Nanofiber filter and method for manufacturing same

Abstract

Disclosed are a nanofiber filter having an excellent pressure loss reduction effect, and a method for manufacturing same. The method for manufacturing a nanofiber filter according to the present invention comprises the steps of: (a) mixing a polymer, an organic solvent, and a salt compound to prepare a composition; and (b) electrospinning the composition on a support to manufacture a nanofiber filter in which nanofibers are attached on the support, wherein the concentration of the salt compound in the step (a) is 0.1-2 wt%, and the average diameter of the nanofibers in the step (b) is 65 nm or less.

Description

Nanofiber filter and its manufacturing method

[0001] The present invention relates to a nanofiber filter having an excellent pressure loss reduction effect and a method for manufacturing the same.

[0002] An air purifier is a device that purifies polluted air indoors and improves indoor air quality.

[0003] Air purifiers have filters that filter out microscopic particles, such as fine dust, bacteria, or viruses, floating in the air. These filters are made of bundles of fibers.

[0004] Air purifier filters primarily utilize a filter layer composed of polypropylene fibers with a diameter of 2 to 3 μm to remove particulate matter. These fibers are manufactured through melt spinning. While the filter layer exhibits high capture efficiency at low pressure loss due to its high electrostatic force, its efficiency rapidly declines with exposure to organic substances and prolonged use.

[0005] In theory, as the diameter of the fibers that make up the filter decreases, it shows excellent collection efficiency for ultrafine dust particles, but there is a disadvantage in that the pressure loss also increases.

[0006] As a method for manufacturing a nanofiber filter related to this, a spinning composition is manufactured by mixing a soluble polymer and a soluble polymer with a solvent, and an ultrafine fiber filter can be manufactured by removing the soluble polymer from microfibers obtained through electrospinning.

[0007] To manufacture ultrafine fiber filters, PAN and PVA polymers are mixed and DMSO is used as a solvent. However, heat treatment at 60-260°C and washing are required to remove the soluble polymer, and the resulting ultrafine fibers have an average diameter of around 250 nm. Specifically, this manufacturing method produces microfibers by removing the soluble polymers mixed in a bundled configuration, rather than a distinct fiber composed of a single strand.

[0008] Ultrafine fibers manufactured using this method fail to achieve an average diameter of 65 nm in terms of pressure loss reduction, and their fiber surfaces appear uneven. For these reasons, it is difficult to expect capture efficiency and pressure loss reduction in air filtration.

[0009] Accordingly, methods for reducing the average diameter of nanofibers are being studied, but reproducibility is low and performance is not sufficiently secured.

[0010] Therefore, a method for manufacturing a nanofiber filter having an average diameter of nanofibers of 65 nm or less is required to secure capture efficiency and pressure loss reduction effects.

[0011] The purpose of the present invention is to provide a nanofiber filter having an excellent pressure loss reduction effect by including nanofibers having an average diameter of 65 nm or less.

[0012] Another object of the present invention is to provide a nanofiber filter having excellent capture efficiency.

[0013] In addition, the purpose of the present invention is to provide a method for manufacturing a nanofiber filter including nanofibers having an average diameter of 65 nm or less while having a complete fiber shape by adding a salt compound to a spinning composition and controlling the nozzle diameter, voltage size, distance between the nozzle and the collecting plate, temperature atmosphere, and concentration of the polymer for electrospinning.

[0014] The objectives of the present invention are not limited to those mentioned above. Other objectives and advantages of the present invention not mentioned above can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the objectives and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0015] In an embodiment, a composition according to the present invention comprises a polymer, an organic solvent and a salt compound, wherein the concentration of the salt compound is 0.1 to 2 wt%.

[0016] The above salt compound may include at least one of sodium chloride (NaCl), calcium chloride (CaCl2), potassium chloride (KCl), lithium chloride (LiCl), and cetrimonium bromide (Ctab).

[0017] The concentration of the above polymer may be 17 to 22 wt%.

[0018]

[0019] In another embodiment, a composition according to the present invention comprises a polymer, an organic solvent and a salt compound, wherein the concentration of the polymer is 17 to 22 wt%.

[0020]

[0021] In another embodiment, a composition according to the present invention comprises a polymer, an organic solvent and a salt compound, wherein the salt compound comprises at least one of sodium chloride (NaCl), calcium chloride (CaCl2), potassium chloride (KCl), lithium chloride (LiCl) and cetrimonium bromide (Ctab).

[0022]

[0023] In an embodiment, a method for manufacturing a nanofiber filter according to the present invention is characterized by including the steps of (a) preparing a composition by mixing a polymer, an organic solvent, and a salt compound; and (b) electrospinning the composition onto a support to manufacture a nanofiber filter having nanofibers attached to the support.

[0024] In another embodiment, a method for manufacturing a nanofiber filter according to the present invention comprises the steps of (a) preparing a composition by mixing a polymer, an organic solvent, and a salt compound; and (b) electrospinning the composition onto a support to manufacture a nanofiber filter having nanofibers attached to the support; wherein in step (a), the concentration of the salt compound is 0.1 to 2 wt%, and in step (b), the average diameter of the nanofibers is 65 nm or less.

[0025] In the above step (a), the salt compound may include at least one of sodium chloride (NaCl), calcium chloride (CaCl2), potassium chloride (KCl), lithium chloride (LiCl), and cetrimonium bromide (Ctab).

[0026] In the above step (a), the concentration of the polymer may be 17 to 22 wt%.

[0027] In the above step (a), the polymer may include at least one of polypropylene (PP), polyurethane (PU), polyether sulfone, polyester (PES), polyimide (PI), polymethyl methacrylate (PMMA), nylon, polystyrene (PS), Teflon (PTFE), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), and polyacrylonitrile (PAN).

[0028] In the above step (a), the organic solvent may include at least one of dimethylformamide (DMF), diethylformamide (DEF), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), and methylpyrrolidone (NMP).

[0029] In the above step (a), the viscosity of the composition may be 1000cp to 9000cp.

[0030] The step (b) above may include: (b1) a step of filling the composition into a syringe, then providing a collecting plate so as to be spaced apart from the syringe, and placing a support on the collecting plate; and (b2) a step of applying voltage to the syringe, so that the composition is discharged as nanofibers from a nozzle of the syringe by the applied voltage, thereby manufacturing a nanofiber filter in which nanofibers are attached to a support.

[0031] The diameter of the above nozzle may be 0.60 mm or less.

[0032] In the above step (b2), a voltage of 9 to 25 kV can be applied.

[0033] The distance between the nozzle and the collecting plate may be 10 to 15 cm.

[0034] In the above step (b), electrospinning can be performed at 22 to 30°C.

[0035]

[0036] In another embodiment, a method for manufacturing a nanofiber filter according to the present invention comprises the steps of (a) preparing a composition by mixing a polymer, an organic solvent, and a salt compound; and (b) electrospinning the composition onto a support to manufacture a nanofiber filter having nanofibers attached to the support; wherein in step (a), the concentration of the salt compound is 0.1 to 2 wt%.

[0037] In another embodiment, a method for manufacturing a nanofiber filter according to the present invention comprises the steps of (a) preparing a composition by mixing a polymer, an organic solvent, and a salt compound; and (b) electrospinning the composition onto a support to manufacture a nanofiber filter having nanofibers attached to the support; wherein, in step (b), the average diameter of the nanofibers is 65 nm or less.

[0038] In another embodiment, a method for manufacturing a nanofiber filter according to the present invention comprises the steps of (a) preparing a composition by mixing a polymer, an organic solvent, and a salt compound; and (b) electrospinning the composition onto a support to manufacture a nanofiber filter having nanofibers attached to the support; wherein the salt compound comprises at least one of sodium chloride (NaCl), calcium chloride (CaCl2), potassium chloride (KCl), lithium chloride (LiCl), and cetrimonium bromide (Ctab).

[0039] In another embodiment, a method for manufacturing a nanofiber filter according to the present invention comprises the steps of (a) preparing a composition by mixing a polymer, an organic solvent, and a salt compound; and (b) electrospinning the composition onto a support to manufacture a nanofiber filter having nanofibers attached to the support; wherein in step (a), the concentration of the polymer is 17 to 22 wt%.

[0040] In another embodiment, a method for manufacturing a nanofiber filter according to the present invention comprises the steps of: (a) preparing a composition by mixing a polymer, an organic solvent, and a salt compound; and (b) electrospinning the composition onto a support to manufacture a nanofiber filter having nanofibers attached to the support; wherein in step (a), the polymer comprises at least one of polypropylene (PP), polyurethane (PU), polyether sulfone, polyester (PES), polyimide (PI), polymethyl methacrylate (PMMA), nylon, polystyrene (PS), Teflon (PTFE), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), and polyacrylonitrile (PAN).

[0041] In another embodiment, a method for manufacturing a nanofiber filter according to the present invention comprises the steps of (a) preparing a composition by mixing a polymer, an organic solvent, and a salt compound; and (b) electrospinning the composition onto a support to manufacture a nanofiber filter having nanofibers attached to the support; wherein in step (a), the organic solvent comprises at least one of dimethylformamide (DMF), diethylformamide (DEF), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), and methylpyrrolidone (NMP).

[0042] In another embodiment, a method for manufacturing a nanofiber filter according to the present invention comprises the steps of (a) preparing a composition by mixing a polymer, an organic solvent, and a salt compound; and (b) electrospinning the composition onto a support to manufacture a nanofiber filter having nanofibers attached to the support; wherein step (b) is characterized in that the electrospinning is performed at 22 to 30°C.

[0043] In another embodiment, a method for manufacturing a nanofiber filter according to the present invention comprises the steps of: (a) preparing a composition by mixing a polymer, an organic solvent, and a salt compound; and (b) electrospinning the composition onto a support to manufacture a nanofiber filter having nanofibers attached to the support; wherein step (b) comprises the steps of: (b1) filling a syringe with the composition, then preparing a collecting plate to be spaced apart from the syringe, and arranging a support on the collecting plate; and (b2) applying a voltage to the syringe to discharge the composition as nanofibers from a nozzle of the syringe by the applied voltage, thereby manufacturing a nanofiber filter having nanofibers attached to the support.

[0044]

[0045] In an embodiment, a nanofiber filter according to the present invention is characterized by including a support; and nanofibers attached to the support and including a polymer and a salt compound.

[0046] In another embodiment, a nanofiber filter according to the present invention comprises a support; and nanofibers attached to the support and comprising a polymer and a salt compound; wherein the average diameter of the nanofibers is 65 nm or less.

[0047] According to the present invention, by controlling the concentration of the salt compound and further controlling at least one of the nozzle diameter of the electrospinning, voltage level, the distance between the nozzle and the collecting plate, the temperature and atmosphere, the concentration of the polymer, and the viscosity of the composition, the average diameter of the nanofibers can be reduced to 65 nm or less. Accordingly, a nanofiber filter with excellent pressure loss reduction effect and superior collection efficiency can be manufactured.

[0048] In addition to the effects described above, specific effects of the present invention are described below while explaining specific details for carrying out the invention.

[0049] Figure 1 is a flowchart showing a method for manufacturing a nanofiber filter according to the present invention.

[0050] Figure 2 is an FE-SEM photograph showing the average diameter of nanofibers according to the concentration of the polymer and the temperature and atmosphere during electrospinning.

[0051] Figure 3 is an FE-SEM photograph (x30,000 magnification) showing the average diameter of nanofibers according to the polymer concentration of 15 wt%, 17 wt%, and 19 wt% and the nozzle diameter of 0.67 mm and 0.40 mm during electrospinning.

[0052] Figure 4 is an FE-SEM photograph showing whether beads were formed according to the concentration of salt compound (LiCl) of 0 to 0.4 wt% when the concentration of polymer was 15 wt% and 19 wt%.

[0053] Figure 5 is an FE-SEM photograph (x30,000 magnification) showing the formation of beads and the average diameter of nanofibers according to the concentration of salt compound (LiCl) of 0 to 0.4 wt% when the concentration of polymer is 15 wt% and 19 wt%.

[0054] Figure 6 is an FE-SEM photograph showing the average diameter of nanofibers under the conditions of 19 wt% of polymer PES7020, DMF:NMP=8:2, 3.3 ㎕ / min, nozzle diameter 22 G (0.40 mm), LiCl:Ctab=0.15 wt%:0.4 wt%, voltage applied during electrospinning of 18 kV, grounding of the collecting plate of -4 kV, distance between the nozzle and the collecting plate of 10 cm, temperature of 24.9 ℃ and humidity of 31% during electrospinning.

[0055] Figure 7 is an FE-SEM photograph showing the average diameter of nanofibers under the conditions of 19 wt% of polymer PES7020, DMF:NMP=8:2, LiCl:Ctab=0.15 wt%:0.4 wt%, discharge amount 3.3㎕ / min, nozzle diameter 22G (0.40 mm), voltage applied during electrospinning 17 kV, grounding part of the collecting plate -4 kV, distance between nozzle and collecting plate 15 cm, temperature 24.8℃ and humidity 30% during electrospinning.

[0056] Figure 8 is an FE-SEM photograph showing the average diameter of nanofibers under the conditions of 19 wt% of polymer PES7020, DMF alone, Ctab=0.4 wt%, discharge amount 3.3 μL / min, nozzle diameter 22 G (0.40 mm), voltage applied during electrospinning 14.5 kV, grounding part of the collecting plate -4 kV, distance between the nozzle and the collecting plate 15 cm, temperature 25°C, and humidity 28% during electrospinning.

[0057] Figure 9 is an FE-SEM photograph showing the average diameter of nanofibers under the conditions of 19 wt% of polymer PES7020, DMF alone, LiCl = 0.1 wt%, discharge amount 3.3 μL / min, nozzle diameter 22 G (0.40 mm), voltage applied during electrospinning 16 kV, grounding part of the collecting plate -4 kV, distance between nozzle and collecting plate 15 cm, temperature 25.2 ℃ and humidity 28% during electrospinning.

[0058] Figure 10 is an FE-SEM photograph showing the average diameter of nanofibers under the conditions of 19 wt% of polymer PES7020, DMF:NMP=8:2, LiCl=0.1 wt%, discharge amount 3.3㎕ / min, nozzle diameter 22G (0.40 mm), voltage applied during electrospinning 16.5 kV, grounding part of the collecting plate -4 kV, distance between nozzle and collecting plate 15 cm, temperature 23.7℃ and humidity 30% during electrospinning.

[0059] Figure 11 is an FE-SEM photograph showing the average diameter of nanofibers under the conditions of 18 wt% of polymer PES7020, DMF:NMP=8:2, Ctab 0.4 wt%, discharge amount 2.5 μL / min, nozzle diameter 22 G (0.40 mm), voltage applied during electrospinning 12.5 kV, grounding part of the collecting plate 0 kV, distance between nozzle and collecting plate 10 cm, temperature 25.2°C and humidity 30% during electrospinning.

[0060] Figure 12 is an FE-SEM photograph showing the average diameter of nanofibers under the conditions of 18.5 wt% of polymer PES7020, DMF:NMP=8:2, LiCl:Ctab=0.1 wt%:0.2 wt%, discharge amount 3.3 ㎕ / min, nozzle diameter 22 G (0.40 mm), voltage applied during electrospinning 10 kV, grounding part of the collecting plate -7 kV, distance between nozzle and collecting plate 10 cm, temperature 23.9 ℃ and humidity 30% during electrospinning.

[0061] Figure 13 is a graph showing the capture efficiency according to the average diameter of nanofibers.

[0062] Figure 14 is a graph showing the filter performance index according to the average diameter of nanofibers.

[0063] Figure 15 is a graph showing the filter performance index according to the average diameter of nanofibers.

[0064] The above-described objects, features, and advantages will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can easily practice the technical idea of ​​the present invention. In describing the present invention, if it is determined that a detailed description of known technologies related to the present invention may unnecessarily obscure the gist of the present invention, a detailed description thereof will be omitted. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to indicate the same or similar components.

[0065] Hereinafter, the phrase "any configuration is placed on (or below)" a component or "on (or below)" a component may mean that any configuration is placed in contact with the upper surface (or lower surface) of said component, and that other configurations may be interposed between said component and any configuration placed on (or below) said component.

[0066] Additionally, when it is described that a component is "connected," "coupled," or "connected" to another component, it should be understood that the components may be directly connected or connected to one another, but that other components may also be "interposed" between the components, or that each component may be "connected," "coupled," or "connected" through another component.

[0067] Hereinafter, a nanofiber filter and a method for manufacturing the same according to some embodiments of the present invention will be described.

[0068] The present invention can discharge nanofibers having a complete fiber shape and an average diameter of 65 nm or less by controlling the concentration of a salt compound and further controlling at least one of the nozzle diameter of the electrospinning, the voltage size, the distance between the nozzle and the collecting plate, the temperature and humidity, the concentration of the polymer, and the viscosity of the composition. The nanofibers discharged in this way are attached to a support and manufactured into a nanofiber filter. The manufactured nanofiber filter can exhibit a pressure loss reduction effect due to a decrease in resistance as air molecules slide on the surface of the nanofibers when the average diameter of the nanofibers approaches 65 nm, and excellent collection efficiency. The average diameter of the nanofibers can mean the distance traveled between different air molecules in the atmosphere.

[0069] In the present invention, "spinning" means converting a polymer composition, which has been heated and melted or dissolved in a solvent, into a thin fiber, i.e., a yarn, by continuously passing it through a small-diameter nozzle or other hole. In this case, electrospinning means applying a high direct current voltage of several thousand to tens of thousands of volts to the composition to produce the composition in the form of a yarn.

[0070] In the present invention, a complete fiber shape may mean that one fiber strand is not connected or joined to another fiber strand, and that the diameter and surface properties of one fiber strand are uniform.

[0071] In the present invention, the target object captured by the filter may include ultra-fine particles such as dust, viruses, metal ions, organic matter, and inorganic particles in the air.

[0072] Pressure loss is caused by the flow rate passing through the filter volume. The pressure loss value is calculated as the difference between the upstream and downstream sides of the filter.

[0073] Pressure loss reduction occurs when the average diameter of the nanofibers in the fabric acting as the filtration layer approaches or is smaller than 65 nm. This reduces airflow resistance due to the sliding effect of air molecules. This, in turn, reduces pressure loss. As the number of particles captured by the filter increases, pressure loss increases. In terms of CADR, increased pressure loss significantly impacts performance because it reduces the airflow of the air purifier.

[0074] In the air purifier industry, energy efficiency and the area cleaned are crucial. Using a filter with a high differential pressure drastically reduces the supply of purified air. To compensate, the fan output of the air purifier must be increased. This increases the air purifier's power consumption and may result in noise. If the fan output remains unchanged, the area cleaned by the filtered device will drastically decrease. This makes it difficult to purify indoor air quality.

[0075] Therefore, it is desirable to reduce the average diameter of the nanofibers constituting the nanofiber filter to ensure a pressure loss reduction effect and excellent capture efficiency.

[0076] Figure 1 is a flowchart showing a method for manufacturing a nanofiber filter according to the present invention.

[0077] As illustrated in FIG. 1, the method for manufacturing a nanofiber filter is characterized by including a step (S110) of preparing a composition by mixing a polymer, an organic solvent, and a salt compound, and a step (S120) of electrospinning the composition onto a support to discharge nanofibers having an average diameter of 65 nm or less, and manufacturing a nanofiber filter with the nanofibers attached to the support.

[0078] First, a composition can be prepared by mixing a polymer, an organic solvent, and a salt compound.

[0079] The composition according to the present invention comprises a polymer, an organic solvent and a salt compound, and is characterized in that the concentration of the salt compound is 0.1 to 2 wt%.

[0080] The composition is extruded and formed into nanofibers, and may include a polymer in powder or chip form as a nanofiber raw material.

[0081] The polymer may include one or more of polypropylene (PP), polyurethane (PU), polyether sulfone, polyester (PES), polyimide (PI), polymethyl methacrylate (PMMA), nylon, polystyrene (PS), Teflon (PTFE), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), and polyacrylonitrile (PAN).

[0082] Polypropylene (PP) is economical, durable, and chemically stable. Polyurethane (PU) offers excellent elasticity and abrasion resistance. Polyester (PES) has excellent heat resistance and high strength. Polymethyl methacrylate (PMMA) offers excellent chemical stability. Nylon offers strength, durability, and abrasion resistance. Polystyrene (PS) offers economic efficiency and lightweight properties. Teflon (PTFE) is chemically very stable and has excellent strength. Polyvinylidene fluoride (PVDF) offers excellent chemical stability, heat resistance, and abrasion resistance. Polyvinyl alcohol (PVA) has excellent solubility, high absorbency, and physical strength. Polyacrylonitrile (PAN) offers excellent strength and abrasion resistance.

[0083] These materials can be made into fine fibers through an electrospinning process to maximize their properties.

[0084] In addition, the weight average molecular weight of the polymer may be 6000 to 9000 g / mol, and preferably 6500 to 8000 g / mol. By satisfying the weight average molecular weight of the polymer of 6000 to 9000 g / mol, there is an advantageous effect in extruding nanofibers having uniform surface properties and a complete fiber shape during electrospinning.

[0085] The composition may contain 17 to 22 wt% of the polymer, preferably 17 to 19 wt%, and more preferably 18 to 19 wt%, based on 100 wt% of the total composition.

[0086] Since the polymer concentration satisfies 17 to 22 wt%, there is a favorable effect in extruding nanofibers with a fine average diameter and a complete shape during electrospinning.

[0087] An organic solvent may be included to dissolve the polymer and control the viscosity of the composition.

[0088] The organic solvent may include at least one of dimethylformamide (DMF), diethylformamide (DEF), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), and methylpyrrolidone (NMP), and preferably may include two or more of them.

[0089] When two or more organic solvents are mixed, dimethylformamide (DMF) may be included as the first solvent, and one or more of diethylformamide (DEF), dimethylacetamide (DMAC), dimethyl sulfoxide (DMSO), and methylpyrrolidone (NMP) may be included as the second solvent. Since the first solvent has a great influence on the polymer, the content of the first solvent is preferably greater than that of the second solvent. Accordingly, the polymer can be melted, thereby producing a radiant composition.

[0090] In this case, the first solvent: second solvent ratio may be 5:5 to 10:0, preferably 6:4 to 10:0, more preferably 7:3 to 10:0, and even more preferably 8:2 to 10:0.

[0091] The content of the organic solvent is the content excluding the content of the polymer and the salt compound described later in the composition, and may be the remainder.

[0092] The average diameter of the nanofibers may be reduced to 65 nm or less, and a salt compound may be included to control the viscosity and electrical conductivity of the composition.

[0093] The salt compound may include one or more cationic surfactants selected from the group consisting of sodium chloride (NaCl), calcium chloride (CaCl2), potassium chloride (KCl), lithium chloride (LiCl), and cetrimonium bromide (Ctab).

[0094] The composition may contain 0.1 to 2 wt% of the salt compound, preferably 0.1 to 1 wt%, and more preferably 0.1 to 0.6 wt%, based on 100 wt% of the total composition.

[0095] By ensuring that the concentration of the salt compound is within the range of 0.1 to 2 wt%, the composition can achieve low viscosity and high electrical conductivity. This has the effect of reducing the average diameter of the nanofibers to 65 nm or less.

[0096] If the electrical conductivity of the composition is low, the discharge state may become unstable due to changes in surface charge, resulting in the discharge of nanofibers having a wide diameter distribution. To solve this problem, a salt compound is added to the polymer to increase the electrical conductivity of the composition and the charge density of the discharge state, thereby minimizing the average diameter of the nanofibers to 65 nm or less. In addition, since the salt compound includes at least one of sodium chloride (NaCl), calcium chloride (CaCl2), potassium chloride (KCl), lithium chloride (LiCl), and cetrimonium bromide (Ctab), there is an effect of preventing the formation of beads in the nanofibers.

[0097] In the step of preparing a composition by mixing a polymer, an organic solvent, and a salt compound, the polymer, an organic solvent, and a salt compound can be mixed at 70 to 80°C for 1 to 24 hours, and preferably, the composition can be prepared by mixing at 70 to 80°C for 10 to 20 hours.

[0098] The viscosity of the prepared composition may be 1000 cp to 9000 cp, preferably 1084 cp to 8900 cp. By satisfying the viscosity of the composition of 1000 cp to 9000 cp, there is an effect of reducing the average diameter of nanofibers discharged during electrospinning to 65 nm or less.

[0099] After measuring the viscosity and electrical conductivity of the composition to determine whether the polymer is completely dissolved in the composition, the composition can be injected into a syringe used for electrospinning.

[0100] Next, the composition is electrospun onto a support to discharge nanofibers having an average diameter of 65 nm or less, and a nanofiber filter with nanofibers attached to the support can be manufactured.

[0101] Specifically, after filling the composition into a syringe, a step of providing a collecting plate so as to be spaced apart from the syringe, placing a support on the collecting plate, and a step of applying voltage to the syringe so that the composition is discharged as nanofibers from a nozzle of the syringe by the applied voltage, thereby manufacturing a nanofiber filter in which nanofibers are attached on the support can be performed.

[0102] The syringe controls the flow rate by a pump. When the pump is used, the composition can be transferred to a metal nozzle through a tubing connecting the syringe while controlling the discharge amount by a motor. The diameter of the metal nozzle may be 0.60 mm or less, preferably 0.1 to 0.5 mm, and more preferably 0.3 to 0.4 mm. By satisfying the nozzle diameter of 0.60 mm or less, there is an advantageous effect in that the average diameter of the nanofibers is 65 nm or less.

[0103] The flow rate of the delivered composition can be adjusted according to the diameter of the nozzle. Furthermore, the nozzle must be connected to a voltage line, allowing voltage to be applied using a high-voltage generator. The collecting plate located opposite the nozzle can be grounded or artificially formed with an electric field by applying a voltage opposite to the voltage applied to the nozzle.

[0104] The collecting plate located opposite the nozzle must be made of a metal material or a material that conducts electricity well. A support capable of collecting nanofibers can be positioned on the collecting plate. The support can protect the nanofibers from the outside. The support can be a porous non-woven fabric or woven fabric made of a fiber material, and can have properties required by the filter, such as durability and chemical stability. From this perspective, the support can include one or more woven or non-woven fabrics selected from polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), polyurethane (PU), polyester (PES), polyimide (PI), polymethyl methacrylate (PMMA), nylon, polystyrene (PS), and polyvinyl alcohol (PVA).

[0105] Polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET) are strong and durable materials that can provide the necessary physical strength and durability in the manufacturing process of dry-laid nonwoven fabrics. These materials are stable at high temperatures, chemically stable, and easy to process, allowing them to be manufactured into a variety of shapes. This provides advantages in diversifying filter designs and structures. Furthermore, these materials can enhance the physical properties of nonwoven fabrics, improving their strength and heat resistance. Their economical efficiency also reduces manufacturing costs.

[0106] The support, with its fine fibers providing a large surface area, functions to physically capture particles and / or gases, and can exhibit high strength and durability. From this perspective, the support may include one or more types of short fibers and long fibers.

[0107] Here, the lengths of the short fibers and long fibers may range from 1 to 1000 μm, and the long fibers may be at least 0.5 times longer than the short fibers, but are not limited thereto. In addition, as long as the short fibers and long fibers can be used as a support, they may be used without limitation.

[0108] A support composed of at least one type of short fiber or long fiber increases the physical particle capture effect of the fine fibers by providing them with a larger surface area. Since the support is composed of at least one type of short fiber or long fiber at different intervals and distributions, fine dust or foreign matter is trapped between the short fibers and / or long fibers. As a result, the dust or foreign matter particles are effectively filtered, which is beneficial for air purification. Furthermore, a support composed of long fibers can have higher strength and durability than short fibers, which is beneficial for extending the life of the filter.

[0109] When the composition begins to form on the nozzle and is visible to the naked eye, a voltage can be applied from a high-voltage generator. At this time, the voltage can be increased so that the external electric field is stronger than the surface tension determined by the viscosity of the composition within the nozzle, thereby stably forming a round droplet into an umbrella-shaped Taylor cone. Through this process, nanofibers in a complete fiber form are ejected from the nozzle, performing electrospinning, and the nanofibers can be attached to the support.

[0110] The average diameter of the extruded nanofibers may be 65 nm or less, and preferably 20 to 65 nm.

[0111] From this perspective, a voltage of 9 to 25 kV can be applied to the nozzle, and preferably a voltage of 9 to 18 kV can be applied. In addition, the distance between the nozzle and the collecting plate can be 10 to 15 cm.

[0112] Additionally, electrospinning can be performed at 22 to 30°C, preferably at 23 to 30°C. In this regard, electrospinning can be performed in an atmosphere with a humidity of 25 to 31%, which may be the temperature and humidity inside the chamber.

[0113] When a nanofiber filter with nanofibers attached to a support is manufactured, the nanofiber filter can be separated from the collection plate to measure the collection efficiency and pressure loss.

[0114] Accordingly, the method for manufacturing a nanofiber filter according to the present invention increases the electrical conductivity and spinnability of the composition by adding a salt compound at a concentration of 0.1 to 2 wt% to a low concentration of polymer. In addition, the manufacturing method lowers the viscosity of the composition by using an organic solvent alone or in combination, and controls at least one of the nozzle diameter of the electrospinning, the applied voltage, and the distance between the nozzle and the collecting plate. Accordingly, the manufacturing method can manufacture a nanofiber filter having a complete fiber form and an average diameter of 65 nm or less.

[0115] A nanofiber filter according to the present invention comprises a support, and nanofibers attached to the support and containing a polymer and a salt compound, wherein the average diameter of the nanofibers is 65 nm or less.

[0116] Nanofibers are formed by electrospinning a composition comprising a polymer, a salt compound, and an organic solvent. Nanofibers contain the polymer and the salt compound, and as the support and nanofibers are identical to those described above, further details will be omitted.

[0117] Although polymer components can be detected in nanofiber filters, salt compounds may be difficult to detect due to the chain structure of the polymer and the swelling phenomenon of the solvent.

[0118] These nanofiber filters can be applied to outdoor and indoor air purifiers.

[0119] Here, specific examples of nanofiber filters and their manufacturing methods are as follows.

[0120] 1. Manufacturing of nanofiber filters

[0121] Nanofiber filters according to FIGS. 2 to 12 were manufactured as follows.

[0122] In order to prepare a composition according to FIGS. 2 to 12, an organic solvent (DMF, NMP) was added to the polymer polyether sulfone and mixed in accordance with the weight % of the polymer, the mixing ratio of the organic solvent, and the weight % of the salt compound described in each drawing description, and then a salt compound (Ctab, LiCl) was added.

[0123] The compositions according to Figs. 2 to 12 were stirred at a temperature of 70 to 80°C for 12 hours or more. To confirm whether the polymer was completely dissolved in the stirred composition, the viscosity and electrical conductivity of the composition were measured, and then the composition was injected into a syringe used for electrospinning. At this time, a nanofiber filter was manufactured according to the electrospinning conditions described in each drawing description, such as the discharge amount, nozzle diameter, applied current during electrospinning, grounding portion of the collecting plate, distance between the nozzle and the collecting plate, and humidity.

[0124] The syringe was used to transfer the composition to the nozzle through tubing while the flow rate was controlled by the pump and the discharge amount was controlled by the motor when the pump was in use.

[0125] The collecting plate located opposite the nozzle was grounded or applied with a voltage opposite to that applied to the nozzle to form an electric field.

[0126] When the composition began to form on the nozzle and was visible to the naked eye, a voltage was applied from a high voltage generator, and the voltage was increased so that the strength of the external electric field was higher than the surface tension determined by the viscosity of the composition inside the nozzle, thereby controlling the formation of round droplets into an umbrella-shaped Taylor cone. A support capable of collecting nanofibers was placed on the collecting plate, and a nanofiber filter with nanofibers attached to the support was manufactured.

[0127] 2. Physical property evaluation method and results

[0128] The average diameter of the nanofibers in FIGS. 2 to 15 was expressed as an average value after measuring the diameters of 30 fibers using the Image J program.

[0129] Figure 2 shows the polymer PESU 6020 (Poly Ether Sulfone, Mw 72,000 g / mol), DMF: NMP = 8:2, discharge amount 3.5 μl / min, nozzle diameter 19 G (0.67 mm), Ctab 0.4 wt% (Cetrimonium bromide, cationic surfactant, C 19 H 42 FE-SEM images (x30,000 magnification) showing the average diameter of nanofibers according to the concentration of polymer and the temperature atmosphere during electrospinning under the conditions of BrN), an applied voltage of 13 kV during electrospinning, -4 kV to the grounded part of the collecting plate, a distance of 15 cm between the nozzle and the collecting plate, and 25% humidity during electrospinning.

[0130] As the polymer concentration decreased, the average diameter of the nanofibers tended to decrease. The average diameter of the nanofibers manufactured under the conditions shown in Figure 2 was very small, ranging from 45.19 to 73.2 nm. However, it also showed that a large number of beads were formed.

[0131] In FE-SEM images, the bead shape can be confirmed in the low-magnification image of Х200 rather than in the high-magnification image.

[0132] Figure 3 shows the polymer PESU 6020 (Poly Ether Sulfone, Mw 72,000 g / mol), DMF:NMP=8:2, discharge amount 3.3 μl / min, Ctab 0.4 wt% (Cetrimonium bromide, cationic surfactant, C 19 H 42 FE-SEM images (x30,000 magnification) showing the average diameter of nanofibers according to the concentration of polymer of 15 wt%, 17 wt%, and 19 wt% and the diameter of nozzle during electrospinning of 0.67 mm and 0.40 mm under the conditions of applied voltage of 13 kV during electrospinning, grounding part of the collecting plate of -4 kV, distance between nozzle and collecting plate of 15 cm, temperature of 30°C, and humidity of 25% during electrospinning.

[0133] During electrospinning, the nozzle diameter was changed from 0.67 mm to 0.40 mm, and the effect of the nozzle diameter on the fiber diameter was dominant. When the nozzle diameter was reduced from 0.67 mm to 0.40 mm, the range of decrease in the average diameter of the nanofibers was from 10 nm to 13 nm. The average diameter of the nanofibers due to the effect of the nozzle inner diameter according to the polymer concentration was confirmed to be 35.2 nm to 57.3 nm.

[0134] Figure 4 is an FE-SEM photograph (magnification x1,000) showing whether beads were formed according to the concentration of a salt compound (LiCl) of 0 to 0.4 wt% when the concentration of the polymer was 15 wt% and 19 wt% under the conditions of a polymer PESU 6020 (Poly Ether Sulfone, Mw 72,000 g / mol), DMF:NMP=8:2, discharge amount 3.3 μL / min, nozzle diameter (inner diameter) 22 G (0.40 mm), voltage applied during electrospinning 9 kV, grounding part of the collecting plate -4 kV, distance between the nozzle and the collecting plate 15 cm, temperature 30°C, and humidity 25% during electrospinning.

[0135] When the electrical conductivity of the composition is low, the discharge state becomes unstable due to changes in surface charge, resulting in the discharge of nanofibers with a wide diameter distribution. To address this issue, a salt compound (LiCl) was added to the polymer to increase the electrical conductivity of the composition and the charge density in the discharge state. Furthermore, beads were formed on the surface of the nanofibers in the absence of the salt compound. However, as the content of the salt compound (LiCl) increased, the bead formation of the nanofibers decreased.

[0136] FIG. 5 is an FE-SEM photograph (magnification x30,000) showing the formation of beads and the average diameter of nanofibers according to the concentration of salt compound (LiCl) of 0 to 0.4 wt% when the concentration of polymer is 15 wt% and 19 wt% under the conditions of polymer PESU 6020 (Poly Ether Sulfone, Mw 72,000 g / mol), DMF: NMP = 8:2, discharge amount 3.3 μl / min, nozzle diameter (inner diameter) 22 G (0.40 mm), applied voltage 9 kV during electrospinning, grounding part of collecting plate -4 kV, distance between nozzle and collecting plate 15 cm, temperature 30 ℃, and humidity 25% during electrospinning.

[0137] It was confirmed that as the amount of salt compound (LiCl) added increased, the amount of beads and the average diameter of nanofibers decreased.

[0138] At a polymer concentration of 15 wt%, complete elimination of beads was impossible, but a limit was identified where bead formation decreased, and an unstable fiber morphology was observed. At a polymer concentration of 19 wt%, a clear decrease in bead formation was observed starting from the addition of 0.01 wt% of the salt compound (LiCl). As the addition of the salt compound (LiCl) increased, the average diameter of the nanofibers also decreased by approximately 22 nm, from 77.4 nm to 55.3 nm.

[0139] Figure 6 is an FE-SEM photograph showing the average diameter of nanofibers under the conditions of 19 wt% of polymer PES7020 (Poly Ether Sulfone, Mw 90,000 g / mol), DMF:NMP=8:2, discharge amount 3.3 μL / min, nozzle diameter 22 G (0.40 mm), LiCl:Ctab=0.15 wt%:0.4 wt%, voltage applied during electrospinning 18 kV, grounding part of the collecting plate -4 kV, distance between nozzle and collecting plate 10 cm, temperature 24.9°C and humidity 31% during electrospinning.

[0140] Referring to Fig. 6, the average diameter of the nanofibers at a polymer concentration of 19 wt% was 59.93 nm, and the standard deviation was 34.42 nm.

[0141] Figure 7 is an FE-SEM photograph showing the average diameter of nanofibers under the conditions of 19 wt% of polymer PES7020 (Poly Ether Sulfone, Mw 90,000 g / mol), DMF:NMP=8:2, LiCl:Ctab=0.15 wt%:0.4 wt%, discharge amount 3.3 ㎕ / min, nozzle diameter 22 G (0.40 mm), voltage applied during electrospinning 17 kV, grounding part of the collecting plate -4 kV, distance between nozzle and collecting plate 15 cm, temperature 24.8 ℃ and humidity 30% during electrospinning.

[0142] Referring to Figure 7, the average diameter of the nanofibers at a polymer concentration of 19 wt% was 60.86 nm, and the standard deviation was 26.44 nm.

[0143] Figure 8 is an FE-SEM photograph showing the average diameter of nanofibers under the conditions of 19 wt% of polymer PES7020 (Poly Ether Sulfone, Mw 90,000 g / mol), DMF alone, Ctab=0.4 wt%, discharge amount 3.3 μl / min, nozzle diameter 22 G (0.40 mm), voltage applied during electrospinning 14.5 kV, grounding part of the collecting plate -4 kV, distance between nozzle and collecting plate 15 cm, temperature 25°C, and humidity 28% during electrospinning.

[0144] Referring to Fig. 8, the average diameter of the nanofibers at a polymer concentration of 19 wt% was 61.06 nm, and the standard deviation was 35.77 nm.

[0145] Figure 9 is an FE-SEM photograph showing the average diameter of nanofibers under the conditions of 19 wt% of polymer PES7020 (Poly Ether Sulfone, Mw 90,000 g / mol), DMF alone, LiCl = 0.1 wt%, discharge amount 3.3 μL / min, nozzle diameter 22 G (0.40 mm), voltage applied during electrospinning 16 kV, grounding part of the collecting plate -4 kV, distance between nozzle and collecting plate 15 cm, temperature 25.2 ℃ and humidity 28% during electrospinning.

[0146] Referring to Figure 9, the average diameter of the nanofibers at a polymer concentration of 19 wt% was 62.8 nm, and the standard deviation was 27.71 nm.

[0147] Figure 10 is an FE-SEM photograph showing the average diameter of nanofibers under the conditions of 19 wt% of polymer PES7020 (Poly Ether Sulfone, Mw 90,000 g / mol), DMF:NMP=8:2, LiCl=0.1 wt%, discharge amount 3.3 μl / min, nozzle diameter 22 G (0.40 mm), voltage applied during electrospinning 16.5 kV, grounding part of the collecting plate -4 kV, distance between nozzle and collecting plate 15 cm, temperature 23.7°C and humidity 30% during electrospinning.

[0148] Referring to Fig. 10, the average diameter of the nanofibers at a polymer concentration of 19 wt% was 53.06 nm, and the standard deviation was 26.30 nm.

[0149] Figure 11 is an FE-SEM photograph showing the average diameter of nanofibers under the conditions of 18 wt% of polymer PES7020 (Poly Ether Sulfone, Mw 90,000 g / mol), DMF:NMP=8:2, Ctab 0.4 wt%, discharge amount 2.5 μL / min, nozzle diameter 22 G (0.40 mm), voltage applied during electrospinning 12.5 kV, grounding part of the collecting plate 0 kV, distance between nozzle and collecting plate 10 cm, temperature 25.2°C and humidity 30% during electrospinning.

[0150] Referring to Figure 11, the average diameter of the nanofibers at a polymer concentration of 18 wt% was 60.66 nm, and the standard deviation was 34.24 nm.

[0151] Figure 12 is an FE-SEM photograph showing the average diameter of nanofibers under the conditions of 18.5 wt% of polymer PES7020 (Poly Ether Sulfone, Mw 90,000 g / mol), DMF:NMP=8:2, LiCl:Ctab=0.1 wt%:0.2 wt%, discharge amount 3.3 μL / min, nozzle diameter 22 G (0.40 mm), voltage applied during electrospinning 10 kV, grounding part of the collecting plate -7 kV, distance between nozzle and collecting plate 10 cm, temperature 23.9°C and humidity 30% during electrospinning.

[0152] Referring to Figure 12, the average diameter of the nanofibers at a polymer concentration of 18.5 wt% was 56.80 nm, and the standard deviation was 25.19 nm.

[0153] Figure 13 is a graph showing the capture efficiency according to the average diameter of nanofibers.

[0154] In Fig. 13, the x-axis is the average diameter of the nanofibers, and the y-axis is the capture efficiency.

[0155] The capture efficiency is measured by using an atomizer, a particle generator, to generate fine particles from an aqueous solution of NaCl or KCl, which are then passed through a diffusion dryer to remove moisture. Subsequently, the particles are converted from a polydisperse state to a monodisperse state through soft X-rays. The efficiency is calculated based on the particle number concentration at the inlet and outlet of the filter, based on the upstream and downstream portions of the filter.

[0156] Figure 13 shows a trend in which capture efficiency increases as the average diameter of the nanofibers decreases. It shows that capture efficiency increases more when the average diameter of the nanofibers decreases to 100 nm than when it is 300 nm.

[0157] Figure 14 is a graph showing the filter performance index according to the average diameter of nanofibers.

[0158] In Fig. 14, the x-axis is the average diameter of the nanofibers, and the y-axis is the filter performance index.

[0159] The filter performance index is calculated using the filter's pressure loss (P) and dust collection efficiency (E).

[0160] Figure 14 shows that the filter performance index tends to increase as the average diameter of the nanofibers decreases. It shows that the filter performance index increases more when the average diameter of the nanofibers decreases to 100 nm than when it is 300 nm.

[0161] Figure 15 is a graph showing the filter performance index according to the average diameter of nanofibers.

[0162] HEPA filter-related test standards stipulate that a HEPA filter achieves an efficiency of 99.97% at a flow rate of 5.3 cm / s for a particle diameter of 0.3 μm (300 nm). This standard demonstrates the filter efficiency of 300 nm particles. The QF (Quality Factor) value, a factor that includes the pressure loss results, demonstrates that a high filter performance index is achieved when the average diameter of the nanofibers is 70 nm, close to 65 nm.

[0163] Although the present invention has been described with reference to the drawings exemplified above, it is to be understood that the present invention is not limited to the embodiments and drawings disclosed herein, and that various modifications may be made by those skilled in the art within the scope of the technical idea of ​​the present invention. Furthermore, even if the operational effects according to the configuration of the present invention have not been explicitly described while describing the embodiments of the present invention, it is natural that the effects predictable by the corresponding configuration should also be acknowledged.

Claims

1. Contains polymers, organic solvents and salt compounds, A composition wherein the concentration of the salt compound is 0.1 to 2 wt%.

2. In paragraph 1, The above salt compound is a composition comprising at least one of sodium chloride (NaCl), calcium chloride (CaCl2), potassium chloride (KCl), lithium chloride (LiCl), and cetrimonium bromide (Ctab).

3. In paragraph 1, A composition wherein the concentration of the polymer is 17 to 22 wt%. 4.(a) A step of preparing a composition by mixing a polymer, an organic solvent, and a salt compound; and (b) a step of electrospinning the composition onto a support to manufacture a nanofiber filter with nanofibers attached onto the support; In the above step (a), the concentration of the salt compound is 0.1 to 2 wt%, A method for manufacturing a nanofiber filter in which, in the step (b) above, the average diameter of the nanofibers is 65 nm or less.

5. In paragraph 4, A method for producing a nanofiber filter, wherein in the step (a), the salt compound comprises at least one of sodium chloride (NaCl), calcium chloride (CaCl2), potassium chloride (KCl), lithium chloride (LiCl), and cetrimonium bromide (Ctab).

6. In paragraph 4, A method for manufacturing a nanofiber filter, wherein in the step (a) above, the concentration of the polymer is 17 to 22 wt%.

7. In paragraph 4, A method for manufacturing a nanofiber filter, wherein in the step (a), the polymer comprises at least one of polypropylene (PP), polyurethane (PU), polyether sulfone, polyester (PES), polyimide (PI), polymethyl methacrylate (PMMA), nylon, polystyrene (PS), Teflon (PTFE), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), and polyacrylonitrile (PAN).

8. In paragraph 4, Step (b) above (b1) a step of filling the composition into a syringe, then providing a collecting plate so as to be spaced apart from the syringe, and placing a support on the collecting plate; and (b2) A method for manufacturing a nanofiber filter, comprising the step of applying voltage to the syringe, thereby manufacturing a nanofiber filter in which nanofibers are attached to a support while the composition is discharged as nanofibers from the nozzle of the syringe by the applied voltage.

9. In paragraph 8, A method for manufacturing a nanofiber filter, wherein the diameter of the above nozzle is 0.60 mm or less.

10. In paragraph 8, A method for manufacturing a nanofiber filter, wherein in the above step (b2), a voltage of 9 to 25 kV is applied.

11. In paragraph 8, A method for manufacturing a nanofiber filter in which the distance between the nozzle and the collecting plate is 10 to 15 cm.

12. In paragraph 4, A method for manufacturing a nanofiber filter, wherein in the step (b) above, electrospinning is performed at 22 to 30°C.

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