Air filter filtration material, method for using air filter filtration material, and air treatment device

Abstract

Provided are an air filter filtration material, a method for using an air filter filtration material, and an air treatment device that suppress mold generation. 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.

Description

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

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

[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 (Japanese Patent Laid-Open Publication No. 2003-205211) proposes an air filter medium in which an antibacterial reinforcing material containing an inorganic, organic, or natural antibacterial agent is laminated to a polytetrafluoroethylene porous membrane.

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

[0005] The air filter medium according to the 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, wherein 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, wherein the thickness of the porous membrane is 100 μm or more.

[0017] The thickness of the porous film 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 with an aqueous solution of isopropyl alcohol having 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, wherein 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 comprises 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.

[0031] 1 is a schematic cross-sectional view showing the layer structure of an antifungal air filter medium 30a. FIG. 2 is a schematic cross-sectional view showing the layer structure of an antifungal air filter medium 30b. FIG. 3 is a schematic cross-sectional view showing the layer structure of an antifungal air filter medium 30c. FIG. 4 is a schematic cross-sectional view showing the layer structure of an antifungal air filter medium 30d. FIG. 5 is a perspective view of the appearance of a filter pack. FIG. 6 is a perspective view of the appearance of an air filter unit. FIG. 7 is a schematic configuration diagram of an air treatment device. FIG. 8 is a photograph showing the state of Example 1 and Comparative Example 1 three days after the start of a test based on the JIS Z2911 fungicide resistance test. FIG. 9 is a photograph showing the state of Example 1 and Comparative Example 1 one week after the start of a test based on the JIS Z2911 fungicide resistance test. FIG. 10 is a photograph showing the state of Example 1 and Comparative Example 1 four weeks after the start of culture in the ISO846 test.

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

[0033] (1) Antifungal air filter material Antifungal air filter material comprises porous membrane.The average height Rc of porous membrane surface is 6 μ m or more.The water contact angle of the membrane surface of porous membrane is 90 degrees or more.According to this antifungal air filter material, it can suppress the generation of mold on porous membrane.

[0034] The antifungal 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) Examples of the Structure of the Antifungal Air Filter Medium The specific structure of the antifungal air filter medium described above is not particularly limited.

[0037] For example, as shown in Fig. 1, antifungal air filter material 30a, can be configured by air permeability support material 21 and porous membrane 31 stacked in order in the air flow direction.Here, porous membrane 31 can be arranged on the upstream side or downstream side of air flow with respect to air permeability support material 21.

[0038] For example, as shown in Fig. 2, the antifungal air filter material 30b may be configured by stacking upstream air permeability support material 21a, porous film 31 and downstream air permeability support material 21b in order in the air flow direction.

[0039] In addition, as shown in Fig. 3, the antifungal air filter material 30c may be configured by stacking upstream air-permeable support material 21a, first porous film 31a, second porous film 31b and downstream air-permeable support material 21b in order in the air flow direction.

[0040] Furthermore, as shown in Fig. 4, the antifungal air filter material 30d may be configured by stacking upstream air-permeable support material 21a, first porous film 31a, intermediate air-permeable support material 21c, second porous film 31b and downstream air-permeable support material 21b in 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 upstream 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. In addition, 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 by first finding 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, 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, for example, in the case of a fluororesin porous film, the average height Rc of the surface of the porous film 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 molded body), and can be increased by increasing the amount of liquid lubricant.In addition, the average height Rc of the porous film obtained can also be adjusted by adjusting the type and compounding ratio of the components mixed when obtaining the fluororesin porous film.Furthermore, in the case of a fluororesin porous film, the average height Rc of the surface of the porous film can be increased by reducing the stretching ratio when stretching the unsintered fluororesin film, and can be decreased by increasing the stretching 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 contact angle of water 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 an isopropyl alcohol aqueous solution having a concentration of 20% by volume is preferably 127 degrees or more, 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 measured by the θ / 2 method. The contact angle of a 20% by volume aqueous solution of isopropyl alcohol is 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 water:IPA volume ratio of 80:20.

[0052] The contact angle of an isopropyl alcohol aqueous solution having a concentration of 30% by volume is preferably 127 degrees or more, 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 measured by the θ / 2 method. The contact angle of a 30% by volume aqueous solution of isopropyl alcohol is 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 water:IPA volume ratio 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. Also, the arithmetic mean roughness Ra of the obtained porous membrane can be adjusted by adjusting the type and compounding ratio of 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, or 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] In addition, when air is passed through the porous membrane at a flow rate of 5.3 cm / sec, the pressure loss 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 mainly composed of a fluororesin and has a porous membrane structure having fibrils (fibers) not shown and nodes (nodes) connected to the fibrils. 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 fluororesin porous membrane can be made of one kind of component, or can be made of two or more kinds of components.In addition, as the fluororesin made of two or more kinds of components, for example, the mixture of three components can be made: fibrous PTFE (hereinafter also referred to as component A), non-fibrous non-thermal melt processable component (hereinafter also referred to as component B), and non-fibrous non-thermal melt processable component (hereinafter also referred to as component C) with melting point less than 320 ℃.Fluororesin porous membrane is preferably made of the combination of these three kinds of components.Compared with the fibrous PTFE (high molecular weight PTFE) porous membrane, the fluororesin porous membrane made of these three kinds of components has more voids and has a thick membrane structure, so that it can capture the fine particles in gas in a wide area in the thickness direction of filter material, thereby improving dust-laden capacity.By making porous membrane made of these three kinds of components, it can increase the dust-laden capacity of liquid particles more than that of solid particles.

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

[0065] (4-1) Component A: Fibrotic PTFE Fibrotic PTFE is, for example, high molecular weight PTFE obtained by emulsion polymerization or suspension polymerization of tetrafluoroethylene (TFE).Here, "high molecular weight" refers to the PTFE that is easily fibrous during stretching when preparing porous membrane, and can obtain long fibrils, and has a standard specific gravity (SSG) of 2.130 to 2.230, and has a molecular weight of such a size that it does not melt flow due to high melt viscosity.The SSG of Fibrotic PTFE is preferably 2.130 to 2.190, more preferably 2.140 to 2.170, from the viewpoint of being easily fibrous and obtaining long fibrils.If SSG is too high, the extensibility of the mixture of components A to C may be deteriorated, and if SSG is too low, the rolling property may be deteriorated, the homogeneity of porous membrane may be deteriorated, and the pressure loss of porous membrane may be increased. Furthermore, PTFE obtained by emulsion polymerization is preferred from the viewpoint of ease of fiberization and the ability to obtain long fibrils. Standard specific gravity (SSG) is measured in accordance with ASTM D 4895.

[0066] Whether or not there is fibrotic property, that is, whether or not it can be fibrotic, can be judged by whether or not paste extrusion is possible, which is the typical method of molding high molecular weight PTFE powder made from TFE polymer.Usually, paste extrusion is possible because high molecular weight PTFE has fibrotic property.If the unsintered molding obtained by paste extrusion has no substantial strength or elongation, for example, elongation is 0%, and when pulled, it breaks, it can be considered that there is no fibrotic property.

[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 any homo-PTFE disclosed in JP 53-60979 A, ​​JP 57-135 A, JP 61-16907 A, JP 62-104816 A, JP 62-190206 A, JP 63-137906 A, JP 2000-143727 A, JP 2002-201217 A, 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-57-135, JP-A-63-137906, JP-A-2000-143727, JP-A-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 modified monomer). Modified PTFE includes, but is not limited to, one that is uniformly modified by the modified monomer, one that is modified at the beginning of polymerization reaction, one that is modified at the end of polymerization reaction, etc. The modified PTFE can be suitably used, for example, those disclosed in 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, etc. Among these, modified PTFE having high stretchability and disclosed in JP-A-61-16907, JP-A-62-104816, JP-A-64-1711, JP-A-11-240917, WO 2003 / 033555, WO 2005 / 061567, WO 2007 / 005361, WO 2011 / 055824, etc. are preferred.

[0069] The modified PTFE contains TFE units based on TFE and modified monomer units based on a modified monomer. The modified monomer units are a part of the molecular structure of the modified PTFE that is derived from the modified monomer. The modified PTFE preferably contains 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 modified monomer is not particularly limited as long as it can be copolymerized 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 ether; perfluoroalkylethylene (PFAE), ethylene, etc. The modified monomer used may be one kind or multiple kinds.

[0071] The perfluorovinyl ether is not particularly limited, and examples thereof include perfluorounsaturated compounds represented by the following general formula (1): CF ２ =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 a perfluorovinyl ether is perfluoro(alkyl vinyl ether) (PAVE), which is represented by the above general formula (1) and in which Rf 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 a perfluoromethyl group, a perfluoroethyl group, a perfluoropropyl group, a perfluorobutyl group, a perfluoropentyl group, and a 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) and perfluorohexylethylene (PFHE).

[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, particularly from the viewpoint that it is easily fibrous and long fibrils can be obtained.

[0077] The PTFE that can be fibrillated may be a combination of a plurality of the above components.

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

[0079] (4-2) B component: non-fibrous non-thermal melt processable component that does not become fibrous The non-fibrous non-thermal melt processable component that does not become fibrous is mainly unevenly distributed in nodule as non-fibrous particles, and plays the role of suppressing the PTFE that can become fibrous from becoming fibrous.

[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 nodes even when processed at a temperature above its melting point. In this specification, low-molecular-weight PTFE refers to a 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 x 10 ５ It is PTFE with a viscosity of Pa·s (see Japanese Patent Laid-Open No. 10-147617).

[0082] As the method for producing low molecular weight PTFE, there can be mentioned the method of contacting the high molecular weight PTFE powder (molding powder) obtained by suspension polymerization of TFE or the high molecular weight PTFE powder (fine powder) obtained by emulsion polymerization of TFE with a specific fluoride at high temperature to cause thermal decomposition (see Japanese Patent Laid-Open No. 61-162503), the method of irradiating the above-mentioned high molecular weight PTFE powder or molding with ionizing radiation (see Japanese Patent Laid-Open No. 48-78252), or the method of directly polymerizing TFE together with a chain transfer agent (see International Publication No. 2004 / 050727, International Publication No. 2009 / 020187, International Publication No. 2010 / 114033, etc.).Low molecular weight PTFE can be homo-PTFE as well as the PTFE that can be fibrillated, and can also be the modified PTFE that contains the above-mentioned modified monomer.

[0083] Low-molecular-weight PTFE does not have fibrous properties. The presence or absence of fibrous properties can be determined by the method described above. Low-molecular-weight PTFE has substantially no 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 1000Pa s or more, more preferably 5000Pa s or more, and even more preferably 10000Pa s or more.Like this, if melt viscosity is high, when producing porous membrane, even if the hot melt processable component that does not become Fibrotic as component C melts, the non-hot melt processable component that does not become Fibrotic can remain in nodule, and can suppress Fibrotic.

[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 them, talc is preferably used in terms of affinity with high molecular weight PTFE that can be fibrous and specific gravity. Inorganic fillers with a particle diameter of 3 μm or more and 20 μm or less are preferably used in terms of forming a stable dispersion during the production of porous membranes. The particle diameter is the average particle diameter and is measured by laser diffraction / scattering method. All of these inorganic fillers are also 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-thermal melt processable component that does not cause fibrous formation is preferably contained in the porous film in an amount of 1% by weight or more and 50% by weight or less.The content of the non-thermal melt processable component that does not cause fibrous formation is 50% by weight or less, so that the fibrous structure of the porous film can be easily maintained.The non-thermal melt processable component that does not cause fibrous formation 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-thermal melt processable component that does not cause fibrous formation is 20% by weight or more and 40% by weight or less, so that the fibrous formation of the PTFE that can cause fibrous formation can be more effectively suppressed.

[0089] (4-3) C component: the composition that can be processed by hot melting and melting point is less than 320 DEG C and can not be fibrous.The composition that can be processed by hot melting and can not be fibrous, and the composition that can be processed by hot melting and melting point is less than 320 DEG C (hereinafter also referred to as the composition that can be processed by hot melting and can not be fibrous) has fluidity when melting, so that when producing porous-film (when stretching), can melt and solidify at nodal part, can improve the strength of porous-film as a whole, and can suppress the deterioration of filter performance even if it is compressed etc. in later process.

[0090] The composition that can be processed by hot melt processing without Fibrosis preferably shows the melt viscosity of less than 10000 Pa s at 380 ℃.In addition, the melting point of the composition that can be processed by hot melt processing without Fibrosis is measured by using differential scanning calorimetry (DSC) to heat up to above melting point at a heating rate of 10 ℃ / min, melt completely once, then cool down to below melting point at a heating rate of 10 ℃ / min, and then heat up again at a heating rate of 10 ℃ / min, and obtain the peak top of the heat of fusion curve.

[0091] As the composition that can be processed by hot melting and does not become fibrous, can be mentioned the resins such as hot meltable fluoropolymer, polystyrene, polyethylene terephthalate (PET), polyester, polyamide, or their mixture, and can fully exhibit the melting property and fluidity at the stretching temperature when producing porous membrane.Among them, from the viewpoint of excellent heat resistance at the stretching temperature when producing porous membrane and excellent chemical resistance, hot meltable fluoropolymer is preferred.Hot meltable fluoropolymer is represented by the following general formula (2): RCF=CR ２ ...(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 R may be the same, or any two R may be the same and the remaining R may be different from these, or all 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 may also be a polymer containing at least one monomer represented by the general formula (2) and a monomer represented by the general formula (1) and / or the following general formula (3): ２ C=CR ２...(3) (wherein R are each 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 of the 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 a plurality of the 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)s (PAVEs), preferably perfluoropropyl vinyl ether (PPVE) and perfluoromethyl vinyl ether (PMVE).

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

[0096] More specific examples of fluoropolymers include the 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), the fluoropolymer derived from the copolymerization of two or more different monomers represented by the general formula (2), and the fluoropolymer derived from the copolymerization of at least one monomer represented by the general formula (2) and at least one monomer represented by the general formula (1) and / or at least one monomer represented by the 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 include 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 non-fibrous heat-melt processable component in porous film is preferably 0.1 wt% or more and less than 20 wt%.Being less than 20 wt%, the non-fibrous heat-melt processable component is dispersed in the part other than the nodule in porous film, and the pressure loss of porous film is prevented from increasing.In addition, being less than 20 wt%, it is easy to perform the stretching at a high ratio of 40 times or more of elongation area ratio described later.Being the content of non-fibrous heat-melt processable component in porous film is 0.1 wt% or more, it is easy to sufficiently prevent the deterioration of the filter performance of porous film even if compressive force etc. is applied in the subsequent process.The content of non-fibrous heat-melt processable component in porous film is preferably 15 wt% or less, more preferably 10 wt% or less.In addition, the content of non-fibrous heat-melt processable component in porous film is preferably 0.5 wt% or more from the viewpoint of ensuring the strength of porous film.Among them, it is particularly preferable that it is about 5 wt%.

[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 elongation area ratio of 40 times or more to 800 times or less.

[0101] In the porous membrane that is made up of the three kinds of components described above, fibril is mainly made up of component A, and node is made up of components A to C. Such node is formed relatively large in the porous membrane, and thus the porous membrane is formed thick. In addition, such node is relatively hard because it contains the component that can be processed by hot melt processing and does not become fibrous, and plays the role of a pillar that supports the porous membrane in the thickness direction. Therefore, even if it is subjected to the compressive force in the thickness direction in the post-process such as laminating the breathable supporting material or the pleating process described later, it is possible to prevent the filter performance of the porous membrane from being deteriorated.

[0102] (4-4) Other properties of the porous membrane 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, it is preferable that the first fluororesin porous membrane, which is arranged upstream of the second fluororesin porous membrane in the airflow, has a larger fiber diameter.

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

[0104] (5) Breathable Support Material The breathable support material supports the porous membrane, making it possible to make the porous membrane stand upright, even if it is difficult for the porous membrane to stand upright due to its thin thickness or the like.

[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 having a surface coated with a heat-fusible resin include PET nonwoven fabrics coated with EVA (ethylene vinyl acetate copolymer resin) and PET nonwoven fabrics coated with an 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 amount compared to the above-mentioned porous membrane, and the pressure loss and collection efficiency may be 5% or less of those of the porous membrane, and may be substantially 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 basis weight of the breathable support material is, for example, 20 g / m ２ 50g / m or more 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 and less than 55 Pa when air is passed through it at a flow rate of 5.3 cm / sec, and more preferably has a pressure loss of 15 Pa or more and 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 70g / m or more ２ and 30 g / m ２ More than 67g / m２ 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, with some raw materials forming a sea portion and other different raw materials forming 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 form fibers while leaving the island portions. Bulk density, stretchability, and other properties can be adjusted 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 discharged from the nozzle per unit time and the blowing speed of heated air, etc., it is possible to obtain threads with a smaller diameter. Furthermore, the physical properties of the threads can also be changed by 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 the material 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 The antifungal air filter medium is 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 device casings), 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, etc., ventilation / internal pressure adjustment applications such as medical ventilation applications; Liquid filtration fields include 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 exterior 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, etc.). 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, using 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 achieving 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 air filter unit 1. As shown in FIG.

[0130] The air filter unit 1 includes the above-described antifungal air filter material or filter pack and a frame 25 for holding the antifungal air filter material or filter pack. In other words, the air filter unit may be fabricated so that the antifungal air filter material 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 Figure 6 is fabricated using the filter pack 20 and the frame 25.

[0131] The frame 25 is made, for example, by combining plate materials or by molding resin, and the gap between the filter pack 20 and the frame 25 is preferably sealed with a sealant. The sealant is used to prevent leakage between the filter pack 20 and the frame 25, and is made of, for example, an 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 filter pack 20 extending in a flat plate shape is held 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 filter packs extending in a flat plate shape are lined up and held in a frame.

[0133] (10) Air Treatment Device 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 anti-mold air filter media (e.g., anti-mold air filter media 30a to 30d, etc.), 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 houses therein the antifungal air filter media 30a to 30d, a heat exchanger 51, a humidity adjustment unit 52, and a fan 53. The antifungal air filter media 30a to 30d, the heat exchanger 51, the humidity adjustment unit 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 part of a refrigerant circuit (not shown), and a refrigerant flows through it. The air that has passed through the antifungal air filter media 30a to 30d is heated or cooled as it passes 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 outdoor 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.

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

[0141] Example 1 As an antifungal air filter medium of Example 1, an antifungal air filter medium having a structure 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 In addition, the first porous membrane 31a that is arranged on the upstream side of the airflow that passes through filter material and the second porous membrane 31b that is arranged on the downstream side are obtained by the following process.

[0143] Mix 66.5% by weight (polymer equivalent) of the PTFE aqueous dispersion (PTFE-A) of SSG 2.160, 28.5% by weight (polymer equivalent) of the low molecular weight PTFE aqueous dispersion (PTFE-B) of 20000Pa s melt viscosity (measured by flow tester method at 380 ℃) and 5% by weight (polymer equivalent) of the FEP aqueous dispersion of melting point 215 ℃, add 500ml of 1% aluminum nitrate aqueous solution as coagulant, and stir to carry out coprecipitating.Then, use sieve to remove water from the powder produced, then further use hot air drying oven at 135 ℃ for 18 hours to dry, obtain the mixed powder of 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) per 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 are stacked, and stretched in longitudinal direction (longitudinal direction) by 6.5 times.Stretching temperature is 280 ℃.Then, the raw tape that is stacked and stretched is stretched in width direction (transverse direction) by 12.0 times using a tenter that can be continuously clipped, and then heat-set.Stretching temperature at this time is 290 ℃, and heat-set temperature is 390 ℃.Therefore, obtain the multi-layer porous membrane that the first porous membrane and the second porous membrane are stacked.Then, use laminating device to bond the upstream air permeability supporting material 21a and the downstream air permeability supporting material 21b to both sides (outer layer side) of the obtained two-layer porous membrane by heat fusion, and obtain the filter material of four-layer structure shown in Fig. 3.

[0146] Example 2 As an 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 embodiment 2, as upstream air permeability propellant 21a and downstream air permeability propellant 21b, use the same as embodiment 1. In addition, the first porous membrane 31a that is arranged on the upstream side of the airflow that passes through filter material and the second porous membrane 31b that is arranged on downstream side are obtained by the following process:

[0148] Mix 66.5% by weight (polymer equivalent) of the PTFE aqueous dispersion (PTFE-A) of SSG 2.160, 28.5% by weight (polymer equivalent) of the low molecular weight PTFE aqueous dispersion (PTFE-B) of 20000Pa s melt viscosity (measured by flow tester method at 380 ℃) and 5% by weight (polymer equivalent) of the FEP aqueous dispersion of melting point 215 ℃, add 500ml of 1% aluminum nitrate aqueous solution as coagulant, and stir to carry out coprecipitating.Then, use sieve to remove water from the powder produced, then further use hot air drying oven at 135 ℃ for 18 hours to dry, obtain the mixed powder of 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) per 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 are stacked, and stretched in longitudinal direction (longitudinal direction) by 6.5 times.Stretching temperature is 280 ℃.Then, the raw tape that is stacked and stretched is stretched in width direction (transverse direction) by 13.7 times using a tenter that can be continuously clipped, and then heat-set.Stretching temperature at this time is 290 ℃, and heat-set temperature is 390 ℃.Therefore, obtain the multi-layer porous membrane that the first porous membrane and the second porous membrane are stacked.Then, use laminating device to bond the upstream air permeability supporting material 21a and the downstream air permeability supporting material 21b to both sides (outer layer side) of the obtained two-layer porous membrane by heat fusion, and obtain the filter material of four-layer structure shown in Fig. 3.

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

[0152] In embodiment 3, as upstream air permeability propellant 21a and downstream air permeability propellant 21b, use the same as embodiment 1. In addition, the first porous membrane 31a that is arranged on the upstream side of the airflow that passes through filter material and the second porous membrane 31b that is arranged on downstream side are obtained by the following process:

[0153] As the raw material of embodiment 3, use 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 of 75:25, which is obtained by coprecipitating and mixing.

[0154] An extrusion aid (liquid lubricant) was added in an amount of 29% by weight of the mixed powder, and a sheet die having 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) having 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 with the above mixed powder in an amount of 24% by weight, and a strip-shaped unsintered fluororesin film (second raw tape) having an average thickness of 300 μm and an average width of 170 mm was obtained by the method of Example 1.

[0156] The first raw tape and the second raw tape are stacked, and stretched in longitudinal direction (longitudinal direction) by 8 times.Stretching temperature is 250 ℃.Then, the raw tape that is stacked and stretched is stretched in width direction (transverse direction) by 20.0 times using a tenter that can be continuously clipped, and then heat-set.Stretching temperature at this time is 290 ℃, and heat-set temperature is 390 ℃.Therefore, obtain the multi-layer porous membrane that the first porous membrane and the second porous membrane are stacked.Then, use laminating device to bond the upstream air permeability supporting material 21a and the downstream air permeability supporting material 21b to both sides (outer layer side) of the obtained two-layer porous membrane by heat fusion, and obtain the filter material of four-layer structure shown in Fig. 3.

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

[0158] In embodiment 4, as upstream air permeability propellant 21a and downstream air permeability propellant 21b, use the same as embodiment 1. In addition, the first porous membrane 31a that is arranged on the upstream side of the airflow that passes through filter material and the second porous membrane 31b that is arranged on downstream side are obtained by the following process:

[0159] As the raw material of embodiment 2, use 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 of 75:25, which is obtained by coprecipitating and mixing.

[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) having an average thickness of 300 μm and an average width of 180 mm was obtained by the method of Example 1.

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

[0162] The first raw tape and the second raw tape are stacked, and stretched in longitudinal direction (longitudinal direction) by 8 times.Stretching temperature is 280 ℃.Then, the raw tape that is stacked and stretched is stretched in width direction (transverse direction) by 22.0 times using a tenter that can be continuously clipped, and then heat-set.Stretching temperature at this time is 290 ℃, and heat-set temperature is 390 ℃.Therefore, obtain the multi-layer porous membrane that the first porous membrane and the second porous membrane are stacked.Then, use laminating device to bond the upstream air permeability supporting material 21a and the downstream air permeability supporting material 21b to both sides (outer layer side) of the obtained two-layer porous membrane by heat fusion, and obtain the filter material of four-layer structure shown in Fig. 3.

[0163] Example 5 As an 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 film 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 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 width direction at a stretch ratio of 32.0 times using a tenter capable of continuous clipping, and heat-set. At this time, stretching temperature is 290 ℃, and heat setting temperature is 390 ℃.By using laminating device, use upstream air permeability propellant 21a and downstream air permeability propellant 21b to be bonded on both sides (outer layer side) of the porous membrane obtained by this by heat fusion, obtain the filter material of three-layer structure shown in Fig. 2.

[0167] Example 6 As an 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 film 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 is stretched in longitudinal direction (longitudinal direction) by 6.5 times.Stretching temperature is 280 ℃.Then, the unsintered PTFE film is stretched in width direction (transverse direction) by 11.0 times using a tenter that can be continuously clipped, and then heat-set.Stretching temperature at this time is 290 ℃, and heat-set temperature is 390 ℃.By using laminating device, upstream air permeability propellant 21a and downstream air permeability propellant 21b are bonded to both sides (outer layer side) of the porous membrane obtained by this, to obtain the filter material of three-layer structure shown in Fig. 2.

[0172] Comparative Example 1 As an air filter medium in 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] (Film Thickness of Porous Film) Using a film thickness meter (Model 1D-110MH, manufactured by Mitutoyo Corporation), five measurement targets were stacked and the total film thickness was measured. The value was divided by 5 to obtain the film thickness of one film.

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

[0176] (Mean pore size of porous membrane) The mean pore size (mean flow pore size) measured in accordance with the description of ASTM F316-86 was taken as the mean pore size (mean flow path diameter) of the porous membrane. Actual measurement was performed using a PMI CapillaryFlow 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 height Rc of the surface of the porous membrane) The average height Rc of the surface of the porous membrane was measured using a laser microscope VK-9710 (manufactured by Keyence Corporation) in accordance with the method described in JIS B 0601: 2013 (ISO 4287: 1997, Amd.1: 2009). Measurement conditions were: microscope magnification: 20x (monitor: 400x), measurement area: 130 μm, roughness standard: ISO 4287 (JISB0601: 2013). Using image analysis software (VK Analyzer), the average height Rc of the surface of the porous membrane was determined from the obtained image. Note that, under the above conditions, three points were measured while changing the measurement point on the surface of the porous membrane, 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 surface of the porous membrane) The arithmetic mean roughness Ra of the surface of the porous membrane was measured using a laser microscope VK-9710 (manufactured by 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 surface of the porous membrane from the obtained image. Note that, under the above conditions, three points were measured while changing the measurement point on the surface of the porous membrane, 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] (Contact angle of water on the surface of porous membrane) The contact angle was determined by the 2 / θ method using Drop Master 501 (manufactured by Kyowa Interface Science Co., Ltd.).

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

[0184] (Contact angle of a liquid of water:IPA=70:30 on the surface of a porous membrane) The contact angle was determined by the 2 / θ method using Drop Master 501 (manufactured by 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] (Weight per unit area of ​​porous membrane) The weight per unit area is calculated by dividing the mass (g) of the sample cut into a rectangular shape with a predetermined area by the area measured with a precision balance.In addition, for the example using two porous membranes, the weight per unit area is calculated by using the one in which a plurality of porous membranes are stacked.

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

[0188] (Collection efficiency of NaCl particles with particle diameter of 0.1 μm) According to the method described in JIS B9928 Appendix 5 (regulation) NaCl aerosol generation method (pressure spray method), the NaCl particles generated by atomizer are classified into particle diameter of 0.1 μm by electrostatic classifier (TSI company manufacture), and particle charge is neutralized by using americium 241, and then the permeation flow rate is adjusted to 5.3 cm / sec, and the particle number before and after the antifungal air filter material as measurement sample is measured by particle counter (TSI company manufacture, CNC), and collection efficiency is calculated by the following formula.

[0189] Transmittance (%) = (CO / CI) × 100 Collection efficiency (%) = 100 - transmittance (%) CO = number of 0.1 µm NaCl particles on the downstream side of the measurement sample CI = number of 0.1 µm NaCl particles on the upstream side of the measurement sample (Mold resistance test (wet method) according to JIS Z2911) A test was conducted on the above-mentioned Example 1, Example 5, and Comparative Example 1 in accordance with the mold resistance test according to 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 Based on the Mold Resistance Test of JIS Z2911) For each of the above Examples and Comparative Examples, a test based on the mold resistance test of JIS Z2911 was conducted by cutting a sample to a predetermined size, placing it on a potato dextrose agar medium, and then inoculating it with a suspension of Aspergillus niger (1000 RLU). The sample was then left at room temperature, and the extent of mold growth on the sample surface was visually observed over time (after 3 days, 1 week, and 2 weeks).

[0193] (ISO 846 Plastics - Evaluation of Microbial Action) For Examples 1 and 3, a test was 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. ６Spore 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 covering 25% or less of the total sample area, was rated "1a"; no mold growth observed with the naked eye, but mold confirmed under a microscope covering 50% or less of the total sample area, was rated "1b"; no mold growth observed with the naked eye, but mold confirmed under a microscope covering more than 50% of the total sample area, was rated "1c"; mycelial growth observed with the naked eye covering less than 25% of the total sample area was rated "2"; mycelial growth observed with the naked eye covering less than 50% of the total sample area was rated "3"; mycelial growth observed with the naked eye covering 50% or more of the total sample area was rated "4"; and vigorous mycelial growth covering the entire sample was rated "5".

[0195] The physical properties of the antifungal air filter media and the physical properties of the porous membranes 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]

[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 growth of mycelia was 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 growth of mycelia was observed did not exceed one-third of the total area).

[0200] In the ISO 846 Plastics - 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 of Examples 1 and 3 after four weeks of culture.

[0201] (Note) 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.

[0202] REFERENCE SIGNS LIST 1 Air filter unit 20 Filter pack 25 Frame 30a, 30b, 30c, 30d Antifungal air filter medium (air filter medium) 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 Inlet 50b Outlet 51 Heat exchanger 52 Humidity adjustment section 53 Fan 100 Outdoor air treatment device

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

Claims

1. An air filter medium having a porous membrane with an average surface height Rc of 6 μm or more and a water contact angle of the membrane surface of 90 degrees or more.

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

3. The air filter medium according to claim 1 or 2, wherein the arithmetic mean roughness Ra of the surface of the porous membrane is 6 μm or more.

4. The air filter medium according to any one of claims 1 to 3, wherein the average pore size of the porous membrane is 2 µm or more.

5. The air filter medium according to any one of claims 1 to 4, wherein the porous membrane has an average pore size of 10 µm or less.

6. The air filter medium according to any one of claims 1 to 5, wherein the porous membrane has a thickness of 100 µm or more.

7. An air filter medium according to any one of claims 1 to 6, which has a contact angle of 127 degrees or more with an aqueous solution of isopropyl alcohol having a concentration of 30% by volume.

8. The air filter medium according to any one of claims 1 to 7, wherein the porous film contains a fluororesin.

9. The air filter medium according to any one of claims 1 to 8, wherein the porous membrane does not contain an antifungal agent.

10. The air filter medium according to any one of claims 1 to 9, which is used in an environment with a relative humidity of 60% or more.

11. A method for using an antifungal air filter medium according to any one of claims 1 to 9 in an environment with a relative humidity of 60% or more.

12. An air treatment device comprising an air filter medium according to any one of claims 1 to 10.

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