WO2023190318A1

WO2023190318A1 - Filter medium

Info

Publication number: WO2023190318A1
Application number: PCT/JP2023/012165
Authority: WO
Inventors: 剛志浜田; 拓也片岡; 康裕浅田
Original assignee: 東レ株式会社
Priority date: 2022-03-30
Filing date: 2023-03-27
Publication date: 2023-10-05

Abstract

The present invention is a filter medium for an air filter including at least a hydrophobic layer and a functional layer. The functional layer includes at least one inorganic chemical agent selected from the group consisting of antibacterial agents, antiviral agents, anti-mold agents, and anti-allergy agents.　Provided is a filter medium which hardly experiences decreases in functionality while efficiently realizing various functions.

Description

filter medium

The present invention relates to a filter medium used for air purification purposes.

In recent years, as air pollution such as PM2.5 has become a problem, demand for filter media such as air purifier filters, automobile cabin filters, and masks is increasing due to the need to live in a cleaner air environment. . Commonly used in these applications is a technology that removes fine dust from the air using a filter medium made of nonwoven fabric or the like. These filter media are required to have high collection efficiency and high air permeability.

In addition, the substances collected by the filter media of the above air purifier filters and automobile cabin filters include allergens derived from dust mites and pollen, mold spores, fungi, viruses, etc. Since it causes diseases, it is desired that it be deactivated on the filter medium where it is collected.

For example, Patent Document 1 discloses an anti-allergenic filter containing a polyphenol compound and an alkaline earth metal salt. Patent Document 2 discloses a filter that has antiviral function while having deodorizing performance. Although the filter itself has a function, in order to deactivate allergens and viruses in the air, it is necessary to capture them on the filter. It was insufficient. Patent Document 3 discloses a filter medium including a collection layer made of a nonwoven fabric treated with electret, and a filter medium including an antibacterial agent. Although contact efficiency has been improved by adding an antibacterial agent to the collection layer, even higher functionality is required. In addition, there was a risk of functional deterioration due to the effects of collected substances and the ingress of water droplets and oil from the outside air. Patent Document 4 discloses a filter material that has water repellency, antibacterial properties, and flame retardancy, and improves performance and shape stability when moisture enters. There was a problem that the efficiency of contact with

Patent No. 4920895 Japanese Patent Application Publication No. 2015-62851 Japanese Patent Application Publication No. 2014-50790 Japanese Patent Application Publication No. 2006-159133

The present invention solves these conventional problems, and provides a filter medium for air filters that exhibits various functions efficiently and is less likely to deteriorate in function.

In order to solve the above problems, the filter medium of the present invention has the following characteristics.

(1) A filter medium for an air filter including at least a liquid repellent layer and a functional layer, wherein the functional layer contains one or more selected from the group consisting of an antibacterial agent, an antiviral agent, an antifungal agent, and an antiallergen agent. Filter media containing inorganic chemicals.

(2) The collection efficiency of the functional layer for particles with a particle size of 0.3 to 0.5 μm is higher than the collection efficiency of the liquid repellent layer for particles with a particle size of 0.3 to 0.5 μm (1) Filter media as described.

(3) The filter medium according to (1) or (2), wherein the functional layer is a charged nonwoven fabric.

(4) The filter medium according to any one of (1) to (3), wherein the liquid-repellent layer contains a fluororesin.

(5) The liquid-repellent layer has a thickness of 0.10 mm or more and 1.00 mm or less, an air permeability of 100 cm ³ /cm ² /sec or more and 500 cm ³ /cm ² /sec or less, and a density of 0.01 g/cm ³ or more. The filter medium according to any one of (1) to (4), which has a content of 0.50 g/cm ³ or less.

(6) The filter medium according to any one of (1) to (5), wherein the liquid-repellent layer and the functional layer are in contact with each other.

(7) The filter medium according to any one of (1) to (6), wherein the inorganic drug contains at least a transition metal.

(8) According to any one of (1) to (7), wherein the inorganic drug contains one or more selected from the group consisting of silver nanoparticles, copper nanoparticles, silver carriers, copper carriers, and zinc oxide. filter medium.

According to the present invention, it is possible to provide a filter medium for an air filter that efficiently exhibits various functions and is less likely to deteriorate in function.

FIG. 1 is a schematic diagram of a collection efficiency measuring device.

The filter medium of the present invention includes a functional layer and a liquid-repellent layer. Hereinafter, the characteristics of the functional layer and the liquid-repellent layer will be explained in detail.

[Functional layer]
The functional layer in the present invention is a nonwoven fabric containing any one or more of antibacterial agents, antiviral agents, antifungal agents, and antiallergen agents.

Antibacterial properties refer to the ability to prevent and suppress the growth of bacteria by reducing or killing the number of bacteria, and the fact that the nonwoven fabric that makes up the functional layer has antibacterial properties means that it inhibits the growth of bacteria on the nonwoven fabric. Indicates that it has been processed. Antibacterial property can be imparted to a nonwoven fabric by applying an agent having an antibacterial function (hereinafter referred to as an antibacterial agent).

The antibacterial agent used in the present invention is not particularly limited, but examples of inorganic antibacterial agents include metal nanoparticles such as silver, copper, and zinc, zeolite, silica gel, glass, calcium phosphate, zirconium phosphate, calcium silicate, and aluminum metasilicate. Supports obtained by adding metals such as silver, copper, and zinc to supports such as magnesium oxide, potassium titanate, and zinc oxide, and metal oxides such as zinc oxide, copper oxide, and titanium dioxide can be suitably used. Examples of organic antibacterial agents include thiazolines such as 2-n-octyl-4-isothiazolin-3-one and 1,2-benzisothiazolin-3-one, carboxylic acids such as sorbic acid, and 3-iodo-2-propynyl. Carbamates such as butyl carbamate, benzalkonium chloride, didecyldimethylammonium chloride, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, dimethyltetradecyl[3-(trimethoxysilyl)propyl]ammonium chloride, hexa Preferably use quaternary ammonium salts such as decylpyridinium chloride, phenols such as 3-methyl-4-isopropylphenol, 4-chloro-3,5-dimethylphenol, 3-methyl-4-chlorophenol, etc. I can do it. Furthermore, antibacterial agents derived from natural products such as catechins and tannins can also be used as appropriate. When pre-mixing an antibacterial agent into the fibers that make up the nonwoven fabric, it is necessary to heat the resin to a high temperature to melt it, so inorganic antibacterial agents that are stable against heat are preferable, and silver is preferable because of its excellent antibacterial properties. More preferred are nanoparticles, copper nanoparticles, silver supports, copper supports, and zinc oxide. Further, a hybrid antibacterial agent in which an organic antibacterial agent is supported on an inorganic carrier can also be suitably used. By using a hybrid antibacterial agent, it has improved heat resistance compared to an organic antibacterial agent alone, and its sustained release function allows it to maintain its effects over a long period of time. An antibacterial agent may be used alone, or a plurality of antibacterial agents may be used in combination.

The antibacterial property can be measured by the antibacterial property test for textile products according to JIS L 1902 (2015). In measuring the filter medium, a suitable method for inoculating the test bacteria with the test piece is a bacterial liquid absorption method in which a test inoculated bacterial solution is directly inoculated onto the test piece. It is preferable that the antibacterial activity value against Staphylococcus aureus and Klebsiella pneumoniae is 2.0 or more. More preferably it is 2.5 or more, still more preferably 3.0 or more.

Antiviral properties refer to the ability to denature or damage the structure of proteins on the surface of viruses, thereby eliminating compatibility with host cell receptors and reducing activity. Also includes degeneration of the envelope in enveloped viruses. When the nonwoven fabric constituting the functional layer has antiviral properties, it means that the nonwoven fabric has been processed to reduce the activity of viruses. Antiviral properties can be imparted to the nonwoven fabric by applying a drug having an antiviral function (hereinafter referred to as an antiviral agent).

The antiviral agent used in the present invention is not particularly limited, but examples of inorganic antiviral agents include metal nanoparticles such as silver, copper, and zinc, metal oxides such as copper oxide, zinc oxide, and titanium oxide, zeolite, Supports such as silica gel, glass, calcium phosphate, zirconium phosphate, calcium silicate, magnesium aluminate metasilicate, potassium titanate, zinc oxide, etc., to which metals such as silver, copper, and zinc are added can be suitably used. can. Organic virus agents include organic benzalkonium chloride, didecyldimethylammonium chloride, dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, dimethyltetradecyl[3-(trimethoxysilyl)propyl]ammonium chloride, In addition to quaternary ammonium salts such as hexadecylpyridinium chloride, carbamates such as 3-iodo-2-propynylbutyl carbamate, antiviral agents derived from natural products such as catechins and tannins can be suitably used. . As mentioned above, when pre-mixing an antiviral agent into the fibers that make up the nonwoven fabric, it is necessary to heat the resin to a high temperature to melt it, so an inorganic antiviral agent that is stable against heat is preferable. Silver nanoparticles, copper nanoparticles, silver carriers, copper carriers, and zinc oxide are more preferred from the viewpoint of excellent viral properties.

The antiviral property can be measured by the antiviral property testing method for textile products of JIS L 1922 (2016). Although the target virus species is not limited, it is preferable that the virus has an antiviral activity value of 2.0 or more against influenza virus (H1N1), for example. More preferably it is 2.5 or more, still more preferably 3.0 or more.

Mildew resistance refers to the ability to enter the inside of mold cells and inhibit the functions necessary for mold growth, thereby suppressing mold growth. When the nonwoven fabric constituting the functional layer has antifungal properties, it means that the nonwoven fabric is processed to suppress the growth of mold. Antifungal properties can be imparted to the nonwoven fabric by applying a chemical agent having an antifungal function (hereinafter referred to as an antifungal agent) to the nonwoven fabric.

The antifungal agent used in the present invention is not particularly limited, but silver nanoparticles, copper nanoparticles, silver supports, copper supports, and zinc oxide can be suitably used as inorganic antifungal agents. Examples of organic fungicides include benzimidazole-based agents such as 2-(4-thiazolyl)-benzimidazole (thiabendazole) and methyl-2-benzimidazole carbamate (carbendazim), N-dichlorofluoromethylthio-N',N' - Sulfamides such as dimethyl-N-phenylsulfamide (dichlorofluanid), N-dichlorofluoromethylthio-N',N'-dimethyl-Np-tolylsulfamide (trifluanid), 2-bromo-2 -Nitropropane-1,3-diol, ortho-phenylphenol, etc. can be suitably used. Moreover, some of the above-mentioned antibacterial agents and antiviral agents have antifungal properties, and these can also be used as appropriate. As mentioned above, when pre-mixing a moldproofing agent into the fibers that make up the nonwoven fabric, it is necessary to raise the temperature to a high temperature to melt the resin, so an inorganic moldproofing agent that is stable against heat is preferable. Silver nanoparticles, copper nanoparticles, silver carriers, copper carriers, and zinc oxide are more preferred from the viewpoint of excellent viral properties.

The mold resistance can be measured by the mold resistance test method of JIS Z 2911 (2018). The type of target mold is not limited, but for example, for Aspergius, Penicillium, Chaetomium, etc., the measured value is 1 (the part of mycelial growth observed in the inoculated part of the sample or test piece). preferably does not exceed 1/3 of the total area), and more preferably a measured value of 0 (no hyphal growth is observed in the inoculated part of the sample or test piece).

Anti-allergenicity refers to the effect of inactivating and rendering harmless allergens, which are the causative substances that cause allergic symptoms in humans, through methods such as adsorption, coating, and denaturation. Allergens include body hair and epithelium of dogs, cats, and birds, pollen from cedar, cypress, and ragweed, and animal and plant proteins such as mold, mites, and cockroach body or excrement. It is a substance that causes

The anti-allergen agent used in the present invention is not particularly limited, but polyphenols derived from natural extracts such as tannic acid and catechins can be suitably used. Inorganic anti-allergen agents such as alkaline earth metal salts such as calcium salts and strontium salts, zirconium salts such as zirconyl chloride, zirconium hydroxide, and zirconium carbonate, and aluminum salts such as alum and aluminum sulfate can also be suitably used. When an anti-allergen agent is kneaded in advance into the fibers constituting the nonwoven fabric, it is necessary to raise the temperature to a high temperature to melt the resin, so an inorganic anti-allergen agent that is stable against heat can be suitably used.

Anti-allergenicity is measured by contacting a stock solution containing an antigen with a non-woven fabric and allowing it to stand, and calculating from the degree of decrease in the number of antigens in the collected solution. Specifically, it is calculated using the following formula.
Allergen reduction rate (%) = number of antigens in solution after collection/number of antigens in stock solution x 100.

Enzyme-linked immunosorbent assay (ELISA) can be suitably used to measure the number of antigens in a solution. The ELISA method performs measurements using the antigen-antibody reaction, which is a reaction of antibodies that specifically bind to the allergen to be measured. Specifically, the antibody that binds to the allergen is labeled with an enzyme, and the antibody that binds to the allergen is labeled with an enzyme. This method is used to quantify the allergen concentration in a sample using a calibration curve that is calculated based on the color development (absorbance) of a standard allergen at a known concentration, after which the substrate is reacted with a color. In particular, among ELISA methods, sandwich ELISA method uses two antibodies against the antigen, the first antibody captures the allergen, and after washing removes impurities other than the captured allergen, the second antibody is used for detection. can be suitably used. This method has high specificity of detection and high reproducibility of measurement, and can be performed in a simple process from sample treatment to measurement. Although the type of target allergen is not limited, for example, an allergen reduction rate of 90% or more is preferable for cedar allergen (crij1) and mite allergen (derf1). More preferably it is 95% or more, still more preferably 99% or more.

Each of the above antibacterial agents, antiviral agents, antifungal agents, and antiallergen agents may be used alone, or two or more types may be used in combination. However, depending on the combination, the functions of each drug may be impaired or the physical properties of the functional layer may deteriorate, so care must be taken. When using two or more types of drugs together, they may be added in the same process or in separate processes, but if they are added in the same process, poor compatibility between the drugs may cause drug aggregation. Because of this concern, it is preferable to add it in a separate process. An example of the addition in a separate step is, for example, a step in which the antibacterial agent is kneaded into the resin in advance, and the antiallergen agent is later applied by spray after the nonwoven fabric is manufactured.

The agent used in the filter medium of the present invention includes one or more inorganic agents selected from the group consisting of antibacterial agents, antiviral agents, antifungal agents, and antiallergen agents. By using an inorganic drug, one or more of antibacterial, antiviral, antifungal, and antiallergenic functions can be enhanced. Further, it is preferable that the inorganic drug contains at least a transition metal. Examples of transition metals include silver and copper. Examples of inorganic agents include silver nanoparticles, copper nanoparticles, silver carriers, copper carriers, and zinc oxide.

Although the nonwoven fabric constituting the functional layer is not particularly limited, it is preferably a charged nonwoven fabric made of electret fibers due to its high air permeability and collection efficiency. As the nonwoven fabric, a nonwoven fabric containing thermoplastic resin fibers, a nonwoven fabric containing natural fibers, or the like is used. Among these, nonwoven fabrics containing thermoplastic resin fibers are preferably used.

Examples of the form of the nonwoven fabric containing thermoplastic resin fibers include, but are not limited to, meltblown nonwoven fabric, spunbond nonwoven fabric, thermal bond nonwoven fabric, needle punched nonwoven fabric, airlaid nonwoven fabric, and the like. Among these, it is possible to reduce the fiber diameter of the fibers that make up the nonwoven fabric, and there is no oil on the surface of the fibers that make up the nonwoven fabric, or even if there is oil on the surface of the fibers that make up the nonwoven fabric, it is very small. From this viewpoint, melt-blown nonwoven fabrics are preferred. Here, examples of the oil agent include silicone oil such as dimethylpolysiloxane, mineral oil, and the like. In addition, when applying electret processing to a nonwoven fabric in order to further improve the collection efficiency of the filter medium, if an oil agent is present on the surface of the fibers constituting the nonwoven fabric, the nonwoven fabric tends not to exhibit sufficient charging ability.

As the thermoplastic resin fibers, those selected from polyester fibers, polylactic acid fibers, vinylon fibers, polyolefin fibers, and mixed fibers of two or more types of these fibers are used. Among these, polyolefin fibers are preferred, and polypropylene fibers (hereinafter sometimes referred to as PP fibers) are more preferred, since the nonwoven fabric has excellent charging ability after being subjected to the above-mentioned electret processing.

Here, the content of PP fibers in the nonwoven fabric is preferably 95% by mass or more, more preferably 97% by mass or more, and even more preferably 98% by mass or more, based on the total mass of the nonwoven fabric. The larger the content of PP fibers in a nonwoven fabric, the better the charging ability of the nonwoven fabric after electret processing tends to be.

The average fiber diameter of the fibers contained in the nonwoven fabric constituting the functional layer is preferably 10.0 μm or less. More preferably, it is 9.0 μm or less, and still more preferably 8.0 μm or less. When the average fiber diameter is 10.0 μm or less, the pore size of the nonwoven fabric becomes fine and sufficient collection efficiency can be obtained. Further, if it is 10.0 μm or less, the surface area of the fiber becomes large and the functions of the present invention can be imparted over a wide range, thereby making it possible to sufficiently obtain the effects of the invention. Although the lower limit of the average fiber diameter is not particularly limited, it is preferable that it is 0.1 μm or more because it can suppress the increase in pressure loss.

In addition, among all the fibers included in the nonwoven fabric, the ratio of the number of fibers with a fiber diameter of 0.1 μm to 10.0 μm (number of fibers with a fiber diameter of 0.1 μm to 10.0 μm/nonwoven fabric) It is preferable that the total number of fibers included (hereinafter sometimes referred to as the number ratio of fine fibers) is 0.7 or more. If the number ratio of fine fibers is 0.7 or more, the nonwoven fabric will contain many fine fibers, and the pore size of this nonwoven fabric will be extremely fine. Therefore, a filter medium using this nonwoven fabric has extremely excellent collection efficiency. From this viewpoint, the ratio of the number of fine fibers is preferably large, more preferably 0.75 or more, and even more preferably 0.80 or more.

Note that fibers with a fiber diameter of 0.1 μm or more and 10.0 μm or less can be obtained by using a known method such as a melt blow method.

The method for calculating the average fiber diameter in this application is as follows. Twenty sample acquisition locations are randomly selected from the surface of a 1000 mm x 1000 mm nonwoven fabric. One measurement sample of length x width = 3 mm x 3 mm is collected from each sample acquisition location. A total of 20 photographs of the surface of the nonwoven fabric, one for each measurement sample, are taken using a scanning electron microscope (magnification: 1000 times), and the fiber diameters of all the fibers in the photographs are measured. Each fiber diameter is measured with a measurement accuracy of 0.1 μm, and the average fiber diameter is calculated from the arithmetic mean.

The number ratio of fine fibers is as follows: (a) is the number of all fibers shown in the photo, (b) is the number of fibers with a fiber diameter of 0.1 μm or more and 10.0 μm or less, and (b) /(a).

When applying electret processing to a nonwoven fabric, the method is not particularly limited, and can be arbitrarily selected from known charging methods such as corona discharge method, pure water charging method, and frictional charging method. Among these, a pure water charging method in which water is applied to a nonwoven fabric and then dried is preferably used.

The fibers contained in the nonwoven fabric used in the functional layer may be fibers containing additives to improve the charging effect through charging processing. As such additives, known additives can be used as appropriate, but hindered amine additives or triazine additives are particularly preferred because they improve the durability of electrostatic force against water and the like. The content of the additive is preferably in the range of 100 to 30,000 ppm, more preferably in the range of 7,000 to 15,000 ppm, based on the total mass of the nonwoven fabric constituting the functional layer. When the content is 100 ppm or more, it becomes easier to obtain the desired high level of electret performance. When the content is 30,000 ppm or less, the additive is easily distributed uniformly in the fiber, and does not affect yarn-spinning properties or film-forming properties.

Examples of hindered amine compounds include poly[(6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl)((2,2,6, 6-tetramethyl-4-piperidyl)imino)hexamethylene ((2,2,6,6-tetramethyl-4-piperidyl)imino)] (manufactured by BASF Japan Co., Ltd., “Kimasorb” (registered trademark) 944LD ), dimethyl-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate succinate (“Tinuvin” (registered trademark) 622LD, manufactured by BASF Japan Ltd.) , and 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonate bis(1,2,2,6,6-pentamethyl-4-piperidyl) (BASF Japan ( Examples include "Tinuvin" (registered trademark) 144) manufactured by Co., Ltd.

In addition, examples of triazine additives include poly[(6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl)((2,2 ,6,6-tetramethyl-4-piperidyl)imino)hexamethylene ((2,2,6,6-tetramethyl-4-piperidyl)imino)] (manufactured by BASF Japan Ltd., "Kimasorb" (registered trademark) )944LD), and 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-((hexyl)oxy)-phenol (manufactured by BASF Japan Co., Ltd., "Tinuvin" (registered) Trademark) 1577FF).

The collection efficiency of the functional layer for particles with a particle size of 0.3 to 0.5 μm is preferably higher than the collection efficiency of the liquid-repellent layer described below for particles with a particle size of 0.3 to 0.5 μm. The functional layer has a higher collection efficiency for particles with a particle size of 0.3 to 0.5 μm, so it can efficiently collect fungi, viruses, and allergens, and has antibacterial, antiviral, and antifungal properties. It is possible to efficiently express anti-allergenic and anti-allergenic properties. The value of collection efficiency can be adjusted according to the purpose of air purifier use, cabin use, etc., and is not particularly limited, but it is effective for static removal of particles with a particle size of 0.3 to 0.5 μm at a wind speed of 4.5 m/min. It is preferable that the collection efficiency of the polystyrene particles is 60% or more. More preferably, it is 75% or more, 90% or more, or 95% or more. In places where a cleaner space is required, a functional layer with a collection efficiency of 99% or more can be suitably used.

The basis weight of the functional layer is preferably in the range of 3 to 100 g/m ² . By setting the basis weight to 3 to 100 g/m ² , preferably 5 to 70 g/m ² , more preferably 10 to 50 g/m ² , it becomes easier to obtain a composite filter with excellent air permeability and dust collection properties.

[Liquid repellent layer]
The liquid repellent layer in the present invention is a layer of nonwoven fabric having liquid repellency.

The nonwoven fabric constituting the liquid-repellent layer is not particularly limited, but preferably contains glass fiber, organic fiber, pulp, and binder resin. By containing glass fiber, organic fiber, pulp, and binder resin, it becomes easier to reduce the thickness and adjust the air permeability while maintaining the strength of the liquid-repellent layer.

The glass fiber content in the liquid repellent layer is preferably 0 to 50% by mass. When the glass fiber content is 50% by mass or less, the scattering of glass fibers is further reduced when pleating the filter.

The organic fibers are not particularly limited, and polyester fibers, vinylon fibers, etc. can be used. The amount of organic fiber in the liquid-repellent layer is preferably 20 to 85% by mass, and when glass fiber is composited with organic fiber, the amount of organic fiber is preferably 25% to 100% by mass based on the mass of the organic fiber. The intertwining properties of the fibers are improved, and the above-mentioned scattering and fluffing of the glass fibers can be further reduced.

In addition, the inclusion of pulp closes the pores of the liquid-repellent layer, making it difficult for droplets and mist containing dust to migrate to the functional layer. The content of pulp in the liquid repellent layer is preferably 5 to 20% by mass. When the content is 5% by mass or more, the liquid becomes more difficult to escape, and when the content is 20% by mass or less, pressure loss can be further reduced.

Binder resin has the function of bonding between fibers and giving strength to the sheet. The binder is not particularly limited, and polyvinyl alcohol resin, vinyl acetate resin, acrylic resin, urethane resin, etc. can be used. In particular, it is preferable to use polyvinyl alcohol resin or acrylic resin because they cause less off-odor. Further, the amount of the binder in the liquid repellent layer is preferably 10 to 40% by mass. If it is 10% by mass or more, the strength of the nonwoven fabric will be more sufficient, and if it is 40% by mass or less, pressure loss can be further reduced.

Methods for producing the nonwoven fabric constituting the liquid-repellent layer are not particularly limited, but include melt blowing, spunbonding, thermal bonding, chemical bonding, needle punching, hydroentanglement, airlaid, wet papermaking, and the like. Can be mentioned.

The fiber diameter of the liquid-repellent layer is preferably larger than the fiber diameter of the functional layer in order to function as a pre-filter for large-sized dust particles. By making the pore diameter of the liquid-repellent layer larger than that of the functional layer, fine dust can pass through the liquid-repellent layer and be efficiently collected by the functional layer. The average fiber diameter of the liquid-repellent layer is not particularly limited as long as it is larger than the average fiber diameter of the functional layer, but is preferably 10.0 μm or more, more preferably 12.0 μm or more.

The thickness of the liquid-repellent layer of the present invention is preferably 0.10 mm or more and 1.00 mm or less. By setting the thickness to 1.00 mm or less, when the filter medium is used in a pleated shape, the ventilation resistance due to the structure can be sufficiently reduced. More preferably, it is 0.50 mm or less. By setting the thickness to 0.10 mm or more, sufficient strength of the liquid-repellent layer can be obtained.

The air permeability of the liquid-repellent layer is preferably 100 cm ³ /cm ² /second or more and 500 cm ³ /cm ² /second or less. By setting the air permeability to 500 cm ³ /cm ² /second or less, it is possible to suppress fine dust collected by the functional layer from moving through the liquid-repellent layer. More preferably, it is 400 cm ³ /cm ² /second or less. More preferably, it is 350 cm ³ /cm ² /sec or less. By setting the air permeability to 100 cm ³ /cm ² /second or more, the air permeability of the filter medium can be ensured.

The density of the liquid-repellent layer is preferably 0.01 g/cm ³ or more and 0.50 g/cm ³ or less. By setting the density to 0.01 g/cm ³ or more, the liquid-repellent layer can obtain sufficient strength, and by setting the density to 0.50 g/cm ³ or less, breathability can be ensured. Preferably it is 0.05 g/cm ³ or more and 0.40 g/cm ³ or less, more preferably 0.10 g/cm ³ or more and 0.30 g/cm ³ or less. Further, in order to maintain the pleat shape during filter processing, it is preferable that the Gurley bending resistance is 300 mg or more.

The liquid repellent layer of the present invention is characterized by having liquid repellency. Having liquid repellency refers to the behavior of repelling droplets when a certain liquid is dropped on the surface of the nonwoven fabric. In this application, it means that the surface test liquid tension required for penetration satisfies 40 mN/m or less in the wetting tension test liquid defined in JIS K6768 (1999). The surface test liquid tension is more preferably 35 mN/m or less, and even more preferably 30 mN/m or less. These values are based on DOP (surface tension: 31 mN/m) and PAO (e.g. Emery 3004, surface tension: 29 mN/m), which are typical oil mist used in evaluation tests of dust masks and air conditioning elements, and oil mist in actual use environments. This value takes into consideration durability against mist.

The liquid-repellent layer is liquid-repellent and has sufficient air permeability, which prevents the accumulation of viruses and virus-containing droplets on the liquid-repellent layer, as well as the accumulation and proliferation of bacteria. It is possible to suppress movement of particles collected in the layer to the liquid-repellent layer. Furthermore, it is possible to suppress the movement of large water droplets and oil droplets to the functional layer via the liquid-repellent layer, and the sustainability of the effect of the functional layer can be increased.

Methods for imparting liquid repellency to nonwoven fabrics include, but are not particularly limited to, a method in which a liquid repellent is mixed into the raw material for spinning the nonwoven fabric, a method in which the nonwoven fabric is brought into contact with a solution containing a liquid repellent, a spray method, and a vapor deposition method. , a method of directly applying a water repellent to a nonwoven fabric, such as a gravure method, can be used as appropriate.

Imparting liquid repellency to the nonwoven fabric may be applied to the liquid repellent layer alone, before laminating the liquid repellent layer and the functional layer, or may be applied after laminating the liquid repellent layer and the functional layer. Preferably, it is a method of imparting liquid repellency before laminating the functional layer. If the liquid repellent layer is laminated after imparting liquid repellency to a single liquid repellent layer, the electret in the functional layer may be deactivated or the antibacterial, antiviral, antifungal, and antiallergenic properties may be reduced during the liquid repellent imparting process. can be prevented. When imparting liquid repellency after lamination with a functional layer, for example, by immersing it in a solution containing a liquid repellent, the electret in the functional layer may be deactivated and the antibacterial, antiviral, antifungal, and antiallergenic properties may occur. Therefore, it is necessary to select a method that imparts liquid repellency only to the surface layer of the liquid repellent layer, such as a spray method, vapor deposition method, or gravure method.

The type of water repellent is not particularly limited, but one containing a fluororesin is preferred. That is, it is preferable that the liquid repellent layer contains a fluororesin. By using a fluororesin-based water repellent, it is possible to lower the surface test liquid tension necessary for penetration in the above-mentioned wetting tension test liquid.

Types of fluororesin include tetrafluoroethylene resin, tetrafluoroethylene/perfluoropropyl vinyl ether copolymer, tetrafluoroethylene/hexafluoropropylene copolymer, chlorotrifluoroethylene resin, ethylene/tetrafluoroethylene copolymer, Vinylidene fluoride resin, vinyl fluoride resin, hexafluoropropylene/vinylidene fluoride copolymer, polyimide-based modified fluororesin, polyphenylene sulfide-based modified fluororesin, epoxy-based modified fluororesin, polyethersulfone-based modified fluororesin, phenol At least one selected from the group consisting of a system-modified fluororesin, an acrylate polymer having a perfluoroalkylethylene group, a methacrylate copolymer having a perfluoroalkylethylene group, etc. can be used.

It is preferable that the functional layer and the liquid-repellent layer are in contact with each other. Although two layers are in contact with each other, it refers to a state in which the two layers are continuously laminated, but a hot melt resin for the purpose of adhesion may be interposed between the two layers. The hot melt resin is not particularly limited, but polyethylene, EVA, etc. can be selected as appropriate. Because the functional layer and the liquid-repellent layer are in contact with each other, the liquid-repellent layer acts as a barrier and prevents the particles collected by the functional layer from moving outside, increasing the efficiency of the functional layer's contact with the fibers and achieving functionality. It becomes easier to do.

Furthermore, it is preferable that the liquid-repellent layer is arranged upstream of the functional layer. By disposing the liquid-repellent layer on the upstream side of the functional layer, it is possible to suppress the intrusion of liquids such as moisture and oil from the suction part, and it is possible to suppress the functional deterioration of the functional layer.

The collection efficiency of the liquid-repellent layer for particles having a particle size of 0.3 to 0.5 μm is preferably lower than the particle size of the functional layer of 0.3 to 0.5 μm. Although not particularly limited, it is preferable that the collection efficiency of static-eliminating polystyrene particles having a particle size of 0.3 to 0.5 μm is 10% or less under the condition of a wind speed of 4.5 m/min. More preferably it is 5% or less. By being within the above range, while suppressing the intrusion of liquids such as rainwater and oil with large particle sizes, viruses and fungi, or small droplets containing them, are not collected by the liquid repellent layer but are captured by the functional layer. It is possible to efficiently express functions.

The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples in any way.

(Thickness evaluation)
Evaluation was performed using a thickness gauge SMD-55J (manufactured by Techlock). The nonwoven fabric was cut to 200 mm x 200 mm, measurements were taken at 16 locations at 40 mm intervals, and the average value was taken as the thickness.

(Air permeability)
It was measured using an air permeability tester KES-F8 (manufactured by Kato Tech). Measurement was performed at 5 points on a nonwoven fabric size of 100 m x 100 mm, and the average value was taken as the air permeability.

(density)
The nonwoven fabric was cut into a size of 100 cm x 100 cm, the weight was measured, the basis weight (g/m ² ) was calculated, and the density was calculated from the basis weight/thickness.

(liquid repellency evaluation)
On the surface of a 100 mm x 100 mm nonwoven fabric, 50 μL of the wet tension test mixture 37 mN/m, 32 mN/m, 27.3 mN/m (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was dropped from a height of 5 mm. After 30 seconds, it was visually checked to see if it had spread. D is one that wets and spreads at 37 mN/m, C is one that does not wet and spread at 37 mN/m, but spreads at 32 mN/m, B is one that does not wet and spread at 32 mN/m, but spreads at 27.3 mN. Those without are marked as A.

(Catching efficiency and pressure loss)
A measurement sample of 150 mm x 150 mm was taken, and the collection efficiency of each sample was measured using the collection efficiency measuring device shown in FIG. In the collection efficiency measuring device shown in FIG. 1, a dust storage box 2 and a static eliminator 9 are connected to the upstream side of a sample holder 1 in which a measurement sample M is set, and a flow meter 3, a flow rate adjustment valve 4, and a static eliminator 9 are connected to the downstream side. A blower 5 is connected. Furthermore, by using a particle counter 6 in the sample holder 1 and using a switching cock 7, it is possible to measure the number of dust particles on the upstream side and the number of dust particles on the downstream side of the measurement sample M, respectively. Furthermore, the sample holder 1 is equipped with a pressure gauge 8, and the static pressure difference between the upstream and downstream sides of the measurement sample M can be read.

In measuring the collection efficiency, a 10% polystyrene 0.309U solution (manufacturer: Nacalai Tesque Co., Ltd.) is diluted up to 200 times with distilled water and filled into the dust storage box 2. Next, set the measurement sample M in the sample holder 1, adjust the air volume with the flow rate adjustment valve 4 so that the filter passing speed is 4.5 m/min, and adjust the dust concentration from 10,000 to 30,000 pieces/2. .83 × ^10-4 m ³ (0.01 ft ³ ), and the number D of dust upstream and the number d downstream of the measurement sample M were counted by particle counter 6 (KC-01D, manufactured by Rion Co., Ltd.). Each measurement sample was measured three times, and the following calculation formula was used to calculate the 0. The collection efficiency (%) of particles of 3 to 0.5 μm was determined. The average value of the three measurement samples was taken as the final collection efficiency.
・Collection efficiency (%) = [1-(d/D)] x 100
(However, d represents the total number of downstream dust particles measured three times, and D represents the total number of upstream dust particles measured three times.)

The higher the collection rate of a nonwoven fabric, the lower the number of downstream dust particles, and therefore the higher the value of collection efficiency. Moreover, the pressure loss was determined by reading the static pressure difference between upstream and downstream of the measurement sample M using a pressure gauge 8 when measuring the collection efficiency. The average value of the five measurement samples was taken as the final pressure drop.

(Antibacterial test)
The antibacterial property was measured based on the antibacterial property test for textile products of JIS L 1902 (2015). For the measurement of the filter medium, the test bacteria and the test piece were inoculated using a bacterial liquid absorption method in which the test inoculum solution was directly inoculated onto the test piece. Specifically, six samples of 0.40 g ± 0.05 g were prepared, each was placed in a vial and sterilized, and then 0.2 mL of the test bacterial solution was inoculated, three of them immediately after inoculation, and the remaining three. One is to wash out after culturing at 37°C for 24 hours. For washing, add 20 mL of SCDLP medium to a vial and shake for 5 seconds x 5 cycles using a vortex mixer. The antibacterial activity value is calculated by calculating the growth value of the sample from the difference between the common logarithm of the arithmetic mean of the number of viable bacteria after culture and the common logarithm of the arithmetic mean of the number of viable bacteria immediately after inoculation, and the difference from the growth value of the standard fabric. do. Regarding the test results, an antibacterial activity value of Staphylococcus aureus of 3.0 or more was rated A, 2.5 or more and less than 3.0 was rated B, 2.0 or more and less than 2.5 was rated C, and less than 2.0 was rated D.

(Antiviral test)
Antiviral properties were measured based on JIS L 1922 (2016) antiviral testing method for textile products. Specifically, 0.40 g ± 0.05 g of a sample cut into a size of 20 mm x 20 mm was placed in a vial and sterilized, then 0.2 mL of virus suspension was inoculated and left at 25°C for 2 hours. and let it work. After the action, 20 mL of SCDLP medium is added to the vial and stirred to wash out the virus, and the infectious titer is measured by the plaque method. The antiviral activity value is calculated from the difference between the virus infectivity of the standard fabric immediately after inoculation with the virus suspension and the infectivity of the evaluation sample after the action. Regarding the test results, antiviral activity value for influenza virus (H1N1) of 3.0 or more is A, 2.5 or more and less than 3.0 is B, 2.0 or more and less than 2.5 is C, and less than 2.0 is D. did.

(Mold resistance test)
The mold resistance was measured based on the mold resistance test method of JIS Z 2911 (2018). Specifically, the test sample is washed with tap water for 24 hours, then cut into pieces of 50 mm x 50 mm, and washed with purified water. After draining, place in the center of the culture medium, spray 1 mL of spore suspension evenly onto the test sample and culture surface, culture at 26°C for 2 weeks, and check the state of mold growth. Regarding the test results, for Aspergius (Aspergillus niger), a measured value of 0 was given as A, a measured value of 1 was given as B, and a measured value of 2 was given as C.

(Anti-allergenicity test)
Antiallergenicity was measured by sandwich ELISA method. Regarding the test results, for mite allergen (derf1), allergen reduction rate of 99% or more was rated A, 95% or more but less than 99% was rated B, 90% or more and less than 95% was rated C, and less than 90% was rated D.

(Deterioration test)
A filter medium cut to 150 mm x 150 mm was set in a holder, and 15 mL of a 0.5% aqueous solution of sodium lauryl sulfate was dropped from the liquid-repellent layer side, left to stand for 1 hour, and then the liquid was wiped off and dried.

(Reference example 1)
100 parts by mass of the base fiber sheet, 30 parts by mass of short polyester fibers with a fineness of 16 dtex (polyethylene terephthalate, melting point 265°C), heat-sealable short polyester fibers with a fineness of 8 dtex (core: polyethylene terephthalate, melting point 265°C, sheath part) : Modified polyester, melting point 155°C) 20 parts by mass, mixed with 50 parts by mass of heat-fused polyester short fibers with a fineness of 4.4 dtex (core: polyethylene terephthalate, melting point 265°C, sheath part: modified polyester, melting point 180°C) The web was spun by passing through a cotton opening machine and a carding machine, overlapped with a cross wrap to obtain the desired mass, and passed through an air through heating furnace on a conveyor to obtain a nonwoven fabric sheet A1 (thickness: 0 .51 mm, air permeability 360 cm ³ /cm ² /sec, density 0.13 g/cm ³ ).

(Reference example 2)
Silicone water repellent "POLON-MK-206" (manufactured by Shin-Etsu Silicone Co., Ltd.) was diluted with water to a concentration of 3% by mass, and the nonwoven fabric A1 obtained in Reference Example 1 was immersed at 100°C after draining. was dried for 30 minutes to obtain a nonwoven fabric sheet A2 (thickness: 0.52 mm, air permeability: 350 cm ³ /cm ² /sec, density: 0.13 g/cm ³ ).

(Reference example 3)
Fluorine-based liquid repellent "AG-E082" (manufactured by Asahi Glass Co., Ltd.) was diluted with water so that the fluororesin concentration was 3% by mass, and the nonwoven fabric A1 obtained in Reference Example 1 was immersed, and then the liquid was drained. It was dried at 150° C. for 5 minutes to obtain a nonwoven fabric sheet A3 (thickness: 0.25 mm, air permeability 250 cm ³ /cm ² /sec, density 0.19 g/cm ³ ).

(Reference example 4)
After producing a fiber aggregate by an inclined wire wet papermaking method, the fiber aggregate is impregnated with a binder and subjected to dry heat treatment to produce a nonwoven fabric sheet B1 (thickness: 0.25 mm, air permeability 280 cm ³ /cm ² /sec, The density was 0.18 g/cm ³ ). The composition is 40% by mass of glass fiber (fineness 11dtex, fiber length 15mm), 5% by mass polyester fiber (fineness 6dtex, fiber length 10mm), 10% by mass vinylon fiber (fineness 15dtex, fiber length 12mm), and 15% by mass of fiber pulp. , the binder resin (styrene acrylic polymer (glass transition temperature Tg 30°C, film forming temperature 45°C) was adjusted to be 30% by mass.

(Reference example 5)
Fluorine-based liquid repellent "AG-E082" (manufactured by Asahi Glass Co., Ltd.) was diluted with water so that the fluororesin concentration was 3% by mass, and the nonwoven fabric B1 obtained in Reference Example 4 was immersed, and then the liquid was drained. It was dried at 150° C. for 5 minutes to obtain a nonwoven fabric sheet B2 (thickness: 0.25 mm, air permeability 250 cm ³ /cm ² /sec, density 0.19 g/cm ³ ).

(Reference example 6)
A nonwoven fabric sheet with an average fiber diameter of 2.0 μm and a basis weight of 30 g/m ² was obtained by melt blowing using a polypropylene resin containing 1% by mass of the hindered amine compound "Kimasorb" (registered trademark) 944 (manufactured by BASF Japan Ltd.). . Next, a 3% by mass aqueous solution of benzalkonium chloride was sprayed at 10 g/m ² and then dried at 100° C. for 10 minutes.

A polyethylene hot melt resin was sprinkled on the obtained nonwoven fabric at a concentration of 6 g/m ² , a nonwoven fabric sheet A2 was laminated thereon, and the hot melt resin was melted by heating to obtain a filter medium of Reference Example 6.

(Reference example 7)
A filter medium of Reference Example 7 was obtained in the same manner as in Reference Example 6 except that 15 g/m ² of a 2% by mass aqueous solution of tannic acid was sprayed in place of benzalkonium chloride and then dried at 100°C for 15 minutes. Ta.

(Reference example 8)
Instead of benzalkonium chloride, a 5% by mass aqueous dispersion of Neosynthol M-30 (manufactured by Sumika Environmental Science Co., Ltd., active ingredient: thiabendazole) as a fungicidal agent was sprayed at 10 g/m ² at 100°C. A filter medium of Reference Example 8 was obtained in the same manner as Reference Example 6 except that it was dried for 15 minutes.

(Example 1)
A nonwoven fabric sheet with an average fiber diameter of 2.0 μm and a basis weight of 30 g/m ² was obtained by melt blowing using a polypropylene resin containing 1% by mass of the hindered amine compound "Kimasorb" (registered trademark) 944 (manufactured by BASF Japan Ltd.). . Next, a silver nanoparticle dispersion (containing 0.3% by mass of silver nanoparticles) was sprayed at 40 g/m ² , and then dried at 100° C. for 15 minutes.

A polyethylene hot melt resin was sprinkled on the obtained nonwoven fabric at a concentration of 6 g/m ² , a nonwoven fabric sheet A2 was laminated thereon, and the hot melt resin was melted by heating to obtain the filter medium of Example 1.

(Example 2)
Using a polypropylene resin containing 1% by mass of the hindered amine compound "Kimasorb" (registered trademark) 944 (manufactured by BASF Japan Ltd.) and 0.5% by mass of silver nanoparticles, the average fiber diameter was 2.5 μm and the basis weight was 30 g by melt blowing. A nonwoven fabric sheet of /m ² was obtained.

A polyethylene hot melt resin was sprinkled on the obtained nonwoven fabric at a concentration of 6 g/m ² , a nonwoven fabric sheet A2 was laminated thereon, and the hot melt resin was melted by heating to obtain a filter medium of Example 2.

(Example 3)
Using a polypropylene resin containing 1% by mass of the hindered amine compound "Kimasorb" (registered trademark) 944 (manufactured by BASF Japan Ltd.) and 0.5% by mass of silver nanoparticles, the average fiber diameter was 2.5 μm and the basis weight was 30 g by melt blowing. A nonwoven fabric sheet of /m ² was obtained. Next, pure water was sprayed at high pressure to spread the pure water over the entire nonwoven fabric sheet, and after draining, the nonwoven fabric was air-dried to obtain an electret melt-blown nonwoven fabric.

A polyethylene hot melt resin was sprinkled on the obtained nonwoven fabric at a concentration of 6 g/m ² , a nonwoven fabric sheet A2 was laminated thereon, and the hot melt resin was melted by heating to obtain the filter medium of Example 3.

(Example 4)
A polypropylene resin containing 1% by mass of the hindered amine compound "Kimasorb" (registered trademark) 944 (manufactured by BASF Japan Ltd.) and 0.3% by mass of zinc oxide was melt-blown with an average fiber diameter of 2.1 μm and a basis weight of 30 g/ A nonwoven fabric sheet of m ² was obtained. Next, pure water was sprayed at high pressure to spread the pure water over the entire nonwoven fabric sheet, and after draining, the nonwoven fabric was air-dried to obtain an electret melt-blown nonwoven fabric.

A polyethylene hot melt resin was sprinkled on the obtained nonwoven fabric at a concentration of 6 g/m ² , a nonwoven fabric sheet A2 was laminated thereon, and the hot melt resin was melted by heating to obtain a filter medium of Example 4.

(Example 5)
A filter medium of Example 5 was obtained in the same manner as in Example 4 except that nonwoven fabric sheet A3 was laminated in place of nonwoven fabric sheet A2.

(Example 6)
Using a polypropylene resin containing 1% by mass of the hindered amine compound "Kimasorb" (registered trademark) 944 (manufactured by BASF Japan Ltd.) and 0.3% by mass of zinc oxide, the average fiber diameter was 2.1 μm and the basis weight was 30 g by melt blowing. A nonwoven fabric sheet of /m ² was obtained. Next, pure water was sprayed at high pressure to spread the pure water over the entire nonwoven fabric sheet, and after draining, the nonwoven fabric was air-dried to obtain an electret melt-blown nonwoven fabric.

Activated carbon with an average particle size of 250 μm and polyethylene hot melt resin were mixed on the obtained nonwoven fabric, and the activated carbon and hot melt resin were sprinkled at 100 g/m ² and 30 g/m ² , respectively, and a nonwoven fabric sheet A3 was laminated. The hot melt resin was melted by heating to obtain the composite filter medium of Example 6. As mentioned above, since activated carbon with an average particle size of 250 μm is mixed with the polyethylene hot melt resin, there is an intermediate layer.

(Example 7)
A filter medium of Example 7 was obtained in the same manner as in Example 4 except that nonwoven fabric sheet B2 was used in place of nonwoven fabric sheet A2.

(Example 8)
A filter medium of Example 8 was obtained in the same manner as in Example 7 except that a polypropylene resin containing 0.3% by mass of copper zeolite was used instead of zinc oxide.

(Example 9)
A filter medium of Example 9 was obtained in the same manner as in Example 7 except that a polypropylene resin containing 0.3% by mass of silver zeolite was used instead of zinc oxide.

(Reference example 9)
Using a polypropylene resin containing 1% by mass of the hindered amine compound "Kimasorb" (registered trademark) 944 (manufactured by BASF Japan Ltd.), a nonwoven fabric sheet with an average fiber diameter of 2.0 μm and a basis weight of 30 g/m ² was obtained by melt blowing. Ta. Next, a 3% by mass aqueous solution of benzalkonium chloride was sprayed at 10 g/m ² and then dried at 100° C. for 10 minutes. Thereafter, an electret treatment was performed using a corona discharge method.

A polyethylene hot melt resin was sprinkled on the obtained nonwoven fabric at a concentration of 6 g/m ² , a nonwoven fabric sheet B2 was laminated thereon, and the hot melt resin was melted by heating to obtain a filter medium of Reference Example 9.

(Reference example 10)
A filter medium of Reference Example 10 was obtained in the same manner as Reference Example 9 except that 15 g/m ² of a 2% by mass aqueous solution of tannic acid was sprayed in place of benzalkonium chloride, and then dried at 100°C for 15 minutes. Ta.

(Example 10)
Using a polypropylene resin containing 1% by mass of the hindered amine compound "Kimasorb" (registered trademark) 944 (manufactured by BASF Japan Ltd.) and 0.5% by mass of silver nanoparticles, the average fiber diameter was 2.5 μm and the basis weight was 30 g by melt blowing. A nonwoven fabric sheet of /m ² was obtained. Next, a 2% by mass aqueous solution of tannic acid was sprayed at 15 g/m ² and then dried at 100° C. for 15 minutes.

A polyethylene hot melt resin was sprinkled on the obtained nonwoven fabric at a concentration of 6 g/m ² , a nonwoven fabric sheet B2 was laminated thereon, and the hot melt resin was melted by heating to obtain a filter medium of Example 10.

(Example 11)
A polypropylene resin containing 1% by mass of the hindered amine compound "Kimasorb" (registered trademark) 944 (manufactured by BASF Japan Ltd.) and 0.3% by mass of zinc oxide was melt-blown with an average fiber diameter of 2.1 μm and a basis weight of 30 g/ A nonwoven fabric sheet of m ² was obtained. Next, a 5% by mass aqueous dispersion of Neosynthol M-30 (manufactured by Sumika Environmental Science Co., Ltd., active ingredient: thiabendazole) was sprayed at 10 g/m ² and then dried at 100° C. for 15 minutes. Thereafter, an electret treatment was performed using a corona discharge method.

A polyethylene hot melt resin was sprinkled on the obtained nonwoven fabric at a concentration of 6 g/m ² , a nonwoven fabric sheet B2 was laminated thereon, and the hot melt resin was melted by heating to obtain a filter medium of Example 11.

(Comparative example 1)
A nonwoven fabric sheet with an average fiber diameter of 2.0 μm and a basis weight of 30 g/m ² was obtained by melt blowing using a polypropylene resin containing 1% by mass of the hindered amine compound "Kimasorb" (registered trademark) 944 (manufactured by BASF Japan Ltd.). .

A polyethylene hot melt resin was sprinkled on the obtained nonwoven fabric at a concentration of 6 g/m ² , a nonwoven fabric sheet A1 was laminated thereon, and the hot melt resin was melted by heating to obtain a filter medium of Comparative Example 1.

(Comparative example 2)
A filter medium of Comparative Example 2 was obtained in the same manner as in Reference Example 7 except that nonwoven fabric sheet A1 was used instead of nonwoven fabric sheet A2.

(Comparative example 3)
A filter medium of Comparative Example 3 was obtained in the same manner as in Reference Example 8 except that nonwoven fabric sheet A1 was used instead of nonwoven fabric sheet A2.

(Comparative example 4)
A filter medium of Comparative Example 4 was obtained in the same manner as in Example 4 except that nonwoven fabric sheet A1 was used instead of nonwoven fabric sheet A2.

(Comparative example 5)
A filter medium of Comparative Example 5 was obtained in the same manner as in Example 8 except that nonwoven fabric sheet A1 was used in place of nonwoven fabric sheet B2.

(Comparative example 6)
A filter medium of Comparative Example 6 was obtained in the same manner as Comparative Example 1 except that nonwoven fabric sheet B2 was used instead of nonwoven fabric sheet A1.

Table 1 shows the composition and physical properties of the functional layer and liquid-repellent layer prepared in Examples and Comparative Examples, and Table 2 shows the collection efficiency, pressure loss, and initial performance of the filter medium, as well as antibacterial, antiviral, and antiallergen properties after deterioration tests. The results of anti-mold performance are shown.

Comparative Examples 1 and 6 do not have a drug in the functional layer, so various functions are not expressed. Comparative Examples 2 to 5 exhibit good initial performance, but the degree of functional decline after the deterioration test is large.

In all Examples 1 to 11, the degree of functional decline after the deterioration test was small, and it can be said that the functionality was efficiently expressed.

As described above, the filter medium of the present invention exhibits its functions efficiently and can suppress performance deterioration.

The filter medium of the present invention can be suitably used for air purifier filters, automobile cabin filters, and the like.

1: Sample holder 2: Dust storage box 3: Flowmeter 4: Flow rate adjustment valve 5: Blower 6: Particle counter 7: Switching cock 8: Pressure gauge 9: Static eliminator M: Measurement sample

Claims

A filter medium for an air filter comprising at least a liquid repellent layer and a functional layer, the functional layer containing one or more inorganic agents selected from the group consisting of antibacterial agents, antiviral agents, antifungal agents, and antiallergen agents. filter media containing.
The functional layer has a higher collection efficiency for particles having a particle size of 0.3 to 0.5 μm than the liquid repellent layer has a collection efficiency for particles having a particle size of 0.3 to 0.5 μm. filter medium.
The filter medium according to claim 1 or 2, wherein the functional layer is a charged nonwoven fabric.
The filter medium according to any one of claims 1 to 3, wherein the liquid repellent layer contains a fluororesin.
The liquid-repellent layer has a thickness of 0.10 mm or more and 1.00 mm or less, an air permeability of 100 cm 3 /cm 2 /sec or more and 500 cm 3 /cm 2 /sec or less, and a density of 0.01 g/cm 3 or more and 0.50 g. The filter medium according to any one of claims 1 to 4, wherein the filter medium has a particle diameter of less than /cm 3 .
The filter medium according to any one of claims 1 to 5, wherein the liquid repellent layer and the functional layer are in contact with each other.
The filter medium according to any one of claims 1 to 6, wherein the inorganic drug contains at least a transition metal.
The filter medium according to any one of claims 1 to 7, wherein the inorganic drug contains one or more selected from the group consisting of silver nanoparticles, copper nanoparticles, silver carriers, copper carriers, and zinc oxide.