Air filter media, method of using air filter media, and air treatment device

Abstract

To provide an air filter filtration material, a method for using an air filter filtration material, and an air treatment device that suppress mold generation.SOLUTION: This air filter filtration material comprises a porous film in which the surface mean height Rc is 6 μm or greater, and the water contact angle of the film surface is 90° or greater.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to air filter media, methods of using air filter media, and air treatment devices. [Background technology]

[0002] Conventionally, mold has sometimes grown on air filter media that capture dust particles and the like contained in the air.

[0003] In response to this, for example, Patent Document 1 (JP 2003-205211 A) proposes an air filter medium in which an antibacterial reinforcing material made of inorganic, organic, or natural antibacterial agents is laminated to a polytetrafluoroethylene porous membrane. DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0004] For such air filter media, a new means for exhibiting antibacterial properties is desired. [Means for solving the problem]

[0005] The air filter medium according to a first aspect includes a porous membrane having an average surface height Rc of 6 μm or more and a water contact angle of 90 degrees or more on the membrane surface.

[0006] The air filter medium is preferably an antifungal air filter medium.

[0007] This air filter medium is resistant to mold growth.

[0008] An air filter medium according to a second aspect is the air filter medium according to the first aspect, wherein the average height Rc of the surface of the porous membrane is 36 μm or more.

[0009] The average height Rc of the surface of the porous membrane is preferably 37 μm or more, more preferably 38 μm or more.

[0010] This air filter medium is likely to inhibit mold growth for a longer period of time.

[0011] An air filter medium according to a third aspect is the air filter medium according to either the first or second aspect, in which the arithmetic mean roughness Ra of the surface of the porous membrane is 6 μm or more.

[0012] This air filter medium is likely to inhibit the growth of mold.

[0013] An air filter medium according to a fourth aspect is the air filter medium according to any one of the first aspect to the third aspect, wherein the porous membrane has an average pore size of 2 μm or more.

[0014] This air filter medium is likely to inhibit the growth of mold.

[0015] An air filter medium according to a fifth aspect is the air filter medium according to any one of the first to fourth aspects, wherein the porous membrane has an average pore size of 10 μm or less.

[0016] An air filter medium according to a sixth aspect is the antifungal air filter medium according to any one of the first to fifth aspects, in which the thickness of the porous membrane is 100 μm or more.

[0017] The thickness of the porous membrane is preferably 150 μm or more.

[0018] This air filter medium is likely to inhibit the growth of mold.

[0019] An air filter medium according to a seventh aspect is the air filter medium according to any one of the first to sixth aspects, wherein the contact angle of an aqueous solution of isopropyl alcohol with a concentration of 30% by volume is 127 degrees or more.

[0020] This air filter medium is capable of suppressing mold growth for a long period of time.

[0021] An air filter medium according to an eighth aspect is the antifungal air filter medium according to any one of the first to seventh aspects, wherein the porous film contains a fluororesin.

[0022] This air filter medium inhibits the growth of mold in the porous film containing fluororesin.

[0023] An air filter medium according to a ninth aspect is the air filter medium according to any one of the first to eighth aspects, in which the porous membrane does not contain an antifungal agent.

[0024] This air filter medium is capable of suppressing the growth of mold even if the porous membrane does not contain an antifungal agent.

[0025] An air filter medium according to a tenth aspect is the air filter medium according to any one of the first to ninth aspects, and is used in an environment with a relative humidity of 60% or more.

[0026] This air filter medium can suppress the growth of mold even when used in an environment where mold is likely to grow.

[0027] A method of using an air filter medium according to an eleventh aspect involves using the air filter medium according to any one of the first to ninth aspects in an environment with a relative humidity of 60% or more.

[0028] According to this method of using the air filter medium, even in an environment where mold is likely to grow, the air filter medium can be used while suppressing mold growth.

[0029] An air treatment device according to a twelfth aspect includes the air filter medium according to any one of the first to tenth aspects.

[0030] This air treatment device allows air to be treated using an air filter medium. [Brief explanation of the drawings]

[0031] [Figure 1] FIG. 2 is a schematic cross-sectional view showing the layer structure of an antifungal air filter medium 30a. [Figure 2] FIG. 2 is a schematic cross-sectional view showing the layer structure of an antifungal air filter medium 30b. [Figure 3] FIG. 2 is a schematic cross-sectional view showing the layer structure of an antifungal air filter medium 30c. [Figure 4] FIG. 2 is a schematic cross-sectional view showing the layer structure of an antifungal air filter medium 30d. [Figure 5] FIG. 2 is an external perspective view of the filter pack. [Figure 6] FIG. 2 is an external perspective view of the air filter unit. [Figure 7] 1 is a schematic diagram of an air treatment device. [Figure 8] 1 is a photograph showing the state of Example 1 and Comparative Example 1 three days after the start of a test based on the fungal resistance test of JIS Z2911. [Figure 9] 1 is a photograph showing the state of Example 1 and Comparative Example 1 one week after the start of a test based on the fungal resistance test of JIS Z2911. [Figure 10] 1 shows photographs illustrating the state of the cultures of Examples 1 and 3 after 4 weeks in the ISO 846 test. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, an embodiment of an anti-fungal air filter material according to the present invention, a method for using an anti-fungal air filter material according to the present invention, and an air treatment device will be described using examples of the present invention.

[0033] (1) Anti-mold air filter media The anti-mold air filter medium includes a porous membrane. The porous membrane has an average surface height Rc of 6 μm or more. The water contact angle of the porous membrane surface is 90 degrees or more. This anti-mold air filter medium makes it possible to suppress the growth of mold on the porous membrane.

[0034] The anti-fungal air filter medium preferably has a particle collection efficiency of 95.0% or more, more preferably 99.5% or more, and even more preferably 99.95% or more, when air containing NaCl particles with a particle diameter of 0.1 μm is passed through the filter medium at a flow rate of 5.3 cm / sec.

[0035] The antifungal air filter medium preferably has a pressure loss of less than 250 Pa, more preferably less than 200 Pa, and may be 30 Pa or more and 190 Pa or less when air is passed through it at a flow rate of 5.3 cm / sec.

[0036] (2) Example of the composition of anti-mold air filter media The specific configuration of the above-described antifungal air filter medium is not particularly limited.

[0037] For example, the antifungal air filter medium 30a shown in Fig. 1 may be configured by stacking an air-permeable support material 21 and a porous membrane 31 in order in the air flow direction. Here, the porous membrane 31 may be arranged on the upstream side or downstream side of the air flow relative to the air-permeable support material 21.

[0038] For example, as shown in FIG. 2, an antifungal air filter medium 30b may be configured by stacking an upstream breathable support material 21a, a porous membrane 31, and a downstream breathable support material 21b in this order in the air flow direction.

[0039] Also, as in the antifungal air filter medium 30c shown in FIG. 3, the upstream breathable support material 21a, the first porous membrane 31a, the second porous membrane 31b, and the downstream breathable support material 21b may be stacked in this order in the air flow direction.

[0040] Furthermore, as in the antifungal air filter medium 30d shown in FIG. 4, an upstream breathable support material 21a, a first porous membrane 31a, an intermediate breathable support material 21c, a second porous membrane 31b, and a downstream breathable support material 21b may be stacked in this order in the air flow direction.

[0041] A pre-collection layer, which is a membrane with a smaller pressure loss and a smaller collection efficiency, may be provided on the upstream side of the porous membrane 31 or the first porous membrane 31a.

[0042] The method of stacking these films, materials, etc. is not particularly limited, and they may be laminated by utilizing the anchor effect caused by partial melting due to heating or melting of hot melt resin, by using a reactive adhesive, etc., or by simply stacking them.

[0043] (3) Porous membrane The porous membrane has an average surface height Rc of 6 μm or more, and a water contact angle on the membrane surface of 90 degrees or more. When the average surface height Rc of the porous membrane is 6 μm or more, it is easy to suppress the penetration of water into the porous membrane, which promotes the growth of mold, and it is easy to maintain the porous membrane in a dry state. Furthermore, when the water contact angle on the membrane surface of the porous membrane is 90 degrees or more, the water repellency on the porous membrane surface is good, water is easily repelled, and water is not easily retained on the surface of the porous membrane. As a result, the growth of mold on the porous membrane is suppressed. The present disclosure was made based on the first discovery that there is a correlation between the likelihood of mold growth in a porous membrane having a water contact angle on the membrane surface of 90 degrees or more and the average surface height Rc of the porous membrane.

[0044] In addition, from the viewpoint of suppressing mold growth for a longer period of time, the average height Rc of the surface of the porous membrane is preferably 36 μm or more, more preferably 37 μm or more, even more preferably 38 μm or more, still more preferably 40 μm or more, and most preferably 100 μm or more.

[0045] The average height Rc of the surface of the porous membrane is not particularly limited, but is preferably, for example, 300 μm or less, more preferably 200 μm or less.

[0046] The average surface height Rc is a value measured in accordance with the method described in JIS B 0601 (2013).

[0047] In addition, in the case of a fluororesin porous membrane, for example, the average height Rc of the porous membrane surface can be reduced by reducing the amount of liquid lubricant used in the manufacturing process (added when the powder obtained by coagulation is extruded using a paste extrusion device to obtain a sheet-shaped compact), and can be increased by increasing the amount of liquid lubricant. The average height Rc of the obtained porous membrane can also be adjusted by adjusting the types and blending ratios of the components mixed when obtaining the fluororesin porous membrane. Furthermore, in the case of a fluororesin porous membrane, the average height Rc of the porous membrane surface can be increased by reducing the stretch ratio when stretching the unsintered fluororesin film, and can be decreased by increasing the stretch ratio.

[0048] The water contact angle of the porous membrane is 90 degrees or more, preferably 120 degrees or more, and more preferably 140 degrees or more, from the viewpoint that water is less likely to be retained on the surface of the porous membrane and the contact area with the porous membrane is easily reduced.

[0049] The water contact angle is determined by the θ / 2 method and is measured 30 seconds after a droplet is dropped onto the surface of the porous membrane.

[0050] The contact angle of a 20% by volume aqueous solution of isopropyl alcohol is preferably 127 degrees or more, and more preferably 130 degrees or more, from the viewpoint that water is less likely to be retained on the surface of the porous membrane and the contact area with the porous membrane is easily reduced.

[0051] The contact angle of a 20% by volume aqueous solution of isopropyl alcohol is the contact angle determined by the θ / 2 method. The contact angle of a 20% by volume aqueous solution of isopropyl alcohol is the contact angle of a droplet measured 30 seconds after the droplet is dropped onto the surface of the porous membrane. The 20% by volume aqueous solution of isopropyl alcohol has a volume ratio of water:IPA of 80:20.

[0052] The contact angle of a 30% by volume aqueous solution of isopropyl alcohol is preferably 127 degrees or more, and more preferably 129 degrees or more, from the viewpoint that water is less likely to be retained on the surface of the porous membrane and the contact area with the porous membrane is easily reduced.

[0053] The contact angle of a 30% by volume aqueous solution of isopropyl alcohol is the contact angle determined by the θ / 2 method. The contact angle of a 30% by volume aqueous solution of isopropyl alcohol is the contact angle of a droplet measured 30 seconds after the droplet is dropped onto the surface of the porous membrane. The 30% by volume aqueous solution of isopropyl alcohol has a volume ratio of water:IPA of 70:30.

[0054] In addition, the surface tension of an aqueous solution containing isopropyl alcohol is lower than that of water, so it can be said to be a liquid that absorbs water more easily than water. For this reason, the contact angle of an aqueous solution containing isopropyl alcohol tends to be smaller than that of water.

[0055] The arithmetic mean roughness Ra of the surface of the porous membrane is preferably 6 μm or more, more preferably 7 μm or more, and even more preferably 20 μm or more, from the viewpoint of suppressing mold growth for a longer period of time. The arithmetic mean roughness Ra of the surface of the porous membrane is not particularly limited, but is, for example, 100 μm or less. The arithmetic mean roughness Ra of the surface is a value measured in accordance with the method described in JIS B 0601 (2013).

[0056] In addition, the arithmetic mean roughness Ra of the surface of the porous membrane can be adjusted by, for example, the amount of liquid lubricant used in the manufacturing process in the case of a fluororesin porous membrane. In addition, the arithmetic mean roughness Ra of the obtained porous membrane can also be adjusted by adjusting the types and compounding ratios of the components mixed when obtaining the fluororesin porous membrane.

[0057] The average pore size of the porous membrane is preferably 2 μm or more, more preferably 2.2 μm or more, from the viewpoint of making it difficult for water to be retained in the porous membrane. The average pore size of the porous membrane may be, for example, 10 μm or less. This average pore size is also called the average flow path diameter, and is measured in accordance with ASTM F316-86.

[0058] The thickness of the porous membrane is, for example, preferably 100 μm or more, more preferably 130 μm or more, and even more preferably 150 μm or more. The thicker the porous membrane, the larger the pore size, making it less likely to retain water and improving the collection efficiency. When multiple porous membranes are stacked, the thickness of the porous membrane refers to the total thickness. When two or more porous membranes are stacked, it is preferable that the porous membrane located upstream of the airflow be thicker and have a larger pore size than the porous membrane located downstream of the airflow. This makes it easier to suppress mold growth on the upstream side of the porous membrane. For example, in the case of a fluororesin porous membrane, the thickness of the porous membrane can be increased by increasing the amount of liquid lubricant used in the manufacturing process and by reducing the stretching ratio.

[0059] In the above-mentioned porous membrane, even if no antifungal agent is contained in the porous membrane, the occurrence of mold can be suppressed.If antifungal agent is contained, it may fall off from the porous membrane and cause the performance of air filter material to deteriorate, so preferably, the antifungal agent such as antibacterial agent is not contained in the porous membrane.It should be noted that the antifungal agent is not particularly limited, and can be enumerated as the organic antifungal agent such as benzimidazole compound, pyrithione compound, isothiazolinone compound, or the inorganic antifungal agent that contains the photocatalyst that contains transition metal element.

[0060] The pressure loss of the porous membrane when air is passed through it at a flow rate of 5.3 cm / sec is, for example, preferably less than 250 Pa, more preferably less than 200 Pa, and may be 30 Pa or more and 190 Pa or less. For example, in the case of a fluororesin porous membrane, the pressure loss of the porous membrane can be reduced by increasing the amount of liquid lubricant used in the manufacturing process, by increasing the stretch ratio, or by increasing the calender temperature.

[0061] (4) Porous membrane containing fluororesin The porous membrane is preferably a fluororesin porous membrane, which is a porous membrane containing a fluororesin. More specifically, the porous membrane is preferably composed mainly of a fluororesin and has a porous membrane structure having fibrils (fibers) and nodes (nodes) connected to the fibrils (not shown). Here, "mainly" means that when multiple types of components are contained, the fluororesin is contained in the largest amount.

[0062] The component different from the fluororesin may be, for example, an inorganic filler which is a non-melt-processable component (component B) that does not form fibers, as described below.

[0063] The fluororesin used in the fluororesin porous membrane may consist of one kind of component, or two or more kinds of components. In addition, as a fluororesin consisting of two or more kinds of components, for example, a mixture of three components can be mentioned: fibrous PTFE (hereinafter also referred to as component A), a non-fibrous non-thermal melt processable component (hereinafter also referred to as component B), and a non-fibrous heat melt processable component with a melting point of less than 320 ° C (hereinafter also referred to as component C). The fluororesin porous membrane is preferably composed of a combination of these three kinds of components. Compared with fibrous PTFE (high molecular weight PTFE) porous membranes, the fluororesin porous membranes composed of these three kinds of components have a membrane structure with more voids and a thicker membrane thickness, so that fine particles in the gas can be captured in a wide area in the thickness direction of the filter material, thereby improving the dust-holding capacity. By constructing the porous membrane from these three kinds of components, it is possible to particularly increase the dust-holding capacity of liquid particles rather than solid particles.

[0064] The above three components will be described in more detail below.

[0065] (4-1) Component A: PTFE that can be fibrillated The fibrous PTFE is, for example, a high-molecular-weight PTFE obtained by emulsion polymerization or suspension polymerization of tetrafluoroethylene (TFE). The term "high molecular weight" as used herein refers to a PTFE that is easily fibrous during stretching during porous membrane production and that can produce long fibrils. The high molecular weight refers to a molecular weight having a standard specific gravity (SSG) of 2.130 to 2.230 and a high melt viscosity that does not substantially melt flow. From the viewpoint of easy fibrous formation and long fibrils, the SSG of the fibrous PTFE is preferably 2.130 to 2.190, more preferably 2.140 to 2.170. If the SSG is too high, the stretchability of the mixture of components A to C may be impaired. If the SSG is too low, the rollability may be impaired, resulting in poor homogeneity of the porous membrane and increased pressure loss of the porous membrane. Furthermore, from the viewpoint of easy fibrous formation and long fibrils, PTFE obtained by emulsion polymerization is preferred. Standard specific gravity (SSG) is measured in accordance with ASTM D 4895.

[0066] The presence or absence of fibrous properties, i.e., whether or not a material can be fibrous, can be determined by whether or not paste extrusion, a typical method for molding high molecular weight PTFE powder made from TFE polymers, is possible. Paste extrusion is usually possible because high molecular weight PTFE has fibrous properties. If the unsintered molded body obtained by paste extrusion has no substantial strength or elongation, for example, if the elongation is 0% and it breaks when pulled, it can be considered to have no fibrous properties.

[0067] The high molecular weight PTFE may be modified polytetrafluoroethylene (hereinafter referred to as modified PTFE), homopolytetrafluoroethylene (hereinafter referred to as homoPTFE), or a mixture of modified PTFE and homoPTFE. The homo-PTFE is not particularly limited, and homo-PTFE disclosed in JP-A-53-60979, JP-A-57-135, JP-A-61-16907, JP-A-62-104816, JP-A-62-190206, JP-A-63-137906, JP-A-2000-143727, JP-A-2002-201217, WO 2007 / 046345 pamphlet, WO 2007 / 119829 pamphlet, WO 2009 / 001894 pamphlet, WO 2010 / 113950 pamphlet, WO 2013 / 027850 pamphlet, etc. can be suitably used. Among these, homo-PTFE having high stretchability and disclosed in JP-A Nos. 57-135, 63-137906, 2000-143727, 2002-201217, WO 2007 / 046345, WO 2007 / 119829, WO 2010 / 113950, etc. is preferred.

[0068] Modified PTFE is composed of TFE and a monomer other than TFE (hereinafter referred to as a modified monomer). Modified PTFE includes, but is not limited to, PTFE uniformly modified with the modified monomer, PTFE modified at the early stage of the polymerization reaction, and PTFE modified at the late stage of the polymerization reaction. Modified PTFEs that can be suitably used include those disclosed in, for example, JP-A-60-42446, JP-A-61-16907, JP-A-62-104816, JP-A-62-190206, JP-A-64-1711, JP-A-2-261810, JP-A-11-240917, JP-A-11-240918, WO 2003 / 033555 pamphlet, WO 2005 / 061567 pamphlet, WO 2007 / 005361 pamphlet, WO 2011 / 055824 pamphlet, WO 2013 / 027850 pamphlet, and the like. Among these, modified PTFEs having high stretchability and disclosed in JP-A Nos. 61-16907, 62-104816, 64-1711, 1999-240917, WO 2003 / 033555, WO 2005 / 061567, WO 2007 / 005361, WO 2011 / 055824, etc. are preferred.

[0069] The modified PTFE contains TFE units derived from TFE and modified monomer units derived from a modified monomer. The modified monomer units are a part of the molecular structure of the modified PTFE and are derived from the modified monomer. The modified PTFE preferably contains the modified monomer units in an amount of 0.001 to 0.500% by weight, more preferably 0.01 to 0.30% by weight, of the total monomer units. The total monomer units are the parts derived from all monomers in the molecular structure of the modified PTFE.

[0070] The modifying monomer is not particularly limited as long as it is copolymerizable with TFE, and examples thereof include perfluoroolefins such as hexafluoropropylene (HFP), chlorofluoroolefins such as chlorotrifluoroethylene (CTFE), hydrogen-containing fluoroolefins such as trifluoroethylene and vinylidene fluoride (VDF), perfluorovinyl ethers, perfluoroalkylethylenes (PFAE), ethylene, etc. The modifying monomer used may be one type or multiple types.

[0071] The perfluorovinyl ether is not particularly limited, and examples thereof include perfluorounsaturated compounds represented by the following general formula (1). CF2 = CF-ORf (1) In the formula, Rf represents a perfluoroorganic group.

[0072] In this specification, a perfluoroorganic group is an organic group in which all hydrogen atoms bonded to carbon atoms are substituted with fluorine atoms. The perfluoroorganic group may have an ether oxygen.

[0073] An example of perfluorovinyl ether is perfluoro(alkyl vinyl ether) (PAVE) in which Rf in the above general formula (1) is a perfluoroalkyl group having 1 to 10 carbon atoms. The number of carbon atoms in the perfluoroalkyl group is preferably 1 to 5. Examples of the perfluoroalkyl group in PAVE include perfluoromethyl group, perfluoroethyl group, perfluoropropyl group, perfluorobutyl group, perfluoropentyl group, and perfluorohexyl group. Preferred PAVEs are perfluoropropyl vinyl ether (PPVE) and perfluoromethyl vinyl ether (PMVE).

[0074] The perfluoroalkylethylene (PFAE) is not particularly limited, and examples thereof include perfluorobutylethylene (PFBE), perfluorohexylethylene (PFHE), and the like.

[0075] The modifying monomer in the modified PTFE is preferably at least one selected from the group consisting of HFP, CTFE, VDF, PAVE, PFAE, and ethylene.

[0076] Homo-PTFE is preferably contained in an amount of more than 50% by weight of the fibrous PTFE, in particular from the viewpoint that it is easily fibrous and long fibrils can be obtained.

[0077] The PTFE that can be made into a fiber may be a combination of two or more of the above components.

[0078] From the viewpoint of maintaining the fibrous structure of the porous membrane, the content of the fibrillable PTFE is preferably more than 50% by weight of the porous membrane.

[0079] (4-2) Component B: A non-thermal melt processable component that does not cause fiber formation The non-thermal melt processable component that does not cause fibrillation is unevenly distributed as non-fibrous particles mainly in the nodules, and acts to inhibit the fibrillation of the PTFE that can cause fibrillation.

[0080] Examples of non-thermal melt processable components that do not cause fiber formation include components having thermoplastic properties such as low molecular weight PTFE, thermosetting resins, inorganic fillers, and mixtures thereof.

[0081] The thermoplastic component preferably has a melting point of 320°C or higher and a high melt viscosity. For example, low-molecular-weight PTFE has a high melt viscosity, so it can remain in the nodules even when processed at a temperature above its melting point. In this specification, low-molecular-weight PTFE refers to PTFE having a number-average molecular weight of 600,000 or less, a melting point of 320°C or higher and 335°C or lower, and a melt viscosity at 380°C of 100 Pa·s to 7.0×10 5 It is PTFE with a Pa·s (see Japanese Patent Application Laid-Open No. 10-147617).

[0082] Examples of methods for producing low-molecular-weight PTFE include a method in which high-molecular-weight PTFE powder (molding powder) obtained by suspension polymerization of TFE or high-molecular-weight PTFE powder (fine powder) obtained by emulsion polymerization of TFE is contacted with a specific fluoride at high temperature to cause thermal decomposition (see JP 61-162503 A), a method in which the high-molecular-weight PTFE powder or molded body is irradiated with ionizing radiation (see JP 48-78252 A), and a method in which TFE is directly polymerized together with a chain transfer agent (see WO 2004 / 050727, WO 2009 / 020187, WO 2010 / 114033, etc.).Like fibrous PTFE, low-molecular-weight PTFE may be homo-PTFE or modified PTFE containing the aforementioned modified monomer.

[0083] Low-molecular-weight PTFE is not fibrous. The presence or absence of fibrous properties can be determined using the method described above. Low-molecular-weight PTFE has no substantial strength or elongation in the unsintered molded body obtained by paste extrusion; for example, the elongation is 0%, and it breaks when pulled.

[0084] Low molecular weight PTFE is not particularly limited, but the melt viscosity at 380 ℃ is preferably 1000 Pa·s or more, more preferably 5000 Pa·s or more, and even more preferably 10000 Pa·s or more.In this way, if the melt viscosity is high, when producing porous membrane, even if the heat melt processable component that does not become fibrous as component C melts, the non-heat melt processable component that does not become fibrous can remain in nodule, and can suppress fibrous.

[0085] Thermosetting resins can be exemplified by epoxy, silicone, polyester, polyurethane, polyimide, phenol, and their mixtures.Thermosetting resins are preferably used in uncured water dispersion from the viewpoint of the workability of the co-coagulation process described later.All of these thermosetting resins can also be obtained as commercial products.

[0086] Examples of inorganic fillers include talc, mica, calcium silicate, glass fiber, calcium carbonate, magnesium carbonate, carbon fiber, barium sulfate, calcium sulfate, and mixtures thereof. Among these, talc is preferred due to its affinity with high-molecular-weight PTFE that can be fiberized and its specific gravity. Inorganic fillers with a particle diameter of 3 μm to 20 μm are preferred because they can form a stable dispersion during the production of porous membranes. The particle diameter is the average particle size and is measured by laser diffraction / scattering. All of these inorganic fillers are commercially available.

[0087] The non-melt-processable component that does not cause fiber formation may be a combination of a plurality of the above-mentioned components.

[0088] The non-fibrous non-thermal melt processable component is preferably contained in the porous membrane in an amount of 1% by weight or more and 50% by weight or less. The content of the non-fibrous non-thermal melt processable component is 50% by weight or less, so that the fibrous structure of the porous membrane can be easily maintained. The non-fibrous non-thermal melt processable component is preferably contained in the amount of 20% by weight or more and 40% by weight or less, more preferably 30% by weight. The content of the non-fibrous non-thermal melt processable component is 20% by weight or more and 40% by weight or less, so that the fibrous PTFE can be more effectively prevented from becoming fibrous.

[0089] (4-3) Component C: A component that can be processed by hot melting and does not cause fiber formation, with a melting point of less than 320°C. The non-fibrous hot melt processable component (hereinafter also referred to as non-fibrous hot melt processable component) has a melting point of less than 320 ℃, so that when it is melted, it can be melted and solidified at the node when it is produced (stretched) by porous membrane, and can increase the strength of the whole porous membrane, and can prevent the deterioration of filter performance even if it is compressed in the subsequent process.

[0090] It is preferable that the non-fibrous heat-melt processable component has a melt viscosity of less than 10,000 Pa·s at 380 ° C. The melting point of the non-fibrous heat-melt processable component is the peak top of the heat of fusion curve obtained by heating it to the melting point or higher at a heating rate of 10 ° C / min using a differential scanning calorimeter (DSC), melting it completely once, cooling it to the melting point or lower at 10 ° C / min, and then heating it again at 10 ° C / min.

[0091] The non-fibrous hot melt processable component includes hot meltable fluoropolymer, polystyrene, polyethylene terephthalate (PET), polyester, polyamide and other resins, or mixtures thereof, which can fully exhibit meltability and fluidity at the stretching temperature during porous membrane production.Among them, hot meltable fluoropolymer is preferred because it has excellent heat resistance and chemical resistance at the stretching temperature during porous membrane production.The hot meltable fluoropolymer is represented by the following general formula (2): RCF=CR2 (2) (wherein each R is independently selected from H, F, Cl, alkyl having 1 to 8 carbon atoms, aryl having 6 to 8 carbon atoms, cyclic alkyl having 3 to 10 carbon atoms, and perfluoroalkyl having 1 to 8 carbon atoms. In this case, all of the R may be the same, or any two of the R may be the same and the remaining R may be different from these, or all of the R may be different from each other.)

[0092] Useful examples of the compound represented by general formula (2) include, but are not limited to, perfluoroolefins such as fluoroethylene, VDF, trifluoroethylene, TFE, and HFP, chlorofluoroolefins such as CTFE and dichlorodifluoroethylene, (perfluoroalkyl)ethylenes such as PFBE and PFHE, perfluoro-1,3-dioxole, and mixtures thereof.

[0093] The fluoropolymer comprises at least one monomer represented by the general formula (2) above, The above general formula (1) and / or the following general formula (3) R2C=CR2 (3) (wherein each R is independently selected from H, Cl, an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 8 carbon atoms, and a cyclic alkyl group having 3 to 10 carbon atoms. In this case, all of the R may be the same, or any two or more R may be the same and these two or more R may be different from the remaining R, or all of the R may be different from each other. When there are multiple other R, they may be different from each other.)

[0094] Useful examples of the compound represented by general formula (1) include perfluoro(alkyl vinyl ether) (PAVE), of which perfluoropropyl vinyl ether (PPVE) and perfluoromethyl vinyl ether (PMVE) are preferred.

[0095] Useful examples of the compound represented by general formula (3) include ethylene, propylene, and the like.

[0096] More specific examples of fluoropolymers include polyfluoroethylene derived from the polymerization of fluoroethylene, polyvinylidene fluoride (PVDF) derived from the polymerization of vinylidene fluoride (VDF), polychlorotrifluoroethylene (PCTFE) derived from the polymerization of chlorotrifluoroethylene (CTFE), fluoropolymers derived from the copolymerization of two or more different monomers represented by the above general formula (2), and fluoropolymers derived from the copolymerization of at least one monomer represented by the above general formula (2) with at least one monomer represented by the above general formula (1) and / or at least one monomer represented by the above general formula (3).

[0097] Examples of such polymers are polymers having copolymer units derived from VDF and hexafluoropropylene (HFP), polymers derived from TFE and at least one copolymerizable comonomer other than TFE (at least 3% by weight). The latter type of fluoropolymers includes TFE / PAVE copolymers (PFA), TFE / PAVE / CTFE copolymers, TFE / HFP copolymers (FEP), TFE / ethylene copolymers (ETFE), TFE / HFP / ethylene copolymers (EFEP), TFE / VDF copolymers, TFE / VDF / HFP copolymers, TFE / VDF / CTFE copolymers, etc., or mixtures thereof.

[0098] In addition, the non-fibrous hot melt processable component may be a combination of a plurality of the above-mentioned components.

[0099] The content of the non-fibrous heat-melt processable component in the porous membrane is preferably 0.1% by weight or more and less than 20% by weight.Being less than 20% by weight, the non-fibrous heat-melt processable component is dispersed in parts other than the nodules in the porous membrane, thereby preventing the pressure loss of the porous membrane from increasing.In addition, being less than 20% by weight, it is easy to perform stretching at a high stretch area ratio of 40 times or more, as described below.Being the content of the non-fibrous heat-melt processable component in the porous membrane is 0.1% by weight or more, it is easy to sufficiently prevent the deterioration of the filter performance of the porous membrane even if a compressive force or the like is applied in a subsequent process.The content of the non-fibrous heat-melt processable component in the porous membrane is preferably 15% by weight or less, more preferably 10% by weight or less.In addition, the content of the non-fibrous heat-melt processable component in the porous membrane is preferably 0.5% by weight or more, from the viewpoint of ensuring the strength of the porous membrane.Among them, about 5% by weight is particularly preferable.

[0100] The content of the non-fibrous, heat-melt processable component is preferably 10% by weight or less in order to perform good stretching at an areal stretching magnification of 40 times or more and 800 times or less.

[0101] In the porous membrane composed of the three components described above, the fibrils are mainly composed of component A, and the nodes are composed of components A to C. Such nodes are formed relatively large in the porous membrane, thereby forming a thick porous membrane. Furthermore, such nodes are relatively hard because they contain a heat-melt processable component that does not become fibrous, and they play the role of pillars that support the porous membrane in the thickness direction. Therefore, even if the porous membrane is subjected to a compressive force in the thickness direction in a post-process such as laminating an air-permeable support material or pleating, which will be described later, it is possible to prevent the filter performance of the porous membrane from decreasing.

[0102] (4-4) Other properties of porous membranes The fluororesin porous membrane preferably has a fiber diameter (average fiber diameter) of 50 nm or more and 250 nm or less, more preferably 60 nm or more and 200 nm or less. In addition, the first fluororesin porous membrane, which is arranged upstream of the second fluororesin porous membrane in the airflow, preferably has a larger fiber diameter.

[0103] The above-mentioned fluororesin porous membrane is not particularly limited, but may be produced by referring to the production method described in JP-A-2017-159281, for example.

[0104] (5) Breathable support material Even if the porous membrane is difficult to stand on its own due to its thin thickness, the breathable supporting material can support the porous membrane and make it stand upright.

[0105] The material and structure of the breathable support material are not particularly limited, but examples include nonwoven fabrics, woven fabrics, metal mesh, and resin nets. Among these, heat-sealable nonwoven fabrics are preferred in terms of strength, collection ability, flexibility, and workability. Preferred nonwoven fabrics include those in which some or all of the constituent fibers have a core / sheath structure, two-layer nonwoven fabrics consisting of a layer of fibers made of a low-melting-point material and a layer of fibers made of a high-melting-point material, and nonwoven fabrics coated with a heat-sealable resin. Examples of such nonwoven fabrics include spunbonded nonwoven fabrics. Furthermore, core / sheath nonwoven fabrics preferably have a core component with a higher melting point than the sheath component. Examples of core / sheath material combinations include PET / PE and high-melting-point polyester / low-melting-point polyester. Examples of low-melting-point / high-melting-point material combinations for two-layer nonwoven fabrics include PE / PET, PP / PET, PBT / PET, and low-melting-point PET / high-melting-point PET. Examples of nonwoven fabrics with a heat-fusible resin applied to the surface include PET nonwoven fabrics coated with EVA (ethylene vinyl acetate copolymer resin) and PET nonwoven fabrics coated with olefin resin.

[0106] The material of the nonwoven fabric is not particularly limited, and polyolefin (PE, PP, etc.), polyamide, polyester (PET, etc.), aromatic polyamide, or a composite material of these may be used.

[0107] The breathable support material can be bonded to the porous membrane by melting a part of the breathable support material by heating, or by melting a hot melt resin, by utilizing the anchor effect, or by utilizing adhesion such as a reactive adhesive.

[0108] The breathable support material has extremely low pressure loss, collection efficiency, and dust capacity compared to the porous membrane described above, and the pressure loss and collection efficiency may be 5% or less of those of the porous membrane, and may be considered to be essentially zero.

[0109] The pressure loss of the breathable support material is, for example, preferably 10 Pa or less, and more preferably 5 Pa or less. The collection efficiency of the breathable support material for NaCl with a particle diameter of 0.1 μm may be, for example, one that can be considered to be substantially 0 or approximately 0.

[0110] The thickness of the breathable support material is preferably, for example, 0.3 mm or less, and more preferably 0.25 mm or less.

[0111] The weight of the breathable support material is, for example, 20 g / m 2 More than 50g / m 2 It is preferable that:

[0112] The above-mentioned breathable support materials have very large openings and poor water retention, so the antifungal performance of the antifungal air filter medium essentially depends on the antifungal properties of the porous membrane.

[0113] (6) Pre-collection material The antifungal air filter medium may include a pre-collection material that is arranged upstream of the porous membrane and that collects part of the dust in the airflow.

[0114] From the viewpoint of keeping the pressure loss of the entire anti-mold air filter medium low, the pre-collection material preferably has a pressure loss of 5 Pa or more but less than 55 Pa when air is passed through it at a flow rate of 5.3 cm / sec, and more preferably 15 Pa or more but less than 45 Pa.

[0115] Furthermore, the pre-trapping material preferably has a trapping efficiency for NaCl with a particle diameter of 0.3 μm of 15% or more and less than 85%, and more preferably 30% or more and less than 75%.

[0116] From the viewpoint of facilitating the folding operation when folding the air filter medium into pleats, the pre-collection material preferably has a thickness of 0.8 mm or less, more preferably 0.7 mm or less, and may be less than 0.4 mm. The thickness of the pre-collection material is not particularly limited, but may be, for example, 0.1 mm or more.

[0117] The average fiber diameter of the pre-collection material is preferably 0.8 μm or more and less than 2.0 μm.

[0118] The basis weight of the pre-collection material is not particularly limited, but is, for example, 10 g / m 2 More than 70g / m 2 and 30 g / m 2 More than 67g / m 2 It is preferable that:

[0119] Such pre-collection materials are not particularly limited, but may be composed of glass fiber filter media, or may be nonwoven fabrics or fiber layer structures composed of fiber materials produced by melt-blown, electrospinning, sea-island, or one of these hybrid methods. Hybrid methods include, for example, melt-spinning and electret-blown. The sea-island method, for example, involves discharging fibers from multiple outlets, varying the raw materials depending on the discharge path, so that some raw materials form a sea portion and other different raw materials form island portions, resulting in a sea-island cross section. Here, a bicomponent or multicomponent sea-island polymer is spun, and the sea component is dissolved in post-processing to produce fibers while leaving the island portions. It is possible to adjust bulk density, stretchability, and other properties by combining raw materials using the discharge path. In the melt-blown method, molten polymer is discharged from a nozzle by an extruder while heated air is blown along the nozzle to form threads. Here, by adjusting the amount of polymer extruded from the nozzle per unit time and the speed at which heated air is blown out, it is possible to obtain threads with a smaller diameter. Furthermore, the physical properties of the threads can also be changed by adjusting the melt viscosity of the polymer used. When the pre-collection material is produced by the melt-blown method, electrospinning method, sea-island method, or one of these hybrid methods, examples of materials include polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyamide (PA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), polyurethane (PU), and mixtures thereof.

[0120] (7) Examples of uses Antifungal air filter media are used for the following purposes, for example.

[0121] ULPA filters (Ultra low Penetration Air Filters) (for semiconductor manufacturing), HEPA filters (for hospitals and semiconductor manufacturing), cylindrical cartridge filters (for industrial use), bag filters (for industrial use), heat-resistant bag filters (for exhaust gas treatment), heat-resistant pleated filters (for exhaust gas treatment), SINBRAN (registered trademark) filters (for industrial use), catalytic filters (for exhaust gas treatment), adsorbent filters (for HDD integration), adsorbent vent filters (for HDD integration), vent filters (for HDD integration, etc.), vacuum cleaner filters (for vacuum cleaners), general-purpose multi-layer felt materials, gas turbine cartridge filters (for gas turbine compatible products), cooling filters (for electronic equipment housings), etc. Freeze-drying materials such as freeze-drying containers, automotive ventilation materials for electronic circuits and lamps, container applications such as container caps, protective ventilation applications for electronic devices, ventilation / internal pressure regulation applications such as medical ventilation applications; Liquid filtration field including semiconductor liquid filtration filters (for semiconductor manufacturing), hydrophilic filters (for semiconductor manufacturing), chemical filters (for chemical liquid treatment), filters for pure water production lines (for pure water production), and backwash type liquid filtration filters (for industrial wastewater treatment).

[0122] The antifungal air filter medium is preferably used in any of food factories, pharmaceutical factories, clean rooms, and air purifiers.

[0123] The antifungal air filter medium is more likely to exhibit its effects when used in an environment where mold growth is particularly a concern. The antifungal air filter medium is preferably used in an environment with a relative humidity of 60% or more, more preferably in an environment with a temperature of 20°C or more and a relative humidity of 60% or more, and even more preferably in an environment with a temperature of 25°C or more and a relative humidity of 70% or more.

[0124] (8) Filter pack Next, the filter pack will be described with reference to FIG.

[0125] FIG. 5 is a perspective view of the appearance of the filter pack 20. As shown in FIG.

[0126] The filter pack 20 includes the above-described antifungal air filter media (e.g., antifungal air filter media 30a-30d). The antifungal air filter media of the filter pack 20 is a processed filter media that has been pleated into a zigzag shape with alternating mountain folds and valley folds. Pleating can be performed, for example, by a rotary folding machine. The folded width of the filter media is not particularly limited, but is, for example, 25 mm or more and 280 mm or less. The pleating of the filter pack 20 increases the folded area of ​​the filter media when used in an air filter unit, thereby providing an air filter unit with high collection efficiency.

[0127] In addition to the antifungal air filter medium, the filter pack 20 may further include spacers (not shown) for maintaining the pleat spacing when used in an air filter unit. The material of the spacers is not particularly limited, but a hot melt resin is preferably used.

[0128] (9) Air filter unit Next, the air filter unit 1 will be described with reference to FIG.

[0129] FIG. 6 is a perspective view of the appearance of the air filter unit 1. As shown in FIG.

[0130] The air filter unit 1 includes the above-described antifungal air filter medium or filter pack, and a frame 25 for holding the antifungal air filter medium or filter pack. In other words, the air filter unit may be fabricated so that the antifungal air filter medium that is not folded in the mountain or valley is held in the frame, or so that the filter pack 20 is held in the frame 25. The air filter unit 1 shown in FIG. 6 is fabricated using the filter pack 20 and the frame 25.

[0131] Frame 25 is made, for example, by combining plate materials or molding resin, and the gap between filter pack 20 and frame 25 is preferably sealed with a sealant. The sealant is used to prevent leakage between filter pack 20 and frame 25, and is made of, for example, epoxy, acrylic, or urethane resin.

[0132] The air filter unit 1, which includes a filter pack 20 and a frame 25, may be a mini-pleat type air filter unit in which one flat filter pack 20 is held and stored inside the frame 25, or may be a V-bank type air filter unit or a single-header type air filter unit in which multiple flat filter packs are arranged and held in a frame.

[0133] (10) Air treatment equipment Next, the air treatment device 100 will be described with reference to FIG.

[0134] FIG. 7 is a perspective view of the air treatment device 100. As shown in FIG.

[0135] The air treatment device 100 includes the above-described antifungal air filter media (for example, antifungal air filter media 30a to 30d), a casing 50, a heat exchanger 51, a humidity adjustment unit 52, and a fan 53.

[0136] The casing 50 has an intake port 50a and an outlet port 50b, and accommodates therein the antifungal air filter media 30a to 30d, a heat exchanger 51, a humidity adjustment section 52, and a fan 53. The antifungal air filter media 30a to 30d, the heat exchanger 51, the humidity adjustment section 52, and the fan 53 are arranged in this order from the intake port 50a toward the outlet port 50b.

[0137] The heat exchanger 51 constitutes a part of a refrigerant circuit (not shown), and a refrigerant flows inside the heat exchanger 51. The air that has passed through the antifungal air filter media 30a to 30d is heated or cooled when passing through the heat exchanger 51.

[0138] The humidity adjusting unit 52 is not particularly limited, but may be a rotor equipped with an adsorption element. The adsorption element may have a temperature-dependent moisture adsorption ability and release absorbed moisture by heating. In this case, a controllable heater is used together with the adsorption element.

[0139] The air treatment device 100 described above may be used as an outside air treatment device in which the intake port 50a of the casing 50 is open to the outdoors and the outlet port 50b of the casing 50 is open to the indoors. [Example]

[0140] Hereinafter, the contents of the present disclosure will be specifically described with reference to examples and comparative examples.

[0141] Example 1 As the antifungal air filter medium of Example 1, an antifungal air filter medium having a configuration as shown in FIG. 3 was prepared.

[0142] Specifically, the upstream breathable support material 21a and the downstream breathable support material 21b are both made of spunbond nonwoven fabric (average fiber diameter 20 μm, basis weight 40 g / m ) made of fibers with a core / sheath structure in which PET is used as the core and PE is used as the sheath. 2 The first porous membrane 31a disposed on the upstream side of the airflow passing through the filter medium and the second porous membrane 31b disposed on the downstream side were obtained by the following process.

[0143] 66.5% by weight (polymer equivalent) of PTFE aqueous dispersion (PTFE-A) with SSG of 2.160, 28.5% by weight (polymer equivalent) of low molecular weight PTFE aqueous dispersion (PTFE-B) with melt viscosity of 20,000 Pa·s measured using a flow tester method at 380 ° C, and 5% by weight (polymer equivalent) of FEP aqueous dispersion with melting point of 215 ° C were mixed, and 500 ml of 1% aluminum nitrate aqueous solution was added as a coagulant, and co-coagulation was carried out by stirring. Then, the resulting powder was drained using a sieve, and further dried in a hot air drying oven at 135 ° C for 18 hours, to obtain a mixed powder of the above three components.

[0144] Next, 36 parts by weight of hydrocarbon oil (IP Solvent 2028, manufactured by Idemitsu Kosan Co., Ltd.) was added as a liquid lubricant (extrusion aid) to 100 parts by weight of the mixed powder at 20°C and mixed. The resulting mixture was then extruded using a paste extrusion device to obtain a sheet-shaped compact. A sheet die with a rectangular extrusion opening measuring 2 mm in width and 180 mm in length was attached to the tip of the paste extrusion device. This sheet-shaped compact was then formed into a film using a calendar roll heated to 70°C to obtain a fluororesin film. This film was passed through a hot air drying oven at 200°C to evaporate and remove the hydrocarbon oil, yielding a strip-shaped unsintered fluororesin film (first green tape) with an average thickness of 300 μm and an average width of 180 mm. A strip-shaped unsintered fluororesin film (second green tape) with an average thickness of 300 μm and an average width of 180 mm was also obtained in the same manner as the first green tape, except that the amount of liquid lubricant added was 34 parts by weight.

[0145] Next, the first raw tape and the second raw tape were stacked and stretched in the longitudinal direction (longitudinal direction) at a stretching ratio of 6.5 times. The stretching temperature was 280 ° C. Next, the stacked and stretched raw tape was stretched in the width direction (transverse direction) at a stretching ratio of 12.0 times using a tenter that can be continuously clipped, and heat-set. The stretching temperature at this time was 290 ° C., and the heat-setting temperature was 390 ° C. As a result, a multi-layer porous membrane was obtained in which the first porous membrane and the second porous membrane were stacked. Then, the upstream breathable support material 21a and the downstream breathable support material 21b were bonded to both sides (outer layer side) of the obtained two-layer porous membrane by heat fusion using a laminating device, to obtain a four-layer structure filter material shown in Figure 3.

[0146] Example 2 As the antifungal air filter medium of Example 2, an antifungal air filter medium having a configuration as shown in FIG. 3 was prepared.

[0147] Specifically, in Example 2, the upstream-permeable support material 21a and the downstream-permeable support material 21b are used as the same as those in Example 1. In addition, the first porous membrane 31a arranged on the upstream side of the airflow that passes through the filter material and the second porous membrane 31b arranged on the downstream side are obtained by the following process.

[0148] 66.5% by weight (polymer equivalent) of PTFE aqueous dispersion (PTFE-A) with SSG of 2.160, 28.5% by weight (polymer equivalent) of low molecular weight PTFE aqueous dispersion (PTFE-B) with melt viscosity of 20,000 Pa·s measured using a flow tester method at 380 ° C, and 5% by weight (polymer equivalent) of FEP aqueous dispersion with melting point of 215 ° C were mixed, and 500 ml of 1% aluminum nitrate aqueous solution was added as a coagulant, and co-coagulation was carried out by stirring. Then, the resulting powder was drained using a sieve, and further dried in a hot air drying oven at 135 ° C for 18 hours, to obtain a mixed powder of the above three components.

[0149] Next, 33.5 parts by weight of hydrocarbon oil (IP Solvent 2028, manufactured by Idemitsu Kosan Co., Ltd.) was added as a liquid lubricant (extrusion aid) to 100 parts by weight of the mixed powder at 20°C and mixed. The resulting mixture was then extruded using a paste extrusion device to obtain a sheet-shaped compact. A sheet die with a rectangular extrusion opening measuring 2 mm in width and 180 mm in length was attached to the tip of the paste extrusion device. This sheet-shaped compact was then formed into a film using a calendar roll heated to 70°C to obtain a fluororesin film. This film was passed through a hot air drying oven at 200°C to evaporate and remove the hydrocarbon oil, yielding a strip-shaped unsintered fluororesin film (first green tape) with an average thickness of 300 μm and an average width of 180 mm. A strip-shaped unsintered fluororesin film (second green tape) with an average thickness of 300 μm and an average width of 180 mm was also obtained in the same manner as the first green tape, except that the amount of liquid lubricant added was 30 parts by weight.

[0150] Next, the first raw tape and the second raw tape were stacked and stretched in the longitudinal direction (longitudinal direction) at a stretching ratio of 6.5 times. The stretching temperature was 280 ° C. Next, the stacked and stretched raw tape was stretched in the width direction (transverse direction) at a stretching ratio of 13.7 times using a tenter that can be continuously clipped, and heat-set. The stretching temperature at this time was 290 ° C., and the heat-setting temperature was 390 ° C. As a result, a multi-layer porous membrane was obtained in which the first porous membrane and the second porous membrane were stacked. Then, the upstream breathable support material 21a and the downstream breathable support material 21b were bonded to both sides (outer layer side) of the obtained two-layer porous membrane by heat fusion using a laminating device, to obtain a four-layer structure filter material shown in Figure 3.

[0151] Example 3 As the antifungal air filter medium of Example 3, an antifungal air filter medium having a configuration as shown in FIG. 3 was prepared.

[0152] In Example 3, the upstream-permeable support material 21a and the downstream-permeable support material 21b are used as the same as those in Example 1. In addition, the first porous membrane 31a arranged on the upstream side of the airflow that passes through the filter material and the second porous membrane 31b arranged on the downstream side are obtained by the following process.

[0153] As the raw material of embodiment 3, use the mixed powder that is obtained by coprecipitating mixing with the fine powder of perfluoroalkyl vinyl ether modified polytetrafluoroethylene, which is the copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, and the fine powder of polytetrafluoroethylene with average molecular weight of 6.5 million (Daikin Industries, Ltd., trade name: F106) by weight ratio 75:25.

[0154] The mixed powder was mixed with an extrusion aid (liquid lubricant) in an amount of 29% by weight, and a sheet die with a rectangular extrusion opening measuring 2 mm in width and 170 mm in length was attached.Using the method of Example 1, a strip-shaped unsintered fluororesin film (first raw tape) with an average thickness of 300 μm and an average width of 170 mm was obtained.

[0155] In addition, an extrusion aid (liquid lubricant) was mixed in an amount of 24% by weight of the above mixed powder, and a strip-shaped unsintered fluororesin film (second raw tape) with an average thickness of 300 μm and an average width of 170 mm was obtained using the method of Example 1.

[0156] The first raw tape and the second raw tape were stacked and stretched in the longitudinal direction (longitudinal direction) at a stretching ratio of 8 times. The stretching temperature was 250 ° C. Next, the stacked and stretched raw tape was stretched in the width direction (transverse direction) at a stretching ratio of 20.0 times using a tenter that can be continuously clipped, and heat-set. The stretching temperature at this time was 290 ° C., and the heat-setting temperature was 390 ° C. As a result, a multi-layer porous membrane in which the first porous membrane and the second porous membrane were stacked was obtained. Then, the upstream breathable support material 21a and the downstream breathable support material 21b were bonded to both sides (outer layer side) of the obtained two-layer porous membrane by heat fusion using a laminating device, and a four-layer structure filter material shown in Figure 3 was obtained.

[0157] Example 4 As the antifungal air filter medium of Example 4, an antifungal air filter medium having a configuration as shown in FIG. 3 was prepared.

[0158] In Example 4, the upstream-permeable support material 21a and the downstream-permeable support material 21b are used as the same as those in Example 1. In addition, the first porous membrane 31a arranged on the upstream side of the airflow that passes through the filter material and the second porous membrane 31b arranged on the downstream side are obtained by the following process.

[0159] As the raw material of embodiment 2, use the mixed powder that is obtained by coprecipitating mixing with the fine powder of perfluoroalkyl vinyl ether modified polytetrafluoroethylene, which is the copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether, and the fine powder of polytetrafluoroethylene with average molecular weight of 6.5 million (manufactured by Daikin Industries, Ltd., trade name: F106) by weight ratio 75:25.

[0160] An extrusion aid (liquid lubricant) was added in an amount of 28% by weight of the mixed powder, and a strip-shaped unsintered fluororesin film (first raw tape) with an average thickness of 300 μm and an average width of 180 mm was obtained using the method of Example 1.

[0161] In addition, an extrusion aid (liquid lubricant) was mixed in an amount of 24% by weight of the above mixed powder, and a strip-shaped unsintered fluororesin film (second raw tape) with an average thickness of 300 μm and an average width of 180 mm was obtained using the method of Example 1.

[0162] The first raw tape and the second raw tape were stacked and stretched in the longitudinal direction (longitudinal direction) at a stretching ratio of 8 times. The stretching temperature was 280 ° C. Next, the stacked and stretched raw tape was stretched in the width direction (transverse direction) at a stretching ratio of 22.0 times using a tenter that can be continuously clipped, and heat-set. The stretching temperature at this time was 290 ° C., and the heat-setting temperature was 390 ° C. As a result, a multi-layer porous membrane in which the first porous membrane and the second porous membrane were stacked was obtained. Then, the upstream breathable support material 21a and the downstream breathable support material 21b were bonded to both sides (outer layer side) of the obtained two-layer porous membrane by heat fusion using a laminating device, and a four-layer structure filter material shown in Figure 3 was obtained.

[0163] Example 5 As the antifungal air filter medium of Example 5, an antifungal air filter medium having a configuration as shown in FIG. 2 was prepared.

[0164] In Example 5, the upstream-permeable support material 21a and the downstream-permeable support material 21b were the same as those in Example 1.

[0165] The porous membrane 31 used was obtained by the following process.

[0166] The raw material for Example 5 was a polytetrafluoroethylene fine powder (manufactured by Daikin Industries, Ltd., product name: F106) with an average molecular weight of 6.5 million. 33 parts by weight of a liquid lubricant was added to 100 parts by weight of the PTFE fine powder and mixed. The resulting mixture was extruded using a paste extrusion device to obtain a round rod-shaped molded body. This round rod-shaped molded body was formed into a film using a calendar roll heated to 70°C to obtain a PTFE film. This film was passed through a hot air drying oven at 200°C to evaporate and remove the hydrocarbon oil, resulting in a strip-shaped unsintered PTFE film with an average thickness of 200 μm and an average width of 150 mm. This unsintered PTFE film was stretched in the longitudinal direction at a stretch ratio of 6.5 times. The stretching temperature was 280°C. Next, the stretched unsintered PTFE film was stretched in the transverse direction at a stretch ratio of 32.0 times using a tenter capable of continuous clipping, and then heat-set. The stretching temperature was 290°C, and the heat-setting temperature was 390°C. The upstream-permeable support material 21a and the downstream-permeable support material 21b were bonded to both sides (outer layer sides) of the porous membrane obtained by this by heat fusion using a laminating device, thereby obtaining a filter medium with a three-layer structure as shown in Figure 2.

[0167] Example 6 As the antifungal air filter medium of Example 6, an antifungal air filter medium having a configuration as shown in FIG. 2 was prepared.

[0168] Specifically, the upstream breathable support material 21a, the intermediate breathable support material 21c, and the downstream breathable support material 21b are all made of spunbond nonwoven fabric (average fiber diameter 20 μm, basis weight 30 g / m) made of fibers with a core / sheath structure in which PET is used as the core and PE is used as the sheath.2 , thickness 0.2 mm) was used.

[0169] The porous membrane 31 used was obtained by the following process.

[0170] 100 parts by weight of the same three-component mixed powder as in Example 1 was used as the raw material, and 34 parts by weight of hydrocarbon oil (IP Solvent 2028 manufactured by Idemitsu Kosan Co., Ltd.) was added as a liquid lubricant (extrusion aid) and mixed at 20°C. The resulting mixture was extruded using a paste extrusion device to obtain a sheet-shaped compact. A sheet die with a rectangular extrusion opening measuring 2 mm in the transverse direction and 220 mm in the longitudinal direction was attached to the tip of the paste extrusion device. This sheet-shaped compact was formed into a film using a calendar roll heated to 70°C to obtain a fluororesin film. This film was passed through a hot air drying oven at 200°C to evaporate and remove the hydrocarbon oil, yielding a strip-shaped unsintered fluororesin film with an average thickness of 300 μm and an average width of 220 mm.

[0171] This unsintered PTFE film was stretched in the longitudinal direction (longitudinal direction) at a stretching ratio of 6.5 times. The stretching temperature was 280 ° C. Next, the stretched unsintered PTFE film was stretched in the width direction (transverse direction) at a stretching ratio of 11.0 times using a tenter that can be continuously clipped, and heat-set. The stretching temperature at this time was 290 ° C., and the heat-setting temperature was 390 ° C. On both sides (outer layer side) of the porous membrane obtained in this way, the upstream breathable support material 21a and the downstream breathable support material 21b were bonded by heat fusion using a laminating device, to obtain a three-layer structure filter material shown in Figure 2.

[0172] (Comparative Example 1) As the air filter medium of Comparative Example 1, a commonly available PTFE air filter medium having a configuration as shown in FIG. 2 was prepared.

[0173] The physical properties measured in the examples and comparative examples are as follows.

[0174] (Thickness of porous membrane) Using a film thickness meter (Model 1D-110MH, manufactured by Mitutoyo Corporation), five measurement targets were stacked and the total film thickness was measured, and the value was divided by 5 to obtain the film thickness of one film.

[0175] In the examples where two porous membranes were used, the total thickness was taken as the membrane thickness.

[0176] (average pore size of porous membrane) The mean flow pore size measured according to ASTM F316-86 was used as the mean pore size (mean flow path diameter) of the porous membrane. The actual measurement was performed using a PMI Capillary Flow Prometer CFP-1100A (manufactured by PIM).

[0177] In the case where a plurality of porous membranes were present, the average pore size was measured for the stack of porous membranes.

[0178] (Average surface height of porous membrane Rc) The average height Rc of the porous membrane surface was measured using a laser microscope VK-9710 (Keyence Corporation) in accordance with the method described in JIS B 0601:2013 (ISO 4287:1997, Amd.1:2009). The measurement conditions were: microscope magnification: 20x (monitor: 400x), measurement area: 130 μm, roughness standard: ISO 4287 (JIS B0601:2013). The average height Rc of the porous membrane surface was determined from the obtained images using image analysis software (VK Analyzer). Note that under the above conditions, measurements were taken at three different locations on the porous membrane surface, and the average height Rc was calculated as the average value.

[0179] In addition, in the case where there were multiple porous membranes, the measurement was performed on the surface of the porous membrane located on the upstream side of the passing airflow.

[0180] (Arithmetic mean roughness Ra of the porous membrane surface) The arithmetic mean roughness Ra of the porous membrane surface was measured using a laser microscope VK-9710 (Keyence Corporation) in accordance with the method described in JIS B 0601 (2013). Measurement conditions were: microscope magnification: 20x (monitor: 400x), magnification: 20x, measurement area: 130 μm, roughness standard: ISO 4287 (JIS B 0601:2013). Image analysis software (VK Analyzer) was used to determine the arithmetic mean roughness Ra of the porous membrane surface from the obtained images. Note that under the above conditions, measurements were taken at three different locations on the porous membrane surface, and the arithmetic mean roughness Ra was calculated as the average value.

[0181] In addition, in the case where there were multiple porous membranes, the measurement was performed on the surface of the porous membrane located on the upstream side of the passing airflow.

[0182] (Water contact angle on the surface of the porous membrane) The contact angle was measured by the 2 / θ method using Drop Master 501 (Kyowa Interface Science Co., Ltd.).

[0183] (Contact angle of porous membrane surface with water:IPA=80:20) The contact angle was measured by the 2 / θ method using Drop Master 501 (Kyowa Interface Science Co., Ltd.).

[0184] (Contact angle of porous membrane surface with water:IPA=70:30) The contact angle was measured by the 2 / θ method using Drop Master 501 (Kyowa Interface Science Co., Ltd.).

[0185] In addition, when there were a plurality of porous membranes, the above contact angles were measured on the surface of the porous membrane located on the upstream side of the passing airflow.

[0186] (Perforated membrane basis weight) The basis weight was determined by dividing the mass (g) of a sample cut into a rectangle of a predetermined area by the area measured with a precision balance. In the examples using two porous membranes, the basis weight was determined for a sample in which multiple porous membranes were stacked.

[0187] (pressure loss) A measurement sample of the antifungal air filter medium was placed in a filter holder with a diameter of 100 mm, and the inlet side was pressurized with a compressor. The air flow rate was adjusted to 5.3 cm / sec using a flow meter. The pressure loss at this time was measured with a manometer.

[0188] (Collection efficiency of NaCl particles with a particle diameter of 0.1 μm) According to the method described in JIS B9928 Appendix 5 (Regulations) NaCl aerosol generation method (pressure spray method), NaCl particles generated by an atomizer were classified to a particle size of 0.1 μm using an electrostatic classifier (TSI). After neutralizing the particle charge using americium-241, the permeation flow rate was adjusted to 5.3 cm / sec. A particle counter (TSI, CNC) was used to determine the number of particles before and after the anti-fungal air filter medium, which was the measurement sample, and the collection efficiency was calculated using the following formula. Transmittance (%)=(CO / CI)×100 Collection efficiency (%) = 100 - transmittance (%) CO = Number of 0.1 μm particles of NaCl downstream of the measurement sample CI = Number of 0.1 μm NaCl particles upstream of the measurement sample (JIS Z2911 mold resistance test (wet method))

[0189] The above-mentioned Examples 1, 5 and Comparative Example 1 were subjected to a test in accordance with the fungal resistance test of JIS Z2911.

[0190] The samples were cut to a specified size and placed on an agar medium containing ammonium nitrate, potassium dihydrogen phosphate, magnesium sulfate heptahydrate, potassium chloride, iron (II) sulfate heptahydrate, agar, and purified water. A mixed spore liquid containing spores of Aspergillus niger, Penicillium citrinum, Chaetomium globosum, and Myrothecium verrucaria molds was sprayed onto the samples, and the condition of mold growth on the sample surface was observed under a temperature condition of 26±2°C.

[0191] Here, in assessing the mold growth status in the mold resistance test, samples in which no hyphae growth was observed with the naked eye were rated 0, samples in which hyphae growth was observed in an area that did not exceed 1 / 3 of the total area were rated 1, and samples in which hyphae growth was observed in an area that exceeded 1 / 3 of the total area were rated 2.

[0192] (Test conforming to JIS Z2911 mold resistance test) For each of the above examples and comparative examples, a test was conducted in accordance with the mold resistance test of JIS Z2911. Samples were cut to a specified size, placed on potato dextrose agar medium, and a suspension of Aspergillus niger (1000 RLU) was spread over them. The samples were then left at room temperature, and the extent of mold growth on the sample surface was observed with the naked eye over time (after 3 days, 1 week, and 2 weeks).

[0193] (ISO 846 Plastics - Evaluation of microbial activity) For Examples 1 and 3, tests were conducted using ISO 846:2019 (Method A) to examine the mold resistance of the specimens. In the test, the test mold was inoculated onto a malt extract agar medium and cultured at 29±1°C for 10 to 20 days. After that, the spore count was increased to 10 using an inorganic salt solution. 6 Spore solutions were prepared to a concentration of 1 / mL, and equal amounts were mixed to form the test spore solution. The test fungi used were Aspergillus niger (NBRC 105649), Penicillium pinophilum (NBRC 100533), Paecilomyces variotii (NBRC 107725), Trichoderma virens (NBRC 6355), and Chaetomium globosum (NBRC 6347). The test samples were inoculated with the test spore solution by spraying and then cultured at 29±1°C and 95% or higher relative humidity for four weeks. After the second and fourth weeks of culture, mold growth on the test samples was observed visually and microscopically.

[0194] The results for mycelial growth were as follows: no mold growth observed under a microscope was rated "0"; no mold growth observed with the naked eye but mold confirmed under a microscope was rated "1a"; no mold growth observed with the naked eye but mold confirmed under a microscope was rated "1b"; no mold growth observed with the naked eye but mold confirmed under a microscope was rated "1c"; mycelial growth observed with the naked eye was rated "2"; mycelial growth observed with the naked eye was rated "3"; mycelial growth observed with the naked eye was rated "4"; and mycelial growth so severe that it covered the entire sample was rated "5".

[0195] The physical properties of the antifungal air filter media and the physical properties of the porous films of each Example and Comparative Example are shown in Table 1 below.

[0196] 8 and 9 show photographs of the samples taken three days and one week after the start of the test in accordance with the JIS Z2911 mold resistance test for Example 1 and Comparative Example 1. Note that the blackened areas in the photographs indicate areas where identification letters were written on the samples and petri dishes, and no mold was found in the blackened areas.

[0197] [Table 1]

[0198] The contact angle (water) was measured according to the sessile drop method, but since the water did not move, the value measured with the needle still attached is shown.

[0199] Furthermore, Examples 1 and 5 achieved a score of 0 (no mycelial growth observed in the inoculated portion of the sample or test piece) in the JIS Z2911 mold resistance test, while Comparative Example 1 achieved a score of 1 (the area in which mycelial growth was observed did not exceed 1 / 3 of the total area).

[0200] In the ISO 846 plastic-microbial activity evaluation, Examples 1 and 3 achieved a score of 0 (no mold growth observed under a microscope) both after two and four weeks of culture. Figure 10 shows photographs of the samples from Examples 1 and 3 after four weeks of culture.

[0201] (Addendum) Although the embodiments of the present disclosure have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the present disclosure as defined in the claims. [Explanation of symbols]

[0202] 1 Air filter unit 20 filter packs 25 Frame 30a, 30b, 30c, 30d Anti-mold air filter media (air filter media) 21 Breathable support material 21a Upstream breathable support material 21b Downstream breathable support material 21c Intermediate breathable support material 31 Porous membrane 31a First porous membrane 31b Second porous membrane 50 casing 50a intake 50b Air outlet 51 Heat exchanger 52 Humidity adjustment section 53 Fans 100 Outdoor air treatment device [Prior art documents] [Patent documents]

[0203] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-205211

Claims

1. An air filter medium having a fluororesin porous membrane, The fluororesin porous membrane has a surface average height Rc of 6 μm or more, a surface arithmetic mean roughness Ra of 6 μm or more, and a water contact angle of the membrane surface of 90 degrees or more. Air filter media.

2. The average height Rc of the surface of the porous membrane is 36 μm or more, The air filter medium according to claim 1.

3. The average pore diameter of the porous membrane is 2 μm or more. The air filter medium according to claim 1 or 2.

4. The average pore size of the porous membrane is 10 μm or less. The air filter medium according to claim 1 or 2.

5. The thickness of the porous membrane is 100 μm or more. The air filter medium according to claim 1 or 2.

6. The contact angle of a 30% by volume aqueous solution of isopropyl alcohol is 127 degrees or more. The air filter medium according to claim 1 or 2.

7. The porous membrane does not contain a mildewproofing agent. The air filter medium according to claim 1 or 2.

8. Used in an environment with a relative humidity of 60% or more. The air filter medium according to claim 1 or 2.

9. 3. A method for using the antifungal air filter medium according to claim 1 or 2 in an environment with a relative humidity of 60% or more.

10. A casing (50) having an intake port (50a) and an outlet port (50b), The air filter medium according to claim 1 or 2, disposed inside the casing (50); a fan (53) disposed inside the casing (50); Equipped with Air treatment equipment.

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