃ for primary heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the second matrix are not more than 15% during the primary heat setting, and the heat setting time is 0.5 minute, so as to obtain the semi-finished product of the degerming film.
I. And (5) performing secondary heat setting: and (3) placing the semi-finished product of the degerming film in an environment with the temperature of 345 ℃ for secondary heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the semi-finished product of the degerming film are not more than 10% during the secondary heat setting, and the secondary heat setting time is 8 minutes, so that the degerming film is obtained.
Example 7 a method for preparing a polytetrafluoroethylene sterilization film comprising the steps of:
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 the remaining preparation conditions were unchanged, to prepare a corresponding aseptic film.
Example 8 a method for preparing a polytetrafluoroethylene sterilization film comprising the steps of:
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 the remaining preparation conditions were unchanged, to prepare a corresponding aseptic film.
Example 9 a method for preparing a polytetrafluoroethylene antibacterial film comprising the steps of:
based on example 1, the number average molecular weight of the polytetrafluoroethylene dispersion resin in step A was 300 ten thousand; and (3) setting the temperature of the second heat setting in the step I to be 360 ℃ (5 ℃ higher than the temperature of the first heat setting), setting the time of the second heat setting to be 5min (3 min more than the time of the first heat setting), and keeping the other conditions unchanged to obtain the degerming film.
Comparative example 1 a method for preparing a polytetrafluoroethylene antibacterial film comprising the steps of:
on the basis of example 1, the flat strip-shaped substrate formed by extrusion was directly dried without carrying out a rolling treatment; meanwhile, the longitudinal shrinkage and the transverse shrinkage of the second matrix are not controlled in the first heat setting, and the longitudinal shrinkage and the transverse shrinkage of the semi-finished product of the degerming film are not controlled in the second heat setting; the other conditions are unchanged, and the corresponding degerming film is prepared.
Comparative example 2 a method for preparing a polytetrafluoroethylene antibacterial film comprising the steps of:
A. mixing: mixing polytetrafluoroethylene dispersion resin and a lubricant according to a weight ratio of 1:0.2, and then placing the mixture into an environment with a temperature of 40 ℃ for curing for 16 hours to obtain paste; the number average molecular weight of the polytetrafluoroethylene dispersion resin is 800 ten thousand; the lubricant is lubricating oil;
B. Blank manufacturing: prepressing the paste into a cylindrical blank body;
C. extrusion: extruding the blank obtained in the step B to form a flat strip-shaped matrix;
D. and (3) drying: drying the strip-shaped matrix to volatilize the lubricant;
E. stretching in the longitudinal direction: longitudinally stretching the dried strip-shaped matrix at 260 ℃ with a longitudinal stretching multiple of 2 times to obtain a first strip-shaped matrix; wherein the machine direction stretch rate is 50%/s;
F. and (3) transversely stretching: transversely stretching the first strip-shaped matrix at 220 ℃ with a transverse stretching multiple of 16 times to obtain a second matrix; wherein the transverse stretching rate is 55%/s;
G. and (3) performing primary heat setting: and (3) placing the second substrate in an environment with the temperature of 355 ℃ for primary heat setting, wherein the heat setting time is 2 minutes, and obtaining the semi-finished product of the degerming film.
H. And (5) performing secondary heat setting: and (3) placing the semi-finished product of the degerming film in the environment with the temperature of 370 ℃ for the second heat setting, wherein the second heat setting time is 14 minutes, and obtaining the degerming film.
The aseptic films prepared in examples 1-9 and comparative examples 1 and 2 were subjected to various tests to obtain the corresponding parameters of IPA bubble point, density, LRV against pseudomonas defectives, gas flux (Gurley), porosity, and tensile strength.
TABLE 1
| Sample preparation | IPA bubble point/MPa | Density kg/m 3 | LRV | Gurley/s.1inch -2 ·100ml -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 |
TABLE 2
| Sample preparation | Thickness/. Mu.m | 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 |
As can be seen from tables 1 and 2, the degerming films prepared in examples 1 to 9 have relatively large film pores and high density, so that the degerming films have high interception efficiency on bacteria, high flux, good tensile strength, high mechanical strength, suitability for various processing treatments and wide application range; the sterilization film prepared in comparative example 1 has relatively large film holes, so that the bacteria interception efficiency is still poor even if the sterilization film is made thick (thick); the sterilization membrane of comparative example 2 ensures the interception efficiency by making the membrane holes small, but the flux of the sterilization membrane can be obviously reduced, and the requirements of practical application cannot be met.
And (3) structural characterization, namely performing morphological characterization on the polytetrafluoroethylene sterilization film obtained in each embodiment by using a scanning electron microscope, so as to obtain corresponding required data.
Table 3: corresponding features of origin and origin aggregates
Comparative examples 1 and 2, because the calendering process was not performed and the shrinkage degree of the film surface was not controlled at the time of 2 heat-setting at the time of preparing the aseptic film, resulted in insufficient fusion degree of the cross-sectional fibers of the corresponding aseptic film in the thickness direction, too small diameters of the formed origin points and the origin point aggregation points, and also small number, and further resulted in too low density of the aseptic film; in comparison with example 7 and example 1, it was found that the transverse stretching rate and the longitudinal stretching rate are too slow, so that the formed primary nodes have too large diameters and too large numbers, and the flux of the degerming membrane of example 7 is obviously reduced compared with that of the degerming membrane of example 1;
however, the diameters of the embodiment 8 and the embodiment are too small, and the number is too small, so that the mechanical strength of the embodiment 8 sterilizing film is obviously reduced compared with that of the embodiment 1 sterilizing film.
Table 4: corresponding features of the support fibres
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Table 5: corresponding features of surface fibres and surface nodes
As can be seen from the above tables, the polytetrachloroethylene sterilizing films prepared in examples 1 to 9 of the present invention all have an ideal fiber structure, which is advantageous in that the polytetrachloroethylene sterilizing film has high tensile strength, high flux and sufficient retention of bacteria.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above examples, and all technical solutions belonging to the concept of the present invention belong to the protection scope of the present invention. It should be noted that modifications and adaptations to the present invention may occur to one skilled in the art without departing from the principles of the present invention and are intended to be within the scope of the present invention.
Claims (17)
1. A polytetrafluoroethylene sterilizing membrane, characterized in that: the device comprises a main body, wherein a non-directional tortuous path is arranged in the main body, one side surface of the main body is a first outer surface, the other side surface of the main body is a second outer surface, and the first outer surface and the second outer surface are basically symmetrical;
the main body comprises original nodes and supporting fibers, and part of adjacent nodes are connected through the supporting fibers; the IPA bubble point of the sterilizing film is 0.14-0.28MPa;
the density of the degerming film is more than 400kg/m 3 ；
The LRV of the degerming film against the pseudomonas defectives is greater than 7;
the Gurley value of the degerming film is 25-50s.1inch -2 ·100ml -1 。
2. A polytetrafluoroethylene sterilization film according to claim 1 wherein:
the IPA bubble point of the sterilizing film is 0.16-0.24MPa;
the density of the degerming film is 430-800kg/m 3 。
3. A polytetrafluoroethylene sterilization film according to claim 1 wherein:
the primary node is in a granular structure, the SEM average diameter is 150-650nm, and the cross-sectional density of the primary node is not less than 40/100 μm 2 。
4. A polytetrafluoroethylene sterilization film according to claim 1 wherein:
the ratio of the SEM average diameter to the film thickness of the original nodes is 0.004-0.016; preferably, the ratio is 0.008 to 0.012.
5. A polytetrafluoroethylene sterilization film according to claim 1 wherein:
the SEM average length of the support fiber is 500-2500nm, and the SEM average diameter of the support fiber is 60-300nm.
6. A polytetrafluoroethylene sterilization film according to claim 1 wherein:
the ratio of the SEM average length to the SEM average diameter of the support fiber is 2-20;
the ratio of the SEM average length of the support fibers to the SEM average diameter of the origin is 1.5-10.
7. A polytetrafluoroethylene sterilization film according to claim 1 wherein:
and stacking a plurality of original nodes to form an original node aggregate, wherein the SEM diameter of the original node aggregate is not less than 0.3 mu m.
8. The polytetrafluoroethylene sterilization membrane as defined in claim 7, wherein:
the SEM average diameter of the primary node aggregates is 0.5-1.4 μm,
the cross-sectional density of the primary node aggregate is 2-18/100 μm 2 。
9. A polytetrafluoroethylene sterilization film according to claim 1 wherein: the first outer surface and the second outer surface each comprise surface fibers and surface nodes; the adjacent surface nodes are connected through the surface fibers, the SEM average length of the surface fibers is 800-2200nm, and the length-diameter ratio of the surface fibers is 4-16.
10. A polytetrafluoroethylene sterilization film according to claim 9 wherein: the SEM average length of the surface nodes is 600-2600nm, and the length-diameter ratio of the surface nodes is 1.5-6.
11. A polytetrafluoroethylene sterilization film according to claim 9 wherein:
the average density S of the film main body is 45% -85%, and the average density S is obtained through the following formula:
S＝D Real world /D×100％；
In the above, D Real world And D is the area of a certain area in the thickness direction of the film main body.
12. A polytetrafluoroethylene sterilization film according to claim 1 wherein: the thickness of the degerming film is 20-90 mu m, and the porosity is 55% -85%; the tensile strength of the degerming film is 10-40MPa.
13. The method for producing a polytetrafluoroethylene antibacterial film according to any one of claims 1 to 12, characterized in that: the method comprises the following steps:
A. mixing: mixing and stirring polytetrafluoroethylene dispersion resin and a lubricant uniformly to obtain paste;
B. blank manufacturing: prepressing the paste into a cylindrical blank body;
C. extrusion: extruding the blank obtained in the step B to form a flat strip-shaped matrix;
D. calendering: calendering the strip-shaped matrix to ensure that the thickness of the strip-shaped matrix after calendering is 15-40% of the thickness of the strip-shaped matrix before calendering;
E. and (3) drying: drying the strip-shaped matrix to volatilize the lubricant;
F. stretching in the longitudinal direction: longitudinally stretching the dried strip-shaped matrix at 200-320 ℃ with a longitudinal stretching multiple of 2-10 times to obtain a first strip-shaped matrix;
G. And (3) transversely stretching: transversely stretching the first strip-shaped matrix at 100-300 ℃ with a transverse stretching multiple of 18-40 times to obtain a second matrix;
H. and (3) performing primary heat setting: placing the second matrix in an environment with the temperature of 330-390 ℃ for primary heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the second matrix are not more than 15% during the primary heat setting, and the heat setting time is 0.2-3 minutes, so as to obtain a semi-finished product of the degerming film;
I. and (5) performing secondary heat setting: and (3) placing the semi-finished product of the degerming film in an environment with the temperature of 330-390 ℃ for secondary heat setting, wherein the longitudinal shrinkage and the transverse shrinkage of the semi-finished product of the degerming film are not more than 10% during the secondary heat setting, and the secondary heat setting time is 5-20 minutes, so that the degerming film is obtained.
14. The method for preparing the polytetrafluoroethylene antibacterial film according to claim 13, wherein:
the number average molecular weight of the polytetrafluoroethylene dispersion resin is 400-1200 ten thousand;
the lubricant is at least one of lubricating oil, palm oil, naphthenic oil, white oil, aviation kerosene, degreasing kerosene and paraffin.
15. The method for preparing the polytetrafluoroethylene antibacterial film according to claim 13, wherein: the step A of mixing specifically comprises the steps of mixing and stirring polytetrafluoroethylene dispersion resin and a lubricant according to a weight ratio of 1:0.1-1:0.3, then placing the mixture into an environment with a temperature of 35-50 ℃ for curing for 8-24 hours, and thus obtaining paste;
The temperature of the second heat setting is at least 10 ℃ higher than that of the first heat setting; the second heat setting is at least 4 minutes longer than the first heat setting.
16. The method for preparing the polytetrafluoroethylene antibacterial film according to claim 13, wherein:
the thickness of the strip-shaped matrix after the casting in the step D is 0.8-1.5mm;
the longitudinal stretching rate in the step F is 8% -75%/s, and the transverse stretching rate in the step G is 25% -70%/s.
17. Use of a polytetrafluoroethylene antibacterial membrane according to any one of claims 1-12, wherein: the polytetrafluoroethylene sterilization film is used for liquid sterilization and/or gas sterilization.
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