Cellulose nanofiber and antibacterial air filter

Abstract

Cellulose nanofibers according to exemplary embodiments of the present invention may have a ratio of the intensity of a second peak to a first peak of 4 to 8, the first peak and second peaks appearing 1530cm-1 to 1750cm-1 and 3000cm-1 to 3600cm-1, respectively, in a Fourier transform infrared spectroscopy spectrum. Accordingly, the cellulose nanofibers can exhibit improved antibacterial properties.

Description

Cellulose nanofibers and antibacterial air filters

[0001] The present invention relates to cellulose nanofibers and an antibacterial air filter. More specifically, the present invention relates to an antibacterial air filter comprising cellulose nanofibers having a concentrated distribution of hydroxyl groups on their surface and a coating layer comprising the cellulose nanofibers.

[0002] As air pollution problems like fine dust and yellow dust become more serious, the need for indoor air purification has increased. Air purification devices, such as air purifiers, utilize various types of filter systems to filter out pollutants and harmful substances contained in the air, providing purified air.

[0003] Generally, pollutants such as dust can be filtered by air filters, but harmful microorganisms smaller than microns, such as mites, bacteria, mold, and viruses, are difficult to filter. While a micropore filter can be additionally applied to filter these harmful microorganisms, the filtered microorganisms can proliferate on the surface of the micropore filter, re-entering the room or causing unpleasant odors.

[0004] The use of antibacterial particles such as zinc oxide, copper, and carbon nanomaterials can reduce antibacterial performance and pose a risk to the human body. Therefore, there is a need to develop an antibacterial filter made of materials that can filter dust and harmful microorganisms, suppress bacterial growth within the filter with high antibacterial performance, and remain harmless to the human body.

[0005] Cellulose is known as a material with excellent fine dust absorption performance that is not harmful to the human body. For example, Korean Patent Publication No. 10-2021-0017971 discloses a filter manufactured using cellulose nanofibers.

[0006] One object of the present invention is to provide cellulose nanofibers with improved antibacterial properties.

[0007] One object of the present invention is to provide an antibacterial air filter with improved antibacterial properties.

[0008] Cellulose nanofibers according to an exemplary embodiment have a Fourier transform infrared spectroscopy spectrum at 1530 cm -1 Height 1750cm -1 The intensity of the first peak appearing at 3000 cm -1 3600cm inland -1 The ratio of the intensities of the second peaks appearing in may be 4 to 8.

[0009] In one embodiment, the cellulose nanofibers have a Fourier transform infrared spectroscopy spectrum at 1400 cm -1 1500cm inland -1 There may be a third peak appearing in .

[0010] In one embodiment, the ratio of the intensity of the second peak to the intensity of the first peak may be 5 to 7.

[0011] An antibacterial air filter according to an exemplary embodiment comprises a substrate layer and a coating layer formed on at least one surface of the substrate layer and comprising cellulose nanofibers, wherein the cellulose nanofibers have a Fourier transform infrared spectroscopy spectrum at 1530 cm -1 Height 1750cm -1 The intensity of the first peak appearing at 3000 cm -1 3600cm inland -1 The ratio of the intensities of the second peaks appearing in may be 4 to 8.

[0012] In one embodiment, the cellulose nanofibers have a Fourier transform infrared spectroscopy spectrum at 1400 cm -1 1500cm inland -1 There may be a third peak appearing in .

[0013] In one embodiment, the ratio of the intensity of the second peak to the intensity of the first peak may be 5 to 7.

[0014] In one embodiment, the content of the cellulose nanofibers may be 90 wt% or more of the total weight of the coating layer.

[0015] In one embodiment, the thickness of the coating layer may be 60 nm to 200 nm.

[0016] In one embodiment, the antibacterial air filter may comply with KS K 0693:2022 and have a bactericidal reduction rate of 99.9% or more measured using Staphylococcus aureus.

[0017] Cellulose nanofibers according to exemplary embodiments may have enhanced antibacterial properties due to the concentrated distribution of hydroxyl groups on their surfaces. Antibacterial air filters manufactured using the cellulose nanofibers can be manufactured in a simple process while preventing the growth of harmful microorganisms on their surfaces.

[0018] Figure 1 is a cross-sectional view of an antibacterial air filter according to one embodiment.

[0019] Figure 2 is a photograph of a nonwoven fabric before forming a coating layer according to Example 1, taken with an optical microscope.

[0020] Figure 3 is a photograph of an antibacterial air filter observed with an optical microscope after forming a coating layer according to Example 1.

[0021] Figure 4 is a graph showing the results of analyzing cellulose nanofibers according to Example 1, Comparative Example 1, and Comparative Example 2 using Fourier transform infrared spectroscopy.

[0022] Figure 5 is a graph showing the intensity of the first peak and the intensity of the second peak in a Fourier transform infrared spectroscopy analysis of cellulose nanofibers according to the number of mechanical extrusions during manufacturing.

[0023] Figure 6 is a graph showing the peak intensity ratio (i.e., the ratio of the intensity of the second peak to the intensity of the first peak) in Fourier transform infrared spectroscopy analysis of cellulose nanofibers according to the number of mechanical extrusions during manufacturing.

[0024] Figure 7 is a graph showing the results of XRD analysis of cellulose nanofibers according to Example 1.

[0025] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below, along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms.

[0026] To clearly explain embodiments of the present invention, portions irrelevant to the description may be omitted. Furthermore, when describing embodiments of the present invention, if a detailed description of a related known configuration or function is deemed to obscure the gist or description of the present invention, a detailed description thereof may be omitted.

[0027] In describing components in this specification, terms such as "first," "second," etc. may be used. These terms are intended to distinguish one component from another for convenience of description, and unless otherwise specified, the nature, order, etc. of the components are not limited by these terms.

[0028] In this specification, unless otherwise specifically defined, when a part such as a layer or plate is said to be “on” or “over” another part, this may include not only cases where it is “directly on” the other part, but also cases where there is another part in between.

[0029] In each of the steps mentioned in this specification, unless the context clearly dictates a specific order, the steps may be performed in a different order than stated. That is, the steps may be performed in the same order as stated, may be performed substantially simultaneously, or may be performed in the opposite order.

[0030] In this specification, “and / or” may mean each of the listed components and any combination of two or more of the listed components. For example, “A, B and / or C” may be used with the same meaning as “at least one of A, B, and C.”

[0031] In this specification, the meaning of “may include a, b, c, etc.” may be a concept including the meaning of “may include at least one of a, b, and c.”

[0032] In this specification, “antimicrobial properties” may mean properties that inhibit the growth or kill microorganisms such as mites, bacteria, fungi, viruses, etc.

[0033] In this specification, unless otherwise defined, “cellulose” may mean bulk cellulose as a polymer aggregate.

[0034] Cellulose nanofibers

[0035] Cellulose nanofibers according to exemplary embodiments have a Fourier Transform Infrared Spectroscopy (FTIR) spectrum at 1530 cm -1 Height 1750cm -1 The intensity of the first peak appearing at 3000 cm -1 3600cm inland -1 The ratio of the intensities of the second peaks appearing therein (hereinafter, may be abbreviated as ‘peak intensity ratio’) may be 4 to 8.

[0036] 1530cm above -1 Height 1750cm-1 The first peak appearing in means a vibration peak corresponding to the CC bond, and is at 3000 cm -1 3600cm inland -1 The second peak appearing in refers to a vibration peak corresponding to an OH bond. For example, the ratio of the intensity of the second peak to the intensity of the first peak can indicate the relative amount of hydroxyl groups (-OH) and C-C bonds present on the surface of the cellulose nanofibers.

[0037] Cellulose possesses a large number of hydroxyl groups in its chemical structure, which allows it to develop a negative charge. This negative charge can inhibit microbial growth. Furthermore, by miniaturizing cellulose into nanomaterials, its specific surface area increases, further increasing the number of negative charges per surface area. Consequently, its antibacterial properties can be enhanced.

[0038] Cellulose (i.e., bulk cellulose) may include crystalline regions and amorphous regions. For example, during the process of pulverizing cellulose (e.g., mechanical extrusion) for manufacturing cellulose nanofibers, the relatively less rigid amorphous regions are destroyed first, so that the relative proportion of the crystalline regions increases, thereby increasing the intensity of the first peak. In addition, the relative proportion of the amorphous regions decreases, thereby increasing the amount of free hydroxyl groups (-OH) exposed on the surface of the cellulose nanofibers (i.e., the amorphous regions are destroyed and the existing internal hydroxyl groups are exposed), so that the intensity of the second peak may increase.

[0039] However, if the cellulose is not sufficiently pulverized, the increase in the specific surface area may be small, and the amorphous region may be less destroyed, resulting in a small increase in the number of free hydroxyl groups (-OH) exposed on the surface of the cellulose nanofibers. Accordingly, the increase in the intensity of the first peak may be small, resulting in a higher peak intensity ratio.

[0040] For example, when the cellulose nanofibers are analyzed by Fourier transform infrared spectroscopy, if the ratio of the intensity of the second peak to the intensity of the first peak satisfies 4 to 8, the specific surface area is high and the relative proportion of the amorphous region decreases (i.e., the relative proportion of the crystalline region increases, thereby increasing the intensity of the first peak), so that the amount of free hydroxyl groups (-OH) exposed on the surface of the cellulose nanofibers may increase. Accordingly, the cellulose nanofibers have improved antibacterial properties and can be used as an antibacterial material in the manufacture of an antibacterial air filter described below.

[0041] For example, if the ratio of the intensity of the second peak to the intensity of the first peak is less than 4, the antibacterial properties may deteriorate because the amount of hydroxyl groups present on the surface of the cellulose nanofibers is small. In addition, if the cellulose is excessively pulverized, the intensity of the second peak increases and the intensity of the first peak increases significantly, so that the peak intensity ratio becomes less than 4, but it may be difficult to stably manufacture an antibacterial air filter.

[0042] For example, if the ratio of the intensity of the second peak to the intensity of the first peak is greater than 8, the increase in the specific surface area is small, the amorphous region is less destroyed, and the increase in the free hydroxyl groups (-OH) exposed on the surface of the cellulose nanofibers is small, so the antibacterial properties may deteriorate. In other words, the antibacterial properties may deteriorate because the negative charges that inhibit the growth of microorganisms are less distributed on the surface of the cellulose nanofibers.

[0043] In one embodiment, the ratio of the intensity of the second peak to the intensity of the first peak of the cellulose nanofibers may be 4.5 to 7.5, 4.5 to 7, 4.5 to 6.5, 5 to 8, 5 to 7, or 5 to 6.5. Within this range, the specific surface area of ​​the cellulose nanofibers is high and the relative proportion of the amorphous region is reduced, thereby increasing the amount of free hydroxyl groups (-OH) exposed on the surface of the cellulose nanofibers, thereby improving the antibacterial properties of the cellulose nanofibers.

[0044] In one embodiment, the cellulose nanofibers have a Fourier transform infrared spectroscopy spectrum at 1400 cm -1 1500cm inland -1 There may be a third peak appearing at 1400 cm -1 1500cm inland -1 The third peak appearing in represents a vibration peak corresponding to the OH bond.

[0045] For example, when analyzing the cellulose nanofibers using Fourier transform infrared spectroscopy, if a third peak is present in addition to the second peak, there may be a large number of hydroxyl groups on the surface of the cellulose nanofibers and a large number of negative charges capable of inhibiting the growth of microorganisms.

[0046] For example, the cellulose nanofibers have a Fourier transform infrared spectroscopy spectrum at 1800 cm -1 2750cm inland -1 There may be no peak in the range of 1800 cm -1 2750cm inland -1 In the range of , no peaks are observed and the spectrum may appear smooth.

[0047] In one embodiment, the cellulose nanofibers include an amorphous region and a crystalline region, and the crystalline region may include crystal grains having a size of 2 nm or more when analyzed by X-ray diffraction (XRD).

[0048] For example, the size of the above crystal grains can be obtained through the Scherrer equation (Equation 1 below) using the full width at half maximum (FWHM) obtained through XRD analysis.

[0049] The term "amorphous region" used in the present application may mean a case where the shape of cellulose included in cellulose nanofibers is amorphous or a case where the particles are so small that it is difficult to measure the size using the Scherrer equation expressed by Equation 1 below during XRD analysis.

[0050] [Formula 1]

[0051]

[0052] In Equation 1, L represents the crystal grain size (nm), λ represents the X-ray wavelength (nm), β represents the half width (rad) of the corresponding peak, and θ represents the diffraction angle (rad). For example, the half width in XRD analysis for measuring the crystal grain size can be measured from the peak of the (200) plane of cellulose included in the cellulose nanofibers.

[0053] For example, the crystal grain size measured during XRD analysis of the cellulose nanofibers may be 2 nm or more, 3 nm or more, 4 nm or more, or 5 nm or more, and 10 nm or less, 11 nm or less, 12 nm or less, 14 nm or less, 17 nm or less, or less than 20 nm. Within the above range, the relative proportion of the crystalline region among the cellulose nanofibers may increase, and the relative proportion of the amorphous region may decrease, so that the amount of free hydroxyl groups (-OH) exposed on the surface of the cellulose nanofibers may increase. Accordingly, hydroxyl groups may be concentratedly distributed on the surface of the cellulose nanofibers, so that antibacterial properties may be improved.

[0054] According to an exemplary embodiment, cellulose nanofibers can be manufactured by cutting plant raw materials, adding water to the cut plant raw materials, heating them, and then mechanically extruding them.

[0055] For example, the plant raw material may include cotton fiber, hemp fiber, paper mulberry fiber, pine fiber, mulberry fiber, turmeric fiber, bamboo pulp, hemp pulp, flax pulp, bagasse pulp, straw pulp, pine pulp, spruce pulp, eucalyptus pulp, oak pulp, etc., and preferably may include cotton fiber.

[0056] The above plant raw material can be cut into a size of 20 µm to 30 µm (meaning particle diameter), for example, 20 µm to 28 µm, 20 µm to 25 µm, 22 µm to 30 µm, 25 µm to 30 µm, or 23 µm to 27 µm.

[0057] In one embodiment, the cut plant material may be dispersed in water and heated so that the temperature of the dispersion is maintained at 50°C to 85°C for 10 seconds to 60 minutes. Accordingly, the relative proportion of crystalline regions increases, and cellulose nanofibers can be produced while maintaining hydroxyl groups.

[0058] For example, the temperature of the dispersion during heating may be 50°C to 80°C, 50°C to 70°C, 50°C to 60°C, 60°C to 85°C, 60°C to 80°C, 60°C to 70°C, 70°C to 85°C, or 70°C to 80°C. For example, the heating time of the dispersion may be 1 minute to 55 minutes, 5 minutes to 50 minutes, 10 minutes to 45 minutes, 20 minutes to 40 minutes, 25 minutes to 35 minutes, 10 minutes to 50 minutes, or 15 minutes to 40 minutes.

[0059] Within the range of temperature and heating time of the above dispersion, the crystal grain size of cellulose increases and a large amount of hydroxyl groups exist on the surface of cellulose nanofibers, so that antibacterial properties can be improved.

[0060] The above mechanical extrusion can be performed by a high-pressure disperser (homogenizer), a high-pressure emulsifier (microfluidizer), a high-speed disintegrator, a high-pressure impact crusher, a water jet crusher, etc., and preferably, a high-pressure disperser can be used.

[0061] In one embodiment, the mechanical extrusion may be performed at a pressure of 800 atm to 1500 atm.

[0062] For example, the pressure at which the mechanical extrusion is performed may be 800 atm to 1400 atm, 800 atm to 1200 atm, 800 atm to 1000 atm, 1000 atm to 1500 atm, 1000 atm to 1400 atm, 1000 atm to 1200 atm, 1200 atm to 1500 atm, or 1200 atm to 1400 atm. Within the above range, the antibacterial properties of the cellulose nanofibers may be improved.

[0063] In one embodiment, mechanical extrusion may be performed after adding elements to the cut and heated plant material. The elements may be used to improve the productivity of cellulose nanofibers.

[0064] The amount of the above-mentioned element added may be 5 wt% to 50 wt% based on the weight of the plant raw material, for example, 10 wt% to 45 wt%, 15 wt% to 40 wt%, or 20 wt% to 35 wt%. Within the above range, productivity can be improved without damaging the cellulose nanofibers.

[0065] In one embodiment, mechanical extrusion may be performed after adding a pretreatment agent to the cut and heated plant material. The pretreatment agent may be a radical oxidizing agent such as 2,2,6,6-tetramethyl-1-piperidinoxoammonium ion (TEMPO) or phosphoric acid, and can be used to easily control the shape of the cellulose nanofibers.

[0066] In one embodiment, mechanical extrusion can be performed without adding alkaline substances such as urea and the above pretreatment agent to the cut and heated plant raw material.

[0067] In one embodiment, the mechanical extrusion may be performed 6 to 10 times. Within this range, the size of the cellulose nanofibers may not be excessively large, and the process cost may not be high. In addition, the relative proportion of the crystalline region increases, the specific surface area of ​​the cellulose nanofibers increases, and the relative proportion of the amorphous region decreases, so that the peak intensity ratio may satisfy the above-described range. Accordingly, the antibacterial properties of an antibacterial air filter manufactured using the cellulose nanofibers may be improved.

[0068] For example, if the mechanical extrusion is performed less than 6 times, the cellulose is not sufficiently pulverized, so the increase in the specific surface area of ​​the cellulose nanofibers is small, and the amorphous region is less destroyed, so the increase in the free hydroxyl groups (-OH) exposed on the cellulose surface is small, which may deteriorate the antibacterial properties. For example, if the mechanical extrusion is performed more than 10 times, the dispersibility, adhesiveness, and stability of the cellulose nanofibers may deteriorate, making it difficult to stably manufacture an antibacterial air filter.

[0069] For example, cellulose nanofibers manufactured by mechanical extrusion may be dispersed in water, and the concentration of cellulose nanofibers in the dispersion may be 0.1 wt% to 5 wt%. For example, the concentration of cellulose nanofibers contained in the dispersion may be 1 wt% to 5 wt%, 0.5 wt% to 4 wt%, 1 wt% to 3 wt%, 1.5 wt% to 2.5 wt%, or 1 wt% to 2 wt%. Within the above range, sufficient antibacterial properties may be exhibited.

[0070] For example, when cellulose nanofibers are manufactured by the process described above (e.g., including mechanical extrusion), more hydroxyl groups contained in the cellulose nanofibers can be maintained than when cellulose nanofibers are manufactured by a chemical method (e.g., including addition of sulfuric acid).

[0071] For example, when manufacturing cellulose nanofibers using the above chemical method, other elements or molecules may bind to the hydroxyl groups on the surface of the cellulose nanofibers, thereby substituting the hydroxyl groups. Consequently, the hydroxyl groups may not be concentrated on the surface of the cellulose nanofibers, which may deteriorate their antibacterial properties. For example, all of the hydroxyl groups on the surface of the cellulose nanofibers may be replaced with other functional groups (e.g., sulfonate groups).

[0072] For example, when cellulose nanofibers are manufactured according to the process described above (e.g., including mechanical extrusion), some of the hydroxyl groups on the surface of the cellulose nanofibers may be substituted, but not all of the hydroxyl groups may be substituted. Furthermore, when hydroxyl groups on the surface of the cellulose nanofibers are substituted, the substituted groups may include hydroxyl groups (i.e., hydroxyl groups separate from the hydroxyl groups present prior to the substitution).

[0073] For example, cellulose nanofibers can be used in the manufacture of antibacterial air filters, as described below, but can also be used in the manufacture of cosmetics. For example, the cellulose nanofibers can be included in a cosmetic composition.

[0074] Antibacterial air filter

[0075] An antibacterial air filter according to exemplary embodiments comprises a substrate layer and a coating layer formed on at least one surface of the substrate layer and comprising cellulose nanofibers, wherein the cellulose nanofibers have a Fourier transform infrared spectroscopy spectrum at 1530 cm -1 Height 1750cm -1The intensity of the first peak appearing at 3000 cm -1 3600cm inland -1 The ratio of the intensities of the second peaks appearing in may be 4 to 8.

[0076] The Fourier transform infrared spectroscopy spectrum, the peaks appearing in the spectrum, and the peak intensity ratios are the same as those described above for cellulose nanofibers. The cellulose nanofibers can be manufactured by the method described above.

[0077] In one embodiment, the cellulose nanofibers have a Fourier transform infrared spectroscopy spectrum at 1400 cm -1 1500cm inland -1 There may be a third peak appearing in .

[0078] The cellulose nanofibers included in the coating layer may have a ratio of the intensity of the second peak to the intensity of the first peak of 5 to 7.

[0079] Figure 1 is a cross-sectional view of an antibacterial air filter according to one embodiment.

[0080] Referring to FIG. 1, an antibacterial air filter (1) may include a substrate layer (10) and a coating layer (20) formed on at least one surface of the substrate layer and including cellulose nanofibers.

[0081] The substrate layer (10) may include a nonwoven fabric or a polymer resin. For example, the nonwoven fabric may include a chemical bonding nonwoven fabric, a thermal bonding nonwoven fabric, an air-laid nonwoven fabric, a wet-laid nonwoven fabric, a needle-punched nonwoven fabric, a spanless nonwoven fabric, a spanbond nonwoven fabric, a melt-blown nonwoven fabric, a stitch-bond nonwoven fabric, an electrospun nonwoven fabric, etc. For example, the polymer resin may include polypropylene, polyester, polyethylene, polyethylene terephthalate, nylon, polyimide, etc.

[0082] The coating layer (20) can be formed by applying the above-described cellulose nanofibers to the substrate layer (10). For example, an aqueous solution in which cellulose nanofibers are dispersed can be coated on at least one surface of the substrate layer (10) by a method such as spraying, rolling, dipping, or slot die, and preferably, one surface of the substrate layer (10) can be coated by spraying. For example, the cellulose nanofibers included in the coating layer (20) can be in a tangled form like a net. The coating layer (20) can perform the function of filtering air.

[0083] For example, an antibacterial air filter (1) can be manufactured by spraying an aqueous solution in which cellulose nanofibers are dispersed onto at least one surface of a substrate layer (10) and then drying the solution at 50°C to 70°C, 55°C to 65°C, 50°C to 60°C, or 60°C to 70°C to form a coating layer (20).

[0084] For example, an antibacterial air filter may be a pre-filter, a deodorizing filter, or a HEPA filter. That is, a coating layer comprising cellulose nanofibers may be incorporated into a pre-filter, a deodorizing filter, or a HEPA filter. For example, if the antibacterial air filter is a HEPA filter, electricity or an electromagnetic field may be applied after the coating layer is formed.

[0085] For example, an antibacterial air filter may include a plurality of coating layers. That is, the antibacterial air filter may include a substrate layer; and a plurality of coating layers including cellulose nanofibers on at least one surface of the substrate layer. For example, the plurality of coating layers may be in a laminated form. The number of coating layers may be two or more, three or more, or three or less, four or less, or five or less. For example, after forming a coating layer on one surface of the substrate layer, a separate coating layer may be further formed on the coating layer. As another example, coating layers may be formed on one surface and the other surface (i.e., the opposite surface) of the substrate layer, and a separate coating layer may be further formed on each surface.

[0086] For example, an antibacterial air filter comprising multiple coating layers may be pleated. That is, the antibacterial air filter may have a structure in which multiple coating layers are laminated and the entire layer (including the substrate layer) is pleated and folded. Accordingly, filtration efficiency may be improved.

[0087] For example, an antibacterial air filter may further include a separate filter layer (provided that the antibacterial properties of the antibacterial air filter are maintained, and the composition thereof is not limited thereto), in which case the coating layer may function as a support layer. That is, the filter layer and the coating layer may be laminated, and the entire layer may be folded into a pleated shape, so that the antibacterial air filter may have a pleated shape.

[0088] In one embodiment, the content of the cellulose nanofibers may be 90 wt% or more of the total weight of the coating layer (20). Accordingly, the cellulose nanofibers included in the coating layer (20) can inhibit microbial growth, and the antibacterial properties of the antibacterial air filter (1) can be improved.

[0089] For example, the content of the cellulose nanofibers may be 95 wt% or more, 98 wt% or more, or 99 wt% or more of the total weight of the coating layer (20). Within the above range, microbial growth in the antibacterial air filter (1) can be suppressed.

[0090] In one embodiment, the thickness of the coating layer (20) may be 60 nm to 200 nm. For example, the thickness of the coating layer (20) may be 60 nm to 180 nm, 60 nm to 150 nm, 60 nm to 120 nm, 80 nm to 180 nm, 80 nm to 150 nm, or 80 nm to 120 nm. Within the above range, the antibacterial properties of the antibacterial air filter (1) may be maintained while the durability and strength may be improved.

[0091] In one embodiment, the antibacterial air filter (1) may comply with KS K 0693:2022 and have a bacteriostatic reduction rate of 99.9% or higher, as measured using Staphylococcus aureus. For example, if the bacteriostatic reduction rate is 99.9% or higher, the antibacterial properties are recognized and the filter may be applicable for industrial use. For example, if the bacteriostatic reduction rate is 99.0%, the number of bacteria may not be sufficiently reduced, making industrial use impossible.

[0092] For example, the antibacterial air filter (1) may be compliant with KS K 0693:2022 and have a bacteriostatic reduction value of 3 to 8, 4 to 7, 4.6 to 8, 4.6 to 7, or 4.6 to 6.6 measured using Staphylococcus aureus.

[0093] The above bacteriostatic reduction rate and bacteriostatic reduction value can be obtained using the number of viable cells immediately after inoculation of the control sample, the number of viable cells after 18 hours of culture of the control sample, and the number of viable cells after 18 hours of culture of the sample, and can be calculated, for example, from the following equations 2 and 3.

[0094] [Formula 2]

[0095] Bacterial reduction rate (%): [(M b - M c) × 100] / M b

[0096] [Formula 3]

[0097] Staphylococcal reduction value (S): log(M b ) - log(M c )

[0098] In equations 2 and 3, M b is the number of viable cells after 18 hours of culture of the control group, and M c may be the viable cell count after 18 hours of culture of the sample.

[0099] Hereinafter, preferred embodiments and comparative examples of the present invention are described. However, the following examples are merely preferred embodiments of the present invention, and the present invention is not limited to the following examples.

[0100] Example 1

[0101] (1) Manufacturing of cellulose nanofibers

[0102] Cotton fibers cut to 25 μm in size were dispersed in water and heated to maintain the temperature of the cotton fiber dispersion at 60°C for 30 minutes. Thereafter, the heated cotton fiber dispersion was mechanically extruded 10 times at 1000 atm using a high-pressure homogenizer (manufactured by Ilshin Autoclave Co., Ltd.) to obtain cellulose nanofibers. The produced cellulose nanofibers were dispersed in water at a concentration of 2 wt%.

[0103] (2) Manufacturing of antibacterial air filters

[0104] An antibacterial air filter was manufactured by spraying the above cellulose nanofiber dispersion onto one side of a nonwoven fabric and drying it at 50°C for 70 seconds to form a coating layer with a thickness of 100 nm.

[0105] Example 2

[0106] Cellulose nanofibers and an antibacterial air filter were manufactured in the same manner as in Example 1, except that the number of mechanical extrusions was changed from 10 to 8.

[0107] Example 3

[0108] Cellulose nanofibers and an antibacterial air filter were manufactured in the same manner as in Example 1, except that the number of mechanical extrusions was changed from 10 to 6.

[0109] Comparative Example 1

[0110] Cellulose nanofibers and an antibacterial air filter were manufactured in the same manner as in Example 1, except that the number of mechanical extrusions was changed from 10 to 5.

[0111] Comparative Example 2

[0112] Cellulose nanofibers and an antibacterial air filter were manufactured in the same manner as in Example 1, except that the number of mechanical extrusions was changed from 10 to 2.

[0113] Comparative Example 3

[0114] Cellulose nanofibers were manufactured using the same method as in Example 1, except that the number of mechanical extrusions was changed from 10 to 14.

[0115] However, when an antibacterial air filter was manufactured using the above cellulose nanofibers in the same manner as in Example 1, the coating layer was peeled off.

[0116] Comparative Example 4

[0117] A 17 wt% cellulose acetate solution obtained using a 75% acetic acid aqueous solution as a solvent was electrospun and deacetylated with a 0.5 N potassium hydroxide / ethanol solution for 3 hours to obtain cellulose nanofibers.

[0118] Thereafter, an antibacterial air filter was manufactured using the same method as Example 1, except that the cellulose nanofibers were used.

[0119] Comparative Example 5

[0120] Cellulose nanofibers manufactured by commercially available chemical methods were purchased.

[0121] Thereafter, an antibacterial air filter was manufactured using the same method as Example 1, except that the cellulose nanofibers were used.

[0122] Experimental Example 1: Surface Analysis Before and After Coating

[0123] In Example 1, the surface of the nonwoven fabric before forming the coating layer and the antibacterial air filter after forming the coating layer were observed using an optical microscope.

[0124] Fig. 2 is a photograph of a nonwoven fabric before forming a coating layer according to Example 1, observed with an optical microscope, and Fig. 3 is a photograph of an antibacterial air filter after forming a coating layer according to Example 1, observed with an optical microscope.

[0125] Referring to FIGS. 2 and 3, it can be seen that a coating layer including cellulose nanofibers is uniformly formed on a nonwoven fabric by applying and drying a cellulose nanofiber dispersion.

[0126] Experimental Example 2: Fourier Transform Infrared Spectroscopy

[0127] For cellulose nanofibers according to the examples and comparative examples, Fourier transform infrared spectroscopy spectra were measured using a Fourier transform infrared spectrometer in ATR mode.

[0128] 1530 cm in the acquired Fourier transform infrared spectroscopy spectrum -1 Height 1750cm -1 The first peak (vibration peak of C-C bond) appearing at 3000 cm -1 3600cm inland -1 The intensity of the second peak (vibration peak of OH bond) appearing in was confirmed, and the ratio of the intensity of the second peak to the intensity of the first peak (i.e., peak intensity ratio) was calculated and recorded in Table 1 below.

[0129] Meanwhile, FIG. 4 is a graph showing the results of analyzing cellulose nanofibers according to Example 1, Comparative Example 1, and Comparative Example 2 using Fourier transform infrared spectroscopy.

[0130] Fig. 5 is a graph showing the intensity of the first peak and the intensity of the second peak in a Fourier transform infrared spectroscopy analysis of cellulose nanofibers according to the number of mechanical extrusions during manufacturing. Specifically, Fig. 5 is a graph drawn based on the results of a Fourier transform infrared spectroscopy analysis of cellulose nanofibers according to Example 1, Comparative Example 1, and Comparative Example 2.

[0131] Fig. 6 is a graph showing the peak intensity ratio (i.e., the ratio of the intensity of the second peak to the intensity of the first peak) in Fourier transform infrared spectroscopy analysis of cellulose nanofibers according to the number of mechanical extrusions during manufacturing. Specifically, Fig. 6 is a graph drawn based on the results of Fourier transform infrared spectroscopy analysis of cellulose nanofibers according to Example 1, Comparative Example 1, and Comparative Example 2.

[0132] Fourier transform infrared spectroscopy spectrumRatio of the intensity of the second peak to the intensity of the first peak (peak intensity ratio)Example 15.5Example 26.2Example 37.6Comparative Example 18.3Comparative Example 29.5Comparative Example 33.6Comparative Example 41.2Comparative Example 51.1

[0133] Experimental Example 3: XRD Analysis

[0134] XRD analysis was performed on the cellulose nanofibers according to Example 1, and the crystal grain size of the cellulose was calculated using the Scherrer equation represented by Equation 1 described above.

[0135] Specific XRD analysis equipment / conditions are as described in Table 2 below.

[0136] XRD(X-Ray Diffractometer) EMPYREANMakerPANalyticalModelEMPYREANAnode materialCuK-Alpha1 wavelength1.540598 ÅGenerator voltage45 kVTube current40 mAScan Range10~120°Scan Step Size0.02°Divergence slit1 / 4°Antiscatter slit1 / 2°

[0137] The measurement results are shown in Table 3 below. Meanwhile, Fig. 7 is a graph showing the results of analyzing cellulose nanofibers according to Example 1 using XRD.

[0138] Cellulose grain size (nm) Example 15

[0139] Experimental Example 4: Antibacterial Evaluation

[0140] The antibacterial activity of the antibacterial air filters according to the examples and comparative examples was measured by the method of Korean Industrial Standard KS K 0693:2022, and the specific measurement conditions are as follows, and the measurement results are shown in Table 4 below. However, in the case of Comparative Example 3, the coating layer was peeled off, making it impossible to perform an antibacterial activity evaluation.

[0141] <Measurement conditions>

[0142] Bacteria used: Staphylococcus aureus (ATCC 6538)

[0143] Nonionic surfactant used: TWEEN 80 (0.05%)

[0144] Proliferation value: Proliferation value of the control group (M b / M a = valid when greater than 10)

[0145] Staphylococcus aureus: 345.5

[0146] Staphylococcal reduction value (S): log(M b ) - log(M c )

[0147] Bacterial reduction rate (%): [(Mb - M c ) × 100] / M b

[0148] M a : Viable bacterial count immediately after inoculation of the control group

[0149] M b : Viable cell count after 18 hours of culture of the control group

[0150] M c : Viable cell count after 18 hours of incubation of the sample

[0151] Antibacterial activity evaluation Bacterial reduction rate (%) Example 199.9 Example 299.9 Example 399.9 Comparative example 199.2 Comparative example 299.1 Comparative example 3-Comparative example 499.0 Comparative example 599.0

[0152] Looking at the analysis and evaluation results of Experimental Examples 2 to 4 (see Table 1 and Table 4 above), in the case of cellulose nanofibers according to Examples 1 to 3, hydroxyl groups were concentratedly distributed on the surface, thereby improving antibacterial properties.

[0153] All embodiments and conditional examples disclosed in this specification are intended to help those skilled in the art understand the principles and concepts of the present invention. Those skilled in the art will appreciate that the present invention can be implemented in modified forms without departing from the essential characteristics thereof. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is set forth in the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being included in the present invention.

Claims

1. 1530 cm in the Fourier transform infrared spectroscopy spectrum -1 Height 1750cm -1 The intensity of the first peak appearing at 3000 cm -1 3600cm inland -1 Cellulose nanofibers having an intensity ratio of the second peak appearing in the range of 4 to 8.

2. In claim 1, 1400 cm in the Fourier transform infrared spectroscopy spectrum -1 1500cm inland -1 Cellulose nanofibers in which a third peak appears.

3. In claim 1, Cellulose nanofibers, wherein the ratio of the intensity of the second peak to the intensity of the first peak is 5 to 7.

4. Base layer; and A coating layer formed on at least one surface of the above substrate layer and including cellulose nanofibers, The above cellulose nanofibers have a Fourier transform infrared spectroscopy spectrum at 1530 cm -1 Height 1750cm -1 The intensity of the first peak appearing at 3000 cm -1 3600cm inland -1 An antibacterial air filter having a ratio of the intensity of the second peak appearing in the range of 4 to 8.

5. In claim 4, The above cellulose nanofibers have a Fourier transform infrared spectroscopy spectrum at 1400 cm -1 1500cm inland -1 An antibacterial air filter in which a third peak appears.

6. In claim 4, An antibacterial air filter, wherein the ratio of the intensity of the second peak to the intensity of the first peak is 5 to 7.

7. In claim 4, An antibacterial air filter in which the content of the cellulose nanofibers is 90% by weight or more of the total weight of the coating layer.

8. In claim 4, An antibacterial air filter, wherein the thickness of the coating layer is 60 nm to 200 nm.

9. In claim 4, An antibacterial air filter that complies with KS K 0693:2022 and has a bacteriostatic reduction rate of 99.9% or higher measured using Staphylococcus aureus.

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