WO2024157756A1

WO2024157756A1 - Antibacterial filter, method for manufacturing antibacterial filter, and air purifier

Info

Publication number: WO2024157756A1
Application number: PCT/JP2024/000225
Authority: WO
Inventors: 洋史阿部
Original assignee: 富士フイルム株式会社
Priority date: 2023-01-26
Filing date: 2024-01-10
Publication date: 2024-08-02

Abstract

To provide an antibacterial filter having excellent antibacterial properties. The present invention also addresses the problem of providing a method for manufacturing an antibacterial filter, and an air purifier.　The antibacterial filter has a filter part that satisfies Requirement A, and an antibacterial part that is disposed on the filter part. The antibacterial part contains a silver-based antibacterial agent and a silicate-based compound. Requirement A: The particle collection rate is at least 99.95% when particles having a particle diameter of 0.3 μm are passed through the filter part, from which static has been eliminated, under the conditions of a wind velocity of 5.3 cm/s and according to the procedure defined in JIS B 9927-5:2022 Annex C.

Description

Antibacterial filter, antibacterial filter manufacturing method, air purifier

The present invention relates to an antibacterial filter, a method for manufacturing an antibacterial filter, and an air purifier.

Conventionally, air purifiers have been known that have the function of purifying air by taking in air into a space such as a room or a vehicle, passing the air through an air purification filter as it moves inside the device, and then discharging the air back into the space.
For example, Patent Document 1 discloses a technique related to an air purifier that includes an air cleaning filter, a dust sensor, a fan, a fan control unit, and the like.

JP 2015-124914 A

In facilities or situations where high-quality air purification functions are always required, such as medical institutions, filters and air purifiers whose collection performance does not deteriorate even after long-term use are required. In addition, in medical institutions, patients suffering from infectious diseases stay for the purpose of treatment, so there are often many pathogens such as pathogenic bacteria and pathogenic viruses floating alone or attached to aerosols in the space.
Here, when ventilation is difficult for equipment or medical reasons, pathogens are often removed by filtering the indoor air with an air purifier. In such cases, it is possible that a very high concentration of pathogens may remain on the filter due to long-term use of the air purifier. As a result, it is possible that workers who are engaged in tasks such as replacing the filters may become infected, or that pathogens may be re-distributed indoors due to a decrease in collection efficiency or damage to the filter.

In view of the above situation, the present invention aims to provide an antibacterial filter with excellent antibacterial properties. It also aims to provide a method for manufacturing an antibacterial filter and an air purifier.

　As a result of extensive research into solving the above problems, the inventors have discovered that the problems can be solved by the following configuration.

[1] An antibacterial filter comprising a filter portion that satisfies requirement A described below, and an antibacterial portion disposed on the filter portion, the antibacterial portion including a silver-based antibacterial agent and a silicate-based compound.
[2] The antibacterial filter according to [1], wherein the silver-based antibacterial agent is a silver-supported inorganic oxide.
[3] The antibacterial filter according to [1] or [2], wherein the antibacterial portion contains alcohol.
[4] The antibacterial filter according to any one of [1] to [3], which is for an air purifier.
[5] A method for producing an antibacterial filter, comprising a step of contacting a filter that satisfies requirement A described below with a composition for forming an antibacterial portion, the composition for forming an antibacterial portion containing a silver-based antibacterial agent and a silicate-based compound precursor.
[6] The method for producing an antibacterial filter according to [5], wherein the process includes a coating process of coating the antibacterial portion-forming composition onto the filter.
[7] The method for manufacturing an antibacterial filter according to [5] or [6], wherein the amount of the antibacterial portion-forming composition applied to the filter in the application step is 50 to 1000 mL/ ^m2 .
[8] The method for producing an antibacterial filter according to any one of [5] to [7], wherein the silver-based antibacterial agent is a silver-supported inorganic oxide.
[9] The method for producing an antibacterial filter according to any one of [5] to [8], wherein the composition for forming the antibacterial portion contains alcohol.
[10] The method for producing an antibacterial filter according to any one of [5] to [9], wherein the antibacterial filter is for an air purifier.
[11] An air purifier comprising an antibacterial filter according to any one of [1] to [4], or an antibacterial filter manufactured by the manufacturing method for an antibacterial filter according to any one of [5] to [10] above.

The present invention can provide an antibacterial filter with excellent antibacterial properties. The present invention can also provide a method for manufacturing an antibacterial filter and an air purifier.

The present invention will be described in detail below.
The following description of the components may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.
In this specification, "(meth)acrylate" refers to acrylate and/or methacrylate (either one or both of acrylate and methacrylate), and "(meth)acryloyl" refers to acryloyl and/or methacryloyl (either one or both of acryloyl and methacryloyl).
In this specification, a numerical range expressed using "to" means a range including the numerical values before and after "to" as the lower limit and upper limit.
In the present specification, each component may use one substance corresponding to the component alone or two or more substances. When two or more substances are used for each component, the content of the component means the total content of the two or more substances, unless otherwise specified.

[Antibacterial filter]
The antibacterial filter of the present invention has a filter part (hereinafter simply referred to as the "filter part") that satisfies requirement A, that is, a particle collection rate measured under specified conditions as described below is 99.95% or more, and an antibacterial part disposed on the filter part, and the antibacterial part contains a silver-based antibacterial agent and a silicate-based compound.
The filter portion and the antibacterial portion of the antibacterial filter of the present invention will be described below in order.

[Filter section]
The filter section has, for example, a filter medium formed in a sheet shape. As the filter medium, a known material used in air purifier filters and clean rooms, etc. can be used. The filter medium may have a single-layer structure made of a single sheet-like filter medium, or a multi-layer structure made of a plurality of sheet-like filter mediums stacked together.
Examples of the filter medium include a fluororesin porous membrane and a filter medium containing glass fibers (glass filter medium), with the fluororesin porous membrane being preferred in terms of low pressure loss.

Examples of the fluororesin constituting the fluororesin porous membrane include polytetrafluoroethylene (PTFE), fluorinated ethylene propylene, perfluoroalkoxy polymer, poly(ethylene-co-tetrafluoroethylene-co-hexafluoropropylene) (EFEP), tetrafluoroethylene hexafluoropropylene vinylidene fluoride (THV), poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP), perfluoroalkoxy (PFA), and ethylene tetrafluoroethylene (ETFE). The fluororesin porous membrane may be composed of one type of fluororesin alone, or may be composed of two or more types of fluororesins. The fluororesin porous membrane may also be composed by laminating a plurality of membranes composed of fluororesins.
The content of the fluororesin in the fluororesin porous membrane is preferably 25% by mass or more, more preferably more than 50% by mass and 100% by mass or less, based on the total mass of the fluororesin porous membrane. The fluororesin porous membrane may contain, for example, an inorganic filler as a component different from the fluororesin.

As a fluororesin porous membrane, a polytetrafluoroethylene porous membrane (hereinafter also referred to as a "PTFE porous membrane") formed using polytetrafluoroethylene is preferred, since it generates less microfibers and has a smaller increase in pressure loss over time.

The thickness of the fluororesin porous membrane, such as the PTFE porous membrane, is not particularly limited, but is preferably 0.1 to 100 μm, and more preferably 1 to 20 μm.

The method for producing the fluororesin porous membrane is not particularly limited, and the membrane can be produced by a known method such as a method in which a sheet-like molded body formed using a fluororesin is biaxially stretched to make it porous.
For example, the manufacturing method of PTFE porous membrane can be the following method. First, add liquid lubricant to PTFE fine powder to form a paste-like mixture, and preform the mixture into a rod shape under a pressure that does not separate the liquid lubricant from the paste-like mixture. Next, extrude or roll the rod-like preform into a strip. Then, stretch the obtained strip-like molded product in the longitudinal direction and the transverse direction. This makes the strip-like molded product porous (fibrillated), and produces a PTFE porous membrane.
The liquid lubricant is not particularly limited as long as it can provide the mixture surface with appropriate wettability, and examples of the liquid lubricant include hydrocarbons such as liquid paraffin, naphtha, and white oil. The liquid lubricant is preferably one that can be removed by extraction or heat treatment.

When manufacturing a fluororesin porous membrane, it is preferable to implement anti-static measures in the equipment used in each process to suppress charging of the molded products, etc. Fluororesins with high electrical resistance, such as PTFE, tend to become charged during the manufacturing process, which can lead to discharges that can cause holes to form in the filter material and affect quality. By taking the above-mentioned anti-static measures, it is possible to reduce the above-mentioned effects associated with charging the filter material.

The filter section preferably has a multi-layer structure in which multiple filter media are laminated. In particular, the filter section more preferably has a multi-layer structure in which a fluororesin porous membrane (more preferably a PTFE porous membrane) and a breathable support material are laminated. Since a fluororesin porous membrane is generally a very thin material with high flexibility, laminating a breathable support material improves the strength of the filter media, suppresses deformation due to the passage of airflow, and improves handling.

An example of the breathable support is a nonwoven fabric that is coarser than the fluororesin porous membrane and allows a larger amount of air to pass through per unit area.
Examples of materials constituting the breathable support (nonwoven fabric) include polyolefins (polyethylene (PE), polypropylene (PP), etc.), polyamides, polyesters (polyethylene terephthalate (PET), etc.), aromatic polyamides, and composites of these.

When the filter section comprises the above-mentioned fluororesin porous membrane and breathable support material, it is preferable that at least one breathable support is disposed upstream of the fluororesin porous membrane in the direction of air flow. This makes it possible to suppress adhesion of coarse particles (such as cotton dust) that cause clogging of the fluororesin porous membrane to the fluororesin porous membrane. It is more preferable that the filter section comprises a fluororesin porous membrane and two breathable supports, and is laminated so that the fluororesin porous membrane is sandwiched between the two breathable supports.
The method for laminating a plurality of filter media is not particularly limited, and can be, for example, thermal lamination by heating.

The filter portion may be pleated so that its cross-sectional shape is a continuous W-shape. That is, the filter portion may be in the form of a so-called "filter pack." It is preferable that the filter portion is pleated, since this increases the surface area and reduces pressure loss.
The pleated filter portion has a pleated shape in which peaks and valleys are alternately repeated along one direction in the filter surface. The pitch of the pleats (e.g., the distance between the peaks of two adjacent peaks with one valley between them) is preferably 2.5 to 5.0 mm, and more preferably 3.0 to 4.0 mm.

The pleating of the filter portion can be performed by a known method. For example, a pleat shape is formed in the filter portion by folding the filter material along mountain folds and valley folds set on the surface of the filter material in one direction within the filter surface using a known pleating machine (rotary pleating machine, reciprocating pleating machine, creasing pleating machine, etc.).

A spacer may be disposed in the pleated filter section to maintain the pleated shape. Examples of spacers include resin strings called beads. The beads are disposed on the surface of the filter section along a direction perpendicular to the mountain fold lines (valley fold lines). It is preferable that the pleated filter section has a plurality of beads disposed at predetermined intervals in the direction along the mountain fold lines (valley fold lines). It is also preferable that the beads are disposed on both the front and back surfaces of the filter section.
The bead is formed, for example, from a yarn separator in which the outer circumference of the yarn is coated with an adhesive such as a synthetic resin, or from a hot melt resin, etc. The bead can be formed, for example, by melting the yarn separator or the hot melt resin by heat and attaching it to a predetermined position of the filter portion.

<Physical properties, etc.>
(Requirement A)
The filter part of the antibacterial filter of the present invention satisfies requirement A that the particle collection efficiency when particles with a particle size of 0.3 μm are passed through the filter part in a state where static electricity has been removed according to the procedure specified in JIS B 9927-5:2022, Annex C, at a wind speed of 5.3 cm/s is 99.95% or more.

A filter that satisfies the above requirement A is characterized in that the particle collection efficiency measured in a state where static electricity has been removed according to a specific static elimination procedure is equal to or greater than the above reference value.
Conventionally, electrically charged filters (electret filters) in which the filter material is electrically charged to improve its dust adsorption capacity have been widely used as filters that have the function of purifying the air in spaces such as indoors or vehicle interiors. However, it is known that the filtering efficiency of electrically charged filters varies depending on the air volume, and that the adsorption capacity and therefore the filtering efficiency decreases as the amount of dust captured increases. Because the filter section of the antibacterial filter of the present invention has an excellent particle collection rate even in a neutralized state as described above, the above-mentioned effects on filtering efficiency that can occur in electrically charged filters are significantly suppressed, and an antibacterial filter can be obtained that is less likely to lose filtering performance even over long periods of use and has a longer service life.

Whether or not the filter portion satisfies requirement A can be confirmed by carrying out the following measurement test (hereinafter also referred to as "test A").
First, the test specimen (filter part) is de-electrified according to the procedure described in JIS B 9927-5:2022, Appendix C, C.3. Specifically, the test specimen is exposed for 24 hours in a chamber filled with saturated IPA vapor at 23±5°C. After the exposure is completed, the test specimen is stabilized by storing it under standard atmospheric conditions (23±5°C, relative humidity (50±15)%) for at least 30 minutes. The IPA used for exposure has a purity of more than 99.9% by volume.
Next, a particle collection test is performed in which particles having a particle size of 0.3 μm are passed through the test specimen subjected to the above-mentioned static elimination procedure under the condition of a wind speed of 5.3 cm/s, and the particle collection rate is measured. Examples of particles having a particle size of 0.3 μm used in the particle collection test include monodisperse aerosols made of polyalphaolefin (PAO, CAS number: 68649-12-7). The particle size of the particles used in the particle collection test refers to the mass average diameter. For the particles and measuring equipment used in the particle collection test, the particles and measuring equipment described in JIS B 9927-2:2022 can be referred to. A test specimen is placed in the measuring equipment, and a particle-containing gas diluted to a predetermined concentration with clean air is passed through the test specimen at a speed of 5.3 cm/s using a suction pump or the like, and the particle collection rate can be obtained from the particle count value on the upstream side and downstream side of the test specimen to be measured.
If the particle collection efficiency measured by the above test A is 99.95% or more, the filter part satisfies requirement A.

From the above viewpoint, it is preferable that the filter section, in a state where static electricity has been removed in accordance with the procedure prescribed in JIS B 9927-5:2022, Appendix C, has a particle capture rate of 99.97% or more when a particle capture test is conducted in which particles with a diameter of 0.3 μm are allowed to pass through at a wind speed of 5.3 cm/s.

Furthermore, a filter that satisfies the above requirements can be produced, for example, by appropriately adjusting the structure and material of the filter medium, as well as the pleat shape formed by the pleating process.

[Antibacterial Section]
The antibacterial portion of the antibacterial filter of the present invention is disposed on the filter portion and contains a silver-based antibacterial agent and a silicate-based compound.
It is presumed that the antibacterial filter of the present invention, by disposing the antibacterial part containing the above-mentioned predetermined component on the filter part, not only captures bacteria and viruses present in the air passing through the antibacterial filter to purify the air, but also more efficiently inactivates the captured bacteria and viruses, thereby improving the antibacterial properties. As a result, it is considered that the antibacterial filter of the present invention can also reduce the risk of infection caused by bacteria and viruses during long-term use of the antibacterial filter or during replacement of the antibacterial filter.

In this specification, the antibacterial portion is "disposed on the filter portion" means that the antibacterial portion is disposed in contact with at least a portion of the filter portion. The position of the antibacterial portion on the filter portion is not particularly limited as long as it does not impede the breathability (capture performance) of the antibacterial filter, and the antibacterial portion may be disposed over the entire surface of the filter portion, or may be disposed in islands on the surface of the filter portion. The antibacterial portion may also be disposed so as to cover the surfaces of the pores in the filter portion and/or the surfaces of the fibers that make up the filter portion.

<Ingredients>
(Silver-based antibacterial agent)
The antibacterial portion contains a silver-based antibacterial agent.
In this specification, a silver-based antibacterial agent means an antibacterial agent that contains silver.
The type of silver-based antibacterial agent is not particularly limited, and examples include known silver-based antibacterial agents.

When composition A contains a silver-based antibacterial agent, composition A has an antibacterial effect not only against Escherichia coli and pathogenic bacteria, but also has antibacterial properties against fungi such as mold and antiviral properties against viruses.
Examples of viruses against which the antiviral agent is effective include influenza virus, SARS coronavirus (SARS-CoV), and novel coronavirus (SARS-CoV-2). The agent is also expected to be effective against novel coronavirus variants (SARS-CoV-2 B.1.17, B.1.351, P.1, B.1.617.2, etc.). A known method can be used to evaluate the antiviral activity. For example, the method shown in ISO 21702 can be used, and the antiviral activity can be measured by changing the test virus to a target virus such as influenza virus, SARS coronavirus, or novel coronavirus. The antiviral activity value may be greater than 1, but is preferably 2.0 or more, and more preferably greater than 2.0.

The form of silver contained in the silver-based antibacterial agent is not particularly limited, and examples thereof include silver particles, silver ions, silver oxide, and silver salts (including silver complexes). In this specification, silver complexes are included in the scope of silver salts.
Examples of silver salts include silver acetate, silver acetylacetonate, silver azide, silver acetylide, silver arsenate, silver benzoate, silver hydrogen fluoride, silver bromate, silver bromide, silver carbonate, silver chloride, silver chlorate, silver chromate, silver citrate, silver cyanate, silver cyanide, (cis,cis-1,5-cyclooctadiene)-1,1,1,5,5,5-hexafluoroacetylacetonate, silver diethyldithiocarbamate, silver fluoride (I), silver fluoride (II), silver 7,7-dimethyl-1,1,1,2,2,3,3-heptafluoro-4,6-octanedionate, silver hexafluoroantimonate, silver hexafluoroarsenate, silver hexafluorophosphate, silver iodate, and silver iodide. Examples of silver isothiocyanate include silver potassium cyanide, silver lactate, silver molybdate, silver nitrate, silver nitrite, silver oxide (I), silver oxide (II), silver oxalate, silver perchlorate, silver perfluorobutyrate, silver perfluoropropionate, silver permanganate, silver perrhenate, silver phosphate, silver picrate monohydrate, silver propionate, silver selenate, silver selenide, silver selenate, silver sulfadiazine, silver sulfate, silver sulfide, silver sulfite, silver telluride, silver tetrafluoroborate, silver tetraiodomucrylate, silver tetratungstate, silver thiocyanate, silver p-toluenesulfonate, silver trifluoromethanesulfonate, silver trifluoroacetate, and silver vanadate.
Examples of the silver complex include a histidine silver complex, a methionine silver complex, a cysteine silver complex, an aspartic acid silver complex, a pyrrolidone carboxylic acid silver complex, an oxotetrahydrofuran carboxylic acid silver complex, and an imidazole silver complex.

As the silver-based antibacterial agent, a silver-supported carrier containing a carrier and silver supported on the carrier is preferred.
The type of the carrier is not particularly limited, and may be any known carrier. Examples of the carrier include inorganic oxides (e.g., zeolite, silica gel, zirconium phosphate, calcium phosphate, etc.); activated carbon; metal carriers; organic metals; polymer particles, etc. In terms of superior antibacterial properties of the composition A, the carrier is preferably an inorganic oxide or polymer particles, and more preferably glass or polymer particles.

A preferred silver-based antibacterial agent is a silver-supported inorganic oxide, which contains an inorganic oxide as a carrier and silver supported on the inorganic oxide.
More specific examples of the inorganic oxide carrier include zinc calcium phosphate, calcium phosphate, zirconium phosphate, aluminum phosphate, aluminum silicate, calcium silicate, activated carbon, activated alumina, silica gel zeolite, apatite, hydroxyapatite, titanium phosphate, potassium titanate, hydrous bismuth oxide, hydrous zirconium oxide, and hydrotalcite.
The carrier may be crystalline or non-crystalline (amorphous), but is preferably amorphous, and more preferably glass. Examples of materials that can form glass include silicates, borosilicates, and phosphates.
As the silver-supported inorganic oxide, silver-supported zeolite, silver-supported apatite, silver-supported zirconium phosphate, silver-supported phosphate glass, or silver-supported calcium silicate is preferable.

Commercially available silver-based antibacterial agents include, for example, silver zeolite-based antibacterial agents such as "Zeomic (registered trademark)" manufactured by Sinanen Zeomic Co., Ltd., "Silwell" manufactured by Fuji Silysia Chemical Co., Ltd., and "Bactenon" manufactured by Japan Electronic Materials Co., Ltd.; silver-based antibacterial agents in which silver is supported on inorganic ion exchange ceramics, such as "Novalon (registered trademark)" manufactured by Toagosei Co., Ltd. and "Atomy Ball (registered trademark)" manufactured by Catalysts and Chemicals Industry Co., Ltd.; silver particles such as "Nano Silver" manufactured by Nippon Ion Co., Ltd.; and silver-supported ceramic particles (silver ceramic particles) in which silver is chemically bonded to ceramics, such as "Bactekiller (registered trademark)" and "Bacterite (registered trademark)" manufactured by Fuji Chemical Co., Ltd.

The silver-based antibacterial agent is preferably in particulate form.
When the silver-based antibacterial agent is in the form of particles, the average particle size is not particularly limited, but is preferably 0.01 μm or more, more preferably 0.3 μm or more, and the upper limit is preferably 3.0 μm or less, more preferably 1.0 μm or less.
The average particle size of the silver-based antibacterial agent can be measured using an electron microscope. Specifically, the average particle size is the average value of the diameters of the primary particles and secondary particles (note that "secondary particles" are defined as aggregates formed by the fusion or contact of primary particles) of the silver-based antibacterial agent particles measured from an image of an electron microscope, and the diameters of the particles in a range of 90% of the total number of particles are averaged, excluding the 5% of the number of particles on the smallest diameter side and the 5% of the number of particles on the largest diameter side. In other words, the average particle size is a value obtained from the primary particles and the secondary particles. The diameter refers to the circumscribed circle equivalent diameter of the particle.
In addition, when there is no significant difference in particle shape, the 50% volume cumulative diameter (D50) may be measured three times using a laser diffraction/scattering type particle size distribution measuring device manufactured by Horiba, Ltd., and the average value of the three measurements may be used as the average particle size.

The average particle size of the silver-based antibacterial agent can be adjusted by a conventional method, such as dry grinding and wet grinding. In dry grinding, for example, a mortar, a jet mill, a hammer mill, a pin mill, a rotary mill, a vibration mill, a planetary mill, a bead mill, etc. are appropriately used. In wet grinding, for example, various ball mills, high-speed rotary grinders, jet mills, bead mills, ultrasonic homogenizers, high-pressure homogenizers, etc. are appropriately used.
For example, in a bead mill, the average particle size can be controlled by adjusting the diameter, type, and mixing amount of beads serving as media.

The content of the silver-based antibacterial agent in the antibacterial part is not particularly limited, but is preferably 0.001 to 50 mass%, more preferably 0.01 to 40 mass%, even more preferably 0.01 to 15 mass%, particularly preferably 0.01 to 10 mass%, and most preferably 0.03 to 5 mass%, relative to the total mass of the antibacterial part.
The silver content in the silver-based antibacterial agent is not particularly limited, but is preferably 0.1 to 30 mass %, more preferably 0.5 to 5 mass %, based on the total mass of the silver-based antibacterial agent.

(Silicate compounds)
In this specification, the silicate-based compound means a compound selected from the group consisting of a compound having a hydrolyzable group bonded to a silicon atom, a hydrolyzate thereof, and a hydrolyzed condensate thereof.
It is presumed that the antibacterial filter of the present invention has an improved capture rate, particularly for hydrophilic aerosol particles, due to the antibacterial portion containing a silver-based antibacterial agent and a silicate-based compound being disposed on the filter portion.

The silicate-based compound may be, for example, at least one selected from the group consisting of a compound represented by the following formula (1), a hydrolyzate thereof, and a hydrolyzed condensate thereof.
Si-(OR) ₄ (1)
In the above formula (1), R represents an alkyl group having 1 to 4 carbon atoms and may be the same or different.
The hydrolysate of the compound represented by formula (1) refers to a compound obtained by hydrolysis of the OR group in the compound represented by formula (1). The hydrolysate may be one in which all of the OR groups are hydrolyzed (complete hydrolysate) or one in which only a part of the OR groups are hydrolyzed (partial hydrolysate). In other words, the hydrolysate may be a complete hydrolysate, a partial hydrolysate, or a mixture thereof.

In addition, the hydrolysis condensate of the compound represented by formula (1) refers to a compound obtained by hydrolyzing the OR group in the compound represented by formula (1) and condensing the obtained hydrolyzate.The hydrolysis condensate may be one in which all OR groups are hydrolyzed and all the hydrolyzates are condensed (complete hydrolysis condensate), or one in which some OR groups are hydrolyzed and some of the hydrolyzates are condensed (partial hydrolysis condensate).In other words, the hydrolysis condensate may be a complete hydrolysis condensate, a partial hydrolysis condensate, or a mixture thereof.
The condensation degree of the hydrolysis condensate is preferably 1-100, more preferably 1-20, and even more preferably 3-15.

As the silicate-based compound, a compound represented by formula (X) is preferred.

In formula (X), R ¹ to R ⁴ each independently represent an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 2 to 100.
n is preferably an integer of 3 to 15, and more preferably an integer of 5 to 10.

Commercially available products of the compound represented by formula (X) include, for example, "Ethyl Silicate 48," "Methyl Silicate 51," and "Methyl Silicate 53" manufactured by Colcoat Co., Ltd., and "MKC Silicate MS51" manufactured by Mitsubishi Chemical Corporation.

The content of the silicate-based compound in the antibacterial portion is not particularly limited, but is preferably 20 to 99.8 mass% relative to the total mass of the antibacterial portion, more preferably 20 to 90 mass%, and even more preferably 40 to 90 mass%.

(Other ingredients)
The antibacterial portion may contain other components in addition to the above components, such as alcohol, an antibacterial agent other than the silver-based antibacterial agent, a catalyst for promoting the condensation of a silicate-based compound, a dispersant, a surfactant, a polymerization initiator, and a fragrance.

The antibacterial portion preferably contains alcohol, since this provides superior disinfecting performance for reducing bacteria and viruses present in the filter portion in which the antibacterial portion is provided.
The alcohols may be used alone or in combination of two or more.
Examples of the alcohol contained in the antibacterial portion include methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol.
When the antibacterial portion contains alcohol, the alcohol content is preferably 1 mass % or less, more preferably 0.5 mass % or less, and even more preferably 0.1 mass % or less, relative to the total mass of the antibacterial portion.

Examples of antibacterial agents other than silver-based antibacterial agents include inorganic antibacterial agents other than silver-based antibacterial agents and organic antibacterial agents.
Examples of inorganic antibacterial agents include antibacterial agents containing metals. Examples of the metals include copper, zinc, mercury, iron, lead, bismuth, titanium, tin, and nickel. The form of the metal contained in the antibacterial agent is not particularly limited, and examples of the form include metal particles, metal ions, metal oxides, and metal salts (including metal complexes).
The antibacterial agent containing a metal is preferably a metal-supported carrier containing a carrier and a metal other than silver supported on the carrier. The carrier, including preferred embodiments thereof, is as described above.
Examples of organic antibacterial agents include quaternary ammonium salts, phenol ether derivatives, imidazole derivatives, sulfone derivatives, N-haloalkylthio compounds, anilide derivatives, pyrrole derivatives, pyridine compounds, triazine compounds, benzoisothiazoline compounds, and isothiazoline compounds.

As the antibacterial agent other than the silver-based antibacterial agent, an inorganic antibacterial agent is preferable, and a copper-based antibacterial agent is more preferable, because it can maintain excellent antibacterial properties for a long period of time. An example of the copper-based antibacterial agent is an antibacterial agent containing copper ions (Cu ⁺ or Cu ²⁺ ). Specifically, an example of the antibacterial agent is "Imadies" manufactured by Koken Co., Ltd.
When the antibacterial portion contains the other antibacterial agent, it is preferable that the total content of the silver-based antibacterial agent and the other antibacterial agent is within the range of the content of the silver-based antibacterial agent.

The type of catalyst that promotes the condensation of the silicate-based compound precursor is not particularly limited, but examples thereof include alkali catalysts and organometallic catalysts.
Examples of the alkali catalyst include sodium hydroxide, potassium hydroxide, and tetramethylammonium hydroxide.
Examples of the organometallic catalyst include aluminum chelate compounds such as aluminum bis(ethylacetoacetate)mono(acetylacetonate), aluminum tris(acetylacetonate), and aluminum ethylacetoacetate diisopropylate; zirconium chelate compounds such as zirconium tetrakis(acetylacetonate) and zirconium bis(butoxy)bis(acetylacetonate); titanium chelate compounds such as titanium tetrakis(acetylacetonate) and titanium bis(butoxy)bis(acetylacetonate); and organotin compounds such as dibutyltin diacetate, dibutyltin dilaurate, and dibutyltin dioctiate.
The type of catalyst is not particularly limited, but an organometallic catalyst is preferable, an aluminum chelate compound or a zirconium chelate compound is more preferable, and an aluminum chelate compound is further preferable.
As the catalyst, commercially available products can be used, specifically, Alumichelate A, Alumichelate D, Alumichelate M, ALCH, and ALCH-TR (all trade names) manufactured by Kawaken Fine Chemical Co., Ltd. can be mentioned.

When the antibacterial portion contains a particulate silver-based antibacterial agent, the antibacterial portion preferably contains a dispersant.
The type of dispersant is not particularly limited, and any known dispersant can be used.
As the dispersant, a nonionic or anionic dispersant is preferred, and from the viewpoint of affinity for the silver-based antibacterial agent, a dispersant having an anionic polar group such as a carboxy group, a phosphate group, or a hydroxyl group (anionic dispersant) is more preferred.
Commercially available anionic dispersants can be used, specific examples of which include DISPERBYK (registered trademark) -110, -111, -116, -140, -161, -162, -163, -164, -170, -171, -174, -180, and -182 (all trade names) manufactured by BYK Corporation.

The antibacterial portion may contain a surfactant, which has the effect of improving the applicability of the antibacterial portion-forming composition described below.
The surfactant is not particularly limited, and examples thereof include nonionic surfactants and ionic surfactants (for example, anionic surfactants, cationic surfactants, and amphoteric surfactants).

Examples of nonionic surfactants include polyethylene glycol monolauryl ether, polyethylene glycol monostearyl ether, polyethylene glycol monocetyl ether, polyethylene glycol monolauryl ester, and polyethylene glycol monostearyl ester.
An example of the nonionic surfactant is EMALEX (registered trademark) 715 manufactured by Nippon Emulsion Co., Ltd.

Examples of ionic surfactants include anionic surfactants such as alkyl sulfates, alkylbenzenesulfonates, and alkyl phosphates; cationic surfactants such as alkyltrimethylammonium salts and dialkyldimethylammonium salts; and amphoteric surfactants such as alkylcarboxybetaines.
Anionic surfactants include sodium di(2-ethylhexyl)sulfosuccinate.

The antibacterial portion may contain a fragrance. There are no limitations on the type of fragrance, and it is preferable to select a fragrance that does not impair the effects of the present invention, such as antibacterial properties.

The content of the antibacterial portion in the antibacterial filter is not particularly limited, but is preferably 0.05 to 2.0 mass %, more preferably 0.1 to 0.7 mass %, relative to the total mass of the antibacterial filter.
The content of the antibacterial portion can be calculated from the measurement results by removing the antibacterial portion by immersing the antibacterial filter in a solvent that may be contained in the composition for forming the antibacterial portion described below, and measuring the weight of the filter before and after removal.

[Filter unit]
The antibacterial filter of the present invention may be used as a filter unit by providing a frame (support frame) that supports the antibacterial filter so as to surround the periphery of the antibacterial filter, if necessary. As the frame that supports the antibacterial filter, a metal or resin member is used depending on the application of the antibacterial filter. When a resin frame is used, the antibacterial filter may be fixed to the frame at the same time as the frame is molded by injection molding.
Furthermore, after a filter unit including a filter portion and a support frame is produced, an antibacterial portion may be provided on the filter portion by the method described below.

[Antibacterial filter performance, etc.]
The antibacterial filter of the present invention preferably has the following properties.

<Particle collection rate>
The antibacterial filter has a more excellent particle collection performance, and when particles having a particle size of 0.3 μm are passed through the antibacterial filter in a state in which static electricity has been removed according to the procedure specified in JIS B 9927-5:2022, Appendix C, at a wind speed of 5.3 cm/s, the particle collection efficiency is preferably 99.95% or more, and more preferably 99.97% or more. The particle collection efficiency may be 100%.
The particle capture rate of the antibacterial filter can be measured by a method similar to Test A above.

<Initial pressure loss>
The initial pressure loss of the antibacterial filter is not particularly limited, but is preferably 50 to 150 Pa, and more preferably 60 to 100 Pa.
Here, the initial pressure loss is a value measured on an unused antibacterial filter using clean air according to the method described in "3.2 Pressure Loss Test" in the appendix of JIS B 9927:1999.
The initial pressure loss of the antibacterial filter can be adjusted by, for example, appropriately selecting the structure and material of the filter medium constituting the filter portion, and the pleat shape of the filter portion.

The shape and size of the antibacterial filter are not particularly limited and may be adjusted as appropriate depending on the application and/or the device in which it is incorporated.

[Method of manufacturing antibacterial filter]
An example of a method for producing the antibacterial filter of the present invention is a method in which an antibacterial portion is formed on the filter portion by contacting the filter portion with an antibacterial portion-forming composition described below. By contacting the filter portion with the antibacterial portion-forming composition to form an antibacterial portion, an antibacterial filter can be produced that not only purifies the air by capturing bacteria and viruses present in the air passing through the antibacterial filter, but also has an excellent function of inactivating the captured bacteria and viruses.
That is, the present invention includes a method for producing an antibacterial filter, comprising the step of contacting a filter satisfying the above requirement A with a composition for forming an antibacterial portion, the composition containing a silver-based antibacterial agent and a silicate-based compound precursor.
The method for producing the antibacterial filter of the present invention will be described in more detail below.
The filter that satisfies requirement A in the manufacturing method of the antibacterial filter of the present invention is the same as the filter portion already explained, including the preferred embodiments.

<Composition for forming antibacterial part (composition A)>
First, the antibacterial portion-forming composition (hereinafter, also referred to as "composition A") used in the production of the antibacterial filter will be described.
Composition A contains at least a silver-based antibacterial agent and a silicate-based compound precursor. The silver-based antibacterial agent contained in composition A, including preferred embodiments thereof, is as already described above.

(Silicate compound precursor)
Examples of the silicate-based compound precursor include compounds that become the above-mentioned silicate-based compounds through one or both of hydrolysis and hydrolysis condensation. That is, the silicate-based compound may be a hydrolysate or hydrolysis condensate of a silicate-based compound precursor.

The silicate compound precursor may be at least one selected from the group consisting of the compound represented by the above formula (1), its hydrolysate, and its hydrolyzed condensate.
The compound represented by formula (1), its hydrolysate, and its hydrolyzed condensate are as already explained, including their respective preferred embodiments.

In composition A, the compound represented by formula (1) is mixed with water to be at least partially hydrolyzed. The hydrolyzate of the compound represented by formula (1) is obtained by reacting the compound represented by formula (1) with water to convert the OR group bonded to silicon to a hydroxy group. It is not necessary for all the OR groups to react during hydrolysis, but it is preferable that as many OR groups as possible are hydrolyzed in order to exhibit hydrophilicity after application. In addition, the minimum amount of water required during hydrolysis is the same molar amount as the OR group of the compound represented by formula (1), but it is preferable that a large excess of water is present in order to smoothly proceed with the reaction.
The hydrolysis and condensation reactions of the silicate compound precursor proceed at room temperature, but may be heated to accelerate the reaction. A longer reaction time is preferable because the reaction proceeds more quickly. In addition, in the presence of a catalyst, it is possible to obtain a hydrolyzate in about half a day.

The content of the silicate compound precursor in composition A is not particularly limited, but is preferably 0.10 to 0.50 mass %, more preferably 0.10 to 0.40 mass %, and even more preferably 0.20 to 0.31 mass %, based on the total mass of the composition.
The preferred content of the silicate-based compound precursor relative to the total solid content of the composition A may be the same as the preferred content of the silicate-based compound relative to the antibacterial portion described above.
The solid content refers to the components in the composition excluding the solvent. Even if the components other than the solvent are in a liquid state, they are counted as solids.

(solvent)
Composition A may contain a solvent, and preferably contains a solvent.
The type of the solvent is not particularly limited, and examples thereof include water and organic solvents.
The water is preferably purified water, more preferably distilled water, ion-exchanged water, RO (reverse osmosis) water, pure water, or ultrapure water, and is more preferably ion-exchanged water in terms of the stability of the antibacterial agent.
The electrical conductivity of the water is preferably 0.1 to 0.2 mS/m.

Examples of organic solvents include alcohol-based solvents such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-pentanol, isopentanol, phenylethyl alcohol, capryl alcohol, lauryl alcohol, and myristyl alcohol; methyl cellosolve, ethyl cellosolve, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, and diethylene glycol monobutyl ether. glycol ether solvents such as propylene glycol monobutyl ether; aromatic hydrocarbon solvents such as benzene, toluene, xylene, and ethylbenzene; alicyclic hydrocarbon solvents such as cyclopentane, cyclohexane, methylcyclohexane, and ethylcyclohexane; ether solvents such as tetrahydrofuran, dioxane, diisopropyl ether, and di-n-butyl ether; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; ester solvents such as methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, hexyl acetate, ethyl propionate, and butyl propionate; hydrophilic solvents such as 10% by mass denatonium benzoate alcohol solution, geraniol, octaacetylated sucrose, brucine, linalool, linalyl acetate, and acetic acid.

The solid content of the composition A is not particularly limited, and is preferably 0.001 to 80 mass%, more preferably 0.01 to 10 mass%, still more preferably 0.1 to 5.0 mass%, and particularly preferably 0.1 to 1.0 mass%, based on the total mass of the composition, in terms of superior coating properties. It is preferable to adjust the content of the solvent in the composition so as to obtain the above solid content.
The solvent may be used alone or in combination of two or more kinds.

Composition A preferably contains alcohol, since it has better short-term disinfecting performance against pathogens, etc. Examples of the alcohol include the above-mentioned alcohol-based solvents.
When composition A contains an alcohol, the content thereof is preferably 82.0% by mass or less based on the total mass of the composition. Although there is no particular lower limit, the content is preferably 20% by mass or more, and more preferably 55.0% by mass or more.
When composition A contains two or more types of alcohol (for example, when ethanol and isopropanol are used), the total amount thereof is preferably within the above range.
In addition, when composition A contains alcohol, it is preferable that composition A further contains water as a solvent in that the aggregation stability of the antibacterial agent is superior.

(Other ingredients)
Composition A may contain other components in addition to the components described above.
Examples of other components include a catalyst that promotes condensation of a silicate-based compound precursor, a dispersant, a surfactant, a polymerization initiator, a film-forming agent, and a fragrance.
The above components have already been explained as other components that may be contained in the antibacterial portion.

When composition A contains the other components described above, the content of each component is appropriately adjusted based on known techniques within a range that does not impair the effects of the present invention, such as antibacterial properties.
When composition A contains a catalyst, the content of the catalyst is preferably from 0.005 to 0.0025% by mass, and more preferably from 0.011 to 0.019% by mass, based on the total mass of the composition.
When composition A contains a particulate silver-based antibacterial agent, composition A preferably contains a dispersant. When composition A contains a dispersant, the content of the dispersant is preferably 40% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, based on the total solid content of the composition. The lower limit is not particularly limited, and may be, for example, 0.01% by mass or more based on the total solid content of the composition.

Composition A preferably contains a surfactant because it has the effect of improving the coatability of composition A. When composition A contains a surfactant, the content of the surfactant is not particularly limited, but is preferably 0.01 mass% or more based on the total solid content of the composition. The upper limit of the content of the surfactant is not particularly limited, but is preferably 10 mass% or less, more preferably 7 mass% or less, based on the total solid content of the composition.
The surfactant may be used alone or in combination of two or more. When two or more surfactants are used, a combination of a nonionic surfactant and an anionic surfactant is preferred from the viewpoint of the aggregation stability of the silver-based antibacterial agent.

The method for preparing composition A is not particularly limited, and it can be prepared by appropriately mixing the above-mentioned components. The order in which the above-mentioned components are mixed is not particularly limited.

<Contacting the filter with composition A>
In the method for producing an antibacterial filter of the present invention, composition A is brought into contact with a filter that satisfies requirement A. This contact step causes the silver-based antibacterial agent and silicate-based compound precursor, etc., to adhere to the surface (including the pore surface) of the filter medium that constitutes the filter. Thereafter, the solvent that has infiltrated the filter is evaporated to form an antibacterial portion that contains the silver-based antibacterial agent and the silicate-based compound and is disposed on the filter.

Examples of the step of contacting the filter with composition A include a step of applying composition A to the filter and a step of immersing the filter in composition A, and a step of applying composition A to the filter is preferred.
In the above-mentioned coating step, the method of coating the composition A on the filter includes, for example, a spray method, a roll coater method, a gravure coater method, a screen method, a spin coater method, a flow coater method, an inkjet method, and a wipe method, and the spray method is preferred. Among these, it is more preferred to coat the composition A on the filter using an air gun (air spray gun).

When carrying out the above-mentioned coating step, the composition A may be applied to the filter only once, but it is preferable to carry out the coating a plurality of times.
More specifically, it is preferable to repeatedly apply composition A to the filter, dry it to form an antibacterial portion, and then apply composition A again and dry it to form the antibacterial portion. In addition, it is preferable to apply composition A to both main surfaces of the filter at least once in order to form a more uniform antibacterial portion.
That is, in the coating process, it is preferable to repeatedly apply composition A to one main surface to form an antibacterial portion at least two times, and to repeatedly apply composition A to the other main surface to form an antibacterial portion at least two times, for a total of four or more applications.
In the above coating step, the number of coatings on each main surface of the filter is preferably 1 to 4 times, more preferably 2 to 4 times, and even more preferably 2 or 3 times.

The amount of composition A applied to the filter in the application step is preferably 50 to 1000 mL/ ^m2 , more preferably 100 to 500 mL/ ^m2 , and even more preferably 150 to 300 mL/ ^m2 , relative to the area of the main surface of the filter. When composition A is applied to the filter multiple times, the above-mentioned application amount is the total application amount of the multiple times. Moreover, the "area of the main surface of the filter" means the area calculated from the outer dimensions of the filter.

After contacting the filter with Composition A, a heat treatment (drying treatment) may be carried out to promote removal of the solvent.
The conditions for the heat treatment are not particularly limited. For example, the heating temperature is preferably 50 to 200° C., and the heating time is preferably 15 to 600 seconds.

[Application]
The antibacterial filter of the present invention can be used, for example, in air purifiers, air conditioners, fan coil units for buildings, and air conditioning equipment for clean rooms, etc. In particular, the effects of the present invention can be more effectively exhibited by using the antibacterial filter of the present invention in an air purifier that has the function of removing harmful substances such as pathogens and purifying the air in spaces where ventilation is difficult, such as the inside of a room or a vehicle.
The antibacterial filter of the present invention can also be used in a mask that is worn on the human body.

[Air cleaner]
A preferred embodiment of the antibacterial filter of the present invention is an air purifier equipped with the antibacterial filter of the present invention.
The air purifier comprises, for example, a casing, an air inlet and an air outlet provided in the casing, the antibacterial filter of the present invention, and air blowing means.
A flow passage is provided in the casing so that air drawn in from the intake port passes through the antibacterial filter and is then discharged from the exhaust port. The blowing means (e.g., turbo fan, etc.) is disposed on the intake port side (upstream side) or the exhaust port side (downstream side) with respect to the antibacterial filter. The blowing means disposed on the intake port side draws air outside the casing through the intake port into the casing. The blowing means disposed on the exhaust port side blows air inside the casing out of the casing. The blowing means may be disposed on both the intake port side and the exhaust port side.
When the blowing means of such an air purifier is operated, air outside the casing is introduced into the casing through the intake port, the introduced air is purified by passing through the antibacterial filter, and then the purified air is exhausted outside the casing through the exhaust port. This achieves the function of the air purifier, which purifies the air outside the machine through the antibacterial filter and then sends it out of the machine again.

The antibacterial filter of the present invention may be used in combination with a prefilter for removing dust such as cotton dust, a deodorizing filter such as a photocatalyst filter having deodorizing properties, and a known filter such as a VOC adsorption filter. That is, an air purifier equipped with the antibacterial filter of the present invention may further include at least one of the above filters. When the air purifier includes the above filter, it is preferable that the above filter (particularly the prefilter) is disposed on the air intake side relative to the antibacterial filter.

The present invention will be described in more detail below based on examples. The materials, amounts used, ratios, processing contents, and processing procedures shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the examples shown below.

[Example 1]
<Preparation of Composition A1>
In a container, while stirring ethanol (760 g), a siloxane compound ("MKC (registered trademark) Silicate MS-51" manufactured by Mitsubishi Chemical Corporation, which corresponds to a compound represented by formula (X); n = 2 to 100) (2.9 g), aluminum chelate D (aluminum bis(ethylacetoacetate) mono(acetylacetonate) manufactured by Kawaken Fine Chemical Co., Ltd., diluted with ethanol: solid content concentration 76% by mass) (0.23 g), isopropyl alcohol (IPA) ( 38.5 g), a nonionic surfactant ("EMALEX 715" manufactured by Nippon Emulsion Co., Ltd., diluted with ion-exchanged water: solids concentration 0.5% by mass) (47.3 g), an anionic surfactant (sodium di(2-ethylhexyl)sulfosuccinate, diluted with ion-exchanged water: solids concentration 1.0% by mass) (2.36 g), and ion-exchanged water (128 g) were added in that order, and then 21.01 g of the antibacterial particle solution prepared in advance was added and stirred for 30 minutes, thereby obtaining composition A1.
The antibacterial particle solution was prepared by adding a dispersant (BYK Corporation's "DISPERBYK-180") (0.61 g) while stirring ethanol (19.6 g) in a container, followed by stirring for 15 minutes, and then adding a silver-loaded glass dispersion (Fuji Chemical Co., Ltd.'s "Bacterite MP-103DV") (0.80 g) and stirring for 15 minutes. The silver-loaded glass dispersion was a dispersion containing a silver-loaded inorganic oxide in which silver was loaded on an inorganic oxide carrier made of phosphate glass, the solids concentration of the dispersion was 25 mass%, and the silver content relative to the total mass of the silver-loaded carrier was 2 mass%.

<Manufacture of antibacterial filters>
As a filter medium used in the manufacture of the antibacterial filter, a sheet-like filter medium ("TEMISH (registered trademark) NTF-9307-L03" manufactured by Nitto Denko Corporation) was prepared, which was made by laminating a PTFE porous membrane and two sheets of nonwoven fabric sandwiching the PTFE porous membrane.
The above filter medium was pleated to produce a filter (filter pack) having outer dimensions of 240 mm in width, 417 mm in length, and 51 mm in thickness, with a pitch of approximately 3.5 mm and pleated shapes having 120 peaks and 120 valleys.
The produced filter was subjected to static electricity removal in accordance with the method already explained as Test A, and then the particle collection efficiency of particles having a particle diameter of 0.3 μm was measured under a wind speed of 5.3 cm/s. As a result, it was confirmed that the particle collection efficiency was 9.97% or more and satisfied requirement A.

The composition A1 prepared above was filled into the container of an air gun (manufactured by Anest Iwata Corporation, product name "WIDER"). Using this air gun, the composition A1 was applied to the entire surface of one of the main surfaces (first surface) of the filter manufactured above, and then the filter on which the coating film of the composition A1 was formed was left in an environment of 20 to 35 ° C. for 1 hour to dry by natural drying. Next, using the air gun, the composition A1 was applied to the entire surface of the other main surface (second surface) opposite to the first surface of the filter, and a drying process was performed under the same conditions. The coating amount of the composition A1 in one coating step was 150 mL/m ² relative to the area of the main surface of the filter, and the total coating amount of the composition A1 applied to the filter was 300 mL/m ² relative to the area of the main surface of the filter.
In this way, an antibacterial filter of the present invention having a filter portion and an antibacterial portion was produced.

[Example 2]
According to the method described in Example 1, a series of treatments consisting of application of composition A1 from the first surface, drying treatment, application of composition A1 from the second surface, and drying treatment were performed, and then a series of treatments consisting of application of composition A1 from the first surface, drying treatment, application of composition A1 from the second surface, and drying treatment were performed again on the filter on which the antibacterial portion was formed. The application amount of composition A1 in one application step was 150 mL/ ^m2 relative to the area of the main surface of the filter, and the total application amount of composition A1 applied to the filter was 600 mL/ ^m2 relative to the area of the main surface of the filter.

[Example 3]
According to the method described in Example 2, a series of processes consisting of applying composition A1 from the first surface, drying treatment, applying composition A1 from the second surface, and drying treatment were repeated twice, and then a series of processes consisting of applying composition A1 from the first surface, drying treatment, applying composition A1 from the second surface, and drying treatment were again performed on the filter on which the antibacterial portion was formed. The amount of composition A1 applied in one application step was 150 mL/ ^m2 relative to the area of the main surface of the filter, and the total amount of composition A1 applied to the filter was 900 mL/ ^m2 relative to the area of the main surface of the filter.

Antibacterial performance tests were conducted on each of the antibacterial filters of Examples 1 to 3, and the results confirmed that the antibacterial filters of Examples 1 to 3 exhibited excellent antibacterial properties and that the present invention has the desired effects.

[Filter performance test]
The antibacterial filter of Example 2 and the reference filter described below were subjected to a filter performance test under the following conditions.
Evaluation device: A filter performance evaluation device conforming to JIS B 9908.
Test powder: SAP test powder 3 type 3 (STP3-3) (calcined Kanto loam) manufactured by the Japan Powder Industry and Technology Association.
Reference filter: Charged HEPA filter ("FZ-14EXSF (product name)" manufactured by Sharp Corporation)
Test air volume: 420 ^m3 /h
Each filter sample was placed in the evaluation device. Then, air was sent in by a blower provided in the evaluation device, and the test powder was gradually introduced from a powder introduction port provided on the upstream side of the filter sample in the device, so that a mixed gas containing the test powder was passed through the filter sample. At the beginning of the introduction of the test powder, the flow rate of the mixed gas passing through the filter sample was adjusted by an orifice provided on the downstream side of the filter sample in the device so that it was equal to the test air volume, and thereafter, the air volume was not adjusted until the end of the test.
The test was terminated when 100 g of the test powder was added. The weight of the filter sample after the test was measured, and the difference (filter weight increase) between the weight of the filter sample before the test, which was measured in advance, was calculated. In addition, the test powder remaining upstream of the filter sample in the evaluation device after the test was completed was collected, and the total weight (unreached powder weight) was measured. The weight of the test powder that reached the filter sample during the test (reached powder weight) was obtained by subtracting the unreached powder weight measured above from the weight (100 g) of the test powder charged into the evaluation device. The percentage of the ratio of the filter weight increase to the obtained reached powder weight ((filter weight increase/reached powder weight) x 100) was calculated as the powder capture rate (%), and the powder capture performance of the filter sample was evaluated.

In addition, in the above filter performance test, the pressure loss of each filter sample was measured immediately before the test powder was added and immediately after the test was completed. The flow rate of the mixed gas was also measured immediately before the test powder was added and immediately after the test was completed.

Table 1 shows the test results.
In the table, the upper row of the "Pressure Loss" column shows the pressure loss of each filter sample measured immediately after the completion of the above-mentioned test, and the lower row in parentheses shows the ratio, expressed as a percentage, of the pressure loss measured immediately after the completion of the test to the pressure loss measured before the start of the test.
In the table, the upper row of the "Air Volume" column shows the flow rate of air passing through the filter sample measured immediately after the completion of the above test, and the lower row in parentheses shows the ratio, expressed as a percentage, of the flow rate measured immediately after the completion of the test to the flow rate measured before the start of the test.
In the table, "Example" means the measurement result of the antibacterial filter of Example 2, and "Reference Example" means the measurement result of the reference filter. In addition, two measurements were taken for each filter, and the respective measurement results are shown in "(1)" and "(2)" of "Example" and "Reference Example".

As shown in the above table, the antibacterial filter of Example 2 achieved a powder capture rate of nearly 100%, and was found to have excellent powder capture performance.
Moreover, the antibacterial filter of Example 2 also suppresses the pressure loss and reduction in air volume after powder capture, and can be judged to be at a level that has sufficient practicality even in light of the track record of conventional electrically charged filters.

Claims

A filter unit that satisfies the following requirement A;
an antibacterial portion disposed on the filter portion,
The antibacterial filter, wherein the antibacterial portion contains a silver-based antibacterial agent and a silicate-based compound.
Requirement A: When particles with a particle size of 0.3 μm are allowed to pass through a filter part that has been destaticized in accordance with the procedure specified in JIS B 9927-5:2022, Annex C, at a wind speed of 5.3 cm/s, the particle collection efficiency is 99.95% or more.
The antibacterial filter according to claim 1, wherein the silver-based antibacterial agent is a silver-supported inorganic oxide.
The antibacterial filter according to claim 1, wherein the antibacterial portion contains alcohol.
The antibacterial filter according to claim 1, which is for use in an air purifier.
The method includes a step of contacting a filter that satisfies the following requirement A with a composition for forming an antibacterial portion,
The method for producing an antibacterial filter, wherein the composition for forming an antibacterial portion contains a silver-based antibacterial agent and a silicate-based compound precursor.
Requirement A: The particle capture efficiency when particles with a diameter of 0.3 μm are passed through a filter in a state where static electricity has been removed in accordance with the procedure specified in JIS B 9927-5:2022, Appendix C, at a wind speed of 5.3 cm/s is 99.95% or more.
The method for manufacturing an antibacterial filter according to claim 5, wherein the process includes a coating process of coating the antibacterial portion-forming composition on the filter.
The method for manufacturing an antibacterial filter according to claim 5 or 6, wherein the amount of the antibacterial portion-forming composition applied to the filter in the application step is 50 to 1000 mL/ m2 .
The method for manufacturing an antibacterial filter according to claim 5 or 6, wherein the silver-based antibacterial agent is a silver-supported inorganic oxide.
The method for manufacturing an antibacterial filter according to claim 5 or 6, wherein the composition for forming the antibacterial portion contains alcohol.
The method for manufacturing an antibacterial filter according to claim 5 or 6, wherein the antibacterial filter is for an air purifier.
An air purifier equipped with an antibacterial filter according to any one of claims 1 to 4.