PM0.5 ultra-permeable air filtering membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of filtering membranes, in particular to a PM 0.5 ultra-permeable air filtering membrane and a preparation method and application thereof. Through a unique retraction shaping process, the internal stress of a molecular chain stretched once is released at the temperature of 115-150 DEG C, and meanwhile, a wafer connection structure is finely tuned, so that tortuous micropores adaptive to PM 0.5 interception are formed through induction, and the high Gurley air permeability of 10-20 s is guaranteed; and the mechanical stability of the fiber network is optimized, so that the tensile strength of the 0.8-5 [mu] m thin film is still maintained to be greater than or equal to 150 MPa, the contradiction that the traditional polyolefin film is poor in air permeability if the PM is 0.5 and low in strength if the film is thinned is thoroughly solved, and the coordination of four properties is realized.

Description

Technical Field

[0001] This invention relates to the field of filter membrane technology, and in particular to a PM0.5 ultra-permeable air filter membrane, its preparation method, and its application. Background Technology

[0002] Polyolefins are currently the mainstream substrate for air filter membranes due to their good chemical stability, strong biocompatibility, and controllable cost. Chinese invention patent CN105032210B mentions a polyolefin air filter membrane and its preparation method, which uses a thermally induced phase separation method to prepare the polyolefin air filter membrane. The membrane has a thickness of 80μm–300μm, a porosity of 50%–80%, and an air permeability of 5–200 L / (m²). 2 Compared to existing technologies, this method is particularly effective at filtering PM2.5, achieving a filtration efficiency of 99%. However, with the increasing demands for public health protection and high-end industries, the efficient retention of PM0.5 (ultra-small particles with a diameter much smaller than PM2.5) has become a major technical challenge in air filtration, preventing chip malfunctions caused by ultra-small particles. These scenarios require filter membranes to not only efficiently retain PM0.5 but also balance high-flux permeability with high strength and thinness.

[0003] Existing polyolefin membranes have significant limitations in PM0.5 filtration, failing to simultaneously achieve "high-efficiency PM0.5 retention, high flux, high strength, and thinness." Retaining PM0.5 requires reducing membrane pore size, which leads to a significant decrease in air permeability. If thinness is pursued for precision applications, membrane strength cannot be guaranteed, while thicker membranes further exacerbate the air permeability problem. Alternative materials (such as polyamide PA membranes) can achieve a certain PM0.5 retention effect, but their raw material costs are 2-3 times that of the polyolefins in this invention, and their complex processes result in high overall costs, hindering large-scale adoption. A few polyolefin solutions that improve PM0.5 efficiency either require "high-cost chemical modification" (such as introducing functional groups) to increase costs or lack acid and alkali resistance and anti-aging properties (the inherent advantages of polyolefins are not retained), making them unsuitable for the disinfection environments of medical settings (such as acid and alkali disinfectants) and the long-term stable operation requirements of semiconductor applications. In addition, existing technologies mostly focus on PM2.5 filtration, with insufficient targeted design for PM0.5. The few solutions that improve PM0.5 efficiency are either too expensive or have unresolved performance contradictions, failing to meet the needs of high-end scenarios.

[0004] In summary, the development of specialized polyolefin membranes for PM0.5 filtration and their preparation methods are of great significance for promoting the upgrading of air filtration technology. Summary of the Invention

[0005] This invention provides a PM0.5 ultra-permeable air filter membrane to at least solve one of the problems existing in related technologies. To achieve this objective, this invention is implemented through the following technical solution.

[0006] In a first aspect, a method for preparing a PM0.5 ultra-permeable air filter membrane includes the following steps:

[0007] S1. Mix polyolefin resin powder, wetting agent and diluent, heat and keep warm to swell, and obtain swollen polyolefin;

[0008] S2. Polyolefin cast film is obtained by co-extrusion of swollen polyolefin;

[0009] S3. The polyolefin cast film is first subjected to a biaxial stretching process using a stretching machine, and then the polyolefin cast film is degreased and dried at room temperature using an extractant to obtain an extract-dried film.

[0010] S4. The extracted and dried membrane is put back into the stretching machine for a second bidirectional shrinkage and shaping.

[0011] S5. The membrane after S4 shrinkage and shaping is placed into a stretching machine for a third biaxial stretching and heat setting treatment to obtain a PM0.5 ultra-permeable air filter membrane.

[0012] In step S1, adding a wetting agent while mixing the polyolefin resin powder and the diluent, and stirring thoroughly, can effectively improve the compatibility and wettability of the polyolefin powder and the diluent.

[0013] In some preferred embodiments, the mass ratio of the polyolefin resin powder, wetting agent, and diluent is 1:(0.05-0.3):(5-15).

[0014] In some preferred embodiments, the first biaxial stretching ratio of S3 is 4~12×4~12 times that of the polyolefin cast film in S2, that is, the stretching ratio in the MD direction is 4~12 times, the stretching ratio in the TD direction is 4~12 times, the stretching temperature is 110~160℃, and the residence time is 1~10min.

[0015] In some preferred embodiments, during the second bidirectional retraction shaping in S4, the bidirectional retraction temperature is 115~150℃ and the dwell time is 1~10min.

[0016] In some preferred embodiments, in the second bidirectional retraction shaping of S4, the stretch ratio after bidirectional retraction shaping is 3 to 12 times that of the S2 polyolefin cast film, that is, the stretch ratio in the MD direction is 3 to 12 times and the stretch ratio in the TD direction is 3 to 12 times.

[0017] Retraction stretching refers to a secondary biaxial retraction stretching at a lower ratio on the extract-dried membrane after primary stretching, performed at a temperature below the melting point of polyolefins but above their glass transition temperature. This process aims to partially spring back and disorient the high-stress molecular chain segments formed during the primary stretching, relaxing internal stress and further fine-tuning the connection points between the wafers. This optimizes the mechanical structure of the fiber network while forming more tortuous channels, laying the foundation for subsequent tertiary biaxial stretching and ultimately achieving a balance between high throughput and high strength.

[0018] In some preferred embodiments, the third biaxial stretching ratio of S5 is 5~15×5~15 times that of the S2 polyolefin cast film, that is, the stretching ratio in the MD direction is 5~15 times, the stretching ratio in the TD direction is 5~15 times, the heat setting temperature is 100~150℃, and the heat setting time is 1~5min.

[0019] In some preferred embodiments, the polyolefin resin powder is at least one of high molecular weight polyethylene powder or high molecular weight polypropylene powder.

[0020] In some preferred embodiments, the wetting agent is a nonionic surfactant, including at least one of self-dehydrated sorbitan fatty acid ester, polyoxyethylene self-dehydrated sorbitan fatty acid ester, and glycerol fatty acid ester, and the diluent includes at least one of liquid paraffin, dioctyl phthalate, dioctyl adipate, white oil, cyclohexane, dibutyl phthalate, and glycerol ester.

[0021] In some preferred embodiments, the extractant includes one of n-hexane, ethanol, heptane, dichloromethane, carbon tetrachloride, dioxane, diethyl ether, dioxane, and methyl ethyl ketone.

[0022] Secondly, a PM0.5 ultra-permeable air filter membrane obtained by the above preparation method, wherein the PM0.5 ultra-permeable air filter membrane has a PM0.5 filtration efficiency of 99.99% and a thickness of 1.1-2 μm.

[0023] In some preferred embodiments, the PM0.5 ultrapermeable air filter membrane has a Gurley permeability of 7.6-11 s / 100 mL.

[0024] Thirdly, an application of the PM0.5 ultra-permeable air filter membrane obtained by the above preparation method is applied to protection in the precision manufacturing, electronics manufacturing, and medical industries.

[0025] The embodiments of the present invention have the following beneficial effects:

[0026] (1) This invention uses a unique shrink-forming process to release the internal stress of the molecular chain after one stretching at a temperature of 115~150℃, while finely adjusting the wafer connection structure: it induces the formation of tortuous micropores adapted to PM0.5 interception, ensuring a high Gurley permeability of 7.6~11s; it also optimizes the mechanical stability of the fiber network, so that the 1.1~2μm thin film still maintains high bidirectional strength of >270MPa in the longitudinal direction and >225MPa in the transverse direction, completely solving the contradiction of traditional polyolefin film that "poor permeability when intercepting PM0.5 and low strength when thin", and achieving synergistic performance of four properties.

[0027] (2) Compared with polyamide (nylon) membrane, the price of polyolefin raw materials of the present invention is only 1 / 3 to 1 / 2 of that of polyamide (nylon) raw materials, the process energy consumption is lower, and the overall cost is reduced by more than 30%. Moreover, without the need for expensive modification, it can achieve the same PM0.5 interception effect as polyamide (nylon) raw materials. It also has the advantages of polyolefin acid and alkali resistance and anti-aging. It has outstanding cost performance in high-end scenarios and is easier to be widely used.

[0028] (3) CN105032210B also mentions a polyolefin air filter membrane similar to this invention. In the traditional thermally induced phase separation membrane fabrication process, this invention creatively introduces a "bidirectional retraction and shaping" step. The addition of this step faces significant technical resistance: First, active thermal retraction on the stretched membrane structure goes against the conventional technical approach of optimizing the orientation structure through continuous stretching, which presents a cognitive obstacle; second, the retraction process window is extremely narrow, and even slight deviations in temperature, magnification, and time can lead to membrane structure collapse or performance degradation, making process control difficult and R&D costs extremely high.

[0029] Furthermore, compared to the shortcomings of the prior art, such as large membrane thickness (80~300μm), poor air permeability (55s / 100mL), and inability to achieve ultra-high efficiency filtration of PM0.5, this invention achieves ultra-thin membrane thickness (1.1~2μm) while possessing groundbreaking performance with PM0.5 filtration efficiency ≥99.99%, Gurley air permeability of 7.6~11s / 100mL, and high bidirectional strength (MD>270MPa, TD>225MPa). It is more suitable for precision manufacturing and electronics, high-end consumer electronics, and medical and health protection fields, and successfully solves the technical contradiction of difficulty in synergistically improving high efficiency, high permeability, thinness, and high strength. Attached Figure Description

[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0031] Figure 1 Scanning electron microscope image of the PM0.5 ultrapermeable air filter membrane prepared in Example 1;

[0032] Figure 2 The pore size distribution diagram of the PM0.5 ultra-permeable air filter membrane prepared in Example 1;

[0033] Figure 3 The pore size distribution of the product prepared in Comparative Example 1 is shown.

[0034] Figure 4 The pore size distribution diagram of the PM0.5 ultra-permeable air filter membrane prepared in Example 2;

[0035] Figure 5 The pore size distribution diagram of the PM0.5 ultra-permeable air filter membrane prepared in Example 3;

[0036] Figure 6 The pore size distribution diagram is shown for the PM0.5 ultra-permeable air filter membrane prepared in Example 4. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the various embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details are presented in the various embodiments of the present invention to facilitate a better understanding of this application. However, the technical solutions claimed in this application can be implemented even without these technical details and various changes and modifications based on the following embodiments. The division of the various embodiments below is for ease of description and should not constitute any limitation on the specific implementation of the present invention. The various embodiments can be combined with and referenced by each other without contradiction.

[0038] The raw material information used in this invention is as follows:

[0039] The wetting agent, specifically sorbitan monooleate, was purchased from Guangzhou Junmu Biotechnology Co., Ltd., and its trade name is sorbitan monooleate.

[0040] The diluent, specifically white oil, was purchased from Maoming Hongtai Petrochemical Co., Ltd., and its trade name is cosmetic grade white oil.

[0041] The extractant, specifically dichloromethane, was purchased from Shandong Hongrun Chemical Co., Ltd., and its trade name is monobromodichloromethane.

[0042] The average molecular weight of the polyolefin resin powder is 5×10 4 ~1.5×10 7 .

[0043] Example 1

[0044] This embodiment provides a PM0.5 ultra-permeable air filter membrane, the preparation method of which includes:

[0045] S1. Polyethylene resin powder, dehydrated sorbitan monooleate and white oil are thoroughly mixed in a mass ratio of 1:0.05:5, heated to 125℃ and kept at that temperature to swell, thus obtaining swollen polyethylene;

[0046] S2. Swelled polyethylene is added to an extruder, and after blending, it is extruded through a die to obtain a polyethylene cast film. The working temperature of the extruder is 230℃.

[0047] S3. The polyethylene cast film is first subjected to biaxial stretching by a stretching machine, and then degreased and dried in a dichloromethane extraction tank at room temperature to obtain an extract-dried film. Its biaxial stretching ratio is 8×8 times that of the S2 cast film, the stretching temperature is 128℃, and the residence time is 5min.

[0048] S4. Place the extracted and dried film back into the biaxial synchronous stretching machine, clamp the film with the clamps of the biaxial synchronous stretching machine, heat and control the shrinkage of the film in the MD and TD directions. After shrinkage reaches the target ratio, keep it at a temperature of 120℃ for 6 minutes. The ratio of the film area after biaxial shrinkage and shaping is 6×6 times that of the S2 polyethylene cast film.

[0049] S5. The film after S4 shrinkage and shaping is placed into a biaxial synchronous stretching machine for a third biaxial stretching and heat setting treatment; the final ratio of the third biaxial stretching is 18×18 times that of the S2 polyethylene cast film, the heat setting temperature is 120℃, and the heat setting time is 5min, to obtain a PM0.5 ultra-permeable air filter membrane.

[0050] Scanning electron microscopy and pore size distribution of the PM0.5 ultrapermeable air filter membrane prepared in Example 1 are shown in Figure 1. Figure 1 and Figure 2 As shown.

[0051] Example 2

[0052] This embodiment provides a PM0.5 ultra-permeable air filter membrane, the preparation method of which includes:

[0053] S1. Polyethylene resin powder, dehydrated sorbitan monooleate and white oil are thoroughly mixed in a mass ratio of 1:0.225:15, heated to 125℃ and kept at that temperature to swell, thus obtaining swollen polyethylene;

[0054] S2. Swelled polyethylene is added to an extruder, and after blending, it is extruded through a die to obtain a polyethylene cast film. The working temperature of the extruder is 200℃.

[0055] S3. The polyethylene cast film is first subjected to biaxial stretching in a stretching machine, and then the polyethylene cast film is degreased and dried in a dichloromethane extraction cell at room temperature to obtain an extracted and dried film. Its biaxial stretching ratio is 9×9 times that of the S2 cast film, the stretching temperature is 128℃, and the residence time is 5min.

[0056] S4. The extracted and dried film is put back into the stretching machine, and the clamps of the biaxial synchronous stretching machine are used to clamp the film. The film is heated and the retraction in the MD and TD directions is controlled. After the retraction reaches the target ratio, it is kept at a constant temperature. The retraction and shaping temperature is 130℃ and the holding time is 5min. The ratio after retraction and shaping is 7×7 times that of S2 polyolefin cast film.

[0057] S5. The film after S4 shrinkage and shaping is placed into a biaxial synchronous stretching machine for a third biaxial stretching and heat setting treatment. The third biaxial stretching ratio is 16×16 times that of the S2 polyethylene cast film. The heat setting temperature is 115℃ and the heat setting time is 1min to obtain a PM0.5 ultra-permeable air filter membrane.

[0058] The pore size distribution of the PM0.5 ultrapermeable air filter membrane prepared in Example 2 is as follows: Figure 4 As shown.

[0059] Example 3

[0060] This embodiment provides a PM0.5 ultra-permeable air filter membrane, the preparation method of which includes:

[0061] S1. Polyethylene resin powder, dehydrated sorbitan monooleate and white oil are thoroughly mixed in a mass ratio of 1:0.1:9, heated to 125℃ and kept at that temperature to swell, thus obtaining swollen polyolefin;

[0062] S2. The swollen polyolefin is added to the extruder, and after blending, it is extruded through the die to obtain a polyethylene cast film. The working temperature of the extruder is 200℃.

[0063] S3. The polyethylene cast film is first subjected to a first biaxial stretching by a stretching machine to obtain a film sheet; then, the polyethylene cast film is degreased and dried at room temperature using dichloromethane to obtain an extract-dried film sheet, which has a biaxial stretching ratio of 7×7 times that of the S2 cast film, a stretching temperature of 122℃, and a residence time of 5min.

[0064] S4. The extracted and dried film is put back into the stretching machine, and the clamps of the biaxial synchronous stretching machine are used to clamp the film. The film is heated and the retraction in the MD and TD directions is controlled. After the retraction reaches the target ratio, it is kept at a constant temperature. The retraction and shaping temperature is 130℃ and the holding time is 5min. The ratio after retraction and shaping is 5×5 times that of S2 polyethylene cast film.

[0065] S5. The film after S4 shrinkage and shaping is placed in a stretching machine for a third biaxial stretching and heat setting treatment; the third biaxial stretching ratio is 17×17 times that of the S2 polyethylene cast film, the heat setting temperature is 116℃, and the heat setting time is 2min, to obtain a PM0.5 ultra-permeable air filter membrane.

[0066] The pore size distribution of the PM0.5 ultrapermeable air filter membrane prepared in Example 3 is as follows: Figure 5 As shown.

[0067] Example 4

[0068] This embodiment provides a PM0.5 ultra-permeable air filter membrane, the preparation method of which includes:

[0069] S1. Polyethylene resin powder, dehydrated sorbitan monooleate and white oil are thoroughly mixed in a mass ratio of 1:0.2:12, heated to 125℃ and kept at that temperature to swell, thus obtaining swollen polyethylene;

[0070] S2. Swelled polyethylene is added to an extruder, and after blending, it is extruded through a die to obtain a polyethylene cast film. The working temperature of the extruder is 210℃.

[0071] S3. The polyethylene cast film is first subjected to a first biaxial stretching by a stretching machine to obtain a film sheet; then, the polyethylene cast film is degreased and dried at room temperature using an extractant to obtain an extract-dried film sheet, with a biaxial stretching ratio of 6×6 times that of S2 polyethylene cast film, a stretching temperature of 120℃, and a residence time of 5min.

[0072] S4. The extracted and dried film is put back into the stretching machine, and the clamps of the biaxial synchronous stretching machine are used to clamp the film. The film is heated and the retraction in the MD and TD directions is controlled. After the retraction reaches the target ratio, it is kept at a constant temperature. The retraction and shaping temperature is 130℃ and the holding time is 5min. The ratio after retraction and shaping is 4×4 times that of S2 polyethylene cast film.

[0073] S5. The extracted membrane is placed in a biaxial synchronous stretching machine for a third biaxial stretching and heat setting treatment; the third biaxial stretching ratio is 15×15 times that of the S2 polyethylene cast film, the heat setting temperature is 110℃, and the heat setting time is 3min, to obtain a PM0.5 ultra-permeable air filter membrane.

[0074] The pore size distribution of the PM0.5 ultrapermeable air filter membrane prepared in Example 4 is as follows: Figure 6 As shown

[0075] Comparative Example 1

[0076] The pore size distribution of the polyolefin air filter membrane and its preparation method described in Example 7 of CN105032210B is as follows: Figure 3 As shown.

[0077] Comparative Example 2

[0078] The implementation method of this comparative example is the same as that of Example 1, except that,

[0079] S1-S3: Completely the same as in Example 1.

[0080] S4: Completely omit the bidirectional retraction and shaping step.

[0081] S5: Try to directly stretch the membrane obtained in S3 by a third time by 18×18 times.

[0082] Because the membrane lacks a stable fiber network reconstructed by S4, it undergoes brittle fracture during stretching and cannot form a film.

[0083] Comparative Example 3

[0084] The implementation method of this comparative example is the same as that of Example 1, except that,

[0085] S1-S3: Completely the same as in Example 1.

[0086] S4: Perform a second bidirectional retraction and shaping of the extracted and dried film, but set the temperature to 110℃, the residence time to 5min, and the retraction ratio to 5×5 times that of the S2 cast film.

[0087] S5: Just like in Example 1, a third stretching and heat setting of 18×18 times is performed.

[0088] The film obtained in this comparative example has a significantly lower tensile strength than that of Example 1, and its physical properties are shown in Table 1.

[0089] Comparative Example 4

[0090] The implementation method of this comparative example is the same as that of Example 1, except that,

[0091] S1-S3: Completely the same as in Example 1.

[0092] S4: Perform a second bidirectional shrinkage shaping at a temperature of 130℃, but excessively shrink it to 2.5 × 2.5 times the size of the S2 cast film.

[0093] S5: Exactly the same as Example 1.

[0094] The film obtained in this comparative example has significantly lower air permeability than that of Example 1, and its physical properties are shown in Table 1.

[0095] Comparative Example 5

[0096] The implementation method of this comparative example is the same as that of Example 1, except that,

[0097] S1-S4: Completely the same as in Example 1.

[0098] S5: Perform a third biaxial stretching and heat setting, but reduce the stretching ratio to 12×12 times and the heat setting time to 10 minutes.

[0099] The film obtained in this comparative example has a significantly lower tensile strength than that of Example 1, and its physical properties are shown in Table 1.

[0100] Comparative Example 6

[0101] The implementation method of this comparative example is the same as that of Example 1, except that,

[0102] S1-S3: Completely the same as in Example 1.

[0103] S4: The extracted and dried membrane is retracted a second time at 130°C to 5×5 times the size of the S2 cast membrane. However, after reaching the target retraction ratio, it is not kept at a constant temperature; the clamp is immediately released and the membrane is cooled, i.e., the dwell time is approximately 0 seconds.

[0104] S5.: The film obtained in S4, which has not been fully heat-set, is immediately subjected to a third biaxial stretching and heat-setting treatment, with a magnification of 17×17 times that of the S2 cast film, and the heat-setting conditions are the same as those in Comparative Example 1.

[0105] The film obtained in this comparative example has significantly lower air permeability than that of Example 1, and its physical properties are shown in Table 1.

[0106] Performance testing

[0107] 1. Gurley breathability:

[0108] Test standard: ASTM-D726

[0109] Testing instrument: Göller air permeability meter

[0110] Test parameters: Test area: 6.45 cm² (1 in²)

[0111] Test pressure difference: 1.22 kPa (0.5 inch water column)

[0112] Test gas volume: 100mL

[0113] Results are expressed as follows: the time required for 100 mL of air to pass through the sample is recorded in seconds (s), and the final result is expressed as "s / 100 mL". Five points are tested for each sample, and the average value is taken.

[0114] 2. Filtration efficiency test:

[0115] Test standard: Refer to national standard GB / T2626-2019.

[0116] Testing instruments: Filter media efficiency testing stand, using a laser particle counter.

[0117] Test aerosols: Sodium chloride (NaCl) aerosols with a counting median diameter (CMD) of 0.3 μm were used.

[0118] Test flow rate: 32L / min.

[0119] Test parameters: PM0.5 filtration efficiency: Measure and calculate the filtration efficiency for 0.3μm particles.

[0120] PM2.5 filtration efficiency: Measure and calculate the total counting efficiency for particles in the 0.3μm-2.5μm particle size range.

[0121] Results are expressed as percentages (%).

[0122] 3. Tensile strength:

[0123] Test standard: Refer to ASTM-D882, American Society for Testing and Materials.

[0124] Testing instrument: Universal testing machine.

[0125] Sample specifications: Cut the membrane sample into a standard dumbbell-shaped sample.

[0126] Test rate: 100 mm / min.

[0127] The results indicate that the maximum stress at which the specimen fractured was recorded, expressed in megapascals (MPa).

[0128] 4. Thickness test:

[0129] Test standard: Refer to national standard GB / T6672-2001.

[0130] Testing instrument: Thin film thickness gauge.

[0131] Test parameters: Measuring head pressure: 0.1 MPa.

[0132] The results are as follows: 10 points were randomly measured on each sample, and the average value was taken. The unit is micrometers (μm).

[0133] The test results are shown in Table 1.

[0134] Table 1

[0135]

[0136] Note: MD stands for Machine Direction, i.e., longitudinal tensile strength; TD stands for Transverse Direction, i.e., transverse tensile strength.

[0137] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a PM0.5 super transparent air filtration membrane, characterized in that, The method comprises the following steps: S1. mixing polyolefin resin powder, wetting agent and diluent, warming and swelling, to obtain swollen polyolefin; S2. obtaining polyolefin casting film by blending and extruding the swollen polyolefin; S3. first bidirectional stretching of the polyolefin casting film, then oil removal and drying of the polyolefin casting film at room temperature by using an extracting agent, to obtain an extracted and dried film piece; S4. second bidirectional shrinkage setting of the extracted and dried film piece; S5. third bidirectional stretching and heat setting of the film piece after the second shrinkage setting, to obtain a PM0.5 super-transparency air filtration membrane.

2. The production method according to claim 1, characterized by, The mass ratio of the polyolefin resin powder, the wetting agent and the diluent is 1: (0.05-0.3): (5-15).

3. The preparation method according to claim 2, characterized in that, The first bidirectional stretching of S3 has a stretching ratio of 4-12×4-12 times of the polyolefin casting film in S2, and the stretching temperature is 110-160℃, and the residence time is 1-10 min.

4. The production method according to claim 3, characterized by, In the second bidirectional shrinkage setting of S4, the bidirectional shrinkage temperature is 115-150℃, the residence time is 1-10 min, and the ratio after bidirectional shrinkage setting is 3-12×3-12 times of the polyolefin casting film in S2.

5. The production method according to claim 4, characterized by, The third bidirectional stretching of S5 has a stretching ratio of 5-15×5-15 times of the polyolefin casting film in S2, and the heat setting temperature is 100-150℃, and the heat setting time is 1-5 min.

6. The method of claim 1, wherein, The polyolefin resin powder is at least one of high molecular weight polyethylene powder or high molecular weight polypropylene powder.

7. The preparation method according to claim 1, characterized in that, The wetting agent is a non-ionic surfactant, including at least one of sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester and glycerol fatty acid ester, and / or the diluent includes at least one of liquid paraffin, dioctyl phthalate, dioctyl adipate, white oil, cyclohexane, dibutyl phthalate and glycerol ester.

8. The PM0.5 super- breathable air filtration membrane prepared by the method of any one of claims 1-7, characterized in that, The PM0.5 super-transparency air filtration membrane has a PM0.5 filtration efficiency of 99.99%, and a thickness of 1.1-2μm.

9. The PM0.5 super-transparent air filtration membrane according to claim 8, characterized in that, The PM0.5 super-transparency air filtration membrane has a Gurley air permeability of 7.6-11s / 100mL.

10. Use of the PM0.5 super transparent air filtration membrane according to claim 8, characterized in that, It is applied to precision manufacturing, electronic manufacturing and medical industry protection.

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