KR102596345B1 - Nanofiber membrane, method of manufacturing the same, and filter - Google Patents

Abstract

The method of manufacturing a membrane made of nanofibers includes preparing a mixed solution by adding sodium dodecyl sulfate (SDS) to polyvinylidene fluoride (PVDF) and electrospinning the mixed solution using an electrospinning method. do.

Description

Membrane made of nanofibers, manufacturing method and filter thereof {NANOFIBER MEMBRANE, METHOD OF MANUFACTURING THE SAME, AND FILTER}

The present invention relates to a membrane made of nanofibers, and more specifically to a ferroelectric PVDF nanofiber membrane for high efficiency PM0.3 air filtration with low air flow resistance.

Particulate matter (PM: PM0.3, PM2.5, PM1.0) has recently emerged as a serious public health problem worldwide due to rapid urbanization and excessive use of fossil fuels. PM0.3 (particle size ≤ 0.3 μm) is the Most Penetration Particle Size (MPPS) by conventional filtration methods and is considered the most harmful component. PM0.3 can directly cause respiratory diseases, posing a serious threat to public health, and long-term exposure to such fine dust can lead to lung cancer and eventually death. Additionally, the recent severe acute respiratory syndrome coronavirus (SARS-CoV-2) spreads rapidly through small droplets, leading to a rapid increase in daily confirmed cases and deaths. Therefore, there is an urgent need for air purification research that can be relevant to public health to prevent the spread of SARS-CoV-2 and provide dust-free air for our breathing. Removing PM (fine dust), which is air that can contain droplets contaminated with viruses, is considered an effective way to improve public health problems.

Various methods have already been proposed to remove PM (fine dust) from the air. However, simple physical filtration of PM using filter membranes is considered a viable solution to alleviate these problems. Fiber web filters have been fabricated using various techniques such as melt blown (MB), needle punching, and wet processes to develop highly efficient air filtration membranes. However, these methods typically suffer from large apertures, limited fiber diameter reduction, and limited air filtration performance for highly agglomerated and bound fine particles. Additionally, remaining limitations such as large fiber diameter, loss of filtration performance and non-reusability must be addressed.

The filter function is mainly based on the electret charge effect, which is effective only under limited conditions, such as environments without oil or alcohol vapors. When the MB filter was exposed to organic solvents such as isopropanol, ethanol, and acetone, a decrease in electrostatic force and filter efficiency was observed due to charge loss. As the demand for masks to prevent COVID-19 has increased recently, there are concerns about the non-reusability of MB filters.

One object of the present invention is to provide a method for manufacturing a ferroelectric polyvinylidene fluoride (PVDF) nanofiber (NF) filter membrane through an electrospinning process.

Another object of the present invention is to provide a high-performance, low-cost air filter membrane.

A method of manufacturing a membrane made of nanofibers for the purpose of the present invention includes the steps of adding sodium dodecyl sulfate (SDS) to polyvinylidene (PVDF) to prepare a mixed solution and electrospinning the mixed solution using an electrospinning method. May include steps.

In one embodiment, the amount of SDS may be 0.2 to 0.8 wt%, preferably 0.3 to 0.7 wt%, more preferably 0.4 to 0.6 wt%, and more preferably 0.5 wt%. It can be.

In one embodiment, the step of electrospinning using the electrospinning method may additionally include alcohol impregnation and heat treatment.

In one embodiment, the diameter of the nanofiber may be 40 to 100 nm, preferably 50 to 90 nm, more preferably 60 to 80 nm, and more preferably 70 nm. there is.

For other purposes of the present invention, a membrane made of nanofibers manufactured according to the above manufacturing method can be manufactured.

In one embodiment, the membrane may have a pressure drop of 2 to 10 mmH ₂ O, preferably 5.2 mmH ₂ O.

In one embodiment, the membrane may have a PM0.3 filtering efficiency (FE) of 90 to 99.9%, preferably 97.4%.

For another purpose of the present invention, a filter including a membrane manufactured according to the above manufacturing method can be manufactured.

By controlling the diameter and uniformity of the electrospun PVDF NF membrane by adding sodium dodecyl sulfate (SDS) as a conductive surfactant, the slip effect of air molecules can be utilized with nanofibers.

The presence of the β phase in the 70 nm membrane can result in the largest phase polarization in the bias voltage curve for the intrinsic piezoelectric/ferromagnetic properties of the PVDF NF material.

The optimized 70 nm PVDF NF membrane can exhibit a low pressure drop of 5.2 mmH ₂ O, a high PM0.3 filtering efficiency (FE) of 97.4%, and a high quality factor (QF) of 0.7 mmH ₂ O ^-1 .

The optimized 70 nm PVDF membrane can exhibit excellent chemical and thermal stability and maintain high air filtration efficiency upon isopropyl alcohol immersion and heat treatment.

1 is a schematic diagram of the PVDF nanofiber air filter of the present invention.
Figure 2 is related to the nanofiber of the present invention, (a) is a curve graph of the particle size with high permeability, (b) is an image showing the slip effect according to the change in fiber diameter, and (c) is a ferroelectric capturing fine dust. This is an image that shows the impact on.
Figure 3 relates to the morphology results of the surface of the nanofiber membrane of various diameters of the present invention. (a) is an image showing the electrospinning processing composition of PVDF polymer and SDS additive, and (b) is an image showing the composition of PVDF nanofibers according to changes in SDS concentration. This image shows the change in fiber diameter, (c) is an image showing the electrospun pure PVDF sample, and (d) is the FE-SEM image of the sample containing 0.5 wt% SDS.
Figure 4 relates to phase identification of PVDF nanofibers of the present invention. (a) is FT-IR (Fourier-transform infrared spectroscopy) in various shapes and diameters of PVDF, and (b) is FT-IR in various shapes and diameters of PVDF. This is a GIXRD (Grazing Incidence X-ray Diffraction) pattern graph.
Figure 5 is a piezoresponse force microscopy (FEM) graph of the PVDF nanofiber of the present invention. (a) is a loop displayed in the form of phase ϕ as a function of DC voltage, and (b) is a loop of the DC voltage. This is a loop shown in the form of amplitude A as a function
Figure 6 is a graph related to the air filtration efficiency performance according to the SDS content and pressure drop of the nanofiber filter. (a) shows the air filtration efficiency of SDS-free PVDF, 0.05 wt%-SDS PVDF, and 0.5 wt%-SDS PVDF filters. is a graph showing the pressure drop, (b) is a graph showing the QF and air filter efficiency of a 0.05 wt%-SDS PVDF filter with an average diameter of 70 nm, and (c) _is a graph showing the SDS- This is a graph showing the QF and air filter efficiency of free PVDF, 0.05 wt%-SDS PVDF, and 0.5 wt%-SDS PVDF filters.
Figure 7 relates to the chemical and thermal stability of the PVDF nanofibers of the present invention. (a) is a graph comparing the filter efficiency of the PVDF nanofiber membrane and PP (polypropylene) MB membrane after IPA treatment, and (b) is a graph comparing the filter efficiency of the PVDF nanofiber membrane after IPA treatment. It is a graph showing the FTIR of PVDF nanofiber membrane and PP MB membrane, (c) is an XRD graph measured at various times of PVDF nanofiber quenched in IPA, and (d) is filtration of PVDF nanofiber membrane treated at high temperature. This is a graph showing the performance, (e) is a graph showing the FTIR of the PVDF nanofiber membrane treated at high temperature, and (f) is the XRD graph of the PVDF nanofiber heat treated for 24 hours at various temperatures.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. Since the present invention can be subject to various changes and have various forms, specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention. While describing each drawing, similar reference numerals are used for similar components.

The terms used in this application are only used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise” or “have” are intended to designate the presence of features, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features or steps. , it should be understood that it does not exclude in advance the possibility of the existence or addition of operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and unless explicitly defined in the present application, should not be interpreted in an ideal or excessively formal sense. No.

This is a technology for manufacturing a membrane filter made of nanofibers to overcome the limitations of existing MB filters and filter PM0.3 fine dust. In the case of membranes for removing very fine dust, there is a problem that the air pressure drop becomes too large and the filtration efficiency decreases. The present invention aims to solve this problem.

Figure 1 is a schematic diagram of the PVDF nanofiber air filter of the present invention, and Figure 2 is related to the nanofiber of the present invention. (a) is a curve graph of the particle size with high permeability, and (b) is the slip effect according to the change in fiber diameter. This is an image showing , and (c) is an image showing the effect of ferroelectrics on capturing fine dust.

Referring to Figures 1 and 2, the method for producing a membrane made of nanofibers includes preparing a mixed solution by adding sodium dodecyl sulfate (SDS) to polyvinylidene fluoride (PVDF) and electrospinning the mixed solution. It may include the step of electrospinning using. In the present invention, to solve the air pressure drop problem, a nanofiber membrane was manufactured using an electrospinning method. In this case, PVDF nanofibers were used and SDS was added as a conductive surfactant. Through this, the filtration efficiency for PM0.3 can be increased through dipole interaction due to the slip effect and spontaneous polarization, which is a characteristic of ferroelectrics.

The amount of SDS may be 0.2 to 0.8 wt%, preferably 0.3 to 0.7 wt%, more preferably 0.4 to 0.6 wt%, and more preferably 0.5 wt%. The more SDS is added, the thinner the fiber diameter will be, but if it is too thin, a web shape for use as a membrane will not be formed, so the above-mentioned amount is preferable. Additionally, if the fiber diameter becomes too thick, the slip effect and ferroelectric effect do not appear, so the above range may be most desirable.

The step of electrospinning using the electrospinning method may additionally include alcohol impregnation and heat treatment. The 70 nm PVDF NF membrane undergoes thermal and chemical degradation with negligible filtration performance degradation (air filtration efficiencies of 95.99 and 87.9 % and pressure drops of 5.6 and 6.65 mmH ₂ O, respectively) after heating at 120 °C for 24 h and soaking in isopropanol for 1 h. Stability can be excellent. Therefore, among various polymers for electrospun NFs, polyvinylidene fluoride (PVDF) can have excellent mechanical properties, good thermal stability, feasible processing, high chemical resistance and flexibility, and high electroactivity properties.

The diameter of the nanofiber may be 40 to 100 nm, preferably 50 to 90 nm, more preferably 60 to 80 nm, and even more preferably 70 nm. To obtain the slip effect and the spontaneous polarization effect, which is a characteristic of ferroelectrics, the diameter of the fiber must be about 70 nm, and to obtain PVDF nanofibers with a diameter of 70 nm, 0.5 wt% of SDS must be added. PVDF consists of five possible crystalline phases including α, β, γ, δ and ε, and β-phase PVDF is a well-known polar phase with excellent ferroelectric and piezoelectric performance, but also thermodynamically stable properties. The phase of PVDF is a non-electrically active α phase, and in this case, PVDF has a β-phase structure, so it can achieve both the effect of trapping fine dust by a built-in electric field with ferroelectric properties due to spontaneous polarization and an effective reduction of pressure drop through the slip effect. .

Ferroelectric 70 nm PVDF nanofiber membranes for PM0.3 filters were successfully fabricated with the introduction of 0.5 wt% SDS surfactant, where the β phase had a high proportion of 87% and exhibited a clear phase polarization with the largest piezoelectric strain. You can.

The application of the slip effect to alleviate the limitations of nanoporous membrane filters for implementation of the present invention is gaining considerable attention. It enables an effective reduction of the pressure drop due to the bypass phenomenon of air molecules through the fiber's mean free path (65.3 nm) and at the same time results in high PM filtering efficiency (Figure 2b). Therefore, the electrospun nanofiber filter can overcome the limitation of large diameter by using the electret filter described above. Electrospinning facilitates the fabrication of ultrathin diameter (10–1000 nm) nanofiber (NF) membranes at high electric fields, which are considered as advanced physical filters that adopt the slip effect regime of air. Methods such as chemical functionalization and filter filling can also be widely implemented as other strategies to improve fine dust capture performance. Among them, ferro/piezoelectricity was used, which shows that its unique electroactive properties with stable spontaneous polarization can be efficient. A large built-in electric field can trap fine dust (Figure 2c) and prevent PM from being inhaled into the respiratory tract.

A membrane made of nanofibers manufactured according to the above-mentioned manufacturing method can be manufactured. Among various polymers for electrospun NFs, polyvinylidene fluoride (PVDF) can have excellent mechanical properties, good thermal stability, feasible processing, high chemical resistance and flexibility, and high electroactivity properties.

The fabricated ultrathin 70 nm PVDF filter membrane reduces PM0.3 from 90 to 99.9% with a low pressure drop of 2 to 10 mmH ₂ O at an airflow of 5.3 cm s ^-1 due to the synergistic combination of ferroelectric effects between slip and dipole interactions. It indicates the filtering efficiency (FE) and the high quality coefficient (QF) can be 0.7 mmH ₂ O ^-1 , but preferably the pressure drop of the membrane is 5.2 mmH ₂ O and the PM0.3 filtering efficiency (FE) of the membrane is 97.4% . In particular, the high-performance ultra-thin 70 nm PVDF membrane maintains high air filtration efficiency even under various processing conditions and has excellent chemical and thermal stability. Therefore, ferroelectric PVDF NF filters can be viewed as a suitable advanced material that can alleviate the problems of fine dust pollutants and temporary COVID-19 prevention.

A filter containing a membrane manufactured by the above-mentioned method can be manufactured.

Example 1: Polymer solution preparation

15 wt% of PVDF powder was dissolved in a 5:5 mixture of DMAc (N,N-dimethylacetamide) and MEK (2-butanon).

Afterwards, various concentrations of SDS and PVDF of 0.05 to 0.5 wt% were added to the polymer and left to stand at 25°C overnight.

Example 2: Fabrication of nanofiber membrane

3A is an image depicting an electric spray system.

Referring to Figure 3a, PVDF nanofibers were produced using an electrospray method. A syringe for the polymer solution containing five metal spinneret needles was set up. Electrospraying of PVDF solution was performed on a movable support frame.

Figure 3 specifically shows the morphology modification of electrospun NF (Nanofiber) under the influence of various amounts of SDS surfactant. In particular, the bead-containing fibers were gradually removed with increasing SDS concentration and finally NF uniformity was achieved. Additionally, as shown in Figure 3c-d, adding SDS can significantly thin the fiber diameter. PVDF NFs without SDS exhibit the largest average diameter of ∼250 nm, while NFs with 0.5 wt%-SDS are very thin and highly homogeneous at ∼70 nm.

Nanofiber-based fillers enable the formation of net-shaped support structures and tortuous pore channels. This allows it to effectively trap dust particles in the air molecules. If the diameter of the nanofibers is close and the average free path length of the gas molecules is 65.3 nm, it causes a slip effect and effectively uses adjacent nanofibers at the periphery of the air flow stream to interact. Through effective control of the conductivity and viscosity of the polymer solution, the PVDF membrane can be tailored to the desired shape using an optimal electrospray process and SDS as an additive. Referring to Figure 3b, it shows non-uniform large diameter fibers of 80-250 nm at a 15 wt% concentration of pure PVDF. As a result, the beads result in low viscosity of the polymer solution and unbalanced surface tension, electrostatic repulsion, and instability of the fibers at the spinneret tip of the Taylor cone. The concentration of the polymer solution decreases due to the non-uniform bead structure. However, uniformity of shape and thin diameter fibers were observed in the conductivity of the polymer solution modified by ionic surfactant. This is due to the reduced surface tension of the solution, which increases the coulombic interaction and the enhanced stretching force of the electrospray solution jet. Therefore, SDS can be introduced to reduce surface tension and enhance charge density or solution conductivity.

Figure 4 shows the results of FRIR and GIXRD measurements to obtain a comprehensive understanding of PVDF polymorphs in electrospun PVDF nanofibers. The FTIR spectrum in Figure 4(a) shows the phase transformation of PVDF from the thermodynamically stable α phase of the powder sample to the ferroelectric β phase of the nanoanchored electrospun nanofiber sample. The 765 cm ^-1 , 855 cm ^-1 , and 976 cm ^-1 vibrational bends of the α phase in the PVDF powder sample gradually faded, indicating the gradual disappearance of the solution cast membrane in the electrosprayed nanofiber sample. it means. The vibration bands of the β phase appeared at 840 cm ^-1 and 1,279 cm ^-1 . It was confirmed that the peak of the β phase was further strengthened in the electrospray nanofibers due to the high electric force. The fraction of the β phase (F(β)) was calculated using the Beer-Lamber equation according to the absorbance value using the FRIR measurement value and is shown in Table 1 below. The value of F(β) showed a large difference when electrospinning was applied and when it was not applied. In particular, the F(β) value of PVDF powder, which is mostly non-polar α phase, was 39.42%, and the F(β) value of the sample cast from the solution into a thin film was 55%. However, the F(β) value of the fiber electrospun without SDS surfactant was 70.15%, and the 70 nm fiber sample with 0.5 wt% SDS was found to increase to 87%.

Sample β fraction(%) A _β /A _α PVDF powder 39.42 - Solution casting PVDF 54.62 0.44 Electrospun PVDF 0 wt% SDS 70.15 0.90 Electrospun PVDF 0.05 wt% SDS 83.70 1.42 Electrospun PVDF 0.5 wt% SDS 87.0 1.61

In addition, in the GIXRD graph of Figure 4(b), the GIXRD diffraction peak of the α(100) phase at 17.7° and the GIXRD diffraction peak of the β(110) phase at 20.26° confirmed the phase change from the α phase to the β phase within the nanofiber. .

According to the FTIR results, the PVDF powder reflected three main XRD peak positions at 18.27°, 19.7°, and 26.5°, which were identical to the single-phase α crystal phase. The phase change to β phase could be clearly confirmed in solution-cast thin films and electrospun PVDF nanofibers. Enhancement of the β diffraction peak was observed with relative increase in SDS content in the polymer solution and decrease in nanofiber diameter. The gradual displacement of the α phase by the β phase in the non-SDS-electric spin fiber is induced by the poling effect of the PVDF chains due to the large electric field during electrorotation. In addition, the high β-phase concentration in the small-diameter sample is because the charge density was enhanced by adding small-diameter SDS and nanoconfinement. The small diameter, low surface tension polymer jet facilitates the transition of the PVDF phase from the α phase to the β phase by the stronger stretching force associated with the high applied electric field.

Figure 5 shows the piezoelectric hysteresis loop of PVDF nanofibers of various diameters, where (a) is the loop in the form of phase ϕ as a function of DC voltage and (b) is the amplitude A as a function of DC voltage. It is a loop shown in the form of .

Referring to Figure 5, it was confirmed that the movement of the loop along the voltage axis occurred due to the asymmetry of the tip/nanofiber/gold configuration. The phase and amplification curves of all nanofibers showed square-shaped and butterfly-shaped hysteresis loops and good reproducibility. In particular, a standard hysteresis loop and good reproducibility were confirmed in the 70 nm diameter nanofiber, which means that the 120 nm and 200 nm nanofibers contain more nonpolar α phase.

Example 3: Chemical and thermal stability experiments of PVDF NF membranes

A filter membrane was manufactured for chemical stability experiments. Various immersion times in IPA (isopropylalcohol) were applied and sequentially dried in the air for 12 hours. For thermal stability testing, the filter membrane was heated in a vacuum oven for 24 hours at different temperatures.

Figure 6 relates to the air filter efficiency of nanofiber filters. (a) is a graph showing the air filtration efficiency and pressure drop of SDS-free PVDF, 0.05 wt%-SDS PVDF, and 0.5 wt%-SDS PVDF filters, and (b) is a graph showing the air filtration efficiency of nanofiber filters. is a graph showing the QF and air filter efficiency of a 0.05 wt%-SDS PVDF filter with an average diameter of 70 nm, and (c) is a graph showing the QF and air filter efficiency of SDS-free PVDF, 0.05 wt%-SDS PVDF, and 0.5 wt%-SDS PVDF at a pressure drop of 3.0-3.1 mmH ₂ O. This is a graph showing the QF and air filter efficiency of the wt%-SDS PVDF filter.

Referring to Figure 6, the fine dust filtering performance of 120 nm and 70 nm PVDF NF webs can be confirmed compared to larger size SDS-free PVDF filters in various mass regions. SDS-free PVDF NF filters have very low filtration efficiency compared to fibers of the same loaded basic weight. Even though the mass area increased to 2.5 gm ^-2 , the filtration efficiency of the SDS-free FVDF NS filter was approximately 46.4% at a pressure drop of 3.05 mmH ₂ O. This is caused by the negative effect of the large fiber diameter and bead structure consuming some of the mass of the injected polymer. However, in the 120 nm PVDF NF membrane, FE was improved to 74.65% at the same pressure drop of 3.0 mmH ₂ O and basis weight of 0.25 gm ^-2 (Figure 6a).

In particular, with a pressure drop of 5.2 mmH ₂ O for air-FE of 97.387%, QF shows the most optimal performance for the 70 nm fiber membrane clearly illustrated in Figure 6b with 0.7 mmH ₂ O ^-1 . According to Figure 6b, FE and QF show a clear increase with decreasing nanofiber diameter. As confirmed by spectroscopic and piezoelectric force microscopy, the largest electric field among 70 nm PVDF nanofibers can have a significant effect on capturing PM0.3 in the nanofiber membrane and thereby improving air filtration efficiency. Moreover, as previously mentioned, the diameter of 70 nm is close to the mean free path of air molecules, which allows air molecules to bypass the thin nanofibers, resulting in a significant reduction in air flow and the pressure generated by the filter membrane.

To clearly evaluate the improvement in PM0.3 filtration performance of smaller diameter PVDF NFs, membranes with three representative nanofiber diameters were fabricated with a pressure drop of approximately 3.0 to 3.1 mmH ₂ O. Referring to Figure 6c, the QF equivalent to the measured filtration efficiency can be confirmed. FE and QF showed a clear increase as the nanofiber diameter decreased. When the nanofiber diameter reached 70 nm, the filtration efficiency of the filter was the highest at 90.1%, the QF was the highest at 0.75 mmH ₂ O ^-1 , and the relative pressure drop was 3.1 mmH ₂ O.

Figure 7 relates to the chemical and thermal stability of PVDF nanofibers. (a) is a graph showing comparison of filter efficiency of PVDF nanofiber membrane and PP MB membrane after IPA treatment, and (b) is a graph showing comparison of filter efficiency of PVDF nanofiber membrane and PP MB membrane after IPA treatment. (c) is a graph showing the FTIR of the membrane, (c) is an This is a graph showing the FTIR of the PVDF nanofiber membrane treated at high temperature, and (f) is the XRD graph of the PVDF nanofiber heat treated for 24 hours at various temperatures.

Referring to Figure 7a-f, it shows the superior filtration efficiency of the PVDF nanofiber membrane over the polypropylene (PP) MB filter (Figure 7a). In particular, the PP MB membrane exhibited FE ranging from 99.91% to nearly 35% after soaking in IPA for 15 min. The significant decline in FE appears to be due to charge loss in the PP MB filter due to IPA penetration. On the contrary, after soaking the PVDF nanofiber membrane in IPA for 60 minutes, it showed a high filtration performance retention rate of 92.63%. The small decrease in FE is due to the degradation of the ferroelectric β phase of the PVDF nanofibers due to solvent impregnation and subsequent dipole loss (Figures 7b, 7c). The thermal stability shows the excellent filtration performance of the PVDF nanofiber membrane at high temperature treatment with a slight FE decrease (ΔFE = 1.89%) at 100 °C (Figure 7d). Additionally, at an increased annealing temperature of 120°C, the

Although the present invention has been described above with reference to preferred embodiments, those skilled in the art can make various modifications and changes to the present invention without departing from the spirit and scope of the present invention as set forth in the following patent claims. You will understand that it is possible.

Claims (16)

Preparing a mixed solution by adding sodium dodecyl sulfate (SDS) to polyvinylidene fluoride (PVDF); and
It includes the step of electrospinning the mixed solution using an electrospinning method,
The amount of SDS is 0.2 to 0.8 wt%,
The diameter of the nanofiber is 40 to 100 nm,
The electrospinning step using the electrospinning method further includes alcohol impregnation and heat treatment,
Method for manufacturing a membrane made of nanofibers. delete According to clause 1,
Characterized in that the amount of SDS is 0.3 to 0.7 wt%,
Method for manufacturing a membrane made of nanofibers. According to clause 1,
Characterized in that the amount of SDS is 0.4 to 0.6 wt%,
Method for manufacturing a membrane made of nanofibers. According to clause 1,
Characterized in that the amount of SDS is 0.5 wt%,
Method for manufacturing a membrane made of nanofibers. delete delete According to clause 1,
Characterized in that the nanofiber diameter is 50 to 90 nm,
Method for manufacturing a membrane made of nanofibers. According to clause 1,
Characterized in that the nanofiber diameter is 60 to 80 nm,
Method for manufacturing a membrane made of nanofibers. According to clause 1,
Characterized in that the nanofiber diameter is 70 nm,
Method for manufacturing a membrane made of nanofibers. Manufactured according to the method of any one of claims 1, 3 to 5, and 8 to 10,
A membrane made of nanofibers. According to clause 11,
The membrane is characterized in that the pressure drop is 2 to 10 mmH ₂ O,
A membrane made of nanofibers. According to clause 11,
The membrane is characterized in that the pressure drop is 5.2 mmH ₂ O.
A membrane made of nanofibers. According to clause 11,
The membrane is characterized in that the PM0.3 filtering efficiency (FE) is 90 to 99.9%,
A membrane made of nanofibers. According to clause 11,
The membrane is characterized in that the PM0.3 filtering efficiency (FE) is 97.4%,
A membrane made of nanofibers. Manufactured according to the method of any one of claims 1, 3 to 5, and 8 to 10,
Filter with membrane.